JPH087122Y2 - Hydraulic supply / discharge device for another work hydraulic circuit that is detachably connected to the pressure supply path of the main work hydraulic circuit. - Google Patents

Description

[Detailed Description of the Invention] << Industrial Application Field >> The present invention relates to a feed line of a main work hydraulic circuit, such as a case where an agricultural loader is detachably attached to an agricultural tractor and hydraulically driven. A hydraulic supply / discharge device that connects and disconnects a hydraulic circuit for another operation with a coupling on the way to supply and discharge pressure oil to this hydraulic circuit for another operation. It is a technology that reduces manufacturing cost and energy loss of hydraulic equipment.

<< Basic Structure as Premise >> Some hydraulic supply / discharge devices of this type have a basic structure as follows.

For example, as shown in FIG. 4 to FIG.
The hydraulic circuit 12 for main work is connected to the discharge port 10a of 10 through the pressure supply passage 11.
Connected to the pressure oil inlet 12a, and the pressure oil inlet 21a of the hydraulic circuit 21 for another work is connected in the middle of the pressure supply path 11 via the inlet side coupling 20.
Is detachably connected.

<< Prior Art >> In the above-mentioned basic structure, the structure of the portion for supplying and discharging the pressure oil to the hydraulic circuit 21 for another operation in the middle of the discharge pressure passage 11 has been conventionally as follows.

◎ Conventional Example 1 (see FIG. 4) The oil discharge port 21b of the hydraulic circuit 21 for another operation is connected to the pressure oil inlet 12a of the hydraulic circuit 12 for the main operation via the outlet side coupling 54 and the pressure supply path 11. When using the hydraulic circuit 21 for another operation, the oil drain port 2
The return oil discharged from 1b is returned to the oil tank 18 through the main work hydraulic circuit 12.

◎ Conventional example 2 (see FIG. 5) In addition to the neutral drainage port 21b, a working drainage port 21c is added to the hydraulic circuit 21 for another work. Further, the neutral oil discharge port 21b is connected to the pressure oil inlet 12a of the main work hydraulic circuit 12 via the oil supply outlet side coupling 54 and the pressure supply passage 11. Further, the work oil drain port 21c is connected to the oil tank 18 in a short-circuit manner via the bypass outlet coupling 80 and the bypass passage 81.

As a result, the separate work hydraulic circuit 21 supplies the return oil from the neutral oil discharge port 21b to the main work hydraulic circuit 12 in the neutral state, while the return oil is supplied to the bypass passage 81 in the hydraulic drive state.
To bypass the oil tank 18.

◎ Conventional example 3 (see FIG. 6) This is an example in which an automatic bypass device 83 is added to the structure of the conventional example 1 (FIG. 4). The automatic bypass device 83 is as follows.

The pressure supply path portion 11b on the downstream side of the hydraulic circuit 21 for another operation
Is branched and connected to the oil tank 18 in a short circuit manner via the constant difference relief valve 84 and the bypass passage 85. The constant difference relief valve 84
When the pressure difference between the pressure supply passage portion 11a on the upstream side of the hydraulic circuit 21 for another operation and the pressure supply passage portion 11b on the downstream side is smaller than the set value, the valve is closed by the spring 86, whereas the set value is When it is larger than that, the valve is opened by the differential pressure.

As a result, when the hydraulic circuit 21 for another work is in the neutral state, the constant difference relief valve 84 is closed, and the hydraulic circuit 12 for main work is closed.
Can be hydraulically driven. On the other hand, when the hydraulic circuit 21 for another work is hydraulically driven, the constant difference relief valve 84 is opened so that the return oil from the hydraulic circuit 21 for another work is short-circuited and returned from the bypass passage 85 to the oil tank 18. It has become.

◎ Conventional example 4 (see FIG. 7)
The automatic bypass device 88 is added. The automatic bypass device 88 is as follows.

