Control calibration device for variable capacity pumps and methods thereof

Abstract

Problem: To provide a control calibration device for a variable-capacity pump that can increase the flow control accuracy of the variable-capacity pump, and a method thereof. Solution: The control calibration device of the variable-capacity pump (3) includes a control device (10) that outputs a current value for a flow rate command of the variable-capacity pump (3), and a flow sensor (11) that measures a flow rate of the variable-capacity pump (3).The control device (10) has a function for obtaining a quadratic function formula which is a current-flow characteristic for the flow control of the variable-capacity pump (3) from a first current value when the maximum flow rate of the variable-capacity pump (3) is measured by the flow rate sensor (11), a second current value when the minimum flow rate of the variable-capacity pump (3) is measured by the flow rate sensor (11), and a fixed current value which corresponds to a fixed flow rate based on the specifications of the variable-capacity pump (3).

Description

Area of ​​Revelation

[0001] The present invention relates to a variable capacity pump control calibration device that sets a current-flow characteristic for flow control of a current-controlled variable capacity pump, and a method thereof. State of the art

[0002] Although the current-controlled variable capacity pump used in a working machine or the like is ideal for linearly changing the flow rate relative to the current in terms of the current-flow characteristic, in practice, there are variations in manufacturing and hysteresis between the rise and fall of the current value for the flow rate command, and there is a large deviation of the actual state from the ideal operation.

[0003] Accordingly, it is known that the current-flow characteristics are calibrated according to the variable capacity pump (see, for example, Patent Documents 1 to 5).

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

[0005] Patent Document 2 describes that a current command value of a variable capacity pump is changed from the minimum to the maximum, and the current command value when a pump discharge pressure starts to increase from a minimum reference value and the current command value when a maximum reference value is reached are actually measured, and the current command value of the variable capacity pump is changed from the maximum to the minimum, and the current command value when the pump discharge pressure starts to decrease from a maximum reference value and the current command value when the minimum reference value is reached are actually measured, and then the current-flow characteristic is calibrated using the detected current command value.

[0006] Patent Literature 3 describes using an oil path of a rod relief valve to actually measure a pump pressure, while changing the current command value in multiple stages to the maximum capacity of the pump while suppressing the increase of the pump pressure, and obtaining a relationship between the control current from the actually measured pump pressure and the pump capacity.

[0007] Patent Document 4 describes setting a fitting line connecting an actual current command value at a maximum flow rate of a variable capacity pump with an actual current command value at a minimum flow rate, and using the fitting line for suppressing the deviation of the hysteresis characteristics.

[0008] Patent Literature 5 describes actually measuring two calibration points of the command value of the currents at a flow rate between the maximum flow rate and the minimum flow rate and setting a straight line connecting these calibration points as a new reference characteristic. State of the art documentsPatent document Patent Document 1: JP 2008-303813A Patent Document 2: JP 2014-177969A Patent Document 3: JP 2019-190443A Patent Literature 4: Republished Patent No. 2019 / 106831 Patent Document 5: JP 2020-128733A Brief description of the inventionProblems to be solved by the invention

[0009] In the invention described in Patent Documents 1 and 2, the accuracy of calibration is problematic because the calibration value is calculated based on the change point of pressure, where the change point is difficult to find.

[0010] Furthermore, in the invention described in Patent Documents 3 to 5, the calibration characteristics are adjusted by a straight line, but there is a problem with the accuracy of the calibration, especially in the case of a variable capacity pump having non-linear characteristics.

[0011] An object of the present invention is to provide a control calibration device for a variable capacity pump capable of improving the flow control accuracy of a variable capacity pump and a method thereof. Means for solving the problem

[0012] The invention according to claim 1 is a control calibration device of a variable capacity pump for setting a current-flow characteristic for flow control of a current-controlled variable capacity pump, wherein the control calibration device comprises a control device for outputting a current value of a flow rate command of the variable capacity pump and a flow sensor for measuring a flow rate of the variable capacity pump, wherein the control device has a function for obtaining a quadratic function formula that represents a current-flow characteristic of the variable capacity pump for flow control from a first current value when a maximum flow rate of the variable capacity pump is measured by the flow rate sensor, a second current value when a minimum flow rate of the variable capacity pump is measured by the flow rate sensor,and a fixed current value corresponding to a fixed flow rate based on the specifications of the variable capacity pump.

[0013] The invention according to claim 2 is a control calibration device of the variable capacity pump, wherein the first current value in the control calibration device of the variable capacity pump according to claim 1 is a current value when the flow rate sensor measures the saturation of the flow rate at a time point at which the current value for the flow rate command of the variable capacity pump increases, and the second current value is a current value when the flow rate sensor measures the saturation of the flow rate at a time point at which the current value for the flow rate command of the variable capacity pump decreases.

[0014] The invention according to claim 3 is a control calibration device of a variable capacity pump, wherein the flow rate sensor in the control calibration device of the variable capacity pump according to claim 1 or 2 is a flow measuring pressure sensor of the variable capacity pump that measures the flow rate based on the discharge flow of the variable capacity pump in relation to a discharge pressure under a fixed throttle condition or a fixed speed condition.

[0015] The invention according to claim 4 is a control calibration method of a variable capacity pump that sets a current-flow characteristic for flow control of a current-controlled variable capacity pump, including obtaining a quadratic function formula from a first current value for a flow rate command when a maximum flow rate of the variable capacity pump is measured, a second current value for a flow rate command when a minimum flow rate of the variable capacity pump is measured, and a fixed current value corresponding to a fixed flow rate based on a specification of the variable capacity pump.

[0016] The invention according to claim 5 is a control calibration method of a variable capacity pump, wherein in the control calibration method of the variable capacity pump according to claim 4, the first current value is a current value when the saturation of the flow rate is measured at a time point when the current value for the flow rate command of the variable capacity pump increases, and the second current value is a current value when the saturation of the flow rate is measured at a time point when the current value for the flow rate command of the variable capacity pump decreases.

[0017] The invention according to claim 6 is a control calibration method of a variable capacity pump, wherein in the control calibration method of the variable capacity pump according to claim 4 or 5, the flow rate of the variable capacity pump is measured based on a discharge pressure. Effect of the invention

[0018] According to the invention described in claim 1, the current-flow characteristic can be made closer to the actual characteristic of the variable capacity pump to improve the accuracy of flow control of the variable capacity pump.

[0019] According to the invention described in claim 2, in a variable capacity pump having hysteresis in the current-flow characteristic, when the value of the current increases and decreases, the first current value and the second current value for obtaining the quadratic function formula can be accurately obtained.

[0020] According to the invention described in claim 3, calibration can be performed using a pre-mounted pressure sensor without the need to install a special calibration instrument or a separate sensor.

[0021] According to the invention described in claim 4, the current-flow characteristic can be made closer to the actual characteristic of the variable capacity pump to improve the accuracy of flow control of the variable capacity pump.

[0022] According to the invention described in claim 5, in a variable capacity pump having hysteresis in the current-flow characteristic, when the value of the current increases and decreases, the first current value and the second current value for obtaining the quadratic function formula can be accurately obtained.

[0023] According to the invention described in claim 6, calibration can be performed using a pre-mounted pressure sensor without the need to install a special calibration instrument or a separate pressure sensor. Short description of the drawings Fig. 1 (a) is a circuit diagram illustrating an embodiment of a control calibration device of a variable capacity pump according to the present invention, and (b) is a circuit diagram for monitoring a flow rate in a calibration mode. Fig. Figure 2 is a graph showing the current-flow characteristic of a variable capacity pump controlled by the same variable capacity pump calibration device. Fig. 3 (a) is a flowchart showing a calibration program of the control calibration device of the same variable capacity pump, (b) is a diagram showing the changes in the current value in the calibration program of the same control calibration device of a variable capacity pump, and (c) is a diagram showing the changes in the detection pressure at the flow rate sensor according to (b). Detailed description of the best mode for carrying out the invention

[0024] Embodiments of the present invention will be described below with reference to the drawings.

[0025] Fig. 1 (a) illustrates a part of the hydraulic circuit 1, that is, for example, a fluid pressure control circuit mounted on a working machine.

[0026] In this work machine, a variable capacity pump 3 (hereinafter referred to as pump 3), which is a fluid pressure pump driven by the vehicle-mounted engine 2, supplies hydraulic oil of the working fluid in the tank 4 to a plurality of directional control valves provided integrally 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 directional control valves, and supplies the hydraulic oil to a plurality of fluid pressure actuators such as a hydraulic motor and a hydraulic cylinder, respectively.

[0027] In such a hydraulic circuit 1, various control valves are operated in accordance with an operation amount of the operating device 6, such as a lever or a pedal.

[0028] A signal corresponding to the operation amount of the operation device 6 is input to an input side of the control device 10, and the discharge amount of the hydraulic oil by the pump 3 is controlled in accordance with a current value of a flow rate command signal output from the control device 10 based on the input signal.

[0029] In other words, the pump 3 is a current-controlled type, and the capacity-variable means such as a swash plate is controlled by a controller 3a operated by a solenoid valve (electromagnetic proportional valve) receiving a command signal output from the control device 10, so that the capacity-variable means can be adjusted according to the load from the minimum flow rate at no load.

[0030] The control device 10 controls the swash plate inclination angle of the pump 3 by activating the controller 3a via the solenoid valve with a command signal corresponding to the target discharge rate of the pump 3.

[0031] Accordingly, the control device 10 has a control table (current-flow characteristic (IQ characteristic)) that controls a relationship between the target discharge rate of the pump 3 and the current value of the preset specification (the 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 control device 10.

[0032] In this case, it would be ideal if the pump 3 would linearly increase or decrease the flow rate with respect to the increase or decrease of the current value in the sense of the current-flow characteristic, but in practice, due to manufacturing errors, a hysteresis occurs between the increase and decrease of the current value for the flow rate command, as shown by the arrows in Fig. 2 is displayed, and the actual deviation from ideal operation is large.

[0033] Accordingly, in the present embodiment, the control device 10 has a calibration mode for calibrating (adjusting) the control table, in other words, the control of the pump 3, based on the measured values ​​for each pump 3, in order to ensure the control accuracy during actual operation.

[0034] Normally, calibration mode is executed when leaving the factory by activating the mode.

[0035] To perform the calibration in the calibration mode, a control device 10 and a flow sensor 11 that detects the delivery flow rate of the pump 3 are used in the present embodiment.

[0036] Preferably, the flow sensor 11 uses a pressure sensor that detects the discharge pressure of the pump 3.

[0037] In other words, the flow sensor 11 is a pressure sensor for flow measurement that measures the flow rate based on a fixed predetermined throttling condition of the hydraulic circuit 1 or a fixed predetermined engine speed or a pump rpm, wherein the discharge flow rate of the pump 3 is linked to the discharge pressure.

[0038] The flow sensor 11 is connected to the pump discharge channel 5, and its output signal is connected to the input side of the control device 10.

[0039] Note that in the present embodiment, the flow rate sensor 11 is installed in the hydraulic circuit 1 as standard to detect the hydraulic power or the hydraulic load for controlling the control valve for normal control, and not specifically for the calibration mode.

[0040] Next, a control calibration procedure of pump 3 is described.

[0041] By setting the calibration mode in the control device 10 by operating a predetermined input means such as an on-board monitor, the control device 10 executes a calibration program.

[0042] In summary, it can be said that, firstly, as in Fig. 1 (b), in a circuit for executing a calibration program in which the pump discharge channel 5 is directly connected to the tank 4 via a discharge port (orifice) 15, the control device 10 monitors the discharge pressure of the pump 3 through the flow 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 sensor 11 is saturated (saturated) as the first current value Imax corresponding to the maximum flow rate Qmax.

[0043] Similarly, the control device 10 monitors the discharge pressure of the pump 3 through the flow rate sensor 11 while decreasing 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 is saturated (saturated) as a second current value Imin corresponding to the minimum flow rate Qmin.

