Patent Publication Number: US-6902509-B2

Title: Toroidal type continuously variable transmission

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
   This application is a division of Application Ser. No. 09/395,216 filed Sep. 14, 1999 now U.S. Pat. No. 6,592,491. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   A toroidal type continuously variable transmission according to the present invention is used, for example, as a speed change unit of a transmission of a motor vehicle or transmissions of various industrial machines, respectively. 
   2. Related Background Art 
   It has been investigated that a toroidal type continuously variable transmission schematically shown in  FIGS. 24 and 25  is used as a transmission of a motor vehicle. For example, as disclosed in Japanese Utility Model Laid-Open No. 62-71465 (1987), in such a toroidal type continuously variable transmission, an input disc  2  is supported coaxially with an input shaft  1  and an output disc  4  is secured to an end of an output shaft  3  disposed coaxially with the input shaft  1 . Within a casing (described later in connection with  FIGS. 26  to  28 ) containing the toroidal type continuously variable transmission, there are provided trunnions  7  rockable around pivot shafts  6  located at positions twisted with respect to the input shaft  1  and the output shaft  3 . 
   That is to say, each trunnion  7  is provided at its both end outer surfaces with the pivot shafts  6  coaxial with each other. Accordingly, the pivot shafts  6  do not intersect with center lines of the discs  2 ,  4  but extend perpendicular to such center lines. Further, central portions of the trunnions  7  support proximal ends of displacement shafts  8  so that inclination angles of the displacement shafts  8  can be adjusted by rocking or swinging the trunnions  7  around the pivot shafts  6 . Power rollers  9  are rotatably supported around the displacement shafts  8  supported by the trunnions  7 . The power rollers  9  are interposed between the input disc  2  and the output disc  4 . Inner surfaces  2   a ,  4   a  of the discs  2 ,  4  which are opposed to each other have concave surfaces obtained by rotating arcs having centers on the pivot shaft  6  around the input shaft  1  and the output shaft  3 . Peripheral surfaces  9   a  of the power rollers  9  having spherical convex shapes abut against the inner surfaces  2   a ,  4   a . A pressing device  10  of loading cam type is disposed between the input disc  2  and the output disc  4  so that the input disc  2  is can be urged elastically toward the output disc  4  by the pressing device  10 . The pressing device  10  comprises a cam plate  11  rotated together with the input shaft  1 , and a plurality (for example, four) of rollers  13  held by a holder  12 . One side surface (left side surface in  FIGS. 24 and 25 ) of the cam plate  11  is constituted as a cam surface  14  having unevenness or undulation extending along a circumferential direction, and an outer surface (right side surface in  FIGS. 24 and 25 ) of the input disc  2  has a similar cam surface  15 . The plurality of rollers  13  are rotatably supported for rotation around axes extending radially with respect to the center line of the input shaft  1 . 
   In use of the toroidal type continuously variable transmission having the above-mentioned construction, when the cam plate  11  is rotated as the input shaft  1  is rotated, the plurality of rollers  13  are urged against the cam surface  15  formed on the outer surface of the input disc  2  by the cam surface  14 . As a result, the input disc  2  is urged against the plurality of power rollers  9 , and, at the same time, due to the frictional engagement between the pair of cam surfaces  14 ,  15  and the plurality of rollers  13 , the input disc  2  is rotated. Rotation of the input disc  2  is transmitted to the output disc  4  through the plurality of power rollers  9 , thereby rotating the output shaft  3  secured to the output disc  4 . 
   Regarding a rotational speed ratio (speed change ratio) between the input shaft  1  and the output shaft  3 , when deceleration is effected between the input shaft  1  and the output shaft  3 , the trunnions  7  are rocked or swung around the pivot shafts  6  in predetermined directions, thereby inclining the displacement shafts  8  so that the peripheral surfaces  9   a  of the power rollers  9  abut against a portion of the inner surface  2   a  of the input disc  2  near the center and a portion of the inner surface  4   a  of the output disc  4  near its outer periphery, respectively, as shown in FIG.  24 . On the other hand, when acceleration is effected, the trunnions  7  are rocked around the pivot shafts  6  in opposite directions, thereby inclining the displacement shafts  8  so that the peripheral surfaces  9   a  of the power rollers  9  abut against a portion of the inner surface  2   a  of the input disc  2  near its outer periphery and a portion of the inner surface  4   a  of the output disc  4  near the center, respectively, as shown in FIG.  25 . If the inclination angles of the displacement shafts  8  are selected to an intermediate value between FIG.  24  and  FIG. 25 , an intermediate speed change ratio can be obtained. 
   When the actual transmission of the motor vehicle is constituted by the above-mentioned the toroidal type continuously variable transmission, it is well known in the art to provide a so-called toroidal type continuously variable transmission of double cavity type in which two sets of input disc  2 , output disc  4  and power rollers  9  are prepared, and such two sets of input disc  2 , output disc  4  and power rollers  9  are arranged in parallel to each other along a power transmitting direction.  FIGS. 26  to  28  show an example of such a toroidal type continuously variable transmission of double cavity type disclosed in Japanese Patent Publication No. 8-23386 (1996). 
   An input shaft la is supported within a casing  5  for only rotation. A cylindrical transmission shaft  16  is rotatably supported around the input shaft  1   a  in coaxial with the latter for rotation relative to the input shaft  1   a . First and second input discs  17 ,  18  corresponding to first and second outer discs of the present invention are supported on both ends of the transmission shaft  16  via ball splines  19  so that inner faces  2   a  of these discs are opposed to each other. Accordingly, the first and second input discs  17 ,  18  are rotatably supported within the casing  5  coaxially with each other and rotate synchronously with each other. 
   Further, first and second output discs  20 ,  21  corresponding to first and second inner discs of the present invention are supported around an intermediate portion of the transmission shaft  16  via a sleeve  22 . An output gear  23  is integrally formed on an outer peripheral surface of an intermediate portion of the sleeve  22 , and the sleeve has an inner diameter greater than an outer diameter of the transmission shaft  16 . The sleeve is rotatably supported by a support wall  24  provided within the casing  5  via a pair of bearings  25  in such a manner than the sleeve is disposed coaxially with the transmission shaft  16  and can merely be rotated. In this way, the first and second output discs  20 ,  21  are spline-connected to both ends of the sleeve  22  rotatably mounted around the intermediate portion of the transmission shaft  16  in a condition that inner surfaces  4   a  of the discs  20 ,  21  are directed toward opposite directions. Accordingly, the first and second output discs  20 ,  21  are supported in coaxial with the first and second input discs  17 ,  18  and are rotated independently from the first and second input discs  17 ,  18  in a condition that the inner surfaces  4   a  are opposed to the respective inner surfaces  2   a  of the first and second input discs  17 ,  18 . 
   Further, two pairs of yokes  26   a ,  26   b  are supported by an inner wall of the casing  5  at both sides of the first and second output discs  20 ,  21  with the interposition of these output discs  20 ,  21 . The yokes  26   a ,  26   b  correspond to yokes constituting first and second supporting means of the present invention and are formed as rectangular frames, respectively, by press-working a metal plate such as steel or forging metal material such as steel. The yokes  26   a ,  26   b  are provided at their four corners with circular support holes  31  for rockably supporting first and second pivot shafts  29 ,  30  provided on both ends of first and second trunnions  27 ,  28  (described later) and are also provided with circular locking holes  32  formed in central portions of the yokes in a width-wise direction (left-and-right direction in  FIGS. 27 and 28 ) thereof at both ends of the transmission shaft  16  in an axial direction (left-and-right direction in  FIG. 26 ) thereof. The pairs of yokes  26   a ,  26   b  each having the above-mentioned configuration are supported by support posts  33   a ,  33   b  formed on opposed portions of the inner wall of the casing  5  for slight displacement. The support posts  33   a ,  33   b  are opposed to each other and are disposed within a first cavity  34  between the inner surface  2   a  of the first input disc  17  and the inner surface  4   a  of the first output disc  20  and a second cavity  35  between the inner surface  2   a  of the second input disc  18  and the inner surface  4   a  of the second output disc  21 . Accordingly, in a condition that the yokes  26   a ,  26   b  are supported by the support posts  33   a ,  33   b , first ends of the yokes  26   a ,  26   b  are opposed to an outer peripheral portion of the first cavity  34  and the other ends are opposed to an outer peripheral portion of the second cavity  35 . 
   Further, a pair of first trunnions  27  are disposed within the first cavity  34  at diametrically opposed positions of the first input disc  17  and the first output disc  20 , and a pair of second trunnions  28  are disposed within the second cavity  35  at diametrically opposed positions of the second input disc  18  and the second output disc  21 . As shown in  FIG. 27 , the four (in total) first pivot shafts  29  which are coaxially provided on both ends of the trunnions  27  (two in each trunnion) are supported by the first ends of the pair of yokes  26   a ,  26   b  for rocking movement and axial displacement. That is to say, the first pivot shafts  29  are supported within the support holes  31  formed in the first ends of the yokes  26   a ,  26   b  via radial needle bearings  36 . Each of the radial needle bearings  36  has an outer race  37  having a spherical convex outer peripheral surface and a cylindrical inner peripheral surface, and a plurality of needles  38 . Accordingly, the first pivot shafts  29  are supported at both axial sides on the first ends of the yokes  26   a ,  26   b  for reversible rocking movement and axial displacement. Further, as shown in  FIG. 28 , the four (in total) second pivot shafts  30  which are coaxially provided on both ends of the second trunnions  28  (two in each trunnion) are supported within the second cavity  35  in the same manner as the first pivot shafts  29  provided on the first trunnions  27 . 
