JP2000081132A - Hydrostatic transmission device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control the output of a hydraulic motor in a high torque or low torque range by providing a first speed/second speed selecting mechanism for moving the swash plates of first and second hydraulic motors to select the capacities of the first and second hydraulic motors. SOLUTION: Operation levers 18, 19 are moved to switch a motor selecting selector valve 16 to a forward side 1st motor on the left of the drawing, and a first speed/second speed selecting selector valve 17 is switched to the second speed position on the right of the drawing. In the second speed state of the 1st motor, discharge oil of a variable displacement pump 1 is guided only to a first hydraulic motor 3 to form the second-speed state where the tilt angle of the first hydraulic motor 3 is minimized. Accordingly, only the first hydraulic motor 3 is highly rotated with a torque lower than in any state. For example, the speed control in the range of low rotation with high torque can be performed by changing the discharge quantity of the variable capacity pump 1 in the first-speed state of a 2nd motor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydrostatic transmission device used as a drive mechanism for a working vehicle such as a road roller.

[0002]

2. Description of the Related Art Although not specifically shown, a hydrostatic transmission device has a closed circuit constituted by a variable displacement pump and a hydraulic motor. That is, when the variable displacement pump is rotated by the driving force of the engine, the variable displacement pump discharges hydraulic oil according to the inclination of the swash plate. Then, the hydraulic motor is rotated by the discharged oil to drive the vehicle,
The hydraulic oil discharged from the hydraulic motor is returned to the variable displacement pump.

[0003] In such a hydrostatic transmission device, if the engine speed is kept constant, the variable displacement pump also rotates at a constant speed. And
In this state, if the swash plate of the variable displacement pump is tilted to control the discharge amount from the minimum to the maximum, the rotation speed of the hydraulic motor, that is, the vehicle speed can be continuously controlled. Therefore, stepless speed change is possible, and for example, smooth start, acceleration, and deceleration can be realized. If the inclination of the swash plate of the variable displacement pump is reversed, the discharge direction can be reversed. Therefore, the vehicle can be made to travel forward or backward by rotating the hydraulic motor in both the forward and reverse directions.

[0004]

In the above-mentioned hydrostatic transmission device, the output of the hydraulic motor can be increased only by operating the variable displacement pump, specifically, by moving the swash plate of the variable displacement pump. Is controlled. An object of the present invention is to provide a hydrostatic transmission device that can control the output of a hydraulic motor in a high torque or low torque range by operating not only a variable displacement pump side but also a hydraulic motor side. It is.

[0005]

SUMMARY OF THE INVENTION The present invention relates to a hydrostatic transmission device, and relates to a variable displacement pump which is linked to a power source rotating in one direction and changes the discharge amount and discharge direction in accordance with the inclination of a swash plate. And allow the flow in both directions, and according to the inclination of the swash plate,
A first fluid pressure motor capable of setting two types of small capacity, and a large size and a small size depending on the inclination of the swash plate, linked to the same swash plate as the first fluid pressure motor while allowing flow in both directions. A second fluid pressure motor capable of setting the displacement of the pump, a forward traveling line connecting one port of the variable displacement pump to one port of the first and second fluid pressure motors in parallel, and the other of the variable displacement pump. A reverse traveling line in which a port is connected in parallel with the other port of the first and second hydraulic motors, an on / off valve provided on both ports of the second hydraulic motor, and an on / off valve are switched to provide a second hydraulic pressure. A motor selection mechanism for communicating the port on the high pressure side with the variable displacement pump side or disconnecting the communication while the port on the low pressure side of the motor is communicated with the variable displacement pump side; First and second fluids By moving the swash plate of the motor, these first, has a feature in that a 1-second speed selection mechanism for selecting the capacity of the second fluid pressure motor.

According to a second aspect, in the first aspect, 1 ·
The second-speed selection mechanism includes a cylinder linked to the swash plates of the first and second fluid pressure motors, and a first- and second-speed selection switching valve for guiding pressure to the cylinder and connecting the cylinder to the tank. When the cylinder communicates with the tank,
The capacity of the first and second fluid pressure motors is maintained at one of large and small, and when pressure is introduced to the cylinder, the swash plate of the first and second fluid pressure motors is moved to increase or decrease the capacity. It is characterized in that it is configured to be either one of them.

