JP2008303813A - Variable displacement pump control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily constitute a variable displacement pump control device capable of providing high flow rate control accuracy only by an existing product, by calibrating a variation in manufacture of a current to flow rate characteristic of a variable displacement pump. <P>SOLUTION: Command pressure is outputted from a solenoid proportional valve 22 in response to a current value for commanding a flow rate inputted from a controller 51. An actuator piston 33 is operated by this command pressure, and a swash plate tilt angle of the variable displacement pump 14 is variably adjusted. An ordinary control mode and a calibration mode are set by a monitor 55 connected to the controller 51. The controller 51 determines the current value in an actual maximum swash plate position corresponding to a change point of a pressure value captured by changing the current value for commanding the flow rate while monitoring the pressure value acting on the actuator piston 33 in the calibration mode, and adds this value to a target swash plate current value Ipump in the ordinary control mode with a difference between this current value and a current value on a preset specification as a correction value Ical. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a variable displacement pump control device that calibrates manufacturing variations of a swash plate tilt angle control system of a variable displacement pump.

  A variable displacement pump using a swash plate tilt angle of an electromagnetic proportional flow control system that outputs a flow rate according to a command current has variations in manufacturing characteristics in the current-flow rate characteristics of the pump.

  Servo control device to correct the deviation of the swash plate position by adjusting the factory shipment precisely or providing the swash plate tilt sensor that detects the actual swash plate tilt position to obtain the flow control accuracy There is a problem that a response delay is likely to occur and cost is required.

  In contrast, a controller, an electromagnetic proportional valve that is driven by a drive current from the controller to generate a command pressure, and a regulator that controls the displacement of the variable displacement hydraulic pump based on the command pressure generated by the electromagnetic proportional valve. And a controller that generates the drive current according to a command signal corresponding to a target displacement of the hydraulic pump. The controller drives the displacement volume control unit using the drive current, and In the hydraulic pump control device that controls the displacement volume, the hydraulic pump control device includes a measurement unit that measures an actual displacement volume of the hydraulic pump, and a mode selection unit that selects either the learning control mode or the normal control mode. From the inverse characteristics of the median tolerance of the input / output characteristics of the regulator Normal control for determining the target command pressure according to the target displacement volume, determining the target drive current according to the target command pressure from the inverse characteristic of the median tolerance of the input / output characteristics of the electromagnetic proportional valve, and generating the drive current And a target command pressure corresponding to an arbitrary target displacement volume from the inverse characteristic of the median tolerance of the input / output characteristics of the regulator when the learning control mode is selected by the mode selection means, and the electromagnetic proportional The target drive current corresponding to the target command pressure is obtained from the inverse characteristic of the median tolerance of the input / output characteristics of the valve, the displacement of the hydraulic pump is controlled by generating the drive current, and the arbitrary target displacement is obtained. Learning calculation means for obtaining a difference between a volume and an actual displacement volume measured by the measurement means; and when the normal control mode is selected by the mode selection means, the learning There is a hydraulic pump control system and a learning correction means for correcting the target displacement volume at that time based on the difference between the actual displacement and any target displacement volume determined by the calculation means.

This hydraulic pump control device has the same actual pump tilt as the actual pump tilt when controlled by the median characteristics, even if the characteristics of the electromagnetic proportional valve and regulator vary within the tolerance range of each individual. As a result, the actual pump tilt can be controlled in the same manner as the target pump tilt, and variations in actual pump tilt can be reduced. For this reason, for example, it is possible to improve the fine operability and operation feeling in the operation that the hydraulic working machine wants the hydraulic operation machine to accurately follow the operator operation, such as horizontal pulling of the excavator, front position alignment, etc., and increase the work efficiency be able to. In normal operation, the actual pump tilt is also controlled by feedback control, which feeds back the tilt angle of the hydraulic pump detected by the tilt angle sensor and takes the difference from the target pump tilt. However, in the normal control mode of this hydraulic pump control device, there is a problem that a response delay occurs in feedback control, and in the unlikely event that the tilt angle sensor fails, control cannot be performed. Since the control is performed in an open loop that does not use the detected value of the tilt angle sensor instead of feedback control, no response delay occurs, and even if the tilt angle sensor breaks down, the work machine can be operated normally Can do. (For example, refer to Patent Document 1).
Japanese Patent No. 3497031 (page 3, page 8, Fig. 1-3)

