JPH10129282A - Hydrostatic transmission - Google Patents

Abstract

(57) Abstract: A charge pump provided in an HST is configured as a hydraulic power source for a switching valve that controls a hydraulic actuator provided outside the HST, and piping between the charge pump and the switching valve is not required. SOLUTION: A hydraulic motor M is fluidly connected to a hydraulic pump P driven by a power input shaft via a closed circuit, and is driven by the power input shaft 3 to a housing for accommodating the hydraulic pump and the hydraulic motor. An HST provided with a charge pump 34 for replenishing oil in the housing to a closed circuit, and switching valves 36 and 37 for controlling a hydraulic actuator provided outside the HST.
In the case 6 that houses the charge pump,
The switching valve is configured to introduce a part of the oil discharged from the charge pump through an oil passage formed in the case, supply the oil to the hydraulic actuator, and return the return oil from the hydraulic actuator to the housing. did.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technology in which a hydraulic source of a hydraulic actuator provided outside an HST is constituted by a charge pump provided in the HST.

[0002]

2. Description of the Related Art Conventionally, in an HST in which a hydraulic pump and a hydraulic motor are fluidly connected by a closed circuit, the hydraulic pump is driven by a power input shaft, pressure oil of the hydraulic pump is supplied to the hydraulic motor, and the speed is changed. The rotation is output from the output shaft. Since the closed circuit with fluid connection causes oil leakage during the HST operation, a charge pump driven by a power input shaft is attached to a housing containing a hydraulic pump and a hydraulic motor to supply oil to the closed circuit. Was.

[0003]

The hydraulic oil from the prior art charge pump is mainly used to replenish the closed circuit, but a part of the hydraulic oil may be supplied to an external hydraulic actuator. Is being done. In this case, a discharge port to which a piping for external extraction is connected to the discharge port of the charge pump is configured, a switching valve is connected to this extraction port via a pipe, and a hydraulic actuator is connected to an output port of the switching valve. They were connected to control the hydraulic actuator. Therefore, oil is supplied from a charge pump, which is a hydraulic pressure source, to a switching valve provided outside the housing via a pipe, so that the piping is complicated and a space for installing the switching valve is required.

[0004]

Means for Solving the Problems In order to solve the above problems, the present invention is configured as follows. That is, a hydraulic motor is fluidly connected to a hydraulic pump driven by a power input shaft via a closed circuit, and a charge pump driven by the power input shaft is attached to a housing that accommodates the hydraulic pump and the hydraulic motor. A hydrostatic transmission (hereinafter referred to as HST) configured to replenish oil in a housing to a closed circuit, wherein a switching valve for controlling a hydraulic actuator provided outside the HST is built in a case containing the charge pump. A part of the oil discharged from the charge pump is introduced into the switching valve through an oil passage in the case to supply the oil to the hydraulic actuator, and further, the return oil from the hydraulic actuator is returned to the housing. It was configured as follows. In addition, while the oil discharged from the charge pump is introduced into the hydraulic oil replenishment circuit of the HST via a pressure reducing valve, the switching valve is constituted by a pair of solenoid valves capable of switching an operation direction of a hydraulic actuator, One of the solenoid valves is configured to function as a resistance valve for the pressure reducing valve when not energized.

[0005]

Next, examples will be described. 1 is a cross-sectional view of the HST to which the present invention is applied, FIG. 2 is a cross-sectional view taken along the line AA of FIG. 1, FIG. 3 is a cross-sectional view taken along the line BB of FIG.
5 is a sectional view taken along the line CC, FIG. 5 is a hydraulic circuit diagram of the HST, FIG.
Is a sectional view showing another embodiment of the HST to which the present invention is applied;
7 is a sectional view taken along the line DD of FIG. 6, FIG. 8 is a sectional view taken along the line EE of FIG. 6, and FIG. 9 is a hydraulic circuit diagram of the embodiment of FIG.

In FIGS. 1 and 2, the HST has a housing composed of a main case 1, a swash plate receiving lid 2 and a center section 5, in which a hydraulic pump P and a hydraulic motor M are housed. The hydraulic pump P has a pump shaft 3 serving also as an input shaft between the swash plate receiving lid 2 and the center section 5.
Is rotatably suspended via a bearing, and one end of the pump shaft 3 penetrates through the swash plate receiving lid 2 and protrudes out of the housing, and a pulley or a sprocket is fixedly provided so that power can be input. . The other end of the pump shaft 3 is the center section 5
, And inserted into a charge pump case 6 described later provided on the outer surface of the center section 5 to drive the charge pump 34. Note that the swash plate receiving lid 2 may be integral with the main case 1.

