JPH11303760A - Variable displacement pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the stability of control by generating a disturbance signal based on the difference between the output of a simulated circuit and the output of a filter, inputting the output difference signal between the output of an actual flow detector and the output of a limiter to the simulated circuit, and adding the output difference signal to a pressure action quantity as the subtraction signal. SOLUTION: The controller of a variable displacement pump receives a pressure action quantity Pu and outputs a pressure signal F. The signal subtracted with a disturbance signal d2 from the output signal Q of an actual flow detector is inputted to a simulated circuit PLm(b).A disturbance signal d1 is generated based on the difference between the output signal P1 from a simulated circuit PLm(s) and the output signal from an actual pressure detector outputted through a low-cut filter 3. A limiter 7 removes the negative electrode component included in the disturbance signal d1 and outputs it as a disturbance signal d2 . The output difference signal between the flow signal Q and the simulated disturbance signal d2 is inputted to the simulated circuit PLm(s) as a simulated pressure differential signal P2 .

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable displacement pump having control means for electrically controlling the discharge pressure and flow rate of hydraulic oil in a closed loop, and more particularly to a control means for performing pressure control. .

[0002]

2. Description of the Related Art In a hydraulic circuit, the pressure and flow rate of hydraulic oil discharged from a variable displacement pump are controlled by changing the angle of a swash plate in the pump. When the pressure control by the swash plate of such a variable displacement pump is performed electrically by closed loop control, a method of controlling by feeding back a differential component of the pressure in order to improve the stability of the pressure control system is generally known. Have been.

[0003]

However, such a conventional pressure control method has the following problems. There is a problem that the pressure signal from the piston of the variable displacement pump has many pulsating components, and it is difficult to extract a differential component. Here, in the pressure control by the pump, the discharge flow rate of the hydraulic oil, that is, the speed signal of the swash plate corresponds to a differential component of the pressure. Therefore, in order to improve the stability of pressure control,
A method of feeding back the speed signal of the swash plate can be considered.

However, since the pressure control of the variable displacement pump is usually performed while discharging a constant flow of hydraulic oil, the flow rate of the hydraulic oil becomes a disturbance, and the stability of the increase in the deviation of the pressure control system deteriorates. There is a problem of doing.

The present invention has been made in view of the above problems, and has as its main object to provide a variable displacement pump capable of improving the stability of pressure control without being affected by disturbance. .

[0006]

SUMMARY OF THE INVENTION In order to achieve the above-mentioned object, a first aspect of the present invention is a variable displacement device having control means for electrically controlling the discharge pressure and discharge flow rate of hydraulic oil by a proportional solenoid valve. A pump having a simulated load characteristic of a pressure control system;
A filter that generates a signal obtained by removing a high-frequency noise component from an output signal of the actual pressure detector; a disturbance signal generating unit that generates a disturbance signal by taking a difference between an output of the simulation circuit and an output of the filter; A limiter for saturating the negative polarity component to a constant value, and input means for taking a difference between an output signal of an actual flow rate detector and an output of the limiter, and inputting the output difference signal to the simulation circuit; It is characterized in that the difference signal is added to the pressure operation amount as a subtraction signal.

According to the present invention, a disturbance signal is generated by a disturbance signal generating means based on a difference between an output from a simulation circuit having a simulation load characteristic of a pressure control system and an output signal of an actual pressure detector output through a filter, ie, a detected pressure value. Is generated, and the disturbance signal is fed back to the pressure control amount through the limiter. That is, the actual disturbance signal included in the signal of the discharge flow rate is estimated using a simulation circuit, and the estimated disturbance signal is fed back to the pressure control amount, so that the discharge flow rate becomes a disturbance and affects the pressure control system. Can be avoided, and the stability can be improved.