  The hydraulic pump control device described in Patent Document 1 includes a measuring unit that measures an actual displacement volume of the hydraulic pump, and the controller uses the inverse characteristic of the median tolerance of the input / output characteristic of the regulator to calculate the displacement. A target command pressure corresponding to the target displacement volume is obtained, a target drive current corresponding to the target command pressure is obtained from a reverse characteristic of a median tolerance of input / output characteristics of the electromagnetic proportional valve, and the drive current is generated, When the learning control mode is selected by the mode selection means, a target command pressure corresponding to an arbitrary target displacement is obtained from the inverse characteristic of the median tolerance of the input / output characteristics of the regulator, and the input / output of the electromagnetic proportional valve is obtained. The target drive current corresponding to the target command pressure is obtained from the reverse characteristic of the median of the characteristic tolerance, and the displacement of the hydraulic pump is controlled by generating the drive current. Then, the difference between the arbitrary target displacement and the actual displacement measured by the measuring means is obtained, and when the normal control mode is selected by the mode selection means, the arbitrary target displacement and the actual displacement are determined. Since the target displacement at that time is corrected based on the difference from the volume, it is necessary to attach a measuring means such as a pump tilt angle sensor, which complicates the structure and the arithmetic circuit of the controller. Such a complex device has problems such as not being easy to design and reducing reliability against failure.

  The present invention has been made in view of the above points, and a variable displacement pump control device that can obtain high flow control accuracy by calibrating the manufacturing variation of the current versus flow characteristics of the variable displacement pump is already known. It is intended to be easily configured only with goods.

  According to the first aspect of the present invention, there is provided an electromagnetic proportional valve that outputs a command pressure corresponding to an input current value for a flow rate command, and a variable displacement pump that is operated by the command pressure output from the electromagnetic proportional valve. The actuator piston that variably adjusts the tilt angle of the swash plate and the actuator piston that is driven via the electromagnetic proportional valve by the current value for the flow rate command that corresponds to the target flow rate of the variable displacement pump. A controller for controlling the swash plate tilt angle and mode setting means capable of setting a normal control mode and a calibration mode are provided, and the controller monitors a pressure value acting on the actuator piston in the calibration mode. The actual minimum swash plate position and the point corresponding to the change point of the pressure value captured by changing the current value for the flow rate command. The current value of at least one of the maximum swash plate positions is obtained, and the difference between the actual current value and the preset current value is used as a correction value and output to the solenoid proportional valve in the normal control mode. This is a variable displacement pump control device having a function of correcting a current value for a flow rate command.

  According to a second aspect of the present invention, the controller in the variable displacement pump control device according to the first aspect is configured such that when the calibration mode is set by the mode setting means, the current value for the flow rate command is increased while the actuator is being increased. The pressure value acting on the piston is monitored, the current value at the actual maximum swash plate position where the pressure value acting on the actuator piston is lower than a certain threshold value is obtained, and the current value at this actual maximum swash plate position is preset. A correction value calculation function for calculating and storing a difference from the current value at the maximum swash plate position according to the specifications as a correction value is provided.

  According to a third aspect of the present invention, the controller in the variable displacement pump control device according to the first or second aspect determines a relationship between a target flow rate of the variable displacement pump and a preset current value. When the normal control mode is set by the flow rate vs. current output control table and the mode setting means, the correction value is added to the current value output from the flow rate vs. current output control table. And an adder for correcting the output current value.

  According to the invention described in claim 1, in the calibration mode, the change point of the pressure value captured by the controller changing the current value for the flow rate command while monitoring the pressure value acting on the actuator piston. The current value of at least one of the actual minimum swash plate position and the maximum swash plate position corresponding to is obtained, and the normal control is performed using the difference between the actual current value and the preset current value as a correction value. In this mode, the current value for the flow rate command output to the electromagnetic proportional valve is corrected, so that the variation in the current-flow characteristic of the variable displacement pump can be calibrated to obtain a high flow control accuracy. The displacement pump control device can be easily configured with only existing products.

  According to the second aspect of the present invention, the pressure value acting on the actuator piston is monitored while increasing the current value for the flow rate command, and the actual maximum value at which the pressure value acting on the actuator piston is lower than a certain threshold value. The current value at the swash plate position is obtained, and the difference between the current value at the actual maximum swash plate position and the current value at the maximum swash plate position according to the preset specifications is calculated and stored as a correction value. The current value at the actual maximum swash plate position that falls below a certain threshold can be reliably captured, and the correction value can be obtained easily and reliably.

  According to the third aspect of the present invention, when the normal control mode is set by the mode setting means, the correction value is added to the current value output from the flow rate versus current output control table, so that the electromagnetic proportional Since the current value output to the valve is corrected, it is possible to easily correct the current value without changing the contents of the flow rate versus current output control table.

  Hereinafter, the present invention will be described in detail with reference to one embodiment shown in FIGS.

  As shown in FIG. 1, a variable displacement pump 14 that is rotated by an external engine 12 via a pump shaft 13 is installed inside the pump unit 11, and the pump discharge passage 15 includes a shuttle valve 16. One inlet 16a is connected, the other pilot pump 17 is connected to the other inlet 16b of the shuttle valve 16, a passage 18 is connected to the outlet 16c of the shuttle valve 16, and this passage 18 is an electromagnetic proportional to the regulator 21. Connected to the inlet port 23 of the valve 22.

  The proportional solenoid valve 22 includes a proportional solenoid 24, a spool 25, and two types of springs 26 and 27. The spool 25 is set according to a current value for a flow rate command input to the proportional solenoid 24. By moving the inlet port 23 to the outlet port 28 and outputting the command pressure to the passage 29, the outlet port 28 is connected to the tank passage 30 and the command pressure is extinguished. Can be switched.

  The passage 29 communicates with the piston chamber 32 via the orifice 31, and the piston chamber 32 is actuated by the command pressure output from the electromagnetic proportional valve 22 to the passage 29 to tilt the swash plate of the variable displacement pump 14. An actuator piston 33 that variably adjusts the angle is fitted. The actuator piston 33 is provided with an internal passage 35 that communicates the passage 29 with the tank 34 to prevent further displacement of the actuator piston 33 when displaced.

  The actuator piston 33 is connected to one end of a swash plate 36 of the variable displacement pump 14, and a piston 37 having a smaller diameter than the actuator piston 33 is connected to the other end of the swash plate 36 via a rod 38. The rod 38 is integrally provided with a feedback member 39, and the one spring 27 is interposed between the feedback member 39 and the spool 25 of the electromagnetic proportional valve 22.

  The passage 18 connected to the outlet 16c of the shuttle valve 16 communicates with the spring chamber 42 through which the small-diameter piston 37 is fitted via the orifice 41. A spring 43 that biases the piston 37 is fitted into the spring chamber 42.

  A control valve 46 is connected to the output port 44 of the pump unit 11 via a discharge line 45, and various actuators 47 such as a hydraulic cylinder and a hydraulic motor are connected to the control valve 46, and the variable displacement pump 14 It is driven by the hydraulic oil as the working fluid supplied from.

  Next, the operation of the pump unit 11 will be described.

