In a method of estimating a signal-to-interference ratio (SIR), a first average channel power per slot of a first channel that is under a fading environment is estimated. A second average channel power per slot of a second channel that is under a fading environment substantially the same as the first channel is estimated, wherein the first and second channels are multiplexed. A second signal power attenuation ratio of the second channel is calculated using the second average power per slot of the second channel. A third average power per slot of the first channel is calculated using the first average power per slot of the first channel and a reciprocal of the second signal power attenuation ratio of the second channel.

1. Field of the Invention
Example embodiments of present invention generally relate to a power control adapted for use in a direct sequence code division multiple access (DS-CDMA) system. More particularly, example embodiments of the present invention relates to a signal-to-interference ratio (SIR) estimation adapted for use in a closed-loop power control.
2. Description of the Related Art
In general, a direct sequence code division multiple access (DS-CDMA) wireless protocol specifies interfaces in wireless communication systems such as a code division multiple access (CDMA) system and a wide-band code division multiple access (W-CDMA) system. In these systems, an accurate power control may be necessary to effectively utilize frequency resources that are commonly shared by a mobile station and a base station according to spread-spectrum characteristics of the wireless communication system.
A system capability, possibly larger in a spread spectrum type system, may be increased when the power is optimally controlled, because the system capability of the CDMA system or the W-CDMA system may be highly correlated with an amount of interference signals received on the system, which may be determined by an intensity of a signal transmitted to/from each mobile device.
The W-CDMA standard is embodied in the 3rd Generation Partnership Project (3GPP) standard. For example, in the first or second generation system, a digital cellular or a personal communication system, data traffic on a reverse link may be substantially equal to data traffic on a forward link, because the first and second generation communication systems were designed to mainly carry speech and low bit-rate data.
However, the third generation communication systems such as W-CDMA are designed to carry not only speech but also packet data having a higher data rate. The third generation communication systems are also adapted to carry higher data-rate wireless Internet services.
One example characteristic of the wireless Internet service is that a forward link may provide a service of downloading a large capacity picture movie, voice data, picture data, and program data. The forward link may have more traffic than a reverse link. Therefore, the traffic on the two links may be asymmetric. In the W-CDMA system, capacity limitation of a mobile device may be more likely to be generated at the forward link rather than the reverse link.
To overcome the capacity limitation, a closed loop power control may be employed in the forward link of the W-CDMA system in the 3GPP standard to efficiently manage resources of the forward link.
The forward closed-loop power control, and those especially based on a signal-to-interference ratio (SIR), may adjust a transmit power of a base station on a forward link based on a received power estimate at a mobile device such that the SIR of each respective mobile device may be constantly maintained. In other words, the transmit power of the base station may be adjusted according to the state of the mobile device, for example by taking into account a near-far effect. Therefore, when the mobile device is not operated (e.g., the mobile device is not connected) but relatively close to a base station or has a relatively low levels of multi-path fading, shadowing, interference from other base stations, etc., transmit power may be reduced. On the other hand, when the mobile device is relatively farther away from the base station, which may create higher bit error rate or a signal reception by the mobile device is poor, the transmit power is increased.
In the closed-loop power control based on the SIR estimation, a reference SIR is compared with an SIR estimate per a predetermined power control period (e.g., 1/1500 sec, in the 3GPP). Therefore, the accuracy of the SIR estimation may greatly affect the stability and accuracy of the transmit power control.
A conventional SIR estimation method in accordance with an NTT DoCoMo wireless protocol is described in "SIR-Based Transmit Power Control of Reverse Link for Coherent DS-CDMA Mobile Radio," IEICE Transactions on Communications, July 1998. According to the above disclosed SIR estimation method, after a tentative decision based on a channel estimation using a pilot symbol, the SIR is estimated using an average power per slot and a mean squared error of a dedicated physical channel (DPCH). The tentative decision herein is made such that a hard decision is made for a phase of a channel compensated received signal to return a phase of a non-channel compensated signal. The tentative decision is used for signal power estimation per slot, using not only a pilot symbol of which a phase is known, but also a random data symbol.
A transmitting signal including the DPCH signal and a common physical channel (CPICH) signal that are coded and multiplexed to be transmitted in parallel may be represented by equation 1, and a received signal passing through a fading channel and Additive White Gaussian Noise (AWGN) may be represented by the following equation 2:
                              S                                (            t            )                          =                              ∑                          i              =                              -                ∞                                      ∞                                          [                          {                                                                    E                                          c                      ,                      cp                                                                      ·                                  G                  p                                ·                                  (                                                                                C                        I                                                                                (                        t                        )                                                              +                                          j                                                                                C                            Q                                                                                (                            t                            )                                                                          ·                                                  (                                                                                W                                                              CP                                                                                                                  i                                                                                                                  N1                                                            I                                                        +                                                          W                                                              CP                                                                                                                  i                                                                                                                  N1                                                            Q                                                                                )                                                                                +                                                                                E                                                      c                            ,                            dp                                                                                ·                                              G                        p                                            ·                                              (                                                                                D                              I                                                                                (                              t                              )                                                                                +                                                      j                                                                                D                                  Q                                                                                (                                  t                                  )                                                                                ·                                                              (                                                                                W                                                                          DP                                                                                                                        i                                                                                                                        N2                                                                        I                                                                    +                                                                      W                                                                          DP                                                                                                                        i                                                                                                                        N2                                                                        Q                                                                                )                                                                                }                                            ·                                              (                                                                              S                                                                                                                i                                                                                                                M                                                        I                                                    +                                                      S                                                                                                                i                                                                                                                M                                                        Q                                                                          )                                                                                [                  Equation                                                              1                ]                                                      r            ~                                          (            t            )                          =                              ∑                          i              =                              -                ∞                                      ∞                                          [                                          a                                                  (                  t                  )                                            ·                                                                 [                                                                                {                                                                                E                                                              c                                ,                                cp                                                                                ·                                                      G                            p                                                    ·                                                      (                                                                                C                                  I                                                                                (                                  t                                  )                                                                                +                                                              j                                                                                C                                      Q                                                                                (                                      t                                      )                                                                                ·                                                                      (                                                                                W                                                                                CP                                                                                                                            i                                                                                                                            N1                                                                                I                                                                            +                                                                              W                                                                                CP                                                                                                                            i                                                                                                                            N1                                                                                Q                                                                                )                                                                                +                                                                                E                                                                          c                                      ,                                      dp                                                                                ·                                                                  G                                  p                                                                ·                                                                  (                                                                                D                                        I                                                                                (                                        t                                        )                                                                                +                                                                          j                                                                                D                                          Q                                                                                (                                          t                                          )                                                                                )                                                                ·                                                                  (                                                                                W                                                                              DP                                                                                                                          i                                                                                                                          N2                                                                            I                                                                        +                                                                          W                                                                              DP                                                                                                                          i                                                                                                                          N2                                                                            Q                                                                                )                                                                                }                                                    ·                                                      (                                                                                S                                                                                                                    i                                                                                                                    M                                                                I                                                            +                                                              S                                                                                                                    i                                                                                                                    M                                                                Q                                                                                )                                                                          ]                                            ·                                              ⅇ                                                  jθ                                                                                (                            t                            )                                                                                +                                                                  n                        ^                                                                                                        i                                                                                                      ]                                                                                [                  Equation                                                              2                ]            Herein,    Ec,cp, Ec,dp: average chip energy of the CPICH and the DPCH    N1, N2: spreading factor (SF) of the CPICH and the DPCH    M: length of a scrambling code    Gp: channel gain of the CPICH    WICP|i|N1+WQCP|i|N1, WIDP|i|N2+WQDP|i|N2: orthogonal variable spreading factor (OVSF) of the CPICH and DPCH    SI|i|M+SQ|i|M: scrambling code    {circumflex over (n)}|i|: AWGN    α(t), θ(t): amplitude and phase of the received signal due to the fading
