JP2986268B2 - Hydraulic transmission bypass operation mechanism - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic transmission for driving a hydraulic motor with hydraulic oil discharged from a hydraulic pump, and mechanically connecting an oil passage connecting the hydraulic pump and the hydraulic motor by an external operation. The present invention relates to a bypass operation mechanism of a hydraulic transmission for opening and obtaining free rotation of a hydraulic motor.

[0002]

2. Description of the Related Art Conventionally, when a vehicle equipped with a hydraulic transmission is towed, a check valve for supplying charge pressure to an oil passage connecting a hydraulic pump and a hydraulic motor is mechanically operated by an external operation. When the hydraulic motor is released to obtain free rotation, there is a problem in that a running disabled state occurs due to forgetting to cancel the bypass operation.
In order to prevent the occurrence of a traveling impossible state due to forgetting to release the vehicle, a technology for automatically releasing the vehicle by interlocking and linking with a depressing operation of a traveling shift pedal or a brake pedal has been filed. However, in the case of the related art, the link system is complicated, and there are problems such as inoperability and high cost due to winding of foreign matter.

[0003]

SUMMARY OF THE INVENTION According to the present invention, in order to prevent the occurrence of an inoperable state caused by forgetting to release the bypass circuit in the prior art, when the engine is started, the charge oil of the charge pump is charged into the cylinder chamber. And the check pin is closed by automatically ejecting the push pin.

[0004]

The problems to be solved by the present invention are as described above. Next, means for solving the problems will be described. That is, the check valve 10 for supplying charge oil to the oil passage connecting the hydraulic pump P and the hydraulic motor M
Is configured such that the push pin 11 is advanced and mechanically opened by an external operation, and a cylinder chamber 36 for moving the piston 1 in a direction in which the push pin 11 retreats is provided. Is a part of the charge oil discharged from the nozzle.

[0005]

Next, the operation will be described. When the engine is started, the charge pump CP rotates, and the charge pressure is discharged. Even if the check valve is pushed to the open position by the push pin due to an operator's operation error, a part of the charge oil is released from the cylinder chamber. 36 is a gap oil passage 37
, And the piston 1 integrally formed with the push pin 11 is moved in the retreating direction, so that the check valve 10 is automatically closed to shift to a running state.

[0006]

Next, an embodiment will be described. FIG. 1 is a plan view of the axle drive unit having the hydraulic transmission according to the present invention, with the upper case 6a removed, and FIG. 2 is a cross-sectional view taken along the line AA of FIG. 1 with the upper case 6a assembled. 3 is a plan view of the center section 4, the piston 1, and the valve case 3; FIG. 4 is a check valve 10 and a charge relief valve 8;
5 is a plan sectional view of the center section 4 at the check valve 10, FIG. 6 is an enlarged rear sectional view of the check valve 10 and the piston 1, and FIG. 7 is a hydraulic transmission of the present invention. FIG. 4 is a hydraulic circuit diagram of a bypass operation mechanism of the device.

Referring to FIGS. 1 and 2, the overall configuration of an axle drive having a hydraulic transmission according to the present invention will be described. The transmission case 6 is configured by joining an upper case 6a and a lower case 6b with a horizontal joint surface. An axle 38a is attached to the joint surface between the upper case 6a and the lower case 6b.
-The 38b bearing part is clamped. In addition, the motor shaft 55 of the hydraulic motor M and the counter shaft 42 have their bearings sandwiched between the horizontal joint surfaces of the upper and lower half cases.
Further, a fixed swash plate support 41 for supporting the fixed swash plate 40 of the hydraulic motor M is also sandwiched and supported by the horizontal joint surface between the upper case 6a and the lower case 6b. The upper surface of the center section 4 is fixed to the lower surface of the upper case 6a at the horizontal joint surface between the upper case 6a and the lower case 6b. As shown in FIG. 5, the center section 4 is formed in a substantially L-shaped rear surface. ing.