[0007] A pump mounting surface 20 is formed on the inner surface of the center section 5 penetrating the pump shaft 3, and the cylinder block 16 abuts on the pump mounting surface 20 so as to be freely slidable. The cylinder block 16 is provided with a plurality of cylinder holes, and pistons 12, 12,... Are reciprocally fitted into the cylinder holes via urging springs. A thrust bearing 10a of a movable swash plate 10 is abutted on the head of the swash plate 10. An opening 10b is provided in the center of the movable swash plate 10 to
Is pierced. The pump shaft 3 is a cylinder block 1
6 are spline-fitted on the rotation axis 6 so that they cannot rotate relative to each other. Thus, the variable displacement hydraulic pump P is configured.

The thrust bearing 1 of the movable swash plate 10
0a is formed in a convex arc portion, and the swash plate receiving cover 2 is formed.
A concave arc portion is formed on the inner surface of the swash plate according to the shape of the arc portion, and the movable swash plate 10 is configured to slide along the concave arc portion. The movable swash plate 10, as shown in FIG.
The control arm 23 is fixed to an operation shaft 22 having a rotation axis perpendicular to the pump shaft 3, and the other end of the operation shaft 22 projects from the swash plate receiving lid 2 and
The movable swash plate 10 is tilted by rotating the speed change arm 24, so that the amount and direction of oil discharge from the hydraulic pump P is changed.

The configuration of the variable displacement hydraulic motor M is such that a motor shaft 4 also serving as an output shaft is rotatably mounted horizontally between a swash plate receiving cover 2 and a center section 5 through a bearing. The left end of 4 penetrates through the center section 5 and protrudes to the outside, and gears, sprockets and the like are fixedly provided to transmit power after continuously variable transmission to the outside. A motor mounting surface 21 is formed on the inner surface of the center section 5 penetrating the motor shaft 4, and the cylinder block 1 is mounted on the motor mounting surface 21.
Reference numeral 7 is rotatably slidably contacted. The cylinder block 17, the piston 13 fitted in the cylinder portion 17, the movable swash plate 11 with which the head of the piston 13 abuts, and the structure in which the movable swash plate 11 is tilted by the shifting arm 26 are the hydraulic pump P Has substantially the same configuration as that of the hydraulic motor M.
The motor capacity is larger than the pump capacity to obtain a hydraulic reduction ratio.

The hydraulic oil from the hydraulic pump P is supplied to the hydraulic motor M via a closed circuit described below in the center section 5.
Refueled. As shown in FIG. 2, the center section 5 is formed in a plate shape, and a pair of arcuate ports 20a and 20b are opened in the pump attaching surface 20 in the vertical direction. And a pair of bow-shaped ports 21a and 21b are also opened in the motor mounting surface 21 in the vertical direction.
Supply / discharge oil from the cylinder block 17 is introduced.

The arcuate ports 20a and 20b of the pump mounting surface 20 and the arcuate ports 21 of the motor mounting surface 41
a and 21b are connected to each other.
5a and 5b are drilled in parallel from the upper end face downward in the left and right direction, and check valves 30 and 31 for replenishing hydraulic oil are arranged in the openings at the upper ends of the oil passages 5a and 5b, respectively. Each of the check valves 30 and 31 is provided with an open push rod 32.
Is protruded upward and outward of the center section 5 and can be opened by manually pushing the outer end thereof,
The pump shaft 3 and the motor shaft 4 can idle. A relief valve 33 for adjusting the discharge pressure of the charge pump 34 to a specified value is disposed between the check valves 30 and 31.

The hydraulic pump P of the center section 5
A charge pump case 6 is fixedly provided on the outer surface on the opposite side to the above. Inside the charge pump case 6, a charge pump 34, a pressure reducing valve 35, a solenoid valve 36 for raising, and An electromagnetic valve 37 and a load check valve 38 are integrally housed. That is, as shown in FIG. 1, the charge pump 34 includes, on the side surface of the center section 5, internal teeth 7 fixed to the left end of the pump shaft 3, and external teeth 8 meshing with the internal teeth on the outside thereof. . As shown in FIGS. 1, 3, and 5, the suction port 6a of the charge pump 34 is connected to the oil passage 6b forming the suction circuit 60, the filter 40 outside the suction port T1, and the housing via the oil tank 41. The lubricating oil in the housing is used as working oil by being communicated with an oil sump in the inside. In this embodiment, the communication hole 1a opened at the upper part of the main case 1 is connected to the oil tank 41. The oil tank 41
Serves as a reservoir tank.

The discharge port of the charge pump 34 communicates with an oil passage 6c in the charge pump case 6 and the oil passage 5c in the center section 5, and the oil passage 5c is connected to the oil passage 5c through a pump port P2. The relief valve 33 for setting the operating pressure of the external hydraulic actuator is connected. The oil passage 6 c is connected to the primary side of the pressure reducing valve 35 via oil passages 6 d and 6 e included in the high-pressure circuit 6, and to a solenoid valve for raising. 3 and 4, the secondary side of the pressure reducing valve 35 is connected to the check valve 30 via an oil passage 6f through a charge port P1 as shown in FIGS. -Communicates with 31. This charge port P
Reference numeral 1 denotes a long groove having a length extending over the inlet ports 30a and 31a of the left and right check valves 30 and 31 at the mating surface of the charge pump case 6 and the center section 5. The drain of the pressure reducing valve 35 is communicated with an oil reservoir in the housing via an oil passage 6g constituting the low pressure circuit 63 and a tank port T2.

The lifting solenoid valve 36 is a solenoid valve having a relief function for switching between two ports and two positions. When its solenoid is not excited, it is subjected to the action of hydraulic oil from a pilot circuit 65 branched from the high pressure circuit 61. It operates as a relief valve for the pressure reducing valve 35 by performing a relief operation. Also,
The secondary side communicates with the inside of the housing via the tank port T3 from the oil passage 6h constituting the low-pressure circuit 63. The lowering solenoid valve 37 and the oil supply / discharge port C1 are connected to the oil passage 6h constituting the supply / discharge circuit 64 on the secondary side of the load check valve 38, and the lowering solenoid valve 37 is a two-port two-position switching electromagnetic. The valve has a secondary side connected to the oil passages 6k and 6h constituting the low-pressure circuit 63 and configured to drain from the tank port T3 to the oil sump in the housing via the oil passage 5c. In this embodiment, the oil supply / discharge port C1 is connected to a hydraulic cylinder 39 as a hydraulic actuator.

In such a configuration, when the pump shaft 3 is driven by a power source such as an engine or an electric motor,
The hydraulic pump P is driven to send pressure oil to the hydraulic motor M from the closed circuit, the angle of the movable swash plates 10 and 11 is changed to adjust the rotation direction and the number of rotations of the motor shaft 4, and The axle and the working machine can be driven, and the charge pump 34 is driven by the rotation of the pump shaft 3 so that even if the amount of circulating oil in the closed circuit decreases due to leakage or the like, the pressure relief valve 35 allows the charge relief. Pressure oil adjusted to pressure is supplied to replenishment circuit 6
2. Pressure oil is supplied to the closed circuit via the charge port P1 and the check valve 30 (or 31) on the low pressure side. And
When the raising solenoid valve 36 is operated to switch to the block position, the oil flowing through the high-pressure circuit 61 is loaded with the load check valve 3.
8 is opened and oil is supplied to the hydraulic cylinder 39 to extend the hydraulic cylinder 39. At this time, the lowering solenoid valve 37 is in the closed position, and the oil supply to the low-pressure circuit 63 is stopped by the check valve inside. When the hydraulic cylinder 39 is to be reduced, the raising solenoid valve 36 is not operated, the pressure oil is prevented from flowing toward the load check valve 38, and the lowering solenoid valve 37 is operated to switch to the open position. Then, the pressure oil in the hydraulic cylinder 39 cannot flow toward the load check valve 38, but flows from the lowering solenoid valve 37 to the low-pressure circuit 63, and the hydraulic cylinder 39 contracts.

Another embodiment of the valve structure provided in the charge pump case integrated with the HST will be described with reference to FIGS. 6, 7, 8, and 9. FIG. HST hydraulic pump P,
The hydraulic motor M, the center section 5 and the charge pump 34 have the same configuration as described above,
Detailed description is omitted. In this embodiment, a manually operated switching valve 45, a relief valve 46 for setting the HST charge pressure, a slow return check valve 47, and a filter 49 are provided.
Is housed in the charge pump case 6 ', and connects the oil passage 6c connected to the discharge port of the charge pump 34 to the pump port P2 and the primary side of the switching valve 45, and the drain side of the switching valve 45 is charged. Relief valve 46, and
Check valve 3 of HST via charge port P1
0.31 are connected. The slow return check valve 47, the filter 49, and the oil supply / discharge port C1 are connected to the secondary side of the switching valve 45 via a check valve 45b that is mechanically opened by contact when the spool 45a is switched to the lower side. It is connected. The switching valve 45 is of a three-port, three-position switching type, and its spool 45a is biased to a neutral position by a spring.
5c is provided so that the check valve 45b comes into contact with the valve body and is pushed up to open it. The slow return check valve 47 includes a check valve 47a and a throttle 47b.

In such a configuration, when the switching valve 45 is in the neutral position, the oil discharged from the charge pump 34
And the charge relief valve 33 at the same time
, The replenishment oil pressure is adjusted to a specified value. When the switching valve 45 is switched to the extension side, the discharge oil opens the check valve 45 b and the check valve 47 of the slow return check valve 47.
a, The oil is supplied to the oil supply / discharge port C1 via the filter 49 to extend the hydraulic cylinder 39. This operating oil pressure is adjusted by the relief valve 33. When the switching valve 45 is switched to the reduction side, the cam portion 45c of the spool 45a pushes up and opens the valve body of the check valve 45b, and the pressure oil in the hydraulic cylinder 39 is filtered by the filter 49 and the throttle 47.
b, the hydraulic cylinder 39 is returned into the housing via the switching valve 45 and the relief valve 46, and the hydraulic cylinder 39 is reduced. In this embodiment, when the hydraulic cylinder 39 is extended, oil is not replenished to the closed circuit, but can be constantly replenished by using the pressure reducing valve shown in the first embodiment.

[0018]

As described above, the present invention has the following advantages. That is, the switching valve for controlling the hydraulic actuator disposed outside the HST is built in the case that houses the charge pump,
It is not necessary to provide a dedicated hydraulic unit for a hydraulic actuator provided in a work vehicle on which the HST is mounted, and cost can be reduced. In addition, since the oil passage between the switching valve and the housing can be formed in the casing, the housing and the charge pump case can be made compact, which contributes to cost reduction.

[Brief description of the drawings]

FIG. 1 is a sectional view of an HST to which the present invention is applied.

FIG. 2 is a sectional view taken along the line AA of FIG.

FIG. 3 is a sectional view taken along the line BB of FIG. 1;

FIG. 4 is a sectional view taken along the line CC of FIG. 1;

FIG. 5 is a hydraulic circuit diagram of the HST.

FIG. 6 is a sectional view showing another embodiment of the HST to which the present invention is applied.

FIG. 7 is a sectional view taken along the line DD in FIG. 6;

8 is a sectional view taken along the line EE in FIG. 6;

FIG. 9 is a hydraulic circuit diagram of the embodiment of FIG.

[Explanation of symbols]

 C1 Oil supply / discharge port P Hydraulic pump M Hydraulic motor 3 Power input shaft 6 Charge pump case 34 Charge pump 35 Pressure reducing valve 36 Raising solenoid valve 37 Lowering solenoid valve 39 Hydraulic actuator

Claims (3)

[Claims] 1. A charge pump driven by a power input shaft in a housing for housing the hydraulic pump and the hydraulic motor while fluidly connecting a hydraulic motor to a hydraulic pump driven by the power input shaft via a closed circuit. A hydrostatic transmission (hereinafter, HST) configured to replenish oil in a housing to a closed circuit, wherein a switching valve for controlling a hydraulic actuator disposed outside the HST is provided for housing the charge pump. A hydrostatic transmission, wherein a part of oil discharged from a charge pump is introduced into the switching valve through an oil passage formed in the case to supply oil to a hydraulic actuator. 2. The hydrostatic transmission according to claim 1, wherein a return oil from the hydraulic actuator is recirculated into the housing. 3. The hydraulic pump according to claim 1, wherein the oil discharged from the charge pump is introduced into a hydraulic oil replenishment circuit of an HST via a pressure reducing valve, and the switching valve is constituted by a pair of solenoid valves capable of switching the operating direction of a hydraulic actuator. 2. The hydrostatic transmission according to claim 1, wherein one of the solenoid valves is configured to function as a resistance valve for the pressure reducing valve when the solenoid valve is not excited.