For an energy-saving type control, a value of a control low rate QP controlled by a flow control valve V is closer to a value of a flow rate required by an output side such as a power cylinder 8, a steering valve 9 or the like, to suppress a driving torque of a pump P. An excitation current I of a solenoid SOL is specified on the basis of a solenoid current instruction value IT based on a steering torque and a solenoid current instruction value IS defining a standby flow rate.

1. Field of the Invention
This invention relates to a power steering including a flow control valve for controlling a flow introduced toward a power cylinder.
2. Description of Related Art
A flow control valve installed in this type of power steering has a spool which is mounted inside a main body and has one end facing one of pilot chambers which is communicated with a pump port at all times and the other end facing the other pilot chamber incorporating a spring. A fixed orifice is formed downstream from the other pilot chamber. Pressure oil is introduced through the fixed orifice into a steering valve for controlling a power cylinder.
on the other hand, movement positions of the spool is controlled with pressure balance between both pilot chambers wherein pressure upstream from the orifice is set as pilot pressure of the one pilot chamber and pressure downstream from there is set as pilot pressure of the other pilot chamber.
It is configured to use the movement position of the spool for distribution of the pressure oil between a control flow rate QP of the flow for introducing the amount of discharge from a pump into the steering valve and a return flow rate QT for making the flow circulation-return toward a tank or a pump.
The above spool is designed to be maintained in a constant state of differential pressure after and before the fixed orifice, to supply a constant control flow rate QP to the steering valve for controlling the power cylinder at all times.
In such conventional power steering, a constant control flow rate QP is supplied from the flow control valve to the steering valve for controlling the power cylinder at all times. In other words, regardless of vehicle speed or steering conditions, the control flow rate QP is continuously supplied to the steering valve at a constant control flow rate QP at all times.
However, if the control flow rate QP is defined regardless of the vehicle speed or a steering status, for example, when a relation of QP with respect to the flow rate QM required by the power cylinder becomes QP greater than QM, the need for returning the resulting surplus flow rate to a tank through the above steering valve arises.
As described above, returning the surplus flow rate to the tank through the steering valve results in increase of a pressure loss in the circuit. Put another way, the pump is required to continue consuming the driving torque to make up for the amount of pressure loss. Therefore, as driving torque increases, energy consumption increases.
Moreover, since the control flow rate QP is set in accordance with the maximum required flow rate for the power cylinder, under present circumstance, some surplus flow rate is often returned to the tank. Thus, the conventional system has a problem associated with increase of energy consumption.
It is an object of the present invention to provide a power steering which in capable of reducing an energy loss to a minimum by controlling a control flow rate QP as travelling conditions or a steering status of a vehicle.
The present invention is predicated on configuration in which: a spool is mounted in a main body and has one of ends facing one of pilot chambers which communicates with a pump port at all times and the other end facing the other pilot chamber incorporating a spring. An orifice is provided downstream from the one pilot chamber. Pressure oil is introduced through the orifice into a steering valve for controlling a power cylinder. A movement position of the spool is controlled with a pressure balance between both the pilot chambers when pressure upstream from the orifice is set as a pilot pressure of the one pilot chamber and pressure downstream from the orifice is set as a pilot pressure of the other pilot chamber. The pressure oil is distributed between a control flow rate QP for introducing the amount of discharge from a pump toward the steering valve, and a return flow rate QT for making the pressure oil circulation-return toward a tank or the pump.
Based on the above power steering, a first invention features as follows: the orifice is a variable orifice controlling the degree of its opening in accordance with an excitation current of a solenoid. Also, a controller is provided for controlling the excitation current of the solenoid for the variable orifice. The controller is connected with a steering torque sensor, and calculates or stores a solenoid current instruction value IT in response to a steering torque signal from the steering torque sensor. Further, a solenoid current instruction value IS for standby is added to the solenoid current instruction value IT. Then the excitation current I of the solenoid SOL for the variable orifice is controlled based on the added instruction value.
According to the power steering of the first invention, the control flow rate QP can be controlled by means of detecting the steering torque. Therefore, the control flow rate QP is appropriately secured to accomplish an energy-saving type control.
Also, when the steering wheel is held stationary, the control flow rate QP can be appropriately secured by means of the steering torque thereby to allow the vehicle to resist a self-aligning torque.
Further, the standby flow rate can be secured even when the solenoid current instruction value IT based on the steering torque is zero, for example, in travel of the vehicle in a straight line. Therefore, the power steering can be prevented from seizure, and is capable of handling disturbances caused by a kick back or the like, and further sufficient response can be ensured.
In any of times when the steering wheel is turned, when the steering wheel is held stationary, and when the vehicle travels in a straight line, the control flow rate QP is appropriately secured not to increase torque for driving the pump P more than necessary thereby to attain the accurate energy-saving control.
In the power steering, a signal of the steering torque, the vehicle speed or the like has been conventionally used for controlling a steering reaction force on the output side or controlling sensitivity of the steering valve. However, the present invention has been made under the theme of energy savings and therefore uses a signal of the steering torque, the vehicle speed or the like to control the control flow rate QP, which has not been seen in prior art.
Moreover, in the present invention, the steering torque is directly detected thereby to obtain a more accurate value without need of other sensors or calculating means.
The present invention approaches the subject of energy savings and has the principal feature in that a signal of the steering torque, the vehicle speed or the like is used.
A second invention has configuration in which the controller is connected to a vehicle speed sensor, and calculates or stores a solenoid current instruction value IV in response to a vehicle speed signal from the vehicle speed sensors while multiplying the solenoid current instruction value IT by the solenoid current instruction value IV, and adding the solenoid current instruction value IS for standby to the multiplied value.
A third invention has configuration in which the controller is connected to a vehicle speed sensor, and calculates or stores a solenoid current instruction value TV in response to a vehicle speed signal from the vehicle speed sensor, while setting the solenoid current instruction value IV in response to the vehicle speed signal as a threshold value based on the solenoid current instruction values IT, and adding a solenoid current instruction value under the set threshold value to the solenoid current instruction value (IS) for standby.
A fourth invention has configuration in which the controller multiplies characteristics of the excitation current I of the solenoid and the control flow rate QP determined by the degree of opening of the variable orifice, and characteristics of the steering torque and the solenoid current instruction value IT together, to allow the steering torque and the control flow rate QP, which is determined by the degree of opening of the variable orifice in accordance with the solenoid current IT, to have linear characteristics.
According to the power steering of the second invention, since the power steering is designed in a speed sensitive types the energy-saving type control in accordance with the vehicle speed is allowed.
According to the power steering of the third invention, it is designed in a vehicle-speed sensitive type, but the solenoid current instruction value IV based on the vehicle speed is used as a limiter, resulting in maintaining further sufficient response.
According to the power steering of the fourth invention, since the control flow rate QP with respect to the steering torque is permitted to have further linear characteristics, a driver""s steering feel is improved.
Based on the aforementioned power steering, a fifth intention features as follows: the orifice is a variable orifice controlling the degree of its opening in accordance with an excitation current I of a solenoid. Also, a controller is provided for controlling the excitation current I of the solenoid for the variable orifice. The controller is connected with a steering angle sensor, to store or calculate a steering angle xcex8 and a steering angular velocity xcfx89 in accordance with a steering angle from the steering angle sensor, while calculating or storing a solenoid current instruction value Ixcex8 in accordance with the steering angle xcex8 and a solenoid current instruction value Ixcfx89 in accordance with the steering angular velocity xcfx89, and adding the solenoid current instruction values Ixcex8 and Ixcfx89, and further adding the added value to a solenoid current instruction value IS for standby, and then controlling the excitation current I of the solenoid for the variable orifice based on the finally added instruction value.
A sixth invention has configuration in which the controller is connected to a vehicle speed sensor, and calculates or stores a solenoid current instruction value IV in response to a vehicle speed signal from the vehicle speed sensor, while multiplying the added value of the solenoid current instruction values Ixcex8 and Ixcfx89 by the solenoid current instruction value IV, and adding the solenoid current instruction value TS for standby to the multiplied value.
A seventh invention has configuration in which the controller is connected to a vehicle speed sensor, and calculates or stores a solenoid current instruction value IV in response to a vehicle speed signal from the vehicle speed sensor, while setting the solenoid current instruction value IV based on the vehicle speed signal as a threshold value with respect to the added value of the solenoid current instruction values Ixcex8, and Ixcfx89, and adding a solenoid current instruction value under the set threshold value to the solenoid current instruction value IS for standby.
Based on the aforementioned power steering, a eighth invention features as follows: the orifice is a variable orifice controlling the degree of its opening in accordance with an excitation current I of a solenoid. Also, a controller is provided for controlling the excitation current I of the solenoid for the variable orifice. The controller is connected with a steering angle sensor to calculate or store a steering angle xcex8 and a steering angular velocity xcfx89 in accordance with a steering angle from the steering angle sensor, while storing or calculating a solenoid current instruction value Ixcex8 in accordance with the steering angle xcex8 and a solenoid current instruction value Ixcfx89, in accordance with the steering angular velocity xcfx89, and selecting any larger solenoid current instruction value from the solenoid current instruction values Ixcex8 and Ixcfx89, and adding a solenoid current instruction value IS for standby to the selected value, and then controlling the excitation current I of the solenoid for the variable orifice based on the finally added instruction values.
According to the power steering of the fifth and eighth inventions, the steering angular velocity xcfx89 is detected thereby to control the control flow rate QP at a value closer to that of the steering torque. Therefore, it is possible to appropriately secure the control flow rate QP to achieve the energy-saving type control.
When the steering wheel is held stationary, the control flow rate QP is appropriately secured by means of the steering angle xcex8, to allow the vehicle to resist the self-aligning torque.
Further, for example, in the vehicle travelling in a straight line, eaten when the solenoid current instruction value Ixcex8 based on the steering angle xcex8 or the solenoid current instruction value Ixcfx89 based on the steering angular velocity xcfx89 is zero, the standby flow rate can be secured. Therefore, the power steering can be prevented from seizure, and is capable of handling disturbances caused by a kick back or the like, and further sufficient response can be ensured.
In any of times when the steering wheel is turned, when the steering wheel is held stationary, and when the vehicle travels in a straight line, the control flow rate QP is appropriately secured not to increase the torque for driving the pump P more than necessary, resulting in making the correct energy-saving control implementable.
In the power steering, a signal of the steering angle, the steering angular velocity, the vehicle speed or the like has been conventionally used for controlling a steering reaction force on the output side or controlling sensitivity of the steering valve. However, the present invention has been made under the theme of energy savings and therefore uses a signal of the steering angle, the steering angular velocity, the vehicle speed or the like to control the control flow rate QP, which has not been seen in prior art.
The present invention approaches the subject of energy savings and has the principal feature in that a signal of the steering angle, the steering angular velocity, the vehicle speed or the like is used.
A ninth invention has configuration in which the controller is connected to a vehicle speed sensor, and calculates or stores a solenoid current instruction value IV in response to a vehicle speed signal from the vehicle speed sensor, while multiplying the any larger value of the solenoid current instruction values Ixcex8 and Ixcfx89 by the solenoid current instruction value IV, and adding the multiplied value to the solenoid current instruction value IS.
According to the power steering of the sixth and ninth inventions, since the power steering is designed in a speed sensitive type, the energy-saving type control in accordance with the vehicle speed is allowed.
A tenth invention has configuration in which the controller is connected to a vehicle speed sensor, and calculates or stores a solenoid current instruction value IV in response to a vehicle speed signal from the vehicle speed sensor, while setting the solenoid current instruction value IV based on the vehicle speed signal as a threshold value with respect to the any larger value of the solenoid current instruction values Ixcex8 and Ixcfx89, and adding a solenoid current instruction value under the set threshold value to the solenoid current instruction value IS.
According to the power steering of the seventh and tenth inventions, it is designed in a vehicle-speed sensitive type, but the solenoid current instruction value IV based on the vehicle speed is used as a limiter, resulting in maintaining further sufficient response.
A eleventh invention has configuration in which the controller multiplies characteristics of the excitation current I of the solenoid and the control flow rate QP determined by the degree of opening of the variable orifice, and characteristics of the steering angle xcex8 and the solenoid current instruction value Ixcex8 together, to allow the steering angle xcex8 and the control flow rate QP determined by the degree of opening of the variable orifice in accordance Faith a solenoid current I1 to have linear characteristics.
A twelfth invention has configuration in which the controller multiplies characteristics of the excitation current I of the solenoid and the control flow rate QP determined by the degree of opening of the variable orifice, and characteristics of the steering angular velocity xcfx89 and the solenoid current instruction value I2 together, to allow the steering angular velocity xcfx89 and the control flow rate QP determined by the degree of opening of the variable orifice in accordance with a solenoid current Ixcfx89 to have linear characteristics.
According to the power steering of the eleventh and twelfth inventions, since the control flow rate QP with respect to the steering angle is permitted to have further linear characteristics, a driver""s steering feel can be improved.
Based on the aforementioned power steering, a thirteenth invention features as follows: the orifice is a variable orifice controlling the degree of its opening in accordance with an excitation current I of a solenoid. Also a controller is provided for controlling the excitation current I of the solenoid for the variable orifice. The controller is connected with a steering angle sensor, to calculate or store a steering angle xcex8 and a steering angular velocity xcfx89 in accordance with a steering angle from the steering angle sensor, while the controller storing or calculating a solenoid current instruction value I74  in accordance with the steering angle xcex8 and a solenoid current instruction value Ixcfx89 in accordance with the steering angular velocity xcfx89, and multiplying the solenoid current instruction value Ixcex8 in accordance with the steering angle xcex8 and a steering-angle current instruction value IV1 in accordance with the vehicle speed together, while the current instruction values Ixcfx89 in accordance with the steering angular velocity xcfx89 being imparted with a threshold value defined by a steering-angular-velocity current instruction value IV2 in response to the vehicle speed signal, and it being determined which of the multiplied value I1 of the solenoid current instruction values Ixcex8 and IV1 and the solenoid current I2 including the steering-angular-velocity current instruction value IV2 as the threshold value is larger, to control the excitation current I of the solenoid for the variable orifice based on the larger value.
According to the thirteenth invention, since the solenoid excitation current I is determined with reference to the steering angle in high-speed travel, the safety of the steering can be ensured.
Also, since the solenoid excitation current I is determined with reference to the steering angular velocity in low-speed travel, the safety of the steering can be ensured.
Additionally, even in high-speed travel, it is possible to ensure the response within the range of the threshold value referred to the vehicle speed when the steering wheel is sharply and abruptly operated. This further improves the safety under the circumstances where the vehicle is steered around an obstacle during high-speed travel, and the like.
Also, when the steering wheel is held stationary, the control flow rate QP is properly secured by meant of the steering angle xcex8, to allow the vehicle to resist the self-aligning torque.
A fourteenth invention has configuration in which the larger current instruction value is added to a solenoid current instruction value IS for standby.
According to the fourteenth invention, it is possible to secure the standby flow rate even when the steering angle xcex8 or the steering angular velocity xcfx89 is zero, for example, in travel of the vehicle in a straight line. Therefore, the power steering can be prevented from seizure, and is capable of handling disturbances caused by a kick back or the like, and further sufficient response can be ensured.
In either of the thirteenth invention or the fourteenth invention, in any of times when the steering wheel is turned, when the steering wheel is held stationary, and when the vehicle travels in a straight line, the control flow rate QP is appropriately secured not to increase the torque for driving the pump P more than necessary. This makes the correct energy-saving control implementable.
In the power steering, a signal of the steering angle, the steering angular velocity, the vehicle speed or the like has been conventionally used for controlling a steering reaction force on the output side or controlling sensitivity of the steering valve. However, the present invention has been made under the theme of energy savings and therefore uses a signal of the steering angle, the steering angular velocity, the vehicle speed or the like to control the control flow rate QP, which has not been seen in prior art.
The present invention approaches the subject of energy savings and has the principal feature in that a signal of the steering angle, the steering angular velocity, the vehicle speed or the like is used.


