JPH03163253A - Hydrostatic continuously variable transmission - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] A. Object of the Invention (1) Industrial Field of Application The present invention provides a cylinder block in which a bomb cylinder of a hydraulic bomb and a motor cylinder of a hydraulic motor are integrated on the same axis, and a large number of cylinders of the bomb cylinders are arranged in an annular manner. An annular inner oil passage surrounding the axis of the cylinder block and an annular outer oil passage surrounding it are formed in the cylinder block between the hole and a large number of annularly arranged cylinder holes of the motor cylinder. One side of the passage is connected to the discharge side cylinder hole of the pump cylinder, and the other side is connected to the same suction side cylinder hole, and the cylinder block is further reciprocated in the radial direction to connect each cylinder hole of the motor cylinder to the inside oil passage. and a hydrostatic continuously variable transmission in which distribution valves are arranged radially and communicated alternately with the outer oil passages, and an eccentric wheel is engaged with these distribution valves to cause the distribution valves to reciprocate as the cylinder block rotates. Regarding. (2) Conventional continuously variable transmissions are already known, as disclosed in, for example, Japanese Unexamined Patent Publication No. 62-20959. (3) Problems to be Solved by the Invention In the continuously variable transmission disclosed in the above publication, in order to freely switch between the hydraulic pump and the hydraulic motor between the power transmission state and the power cut-off state, both the inner and outer A large number of clutch valves that open and close between oil passages by radial movement are arranged radially in parallel with the distribution valve in the axial direction, and these clutch valves are opened and closed by eccentric wheels dedicated to each clutch valve.

However, in these systems, the distribution valve and the clutch valve are arranged in the axial direction, so the cylinder block,
As a result, the transmission inevitably becomes larger in the axial direction, and furthermore, since it requires an eccentric wheel exclusively for actuating the clutch valve, there is a problem that the structure becomes complicated.

The present invention has been made in view of the above-mentioned circumstances, and provides a clutch valve function to a distribution valve, thereby allowing power transmission state and power cutoff state to be established without increasing the size of the cylinder block or complicating the structure. It is an object of the present invention to provide a continuously variable transmission capable of switching between the two clutches and easily achieving a half-clutch state during the switching.

B. Structure of the Invention (1) Means for Solving the Problems In order to achieve the above object, the present invention provides an eccentric wheel at a clutch-on position where the eccentric wheel imparts normal reciprocating motion to the distribution valve;
The distribution valve is movable so as to be movable between a clutch-off position and a clutch-off position where the two oil passages are reciprocated to a short-circuit position. The present invention is characterized in that a constriction portion is provided to gradually reduce the area of the short-circuit flow path between the two oil passages.

(2) Function In the above configuration, if the eccentric wheel is placed in the clutch-on position, the high-pressure hydraulic oil discharged from the hydraulic bomb will flow through the distribution valve and one of the oil passages to the cylinder hole of the hydraulic motor's expansion stroke. The low-pressure hydraulic oil that is supplied and discharged from the cylinder hole during the contraction stroke of the hydraulic motor is sucked into the hydraulic pump via the distribution valve and the other oil passage. In this way, the hydraulic fluid is repeatedly exchanged between the hydraulic pump and the hydraulic motor, and power is transmitted from the hydraulic pump to the hydraulic motor.