  When the pump shaft 13 is driven to rotate by the engine 12, the axial piston (not shown) of the variable displacement pump 14 reciprocates at a stroke corresponding to the tilt angle of the swash plate 36 while rotating on the swash plate 36. Then, the working fluid (working oil) is discharged.

  At this time, the working fluid discharged from the variable displacement pump 14 (or the working fluid supplied from the pilot pump 17 when the discharge pressure from the variable displacement pump 14 is low) passes through the shuttle valve 16 and then the regulator. It is fed to the right end of the actuator piston 33 through 21 electromagnetic proportional valves 22. The actuator piston 33 moves the swash plate 36 and controls the discharge flow rate.

  The electromagnetic proportional valve 22 that controls the swash plate 36 of the variable displacement pump 14 controls the flow rate in accordance with the current value I input to the proportional solenoid 24, and the current value I input to the proportional solenoid 24 is controlled. When changed, the excitation force changes in level, and the position of the spool 25 is displaced by the fluctuating excitation force, and electromagnetic proportional flow control is performed to increase or decrease the flow rate according to the position of the spool 25. The spool 25 of the electromagnetic proportional valve 22 is pushed leftward by the spring 26 and the spring 27.

  When the current value I is low, the excitation force is low, so the spool 25 is moved to the left by the spring 26 and the spring 27, and the passage 18 and the passage 29 are communicated. Since the pressure in the passage 18 enters the piston chamber 32 of the actuator piston 33 via the electromagnetic proportional valve 22 and the passage 29, the actuator piston 33 is pushed to the left, and the swash plate 36 is rotated clockwise.

  The rotational force of the swash plate 36 opposes the force of the piston 37 pushed to the left by the pressure from the passage 18 through the rod 38. Since the actuator piston 33 has a larger area than the piston 37, even if an equal pressure is applied from the common passage 18 to the actuator piston 33, the piston 37 is pushed to the right, and the swash plate 36 rotates clockwise, so that the variable capacity The discharge flow rate from the mold pump 14 is reduced.

  On the other hand, when the current value I increases, the exciting force of the proportional solenoid 24 increases, the spool 25 is moved to the right against the springs 26 and 27, and the passage 29 and the tank passage 30 communicate with each other. The piston chamber 32 of 33 is connected to the tank passage 30 via the electromagnetic proportional valve 22 and becomes a low pressure.

  When the piston chamber 32 of the actuator piston 33 becomes low pressure, the swash plate 36 is rotated counterclockwise via the rod 38 by the pressure acting on the right end of the small-diameter side piston 37. The flow rate increases.

  When the piston 37 moves to the left, the feedback member 39 also works to the left and compresses the spring 27, so that the spool 25 is urged to the left and closes the passage 29 and the tank passage 30. As a result, the tilt of the swash plate 36 stops and the flow rate corresponding to the exciting force is maintained.

  Since this exciting force is proportional to the current value I supplied to the proportional solenoid 24 of the electromagnetic proportional valve 22, the flow rate increases as the current value I is increased.

  Next, a pump control controller 51 is connected to the proportional solenoid 24 of the electromagnetic proportional valve 22. This controller 51 originally controls the actuator piston 33 via the electromagnetic proportional valve 22 with the flow rate command target swash plate current value Ipump corresponding to the target flow rate Q of the variable displacement pump 14, so that the variable displacement pump 14 is a control table 52 for controlling the relationship between the pump discharge pressure P of the variable displacement pump 14 and the target flow Q to a constant horsepower state, and the target of the variable displacement pump 14. A flow rate vs. current output control table 53 is provided for controlling the relationship between the flow rate Q and the target swash plate current value Ipump on a preset specification (spec).

  The controller 51 is connected to a rotational speed sensor 54 that detects the engine rotational speed, and is connected to a monitor 55 as mode setting means that can set a normal control mode and a calibration mode. A pressure sensor 56 for detecting the pump discharge pressure is connected.

