JPH0726676B2 - Hydrostatic continuously variable transmission - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention comprises a pump cylinder having a large number of pump cylinder holes arranged in an annular arrangement, and a motor cylinder having a large number of motor cylinder holes arranged in an annular arrangement, which are coaxially and integrally coupled. A shaft that extends axially on both sides in the axial direction and is rotatably supported by the casing is coaxially coupled to the cylinder block. Inside the cylinder block and inside the cylinder block between the plurality of pump cylinder holes and the plurality of motor cylinder holes. A peripheral annular oil passage and an outer peripheral annular oil passage are concentrically formed, and a first distribution valve for alternately connecting the pump cylinder hole to the inner peripheral annular oil passage and the outer peripheral annular oil passage in the cylinder block between the both annular oil passages. Are slidably fitted with a large number of first valve holes that slidably engage with each other, and a second distribution valve that alternately connects the motor cylinder holes with the inner peripheral annular oil passage and the outer peripheral annular oil passage. About hydrostatic continuously variable transmission and a plurality of second valve hole to are disposed radially.

[0002]

2. Description of the Related Art Conventionally, such a continuously variable transmission is disclosed in, for example, Japanese Unexamined Patent Publication No. 1-93661.
Already known.

[0003]

By the way, in the continuously variable transmission disclosed in the above publication, the shaft is inserted and fixed in the through hole provided in the cylinder block, and the inner circumference is provided between the shaft and the cylinder block. An annular oil passage is formed. However, the hydraulic pressure in the inner peripheral annular oil passage is low at normal operating conditions, but becomes high during engine braking. In order to prevent leakage, it is necessary to interpose a seal member between the shaft and the cylinder block, which increases the number of parts.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a hydrostatic continuously variable transmission having a simplified seal structure for an inner peripheral annular oil passage.

[0005]

In order to achieve the above object, according to the invention as set forth in claim 1, a through hole is provided in the central portion of the cylinder block so as to extend between both ends in the axial direction thereof, and the through hole is inserted into the through hole. The shaft and the cylinder block are welded at least on both sides of the first and second valve holes over the entire circumference, and in the central hole provided coaxially with the shaft, the inner peripheral annular oil is provided between the central hole and the inner surface of the central hole. A cylinder forming a passage is mounted.

According to the second aspect of the invention, a small diameter hole for opening the first and second valve holes to the inner surface and large diameter holes on both sides of the small diameter hole are coaxial with each other in the center of the cylinder block. Shafts that are provided in the large diameter holes and that cooperate with the inner surface of the small diameter hole to form the central hole are inserted and joined, respectively, and between the cylindrical body mounted in the central hole and the inner surface of the small diameter hole. An inner peripheral annular oil passage is formed at.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a hydrostatic continuously variable transmission for a motorcycle will be described below with reference to the drawings.

1 to 5 show a first embodiment of the present invention. FIG. 1 is an enlarged cross-sectional plan view of a hydrostatic continuously variable transmission, and FIG. 2 is an enlarged view of a main portion of FIG. 3 is a sectional view taken along line 3-3 of FIG. 1, FIG. 4 is a sectional view taken along line 4-4 of FIG. 1, and FIG.
FIG. 5 is a sectional view taken along line -5.

First, in FIG. 1, in a hydrostatic continuously variable transmission, a constant displacement type swash plate type hydraulic pump P and a variable displacement type swash plate type hydraulic motor M are connected to a low pressure path during normal load operation. However, the inner peripheral annular oil passage 1 becomes a high-pressure passage during reverse load operation.
1 and a hydraulic closed circuit is formed via an outer peripheral annular oil passage 12 which becomes a high pressure passage during normal load operation, but becomes a low pressure passage during reverse load operation.

The swash plate hydraulic pump P includes an input cylinder shaft 14 having an input gear 13, a pump cylinder 16 rotatably supported by an inner peripheral wall of the input cylinder shaft 14 via a ball bearing 15. A plurality of pump plungers 18 ... Slidably fitted in a large number and odd number of pump cylinder holes 17 provided in the pump cylinder 16 in an annular arrangement so as to surround the rotation axis thereof, and each pump plunger 18 ... Pump swash plate 1 that engages and abuts the front surface on the outer end
9 and the thrust bearing 20 and the radial bearing 21 in order to keep the pump swash plate 19 inclined at a constant angle with respect to the axis of the pump cylinder 16 about a virtual trunnion axis O ₁ orthogonal to the axis of the pump cylinder 16. And a pump swash plate holder 22 which supports the swash plate 19 via the. Thus, the pump swash plate holder 22
Is formed integrally with the input cylinder shaft 14.

