JP3769369B2 - Hydraulic control circuit - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to prevention of cavitation in a hydraulic control circuit of a traveling hydraulic motor used in a hydraulically driven vehicle such as a hydraulic excavator.
[0002]
[Prior art]
Conventionally, as this type of hydraulic control circuit, as shown in FIG. 3, a hydraulic motor 2 to which pressure oil from a hydraulic pump 1 driven by a prime mover (not shown) is supplied, and a direction switching valve for controlling the hydraulic motor 2 are used. 3, pipelines 4 a, 4 b, 4 c, 4 d connecting the hydraulic motor 2 and the direction switching valve 3, a counter balance valve 5 provided between these pipelines 4 a, 4 b, 4 c, 4 d, a counter Some include a pair of shockless relief valves 7 a and 7 b disposed between the balance valve 5 and the hydraulic motor 2.
[0003]
In this hydraulic control circuit, when the direction switching valve 3 is switched to either the left or right position and the counter balance valve 5 is in the flow position and the hydraulic motor 2 is driven, a vehicle (not shown) In order to brake the hydraulic motor to be stopped, the direction switching valve 3 is switched to the neutral position and the counter balance valve 5 is returned to the neutral position to form a closed circuit. In this closed circuit, the hydraulic motor 2 rotates with inertia. .
[0004]
As a result, the hydraulic motor 2 sucks oil from one pipe 4a (or 4b) and discharges oil to the other pipe 4b (or 4a). At this time, the counter balance valve 5 is limited in speed by the throttles 5a and 5b, moves to the neutral position, shuts off the pipes 4a and 4b, and the pressure in the pipe 4a or 4b becomes higher than the set pressure. One of the shockless relief valves 7a or 7b is opened, the high pressure side is allowed to escape to the low pressure side conduit, and oil is supplied to the suction side of the hydraulic motor 2 to prevent cavitation.
[0005]
[Problems to be solved by the invention]
By the way, in the above conventional example, in order to brake the hydraulic motor that should stop the vehicle (not shown), the direction switching valve is switched to the neutral position, the counter balance valve is returned to the neutral position, and a closed circuit is formed. When the hydraulic motor rotates by inertia in the circuit and the pressure in the pipeline becomes higher than the set pressure, either shockless relief valve is opened, the high pressure side is released to the low pressure side pipeline, and the suction of the hydraulic motor In order to replenish the shortage of hydraulic oil on the suction side of the hydraulic motor in the closed circuit, a pair of shockless relief valves are installed in the closed circuit. There is a problem that it is necessary to dispose, and the cost increases, and it is difficult to reduce the cost.
[0006]
In addition, if the relief valve is excluded and the same operation is performed using the direction switching valve, the direction switching valve is supplied to the hydraulic motor when the hydraulic motor is braked due to the opening characteristics of the switching valve. Since there is a region where oil is insufficient, there is a problem that the suction port side of the hydraulic motor becomes negative pressure and cavitation may occur.
[0007]
Accordingly, the present invention eliminates the pair of shockless relief valves disposed between the counter balance valve and the hydraulic motor, and replenishes the shortage of hydraulic oil on the suction side of the hydraulic motor when the hydraulic motor is braked. Therefore, it is an object of the present invention to provide a hydraulic control circuit that is provided with a regeneration circuit in a direction switching valve so as to supply hydraulic oil to the suction side of a hydraulic motor to prevent cavitation and to reduce the cost.
[0008]
[Means for Solving the Problems]
In the first invention, a hydraulic pump, a hydraulic motor to which pressure oil is supplied from the hydraulic pump, a direction switching valve for controlling the hydraulic motor, a pipe line connecting the hydraulic motor and the direction switching valve, and the pipe In the hydraulic control circuit including a counter balance valve provided between the roads, the direction switching valve supplies A and C positions for supplying hydraulic oil from the hydraulic pump to the hydraulic motor to drive the hydraulic motor in both forward and reverse directions. And a B position for stopping the supply of pressure oil from the hydraulic pump to the hydraulic motor, and a regeneration circuit is provided at the A and C positions of the direction switching valve, and between the hydraulic motor and the direction switching valve via the regeneration circuit. to constitute a closed circuit, so as to supply the return oil from the hydraulic motor to the suction side, it is provided a throttle in a passage for guiding the pilot pressure of the counterbalance valve is provided in the directional control valve play The passage is provided with a check valve that allows flow only from the return side port to the supply side port between the supply side port and the return side port, and a throttle is provided at the return side port, and the position of the direction switching valve is set to the A and C positions. In the process of switching from the B position to the B position, as the flow path for supplying hydraulic oil from the hydraulic pump to the hydraulic motor is throttled, the check valve opens to replenish the supply side port with oil on the return side port to prevent cavitation To do .
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. The same components as those in the conventional example will be described with the same names and symbols.
