Electric vehicles

Abstract

To improve motor efficiency in a low-torque region and ensure maximum torque needed by a vehicle.SOLUTION: In an electric vehicle including a motor 2 and an inverter 4, the motor 2 is configured so as to house, in one housing: a rotor 20 which rotates integrally with a shaft, and to which permanent magnets are fixed; a first stator 21 which is arranged coaxially with the shaft, and around which a first coil 21B allowing a three-phase AC current to flow therethrough is wound; and a second stator 22 which is arranged coaxially with the shaft and adjacently to the first stator 21 in an axial direction, and around which a second coil 22B connected in parallel with the first coil 21B and allowing a three-phase AC current to flow therethrough is wound. The inverter 4 includes: a first drive part 41 for causing the current to flow to the first stator 21; a second drive part 42 for causing the current to flow to the second stator 22; and a control part 40 for controlling the two drive parts 41 and 42 independently. The control part 40 drives at least one of the two drive parts 41 and 42 according to request torque for the electric vehicle.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to an electric vehicle that runs on a drive motor, and more particularly to the configuration of the motor and inverter. [Background technology]

[0002] A drive motor mounted on an electric vehicle such as a hybrid vehicle or an electric vehicle is generally most efficient in an operating region where the output torque is about half of the maximum output torque and the rotation speed is about half of the maximum rotation speed, and is less efficient in a low torque region or a low rotation speed region. However, the operating region of a motor often used for normal driving in an electric vehicle is mostly in a low torque region. For this reason, during normal driving of an electric vehicle, the motor is driven in a region where the motor's efficiency is not high, and there is room for improvement. In addition, Patent Document 1 focuses on the rotation speed and discloses a motor configuration in which at least two or more windings connected in series are provided in one phase, and an inverter circuit that drives at low speed and high speed can be switched to achieve high efficiency in the low speed rotation range. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2016-131444 A Summary of the Invention [Problem to be solved by the invention]

[0004] For example, by designing the maximum output torque of the motor to be about twice the torque (low torque) often used during normal driving of an electric vehicle, it becomes possible to use a more efficient operating range during normal driving. However, when designed in this way, the maximum output torque of the motor becomes small, which leads to a decrease in hill-climbing performance and acceleration performance, and there is an issue that the range of use for the electric vehicle is limited.

[0005] The electric vehicle of the present invention has been devised in view of these problems, and has as one of its objectives to increase the motor efficiency in the low torque region often used in normal driving, and to ensure the maximum torque required by the vehicle. However, this objective is not the only objective, and another objective of the present invention is to achieve effects that cannot be obtained by conventional techniques, which are derived from the configurations shown in the below-mentioned embodiments of the invention. [Means for solving the problem]

[0006] The disclosed electric vehicle can be realized as the aspects or application examples disclosed below, and solves at least some of the above problems. The disclosed electric vehicle is an electric vehicle equipped with a synchronous motor having a function of driving wheels, and an inverter that controls the operation of the synchronous motor. The synchronous motor is configured by housing, in one housing, a rotor that rotates integrally with a shaft and has a permanent magnet fixed thereto, a first stator that is arranged coaxially with the shaft and has a first coil wound therearound through which a three-phase AC current flows, and a second stator that is arranged coaxially with the shaft and adjacent to the first stator in the axial direction, has a second coil wound therearound through which a three-phase AC current flows, and is connected in parallel with the first coil. In addition, an output torque of the first stator outputted by the three-phase AC current flowing through the first coil and an output torque of the second stator outputted by the three-phase AC current flowing through the second coil are set to be equal to each other. . The inverter includes a first drive unit that supplies the three-phase AC current to the first stator, a second drive unit that supplies the three-phase AC current to the second stator, and a control unit that independently controls the first drive unit and the second drive unit. Before driving at least one of the first driving unit and the second driving unit When driving either the first drive unit or the second drive unit in response to the required torque, the first drive unit and the second drive unit are alternately used. . Effect of the Invention