An electromagnetically operated directional control valve 89 is interposed in the pressure supply path portion 11b on the downstream side of the separate work hydraulic circuit 21. The electromagnetically operated directional control valve 89 is interlocked with the hydraulically driven directional control valve 90 of the hydraulic circuit 21 for another operation via the switch 91, and the pressure feed position M
To the bypass return position N.

In the rest state in which the hydraulic drive operation directional control valve 90 is in the neutral state, the switch 91 is turned off, and the electromagnetically operated directional control valve 89 is closed by the spring 92 at the pressure feeding position M. This allows
The return oil from the separate work hydraulic circuit 21 is pressure-fed to the main work hydraulic circuit 12 from the pressure supply path portion 11b on the downstream side, so that the main work hydraulic circuit 12 can be driven.

On the other hand, in the drive state in which the hydraulic drive operation direction switching valve 90 is switched to the hydraulic work position, the switch 91 is turned on,
The electromagnetically operated directional control valve 89 is electromagnetically operated to the bypass return position N, and the return oil from the hydraulic circuit 21 for another operation is bypassed.
It is short-circuited and returned to the oil tank 18 from 93.

<< Problems to be Solved by the Invention >> The above-mentioned conventional examples have the following problems.

◎ Conventional Example 1 (see FIG. 4) (a) Energy loss is large.

In the hydraulically driven state of the separate work hydraulic circuit 21, the return oil flowing out from the neutral drainage port 21b flows in the pressure supply passage 11 and the main work hydraulic circuit 12, so that the flow resistance is large and the energy of the hydraulic system is high. There is a lot of loss.

Moreover, if the hydraulic cylinders 95/96 are double-acting type,
In the hydraulically driven state of the hydraulic circuit 21 for another operation, the back pressure of the neutral oil discharge port 21b increases due to the above-mentioned flow resistance, so the outputs of the hydraulic cylinders 95 and 96 must be reduced.

◎ Conventional example 2 (See FIG. 5) (B) Attachment and detachment operations are troublesome.

In order to connect / disconnect the hydraulic circuit 21 for another operation to the pressure supply passage 11, it is necessary to connect / disconnect the three couplings 20, 54/80, and it is necessary to operate one extra coupling. Therefore, it is troublesome to attach and detach.

◎ Conventional example 3 (See Fig. 6) (c) The manufacturing cost of the hydraulic circuit for another work is high.

At the time of hydraulic drive in the main work hydraulic circuit 12, pressure rises in the return oil passages of the direction switching valves 31 and 32 of the separate work hydraulic circuit 21, so there is no choice but to increase the wall thickness of that part, and separate work The manufacturing cost of the hydraulic circuit 21 for use is high.

◎ Conventional example 4 (see Fig. 7) (d) The manufacturing cost of the hydraulic pressure supply / discharge device is high.

The electromagnetically operated directional control valve 89 has a complicated structure and is expensive because the electromagnetic actuator 97 and its electric control device 98 are required, so that the manufacturing cost of the hydraulic pressure supply / discharge device is high.

An object of the present invention is to quickly hydraulically drive a hydraulic circuit for another operation, reduce manufacturing cost and energy loss of a hydraulic device.

<Means for Solving the Problems> In order to achieve the above-mentioned object, the present invention uses a pressure oil in the middle of the pressure supply passage 11 in the basic structure as shown in FIGS. 1 to 3, for example. It is characterized in that the structure of the portion for supplying / discharging to / from the separate work hydraulic circuit 21 is configured as follows.