[0012]
In the hydraulic control circuit according to this embodiment, as shown in FIG. 1A, reference numeral 1 denotes a hydraulic pump that is driven by a prime mover (not shown) and connected to suck and supply oil from a tank 6. is there.
[0013]
Reference numeral 2 denotes a hydraulic motor that operates with hydraulic pressure supplied from the hydraulic pump 1.
[0014]
Reference numeral 3 denotes a direction switching valve that controls the hydraulic pressure supplied to the hydraulic motor 2.
[0015]
Reference numerals 4a, 4b, 4c and 4d are supply / exhaust pipes provided so as to connect the hydraulic motor 2 and the direction switching valve 4. The counter balance valve 5 is arranged in the pipes 4a, 4b, 4c and 4d. It is installed.
[0016]
The direction switching valve 3 is a switching valve having 6 ports and 3 positions. As shown in FIG. 1B, in the A position, the a port and the d port are connected via a throttle 8, and b A regenerator circuit R is provided in which a check valve 9 is provided between the a and b ports and permits flow only from the a port side to the b port side between the a and b ports, and the c and f ports are closed. .
[0017]
In the B position, the a, b, d, and e ports are all connected, and the c and f ports are connected.
[0018]
In the C position, the a port and the e port are connected, the b port and the d port are connected via the aperture 8, and the flow between the a and b ports only from the b port side to the a port side. The regeneration circuit R is provided with a check valve 9 to permit, and the ports c and f are closed.
[0019]
The counter balance valve has 4 ports (a to d) and 3 positions (D to F), and pilot pressure is inserted from the pipelines 4c and 4d through the throttles 5a and 5b.
[0020]
Next, the operation will be described.
Now, when the direction switching valve is switched to the C position, as shown in FIG. 2, the pressure oil discharged from the pump 1 is supplied to the supply side e port, a port, and the pipeline 4c in the direction switching valve 3. Is supplied to the hydraulic motor 2 through the c and a ports and the pipe line 4a in the D position of the counter balance valve, and the return oil from the hydraulic motor 2 is b and d at the D position of the pipe line 4b and the counter balance valve 5. Returning from the port to the tank 6 from the b-port on the return side of the direction switching valve 3, the throttle 8, and the d-port to the tank 6 through the conduit 4d, the hydraulic motor 2 is rotated, and the vehicle wheel (not shown) is rotated.
[0021]
And, in order to brake the hydraulic motor 2 that should stop the vehicle (not shown), in the process of switching the direction switching valve 3 from the C position to the neutral B position, the opening characteristics of the direction switching valve 3 The flow path between the supply side e and a ports at the C position of the direction switching valve 3 is throttled. At this time, the speed of the counter balance valve 5 is limited by the throttles 5a and 5b, and the return to the neutral E position is delayed. The counter balance valve 5 is not fully closed, and the hydraulic motor 2 is inertial. It is rotating.
[0022]
As described above, in the process of switching the direction switching valve 3 from the C position to the neutral B position, the flow between the supply side e and a ports at the C position of the direction switching valve 3 depends on the opening characteristics of the direction switching valve 3. When the passage is throttled, it enters a region where the supply of hydraulic oil from the pump 1 is insufficient, and the pressure drops. However, due to the throttle 8 provided between the return side b and d ports in the C position of the direction switching valve 3 When a back pressure is generated and a differential pressure is generated before and after the check valve 9 disposed between the a and b ports, the check valve 9 is opened and the a and b ports communicate with each other between the hydraulic motor 2 and the direction switching valve 3. Thus, a closed circuit is configured, and the oil on the return side of the hydraulic motor 2 is supplied to the suction side via the check valve 9 to supplement the insufficient oil on the suction side, thereby preventing cavitation.
[0023]
Then, as the counter balance valve 5 returns to the neutral E position, the pipelines 4a and 4b are gradually cut off, the amount of oil is reduced, and the hydraulic motor 2 gradually decelerates and stops operating.
[0024]
In this way, the regeneration circuit R is provided in the direction switching valve 3, and a closed circuit is formed between the hydraulic motor 2 and the direction switching valve 3 via the regeneration circuit R, and the return oil from the hydraulic motor 2 is supplied to the suction side. Therefore, even if the relief valves 7a and 7b are not used as in the conventional example, when the hydraulic motor 2 is braked, the oil on the return side of the hydraulic motor 2 is supplied to the suction side and the insufficient oil is replenished. Thus, cavitation can be prevented and the relief valve can be eliminated, thereby greatly reducing the cost.
[0025]
Further, since the return oil from the hydraulic motor 2 is joined with the oil on the discharge side of the pump 1 via the regeneration circuit R, the supply of oil to the hydraulic motor 2 increases, and the hydraulic motor 2 The number of revolutions can be increased.
