JPH03282063A - Hydraulic circuit for closed circuit hydraulic transmission - Google Patents

Abstract

PURPOSE:To facilitate operation by controlling running of a vehicle by variation of capacity and the delivery directions of variable capacity type hydraulic pumps on both sides through operation of a single lever. CONSTITUTION:Pressure oil is fed to servo cylinders 9 and 10, varying capacity and the delivery directions of variable capacity type hydraulic pumps 1 and 5 on both sides, by means of control valves 11 and 12. A hydraulic pilot valve 14 having first - fourth pressure reducing valves 16-19 operated by longitudinal and lateral swinging of a lever 15 is provided, and the control valves are switched by means of the output pressures of the first - fourth pressure reducing valves. Through longitudinal, left oblique longitudinal, and right oblique longitudinal swinging of the lever 15 of the hydraulic pilot valve 14, the control valves 11 and 12 on both sides are brought into a forward position and a reverse position. Capacity and the delivery directions of the variable capacity type hydraulic pumps 1 and 5 on both sides are varied to control the rotation directions and the rotations speeds of the hydraulic motors 2 and 6 on both sides. Therefore, through operation of the single lever 15, forward, reverse, leftward and rightward forward cornering, and leftward and rightward reverse cornering are practicable.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a hydraulic circuit of a closed circuit hydraulic transmission in a hydraulically driven vehicle equipped with a pair of left and right hydraulic transmissions in which a variable displacement hydraulic pump and a hydraulic motor are connected in a closed circuit; In particular, the present invention relates to an operating device that controls the running of a vehicle by changing the capacity and discharge direction of a left and right displacement hydraulic pump.

[Conventional technology]

A hydraulic circuit for a closed circuit hydraulic transmission disclosed in Japanese Patent Application Laid-open No. 58-128558 is known.

In other words, a pair of left and right hydraulic transmissions are provided, in which a variable displacement hydraulic pump and a hydraulic motor are connected in a closed circuit through the first and second main circuits, and the capacity and discharge direction of the variable displacement hydraulic pumps of the left and right hydraulic transmissions are controlled. This is a hydraulic circuit that allows the vehicle to travel forward, backward, and turn left and right by varying the rotational speed of the hydraulic transmission.

[Problem to be solved by the invention]

In such a hydraulic circuit, travel is controlled by changing the capacity and discharge direction of the left and right variable displacement hydraulic pumps.
Since left and right levers are provided to change the capacity and discharge direction of the left and right variable displacement hydraulic pumps, the operator must operate two levers, which is very troublesome.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a hydraulic circuit for a closed-circuit hydraulic transmission that can solve the above-mentioned problems.

[Means and actions for solving the problem] A control valve supplies pressure oil to a servo cylinder that changes the capacity and discharge direction of a left-right variable displacement hydraulic pump, and a hydraulic pump is operated by swinging a lever back and forth and left and right. A hydraulic pilot valve equipped with first to fourth pressure reducing valves is provided, and the control valves are switched by the output pressure of the first to fourth pressure reducing valves, so that the left and right variable displacement hydraulic pump can be operated by operating one lever. The vehicle can be controlled by changing the capacity and discharge direction.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

(Overall outline) As shown in Fig. 1, a left hydraulic transmission A, a right hydraulic transmission B, and a steering operation part C constitute a closed circuit hydraulic transmission, and by operating the steering operation part C, the left and right hydraulic By controlling the rotational speed and direction of transmissions A and B, the left sprocket D and right sprocket E are rotated to allow the vehicle to travel straight and turn.

The left hydraulic transmission A includes a left variable displacement hydraulic pump 1 (hereinafter referred to as left bending pressure pump 1) and a left hydraulic motor 2.
are connected in a closed circuit with the left first and second main circuits 3 and 4, and the right hydraulic transmission B is connected to the right variable displacement hydraulic pump 5.
(hereinafter referred to as oil pressure pump 5) and right hydraulic motor 6 are connected in a closed circuit through right first and second main circuits 7 and 8.

The left and right hydraulic pumps 1, 5 are variable displacement hydraulic pumps of the swash plate type that can vary the capacity, that is, the discharge amount per revolution by changing the angles of the swash plates 1a, 5a.
, 5a are tilted by left and right servo cylinders 9.10, and pressure oil discharged from the auxiliary hydraulic pump 13 is supplied to the left and right servo cylinders 9.10 by left and right control valves 11.12.

