STATIC HYDRAULIC PRESSURE TYPE CONTINUOUSLY VARIABLE TRANSMISSION

Abstract: A static hydraulic pressure type continuously variable transmission (T) formed with a hydraulic closed circuit between a swashplate type hydraulic pump (P) and a swashplate type hydraulic motor (M), the hydraulic motor (M) being constructed such that its motor cylinder (17) is integrally connected to an output shaft (25) which extends through a motor swashplate (20) and a swashplate holder (22) for supporting the back surface of the motor swashplate, a swashplate anchor (23) for supporting the back surface of the swashplate holder (22) being axially immovabiy con­ nected to the output shaft (25) through a thrust bearing (32), and that the swashplate anchor (23) is unrotatably connected to a casing (14) which rotatably supports the output shaft (25). The motor cylinder (17) and a pump cylinder (7) of the hydraulic pump (p) are provided coaxially with the hydraulic closed circuit interposed therebetween. The hydraulic closed circuit is provided with a distribution valve (44) for bringing low and high pressure oil passages (41, 40), which are in communication with cylinder bores (8) of the pump cylinder (7), into selective communication with cylinder bored (18) of the motor cylinder (17), and a clutch valve (80) for controlling communication between the low and high pressure oil passages (41, 40). Where the swashplate type hydraulic motor (M) is of a variable capacity type, means (60) is provided which adjusts an angle of inclination of the motor swashplate (20) to effect speed change control.

Description: This invention relates to a static hydraulic pressure type continuously variable transmission, and more particularly to such a transmission in which a hydraulic closed circuit is formed between a swashplate type hydraulic pump and a swashplate type hydraulic motor, as disclosed for example in Japanese Patent Application Laid-Open No. 70968/82 and Japanese Patent Publication No. 38467/84. In known transmissions of this type it is usually the case that thrust loads produced in operation by the pump and the motor are borne by a casing of the transmission, and consequently such casing has to be of a sufficiently thick and rigid construction to withstand such loads, which makes for an undesirably heavy and expensive structure. US-A-2844002 discloses in accordance with the preamble of claim 1 a static hydraulic pressure type continuously variable transmission comprising: a casing; a swashplate type hydraulic pump having a pump cylinder; a swashplate type hydraulic motor having a motor cylinder, the pump cylinder and the motor cylinder being integrally connected with each other on the same axis; a hydraulic closed circuit between said hydraulic pump and said hydraulic motor; and a transmission shaft rotatably supported on said casing. The present invention is characterised in that both said pump cylinder and said motor cylinder are supported on said transmission shaft, and an input member which directly drives the pump swashplate is mounted around said transmission shaft in relatively rotatable but axially immovable fashion, whereby thrust force generated from said hydraulic pump is received and supported by said transmission shaft. With such an arrangement, as thrust force generated from the hydraulic pump is received and supported by the transmission shaft, such thrust force is not applied to a casing of the transmission, which casing may therefore be of lighter construction than hitherto. In a preferred form of the invention a non-rotatable motor swashplate anchor is mounted axially immovably on said transmission shaft and tiltably supports the motor swashplate, whereby thrust force generated by said hydraulic motor is received and supported by said transmission shaft, thus making a further contribution to reducing the weight and rigidity of the transmission casing. Preferably the said transmission shaft is the power output shaft of the transmission. An embodiment of the invention will now be described by way of example and with reference to the accompanying drawings, in which:- FIG. 1 is a longitudinal plan view of a static hydraulic pressure type continously variable transmission incorporated in a power transmission system of a motor-cycle; FIGS. 2 and 3 are sectional views taken on line II-II and line III-III, respectively, of FIG. 1; and FIG. 4 is an exploded perspective view of major components of FIG. 1. Referring now to the drawings and more particularly to FIG. 1, power of a motor-cycle engine is transmitted from a crank shaft 1 to an unshown rear wheel via a chain type primary reduction gear 2, a static hydraulic pressure type continuously