Calibration method for variable capacity hydraulic pumps

Abstract

Problem: Provide a calibration system for a variable capacity hydraulic pump that can improve the accuracy of flow rate control. Solution: A calibration system (2) for a variable capacity hydraulic pump includes a variable capacity hydraulic pump (4); a regulator (6) configured to adjust the capacity of the pump (4) proportionally to an input command current; and a controller (8) configured to output a command current to the regulator (6). The controller (8) is configured to perform the following steps: when the discharge pressure of the pump (4) is set to a first pressure, determine a first reference table representing 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 set to a second pressure, determine a second reference table representing the relationship between the command current to the regulator (6) and the capacity of the pump (4); and determine multiple calibration tables representing the relationship between the discharge pressure of the pump (4) and the command current to the regulator (6) based on the first and second reference tables.

Description

Technical Field

[0001] The present invention relates to a calibration system for a variable capacity hydraulic pump, comprising a variable capacity hydraulic pump; a regulator configured to adjust the pump capacity proportionally to an input command current; and a controller configured to output a command current to the regulator. Background Technology

[0002] Patent document 1 mentioned below discloses a calibration system for a variable capacity hydraulic pump, the capacity of which is controlled based on a command current output from a controller. The system includes a calibration data acquisition device for acquiring measured pump pressure data corresponding to each command current by measuring the pump pressure in each command current as it is changed from a minimum to a maximum value in a multi-step manner from a command current output from the controller; a first table generation device for generating a first table representing the relationship between coefficients and pump pressure by calculating coefficients representing the relationship between pump flow rate determined by a pump capacity based on a specification at a preset reference command current and the measured pump pressure determined by the calibration data acquisition device; a second table generation device for generating a second table representing the relationship between each command current and the measured pump pressure based on data acquired by the calibration data acquisition device; a third table generation device for generating a third table representing the relationship between pump flow rate and command current by converting the measured pump pressure in the second table into pump flow rate using coefficients in the first table; and a pump control table generation device for generating a pump control table representing the relationship between pump capacity and command current from engine speed during pump pressure measurement, as well as the third table; wherein the pump control table generated by the pump control table generation device is used as a calibrated pump control table. Then, using this system, a pump control table can be generated, in which the value of the pump capacity relative to each command current is calibrated over the entire range of the command current, and thus the calibration of the pump control table can be performed with high precision.

[0003] Existing technical documents

[0004] [Patent Literature]

[0005] Patent Document 1: Japanese Patent Application No. 2019-190443 Summary of the Invention

[0006] [The problem this invention aims to solve]

[0007] However, in the technology disclosed in the aforementioned Patent Document 1, the pump is based on small fluctuations in the position of the rotating swashplate according to the discharge pressure, thus there is a problem that it is difficult to perform accurate calibration when the position of the rotating swashplate of the pump fluctuates significantly according to the discharge pressure.

[0008] In view of the above facts, even though the position of the pump's swashplate fluctuates significantly depending on the discharge pressure, the object of the present invention is to correct the deviation between the pump's target discharge rate and the pump's actual discharge rate, and to provide a calibration system for a variable capacity hydraulic pump that can improve the accuracy of flow rate control.

[0009] [Problem-solving methods]

[0010] According to the present invention, a calibration system for a variable capacity hydraulic pump is provided to address the problem mentioned above. Specifically, a calibration system for a variable capacity hydraulic pump is provided, comprising: a variable capacity hydraulic pump; a regulator configured to adjust the pump capacity proportionally to an input command current; and a controller configured to output a command current to the regulator, wherein the controller is configured to perform the following steps: when the pump discharge pressure is set to a first pressure, determining a first reference table representing the relationship between the command current to the regulator and the pump capacity; when the pump discharge pressure is set to a second pressure, determining a second reference table representing the relationship between the command current to the regulator and the pump capacity; and determining a plurality of calibration tables representing the relationship between the pump discharge pressure and the command current to the regulator based on the first and second reference tables.

[0011] Preferably, in the step of determining the first reference table, the controller calculates the maximum capacity and minimum capacity of the pump, determines the maximum command current when the pump capacity becomes the maximum capacity, determines the minimum command current when the pump capacity becomes the minimum capacity, and determines the first reference table based on the maximum capacity, minimum capacity, maximum command current, and minimum command current.

