JPH07112827B2 - Closed circuit hydraulic transmission hydraulic circuit - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a hydraulic circuit for a closed circuit hydraulic transmission in a hydraulically driven vehicle having 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 traveling of a vehicle by changing the displacement and the discharge direction of a left and right variable displacement hydraulic pump.

[Conventional technology]

A hydraulic circuit of a closed circuit hydraulic transmission disclosed in Japanese Patent Laid-Open No. 58-128558 is known.

That is, 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 by the first and second main circuits are provided, and the displacement and the discharge direction of the variable displacement hydraulic pumps of the left and right hydraulic transmissions are controlled to control the left and right. It is a hydraulic circuit that travels forward, backward, and turns left and right by varying the rotational speed of the hydraulic transmission and the rotational speed.

[Problems to be Solved by the Invention]

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

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 Problems]

The left variable displacement hydraulic pump 1 and the left hydraulic motor 2 are connected to the left first
The left hydraulic transmission A, the right variable displacement hydraulic pump 5 and the right hydraulic motor 6 which are closed-circuit connected by the second main circuits 3 and 4.
In a hydraulic circuit of a closed circuit hydraulic transmission including a right hydraulic transmission B in which a closed circuit is connected by first and second main circuits 7 and 8, the left variable displacement hydraulic pump 1 is configured to change the displacement and the discharge direction. Servo cylinder 9 and left control valve 11 are
When 11 is in the neutral position e, the capacity becomes zero and the left control valve 11
Is moved from the neutral position e to the forward position f, the hydraulic pump 1 discharges pressure oil to the left first main circuit 3, and the left control valve 11
When the left control valve 11 moves from the neutral position e to the reverse position g, the hydraulic pump 1 discharges pressure oil to the left second main circuit 4 and the movement stroke of the left control valve 11 When the pressure oil is supplied to the first pressure receiving portion 11a, the left control valve 11 is moved to the forward movement position f by a moving stroke proportional to the pressure of the pressure oil, and the third pressure receiving portion 11a is moved. When the pressure oil is supplied to the portion 11c, the reverse position g is moved by a moving stroke proportional to the pressure of the pressure oil.
To the first pressure receiving portion 11a, the second pressure receiving portion 11b, and the fourth pressure receiving portion.
When the pressure oil is supplied to 11d, it moves to the forward position f by a movement stroke proportional to the pressure difference between the pressure oil pressure of the first pressure receiving portion 11a and the pressure oil pressure of the fourth pressure receiving portion 11d, and the third pressure receiving portion f When pressure oil is supplied to 11c and the second and fourth pressure receiving portions 11b and 11d, the reverse position is moved by a moving stroke proportional to the pressure difference between the pressure oil of the third pressure receiving portion 11c and the pressure oil of the second pressure receiving portion 11b. The right servo cylinder 10 and the right control valve 12 for changing the displacement and the discharge direction of the right variable displacement hydraulic pump 5 are connected to the right control valve.
When 12 is in the neutral position e, the capacity becomes zero and the right control valve 12
Is moved from the neutral position e to the forward position f, the hydraulic pump 5 discharges pressure oil to the right first main circuit 7, and the right control valve 12
When the right control valve 12 moves from the neutral position e to the reverse position g, the hydraulic pump 5 discharges pressure oil to the right second main circuit 8 and the moving stroke of the right control valve 12 When the pressure oil is supplied to the first pressure receiving portion 12a, the right control valve 12 is moved to the forward movement position f by a movement stroke proportional to the pressure of the pressure oil, and the third pressure receiving portion When the pressure oil is supplied to the portion 12c, the reverse position g is moved by a moving stroke proportional to the pressure of the pressure oil.
To the first pressure receiving portion 12a, the second pressure receiving portion 12b, and the fourth pressure receiving portion.
When pressure oil is supplied to 12d, it moves to the forward position f by a movement stroke proportional to the pressure difference between the pressure oil pressure of the first pressure receiving portion 12a and the pressure oil pressure of the fourth pressure receiving portion 12d, and the third pressure receiving portion 12d. When pressure oil is supplied to 12c and the second and fourth pressure receiving portions 12b and 12d, the reverse position is moved by a moving stroke proportional to the pressure difference between the pressure oil of the third pressure receiving portion 12c and the pressure oil of the second pressure receiving portion 12b. The hydraulic pilot valve 14 that operates the first, second, third, and fourth pressure reducing valves 16, 17, 18, 19 by swinging the lever 15 back and forth and left and right is provided. First pressure reducing valve 16 that operates by swinging 15 forward
The output side of is connected to the first pressure receiving portions 11a, 12a of the left and right control valves 11, 12 and is operated by swinging the lever 15 rearward.
The output side of the pressure reducing valve 17 is connected to the third pressure receiving portion 1 of the left and right control valves 11 and 12.
The output side of the third pressure reducing valve 18 which is connected to 1c and 12c and is operated by swinging the lever 15 to the left is connected to the second and fourth pressure receiving portions 11b and 11d of the left control valve 11, and the lever is connected. The output side of the fourth pressure reducing valve 19 which operates by swinging 15 to the right is connected to the right control valve 12
A hydraulic circuit for a closed-circuit hydraulic transmission, characterized in that the hydraulic circuit is connected to the second and fourth pressure receiving portions 12b, 12d.

