Continuously variable transmission for vehicle

Abstract: A continuously variable non-stage transmission for a vehicle includes a pair of pulleys (4,6) with a belt (8) wound around them, and means (18) cooperable with the pulleys for varying the radius of gyration of the belt. A fluid coupling (50), a reverse drive brake (42), a neutral clutch (68), and one of the pulleys are positioned in a row beginning at the vehicle engine and extending along a rotatable shaft (46). The fluid coupling includes a pump impeller (40), a turbine runner (48), and a stator wheel (44) which is lockable against rotation by the brake to provide reverse rotation of the turbine runner. A direct clutch (62) is built into the fluid coupling and prevents cavitation in the fluid coupling. An operating mechanism of the brake is fitted in a hollow cavity in the case (60) of the transmission. The cavity is formed by a retaining portion of the transmission case, which retaining portion supports a bearing of the rotatable shaft.

Description: The invention relates to a continuously variable transmission for a vehicle to change the reduction ratio and thereby to control the speed of the vehicle. EP-A 139 578 discloses a continuously variable transmission for a vehicle that varies groove width of adjustable input and output pulleys, each of said pulleys including an axially stationary pulley member and an axially movable pulley member supported so as to be capable of moving toward and away from the stationary pulley member, for changing the contact radius with a belt wound around said pulleys to vary the speed reduction ratio and thereby control speed. A torque converter is provided having a pump impeller connected with an output shaft of an internal combustion engine, a turbine runner is either lockable against rotation by a braking mechanism or drivingly connectable by a clutch with said stationary input pulley member, and a stator wheel is fixed on an output side shaft and drivingly connected with said stationary input pulley member. The torque converter is arranged to provide forward or reverse drive by releasing and locking the rotation of said turbine runner by means of said braking mechanism. A brake side casing is provided inside the transmission casing and houses said clutch, said braking mechanism and a braking operator actuating the latter. A bearing is provided between said brake side casing and said stationary input pulley member. It is the object of the invention to design a minimally-sized continuously variable transmission which can easily be arranged in an engine room. This object is achieved by the features of claim 1. By such a construction the transmission can be made small in overall length and can be designed to a minimum size and length. The invention is described in more detail in connection with the drawings. Figure 1 is a schematic sectional view showing a non-stage transmission equipped with a fluid coupling; Figure 2 is a detailed sectional view showing a non-stage transmission equipped with a fluid coupling; Figure 3 is an enlarged fragmentary sectional view of Figure 2; Figure 4 is a schematic diagram showing the location of shafts; Figure 5 is a schematic diagram showing the status of the fluid coupling with its turbine runner rotating in the normal direction; Figure 6 is a schematic diagram showing the status of the fluid coupling with its turbine runner rotating in the reverse direction; Figure 7 is an enlarged detailed sectional view of the fluid coupling of Figure 1; Figure 8 is a sectional view showing a non-stage automatic transmission for a vehicle; Figure 9 is an exploded sectional view showing a non-stage automatic transmission for a vehicle; and Figures 10-14 are explanatory drawings showing access procedures. In the drawings (Figures 1 and 2), 2 is a non-stage or continuously variable transmission for a vehicle, 4 is an adjustable driving side pulley, 6 is an adjustable driven side pulley, and 8 is a belt. The driving side pulley 4 has a pulley member or half 14 axially and nonrotatably fixed on a driving side shaft 12 and a pulley member or half 16 nonrotatably attached on the driving side shaft 12 but movable axially with respect thereto. Oil is conducted into an oil chamber 20 between the pulley member 16 and a housing 18 positioned on the back side of the pulley member 16. The pulley member 16 is axially moved with respect to the shaft 12 by applying hydraulic pressure thereto, and thus the width of a driving groove 22 formed between the pulley members 14 and 16 is varied. Moreover, the driven