[0012] Preferably, in the step of determining the second reference table, the controller calculates the first capacity and the second capacity of the pump, determines the first command current when the pump capacity changes to the first capacity, determines the second command current when the pump capacity changes to the second capacity, and determines the second reference table based on the first capacity, the second capacity, the first command current and the second command current.

[0013] Preferably, in the step of determining multiple calibration tables, the controller calculates a third capacity corresponding to the first command current, calculates a first current difference corresponding to the difference between the third capacity and the first capacity using a first reference table, and determines a first calibration table based on the first pressure, the second pressure, the first command current, and the first current difference, which represents the relationship between the pump discharge pressure and the command current to the regulator when the pump capacity becomes constant at the third capacity.

[0014] Preferably, in the step of determining multiple calibration tables, the controller calculates a fourth capacity corresponding to the second command current, calculates a second current difference corresponding to the difference between the fourth capacity and the second capacity using a first reference table, and determines a second calibration table based on the first pressure, the second pressure, the second command current, and the second current difference, which represents the relationship between the pump discharge pressure and the command current to the regulator when the pump capacity becomes constant at the fourth capacity.

[0015] Preferably, in the step of determining multiple calibration tables, the controller calculates other calibration tables besides the first and second calibration tables by linear interpolation based on the first and second calibration tables.

[0016] [Beneficial effects of the present invention]

[0017] According to the present invention, by correcting the command current according to multiple calibration tables representing the relationship between the pump discharge pressure and the command current to the regulator, even if the pump swashplate position fluctuates significantly according to the discharge pressure, the deviation between the pump's target discharge rate and the pump's actual discharge rate can be corrected, thereby improving the accuracy of flow rate control. Attached Figure Description

[0018] Figure 1 This is a circuit diagram of a calibration system for a variable capacity hydraulic pump configured according to the present invention.

[0019] Figure 2 It is by Figure 1 The flowchart shows the calibration method performed by the controller.

[0020] Figure 3 It means Figure 1 The command current to the regulator shown is Figure 1 The graph shows the relationship between the pump capacities.

[0021] Figure 4 It means Figure 1 The pump discharge pressure shown is... Figure 1 The graph shows the relationship between the pump capacities.

[0022] Figure 5 It is shown by Figure 1 The graph shows the curves of multiple calibration tables determined by the controller.

[0023] Figure 6 It means Figure 1 The command current to the regulator shown is Figure 5 The graph shows the relationship between the gradients of the multiple correction tables. Detailed Implementation

[0024] Now, an embodiment of a calibration system for a variable capacity hydraulic pump configured according to the present invention will be described below with reference to the accompanying drawings.

[0025] refer to Figure 1 Description provided; A calibration system for a variable capacity hydraulic pump, the entire system indicated by reference numeral 2 (hereinafter referred to as "System 2"), includes a variable capacity hydraulic pump 4 (hereinafter referred to as "Pump 4"); a regulator 6 configured to proportionally adjust the capacity of Pump 4 according to an input command current; and a controller 8 configured to output a command current to Regulator 6. System 2 can be installed on construction machinery such as hydraulic excavators.

[0026] like Figure 1 As shown, pump 4 is driven by engine 10, and engine 10 is equipped with engine speed sensor 12. Engine 10 and engine speed sensor 12 are electrically connected to controller 8. The drive of engine 10 is controlled by controller 8, and the speed of engine 10 detected by engine speed sensor 12 is input to controller 8.

[0027] Pump 4 is connected to control valve 16 via pump pipe 14, and hydraulic oil discharged from pump 4 is supplied to control valve 16 via pump pipe 14. Pump pipe 14 is equipped with a pressure sensor 18, which is electrically connected to controller 8. The discharge pressure of pump 4 detected by pressure sensor 18 is input to controller 8. In the illustrated embodiment, pressure sensor 18 is attached to control valve 16; however, pressure sensor 18 may be placed on pump pipe 14 and may not be attached to control valve 16.