If the eccentric wheel is shifted to the clutch-off position from this state, the distribution valve short-circuits both oil passages, and the hydraulic pressure transmission from the hydraulic pump to the hydraulic pressure, that is, the power transmission, is cut off. Furthermore, if the eccentric wheel is moved from the clutch-off position to the clutch-on position, communication between both oil passages is gradually narrowed by the throttle part of the distribution valve while moving from just before the clutch-on position to the clutch-on position. The shape of the bear is easily obtained,
Power transmission starts smoothly. (3) Example An example of the present invention will be described below with reference to the drawings.
First, in FIG. 1, a power unit U of a motorcycle consists of an engine E and a hydrostatic continuously variable transmission T, and the crankshaft l of the engine E and the transmission T are housed and supported in a common casing 4. Ru. The continuously variable transmission T is arranged with an input cylinder shaft 5 and an output shaft 3l parallel to the crankshaft 1, the crankshaft l drives the input cylinder shaft 5 via the primary reduction gear 2, and the output shaft 31 drives the input cylinder shaft 5 through the primary reduction gear 2. It is designed to drive a rear wheel (not shown) of a motorcycle via a secondary reduction gear 3. In FIG. 2, the continuously variable transmission @T consists of a constant displacement swash plate type hydraulic pump P and a variable displacement swash plate type hydraulic motor M. The hydraulic pump P is the output subrocket 2 of the primary reduction gear 2
an input cylindrical shaft 5 as an input member equipped with a pump cylinder 7, which is fitted to the inner circumferential wall of the input cylindrical shaft 5 through a twenty dollar bearing 6 so as to be relatively rotatable; A large number of pump plungers 9.9, which are respectively slidably engaged with a large number of odd numbered cylinder holes 8, 8, arranged in an annular arrangement surrounding the axis of rotation, and these pump plungers 9,9... A pump swash plate 10 whose front surface is in contact with the outer end of the pump swash plate 10, and a state in which this bomb swash plate 10 is tilted at a certain angle with respect to the axis of the pump cylinder 7 with the virtual trunnion axis 01 orthogonal to the axis of the bomb cylinder 7 as the center. The pump swash plate holder 12 supports the swash plate 10 through a thrust bearing 11 and a radial bearing 11' to hold the swash plate 10 in place. The pump swash plate holder 12 is connected to the manual cylinder shaft 5.

Thus, the pump swash plate 1O can give reciprocating motion to the pump plunger 9.9 when the human cylinder shaft 5 is rotated, thereby repeating the suction and discharge strokes. On the other hand, hydraulic motor M
The motor cylinder 17 is arranged coaxially with the pump cylinder 7 and to the left thereof, and the cylinder hole 8 is provided in the motor cylinder 17 so as to surround its rotation axis.
Among the many motor plungers 19, 19... which are respectively slid into the same number of cylinder holes 18, 18... as 8...
, a motor swash plate 20 whose front surface is brought into contact with the outer ends of these motor plungers 19, 19, and this motor swash plate 2.
0 to thrust bearing 21 and radial bearing 2
1', and a motor swash plate anchor 23 that supports the back surface of the motor swash plate holder 22.

Opposing surfaces f+ and fz of the motor swash plate holder 22 and the motor swash plate anchor 23 that come into contact with each other are formed into spherical surfaces centered on the intersection of the axis of the motor cylinder 17 and the trunnion axis 02. Further, the motor swash plate holder 22 is
A pair of semi-cylindrical trunnion shafts 22 arranged on the trunnion axis Ot perpendicular to the rotational axis of the motor cylinder 17
a, 22a are integrally provided at both ends, and these trunnion shafts 2
2a, 22a are rotatably fitted into a pair of semi-cylindrical recesses 23a, 23a formed at both ends of the motor swash plate anchor 23, respectively.

A cylindrical cylinder holder 24 is integrally connected to the right end of the motor swash plate anchor 23, and this cylinder holder 24 rotatably supports the outer peripheral surface of the motor cylinder 17 via a ball bearing 25. The motor swash plate 20 is mounted on the motor cylinder 1 by rotating the motor swash plate holder 22 around the trunnion axis O through a reduction gear train 78' and a ball screw mechanism 79 using a pulse motor 80 (see FIG. 1).
It is adapted to move between an upright position perpendicular to the axis of 7 and a maximum tilted position at an angle;
In this inclined state, as the motor cylinder 17 rotates, the motor plungers 19, 19, . The bomb cylinder 7 and the motor cylinder 17 are integrally connected to each other and form a cylinder block B, through which an output shaft 3l passes through the center of the cylinder block B. The cylinder block B is spline-coupled 32 to the output shaft 31 and fixed onto the output shaft 31 by an annular shoulder 34 on the outer periphery of the output shaft 31 and a stopper ring 33 split in half. The right end of the output shaft 31 also passes through the pump swash plate lO and the bomb swash plate holder l2, and the pump swash plate holder 1
A highly rigid flange 37 is integrally provided to support the back surface of the roller 2 via a thrust roller bearing 40. Further, the output shaft 31 rotatably supports the bomb swash plate holder 12 via a twenty dollar bearing 42. The left end of the output shaft 31 extends through the motor swash plate 2o, the motor slant temporary holder 22, and the motor swash plate anchor 23, and is connected to the outer periphery of this left end by a spline 43 and fixed with a split cotter 44. A retainer 46 and a thrust roller bearing 47 are sequentially interposed between the support cylinder 45 and the motor swash plate anchor 23 from the swash plate anchor 23 side. Further, the output shaft 31 is rotatably supported by the swash plate anchor 23 via a twenty dollar bearing 48 and the retainer 46. Input sprocket 3a of the secondary reduction gear 3
is attached to the output shaft 31 via the support tube 45. In this way, all the structural members of the transmission T from the input cylinder shaft 5 to the output shaft 31 are assembled as one assembly,
It is then assembled into casing 4. When the variable speed 1iT is assembled into the casing 4, the pump swash plate holder l2 is supported on the right side wall of the casing 4 via the ball bearing 41. Also, on the left side wall of casing 4,
An oil seal 56 is fitted in close contact with the outer peripheral surface of the support tube 45. In order to rotate the pump swash plate 10 synchronously with the pump cylinder 7, the bomb swash plate 10 is formed with a spherical recess 10a in which the spherical end 9a of the corresponding bomb plunger 9 engages.

