JP2012007717A - Hydraulic circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid a supply amount to an actuator having a set upper limit value for a supply flow amount from exceeding the set upper limit value in any case.SOLUTION: In this hydraulic circuit, selector valves V1, v2, v3 are provided for a plurality of actuators, respectively, the selector valves are connected to a pump P, and meanwhile, when each selector is at a neutral position, oil discharged from the pump is introduced via a neutral flow path 2 for the plurality of selector valves into a tank T. At least one selector valve V1 out of the selector valves includes a connection passage 15 communicating a flow path 14 communicating a pump port 7 with an actuator port 11, with the tank T, and a throttle 16 provided in the connection passage 15, and enables bleed-off control via the throttle 16. A check valve 17 is provided in a passageway from a connection point 18 between the flow path 14 and the connection passage 15 to the actuator X for allowing only distribution from the pump port 7 to the actuator X.

Description

  The present invention relates to a hydraulic circuit in which a plurality of actuators are connected to one pump.

2. Description of the Related Art Conventionally, a hydraulic circuit that requires operation of a plurality of actuators such as construction machines is known as shown in FIG.
This circuit is a circuit for controlling the three actuators X, Y, and Z with one pump P, and the first control valve v1 and the second control for controlling the supply of hydraulic oil to each actuator X, Y, and Z. A valve v2 and a third control valve v3 are provided.
These control valves v1, v2, v3 are connected in series to a neutral passage 2 connected to the pump discharge passage 1, and when all these control valves v1, v2, v3 are in the neutral position, the total discharge flow rate of the pump P Is guided to the tank passage 3 through the neutral passage 2.

Further, supply passages 4, 5, 6 connected to the first to third control valves v1, v2, v3 are connected in parallel to the discharge passage 1 of the pump.
The first to third control valves v1, v2, and v3 include a pump port 7 connected to the supply passages 4, 5, and 6, a tank port 8 connected to the tank passage 3, and a neutral passage in the control valve. 2 includes an inflow port 9 and an outflow port 10 corresponding to both ends, and first and second actuator ports 11 and 12 connected to the actuators X, Y, and Z.

Further, the first control valve v1 is placed in an internal passage that connects the inflow port 9 and the outflow port 10 when switched to the left switching position A or the right switching position B with reference to the neutral position shown in the figure. A diaphragm 13 is formed.
On the other hand, the second and third control valves v2, v3 are configured to block communication between the inflow port 9 and the outflow port 10 when switched to the switching position A or the switching position B.

When the first to third control valves v1, v2, v3 are switched to the switching position A, the pump port 7 is connected to the first actuator port 11 and the second actuator port 12 is connected to the tank. When connected to the port 8 and switched to the switching position B, the pump port 7 is connected to the second actuator port 12 and the first actuator port 11 is connected to the tank port 8.
That is, the actuators X, Y, and Z can be operated by switching the first to third control valves v1, v2, and v3 connected to the actuators X, Y, and Z, respectively.

The first control valve v1 is formed with a throttle 13 connected to the neutral passage 2 at the left and right switching positions A and B. Therefore, when only the first control valve v1 is switched, the discharge passage is formed. A part of the flow rate of 1 flows to the tank passage 3 via the throttle 13 and the connection passage 2, and the remaining flow rate is supplied to the actuator X.
Therefore, if the flow rate exceeding the upper limit value of the flow rate that can be supplied to the actuator X out of the discharge amount of the pump P is set to flow through the throttle 13, the flow rate exceeding the upper limit value is set to the neutral passage 2. Therefore, the flow rate exceeding the upper limit value is not supplied to the actuator X.

The upper limit value of the actuator X is set according to the rating of the actuator X and the usage mode of the actuator X. For example, in the case where the actuator X is a traveling motor, supplying a large flow rate exceeding the rating and rotating the actuator at a high speed may damage the motor. In addition, even if the motor is not damaged, it is dangerous if a large flow rate is supplied and the vehicle runs at an unexpected high speed.
Therefore, the upper limit value of the supply flow rate may be set within a range where there is no danger in the rating of the actuator such as a motor and the usage mode.

