JP2000240602A - Directional control valve operating circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inexpensive, directional control valve operating circuit for moving an actuator without a shock in the switching timing of the directional control valve. SOLUTION: One out of a plurality of directional control valves is of a communicated type directional control valve 7 provided with communicating passages 17a, 17b, which are cut off when the directional control valve is on the normal position but communicate both pilot chambers when the directional control valve is switched over, in addition to control restrictors 19a, 19b, which are installed in the communicating passages 17a, 17b for enlarging the opening of the directional control valve corresponding to the changing quantity of the directional control valve. The other one of the directional control valves is of a pilot chamber non-communicated type directional control valve 108 in which both pilot chambers are not communicated with each other. Pilot chambers 7a, 7b, 108a, 108b on both sides of a plurality of directional control valves are connected in parallel with respect to a pilot flow generating means Pp, while restrictors 101a, 101b are installed in connecting passages 111, 112 for connecting both pilot chambers 108a, 108b on both sides of the pilot chamber non-communicated type directional control valve 108 with the pilot flow generating means Pp.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a switching valve operating circuit for controlling a plurality of switching valves by pilot pressure.

[0002]

2. Description of the Related Art FIG. 6 shows a conventional switching valve operation circuit. This switching valve operation circuit joins the fluids of the two pumps 1 and 2 and supplies them to the actuator. The first pump 1 is connected to an actuator (not shown) via a first communication path switching valve 7 connected to the pump passage 3 and actuator passages A and B. Similarly, the second pump 2 is connected to an actuator (not shown) via a second communication path switching valve 8 connected to the pump passage 4 and actuator passages A and B. Also, the actuator passages A, B connected to the switching valve 8 with the second communication passage are connected to the actuator passages A, B connected to the switching valve 7 with the first communication passage.
B are connected as shown to join the fluids.

The switching valves 7 and 8 with the first and second communication passages are
The first and second pumps 1 and 2 respectively connect and disconnect an actuator (not shown). When the switching valves with communication passages 7 and 8 move rightward in the figure and switch to the left position, the pump ports 3 and 4 communicate with the actuator passage B and the tank passage 5 communicates with the actuator passage A. Conversely, when the switching valves with communication passages 7, 8 move leftward in the figure and switch to the right position, the pump ports 3, 4 communicate with the actuator passage A, and the tank passage 5 communicates with the actuator passage B. .

[0004] Pilot chambers 7a and 7b are provided on both sides of the switching valve 7 with the first communication passage.
The elastic forces a and 9b are applied. Similarly, pilot chambers 8a and 8b are provided on both sides of the switching valve 8 with the second communication passage, and the elastic force of the springs 10a and 10b is applied. The elastic force of the springs 10a and 10b is applied to the spring 9 acting on the switching valve 7 with the first communication passage.
a, 9b are made stronger than the elastic force. The pilot chambers 7a and 8a are connected in parallel to one port of a variable pilot pump Pp via a pilot passage 11, and the pilot chambers 7b and 8b are connected to the other of the variable pilot pump Pp via a pilot passage 12. Ports are connected in parallel.

On the other hand, the first and second switching valves with communication paths 7,
8 are pilot ports 13a, 13b and 14 respectively.
a and 14b. These pilot ports 1
3a, 13b, 14a, and 14b have passages 15 respectively.
a, 15b, 16a, and 16b are connected. Of these passages, passages 15a and 16a are connected to the pilot passage 1
1 and the passages 15 b and 16 b are connected to the pilot passage 12. Further, the first and second switching valves with communication passages 7 and 8 are connected to the two pilot ports 13a and 13
b and communication passages 17a, 17 communicating with 14a, 14b
b, 18a, 18b. The communication paths 17a, 17b, 18a, and 18b are provided with control throttles 19a, 19b, 20a, and 20b that vary the opening according to the amount of movement of the switching valve with the communication path. These control throttles 19a, 19b, 20a, and 20b have the maximum opening when the amount of movement of the switching valve with a communication passage becomes maximum.

FIG. 6 shows a neutral state in which the first and second switching valves with communication passages 7 and 8 are in a neutral position. At this time, the pilot ports 13a, 13b, 14a and 14b are shut off. When the first and second switching valves with communication passages 7 and 8 move rightward in the drawing from the neutral state, both pilot ports 13a and 13b of the switching valve with first communication passage 7 communicate with each other through the communication passage 17a. The two pilot ports 14a and 14b of the switching valve 8 with the second communication passage communicate with each other through the communication passage 18a. Thus, both pilot ports 13
a, 13b, 14a and 14b communicate with each other, the two pilot chambers 7a and 7b of the switching valve 7 with the first communication passage are connected to the passage I5.
a, the pilot port 13a, the communication passage 17a, the pilot port 13b, and the communication passage via the passage 15b. Similarly, both the pilot chambers 8a and 8b of the switching valve 8 with the second communication passage also have the passage 16a, the pilot port 14a, and the communication passage I8a. , A pilot port I4b and a passage 16b.

Contrary to the above, when the first and second switching valves with communication passages 7 and 8 move to the left in the drawing, both pilot ports 13a and 13a of the first and second switching valves with communication passages 7 and 8 move. 13b,
The communication passages 14a and 14b communicate with each other through the communication passages 17b and 18b. Therefore, the first and second switching valves with communication passages 7, 8
The two pilot chambers 7a, 7b, 8a, 8b also communicate with each other.

Next, the operation of the above conventional technique will be described. The variable pilot pump Pp transfers the fluid to the pilot passage 11.
When the fluid is discharged to the side, the fluid is supplied to the pilot chambers 7a and 8a connected in parallel via the pilot passage 11. Since the communication with the pilot passage 12 is interrupted, the pilot chambers 7a and 8a
Fluid pressure is generated at a and 8a. By this fluid pressure, a rightward force in the figure acts on the first and second switching valves with communication passages 7 and 8. The rightward force due to this fluid pressure is applied to the spring 9b,
When the elastic force becomes greater than 10b, the first and second switching valves with communication passages 7, 8 move rightward in the figure against the springs 9b, 10b. However, the spring 9 acting on the switching valve 7 with the first communication passage and the switching valve 8 with the second communication passage 8
Since the elastic forces of b and 10b are different, the movement timing is also different. That is, the switching valve with a communication passage 7 in which the acting spring 9b has a weak elastic force moves before the switching valve with the second communication passage 8.

When the switching valve with the first communication passage 7 moves rightward in the drawing, the communication passage 1 formed in the switching valve with the first communication passage 7 is formed.
The pilot ports 13a and 13b communicate with each other via 7a. When the two pilot ports 13a and 13b communicate with each other, the fluid of the variable pilot pump Pp flows in the order of the pilot passage 11, the passage 15a, the pilot port 13a, the communication passage 17a, the pilot port 13b, the passage 15b, and the pilot passage 12. At this time, the control aperture 19a
Due to the pressure loss of the fluid flowing through both pilot chambers 7
A differential pressure is generated between a and 7b. Due to this differential pressure, a rightward force in the figure acts on the first switching valve with a communication passage 7. Therefore, the switching valve 7 with the first communication passage moves to a position where the force due to the differential pressure and the elastic force due to the spring 9b are balanced.

When the switching valve 7 with the first communication passage moves to the right in the drawing, the pump passage 3 and the actuator passage B communicate with each other, and the tank passage 5 and the actuator passage A communicate with each other. Therefore, the fluid of the first pump 1 is supplied to an actuator (not shown), and the return fluid of the actuator is discharged to the tank T. The pump passage 3
The degree of opening of communication between the actuator and the actuator port B corresponds to the amount of movement of the switching valve 7 with the first communication path. In other words, if the amount of movement of the switching valve 7 with the first communication passage is large, the communication opening degree is also large, but if the movement amount is small, the communication opening degree is small.
When the communication opening increases, the flow rate supplied to the actuator (not shown) increases. However, when the communication opening decreases, the supply amount decreases.

The moving amount of the switching valve 7 with the first communication passage corresponds to the flow rate of the variable pilot pump Pp. In other words, if the flow rate of the variable pilot pump Pp is small, the amount of movement is small because the differential pressure between the pilot chambers 7a and 7b of the switching valve 7 with a communication passage is small, but if the flow rate is large,
Since the differential pressure increases, the moving amount also increases. FIG. 7 is a graph showing the relationship between the pilot flow rate of the variable pilot pump Pp and the flow rate supplied to the actuator. In the graph of FIG. 7, the horizontal axis represents the pilot flow rate of the variable pilot pump Pp, and the vertical axis represents the flow rate supplied to the actuator. The point s in this graph indicates a position where the first switching valve with a communication path 7 has been fully stroked rightward. At point s, the first pump 1
And the communication opening degree with an actuator not shown is maximized, and the flow rate of the first pump 1 supplied to this actuator is maximized.