Further, in order to rotate the motor swash plate 20 synchronously with the motor cylinder 17, the motor swash plate 20 is formed with a spherical recess 20a in which the spherical end 19a of the corresponding motor plunger l9 engages.

Each of the spherical recesses 10a, 20a is formed with a radius larger than the radius of the corresponding spherical end 9a, 19a, and the spherical recess 10a, 20a is formed at any position.
The state of engagement with 19a is ensured. 2 to 4, the cylinder block B has an output shaft 3l between the cylinder holes 8, 8,... group of the pump cylinder 7 and the cylinder holes 18, 18,... group of the motor cylinder 17. An annular inner oil passage 52 and an outer oil passage 53 arranged concentrically with the cylinder holes 8 and 8 radially penetrating the annular partition wall between the oil passages 52 and 53 and the outer circumferential wall of the outer oil passage 53; ... and the same number of first, second, and third valve holes 54...55..., 56... are provided. At that time, the first and second valve holes 54, 54...; 55
, 55... are arranged in the axial direction of the cylinder block B with the former placed on the cylinder hole 8.8... side, or the second and third valve holes 55, 55... 56, 56... are arranged alternately in the circumferential direction of cylinder block B. The cylinder block B further includes adjacent cylinder holes 8.
．． 8... and the first valve holes 54, 54... mutually communicate with each other, and the adjacent cylinder holes 1
8.18... and a large number of motor boats b, b... that communicate with each other the second valve holes 55, 55... are provided. The inner oil passage 52 is formed as an annular groove on the inner peripheral surface of the cylinder block B, and its open surface is closed by the outer peripheral surface of the output shaft 3l.

Subur type l-th distribution valves 60, 60, etc. are installed in the l-th valve holes 54, 54, and the second valve holes 55, 55, . . .
... also has a Subur type second distribution valve 61.61.
. . . Further, similarly spool-type clutch valves 63, 63 . . . are slidably engaged with the third valve holes 56, 56 . A first eccentric wheel 63 surrounding the first distribution valves 60, 60... is provided at the outer end of the first distribution valve 60, 60...
1.61... and clutch valves 62, 62... are engaged with second eccentric wheels 64 surrounding them via ball bearings 65, 66, respectively, to force their engagement. The outer ends of the l-th distribution valves 60, 60, . The outer ends of the valves 62, 62... are the second eccentric wheels 64.6.
4... are mutually connected by a second forced ring 68 in a concentric relationship.

The first eccentric wheel 63 is fixed to the input cylinder shaft 5, and is held at a position offset by a predetermined distance ε1 from the center of the output shaft 31 along the virtual trunnion axis OI, as shown in FIG. Therefore, when relative rotation occurs between the input cylinder shaft 5 and the bomb cylinder 7, each l-th distribution valve 60 moves a distance twice the eccentricity ε, in the first valve hole 54 by the first eccentric wheel 63. As a stroke, the pump cylinder 7 reciprocates between the radially inner and outer positions. As shown in FIG. 3, in the discharge area D of the hydraulic pump P, the first distribution valve 60 moves to the inner position side to communicate the corresponding pump boat a with the outer oil passage 53, and also connects the inner oil Road 52 was cut off.
Hydraulic oil is force-fed from the cylinder hole 8 to the outer oil passage 53 by the pump plunger 9 during the discharge stroke. Also, the suction area S
Then, the first distribution valve 60 moves to the outer position to communicate the corresponding pump bow }a with the inner oil passage 52 and disconnect it from the outer oil passage 53, and the pump plunger 9 during the suction stroke Hydraulic oil is sucked into the cylinder hole 8 from the oil passage 52. As shown in FIG. 4A, the second eccentric wheel 64 has a pivot shaft 70 parallel to the output shaft 3l on the cylinder holder 24.
The clutch is connected to be able to swing between a clutch-on position n and a clutch-off position f. and the second eccentric wheel 6
4 occupies a position eccentric by a predetermined distance ε2 from the center of the output shaft 31 along the trunnion axis 02 at the clutch-on position n, and by the eccentric amount ε.4 from the center of the output shaft 31 at the clutch-off position f. The second eccentric wheel 6 occupies an eccentric position with a distance ε greater than .
A notch 71 is provided on the outer peripheral surface of 4, and this notch 7
A stopper 72 that can come into contact with both inner end surfaces of the casing 4
It is formed integrally with the That is, this stopper 72 is connected to the notch 7.
1 by contacting one inner end surface of the second eccentric wheel 64.
The clutch-on position n of the second eccentric wheel 64 also comes into contact with the other inner end surface of the notch 71, whereby the clutch-off position f of the second eccentric wheel 64 is regulated. Referring again to FIGS. 2 and 4, a camshaft 74 disposed parallel to the output shaft 31 is inserted into a through hole 73 formed in an example part of the second eccentric wheel 64. A slipper plate 75 that engages with the second eccentric ring 64 is fixed to the second eccentric ring 64 so as to cover one side of the through hole 73 .

The corner portion of the slipper plate 75 is provided with a slope 75a that engages when the camshaft 74 rotates by a predetermined angle. As shown in FIG. 2, the camshaft 74 is supported by the casing 4 via a pair of right and left hair rings 77, 77', and when rotated by the operation of a clutch lever (not shown), pushes the slipper plate 75. The second eccentric wheel 64 can be swung to the clutch-off position Wr. Further, as shown in FIG. 4, a clutch spring 69 is connected to the second eccentric wheel 64 to bias it toward the clutch-on position IIn. Therefore, the camshaft 74 is connected to the slipper plate 75.
If the second eccentric wheel 64 is operated to move backward from the clutch position, the second eccentric wheel 64 can be swung to the clutch-on position n by the force of the clutch spring 69.

Here, the structures of the second distribution valve 61 and the clutch valve 62 will be explained in detail. First, as shown in FIGS. 5 to 8, the second distribution valve 61 has a first land 8l having a long axial length, a second land 82 having a short axial length, and both lands 81.82. The annular groove 83 of the l-th land 81 is provided with a sandwiched annular groove 83.
A plurality of notches 84 are provided on the third side edge. Further, the outer peripheral surface of the second land 82 has a plurality of grooves 85 extending in the axial direction.
... are formed at equal intervals in the circumferential direction. At that time, inside each groove 85. The outer end portions 85a and 85b are formed in a shape, for example, a semicircular shape, in which the cross-sectional area of the groove gradually decreases toward the tip.
The inner semicircular ends 85a are connected to the second land 8.
The outer semicircular ends 85b communicate with each other via the second circumferential groove 87 of the second land 82.

As clearly shown in FIG. 8, the first circumferential groove 86 has a V-shaped cross section, and the slope 86 on the inner end side of the second land 82
The slope a is formed to be a gentler slope than the slope 86b on the opposite side. The second circumferential groove 87 also has a V-shaped cross section, and the slope 87a on the outer end side of the second land 82 is different from the slope 87b on the opposite side.
It is formed on a gentler slope. This second distribution valve 61 is arranged with the first land 8l facing outward in the radial direction of the cylinder block B. Next, the clutch valve 62 is arranged between a first land 89 having a long axial length, a second land 90 having a short axial length, and both lands 89 and 90, as shown in FIG. It is provided with an annular groove 91 to be sandwiched.

