JPS62253969A - Capacity controller for variable capacity type pump - Google Patents

Abstract

PURPOSE:To improve responsiveness and precision by controlling the discharge flow rate and discharge pressure by using a proportional control valve having a proportional solenoid which operates in proportion to the electric current value. CONSTITUTION:A proportional control valve 20 having a proportional solenoid 21 which operates in proportion to the electric current value supplied from a flow rate instruction device 33, pressure instruction device 34, selecting means 35 which selects the both, and a subtraction circuit 36 which comparison- calculates the selected signal and the signal supplied from a flow rate detector 31 is installed into a control passage 24. Therefore, the need of using a throttle valve besides a solenoid valve as in the conventional is avoided, and since the opening quantity to a pressure line 26 of the control passage 24 which is controlled by the proportional control valve 20 can be controlled by each instruction device 33, 34, responsiveness and precision can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a capacity control device for a variable displacement pump, specifically, a variable control element that adjusts the discharge amount and an operation plunger that adjusts the displacement of the variable control element. The present invention relates to a capacity control device for a variable displacement pump.

(Prior art) Conventionally, the capacity control of variable displacement pumps has been remotely controlled using electric servo valves and electro-hydraulic servo valves.
In addition, as shown in Japanese Utility Model Application Publication No. 55-180084, a double rod type operation cylinder and an electromagnetic switching valve are used as variable control elements, and capacity control is remotely controlled by on/off feedback control. What has been done is known.

The conventional example of performing this on/off feedback control is
As shown in FIG. 2, a variable displacement pump (P) has two ports that control its variable control elements.

A cylinder (C) is provided to operate the cylinder (C).
The throttle valve (A) (
A) and check valve (B) through a parallel circuit of (B) 3 position 4
Connect the electromagnetic switching valve (v) of the port, and connect the inlet/outlet port (P2) to the tank (T) and the discharge line (D) of the pump (P) via the switching valve (V).
a potentiometer (E) that detects the amount of displacement of the rod of the cylinder (C), and a displacement signal of this potentiometer (E) and a command from a command signal section (F). A function circuit (H) and a drive circuit (J) having a dead zone are provided, and the output side of the drive circuit (J) is connected to the switching valve (V). Solenoid (SO
LA) (SOLB).

When the command signal set in the th age multiple signal section F) is output, this command signal and the displacement signal from the potentiometer (E) are compared, and the signal difference between these signals is calculated. , when the dead band width set by the function circuit (H) based on the tolerance is exceeded, a positive or negative output signal is output depending on the polarity of the signal, and the signal is outputted via the drive circuit (J). The solenoid of the switching valve (V) (
SOLA) (SOLB) is energized, one of the inlet/outlet ports (P,) (P,) in the operating cylinder (C) is communicated with the discharge line (D), and the position of the variable connection element is controlled. It is possible.

(Problems to be Solved by the Invention) According to the conventional example described above, since no servo valve is used, the flow ff1ff! There is no need for a controller, and maintenance is easy. However, since the position of the variable control element is set by the on-fist off operation of the solenoid switching valve (V), conventional methods are required to improve position accuracy. As in the example, it is necessary to use the throttle valves (A) (A) to throttle the passages to each inlet/outlet port (P,) (P,) of the operating cylinder (C), but the throttle valves (A) ( The aperture according to A) does not change as it approaches the target value, but is set to a constant aperture amount, so increasing the aperture amount causes the problem of poor response, while decreasing the aperture amount causes the problem. This results in a problem of lack of accuracy.

Furthermore, since the variable control element is controlled by on/off feedback control using the electromagnetic switching valve (V) as described above, a function circuit (H) having a dead band is provided, so that when the input signal exceeds the dead band width, It is necessary to control the output signal so that it outputs an output signal at
), and the PC compensates for the pressure at the minimum flow rate.
Since the control (pressure convencator control) cannot be performed, there is also the problem of power loss.

An object of the present invention is to remotely control the discharge amount of a variable displacement pump continuously and with high precision using a single proportional control valve having a proportional solenoid that operates in proportion to the current value. Furthermore, pressure control is also possible.

(Means for Solving the Problems) In order to solve the above problems, the present invention provides a variable control element (2) for adjusting the discharge amount, and a variable control element (2) for adjusting the discharge amount, as shown in FIG. ) is a displacement control device for a variable displacement pump equipped with an operation plunger (6) for adjusting the amount of displacement of a pressure sensor (31), a flow rate command device (33) for outputting a flow rate command signal, A pressure command device (34) that outputs a command signal, and a selection means (35) that selects one of the flow ffl command device (33) and the pressure command 'IA (34).
, a subtraction circuit (38) that compares and calculates the command signal output from the selected one of the command devices (33 or 34) and the flow rate detection signal from the flow rate detector (31), and this subtraction circuit (36). It has a proportional solenoid (21) that operates in proportion to the current value output from the operation plunger (6).
a proportional control valve that switches a control passage (24) leading to the rear chamber (6a) of the tank line (25) or the pressure line (26) to one of the tank line (25) and the pressure line (26), and controls the opening amount with the pressure line (26); (20).

(Function) Depending on the current value output based on the comparison between the flow rate or pressure command signal set by the flow rate command device (33) or pressure command device (34) and the flow rate detection signal from the flow rate detector (31), The proportional control valve (20) operates to actuate the operating plunger (6) and adjust the displacement amount of the variable control element (2), and the control passage (20) by the proportional control valve (20)
24) to the pressure line (26) is controlled to an opening amount corresponding to a target value set by the command device (33 or 34), and the variable control element (2) Positioning can be done with responsiveness and crystal precision.

Moreover, the operation of the proportional control valve (20) is controlled by one of the flow rate command device (33) and pressure command device (34) selected by the selection means (35).
) is controlled by comparing a command signal from a flow rate detection signal with a flow rate detection signal, and a single proportional control valve (20) can perform flow rate control and pressure control.

(Example) The variable displacement pump (1) shown in Fig. 1 has a swash plate (2) as a variable control element that adjusts the discharge amount.
This pump (1) is equipped with a cylinder block (4) having a main shaft (3) and a plurality of pistons (4a) spline-coupled to the main shaft (3). , the head of the piston (4a) is brought into sliding contact with the swash plate (2), and the -side of the cylinder block (4) is brought into contact with the swash plate (2); The displacement ff1 (inclination angle) of the spring (5
) is provided with an operating plunger (6) for adjustment in the neutral direction.

Further, the discharge passage (7) of the pump (1) is provided with a switching valve (
The fluid motor (11) and cylinders (12) and (13) are connected via 8) (9) (to), and the pump (1)
) to control the speed of the motor (11) and cylinders (12) and (13) by adjusting the inclination angle of the swash plate (2) to adjust the discharge amount. ing.

Therefore, the control of the swash plate (2) in the variable displacement pump configured as described above is performed using a single proportional solenoid (21) that operates in proportion to the current value. This is done by a proportional control valve (20), and the operation of this proportional control valve (20) enables flow rate control and pressure control, that is, PC control that compensates for pressure at the minimum discharge flow rate.

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The noid (21) and this proportional solenoid (21)
a spool (22) that reciprocates in conjunction with the movable iron core;
A control passage (24) leading to the rear chamber (6a) of the operating plunger (6) is connected to the tank line (
25) and a pressure line (
26) and said pressure line (26).
), and the operating plunger (6) is controlled by the operation of the proportional control valve (20) to move the swash plate (2) from the maximum inclination position to the neutral position. position, adjust its inclination angle, control the discharge flow n and, for example, compensate the pressure at the minimum discharge flow rate.
This makes it possible to control the pressure.