In the case of the hydraulic circuit of such a closed circuit hydraulic transmission, when the lever 15 of the hydraulic pilot valve 14 is swung forward, pressure oil is supplied to the first pressure receiving portions 11a, 12a of the left and right control valves 11, 12 to advance the same stroke. Since the position is f, the left and right hydraulic motors 2, 6 rotate forward and the vehicle moves forward.

When the lever 15 of the hydraulic pilot valve 14 is swung backward, pressure oil is supplied to the third pressure receiving portions 11c and 12c of the left and right control valves 11 and 12, respectively, and the left and right hydraulic motors 2 and 6 are moved to the same stroke backward position g. The vehicle turns backward by rotating to the reverse side.

When the lever 15 of the hydraulic pilot valve 14 is swung to the left with the lever 15 being swung forward, pressure oil is supplied to the first pressure receiving portions 11a and 12a of the left and right control valves 11 and 12 to be in the forward movement position f, and the left control is performed. When the pressure oil is supplied to the second and fourth pressure receiving portions 11b and 11d of the valve 11, the stroke of the left control valve 11 at the forward position f becomes smaller than the stroke of the right control valve 12, and the left variable displacement hydraulic pump 1 The capacity is small and the capacity of the right variable displacement hydraulic pump 5 is large, the left hydraulic motor 2 rotates at low speed to the forward side, the right hydraulic motor 6 rotates at high speed to the forward side, and the vehicle turns left.

When the lever 15 of the hydraulic pilot valve 14 is swung to the right with the lever 15 being swung forward, pressure oil is supplied to the first pressure receiving portions 11a and 12a of the left and right control valves 11 and 12 to be in the forward movement position f, and the right control is performed. Pressure oil is supplied to the second and fourth pressure receiving portions 12b, 12d of the valve 12, and the stroke of the right control valve 12 at the forward movement position f becomes smaller than the stroke of the left control valve 11 so that the right variable displacement hydraulic pump 5 has The capacity is small and the capacity of the left variable displacement hydraulic pump 1 is large, the right hydraulic motor 6 rotates at a low speed to the forward side, the left hydraulic motor 2 rotates at a high speed to the forward side, and the vehicle turns right forward.

When the lever 15 of the hydraulic pilot valve 14 is swung to the left in a state of being swung backward, pressure oil is supplied to the third pressure receiving portions 11c and 12c of the left and right control valves 11 and 12, respectively, to the reverse position g and the left control valve. The pressure oil is supplied to the second and fourth pressure receiving portions 11b and 11d of 11 so that the stroke of the backward position g of the left control valve 11 becomes smaller than the stroke of the right control valve 12 and the displacement of the left variable displacement hydraulic pump 1 is increased. Is small, the capacity of the right variable displacement hydraulic pump 5 is large, the left hydraulic motor 2 rotates at a low speed to the reverse side, and the right hydraulic motor 6 rotates at a high speed to the reverse side, so that the vehicle turns to the left reverse direction.

