JP2000110937A - Hydrostatic transmission device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydrostatic transmission device capable of controlling the output of a hydraulic motor in a high torque range or a low torque range through automatic control of the hydraulic motor side. SOLUTION: A hydrostatic transmission device is equipped with on-off valves 15 and 16 to turn on and off a second hydraulic motor 4 from the side with a variable displacement pump 1 in accordance with the pressures in a forward 2 and a reverse running line 5, a selector valve 21 to put the ports 4a and 4b of the second hydraulic motor 4 in communication with the side with a charge pump 19 when the valves 15 and 16 are in shut-off position and shut off the ports 4a and 4b from the side with the charge pump 19 when the valves 15 and 16 are in communicating position, and first - second range selecting mechanisms 10 and 12 to select the first - second range situation of the first and second hydraulic motors 3 and 4 in accordance with the pressures in the forward 2 and reverse running lines 5.

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 automatically control the hydraulic motor side and control the output of the hydraulic motor in a high torque or low torque range.

[0005]

A first aspect of the present invention relates to a hydrostatic transmission device, which is linked to a power source which rotates in one direction, and which changes a discharge amount and a discharge direction according to a tilt of a swash plate. Type fluid pump, a first fluid pressure motor that allows flow in both directions and can set two types of large and small displacements according to the inclination of the swash plate, and a first fluid pressure motor that allows flow in both directions. Linked to the same swash plate, and large / small 2 depending on the inclination of the swash plate.
A second fluid pressure motor capable of setting different types of displacements, 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 Port is connected in parallel to the other port of the first and second hydraulic motors, and a closed circuit comprising the variable displacement pump, the first and second hydraulic motors, and the forward and backward traveling lines. The second fluid pressure motor is variable when the pressure of the charge pump that supplies the hydraulic oil and the line of the forward traveling line or the reverse traveling line on which the variable displacement pump discharges the hydraulic oil is lower than the on / off set pressure. The on-off position at the shut-off position for shutting off from the displacement side pump, and the on-off position at the communication position for communicating the second fluid pressure motor to the variable displacement side when the pressure of the line exceeds the on / off set pressure. When the valve and the on-off valve are in the shut-off position, each port of the second hydraulic motor is in a communication position communicating with the charge pump side, and when the on-off valve is in the communication position, each port of the second hydraulic motor is connected. The pressure of the switching valve at the shut-off position for shutting off from the charge pump side and the pressure of the line on the side on which the variable displacement pump discharges hydraulic oil out of the forward traveling line or the reverse traveling line is lower than the first and second speed selection set pressure. Sometimes the first and second
By controlling the tilt angle of the fluid pressure motor, the first and second fluid pressure motors are set to the second speed state with a small capacity, and when the pressure of the line exceeds the set pressure for selecting the first and second speeds, the first , Second
The present invention is characterized in that a first- and second-speed selection mechanism is provided for controlling the tilt angle of the fluid pressure motor to set the first and second fluid pressure motors to the first speed state having a large capacity.

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 hydraulic motors, and a first- and second-speed selection switching valve for guiding pilot pressure to the cylinder and connecting the cylinder to a tank. When the pressure of the line on the side from which the variable displacement pump discharges the hydraulic oil in the forward traveling line or the reverse traveling line is lower than the first- or second-speed selection set pressure, the first- or second-speed selection switching valve is: The cylinder is connected to the tank, and the first and second fluid pressure motors
When the line pressure exceeds the set pressure for selecting the first and second speeds, the switching valve for selecting the first and second speeds guides the pilot pressure to the cylinder to increase the capacity of the first and second fluid pressure motors. The feature is that the first speed state with a large capacity is configured.

[0007]

1 and 2 show an 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 first and second hydraulic motors 3, 4
Are connected in parallel to one of the ports 3a, 4a. Also,
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 traveling line 5.
Therefore, the variable displacement pump 1, the first and second hydraulic motors 3, 4, and the forward and backward traveling lines 2, 5 constitute 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 and 4 are rotated 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 are rotated 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. The one-cylinder block type hydraulic motor is simply shown in FIG. 2. In one cylinder block 6, a first plunger group 7 forming the first hydraulic motor 3 and a second plunger forming the second hydraulic motor 4 are formed. Two plunger groups 8 are incorporated on a concentric circle. Then, the first and second plunger groups 7 and 8 are linked to the same swash plate 9, and the first and second plunger groups 7 and 8 are reciprocated along the swash plate 9, whereby the motors are respectively driven. It works.

