Control calibration device and method for variable pump

Abstract

[Problem] To provide a control calibration apparatus for a variable displacement pump and a method therefor, which can increase the accuracy of flow control of the variable displacement pump. A control calibration device for a variable displacement pump (3) includes a controller (10) that outputs a current value for a flow rate command of the variable displacement pump (3) and a flow sensor (11) that measures a flow rate of the variable displacement pump (3). The controller (10) has a function for obtaining a quadratic function formula from a first current value when the maximum flow rate of the variable pump (3) is measured by the flow sensor (11), a second current value when the minimum flow rate of the variable pump (3) is measured by the flow sensor (11), and a fixed current value corresponding to a fixed flow rate based on the specification of the variable pump (3), the quadratic function formula is a current flow characteristic for flow control of the variable pump (3).

Description

[0001] Public domain

[0002] The present invention relates to a control calibration device for a variable displacement pump and a method thereof, the control calibration device setting current flow characteristics for flow control of a current control type variable displacement pump. Background Art

[0003] Although a current-controlled variable displacement pump used in a working machine or the like is ideal in terms of current flow characteristics for linearly changing the flow rate relative to the current, variations in manufacturing and hysteresis between rise and fall of the current value for the flow rate instruction occur in actual applications, and there is a large deviation from the ideal operation in an actual state. Therefore, it is known to calibrate the current flow characteristics according to the variable displacement pump (see, for example, Patent Documents 1 to 5).

[0004] Patent document 1 describes that by changing the current value used for the flow rate instruction while monitoring the pressure acting on the actuator piston, the current value at the actual minimum or maximum swash plate position corresponding to the change point of the captured pressure value is obtained, and the difference between the obtained current value and the current value on the preset specification as a correction value is added to the target value.

[0005] Patent document 2 describes changing the command current value of a variable pump from a minimum value to a maximum value, and actually measuring the command current value when the pump discharge pressure starts to increase from a minimum reference value and the command current value when the maximum reference value is reached, and changing the command current value of a variable pump from a maximum value to a minimum value, and actually measuring the command current value when the pump discharge pressure starts to decrease from a maximum reference value and the command current value when the minimum reference value is reached, and then using the detected command current value to calibrate the current flow characteristics.

[0006] Patent document 3 describes using an oil circuit of a rod-type unloading valve to actually measure the pump pressure, while changing the command current value to the maximum capacity of the pump in multiple stages while suppressing the rise in pump pressure, and obtaining the relationship between the control current and the pump capacity from the actually measured pump pressure.

[0007] Patent Document 4 describes providing an adjustment line connecting an actual command current value at a maximum flow rate and an actual command current value at a minimum flow rate of a variable displacement pump, and using the adjustment line to suppress the deviation of the hysteresis characteristic.

[0008] 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.

[0009] Prior art literature

[0010] Patent Literature

[0011] Patent Document 1: JP 2008-303813A

[0012] Patent Document 2: JP 2014-177969A

[0013] Patent Document 3: JP 2019-190443A

[0014] Patent Document 4: Republished Patent No. 2019 / 106831

[0015] Patent Document 5: JP 2020-128733A Summary of the invention

[0016] Problems to be solved by the present invention

[0017] In the case of the present invention described in Patent Documents 1 and 2, there is a problem regarding calibration accuracy because the calibration value is calculated based on a change point of pressure at which it is difficult to find the change point. In addition, in the case of the present invention described in Patent Documents 3 to 5, the calibration property is set by a straight line, however, particularly in the case of a variable pump having a nonlinear property, there is a problem with the accuracy of calibration.

[0018] An object of the present invention is to provide a control calibration device and method for a variable displacement pump capable of improving the flow control accuracy of the variable displacement pump.

[0019] Means of solving the problem

[0020] The present invention according to claim 1 is a control calibration device for a variable pump, which is used to set the current flow characteristics for flow control of a current-controlled variable pump, wherein the control calibration device includes: a controller, which is used to output the current value of the flow rate instruction of the variable pump; and a flow sensor, which is used to measure the flow rate of the variable pump, wherein the controller has a function for obtaining a quadratic function formula based on the specifications of the variable pump, according to a first current value when the flow sensor measures the maximum flow rate of the variable pump, a second current value when the flow sensor measures the minimum flow rate of the variable pump, and a fixed current value corresponding to a fixed flow rate, and the quadratic function formula is the current flow characteristics of the variable pump for flow control.

