JPS60260703A - Oil pressure control system - Google Patents

Abstract

PURPOSE:To prevent securely the overrun of load and cavitation by interposing reducing valves in which a prescribed pressure is decreased under a particular condition in the piping lines which connect a main changeover valve connected to the discharge side of an oil pressure with a pilot valve which controls the main changeover valve. CONSTITUTION:Oil pressure packs 24a and 24b at the both ends of a main changeover valve 14A which is interposed in the circuit connecting a variable capacity type oil pressure pump 10A with an actuator 12 are connected to the outlet side of a pilot valve 28 via piping lines 26a and 26b. And throttle valves 30a and 30b each having a one-way valve are interposed in two piping lines 19a and 19b which connect the actuator 12 with the ports A and B of the main changeover valve 14A. And futher, reducing valves 32a and 32b in which a prescribed pressure in decreased in response to the increase of oil pressure difference between the throttle valves 30a and 30b exceeding a certain value are interposed in the said piping lines 26a and 26b. Thus, counterbalancing function can be provided to the main changeover valve 14A itself, and miniaturization etc. of the device can be achieved.

Description

[Detailed Description of the Invention] The present invention relates to a hydraulic control device for construction machines, material dumping machines, etc. that have large inertial loads, and more specifically, the present invention is configured to more effectively prevent load runaway and cavitation in actuators. It relates to a hydraulic control device.

In general, in a hydraulic control device that controls hydraulic equipment with a relatively large inertial load, such as that found in swingable construction machinery, in addition to the main switching valve, a counterbalance valve is installed in the circuit connecting the main switching valve and the actuator. is installed to prevent load deviation and cavitation that occurs in the actuator.

Conventionally, a hydraulic control device as shown in FIG. 1, for example, has been employed as this type of device.

In this hydraulic control device, first, a main switching valve 4 is interposed in the circuit connecting a hydraulic pump 10, which is a hydraulic pressure source, and an actuator 12, which is a hydraulic motor.
Switching is performed using pilot pressure by operating a pilot valve (not shown).

On the other hand, a counterbalance valve 16 consisting of a four-way switching valve is installed in the middle of the circuit connecting the actuator 12 and the main switching valve 14.
is interposed, and this counterbalance valve 16 switches in response to the pump pressure introduced via the main switching valve 14.

Therefore, if the main switching valve 14 is now switched to the neutral position by a pilot valve (not shown) in order to stop the operation of the continuously rotating actuator 12, the pressure oil from the hydraulic pump 10 will be transferred to the bypass port of the main switching valve 14 and the bypass pipe. Since it is bypassed to the tank 17 side through passage 18,
The pump pressure acting on the counterbalance valve 16 decreases and the counterbalance valve 16 is switched to the neutral position.

As a result, two pipe lines 19a and 1 are connected between the actuator 12 and the A port and the B port of the main switching valve 14.
9b are both cut off, while the actuator 12 and both the circuits 19a and 19 near the actuator 12 are cut off.
9b and also connect relief valves 20a, 2 in the middle.
A closed circuit is formed with the pipes 22a and 22b in which the 0b is inserted (see the arrow in FIG. 1).

As a result, even if the actuator 12 rotates after receiving the inertial load of the hydraulic equipment, hydraulic oil will always circulate in the actuator 12, preventing a temporary pressure drop on the suction side, and reducing the load. Issomura FF7? +, x-outside 0 and 41 ya 5.1 The occurrence of bitation etc. is avoided.

However, with such conventional hydraulic control devices,
Since the counterbalance valve 16 is constructed of a so-called direct-acting switching valve that responds directly to pump pressure, there is an operational problem in that the counterbalance valve 16 is prone to hunting. Since the valve cannot be made infinitely smaller, valve costs are rising.
There was a problem that the device as a whole was expensive.

Furthermore, in the prior art, there is a method of adding a large-capacity meter amplifier check to the actuator 12 as a means to prevent cavitation of the actuator 12, but in this case, cavitation at low temperatures cannot be completely prevented. First, there is a risk that the actuator 12 itself may be damaged.

