JPH01176803A - Operation controller for plurality of actuators having flow control valve combined with variable displacement pump - Google Patents

Abstract

PURPOSE:To retain operation of a high load actuator so as to improve the controllability by automatically decreasing the flow passing through a flow control valve, when the total flow passing through respective flow control valves of plural actuators mounted on a construction machine or the like becomes larger than a discharge from a pump. CONSTITUTION:Each compensator valve 9, 10 is provided with a control cylinder 28 which varies the spring force of a compensator spring 13. The control cylinder 28 introduces pump discharge pressure into one chamber 30 from a discharge circuit 4, and introduces the highest load pressure out of the load pressures on respective actuators 1, 2 into the other chamber 32. When the necessary flow for both flow control valves 7, 8 becomes larger then the total discharge from a pump 3, the control cylinder 28 controls the spring force of the compensator spring 13 so as to supply flow to the higher load side actuator and dissolves inconvenient stop of the actuator.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a flow control valve that combines the operation of multiple actuators installed in industrial machines such as construction machines and loading machines with one variable displacement pump. The present invention relates to a device whose operation is controlled by

(Prior Art) Conventionally, as shown in FIG. A flow rate control valve f consisting of a switching valve i with a compensator valve e is provided in the connection circuit d, and a pump control device g for controlling the pump capacity provided in the variable displacement pump b is connected to a flow rate control valve f consisting of a switching valve i with a compensator valve e. The highest load pressure is introduced through the pilot piping, and the discharge pressure of the pump b is also introduced, and the pressure and flow rate according to the load of each actuator are controlled by the operation of the pump control device g. There is.

For example, as shown in the second diagram, the compensator valve e connects a plunger k, which is urged by a compensator spring j and is subjected to the load pressure of an actuator a, to a flow path I.
and is configured such that fluid pressure downstream of a restriction m provided on the plunger k acts on the plunger k in opposition to the spring j. Then, when the switching valve i is operated, the actuator a is connected from the discharge circuit C through the connection circuit d.
When the controlled flow rate flows to the plunger, the plunger moves to a position where the force due to the spring j and the load pressure balances the force due to the fluid pressure downstream of the throttle m, thereby controlling the area of the throttle m,
The control flow rate is pressure compensated.

The pump control device g also includes a pressure control valve p and a flow rate control valve q that control the introduction and discharge of fluid into the tilt cylinder 0 to change the pump capacity, and the pressure control valve p controls the pressure of the discharge circuit C. The fluid in the discharge circuit C is guided to the tilting cylinder 0 so that the pump capacity is reduced when the flow rate exceeds the set value, and the flow control valve q is connected to the highest flow rate among the actuators aSa introduced through the pilot piping. When the difference between the load pressure and the pump discharge pressure exceeds a set value, the fluid in the discharge circuit C is guided to the tilting cylinder 0, and the pump capacity, that is, the pump discharge amount of the pump b is reduced. In FIG. 1, r indicates a safety valve, S indicates an oil tank, and t indicates a shuttle valve.

(Problems to be Solved by the Invention) In the device shown in the first diagram, the switching valve i of each flow control valve f is provided with a compensator valve e, so that the switching valve can be opened without being affected by the load. It is designed to flow at a flow rate depending on the temperature. Further, the flow rate required by the entire flow rate control valve is controlled by the flow rate control valve q of the pump control device g so that the variable displacement pump b discharges the required flow rate.

However, if the flow rate required by the entire flow control valve becomes greater than the total pump discharge, control becomes uncontrollable, and the flow rate that should flow into the actuator on the high load side flows into the actuator on the light load side. This state is graphed as shown in Figure 3, where the curve Ql is the change in flow rate when the flow control valve to the actuator on the high load side is set so that a constant flow flows, and the curve Q2 is the change in flow rate when the flow control valve to the actuator on the high load side is set to flow at a constant flow rate. This shows the change in flow rate when the opening degree of the flow control valve is gradually increased to increase the flow rate. As seen in this figure, the flow rate Ql does not change in the range In this range, control becomes uncontrollable, and the flow rate of Ql that had been flowing to the actuator on the high load side flows to the actuator on the light load side, increasing Q2, and eventually Ql decreases to zero.

Considering this phenomenon in terms of the movement of actuators such as cylinders, if one actuator is moving and another actuator is moved, the actuator that was moving will stop, which poses a control problem.

To solve this problem, if the pump discharge volume is insufficient, the flow rate flowing through the flow control valve is reduced accordingly, so that when another actuator is moved, the speed of the actuator that was previously moving becomes slower. Therefore, it is an object of the present invention to provide a solution that satisfies this requirement.