   The first and second trunnions  27 ,  28  supported within the casing  5  for rocking movements and displacements in axial directions of first and second pivot shafts  29 ,  30  in this way are provided at their intermediate portions with circular holes  39 , as shown in  FIGS. 27 and 28 . The first and second displacement shafts  40 ,  41  are supported in these circular holes  39 . The first and second displacement shafts  40 ,  41  have support shaft portions  42  parallel with and eccentric with each other, and pivot shaft portions  43 . The support shaft portions  42  are rotatably supported within the circular holes  39  via radial needle bearings  44 . Further, first and second power rollers  45 ,  46  are rotatably supported around the pivot shaft portions  43  via other radial needle bearings  47 . 
   Incidentally, the pair of first and second displacement shafts  40 ,  41  provided for each of the first and second cavities  34 ,  35  are disposed at opposite directions (diametrically opposed at 180 degrees) with respect to the input shaft  1   a  and the transmission shaft  16  for each of the first and second cavities  34 ,  35 . Further, directions along which the pivot shaft portions  43  of the first and second displacement shafts  40 ,  41  are offset (eccentric) from the support shaft portions  42  are the same (up-and-down opposite directions in  FIGS. 27 and 28 ) with respect to the rotational direction of the first and second input and output discs  17 ,  18 ,  20 ,  21 . Further, the eccentric directions are substantially perpendicular to an installation direction of the input shaft  1   a . Accordingly, the first and second power rollers  45 ,  46  are supported for slight displacement in the installation direction of the input shaft  1   a  and the transmission shaft  16  (slight axial displacement). As a result, if the first and second power rollers  45 ,  46  tend to be displaced in the axial direction of the input shaft  1   a  and the transmission shaft  16  (left-and-right direction in  FIG. 26 , and, direction perpendicular to the planes of  FIGS. 27 and 28 ) by change in elastic deformation amount of structural parts due to fluctuation in torque to be transmitted by the toroidal type continuously variable transmission, such displacement can be absorbed without acting any excessive stress on the structural parts. 
   Further, between outer surfaces of the first and second power rollers  45 ,  46  and inner surfaces of intermediate portions of the first and second trunnions  27 ,  28 , there are provided, in order from the outer surfaces of the first and second power rollers  45 ,  46 , thrust ball bearings  48 , and thrust bearings  49  such as sliding bearings or needle bearings. The thrust ball bearings  48  serve to support thrust load acting on the first and second power rollers  45 ,  46  and to allow rotations of the first and second power rollers  45 ,  46 . Further, the thrust bearings  49  serve to support thrust loads acting on outer races  50  of the thrust ball bearings  48  and to allow the pivot shaft portions  43  and the outer races  50  to rock around the support shaft portions  42 . 
   Further, drive rods  51  are connected to one end (lower ends in  FIGS. 27 and 28 ) of each of the first and second trunnions  27 ,  28 , and drive pistons  52  are secured to outer surfaces of intermediate portions of the drive rods  51 . The drive pistons  52  are slidably mounted within drive cylinders  53  in an oil-tight fashion. The drive pistons  52  and the drive cylinders  53  constitute actuators for displacing the first and second trunnions  27 ,  28  along the axial directions of the first and second pivot shafts  29 ,  30 . Further, pressurized oil can be supplied within the drive cylinders  53  in response to switching of a control valve (not shown). 
   Further, an pressing device  10  of loading cam type is disposed between the input shaft  1   a  and the first input disc  17 . The pressing device  10  includes a cam plate  11  spline-connected to the intermediate portion of the input shaft  1   a  so that it can be rotated together with the input shaft  1   a  but cannot be displaced in the axial direction, and a plurality of rollers  13  rotatably held by a holder  12 . When the input shaft  1   a  is rotated, the pressing device serves to rotate the first input disc  17  while urging it toward the second input disc  18 . 
   When the toroidal type continuously variable transmission having the above-mentioned construction is driven, the rotation of the input shaft  1   a  is transmitted to the first input disc  17  through the pressing device  10 , so that the first and second input discs  17 ,  18  are rotated in synchronous with each other. The rotation of the first and second input discs  17 ,  18  is transmitted to the first and second output discs  20 ,  21  through the pairs of first and second power rollers  45 ,  46  disposed within the first and second cavities  34 ,  35 . The rotation of the first and second output discs  20 ,  21  is picked-up by the output gear  23 . When the rotational speed ratio between the input shaft  1   a  and the output gear  23  is changed, by switching the control valve, the pairs of drive pistons  52  corresponding to the first and second cavities  34 ,  35  are displaced in opposite directions by the same distance for the cavities  34 ,  35 , respectively. 
   When the drive pistons  52  are displaced, two pairs (four in total) of trunnions  27 ,  28  are displaced in opposite directions, so that, for example, the first and second power rollers  45 ,  46  at the right in  FIGS. 27 and 28  are shifted downwardly ( FIGS. 27 and 28 ) and the first and second power rollers  45 ,  46  at the left in  FIGS. 27 and 28  are shifted upwardly (FIGS.  27  and  28 ). As a result, directions of tangential forces acting on the contact areas between the peripheral surfaces  9   a  of the first and second power rollers  45 ,  46  and the inner surfaces  2   a ,  4   a  of the first and second input discs  17 ,  18  and the first and second output discs  20 ,  21  are changed. As the directions of forces are changed, the first and second trunnions  27 ,  28  are rocked in opposite directions around the first and second pivot shafts  29 ,  30  supported by the yokes  26   a ,  26   b . As a result, as shown in  FIGS. 24 and 25 , the contact areas between the peripheral surfaces  9   a  of the first and second power rollers  45 ,  46  and the inner surfaces  2   a ,  4   a  of the discs  17 ,  18 ,  20 ,  21  are changed, thereby changing the rotational speed ratio between the input shaft  1   a  and the output gear  23 . 
   In the conventional arrangement shown in  FIGS. 26  to  28 , the first and second trunnions  27 ,  28  are supported within the casing through the support posts  33   a ,  33   b  and the yokes  26   a ,  26   b . Thus, since the number of parts is increased, not only manufacture, control and assembling of the parts become troublesome, but also height of the toroidal type continuously variable transmission in the up-and-down direction in  FIGS. 26  to  28  is increased, so that it is hard to make the transmission compact and light-weight. Further, if the transmission is forcibly made compact and light-weight to permit installation of the transmission within a limited space, strength of parts is decreased, thereby worsening endurance. 
   Japanese Patent Laid-Open No. 10-274300 (1998) discloses an arrangement in which pivot shafts provided on both ends of trunnions in a toroidal type continuously variable transmission are supported by support members directly secured to an inner surface of a casing. With this arrangement, since the number of parts is decreased, the transmission can be made compact and light-weight. However, in case of the toroidal type continuously variable transmission disclosed in this document, the support members for supporting the pivot shafts provided on both ends of the trunnions are independently provided for each trunnion. 
   Thus, in the arrangement disclosed in the above Japanese Patent Laid-Open No. 10-274300, loads acting on the trunnions when the toroidal type continuously variable transmission is driven directly act on the casing. More specifically, when the toroidal type continuously variable transmission is driven, since pressure acting on contact areas between inner surfaces of input and output discs and peripheral surfaces of power rollers is great, the power rollers are subjected to great thrust loads. Such thrust loads act on the support portions for the pivot shafts provided on both ends of the trunnions through the trunnions. In the arrangement disclosed in above-mentioned document, the great loads acting on the pivot shafts in this way act on the casing as they are. In many cases, since the casing of the transmission is made of light alloy such as aluminium alloy to reduce the weight, in order to prevent displacement of the pivot shafts and to ensure the endurance of the casing regardless of great loads, it is necessary to increase a wall thickness of the casing, with the result that it is hard to make the transmission compact and light-weight. 
   Further, when the toroidal type continuously variable transmission is driven, due to the great loads acting on the trunnions from the power rollers, the trunnions are elastically deformed so that the inner surfaces thereof becomes concave. As a result, parallelism between central axes of the pivot shafts provided on the ends of the trunnions and central axes of circular holes formed in the support members secured to the inner surface of the casing is lost more or less. In the arrangement disclosed in above-mentioned document, it is not considered that the trunnions can be displaced smoothly without damaging any parts even if such a condition occurs. 
   SUMMARY OF THE INVENTION 
   In consideration of the above circumstances, a toroidal type continuously variable transmission according to the present invention is devised. 
   As is in conventional toroidal type continuously variable transmissions, a toroidal type continuously variable transmission according to the present invention comprises a casing, input and output discs supported within the casing coaxially with each other and capable of being rotated independently, the even number of pivot shafts disposed coaxially with or parallel with each other between the discs at twisted positions where the pivot shafts do not intersect with a central axis of the discs but extend toward directions perpendicular to the central axis, a plurality of trunnions rockable around the pivot shafts, displacement shafts protruded from inner surfaces of the trunnions, a plurality of power rollers rotatably supported around the displacement shafts and interposed between inner surfaces of the input and output discs, and support means provided at sides of the power roller and adapted to support the pivot shafts for rocking displacement and axial displacement. 
   Further, as is in conventional toroidal type continuously variable transmissions, a toroidal type continuously variable transmission according to the present invention comprises a casing, first and second outer discs supported within the casing coaxially with each other and capable of being rotated synchronously so that inner surfaces of the discs are opposed to each other, a first inner disc supported coaxially with the first and second outer discs and capable of being rotated independently from the first and second outer discs and having an inner surface opposed to the inner surface of the first outer disc, a second inner disc supported coaxially with the first inner disc and capable of being rotated synchronously with the first inner disc and having an inner surface opposed to the inner surface of the second outer disc, four first pivot shafts disposed coaxially with or parallel with each other between the first outer disc and the first inner disc at twisted positions where the pivot shafts do not intersect with a central axis of these discs but extend toward directions perpendicular to the central axis, a pair of first trunnions rockable around the first pivot shafts, first displacement shafts protruded from inner surfaces of the first trunnions, a pair of first power rollers rotatably supported around the first displacement shafts and interposed between the inner surface of the first outer disc and the inner surface of the first inner disc, four second pivot shafts disposed coaxially with or parallel with each other between the second outer disc and the second inner disc at twisted positions where the pivot shafts do not intersect with a central axis of these discs but extend toward directions perpendicular to the central axis, a pair of second trunnions rockable around the second pivot shafts, second displacement shafts protruded from inner surfaces of the second trunnions, a pair of second power rollers rotatably supported around the second displacement shafts and interposed between the inner surface of the second outer disc and the inner surface of the second inner disc, and first and second support means provided substantially in parallel with each other at sides of the first and second inner discs with the interposition of the first and second inner discs in such a manner that one ends are disposed between the first outer disc and the first inner disc and the other ends are disposed between the second outer disc and the second inner disc; and the first support means supports two of the four first pivot shafts and two of the four second pivot shafts for rocking movement and axial displacement, and the second support means supports the other two of the four first pivot shafts and the other two of the four second pivot shafts for rocking movement and axial displacement. 
   Particularly, the toroidal type continuously variable transmission according to the present invention is characterized in that members constituting the support means or the first and second support means are directly supported by and secured to an inner surface of the casing. 
   According to the toroidal type continuously variable transmission of the present invention having the above-mentioned arrangements, a rotational force is transmitted between the input disc or the first and second outer discs and the output disc or the first and second inner discs, and, a speed change ratio between the input disc or the first and second outer discs and the output disc or the first and second inner discs can be changed in the same manner as the conventional toroidal type continuously variable transmissions. 
   Particularly, in the toroidal type continuously variable transmission of the present invention, since the members constituting the support means or the first and second support means are directly supported by and secured to the inner surface of the casing, the number of parts is reduced to facilitate manufacture, control and assembling of the parts, and a height of the toroidal type continuously variable transmission is decreased to make the transmission compact and light-weight while ensuring the endurance. 
   In a toroidal type continuously variable transmission according to another aspect of the present invention, yokes having ends for supporting the pivot shafts provided on the ends of the plurality of trunnions forming a part of the support means are directly supported by and secured to the inner surface of the casing. Further, it is designed so that the pivot shafts can be displaced axially, by splines, with respect to the ends of the yokes, and needle bearings for rockably supporting the pivot shafts are provided within the inside of the splines. 
   In a toroidal type continuously variable transmission according to a further aspect of the present invention, yokes having four corners for supporting the pivot shafts provided on the ends of the plurality of trunnions forming a part of the first and second support means are directly supported by and secured to the inner surface of the casing. Further, it is designed so that the pivot shafts can be displaced axially, by splines, with respect to the four corners of the yokes, and needle bearings for rockably supporting the pivot shafts are provided within the inside of the splines. 
   In this way, in the toroidal type continuously variable transmission of the present invention, since the yokes constituting the support means or the first and second support means are directly supported by and secured to the inner surface of the casing, the number of parts is reduced to facilitate manufacture, control and assembling of the parts, and a height of the toroidal type continuously variable transmission is decreased to make the transmission compact and light-weight while ensuring the endurance. 
   Furthermore, since the yokes support the pivot shafts provided on the ends of the plurality of trunnions, all or part of forces acting on the plurality of trunnions can be canceled in the yokes. Thus, since a great load does not act on the casing supporting the yokes, it is not required that the wall thickness of the casing be increased in order to prevent displacement of the support portions for the pivot shafts and reduction in endurance of the casing. 
   In addition, since the splines and the needle bearings are provided between the pivot shafts and the yokes, the displacement of the trunnions with respect to the yokes can be effected smoothly and correctly. 
   It may be designed so that the splines are ball splines, and outer peripheral surfaces of outer races formed in inner peripheral surfaces of ball spline grooves constituting the ball splines are formed as semi-spherical convex surfaces, and the convex surfaces are rockably received in circular holes formed in the yokes. 
   Incidentally, a gear transmitting mechanism may be provided between the plurality of trunnions to synchronize the inclination movements of the trunnions. 
   A toroidal type continuously variable transmission according to a further aspect of the present invention comprises a casing, input and output discs supported within the casing coaxially with each other and capable of being rotated independently so that inner surfaces of the discs are opposed to each other, four or more and the even number of pivot shafts disposed coaxially with or parallel with each other between the input disc and the output disc at twisted positions where the pivot shafts do not intersect with a central axis of the discs but extend toward directions perpendicular to the central axis, a plurality of trunnions rockable around the pivot shafts, displacement shafts protruded from inner surfaces of the trunnions, a plurality of power rollers rotatably supported around the displacement shafts and interposed between an inner surface of the input disc and an inner surface of the output disc, and a plurality of actuators having the same number as that of the trunnions and adapted to displace the trunnions along axial directions of the pivot shafts. 
   A toroidal type continuously variable transmission according to a still further aspect to the present invention comprises a casing, first and second outer discs supported within the casing coaxially with each other and capable of being rotated synchronously so that inner surfaces of the discs are opposed to each other, a first inner disc supported coaxially with the first and second outer discs and capable of being rotated independently from the first and second outer discs and having an inner surface opposed to the inner surface of the first outer disc, a second inner disc supported coaxially with the first inner disc and capable of being rotated synchronously with the first inner disc and having an inner surface opposed to the inner surface of the second outer disc, four or more and the even number of first pivot shafts disposed in coaxial with or parallel with each other between the first outer disc and the first inner disc at twisted positions where the pivot shafts do not intersect with a central axis of these discs but extend toward directions perpendicular to the central axis, a plurality of first trunnions rockable around the first pivot shafts, first displacement shafts protruded from inner surfaces of the first trunnions, a plurality of first power rollers rotatably supported around the first displacement shafts and interposed between the inner surface of the first outer disc and the inner surface of the first inner disc, four or more and the even number of second pivot shafts disposed coaxially with or parallel with each other between the second outer disc and the second inner disc at twisted positions where the pivot shafts do not intersect with a central axis of these discs but extend toward directions perpendicular to the central axis, a plurality of second trunnions rockable around the second pivot shafts, second displacement shafts protruded from inner surfaces of the second trunnions, a plurality of second power rollers rotatably supported around the second displacement shafts and interposed between the inner surface of the second outer disc and the inner surface of the second inner disc, and a plurality of actuators having the same number as that of the trunnions and adapted to displace the trunnions along axial directions of the pivot shafts. 
   Particularly, in the toroidal type continuously variable transmission of the present invention, there is provided a synchronizing mechanism for mechanically synchronizing the displacement movements of the trunnions along the axial directions of the pivot shafts effected by the actuators. 
   For example, such a synchronizing mechanism may comprise receiving pieces having proximal ends secured to the ends of the trunnions and secured to tip ends of drive rods capable of being displaced axially by the actuators to displace the trunnions along the axial directions of the pivot shafts, and rocking arms having ends engaged by the receiving pieces to be merely rocked and central portions pivotally supported by a second pivot shaft (fixed portion) arranged in parallel with a rotational center line of the discs. 
   As is in conventional toroidal type continuously variable transmissions, in the toroidal type continuously variable transmission of the present invention having the above-mentioned arrangement, the rotational force is transmitted between the input disc and the output disc or between the first and second outer discs and the first and second inner discs, and, further, by changing the inclination angles of the trunnions, the rotational speed ratio between the discs is changed. 
   Particularly in the toroidal type continuously variable transmission of the present invention, since the displacement movements of the trunnions along the axial directions of the pivot shafts effected by the actuators are mechanically synchronized, even when a quick speed change operation is performed, the inclination angles of the trunnions can be coincided with each other exactly. 
   Other objects and features of the present invention will be apparent from the following detailed explanation of the invention referring to the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a sectional view corresponding to a sectional view taken along the line A—A in  FIG. 26 , showing a first embodiment of the present invention; 
       FIG. 2  is a sectional view taken along the line B—B in  FIG. 1 ; 
       FIG. 3  is an enlarged sectional view showing a right portion of  FIG. 1 ; 
       FIG. 4  is a view corresponding to a portion C in  FIG. 1 , showing a condition that assembling is being effected; 
       FIG. 5  is a view corresponding to a portion C in  FIG. 1 , showing a condition that the assembling is completed; 
       FIG. 6  is a view showing a condition that forces act on yokes in a toroidal type continuously variable transmission of double cavity type, looked at from above in  FIG. 1 ; 
       FIG. 7  is a partial sectional view corresponding to a right upper portion of  FIG. 1 , showing a deformed condition of a trunnion during operation in an exaggerated manner; 
       FIGS. 8A and 8B  are views similar to  FIG. 6 , showing a condition that forces act on yokes in a toroidal type continuously variable transmission of single cavity type; 
       FIG. 9  is a sectional view corresponding to a sectional view taken along the line A—A in  FIG. 26 , showing a second embodiment of the present invention; 
       FIG. 10  is an enlarged view of a portion D in  FIG. 9 , where an area above a line a shows a sectional view taken along the line E-O-F in FIG.  11  and an area below the line a shows sectional view taken along the line E-O-G in  FIG. 11 ; 
       FIG. 11  is a view looked at from above in  FIG. 10 , with a casing omitted; 
       FIG. 12  is a view similar to  FIG. 3 , showing a third embodiment of the present invention; 
       FIG. 13  is a sectional view corresponding to a sectional view taken along the line A—A in  FIG. 26 , showing a fourth embodiment of the present invention; 
       FIG. 14  is a view corresponding to a portion I in  FIG. 13 ; 
       FIG. 15  is a sectional view corresponding to a sectional view taken along the line A—A in  FIG. 26 , showing a fifth embodiment of the present invention; 
       FIG. 16  is an enlarged view showing a portion J in  FIG. 15 ; 
       FIG. 17  is a perspective view of a receiving piece; 
       FIG. 18  is a view looked at from below in  FIG. 15 , showing a mechanism for synchronizing axial displacement movements of drive rods; 
       FIG. 19  is a view looked at from a direction shown by arrow K in  FIG. 15 ; 
       FIG. 20  is a view looked at from below in  FIG. 15 , showing a gear transmitting mechanism; 
       FIG. 21  is a substantially plan view of a toroidal type continuously variable transmission, for explaining a measured portion in a test effected to confirm an effect of the invention; 
       FIGS. 22A and 22B  are graphs showing displacement conditions of trunnions in the toroidal type continuously variable transmission of the present invention; 
       FIGS. 23A and 23B  are graphs showing displacement conditions of trunnions in a conventional toroidal type continuously variable transmission; 
       FIG. 24  is a side view showing a fundamental construction of a conventional toroidal type continuously variable transmission, in a maximum deceleration condition; 
       FIG. 25  is a side view similar to  FIG. 24 , in a maximum acceleration condition; 
       FIG. 26  is a sectional view showing a specific example of a conventional construction; 
       FIG. 27  is a sectional view taken along the line A—A in  FIG. 26 ; 
       FIG. 28  is a sectional view taken along the line H—H in  FIG. 26 ; 
       FIG. 29  is a sectional view showing a first example of a conventional synchronizing mechanism using a cable; and 
       FIG. 30  is a sectional view showing a second example of a conventional synchronizing mechanism using a cable. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   &lt;First Embodiment&gt; 
     FIGS. 1  to  7  show a first embodiment of the present invention. Incidentally, the characteristics of this embodiment include a construction of parts for supporting first pivot shafts  29  provided on both ends of first trunnions  27  with respect to a casing  5  and a construction for positively synchronizing inclination angles of the trunnions  27 . Since the other constructions and functions are the same as those of the conventional technique shown in  FIGS. 26  to  28 , illustration and explanation thereof are omitted or briefly described, and the characteristics of this embodiment will be mainly explained. Further, second pivot shafts  30  ( FIG. 28 ) provided on both ends of second trunnions  28  are also supported with respect to the casing  5  and inclination angles of the second trunnions  28  are positively synchronized by the same construction as the construction regarding the first pivot shafts  29 . In the following explanation, as a rule, only the first trunnions  27  will be described, except for cases where the second trunnions  28  and associated parts must be explained. 
   A pair of yokes  54 ,  55  constituting first and second support means are disposed in parallel with each other and are directly secured to opposed portions of the casing  5 . Incidentally, positioning accuracy of the yokes  54 ,  55  with respect to the casing  5  is exactly regulated by engagement between knock pins protruded from one of the yokes and casing and lock holes formed in the other of the yokes and casing. Circular support holes  31  are formed in four corners of the yokes  54 ,  55  at engagement positions. Among these support holes  31 , within the support holes  31  formed in first ends of the yokes  54 ,  55 , the first pivot shafts  29  are supported via ball splines  56  and radial needle bearings  57  for axial displacement and rocking movement. 
   Ball spline outer races  58  of the ball splines  56  are fitted into open half sides of the support holes  31  in a condition that the outer races can slightly be rocked and axial displacement of the races is limited. To this end, the open half sides of the support holes  31  are provided with small diameter portions  59  having front diameters smaller than rear diameters. The ball spline outer races  58  of the ball splines  56  are fitted into the smaller diameter portions  59 . Outer peripheral surfaces of intermediate portions of the ball spline outer races  58  are formed as partial spherical convex surfaces  60 . A radius of curvature of each convex surface  60  is substantially equal to a half (½) of an inner diameter of each support hole  31 . 
   Further, outwardly directed circumferential flanges  61  are formed on outer peripheral surfaces at axial first ends of the ball spline outer races  58  and circumferential locking grooves  62  are formed in outer peripheral surfaces at the other axial ends of the ball spline outer races. Such ball spline outer races  58  are assembled in such a manner that the flanges  61  are positioned at rear sides of the support holes  31  and the smaller diameter portions  59  are sandwiched from both sides between the flanges  61  and stop rings  63  locked to the locking grooves  62 . Incidentally, in this condition, a distance between each flange  61  and the corresponding stop ring  63  is selected to be greater than an axial length of the corresponding smaller diameter portion  59 . Accordingly, the ball spline outer races  58  are supported within the support holes  31  for slight rocking movement. 
   Further, a plurality of outer race side ball spline grooves  64  extending in an axial direction (up-and-down direction in FIG.  1  and  FIGS. 3  to  5 ) are formed in outer races  58 , and inner races  65  (also acting as outer races of the radial needle bearings  57 ) are disposed within the interiors of the ball spline outer races  58  concentrically with the radial needle bearings  57 . Inner race side ball spline grooves  66  extending in an axial direction are formed in portions of the outer peripheral surfaces of the ball spline inner races  65  which are opposed to the outer race side ball spline grooves  64 . A plurality of balls  67  are disposed between the respective inner race side ball spline grooves  66  and the respective outer race side ball spline grooves  64 , thereby constituting the ball splines  56 . 
   Cylindrical outer race tracks  68  for the radial needle bearings  57  are provided on inner peripheral surfaces of the ball spline inner races  65 . A plurality of needles  70  are disposed between the respective outer race tracks  68  and respective cylindrical inner race tracks  69  formed on the outer peripheral surfaces of the first pivot shafts  29  provided on both ends of the first trunnions  27 , thereby constituting the radial needle bearings  57 . 
   Among the first pivot shafts  29  provided on both ends of the first trunnions  27 , tip end portions of the first pivot shafts  29  connected to the drive rods  51  at one side (lower end side in  FIGS. 1 and 3 ) have pinions  72  (constituting a gear transmitting mechanism  71  which will be described later) secured thereto. On the other hand, circular hold-down plates  73  are secured to tip ends of the first pivot shafts  29  at the other side (upper end side in  FIGS. 1 and 3 ) remote from the drive rods  51 , by threading threaded rods  74  provided on central portions of the hold-down plates into threaded holes  75  formed in the central portions of the first pivot shafts  29 . Such pinions  72  and hold-down plates  73  serve to prevent axial shifting movement of the ball spline inner races  65  and dislodging of the balls  67 . Incidentally, dislodging of the balls  67  in the opposite direction is prevented by stop rings  85  locked to the outer peripheral surfaces of proximal ends (ends near the axial central portions of the first trunnions  27 ) of the ball spline inner races  65 . 
   Incidentally, among the construction according to the illustrated embodiment, the ball spline  56  and the radial needle bearing  57  are assembled as follows. As shown in  FIG. 4 , the radial needle bearing  57  including the ball spline inner race  65  is previously mounted on the first pivot shaft  29  provided on the other end of the corresponding first trunnion  27  and is prevented from dislodging by means of a washer  76  and a stop ring  77 . Further, as shown in  FIG. 4 , the ball spline outer race  58  is previously mounted within the support hole  31  formed in the yoke  54 . In this condition, the plurality of balls  67  for constituting the ball spline  56  are inserted between the respective inner race side ball spline grooves  66  formed in the outer peripheral surface of the ball spline inner race  65  and the respective outer race side ball spline grooves  64  formed in the inner peripheral surface of the ball spline outer race  58 , through hole  86  formed in a portion of the casing  5  aligned with the support hole  31 . After insertion, as shown in  FIG. 5 , the hold-down plate  73  is mounted, and then, the through hole  87  is closed by a lid plate  87 . 
   By the way, in case of the toroidal type continuously variable transmission of the present invention including the arrangement according to the illustrated embodiment, since the yokes  54 ,  55  are not displaced, the yokes  54 ,  55  do not have functions for coinciding the inclination angles of the pair of opposed first power rollers  45  with each other. That is to say, although such inclination angles are adjusted by the axial displacement amounts of the drive rods  51  controlled by supplying or discharging the pressurized oil with respect to the drive cylinders  53 , it is difficult to exactly coincide the inclination angles of the pair of first power rollers  45  with each other by such axial displacement amounts. Thus, in the conventional arrangements, the inclination angles of the pair of first power rollers  45  have been exactly coincided with each other by permitting the displacement of the yokes  26   a  and by supporting the first power rollers  45  in a so-called floating fashion. However, in the toroidal type continuously variable transmission of the present invention, the inclination angles of the pair of first power rollers  45  cannot be coincided with each other by the displacement of the yokes  54 ,  55 . 
   Thus, in the illustrated embodiment, the pair of opposed first trunnions  27  are interconnected through the gear transmitting mechanism  71  so that the pair of first power rollers  45  supported by the first trunnions  27  can be coincided with each other exactly. To install the gear transmitting mechanism  71 , one (lower one ( 55 ) in  FIGS. 1  to  3 ) of the yokes is provided with a recessed portion  78 . Accordingly, in a condition that the yoke  55  and a cylinder case  79  are overlapped with each other, a space  80  for containing the gear transmitting mechanism  71  is defined between these members  55 ,  79 . The gear transmitting mechanism  71  contained in this space  80  includes a pair of pinions  72  having the same configuration and the same number of teeth, and a rack  81  having toothed portions provided on both end portions and having the same pitch. The pinions  72  are fitted onto the secured to non-cylindrical portions formed on the top ends of the first pivot shafts  29  provided on the ends of the first trunnions  27 . Accordingly, the first trunnions  27  are rotated synchronously with the pinions  72 . Incidentally, when the speed change ratio is changed, the first trunnions  27  are displaced in the axial directions of the first pivot shafts  29 . Accordingly, by providing moderate (an amount which does not give rise to any problem regarding the coincidence of the inclination angles) backlash in engagement areas between the pinions  72  and the rack  81 , relative displacement between the pinions  72  and the rack  81  is permitted. 
   The rack  81  can be displaced only along the axial direction (direction perpendicular to the planes of  FIGS. 1 and 3 ) of the input shaft  1   a  and is supported within the space  80 . To this end, in the illustrated embodiment, the rack  81  is supported by translation rolling bearings (linear bearings)  82  for parallel shifting movement with respect to the yoke  55 . More specifically, guide recessed portions  83  extending in the displacing direction of the rack  81  are formed in a portion (opposed to the rack  81 ) of a lower surface of the yoke  55  secured to the inner surface of the casing  5 . 
   Further, guide flanges  84  are formed on portions (aligned with the guide recessed portions  83 ) of an intermediate part of the rack  81 . A thickness of each guide flange  84  is selected to be smaller than a width of each guide recessed portion  83  so that the guide flanges  84  are loosely inserted within the guide recessed portions  83 . The rolling bearings  82  are disposed between respective surfaces of the flanges  84  and the respective inner surfaces of the guide recessed portions  83 . Such rolling bearings  82  are disposed at positions where they sandwich the flanges  84  provided on the rack from both sides (or, conversely to illustration, positions where the flanges  84  sandwich the rolling bearings  82  from both sides). 
   Accordingly, the rack  81  can smoothly be displaced with respect to the yoke  55  with a light force without inclining toward the guide recessed portions  83 . Further, if a force directing perpendicular to the displacing direction acts on the rack  81 , any one of the pair of rolling bearings  82  of the rack  81  will support such force, thereby compensating for smooth displacement of the rack  81 . 
   The pinions  72  and rack  81  supported in this way are assembled in such a manner that teeth formed on outer peripheral edges of the pinions  72  are meshed with the toothed portions formed provided on both end portions of the rack  81 , thereby constituting the gear transmitting mechanism  71 . The gear transmitting mechanism  71  serves to minimize backlash and to increase pitch circle diameters of the pinions  72  to some extent (within a range that can prevent interference with other members). Accordingly, the inclination angles of the first trunnions  27  to which the pinions  72  are secured can exactly be coincided with the inclination angles of the first power rollers  45  supported by the first trunnions  27 . Incidentally, although not shown, another gear transmitting mechanism having the same construction as the mechanism  71  is provided between the first trunnions  27  and the second trunnions  28  ( FIG. 28 ) to coincide the inclination angles of the first trunnions  27  with the inclination angles of the second trunnions  28 . 
   As mentioned above, in the toroidal type continuously variable transmission according to the present invention, the yokes  54 ,  55  as members constituting the first and second support means are directly supported by and secured to the inner surface of the casing  5 . Thus, the posts  33   a ,  33   b  ( FIGS. 26  to  28 ) which were required for the above-mentioned conventional arrangement can be omitted, with the result that the number of parts is reduced to facilitate manufacture, control and assembling of the parts, and a height of the toroidal type continuously variable transmission is decreased to make the transmission compact and light-weight while ensuring the endurance. 
   In the present invention, the yokes  54 ,  55  support, at their four corners, the first and second pivot shafts  29 ,  30  provided on the ends of the four (in total) trunnions  27 ,  28  (two first trunnions  27  and two second trunnions  28 ). Thus, all of the forces acting on the first and second trunnions  27 ,  28  can be canceled within the yokes  54 ,  55 . Now, this will be described with reference to FIG.  6 . As mentioned above, when the toroidal type continuously variable transmission is driven, great thrust loads from the first and second power rollers  45 ,  46  act on the first and second trunnions  27 ,  28  along directions shown by the arrows α in FIG.  6 . Each thrust load can be divided into a force component shown by the arrow β in  FIG. 6  along the diametrical direction of the first or second cavity  34  or  35  ( FIG. 1 ) and a force component shown by the arrow γ in  FIG. 6  along the axial direction of the input shaft  1   a.    
   As apparent from  FIG. 6  showing such directions of forces, the force components β along the diametrical directions of the first and second cavities  34 ,  35  have same magnitude and are directed in opposite directions at the first and second trunnions  27 ,  28  arranged in the same cavity. Further, the force components γ along the axial direction of the input shaft  1   a  have same magnitude and are directed in opposite directions at the first and second trunnions  27 ,  28  disposed in the adjacent cavities. Accordingly, all of the forces acting on the first and second trunnions  27 ,  28  are canceled within the yokes  54 ,  55  with the result that such forces do not act on the casing  5  supporting the yokes  54 ,  55 . Thus, since the casing  5  is not subjected to great load, even when the wall thickness of the casing  5  is not increased so great, displacement of the support portions for the first and second pivot shafts  29 ,  30  can be prevented or the endurance of the casing  5  is not worsened. 
   Further, since the ball splines  56  and the radial needle bearings  57  are disposed between the first pivot shafts  29  and the yokes  54 ,  55 , the first trunnions  27  can be displaced smoothly and correctly with respect to the yokes  54 ,  55 . That is to say, as apparent from the aforementioned explanation, during the speed change operation of the toroidal type continuously variable transmission, the first trunnions  27  are displaced in the axial directions of the first pivot shafts  29 , with the result that the first trunnions are rockingly displaced around the first pivot shafts  29 . In the illustrated embodiment, among such displacements, the axial displacement is effected smoothly by the ball spline  56  and the rocking displacement is effected smoothly by the radial needle bearing  57 , with the result that the speed change operation of the toroidal type continuously variable transmission based on such displacements can be effected quickly and correctly. 
   Further, since the outer peripheral surfaces of the ball spline outer races  58  are formed as the semi-spherical convex surfaces  60 , regardless of elastic deformation of the first trunnions  27 , edge load can be prevented from acting on the contact areas between the rolling surfaces of the needles  70  constituting the radial needle bearings  57  and the outer race track  68  and the inner race track  69 . When the toroidal type continuously variable transmission is driven, the great thrust loads act on the first power rollers  45 , and, due to such thrust loads, the first trunnions  27  are elastically deformed so that the opposed inner surfaces thereof become concave, as shown in  FIG. 7  in an aggregated manner. Due to such elastic deformation, the central axes of the first pivot shafts  29  are slightly deviated from the central axes of the support holes  31 . To cope with this, in the arrangement according to the illustrated embodiment, the ball spline outer races  58  are rockingly displaced within the support holes  31 . The central axes of the ball spline outer races  58  and the central axes of the ball spline inner races  65  (which also act as the outer races of the radial needle bearings  57 ) disposed within the ball spline outer races are maintained to be aligned with each other. In the arrangement according to the illustrated embodiment, misalignment between the central axes of the first pivot shafts  29  and the central axes of the support holes  31  is compensated in this way, thereby preventing application of the edge loads. 
   Further, as is in the illustrated embodiment, since the inclination angles of the first power rollers  45  are coincided with each other by the gear transmitting mechanism  71 , great slip is prevented from occurring at the contact areas between the peripheral surfaces  9   a  of the first power rollers  45  and the inner surfaces  2   a ,  4   a  of the discs  17 ,  20 , thereby well ensuring the efficiency of the toroidal type continuously variable transmission. Incidentally, although the gear transmitting mechanism  71  is effective to coincide the inclination angles of the first power rollers  45  with each other exactly and to coincide the inclination angles of the first power rollers  45  with and the inclination angles of the second power rollers  46  ( FIG. 28 ) exactly, when the present invention is carried out, a synchronizing mechanism for coinciding the inclination angles of the first power rollers  45  with and the inclination angles of the second power rollers  46  is not limited to the illustrated gear transmitting mechanism  71 . A synchronizing mechanism of cable type which is well known in the art and shown in  FIGS. 29 and 30  may be used. 
   Further, the present invention is effective when it is applied to a toroidal type continuously variable transmission of double cavity type, in the points that the loads acting on the yokes can be substantially canceled within the yokes and the great load can be prevented from acting on the casing supporting the yokes. However, as shown in  FIGS. 24 and 25 , even in the toroidal type continuously variable transmission of single cavity type in which the single input disc  2  and the single output disc  4  are provided, a measure of effect can be expected. However, when the present invention is applied to the toroidal type continuously variable transmission of single cavity type, as shown in  FIGS. 8A and 8B , in dependence upon the driving condition, a part of loads acting on the trunnions  7  from the power rollers  9  may act on the casing to which the yoke  88  is secured. 
   That is to say, when the rotational speed of the input disc  2  is the same as the rotational speed of the output disc  4  (speed change ratio=1), as shown in  FIG. 8A , loads having the same magnitude and directing in opposite directions act on the trunnions  7 . Accordingly, the loads acting on the trunnions  7  are substantially canceled within the yoke  88 , with the result that any load does not act on the casing supporting the yoke  88 . On the other hand, when the rotational speed of the input disc  2  differs from the rotational speed of the output disc  4  (speed change ratio≠1), as shown in  FIG. 8B , among the loads acting on the trunnions  7 , a load component along the axial direction of the input disc  2  and the output disc  4  cannot be canceled, and such load component acts on the casing. Since the load component acting on the casing in this way is smaller than the loads acting on the trunnions  7 , when the yoke  88  is secured to the casing at plural locations, as is in the arrangement disclosed in the above Japanese Patent Laid-Open No. 10-274300, unlike to the arrangement in which the loads acting on the trunnions is transmitted to the casing as they are, there arises no practical problem regarding prevention of deformation of the casing and assurance of endurance of the casing. 