Dividing valve 41 and pilot-operated circuit selection valve in pressure supply line 11
42 in order, and the shunt valve 41 and the circuit selection valve
42 and 42 are incorporated into one valve box 47, and the flow dividing valve 41 is switched to the throttle position C when the hydraulic pressure on the inlet side of the inlet passage 43 is lower than the set inlet pressure, and at the inlet side of the inlet passage 43. When the hydraulic pressure is equal to or higher than the set inlet pressure, it is configured to switch to the diversion position D, and at the throttle position C, the inlet passage 43 is connected to the separate work side outlet port B of the circuit selection valve 42 via the throttle passage 45. On the other hand, at the diversion position D, by branching the inlet passage 43 into the main passage 44 and the throttle passage 45, the main passage 44 is connected to the inlet port P ₁ of the circuit selection valve 42, and the throttle passage 45 is provided on another working side. The circuit selection valve 42, which is configured to be connected to the outlet port B, is switched to the main work selection position X when the hydraulic pressure of the pilot passage 53 connected to the different work side outlet port B is lower than the set outlet pressure. With
When the hydraulic pressure in the pilot passage 53 is equal to or higher than the set outlet pressure, it is configured to switch to another work selection position Y, and at the main work selection position X, the inlet port P _{1 is changed} to the main work side outlet port A.
In contrast to the connection to the
Configured to connect P ₁ to another working outlet port B,
The main work side outlet port A is connected to the pressure oil inlet 12a of the main work hydraulic circuit 12 via the pressure supply passage 11, and the other work side outlet port B is connected.
Is connected to the pressure oil inlet 21a of the hydraulic circuit 21 for another operation via the coupling 20 on the inlet side, and the drain port 21b of the hydraulic circuit 21 for another operation is connected.
Is connected to the oil tank 18 via an outlet side coupling 54.

<< Operation >> The present invention operates, for example, as shown in FIG. The figure shows a state in which both the main work hydraulic circuit 12 and the separate work hydraulic circuit 21 are switched to the neutral state, and the circuit selection valve 42 is
The pressure in the pilot passage 53 is low, and the main work selection position X is switched.

When pressure oil is sent from the hydraulic pump 10 to the diversion valve 41 and the hydraulic pressure on the inlet side of the inlet passage 43 of the diversion valve 41 becomes equal to or higher than the set inlet pressure, the diversion valve 41 moves from the throttle position C to the diversion position D.
Switch to.

Then, the pressure oil from the hydraulic pump 10 is sent to the separate work side outlet port B of the circuit selection valve 42 through the throttle passage 45 of the flow dividing valve 41, and also passes through the main flow passage 44 of the flow dividing valve 41. Sent to 42 entrance port P ₁ . Further, the pressure oil from the hydraulic pump 10 is sent to the pilot passage 53 of the circuit selection valve 42 from the separate work side outlet port B.

In this state, when the main work hydraulic circuit 12 is switched from the neutral state to the hydraulically driven state, the pressure oil from the hydraulic pump 10 is transferred to the main flow passage 44 of the shunt valve 41 and the inlet port of the circuit selection valve 42.
P ₁・ Main work side outlet port A through main work hydraulic circuit 12
Is supplied to the pressure oil inlet 12a, hydraulically drives the main work hydraulic circuit 12, and then is returned to the oil tank 18.

On the other hand, when the hydraulic circuit 21 for another work is switched to the hydraulically driven state from the neutral state, the driving resistance of the lift hydraulic cylinder 24 or the bucket hydraulic cylinder 26 in the another work hydraulic circuit 21 causes another work side outlet port B Oil pressure increases. And
When the hydraulic pressure in the pilot passage 53 rises and becomes equal to or higher than the set outlet pressure, the circuit selection valve 42 is switched from the main work selection position X to another work selection position Y.

As a result, the entire amount of the pressure oil supplied from the hydraulic pump 10 is pressure-fed to the separate work hydraulic circuit 21 via the flow dividing valve 41 and the circuit selection valve 42, and the separate work hydraulic circuit 21 is hydraulically driven, and then the oil discharge port is discharged. It is returned to the oil tank 18 via 21b.

Further, when the pressure of the pressure oil sent from the hydraulic pump 10 to the inlet passage 43 is lower than the set inlet pressure, such as when the engine for driving the hydraulic pump 10 is started, the diversion valve 41 is set to the throttle position C. By switching, the pressure oil from the hydraulic pump 10 is not supplied to the inlet port P ₁ side of the circuit selection valve 42,
It is entirely supplied to the outlet port B side of another work side through the throttle passage 45 of 41.

