JPH07332247A - Control device for variable displacement hydraulic pump - Google Patents

Abstract

PURPOSE:To perform constant stable control of torque through prevention of the occurrence of a delay in operation of a hydraulic control system. CONSTITUTION:The delivery pressure of a capacity variable hydraulic pump 1 is detected by a pressure sensor 12 and a detecting result is fed to the computing part 13 of a controller 15. A target value of a pump delivery flow rate by which torque is controlled to a constant value through compensation computation of a phase delay by the computing part 13 is calculated. A flow rate command signal responding to the flow rate target value is fed to an electromagnetic proportional valve 9 from a control signal output part 14. An actuator 2 is operated through a servo valve 4 and the inclination angle of a pump 1 is controlled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a controller for a variable displacement hydraulic pump that performs constant torque control.

[0002]

2. Description of the Related Art Conventionally, a control device for performing constant torque control by changing the tilt angle (discharge flow rate) according to the discharge pressure of a variable displacement hydraulic pump is shown in Japanese Utility Model Publication No. 5-558. As is known.

In this known control device, the pump discharge pressure is detected by the pressure detecting means, the pump flow rate for constant torque control is obtained from the detected pump discharge pressure, and an electric signal corresponding to this pump flow rate is obtained. The configuration is such that the actuator (cylinder) for controlling the tilting angle of the pump is operated by sending it to the control valve device and via the control valve device and the servo valve.

[0004]

However, in any of the known control devices, the pump discharge flow rate is obtained based on the pump discharge pressure at the time of detection, and is converted into an electric signal and sent to the control valve device. Therefore, when the fluidity of the oil decreases especially in low temperatures such as in winter, there is a delay in the operation of the hydraulic control system (control valve device, servo valve, actuator), and this delay causes the entire pump control system to operate. There is a problem that hunting causes unstable torque control.

Therefore, the present invention provides a control device for a variable displacement hydraulic pump capable of performing stable torque constant control by preventing operation delay of a hydraulic control system.

[0006]

According to a first aspect of the present invention, there is provided a variable displacement hydraulic pump, an actuator for controlling a tilt angle of the pump, a control valve device for controlling the operation of the actuator, and a pump discharge pressure. Pressure detecting means for detecting,
A controller for outputting an operation signal to the control valve device, the controller performing a phase delay compensation calculation for compensating a phase delay of control from a time series value of the pump discharge pressure detected by the pressure detecting means. Section, the pump discharge flow rate for performing constant torque control is calculated from the pressure value calculated by this calculation section and the preset torque value, and a flow rate command signal for obtaining this pump discharge flow rate is supplied to the control valve. And a control signal output unit for outputting to the device.

According to a second aspect of the present invention, in the configuration of the first aspect, as the control valve device, an electromagnetic proportional pressure reducing valve that outputs a secondary pressure corresponding to an operation signal from the controller, and a secondary of the electromagnetic proportional pressure reducing valve. A servo valve that operates by pressure to control the actuator is provided.

[0008]

According to the above structure, the calculation unit performs the phase delay compensation calculation, and the pump discharge flow rate for performing the constant torque control is calculated based on the compensated pump discharge pressure.
Since the control valve device is controlled, it is possible to prevent operation delay of the hydraulic control system and perform stable torque constant control.

Further, according to the second aspect of the present invention, since the servo valve is driven by the electromagnetic proportional pressure reducing valve and the actuator is operated by this servo valve, the flow rate control of the pump is simplified based only on the pump discharge pressure. Can be done.

[0010]

Embodiments of the present invention will be described with reference to the drawings.

First Embodiment (see FIGS. 1 and 2) 1 is a variable displacement hydraulic pump, 2 is an actuator for controlling the tilt angle of the pump 1, 3 is a piston of this actuator, and this piston 3 is the left and right of the drawing. The pump tilt angle (discharge flow rate) is changed by moving in the direction.

Reference numeral 4 is a servo valve for controlling the operation of the actuator 2. Reference numeral 5 is a spool of the servo valve 4. Reference numeral 6 is a piston connected to the spool 5. Reference numeral 7 is a pressure for applying a pressure to the piston 6 against the spring 8. In this chamber, a secondary side conduit 10 of an electromagnetic proportional pressure reducing valve (hereinafter, simply referred to as a proportional valve) 9 is connected to the pressure chamber 7, and the secondary pressure of the proportional valve 9 causes the servo valve 4 to move in one direction (to the right in the figure). ) Is driven.

Further, in the servo valve 4, the input / output port 4a is connected to the extension side oil chamber 2a of the actuator 2, the pressure port 4b is connected to the auxiliary hydraulic power source 11, and the tank port 4c is connected to the tank T. There is.

On the other hand, the contraction side oil chamber 2b of the actuator 2
Is connected to the auxiliary hydraulic power source 11, and the position of the actuator 2 (position of the piston 3 = pump tilt angle) is determined by the pressure of the auxiliary hydraulic power source 11 and the pressure determined by the position of the servo valve 4. ing.

Reference numeral 12 is a pressure sensor for detecting the discharge pressure of the pump 1, and the pressure signal of this pressure sensor 12 is calculated by the arithmetic unit 13
And the control signal output unit 14 are input to the arithmetic unit 13 of the controller 15.

The calculation unit 13 obtains a target value qa of the pump discharge flow rate for performing constant torque control based on the pressure signal, and an electric signal (flow rate command signal) ia corresponding to the obtained flow rate qa is a control signal. It is sent from the output unit 14 to the proportional valve 9.

As a result, the proportional valve 9 causes the flow rate command signal ia.
Is output to the pressure chamber 7 of the servo valve 4, and the servo valve 4 is set at a position determined by the secondary pressure and the force of the spring 8.