The present invention was made by focusing on these problems.
It is an object of the present invention to provide a hydraulic control device that can effectively prevent load runaway and actuator cavitation only by switching a main switching valve.

In order to achieve the above object, the present invention includes a hydraulic pump, a main switching valve that is connected to the discharge side of the hydraulic pump to supply pressure oil to an actuator, and a main switching valve that is operated by pilot pressure. A pilot valve is provided, and a throttle valve is provided in both or one of the inlet side and outlet side conduits of the actuator, and a conduit connecting the main switching valve and the pilot valve is provided with a throttle valve upstream and downstream of the throttle valve. It is characterized by interposing a pressure reducing valve that reduces the set pressure as the pressure difference increases when the pressure difference between the side pipes exceeds a certain value.

EMBODIMENT OF THE INVENTION Hereinafter, preferred embodiments of a hydraulic control device according to the present invention will be described in detail based on the accompanying drawings. In addition,
In this case, the same reference numerals are given to the same components as those shown in FIG. 1, and detailed explanation thereof will be omitted.

FIG. 2 shows a first embodiment of a hydraulic control device according to the present invention. As shown in the figure, a main switching valve 14 is installed in the hydraulic circuit connecting the variable displacement hydraulic pump IOA and the actuator 12.
A is provided. In this main switching valve 14A, hydraulic bags 24a and 24b provided at both ends of the main switching valve 14A are connected to pipes 26a and 26b.
are respectively connected to the pilot valves 28 via. Throttle valves 30a and 30b with one-way valves are interposed in the middle of two pipe lines 19a and 19b connecting the actuator 12 and the A boat and B boat of the main switching valve 14A, respectively.

On the other hand, pressure reducing valves 32a and 32b are interposed in pipes 26a and 26b connecting the main switching valve 14A and the pilot valve 28, respectively. These pressure reducing valves 32a and 32b function to reduce the set pressure in accordance with an increase in the pressure difference between the hydraulic pressures in the throttle valves 30a and 30b when the pressure difference exceeds a certain value. That is, the pressure reducing valves 32a and 32b have valve bodies 34a and 34b that control the opening and closing of the pipes 26a and 26b, and a spring 36 that determines the set pressure of the valve body parts 34a and 134b.
a, 36b, and piston portions 42a, 42b that engage with the springs 36a, 36b. The piston part 42a
is connected to the oil chambers 38a+, 3B, etc.1 on both sides of the oil chambers 40a1.
The piston part 42b slides due to the pressure difference of the throttle valve 30b acting through the piston 40a2, and the piston part 42b slides due to the pressure difference of the throttle valve 30b acting on the oil chambers 38b+ and 38shi9 on both sides thereof through the pipes 40b+ and 40b2. It is configured to slide due to the difference.

Furthermore, A of the actuator 12 and the main switching valve 14A
Two pipe lines 19a, 19 connecting the boat and B port
b is connected to the main switching valve 1 via a joint 44 with check valves on both sides.
A pipe line 48 branched from a return side pipe line 46 connecting the R port of 4A and the tank 17 is connected. A bypass pipe 18 branched from a pipe 50 connecting the hydraulic pump IOA and the P boat of the main switching valve 14A is connected to the return pipe 46 via the bypass port of the main switching valve 14A.

Next, a controller 52 for controlling the discharge pressure of the hydraulic pump IOA is connected to the hydraulic pump IOA, and a pressure chamber of the controller 52 is connected to a shuttle valve 56 via a conduit 54. The pipe line 26a and the pipe line 26b are respectively connected to both sides of the shuttle valve 56 via a pipe line 58, and the pilot valve 28 is also connected to both sides of the shuttle valve 56 via a pipe line, respectively.

In this case, the controller 52 is configured so that the pump discharge amount increases as the pilot pressure acting on the pressure chamber increases.

In the figure, reference numeral 60 indicates a main relief valve interposed in the pipe line 50 connecting the P boat and bypass port of the main switching valve 14A to the hydraulic pump IOA.

The hydraulic control device according to the present invention is basically constructed as described above, and its operation and effects will be explained next.