Therefore, even if the hydraulic circuit 21 for another work is switched to the hydraulically driven state when the hydraulic pressure on the inlet side of the inlet passage 43 of the flow dividing valve 41 is lower than the set inlet pressure, such as immediately after the engine is started, the hydraulic pump 10 will not The hydraulic oil in the pilot passage 53 is rapidly raised to switch the circuit selection valve 42 from the main work selection position X to another work selection position Y in a short time by the amount that the pressure oil of is not supplied to the main work side outlet port A side. You can That is, it is possible to quickly supply the hydraulic circuit 21 for another work hydraulically by supplying the entire amount of pressure oil to the hydraulic circuit 21 for another work in a short time even immediately after the engine is started.

<< Effects of the Invention >> The present invention has the following effects because it is configured and operates as described above.

(A) When the oil pressure on the inlet side of the inlet passage of the flow dividing valve is lower than the set inlet pressure, the flow dividing valve switches to the throttle position,
Since the pressure oil from the hydraulic pump is all supplied to the outlet port side on the other work side through the throttle passage of the diversion valve, the pressure oil from the hydraulic pump is low when the pressure is low, such as immediately after the engine is started. Even if the working hydraulic circuit is switched to the hydraulic drive state,
Since the hydraulic oil from the hydraulic pump is not supplied to the main work side outlet port side, the hydraulic pressure in the pilot passage can be raised quickly to switch the circuit selection valve from the main work selection position to another work selection position in a short time. it can. That is, it is possible to quickly supply the hydraulic circuit for another work with hydraulic pressure by supplying the entire amount of pressure oil to the hydraulic circuit for another work in a short time even immediately after the engine is started.

(B) Since the diversion valve and the circuit selection valve are integrated in one valve box, the diversion valve and the circuit selection valve are separated from each other as compared with the case where they are housed in independent boxes. Piping pipes and joints with the circuit selection valve can be omitted,
Manufacturing costs can be reduced.

(C) Moreover, since the diversion valve and the circuit selection valve are arranged in the same valve box, the distance between the diversion valve and the circuit selection valve can be shortened, which can shorten the oil passage and reduce the flow resistance. it can. Therefore, the energy loss of the hydraulic device can be reduced.

<< Embodiment >> An embodiment of the present invention will be described below with reference to the drawings.

(First Embodiment) FIGS. 1 to 3 show a first embodiment.

In FIG. 2, a hydraulic main working machine 3 is connected to a rear portion of a vehicle body 2 of an agricultural tractor 1, and a hydraulic agricultural loader 6 is mounted on a base 5 fixed to a front portion of the vehicle body 2. There is. The hydraulic system of this tractor 1 is as shown in FIG.

First, the hydraulic device of the main work machine 3 will be described. The hydraulic pump 10 is connected to the engine 9 in the vehicle body 2 and
The pressure oil inlet 12a of the main work hydraulic circuit 12 is connected to the discharge port 10a of the above through the pressure supply path 11. By extending and retracting the main work hydraulic cylinder 13 with this main work hydraulic circuit 12,
The working machine main body 15 is swung in the vertical direction via the link mechanism 14. The main working machine hydraulic cylinder 13 is configured as a double-acting type, and each cylinder chamber partitioned by the piston 16 is connected to the pressure oil inlet 12a or the oil tank 18 by the main working machine direction switching valve 17. is there.

