JP2519147Y2 - Hydraulic circuit for traveling - Google Patents

Description

TECHNICAL FIELD The present invention relates to a hydraulic circuit used when a crawler vehicle or the like is driven and driven.

2. Description of the Related Art Generally, in a crawler vehicle or the like, when a load acting on the crawler vehicle is small, for example, traveling at a high speed when traveling on a flat surface, and when the load is large, for example, traveling at a low speed during traveling on an uphill road. There is.

Conventionally, in order to drive the vehicle at such high and low speeds, for example, as described in Japanese Patent Laid-Open No. 48-039868, a variable displacement hydraulic engine is used as a vehicle driving motor and a pilot engine is used. A pilot valve that opens and closes by pressure is installed in the middle, and a high-pressure passage that guides the high-pressure fluid in the high-pressure side supply / discharge passage taken out by a pair of check valves to the piston cylinder that changes the capacity of the hydraulic engine is provided. Things are known. When the pilot pressure is less than the predetermined pressure, the pilot valve is open, so that the high-pressure fluid is guided to the piston-cylinder and the hydraulic prime mover rotates at a high speed with a small torque. If the pressure rises above the pressure, the pilot valve will close and high-pressure fluid will not be guided to the piston-cylinder.
The hydraulic prime mover rotates at a low speed and a large torque so that the two-stage switching is performed. However, the one described in the above-mentioned publication is for a closed circuit, but if this is applied to an open circuit, a switching valve for switching the flow direction in the supply / discharge passage and this switching valve and a hydraulic engine are provided. A counter balance valve provided in the supply / discharge passage between the two is required.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention Here, as such a counterbalance valve, for example, as described in JP-A-57-110856,
It is also possible to use a counterbalance valve having a high-pressure port to selectively take out high-pressure oil, and to guide the high-pressure oil taken out from this high-pressure port as pilot pressure to the pilot valve described above to open and close the pilot valve. It is conceivable, however, that in the circuit combining these two publications, the special pipe extending from the supply / discharge passage to the pair of check valves and the fluid supplied to the piston cylinder are selected from the supply / discharge passage. There is a problem in that an extra pair of check valves to be taken out is required, the circuit becomes complicated and large, and the cost becomes high.

An object of the present invention is to provide a traveling hydraulic circuit having a simple structure, a small size, and a low cost.

Means for Solving the Problems An object of the present invention is to provide a variable displacement hydraulic motor that applies traveling driving force to a vehicle, a switching valve that switches the flow direction of pressure oil supplied to and discharged from the hydraulic motor, and a switching valve. When connecting to a hydraulic motor and the load acting on the hydraulic motor exceeds a certain value, the internal pressure on the high pressure side rises above a predetermined pressure With a check valve that allows only the flow of pressure oil to go,
A counterbalance valve having a high-pressure port for selecting and extracting high-pressure oil from the supply / discharge passage on the switching valve side of the check valve, and a high-pressure oil connected to the high-pressure port of the counterbalance valve to guide the high-pressure oil extracted to the high-pressure port. The high pressure passage, the speed switching valve interposed in the middle of the high pressure passage, the high pressure passage between the high pressure port and the speed switching valve, and the speed control valve are connected to each other, and the high pressure oil introduced from the high pressure passage is less than a predetermined pressure. And a pilot passage for switching the speed switching valve to the first position when the high pressure oil is above a predetermined pressure,
When the speed switching valve is connected to the high pressure passage and the speed switching valve is located at the first position, the displacement of the hydraulic motor is reduced to rotate the hydraulic motor at high speed with a small torque, while the speed switching valve is moved to the second position.
It can be achieved by providing an actuator that increases the displacement of the hydraulic motor when it is located in the position to rotate the hydraulic motor at a low speed and a large torque.