On the other hand, the elastic force of the spring 10b is such that when the pilot flow reaches the point m on the graph, the pressure difference between the pilot chambers 8a and 8b causes the switching valve 8 with the second communication passage to move. You have set. Therefore, at point s on the graph, that is, at the point where the first switching valve with a communication path 7 has reached a full stroke, the pilot flow reaches point m, and the switching valve 8 with the second communication path moves rightward in the figure. The switching valve 8 with the second communication passage, like the switching valve 7 with the first communication passage, is provided with a force generated by a differential pressure between the pilot chambers 8a and 8b,
It moves to a position where the elastic force of the spring 10b balances.

As described above, when the switching valve 8 with the second communication passage moves rightward in the drawing, the pump passage 4 and the actuator passage B communicate with each other, and the tank passage 6 and the actuator passage A
Communicates with Therefore, the fluid of the second pump 8 joins the fluid of the first pump 7 and is supplied to an actuator (not shown), and the return fluid from the actuator is discharged to the tank T.

Further, the switching valve 8 with the second communication passage has a characteristic that the characteristic of the supply flow rate to the actuator with respect to the pilot flow rate is as follows.
The control throttle 20a is set so as to be the same as the switching valve 7 with the first communication path. That is, the inclination of the switching valve 8 with the second communication path in FIG. 7 is the same as the inclination of the switching valve 7 with the first communication path. Therefore, when the first switching valve with a communication path 7 has a full stroke and the fluid of the second pump 2 is joined in a state where the maximum flow rate of the first pump 1 is supplied,
The graph increases with the same slope. Therefore, if the switching valve 8 with the second communication path is moved at the same time when the switching valve 7 with the first communication path has made a full stroke, the actuator can be operated in proportion to the pilot flow rate of the variable pilot pump Pp. Note that the point n in this graph indicates a state in which the second switching valve with a communication passage 8 has been fully stroked rightward.
At this time, the entire flow rates of the first and second pumps 1 and 2 are supplied to an actuator (not shown).

When the variable pilot pump Pp discharges fluid to the pilot passage 12, the first and second switching valves with communication passages 7, 8 move leftward in the figure, which is opposite to the above case. Switches to the right position. The first and second pumps 1 and 2 communicate with the actuator passage A via the pump passages 3 and 4, and the tank passages 5 and 6 communicate with the actuator passage B. Therefore, the first and second pumps 1 and 2 are connected to the actuator (not shown) on the opposite side to the above case.
Supply 2 fluids. However, also in this case, the relationship between the pilot flow rate and the flow rate supplied to the actuator is the same as in FIG.

[0016]

In such a conventional switching valve operating circuit, the timing at which the switching valve with the first communication passage 7 and the switching valve with the second communication passage 8 starts moving, that is, the switching timing, is determined. It was determined only by the elastic force of the spring.
However, the control throttles 20a, 20
0b, the differential pressure of the control throttles 20a, 20b precedes the increase in the flow rate of the variable pilot pump Pp, which overcomes the elastic force of the springs 10a, 10b, and the switching speed of the switching valve 8 with the second communication passage. There was a problem that became sudden.

That is, since the elastic force of the springs 10a and 10b of the switching valve 8 with the second communication passage is stronger than the elastic force of the springs 9a and 9b of the switching valve 7 with the first communication passage, the flow rate of the variable pilot pump Pp is reduced. After the stroke becomes larger and the first switching valve with a communication path 7 is switched and the stroke is completed, the fluid pressure generated in the pilot chambers 8a and 8b suddenly increases, and the switching valve with the second communication path is switched. Since the speed is not controlled by an orifice or the like, the opening speed is fast, and when a large flow rate flows to the actuator in a short time, the actuator moves rapidly and a shock is large. Conversely, even when the flow rate of the variable pilot pump Pp decreases, the speed at which the switching valve with the second communication passage closes is not controlled, so that the switching valve with the second communication passage 8 is closed. Since the switching speed is also fast,
As described above, the flow rate to the actuator decreases in a short time, and the movement of the actuator suddenly slows down, causing a large shock. In other words, the speed at which the switching valve with the second communication passage opens also
The closing speed is not controlled by the orifice, etc., so the opening speed may be fast, but the closing speed should be slow, or vice versa, but the opening speed may be slow, but the closing speed is better. In any case, in any case, the switching speed of the switching valve 8 with the second communication passage is not controlled, and the movement of the actuator rapidly increases or decreases as described above, resulting in a large shock.

Further, since the plurality of first and second switching valves with communication passages 7 and 8 each have a communication passage, the pilot flow rate constantly flowing through the communication passages while operating the switching valve with communication passage is controlled. In many cases, a large-capacity pilot pump must be used.

Further, the use of a plurality of expensive switching valves having a communication passage having a pilot port and a communication passage increases the cost. It is an object of the present invention to provide an inexpensive switching valve operation circuit in which an actuator moves without a shock at the switching timing of a switching valve.

[0020]

According to the present invention, a plurality of switching valves, a spring for holding the switching valves in a normal position, a pilot chamber provided on both sides of the switching valve, and a pilot valve are provided. A switching valve operating circuit having a pilot flow rate generating means for supplying a fluid to the chamber, wherein one of the plurality of switching valves is shut off when the switching valve is in a normal position, and when the switching valve is switched, A communication-type switching valve including communication paths 17a and 17b for communicating the two pilot chambers, and control throttles 19a and 19b provided in the communication paths 17a and 17b to increase the opening according to the switching amount of the switching valve. The other switching valves are pilot chamber non-communication type switching valves 108 in which both pilot chambers are not in communication with each other, and the pilot chambers 7a, 7 on both sides of the plurality of switching valves.
b, 108a, 108b to pilot flow rate generating means Pp
And the connecting passages 111, 11 between the pilot chambers 108a, 108b on both sides of the pilot chamber non-communication switching valve 108 and the pilot flow rate generating means Pp.
2 has apertures 101a and 101b, respectively.

According to the first aspect of the present invention, the switching speed of the second switching valve can be suppressed low by the throttles 101a and 101b both when the flow rate of the pilot flow rate generating means increases and decreases. Movement is smooth without shock.

Furthermore, since the pilot chambers use a non-communicating pilot chamber switching valve in which both pilot chambers do not communicate with each other except for one of the plurality of switching valves, the capacity of the pilot pump can be reduced and the cost can be reduced. it can. Further, the switching speed of the pilot chamber non-communication type switching valve can be arbitrarily reduced by the throttle. Further, the degree of opening of the throttle can be set accurately and easily. Therefore, the switching speed can be set accurately. Since the pilot chamber non-communication switching valve does not have a pilot port and a communication passage, component costs, assembling costs, and manufacturing costs can be reduced.

According to a second aspect of the present invention, a plurality of switching valves, a spring for holding the switching valves in a normal position, a pilot chamber provided on both sides of the switching valve, and a fluid supply to the pilot chamber. A switching valve operating circuit including a pilot flow rate generating means, wherein one of the plurality of switching valves is shut off when the switching valve is in a normal position;
Communication passages 17a and 17b for communicating the two pilot chambers when the switching valve is switched, and the communication passages 17a and 17b;
b, a communication-type switching valve 7 provided with control throttles 19a and 19b for increasing the opening in accordance with the switching amount of the switching valve. A communication type switching valve 108 is provided, and the pilot chambers 7a, 7b, 108a, 10 on both sides of the plurality of switching valves are provided.
8b is connected in parallel to the pilot flow generating means Pp, and the throttles 1 are respectively connected to the connecting passages 111 and 112 between the pilot chambers 108a and 108b on both sides of the pilot chamber non-communication switching valve 108 and the pilot flow generating means Pp.
01a, 101b and check valves 102a, 102b are provided in parallel.

According to the second aspect of the present invention, when the opening speed of the pilot chamber non-communication switching valve may be high but the closing speed is preferably low, when the flow rate of the pilot flow rate generating means increases, Since the switching speed of the pilot chamber non-communication type switching valve switches at a high speed, the actuator moves responsively, and when the flow rate of the pilot flow rate generating means decreases, the switching speed of the pilot chamber non-communication type switching valve is suppressed to a low value. Therefore, the actuator can move smoothly without shock. On the contrary, the opening speed of the pilot chamber non-communication switching valve should be slow and the closing speed can be fast,
When the flow rate of the pilot flow rate generating means increases, the switching speed of the pilot chamber non-communication type switching valve can be kept low, so that the actuator can move smoothly without shock and the flow rate of the pilot flow rate generating means decreases. At this time, the switching speed of the pilot chamber non-communication switching valve is switched at a high speed, so that the actuator can move with good responsiveness.

