JPH05215101A - Control method of pump inclination quantity - Google Patents

Abstract

PURPOSE:To improve the operability of an operation lever by regulating an inclination quantity of a veriable displacement pump by comparison computation, in starting actuation of a hydraulic actuator, of a pump inclination quantity corresponding to a standard load at an engine rotation speed at the time, based on a signal from a pressure sensor. CONSTITUTION:When a working load applied to a hydraulic cylinder 4 is large, an actuation pressure of an actuation circuit 20-28 for the hydraulic cylinder 4 of which pressure is increased in starting operation of an operation lever 7 is detected by a pressure sensor 27, a pump inclination quantity corresponding to a standard load at an engine rotation speed at the time is compared and computed by a controller 24 based on its signal and a signal from an engine rotation speed detector 14, and a pump inclination instruction signal is outputted to a proportional pressure reducing solenoid valve 26. The pressure reducing valve 26 is actuated, a regulator 9' is actuated by an introduced pilot pressure, and the pump inclination quantity is regulated. When the working load is large, therefore, a pump discharge flow is increased correspondingly, and an operation quantity of the operation lever 7 when it starts moving can be set to be almost similar to that for a standard load.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling a variable pump mounted on a construction machine such as a hydraulic excavator.

[0002]

2. Description of the Related Art FIG. 3 is a diagram showing a control circuit for an engine 1 and a variable pump (more specifically, a variable displacement hydraulic pump) 2 mounted on a hydraulic excavator (not shown). In the figure, 3 is a work attachment mounted on the front part of the hydraulic excavator, 4 is one hydraulic cylinder of a plurality of hydraulic actuators arranged in the work attachment 3, and 5 is a control cylinder for controlling the hydraulic cylinder 4. A pilot switching valve, 6 is a hydraulic remote control valve, 7 is an operation lever for the hydraulic remote control valve 6, 8 is a pilot pump, 9 is a regulator for adjusting the swash plate tilt angle of the variable pump 2, and 10 is a governor device of the engine 1. , 11 is a governor lever of the governor device 10, 12 is a control motor such as a so-called stepping motor, 13 is a drive lever of the control motor 12, 14 is a rotation speed detector for detecting the rotation speed of the engine 1, 15 is a controller, and 16 is a mode. Changeover switch, 17 is an accelerator lever device, 18 is an accelerator lever of the accelerator lever device 17, 19 Potentiometer for detecting an operation position of the accelerator lever 18, reference numeral Ii, Loro shows the connection in the pilot conduit which communicates the hydraulic remote control valve 6 and the pilot changeover valve 5. In addition, by switching the engine speed control mode changeover switch 16 according to the magnitude of the work load during the work of the hydraulic excavator, H (for heavy load),
It is possible to respectively select a plurality of work modes of S (for normal load) and FC (for fine operation work). When the accelerator lever 18 is operated in the direction of arrow L, the engine speed is low idling rotation (engine low speed rotation).
When operated in the direction of arrow H, high idling rotation (engine high speed rotation) is achieved.

As shown in FIG. 3, a control circuit for a hydraulic excavator of the prior art is equipped with an engine 1 and a variable pump 2 driven by the engine 1, and controls the rotational speed of the engine 1 via a controller 15. I am trying to do it. Further, the tilting amount of the variable pump 2 is adjusted according to the work load acting on the hydraulic cylinder 4. As a result, when the operating pressure of the hydraulic cylinder 4, that is, the pump pressure of the variable pump 2, changes according to the work load, the pump pressure acts on the regulator 9 via the pipe lines 20, 21, the throttle portion 22, and the pipe line 23. Since the regulator 9 operates to adjust the tilt angle of the swash plate, it is possible to automatically change the pump flow rate.

