Abstract:
The present invention relates to a toroidal-type continuously variable transmission which comprises: a casing; input and output disks respectively including inner surfaces, disposed concentrically with each other inside the casing, and supported so as to rotated independently of each other; a plurality of trunnions each including even-numbered pivot shafts existing at right angles to a central-axis direction of the disks and disposed concentrically with to in parallel to each other, and being swingable about the pivot shafts; a plurality of shift shafts respectively projected out from the trunnions; a plurality of power rollers held by and between respective inner surfaces of the disks so as to be rotatably supported on the shift shafts; and a support member fixed directly to the casing and supporting the pivot shafts so as to be shifted in an axial and an inclined rotation direction thereof.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The present invention relates to a toroidal-type continuously variable transmission which can be used as a transmission for vehicles and various industrial machines.  
           [0002]    A toroidal-type continuously variable transmission of a double cavity system, which is used, for example, as a transmission for a car, is structured as shown in FIGS. 15 and 16. That is, as shown in FIG. 15, inside a casing  1 , an input shaft  2  is rotatably supported. On the outer periphery of the input shaft  2 , a circular-pipe-shaped transmission shaft  3  is supported. In this case, the transmission shaft  3  is arranged concentrically with the input shaft  2  and can be rotated with respect to the input shaft  2 .  
           [0003]    On the near-to-two-end-portions of the transmission shaft  3 , first and second input disks  4  and  5  are supported respectively through their associated ball splines  6 . In this case, the first and second input disks  4  and  5  are disposed concentrically with each other, and their respective inner surfaces  4   a  and  5   a  mutually opposed to each other. In addition the first and second input disks  4  and  5  can be rotated in synchronization with each other inside the casing  1 .  
           [0004]    On the periphery of the middle portion of the transmission shaft  3 , first and second output disks  7  and  8  are supported through a sleeve  9 . On the outer peripheral surface of the middle portion of the sleeve  9 , an output gear  10  is disposed in such a manner that they are united together as an integral body. This output gear  10  is arranged concentrically with the transmission shaft  3  and has an inside diameter larger than the outside diameter of the transmission shaft  3 . Also, the output gear  10  is rotatably supported through a pair of rolling bearings  12  on a support wall  11  disposed within the casing  1 .  
           [0005]    The first and second output disks  7  and  8  are spline engaged with the two end portions of the sleeve  9 . In this case, the first and second output disks  7  and  8  are disposed such that their respective inner surfaces  7   a  and  8   a  are directed in the mutually opposite directions. Therefore, the inner surfaces  4   a  and  7   a  of the first input and output disks  4  and  7  are opposed to each other, while the outer surfaces  5   a  and  8   a  of the second input and output disks  5  and  8  are opposed to each other.  
           [0006]    As shown in FIG. 16, laterally of the first and second output disks  7  and  8  inside the casing  1 , a pair of yokes  13   a  and  13   b  are supported in such a manner that they sandwich the two disks  7  and  8  from both sides thereof. The pair of yokes  13   a  and  13   b  are formed of metal such as steel by press working or by forging in a rectangular shape. In addition, in order to support pivot shafts  16  respectively disposed on the respective two end portions of two trunnions  14  (which will be discussed later) in such a manner that they can be swung, there are formed circular-shaped support holes  18  in the four corners of the yokes  13   a  and  13   b.  In the width-direction central portions of the yokes  13   a  and  13   b,  there are formed circular-shaped securing holes  19 .  
           [0007]    The pair of yokes  13   a  and  13   b  are supported on a pair of spherical-surface-shaped support posts  20   a  and  20   b  respectively formed in the mutually opposed portions of the inner surface of the casing  1  in such a manner that they can be shifted slightly. The two support posts  20   a  and  20   b  are respectively disposed in a first cavity  21  and a second cavity  22  in such a manner that they are opposed to each other. The first cavity  21  is an intermediate portion between the inner surface  4   a  of the first input disk  4  and the inner surface  7   a  of the first output disk  7 . The second cavity  22  is an intermediate portion between the inner surface  5   a  of the second input disk  5  and the inner surface  8   a  of the second output disk  8 . Therefore, in the state of that the pair of yokes  13   a  and  13   b  are supported on their associated support posts  20   a  and  20   b,  they are disposed in such a manner that the one-end portions of the pair of yokes  13   a  and  13   b  are opposed to the outer peripheral portion of the first cavity  21 , and the other-end portions thereof are opposed to the outer peripheral portion of the second cavity  22  in an axial direction of the transmission shaft  3 .  
           [0008]    The first and second cavities  21  and  22  are the same in structure. Therefore, the description thereof will be given below only of the first cavity  21 .  
           [0009]    In the first cavity  21 , there are disposed a pair of trunnions  14 . On the two end portions of each of the trunnions  14 , pivot shafts  16  are disposed so as to be concentric with each other. These pivot shafts  16  are supported on the one-end portions of the pair of yokes  13   a  and  13   b  in such a manner that they can be swung and can be shifted in the axial direction thereof. That is, the pivot shafts  16  are supported inside support holes  18  formed in the one-end portions of the pair of yokes  13   a  and  13   b  by radial needle roller bearings  26  respectively. Each of the radial needle roller bearings  26  is composed of an outer race  27 , the outer peripheral surface thereof has a spherical-shaped convex surface and the inner peripheral surface thereof has a cylindrical-shaped surface, and a plurality of needle rollers  28 .  
           [0010]    There is circular hole  30  on an intermediate of the respective trunnions  14 . In the respective circular holes  30 , shift shafts  31  are supported. Each of the shift shafts  31  includes a support shaft portion  33  and a pivot support shaft portion  34  which are parallel to each other but are eccentric with respect to each other. The support shaft portion  33  is supported inside the circular hole  30  through a radial needle roller bearing  35 . On the periphery of the pivot support shaft portion  34 , there is supported a power roller  36  through another radial needle roller bearing  38 .  
           [0011]    By the way, a pair of the shift shafts  31  are provided in every set of first and second cavities  21 ,  22 . The pair of the shift shafts  31  are disposed in such a manner that they are situated on the 180° opposite side to the input shaft  2  and transmission shaft  3  respectively in every set of first and second cavities  21 ,  22 . Also, the directions of the pivot support shaft portions  34  of the shift shafts  31  are eccentric with respect to the support shaft portions  33  of the shift shafts  31 . The direction of the pivot support portion  34  is the same direction as the rotation direction of the first and second input disks  4 ,  5  as well as first and second output disks  7 ,  8 . Further, the eccentric direction is also substantially perpendicular to the mounting direction of the input shaft  2 . Therefore, each power roller  36  is supported in such a manner that it can be slightly shifted along the longitudinal direction of the input shaft  2  and transmission shaft  3 . As a result of this, there is a case where the power roller  36  tends to shift in the axial direction of the input shaft  2  and transmission shaft  3  due to variations in the elastic deformation amount of component members caused by variations in the torque that is transmitted from the toroidal-type continuously variable transmission. In this case, there can be avoided the possibility that an unreasonable force can be applied to the component members, and thus the shifting movement of the power roller  36  can be absorbed.  
