Electric pump

Abstract

To provide an electric pump that can reduce heat generation from a drive circuit and a motor and reduce energy loss.SOLUTION: An electric pump 1 includes: at least one or more pumps 21, 22; a motor 3 including a plurality of systems of coils 33A, 33B and driving the pumps 21, 22; and a plurality of drive circuits 4, 5 for feeding power to the coils 33A, 33B of the mutually different systems.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an electric pump. [Background technology]

[0002] In vehicles that use idling stop systems to reduce greenhouse gas emissions, electric pumps are installed in the vehicles to supply hydraulic pressure to the transmission and other components even when the engine is stopped, and electric pumps are also used in a wide range of equipment.

[0003] Such an electric pump is configured, for example, with a pump, a motor that drives the pump, and a drive circuit that supplies power to the motor's windings. However, since the drive circuit and the motor generate heat when the motor is driven, attempts have been made to limit the current command to suppress excessive output and reduce heat generation (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-034932 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in conventional electric pumps, although heat generation from the drive circuit and motor can be reduced by controlling the drive circuit, there are cases where heat generation cannot be reduced sufficiently in situations where high output is required.

[0006] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an electric pump that can reduce the amount of heat generated and the energy loss in the drive circuit and motor. [Means for solving the problem]

[0007] In order to achieve the above object, the electric pump of the present invention includes at least one pump, a motor having multiple systems of windings to drive the pump, and multiple drive circuits that supply power to the windings of different systems.

[0008] In an electric pump configured in this manner, a motor having multiple systems of windings is driven by multiple drive circuits that supply power to windings in different systems. Therefore, when the motor is driven at the same rotation speed or torque, the current flowing through each drive circuit can be made smaller than in conventional electric pumps that drive the motor with only one drive circuit.

[0009] Furthermore, the drive circuit of the electric pump may supply electric power equally to the windings of each system when the motor can be driven normally. With an electric pump configured in this way, the maximum current flowing through each drive circuit is equal, thereby minimizing the amount of heat generated by the drive circuit and the motor and minimizing energy loss.

[0010] Furthermore, the number of drive circuits in the electric pump may be the same as the number of winding systems in the motor. With an electric pump configured in this way, the motor can be driven with reduced ripple even when power is supplied equally to each drive circuit, making it optimal for driving the motor and efficiently reducing heat generation and energy loss. [Effects of the Invention]

[0011] According to the electric pump of the present invention, heat generated by the drive circuit and the motor can be reduced, and energy loss can be reduced. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a configuration diagram of an electric pump according to an embodiment. [Figure 2] FIG. 2 is a diagram illustrating a drive circuit of an electric pump and a circuit of a motor winding in one embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0013] The present invention will be described below based on the embodiment shown in the drawings. As shown in Figure 1, the electric pump 1 of this embodiment includes a tandem pump 2, a motor 3 that drives the tandem pump 2, and drive circuits 4 and 5 that drive the motor 3.

[0014] Each component of the electric pump 1 of this embodiment will be described in detail below. The tandem pump 2 includes a first pump 21 and a second pump 22 that share a drive shaft 23. Both the first pump 21 and the second pump 22 are driven by the rotation of the drive shaft 23, allowing the first pump 21 and the second pump 22 to discharge fluid at flow rates according to their respective capacities. As described above, in this embodiment, the tandem pump 2 includes two pumps, the first pump 21 and the second pump 22. However, the tandem pump 2 may be configured to be capable of driving three or more pumps by driving a single drive shaft 23. Furthermore, in this embodiment, the electric pump 1 is described as a tandem pump 2 that includes multiple pumps 21, 22, but it may also be configured to include only one pump.

[0015] Although not shown in detail, the motor 3 includes a stator housed in a case 31, and a rotor 32 rotatably inserted into the case 31 and connected at its tip to the drive shaft 23. As shown in Fig. 2, the stator (not shown) of the motor 3 includes a three-phase winding 33A of system A consisting of U-phase, V-phase, and W-phase, and a three-phase winding 33B of system B consisting of U-phase, V-phase, and W-phase. The windings 33A of system A and the windings 33B of system B are independent of each other, and for example, by supplying power to one or both of the windings 33A of system A and the windings 33B of system B by 120-degree energization drive, a rotating magnetic field can be generated to rotate the rotor 32.

[0016] The drive circuits 4 and 5 supply power to the windings 33A and 33B of different systems, with the drive circuit 4 connected to the winding 33A of system A and supplying power only to the winding 33A, and the drive circuit 5 connected to the winding 33B of system B and supplying power only to the winding 33B.

[0017] Specifically, as shown in Fig. 2, the drive circuits 4, 5 include three legs 41, 51 each having two switching elements 42, 52 corresponding to the three-phase windings 33A, 33B of the A and B systems of the motor 3, and the switching elements 42, 52 of each leg 41, 51 are connected to the ends of the Y-connected U-phase, V-phase, and W-phase windings, respectively. As described above, in this embodiment, the drive circuits 4, 5 are configured as three-phase output inverters that connect power supplies 43, 53 to any two-phase windings and supply power to the windings 33A, 33B of each system by turning the switching elements 42, 52 on and off. Note that the power supplies 43, 53 in the drive circuits 4, 5 may be integrated into a single power supply.

[0018] The drive circuits 4 and 5 are controlled by a controller 6. For example, the controller 6 detects or estimates the electrical angle of the rotor 32 of the motor 3, calculates the speed of the motor 3 from the obtained electrical angle of the rotor 32, calculates a q-axis current command from the deviation between the calculated speed and a speed command, sets the d-axis current command to zero, calculates a q-axis voltage command and a d-axis voltage command from the deviation between the q-axis current and the q-axis current command calculated from the currents in each phase of the windings 33A and 33B of each system and the deviation between the d-axis current and the d-axis current command calculated from the currents in each phase, converts the d-axis voltage command and the d-axis voltage command into three-phase voltage commands using the electrical angle of the rotor 32, generates PWM signals for controlling the on / off of switching elements 42 and 52 of the drive circuits 4 and 5 based on the voltage commands, and controls the on / off of the switching elements 42 and 52 to PWM-control the motor 3. Note that the configuration of the controller 6 described above is an example, and the design can be changed as long as it can drive the motor 3. When determining the voltage command from the speed command, the controller 6 may receive a speed command from a higher-level control device and generate a voltage command to be given to the motor 3, or if control of the speed is not required, the controller 6 may determine the voltage command from the torque command.

[0019] Furthermore, when the motor 3 can be driven normally, the controller 6 controls the drive circuits 4, 5 so that power is supplied equally from the drive circuits 4, 5 to the A-phase winding 33A and the B-phase winding 33B. Therefore, in this embodiment, the two drive circuits 4, 5 supply power to the corresponding windings 33A, 33B, respectively, and the current flowing through the drive circuits 4, 5 is reduced by half compared to a conventional electric pump in which only one drive circuit supplies power to the motor.

[0020] Furthermore, since the electric pump 1 of this embodiment simultaneously drives the first pump 21 and the second pump 22 in the tandem pump 2, power is supplied from the drive circuits 4 and 5 to the windings 33A and 33B of each system so as to satisfy the flow rates required for both the first pump 21 and the second pump 22. In other words, when the rotational speed required for the first pump 21 and the rotational speed required for the second pump 22 differ, power is supplied from the drive circuits 4 and 5 so as to achieve the faster rotational speed.

[0021] Furthermore, if there is a fault in one of the drive circuits 4, 5, the electric pump 1 may output the equally divided power that should be output from each drive circuit 4, 5 from the drive circuit that is not faulty, or may supply power so as to satisfy both the rotational speed required for the first pump 21 and the rotational speed required for the second pump 22.

[0022] As described above, the electric pump 1 of this embodiment includes at least one pump 21, 22, a motor 3 having multiple systems of windings 33A, 33B to drive the pumps 21, 22, and multiple drive circuits 4, 5 that supply power to the windings 33A, 33B of different systems.

[0023] In the electric pump 1 configured as described above, the motor 3 having multiple windings 33A, 33B is driven by multiple drive circuits 4, 5 that supply power to the windings 33A, 33B of different systems. Therefore, when driving the motor at the same rotation speed or torque, the current flowing through each drive circuit 4, 5 can be reduced compared to a conventional electric pump that drives the motor with only one drive circuit. Therefore, with the electric pump 1 of this embodiment, the current flowing through the drive circuits 4, 5 can be reduced. Because the heat generated by the drive circuits 4, 5 and the windings 33A, 33B of the motor 3 is proportional to the square of the current, the overall heat generated by the electric pump 1 can be reduced to about one-fourth that of a conventional electric pump. Energy loss is also reduced accordingly. Furthermore, because multiple drive circuits 4, 5 are provided, even if one of the drive circuits 4, 5 fails, the remaining functioning drive circuits 4, 5 can continue to drive the motor 3. In addition, since the current flowing through the drive circuits 4 and 5 can be reduced, the heat generation of the switching elements 42 and 52 of the drive circuits 4 and 5 and the heat generation of the motor 3 can be reduced, so the heat sinks attached to the switching elements 42 and 52 and the stator of the motor 3 can be made smaller, and the entire electric pump 1 can be made smaller and costs can be reduced.

[0024] Furthermore, in the electric pump 1 of this embodiment, when the drive circuits 4, 5 are able to drive the motor 3 normally, power is supplied equally to the windings 33A, 33B of each system, and the maximum current flowing through each drive circuit 4, 5 is equal, which minimizes the amount of heat generated by the drive circuits 4, 5 and the motor 3, thereby minimizing energy loss.

[0025] Furthermore, in the electric pump 1 of this embodiment, the same number of drive circuits 4, 5 as the number of systems of windings 33A, 33B of the motor 3 are provided. Therefore, the windings 33A of system A correspond to the drive circuit 4, and the windings 33B of system B correspond to the drive circuit 5. Therefore, even if power is supplied equally to each drive circuit 4, 5, the motor 3 can be driven while reducing ripples, which is optimal for driving the motor 3 and efficiently reduces heat generation and energy loss.

[0026] Although the motor 3 of this embodiment has two systems of windings 33A, 33B, it may have three or more systems of windings. In that case, a drive circuit may be provided for each system of windings, or if the number of drive circuits installed is less than the number of winding systems, some drive circuits may supply power to multiple systems of windings.

[0027] Furthermore, in the electric pump 1 of this embodiment, the motor 3 drives the first pump 21 and the second pump 22 of the tandem pump 2. When driving the first pump 21 and the second pump 22 in this manner, the motor 3 is required to output a larger torque than when driving only one pump, and a larger current is likely to flow through the drive circuit. However, in the electric pump 1 of this embodiment, multiple drive circuits 4 and 5 supply power to the motor 3, so the current flowing through each drive circuit 4 and 5 can be reduced, significantly reducing heat generation and energy loss. Therefore, when the electric pump 1 of this embodiment is used to drive a tandem pump 2 in which multiple pumps are driven by a single drive shaft, heat generation and energy loss can be effectively reduced, which is advantageous in terms of miniaturizing and reducing the cost of the drive circuits 4 and 5.

[0028] Although the preferred embodiment of the present invention has been described in detail above, modifications, variations and changes can be made without departing from the scope of the appended claims. [Explanation of symbols]

[0029] 1 electric pump, 3 motor, 4, 5 drive circuit, 21 first pump (pump), 22 second pump (pump), 33A, 33B winding

Claims

1. at least one pump; a motor having a plurality of windings for driving the pump; and a plurality of drive circuits for supplying power to windings of different systems. An electric pump characterized by:

2. The drive circuit supplies power equally to the windings of each system when the motor can be driven normally.

2. The electric pump according to claim 1.

3. The drive circuit is provided for each of the systems.

2. The electric pump according to claim 1.

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