When the input cylinder shaft 14 is rotated, the pump swash plate 19 can reciprocate the pump plungers 18 to repeat the suction and discharge strokes.

The hydraulic motor M includes a motor cylinder 27 arranged coaxially with the pump cylinder 16 on the left side of FIG.
A plurality of motor plungers 29 that are slidably fitted in motor cylinder holes 28 that are provided in the motor cylinder 27 so as to surround the axis of rotation, and a front surface is attached to the outer ends of the motor plungers 29. In this case, the motor swash plate 30 to be brought into contact, the motor swash plate holder 33 that supports the motor swash plate 30 via the thrust bearing 31 and the radial bearing 32, and the back surface of the motor swash plate holder 33 are supported to support the casing 44. And a motor swash plate anchor 34 fixed to. The motor cylinder hole 28 ...
Are formed in the motor cylinder 27 in the same number as the pump cylinder holes 17 ... In the hydraulic pump P. The opposing contact surfaces of the motor swash plate holder 33 and the motor swash plate anchor 34 that abut each other have trunnion axis O ₂ parallel to the axis of the motor cylinder 27 and the virtual trunnion axis O _1.
It is formed in a spherical shape centered on the intersection point with. Moreover, the motor swash plate holder 33 is supported by the motor swash plate anchor 34 so as to be capable of relative rotation around the trunnion axis O ₂ .

Motor cylinder 2 of motor swash plate anchor 34
A cylindrical cylinder holder 35 is continuously provided at the end on the seventh side, and a ball bearing 36 is provided between the cylinder holder 35 and the outer periphery of the motor cylinder 27.

The motor swash plate 30 is perpendicular to the axis of the motor cylinder 27 by rotating the motor swash plate holder 33 around the trunnion axis O ₂ by the ball screw mechanism 38 connected to the pulse motor 37. Between the upright position and a maximum tilt position that tilts at a certain angle, and in that tilt state, the motor plungers 29 reciprocate as the motor cylinder 27 rotates and expand and contract strokes. Can be repeated.

In FIG. 2, the pump cylinder 16 and the motor cylinder 27 are integrally connected to each other to form a cylinder block B, and a shaft 41 is coaxially connected to the cylinder block B. That is, a through hole 23 extending axially between both ends of the cylinder block B is coaxially provided, and the outer surface of the shaft 41 inserted into the through hole 23 and the inner surface of the through hole 23 are entirely formed. Are welded together by brazing (hatched portion in FIG. 2).

Both ends of the shaft 41 project from the cylinder block B to both sides. Thus, one end of the shaft 41 penetrates the pump swash plate 19 and the pump swash plate holder 22, and an angular contact ball bearing 43 is provided between the shaft 41 and the pump swash plate holder 22, and a pump swash plate holder is also provided. A ball bearing 45 is provided between the housing 22 and the casing 44.

The other end of the shaft 41 is connected to the motor swash plate 30,
An output sprocket 46 is fixed to the shaft 41 so as to extend through the motor swash plate holder 33 and the motor swash plate anchor 34, and on the axially outer side of the motor swash plate anchor 34. An angular contact ball bearing 47 is interposed between the motor swash plate anchor 34 and the shaft 41.

A central hole 49 which forms a replenishment oil passage 48 is coaxially provided in the shaft 41, and an end of the central hole 49 on the sprocket 46 side is closed by a screw plug 50.

Pump cylinder hole 1 of pump cylinder 16
7 ... Group and motor cylinder hole 28 of motor cylinder 27 ...
Between the group, an inner peripheral annular oil passage 11 is formed on the inner peripheral side of the cylinder block B, and an outer peripheral annular oil passage 12 concentrically surrounding the inner peripheral annular oil passage 11 is formed on the outer peripheral side of the cylinder block B. It is formed.

