JP2023174096A - Control calibration device of variable displacement pump and method thereof - Google Patents

Abstract

To provide a control calibration device of a variable displacement pump capable of enhancing flow rate control accuracy of a variable displacement pump, and a method thereof.SOLUTION: A control calibration device of a variable displacement pump 3 comprises a controller 10 that outputs a current value for a flow rate command of the variable displacement pump 3, and a flow rate sensor 11 that measures a flow rate of the variable displacement pump 3. The controller 10 has a function of determining a quadratic function equation that is a current versus flow rate characteristic for controlling the flow rate of the variable displacement pump 3, based on a first current value when the maximum flow rate of the variable displacement pump 3 is measured by the flow rate sensor 11, a second current value when the minimum flow rate of the variable displacement pump 3 is measured by the flow rate sensor 11, and a fixed current value corresponding to a fixed flow rate based on the specifications of variable displacement pump 3.SELECTED DRAWING: Figure 1

Description

The present invention relates to a control calibration device and method for a variable displacement pump that sets a current versus flow rate characteristic for controlling the flow rate of a current-controlled variable displacement pump.

Current-controlled variable displacement pumps used in working machines, etc. ideally have a current vs. flow rate characteristic where the flow rate changes linearly with the current, but in reality, there are manufacturing variations and flow rate command fluctuations. Hysteresis occurs when the current value increases and decreases, and there is a large discrepancy between the actual situation and the ideal operation. Therefore, methods are known in which the current versus flow rate characteristics are calibrated according to the variable displacement pump (for example, see Patent Documents 1 to 5).

Patent Document 1 discloses that by changing the current value for flow command while monitoring the pressure acting on the actuator piston, the actual minimum swash plate position or maximum swash plate position corresponding to the change point of the detected pressure value is determined. It is described that the current value is determined at , and the difference between the determined current value and the current value according to the preset specifications is added to the target current value as a correction value.

Patent Document 2 discloses that the command current value of a variable displacement pump is changed from the minimum to the maximum, and the command current value when the pump discharge pressure starts to increase from the minimum reference value and the command current value when it reaches the maximum reference value. At the same time, the command current value of the variable displacement pump was changed from maximum to minimum, and the command current value when the pump discharge pressure started to decrease from the maximum reference value and the command current value when it reached the minimum reference value were actually measured. It is described that the current versus flow rate characteristics are calibrated using the detected command current values.

Patent Document 3 discloses that using the oil passage of a stick unload valve, the pump pressure is actually measured while changing the command current value in multiple steps up to the maximum capacity of the pump while suppressing the increase in pump pressure, and the measured pump pressure is It is described that the relationship between control current and pump capacity can be found from

In Patent Document 4, an adjustment line is set that connects the actually measured command current value at the maximum flow rate of a variable displacement pump and the actually measured command current value at the minimum flow rate, and the adjustment line is used to suppress deviations in hysteresis characteristics. It is stated that.

Patent Document 5 describes that two calibration points of the command current value are actually measured at a flow rate between the maximum flow rate and the minimum flow rate, and a straight line connecting these calibration points is set as a new reference characteristic. .

JP2008-303813A Japanese Patent Application Publication No. 2014-177969 JP 2019-190443 Publication Re-published patent No. 2019/106831 JP 2020-128733 Publication

In the case of the inventions described in Patent Documents 1 and 2, calibration values are calculated based on pressure change points that are difficult to find, so there is a problem with the accuracy of calibration. Further, in the case of the inventions described in Patent Documents 3 to 5, since the characteristics for calibration are set as a straight line, there is a problem in the accuracy of calibration, especially in the case of a variable displacement pump having nonlinear characteristics.

The present invention has been made in view of the above points, and an object of the present invention is to provide a control calibration device and method for a variable displacement pump that can improve the accuracy of flow rate control of a variable displacement pump. .

The invention according to claim 1 is a control calibration device for a variable displacement pump that sets a current vs. flow rate characteristic for flow rate control of a current-controlled variable displacement pump, the device comprising: The controller includes a controller that outputs a value, and a flow rate sensor that measures the flow rate of the variable displacement pump, and the controller outputs a first current value when the maximum flow rate of the variable displacement pump is measured by the flow rate sensor, and a flow rate sensor that measures the flow rate of the variable displacement pump. The second current value when measuring the minimum flow rate of the variable displacement pump, the fixed current value corresponding to the fixed flow rate based on the specifications of the variable displacement pump, and the current vs. flow rate characteristic for flow rate control of the variable displacement pump. It has the function of finding the quadratic function formula.

The invention according to claim 2 is such that the first current value in the control calibration device for a variable displacement pump according to claim 1 is such that the flow rate sensor measures the saturation of the flow rate when the current value for the flow rate command of the variable displacement pump increases. Control calibration of a variable displacement pump where the second current value is the current value when the flow rate sensor measures saturation of the flow rate when the current value for the flow rate command of the variable displacement pump is decreasing. It is a device.

The invention according to claim 3 is such that the flow rate sensor in the control calibration device for a variable displacement pump according to claim 1 or 2 is configured such that the discharge flow rate of the variable displacement pump is determined under a fixed throttling condition or a fixed rotation speed condition. This is a control calibration device for a variable displacement pump, which is a flow rate measuring pressure sensor that measures the flow rate based on being linked to the pressure.

The invention according to claim 4 is a control calibration method for a variable displacement pump that sets a current vs. flow rate characteristic for flow rate control of a current-controlled variable displacement pump, the method comprising: measuring the maximum flow rate of the variable displacement pump; the first current value for the flow rate command when the minimum flow rate of the variable displacement pump is measured, and the fixed current value corresponding to the fixed flow rate based on the specifications of the variable displacement pump. A quadratic function equation is calculated from the current value and the current vs. flow rate characteristic for controlling the flow rate of a variable displacement pump.

The invention as set forth in claim 5 provides a control calibration method for a variable displacement pump as set forth in claim 4, in which the current value when the saturation of the flow rate is measured when the current value for the flow rate command of the variable displacement pump is increased. This is a control calibration method for a variable displacement pump in which one current value is set and a second current value is a current value when saturation of the flow rate is measured when the current value for flow command of the variable displacement pump decreases.

The invention according to claim 6 is a control calibration method for a variable displacement pump according to claim 4 or 5, in which the flow rate of the variable displacement pump is measured based on the discharge pressure.

According to the first aspect of the invention, it is possible to bring the current versus flow rate characteristics closer to the characteristics of an actual variable displacement pump, thereby increasing the accuracy of flow rate control of the variable displacement pump.

According to the invention as set forth in claim 2, in the variable displacement pump having hysteresis in the current vs. flow rate characteristic when the current value increases and decreases, the first current value and the second current value for determining the quadratic function expression. Values can be obtained with high accuracy.

According to the third aspect of the present invention, calibration can be performed using a pre-installed pressure sensor without separately installing a dedicated instrument or sensor for calibration.

According to the fourth aspect of the invention, it is possible to bring the current versus flow rate characteristics closer to the characteristics of an actual variable displacement pump, thereby increasing the accuracy of flow rate control of the variable displacement pump.

According to the invention as set forth in claim 5, in the variable displacement pump having hysteresis in the current vs. flow rate characteristic when the current value increases and decreases, the first current value and the second current value for determining the quadratic function expression. Values can be obtained with high accuracy.

According to the invention as set forth in claim 6, calibration can be performed using a pre-installed pressure sensor without separately installing a dedicated instrument or sensor for calibration.

(a) is a circuit diagram showing an embodiment of a control calibration device for a variable displacement pump according to the present invention, and (b) is a circuit diagram for monitoring flow rate in a calibration mode. It is a graph which shows the current vs. flow rate characteristic of a variable displacement type pump controlled by the control calibration device of a variable displacement type pump same as the above. (a) is a flowchart showing the calibration program of the control calibration device for the variable displacement pump same as above, (b) is a graph showing the change in current value in the calibration program of the control calibration device for the variable displacement pump same as above, (c ) is a graph showing changes in the detected pressure at the flow rate sensor according to (b).

Hereinafter, the present invention will be explained in detail based on an embodiment shown in FIGS. 1 to 3.

FIG. 1(a) shows a part of a hydraulic circuit 1, which is a fluid pressure control circuit mounted on, for example, a working machine. In this working machine, a variable displacement pump 3 (hereinafter simply referred to as pump 3) as a fluid pressure pump driven by an on-vehicle engine 2 supplies hydraulic oil, which is a working fluid in a tank 4, to a pump discharge passage 5. The hydraulic oil is supplied to multiple spool valves assembled in one block as a control valve, and the direction and flow rate of the hydraulic fluid are controlled by the direction and amount of displacement of these spool valves to control hydraulic oil, hydraulic motors, hydraulic cylinders, etc. The fluid pressure is supplied to each of the plurality of fluid pressure actuators.