[0007]

1 and 2 show a first embodiment of a hydrostatic transmission device according to the present invention. As shown in FIG. 1, the variable displacement pump 1 is linked to an engine E which is a power source thereof. Then, one port 1a of the variable displacement pump 1 is connected to a first and second hydraulic motors 3,
4 are connected in parallel to one of the ports 3a, 4a. The other port 1b of the variable displacement pump 1 is connected in parallel to the other ports 3b, 4b of first and second hydraulic motors 3, 4 to be described later via a reverse travel line 5. Therefore, the variable displacement pump 1 and the first and second hydraulic motors 3 and 4 form a closed circuit.

The variable displacement pump 1 is rotated in the direction of rotation of the engine E. When the swash plate of the variable displacement pump 1 is tilted in the forward traveling range, the variable displacement pump 1 discharges hydraulic oil from the port 1a to the forward traveling line 2 side. Therefore, the first and second hydraulic motors 3, 4 rotate forward in accordance with the discharge amount, and the vehicle travels forward. Conversely, if the swash plate of the variable displacement pump 1 is tilted in the reverse traveling range, the variable displacement pump 1 discharges hydraulic oil from the port 1b to the reverse traveling line 5 side. Therefore, the first and second hydraulic motors 3 and 4 rotate in reverse according to the discharge amount, and the vehicle travels backward.

Here, the first and second hydraulic motors 3, 4
For this purpose, a so-called one-cylinder block type hydraulic motor is used. As shown in FIG. 2, a one-cylinder block type hydraulic motor is a type in which a first hydraulic motor 3 constituting a first hydraulic motor 3 is provided in one cylinder block 6.
A plunger group 7 and a second plunger group 8 constituting the second hydraulic motor 4 are assembled on a concentric circle.
Then, the first and second plunger groups 7, 8 are linked to the same swash plate 24, and the first and second plunger groups are moved along the swash plate 24.
By reciprocating the plunger groups 7 and 8, each performs a motor operation.

The first and second hydraulic motors 3,
4, on both ports 4a and 4b of the second hydraulic motor 4, as shown in FIG. 1, on-off valves 9a and 9b are provided. These on / off valves 9a and 9b are in a normal state held by springs 10a and 10b,
It is in a communication position where the ports 4a and 4b are connected to the variable displacement pump 1 side. In this communication position, the variable displacement pump 1
Is guided to both the first and second hydraulic motors 3 and 4 to rotate the first and second hydraulic motors 3 and 4. Then, when the pilot pressure is led to the pilot chambers 11a and 11b, the ports 4a and 4b are switched to the shut-off position where the ports 4a and 4b are shut off from the variable displacement pump 1 side. For example, when the on / off valve 9a on the port 4a side is switched to the shut-off position while the vehicle is traveling forward, the discharge oil of the variable displacement pump 1 is not guided to the second hydraulic motor 4, and all of the oil is discharged to the second hydraulic motor 4. 1 Guided to the hydraulic motor 3 side. Therefore, only the first hydraulic motor 3 exerts a driving force, because the second hydraulic motor 4 only rotates idly.

Further, the first and second hydraulic motors 3, 4
Then, the swash plate 2 in which the first and second plunger groups 7 and 8 are linked.
By changing the inclination of 4 in two steps, the capacity can be set to two types, large and small. In the first speed state in which the tilt angles of the first and second hydraulic motors 3 and 4 are large, the capacities of the first and second hydraulic motors 3 and 4 are large, and the motors rotate at high torque and low speed. On the other hand, in the second speed state in which the tilt angle is small, the capacities of the first and second hydraulic motors 3 and 4 become small, and the motor rotates at high speed with low torque.

The first and second hydraulic motors 3,
The fourth swash plate 24 is moved by the cylinder 12. When pressure oil is not guided to the bottom chamber of the cylinder 12, the tilt angle is kept large by the spring 13,
The first and second hydraulic motors 3, 4 are maintained in the first speed state described above. When the pressure oil is guided to the bottom chamber of the cylinder 12, the cylinder 12 operates against the spring 13 to reduce the tilt angle, and the first and second hydraulic motors 3, 4 are operated as described above. Change to second gear.