  This pressure sensor 56 is normally installed in the port M of the pump unit 11 communicated with the pump discharge passage 15, but communicates with the piston chamber 32 of the actuator piston 33 during factory shipment adjustment (calibration). Connected to port M1.

When the calibration mode is set by the monitor 55, the current value I for the flow rate command is changed while monitoring the pressure value _PM1 acting on the actuator piston 33, as shown by the solid line in FIG. The pressure value P _M1 and the pump discharge flow rate Q fluctuate in conjunction with each other. However, as shown by the dotted line in FIG. 2, the characteristic on the specification (on the specification) located at the center of the tolerance and the solid line in FIG. There is an error between the actual characteristics.

Here, the change point of the pressure value P _M1 captured by changing the current value I for flow rate instruction A, and B, and the actual minimum flow rate (minimum swash plate position) and the maximum flow rate (maximum swash plate position) since but corresponding, controller 51, the change point of the pressure value P _M1 captured by changing the current value I for flow rate instruction a, corresponding to B, and the actual minimum swash plate position of and the maximum swash plate position Normal control mode, using the differences Ia and Ib between these actual current values and the current values at the minimum and maximum swashplate positions as specified in the specifications. Has a function of interpolating and correcting the current value I for the flow rate command output to the electromagnetic proportional valve 22.

In order to simplify the explanation, as shown in FIG. 3, when the case where Ia = Ib, where the actual characteristic is in parallel with the standard characteristic on the spec, is considered, the controller 51 serves as the mode setting means. when the calibration mode is set by the monitor 55, the pressure value P _M1 acting on the actuator piston 33 while increasing the current value for the flow rate command monitoring, pressure value P _M1 that acts on the actuator piston 33 is constant The current value at the actual maximum swash plate position that is lower than the threshold value Pth is obtained, and the current value I at the actual maximum swash plate position and the standard characteristic current value In at the maximum swash plate position according to preset specifications are calculated. The difference is calculated as a correction value Ical, and the correction value calculation function for storing this correction value Ical in the nonvolatile memory is provided, and the normal control mode is set on the monitor 55. Is added to correct the current value output to the electromagnetic proportional valve 22 by adding the correction value Ical to the target swash plate current value Ipump output from the flow rate versus current output control table 53. A container 57 is provided.

  In short, by adding the error in the input / output characteristics of regulator 21 to the conventional controller output as a correction value, the relationship between the flow rate vs. current output value on the spec and the relationship between the actual flow rate vs. current output value is corrected. ing.

  Next, calibration work performed on the machine body side will be described.

Normally, a pressure sensor 56 for detecting the pump discharge pressure is installed at the port M of the pump unit 11 to detect the hydraulic power and the hydraulic load for controlling the control valve. In performing calibration (calibration), the pressure sensor 56 is temporarily replaced with the port M1 of the pump unit 11, and the pressure value P _M1 acting on the actuator piston 33 of the electromagnetic proportional flow rate control is detected by the pressure sensor 56. .

  At this time, an accelerator dial (not shown) for setting the engine rotation speed is set to the maximum dial value “10”, and after the engine rotation speed has settled in the idle state of the maximum dial value “10”, The controller 51 is caused to execute the calibration mode. The setting of the calibration mode is changed on the monitor 55.

The pressure value P _M1 acting on the actuator piston 33 is a driving source pressure while it is hitting the minimum flow rate stopper, a drain pressure when hitting the maximum flow rate stopper, and an intermediate pressure for driving the swash plate 36 during that time. Become. The current value at the minimum swash plate position is stored in the nonvolatile memory at the pressure change point A from the driving source pressure to the intermediate pressure, and the maximum swash plate position at the pressure change point B from the intermediate pressure to the drain pressure. Calibration is performed by storing the current value in a non-volatile memory.

  When calibration is completed, the pressure sensor 56 is returned from the port M1 to the original port M.