When the lever 15 of the hydraulic pilot valve 14 is swung to the right in the state of being swung backward, pressure oil is supplied to the third pressure receiving portions 11c and 12c of the left and right control valves 11 and 12, respectively, to the reverse position g and the right control valve. The pressure oil is supplied to the second and fourth pressure receiving portions 12b and 12d of 12 and the stroke of the reverse position g of the right control valve 12 becomes smaller than the stroke of the left control valve 11 so that the capacity of the right variable displacement hydraulic pump 5 is increased. Is small, the displacement of the left variable displacement hydraulic pump 1 is large, the right hydraulic motor 2 rotates at a low speed to the reverse side, the left hydraulic motor 2 rotates at a high speed to the reverse side, and the vehicle turns to the right reverse 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 circuit hydraulic transmission A, a right hydraulic transmission B, and a steering operation section C constitute a closed-circuit hydraulic transmission. By controlling the rotational speeds and rotational directions of the transmissions A and B, the left sprocket D and the right sprocket E are rotated to travel straight and turn.

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

The left and right hydraulic pumps 1 and 5 are variable displacement hydraulic pumps of a swash plate type in which the displacement, that is, the discharge amount per one rotation is variable by changing the angles of the swash plates 1a and 5a. The left and right servo cylinders 9, 9 are tilted by the servo cylinders 9, 10.
The discharge pressure oil of the auxiliary hydraulic pump 13 is supplied to the left and right control valves 11 and 12.

The steering operation section C serves as a hydraulic pilot valve 14, and the hydraulic pilot valve 14 swings one lever 15 back and forth to operate the first and second pressure reducing valves 16 and 17, thereby moving the lever 15 to the left and right. The third and fourth pressure reducing valves 18 and 19 are operated when rocking to, and each pressure reducing valve outputs the pressure oil discharged from the auxiliary hydraulic pump 13 in proportion to the operation stroke of the lever 15.

Next, the details of each part will be described.

The left first and second main circuits 3 and 4 have a pair of check valves 20 and 20.
The left high voltage circuit 22 and the left low voltage circuit 23 are connected to the high pressure side main circuit and the low pressure side main circuit by the left shuttle valve 24 so that the left first and second main circuits 3 and 4 are connected. The high pressure oil in the above 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, respectively.

A pair of check valves 25, 25 are provided on the right first and second main circuits 7, 8.
The right high-voltage circuit 27 and the right low-voltage circuit 28 are connected to the high-pressure side main circuit and the low-pressure side main circuit by the right shuttle valve 29 via the right charge circuit 26 and the right first and second main circuits 7, 8 respectively. The high pressure oil in the above can be introduced into the right high pressure circuit 27, and the low pressure oil in the right low pressure circuit 28 can be introduced.

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 a safety valve 30 is provided.

The left high voltage circuit 22 and the right high voltage circuit 27 are a pair of check valves 3
Connected via 1,31, and further left high voltage circuit 22 and right high voltage circuit
The inlet sides of the pair of check valves 31, 31 in 27 communicate with each other through an equalize valve 32.

The equalize valve 32 is configured to be held at the communication position a having 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 and 27, and switched to the shut-off position b when there is a pressure difference.

The left low-pressure circuit 23 and the right low-voltage circuit 28 are connected, and the left and right hydraulic motors are passed through a low-pressure relief valve 33 and an oil cooler 34.
It is connected to 2, 6 cooling circuits 2a, 6a.

A pair of check valves 31, 31 in the left and right high pressure circuits 22, 27
Between the neutral bypass valve 35 is the left and right chage circuits 21, 26,
That is, it is connected to the discharge passage 13a of the auxiliary hydraulic pump 13 and is connected to the inlet side of the low pressure relief valve 33 by the safety valve 36.

The neutral bypass valve 35 is held at the communication position c by the spring force 35a, and is switched to the cutoff position d by the pilot pressure oil of the pressure receiving portion 35b.

