Belt type continuously variable transmission

A belt type continuously variable transmission in which a pulley shaft is supported by bearings provided at two positions that are apart from each other in an axial direction of the pulley shaft and a supply oil passage for supplying hydraulic fluid to a pulley hydraulic chamber includes a radial direction oil passage that is formed in the pulley shaft, the radial direction oil passage is formed on an outside of an area between the two positions. Also, one of the bearings is provided near the radial direction oil passage and on an outer surface side of a cylinder member whose inner surface side forms the pulley hydraulic chamber for a movable sheave that is fixed to the pulley shaft. With this structure, concentration of stress on the radial direction oil passage can be avoided, and therefore strength of the pulley shaft can be secured.

The disclosure of Japanese patent application no. 2004-085688 filed on Mar. 23, 2004, including the specification, drawings and Abstract is incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a belt type continuously variable transmission which can achieve a desired speed ratio by changing a winding radius of a belt.

2. Description of the Related Art

A belt type continuously variable transmission has been known as a transmission for a vehicle. The belt type continuously variable transmission of this type includes a primary shaft (a rotating shaft on the driving side) and a secondary shaft (a rotating shaft on the driven side) which are provided in parallel with each other; a primary pulley which is attached to the primary shaft; and a secondary pulley which is attached to the secondary shaft. Each of the primary pulley and the secondary pulley includes a fixed sheave, and a movable sheave which is movable with respect to the fixed sheave. Each movable sheave is provided so as to be movable in the axial direction and immovable in the circumferential direction with respect to the corresponding rotating shaft via a ball, a ball groove (ball spline), and the like. A substantially V-shaped pulley groove is formed between the fixed sheave and the movable sheave. An endless belt is wound on the pulley grooves of the primary pulley and the secondary pulley. A pulley hydraulic chamber for making the movable sheave come close to/move away from the corresponding fixed sheave is provided for each of the primary pulley and the secondary pulley. The hydraulic pressure of the pulley hydraulic chamber for the primary pulley and the hydraulic pressure of the pulley hydraulic chamber for the secondary pulley are controlled separately. Thus, a groove width of the pulley is changed, and therefore a belt winding radius is changed. As a result, a speed ratio of the belt type continuously variable transmission is set to a desired value, and a tension of the belt is adjusted.

Japanese Patent Application Publication JP(A) 11-141633 discloses a technology related to the above-mentioned belt type continuously variable transmission. In this belt type continuously variable transmission, oil passages for supplying hydraulic fluid to the above-mentioned pulley hydraulic chamber are formed along the axis of a pulley shaft and in the radial direction of the pulley shaft, and the radial direction oil hole is formed in a spline shaft portion of the pulley shaft on the shaft end side. The movable sheave is attached to the spline shaft portion by spline-coupling. As a result, concentration of stress that occurs in the oil hole is reduced.

According to the technology disclosed in Japanese Patent Application Publication JP(A) 11-141633, the radial direction oil hole is formed in the spline shaft portion on the shaft end side, and therefore concentration of stress that occurs in the oil hole can be reduced to a certain extent. However, since the radial direction oil hole is formed in an area between two bearings which support the pulley shaft, the pulley shaft may be deformed by a bending load due to a belt tension applied to the pulley shaft, and the stress may be concentrated on the radial direction oil hole. As a result, considering the concentration of stress, the number of the radial direction oil holes need to be reduced, a diameter of the oil hole need to be decreased, or a diameter of the pulley shaft need to be increased, which causes problems such as an increase in cost and an increase in weight.

SUMMARY OF THE INVENTION

It is an object of the invention to solve the above-mentioned problems, and provide a belt type continuously variable transmission which can avoid concentration of stress on a radial direction oil hole and which can secure strength of a pulley shaft.

According to an aspect of the invention, there is provided a belt type continuously variable transmission in which a pulley shaft is supported by bearings provided at two positions that are apart from each other in the axial direction of the pulley shaft and a supply oil passage for supplying hydraulic fluid to a pulley hydraulic chamber includes a radial direction oil passage that is formed in the pulley shaft in the radial direction of the pulley shaft. The belt type continuously variable transmission is characterized in that the radial direction oil passage is formed on the outside of an area between the two positions which are apart from each other and at which the bearings are provided.

