Title of Invention: Input key and input apparatus Abstract: An input key which is assigned a plurality of information items to be inputted, of the present invention, includes a key top which can incline relative to a support plate for supporting the input key; a key top supported portion provided on an opposite surface in the key top to the support plate and arranged to be pushed together with the key top; a key top supporting portion provided on the support plate, and arranged to come into contact with the key top supported portion during a push on the key top and to support the key top supported portion so as to permit the key top to incline in a state of the contact with the key top supported portion; at least one inclination detector provided in a direction assigned one of the information items to be inputted, on an opposite surface in the support plate to the key top or on the opposite surface in the key top to the support plate; push detecting means for detecting a push on the input key; and inclination direction detecting means for detecting an inclination direction of the key top when the push detecting means detects a push on the input key. Detailed Description: Part general_description_paragraphs: Part BACKGROUND OF THE INVENTION: 1. Field of the Invention The present invention relates to an input apparatus having at least one input key assigned a plurality of information items to be inputted, and to the input key. 2. Related Background Art The portable terminals such as cell phones need to be compact enough to be carried by users. For this reason, where the portable terminals are provided with a keyboard, the number of keys in the keyboard is often much smaller than that in the so-called full keyboard. In the case as described above, it is common practice to assign one key a plurality of symbols. A conventionally proposed method of inputting a plurality of symbols through one key is to detect a direction of a force exerted on the key and input an independent symbol by the direction. For example, Japanese Patent Application Laid-Open No. 2003-296001 discloses the following technology of detecting the direction of the push on the key, for substantializing this idea. This technology is such that switches and protruding portions according to push directions are provided inside the key, and with a push, a protruding portion turns on a switch according to a direction of the push, thereby detecting the direction of the push. Part SUMMARY OF THE INVENTION: However, the above method requires a considerably careful operation to avoid actuation of the switch in the central direction (vertical direction) during a push in the forward, backward, left, or right direction, and there is thus still room for improvement in an aspect of operability. The present invention has been accomplished in order to solve the above problem and an object of the present invention is to provide an input key and an input apparatus superior in operability. In order to achieve the above object, an input key according to the present invention is an input key which is assigned a plurality of information items to be inputted, comprising: a key top which can incline relative to a support plate for supporting the input key; a key top supported portion provided on an opposite surface in the key top to the support plate and arranged to be pushed together with the key top; a key top supporting portion provided on the support plate, and arranged to come into contact with the key top supported portion during a push on the key top and to support the key top supported portion so as to permit the key top to incline in a state of the contact with the key top supported portion; at least one inclination detector provided in a direction assigned one of the information items to be inputted, on an opposite surface in the support plate to the key top or on the opposite surface in the key top to the support plate; push detecting means for detecting a push on the input key; and inclination direction detecting means for detecting an inclination direction of the key top when the push detecting means detects a push on the input key. Here the term “information items to be inputted” includes information generally assigned to each of input keys in the so-called full keyboard, e.g., information such as symbols, numbers, and marks, information of the linefeed code and control code, and so on. A user of the input key according to the present invention pushes an input key corresponding to an information item to be inputted, while inclining a key top of the input key in a direction corresponding to the information item to be inputted. In the input key, first the push brings the key top supported portion into contact with the key top supporting portion to establish a supported state. Subsequently, the key top inclines into the direction in which the user inclines it, in the supported state (a stable state with the key top supporting portion and the key top supported portion serving as an axis). This causes an inclination detector corresponding to the direction of the inclination to come into contact with a surface opposed to the inclination detector (e.g., the support plate, or the opposite surface on the key top side (or the key top supported portion)). Then the push detecting means detects the push on the input key. When the push is detected, the inclination direction detecting means detects the contact of the inclination detector with the surface on the opposite side. This makes it feasible to specify information corresponding to the direction of the inclination of the key top by the user (an information item to be inputted). The detection by the inclination direction detecting means (the detection of the contact of the inclination detector with the opposite surface) is implemented, for example, by the following method. Describing an example of the contact of