Calibration system for variable displacement hydraulic pumps

Abstract

To provide a calibration system of a variable displacement hydraulic pump capable of improving flow rate control accuracy.SOLUTION: A calibration system 2 of a variable displacement hydraulic pump is equipped with a variable displacement hydraulic pump 4, a regulator 6 that adjusts the capacity of the pump 4 according to an inputted command current, and a controller 8 that outputs the command current to the regulator 6. The controller 8 executes a step of obtaining a first reference table indicating a relationship between the command current to the regulator 6 and the capacity of the pump 4 when the discharge pressure of the pump 4 is a first pressure, a step of obtaining a second reference table indicating a relationship between the command current to the regulator 6 and the capacity of the pump 4 when the discharge pressure of the pump 4 is a second pressure, and a step of obtaining a plurality of correction tables indicating a relationship between the discharge pressure of the pump 4 and the command current to the regulator 6 on the basis of the first reference table and the second reference table.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a calibration system for a variable displacement hydraulic pump including a variable displacement hydraulic pump, a regulator that adjusts the displacement of the pump according to an input command current, and a controller that outputs the command current to the regulator. [Background technology]

[0002] The following Patent Document 1 discloses a calibration system for a variable displacement hydraulic pump whose displacement is controlled based on a command current output from a controller. This system includes a calibration data acquisition means for measuring the pump pressure at each command current while changing the command current output from the controller in multiple steps from a minimum value to a maximum value, and acquiring data on the measured pump pressure corresponding to each command current, a first table creation means for determining a coefficient representing the relationship between the pump pressure and the pump flow rate based on a pump flow rate determined from a pump displacement in specifications at a preset reference command current and the measured pump pressure determined by the calibration data acquisition means, and creating a first table showing the relationship between the coefficient and the pump pressure, a second table creation means for creating a second table showing the relationship between each command current and the measured pump pressure based on the data acquired by the calibration data acquisition means, a third table creation means for converting the measured pump pressure of the second table to a pump flow rate using the coefficient of the first table, and creating a third table showing the relationship between the pump flow rate and the command current, and a pump control table creation means for creating a pump control table showing the relationship between the pump displacement and the command current from the engine speed at the time of pump pressure measurement and the third table, and is characterized in that the pump control table created by the pump control table creation means is used as a calibrated pump control table. According to this system, a pump control table can be created in which the pump displacement value for each command current is calibrated over the entire range of command currents, and the pump control table can be calibrated with high accuracy. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2019-190443 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, the technology disclosed in Patent Document 1 above is based on the premise that the pump's swash plate position varies only slightly with discharge pressure, and there is a problem in that accurate calibration is difficult when the pump's swash plate position varies significantly with discharge pressure.

[0005] In view of the above, an object of the present invention is to provide a calibration system for a variable displacement hydraulic pump that can correct the difference between the target discharge volume of the pump and the actual discharge volume of the pump, thereby improving the accuracy of flow control, even when the swash plate position of the pump varies significantly depending on the discharge pressure. [Means for solving the problem]

[0006] According to the present invention, there is provided a calibration system for a variable displacement hydraulic pump that solves the above-mentioned problems. That is, the calibration system for a variable displacement hydraulic pump includes a variable displacement hydraulic pump, a regulator that adjusts the displacement of the pump according to an input command current, and a controller that outputs a command current to the regulator, in which the controller executes the steps of: determining a first reference table indicating the relationship between a command current to the regulator and the displacement of the pump when the discharge pressure of the pump is a first pressure; determining a second reference table indicating the relationship between a command current to the regulator and the displacement of the pump when the discharge pressure of the pump is a second pressure; and determining a plurality of correction tables indicating the relationship between the discharge pressure of the pump and the command current to the regulator based on the first reference table and the second reference table. and, in the step of obtaining the second reference table, the controller calculates a first displacement and a second displacement of the pump, obtains a first command current at which the displacement of the pump becomes the first displacement, obtains a second command current at which the displacement of the pump becomes the second displacement, and obtains the second reference table based on the first displacement, the second displacement, the first command current, and the second command current. In the step of obtaining the plurality of correction tables, the controller calculates a third displacement corresponding to the first command current using the first reference table, and calculates a first current difference corresponding to a difference between the third displacement and the first displacement, and obtains a first correction table indicating a relationship between a discharge pressure of the pump and a command current to the regulator at which the displacement of the pump is constant at the third displacement, based on the first pressure, the second pressure, the first command current, and the first current difference. A system for calibrating a variable displacement hydraulic pump is provided.

[0007] Preferably, in the step of obtaining the first reference table, the controller calculates a maximum capacity and a minimum capacity of the pump, obtains a maximum command current at which the capacity of the pump becomes the maximum capacity, obtains a minimum command current at which the capacity of the pump becomes the minimum capacity, and obtains the first reference table based on the maximum capacity, the minimum capacity, the maximum command current, and the minimum command current.

[0010] It is preferable that in the step of obtaining the multiple correction tables, the controller uses the first reference table to calculate a fourth displacement corresponding to the second command current, and calculates a second current difference corresponding to the difference between the fourth displacement and the second displacement, and obtains a second correction table indicating the relationship between the discharge pressure of the pump and the command current to the regulator, at which the displacement of the pump is constant at the fourth displacement, based on the first pressure, the second pressure, the second command current, and the second current difference.

[0011] In the step of determining the plurality of correction tables, the controller preferably calculates a correction table other than the first correction table and the second correction table by linear interpolation based on the first correction table and the second correction table. Effect of the Invention

[0012] According to the present invention, by correcting the command current according to a plurality of correction tables showing the relationship between the pump discharge pressure and the command current to the regulator, even when the pump swash plate position varies significantly depending on the discharge pressure, the deviation between the pump's target discharge volume and the pump's actual discharge volume can be corrected, thereby improving the accuracy of flow control. [Brief description of the drawings]

[0013] [Figure 1] 1 is a circuit diagram of a calibration system for a variable displacement hydraulic pump constructed in accordance with the present invention; [Diagram 2] 2 is a flowchart of a calibration method executed by the controller shown in FIG. 1 . [Diagram 3] 2 is a graph showing the relationship between a command current to a regulator shown in FIG. 1 and the displacement of a pump shown in FIG. [Figure 4] 2 is a graph showing the relationship between the discharge pressure of the pump shown in FIG. 1 and the capacity of the pump shown in FIG. [Diagram 5] 2 is a graph showing a plurality of correction tables obtained by the controller shown in FIG. 1; [Figure 6] 6 is a graph showing the relationship between a command current to the regulator shown in FIG. 1 and the slopes of the multiple correction tables shown in FIG. 5; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of a calibration system for a variable displacement hydraulic pump configured according to the present invention will be described with reference to the drawings.

[0015] Explaining with reference to Fig. 1, a calibration system for a variable displacement hydraulic pump (hereinafter referred to as "system 2") generally designated by reference numeral 2 includes a variable displacement hydraulic pump 4 (hereinafter referred to as "pump 4"), a regulator 6 that adjusts the displacement of the pump 4 according to an input command current, and a controller 8 that outputs a command current to the regulator 6. The system 2 can be mounted on a construction machine such as a hydraulic excavator.

[0016] 1, the pump 4 is driven by an engine 10, which is equipped with a revolution speed sensor 12. The engine 10 and the revolution speed sensor 12 are electrically connected to a controller 8, the operation of the engine 10 is controlled by the controller 8, and the revolution speed of the engine 10 detected by the revolution speed sensor 12 is input to the controller 8.

[0017] The pump 4 is connected to a control valve 16 by a pump line 14, and hydraulic oil discharged from the pump 4 is supplied to the control valve 16 via the pump line 14. A pressure sensor 18 is provided in the pump line 14, and the pressure sensor 18 is electrically connected to the controller 8. The discharge pressure of the pump 4 detected by the pressure sensor 18 is input to the controller 8. Note that, in the illustrated embodiment, the pressure sensor 18 is attached to the control valve 16, but the pressure sensor 18 need only be installed on the pump line 14 and does not have to be attached to the control valve 16.

[0018] The control valve 16 is equipped with a plurality of spools 16a, 16b, 16c, and 16d for controlling hydraulic oil supplied to a plurality of hydraulic actuators (not shown), such as hydraulic cylinders and hydraulic motors. The control valve 16 in the illustrated embodiment is provided with a bypass line 22 connected to a hydraulic oil tank 20, and a variable throttle spool 24 is disposed in the bypass line 22.