           [0012]    Also, between the outer peripheral surface of the power roller  36  and the inner peripheral surface of the middle portion of the trunnion  14 , there are interposed a thrust ball bearing  39  and a thrust bearing  40  such as a sliding bearing or a needle roller bearing by turns from the outer surface of the power roller  36 . The thrust ball bearing  39 , while supporting a thrust-direction load to be applied to the power roller  36 , allows the power roller  36  to rotate. Also, the thrust bearing  40 , while supporting a thrust load to be applied to the outer race  41  of the thrust ball bearing  39  from the power roller  36 , allows the pivot support shaft portion  34  and outer race  41  to be swung about the support shaft portion  33 .  
           [0013]    To one end portion of each of the trunnions  14 , there is connected a drive rod  42 . To the outer peripheral surface of the middle portion of the drive rod  42 , there is fixed a drive piston  43 . This drive piston  43  is fitted oil-tight into a drive cylinder  44 . And, the drive piston  43  forms an actuator, which is used to shift the trunnion  14  in the axial direction thereof.  
           [0014]    As shown in FIG. 15, between the input shaft  2  and first input disk  4 , there is interposed a pressure device  45  of a loading cam type. This pressure device  45  includes a cam plate  46  and a plurality of rollers  48  and is arranged such that, due to the rotation of the input shaft  2 , it can press the first input disk  4  toward the second input disk  5  and rotate the first input disk  4 . In this case, the cam plate  46  is spline engaged with the middle portion of the input shaft  2 . The cam plate  46  is also supported in such a manner that it is prevented from shifting in the axial direction of the input shaft  2 . The cam plate  46  can be rotated together with the input shaft  2 . Also, the plurality of rollers  48  are rollably held on a retainer  47 .  
           [0015]    When the above toroidal-type continuously variable transmission is in operation, the rotation of the input shaft  2  is transmitted through the pressure device  45  to the first input disk  4 , so that the first and second input disks  4  and  5  are rotated in synchronization with each other. The rotational movements of the first and second input disks  4  and  5  are transmitted through the power rollers  36  to the first and second output disks  7  and  8 . The rotational movements of the first and second output disks  7  and  8  are taken out by the output gear  10 .  
           [0016]    To change a rotation speed ratio between the input shaft  2  and output gear  10 , in accordance with the switching operation of a control valve (not shown), the drive pistons  43 , a pair of which are disposed in each of the first and second cavities  21  and  22 , may be shifted by the same distance in the mutually opposite directions in every cavities  21  and  22 . With the shifting movements of the drive pistons  43 , two pairs of trunnions  14 , that is, a total of four trunnions  14  are respectively shifted in the opposite directions, so that one power roller  36  is shifted downward and the other power roller  36  is shifted upward. This changes the direction of a tangential-direction force which acts on the contact portion between the peripheral surfaces of the respective power rollers  36  and the inner surfaces  4   a,    5   a  of the first and second input disks  4 ,  5  and the inner surfaces  7   a,    8   a  of the first and second output disks  7 ,  8 . In addition, with such change in the direction of the tangential-direction force, the trunnions  14  are swung in the opposite directions about the pivot shafts  16  pivotally supported on the yokes  13   a  and  13   b.  This changes the contact positions between the peripheral surfaces of the power rollers  36  and the first and second input disks  4 ,  5  as well as first and second output disks  7 ,  8 , thereby changing the rotation speed ratio between the input shaft  2  and output gear  10 .  
           [0017]    However, in the above-structured conventional toroidal-type continuously variable transmission, since the trunnions  14  are supported inside the casing  1  through the support posts  20   a,    20   b  and yokes  13   a,    13   b,  the number of parts is increased. This complicates the manufacturing operation of the parts, the managing operation of the parts and the assembling operation of the parts. This also increases the height dimension of the toroidal-type continuously variable transmission to thereby be unable to reduce the size and weight of the toroidal-type continuously variable transmission.  
           [0018]    Also, generally, in the case of a vehicle of an FR system, in order to be able to secure living space within the vehicle, the upper portion of the casing  1  must be formed compact. That is, as shown in FIG. 17, when the casing  1  is viewed from the axial direction thereof, it provides a projecting shape; and, the inside space of the casing upper portion  1   a  is formed narrower than the inside space of the casing lower portion  1   b.    
           [0019]    In the above-mentioned conventional toroidal-type continuously variable transmission, the upper and lower portions of the trunnions  14  are swingably supported inside the casing  1  through the support posts  20   a,    20   b  and yokes  13   a,    13   b.  Then, in order to the upper yoke  13   a  can be swung about the support post  20   a  in the gear change operation, a sufficient inside space must be secured in the casing upper portion la. However, as described above, in case where the upper portion of the casing  1  must be formed compact, a sufficient inside space cannot be secured in the casing upper portion  1   a.    
           [0020]    Also, there is a case where the upper and lower pivot shafts  16  of the trunnions  14  are swingably supported inside the casing  1  through the support posts  20   a,    20   b  and yokes  13   a,    13   b.  In this case, the number of parts increases, and it complicates that the operation to manufacture the parts, the operation to manage the parts and the operation to assemble the parts.  
           [0021]    Further, the upper yoke  13   a  is connected to the upper pivot shaft  16  of the trunnion  14  through the radial needle roller bearing  26  restricted by an axial-direction restrict member which is designated by a numeral  49  in FIG. 17. However, in this structure, when the upper pivot shaft  16  of the trunnion  14  is swung, stresses are concentrated on the portions thereof which are contacted with the axial-direction restrict member  49  and radial needle roller bearing  26 , which degrades the durability of the pivot shaft  16 .  
           [0022]    In view of the above, for example, as shown in FIG. 4 of Japanese Patent Unexamined Publication No. 2000-9200, there has been developed a structure in which a yoke is fixed directly to the inside of a casing. In addition there has been also developed two pivot shafts disposed on the two end portions of each trunnion are supported on the yoke through ball splines in such a manner that they can be moved in the vertical direction.  
           [0023]    According to the above structure, since the yoke is fixed directly to the casing, the number of parts can be reduced. This can simplify the parts manufacturing operation, the parts managing operation and the parts assembling operation. In addition, this can also decrease the height dimension of the toroidal-type continuously variable transmission to thereby able to reduce the size and weight of the toroidal-type continuously variable transmission.  
           [0024]    However, in the above-mentioned toroidal-type continuously variable transmission disclosed in Japanese Patent Unexamined Publication 2000-9200, the ball spline is formed in the pivot shaft of the trunnion and thus the pivot shaft is able to move in the vertical direction. Also, the outer race of the ball spline provides a spherical surface, whereby, when the trunnion is elastically deformed, the trunnion can be prevented from application of the edge loads. Further, due to the needle roller bearing of the inner race of the ball spline, the trunnion is able to rotate inclinedly about the pivot shaft.  
           [0025]    Therefore, the trunnion support structure is complicated and thus the number of parts is also large. Also, when a ball is assembled into the upper ball spline, a hole must be made in the casing, which lowers the rigidity of the casing. Further, in the case of the ball spline which allows the trunnion to move in the vertical direction, as the ball movements, there coexist a sliding movement and a rolling movement according to the positions of the ball when assembling the ball into the upper ball spline. Generally, the friction coefficient of the rolling movement is at least one digit smaller than that of the sliding movement; and, for this reason, in case where a sliding movement exists together with the vertical-direction movements of the trunnions, the vertical-direction forces in the respective trunnions are uneven.  