The low pressure side of the safety valve 30 is the cooling circuit 1 for the left and right hydraulic pumps 1, 5.
It is connected to b and 5b.

The left and right control valves 11, 12 are held in the drain position e by spring force, and the first and second pressure receiving portions 11a, 11b, 12a, 12b and the third, fourth
When the left and right control valves 11 and 12 are in the forward drive position f, the auxiliary hydraulic pump 1 is configured so that the forward drive position f and the reverse drive position g can be switched by the pressure difference of the pilot pressure oil in the pressure receiving portions 11c, 11d, 12c and 12d.
Discharge pressure oil of 3 is the first chamber 9a, 10a of the left and right servo cylinders 9, 10.
And the swash plates 1a, 5a of the left and right hydraulic motors 1, 5 tilt forward and discharge high-pressure oil to the first left and right main circuits 3, 7 and the left and right hydraulic motors 2, 6 rotate in the forward direction. Move forward, left and right control valves 11,12
Is set to the reverse position g, the hydraulic fluid discharged from the auxiliary hydraulic pump 13 is supplied to the second chambers 9b and 10b of the left and right servo cylinders 9 and 10, and the swash plates 1a and 5b of the left and right hydraulic motors 1 and 5 tilt to the reverse side. Left and right second
High-pressure oil is discharged to the main circuits 4 and 8, the left and right hydraulic motors 2 and 6 rotate in reverse, and the vehicle moves backward.

The inlet port 40 of each pressure reducing valve of the hydraulic pilot valve 14 is connected to the auxiliary hydraulic pump via a first switching valve 41 and a manual opening / closing valve 42.
13 is connected to the discharge passage 13a, and its inlet port 40 is connected to the lever 15
Is shut off when not operated, and is communicated with the outlet port 43 by operating the lever 15, and the outlet port of the first pressure reducing valve 16
The first pilot path 44 is connected to 43, and the second, third, and fourth
Second, third and fourth pilot passages 45, 46 and 47 are connected to the outlet ports 43 of the pressure reducing valves 17, 18 and 19, respectively.

The tank port 48 of the first and second pressure reducing valves 16 and 17 has a throttle 4
It is connected to the tank side via 9.

The first pilot passage 44 is the first pressure receiving portion 11a of the left control valve 11.
To the first pressure receiving portion 12a of the right control valve 12, the second pilot passage 45 is connected to the third pressure receiving portion 11c of the left control valve 11 and the third pressure receiving portion 12c of the right control valve 12, and the third pilot passage 46 is the left control valve 1
The first pilot passage 47 is connected to the second and fourth pressure receiving portions 11b and 11d of 1 and the fourth pilot passage 47 is connected to the second and fourth pressure receiving portions 12b and 12d of the right control valve 12.

The first switching valve 41 is held at the communication position i, and the operation member,
For example, when the inching / brake pedal is operated toward the shut-off position j and the first switching valve 41 is set to the shut-off position j, the inlet port 40 of each pressure reducing valve of the hydraulic pilot valve 14 communicates with the drain, and the left and right control valves 11, 12 are connected. The respective pressure receiving portions are communicated with the drain so that the left and right control valves 11 and 12 are at the drain position e, and the swash plates 1a and 5a of the left and right hydraulic motors 1 and 5 are at the minimum angular positions to have the minimum capacity.

The first and second pilot passages 44 and 45 are connected to a pressure detection circuit 51 by a shuttle valve 50, and the pressure detection circuit 51 is connected to a pressure receiving portion 35b of the neutral bypass valve 35 to swing the lever 15 back and forth. When the vehicle is traveling as described above, the pilot pressure oil in the first pilot path 44 or the second pilot path 45 is detected by the shuttle valve 50 in the pressure detection circuit 51, and the pressure oil is received by the pressure receiving portion of the neutral bypass valve 35. It is supplied to 35b and is set to the blocking position d.

The left and right sprockets D and E include a parking brake 60, and the parking brake 60 includes a brake plate 61 and a brake cylinder 62.
The brake cylinder 62 is stretched and urged by the spring 63 to bring it into a braking state, and when the brake cylinder 62 is reduced by supplying pressure oil to the reduction chamber 64, the brake cylinder 62 is released and the reduced chamber is
64 is connected to the brake circuit 65.