the inclination detector with the support plate, an electrode to conduct electricity upon the contact of the inclination detector with the support plate is embedded in the support plate and the electric conduction is detected to detect the contact of the inclination detector with the opposite surface. In another configuration, a button or a switch or the like is provided at the contact part in the support plate in contact with the inclination detector and a push on the button or the switch or the like is detected. In still another configuration, a piezoelectric device or a strain gage or the like is provided at the contact part in the support plate in contact with the inclination detector and the push is detected by the piezoelectric device or the strain gage or the like. The foregoing “means for detecting the contact” such as the electrode to conduct electricity upon the contact, the button, the switch, the piezoelectric device, and the strain gage will be referred to hereinafter as “contact detecting means”. As described above, the present invention enables stabler input based on the inclination of the key top around the axis on the key top supported portion and the key top supporting portion arranged to contact each other upon a push on the key top, thereby achieving better operability. More specifically, the input key according to the present invention preferably has a configuration wherein the inclination detector is of such a protruding shape as to facilitate contact with the surface opposite to the surface where the inclination detector is provided, and wherein the inclination direction detecting means detects the contact of the inclination detector with the opposite surface to detect the inclination direction of the key top. The input key according to the present invention also preferably has a configuration wherein the inclination detector is comprised of one or two out of: a key-top-side slope portion forming a part of the opposite surface in the key top to the support plate and formed so as to increase distance to the support plate from the interior side toward the exterior side; and a support-plate-side slope portion forming a part of the opposite surface in the support plate to the key top and formed so as to increase distance to the key top from the interior side toward the exterior side; and wherein the inclination direction detecting means detects contact of the inclination detector with the opposite surface to detect the inclination direction of the key top. The input key according to the present invention also preferably has a configuration further comprising a key top periphery supporting portion formed of an elastically deformable material and arranged to support a peripheral portion in the key top so as to keep the distance substantially constant between the key top and the support plate. The input key according to the present invention also preferably has a configuration wherein the inclination detector is provided on the opposite surface in the key top to the support plate, and wherein when the key top is inclined during a push on the key top, the key top supported portion comes into contact with the key top supporting portion to be supported by the key top supporting portion and the inclination detector comes into contact with the support plate. The input key according to the present invention also preferably has a configuration wherein the inclination detector is provided on the opposite surface in the support plate to the key top, and wherein when the key top is inclined during a push on the key top, the key top supported portion comes into contact with the key top supporting portion to be supported by the key top supporting portion and the inclination detector comes into contact with the key-top-side opposite surface or with the key top supported portion. More specifically, the input key according to the present invention preferably has a configuration wherein one of the key top supported portion and the key top supporting portion is of a convex shape and the other is of a concave shape. The above shapes enable securer support between the key top supported portion and the key top supporting portion, and the key top supported portion and the key top supporting portion function as an axis during the inclination of the key top, thereby enabling smoother inclination. More specifically, the input key according to the present invention preferably has a configuration wherein contact detecting means for detecting contact is placed on both or either one of the inclination detector, and a surface with which the inclination detector comes into contact during an inclination of the key top, and wherein the inclination direction detecting means detects the contact of the inclination detector with the foregoing surface by the contact detecting means to detect the inclination direction of the key top. In particular, a button, a switch, a piezoelectric device, a strain gage, or the like may be placed on both or one of the inclination detector, and the surface to contact the inclination detector; or the both surfaces may be provided with electrodes to conduct electricity upon the contact. The piezoelectric device as an example of the contact detecting means is a device that generates a voltage upon occurrence of stress and is able to detect a pressure due to a push of the inclination detector. In the “arrangement” of the piezoelectric device, the piezoelectric device may be attached onto the both or one of the inclination detector and the surface to contact it or may be embedded in the both or one of the inclination detector and the surface to contact it. The input key according to the present invention also preferably has a configuration wherein the support plate is formed of an elastically deformable material. Namely, when the user pushes the input key, the key top supported portion pushes the