JP3192054B2 - Tilt angle control device for hydraulic pump - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tilt angle control device for a variable displacement hydraulic pump, and more particularly to a control gain that is changed based on a physical quantity correlated with the viscosity of hydraulic oil to improve control accuracy. The present invention relates to a tilt angle control device for a hydraulic pump.

[0002]

2. Description of the Related Art The viscosity of hydraulic oil varies greatly with temperature, and is high at low temperatures and low at high temperatures. When the hydraulic oil has high viscosity, the sliding resistance of the hydraulic pump increases, so if a large amount of hydraulic oil is sucked into or discharged from the pump, cavitation occurs in the hydraulic pump, which adversely affects the life of the hydraulic pump. Become. Therefore, the viscosity of the hydraulic oil is detected, and when the viscosity is high, the tilt angle of the pump is suppressed, and the flow rate and flow rate of the hydraulic oil sucked and discharged to the hydraulic pump are suppressed to prevent cavitation from occurring in the pump. A hydraulic circuit is disclosed in JP-A-53-78402. In this hydraulic circuit, the viscosity μ of the hydraulic oil is obtained from the following formula obtained from the relationship shown in FIG.

Μ = K · P2 / √ (P1-P2)
(1) A change in the viscosity μ of the hydraulic oil is detected as a change in the pressure, and FIG.
The circuit shown in FIG. 1 is configured to suppress the pump tilt angle according to the viscosity μ of the hydraulic oil. Note that K
Is a collection of constants such as gravitational acceleration and flow coefficient.

In the circuit, when the temperature is low, the pressure P2 between the orifice 68 and the choke 69 of the viscosity detecting circuit 73
When the directional control valve 71 overcomes the spring 70 and is switched to the position b by the pressure P2, the left chamber of the cylinder 62 that changes the tilt angle of the main pump 60 communicates with the oil tank, The piston 63 is moved to the left by the spring 65 incorporated in the right chamber, the tilt angle of the main pump 60 is reduced, and the discharge flow rate is reduced. At this time, since the pressure oil from the direction switching valve 64 that determines the tilt angle of the main pump 60 based on the operation amount of the operator is blocked by the direction switching valve 71, the viscosity of the working oil is higher than a predetermined value. During this time, the main pump 60 is operated at a small tilt angle regardless of the position of the direction switching valve 64, so that the flow rate and the flow velocity of the hydraulic oil sucked and discharged by the main pump 60 are also reduced, and cavitation is generated. Is prevented.

When the oil temperature rises and the viscosity μ of the hydraulic oil decreases, the pressure P2 also decreases, and the directional control valve 71 is in the state shown in the figure. It is controlled accordingly.

FIG. 5 shows an example of a hydraulic circuit diagram of a hydraulic pump control system of a hydraulic shovel equipped with a variable displacement hydraulic pump, and FIG. 6 is a block diagram showing an example of tilt angle control. In FIG. 5, an actuator 26 is provided between a variable displacement hydraulic pump 1 (hereinafter, referred to as a pump 1) driven by a prime mover such as an engine and an actuator 26 driven by pressure oil discharged from the pump 1. A direction switching valve 25 for controlling the driving of the actuator by controlling the direction and flow rate of the pressure oil supplied to the valve is provided. Pressure) is output, the switching operation is arbitrarily performed. The pump 1 is provided with a regulator 2 for changing the tilt angle and a tilt angle detector 5 for detecting the tilt angle. The tilt angle of the pump 1 is determined by the control device 4 based on a pilot pressure detector 21 for detecting a pilot pressure output from the operating device 24 and a pressure signal of a discharge pressure detector 22 for detecting a discharge pressure of the pump 1. Controlled. In the drawing, reference numeral 3 denotes a control object including the variable displacement hydraulic pump 1 and the regulator 2.

