JPH02161185A - Controller for variable capacity type pump - Google Patents

Abstract

PURPOSE:To properly control a variable capacity type pump with high precision by controlling the tilt angle of a discharge quantity varying control element of the variable capacity type pump on the basis of the difference of the discharge quantity and the difference of the discharge pressure of the variable capacity type pump. CONSTITUTION:The difference between the detection value of the discharge quantity and an aimed value is obtained by the first difference calculating means 11 on the basis of each output of a discharge quantity detecting means 5 of a variable capacity type pump 1 and an aimed discharge quantity setting means 7. Similarly, the difference between the detection value of the discharge pressure and an aimed value is calculated by the second difference calculating means 12 on the basis of the outputs of the discharge pressure detecting means 6 of the variable capacity type pump 1 and an aimed discharge pressure setting means 8. Then, an electricity/hydraulic pressure control means 15 is controlled by an electric control means 14 on the basis of the outputs of the both difference calculating means 11 and 12, and the tilt angle of a discharge quantity varying control element 1a of the variable capacity type pump 1 is adjusted. Therefore, the discharge quantity and the discharge pressure of the variable capacity type pump 1 are controlled to each proper value.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an improvement of a control device that controls the discharge amount of a variable displacement pump using an electric feedback method. This invention relates to a device that can also perform discharge pressure control.

(Prior art) In general, when feedback controlling the discharge amount of a variable displacement pump to a target value, if the feedback method is an electric type, it has higher accuracy and higher accuracy than a mechanical or hydraulic type. In response, (7) is also preferable because the discharge amount can be feedback-controlled to the target value easily and with low power consumption.

Therefore, conventionally, as a discharge amount control device for a variable displacement pump using an electric feedback method, for example,
As disclosed in Japanese Patent No. 180084, a discharge amount detection means such as a potentiometer that detects the discharge amount based on the inclination angle of the variable discharge amount control element of a variable displacement pump, and a target inclination angle of the variable discharge amount control element. a target discharge rate setting means for setting a target discharge rate; and a discharge rate variable control element of the variable displacement pump that receives the outputs of the discharge rate detection means and the target discharge rate setting means so that the actual discharge rate becomes the target discharge rate. It is known that the actual discharge amount is precisely controlled to the target discharge amount by an electric feedback system of the actual discharge amount from the discharge amount detection means.

(Problem to be Solved by the Invention) By the way, in a practical hydraulic circuit, such as a hydraulic circuit of an injection molding machine, in which it is necessary to variably control both the operating speed of the load and the supply pressure according to the load condition, the conventional hydraulic circuit described above cannot be used. In addition to controlling the discharge amount of a variable displacement pump such as the conventional technique, it is desired to control the discharge pressure thereof.

However, in this case, since the current direction of discharge amount control and discharge pressure control is required, it changes over time depending on the load condition. and it is necessary to judge over time.
For this reason, it is predicted that it is quite difficult to appropriately electrically feedback control both the discharge amount and the discharge pressure. For example, when simply adding the deviation of the actual discharge rate to the target discharge rate and the deviation of the actual discharge pressure to the target discharge pressure, and performing slope control on the variable displacement control element of the variable displacement pump based on the addition result, In this case, the discharge amount control and the discharge pressure control may interfere with each other, and both the discharge amount and the discharge pressure are not properly controlled.

Therefore, as shown in FIG.
In the discharge pressure/discharge rate characteristic diagram in which the characteristic curve of (0) and the characteristic curve of the target discharge pressure (P) are drawn, only three of the four areas divided by broken lines, that is, only the discharge rate reduction control is controlled. There is a region (■) that requires control, a region (■) that only requires control to reduce the discharge pressure, and a area (■ that requires control to reduce both).
Actual discharge ff1 (target discharge jA of Qfl)
(0) deviation (Qf-0) and actual discharge pressure (P'
), we examined the relationship between the deviation (Pf - P) and the target discharge pressure CP), and found that in (1) region
In region 2, Qf'-Q<01pr-P≧.