The inner peripheral annular oil passage 11 has a central hole 49 of the shaft 41.
It is formed between the cylindrical body 51 and the inner surface of the central hole 49 which are mounted by press fitting or the like. The outer peripheral annular oil passage 12 has an annular recess 52a provided on the outer periphery of the cylinder block B at a portion near the pump cylinder holes 17 ... Group between the pump cylinder holes 17 ... Group and the motor cylinder holes 28 ... Group,
Pump cylinder hole 17 ... Group and motor cylinder hole 28
The motor cylinder hole 28 between the groups is provided on the outer periphery of the cylinder block B in a portion near the group corresponding to the motor cylinder hole 28, and the annular recess 52a is provided.
Is formed by covering a large number of individual recesses 52b ... Commonly connected to each other with a ring body 53 that is brazed to the outer periphery of the cylinder block B in common.

Referring also to FIGS. 3 and 4, a cylinder block B, a shaft 41 and a ring are provided between the pump cylinder hole 17 group of the pump cylinder 16 and the motor cylinder hole 28 group of the motor cylinder 27. The first and second valve holes 57 ... 58 are provided in the same number as the pump cylinder holes 17 so as to radially penetrate the body 53.
Moreover, the first valve holes 57 are arranged on the pump cylinder hole 17 group side, and the second valve holes 58 are arranged on the motor cylinder hole 28 group side.

The first valve hole 57 ... Has a spool type first
The distribution valves 61 ... And the spool type second distribution valves 62 ... Are slidably fitted in the second valve holes 56, respectively. A first eccentric ring 63 that surrounds the first distribution valves 61 ... Is provided on the outer ends of the first distribution valves 61 ... And a second eccentric ring that surrounds the first distribution valves 62 ... Ring 6
4 are engaged via ball bearings 65 and 66, respectively. Moreover, the outer ends of the first distribution valves 61 ... Are connected to each other by the first compulsory wheel 67 that is concentric with the first eccentric wheel 63, and the outer ends of the second distribution valves 62 ... Are connected to the second eccentric wheel 64. They are connected to each other by a second forced wheel 68 having a concentric relationship.

The first eccentric wheel 63 is provided integrally with the input cylinder shaft 14.
Virtual trunnion as shown in FIG.
Axis O₁Along a predetermined distance from the center of the cylinder block B
Separation ε ₁Only eccentrically placed. Also, the second eccentric wheel 64
It is connected to the cylinder holder 35 and is shown in FIG.
So trunnion axis O₂Cylinder block along
Predetermined distance ε from the center of B₂Are eccentrically arranged.

The operation of the first distribution valve 61 will now be described. When relative rotation occurs between the input cylinder shaft 14 and the pump cylinder 16, that is, the cylinder block B, each first distribution valve 61 will be described.
The distribution valve 61 is reciprocated by the first eccentric wheel 63 between the radially inner position and the outer position of the pump cylinder 16 with a stroke of a distance twice the eccentric amount ε ₁ in the first valve hole 57. Then, as shown in FIG. 3, the hydraulic pump P
In the discharge region D of 1, the first distribution valve 61 moves toward the inner position side to communicate the corresponding pump cylinder hole 17 with the outer peripheral annular oil passage 12 and make the inner peripheral annular oil passage 11 incommunicable. The hydraulic oil is pumped from the pump cylinder hole 17 to the outer peripheral annular oil passage 12 by the pump plunger 18 during the discharge stroke. Further, in the suction region S of the hydraulic pump P, the first distribution valve 61 moves to the outer position side to communicate the corresponding pump cylinder hole 17 with the inner peripheral annular oil passage 11 and not communicate with the outer peripheral annular oil passage 12. As a result, the working oil is sucked into the pump cylinder hole 17 from the inner peripheral annular oil passage 11 by the pump plunger 18 during the suction stroke.

The operation of the second distributing valve 62 will be described. The motor cylinder 27, that is, the cylinder block B.
When each of the second distribution valves 62 is rotated, the second eccentric ring 64 causes the second eccentric ring 64 to move between the radially inner position and the outer position of the cylinder block B with a stroke that is twice the eccentric amount ε ₂ in the second valve hole 58. Is reciprocated. Thus, as shown in FIG. 4, in the expansion region Ex of the hydraulic motor M, the second distribution valve 6
2 moves on the inner side, connects the corresponding motor cylinder hole 28 to the outer peripheral annular oil passage 12, and makes the motor cylinder hole 28 and the inner peripheral annular oil passage 11 incommunicable;
As a result, high-pressure hydraulic oil is supplied from the outer peripheral annular oil passage 12 to the motor cylinder hole 28 of the motor plunger 29 during the expansion stroke. Further, in the contraction region Sh of the hydraulic motor M, the second distribution valve 62 moves to the outer position side so that the corresponding motor cylinder hole 28 communicates with the inner peripheral annular oil passage 11, and the motor cylinder hole 28 and the outer peripheral annular ring are connected. The oil passages 12 are cut off from each other, so that the motor plunger 2 during the contraction stroke
The hydraulic oil is discharged from the motor cylinder hole 28 of 9 to the inner peripheral annular oil passage 12.