A conjugated diene rubber composition for tires comprising (I) 2-100 weight parts of a high-cis conjugated diene polymer rubber, which is a polymer of conjugated diene monomer alone or with a copolymerizable monomer, and has a cis-bond unit content of at least 40% in the conjugated diene monomer units, and a weight average molecular weight (Mw) of 20,000-10,000,000, and in which the ratio (Mw/Mn) of weight average molecular weight (Mw) to number average molecular weight (Mn) and the weight average molecular weight (Mw) satisfy the formula: log(Mw/Mn) less than 0.162xc3x97log(Mw)xe2x88x920.682, and (II) 0-98 weight parts of other polymer rubber. A tire comprising at least a tread composed of the above-mentioned conjugated diene rubber composition has very high rebound resilience.

This invention relates to a novel conjugated diene rubber composition for tires having excellent rebound resilience, and a tire comprising the same.
In recent years, as protection of the environment and energy-saving have gained importance because of the global warming problem, there are increasing demands for low fuel consumption by automobiles. To achieve low fuel consumption by automobiles, low rolling resistance of tires is demanded. To enhance low rolling resistance of tires, it is generally effective to use a rubber material capable of providing a cured rubber having a low hysteresis loss. Conventionally, diene rubbers such as natural rubber(NR), polybutadiene(BR), polyisoprene(IR), styrene-butadiene copolymer rubber are used as a rubber material for tires. These diene rubbers are selected and used singly or in combination, depending on the type of a tire and a part where the rubber material is used. Of these diene rubbers, 1,4-polybutadiene having a high cis-bond content is capable of providing a cured rubber having the highest rolling resistance, i.e., the smallest hysteresis loss; however, conventional 1,4-polybutadiene having a high cis-bond content has a problem in that the hysteresis loss is increased owing to the low molecular weight portion present in its wide molecular weight distribution. It is known that high cis 1,4-polybutadiene having a cis-1,4 bond content of at least 90% is produced by polymerization using a typical coordinated polymerization catalyst which is a combination of an organic aluminum compound with a transition metal compound, i.e., Co-, Ni-, Ti- or Nd-compound, or a rare earth metal compound. When these catalysts are used, however, high-cis 1,4-polybutadiene having narrow molecular weight distribution is not obtained, because as the weight average molecular weight (Mw) increases, the molecular weight distribution (Mw/Mn) becomes wider. Hence, it is known that polybutadiene having a high strength has an undesirably high hysteresis loss.
On the other hand, polybutadiene having a high molecular weight and a narrow molecular weight distribution can be obtained by using an organic lithium catalyst; however, the thus-obtained polybutadiene has a cis-1,4-bond content of not larger than 40% and a low rebound resilience.
As a catalyst for polymerization of olefins, a combination of methylaluminoxane with metallocene type catalyst of a transition metal such as Ti, Zr and Hf has been developed and attracted attention. It is known that, by using these catalysts, xcex1-olefin such as ethylene and propylene can be polymerized with high efficiency to yield a polymer having a narrow molecular weight distribution as well as a narrow composition distribution in the case of copolymers. On the other hand, although there have been attempts to polymerize a conjugated diene such as butadiene and isoprene by using metallocene catalysts, stereo-regulation of a polymer thus obtained has been insufficient.
For example, copolymerization of ethylene or xcex1-olefin with butadiene is disclosed in Macromol. Chem., Macromol. Symp., 1986, vol. 4, page 103-118; Macromol. Chem., 1991, vol. 192, page 2591-2601; and Japanese Patent Publication (Tokuhyou, publication of a translated version of international application) No. H1-501633. In Japanese Unexamined Patent Publication (hereinafter abbreviated to xe2x80x9cJP-Axe2x80x9d) No. H7-112986, a rare earth metal-toluene complex is disclosed as a component of a catalyst, however, the catalyst does not exhibit a high activity for polymerization of a conjugated diene monomer such as butadiene or isoprene, and stereo-regulation of a polymer is difficult.
A catalyst comprising a combination of methylaluminoxane with a metallocene compound selected from (C5H5)TiCl3, (C5H5)Ti(OBu)3, (C5H5)TiCl3.2THF and [(C5H5)TiCl2]n for polymerization of 1,3-dienes is described in Makromol. Chem., Macromol. Symp., 1995, vol.89, p383-392. A catalyst comprising a combination of an aluminoxane with a transition metal compound for polymerization of 1,3-dienes is described in JP-A H1-254713, JP-A H3-188109 and JP-A H4-331213. When butadiene is polymerized by these catalysts, a polymer having a relatively high cis-bond content is obtained, but, the molecular weight of the polymer thus obtained is relatively low.
A catalyst for polymerization of a conjugated diene comprising a combination of aluminoxane with a transition metal compound of group IV of the periodic table is described in JP-A H9-77818, which has a high activity and gives a polymer with controlled stereoregularity. It is described that, when butadiene was polymerized with this catalyst, the polymerization proceeded at a high activity and a polymer having a cis-bond content of 96% was obtained. However, this patent publication is silent on the molecular weight of the polymer and regulation of the molecular weight distribution.
As stated above, by using conventional methods, it has been difficult to polymerize a conjugated diene monomer with high efficiency to a polymer having a high molecular weight, a narrow molecular weight distribution and a high cis-bond content.
Incidentally, a metallocene catalyst represented by the following formula: CH3O(CO)CH2(C5H5)TiCl3 is described in Makromol. Chem., Macromol. Symp., 1997, vol.118, p55-60. But, this catalyst is not known to be used for polymerization of a conjugated diene monomer.
Further, in Japanese Examined Patent Publication H6-43517, main-chain modified high-cis poly butadiene is described as preferable from the aspect of rolling resistance and abrasion resistance of tires, but any specific example is not disclosed. In Makromol. Chem., Macromol. Symp., 1997, vol.118, p55-60, a process for preparing a high cis poly butadiene by using a new catalyst is disclosed, but little is reported about the properties of polymer thus obtained, hence it is not known if thus-obtained polymer is usable for tires.
Objects of the present invention are to provide a novel conjugated diene rubber composition for tires having an improved rebound resilience and a tire comprising the same, wherein said conjugated diene rubber composition has a high cis-bond content and a low ratio (Mw/Mn) of weight average molecular weight (Mw) to number average molecular weight (Mn).
Thus, according to the present invention, there is provided a conjugated diene rubber composition for tires comprising:
(I) 2 to 100 percent by weight of a conjugated diene polymer rubber having a high cis-bond content, which is a polymer of conjugated diene monomer or monomers alone or a copolymer of a conjugated diene monomer with a monomer copolymerizable therewith, and characterized in that the content of units having a cis-bond in the total units derived from the conjugated diene monomer is at least 40%; the weight average molecular weight (Mw) is in the range of 20,000 to 10,000,000; and the ratio (Mw/Mn) of weight average molecular weight (Mw) to number average molecular weight (Mn) and the weight average molecular weight (Mw) satisfy the following formula (1):
log(Mw/Mn) less than 0.162xc3x97log(Mw)xe2x88x920.682xe2x80x83xe2x80x83(1)
and
(II) 0 to 98 percent by weight of other polymer rubber.
Further, according to the present invention, there is provided a tire comprising at least a tread which is composed of the above-mentioned conjugated diene rubber composition.
Conjugated Diene Polymer Having a High Cis-Bond Content (High-Cis Conjugated Diene Polymer)
A high-cis conjugated diene polymer rubber used in the present invention is a polymer of conjugated diene monomer or monomers alone, i.e., a homopolymer of a conjugated diene monomer or a copolymer among conjugated diene monomers, or a copolymer of a conjugated diene monomer with a monomer copolymerizable therewith, and characterized in that the content of units having a cis-bond in the total units derived from the conjugated diene monomer is at least 40%; the weight average molecular weight (Mw) is in the range of 20,000 to 10,000,000; and the ratio (Mw/Mn) of weight average molecular weight (Mw) to number average molecular weight (Mn) and the weight average molecular weight (Mw) satisfy the following formula (1):
log(Mw/Mn) less than 0.162xc3x97log(Mw)xe2x88x920.682xe2x80x83xe2x80x83(1)
In the case of a copolymer, the content of conjugated diene monomer units is preferably at least 50% by weight, more preferably at least 70% by weight, and most preferably at least 90% by weight, based on the total monomer units.
As specific examples of the conjugated diene monomer, there can be mentioned 1,3-butadiene, 2-methyl-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, 2-chloro-1,3-butadiene, 1,3-pentadiene and 1,3-hexadiene. Of these, 1,3-butadiene is preferable. As specific examples of the monomers copolymerizable with the conjugated monomers, there can be mentioned aromatic vinyl monomers such as styrene, o-methylstyrene, p-methylstyrene, m-methylstyrene, 2,4-dimethylstyrene, ethylstyrene, p-tert.-butylstyrene, xcex1-methylstyrene, xcex1-methyl-p-methylstyrene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, p-bromostyrene, 2-methyl-1,4-dichlorostyrene, 2,4-dibromostyrene and vinylnaphthalene; and non-conjugated dienes such as dicyclopentadiene, 5-ethylidene-2-norbornene and 1,5-hexadiene. These conjugated diene monomers may be used either alone or as a combination of at least two thereof.