After performing descrambling and dispreading processes, respective signals of the DPCH and CPICH that are on a chip basis are converted to signals ZDPCH and ZCPICH that are on a symbol basis, which are represented by equations 3 and 4:
                              Z          DPCH                =                                            1                              N                2                                                                                ∑                                  k                  =                  0                                                                      N                    2                                    -                  1                                                                                [                                                      a                                                              (                      k                      )                                                        ·                                      [                                                                                E                                                      c                            ,                            cp                                                                                ·                                              (                                                                                D                              I                                                                                (                              k                              )                                                                                +                                                      j                                                                                D                                Q                                                                                (                                k                                )                                                                                )                                                              ]                                    ·                                      ⅇ                                          jθ                                                                    (                        k                        )                                                                                ]                                              +                                    1                              N                2                                                                                ∑                                  k                  =                  0                                                                      N                    2                                    -                  1                                                                                W                                  dp                                                                            k                                                                                                    [                  Equation                                                              3                ]                                          Z          CPICH                =                                            1                              N                1                                                                                ∑                                  k                  =                  0                                                                      N                    1                                    -                  1                                                                                [                                                      a                                                              (                      k                      )                                                        ·                                      [                                                                                E                                                      c                            ,                            cp                                                                                ·                                              (                                                                                C                              I                                                                                (                              k                              )                                                                                +                                                      j                                                                                C                                Q                                                                                (                                k                                )                                                                                )                                                              ]                                    ·                                      ⅇ                                          jθ                                                                    (                        k                        )                                                                                ]                                              +                                    1                              N                1                                                                                ∑                                  k                  =                  0                                                                      N                    1                                    -                  1                                                                                W                                  cp                                                                            k                                                                                                    [                  Equation                                                              4                ]            Herein,WDP|i|=(nI|i|+nQ|i|)·(SI|i|M+SQ|i|M)*·(WIDP|i|N2+WQDP|i|N2)*WCP|i|=(nI|i|+nQ|i|)·(SI|i|M+SQ|i|M)*·(WIDP|i|N1+WQDP|i|N1)*
After a tentative decision is made for the DPCH symbol, the DPCH symbol is rewritten as equation 5 and the signal power at the time of the SIR estimation is represented as the average power of the DPCH symbol per slot, for which the tentative decision is made as in equation 6:
                                          Z            )                    DPCH                =                                                            E                                  c                  ,                  dp                                                      ·                          1                              N                2                                              +                      j                                      [                                                                                E                                              c                        ,                        dp                                                                              ·                                      1                                          N                      2                                                                                ∑                                          k                      =                      0                                                                                N                        2                                            -                      1                                                                                [                                                                                a                                                                                (                            k                            )                                                                          ·                        sin                                                                                θ                                                                          (                          k                          )                                                                                ]                                                              ]                                +                                    1                                                N                  2                                                                                ∑                                  k                  =                  0                                                                      N                    2                                    -                  1                                                                                Z                                                    k                                                  I                                              +                      Z                                        k                                      Q                                              [                  Equation                                                              5                ]                                                      E                                      [                                                Z                  )                                DPCH                            ]                                slot          2                =                                            E                              c                ,                dp                                      ·                          [                                                                    (                                                                  1                                                  S                          2                                                                                1                                                  N                          2                                                                                ∑                                                      s                            =                            0                                                                                S                              2                                                        -                            1                                                                                ∑                                                          k                              =                              0                                                                                N                                2                                                            -                              1                                                                                [                                                                                a                                                                                (                                                                          s                                      ,                                      k                                                                        )                                                                                ·                                cos                                                                                θ                                                                                (                                                                      s                                    ,                                    k                                                                    )                                                                                ]                                                                                )                                    2                                +                                                      (                                                                  1                                                  S                          2                                                                                1                                                  N                          2                                                                                ∑                                                      s                            =                            0                                                                                S                              2                                                        -                            1                                                                                ∑                                                          k                              =                              0                                                                                N                                2                                                            -                              1                                                                                [                                                          a                                                                                (                                                                      s                                    ,                                    k                                                                    )                                                                ·                                cos                                                                                θ                                                                                (                                                                      s                                    ,                                    k                                                                    )                                                                                ]                                                                                )                                    2                                            ]                                =                                    E                              c                ,                dp                                      ·                          K              DPCH                                                          [                  Equation                                                              6                ]            Herein,Z |k|=ZI|k|+ZQ|k|=w|k|·(DI(K)+jDQ(K))*    S2: a number of DPCH symbols per slot    average AWGN per slot:
            1              S        2                        1              N        2                                ∑                  s          =          0                                      S            2                    -          1                                                                      ∑                      k            =            0                                              N              2                        -            1                                            (                                    Z                                                                s                  ,                  k                                                            I                        +                          j                                                                                Z                                                                        s                    ,                    k                                                                    Q                                              )                      ≅  0
It can be determined from equation 6 that the signal power is affected by the fading with a signal power attenuation ratio KDPCH. The signal power affected by the fading with the signal power attenuation ratio KDPCH can be experimentally identified.
FIG. 1 is a graph illustrating a power attenuation of a signal on a dedicated physical channel (DPCH) that undergoes fading.
Referring to FIG. 1, as the fading becomes faster, the power attenuation of a signal becomes greater. Compared with an ideal case where there is no fading (101), the signal power attenuation is generated when a mobile device is moving at a speed of about 120 km/h (103) and when a mobile device is moving at a speed of about 250 km/h (105).
When energy per symbol to interference power density ratio (Es/No) is low, the AWGN may not approach zero, which may generate an error between an actual signal power attenuation and a calculated value by the signal power attenuation ratio KDPCH. When the energy per symbol to interference power density ratio (Es/No) is relatively high, the AWGN may approach zero so that the signal power attenuation is nearly equal to the signal power attenuation ratio KDPCH.
Therefore, in the conventional SIR estimation method, the SIR estimation may not be sufficiently accurate due to the signal power attenuation of a received signal in the fading environment, especially in a fast fading environment. Accordingly, accurate power control depending on a state of a wireless mobile channel may be difficult.