[0019] A solenoid 24a is attached to the variable throttle spool 24, which adjusts the throttle opening (cross-sectional area of ​​the throttle) of the variable throttle spool 24 in response to an input drive current. The solenoid 24a is electrically connected to the controller 8, and a drive current is input from the controller 8 to the solenoid 24a. For convenience, the control valve 16 in Fig. 1 shows spools 16a-16d and the variable throttle spool 24, but appropriate hydraulic members such as spools other than the spools 16a-16d and the variable throttle spool 24 and relief valves may be attached.

[0020] The regulator 6 includes a piston rod 26 connected to the swash plate 4a of the pump 4, and a solenoid valve 28 that operates the piston rod 26. The solenoid valve 28 has a solenoid 28a that operates the piston rod 26 in response to an input command current. The solenoid 28a is electrically connected to the controller 8, and a command current is input from the controller 8 to the solenoid 28a.

[0021] In the regulator 6, the piston rod 26 is operated to control the inclination of the swash plate 4a of the pump 4 so that the capacity of the pump 4 is increased as the command current from the controller 8 increases, and the capacity of the pump 4 is decreased as the command current from the controller 8 decreases. As shown in FIG. 1, an orifice 30 is provided between the regulator 6 and the hydraulic oil tank 20. When the solenoid 28a is not excited, the discharge pressure of the pump 4 is input to the spring chamber 6a of the regulator 6 as a control signal, and the piston rod 26 is operated according to the discharge pressure of the pump 4, thereby controlling the swash plate 4a of the pump 4. On the other hand, when the solenoid 28a is excited, the solenoid valve 28 on the left side of FIG. 1 is operated to connect the port 28b to the port 28c. Then, most of the hydraulic oil that has passed through the spring chamber 6a returns to the hydraulic oil tank 20 without passing through the orifice 30. The pump 4 is provided with a limiting means (not shown) for limiting the inclination of the swash plate 4a to a predetermined range.

[0022] The controller 8 is composed of a computer including a processor that performs calculations according to a control program and a memory that stores the control program, calculation results, etc., and is configured to control the operation of the system 2. For example, the controller 8 adjusts the inclination of the swash plate 4a of the pump 4 by increasing or decreasing the command current output to the solenoid 28a of the regulator 6 to control the capacity of the pump 4, and adjusts the throttle opening of the variable throttle spool 24 by increasing or decreasing the drive current output to the solenoid 24a of the variable throttle spool 24. The controller 8 also adjusts the throttle opening of the variable throttle spool 24 and the rotation speed of the engine 10 to control the discharge pressure of the pump 4.

[0023] Next, a method for calibrating the pump 4 executed by the controller 8 in the system 2 described above will be described.

[0024] As shown in FIG. 2, the controller 8 first executes step S1 to obtain a first reference table indicating the relationship between the command current to the regulator 6 and the displacement of the pump 4 when the discharge pressure of the pump 4 is a first pressure.

[0025] In step S1, first, the engine 10 is rotated at a relatively high rotation speed N h and the cross-sectional area of ​​the throttle of the variable throttle spool 24 is relatively small, that is, the cross-sectional area A l and the capacity q of the pump 4 when the discharge pressure of the pump 4 is the relatively low first pressure P1. a is calculated using the following formulas (1) and (2). Note that the following formulas (1) and (2) are stored in the controller 8 in advance.

[0026]

number

number

[0027] In the above formula (1), Q is the discharge volume of the pump 4, α is a coefficient, A is the cross-sectional area of ​​the throttle of the variable throttle spool 24, and P P is the discharge pressure (pump pressure) of pump 4, P T is the pressure of the hydraulic oil in the hydraulic oil tank 20 (tank pressure), and ρ is the viscosity of the hydraulic oil. In addition, in the above formula (2), q is the capacity of the pump 4, and N is the rotation speed of the engine 10.