The brake circuit 65 includes a second switching valve 66 and the auxiliary hydraulic pump.
It is connected between the manual on-off valve 42 and the first switching valve 41 in the discharge passage 13a of 13, and the second switching valve 66 is held at the drain position k by the spring force, and the pilot pressure oil of the pressure receiving portion 66a is used. In the communication position l, the pressure receiving portion 66a is connected to the pressure detecting circuit 51, and when the vehicle travels as described above, pilot pressure oil is supplied to the pressure receiving portion 66a of the second switching valve 66 for communication. At the position 1, the pressure oil discharged from the auxiliary hydraulic pump 13 is supplied to the brake circuit 65, and the parking brake 60 is released.

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 traveling of the vehicle by changing the capacity and discharge direction of the hydraulic pump according to the present invention will be described.

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 11 will be described.

As shown in FIG. 2, the left control valve 11 includes a spool 70, one end of a lever 71 pivotally attached to the spool 70 moves the left servo cylinder 9 to tilt the swash plate 1a, and the other end switches. The spool 72 is switched and the swash plate 1a is tilted as much as the moving stroke of the spool 70. This configuration is well known in the art, and a detailed description thereof 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, 11b, 11c, and 11d, and the spool 70 is formed by the pressure oil of the first pressure receiving portion 11a. Is pushed forward, the free piston 73 is pushed toward the second pressure receiving portion 11b side, and the spool 70 is pushed backward by the pressure oil of the third pressure receiving portion 11c. At the same time, the free piston 73 is pushed toward the fourth pressure receiving portion 11d. When pressure oil is supplied to the first pressure receiving portion 11a and the spool 70 is pushed to the right, the lever 71 tilts about the left servo cylinder 9 as a fulcrum to switch the switching spool 72 to switch the left servo cylinder 9 The pressure oil is supplied to one of the chambers to tilt the swash plate 1a forward by a predetermined angle, whereby the lever 71 tilts about the spool 70 to return the switching spool 72 to the neutral position, and the swash plate 1a is moved. Tilt forward to match the stroke of 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 backward as much as the spool stroke, as described above.

When the lever 15 is swung forward and the first pressure reducing valve 16 is operated, pilot pressure oil is supplied from the first pilot passage 44 to the first pressure receiving portions 11a, 12a of the left and right control valves 11, 12 to control the left and right. Since the valves 11 and 12 are in the forward drive position f, they advance to the vehicle as described above.

When the second pressure reducing valve 17 is operated by swinging the lever 15 rearward, the third pilot pressure receiving portion 11 of the left and right control valves 11, 12 is moved from the second pilot passage 45.
Since the pilot pressure oil is supplied to c and 12c and the left and right control valves 11 and 12 are set to the reverse position g, the vehicle moves backward as described above.

While the lever 15 is swung forward, pilot pressure oil is supplied to each of the first pressure receiving portions 11a and 12a, and the left and right control valves 11 and 12 are set to the forward position f. When the third pressure reducing valve 18 is rocked to operate, the third pilot passage 46
The pilot pressure oil is also supplied to the second and fourth pressure receiving portions 11b and 11d of the left control valve 11, respectively.

As a result, the force for moving the free piston 73 to the right in FIG. 2 acts on the pilot pressure oil supplied to the second pressure receiving portion 11b, but the free piston 73 is not supplied with the pilot pressure supplied to the first pressure receiving portion 11a. Since the oil is pushed to the left, the free piston 73 does not move to the right.

On the other hand, the free piston 73 is pushed to the left by the pilot pressure oil supplied to the fourth pressure receiving portion 11d, and the third pressure receiving portion 11c is connected to the tank. Push the spool 70 back towards the neutral position via 73.