An engine cover system for joining a cover with an intake manifold body. A plurality of structural ribs project from an external surface of the body including a pair of parallel ribs. Each parallel rib carries an integrally-molded U-shaped receiver strip extending transversely from the parallel ribs to form slots having closed ends proximate a first edge of the body and slot openings defined by respective edges of the receiver strips. The engine cover is comprised of a shroud, first and second radial arms, and first and second hinge pins projecting from the first and second radial arms, respectively. The hinge pins are configured to slide into the slots via the slot openings into the closed ends. First and second elastomeric ferrules are installed on the first and second hinge pins, respectively, configured to be compressed by the receiver strips when captured at the closed ends.

The present invention relates in general to decorative covers installed on internal combustion engines for automotive vehicles, and, more specifically, to the mounting of an engine cover to an air intake manifold.
The engine compartment of a vehicle presents various challenges for vehicle engineers and designers in providing functionality, serviceability, and aesthetics in a relatively small space. Consideration must also be given to manufacturing and assembly costs in addition to weight, which ultimately impacts fuel economy, to deliver a competitive product. An engine cover is typically used in order to enhance the overall appearance of the engine compartment and to reduce the propagation of engine noise. Injection molded polymers are commonly used to fabricate an engine cover.
The mounting of an engine cover to an engine typically is comprised of several steel brackets, fasteners, or other joining structures such as hooks or clamps. The use of several intermediate components which attach on one side to the engine cover and on the other side to an engine component (e.g., an air intake manifold or a cam cover) creates many potential sites for NVH (noise, vibration, and harshness) problems such as squeak and rattle. A relatively large part count leads to added part costs and an associated increase in manufacturing/assembly costs.
The air intake manifold which directs incoming air to the respective engine cylinders of a combustion engine has historically been fabricated from metal. More recently, various molded materials including thermoplastics, resins, and polymers have been used to manufacture intake manifolds. Preferred materials may include nylon or other polyamides which may further include filler materials such as glass fibers. A switch to plastic materials has achieved a reduction in weight, but reliance on brackets and fasteners with a high parts count have continued.
In co-pending U.S. application Ser. No. 14/525,578, filed Oct. 28, 2014, entitled "Integrally-Molded Intake Manifold Connector for Engine Cover of Combustion Engine," which is incorporated herein by reference in its entirety, a hinged connection is disclosed wherein hinge pins extending from radial arms of the engine cover each carry an elastomeric ferrule and wherein the hinge pins are received in slots formed by transverse strips carried by structural ribs of the manifold body. A potential disadvantage of such a structure relates to manufacturing and assembly of the ferrules (e.g., O-rings) onto the hinge pins. The proper placement of the ferrules is critical for proper NVH (noise, vibration, and harshness) performance. However, the disclosed arrangement may be difficult to reliably implement with automated manufacturing techniques.


Techniques for executing flashback queries using domain indexes in a database system are provided. In one technique, a flashback parameter of the flashback query is not included in a call-out invocation of domain index routines that implement a domain index. A call-back query execution unit nonetheless retrieves, for call-back queries issued by the domain index routines, call-back query results that reflect the state of a database in the database system as of the time specified in the flashback parameter. In another technique, a call-out invocation of domain index routines includes the flashback parameter of a flashback query. The domain index routines issue call-back queries that require the retrieval of data which reflects the state of a database as of the time specified in the flashback parameter, which are executed by the call-back query execution unit.

Domain Indexes
"Domain indexes" are indexes that are not natively supported by a database system. One technique for using domain indexes in a database system is described in Extensible Indexing, which is referenced above. Using the techniques described in Extensible Indexing, user-implemented routines for maintaining and using domain indexes are registered with a database system. Such routines are referred to herein as "domain index routines".
Once domain index routines have been registered with the database system, the database system is able to invoke the domain index routines as necessary to perform more efficient query processing. Specifically, in response to requests from a client, the database server interacts with the domain index routines to build, maintain, and employ instances of the newly defined and registered domain index type. The instances of an index type are known as index objects, and contain an index key and may contain, for each index key, an associated data segment managed by the index routines. In some implementations, the data segment may be data from a row in a table associated with the index key.
When a database system receives queries that reference a table on which a domain index has been created, an optimizer within the database system determines whether to make use of domain index to process the query. If the optimizer determines that a domain index is to be used in processing the query, then the database server can invoke the domain index routines for that index type. Queries that are processed using domain indexes are referred to herein as "domain index queries".
The invocation of a domain index routine is referred to herein as a call-out, since the domain index routine code is not built-in to the database server. According to an approach described in Extensible Indexing, the call-outs are invocations of routines that retrieve data using existing index objects. These routines include i_open, i_close, i_start, and i_fetch.
When invoked, the domain index routines perform actions dictated by the logic internal to the domain index routines. During the execution of this logic, the routines may issue one or more queries back to the database system. Queries that are issued by the domain index routines back to the database system are referred to herein as "call-back queries". In one approach, the call-back queries may be SQL queries.
Within the database system, a call-back query execution unit receives the call-back queries, executes the call-back queries, and returns data that satisfy the conditions of the call-back queries. The data returned by the call-back query execution unit is referred to herein as the "call-back response data". The call-back response data typically contains identifiers identifying records in the database. The identifiers may, for example, be row identifiers (rowids) that identify rows, within relational tables managed by the database system, that satisfy the selection criteria of the call-back queries.
A domain index routine that issues a call-back receives the call-back response data, performs some steps internally according to its internal logic, and returns information to the database server routine that invoked the domain index routine. The information returned by the domain index routine is referred to herein as "call-out response data". Typically, the call-out response data is largely based on the call-back response data. Similar to the call-back response data, the call-out response data often contains the rowids of rows, within the database, that satisfy certain criteria.
The database server receives the call-out response data, and uses the call-out response data to perform whatever additional processing is required by the query that was received by the database system. That additional processing may involve, for example, sorting rows or performing joins between rows from different tables.
Flashback Queries
Techniques have also been developed that allow users to submit queries that specify retrieval of data as of prior points in time. Those queries are referred to herein as flashback queries. One way to implement flashback queries is described in System and Method for Providing Fine-Grained Temporal Database Access, cited above.
Modifications to the SQL language allow the client to express the desired prior point in time in a flashback query, herein known as the flashback time. The SQL query language is modified to include "AS OF" to indicate that a query uses flashback. A System Change Number (SCN) or timestamp may be used to specify the flashback time. In the examples below, both queries look for rows that satisfy the predicate "WHERE eq(name, 'Fred')=1" as of the prior point in time stated in the query.

Flashback support for domain index queries


Plural arbiters arbitrate over a set of queues. The arbiters are constructed as a series of pipelined stages. Conflict detection logic detects conflicts among the arbiters in arbitrating across the queues, and, when a conflict is detected, the conflict detection logic alters processing related to conflicting queues in one arbiter when another arbiter has not passed a predetermined commit point in processing the queue.