(3) In region ■, Qf'-Q≧0, Pi'-P≧0
Therefore, when simply adding the discharge amount deviation and the discharge pressure deviation, the positive value of the discharge amount deviation (Qf-0
), the negative value of the discharge pressure deviation (
Pf'-P) interferes with the discharge pressure deviation (Pf'-P), and in region (2), the negative discharge amount deviation (Qf-0) interferes with the discharge pressure reduction control caused by the positive discharge pressure deviation (PI'-P). In addition, by focusing on the fact that there is no mutual interference in area (3) and converting this into "Om" when the deviation is a negative value, it is possible to appropriately control the discharge amount and discharge pressure according to the load condition. I found it.

In this case, in region (2) excluding the above regions (2), (2), and (2), both the discharge amount deviation (Qf-0) and the discharge pressure deviation (Pr-P) are negative values, so the deviation is expressed as a negative value as described above. “0”
If this is converted to , an inconvenience arises in that, although it is necessary to control the increase in the discharge amount and the discharge pressure, it becomes impossible to control the increase. The present invention has also focused on this point, and in particular, in a type of variable displacement pump in which the discharge amount variable control element is always biased in the direction of the maximum inclination angle, the discharge amount and the discharge amount are increased in the region (3) as described above. Even if both pressure deviations are converted to 0°, the variable discharge rate control element is urged in the direction of the maximum inclination angle by its biasing force, increasing the discharge rate and the discharge pressure. There is no need to specifically convert both the deviation of the discharge amount and the discharge pressure in the area ■, and if the deviation is converted to "0" when the deviation is a negative value in all the areas ■~■, all the areas ■~ It has been found that in (2) both the discharge amount and the discharge pressure can be appropriately controlled without interfering with each other.

In addition, as another solution other than the above solution, for example, the calculation formula for the deviation in the above regions ■ to ■ may be different, and in the region ■, only the discharge amount deviation (Qf -0) is calculated, and in the region ■, It is conceivable to calculate only the discharge pressure deviation CPr - P), and calculate the total value of the discharge amount deviation and discharge pressure deviation + (Qf - 0) + (Pr - P)) in the area ■ and area ■. In this case, the calculation result of the deviation is discontinuous before and after each characteristic curve of the discharge Et (0) and the discharge pressure (P), so the control stability is poor and it is difficult to adopt this method.

In view of the above, an object of the present invention is to provide a control device that performs electrical feedback control of a variable displacement pump by determining the sign of the deviation between the actual discharge amount and the target discharge amount, and the deviation between the actual discharge pressure and the target discharge pressure. When the value is negative, it is converted to "0", and the variable displacement pump's discharge rate variable control element is energized in the direction of the maximum inclination angle, thereby controlling the discharge rate necessary for the current load state. Alternatively, by automatically selecting the discharge pressure control over time and performing this appropriately, it is possible to increase the discharge volume and discharge pressure when both the discharge volume deviation and the discharge pressure deviation are converted to "0" value. Another object of the present invention is to enable electric feedback control of both the discharge amount and the discharge pressure of a variable displacement pump to respective target values.

(Means for Solving the Problems) In order to achieve the above object, the solving means of the present invention provides a swingable discharge amount variable control element (1a ) variable displacement pump (1
), an electric/hydraulic pressure control means (15) for adjusting the inclination angle of the variable discharge amount control element (1a); and a discharge amount detection means (15) for detecting the discharge amount (Qf >) of the variable displacement pump (1). 5) and the discharge pressure (P
A discharge pressure detection means (6) for detecting the target discharge pressure Q(0), a target discharge amount setting means (7) for setting the target discharge Q(0), and a target discharge pressure setting means (8) for setting the target discharge pressure CP).
). Then, upon receiving the outputs of the discharge amount detection means (5) and the target discharge amount setting means (7), the target discharge amount m
(0) Actual discharge amount (Qf) (7) Deviation (Q
When f−0) is a positive value (Ql” −Q≧0), the deviation (Qf−0) is output as is, and a negative value (Qf−Q<0)
When , the first deviation calculation means (11) converts the deviation <Qr-0) to "0" and outputs it, and receives the outputs of the discharge pressure detection means (6) and the target discharge pressure setting means (8). , when the deviation (Pf-P) of the actual discharge pressure (Pfl) from the target discharge pressure (P) is a positive value (Pr -P≧0), the deviation (Pf-P) is output as is, and a negative value (PI'-
Pro), the second deviation calculation means (12) converts the deviation (Pf-P) into 40" and outputs it, and receives the outputs of the above-mentioned both deviation calculation means (11) and (12), and calculates both deviations. Based on this, the electric control means (14, 30) controls the input current to the electric/hydraulic control means (15).