[0044] Further, according to the specification of the pump 3, a fixed current value Qmid corresponding to the fixed flow rate Qmid is inputted or stored in advance in the control device 10 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.

[0045] That is, in the present embodiment, the fixed flow rate Qmid is a flow rate (Qmin < Qmid < Qmax) that is larger than the minimum flow rate Qmin and smaller than the maximum flow rate Qmax.

[0046] 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 pump 3 and are detected or provided for each pump 3 by an output control performed only by the manufacturer of pump 3.

[0047] Then, as in Fig. 2, on a coordinate plane in which 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 speaking, the quadratic function formula f passing through three points is uniquely determined) can be obtained through three points: point P1 (Imax, Qmax), point P2 (Imin, Qmin) and point P3 (Imid, Qmid), and the quadratic function formula f is stored (set) in a non-volatile memory as a control table.

[0048] By executing the calibration program on the control device 10, these sequences of processes are performed automatically.

[0049] The operations in the calibration mode are described with reference to Fig. 3 (a) to 3 (c) are described in detail.

[0050] First, in step S1, the control device 10 forms a circuit for executing the calibration program, which connects the pump discharge channel 5 directly to the tank 4 via the opening 15 installed as standard in the hydraulic circuit 1 by outputting a command signal to a valve or the like installed in the hydraulic circuit 1 ( Fig. 1 (b)).

[0051] Then, in step S2, the control device 10 increases the current value I for the flow rate command from a small current value such as 0.

[0052] The increase of the current value I can be increased sequentially (linearly), as in Fig. 3 (b), or can be increased step by step by a predetermined current.

[0053] In step S3, the flow rate is monitored by measuring the discharge pressure P of pump 3 ( Fig. 3 (c)) using the flow sensor 11.

[0054] In step S4 it is then determined whether the discharge pressure P has increased or not.

[0055] If it is determined in step S4 that the discharge pressure P has increased, the process returns to step S2, and if 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 stored or inputted for each pump 3 in advance, and in step S5, the current value at that time is stored as the first current value Imax.

[0056] In step S6, the control device 10 then reduces the value of the current I for the flow rate command.

[0057] The reduction of the current value I can be reduced sequentially (linearly), as in Fig. 3 (b), or can be gradually reduced by a predetermined current.

[0058] In step S7, the flow rate is monitored by measuring the discharge pressure P of pump 3 ( Fig. 3 (c)) using the flow sensor 11.

[0059] In step S8 it is then determined whether the discharge pressure P has fallen or not.

[0060] If it is determined in step S8 that the discharge pressure P has dropped, the process returns to step S6, and if it is determined in step S8 that the discharge pressure P has not dropped, it is determined that the flow rate of the pump 3 has reached the minimum flow rate Qmin stored or inputted for each pump 3 in advance, and in step S9, the current value at that time is stored as the second current value Imin.

[0061] Note that steps S2 to S5 and steps S6 to S9 can be performed in reverse order.

[0062] Furthermore, in step S10, from 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 fixed current value Imid corresponding to the fixed flow rate Qmid based on the specifications of the pump 3 stored or input in advance, a quadratic function formula f for the flow control of the pump 3 is obtained in a coordinate plane, where the current value is taken as the x-axis and the flow rate is taken as the y-axis.

[0063] If the formula of the quadratic function f passing through the three points (x1, y1), (x2, y2) and (x3, y3) in the coordinate plane is y = ax2 + bx + c (where a, b and c are each real numbers), a, b and c are determined by the following formulas, respectively: 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⋅x12−b⋅x1

[0064] Therefore, by substituting the current values ​​Imax, Imin and Imid into x1, x2 and x3 of the above formulas and by substituting the flow rates Qmax, Qmin and Qmid into y1, y2 and y3 respectively, a specific quadratic function formula f can be obtained.

[0065] Then, in step S11, the quadratic function formula f obtained in step S10 is stored in the non-volatile memory as a characteristic table, and the calibration program is terminated.

[0066] If a characteristic table or the like based on the standard specifications of Pump 3 is saved in advance in the non-volatile memory, it can be corrected or re-saved.