In such a hydraulic circuit 1, various spool valves are operated according to the amount of operation of an operating device 6 such as a lever or a pedal. A signal corresponding to the operation amount of the operating device 6 is input to the input side of the controller 10, and the pump 3 is operated according to the current value of the command signal for flow rate command output from the controller 10 based on the input signal. The amount of oil discharged is controlled.

That is, the pump 3 is of a current control type, and a capacity variable means such as a swash plate is controlled by a regulator 3a operated by a solenoid valve (electromagnetic proportional valve) that receives a command signal output from a controller 10. This makes it possible to variably adjust the flow rate from the minimum flow rate when no load is applied depending on the load.

The controller 10 controls the tilt angle of the swash plate of the pump 3 by operating the regulator 3a via a solenoid valve in response to a command signal corresponding to a target flow rate of the pump 3. Therefore, the controller 10 has a control table (current vs. flow rate characteristic (IQ characteristic)) that controls the relationship between the target flow rate of the pump 3 and the current value according to the specifications (on the specifications) set in advance. Now, based on this control table, the flow rate of the pump 3 is controlled according to the current value of the command signal output from the controller 10.

Here, in the current vs. flow rate characteristics of the pump 3, ideally the flow rate increases or decreases linearly as the current value increases or decreases, but in reality, manufacturing variations and the arrows in FIG. As shown, hysteresis occurs when the current value for flow rate command increases and decreases, and there is a large deviation between the actual situation and the ideal operation.

Therefore, in order to ensure control accuracy during actual operation, in the present embodiment, the controller 10 uses a control table, that is, a calibration mode in which the control of the pump 3 is calibrated (set) based on the actual measured value for each pump 3. has. Usually, the calibration mode is activated and executed at the time of factory shipment.

In order to perform calibration in the calibration mode, this embodiment uses a controller 10 and a flow rate sensor 11 that detects the discharge flow rate of the pump 3. Preferably, the flow rate sensor 11 is a pressure sensor that detects the discharge pressure of the pump 3. That is, the flow rate sensor 11 measures the flow rate based on the fact that the discharge flow rate of the pump 3 is linked to the discharge pressure under a fixed predetermined throttling condition of the hydraulic circuit 1 or a fixed predetermined engine rotation speed or pump rotation speed. It is a flow measurement pressure sensor. The flow rate sensor 11 is connected to the pump discharge passage 5, and its output signal is connected to the input side of the controller 10. In this embodiment, the flow rate sensor 11 is installed as standard in the hydraulic circuit 1 in order to detect hydraulic power or hydraulic load for control valve control in normal control. It is not exclusive to application mode.

Next, a control calibration method for the pump 3 will be explained.

The controller 10 executes a calibration program by setting a calibration mode in the controller 10 by operating a predetermined input means such as an in-vehicle monitor.

Briefly, first, as shown in FIG. 1(b), in a circuit for executing a calibration program in which a pump discharge passage 5 is directly connected to a tank 4 via an orifice 15, a controller is installed. 10 monitors the discharge pressure of the pump 3 with the flow rate sensor 11 while increasing the current value for flow rate command to the pump 3, and determines the current value when the discharge pressure of the flow rate sensor 11 is saturated as the maximum flow rate. It is stored as a first current value Imax corresponding to Qmax. Similarly, the controller 10 monitors the discharge pressure of the pump 3 using the flow rate sensor 11 while lowering the current value for flow rate command to the pump 3, and determines the current value when the discharge pressure of the flow rate sensor 11 is saturated. The value is stored as a second current value Imin corresponding to the minimum flow rate Qmin. The controller 10 also has a fixed flow rate Qmid based on the specifications of the pump 3 as an intermediate point between a first current value Imax corresponding to the maximum flow rate Qmax and a second current value Imin corresponding to the minimum flow rate Qmin. A fixed current value Qmid is input or stored in advance. That is, in this embodiment, the fixed flow rate Qmid is a flow rate larger than the minimum flow rate Qmin and smaller than the maximum flow rate Qmax (Qmin<Qmid<Qmax). The maximum flow rate Qmax, the minimum flow rate Qmin, the fixed flow rate Qmid, and the fixed current value Imid are each detected and provided for each pump 3 through a shipping test of the pump 3 alone conducted by the manufacturer of the pump 3. It is a known value based on the specifications. As shown in FIG. 2, on a coordinate plane with the current value as the x-axis (horizontal axis) and the flow rate as the y-axis (vertical axis), point P1 (Imax, Qmax), point P2 (Imin, Qmin) , a quadratic function formula f passing through three points, point P3 (Imid, Qmid) (mathematically, a quadratic function formula f passing through three points is uniquely determined), and converting the quadratic function formula f into the current versus flow rate Characteristics, that is, stored (set) in nonvolatile memory as a control table. A series of these processes is automatically performed by executing a calibration program in the controller 10.