A tapered portion 89a is provided at the edge of the first land 89 on the annular groove 91 side.
A plurality of notches 92 are formed in the second land 90 along its entire length. This clutch valve 62 is
The first land 89 is arranged with the first land 89 facing outward in the radial direction of the cylinder block B.

Thus, when the second eccentric wheel 64 occupies the clutch-on position fin (see FIG. 4), when the motor cylinder 17 rotates, the second distribution valve 61 and the clutch valve 62 are The second valve hole 55 and the third valve hole 56 are reciprocated between the inner and outer positions in the radial direction of the cylinder block B, with the stroke being twice the eccentricity ε2. In the expansion region Ex of the hydraulic motor M, the second
The distribution valve 61 moves to the inner position side, communicates the corresponding motor boat b with the outer oil passage 53 via the annular groove 83, and connects the motor boat b and the inner oil passage 52 with the second land 82. High-pressure hydraulic oil is supplied from the outer oil passage 53 to the cylinder hole 18 of the motor plunger 19 during the expansion stroke. Further, in the contraction region sh, the second distribution valve 6
1 moves to the outer position side to communicate the corresponding motor boat b with the inner oil passage 52, and also disconnects communication between the motor boat b and the outer oil passage 53 by the second land 82,
Hydraulic oil is discharged from the cylinder hole 18 of the motor plunger l9 to the inner oil passage 52 during the contraction stroke.

On the other hand, the clutch valve 62 has a second reciprocating stroke.
As long as the distance is less than or equal to twice the eccentricity ε2, the first land 8
9 crosses the outer oil passage 53, and both the inner and outer oil passages 52
, 53 have been cut off.

Thus, the cylinder block B is connected to the pump swash plate 10 via the pump plunger 9 in which the pump cylinder 7 is in the discharge stroke.
The motor cylinder I7 is rotated by the sum of the reaction torque received from the motor cylinder I7 and the reaction torque received from the motor swash plate 20 via the motor plunger 19 during the expansion stroke, and the rotational torque is transmitted from the output shaft 31 to the secondary reduction gear 3. Ru.

In this case, the gear ratio of the output shaft 3I to the manual cylinder shaft 5 is given by the following equation.

Capacity of Hydraulic Pump P Therefore, by changing the capacity of hydraulic motor M from zero to a certain value, the gear ratio can be changed from l to a certain required value. Furthermore, since the capacity of the hydraulic motor M is determined by the stroke of the motor plunger 19, by tilting the motor swash plate 20 from an upright position to a certain inclined position, the gear ratio can be changed steplessly from 1 to a certain value. It can be controlled. Next, when the second eccentric wheel 64 is shifted to the clutch-off position f (see FIG. 4A), as the motor cylinder 17 rotates, the second eccentric wheel 64 causes the second distribution valve 61 and the clutch valve 62 to become the second valve. In the hole 55 and the third valve hole 56, the cylinder block B is reciprocated between a radially inner position and an outer position with a stroke of twice the eccentricity ε3.

At the inner position of the second distribution valve 61 , the two oil passages 52 and 53 are short-circuited via the annular groove 83 and the groove 85 , and at the outer position of the second distribution valve 61 , the oil passages 52 and 53 are short-circuited via the annular groove 83 and the groove 85 . Therefore, both oil passages 52 and 53 are short-circuited. Further, at the outer position of the clutch valve 62, the two oil passages 52, 53 are short-circuited via the annular groove 91 and the notch 92.