Next, the contents of the control of the tilt angle by the control device 4 will be described with reference to the block diagram of FIG. The target tilt angle of the pump 1 is calculated by the target tilt angle calculating device 6 based on the pilot pressure according to the operation amount of the operating device 24 and the discharge pressure of the pump 1. The target tilt angle calculated here is a pump tilt angle determined by positive control (so-called positive control) that increases the pump tilt angle in accordance with the operation amount of the operating device 24, and the discharge pressure of the pump 1 increases. In this case, a small value is selected from the pump tilt angles determined by the control for suppressing the pump tilt angle (so-called total horsepower control), and that value is set as the target tilt angle. The difference between the target tilt angle calculated by the target tilt angle calculating device 6 and the actual tilt angle detected by the tilt angle detector 5 is calculated by the difference device 7. Then, the deviation in the steady state is eliminated by integrating this deviation in the steady state deviation compensator 8, and the value is input to the stabilization compensator 13. The stabilizing compensator 13 is, for example, a PI compensator. The stabilizing compensator 13 converts the value integrated by the steady-state deviation compensator 8 into a signal of a command value that changes the dynamic characteristic of the control of the pump tilt angle, and outputs the signal to the regulator 2. Then, control is performed so that the tilt angle of the pump approaches the target value.

[0007]

The viscosity of the hydraulic oil flowing through the variable displacement hydraulic pump changes greatly depending on the temperature. The viscosity decreases as the temperature increases, and the viscosity increases as the temperature decreases. When the viscosity of the hydraulic oil is low, the response of the pump tilt angle control system is good because the viscosity resistance of the hydraulic oil flowing through the pump tilt angle moving mechanism is small, and the control gain of the pump is relatively low in this state. There is no problem even if it is set.

On the other hand, when the temperature of the hydraulic oil in a cold region or winter becomes 0 ° C. or less, the hydraulic oil becomes highly viscous, and the viscous resistance of the hydraulic oil increases, so that the operation mechanism of the moving mechanism of the pump tilt angle is operated. The movement speed of the tilt angle becomes slower because the oil is hardly removed. Therefore, there is a possibility that the pump tilt angle cannot be instantaneously changed with respect to the above-described command value. In this case, it is necessary to increase the control gain to improve the responsiveness. However, if the control gain is set high in accordance with the state where the hydraulic oil temperature is low and the viscosity is high, when the hydraulic oil temperature rises and the viscosity decreases, the control gain becomes too high with respect to the viscosity of the hydraulic oil. Then, hunting occurs in the pump, and the actuator driven by the discharge pressure oil of the pump becomes vibratory.
Conversely, if the control gain is set to a low value in accordance with the low viscosity of the hydraulic oil, the shift of the pump tilt angle may be reduced in the winter and cold regions when the temperature of the hydraulic oil is low and the viscosity is high. The response becomes poor, and the movement of the actuator becomes slow. As described above, the dynamic characteristics in the tilt angle control of the hydraulic pump greatly changes depending on the viscosity of the hydraulic oil.

The hydraulic circuit disclosed in Japanese Patent Application Laid-Open No. 53-78402 detects the viscosity of hydraulic oil as a change in pressure in the hydraulic circuit by a viscosity detecting circuit using an orifice, a choke, or the like. When the viscosity is higher than the preset viscosity, the tilt angle of the pump is suppressed, the flow rate and flow rate of the hydraulic oil sucked and discharged by the pump are suppressed, and cavitation is prevented from being generated inside the pump. is there. However, this hydraulic circuit only controls the change of the tilt angle itself according to the viscosity, and improves the responsiveness and hunting performance when controlling the tilt angle to the target value regardless of the viscosity. I have not been able to.

An object of the present invention is to suppress a change in dynamic characteristics of a hydraulic pump irrespective of a change in viscosity of a hydraulic oil, and change the viscosity so that the movement of an actuator driven by the discharge oil of the pump becomes oscillating. An object of the present invention is to provide a tilt angle control device for a hydraulic pump that prevents sluggishness.