side pulley 6 has a pulley member or half 26 axially and nonrotatably fixed on a driven side shaft 24 and a pulley member or half 28 nonrotatably attached on the driven side shaft 24 but movable axially with respect thereto. Oil is conducted into an oil chamber 32 formed between the pulley member 28 and a housing 30 positioned on the back side of the pulley member 28. The pulley member 28 is axially moved with respect to the driven side shaft 24 by applying hydraulic pressure thereto, whereby the width of the groove 34 formed between the pulley members 26 and 28 is varied. In the oil chamber 32, a pressing spring 36, urging the member 28 toward the pulley member 26, is compressively positioned. The belt 8 is wound around the driving side groove 22 of the driving side pulley 4 and the driven side groove 34, and is tensioned between the pulleys 4 and 6. In a housing 38 located between the engine and the driving side pulley 4, a fluid coupling (i.e. a torque convertor) 50 is positioned and has a pump impeller 40 connectedly positioned at the side of the internal combustion engine, a stator 44 lockable by a braking mechanism 42, and a turbine runner 48 fixed on an output side shaft 46 is connectable with the driving side shaft 12 on the pulley side. The turbine runner 48 can rotate normally and reversely by releasing and locking the stator wheel 44, thus enabling the output side shaft 46 to rotate normally and reversely and to change the direction of rotation of the belt 8. A drive plate 54 for driving the fluid coupling 50 is fixed on an internal combustion engine output shaft 52. The fluid coupling 50 has the pump impeller 40, stator wheel 44, and turbine runner 48 disposed in a coupling side housing 56. The pump impeller 40 is connected with the drive plate 54 through the coupling side housing 56. Also, the stator wheel 44 is connected with the braking mechanism 42, as fitted inside of a brake side casing 60 positioned between the pulley side housing 10 and the coupling side housing 56, through a first connecting member 58. Thus, the stator wheel 44 can be locked and released from the brake side casing 60 according to the operating condition of the braking mechanism 42. Moreover, in the coupling side housing 56, a direct clutch 62 is positioned to engage the coupling side housing 56 and the turbine runner 48 with each other or to separate them from each other. That is, the direct clutch 62 can connect the internal combustion engine output shaft 52 and the output side shaft 46. In the torque convertor 50, the direct clutch 62 is built in the torque convertor to prevent a cavitation by engaging and releasing in interlocking with the brake 42. When fitting the direct clutch 62 in the torque convertor 50, as shown in Figures 1 and 7, the pump impeller 40, the stator 44, the turbine runner 48, and the direct clutch 62 are in turn positioned along the direction of hydraulic pressure fluid circulation in the torque convertor 50. Thus, when said stator 44 is not locked on the transmission case 60 by the brake 42, the direct clutch 62 is able to be engaged, and the oil passes freely through the stator 44, flowing into the front side of the turbine runner 48. Thus, as shown in Figure 5, the fluid coupling comes into a mode of fluid coupling and in a phase of normal direction (normal rotation). When the stator 44 is locked to the transmission case 60 with the brake 42 applied through a line pressure, the direct clutch 62 is not engaged and the oil reverses the direction of flow in the stator 44 and flows into the back side of the turbine runner 48. Thus, as shown in Figure 6, the fluid coupling 50 comes into a mode of torque convertor and in a phase of reverse direction (reverse rotation). Moreover, by controlling an operation of the direct clutch 62 properly, it is possible to produce, as desired, a slip between the pump impeller 40 and the turbine runner 48. Thus, a damping function is created by the torque convertor. Further, when the direct clutch 62 operates, that is, when it is disconnected upon reverse operation, the normal reversing state cannot be assured, so that upon reverse operation, the direct clutch 62 is not moved with a pressure in the direction such as to remove the direct clutch away from the drive plate 54 while interlocking with the brake 42, that is, toward the side of the turbine impeller 48. Thus, cavitation can be securely avoided by the direct clutch 62, and improved transmission efficiency of driving power from the pump impeller 40 to the turbine runner 48 can be achieved. In addition, fitting