key top supporting portion and the pertinent part of the support plate gets dented by the pressure of the push to elastically deform the support plate into a concave shape. This causes the peripheral part of the key top supporting portion in the support plate (i.e., the part where the inclination detector is placed or the part where the inclination detector contacts the support plate) to relatively bulge, thereby decreasing the clearance between the inclination detector and the surface to contact the inclination detector. This results in decreasing the inclination amount into the direction corresponding to the information item to be inputted by the user, which makes the input of information easier. The input key according to the present invention also preferably has a configuration wherein one portion or both portions in at least one combination out of combinations of portions to come into contact with each other inside the input key during a push on the input key are of an embossed structure. The embossed structure is a sheetlike structure bulging in the center. When a force over a given level is applied to the bulging portion, the central bulging portion collapses at a stretch to get dented to the other side. When the force over the given level is removed, the central bulging portion dented to the other side bulges (or recovers). Once the bulging portion bulges to a certain shape, it returns into the original bulging state at a breath. The embossed structure is formed of an embossed sheet or the like made of soft vinyl or the like. As the user pushes the input key, the input key according to the present invention is subject to a reaction force from the embossed sheet before the force of the push reaches the aforementioned given level. However, once the user applies the force over the given level, the embossed sheet collapses at a stretch to be dented, so as to decrease the reaction at a breath. This permits the user to sense the decrease of the reaction at a fingertip during the push on the input key with a user's finger. As the user lifts the finger from the input key, the part of the embossed structure gradually returns from the dented state of the central bulging portion to the original shape to elevate the input key. When it returns up to a certain shape, the central bulging portion suddenly generates a strong restoring force to quickly increase the force to lift the input key. As described above, the present invention permits the user of the input key to have a touch of a push on the key top, so called a “click feel”, and thereby obtain a light keying feel. In order to achieve the above object, an input apparatus according to the present invention is an input apparatus for input of information through at least one input key assigned a plurality of information items to be inputted, comprising: (1) an input key comprising: (1a) a key top which can incline relative to a support plate for supporting the input key; (1b) a key top supported portion provided on an opposite surface in the key top to the support plate and arranged to be pushed together with the key top; (1c) a key top supporting portion provided on the support plate, and arranged to come into contact with the key top supported portion during a push on the key top and to support the key top supported portion so as to permit the key top to incline in a state of the contact with the key top supported portion; and (1d) at least one inclination detector provided in a direction assigned one of the information items to be inputted, on an opposite surface in the support plate to the key top or on the opposite surface in the key top to the support plate; (2) assignment information holding means for holding assignment information of each of the information items to be inputted, according to an inclination direction of the key top of the input key; (3) push detecting means for detecting a push on the input key; (4) inclination direction detecting means for detecting an inclination direction of the key top when the push detecting means detects a push on the input key; and (5) information determining means for determining an information item to be inputted, based on the inclination direction detected by the inclination direction detecting means and the information held in the assignment information holding means and fed according to the inclination direction. Processing executed in the input apparatus according to the present invention will be described below. A user of the input apparatus pushes an input key corresponding to an information item to be inputted, while inclining the key top in a direction corresponding to the information item to be inputted. In the input key, first, the push brings the key top supported portion into contact with the key top supporting portion to establish a supported state. Subsequently, in this supported state (a stable state with the key top supporting portion and the key top supported portion serving as an axis), the key top inclines into the direction in which the user inclines the key top. This causes an inclination detector corresponding to the direction of the inclination to come into contact with a surface on the side opposite the inclination detector (e.g., the support plate, or the opposite surface on the key top side (or the key top supported portion)). Then the push detecting means detects the push on the input key. When the push is detected, the inclination direction detecting means detects the contact of the inclination detector with the surface on the opposite side. Subsequently, the information determining means determines the information item to be inputted, based on the detected inclination direction and the information held in the assignment information holding means. This makes it feasible to specify information corresponding to the direction of the inclination of the key top by the user (an information