[0011]

The present invention will be described with reference to FIGS. 1 and 2 showing an embodiment. The present invention relates to a variable displacement hydraulic pump 1 and a variable displacement hydraulic pump 1 according to the present invention.
Angle changing means 2 for changing the tilt angle of the nozzle and adjusting the discharge flow rate
A tilt angle detector 5 for detecting an actual tilt angle of the variable displacement hydraulic pump 1, a target tilt angle calculating means 6 for calculating a target tilt angle of the variable displacement hydraulic pump 1, A difference unit 7 for calculating a deviation between the target tilt angle calculated by the target tilt angle calculation means 6 and an actual tilt angle detected by the tilt angle detector 5; A stabilizing compensator (20, 20) that outputs a command value for controlling the tilt angle changing means 2 to the target value based on the control gain and the control gain.
51) is applied to a tilt angle control device for a hydraulic pump having: According to the first aspect of the present invention, as shown in FIG. 1, a physical quantity detecting means (23) for detecting a physical quantity correlated with the viscosity of the pressure oil supplied to the variable displacement hydraulic pump 1.
The above-described object is achieved by providing a gain changing means for changing the gain based on the physical quantity detected by the physical quantity detecting means (23). The invention of claim 2 provides a steady-state deviation compensator 8 for integrating the deviation.
The stabilization compensator 20 includes a proportional gain setter 14 and an integral gain setter 15 that respectively output a control gain according to the physical quantity, and an output value from the steady-state deviation compensator 8 and a proportional gain setter. A first multiplier 16 for multiplying the output value output from the output unit 14, a second multiplier 17 for multiplying the output value from the steady-state deviation compensator 8 and the output value from the integral gain setting unit 15, , An integrator 18 for integrating the output value from the second multiplier 17, and the output value from the integrator 18 and the output value from the first multiplier 16 to add the tilt angle changing means 2 And a PI control system having an adder 19 that outputs the command value. Claim 3
As shown in FIG. 2, the invention comprises a steady-state deviation compensator 8 for integrating the deviation, wherein the stabilization compensator 51 includes a first gain setting unit 41 for outputting a control gain according to the physical quantity. A multiplier 40 for multiplying the output value of the first gain setting device 41 by the output value of the steady-state deviation compensator 8; and the tilt based on a command value output to the tilt angle changing means 2. A state observer for estimating a state quantity of the angle changing means 2 and an output from the state observer based on an output value from the state observer and an actual tilt angle detected by the tilt angle detector 5. State observer correction unit (35, 36, 4)
5, 46, 47) and a second gain setter (42, 43) that outputs a gain that corrects the correction state quantity output from the state observer correction unit and that is determined based on the physical quantity. ) And a state feedback unit (37, 38, 42, 43, 43) that corrects the state quantity based on the gain and outputs the correction value as a feedback signal.
49), and a state feedback control system having a differentiator 50 for differentiating the output value of the multiplier 40 and the feedback signal output from the state feedback unit. According to a fourth aspect of the present invention, the gain is set higher as the viscosity of the hydraulic oil is higher based on the physical quantity. According to a fifth aspect of the present invention, the physical quantity detecting means is a hydraulic oil temperature detector 23 for detecting a physical quantity correlated with the viscosity of the hydraulic oil as a temperature of the hydraulic oil.

[0012]