With the above-mentioned belt type continuously variable transmission, the pulley shaft is supported by the bearings which are provided at the two positions that are apart from each other in the axial direction of the pulley shaft, and the radial direction oil passage for supplying the hydraulic fluid to the pulley hydraulic chamber is formed on the outside of the area between the two positions which are apart from each other and at which the bearings are provided. Therefore, a portion in which the radial direction oil passage of the pulley shaft is formed does not directly receive a load applied by the belt. Accordingly, concentration of stress on the radial direction oil passage does not occur, and the strength of the pulley shaft can be secured.

One of the bearings may be provided near the radial direction oil passage and on the outer surface side of a cylinder member whose inner surface side forms the pulley hydraulic chamber for a movable sheave that is attached to the pulley shaft so as to be fixed with respect to the pulley shaft in the rotational direction of the pulley shaft and so as to be slidable in the axial direction of the pulley shaft.

With the structure in which one of the bearings is provided near the radial direction oil passage and on the outer surface side of the cylinder member whose inner surface side forms the pulley hydraulic chamber for the movable sheave that is attached to the pulley shaft so as to be fixed with respect to the pulley shaft in the rotational direction of the pulley shaft and so as to be slidable in the axial direction of the pulley shaft, in addition to the above-mentioned effect, the following effect can be obtained. A reaction force against the force applied by the belt is received not by the cylinder member, but by the bearing, which makes it possible to suppress increases in size and thickness of the cylinder member.

Further, the radial direction oil passage may be located on the outer side of a spline portion, which is formed in the pulley shaft, in the axial direction of the pulley shaft. Also, the spline portion formed in the pulley shaft may be engaged with a spline portion formed in the movable sheave on the inner surface side.

The pulley hydraulic chamber may include a first hydraulic chamber, and the first hydraulic chamber may be a space formed by a back surface of the movable sheave and the cylinder member which faces the movable sheave in the axial direction of the pulley shaft; and the pulley hydraulic chamber may include a first hydraulic chamber, and the first hydraulic chamber may be a space formed by a ring-shaped member which is fixed to a back surface of the movable sheave, an inner cylindrical portion of the movable sheave, and the cylinder member which faces the movable sheave in the axial direction of the pulley shaft.

The pulley hydraulic chamber may include a second hydraulic chamber, and the second hydraulic chamber may be a space formed by an end surface of an inner cylindrical portion of the movable sheave and the cylinder member.

The cylinder member may further include a first radial direction portion which extends in the radial direction of the pulley shaft; a first cylindrical portion which extends from the first radial direction portion so as to be substantially parallel with the axis line of the pulley shaft; a second radial direction portion which extends from the first cylindrical portion along the back surface of the movable sheave in the radial direction of the pulley shaft; and a second cylindrical portion which extends from the second radial direction portion so as to be substantially parallel with the axis line of the pulley shaft.

With the belt type continuously variable transmission having the above-mentioned structure, the radial direction oil passage is located on the outer side of the spline portion, which is formed in the pulley shaft, in the axial direction. Therefore, in addition to the above-mentioned effects, the following effect can be obtained. A torsional load applied by the belt or the pulley shaft is not directly received by the portion of the pulley shaft, in which the radial direction oil passage is formed. Therefore, concentration of stress on the radial direction oil passage does not occur, and the strength of the pulley shaft can be secured.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following description and the accompanying drawings, the present invention will be described in more detail in terms of an exemplary embodiment.

FIG. 1is a view schematically showing part of a vehicle to which a belt type continuously variable transmission according to the invention is applied. A vehicle1shown inFIG. 1is configured as a so-called FF vehicle (front engine front drive: front engine front wheel drive), and includes an engine2serving as a drive power source. As the engine2, a gasoline engine, a diesel engine, a LPG engine, a hydrogen engine, a bi-fuel engine or the like may be employed. In this specification, the description will be made on the assumption that a gasoline engine is used as the engine2.

As shown inFIG. 1, the vehicle1includes a transaxle3which is provided adjacent to the transverse engine2and which is coupled with a crankshaft SC of the engine2. The transaxle3includes a transaxle housing4, a transaxle case5, and a transaxle rear cover6. The transaxle housing4is provided adjacent to the engine2, and the transaxle case5is fixed to an open end of the transaxle housing4, which is on the opposite side of the engine2. Also, the transaxle rear cover6is fixed to an open end of the transaxle case5, which is on the opposite side of the transaxle housing4. A torque converter7is provided inside of the transaxle housing4. A forward/reverse running changing mechanism8, a belt type continuously variable transmission (CVT)9according to the invention, and a final reduction gear (differential gear)10are provided in the transaxle case5and the transaxle rear cover6.