  Next, by setting the calibration mode by operating the switch of the monitor 55, the controller 51 for controlling the pump performs calibration as shown in the flowchart of FIG. 3A and the characteristic diagram of FIG. Execution program.

(Step S1)
The initial current value Io when starting the current scan by changing the current value I for the flow rate command is set. This initial current value Io is a current value sufficiently smaller than the current value corresponding to the minimum swash plate position.

(Step S2)
Command to output the current value I.

(Step S3)
Detection was monitored by the pressure sensor 56 the pressure value P _M1 at port M1.

(Step S4)
Pressure value P _M1 determines whether small or not than the threshold value Pth.

(Step S5)
If the pressure value P _M1 is not smaller than the threshold value Pth, the increment Istep is added to the current value I, and the process returns to step S2, while the increment Istep is added until the pressure value P _M1 becomes smaller than the threshold value Pth. Step S5 is repeated to increase the current value I.

In short, the pressure value P _M1 acting on the actuator piston 33 is monitored while gradually increasing the current value for the flow rate command from the initial current value Io sufficiently smaller than the current value corresponding to the minimum swash plate position. At this time, avoid calibration when the pressure value P _M1 acting on the actuator piston 33 is unstable, wait for a predetermined time until the pressure value P _M1 acting on the actuator piston 33 becomes stable, and confirm that it is stable. Then, increase the flow command current value.

(Step S6)
While increasing the flow rate command current value, the pressure value P _M1 acting on the actuator piston 33 is monitored, and when this pressure value P _M1 becomes smaller than a certain threshold value Pth, the actual current value I at that time is The difference (I−In) from the standard characteristic current value In is set as a correction value Ical, and this correction value Ical is stored in the nonvolatile memory.

  Next, after the calibration is completed, the pressure sensor 56 is returned to the port M of the pump unit 11 to return to the normal pump control program, and the pump control controller 51 outputs the current as shown in the flowchart of FIG. Correct the command value.

(Step S7)
For the pressure (pump discharge pressure) P _{M of} the port M detected by the pressure sensor 56, the target flow rate Q of constant horsepower characteristics is obtained by the control table 52, and further, the engine rotational speed is obtained by the control table 53 of flow rate versus current output. Based on the engine speed detected by the sensor, etc., a target swash plate current value Ipump on the spec corresponding to the target flow rate Q is calculated.

(Step S8)
The adder 57 outputs a current value I obtained by adding the target swash plate current value Ipump and the correction value Ical stored in the nonvolatile memory. That is, by adding the correction value Ical to the flow rate vs. current output control table 53 stored in the nonvolatile memory of the controller 51, the flow rate vs. current output relationship is translated in the current direction, Correct the relationship between the flow rate and the current output value.

  In this way, the pressure sensor 56 for detecting the pressure acting on the actuator piston 33 for electromagnetic proportional flow control is temporarily attached to the port M1 of the pump unit 11 during factory shipment adjustment, and idling while monitoring the pressure of the actuator piston 33. In this state, the flow rate command current is raised and lowered to capture the pressure change point of the actuator piston 33, and at least one of the minimum swash plate position current and the maximum swash plate position current is stored in the nonvolatile memory, and then based on the pressure sensor 56 In normal pump control, the flow rate command current value corrected by interpolation with the memory value is used.

  Next, effects of the embodiment will be described.

In the calibration mode, the controller 51 changes the pressure value P _M1 captured by changing the current value I for the flow rate command while monitoring the pressure value P _M1 acting on the actuator piston 33 with the pressure sensor 56. The current value of at least one of the actual minimum swash plate position and the maximum swash plate position is calculated, and the normal control is performed using the difference between the actual current value and the preset current value as the correction value Ical. In the mode, the current value I for the flow rate command output to the electromagnetic proportional valve 22 is corrected, so that the manufacturing variation in the current-flow rate characteristic of the variable displacement pump 14 can be calibrated to obtain high flow control accuracy. A variable displacement pump control device that can be configured easily with only existing products. Furthermore, since the apparatus can be prevented from becoming complicated, the design is easy and the reliability against failure can be ensured.