The high-cis conjugated diene polymer used in the present invention is characterized in that the content of cis-bond in the total units derived from a conjugated diene monomer is at least 40%, preferably at least 80% and more preferably at least 90%. If the content of cis-bond is too small, rebound resilience is reduced. There are no particular limitations for the types of bonds other than cis-bond, i.e., trans-bond and vinyl-bond.
The high-cis conjugated diene polymer used in the present invention has a weight average molecular weight (Mw) in the range of 20,000 to 10,000,000, preferably 50,000 to 5,000,000 and more preferably 100,000 to 3,000,000, as determined by gel permeation chromatography (GPC) using a calibration curve drawn on a standard polybutadiene. If the weight average molecular weight is too small, the mechanical strength such as tensile strength becomes reduced. In contrast, if the weight average molecular weight is too large, viscosity during mixing procedure increases and a burning through molding may be brought about.
In the high-cis conjugated diene polymer used in the present invention, the following formula (2) between weight average molecular weight (Mw) and the ratio (Mw/Mn) of weight average molecular weight (Mw) to number average molecular weight (Mn) is satisfied when A=0.162 and B=0.682
log(Mw/Mn) less than Axc3x97log(Mw)xe2x88x92Bxe2x80x83xe2x80x83(2)
Formula (2) is preferably satisfied when A=0.161 and B=0.682, more preferably satisfied when A=0.160, and most preferably satisfied when A=0.159. Further, Formula (2) is preferably satisfied when B=0.684, more preferably satisfied when B=0.684, and most preferably satisfied when B=0.690.
In the high-cis conjugated diene polymer used in the present invention, a low ratio (Mw/Mn) of weight average molecular weight (Mw) to number average molecular weight (Mn) is preferable for any weight average molecular weight (Mw). The ratio is preferably not larger than 1.9, more preferably not larger than 1.7, and most preferably not larger 1.5. If the ratio is too low, rebound resilience generally becomes superior.
Process for Producing Conjugated Diene Polymer
A process for producing conjugated diene polymer used in the present invention is not particularly limited. For example, the conjugated diene polymer is produced by carrying out polymerization in the presence of a catalyst comprising (A) a compound of a transition metal of group IV of the periodic table having a cyclopentadienyl structural unit having a carbonyl group or a sulfonyl group as a substituent, and (B) an aluminoxane or (C) an ionic compound capable of reacting with the transition metal compound (A) to give a cationic transition metal compound.
The above-mentioned transition metal compound (A) with a cyclopentadienyl structural unit having a carbonyl substituent or a sulfonyl substituent is preferably a compound of a transition metal of group IV of the periodic table represented by the following formula (3):
wherein M is a transition metal of group IV; X1, x2 and X3 are hydrogen, a halogen, a C1-12 hydrocarbon group or a C1-12 hydrocarbon-oxy group; Y is hydrogen or a C1-20 hydrocarbon group which may form a ring together with the cyclopentadienyl group; Z1 and Z2 are hydrogen or a C1-12 hydrocarbon group; A is oxygen or sulfur; R1 is hydrogen, a C1-12 hydrocarbon group or a C1-12 hydrocarbon-oxy group; and n is an integer of 0 to 5.
The transition metal compound of formula (3) is preferably a metallocene compound having as a ligand one cyclopentadienyl group or cyclopentadienyl group with a substituent such as an alkyl, aryl or cycloalkyl group, or fused cyclic substituents. The cyclopentadienyl group as a ligand has an atomic group having a structural unit represented by  greater than Cxe2x95x90O or  greater than Cxe2x95x90S as a substituent. The transition metal (M in formula (3)) of group IV of the periodic table is preferably Ti, Zr or Hf, and more preferably Ti.
As preferable examples of X1, X2 and X3, there can be mentioned halogens such as chlorine; hydrocarbon groups including alkyl groups such as methyl and neopentyl, and aralkyl groups such as benzyl; and hydrocarbon-oxy groups including alkoxy groups such as methoxy, ethoxy and isopropoxy, and aralkyloxy groups such as benzyloxy. Of the hydrocarbon-oxy groups, an alkoxy group is preferable. As specific examples of Y, there can be mentioned hydrogen, alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl and t-butyl, aryl groups such as phenyl, and aralkyl groups such as benzyl. Y may include a hydrocarbon group containing a silicon atom, such as trimethylsilyl. Y connected to the cyclopentadienyl ring may form, together with the cyclopentadienyl group, a polycyclic group, for example, indenyl and fluorenyl groups.
As specific examples of Z1 and Z2, there can be mentioned hydrogen, alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl and t-butyl, aryl groups such as phenyl, and aralkyl groups such as benzyl. R1 includes hydrogen, hydrocarbon groups and hydrocarbon-oxy groups. As specific examples of the hydrocarbon groups, there can be mentioned alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl and t-butyl, aryl groups such as phenyl, and aralkyl groups such as benzyl; and, as specific examples of the hydrocarbon-oxy groups, there can be mentioned alkoxy groups such as methoxy, ethoxy, propoxy, isopropoxy, butoxy and t-butoxy, aryloxy groups such as phenoxy, and aralkyloxy groups such as benzyloxy. Of these, alkoxy groups are preferable as hydrocarbon-oxy groups, and n is preferably 1 or 2, and more preferably 1.
As specific examples of the compound (A) with a transition metal of group IV of the periodic table represented by the formula (3), there can be mentioned those which are represented by the formulae: MeO(CO)CH2CpTiCl3, MeO(CO)CH(Me)CpTiCl3 and {3-[MeO(CO)CH2]}(1-Me)CpTiCl3, wherein Me is a methyl group and Cp is a cyclopentadienyl group.
The procedure by which the transition metal compound (A) represented by the formula (3) is prepared is not particularly limited. For example, MeO(CO)CH2CpTiCl3 can be prepared by the procedure described in Macromol. Symp., 1997, vol. 118, p55-60.
An aluminoxane used in combination with the compound (A) with a transition metal of group IV of the periodic table, is a straight-chain or cyclic polymer, which is an organic aluminumoxy compound and is represented by the following formula (4):
(xe2x80x94Al(R2)Oxe2x80x94)nxe2x80x83xe2x80x83(4)
wherein R2 is a C1-10 hydrocarbon group, which includes, for example, alkyl groups such as methyl, ethyl, propyl and isobutyl. Of these, methyl is most preferable. R may have a substituent such as halogen and/or an R3O group wherein R3 is a C1-10 hydrocarbon group, which includes, for example, alkyl groups such as methyl, ethyl, propyl and isobutyl. Of these, methyl is most preferable, and n is a degree of polymerization, and at least 5, preferably at least 10.
As specific examples of the ionic compound (C) capable of reacting with the transition metal compound (A) to form a cationic complex, there can be mentioned ionic compounds which are a combination of tetrakis(pentafluorophenyl) borate anion with an amine cation having an active proton such as, for example, (CH3)2N(C6H5)H+, a tri-substituted carbonium cation such as (C6H5)3C+, a carborane cation, a metal carborane cation or a transition metal-having ferrocenium cation.
The catalyst of the present invention may be used, for polymerization of a conjugated monomer, in combination with a hydrogenated metal compound, an organic metal compound containing a main-group metal element of groups I, II and III of the periodic table, an organic metal halide compound and a hydrogenated organic metal compound.
Specific examples include hydrogenated metal compounds such as NaH, LiH, CaH2, LiAlH4 and NaBH4; main-metal group-containing organic metal compounds such as methyllithium, butyllithium, phenyllithium, dibutylmagnesium, trimethylaluminum, triethylaluminum, triisobutylaluminum, trihexylaluminum and trioctylaluminum; organic metal halide compounds such as ethylmagnesium chloride, butylmagnesium chloride, dimethylaluminum chloride, diethylaluminum chloride, sesquiethylaluminum chloride and ethylaluminum dichloride; and hydrogenated organic metal compounds such as diethylaluminum hydride and sesquiethylaluminum hydride.
The transition metal compound and/or the ionic compound used in the present invention can be used in a form supported by a carrier. The carrier includes inorganic compounds and organic polymers.
The inorganic compounds preferably include inorganic oxides, inorganic chlorides and inorganic hydroxides. The inorganic compounds may contain a minor amount of carbonate salts or sulfate salts. As preferable specific examples of the inorganic compounds, there can be mentioned inorganic oxides such as silica, alumina, magnesia, titania, zirconia and calcia, and inorganic chlorides such as magnesium chloride. These inorganic compounds are preferably in the form of finely divided porous particles having an average particle diameter of 5 to 150 xcexcm and a specific surface area of 2 to 800 m /g. The porous particles may be heat-treated, for example, at a temperature of 100 to 800xc2x0 C. to remove volatile compounds.
The organic polymers preferably include those which have as a side chain an aromatic ring, a substituted aromatic ring, or functional groups such as hydroxyl, carboxyl, ester and halogen. As specific examples of the organic polymers, there can be mentioned homopolymers and copolymers of a-olefin such as ethylene, propylene and butene which have a functional group introduced therein by chemical modification and copolymers of ethylene, propylene or butene; and homopolymers, copolymers and chemically modified polymers thereof of monomers such as acrylic acid, methacrylic acid, vinyl chloride, vinyl alcohol, styrene and divinylbenzene. The organic polymers are preferably in the form of finely divided spherical particles having an average particle diameter of 5 to 250 xcexcm. When the transition metal compound and/or the ionic compounds are supported by these carriers, deposition of the catalyst onto a polymerization reactor can be prevented.
