JPH0714641Y2 - Hydraulic actuator drive circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a drive circuit of an actuator used in, for example, a hydraulic circuit of a construction machine.

[Conventional technology]

Conventionally, as a drive circuit for this type of actuator, there is one shown in FIG. 3 (Japanese Patent Laid-Open No. 55-135205). Less than,
This conventional technique will be described.

In FIG. 3, 1 is a first pump, 2c is a first actuator, 3c is a first switching valve for controlling the driving direction and driving speed of the first actuator 2c, and these constitute a first circuit Ic, and 4 is a A second pump, 5 is a second actuator, 6 is a second switching valve for controlling the driving direction and the driving speed of the second actuator 5, and these constitute a second circuit IIc.

The first switching valve 3c has an unload passage 7c for unloading the discharge pressure oil of the first pump 1, and merge operation positions 8c, 9c for closing the unload passage 7c and the unload passage 7c. It is provided with a neutral position 10c communicating with each other. The second switching valve 6 has an unload passage 11, and merge operation positions 12 and 13 for closing the unload passage 11, single operation positions 14 and 15 for communicating the unload passage 11 and a neutral position. It has position 16. The downstream side of the unload passage 7c of the first switching valve 3c is connected to the upstream side of the unload passage 11 of the second switching valve 6 and is connected to the oil tank 43 via the discharge passage 17. 20
Is a first merging circuit that connects the downstream side of the unload passage 7c of the first switching valve 3c and the discharge passage 19 of the second pump 4, and
A check valve 21 that allows the flow of the hydraulic oil to the discharge passage 19 of the second pump 4 and blocks the reverse flow is provided in the merging circuit 20. 22c is a second merging circuit that connects the discharge passage 19 of the second pump 4 and the discharge passage 18 of the first pump 1, and the flow of the hydraulic oil to the discharge passage 18 of the first pump 1 is in the second merging circuit 22c. And a check valve 23 for preventing backflow are provided, and a bleed-off type pressure compensating valve 24 is provided between the check valve 23 and the discharge passage 19. The second pump 4 is installed in the pilot chamber 24a of the pressure compensation valve 24.
The pressure in the discharge passage 19 acts through the pilot passage 25,
In the spring chamber 24b facing the pilot chamber 24a, the spring 30
And the load pressure of the second actuator 5 acts via the shuttle valve 28 through the supply / discharge passages 26, 27 and the pilot passage 29. Reference numeral 40 denotes a bleed-off type pressure compensating valve, which is provided in a bypass passage 34 connecting the discharge passage 18 of the first pump 1 and the downstream side of the unload passage 7c of the first switching valve 3c. The pressure of the discharge passage 18 of the 1st pump 1 acts through the pilot passage 35, and the spring 40c is arranged in the spring chamber 40b facing the pilot chamber 40a, and the first actuator 2c is provided via the shuttle valve 36. Load pressure of supply / discharge passages 37, 38, pilot passage
Acts via 39. An opening / closing valve 42 is provided in a passage 41 that connects the pressure compensating valve 24 and the check valve 23 of the second merging circuit 22c and the upstream side of the unloading passage 11 of the second switching valve 6 with the opening / closing valve. The valve 42 is configured to open when receiving the pressure in the pilot passage 29. 32 and 33 are relief valves that regulate the maximum pressure in each passage.

Next, the operation will be described.

When only the first actuator 2c is driven, the first switching valve 3c is operated to the merging operation position 8c or 9c while the second switching valve 6 is held at the neutral position 16. The unload passage 7c is closed in this operating position. At this time, the discharge pressure oil of the first pump and the discharge pressure oil of the second pump are combined and supplied to the discharge passage 18, and the pressure compensating valve 40 adjusts the amount of oil according to the opening degree of the throttle formed by the first switching valve 3c. Is supplied to the first actuator 2c, and excess oil is supplied to the bypass passage 34 and the unload passage of the second switching valve 6.
11. The first actuator 2c can be controlled from a low speed to a high speed according to the operation of the first switching valve 3c, because the first actuator 2c operates so as to flow back to the oil tank 43 through the discharge passage 17.

When only the second actuator 5 is driven, the second switching valve 6 is kept in the neutral position 10c while the second switching valve 6 is in communication with the unloading passage 11 in the single operation position 14 or 15.
When operated to, the discharge pressure oil of the first pump 1 is discharged to the discharge passage 1
8, the unload passage 7c of the first switching valve 3c, the unload passage 11 of the second switching valve 6, and the discharge passage 17 are returned to the oil tank 43, so that the discharge pressure of the second pump 4 is applied to the second actuator 5. Only the oil is supplied, and the pressure compensating valve 24 supplies the second actuator 5 with the oil amount corresponding to the opening degree of the throttle formed by the second switching valve 6.
To supply the excess oil to the second merging circuit 22c, the opening / closing valve 42, the passage 4
1. Since it acts to recirculate to the oil tank 43 through the unload passage 11 and the discharge passage 17 of the second switching valve 6, the second actuator 5 can perform speed control according to the operation of the second switching valve 6. it can. Further, when the unloading passage 11 is closed by operating the merging operation position 12 or 13, the discharge pressure oil of the first pump 1 is checked by the unloading passage 7c of the first switching valve 3c and the first merging circuit 20. 2nd pump 4 through valve 21
Flow into the discharge passage 19 of the
Since the discharge pressure oil of the pump 1 and the discharge pressure oil of the second pump 4 merge and flow in, the second actuator 5 can be driven at high speed.