[0026]
The regeneration circuit R provided in the direction switching valve 3 is provided with a check valve 9 that allows flow only from the return side port to the supply side port between the supply side port and the return side port, and a throttle 8 is provided at the return side port. Since it is provided and configured, it can be configured simply by disposing the check valve 9 and the throttle 8 in the direction switching valve in the conventional example, and the cost can be reduced.
[0027]
Further, by changing the throttle 8 in the regeneration circuit R, the return side pipe pressure of the hydraulic motor 2 is changed. When the system pressure is low, the rotation of the hydraulic motor 2 is increased, and when the system pressure is high, the regeneration function is increased. It is also possible to make the speed variable such as not to act.
[0028]
【The invention's effect】
According to the first invention, a hydraulic pump, a hydraulic motor to which pressure oil from the hydraulic pump is supplied, a direction switching valve that controls the hydraulic motor, a pipe line that connects the hydraulic motor and the direction switching valve, In the hydraulic control circuit including a counter balance valve provided between the pipes, the direction switching valve supplies pressure oil from the hydraulic pump to the hydraulic motor to drive the hydraulic motor in both forward and reverse directions. , C position and B position for stopping the supply of pressure oil from the hydraulic pump to the hydraulic motor, a regeneration circuit is provided at the A, C position of the direction switching valve, and the hydraulic motor constitute a closed circuit between the directional control valve, so as to supply the return oil from the hydraulic motor to the suction side, is provided a throttle in a passage for guiding the pilot pressure of the counterbalance valve is provided in the directional control valve The raw circuit is provided with a check valve that allows a flow only from the return side port to the supply side port between the supply side port and the return side port, and a throttle is provided at the return side port. As the flow path for supplying hydraulic oil from the hydraulic pump to the hydraulic motor is throttled in the process of switching from the position to the B position, the check valve opens and replenishes the supply side port with oil from the return side port for cavitation. since prevented, without using a relief valve as in the prior art, at the time of braking operation of the hydraulic motor, and supplies the return side of the oil of the hydraulic motor to the suction side, to replenish the oil shortage, preventing cavitation In addition, the relief valve can be eliminated and the cost can be greatly reduced. Return oil from the hydraulic motor can be passed through the regeneration circuit. To adapted to merge with the oil discharge side of the pump Te, and increases the supply of oil to the hydraulic motor, there is an effect that can be up to rotational speed of the hydraulic motor.
[0029]
The regenerative circuit provided in the direction switching valve is provided with a check valve that allows flow only from the return side port to the supply side port between the supply side port and the return side port, and a throttle is provided at the return side port. Therefore, the directional switching valve in the conventional example can be configured only by disposing the check valve 9 and the throttle, and there is an effect that the cost can be reduced.
[Brief description of the drawings]
FIG. 1 (a) is a hydraulic control circuit diagram showing an embodiment of the present invention.
(B) It is an enlarged view of the direction switching valve in the same figure (a).
FIG. 2 is an explanatory view for explaining the flow of oil in the hydraulic control circuit diagram in FIG. 1 (a).
FIG. 3 is a hydraulic control circuit diagram showing a conventional example.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Hydraulic pump 2 Hydraulic motor 3 Directional switching valve 4a, 4b, 4c, 4d Pipe line 5 Counter balance valve 5a, 5b Throttle 6 Tank 7a, 7b Relief valve 8 Throttle 9 Check valve A, B, C Directional switching valve position D , E, F Counter balance valve positions a, b, c, d, e, f Valve port R Regeneration circuit

Claims (1)

A hydraulic pump, a hydraulic motor to which pressure oil from the hydraulic pump is supplied, a direction switching valve for controlling the hydraulic motor, a pipe line connecting the hydraulic motor and the direction switching valve, and a counter provided between the pipes In the hydraulic control circuit including a balance valve, the direction switching valve supplies the hydraulic oil from the hydraulic pump to the hydraulic motor to drive the hydraulic motor in both forward and reverse directions and the hydraulic pump from the hydraulic motor. And a B circuit for stopping the supply of pressure oil to the directional switching valve. A regenerative circuit is provided at the A and C positions of the directional switching valve, and a closed circuit is formed between the hydraulic motor and the directional switching valve via the regenerating circuit. , so as to supply the return oil from the hydraulic motor to the suction side, said aperture is provided in the passage for guiding the pilot pressure of the counterbalance valve, reproducing circuit provided in the directional control valve is supplied side port A check valve that allows flow only from the return side port to the supply side port is provided between the return port and the return side port, and a throttle is provided at the return side port to switch the position of the direction switching valve from the A, C position to the B position. As the flow path for supplying hydraulic oil from the hydraulic pump to the hydraulic motor is throttled in the process, the check valve is opened to replenish the supply side port with oil on the return side port to prevent cavitation. Hydraulic control circuit to do.

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