drive device

Abstract

The present disclosure provides a driving device that causes electric current to flow equally through three-phase coils of an electric motor in a state in which a rotor is not rotating. When performing a heat creation control that heats a battery by outputting zero torque from the electric motor in a state in which rotation of the rotor is stopped, in order to make the output torque of the electric motor be a value of 0, an electric lead angle is set to +90 degE or -90 degE and a current frequency is set, and a switching element of an inverter is switched by current feedback control to be the set electric lead angle and the current frequency.

Description

Technical Field

[0001] This disclosure relates to a drive device, and more particularly, to a drive device having a motor, an inverter, and a battery. Background Technology

[0002] Conventionally, a drive device has been proposed that, before starting, applies an electrical lead angle that makes the motor's output torque zero, thereby heating the lubricating oil through heat generated by the copper losses in the coils and the iron losses in the motor's core (see, for example, Patent Document 1). In this device, a first current that makes the electrical lead angle +90°E and a second current that makes the electrical lead angle -90°E are alternately applied to the motor's coils as the current that makes the electrical lead angle zero.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2011-089625 Summary of the Invention

[0006] The problem that the invention aims to solve

[0007] However, in the aforementioned drive system, because a first current with an electrical lead angle of +90°E and a second current with an electrical lead angle of -90°E are alternately energized to the motor coils, the change in magnetic flux in the motor's magnetic circuit increases, leading to greater heat generation due to iron losses. This can sometimes cause thermal demagnetization in the magnets mounted on the rotor. Furthermore, when the rotor is not rotating, current flowing through specific phase coils of the three-phase coils can sometimes cause coil damage due to temperature rise.

[0008] The main objective of the drive device disclosed herein is to ensure that current flows equally through the three-phase coils of the motor while the rotor is not rotating.

[0009] Solution for solving the problem

[0010] To achieve the aforementioned main objectives, the drive device of this disclosure adopts the following scheme.

[0011] The drive device disclosed herein includes:

[0012] An electric motor having permanent magnets in its rotor and its three-phase stator coils connected in a star configuration;

[0013] Inverter, which drives the motor;

[0014] A battery that supplies DC power to the inverter; and

[0015] The control device receives the electrical lead angle and current frequency as inputs and controls the switching elements of the inverter through current feedback control.

[0016] Its features are,

[0017] When the control device performs heat creation control by outputting zero torque from the motor when the rotor has stopped rotating, in order to make the output torque of the motor reach a value of 0, the electrical lead angle is set to +90°E or -90°E and the current frequency is set. The switching elements of the inverter are switched through the current feedback control to achieve the set electrical lead angle and current frequency.

[0018] In the drive device disclosed herein, during heat generation control, to achieve a motor output torque of 0, the electrical lead angle is set to +90°E or -90°E, and the current frequency is set. Current feedback control is used to control the switching elements of the inverter to achieve the set electrical lead angle and current frequency. This allows the motor output torque to be zero and the current to flow evenly through the three-phase coils. Consequently, adverse conditions caused by excessive current flowing through specific phase coils can be suppressed, such as thermal demagnetization in the rotor magnets and damage to specific phase coils. Furthermore, the battery can be heated while the motor output torque is zero.

[0019] In the drive device disclosed herein, the control device may set the electrical lead angle to -90°E when performing the heat generation control. This way, when the inverter's switching elements are switched via current feedback control, even if the electrical lead angle deviates slightly from the target -90°E, the torque output from the motor can be kept small. This is based on the fact that in the motor's current / torque characteristics, the torque near an electrical lead angle of -90°E is less than the torque near an electrical lead angle of +90°E.

[0020] In the drive device disclosed herein, the control device may set the current frequency within a range suitable for PWM control when performing the heat-generating control. This allows for the application of three-phase alternating current to the three-phase coils of the motor, suppressing unexpected torque output from the motor.