A. Field of the Invention
The present invention relates generally to arbitration, and more particularly, to a high performance dequeuing arbitration scheme.
B. Description of Related Art
Routers receive data on a physical media, such as optical fiber, analyze the data to determine its destination, and output the data on a physical media in accordance with the destination. Routers were initially designed using a general purpose processor executing large software programs. As line rates and traffic volume increased, however, general purpose processors could not scale to meet these new demands. For example, as functionality was added to the software, such as accounting and policing functionality, these routers suffered performance degradation. In some instances, the routers failed to handle traffic at the required line rate when the new functionality was enabled.
To meet the new demands, purpose-built routers were designed. Purpose-built routers are designed and built with components optimized for routing. They not only handle higher line rates and higher network traffic volume, but they also add functionality without compromising line rate performance.
A purpose-built router may include a number of input and output ports from which it transmits and receives information packets. A switching fabric may be implemented in the router to carry the packets between ports.
In order to control their high packet throughput, purpose-built routers use buffers to temporarily queue packets waiting to be processed. Arbiters may control the dequeuing of packets from the buffers. Different arbiters may operate on the same buffer to control different aspects of the buffering and dequeuing process. For example, one arbiter may select packets from the queues for transmission while another arbiter may examine the queues for congestion and drop packets from congested queues.
When using multiple arbiters that arbitrate over the same set of queues, it is desirable to implement the arbiters in a manner that is as efficient as possible. Preferably, total bandwidth through the arbiters should be maximized while sharing common resources related to the buffers.

This patent is subject to a terminal disclaimer.


A pressure sensing apparatus including a thin disc of a metal having a ceramic material layer and piezoresistive elements formed thereon. A surface of the disc is bonded to a diaphragm assembly on a pressure port base constructed of a low cost metal. The bonding process is performed at low temperatures, (<700° C.), so that the diaphragm assembly and pressure port do not require high temperature corrosion resistance, and can thus be formed of less expensive materials. The inventive apparatus provides a lower cost alternative to conventional high pressure sensors since less material is used, less expensive materials are used, and fabrication is less complex. The inventive apparatus is also more reliable and exhibits greater thermal stability than conventional high pressure sensors.

1. Field of the Invention
The invention relates to pressure sensors. In particular, it relates to high pressure sensors having increased reliability, thermal stability and adhesion properties, while being inexpensive to fabricate.
2. Description of the Related Art
For years, those skilled in the art have made continuous efforts to develop pressure sensors that are low in cost and capable of being mass produced, while exhibiting high reliability, sensitivity and linearity. Certain-conventionally known pressure sensors have been known to include semiconductor materials with a micromachined sensing diaphragm. In the processing of such structures, a thin diaphragm is often formed in a silicon wafer through chemical etching. Ion implantation and diffusion techniques are then used to drive doping elements into the diaphragm, forming piezoresistive elements whose electrical conductivity changes with strain, such that deflection or deformation of the diaphragm causes a change in resistance value of the piezoresistive element. These changes correspond to the magnitude of pressure applied to the diaphragm. However, silicon is susceptible to chemical attack and erosion, particularly in environments such as where a high-pressure medium is to be sensed, such as automotive applications that involve sensing pressures of brake fluid, oil, coolant, transmission fluid, hydraulic fluid, fuel, or steering fluid, at pressures of two atmospheres or more. For such applications, a pressure sensor must be physically resilient, and resistant to the hostile environment of a sensed medium.
Presently used methods for producing media-compatible sensors include enclosing a silicon sensing chip in an inert fluid, such as a silicone oil or gel, and then further separating the sensing chip from a medium to be sensed with a metal diaphragm, such that pressure must be transmitted through the metal diaphragm and the fluid to the sensing chip. Unfortunately, the manufacturing processes for these sensors are expensive and complex. As a result, these sensors are unsuitable for mass production.
Another known process involves the formation of a capacitor plate on a ceramic diaphragm, which is then bonded to a base with a second capacitor plate. The use of a chemically-resistant and mechanically-tough ceramic materials, such as aluminum oxide or zirconium oxide, allow the diaphragm to directly contact the medium whose pressure is to be measured. As the ceramic diaphragm deforms or deflects under the influence of pressure, the space between the capacitor plates changes, thereby causing a change in capacitance that corresponds to the applied pressure. However, the circuits required to detect such capacitance changes are often complex and subject to noise corruption. Furthermore, attaining an adequate seal between the ceramic diaphragm and the base for high pressure applications is often difficult.
Yet another known approach involves the use of a chemically resistant ceramic diaphragm having thick-film piezoresistors screen-printed thereon. As with ceramic capacitive pressure sensors, the ceramic material allows direct contact with the medium whose pressure is to be sensed, eliminating the need for protective packaging. However, while the signal detection circuitry may be less complicated, it is difficult to reliably seal the ceramic diaphragm with a base.
Further, it is known in the art to employ a metal diaphragm as the sensing element. Because metal diaphragms generally deform more for a given thickness and pressure than ceramic diaphragms, which exhibit lower elongations before breaking and are therefore designed to deform less under pressure, sensing is performed by thin-film polysilicon resistors. The metal diaphragm is first coated with a thin-film layer of typically silicon dioxide or silicon nitride to electrically insulate the diaphragm from thin-film resistors and their conductors. A thin-film polysilicon layer is then deposited on the insulating layer by chemical vapor deposition (CVD), and then etched through a mask formed by spinning a liquid photoresistive material onto the polysilicon layer. The photoresistive material is exposed and developed to obtain the pattern required for the resistors, and thin-film conductors are then formed by evaporation. However, the equipment necessary to deposit the insulating and polysilicon layers is expensive, and deposition rates are extremely slow. Deposition of the thin-film layers requires multiple patterning, exposure, developing and stripping steps for the required thin-film spun-on photoresists and metallization, and must be carried out in a controlled environment to avoid surface defects. In addition, such processes typically deposit thin-films no thicker than about 10,000 angstroms, requiring the surface of the metal diaphragm to be extremely smooth to avoid defects.
Metal diaphragm sensors have also been produced with thick-film metal oxide resistors. A thick-film oxide layer is formed by printing and firing a thick-film ink, after which a thick-film metal oxide layer is printed and fired on the insulating layer to form resistors. Thick-film conductors are typically employed with this type of sensor. However, since thick film materials fire at very high temperatures, for example in the range of 800° C. to 1000° C. and above, the diaphragm must then be formed of a metal having excellent high temperature corrosion resistance. While several high temperature resistant specialty metals are known in the art, they are very expensive and difficult to machine. Another option is to attach a small metal diaphragm "button" of specialty metal to a pressure port base made of a cheaper material. However, these structures are often unreliable at higher pressures.
Clearly, a need for further improvement exists in the art of pressure sensors, particularly in the formation of pressure sensors which are lower in cost to produce, while still being reliable at high pressures. The present invention provides a solution to this problem. The invention provides a pressure sensing apparatus which includes a thin disc of a specialty metal or ceramic, having a ceramic material layer and piezoresistive elements formed thereon. This structure is bonded to a diaphragm assembly on a pressure port base constructed of a low cost metal. The bonding process is performed at low temperatures, (<700° C.), so that the diaphragm assembly and pressure port do not require high temperature corrosion resistance, and can thus be formed of less expensive materials.
The inventive pressure sensing apparatus provides a lower cost alternative to conventional high pressure sensors since less material is used, less expensive materials are used, and fabrication is less complex. The inventive apparatus is also more reliable and exhibits greater thermal stability than conventional high pressure sensors.