[0028] The coefficient α and the viscosity ρ of the hydraulic oil are fixed values, and it is possible to use appropriate values ​​that are previously stored in the controller 8. The cross-sectional area A of the throttle can be determined from a table (not shown, but a table previously stored in the controller 8) that indicates the relationship between the drive current output from the controller 8 to the solenoid 24a of the variable throttle spool 24 and the cross-sectional area A of the throttle.

[0029] The engine speed N of the engine 10 may be determined based on a command from the controller 8, or may be determined based on the engine speed detected by the engine speed sensor 12. P The tank pressure P is detected by the pressure sensor 18. T A fixed value stored in advance in the controller 8 may be used, or a tank pressure sensor (not shown) that measures the tank pressure may be provided in the system 2, and the tank pressure detected by the tank pressure sensor may be used.

[0030] Pump 4 capacity q a After calculating, the engine 10 speed is set to N h and the cross-sectional area of ​​the throttle of the variable throttle spool 24 is set to A l Then, while changing the command current to the solenoid 28a of the solenoid valve 28 of the regulator 6, the transition of the discharge pressure of the pump 4 is measured by the pressure sensor 18, and the command current I a Calculate the command current I a is the discharge pressure of the pump 4 is the first pressure P1, and the rotation speed of the engine 10 is N h , the cross-sectional area of ​​the throttle of the variable throttle spool 24 is A l In the case where the capacity of pump 4 is q a This is the command current.

[0031] Pump 4 capacity q a and the command current I a When calculating, the maximum capacity q of pump 4 is max The maximum command current I max As described above, the pump 4 is provided with a limiting means for limiting the inclination of the swash plate 4a to a predetermined range, so that the capacity of the pump 4 is limited to the maximum capacity q max Since the stable value is reached when max can be determined with high accuracy.

[0032] Command current I a After calculating, the engine speed of engine 10 is N h Lower rotation speed Nl (N l <N h ) and the cross-sectional area of ​​the throttle of the variable throttle spool 24 is A l Cross-sectional area A is larger than h (A h >A l ) and the capacity q of the pump 4 when the discharge pressure of the pump 4 is the first pressure P1 b is calculated using the above formulas (1) and (2).

[0033] Pump 4 capacity q b After calculating, the engine 10 speed is set to N l and the cross-sectional area of ​​the throttle of the variable throttle spool 24 is set to A h After setting the pressure sensor 18 to the first pressure P1, the pressure sensor 18 measures the change in the discharge pressure of the pump 4 while changing the command current to the regulator 6. b Calculate the command current I b is the discharge pressure of the pump 4 is the first pressure P1, and the rotation speed of the engine 10 is N l , the cross-sectional area of ​​the throttle of the variable throttle spool 24 is A h In the case where the capacity of pump 4 is q b This is the command current.

[0034] Pump 4 capacity q b and the command current I b When calculating, the minimum capacity q of pump 4 is min The minimum command current I min As described above, the pump 4 is provided with a limiting means for limiting the inclination of the swash plate 4a to a predetermined range, so that the capacity of the pump 4 is limited to a minimum capacity q min Since the minimum command current I min can be determined with high accuracy.

[0035] Command current I b After calculating the capacitance q a , q b and the command current I a , I bIn the illustrated embodiment, the first reference table is determined based on the maximum capacity q max , minimum capacitance q min , maximum command current I max and the minimum command current I min An example of obtaining the first reference table based on the above will be described.

[0036] As shown in FIG. 3, the horizontal axis represents the command current I to the regulator 6, the vertical axis represents the capacity q of the pump 4, and the maximum command current I max and maximum capacity q max and the minimum command current I min and the minimum capacitance q min This linearly connects the point B specified by the first pressure P1 to the point B specified by the first pressure P2. This creates a first reference table T P1 can be sought.

[0037] In step S1 of the illustrated embodiment, first, the capacitance q a (q max ) and then calculate the command current I a (I max ) and then calculate the capacity q b (q min ) is calculated, and then the command current I b (I min ), but the order in which the capacity is calculated and the command current is calculated can be arbitrary.

[0038] First reference table T P1 After executing step S1 for obtaining the second reference table, as shown in FIG. 2, step S2 is executed for obtaining a second reference table indicating the relationship between the command current to the regulator 6 and the capacity of the pump 4 when the discharge pressure of the pump 4 is the second pressure.