The steering operation section C becomes a hydraulic pilot valve 14, and the hydraulic pilot valve 14 operates the first and second pressure reducing valves 16 and 17 by swinging one lever 15 back and forth, and the lever 15 is moved left and right. When it swings, the third and fourth pressure reducing valves 18.19
Each pressure reducing valve is configured to output pressure oil discharged from the auxiliary bending pump 13 in proportion to the operation stroke of the lever 15.

Next, details of each part will be explained.

A pair of check valves 2 are provided in the left first and second main circuits 3.4.
0.20, the left charge circuit 21 is connected, and the left high pressure circuit 22 and left low pressure circuit 23 are connected to the high pressure side main circuit and the low pressure side main circuit by the left shuttle valve 24, and the left first and second main circuits are connected. 3.4, the high pressure oil can be introduced into the left high pressure circuit 22, and the low pressure oil can be introduced into the left low pressure circuit 23.

A pair of chinic valves 2 are connected to the right first and second main circuits 7.8.
Right charge circuit 26 is connected through 5.25, right high pressure circuit 27 and right low pressure circuit 28 are connected to the high pressure side main circuit and low pressure side main circuit by right shuttle valve 29. Right first and second main circuits The high-pressure oil at 7 and 8 can be introduced into the right high-pressure circuit 27, and the low-pressure oil can be introduced into the right low-pressure circuit 28, respectively.

The left charge circuit 21 and the right charge circuit 26 are connected to the discharge passage 13a of the auxiliary hydraulic pump 13, and are provided with a safety valve 30.

The left high voltage circuit 22 and the right high voltage circuit 27 are connected via a pair of check valves 31.31, and the pair of check valves 31.3 in the left high voltage circuit 22 and the right high voltage circuit 27 are connected to each other via a pair of check valves 31.31.
The inlet side of the valve 1 is connected to the valve 1 through an equalization valve 32.

The equalizing valve 32 is held at the communicating position a with the throttle 32a when there is no pressure difference between the left and right high pressure oils in the left and right high pressure circuits 22, 27, and is switched to the blocking position when there is a pressure difference.

The left low pressure circuit 23 and the right low pressure circuit 28 are connected, and the cooling circuit 2a for the left and right hydraulic motors 2 and 6 is connected via a low pressure relief valve 33 and an oil cooler 34.

Connected to 6a.

Between the pair of check valves 31 and 31 in the left and right high pressure circuits 22 and 27, a neutral bypass valve 35 connects the left and right change circuits 21 and 26, that is, the discharge path 1 of the auxiliary hydraulic pump 13.
3a, and the safety valve 36 connects the low pressure relief valve 3
It is connected to the entrance side of 3.

The neutral bypass valve 35 is held at the communicating position Mc by a spring force 35a, and is kept at the blocking position 1d by pilot pressure oil of the pressure receiving part 35b.
This configuration switches to

The low pressure side of the safety valve 30 is connected to the cooling circuits 1b and 5b of the left and right hydraulic pumps 1.5.

The left and right control valves 11.12 are held at the drain position e by spring force, and the first and second pressure receiving portions 11a.

11b, 12a, 12b and third and fourth pressure receiving parts 11c, l
The configuration is such that the forward position fief and the reverse position 1g are switched by the pressure difference between the pilot pressure oils id, 12c, and 12d, and when the left and right control valves 11.12 are in the forward position f, the pressure oil discharged from the auxiliary hydraulic pump 13 is switched to the left and right servo positions. The left and right hydraulic motors are supplied to the first chambers 9a and 10a of the cylinders 9 and 10.
The swash plates 1a and 5a tilt toward the forward side, and the left and right first main circuits 3
．． 7, the left and right hydraulic motors 2.6 rotate forward to move the vehicle forward, and when the left and right control valves 11.12 reach the reverse position g, the pressure oil discharged from the auxiliary hydraulic pump 13 is applied to the left and right servo cylinders 9°. 10, the swash plates 1a, 5b of the left and right hydraulic motors 1.5 tilt toward the reverse side, and discharge high-pressure oil to the left and right second main circuits 4, 8. .6 is reversed and the vehicle moves backward.

Inlet port 40 of each pressure reducing valve of the hydraulic pilot valve 14
is connected to the discharge passage 13a of the auxiliary hydraulic pump 13 via a first switching valve 41 and a manual on-off valve 42, and its inlet boat 40 is shut off when the lever 15 is not operated, and the outlet boat 40 is closed by operating the lever 15. 43, the first
A first pilot passage 44 is connected to the outlet boat 43 of the pressure reducing valve 16, and second, third and fourth pilot passages 45.
46 and 47 are connected respectively.