The shaft protruding above the upper case 6a includes a pump shaft 5, a speed change operation shaft 33, and a neutral position adjustment shaft 34.
It is. As shown in FIG.
The cylinder block 28 of the hydraulic pump P is rotatably mounted on the upper surface of the hydraulic pump P. A pump piston 27 is loosely fitted in a plurality of cylinder holes of the cylinder block 28. The pump piston 27 discharges pressure oil by moving back and forth along the movable swash plate 26. The movable swash plate 26 is supported by a movable swash plate support 25. Rotating the movable swash plate support 25 for shifting is performed by a shift lever 29, a shift operation shaft 33, a shift arm 31, and a shift lever 3.
0. A neutral position urging spring 32 is fitted around a speed change operation shaft 33 so that the neutral position urging spring 32 returns to the neutral position when the shift lever 29 is not operated.
The speed change arm 31 is held between them. The neutral position adjusting shaft 34 determines the neutral position when the neutral position urging spring 32 returns to its original position. The neutral position adjusting shaft 34 can be adjusted from outside the transmission case 6.

The hydraulic oil discharged from the hydraulic pump P is applied to a semi-lunar oil passage 20 opened on the upper surface of the center section 4.
a. 20b, drilling oil passage 1 in center section 4
4a and 14b, and the hydraulic motor M from the oil passages 21a and 21b opened to the side of the center section 4.
Flows into the cylinder block 35. A plurality of cylinder holes are opened in the cylinder block 35, and a plurality of motor pistons 39 are loosely fitted therein, and advance and retreat along the fixed swash plate 40 by the pressurized oil. Rotate 55. The fixed swash plate 40 is supported by a fixed swash plate support 41 and is sandwiched between horizontal joint surfaces of the upper case 6a and the lower case 6b.

A brake cam ball 49 is fitted on the surface of the fixed swash plate support 41 on the side opposite to the hydraulic motor M, and the brake actuator 49 moves forward and backward to press and brake the brake disk 48. The motor shaft 55
The large-diameter gear 43 of the counter shaft 42 meshes with the engraving gear 44, and the engraving gear 45 of the counter shaft 42 meshes with the ring gear 46. A differential gear mechanism 47 is formed inside the ring gear 46.
Drives the left and right axles 38L and 38R. FIG. 1 shows an iron powder-attached magnet 51 fixedly fastened to the center section 4.

Next, referring to FIGS. 3 and 4, a description will be given of a bypass operation mechanism of the hydraulic transmission according to the present invention which opens and closes a bypass circuit. A bypass operation lever shaft 22 protrudes from the upper case 6a, and a bypass operation lever 24 is fixed to a projecting portion of the bypass operation lever shaft 22. An eccentric cam 23 is fixed to a portion where the bypass operation lever shaft 22 protrudes into the transmission case 6 so as to be eccentric with respect to the axis of the bypass operation lever shaft 22. Is configured to be pressed. The distal end of the branch press body 2 is bifurcated to form branch press parts 2a and 2b.
The branch pressing portions 2a and 2b press the pistons 1a and 1b. The pistons 1a and 1b are fitted and slide in a cylinder chamber 36 formed in the valve cases 3a and 3b. And push pins 11a
11b is provided integrally with the push pin 11a.
11b and the gap oil passage 37 between the valve cases 3a and 3b.
a.37b. After passing through the gap oil passage 37, the pressure oil of the charge pump CP is released from the cylinder chambers 36a.3.
6b, the pistons 1a and 1b that have been forgotten to be returned are returned to the original closed positions of the push pins 11a and 11b.

The valve cases 3a and 3b
And the valve seat of the check valve 10. The valve cases 3a and 3b are fitted and disposed inside the oil passages 14a and 14b formed in the cylinder from the side opposite to the hydraulic motor M. Check valve 10 is a return biasing spring 13a / 1 supported by spring receivers 12a / 12b.
It is urged in the return direction by 3b. The charge oil passage 16 is provided between the valve seat of the check valve 10 and the gap oil passage 37.
a and 16b are open. The charge oil passage 16a
Reference numeral 16b communicates with the oil passage 56 of the charge relief valve 8 via the charge oil passage 15.