In the first and second hydraulic motors 3 and 4, the inclination of the swash plate 9 associated with the first and second plunger groups 7 and 8 is changed in two stages, so that the capacity is large and small. Can be set to. In the first speed state in which the tilt angles of the first and second hydraulic motors 3 and 4 are increased, the capacities of the first and second hydraulic motors 3 and 4 increase, and the motors rotate at high torque and at low speed. On the other hand, in the second speed state where the tilt angle is reduced, the first,
The capacity of the second hydraulic motors 3, 4 is reduced, and the motors are rotated at high speed with low torque.

As shown in FIG. 1, the swash plate 9 of the first and second hydraulic motors 3, 4 is linked to a cylinder 10 to control the tilt angle. That is,
When the bottom chamber of the cylinder 10 is at the tank pressure, the tilt angle is kept large by the spring 11, and the first and second hydraulic motors 3, 4 are maintained in the above-mentioned first speed state. On the other hand, when the pilot pressure is guided to the bottom chamber of the cylinder 10, the cylinder 10 operates against the spring 11 to reduce the tilt angle, thereby reducing the first and second cylinders.
The hydraulic motors 3 and 4 are set to the above-described second speed state.

The pressure in the bottom chamber of the cylinder 10 is controlled by the first / second speed selection switching valve 12. The first / second speed selection switching valve 12 is in the second speed position in a normal state maintained by the spring 13, and the pressure of the forward travel line 2 and the reverse travel line 5 is supplied to the bottom chamber of the cylinder 10 by the shuttle valve 14. High pressure select and guide. Further, the switching valve 12 for selecting the first and second speeds is used.
The pressure of the forward travel line 2 is guided to one pilot chamber 12a, and the pressure of the reverse travel line 5 is guided to the other pilot chamber 12b. When the pressure of the line on the side from which the variable displacement pump 1 discharges the hydraulic oil in the forward traveling line 2 or the reverse traveling line 5 reaches the set pressure for selecting the first and second speeds, this first and second speed selection is performed. The switching valve 12 is switched to the first speed position so that the bottom chamber of the cylinder 10 communicates with the tank.

On the other hand, among the first and second hydraulic motors 3 and 4, ports 4a and 4b of the second hydraulic motor 4
As shown in the figure, on / off valves 15 and 16 are provided. The on-off valves 15 and 16 are provided with springs 17 and 1
8 is in the shut-off position in the normal state maintained by. When in the shut-off position, the discharge oil of the variable displacement pump 1 is not guided at all to the second hydraulic motor 4, but is entirely guided to the first hydraulic motor 3 side.

The pressure of the forward traveling line 2 is guided to the pilot chambers 15a and 16a of the on / off valves 15 and 16, and the reverse traveling line is supplied to the pilot chambers 15b and 16b independent of the pilot chambers 15a and 16a. 5 pressure. When the pressure of the line on the side on which the variable displacement pump 1 discharges the hydraulic oil in the forward travel line 2 or the reverse travel line 5 reaches the on / off set pressure, the on / off valves 15 and 16 are brought to the communicating position. The switching is performed so that the second hydraulic motor 4 communicates with the variable displacement pump 1.

Here, a charge pump 19 is connected to the variable displacement pump 1. Therefore, the charge pump 19 rotates together with the variable displacement pump 1 by the driving force of the engine E, and discharges a fixed amount of hydraulic oil. Generally, in a hydrostatic transmission device, since hydraulic oil is circulated through a closed circuit, a problem such as heat generation occurs. Then, in order to avoid such a problem, a charge pump 19 is provided, and the discharge oil is supplied to the closed circuit via the check valves 20a and 20b. Although not specifically shown,
The same amount of hydraulic oil as supplied from the charge pump 19 is returned from the closed circuit to the tank.

In this embodiment, the ports 4a and 4b of the second hydraulic motor 4 are connected to the charge pump 19 via the switching valve 21, specifically, the check valve 20.
a and 20b. The switching valve 21 is in a communication state where the ports 4 a and 4 b of the second hydraulic motor 4 communicate with the charge pump 19 in a normal state maintained by the spring 22. The switching valve 21
The pressure of the forward traveling line 2 is guided to one pilot room 21a, and the pressure of the reverse traveling line 5 is guided to the other pilot room 21b. When the pressure of the line on the side on which the variable displacement pump 1 discharges the hydraulic oil in the forward traveling line 2 or the reverse traveling line 5 reaches the above-described on / off set pressure, the switching valve 21 is turned off. To the ports 4a, 4a of the second hydraulic motor 4.
b is cut off from the charge pump 19 side.