Further, since the pilot chambers use a non-communicating pilot chamber switching valve in which both pilot chambers do not communicate with each other except for one of the plurality of switching valves, the capacity of the pilot pump can be reduced and the cost can be reduced. it can. Further, the switching speed of the pilot chamber non-communication type switching valve can be arbitrarily reduced by the throttle. Further, the degree of opening of the throttle can be set accurately and easily. Therefore, the switching speed can be set accurately. Since the pilot chamber non-communication switching valve does not have a pilot port and a communication passage, component costs, assembling costs, and manufacturing costs can be reduced.

[0026]

FIG. 1 shows a first embodiment of the present invention.
Shown in In this first embodiment, a pilot chamber non-communication switching valve is provided except for one communication switching valve among a plurality of switching valves, and a connection circuit between the pilot chamber non-communication switching valve and the pilot pump is provided as described above. This is different from the example shown in the prior art. However, the other components are the same as those of the above-described conventional technology, and thus the same reference numerals are used for the same components, and detailed description thereof will be omitted.

In the first embodiment shown in FIG. 1, the structure of the switching valve 7 with a communication passage is the same as that of the conventional switching valve 7 with a communication passage. The first switching valve 108 is a three-position switching valve, does not include a pilot port and a communication passage as provided in the switching valve 7 with a communication passage, and has a pilot chamber non-communication type in which both pilot chambers are not communicated with each other. It is a switching valve. Pilot chambers 7a and 7b are provided on both sides of the switching valve 7 with a communication passage, and the elastic force of the springs 9a and 9b is applied.
Similarly, the pilot chamber 1 is provided on both sides of the first switching valve 108.
08a, 108b and the spring 110
a, 110b elastic force is applied. The elastic force of the springs 110a and 110b is stronger than the elastic force of the springs 9a and 9b acting on the switching valve 7 with the communication passage.

The pilot chambers 7a, 108a
Are connected in parallel to one port of a variable pilot pump Pp, which is a pilot flow generating means, via a pilot passage 11, and the pilot chambers 7b and 108b
Is connected in parallel via a pilot passage 12 to the other port of a variable pilot pump Pp, which is a pilot flow rate generating means. The pilot flow rate generating means may be a combination of a pump and a valve for controlling the flow rate from the pump.

Then, the pilot chamber 108a on the left side of the first switching valve 108 in the figure is connected to the pilot passage 111 branched from the pilot passage 11, and the pilot chamber 1 on the right side is connected.
08b is connected to a pilot passage 112 branched from the pilot passage 12. Pilot passages 111, 11
2 are provided with apertures 101a and 101b, respectively. The throttles 101a and 101b are connected to a first switching valve 108.
Controls the speed at which is switched.

Next, the operation of the above embodiment will be described. The variable pilot pump Pp transfers the fluid to the pilot passage 11.
When the fluid is discharged to the side, the fluid is supplied to the pilot chambers 7a and 108a connected in parallel via the pilot passage 11. Since the communication with the pilot passage 12 is interrupted in the pilot chamber 7a, a fluid pressure is generated in the pilot chamber 7a. By this fluid pressure, a rightward force in the figure acts on the switching valve 7 with the communication passage. When the rightward force due to the fluid pressure becomes larger than the elastic force of the spring 9b, the switching valve with communication passage 7 moves rightward in the figure against the spring 9b.

When the switching valve with communication passage 7 moves rightward in the figure, the pilot ports 13a and 13b communicate with each other via the communication passage 17a formed in the switching valve with communication passage 7. When the two pilot ports 13a and 13b communicate with each other, the fluid of the variable pilot pump Pp flows from the pilot passage 11 → the passage 15a → the pilot port 13a → the communication passage 17a → the pilot port 13b → the passage 15b → the pilot passage l.
It flows in the order of 2. At this time, a pressure difference is generated between the pilot chambers 7a and 7b due to a pressure loss of the fluid flowing through the control throttle 19a. Due to this differential pressure, a force in the right direction in the figure acts on the switching valve with communication passage 7. Therefore, the switching valve with communication passage 7 moves to a position where the force due to the differential pressure and the elastic force due to the spring 9b are balanced.

At this time, the same pressure as the fluid pressure in the pilot passage 11 is generated in the pilot chamber 108a of the first switching valve 108 via the pilot passage 111, and is generated in the pilot chamber 108b via the pilot passage 112. Since the same pressure as the fluid pressure in the pilot passage 12 is generated, a differential pressure is generated between the pilot chambers 108a and 108b. However, while the rightward force due to this differential pressure is smaller than the elastic force of the spring 110b, the first switching valve 108
Is not switched yet, so that no flow occurs in the throttle 101a, and therefore no pressure loss occurs due to the throttle 101a. Then, the flow rate of the pilot pump Pp increases,
The pressure in the pilot chamber 108a of the first switching valve 108 increases, and a rightward force due to this differential pressure is applied to the spring 110.
When the elastic force becomes larger than the elastic force b, the first switching valve 108
It moves rightward in the figure against the spring 110b. Then, fluid corresponding to the amount of movement of the first switching valve 108 flows through the throttle 108a and flows into the pilot chamber 108a, so that a pressure loss is generated by the throttle 101a, and the pressure in the pilot chamber 108a increases slowly. Further, the fluid in the pilot chamber 108b flows through the throttle 101b, flows through the pilot passage 112, and flows into the pilot passage 12, so that the pressure of the pilot chamber 108b decreases by the throttle 101b. Therefore, both pilot chambers 108a,
Since the increasing speed of the differential pressure between the pressures 108b is reduced, the increasing speed of the force for moving the first switching valve 108 rightward due to the differential pressure is reduced, and the moving speed of the first switching valve 108 is reduced. That is, the first switching valve switches slowly.
Then, the movement of the first switching valve stops at a position where the rightward force due to the pressure difference between the two pilot chambers 108a and 108b and the elastic force of the spring 110b are balanced.

When the first switching valve 108 moves rightward in the drawing as described above, the pump passage 4 and the actuator passage B
And the tank passage 6 and the actuator passage A communicate with each other. Therefore, the fluid of the second pump 2 joins the fluid of the first pump 1 and is supplied to an actuator (not shown), and the return fluid from the actuator is discharged to the tank T. At this time, the fluid of the second pump merges with the fluid of the first pump, as described above.
The switching speed of the first switching valve 108 is limited to the throttles 101a and 101b.
As a result, the flow rate of the merged flow is moderated, and the flow rate supplied to the actuator does not increase abruptly, so that the actuator can move smoothly without shock.

Next, the flow rate of the pilot pump Pp decreases, and the pressure difference between the two pilot chambers 108a and 108b decreases.
When the elastic force becomes smaller than the elastic force b, the first switching valve 108 starts to move leftward in the drawing so as to return to the neutral position by the elastic force of the spring 110b. Then, the fluid corresponding to the amount of movement of the first switching valve 108 flows through the throttle 108a.
Due to 01a, the pressure in the pilot chamber 108a decreases at a slower rate. Fluid flows into the pilot chamber 108b from the pilot passage 12 via the pilot passage 112 and flows through the throttle 101b. The throttle 101b causes the pressure in the pilot chamber 108b to increase at a slower rate. Accordingly, the rate of decrease in the pressure difference between the pilot chambers 108a and 108b is reduced, and the first switching valve 108 is operated by the pressure difference.
Is reduced, and the moving speed of moving the first switching valve 108 to the left in the drawing to return to the neutral position is reduced. That is, the first switching valve 108 slowly moves in the direction to return to the neutral position. The rightward force due to the pressure in the pilot chamber 108a and the spring 11
The movement of the first switching valve 108 stops at the position where the elastic force of 0b is balanced. At this time, even when the flow rate at which the fluid of the second pump and the fluid of the first pump join decreases, as described above, the switching speed of the first switching valve 108 also decreases the throttles 101a, 1a.
01b, the actuator is pressed low and moves slowly, so that the decrease in the combined flow rate becomes gentle, and the flow rate supplied to the actuator does not decrease abruptly, so that the actuator can move without a shock while smoothly reducing the speed.