(Function) As described above, in the present invention, the deviation (Qf-0), CPr-
P) is a positive value, the discharge amount variable control element (1) of the variable displacement pump (1) is controlled by the electric/hydraulic control means (15).
The inclination angle of a) is controlled.

That is, when only the discharge amount deviation is a negative value (Qf - Q < 0), this is determined by the first deviation calculation means (11) as "θ
'', the positive discharge pressure deviation cpr-P≧
0) is selected and is properly performed, while only the discharge pressure deviation has a negative value (Pf-P<0
), this is converted to "0" by the second deviation calculation means (12), so that a positive discharge amount deviation CQr -
Discharge amount control based on Q≧0) is selected and appropriately performed.

Also, if both deviations are positive values, Qf-Q≧0, P"-P≧0
In this case, both the discharge amount and the discharge pressure are appropriately controlled based on both deviations.

Furthermore, if both deviations are negative values, Qr-Q<01Pr-p<
In the case of o, each individual difference is converted to "0" by the first and second deviation calculation means (11) and (12), respectively, so the electric/hydraulic pressure control means (15) is in a non-control state. Therefore, the variable discharge amount control element (1a) is allowed to be displaced in the direction of the maximum inclination angle by its biasing force, and the inclination angle increases, so both the discharge amount and the discharge pressure increase. Become.

Moreover, although each deviation Qr-Q, Pr-P is converted into a negative value "0" by sign judgment, the addition result (
Since QC-0)+(Pr-P)l;i is continuous in the entire region, good control stability is ensured.

(Example) Hereinafter, an example of the present invention will be described based on the drawings from FIG. 2 onwards.

FIG. 2 shows the overall configuration of a control device for a variable displacement pump according to the present invention, and (A) is a variable displacement pump unit, in which a built-in variable displacement pump (1) has a variable discharge volume. The discharge amount changes depending on the inclination angle of a swingable swash plate (1a) as a control element, and a tank (2) for storing fluid (for example, oil) is connected to the suction side. In addition, on the discharge side, there is a user side pump boat (Pu) for connecting the user's equipment, and the swash plate (1).
a) Self-controlling pump boat (P
l) are connected in parallel with each other.

The variable displacement pump (1) also includes a swash plate (1a).
The discharge amount control section (3) is provided with a discharge amount control section (3) that adjusts the inclination angle of the spring chamber (3b) and the liquid by means of a piston (3a) that swings the swash plate (1a). Pressure chamber (
3C), and the spring chamber (3b) is equipped with a spring (3d) that urges the piston (3a) to the right in the figure to position the swash plate (1a) at the maximum inclination angle position. ing.

Therefore, in the non-control state when no hydraulic pressure is acting on the hydraulic pressure chamber (3c), the spring (3d) urges the piston (3a) to the right in the figure to move the swash plate (1a) to the maximum inclination angle position. On the other hand, during control in which hydraulic pressure acts on the hydraulic pressure chamber (3c), the piston (3a) is moved to the left in the figure against the biasing force of the spring (3d) due to the hydraulic pressure in the hydraulic pressure chamber (3c). By moving the swash plate (1a), the swash plate (1a) is swung in the neutral direction.