[0004]

In the control circuit of the hydraulic excavator, as shown in FIG. 3, the pump pressure of the variable pump 2 set to a predetermined horsepower exceeds the so-called pump characteristic PQ line (not shown). At that time, the pump pressure acts on the regulator 9 to reduce the amount of tilting of the pump and prevent the engine 1 from being overloaded. However, the operation angle of the operation lever 7 differs depending on whether the work load of the hydraulic cylinder 4 is small or large when the operation of the operation lever 7 for the hydraulic remote control valve (6) is started. FIG. 4 is a chart showing the relationship between the operation angle θ of the operation lever corresponding to the large and small work loads and the amount Q of oil flowing into the hydraulic actuator. When the operation lever is operated at the same operation angle (an operation angle for similarly deriving the pilot secondary pressure from the hydraulic remote control valve) at the start of operation, the amount of oil flowing into the hydraulic actuator is small when the work load is large. Therefore, since the operating lever is operated to a considerably large angular position in order to increase the working pressure by increasing the pump flow rate, the operating control range of the operating lever becomes narrow, and the responsiveness and inching performance deteriorate. It is an object of the present invention to provide a method for controlling a pump displacement amount that can solve the above problems.

[0005]

According to the control method of the present invention,
A standard load is set as a reference work load that can act on the hydraulic actuator according to the engine speed, and the operation angle of the operating lever when operating the hydraulic actuator under the standard load is stored in the controller. In addition, a pressure sensor is placed in the hydraulic actuator operating circuit, and the pressure detection signal from the pressure sensor is input to the controller.When the hydraulic actuator starts operating, the controller outputs the pressure detection signal from the pressure sensor. Based on this, a comparison is made with the pump displacement amount corresponding to the standard load at the engine speed at that time, and a judgment is made based on the calculation result, and a pump displacement command signal is output to the regulator via the electro-hydraulic converter to make it variable. By adjusting the amount of tilt of the pump, the load acting on the hydraulic actuator can be increased. An operation amount of the movement start of the operation lever regardless, was made to be approximately the same as the operation amount of the movement start during operation load.

[0006]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a main part control circuit diagram according to the present invention. In the figure, the same reference numerals are given to those using the same constituent elements as those in the prior art. 9'is a regulator of the variable pump 2, 24 is a controller, 25 is a memory of the controller 24, 26 is an electromagnetic proportional pressure reducing valve which is an electro-oil converter, and 27 is a pressure sensor. FIG. 2 shows the relationship between the pilot secondary pressure Pi derived from the hydraulic remote control valve 6 and the pump displacement (the discharge flow rate CC / rev per one rotation of the pump shaft) when the work load is large in the present invention. It is a chart.

Next, the control method of the present invention will be described with reference to FIGS. According to the control method of the present invention, a standard load is set as a reference work load that can act on the hydraulic cylinder 4 in accordance with the engine speed, and the operating lever when starting operation of the hydraulic cylinder 4 on which the standard load acts. 7 is stored in the memory (ROM) 25 of the controller 24, and the operating circuit of the hydraulic cylinder 4 (20-2
8), the pressure sensor 27 is arranged, and the pressure detection signal from the pressure sensor 27 is input to the controller 24. When the operation of the hydraulic cylinder 4 is started, the controller 24 is operated based on the pressure detection signal from the pressure sensor 27. Then, the pump displacement amount corresponding to the standard load at the engine speed at that time is comparatively calculated, and it is judged based on the calculation result, and the pump displacement command signal is output to the regulator 9 ′ via the electromagnetic proportional pressure reducing valve 26. By adjusting the tilt amount of the variable pump 2, the operation amount at the start of movement of the operation lever 7 becomes almost the same as the operation amount at the start of the standard load regardless of the load acting on the hydraulic cylinder 4. I tried to be. The standard load is 0 load.
A load close to (zero) or 0 (zero) may be set as the standard load. Further, the tilting amount adjustment of the variable pump 2 is performed within a range that does not exceed the pump absorption horsepower equivalent to the engine horsepower in order to prevent engine stall.