[0067] Then, in the normal control mode, the control device 10 outputs a command signal that controls the flow rate of the pump 3 based on the characteristic table stored in step S11.

[0068] As described above, by obtaining a quadratic function formula from the first current value for the flow rate command when the maximum flow rate of the pump 3 is measured, the second current value for the flow rate command when the minimum flow rate of the pump 3 is measured, and the fixed current value corresponding to the fixed flow rate based on the specifications of the pump 3, the current-flow characteristic of the pump 3 can be approximated to the actual characteristics of the pump 3, which serves as a current-flow characteristic for the flow rate control of the pump 3, thereby improving the flow control accuracy of the pump 3.

[0069] In addition, since only two data points are obtained through an actual measurement, it is not necessary to measure a large number of points, so calibration is possible in a short time without complicated calculations.

[0070] By taking the current value at which the saturation of the flow rate is measured when the current value for the flow rate command of the pump 3 increases as the first current value and taking the current value at which the saturation of the flow rate is measured when the current value for the flow rate command 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 in the pump 3 which has hysteresis in the current-flow rate characteristic when the current value increases and decreases can be accurately obtained.

[0071] 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 opening condition or a fixed engine rpm condition, the pressure sensor pre-installed in the hydraulic circuit 1 can be used as the flow sensor 11 to perform calibration without having to separately install a special calibration instrument or a sensor.

[0072] Note that in the above embodiment, the accuracy of the quadratic function formula can be further improved by comparing the first current value and the second current value (steps S2 to S9 in FIG.

[0073] 3 (a)) is obtained multiple times and the formula of the quadratic function is found using representative values ​​such as the average value and the most frequent value. Industrial applicability

[0074] The present invention has industrial potential for an entrepreneur who manufactures, sells, or the like a working machine such as a hydraulic excavator equipped with a variable capacity pump. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] JP 2008-303813A

[0008] JP 2014-177969

[0008] JP 2019-190443

[0008] JP 2020-128733A

[0008]

Claims

[1] A variable capacity pump control calibration device for setting a current-flow characteristic curve for flow control of a current-controlled variable capacity pump, the control calibration device comprising: a control device for outputting a current value of a flow rate command of the variable capacity pump; and a flow sensor for measuring the flow rate of the variable capacity pump, wherein the control device has a function of obtaining a quadratic function formula which is a current-flow characteristic of the variable capacity pump for flow control from a first current value when a maximum flow rate of the variable capacity pump is measured by the flow sensor, a second current value when a minimum flow rate of the variable capacity 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 capacity pump. [2] A variable capacity pump control calibration device according to claim 1, wherein the first current value is a current value when the flow sensor measures the saturation of the flow rate at a time when the current value for the flow rate command of the variable capacity pump increases, and the second current value is a current value when the flow sensor measures the saturation of the flow rate at a time when the current value for the flow rate command of the variable capacity pump falls. [3] A variable capacity pump control calibration device according to claim 1 or 2, wherein the flow sensor is a variable capacity pump flow measuring pressure sensor that measures the flow rate based on the flow rate of the variable capacity pump with respect to a discharge pressure under a fixed throttle condition or a fixed speed condition. [4] Variable capacity pump control calibration method that sets a current-flow characteristic for flow control of a current-controlled variable capacity pump, including: Obtaining a quadratic function formula from a first current value for a flow rate command when a maximum flow rate of the variable capacity pump is measured, a second current value for a flow rate command when a minimum flow rate of the variable capacity pump is measured, and a fixed current value corresponding to a fixed flow rate based on a specification of the variable capacity pump. [5] A variable capacity pump control calibration method according to claim 4, wherein the first current value is a current value when the saturation of the flow rate is measured at a time when the current value for the flow rate command of the variable capacity pump increases, and the second current value is a current value when the saturation of the flow rate is measured at a time when the current value for the flow rate command of the variable capacity pump falls. [6] The control calibration method of the variable capacity pump according to claim 4 or 5, wherein the flow rate of the variable capacity pump is measured based on a discharge pressure.

Images