Next, the operation of the hydrostatic transmission device of the above embodiment will be described. In a working vehicle such as a load roller, when the rotation speed of the engine E is kept constant and the vehicle speed is changed, an operation lever (not shown) is moved to operate the swash plate of the variable displacement pump 1. Hereinafter, a case where the vehicle travels forward, that is, a situation where the swash plate of the variable displacement pump 1 is tilted in the forward travel range of the vehicle will be described. In the forward traveling range of the vehicle, the variable displacement pump 1 discharges hydraulic oil to the forward traveling line 2 as described above.

When the vehicle starts to move, the load is large and the pressure of the forward traveling line 2 is high. In this state, the pressure of the forward traveling line 2 is
a, 16a, the on / off valves 15, 16
The second hydraulic motor 4 is switched to a communication position where the second hydraulic motor 4 communicates with the variable displacement pump 1. Therefore, the discharge oil of the variable displacement pump 1 is guided to both the first and second hydraulic motors 3, 4. Further, the pressure of the forward traveling line 2 is
Guided by a, the switching valve 21 switches to the shut-off position.
Therefore, the discharge oil of the charge pump 19 is not guided to the second hydraulic motor 4 side.

On the other hand, the pressure of the forward traveling line 2 is led to the pilot chamber 12a, and the first and second speed selection switching valve 12 is selected.
Is switched to the first speed position, and the bottom chamber of the cylinder 10 communicates with the tank. When the bottom chamber of the cylinder 10 communicates with the tank, the tilt angle is kept large by the spring 11, and the first and second hydraulic motors 3 and 4 are in the first speed state, and try to rotate at high torque and low speed. I do. As described above, when the pressure of the forward traveling line 2 is high, that is, when a torque is required, the second motor is in the first speed state, and the first and second hydraulic motors 3 and 4 are rotated at a high torque and a low rotation speed. Can be done.

When the vehicle starts running from the two-motor first-speed state, the pressure of the forward running line 2 slightly decreases. Then, when the pressure of the forward traveling line 2 becomes lower than the set pressure for on / off, the on / off valves 15, 16 return to the shut-off position by the springs 17, 18. Therefore,
All of the discharge oil of the variable displacement pump 1 will be guided to the first hydraulic motor 3 side, and the flow rate will increase.
The first hydraulic motor 3 attempts to rotate at that high speed. Also, when the pressure of the forward traveling line 2 becomes lower than the set pressure for on / off, the switching valve 21 is returned to the communication position by the spring 22 almost at the same time. Therefore, the second hydraulic motor 4 rotates idly while circulating the discharge oil of the charge pump 19, and can prevent burning.

However, at this ON / OFF set pressure, 1 ·
The second speed selection switching valve 12 maintains the first speed position, and communicates the bottom chamber of the cylinder 10 with the tank. Therefore, the tilt angle is kept large by the spring 11, and the first and second hydraulic motors 3, 4 try to rotate at a high torque and a low speed in the first speed state. In the one-motor one-speed state, only the first hydraulic motor 3 can be rotated at a high speed with a low torque compared to the two-motor one-speed state.

As the speed of the vehicle increases from the one-motor one-speed state, the pressure of the forward traveling line 2 further decreases. When the pressure of the forward traveling line 2 becomes lower than the set pressure for selecting the first and second speeds, the ON / OFF valves 15, 16 and the switching valve 21 are not only in the shut-off position and the communication position, but also for the first and second speed selection. The valve 12 also returns to the second speed position. Accordingly, the pressure of the forward traveling line 2 is selected and guided to the bottom chamber of the cylinder 10 at a high pressure, and the cylinder 10 reduces the tilt angles of the first and second hydraulic motors 3 and 4. Then, when the tilt angles of the first and second hydraulic motors 3 and 4 become small, the first and second hydraulic motors 3 and 4 enter the second speed state and try to rotate at high speed with low torque. 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 first and second hydraulic motors 3, 4 are in the second-speed state. Therefore, only the first hydraulic motor 3 can be rotated at a higher speed with a lower torque as compared with the one-motor one-speed state.