Action It is assumed that the vehicle is traveling with a light load, for example, traveling on a level ground. At this time, since the load acting on the hydraulic motor is less than a certain value, the internal pressure of the high pressure side supply / discharge passage located on the switching valve side of the check valve of the counterbalance valve is less than the predetermined pressure. Then, the high-pressure oil having a pressure less than the predetermined pressure is selected by the counter balance valve and taken out to the high-pressure port, then guided to the speed switching valve through the high-pressure passage and the pilot passage, and switches the speed switching valve to the first position. As a result, for example, high-pressure oil below a predetermined pressure is guided to the actuator through the high-pressure passage, and the actuator is operated to reduce the capacity of the hydraulic motor to rotate the hydraulic motor at high speed and small torque. Next, when a heavy load is applied to the running vehicle, for example, by climbing a hill, and the load applied to the hydraulic motor exceeds a certain value, the internal pressure of the high pressure side supply / discharge passage rises above a predetermined pressure. Therefore, the pilot pressure taken out from the high pressure port of the counter balance valve and guided to the speed switching valve also becomes equal to or higher than the predetermined pressure, and the speed switching valve switches to the second position. As a result, the actuator operates so as to increase the displacement of the hydraulic motor, and causes the hydraulic motor to rotate at a low speed and a large torque. In this way, the capacity of the hydraulic motor is changed according to the change in the internal pressure of the supply / discharge passage based on the load change of the hydraulic motor, and the rotational speed of the hydraulic motor is switched between the high and low stages. Here, pilot pressure (fluid) for switching the speed switching valve
Since both of the fluid for operating the actuator and the fluid for operating the actuator use the pressure oil extracted from the high pressure port of the existing counterbalance valve, no special piping or check valve is required and the structure is simple and compact. It can be made inexpensive.

Further, according to the second aspect of the invention, it is possible to eliminate the need for a special high pressure selection valve for negative brake and piping, and to further simplify and downsize the structure.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, reference numeral 1 denotes a variable displacement type hydraulic motor for applying a traveling driving force to a crawler vehicle, for example, a swash plate type hydraulic motor. The hydraulic motor 1 has a variable capacity that changes the displacement of the hydraulic motor 1 by changing its position. It has a member 2, for example a swash plate. A switching valve 3 is connected to the pump 4 and the tank 5, and the switching valve 3 switches the flow direction of the pressure oil supplied to and discharged from the hydraulic motor 1. The hydraulic motor 1 and the switching valve 3 are connected by a pair of supply / discharge passages 8 and 9, and the supply / discharge passages 8 and 9 on the high-pressure side communicating with the pump 4 among the supply / discharge passages 8 and 9 are When a heavy load is applied to the crawler vehicle, for example, by climbing uphill, and as a result, a load of a certain value or more is applied to the hydraulic motor 1, the internal pressure thereof rises to a predetermined value or more. From the switching valve 3 to the hydraulic motor 1 in the supply / discharge passages 8 and 9.
A counterbalance valve 12 including check valves 10 and 11 that allow only the flow of pressure oil toward the valve is interposed. The counterbalance valve 12 has a high-pressure port 13 at which the spool 14 of the counterbalance valve 12 is displaced from the neutral position A, for example, the first position B or the second position B.
When in position C, high-pressure oil is selected and taken out from the supply / discharge passages 8, 9 on the high-pressure side of the supply / discharge passages 8, 9 on the switching valve 3 side of the check valves 10, 11. Reference numeral 16 is a speed switching valve interposed in the middle of a high pressure passage 17 connected to the high pressure port 13, and the high pressure passage 17 guides the high pressure oil taken out from the high pressure port 13 to a cylinder described later. One end of 18 is in the middle of the high pressure passage 17 between the high pressure port 13 and the speed switching valve 16 and the other end is the speed switching valve.
This is a pilot passage connected to 16, and the pilot passage 18 guides the high-pressure oil taken out from the high-pressure port 13 to the high-pressure passage 17 to the speed switching valve 16 as a pilot pressure.
When the pilot pressure guided from the high pressure passage 17 is less than a predetermined pressure, the total force of the pressing force by the pilot pressure and the urging force by the spring 19 is smaller than the pressing force by the pressure oil in the control passage 20, The speed switching valve 16 is switched to a first position D, which is an open position in this embodiment. On the other hand, when the pilot pressure becomes equal to or higher than the predetermined pressure, the total force becomes larger than the pressing force by the pressure oil in the control passage 20, and the speed switching valve 16 is switched to the second position E, which is the closed position in this embodiment. . Reference numeral 26 is a cylinder as an actuator in which the piston rod 27 is connected to the variable capacity member 2, and the cylinder 26 is connected to the high pressure passage 17. The cylinder 26 is provided with the counter balance valve 12 when the speed switching valve 16 is located at the first position D (when it is open).
Since the high-pressure oil extracted from the inflows, the variable volume member 2
Is displaced to reduce the capacity of the hydraulic motor 1, and the hydraulic motor 1 is rotated at a high speed with a small torque. On the other hand, when the speed switching valve 16 is located in the second position E (closed), the high pressure oil taken out from the counter balance valve 12 does not flow into the cylinder 26, so that the variable capacity member 2
Has a structure in which the cylinder 26 is displaced while being pressed by a spring force or the like acting on the cylinder 26 to increase the capacity of the hydraulic motor 1 and rotate the hydraulic motor 1 at a low speed and a large torque. Reference numeral 31 is a negative brake attached to the rotary shaft of the hydraulic motor 1. The negative brake 31 releases the brake for the hydraulic motor 1 when high pressure oil is supplied to the brake chamber 32, while the negative brake 31 is released. When the high-pressure oil is no longer supplied to 32, the spring 33 applies a brake to the hydraulic motor 1. One end of 34 is connected to the high pressure passage 17 between the high pressure port 13 and the speed switching valve 16, and the other end thereof is the brake chamber 32 of the negative brake 31.
Is a brake passage connected to the brake passage 34.
A control valve 35 is interposed in the middle of the. The control valve 35 is opened when high-pressure oil is flowing in either the supply / discharge passages 8 or 9, and the high-pressure oil taken out from the high-pressure port 13 of the counterbalance valve 12 is passed through the brake passage 34 to the brake chamber. On the other hand, when both the supply and discharge passages 8 and 9 have the tank pressure, the pressure is closed and the pressure oil in the brake chamber 32 is discharged to the tank 5. Here, as described above, the negative brake 31 that releases the brake to the hydraulic motor 1 when the high pressure oil is supplied is provided, and the high pressure oil taken out from the high pressure port 13 of the counter balance valve 12 is provided to the negative brake 31. If the brake passage 34 for guiding is provided, a special high-pressure selection valve and piping for the negative brake 31 can be dispensed with, and the structure can be simplified and downsized.