Thus, in the cylinder block B, the reaction torque that the pump cylinder 16 receives from the pump swash plate 19 via the pump plunger 18 in the discharge stroke, and the motor swash plate 30 via the motor plunger 29 in the expansion stroke of the motor cylinder 27. It is rotated by the sum of the reaction torque received from the output sprocket 46 of the shaft 41.
Is output from.

In this case, the gear ratio of the shaft 41 to the input cylinder shaft 14 is given by {gear ratio = 1 + (capacity of hydraulic motor M / capacity of hydraulic pump P)}. Therefore, if the capacity of the hydraulic motor M is changed from zero to a certain value, the gear ratio can be changed from 1 to a certain required value. Moreover, since the capacity of the hydraulic motor M is determined by the stroke of the motor plunger 29, the gear ratio is continuously controlled from 1 to a certain value by tilting the motor swash plate 30 from the upright position to a certain tilt position. can do.

Referring also to FIG. 5, in the outer peripheral portion of the cylinder block B, the first valve holes 57, 57, which are adjacent to each other, at positions at equal intervals of 120 degrees in the circumferential direction.
Between 57 and between the second valve holes 58, 58, the clutch valves 69 are arranged so as to be reciprocable in a direction parallel to the axis of the cylinder block B and across the annular recess 52a of the outer peripheral annular oil passage 12. To be done. That is, on the outer peripheral portion of the cylinder block B, three sliding holes 70 ... Into which the clutch valve 69 which is basically formed in a rod shape is slidably fitted are arranged in parallel with the axis of the cylinder block B. The holes are formed at equal intervals in the circumferential direction. Further, the cylinder block B has three communication passages, each of which has an inner end opened to the inner circumferential annular oil passage 11 and an outer end closed by the ring body 53 and extends in the radial direction and traverses each of the sliding holes 70. Hole 7
1 and three concave portions 72 formed by boring the annular concave portion 52a in the outer peripheral annular oil passage 12 into a semicircular shape.

One end of each clutch valve 69 is connected to the inner circumference of an operation wheel 73 surrounding the motor cylinder 27 in the cylinder block B. The motor swash plate anchor 334 supports an operation shaft 74 that is movable along the axial direction of the cylinder block B.
4 has an operating wheel 73 at one end through a ball bearing 75.
Are connected. Further, the other end of the operation shaft 74 is connected with a rotating shaft 76 having an axis line orthogonal to the axis line of the cylinder block B and rotating according to the operation of a clutch lever (not shown).

Such a clutch valve 69 ... A clutch-on position for disconnecting between the communication hole 71 ... And the outer peripheral annular oil passage 12 communicating with the inner peripheral annular oil passage 11 by operating the clutch lever, and the clutch on-position. 5 to the right in FIG. 5, the clutch-off position for communicating between the communication holes 71 ... And the outer peripheral annular oil passage 12, and the clutch-off position further forward to communicate with the communication holes 71.
The communication holes 71 ... And the communication / release position for opening the outer peripheral annular oil passage 12 to the outside can be switched and moved.

Referring again to FIG. 1, an oil filter 77 is provided at the other end of the central hole 49 whose one end is closed by the screw plug 50.
Is fitted in and fixed to the oil filter 77.
The hydraulic oil pumped by the replenishment pump 79 from 8 is supplied,
The supply pump 77 is driven by a gear 80 provided on the input cylinder shaft 14.

By press-fitting the cylindrical body 51 into the central hole 49, the inner peripheral annular oil passage 11 and the annular connecting oil passage 87 are formed between the cylindrical body 51 and the inner surface of the central hole 49. A communication passage 88 that communicates the annular recess 52a in the outer peripheral annular oil passage 12 with the annular communication oil passage 87 is formed in the cylinder block B and the shaft 41. In addition, in the cylindrical body 51,
A communication hole 89 for avoiding dividing the replenishment oil passage 48 by the cylindrical body 51 is provided at an eccentric position in the axial direction between both ends.