A recording and reproducing apparatus includes an RLL encoder that encodes an information bit string to a code bit string and a RLL decoder that decodes the code bit string to the information bit string. The RLL encoder encodes the information bit string to the code bit string of a run-length-limited code at a high encoding rate satisfying a plurality of conditions of constraint regarding a string of successive zeros. The RLL decoder decodes the code bit string encoded by the RLL encoder to the information bit string.

1) Field of the Invention
The present invention relates to a technology for recording and reproducing apparatuses, and more particularly, to a recording and reproducing apparatus that can be used for run-length-limited code at a high encoding rate satisfying a plurality of conditions of constraint regarding a string of successive zeros.
2) Description of the Related Art
Conventionally, a recording and reproducing apparatus having an encoder for encoding an information bit string to an encoded bit string and a decoder for decoding the encoded bit string to an information bit string has been widely used as a recording and reproducing apparatus for magnetic disks, optical disks, magneto-optical disks, etc. In such a recording and reproducing apparatus, for data recording, error correcting code (ECC) encoding is first performed and then run-length-limited (RLL) encoding is performed. For data reproduction, RLL decoding is first performed and then ECC decoding is performed. With such a configuration, errors tend to be propagated at the time of RLL decoding, and will exceed the limitation of error correction in ECC decoding. For example, Japanese Patent Laid-Open Publication No. 2003-68024 discloses a recording and reproducing apparatus of a conventional technology, in which, for data recording, ECC encoding is first performed and then RLL encoding is performed and, for data reproduction, RLL decoding is first performed and then ECC decoding is performed.
In a permutation scheme, the order of RLL encoding and ECC encoding and the order of RLL decoding and ECC decoding are each reversed. That is, error correction is performed with ECC decoding, and then RLL decoding is performed. Therefore, RLL code at a high encoding rate can be applied, thereby improving a signal-to-noise ratio. Also, in the permutation scheme, since RLL code at a high encoding rate is used, a replacement scheme with a small amount of calculation and a small circuit size is expected to be applied. A conventional technology regarding such a replacement scheme is disclosed in, for example, A. J. van Wijingaarden and K. A. Schouhamer Immink, "Construction of Constrained Codes employing Sequence Replacement Techniques", Proc. IEEE ISIT97, Ulm, Germany, pp. 144, Jun. 29, 1997.
However, in the conventional replacement scheme, although a G condition of constraint that limits a maximum number of bits of successive zeros (hereinafter, "0-run") is satisfied, an I condition of constraint that limits a maximum number of bits of 0-run for every two bits is not satisfied. Also, a process between code bit strings has such a problem as that the I condition of constraint is not satisfied, although the G condition of constraint is satisfied.


A pressure-tight stem cylinder seal and a self-energizing stem shoulder seal matching the stem cylinder seal that both use an equilaterally triangular soft ring as their sealing element, wherein their designing rules are first, by means of wedging function of a hard gland coaxial with the stem cylinder, to convert their original axial tightening force 2f respectively into a radial compression force 4f/√3 of their soft ring 04 on the stem 02 cylinder and another radial compression force 2f of their soft ring 06 on the stem 02 shoulder and ensure that the two soft rings are so compressed from a great room to a small room as to be able to pass a pressure or stress exactly to each different direction, then to cut off their off-stem corners to give their cavities an opening or give each soft ring an axial compressing allowance, and last, by means of anti-extrusion metallic C-rings without axial resistance, to close each opening to provide a full support for the sealing deformation of their soft rings compressed in their cavities.