(Means for solving the problem) In the present invention, in order to achieve the above object, a plurality of actuators are connected in parallel to the discharge circuit of one variable displacement pump, and each connection circuit to each actuator is connected to the discharge circuit of one variable displacement pump. Each of the variable displacement pumps is provided with a flow control valve with a compensator valve having a compensator spring as a control element,
A pump control device is provided that controls the pump capacity of the pump according to the highest load pressure among the load pressures of each actuator and the discharge pressure of the pump,
A control cylinder is provided with a piston that is subjected to a force in one direction due to a control spring and a high load pressure, and is also subjected to a force in the opposite direction due to the discharge pressure, The control cylinder is connected to the compensator valve so that the rod of the piston deflects the compensator spring when a force in the opposite direction becomes dominant.

(Function) For example, two actuators are connected in parallel to the variable displacement pump, and one of the actuators is currently being supplied with a constant flow rate by operating a flow rate control valve in a connected circuit, and is operating under a high load. It is assumed that At this time, when the other flow control valve is operated to operate the other light-load actuator and the flow rate to that actuator is gradually increased, the total flow rate of both flow control valves is increased as shown in Fig. 4. When Ql+02 is in the range X of the discharge amount that the pump can discharge, the difference between the pump discharge pressure P1 and the highest load pressure P2 is maintained at a constant difference by the compensator valve.
In the range Y where Ql+02 is equal to or greater than the pump discharge amount, a phenomenon was observed in which the pump discharge pressure PI and the load pressure P2 become approximately the same pressure. The present invention utilizes the properties of this phenomenon,
Pump discharge pressure P1 and load pressure P2 are introduced into a control cylinder connected to the compensator valve, and P+ =! :
When the differential pressure of P2 reaches a range of Y where the pressure difference decreases, the piston and piston rod are moved away by the control spring of the control cylinder, weakening the spring force of the compensator spring, thereby lowering the differential pressure that determines the flow rate of the flow control valve. The compensator valve operates as follows. When the differential pressure of the compensator valve decreases, the flow rate through the flow control valve decreases, so the maximum flow rate of Q2 decreases, and Ql can be maintained even if the pump discharge volume is insufficient, stopping the movement of the actuator under high load. It can continue to operate without any problems. In addition, in the range Increase the differential pressure that determines the flow rate of the flow control valve.

(Embodiment) An embodiment of the present invention will be explained with reference to the case where two actuators are operated by one variable displacement pump. In FIG. ) is a variable displacement pump, (4) is the pump (
3) discharge circuit, (5) and (6) are connection circuits that branch from the discharge circuit (4) and supply fluid to each actuator (1) and (2), and (7) and (8) are each connection circuit ( 5)
The compensator valve (9) installed in (6) (shows the flow rate side control valve consisting of a switching valve ('Ivaz) with IO. Each flow rate control valve (7) (8) is connected to the operating stroke of its switching valve (Ivo) The opening degree is changed accordingly, and the compensator valve (9) (IO controls the differential pressure before and after each switching valve I'Iv■) so that the flow rate corresponds to the opening degree.

Each compensator valve (9) (The structure of the IO itself is almost the same as the conventional one as shown in Figure 6, and the compensator spring a3 springs from one end side aΦ and the one end side (+4) has a chamber. (A movable plunger aO that is affected by the load pressure of the actuator (1) or (2) introduced into I5+ is provided in the flow path (+7) connected to the discharge circuit (4), and a variable throttle provided on the plunger 11o. (The fluid pressure downstream of Ie is configured to act on the one end side (the other end (+9) opposite IΦ) of the plunger (IO.Then, the switching valve a11) or a2 is operated and the throttle (181 through the actuator (1) or (
2) When the fluid flows to the plunger (Io is one end side a
The force due to the spring (13 and load pressure acting on the spring (13) and the load pressure acting on the other end (+! The pressure is compensated so that the flow rate corresponds to the opening degree of the switching valve (Ivaz).

The variable displacement pump (3) is equipped with a pump control device (2) consisting of a pressure control valve (0) and a flow rate control valve (2) for controlling the introduction and discharge of fluid into the tilting cylinder (2) for changing the pump capacity. The pressure control valve σ guides the fluid in the discharge circuit (4) to the tilting cylinder (■) so as to reduce the pump capacity when the pressure introduced from the discharge circuit (4) becomes higher than a set value. Flow rate control valve ■ is shuttle valve QΦ
Activates when the difference between the highest load pressure of each actuator (1) (2) introduced through the and pilot piping ■ and the pump discharge pressure introduced from the discharge circuit (4) exceeds the set value. and connect the discharge circuit (4) to the tilting cylinder ■.
) to guide the fluid. This pump control device (2) controls the pump capacity according to the pump discharge pressure or the load pressure of the actuator by operating each control valve (0), and the pump (3) discharges a flow rate according to the pressure. ■ is a safety valve, and ■ is an oil tank.