variable transmission T and a chain type secondary reduction gear 3. The continuously variable transmission T comprises a swashplate type hydraulic pump P of a constant capacity type and a swashplate type hydraulic motor M of a variable capacity type, which are accommodated within a crank case 4 as a casing which carries the crank shaft 1. The hydraulic pump P comprises a cup-like input member 5 integrally provided with an output sprocket 2a of the primary reduction gear 2, a pump cylinder 7 relatively rotatably fitted in the inner peripheral wall of the input member 5 through a needle bearing 6, pump plungers 9, 9 ... slidably fitted in a plurality and odd-number of annularly disposed cylinder bores 8, 8 provided in the pump cylinder 7 so as to surround the rotary center thereof, and a pump swashplate 10 in contact with the outer ends of the pump plungers 9, 9 ... The back surface of the pump swashplate 10 is rotatably supported on the inner end wall of the input member 5 in an attitude inclined by a predetermined angle with respect to the axis of the pump cylinder 7 through a thrust roller bearing 11 so that when the input member 5 is rotated, the pump plungers 9, 9 ... are reciprocated to repeatedly effect suction and exhaust strokes. The back surface of the input member 5 is supported on a support sleeve 13 through a thrust roller bearing 12. On the other hand, the hydraulic motor M comprises a motor cylinder 17 coaxially and closely coupled to the pump cylinder 7, a support shaft 24 and an output shaft 25 integrally formed to central parts of both inner and outer ends of the motor cylinder 17 and extending in an axial direction, motor plungers 19, 19 ... respectively slidably fitted in a plurality and odd-number of annularly disposed cylinder bores 18, 18 ... provided in the motor cylinder 17 so as to surround the rotary center thereof, a motor swashplate 20 in contact with outer ends of the motor plungers 19, 19 ..., a swashplate holder 22 for supporting the back surface of the motor swashplate 20 through a thrust roller bearing 21, and a swashplate anchor 23 for supporting the back surface of the swashplate holder 22. The motor swashplate 20 is tiltingly movable between an upright position at right angles to the axis of the motor cylinder 17 and a position inclined at a certain angle. In the inclined position, the motor plungers 19,19 ... are reciprocated upon rotation of the motor cylinder 17 to repeatedly effect expansion and contraction strokes. The aforesaid support shaft 24 extends through the central portion of the pump cylinder 7, with which a nut 26 is threadedly engaged whereby the pump cylinder 7 and the motor cylinder 17 are integrally connected to each other. The support shaft 24 further extends through the input member 5 and rotatably supports the input member 5 through a needle bearing 27. On the outer periphery of the support shaft 24, the support sleeve 13 is splined-fitted and secured by means of a nut 30. The support shaft 24 is rotatably supported on the crank case 4 through the support sleeve 13 and a roller bearing 31. The aforesaid output shaft 25 extends through the central portion of the motor swashplate 20, the swashplate holder 22 and the swashplate anchor 23, and a support sleeve 33 for supporting the back surface of the swashplate anchor 23 through a thrust roller bearing 32 is splined-fitted to the end of the shaft 25 and is secured by means of a nut 34 with an input sprocket 3a of the secondary reduction gear 3. The output shaft 25 is rotatably supported on the crank case 4 through the support sleeve 33 and a roller bearing 35. Secured to the support shaft 24 is a spherical spline member 36 in spline engagement with the inner peripheral surface of the pump swashplate 10 in a manner relatively tiltable in all directions, and secured to the output shaft 25 is a spherical spline member 37 in spline engagement with the inner peripheral surface of the motor swashplate 20 in a manner relatively tiltably in all directions. This suppresses to the minimal extent frictional contact between the group of pump plungers 9, 9 ... and the pump swashplate 10 and between the motor plungers 19, 19 ... and the motor swashplate 20. Between the hydraulic pump P and the hydraulic motor M is formed a hydraulic closed circuit as described hereinafter. In the motor cylinder 17, an annular high pressure oil passage 40 and an annular low pressure oil passage 41 to encircle the oil passage 40 are provided between the group of cylinder bores 8, 8 ... of the pump cylinder 7 and the group of cylinder bores 18, 18 ... of the motor cylinder 17, the high pressure oil passage 40 being communicated with the