Fluid power transmitting systems need a piston rod for passing out fluid power in the cylinder barrel (rod housing), and fluid medium conveying systems need an operating stem for controlling the flow of fluids through the valve body (stem housing). This moving rod or stem needs a seal between it and its housing. A seal whose tightness is caused by an installed stress is called a pressure-tight seal, and a seal whose tightness is caused by a fluid pressure is called a self-energizing seal. The material as an indispensable pressure-tight cylinder-sealing ring between that moving rod or stem and its housing shall at least be soft and wear-resistant, and have a cross-sectional shape beneficial to the converting of its original axial tightening force into its radial sealing force, or any pressure-tight soft ring seal for moving rod or shaft cylinders shall at least have an ability to effectively orthogonally transmit an installed stress. However, it is well known that objects that can effectively orthogonally transmit a stress can only be either a rigid body with wedging function or a closed liquid without extrusion gap.
From the material's sealing mechanism proposed by the inventor (see ZL201210070823.2), it can be seen that:                the ability for a liquid to transmit a pressure in time equally in each direction originates from its softness and its volume incompressibility—its softness can cause it to have a deforming and flowing power on being compressed, and its volume incompressibility can cause it to have an identical deforming and flowing power in each direction;        it can be seen from bulk modulus K=E/[3(1−2μ)] that an object whose Poisson's ratio μ is closer to 0.5 has a volume incompressibility closer to infinity;        the Poisson's ratio of a general object under normal temperature is greater than 0 and smaller than 0.5, but will be close to 0.5 when its homologous temperature, which is the ratio of its absolute temperature to its melting absolute temperature, is higher than 0.5, and the closer to 1 (the melting point) its homologous temperature, the closer to 0.5 its Poisson's ratio, and vice versa; thus        it can be said that the Poisson's ratio μ is an index of liquid behavior and incompressibility of a general object; or a general solid object under normal temperature has both a solid property and a liquid property, and the closer to 0.5 its Poisson's ratio, the fuller its liquid behavior; therefore,        any pliable material that has a Poisson's ratio close to 0.5, such as rubber, PTFE, lead, gold etc., can be simply used for sealing rings that need to orthogonally transmit a pressure or stress under normal temperature;        since material's Poisson's ratio μ is the ratio of its strain in the non-compressed transverse direction to its strain in the compressed longitudinal direction, any pliable material whose Poisson's ratio is smaller than 0.5 can be used for a sealing ring needing to orthogonally transmit a pressure or stress under normal temperature by compensating for its orthogonal strain ratio to 0.5 by a Poisson's deformation compensation angle—actually, the Poisson's deformation compensation angle is enabling a general compressible sealing ring to be compressed from a great room to a small room to cause it to have an additional deformation increment in the non-compressed direction perpendicular to the compressing force.        not only the angle Arctan(h/d), where h=the height of sealing rings and d=the internal diameter of sealing rings, used to compensate for Poisson's deformation of sealing rings from 0 to 0.5 or from 0.5 to 0 is very small, but also what the angle changes is only the response time for the ring material to reach its Poisson's ratio limit 0.5 or 0 but never the magnitude of the two limits, or at most eliminates the lagging of its orthogonal deformation ratio behind its final value, and thus any ring-containing cavity is eligible as long as it has an angle not smaller than the angle Arctan(h/d) and can cause the ring therein to be compressed from a great room to a small room; and        the Poisson's ratio of a general material not only changes with its temperature and loading pressure but also lags behind its loading pressure, and so any material even with a Poisson's ratio of 0.5 under atmospheric temperature and pressure also needs a Poisson's deformation compensation angle to enable its sealing ring to orthogonally transmit a pressure or stress at any working pressure and temperature within ratings in time effectively.
Therefore, as shown in FIGS. 1 to 3, it is only a triangular soft sealing ring that can utilize the wedging function of its hard gland to amplify its original axial tightening force into another force causing the whole soft ring to be compressed from a great room to a small room on its sealed stem to provide a radial sealing compression stress for the stem in time and effectively.
From the sealing theory proposed by the inventor (see ZL201210070823.2), it can be seen that:                A fully leak-free connection state results from a full deformation complementary to irregularities of sealed surfaces that is produced and maintained by a sealing surface compressed on the sealed surface, and hence a softer and inelastic sealing surface more easily produces a full sealing deformation under compression, and a stronger and elastic sealing surface support more easily provides a full deforming and maintaining power for the sealing surface under compression; or the difficulty for a sealing element to achieve or maintain its fully tight contact state is determined by the ratio, called the sealing difficulty factor m1, of the effective elastic modulus Ec of its sealing surface to the effective elastic modulus Es of its body, and m1max=Ec/Es=1;        an O-ring of infinitely thin wall metallic tubing fully filled with liquid can be used to simulate solid soft O-rings, where the metallic tubing represents their fixed shape, the liquid represents their liquid property, and it is very obvious that the closer to 0.5 their Poisson's ratio, the thinner the wall thickness of their simulating ring of metallic tubing for the same soft rings made of the same material and vise versa, so that:                    first from the fact that the simulating ring of metallic tubing and the simulated soft ring have the same circumferential tensile strength, it can be seen that 2πruδkRmk=πru2Rmr→2πrukruRmk=πru2Rmr→kRmk=0.5Rmr, and            then from the equation "pm=Rmδ/r" for the pressure that a common metallic thin wall tubing can withstand, it can be seen that the equation "pmr≡Rmkδk≡constant" is tenable to a ring of metallic tubing for simulating identical solid soft rings at any extrusion arc radius r, and further that the equation pmrre=puru=(Rmkδk/ru)ru=Rmkkru=0.5Rmrru is tenable to any soft ring or            the maximum pressure that any soft ring in its cavity can withstand is pmr=puru/re=0.5Rmrru/re,
where pu=0.5Rmr=the maximum pressure that the simulating O-ring of metallic tubing can withstand before installed into its cavity,
ru=the cross-sectional radius of the soft O-ring and its simulating O-ring of metallic tubing before installed into its cavity,
re=the maximum extrusion arc radius of the soft O-ring in its cavity,
δk=kru=the wall thickness of the simulating O-ring of metallic tubing,
Rmk=the material's strength of the simulating O-ring of metallic tubing,
Rmr=the material's strength of the soft O-ring,
Rm=the material's strength of a common metallic thin wall tubing,
δ=the wall thickness of a common metallic thin wall tubing,
r=the cross-sectional radius of a common metallic thin wall tubing; and                any self-energizing seal at its maximum allowable working pressure has a compressive stress or a sealing stress equal to its maximum allowable working pressure, and so the maximum compressive stress provided for the sealing surface by any soft sealing ring that can effectively orthogonally transmit a pressure or stress is mainly not determined by material's strength and wall thickness of the soft ring but by its maximum extrusion arc radius re in the cavity, for example, the maximum allowable working pressure of a rubber O-ring, or the maximum compressive stress that a rubber O-ring can provide for its sealing surface, is infinite when its extrusion gap or its extrusion arc radius is zero in the cavity.
Therefore, a pressure-tight sealing ring whose material is softer and inelastic and whose cavity has a smaller extrusion gap or is more closed can more cause its sealing surface to have a full sealing deformation and support when it is compressed in its cavity, which is entirely beyond the general traditional design concept of meeting the requirement of service pressure by computing and designing material's strength and wall thickness of sealing rings.
In clauses UG-101(a) (1) and (2) of ASME BPVC Section VIII Division 1 Rules for Construction of Pressure Vessels, it is explicitly stipulated that any vessel or vessel part whose strength and thickness cannot be accurately computed in accordance with its maximum allowable working pressure shall pass either a proof test based on yield limit of its material or a burst test based on burst limit of its material.
There is no seal that can be designed and computed before ZL201210070823.2, and by rights any seal shall be more required to pass, with its vessel, either a proof test with its test pressure at least equal to 1.5 or 2 times its maximum allowable working pressure or a burst test with its test pressure at least equal to 4 times its maximum allowable working pressure. However, the relevant standards, such as ISO 5208, ASME B16.34 etc., only require a seal to pass a test without visually detectable leakage at 1.1 times its maximum allowable working pressure, thus causing the safety of global pressure vessels and systems to be governed by their seal.
In ZL201210070823.2, the inventor only resolves the design and computation of rectangular and O-shaped ring seals, which cannot be used as pressure-tight seals for a moving rod, in accordance with their maximum allowable working pressure. In ZL200510097905.6 and ZL200810172830.7, the inventor only proposes that the cross-sectional shape of pressure-tight stem seals shall be an equilateral triangle, but does not resolve their design and computation in accordance with their maximum allowable working pressure.


A display apparatus in which light outputted from an LED array arranged in a column is reflected by a vibrating mirror such that a two-dimensional image is obtained, comprising: a half mirror which reflects light having a wavelength identical with a light emitting wavelength of the LED array and transmits therethrough visible light having other wavelengths than the light emitting wavelength; the half mirror being so disposed as to not only transmit therethrough the visible light from outside but also reflect the light proceeding from the LED array via the vibrating mirror such that the two-dimensional image has an outer scene as its background.