           [0026]    Also, according to the above-mentioned toroidal-type continuously variable transmission disclosed in Japanese Patent unexamined Publication 2000-9200, by fixing all yokes directly to the inside of the casing, the number of parts is reduced, which makes it unnecessary to secure the inner space of the casing. However, there is no system which, in the gear change operation, can mechanically guarantee the synchronization of the vertical-direction movements of all trunnions, so that the vertical-direction movements of the trunnions are unstable.  
         SUMMARY OF THE INVENTION  
         [0027]    The present invention aims at eliminating the drawbacks found in the above-mentioned toroidal-type continuously variable transmissions. Accordingly, it is an object of the invention to provide a toroidal-type continuously variable transmission which omits the ball spline from the trunnions to thereby be able to reduce the number of parts and facilitate the assembling of the parts. It is also an object of the invention to provide a toroidal-type continuously variable transmission which is also able to equalize or standardize the vertical-direction movements of the respective trunnions.  
           [0028]    Also, it is another object of the invention to provide a toroidal-type continuously variable transmission which can make the casing compact in order to enhance the mountability of the present transmission into a vehicle. In addition, it is another object of the invention to provide a toroidal-type continuously variable transmission which can enhance the guarantee of the synchronization of the vertical-direction movements of all trunnions in the gear change operation.  
           [0029]    In attaining the above objects, according to a first aspect of the invention, there is provided a toroidal-type continuously variable transmission, comprising: a casing; input and output disks respectively including inner surfaces, disposed concentrically with each other inside the casing, and supported in such a manner that they are rotated independently of each other; a plurality of trunnions each including even-numbered pivot shafts existing at twisted positions which are at right angles to a central-axis direction of the input and output disks and disposed concentrically with to in parallel to each other, and being swingable about the pivot shafts; a plurality of shift shafts respectively projected out from an inner surfaces of the trunnions; a plurality of power rollers held by and between respective facing inner surfaces of the input and output disks in such a manner that they are rotatably supported on the shift shafts; and a support member fixed directly to the casing and supporting the pivot shafts of the trunnions in such a manner that they are shifted in an axial direction thereof and in an inclined rotation direction thereof.  
           [0030]    It is preferable that the above toroidal-type continuously variable transmission further includes: a plurality of needle roller bearings for supporting the pivot shafts of the trunnions on the support member; and a plurality of spherical-surface bearings for supporting the needle roller bearings; wherein the spherical-surface bearings each includes spherical-surface-shaped inner and outer races.  
           [0031]    It is preferable that, in the above toroidal-type continuously variable transmission, wherein the outer race of the spherical-surface bearing include one cut-out portion in an inner peripheral surface of spherical surface thereof, and the inner race is press-fitted the outer race from the cut-out portion to thereby unite the inner and outer races as an integral body.  
           [0032]    It is preferable that, in the above toroidal-type continuously variable transmission, wherein the support member and the outer race of the spherical-surface bearing are formed as an integral body.  
           [0033]    It is preferable that, in the above toroidal-type continuously variable transmission, wherein the axial-direction shifting movement of the trunnion is carried out between the pivot shaft and the needle roller bearing by a sliding movement of the trunnion.  
           [0034]    It is preferable that, in the above toroidal-type continuously variable transmission, wherein the axial-direction shifting movement of the trunnion is carried out between the needle roller bearing and the spherical-surface bearing by a sliding movement of the trunnion.  
           [0035]    It is preferable that the above toroidal-type continuously variable transmission comprises: a casing; input and output disks respectively including inner surfaces, disposed concentrically with each other inside the casing, and supported in such a manner that they are rotated independently of each other; a plurality of trunnions each including an even-numbered pivot shafts of upper and lower portions thereof existing at twisted positions which are at right angles to a central-axis direction of the input and output disks and disposed concentrically with or in parallel to each other, the trunnions respectively being swingable about the pivot shafts; a plurality of shift shafts respectively projected out from the inner surfaces of the trunnions; a plurality of power rollers held by and between respective facing inner surfaces of the input and output disks in such a manner that they are rotatably supported on the shift shafts; and upper and lower support members respectively supporting the pivot shafts of upper and lower portions of the trunnions, wherein one of the upper and lower support members is fixed directly to the casing and the other of the upper and lower support members is swingably supported on the casing.  
           [0036]    It is preferable that, in the above toroidal-type continuously variable transmission, wherein the toroidal-type continuously variable transmission is installed into a vehicle of an FR type, the upper support member is fixed directly to the casing, and the lower support member is swingably supported on the casing.  
           [0037]    It is preferable that, in the above toroidal-type continuously variable transmission, wherein the pivot shafts of the trunnions are respectively supported by their associated radial needle roller bearings and ball splines in such a manner that they are swingingly shifted and are shifted in an axial direction thereof.  
           [0038]    It is preferable that, in the above toroidal-type continuously variable transmission, wherein each of the ball splines is disposed on an outer periphery of the radial needle roller bearing.  
           [0039]    According to the above structure, the vertical-direction movements of the respective trunnions are smooth and the forces can be equalized in the respective trunnions. Also, when the pivot shafts of the trunnions are shifted in the vertical direction thereof, the trunnions are rotated about the pivot shafts of the trunnions simultaneously with the vertical-direction shifting movements of the pivot shafts. Therefore, the movements of the trunnions provide rolling movements although they include slight degrees of sliding movements. This can reduce the frictional forces much more than a simple sliding movement, thereby being able to enhance the synchronization and stability of the vertical-direction movements of the trunnions in the gear change operation. Also, the position, which is at right angle to a central-axis, is herein after referred to as “twisted position”.  
           [0040]    Also, according to a second aspect of the invention, there is provided a toroidal-type continuously variable transmission, comprising: a casing; input and output disks respectively including inner surfaces, and supported concentrically with each other in such a manner that their respective inner surfaces opposed to each other and they are supported rotatably in an inside of the casing; a plurality of trunnions respectively including a plurality of pivot shafts disposed at twisted positions with respect to a central-axes of the input and output disks, wherein the trunnions being swingable about the pivot shafts; a plurality of shift shafts supported in such a manner that they are projected from an inner surfaces of the trunnions; a plurality of power rollers respectively held by and between the input and output disks in such a manner that they are rotatably supported on peripheries of the shift shafts; and a yoke fixed directly to the casing and including a bearing for supporting the pivot shafts of the trunnions.  
           [0041]    It is preferable that, in the above toroidal-type continuously variable transmission, wherein the bearing disposed on the yoke, comprising: an outer race fixed to the yoke; an inner race formed by an outer peripheral surface of the pivot shaft of the trunnion; and a roller rollably interposed between the outer race and the inner race, wherein the bearing supports the pivot shafts of each of the trunnions in such a manner that the pivot shafts shift in an axial direction thereof and in an inclined rotation direction thereof, a raceway surface of the inner race is formed as a straight-shaped surface extending in the axial direction of the pivot shaft, a raceway surface of the outer race is formed as a curved surface having a given radius of curvature, and an outer peripheral surface of the roller to be contacted with the inner race and the outer race is formed as a curved surface having a given radius of curvature.  