In the cylindrical body 51, there is provided a first check valve 91 for preventing backflow of hydraulic oil from the inner peripheral annular oil passage 11 to the supplementary oil passage 48, and the outer peripheral annular oil passage 12 or the annular connecting oil passage 87.
Second check valve 92 for preventing the backflow of hydraulic oil from the replenishment oil passage 48, and the outer peripheral annular oil passage 12, that is, the annular connecting oil passage 87 and the inner peripheral annular passage to prevent an excessive increase in the hydraulic pressure of the outer peripheral annular oil passage 12. A pressure regulating valve 93 provided between the oil passages 11 is provided.

Next, the operation of the first embodiment will be described. The shaft 41 and the cylinder block B, which are inserted into the through holes 23 of the cylinder block B, are brazed over their entire surfaces, and the inside of the center hole 49 of the shaft 41. Since the cylindrical body 51 forming the inner peripheral annular oil passage 11 and the annular communication oil passage 87 is press-fitted into the inner surface of the center hole 49, the seal of the inner peripheral annular oil passage 11 which has a high pressure during engine braking. No member is needed.

In the first embodiment, the outer surface of the shaft 41 and the entire inner surface of the through hole 23 are brazed.
The shaft 41 is press-fitted into the through hole 23 and the cylinder block B and the shaft 41 are inserted at both ends of the through hole 23.
And may be welded over the entire circumference.

FIG. 7 shows a third embodiment of the present invention, and the portions corresponding to the respective embodiments described above are designated by the same reference numerals.

At the center of the cylinder block B ', there is a first
And a small diameter hole 2 for opening the second valve holes 57, 58 on the inner surface.
4 and the large diameter holes 25 and 26 on both sides of the small diameter hole 24 are provided coaxially. Thus, the cylindrical shaft 42a is inserted into one large diameter hole 25 and joined by brazing over the entire circumference, and the cylindrical shaft 42b is inserted into the other large diameter hole 26. At the same time, the entire circumference is joined by brazing (hatched portion in FIG. 7) or the like. Moreover, both shafts 42
The inner surfaces of a and 42b are flush with the inner surface of the small diameter hole 24, and a central hole 49 is coaxially formed in the central portions of both the shafts 42a and 42b and the cylinder block B '. Thus, the cylindrical body 51 is press-fitted into the center hole 49.
And the inner surface of the small diameter hole 24, the inner peripheral annular oil passage 11 is formed.

According to the third embodiment, not only the sealing structure of the inner peripheral annular oil passage 11 can be simplified as in the first embodiment, but also the first and second valve holes are formed in the shafts 42a and 42b. 57 and 58 are not perforated,
Further, it is possible to improve the processing accuracy of the intermediate portions of the second valve holes 57 and 58, and to make the operation of the first and second distribution valves 61 and 62 smooth.

Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above embodiments, and various small design changes can be made without departing from the present invention described in the claims. It is possible to

[0040]

As described above, according to the first aspect of the invention, the cylinder block is provided with a through hole extending in the axial direction between both ends thereof, and the shaft inserted into the through hole and the cylinder block. A cylindrical body, which is welded at least on both sides of the first and second valve holes over the entire circumference thereof and is coaxial with the shaft, is provided with a cylindrical body forming an inner circumferential oil passage between the central hole and the inner surface of the central hole. Therefore, the seal structure of the inner peripheral annular oil passage can be simplified.

According to the second aspect of the invention, a small diameter hole for opening the first and second valve holes to the inner surface and large diameter holes on both sides of the small diameter hole are coaxial with each other at the center of the cylinder block. Shafts that are provided in the large diameter holes and that cooperate with the inner surface of the small diameter hole to form the central hole are inserted and joined, respectively, and between the cylindrical body mounted in the central hole and the inner surface of the small diameter hole. Since the inner peripheral annular oil passage is formed, the working accuracy of the intermediate portion of the first and second valve holes is improved, and the seal structure of the inner peripheral annular oil passage can be simplified.

[Brief description of drawings]

FIG. 1 is an enlarged transverse plan view of a hydrostatic continuously variable transmission according to a first embodiment.

FIG. 2 is an enlarged view of a main part of FIG.

3 is a sectional view taken along line 3-3 of FIG.

4 is a sectional view taken along line 4-4 of FIG.

5 is a sectional view taken along line 5-5 of FIG.