The present invention relates to a display apparatus suitable for operating a computer or various electronic appliances such that an operator can operate the computer or the electronic appliances while viewing display of the display apparatus.
FIG. 1 shows one example of a display unit 60 of a known display apparatus disclosed in Japanese Application No. 63-93845 filed Apr. 15, 1988. As taught in that application, and as further taught in Japanese Patent Application No. 63-108778, filed Apr. 30, 1988, an operator puts on the known display apparatus as shown in FIG. 2. In FIG. 1, an LED array 61 acting as a light source is provided at a lower portion of a casing 62. The LED array 61 is formed by a one-dimensional high-density monolithic array of, for example, 32 dots/mm or so. In FIG. 1, only one element of the LED array 61 is shown but actually, a plurality of the elements are arranged in series in the direction perpendicular to the sheet of FIG. 1. Supposing that the LED array 61 has a length of, for example, about 8.4 mm, a total of the elements are constituted by 280 dots. In order to obtain a two-dimensional image of the light source, a vibrating mirror 63 is provided so as to confront the light source. A resonance type scanner 64 is provided for vibrating the vibrating mirror 63 at high speed. When the LED array 61 is flickered in response to a data signal synchronously with vibrations of the vibrating mirror 63, a planar image is reflected in the vibrating mirror 63 as a virtual image. Thus, signals for one picture are transmitted during one period of vibrations of the vibrating mirror 63. The LED array 61 is provided at a focal point of a lens 65. Light from the LED array 61 is reflected by the vibrating mirror 63 and is changed into parallel light by the lens 65 such that the parallel light reaches an eye 66 of the operator. In this case, the lens 65 may also be provided between the LED array 61 and the vibrating mirror 63.
As shown in FIG. 2, the display unit 60 is attached to one end of a frame 70 and the other end of the frame 70 is mounted on a head set 72 through a rotary support member 71. The display unit 60 is rotated about the rotary support member 71 in a lateral direction so as to be changed over to an observational position and a nonobservational position. Meanwhile, a lead wire 73 is attached to a garment of the operator by a clip 74 so as not to disturb operation of the computer or the electronic appliances and is connected to a host portion (not shown) placed at another location. The operator puts the head set 72 on his head and positions the display unit 60 in front of an eye of the operator so as to view an image displayed by the display unit 60.
Meanwhile, in the known display apparatus referred to above, such a problem arises that since the display unit 60 obstructs the operator from viewing a subject or a scene in front of the display unit 60, it is difficult for the operator to manipulate switches, etc. in front of the display unit 60 while viewing an image displayed by the display unit 60. Furthermore, the display known apparatus has such a drawback that since an image, for example, a red image is displayed in the black background in the display unit 60, the eye of the operator is readily fatigued.
As shown in FIG. 3, a display window 68 is provided at either one of right and left sides of the display unit 60 such that the operator can view the background, e.g. a keyboard of the computer with one of his eyes while viewing a screen of the display unit 60 with the other one of his eyes. FIG. 3 shows a case in which the operator views the background with his right eye while viewing the screen of the display unit 60 with his left eye. In the case where the operator views the background with his left eye while viewing the screen of the display unit 60 with his right eye by using the display unit 60, the display unit 60 may be turned upside down as shown in FIG. 4. However, when the display unit 60 has been turned upside down, a picture on the screen of the display unit 60 is also seen upside down if no measures are not taken. Thus, a changeover switch 69 for changing over vertical orientation of the picture is provided. If the displayed picture is seen upside down, vertical orientation of the picture is changed over by operating the changeover switch 69.
Meanwhile, image signals corresponding to one page of the screen of the display unit 60 are stored in a data storage formed by, for example, a DRAM (dynamic random access memory) provided at the host portion so as to be transferred to the LED array 61 through the lead wire 73. However, in the case where vertical orientation of the picture of the display unit 60 has been changed over by operating the changeover switch 69, picture elements to be transferred are transmitted by converting sequence of transfer of the picture elements.
However, the methods disclosed in Japanese Patent Applications 63-93845 and 63-108778 have an inconvenience in that the circuit configuration used becomes complicated for the following reason. The LED array 61 is usually provided in a zigzag shape so as to increase density of the picture elements such that one column of the LED array 61 are turned on several rows later than the other column of the LED array 61. FIG. 5 shows prior art LED drivers 81 and 82 for driving the LED array 61. In the LED array 61, one column of 100 LEDs 1D to 100D of 100 dots and the other column of 100 LEDs 1E to 100E of 100 dots are staggered so as to have 200 dots. The two columns are spaced a distance corresponding to three rows from each other. By wire bonding, the LED array 61 is connected to the LED drivers 81 and 82 including a shift register and a latch. Characters Dd and De denote image signals and the arrow X represents a scanning direction based on vibrations of the mirror.
If an image of one column formed by the image signals Dd and De is displayed on a straight line by an array of 200 dots, namely, 1D, 1E, 2D, 2E,--99D, 99E, 100D and 100E, the LEDs 1D to 100D are required to be turned on later than the LEDs 1E to 100E by a duration corresponding to three rows. Thus, although there is time difference between turning on of the two columns of the LEDs, the turned on images are seen as being arranged in a column of the LEDs 1D, 1E, 2D, 2E,--99D, 99E, 100D and 100E by effect of afterimage. Characters SR1, SR2, SR3 and SR4 denote 100-bit shift registers for making the above mentioned time difference of three rows. The shift registers SR2 and SR3 are not used for making the time difference but are used for changing sequence of array so as to prevent formation of reverse array caused by the fact that the LED drivers 81 and 82 are constituted by an identical element. If a bidirectional shift register having up/down function is employed as a shift register SR0 of the LED drivers 81 and 82, the shift registers SR2 and SR3 can be deleted.
In the above described circuit configuration, it will be readily seen that if correspondence between a bit map of display and a bit map of memory is obtained, it is difficult that changeover of vertical orientation of the displayed image through change of sequence of the image signals Dd and De is performed by merely converting sequence of transfer of the picture elements from the data storage.
Therefore, the known display apparatus described in the two applications above has been disadvantageous in that the circuit configuration becomes complicated in order to change over vertical orientation of the picture in response to changeover of vertical orientation of the display apparatus.


A recording/reproducing manage unit 25, in response to an instruction, records the images of program into the recording files in order by changing the target recording file in a predetermined interval. Then the unit 25, in response to another instruction, reproduces the recording files in its recorded order. Thereby a recording/reproducing device of broadcasting signals of the invention can complete reproduction of a program at almost the same timing as an end time of real broadcasting of the program, even if the reproduction is started a long time behind the starting of the real broadcasting of the program.

1. Field of the Invention
The invention relates to a method and a device for recording/reproducing digital broadcasting signals of a program and in particular, to a method and a device which can perform time-shift reproducing (delayed reproducing) of the program.
2. Description of the Related Art
An analog VTR (Video Tape Recorder) has been spread to record broadcasting signals of a program. When the VTR records broadcasting signals of the program, the VTR receives the broadcasting signals from a broadcasting station via an antenna, and transforms the received signals into predetermined form of signals for recording. And then, the VTR records the transformed signals on a magnetic tape using a magnetic head. Such the processes are well known in the public
Also, after the VTR records broadcasting signals of a program in response to an instruction of a user, the VTR can again display the recorded signals of the program on a television set, by rewinding the tape and reproducing the signals of the program.
In such the VTR, it is impossible to record image data and sound data of the program to a magnetic tape and reproduce the data from the magnetic tape, simultaneously. For example, the VTR can not record a program which starts at 8:00 p.m. and ends at 10:00 p.m. while reproduction of the program is started at 9:00 p.m. from the beginning of the program. Furthermore, the VTR can not receive and record a program while performing special reproduction such as fast-forward reproduction of the recorded signals of the program.
In this regard, a conventional delay reproducing apparatus is disclosed in Japanese Laid Open Publication No. H07-336253(namely, 336253/1995). The conventional delay reproducing apparatus stores signals of a program to a RAM (random access memory) or a magnetic tape to pretend that broadcasting of the program is paused for a predetermined duration. Thus, in the apparatus, when a user starts watching a program, which is broadcast from 8:00 p.m. to 10:00 p.m., at 9:00 p.m. from the beginning of the program, the recording of the program is started at 8:00 p.m. and the reproducing of the recorded signals of the program is started at 9:00 p.m. The reproducing of the recorded signals of the program can be started at a timing an hour later than a timing when broadcasting of the program is actually started by continuing the recording of signals of the program to the RAM or an endless tape.
However, in the conventional apparatus, although data of a program can be reproduced at a timing delayed by a predetermined duration from an actual broadcasting time of the program, the delayed duration is limited to a very short time due to a small capacity of the RAM or the endless magnetic tape.
Also, recently, a DVR (Digital Video Recorder) has been known which can record data of a TV program (contents) to a HDD (hard disk drive). The DVR can "rewind" and reproduce a missed signals (image data or sound data) which are broadcast in several seconds before, while data of a program being recorded. This function is referred to as "time-shift reproduction".
The DVR is, for example, disclosed in a Japanese magazine "NIKKEI Pasokon" published in Jan. 24, 2000, page 28.
But, the DVR disclosed in the above magazine can not complete reproduction of a program at almost the same timing as an end time of real broadcasting of the program, even if the reproduction is started a long time behind the starting of the real broadcasting of the program.
Also, the magazine does not disclose a method of preventing a file from destruction when a power of the DVR is suddenly shut down during the DVR records signals of the program and a method of recording a full-length program to a small amount of storage medium. Therefore, the magazine does not disclose a specific effective configuration of the DVR at all.