When the variable pilot pump Pp discharges fluid to the pilot passage 12 side, the switching valve with communication passage 7 and the second switching valve 108 move to the left in the drawing, which is opposite to the above case, and move to the right. Switch to position. The first and second pumps 1 and 2 communicate with the actuator passage A via the pump passages 3 and 4, and the tank passages 5 and 6 communicate with the actuator passage B. Therefore, the first and second actuators, not shown, are placed on the opposite side to the above case.
The fluid of the pumps 1 and 2 is supplied. The operation is different from the case where the variable pilot pump Pp discharges the fluid to the pilot passage 12 side only in that the switching valve 7 with the communication passage and the second switching valve 108 move in opposite directions, but the other operations are the same, and therefore the description is omitted. .

As described above, according to the first embodiment, the switching speed of the first switching valve 108 can be kept low both when the flow rate of the variable pilot pump increases and decreases, so that the movement of the actuator is reduced. Smooth without shock.

Further, according to the first embodiment, since the switching valve having no communication passage is used among the plurality of switching valves, the capacity of the pilot pump can be reduced, and the cost can be reduced. Further, the switching speed of the switching valve can be arbitrarily reduced by the throttle. Further, the degree of opening of the throttle can be set accurately and easily compared to the setting of the elastic force of the spring. Therefore, the switching speed can be set accurately. Since the first switching valve does not have the pilot port and the communication passage, the cost of parts, the cost of assembly, and the cost of manufacturing can be reduced.

Next, a specific example of the switching valve operation circuit of the first embodiment is shown in FIG. However, the same members as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted. As shown in FIG. 2, the switching valve with a communication passage 7 has a pilot chamber 7 on both sides of the casing 27.
pilot caps 29a, 29b formed with a, 7b
Is installed. A spool 28 is slidably provided in the casing 27, and both ends of the spool 28 are
a, 7b. In addition, the pilot rooms 7a, 7
b, springs 9a and 9b are provided, and the elastic force of the springs 9a and 9b is applied to the spool 2 via spring receivers 30a and 30b.
8 act on both ends. These spring receivers 30a, 3
Ob forms communication holes 32a and 32b and presses the ends of the communication holes 32a and 32b against the casing 27 by the elastic force of the springs 9a and 9b. Steps 31a and 31b are formed on both sides of the spool 28.
a, 31b and the casing 27 combine to control the throttle
a, l9b.

On the other hand, the first switching valve 108 is
Pilot caps 29a and 29b, in which pilot chambers 108a and 108b are formed, are attached to both sides of 7, respectively. A spool 128 is provided in the casing 27 so as to slide freely, and both ends of the spool 128 are connected to the pilot chambers 108a and 108a.
08b. In addition, the pilot room 108a,
The spring 108a is provided with springs 110a and 110b, and the elastic force is applied to both ends of the spool 128 via spring receivers 30a and 30b. The ends of the spring receivers 30a and 30b are connected to the spring 1
It is pressed against the casing 27 by the elastic force of 10a and 110b. The spool 128 does not have a stepped portion as in the spool 28 of the switching valve 7 with a communication passage.
The first switching valve 108 has no control throttle.

The pilot chambers 7a and 10a
8a is connected in parallel to one port of a variable pilot pump Pp via a pilot passage 11, and the pilot chambers 7b and 108b are connected in parallel to the other port of the variable pilot pump Pp via a pilot passage 12. ing.

The pilot chamber 108a on the left side of the first switching valve 108 in the figure is connected to a pilot passage 111 branched from the pilot passage 11, and the pilot chamber 1 on the right side is connected.
08b is connected to a pilot passage 112 branched from the pilot passage 12. Pilot passages 111, 11
2 are provided with apertures 101a and 101b, respectively. The throttles 101a and 101b are connected to a first switching valve 108.
Controls the speed at which is switched.

Next, the operation of this embodiment will be described. When the variable pilot pump Pp discharges fluid to the pilot passage 22 side, the fluid is discharged to the pilot chamber 7a and the passage 1
The signal is supplied to the pilot port 13b via 5a. At this time, since the pilot port 13b is blocked by the spool 28, fluid pressure is generated in the pilot chamber 7a, and a rightward force acts on the spool 28 in the drawing. When the rightward force becomes larger than the elastic force of the spring 9b, the spool 28 moves rightward in the drawing. When the spool 28 moves, the step 3 formed on the spool 28
1a communicates with the pilot port 13a. Therefore, the fluid in the pilot chamber 7a flows from the communication hole 32a to the step 3
It flows in the order of 1a → pilot port 13a → passage 15b → pilot chamber 7b. Then, the fluid supplied to the pilot chamber 7b flows through the pilot passage 12 and returns to the variable pilot pump Pp.

When the fluid flows as described above, the step 31a
Pressure loss of the fluid occurs due to the gap between the fluid and the casing 27. As a result, a pressure difference is generated between the pilot chambers 7a and 7b, and a rightward force is applied to the spool 28 in the figure, and the spool 28 exerts a rightward force due to the differential pressure and a leftward elastic force due to the spring 9b. Moves to a position where it balances.

On the other hand, a pressure difference also occurs between the pilot chambers 108a and 108b of the first switching valve 108. However, while the rightward force due to the differential pressure is smaller than the elastic force of the spring 110b, the first switching valve 108 has not yet switched, so that no flow occurs in the throttle 101a, and therefore, the pressure loss due to the throttle 101a Also does not occur. When the flow rate of the pilot pump Pp increases and the pressure in the pilot chamber 108a of the first switching valve 108 increases, and the rightward force due to this differential pressure becomes greater than the elastic force of the spring 110b, the spool 128 , And moves rightward in the figure against the spring 110b. Then, the spool 128
The amount of fluid corresponding to the amount of movement flows through the throttle 108a and flows into the pilot chamber 108a, so that a pressure loss occurs due to the throttle 101a, and the pressure in the pilot chamber 108a rises slowly. Further, the fluid in the pilot chamber 108b flows through the throttle 101b and then flows through the pilot passage 112 into the pilot passage 12, so that the pressure of the pilot chamber 108b lowers due to the throttle 101a. Therefore, the rising speed of the differential pressure between the two pilot chambers 108a and 108b becomes slow, and the first switching valve 108 due to this differential pressure is increased.
The speed at which the force for moving the spool 128 to the right moves increases, and the moving speed of the spool 128 decreases.
That is, the first switching valve 108 switches slowly. Then, the movement of the spool 128 stops at a position where the rightward force due to the pressure difference between the pilot chambers 108a and 108b and the elastic force of the spring 110b are balanced.

The operation when the flow rate of the pilot pump Pp decreases is the same as that in the first embodiment, and will not be described.

In this specific example, similarly to the first embodiment, when the spool 128 of the switching valve 7 with the communication passage and the first switching valve 108 is switched, the pump is not shown in the drawing. The actuator is in communication with the tank, and the actuator is in communication with a tank (not shown).

In the first embodiment, two switching valves 7,
Although the switching valve 108 is connected, the switching valve operation circuit of the present invention is not limited to two switching valves, but can connect a plurality of switching valves.

Next, a second embodiment will be described. In the second embodiment shown in FIG. 3, a second switching valve 208, which is the same switching valve as the first switching valve 108, is added to the switching valve operation circuit of the first embodiment. Third pump 2
a is connected to an actuator (not shown) via the second switching valve 208 connected to the pump passage 4a and the actuator passages A and B. Further, the switching valve 7 with a communication passage is provided.
The first switching valve 1 is connected to the actuator passages A and B connected to
The actuator paths A and B connected to the second switching valve 08 and the actuator paths A and B connected to the second switching valve 208 are connected as shown in the figure to join the fluids. The second switching valve 208 is a three-position switching valve, does not have a pilot port and a communication path as provided in the switching valve 7 with a communication path, and has a pilot chamber non-communication type switching in which both pilot chambers are not in communication with each other. It is a valve. Pilot chambers 7a and 7b are provided on both sides of the switching valve 7 with a communication passage, and the elastic force of the springs 9a and 9b is applied. Similarly, the pilot chamber 108 is provided on both sides of the first switching valve 108.
a, 108b, and the springs 110a,
The elastic force of 110b is applied. This spring 1
The elastic forces of 10a and 110b are made stronger than the elastic forces of the springs 9a and 9b acting on the switching valve 7 with the communication passage. Pilot chambers 208a and 208b are provided on both sides of the second switching valve 208, and the spring 2
The elastic force of 10a, 210b is applied. The elastic forces of the springs 210a and 210b are stronger than the elastic forces of the springs 110a and 110b acting on the first switching valve 108.