In addition, the tank port 48 of the first and second pressure reducing valves 16 and 17
is connected to the tank side through a throttle 49.

The first pilot passage 44 is connected to the first pressure receiving part 11a of the left control valve 11 and the first pressure receiving part 12a of the right control valve 12, and the second pilot passage 45 is connected to the third pressure receiving part 11c of the left control valve 11.
and the m3 pressure receiving part 12c of the right control valve 12, and the third pilot path 46 is connected to the second and fourth pressure receiving parts 11b of the left control valve 11.
.

The fourth pilot passage 47 is connected to the right control valve 12.
ff52 and the fourth pressure receiving portions 12b and 12d.

The first switching valve 41 is held at the communicating position 1t, and is operated toward the blocking position j by an operating member such as an inching brake pedal, and when the first switching valve 41 is set at the blocking position Wtj, each pressure reduction of the hydraulic pilot valve 14 The inlet boat 40 of the valve communicates with the drain, and each pressure receiving part of the left and right control valves 11.12 communicates with the drain, so that the left and right control valves 11.12 are in the drain position 1ile, and the swash plate 1a of the left and right hydraulic motors 1.5.

5a is the minimum angular position and has the minimum capacity.

The first and second pilot paths 44 and 45 are connected to the shuttle valve 5.
0 to connect to the pressure detection circuit 51, and the pressure detection circuit 51
is connected to the pressure receiving part 35b of the neutral bypass valve 35, and when the lever 15 is swung back and forth to drive the vehicle as described above, the lever 15 is connected to the first pilot path 44 or the second pilot path 45.
The pilot pressure oil is detected by the shuttle valve 50 and the pressure detection circuit 51.
is detected, and the pressure oil is supplied to the pressure receiving part 35b of the neutral piston valve 35 to set it to the shutoff position 1fd.

The left and right sprockets D and E are equipped with a parking brake 60, which consists of a brake plate 61 and a brake cylinder 62, and the brake cylinder 62 is connected to a spring 63.
When the brake cylinder 62 is compressed by supplying pressurized oil to the contraction chamber 64 and the brake cylinder 62 is compressed, the brake cylinder 62 is brought into a released state, and the contraction chamber 64 is connected to a brake circuit 65 .

The brake circuit 65 has a second switching valve 66 that connects the manual on-off valve 42 and the first switching valve in the discharge passage 13a of the auxiliary hydraulic pump 13.
The second switching valve 66 is connected between the switching valve 41 and the switching valve 41 .
is held at the drain position k by a spring force, and brought to the communication position g by pilot pressure oil in the pressure receiving part 66a, and the pressure receiving part 66a is connected to the pressure detection circuit 51, and the vehicle runs as described above. Sometimes the pressure receiving part 66 of the second switching valve 66
Pilot pressure oil is supplied to a to set the communication position p, and pressure oil discharged from the auxiliary hydraulic pump 13 is supplied to the brake circuit 65 to release the parking brake 60.

A hydraulic pressure supply port 67 equipped with a check valve 66 is provided on the inlet side of the first switching valve 41 so that pressure oil can be supplied to the inlet side of the first switching valve 41 from another hydraulic pressure source.

Next, the details of the device for controlling the running of a vehicle by changing the capacity and discharge direction of a hydraulic pump according to the present invention will be explained.

Since the left and right servo cylinders 9 and 10 and the left and right control valves 11 and 12 have the same structure, the left servo cylinder 9 and the left control valve 1
1 will be explained.

As shown in FIG. 2, the left control valve 11 is equipped with a spool 70, and one end of a lever 71 pivotally connected to the spool 70 moves the left servo cylinder 9 to tilt the swash plate 1a, and the other end moves the lever 71 for switching. The spool 72 is switched so that the swash plate 1a is tilted in proportion to the movement stroke of the spool 70.
Since this configuration is conventionally known, detailed explanation will be omitted.