[0039] In step S2, first, the rotation speed of the engine 10 is set to N l and the cross-sectional area of ​​the throttle of the variable throttle spool 24 is A lThe capacity (first capacity q1) of the pump 4 when the discharge pressure of the pump 4 is the second pressure P2 (P2>P1) higher than the first pressure P1 is calculated using the above formulas (1) and (2). As shown in FIG. 3, the first capacity q1 is calculated as the minimum capacity q min and maximum capacity q max The capacity between (q min <q1<q max ).

[0040] After calculating the first capacity q1, the rotation speed of the engine 10 is set to N l and the cross-sectional area of ​​the throttle of the variable throttle spool 24 is set to A l After setting the value at the time of the first command current I1, the pressure sensor 18 measures the change in the discharge pressure of the pump 4 while changing the command current to the regulator 6, and determines the first command current I1 at which the discharge pressure of the pump 4 becomes the second pressure P2. l , the cross-sectional area of ​​the throttle of the variable throttle spool 24 is A l When the displacement of the pump 4 is the first displacement q1, the first command current I1 is a command current that is equal to the minimum command current I min and maximum command current I max is the current value between min <I1<I max ).

[0041] After the first command current I1 is calculated, the rotation speed of the engine 10 is set to N h and the cross-sectional area of ​​the throttle of the variable throttle spool 24 is A h The capacity of the pump 4 (second capacity q2) when the discharge pressure of the pump 4 is the second pressure P2 is calculated using the above formulas (1) and (2). As shown in FIG. 3, the second capacity q2 is calculated by multiplying the first capacity q1 by the maximum capacity q max The capacitance between <q2<q max ).

[0042] After calculating the second capacity q2, the rotation speed of the engine 10 is set to N h and the cross-sectional area of ​​the throttle of the variable throttle spool 24 is set to A hAfter setting the value at the time of the second command current I2, the pressure sensor 18 measures the change in the discharge pressure of the pump 4 while changing the command current to the regulator 6, and determines the second command current I2 at which the discharge pressure of the pump 4 becomes the second pressure P2. h , the cross-sectional area of ​​the throttle of the variable throttle spool 24 is A h When the displacement of the pump 4 is equal to the second displacement q2, the second command current I2 is the sum of the first command current I1 and the maximum command current I max The current value between (I1 <I2<I max ).

[0043] After the second command current I2 is calculated, a second reference table is calculated based on the first capacity q1, the second capacity q2, the first command current I1, and the second command current I2. Specifically, as shown in Fig. 3, the command current I to the regulator 6 is plotted on the horizontal axis, and the capacity q of the pump 4 is plotted on the vertical axis, and a point C specified by the first command current I1 and the first capacity q1 is connected to a point D specified by the second command current I2 and the second capacity q2 in a linear function. This produces a second reference table T which shows the relationship between the command current I to the regulator 6 and the capacity q of the pump 4 when the discharge pressure of the pump 4 is the second pressure P2. P2 can be sought.

[0044] In step S2 of the illustrated embodiment, first, the first capacity q1 is calculated, then the first command current I1 is obtained, then the second capacity q2 is calculated, and then the second command current I2 is obtained. However, the order in which the capacities are calculated and the command currents are obtained may be arbitrary.

[0045] Second reference table T P2 After performing step S2 to obtain the first reference table T P1 and a second reference table T P2 Based on the above, step S3 is executed to obtain a plurality of correction tables showing the relationship between the discharge pressure of the pump 4 and the command current to the regulator 6.

[0046] In step S3, first, the first reference table T shown in FIG. P1 A third displacement q3 corresponding to the first command current I1 is calculated using the above equation. As can be understood by referring to Fig. 3, the third displacement q3 is the displacement of the pump 4 related to point E, and is larger than the first displacement q1 when the first command current I1 is input to the regulator 6 in a case where the discharge pressure of the pump 4 is the second pressure P2 (q3>q1).

[0047] FIG. 4 shows a table T in which the horizontal axis represents the discharge pressure P of the pump 4 and the vertical axis represents the capacity q of the pump 4, and a point E' (corresponding to point E in FIG. 3) determined by the first pressure P1 and the third capacity q3 and a point C' (corresponding to point C in FIG. 3) determined by the second pressure P2 and the first capacity q1 are linearly connected. I1 Table T I1 4 shows the relationship between the discharge pressure P of the pump 4 and the capacity q of the pump 4 when the command current to the regulator 6 is constant at the first command current I1.

