JP2014009655A - Electric pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make power consumption for driving a pump more efficient by suppressing an excess output larger than a required hydraulic pressure, and reduce the number of current value signal lines connecting a vehicle ECU and a pump ECU.SOLUTION: An electric pump includes: motor rotational velocity detection means for detecting a rotational velocity of a motor; motor current consumption detection means for detecting a current consumption of the motor; relief valve operation starting point detection means for detecting an operation starting point of a relief valve on the basis of the rotational velocity of the motor detected by the motor rotational velocity detection means and the current consumption of the motor detected by the motor current consumption detection means; and motor control means for controlling at least one of the rotational velocity of the motor and the current supplied to the motor on the basis of at least one of the rotational velocity of the motor and the current consumption of the motor at the operation starting point of the relief valve detected by the relief valve operation starting point detection means.

Description

  The present invention relates to an electric pump driven by a motor.

  As shown in Patent Document 1, a vehicle having an idling stop function generally includes an electric oil pump. In such vehicles, the mechanical pump driven by the engine is stopped while idling is stopped, but the electric oil pump supplies the minimum necessary hydraulic pressure to the transmission, torque converter, etc. The vehicle can be supplied quickly and restarted.

  Such an electric oil pump includes an outer rotor in which inner teeth formed with a trochoid curve are formed on the inner periphery, an inner rotor formed with outer teeth that are formed with a trochoid curve and mesh with the inner teeth, The trochoid pump is composed of a housing that rotatably accommodates the outer rotor and the inner rotor, and a motor that rotates the inner rotor. The electric oil pump also includes a pump ECU that controls the discharge hydraulic pressure.

  In addition, such a vehicle is provided with a relief valve for making the hydraulic pressure supplied to the hydraulic pressure required portion constant, a hydraulic pressure sensor for detecting the hydraulic pressure at the hydraulic pressure required location, and a vehicle ECU for controlling the hydraulic pressure required location. ing. The vehicle ECU outputs a command for a current value to be supplied to the motor to the pump ECU based on the detection value from the hydraulic sensor, and controls the discharge hydraulic pressure of the electric oil pump. This discharge hydraulic pressure is set to a pressure higher than the opening pressure at which the relief valve opens. The vehicle ECU and the pump ECU are connected by a current value command signal line for transmitting a command of a current value supplied to the motor.

JP 2001-227606 A

  In the vehicle disclosed in Patent Document 1, it is necessary to provide a hydraulic pressure sensor and a current value command signal line for connecting the vehicle ECU and the pump ECU at a location where the hydraulic pressure is required, which increases the cost. Further, the accuracy of the hydraulic sensor attached to the vehicle is low, and there is variation in the measurement of the hydraulic pressure by the hydraulic sensor. For this reason, in order to cope with this variation, the hydraulic oil pump discharges excess hydraulic pressure and flow rate oil, and sometimes operates the relief valve to keep the hydraulic pressure supplied to the required hydraulic pressure above the required value. Yes. For this reason, there has been a problem that losses due to excess oil pressure and flow rate oil discharged by the electric oil pump occur.

  The present invention has been made in view of such circumstances, and suppresses an excessive output exceeding the required hydraulic pressure, improves the power consumption for driving the pump, and connects the vehicle ECU and the pump ECU. An electric pump capable of reducing value signal lines is provided.

  (Embodiment 1) An electric pump according to the present invention is an electric pump having a pump body for feeding fluid and a motor for driving the pump body, and the discharge pressure of the fluid discharged by the pump body by a relief valve The motor rotation speed detection means for detecting the rotation speed of the motor, the motor consumption current detection means for detecting the consumption current of the motor, and the rotation speed of the motor detected by the motor rotation speed detection means And a relief valve operation start point detection means for detecting an operation start point of the relief valve based on the current consumption of the motor detected by the motor consumption current detection means, and the relief valve operation start point detection means detected Based on at least one of the rotational speed of the motor and the current consumption of the motor at the starting point of operation, Further comprising a motor control means for controlling at least one of the rotational speed and the current supplied to the motor of the motor.

(Claim 2)
The relief valve operation start point detecting means gradually decreases or gradually increases the rotation speed of the motor, detects a plurality of current consumptions of the motor at the changed rotation speed of the motor, and rotates the rotation speed of the motor. And calculating an approximate curve representing the relationship between the motor current consumption and whether or not the relationship between the changed motor rotation speed and the motor current consumption deviates from the approximate curve by a predetermined amount. By doing so, it is preferable to detect the operation start point of the relief valve.

(Claim 3)
The relief valve operation start point detecting means changes the rotation speed of the motor within a predetermined range, detects a plurality of consumption currents of the motor at the changed rotation speed of the motor, and A first approximate curve representing the relationship between the motor rotation speed and the motor current consumption is calculated, and the motor rotation speed is lower than the range of the motor rotation speed changed when the first approximate curve is calculated. A plurality of current consumptions of the motor are detected in a range of the rotational speed, and a second approximate curve representing a relationship between the rotation speed of the motor and the current consumption of the motor when the relief valve is not operated is calculated, It is preferable to detect the intersection of the first approximate curve and the second approximate curve as the operation start point of the relief valve.

(Claim 4)
The relief valve operation start point detecting means changes the rotation speed of the motor within a predetermined range, detects a plurality of current consumptions of the motor at the changed rotation speed of the motor, In the range of the number of rotations of the motor that is lower than the range of the rotation speed of the motor changed when calculating the first approximate curve, calculating a first approximate curve that represents the relationship with the current consumption of the motor, A plurality of current consumptions of the motor are detected, a second approximate curve representing the relationship between the rotation speed of the motor and the current consumption of the motor is sequentially calculated, and the second approximate curve changes from the first approximate curve It is preferable to detect the operation start point of the relief valve by detecting whether or not the operation has been performed.

(Claim 5)
The motor control means controls the motor at a rotation speed that is lower than the rotation speed of the motor at the operation start point, or a current that is lower than the current consumption of the motor at the operation start point. Is preferably supplied to the motor.

  (First aspect) According to the electric pump of the present invention, the relief valve operation start point detecting means detects the operation start point of the relief valve based on the rotational speed of the motor and the current consumption of the motor. The motor control means controls at least one of the rotation speed of the motor and the current supplied to the motor based on at least one of the rotation speed of the motor and the current consumption of the motor at the operation start point of the relief valve. Thereby, the electric pump itself can control the discharge hydraulic pressure of the electric pump in the vicinity of the operation start point of the relief valve. For this reason, regardless of variations in the hydraulic pressure sensor on the vehicle side, an excessive output exceeding the required hydraulic pressure can be suppressed, oil can be discharged close to the required hydraulic pressure, and the power consumption for driving the pump can be made more efficient. It is possible to provide an electric pump that can reduce the current value signal line connecting the pump ECU.

  (Claim 2) The relief valve actuation start point detecting means gradually decreases or gradually increases the rotation speed of the motor, detects a plurality of motor current consumption at the changed rotation speed of the motor, and rotates the rotation speed of the motor. By calculating an approximate curve representing the relationship between the motor current consumption and the motor current consumption, and determining whether the motor current consumption at the changed motor speed deviates from the approximate curve by a predetermined amount. Detect the starting point. In other words, when the relief valve is operated, the discharge hydraulic pressure of the electric pump is limited to a constant pressure by the operation of the relief valve, the load on the motor is reduced with respect to the oil discharge flow rate, and the current consumption of the motor at the changed motor rotation speed is reduced. Deviate from the approximate curve. As described above, the relief valve operation start point detecting means reliably determines the relief valve operation start point by determining whether or not the motor consumption current at the changed motor rotation speed deviates from a predetermined amount from the approximate curve. Can be detected.

  (Claim 3) When the relief valve operation start point detecting means calculates a first approximate curve representing the relationship between the motor rotation speed and the motor current consumption during the relief valve operation, the first approximate curve is calculated. A second approximate curve representing the relationship between the motor rotation speed and the motor current consumption when the relief valve is not operated in the range of the motor rotation speed lower than the range of the motor rotation speed changed to The intersection of the first approximate curve and the second approximate curve is detected as the operation start point of the relief valve. The intersection of the first approximate curve and the second approximate curve is the point where the relief valve in the non-actuated state starts to operate. Thus, by detecting the intersection of the first approximate curve and the second approximate curve as the operation start point of the relief valve, the operation start point of the relief valve can be detected with high accuracy.

  (Claim 4) The relief valve operation start point detecting means changes the rotation speed of the motor within a predetermined range, calculates a first approximate curve representing the relationship between the rotation speed of the motor and the consumption current of the motor, The relationship between the motor rotation speed and the motor consumption current is detected by detecting multiple motor consumption currents in the range of motor rotation speeds lower than the range of motor rotation speeds that were changed when calculating one approximate curve. Is calculated sequentially, and it is detected whether the second approximate curve has changed from the first approximate curve, thereby detecting the operation start point of the relief valve. The point at which the second approximate curve changes from the first approximate curve is the point at which the relief valve in the inactive state starts to operate. In this way, by detecting whether or not the second approximate curve has changed from the first approximate curve, the operation start point of the relief valve can be detected with high accuracy.

  (Claim 5) The motor control means controls the motor at a rotational speed that is lower than the rotational speed of the motor at the operation start point, or a current that is lower than the current consumption of the motor at the operation start point. Is supplied to the motor. As a result, it is possible to keep the hydraulic pressure supplied to the required hydraulic pressure constant without operating the relief valve. For this reason, it is not necessary to keep the hydraulic pressure supplied to the required oil pressure constant by always discharging the excess flow of oil with the electric oil pump and always operating the relief valve. Loss caused by flow rate oil can be reduced.

It is explanatory drawing of the oil flow path of the vehicle by which the electric oil pump of this embodiment is mounted. It is a schematic diagram of a vehicle in which the electric oil pump of this embodiment is mounted. It is AA sectional drawing of FIG. 2, and is sectional drawing of a pump part. It is the graph showing the relationship between the rotational speed of a motor and the consumption current of a motor in each state in which a relief valve is in operation / non-operation. It is a flowchart of the pump control process of 1st embodiment. It is explanatory drawing which showed the outline | summary of the pump control processing of 1st embodiment. It is a flowchart of the pump control process of 2nd embodiment. It is explanatory drawing which showed the outline | summary of the pump control processing of 2nd embodiment. It is a flowchart of the pump control process of 3rd embodiment. It is explanatory drawing which showed the outline | summary of the pump control processing of 3rd embodiment.

(Vehicle overview)
Hereinafter, an embodiment in which the pump of the present invention is embodied will be described with reference to the drawings. First, a vehicle 900 on which the electric oil pump 100 of this embodiment is mounted will be described with reference to FIGS. 1 and 2. As shown in FIGS. 1 and 2, a vehicle 900 includes an electric oil pump 100, a relief valve 15, a check valve 200, a valve body 300, a hydraulic pressure required portion 400, a mechanical oil pump 500, an oil pan 600, an engine 700, and a vehicle ECU 800. It has.

  The electric oil pump 100 is a pump that drives the pump main body 10 by the motor 20. The electric oil pump 100 sucks oil from the oil pan 600 and supplies the oil to the hydraulic pressure required portion 400 through the check valve 200 and the valve body 300. The relief valve 15 regulates the hydraulic pressure discharged from the electric oil pump 100 at a constant level. The electric oil pump 100 and the relief valve 15 will be described in detail later.

  The check valve 200 is provided between the suction passage 11c (shown in FIGS. 2 and 3) of the electric oil pump 100 and the valve body 300, and allows oil to flow from the electric oil pump 100 to the valve body 300. The reverse flow of oil from the valve body 300 to the electric oil pump 100 is prevented.

  The mechanical oil pump 500 is driven by the rotational driving force of the engine 700 (shown in FIG. 2), sucks oil from the oil pan 600, and supplies the oil to the hydraulic pressure required point 400 via the valve body 300. is there. Of course, the mechanical oil pump 500 does not supply oil when the engine 700 is stopped.

  In response to a command from the vehicle ECU 800, the valve body 300 switches the inflow side flow path of oil flowing into itself to either the electric oil pump 100 (check valve 200) side or the mechanical oil pump 500 side.

  The hydraulic pressure required portion 400 is, for example, a transmission that decelerates the rotational driving force input from the engine 700 at a predetermined gear ratio and outputs it to the differential, or amplifies the rotational torque output from the output shaft of the engine 700 to the transmission. Input torque converter or the like.

  The oil pan 600 is supplied to the hydraulic pressure required portion 400 and stores oil discharged from the hydraulic pressure required portion 400.