Next, when the first actuator 2c and the second actuator 5 are driven simultaneously, the first switching valve 3c is moved to the merging operation position 8c.
Or 9c, the second switching valve 6 is operated independently.
Operate to 14 or 15. In this case, the first pump 1
The first actuator 2c is driven by the discharge pressure oil of
The second actuator 5 is driven by the pressure oil discharged from the second pump 4. When the second switching valve 6 is in the independent operation positions 14 and 15, the unload passage 11 is in communication, so that the excess oil discharged from the pressure compensating valves 40 and 24 is the first actuator 2c and the second oil. The oil is returned to the oil tank 43 in the same manner as when the actuators 5 are individually operated.

[Problems to be solved by the device]

In the prior art as described above, the second switching valve 6 is operated to the independent operation position 14 or 15 where the unload passage 11 communicates, and
When operating the operation valve 3c to the merging operation position 8c or 9c and closing the unloading passage 7c, in order to operate the pressure compensation valve 24 normally, the excess oil discharged from the pressure compensation valve 24 is recirculated to the oil tank. Since the valve 42 is required, the circuit is complicated.

An object of the present invention is to provide a drive circuit for an actuator in which the pressure compensating valve 24 operates normally with a simple circuit configuration in which the opening / closing valve 42 that is conventionally provided is omitted.

[Means for Solving the Problems]

Means of the present invention for solving the above-mentioned problems of the prior art are
A first circuit in which a first actuator is connected to the discharge side of the first pump via a first switching valve, and a second circuit in which a second actuator is connected to the discharge side of the second pump via a second switching valve. Two circuits, and when the second switching valve is operated to the merging operation position between the first switching valve and the second switching valve,
A first merging circuit that connects the discharge side of the first pump to the discharge side of the second pump via a first switching valve and a check valve is provided, and the first merging circuit is provided between the discharge sides of the first pump and the second pump. When the first switching valve is operated to the merging operation position, the second
A second merging circuit that connects the discharge side of the pump to the discharge side of the first pump via a check valve is provided, and the second switching valve has a single operating position between the neutral position and the merging operating position. In a drive circuit of an actuator in which a pressure compensating valve for maintaining a constant differential pressure across a throttle formed by an operating position is provided in the second merging circuit, between a pressure compensating valve and a check valve of the second merging circuit. An unload circuit that branches off and is connected to the first switching valve is provided, and a single operation position that connects the unload circuit is provided between the neutral position of the first switching valve and the merging operation position. Characterize.

[Action]

According to the present invention having the above-mentioned means, an unload circuit that branches from between the pressure compensating valve and the check valve of the second merging circuit and is connected to the first switching valve is provided, and the merging with the neutral position of the first switching valve is performed. By providing an independent operation position for communicating the unload circuit with the operation position, even if both the switching valve and the first switching valve in FIG. Since the downstream side of the compensating valve communicates with the oil tank through the unload circuit, the first switching valve, the switching valve shown in FIG. 2, and the discharge passage, the pressure compensating valve can operate normally without the on-off valve. it can.

〔Example〕

An embodiment of the present invention will be described with reference to the circuit diagrams of FIGS. FIG. 1 shows a first embodiment in which a pressure compensating valve is provided only in the second circuit IIa, and FIG. 2 shows a second embodiment in which a pressure compensating valve is provided for both the first circuit Ib and the second circuit IIa. In the description, the same components as those in the related art and the embodiment will be denoted by the same symbols, and detailed description thereof will be omitted.

In FIG. 1, 1 is a first pump, 2a is a first actuator, 3a is a first switching valve for controlling the driving direction and driving speed of the first actuator 2a, and these constitute a first circuit Ia, and 4 is A second pump, 5 is a second actuator, 6 is a second switching valve for controlling the driving direction and the driving speed of the second actuator 5, and these constitute a second circuit IIa. The first switching valve 3a has an unload passage 7a for unloading the discharge pressure oil of the first pump 1.
Merging operation positions 8a, 9a for closing 7a, single operation positions 51a, 52a for communicating the unload passage 7a, and a neutral position 10
equipped with a. Further, the first switching valve is branched from between the pressure compensating valve 24 and the check valve 23 provided in the second merging circuit 22a connecting the discharge passage 19 of the second pump 4 and the discharge passage 18 of the first pump 1. An unload circuit 53 connected to 3a is provided. The unload circuit 53 communicates with the upstream side of the unload passage 11 of the second switching valve 6 when the first switching valve 3a is operated to the neutral position 10a and the single operation positions 51a and 52a, and the merging operation position 8a is provided. , 9a is configured to be closed when operated.