Here, the simulation circuit has a load characteristic of the pressure control system in a simulated manner.
That is, a signal obtained by subtracting the disturbance signal (estimated disturbance signal) generated by the disturbance signal generation means from the flow rate detection value is input. This is because the actual flow rate detection value includes a flow rate disturbance, so that such a disturbance component is removed.
Therefore, the stability of the pressure control system can be improved by the simulation circuit. The configuration of the simulation circuit is not particularly limited as long as it has the simulation load characteristic of the pressure control system. For example, the simulation circuit can be configured to include an integral element, a higher-order transfer function, a non-linear function, and the like.

Further, since the filter according to the present invention removes high-frequency noise components from the output signal from the actual pressure detector, a stable output signal without distortion can be input to the disturbance signal generation means, and the pressure control can be performed. The stability of the system can be further improved.

The limiter of the present invention saturates the negative component of the disturbance signal to a constant value. Therefore, even when the disturbance signal becomes negative, the negative portion is cut off and is not fed back to the pressure control amount. A diode circuit or the like can be used as such a limiter.

According to a second aspect of the present invention, in the variable displacement pump according to the first aspect, the simulation circuit includes a circuit including an integrating element.

The present invention is a preferred embodiment of the simulation circuit according to the first aspect of the present invention. Since the load of the pressure control system generally has an integral characteristic, the simulated circuit is made into a circuit including an integral element in accordance with the actual load, and the simulated load characteristic of the simulated circuit is approximated to the actual load, so that the pressure control system is Can be further improved in stability.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of a control unit of the variable displacement pump according to the present embodiment. The control unit of the present embodiment inputs the pressure operation amount Pu,
It outputs a pressure signal P, and a pump P (s) to be controlled is directly connected to an actual load section PL (s).
The control unit includes a simulation circuit PLm (s) and a limiter 7.
Are connected in parallel to the actual load section PL (s). Furthermore,
The low-frequency cutoff filter 3 is connected to a feedback element on the output side of the actual load section PL (s).

The low-frequency cutoff filter 3 receives the pressure signal P, removes high-frequency noise from the pressure signal P, and outputs the signal.

The simulation circuit PLm (s) is a circuit including an integral element. That is, PLm (s) is represented by the equation (1).

[0016]

## EQU1 ## PLm (s) = K / s (K: constant)

Therefore, when the output of the simulation circuit matches the pressure signal that is the output of the actual pressure detector, the input signal of the simulation circuit is equal to the differential signal of the pressure, and the pressure differential is pseudo. Feedback is possible.

The simulation circuit PLm (s) receives a disturbance signal d2 (described later) from the flow signal Q in order to artificially remove a flow disturbance from an output signal Q (flow signal) of an actual flow detector (not shown). The reduced signal is input. And the simulation circuit P
A disturbance signal d1 is generated from a difference between the output signal P1 from Lm (s) and the pressure signal P from the actual pressure detector output through the low-pass filter 3.

That is, in the control unit of the present embodiment, the difference between the actual pressure P and the output P1 of the simulation circuit PLm (s) is simulated as a disturbance component of the pressure control system. Here, FIG.
2A is a diagram showing transition of the pressure signal P and the output signal P1 of the simulation circuit when there is a flow disturbance, and FIG.
(B) is a diagram showing a transition of a disturbance signal d1 generated from a difference between the pressure signal P and the output signal P1. The disturbance signal d1 generated in this manner is input to the limiter 7.

The limiter 7 is formed of a diode circuit. When the disturbance signal d1 contains a negative component, the limiter 7 removes the negative component and outputs it as a disturbance signal d2. That is, when the response of the output signal P1 of the simulation circuit PLm (s) to the pressure signal P is delayed, the disturbance component d1 is calculated as shown in FIG.
As shown in (b), the polarity changes from negative to positive. When the disturbance signal d1 has a negative polarity, the limiter 7 cuts off this component and feeds it back to the pressure manipulated variable.
This makes it possible to configure the first half of the transient response characteristic only with the flow signal. Therefore, even when the phase of the pressure signal P is delayed by the low-frequency cutoff filter 3, the influence on the waveform of the pseudo-pressure differential signal P2, which is the feedback amount to the pressure control amount, can be minimized. FIG. 3 shows, as an example, a transition diagram of a pseudo-pressure differential signal P2 generated by removing a negative component when the disturbance signal d1 has a negative component.