cylinder bores 8, 8 ... of the pump cylinder 7 through discharge valves 42, 42 ..., the low pressure oil passage 41 being likewise communicated with the cylinder bores 8, 8 ... through intake valves 43, 43 ... Accordingly, the discharge valves 42 and the intake valves 43 are respectively provided in the same number as that of the pump plungers 9, 9 ... These high and low pressure oil passages 40, 41 are both communicated with the cylinder bores 18, 18 ... of the motor cylinder 17 through respective distribution valves 44, 44 ... Accordingly, the distribution valves 44 are provided in the same number as that of the motor plungers 19, 19 ... The distribution valves 44, 44 ..., which are of a spool type, are slidably fitted into valve holes 45, 45 ... radially provided in the motor cylinder 17 between the group of cylinder bores 18, 18 ... and the high and low pressure oil passages 40, 41, whereby when the valve 44 occupies the radial inward position in the valve hole 45, there is provided a communication between the corresponding cylinder bore 18 and high pressure oil passage 40 whilst the cylinder bore 18 is shut off from the low pressure oil passage 41, and when the valve 44 occupies the radial outward position in the valve hole 45, there is provided a communication between the corresponding cylinder bore 18 and low pressure oil passage 41 whilst the bore is cut off its communication with the high pressure oil passage 40. Valve springs 46, 46 ... for biasing the distribution valves 44, 44 .. radially outwardly are accommodated within the valve holes 45, 45 ... to control the distribution valves 44, 44 ..., and the inner peripheral surface of an eccentric ring 47 is engaged with the outer end of each distribution valve 44. The eccentric ring 47 is formed of an inner race of a ball bearing 48 snapped in and secured to the crank case 4, and as shown in FIG. 2, the ring 47 is installed at such a position that the center thereof is to be eccentric a predetermined distance ε from the center of the motor cylinder 17 in a direction of the tilting axis 0 of the motor swashplate 20. Accordingly, when the motor cylinder rotates, each of the distribution valves 44 takes the stroke of 2ε which is twice the eccentric amount ε of the eccentric ring 47, within the valve hole 45 and reciprocates between the aforesaid outward position and inward position. The distribution valve 44 also has a function to bring a replenishing oil passage 49 into communication with the low pressure oil passage 41 when the valve assumes the inward position in the valve hole 45. The replenishing oil passage 49 is provided in the central portion of the support shaft 24 and connected to the discharge port of a replenishing pump 50. The pump 50 is driven by the crank shaft 1 to supply oil stored in an oil reservoir 51 at the bottom of the crank case 4 to the oil passage 49 under relatively low pressure. Referring to FIGS. 1, 3 and 4, an outer peripheral surface 20a of the motor swashplate 20 is formed into a spherical surface having its center at the tilting axis 0. A spherical recess 52 is formed in the front surface of the swashplate holder 22 so as to receive the motor swashplate 20 along with the thrust roller bearing 21. A back surface 22a of the swashplate holder 22 is formed in a circular surface about the tilting axis 0 of the motor swashplate 20, and a semi-cylindrical recess 53 is formed in the front surface of the swashplate anchor 23 so as to support the swashplate holder 22 rotatably about the tilting axis 0. This swashplate anchor 23 is connected to the crank case 4 through locating pins 54 so that the anchor may not be rotated about the output shaft 25. A pair of trunnion shafts 55, 55' aligned on the tilting axis 0 are integrally projected on both ends of the swashplate holder 22, the trunnion shafts 55, 55' being rotatably supported on the swashplate anchor 23 through needle bearings 56. In other words, the tilting axis 0 is defined by the trunnion shafts 55, 55'. An operating lever 57 is fixedly mounted on the outer end of one trunnion shaft 55. When the trunnion shaft 55 is rotated by the operating lever 57, the swashplate holder 22 integral therewith also rotates and the latter can be tilted even during the rotation of the motor swashplate 20. With the arrangement as described above, when the input member 5 of the hydraulic pump P is rotated from the primary reduction gear 2, suction and exhaust strokes are alternately imparted by the pump swashplate 10 to the pump plungers 9, 9 ... Then, each pump plunger 9, in suction stroke, intakes working fluid from the low pressure oil passage 41, and in exhaust stroke, feeds high pressure working fluid