Thus, high-pressure hydraulic oil is no longer supplied to the hydraulic motor M, and power transmission between the hydraulic pump P and the hydraulic motor M is cut off. In other words, a so-called clutch-off state is obtained. In this case, as described above, both the second distribution valve 61 and the clutch valve 62 are involved in the short circuit between the two oil passages 52 and 53, so the flow resistance of the short circuit system is extremely small, and as a result, the hydraulic bomb P A stable clutch-off state can be obtained by suppressing pressure pulsations caused by the operation of the clutch. Further, a large number of second distribution valves 61, 61... and clutch valves 62, 62... are arranged alternately in the circumferential direction of the cylinder block B, and are driven by a common second eccentric wheel 64. Therefore, by installing the clutch valves 62, 62, etc., it is possible to avoid not only the complication of the structure but also the increase in the axial length of the cylinder block B. Next, a case in which the second eccentric wheel 64 is returned from the clutch-off position f to the clutch-on position n will be described. In this case, when the eccentricity of the second eccentric wheel 64 approaches ε2, the second distribution valve 61 that has come to the radially inward position is located at the semicircular end of the groove 85 on the inner oil passage 52 side. 85b and the gentle slope 87a of the second circumferential groove 87, both oil passages 52, 53
The second distribution valve 61 which has narrowed the communication between the two and has come to the radially outward position is located at the semicircular end 85 of the concave groove 85 on the outer oil passage 53 side.
a and the gentle slope 86a of the first circumferential groove 86 restrict the communication between both oil passages 52,53, and the clutch valve 62, which has come to the radially outward position, is moved by the tapered portion 8 of the first land 89
9a restricts communication between both oil passages 52 and 53. Such a constricted state is caused by the semicircular end portion 85.
a. 85b, the gentle slopes 86a, 86b, and the tapered portion 89a, they are gradually strengthened as the second eccentric wheel 64 moves to the clutch-on position n, so that a good half-clutch state can be obtained during this time. As a result, power transmission between the hydraulic bomb P and the hydraulic motor M can be resumed smoothly.

Further, such a half-clutch state is also a region where the camshaft 74 engages with the corner slope 75a of the slipper F1.75, and therefore, the movement of the second eccentric wheel 64 is slowly controlled by the rotation of the camshaft 74. This makes it easier to achieve this half-clutch state. Referring again to FIG. 2, a central oil passage 95 is bored in the center of the output shaft 3l, and an oil filter 96 is installed on the inlet side of the central oil passage 95. This central oil passage 95 is supplied with hydraulic oil from an oil reservoir 100 by a replenishment pump 99 driven from the input cylinder shaft 5. An oil filter 101 is also installed immediately after the replenishment pump 99. A valve cylinder 102 with both ends open is fitted in the center of the central oil passage 95, and the valve cylinder 102 is fixed to the output shaft 31 by a communicating pipe 103 extending linearly through the valve cylinder 102. This communication pipe 103 has a through hole 10 that opens into the valve cylinder 102.
4, and both ends thereof are open to the inner oil passage 52 to communicate the inside of the valve cylinder 102 with the inner oil passage 52.

A chamfered portion 105 is formed on the outer circumferential surface of the valve cylinder 102 and communicates between both ends thereof. The valve cylinder 102 also includes an inner oil passage 5.
2 to the central oil passage 95.
Check valves 106 and 106 are arranged symmetrically across the communication pipe 103. Further, the output shaft 31 and the cylinder block B are provided with a series of replenishment oil passages 107 that connect the outer oil passage 53 and the center oil passage 95.
A second check valve 10B that prevents oil from flowing backward from the outer oil passage 53 to the central oil passage 95 is interposed therein. Furthermore, output shaft 3
1 has radial orifice holes 109 drilled at appropriate locations for supplying lubricating oil from the central oil passage 95 to each part of the gearshift jaT. During normal load operation in which the hydraulic motor M is hydraulically driven from the hydraulic pump P, the pressure in the inner oil passage 52 on the low pressure side increases to the pressure in the central oil passage 95 due to oil leakage from the hydraulic closed circuit between the two. When the pressure decreases below , the first check valve 106 opens and hydraulic oil is replenished from the central oil passage 95 to the inner oil passage 52. On the other hand, at this time, the hydraulic oil in the high-pressure side outer oil passage 53 is prevented from flowing into the central oil passage 95 by the second check valve 10B.

Furthermore, during reverse load operation, that is, during engine braking, the hydraulic motor M performs a pumping action, and the hydraulic pump P performs a motor action, thus changing the outer oil passage 53 to low pressure and the inner oil passage 52 to high pressure. Therefore, if the pressure in the outer oil passage 53 drops below the pressure in the central oil passage 95 due to oil leakage,
The second check valve l08 opens and the center oil passage 95 is opened to the outer oil passage 5.
Hydraulic oil is supplied to 3, and from the inner oil passage 52 to the center oil passage 95.
The first check valve 106 prevents the hydraulic oil from flowing out. Furthermore, since the oil in the central oil passage 95 is supplied to each part of the transmission T while its flow rate is restricted by the orifice hole 109,
Due to this supply, the pressure in the central oil passage 95 does not drop excessively, and therefore, there is no problem in supplying hydraulic oil from the central oil passage 95 to the inner oil passage 52 and the outer oil passage 53.