Now, the main switching valve 14A is switched in a predetermined direction by operating the viroft valve 28, and the pressure oil from the hydraulic pump IOA is supplied to the actuator 12.
2 is rotating in a predetermined direction.

To stop the rotation of the actuator 12 from this state, the lever of the pilot valve 28 may be moved to the neutral position. That is, as a result, the pressure difference between the biloft pressures acting on both hydraulic packs 24a and 24b of the main switching valve 14A via the pipes 25a and 26b gradually decreases, so the main switching valve 14A begins to move to the neutral position. Eventually, the pressure difference disappears and the main switching valve 14A is completely switched to the neutral position.

At this time, the A port and B port of the main switching valve 14A are both closed, and the A port, B boat, and actuator 12 are closed.
Pipe lines 19a and 19b connecting the two are locked together.

Therefore, a closed circuit is formed by the actuator 12 and the pipes 22a and 22b, in which relief valves 20a and 20b are interposed in the pipes 19a and 19b1 connected to the actuator 12 (arrows in FIG. 2). reference).

As a result, hydraulic oil is constantly circulated through the actuator 12, and as described above, load escape when the actuator 12 is stopped and cavitation occurring in the actuator itself can be avoided. Further, at this time, the hydraulic oil for the drain of the actuator 12 is introduced from the tank 17 side via the pipe line 48 and the joint 44. Furthermore, in this state, the hydraulic pump IOA
Since the pilot pressure acting on the pressure chamber of the controller I roller 52 is reduced, the pump discharge amount of the hydraulic pump IOA is reduced, and the pump load is reduced.

Then, during the rotation operation of the actuator 12, the actuator 12 is rotated more than necessary due to the inertial load, and the discharge amount of the hydraulic pump IOA is reduced by the amount of the actuator 12.
The case where the flow rate is less than the required flow rate will be explained.

That is, in the above state, the throttle valves 3Qa, 30b installed in the pipes 19a, 19b connecting the actuator 12 and the A port and B boat of the main switching valve 14A
In this case, the pressure difference between the pressure oil on the primary and secondary sides exceeds a certain value. Therefore, the pressure reducing valve 32 responds to this pressure difference.
In a and 32b, due to an increase in the pressure in the oil chamber 38a, the piston portions 42a and 42b move in a direction that reduces the load on the springs 36a and 36b, and the set pressure thereof decreases.

As a result, the pilot pressure acting on the main switching valve 14A via the pipes 26a and 26b in which the pressure reducing valves 32a and 32b are installed also decreases, and the main switching valve 14A moves from the predetermined switching position to the neutral position side. Decrease the opening of the shiso. In other words, the opening area of the R boat of the main switching valve is reduced.

As a result, the speed of the actuator 12 is suppressed to a predetermined value or less, and a temporary pressure drop on the suction side of the actuator 12 in this state is prevented.
The occurrence of cavitation and load escape are avoided.

Furthermore, when it is desired to rotate the actuator 12 in a predetermined direction from the state shown in FIG. 2, the lever of the pilot valve 28 can be switched to a position corresponding to the switching direction. As a result, a pressure difference is created between the pilot pressures acting on both the hydraulic blowouts 24a and 24b of the main switching valve 14A via the pipes 25a and 26b, and the main switching valve 14A is gradually switched in a predetermined direction. At this time, since the controller 52 of the hydraulic pump IOA also moves in a predetermined direction in accordance with the increase in the pilot pressure, the main switching valve 14A is eventually switched gradually in accordance with the increase in pump pressure. In other words, , , (1) The same effect as that of the device having the counterbalance valve 16 shown in FIG. 1 is performed. Next, FIG. 3 shows a second embodiment of the hydraulic control device according to the present invention. In this embodiment, the same reference numerals as those shown in FIGS. 1 and 2 indicate the same components.

This embodiment uses the throttle valves 30a, 3 in the device shown in FIG.
A throttle valve 30c corresponding to 0b is interposed in the return pipe 46 connecting to the R boat of the main switching valve 14a, and the pressure inside the pipe on the upstream and downstream sides is adjusted to the pipes 40a1, 40a2, 40b+, 40 and 2 to the oil chambers 38aI, 38a2 and 38 of the pressure reducing valves 32a, 32b similar to the device shown in FIG.
b+ and 38b2, respectively.