In addition, (5) is the swash plate (1) of the variable displacement pump (1).
(a) A discharge rate sensor as a discharge rate detection means that detects the discharge rate (Qf) by the inclination angle; This is a discharge pressure sensor as a discharge pressure detection means for detecting the discharge pressure (Pf') of the variable displacement pump (1). Furthermore, (7) is a target discharge amount setting device as a target discharge amount setting means for setting the target discharge 31 (0) as shown in FIG. 4, and (8) is a target discharge pressure CP) as shown in the same figure. A target discharge pressure setting device as a target discharge pressure setting means for setting the above-mentioned two sensors (5), (6) and two setting devices (7), (8).
Each output is input to a controller (10) for electrical feedback control of the inclination angle of the swash plate (la) of the variable displacement pump (1>).

The controller (10) includes the discharge amount sensor (5).
The actual discharge m (Qf) of the variable displacement pump (1) detected by
) is detected by the first deviation calculation unit (11) as a first deviation calculation means that compares the magnitude of m (0) with the target discharge m (0) of the target discharge amount setter (7), and the discharge pressure sensor (6). a second deviation calculation section (as a second deviation calculation means for processing the actual discharge pressure CPr) of the variable displacement pump (1) compared with the target discharge pressure (P) of the target discharge pressure setting device (8); 12), and the output from the controller (10) is a servo amplifier (14) for voltage-current conversion.
via the swash plate (1a) of the variable displacement pump (1).
It is input to an electro-hydraulic servo valve (15) as an electric/hydraulic pressure control means for swinging control.

The electro-hydraulic servo valve (15) consists of a pressure control pilot valve (16) and a differential pressure valve (17). The pressure control pilot valve (16) displaces the nozzle flapper (18a) to the left in the figure depending on the magnitude of the output current value (positive value) received from the controller (10) via the servo amplifier (14). A torque motor (18) whose amount increases or decreases, and a nozzle flapper (18a) of the torque motor (18).
A pair of fixed orifices (19
a), (19a) and each fixed orifice (19a), (
A hydraulic pressure converter (19) having a first hydraulic chamber (19c) and a second hydraulic chamber (19d) formed with other fixed orifices (19b), (19b) each separated from 19a) by a predetermined pressure. and a first . The second hydraulic chambers (19c) and (19d) include a hydraulic passage (19e) and a communication passage (20) of the hydraulic pressure converter (19), and a hydraulic boat (17f) of the differential pressure valve (17), respectively.
) of the self-control pump boat (Pa ) of the variable displacement pump unit (A) acts on the output current value (positive value) of the controller (10). Accordingly, the nozzle flapper (18a) of the torque motor (18) is displaced to the left in the figure, and the liquid in the first hydraulic pressure chamber (19c) of the hydraulic pressure converter (19) is pressure (Pl) and the second hydraulic pressure chamber (19
A differential pressure (Ps-Pl) corresponding to the output current value from the controller (10) is generated between the hydraulic pressure (Pl) of d).

The differential pressure valve (17) also includes a differential pressure spool (17b) that slides from side to side in the drawing on the inner wall of the internal space (17a), and hydraulic chambers formed on the left and right sides of the differential pressure spool (17b), respectively. (17c) and a spring chamber (17d). A pressure chamber (19c) is communicated with the pressure chamber (19c). On the other hand, the spring chamber (17
d) is equipped with a spring (17e) for a set pressure (Ps) that urges the differential pressure spool (17b) to the left in the figure, and is connected to the hydraulic pressure converter via the communication path (26). (19)
The second hydraulic pressure chamber (19d) is in communication with the second hydraulic pressure chamber (19d). Further, on the inner wall of the internal space (17a), a self-control pump boat (Pg+) of the variable displacement pump unit (A) is provided.
A hydraulic boat (171) that communicates with the
') and the discharge amount control section (
A control boat (17g) that communicates with the hydraulic pressure chamber (3c) of 3) via a communication passage (28), and a tank boat (17h) that communicates with the tank (2) via a tank passage (29).
are open, and the first hydraulic chamber (19c) and second hydraulic chamber (19d) of the pressure control pilot valve (16) are open.
), when the differential pressure (P+ - p, ) is greater than the set pressure (Ps ) of the spring (17e), this differential pressure (P+ - P, 1)
Therefore, the differential pressure spool (17b) is moved to the right in the figure against the set pressure (Ps) of the spring (17e), and the hydraulic boat (17r) is opened to communicate with the control boat (17g). By doing so, hydraulic pressure is applied to the hydraulic pressure chamber (3c) of the discharge rate control section (3) of the variable displacement pump unit (A), and the swash plate (1a) of the variable displacement pump (1) is moved to the neutral side. while the above-mentioned No. 1. Second hydraulic chamber (19c
), (19d) is the pressure difference (PI-Pl) between spring (1
When the pressure is less than the set pressure (Ps) of spring (17e),
With the set pressure (Ps) of e), the differential pressure spool (17b
) to the left in the figure, and hydraulic bow) (17f'
) and close the control boat (17g) tank boat)
(17h), the hydraulic pressure chamber (3c) of the discharge amount control unit (3) is opened to the tank (2), and the swash plate (1a) is swung to the maximum inclination side. It is configured as follows. In addition, in the differential pressure valve (17), (17
1) is an adjustment screw that adjusts the set pressure (Ps) of the spring (17e).

Next, FIG. 3 shows the internal configuration of the controller (10). In the same figure, the first deviation calculation unit (11) calculates the difference CQt- 0) and the output from the subtracter (11a), the deviation (Qf-0) is a positive value (Qf -Q
2:0), the deviation (Qf-0) is output as is to the subsequent stage, and when it is a negative value (Qf-Q<0), the deviation (Qf-0) is output as is.
A deviation conversion circuit (1, 1b) consisting of a limiter etc. that converts f-0) to 0° and outputs it to the subsequent stage, and a gain adjuster (1, 1b) that adjusts the gain of the converted deviation signal from the deviation conversion circuit (1lb). 11c).

Further, the second deviation calculation unit (12) includes a discharge pressure sensor (6
) from the actual discharge pressure (Pr ) and the target discharge pressure setting device (
8) and a subtractor (12a) that calculates the deviation <pr-p> from the target discharge pressure (P), and receives the output from the subtractor (12a), and determines that the deviation (Pf'-P) is a positive value ( Pr-P≧0)
When , the deviation CPr-P) is output as is to the subsequent stage, and when it is a negative value (Pf -Pro), the deviation (Pr-P) is output as is.
A deviation conversion circuit (
12b) and a gain adjuster (12c) that adjusts the gain of the converted deviation signal from the deviation conversion circuit (12b).

Inside the controller (10), first and second deviation calculation units (11) and (12) amplifiers (11c) are provided.
), (12c) adder (30
), the output of the adder (30) is input to the servo amplifier (14), and with this configuration, the outputs of the first and second deviation calculation means (11) and (12) are input to the servo amplifier (14). Based on these two deviations, the above electro-hydraulic servo valve (
15) constitutes an electric control means (14, 30) configured to control the input current to the input current.

Therefore, in the above embodiment, as shown in FIG. (1' 1), the deviation (QC-0) is “
0°, the actual discharge pressure CPr) becomes the target discharge pressure (
In the region of (Pr-F'<0) which is less than the characteristic curve of P), the second deviation calculation unit (12) calculates the deviation (P
) is converted to 0'', and as a result, in the case of area ■ and area ■ in the figure, the output from the controller (10) is related only to the discharge amount deviation (Qf-Q≧0), and ■
Then, the discharge amount deviation CQr-0) is the electric-hydraulic servo valve (
15) The set pressure (P) of the spring (17c) of the differential pressure valve (17)
s), the differential pressure valve (17) opens and the variable displacement pump (1)
The swash plate (1a) swings in the neutral direction, and the discharge amount (Qf)
decreases, while in region ■, the discharge amount deviation (Qf-0)
is less than the above minute flow rate (Δ0), so the differential pressure valve (17
) closes and the swash plate (1a) of the variable displacement 41 type pump (1) closes.
) swings in the direction of the maximum inclination position, the discharge amount (Qf) increases, and the above operation is repeated until the discharge In(Q
) is adjusted to a control flow rate value (Q+Δ0) that is larger than the target discharge amount (0) by the minute flow rate (Δ0).

