JPH02248705A - hydraulic circuit - Google Patents

Abstract

PURPOSE:To control a hydraulic actuator to obtain the optimum flow by setting each pressure compensation valve to a pressure matching a load pressure and setting the same to a pressure matching the maximum load pressure when plural valves are operated simultaneously. CONSTITUTION:The first valve 11 and the second valve 12 are respectively constructed so that the first and second pump ports 3a, 3b, an inlet port 3c, an outlet port 3d, a tank port 3e and the first and second operating ports 3f, 3g are communicated and intercepted by a spool 3, and a pressure compensation valve 4 disposed between the inlet port 3c and the outlet port 3d is adapted to set the first or second operating port 3f, 3g to pressure corresponding to load pressure to drive actuators 21, 22. The output sides of the pressure compensation valves 4 are communicated with each other through a check valve 5, and when plural valves 1 are operated at the same time, a pressure matching the maximum load pressure is set on a pressure compensation valve 4. Thus, the operability can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a hydraulic circuit that supplies hydraulic pressure to hydraulic actuators such as boom cylinders and arm cylinders of power shovels.

[Conventional technology]

A power excavator is equipped with multiple hydraulic actuators such as a boom cylinder, arm cylinder, packet cylinder, travel motor, and swing motor, and the hydraulic circuit that supplies hydraulic pressure to these hydraulic actuators includes multiple valves in the discharge path of the hydraulic pump. It is known that hydraulic pressure is supplied to each hydraulic actuator by switching three valves.

However, when a plurality of valves are operated simultaneously, hydraulic pressure is supplied to the hydraulic actuator with a small load pressure, and no hydraulic pressure is supplied to the hydraulic actuator with a large load pressure.

Therefore, a hydraulic circuit is known that uses a pressure-compensated valve shown in Japanese Patent Application Laid-open No. 80-188604, which can distribute and supply hydraulic pressure to each hydraulic actuator when a plurality of valves are operated simultaneously. ing.

As shown in FIG. 5, the pressure-compensated valve has a spool b on the valve body a to communicate and cut off the inlet boats c and d to the operating boats e and f, and to communicate and cut off the inlet boats c and d with the operating ports e and f. A pressure compensating valve is provided in the bridge passage g, and this pressure compensating valve is configured to be set by the highest operating pressure of the plurality of hydraulic valves, so that the pressure compensating valve is set to the highest operating pressure of the plurality of hydraulic valves, and Ensures uniform flow,
By doing so, even if the load pressures differ when a plurality of hydraulic actuators are operated simultaneously, a uniform flow rate can be supplied to each hydraulic actuator.

[Problem to be solved by the invention]

In such a pressure compensated valve, the flow rate to be supplied is set by changing the opening area of the meter-in metering part according to the stroke of the spool, so when multiple pressure compensated valves are operated simultaneously, the flow rate is set by changing the opening area of the meter-in metering part according to the stroke of the spool. In order to vary the supplied flow rate, it is necessary to vary the stroke of the spool of each pressure compensated valve, which not only impairs operability, but also limits the flow rate difference to a certain range, making it difficult to obtain a large flow rate difference. I can't.

For this reason, for example, when hydraulic pressure is supplied to the boom cylinder and arm cylinder of a power excavator at the same time, the capacity of the boom cylinder is large, so a large amount of liquid is supplied to the boom cylinder, and a small amount of liquid is supplied to the arm cylinder. However, in a conventional hydraulic circuit using a pressure-compensated valve, it may not be possible to supply hydraulic pressure to the boom cylinder and the arm cylinder, as described above.

Therefore, an object of the present invention is to provide a hydraulic circuit that can solve the above-mentioned problems.

[Means and operations for solving the problem] Some valves in the plurality of valves equipped with pressure compensation valves are structured to supply the discharge hydraulic pressure of the first and second hydraulic pumps to the hydraulic actuator, and other This is a hydraulic circuit in which the valve is configured to supply the discharge hydraulic pressure of the first hydraulic pump to the hydraulic actuator, and by this, the discharge hydraulic pressure of the first and second hydraulic pumps is combined by several valves. The first hydraulic pump can supply the discharge hydraulic pressure of the first hydraulic pump to the hydraulic actuator by means of another valve.

〔Example〕

As shown in FIG. 2, first to seventh valves 11 are provided in the discharge passage Pa of the first hydraulic pump P1 and the discharge passage Pb of the second hydraulic pump P2.
.about.17 are provided and the first to seventh actuators 21 to 2
2 to supply hydraulic pressure.

The first valve 11 and the second valve 12 are equipped with a spool 3 and a pressure compensating valve 4 as shown in FIG.
, tank boat 3e.