The polymerization of a conjugated diene monomer or monomers alone or in combination with a copolymerizable monomer is carried by a method selected from the following methods (1) to (6) using a catalyst comprising the transition metal compound (A) and the aluminoxane (B) and/or the ionic compound (C).
(1) Component (A) is previously contacted with component (B) or component (C), and then the mixture is placed into contact with a monomer to conduct polymerization.
(2) Component (A) is previously contacted with a monomer, and then the mixture is placed into contact with component (B) or component (C) to conduct polymerization.
(3) Component (B) or component (C) is previously contacted with a monomer, and then the mixture is placed into contact with component (A) to conduct polymerization.
(4) A solution of component (A) and a solution of component (B) or component (C) are mixed together, the mixed solution is placed in contact with a carrier, the thus-formed supported catalyst is separated from the mixed solution, and then the supported catalyst is placed into contact with a monomer to conduct polymerization.
(5) A solution of component (A) is contacted with a carrier, the thus-obtained solution is then contacted with a solution of component (B) or component (C), and the thus-formed supported catalyst is separated from the mixed solution, and then the supported catalyst is placed into contact with a monomer to conduct polymerization.
(6) A solution of component (B) or component (C) is contacted with a carrier, the thus-obtained solution is then contacted with a solution of component (A), and the thus-formed supported catalyst is separated from the mixed solution, and then the supported catalyst is placed into contact with a monomer to conduct polymerization.
Of these procedures (1) to (6), from the aspect of enhancement of efficiency of polymerization initiator, polymerization activity and narrower molecular weight distribution, procedures (1), and (4) to (6) are preferable, wherein transition metal compound (A) and the aluminoxane (B) and/or the ionic compound (C) are previously contacted with each other, and, after a lapse of aging time, a monomer is placed. Procedure (1) is most preferable. By using this procedure, a conjugated diene polymer having a very low ratio (Mw/Mn) of weight average molecular weight (Mw) to number average molecular weight (Mn) is easily obtained.
The transition metal compound (A), component (B) and component (C) may be used either in a state of a solution or a slurry, and may be in a different state from each other, unless otherwise described. A solution state is preferable because of high polymerization activity. The liquid medium used to form a solution or a slurry includes inert hydrocarbons such as butane, pentane, hexane, heptane, octane, cyclohexane, mineral oil, benzene, toluene and xylene; and halogenated hydrocarbons such as chloroform, methylene chloride, dichloroethane and chlorobenzene.
Contact of component (A), component (B) or component (C) with the monomer is usually carried out at a temperature range of xe2x88x92100xc2x0 C. to +100xc2x0 C. for 1 second to 180 minutes.
The amount of the catalyst used is such that the amount of the transition metal compound (A) is usually in the range of 100 to 0.001 milli-moles, preferably 10 to 0.01 milli-moles and more preferably 5 to 0.1 milli-moles, per mole of the monomer. When an aluminoxane is used as a component, the ratio by mole of aluminoxane/transition metal compound is usually in the range of 10 to 10,000, preferably 5.0 to 100. When the ionic compound is used as a component, the ratio by mole of ionic compound/transition metal compound is usually in the range of 0.01 to 100, preferably 0.1 to 10. Further, when an organic metal compound is also used, the ratio by mole of organic metal compound/transition metal compound is usually in the range of 0.1 to 10,000, preferably 1 to 1,000.
The homopolymerization of a conjugated diene monomer, and the copolymerization of a conjugated diene monomer with a copolymerizable monomer are usually carried out in an inert hydrocarbon medium by solution polymerization, slurry polymerization, or bulk polymerization in which a monomer is used as a diluent. A vapor phase polymerization procedure using a vapor phase stirred reaction vessel or a vapor phase fluidized bed can also be employed. These polymerization procedures can be carried out at a temperature of xe2x88x92100xc2x0 C. to +110xc2x0 C. and a pressure of ordinary pressure to 30 kg/cm2 for 1 second to 360 minutes. The inert hydrocarbon medium used includes those which are hereinbefore recited.
It is possible that a conjugated diene monomer is preliminary polymerized by the above-mentioned polymerization procedure, and, by using the thus-obtained polymer as a catalyst, a further conjugated diene monomer is polymerized. This procedure is advantageous for enhancing polymerization activity, keeping the form of a solid catalyst, making easy the operation of introducing a catalyst into a polymerization vessel for the further polymerization, preventing or minimizing the deposition of catalyst on a wall of the polymerization vessel, and enhancing the fluidity of the reaction mixture in a vapor phase polymerization vessel.
To control the molecular weight of a polymer, a chain transfer agent can be added. As the chain transfer agent, those which are conventionally used for the production of cis-1,4-polybutadiene are used. Arenes such as 1,2-butadiene and cyclic dienes such as cyclooctadiene are especially preferable.
As a process for polymerizing conjugated diene monomers using the catalyst, a continuous polymerization process, a semi-batch polymerization process and a batch polymerization process can be employed. To obtain low Mw/Mn ratio, a semi-batch polymerization process or a batch polymerization process is preferable, and a batch polymerization process is more preferable.
The termination of polymerization is usually carried out by adding an active proton compound such as an alcohol, water, a primary amine or a secondary amine into the polymerization system when the predetermined conversion is reached. The alcohol used may be, for example, methanol, ethanol, propanol, isobutanol or butanol.
After the termination of polymerization, an antioxidant, a neutralizing agent, a dispersing agent etc. are added, according to the need, to polymerization reaction mixture which is a rubber-like polymer solution.
The kind and amount of a stabilizer used, according to the need, in the present invention are not particularly limited. The antioxidant includes, for example, phenolic stabilizers, sulfur-containing stabilizers, phosphorus-containing stabilizers and amine stabilizers. The phenolic stabilizers are described, for example, in JP-A H4-252243. As specific examples of the phenolic stabilizers, there can be mentioned 2,6-di-tert.-butyl-4-methylphenol, 2,6-di-tert.-butyl-4-ethylphenol, 2,6-di-tert.-butyl-4-butylphenol, 2,6-di-tert.-butyl-4-isobutylphenol, 2-tert.-butyl-4,6-dimethylphenol, 2,4,6-tricyclohexylphenol, 2,6-di-tert.-butyl-4-methoxylphenol, 2,6-di-phenol-4-octadecyloxyphenol, n-octadecyl-3-(3xe2x80x2,5xe2x80x2-di-tert.-butyl-4-hydroxyphenyl) propionate, tetrakis-[methylene-3-(3xe2x80x2,5xe2x80x2-di-tert.-butyl-4xe2x80x2-hydroxyphenyl)-propionate]-methane, 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert.-butyl-4-hydroxybenzyl)benzene, 2,4-bis-(octylthiomethyl)-6-methylphenol, 2,4-bis(2xe2x80x2,3xe2x80x2-dihydroxypropylthiomethyl)-3,6-dimethylphenol and 2,4-bis(2xe2x80x2-acetyloxyethylthiomethyl)-3,6-dimethylphenol. As specific examples of the sulfur-containing stabilizers, there can be mentioned dilauryl thiodipropionate, distearyl thiodipropionate, aminothioglycolate, 1,1xe2x80x2-thiobis(2-naphthol), ditridecyl thiodipropionate and distearylxcex2,xcex2xe2x80x2-thiodipropionate. The phosphorus-containing stabilizers are also known, and, as specific examples thereof, there can be mentioned tris(nonylphenyl)phosphite, cyclic neopentanetetraylbis-(octadecylphosphite) and tris(2,4-di-tert.-butylphenyl)-phosphite. As specific examples of the amine stabilizers, there can be mentioned phenyl-xcex1-naphthylamine, phenyl-xcex2-naphthylamine, aldol-xcex2-naphthylamine, p-isopropoxy-diphenylamine, p-(p-toluenesulfonylamide)-diphenylamine, bis(phenylisopropylidene)-4,4xe2x80x2-diphenylamine, N,Nxe2x80x2-diphenylethylenediamine, N,Nxe2x80x2-diphenylpropylenediamine, octylated diphenylamine, N,Nxe2x80x2-diphenyl-p-phenylenediamine and N-isopropyl-Nxe2x80x2-phenyl-p-phenylenediamine.
The amount of the stabilizer is usually in the range of 0.01 to 5.0 parts by weight, preferably 0.05 to 2.5 parts by weight, based on 100 parts by weight of the conjugated diene polymer. When the amount of the stabilizer is too small, the effect of the antioxidant is not manifested and the polymer has poor heat-resistance. In contrast, when the amount of the stabilizer is too large, the conjugated diene polymer exhibits heat discoloration. The antioxidant may be used alone or as a combination of at least two thereof.
The stabilizer can be added simultaneously when the polymerization terminator is added, or can be added to rubber-like polymer solution after the addition of the polymerization terminator. When two or more kinds of stabilizers are used, they can be pre-mixed or added separately. The stabilizer may be compounded by using mixing machines such as single or twin screw extruder, Banbury mixer, roll and kneader; however, addition thereof after the polymerization step in polymerization process is preferable to prevent deterioration caused by heat-treatment in a drying process.
When halogen-containing compound is used as a compound of a transition metal of group IV of the periodic table, it is preferable to neutralize butadiene polymer solution. As a neutralizing agent to be compounded, there can be mentioned basic oxide of alkali metal or alkali earth metal, hydroxide of alkali metal or alkali earth metal, salt of strong alkali with weak acid, ammonia, or nitrogen-containing organic compound.