Here, a charge pump 14 is connected to the variable displacement pump 1. Therefore, the charge pump 14 rotates together with the variable displacement pump 1 by the driving force of the engine E, and discharges a certain amount of hydraulic oil. In the hydrostatic transmission device, since the operating oil is circulated through the closed circuit, a problem such as heat generation occurs. In order to avoid such a problem, a charge pump 14 is generally provided, and the discharge oil is supplied to a closed circuit via check valves 15a and 15b. Although not specifically shown,
The same amount of hydraulic oil as supplied from the charge pump 14 is returned from the closed circuit to the tank.

In the first embodiment, the charge pump 14 is connected to the pilot chambers 11a, 11b of the on / off valves 9a, 9b via a motor selection switching valve 16.
1b. In addition, the charge pump 14
The cylinder 1 through the second-speed selection switching valve 17;
2 is connected to the bottom side chamber. That is, the charge pump 14 is used as a hydraulic pressure source for switching the on / off valves 9a and 9b and as a hydraulic pressure source for operating the cylinder 12.

In the normal state, the switching valve 16 for motor selection is located at two motor positions for communicating the pilot chambers 11a and 11b of the on / off valves 9a and 9b with the tank, as shown in FIG. Then, when the operation lever 18 is moved to switch to the forward one motor position on the left side of the drawing, the pilot chamber 11b of the on / off valve 9b on the port 4b side is kept connected to the pilot chamber of the on / off valve 9a on the port 4a side. Charge pump 1 for 11a
4 will be guided. Further, when the operating lever 18 is moved to switch to the reverse one motor position on the right side of the drawing, the pilot chamber 11a of the on / off valve 9a on the port 4a side remains in communication with the tank, contrary to the forward one motor position. The oil discharged from the charge pump 14 is guided to the pilot chamber 11b of the on / off valve 9b on the port 4b side.

On the other hand, the first and second speed switching valve 17 is selected.
Is in a first speed position in the normal state where the bottom chamber of the cylinder 12 communicates with the tank. When the operation lever 19 is moved to switch to the second speed position on the right side of the drawing, the discharge oil of the charge pump 14 is guided to the bottom chamber of the cylinder 12.

Next, the operation of the hydrostatic transmission of the first embodiment will be described. In a working vehicle such as a road roller, the number of revolutions of the engine E is kept constant. When changing the vehicle speed, the swash plate of the variable displacement pump 1 is operated by moving an operation lever (not shown). First, the case where the vehicle travels forward, that is, the case where the swash plate of the variable displacement pump 1 is inclined in the forward travel range of the vehicle will be described. In the forward traveling range of the vehicle, as described above, the variable displacement pump 1
The hydraulic oil is discharged to The following description is based on the premise that the tilt angle of the variable displacement pump 1 is at a certain angle.

It is now assumed that both the motor selection switching valve 16 and the first and second speed selection switching valves 17 are in the normal state without moving the operation levers 18 and 19. In this state, as shown in FIG. 1, the motor selection switching valve 16 is located at the second motor position, and the on / off valves 9a, 9b
The pilot chambers 11a and 11b are communicated with the tank. Therefore, both of the on / off valves 9a and 9b
The ports 4a and 4b of the hydraulic motor 4 are connected to the variable displacement pump 1
The discharge oil of the variable displacement pump 1 is guided to both the first and second hydraulic motors 3 and 4 at the communication position connected to the side. Further, the first / second speed selection switching valve 17 is located at the first speed position, and communicates the bottom chamber of the cylinder 12 with the tank.
Accordingly, the tilt angle is kept large by the spring 13, and the first and second hydraulic motors 3, 4 are maintained in the first speed state, and try to rotate at high torque and low speed. This is 2
In the first motor speed state, the first and second hydraulic motors 3, 4
It will rotate at low torque with high torque.

From the two-motor first-speed state, the operation lever 1
8 is moved to switch the motor selection switching valve 16 to the forward one motor position on the left side of the drawing. In this state, as shown in FIG.
Is in the first speed position, and the bottom chamber of the cylinder 12 remains in communication with the tank. Therefore, the tilt angle is kept large by the spring 13, and the first hydraulic motor 3 attempts to rotate at a high torque and a low speed in the first speed state. However,
Since the motor selection switching valve 16 is switched to the forward one motor position on the left side of the drawing as described above, the discharge pressure of the charge pump 14 is guided to the pilot chamber 11a of the on / off valve 9a on the port 4a side, and this on / off Valve 9a
Is switched to the shut-off position where the port 4a is shut off from the variable displacement pump 1 side. Therefore, the discharge oil of the variable displacement pump 1 is guided only to the first hydraulic motor 3 and the flow rate increases, so that the first hydraulic motor 3 tends to rotate at a higher speed. In the single-motor first-speed state, only the first hydraulic motor 3 rotates at a lower torque and higher rotation than in the two-motor first-speed state.