           [0042]    According to the second aspect of the invention, because the roller is embraced by the curved surface of the outer race, the axial-direction movement of the trunnion is made only on the inner race side. That is, the trunnion axial-direction movement is carried out not on the outer race side, where the contact area of the trunnion with the roller increases due to the spherical surface contact between them. However, the trunnion axial-direction movement is carried out on the inner race side, where the contact area of the trunnion with the roller decreases due to the point contact between the linear-shaped rolling surface and the curved surface. This can reduce the dynamic friction of the trunnion when the trunnion moves in the axial direction thereof, which leads to the stabilized gear change operation.  
           [0043]    Further, according to a third aspect of the invention, in a toroidal-type continuously variable transmission as set forth in the second aspect of the invention, wherein the bearing disposed on the yoke, comprising: an outer race fixed to the yoke; an inner race formed by an outer peripheral surface of the pivot shaft of the trunnion; and a roller rollably interposed between the outer race and the inner race, wherein the bearing supports the pivot shafts of each of the trunnions in such a manner that the pivot shafts shift in an axial direction thereof and in an inclined rotation direction thereof, a raceway surface of the outer race is formed in a straight-shaped surface extending in the axial direction of the pivot shaft, a raceway surface of the inner race is formed as a curved surface having a given radius of curvature, and a outer peripheral surface of the roller to be contacted with the inner race and the outer race is formed as a curved surface having a given radius of curvature.  
           [0044]    Therefore, according to the third aspect of the invention, the axial-direction movement of the trunnion is made only on the outer race side which has a small contact area. This can reduce the dynamic friction of the trunnion when the trunnion moves in the axial direction, which leads to the stabilized gear change operation. Also, generally, in the case of a bearing, the inner race side is severer in surface pressure than the outer race side. Therefore, under the using condition which requires a severe surface pressure, as in the third aspect of the invention, in case where the raceway surface of the inner race is formed as a curved surface and the raceway surface of the outer race is formed as a linear-shaped surface, the surface pressure can be reduced.  
           [0045]    According to a fourth aspect of the invention, in a toroidal-type continuously variable transmission as set forth in the second aspect of the invention, wherein the bearing disposed on the yoke, comprising: a needle roller to be contacted with the pivot shaft of the trunnion; and a spherical-surface bearing, wherein the bearing supports the pivot shafts of the trunnion in such a manner that the pivot shafts can be shifted in an axial direction thereof and in an inclined rotation direction thereof, and the needle roller is divided in the axial direction of the pivot shaft into a plurality of parts.  
           [0046]    Therefore, according to the fourth aspect of the invention, since the needle roller is divided into two sections, not only the edge load can be reduced but also the gear change operation of the trunnion can be executed smoothly.  
           [0047]    According to a fifth aspect of the invention, a toroidal-type continuously variable transmission as set forth in the second aspect of the invention, wherein the bearing disposed on the yoke, comprising: a needle roller to be contacted with the pivot shaft of the trunnion; and a spherical-surface bearing, wherein the bearing supports the pivot shafts of the trunnion in such a manner that the pivot shafts shift in an axial direction thereof and in an inclined rotation direction thereof, and wherein the spherical-surface bearing includes an outer race fixed to the yoke and an inner race to be spherical-surface connected to the outer race and holding the needle roller, a center of curvature of connecting surface of the inner race to be spherical-surface connected to the outer race of the spherical-surface bearing lies on the inclined rotation axis of the trunnion, a center of curvature of connecting surface of the outer race to be spherical-surface connected to the inner race lies to keep away from the inclined rotation axis of the trunnion, and the radius of curvature of connecting surface of the inner race is set smaller than the radius of curvature of connecting surface of the outer race.  
           [0048]    Therefore, according to the fifth aspect of the invention, the elastic deformation of the trunnion can be absorbed easily.  
           [0049]    According to a sixth aspect of the invention, a toroidal-type continuously variable transmission as set forth in the second aspect of the invention, wherein the bearing disposed on the yoke, comprising: a needle roller to be contacted with the pivot shaft of the trunnion; and a spherical-surface bearing, wherein the bearing supports the pivot shafts of the trunnion in such a manner that the pivot shafts can be shifted in an axial direction thereof and in an inclined rotation direction thereof, the spherical-surface bearing includes an outer race fixed to the yoke, an inner race to be spherical-surface connected to the outer race and holding the needle roller, a clearance is formed between the inner race and the outer race, and the central-axis of the outer race of the spherical-surface bearing is offset with respect to the inclined rotation axis of the trunnion.  
           [0050]    It is preferable that, in the above toroidal-type continuously variable transmission, wherein a center of curvature of connecting surface of the inner race to be spherical-surface connected to the outer race of the spherical-surface bearing lies on an inclined rotation axis of the trunnion, a center of curvature of connecting surface of the outer race to be spherical-surface connected to the inner race lies to keep away from the inclined rotation axis of the trunnion, and the radius of curvature of connecting surface of the inner race is set smaller than the radius of curvature of connecting surface of the outer race.  
           [0051]    It is preferable that, in the above toroidal-type continuously variable transmission, wherein the radius of curvature of connecting surface of the inner race and the radius of curvature of connecting surface of the outer race are set equal to each other.  
           [0052]    It is preferable that, in the above toroidal-type continuously variable transmission, wherein the connecting surface of the outer race is formed as a straight-shaped surface.  