[0007] According to the disclosed electric vehicle, it is possible to increase motor efficiency in the low torque range that is often used during normal driving, and to ensure the maximum torque required by the vehicle. [Brief description of the drawings]

[0008] [Figure 1]1 is a diagram illustrating a configuration of an electric vehicle according to an embodiment. [Diagram 2] 2 is a cross-sectional view for explaining the configuration of a motor mounted on the electric vehicle of FIG. 1. [Diagram 3] 2 is a circuit diagram including a motor and an inverter mounted on the electric vehicle of FIG. 1. [Figure 4] FIG. 11 is a diagram showing motor characteristics when operating with one stator. [Diagram 5] FIG. 13 is a diagram showing motor characteristics when operating with two stators. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] An electric vehicle according to an embodiment will be described with reference to the drawings. The embodiments described below are merely examples, and are not intended to exclude various modifications or application of techniques not clearly stated in the following embodiments. The configurations of the embodiments can be modified in various ways without departing from the spirit of the embodiments. In addition, the embodiments can be selected as necessary, or can be combined as appropriate.

[0010] [1. Overall composition] 1 is a block diagram illustrating the configuration of an electric vehicle 1 (hereinafter, simply referred to as vehicle 1) according to an embodiment. Specific types of vehicle 1 include an electric vehicle (EV), a hybrid vehicle (HEV), a plug-in hybrid vehicle (PHEV), and the like.

[0011] The vehicle 1 is equipped with at least a motor 2 as a drive source and a battery 3 as a power source. The battery 3 is a secondary battery such as a lithium ion secondary battery or a nickel metal hydride battery. The motor 2 is a three-phase AC permanent magnet synchronous motor (synchronous motor) and has a function of driving the wheels with power from the battery 3. The motor 2 in this embodiment is a motor generator (electric motor / generator) that also has a function of charging the battery 3 with power generated by regeneration. The specific configuration of the motor 2 will be described later.

[0012] The wheels (drive wheels) driven by the motor 2 may be the front wheels, rear wheels, or all the wheels. The number of motors 2 mounted and the number of drive wheels are not important. Furthermore, one drive wheel may be driven by one motor 2, multiple drive wheels may be driven by one motor 2, one drive wheel may be driven by multiple motors 2, or multiple drive wheels may be driven by multiple motors 2. Furthermore, a speed change mechanism (not shown) may be interposed on the power transmission path connecting the motor 2 and the drive wheels.

[0013] Although only a motor 2 as a drive source is shown in the vehicle 1 in FIG. 1, the vehicle may be a hybrid vehicle (hybrid electric vehicle, HEV) or a plug-in hybrid vehicle (plug-in hybrid electric vehicle, PHEV) equipped with an engine as a second drive source and a generator as a power generation device (both not shown). A hybrid vehicle refers to a vehicle equipped with an engine and a motor 2 as drive sources. A plug-in hybrid vehicle refers to a hybrid vehicle that allows external charging of the battery 3 or external power supply from the battery 3. A plug-in hybrid vehicle is provided with a charging port (inlet) for inserting a charging cable that supplies power from an external charging facility, and an external power supply outlet (outlet, both not shown) for inserting a power supply cable that supplies power to an external device.

[0014] Power from the battery 3 is supplied to the motor 2 via the inverter 4. The inverter 4 has the function of supplying AC driving power to the motor 2, and controls the operation of the motor 2. When multiple motors 2 are mounted on the vehicle 1, multiple inverters 4 (the same number as the motors 2) are also mounted. The operating state of the inverter 4 is controlled by a control unit 40 (see FIG. 3 ) described below that is provided in the inverter 4. Note that commands (signals) and information are sent to the control unit 40 by the control device 5. In other words, it can be said that the inverter 4 is controlled by the control device 5.

[0015] The control device 5 is one of the electronic control units (ECU, Electronic Control Unit) mounted on the vehicle 1. The control device 5 is equipped with, for example, a processor (microprocessor) such as a CPU (Central Processing Unit) or an MPU (Micro Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), a non-volatile memory, and the like.

[0016] The processor is an arithmetic processing device incorporating a control unit (control circuit), an arithmetic unit (arithmetic circuit), a cache memory (register group), etc. The ROM, RAM, and non-volatile memory are memory devices in which programs and data during operation are stored. The control contents performed by the control device 5 are recorded and saved in the memory as firmware or application programs, and when a program is executed, the contents of the program are expanded in the memory space and executed by the processor.

[0017] The vehicle 1 is provided with sensors for acquiring various information about the vehicle 1. In the example shown in FIG. 1, a vehicle speed sensor 6, an accelerator sensor 7, and a motor revolution speed sensor 8 are provided, and the sensors 6 to 8 are connected to the control device 5. The vehicle speed sensor 6 is a sensor that detects the vehicle speed of the vehicle 1 (or the wheel speed or vehicle body speed equivalent to the vehicle speed), and the accelerator sensor 7 is a sensor that detects the accelerator operation by the driver (the amount of depression of the accelerator pedal and the depression speed). The motor revolution speed sensor 8 is a sensor that detects the number of revolutions (rotation speed) of the motor 2. Information (sensor values) detected by these sensors 6 to 8 are transmitted to the control device 5.

[0018] The control device 5 controls the operating states of the motor 2 (inverter 4) and the battery 3, and also controls the operating states of the engine and generator if one is installed. The control device 5 of this embodiment constantly calculates the required torque (also called required driving force or required output) for the vehicle 1 based on various sensor values ​​while the vehicle is traveling (for example, at a predetermined calculation period). For example, sensor values ​​from the vehicle speed sensor 6 and accelerator sensor 7 are used in this calculation. The control device 5 may calculate the required torque more accurately by taking into account parameters such as longitudinal acceleration, lateral acceleration, steering angle, and vehicle body inclination.

[0019] [2.Main part configuration] FIG. 2 is a cross-sectional view for explaining the configuration of the motor 2, and FIG. 2, the motor 2 is configured by housing a rotor 20 that rotates integrally with the shaft 10, and a first stator 21 and a second stator 22 that are arranged coaxially with the shaft 10, all in a single housing 23. That is, the motor 2 is an inner rotor type motor that has one rotor 20 and two stators 21, 22 that are split into two in the axial direction (arranged side by side).

[0020] The rotor 20 has a rotor core 20A having a through hole in the center to which the shaft 10 is fixed, and a plurality of permanent magnets 20B fixed to the rotor core 20A. Here, the rotor 20 is illustrated with the permanent magnets 20B embedded in the rotor core 20A, but the method of fixing the permanent magnets 20B is not limited to this. Both ends of the shaft 10 are rotatably supported via bearings 24 fixed to a housing 23. In the motor 2 of this embodiment, a motor rotation speed sensor 8 and a board (not shown) are attached to one end side (left side in the figure) of the shaft 10, and the other end side (right side in the figure) of the shaft 10 protrudes outside the housing 23 and functions as an end for extracting output.

[0021] The first stator 21 is formed by winding a first coil 21B, through which a three-phase AC current flows, around a first stator core 21A. The second stator 22 is formed by winding a second coil 22B, through which a three-phase AC current flows, around a second stator core 22A, and is disposed adjacent to the first stator 21 in the axial direction. In the motor 2 of this embodiment, the first stator 21 is disposed at one end side within the housing 23, and the second stator 22 is disposed at the other end side. Note that coils 21B, 22B are wound around each of the stator cores 21A, 22A, but the two stators 21, 22 have coils 21B , 22B are arranged with a gap therebetween so as not to come into contact with each other. A three-phase wire 25 connected to first coil 21B and a three-phase wire 26 connected to second coil 22B are drawn out from housing 23 to the outside.

[0022] The permanent magnet 20B of the rotor 20 and each of the stator cores 21A, 22A are disposed facing each other in the radial direction with a gap therebetween. In the motor 2 of this embodiment, the permanent magnet 20B is not disposed between the two stator cores 21A, 22A. That is, the permanent magnet 20B is also divided in the axial direction, and two permanent magnets are arranged side by side in the axial direction at the same circumferential position. However, the permanent magnet 20B may not be divided in the axial direction.

[0023] As shown in Fig. 3, the first coil 21B and the second coil 22B are connected in parallel to each other via the inverter 4. The inverter 4 includes a first drive unit 41 that passes a three-phase AC current through the first stator 21, a second drive unit 42 that passes a three-phase AC current through the second stator 22, and a control unit 40 that independently controls the two drive units 41, 42. As a result, the two drive units 41, 42 can operate independently of each other, and different three-phase AC currents flow through the first coil 21B and the second coil 22B. Hereinafter, the three-phase AC current will also be simply referred to as "current".

[0024] The first drive unit 41 is configured with three pairs of switching elements, each pair being connected to a U-phase wire, a V-phase wire, and a W-phase wire of the first stator 21. The connection state of each switching element is intermittently switched to generate an AC current to be supplied to the first coil 21B of the first stator 21. The switching elements are implemented by semiconductor elements such as an IGBT (Insulated Gate Bipolar Transistor) or a power MOSFET (Metal Oxide Semiconductor Field-Effect Transistor).

[0025] Similarly, the second drive unit 42 is configured with three pairs of switching elements, each pair of which is connected to a U-phase wire, a V-phase wire, and a W-phase wire of the second stator 22. The connection state of each switching element is intermittently switched, thereby generating an AC current to be supplied to the second coil 22B of the second stator 22. The inverter 4 is provided with a capacitor 43 connected in parallel to each of the first drive unit 41 and the second drive unit 42. The capacitor 43 is an electronic component for smoothing the power supplied to each of the drive units 41, 42.

[0026] The characteristics of the motor 2 configured as described above are shown in Figures 4 and 5. In these figures, the horizontal axis represents the motor rotation speed, and the vertical axis represents torque. Figure 4 shows the output torque characteristics of the motor 2 when current flows only through the first coil 21B of the first stator 21, and Figure 5 shows the output torque characteristics of the motor 2 when current flows through both coils 21B, 22B of the two stators 21, 22. The thick solid line in the figures represents the maximum torque that can be output by the motor 2. The thin solid lines in the figures are curves connecting operating points at which the same motor efficiency is obtained at certain motor efficiency intervals, and are isopleths for high and low motor efficiency, with the efficiency increasing further inside the isopleths.

[0027] In the motor 2 of this embodiment, the output torque of the first stator 21, which is output when a current flows through the first coil 21B, and the output torque of the second stator 22, which is output when a current flows through the second coil 22B, are set to be equal to each other. That is, in the motor 2 of this embodiment, even when a current flows only through the second coil 22B of the second stator 22, the same characteristics as those shown in FIG. 4 can be obtained.

[0028] Furthermore, as shown in Fig. 5, the characteristics when current is passed through the coils 21B, 22B of the two stators 21, 22 respectively are approximately twice as large as the characteristics shown in Fig. 4 in the vertical direction. In other words, the maximum torque of the motor 2 when only one of the stators 21, 22 is used is set to approximately half of the maximum torque of the motor 2 when the two stators 21, 22 are used.

[0029] The control unit 40 drives at least one of the first drive unit 41 and the second drive unit 42 in accordance with the required torque for the vehicle 1. The control unit 40 receives the required torque calculated by the control device 5 and performs control in accordance with the required torque. The control unit 40 of this embodiment controls each of the drive units 41, 42 using a preset control map. For example, when the required torque received from the control device 5 is in a low torque region, the control unit 40 drives one of the two drive units 41, 42, and when the required torque is in a medium torque region or a high torque region, the control unit 40 drives both of the two drive units 41, 42.

[0030] For example, as shown by operating point X (revolutions per minute Nx, torque Tx) in Figures 4 and 5, when the required torque is in a low torque region, the control unit 40 drives one of the two drive units 41, 42 and uses only one of the two stators 21, 22 to output the required torque from the motor 2. As a result, when the torque required (required torque) is small, for example, during normal driving, the motor 2 can be driven in a more efficient operating region compared to when the two stators 21, 22 are used, as shown in Figures 4 and 5.

[0031] Furthermore, for example, as shown by operating point Y (revolutions per minute Ny, torque Ty) in the figure, when the required torque is in the medium torque region, the control unit 40 drives both of the two drive units 41, 42 and uses both of the two stators 21, 22 to output the required torque from the motor 2. As a result, when the torque required (required torque) is relatively large, for example, during acceleration, the motor 2 can be driven in a more efficient operating region compared to using one stator 21, 22 as shown in Figures 4 and 5.

[0032] 5, when the required torque is in a high torque region, the control unit 40 drives both of the two drive units 41, 42 and uses both of the two stators 21, 22 to output the required torque from the motor 2. As a result, even if the torque required (required torque) is large, for example, when traveling uphill, the required torque can be realized and the range of use is not limited.

[0033] However, in the medium torque region, depending on the operating point, there are cases where higher motor efficiency can be obtained by driving one of the two drive units 41, 42, and cases where higher motor efficiency can be obtained by driving both of the two drive units 41, 42. Therefore, it is preferable that the control map used by the control unit 40 is set based on the motor characteristics for each usage mode, as shown in Figures 4 and 5.

[0034] The control map has, for example, vehicle speed on the horizontal axis and required torque on the vertical axis, and is set so as to select the higher efficiency between the motor efficiency when one of the two drive units 41, 42 is driven and the motor efficiency when both of the two drive units 41, 42 are driven. This setting can be performed based on the results of advance measurement of the motor efficiency. Note that, if the same motor efficiency can be obtained regardless of the usage, the usage in which one is driven may be selected, or the usage in which both are driven may be selected.

[0035] When driving either the first drive unit 41 or the second drive unit 42 in response to the required torque, the control unit 40 of this embodiment alternates between the two drive units 41, 42 so that the frequency of use of the two stators 21, 22 is approximately equal. For example, when one driving cycle is defined as the period from start (Ready on) to end (Ready off) of the vehicle 1, the two drive units may be alternately used for each driving cycle. Alternatively, the time during which only one of the stators 21, 22 is used may be counted, and when a predetermined usage time has elapsed, the other stator 22, 21 may be used by managing the time.

[0036] The control unit 40 controls each of the driving units 41, 42, for example, at a predetermined control cycle. For example, assume a case where the state 1 in which both the driving units 41, 42 are driven is switched to the state 2 in which only the first driving unit 41 is driven (i.e., the second driving unit 42 is stopped and only the first driving unit 41 continues to be driven). In this case, the control unit 40 stops the switching operation of the second driving unit 42 at the timing of switching from the state 1 to the state 2, so that no current flows through the second coil 22B. In addition, the control unit 40 continues the switching operation of the first driving unit 41 at the same timing, but controls the first driving unit 41 so that the required torque at that time can be satisfied only by the first stator 21. Since these controls are performed by a single control unit 40, there is no control delay or torque loss at the timing of switching.

[0037] [3. Effects] In the above-described vehicle 1, the motor 2 is provided with two stators 21, 22, and a first drive unit 41 that passes a three-phase AC current through the first coil 21B wound around the first stator 21 and a second drive unit 42 that passes a three-phase AC current through the second coil 22B wound around the second stator 22 are independently controlled. Then, the control unit 40 drives at least one of the first drive unit 41 and the second drive unit 42 in accordance with the required torque for the vehicle 1.

[0038] Therefore, when the required torque is in a low torque region that is often used for normal driving, by driving either the first drive unit 41 or the second drive unit 42, one of the two stators 21, 22 is used, and the motor 2 can be operated in an operation region with higher efficiency. This makes it possible to achieve high efficiency in the low torque region. Also, for example, when the required torque is in a medium torque region or a high torque region, by driving both the first drive unit 41 and the second drive unit 42, the two stators 21, 22 are used, and it is also possible to handle high output torque. Therefore, it is possible to increase the motor efficiency in the low torque region that is often used for normal driving, and to ensure the maximum torque required by the vehicle 1.

[0039] The control unit 40 described above uses a preset control map to control the drive units 41, 42. This control map is set so that the higher efficiency is selected between the motor efficiency when one of the two drive units 41, 42 is driven and the motor efficiency when both of the two drive units 41, 42 are driven. This makes it possible to operate the motor 2 in a state of always higher efficiency with a simple configuration.

[0040] In the above motor 2, the output torque of the first stator 21 and the output torque of the second stator 22 are set to be equal to each other, and the control unit 40 alternately uses the drive units 41, 42 when driving either one of them in response to the required torque. This results in the two stators 21, 22 being used with equal frequency, which makes it possible to extend the life of the motor 2 compared to a case in which either one of the stators 21, 22 is used more frequently.

[0041] [4.Other] The configurations of the motor 2 described above are merely examples, and the invention is not limited to the above. For example, the output torque of the first stator 21 outputted by a three-phase AC current flowing through the first coil 21B may be set to be larger than the output torque of the second stator 22 outputted by a three-phase AC current flowing through the second coil 22B. In this case, when driving either the first drive unit 41 or the second drive unit 42 in response to the required torque, it is preferable that the control unit 40 drives the first drive unit 41.

[0042] According to such a configuration, the first stator 21 can serve as a main stator, and the second stator 22 can serve as an assist stator. In other words, since the torque that can be output by the first stator 21 alone is large, it is basically possible to cover a range from a low torque region to a medium torque region by using only the first stator 21, and the control configuration can be further simplified.

[0043] The above-mentioned contents and setting method of the control map are merely examples and are not limited to the above. By using the control map, it is possible to improve the motor efficiency by taking into account the speed information (vehicle speed and motor rotation speed), but when only the torque is the focus, the control map may be omitted. [Explanation of symbols]

[0044] 1 Vehicle (electric vehicle) 2 Motor (synchronous motor) 4 Inverter 10 Shaft 20 Rotors 20B permanent magnet 21 First stator 21B First coil 22 Second stator 22B Second coil 23 Case 40 Control section 41 First Drive Unit 42 Second Drive Unit

Claims

1. An electric vehicle including a synchronous motor having a function of driving wheels and an inverter that controls the operation of the synchronous motor, The synchronous motor is configured by housing, in one housing, a rotor which rotates integrally with a shaft and has a permanent magnet fixed thereto, a first stator which is arranged coaxially with the shaft and has a first coil wound therearound through which a three-phase AC current flows, and a second stator which is arranged coaxially with the shaft and adjacent to the first stator in the axial direction, has a second coil wound therearound through which a three-phase AC current flows, the second stator being connected in parallel with the first coil, and has a second coil wound therearound through which a three-phase AC current flows, and an output torque of the first stator which is output when the three-phase AC current flows through the first coil and an output torque of the second stator which is output when the three-phase AC current flows through the second coil are set to be equal to each other, the inverter includes a first drive unit that causes the three-phase AC current to flow through the first stator, a second drive unit that causes the three-phase AC current to flow through the second stator, and a control unit that independently controls the first drive unit and the second drive unit; The control unit drives at least one of the first drive unit and the second drive unit in response to a required torque for the electric vehicle, and when driving either the first drive unit or the second drive unit in response to the required torque, alternately uses the first drive unit and the second drive unit. An electric vehicle characterized by:

2. The control unit performs control using a preset control map, The control map is set so as to select a higher efficiency between the efficiency of the synchronous motor when one of the first drive unit and the second drive unit is driven and the efficiency of the synchronous motor when both the first drive unit and the second drive unit are driven.

2. The electric vehicle according to claim 1 .

3. When driving either the first drive unit or the second drive unit, the control unit alternately uses the first drive unit and the second drive unit for each driving cycle from start to end of the electric vehicle.

3. The electric vehicle according to claim 1 or 2.

4. The control unit counts the time when only the first drive unit is used and the time when only the second drive unit is used, and when a predetermined usage time has elapsed for either the first drive unit or the second drive unit, the control unit uses the other of the first drive unit and the second drive unit.

3. The electric vehicle according to claim 1 or 2.

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