As specific examples of the basic oxide of alkali metal, there can be mentioned Na2O, K2O and Li2O. As specific examples of the basic oxide of alkali earth metal, there can be mentioned CaO, MgO and BaO. As specific examples of the hydroxide of alkali metal, there can be mentioned NaOH, KOH and LIOH. As specific examples of the hydroxide of alkali earth metal, there can be mentioned Ca(OH)2, Mg(OH)2 and Ba(OH)2. As specific examples of the salt of strong alkali with weak acid, there can be mentioned Na2CO3, K2CO3 and Li2CO3, CH3COONa, CH3COOK and CH3COOLi. Examples of the nitrogen-containing organic compound are amines and nitrogen-containing hetero-cyclic compounds. As specific examples of the amines, there can be mentioned amino alcohols such as ethanolamine, N,N-diethyl-ethanolamine, N,N-dimethyl-ethanolamine, N-methyl-N,N-diethanolamine, N,N-dibutyl-ethanolamine, N-methyl-ethanolamine; ethylamine, diethylamine, triethylamine, 2-ethyl-hexylamine, di-2-hexyl amine, diisobutylamine, propylamine; ethyleneamines such as ethylenediamine, diethylenetriamine, triethylenetatraamine, tetraethylenepentaamine, pentaethylenehexaamine; cyclohexylamine, methylamine, dimethylamine, trimethylamine, diphenylamine, dibenzylamine, benzylamine, aniline, N-ethylaniline, N,Nxe2x80x2-dimethylaniline, benzylethylaniline. As specific examples of the nitrogen-containing hetero-cyclic compounds, there can be mentioned pyridines, piperidine, piperazine. Of these, hydroxide of alkali metal or alkali earth metal, and salts of strong alkali with weak acid are preferable.
The amount of the neutralizing agent is preferably in the range of 0.1 to 10 equivalents, more preferably in the range of 0.3 to 5 equivalents, and most preferably in the range of 0.5 to 3 equivalents to halogen in the halogen-containing transition metal compound.
The procedure of recovering the conjugated diene polymer from a polymer solution using the above-mentioned catalyst is not particularly limited. For example, a steam-stripping procedure which is a conventional procedure for recovering a polymer from a rubber-like polymer solution can be used. A procedure to dehydrate and dry a butadiene polymer crumb after steam-stripping is not particularly limited. Conventional dehydration procedures can be used. As an example of the conventional procedure, there can be used a process in which the conjugated diene polymer crumb is separated from hot water using an oscillating screen, placed into compression water squeezer to reduce the water content in the crumb to 5 to 25% by weight, and is dried by extrusion dryer and/or hot air dryer to the water content of at most 1% by weight.
The rubber composition for tires of the present invention comprises (I) 2 to 100 percent by weight of the above-mentioned conjugated diene polymer rubber having a high cis-bond content, (II) 0 to 98 percent by weight of other polymer rubber, and ingredients for rubber composition conventionally used in the rubber industry. As the polymer rubber (II), diene rubbers other than above-mentioned high-cis conjugated diene polymer rubber are preferable. The amount of the high-cis conjugated diene polymer rubber is preferably in the range of 10 to 100% by weight, more preferably in the range of 20 to 90% by weight, and most preferably in the range of 30 to 80% by weight, based on the total weight of the polymer rubbers. If the amount of the high-cis conjugated diene polymer rubber is too small, the effect of the present invention is not manifested.
As the diene rubber (II) used together with the conjugated diene polymer rubber (I), there can be mentioned, for example, natural rubber (NR), polyisoprene rubber (IR), styrene-butadiene copolymer rubber (SBR) produced by emulsion polymerization, random SBR (bound styrene content: 5-50% by weight, 1,2-vinyl content of butadiene units: 10-80%) produced by solution polymerization, high-trans SBR (1,4-trans content of butadiene units: 70-95%), low-cis polybutadiene rubber (BR), high-trans BR (1,4-trans content of butadiene units: 70-95%), styrene-isoprene copolymer rubber (SIR), butadiene-isoprene copolymer rubber, random styrene-butadiene-isoprene copolymer rubber (SIBR) produced by solution polymerization, random styrene-butadiene-isoprene copolymer rubber produced by emulsion polymerization, styrene-acrylonitrile-butadiene copolymer rubber produced by emulsion polymerization, acrylonitrile-butadiene copolymer rubber, and block copolymers, for example, high-vinyl SBR-low-vinyl SBR block copolymer rubber and polystyrene-polybutadiene-polystyrene block copolymer. These rubbers can be appropriately selected so as to satisfy the properties required for the rubber composition. Of these, preferred are NR, IR, SBR and SIBR with NR and IR being particularly preferred in view of the processability. These diene rubbers can be used singly or in combination of at least two thereof.
Preferred ratio of the high-cis conjugated diene polymer rubber to the diene rubber is in the range of 10/90 to 90/10 by weight, preferably 20/80 to 70/30 in the case of the high-cis conjugated diene polymer rubber/natural rubber or synthetic isoprene rubber, and 80-20/10-70/10-70 by weight in the case of the high-cis conjugated diene polymer rubber/natural rubber or synthetic isoprene rubber/styrene-butadiene copolymer rubber.
As the ingredients for rubber composition, there can be used, for example, a reinforcing agent, an extender oil and a vulcanizing agent. As to the reinforcing agent, there is no particular limitation, and there can be used, for example, carbon black, silica, and various reinforcing agents conventionally used for general purpose rubbers.
As specific examples of carbon black, there can be mentioned various grades such as SAF, ISAF, ISAF-HS, ISAF-LS, HAF, HAF-HS, HAF-LS and FEE, and can be appropriately chosen according to the application purpose. The amount of carbon black used is preferably 20 to 150 parts by weight, more preferably 30 to 120 parts by weight, and most preferably 40 to 100 parts by weight per 100 parts by weight of the rubber component. If the amount of the reinforcing agent is too small, tensile strength and abrasion resistance are lowered because of low reinforcing effect; in contrast, if the amount is too large, rebound resilience and exothermic property are undesirably poor.
Moreover, silica can be used as a reinforcing agent. As silica used in the present invention, silica conventionally used for general purpose rubbers can be used. As examples of silica, there can be mentioned, dry method white carbon, wet method white carbon, colloidal silica and precipitated silica disclosed in JP-A S62-62838. Of these, particularly preferred is wet method white carbon composed mainly of hydrated silica. There is no particular restriction as to the specific surface area of the silica, but is preferably in the range of 50 to 400 m2/g, more preferably 100 to 250 m2/g, and most preferably 120 to 190 m2/g, as measured by nitrogen adsorption according to the BET method. If the specific surface area of silica is too small, reinforcing effect becomes insufficient; in contrast, if the specific surface area is too large, processability is insufficient. The specific surface area measured by nitrogen adsorption is a value measured according to the BET method specified by ASTM D 3037-81. The amount of silica or other reinforcing agent used is preferably 10 to 150 parts by weight, more preferably 20 to 120 parts by weight, and most preferably 40 to 80 parts by weight per 100 parts by weight of the rubber component. If the amount is too small, reinforcing effect is reduced; in contrast, if the amount is too large, processability is undesirably lowered because of viscosity-increase of unvulcanized rubber composition.
These reinforcing agents can be used singly or in combination of two or more of them. When silica is used as a reinforcing agent, it is preferable to add a silane coupling agent to improve rebound resilience and abrasion resistance. There is no particular limitation as to the kind of silane coupling agent. Commercially available silane coupling agents can be used.
The extender oil is selected from those of paraffinic type, naphthenic type and aromatic type so as to meet the intended application of the rubber composition. The amount of the extender oil used is in the range of 1 to 150 parts by weight, more preferably 2 to 100 parts by weight, and most preferably 3 to 60 parts by weight per 100 parts by weight of the rubber component. If the content of the extender oil is too small, the reinforcing agent is not well dispersed; in contrast, if the content is too large, tensile strength and abrasion resistance are undesirably lowered.
As the vulcanizing agent, there can be used sulfur vulcanizing agents such as sulfur and sulfur donating compound, and peroxides vulcanizing agents. The amount of the vulcanizing agent used is preferably in the range of 0.05 to 5 parts by weight per 100 parts by weight of the rubber component. When sulfur is used as a vulcanizing agent, the amount thereof is preferably 1 to 3 parts by weight per 100 parts by weight of the rubber component.
The rubber composition of the present invention can comprise, besides the above-mentioned components, other ingredients according to applications of the present invention. Other ingredients include a vulcanizing aid such as stearic acid or zinc white, a vulcanization accelerator such as sulfenamide type, thiuram type or guanidine type vulcanization accelerator, a filler such as calcium carbonate or talc, an antioxidant of amine type or phenol type, an antiozonant, a processing aid, an adherence-imparting agent, and a wax.
The rubber composition of the present invention can be produced by mixing the above-mentioned ingredients using a known kneader for rubber, for example, a roll or a Banbury mixer.
Most important application of the rubber composition of the present invention is tires. The rubber composition is molded to tires by the same procedure with that of for other diene rubbers. It is preferable to compose the whole parts of a tire by the rubber composition of the present invention; however, while a tread part is composed by the rubber composition of the present invention, other parts of a tire such as a carcass, a side-wall and a bead may be composed of other type rubbers. As the other type rubbers, it is preferable to select among polymer rubbers exemplified as the other diene rubber used for preparing the rubber composition of the present invention together with the high-cis conjugated diene polymer rubber.