           [0053]    Therefore, according to the sixth aspect of the invention, when the trunnion is elastically deformed, the deformation of the trunnion can be absorbed by a clearance formed between the inner and outer races. Therefore, even in case where the trunnion is deformed, the deformation has no ill effects on the gear change operation. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0054]    [0054]FIG. 1 shows a toroidal-type continuously variable transmission according to a first embodiment of the invention, specifically, a section view thereof corresponding to the section view taken along the line A-A shown in FIG. 15;  
         [0055]    [0055]FIGS. 2A to  2 C show an outer race of a spherical-surface bearing employed in the first embodiment, specifically, FIG. 2A is a plan view thereof, FIG. 2B is a section view thereof taken along the line B-B shown in FIG. 2A, and FIG. 2C is a section view taken along the line C-C shown in FIG. 2A;  
         [0056]    [0056]FIG. 3 shows a toroidal-type continuously variable transmission according to a second embodiment of the invention, specifically, a section view thereof corresponding to the section view taken along the line A-A shown in FIG. 15;  
         [0057]    [0057]FIG. 4 is a section view of a support structure of a pivot shaft of a trunnion employed in a toroidal-type continuously variable transmission according to a third embodiment of the invention;  
         [0058]    [0058]FIG. 5 is a longitudinal section view of a toroidal-type continuously variable transmission according to a fourth embodiment of the invention;  
         [0059]    [0059]FIG. 6 is a section view of a structure for supporting an upper pivot shaft of a trunnion employed in a toroidal-type continuously variable transmission according to a fifth embodiment of the invention;  
         [0060]    [0060]FIG. 7 is a section view of the main portions of a toroidal-type continuously variable transmission according to a sixth embodiment of the invention;  
         [0061]    [0061]FIG. 8 is a section view of the main portions of a toroidal-type continuously variable transmission according to a seventh embodiment of the invention;  
         [0062]    [0062]FIG. 9 is an enlarged view of the main portions of the structure shown in FIG. 7;  
         [0063]    [0063]FIG. 10 is a section view of the main portions of a toroidal-type continuously variable transmission according to an eighth embodiment of the invention;  
         [0064]    [0064]FIG. 11 is a section view of the main portions of a toroidal-type continuously variable transmission according to a ninth embodiment of the invention;  
         [0065]    [0065]FIG. 12 is a section view of the main portions of a toroidal-type continuously variable transmission according to a first example of a tenth embodiment of the invention;  
         [0066]    [0066]FIG. 13 is a section view of the main portions of a toroidal-type continuously variable transmission according to a second example of the tenth embodiment of the invention;  
         [0067]    [0067]FIG. 14 is a section view of the main portions of a toroidal-type continuously variable transmission according to a third example of the tenth embodiment of the invention;  
         [0068]    [0068]FIG. 15 is a section view of a conventional toroidal-type continuously variable transmission;  
         [0069]    [0069]FIG. 16 is a section view taken along the line A-A shown in FIG. 15;  
         [0070]    [0070]FIG. 17 is a section view of another conventional toroidal-type continuously variable transmission, corresponding to the section view shown in FIG. 16;  
         [0071]    [0071]FIG. 18 is a section view of a trunnion, explaining the elastic deformation of the trunnion; and,  
         [0072]    [0072]FIG. 19 is a section view of the trunnion shown in FIG. 17, showing a state in which the trunnion is elastically deformed. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0073]    Now, description will be given below of the preferred embodiments of a toroidal-type continuously variable transmission according to the invention with reference to the accompanying drawings. However, in the following embodiments, parts, which are the same in structure as the previously described conventional transmissions, are given the same designations and thus the description thereof omitted.  
         [0074]    [0074]FIGS. 1 and 2 show a first embodiment of a toroidal-type continuously variable transmission according to the invention. That is, FIG. 1 is a section view of the first embodiment, corresponding to the line A-A shown in FIG. 15. FIGS. 2A to  2 C show an outer race used in a needle roller bearing; and, specifically, FIG. 2A is a plan view of the outer race, FIG. 2B is a section view taken along the line B-B shown in FIG. 2A, and FIG. 2C is a section view taken along the line C-C shown in FIG. 2A.  
         [0075]    As shown in FIG. 1, in the inside portions of a casing  1  that are opposed to each other, there are directly fixed an upper yoke  51  and a lower yoke  52  serving as support members. On the upper and lower yokes  51  and  52 , needle roller bearings  53  are disposed respectively. Each of the needle roller bearings  53  is supported by a spherical-surface bearing  50  and supports the pivot shafts  16  of a trunnion  14  in such a manner that the pivot shafts  16  can be shifted in the axial (vertical) direction thereof and in the inclined rotation direction thereof.  
         [0076]    That is, each spherical-surface bearing  50  includes an inner race  54  and an outer race  55 . The inner and outer races  54  and  55  respectively include spherical surfaces  54   a  and  55   a  that can be spherical-surface connected with each other. In the two end portions of the outer race  55 , as shown in FIGS. 2A to  2 C, a plurality of bolt holes  56  are formed. The outer race  55  is fixed to the upper yoke  51  or lower yoke  52  through bolts  57  respectively inserted into their associated bolt holes  56 . In the present embodiment, holes formed in the upper and lower yokes  51  and  52  and the outer races  55  of the spherical-surface bearings are positioned through intermediate-quality fit with high accuracy with respect to the casing  1 . By the way, since the positions of the spherical-surface bearings  50  determine the positions of the trunnions  14 , the spherical-surface bearings  50  can also be positioned accurately by positioning pins with respect to the upper and lower yokes  51  and  52 . In the two portions of the inner peripheral surface of the outer race  55 , two cut-out portions  58  are formed. By pressure inserting the inner race  54  into the outer race  55  from the two cut-out portions  58 , the inner and outer races  54  and  55  can be united together into an integral body.  
         [0077]    And, on the inner race  54  of the spherical-surface bearing  50 , the pivot shaft  16  of the trunnion  14  is supported. Since the pivot shaft  16  serves as the rolling surface of the needle roller bearing  53 , the pivot shaft  16  is heat treated by high-frequency quenching and the hardness of the pivot shaft  16  is thereby enhanced. Further, in the upper and lower yokes  51  and  52 , lubricating oil passages  59  are formed. The lubricating oil passages  59  respectively communicate with the spherical-surface bearings  50  and needle roller bearings  53 . In the outer races  55  and pivot shafts  16 , oil holes are formed, whereby a sufficient quantity of lubricating oil can be supplied to the spherical-surface bearings  50  and needle roller bearings  53 . Also, the lubricating oil passages  59  are formed so as to communicate up to the radial needle roller bearings  35  of the trunnions  14 .  
         [0078]    Further, since the trunnion  14  is free to shift in the vertical direction thereof, in the portion A between the lower surface of the outer race  55  and the upper surface of the trunnion  14 , in the portion B between the upper surface of the outer race  55  and the lower surface of the trunnion  14 , in the portion C between the lower surface of the outer race  55  and the upper surface of a pulley  60  for a safety cable, and in the portion D between the pulley  60  for a safety cable and the lower yoke  52 , there are formed clearances which correspond to the vertical stroke of the trunnion  14 . Since the stroke quantity of the trunnion  14  is determined by the stroke quantity of a drive piston  43 , the clearances in the portions A, B, C and D are designed slightly larger than the strokes E, F of the drive pistons  43 . Therefore, preventing interference when the trunnion  14  shifts in the vertical direction thereof.  
         [0079]    Referring to the order for assembling the trunnion part of the thus structured toroidal-type continuously variable transmission, the upper yoke  51  and the inner and outer races  54 ,  55  of the spherical-surface bearings  50 , while they are united together as an integral body, are assembled into the casing  1 . Next, the pivot shafts  16  of the trunnions  14  having the power rollers  36  mounted thereon, are assembled onto the inner races of the spherical-surface bearings  50 . Finally, the lower yoke  52 , which is united with the inner and outer races  54 ,  55  of the spherical-surface bearings  50  as an integral body, is assembled into the casing  1  from bottom. Therefore, without making any hole in the casing  1 , the trunnion part can be assembled, which can prevent the lowered rigidity of the casing  1 .  
         [0080]    Also, conventionally, in the case of ball splines which allow the trunnions to move in the vertical direction, depending on the positions of the balls when assembling the trunnion part, a sliding movement and a rolling movement of the balls coexist in each of the balls. This causes the vertical-direction forces of the trunnions to vary unevenly. On the other hand, according to the above-structured toroidal-type continuously variable transmission of the invention, the vertical-direction movements of the trunnions  14  consist only of a single kind of movement, thereby being able to equalize the forces in the respective trunnions  14 . Further, when the pivot shafts  16  of the trunnions  14  are shifted in the vertical direction thereof, the trunnions  14  are rotated about the pivot shafts  16  simultaneously with the vertical-direction shifting movements of the pivot shafts  16 . Therefore, the movements of the trunnions  14  provide rolling movements although they include slight degrees of sliding movements. This can reduce the frictional forces much more than a simple sliding movement, thereby being able to enhance the synchronization and stability of the movements of the trunnions in the gear change operation.  