Similarly, when the vehicle travels backward, the 1-motor state or 2-motor state, and the 1st-speed state or 2nd-speed state are automatically selected according to the pressure of the reverse traveling line 5 in the same manner. It has become. In this embodiment, the on-off valves 15 and 16 and the switching valve 2 are used while the pressure of the forward traveling line 2 is decreasing.
After switching 1 to the shut-off position and the communication position,
The second speed selection switching valve 12 is switched to the second speed position. That is, the set pressure for on / off is set higher than the set pressure for first and second speed selection. However, on the contrary, the first and second speed selection switching valve 12 may be switched to the second speed position, and then the on / off valves 15, 16 and the switching valve 21 may be switched to the shut-off position and the communication position, respectively. That is, the first and second speed selection set pressure may be set higher than the on / off set pressure.

In the above embodiment, the on / off valves 15, 1
6 and the switching valve 21, and the switching valve 1 for selecting the first and second speeds
2 is switched by the pressure action of the traveling lines 2 and 5, it may be switched electrically. That is,
Although not specifically shown, pressure sensors are provided on the traveling lines 2 and 5, and based on the pressure detected by the pressure sensors,
What is necessary is just to make the controller switch the on / off valves 15, 16 and the switching valve 21, and the switching valve 12 for selecting the first and second speeds. In the above embodiment, the cylinder 1
Although the pressure of the traveling lines 2 and 5 is introduced as pilot pressure to the bottom side chamber of 0, other pressures may be introduced. For example, the charge pump 19 may be used as a pilot pressure source.

[0025]

According to the present invention, not only the tilt angle of the variable displacement pump is changed, but also the one-motor state, the two-motor state, and the one-speed state according to the pressure of the forward traveling line or the reverse traveling line. Alternatively, the output of the fluid pressure motor in the high torque or low torque range can be controlled by automatically selecting the second speed state. Further, when only the first fluid pressure motor is in the one-motor state in which the driving force is exerted, each port of the second fluid pressure motor can be connected to the charge pump side. Therefore, the second fluid pressure motor idles while circulating the discharge oil of the charge pump, thereby preventing burning.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a hydrostatic transmission device according to an embodiment of the present invention.

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

[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 (First, second hydraulic motor 3, 4)
Swash plate 10 Cylinder 12 Switching valve for selecting 1st and 2nd speed 15, 16 On / off valve 19 Charge pump 21 Switching valve

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 the variable displacement pump,
A charge pump for supplying hydraulic oil to a closed circuit comprising a second fluid pressure motor and a forward / backward traveling line; and a pressure of a line of the forward traveling line or the backward traveling line on which the variable displacement pump discharges hydraulic oil. When the pressure is lower than the on / off set pressure, the second hydraulic motor is in the shut-off position for shutting off the second hydraulic motor from the variable displacement pump side. When the on / off valve is in the communication position communicating with the side pump side and the on / off valve is in the shut-off position, each port of the second hydraulic motor is in the communication position communicating with the charge pump side, and the on / off valve is in the communication position. When the second
A switching valve at a shut-off position for shutting off each port of the fluid pressure motor from the charge pump side, and a pressure of a line of the forward traveling line or the reverse traveling line on which the variable displacement pump discharges hydraulic oil is 1.2. When the pressure is lower than the speed selection set pressure, the tilt angles of the first and second fluid pressure motors are controlled to bring the first and second fluid pressure motors into the second speed state with a small capacity. When the set pressure for selecting the second speed is exceeded, the tilt angles of the first and second fluid pressure motors are controlled to bring the first and second fluid pressure motors into the first speed state having a large capacity. A hydrostatic transmission device comprising a speed selection mechanism. 2. The 1.2 speed selecting mechanism includes a cylinder connected to a swash plate of the first and second hydraulic motors, and a pilot gear that guides pilot pressure to the cylinder and connects the cylinder to a tank. A switching valve for speed selection, and when the pressure of the line on the side on which the variable displacement pump discharges hydraulic oil in the forward travel line or the reverse travel line is lower than the 1.2-speed selection set pressure, 1.2 Switching valve for speed selection
The cylinder is communicated with the tank, and the first and second fluid pressure motors are set in the second speed state having a small capacity.
When the set pressure for selecting the second speed is exceeded, the switching valve for selecting the first and second speeds is configured to guide the pilot pressure to the cylinder to set the capacity of the first and second fluid pressure motors to the first speed state where the capacity is large. The hydrostatic transmission device according to claim 1, wherein: