Drive unit

Abstract

To provide a technique capable of suppressing a temperature difference between two drive motors during charge of a battery.SOLUTION: A drive unit for an electric motor car with a battery may include a first motor and a second motor which are electrically connected to a battery and drive at least one drive wheel. The drive unit may include a controller which controls each of current flowing through the first motor and current flowing through the second motor. The controller may be configured to be capable of executing: charge processing which supplies the electric power of an external power source to the battery through a neutral point of the first motor; and electrification processing which distributes d-axis current to the second motor during the charge processing.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The technology disclosed in this specification relates to a drive device for an electric vehicle. [Background technology]

[0002] Patent Document 1 discloses an electric vehicle equipped with two drive motors that drive at least one drive wheel of the electric vehicle. As pointed out in Patent Document 1, in such an electric vehicle, if the temperature difference between the two drive motors becomes large, the torque output from each of the two drive motors becomes unbalanced, resulting in a decrease in running stability. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2016-63587 A Summary of the Invention [Problem to be solved by the invention]

[0004] Meanwhile, electric vehicles configured to be able to charge the battery via one of two drive motors are being developed. In such electric vehicles, the temperature difference between the drive motor used for charging and the drive motor not used for charging becomes large while the battery is being charged. For this reason, there is a concern that the running stability of the electric vehicle may decrease when the electric vehicle is driven after charging is completed. This specification provides a technology that can suppress the temperature difference between the two drive motors while the battery is being charged. [Means for solving the problem]

[0005] The technology disclosed in this specification may be applied to a drive device for an electric vehicle having a battery. The drive device may include a first motor and a second motor electrically connected to the battery and driving at least one drive wheel of the electric vehicle. The drive device may include a control device that controls a current flowing through the first motor and a current flowing through the second motor. The control device may be configured to be capable of executing a charging process that supplies power from an external power supply to the battery via a neutral point of the first motor, and a current supply process that supplies a d-axis current to the second motor during the charging process.

[0006] According to the above drive device, by passing a d-axis current through the second motor that is not being used for charging, the temperature of the second motor that is not being used for charging increases, and the temperature difference between the first and second motors becomes smaller. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a block diagram of an electric vehicle. [Diagram 2] 4 is a flowchart of a warm-up process for a drive motor. [Figure 3A] 11 is a diagram for explaining a state in which an electric vehicle travels straight when there is a large magnet temperature difference between the left and right drive motors; FIG. [Figure 3B] 11 is a diagram for explaining a state in which an electric vehicle travels straight when the magnet temperature difference between the left and right drive motors is small. FIG. [Figure 4] FIG. 1 is a block diagram of an electric vehicle 1 as viewed from above. [Diagram 5] 5 is a cross-sectional view taken along line VV in FIG. 4. [Figure 6] FIG. 3 is a block diagram of an electric vehicle 301 as viewed from above. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] In one embodiment of the present technology, the control device may execute the current application process when a temperature difference between the first motor and the second motor is equal to or greater than a predetermined value during the charging process.

[0009] According to this configuration, for example, when the temperature difference between the first motor and the second motor is small, the power supply process is not executed, and therefore the temperature increase process can be executed with high energy efficiency.

[0010] In one embodiment of the present technology, the temperature difference may be a difference between a magnet temperature of a rotor of the first motor and a magnet temperature of a rotor of the second motor.

[0011] The torques output by the first and second motors depend on the magnet temperatures of the rotors. With the above configuration, it is possible to reduce the temperature difference between the magnet temperatures of the rotors of the first motor and the second motor, thereby reducing the difference in output torque.

[0012] In one embodiment of the present technology, the control device may control a magnitude of the d-axis current passed through the second motor in accordance with a temperature difference between the first motor and the second motor.

[0013] According to such a configuration, for example, when the temperature difference is small, the energizing current can be reduced, and the temperature increasing process can be performed with high energy efficiency.

[0014] In one embodiment of the present technology, the control device may be further configured to execute a first estimation process to estimate a required charging time until charging of the battery is completed by the charging process, and a second estimation process to estimate a required temperature rise time until a temperature difference between the first motor and the second motor becomes equal to or less than a predetermined value by the current supply process. The control device may start the current supply process in response to the required charging time being reduced to equal to or less than the required temperature rise time.

[0015] With this configuration, the time required for charging and the time required for temperature rise can be made to coincide with each other, and therefore the temperature difference can be kept within a predetermined value when charging is completed.

[0016] In one embodiment of the present technology, the control device may be configured to execute a process of monitoring the temperature difference during the charging process, and may execute the first estimation process and the second estimation process in response to the temperature difference becoming equal to or greater than the predetermined value.

[0017] With this configuration, for example, when the temperature difference between the first motor and the second motor is small, the first estimation process and the second estimation process may not be executed, which reduces the burden on the control device.

[0018] In one embodiment of the present technology, the drive wheels may be left and right wheels, and the first motor may drive one of the left and right wheels, and the second motor may drive the other of the left and right wheels.

[0019] In one embodiment of the present technology, the drive wheels may be front wheels and rear wheels of the electric vehicle. The first motor may drive one of the front wheels and the rear wheels, and the second motor may drive the other of the front wheels and the rear wheels.

[0020] In one embodiment of the present technology, the battery may further include an inverter circuit having a plurality of switching elements and electrically connected between the battery and the first motor. The control device may control the plurality of switching elements in the charging process to cause the inverter circuit to function as a boost circuit together with a plurality of coils of the first motor.

[0021] With this configuration, it is possible to charge the battery via the first motor. EXAMPLES

[0022] 1, the electric vehicle 1 includes a battery pack 2, a left drive unit 3, a right drive unit 4, a motor control device 5, and a charging inlet 6. In this specification, the term "electric vehicle" includes a battery electric vehicle (BEV), a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), a fuel cell electric vehicle (FCEV), etc.

[0023] The left drive unit 3 is provided corresponding to the left drive wheel of the electric vehicle 1, and includes a first inverter INV1 and a first drive motor M1. The first inverter INV1 is a three-phase inverter circuit. In the first inverter INV1, a DC positive terminal is connected to the positive electrode of the battery pack 2, a DC negative terminal is connected to the negative electrode of the battery pack 2, and the midpoint of each phase arm is connected to the first drive motor M1. The first inverter INV1 is appropriately controlled by a first control signal PWM1 output from the motor control device 5. The first drive motor M1 is a three-phase AC motor having three coils. One end of each of the three coils is connected to the midpoint of the corresponding phase arm of the first inverter INV1, and the other end of each of the three coils is connected at the neutral point by star coupling.

[0024] The left drive unit 3 has current sensors provided in each of two phase cables (e.g., V phase and W phase) of the cables from the first inverter INV1 to the first drive motor M1. These current sensors measure the current Iv1 flowing through the V phase cable and the current Iw1 flowing through the W phase cable, and output the measured currents Iv1 and Iw1 to the motor control device 5. The left drive unit 3 further has a temperature sensor and a rotation angle sensor provided in the first drive motor M1. The temperature sensor outputs the measured motor temperature T1 to the motor control device 5. The rotation angle sensor measures the rotation angle Q1 of the first drive motor M1 (i.e., the rotational position of the rotor with respect to the stator), and outputs the measured rotation angle Q1 to the motor control device 5.

[0025] The right drive unit 4 is provided corresponding to the right drive wheel of the electric vehicle 1, and has a second inverter INV2 and a second drive motor M2. The configuration of the right drive unit 4 is substantially the same as the configuration of the left drive unit 3, so a description thereof will be omitted.

[0026] The motor control device 5 is configured to generate a first control signal PWM1 for controlling the first inverter INV1 and generate a second control signal PWM2 for controlling the second inverter INV2. In a mode for driving the drive motors M1, M2, the motor control device 5 generates the control signals PWM1, PWM2 based on a torque command value. As described below, in a mode for charging the battery pack 2, the motor control device 5 generates the control signals PWM1, PWM2 based on a d-axis current command value. Note that the d-axis and q-axis currents measured based on the currents Iv1, Iw1 and the rotation angle Q1 are used for feedback control when generating the control signals PWM1, PWM2.

[0027] The charging inlet 6 is provided on the body of the electric vehicle 1. The charging inlet 6 is configured to be connected to an external DC power source 7 (e.g., a charging stand) via a power cable. The charging inlet 6 is provided corresponding to either the left drive unit 3 or the right drive unit 4, and in this example, the charging inlet 6 is provided corresponding to the left drive unit 3. One of a pair of terminals of the charging inlet 6 is connected to the neutral point of the first drive motor M1, and the other of the pair of terminals of the charging inlet 6 is connected to the negative electrode of the battery pack 2 via the first inverter INV1.

[0028] In the wiring from the charging inlet 6 to the battery pack 2, a boost circuit is formed by a lower switching element and an upper diode that constitute one of the three phase arms of the first inverter INV1, and a coil of the first drive motor M1 that is connected to the midpoint of that phase arm. Similarly, each of the three phase arms constitutes a boost circuit. In this manner, the first inverter INV1 and the first drive motor M1 can be regarded as three boost circuits connected in parallel between the charging inlet 6 and the battery pack 2. By using the first inverter INV1 and the first drive motor M1 as a boost circuit, the electric vehicle 1 can rapidly charge the battery pack 2 even if the output voltage of the external DC power source 7 is lower than that of the battery pack 2.

[0029] The warm-up process executed by the motor control device 5 will be described below with reference to Fig. 2. When the power cable of the external DC power source 7 is connected to the charging inlet 6 and the user turns on a charging switch (not shown), the process of Fig. 2 is executed. The motor control device 5 estimates the magnet temperature of the rotor of the first drive motor M1 from the motor temperature T1 measured by the first temperature sensor 39L provided on the first drive motor M1, and estimates the magnet temperature of the rotor of the second drive motor M2 from the motor temperature T2 measured by the second temperature sensor 39R provided on the second drive motor M2 (step S1). The estimation of the magnet temperature is not particularly limited, and may be performed using a predetermined function, for example, or may be performed using a table that describes the correspondence between the motor temperature and the magnet temperature.

[0030] Next, the motor control device 5 determines whether the difference between the estimated magnet temperature of the first drive motor M1 and the estimated magnet temperature of the second drive motor M2 is equal to or greater than the deflection tolerance magnet temperature difference (step S2). If the estimated magnet temperature difference is smaller than the deflection tolerance magnet temperature difference, the process ends. Then, the process returns to step S1, and loop processing is performed. The loop processing may be performed at a predetermined interval. The loop processing may also be performed during a period in which a charging switch (not shown) is in an on state. If the estimated magnet temperature difference is equal to or greater than the deflection tolerance, the process proceeds to step S3.

[0031] Here, the torque output by the drive motors M1, M2 depends on the magnet temperature of the drive motors M1, M2, and increases as the magnet temperature decreases. The magnet temperature of the first drive motor M1 rises because the first drive motor M1 is used for neutral point charging. For this reason, as the charging time increases, the difference between the magnet temperature of the first drive motor M1 and the magnet temperature of the second drive motor M2 increases. FIG. 3A shows the state of the electric vehicle 1 when traveling straight when the magnet temperature difference is greater than the deflection allowable magnet temperature difference, and FIG. 3B shows the state of the electric vehicle 1 when traveling straight when the magnet temperature difference is within the deflection allowable magnet temperature difference. When the magnet temperature difference becomes greater than the deflection allowable magnet temperature difference, the difference between the torque output by the first drive motor M1 and the torque output by the second drive motor M2 increases, and deflection occurs when traveling straight (see FIG. 3A). The deflection allowable magnet temperature difference is set as the magnet temperature difference that causes the maximum allowable deflection when the electric vehicle 1 travels straight.

[0032] The motor control device 5 estimates a charging completion time from the estimated SOC value and the charging current value of the battery pack 2 (step S3). The charging completion time is the time required for charging to be completed. Next, the motor control device 5 estimates the time required for the difference between the estimated magnet temperature value of the first drive motor M1 and the estimated magnet temperature value of the second drive motor M2 to become equal to or smaller than the deflection allowable magnet temperature difference when a predetermined d-axis current is applied to the second drive motor M2 to heat up the magnet of the second drive motor M2, that is, the temperature rise completion time of the second drive motor M2 (step S4). The temperature rise completion time may be calculated as the time required for the estimated magnet temperature difference to match the deflection allowable magnet temperature difference plus a predetermined time.

[0033] The motor control device 5 determines whether the charging completion time estimated in step S3 is equal to or shorter than the temperature rise completion time estimated in step S4 (step S5). If the charging completion time is longer than the temperature rise completion time, the process ends. Then, the process returns to step S1, and loop processing is performed. If the charging completion time is equal to or shorter than the temperature rise completion time, the process proceeds to step S6.

[0034] The motor control device 5 generates a second control signal PWM2 based on the d-axis current command value, and supplies a predetermined d-axis current to the second drive motor M2. Since only the d-axis current is supplied to the second drive motor M2, the second drive motor M2 does not output torque. Since the charging completion time and the temperature increase completion time are aligned by step S5, charging and temperature increase are completed at almost the same time. Therefore, when charging is completed, the difference between the estimated value of the magnet temperature of the first drive motor M1 and the estimated value of the magnet temperature of the second drive motor M2 becomes equal to or smaller than the deflection allowable magnet temperature difference. As a result, when the user starts driving the electric vehicle 1 immediately after charging and tries to drive the electric vehicle 1 straight, the difference between the torque output by the first drive motor M1 and the torque output by the second drive motor M2 is sufficiently small, so stable driving is possible (see FIG. 3B).

[0035] (effect) In the drive motor warm-up process shown in Fig. 2, the temperature rise of the second drive motor M2 is completed when charging is completed. Therefore, the estimated value difference of the magnet temperature can be kept within the deflection allowable magnet temperature difference at the time of charging completion while suppressing power consumption. Note that, if necessary, the temperature rise of the second drive motor M2 may be executed at any time during charging when the estimated value difference of the magnet temperature becomes equal to or larger than the deflection allowable magnet temperature difference.

[0036] 2, when the temperature difference between the estimated magnet temperature of the first drive motor M1 and the estimated magnet temperature of the second drive motor M2 is equal to or greater than the deflection allowable magnet temperature difference (S2:Y) ​​during the period when the charging switch is on (i.e., during charging), the energization process of step S6 can be executed. This makes it possible to not execute the energization process of step S6 when the temperature difference between the first drive motor M1 and the second drive motor M2 is small, for example. Therefore, the warm-up process can be executed with high energy efficiency.

[0037] 2, during the period when the charging switch is in the ON state (i.e., during charging processing), the temperature difference between the estimated value of the magnet temperature of the first drive motor M1 and the estimated value of the magnet temperature of the second drive motor M2 can be monitored. Then, when the temperature difference becomes equal to or greater than the deflection allowable magnet temperature difference, a process for estimating the charging completion time (S3) and a process for estimating the temperature rise completion time (S4) can be executed. As a result, for example, when the temperature difference between the first drive motor M1 and the second drive motor M2 is small, the processes of steps S3 and S4 can be prevented from being executed. This makes it possible to reduce the burden on the motor control device 5. EXAMPLES

[0038] Example 2 is a specific configuration example of the contents described in Example 1. Fig. 4 is a block diagram of an electric vehicle 1 equipped with a drive unit 20, seen from above. In Fig. 4, the front of the electric vehicle 1 is indicated as "FR", the left as "LH", and the top as "UP". The same applies to the subsequent drawings.

[0039] In addition to the drive device 20, the electric vehicle 1 further includes a vehicle body 12, a battery pack 2, a pair of left and right front wheels 4L, 4R, a pair of left and right rear wheels 5L, 5R, and a charging inlet 6. The drive device 20 includes a first drive motor M1, a second drive motor M2, a first inverter INV1, a second inverter INV2, a first power transmission mechanism 50L, and a second power transmission mechanism 50R.

[0040] The drive device 20 drives the pair of front wheels 4L, 4R by supplying electric power from the battery pack 2 to the first drive motor M1 and the second drive motor M2. This drives the electric vehicle 1. In other words, the pair of front wheels 4L, 4R are the drive wheels of the electric vehicle 1. In a modified example, the pair of rear wheels 5L, 5R may be the drive wheels of the electric vehicle 1.

[0041] The first drive motor M1 and the second drive motor M2 are arranged symmetrically with respect to a center line CL1 in the left-right direction of the electric vehicle 1, and have the same structure. The first drive motor M1 is located to the left of the center line CL1, and the second drive motor M2 is located to the right of the center line CL1. The first inverter INV1 is arranged above the first drive motor M1, and the second inverter INV2 is arranged above the second drive motor M2. The first drive motor M1 and the first inverter INV1 are electrically connected to each other, and the second drive motor M2 and the second inverter INV2 are electrically connected to each other. The first power transmission mechanism 50L and the second power transmission mechanism 50R are mechanically connected to the first drive motor M1 and the second drive motor M2, respectively.

[0042] The charging inlet 6 is disposed on the right side surface of the vehicle body 12. The charging inlet 6 is configured to be connected to an external DC power source 7 (for example, a charging stand) via a power cable 8.

[0043] A detailed structure of the drive device 20 will be described with reference to Fig. 5. Fig. 5 is a cross-sectional view taken along line VV in Fig. 4. The drive device 20 further includes a motor control device 5 in addition to the first drive motor M1 and second drive motor M2 described above.

[0044] The first drive motor M1 of the drive device 20 includes a first motor case 32L, a first motor bearing 33L, a first rotor 34L, a first stator 35L, and a first temperature sensor 39L. The first motor case 32L houses the first rotor 34L, the first stator 35L, and the first temperature sensor 39L. The first rotor 34L has a first permanent magnet 36L. The first stator 35L faces the first rotor 34L from the radial outside. The outer periphery of the first stator 35L is covered by a U-phase coil 35U, a V-phase coil 35V, and a W-phase coil 35W (see FIG. 1). The first temperature sensor 39L is fixed to the left end face of the first stator 35L. The first temperature sensor 39L detects a motor temperature T1 of the first drive motor M1 and transmits it to the motor control device 5. In a modified example, the first temperature sensor 39L may be fixed to, for example, the inner wall of the first motor case 32L. The first motor bearing 33L is, for example, a ball bearing. The first motor bearing 33L rotates the first motor shaft 51L by rolling balls along an inner raceway.

[0045] As described above, the second drive motor M2 has the same configuration as the first drive motor M1. Therefore, like the first drive motor M1, the second drive motor M2 includes a second motor case 32R, a second motor bearing 33R, a second rotor 34R having a second permanent magnet 36R, a second stator 35R, and a second temperature sensor 39R. The second motor bearing 33R rotates the second motor shaft 51R. The second temperature sensor 39R detects the motor temperature T2 of the second drive motor M2 and transmits it to the motor control device 5.

[0046] The first power transmission mechanism 50L transmits the power of the first drive motor M1 to the first drive shaft 14L. The first drive shaft 14L is connected to the front wheels 4L. The first power transmission mechanism 50L includes a plurality of bearings 53L, 56L, 58L, a plurality of gears 54L, 57L, 60L, 61L, 62L, and a plurality of shafts 55L, 59L. The first power transmission mechanism 50L reduces the rotation speed of the first drive motor M1 by using, for example, the plurality of gears 54L, 57L, 60L, 61L, 62L, etc., to drive the first drive shaft 14L. The first power transmission mechanism 50L further includes a parking gear 70.

[0047] The second power transmission mechanism 50R transmits the power of the second drive motor M2 to the second drive shaft 14R. The second power transmission mechanism 50R has a structure symmetrical to the first power transmission mechanism 50L described above. For this reason, the second power transmission mechanism 50R includes a plurality of bearings 53R, 56R, 58R, a plurality of gears 54R, 57R, 60R, 61R, 62R, and a plurality of shafts 55R, 59R. The second power transmission mechanism 50R reduces the rotation speed of the second drive motor M2 by using, for example, the plurality of gears 54R, 57R, 60R, 61R, 62R, etc., to rotate the second drive shaft 14R. EXAMPLES

[0048] The third embodiment is different from the second embodiment in that the drive wheels driven by the first drive motor M1 and the second drive motor M2 are different. The same components in the third embodiment and the first embodiment are denoted by the same reference numerals and will not be described. Fig. 6 shows a block diagram of an electric vehicle 301 in the third embodiment. Fig. 6 is the same as Fig. 4.

[0049] The drive device 20F includes a first drive motor M1, a first inverter INV1, and a first power transmission mechanism 50F. The first power transmission mechanism 50F transmits the power of the first drive motor M1 via a first drive shaft 14 to the front wheels 4L and 4R.

[0050] The drive unit 20B includes a second drive motor M2, a second inverter INV2, and a second power transmission mechanism 50B. The second power transmission mechanism 50B transmits the power of the second drive motor M2 via a second drive shaft 15 to the rear wheels 5L and 5R.

[0051] In the electric vehicle 301 of the third embodiment, the warm-up process described with reference to FIG. 2 can also be performed, and therefore the same effects as those of the electric vehicle 1 of the first embodiment can be obtained.

[0052] Although the embodiments have been described in detail above, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes to the specific examples exemplified above. The technical elements described in this specification or drawings exhibit technical utility alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology exemplified in this specification or drawings achieves multiple objectives simultaneously, and achieving one of the objectives itself has technical utility.

[0053] (Modification) In the process of passing the d-axis current (step S6), the motor control device 5 may control the magnitude of the d-axis current passed through the second drive motor M2 in accordance with the temperature difference calculated in step S2. For example, the value of the d-axis current may be increased as the temperature difference increases. At this time, the value of the d-axis current may be proportional to the temperature difference. As a specific example, the value of the d-axis current may be calculated by multiplying the temperature difference by a predetermined conversion value. In this way, the value of the d-axis current can be increased as the temperature difference increases, making it possible to increase the amount of heat generated by the second drive motor M2. Therefore, the warm-up process can be performed with high energy efficiency. [Explanation of symbols]

[0054] 1: electric vehicle, 2: battery pack, 3: left drive unit, 4: right drive unit, 5: motor control device, 6: charging inlet, 7: external DC power supply, INV1: first inverter, INV2: second inverter, M1: first drive motor, M2: second drive motor

Claims

1. A drive device for an electric vehicle having a battery, comprising: a first motor and a second motor electrically connected to the battery and configured to drive at least one drive wheel of the electric vehicle; a control device that controls a current flowing through the first motor and a current flowing through the second motor, The control device includes: a charging process for supplying electric power from an external power source to a battery via a neutral point of the first motor; a current supply process for supplying a d-axis current to the second motor during the charging process; A drive device configured to be able to execute the above steps.

2. The drive device according to claim 1 , wherein the control device executes the energization process when a temperature difference between the first motor and the second motor is equal to or greater than a predetermined value during the charging process.

3. The drive device according to claim 2 , wherein the temperature difference is a difference between a magnet temperature of a rotor of the first motor and a magnet temperature of a rotor of the second motor.

4. The drive device according to claim 1 , wherein the control device controls a magnitude of the d-axis current supplied to the second motor in accordance with a temperature difference between the first motor and the second motor.

5. The control device includes: a first estimation process for estimating a charging time required until charging of the battery is completed by the charging process; a second estimation process for estimating a temperature rise time required for the temperature difference between the first motor and the second motor to become equal to or less than a predetermined value by the power supply process; and further configured to execute the The drive device according to claim 1 , wherein the control device starts the current application process in response to the required charging time being reduced to equal to or less than the required temperature rise time.

6. The control device is configured to execute a process of monitoring the temperature difference during the charging process, The drive device according to claim 5 , further comprising: a controller configured to execute the first estimation process and the second estimation process in response to the temperature difference becoming equal to or greater than the predetermined value.

7. The drive wheels are a left wheel and a right wheel, The drive device according to claim 1 , wherein the first motor drives one of the left and right wheels, and the second motor drives the other of the left and right wheels.

8. the drive wheels are front and rear wheels of the electric vehicle, 2. The drive device according to claim 1, wherein the first motor drives one of the front wheels and the rear wheels, and the second motor drives the other of the front wheels and the rear wheels.

9. an inverter circuit having a plurality of switching elements and electrically connected between the battery and the first motor; The drive device according to claim 1 , wherein the control device controls the plurality of switching elements in the charging process to cause the inverter circuit to function as a boost circuit together with the plurality of coils of the first motor.

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