[0021] The present invention according to claim 2 is a control calibration device for a variable pump, wherein the first current value in the control calibration device for a variable pump according to claim 1 is a current value at the saturation of the flow rate when the flow rate sensor measures an increase in the current value of the flow rate instruction for the variable pump, and the second current value is a current value at the saturation of the flow rate when the flow rate sensor measures a decrease in the current value of the flow rate instruction for the variable pump.

[0022] The present invention according to claim 3 is a control calibration device for a variable pump, wherein the flow rate sensor in the control calibration device for a variable pump according to claim 1 or 2 is a flow measurement pressure sensor of the variable pump, which measures the flow rate based on the discharge flow rate of the variable pump relative to the discharge pressure in a fixed throttling state or a fixed speed state.

[0023] The present invention according to claim 4 is a control calibration method for a variable pump, which sets the current flow characteristics for flow control of a current-controlled variable pump, including obtaining a quadratic function formula based on a first current value used for a flow rate instruction when measuring the maximum flow rate of the variable pump, a second current value used for the flow rate instruction when measuring the minimum flow rate of the variable pump, and a fixed current value corresponding to a fixed flow rate based on the specifications of the variable pump.

[0024] The present invention according to claim 5 is a control calibration method for a variable pump, wherein in the control calibration method for a variable pump according to claim 4, the first current value is a current value when the saturation of the flow rate is measured when the current value of the flow rate instruction for the variable pump increases, and the second current value is a current value when the saturation of the flow rate is measured when the current value of the flow rate instruction for the variable pump decreases.

[0025] The present invention according to claim 6 is a control calibration method of a variable pump, wherein in the control calibration method of a variable pump according to claim 4 or 5, the flow rate of the variable pump is measured based on the discharge pressure.

[0026] Effects of the Invention

[0027] According to the present invention of claim 1, the current flow characteristics can be made closer to the actual characteristics of the variable pump to improve the flow control accuracy of the variable pump.

[0028] According to the present invention of claim 2, in a variable displacement pump having hysteresis in current flow characteristics when the current value increases and decreases, the first current value and the second current value for obtaining the quadratic function formula can be accurately obtained.

[0029] According to the present invention of claim 3, calibration can be performed by using the pre-installed pressure sensor without separately installing a dedicated calibration instrument or sensor.

[0030] According to the present invention of claim 4, the current flow characteristics can be made closer to the actual characteristics of the variable pump to improve the flow control accuracy of the variable pump.

[0031] According to the invention of claim 5, in a variable displacement pump having a hysteresis in current flow characteristics when a current value rises and falls, the first current value and the second current value for obtaining a quadratic function formula can be accurately obtained.

[0032] According to the present invention of claim 6, calibration can be performed by using the pre-installed pressure sensor without separately installing a dedicated calibration instrument or pressure sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 (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 a flow rate in a calibration mode.

[0034] Figure 2 is a graph showing current flow characteristics of a variable pump controlled by the same control calibration device of the variable pump.

[0035] Figure 3 (a) is a flow chart showing a calibration procedure of a control calibration device of the same variable pump, (b) is a graph showing changes in current values ​​in the calibration procedure of the control calibration device of the same variable pump, and (c) is a graph showing changes in detected pressure at a flow sensor according to (b). DETAILED DESCRIPTION

[0036] Embodiments of the present invention will be described below with reference to the accompanying drawings.

[0037] Figure 1 (a) shows a part of a hydraulic circuit 1, i.e., a fluid pressure control circuit installed on, for example, a working machine. In the working machine, a variable displacement pump 3 (hereinafter referred to as pump 3) as a fluid pressure pump driven by an onboard engine 2 supplies hydraulic oil of a working fluid in an oil tank 4 to a plurality of slide valves integrally provided in a block as a control valve connected to a pump discharge passage 5, performs direction control and flow control of the hydraulic oil according to the displacement direction and displacement amount of the slide valves, and supplies the hydraulic oil to a plurality of fluid pressure actuators such as a hydraulic motor and a hydraulic cylinder, respectively.

[0038] In this hydraulic circuit 1, various slide valves are operated according to the operation amount 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 discharge amount of the hydraulic oil of the pump 3 is controlled according to the current value of the command signal for the flow rate command output from the controller 10 based on the input signal.

[0039] In other words, the pump 3 is of current-controlled type, and a variable device such as a swash plate is controlled by a regulator 3a, which is operated by a solenoid valve (electromagnetic proportional valve) that receives a command signal output from the controller 10, and the variable device can be adjusted according to the load at the minimum flow rate when there is no load.

[0040] The controller 10 controls the swash plate inclination angle of the pump 3 by actuating the regulator 3a via the solenoid valve by means of a command signal corresponding to the target flow rate of the pump 3. Therefore, the controller 10 has a control table (current flow characteristic (IQ characteristic)) for controlling the relationship between the target flow rate of the pump 3 and the current value of the preset specification (SPEC), and in the normal control mode, the flow rate of the pump 3 is controlled based on the control table according to the current value of the command signal output from the controller 10.

[0041] Here, it is ideal that the pump 3 linearly increases or decreases the flow rate with respect to the increase or decrease of the current value according to the current flow characteristics, but in actual application, due to manufacturing errors, a lag occurs between the rise and fall of the current value for the flow rate instruction, such as Figure 2 As shown by the arrow in , the actual deviation from the ideal operation is large.

[0042] Therefore, in the present embodiment, the controller 10 has a calibration mode for calibrating (setting) the control table based on the measured values ​​of each pump 3, or in other words, the control of the pump 3, so as to ensure the control accuracy during actual operation. Usually, the calibration mode is performed by activating the mode at the factory.

[0043] In order to perform calibration in the calibration mode, the present embodiment uses the controller 10 and the flow sensor 11 that detects the discharge flow rate of the pump 3. Preferably, the flow sensor 11 uses a pressure sensor that detects the discharge pressure of the pump 3. In other words, the flow sensor 11 is a flow measurement pressure sensor that measures the flow rate based on a fixed predetermined throttling condition of the hydraulic circuit 1 or a fixed predetermined engine speed or pump rpm, wherein the discharge flow rate of the pump 3 is associated with the discharge pressure. The flow sensor 11 is connected to the pump discharge passage 5, and its output signal is connected to the input side of the controller 10. Note that in the present embodiment, the flow rate sensor 11 is installed in the hydraulic circuit 1 as a standard for detecting hydraulic power or hydraulic load for controlling the control valve for normal control, and is not specifically used for the calibration mode.

[0044] Next, a control calibration method of the pump 3 will be described.

[0045] By operating a predetermined input device such as an on-vehicle monitor to set a calibration mode in the controller 10, the controller 10 executes a calibration process.

[0046] In short, first of all, Figure 1(b), in the circuit for performing the calibration procedure, where the pump discharge passage 5 is directly connected to the tank 4 via the orifice (hole) 15, the controller 10 monitors the discharge pressure of the pump 3 through the flow rate sensor 11 while increasing the current value for the flow rate command relative to the pump 3, and stores the current value when the discharge pressure of the flow rate sensor 11 saturates as the first current value Imax corresponding to the maximum flow rate Qmax. Similarly, the controller 10 monitors the discharge pressure of the pump 3 through the flow rate sensor 11 while decreasing the current value of the flow rate command relative to the pump 3, and stores the current value when the discharge pressure of the flow rate sensor 11 saturates as the second current value Imin corresponding to the minimum flow rate Qmin. In addition, according to the specifications of the pump 3, a fixed current value Qmid corresponding to the fixed flow rate Qmid is pre - input or stored in the controller 10 as the mid - point between the first current value Imax corresponding to the maximum flow rate Qmax and the second current value Imin corresponding to the minimum flow rate Qmin. That is, in this embodiment, the fixed flow rate Qmid is a flow rate greater than the minimum flow rate Qmin and less 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 known values based on the specifications of the pump 3, and they are respectively detected and provided to each pump 3 through an output check separately performed by the manufacturer of the pump 3. Then, as Figure 2 shown, in the coordinate plane where the current value is on the x - axis (horizontal axis) and the flow rate is on the y - axis (vertical axis), a quadratic function formula f (mathematically, the quadratic function formula f passing through three points is uniquely determined) can be obtained through three points: The points P1(Imax, Qmax), P2(Imin, Qmin), and P3(Imid, Qmid) and the quadratic function formula f are stored (set) in the non - volatile memory as a control table. By executing the calibration procedure at the controller 10, these processing sequences are automatically performed.

