Title of Invention	"V -BELT AUTOMATIC TRANSMISSION"
Abstract	[Object] To eliminate a change in bearing clearance due to thermal deformation of a fixed pulley half and a movable pulley half constituting a driven pulley of a V-belt automatic transmission, thereby improving bearing durability and eliminating play between the two pulley halves during rotation thereof. [Constitution] In a V-belt automatic transmission including a fixed pulley half 61 integrally formed of an aluminum material and supported to a rotating shaft 45, a movable pulley half 62 integrally made from an aluminum material and slidably supported through a bearing to a cylindrical shaft 61a of the fixed pulley half 61 so as to be opposed to the fixed pulley half 61 to hold a V-belt 55 in cooperation therewith, and a torque cam mechanism 75 and 61c provided at axial ends of the cylindrical shafts 61a and 62a of the pulley halves 61 and 62 to change rotation of the movable pulley half 62 relative to the fixed pulley half 61 into axial thrust of the movable pulley half 62; the bearing between the cylindrical shafts 61a and 62a of the pulley halves 61 and 62 is a cylindrical sliding member 65, which has a sliding layer supported to an inner circumferential surface of the cylindrical shaft 62a of the movable pulley half 62 and formed of a self-lubricating synthetic resin, the sliding layer having a small thickness so set as to compensate for thermal dimensional changes of the cylindrical shaft 61a of the fixed pulley half 61 and the cylindrical shaft 62a of the movable pulley half 62 and thereby to maintain a bearing clearance between the two cylindrical shafts 61a and 62a substantially constant. [SELECTED FIGURE] FIG. 3

Title of Invention

"V -BELT AUTOMATIC TRANSMISSION"

Abstract

[Object] To eliminate a change in bearing clearance due to thermal deformation of a fixed pulley half and a movable pulley half constituting a driven pulley of a V-belt automatic transmission, thereby improving bearing durability and eliminating play between the two pulley halves during rotation thereof. [Constitution] In a V-belt automatic transmission including a fixed pulley half 61 integrally formed of an aluminum material and supported to a rotating shaft 45, a movable pulley half 62 integrally made from an aluminum material and slidably supported through a bearing to a cylindrical shaft 61a of the fixed pulley half 61 so as to be opposed to the fixed pulley half 61 to hold a V-belt 55 in cooperation therewith, and a torque cam mechanism 75 and 61c provided at axial ends of the cylindrical shafts 61a and 62a of the pulley halves 61 and 62 to change rotation of the movable pulley half 62 relative to the fixed pulley half 61 into axial thrust of the movable pulley half 62; the bearing between the cylindrical shafts 61a and 62a of the pulley halves 61 and 62 is a cylindrical sliding member 65, which has a sliding layer supported to an inner circumferential surface of the cylindrical shaft 62a of the movable pulley half 62 and formed of a self-lubricating synthetic resin, the sliding layer having a small thickness so set as to compensate for thermal dimensional changes of the cylindrical shaft 61a of the fixed pulley half 61 and the cylindrical shaft 62a of the movable pulley half 62 and thereby to maintain a bearing clearance between the two cylindrical shafts 61a and 62a substantially constant. [SELECTED FIGURE] FIG. 3