The operation in the calibration mode will be described in detail with reference to FIGS. 3(a) to 3(c).

First, in step S1, the controller 10 outputs a command signal to a valve installed in the hydraulic circuit 1 to direct the pump discharge passage 5 through the orifice 15 installed as standard in the hydraulic circuit 1. A circuit for executing the calibration program is configured which is directly connected to the tank 4 (FIG. 1(b)).

Next, in step S2, the controller 10 increases the current value I for flow rate command from a small current value such as 0. The current value I may be increased continuously (linearly) as shown in FIG. 3(b), or may be increased stepwise by a predetermined current width.

In step S3, the flow rate is monitored by detecting the discharge pressure P of the pump 3 (FIG. 3(c)) using the flow rate sensor 11.

Next, in step S4, it is determined whether the discharge pressure P has increased.

In step S4, if it is determined that the discharge pressure P has increased, the process returns to step S2; if in step S4, it is determined that the discharge pressure P has not increased, the flow rate of the pump 3 is It is determined that the maximum flow rate Qmax, which is stored or input in advance, has been reached, and in step S5, the current value at that time is stored as the first current value Imax.

Next, in step S6, the controller 10 decreases the current value I for flow rate command. The current value I may be decreased continuously (linearly) as shown in FIG. 3(b), or may be decreased stepwise by a predetermined current width.

In step S7, the flow rate is monitored by detecting the discharge pressure P of the pump 3 (FIG. 3(c)) using the flow rate sensor 11.

Next, in step S8, it is determined whether the discharge pressure P has decreased.

In step S8, if it is determined that the discharge pressure P has decreased, the process returns to step S6; if in step S8, it is determined that the discharge pressure P has not decreased, the flow rate of the pump 3 is It is determined that the minimum flow rate Qmin, which is stored or inputted in advance, has been reached, and in step S9, the current value at that time is stored as the second current value Imin.

Note that the order of steps S2 to S5 and steps S6 to S9 may be reversed.

Furthermore, in step S10, the first current value Imax when the maximum flow rate Qmax of the pump 3 is measured, the second current value Imin when the minimum flow rate Qmin of the pump 3 is measured, and the pump From the fixed current value Imid corresponding to the fixed flow rate Qmid based on the specifications of No. 3, the quadratic current value that becomes the current vs. flow rate characteristic for flow rate control of the pump 3 in the coordinate plane with the current value as the x-axis and the flow rate as the y-axis. Find the functional formula f.

Here, the quadratic function equation f passing through the three points (x1, y1), (x2, y2), (x3, y3) on the coordinate plane is expressed as y=ax ² +bx+c (a, b, c are real numbers, respectively). In this case, a, b, and c are each calculated using the following formulas.

a={(y1-y2)・(x1-x3)-(y1-y3)・(x1-x2)}/{(x1-x2)・(x1-x3)・(x2-x3)}
b=(y1-y2)/(x1-x2)-a・(x1+x2)
c=y1-a・x1 ² -b・x1
Therefore, by substituting current values Imax, Imin, and Imid into x1, x2, and x3 in the above equations, and substituting flow rates Qmax, Qmin, and Qmid into y1, y2, and y3, a specific quadratic function equation f can be obtained. You can ask for it.

Then, in step S11, the quadratic function equation f obtained in step S10 is stored in a nonvolatile memory as a characteristic table, and the calibration program is ended. Note that if a characteristic table or the like based on the standard specifications of the pump 3 is previously stored in the nonvolatile memory, it may be corrected or may be newly stored.

Thereafter, in the normal control mode, the controller 10 outputs a command signal to control the flow rate of the pump 3 based on the characteristic table stored in step S11.