The pilot chambers 7a and 108a
And 208a are connected in parallel to one port of a variable pilot pump Pp, which is a pilot flow rate generating means, via a pilot passage 11, and the pilot chamber 7b,
108a and 208a are connected in parallel via a pilot passage 12 to the other port of the variable pilot pump Pp which is a pilot flow rate generating means. The pilot flow rate generating means may be a combination of a pump and a valve for controlling the flow rate from the pump. The other configuration is the same as that of the first embodiment, and the description is omitted.

The pilot chamber 108a on the left side of the first switching valve 108 in the figure is connected to a pilot passage 111 branched from the pilot passage 11, and the pilot chamber 208a on the left side of the second switching valve 208 in the figure is connected to the pilot passage 11. The first pilot valve 211 is connected to the branched pilot passage 211, and the pilot chamber 108 b on the right side of the first switching valve 108 is connected to the pilot passage 112 branched from the pilot passage 12.
A pilot chamber 208 b on the right side of the switching valve 208 is connected to a pilot passage 212 branched from the pilot passage 12. Pilot passages 111, 112, 211, 21
2 have apertures 101a, 101b, 201a,
201b is provided. These apertures 101a, 101b
Controls the speed at which the first switching valve 108 is switched, and the throttles 201a, 201b control the speed at which the second switching valve 208 is switched.

Next, the operation of the above embodiment will be described. The variable pilot pump Pp transfers fluid to the pilot passage 11.
When the fluid is discharged to the side, the fluid is supplied to pilot chambers 7a and 8a connected in parallel via a pilot passage 11. Since the communication with the pilot passage 12 is interrupted in the pilot chamber 7a, a fluid pressure is generated in the pilot chamber 7a. By this fluid pressure, a rightward force in the figure acts on the switching valve 7 with the communication passage. When the rightward force due to the fluid pressure becomes larger than the elastic force of the spring 9b, the switching valve 7 with the first communication path moves rightward in the figure against the spring 9b.

When the switching valve with communication passage 7 moves rightward in the figure, the two pilot ports 13a and 13b communicate with each other via the communication passage 17a formed in the switching valve with communication passage 7. When the two pilot ports 13a and 13b communicate with each other, the fluid of the variable pilot pump Pp flows from the pilot passage 11 → the passage 15a → the pilot port 13a → the communication passage 17a → the pilot port 13b → the passage 15b → the pilot passage l.
It flows in the order of 2. At this time, a pressure difference is generated between the pilot chambers 7a and 7b due to a pressure loss of the fluid flowing through the control throttle 19a. Due to this differential pressure, a force in the right direction in the figure acts on the switching valve with communication passage 7. Therefore, the switching valve with communication passage 7 moves to a position where the force due to the differential pressure and the elastic force due to the spring 9b are balanced.

At this time, the same pressure as the fluid pressure in the pilot passage 11 is generated in the pilot chamber 108a of the first switching valve 108 via the pilot passage 111, and is generated in the pilot chamber 108b via the pilot passage 112. Since the same pressure as the fluid pressure in the pilot passage 12 is generated, a differential pressure is generated between the pilot chambers 108a and 108b. However, while the rightward force due to this differential pressure is smaller than the elastic force of the spring 110b, the first switching valve 108
Is not switched yet, so that no flow occurs in the throttle 101a, and therefore no pressure loss occurs due to the throttle 101a. Then, the flow rate of the pilot pump Pp increases,
When the pressure in the pilot chamber 108a of the first switching valve 108 increases and the rightward force due to the pressure difference between the pilot chambers 108a and 108b becomes larger than the elastic force of the spring 110b, the first switching valve 108 sets 110b
Move to the right in the figure against. Then, the first switching valve 1
Since the fluid corresponding to the movement amount of 08 flows through the throttle 108a and flows into the pilot chamber 108a, a pressure loss occurs due to the throttle 101a, and the pressure in the pilot chamber 108a rises slowly. Further, the fluid in the pilot chamber 108b flows through the throttle 101b, flows through the pilot passage 112, and flows into the pilot passage 12, so that the pressure of the pilot chamber 108b decreases by the throttle 101b. Accordingly, the rate of increase in the differential pressure between the pilot chambers 108a and 108b is reduced, and the rate of increase in the force for moving the first switching valve 108 to the right due to the differential pressure is reduced, and the moving speed of the first switching valve 108 is reduced. Will go down. That is, the first switching valve 108 switches slowly. Then, the movement of the first switching valve 108 stops at a position where the rightward force due to the pressure difference between the pilot chambers 108a and 108b and the elastic force of the spring 110b are balanced.

At this time, the same pressure as the fluid pressure in the pilot passage 11 is generated in the pilot chamber 208a of the second switching valve 208 via the pilot passage 211, and is generated in the pilot chamber 208b via the pilot passage 212. Since the same pressure as the fluid pressure in the pilot passage 12 is generated, a differential pressure is generated between the pilot chambers 208a and 208b. However, while the rightward force due to this differential pressure is smaller than the elastic force of the spring 210b, the second switching valve 208
Is not switched yet, so that no flow occurs in the throttle 201a, and thus no pressure loss occurs due to the throttle 201a. Then, the flow rate of the pilot pump Pp increases,
When the pressure in the pilot chamber 208a of the second switching valve 208 increases and the rightward force due to the pressure difference between the two pilot chambers 208a and 208b becomes larger than the elastic force of the spring 210b, the second switching valve 208 operates as a spring. 210b
Move to the right in the figure against. Then, the second switching valve 2
Since the fluid corresponding to the movement amount of 08 flows through the throttle 208a and flows into the pilot chamber 208a, a pressure loss is generated by the throttle 201a, and the pressure in the pilot chamber 208a rises slowly. Further, the fluid in the pilot chamber 208b flows through the throttle 201b and then flows through the pilot passage 212 into the pilot passage 12, so that the pressure of the pilot chamber 208b decreases due to the throttle 201b. Therefore, the rate of increase in the differential pressure between the pilot chambers 208a and 208b is reduced, and the rate of increase in the force for moving the second switching valve 208 to the right due to the differential pressure is reduced.
The moving speed of the second switching valve 208 decreases. That is, the second switching valve 208 switches slowly. Then, the movement of the second switching valve 208 stops at a position where the rightward force due to the pressure difference between the pilot chambers 208a and 208b and the elastic force of the spring 210b are balanced.

When the first switching valve 108 moves rightward in the figure as described above, the pump passage 4 and the actuator passage B
And the tank passage 6 and the actuator passage A communicate with each other. Therefore, the fluid of the second pump 2 joins the fluid of the first pump 1 and is supplied to an actuator (not shown), and the return fluid from the actuator is discharged to the tank T. At this time, the fluid of the second pump merges with the fluid of the first pump, as described above.
The switching speed of the first switching valve 108 is limited to the throttles 101a and 101b.
As a result, the flow rate of the merged flow is moderated, and the flow rate supplied to the actuator does not increase abruptly, so that the actuator can move smoothly without shock.

Further, when the second switching valve 208 moves rightward in the drawing as described above, the pump passage 4a communicates with the actuator passage B, and the tank passage 6a communicates with the actuator passage A. Therefore, the fluid of the third pump 2a joins the fluid of the first pump 1 and the fluid of the second pump 2 and is supplied to an actuator (not shown), and the return fluid from the actuator is discharged to the tank T. You. At this time, the fluid of the third pump 2a is
However, as described above, the switching speed of the second switching valve 208 is controlled by the throttles 201a and 201b.
Since the pressure is kept low and the switching is performed slowly, the increase in the combined flow rate becomes slow, and the flow rate supplied to the actuator does not increase rapidly, so that the actuator can move smoothly without shock.

Next, the flow rate of the pilot pump Pp decreases, and the two pilot chambers 208a,
When the pressure difference between the pressures 208b decreases and the rightward force due to the pressure difference becomes smaller than the elastic force of the spring 210b, the second switching valve 208 starts moving leftward in the drawing so as to return to the neutral position by the elastic force of the spring 210b. . Then, the second
The amount of fluid corresponding to the amount of movement of the switching valve 208 is reduced by the throttle 208a.
Flow through the pilot chamber 208 by the throttle 201a.
The lowering speed of the pressure a decreases. In addition, pilot room 2
Fluid 08b flows from pilot passage 12 through pilot passage 212 through pilot passage 212 and flows into throttle 201b, and the pressure in pilot chamber 208b rises slowly due to throttle 201b. Accordingly, both pilot chambers 208a, 20
8b, the rate of decrease in the force for moving the first switching valve 108 to the right due to this differential pressure is slow, so that the second switching valve 208 returns to the neutral position in the left of the figure. The speed of movement in the direction will decrease. That is, the second
The switching valve 208 slowly moves in a direction to return to the neutral position.
Then, the movement of the second switching valve 208 stops at a position where the rightward force due to the pressure of the pilot chamber 208a and the elastic force of the spring 210b are balanced. At this time, the third pump 2
Although the flow rate at which the fluid a and the fluids of the first and second pumps merge decreases, the switching speed of the second switching valve 208 is suppressed low by the throttles 201a and 201b, as described above.
The slow movement reduces the merged flow rate, and the flow rate supplied to the actuator does not decrease abruptly. Therefore, the actuator can move smoothly while reducing the speed without shock.