The pressure compensating valve 4 is provided between the inlet boat 3C and the outlet boat 3d, that is, on the downstream side of the meter-in metering section, and communicates and shuts off the first and second working boats 3f and 3g. Alternatively, the pressure of either one of the second operating boats 3g is set to a pressure corresponding to the load pressure, and the output side of the three-valve pressure compensating valve 4 is communicated via a chain valve 5, and a plurality of valves are connected. When the two are operated simultaneously, the highest load pressure is introduced and the pressure is set to match the highest load pressure.

The spool 3 of the first valve 1 is in a neutral position (A) that blocks each boat, the first pump port 3a and the inlet port 3c,
A first position (where the exit boat 3d and the first working boat 3f, and the second working boat 3g and the tank port) 3e are communicated with each other.
b), first pump boat 3a and inlet port 3c, exit robot 3d and second operating boat 3g, first operating port) 3
It is switched to the second position (c) where f and tank boat 3e are communicated with each other.

The spool 3 of the second valve 12 is in a neutral position (a) where each boat is shut off, the first and second pump ports) 3a, 3b, the inlet boat 3c, the outlet boat 3d, the first working boat 3f, and the second working boat 3g. and a first position (b) that communicates with the tank boat 3e, the first pump boat 3a, and the inlet boat 3c.

A second position that communicates the outlet boat 3d with the second working boat 3g1 and the first working port 3f with the tank boat 3e, respectively (
c).

In other words, the first valve 1. has a first meter-in metering section 6 that meters the hydraulic pressure of the first hydraulic pump P to the inlet boat 3C, and a second valve 12 is connected to the first meter-in metering section 6 and the second hydraulic pressure It has a second meter-in metering section 7 that meters the hydraulic pressure of the pump P2 to the inlet boat 3C.

The detected highest load pressure is supplied to the capacity control member 8 of the first and second hydraulic pumps P1+P2,
Set the discharge pressure to a predetermined pressure, e.g. 20 k, from the highest load pressure.
g/ (J is controlled to be high.

However, the first valve 1. When only the second valve 12 is switched, the discharge hydraulic pressure of the first hydraulic pump P1 is supplied to the first hydraulic actuator 21, and when only the second valve 12 is switched, the discharge hydraulic pressure of the first hydraulic pump P1 is supplied to the fourteenth second hydraulic pump P.

When the discharge hydraulic pressure of P2 is supplied to the second hydraulic actuator 22 and the first valve 11 and the second valve 21 are switched at the same time, the pressure compensating valve 4 is set to match the higher load pressure. The discharge hydraulic pressure of the first hydraulic pump P1 is applied to the first hydraulic actuator 2. is distributed and supplied to the second hydraulic actuator 22, and a large amount of hydraulic pressure can be supplied to the second hydraulic actuator 22.
A small amount of hydraulic pressure can be supplied to 1.

Next, an example of the valve will be explained.

As shown in FIG. 3, a spool 12 is fitted into the valve hole 11 of the valve body lO, and an outlet boat 13 is formed in the axial middle of the valve hole 11. 1 and 2nd pump boats) 14 and 15, 1st and 2nd boats 16° 17, 1st and 2nd operation boats) 18 and 19, and 10th and 2nd tank boats 20 and 21, respectively, are formed.
The first and second pump ports 14 and 15 communicate with the discharge sides of the first and second hydraulic pumps p, p2, respectively, and
The actuating boat 18,19 is the first of the hydraulic actuators 23.
It communicates with the chamber 231 and the second chamber 232, and the first and second tank boats 20.21 communicate with the tank 24, respectively.

The spool 12 is held at a neutral position where each boat is blocked by a spring 25, and when pilot pressure is supplied to the first pressure receiving chamber 26 or the second pressure receiving chamber 262, it moves from the neutral position to the left and right and moves to the first and second pressure receiving chambers. This will be the 2nd position.

A first passage 27 communicating between the outlet boat 13 and the first boat 16 is provided with a first pressure compensating valve 28, and a second passage 29 communicating the outlet boat 13 and the second boat 16 is provided.
A second pressure compensating valve 30 is provided.

The first pressure compensation valve 28 connects the poppet valve 31 to the valve seat 27a.
The poppet valve 31 is pressed against the check valve 3.
2 to form a back pressure chamber 34, which communicates with the first boat 16 through a small hole 35 and through a liquid hole 36 formed in the piston 33. Communication Q is cut off to the pressure receiving chamber 37, and the poppet 31 is connected to the back pressure chamber 3.
4 and the pressure receiving chamber 37 are pressed against the valve seat 27a by the hydraulic pressure in the pressure receiving chamber 37, and the pressure receiving chamber 37 is further connected to the pressure introduction boat 3 through the small hole 38.
9, and the piston 3 is opened by a spring 40.
3 is pressed against the bottom surface 37a of the pressure receiving chamber 37.