FIG. 6 is a sectional view corresponding to FIG. 2 of the second embodiment.

FIG. 7 is a sectional view corresponding to FIG. 2 of the third embodiment.

[Explanation of symbols]

 11 ··· Inner peripheral annular oil passage 12 ·· Outer peripheral annular oil passage 16 ··· Pump cylinder 17 ··· Pump cylinder hole 23 ··· Holes 24 ・ ・ Small diameter holes 25, 26 ・ ・ ・ ・ Large diameter holes 27 ・ ・ ・ ・ Motor cylinder 28 ・ ・ ・ ・ Motor cylinder holes 41, 42a, 42b・ ・ Shaft 44 ・ ・ ・ ・ ・ ・ Casing 49 ・ ・ ・ ・ ・ ・ Center hole 51 ・ ・ ・ ・ ・ ・ Cylinder 57 ・ ・ First valve hole 58 ・ ・ ・ ・ ・ ・ Second valve Hole 61 ... First distribution valve 62. Second distribution valve B, B '... Cylinder block

Claims (2)

[Claims] 1. A pump cylinder (16) having a large number of pump cylinder holes (17) arranged in an annular arrangement, and a motor cylinder (27) having a large number of motor cylinder holes (28) arranged in an annular arrangement on the same axis. A shaft (41) which extends axially on both sides of the cylinder block (B) and is rotatably supported by a casing (44) is coaxially connected to the cylinder block (B) integrally connected to the cylinder block (B). Further, an inner peripheral annular oil passage (11) and an outer peripheral annular oil passage (12) are concentrically formed on the outer periphery of the cylinder block (B) between the plurality of motor cylinder holes (28), and both annular oil passages ( A first distribution valve (61) for alternately connecting the pump cylinder hole (17) to the inner peripheral annular oil passage (11) and the outer peripheral annular oil passage (12) in the cylinder block (B) between (11, 12). Sliding itself Many first valve holes (5
7) and a second distribution valve (62) for alternately communicating the motor cylinder hole (28) with the inner peripheral annular oil passage (11) and the outer peripheral annular oil passage (12) are slidably fitted to each other. In the hydrostatic continuously variable transmission in which the second valve holes (58) are radially arranged, a through hole (23) is provided in the center of the cylinder block (B) so as to extend between both ends in the axial direction. The shaft (41) inserted through the hole (23) and the cylinder block (B) have at least the first and second valve holes (57, 57).
58) welded around both sides on both sides of the shaft (4)
A cylindrical body (51) forming an inner peripheral annular oil passage (11) with the inner surface of the center hole (49) is mounted in the center hole (49) provided coaxially with 1). A hydrostatic continuously variable transmission. 2. A pump cylinder (16) having a large number of pump cylinder holes (17) arranged in an annular arrangement, and a motor cylinder (27) having a large number of motor cylinder holes (28) arranged in an annular arrangement on the same axis. A shaft (41) which extends axially on both sides of the cylinder block (B ') and is rotatably supported by the casing (44) is coaxially connected to the cylinder block (B') integrally formed, and the plurality of pump cylinder holes (17) are provided. )
And the inner peripheral annular oil passage (1) on the outer periphery of the cylinder block (B ') between the plurality of motor cylinder holes (28).
1) and the outer peripheral annular oil passage (12) are formed concentrically, and the cylinder block (B ') is provided between both annular oil passages (11, 12).
The first distribution valve (61) for alternately communicating the pump cylinder hole (17) with the inner peripheral annular oil passage (11) and the outer peripheral annular oil passage (12) is slidably fitted into a plurality of first distribution valves (61). The first valve hole (57) and the second distribution valve (62) for alternately communicating the motor cylinder hole (28) with the inner peripheral annular oil passage (11) and the outer peripheral annular oil passage (12) are slidably fitted. In a hydrostatic continuously variable transmission in which a large number of second valve holes (58) to be combined are radially arranged, the first and second valve holes (57, 57, The small diameter hole (24) for opening the inner surface of the small diameter hole (58) and the large diameter holes (25, 26) on both sides of the small diameter hole (24) are coaxially provided. The shafts (42a, 42b) forming the central hole (49) in cooperation with the inner surface of the small diameter hole (24) are inserted and joined, respectively. The inner peripheral annular oil passage (11) is formed between the cylindrical body (51) mounted in the central hole (49) and the inner surface of the small diameter hole (24). Gearbox.