JPH0972301A - Pump control circuit for construction machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the operating ability of a pump control circuit, and to make the control of a pump possible even in case of the occurrence of electrical trouble by varying the tilting angle of the variable displacement type pump from pure hydraulic control into pure electric control. SOLUTION: External signal pressure (a) is made to act on a regulator 17 from a hydraulic source 18 through a proportional pressure reducing valve 19 to carry out the maximum flow rate control of a pump 11. The self pressure (b) of the pump 11 is made to act on a regulator 17 to carry out the fixed horse-power control of the pump 11. The pressure of the hydraulic source 18 is selected into high and low pressures by a solenoid change-over valve 20 and made to act as signal pressure (c) on the regulator 17 for carrying out the horse-power shift control of the pump 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pump control circuit for a construction machine, and more particularly to a construction machine in which the maximum flow rate is controlled by an external signal pressure and the constant horsepower is controlled by the self pressure of the pump. The present invention relates to a pump control circuit.

[0002]

2. Description of the Related Art A conventional pump control circuit for a construction machine is shown in FIG.
Shown in A directional control valve 3 having a center bypass is provided between the variable displacement pump 1 and the actuator 2.
A negative control throttle (hereinafter referred to as “negative control throttle”) 5 is provided downstream of the bypass oil passage 4 and communicates with the tank 6. The pressure generated by the negative control throttle 5 is applied as an external signal pressure a from the oil passage 7 to the regulator 8 to control the maximum flow rate of the pump 1.

Further, the self-pressure b of the pump 1 is taken out from between the pump 1 and the direction control valve 3 and acted on the regulator 8, the constant horsepower control of the pump 1 is performed according to the self-pressure b, and the hydraulic power source 9 is used. This pressure oil is applied to the regulator 8 as the signal pressure c via the proportional pressure reducing valve 10 to perform the horsepower shift control of the pump 1.

FIG. 3 is a block diagram showing the function of the regulator 8 based on the external signal pressure a by the negative control throttle 5, the self pressure b of the pump 1, and the signal pressure c from the proportional pressure reducing valve 10. External signal pressure a generated by
The maximum flow rate Q ₁ is decreased as is increased. Further, when the self-pressure b of the pump 1 increases, the flow rate Q ₂ is reduced in order to effectively use the horsepower from the driving source, and further the horsepower curve is increased or decreased by the action of the signal pressure c from the proportional pressure reducing valve 10. Shift to. Thus, the external signal pressure a and the self pressure b
And the signal pressure c are used to control the discharge amount Q of the pump 1 to be optimum.

[0005]

In a conventional pump control circuit for a construction machine, a regulator is adjusted by an external signal pressure generated by a negative control throttle or a pure hydraulic action such as self-pressure of the pump. Therefore, in order to smoothly change the pump discharge rate and the actuator speed in proportion to the lever operation, it is necessary to finely adjust the opening characteristics of the directional control valve. It becomes difficult to respond.

Here, it is conceivable that the tilt angle of the pump is controlled purely electrically to cope with the complex operation, but there is a problem that the pump becomes out of control when a trouble occurs in the electric system.

Therefore, the tilt angle of the variable displacement pump is changed from pure hydraulic control to pure electric control to improve operability, and even if a trouble occurs in the electric system, the pump is changed. Therefore, the technical problem to be solved in order to enable the control of (1) arises, and the present invention aims to solve this problem.

[0008]

SUMMARY OF THE INVENTION The present invention has been proposed in order to achieve the above-mentioned object, and provides an external signal pressure generated by a negative control throttle, a pump self pressure, and a signal pressure from a proportional pressure reducing valve. In the pump control circuit of the construction machine that controls the maximum flow rate of the pump, the constant horsepower control, and the horsepower shift control, and the external signal pressure for the maximum flow rate control is from the hydraulic source. The present invention provides a pump control circuit for a construction machine that acts on a regulator via a proportional pressure reducing valve, and selects a high pressure or a low pressure on a signal pressure for horsepower shift control by an electromagnetic switching valve to act on the regulator.

[0009]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows a pump control circuit for a construction machine, in which a directional control valve 13 having a center bypass is provided between a variable displacement pump 11 and an actuator 12.
Downstream of the bypass oil passage 14, directional control valves 15a and 15b for controlling other actuators are provided and a tank 16 is provided.
Is in communication with.