[0028] Multiple valve spools 16a, 16b, 16c, 16d for controlling the hydraulic oil supplied to multiple hydraulic actuators (not shown), such as hydraulic cylinders and hydraulic motors, are attached to control valve 16. In the illustrated embodiment, control valve 16 is provided with a bypass pipe 22 connected to hydraulic oil tank 20, and a variable throttle valve spool 24 is arranged on bypass pipe 22.

[0029] The variable throttle valve spool 24 is equipped with a solenoid 24a, which is configured to proportionally adjust the throttle valve opening (cross-sectional area of ​​the throttle valve) of the variable throttle valve spool 24 in accordance with the input drive current. The solenoid 24a is electrically connected to the controller 8, and the drive current is input from the controller 8 to the solenoid 24a. Figure 1 In the control valve 16, for convenience, valve cores 16a to 16d and variable throttle valve core 24 are shown; however, in addition to valve cores 16a to 16d and variable throttle valve core 24, suitable hydraulic components, such as valve cores and safety valves, may be attached.

[0030] The regulator 6 includes a piston rod 26 coupled to a rotating swashplate 4a of the pump 4 and a solenoid valve 28 for operating the piston rod 26. The solenoid valve 28 has a solenoid 28a for operating the piston rod 26 in response to an input command current. The solenoid 28a is electrically connected to a controller 8, and a command current is input from the controller 8 to the solenoid 28a.

[0031] Then, in regulator 6, the inclination of the rotating swashplate 4a of pump 4 is controlled by operating piston rod 26, so that the capacity of pump 4 increases with an increase in the command current from controller 8, and decreases with a decrease in the command current from controller 8. Further, as... Figure 1 As shown, orifice 30 is located between regulator 6 and hydraulic tank 20. When solenoid 28a is not energized, the discharge pressure of pump 4 is input as a control signal to spring chamber 6a of regulator 6, and piston rod 26 operates in response to the discharge pressure of pump 4 to control the rotation of swashplate 4a of pump 4. On the other hand, when solenoid 28a is energized, solenoid valve 28 is operated to... Figure 1 On the left side, ports 28b and 28c are connected to each other. By doing so, most of the hydraulic oil that has passed through the spring chamber 6a will return to the hydraulic oil tank 20 without passing through the orifice 30. The pump 4 is provided with a limiting device (not shown) for limiting the inclination of the rotating swashplate 4a within a predetermined range.

[0032] The controller 8 consists of a computer and a memory. The computer includes a processor configured to perform calculations according to a control program, and the memory stores the control program and calculation results, and is adapted to control the operation of the system 2. For example, the controller 8 is configured to adjust the slope of the rotating swashplate 4a of the pump 4 by increasing or decreasing the command current output to the solenoid 28a of the regulator 6, thereby controlling the capacity of the pump 4. Simultaneously, it is configured to adjust the throttle valve opening of the variable throttle valve core 24 by increasing or decreasing the drive current output to the solenoid 24a of the variable throttle valve core 24. Furthermore, the controller 8 is configured to control the discharge pressure of the pump 4 by adjusting the throttle valve opening of the variable throttle valve core 24 and simultaneously adjusting the speed of the engine 10.

[0033] Next, the calibration method of pump 4 performed by controller 8 in system 2 as described above will be explained.

[0034] like Figure 2 As shown, the controller 8 is first configured to execute step S1 of determining a first reference table when the discharge pressure of the pump 4 is set to a first pressure. The first reference table represents the relationship between the command current to the regulator 6 and the capacity of the pump 4.

[0035] In step S1, firstly, when the speed of engine 10 is a relatively high speed Nh, the cross-sectional area of ​​the throttle valve of variable throttle valve core 24 is a relatively small cross-sectional area Al, and the discharge pressure of pump 4 is a relatively low first pressure P1, the capacity qa of pump 4 is calculated using the following equations (1) and (2). The following equations (1) and (2) are pre-stored in controller 8.

[0036] Mathematical Formula 1

[0037]

[0038] Mathematical formula 2

[0039] Q = qN (2)

[0040] In equation (1) above, Q is the discharge volume of pump 4, α is a coefficient, A is the cross-sectional area of ​​the throttle valve of the variable throttle valve core 24, PP is the discharge pressure (pump pressure) of pump 4, PT is the pressure (tank pressure) of the hydraulic oil in the hydraulic oil tank 20, and ρ is the viscosity of the hydraulic oil. Furthermore, in equation (2) above, q is the capacity of pump 4, and N is the speed of engine 10.