In flow rate while increasing the current value I for the command to monitor the pressure value P _M1 acting on the actuator piston 33, the pressure value P _M1 that acts on the actuator piston 33 is lower than a predetermined threshold value Pth actual maximum swash plate position Since the current value is obtained and the difference between the current value at the actual maximum swash plate position and the current value at the maximum swash plate position set in advance is calculated and stored as the correction value Ical, the pressure value P _M1 is constant. The current value at the actual maximum swash plate position that is lower than the threshold value Pth can be reliably captured, and the correction value Ical can be obtained easily and reliably.

  When the normal control mode is set on the monitor 55, the correction value Ical is added to the target swash plate current value Ipump output from the flow rate versus current output control table 53. Therefore, the current value can be easily corrected without changing the contents of the flow rate versus current output control table 53.

The controller 51 repeats the search for the current value corresponding to the changing point of the pressure value P _M1 in the calibration mode a plurality of times, and the value obtained by averaging the plurality of current values is set as the actual current value. The difference may be obtained by comparing the value with the current value on the specification. In this way, it is possible to reduce errors due to variations in current value corresponding to the change point of the pressure value P _M1.

  The present invention is applicable to a variable displacement pump control device that controls a variable displacement pump mounted on a work machine such as a hydraulic excavator.

1 is a circuit diagram showing an embodiment of a variable displacement pump control device according to the present invention. FIG. (A) is a characteristic diagram showing the relationship between the flow rate command current of the control device and the pressure acting on the actuator piston, and (b) is a characteristic diagram showing the relationship between the flow rate command current and the pump flow rate. (A) is a flowchart which shows the calibration program of a control apparatus same as the above, (b) is a characteristic figure related to the program content. It is a flowchart which shows the pump swash plate command current output program of a control apparatus same as the above.

Explanation of symbols

14 Variable displacement pump
22 Solenoid proportional valve
33 Actuator piston
51 Controller
53 Flow rate vs. current output control table
55 Monitor as mode setting means
57 Adder

Claims (3)

An electromagnetic proportional valve that outputs a command pressure according to the current value for the input flow rate command;
An actuator piston that is operated by the command pressure output from the electromagnetic proportional valve and variably adjusts the swash plate tilt angle of the variable displacement pump;
A controller that controls the tilt angle of the swash plate of the variable displacement pump by driving the actuator piston via an electromagnetic proportional valve with a flow command current value corresponding to the target flow rate of the variable displacement pump;
Comprising mode setting means capable of setting a normal control mode and a calibration mode;
The controller
In calibration mode, the actual minimum swash plate position and maximum swash plate position corresponding to the change point of the pressure value captured by changing the current value for flow rate command while monitoring the pressure value acting on the actuator piston The current value of at least one of the current value and the difference between the actual current value and the preset current value is used as a correction value. A variable displacement pump control device having a function of correcting a current value. The controller
When the calibration mode is set by the mode setting means, the pressure value acting on the actuator piston is monitored while increasing the current value for the flow rate command, and the pressure value acting on the actuator piston is actually lower than a certain threshold value. A correction value calculation that obtains a current value at the maximum swash plate position and calculates and stores the difference between the current value at the actual maximum swash plate position and the current value at the maximum swash plate position according to a preset specification as a correction value. The variable displacement pump control device according to claim 1, comprising a function. The controller
A flow rate vs. current output control table that determines the relationship between the target flow rate of the variable displacement pump and a preset current value;
When the normal control mode is set by the mode setting means, the current value output to the electromagnetic proportional valve is corrected by adding the correction value to the current value output from the flow rate versus current output control table. The variable displacement pump control device according to claim 1, further comprising an adder.

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