         [0081]    Now, FIG. 3 shows a second embodiment of a toroidal-type continuously variable transmission according to the invention. In the second embodiment, parts having the same structures as the first embodiment are given the same designations and thus the description thereof is omitted. In the present embodiment, the upper and lower yokes  51  and  52  are united with the outer races  55  of the spherical-surface bearings  50  as an integral body. This not only can omit time and labor for fixing the outer races  55  to the upper and lower yokes  51  and  52  using the bolts  57  but also can reduce the number of parts.  
         [0082]    [0082]FIG. 4 shows a third embodiment of a toroidal-type continuously variable transmission according to the invention. In the third embodiment, parts having the same structures as the first embodiment are given the same designations and thus the description thereof is omitted. In the first embodiment, when the trunnions  14  shift in the vertical direction, they slide between the pivot shafts  16  of the trunnions  14  and the needle roller bearings  53 . On the other hand, in the present embodiment, when the trunnions  14  shift in the vertical direction, they slide between the needle roller bearings  53  and the inner races  54  of the spherical-surface bearings  50 .  
         [0083]    Now, FIG. 5 shows a fourth embodiment of a toroidal-type continuously variable transmission according to the invention. In the fourth embodiment, on the inner surface of the casing  1 , more specifically, laterally of the first and second output disks  7 ,  8 , there are supported an upper yoke  51  and a lower yoke  52  in such a manner that they hold the two disks  7 ,  8  from both sides.  
         [0084]    The upper yoke  51  is fixed to the inner wall of the casing  1  (the inner wall of the casing upper portion  1   a ) through a fixing member, whereas the lower yoke  52  is swingably disposed within the inner space of the casing lower portion  1   b.    
         [0085]    In the four corners of the upper yoke  51 , there are formed support holes  18  respectively and, in each of the four support holes  18 , there is disposed a needle roller bearing  53 . The needle roller bearing  53  is supported by a spherical-surface bearing  54  in contact with the inner periphery of the support hole  18 . Whereby, the upper pivot shaft  16  of the trunnion  14  is supported in such a manner that it can be shifted not only in the axial direction (vertical direction) thereof but also in the inclined rotation direction thereof.  
         [0086]    According to the above-structured toroidal-type continuously variable transmission, since the upper yoke  51  is fixed to the inner wall of the casing upper portion  1   a,  there is eliminated the need for securing a space for swinging the yoke as in the conventional toroidal-type continuously variable transmission. Therefore, this structure is ideal for the case where, as in an FR vehicle, the upper portion of the casing  1  must be made compact in order to be able to secure living space within the vehicle. Namely, it is ideal for the casing  1  in which, as shown in FIG. 5, the inside space of the casing upper portion  1   a  is narrower than the inside space of the casing lower portion  1   b.    
         [0087]    Also, since the upper yoke  51  is fixed to the inner wall  1   a  of the casing upper portion  1   a,  the number of parts is reduced, which makes it possible to facilitate the manufacturing of the parts, managing of the parts and assembling of the parts.  
         [0088]    Further, since no limitation is put on the dimension of the lower portion of the casing and, as in the present embodiment, the lower yoke  52  of an a winging type can be mounted into the inside space of the casing lower portion  1   b.  When compared with the toroidal-type continuously variable transmission which is disclosed in Japanese Patent Unexamined Publication 2000-9200 and in which all yokes are fixed directly to the inside of the casing, the synchronizing movements of all trunnions  14  in the vertical direction in the gear change operation can be guaranteed with more accuracy.  
         [0089]    Also, the yoke has a function to cancel the thrust force applied from the four power rollers  36  within the yoke, which makes it necessary that the yoke is formed as thick and large as possible. However, the fixation of the upper yoke  51  to the casing  1  eliminates the provision of the support post and the portion, from which the support post has been eliminated, can be used to increase the thickness of the yoke  51 . This makes it possible to enhance the durability of the upper yoke  51 .  
         [0090]    Next, FIG. 6 shows a fifth embodiment of a toroidal-type continuously variable transmission according to the invention. In FIG. 6, there is shown how to support the upper pivot shaft  16  of the trunnion  14 . Specifically, in the present embodiment, the upper pivot shaft  16  is supported in the support hole  18  of the upper yoke  51  by a radial roller bearing  73  and a ball spline  74  disposed on the outer periphery of the radial roller bearing  73  in such a manner that it can be not only swung and shifted but also shifted in the axial direction (vertical direction) thereof. According to this structure, the trunnion  14  can be shifted smoothly in the axial direction of the upper pivot shaft  16 .  
         [0091]    By the way, in the embodiments respectively shown in FIGS. 5 and 6, the upper yoke  51  is fixed to the casing  1  and the lower yoke  52  is formed so as to be swingable. However, for example, when a larger dimensional limit is put on the lower portion of the casing  1  than on the upper portion thereof, in case where the upper yoke is formed so as to be swingable and the lower yoke is fixed to the casing  1  to thereby be able to escape from the dimensional limit. Therefore, there can be obtained a similar effect to the previously-described embodiments.  
         [0092]    Now, FIG. 7 shows a sixth embodiment of a toroidal-type continuously variable transmission according to the invention. The present embodiment is characterized in that the pivot shaft of the trunnion is supported in such a manner that, even the trunnion is deformed when the toroidal-type continuously variable transmission is in operation, the deformation of the trunnion cannot have any ill influence on the gear change operation. In detail, on yokes  51 ,  52  (see FIGS. 1 and 7) fixed directly to the inside of the casing  1 , pivot shafts  16  mounted on the two end portions of the trunnion  14  are supported in such a manner that the pivot shafts  16  can be shifted not only in the axial direction (the vertical direction, that is, in FIG. 7, a direction shown by arrow marks) but also in the inclined rotation direction through their respective bearings  70  which have the characteristic members of the invention. Each of the bearings  70  is composed of an outer race  55  fixed to its corresponding yoke  51  or  52 , an inner race  16   a  formed by the outer peripheral surface of the pivot shaft  16  of the trunnion  14 , and barrel-shaped rollers rollably interposed between the outer and inner races  55  and  16   a.  In this case, the raceway surface of the inner race  16   a  is formed in a linear-shaped (straight-shaped) surface. Also, the raceway surface  55   a  of the outer race  55  is formed as a curved surface having a radius of curvature R. Further, the outer surface  71   a  of the roller  71  to be contacted with the inner race  16   a,  and the outer surface  71   b  of the roller  71  to be contacted with the outer race  55 , are respectively formed as a curved surface having a radius of curvature r.  
         [0093]    In the present structure, since the rollers  71  are embraced by the curved surface of the outer race  55  having a radius of curvature R, in the gear change operation, the movement of the trunnion  14  in the axial direction (vertical direction) is not made between the rollers  71  and outer race  55 . Therefore, the axial-direction (vertical-direction) movement of the trunnion  14  is made between the straight-surface shaped inner race  16  and rollers  71 .  