   &lt;Second Embodiment&gt; 
     FIGS. 9  to  11  show a second embodiment of the present invention. The second embodiment differs from the first embodiment, regarding an arrangement for supporting the first pivot shafts  29  remote from the drive rods  51  (among the first pivot shafts  29  provided on both ends of the first trunnions  27 ) with respect to the casing  5 . That is to say, in the second embodiment, when the ball splines  56  for supporting the first pivot shafts  29  remote from the drive rods  51  with respect to the yoke  54  are assembled, the through hole  86  ( FIGS. 4 and 5 ) used in the first embodiment is omitted and the lid plate  87  ( FIG. 5 ) for closing the through hole  86  is also omitted, thereby reducing the cost and improving the strength of the casing  5 . 
   To this end, in the second embodiment, notches  89  caved in the diametrical direction of the support hole  31  are formed in diametrically opposed positions (two positions) of the smaller diameter portion  59  formed in the half part of the open portion of the support hole  31  of the yoke  54 . Further, protrusions  90  capable of passing through the notches  89  are formed on diametrically opposed positions (two positions) of the outer peripheral surface of the proximal end (upper end in  FIGS. 9 and 10 ) of the ball spline outer race  58 . A locking notch  91  is formed in a central portion of an outer peripheral edge of one of the protrusions  90  (protrusion at the right in FIG.  10  and at the right and upper in FIG.  11 ). Further, in correspondence to the smaller diameter portion  59  of the support hole  31  formed in the yoke  54 , a threaded hole  92  is formed in a portion aligned with the locking notch  91  between the notches  89 , and a tip end of a set screw  93  threaded in the threaded hole  92  is engaged by the locking notch  91 . 
   The construction according to the illustrated embodiment as mentioned above is assembled as follows. The radial needle bearing  57  and the ball spline  56  are previously attached to the end of the first pivot shaft  29 . The dislodging of the plurality of balls  67  constituting the ball spline  56  is prevented by the stop ring locked to the inner peripheral surface of the end of the ball spline outer race  58  or the outer peripheral surface of the end of the ball spline inner race  65 . In a condition that the notches  89  are aligned with the protrusions  90 , the protrusions  90  are inserted into the support hole  31 . Then, the ball spline outer race  58  is rotated by 90 degrees to align the locking notch  91  with the threaded hole  92 . Then, the set screw  93  is threaded into the threaded hole  92  to enter the tip end of the set screw  93  into the locking notch  91 . As a result, the notches  89  are deviated from the protrusions  90  and the ball spline outer race  58  can be maintained within the support hole  31 . Since the other constructions and functions are the same as those in the first embodiment, the same elements are designated by the same reference numerals and duplicated explanation will be omitted. 
   &lt;Third Embodiment&gt; 
     FIG. 12  shows a third embodiment of the present invention. In the third embodiment, rollers  94  are disposed between the outer race side ball spline grooves  64  formed in the inner peripheral surface of the ball spline outer race  58  and the inner race side ball spline grooves  66  formed in the outer peripheral surface of the ball spline inner race  65 , respectively. Accordingly, radial load capacity of the spline portion can be made greater. Incidentally, the rollers  94  are not rolling as the first pivot shafts  29  are shifted in the axial direction. Accordingly, in the third embodiment, although the force required for shifting the first pivot shafts  29  becomes greater than those in the first and second embodiments, since the axial shifting movement of the first pivot shafts  29  is effected by the drive cylinder  53  ( FIGS. 1 and 9 ) with a strong force, so long as the diameter and oil pressure of the drive cylinder  53  are reserved, adequate practical response ability can be obtained. The other constructions and functions are the same as those in the first embodiment. 
   &lt;Fourth Embodiment&gt; 
   Next, a fourth embodiment of the present invention shown in  FIGS. 13 and 14  will be explained. Incidentally, explanation of the same elements as those in the previous embodiments will be omitted. 
   In the fourth embodiment, among support holes  131 , within the support holes  131  formed on one ends of yokes  154 ,  155 , first pivot shafts  129  are supported by radial needle bearings  136  for rocking movement and axial displacement. Incidentally, outer peripheral surfaces of outer races  137  for constituting the radial needle bearings  136  are formed as spherical convex surfaces so that edge loads are prevented from acting on contact areas between rolling surface of needles  138  constituting the radial needle bearings  136  and associated surfaces, regardless of elastic deformation of first trunnions  127 . 
   When the toroidal type continuously variable transmission is driven, great thrust loads act on first power rollers  145 , with the result that the first trunnions  127  are elastically deformed so that opposed inner surfaces thereof become concave by the thrust loads. Due to such elastic deformation, central axes of the first pivot shafts  129  are slightly deviated from central axes of the support holes  131 . In such a case, the deviation is compensated by rocking the outer races  137  within the support holes  131 , thereby preventing application of the edge load. 
   In case of the toroidal type continuously variable transmission of the present invention including the construction according to the illustrated embodiment, unlike to the conventional construction shown in  FIGS. 26  to  28 , since the yokes  154  are not displaced, the deviation between the central axes of the first pivot shafts  129  and the central axes of the support holes  131  is limited. More specifically, in the conventional construction, the inclination angles of the pair of opposed first power rollers  145  are coincided with each other by supporting the yokes  126   a ,  126   b  for slight displacement with respect to the casing  105  via the support posts  133   a ,  133   b . Thus, when the toroidal type continuously variable transmission is driven, the central axes of the first pivot shafts  129  are deviated from the central axes of the support holes  131  not only by elastic deformation of the first trunnions  127  but also by displacement of the yokes  126   a ,  126   b . Accordingly, in the conventional construction, it is inevitable that the radial needle bearings  136  are provided with the outer races  137  having spherical convex outer peripheral surfaces. To the contrary, in the illustrated embodiment, since the yokes  154 ,  155  are not displaced, as mentioned above, the deviation between the central axes of the first pivot shafts  129  and the central axes of the support holes  131  is limited. Accordingly, so long as occurrence of edge load can be prevented, for example, by providing “crowns” on the needles  138 , as shown in  FIG. 14 , the outer races  137  can be omitted from the radial needle bearings  136 . 
   Further, as mentioned above, in case of the toroidal type continuously variable transmission of the present invention including the construction according to the illustrated embodiment, since the yokes  154 ,  155  are not displaced, the yokes do not have functions for coinciding the inclination angles of the pair of opposed first power rollers  145  with each other. That is to say, although the inclination angles are adjusted by axial displacement amounts of drive rods  151  controlled by supplying or discharging the pressurized oil with respect to the drive cylinders  153 , it is difficult to exactly coincide the inclination angles of the pair of first power rollers  145  by such axial displacement amounts. Thus, in the conventional construction, the inclination angles of the pair of first power rollers  145  have been exactly coincided with each other by permitting the displacement of the yokes  126   a  and by supporting the first power rollers  145  in a so-called floating fashion. However, in the toroidal type continuously variable transmission of the present invention, the inclination angles of the pair of first power rollers  145  cannot be coincided with each other by the displacement of the yokes  154 ,  155 . Thus, in the illustrated embodiment, the inclination angles of the pair of first power rollers  145  supported by the first trunnions  127  are coincided with each other exactly by interconnecting the pair of opposed first trunnions  127  through a gear transmitting mechanism  156 . 
   To install the gear transmitting mechanism  156 , one (lower one ( 155 ) in  FIG. 13 ) of the yokes is provided with a recessed portion  157 . Accordingly, in a condition that the recessed portion  157  and a cylinder case  158  are overlapped with each other, a space  159  for containing the gear transmitting mechanism  156  is defined between these members  155 ,  158 . The gear transmitting mechanism  156  contained in this space  159  includes a pair of pinions  160  having the same configuration and the same number of teeth, and a rack  161  having toothed portions provided on both end portions and having the same pitch. The pinions  160  are fitted onto and secured to non-cylindrical portions formed on the tip ends of the first pivot shafts  129  provided on the ends of the first trunnions  127 , or are supported by ball splines and the like for axial shifting movement without relative rotation. Accordingly, the first trunnions  127  are rotated synchronously with the pinions  160 . 
   The rack  161  can be displaced only along the axial direction (direction perpendicular to the plane of  FIG. 13 ) of an input shaft  101   a  and is supported within the space  159 . To this end, in the illustrated embodiment, a guide protruded portion  162  formed on a side surface of the rack  161  is engaged by a guide groove  163  formed in the bottom of the recessed portion  157 . Further, a sliding protruded portion  166  is formed on the other side surface of the rack  161 , and the sliding protruded portion  166  is slid with respect to the cylinder case  158 , thereby preventing the rack  161  from shifting toward a fallen direction. Incidentally, a structure for supporting the rack  161  for parallel shifting movement only in one direction is not limited to the illustrated structure, but, various structures known in the art can be used. For example, an elongated hole extending the direction perpendicular to the plane of  FIG. 13  may be formed in the rack  161 , and a plurality of guide pins fixed along the direction perpendicular to the plane of  FIG. 13  within the space  159  may be engaged by the elongated hole. 
   The pinions  160  and rack  161  supported in this way are assembled in such a manner that teeth formed on outer peripheral edges of the pinions  160  are meshed with the toothed portions formed provided on both end portions of the rack  161 , thereby constituting the gear transmitting mechanism  156 . The gear transmitting mechanism  156  serves to minimize backlash and to increase pitch circle diameters of the pinions  160  to some extent (within a range that can prevent interference with other members). Accordingly, the inclination angles of the first trunnions  127  to which the pinions  160  are secured can exactly be coincided with the inclination angles of the first power rollers  145  supported by the first trunnions  127 . Incidentally, although not shown, another gear transmitting mechanism having the same construction as the mechanism  156  is provided between the first trunnions  127  and second trunnions  128  (refer to the reference numeral  28  in  FIG. 28 ) to coincide the inclination angles of the first trunnions  127  with the inclination angels of the second trunnions  128 . 