Full Text	[DETAILED DESCRIPTION OF THE INVENTION] [Field of the Invention] The present invention relates to a v-belt automatic transmission used in a motorcycle or the like, and more particularly to a V-belt automatic transmission intended to eliminate a change in bearing clearance due to thermal deformation of a fixed pulley half and a movable pulley half constituting a driven pulley, thereby improving bearing durability and eliminating play between the two pulley halves during rotation thereof. [Prior Art and Problems to Be Solved by the Invention] A V-belt automatic transmission includes a drive pulley, a driven pulley, and an endless V-belt having a V-shaped cross section and wrapped between the two pulleys, in which the effective radius of each pulley is automatically changed according to engine speed to transmit power. Each pulley consists of a fixed pulley half and a movable pulley half axially slidable. The V-belt is held between the fixed pulley half and the movable pulley half, and the effective radius of the pulley is changed according to an axial position of the movable pulley half relative to the fixed pulley half. The movable pulley half is normally biased toward the fixed pulley half by a spring to increase the effective radius of the V-belt and thereby to apply tension to the V-belt. When load variations are large, the biasing force of the spring is overcome to cause slippage between the pulley and the belt. To prevent such slippage, there has been proposed a V-belt automatic transmission having a torque cam mechanism for changing rotation of the movable pulley half relative to the fixed pulley half into axial thrust of the movable pulley half. Such a V-belt automatic transmission having a torque cam mechanism is described in Japanese Patent Application No. 8-101187 filed by the present applicant (see FIG. 24). Referring to FIG. 24, the torque cam mechanism is composed of a movable cam portion 062c axially extending from one end of a cylindrical shaft 062a of a movable pulley half 062, and a fixed cam portion 075 radially outwardly extending from one outer end of a cylindrical shaft 061a of a fixed pulley half 061 so as to engage the movable cam portion 062c in a meshing fashion. A clearance between the movable cam portion 062c and the fixed cam portion 075 in their rotational direction is small, thereby obtaining smooth acceleration feel and good serviceability of the torque cam mechanism. In FIG. 24, reference numerals 022, 045, and 047 denote a reduction gearing, an input shaft of the reduction gearing, and a rear axle, respectively. However, no sufficient consideration has been given to a deterioration in wear resistance of a bearing 027 provided between the cylindrical shafts 061a and 062a of the pulley halves 061 and 062 and also to supporting of the bearing 027. More specifically, each of the pulley halves 061 and 062 is integrally formed of aluminum by casting, and accordingly the use of a self-lubricating synthetic resin as described in Japanese Patent Laid-open No. 4-258559 has been considered as the material for the bearing 027 between the cylindrical shafts 061a and 062a of the pulley halves 061 and 062. However, such a resin bearing is softer than a metal bearing, and has a larger thermal expansion, so that it is easily worn depending upon use conditions. Thus, it has been desired to improve the durability of the bearing. Further, it has also considered to form a hard alumite coating as described in Japanese utility Model Laid-open No. 53-107780 on the sliding surfaces of the cylindrical shafts 061a and 062a of the pulley halves 061 and 062 each formed of aluminum. However, no consideration has been given to thermal expansion of the cylindrical shafts 061a and 062a, causing play between the two pulley halves 061 and 062 during rotation thereof due to a change in bearing clearance. Further, as to means for supporting the bearing 027 between the cylindrical shafts 061a and 062a of the pulley halves 061 and 062, no consideration has been given in the prior art. In the case that a consideration has been given, a clip for preventing escape of the bearing 027 has been provided on the inner circumferential surface of the cylindrical shaft 062a of the movable pulley half 062 at its one end (see Japanese Patent Laid-open No. 4-224345). In the former case of no supporting means, there is a possibility of escape of the bearing, while in the latter case, the wall thickness of the cylindrical shaft 062a of the movable pulley half 062 at its one end must be increased for the provision of the clip. If the wall thickness of the cylindrical shaft 062a of the movable pulley half 062 at its one end is increased, and the torque cam mechanism is formed at the axial ends of the cylindrical shafts 061a and 062a of the pulley halves 061 and 062 as in the prior invention by the present applicant, the radius of the movable cam portion 062c is increased, with the result that when torque applied to the torque cam mechanism is fixed, a cam force generated in the torque cam mechanism (a rotational force of the movable cam portion 062c against the fixed cam portion 075) is reduced, and an axial component of the cam force is therefore reduced. As a result, a thrust for biasing the movable pulley half 062 toward the fixed pulley half 061 is reduced, and it is accordingly necessary to set large the spring load of a spring 080 for biasing the movable pulley half 062 toward the fixed pulley half 061. Such increasing the spring load causes a reduction in durability of a V-belt 055 always held between the two pulley halves 061 and 062 under the spring load. Further, a clip 078 is used to prevent escape of a drive plate 072 of a clutch 070. The drive plate 072 is spline-engaged with an end portion 061b of the cylindrical shaft 061a of the fixed pulley half 061. The clip 078 is a usual cut-ring clip, so that when a centrifugal force is applied, the diameter of the clip 078 tends to be increased. Accordingly, an excess tightening force for the clip 078 is required to endure the centrifugal force applied, causing a reduction in mountability. Further, the manufacture of the clip 078 requires much time and labor, for example, material selection or treatment for the purpose of obtaining a stress enduring material. If a nut is used in place of the clip 078, an extra space for providing the nut is required. Further, the shape of a root portion 061d of the cylindrical shaft 061a of the fixed pulley half 061 is designed so that a stress generated in this portion cannot be efficiently diffused. Accordingly, the root portion 061d has a large size for the sake of strength. In view of the above problems, it is an object of the present invention to improve the durability of the bearing 027 between the cylindrical shafts 061a and 062a of the fixed and movable pulley halves 061 and 062, and to provide means for preventing escape of the bearing 027 without the need for increasing the wall thickness of an end portion of each of the cylindrical shafts 061a and 062a of the pulley halves 061 and 062, thereby improving the durability and function of the structure of the driven pulley and its associated parts in a V-belt automatic transmission, and reducing the size and weight of the structure. [Means for Solving the Problem, Operation, and Effect] In accordance with the invention as defined in claim 1, there is provided in a V-belt automatic transmission including a fixed pulley half integrally formed of an aluminum material and supported to a rotating shaft, a movable pulley half integrally formed of an aluminum material and slidably supported through a bearing to a cylindrical shaft of said fixed pulley half so as to be opposed to said fixed pulley half to hold a V-belt in cooperation therewith, and a torque cam mechanism provided at an axial end of said cylindrical shaft of said fixed pulley half and an axial end of a cylindrical shaft of said movable pulley half to change rotation of said movable pulley half relative to the fixed pulley half into axial thrust of said movable pulley half; the improvement wherein said bearing between said cylindrical shafts of said fixed and movable pulley halves is a cylindrical sliding member; said cylindrical sliding member having a sliding layer supported to an inner circumferential surface of said cylindrical shaft of said movable pulley half and formed of a self-lubricating synthetic resin; said sliding layer having a small thickness so set as to compensate for thermal dimensional changes of said cylindrical shaft of said fixed pulley half and said cylindrical shaft of said movable pulley half and thereby to maintain a bearing clearance between said two cylindrical shafts substantially constant. With this configuration, even when the fixed pulley half and the movable pulley half each formed integrally of an aluminum material are deformed by thermal expansion to cause an increase in bearing clearance between the cylindrical shafts of the two pulley halves, the bearing formed as the sliding member having the thin sliding layer formed of a self-lubricating synthetic resin having a coefficient of thermal expansion larger than that of each pulley half is expanded so as to compensate for the increase in bearing clearance, thereby maintaining the bearing clearance always substantially constant and preventing wear of the bearing to improve the durability. Further, play between the two pulley halves during rotation thereof can also be prevented. By configurating the invention of claim 1 according to claim 2, a bearing highly excellent in heat resistance and corrosion resistance can be obtained. By configurating the invention of claim 1 or 2 according to claim 3, the clip for supporting the sliding member forming the bearing is not required to be provided on the inner circumferential surface of the cylindrical shaft of the movable pulley half at its one end where the torque cam mechanism is provided. Accordingly, it is unnecessary to increase the wall thickness of the cylindrical shaft of the movable pulley half at this portion, so that the outer diameter of this portion can be reduced and accordingly the radius of the movable cam portion of the torque cam mechanism formed at this portion can be reduced. As a result, a cam force generated in the torque cam mechanism cam be increased, and an axial component of the cam force can also be increased. Therefore, a spring load biasing the movable pulley half toward the fixed pulley half can be set to a small value, thereby improving the durability of the V-belt held between the two pulley halves. Accordingly, the present invention relates to a V-belt automatic transmission including a fixed pulley half integrally formed of an aluminum material and supported to a rotating shaft, a movable pulley half integrally formed of an aluminum material and slidably supported through a bearing to a cylindrical shaft of said fixed pulley half opposed to said fixed pulley half to hold to V-belt in cooperation therewith, and a torque cam mechanism provided at an axial end of said cylindrical shaft of said fixed pulley half and an axial end of a cylindrical shaft of said movable pulley of half to change rotation of said movable pulley half relative to that of the fixed pulley into axial thrust of said movable pulley half, characterized in that said bearing between said cylindrical shafts of said fixed and movable pulley halves in a cylindrical sliding member, said cylindrical sliding member having a sliding layer supported to an inner circumferential surface of said cylindrical shaft of said movable pulley half and formed of a self-lubricating synthetic resin, said sliding layer having a small thickness to compensate for thermal dimensional changes of said cylindrical shaft of said fixed pulley half and said cylindrical shaft of said movable pulley half and to thereby maintain a bearing clearance between said two cylindrical shafts constant. [BRIEF DESCRIPTION OF THE DRAWINGS] [FIG. 1] FIG. 1 is a general side view of a scooter type motorcycle employing a v-belt automatic transmission according to a preferred embodiment of the present invention as defined in claims 1 to 3 in this specification. [FIG. 2] FIG. 2 is a cross section of a power unit taken along the line II-II in FIG. 1. [FIG. 3] FIG. 3 is a sectional view of an essential part of a rear portion of the power unit shown in FIG. 2. [FIG. 4] FIG. 4 is an elevational view of a movable pulley half of a driven pulley in this preferred embodiment. [FIG. 5] FIG. 5 is a cross section taken along the line V-v in FIG. 4. [FIG. 6] FIG. 6 is a view similar to FIG. 4, showing a modification of the movable pulley half. [FIG. 7] FIG. 7 is a sectional view of a fixed pulley half of the driven pulley. [FIG. 8] FIG. 8 is an enlarged view of an encircled portion VIII shown in FIG. 7. [FIG. 9] FIG. 9 is a sectional view of a spring guide in this preferred embodiment. [FIG. 10] FIG. 10 is a sectional view of a bearing bush in this preferred embodiment. [FIGc. 11] FIG. 11 is an enlarged view of an encircled portion XI shown in FIG. 10. [FIG. 12] FIG. 12 is a graph for illustrating the operation of the bearing bush. [FIG. 13] FIG. 13 is an elevational view of a clip for preventing escape of the bearing bush. [FIG. 14] FIG. 14 is a side view of the clip shown in FIG. 13. [FIG. 15] FIG. 15 is an elevational view of a drive plate in this preferred embodiment. [FIG. 16] FIG. 16 is a cross section taken along the line XVI-XVI in FIG. 15. [FIG. 17] FIG. 17 is a cross section taken along the line XVII-XVII in FIG. 15. [FIG. 18] FIG. 18 is a development showing an engaged condition of fixed cam portions and movable cam portions in this preferred embodiment. [FIG. 19] FIG. 19 is a graph showing the relation between engine speed and vehicle speed in this preferred embodiment. [FIG. 20] FIG. 20 is a view similar to FIG. 18, showing an engaged condition of a modification of the fixed cam portions and the movable cam portions. [FIG. 21] FIG. 21 is an elevational view of a wire type clip for preventing escape of the drive plate. [FIG. 22] FIG. 22 is a side view of the wire type clip shown in FIG. 21. [FIG. 23] FIG. 23 is an enlarged view of an encircled portion XXIII shown in FIG. 3. [FIG. 24] FIG. 24 is' a sectional view showing a conventional pulley structure. [Preferred Embodiment] There will now be described a preferred embodiment of the present invention as defined in claims 1 to 3 in this specification with reference to FIGS. 1 to 23. FIG. 1 is a general side view of a scooter type motorcycle 1 to which the V-belt automatic transmission according to the present invention is applied. The scooter type motorcycle 1 has a front body portion 2, a rear body portion 3, and a floor portion 4 connecting the front body portion 2 and the rear body portion 3. A body frame 5 extends obliquely downward from the front body portion 2 and further extends horizontally rearward along the floor portion 4. The body frame 5 rises from the rear end of the floor portion 4 and further extends obliquely upward to the rear end of the rear body portion 3. A front fork 8 is pivotably supported to a front portion of the body frame 5. A steering handle 6 is provided at the upper end of the front fork 8, and a front wheel 7 is rotatably supported to the lower ends of the front fork 8. A swing type power unit 20 is vertically swingably supported at its front lower portion through a link 10 to a rear rising portion of the body frame 5. A rear wheel 9 is rotatably supported through an axle to the rear end of the power unit 20. A rear cushion 11 is interposed between a rear upper portion of the power unit 20 and a rear inclined portion of the body frame 5. The front body portion 2 is covered with a leg shield 15. The floor portion 4 is provided with a step floor 16. The rear body portion 3 is covered with a body cover 17. A seat 18 is provided at an upper portion of the body cover 17. The power unit 20 includes a single-cylinder 2-cycle internal combustion engine 21 located at a front portion, a reduction gearing 22 located at a rear portion, and a v-belt automatic transmission 23 located between the internal combustion engine 21 and the reduction gearing 22. These members are united together and accommodated in a unit case 25. The structure of the power unit 20 is shown in FIG. 2. The unit case 25 is composed of a longitudinally elongated left case 26 accommodating the V-belt automatic transmission 23 and the reduction gearing 22 and constituting a left half