[0041] The coefficient α and viscosity ρ of the hydraulic oil are represented by fixed values, and appropriate values ​​can be used pre-stored in the controller 8. The cross-sectional area A of the throttle valve is determined by a table (not shown, but pre-stored in the controller 8) showing the relationship between the drive current of the solenoid 24a output from the controller 8 to the variable throttle valve core 24 and the cross-sectional area A of the throttle valve.

[0042] Regarding the speed N of engine 10, a value based on a command from controller 8 can be used, or the speed detected by engine speed sensor 12 can be used. The discharge pressure PP of pump 4 uses the discharge pressure detected by pressure sensor 18. The tank pressure PT can use a fixed value pre-stored in controller 8, or the tank pressure detected by a tank pressure sensor can be used, provided by a tank pressure sensor (not shown) for measuring tank pressure in system 2.

[0043] In addition to setting the speed of engine 10 to Nh and simultaneously setting the cross-sectional area of ​​the throttle valve of variable throttle valve core 24 to Al, after calculating the capacity qa of pump 4, the change in the discharge pressure of pump 4 is measured by pressure sensor 18, and the command current of solenoid 28a of solenoid valve 28 of regulator 6 is changed to determine the command current Ia when the discharge pressure of pump 4 becomes the first pressure P1. The command current Ia is the command current when the discharge pressure of pump 4 is the first pressure P1, the speed of engine 10 is Nh, and the cross-sectional area of ​​the throttle valve of variable throttle valve core 24 is Al, at which the capacity of pump 4 becomes qa.

[0044] When determining the capacity qa and command current Ia of the pump 4, it is preferable to determine the maximum command current Imax for achieving the maximum capacity qmax of the pump 4 (see Figure 3 ). As described above, since the pump 4 is provided with a limiting device for limiting the slope of the swash plate 4a within a predetermined range, when the maximum capacity qmax is reached, the capacity of the pump 4 becomes a stable value, and as a result, the maximum command current Imax can be accurately determined.

[0045] After determining the command current Ia, when the speed of the engine 10 is Nl which is less than Nh (Nl < Nh), the throttle cross-sectional area of the variable throttle valve spool 24 is Ah which is greater than Al (Ah > Al), and the discharge pressure of the pump 4 is the first pressure P1, the capacity qb of the pump 4 is calculated using the above equations (1) and (2).

[0046] In addition to setting the speed of the engine 10 to Nl and simultaneously setting the throttle cross-sectional area of the variable throttle valve spool 24 to Ah, after calculating the capacity qb of the pump 4, the change in the discharge pressure of the pump 4 is measured by the pressure sensor 18 while changing the command current to the regulator 6, and the command current Ib at which the discharge pressure of the pump 4 becomes the first pressure P1 is determined. The command current Ib is the command current at which the capacity of the pump 4 becomes qb when the discharge pressure of the pump 4 is the first pressure P1, the speed of the engine 10 is Nl, and the throttle cross-sectional area of the variable throttle valve spool 24 is Ah.

[0047] When determining the capacity qb and command current Ib of the pump 4, it is preferable to determine the minimum command current Imin for achieving the minimum capacity qmin of the pump 4 (see Figure 3 ). As described above, since the pump 4 is provided with a limiting device for limiting the slope of the swash plate 4a within a predetermined range, even when the minimum capacity qmin is reached, the capacity of the pump 4 becomes a stable value, and as a result, the minimum command current Imin can be accurately determined.

[0048] After determining the command current Ib, a first reference table is determined based on the capacities qa, qb and command currents Ia, Ib. In the illustrated embodiment, an example of determining the first reference table based on the maximum capacity qmax, minimum capacity qmin, maximum command current Imax and minimum command current Imin is described.

[0049] As Figure 3As shown, the horizontal axis represents the command current I to regulator 6, and the vertical axis represents the capacity q of pump 4. Point A, specified by the maximum command current Imax and the maximum capacity qmax, and point B, specified by the minimum command current Imin and the minimum capacity qmin, are connected according to a linear function. This allows the determination of a first reference table TP1, which represents the relationship between the command current I to regulator 6 and the capacity q of pump 4 when the discharge pressure of pump 4 is a first pressure P1.

[0050] In step S1 of the illustrated embodiment, the capacity qa (qmax) is first calculated, then the command current Ia (Imax) is determined, followed by the capacity qb (qmin); subsequently, the command current Ib (Imin) is determined. However, the order in which the capacity is calculated and the command current is determined can be arbitrary.

[0051] After performing step S1 to determine the first reference table TP1, as follows Figure 2 As shown, step S2, which determines the second reference table, is executed. The second reference table represents the relationship between the command current of the regulator 6 and the capacity of the pump 4 when the discharge pressure of the pump 4 is set to the second pressure.

[0052] In step S2, firstly, when the speed of engine 10 is N1, the cross-sectional area of ​​the throttle valve of variable throttle valve core 24 is A1, and the discharge pressure of pump 4 is a second pressure P2 (P2>P1) higher than the first pressure P1, the capacity of pump 4 (first capacity q1) is calculated using the above equations (1) and (2). Figure 3 As shown, the first capacity q1 is the capacity between the minimum capacity qmin and the maximum capacity qmax (qmin <q1<qmax)。

[0053] In addition to setting the speed of engine 10 to Nl and simultaneously setting the cross-sectional area of ​​the throttle valve of the variable throttle valve core 24 to Al, after calculating the first capacity q1, the change in the discharge pressure of pump 4 is measured by pressure sensor 18, and the command current to regulator 6 is changed accordingly. A first command current I1 is then determined to change the discharge pressure of pump 4 to the second pressure P2. The first command current I1 is the command current at which the capacity of pump 4 changes to the first capacity q1 when the discharge pressure of pump 4 is the second pressure P2, the speed of engine 10 is Nl, and the cross-sectional area of ​​the throttle valve of the variable throttle valve core 24 is Al. Figure 3 As shown, the first command current I1 is the current value between the minimum command current Imin and the maximum command current Imax (Imin... <I1<Imax)。

[0054] After determining the first command current I1, when the speed of engine 10 is Nh, the cross-sectional area of ​​the throttle valve of variable throttle valve core 24 is Ah, and the discharge pressure of pump 4 is the second pressure P2, the capacity of pump 4 (second capacity q2) is calculated using the above equations (1) and (2). Figure 3 As shown, the second capacity q2 is the capacity between the first capacity q1 and the maximum capacity qmax (q1 <q2<qmax)。

[0055] In addition to setting the engine speed of 10 to Nh and the cross-sectional area of ​​the throttle valve of the variable throttle valve core 24 to Ah, after calculating the second capacity q2, the change in the discharge pressure of pump 4 is measured by pressure sensor 18, and the command current to regulator 6 is changed accordingly. A second command current I2 is then determined to change the discharge pressure of pump 4 to the second pressure P2. The second command current I2 is the command current that changes the capacity of pump 4 to the second capacity q2 when the discharge pressure of pump 4 is the second pressure P2, the engine speed of 10 is Nh, and the cross-sectional area of ​​the throttle valve of the variable throttle valve core 24 is Ah. Figure 3 As shown, the second command current I2 is the current value between the first command current I1 and the maximum command current Imax (I1... <I2<Imax)。

[0056] After determining the second command current I2, a second reference table is determined based on the first capacity q1, the second capacity q2, the first command current I1, and the second command current I2. Specifically, as follows... Figure 3 As shown, the horizontal axis represents the command current I to regulator 6, and the vertical axis represents the capacity q of pump 4. Point C, specified by the first command current I1 and the first capacity q1, and point D, specified by the second command current I2 and the second capacity q2, are connected according to the 1chA function. This allows the determination of the second reference table TP2, which represents the relationship between the command current I to regulator 6 and the capacity q of pump 4 when the discharge pressure of pump 4 is the second pressure P2.

[0057] In step S2 of the illustrated embodiment, the first capacity q1 is first calculated, then the first command current I1 is determined, followed by the calculation of the second capacity q2; subsequently, the second command current I2 is determined. However, the order in which the capacity is calculated and the command current is determined can be arbitrary.

[0058] After performing step S2 to determine the second reference table TP2, as follows Figure 2 As shown, step S3 is performed based on the first reference table TP1 and the second reference table TP2 to determine multiple calibration tables representing the relationship between the discharge pressure of pump 4 and the command current to regulator 6.

