Drive unit

Abstract

The current is evenly distributed through the three-phase coils of the motor while the rotor is not rotating. [Solution] When performing heat generation control to heat the battery by outputting zero torque from the motor while the rotor rotation is stopped, the electrical advance angle is set to +90degE or -90degE and the current frequency is set in order to set the motor output torque to a value of 0, and the switching elements of the inverter are switched by current feedback control so that the set electrical advance angle and current frequency are achieved.

Description

Technical Field

[0001] The present disclosure relates to a drive device, and more particularly to a drive device having a motor, an inverter, and a battery.

Background Art

[0002] Conventionally, as this type of drive device, there has been proposed a device that warms lubricating oil by passing a current of an electrical advance angle at which the output torque of the motor becomes 0 torque before starting, due to heat generation by copper loss of the coil and heat generation by iron loss of the motor core (see, for example, Patent Document 1). In this device, as the current of the electrical advance angle that becomes 0 torque, a first current with an electrical advance angle of +90 degE and a second current with an electrical advance angle of -90 degE are alternately passed through the motor coil.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the above-described drive device, since the first current with an electrical advance angle of +90 degE and the second current with an electrical advance angle of -90 degE are alternately passed through the motor coil, the magnetic flux change in the magnetic path of the motor becomes large, the heat generation from the iron loss becomes large, and thermal demagnetization may occur in the magnet attached to the rotor. Also, when the rotor is not rotating, current may flow through a specific phase coil of the three-phase coil, and damage to the coil due to temperature rise may occur.

[0005] The main object of the drive device of the present disclosure is to evenly pass current through the three-phase coils of the motor in a state where the rotor is not rotating.

Means for Solving the Problems

[0006] The drive device of this disclosure employs the following means to achieve the main objective described above.

[0007] The drive device of this disclosure is A motor having permanent magnets in the rotor and three-phase coils in the stator connected in a star configuration, An inverter that drives the motor, A battery that supplies DC power to the inverter, A control device that takes electrical advance angle and current frequency as input and controls the switching elements of the inverter by current feedback control, A drive device equipped with, When the control device performs thermal control to heat the battery by outputting zero torque from the motor while the rotor rotation is stopped, it sets the electrical advance angle to +90 degrees E or -90 degrees E and the current frequency to set the output torque of the motor to 0, and controls the switching element of the inverter by current feedback control so that the set electrical advance angle and current frequency are achieved. It is characterized by the following:

[0008] In the drive device of this disclosure, when performing heat generation control, the electrical advance angle is set to +90 degrees E or -90 degrees E and the current frequency is set in order to set the motor output torque to a value of 0, and the switching elements of the inverter are switched by current feedback control so that the set electrical advance angle and current frequency are achieved. As a result, the motor output torque can be set to a value of 0 and current can be supplied evenly to the three-phase coils. As a result, it is possible to suppress the disadvantages caused by supplying a large current to a specific phase coil, such as thermal demagnetization of the magnet attached to the rotor or damage to a specific phase coil. Moreover, the battery can be heated while the motor output torque is set to a value of 0.

[0009] In the drive device of this disclosure, the control device may set the electrical advance angle to -90 degrees when performing the heat generation control. In this way, even if the electrical advance angle deviates slightly from the target -90 degrees when the switching elements of the inverter are switched by current feedback control, the torque output from the motor can be kept small. This is based on the fact that in the current-torque characteristics of the motor, the torque near an electrical advance angle of -90 degrees is smaller than the torque near an electrical advance angle of +90 degrees.

[0010] In the drive device of this disclosure, the control device may set the current frequency within a range in which PWM control is possible when performing the heat generation control. In this way, a three-phase alternating current can be applied to the three-phase coil of the motor, and unexpected torque output from the motor can be suppressed.

[0011] In the drive device of this disclosure, there is a fixing means for fixing the rotor so that it cannot rotate, and the control device may fix the rotor so that it cannot rotate using the fixing means when performing the heat generation control. In this way, even if the output torque is zero in the electrical cycle, the rotation of the rotor can be suppressed by the torque generated within the cycle. Here, examples of fixing means include fixing the rotating shaft connected to the rotor, and fixing other shafts mechanically connected to this rotating shaft. For example, if the rotor of the motor is connected to the drive shaft of a vehicle equipped with a drive device, this also includes a parking gear that mechanically fixes the drive shaft and a hydraulic brake that fixes the rotation of the drive wheel connected to the drive shaft. [Brief explanation of the drawing]