[0048] Table T I1 As can be understood by referring to the above, in system 2, when the discharge pressure of pump 4 is the first pressure P1 and the command current to regulator 6 is set to the first command current I1, the capacity of pump 4 (third capacity q3) is different from the capacity of pump 4 (first capacity q1) when the discharge pressure of pump 4 is the second pressure P2 and the command current to regulator 6 is set to the first command current I1.

[0049] That is, in the system 2, even if the command current to the regulator 6 is the same as the first command current I1, when the discharge pressure of the pump 4 increases from the first pressure P1 to the second pressure P2, the capacity of the pump 4 is reduced from the third capacity q3 to the first capacity q1, and the power is reduced as the discharge pressure of the pump 4 increases. Therefore, in the system 2, if the discharge pressure of the pump 4 differs, the capacity of the pump 4 differs even with the same command current, and therefore, unless correction is made, a discrepancy will occur between the target discharge amount of the pump 4 and the actual discharge amount of the pump 4 depending on the discharge pressure of the pump 4.

[0050] Continuing with the explanation with reference to FIG. 3, after the third capacitance q3 is calculated, the first reference table T P1 A first current difference ΔI1 corresponding to the difference between the third capacity q3 and the first capacity q1 is calculated using the above equation. A value I1+ΔI1 obtained by adding the first current difference ΔI1 to the first command current I1 is a command current at which the capacity of the pump 4 becomes the third capacity q3 when the discharge pressure of the pump 4 is the second pressure P2.

[0051] After calculating the first current difference ΔI1, a first correction table is obtained based on the first pressure P1, the second pressure P2, the first command current I1, and the first current difference ΔI1, which indicates the relationship between the discharge pressure of the pump 4 and the command current to the regulator 6, at which the capacity of the pump 4 becomes constant at the third capacity q3.

[0052] Specifically, as shown in FIG. 5, the horizontal axis represents the discharge pressure P of the pump 4, the vertical axis represents the command current I to the regulator 6, and the vertical axis represents a point E″ (corresponding to point E in FIG. 3 and point E′ in FIG. 4) determined by the first pressure P1 and the first command current I1, and a correction point C determined by the value I1+ΔI1 obtained by adding the first command current I1 to the first current difference ΔI1 and the second pressure P2. C The first correction table T q3 can be sought.

[0053] When the first command current I1 is output to the regulator 6, a first current difference ΔI1 to be added to the first command current I1 is calculated based on a first correction table T q3 The command current to the regulator 6 is corrected by adjusting the displacement of the pump 4 according to the above. As a result, the displacement of the pump 4 can be set to the third displacement q3 regardless of the discharge pressure of the pump 4, and power down does not occur even if the discharge pressure of the pump 4 increases. As can be understood by referring to Fig. 5, ΔI1 = 0 at the first pressure P1, and ΔI1 becomes a negative value when the discharge pressure of the pump 4 becomes lower than the first pressure P1, and ΔI1 becomes a positive value when the discharge pressure of the pump 4 becomes higher than the first pressure P1.

[0054] First correction table T q3 After obtaining the above, the first reference table T P1 3, the fourth capacity q4 corresponding to the second command current I2 is calculated. The fourth capacity q4 is the capacity of the pump 4 related to point F, and is larger than the second capacity q2 when the second command current I2 is input to the regulator 6 in the case where the discharge pressure of the pump 4 is the second pressure P2 (q4>q2).

[0055] FIG. 4 shows a table T that linearly connects a point F' (corresponding to point F in FIG. 3) determined by the first pressure P1 and the fourth capacitance q4 and a point D' (corresponding to point D in FIG. 3) determined by the second pressure P2 and the second capacitance q2. I2 Table T is also shown. I2 4 shows the relationship between the discharge pressure P of the pump 4 and the displacement of the pump 4 when the command current to the regulator 6 is constant at the second command current I2.