According to the present invention, the target tilt angle of the hydraulic pump 1 is calculated and output by the target tilt angle calculating means 6. The difference between the output target tilt angle and the actual tilt angle of the pump detected by the tilt angle detector 5 is calculated by the differentiator 7. The calculated deviation is input to the stabilizing compensator 20, where the control gain of the tilt angle changing means 2 is changed based on the physical quantity from the physical quantity detecting means (23) and the deviation. According to the second aspect of the present invention, the proportional gain setter provided in the stabilization compensator 20 composed of the PI control system,
The integral gain setter 15 outputs a control gain corresponding to a physical quantity correlated with a viscosity such as a working oil temperature detected by the physical quantity detecting means (23). The output control gain is multiplied by the output value output from the steady-state deviation compensator 8 by the first and second multipliers 16 and 17, respectively.
The value multiplied by the second multiplier 17 is integrated by the integrator 18, added to the output value of the first multiplier 16 by the adder 19, and output as the command value of the tilt angle changing means 2. You. According to the third aspect of the present invention, the state observer provided in the stabilization compensator 51 uses the state value (position of the tilt angle) of the variable displacement hydraulic pump 1 based on the command value output to the tilt angle changing means 2. , The moving speed of the tilt angle, etc.). The state observer correction unit corrects the state quantity estimated by the state observer based on the state quantity output from the state observer and the actual tilt angle detected by the tilt angle detector 5. I do. The second gain setting device (42, 43) outputs a gain according to the detected physical quantity. The state feedback unit (49) further corrects the correction state amount based on the gain and outputs the corrected state amount as a feedback signal.
The output value of the steady-state deviation compensator 8 and the first gain setter 4
Multiplier 4 for multiplying by the control gain output from 1
The difference between the output value of 0 and the feedback signal is obtained by the differentiator 50 and output to the tilt angle changing means 2 as a command value. According to the fourth aspect of the present invention, the gain is set higher as the physical quantity indicates a higher viscosity of the hydraulic oil. According to the invention of claim 5, the hydraulic oil temperature detector 2
3 detects a hydraulic oil temperature correlated with the viscosity of the hydraulic oil, and determines the control gain from the temperature of the hydraulic oil.

In the means and means for solving the above-mentioned problems which explain the constitution of the present invention, in order to make the present invention easy to understand, the drawings of the embodiments are used. However, the present invention is not limited to this.

[0014]

【Example】

First Embodiment FIG. 1 is a block diagram of a control system in a tilt angle control device for a hydraulic pump according to a first embodiment of the present invention. The same components as those shown in FIGS. 5 and 6 are denoted by the same reference numerals, and detailed description thereof will be omitted.

In this embodiment, the control device 4 shown in FIG.
The control device 30 includes a target tilt angle of the pump 1 based on the pilot signal and the discharge pressure signal output from the pilot pressure detector 21 and the discharge pressure detector 22, respectively. And a differentiator for calculating the deviation between the target tilt angle output from the target tilt angle calculator 6 and the actual tilt angle detected from the tilt angle detector 5. 7, a steady-state error compensator 8 that integrates the error output from the differentiator 7, and a stabilizing compensator 20 that calculates a command value to the control target 3 based on the output value of the steady-state error compensator 8. .

In this embodiment, the stabilizing compensator 20 is a PI
A proportional gain table 14 and an integral gain table 15 which are constituted by a control system and output a control gain in accordance with a hydraulic oil temperature detected by a hydraulic oil temperature sensor 23; an output value of the steady-state deviation compensator 8; 14, and multipliers 16 and 17 for multiplying the control gains output from the integration gain table 15, respectively, an integrator 18 for integrating the output value of the multiplier 17, and an output value of the multiplier 16 and an output of the integrator 18. And an adder 19 for adding a value and outputting a command value of the control target 3.

In the first embodiment configured as described above, in the target tilt angle calculating device 6, the tilt angle obtained in proportion to the pilot pressure according to the operation amount of the operating device 24, and the pump 1 A smaller value is selected from the pump tilt angles determined in inverse proportion to the discharge pressure of the pump, and that value is output as the target tilt angle. The difference between the target tilt angle calculated by the target tilt angle calculation device 6 and the actual tilt angle detected by the tilt angle detector 5 is obtained by a differentiator 7, and the difference is a deviation in a steady state. Are integrated by the steady-state error compensator 8 in order to eliminate.
The output value of the steady state deviation compensator 8 is input to the stabilization compensator 20. In the stabilizing compensator 20, the control gain according to the detection value of the hydraulic oil temperature sensor 23 is stored in the proportional gain table 14,
The control gain and the output value of the steady-state deviation compensator 8 are output in parallel from the integration gain table 15, and are multiplied in parallel by multipliers 16 and 17, respectively.