Ru.

Similarly, the discharge pressure deviation (Pr-
P≧0), so in region ①, the discharge pressure deviation CPr-P≧∆ is greater than the minute pressure (∆P) corresponding to the set pressure (Ps) of the spring (17e) of the differential pressure valve (17).
P) causes the differential pressure valve (17) to open, and the inclination angle of the swash plate (1a) of the variable displacement pump (1) decreases, while
In region ■, the differential pressure valve (17) closes due to the discharge pressure deviation (PI-P<ΔP) that is less than the minute pressure (ΔP), and the inclination angle of the swash plate (1a) increases, so that the discharge The pressure (Pr) is eventually adjusted to a control pressure value (P+ΔP) which is the target discharge pressure (P) plus the above-mentioned minute pressure (ΔP).

In the transient region ■ between the controlled discharge amount (Q+Δ0) characteristic curve and the controlled pressure (P+ΔP) characteristic curve, the discharge j
ltQ difference (Qf-0) and discharge pressure deviation <pj-p>
are both positive values, and the total value of both deviations is output from the controller (10), but vI control positive pressure P+ΔP
) When transitioning to the characteristic curve, the discharge pressure deviation (Pr-P)
Due to the increase in the differential pressure valve (17), the inclination angle of the swash plate (1a) of the variable displacement pump (1) becomes smaller, and the discharge amount (CQr) gradually decreases accordingly.
When the target discharge amount (0) is reached, $I3 control pressure + Δ
P) corresponds to the characteristic curve. On the other hand, the controlled discharge amount (Q+Δ0
) $ At the time of transition to the control curve, the discharge pressure deviation ffi (P
As f-P) decreases, the differential pressure valve (17) tends to close, and the inclination angle of the swash plate (1a) of the variable displacement pump (1) increases, so the discharge amount CQr) increases accordingly. When the set pressure (P) is reached, the controlled discharge m (Q + Δ
0) Matches the characteristic curve.

In region ■, the discharge amount (-difference (Q['-0)) and discharge pressure deviation (PI'-P) are both negative values, and the output of the controller (10) is "0" value, so the difference Pressure valve (17)
is quickly closed by the set pressure (Ps) of the spring (17e), and the swash plate (1a) of the variable displacement pump (1) is positioned at the maximum inclination position, and as a result, the discharge mCQ
r) increases rapidly, and the discharge pressure (P'') increases.

At that time, each setter (7) sets the target discharge amount (0) and target discharge pressure (P) to values according to the usage mode of the user.

In (8), just manually input the controller (10) as appropriate.
Since the discharge m (Qf) and the discharge pressure (Pf) can be accurately controlled to each of the above target values, even a person without specialized knowledge can perform simple control.

Further, since the pump discharge pressure (Pi') becomes a load pressure that can be used by the user as it is, there is no pressure loss and energy saving can be achieved. Moreover, since an electro-hydraulic servo valve (15) is used, the servo amplifier (
The output current from 14) can be as small as several tens of milliamperes, making it possible to save even more energy.

In addition, the addition result of the deviation ((Q
Since f-0) + (Pr-P)l is the same and the deviation changes continuously, the swash plate (1a) of the variable displacement pump (1)
) does not suddenly increase or decrease,
Good control stability can be ensured.

Therefore, the discharge amount sensor (5) and the discharge pressure sensor (6)
), the discharge volume of the variable displacement pump (1) CQr )
and discharge pressure (P") are electrically fed back, and the discharge m (Ql") and discharge pressure (P") are adjusted to target discharge amount (0) and target discharge pressure CP according to the load, respectively.
) can be continuously controlled with high precision, high response, simplicity, and low power consumption.