         [0094]    As described above, according to the present embodiment, the vertical-direction movement of the trunnion  14  is made only on the inner race  16  side. That is, the vertical-direction movement of the trunnion  14  is made not on the outer race  55  side, where the contact area of the outer race  55  with the rollers  71  increases due to the spherical-surface contact between the R curved surface and r curved surface. The vertical-direction movement of the trunnion  14  is made on the inner race  16   a  side where the contact area of the inner race  16   a  with the rollers  71  decreases due to the point contact between the straight-shaped rolling surface and the r curved surface. For this reason, there is reduced the dynamic friction of the trunnion  14  when the trunnion  14  moves in the vertical direction thereof, which makes it possible to stabilize the gear change operation. That is, in case where the raceway surface  55   a  of the outer race  55  is formed as a curved surface having a radius of curvature R and the raceway surface of the inner race  16   a  is formed as a straight-surface-shaped surface, the skew of the trunnion can be reduced.  
         [0095]    Also, in the present embodiment, the roller  71 , which is involved in the axial-direction movement and swung rotation of the trunnion  14 , is formed as a barrel-shaped roller  71  having a radius of curvature r. Therefore, even in case where the trunnion  14  is elastically deformed, the self-alignment of the trunnion  14  is achieved excellently by the barrel-shaped roller  71 . Namely, as shown in FIG. 17, according to the conventional toroidal-type continuously variable transmission, the roller for supporting the pivot shaft of the trunnion  14  is a needle roller  72  having in the end portion thereof a crowning of the order of several microns. Then, an edge load is easy to be applied to the needle roller. On the other hand, according to the present embodiment, since the roller  71  is a barrel-shaped roller, such an edge load as shown in FIG. 19 can be prevented from being applied to the roller, which makes it possible to carry out the gear change operation with high accuracy.  
         [0096]    Also, according to the present embodiment, since the vertical-direction movement, inclined rotation and elastic deformation of the trunnion  14  in the gear change operation are received only by the bearing  70 , in other words, the vertical-direction movement, inclined rotation and elastic deformation of the trunnion  14  are received substantially only by the outer race  55  and roller  71 , the number of parts is reduced and the structure is simplified. Especially, this arrangement is useful in a structure in which, as in the present embodiment, the yokes  51 ,  52  are fixed directly to the casing  1 . Namely, with use of this arrangement, the number of parts can be reduced, the parts manufacturing operation, parts managing operation and parts assembling operation can be simplified. In addition, the height dimensions of the toroidal-type-continuously variable transmission can be reduced further, thereby being able to promote reduction in the size and weight of the toroidal-type continuously variable transmission over the conventional toroidal-type continuously variable transmission.  
         [0097]    By the way, in the present embodiment, as shown in FIG. 9, the radius of curvature R of the raceway surface of the outer race  55  may also be set larger than the radius of curvature r of the outer peripheral surfaces ( 71   b,    71   a ) of the rollers  71 .  
         [0098]    Now, FIG. 8 shows a seventh embodiment of a toroidal-type continuously variable transmission according to the invention. By the way, in the present embodiment, parts used in common with the sixth embodiment are given the same designations and thus the description thereof is omitted here.  
         [0099]    As shown in FIG. 8, in the present embodiment, the shape of the raceway surface is reversed with respect to the sixth embodiment. That is, the raceway surface of the inner race  16   a  holding the roller  71  is formed as a curved surface having the radius of curvature R, whereas the raceway surface  55   a  of the outer race  55  holding the roller  71  is formed as a linear-shaped (that is, straight-shaped) surface. Also, the outer peripheral surface  71   a  of the roller  71  to be contacted with the inner race  16   a,  and the outer peripheral surface  71   b  of the roller  71  to be contacted with the outer race  55 , are both formed as a curved surface having the radius of curvature r.  
         [0100]    In this arrangement, since the roller  71  is embraced by the curved surface of the inner race  16   a  having the radius of curvature R, in the gear change operation, the axial-direction (vertical-direction) movement of the trunnion  14  is not made between the roller  71  and inner race  16   a.  Therefore, the axial-direction (vertical-direction) movement of the trunnion  14  is made between the straight-surface-shaped outer race  55  and the roller  71 .  
         [0101]    In this manner, the vertical-direction movement of the trunnion  14  is made only on the outer race  55  side where the contact area is small. This can reduce the dynamic friction of the trunnion  14  in the vertical-direction movement of the trunnion  14 , which leads to the stabilized gear change operation. Also, generally, in a bearing, the inner race side thereof is severer in the surface pressure than the outer race side thereof, under the using condition where the surface pressure is severe. Therefore, since the raceway surface of the inner race  16   a  is formed as a curved surface having the radius of curvature R and the raceway surface  55   a  of the outer race  55  is formed so as to be a straight-shaped surface, the surface pressure of the bearing can be reduced.  
         [0102]    Now, FIG. 10 shows an eighth embodiment of a toroidal type continuously variable transmission according to the invention. By the way, in the present embodiment, parts used in common with the sixth embodiment are given the same designations and thus the description thereof is omitted here.  
         [0103]    As shown in FIG. 10, in the present embodiment, the pivot shafts  16  disposed on the two end portions of the trunnion  14  are supported on the yokes  51 ,  52  through the needle roller bearing (needle roller)  64  and spherical-surface bearing  80  in such a manner that the pivot shafts  16  can be shifted in the axial direction (vertical direction) thereof and in the inclined rotation direction thereof. In this case, the spherical surface bearing  80  includes outer races  55  which are respectively fixed to their corresponding yokes  51  and  52 . Also, the needle roller  64  has such a shape that can be obtained when the conventional needle roller  72  shown in FIG. 17, and is divided into two parts in the axial direction of the pivot shaft  16 . The thus-divided two needle rollers  64   a  and  64   b  include a spacer  62  interposed between them, and are supported by a retainer (inner race)  66  which is used to facilitate the assembling of the needle roller  64 . By the way, in the present embodiment, there is shown an example in which the needle roller  64  is divided into two parts. However, the invention is not limited to such division-into-two-parts but the needle roller  64  may only be divided into two or more parts.  
         [0104]    As described above, in case where the needle roller  64  is divided into two parts, not only the edge load of the trunnion  14  can be reduced, but also the gear change operation of the trunnion  14  can be carried out smoothly.  
         [0105]    Now, FIG. 11 shows a ninth embodiment of a toroidal-type continuously variable transmission according to the invention. By the way, in the present embodiment, parts used in common with the sixth and eighth embodiments are given the same designations and thus the description thereof is omitted here.  
         [0106]    As shown in FIG. 11, in the present embodiment, the needle roller  64  (as shown in the eighth embodiment) is not divided into two parts. However, the connecting surface  66   a  of the inner race  66  of the spherical-surface bearing  80  is formed as a curved surface having the radius of curvature r. The connecting surface  55   a  of the outer race  55  of the spherical-surface bearing  80  is formed as a curved surface having the radius of curvature R. In this case, the center of curvature O 3  of the connecting surface  66   a  of the inner race  66  exists on the inclined rotation axis O 1  of the trunnion  14 . However, the center of curvature O 2  of the connecting surface  55   a  of the outer race  55  does not exist on the inclined rotation axis O 1  of the trunnion  14 , so that r&lt;R (R is larger than r). In the case of such structure, the elastic deformation of the trunnion  14  can be absorbed easily.  