[0059] In step S3, firstly, by using Figure 3The first reference table TP1 shown calculates the third capacity q3 corresponding to the first command current I1. (Reference) Figure 3 It is understandable that when the discharge pressure of pump 4 is the second pressure P2, when the first command current I1 is input to regulator 6, the third capacity q3, which is associated with the capacity of pump 4 at point E, is greater than the first capacity q1 (q3>q1).

[0060] exist Figure 4 In the diagram, the horizontal axis represents the discharge pressure P of pump 4, and the vertical axis represents the capacity q of pump 4. The diagram shows the point E' (corresponding to the first pressure P1 and the third capacity q3) connected by a linear function. Figure 3 Point E in the equation) and point C' (corresponding to the second pressure P2 and the first capacity q1) are specified by the second pressure P2 and the first capacity q1. Figure 3 Table TI1 is obtained from point C in the table. Table TI1 shows the relationship between the discharge pressure P of pump 4 and the capacity q of pump 4 when the command current to regulator 6 becomes constant after the first command current I1 becomes constant.

[0061] As can be understood by referring to Table TI1, in system 2, the capacity (third capacity q3) of pump 4 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 is different from the capacity (first capacity q1) of pump 4 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.

[0062] In other words, in system 2, even if the command current to regulator 6 is the same as the first command current I1, when the discharge pressure of pump 4 increases from the first pressure P1 to the second pressure P2, the capacity of pump 4 decreases from the third capacity q3 to the first capacity q1, and pump 4 will eventually be de-energized as the discharge pressure of pump 4 increases. Therefore, in system 2, based on the fact that if the discharge pressures of pump 4 are different from each other, then even for the same command current, the capacity of pump 4 will be different from each other, and unless corrected, a deviation may occur between the target discharge rate and the actual discharge rate of pump 4 depending on the discharge pressure of pump 4.

[0063] Continue to refer to Figure 3 To explain, after calculating the third capacity q3, a first current difference ΔI1 corresponding to the difference between the third capacity q3 and the first capacity q1 is calculated using a first reference table TP1. When the discharge pressure of pump 4 is the second pressure P2, the value I1+ΔI1 obtained by adding the first current difference ΔI1 to the first command current I1 is the command current for changing the capacity of pump 4 to the third capacity q3.

[0064] After calculating the first current difference ΔI1, based on the first pressure P1, the second pressure P2, the first command current I1, and the first current difference ΔI1, the first calibration table shows the relationship between the discharge pressure of pump 4 (at which the capacity of pump 4 becomes constant at the third capacity q3) and the command current to regulator 6.

[0065] Specifically, such as Figure 5 As shown, the horizontal axis represents the discharge pressure P of pump 4, and the vertical axis represents the command current I of regulator 6. The point E (corresponding to the first pressure P1 and the first command current I1) is connected by a linear function. Figure 3 Point E and Figure 4 The first calibration table Tq3 can be determined from point E' in the table; and the calibration point CC is specified by the value I1+ΔI1 obtained by adding the first current difference ΔI1 to the first command current I1 and the second pressure P2.

[0066] Then, when the first command current I1 is output to the regulator 6, the command current to the regulator 6 is corrected as a function of the discharge pressure of the pump 4 by adjusting the first current difference ΔI1 to be added to the first command current I1 according to the first correction table Tq3. As a result, the capacity of the pump 4 can be set to a third capacity q3, independent of the discharge pressure of the pump 4, and no power outage will occur even if the discharge pressure of the pump 4 increases. (Reference) Figure 5 It can be understood that ΔI1 = 0 is maintained at the first pressure P1. When the discharge pressure of pump 4 becomes lower than the first pressure P1, ΔI1 takes a negative value. When the discharge pressure of pump 4 becomes higher than the first pressure P1, ΔI1 takes a positive value.

[0067] After determining the first correction table Tq3, by using... Figure 3 The first reference table TP1 shown calculates the fourth capacity q4 corresponding to the second command current I2. For example... Figure 3 As shown, when the discharge pressure of pump 4 is the second pressure P2, the fourth capacity q4, which is the capacity of pump 4 associated with point F, is greater than the second capacity q2 when the second command current I2 is input to regulator 6 (q4>q2).