[0012] [Figure 1] This diagram shows a schematic configuration of an electric vehicle 20 equipped with a drive unit as an embodiment of the present disclosure. [Figure 2] This flowchart shows an example of a heat generation control process performed by the electronic control unit 50. [Figure 3]This is an explanatory diagram showing an example of the output torque from motor 32 during one electrical cycle when zero torque output is being performed by the heat generation control of motor 32. [Figure 4] This is an explanatory diagram showing an example of the relationship between the electrical advance angle θ of the current in motor 32 and the torque. [Modes for carrying out the invention]

[0013] Next, embodiments for implementing this disclosure will be described. Figure 1 is a schematic diagram showing the configuration of an electric vehicle 20 equipped with a drive unit 30 as an embodiment of this disclosure. As shown in the figure, the electric vehicle 20 of the embodiment includes a driving motor 32, an inverter 34, a battery 36, and an electronic control unit 50.

[0014] The motor 32 is configured as a well-known permanent magnet synchronous generator motor, comprising a rotor with permanent magnets embedded in the rotor core and a stator with three-phase coils wound around the stator core in a star configuration. The rotor of the motor 32 is connected to a drive shaft 26 which is connected to the drive wheels 22a and 22b via a differential gear 24.

[0015] The inverter 34 is used to drive the motor 32. The inverter 34 is connected to the battery 36 via a power line 38 and has six switching elements, transistors T11 to T16, and six diodes D11 to D16 connected in parallel to each of the six transistors T11 to T16. The transistors T11 to T16 are arranged in pairs, with the source and sink sides being the positive and negative terminal lines of the power line 38, respectively. The connection points of the two transistors in each pair are connected to the coils of the corresponding phases (U phase, V phase, W phase) of the motor 32. Therefore, when voltage is applied to the inverter 34, the electronic control unit 50 adjusts the ratio of the on-times of the paired transistors T11 to T16, thereby forming a rotating magnetic field in the three-phase coils and driving the motor 32 to rotate.

[0016] The battery 36 is configured as a lithium-ion secondary battery or a nickel-metal hydride secondary battery, and is connected to the inverter 34 via the power line 38. A capacitor 39 for smoothing is attached to the power line 38.

[0017] The electric parking brake 27 is attached to the drive shaft 26, and operates when the shift lever 61 is moved from a non-parking position (a position other than the P position) to the parking position (the P position), and is released when the shift lever 61 is moved from the parking position to a non-parking position.

[0018] The electronic control unit 50 is configured as a microcomputer having a CPU, ROM, RAM, flash memory, and input / output ports. The electronic control unit 50 inputs the rotational position θm of the rotor of the motor 32 from the rotational position sensor 32a, the phase currents Iu and Iv of the U and V phases of the motor 32 from the current sensors 32u and 32v, the voltage Vb of the battery 36 from the voltage sensor 36a, the current Ib of the battery 36 from the current sensor 36b, the temperature Tb of the battery 36 from the temperature sensor 36c, and the voltage VL of the power line 38 (capacitor 39) from the voltage sensor 39a. The start signal from the start switch 60, the shift position SP which is the operation position of the shift lever 61 from the shift position sensor 62, the accelerator opening Acc which is the depression amount of the accelerator pedal 63 from the accelerator pedal sensor 64, the brake pedal position BP which is the depression amount of the brake pedal 65 from the brake pedal sensor 66, and the vehicle speed V from the vehicle speed sensor 67 are also input.

[0019] The electronic control unit 50 outputs switching control signals for switching the transistors T11 to T16 to the inverter 34, drive control signals to the electric parking brake 27, and the like. The electronic control unit 50 calculates the electrical angle θe and the rotational speed Nm of the motor 32 based on the rotational position θm, and estimates the output torque Tm of the motor 32 based on the phase currents Iu, Iv and the electrical angle θe. The estimation of the output torque Tm is performed, for example, by assuming that the sum of the currents of each phase of the motor 32 is 0, performing coordinate transformation (three-phase to two-phase transformation) of the phase currents Iu, Iv of the U-phase and V-phase into the d-axis and q-axis currents Id, Iq using the electrical angle θe of the motor 32, and applying the d-axis and q-axis currents Id, Iq to a predetermined relationship between the currents Id, Iq and the output torque Tm to derive the output torque Tm.

[0020] In the electric vehicle 20 of the embodiment, the electronic control unit 50 sets the driving request torque Td* (requested for the drive shaft 26) required for running to the torque command Tm* of the motor 32, and controls the transistors T11 to T16 of the inverter 34 so that the motor 32 is driven by the torque command Tm*. Here, the driving request torque Td* is set based on the accelerator opening Acc and the vehicle speed V. The control of the inverter 34 is performed, for example, by pulse width modulation (PWM) control.

[0021] In PWM control, first, assuming that the sum of the currents of each phase of the motor 32 is 0, coordinate transformation (three-phase to two-phase transformation) of the phase currents Iu, Iv of the U-phase and V-phase into the d-axis and q-axis currents Id, Iq is performed using the electrical angle θe of the motor 32. Subsequently, d-axis and q-axis current commands Id*, Iq* are set based on the torque command Tm*, and d-axis and q-axis voltage commands Vd*, Vq* are calculated so that the difference between the d-axis and q-axis current commands Id*, Iq* and the currents Id, Iq is canceled. Then, using the electrical angle θe of the motor 32, the d-axis and q-axis voltage commands Vd*, Vq* are coordinate-transformed (two-phase to three-phase transformation) into the phase voltage commands Vu*, Vv*, Vw*, and PWM signals of the transistors T11 to T16 are generated by comparing the voltage commands Vu*, Vv*, Vw with the carrier voltage to perform switching control of the transistors T11 to T16.

[0022] Next, the operation of the electric vehicle 20 of the embodiment will be described, in particular, the operation when performing heat generation control, which heats the battery 36 by outputting zero torque from the motor 32 while the rotation of the motor 32's rotor is stopped. Figure 2 is a flowchart showing an example of the heat generation control process performed by the electronic control unit 50.

[0023] When the heat generation control process is executed, the electronic control unit 50 first determines whether the vehicle is stationary or not (step S100). This determination determines whether the vehicle can maintain its stationary state even if a small amount of torque is output from the motor 32. For example, the vehicle is determined to be stationary when the electric parking brake 27 is on, or when the vehicle speed V is 0 and the brake pedal 65 is pressed down with sufficient force. Figure 3 shows an example of the output torque from the motor 32 in one electrical cycle when zero torque output is performed in the heat generation control of the motor 32. As shown in Figure 3, the zero torque output in the heat generation control of the motor 32 is zero torque output in total for one electrical cycle, and a small amount of torque output is performed in the positive and negative directions within one electrical cycle. For this reason, it is necessary to maintain the stationary state even if a small amount of torque is output from the motor 32. In step S100, it is determined whether it is possible to maintain such a stationary state. If it is determined in step S100 that the vehicle is not in a stationary state, it is decided that the heat generation control of the motor 32 should not be performed, and this process is terminated.

[0024] When it is determined in step S100 that the vehicle is stopped, the electrical advance angle θ is set to -90 degrees (step S110), a predetermined frequency Fset is set for the current frequency F (step S120), and the motor 32 is started to generate heat by initiating switching control of transistors T11 to T16 of the inverter 34 using current feedback control with the set electrical advance angle θ and current frequency F (step S130). The reason for setting the electrical advance angle θ to -90 degrees is to reduce the torque output from the motor 32 when the electrical advance angle θ deviates slightly from the set value due to current feedback control, compared to the electrical advance angle θ of +90 degrees where the motor 32 outputs zero torque. An example of the relationship between the current advance angle of the motor 32 and torque is shown in Figure 4. As shown in the figure, the torque near an electrical advance angle θ of -90 degrees is smaller than the torque near an electrical advance angle θ of +90 degrees. In other words, the rate of change of torque with respect to the electrical advance angle θ near -90 degrees E is smaller than the rate of change of torque with respect to the electrical advance angle θ near +90 degrees E. For this reason, when current feedback control is performed with the electrical advance angle θ set to -90 degrees E, the output torque from the motor 32 with respect to deviations in the electrical advance angle θ during current feedback control can be reduced compared to when current feedback control is performed with the electrical advance angle θ set to +90 degrees E. Furthermore, the predetermined frequency Fset can be any frequency as long as it is below the upper limit frequency obtained by converting the upper limit rotational speed of the motor 32 that can be PWM controlled by the inverter 34 into a frequency; for example, a frequency of about half the upper limit frequency may be used. When the heat generation control of the motor 32 is started, a three-phase AC current with an electrical advance angle θ of -90 degrees E and a current frequency F of the predetermined frequency Fset flows to the three-phase coil of the motor 32, and the battery 36 is heated by the zero torque output of the motor 32.

[0025] The heat generation control of the motor 32 is performed until termination is determined (step S140). Once termination of the heat generation control is determined, the inverter 34 is shut down (step S150), and this process ends. The heat generation control is terminated when the temperature of the battery 36 reaches a temperature suitable for charging.

[0026] In the drive device 30 of the embodiment described above, after confirming that the vehicle is stopped, the electrical advance angle θ is set to -90degE and the current frequency F is set to a predetermined frequency Fset. Using the set electrical advance angle θ and current frequency F, the switching control of transistors T11 to T16 of the inverter 34 by current feedback control is started to initiate the heat generation control of the motor 32. In this heat generation control of the motor 32, a three-phase AC current with an electrical advance angle θ of -90degE and a current frequency F of a predetermined frequency Fset flows through the three-phase coils of the motor 32. This prevents current from flowing only through specific phase coils, thereby suppressing problems caused by current flowing only through specific phase coils, such as damage to permanent magnets attached to the rotor of the motor 32 or damage to the three-phase coils.

[0027] In the drive device 30 of this embodiment, the motor 32 is controlled for heat generation by current feedback control with the electrical advance angle θ set to -90 degrees E. Compared to when the motor 32 is controlled for heat generation by current feedback control with the electrical advance angle θ set to +90 degrees E, the output torque from the motor 32 in response to deviations in the electrical advance angle θ during current feedback control can be reduced. Note that if the current flowing during the heat generation control of the motor 32 is reduced, the output torque from the motor 32 in response to deviations in the electrical advance angle θ during current feedback control will also be reduced, so it is also possible to set the electrical advance angle θ to +90 degrees E and control the motor 32 for heat generation by current feedback control.

[0028] In this embodiment, the drive unit 30 is mounted on an electric vehicle 20, but the drive unit 30 may also be mounted on a hybrid vehicle or a fuel cell vehicle. Furthermore, the drive unit 30 may not be mounted on a vehicle at all.

[0029] The correspondence between the main elements of the embodiment and the main elements of the invention described in the section on means for solving the problem will be explained. In the embodiment, motor 32 corresponds to "motor", inverter 34 corresponds to "inverter", battery 36 corresponds to "battery", and electronic control unit 50 corresponds to "control device".

[0030] Furthermore, the correspondence between the main elements of the embodiment and the main elements of the invention described in the section on means for solving the problem is merely an example to specifically explain the form in which the embodiment implements the invention described in the section on means for solving the problem, and does not limit the elements of the invention described in the section on means for solving the problem. In other words, the interpretation of the invention described in the section on means for solving the problem should be based on the description in that section, and the embodiment is merely one specific example of the invention described in the section on means for solving the problem.

[0031] Although the embodiments for implementing this disclosure have been described above, this disclosure is not limited in any way to these embodiments, and can of course be implemented in various forms without departing from the gist of this disclosure. [Industrial applicability]

[0032] This disclosure can be used in industries such as the manufacturing of drive systems. [Explanation of symbols]

[0033] 20 Electric vehicle, 22a, 22b Drive wheels, 24 Differential gear, 26 Drive shaft, 27 Electric parking brake, 30 Drive unit, 32 Motor, 32a Rotation position sensor, 32u, 32v Current sensor, 34 Inverter, 36 Battery, 36a Voltage sensor, 36b Current sensor, 36c Temperature sensor, 38 Power line, 39 Capacitor, 39a Voltage sensor, 50 Electronic control unit, 60 Start switch, 61 Shift lever, 62 Shift position sensor, 63 Accelerator pedal, 64 Accelerator pedal sensor, 65 Brake pedal, 66 Brake pedal sensor, 67 Vehicle speed sensor, T11~T16 Transistors, D11~D16 Diodes.

Claims

1. A motor having permanent magnets in the rotor and three-phase coils in the stator connected in a star configuration, An inverter that drives the motor, A battery that supplies DC power to the inverter, A control device that takes electrical advance angle and current frequency as input and controls the switching elements of the inverter by current feedback control, A drive device equipped with, When the control device performs heat generation control to heat the battery by outputting zero torque from the motor while the rotor rotation is stopped, it sets the electrical advance angle to +90 degrees E or -90 degrees E and sets the current frequency in order to set the output torque of the motor to 0, and controls the switching element of the inverter by current feedback control so that the set electrical advance angle and current frequency are achieved. A drive device characterized by the following features.

2. A drive device according to claim 1, When the control device performs the heat generation control, it sets the electrical advance angle to -90 degrees. Drive unit.

3. A drive device according to claim 1, When performing the heat generation control, the control device sets the current frequency within the range in which PWM control is possible. Drive unit.

4. A drive device according to any one of claims 1 to 3, The rotor has a fixing means for fixing it so that it cannot rotate, When the control device performs the heat generation control, it fixes the rotor so that it cannot rotate using the fixing means. Drive unit.

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