Next, the agricultural loader 6 will be described. A pressure oil inlet 21a of another working hydraulic circuit 21 is detachably connected to the pressure supply path 11 via an inlet side coupling 20. Then, in the hydraulic circuit 21 for another operation, a lift arm 23 pivotally supported on the upper portion of the base 5 is vertically moved by a lift hydraulic cylinder 24, and a bucket pivotally supported at the front end of the lift arm 23. The bucket hydraulic cylinder 26 swings the bucket 25 in the vertical direction. The lift hydraulic cylinder 24 is configured as a double-acting type, and the ascending side drive oil chamber 29 and the descending side drive oil chamber 30 partitioned by the piston 28 are
The pressure oil inlet 21a or the oil discharge port 2 via the lift direction switching valve 31.
It is possible to selectively communicate with 1b. The lift direction switching valve 31 is of a three-position, four-connection center bypass type, and the lift arm 23 operates as follows in a state in which the switching operation is performed at each of the switching positions E, F, and G.

In the state where the switching operation is performed to the ascending position E, the ascending side drive oil chamber 29 of the lift hydraulic cylinder 24 is communicated with the pressure oil inlet 21a, and the descending side drive oil chamber 30 is allowed to be communicated with the drainage port 21b. . As a result, the lift hydraulic cylinder 24 extends and the lift arm 23 is raised. On the other hand, in the state where the operation is switched to the lowered position F, the lift hydraulic cylinder 24
The descending side drive oil chamber 30 is communicated with the pressure oil inlet 21a, and the ascending side drive oil chamber 29 is communicated with the oil drain port 21b. As a result, the lift hydraulic cylinder 24 contracts and the lift arm 23 descends. Further, when the switching operation is performed to the center position G, the lift arm 23 is held in a predetermined posture.

The bucket hydraulic cylinder 26 and the bucket directional switching valve 32 are also constructed in the same manner as described above, and when the lift directional switching valve 31 is switched to the center position G, it is partitioned by the piston 34 of the bucket hydraulic cylinder 26. The upper swing-side drive oil chamber 35 and the lower swing-side drive oil chamber 36 can be selectively communicated with the pressure oil inlet 21a or the oil drain 21b via the bucket directional switching valve 32. . When the bucket directional control valve 32 is switched to each of the switching positions U, V, W, the bucket 25 operates as follows.

When the switching operation is performed to the upward swing position U, the upward swing side drive oil chamber 35 of the bucket hydraulic cylinder 26 is moved to the pressure oil inlet 21.
It is possible to communicate with a, and the lower swing side drive oil chamber 36
Is communicated with the oil drain port 21b. As a result, the bucket hydraulic cylinder 26 contracts and the bucket 25 swings upward.
On the other hand, in the state of switching to the lower swing position V, the lower swing side drive oil chamber 36 of the bucket hydraulic cylinder 26 is communicated with the pressure oil inlet 21a, and the upper swing side drive oil chamber 35 is drained. Connected to mouth 21b. As a result, the bucket hydraulic cylinder 26 extends and the bucket 25 swings downward. Further, when the switching operation is performed to the center position W, the bucket
25 is held in a predetermined posture.

In the above structure, in order to connect and operate the hydraulic pump 10 and the oil tank 18 to the main work hydraulic circuit 12 or the separate work hydraulic circuit 21, the hydraulic pressure supply / discharge switching is performed to the pressure supply passage portion 11a on the upstream side of the pressure supply passage 11. The valve device 40 is provided. As shown in FIGS. 1 and 3, the valve device 40 includes a flow dividing valve 41 and a pilot-operated circuit selection valve 42 in the pressure supply path 11 which are sequentially interposed from the upstream side.

First, the flow dividing valve 41 will be described. As shown in FIG. 1, the flow dividing valve 41 divides the pressure oil at the discharge port 10a of the hydraulic pump 10 from the inlet passage 43 to the main flow passage 44 and the throttle passage 45. As shown in FIG. 3, it has a spool shape.

That is, the tubular flow dividing valve body 48 is inserted in the lower portion of the valve box 47 so as to be slidable in the left-right direction in an oil-tight manner. This diversion valve body 48
Is pressed by the compression coil spring 49 to the left throttle position C when the hydraulic pump 10 is stopped. If the hydraulic pump 10 is operated in this state, pressure oil will flow through the inlet passage 43.
Then, it starts to flow to the outlet port B of another working side through the orifice 50 of the throttle passage 45. Then, a differential pressure is generated before and after the orifice 50, and the flow dividing valve body 48 is moved to the right side against the compression coil spring 49 by the differential pressure, and the inlet passage 43 is also communicated with the main flow passage 44.