Further, the flow rate of the pilot pump Pp decreases, and both pilot chambers 108a,
When the pressure difference between the pressures 108b decreases and the rightward force due to the pressure difference becomes smaller than the elastic force of the spring 110b, the first switching valve 108 starts moving leftward in the drawing to return to the neutral position by the elastic force of the spring 110b. . Then, the first
The amount of fluid corresponding to the amount of movement of the switching valve 108 is reduced by the throttle 108a.
Flow through the pilot chamber 108 by the throttle 101a.
The lowering speed of the pressure a decreases. In addition, pilot room 1
Fluid 08b flows from pilot passage 12 through pilot passage 112 through pilot passage 112 and flows into throttle 101b, and the pressure in pilot chamber 108b rises slowly due to throttle 101b. Accordingly, the differential pressure between the pilot chambers 108a and 108b of the first switching valve 108 decreases at a lower rate, and the differential pressure decreases the reduction rate of the force for moving the first switching valve 108 to the right. The moving speed that moves leftward in the figure to return to the neutral position of the switching valve 108 decreases. That is, the first switching valve 108 slowly moves in the direction to return to the neutral position. And the pilot room 108a
The movement of the first switching valve 108 stops at a position where the rightward force due to the pressure of (1) and the elastic force of the spring 110b are balanced. At this time, although the flow rate at which the fluid of the second pump and the fluid of the first pump join decreases, as described above, the switching speed of the first switching valve 108 is suppressed low by the throttles 101a and 101b, and slowly. The movement causes the merged flow rate to decrease gradually, and the flow rate supplied to the actuator does not decrease abruptly, so that the actuator can move without a shock while smoothly reducing the speed.

When the variable pilot pump Pp discharges fluid to the pilot passage 12 side, the switching valve with communication passage 7 and the first and second switching valves 108 and 208 move to the left in the figure opposite to the above case. Then, it switches to the right position.
The first, second, and third pumps 1, 2, and 2a communicate with the actuator passage A via the pump passages 3, 4, and 4a, and the tank passages 5, 6, and 6a communicate with the actuator overnight passage B. . Therefore, the first, second and third pumps 1 and
2, 2a fluid is supplied. The operation is the same as when the variable pilot pump Pp discharges fluid to the pilot passage 12 side than when the variable pilot pump Pp discharges fluid to the pilot passage 12 side.
208 is different only in that it moves in the opposite direction, but the other parts are the same and will not be described.

As described above, according to the second embodiment, the switching speed of the first and second switching valves 108 and 208 can be kept low even when the flow rate of the variable pilot pump increases or decreases. The movement of the actuator is smooth without shock.

Further, according to the second embodiment, a switching valve having no communication passage is used among a plurality of switching valves.
The capacity of the pilot pump can be reduced, and the cost can be reduced. Further, the switching speed of the switching valve can be arbitrarily reduced by the throttle. Further, the degree of opening of the throttle can be set accurately and easily compared to the setting of the elastic force of the spring. Therefore, the switching speed can be set accurately. Since the first and second switching valves 108 and 208 do not have a pilot port and a communication path, component costs, assembling costs, and manufacturing costs can be reduced.

Next, a third embodiment of the present invention is shown in FIG. In the third embodiment, throttles 101a, 101a, which are provided in pilot passages 111, 112 of the first embodiment, respectively.
The pilot passage 11 is connected so as to flow from the pilot passage 111 to the pilot chamber 108a and from the pilot passage 112 to the pilot chamber 108b in parallel with the pilot passage 101b.
1 is provided with a check valve 102a, and the pilot passage 112 is provided with a check valve 102b. The other configuration is the same as that of the first embodiment, and the description is omitted. This aperture 10
1a, 101b and the check valves 102a, 102b control the speed at which the first switching valve 108 returns to the neutral position.

Next, the operation of the third embodiment will be described. When the variable pilot pump Pp discharges fluid to the pilot passage 11 side, the fluid
Are supplied to the pilot chambers 7a and 8a connected in parallel via the. Since the communication with the pilot passage 12 is interrupted in the pilot chamber 7a, a fluid pressure is generated in the pilot chamber 7a. By this fluid pressure, a rightward force in the figure acts on the switching valve 7 with the communication passage. When the rightward force due to the fluid pressure becomes larger than the elastic force of the spring 9b, the switching valve with communication passage 7 moves rightward in the figure against the spring 9b.

When the switching valve with communication passage 7 moves rightward in the figure, the pilot ports 13a and 13b communicate with each other via the communication passage 17a formed in the switching valve with communication passage 7. When the two pilot ports 13a and 13b communicate with each other, the fluid of the variable pilot pump Pp flows from the pilot passage 11 → the passage 15a → the pilot port 13a → the communication passage 17a → the pilot port 13b → the passage 15b → the pilot passage l.
It flows in the order of 2. At this time, a pressure difference occurs between the pilot chambers 7a and 7b due to the pressure loss of the fluid flowing through the control throttle 19a. Due to this differential pressure, a force in the right direction in the figure acts on the switching valve with communication passage 7. Therefore, the switching valve with communication passage 7 moves to a position where the force due to the differential pressure and the elastic force due to the spring 9b are balanced.

At this time, the same pressure as the fluid pressure in the pilot passage 11 is generated in the pilot chamber 108a of the first switching valve 108 via the pilot passage 111, and the pilot chamber 108b is controlled through the pilot passage 112. Since the same pressure as the fluid pressure in the pilot passage 12 is generated, a differential pressure is generated between the pilot chambers 108a and 108b. However, while the rightward force due to this differential pressure is smaller than the elastic force of the spring 110b, the first switching valve 108
Does not switch yet. And the pilot pump Pp
Of the pilot chamber 1 of the first switching valve 108
When the pressure at 08a increases and the rightward force due to this differential pressure becomes greater than the elastic force of the spring 110b, the first switching valve 108 moves rightward in the figure against the spring 110b. Then, the fluid corresponding to the moving amount of the first switching valve 108 does not flow through the restrictor 108a having resistance but flows through the check valve 102a to the pilot chamber 108a. At this time, unlike the first embodiment, since the switching speed of the first switching valve 108 does not decrease, the switching is performed at a high speed.

When the first switching valve 108 moves rightward in the drawing as described above, the pump passage 4 and the actuator passage B
And the tank passage 6 and the actuator passage A communicate with each other. Therefore, the fluid of the second pump 2 joins the fluid of the first pump 1 and is supplied to an actuator (not shown), and the return fluid from the actuator is discharged to the tank T. At this time, the fluid of the second pump merges with the fluid of the first pump, as described above.
Since the switching speed of the first switching valve 108 is switched at a high speed, the increase in the combined flow rate is fast, and the flow rate supplied to the actuator is increased at a high speed, so that the actuator can move responsively.

Next, the flow rate of the pilot pump Pp decreases, and the differential pressure between the pilot chambers 108a and 108b decreases.
When the elastic force becomes smaller than the elastic force b, the first switching valve 108 starts to move leftward in the drawing so as to return to the neutral position by the elastic force of the spring 110b. Fluid corresponding to the amount of movement of the first switching valve 108 is shut off by the check valve 102a, and the throttle 101a
Flow through the pilot chamber 108 by the throttle 101a.
The lowering speed of the pressure a decreases. In addition, pilot room 1
08b, the fluid does not flow from the pilot passage 12 through the pilot passage 112 and through the restrictor 101b having resistance.
The gas flows through the check valve 102b. Accordingly, the differential pressure between the two pilot chambers 108a and 108b has a lowering speed, and the speed of decreasing the force for moving the first switching valve 108 to the right due to this differential pressure becomes slower. The moving speed moving leftward in the figure so as to return to becomes lower. That is, the first switching valve 108 slowly moves in the direction to return to the neutral position. And both pilot rooms 108
a and rightward force due to the pressure difference between 108a and 108b
10b at the position where the elastic force of 10b is balanced.
Stops moving. At this time, the flow rate at which the fluid of the second pump and the fluid of the first pump merge decreases, but as described above, the switching speed of the first switching valve 108 is reduced by the throttles 101a and 101a.
By 1b, the actuator is pressed low and moves slowly, so that the decrease in the combined flow rate becomes gentle, and the flow rate supplied to the actuator does not decrease abruptly, so that the actuator can move smoothly without shock.