portion of a crankcase of the internal combustion engine 21, a right case 27 joined to a front portion of the left case 26 and constituting a right half of the crankcase, a transmission case cover covering a left opening of the left case 26, and a gear case 29 covering a left side of the reduction gearing 22. A crankshaft 31 is rotatably supported through a pair of main bearings 30 to the crankcase formed by the left case 26 and the right case 27. A cylinder block 21a and a cylinder head 21b are joined in this order to an upper end of the crankcase, and this assembly projects upward so as to be slightly inclined rearward. A piston 32 sliding in the cylinder block 2la is connected through a connecting rod 33 to the crankshaft 31. An AC generator 34 and a cooling fan 35 are provided at a right end of the crankshaft 31, and an engine cover 36 is provided to commonly cover the outer peripheries of the internal combustion engine 21, the AC generator 34, and the cooling fan 35. A drive pulley 40 of the V-belt automatic transmission 23 is provided at a left end of the crankshaft 31. The drive pulley 40 is composed of a fixed pulley half 41 fixed to the left end of the crankshaft 31 and a movable pulley half 42 axially slidably supported to the crankshaft 31 so as to be opposed to the fixed pulley half 41. A plurality of centrifugal weights 44 are radially movably interposed between the movable pulley half 42 and a ramp plate 43 fixed to the crankshaft 31. Movement of the centrifugal weights 44 in their centrifugal directions makes the movable pulley half 42 approach the fixed pulley half 41, thereby allowing an increase in effective radius of a V-belt 55 held between the two pulley halves 41 and 42. As shown in FIG. 3, the reduction gearing 22 provided in a space defined by a rear portion of the left case 26 and the gear case 29 includes an input shaft 45, a rear axle 47 as an output shaft, an intermediate shaft 46 provided between the input shaft 45 and the rear axle 47, an input gear 48 mounted on the input shaft 45, a large-diameter intermediate gear 49 mounted on the intermediate shaft 46 and meshing with the input gear 48, a small-diameter intermediate gear 50 mounted on the intermediate shaft 46, and an output gear 51 mounted on the rear axle 47 and meshing with the small -diameter intermediate gear 50, thus configuring a reduction mechanism. As shown in FIG. 3, the input shaft 45 of the reduction gearing 22 extends leftward from the gear case 29, and a driven pulley 60 and a clutch 70 are provided on such a left extending portion of the input shaft 45. The driven pulley 60 is composed of a pair of fixed pulley half 61 and movable pulley half 62 opposed to each other. Both the fixed pulley half 61 and the movable pulley half 62 are made from aluminum. As shown in FIG. 7, the fixed pulley half 61 is composed generally of an annular conical body portion and a cylindrical inner sleeve portion (cylindrical shaft) 61a extending axially from an inner circumferential portion of the body portion 61e. The inner sleeve portion 61a is slightly reduced in diameter at its left end portion to form a mounting portion 61b having a serrated outer circumference. The mounting portion 61b is formed at its left end portion with a circumferentially extending clip groove 61c for engaging a wire type clip 78 for preventing escape of a drive plate 72 of the clutch 70 to be hereinafter described. The clip groove 61c has a substantially semicircular cross section. The fixed pulley half 61 is integrally formed by aluminum die casting. Further, a large stress due to a tension of the V-belt 55 is generated in a root portion 61d of the inner sleeve portion 61a of the fixed pulley half 61. Conventionally, such a root portion is enlarged in size to ensure its strength, resulting in an increase in weight. In this preferred embodiment, however, the root portion 61d has such a shape that an apex angle a (α1, α2, etc.) formed between tangent lines each touching a curved line having a maximum curvature of different curvatures of plural curved lines forming a sectional contour line of the root portion 61d is not less than a given angle (see FIGS. 7 and 8). With this configuration, a stress generated in the root portion 61d can be efficiently diffused without changing a conventional basic shape of the fixed pulley half 61, thereby maintaining the strength of the root portion 61d. Accordingly, the strength of the root portion 61d can be obtained with its smaller size, thereby expecting a reduction in size and weight of the fixed pulley half 61. In an experiment on this preferred embodiment, a stress generated in the root portion 61d could be most efficiently diffused by setting a ≥ 90° under the conditions that the outer diameter DI of the inner sleeve portion 6 la of the fixed pulley half 61 is 34 mm, the outer diameter D2 of the body portion 61e of the fixed pulley half 61 is 118 mm, the maximum diameter D3 of the root portion 61d is 45 mm, the maximum wall thickness t of the body portion 61e of the fixed pulley half 61 is 5 mm, the inclination angle ß of the body portion 61e is 15°, and the maximum curvature R3 of the contour line of the root portion 61d is 5.5 mm. In this case, the curvatures R1 and R2 of the contour line components adjacent to the contour line component having the maximum curvature R3 = 5.5 mm were 2.2 mm and 2.0 mm, respectively. As shown in FIGS. 4 and 5, the movable pulley half 62 is composed generally of an annular conical body portion 62g and a cylindrical outer sleeve portion (cylindrical shaft) 62a extending axially from an inner circumferential portion of the body portion 62g. The outer sleeve portion 62a has an inner diameter slightly larger than the outer diameter of the inner sleeve portion 61a of the fixed pulley half 61. The outer sleeve portion 62a is formed at its left end portion with three axial projections 62b circumferentially spaced at equal intervals. Each projection 62b has an arcuate shape in cross section. Each projection 62b is bent at its front end portion clockwise as viewed in FIG. 4 to form a movable cam portion 62c. The movable cam portion 62c has circumferentially opposite inclined end faces serving as an outward cam face 62co and an inward cam face 62ci. In this preferred embodiment, each of the three movable cam portions 62c is formed with a triangular projected portion projecting in a direction (clockwise direction as viewed in FIG. 4) opposite to a rotational direction of the driven pulley 60, thus forming the inward cam face 62ci. Alternatively, only one of the three movable cam portions 62c may be formed with such a triangular projected portion to form the single inward cam face 62ci (see FIG. 6), because the inward cam face 62ci functions to restrict rotation of the movable cam portions 62c relative to fixed cam portions 75 to be hereinafter described, and a large load is therefore not applied to the inward cam face 62ci. The movable pulley half 62 is integrally formed by aluminum die casting. The outer sleeve portion 62a of the movable pulley half 62 is formed at its root portion joined to the body portion 62g with an annular groove 62d. Further, the body portion 62g is formed at its inner circumferential portion on the side opposite to the outer sleeve portion 62a with a circular clip groove 62e for engaging a circular clip 66 (see FIGS. 13 and 14) for preventing escape of a bearing bush 65 (which will be hereinafter described) interposed between the outer sleeve portion 62a of the movable pulley half 62 and the inner sleeve portion 61a of the fixed pulley half 61. As shown in FIGS. 13 and 14, the circular clip 66 is a wire type clip similar to a wire type clip 78 for preventing escape of a drive plate 72 of the clutch 70 to be hereinafter described. Accordingly, when the circular clip 66 is engaged with the clip groove 62e of the movable pulley half 62, the clip 66 exerts an elastic restoring force against a shoulder portion formed at the right end of the bearing bush 65 to thereby bias the bearing bush 65 toward the left end of the outer sleeve portion 62a, thus reliably preventing escape of the bearing bush 65. As shown in FIG. 3, the fixed pulley half 61 of the driven pulley 60 is rotatably mounted at its inner sleeve portion 61a on the left portion of the input shaft 45 through a needle bearing 63 and a ball bearing 64, and the movable pulley half 62 is slidably mounted at its outer sleeve portion 62a on the outer circumference of the inner sleeve portion 61a of the fixed pulley half 61 through the bearing bush 65. The body portion 61e of the fixed pulley half 61 and the body portion 62g of the movable pulley half 62 are opposed to each other, and relative axial slide and relative rotation between the two pulley halves 61 and 62 are allowed. FIGS. 10 and 11 show a detailed structure of the bearing bush (sliding member) 65 in this preferred embodiment. The bearing bush 65 has a thin-walled multilayer structure consisting of a back metal layer 65a formed by plating a steel surface with copper, and a sliding layer 65b fixed to the inner circumferential surface of the back metal layer 65a. The sliding layer 65b is formed of a self-lubricating synthetic resin (e.g., polytetrafluoroethylene). The bearing bush 65 is press-fitted with the inner circumferential surface of the outer sleeve portion 62a of the movable pulley half 62, and the sliding layer 65b is brought into smooth sliding contact with the outer circumferential surface of the inner sleeve portion 61a of the fixed pulley half 61 owing to the self-lubricating property of the sliding layer 65b. Thus, the movable pulley half 62 is smoothly slidably supported to the fixed pulley half 61 by the bearing bush 65. In FIG. 11, reference numeral 65c denotes a sintered layer for facilitating fixation of the sliding layer 65b to the back metal layer 65a. The sliding layer 65b of the bearing bush 65 has a coefficient of thermal expansion larger than that of the pulley halves 61 and 62 each formed of aluminum, and has a given small thickness. Accordingly, even when a thermal change a in outer diameter of the inner sleeve portion 61a of the fixed pulley half 61 and a thermal change b (b > a) in inner diameter of the outer sleeve portion 62a of the movable pulley half 62 cause an increase d in bearing clearance c between the inner and outer diameters, the increase d can be just canceled by the amount of thermal expansion of the sliding layer 65b, thereby maintaining the bearing clearance c at an initial substantially constant value (see FIG. 12). Accordingly, there is no possibility that the bearing bush 65 may be increased in diameter beyond the increase d in bearing clearance c due to the increases in diameters of the sleeve portions 61a and 62a of the pulley halves 61 and 62 to undergo severe sliding wear from the sliding surfaces of the sleeve portions 61a and 62a, and there is also no possibility of rotational play between the two pulley halves 61 and 62 of the driven pulley 60 due to an increase in bearing clearance c. In an experiment on this preferred embodiment, the bearing clearance c could be maintained at an initial substantially constant value by setting the thickness hi of the sliding layer 65b to 0.75 ram under the conditions that the outer diameter D! of the inner sleeve portion 61a of the fixed pulley half 61 is 34 mm, the inner diameter D4 of the outer sleeve portion 62a of the movable pulley half 62 is 37 mm, and the wall thickness h of the bearing bush 65 is 2 mm. Such dimensional setting of the thickness hi of the sliding layer 65b can be easily achieved by machining the surface of the sliding layer 65b. When the bearing bush 65 is interposed between the sleeve portions 61a and 62a of the pulley halves 61 and 62, one end of the bearing bush 65 abuts against shoulders 62f formed between the inner circumferential surface of the outer sleeve portion 62a of the movable pulley half 62 and root portions of the projections 62b, and the other end of the bearing bush 65 is supported by the clip 66 engaged with the clip groove 62e formed on the inner circumferential surface of the body portion 62g of the movable pulley half 62 at its end opposite to the outer sleeve portion 62a as mentioned above, thus restricting axial movement of the bearing bush 65. The clip 66 for preventing escape of the bearing bush 65 is not located on the inner circumferential surface of the outer sleeve portion 62a of the movable pulley half 62 on the projections 62b side, so that it is unnecessary to increase the wall thickness of this portion of the outer sleeve portion 62a, and the outer diameter of this portion can be reduced. Accordingly, in the case that the torque applied to a torque cam mechanism to be hereinafter described is constant, a cam force generated in the torque cam mechanism can be increased, and therefore its axial component urging the movable pulley half 62 against the fixed pulley half 61 can also be increased. As a result, the spring load of a spring 80 for biasing the movable pulley half 62 toward the fixed pulley half 61 can be set to a small value, so that the durability of the V-belt 55 held between the two pulley halves 61 and 62 can be improved The clutch 70 and the torque cam mechanism will now be described. The clutch 70 is provided at the left end of the input shaft 45 of the reduction gearing 22 and the mounting portion 61b of the inner sleeve portion 61a of the fixed pulley half 61. The clutch 70 has a flat cylindrical clutch outer 71 having a bottom wall 71a. The bottom wall 71a has a center hole engaged through a collar 79 with a threaded portion formed at the left end of the input shaft 45, and the bottom wall 71a is fastened by tightening a nut 67 to the threaded portion of the input shaft 45. The bottom wall 71a continues to a cylindrical wall 71b opening rightward. A drive plate 72 as a clutch inner is accommodated in the clutch outer 71 and is mounted through serration engagement on the left end mounting portion 61b of the inner sleeve portion 61a of the fixed pulley half 61 as shown in FIG. 3. A wire type clip 78 is engaged with a clip groove 61c formed on the outer circumferential surface of the mounting portion 61b, so as to fix the serration engagement. The wire type clip 78 engaged with the clip groove 61c elastically abuts against a chamfered portion 72e formed at the left end of a serrated portion 72a of the drive plate 72 to be hereinafter described, thereby normally biasing the drive plate 72 toward the body portion 61e of the fixed pulley half 61 (see FIGS. 21 to 23). As shown in FIGS. 21 to 23, the wire type clip 78 is a ringlike member with its arcuate portion slightly cut out and its opposite ends slightly deviated from each other in the natural condition. Accordingly, when the clip 78 is engaged with the clip groove 61c, the clip 78 exerts an elastic restoring force F1 on the chamfered portion 72e of the drive plate 72 to thereby strongly press the chamfered portion 72e in the axial direction (toward the body portion 61e of the fixed pulley half 61). As a result, even when the drive pulley 60 is rotated at high speeds to cause application of a centrifugal force F2 to the wire type clip 78, a reaction of a resultant force F of these forces F1 and F2 is effectively applied to the clip 78 from a contact between the clip 78 and the chamfered portion 72e, thereby preventing an increase in diameter of the clip 78 and accordingly preventing escape of the clip 78 from the clip groove 61c. Furthermore, since the wire type clip 78 is simple in structure and inexpensive, and can be easily installed even in a narrow space. As shown in FIGS. 15 and 16, the drive plate 72 is formed at its inner circumference with a flat cylindrical serrated portion 72a. Further, three core portions 72b extend radially from the outer circumferential surface of the serrated portion 72a, and an outer circumferential plate portion 72c is connected to the core portions 72b so as to have a slightly stepped portion 72f. The outer circumferential plate portion 72c is provided with three pins 73 circumferentially spaced at equal intervals. A clutch shoe 74 (see FIG. 3) is supported to each pin 73. A fixed cam portion 75 is integrally mounted on each core portion 72b by molding a self -lubricating resin. That is, three fixed cam portions 75 mounted on the three core portions 72b are circumferentially spaced at equal intervals. Three openings 72d are formed through the outer circumferential plate portion 72c in