JPS5916563Y2 - Closed circuit flushing circuit - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a closed flushing circuit having a hydraulic cylinder and a hydraulic motor.

When a hydraulic motor is driven in a closed circuit, the amount of oil on the forward and return sides of the hydraulic motor is equal, so the discharge amount of the charge pump is determined by the amount of oil to compensate for the oil escaping from the circuit as drain or to cool the circuit. The amount of oil required for flushing is sufficient, and the capacity of the charge pump may be small.

However, when driving a single-rod hydraulic cylinder in a closed circuit, the amount of oil in the circuit changes depending on the driving direction, so a large-capacity charge pump is installed to replenish this change. There is a need.

However, when a large capacity charge pump is installed,
A prime mover with a large output is required, resulting in a large horsepower loss.

In particular, hydraulic cylinders such as hydraulic excavators are driven by high hydraulic pressure, but in order to increase the buckling strength of the rod,
Since the diameter of the rod is increased, the amount of oil in the circuit changes greatly.

Therefore, when driving a single-rod hydraulic cylinder in a closed circuit, a circuit that combines a charge pump and a pressure accumulator is used.

FIG. 1 shows a closed circuit with a conventional flushing circuit.

In the figure, 1 is a double tilting hydraulic pump, 2 and 3 are single-rod hydraulic cylinders and hydraulic pumps connected to the hydraulic pump 1 in a closed circuit, and 4 and 5 are connecting the hydraulic pump 1, the hydraulic cylinder 2, and the hydraulic pump 3. When the switching valves 4 and 5 open and close the hydraulic cylinder and hydraulic motor simultaneously, the speed of the hydraulic cylinder 2 and the hydraulic motor 3 will change depending on the discharge amount and direction of the hydraulic pump 1. Since it is impossible to control the direction of operation, the switching valves 4 and 5 are controlled so that they do not open at the same time.

6 is a pressure accumulator, 7 is a relief valve, 8 is a tank, and 9 is a charge pump. The charge pump 9 is connected to both discharge pipes of the hydraulic pump 1, and is also connected to the pressure accumulator 6 and the relief valve 7.

10.11 is a check valve provided between both discharge pipes of the charge pump 9 and the hydraulic pump 1; check valve 10;
, 11 block the flow from both discharge pipes of the hydraulic pump 1 to the discharge side pipe of the charge pump 9.

12 is a flushing valve, and the flushing valve 12 connects the low pressure side of the discharge pipe of the hydraulic pump 1 to the pressure accumulator 6 and the relief valve 7.

In this hydraulic circuit, when the switching valve 4 is opened, the hydraulic cylinder 2 is driven by the hydraulic pump 1.

When the hydraulic cylinder 2 contracts, the amount of oil in the closed circuit remains, and the flushing valve 12 connects the low pressure side of the discharge pipe of the hydraulic pump 1 to the pressure accumulator 6, causing oil to flow into the pressure accumulator 6. When the pressure at 6 exceeds the set pressure at relief valve 7, oil escapes to tank 8.

Furthermore, when the hydraulic cylinder 2 extends, the amount of oil in the closed circuit is insufficient, so the oil in the pressure accumulator 6 flows into the low pressure side of the closed circuit through the check valve 10 or 11.

The charge pump 9 also serves as a drain to replenish the oil that has escaped from the circuit to the tank 8 and the oil that has escaped from the relief valve 7, and to replenish the pressure accumulator 6.

Furthermore, when the switching valve 5 is opened, the hydraulic pump 1
The hydraulic motor 3 is driven, and the charge pump 9 replenishes the oil that has flowed out from the closed circuit as a drain via the check valve 10 or 11.

However, in this hydraulic circuit, when the switching valve 4 is open, the amount of oil in the closed circuit changes due to the area difference between the rod side and the head side of the hydraulic cylinder 2, so the oil in the closed circuit is flushed. (in and out), the oil in the closed circuit is forcibly circulated, whereas when the switching valve 5 is opened, all the oil discharged from the charge pump 9 except for the drain is from the relief valve 7. Due to the leakage, sufficient oil circulation within the closed circuit is not achieved.