to the high pressure oil passage 40. The high pressure working fluid fed to the high pressure oil passage 40 is supplied to the cylinder bore 18 accommodating the motor plunger 19 in expansion stroke through the distribution valve 44 at the inward position whereas the working fluid within the cylinder bore 18 accommodating the motor plunger 19 in contraction stroke is discharged into the low pressure oil passage 41 through the distribution valve 44 at the outward position. During this operation, the pump cylinder 7 and motor cylinder 17 are rotated by the sum of reaction torque received by the pump cylinder 7 from the pump swashplate 10 through the pump plungers 9 in exhaust stroke and reaction torque received by the motor cylinder 17 from the motor swashplate 20 through the motor plunger 19 in expansion stroke, which rotary torque is transmitted from the output shaft 25 to the secondary reduction gear 3. In this case, the speed change ratio of the output shaft 25 with respect to the input member 5 is given by the following equation: Thus, if the capacity of the hydraulic motor M is changed from zero to a certain value, the speed change ratio can be changed from 1 to a required value. Incidentally, since the capacity of the hydraulic motor M is determined by the stroke of the motor plunger 19, the motor swashplate 20 can be tilted from an upright position to an inclined position to thereby steplessly control the ratio from 1 to a certain value. During the operation of the hydraulic pump P and hydraulic motor M as described above, the pump swashplate 10 and motor swashplate 20 receive the opposite thrust load from the group of pump plungers 9, 9 ... and the group of motor plungers 19, 19 ... respectively. The thrust load applied to the pump swashplate 10 is carried by the support shaft 24 through the thrust roller bearing 11, input member 5, thrust roller bearing 12, support sleeve 13 and nut 30, whereas the thrust load applied to the motor swashplate 20 is carried by the output shaft 25 through the thrust roller bearing 21, swashplate holder 22, swashplate anchor 23, thrust roller bearing 32, support sleeve 33, sprocket 3a and nut 34. Since the support shaft 24 and output shaft 25 are integrally connected together through the motor cylinder 17, the aforesaid thrust load merely gives rise to tensile stress caused in the motor cylinder 17 system and exerts no action on the crank case 4 which supports the support shaft 24 and the output shaft 25. If working fluid leaks from the hydraulic closed circuit between the hydraulic pump P and the hydraulic motor M during the aforementioned operation, when the distribution valve 44 assumes the inward position in the valve hole 45, working fluid in the leaked amount is replenished from the replenishing oil passage 49 to the low pressure oil passage 41 through that distribution valve 45. Turning again to FIG. 1, a speed change control device 60 is connected to the operating lever 57 of the trunnion shaft 55 for the tilting operation of the motor swashplate 20. The speed change control device 60 comprises a cylinder 61 secured to the swashplate anchor 23, and a pair of first and second pistons 62₁, 62₂ which are slidably fitted in the cylinder 61 and are opposed to each other so as to hold a tip end of the operating lever 57 therebetween in their rotary direction, the pistons 62₁, 62₂ being arranged so as to enable rotation of the operating lever 57 by their sliding movement. The first and second pistons 62₁, 62₂ define first and second oil chambers 63₁, 63₂ against respective opposed end walls of the cylinder 61, which chambers 63₁, 63₂ accommodate therein springs 64₁, 64₂ for urging the corresponding pistons 62₁, 62₂ toward the operating lever 57. The first and second oil chambers 63₁, 63₂ are communicated with each other through a hydraulic conduit 66 incorporating therein a speed change control valve 65, within which conduit is filled working fluid. The speed change control valve 65 comprises a fixed valve casing 67 and a rotary valve 69 rotatably fitted in a valve port 68 of the valve casing 67, the rotary valve 69 being operated for rotation between a hold position A, a speed reduction position B and a speed increasing postion C on both sides of the position A by means of a speed change lever 70 secured to the outer end of the rotary valve 69. The rotary valve 69 is provided with a communication port 72 incorporating a check valve 71. The valve casing 67 includes a first forked port 73₁ connected to the first oil chamber 63₁ and opening to one side of the valve port 68, and a second forked port 73₂ connected to the second oil chamber 63₂ and opening to the other side of the