  The vehicle ECU 800 performs overall control of the vehicle 900 and controls the engine 700 and the hydraulic pressure required portion 400 of the transmission. The vehicle ECU 800 stops the engine 700 when it is determined that the running vehicle 900 is stopped and the idling stop stop condition is satisfied based on vehicle speed information detected by a vehicle speed sensor (not shown). A “pump start command” is output to the pump ECU 40. Further, the vehicle ECU 800 determines whether the brake pedal is released or the accelerator is released in the stopped vehicle 900 based on the brake information detected by a brake sensor (not shown) or the accelerator opening information detected by an accelerator opening sensor (not shown). When it is determined that the idling stop cancellation condition such as being stepped on is satisfied, the engine 700 is started and a “pump stop command” is output to the pump ECU 40.

(Electric oil pump)
The electric oil pump 100 has a pump body 10 and a motor 20. The pump main body 10 is driven by the motor 20 and supplies the oil pressure necessary point 400 during idling stop (when the engine 700 is stopped). The pump body 10 will be described in detail later.

  The motor 20 outputs a rotational driving force to the pump body 10. In this embodiment, the motor 20 is a direct current brushless motor, and is a stator 22 fixed to the casing 21 and configured by a coil, and a rotor 23 that is rotatably provided on the inner peripheral side of the stator 22 and is configured by a permanent magnet. And a rotating shaft 24 of the rotor 23. The motor 20 is provided with a rotation speed sensor 25 for detecting the rotation speed of the motor 20 (rotation speed of the rotor 23) and detecting the rotation speed of the motor 20. The “motor rotational speed”, which is the rotational speed of the motor 20 detected by the rotational speed sensor 25, is input to the pump ECU 40.

  The motor driver 30 is connected to a vehicle battery (not shown) and supplies current to the stator 22 of the motor 20 based on a control signal from the pump ECU 40. The vehicle 900 includes a motor current detection unit 31 such as an ammeter that detects a “motor current” that is a current value of a current supplied from the motor driver 30 to the motor 20. The “motor current” detected by the motor current detector 31 is input to the pump ECU 40.

  The pump ECU 40 is communicably connected to the vehicle ECU 800 and the motor driver 30, and outputs a control signal to the motor driver 30 based on a command from the vehicle ECU 800. Specifically, the pump ECU 40 controls the discharge hydraulic pressure of the oil supplied by the pump body 10 by controlling the current supplied to the motor 20 and the rotational speed of the motor 20.

  The pump ECU 40 includes a microcomputer, and the microcomputer includes an input / output interface, a CPU, a RAM, and a “storage unit” such as a ROM and a nonvolatile memory, which are connected via a bus. The CPU executes a program corresponding to the flow shown in FIGS. The RAM temporarily stores variables necessary for executing the program. The “storage unit” stores the program and programs for executing the flows shown in FIGS. 5, 7, and 9. The control by the pump ECU 40 will be described in detail later.

(Pump body)
Below, the structure of the pump main body 10 is demonstrated using FIG.2 and FIG.3. The pump body 10 includes a housing 11, an inner rotor 12, an outer rotor 13, a seal member 14, and a relief valve 15.

  The housing 11 has a block shape, and a pump chamber 11b which is a flat cylindrical space is formed therein. As shown in FIG. 2, an insertion hole 11 a communicating with the pump chamber 11 b is formed in the center of the housing 11. The rotating shaft 24 of the motor 20 is inserted through the insertion hole 11a. A ring-shaped seal member 14 is attached to the insertion hole 11 a so as to be in contact with the rotary shaft 24 over the entire circumference and seal between the housing 11 and the rotary shaft 24.

  As shown in FIG. 3, an outer rotor 13 is rotatably mounted in the pump chamber 11b. The outer rotor 13 has a flat cylindrical shape having a circular cross section, and an inner tooth 13a that is a space is formed on the inner peripheral side. An inner rotor 12 is rotatably provided in the inner teeth 13a. The inner rotor 12 has a ring shape, and outer teeth 12a are formed on the outer edge. The inner teeth 13a and the outer teeth 12a are constituted by a plurality of trochoid curves. The number of teeth of the external teeth 12a is smaller than the number of teeth of the internal teeth 13a. The outer teeth 12a and the inner teeth 13a mesh with each other. The rotation center of the outer rotor 13 is eccentric with respect to the rotation center of the inner rotor 12. The center of the inner rotor 12 and the rotating shaft 24 of the motor 20 are fitted, and the inner rotor 12 and the rotating shaft 24 rotate integrally.

  As shown in FIGS. 2 and 3, a crescent-shaped suction side groove 11e and a discharge side groove 11f are recessed at predetermined intervals along the circumferential direction of the bottom of the pump chamber 11b at the bottom of the pump chamber 11b. Is formed. The suction side groove 11e and the discharge side groove 11f face each other at the bottom of the pump chamber 11b. Further, the positions where the suction side groove 11e and the discharge side groove 11f are formed are formed in a locus along which the space formed between the outer teeth 12a and the inner teeth 13a moves. As shown in FIG. 3, the side of the pump chamber 11b where the suction side groove 11e is formed is the suction side, and the side of the pump chamber 11b where the discharge side groove 11f is formed is the discharge side.

  The housing 11 is formed with a suction channel 11c that communicates with the bottom of the suction side groove 11e and communicates with the pump chamber 11b. The position where the suction channel 11c communicates with the bottom of the suction side groove 11e is that the space formed between the outer teeth 12a and the inner teeth 13a is the start end of the suction side groove 11e that first passes through the suction side groove 11e. is there. The housing 11 is formed with a discharge passage 11d that communicates with the bottom of the discharge side groove 11f and communicates with the pump chamber 11b. The position where the discharge channel 11d communicates with the bottom of the discharge side groove 11f is the end portion of the discharge side groove 11f where the space formed between the external teeth 12a and the internal teeth 13a finally passes through the discharge side groove 11f. is there. The suction channel 11c is connected to the oil pan 600 by a suction pipe 91 (shown in FIGS. 1 and 2). Further, the discharge flow path 11 d is connected to the check valve 200 by a discharge pipe 92.