Free pistons 73 are provided at both ends of the spool 70 to form first, second, third, and fourth pressure receiving portions 11a. llb
.
3 toward the second pressure receiving section 11b, and pressurized oil from the third pressure receiving section 11C pushes the spool 70 toward the reverse side, and at the same time pushes the free piston 73 toward the fourth pressure receiving section lid. When pressure oil is supplied to the pressure receiving part 11a and the spool 70 is pushed to the right, the lever 71 tilts with the left servo cylinder 9 as a fulcrum, switches the switching spool 72, and supplies pressure oil to one chamber of the left servo cylinder 9. The swash plate 1a is tilted forward at a predetermined angle, thereby causing the lever 71 to move toward the spool 7.
0, the switching spool 72 is returned to the neutral position, and the swash plate 1a is tilted forward by an amount corresponding to the stroke of the spool 70.

When pressure oil is supplied to the third pressure receiving portion 11c and the spool 70 is moved to the left, the swash plate 1a is tilted to the reverse side by an amount commensurate with the spool stroke in the same manner as described above.

Then, the lever 15 is swung forward and the first pressure reducing valve 16 is opened.
When the left and right control valves 11 are operated, the first pilot passage 44
．． 12 first pressure receiving portions 11a.

Pilot pressure oil is supplied to the left and right control valves 11.12a.
12 is the forward position f, so the vehicle moves forward as described above.

When the lever 15 is swung rearward to operate the second pressure reducing valve 17, pilot pressure oil is supplied from the second pilot passage 45 to the third pressure receiving portions 11c and 12c of the left and right control valves 11.12. Since .degree. 12 becomes the reverse movement value ifg, the vehicle moves backward as described above.

By swinging the lever 15 forward, each first pressure receiving part 11a, 12
While driving forward with pilot pressure oil supplied to a and the left and right control valves 11 and 12 set to the forward position f, the lever 15
When the third pressure reducing valve 18 is actuated by swinging diagonally to the left, pilot pressure oil is also supplied to the third pilot passage 46, and pilot pressure is also applied to the second and fourth pressure receiving parts 11b and lid of the left control valve 11. Oil is supplied respectively.

As a result, a force is applied to move the free piston 73 to the right in FIG. 2 by the pilot pressure oil supplied to the second pressure receiving part 11b, but the free piston 73 is
The free piston 73 does not move to the right because it is pushed to the left by the pilot pressure oil supplied to the free piston 73.

On the other hand, the free piston 73 is pushed to the left by the pilot pressure oil supplied to the fourth pressure receiving part lid, and the third pressure receiving part 1
Since 1C is connected to the tank, the spool 70 is pushed back toward the neutral position via the free piston 73 according to the pressure of the pilot pressure oil.

At this time, since the pilot pressure oil is proportional to the operating stroke of the lever 15, the spool 70 is pushed back to the neutral position in accordance with the stroke of swinging the lever 15 diagonally to the left, and the swash plate angle of the left hydraulic pump 1 is shifted to the right. The swash plate angle of the hydraulic pump 5 becomes smaller, the capacity decreases, and the rotation speed of the left hydraulic transmission A becomes lower than the rotation speed of the right hydraulic transmission B.
Since the rotation speed is slower than the rotation speed of the lever 15, the vehicle moves forward and turns left at a turning angle corresponding to the operation stroke of the lever 15.

When the lever 15 is swung diagonally to the right while the lever 15 is swung forward and the fourth pressure reducing valve 19 is actuated, pilot pressure oil is also supplied to the fourth pilot passage 47 and the fourth pressure reducing valve 19 is actuated. 2. Since pilot pressure oil is also supplied to the fourth pressure receiving parts 12b and 12d, the swash plate angle of the right hydraulic pump 5 becomes smaller than the swash plate angle of the left hydraulic pump 1, as described above.
The capacity of the right hydraulic pump 5 becomes smaller than the capacity of the left hydraulic pump 5, the rotational speed of the right hydraulic transmission B becomes slower than the rotational speed of the left hydraulic transmission A, and the vehicle rotates at a turning angle commensurate with the operating stroke of the operating lever 15. Drive forward and turn right.

When the third pressure reducing valve 18 is activated by swinging the lever 15 diagonally to the left while the lever 15 is swinging backward, the capacity of the left hydraulic pump 1 becomes smaller than the capacity of the right hydraulic pump 5, as described above. Therefore, the vehicle moves backward and turns to the left at a turning angle that corresponds to the operating stroke of the operating lever 15.

When the lever 15 is swung diagonally to the right while the lever 15 is swung backwards to operate the fourth pressure reducing valve 19, the fourth pressure reducing valve 19 is activated.
Pilot pressure oil is also supplied to the pilot 47, and the capacity of the right hydraulic pump 5 becomes smaller than the capacity of the left hydraulic pump 1, as described above, and the vehicle moves backward and turns to the right at a turning angle commensurate with the operation stroke of the lever 15. .