Note that the second pressure compensation valve 30 is the same as the first pressure compensation valve 28.

Next, the operation will be explained.

When pilot pressure oil is supplied to the first pressure receiving chamber 261 and the spool 12 is moved toward the first position on the left as shown in FIG. 4, the first pump boat 14 and the outlet boat 13 are brought into communication.
The first boat 16 and the first working boat 18 communicate with each other, and the second working boat 19 communicates with the second tank boat 21.

As a result, the discharge pressure liquid of the first hydraulic pump P passes from the first pump boat 14 to the metering M, and the discharge pressure liquid of the second hydraulic pump P2 passes from the outlet boat 13 to the first passage 27 through the metering M2. - first pressure compensation valve 28 - first
It flows from the boat 16 to the first operating boat 18 and is supplied to the first chamber 231 of the hydraulic actuator 23, and the second chamber 23 is supplied to the first chamber 231 of the hydraulic actuator 23.
The hydraulic pressure in 2 is the second working boat 19 → the second tank boat 2
1 flows out into the tank 24.

When setting the flow rate for only one hydraulic pump, the flow rate setting can be easily made by removing the metering M2.

At this time, the liquid pressure flowing out from the outlet boat 13 acts on the front surface of the poppet valve 31, moves the poppet valve 31 away from the valve seat 27a, and flows to the first boat 16.
The pressure of 8, that is, the load pressure flows through the small hole 35, the back pressure chamber 34, the liquid hole 36, and the pressure receiving chamber 37, and is led to the pressure introduction boat 39.

On the other hand, since this pressure introduction port 39 is communicated with each other in a plurality of valves, the pressure in the pressure receiving chamber 37 becomes the maximum pressure, that is, the pressure corresponding to the hydraulic actuator with the highest load pressure, and the poppet valve 31 is activated. Since the force pressing against the seat 27a is determined by the pressure, the first pressure compensating valve 28
The set pressure corresponds to the hydraulic actuator with the highest load pressure.

The pressure introduction port 39 is connected to the first and second hydraulic pumps P,
P, the capacity of the first and second hydraulic pumps P1 r P2 is controlled such that the discharge pressure thereof is a predetermined pressure, for example, 20 kg/c- higher than the detected maximum pressure. The meter-ine pressure difference ΔP, that is, the pressure difference between the first pump boat 14 and the outlet boat 13 due to the communication area between the ji1 pump boat 14 and the outlet boat 13, is controlled to be constant, for example, 20 kg/c-.

In addition, since the meter-in pressure difference in the plurality of valves is the same, when the plurality of valves are operated simultaneously, the discharge hydraulic pressure of the hydraulic pump can be distributed and supplied to each hydraulic actuator and operated simultaneously.

〔Effect of the invention〕

Since the pressure compensating valves 4 provided in the three valves are set to a pressure corresponding to the maximum load pressure, a plurality of valves can be operated simultaneously to simultaneously supply hydraulic pressure to a plurality of hydraulic actuators.

Further, the discharge hydraulic pressure of the first hydraulic pump P1 is supplied to the hydraulic actuator together with the discharge hydraulic pressure of the second hydraulic pump P2 by some valves, and the other valves are supplied with the discharge hydraulic pressure of the first hydraulic pump P1. When multiple valves are operated simultaneously, a large amount of hydraulic pressure can be supplied to one hydraulic actuator and a small amount of hydraulic pressure can be supplied to other hydraulic actuators. The flow rate can be controlled to the optimum flow rate for the pressure actuator, improving operability.

[Brief explanation of drawings]

Fig. 1 is a hydraulic circuit diagram showing an embodiment of the present invention, Fig. 2 is an overall schematic diagram, Fig. 3 is a sectional view showing an example of a valve, Fig. 4 is an explanatory diagram of operation, and Fig. 5 is a diagram of a conventional example. FIG. Pl*P2 are first and second hydraulic pumps, Pa. Pb is the discharge path; 1. -11 are first to seventh valves, 3 is a spool, and 4 is a pressure compensating valve.

Claims (1)

[Claims] The discharge path Pa of the first hydraulic pump P_1 and the second hydraulic pump P
A plurality of valves including a pressure compensating valve 4 are provided in the discharge path Pb of _2, and some of the valves are used to meter the discharge hydraulic pressure of the first and second hydraulic pumps P_1 and P_2. A structure is adopted in which the pressure is supplied to the inlet side of the pressure compensating valve 4, and several other valves are structured to meter the discharge hydraulic pressure of the first hydraulic pump P_1 and supply it to the inlet side of the pressure compensating valve 4. A hydraulic circuit characterized in that each of the pressure compensating valves 4 is set to a pressure commensurate with the load pressure, and is configured such that when a plurality of valves are operated simultaneously, the pressure is set to a pressure commensurate with the maximum load pressure.