item to be inputted). According to the present invention, as described above, the key top is inclined about the axis on the key top supported portion and the key top supporting portion in contact with each other, so as to enable stabler input and achieve better operability. In the input apparatus according to the present invention, preferably, one of the key top supported portion and the key top supporting portion is of a convex shape and the other is of a concave shape. The input apparatus according to the present invention also preferably has a configuration wherein contact detecting means for detecting contact is placed on both or either one of the inclination detector, and a surface with which the inclination detector comes into contact during an inclination of the key top, and wherein the inclination direction detecting means detects the contact of the inclination detector with the foregoing surface by the contact detecting means to detect the inclination direction of the key top. In particular, a button, a switch, a piezoelectric device, a strain gage, or the like may be placed on both or one of the inclination detector, and the surface to contact the inclination detector; or the both surfaces may be provided with electrodes to conduct electricity upon the contact. In the input apparatus according to the present invention, the support plate is preferably formed of an elastically deformable material. Furthermore, the input apparatus according to the present invention preferably has a configuration wherein one portion or both portions in at least one combination out of combinations of portions to come into contact with each other inside the input key during a push on the input key are of an embossed structure. This configuration permits the user of the input key to have a touch of a push on the key top, so called a “click feel”, and thereby to obtain a light keying feel. Incidentally, in a desired configuration of the input apparatus according to the present invention, the input apparatus further comprises controlling means for, during a push operation on an input key, outputting assignment information of a plurality of input information elements to the input key at a time of the operation, to an external display device and for making the display device highlight information of an input candidate corresponding to the push operation at the time, out of the plurality of input information elements. This achieves the following three effects. Namely, (1) in a case where the assignment of the plurality of input information elements to the input key is changed according to frequencies of use or the like, the user can check the up-to-date assignment information on the external display device during a push operation on the input key. (2) For example, in a case where the input mode is switched from an input mode of Japanese hiragana writing symbols to an alphabet input mode, it is feasible to feed back to the user the assignment information of input information about the input mode after the switch, which cannot be readily displayed by only the display on the key top. Furthermore, (3) the user can also check the information as an input candidate corresponding to a push operation at the time of the operation (information selected at the time). The feedback function of up-to-date assignment information as described above can dramatically improve easiness and certainty of user operation. The present invention enables stabler input and achieves better operability, based on the configuration of inclining the key top around the axis on the key top supported portion and the key top supporting portion in contact with each other during a push on the key top. Part DESCRIPTION OF THE PREFERRED EMBODIMENTS: Various embodiments of the present invention will be described below with reference to the drawings. The following description will concern the first to fourth embodiments in configurations wherein inclination detectors of an input key according to the present invention are provided in a protruding shape on a support plate (i.e., on an opposite surface to a key top), the fifth to seventh embodiments in configurations wherein inclination detectors of an input key according to the present invention are provided in a protruding shape on a key top (i.e., on an opposite surface to a support plate), and the eighth embodiment in a configuration wherein inclination detectors of an input key according to the present invention constitute a part of an opposite surface in a key top to a support plate and are comprised of a key-top-side slope portion formed so as to increase the distance to the support plate from the interior side toward the exterior side, which will be described below in order. Part First Embodiment: FIG. 1 shows an exterior configuration of an input apparatus 200 in the first embodiment. As shown in FIG. 1, the input apparatus 200 is provided with twelve input keys 10 (generically used to refer to input keys 10a–101) of 4 vertical and 3 horizontal. Here the input apparatus 200 is used in various portable terminals such as mobile communication terminals typified by cell phones, PDAs (Personal Digital Assistants), and so on. Each input key 10 is assigned at least one symbol according to a direction of an inclination of a key top. In the description hereinafter, the hiragana writing symbols being one of the Japanese symbol formats will be used as an example of symbols to be inputted through the input keys 10. The Japanese hiragana writing symbols can be classified into a plurality of subgroups, and each subgroup consists of five symbols. These subgroups include the “ line” group consisting of five symbols () corresponding to five basic vowels, the “ line” group consisting of five symbols () corresponding to the foregoing five vowels coupled with a specific consonant “K”, the “ line” group consisting of five symbols () corresponding to the foregoing five vowels coupled with a specific consonant “S”, the “ line” group consisting of five symbols () corresponding to the foregoing five vowels coupled with a specific consonant “T”, and so on. For example, the input key 10a is assigned a symbol group of the “ line group” according to directions of force as follows: “” in “up”; “” in “right”; “” in “down”; “” in “left”; “” in “center”. In addition, as shown in FIG. 1, indications to display the assignment are provided on the surface of the key top of the input key 10a. Similarly, the input key 10b is assigned a symbol group of the “ line group”, and the input key 10c a symbol group of the “ line group”. The “directions” in the present embodiment will be described below with reference to FIG. 2. As shown in FIG. 2, the input key 10a is placed on a support plate 60. A “direction” in the present embodiment indicates “up”, “down”, “left”, “right”, or “center” with respect to the plane of support plate 60. The “center” refers to a state in which during a push on the input key 10 no force is applied in either direction, i.e., a state in which a force vertical to the support plate 60 is exerted. FIG. 3 shows a functional configuration of the input apparatus 200. As shown in FIG. 3, the input apparatus 200 has input keys 10 (only the input key 10a shown), an assignment information holder 34, a push detector 36, an inclination direction detector 38, and a symbol determiner 40. The push detector 36 corresponds to the push detecting means according to the present invention, the inclination direction detector 38 to the inclination direction detecting means according to the present invention, and the symbol determiner 40 to the information determining means according to the present invention. The upper part (the part surrounded by a dotted line in FIG. 2) of each input key 10 is a portion which is called a key top 220 and to which force is applied during a push on the input key 10. The assignment information holder 34, push detector 36, inclination direction detector 38, and symbol determiner 40 each may be constructed separately from the input keys 10 or integrally therewith. When a user of the input apparatus 200 enters a symbol, the user pushes an input key 10. Namely, where the user enters a symbol in the “ line group”, the user exerts a force on the key top 220 of the input key 10a to push it. The user can specify a symbol by pushing the key top with an inclination in one direction of “up”, “down”, “left”, or “right” or by pushing the key top in the “center” direction without inclination in any direction when exerting the force on the key top 220 of the input key 10a. The assignment information holder 34 has a symbol conversion table as shown in FIG. 14 and holds the assignment information of each of information items to be inputted, according to inclination directions of the key top 220 in the input key 10. For example, FIG. 14 shows that “” corresponds to the center direction of the input key 10a, “” to the up direction, “” to the right direction, “” to the down direction, and “” to the left direction. Similarly, the assignment information holder 34 has symbol conversion tables corresponding to the input keys 10b to 101. The symbol conversion tables may be arranged to permit the user to freely set corresponding symbols. The contents of the symbol conversion tables may be arranged to be automatically updated according to statistical results of user's symbol input. For example, a symbol at a high user's input frequency may be automatically assigned to a direction or an input key 10 easier to incline. The push detector 36 detects a push on an input key 10 (the details of the detection method will be described later). The inclination direction detector 38 has a decision table shown in FIG. 13, and detects a direction of an inclination of the key top 220. The decision table, as shown in FIG. 13, stores conditions corresponding to inclination directions of the key top 220, based on inclination directions and times of the key top 220 detected (the details of which will be described later). The symbol determiner 40 determines a symbol to be inputted, from the detected direction on the basis of the symbol conversion table held by the assignment information holder 34. As shown in FIG. 4, the assignment information holder 34, push detector 36, inclination direction detector 38, and symbol determiner 40 are constructed as an integral device provided with a processor 45, a program executed by the processor 45, a memory 46 storing various tables and various data, an input interface 47 for receiving various signals, and an output interface 48 for outputting a symbol as a determination result to the outside. FIG. 5 shows a vertical cross section of an input key 10. As shown in FIG. 5, an input key 10 is comprised of a key top 220, a key skirt 230, a key top supported portion 20, a key top supporting portion 30, and four inclination detectors 54 (two of which are illustrated) in the up, down, left, and right directions on a support plate 60, and is provided on the support plate 60. The key top 220 is a portion to which force is applied during a push on the input key 10, and is made of a material with some hardness, for example, such as hard plastic or metal, in order to enhance sensation of a push on the input key. The key skirt 230 is connected perpendicularly to the support plate 60 and holds the key top 220 with a constant space from the support plate 60 in a state without force on the key top 220. The key skirt 230 is made of an elastically deformable material, e.g., synthetic rubber, soft plastic, soft vinyl, or the like. As shown in FIGS. 10 and 11, the key skirt 230 is elastically deformed to enable the key top 220 to undergo a push and inclination relative to the support plate 60. The periphery of the upper surface of the key top 220 