[0021] In the drive device disclosed herein, a fixing mechanism may be provided to fix the rotor so that it cannot rotate. When the control device performs the heat-generating control, the fixing mechanism fixes the rotor so that it cannot rotate. In this way, even if the output torque is zero during an electrical cycle, rotor rotation caused by the torque generated during the cycle can be suppressed. Here, the fixing mechanism can be exemplified by mechanisms that fix a rotating shaft connected to the rotor, mechanisms that fix other shafts mechanically connected to the rotating shaft, etc. For example, in the case where a motor rotor is connected to the drive shaft of a vehicle equipped with the drive device, it may also include a parking gear that mechanically fixes the drive shaft, a hydraulic brake that fixes the rotation of the drive wheel connected to the drive shaft, etc. Attached Figure Description

[0022] Figure 1 This is a schematic structural diagram showing the structure of an electric vehicle 20 equipped with a drive device as an embodiment of the present disclosure.

[0023] Figure 2 This is a flowchart illustrating an example of thermal control processing performed by the electronic control unit 50.

[0024] Figure 3 This is an explanatory diagram illustrating an example of the output torque from motor 32 during one electrical cycle when zero torque output is achieved through the thermal control of motor 32.

[0025] Figure 4 This is an explanatory diagram illustrating an example of the relationship between the electric lead angle θ of the motor 32 current and the torque. Detailed Implementation

[0026] The following describes the methods (implementation methods) used to carry out this disclosure. Figure 1 This is a schematic structural diagram showing the structure of an electric vehicle 20 equipped with a drive unit 30 as an embodiment of this disclosure. As shown, the electric vehicle 20 of this embodiment includes a driving motor 32, an inverter 34, a battery 36, and an electronic control unit 50.

[0027] The motor 32 is configured as a known permanent magnet synchronous generator motor, and includes: a rotor in which permanent magnets are embedded in the rotor core and a stator in which three-phase coils with star connections are wound on the stator core. The rotor of the motor 32 is connected to a drive shaft 26 which is connected to drive wheels 22a and 22b via a differential gear 24.

[0028] Inverter 34 drives motor 32. Inverter 34 is connected to battery 36 via power line 38 and has six transistors T11-T16 as switching elements and six diodes D11-D16 connected in parallel with each of the six transistors T11-T16. Transistors T11-T16 are arranged in pairs, with the source side and drain side respectively relative to the positive and negative sides of power line 38. 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 motor 32. Therefore, when voltage is applied to inverter 34, the electronic control unit 50 adjusts the ratio of the conduction time of the paired transistors T11-T16, thereby generating a rotating magnetic field in the three-phase coils and driving motor 32 to rotate.

[0029] Battery 36 is configured as a lithium-ion secondary battery or a nickel-metal hydride secondary battery and is connected to inverter 34 via power line 38. A smoothing capacitor 39 is installed on power line 38.

[0030] The electric parking brake 27 is mounted on the drive shaft 26 and operates when the gear lever 61 changes from the non-parking position (position other than P position) to the parking position (P position), and is released when the gear lever 61 changes from the parking position to the non-parking position.

[0031] The electronic control unit 50 is configured as a microcomputer with a CPU, ROM, RAM, flash memory, and input / output ports. The electronic control unit 50 receives inputs from the rotational position θm of the motor 32 rotor from the rotational position sensor 32a, the phase currents Iu and Iv of the motor 32's U and V phases 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. It also receives inputs from the starter switch 60, the gear position SP (operating position of the gear lever 61) from the gear position sensor 62, the accelerator opening Acc (accelerator pedal 63's pedal position) from the accelerator pedal sensor 64, the brake pedal position BP (brake pedal 65's pedal position) from the brake pedal sensor 66, and the vehicle speed V from the vehicle speed sensor 67.

[0032] The electronic control unit 50 outputs switching control signals to the inverter 34 to control the switching of transistors T11 to T16, and drive control signals to the electric parking brake 27. The electronic control unit 50 calculates the electrical angle θe and 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 and Iv and the electrical angle θe. For example, by setting the sum of the currents in each phase of the motor 32 to 0, the phase currents Iu and Iv of phases U and V are converted into d-axis and q-axis currents Id and Iq through coordinate transformation (three-phase to two-phase transformation) using the electrical angle θe of the motor 32. The d-axis and q-axis currents Id and Iq are then applied to a predetermined relationship between the currents Id and Iq and the output torque Tm to derive the output torque Tm, thereby estimating the output torque Tm.

[0033] In the electric vehicle 20 of this embodiment, the electronic control unit 50 sets the required driving torque Td* (required by the drive shaft 26) to the torque command Tm* of the motor 32, and controls the transistors T11-T16 of the inverter 34 to drive the motor 32 by the torque command Tm*. Here, the required driving torque Td* is set based on the accelerator opening Acc and the vehicle speed V. The inverter 34 is controlled, for example, by pulse width modulation (PWM) control.

[0034] In PWM control, firstly, the sum of the currents in all phases of motor 32 is set to 0. Using the electrical angle θe of motor 32, the phase currents Iu and Iv of phases U and V are converted into d-axis and q-axis currents Id and Iq through coordinate transformation (three-phase to two-phase transformation). Next, based on the torque command Tm*, the current commands Id* and Iq* of the d-axis and q-axis are set, and the voltage commands Vd* and Vq* of the d-axis and q-axis are calculated to eliminate the deviation between the current commands Id* and Iq* and the currents Id and Iq. Then, using the electrical angle θe of motor 32, the voltage commands Vd* and Vq* of the d-axis and q-axis are converted into voltage commands Vu*, Vv*, and Vw* for each phase through coordinate transformation (three-phase to two-phase transformation). By comparing these voltage commands Vu*, Vv*, and Vw with the carrier voltage, PWM signals for transistors T11 to T16 are generated, and the switching control of transistors T11 to T16 is performed.

[0035] The operation of the electric vehicle 20 according to the embodiment, especially the operation of heating the battery 36 by outputting zero torque from the motor 32 when the rotation of the rotor of the motor 32 is stopped, will be described below. Figure 2 This is a flowchart illustrating an example of thermal control processing performed by the electronic control unit 50.

[0036] When performing the heat control process, the electronic control unit 50 first determines whether the vehicle is in a parking state (step S100). This determination is based on whether the vehicle can maintain a parking state even if the motor 32 outputs a slight torque. For example, the vehicle is in a parking state when the electric parking brake 27 is engaged, or when the brake pedal 65 is pressed with sufficient force at a vehicle speed V of 0. Figure 3 This represents an example of the output torque from motor 32 during one electrical cycle when zero torque output is achieved under the thermal control of motor 32. For example... Figure 3 As shown, the zero torque output in the heat-generating control of motor 32 refers to a total zero torque output within one electrical cycle, with a slight torque output in both the positive and negative directions within one electrical cycle. Therefore, it is necessary to maintain a stopped state even when the motor 32 outputs a slight torque. In step S100, it is determined whether such a stopped state can be maintained. If it is determined in step S100 that a stopped state is not being maintained, it is determined that heat-generating control of motor 32 should not be performed, and this process ends.

[0037] When the parking state is determined in step S100, the electrical lead angle θ is set to -90°E (step S110) and the current frequency F is set to a predetermined frequency Fset (step S120). Using the set electrical lead angle θ and current frequency F, the switching control of transistors T11 to T16 of the inverter 34 is started through current feedback control, thereby initiating the heating control of the motor 32 (step S130). The electrical lead angle θ is set to -90°E because compared to the electrical lead angle θ of +90°E that provides zero torque output from the motor 32, the torque output from the motor 32 is reduced when the electrical lead angle θ deviates slightly from the set value due to current feedback control. Figure 4This is an example illustrating the relationship between the current lead angle and torque of motor 32. As shown in the figure, the torque near an electrical lead angle θ of -90°E is less than the torque near an electrical lead angle θ of +90°E. That is, the rate of change of torque near an electrical lead angle θ of -90°E with respect to the electrical lead angle is less than the rate of change of torque near an electrical lead angle θ of +90°E with respect to the electrical lead angle. Therefore, compared to current feedback control with an electrical lead angle θ set to +90°E, current feedback control with an electrical lead angle θ set to -90°E can reduce the output torque from motor 32 that deviates from the electrical lead angle θ in current feedback control. Furthermore, the specified frequency Fset can be any frequency as long as it is a frequency below the upper limit frequency obtained by converting the upper limit speed of motor 32, which can be PWM controlled by inverter 34, into a frequency. For example, a frequency approximately half the upper limit frequency can also be used. After the start of the heating control of motor 32, a three-phase AC current with an electric lead angle θ of -90°E and a current frequency F of a specified frequency Fset passes through the three-phase coil of motor 32 and heats battery 36 through the zero torque output of motor 32.

[0038] The heat-induced control of the motor 32 continues until the determination of the end (step S140). When the determination of the end of heat-induced control is made, the inverter 34 is turned off (step S150), and the process ends. In addition, the heat-induced control ends when the temperature of the battery 36 reaches a temperature suitable for charging.

[0039] In the drive unit 30 of the above-described embodiment, after confirming that it is in a stopped state, the electrical lead angle θ is set to -90°E and the current frequency F is set to a predetermined frequency Fset. Using the set electrical lead angle θ and current frequency F, the switching control of transistors T11 to T16 of the inverter 34 is started through current feedback control, thereby initiating the heat-generating control of the motor 32. In such heat-generating control of the motor 32, since the three-phase AC current with an electrical lead angle θ of -90°E and a current frequency F of the predetermined frequency Fset flows through the three-phase coils of the motor 32, it is possible to suppress the current from flowing only through specific phase coils, thus suppressing adverse conditions caused by the current flowing only through specific phase coils. For example, it is possible to suppress damage to the permanent magnets of the rotor and the three-phase coils mounted on the motor 32.

[0040] In the drive device 30 of the embodiment, the heating control of the motor 32 is performed by setting the electrical lead angle θ to -90°E through current feedback control. Therefore, compared with the heating control of the motor 32 by setting the electrical lead angle θ to +90°E through current feedback control, the output torque from the motor 32 that deviates from the electrical lead angle θ in the current feedback control can be reduced. Furthermore, if the current flowing through the motor 32 during heating control is reduced, the output torque from the motor 32 that deviates from the electrical lead angle θ in the current feedback control is also reduced. Therefore, the heating control of the motor 32 can also be performed by setting the electrical lead angle θ to +90°E through current feedback control.

[0041] In one embodiment, the drive unit 30 is mounted on the electric vehicle 20, but the drive unit 30 can also be mounted on a hybrid vehicle or a fuel cell vehicle. Alternatively, the drive unit 30 may not be mounted on the vehicle.

[0042] The correspondence between the main elements of the implementation method and the main elements of the invention listed in the solution to the problem section will be explained. In the implementation method, motor 32 is equivalent to "motor", inverter 34 is equivalent to "inverter", battery 36 is equivalent to "battery", and electronic control unit 50 is equivalent to "control device".

[0043] Furthermore, the correspondence between the main elements of the implementation method and the main elements of the invention listed in the "Solution to Solve the Problem" column is merely an example of how the implementation method is used to carry out the invention listed in the "Solution to Solve the Problem" column, and therefore does not limit the elements of the invention listed in the "Solution to Solve the Problem" column. That is, the interpretation of the invention listed in the "Solution to Solve the Problem" column should be based on the description in that column, and the implementation method is merely a specific example of the invention listed in the "Solution to Solve the Problem" column.

[0044] The above describes the methods for implementing this disclosure using the embodiments, but this disclosure is not limited to such embodiments, and can of course be implemented in various ways without departing from the spirit of this disclosure.

[0045] Industrial availability

[0046] This disclosure can be applied to the manufacturing of drive devices, etc.

Claims

1. A driving device, the driving device comprising: An electric motor having permanent magnets in its rotor and its three-phase stator coils connected in a star configuration; Inverter, which drives the motor; A battery that supplies DC power to the inverter; and The control device receives the electrical lead angle and current frequency as inputs and controls the switching elements of the inverter through current feedback control. Its features are, When the control device performs heat creation control by outputting zero torque from the motor when the rotor has stopped rotating, in order to make the output torque of the motor reach a value of 0, the electrical lead angle is set to +90°E or -90°E and the current frequency is set. The switching elements of the inverter are switched through the current feedback control to achieve the set electrical lead angle and current frequency.

2. The driving device according to claim 1, characterized in that, When performing the thermal control, the control device sets the electrical lead angle to -90°E.

3. The driving device according to claim 1, characterized in that, When performing the thermal control, the control device sets the current frequency within the range where PWM control is possible.

4. The driving device according to any one of claims 1 to 3, characterized in that, It has a fixing mechanism that fixes the rotor so that it cannot rotate. When performing the thermal control, the control device fixes the rotor so that it cannot rotate through the fixing mechanism.

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