The torque converter7has a drive plate11, and a front cover12which is fixed to the crankshaft SC of the engine2via the drive plate11. As shown inFIG. 1, a pump impeller14is attached to the front cover12. The torque converter7also includes a turbine runner15which can rotate while facing the pump impeller14.

The turbine runner15is fixed to an input shaft SI which extends substantially coaxially with the crankshaft SC. In addition, a stator16is provided on the inner side of the pump impeller14and the turbine runner15. The direction in which the stator16rotates is set to only one direction by a one way-clutch17. A hollow shaft18is fixed to the stator16via the one-way clutch17, and the input shaft SI is provided so as to penetrate the hollow shaft18. A lock-up clutch20is attached to an end portion of the input shaft SI on the front cover12side via a damper mechanism19.

The above-mentioned pump impeller14, the turbine runner15, and the stator16form an hydraulic fluid chamber, and hydraulic fluid is supplied to the hydraulic fluid chamber from an oil pump21provided between the toque converter7and the forward/reverse running changing mechanism8. When the engine2operates and the front cover12and the pump impeller14rotate, the turbine runner15starts to rotate due to a flow of the hydraulic fluid in accordance with the rotation of the front cover12and the pump impeller14. Also, the stator16changes the direction of the flow of the hydraulic fluid to the direction in which rotation of the pump impeller14is assisted, when the difference in the rotational speed between the pump impeller14and the turbine runner15is large.

Thus, the torque converter7serves as a torque amplifier when the difference in the rotational speed between the pump impeller14and the turbine runner15is large, and serves as a fluid coupling when the difference in the rotational speed becomes small. When the vehicle speed reaches a predetermined value after the vehicle1takes off, the lock-up clutch20is operated and the power transmitted from the engine2to the front cover12is transmitted to the input shaft SI mechanically and directly. Also, fluctuation of the torque transmitted from the front cover12to the input shaft SI is absorbed by the damper mechanism19.

The oil pump21provided between the torque converter7and the forward/reverse running changing mechanism8includes a rotor22, and the rotor22is connected to the pump impeller14via a hub23. A body24of the oil pump21is fixed on the transaxle case5side. Accordingly, the power of the engine2is transmitted to the rotor22via the pump impeller14. Then, the oil pump21is driven.

The forward/reverse changing mechanism8includes a planetary gear set25of a double pinion type. The planetary gear set25includes a sun gear26which is attached to an end portion of the input shaft SI on the continuously variable transmission9side; a ring gear27which is provided on the outer peripheral side of the sun gear26so as to be coaxial with the sun gear26; multiple pinions28which are meshed with the sun gear26; multiple pinions29which are meshed with both the ring gear27and the pinions28; and a carrier30which supports the pinions28and29such that the each of the pinions can rotate on its axis, and which supports the pinions28and29such that the pinions28and29can revolve around the sun gear26.

The carrier30of the forward/reverse running changing mechanism8is fixed to a primary shaft SP included in the belt type continuously variable transmission9, and a power transmission path between the carrier30and the input shaft SI is connected/interrupted by a forward clutch CR. The forward/reverse running changing mechanism8includes a reverse brake BR which controls rotation/non-rotation of the ring gear27.

The belt type continuously variable transmission9according to the invention includes the above-mentioned primary shaft (the rotating shaft on the driving side) SP which extends substantially coaxially with the input shaft SI, and a secondary shaft (the rotating shaft on the driven side) SS which is provided so as to be parallel with the primary shaft SP. The primary shaft SP is rotatably supported by bearings31and32, and the secondary shaft SS is rotatably supported by bearings33and34. A primary pulley35is attached to the primary shaft SP, and a secondary pulley36is attached to the secondary shaft SS.

The primary pulley35includes a fixed sheave37which is fixed integrally to the outer periphery of the primary shaft SP, and a movable sheave38which is slidably attached to the outer periphery of the primary shaft SP. The fixed sheave37and the movable sheave38face each other, and a substantially V-shaped pulley groove39is formed between the fixed sheave37and the movable sheave38. The movable sheave38is movable with respect to the fixed sheave37in the axial direction of the primary shaft SP. The continuously variable transmission9includes a hydraulic actuator40which makes the movable sheave38come close to/move away from the fixed sheave37by moving the movable sheave38in the axial direction of the primary shaft SP.