The control gain is set low when the temperature of the hydraulic oil is high (the viscosity is low), and is set high when the temperature of the hydraulic oil is low (the viscosity is high). This value is set in advance based on empirical values and experimental values in consideration of the response of the pump tilt angle control based on the viscosity (movement speed of the pump tilt angle, hunting, etc.).

The output value of the multiplier 17 is integrated by the integrator 18. Then, the output value of the integrator 18 and the output value of the multiplier 16 are added by the adder 19 and output as a command value to the control target 3.

In this embodiment, the viscosity of the hydraulic oil is detected based on the temperature. When the temperature is high, the control gain is lowered, and when the temperature is low, the control gain is raised. As a result, it is possible to prevent the pump from hunting due to a change in viscosity due to a change in the temperature of the hydraulic oil, or from having a slow response.

Second Embodiment Next, FIG. 2 shows a second embodiment. The same components as those in the first embodiment are denoted by the same reference numerals, and differences will be mainly described. This embodiment is different from the control device 30 according to the first embodiment.
Instead of the stabilizing compensator 20 of the PI control system, a control device 44 having a built-in stabilizing compensator 51 of a state feedback control system is used. The control device 44 calculates a target tilt angle of the pump and outputs the calculated target tilt angle in the same manner as in the first embodiment, and the target tilt angle and tilt angle detector 5.
, Which calculates the deviation from the actual tilt angle of the pump 1 detected by the above, a steady-state deviation compensator 8 which integrates the deviation calculated by the difference unit 7, and control based on the output value of the steady-state deviation compensator 8. And a stabilizing compensator 51 for calculating a command value to the regulator 2 of the target 3.

The above-mentioned stabilizing compensator 51 includes gain setting units 33, 34, 39, integrators 31, 32, and an adder 4
A state observer (hereinafter, referred to as an observer) including the gain observers 7 and 48, a state observer correction unit including the gain setting units 35 and 36, the difference unit 45, and the adders 46 and 47;
A state feedback unit composed of multipliers 37 and 38 and an adder 49, a first gain table 41 for setting a control gain Ki of an output value of the steady-state deviation compensator 8, an output value of the steady-state deviation compensator 8, Multiplier 40 for multiplying by gain Ki set by first gain table 41
And second and third gain tables 42 and 43 for setting gains K1 and K2 for the output values of the integrators 31 and 32 of the observer, and the difference between the output value of the multiplier 40 and the feedback signal from the state feedback unit. , And outputs a command value to the regulator 2 of the controlled object 3. The second and third gain tables 42 and 43 determine the gain for correcting the state quantity of the pump 1 affected by the temperature (viscosity) of the hydraulic oil. 33, 34, 39, 3
Numerals 5 and 36 are obtained from experimental values and empirical values as design parameters, and are set in advance as values that do not significantly affect the pump control characteristics even if the viscosity of the hydraulic oil changes.

The operation of the second embodiment configured as described above will be described. The observer in the stabilizing compensator 51 outputs the state quantity of the pump 1 (the pump tilt angle based on the command value to the control target 3 output from the differentiator 50 and the gain setting units 33, 34, 39). The position X1 and the moving speed X2) of the pump tilt angle are estimated. Initial values of the position X1 are the minimum tilt position, and X2 is the speed 0. When the control of the pump is started from this state, the initial value X2 of the pump 1 is multiplied by the gain set in the gain setting unit 34, and the initial value X2
1 is multiplied by the gain setting unit 33. These values are added by the adder 48, and a value obtained by multiplying the command value of the pump 1 by the gain set in the gain setting device 39 is added to the added value by the adder 47. By integrating the value calculated by the adder 47 by the integrator 32, the moving speed X2 of the tilt angle of the pump 1 at that time is calculated, and the moving speed X2 is integrated by the integrator 31. By doing so, the position X1 of the pump tilt angle is calculated. These X1 and X2 are estimated state quantities of the pump 1. Here, the gain set by the gain setting units 33 and 34 is a feedback gain, and has a role of preventing the output values of the integrators 31 and 32 from diverging.