Next, the pilot operated circuit selection valve 42 will be explained. As shown in FIGS. 1 and 3, the spool type valve body 52 for circuit selection is operated separately from the main work selection position X by pilot pressure. By switching to the selected position Y, the inlet port P ₁ is selectively switched and connected to the main working side outlet port A and the different working side outlet port B. The main flow passage of the flow dividing valve 41 is connected to the inlet port P ₁ of the circuit selection valve 42.
44 are communicated. Further, the main work side outlet port A is communicated with the pressure oil inlet 12a of the main work hydraulic circuit 12 via the downstream pressure supply passage portion 11b, and the other work side outlet port B connects the inlet side coupling 20. It is communicated with the pressure oil inlet 21a of the hydraulic circuit 21 for another work via. Further, the throttle port 45 of the diversion valve 41 and the pilot passage 53 of the circuit selection valve 42 communicate with the outlet port B on the side of another operation. In addition, the hydraulic circuit for separate work 21
The oil drain port 21b of the oil tank 1 via the outlet side coupling 54
Connected to 8.

The structure of the circuit selection valve 42 is as follows, as shown in the neutral state of FIG.

A spool type valve body 52 for circuit selection is inserted in the upper part of the valve box 47 so as to be oil-tightly slidable in the left-right direction.
In the state where the hydraulic pressure is not applied to the inlet ports P ₁ and P ₂ , the pressure is elastically pressed to the main work selection position X on the right side by the tension of the compression coil spring 55.

Then, the main work hydraulic circuit 12 and the separate work hydraulic circuit 21
When the main working machine 3 is driven from the neutral state, the switching valve 17 of the main working hydraulic circuit 12 is switched to the driving position. Then, the pressure oil flows from the inlet passage 43 of the flow dividing valve 41 through the throttle passage 45 to the separate work side outlet port B.
As a result, the flow dividing valve is operated by the differential pressure generated before and after the orifice 50.
By moving 41 to the right (diversion position D), the main flow passage 44 is also communicated with the inlet port P ₁ . Then, the valve body 52 of the circuit selection valve 42 is held at the right main work selection position X by the pressure of the inlet port P _{1, and} the pressure oil flowing from the main flow passage 44 to the inlet port P ₁ is held at the main work side outlet port. It is supplied from A to the pressure oil inlet 12a of the main work hydraulic circuit 12 to drive the working machine 3.

On the other hand, when driving the agricultural loader 6, the main work hydraulic circuit 12 and the separate work hydraulic circuit 21 are neutralized, and then the separate work hydraulic circuit 21 is moved to the lift direction switching valve.
31 or the bucket directional control valve 32 is switched to the drive side to bring it into a hydraulically driven state. Then, similarly to the above, the flow dividing valve 41 is moved to the right by the pressure difference generated before and after the orifice 50 to communicate the main flow passage 44 with the inlet port P ₁ , and
The pressure in the pilot passage 53, which rises as the pressure of the outlet port B on the different operation side rises, overcomes the tension of the compression coil spring 55, and moves the valve element 52 of the circuit selection valve 42 to the left side position (the different operation selection position Y). Then, the main work side outlet port A is closed. Then, the pressure oil flowing from the inlet ports P ₁ and P ₂ to the different work side outlet port B is supplied to the pressure oil inlet 21a of the different work hydraulic circuit 21 to drive the agricultural loader 6.

The oil discharge port 21a of the separate work hydraulic circuit 21 is connected to the oil tank 18 via the return port R and the tank port T of the valve box 47.
Be communicated to.