The above configuration is almost the same as the conventional one, and the flow control valve (
7) The compensator valve (9) (If) performs pressure compensation control so that the flow 2 corresponding to the opening degree of the switching valve (It) (IZ) in (8) flows to each actuator (1) (2). The flow rate required by the flow rate control valves (7) and (8) is similar to the conventional one, in that the pump (3) discharges the required flow rate depending on the flow rate control valve of the pump control device (■). In the configuration, if the flow rate required by both flow control valves (7) and (8) becomes greater than the total discharge amount of the pump (3), control becomes uncontrollable, and the flow rate that should flow into the actuator on the high load side is reduced. There is an inconvenience that the liquid flows into the actuator on the low load side, and as a result, the operation of the actuator on the high load side stops.

Therefore, in the present invention, each compensator valve (
9) (The IO is provided with a control cylinder (■) that changes the spring force of the compensator spring ('le), so that the flow rate required by both flow rate control valves (7) (8) as described above is equal to the total flow rate of the pump (3). When the amount exceeds the discharge amount, the control cylinder (2) controls the spring force of the compensator spring (1'3) to allow the flow to flow to the actuator on the high load side, thereby eliminating the inconvenience of the actuator stopping. The details of the control cylinder (2) are as shown in FIG.
It is configured to introduce the highest load pressure among the load pressures of each actuator (1) (2) extracted by the control subrig ■ and the shuttle valve (24+, and the rod Gl) is connected to the spring seat ■ of the compensator spring G3. connected to.

When the pump discharge pressure is higher than the highest load pressure by the force exerted by the control spring ■, that is, in the range X in Fig. 4, the control cylinder ■ overcomes the control spring ■ and the piston ■ and rod 01) The compensator spring (131) is moved to deflect, thereby causing the compensator valve (9) or 00 to increase the differential pressure that determines the flow rate of the flow rate control valve (7) or (8).On the contrary,
When the pump discharge pressure and the highest load pressure become almost the same pressure, that is, in the range Y in Fig. 4, the control spring ■
As a result, the piston (2) and the rod (Gl) move back, and the compensator spring (131) becomes weaker, so the differential pressure that determines the flow rate of the flow control valve (7) or (8) decreases.This action reduces the flow rate to the actuator on the light load side. Q2
Since the maximum value of is reduced, even if the discharge amount of the pump (3) decreases, the flow m Q l to the actuator on the high load side can be secured, and control operations can be performed without stopping the movement of the actuator on the high load side. Ru.

(Effects of the Invention) As described above, according to the present invention, the compensator spring of the compensator valve provided in the flow control valve is
A control cylinder is provided that weakens the spring force of the spring when the differential pressure between the highest of the load pressures of multiple actuators and the pump discharge pressure becomes less than a set value, so multiple actuators If the total flow rate of each flow control valve that controls the operation of the actuator exceeds the pump discharge amount, the flow rate of the flow control valve will automatically decrease, allowing the highly loaded actuator to continue operating without stopping. This has the effect of improving controllability.

[Brief explanation of the drawing]

Fig. 1 is a diagram of the conventional example, Fig. 2 is a diagram showing the change characteristics of the flow rate to the actuator of the one shown in Fig. 1, Fig. 3 is a detailed view of the compensator valve shown in Fig. 1, and Fig. 4 is a diagram of the present invention. FIG. 5 is a diagram showing the variation characteristics of the flow rate to the actuator by the inventive device, FIG. 5 is a diagram of an embodiment of the present invention, and FIG. 6 is a detailed view of the control cylinder shown in FIG. (1) (2)...Actuator (3)...Variable displacement pump (4)...Discharge circuit (5) (6)...Connection circuit (7) (8)...Flow rate control valve (9) (10... Compensator valve (I3...
・Compensator spring■...Pump control device■...Control cylinder■...Piston■...Rod■...Control spring

Claims (1)

[Claims] A plurality of actuators are connected in parallel to the discharge circuit of one variable displacement pump, and each connection circuit to each actuator is provided with a flow control valve with a compensator valve having a compensator spring as a control element, and the variable displacement pump is connected in parallel to the discharge circuit of one variable displacement pump. The pump is provided with a pump control device that controls the pump capacity of the pump according to the highest load pressure among the load pressures of each actuator and the discharge pressure of the pump, and the control spring and the A control cylinder is provided with a piston that receives a force in one direction due to the highest load pressure and a force in the opposite direction due to the discharge pressure. a flow control valve in combination with a variable displacement pump, characterized in that the control cylinder is connected to a compensator valve so as to deflect either the rod of the piston or the compensator spring when a force on the piston becomes predominant. Operation control device for the actuator.