The pseudo disturbance signal d2 output from the limiter 7 is subtracted from the flow signal Q from the actual flow detector (not shown), and the output difference signal is input to the simulation circuit PLm (s), ie, the pseudo signal. It becomes the pressure differential signal P2. Then, the pseudo pressure differential signal P2 is fed back to the pressure operation amount Pu.

As described above, the control section of the variable displacement pump according to the present embodiment is provided with the simulation circuit PLm (s), and simulates the output signal P1 of the simulation circuit and the pressure signal P from the actual pressure detector. Since the disturbance signals d1 and d2 are generated and the pseudo pressure differential signal P2 is generated and fed back to the pressure manipulated variable Pu, the discharge flow rate becomes a disturbance and affects the pressure control system. Can be avoided and stability can be improved.

[0023]

As described above, the present invention provides a simulation circuit having a simulated load characteristic of a pressure control system, and a disturbance signal generation circuit for generating a disturbance signal by taking a difference between an output of the simulation circuit and an output of a filter. Means, and input means for taking the difference between the output signal of the actual flow rate detector and the output of the limiter, and inputting this output difference signal to the simulation circuit, and subtracting the output difference signal from the pressure control amount. Since the pressure control system is feedback-controlled by adding the pressure control system, it is possible to prevent the discharge flow rate of the hydraulic oil from disturbing the pressure control system and to improve the stability.

[Brief description of the drawings]

FIG. 1 is a control block diagram of a variable displacement pump control unit according to the present embodiment.

FIG. 2 is a state transition diagram of a pressure signal P and an output signal P1 of a simulation circuit when a flow rate disturbance exists in a variable displacement pump control unit according to the present embodiment. FIG. 2A is a state transition diagram of the pressure signal P and the output signal P1 of the simulation circuit,
FIG. 2B is a state transition diagram of the disturbance signal d1 generated from the difference between the pressure signal P and the output signal P1.

FIG. 3 is a state transition diagram of a flow rate signal, a pseudo disturbance signal, and a pseudo pressure differential signal in the variable displacement pump control unit according to the embodiment. FIG. 3A is a state transition diagram of the flow signal and the pseudo disturbance signal, and FIG. 3B is a state transition diagram of the pseudo pressure differential signal.

[Explanation of symbols]

 1: Swash plate control loop (flow control loop) 3: Low-pass cutoff filter 5: Disturbance signal generator 7: Limiter 9: Output difference signal input unit Pu: Pressure manipulated variable Q: Flow signal P (s): Variable displacement type Pump PL (s): actual load PLm (s): simulation circuit P: pressure signal P1: output signal of simulation circuit P2: pseudo pressure differential signal d1, d2: pseudo disturbance signal

Claims (2)

[Claims] 1. A variable displacement pump having control means for electrically controlling a discharge pressure and a discharge flow rate of hydraulic oil by a proportional solenoid valve in a closed loop, wherein the control means has a simulated load characteristic of a pressure control system. A filter that generates a signal obtained by removing a high-frequency noise component from an output signal of the actual pressure detector; a disturbance signal generating unit that generates a disturbance signal by taking a difference between an output of the simulation circuit and an output of the filter; A limiter for saturating the negative polarity component of the signal to a constant value, and input means for taking the difference between the output signal of the actual flow rate detector and the output of the limiter, and inputting the output difference signal to the simulation circuit. A variable displacement pump, wherein the output difference signal is added as a subtraction signal to a pressure control amount. 2. The variable displacement pump according to claim 1, wherein the simulation circuit comprises a circuit including an integral element.