Here, the position X1 of the pump tilt angle is input to a differentiator 45, and a deviation from the actual tilt angle which is an output value of the tilt angle detector 5 is calculated, and a gain is set for each of the deviations. By multiplying the gains set in the units 35 and 36 in parallel and inputting them to the adders 46 and 47, the error between the estimated value and the actual value of the state quantity of the pump 1 that changes with time is corrected. This is the operation of the state observer correction unit.

The state variables X2 and X1 estimated by the observer are added to the second and third gain tables 42 and 43.
Are multiplied by multipliers 38 and 37, respectively, and the state quantities are corrected based on the operating oil temperature. These values are added by an adder 49 and fed back to a differentiator 50. This is the operation of the state feedback unit.

The output value of the steady-state deviation compensator 8 and a first gain table set to lower the control gain when the temperature of the hydraulic oil is high and to increase the control gain when the temperature of the hydraulic oil is low. The output value of 41 is the multiplier 4
The difference value is multiplied by 0, and the difference between the value and the output value from the above-described state feedback unit is obtained by the differentiator 50, whereby the command value for the control target 3 is calculated and output to the control target 3.

In this embodiment, a change in the internal state quantity of the pump 1 due to a change in the temperature of the hydraulic oil is estimated, and a command value to be output to the control target 3 can be determined based on the value. The controllability is further improved as compared with the embodiment. Although the observer in this embodiment is a secondary system having two integrators 31 and 32, the number of integrators can be increased in accordance with the operation characteristics of the controlled object. If the observer gain, depending on the number of its integrators,
The gain in the state observer correction unit, the adder, the gain table in the state feedback unit, and the like may be added according to this embodiment.

The proportional gain table 14, the integral gain table 15, the first gain table 41, the second gain table 42, and the third gain table 43 described in each of the above-described embodiments correspond to the viscosity of the hydraulic oil due to a temperature change. It is set in advance in consideration of the response of the control based on the change. Although the viscosity is estimated by detecting the hydraulic oil temperature, the viscosity itself of the hydraulic oil may be measured, or other physical quantities correlated with the viscosity, such as the engine cooling water temperature and the ambient temperature, may be detected. In the above description, the variable displacement hydraulic pump used for the open circuit is described as an example. However, the present invention can be applied to the tilt angle control of the variable displacement hydraulic pump used for the closed circuit.

In the above embodiment, the regulator 2 serves as the tilt angle changing means, the target tilt angle calculating device 6 serves as the target tilt angle calculating means, the hydraulic oil temperature sensor 23 serves as the physical quantity detecting means, and the proportional gain table 14 , Integral gain table 15
And the multipliers 16 and 17 are a gain changing means, the proportional gain table 14 is a proportional gain setter, the integral gain table 15 is an integral gain setter, the first gain table 41 is a first gain setter, Second and third gain tables 42 and 43 constitute a second gain setting device, respectively.

[0030]

According to the present invention, the gain in the tilt angle control of the variable displacement hydraulic pump is made variable based on the physical quantity (for example, the temperature of the hydraulic oil) correlated with the viscosity of the hydraulic oil.
The fluctuation of the dynamic characteristics of the pump tilt angle can be suppressed regardless of the viscosity, and the change in the viscosity can prevent the actuator driven by the variable displacement hydraulic pump from vibrating or slowing down. . If the stabilizing compensator is a state observer, a state observer correction unit, and state feedback control having a state feedback unit,
The state quantity of the variable displacement hydraulic pump can be estimated, and the pump tilt angle can be controlled based on the value, and higher controllability can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram of a control system in a first embodiment of a tilt angle control device for a hydraulic pump according to the present invention.

FIG. 2 is a block diagram of a control system in a second embodiment of the tilt angle control device for a hydraulic pump according to the present invention.

FIG. 3 is a circuit diagram of a conventional tilt angle control device for a hydraulic pump.

FIG. 4 is a circuit diagram of a conventional tilt angle control device for a hydraulic pump.

FIG. 5 is a circuit diagram of the tilt angle control device for the hydraulic pump in FIGS. 1, 2 and 6;

FIG. 6 is a block diagram of a control system in a tilt angle control device for a hydraulic pump according to the related art.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Variable displacement hydraulic pump 2 Regulator 5 Tilt angle detector 6 Target tilt angle calculating device 7 Difference device 8 Steady-state deviation compensator 14 Proportional gain table 15 Integral gain table 16 Multiplier 17 Multiplier 20 Stabilizing compensator 41 1 gain table 42 second gain table 43 third gain table 50 differentiator 51 stabilizing compensator

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁷ , DB name) F04B 49/00 341 F04B 1/20

Claims (5)

(57) [Claims] 1. A variable displacement hydraulic pump, displacement angle changing means for changing a displacement angle of the variable displacement hydraulic pump and adjusting a discharge flow rate, and detecting an actual displacement angle of the variable displacement hydraulic pump. Tilt angle detector, target tilt angle calculating means for calculating a target tilt angle of the variable displacement hydraulic pump, and a target tilt angle and tilt angle detection calculated by the target tilt angle calculating means. And a command value for controlling the tilt angle changing means to the target value based on the difference calculated by the differentiator and the control gain. A tilt angle control device for a hydraulic pump, comprising: a stabilizing compensator that outputs a physical quantity; a physical quantity detecting unit that detects a physical quantity correlated with a viscosity of pressure oil supplied to the variable displacement hydraulic pump; Based on the physical quantity detected by the means And a gain changing means for changing the gain. 2. A stabilization compensator for integrating the deviation, wherein the stabilization compensator outputs a control gain corresponding to the physical quantity and a proportional gain setter and an integral gain setter, respectively, A first multiplier for multiplying the output value from the multiplier and the output value output from the proportional gain setting device, and multiplying the output value from the steady-state deviation compensator by the output value from the integration gain setting device. A second multiplier, an integrator for integrating an output value from the second multiplier, and an output value from the integrator and an output value from the first multiplier to add the tilt value. The tilt angle control device for a hydraulic pump according to claim 1, wherein the tilt angle control device is a PI control system having a PI control system having an adder that outputs a command value of the turning angle changing means. 3. A stabilizing compensator that integrates the deviation, wherein the stabilizing compensator outputs a first gain setter that outputs a control gain corresponding to the physical quantity; A multiplier that multiplies the output value by the output value of the steady-state deviation compensator; and a state observer that estimates a state quantity of the tilt angle changing unit based on a command value output to the tilt angle changing unit. A state observer correction unit that corrects a signal output from the state observer based on an output value from the state observer and an actual tilt angle that is a detection value of the tilt angle detector,
A second gain setting device that outputs a gain determined based on the physical quantity, the gain being a gain for correcting the correction state quantity output from the state observer correction unit, and correcting the state quantity based on the gain. And a state feedback control system having a state feedback unit that outputs the correction value as a feedback signal, and a difference unit that differentiates an output value of the multiplier from a feedback signal output from the state feedback unit. The tilt angle control device for a hydraulic pump according to claim 1, wherein: 4. The tilt angle control device for a hydraulic pump according to claim 1, wherein the gain is set higher as the viscosity of the hydraulic oil is higher based on the physical quantity. 5. The hydraulic oil temperature detector according to claim 1, wherein the physical quantity detecting means is a hydraulic oil temperature detector that detects a physical quantity correlated with a viscosity of the hydraulic oil as a temperature of the hydraulic oil. 3. The tilt angle control device for a hydraulic pump according to claim 1.