[0056] Table T I2As can be understood by referring to Table T, in the system 2, when the discharge pressure of the pump 4 is the first pressure P1 and the command current to the regulator 6 is the second command current I2, the capacity of the pump 4 (fourth capacity q4) is different from the capacity of the pump 4 (second capacity q2) when the discharge pressure of the pump 4 is the second pressure P2 and the command current to the regulator 6 is the second command current I2. I1 In the system 2, even if the command current to the regulator 6 is the same as the second command current I2, when the discharge pressure of the pump 4 increases from the first pressure P1 to the second pressure P2, the capacity of the pump 4 is reduced from the fourth capacity q4 to the second capacity q2.

[0057] Continuing with the explanation with reference to FIG. 3, after the fourth capacitance q4 is calculated, the first reference table T P1 A second current difference ΔI2 corresponding to the difference between the fourth capacity q4 and the second capacity q2 is calculated using the above formula: A value I2+ΔI2 obtained by adding the second current difference ΔI2 to the second command current I2 is a command current at which the capacity of the pump 4 becomes the fourth capacity q4 when the discharge pressure of the pump 4 is the second pressure P2.

[0058] After calculating the second current difference ΔI2, a second correction table is obtained based on the first pressure P1, the second pressure P2, the second command current I2, and the second current difference ΔI2, which indicates the relationship between the discharge pressure of the pump 4 and the command current to the regulator 6, at which the capacity of the pump 4 becomes constant at the fourth capacity q4.

[0059] Specifically, as shown in FIG. 5, a point F″ (corresponding to point F in FIG. 3 and point F′ in FIG. 4) determined by the first pressure P1 and the second command current I2, and a correction point D determined by the second pressure P2 and a value I2+ΔI2 obtained by adding the second command current I2 to the second current difference ΔI2 are C The second correction table T q4 can be sought.

[0060] When the second command current I2 is output to the regulator 6, a second current difference ΔI2 to be added to the second command current I2 is calculated based on the second correction table T q4 The command current to the regulator 6 is corrected by adjusting the discharge pressure of the pump 4 according to the above. As a result, the capacity of the pump 4 can be set to the fourth capacity q4 regardless of the discharge pressure of the pump 4, and power down does not occur even if the discharge pressure of the pump 4 increases. As can be understood by referring to Fig. 5, ΔI2 = 0 at the second pressure P2, and ΔI2 becomes a negative value when the discharge pressure of the pump 4 is lower than the second pressure P2, and ΔI2 becomes a positive value when the discharge pressure of the pump 4 is higher than the second pressure P2.

[0061] Second correction table T q4 After obtaining the first correction table T q3 and the second correction table T q4 Based on the above, a first correction table T q3 and the second correction table T q4 The other correction tables are calculated by linear interpolation.

[0062] Explaining this with reference to FIG. 6, the command current I to the regulator 6 is plotted on the horizontal axis, and the slope g of the correction table shown in FIG. 5 is plotted on the vertical axis. The first command current I1 and the first correction table T q3 A point H specified by the slope g1 of the second command current I2 and the second correction table T q4 A gradient table T is created by linearly connecting the point J specified by the gradient g2 of the correction table and the command current I to the regulator 6, which indicates the relationship between the gradient g of the correction table. g Then, the tilt table T g The first correction table T q3 and the second correction table T q4 Calculate the other correction table.

[0063] For example, the tilt table T shown in Figure 6 g According to the above, the command current to the regulator 6 is an arbitrary command current I that is smaller than the first command current I1.m In the case of, the slope of the correction table is less than the slope g1 of the first correction table T q3 and is a slope g m (g m < g1), and using this slope g m , the correction table T shown in FIG. 5 qm can be calculated. The correction table T qm is a table showing the relationship between the discharge pressure of the pump 4 when the capacity of the pump 4 is constant at the capacity q m and the command current to the regulator 6.

[0064] Also, according to the slope table T shown in FIG. 6 g , in the case where the command current to the regulator 6 is any command current I greater than the second command current I2 n , the slope of the correction table is greater than the slope g2 of the second correction table T q4 and is a slope g n (g n > g2), and using this slope g n , the correction table T shown in FIG. 5 qn can be obtained. The correction table T qn is a table showing the relationship between the discharge pressure of the pump 4 when the capacity of the pump 4 is constant at the capacity q n and the command current to the regulator 6.