such a manner that each opening 72d is located between the adjacent fixed cam portions 75. The three openings 72d allow reception of the three movable cam portions 62c of the movable pulley half 62, respectively, thereby providing meshing engagement of the fixed cam portions 75 and the movable cam portions 62c. As shown in FIG. 17, each fixed cam portion 75 is fixed to the corresponding bent core portion 72b, and has a substantially trapezoidal cross section so as to have an inward cam face 75i formed as a circumferentially inclined flat surface and an outward cam face 75o formed as a curved surface. The drive plate 72 is provided in the clutch outer 71. The clutch shoes 74 supported to the pins 73 are swung radially outward by a centrifugal force against clutch springs 76. As a result, a friction member 74a provided on the outer circumference of each clutch shoe 74 comes into contact with the inner circumferential surface of the cylindrical wall 71b of the clutch outer 71. The drive plate 72 is integrally mounted by serration engagement on the left end mounting portion 61b of the inner sleeve portion 61a of the fixed pulley half 61. Therefore, the drive pulley 72 is rotated integrally with the fixed pulley half 61. [OOS^J As shown in FIG. 3, the movable pulley half 62 is slidably supported between the drive plate 72 and the body portion 61e of the fixed pulley half 61. A coiled spring 80 formed of spring steel is mounted closely around the outer circumference of the outer sleeve portion 62a of the movable pulley half 62. The spring 80 is interposed between the drive plate 72 and the body portion 62g of the movable pulley half 62 to bias the body portion 62g toward the body portion 61e of the fixed pulley half 61. A spring guide 81 formed of resin is interposed between the inner circumference of the spring 80 and the outer circumference of the outer sleeve portion 62a. As shown in FIG. 9, the spring guide 81 is cylindrical, and has a flange 81a at one end. The spring guide 81 has an inner diameter slightly larger than the outer diameter of the outer sleeve portion 62a, and the inner diameter at the flange 81a is slightly enlarged. When the spring guide 81 is mounted on the outer circumference of the outer sleeve portion 62a, and the drive plate 72 is mounted on the mounting portion 61b of the inner sleeve portion 61a, the fixed cam portion 75 is engaged with the inner circumference of the large-diameter left end portion of the spring guide 81 to support the spring guide 81, and the flange 81a of the spring guide 81 abuts against the stepped portion 72f of the outer circumferential plate portion 72c of the drive plate 72. An annular spring seat 82 made from iron is fitted with the annular groove 62d formed on the outer circumference of the root portion of the outer sleeve portion 62a of the movable pulley half 62. The spring 80 is interposed between the spring seat 82 and the flange 81a of the spring guide 81 in such a manner that the opposite ends of the spring 80 abuts against the spring seat 82 and the flange 81a. A front portion of the v-belt 55 is wrapped around the drive pulley 40, and a rear portion of the V-belt 55 is wrapped around the driven pulley 60 in such a manner as to be resiliently held between the fixed pulley half 61 and the movable pulley half 62d biased toward the fixed pulley half 61 by the spring 80, thereby increasing the effective radius of the V-belt 55 on the driven pulley 60 to apply tension to the V-belt 55. Further, the three movable cam portions 62c formed at the left end of the outer sleeve portion 62a of the movable pulley half 62 are exposed to the three openings 72d of the drive plate 72 rotating with the fixed pulley half 61, and are engaged with the three fixed cam portions 75 of the drive plate 72. Such an engaged condition of the three movable cam portions 62c and the three fixed cam portions 75 is shown in FIG. 18. As shown in FIG. 18, the inward cam face 75i and the outward cam face 75o of each fixed cam portion 75 are respectively opposed to the inward cam face 62ci and the outward cam face 62co of the corresponding movable cam portion 62c with a small clearance C measured in the rotational direction of the driven pulley 60, so that the opposed cam faces can easily come into contact with each other. Accordingly, an angle of rotation of each movable cam portion 62c relative to the corresponding fixed cam portion 75 is restricted to a small value. [ 0059 ] ' The operation of the V-belt automatic transmission 23 in this preferred embodiment will now be described. When the rotating speed of the internal combustion engine 21 is low, the centrifugal weights 44 adapted to radially move along the ramp plate 43 on the drive pulley 40 side are present at a radially central position as shown by the solid line in FIG. 2, so that the movable pulley half 42 of the drive pulley 40 is spaced apart from the fixed pulley half 41, and the effective radius of the V- belt 55 on the drive pulley 40 is therefore small. As a result, the movable pulley half 62 of the driven pulley 60 is biased by the spring 80 to approach the fixed pulley half 61, thereby increasing the effective radius of the V-belt 55 on the driven pulley 60. Accordingly, power is transmitted at a large reduction ratio. When the rotating speed of the engine 21 is increased, the centrifugal weights 44 are moved in the centrifugal directions to make the movable pulley half 42 of the drive pulley 40 approach the fixed pulley half 41 as shown by the phantom line in FIG. 2, thereby increasing the effective radius of the V-belt 55 on the drive pulley 40. As a result, the movable pulley half 62 of the driven pulley 60 is moved away from the fixed pulley half 61 against the spring 80, thereby decreasing the effective radius of the V-belt 55. As a result, the reduction ratio is gradually decreased. At this time, the clutch 70 is in the engaged condition, so that the rotating speed of the rear wheel 9 is increased. When the movable pulley half 62 is moved away from the fixed pulley half 61 in association with an increase in engine speed as mentioned above, the movable cam portions 62c integral with the movable pulley half 62 are deeply inserted through the openings 72d among the fixed cam portions 75 as shown by the phantom line in FIG. 18. The movable cam portions 62c shown by the phantom line in FIG. 18 exhibit a TOP ratio condition corresponding to the above small reduction ratio, and the movable cam portions 62c shown by the solid line in FIG. 18 exhibit a LOW ratio condition corresponding to the above large reduction ratio. In the case that the tension of the v-belt 55 is rapidly increased at rapid acceleration upon starting or the like, there is a possibility of slippage between the V-belt 55 and the fixed pulley half 61 connected to the rear wheel 9 to receive a large load, and there is also a possibility that the movable pulley half 62 tends to rotate integrally with the v-belt 55 because the load from the rear wheel 9 is not directly applied to the movable pulley half 62 that is rotatable relative to the fixed pulley half 61. UHI&31] Thus, rotation of the movable pulley half 62 relative to the fixed pulley half 61 occurs. Accordingly, the movable cam portions 62c integral with the movable pulley half 62 rotates prior to the fixed cam portions 75 fixed to the drive plate 72 integrated with the fixed pulley half 61. As a result, the movable cam portions 62c move relative to the fixed cam portions 75 in the direction of arrow A shown in FIG. 18. As a result, the outward cam faces 62co of the movable cam portions 62c come into abutment against the outward cam faces 75o of the fixed cam portions 75, and the movable cam portions 62c reactively receive a force having a direction shown by arrow B, thereby moving the movable pulley half 62 toward the fixed pulley half 61 to increase a holding pressure applied to the V-belt 55. Accordingly, the above-mentioned slippage of the V-belt 55 can be prevented. [ 0063 ] Each fixed cam portion 75 and the corresponding movable cam portion 62c are engaged in a meshing fashion with the small clearance C defined therebetween. Accordingly, even when the outward cam face 62co of each movable cam portion 62c is separated from the outward cam portion 75o of the corresponding fixed cam portion 75, the spacing therebetween becomes the small clearance C at the maximum. At rapid acceleration upon starting or the like, the two cam faces 62co and 75o immediately come into contact to operate the torque cam mechanism. Thus, a time lag until prevention of the slippage can be shortened to thereby substantially prevent acceleration delay and obtain always smooth acceleration feel. FIG. 19 is a graph showing the relation between engine speed Ne and vehicle speed V. It is apparent from FIG. 19 that when the clutch 70 is engaged at a certain engine speed n0 to transmit power to the rear wheel 9, the torque cam mechanism operates as mentioned above to smoothly accelerate the vehicle without delay after clutch engagement as shown by the solid line. In FIG. 19, the broken line shows the relation in a conventional torque cam mechanism. In this case, the time duration of slippage of the v-belt 55 is long after clutch engagement to exhibit acceleration delay and lack smooth acceleration feel at starting Further, the clearance C between each fixed cam portion 75 and the corresponding movable cam portion 62c is small, and the inward cam face 75i and the outward cam face 75o of each fixed cam portion 75 made from resin come to contact with the inward cam face 62ci and the outward cam face 62co of the corresponding movable cam portion 62c, respectively. Accordingly, wear and fatigue can be reduced to improve the durability. In addition, the three movable cam portions 62c are collectively formed at the axial end of the outer sleeve portion 62a, thereby improving the serviceability. Each of the fixed pulley half 61 and the movable pulley half 62 is integrally formed of aluminum by die casting. Accordingly, the number of parts can be reduced and the structure can be simplified, thereby improving the productivity. Further, the fixed cam portions 75 are integrally mounted by resin molding on the core portions 72b of the drive plate 72. Accordingly, the work for separately manufacturing a cam portion and mounting it can be eliminated, thereby further improving the productivity. As shown in FIG. 17, each core portion 72b of the drive plate 72 is branched into two parts for each fixed cam portion 75, and each of the two parts is bent as viewed in cross section. Accordingly, each fixed cam portion 75 integrally molded with resin can be reliably fixed with no play. Various fixing structures for each fixed cam portion 75 may be considered otherwise. FIG. 20 shows another fixing structure. In this case, each core portion 90 of the drive plate 72 has a complex bent shape as viewed in cross section, and a fixed cam portion 91 is integrally mounted on each core portion 90 by resin molding. Also by using such a complex-shaped core portion 90, the fixed cam portion 91 can be reliably fixed with no play. FIG. 20 is a development showing an engaged condition of the fixed cam portions 91 and movable cam portions 92, and the shapes of the cam portions 91 and 92 are substantially the same as those in the above preferred embodiment. In the above preferred embodiment, the bearing bush 65 is used as a bearing between the inner sleeve portion 61a of the fixed pulley half 61 and the outer sleeve portion 62a of the movable pulley half 62. That is, a separate part as the bearing bush 65 is necessary, causing a disadvantage such that the number of parts is increased to invite a troublesome assembly step. To eliminate this disadvantage, the following means may be adopted instead. That is, the outer circumferential surface of the inner sleeve portion 61a of the fixed pulley half 61 and the inner circumferential surface of the outer sleeve portion 62a of the movable pulley half 62 are subjected to anodic oxidation to form porous coatings, which are in turn impregnated with a lubricant such as molybdenum disulfide. In this manner, the bearing between the inner sleeve portion 61a of the fixed pulley half 61 and the outer sleeve portion 62a of the movable pulley half 62 is constructed as coaxial structural bearings integrally formed on these sleeve portions 61a and 62a (cylindrical shafts). Then, a grease is applied between these coaxial structural bearings, and sealed by oil seals. With this configuration, even when the inner sleeve portion 61a of the fixed pulley half 61 and the outer leeve portion 62a of the movable pulley half 62 are thermally expanded during rotation of the driven pulley 60 driven by the V-belt 55, heat dissipation from the sleeve portions 61a and 62a is good, so that a change in bearing clearance between the sleeve portions 61a and 62a can be reduced. Further, since the bearing is provided by the coatings on the sliding surfaces of the sleeve portions 61a and 62a and the grease, any separate parts such as a bearing bush are not especially required, thereby reducing the number of parts and simplifying the assembly step. Further, the weight can also be reduced by the reduction in parts count. [Explanation of Reference Numerals] 1: scooter type motorcycle 2: front body portion 3: rear body portion 4: floor portion 5: body frame 6: steering handle 7: front wheel 8: front fork 9: rear wheel 10: link 11: rear cushion 15: leg shield 16: step floor 17: body cover 18: seat 20: power unit 21: internal combustion engine 22: reduction gearing 23: V-belt automatic transmission 25: unit case 26: left case 27: right case 28: transmission case cover 29: gear case 30: main bearing 31: crankshaft 32: piston 33: connecting rod 34: AC generator 35: cooling fan 36: engine cover 40: drive pulley 41: fixed pulley half 42: movable pulley half 43: ramp plate 44: centrifugal weight 45: input shaft 46: intermediate shaft 47: rear axle 48: input gear 49: intermediate gear 50: intermediate gear 51: output gear 55: V-belt 60: driven pulley 61: fixed pulley half 61a: inner sleeve portion (cylindrical shaft) 62: movable pulley half 62a: outer sleeve portion ( cylindrical shaft) 62c: movable cam portion 63: needle bearing 64: ball bearing 65: bearing bush (sliding member) 65b: sliding layer 66: clip 70: clutch 71: clutch outer 72: drive plate 73: pin 67: nut 74: clutch shoe 75: fixed cam portion 76: clutch spring 78: wire type clip 79: collar 80: spring 81: spring guide 82: spring seat 90: core portion 91: fixed cam portion 92: movable cam portion We claim: 1. A V-belt (55) automatic transmission having a fixed pulley half (61) formed of an aluminum material and supported to a rotating shaft, a movable pulley half (62) formed of an aluminum material and slidably supported through a bearing to a cylindrical shaft of said fixed pulley half opposed to said fixed pulley half to hold the V-belt in cooperation therewith, and a torque cam mechanism provided at an axial end of said cylindrical shaft of said fixed pulley half and an axial end of a cylindrical shaft of said movable pulley to change rotation of said movable pulley half relative to that of the fixed pulley into axial thrust of said movable pulley half, characterized in that: said bearing between said cylindrical shafts of said fixed and movable pulley halves (61, 62) in a cylindrical sliding member; said cylindrical sliding member having a sliding layer (65b) supported to an inner circumferential surface of said cylindrical shaft of said movable pulley half and formed of a self-lubricating synthetic resin; said sliding layer having a small thickness to compensate for thermal dimensional changes of said cylindrical shaft of said fixed pulley half (61) and said cylindrical shaft of said movable pulley half (62) and to thereby maintain a bearing clearance between said two cylindrical shafts constant. 2. A V-belt automatic transmission as claimed in claim 1, wherein said small thickness of said sliding layer is provided by machining a polytetrafluoroethylene layer. 3. A V-belt automatic transmission as claimed in claims 1 or 2, wherein said sliding member is prevented from escaping from said cylindrical shaft of said movable pulley half by a clip (66) provided at another end of said cylindrical shaft of said movable pulley half (62) opposite to said torque cam mechanism. 4. A V-belt automatic transmission substantially as hereinbefore described with reference to the accompanying drawings.