 Next, the operation of the embodiment of the present invention will be described.

Now, it is assumed that the switching valve 3 is located at the neutral position J and the crawler vehicle is stopped. At this time, the counter balance valve
The spool 14 of 12 is located in the neutral position A, and the speed switching valve
16 is in the first position D, and the control valve 35 is in the closed position F. As a result, the hydraulic motor 1 stops rotating and the negative brake 31 applies a brake.

Next, when the switching valve 3 is switched to the parallel flow position K, for example,
The high-pressure oil discharged from the pump 4 is supplied to the hydraulic motor 1 through the supply / discharge passage 8, rotates the hydraulic motor 1, and the pressure oil flowing out of the hydraulic motor 1 is discharged to the tank 5 through the supply / discharge passage 9. . At this time, the spool 14 of the counterbalance valve 12 is switched to the first position B, the high pressure oil in the supply / discharge passage 8 located closer to the switching valve 3 than the check valve 10 is selected, and the high pressure port 13 of the counterbalance valve 12 is selected. Taken out. The high pressure oil taken out to the high pressure port 13 switches the control valve 35 to the open position G, and then the negative brake 31
Of the negative brake 31, the negative brake 31 is released from the brake chamber 32, and is guided to the speed switching valve 16 through the high pressure passage 17. At this time, the crawler vehicle travels on a flat ground and only a light load acts on the crawler vehicle.
The load acting on the hydraulic motor 1 is less than a certain value, and as a result, the internal pressure of the high pressure side supply / discharge passage 8 located closer to the switching valve 3 than the check valve 10 is less than a predetermined pressure. Therefore,
Speed switching valve 16 from high pressure passage 17 through pilot passage 18
Also, the pilot pressure guided to becomes less than the predetermined pressure, and the speed switching valve 16 switches to the first position D. As a result, the high-pressure oil in the high-pressure passage 17 that is less than the predetermined pressure is supplied into the cylinder 26 to project the piston rod 27 and displace the displacement variable member 2 of the hydraulic motor 1 so that the displacement of the hydraulic motor 1 becomes smaller. As a result, the hydraulic motor 1 rotates at a high speed and a small torque suitable for running on level ground.