Further, from the above-mentioned two-motor first-speed state, the operating lever 19 is moved to select the first- and second-speed selection switching valve 17.
Is switched to the second speed position on the right side of the drawing. In this state, as shown in FIG. 1, the motor selection switching valve 16 is at the second motor position, and the pilot chambers 11a and 11b of the on / off valves 9a and 9b remain in communication with the tank. Therefore, the discharge oil of the variable displacement pump 1 is guided to both the first and second hydraulic motors 3, 4. However,
Since the first- and second-speed selection switching valve 17 is switched to the second-speed position on the right side of the drawing as described above, the discharge oil of the charge pump 14 is guided to the bottom chamber of the cylinder 12,
2 operates to reduce the tilt angles of the first and second hydraulic motors 3 and 4. Therefore, the first and second hydraulic motors 3 and 4 enter the second speed state, and the first and second hydraulic motors 3 and 4
No. 4 tries to rotate at high speed with low torque. This is 2
In the second motor state, the first and second hydraulic motors 3, 4
As compared with the two-motor first-speed state, the motor rotates at a high torque with a low torque.

From any of the above states, the operation lever 1
Suppose that the motor selection switch valve 16 is switched to the forward one motor position on the left side of the drawing by moving the gears 8 and 19, and the 1.2 / speed selection switching valve 17 is switched to the second speed position on the right side of the drawing. In the one-motor two-speed state, the discharge oil of the variable displacement pump 1 is guided only to the first hydraulic motor 3, and
The second speed state is established in which the tilt angle of the first hydraulic motor 3 becomes small. Therefore, only the first hydraulic motor 3 rotates at a higher torque with a lower torque than any of the above states.

The above description has been made on the assumption that the tilt angle of the variable displacement pump 1 is at a certain angle.
Of course, in any of the above states, the variable displacement pump 1
, The speed can be controlled within the range of the state. For example, if the discharge amount of the variable displacement pump 1 is changed in the two-motor first-speed state, it is possible to control the speed in a range where the rotation is high and the rotation is low.

When the vehicle travels in the reverse direction, similarly to the case in which the vehicle travels in the forward direction, the state of one motor or two motors is set.
And a first-speed state or a second-speed state can be selected. However, when selecting the one-motor state or the two-motor state, since the variable displacement pump 1 discharges the operating oil to the reverse traveling line 5, the on / off valve on the port 4b side which is the suction side of the second hydraulic motor 4 is provided. 9b is switched.

In the first embodiment, the ports 4a, 4b of the second hydraulic motor 4 are shut off from the variable displacement pump 1 via the throttles 20a, 20b at the shut-off positions of the on / off valves 9a, 9b. are doing. However, the on / off valves 9a and 9b shut off only the high pressure side port 4a or 4b of the second hydraulic motor 4 and do not shut off the low pressure side port 4b or 4a.
Is maintained at a low pressure. Therefore, the aperture 20a,
Even if there is no 20b, no burning occurs, and these throttles 20a, 20b are eliminated, and the on / off valve 9a,
It is also possible to completely shut off at the shut-off position 9b.

In the second embodiment shown in FIG. 3, the switching valve 16 for selecting the motor and the switching valve 17 for selecting the first and second speeds are not switched by operating levers 18 and 19 as in the first embodiment. The switching is performed by the solenoids 21a and 21b and the solenoid 21. For example,
To switch the motor selection switching valve 16 to the forward one motor position on the left side of the drawing, the switch 22a is turned on to excite the solenoid 21a. Conversely, when switching to the reverse 1 motor position on the right side of the drawing, switch 2
The solenoid 2b may be turned on to excite the solenoid 21b. Similarly, when the first / second speed selection switching valve 17 is switched to the second speed position on the right side of the drawing, the switch 22 may be turned on to excite the solenoid 21.