   Further, a stopper plate  164  provided at an upper central part in  FIG. 13  serves to prevent the inclination angles of the first trunnions  127  from becoming too great and is disposed around a nozzle from  165  for supplying lubricating oil to contact areas between peripheral surfaces  109   a  of the first power rollers  145  and inner surfaces  102   a  of a first input disc  117  and inner surface  104   a  ( FIG. 26 ) of a first output disc  120 . Incidentally, in the above explanation, an example that the present invention is applied to the toroidal type continuously variable transmission of double cavity type was described. Although the present invention can achieve remarkable effect when it is applied to the toroidal type continuously variable transmission of double cavity type, the present invention can also be applied to a toroidal type continuously variable transmission of single cavity type as shown in  FIGS. 24 and 25 . 
   As mentioned above, in the toroidal type continuously variable transmission according to the present invention, the yokes  154 ,  155  as members constituting the first and second support means are directly supported by and secured to the inner surface of the casing  105 . Thus, the posts  133   a ,  133   b  which were required for the above-mentioned conventional arrangement can be omitted and the outer races  137  for constituting the radial needle bearings  136  can also be omitted, with the result that the number of parts is reduced to facilitate manufacture, control and assembling of the parts, and a height of the toroidal type continuously variable transmission is decreased to make the transmission compact and light-weight while ensuring the endurance. Further, as is in the illustrated embodiment, since the inclination angles of the first power rollers  145  are coincided with each other by the gear transmitting mechanism  156 , considerable slip can be prevented from occurring in the contact areas between the peripheral surfaces  109   a  of the first power rollers  145  and inner surfaces  102   a ,  104   a  of the discs, thereby well ensuring the efficiency of the toroidal type continuously variable transmission. 
   Since the present invention has the above-mentioned arrangement and function, a toroidal type continuously variable transmission which can be manufactured cheaply with compact and light-weight form and which has excellent transmitting efficiency can be provided. 
   &lt;Fifth Embodiment&gt; 
   Now, a fifth embodiment of the present invention will be described. 
   The above-mentioned gear transmitting mechanism  71  (or  156 ) is designed in consideration of the fact that the inclination angles of the trunnions and accordingly the power rollers caused by the axial displacement of the drive rods  51  (or  151 ) are coincided with each other, but is not intended to synchronize the axial displacements of the drive rods  51  themselves. The axial displacements of the drive rods  51  are synchronized by controlling the oil pressure introduced into the drive cylinders  53 . Thus, in the transition immediately after the speed change operation is started, the inclination angles of the trunnions  27 ,  28  differ from each other slightly, and, as the case may be, slip may occur in the contact areas between the peripheral surfaces  9   a  of the power rollers  45 ,  46  and the inner surfaces  2   a ,  4   a  of the discs  2 ,  4 ,  17 ,  18 ,  20 ,  21 . 
   The slip generated in the contact areas for this reason is apt to occur when the trunnions  27 ,  28  are quickly shifted in the axial directions of the pivot shafts  29 ,  30  in order to effect the speed change operation quickly. If the slip is generated, since not only the power transmitting efficiency is worsened but also life of rolling fatigue of each surface is shortened, the occurrence of the slip is not preferable. In order to permit the quick speed change operation while preventing the transmitting efficiency from worsening and the life of rolling fatigue from shortening, it is necessary to realize a structure in which the axial displacements of the drive rods  51  themselves are synchronized with each other exactly. 
   A toroidal type continuously variable transmission according to the fifth embodiment is devised in consideration of the above circumstances. 
     FIGS. 15  to  20  show the fifth embodiment of the present invention. Incidentally, this embodiment is characterized in that it has a specific construction for positively synchronizing inclination angles of first trunnions  227  with inclination angles of second trunnions  228  (refer to reference numeral  28  in  FIG. 28 ) and a specific construction for supporting first pivot shafts  229  provided on both ends of the first trunnions  227  and second pivot shafts  230  (refer to reference numeral  30  in  FIG. 28 ) provided on both ends of the second trunnions  228 . Since the other constructions and functions are the same as those of the conventional technique shown in  FIGS. 26  to  28 , illustration and explanation of the similar elements are omitted or simplified, and the characteristics of this embodiment will be described mainly. 
   A pair of yokes  258 ,  259  are directly secured to opposed portions of the casing  205 . Circular support holes  231  are formed in four corners of the yokes  258 ,  259  at areas aligned with each other. Within the support holes  231 , the first pivot shafts  229  are supported via ball splines  260  and radial needle bearings  261  for axial displacement and rocking movement. 
   Ball spline outer races  262  for constituting the ball splines  260  are fitted into the support holes  231  in a condition that the axial displacement of the races is limited. A plurality of outer race side ball spline grooves  263  extending in an axial direction (up-and-down direction in  FIGS. 15 and 16 ) are formed in inner peripheral surfaces of the ball spline outer races  262 . And, ball spline inner races  264  (also acting as outer races of the radial needle bearings  261 ) are disposed within the interiors of the ball spline outer races  262  concentrically with the radial needle bearings  261 . Inner race side ball spline grooves  265  extending in an axial direction are formed in portions of the outer peripheral surfaces of the ball spline inner races  264  which are opposed to the outer race side ball spline grooves  263 . A plurality of balls  266  are disposed between the respective inner race side ball spline grooves  265  and the respective outer race side ball spline grooves  263 , thereby constituting the ball splines  260 . Incidentally, any play of the ball spline outer races  262  is prevented by elastic members such as coned disc springs  290 . 
   Cylindrical outer race tracks  267  for the radial needle bearings  261  are provided on inner peripheral surfaces of the ball spline inner races  264 . A plurality of needles  269  are disposed between the respective outer race tracks  267  and respective cylindrical inner race tracks  268  formed on the outer peripheral surfaces of the first pivot shafts  229  provided on both ends of the first trunnions  227 , thereby constituting the radial needle bearings  261 . 
   Drive rods  251  having proximal ends (upper ends in  FIG. 15 ) connected to ends of lower first pivot shafts among the first pivot shafts  229  provided on both ends of the first trunnions  227  extend through through-holes  271  formed in a valve body  270  secured to the casing  205 . Receiving pieces  272  as shown in  FIG. 17  are secured to tip ends (lower ends in  FIG. 15 ) of the drive rods  251  protruded from an outer surface (lower surface in  FIG. 15 ) of the valve body  270 . The receiving pieces  272  are constituted by circumferential parts of peripheral edges of a pair of parallel ring portions  273   a ,  273   b  via a partial cylindrical connecting portion  274 , and an opening portion  275  is defined by portions deviated from the connecting portion  274 . Among the ring portions  273   a ,  273   b , an inner diameter of one (upper one in  FIGS. 15 and 17 ) ring portion  273   a  is relatively small so that only a male threaded portion formed on the drive rod  251  can pass through such a ring portion. On the other hand, an inner diameter of the other (lower one is  FIGS. 15 and 17 ) ring portion  273   b  is relatively great so that a nut  276  to be threaded onto the male threaded portion and a tool for tightening the nut  276  can pass through such a ring portion. 
   Pivot brackets  279  having second pivot shafts  278  are provided on attachment substrate plates  277  secured to the outer surface of the valve body  270 . The second pivot shafts  278  extend in parallel with rotational axes of first and second input discs  217  and first and second output discs  220 ,  221  ( FIG. 12 ) and are disposed at positions opposed to sides of first and second cavities  234 ,  235  (FIG.  12 ). The second pivot shafts  278  rockably support width-wise (left-and-right direction in  FIG. 18 ) central portions of both longitudinal (up-and-down direction in  FIG. 18 ) ends of a rocking arm  280  formed as a substantially square frame as shown in FIG.  18 . Accordingly, both width-wise ends of the rocking arm  280  are displaced in opposite directions by the same amount with respect to the axial direction of the drive rods  251 . 
   Both longitudinal ends of both width-wise ends of the rocking arm  280  are engaged by the opening portion  275  between the pair of ring portions  273   a ,  273   b  of the receiving pieces  272  so that play is not generated even when the rocking arm is rocked around the second pivot shafts  278 . To this end, in the illustrated embodiment, small projections  281  are formed on areas of both surfaces of the longitudinal ends of both width-wise ends of the rocking arm  280  which are opposed to the ring portions  273   a ,  273   b , and tip ends of the small projections  281  abut against opposed surfaces of the ring portions  273   a ,  273   b . Accordingly, axial displacements (along the axial directions of the first and second pivot shafts  229 ,  230 ) of the receiving pieces  272  and of the first and second trunnions  227 ,  228  fixedly connected to the receiving pieces  272  via the drive rods  251  are mechanically synchronized exactly. Incidentally, a precess cam is secured to any trunnion or the drive rod fixedly connected to any trunnion so that feedback control for activating a control valve for supplying or discharging pressurized oil with respect to the drive cylinders  253  is effected by the precess cam. 
   Further, in the illustrated embodiment, the first and second trunnions  227 ,  228  are interconnected by a gear transmitting mechanism  282 . To install the gear transmitting mechanism  282 , one (lower one ( 259 ) in  FIG. 15 ) of the yokes is provided with a recessed portion  284 . Accordingly, in a condition that the yoke  259  and a cylinder case  285  are overlapped with each other, a space  289  for containing the gear transmitting mechanism  282  is defined between these members  259 ,  285 . The gear transmitting mechanism  282  contained in this space  289  includes two pairs of pinions  283  having the same configuration and the same number of teeth, and four racks  287   a ,  287   b  having toothed portions provided on both end portions and having the same pitch. The pinions  283  are fitted onto and secured to non-cylindrical portions formed on the tip ends of the first and second pivot shafts  229 ,  230  provided on the ends of the first and second trunnions  227 ,  228 . Accordingly, the first and second trunnions  227 ,  228  are rotated synchronously with the pinions  283 . Incidentally, when the speed change ratio is changed, the first and second trunnions  227 ,  228  are displaced in the axial directions of the first and second pivot shafts  229 ,  230 . Accordingly, by providing moderate (an amount which does not arise any problem regarding the coincidence of the inclination angles) backlash in engagement areas between the pinions  283  and the racks  287   a ,  287   b , relative displacement between the pinions  283  and the racks  287   a ,  287   b  is permitted. 