[0065] In this way, by using the slope table T shown in FIG. 6 g and calculating a plurality of slopes in the case where the command current to the regulator 6 is a command current other than the first and second command currents I1 and I2, a plurality of correction tables other than the first and second correction tables T q3 , T q4 can be calculated.

[0066] As described above, according to the illustrated embodiment of the system 2, by correcting the command current according to a plurality of correction tables showing the relationship between the discharge pressure of the pump 4 and the command current to the regulator 6, even when the swash plate position of the pump 4 varies significantly depending on the discharge pressure (i.e., the capacity of the pump 4 varies significantly), the deviation between the target discharge amount of the pump 4 and the actual discharge amount of the pump 4 can be corrected, thereby improving the accuracy of flow rate control. P1 and a second reference table T P2 Since a plurality of correction tables can be calculated based on the above, the number of times the discharge pressure and command current of the pump 4 are calculated can be reduced, and calibration can be performed in a short time. [Explanation of symbols]

[0067] 2: Calibration system for variable displacement hydraulic pumps 4: Variable displacement hydraulic pump 6: Regulator 8: Controller P1: First pressure P2: Second pressure T P1 :First reference table T P2 : Second reference table T q3 : First correction table T q4 : Second correction table T qm :Other correction tables T qn :Other correction tables q max :Maximum capacity q min :Minimum capacity q1: first capacity Q2: Second capacity Q3:Third capacity Q4: The fourth capacity I max :Maximum command current I min :Minimum command current I1: First command current I2: Second command current ΔI1: First current difference ΔI2: Second current difference

Claims

1. A calibration system for a variable displacement hydraulic pump comprising: a variable displacement hydraulic pump; a regulator that adjusts the displacement of the pump in response to an input command current; and a controller that outputs a command current to the regulator, The controller: obtaining a first reference table indicating a relationship between a command current to the regulator and a displacement of the pump when a discharge pressure of the pump is a first pressure; obtaining a second reference table indicating a relationship between a command current to the regulator and a displacement of the pump when a discharge pressure of the pump is a second pressure; determining a plurality of correction tables indicating a relationship between a discharge pressure of the pump and a command current to the regulator based on the first reference table and the second reference table; In the step of obtaining the second reference table, the controller Calculating a first displacement and a second displacement of the pump; determining a first command current at which the displacement of the pump becomes the first displacement; determining a second command current at which the displacement of the pump becomes the second displacement; determining the second reference table based on the first capacity, the second capacity, the first command current, and the second command current; In the step of obtaining the plurality of correction tables, the controller calculating a third capacity corresponding to the first command current using the first reference table, and calculating a first current difference corresponding to a difference between the third capacity and the first capacity; A calibration system for a variable displacement hydraulic pump that determines a first correction table indicating a relationship between a discharge pressure of the pump and a command current to the regulator, at which the displacement of the pump becomes constant at the third displacement, based on the first pressure, the second pressure, the first command current, and the first current difference.

2. In the step of obtaining the first reference table, the controller Calculating the maximum and minimum displacements of the pump; A maximum command current at which the displacement of the pump becomes the maximum displacement is obtained; A minimum command current at which the displacement of the pump becomes the minimum displacement is obtained; 2. The calibration system for a variable displacement hydraulic pump according to claim 1, wherein the first reference table is determined based on the maximum displacement, the minimum displacement, the maximum command current, and the minimum command current.

3. In the step of obtaining the plurality of correction tables, the controller calculating a fourth capacity corresponding to the second command current using the first reference table, and calculating a second current difference corresponding to a difference between the fourth capacity and the second capacity; 2. The calibration system for a variable displacement hydraulic pump according to claim 1, further comprising: a second correction table that indicates a relationship between a discharge pressure of the pump and a command current to the regulator, at which the displacement of the pump becomes constant at the fourth displacement, based on the first pressure, the second pressure, the second command current, and the second current difference.

4. In the step of obtaining the plurality of correction tables, the controller 4. The calibration system for a variable displacement hydraulic pump according to claim 3, wherein a correction table other than the first correction table and the second correction table is calculated by linear interpolation based on the first correction table and the second correction table.

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