In the third embodiment shown in FIG. 4, the on / off valves 9a and 9b are directly switched by solenoids 23a and 23b instead of the pressure action as in the first and second embodiments. It is. Of course, when the vehicle travels forward, only the on / off valve 9a is switched, and the on / off valve 9b is not switched.
Similarly, when the vehicle travels backward, the on-off valve 9
Only the b is switched, and the on / off valve 9a is not switched. For example, the forward / backward traveling of the vehicle is distinguished by feeding back the tilt angle of the variable displacement pump 1, and when the vehicle travels forward, the on / off valve 9b is not switched and the vehicle travels backward. When traveling, control may be performed so that the on / off valve 9a is not switched.

The fourth embodiment shown in FIG. 5 does not use two on / off valves 9a and 9b as in the first embodiment, but uses a single on / off valve 9 that combines them. In its normal state, the on / off valve 9 connects the ports 4a, 4b of the second hydraulic motor 4 to the variable displacement pump 1 side, respectively. And solenoid 2
When exciting 3a and switching to the forward position on the upper side of the drawing,
While the port 4b is in communication with the variable displacement pump 1, the port 4a is shut off from the variable displacement pump 1. Also,
When the solenoid 23b is excited to switch to the reverse position on the lower side of the drawing, the port 4b is cut off from the variable displacement pump 1 while the port 4a is connected to the variable displacement pump 1 side. Also in this case, the forward / backward traveling of the vehicle is distinguished by feeding back the tilt angle of the variable displacement pump 1 and the on / off valve 9 is switched to only the forward position when the vehicle travels forward. When the vehicle travels backward, it is desirable that the setting be made so that the vehicle is switched to only the reverse position.

[0028]

According to the present invention, not only can the tilt angle of the variable displacement pump be changed, but also the hydraulic motor can be operated in one-motor one-speed state, one-motor two-speed state, two-motor one-speed state, and two-motor two-speed state.
By changing to the high speed state, the output of the hydraulic motor in the high torque or low torque range can be controlled.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a hydrostatic transmission device according to a first embodiment.

FIG. 2 is a diagram simply showing the structure of first and second hydraulic motors 3 and 4;

FIG. 3 is a circuit diagram showing a hydrostatic transmission device according to a second embodiment.

FIG. 4 is a circuit diagram showing a hydrostatic transmission device according to a third embodiment.

FIG. 5 is a circuit diagram showing a hydrostatic transmission device according to a fourth embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Variable displacement pump 1a, 1b Port 2 Forward traveling line 3 First hydraulic motor 4 Second hydraulic motor 3a, 4a One port 3b, 4b The other port 5 Reverse traveling line 9, 9a, 9b On-off valve 12 Cylinder 16 Motor Switching valve for selection 17 Switching valve for 1-2 speed selection 24 Swash plate

Claims (2)

[Claims] 1. A variable displacement pump which is linked to a power source rotating in one direction and changes a discharge amount and a discharge direction according to the inclination of a swash plate. A first fluid pressure motor capable of setting two types of large and small capacities in accordance with the flow rate and a flow in both directions. 2nd that can set two small capacities
Connect the fluid pressure motor and one port of the variable displacement pump to
A forward traveling line connected in parallel to one port of the first and second hydraulic motors, and a reverse traveling line connected in parallel to the other port of the variable displacement pump to the other port of the first and second hydraulic motors. And an on / off valve provided on both ports of the second fluid pressure motor and an on / off valve, so that the low pressure side port of the second fluid pressure motor is connected to the variable displacement pump side while the high pressure side is connected. The first and second fluids are moved by moving a swash plate of the first and second fluid pressure motors and a motor selection mechanism for communicating the port with the variable displacement pump side or cutting off the communication. A hydrostatic transmission device comprising: a first and second speed selection mechanism for selecting a capacity of a pressure motor. 2. The first / second speed selecting mechanism includes a cylinder linked to a swash plate of the first and second fluid pressure motors, and a cylinder which guides pressure to the cylinder and connects the cylinder to a tank. When the cylinder communicates with the tank, the capacity of the first and second fluid pressure motors is maintained at one of large and small. 2. The hydrostatic transmission device according to claim 1, wherein the swash plate of the two-fluid pressure motor is moved so that the capacity thereof is either large or small.