Method and device for recording/reproducing broadcasting signals of a program


The present invention relates to acrylic block copolymers synthesized by a controlled radical process, and their use as thickeners in oil-based compositions. The acrylic copolymers are especially useful as viscosity index improvers in lubricating oil.

Lubricating oils, such as motor oils, gear oils, hydraulic fluids and transmission fluids typically contain several additives to improve their performance. These can include dispersants, antioxidants, detergents, friction modifiers, de-foaming agents, pour point depressants, and viscosity index improvers.
The viscosities of lubricating oils are temperature dependent, thus as the temperature of the oil is increased the viscosity typically decreases, and conversely as the temperature of an oil decreases the viscosity will increase. A significant loss of viscosity can be detrimental as it may cause wear between engine parts it is designed to protect. A viscosity index improver (VII) is typically a polymeric material, which principally functions by minimizing the viscosity variations over a wide range of temperatures. Normally these are used to reduce the viscosity loss of lubricating oils upon heating.
Random copolymers are commonly used as VIIs. To ensure solubility in a lubricating oil base, these copolymers are formed from at least one monomer whose homopolymer is oil-soluble. Three types of random copolymers commonly used as VIIs are: polymethacrylates (U.S. Pat. No. 6,124,249), olefinic copolymers (US 2003/0073785), and conjugated dienes (U.S. Pat. No. 6,319,881).
Polymers having a controlled architecture, including star copolymers (U.S. Pat. No. 6,034,042) and block copolymers have been described in the art. These polymers can be prepared through a variety of living anionic and living (or controlled) free radical polymerization techniques. These techniques have been used primarily to control the molecular weight distribution.
U.S. Pat. No. 6,538,091 describes a process for the control of a polymer architecture using an atom transfer process (ATRP) based on a redox reaction with a transition metal compound. This process uses an initiating system resulting in a copolymer having a predictable molecular weight and a controlled polydispersity. Polymers made by the process are described as useful for molding materials, barrier materials, thermoplastic elastomers, and amphiphilic surfactants. This controlled radical polymerization technique has several drawbacks such as, residual metallic by-products which can be detrimental to many applications (for example see U.S. Pat. No. 6,610,802) and limitations in polymer composition. Furthermore, the reference does not describe the use of any of the copolymers in lubricating oils.
Random copolymers made by ATRP have been used as pour point depressants (U.S. Pat. No. 6,391,996), and viscosity index improvers (US2002/0188081). The '081 reference mentions that the ATRP process could be used for blocky copolymers, but fails to exemplify such a use, or recognize the large VII benefit of using such block copolymers in lubricating oils. Also, gradient copolymers synthesized by ATRP have been shown useful as pour point depressants in U.S. Pat. No. 6,403,745. Again, the use of relatively high catalytic amounts of metal compounds leads to product containing residual metal contamination. These metallic by-products are detrimental in engine-type lubricant applications and require removal, which is difficult and requires laborious procedures.
The use of multifunctional lubricant additives has been described in U.S. Pat. No. 6,319,881.
Block copolymers have also been shown to be useful as VIIs. Block copolymers of a vinyl aromatic monomer and a vinyl aromatic-co-acrylic block prepared by stabilized free radical polymerization are described in U.S. Pat. No. 6,531,547. These patents describe the use of TEMPO-based nitroxide derivatives for the synthesis of the corresponding block copolymers. This class of free radical control agent does not provide control over acrylic type monomers. Specifically, the use of methacrylics will lead to side and termination reactions such as disproportionation, which inhibits the formation of block copolymers and long chain molecules (as described by Ananchenko et. al. in the Journal of Polymer Science: Part A: Polymer Chemistry, Vol. 40 pp 3264-3283). Also, block copolymers of ethylene and alpha-olefins have been described in US 2003/0073785 and block copolymers of poly(conjugated dienes) and poly(monovinyl aromatic hydrocarbons have been described in U.S. Pat. No. 6,303,550. None of the above references makes use of a controlled architecture copolymer having at least one pure acrylic block segment for use as a VII.
U.S. Pat. No. 5,002,676 describes the preparation of block copolymers containing selectively hydrogenated conjugated dienes and t-butyl methacrylate. U.S. Pat. No. 6,350,723 teaches the synthesis of block copolymers through the living anionic polymerization of a conjugated diene and an alkyl methacylate monomer. These references exemplify the use of block copolymers containing conjugated dienes and hydrogenated dienes, but fail to teach the specific copolymers of the present invention. Also these references do not teach the significance of tailoring block solubilities or allow for the formation of gradient compositions. Furthermore, living anionic polymerization suffers from several drawbacks, such as, ineffectiveness at temperatures above −20° C., poor copolymerization between polar and non-polar comonomers, and the inability to use monomers that can be easily deprotonated. Therefore functional monomers cannot be incorporated, and the copolymerization of monomer mixtures can be problematic and/or unusable. Furthermore this process can be expensive and difficult or impractical to carry out on an industrial scale as bulk or emulsion techniques cannot be used, extremely pure reagents are necessary (even trace amounts of protic material inhibits polymerization), and an inert atmosphere is requisite.
A process for preparing copolymers in the presence of a stable free radical from the nitroxide family is described in U.S. Pat. No. 6,255,402. Nitroxide-mediated stable radicals have been used to produce controlled block copolymers, as described in U.S. Pat. No. 6,255,448, and US 2002/0040117. These references, incorporated herein by reference, do not describe the use of the copolymers in lubricating oils.
Surprisingly it has now been found that an acrylic block copolymer formed by a controlled radical polymerization, produces excellent viscosity index improvement in lubricating oils. The polymers of the invention produce a greater VI improvement than found in random copolymers or other block copolymers currently used. While the properties attained in traditional copolymers are typically an average of the properties imparted by the resultant monomers incorporated, block copolymers lead to a material containing the characteristic properties inherent to the parent homopolymers comprising each segment. Therefore, the use of block copolymers is particularly adventitious for the formation of materials containing multifunctional properties. Furthermore, this class of polymers should provide enhanced shear stability due to the selected monomer composition, the controlled molecular weights, and molecular weight distribution provided by the controlled polymerization process. The viscosity modifying advantages of these copolymers for lubricant oil applications can be exemplified by the excellent performance demonstrated in typical SAE Standard J300 viscosity classification testing and ASTM D 2270 testing. Furthermore these block copolymers can be used to thicken any number of oil-based compositions.

Controlled radical acrylic copolymer thickeners