An external signal pressure a acts from a hydraulic pressure source 18 via a proportional pressure reducing valve 19 on a regulator 17 for adjusting the tilt angle of the pump 11. Controller (not shown)
By adjusting the electric signal to the solenoid 19a of the proportional pressure reducing valve 19, the external signal pressure a output from the proportional pressure reducing valve 19 is arbitrarily increased or decreased, which may cause load fluctuation of the actuator 12 or complex operation with other actuators. Depending on,
It is possible to control the maximum flow rate of the pump 11 to an optimum state.

Further, similarly to the conventional case, the self-pressure b of the pump 11 is taken out from between the pump 11 and the direction control valve 13 and applied to the regulator 17, and the constant horsepower control of the pump 11 is performed according to the self-pressure b. To do.

Further, the signal pressure c is applied to the regulator 17 from the hydraulic power source 18 via the electromagnetic switching valve 20, and the horsepower shift control of the pump 11 is performed by the signal pressure c. When the solenoid 20a of the electromagnetic switching valve 20 is not excited, the electromagnetic switching valve 20 is at the position "a", the signal pressure c becomes low, and the set horsepower of the pump 11 becomes the minimum level. On the other hand, when the solenoid 20a of the electromagnetic switching valve 20 is excited by the controller, the electromagnetic switching valve 20
Is switched to the position of “B”, the pressure of the hydraulic power source 18 acts on the regulator 17 as a high signal pressure c, and the pump 1
The set horsepower of 1 is shifted to the highest level.

Then, with the electromagnetic switching valve 20 in the "B" position, the high pressure signal pressure c is applied to the regulator 17 to maximize the set horsepower of the pump 11, and the proportional pressure reducing valve 19 is used. The external signal pressure a acting on the regulator 17 is controlled, the tilt angle of the pump 11 is adjusted, and the discharge amount is controlled to an optimum state.

As described above, by controlling the tilt angle of the pump 11 purely electrically, even when a plurality of actuators are operated in combination, the pump discharge amount and the speed of the actuator are proportional to the operation of the lever. Can be changed smoothly, and operability is significantly improved.

If a trouble should occur in the electric system, the electric signal does not act on the solenoid 19a of the proportional pressure reducing valve 19, the external signal pressure a from the proportional pressure reducing valve 19 becomes zero, and the pump 11 The maximum flow rate control is no longer performed. Further, the solenoid 20 of the electromagnetic switching valve 20
Also, a is no longer excited, the electromagnetic switching valve 20 is switched to the position "a", and the set horsepower of the pump 11 is shifted to the lowest level. Therefore, the pump 11 is purely hydraulic and self-pressure b.
The discharge amount is adjusted by the constant horsepower control by, and the pump control can be continued even if a trouble occurs in the electric system.

The present invention can be variously modified without departing from the spirit of the present invention, and it goes without saying that the present invention extends to the modified ones.

[0017]

As described above, according to the present invention, the operability is remarkably improved by changing the tilt angle of the variable displacement pump from pure hydraulic control to pure electric control. Also, if a trouble occurs in the electrical system, it is possible to continue control of the pump by purely hydraulic control.
Safety and reliability can be secured.

[Brief description of drawings]

FIG. 1 is a pump control circuit diagram showing an embodiment of the present invention.

FIG. 2 is a conventional pump control circuit diagram.

FIG. 3 is a block diagram showing a function of a regulator.

[Explanation of symbols]

 11 pump 17 regulator 18 hydraulic source 19 proportional pressure reducing valve 20 electromagnetic switching valve

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display area F15B 11/04 B

Claims (1)

[Claims] 1. An external signal pressure generated by a negative control throttle, a self pressure of the pump, and a signal pressure from a proportional pressure reducing valve are applied to a regulator to control the maximum flow rate of the pump, constant horsepower control, and horsepower shift. In the pump control circuit of the construction machine configured to perform the control, the external signal pressure for controlling the maximum flow rate is applied to the regulator from the hydraulic pressure source via the proportional pressure reducing valve, and the signal pressure for controlling the horsepower shift is also applied. Is a pump control circuit for construction machinery, characterized in that high or low pressure is selected by an electromagnetic switching valve to act on a regulator.