valve port 68. The communication port 72 is designed such that in the hold position A of the rotary valve 69, the communication port 72 does not communicate with either forked ports 73₁, 73₂; in the speed reduction position B, the port 72 communicates with both the forked ports 73₁, 73₂ to allow a flow of oil only in one direction from the former 73₁ to the latter 73₂; and in the speed increasing position C, the port 72 communicates with both forked ports 73₁, 73₂ so as to allow oil flow only in the direction from the latter 73₂ to the former 73₁. Since the number of the motor plungers 19, 19 ... is odd, the thrust load applied by the group of motor plungers 19, 19 ... to the motor swashplate 20 during the rotation of the motor cylinder 17 alternately varies in intensity between one side and the other with the tilting axis of the motor swashplate 20 as a border, and vibratory tilting torque acts on the motor swashplate 20. This vibratory tilting torque alternately acts as a pressing force on the first and second pistons 62₁, 62₂ through the operating lever 57. With this, when the speed change lever 70 is shifted to the reduction position B as shown, the flow of oil from the first oil chamber 63₁ to the second oil chamber 63₂ is permitted by the check valve 71 but the opposite flow is inhibited. Thus, only when the pressing force acts on the first piston 62₁ from the operating lever 57, the oil flows from the first oil chamber 63₁ to the second oil chamber 63₂, as a consequence of which both the pistons 62₁, 62₂ are moved toward the first oil chamber 63₁ to turn the operating lever 57 in the direction of increasing the inclination of the motor swashplate 20. On the contrary, when the lever 70 is shifted to the increasing position C, the flow of oil from the second oil chamber 63₂ to the first oil chamber 63₁ is permitted by the check valve 71 but the opposite flow is inhibited. Thus, only when the pressing force acts on the second piston 62₂ from the operating lever 57, the oil flows from the second oil chamber 63₂ to the first oil chamber 63₁, as a consequence of which both the pistons 62₁, 62₂ are moved toward the second oil chamber 63₂ to turn the operating lever 57 in the upright direction of the motor swashplate 20. When the speed change lever 70 is returned to the hold position A, communication between both the oil chambers 63₁, 63₂ is completely cut off and the flow of oil therebetween is inhibited. Therefore, both the pistons 62₁, 62₂ become disabled to move. The operating lever 57 is held at its position to lock the motor swashplate 20 at the upright position or inclined position. Between the high and low pressure oil passages 40, 41, there is provided one or more piston type clutch valves 80. This clutch valve 80 is slidably fitted in a radial valve port 81 which extends from the high pressure oil passage 40 to the low pressure oil passage 41 and opens to the outer peripheral surface of the motor cylinder 17 whereby when the valve occupies the radial inward position (clutch ON position) in the valve port 81, communication between the oil passages 40, 41 is interrupted whereas when occupying the radial outward position (clutch OFF position), both the oil passages 40, 41 are brought into communication with each other. In order that the clutch valve 80 is urged toward the clutch OFF position, the inner end thereof receives oil pressure of the high pressure oil passage 40. A common clutch control ring 82 is slidably provided around the outer periphery of the pump cylinder 7 and is engaged with the outer end of valve 8. The clutch control ring 82 includes a cylindrical inner peripheral surface 82a for defining the clutch ON position of the clutch valve 80 and a tapered surface 82b joined to one end of said inner peripheral surface to define the clutch OFF position of the clutch valve 80, and the ring is urged by means of a spring 83 toward the side wherein the clutch valve 80 is held in the clutch ON position. This spring 83 is compressed between the clutch control ring 82 and a retainer 84 engaged on the outer periphery of the pump cylinder 7. The clutch control ring 82 is connected to a not-shown clutch operating lever through a shift fork 85, an intermediate lever 86 and a clutch wire 87. The shift fork 85 engages an outer peripheral groove 88 of the clutch control ring 82, and an operating rod 89 secured to the base of the shift fork 85 extends through the crank case 4 and is operatively connected to the intermediate lever 86. With this, when the clutch control ring 82 is moved to the right as viewed in the figure against the force of the spring 83 through the shift fork 85 by pulling the clutch wire 87, the