  In the circuit shown in FIG. 2, when it is switched to the first control valve v1 connected to the actuator X provided with the upper limit value of the supply flow rate, it is a part of the flow rate of the discharge passage 1 and exceeds the upper limit value. A throttle 13 is set in the internal passage so as to flow to the tank passage 3 through the neutral passage 2.

  On the other hand, when the second and third control valves v2 and v3 are switched to one of the switching positions A and B, the communication between the inflow port 9 and the outflow port 10 is cut off. Will be interrupted. Therefore, when the second and third control valves v2 and v3 are individually switched, the total flow rate of the discharge passage 1 is supplied to the actuator Y or the actuator Z from any of the first and second actuator ports 11 and 12 described above. Is done.

JP 2007-333017 A

As described above, in the conventional hydraulic circuit shown in FIG. 2, when only the first control valve v <b> 1 is switched, a part of the discharge flow rate from the pump P is neutral through the internal passage provided with the throttle 13. 2 flows into the tank passage 3 and the actuator X is supplied with a flow rate not more than a preset upper limit value.
However, when one of the second and third control valves v2 and v3 is switched simultaneously with the first control valve v1, the neutral passage 2 connecting the throttle 13 and the tank passage 3 becomes the second control valve v2 or the second control valve v2. 3 is blocked by the control valve v3. For this reason, the discharge flow rate of the pump P is not returned to the tank T via the neutral passage 2. That is, the total discharge amount of the pump P is supplied to the actuator connected to the switched control valve.

Thus, since the total discharge amount from the pump P is supplied to the actuator without being restricted, a flow rate exceeding the upper limit value of the actuator X is supplied to the actuator X connected to the first control valve v1. there is a possibility. When the flow rate exceeding the upper limit value is supplied to the actuator X, the above-described problem occurs.
An object of the present invention is to provide a hydraulic circuit in which the supply amount to the actuator for which the upper limit value of the supply flow rate is set does not exceed the set upper limit value at any time.

  The present invention provides a switching valve for each of a plurality of actuators, and connects the switching valves to a pump. On the other hand, when each of the switching valves is in a neutral position, the discharge oil of the pump is neutral flow paths of the plurality of switching valves. Assuming a hydraulic circuit that is led to the tank via the tank, there is provided a connection passage for communicating with the tank at least one switching valve of the above-mentioned switching valve that communicates the pump port and the actuator port. A passage is provided with a restriction, enabling bleed-off control through the restriction, and in the passage process from the connection point between the passage connecting the pump port and the actuator port and the connection passage to the actuator. It is characterized in that a check valve that allows only the flow from the pump port to the actuator is provided.

According to this invention, at least one of the plurality of control valves is provided with a connection passage inside the valve that bleeds off a part of the discharge amount of the pump to the tank. The connection passage is not blocked depending on the position. That is, in the control valve having the connection passage, bleed-off control is always possible.
Therefore, the actuator connected to the control valve having the connection passage can be prevented from being supplied with a flow rate exceeding a preset upper limit value regardless of the switching state of other control valves.

1 is a hydraulic circuit diagram of an embodiment of the present invention. It is a conventional hydraulic circuit diagram.

The hydraulic circuit of the embodiment of the present invention shown in FIG. 1 is a circuit for controlling a plurality of actuators X, Y, Z. Each actuator X, Y, Z has first to third control valves V1, v2 respectively. , V3 are connected.
In this embodiment, the same reference numerals are used for the same elements as those in the conventional hydraulic circuit shown in FIG.

Also in the hydraulic circuit of this embodiment, the first to third control valves V1, v2, v3 are connected in series to the neutral passage 2, and when all the control valves V1, v2, v3 are in the neutral position, The discharge passage 1 is connected to the tank passage 3 through the neutral passage 2 so as to guide the total discharge amount of the pump P to the tank.
Moreover, it is the same as that of the conventional hydraulic circuit that the supply paths 4, 5, and 6 connected to the pump port 7 of each control valve are connected in parallel.

In the hydraulic circuit of this embodiment, the second and third control valves v2 and v3 connected to the actuators Y and Z have the same configuration as the conventional second and third control valves v2 and v3. The connected first control valve V1 is different from the conventional first control valve v1.
The first control valve V1 has two positions, a normal position shown in the drawing and a switching position A on the left side in the drawing, and supplies the hydraulic oil to the actuator X when switching to the switching position A. When the actuator X is, for example, a hydraulic motor that rotates in one direction, the first control valve V1 does not need to switch the supply direction of the hydraulic oil, so that a two-position control valve as in this embodiment is used. it can.