is of such a bulging structure as to facilitate the inclination with a force applying finger or the like being caught thereon during the inclination of the key top 220. The key top supported portion 20 is of a protruding shape and is provided in the center on an opposite surface in the key top 220 to the support plate 60. The distal end of the key top supported portion 20 is of a semispherical convex shape and an electrode 21 is attached to that portion. The electrode 21 is made of a uniform conductor such as a metal piece. The key top supporting portion 30 is provided on the support plate 60 so as to rise from the other part of the support plate 60 (as being integral with the support plate 60), and is located with a space to the opposed part of the key top supported portion 20. When the key top 220 is pushed, the key top supporting portion 30 comes into contact with the key top supported portion 20. The contact part of the key top supporting portion 30 is of such a semispherical concave shape as to be able to support the convex part at the distal end of the key top supported portion 20. As shown in FIG. 11, the concavo-convex structure of the key top supported portion 20 and the key top supporting portion 30 enables the key top supported portion 20 to incline together with the key top 220 in a state in which the key top 220 is supported on the key top supporting portion 30 while being pushed. An electrode 31 is attached to the concave part of the key top supporting portion 30. FIG. 7(a) shows a vertical cross section of the electrode 31 and FIG. 7(b) a top plan view of the electrode 31. As shown in FIG. 7, the electrode 31 is provided with a plurality of electric contacts 31a, and these contacts 31a are connected to either a wiring line 32a or a wiring line 32b. When the input key 10 is pushed to bring the key top supported portion 20 into contact with the key top supporting portion 30 as shown in FIG. 10, the electrode 21 attached to the key top supported portion 20 comes into contact with a plurality of contacts 31a of the electrode 31 attached to the key top supporting portion 30, so that the wiring line 32a and the wiring line 32b turn into an electrically conducting state through the contacts 31a and electrode 21. This causes the push detector 36 to detect the conducting state and thereby detect the push on the input key 10. The inclination detectors 54 are provided in the respective directions of up, down, left, and right around the key top supporting portion 30 on the support plate 60 and are arranged to further rise from the key top supporting portion 30. The inclination detectors 54 are of an elongated convex shape as shown in FIGS. 6 and 8, and an electrode 55 is attached to the distal part of each detector. As shown in FIG. 8, an electrode 55 is provided with a plurality of electric contacts 55a exposed in the form of a line on the surface of the corresponding inclination detector 54, and those contacts 55a are connected to either a wiring line 56a or a wiring line 56b. FIG. 6 shows the opposite surface in the support plate 60 to the key top 220. As shown in FIG. 6, the electrode 31 attached to the key top supporting portion 30 is located in the center of the opposite surface and the electrodes 55 attached to the inclination detectors 54 are located in the respective directions of up, down, left, and right. When the key top 220 is pushed with inclination, an inclination detector 54 comes into contact with the opposite surface on the key top 220 side, as shown in FIG. 11. Electrode 51 are attached to corresponding portions of the contact of the opposite surface on the key top 220 side. The detection of the contact of the inclination detector 54 with the opposite surface on the key top 220 side is carried out in a manner similar to the detection of the contact of the key top supported portion 20 with the key top supporting portion 30. It is assumed herein that the relation of d1<d2 is satisfied by the distance d1 between the key top supported portion 20 and the key top supporting portion 30 and the distance d2 between the inclination detectors 54 and the key top 220 in a state without force on the key top 220. This is for assuring establishment of a state in which the key top supported portion 20 comes into contact only with the key top supporting portion 30 when a force vertical to the key top 220 is exerted, and is also for assuring establishment of a state in which the key top supported portion 20 is always supported by the key top supporting portion 30 when an inclination detector 54 is in contact with the key top 220. Namely, this is for assuring establishment of a state in which a clearance is secured for a structure wherein the key top supported portion 20 comes into contact only with the key top supporting portion 30 and an inclination detector 54 is not in contact with the opposite surface when a force vertical to the key top 220 is exerted, and a push vertical to the key top 220 can be achieved surely, and is also for assuring establishment of a state in which the key top supported portion 20 supported on the key top supporting portion 30 is made to function as a fulcrum of inclination during the inclination of the key top 220. The detection of the contact may also be implemented by any other method, e.g., a method of detecting the contact by a button, a switch, or the like set in the contact part, instead of the method of attaching the electrodes to the contact parts as described above. The processing executed in the input apparatus 200 according to the present embodiment will be described below with reference to the flowchart of FIG. 9. When the user pushes an input key 10, the processing is started. The user pushes an input key 10 assigned a symbol to be inputted, while exerting a force so as to incline the key top 220 in a direction corresponding to the symbol to be inputted. For