Conjugated diene rubber composition for tire use and tire


A resistance dividing circuit including silicide layers respectively formed only on branch portions of a linear polysilicon resistance wiring having the branch portions. Contact plugs are connected to the resistance wiring via the silicide layers, and fetching electrodes are respectively connected to the contact plugs.

The present invention relates to a resistance dividing circuit employed in a semiconductor integrated circuit and a method for manufacturing the resistance dividing circuit, using a salicide process.
A resistance dividing circuit has such a shape as shown in FIG. 6 by way of example, illustrated in plan view. The resistance dividing circuit shown in FIG. 6 has a configuration wherein contact plugs are respectively connected to plural points of a resistance wiring composed of polysilicon, and metal wirings are respectively connected to the contact plugs. The metal wirings serve as connecting terminals of the resistance dividing circuit. Arbitrary resistances can be obtained by selecting the connecting terminals. The resistance dividing circuit having such a configuration has been described in a patent document 1 (see Japanese Patent Publication No. Hei 5(1993)-30072).
In the resistance dividing circuit disclosed in FIG. 6, however, the contact plugs are directly connected to their corresponding polysilicon layer. Such a resistance dividing circuit as disclosed in FIG. 6 is normally configured such that its upper side is covered with an insulating layer. Thus, in order to form the contact plugs, there is a need to form contact holes in the insulating layer lying on the polysilicon layer. Upon opening the contact holes, it is hard to provide a suitable etching selection ratio between the insulating layer and the polysilicon layer because the insulating layer is normally SiO2. Therefore, there is a high fear that etching will extend to the polysilicon layer upon opening of the contact holes. In doing so, the resistance of a portion where each of the contact plugs and the polysilicon layer contact varies.
In order to solve such a problem, the polysilicon layer and each contact plug may be connected with a silicide layer interposed therebetween. Since, however, the silicide layer is a material low in resistivity, the values of resistances of portions where the silicide layers are formed, decrease when the silicide layers are formed on the polysilicon layer corresponding to the resistance wiring. Even if the decreases in resistance value are slight, they are piled or built up since the contact plugs are arranged in series on the resistance wiring. Thus, the decreases in resistance value of the circuit as a whole cannot be ignored.

Resistance dividing circuit and manufacturing method thereof


A novel relationship between pancreatico-biliary secretion and autistic syndrome is disclosed. This relationship enables a novel therapy for the treatment of the symptoms of autistic syndromes, comprising the administration of a therapeutically effective, preferably intravenous, dose of secretin to an individual with autistic syndrome. The relationship further enables a differential diagnosis for autistic syndrome, comprising an analysis of an individual's blood and/or intestinal tissue for the presence of secretin and comparison of the level of secretin to known norms.