         [0107]    Now, FIGS.  12  to  14  show a tenth embodiment of a toroidal-type continuously variable transmission according to the invention. By the way, in the present embodiment, parts used in common with the ninth embodiment are given the same designations and thus the description thereof is omitted here.  
         [0108]    [0108]FIG. 12 shows a first example of the tenth embodiment. In the first example of the tenth embodiment, in addition to the structure of the ninth embodiment, between the inner race  66  and outer race  55 , a clearance S is formed. Namely, the center axis O 4  of the outer race  55  of the spherical-surface  80  is offset with respect to the inclined rotation axis O 1  of the trunnion  14 .  
         [0109]    According to this structure, in the connecting surface (in FIG. 12, the Q portion that is shown by oblique lines) between the outer peripheral surface of the pivot shaft  16  of the trunnion  14  and the needle roller  64 , the vertical-direction movement and inclined rotation of the trunnion  14  are made. In addition, the contact between the inner race  66  and outer race  55  is made only at the point P 1 .  
         [0110]    Also, in the case of a second example of the tenth embodiment shown in FIG. 13, between the inner race  66  and outer race  55 , a clearance S is formed. The center axis O 4  of the outer race  55  of the spherical-surface bearing  80  is offset with respect to the inclined rotation axis O 1  of the trunnion  14 . However, the radius of curvature of the connecting surface  66   a  of the inner race  66  is set equal to the radius of curvature of the connecting surface  55   a  of the outer race  55 . In the case of the second example, the vertical-direction movement and inclined rotation of the trunnion  14  are made on the connecting surface (in FIG. 13, the Q portion shown by oblique lines) between the needle roller  64  and the outer peripheral surface of the pivot shaft  16  of the trunnion  14 .  
         [0111]    Further, in a third example of the tenth embodiment shown in FIG. 14, between the inner race  66  and outer race  55 , a clearance S is formed. The center axis O 4  of the outer race  55  of the spherical-surface bearing  80  is offset with respect to the inclined rotation axis O 1  of the trunnion  14 . However, the connecting surface  55   a  of the outer race  55  is formed so as to be a straight-shaped surface. In the case of this structure, the vertical-direction movement of the trunnion  14  is made on the contact portion (in FIG. 14, the R portion shown by oblique lines) between the straight-shaped connecting surface  55   a  of the outer race  55  and the connecting surface  66   a  of the inner race  66 . On the other hand, the inclined rotation of the trunnion  14  is made on the connecting surface (in FIG. 14, the Q portion shown by oblique lines) between the needle roller  64  and the outer peripheral surface of the pivot shaft  16  of the trunnion  14 . By the way, in FIG. 14, reference character  90  designates a spacer and reference character  91  stands for a retaining ring.  
         [0112]    As described above, in the present embodiment (the three examples thereof), between the inner race  66  and outer race  55 , a clearance S is formed. In addition, the center axis O 4  of the outer race  55  of the spherical-surface bearing  80  is offset with respect to the inclined rotation axis O 1  of the trunnion  14 . Therefore, when the trunnion  14  is deformed as shown in FIG. 18, the elastic deformation of the trunnion  14  is absorbed by the clearance S formed between the inner race  66  and outer race  55 . Namely, even in case where the trunnion  14  is elastically deformed, the elastic deformation of the trunnion  14  has no ill influences on the gear change operation.  
         [0113]    As described heretofore, according to the invention, the pivot shaft of the trunnion is supported on the support member in such a manner that it can be shifted in the axial direction thereof and in the inclined rotation direction thereof. Therefore, the number of parts can be reduced and the assembling operation of the parts can be facilitated. Also, when the pivot shaft of the trunnion moves in the vertical direction thereof, the trunnion rotates about the pivot shaft of the trunnion simultaneously with the vertical-direction movement of the pivot shaft of the trunnion. Namely, the trunnion provides a rolling movement. Therefore, reducing the frictional force of the trunnion greatly. Thanks to this, the vertical-direction movements of the respective trunnions can be made uniform and, in the gear change operation, the synchronization and stability of the vertical-direction movements of the respective trunnions can be enhanced.  
         [0114]    Also, according to the invention, one of the upper support member and lower support member is fixed directly to the casing, and the other of the upper and lower support member is supported so as to be swingable. Therefore, not only the number of parts can be reduced, but also the parts manufacturing operation, parts managing operation and parts assembling operation can be facilitated respectively.  
         [0115]    And, since the support member has a function to cancel the thrust force applied from the power roller, it is necessary to increase the thickness of the support member as much as possible. However, the direct fixation of one of the upper and lower support member to the casing eliminates the provision of a support post. Thus, the support post elimination portion can be used to increase the thickness of the support member. This can enhance the durability of the support member fixed to the casing.  
         [0116]    Further, according to the invention, since the upper support member is fixed to the inner wall of the casing, the need for provision of a space for swinging the support member is eliminated as in the conventional toroidal-type continuously variable transmission. Therefore, the present structure is ideal for the case where the upper portion of the casing must be formed compact so as to be able to secure living space within the vehicle, for example in a vehicle of an FR type. Because, the inside space of the upper portion of the casing is formed narrower than the inside space of the lower portion of the casing.  
         [0117]    Moreover, in the case of the vehicle of an FR type, no dimensional limit is placed on the lower portion of the casing and thus the lower support member of an swinging type is mounted into the inside space of the lower portion of the casing. This makes it possible to guarantee the synchronization of the vertical-direction movements of all trunnions in the gear change operation.  
         [0118]    In addition, according to the invention, since the roller is embraced by the curved surface of the outer race, the axial-direction movement of the trunnion is made only on the inner race side thereof. That is, the axial-direction movement of the trunnion is made not on the outer race side where the contact area of the trunnion with the roller is increased due to the spherical-surface contact thereof, but on the inner race side where the contact area of the trunnion with the roller is decreased due to the point contact between the curved surface and the straight-shaped rolling surface. For this reason, the dynamic friction of the trunnion in the axial-direction movement of the trunnion can be reduced, thereby being able to stabilize the gear change operation.  
         [0119]    Also, according to the invention, the axial-direction movement of the trunnion is made only on the outer race side where the contact area of the trunnion is small. Therefore, the dynamic friction of the trunnion in the axial-direction movement of the trunnion can be reduced, thereby being able to stabilize the gear change operation. Also, generally, in a conventional bearing, since the inner race side thereof is severer in the surface pressure than the outer race side thereof, under the using condition where the surface pressure is severe. In the case, as described above, where the raceway surface of the inner race is formed as a curved surface and the raceway surface of the outer race is formed as a straight-shaped surface, the surface pressure can be lowered.  
         [0120]    According to the invention, since the needle roller is divided into two parts, not only the edge load can be reduced, but also the gear change operation of the trunnion can be carried out smoothly.  
         [0121]    According to the invention, the elastic deformation of the trunnion can be absorbed easily.  
         [0122]    According to the invention, when the trunnion is deformed elastically, the elastic deformation of the trunnion is absorbed by a clearance formed between the inner and outer races. Therefore, even in case where the trunnion is deformed, the deformation of the trunnion has no ill influences on the gear change operation.