In FIG. 1, (27) is a safety valve which operates when the discharge pressure reaches the maximum pressure set by the spring (28) and connects the control passage (24) to the pressure line (2).
6) to control the swash plate (2) and the neutral position.

Next, the electric circuit for controlling the proportional control valve (20) constructed as above will be explained.

What is shown in FIG. 1 is a flow rate detector (31) mainly consisting of a differential transformer for detecting the inclination angle of the swash plate (2).
and a pressure detector (32) that detects the discharge pressure, and a flow mtta
A flow rate command device (33) that outputs a command signal sound signal and a pressure command device (34) that outputs a pressure command signal are used. (
A selection means (35) mainly consisting of a changeover switch is connected to select one of the selection means (34).
5), one of the selected command units (33 or 3) is connected to the output side of the
an amplifier (3E3 a) that compares and calculates the command signal output from
) is connected to the subtraction circuit (36), and this subtraction circuit (
36) is connected to the proportional solenoid (21).

The selection operation of the selection means (35) uses a switch operation circuit (37), and the output of this operation circuit (37) is used to connect the connection position to the flow rate command device (33) to the pressure command device (34). the first position;
In the figure, on the input side of the operating circuit (37), there is a comparator (38) that compares the pressure detection signal detected by the pressure detector (32) with the pressure command signal set by the pressure command device (32). ) is connected so that when the pressure detection signal becomes a pressure command signal, an output signal is output from the actuation circuit (37). The operating circuit (37) may be configured to output based on the comparison signal from the comparator (38), or may be configured to output based on an external input.

Therefore, the command signal output from one of the command devices (33 or 34) selected as described above and the flow rate detector (31
) A predetermined current value corresponding to the output signal is applied to the proportional solenoid (21) by the output signal outputted by the comparison operation in the subtraction circuit (3B) with the flow rate detection signal from the subtraction circuit (3B). The proportional control valve (20) operates with an opening proportional to this current value, and the swash plate (2)
This control is negative feedback control performed based on the flow rate detection signal, and can be accurately controlled to the target value set by the command device (33 or 34).

In the case shown in FIG. 1, a potentiometer (39) is provided in the cylinder (13) to detect the speed of the rod (13a), and this speed information is sent to the flow rate command device (33).
A pressure detection signal (discharge pressure information) detected by the pressure detector (32) is provided on the output side of the pressure command device (34). I am inputting it to the pressure side subtraction circuit (41),
The output signals output from these subtraction circuits (40 or 41) are input to the subtraction circuit (36) provided on the output side of the selection means (35).

Next, the operation of the capacity control device configured as above will be explained.

Based on the operating cycles of the fluid motor (11) and cylinders (12) and (13), the discharge flow rate and discharge pressure of the pump (1) required by these actuators are set over time, and these are set by the flow rate command device (33). and a pressure command device (34) in advance, and a predetermined flow rate command signal and pressure command signal corresponding to this set are outputted as they change over time.

In the system shown in FIG. 1, the swash plate (2) is in a neutral position when the flow rate control system of the control device (33) is selected for the flow rate by the selection means (35), and the discharge flow rate is the minimum. It is in a state where the flow rate is high.

In this case, the target value of the discharge flow rate set by the flow rate command device (33) is the minimum, and the flow rate detector (31)
) has also become small, and therefore, the output signal output from the subtraction circuit (86) changes the current value applied to the proportional renoid (21) from the first
The spool (22) of the proportional control valve (20) is connected to the spring (
The pressure in the control passage (24) is applied to the spring (23) against the spring (23).
5) is the current value to bring the swash plate (2) to a control position such as the pressure necessary to hold it neutrally.

When a command signal to increase the flow rate is output in this state, since the flow rate detection signal is small, the output signal output from the subtraction circuit (36) is large, that is, the signal difference with the flow rate detection signal becomes large. , the current value applied to the proportional solenoid (21) increases and the spool (22)
moves to the left, and the pressure line (26) of the control passage (24)
The amount of opening to the tank line (25) decreases, while the amount of opening to the tank line (25) increases, causing the swash plate (2) to tilt from the neutral position shown in FIG. 1 in the direction of maximum inclination.