In the above embodiment, the set pressure (Ps) of the spring (17e) of the differential pressure valve (17) is set between the target value (P), (0) and the actual control value (Pr), (Qf), respectively. Deviations (ΔP) and (Δ0) corresponding to , (8), the board inspection values (P-ΔP) and (Q-Δ0) can be calculated by subtracting the deviations (ΔP) and (Δ0), respectively.

Further, in the above embodiment, an electric-hydraulic servo valve (15) consisting of a pressure control pilot valve (16) and a differential pressure valve (17) was used as the electric-hydraulic $11 rB means, but the present invention However, the present invention is not limited to this, and a conventionally known electric/hydraulic servo valve such as an electromagnetic proportional control valve having a proportional solenoid that directly drives the spool may be used.

(Effects of the Invention) As explained above, according to the variable displacement pump control device of the present invention, when the discharge amount (-difference or discharge pressure deviation) is a negative value, the deviation can be converted to a "0" value. This enables continuous electrical feedback control of both the discharge amount and discharge pressure of a variable displacement pump depending on the load, making it possible to implement a practical hydraulic circuit that requires variable control of both load operating speed and supply pressure. It can be applied easily and with low power consumption, and is convenient in practice.

Moreover, since a variable displacement pump is used in which the variable discharge amount control element is biased in the direction of maximum inclination, the discharge amount deviation and discharge pressure deviation can be suppressed even in areas where an increase in the discharge amount and discharge pressure is required. There is no need for specific conversion, and control can be simplified.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of the present invention. Figures 2 to 4 show embodiments of the present invention, with Figure 2 being a general schematic diagram, Figure 3 being a diagram showing the internal configuration of the controller, and Figure 4 being the target discharge amount characteristic and target discharge pressure characteristic. FIG. (1)...Variable displacement pump, (1a)...Swash plate (
(discharge rate variable control element), (3)...discharge rate control section, (
5) Discharge amount sensor (discharge amount detection means), (6)
・・Discharge pressure sensor (discharge pressure detection means), (7)・・
・Target discharge amount setting device (target discharge amount setting means), (8)・
・Target discharge pressure setting device (target discharge pressure setting means), (
10)...Controller, (11)...First deviation calculation section (first deviation calculation means), (12)...Second deviation calculation section (second deviation calculation means), (14)...・Servo amplifier, (15)...Electro-hydraulic servo valve (electro-hydraulic pressure control means), (16)...Pressure control pilot valve, (1
7)... Differential pressure valve, (30)... Adder. 2 idiots

Claims (1)

[Claims] (1) Electricity for adjusting the inclination angle of the variable discharge rate control element (1a) of a variable displacement pump (1) equipped with a swingable discharge rate variable control element (1a) that is biased to the maximum inclination angle.・Liquid pressure control means (15), discharge amount detection means (5) for detecting the discharge amount (Qf) of the variable displacement pump (1), and discharge pressure (Pf) of the variable displacement pump (1). a discharge pressure detection means (6) for detecting the discharge pressure, a target discharge amount setting means (7) for setting the target discharge amount (Q), and a target discharge pressure (P).
A target discharge pressure setting means (8) for setting a target discharge rate, and outputs from the discharge rate detection means (5) and target discharge rate setting means (7) are received, and the deviation of the actual discharge rate (Qf) from the target discharge rate (Q) is determined. When (Qf-Q) is a positive value (Qf-Q≧0), the deviation (Qf-Q) is output as is, and a negative value (Qf-Q<
0), the first deviation calculation means (11) converts the deviation (Qf-Q) into "0" and outputs it, and the outputs of the discharge pressure detection means (6) and target discharge pressure setting means (8). and the actual discharge pressure (Pf) with respect to the target discharge pressure (P)
) is a positive value (Pf-P≧0), the deviation (Pf-P) is output as is, and a negative value (Pf-P) is output as is.
a second deviation calculation means (12) which converts the deviation (Pf-P) into "0" and outputs it when P<0), and receives the outputs of both the deviation calculation means (11) and (12); A control device for a variable displacement pump, comprising: electric control means (14, 30) for controlling the input current to the electric/hydraulic pressure control means (15) based on both deviations.