Next, the operation of the first embodiment will be described. When only the first actuator 2a is driven, the first switching valve 3a is unloaded while the second switching valve 6 is held at the neutral position 16.
When operated to the independent operation position 51a where 52 communicates, or 52a,
Only the pressure oil discharged from the first pump 1 is supplied to the first actuator 2a, and the first actuator 2a is driven. Also,
When operated to the merging operation position 8a or 9a, the discharge pressure oil of the first pump and the discharge pressure oil of the second pump 4 merge and are supplied to the first actuator 2a, and the first actuator 2a is driven at high speed. When only the second actuator 5 is driven,
With the first switching valve 3a held at the neutral position 10a, the second switching valve 6 communicates with the unload passage 11 in the independent operation positions 14, 15
When it is operated to, only the discharge pressure oil of the second pump 4 is supplied to the second actuator 5, and the pressure compensating valve 24 becomes the second switching valve 6
Is supplied to the second actuator 5 with an oil amount corresponding to the opening degree of the throttle formed by the second merging circuit 22a, the unload circuit 53, the unload passage 7a of the first switching valve 3a, and the second switching valve. The second actuator 5 can perform speed control according to the operation of the second switching valve 6, because the second actuator 5 is returned to the oil tank 43 through the unloading passage 11 and the discharge passage 17 of No. 6. When operated to the merging operation position 12 or 13, the discharge oil of the first pump 1 and the discharge oil of the second pump 4 merge and are supplied to the second actuator 5, and the second actuator 5 is driven at high speed.

When the first actuator 2a and the second actuator 5 are driven simultaneously, both the first switching valve 3a and the second switching valve 6 may be operated to the single operation position. In this case, the discharge pressure oil of the first pump 1 drives the first actuator 2a, and the discharge pressure oil of the second pump 4 drives the second actuator 5. When the second switching valve 6 and the first switching valve 3a are in the independent operation positions 14, 15, 51a, 52a, the unload passages 11, 7a are in communication with each other. The oil is returned to the oil tank 43 as in the case where only the second actuator 5 is driven.

Next, a second embodiment in which a pressure compensation valve is provided in both the first circuit Ib and the second circuit IIa will be described with reference to FIG. In this example, the first actuator 2a is controlled by the pressure compensation valve 40,
A bypass passage 34, which connects the discharge passage 18 of the first pump 1 and the downstream side of the unload passage 7b of the first switching valve 3b and has a pressure compensating valve 90, is added to the first embodiment (FIG. 1). It has been configured.

[Effect of device]

In the present invention having the above configuration, the first switching valve and the second switching valve have the same configuration, the on-off valve can be omitted, and the operation can be the same as that of the conventional circuit. Therefore, the circuit configuration is simplified, and the operation feelings of the first switching valve and the second switching valve are the same.

[Brief description of drawings]

1 and 2 are circuit diagrams of an embodiment of the present invention (FIG. 1 shows a first embodiment in which a pressure compensating valve is provided only in the passage shown in FIG. 2, and FIG. 2 shows both the first circuit and the second circuit. Second embodiment provided with a pressure compensation valve). FIG. 3 is a circuit diagram of a conventional technique. 1 ... 1st pump 2a ... 1st actuator 3a, 3b ... 1st switching valve 4 ... 2nd pump 5 ... 2nd actuator 6 ... 2nd switching valve 8a, 8b ... Merging operation position 9a, 9b …… Merge operation position 12, 13 …… Merge operation position 10a, 10b …… Neutral position 16 …… Neutral position 14, 15 …… Single operation position 51a, 51b …… Single operation position 52a, 52b …… Single operation position 20 …… First merging circuit 21, 23 …… Check valve 22a …… Second merging circuit 24,40 …… Pressure compensation valve 53 …… Unload circuit Ia, Ib …… First circuit IIa, IIb …… Second circuit

Claims (1)

[Scope of utility model registration request] 1. A first circuit comprising a first actuator connected to a discharge side of a first pump via a first switching valve, and a second actuator connected to a discharge side of a second pump via a second switching valve. A second circuit connected to the first switching valve and the second switching valve between the first switching valve and the second switching valve when the second switching valve is operated to the merging operation position. A first merging circuit connected to the discharge side of the second pump via the first switching valve and the check valve is provided, and the first switching valve is operated to the merging operation position between the discharge sides of the first pump and the second pump. And a second merging circuit that connects the discharge side of the second pump to the discharge side of the first pump via a check valve when
The second switching valve has an independent operating position between a neutral position and a merging operating position, and a pressure compensating valve for maintaining a constant differential pressure across the throttle formed by the single operating position is inserted in the second merging circuit. In the drive circuit of the actuator described above, an unload circuit that branches from between the pressure compensation valve and the check valve of the second merging circuit and connects to the first switching valve is provided, and the neutral position of the first switching valve and the merging operation are performed. A drive circuit for a hydraulic actuator, characterized in that an independent operation position for communicating the unload circuit with the position is provided.