Next, for example, when the crawler vehicle that is running starts climbing a hill and a heavy load acts on the crawler vehicle, and the load acting on the hydraulic motor 1 increases to a certain value or more,
The internal pressure of the supply / discharge passage 8 on the high pressure side rises above a predetermined pressure. As a result, the pilot pressure acting on the speed switching valve 16 through the pilot passage 18 also becomes equal to or higher than the predetermined pressure. At this time, the total force of the pressing force of the pressure oil equal to or higher than the predetermined pressure and the urging force of the spring 19 is the control passage. Since the pressing force due to the pressure oil in 20 becomes greater, the speed switching valve 16 is set to the first position D.
To the second position E. As a result, the speed switching valve 16 is closed and the high pressure oil is not supplied to the cylinder 26, and the pressure oil in the cylinder 26 is discharged to the tank 5.
Cylinder 26 becomes the tank pressure. This allows the cylinder 26
The piston rod 27 of is retracted and the variable capacity member 2
Is displaced so as to increase the capacity of the hydraulic motor 1. As a result, the hydraulic motor 1 rotates at a low speed and large torque suitable for climbing a slope. As described above, in this embodiment, the capacity of the hydraulic motor 1 is changed in accordance with the change in the internal pressure of the supply / discharge passage 8 based on the load change of the hydraulic motor 1.
The rotation speed of is switched between high and low stages suitable for the magnitude of load, that is, high speed rotation for light loads and low speed rotation for heavy loads. And in this example,
Since both the pilot pressure (fluid) for switching the speed switching valve 16 and the fluid for operating the cylinder 26 use the pressure oil extracted from the high pressure port 13 of the existing counterbalance valve 12, No special piping or check valve is required, the structure can be simplified and downsized, and the manufacturing cost can be reduced.

As described above, according to the present invention, both the pilot pressure (fluid) guided to the speed switching valve and the fluid for operating the actuator are pressurized oil extracted from the high pressure port of the existing counterbalance valve. Since no special piping or check valve is required, the structure can be simplified and downsized, and the cost can be reduced.

[Brief description of drawings]

FIG. 1 is an overall rotation diagram showing an embodiment of the present invention. 1 ... hydraulic motor, 3 ... switching valve 8,9 ... supply / discharge passage, 12 ... counter balance valve 13 ... high pressure port, 16 ... speed switching valve 17 ... high pressure passage, 18 ... pilot passage 26 ...... Actuator

Claims (2)

(57) [Scope of utility model registration request] 1. A variable displacement hydraulic motor for applying a driving force to a vehicle, a switching valve for switching a flow direction of pressure oil supplied to and discharged from the hydraulic motor, and the switching valve and the hydraulic motor are connected to each other.
When the load acting on the hydraulic motor exceeds a certain value, the internal pressure on the high-pressure side rises above a predetermined pressure, and only the flow of pressure oil from the switching valve to the hydraulic motor is provided in the middle of the supply / exhaust passage. A counterbalance valve that has a check valve that allows it and that has a high-pressure port that selects and takes out high-pressure oil from the supply / discharge passage on the switching valve side of the check valve, and a high-pressure port of the counterbalance valve that is connected to the high-pressure port. A high-pressure passage for guiding the high-pressure oil taken out to the port, a speed switching valve interposed in the middle of the high-pressure passage, a high-pressure passage between the high-pressure port and the speed switching valve, and the speed control valve are connected to each other to connect the high-pressure passage. Connected to the high-pressure passage and a pilot passage for switching the speed switching valve to the first position when the high-pressure oil introduced from the valve is below a predetermined pressure, and to the second position when the high-pressure oil is above the predetermined pressure. When the switching valve is located at the first position, the displacement of the hydraulic motor is reduced to rotate the hydraulic motor at high speed with a small torque, while when the speed switching valve is located at the second position, the displacement of the hydraulic motor is increased. Then, an actuator for rotating the hydraulic motor at a low speed and a large torque is provided, and a hydraulic circuit for traveling is provided. 2. A negative brake for releasing a brake to a hydraulic motor when high pressure oil is supplied, and a high pressure oil taken out from the high pressure port of a counter balance valve to the negative brake, which is provided with a control valve on the way. The hydraulic circuit for traveling according to claim 1, further comprising: a brake passage that guides the brake passage.