In FIG. 4, the charge relief valve 8
The configuration of the assembling hydraulic oil supply port 9 and the charge pump CP will be described. The charge pump CP is constituted by a trochoid gear pump. A trochoid gear and a pump chamber are formed at a portion where the lower end of the pump shaft 5 projects into the charge pump case 7, and the gear and the lower end of the pump shaft 5 are fixedly provided. Rotate. The discharge oil from the charge pump CP is discharged to the oil passage 57 of FIG. 4 and adjusted to an appropriate oil pressure by the charge relief valve 8, reaches the oil passage 56, and is guided to the charge oil passage 15 of the center section 4. . Check valves 10a and 10
This is guided to the charge oil passages 16a and 16b of b.

The oil passage 5 discharged from the charge pump CP
The charge relief valve 8 provided at the portion 7 is constituted by assembling an urging spring 18 and a spring receiving case 19 into the charge pump case 7. The hydraulic oil is sucked into the charge pump CP from the suction oil passage 58 of the charge pump case 7 shown in FIG. The suction oil passage 58
Is opened inside the oil filter 17 sandwiched between the charge pump case 7 and the lower case 6b, and sucks the working oil filtered by the oil filter 17.

[0015]

As described above, the present invention has the following advantages. That is, first, when the charge pump CP is rotated by the start of the engine, the discharge oil from the charge pump CP acts in a direction to push back the piston 1 maintained in the open state. Can be closed automatically. Therefore, when the operator changes,
In the case of a novice operator, the check valve 10a
It is possible to prevent an erroneous operation in which the hydraulic motor M does not rotate and the body does not run with the 10b kept open.

Secondly, there is no need to provide a relief mechanism that is linked and connected as in the prior art for the return of the bypass circuit.
In addition, since the bypass can be automatically closed when the engine is started, a reliable operating state can be obtained. In addition, compared to the conventional mechanism, it is possible to configure the device at a compact size and at low cost.

[Brief description of the drawings]

FIG. 1 is a plan view of an axle drive device having a hydraulic transmission according to the present invention with an upper case 6a removed.

FIG. 2 is a sectional view taken along the line AA in an assembled state of the upper case 6a of FIG. 1;
Arrow sectional drawing.

FIG. 3 is a plan view of a center section 4, a piston 1, and a valve case 3;

FIG. 4 is a rear sectional view of a portion including a check valve 10 and a charge relief valve 8.

FIG. 5 is a plan cross-sectional view of the center section 4 in the portion of the check valve 10.

FIG. 6 is an enlarged rear cross-sectional view of a portion of a check valve 10 and a piston 1.

FIG. 7 is a hydraulic circuit diagram of a bypass operating mechanism of the hydraulic transmission according to the present invention.

[Explanation of symbols]

 P Hydraulic pump M Hydraulic motor 1 Piston 2 Branch presser 3 Valve case 4 Center section 5 Pump shaft 6 Transmission case 7 Charge pump case 8 Charge relief valve 10 Check valve 36 Cylinder chamber 37 Gap oil passage

──────────────────────────────────────────────────続 き Continued on the front page (56) References Japanese Utility Model 3-100659 (JP, U) Japanese Utility Model 3-108957 (JP, U) Japanese Utility Model 1-154359 (JP, U) Japanese Utility Model 2 105653 (JP, U) Japanese Utility Model 5-45322 (JP, U) Japanese Utility Model 5-14732 (JP, U) Japanese Utility Model 4-110262 (JP, U) Japanese Utility Model 5-45308 (JP, U) (58) Field surveyed (Int.Cl. ⁶ , DB name) F16H 61/40-61/46

Claims (1)

(57) [Claims] 1. A check valve 10 for supplying charge oil to an oil passage connecting a hydraulic pump P and a hydraulic motor M,
The push pin 11 is advanced and mechanically opened by an external operation, and a cylinder chamber 36 for moving the piston 1 in a direction in which the push pin 11 retreats is provided. The cylinder chamber 36 is discharged from the charge pump CP. A bypass operation mechanism for a hydraulic transmission, wherein a part of the charge oil to be introduced is guided.