Full Text

[DETAILED DESCRIPTION OF THE INVENTION]
[Field of the Invention]
The present invention relates to a v-belt automatic transmission used in a motorcycle or the like, and more particularly to a V-belt automatic transmission intended to eliminate a change in bearing clearance due to thermal deformation of a fixed pulley half and a movable pulley half constituting a driven pulley, thereby improving bearing durability and eliminating play between the two
pulley halves during rotation thereof.
[Prior Art and Problems to Be Solved by the Invention]
A V-belt automatic transmission includes a drive pulley, a driven pulley, and an endless V-belt having a V-shaped cross section and wrapped between the two pulleys, in which the effective radius of each pulley is automatically changed according to engine speed to transmit power. Each pulley consists of a fixed pulley half and a movable pulley half axially slidable. The V-belt is held between the fixed pulley half and the movable pulley half, and the effective radius of the pulley is changed according to an axial position of the movable pulley half relative to the fixed pulley half.
The movable pulley half is normally biased toward the fixed pulley half by a spring to increase the effective radius of the V-belt and thereby to apply tension to the V-belt. When load variations are large, the biasing force of the spring is overcome to cause slippage between the pulley and the belt. To prevent such slippage, there has been proposed a V-belt automatic transmission having a torque cam mechanism for changing rotation of the movable pulley half relative to the fixed pulley half into axial thrust of
the movable pulley half.
Such a V-belt automatic transmission having a torque cam mechanism is described in Japanese Patent Application No. 8-101187 filed by the present applicant (see FIG. 24). Referring to FIG. 24, the torque cam mechanism is composed of a movable cam portion 062c axially extending from one end of a cylindrical shaft 062a of a movable pulley half 062, and a fixed cam portion 075 radially outwardly extending from one outer end of a cylindrical shaft 061a of a fixed pulley half 061 so as to engage the movable cam portion 062c in a meshing fashion. A clearance between the movable cam portion 062c and the fixed cam portion 075 in their rotational direction is small, thereby obtaining smooth acceleration feel and good serviceability of the torque cam mechanism. In FIG. 24, reference numerals 022, 045, and 047 denote a reduction gearing, an input shaft of the reduction gearing, and a rear axle, respectively.
However, no sufficient consideration has been given to a deterioration in wear resistance of a bearing 027 provided between the cylindrical shafts 061a and 062a of the pulley halves 061 and 062 and also to supporting of the
bearing 027. More specifically, each of the pulley halves 061 and 062 is integrally formed of aluminum by casting, and accordingly the use of a self-lubricating synthetic resin as described in Japanese Patent Laid-open No. 4-258559 has been considered as the material for the bearing 027 between the cylindrical shafts 061a and 062a of the pulley halves 061 and 062. However, such a resin bearing is softer than a metal bearing, and has a larger thermal expansion, so that it is easily worn depending upon use conditions. Thus, it has been desired to improve the durability of the bearing.
Further, it has also considered to form a hard alumite coating as described in Japanese utility Model Laid-open No. 53-107780 on the sliding surfaces of the cylindrical shafts 061a and 062a of the pulley halves 061 and 062 each formed of aluminum. However, no consideration has been given to thermal expansion of the cylindrical shafts 061a and 062a, causing play between the two pulley halves 061 and 062 during rotation thereof due to a change in bearing clearance.
Further, as to means for supporting the bearing 027 between the cylindrical shafts 061a and 062a of the pulley
halves 061 and 062, no consideration has been given in the prior art. In the case that a consideration has been given, a clip for preventing escape of the bearing 027 has been provided on the inner circumferential surface of the cylindrical shaft 062a of the movable pulley half 062 at its one end (see Japanese Patent Laid-open No. 4-224345). In the former case of no supporting means, there is a possibility of escape of the bearing, while in the latter case, the wall thickness of the cylindrical shaft 062a of the movable pulley half 062 at its one end must be increased for the provision of the clip.
If the wall thickness of the cylindrical shaft 062a of the movable pulley half 062 at its one end is increased, and the torque cam mechanism is formed at the axial ends of the cylindrical shafts 061a and 062a of the pulley halves 061 and 062 as in the prior invention by the present applicant, the radius of the movable cam portion 062c is increased, with the result that when torque applied to the torque cam mechanism is fixed, a cam force generated in the torque cam mechanism (a rotational force of the movable cam portion 062c against the fixed cam portion 075) is reduced, and an axial component of the cam force is therefore reduced. As a result, a thrust for biasing the movable
pulley half 062 toward the fixed pulley half 061 is reduced, and it is accordingly necessary to set large the spring load of a spring 080 for biasing the movable pulley half 062 toward the fixed pulley half 061. Such increasing the spring load causes a reduction in durability of a V-belt 055 always held between the two pulley halves 061 and 062 under the spring load.
Further, a clip 078 is used to prevent escape of a drive plate 072 of a clutch 070. The drive plate 072 is spline-engaged with an end portion 061b of the cylindrical shaft 061a of the fixed pulley half 061. The clip 078 is a usual cut-ring clip, so that when a centrifugal force is applied, the diameter of the clip 078 tends to be increased. Accordingly, an excess tightening force for the clip 078 is required to endure the centrifugal force applied, causing a reduction in mountability. Further, the manufacture of the clip 078 requires much time and labor, for example, material selection or treatment for the purpose of obtaining a stress enduring material. If a nut is used in place of the clip 078, an extra space for providing the nut is required.
Further, the shape of a root portion 061d of the
cylindrical shaft 061a of the fixed pulley half 061 is designed so that a stress generated in this portion cannot be efficiently diffused. Accordingly, the root portion 061d has a large size for the sake of strength.
In view of the above problems, it is an object of the present invention to improve the durability of the bearing 027 between the cylindrical shafts 061a and 062a of the fixed and movable pulley halves 061 and 062, and to provide means for preventing escape of the bearing 027 without the need for increasing the wall thickness of an end portion of each of the cylindrical shafts 061a and 062a of the pulley halves 061 and 062, thereby improving the durability and function of the structure of the driven pulley and its associated parts in a V-belt automatic transmission, and reducing the size and weight of the structure.
[Means for Solving the Problem, Operation, and Effect] In accordance with the invention as defined in claim 1, there is provided in a V-belt automatic transmission including a fixed pulley half integrally formed of an aluminum material and supported to a rotating shaft, a movable pulley half integrally formed of an
aluminum material and slidably supported through a bearing to a cylindrical shaft of said fixed pulley half so as to be opposed to said fixed pulley half to hold a V-belt in cooperation therewith, and a torque cam mechanism provided at an axial end of said cylindrical shaft of said fixed pulley half and an axial end of a cylindrical shaft of said movable pulley half to change rotation of said movable pulley half relative to the fixed pulley half into axial thrust of said movable pulley half; the improvement wherein said bearing between said cylindrical shafts of said fixed and movable pulley halves is a cylindrical sliding member; said cylindrical sliding member having a sliding layer supported to an inner circumferential surface of said cylindrical shaft of said movable pulley half and formed of a self-lubricating synthetic resin; said sliding layer having a small thickness so set as to compensate for thermal dimensional changes of said cylindrical shaft of said fixed pulley half and said cylindrical shaft of said movable pulley half and thereby to maintain a bearing clearance between said two cylindrical shafts substantially constant.
With this configuration, even when the fixed pulley half and the movable pulley half each formed integrally of
an aluminum material are deformed by thermal expansion to cause an increase in bearing clearance between the cylindrical shafts of the two pulley halves, the bearing formed as the sliding member having the thin sliding layer formed of a self-lubricating synthetic resin having a coefficient of thermal expansion larger than that of each pulley half is expanded so as to compensate for the increase in bearing clearance, thereby maintaining the bearing clearance always substantially constant and preventing wear of the bearing to improve the durability. Further, play between the two pulley halves during rotation thereof can also be prevented.
By configurating the invention of claim 1 according to claim 2, a bearing highly excellent in heat resistance and corrosion resistance can be obtained.
By configurating the invention of claim 1 or 2 according to claim 3, the clip for supporting the sliding member forming the bearing is not required to be provided on the inner circumferential surface of the cylindrical shaft of the movable pulley half at its one end where the torque cam mechanism is provided. Accordingly, it is unnecessary to increase the wall thickness of the
cylindrical shaft of the movable pulley half at this portion, so that the outer diameter of this portion can be reduced and accordingly the radius of the movable cam portion of the torque cam mechanism formed at this portion can be reduced. As a result, a cam force generated in the torque cam mechanism cam be increased, and an axial component of the cam force can also be increased. Therefore, a spring load biasing the movable pulley half toward the fixed pulley half can be set to a small value, thereby improving the durability of the V-belt held between the two pulley halves.
Accordingly, the present invention relates to a V-belt automatic transmission including a fixed pulley half integrally formed of an aluminum material and supported to a rotating shaft, a movable pulley half integrally formed of an aluminum material and slidably supported through a bearing to a cylindrical shaft of said fixed pulley half opposed to said fixed pulley half to hold to V-belt in cooperation therewith, and a torque cam mechanism provided at an axial end of said cylindrical shaft of said fixed pulley half and an axial end of a cylindrical shaft of said movable pulley of half to change rotation of said movable pulley half relative to that of the fixed pulley into axial thrust of said movable pulley half, characterized in that said bearing between said cylindrical shafts of said fixed and movable pulley halves in a cylindrical sliding member, said cylindrical sliding member having a sliding layer supported to an inner circumferential surface of said cylindrical shaft of said movable pulley half and formed of a self-lubricating synthetic resin, said sliding layer having a small thickness to compensate for thermal dimensional changes of said cylindrical shaft of said fixed pulley half and said cylindrical shaft of said movable pulley half and to thereby maintain a bearing clearance between said two cylindrical shafts constant.
[BRIEF DESCRIPTION OF THE DRAWINGS] [FIG. 1]
FIG. 1 is a general side view of a scooter type motorcycle employing a v-belt automatic transmission according to a preferred embodiment of the present invention as defined in claims 1 to 3 in this specification. [FIG. 2]
FIG. 2 is a cross section of a power unit taken along the line II-II in FIG. 1. [FIG. 3]
FIG. 3 is a sectional view of an essential part of a rear portion of the power unit shown in FIG. 2. [FIG. 4] FIG. 4 is an elevational view of a movable pulley half of a driven pulley in this preferred embodiment. [FIG. 5]
FIG. 5 is a cross section taken along the line V-v in FIG. 4. [FIG. 6]
FIG. 6 is a view similar to FIG. 4, showing a modification of the movable pulley half. [FIG. 7]
FIG. 7 is a sectional view of a fixed pulley half of the driven pulley. [FIG. 8]
FIG. 8 is an enlarged view of an encircled portion VIII shown in FIG. 7. [FIG. 9]
FIG. 9 is a sectional view of a spring guide in this preferred embodiment. [FIG. 10]
FIG. 10 is a sectional view of a bearing bush in this preferred embodiment. [FIGc. 11]
FIG. 11 is an enlarged view of an encircled portion XI shown in FIG. 10. [FIG. 12]
FIG. 12 is a graph for illustrating the operation of the bearing bush. [FIG. 13]
FIG. 13 is an elevational view of a clip for preventing escape of the bearing bush. [FIG. 14]
FIG. 14 is a side view of the clip shown in FIG. 13. [FIG. 15]
FIG. 15 is an elevational view of a drive plate in this preferred embodiment. [FIG. 16]
FIG. 16 is a cross section taken along the line XVI-XVI in FIG. 15. [FIG. 17]
FIG. 17 is a cross section taken along the line XVII-XVII in FIG. 15. [FIG. 18]
FIG. 18 is a development showing an engaged condition of fixed cam portions and movable cam portions in this preferred embodiment. [FIG. 19]
FIG. 19 is a graph showing the relation between engine speed and vehicle speed in this preferred embodiment. [FIG. 20]
FIG. 20 is a view similar to FIG. 18, showing an
engaged condition of a modification of the fixed cam portions and the movable cam portions. [FIG. 21]
FIG. 21 is an elevational view of a wire type clip for preventing escape of the drive plate. [FIG. 22]
FIG. 22 is a side view of the wire type clip shown in FIG. 21. [FIG. 23]
FIG. 23 is an enlarged view of an encircled portion XXIII shown in FIG. 3. [FIG. 24]
FIG. 24 is' a sectional view showing a conventional pulley structure.
[Preferred Embodiment]
There will now be described a preferred embodiment of the present invention as defined in claims 1 to 3 in this specification with reference to FIGS. 1 to 23.
FIG. 1 is a general side view of a scooter type motorcycle 1 to which the V-belt automatic transmission according to the present invention is applied.
The scooter type motorcycle 1 has a front body portion 2, a rear body portion 3, and a floor portion 4 connecting the front body portion 2 and the rear body portion 3. A body frame 5 extends obliquely downward from