[Brief description of drawings]

1 to 3 show an embodiment of the present invention, FIG. 1 is an overall system diagram of a hydraulic pressure supply / discharge device, FIG. 2 is a side view of a tractor, and FIG. 3 is a hydraulic pressure supply / discharge valve device. FIG. FIGS. 4 to 7 show Conventional Example 1 and Conventional Example 2 respectively.
It is a figure corresponding to FIG. 1 which shows the prior art example 3 and the prior art example 4. 10 …… hydraulic pump, 10a …… discharge port, 11 …… pressure passage, 12
...... Main work hydraulic circuit, 12a …… Pressure oil inlet, 18 …… Oil tank, 20 …… Inlet side coupling, 21 …… Other work hydraulic circuit, 21a …… Pressure oil inlet, 21b …… Drain oil Mouth, 41 …… Shunt valve, 42 …… Circuit selection valve, 43 …… Inlet passage, 44 …… Main passage, 45 …… Throttle passage, 47 …… Valve box, 53 …… Pilot passage, 54 …… Outlet side Coupling, A ... Main working side outlet port, B ... Other working side outlet port, P ₁ ... Inlet port,
C: throttle position, D: diversion position, X: main work selection position, Y: separate work selection position.

Claims (1)

[Scope of utility model registration request] 1. A pressure oil inlet (12a) of a main work hydraulic circuit (12) is connected to a discharge port (10a) of a hydraulic pump (10) through a pressure supply passage (11), and the pressure supply passage is provided. A pressure line for the main work hydraulic circuit, which is configured by detachably connecting the pressure oil inlet (21a) of the separate work hydraulic circuit (21) via the inlet side coupling (20) in the middle of (11). In the hydraulic pressure supply / discharge device for the hydraulic circuit for another work detachably connected to the above, in the above pressure supply passage (11), the shunt valve (41) and the pilot operated circuit selection valve (42) are intervened in order. , The above-mentioned diversion valve (41) and the above-mentioned circuit selection valve (42) are incorporated into one valve box (47), and the above-mentioned diversion valve (41) has a hydraulic pressure on the inlet side of the inlet passage (43). When the pressure is lower than the set inlet pressure, the throttle valve is switched to the throttle position (C) and the oil pressure on the inlet side of the inlet passage (43) is equal to or higher than the set inlet pressure. Diverted position in case (D)
It is configured to switch to the above-mentioned aperture position (C).
In contrast, the inlet passage (43) is connected to the separate work side outlet port (B) of the circuit selection valve (42) through the throttle passage (45), whereas the inlet is provided at the diversion position (D). By branching the passage (43) into the main passage (44) and the throttle passage (45), the main passage (44) is connected to the inlet port (P ₁ ) of the circuit selection valve (42). The throttle passage (45) is configured to be connected to the another work side outlet port (B), and the circuit selection valve (42) is connected to the another work side outlet port (B). When the oil pressure in the pilot passage (53) is lower than the set outlet pressure, it switches to the main work selection position (X), and when the oil pressure in the pilot passage (53) is equal to or higher than the set outlet pressure, another It is configured to switch to the work selection position (Y), and the main work selection position described above is selected. The (X) In the above the inlet port (P ₁₎ to connect to the main working side outlet port (A), another operation selection position of the (Y) in the above inlet port (P ₁₎ to another of the It is configured to connect to the working side outlet port (B), and the main working side outlet port (A) is connected to the pressure supply passage (11).
Through the pressure oil inlet (12) of the main working hydraulic circuit (12)
a), the above-mentioned another work side outlet port (B) is connected to the above-mentioned another work hydraulic circuit (21) pressure oil inlet (21a) through the above-mentioned inlet side coupling (20), The oil discharge port (21b) of the hydraulic circuit (21) for separate work described above is connected to the oil tank (18) via the coupling (54) on the outlet side, and the hydraulic circuit for main work is characterized in that A hydraulic pressure supply / discharge device for the hydraulic circuit for another work detachably connected to the pressure path.