Similarly, the secondary pulley36includes a fixed sheave41which is fixed integrally to the outer periphery of the secondary shaft SS, and a movable sheave42which is slidably attached to the outer periphery of the secondary shaft SS. The fixed sheave41and the movable sheave42face each other, and a substantially V-shaped pulley groove44is formed between the fixed sheave41and the movable sheave42. The movable sheave42is movable with respect to the fixed sheave41in the axial direction of the secondary shaft SS. The continuously variable transmission9includes a hydraulic actuator45which makes the movable sheave42come close to/move away from the fixed sheave41by moving the movable sheave42in the axial direction of the secondary shaft SS.

A belt B formed of many metal pieces and multiple steel rings is wound on the pulley groove39of the primary pulley35and the pulley groove44of the secondary pulley36. Then, the hydraulic pressure supplied from the hydraulic actuator40and the hydraulic pressure supplied from the hydraulic actuator45are controlled separately. Thus, the groove widths of the primary pulley35and the secondary pulley36are changed, and the winding radius of the belt B is changed. As a result, the speed ratio of the continuously variable transmission9is set to a desired value, and the tension of the belt B is adjusted. The bearing34which supports the secondary shaft SS is fixed to the transaxle rear cover6, and a parking gear PG is provided between the bearing34and the secondary pulley36.

As shown inFIG. 1, a shaft48which is supported by bearings46and47is coupled with the secondary shaft SS of the belt type continuously variable transmission9. A counter drive gear49is fixed to the shaft48, and power is transmitted from the belt type continuously variable transmission9to the final reduction gear10via the counter drive gear49. The final reduction gear10includes an intermediate shaft50which is provided so as to be parallel with the secondary shaft SS. The intermediate shaft50is supported by bearings51and52. A counter driven gear53which is meshed with the counter drive gear49of the secondary shaft SS and a final drive gear54are fixed to the intermediate shaft50.

The final reduction gear10includes a hollow differential case55. The differential case55is rotatably supported by bearings56and57, and a ring gear58is provided on the outer peripheral side of the differential case55. The ring gear58is meshed with the final drive gear54of the intermediate shaft50. In addition, the differential case55supports a pinion shaft59therein, and two pinions60are held by the pinion shaft59. Two side gears61are meshed with each of the pinions60. Each front drive shaft62is connected to the side gear61. A wheel (front wheel) FW is fixed to each drive shaft62.

FIG. 2is an enlarged cross sectional view showing a main portion of the belt type continuously variable transmission9according to the invention.FIG. 2shows a structure related to the primary pulley35and the primary shaft SP of the continuously variable transmission9. The primary shaft SP can rotate about its axis line. The fixed sheave37is formed integrally with one end of the primary shaft SP, and an oil passage SPA is formed inside of the primary shaft SP in the axial direction. The primary shaft SP is rotatably supported by the bearing31fixed to the transaxle case5on the outer side of the fixed sheave37. The oil passage SPA formed inside of the primary shaft SP in the axial direction is communicated with a hydraulic circuit of a hydraulic control apparatus (not shown). Also, an oil passage SPB which extends toward the outer surface of the primary shaft SP in the radial direction of the primary shaft SP, and which is communicated with the oil passage SPA is formed in the primary shaft SP.

The movable sheave38has an inner cylindrical portion38A which slides along the outer surface of the primary shaft SP; a radial direction portion38B which extends from an end portion of the inner cylindrical portion38A on the fixed sheave37side toward the outer peripheral side; and an outer cylindrical portion38C which extends from an outer end of the radial direction portion38B and which extends toward the bearing32side in the axial direction. An oil passage38D which penetrates the inner cylindrical portion38A from the inner surface of the inner cylindrical portion38A to the outer surface thereof is formed in the inner cylindrical portion38A. Communication between the oil passage38D and the oil passage SPB is permitted through an after-mentioned spline portion formed in the outer surface of the primary shaft SP.