At this time, since the pilot pressure oil is proportional to the operation stroke of the lever 15, the spool 70 is pushed back to the neutral position side in accordance with the stroke of swinging the lever 15 to the left side, and the swash plate angle of the left hydraulic pump 1 becomes right. Since the displacement is smaller than the swash plate angle of the hydraulic pump 5 and the rotational speed of the left hydraulic transmission A is lower than the rotational speed of the right hydraulic transmission B, the vehicle moves forward left-handed at a turning angle commensurate with the operation stroke of the lever 5. Travel once.

When the lever 15 is swung forward and the lever 15 is swung diagonally to the right and the fourth pressure reducing valve 19 is operated, pilot pressure oil is also supplied to the fourth pilot passage 47 and the right control valve 12 2. Since pilot pressure oil is also supplied to the second and fourth pressure receiving portions 12b and 12d, the swash plate angle of the right hydraulic pump 5 becomes smaller than that of the left hydraulic pump 1 and 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 lower than the rotational speed of the left hydraulic transmission A, and the vehicle operates the operating lever.
Turn forward and turn right at a turning angle that matches the 15 operation strokes.

When the lever 15 is swung rearward and the lever 15 is swung diagonally leftward to operate the third pressure reducing valve 18, the capacity of the left hydraulic pump 1 becomes smaller than that of the right hydraulic pump 5 as described above. Therefore, the vehicle makes a backward left turn traveling at a turning angle corresponding to the operation stroke of the operation lever 15.

When the lever 15 is swung rearward and the lever 15 is swung diagonally to the right to operate the fourth pressure reducing valve 19, pilot pressure oil is also supplied to the fourth pilot 47 and the right pressure is applied as described above. The capacity of the hydraulic pump 5 becomes smaller than the capacity of the left hydraulic pump 1, and the vehicle makes a reverse right turn traveling 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 portions 11a, 11b, 11c, 11 are provided.
Although the pressure receiving areas of d, 12a, 12b, 12c and 12d are the same, as shown in FIG. 3, the free piston 73 has a larger diameter than the spool 70, and the second pressure receiving portions 11b and 12b and the fourth pressure receiving portions 11d and 12d have the same diameter. The pressure receiving area may be larger than the pressure receiving areas of the first pressure receiving portions 11a, 12a and the third pressure receiving portions 11c, 12c.

With this configuration, when the pilot pressure oil is supplied to the first pressure receiving portion 11a and the spool 70 is set to the forward position side, the spool 70 is moved when the pilot pressure oil is supplied to the second and fourth pressure receiving portions 11b and 11d. When the force that moves toward the neutral position becomes large and the pilot pressure oil of the second and fourth pressure receiving portions 11b and 11d becomes higher than a certain value, the spool 70 can be moved to the reverse position beyond the neutral position. When the discharge direction of 1 is reversed and the left traveling motor 2 is in the backward traveling state, the vehicle can make a turning turn.

〔The invention's effect〕

When the lever 15 of the hydraulic pilot valve 14 is swung forward, the pressure oil is supplied to the first pressure receiving portions 11a, 12a of the left and right control valves 11, 12 to reach the same stroke forward position f, so that the left and right hydraulic motors 2, 6 Rotates to the forward side and the vehicle moves forward.

When the lever 15 of the hydraulic pilot valve 14 is swung backward, pressure oil is supplied to the third pressure receiving portions 11c and 12c of the left and right control valves 11 and 12, respectively, and the left and right hydraulic motors 2 and 6 are moved to the same stroke backward position g. The vehicle turns backward by rotating to the reverse side.

When the lever 15 of the hydraulic pilot valve 14 is swung to the left with the lever 15 being swung forward, pressure oil is supplied to the first pressure receiving portions 11a and 12a of the left and right control valves 11 and 12 to be in the forward movement position f, and the left control is performed. When the pressure oil is supplied to the second and fourth pressure receiving portions 11b and 11d of the valve 11, the stroke of the left control valve 11 at the forward position f becomes smaller than the stroke of the right control valve 12, and the left variable displacement hydraulic pump 1 The capacity is small and the capacity of the right variable displacement hydraulic pump 5 is large, the left hydraulic motor 2 rotates at low speed to the forward side, the right hydraulic motor 6 rotates at high speed to the forward side, and the vehicle turns left.