Autistic syndrome (or autism) is a pervasive developmental behavioral disorder of very early onset that is characterized by a fundamental lack of normal interest in other people. (Original description, Kanner L. Autistic disturbances of affective contact. Nervous Child 1943;2:217–250.) The recent diagnostic criteria (DSM IV) for autistic disorder are shown in Table 3 below from the American Psychiatric Association1.
Epidemiologic studies suggested a prevalence rate of autistic behavior of approximately 2 to 5 cases in 10,000, however, recent surveys including the entire spectrum of the disease indicate that rates of 15 per 10,000 are a more accurate disease prevalence2,3. Such figures indicate that this disorder affects four hundred thousand Americans, with significant social and public health costs.
Despite the substantial body of evidence implicating neurobiological factors in the pathogenesis, precise etiologic mechanisms of autism have yet to be identified. In the absence of a clear etiology, although both behavioral and medical interventions are available to improve learning and behavior, there is no evidence of a cure for autism, nor any efficient psychopharmacological treatments for the core symptoms.
Autism is a syndrome with multiple etiologies, as is made clear both by the evidence of neurobiological research and by the catalog of disorders that are present with autistic behaviors4. Based on clinical observations, there are subgroups and subtypes of subjects with significantly different patterns of strengths and deficits, different patterns of comorbidity, levels of severity, and different psychological/cognitive profiles. The response to therapeutic trials also showed a wide variety of outcomes, which may support the possibility that there are multiple etiologies for autism. Although we know that genetic, infectious, metabolic, immunologic, neurophysiological, and environmental causes may lead to similar patterns of altered development with autistic behavior, the recognition of these clear neuropathological disorders does not help us to understand the basic pathogenic mechanism of autism.
There is no clear biological marker of autism to allow early diagnosis or screening of this disease even though it is generally believed that early recognition and management is crucial in the prognosis. Under these circumstances, every clinical observation is important and may lead us to a better understanding of this disorder.
While the specific neuropathological mechanism that produces autism is unknown, it is thought to be the result of a dysfunction of particular groups of neurons in the central nervous system. The primary structures implicated in the autistic disorder are the cerebellum, cerebral cortex, and medial temporal structures. One study showed a significant loss of Purkinje cells, and to lesser extent, of granular cells in the cerebellar hemispheres of six autistic subjects5. Studies of two patients with autism showed that the hippocampal pyramidal neurons in the CA1 and CA4 fields displayed a decrease in dendritic branching6. Metabolic dysfunction of cortical areas was found through measurements by Single Photon Emission Computed Tomography (SPECT)7. In addition, involvement of the medial temporal lobe has been implicated by autopsy studies demonstrating increased cell density, and small cell size in the hippocampus, amygdala, enthorhinal cortex and septal nuclei8. An additional argument for the temporal lobe involvement is the case report describing a child with a left lateral oligodendroglioma, who fulfilled the criteria of autistic behavior9. This case supports the hypothesis that damage to mesial-temporal structures at an early developmental period may lead to the autistic syndrome. Experimental evidence also supports this argument. A two-stage removal of the amygdalo-hippocampal complex in newborn monkeys resulted in behavioral changes (abnormalities of social interactions, absence of facial and body expressions and stereotypical behavior), resembling autism in children10. It is important to note that subgroups of autistic children displayed distinct patterns of brain activity in the frontal and temporal regions. Differences were more prominent in the left than the right hemisphere11. Four adult patients with autism had regionally decreased blood flow in the right lateral temporal, and in the right, left, and midfrontal lobes compared with controls12.
The neurobiological etiology of autism is supported by the observation that epilepsy is a common concomitant of autism13, affecting approximately one-third of adults who had childhood autism which usually had began in infancy or adolescence. In addition, different subgroups of patients have exhibited a variety of biochemical/immunological abnormalities. For example, in 20–40% of patients, whole blood serotonin levels are elevated14, and platelet serotonin is altered. Other observations include changes in the levels of dopamine-beta-hydroxylase (DBH) in plasma15, elevations in the levels of beta-endorphin, norepinephrine, arginine-vasopressin, and abnormally low levels of adrenocorticotropic hormone in 70% of autistic children16, however, there are no supporting data for the autoimmune mechanism and the therapeutic trials with steroid treatment are disappointing so far.
Drug trials for autism have included tests of the effects of dopamine agonists, and antagonists to dopamine, serotonin and opiates, as well as beta blockers, ACTH analogs, and oxytocin18. Most of these treatments were associated with some beneficial effect in small groups of patients. The broad range of biochemical abnormalities that stimulated this wide diversity of pharmacotherapeutic trials is a clear indication that we are still far from the understanding the main pathological events in the brain resulting in autistic behavior.
Two recent hypotheses of autism are the opioid- and the immune theory. The opioid theory is based on the observation that the main features of autism are similar to features of opiate addiction. The autistic-like behavior elicited by opiate administration include: reduced socialization, affective lability, repetitive stereotyped behavior, episodes of increased motor activity, diminished crying, insensitivity to pain, and poor clinging. Motivated by this similarity, clinical trials have been conducted by using an opioid antagonist, naltrexone, in autistic patients. In an open trial, 8 to 10 children were judged to show a positive response to naltrexone19. However, more recent double-blinded studies found that naltrexone treatment failed to produce significant changes in social behavior20.
Other researchers suppose that the opioids are derived from food sources. The enzymatic digest of casein and gluten contains peptides with opioid activity21. Fukudome and Yoshikawa isolated four opioid peptides from the digest of wheat gluten22. One of these peptides occurred in 15 different sites in the primary structure of glutenin, which is high molecular weight protein in wheat and considered as innocent protein in celiac disease. An additional indirect argument for the possible role of exogenous peptides was the presence of an abnormal urinary peptide pattern in patients with autism23. Although there is no scientific evidence that these exogenous peptides may enter the bloodstream, open clinical trials in Norway have been undertaken with the long-term elimination of gluten and casein from the diet of patients with autistic behavior and found only mild improvement24. As can be seen by prior research studies, while administration of opioids causes autistic behavior trials with specific and very restricted diets and opioid antagonists have not resulted in evident improvement in the behavior and health of autistic patients.
Certain immune-system abnormalities have been observed in connection with autism, such as cell-mediated immune response in human myelin basic protein17 and changes in the percentage of different subpopulations of lymphocytes25. The followers of immunopathogenesis theory are trying to use large doses of steroids. The administration of steroids resulted in some improvement in the behavior of few patients. However, to maintain this improvement, continuous administration of large doses of steroid were necessary, accompanied by all the side effect of chronic steroid administration. A tapering of the therapeutic dosage of steroid resulted in an immediate relapse.
A significant portion of patients with autistic behavior also suffer from mild gastrointestinal symptoms, such as abdominal distension, constipation, or chronic loose stools. Although these gastrointestinal problems are well known, they are not considered as important clinical features of the autistic syndromes, nor have they been treated except symptomatically. Autistic children with chronic diarrhea are not referred routinely to a pediatric gastroenterologist. In a recent study, 43% of patients had altered intestinal permeability26, which is a strong argument for an intestinal dysfunction in a significant portion of autistic patients.
Secretin is a 27-amino acid peptide hormone produced by the S-dells of the small intestine that are spatially distributed from the upper crypt to the villus tip, being particularly numerous in the upper two-thirds of the villi27. The release of secretin is increased by the products of protein digestion, acid bathing, fat, sodium-oleate, bile and herbal extracts28 (see FIG. 1A). Secretin increases the secretion of bicarbonate in the pancreas and biliary tract, resulting in secretion of a watery, alkaline pancreatic fluid (see FIG. 1B). The effect of secretin on the pancreas and bile duct is mediated primarily by secretin-induced elevation of cyclic AMP29, and does not involve the inositol phosphates signal transduction pathway (see FIG. 1C).
Secretin regulates the growth and development (enzyme composition) of the stomach, small intestine, and pancreas30, and stimulates pancreatic fluid secretion, and bile secretion31. In addition, secretin has secretory, motility and circulatory effects in the gastrointestinal tract. Secretin stimulates immunoglobulin excretion through bile32. Secretin increases superior mesenteric blood flow, and its distribution within the mucosa and submucosa33, as well as lymph flow34 (see Table 1).
Thus far, the clinical uses of secretin are based on its secretory and vascular effects. The two most important diagnostic applications are the examination of pancreatic function, and the diagnosis of gastrinoma. There is no accepted therapeutic use. A trial to use secretin in intrahepatic cholestasis in small numbers of patients initially was encouraging35, however, a double-blind placebo-controlled multicentric trial found no statistically significant differences in the reduction of serum bilirubin levels between secretin and placebo groups36.
The structure of porcine secretin has been known for some time and it has been isolated from porcine intestine, and has been found to be constituted by a peptide composed of 27 amino acid residues37. Moreover, it has been found that bovine and porcine secretins are identical but that they are markedly different from chicken secretin38. Although bovine and porcine secretins behave identically with human secretin in some respects they are not structurally identical (4,806,336 Carlquist et al. February 1989). U.S. Pat. No. 4,806,336 (Carlquist et al.) discloses the chemical composition of human secretin, a method for administering secretin for diagnostic use in determining pancreatic or gallbladder function, and a method for stimulating pancreatic secretion in man.
There is no published information suggesting a direct relationship between autism and secretin. However, it has been proposed that secretin and receptors of secretin are present in the brain areas that are thought to be involved in autism. Although exactly how secretin works in the brain is not yet fully understood, it seems likely that secretin regulates neurotransmitters and influences the function of a variety of cells, especially in the "hippocampal" and "amygdaloid" brain areas, where seem to be impaired in autism. (See Table 2.)
Our observations described in detail herein suggest that secretin is effective in the treatment of both gastrointestinal and behavioral/developmental problems in some children with autism. We observed that a group of young autistic children with chronic diarrhea, while they were undergoing tests involving an injection of secretin, had an extraordinary increase in the production of fluid from their pancreas. During the follow-up clinical visits these same children showed impressive progress in their social, behavioral and language skills, which appears so far to be permanent. We also found that the children who showed these responses to injected secretin produced only small amounts of their own secretin, and when given a dose of secretin by injection, they were able to produce an elevation in the blood level of another hormone, serotonin, which has effects on the brain.
These observations demonstrate the close relationship between secretin and serotonin in a group of autistic children. Our findings suggest that there are two subgroups of autistic patients, distinguished on the basis of gastrointestinal symptoms, their own blood secretin levels, the increase in serotonin level after secretin injection and the quantity and quality of fluid produced for secretin stimulation. In addition, we found high prevalence of other gastrointestinal abnormalities (inflammation in the esophagus, digestive enzyme deficiencies) in children with autistic behavior which adds further support to a relationship between the presence of gastrointestinal dysfunctions and autism.
Thus, we have discovered that the gastrointestinal/brain hormone secretin has a beneficial therapeutic effect on the gastrointestinal and brain function in certain autistic children. Our findings are the first clear evidence for an association between brain and gastrointestinal dysfunctions in autistic children.
With no prior findings of secretin having the capability to influence human behavior, there has been no research into the effect of secretin on autistic disorder. This invention is based on the unique and dramatic clinical observations of the effect of secretin administered for the diagnostic evaluation of gastrointestinal function in children with autistic behavior. These observations included:                (1) significant improvement in the social communication (language) and behavioral skills; and        (2) hypersecretion of pancreato-biliary fluid in children with autism and chronic loose stools. These observations described here open an entirely new direction in the autism research and may help to understand the pathogenesis of this disease. In addition, it may lead to a better understanding of the role of gut peptide hormones in the brain function. The existence of the gut-brain axis has been hypothesized, however, there was no clear clinical entity associated with this axis until now. This observation is the first clear evidence for an association between gastrointestinal and brain dysfunctions.