the front body portion 2 and further extends horizontally rearward along the floor portion 4. The body frame 5 rises from the rear end of the floor portion 4 and further extends obliquely upward to the rear end of the rear body portion 3.
A front fork 8 is pivotably supported to a front portion of the body frame 5. A steering handle 6 is provided at the upper end of the front fork 8, and a front wheel 7 is rotatably supported to the lower ends of the front fork 8.
A swing type power unit 20 is vertically swingably supported at its front lower portion through a link 10 to a rear rising portion of the body frame 5. A rear wheel 9 is rotatably supported through an axle to the rear end of the power unit 20. A rear cushion 11 is interposed between a rear upper portion of the power unit 20 and a rear inclined portion of the body frame 5.
The front body portion 2 is covered with a leg shield 15. The floor portion 4 is provided with a step floor 16. The rear body portion 3 is covered with a body cover 17. A seat 18 is provided at an upper portion of the body cover 17.
The power unit 20 includes a single-cylinder 2-cycle internal combustion engine 21 located at a front portion, a reduction gearing 22 located at a rear portion, and a v-belt automatic transmission 23 located between the internal combustion engine 21 and the reduction gearing 22. These members are united together and accommodated in a unit case 25.
The structure of the power unit 20 is shown in FIG. 2. The unit case 25 is composed of a longitudinally elongated left case 26 accommodating the V-belt automatic transmission 23 and the reduction gearing 22 and constituting a left half portion of a crankcase of the internal combustion engine 21, a right case 27 joined to a front portion of the left case 26 and constituting a right half of the crankcase, a transmission case cover covering a left opening of the left case 26, and a gear case 29 covering a left side of the reduction gearing 22. A crankshaft 31 is rotatably supported through a pair of main bearings 30 to the crankcase formed by the left case 26 and the right case 27. A cylinder block 21a and a cylinder head 21b are joined in this order to an
upper end of the crankcase, and this assembly projects upward so as to be slightly inclined rearward.
A piston 32 sliding in the cylinder block 2la is connected through a connecting rod 33 to the crankshaft 31.
An AC generator 34 and a cooling fan 35 are provided at a right end of the crankshaft 31, and an engine cover 36 is provided to commonly cover the outer peripheries of the internal combustion engine 21, the AC generator 34, and the cooling fan 35.
A drive pulley 40 of the V-belt automatic transmission 23 is provided at a left end of the crankshaft 31. The drive pulley 40 is composed of a fixed pulley half 41 fixed to the left end of the crankshaft 31 and a movable pulley half 42 axially slidably supported to the crankshaft 31 so as to be opposed to the fixed pulley half 41. A plurality of centrifugal weights 44 are radially movably interposed between the movable pulley half 42 and a ramp plate 43 fixed to the crankshaft 31.
Movement of the centrifugal weights 44 in their centrifugal directions makes the movable pulley half 42 approach the fixed pulley half 41, thereby allowing an
increase in effective radius of a V-belt 55 held between the two pulley halves 41 and 42.
As shown in FIG. 3, the reduction gearing 22 provided in a space defined by a rear portion of the left case 26 and the gear case 29 includes an input shaft 45, a rear axle 47 as an output shaft, an intermediate shaft 46 provided between the input shaft 45 and the rear axle 47, an input gear 48 mounted on the input shaft 45, a large-diameter intermediate gear 49 mounted on the intermediate shaft 46 and meshing with the input gear 48, a small-diameter intermediate gear 50 mounted on the intermediate shaft 46, and an output gear 51 mounted on the rear axle 47 and meshing with the small -diameter intermediate gear 50, thus configuring a reduction mechanism.
As shown in FIG. 3, the input shaft 45 of the reduction gearing 22 extends leftward from the gear case 29, and a driven pulley 60 and a clutch 70 are provided on such a left extending portion of the input shaft 45.
The driven pulley 60 is composed of a pair of fixed pulley half 61 and movable pulley half 62 opposed to each other. Both the fixed pulley half 61 and the movable pulley half 62 are made from aluminum.
As shown in FIG. 7, the fixed pulley half 61 is composed generally of an annular conical body portion and a cylindrical inner sleeve portion (cylindrical shaft) 61a extending axially from an inner circumferential portion of the body portion 61e. The inner sleeve portion 61a is slightly reduced in diameter at its left end portion to form a mounting portion 61b having a serrated outer circumference. The mounting portion 61b is formed at its left end portion with a circumferentially extending clip groove 61c for engaging a wire type clip 78 for preventing escape of a drive plate 72 of the clutch 70 to be hereinafter described. The clip groove 61c has a substantially semicircular cross section. The fixed pulley half 61 is integrally formed by aluminum die casting.
Further, a large stress due to a tension of the V-belt 55 is generated in a root portion 61d of the inner sleeve portion 61a of the fixed pulley half 61. Conventionally, such a root portion is enlarged in size to ensure its strength, resulting in an increase in weight. In this preferred embodiment, however, the root portion 61d has such a shape that an apex angle a (α1, α2, etc.) formed between tangent lines each touching a curved line having a
maximum curvature of different curvatures of plural curved lines forming a sectional contour line of the root portion 61d is not less than a given angle (see FIGS. 7 and 8).
With this configuration, a stress generated in the root portion 61d can be efficiently diffused without changing a conventional basic shape of the fixed pulley half 61, thereby maintaining the strength of the root portion 61d. Accordingly, the strength of the root portion 61d can be obtained with its smaller size, thereby expecting a reduction in size and weight of the fixed pulley half 61.
In an experiment on this preferred embodiment, a stress generated in the root portion 61d could be most efficiently diffused by setting a ≥ 90° under the conditions that the outer diameter DI of the inner sleeve portion 6 la of the fixed pulley half 61 is 34 mm, the outer diameter D2 of the body portion 61e of the fixed pulley half 61 is 118 mm, the maximum diameter D3 of the root portion 61d is 45 mm, the maximum wall thickness t of the body portion 61e of the fixed pulley half 61 is 5 mm, the inclination angle ß of the body portion 61e is 15°, and the maximum curvature R3 of the contour line of the root
portion 61d is 5.5 mm. In this case, the curvatures R1 and R2 of the contour line components adjacent to the contour line component having the maximum curvature R3 = 5.5 mm were 2.2 mm and 2.0 mm, respectively.
As shown in FIGS. 4 and 5, the movable pulley half 62 is composed generally of an annular conical body portion 62g and a cylindrical outer sleeve portion (cylindrical shaft) 62a extending axially from an inner circumferential portion of the body portion 62g. The outer sleeve portion 62a has an inner diameter slightly larger than the outer diameter of the inner sleeve portion 61a of the fixed pulley half 61. The outer sleeve portion 62a is formed at its left end portion with three axial projections 62b circumferentially spaced at equal intervals. Each projection 62b has an arcuate shape in cross section. Each projection 62b is bent at its front end portion clockwise as viewed in FIG. 4 to form a movable cam portion 62c. The movable cam portion 62c has circumferentially opposite inclined end faces serving as an outward cam face 62co and an inward cam face 62ci.
In this preferred embodiment, each of the three movable cam portions 62c is formed with a triangular
projected portion projecting in a direction (clockwise direction as viewed in FIG. 4) opposite to a rotational direction of the driven pulley 60, thus forming the inward cam face 62ci. Alternatively, only one of the three movable cam portions 62c may be formed with such a triangular projected portion to form the single inward cam face 62ci (see FIG. 6), because the inward cam face 62ci functions to restrict rotation of the movable cam portions 62c relative to fixed cam portions 75 to be hereinafter described, and a large load is therefore not applied to the inward cam face 62ci.
The movable pulley half 62 is integrally formed by aluminum die casting.
The outer sleeve portion 62a of the movable pulley half 62 is formed at its root portion joined to the body portion 62g with an annular groove 62d. Further, the body portion 62g is formed at its inner circumferential portion on the side opposite to the outer sleeve portion 62a with a circular clip groove 62e for engaging a circular clip 66 (see FIGS. 13 and 14) for preventing escape of a bearing bush 65 (which will be hereinafter described) interposed between the outer sleeve portion 62a of the movable pulley half 62 and the inner sleeve portion 61a of the fixed
pulley half 61.
As shown in FIGS. 13 and 14, the circular clip 66 is a wire type clip similar to a wire type clip 78 for preventing escape of a drive plate 72 of the clutch 70 to be hereinafter described. Accordingly, when the circular clip 66 is engaged with the clip groove 62e of the movable pulley half 62, the clip 66 exerts an elastic restoring force against a shoulder portion formed at the right end of the bearing bush 65 to thereby bias the bearing bush 65 toward the left end of the outer sleeve portion 62a, thus reliably preventing escape of the bearing bush 65.
As shown in FIG. 3, the fixed pulley half 61 of the driven pulley 60 is rotatably mounted at its inner sleeve portion 61a on the left portion of the input shaft 45 through a needle bearing 63 and a ball bearing 64, and the movable pulley half 62 is slidably mounted at its outer sleeve portion 62a on the outer circumference of the inner sleeve portion 61a of the fixed pulley half 61 through the bearing bush 65.
The body portion 61e of the fixed pulley half 61 and the body portion 62g of the movable pulley half 62 are opposed to each other, and relative axial slide and
relative rotation between the two pulley halves 61 and 62 are allowed.
FIGS. 10 and 11 show a detailed structure of the bearing bush (sliding member) 65 in this preferred embodiment. The bearing bush 65 has a thin-walled multilayer structure consisting of a back metal layer 65a formed by plating a steel surface with copper, and a sliding layer 65b fixed to the inner circumferential surface of the back metal layer 65a. The sliding layer 65b is formed of a self-lubricating synthetic resin (e.g., polytetrafluoroethylene). The bearing bush 65 is press-fitted with the inner circumferential surface of the outer sleeve portion 62a of the movable pulley half 62, and the sliding layer 65b is brought into smooth sliding contact with the outer circumferential surface of the inner sleeve portion 61a of the fixed pulley half 61 owing to the self-lubricating property of the sliding layer 65b. Thus, the movable pulley half 62 is smoothly slidably supported to the fixed pulley half 61 by the bearing bush 65. In FIG. 11, reference numeral 65c denotes a sintered layer for facilitating fixation of the sliding layer 65b to the back metal layer 65a.
The sliding layer 65b of the bearing bush 65 has a coefficient of thermal expansion larger than that of the pulley halves 61 and 62 each formed of aluminum, and has a given small thickness. Accordingly, even when a thermal change a in outer diameter of the inner sleeve portion 61a of the fixed pulley half 61 and a thermal change b (b > a) in inner diameter of the outer sleeve portion 62a of the movable pulley half 62 cause an increase d in bearing clearance c between the inner and outer diameters, the increase d can be just canceled by the amount of thermal expansion of the sliding layer 65b, thereby maintaining the bearing clearance c at an initial substantially constant value (see FIG. 12).
Accordingly, there is no possibility that the bearing bush 65 may be increased in diameter beyond the increase d in bearing clearance c due to the increases in diameters of the sleeve portions 61a and 62a of the pulley halves 61 and 62 to undergo severe sliding wear from the sliding surfaces of the sleeve portions 61a and 62a, and there is also no possibility of rotational play between the two pulley halves 61 and 62 of the driven pulley 60 due to an increase in bearing clearance c.
In an experiment on this preferred embodiment, the bearing clearance c could be maintained at an initial substantially constant value by setting the thickness hi of the sliding layer 65b to 0.75 ram under the conditions that the outer diameter D! of the inner sleeve portion 61a of the fixed pulley half 61 is 34 mm, the inner diameter D4 of the outer sleeve portion 62a of the movable pulley half 62 is 37 mm, and the wall thickness h of the bearing bush 65 is 2 mm. Such dimensional setting of the thickness hi of the sliding layer 65b can be easily achieved by machining the surface of the sliding layer 65b.
When the bearing bush 65 is interposed between the sleeve portions 61a and 62a of the pulley halves 61 and 62, one end of the bearing bush 65 abuts against shoulders 62f formed between the inner circumferential surface of the outer sleeve portion 62a of the movable pulley half 62 and root portions of the projections 62b, and the other end of the bearing bush 65 is supported by the clip 66 engaged with the clip groove 62e formed on the inner circumferential surface of the body portion 62g of the movable pulley half 62 at its end opposite to the outer sleeve portion 62a as mentioned above, thus restricting axial movement of the bearing bush 65.
The clip 66 for preventing escape of the bearing bush 65 is not located on the inner circumferential surface of the outer sleeve portion 62a of the movable pulley half 62 on the projections 62b side, so that it is unnecessary to increase the wall thickness of this portion of the outer sleeve portion 62a, and the outer diameter of this portion can be reduced. Accordingly, in the case that the torque applied to a torque cam mechanism to be hereinafter described is constant, a cam force generated in the torque cam mechanism can be increased, and therefore its axial component urging the movable pulley half 62 against the fixed pulley half 61 can also be increased. As a result, the spring load of a spring 80 for biasing the movable pulley half 62 toward the fixed pulley half 61 can be set to a small value, so that the durability of the V-belt 55 held between the two pulley halves 61 and 62 can be improved The clutch 70 and the torque cam mechanism will now be described.
The clutch 70 is provided at the left end of the input shaft 45 of the reduction gearing 22 and the mounting portion 61b of the inner sleeve portion 61a of the fixed pulley half 61.
The clutch 70 has a flat cylindrical clutch outer 71 having a bottom wall 71a. The bottom wall 71a has a center hole engaged through a collar 79 with a threaded portion formed at the left end of the input shaft 45, and the bottom wall 71a is fastened by tightening a nut 67 to the threaded portion of the input shaft 45. The bottom wall 71a continues to a cylindrical wall 71b opening rightward.
A drive plate 72 as a clutch inner is accommodated in the clutch outer 71 and is mounted through serration engagement on the left end mounting portion 61b of the inner sleeve portion 61a of the fixed pulley half 61 as shown in FIG. 3.
A wire type clip 78 is engaged with a clip groove 61c formed on the outer circumferential surface of the mounting portion 61b, so as to fix the serration engagement. The wire type clip 78 engaged with the clip groove 61c elastically abuts against a chamfered portion 72e formed at the left end of a serrated portion 72a of the drive plate 72 to be hereinafter described, thereby normally biasing the drive plate 72 toward the body portion
61e of the fixed pulley half 61 (see FIGS. 21 to 23).
As shown in FIGS. 21 to 23, the wire type clip 78 is a ringlike member with its arcuate portion slightly cut out and its opposite ends slightly deviated from each other in the natural condition. Accordingly, when the clip 78 is engaged with the clip groove 61c, the clip 78 exerts an elastic restoring force F1 on the chamfered portion 72e of the drive plate 72 to thereby strongly press the chamfered portion 72e in the axial direction (toward the body portion 61e of the fixed pulley half 61). As a result, even when the drive pulley 60 is rotated at high speeds to cause application of a centrifugal force F2 to the wire type clip 78, a reaction of a resultant force F of these forces F1 and F2 is effectively applied to the clip 78 from a contact between the clip 78 and the chamfered portion 72e, thereby preventing an increase in diameter of the clip 78 and accordingly preventing escape of the clip 78 from the clip groove 61c. Furthermore, since the wire type clip 78 is simple in structure and inexpensive, and can be easily installed even in a narrow space.
As shown in FIGS. 15 and 16, the drive plate 72 is formed at its inner circumference with a flat cylindrical
serrated portion 72a. Further, three core portions 72b extend radially from the outer circumferential surface of the serrated portion 72a, and an outer circumferential plate portion 72c is connected to the core portions 72b so as to have a slightly stepped portion 72f.
The outer circumferential plate portion 72c is provided with three pins 73 circumferentially spaced at equal intervals. A clutch shoe 74 (see FIG. 3) is supported to each pin 73.
A fixed cam portion 75 is integrally mounted on each core portion 72b by molding a self -lubricating resin. That is, three fixed cam portions 75 mounted on the three core portions 72b are circumferentially spaced at equal intervals.
Three openings 72d are formed through the outer circumferential plate portion 72c in such a manner that each opening 72d is located between the adjacent fixed cam portions 75. The three openings 72d allow reception of the three movable cam portions 62c of the movable pulley half 62, respectively, thereby providing meshing engagement of the fixed cam portions 75 and the movable cam portions 62c.
As shown in FIG. 17, each fixed cam portion 75 is
fixed to the corresponding bent core portion 72b, and has a substantially trapezoidal cross section so as to have an inward cam face 75i formed as a circumferentially inclined flat surface and an outward cam face 75o formed as a curved surface.
The drive plate 72 is provided in the clutch outer 71. The clutch shoes 74 supported to the pins 73 are swung radially outward by a centrifugal force against clutch springs 76. As a result, a friction member 74a provided on the outer circumference of each clutch shoe 74 comes into contact with the inner circumferential surface of the cylindrical wall 71b of the clutch outer 71.
The drive plate 72 is integrally mounted by serration engagement on the left end mounting portion 61b of the inner sleeve portion 61a of the fixed pulley half 61. Therefore, the drive pulley 72 is rotated integrally with the fixed pulley half 61. [OOS^J
As shown in FIG. 3, the movable pulley half 62 is slidably supported between the drive plate 72 and the body portion 61e of the fixed pulley half 61. A coiled spring 80 formed of spring steel is mounted closely around the
outer circumference of the outer sleeve portion 62a of the movable pulley half 62. The spring 80 is interposed between the drive plate 72 and the body portion 62g of the movable pulley half 62 to bias the body portion 62g toward the body portion 61e of the fixed pulley half 61.
A spring guide 81 formed of resin is interposed between the inner circumference of the spring 80 and the outer circumference of the outer sleeve portion 62a.
As shown in FIG. 9, the spring guide 81 is cylindrical, and has a flange 81a at one end. The spring guide 81 has an inner diameter slightly larger than the outer diameter of the outer sleeve portion 62a, and the inner diameter at the flange 81a is slightly enlarged.
When the spring guide 81 is mounted on the outer circumference of the outer sleeve portion 62a, and the drive plate 72 is mounted on the mounting portion 61b of the inner sleeve portion 61a, the fixed cam portion 75 is engaged with the inner circumference of the large-diameter left end portion of the spring guide 81 to support the spring guide 81, and the flange 81a of the spring guide 81 abuts against the stepped portion 72f of the outer circumferential plate portion 72c of the drive plate 72.
An annular spring seat 82 made from iron is fitted with the annular groove 62d formed on the outer circumference of the root portion of the outer sleeve portion 62a of the movable pulley half 62. The spring 80 is interposed between the spring seat 82 and the flange 81a of the spring guide 81 in such a manner that the opposite ends of the spring 80 abuts against the spring seat 82 and the flange 81a.
A front portion of the v-belt 55 is wrapped around the drive pulley 40, and a rear portion of the V-belt 55 is wrapped around the driven pulley 60 in such a manner as to be resiliently held between the fixed pulley half 61 and the movable pulley half 62d biased toward the fixed pulley half 61 by the spring 80, thereby increasing the effective radius of the V-belt 55 on the driven pulley 60 to apply tension to the V-belt 55.
Further, the three movable cam portions 62c formed at the left end of the outer sleeve portion 62a of the movable pulley half 62 are exposed to the three openings 72d of the drive plate 72 rotating with the fixed pulley half 61, and are engaged with the three fixed cam portions
75 of the drive plate 72. Such an engaged condition of the three movable cam portions 62c and the three fixed cam portions 75 is shown in FIG. 18.
As shown in FIG. 18, the inward cam face 75i and the outward cam face 75o of each fixed cam portion 75 are respectively opposed to the inward cam face 62ci and the outward cam face 62co of the corresponding movable cam portion 62c with a small clearance C measured in the rotational direction of the driven pulley 60, so that the opposed cam faces can easily come into contact with each other. Accordingly, an angle of rotation of each movable cam portion 62c relative to the corresponding fixed cam portion 75 is restricted to a small value. [ 0059 ] '
The operation of the V-belt automatic transmission 23 in this preferred embodiment will now be described.
When the rotating speed of the internal combustion engine 21 is low, the centrifugal weights 44 adapted to radially move along the ramp plate 43 on the drive pulley 40 side are present at a radially central position as shown by the solid line in FIG. 2, so that the movable pulley half 42 of the drive pulley 40 is spaced apart from the fixed pulley half 41, and the effective radius of the V-
belt 55 on the drive pulley 40 is therefore small. As a result, the movable pulley half 62 of the driven pulley 60 is biased by the spring 80 to approach the fixed pulley half 61, thereby increasing the effective radius of the V-belt 55 on the driven pulley 60. Accordingly, power is transmitted at a large reduction ratio.
When the rotating speed of the engine 21 is increased, the centrifugal weights 44 are moved in the centrifugal directions to make the movable pulley half 42 of the drive pulley 40 approach the fixed pulley half 41 as shown by the phantom line in FIG. 2, thereby increasing the effective radius of the V-belt 55 on the drive pulley 40. As a result, the movable pulley half 62 of the driven pulley 60 is moved away from the fixed pulley half 61 against the spring 80, thereby decreasing the effective radius of the V-belt 55. As a result, the reduction ratio is gradually decreased. At this time, the clutch 70 is in the engaged condition, so that the rotating speed of the rear wheel 9 is increased.
When the movable pulley half 62 is moved away from the fixed pulley half 61 in association with an increase in engine speed as mentioned above, the movable cam portions
62c integral with the movable pulley half 62 are deeply inserted through the openings 72d among the fixed cam portions 75 as shown by the phantom line in FIG. 18.
The movable cam portions 62c shown by the phantom line in FIG. 18 exhibit a TOP ratio condition corresponding to the above small reduction ratio, and the movable cam portions 62c shown by the solid line in FIG. 18 exhibit a LOW ratio condition corresponding to the above large reduction ratio.
In the case that the tension of the v-belt 55 is rapidly increased at rapid acceleration upon starting or the like, there is a possibility of slippage between the V-belt 55 and the fixed pulley half 61 connected to the rear wheel 9 to receive a large load, and there is also a possibility that the movable pulley half 62 tends to rotate integrally with the v-belt 55 because the load from the rear wheel 9 is not directly applied to the movable pulley half 62 that is rotatable relative to the fixed pulley half 61. UHI&31]
Thus, rotation of the movable pulley half 62 relative to the fixed pulley half 61 occurs. Accordingly, the movable cam portions 62c integral with the movable
pulley half 62 rotates prior to the fixed cam portions 75 fixed to the drive plate 72 integrated with the fixed pulley half 61. As a result, the movable cam portions 62c move relative to the fixed cam portions 75 in the direction of arrow A shown in FIG. 18.
As a result, the outward cam faces 62co of the movable cam portions 62c come into abutment against the outward cam faces 75o of the fixed cam portions 75, and the movable cam portions 62c reactively receive a force having a direction shown by arrow B, thereby moving the movable pulley half 62 toward the fixed pulley half 61 to increase a holding pressure applied to the V-belt 55. Accordingly, the above-mentioned slippage of the V-belt 55 can be prevented. [ 0063 ]
Each fixed cam portion 75 and the corresponding movable cam portion 62c are engaged in a meshing fashion with the small clearance C defined therebetween. Accordingly, even when the outward cam face 62co of each movable cam portion 62c is separated from the outward cam portion 75o of the corresponding fixed cam portion 75, the spacing therebetween becomes the small clearance C at the maximum. At rapid acceleration upon starting or the like,
the two cam faces 62co and 75o immediately come into contact to operate the torque cam mechanism. Thus, a time lag until prevention of the slippage can be shortened to thereby substantially prevent acceleration delay and obtain always smooth acceleration feel.
FIG. 19 is a graph showing the relation between engine speed Ne and vehicle speed V. It is apparent from FIG. 19 that when the clutch 70 is engaged at a certain engine speed n0 to transmit power to the rear wheel 9, the torque cam mechanism operates as mentioned above to smoothly accelerate the vehicle without delay after clutch engagement as shown by the solid line.
In FIG. 19, the broken line shows the relation in a conventional torque cam mechanism. In this case, the time duration of slippage of the v-belt 55 is long after clutch engagement to exhibit acceleration delay and lack smooth acceleration feel at starting
Further, the clearance C between each fixed cam portion 75 and the corresponding movable cam portion 62c is small, and the inward cam face 75i and the outward cam face 75o of each fixed cam portion 75 made from resin come to contact with the inward cam face 62ci and the outward cam
face 62co of the corresponding movable cam portion 62c, respectively. Accordingly, wear and fatigue can be reduced to improve the durability.
In addition, the three movable cam portions 62c are collectively formed at the axial end of the outer sleeve portion 62a, thereby improving the serviceability.
Each of the fixed pulley half 61 and the movable pulley half 62 is integrally formed of aluminum by die casting. Accordingly, the number of parts can be reduced and the structure can be simplified, thereby improving the productivity.
Further, the fixed cam portions 75 are integrally mounted by resin molding on the core portions 72b of the drive plate 72. Accordingly, the work for separately manufacturing a cam portion and mounting it can be eliminated, thereby further improving the productivity.
As shown in FIG. 17, each core portion 72b of the drive plate 72 is branched into two parts for each fixed cam portion 75, and each of the two parts is bent as viewed in cross section. Accordingly, each fixed cam portion 75 integrally molded with resin can be reliably fixed with no
play.
Various fixing structures for each fixed cam portion 75 may be considered otherwise. FIG. 20 shows another fixing structure. In this case, each core portion 90 of the drive plate 72 has a complex bent shape as viewed in cross section, and a fixed cam portion 91 is integrally mounted on each core portion 90 by resin molding. Also by using such a complex-shaped core portion 90, the fixed cam portion 91 can be reliably fixed with no play.
FIG. 20 is a development showing an engaged condition of the fixed cam portions 91 and movable cam portions 92, and the shapes of the cam portions 91 and 92 are substantially the same as those in the above preferred embodiment.
In the above preferred embodiment, the bearing bush 65 is used as a bearing between the inner sleeve portion 61a of the fixed pulley half 61 and the outer sleeve portion 62a of the movable pulley half 62. That is, a separate part as the bearing bush 65 is necessary, causing a disadvantage such that the number of parts is increased to invite a troublesome assembly step. To eliminate this disadvantage, the following means may be adopted instead.
That is, the outer circumferential surface of the inner sleeve portion 61a of the fixed pulley half 61 and the inner circumferential surface of the outer sleeve portion 62a of the movable pulley half 62 are subjected to anodic oxidation to form porous coatings, which are in turn impregnated with a lubricant such as molybdenum disulfide. In this manner, the bearing between the inner sleeve portion 61a of the fixed pulley half 61 and the outer sleeve portion 62a of the movable pulley half 62 is constructed as coaxial structural bearings integrally formed on these sleeve portions 61a and 62a (cylindrical shafts). Then, a grease is applied between these coaxial structural bearings, and sealed by oil seals.
With this configuration, even when the inner sleeve portion 61a of the fixed pulley half 61 and the outer
leeve portion 62a of the movable pulley half 62 are thermally expanded during rotation of the driven pulley 60 driven by the V-belt 55, heat dissipation from the sleeve portions 61a and 62a is good, so that a change in bearing clearance between the sleeve portions 61a and 62a can be reduced.
Further, since the bearing is provided by the coatings on the sliding surfaces of the sleeve portions 61a and 62a and the grease, any separate parts such as a bearing bush are not especially required, thereby reducing the number of parts and simplifying the assembly step. Further, the weight can also be reduced by the reduction in parts count.
[Explanation of Reference Numerals]
1: scooter type motorcycle 2: front body portion 3: rear body portion 4: floor portion 5: body frame 6: steering handle 7: front wheel 8: front fork 9: rear wheel 10: link 11: rear cushion 15: leg shield 16: step floor 17: body cover 18: seat 20: power unit 21: internal combustion engine 22: reduction gearing 23: V-belt automatic transmission 25: unit case 26: left case 27: right case 28: transmission case cover 29: gear case 30: main bearing 31: crankshaft 32: piston 33:
connecting rod 34: AC generator 35: cooling fan 36: engine cover 40: drive pulley 41: fixed pulley half 42: movable pulley half 43: ramp plate 44: centrifugal weight 45: input shaft 46: intermediate shaft 47: rear axle 48: input gear 49: intermediate gear 50: intermediate gear 51: output gear 55: V-belt 60: driven pulley 61: fixed pulley half 61a: inner sleeve portion (cylindrical shaft) 62: movable pulley half 62a: outer sleeve portion ( cylindrical shaft) 62c: movable cam portion 63: needle bearing 64: ball bearing 65: bearing bush (sliding member) 65b: sliding layer 66: clip 70: clutch 71: clutch outer 72: drive plate 73: pin 67: nut 74: clutch shoe 75: fixed cam portion 76: clutch spring 78: wire type clip 79: collar 80: spring 81: spring guide 82: spring seat 90: core portion 91: fixed cam portion 92: movable cam portion

We claim:
1. A V-belt (55) automatic transmission having a fixed pulley half (61)
formed of an aluminum material and supported to a rotating shaft, a
movable pulley half (62) formed of an aluminum material and
slidably supported through a bearing to a cylindrical shaft of said
fixed pulley half opposed to said fixed pulley half to hold the V-belt in
cooperation therewith, and a torque cam mechanism provided at an
axial end of said cylindrical shaft of said fixed pulley half and an
axial end of a cylindrical shaft of said movable pulley to change
rotation of said movable pulley half relative to that of the fixed pulley
into axial thrust of said movable pulley half, characterized in that:
said bearing between said cylindrical shafts of said fixed and
movable pulley halves (61, 62) in a cylindrical sliding member;
said cylindrical sliding member having a sliding layer (65b) supported to an inner circumferential surface of said cylindrical shaft of said movable pulley half and formed of a self-lubricating synthetic resin;
said sliding layer having a small thickness to compensate for thermal dimensional changes of said cylindrical shaft of said fixed pulley half (61) and said cylindrical shaft of said movable pulley half (62) and to thereby maintain a bearing clearance between said two cylindrical shafts constant.
2. A V-belt automatic transmission as claimed in claim 1, wherein said
small thickness of said sliding layer is provided by machining a
polytetrafluoroethylene layer.
3. A V-belt automatic transmission as claimed in claims 1 or 2, wherein
said sliding member is prevented from escaping from said cylindrical
shaft of said movable pulley half by a clip (66) provided at another
end of said cylindrical shaft of said movable pulley half (62) opposite
to said torque cam mechanism.
4. A V-belt automatic transmission substantially as hereinbefore described with reference to the accompanying drawings.