For this reason, if the load conditions are severe while driving the hydraulic motor 3, the oil temperature in the closed circuit will rise, causing deterioration of the hydraulic oil and eventually leading to damage to the hydraulic equipment.

Furthermore, if the amount of drain from the hydraulic pump 1, hydraulic motor 3, etc. is increased to the extent necessary to cool the oil in the closed circuit, the efficiency of the hydraulic circuit will deteriorate.

FIG. 2 is a diagram showing a closed circuit having a conventional flushing circuit that solves the above-mentioned problems.

In the figure, reference numeral 13 indicates a flushing valve provided between the pipe line connecting the hydraulic cylinder 2 and the switching valve 4.
The outlet port of 3 is connected to a pressure accumulator 6 and a relief valve 7, and the pressure accumulator 6 is connected to a charge pump 9.
A check valve 14 is provided to prevent flow from the charge pump 9 to the discharge line of the charge pump 9.

15.16 is a check valve provided between the pipe connecting the hydraulic cylinder 2 and the switching valve 4;
The oil in the pressure accumulator 6 is configured to flow into a conduit connecting the hydraulic cylinder 2 and the switching valve 4 through the hydraulic cylinder 2 and the switching valve 4.

Reference numeral 17 denotes a flushing valve provided between a pipe connecting the hydraulic motor 3 and the switching valve 5. The outlet port of the flushing valve 17 is connected to the tank 8 via a relief valve 18, and the set pressure of the relief valve 18 is is lower than the set pressure of the relief valve 7.

Next, the operation will be explained.

First, the operation when the switching valve 4 is opened and the hydraulic cylinder 2 is driven by the hydraulic pump 1 will be described.

When the hydraulic cylinder 2 extends, the oil discharged from the hydraulic pump 1 flows into the head side of the hydraulic cylinder 2, driving the piston of the hydraulic cylinder 2 to the left in the drawing, and the oil on the rod side flows into the suction port of the hydraulic pump 1. return.

At this time, if the pressure on the rod side is lower than the pressure on the head side, the insufficient amount of oil on the rod side flows from the charge pump 9 to the suction port of the hydraulic pump 1 via the check valve 10.

Also, if the discharge amount of the charge pump 9 is insufficient,
Oil in the pressure accumulator 6 is replenished via a check valve 15.

Further, when the hydraulic cylinder 2 contracts, that is, when the piston of the hydraulic cylinder 2 is driven to the right in the drawing, the pressure oil discharged from the hydraulic pump 1 is sent to the rod side of the hydraulic cylinder 2.

When the pressure on the head side of the hydraulic cylinder 2 is lower than that on the rod side, the flushing valve 13 connects the head side conduit and the pressure accumulator 6, and excess oil on the head side is sent to the pressure accumulator 6.

When the pressure accumulator 6 is filled and the pressure exceeds the set pressure of the IJ valve 7, it flows into the tank 8.

Note that even when the load acting on the hydraulic cylinder 2 is in the opposite direction to the above explanation, when the hydraulic cylinder 2 extends,
Oil is supplied from the charge pump 9 and the pressure accumulator 6 to the low pressure side of the closed circuit, and when the hydraulic cylinder 2 contracts, the low pressure side and the pressure accumulator 6 are connected, and oil flows out from the closed circuit to the pressure accumulator 6.

Further, when the switching valve 5 is opened to drive the hydraulic motor 3, the low pressure side of the pipe connecting the hydraulic motor 3 and the switching valve 5 is connected to the relief valve 18 via the flushing valve 17.

Also, the discharge oil from the charge pump 9 flows into the pressure accumulator 6, but when the pressure accumulator 6 is filled and the pressure inside the pressure accumulator 6 exceeds the set pressure of the relief valve 18, the oil is discharged through the check valve 10 or the check valve 11. Then, the oil discharged from the charge pump 9 flows into the low pressure side of the closed circuit, goes around the circuit, passes through the flushing valve 17 and the relief valve 18, and returns to the tank 8, performing a flushing action.