[0047] Reference will be made to Figure 3 (a) to 3(c) for a detailed description of the operations in the calibration mode.

[0048] First, in step S1, the controller 10 forms a circuit for performing the calibration procedure of directly connecting the pump discharge passage 5 to the tank 4 via the orifice 15 standardly installed in the hydraulic circuit 1 by outputting a command signal to a valve or the like installed in the hydraulic circuit 1 ( Figure 1 (b)).

[0049] Then, in step S2, the controller 10 increases the current value I for the flow rate command from a small current value such as 0. The increase in the current value I can be increased sequentially (linearly) as Figure 3 (b) shows, or can be increased step - by - step by a predetermined current width.

[0050] In step S3, the discharge pressure P( Figure 3 (c)) to monitor the flow rate.

[0051] Then, in step S4, it is determined whether the discharge pressure P has increased.

[0052] When it is determined in step S4 that the discharge pressure P has increased, the process returns to step S2. When it is determined in step S4 that the discharge pressure P has not increased, it is determined that the flow rate of the pump 3 has reached the maximum flow rate Qmax pre-stored or input for each pump 3, and in step S5, the current value at this time is stored as the first current value Imax.

[0053] Then, in step S6, the controller 10 reduces the current value I used for the flow rate command. The reduction of the current value I can be as follows: Figure 3 (b) is shown as decreasing sequentially (linearly), or the predetermined current width may be decreased stepwise.

[0054] In step S7, the discharge pressure P( Figure 3 (c)) to monitor the flow rate.

[0055] Then, in step S8, it is determined whether the discharge pressure P has decreased.

[0056] When it is determined in step S8 that the discharge pressure P has decreased, the process returns to step S6. When it is determined in step S8 that the discharge pressure P has not decreased, it is determined that the flow rate of pump 3 has reached the minimum flow rate Qmin pre-stored or input for each pump 3. In step S9, the current value at this time is stored as the second current value Imin.

[0057] Note that the order of steps S2 to S5 and steps S6 to S9 may be reversed.

[0058] Moreover, in step S10, a quadratic function formula f for flow control of the pump 3 is obtained in a coordinate plane with the current value as the x-axis and the flow rate as the y-axis from the first current value Imax when measuring the maximum flow rate Qmax of the pump 3, the second current value Imin when measuring the minimum flow rate Qmin of the pump 3, and the fixed current value Imid corresponding to the fixed flow rate Qmid based on the specifications of the pump 3 stored or input in advance.

[0059] Here, when the quadratic function formula f passing through the three points (x1, y1), (x2, y2) and (x3, y3) on the coordinate plane is y=ax 2 +bx+c (where a, b, and c are real numbers), a, b, and c are each determined by the following formula:

[0060] a={(y1-y2)·(x1-x3)-(y1-y3)·(x1-x2)} / {(x1-x2)·(x1-x3)·(x2-x3)}

[0061] b=(y1-y2) / (x1-x2)-a·(x1+x2)

[0062] c=y1-a·x1 2 -b x1

[0063] Therefore, by substituting the values ​​of currents Imax, Imin and Imid in x1, x2 and x3 of the above formula, and substituting flow rates Qmax, Qmin and Qmid in y1, y2 and y3 respectively, a specific quadratic function formula f can be obtained.

[0064] Then, in step S11, the quadratic function formula f obtained in step S10 is stored as a characteristic table in the nonvolatile memory, and the calibration procedure is terminated. Note that if a characteristic table based on the standard specifications of the pump 3 or the like is stored in the nonvolatile memory in advance, it may be corrected or may be newly stored.