Next, the operation of the control method of the present invention will be described. Generally, when the load pressure of the hydraulic cylinder is P, the pump discharge flow rate is Q, the opening area of the spool is S, and the coefficient is K, there is a relation of P = K (Q / S) ² . Therefore, when the opening area S of the spool is always operated to be the same, when the load pressure P is large, the pump flow rate Q does not increase and the generated pressure for operating the hydraulic cylinder becomes insufficient. Therefore, in the conventional control circuit, when the work load is large, the operation amount of the operation lever 7 at the start of movement has to be increased. However, in the control method of the present invention, the hydraulic cylinder 4
The pressure sensor 27 detects the operating pressure of the hydraulic cylinder 4 operating circuit (20-28) whose pressure has risen when the operation lever 7 is started when the work load acting on the is large. The pressure detection signal from the pressure sensor 27 and the engine rotation speed detection signal from the rotation speed detector 14 are input to the controller 24. In the controller 24, based on the pressure detection signal and the engine speed detection signal, the pump displacement amount corresponding to the standard load at the engine speed at that time is compared and calculated, and it is determined based on the calculation result.
A pump displacement command signal is output to the electromagnetic proportional pressure reducing valve 26. The electromagnetic proportional pressure reducing valve 26 operates, and the derived pilot pressure acts on the regulator 9 ′. Since the regulator 9 ′ operates to adjust the pump tilting amount, when the work load is large, the pump discharge flow rate is increased accordingly, and the operation amount of the operation lever 7 at the start of movement is set to that of the movement at the standard load. It can be almost the same as the manipulated variable.

[0009]

According to the control circuit of the prior art, when operating the hydraulic actuator equipped on the construction machine, if the operating lever is operated at the same operating angle at the start of operation, the amount of oil flowing into the hydraulic actuator when the work load is large. Less is. For this reason, the operating angle of the operating lever has to be set large, so that the hydraulic actuator has poor responsiveness and inching operability, which hinders work.
However, in the control method of the present invention, a standard load is set as a reference work load that can act on the hydraulic actuator in accordance with the engine speed, and the operation lever of the operation lever when starting operation of the hydraulic actuator on which the standard load acts is set. The operation angle amount is stored in the memory of the controller, a pressure sensor is arranged in the hydraulic actuator operation circuit, and the pressure detection signal from the pressure sensor is input to the controller. Based on the pressure detection signal from the sensor, the controller compares and calculates the pump displacement amount corresponding to the standard load at the engine speed at that time, makes a determination based on the calculation result, and outputs the pump displacement command signal to the electromagnetic proportional pressure reducing valve. Output to the regulator via the so that the tilt amount of the variable pump can be adjusted. . As a result, when the operation of the hydraulic actuator is started, the operation amount at the beginning of movement of the operation lever can be made substantially the same as the operation amount at the beginning of movement at the standard load regardless of the magnitude of the load acting on the hydraulic actuator. Therefore, according to the pump tilting amount control method of the present invention, it is possible to improve the operability of the operation lever for the hydraulic actuator of the construction machine and improve the workability.

[Brief description of drawings]

FIG. 1 is a main part control circuit diagram according to the present invention.

FIG. 2 is a chart showing a relationship between a pilot secondary pressure derived from a hydraulic remote control valve and a pump displacement amount when a work load is large in the present invention.

FIG. 3 is a diagram showing a conventional control circuit.

FIG. 4 is a chart showing a relationship between an operation angle of an operation lever in the related art corresponding to a large work load and a small work load, and an oil amount flowing into a hydraulic actuator.

[Explanation of symbols]

 1 Engine 2 Variable Pump 4 Hydraulic Cylinder 7 Operating Lever 9,9 'Regulator 14 Rotation Speed Detector 15, 24 Controller 25 Memory 26 Electromagnetic Proportional Pressure Reduction Valve 27 Pressure Sensor

Claims (1)

[Claims] 1. An engine and a variable pump driven by the engine, the engine speed is controlled via a controller, and the tilt amount of the variable pump is adjusted according to the work load acting on the hydraulic actuator. In the control circuit of the construction machine that adjusts, set a standard load as a reference work load that can act on the hydraulic actuator according to the engine speed, and operate the hydraulic actuator on which the standard load acts. When the operating angle of the operating lever is stored in the controller, a pressure sensor is placed in the hydraulic actuator operating circuit, and the pressure detection signal from the pressure sensor is input to the controller, and the hydraulic actuator starts operating. At this time, the controller uses the pressure detection signal from the pressure sensor , Comparing the pump displacement corresponding to the standard load at the engine speed at that time, making a judgment based on the calculation result, and outputting the pump displacement command signal to the regulator via the electro-hydraulic converter to make the variable pump By adjusting the tilting amount of the control lever, the operation amount at the beginning of movement of the operating lever is made to be almost the same as the operation amount at the beginning of movement under standard load, regardless of the magnitude of the load acting on the hydraulic actuator. A characteristic method for controlling the pump displacement.