  When the motor 20 rotates, the inner rotor 12 rotates, and the outer rotor 13 meshed with the outer teeth 12a by the inner teeth 13a also rotates. Then, the space formed between the external teeth 12a and the internal teeth 13a sequentially moves to the suction flow path 11c, the suction side groove 11e, the discharge side groove 11f, and the discharge flow path 11d, and from the suction flow path 11c to the discharge flow path 11d. Oil is fed to

(Relief valve)
Next, the relief valve 15 will be described with reference to FIG. The relief valve 15 includes a relief flow path 11g, a spool 16, a spring receiving member 17, and a spring 18. The relief channel 11g communicates the discharge side groove 11f and the suction side groove 11e. A receiving portion 11h, which is a space corresponding to the outer shape of a closing portion 16a of the spool 16 described later, is formed in the opening facing the suction side groove 11e of the relief flow channel 11g.

  The housing 11 is formed with a sliding hole 11j communicating with the outside and the suction side groove 11e. The spool 16 is slidably provided in the sliding hole 11j, and a closing portion 16a formed at the tip is received in the receiving portion 11h.

  The spring receiving member 17 is attached to the opening of the sliding hole 11j to the outside of the housing 11. The spring 18 is provided between the spring receiving member 17 and the end of the spool 16, and biases the spool 16 toward the receiving portion 11h. For this reason, the closing part 16a is pressed against the bottom of the receiving part 11h and closes the relief flow path 11g.

  When the hydraulic pressure on the discharge side of the pump chamber 11b becomes equal to or higher than the opening pressure (operation start pressure) of the relief valve 15, the spool 16 slides toward the spring receiving member 17 against the biasing force of the spring 18, and the relief flow path 11g. And the suction side groove 11e communicate with each other. Then, the oil in the discharge side groove 11f is discharged to the suction side groove 11e. When the oil in the discharge side groove 11f is discharged to the suction side groove 11e, the oil pressure on the discharge side of the pump chamber 11b decreases. When the hydraulic pressure on the discharge side of the pump chamber 11b is lower than the opening pressure, the spool 16 slides toward the receiving portion 11h, and the closing portion 16a closes the relief flow path 11g. In this way, the relief valve 15 is operated and the closing portion 16a of the spool 16 opens or closes the relief flow path 11g, whereby the discharge pressure of the oil discharged from the pump body 10 is maintained at the open pressure. Note that the release pressure of the relief valve 15 is set to a hydraulic pressure that is higher than the required hydraulic pressure at the required hydraulic pressure point 400 by a predetermined hydraulic pressure.

(Relationship between motor rotation speed and current consumption when the relief valve is activated or deactivated)
A graph showing the relationship between the rotational speed of the motor 20 and the current consumption of the motor 20 in each state where the relief valve 15 is activated and deactivated will be described below with reference to FIG. As shown in FIG. 4, the current consumption of the motor 20 increases as the rotational speed of the motor 20 increases. The rotational speed of the motor 20 and the oil discharge flow rate of the electric oil pump 100 are in a proportional relationship. When the rotational speed of the motor 20 and the current consumption of the motor 20 increase and the relief valve 15 starts operating, the current consumption of the motor 20 relative to the rotational speed of the motor 20 compared to when the relief valve 15 does not start operating. The amount of increase is small. This is because the discharge hydraulic pressure of the electric oil pump 100 is limited to the opening pressure of the relief valve 15 by the operation of the relief valve 15, and the load on the motor 20 with respect to the oil discharge flow rate (proportional to the rotational speed of the motor 20) is reduced. This is because the amount of increase in current consumption of the motor 20 is small. In the following description, the point (inflection point) at which the curve of the relationship between the rotational speed of the motor 20 and the current consumption of the motor 20 changes and the relief valve 15 in the non-operating state changes is referred to as “relief valve”. This is the “operation start point”.

  Note that the curve representing the relationship between the rotational speed of the motor 20 and the current consumption of the motor 20 is a downwardly convex curve both when the relief valve 15 is not operated and when it is operated. Moreover, even if the vehicle has the same specification, there are variations in the amount of oil leakage at the hydraulic pressure required point 400 depending on the vehicle. As indicated by the solid line and the dotted line in FIG. The relationship of the current consumption of 20 is different. For this reason, the “relief valve operation start point” varies depending on the vehicle.

(Pump control processing of the first embodiment)
Next, the “pump control process” of the first embodiment will be described with reference to the flowchart of FIG. 5 and the explanatory diagram of FIG. When the vehicle 900 is ready to travel, the program proceeds to S11. In S11, when the pump ECU 40 determines that the “pump start command” is input from the vehicle ECU 800 (S11: YES), the program proceeds to S12, and the “pump start command” is not input from the vehicle ECU 800. If it is determined (S11: NO), the process of S11 is repeated.

  In S12, the pump ECU 40 starts control to set the motor 20 to the maximum rotational speed set in the motor 20, and advances the program to S13. In S13, when the pump ECU 40 determines that the rotational speed of the motor 20 has reached the maximum rotational speed set for the motor 20 (S13: YES) ((1) in FIG. 6A), When the program proceeds to S14 and it is determined that the rotational speed of the motor 20 has not reached the maximum rotational speed set for the motor 20 (S13: NO), the process of S13 is repeated. When the rotation speed of the motor 20 reaches the maximum rotation speed set for the motor 20, the relief valve 15 is activated, and the discharge hydraulic pressure of the electric oil pump 100 is reduced by the relief valve 15. The pressure is adjusted to the opening pressure.

  In S14, the pump ECU 40 decreases the rotation speed of the motor 20 by a predetermined rotation speed (for example, 50 rpm), detects the current consumption of the motor 20 at the rotation speed of the motor 20 that has decreased the rotation, The current consumption of the motor 20 is stored in the “storage unit” in association with the rotational speed of the motor 20 ((2) in FIG. 6A). Hereinafter, the relationship between the rotation speed of the motor 20 stored in the “storage unit” and the current consumption of the motor 20 is referred to as a “detection point”. When S14 ends, the program proceeds to S15.

  In S15, the pump ECU 40 detects the “relief valve operation start point”. Specifically, the pump ECU 40 is based on three or more “detection points” stored in the “storage unit”, such as a quadratic function representing a relationship between the rotation speed of the motor 20 and the current consumption of the motor 20. The “first approximate curve” (solid line in FIG. 6) is calculated ((3) in FIG. 6A). The “detection point” ((4) in FIG. 6) at which the rotation speed of the motor 20 is the lowest is not included in the calculation of the approximate curve. Next, when the consumption current of the “detection point” at which the rotation speed of the motor 20 is the lowest exceeds the “regulation error” from the “first approximate curve”, the pump ECU 40 has the highest rotation speed of the motor 20. It is determined that there is a “relief valve operation start point” between the low “detection point” ((4) in FIG. 6) and the “detection point” ((5) in FIG. 6) having the second lowest rotation speed. To do.

  Next, the pump ECU 40 increases the rotation speed of the motor 20 by a predetermined rotation speed (for example, 10 rpm) from the “detection point” where the rotation speed is the lowest, and the rotation speed of the motor 20 that has increased the rotation. Is stored in the “storage unit” ((6) in FIG. 6B), and the motor is based on three “detection points” that are higher by a predetermined rotational speed from the “detection point” having the lowest rotational speed. A “second approximate curve” (dotted line in FIG. 6) such as a quadratic function representing the relationship between the rotational speed of 20 and the current consumption of the motor 20 is calculated ((7) in FIG. 6B). The range of the rotational speed of the motor 20 at the “detection point” detected when calculating the “second approximate curve” is larger than the range of the rotational speed of the motor 20 when the “first approximate curve” is calculated. This is the range of the rotation speed of the low motor 20.

  Next, the pump ECU 40 calculates the intersection of the “first approximate curve” and the “second approximate curve” and detects the intersection as the “relief valve operation start point” ((8) in FIG. 6B). . When the pump ECU 40 detects the “relief valve operation start point” by the above method (S15: YES), the program proceeds to S16, and when the “relief valve operation start point” is not detected (S15: NO). Return the program to S14.

  In S16, the pump ECU 40 determines the rotational speed of the motor 20 at the time of idling stop based on the “relief valve operation start point” detected in S15. Specifically, the pump ECU 40 determines a rotational speed slightly lower than the rotational speed of the motor 20 at the “relief valve operation start point” (for example, 50 rpm) as the rotational speed of the motor 20 when idling is stopped. To do. When S16 ends, the process proceeds to S17.

  In S17, the pump ECU 40 controls the motor 20 to the rotational speed determined in S16. When S17 ends, the program proceeds to S18.

  If the pump ECU 40 determines in S18 that a “pump stop command” has been input from the vehicle ECU 800 (S18: YES), the electric oil pump 100 is stopped and the program is returned to S11. If it is determined that the “stop command” has not been input (S18: NO), the process of S18 is repeated.

(Pump control processing of the second embodiment)
Next, the “pump control process” of the second embodiment will be described with reference to the flowchart of FIG. 7 and the explanatory diagram of FIG. When the vehicle 900 is ready to travel, the program proceeds to S21. Since the processes of S21, S22, and S23 of the “pump control process” of the second embodiment are the same as the processes of S11, S12, and S13 of the “pump control process” of the first embodiment, respectively. Description is omitted. In S23, when the pump ECU 40 determines that the rotational speed of the motor 20 has reached the set maximum rotational speed (S23: YES) ((1) in FIG. 8A), the program is executed in S24. Proceed to

  In S24, the pump ECU 40 calculates a “first approximate curve” such as a quadratic function. Specifically, as shown in (2) of FIG. 8A, the pump ECU 40 detects three or more “detection points” at a rotational speed of the motor 20 in a certain range, and detects the detected three or more “ Based on the “detection point”, a “first approximate curve” (solid line in FIG. 6) representing the relationship between the rotation speed of the motor 20 and the current consumption of the motor 20 is calculated ((3) in FIG. 8A). When S24 ends, the process proceeds to S25.

  In S25, the pump ECU 40 calculates a “second approximate curve” such as a quadratic function. Specifically, as shown in (4) of FIG. 8A, the pump ECU 40 has a range lower than the rotational speed of the motor 20 that has detected the “detection point” when calculating the “first approximate curve”. In the rotational speed of the motor 20, three or more “detection points” are detected, and a “second” representing the relationship between the rotational speed of the motor 20 and the current consumption of the motor 20 based on the detected three or more “detection points”. An “approximate curve” (dotted line in FIG. 8) is calculated ((5) in FIG. 8A). When S25 ends, the process proceeds to S26.

  In S26, as shown in FIG. 8B, the pump ECU 40 determines that one of the “first approximate curve” and the “second approximate curve” is an upwardly convex curve. It is determined that either of the “first approximate curve” and the “second approximate curve” has a “relief valve operation start point” (S26: YES), the program proceeds to S27, and the “first approximate curve” and “ If it is determined that none of the “second approximate curve” is an upwardly convex curve, it is determined that neither the “first approximate curve” nor the “second approximate curve” has a “relief valve operation start point”. (S26: NO), the program proceeds to S28.

  In S27, the pump ECU 40 detects the current consumption of the motor 20 for the “first approximate curve” or the “second approximate curve” determined to have the “relief valve operation start point” in S26. The “detection point” is detected by changing the rotation speed, and the “first approximate curve” or the “second approximate curve” is calculated again based on the “detection point”. When S27 ends, the program proceeds to S26.

  In S28, when the pump ECU 40 determines that the “first approximate curve” and the “second approximate curve” are the same or approximate (S28: YES), the program proceeds to S29, and the “first approximate curve” And “second approximate curve” are not identical and are not approximated (S28: NO), the program proceeds to S30.

  In S29, the pump ECU 40 detects the “detection point” by making the rotation speed range of the motor 20 different from the range of the rotation speed of the motor 20 that detected the “detection point” when calculating the “second approximate curve” last time. Then, the “second approximate curve” is calculated again based on the “detection point”. When S29 ends, the program proceeds to S26.

  In S30, the pump ECU 40 calculates an intersection between the “first approximate curve” and the “second approximate curve” and detects the intersection as a “relief valve operation start point” ((6) in FIG. 8A). . When S30 ends, the program proceeds to S31.

  Since the processes of S31, S32, and S33 of the “pump control process” of the second embodiment are the same as the processes of S16, S17, and S18 of the “pump control process” of the first embodiment, the description is omitted. .

(Pump control processing of the third embodiment)
Next, the “pump control process” of the third embodiment will be described with reference to the flowchart of FIG. 9 and the explanatory diagram of FIG. When the vehicle 900 is ready to travel, the program proceeds to S41. Note that the processes of S41 and S42 of the “pump control process” of the third embodiment are the same as the processes of S11 and S12 of the “pump control process” of the first embodiment, respectively, and thus description thereof is omitted. .

  When the pump ECU 40 determines in S43 that the rotation speed of the motor 20 has reached the set maximum rotation speed (S43: YES) ((1) in FIG. 10A), the program is executed in S44. Proceed to

  In S44, the pump ECU 40 calculates a “first approximate curve” such as a quadratic function. Specifically, as shown in (2) of FIG. 10A, the pump ECU 40 detects three or more “detection points” at a rotational speed of the motor 20 within a certain range, and detects the detected three or more “ Based on the “detection point”, a “first approximate curve” (solid line in FIG. 10) such as a quadratic function representing the relationship between the rotation speed of the motor 20 and the current consumption of the motor 20 is calculated ((A) in FIG. 3)). When S44 ends, the process proceeds to S45.

  In S45, the pump ECU 40 calculates a “second approximate curve” such as a quadratic function. Specifically, as shown in (4) of FIGS. 10A and 10B, the pump ECU 40 determines the rotation speed of the motor 20 that has detected the “detection point” when calculating the “first approximate curve”. 3 or more “detection points” are detected at the rotation speed of the motor 20 in the lower range, and the relationship between the rotation speed of the motor 20 and the current consumption of the motor 20 is represented based on the detected three or more “detection points”. A “second approximate curve” (dotted line in FIG. 10) such as a quadratic function is calculated ((5) in FIGS. 10A and 10B). When S45 ends, the process proceeds to S46.

  In S46, when the pump ECU 40 determines that one of the “first approximate curve” and the “second approximate curve” is an upward convex curve, the “first approximate curve” and the “second approximate curve” It is determined that there is a “relief valve operation start point” in any of the “curves” (S46: YES), the program proceeds to S47, and both the “first approximate curve” and the “second approximate curve” are If it is determined that the curve is not a convex curve, it is determined that neither the “first approximate curve” nor the “second approximate curve” has a “relief valve actuation start point” (S46: NO), and the program proceeds to S48. .

  In S47, the pump ECU 40 detects the current consumption of the motor 20 for the “first approximate curve” or the “second approximate curve” determined to have the “relief valve operation start point” in S46. The “detection point” is detected by changing the rotation speed, and the “first approximate curve” or the “second approximate curve” is calculated again based on the “detection point”. When S47 ends, the program proceeds to S46.

  In S48, when the pump ECU 40 determines that the "first approximate curve" and the "second approximate curve" are the same or approximate as shown in FIG. 10A (S48: YES), When the program proceeds to S49 and it is determined that the “first approximate curve” and the “second approximate curve” are not identical and not approximated as shown in FIG. "Is changed with respect to the" first approximate curve "(S48: NO), the program proceeds to S50.

  In S <b> 49, the pump ECU 40 determines the rotation speed range in which the rotation speed of the motor 20 is lower than the rotation speed range of the motor 20 that detected the “detection point” when calculating the “second approximate curve” last time. The “detection point” is detected, and the “second approximate curve” is calculated again based on the “detection point”. When S49 ends, the program proceeds to S46.

  In S50, the pump ECU 40 determines that the “detection point” ((6) in FIG. 10B) having the lowest rotation speed among the “detection points” detected when the “first approximate curve” is calculated, Among the “detection points” detected when calculating the “second approximate curve”, the “relief valve operation start point” between the “detection points” ((7) in FIG. 10B) with the highest rotation speed. It is determined that there is a “relief valve operation start point”. For example, the pump ECU 40 calculates and detects the “relief valve operation start point” by averaging the power consumption and the rotational speed of the motor 20 at the “detection point” in (6) and the “detection point” in (7). ((8) in FIG. 10B). When S50 ends, the program proceeds to S51.

  Since the processes of S51, S52, and S53 of the “pump control process” of the third embodiment are the same as the processes of S16, S17, and S18 of the “pump control process” of the first embodiment, description thereof is omitted. .

(Effect of this embodiment)
As described above in detail, according to the electric oil pump 100 (electric pump) according to the present embodiment, as shown in S15 of FIG. 5 and FIG. 6, as shown in S30 of FIG. As shown in S50 of FIG. 9 and FIG. 10, the pump ECU 40 (relief valve operation start point detecting means) determines the “relief valve operation start point” based on the rotational speed of the motor 20 and the current consumption of the motor 20 (see FIG. 6 (B) (8), FIG. 8 (A) (6), and FIG. 10 (B) (8)) are detected. Then, in S16 and S17 in FIG. 5, S31 and S32 in FIG. 7, or S51 and S52 in FIG. 9, the pump ECU 40 (motor control means) is based on the rotational speed of the motor 20 at the “relief valve operation start point”. Thus, the rotational speed of the motor 20 is controlled. Thereby, the electric oil pump 100 itself can control the discharge hydraulic pressure of the electric oil pump 100 in the vicinity of the “relief valve operation start point”. For this reason, regardless of variations in the hydraulic sensor on the vehicle side, an excessive output exceeding the required hydraulic pressure can be suppressed, oil can be discharged close to the required hydraulic pressure, and power consumption for driving the pump body 10 can be made efficient, Electric oil pump 100 that can reduce the current value signal line connecting vehicle ECU 800 and pump ECU 40 can be provided.

  As shown in S15 and S14 of FIG. 5 and FIG. 6, the pump ECU 40 (relief valve operation start point detecting means) gradually decreases the rotation speed of the motor 20, and the motor 20 at the decreased rotation speed of the motor 20 is reduced. A plurality of consumption currents are detected, a “first approximate curve” ((3) in FIG. 6) representing the relationship between the rotation speed of the motor 20 and the consumption current of the motor 20 is calculated, and the rotation of the motor 20 is reduced. The "relief valve operation start point" is detected by judging whether or not the current consumption of the motor 20 at the speed ((4) in FIG. 6) exceeds a predetermined "regulation error" from the "first approximate curve". To do. That is, when the relief valve 15 changes from the operating state to the non-operating state, the discharge flow rate of the pump body 10 decreases and the rotation speed of the motor 20 decreases. For this reason, the consumption current of the motor 20 decreases with respect to the rotation speed of the motor 20, and the consumption current of the motor 20 at the reduced rotation speed of the motor 20 deviates from the “first approximate curve”. As described above, the pump ECU 40 determines whether or not the current consumption of the motor 20 at the reduced rotational speed of the motor 20 exceeds a predetermined “regulation error” from the “first approximate curve”. It is possible to reliably detect the “valve activation start point”.

  As shown in (3) of FIG. 6 (A) in S15 of FIG. 5 or (3) of FIG. 8 (A) in S24 of FIG. 7, the pump ECU 40 operates when the relief valve 15 is in operation. A “first approximate curve” representing the relationship between the rotational speed of the motor 20 and the current consumption of the motor 20 is calculated. Then, as shown in (3) of FIG. 6B in S15 of FIG. 5 or as shown in (5) of FIG. 8 (A) in S25 of FIG. The relationship between the rotational speed of the motor 20 and the current consumption of the motor 20 when the relief valve 15 is not operated in the rotational speed range of the motor 20 that is lower than the rotational speed range of the motor 20 changed when calculating the “curve”. “Second approximate curve” is calculated. Then, as shown in (8) of FIG. 6 (B) in S15 of FIG. 5, or as shown in (6) of FIG. 8 in S30 of FIG. 7, the pump ECU 40 becomes “first approximate curve”. The intersection with the “second approximate curve” is detected as the “relief valve operation start point”. The intersection of the “first approximate curve” and the “second approximate curve” is the point at which the relief valve 15 in the inactive state starts to operate. Thus, by detecting the intersection of the “first approximate curve” and the “second approximate curve” as the “relief valve operation start point”, the “relief valve operation start point” can be detected with high accuracy.

  In S44 of FIG. 9, as shown in (2) of FIG. 10, the pump ECU 40 changes the rotational speed of the motor 20 within a predetermined range, and expresses the relationship between the rotational speed of the motor 20 and the consumption current of the motor 20. The calculated “first approximate curve” is calculated ((3) in FIG. 10). Next, in S45 and S49 in FIG. 9, the pump ECU 40 determines the motor 20 having a lower speed than the range ((2) in FIG. 10) of the rotation speed of the motor 20 that is changed when the “first approximate curve” is calculated. In the range of rotation speed ((4) in FIG. 10), a plurality of current consumptions of the motor 20 are detected, and a “second approximate curve” representing the relationship between the rotation speed of the motor 20 and the current consumption of the motor 20 is sequentially applied. Calculate ((5) in FIG. 10). Next, in S48 of FIG. 9, the pump ECU 40 detects the “relief valve operation start point” by detecting whether or not the “second approximate curve” has changed from the “first approximate curve”. The point at which the “second approximate curve” changes from the “first approximate curve” ((8) in FIG. 10 (B)) is that the relief valve 15 in the operating state becomes inoperative, in other words, inactive. This is the point where the relief valve 15 in the state starts to operate. Thus, by detecting whether or not the “second approximate curve” has changed from the “first approximate curve”, the “relief valve operation start point” can be detected with high accuracy.

  In S17 of FIG. 5, S32 of FIG. 7, and S52 of FIG. I have control. As a result, it is possible to keep the hydraulic pressure supplied to the required hydraulic pressure constant without operating the relief valve 15. For this reason, the electric oil pump 100 does not need to keep the hydraulic pressure supplied to the hydraulic pressure required point 400 constant by operating the relief valve 15 by always discharging the excess flow amount of oil with the electric oil pump 100. It is possible to reduce a loss caused by an excessive amount of discharged oil.

  Further, in S11 of FIG. 5, S21 of FIG. 7, and S41 of FIG. 9, every time a “pump start command” is input from the vehicle ECU 800 to the pump ECU 40, the “pump control process” of the first to third embodiments. Is started. For this reason, even when the oil temperature at the hydraulic pressure required portion 400 changes or when the oil leakage amount at the hydraulic pressure required location 400 changes due to the secular change of the vehicle 900, it is based on the “relief valve operation start point”. By controlling the discharge pressure and the discharge flow rate of the electric oil pump 100, the oil temperature at the hydraulic pressure required portion 400 can be changed and the amount of leakage can be accommodated.

(Another embodiment)
In the embodiment described above, in S16 of FIG. 5, S31 of FIG. 7, and S51 of FIG. 9, the pump ECU 40 sets the rotational speed slightly lower than the rotational speed of the motor 20 at the “relief valve operation start point” to the idling stop. It is determined as the rotational speed of the motor 20 at the time. However, there may be an embodiment in which the pump ECU 40 determines a current slightly smaller than the consumption current of the motor 20 at the “relief valve operation start point” as the supply current of the motor 20 at the time of idling stop. In the case of this embodiment, the pump ECU 40 outputs a command for supplying the determined supply current to the motor 20 to the motor driver 30 in S16 of FIG. 5, S31 of FIG. 7, and S51 of FIG.

  Alternatively, in S16 of FIG. 5, S31 of FIG. 7, and S51 of FIG. 9, the pump ECU 40 sets a rotational speed slightly lower than the rotational speed of the motor 20 at the “relief valve operation start point” at the time of idling stop. In the embodiment, the rotational speed is determined, and a current slightly smaller than the current consumption of the motor 20 at the “relief valve operation start point” is determined as the supply current of the motor 20 when idling is stopped. In the case of this embodiment, the pump ECU 40 controls the motor 20 so that the rotational speed of the motor 20 is determined in S17 of FIG. 5, S32 of FIG. 7, and S52 of FIG. A command for supplying current to the motor 20 is output to the motor driver 30.

  Further, in S16 of FIG. 5, S31 of FIG. 7, and S51 of FIG. 9, the pump ECU 40 has a rotational speed slightly higher than the rotational speed of the motor 20 at the “relief valve operation start point”. There is no problem even if the embodiment determines the rotation speed. Further, the pump ECU 40 may be an embodiment in which the current slightly larger than the current consumption of the motor 20 at the “relief valve operation start point” is determined as the supply current of the motor 20 at the time of idling stop.

  Further, in S15 of FIG. 5, the pump ECU 40 may detect the “detection point” exceeding the predetermined “regulation error” from the “first approximate curve” as the “relief valve operation start point”. No.

In the embodiment described above, in S14 to S15 of FIG.
The rotational speed of the motor 20 is gradually reduced, and a plurality of current consumptions of the motor 20 at the reduced rotational speed of the motor 20 are detected. As shown in FIG. The “first approximate curve” representing the relationship with the current consumption of the motor 20 is calculated, and the current consumption of the motor 20 at the rotation speed of the motor 20 that is changed last is determined from the “first approximate curve” by a predetermined “regulation”. By judging whether or not the “error” is exceeded, the “relief valve operation start point” is detected. However, in S14 to S15 of FIG. 5, the pump ECU 40 gradually increases the rotational speed of the motor 20, detects a plurality of current consumptions of the motor 20 at the increased rotational speed of the motor 20, and the relief valve 15 is not activated. The “second approximate curve” representing the relationship between the rotational speed of the motor 20 and the current consumption of the motor 20 at the time is calculated, and the current consumption of the motor 20 at the last changed rotational speed of the motor 20 is “second It may be an embodiment in which the “relief valve operation start point” is detected by determining whether or not a predetermined “regulation error” is exceeded from the “approximate curve”.

  9, among the “detection points” detected when the pump ECU 40 calculates the “second approximate curve”, the “detection point” having the highest rotational speed ((7 in FIG. 10B)). )) May be detected as the relief valve operation start point.

  Note that the “first approximate curve” and the “second approximate curve” calculated by the pump ECU 40 are not limited to quadratic functions, and may be functions such as cubic functions or sin functions.

  In the embodiment described above, the inflow side of the flow path of the relief valve 15 communicates with the discharge side groove 11f, and the outflow side of the flow path of the relief valve 15 communicates with the suction side groove 11e. However, the inflow side of the flow path of the relief valve 15 communicates with the discharge flow path 11d and the discharge pipe 92, or the outflow side of the flow path of the relief valve 15 communicates with the suction flow path 11c and the suction pipe 91. Even if it is a form, it does not interfere. In the embodiment described above, the relief valve 15 is provided integrally with the electric oil pump 100. However, the embodiment may be provided separately from the relief valve 15 and the electric oil pump 100. For example, the inflow side of the relief valve may be an embodiment provided in the check valve 200, the valve body 300, the hydraulic pressure required portion 400, or a flow path connecting them. Even in these embodiments, the pump ECU 40 can detect the “relief valve operation start point” by executing the “pump control process” of the first to third embodiments described above.

  In the embodiment described above, the pump body 10 driven by the motor 20 is a trochoid pump. However, the pump body 10 is not limited to a trochoid pump, and may be a volumetric pump that applies pressure to oil with rotating parts such as a gear pump. The gear pump has a structure in which gears meshing with each other are provided in parallel so as to be rotatable in the housing, and the inner peripheral surface of the housing is formed along the outer periphery of the gear. In this gear pump, when the meshing gears rotate, the space between the gear and the housing sequentially moves from the suction port formed in the housing to the discharge port side, and the fluid is sent from the suction channel 11c to the discharge channel 11d. Be paid.

  In the embodiment described above, the motor 20 is a DC brushless motor, but may be a DC brush motor or an AC motor.

  In the embodiment described above, the “motor current” is detected by the motor current detection unit 31. However, the motor driver 30 and the pump ECU 40 may be embodiments that detect “motor current”. In the embodiment described above, the “motor rotational speed” is detected by the rotational speed sensor 25 that detects the rotational speed of the motor 20. However, the motor driver 30 or the pump ECU 40 may be an embodiment that detects the “motor rotational speed”.

  The rotational speed of the motor 20 and the discharge flow rate of the pump body 10 are in a proportional relationship. Therefore, instead of the rotation speed of the motor 20, the discharge flow rate of the pump main body 10 may be measured, and the rotation speed of the motor 20 may be estimated from the discharge flow rate of the pump main body 10.

  In the above description, the pump has been described with respect to an embodiment in which oil is supplied as a fluid. However, a pump that supplies fluid such as water may be used.

  DESCRIPTION OF SYMBOLS 10 ... Pump main body, 15 ... Relief valve, 20 ... Motor, 25 ... Rotational speed sensor (motor rotational speed detection means), 31 ... Motor current detection part (motor consumption current detection means), 40 ... Pump ECU (relief valve operation start) Point detection means, motor control means), 100 ... electric oil pump (electric pump)

Claims (5)

An electric pump having a pump body for feeding fluid and a motor for driving the pump body,
The relief valve regulates the discharge pressure of the fluid discharged from the pump body,
Motor rotation speed detection means for detecting the rotation speed of the motor;
Motor consumption current detection means for detecting consumption current of the motor;
Relief valve operation start check for detecting an operation start point of the relief valve based on the rotation speed of the motor detected by the motor rotation speed detection means and the consumption current of the motor detected by the motor consumption current detection means. Means of exiting,
Based on at least one of the rotation speed of the motor and the current consumption of the motor at the operation start point detected by the relief valve operation start point detection means, at least one of the rotation speed of the motor and the current supplied to the motor is calculated. An electric pump further comprising motor control means for controlling. In claim 1,
The relief valve operation start point detecting means gradually decreases or gradually increases the rotation speed of the motor, detects a plurality of current consumptions of the motor at the changed rotation speed of the motor, and rotates the rotation speed of the motor. And calculating an approximate curve representing the relationship between the motor current consumption and whether or not the relationship between the changed motor rotation speed and the motor current consumption deviates from the approximate curve by a predetermined amount. An electric pump that detects an operation start point of the relief valve. In claim 1,
The relief valve actuation start point detecting means is
The rotation speed of the motor is changed within a predetermined range, a plurality of consumption currents of the motor at the changed rotation speed of the motor are detected, and the rotation speed of the motor and the consumption current of the motor when the relief valve is operated Calculate the first approximate curve that represents the relationship with
In the range of the rotation speed of the motor that is lower than the range of the rotation speed of the motor that is changed when the first approximate curve is calculated, a plurality of current consumptions of the motor are detected, and the relief valve is not operated. Calculating a second approximate curve representing the relationship between the rotational speed of the motor and the current consumption of the motor;
An electric pump that detects an intersection of the first approximate curve and the second approximate curve as an operation start point of the relief valve. In claim 1,
The relief valve actuation start point detecting means is
The rotation speed of the motor is changed within a predetermined range, and a plurality of consumption currents of the motor at the changed rotation speed of the motor are detected to express the relationship between the rotation speed of the motor and the consumption current of the motor. Calculate the first approximate curve,
In the range of the rotation speed of the motor that is lower than the range of the rotation speed of the motor changed when the first approximate curve is calculated, a plurality of consumption currents of the motor are detected, and the rotation speed of the motor Calculate a second approximate curve that represents the relationship with the motor current consumption,
An electric pump that detects an operation start point of the relief valve by detecting whether or not the second approximate curve has changed from the first approximate curve. In any one of Claims 1-4,
The motor control means controls the motor at a rotation speed that is lower than the rotation speed of the motor at the operation start point, or a current that is lower than the current consumption of the motor at the operation start point. An electric pump for supplying the motor to the motor.

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