example, when the user desires to enter a symbol of “”, the user pushes the input key 10a assigned “”, while applying a force so as to incline the key top 220 in the right direction corresponding to “” as shown in FIG. 11. Here how to incline the key top 220 in a direction corresponding to a symbol to be inputted is a method of once pushing the key top 220 vertically and then inclining the key top in a state in which the key top supported portion 20 is supported by the key top supporting portion 30. It is also possible to adopt a method of pushing the key top 220 while directly inclining it. In that case, the key top supported portion 20 comes into contact with the key top supporting portion 30 at an initial stage of a push to be supported, and the subsequent inclination is implemented in a state in which the key top supported portion 20 is supported by the key top supporting portion 30. This inclination method permits the user to perform the push and inclination as a continuous operation, without being conscious of the two-step operations of the push and inclination. In either of the inclination methods, the inclination is performed in a stable state in which the key top supported portion 20 supported by the key top supporting portion 30 serves as a fulcrum. With the push, as shown in FIGS. 10 and 11, the electrode 21 attached to the key top supported portion 20 comes into contact with the electrode 31 attached to the key top supporting portion 30, whereby the line 32a and the line 32b turn into the electrically conducting state through the contacts 31a and electrode 21. This causes the push detector 36 to detect the conducting state and to detect a start of the push on the input key 10 to start counting a continuation duration of the push (S11). Subsequently, the inclination direction detector 38 detects an inclination of the key top 220 as shown in FIG. 11, in a manner similar to the method of the detection of the push (S12), and counts a continuation duration of the inclination (S13). The directions of the inclination are defined by “A” for the center, “B” for the left direction, “C” for the right direction, “D” for the up direction, and “E” for the down direction, as shown in FIG. 12, and the continuation durations of the inclination will be denoted by tA, tB, tC, tD, and tE, respectively. The unit of time herein is an extremely small time unit, e.g., millisecond. Subsequently, the push detector 36 detects an end of the push on the input key 10. The detection of the push end on the input key 10 is implemented by determining whether a duration to of a non-conducting state in which the electrode 21 attached to the key top supported portion 20 stays away from the electrode 31 attached to the key top supporting portion 30, exceeds a given value T0 (>0) (S14). When the push on the input key 10 is not finished, the processes of S12 to S14 are continuously performed. The determination on the duration of the non-conducting state is preferably carried out at very short time intervals, e.g., on the millisecond time scale. When the push on the input key 10 is finished, the inclination direction detector 38 determines an inclination direction of the key top 220 in a manner as described below, from values tA to tE of the continuation durations of the inclination directions obtained as described above, based on the decision table (S15). First, a decision on a push in the center direction (a push in a state in which the key top 220 does not incline in either direction) is made as follows. Values of rAB=tB/tA and others are derived from the duration tA of the push in the center direction and the duration tB of the inclination in the left direction and others (rXY hereinafter refers to tY/tX (X, Y=any two of A to E). Using these values, it is determined that the push in the center direction was made, if the following conditions are satisfied, as in the decision table shown in FIG. 13. (1) tA>TA (2) rAB≦RA and rAC≦RA and rAD≦RA and rAE≦RA Here TA and RA are positive constant values. The condition of (1) indicates that the push in the center direction continues over the constant time. Therefore, TA is an appropriate value to assume a push. The condition of (2) indicates that the durations of inclination in all the directions are not more than the fixed ratio to the duration of the push in the center direction. Therefore, RA is preferably a value such as 0.05 (a duration of inclination in any direction is 5% of the duration of the push in the center direction). This condition is given for eliminating a chance of determining that some shake in the up, down, left, and right directions with the intension of the push in the center direction is an inclination in one direction. Next, a decision on an inclination in one direction of the key top 220 during a push on the input key 10 is made as follows. A case of the inclination in the right direction will be described as an example. Just as in the above case, it is determined that the key top was inclined in the right direction, if the following conditions are satisfied, as in the decision table shown in FIG. 13. (1) tC>TC (2) rAC>α (3) rCB≦RC and rCD≦RC and rCE≦RC Here TC, α, and RC are positive constant values. The condition of (1) indicates that the inclination in the right direction continues over the constant time. Therefore, TC is set to an appropriate value to assume an inclination. The condition of (2) indicates that the duration of the inclination in the right direction exceeds the constant ratio to the duration of the push in the center direction. This is because the key top supported portion 20 is in contact with the key top supporting portion 30 even during the inclination of the key top 220 in any direction and the push in the center direction is also detected. Therefore, α is preferably a value of approximately 0.70 (the duration of the inclination in the right