Namely, as shown inFIG. 2, multiple spline teeth (grooves)38S are formed in the inner surface of the inner cylindrical portion38A of the movable sheave38. Also, multiple spline grooves (teeth) SPG are formed in the outer surface of the primary shaft SP which slidably supports the movable sheave38. The spline teeth38S and the spline grooves SPG are formed such that the tooth surface or the groove surface forms an involute curve. The primary shaft SP and the movable sheave38can be moved smoothly with respect to each other in the axial direction of the primary shaft. However, the primary shaft SP and the movable sheave38cannot be moved with respect to each other in the circumferential direction.

The radial direction oil passage SPB is located on the outer side of the spline grooves SPG, which are formed in the primary shaft SP, in the axial direction of the primary shaft SP. Thus, the radial direction oil passage SPB is located outside of the transmission path of the torque transmitted from the primary shaft SP to the belt B via the movable sheave38. Therefore, concentration of stress on the radial direction oil passage SPB does not occur, and the strength of the primary shaft SP can be secured.

In addition, the belt type continuously variable transmission9includes a cylinder member70which is a ring-shaped partition member. As shown inFIG. 2, the cylinder member70includes a first radial direction portion70A which extends in the radial direction of the primary shaft SP; a first cylindrical portion70B which extends from the first radial direction portion70A so as to be substantially parallel with the axis line of the primary shaft SP; a second radial direction portion70C which extends from the first cylindrical portion70B along a back surface of the movable sheave38in the radial direction of the primary shaft SP; and a second cylindrical portion70D which extends from the second radial direction portion70C so as to be substantially parallel with the axis line of the primary shaft SP through a curved portion corresponding to the outer cylindrical portion38C of the movable sheave38.

A small diameter portion located at an end of the primary shaft SP is pressed into a center hole portion formed in the first radial direction portion70A of the cylinder member70. The cylinder member70is fixed to a portion between a step portion of the primary shaft SP and a lock nut80by the lock nut80. The first cylindrical portion70B of the cylinder member70is rotatably supported by the bearing32which is fixed to the transaxle rear cover6by a ring-shaped bearing retainer and a bolt (not shown). Thus, as described later in detail, in the belt type continuously variable transmission9, the primary shaft SP is rotatably supported by the bearing32via the cylinder member70(the first cylindrical portion70B) while being supported by the bearing31.

Also, a seal member72is provided in an outer peripheral portion of the outer cylindrical portion38C of the movable sheave38so as to slidably contact the inner surface of the second cylindrical portion70D of the cylinder member70. Also, an after-mentioned second sliding portion38F, which slidably contacts the first cylindrical portion70B of the cylinder portion70on the inner surface side, is formed in an axial direction end portion of the inner cylindrical portion38A of the movable sheave38on the outer surface side. Thus, the inner cylindrical portion38A, the radial direction portion38B, the outer cylindrical portion38C of the movable sheave38and the cylinder member70form a first hydraulic chamber40A which constitutes the hydraulic actuator40. Meanwhile, the first radial direction portion70A, the first cylindrical portion70B of the cylinder member70, the axial direction end portion of the inner cylindrical portion38A of the movable sheave38, and the primary shaft SP form a second hydraulic chamber40B which constitutes the hydraulic actuator40. By controlling the hydraulic pressure in the first hydraulic chamber40A and the hydraulic pressure in the second hydraulic chamber40B, the movable sheave38is moved with respect to the fixed sheave37, and the winding radius of the belt B is changed. As a result, a desired speed ratio can be achieved.

A first sliding portion38E and the second sliding portion38F are provided for the movable sheave38so as to be apart from each other in the axial direction of the primary shaft SP. From among the two sliding portions for the movable sheave38, the first sliding portion38E is located on the fixed sheave37side with respect to the spline teeth38S in the axial direction of the primary shaft SP, and is formed in the inner surface of the movable sheave38. The first sliding portion38E contacts the outer surface of the primary shaft SP. Meanwhile, the second sliding portion38F is located, as mentioned above, so as to be apart from the first sliding portion38E in the axial direction, and is formed in the outer surface of the axial direction end portion of the inner cylindrical portion38A of the movable sheave38. As shown inFIG. 2, the second sliding portion38F contacts not the primary shaft SP, but the inner surface of the first cylindrical portion70B of the cylinder member70.