The position of the servo valve 4 determines the position of the piston 3 of the actuator 2, and the tilt angle (discharge flow rate) of the pump 1 is determined.

Here, for example, at low temperature, the hydraulic control system (proportional valve 9, servo valve 4, actuator 2) is delayed in operation due to a decrease in the fluidity of the oil, and as a result, the entire pump control system easily causes hunting. .

Therefore, the calculation unit 13 performs the following phase delay compensation calculation.

Referring to FIG. 2 together, the calculation unit 13
Is a pump discharge pressure (hereinafter, referred to as an input value) Pin detected by the pressure sensor 12 is sampled at a sampling time T of a minute time, and an output value Pout considering a delay of a hydraulic control system is used by using this sampling value. The target flow rate qa is calculated from this output value Pout and the preset pressure-flow rate characteristic for torque constant control (see the Pq characteristic diagram in FIG. 2), and this is calculated by the control signal output unit. Send to 14.

When the above is expressed by a mathematical expression,

[0023]

[Equation 1]

It becomes Here, T: sampling time, d: coefficient, k: current sampling time, k-1: sampling before one time, a: delay time constant, b: advance time constant, and Pout (k-1) is 1 Output value before time point, Pin
(K) is the input value at the current time, and Pin (k-1) is the input value one time before.

In this phase delay compensation calculation, by appropriately setting a and b, an output value suitable for the pressure fluctuation frequency and the delay of the hydraulic control system is obtained, and the pump discharge flow rate is set based on this output value. Therefore, it is possible to prevent operation delay of the hydraulic control system and prevent hunting of the entire pump control system.

As the phase delay compensation calculation in the calculation unit 13 of the controller 15, compensation calculation based only on differentiation may be performed as shown in FIG.

In this way, since the phase lead is only 90 ° at all frequencies, there is the drawback that fine compensation cannot be performed and it is easily affected by noise.
There is an advantage that the arithmetic expression is simplified and the arithmetic speed can be increased.

Second Embodiment (Refer to FIG. 4) Only differences from the first embodiment will be described.

In the second embodiment, first and second high speed electromagnetic switching valves (hereinafter, simply referred to as first switching valve and second switching valve) 16 and 17 are used as control valve devices controlled by the controller 15. Has been.

The first switching valve 16 is provided between the auxiliary hydraulic power source 11 and the extension side oil chamber 2a of the actuator 2, and makes them communicate with each other in the state where no drive signal is input.

On the other hand, the second switching valve 17 is provided between the extension side oil chamber 2a of the actuator 2 and the tank T, and shuts off these when the drive signal is not input.

Reference numeral 18 is a flow rate detecting device for detecting the pump discharge flow rate from the tilt angle of the pump 1, and this flow rate signal is sent to the arithmetic unit 13 of the controller 15 together with the pressure signal from the pressure sensor 12.

The calculation unit 13 indexes the target flow rate through the delay compensation calculation based on the pressure signal, and the control signal output unit 14 outputs the target flow rate so that the flow rate detected by the flow rate detection device 18 (actual flow rate) becomes the target flow rate. First and second switching valves 16, 17
The on / off signal is repeatedly output to.

As a result, both switching valves 16 and 17 are switched at high speed between the communicating and blocking positions, and every time the second switching valve 17 is set to the communicating position, the extension side oil chamber 2a of the actuator 2 is stored in the tank. By communicating with T, the actuator 2 moves in small steps toward the contraction side, that is, the tilt angle of the pump 1 changes and the discharge flow rate changes toward the target flow rate.

[0035]

As described above, according to the present invention, the discharge pressure of the pump is detected by the pressure detecting means and sent to the arithmetic unit, and the arithmetic unit performs the phase lag compensation calculation to perform the constant torque control. Since the pump discharge flow rate is indexed and the control valve device is controlled based on this index, operation delay of the hydraulic control system at low temperature, etc., and hunting of the entire pump control system due to this are prevented and stable. Torque constant control can be performed.

Further, according to the invention of claim 2, since the servo valve is driven by the electromagnetic proportional pressure reducing valve and the actuator is actuated by the servo valve, the flow rate control of the pump is simplified based only on the pump discharge pressure. Can be done.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of a pump control device according to a first embodiment of the present invention.

FIG. 2 is a diagram for explaining an operation of a control system in the same device.

FIG. 3 is a diagram corresponding to FIG. 2 for explaining another example of the phase delay compensation calculation by the control system.

FIG. 4 is an overall configuration diagram of a pump control device according to a second embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Variable displacement hydraulic pump 2 Actuator 4 Servo valve which constitutes a control valve device 9 Electromagnetic proportional valve which constitutes a control valve device 12 Pressure sensor as pressure detection means 15 Controller 13 Calculation part 14 Control signal output part 16 and 17 Control valve device High-speed solenoid directional control valve

Claims (2)

[Claims] 1. A variable displacement hydraulic pump, an actuator for controlling a tilt angle of the pump, a control valve device for controlling the operation of the actuator, a pressure detecting means for detecting a pump discharge pressure, and the control valve device. And a controller for outputting an operation signal to the controller, the controller performing a phase delay compensation calculation for compensating the phase delay of the control from the time series value of the pump discharge pressure detected by the pressure detecting means, and A pump discharge flow rate for performing constant torque control is calculated from the pressure value calculated by the calculation unit and a preset torque value, and a flow rate command signal for obtaining this pump discharge flow rate is sent to the control valve device. A control device for a variable displacement hydraulic pump, comprising: a control signal output section for outputting. 2. An electromagnetic proportional pressure reducing valve for outputting a secondary pressure according to an operation signal from a controller, as a control valve device,
The control device for a variable displacement hydraulic pump according to claim 1, further comprising a servo valve that operates by a secondary pressure of the electromagnetic proportional pressure reducing valve to control an actuator.