direction is 70% of the duration of the push in the center direction). The appropriate value of α differs depending upon the operation speed or the like from familiarity to the push operation. For this reason, α is preferably determined according to the operation speed or the like from familiarity to the push operation. The condition of (3) indicates that the durations of inclination in all the directions except for the right direction are not more than the constant ratio to the duration of inclination in the right direction. Therefore, RC is preferably set to a value of about 0.05 (the duration of inclination in any direction except for the right direction is 5% of the duration of inclination in the right direction). This condition is given for eliminating a chance of determining that some shake in the other directions with the intension of the inclination in the right direction is an inclination in one direction except for the right direction. Inclinations in the other directions are also determined in similar fashion. Subsequently, the symbol determiner 40 determines a symbol to be inputted, based on the symbol conversion table as shown in FIG. 14, which is held in the assignment information holder 34, from the information about the detected direction and the input key 10 pushed (S16). For example, in a case where the detected direction is “right” and where the input key 10 pushed is “key 10a”, the symbol to be inputted is determined to be “”, based on the symbol conversion table corresponding to the key 10a as shown in FIG. 14. Subsequently, the symbol determiner 40 outputs the symbol thus determined (S17). As described above, the input apparatus 200 of the present embodiment enables stabler input based on the inclination of the key top 220 around the axis on the key top supported portion 20 in the input key 10. This makes it feasible to substantialize the input apparatus 200 superior in terms of operability. The key top 220 can be made in simpler structure, without need for providing the key top 220 with a plurality of projections, so that it becomes feasible to facilitate the production of input apparatus 200 and to decrease the cost of production. In the present embodiment, as shown in FIGS. 27 and 28, a guard portion 301 bulging high so as to implement easier support of the key top supported portion 20 may be provided around the part to support the key top supported portion 20, in the key top supporting portion 30. In this configuration, the distal end of the key top supported portion 20 is arranged to be lower with respect to the plane of the support plate 60 than the distal end of the guard portion 301 in a state in which the input key 10 is not pushed. However, the height of the guard portion 301 should be determined so as to prevent the key top supported portion 301 from hitting the guard portion 301 during inclination of the key top 220 to impede the inclination detector 54 from coming into contact with the key top 220. The guard portion 301 is made of a material so hard as to function as a guard and, normally, may be made of a material similar to the support plate 60. In the present embodiment, as shown in FIG. 15, it is possible to adopt a configuration wherein a key top periphery support 231 made of an elastically deformable material such as a spring, synthetic rubber, soft plastic, or soft vinyl horizontally supports the key top 220, instead of the key skirt 230. In the present embodiment, as shown in FIG. 25, it is also possible to adopt a structure wherein during an inclination of the key top 220 an inclination detector 54 comes into contact with the key top supported portion 20. In the case of this structure, the electrodes 51, which were attached to the key top 220 in the configuration described above, are attached to the side part in the key top supported portion 20 to come into contact with the inclination detectors 54, in fit with the shape of that part, so as to detect the inclination direction of the key top 220. In this case, in order to securely support the key top supported portion 20 on the key top supporting portion 30, the distal end of the key top supported portion 20 is set to be lower with respect to the plane of the support plate 60 than the distal portion of the inclination detectors 54 in a state in which the input key 10 is not pushed. In order to prevent the electrode 21 attached to the tip of the key top supported portion 20 from touching the electrodes 55 of the inclination detectors 54, the electrode 21 is set to be lower with respect to the plane of the support plate 60 than the electrodes 55 in a state in which the input key 10 is not pushed. The input key is constructed in the structure capable of securing an appropriate distance enough to avoid contact between the electrodes 51 on the side of the key top supported portion 20 and the electrodes 55 of the inclination detectors 54 even with some shake of the key top during the push in the center direction on the key top 220. In the present embodiment the push detector 36 and the inclination direction detector 38 are constructed separately from the input key 10, but they may be constructed integrally with the input key 10 as shown in FIG. 16. The above system adopts the key input based on one symbol per push, but it is also possible to adopt continuous input of symbols based on continuation of a push state on the input key 10 as described below. In the above-stated system, the inclination direction of the key top 220 was determined when the push on the input key 10 was finished, that is, when the duration to of the non-conducting state exceeded the constant value
{'bibliographic_information': "{'country': 'US', 'doc-number': '11000227', 'kind': 'B2', 'date': '20041201', 'extension': '40', 'invention_title': 'Input key and input apparatus'}", 'source_file': './grant/2006/ipg060207.xml', 'source_data': 'USPTO-Grant'}