At this time, the oil in the pressure accumulator 6 does not flow into the closed circuit due to the action of the check valve 14.

Furthermore, when both the switching valves 4 and 5 are closed and the actuator is not being driven, the charge pump 9 is connected to the pressure accumulator 6.
and the drain amount of the hydraulic pump 1.

In this way, in this flushing circuit, the closed circuit can be forcibly flushed when the hydraulic motor is driven, so the oil temperature in the closed circuit does not rise, preventing deterioration of the hydraulic oil and damage to hydraulic equipment. will not occur.

By the way, when the hydraulic cylinder 2 is driven to the left in the drawing and a load is acting to the right in the drawing, that is, when the pressure on the head side is greater than the pressure on the rod side, the capacity of the charge pump 9 is larger than the rod of the hydraulic cylinder 2. Since the oil flowing into the hydraulic pump 1 from the side does not meet the shortage, the oil stored in the pressure accumulator 6 flows into the hydraulic pump 1 via the check valve 15 and the switching valve 4.

Therefore, the flow rate flowing through the switching valve 4 is the sum of the flow rate flowing out from the rod side of the hydraulic cylinder 2 and the flow rate flowing out from the pressure accumulator 6, so the pressure loss in the switching valve 4 becomes large, and the pressure loss in the pressure accumulator 6 increases. It is necessary to set the pressure of the pressure accumulator 6 to a higher pressure than the above pressure loss, and when the pressure of the pressure accumulator 6 is set to a high pressure, the energy loss of the charge pump 9 becomes large, and the strength of the pressure accumulator 6 must be increased. Must be.

Incidentally, if the switching valve 4 is made larger, the pressure loss can be reduced, but if the switching valve 4 is made larger, the price becomes higher and problems arise in terms of structure.

This invention was made to solve the above-mentioned problems, and provides a closed flushing circuit that does not require increasing the pressure in the pressure accumulator or increasing the size of the hydraulic cylinder switching valve. The purpose is to

In order to achieve this purpose, this invention uses a single-rod hydraulic cylinder in a closed circuit with a displacement that differs depending on at least one driving direction and a hydraulic motor that does not differ in displacement depending on at least one driving direction in one double-swivel hydraulic pump. and a hydraulic cylinder switching valve for opening and closing a pipe connecting the double tilting hydraulic pump and the single rod hydraulic cylinder, and a pipe connecting the double tilting hydraulic pump and the hydraulic motor. A switching valve for the hydraulic motor that opens and closes is provided, and the discharge side pipe of the charge pump is connected to both discharge pipes of the double tilting hydraulic pump, and the discharge pipe of the charge pump is connected from both discharge pipes of the double tilting hydraulic pump to the discharge pipe of the charge pump. A first flushing valve is provided between the pipes connecting the single-rod hydraulic cylinder and the hydraulic cylinder switching valve through a check valve that prevents flow to the hydraulic cylinder; In a closed flushing circuit in which a second flushing valve is provided between the pipelines connecting the switching valve, a pressure accumulator is connected to the outlet port of the first flushing valve, and the pressure accumulator is connected to the discharge port of the charge pump. The pressure accumulator is connected to the side pipe through a check valve that prevents flow from the pressure accumulator to the discharge side pipe of the charge pump, and the pressure accumulator is connected to the rod of the single rod hydraulic cylinder of the double tilting hydraulic pump. A discharge pipe connected to the side is closed when pressure oil is supplied to the pilot port, and a check is provided to prevent flow from the discharge pipe to the pressure accumulator when the pilot I port is communicated with the tank. It is connected through a functional pilot check valve, and supplies pressure oil to the pilot port when all of the hydraulic cylinder switching valves are closed.
Means is provided for communicating the pilot port with the tank when at least one of the hydraulic cylinder switching valves is opened.

FIG. 3 is a diagram showing a closed flushing circuit according to this invention.