When the lever 15 of the hydraulic pilot valve 14 is swung to the right with the lever 15 being swung forward, pressure oil is supplied to the first pressure receiving portions 11a and 12a of the left and right control valves 11 and 12 to be in the forward movement position f, and the right control is performed. Pressure oil is supplied to the second and fourth pressure receiving portions 12b, 12d of the valve 12, and the stroke of the right control valve 12 at the forward movement position f becomes smaller than the stroke of the left control valve 11 so that the right variable displacement hydraulic pump 5 has The capacity is small and the capacity of the left variable displacement hydraulic pump 1 is large, the right hydraulic motor 6 rotates at a low speed to the forward side, the left hydraulic motor 2 rotates at a high speed to the forward side, and the vehicle turns right forward.

When the lever 15 of the hydraulic pilot valve 14 is swung to the left in a state of being swung backward, pressure oil is supplied to the third pressure receiving portions 11c and 12c of the left and right control valves 11 and 12, respectively, to the reverse position g and the left control valve. The pressure oil is supplied to the second and fourth pressure receiving portions 11b and 11d of 11 so that the stroke of the backward position g of the left control valve 11 becomes smaller than the stroke of the right control valve 12 and the displacement of the left variable displacement hydraulic pump 1 is increased. Is small, the capacity of the right variable displacement hydraulic pump 5 is large, the left hydraulic motor 2 rotates at a low speed to the reverse side, and the right hydraulic motor 6 rotates at a high speed to the reverse side, so that the vehicle turns to the left reverse direction.

When the lever 15 of the hydraulic pilot valve 14 is swung to the right in the state of being swung backward, pressure oil is supplied to the third pressure receiving portions 11c and 12c of the left and right control valves 11 and 12, respectively, to the reverse position g and the right control valve. The pressure oil is supplied to the second and fourth pressure receiving portions 12b and 12d of 12 and the stroke of the reverse position g of the right control valve 12 becomes smaller than the stroke of the left control valve 11 so that the capacity of the right variable displacement hydraulic pump 5 is increased. Is small, the displacement of the left variable displacement hydraulic pump 1 is large, the right hydraulic motor 2 rotates at a low speed to the reverse side, the left hydraulic motor 2 rotates at a high speed to the reverse side, and the vehicle turns to the right reverse direction.

Therefore, the vehicle can be operated forward, backward, left forward turning, right forward turning, left backward turning, and right backward turning by operating one lever 15, which simplifies the operation.

Further, the output sides of the first, second, third and fourth pressure reducing valves 16, 17, 18, 19 of the hydraulic pilot valve 14 are connected to the first and second pressure receiving portions 11a, 11b, 11c of the left and right control valves 11, 12. , 11d, 12a, 12b, 12c, 12d, the connection work is simple and the piping structure is simple.

[Brief description 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 a modification thereof. A is a left hydraulic transmission, B is a right hydraulic transmission, 1 is a left variable displacement hydraulic pump, 2 is a left hydraulic motor, 3 is a left first main circuit, 4 is a left second main circuit, and 5 is a right variable displacement hydraulic. Pump, 6 is a right hydraulic motor, 9 and 10 are left and right servo cylinders, 11 and 12 are left and right control valves, 14 is a hydraulic pilot valve, 15 is a lever, and 16, 17, 18, and 19 are first to fourth pressure reducing valves.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-56-124564 (JP, A) JP-A-57-7765 (JP, A) Actually opened 60-160274 (JP, U) Actually opened 61- 186862 (JP, U) Actual Kaihei 1-101980 (JP, U) Japanese Patent Sho 56-35776 (JP, B2)

Claims (1)