tapered surface 82b of the clutch control ring 82 assumes a position opposed to the clutch valve 80. Therefore the clutch valve 80 is moved by the pressure of the high pressure oil passage 40 to the outward position, namely, to the clutch OFF position. As the result, the high pressure oil passage 40 and low pressure oil passage 41 are short-circuited through the valve port 81, and so the pressure of the high pressure oil passage 40 lowers to disable the feed of pressure oil to the hydraulic motor M to make the hydraulic motor M inoperative. In this case, if a plurality of clutch valves 80 are arranged in the circumferential direction of the high and low pressure oil passages 40, 41, it is effective in terms of decreasing the short-circuiting resistance of both the oil passages 40, 41. When the clutch control ring 82 is moved to left to operate the clutch valve 80 toward the clutch ON position, the working fluid is circulated between the hydraulic pump P and the hydraulic motor M through the high and low pressure oil passages 40, 41 in a manner as previously mentioned, and the hydraulic motor M is returned to its operating condition. In an intermediate postion between the aforesaid rightward position and leftward postion of the clutch control ring 82, a communication opening between both the oil passages 40, 41 is moderately adjusted and the working fluid may be circulated according to the opening degree thereof to place the hydraulic motor M in a half-clutch state.

Claims: A static hydraulic pressure type continuously variable transmission (T) comprising: a casing (4); a swashplate type hydraulic pump (P) having a pump cylinder (7); a swashplate type hydraulic motor (M) having a motor cylinder (17), the pump cylinder (7) and the motor cylinder (17) being integrally connected with each other on the same axis; a hydraulic closed circuit between said hydraulic pump (P) and said hydraulic motor (M); and a transmission shaft (24,25) rotatably supported on said casing (4); characterised in that both said pump cylinder (7) and said motor cylinder (17) are supported on said transmission shaft (24,25), and an input member (5) which directly drives the pump swashplate (10) is mounted around said transmission shaft in relatively rotatable but axially immovable fashion, whereby thrust force generated from said hydraulic pump is received and supported by said transmission shaft (24,25). A transmission as claimed in claim 1, wherein said pump cylinder (7) and said motor cylinder (17) are integrally connected with each other to form a cylinder block. A transmission as claimed in claim 2, wherein said transmission shaft (24,25) projects from opposite sides of said cylinder block. A transmission as claimed in claim 2 or 3, wherein said transmission shaft (24,25) is integrally connected to said cylinder block. A transmission as claimed in any of claims 2 to 4, wherein said hydraulic closed circuit is integrally formed with said cylinder block between said pump cylinder (7) and said motor cylinder (17). A transmission as claimed in any preceding claim, including a non-rotatable motor swashplate anchor (23) mounted axially immovably on said transmission shaft (24,25) and tiltably supporting the motor swashplate (20), whereby thrust force generated by said hydraulic motor (M) is received and supported by said transmission shaft. A transmission as claimed in any preceding claim, wherein said transmission shaft (24,25) is the power output shaft (25). A transmission as claimed in any preceding claim, wherein said transmission shaft (24,25) is of rod-like form. A transmission as claimed in any preceding claim, wherein said hydraulic closed circuit comprises a high pressure oil passage (40) and a low pressure oil passage (41) and wherein a number of pump cylinder bores (8) are arranged in said pump cylinder (7) and a number of motor cylinder bores (18) are arranged in said motor cylinder (17), said pump cylinder bores and said motor cylinder bores being placed in communication with said high pressure oil passage and said low pressure oil passage via a distribution device (44 etc). A transmission as claimed in claim 9, wherein said high pressure oil passage (40) and said low pressure oil passage (41) are arranged annularly within said cylinder block and are disposed concentrically with respect to each other. A transmission as claimed in claim 9 or 10, wherein said distribution device (44 etc) is rotatable together with said pump cylinder (7) and said motor cylinder (17).

Inventors: HASHIMOTO, EIICHI, HAYASHI, TSUTOMU
Applicants: HONDA GIKEN KOGYO KABUSHIKI KAISHA
Application year: 1985
Main classification: F16H39
IPC codes: F16H61, F16H39