   The racks  287   a ,  287   b  can be displaced only along the axial direction (direction perpendicular to the plane of  FIG. 15  or left-and-right direction in  FIG. 15 ; left-and-right direction or up-and-down direction in  FIG. 20 ) of the input shaft  201   a  and are supported within the space  289 . To this end, in the illustrated embodiment, the racks  287   a ,  287   b  are supported by pairs of translation rolling bearings (linear bearings)  288  for parallel shifting movement with respect to the yokes  259 . Accordingly, the racks  287   a ,  287   b  can smoothly be displaced with a light force without inclination. Further, if a force directing perpendicular to the displacing direction acts on the racks  287   a ,  287   b , any one of the pair of rolling bearings  288  of the racks  287   a ,  287   b  will support such force, thereby compensating for smooth displacement of the racks  287   a ,  287   b.    
   The pinions  283  and racks  287   a ,  287   b  supported in this way are assembled in such a manner that teeth formed on outer peripheral edges of the pinions  283  are meshed with the teeth formed provided on both end portions of the racks  287   a ,  287   b , thereby constituting the gear transmitting mechanism  282 . The gear transmitting mechanism  282  serves to minimize backlash and to increase pitch circle diameters of the pinions  283  to some extent (within a range that can prevent interference with other members). Accordingly, the inclinations angles of the first and second trunnions  227 ,  228  to which the pinions  283  are secured can exactly be coincided with the inclination angles of the first and second power rollers  245 ,  246  supported by the first and second trunnions  227 ,  228 . 
   As mentioned above, in the toroidal type continuously variable transmission of the present invention, the displacements of the first and second trunnions  227 ,  228  along the axial directions of the first and second pivot shafts  229 ,  230  are mechanically synchronized with each other exactly by the rocking arm  280 . Accordingly, during the speed change operation, the displacement amounts of the first and second trunnions  227 ,  228  are coincided with each other quickly and exactly, with the result that, during the speed change operation, any slip can be prevented from generating in the contact areas between the inner surfaces  202   a ,  204   a  ( FIG. 26 ) of the first and second input discs  217 ,  218  and the first and second output discs  220 ,  221  and the peripheral surfaces  209   a  ( FIGS. 15 ,  27  and  28 ) of the first and second power rollers  245 ,  246 . 
   A result of tests conducted for ascertaining the effect of the present invention will now be explained with reference to  FIGS. 22A  to  23 B. The tests were carried out by using the toroidal type continuously variable transmission of double cavity type in which a pair of power rollers are provided for each of the cavities, as shown in FIG.  21 . In the tests, regarding four trunnions  227 ,  228  supporting front right (FR) and front left (FL) power rollers near the pressing device  210  and rear right (RR) and rear left (RL) power rollers remote from the pressing device, respectively (i.e., supporting four (in total) power rollers  245 ,  246 ), during the speed change operation, the axial displacement amounts and rocking angles of the trunnions  227 ,  228  caused after predetermined pressurized oil was introduced into the drive cylinders were measured in connection with elapsed time.  FIGS. 22A and 22B  show a test result of the toroidal type continuously variable transmission of the present invention, where  FIG. 22A  shows the axial displacement amounts of the trunnions, and  FIG. 22B  shows the rocking angles of the trunnions.  FIGS. 23A and 23B  show a case where the displacements of the trunnions were adjusted only by adjusting the oil pressure, where  FIG. 23A  shows the axial displacement amounts of the trunnions, and  FIG. 23B  shows the rocking angles of the trunnions. As apparent from  FIGS. 22A  to  23 B showing the test results, according to the present invention, even when the quick speed change operation is effected, the displacements of the trunnions can positively be synchronized with each other. 
   Further, in the toroidal type continuously variable transmission according to the illustrated embodiment, the yokes  258 ,  259  constituting the first and second support means are directly supported by and secured to the inner surface of the casing  205 . Thus, the support posts (refer to reference numerals  33   a ,  33   b  in  FIGS. 27 and 28 ) which were required in the conventional arrangement can be omitted, with the result that the number of parts is reduced to facilitate manufacture, control and assembling of the parts, and a height of the toroidal type continuously variable transmission is decreased to make the transmission compact and light-weight while ensuring the endurance. 
   Further, since the ball splines  260  and the radial needle bearings  261  are disposed between the first pivot shafts  229  and the yokes  258 ,  259 , the displacements of the first and second trunnions  227 ,  228  with respect to the yokes  258 ,  259  can be effected smoothly and correctly. That is to say, as apparent from the aforementioned explanation, during the speed change operation of the toroidal type continuously variable transmission, the first and second trunnions  227 ,  228  are displaced along the axial directions of the first and second pivot shafts  229 ,  230 , with the result that the trunnions are rockingly displaced around the first and second pivot shafts  229 ,  230  due to the axial displacements. In the illustrated embodiment, among these displacements, the axial displacements are effected smoothly by the ball splines  260  and the rocking displacements are effected smoothly by the radial needle bearings  261 , so that the speed change operation of the toroidal type continuously variable transmission based on such displacement can be effected quickly and correctly. 
   Further, as is in the illustrated embodiment, since the gear transmitting mechanism  282  is provided, even if an oil pressure supplying circuit for the drive cylinders  252  is damaged, the inclination angles of the first and second power rollers  245  can be coincided with each other. Thus, even in malfunction, any severe slip can be prevented from generating in the contact areas between the peripheral surfaces  209   a  of the first and second power rollers  245  and the inner surfaces  202   a ,  204   a  of the discs  217 ,  218 ,  220 ,  221 , thereby preventing damage of the toroidal type continuously variable transmission. 
   Since the present invention has the above-mentioned construction and function, the quick speed change operation can be effected while ensuring the endurance, and, thus, possibility of application of the toroidal type continuously variable transmission to high performance vehicles such as sports cars is increased. Therefore, the present invention contributes to practical use of toroidal type continuously variable transmissions. 
   Incidentally, when the present invention is carried out, a mechanism for coinciding the inclination angles of the trunnions with each other is not limited to the gear transmitting mechanisms  282 ,  71 ,  156 , but, a mechanism using a cable as shown in  FIGS. 29 and 30  may be used. 
   Now, a conventional synchronizing mechanism using a cable will be described with reference to  FIGS. 29 and 30 . 
   Such mechanisms are well-known as disclosed in Japanese Patent Laid-Open Nos. 63-67458 (1988) and 4-327051 (1992) and Japanese Utility Model Laid-Open No. 62-200852 (1987). Among them,  FIGS. 29 and 30  show two examples disclosed in the Japanese Patent Laid-Open No. 4-327051. On the basis of  FIGS. 29 and 30 , a mechanism for synchronizing the rocking movements of the first and second trunnions  327 ,  328  in the toroidal type continuously variable transmission of double cavity type with each other will now be explained. 
   In order to construct the synchronizing mechanism, pulleys  354  are secured to the axial (direction perpendicular to the planes of  FIGS. 29 and 30 ) ends of the first and second trunnions  327 ,  328 . Peripheral surfaces of the pulleys  354  are formed as arc surfaces coaxial with the pivot shafts of the trunnions (refer to reference numerals  29 ,  30  in FIGS.  27  and  28 ). Portions of cable  355 ,  355   a ,  355   b  are fitted into and wound around grooves formed in the peripheral surfaces of the pulleys  354  so that four (in total) first and second trunnions  327 ,  328  are rocked in a synchronous manner. In these arrangements, each cable  355  extends between and wound around the pair of pulleys  354  secured to the ends of the first and second trunnions  327 ,  328  constituting each pair in a cross belting fashion. Accordingly, the pair of first and second trunnions  327 ,  328  (located within the same cavity) can be rotated in opposite directions by the same angle. The pulleys  354  arranged along a diagonal line (located within different cavities and situated at diametrically opposed position with respect to the input shaft  301   a ) can be rotated in the same direction by the same amount. 
   To this end, in the arrangement according to the first example shown in  FIG. 29 , the cable  355   a  is mounted only between the pulleys  354  arranged along the diagonal line, and the cable  355   a  is secured to the pulleys  354  arranged along the diagonal line by fasteners  356 . On the other hand, in the arrangement according to the second example shown in  FIG. 30 , the cable  355   b  is wound around all of the pulleys  354 , and the cable  355   b  is secured to only the pair of pulleys  354  arranged along the diagonal line by fasteners  356 . Any slip can be generated between the remaining pulleys  354  and the cable  355   b  so that the movement of the cable  355   b  is not transmitted to the remaining pulleys  354 . The arrangement shown in  FIG. 30  is adopted in order to prevent interference between the cable  355   b  and other members constituting the toroidal type continuously variable transmission such as first and second output discs  320 ,  321  and large diameter output gear  323 . Incidentally, also in the toroidal type continuously variable transmission of so-called single cavity type in which a single input disc and a single output disc are provided, by providing the cable  355  of cross belting type shown in  FIGS. 29 and 30 , the rocking movements of the plurality of trunnions are synchronized with each other. Further, although not shown, Japanese Utility Model Publication No. 4-52512 (1992) and Japanese Patent Laid-Open Nos. 6-117515 (1994) and 7-243496 (1995) disclose techniques in which a mechanism for synchronizing inclination angles of a plurality of trunnions with each other is constituted by a gear transmitting mechanism. 
   Many widely different embodiments of the present invention may be constructed without departing from the spirit and scope of the present invention. It should be understood that the present invention is not limited to the specific embodiments described in the specification, except as defined in the appended claims.