C. Effects of the Invention As described above, according to the present invention, the eccentric wheel can be placed in a clutch-on position where it causes the distribution valve to move in a normal reciprocating manner, and at a clutch-off position where it causes the distribution valve to reciprocate to the short-circuit position of both oil passages. The distribution valve is configured to be movable so as to be able to move between the oil passages, and the distribution valve includes a throttle portion that gradually reduces the short-circuit passage area between the two oil passages in accordance with the transition from the clutch-on position of the eccentric wheel to the clutch-off position. Because of this, it is possible to provide the distribution valve with the function of a clutch valve, thereby avoiding an increase in the axial length of the cylinder block and complication of the structure.
It is possible to provide a continuously variable transmission that is compact and has a simple structure.

[Brief explanation of the drawing]

Figure 1 is a plan view of a power unit for a motorcycle, Figure 2 is an enlarged sectional view taken along the line ■-■ in Figure I, and Figure 3 is an enlarged cross-sectional view taken along the line ■-■ in Figure 2.
■ Line sectional view, Figure 4 is a sectional view taken along the line IV-IV in Figure 2 shown in the clutch-on state, Figure 4A is a sectional view taken along the IV-IVA line in Figure 2 shown in the clutch-off state, Figure 5 is a side view of the second distribution valve, and Figures 6, 7, and 8 are V in Figure 5.
9 is a side view of the clutch valve, and FIG. 10 is an enlarged sectional view taken along the line X-X of FIG. 9. B...Cylinder block, M...Hydraulic motor, P.
...Hydraulic pump, T...Continuously variable transmission, a...Pump port, b...Motor boat, f...Clutch off position, n...Clutch on position 5...As input member input sleeve, 7...pump cylinder, 8...its cylinder hole, 9...pump plunger, 10...pump swash plate, 17...motor cylinder, 18...its cylinder hole, l9 ...Motor plunger, 20...Motor swash plate, 31...Output shaft,
61... Distribution valve, 64... Eccentric wheel, 81... First
Land, 82... Second land, 83... Annular groove, 8
5a, 85b... Semicircular end as a constriction part, 8'6
a, 87a... Gentle slope as a constriction part

Claims (1)

[Claims] The pump cylinder (7) of the hydraulic pump (P) and the motor cylinder (17) of the hydraulic motor (M) are coaxially integrated to constitute a cylinder block (B), and the pump cylinder (
7), and a large number of annularly arranged cylinder holes (18) of the motor cylinder (17), surrounding the axis of the cylinder block (B). An annular inner oil passage (52) and an annular outer oil passage (53) surrounding it are formed, and one of these oil passages (52, 53) is connected to the discharge side cylinder hole (8) of the pump cylinder (7). and the other side to the same suction side cylinder hole (
8), and further communicates with the cylinder block (B).
The motor cylinder (17) reciprocates in its radial direction.
Distribution valves (61) are arranged radially to alternately communicate each cylinder hole (18) with the inner oil passage (52) and the outer oil passage (53), and these distribution valves (61) are connected to the cylinder block ( B) In a hydrostatic continuously variable transmission that engages an eccentric (64) that gives reciprocating motion to the distribution valve (61) as the distribution valve (61) rotates, the eccentric (64) is normally connected to the distribution valve (61). movable so as to be movable between a clutch-on position (n) that provides a reciprocating motion of the distribution valve and a clutch-off position (f) that reciprocates the distribution valve to a short-circuit position of both oil passages (52, 53);
The distribution valve (61) has a short-circuit flow path area between the two oil passages (52, 53) according to the transition from the clutch-on position (n) of the eccentric wheel (64) to the clutch-off position (f). A hydrostatic continuously variable transmission characterized in that a throttle portion (85a, 85b, 86a, 87a) is provided to gradually reduce the amount.