As shown in the figure, the pressure accumulator 6 has flushing valves 13a, 1
It is connected to the outlet port of 3b, and is also connected to the check valve 1.
4 to the charge pump 9, and is further connected to the discharge pipe connected to the rod side of the single-rod hydraulic cylinders 2a, 2b of the hydraulic pump 1 via the pilot check valve 19. prevents the flow from the discharge pipe to the pressure accumulator 6.

Further, the hydraulic power source 20 is connected to the check valve 19 via the solenoid valve 21.
is connected to the pilot port 22 of.

Then, when at least one of the hydraulic cylinder switching valves 4a and 4b is opened by the OR gate 23, the solenoid valve 21 is in the B position, and at other times, that is, both switching valves 4a and 4b are closed. At this time, the solenoid valve 21 is in the A position.

Note that 16a and 16b are check valves.

FIG. 4 is a sectional view showing the pilot check valve 19.

In the figure, 24 is the valve body, 25 is a poppet slidably attached to the valve body 24, 26 is a spring provided between the valve body 24 and the poppet 25, and 27 is the valve body 2.
4 is a pin slidably attached, 28 is a port connected to the pressure accumulator 6), and 29.30 is a port connected to the hydraulic pump 1.

Next, the operation will be explained.

First, when both the switching valves 4a and 4b are closed, the solenoid valve 21 is in the A position, and the pressure oil from the hydraulic source 20 is supplied to the port 22.
Since the pin 27 is pressed against the poppet 25, the check valve 19 is closed.

Then, when at least one of the switching valves 4a and 4b is opened, the solenoid valve 21 becomes the B position, and the port 22 communicates with the tank 8.

Therefore, the check valve 19 comes to perform a check function.

For this reason, for example, the hydraulic cylinder 2a is driven to the left in the drawing, a load is applied to the right in the drawing, and the capacity of the charge pump 9 is reduced from the rod side of the hydraulic cylinder 2 to the hydraulic pump 1.
When the amount of oil flowing into the switch is not sufficient, the switching valve 4a
Since the pressure in the pipe line 31 connecting the hydraulic pump 1 and the pump 1 becomes low, the poppet 25 moves against the spring 26, the check valve 19 opens, and the pressure oil in the pressure accumulator 6 flows into the hydraulic pump 1. Supplied.

Note that even if at least one of the switching valves 4a, 4b is open, the check valve 19 is closed when the pressure in the pipe line 31 is high.

In this embodiment, electromagnetic valves are used as the switching valves 4a and 4b, but switching valves 4a and 4b that are operated by pilot pressure may also be used.

In this case, the pilot pressure of the switching valves 4a, 4b is guided to the shuttle valve, and the high pressure side of the pilot pressure is guided to the pilot port of the pilot operated switching valve provided between the check valve 19 and the hydraulic power source 20. , the same effect as the circuit shown in FIG. 3 can be obtained.

FIG. 5 is a diagram showing another closed flushing circuit according to this invention.

In the figure, 328 and 32b are hydraulic cylinder switching valves,
Logic valves are used as the switching valves 32a and 32b.

33a, 33b are electromagnetic valves, 34a to 36a, 34b to 3
6b is a shuttle valve, 37a, 38a, 37b,
38b is a poppet, and 39 is a shuttle valve.

Next, the operation will be explained.

First, when the solenoid valves 33a and 33b are in the A position, the switching valve 32a.

The highest pressure at port 32b is the shuttle valve 34a to 36
a, 34b to 36b, and the highest pressure is selected by poppet 37a, 38a, 37b, 38
The switching valves 32a and 32b are closed because the switching valves 32a and 32b act on the back of the cylinder.

Furthermore, when the solenoid valves 33a, 33b are in the B position, the backs of the poppets 37a, 38a, 37b, 38b communicate with the tank 8, so the switching valves 32a, 32b
Due to the pressure acting on the port of the poppet 37a,
38a, 37b, and 38b are pushed up, and the switching valves 32a and 32b are opened.

Further, when both the switching valves 32a and 32b are closed, the maximum pressure acts on the port 22 via the shuttle valve 39, so the check valve 19 is closed and the switching valve 32a is closed.
, 32b is opened, the port 22 is connected to the shuttle valve 39, the solenoid valve 33a or 33b.
Since the check valve 19 is connected to the tank 8 through the check valve 19, the check valve 19 performs a check function.