As described above, according to the above embodiment, the first current value for the flow rate command when the maximum flow rate of the pump 3 is measured, and the first current value for the flow rate command when the minimum flow rate of the pump 3 is measured. The current vs. flow rate characteristic can be calculated by calculating a quadratic function equation that is the current vs. flow rate characteristic for flow rate control of the pump 3 from the second current value and the fixed current value corresponding to the fixed flow rate based on the specifications of the pump 3. The characteristics of the actual pump 3 can be approximated, and the flow rate control accuracy of the pump 3 can be improved.

In addition, data from only two points is acquired through actual measurement, and there is no need to actually measure a large number of points. Therefore, complicated calculations are not required, and calibration can be performed in a short time.

The current value when the saturation of the flow rate is measured when the current value for the flow rate command of the pump 3 increases is set as the first current value, and the current value when the saturation of the flow rate is measured when the current value for the flow rate command of the pump 3 decreases. By setting the current value as the second current value, in the pump 3 which has hysteresis in the current vs. flow rate characteristic when the current value increases and decreases, Current values can be obtained with high accuracy.

By measuring the flow rate of the pump 3 based on the fact that the discharge flow rate of the pump 3 is linked to the discharge pressure under a fixed throttling condition or a fixed engine speed condition, the pressure installed in the hydraulic circuit 1 in advance can be measured. By using the sensor as the flow rate sensor 11, calibration can be performed without separately installing a dedicated instrument or sensor for calibration.

In the above embodiment, for example, the first current value and the second current value are acquired multiple times (steps S2 to S9 in FIG. 3(a)), and their average value, mode, etc. The accuracy of the quadratic function formula may be further improved by determining the quadratic function formula using representative values.

INDUSTRIAL APPLICABILITY The present invention has industrial applicability for businesses involved in the manufacturing and sales of working machines such as hydraulic excavators equipped with variable displacement pumps.

3 Variable displacement pump 10 Controller 11 Flow rate sensor

Claims (6)

A control calibration device for a variable displacement pump that sets a current vs. flow rate characteristic for flow rate control of a current-controlled variable displacement pump,
a controller that outputs a current value for a flow rate command of a variable displacement pump;
Equipped with a flow rate sensor that measures the flow rate of the variable displacement pump,
The controller receives a first current value when the maximum flow rate of the variable displacement pump is measured by the flow sensor, a second current value when the minimum flow rate of the variable displacement pump is measured by the flow sensor, and a second current value when the minimum flow rate of the variable displacement pump is measured by the flow sensor. A control calibration for a variable displacement pump characterized by having a function of determining a quadratic function equation that is a current vs. flow rate characteristic for flow rate control of a variable displacement pump from a fixed current value corresponding to a fixed flow rate based on specifications. Device. The first current value is a current value when the flow rate sensor measures the saturation of the flow rate when the current value for the flow rate command of the variable displacement pump increases,
2. The variable displacement pump according to claim 1, wherein the second current value is a current value when the flow rate sensor measures saturation of the flow rate when the current value for the flow rate command of the variable displacement pump is decreasing. Control calibration equipment. A claim characterized in that the flow rate sensor is a flow rate measurement pressure sensor that measures the flow rate based on the fact that the discharge flow rate of the variable displacement pump is linked to the discharge pressure under a fixed throttle condition or a fixed rotation speed condition. 3. A control calibration device for a variable displacement pump according to 1 or 2. A control calibration method for a variable displacement pump that sets a current vs. flow rate characteristic for flow rate control of a current-controlled variable displacement pump, the method comprising:
The first current value for the flow rate command when the maximum flow rate of the variable displacement pump is measured, the second current value for the flow rate command when the minimum flow rate of the variable displacement pump is measured, and the second current value for the flow rate command when the minimum flow rate of the variable displacement pump is measured. A control calibration method for a variable displacement pump, characterized in that a quadratic function equation that is a current vs. flow rate characteristic for controlling the flow rate of a variable displacement pump is determined from a fixed current value corresponding to a fixed flow rate based on the specifications of the variable displacement pump. The first current value is the current value when saturation of the flow rate is measured when the current value for the flow rate command of the variable displacement pump increases,
The control calibration method for a variable displacement pump according to claim 4, characterized in that the second current value is a current value when saturation of the flow rate is measured when the current value for the flow rate command of the variable displacement pump decreases. . The control calibration method for a variable displacement pump according to claim 4 or 5, wherein the flow rate of the variable displacement pump is measured based on the discharge pressure.

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