the direct clutch 62 into the torque convertor 50 enables the total length of the non-stage transmission to be made smaller, that is, the non-stage transmission can be minimized in size and can be easily arranged in the limited engine room. Besides, by properly controlling operation of the direct clutch 62 to slip the clutch, a desired slip can be produced between the pump impeller 40 and the turbine runner 48. Thus, a damping function can be imparted to said torque convertor, and the non-stage transmission will therefore be improved in usage. The shaft 12 is supported with an intermediate bearing 64. Also, a second connecting member 66 is fixed on the output side shaft 46 and connected with a neutral clutch 68. The neutral clutch 68 operates depending upon the hydraulic pressure and connects and disconnects the output side shaft 46 and the driving side shaft 12. Thereby, the turbine runner 48 can be intermittently connected with the driving side pulley member 14 by the neutral clutch 68. That is, the locking and releasing of the neutral clutch 68 causes power transmitted from the turbine runner 48 to the output side shaft 46 to be intermittently transmitted, through the driving pulley 4 and the driven pulley 6, to the following power transmission device, and thus a neutral condition is also possible. The normal and reverse rotation of the turbine runner 48 of the fluid coupling 50 is as shown in Figures 5 and 6. That is, releasing the braking mechanism 42 from the brake side casing 60 causes the stator wheel 44 to rotate freely, and the oil passing through vanes of the stator wheel 44 rotates the turbine runner 48 in the same direction as the pump impeller 40, that is, in the normal direction (refer to Figure 5). Otherwise, locking the braking mechanism 42 with the brake side casing 60 causes the rotation of the stator wheel 44 to be blocked, and the direction of kinetic energy transmitted from the pump impeller is reversed by the vanes of the stator wheel 44, and the oil flows into the vanes of the turbine runner 48, and thereby the turbine runner rotates in the direction reverse to the pump impeller 40 (Figure 6). Accordingly, since the shift of normal and reverse rotation of the output side shaft 46, or the shift of rotation of the belt 8, either of them is made through the turbine runner 48, locking and releasing the neutral clutch 68 can ensure the conditions of driving and neutral. Moreover, the coupling side housing 56 forms with the turbine runner 48 a body which is connected to the oil pump 70. Therefore the oil pump 70 will be directly operated by the internal combustion engine side shaft 52. The oil pump 70 connects with the hydraulic chambers 20 and 32 through oil passages (not shown). The fluid coupling 50 may be, for example, a three-element one-stage type of torque convertor. The oil pump 70, the reverse driving brake 42, a forward-reverse shift clutch 68, and the driving pulley 4 are in turn positioned in line from the engine side. Meanwhile, along the flow of hydraulic pressure circulation, the pump impeller 40, a stator wheel 44, turbine runner 48, and wet direct clutch 62 utilizing friction are in turn positioned, and the direct clutch 62 is built in the torque convertor. In the belt drive type of non-stage automatic transmission 2, the oil pump 70 operates according to the rotation of the engine side shaft 52, and the oil is sucked from the bottom of the transmission. The pump or line pressure is applied to the torque convertor and other components respectively, passing through a line pressure control valve (not shown). Moreover, when said stator wheel 44 is not fixed to the transmission case 60 by the brake 42, the direct clutch 62 is able to be engaged and the oil flows into the front of the turbine runner 48 passing through the stator wheel 44. Thus, as shown in Figure 5, the flow of oil is in the fluid coupling mode and is in the phase of normal direction (normal rotation). On the contrary, when said stator wheel 44 is fixed to the transmission case 60 by the brake 42 receiving line pressure, the direct clutch 62 is not engaged, then the oil redirects and flows reversely into the back side of the turbine runner 48, as shown in Figure 6, and the flow of oil is in the torque convertor mode and is in the phase of reverse direction (normal rotation). Moreover, in usual automatic transmissions, combinations of each shift point - P (parking), R (reverse), N (neutral), D start (drive starting), and D cruise (drive cruising), and said reverse driving brake 42 and forward-reverse shift clutch 68 are as follows: direct clutch (62) reverse driving brake (42) forward-reverse shift clutch (68) P X X X R X ○ ○ N X X X D start X X ○ D cruise ○ X ○ Thus, on the engine side shaft 52 of the automatic transmission, the three-element one-stage type of torque convertor having normal and reverse functions, said oil pump 70 producing a driving hydraulic pressure, the reverse driving brake 42, the forward-reverse shift clutch 68, and the driving side pulley 4 are positioned in line from the engine side, and the overall length of the non-stage automatic transmission can be smaller in size. Additionally, normal and reverse output, both driven from the engine side shaft 52, are constantly achieved through the turbine runner 48 of the torque convertor. A driving or neutral phase can be selected by locking up or releasing the forward-reverse shift clutch 68, and the usability of the non-stage automatic transmission becomes higher. Meanwhile, as shown in Figures 2 and 3, a retaining portion 60a supporting the bearing 64 is formed in the brake side casing 60. In a hollow cavity 72 formed between the retaining portion 60a and the covering portion 60b positioned in the axial direction of the output side shaft 46, a brake piston 76, a braking operator composing an operating mechanism 74 actuating the braking mechanism 42, is placed. The brake piston 76 is movable in the axial direction of the output side shaft 46 along the first sliding surface 60e of the retaining portion 60a and the second sliding surface 60f of the covering portion 60b which are parallel to the brake piston 76 by applying a hydraulic pressure through an oil passage 78 formed in the side portion 60c, and contacting with the end 80a of an operating ring 80 positioned outside of the neutral clutch 68. The brake piston 76 controls the operation of the braking mechanism 42 with the operating ring 80. That is, said operating mechanism 74 comprises the brake piston 76 and the operating ring 80. Otherwise, a stopper 81 causes the brake piston 76 to stop moving. The non-stage transmission 2 varies the contact radius of the belt 8 as engaged around the driving pulley 4 and the driven pulley 6, and thus changes the speed reduction ratio steplessly and controls speed. Meanwhile, a reduction drive gear 82 is fixed on the reduction driven shaft 24, and a reduction driven gear 86 fixed on a supporting shaft 84 engages with the reduction drive gear 82. A final drive gear 88 is fixed on the supporting shaft 84, and a final gear 92 of a differential unit 90 engages with the final drive gear 88. The differential unit 90 is connected to wheels (not shown). The internal combustion engine side shaft 52 rotates by the action of an internal combustion engine, and the rotation causes the drive plate 54 to rotate and the fluid coupling 50 to drive. In the fluid coupling 50, when the removal of the brake piston 76 allows the braking mechanism 42 to release from the brake side casing 60 with the operating ring 80, the direct clutch 62 is able to be engaged and the stator wheel 44 is in free-wheeling rotation, and the oil freely passes through the vanes of the stator wheel 44 and hits the vanes of the turbine runner 48. Thus, the turbine runner 48 rotates in the same direction as the pump impeller 40 rotates, or in the normal direction (Figure 5). Thus, the vehicle drives forward. Otherwise, when the braking mechanism 42 is locked to the brake side casing 60, since the direct clutch 62 is not engaged and is locked and the stator wheel 44 stops rotating, the direction of oil flow is reversed by the vanes of the stator wheel 44, and the oil flows into the back of the turbine runner 48. Thus, the turbine runner 48 rotates in the direction reverse to the rotation of the pump impeller 40 (Figure 6). Thus, the vehicle drives in reverse. At this time, the oil pump 70 operates with the rotation of the internal combustion engine side shaft 52, sucks the oil from an oil pan (not shown), and supplies oil to the fluid coupling 50 and other portions. Then, according to variations of the width of the driving side groove 22 of the driving side pulley 4 and the width of the driven side groove 34 of the driven side pulley 6, the non-stage transmission 2 changes the contact radius of the belt 8 and steplessly controls the speed reduction. Thus, power of an internal combustion engine is output from the internal combustion engine shaft 52, and the direction of rotation of the belt 8 is decided according to the direction of the turbine runner 48 of the fluid coupling 50. Then, the power