According to this, when the actuator 12 is rotated more than necessary due to inertial load during the rotation operation of the actuator 12, the throttle valve 3 interposed in the return side pipe 46
The pressure difference between the upstream side and the downstream side of 0c exceeds a certain value, and the pressure reducing valve 32a responds to the pressure difference.
32b causes the two main switching valves 14A to move from the predetermined switching position to the neutral position and reduce their opening degree. Therefore, as in FIG. 2, load escape and cavitation in this state are prevented. Furthermore, this embodiment has the advantage that only one throttle valve 30c is required, so piping and the like can be simplified.

As explained above, according to the present invention, a throttle valve is provided in both or one of the inlet side and outlet side pipelines of a hydraulic actuator, and the throttle valve is provided in the pipeline connecting the main switching valve and the pilot valve. When the pressure difference between the upstream and downstream pipe lines of the throttle valve exceeds a certain value, a pressure reducing valve is provided that reduces the set pressure as the pressure difference increases, and the main switching valve itself has a counterbalance function. I have to. Therefore, the device itself becomes smaller, has a simple structure, and is inexpensive. Furthermore, it is possible to reliably prevent load runaway and cavitation. Furthermore, since a counterbalance valve that responds to pump pressure is not used, problems such as valve hunting are also eliminated.

Although the present invention has been described above with reference to preferred embodiments, the present invention is not limited to these embodiments, and various improvements and changes in design can be made without departing from the gist of the present invention. Of course.

[Brief explanation of the drawing]

Fig. 1 is a hydraulic circuit diagram of a conventional hydraulic control device, Fig. 2 is a hydraulic circuit diagram showing a first embodiment of a hydraulic control device according to the present invention, and Fig. 3 is a hydraulic circuit diagram showing a second embodiment of a hydraulic control device of the present invention. FIG. 2 is a hydraulic circuit diagram showing an embodiment of the present invention. 10, IOA...Hydraulic pump 12...Actuator 14.14A...Main switching valve 16...Counter balance valve 17...Tank 18...Bypass pipe line 19a, 19
b...Pipe line 20a120b...Relief valve 22a122b...Pipe line 24a, 24b...Hydraulic puncture 26a, 26b...Pipe line 2nd...Pilot valve 30a
~30c... Throttle valve 32a, 32b... Pressure reducing valve 3
4a, 34b... Valve body portion 36a, 36b... Spring 38a1.38a2.38b+, 381) 2... Oil chamber 40a+, 40a2.40151.4o etc. 2... Pipe line 4
2a, 42b...Piston portion 44...Joint 46...Return side pipe 48...Pipe line 5o...Pipe line 52...Controller 54...Pipe line 56...Shuttle valve 58...Pipe line 60... main relief valve

Claims (1)

[Claims] (1) A hydraulic pump; a main switching valve connected to the discharge side of the hydraulic pump to supply pressure oil to an actuator;
a pilot valve for operating this main switching valve with pilot pressure, and a throttle valve is provided on both or either one of the inlet side and outlet side pipes of the actuator;
A pressure reducing valve in which the pressure difference between the upstream and downstream pipes of the throttle valve in a pipe connecting the main switching valve and the pilot valve exceeds a certain value, and the set pressure decreases as the pressure difference increases. A hydraulic control device characterized by intervening. (2. In the device set forth in claim 1, the pressure reducing valve includes a valve body for controlling the opening and closing of the pipe, a spring that determines the set pressure of this valve body, and a spring that engages with the spring and has oil on both sides of the valve body. A hydraulic control device comprising a piston portion to which the pressures of the pipes on the upstream side and the downstream side of the throttle valve are respectively applied to a chamber. (3) In the device according to claim 1 or 2. , a hydraulic control device configured such that the throttle valve is provided in two pipes connecting the actuator and the A port and B boat of the main switching valve, respectively. (4) A hydraulic control device according to claim 1 or 2. In this hydraulic control device, the throttle valve is installed in a conduit connected to the R boat of the main switching valve.