FIG. 3is an enlarged cross sectional view showing another main portion of the belt type continuously variable transmission9according to the invention.FIG. 3shows the structure related to the secondary pulley36and the secondary shaft SS of the continuously variable transmission9. The secondary shaft SS can rotate about its axis line. The fixed sheave42is formed integrally with an end portion of the secondary shaft SS, and an oil passage SSA is formed inside of the secondary shaft SS in the axial direction of the secondary shaft SS. The secondary shaft SS is rotatably supported, along with the parking gear PG, by the bearing34fixed to the transaxle rear cover6on the outer side of the fixed sheave42in the axial direction of the secondary shaft SS. The oil passage SSA formed inside of the secondary shaft SS in the axial direction of the secondary shaft SS is communicated with a hydraulic circuit of a hydraulic control apparatus (not shown). In addition, an oil passage SSB which extends toward the outer surface of the secondary shaft SS and which is communicated with the oil passage SSA is formed in the secondary shaft SS.

A movable sheave43has a cylindrical portion43A which slides along the outer surface of the secondary shaft SS; and a radial direction portion43B which extends from an end portion of the cylindrical portion43A on the fixed sheave42side toward the outer peripheral side. A ring-shaped member75is fixed to the moving shave43at a back surface of the radial direction portion43B. The ring-shaped member75has an outer cylindrical portion75B which is continuous with an outer peripheral end of a radial direction portion75A of the ring-shaped member75and which extends toward the bearing33side in the axial direction of the secondary shaft SS. An oil passage43C which penetrates the cylindrical portion43A from the inner surface of the cylindrical portion43A to the outer surface thereof is formed in the cylindrical portion43A of the movable sheave43. Communication between the oil passage43C and the oil passage SSB is permitted through an after-mentioned spline portion formed in the outer surface of the secondary shaft SS.

Namely, as shown inFIG. 3, multiple spline teeth (grooves)43S are formed in the inner surface of the cylindrical portion43A of the movable sheave43. Also, multiple spline grooves (teeth) SSG are formed in the outer surface of the secondary shaft SS which slidably supports the movable sheave43. The spline teeth43S and the spline grooves SSG are formed such that a tooth surface or a groove surface forms an involute curve. The secondary shaft SS and the movable sheave43can smoothly move with respect to each other in the axial direction of the secondary shaft SS. However, the secondary shaft SS and the movable sheave43cannot move with respect to each other in the circumferential direction.

In addition, the belt type continuously variable transmission9includes a cylinder member90which is a ring-shaped partition member. As shown inFIG. 3, the cylinder member90includes a first radial direction portion90A which extends in the radial direction of the secondary shaft SS; a first cylindrical portion90B which extends from the first radial direction portion90A so as to be substantially parallel with the axis line of the secondary shaft SS; a second radial direction portion90C which extends from the first cylindrical portion90B in the radial direction of the secondary shaft SS while bending toward the back surface of the movable sheave43; and a second cylindrical portion90D which extends from the second radial direction portion90C so as to slidably contact the outer surface of the outer cylindrical portion75B of the ring-shaped member75fixed to the movable sheave43and so as to be parallel with the outer cylindrical portion75B.

A small diameter portion formed at an end portion of the secondary shaft SS is pressed into a center hole portion which is formed in the first radial direction portion90A of the cylinder member90. The cylinder member90is fixed to a portion between a step portion of the secondary shaft SS and a lock nut100by the lock nut100. The first cylindrical portion90B of the cylinder member90is rotatably supported by the bearing33fixed to the transaxle case5. Thus, in the belt type continuously variable transmission9, as described later in detail, the secondary shaft SS is rotatably supported by the bearing33via the cylinder member90(the first cylindrical portion90B) while being supported by the bearing34.

An after-mentioned second sliding portion43F, which slidably contacts the inner peripheral side of the first cylindrical portion90B of the cylinder member90, is formed in the axial direction end portion of the cylindrical portion43A of the movable sheave43on the outer peripheral side of cylindrical portion43A. Thus, the cylindrical portion43A and the radial direction portion43B of the movable sheave43, the ring-shaped member75and the cylinder member90form a first hydraulic chamber45A which constitutes the hydraulic actuator45. The first radial direction portion90A and the first cylindrical portion90B of the cylinder member90, the axial direction end portion of the cylindrical portion43A of the movable sheave43, and the secondary shaft SS form a second hydraulic chamber45B which constitutes the hydraulic actuator45. By controlling the hydraulic pressure in the first hydraulic chamber45A and the hydraulic pressure in the second hydraulic chamber45B, the movable sheave43is moved with respect to the fixed sheave42, and the winding radius of the belt B is changed. As a result, a desired shift speed can be obtained.

A first sliding portion43E and the second sliding portion43F are provided for the movable sheave43so as to be apart from each other in the axial direction of the secondary shaft SS. From among the two sliding portions for the movable sheave43, the first sliding portion43E is located on the fixed sheave42side with respect to the spline teeth43S in the axial direction of the secondary shaft SS, and is formed in the inner surface of the movable sheave43. The first sliding portion43E contacts the outer surface of the secondary shaft SS. Meanwhile, the second sliding portion43F is located, as mentioned above, so as to be apart from the first sliding portion43E in the axial direction, and is formed in the outer surface of the axial direction end portion of the cylindrical portion43A of the movable sheave43. As shown inFIG. 3, the second sliding portion43F contacts not the secondary shaft SS, but the inner surface of the first cylindrical portion90B of the cylinder member90. The radial direction oil passage SSB is located on the outer side of the spline grooves SSG, which are formed in the secondary shaft SS, in the axial direction of the secondary shaft SS.

Hereafter, relationships in position and force between the bearings and the radial direction oil passages according to the embodiment of the invention will be described in more detail. In the primary pulley35, the oil passage SPB is located outside of the area between the two positions at which the bearings31and32are provided so as to be apart from each other in the axial direction of the primary shaft SP. Similarly, in the secondary pulley36, the oil passage SSB is located outside of the area between the two positions at which the bearings33and34are provided so as to be apart from each other in the axial direction of the secondary shaft SS. In these cases, the portion, in which the oil passage SPB is formed, in the primary shaft SP and the portion, in which the oil passage SSB is formed, in the secondary shaft SS do not directly receive the load applied by the belt. This effect can be obtained both on the primary pulley35side and the secondary pulley36side based on the same principle. Therefore, the following description will be made with reference toFIGS. 4A and 4B, by taking the primary pulley35side as an example. Namely, the following description will be made, with reference toFIGS. 4A and 4B, concerning the relationship in the position and force between the bearings31and32that support the primary shaft SP, which is the pulley shaft of the primary pulley35, at the two positions apart from each other in the axial direction of the primary shaft SP, and the oil passage SPB which is the radial direction oil passage for supplying hydraulic fluid to the first hydraulic chamber40A and the second hydraulic chamber40B that are the pulley hydraulic chambers.

FIG. 4A is a view showing how the load applied by the belt acts on the pulley shaft in the case of the conventional arrangement in which the oil passage SPB is formed in the area between the two positions at which the bearings31and32are provided so as to be apart from each other in the axial direction of the primary shaft SP.FIG. 4Bis a view showing the case of the arrangement according to the invention, in which the oil passage SPB is formed outside of the area between the two positions at which the bearings31and32are provided so as to be apart from each other in the axial direction of the primary shaft SP. InFIGS. 4A and 4B, M1and M2are moment forces applied from the belt B to the fixed sheave37and the movable sheave38, respectively. Each of F1and F2is a force applied from the movable sheave38to the primary shaft SP which is the pulley shaft. F3and F4are forces applied from the primary shaft SP, which is the pulley shaft, to the bearings31and32, respectively. Note that a reference character “X” shows a position in the primary shaft SP, at which the oil passage SPB is formed.

With the conventional arrangement, as shown inFIG. 4A, the forces F1and F2(especially, the force F2which is applied at a position closer to the position X) for attempting to rotate the movable sheave38using the axis line which extends in the direction perpendicular to the pulley axis line as the center of rotation are applied to the primary shaft SP, which is the pulley shaft, due to tension of the belt, and the force F4(reaction force) from the bearing32is also applied to the primary shaft SP. As a result, a large bending occurs at the position X at which the oil passage SPB is located. In contrast to this, with the arrangement according to the invention, even if the forces F1and F2using the axis line in the direction perpendicular to the pulley axis line as the center of rotation are applied from the movable sheave38, as shown inFIG. 4B, the force F2which is applied at the position closer to the position X is directly supported by the bearing32(via the cylinder member70in the above-mentioned embodiment), and is not input in the primary shaft SP that is the pulley shaft. As a result, a bending hardly occurs at the position X at which the oil passage SPB is located. Accordingly, concentration of stress on the radial direction oil passage SPB does not occur, and the strength of the pulley shaft can be secured. The above description is made concerning the structure on the primary pulley35side. It is needless to say that the above description can be applied to the structure on the secondary pulley36side.