[0068] exist Figure 4 The diagram also shows how to connect the point F' (corresponding to the first pressure P1 and the fourth capacity q4) according to a linear function. Figure 3 Point F in the middle) and point D' (corresponding to the second pressure P2 and the second capacity q2) are specified by the second pressure P2 and the second capacity q2. Figure 3 Table TI2 is obtained from point D in the table. Table TI2 shows the relationship between the discharge pressure P of pump 4 and the capacity of pump 4 when the command current to regulator 6 becomes constant in the second command current I2.

[0069] As can be understood by referring to Table TI2, in System 2, when the discharge pressure of pump 4 is the first pressure P1, the capacity of pump 4 (fourth capacity q4) when the command current to regulator 6 is set to the second command current I2 is different from the capacity of pump 4 (second capacity q2) when the discharge pressure of pump 4 is the second pressure P2. This is the same as the situation already explained with reference to Table TI1. However, in System 2, even if the command current to regulator 6 is the same as the second command current I2, when the discharge pressure of pump 4 increases from the first pressure P1 to the second pressure P2, the capacity of pump 4 will eventually decrease from the fourth capacity q4 to the second capacity q2.

[0070] Continue to refer to Figure 3 To explain, after calculating the fourth capacity q4, a second current difference ΔI2 corresponding to the difference between the fourth capacity q4 and the second capacity q2 is calculated using the first reference table TP1. When the discharge pressure of pump 4 is the second pressure P2, the value I2+ΔI2 obtained by adding the second current difference ΔI2 to the second command current I2 is the command current for changing the capacity of pump 4 to the fourth capacity q4.

[0071] After calculating the second current difference ΔI2, based on the first pressure P1, the second pressure P2, the second command current I2, and the second current difference ΔI2, the second calibration table shows the relationship between the discharge pressure of pump 4 (at which the capacity of pump 4 becomes constant at the fourth capacity q4) and the command current to regulator 6.

[0072] Specifically, such as Figure 5 As shown, the point F specified by the first pressure P1 and the second command current I2 can be connected according to a linear function (corresponding to...). Figure 3 Point F and Figure 4 The second calibration table Tq4 is determined by the point F' in the table; and the calibration point DC is specified by the value I2+ΔI2 obtained by adding the second current difference ΔI2 to the second command current I2 and the second pressure P2.

[0073] Then, when the second command current I2 is output to the regulator 6, the command current to the regulator 6 is corrected as a function of the discharge pressure of pump 4 by adjusting the second current difference ΔI2 to be added to the second command current I2 according to the second correction table Tq4. As a result, the capacity of pump 4 can be set to a fourth capacity q4, independent of the discharge pressure of pump 4, and no power outage will occur even if the discharge pressure of pump 4 increases. (Reference) Figure 5 It can be understood that ΔI2 = 0 is maintained at the second pressure P2. When the discharge pressure of pump 4 becomes lower than the second pressure P2, ΔI2 takes a negative value, and when the discharge pressure of pump 4 becomes higher than the second pressure P2, ΔI2 takes a positive value.

[0074] After determining the second correction table Tq4, based on the first correction table Tq3 and the second correction table Tq4, other correction tables except the first correction table Tq3 and the second correction table Tq4 are calculated by linear interpolation.

[0075] Reference Figure 6 is explained, where the horizontal axis represents the command current I to the regulator 6, and the vertical axis represents Figure 5 the gradient g of the correction table shown. The gradient table Tg representing the relationship between the command current I to the regulator 6 and the gradient g of the correction table is determined by connecting the point H specified by the first command current I1 and the gradient g1 of the first correction table Tq3 and the point J specified by the second command current I2 and the gradient g2 of the second correction table Tq4 according to a linear function. Then, by using the gradient g determined from the gradient table Tg, other correction tables except the first correction table Tq3 and the second correction table Tq4 are calculated.

[0076] For example, according to Figure 6 the gradient table Tg shown, when the command current to the regulator 6 is any command current Im less than the first command current I1, the gradient of the correction table becomes a gradient gm (gm < g1) less than the gradient g1 of the first correction table Tq3, and then the correction table Figure 5 shown as Tqm can be calculated by using the gradient gm. The correction table Tqm is a table representing the relationship between the discharge pressure of the pump 4 (at which the capacity of the pump 4 becomes constant at the capacity qm) and the command current to the regulator 6.

[0077] Furthermore, according to Figure 6 the gradient table Tg shown, when the command current to the regulator 6 is any command current In greater than the second command current I2, the gradient of the correction table becomes a gradient gn (gn > g2) greater than the gradient g2 of the second correction table Tq4, and then the correction table Figure 5 shown as Tqn can be determined by using the gradient gn. The correction table Tqn is a table representing the relationship between the discharge pressure of the pump 4 (at which the capacity of the pump 4 becomes constant at the capacity qn) and the command current to the regulator 6.

[0078] In this way, when the command current to the regulator 6 is a command current other than the first and second command currents I1 and I2, by using Figure 6 the gradient table Tg shown, by calculating multiple gradients, multiple other correction tables except the first and second correction tables Tq3 and Tq4 can be calculated.

[0079] As described above, according to System 2 of the illustrated embodiment, by correcting the command current based on multiple calibration tables representing the relationship between the discharge pressure of pump 4 and the command current to regulator 6, the deviation between the target discharge volume and the actual discharge volume of pump 4 can be corrected, thereby improving the flow rate control accuracy even if the swashplate position of pump 4 fluctuates significantly according to the discharge pressure (i.e., the capacity of pump 4 fluctuates significantly). Furthermore, in System 2, since multiple calibration tables can be determined based on the first reference table TP1 and the second reference table TP2, the number of times the discharge pressure, command current, etc., of pump 4 can be determined can be reduced, and calibration can be performed in a short time.

Claims

1. A calibration system for a variable capacity hydraulic pump, comprising the variable capacity hydraulic pump; A regulator configured to adjust the pump capacity in proportion to the input command current; and a controller configured to output a command current to the regulator. The controller is configured to perform the following steps: When the discharge pressure of the pump is set to a first pressure, a first reference table is determined, representing the relationship between the command current to the regulator and the capacity of the pump; When the discharge pressure of the pump is set to a second pressure, a second reference table representing the relationship between the command current to the regulator and the capacity of the pump is determined; as well as Based on the first reference table and the second reference table, a plurality of correction tables are determined to represent the relationship between the pump's discharge pressure and the command current to the regulator. In the step of determining the second reference table, the controller... Calculate the first and second capacities of the pump. Determine the first command current when the pump's capacity changes to the first capacity. Determine the second command current when the pump's capacity changes to the second capacity, and The second reference table is determined based on the first capacity, the second capacity, the first command current, and the second command current. In the step of determining the plurality of calibration tables, the controller, Calculate the third capacity corresponding to the first command current, and simultaneously calculate the first current difference corresponding to the difference between the third capacity and the first capacity using the first reference table. A first calibration table is determined based on the first pressure, the second pressure, the first command current, and the first current difference, which represents the relationship between the pump's discharge pressure and the command current to the regulator when the pump's capacity becomes constant at the third capacity.

2. The calibration system for a variable capacity hydraulic pump according to claim 1, wherein the controller, in the step of determining the first reference table, Calculate the maximum and minimum capacity of the pump. Determine the maximum command current when the pump's capacity becomes the maximum capacity. Determine the minimum command current when the pump's capacity becomes the minimum capacity, and The first reference table is determined based on the maximum capacity, the minimum capacity, the maximum command current, and the minimum command current.

3. The calibration system for a variable capacity hydraulic pump according to claim 1, wherein the controller, in the step of determining the plurality of calibration tables, Calculate the fourth capacity corresponding to the second command current, and simultaneously calculate the second current difference corresponding to the difference between the fourth capacity and the second capacity using the first reference table. A second calibration table is determined based on the first pressure, the second pressure, the second command current, and the second current difference, which represents the relationship between the pump's discharge pressure and the command current to the regulator when the pump's capacity becomes constant at the fourth capacity.

4. The calibration system for a variable capacity hydraulic pump according to claim 3, wherein the controller, in the step of determining the plurality of calibration tables, Based on the first and second correction tables, other correction tables besides the first and second correction tables are calculated by linear interpolation.

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