When the variable pilot pump Pp discharges fluid to the pilot passage 12 side, the switching valve with communication passage 7 and the first switching valve 108 move leftward in the drawing opposite to the above case, and move to the right. Switch to position. The first and second pumps 1 and 2 communicate with the actuator passage A via the pump passages 3 and 4, and the tank passages 5 and 6 communicate with the actuator passage B. Therefore, the first and second actuators, not shown, are placed on the opposite side to the above case.
The fluid of the pumps 1 and 2 is supplied. The operation is different from the case where the variable pilot pump Pp discharges the fluid to the pilot passage 12 side only in that the switching valve 7 with the communication passage and the second switching valve 108 move in opposite directions, but the other operations are the same, and therefore the description is omitted. .

As described above, according to the third embodiment, when the flow rate of the variable pilot pump increases, the switching speed of the first switching valve 108 switches to high speed, so that the actuator moves with good responsiveness, When the flow rate of the pilot pump decreases, the switching speed of the first switching valve 108 can be kept low, so that the actuator can move smoothly without shock. The check valve 102a provided in the pilot passage 111 and the pilot passage 1
When the check valve 102b provided in the valve 12 is turned in the opposite direction to that in FIG. 4 and the above description, the variable pilot pump Pp
When the flow rate of the variable pilot pump Pp decreases, the switching speed of the first switching valve 108 can be suppressed to a low value, so that the actuator can move smoothly without shock. Valve 108
Is switched at a high speed, so that the actuator can move with good responsiveness.

Further, as in the first embodiment, according to the third embodiment, since the switching valve having no communication passage is used among the plurality of switching valves, the capacity of the pilot pump can be reduced, and Cost can be reduced. Further, the switching speed of the switching valve can be arbitrarily reduced by the throttle. Further, the degree of opening of the throttle can be set accurately and easily compared to the setting of the elastic force of the spring. Therefore, the switching speed can be set accurately. Since the first switching valve 108 does not have a pilot port and a communication path, parts costs, assembling costs, and manufacturing costs can be reduced.

Next, a fourth embodiment of the present invention is shown in FIG. In the fourth embodiment, a pilot is provided so as to flow from the pilot passage 111 to the pilot chamber 108a in parallel with the throttles 101a, 101b, 201a and 201b provided in the pilot passages 111, 112, 211 and 212 of the second embodiment. The pilot passage 2 is set so as to flow from the passage 112 to the pilot room 108b and from the pilot passage 211 to the pilot room 208a.
12 to the pilot chamber 208b, the check valve 102a to the pilot passage 111, the check valve 102b to the pilot passage 112, the check valve 202a to the pilot passage 211, and the check valve 202b to the pilot passage 212.
Respectively. The other configuration is the same as that of the second embodiment, and the description is omitted. This aperture 101a, 1
01b, 201a, 201b and check valves 102a, 102
b, 202a and 202b are the first and second switching valves 108 and 2
08 controls the speed of returning to the neutral position.

Next, the operation of the fourth embodiment will be described. When the variable pilot pump Pp discharges fluid to the pilot passage 11 side, the fluid
Are supplied to the pilot chambers 7a and 8a connected in parallel via the. Since the communication with the pilot passage 12 is interrupted in the pilot chamber 7a, a fluid pressure is generated in the pilot chamber 7a. By this fluid pressure, a rightward force in the figure acts on the switching valve 7 with the communication passage. When the rightward force due to the fluid pressure becomes larger than the elastic force of the spring 9b, the switching valve with communication passage 7 moves rightward in the figure against the spring 9b.

When the switching valve with communication passage 7 moves rightward in the figure, the pilot ports 13a and 13b communicate with each other via the communication passage 17a formed in the switching valve with communication passage 7. When the two pilot ports 13a and 13b communicate with each other, the fluid of the variable pilot pump Pp flows from the pilot passage 11 → the passage 15a → the pilot port 13a → the communication passage 17a → the pilot port 13b → the passage 15b → the pilot passage l.
It flows in the order of 2. At this time, a pressure difference occurs between the pilot chambers 7a and 7b due to the pressure loss of the fluid flowing through the control throttle 19a. Due to this differential pressure, a force in the right direction in the figure acts on the switching valve with communication passage 7. Therefore, the switching valve with communication passage 7 moves to a position where the force due to the differential pressure and the elastic force due to the spring 9b are balanced.

At this time, the same pressure as the fluid pressure in the pilot passage 11 is generated in the pilot chamber 108 a of the first switching valve 108 via the pilot passage 111, and the pilot chamber 108 b is controlled through the pilot passage 112. Since the same pressure as the fluid pressure in the pilot passage 12 is generated, a differential pressure is generated between the pilot chambers 108a and 108b. However, while the rightward force due to this differential pressure is smaller than the elastic force of the spring 110b, the first switching valve 108
Does not switch yet. And the pilot pump Pp
Of the pilot chamber 1 of the first switching valve 108
08a becomes high, and both pilot chambers 108a,
When the pressure difference between the pressures 108b increases and the rightward force due to the pressure difference becomes larger than the elastic force of the spring 110b, the first switching valve 108 moves rightward in the figure against the spring 110b. Then, the fluid corresponding to the moving amount of the first switching valve 108 does not flow through the restrictor 101a having resistance, but passes through the check valve 102a and the pilot chamber 108a.
Flows to At this time, as in the third embodiment, the switching speed of the first switching valve 108 does not decrease, so that the switching is performed at a high speed.

At this time, the same pressure as the fluid pressure in the pilot passage 11 is generated in the pilot chamber 208a of the second switching valve 208 via the pilot passage 211.
Since the same pressure as the fluid pressure in the pilot passage 12 is generated in the pilot chamber 208b via the pilot passage 212, a differential pressure is generated between the pilot chambers 208a and 208b. However, while the rightward force due to this differential pressure is smaller than the elastic force of the spring 210b, the second switching valve 208 has not been switched yet. Further, the flow rate of the pilot pump Pp further increases, and the second switching valve 20
When the pressure in the pilot chamber 108a increases and the differential pressure between the pilot chambers 208a and 208b increases, and the rightward force due to this differential pressure becomes greater than the elastic force of the spring 110b, the second switching valve 208 Moves rightward in the figure against the spring 210b. Then, the second
The fluid corresponding to the amount of movement of the switching valve 208 does not flow through the restrictor 201a having resistance but flows through the check valve 202a to the pilot chamber 208a. At this time, the switching speed is high because the switching speed of the second switching valve 208 does not decrease, as described above.

When the first switching valve 108 moves rightward in the drawing as described above, the pump passage 4 and the actuator passage B
And the tank passage 6 and the actuator passage A communicate with each other. Therefore, the fluid of the second pump 2 joins the fluid of the first pump 1 and is supplied to an actuator (not shown), and the return fluid from the actuator is discharged to the tank T. At this time, the fluid of the second pump merges with the fluid of the first pump, as described above.
Since the switching speed of the first switching valve 108 is switched at a high speed, the increase in the combined flow rate is fast, and the flow rate supplied to the actuator is increased at a high speed, so that the actuator can move responsively.

Further, when the second switching valve 208 moves rightward in the drawing as described above, the pump passage 4a communicates with the actuator passage B, and the tank passage 6a communicates with the actuator passage A. Therefore, the fluid of the third pump 2a joins the fluid of the first pump 1 and the fluid of the second pump 2 and is supplied to an actuator (not shown), and the return fluid from the actuator is discharged to the tank T. You. At this time, the fluid of the third pump 2a is first,
Although the fluid merges with the fluid of the second pump, as described above, the switching speed of the second switching valve 208 switches at a high speed, so that the merged flow rate increases quickly and the flow rate supplied to the actuator increases at a high speed. Thus, the actuator can move responsively.