[Claims] 1. A left hydraulic transmission A in which a left variable displacement hydraulic pump 1 and a left hydraulic motor 2 are connected in a closed circuit by left first and second main circuits 3 and 4, a right variable displacement hydraulic pump 5 and a right hydraulic pressure. In a hydraulic circuit of a closed circuit hydraulic transmission equipped with a right hydraulic transmission B in which a motor 6 is connected in a closed circuit by first right and second main circuits 7 and 8, the capacity and discharge direction of the left variable displacement hydraulic pump 1 are changed. The left servo cylinder 9 and the left control valve 11 are
When 11 is in the neutral position e, the capacity becomes zero and the left control valve 11
Is moved from the neutral position e to the forward position f, the hydraulic pump 1 discharges pressure oil to the left first main circuit 3, and the left control valve 11
When the left control valve 11 moves from the neutral position e to the reverse position g, the hydraulic pump 1 discharges pressure oil to the left second main circuit 4 and the movement stroke of the left control valve 11 When the pressure oil is supplied to the first pressure receiving portion 11a, the left control valve 11 is moved to the forward movement position f by a moving stroke proportional to the pressure of the pressure oil, and the third pressure receiving portion 11a is moved. When the pressure oil is supplied to the portion 11c, the reverse position g is moved by a moving stroke proportional to the pressure of the pressure oil.
To the first pressure receiving portion 11a, the second pressure receiving portion 11b, and the fourth pressure receiving portion.
When the pressure oil is supplied to 11d, it moves to the forward position f by a movement stroke proportional to the pressure difference between the pressure oil pressure of the first pressure receiving portion 11a and the pressure oil pressure of the fourth pressure receiving portion 11d, and the third pressure receiving portion f When pressure oil is supplied to 11c and the second and fourth pressure receiving portions 11b and 11d, the reverse position is moved by a moving stroke proportional to the pressure difference between the pressure oil of the third pressure receiving portion 11c and the pressure oil of the second pressure receiving portion 11b. The right servo cylinder 10 and the right control valve 12 for changing the displacement and the discharge direction of the right variable displacement hydraulic pump 5 are connected to the right control valve.
When 12 is in the neutral position e, the capacity becomes zero and the right control valve 12
Is moved from the neutral position e to the forward position f, the hydraulic pump 5 discharges pressure oil to the right first main circuit 7, and the right control valve 12
When the right control valve 12 moves from the neutral position e to the reverse position g, the hydraulic pump 5 discharges pressure oil to the right second main circuit 8 and the moving stroke of the right control valve 12 When the pressure oil is supplied to the first pressure receiving portion 12a, the right control valve 12 is moved to the forward movement position f by a movement stroke proportional to the pressure of the pressure oil, and the third pressure receiving portion When the pressure oil is supplied to the portion 12c, the reverse position g is moved by a moving stroke proportional to the pressure of the pressure oil.
To the first pressure receiving portion 12a, the second pressure receiving portion 12b, and the fourth pressure receiving portion.
When pressure oil is supplied to 12d, it moves to the forward position f by a movement stroke proportional to the pressure difference between the pressure oil pressure of the first pressure receiving portion 12a and the pressure oil pressure of the fourth pressure receiving portion 12d, and the third pressure receiving portion 12d. When pressure oil is supplied to 12c and the second and fourth pressure receiving portions 12b and 12d, the reverse position is moved by a moving stroke proportional to the pressure difference between the pressure oil of the third pressure receiving portion 12c and the pressure oil of the second pressure receiving portion 12b. The hydraulic pilot valve 14 that operates the first, second, third, and fourth pressure reducing valves 16, 17, 18, 19 by swinging the lever 15 back and forth and left and right is provided. First pressure reducing valve 16 that operates by swinging 15 forward
The output side of is connected to the first pressure receiving portions 11a, 12a of the left and right control valves 11, 12 and is operated by swinging the lever 15 rearward.
The output side of the pressure reducing valve 17 is connected to the third pressure receiving portion 1 of the left and right control valves 11 and 12.
The output side of the third pressure reducing valve 18 which is connected to 1c and 12c and is operated by swinging the lever 15 to the left is connected to the second and fourth pressure receiving portions 11b and 11d of the left control valve 11, and the lever is connected. The output side of the fourth pressure reducing valve 19 which operates by swinging 15 to the right is connected to the right control valve 12
A hydraulic circuit for a closed-circuit hydraulic transmission, characterized in that the hydraulic circuit is connected to the second and fourth pressure receiving portions 12b, 12d.