is in turn transmitted through the driving side pulley 4, the belt 8, the driven side pulley 6, the reduction drive gear 82, the reduction driven gear 86, the final drive gear 88, and finally is branched with the differential unit 90 and is transmitted to each wheel. Meanwhile, in the embodiment, the space for placing the brake piston 76 is minimized by arranging the brake piston 76 in the hollow 72 of the brake side casing 60, and a saving of space is achieved. Accordingly, the overall length of the non-state transmission 2 can be minimized, and the compact non-stage transmission 2 can be composed. Thereby, the non-stage transmission 2 can be easily installed in the limited engine room. Referring to Figure 8, which is generally similar to Figure 2, another feature of the invention will be described. In some instances in Figures 8-14, parts which have previously been described are designated by the previously assigned references numerals. Fluid pressure is applied to the hydraulic chamber 20 formed within moving cylinder 122 fixed on a back side of the pulley member 16, and a stationary cylinder 124 on which the moving cylinder 122 slides. The cylinder 124 is fixed on shaft 12, and the fluid pressure causes the pulley member 16 to move in the axial direction of the shaft 12, whereby groove width 22 is changed. Moreover, fluid pressure is applied to a driven side hydraulic chamber 140 formed within a moving cylinder 136 fixed on a back side of the movable pulley member 28, and a stationary cylinder 138 on which the moving cylinder 136 slides. The cylinder 138 is fixed on said driven side shaft 24, and groove width 34 is changed by the fluid pressure in chamber 140. A driving-power transmitting mechanism 600 comprises transfer gearing 146 and a differential gear mechanism 148. The transfer gearing 146 comprises a transfer drive gear 82 fixed on the driven side shaft 24 of the driven side pulley 6, a transfer driven gear 154 fixed on a rotatable transfer gear shaft 152 engaged with the transfer drive gear 82, a final drive gear 88 fixed on the transfer shaft 152, and a final driven gear 92 engaged with the final drive gear 88. The differential gear mechanism 148 comprises a rotatable differential gear casing 160 having fixed thereon said final driven gear 92, and small differential gears 162 and large differential gear 164 placed in the differential gear casing 160. As shown in Figure 8, a transmission case 800 comprises a main case 166, a front case 168 fitted on the side of the main case close to the internal combustion engine (not shown), and a rear case 170 fitted on the side of the main case 166 opposite the internal combustion engine. One end of each of the driving side shaft 12, the driven side shaft 24, the transfer gear shaft 152, and the differential gear case 160 is respectively supported, enclosed, and installed in said main case 166 through bearings 64, 174, 176, and 178. Moreover, the other ends of said driving side shaft 12, said driven side shaft 24, the transfer gear shaft 152, and the differential gear case 160 are, through respective bearings 180, 182, 184, and 186, supported, enclosed, and installed in either said front case 168 or said rear case 170. An oil pump mechanism 192 includes the oil pump 70 placed in an oil pump housing 108 through a connecting member 106. The oil pump housing 108 is installed in the main case 166. A clutch-brake mechanism 94 includes the clutch 68 and the brake 42. Reference numeral 122 is a control valve mechanism and 124 is an oil pan enclosing the control valve mechanism 122. One end of each of the driving side shaft 12, driven side shaft 24, (rotation shafts of said belt type transmission mechanism), the transfer gear shaft 152, (a rotation shaft of the transfer gear 146), and the differential gear case 160, (a rotation shaft of the differential gear mechanism 148), which compose the driving-power transmitting mechanism 600 is, through the respective bearings 64, 174, 176, and 178, supported, enclosed, and installed by said main case 166. The other ends of the driving side shaft 12 and driven side shaft 24 are, through the respective bearings 180 and 182, supported, enclosed, and installed by said rear case 170, and the other ends of the transfer gear shaft 152 and differential gear case 160, or rotation shafts, are, through the respective bearings 184 and 186, supported, enclosed, and installed by said front case 168. Therefore, since components referred to in the prior art as a subcase, a front cover, and a rear cover can be eliminated, the number of