Therefore, when the pressure in the pipe line 31 becomes low, the pressure oil in the pressure accumulator 6 is supplied to the hydraulic pump 1.

As explained above, in the closed flushing circuit according to this invention, pressure oil from the pressure accumulator can be supplied to the double tilting hydraulic pump without going through the hydraulic cylinder switching valve. There is no need to consider pressure loss in the valve, and there is no need to increase the pressure in the pressure accumulator, so the structure of the pressure accumulator can be simplified, the energy loss of the charge pump is small, and it is easy to use for hydraulic cylinders. The switching valve can be made smaller.

In this way, the effects of this invention are remarkable.

[Brief explanation of the drawing]

Figures 1 and 2 are diagrams showing conventional closed circuit flushing circuits, Figures 3 and 5 are diagrams respectively showing closed circuit flushing circuits according to this invention, and Figure 4 is a diagram showing a pilot check valve. FIG. 1... Double tilting hydraulic pump, 2a, 2b...
... Single rod hydraulic cylinder, 3 ... Hydraulic motor, 4a, 4b ... Hydraulic cylinder switching valve, 6.
... Pressure accumulator, 9 ... Charge pump, 1
3a, 13b...Flushing valve, 14...
... Check valve, 19 ... Pilot check valve, 20 ... Hydraulic pressure source, 21 ... Solenoid valve, 23 ... Or gate, 25 ... ...Poppet, 26...Spring, 27...
- Pin, 32a, 32b... Hydraulic cylinder switching valve, 33 a, 33 b - Solenoid valve, 34
a ~ 36 a, 34 b ~ 36 b... Shuttle valve, 37 a, 38 a, 37 b, 38
b...Popets 1~. Three... Shuttle valves.

Claims (1)

[Claims for Utility Model Registration] One double tilting hydraulic pump 1 includes single-rod hydraulic cylinders 2a, 2b in a closed circuit whose discharge amount varies depending on at least one drive direction, and hydraulic pressure whose discharge amount does not vary depending on at least one drive direction. Hydraulic cylinder switching valves 4a, 4 to which the motor 3 is connected and which open and close pipes connecting the double tilting hydraulic pump 1 and the single rod hydraulic cylinders 2a, 2b;
b, the double tilting hydraulic pump 1 and the hydraulic motor 3 are provided.
A hydraulic motor switching valve 5 is provided to open and close a pipe connecting the two, and the discharge side pipe of the charge pump 9 is connected to both discharge pipes of the double tilting hydraulic pump 1. The single-rod hydraulic cylinders 2a, 2b and the hydraulic cylinder switching valve 4a are connected via check valves 10, 11 that prevent flow from the discharge pipe to the discharge side pipe of the charge pump 9. A first flushing 13a is provided between the pipes connecting the pipes 4b and 4b. 13b, and a second flushing valve 17 between the pipes connecting the hydraulic motor 3 and the hydraulic motor switching valve 5. In a closed flushing circuit, the pressure accumulator 6 is connected to the first flushing valve 13a. . 13b and connects the pressure accumulator 6 to the discharge line of the charge pump 9 via a check valve 14 that prevents flow from the pressure accumulator 6 to the discharge line of the charge pump 9. At the same time, the pressure accumulator 6 is connected to the single rod hydraulic cylinder 2a of the double tilting hydraulic pump 1.
, 2b is closed when pressure oil is supplied to the pilot port 22, and when the pilot port 22 is communicated with the tank 8, the discharge pipe is connected to the pressure accumulator 6. It is connected via a pilot check valve 19 that performs a check function to prevent the flow of oil, and when all of the hydraulic cylinder switching valves 4a and 4b are closed, pressure oil is supplied to the pilot port 22, and the hydraulic cylinder switching valve A closed flushing circuit characterized in that means is provided for communicating the pilot port 22 with the tank 8 when at least one of the valves 4a and 4b is opened.