Documents:

966-del-1998-abstract.pdf

966-del-1998-claims.pdf

966-del-1998-correspondence-others.pdf

966-del-1998-correspondence-po.pdf

966-del-1998-description (complete).pdf

966-del-1998-drawings.pdf

966-del-1998-form-1.pdf

966-del-1998-form-13.pdf

966-del-1998-form-19.pdf

966-del-1998-form-2.pdf

966-del-1998-form-3.pdf

966-del-1998-form-4.pdf

966-del-1998-form-6.pdf

966-del-1998-gpa.pdf

966-del-1998-petition-137.pdf

966-del-1998-petition-138.pdf

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Patent Number

232480

Indian Patent Application Number

966/DEL/1998

PG Journal Number

13/2009

Publication Date

27-Mar-2009

Grant Date

17-Mar-2009

Date of Filing

15-Apr-1998

Name of Patentee

HONDA GIKEN KOGYO KABUSHIKI KAISHA

Applicant Address

1-1, MINAMIAOYAMA 2-CHOME, MINATO-KU, TOKYO, JAPAN

Inventors:

#	Inventor's Name	Inventor's Address
1	KAORU HANAWA	C/O KABUSHIKI KAISHA HONDA GIJUTSU KENKYUSHO, OF 4-1, CHUO 1-CHOME, WAKO-SHI, SAITAMA, JAPAN.
2	SHINJI KUGA	C/O KABUSHIKI KAISHA HONDA GIJUTSU KENKYUSHO, OF 4-1, CHUO 1-CHOME, WAKO-SHI, SAITAMA, JAPAN

PCT International Classification Number

F16H 59/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	HEI-9-125410	1997-05-15	Japan