[0065] Then, in the normal control mode, the controller 10 outputs a command signal for controlling the flow rate of the pump 3 based on the characteristic table stored in step S11 .

[0066] As described above, according to the aforementioned embodiment, by obtaining a quadratic function formula of the current flow characteristics used for flow control of the pump 3 based on the first current value used for the flow rate instruction when measuring the maximum flow rate of the pump 3, the second current value used for the flow rate instruction when measuring the minimum flow rate of the pump 3, and the fixed current value corresponding to the fixed flow rate based on the specifications of the pump 3, the current flow characteristics of the pump 3 can be made closer to the actual characteristics of the pump 3, thereby improving the flow control accuracy of the pump 3.

[0067] Furthermore, since only two data points are obtained by actual measurement, there is no need to actually measure a large number of points, so calibration can be performed in a short time without complicated calculations.

[0068] By measuring the current value when the saturation of the flow rate is measured when the current value of the flow rate instruction of the pump 3 increases as the first current value, and measuring the current value when the saturation of the flow rate is measured when the current value of the flow rate instruction of the pump 3 decreases as the second current value, the first current value and the second current value for obtaining the quadratic function formula can be accurately obtained in the pump 3 having a lag in the current flow characteristic when the current value increases and decreases.

[0069] By measuring the flow rate of the pump 3 based on the fact that the discharge flow rate of the pump 3 is correlated with the discharge pressure under a fixed opening condition or a fixed engine speed condition, a pressure sensor pre-installed in the hydraulic circuit 1 can be used as the flow sensor 11 to perform calibration without separately installing a dedicated calibration instrument or sensor.

[0070] Note that in the above-described embodiment, by obtaining the first current value and the second current value ( Figure 3 (a) and using representative values ​​such as average values ​​and most frequent values ​​to find the quadratic function formula can further improve the accuracy of the quadratic function formula.

[0071] Industrial Applicability

[0072] The present invention has industrial potential for business operators engaged in the manufacture, sale, etc. of working machines such as hydraulic excavators equipped with variable displacement pumps.

Claims

1. A control calibration device for a variable displacement pump for setting current flow characteristics for flow control of a current-controlled variable displacement pump, wherein the control calibration device comprises: A controller, the controller is used to output a current value of a flow rate instruction of the variable pump; as well as a flow sensor, the flow sensor being used to measure the flow rate of the variable pump, The controller has the following function: to obtain a quadratic function formula based on a first current value when the maximum flow rate of the variable pump is measured by the flow sensor, a second current value when the minimum flow rate of the variable pump is measured by the flow sensor, and a fixed current value corresponding to a fixed flow rate based on the specifications of the variable pump, wherein the quadratic function formula is a current flow characteristic for flow control of the variable pump.

2. The control calibration device for a variable displacement pump according to claim 1, wherein The first current value is a current value when the flow sensor measures the saturation of the flow rate when the current value of the flow rate command of the variable pump increases, and The second current value is a current value when the flow sensor measures the saturation of the flow rate when the current value of the flow rate command of the variable pump decreases.

3. The control calibration device for a variable displacement pump according to claim 1 or 2, wherein The flow sensor is a flow measurement pressure sensor of the variable pump, and the flow measurement pressure sensor measures the flow rate based on the discharge flow rate of the variable pump relative to the discharge pressure in a fixed throttle state or a fixed rotation speed state.

4. A control calibration method for a variable displacement pump, the control calibration method for a variable displacement pump setting a current flow characteristic for flow control of a current-controlled variable displacement pump, comprising: A quadratic function formula is obtained based on a first current value used for a flow rate instruction when measuring a maximum flow rate of the variable pump, a second current value used for a flow rate instruction when measuring a minimum flow rate of the variable pump, and a fixed current value corresponding to a fixed flow rate based on specifications of the variable pump.

5. The control calibration method of a variable displacement pump according to claim 4, wherein The first current value is a current value when the saturation of the flow rate is measured when the current value of the flow rate command of the variable pump increases, and The second current value is a current value when the saturation of the flow rate is measured when the current value of the flow rate command of the variable pump decreases. 6 . The control calibration method of a variable displacement pump according to claim 4 , wherein the flow rate of the variable displacement pump is measured based on a discharge pressure.

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