As described above, the opening amount is continuously reduced as the current value changes, and since the opening amount is controlled to correspond to the target value, the discharge amount can be controlled with good responsiveness. Moreover, since there is no need to provide a dead zone in the control system, the discharge amount can be controlled with high precision.

That is, the position of the swash plate (2) can be set in proportion to the current value applied to the proportional solenoid (21), and in other words, the discharge amount can be accurately controlled based on the flow rate command set by the flow rate command device (33). can be done.

On the other hand, the actuator can be controlled to a desired operation by controlling the discharge flow rate as described above, but when the discharge pressure reaches the target value set by the pressure command device (34), the selection means (35) The pressure command device (34)
The pressure control system is switched to the pressure control system, and the swash plate (2) is controlled to the target value set by the pressure command device (34), and pressure compensation is performed at the minimum flow rate under a predetermined pressure. be.

In the embodiment described above, a differential transformer is used as the flow rate detector (31) to indirectly detect the flow rate by detecting the position of the swash plate (2). , the position of the operating plunger (6) may be detected.

Further, a flow rate detection sensor may be disposed in the discharge passageway (7) to directly detect the flow rate, or as shown in FIG. f
It is also possible to perform fl detection. Also, swash plate (2)
In addition to a swash plate type axial piston pump using a swash plate type axial piston pump, a slanted shaft type axial piston pump or a vane pump using a cam ring may also be used.

(Effects of the Invention) As described above, the present invention controls the discharge flow rate and discharge pressure using one proportional control valve (20) having a proportional solenoid (21) that operates in proportion to the current value. Therefore, in addition to the electromagnetic switching valve (V) as in the conventional example, a throttle valve (A) is installed.
There is no need to use the proportional control valve (20).
Pressure line (26) of control passage (24) controlled by
The opening amount is controlled to the opening amount corresponding to the target value set by each of the control devices (33 or 34), and the operating plunger (6) is operated based on this opening amount. The responsiveness can be improved compared to the conventional method, and since it does not control a dead zone, it can be controlled with high precision.

Moreover, a proportional solenoid (2
Since a single proportional control valve (20) having 1) can control the discharge flow rate and control the discharge pressure at the same time, the structure can be simplified and costs can be reduced.

[Brief explanation of drawings]

FIG. 1 is a fluid and electrical circuit diagram showing an embodiment of the present invention, and FIG. 2 is an explanatory diagram of a conventional example. (1)... Pump (2)... Swash plate (variable control element) (6)...
...Operating plunger (6a) ...Back chamber (20) ...Proportional control valve (21) ...Proportional solenoid (24) ...Control passage (25)...Tank line (26)...Pressure line (31)...Flow rate detector (33)...Fluid command unit (34) ...Pressure command device (35) ...Selection means (3B) ...Subtraction circuit

Claims (1)

[Claims] A capacity control device for a variable displacement pump, comprising a variable control element (2) for adjusting the discharge amount and an operating plunger (6) for adjusting the displacement amount of the variable control element (2), the device comprising: a flow rate detector ( 31) and a flow rate command device (
33) and a pressure command device (34) that outputs a pressure command signal.
and a selection means (35) for selecting one of the flow rate command device (33) and the pressure command device (34), and a command signal output from the selected one of the command devices (33 or 34) and the flow rate detection. It has a subtraction circuit (36) that compares and calculates the flow rate detection signal from the device (31), and a proportional solenoid (21) that operates in proportion to the current value output from the subtraction circuit (36). 6) Switching the control passage (24) leading to the rear chamber (6a) to one of the tank line (25) and the pressure line (26), and controlling the opening amount with the pressure line (26). Control valve (20)
A capacity control device for a variable displacement pump, comprising: