Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
  • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
  • F04B1/00—Multi-cylinder machines or pumps characterised by number or arrangement of cylinders
  • F04B1/12—Multi-cylinder machines or pumps characterised by number or arrangement of cylinders having cylinder axes coaxial with, or parallel or inclined to, main shaft axis
  • F04B1/26—Control
  • F04B1/28—Control of machines or pumps with stationary cylinders
  • F04B1/29—Control of machines or pumps with stationary cylinders by varying the relative positions of a swash plate and a cylinder block
  • F04B1/295—Control of machines or pumps with stationary cylinders by varying the relative positions of a swash plate and a cylinder block by changing the inclination of the swash plate
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
  • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
  • F04B1/00—Multi-cylinder machines or pumps characterised by number or arrangement of cylinders
  • F04B1/12—Multi-cylinder machines or pumps characterised by number or arrangement of cylinders having cylinder axes coaxial with, or parallel or inclined to, main shaft axis
  • F04B1/26—Control
  • F04B1/30—Control of machines or pumps with rotary cylinder blocks
  • F04B1/32—Control of machines or pumps with rotary cylinder blocks by varying the relative positions of a swash plate and a cylinder block
  • F04B1/324—Control of machines or pumps with rotary cylinder blocks by varying the relative positions of a swash plate and a cylinder block by changing the inclination of the swash plate
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
  • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
  • F04B49/00—Control, e.g. of pump delivery, or pump pressure of, or safety measures for, machines, pumps, or pumping installations, not otherwise provided for, or of interest apart from, groups F04B1/00 - F04B47/00
  • F04B49/06—Control using electricity
  • F04B49/065—Control using electricity and making use of computers
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
  • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
  • F04B51/00—Testing machines, pumps, or pumping installations

Definitions

• the present invention relates to a calibration system for variable capacity hydraulic pump comprising a variable capacity hydraulic pump; a regulator configured to adjust a capacity of the pump in proportion to an input command current; and a controller configured to output a command current to the regulator.
• Patent Literature 1 discloses a calibration system for variable capacity hydraulic pump whose capacity is controlled on the basis of a command current output from a controller.
• This system comprises a calibration data acquisition means for acquiring measured pump pressure data corresponding to each command current by measuring a pump pressure in each command current while changing command currents output from the controller in a multi-step manner from minimum value to maximum value; a first table creation means, by calculating a coefficient representing a relationship between the pump pressure vs. pump flow rate on the basis of the pump flow rate determined from specificationbased pump capacity at preset reference command current vs. the measured pump pressure determined by the calibration data acquisition means, so as to create a first table representing a relationship between the coefficient vs.
• a second table creation means for creating a second table representing a relationship between each command current vs. the measured pump pressure on the basis of the data acquired by the calibration data acquisition means; a third table creation means, by converting the measured pump pressure in the second table into the pump flow rate using the coefficient in the first table, so as to create a third table representing a relationship between the pump flow rate vs. the command current; and a pump control table creation means for creating a pump control table representing a relationship between the pump capacity vs. the command current from an engine speed during pump pressure measurement and the third table; wherein the pump control table created by the pump control table creation means is used as the pump control table calibrated. Then, with this system, it is possible to create the pump control table in which the value of the pump capacity with respect to each command current is calibrated over the entire range of command currents, and thus the calibration of the pump control table can be performed with a high accuracy.
• PATENT LITERATURE 1 Japanese Patent Application Laid-Open No. 2019- 190443
• the object of the present invention made in view of the fact as noted above is to correct deviation between a target discharge amount of the pump and an actual discharge amount of the pump even if the swash plate positions of the pump significantly fluctuate depending on the discharge pressure, and to provide a calibration system for variable capacity hydraulic pump capable of improving flow rate control accuracy.
• a calibration system for variable capacity hydraulic pump comprising a variable capacity hydraulic pump; a regulator configured to adjust a capacity of the pump in proportion to an input command current; and a controller configured to output a command current to the regulator, wherein the controller is configured to execute the steps of: determining a first reference table representing a relationship between the command current to the regulator vs. the capacity of the pump when a discharge pressure of the pump is set to a first pressure; determining a second reference table representing a relationship between the command current to the regulator vs.
• the controller in the step of determining the first reference table, calculates a maximum capacity and a minimum capacity of the pump, determines a maximum command current at which the capacity of the pump becomes the maximum capacity, determines a minimum command current at which the capacity of the pump becomes the minimum capacity, and determines the first reference table on the basis of the maximum capacity, the minimum capacity, the maximum command current, and the minimum command current.
• the controller in the step of determining the second reference table, calculates a first capacity and a second capacity of the pump, determines a first command current at which the capacity of the pump becomes the first capacity, determines a second command current at which the capacity of the pump becomes the second capacity, and determines the second reference table on the basis of the first capacity, the second capacity, the first command current, and the second command current.
• the controller in the step of determining the plurality of correction tables, calculates a third capacity corresponding to the first command current, and at the same time, calculates a first current difference corresponding to a difference between the third capacity and the first capacity, by using the first reference table, and determines a first correction table representing a relationship between the discharge pressure of the pump at which the capacity of the pump becomes constant at the third capacity vs. the command current to the regulator, on the basis of the first pressure, the second pressure, the first command current, and the first current difference.
• the controller in the step of determining the plurality of correction tables, calculates a fourth capacity corresponding to the second command current, and at the same time, calculates a second current difference corresponding to a difference between the fourth capacity and the second capacity, by using the first reference table, and determines a second correction table representing a relationship between the discharge pressure of the pump at which the capacity of the pump becomes constant at the fourth capacity vs. the command current to the regulator, on the basis of the first pressure, the second pressure, the second command current, and the second current difference.
• the controller in the step of determining the plurality of correction tables, calculates other correction tables except for the first correction table and the second correction table, through a linear interpolation, on the basis of the first correction table and the second correction table.
• a deviation between a target discharge amount of the pump and an actual discharge amount of the pump can be corrected so as to be able to improve flow rate control accuracy, even if swash plate positions of the pump fluctuate significantly depending on the discharge pressure.
• FIG. 1 is a circuit diagram of a calibration system for variable capacity hydraulic pump configured in accordance with the present invention.
• FIG. 2 is a flowchart for a calibration method executed by a controller shown in FIG. 1.
• FIG. 3 is a graph representing a relationship between a command current to a regulator shown in FIG. 1 vs. a capacity of the pump shown in FIG. 1.
• FIG. 4 is a graph representing a relationship between a discharge pressure of the pump shown in FIG. 1 vs. the capacity of the pump shown in FIG. 1.
• FIG. 5 is a graph showing a plurality of correction tables determined by the controller shown in FIG. 1.
• FIG. 6 is a graph representing a relationship between the command current to the regulator shown in FIG. 1 vs. gradients of the plurality of correction tables shown in FIG. 5.
• a calibration system for variable capacity hydraulic pump the entire system of which denoted by reference numeral 2 (hereinafter referred to as “system 2”), comprises a variable capacity hydraulic pump 4 (hereinafter referred to as “pump 4”), a regulator 6 configured to adjust a capacity of the pump 4 in proportion to an input command current, and a controller 8 configured to output the command current to the regulator 6.
• the system 2 may be mounted on a construction machine such as a hydraulic shovel.
• the pump 4 is driven by an engine 10, and the engine 10 is provided with an engine speed sensor 12.
• the engine 10 and the engine speed sensor 12 are electrically connected to the controller 8, the drive of the engine 10 is controlled by the controller 8, and a speed of the engine 10 detected by the engine speed sensor 12 is input to the controller 8.
• the pump 4 is connected to a control valve 16 by a pump line 14, and a hydraulic oil discharged from the pump 4 is supplied to the control valve 16 via the pump line 14.
• the pump line 14 is provided with a pressure sensor 18, 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.
• the pressure sensor 18 is attached to the control valve 16, but the pressure sensor 18 may be placed on the pump line 14 and may not be attached on the control valve 16.
• a plurality of spools 16a, 16b, 16c, 16d for controlling the hydraulic oil to be supplied to a plurality of hydraulic actuators (not shown) such as hydraulic cylinders and hydraulic motors are attached to the control valve 16.
• the control valve 16 of the illustrated embodiment is provided with a bypass line 22 connected to a hydraulic oil tank 20, and a variable throttle spool 24 is arranged on the bypass line 22.
• the variable throttle spool 24 is provided with a solenoid 24a configured to adjust a throttle opening (cross-sectional area of throttle) of the variable throttle spool 24 in proportion 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.
• the spools 16a to 16d and the variable throttle spool 24 are shown for convenience; however, appropriate hydraulic members such as spools and relief valves, etc. other than the spools 16a to 16d and the variable throttle spool 24 may be attached.
• the regulator 6 includes a piston rod 26 coupled to a swash plate 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 the controller 8, and a command current is input from the controller 8 to the solenoid 28a.
• slopes of the swash plate 4a of the pump 4 are controlled by operating the piston rod 26, so that the capacity of the pump 4 increases as the command current from the controller 8 increases, and the capacity of the pump 4 decreases as the command current from the controller 8 decreases.
• an orifice 30 is provided between the regulator 6 and the hydraulic oil tank 20.
• the pump 4 is provided with a limiting means (not shown) for limiting the slopes of the swash plate 4a within a predetermined range.
• the controller 8 is composed of a computer including a processor configured to perform calculations according to a control program and a memory which stores the control program and calculation results, etc., and is adapted to control the operation of the system 2.
• the controller 8 is configured to adjust the slopes of the swash plate 4a of the pump 4 so as to control the capacity of the pump 4, by increasing or decreasing the command current to be output to the solenoid 28a of the regulator 6, and at the same time, configured to adjust a throttle opening of the variable throttle spool 24, by increasing or decreasing a drive current output to the solenoid 24a of the variable throttle spool 24.
• controller 8 is configured to control the discharge pressure of the pump 4, by adjusting the throttle opening of the variable throttle spool 24 and at the same time, adjusting the speed of the engine 10.
• the controller 8 first, is configured to execute a step SI of determining a first reference table representing a relationship between the command current to the regulator 6 vs. the capacity of the pump 4 when the discharge pressure of the pump 4 is set to a first pressure.
• step SI first, a capacity qa of the pump 4 is calculated using the following equations (1) and (2) when the speed of the engine 10 is a relatively high speed Nh, the cross-sectional area of the throttle of the variable throttle spool 24 is a relatively small cross-sectional area Al, and the discharge pressure of the pump 4 is a first pressure Pl which is relatively low.
• the following equations (1) and (2) are stored in the controller 8 in advance.
• Q is a discharge amount of the pump 4
• a is a coefficient
• A is a cross-sectional area of the throttle of the variable throttle spool 24
• PP is a discharge pressure of the pump 4 (pump pressure)
• PT is a pressure of hydraulic oil in the hydraulic oil tank 20 (tank pressure)
• p is a viscosity of the hydraulic oil.
• q in the above equation (2) is the capacity of the pump 4, and N is the speed of the engine 10.
• the coefficient a and the viscosity p of the hydraulic oil are expressed by fixed values, and appropriate values which are stored in the controller 8 in advance can be used.
• the cross-sectional area A of the throttle an area determined from a table (not shown, but a table stored in the controller 8 in advance) representing a relationship between the drive current output from the controller 8 to the solenoid 24a of the variable throttle spool 24 vs. the cross- sectional area A of the throttle.
• a value based on a command from the controller 8 may be used, or a speed detected by the engine speed sensor 12 may be used.
• the discharge pressure PP of the pump 4 uses a discharge pressure detected by the pressure sensor 18.
• the tank pressure PT may use a fixed value stored in advance in the controller 8, or by providing a tank pressure sensor (not shown) for measuring the tank pressure in the system 2, a tank pressure detected by the tank pressure sensor may be used.
• transition of the discharge pressures of the pump 4 is measured by the pressure sensor 18, while changing the command current to the solenoid 28a of the solenoid valve 28 of the regulator 6, and a command current la at which the discharge pressure of the pump 4 becomes the first pressure Pl is determined.
• the command current la is a command current at which the capacity of the pump 4 becomes qa, when the discharge pressure of the pump 4 is the first pressure Pl, the speed of the engine 10 is Nh, and the cross- sectional area of the throttle of the variable throttle spool 24 is Al.
• a capacity qb of the pump 4 is calculated using the above equations (1) and (2) when the speed of the engine 10 is Nl (Nl ⁇ Nh) being smaller than Nh, the cross-sectional area of the throttle of the variable throttle spool 24 is Ah (Ah>Al) being greater than Al, and the discharge pressure of the pump 4 is the first pressure Pl.
• transition of the discharge pressures of the pump 4 is measured by the pressure sensor 18, while changing the command current to the regulator 6, and a command current lb at which the discharge pressure of the pump 4 becomes the first pressure Pl is determined.
• the command current lb is a command current at which the capacity of the pump 4 becomes qb, when the discharge pressure of the pump 4 is the first pressure Pl, the speed of the engine 10 is Nl, and the cross-sectional area of the throttle of the variable throttle spool 24 is Ah.
• the capacity qb of the pump 4 and the command current lb it is preferable to determine a minimum command current Imin at which a minimum capacity qmin of the pump 4 is reached (see FIG. 3).
• the pump 4 is provided with the limiting means for limiting the slopes of the swash plate 4a within a predetermined range, the capacity of the pump 4 becomes a stable value even if the minimum capacity qmin is reached, with the result that the minimum command current Imin can be determined accurately.
• the first reference table is determined on the basis of the capacities qa, qb and the command currents la, lb.
• an explanation is provided on an example of determining the first reference table on the basis of the maximum capacity qmax, the minimum capacity qmin, the maximum command current Imax, and the minimum command current Imin.
• step SI of the illustrated embodiment first, the capacity qa (qmax) is calculated, then the command current la (Imax) is determined, and then the capacity qb (qmin) is calculated; thereafter, the command current lb (Imin) is determined.
• the order in which the capacities are calculated and the command currents are determined may be arbitrary.
• step S2 After executing the step SI of determining the first reference table TP1, as shown in FIG. 2, there is executed step S2 of determining a second reference table representing a relationship between the command current to the regulator 6 vs. the capacity of the pump 4 when the discharge pressure of the pump 4 is set to a second pressure.
• a capacity of the pump 4 (a first capacity ql) is calculated using the above equations (1) and (2), when the speed of the engine 10 is Nl, the cross-sectional area of the throttle of the variable throttle spool 24 is Al, and the discharge pressure of the pump 4 is a second pressure P2 (P2>P1) being higher than the first pressure Pl.
• the first capacity ql is a capacity between the minimum capacity qmin and the maximum capacity qmax (qmin ⁇ ql ⁇ qmax).
• the first command current II is a command current at which the capacity of the pump 4 becomes the first capacity ql when the discharge pressure of the pump 4 is the second pressure P2, the speed of the engine 10 is Nl, and the cross-sectional area of the throttle of the variable throttle spool 24 is Al.
• the first command current II is a current value between the minimum command current Imin and the maximum command current Imax (Imin ⁇ Il ⁇ Imax).
• a capacity of the pump 4 (a second capacity q2) is calculated using the above equations (1) and (2), when the speed of the engine 10 is Nh, the cross-sectional area of the throttle of the variable throttle spool 24 is Ah, and the discharge pressure of the pump 4 is the second pressure P2.
• the second capacity q2 is a capacity between the first capacity ql and the maximum capacity qmax (ql ⁇ q2 ⁇ qmax).
• the second command current 12 is a command current at which the capacity of the pump 4 becomes the second capacity q2, when the discharge pressure of the pump 4 is the second pressure P2, the speed of the engine 10 is Nh, and the cross-sectional area of the throttle of the variable throttle spool 24 is Ah.
• the second command current 12 is a current value between the first command current Il and the maximum command current Imax (Il ⁇ I2 ⁇ Imax).
• a second reference table is determined on basis of the first capacity ql, the second capacity q2, the first command current II and the second command current 12. Specifically, as shown in FIG. 3, with the horizontal axis representing the command current I to the regulator 6, and the vertical axis representing the capacity q of the pump 4, a point C specified by the 1st command current II and the 1st capacity ql, and a point D specified by the 2nd command current 12 and the 2nd capacity q2 are connected according to a Icha function. This enables the determination of a second reference table TP2 representing a relationship between the command current I to the regulator 6 vs. the capacity q of the pump 4 when the discharge pressure of the pump 4 is the second pressure P2.
• step S2 of the illustrated embodiment first, the first capacity ql is calculated, then the first command current II is determined, and then the second capacity q2 is calculated; thereafter, the second command current 12 is determined.
• the order in which the capacities are calculated and the command currents are determined may be arbitrary.
• step S3 of determining a plurality of correction tables representing a relationship between the discharge pressure of the pump 4 vs. the command current to the regulator 6 is executed on the basis of the first reference table TP1 and the second reference table TP2.
• step S3 first, a third capacity q3 corresponding to the first command current II is calculated by using the first reference table TP1 shown in FIG. 3.
• the third capacity q3, which is a capacity of the pump 4 associated with a point E, is greater than the first capacity ql (q3>ql) when the first command current II is input to the regulator 6 when the discharge pressure of the pump 4 is the second pressure P2.
• FIG. 4 with the horizontal axis representing the discharge pressure P of the pump 4, and the vertical axis representing the capacity q of the pump 4, there is shown a table Til obtained by connecting according to a linear function a point E' (a point corresponding to the point E in FIG. 3) specified by the first pressure Pl and the third capacity q3 and a point C (a point corresponding to the point C in FIG. 3) specified by the second pressure P2 and the first capacity ql .
• the table Til represents a relationship between the discharge pressure P of the pump 4 vs. the capacity q of the pump 4 when the command current to the regulator 6 becomes constant at the first command current II.
• the capacity of the pump 4 (the third capacity q3) when the command current to the regulator 6 is set to the first command current II when the discharge pressure of the pump 4 is the first pressure Pl
• the capacity of the pump 4 (the first capacity ql) when the command current to the regulator 6 is set to the first command current Il when the discharge pressure of the pump 4 is the second pressure P2
• a first current difference All corresponding to a difference between the third capacity q3 and the first capacity ql is calculated by using the first reference table TP1.
• a value II + All obtained by adding the first current difference All to the first command current II, 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.
• a first correction table representing a relationship between the discharge pressure of the pump 4 at which the capacity of the pump 4 becomes constant at the third capacity q3 vs. the command current to the regulator 6, on the basis of the first pressure Pl, the second pressure P2, the first command current II, and the first current difference All.
• a 1st correction table Tq3 can be determined by connecting according to a linear function a point E" (a point corresponding to the point E in FIG. 3 and the point E' in FIG. 4) specified by the 1st pressure Pl and the 1st command current II; and a correction point CC specified by a value II + All obtained by adding the 1st current difference All to the 1st command current Il and the 2nd pressure P2.
• the command current to the regulator 6 is corrected, by adjusting in accordance with the first correction table Tq3 the first current difference All to be added to the first command current II, as a function of the discharge pressure of the pump 4.
• the capacity of the pump 4 can be set to the third capacity q3, without depending on the discharge pressure of the pump 4, and power-down will never occur even if the discharge pressure of the pump 4 increases.
• All 0 holds at the first pressure Pl, and when the discharge pressure of the pump 4 becomes lower than the first pressure Pl, All takes a negative value, and when the discharge pressure of 4 becomes higher than the first pressure Pl, All takes a positive value.
• a fourth capacity q4 corresponding to the second command current 12 is calculated by using the first reference table TP1 shown in FIG. 3. As shown in FIG. 3, the fourth capacity q4, which is a capacity of the pump 4 associated with a point F, is greater than the second capacity q2 (q4>q2) when the second command current 12 is input to the regulator 6 when the discharge pressure of the pump 4 is the second pressure P2.
• FIG. 4 there is also shown a table TI2 obtained by connecting according to a linear function a point F' (a point corresponding to the point F in FIG. 3) specified by the first pressure Pl and the fourth capacity q4, and a point D' (a point corresponding to the point D in FIG. 3) specified by the second pressure P2 and the second capacity q2.
• the table TI2 represents a relationship between the discharge pressure P of the pump 4 vs. the capacity of the pump 4 when the command current to the regulator 6 becomes constant at the second command current 12.
• the capacity of the pump 4 (the fourth capacity q4) when the command current to the regulator 6 is set to the second command current 12 when the discharge pressure of the pump 4 is the first pressure Pl
• the capacity of the pump 4 (the second capacity q2) when the command current to the regulator 6 is set to the second command current 12 when the discharge pressure of the pump 4 is the second pressure P2
• a second current difference AI2 corresponding to a difference between the fourth capacity q4 and the second capacity q2 is calculated by using the first reference table TP1.
• a value 12 + AI2 obtained by adding the second current difference AI2 to the second command current 12 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.
• a second correction table representing a relationship between the discharge pressure of the pump 4 at which the capacity of the pump 4 becomes constant at the fourth capacity q4 vs. the command current to the regulator 6, on the basis of the first pressure Pl, the second pressure P2, the second command current 12 and the second current difference AI2.
• a 2nd correction table Tq4 can be determined by connecting according to a linear function a point F" (a point corresponding to the point F in FIG. 3 and the point F' in FIG. 4) specified by the 1st pressure Pl and the 2nd command current 12; and a correction point DC specified by a value 12 + AI2 obtained by adding the 2nd current difference AI2 to the 2nd command current 12 and the 2nd pressure P2.
• the command current to the regulator 6 is corrected, by adjusting in accordance with the second correction table Tq4 the second current difference AI2 to be added to the second command current 12, as a function of the discharge pressure of the pump 4.
• the capacity of the pump 4 can be set to the fourth capacity q4 without depending on the discharge pressure of the pump 4, and power-down will never occur even if the discharge pressure of the pump 4 increases.
• AI2 0 holds at the second pressure P2, and when the discharge pressure of the pump 4 becomes lower than the second pressure P2, AI2 takes a negative value, and when the discharge pressure of 4 becomes higher than the second pressure P2, AI2 takes a positive value.
• a gradient table Tg representing a relationship between the command current I to the regulator 6 vs. the gradient g of the correction table is determined, by connecting according to a linear function a point H specified by the first command current II and a gradient gl of the first correction table Tq3, and a point J specified by the second command current 12 and a gradient g2 of the second correction table Tq4. Then, other correction tables except for the first correction table Tq3 and the second correction table Tq4 are calculated, by using the gradient g determined from the gradient table Tg.
• the gradient of the correction table becomes a gradient gm (gm ⁇ gl) being smaller than a gradient gl of the first correction table Tq3, and then a correction table Tqm shown in FIG. 5 can be calculated by using this gradient gm.
• the correction table Tqm is a table representing a relationship between the discharge pressure of the pump 4 at which the capacity of the pump 4 becomes constant at a capacity qm vs. the command current to the regulator 6.
• the gradient of the correction table becomes a gradient gn (gn>g2) being greater than the gradient g2 of the second correction table Tq4, and then a correction table Tqn shown in FIG. 5 can be determined by using this gradient gn.
• the correction table Tqn is a table representing a relationship between the discharge pressure of the pump 4 at which the capacity of the pump 4 becomes constant at the capacity qn vs. the command current to the regulator 6.
• a plurality of other correction tables except for the first and second correction tables Tq3 and Tq4 can be calculated, by using the gradient table Tg shown in FIG. 6, by calculating a plurality of gradients when the command current to the regulator 6 is a command current except for the first and second command currents II and 12.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Computer Hardware Design (AREA)
• Control Of Positive-Displacement Pumps (AREA)

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Citations (4)

• 2020
  • 2020-11-10 JP JP2020186949A patent/JP2022076550A/ja active Pending
• 2021
  • 2021-11-09 WO PCT/EP2021/025435 patent/WO2022100884A1/en active Application Filing
  • 2021-11-09 CN CN202180075377.1A patent/CN116568925A/zh active Pending

Patent Citations (5)

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