The first control valve V <b> 1 is configured to block communication between the inflow port 9 and the outflow port 10 when switched to the switching position A.
Further, in the first control valve V 1, a flow path 14 for communicating the pump port 7 and the first actuator port 11 at the switching position A is provided with a connection passage 15 for communicating with the tank port 8. Is provided with a diaphragm 16.

  Therefore, when the first control valve V1 is switched to the switching position A, a part of the flow rate discharged from the pump P is bleed off from the connection passage 15 to the tank T through the tank passage 3, and the remaining flow rate is reduced. It is supplied from the flow path 14 to the actuator X via the first actuator port 11.

  Therefore, if the flow rate returned to the tank T via the connection passage 15 is set by the throttle 16, the upper limit value of the flow rate supplied from the first actuator port 11 to the actuator X can be set.

In the figure, reference numeral 17 denotes a check valve that allows only the flow from the pump port 7 to the first actuator port 11, and indicates that hydraulic fluid flows back from the actuator X to the tank port 8 through the connection passage 15. It is for preventing.
The check valve 17 can prevent the reverse flow wherever it is provided in the course of the path from the connection point 18 between the flow path 14 and the connection path 15 to the actuator X. That is, the check valve 17 may be provided in a passage outside the first control valve V1.

  In the hydraulic circuit of this embodiment configured as described above, since the connection passage 15 connected to the tank passage 3 is provided in the first control valve V1, any of the second and third control valves v2 and v3 is provided. Even if the communication of the neutral passage 2 is cut off by switching the above, the communication between the connection passage 15 and the tank passage 3 is not cut off.

  That is, when the first control valve V1 is switched to the switching position A, the bleed-off amount set by the throttle 16 is always maintained. Therefore, when the first control valve V1 is switched to the switching position A, the flow rate exceeding the preset upper limit value is not supplied to the actuator X regardless of the switching state of the other control valves v2 and v3. .

  In this embodiment, the first control valve V1 is a two-position valve, that is, a neutral position and a switching position A. However, the actuator X needs to switch the supply direction of hydraulic oil, for example, as in a double-rotation motor. In this case, it is necessary to use a three-position valve provided with the switching position B for the first control valve V1 as well as the other control valves.

  In the case of a three-position valve, when switching to the switching position B, there is provided a connection passage for communicating with the tank a passage that communicates with the pump port 7 and the second actuator port 12, a throttle is provided in the connection passage, and the pump It is necessary to provide a check valve that allows only the flow from the pump port 7 to the actuator X in the path process from the connection point between the connection path and the flow path connecting the port 7 and the second actuator port 12 to the actuator X. There is.

  In this embodiment, the control valve V1 that enables the bleed-off control is connected to the actuator X. However, the control valve V1 is connected to an actuator that needs to limit the upper limit value of the hydraulic oil to be supplied. And the position can be anywhere. In addition, as with the first control valve V1, a plurality of control valves that enable bleed-off control can be provided as necessary.

DESCRIPTION OF SYMBOLS 1 Discharge passage 2 Neutral passage 3 Tank passage 7 Pump port 11 1st actuator port 12 2nd actuator port 14 Flow path 15 Connection passage 16 Restriction 17 Check valve 18 Connection point V1 1st control valve X Actuator Y Actuator Z Actuator P Pump T tank

Claims (1)

  A switching valve is provided in each of the plurality of actuators, and these switching valves are connected to the pump. On the other hand, when each of the switching valves is in the neutral position, the oil discharged from the pump passes through the neutral flow paths of the plurality of switching valves. In the hydraulic circuit led to the tank, there is provided a connection passage for communicating with the tank, which is at least one switching valve of the above-described switching valve, and which communicates the pump port and the actuator port, and this connection passage is provided with a throttle. The bleed-off control can be performed through the throttle, and the path from the connection point between the flow path connecting the pump port and the actuator port and the connection path to the actuator can be changed from the pump port to the actuator. Hydraulic circuit with a check valve that allows only circulation.

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