components composing a transmission case 180 can be decreased to fewer than the existing case, including an oil pan 124. Thus, costs can be reduced. For convenience of illustration, the aforementioned parts of the transmission case 800 and the bearings housed therein are indicated in the diagrammatic view of Figure 1. In addition, removing either the front case 168 or the rear case 170 can make access to mechanisms easy. For example, as shown in Figure 10, removing the rear case 170 out of the main case 166 allows easy access to the belt type transmission mechanism. Meanwhile, in this case, it is assumed that the diameter D1 of the transfer drive gear 82 fixed on the driven side shaft 24 of the driven pulley 6 is smaller than the diameter D2 of the hole formed inside of the main case 166 for the bearing 174. Also, as shown in Figure 11, removing the front case 168 out of the main case 166 provides easy access to the transfer gearing 146 and differential gear mechanism 148 composing the driving-power transmitting mechanism. Meanwhile, in this case, before removing the front case 168, the internal combustion engine side shaft 52, the drive plate 54, and the fluid coupling mechanism 50 should be removed. Thus, since removing either the front case 168 or the rear case 170 enables simple access to mechanisms, maintenance can be easily performed. Besides, it is obvious that the fluid coupling mechanism 50 can be removed without touching the belt type transmission mechanism 4, and therefore maintenance can be easily accomplished. Moreover, as shown in Figure 12, access to the oil pump 70 can be simply achieved by removing the oil pump housing 108 of the oil pump mechanism 192 from the main case 166. Furthermore, as shown in Figure 13, removal of the oil pump mechanism 192 provides simple access to the clutch-brake mechanism 94. Also, the control valve mechanism 122, as shown in Figure 14, will be easily accessible by removing the oil pan 124. As described above, in the non-stage automatic transmission 2 simple access to mechanisms allows maintenance to be easily carried out, which is essential in practice.

Claims: A continuously variable transmission for a vehicle that varies groove width of adjustable input and output pulleys (14, 26 and 16, 28), each of said pulleys including an axially stationary pulley member (14, 26) and an axially movable pulley member (16, 28) supported so as to be capable of moving toward and away from the stationary pulley member, for changing the contact radius with a belt wound around said pulleys to vary the speed reduction ratio and thereby control speed, comprising: a casing, an oil pump (70) producing hydraulic pressure, a torque converter (50) having a pump impeller (40) connected with an output shaft (52) of an internal combustion engine, a stator wheel (44) lockable against rotation by a braking mechanism (42), and a turbine runner (48) fixed on an output side shaft (46) and drivingly connectable by a clutch (68) with said stationary input pulley member 14) to provide forward or reverse drive, said transmission being capable of rotating said turbine runner normally and reversely by releasing and locking the rotation of said stator wheel by means of said braking mechanism, a direct clutch (62) fitted in the torque converter to connect said engine output shaft (52) with said output side shaft, and a brake side casing (60) housing said clutch, said braking mechanism and a braking operator (76) which is arranged in a hollow cavity (72), which cavity is formed by a retaining portion (60a) of said brake side casing, and a bearing (64) being seated between said retaining portion and said stationary input pulley member (14). Transmission according to claim 1, wherein the torque converter (50), the oil pump (70), the brake mechanism (42) and the clutch (68) are positioned in this sequential order along the output side shaft (46) of the torque converter before the stationary input pulley member (14), the torque converter being closest to the engine output shaft (52). Transmission according to claim 1, wherein the pump impeller (40), the stator wheel (44), the turbine runner (48) and the direct clutch (62) are positioned in the casing in this sequential order relative to the direction of the hydraulic fluid cirulation in the casing as caused by rotation of the pump impeller (40).

Inventors: TANIGUCHI KATUHIKO, UCHIYAMA HISAO, TANIGUCHI, KATUHIKO, UCHIYAMA, HISAO
Applicants: SUZUKI MOTOR CO, SUZUKI MOTOR CORPORATION
Application year: 1989
Main classification: F16H47
IPC codes: F16H37, F16H47