Next, the flow rate of the pilot pump Pp decreases, and both pilot chambers 208a,
When the pressure difference between the pressures 208b decreases and the rightward force due to the pressure difference becomes smaller than the elastic force of the spring 110b, the first switching valve 108 starts moving leftward in the drawing so as to return to the neutral position by the elastic force of the spring 110b. . Second switching valve 2
Fluid corresponding to the movement amount of 08 is shut off by the check valve 202a and flows through the throttle 208a, so that the pressure of the pilot chamber 208a decreases by the throttle 201a at a slower rate. Further, the fluid flows into the pilot chamber 208b from the pilot passage 12 through the pilot passage 212, does not flow through the throttle 201b having resistance, but flows through the check valve 202b. Accordingly, the differential pressure between the two pilot chambers 208a and 208b has a lowering speed, and the force for moving the second switching valve 208 to the right due to the differential pressure has a lowering speed. The moving speed moving leftward in the figure so as to return to becomes lower. That is, the first switching valve 208 slowly moves in the direction to return to the neutral position. Then, the movement of the second switching valve 208 stops at a position where the rightward force due to the pressure difference between the pilot chambers 208a and 208b and the elastic force of the spring 210b are balanced. At this time, when the combined flow of the fluid of the third pump 2a and the fluids of the first and second pumps 1 and 2 decreases, as described above, the second
The switching speed of the switching valve 208 is held low by the throttles 201a and 201b and moves slowly, so that the flow rate of the combined flow decreases slowly, and the flow rate supplied to the actuator does not decrease rapidly, so that the actuator moves smoothly without shock. be able to.

Further, the flow rate of the pilot pump Pp decreases, and the first switching valve 108 and both pilot chambers 108a, 1
When the pressure difference between the pressures 08b and 08b decreases, and the rightward force due to the pressure difference becomes smaller than the elastic force of the spring 110b, the first switching valve 108 starts moving leftward in the drawing to return to the neutral position by the elastic force of the spring 110b. . First switching valve 10
Fluid corresponding to the amount of movement of 8 is blocked by the check valve 102a and flows through the throttle 108a.
The descending speed of the pressure in the pilot chamber 108a decreases. In addition, fluid is supplied to the pilot passage 1b in the pilot chamber 108b.
2 through the pilot passage 112 and the restrictor 10 having resistance.
1b, it flows through the check valve 102b and flows in.
Therefore, the differential pressure between the two pilot chambers 108a and 108b decreases at a lower speed, and the first switching valve 10
Since the force for moving the shutter 8 in the right direction decreases at a slower rate, the moving speed for moving the first switch valve 108 to the left in the figure to return to the neutral position decreases. That is, the first switching valve 108
Moves slowly back to the neutral position. Then, the movement of the first switching valve stops at a position where the rightward force due to the pressure difference between the two pilot chambers 108a and 108b and the elastic force of the spring 110b are balanced. At this time, when the flow rate at which the fluid of the second pump and the fluid of the first pump merge decreases, as described above, the switching speed of the first switching valve 108 is suppressed low by the throttles 101a and 101b, and is slowly reduced. Therefore, the combined flow rate decreases gradually, and the flow rate supplied to the actuator does not decrease rapidly, so that the actuator can move smoothly without shock. Further, a check valve 102 provided in the pilot passage 111 is provided.
a, when the check valve 102b provided in the pilot passage 112, the check valve 202a provided in the pilot passage 211, and the check valve 202b provided in the pilot passage 212 are oriented in the opposite direction to FIG. 5 and the above description. When the flow rate of the variable pilot pump Pp increases, the first and second switching valves 1
The switching speed of the first and second switching valves 108 and 208 can be reduced when the flow rate of the variable pilot pump Pp is reduced. Since the switching is performed at high speed, the actuator can move with good responsiveness.

When the variable pilot pump Pp discharges fluid to the pilot passage 12 side, the switching valve 7 with the communication passage and the first and second switching valves 108 and 208 move leftward in the figure opposite to the above case. Move to switch to the right position. Then, the first, second, and third pumps 1, 2, and 2a communicate with the actuator passage A via the pump passages 3, 4, and 4a, and the tank passages 5, 6, and 6a communicate with the actuator passage B. Therefore, the fluid of the first, second, and third pumps 1, 2, and 2a is supplied to the actuator (not shown) on the side opposite to the above case. The operation is the same as that in the case where the variable pilot pump Pp discharges fluid to the pilot passage 12 side.
08 and 208 differ only in that they move in opposite directions, but are otherwise identical and will not be described.

As described above, according to the fourth embodiment, when the flow rate of the variable pilot pump increases, the switching speed of the first and second switching valves 108 and 208 is switched at a high speed. When the flow rate of the variable pilot pump decreases, the switching speed of the first and second switching valves can be kept low, so that the actuator can move smoothly without shock. The check valve 102a provided in the pilot passage 111, the check valve 102b provided in the pilot passage 112, the check valve 202a provided in the pilot passage 211, and the check valve 202b provided in the pilot passage 212 are shown in FIG. In the case where the flow direction of the variable pilot pump increases when the direction is reversed, the first and second switching valves 108 and 20 are used.
8, the switching speed can be kept low, the actuator can move smoothly without shock, and when the flow rate of the variable pilot pump decreases, the first and second switching speeds can be reduced.
Since the switching speed of the switching valves 108 and 208 is switched at a high speed, the actuator can move with good responsiveness.

Further, like the second embodiment, according to the fourth embodiment, a switching valve having no communication passage is used among a plurality of switching valves, so that the capacity of the pilot pump can be reduced, Cost can be reduced. Further, the switching speed of the switching valve can be arbitrarily reduced by the throttle. Further, the degree of opening of the throttle can be set accurately and easily compared to the setting of the elastic force of the spring. Therefore, the switching speed can be set accurately. Then, the first and second switching valves 108 and 2
08 does not have a pilot port and a communication path, so that parts costs, assembling costs, and manufacturing costs can be reduced.

[Brief description of the drawings]

FIG. 1 shows a first embodiment of the present invention.

FIG. 2 shows a specific example of the first embodiment of the present invention.

FIG. 3 shows a second embodiment of the present invention.

FIG. 4 shows a third embodiment of the present invention.

FIG. 5 shows a fourth embodiment of the present invention.

FIG. 6 shows a conventional switching valve operation circuit.

FIG. 7 is a graph showing a pilot flow rate of a conventional switching valve operation circuit and a supply flow rate to an actuator.

[Explanation of symbols]

Pp: Variable pilot pump, 7: Switching valve with communication passage, 1
08: first switching valve, 208: second switching valve, 9a, 9b,
110a, 110b, 210a, 210b ... spring, 7a, 7b, 108a, 108b, 208a, 20
8b, ... pilot room, 17a, 17b, 18a, 18
b: communication passage, 19a, 19b, 20a, 20b: control throttle, 101a, 101b, 201a, 201b: throttle,
102a, 102b, 202a, 202b ... check valves.

Claims (2)

[Claims] A plurality of switching valves, a spring for holding the switching valves in a normal position, a pilot chamber provided on both sides of the switching valve, and a pilot flow generating means for supplying a fluid to the pilot chamber. In the switching valve operating circuit, one of the plurality of switching valves is shut off when the switching valve is in the normal position, and the communication passages (17a, 17b) communicating the two pilot chambers when the switching valve is switched. )When,
A communication-type switching valve (7) provided in the communication path (17a, 17b) and having a control throttle (19a, 19b) for increasing the opening in accordance with the switching amount of the switching valve, and the other switching valves are A pilot chamber non-communication type switching valve (108) in which both pilot chambers are not in communication with each other, and pilot chambers (7a, 7b, 108) on both sides of the plurality of switching valves.
a, 108b) are connected in parallel to the pilot flow generation means (Pp), and the pilot chambers (108a, 108b) and the pilot flow generation means (Pp) on both sides of the pilot chamber non-communication switching valve (108). To the connecting passages (111, 112)
A switching valve operation circuit, comprising: b). 2. A switch valve comprising: a plurality of switching valves; a spring for holding the switching valves in a normal position; a pilot chamber provided on both sides of the switching valve; and a pilot flow rate generating means for supplying a fluid to the pilot chamber. In the switching valve operating circuit, one of the plurality of switching valves is shut off when the switching valve is in the normal position, and the communication passages (17a, 17b) communicating the two pilot chambers when the switching valve is switched. )When,
A communication-type switching valve (7) provided in the communication path (17a, 17b) and having a control throttle (19a, 19b) for increasing the opening in accordance with the switching amount of the switching valve, and the other switching valves are A pilot chamber non-communication type switching valve (108) in which both pilot chambers are not in communication with each other, and pilot chambers (7a, 7b, 108) on both sides of the plurality of switching valves.
a, 108b) are connected in parallel to the pilot flow generation means (Pp), and the pilot chambers (108a, 108b) and the pilot flow generation means (Pp) on both sides of the pilot chamber non-communication switching valve (108). To the connecting passages (111, 112)
b) and a check valve (102a, 102b) provided in parallel.