In the above embodiment, the free piston 73 has the same diameter as the spool 70, and the first, second, third, and fourth pressure receiving parts 11a, l
lb, llc, lid.

12a, 12b, 12c, and 12d have the same pressure receiving area, but as shown in FIG.
The pressure receiving area of the second pressure receiving portions 11b, 12b and the fourth pressure receiving portions lid, 12d is set as a diameter larger than 0.
a, the pressure receiving area may be larger than that of the third pressure receiving portions 11c and 12c.

In this way, the pilot pressure oil is supplied to the first pressure receiving part 11a and the spool 70 is set to the forward position side.
, when pilot pressure oil is supplied to the fourth pressure receiving parts 11b and 11d, the force that moves the spool 70 toward the neutral position increases, and the pilot pressure oil of the second and fourth pressure receiving parts 11b and lid becomes higher than a certain value. Then, since the spool 70 can be moved beyond the Chinese position to the reverse position, the discharge direction of the left hydraulic pump 1 is reversed, the left travel motor 2 is placed in the reverse travel state, and the vehicle can turn around.

〔Effect of the invention〕

By swinging the lever 15 of the hydraulic pilot valve 14 back and forth, diagonally left back and forth, and right back and forth, the left and right control valves 11.12 are placed in the forward and reverse positions, thereby controlling the capacity and discharge of the left and right variable displacement hydraulic pumps 1.5. The direction changes and the left and right hydraulic motors 2.
Since the rotation direction and rotation speed of the lever 6 are controlled, by operating one lever 15, the vehicle can be moved forward, backward, left and right forward turns, and left and right backward turns.

[Brief explanation of drawings]

FIG. 1 is a hydraulic circuit diagram showing an embodiment of the present invention, FIG. 2 is a detailed sectional view of a control valve and a servo piston, and FIG. 3 is a sectional view of an example of the same. A is the left hydraulic transmission, B is the oil pressure transmission, 1 is the left variable displacement hydraulic pump, 2 is the left hydraulic motor, 3 is the left first main circuit, 4 is the left second main circuit, 5 is the right variable displacement hydraulic Pump, 6 is right hydraulic motor, 9.10 is left and right servo cylinder, 11.12 is left and right control valve, 14 is hydraulic pilot valve, 15 is lever 16.17° 18.1
9 is the first to fourth pressure reducing valves.

Claims (1)

[Claims] The left variable displacement hydraulic pump 1 and the left hydraulic motor 2 are connected to the left variable displacement hydraulic pump 1 and the left hydraulic motor 2.
The left hydraulic transmission A is connected in a closed circuit through the second main circuits 3 and 4, and the right hydraulic transmission is connected in a closed circuit between the right variable displacement hydraulic pump 5 and the right hydraulic motor 6 through the right first and second main circuits 7 and 8. In the hydraulic circuit of the closed circuit hydraulic transmission equipped with B, left and right control valves 11 and 12 supply pressure oil to left and right servo cylinders 9 and 10 that change the capacity and discharge direction of the left and right variable displacement hydraulic pumps 1 and 5, respectively. , becomes neutral position due to spring force,
The pressure oil in the first pressure receiving part is the forward position f, the pressure oil in the third pressure receiving part is the reverse position g, and with the pressure oil being supplied to the first or third pressure receiving part, the pressure is being applied to the second and fourth pressure receiving parts. When oil is supplied, the stroke amount to the forward position g or reverse position h is limited, and by swinging the lever 15 back and forth and left and right, the first, second,
A hydraulic pilot valve 14 that operates the third and fourth pressure reducing valves 16, 17, 18, and 19 is provided, and the output side of the first pressure reducing valve 16, which is operated by swinging the lever 15 forward, is connected to the left and right control valve 11. , 12, and the output side of a second pressure reducing valve 17, which is activated by swinging the lever 15 backward, is connected to the second pressure receiving part of the left and right control valves 11 and 12, and the lever 15 The third pressure reducing valve 18 is activated by swinging to the left.
The output side of the fourth pressure reducing valve 19, which is activated by swinging the lever 15 to the right, is connected to the second and fourth pressure receiving parts of the left control valve 11. 2. A hydraulic circuit for a closed circuit hydraulic transmission, characterized in that it is connected to a fourth pressure receiving section.