Method for assisting in differential diagnosis and treatment of autistic syndromes


A lid member is mounted to the fuel tank to cover an opening of the fuel tank. A fuel pump is arranged in the fuel tank to pump fuel in the fuel tank. A module case supports the fuel pump. A pump module includes fuel component protruding from a lateral side of the module case in a projection, which is viewed from a side of the lid member. A supporting member is connected with the lid member and the module case to support the pump module in the fuel tank. The lid member supports the pump module via the supporting member. The module case includes a connecting portion that connects with the supporting member. The connecting portion protrudes from the module case to the lateral side of the module case. The connecting portion is arranged in an imaginary circle that passes through outer peripheries of the module case and the fuel component in the projection. The imaginary circle accommodates the module case and the fuel component in the projection.

An in-tank type fuel feed apparatus disclosed in U.S. Pat. No. 5,900,148, U.S. Pat. No. 5,785,032, U.S. Pat. No. 5,782,223, U.S. Pat. No. 5,778,926, and U.S. Pat. No. 5,649,514 (WO9623967A1) is accommodated in a fuel tank to supply fuel in the fuel tank to the outside of the fuel tank. In this structure, a lid of a filter housing of a fuel filter is mounted to the fuel tank, so that the lid covers an opening formed in the fuel tank. The filter housing supports the fuel pump. The filter housing has an inlet pipe that directly connects to a discharge pipe of a fuel pump.
As shown in FIG. 4, a fuel feed apparatus 200 has a conventional structure, in which a discharge port 203 of a fuel pump 202 is connected with a suction port 206 of a filter housing 205 of a fuel filter 204 through a connecting member 208. The fuel pump 202 is supported by the filter housing 205 in the fuel feed apparatus 200, similarly to the structure disclosed in U.S. Pat. No. 5,900,148, U.S. Pat. No. 5,785,032, U.S. Pat. No. 5,782,223, U.S. Pat. No. 5,778,926, and U.S. Pat. No. 5,649,514. A lid 210 covers an opening formed in the fuel tank (not shown). The lid 210 is connected with the filter housing 205 by welding or the like.
However, in the fuel feed apparatus disclosed in U.S. Pat. No. 5,900,148, U.S. Pat. No. 5,785,032, U.S. Pat. No. 5,782,223, U.S. Pat. No. 5,778,926, and U.S. Pat. No. 5,649,514, and in the fuel feed apparatus 200 shown in FIG. 4, a pump module, which includes the fuel pump and the fuel filter, is directly mounted to the fuel tank. Accordingly, when the pump module is used in various fuel tanks, which have depth different from each other, the height of the pump module needs to be changed corresponding to the fuel tanks. As a result, the structure of the filter housing needs to be changed for adapting to the fuel tanks. Specifically, in the fuel feed apparatus shown in FIG. 4, the connecting member 208 needs to be changed corresponding to the fuel tanks. Thus, in this structure, a component constructing the pump module needs to be changed in accordance with the depth of the fuel tank. As a result, commonality of components is not sufficient in this structure.
A fuel feed apparatus may include a supporting member that connects a lid member, which is mounted to a fuel tank to cover an opening formed in the fuel tank, with a module case of a pump module, so that the lid member supports the pump module via the supporting member. In this structure, the distance between the lid member and the pump module can be easily changed by adjusting the length of the supporting member.
In this structure, the fuel feed apparatus can be installed in fuel tanks, which have the depth different from each other, without changing the structure of the pump module, so that the pump module can be commonly used in various fuel tanks. The supporting member is connected with the module case. Specifically, a connecting portion is provided to laterally protrude from the sidewall of the module case, so that the module case is connected with the supporting member via the connecting portion.
However, in this structure, the pump module may be radially jumboized. As a result, it may be difficult to insert the pump module into the fuel tank through the opening formed in the fuel tank. The opening of the fuel tank may be widened, so that the pump module can be easily inserted into the fuel tank through the opening. However, when the diameter of the opening is increased, strength of the fuel tank may decrease, and the sealing area may increase.

Fuel feed apparatus having small sized structure


A battery-powered tool (10) generally comprises a motor (24) having a positive terminal (64) and a negative terminal (66) extending therefrom for continuous engagement to a rotatable actuator (26). Actuator (26) has a plurality of conductive arms (28) extending therefrom for contact with a battery assembly (20) such that the actuator (26) can be selectively rotated to engage the motor (24) in both high speed and low speed operations.

There has been an increased demand for lightweight miniature tools with simplified internal working parts. Tools such as draftsmen's erasers that have a rotating head attached to a hand-held handle have been used for several years. Unfortunately, these hand-held tools were encumbered by an electrical line which had to be plugged into an AC outlet.
A need arose for a hand-held tool that could use standard direct current battery cells for powering the motor. To meet this demand, manufacturers assembled miniature hand-held tools that served the immediate purpose. However, they require electrical connection or wiring within the tool that complicated assembly and created electrical losses. The electrical losses caused increased demand on the battery cells, and accordingly, resulted in a shortened life for the battery cells in these applications.
A need has therefore risen for an improved hand-held battery-powered tool which does not have the unwanted internal wiring complications as do other battery-powered hand-held tools.
One aspect of the present invention comprises a battery-powered hand-held motor tool for rotating a bit and which generally comprises a substantially cylindrical-shaped housing having a direct-current motor mounted therein. As with most conventional motors, the motor has a shaft at one end and first and second terminals at its other end. The first and second terminals correspond to the positive and negative poles of the motor. Connected to the shaft is a substantially cylindrical-shaped collet for selective engagement with a bit. The bit may be one of a number of items, such as a drill or a sander.
To power the motor, a battery assembly having a plurality of battery cells contained therein is slidably engaged into the housing and clipped to the housing of the tool. The battery cells are conveniently recharged by a battery charger which has an AC wall plug integrally connected thereto for engaging into a standard AC outlet.
A substantially disc-shaped actuator is rotatably held in the housing. The actuator is coaxially aligned with the motor and battery assembly. In operation, the actuator is positioned between the motor and the battery assembly. The motor is electrically attached to the actuator at one end. The actuator has a first set of arms, a second set of arms and a third set of arms extending therefrom for selective electrical engagement with the battery assembly contacts. Specifically, the first, second and third sets of arms are selectively connected to the battery assembly contacts by rotation of the actuator to a first position in order to couple the batteries in series and cause the motor to rotate the bit at high speed. Additionally, the first and second sets of arms are selectively connected to battery contacts by rotating the actuator to a second position to contact the battery assembly such that the batteries are coupled in a parallel condition with the motor to rotate the bit at a low speed.
The present invention presents several technical advantages over the convention battery-powered hand-held motor tools.
Since the battery assembly is one piece, it can be easily removed from the housing and the battery cells can be recharged with the battery charger. In addition, because of the orientation of the battery cells within the battery assembly and the ability to have the actuator rotate to selectively contact the battery assembly, internal wiring can be greatly reduced, and accordingly, the load on battery cells can be reduced.


Disclosed is a sliding-type portable terminal including a first housing; a second housing coupled to the first housing so as to slide while facing the first housing; and a sliding module for slidably coupling the first and second housings to each other. The sliding module includes a sliding guide mounted on the first housing, the sliding guide having at least one slit extending in a longitudinal direction; a sliding plate mounted on the second housing, the sliding plate being slidably coupled to the sliding guide and facing the sliding guide; and a hook extending from the sliding plate so as to slide in the slit, the hook extending into the first housing via the slit, an end of the hook being bent so as to face an inner surface of the sliding guide.

1. Field of the Invention
The present invention relates to a portable terminal, and more particularly to a sliding-type portable terminal having a pair of housings coupled to each other while being able to slide with request to each other.
2. Description of the Related Art
In general, portable terminals are basically used for mobile communication. However, recent portable terminals can provide not only conventional mobile communication, but also various types of services including multimedia services (e.g. playing music and moving picture files) and financial services (e.g. micro payment, mobile banking).
Portable terminals are classified into bar-type terminals, flip-type terminals, and folder-type terminals according to their appearance. In addition, sliding-type terminals have recently appeared and, together with folder-type terminals, occupy a dominant position in the portable terminal market.
Bar-type terminals have an input/output device (e.g. keypad, transmitter), a display device, and an output device (e.g. receiver), all of which are positioned on a single housing. Although the bar-type terminals have an advantage of simple construction, the fact that a distance must be secured between the transmitter and the receiver for voice communication adversely affects their compactness.
Flip-type terminals have a bar-type body and a flip cover rotatably mounted on the body. Although the flip-type terminals are advantageous in that their input device (e.g. keypad) is covered in a standby mode so as to avoid erroneous operations, the fact that a distance must be secured between their transmitter and receiver for voice communication adversely affects their compactness, as in the case of the bar-type terminals.
Folder-type terminals have a pair of housings coupled to each other so as to fold on and unfold from each other, as well as voice input and output devices positioned on different housings. Such construction easily secures a distance between the transmitter and receiver without degrading the compactness. Therefore, the folder-type terminals have been dominant in the portable terminal market for a long period of time.
Sliding-type terminals have a pair of housings coupled to each other so that they can slide relative to each other, as well as voice input and output devices positioned on different housings. Input device, e.g. the keypad, is adapted to be exposed/covered as the housings slide relative to each other. Therefore, erroneous operations are avoided in a standby mode, and a distance is easily secured between the voice input and output devices in a communication mode without degrading the compactness. For these reasons, the sliding-type terminals have overtaken the folder-type terminals in the market.
Particularly, sliding-type portable terminals have sliding members mounted on their main body and sub-body which are coupled to each other while being able to slide. However, conventional sliding-type portable terminals have a problem in that it is not easy to prevent the sub-body from playing with regard to the main body while maintaining smooth upward/downward sliding movements of the bodies. More specifically, if the play of the sub-body in the forward/rearward or leftward/rightward direction relative to the main body is reduced, the increased frictional force adversely affects the upward/downward sliding movements. If the frictional force is reduced for smooth sliding movements, play in the forward/rearward or leftward/rightward direction inevitably increases.