JP6551667B2 - Climbing start motor controller for electric car - Google Patents

Description

  The present invention relates to a climbing start motor control apparatus for an electric vehicle.

  Many electric vehicles (electric vehicles) convert the DC power of an on-board battery into AC power by an inverter to drive a traveling motor (for example, a synchronous AC three-phase motor), and output the traveling motor via a drive shaft Transmission to the drive wheels. Specifically, in the inverter, three-phase IGBTs (Insulated Gate Bipolar Transistors) such as U-phase, V-phase, and W-phase are used as switching elements. Then, the ECU (control unit) controls (switches) the IGBT according to the state of the traveling motor, and uses the generated three-phase alternating current (U phase, V phase, W phase) for traveling according to the accelerator pedal operation. The torque is output to the motor to apply a torque to the traveling motor.

  By the way, IGBT of the inverter mounted in an electric vehicle is a component which is easy to generate heat. That is, as shown in FIG. 7A, when the traveling motor rotates at high speed, the switching cycle is short and the frequency is high, so the current flowing in the U-phase, V-phase, and W-phase IGBTs is Although the temperature is increased or decreased at a short cycle and the temperature rise of the IGBT is small, as shown in FIG. 7 (b), as the rotation of the traveling motor becomes slower, the switching cycle becomes longer and the frequency decreases. The current flowing through the V-phase and W-phase IGBTs is increased or decreased in a slow cycle, and the temperature of the IGBT increases. Further, as shown in FIG. 7C, when the traveling motor is in a locked state, the current that should flow in the U phase, V phase, and W phase continues to flow in a large current concentrated in the one phase IGBT Therefore, the one-phase IGBT rapidly generates heat, causing a rapid temperature rise.

The characteristics of the IGBT have an influence when the electric vehicle starts uphill.
That is, normally, when the electric vehicle starts uphill, when the accelerator pedal is depressed, three-phase alternating current with a cycle corresponding to the state of the traveling motor is output to the traveling motor to apply torque to the traveling motor. At this time, in the case of a flat road as shown in FIG. 8, the temperature of the IGBT does not rise because the traveling motor immediately starts to move and accelerates. Also, in the case of uphill roads, as shown in FIG. 8, as the slope of the uphill roads becomes steeper, the rotation of the traveling motor becomes difficult to increase, so the temperature of the IGBT rises when the accelerator pedal is depressed. After that, since the current flowing through the IGBT is increased or decreased at an early cycle due to the start of movement of the traveling motor, the temperature of the IGBT decreases.

  However, normally, the allowable temperature for protection is set so that the IGBT is protected from an excessive temperature rise (the IGBT is broken when the temperature becomes excessive). That is, for example, when starting the slope of an uphill road where the IGBT temperature such as a1 in FIG. A control to suppress the torque applied to the drive motor works to stop the motor (torque suppression).

Since the IGBT is a component whose temperature changes in units of time of “ms”, the temperature of the IGBT immediately falls below the upper limit value when torque suppression (energization stop) is performed as described above.
However, when the IGBT falls below the upper limit value, switching is performed again, and a three-phase alternating current is output to the traveling motor to apply torque to the traveling motor, but the slope of the uphill does not change. The temperature rises until the upper limit of the allowable range is exceeded. That is, in the case of a steep slope that causes an excessive temperature rise of the IGBT, the electric vehicle may apply torque to the traveling motor or suppress the torque by the protection function of the IGBT. Just by repeating, the electric vehicle stops on the uphill road and cannot start.

  On the other hand, in the control for starting the uphill road of the electric vehicle, a control is disclosed that starts the uphill road by setting a torque value that can start climbing on the maximum slope that can be climbed in advance. However, there is no technology that prompts a start from a gradient that causes an excessive temperature rise of the IGBT.

JP 2003-199205

For this reason, it is difficult for the electric vehicle to ensure the uphill road start performance exceeding the limit of the uphill performance because the protection function for suppressing the excessive temperature rise of the IGBT becomes an obstacle.
Therefore, an object of the present invention is to provide an uphill start motor control apparatus for an electric automobile that enables uphill start even when the slope of the uphill road is considered to be difficult due to the upper limit of the allowable temperature of the switching element.

  According to an aspect of the present invention, an inverter having a plurality of switching elements for converting direct current power to alternating current power, a traveling motor connected to the inverter, a drive shaft for transmitting the output of the traveling motor to drive wheels, and accelerator pedal operation And a control unit for outputting alternating current from the switching element to apply torque to the traveling motor, and when starting the uphill road of the electric vehicle, when the temperature of the switching element rises to the upper limit value of the allowable temperature, An uphill start motor control apparatus for an electric vehicle that reduces applied torque, wherein the control unit is configured to drive the drive shaft in the opposite direction and forward drive of the drive shaft generated on the drive shaft immediately after suppressing the torque when starting uphill on the electric vehicle. A vibration period detector that detects the period of the damped vibration that alternately vibrates in the rotation direction, and the number of detected drive shafts In accordance with the vibration cycle it was assumed to have a re-torque applying unit for applying a torque to the traction motor.

  According to the present invention, the temperature of the switching element reaches the upper limit value of the allowable temperature due to the steep slope at the start of the uphill road of the electric vehicle, and the torque applied to the traveling motor is suppressed to protect the switching element. Immediately after that, torque is applied to the drive motor according to the opposite drive direction of the drive shaft and the cycle of the damped vibration that vibrates in the drive direction, so that the drive motor is twisted due to the damped vibration of the drive shaft. It starts to move with the support of torque.

  Therefore, the electric motor vehicle can start uphill from a slope which is considered to be difficult to start due to the upper limit of the allowable temperature, with the help of the torsional torque of the drive shaft brought about by damping vibration. It is possible to give the starting performance of the uphill road exceeding.

The block diagram which shows each part of the uphill starting motor control apparatus of the 1st Embodiment of this invention with the principal part of an electric vehicle (electric vehicle). The flowchart of the control performed with a slope start motor control apparatus. The time chart for demonstrating the damped vibration which generate | occur | produces in a drive shaft, when an electric vehicle receives the restriction | limiting of IGBT upper limit and the torque is suppressed. The time chart for demonstrating when applying a torque to a driving motor according to the period of damping vibration. The perspective view explaining that the torsion torque of the drive shaft brought about by the damped vibration is combined with the torque of the traveling motor and transmitted to the drive wheels. The flowchart which shows application control of the torque according to the different damping oscillation period which becomes the principal part of the 2nd Embodiment of this invention. The time chart explaining the temperature rise characteristic of IGBT which changes according to the revolving speed of the motor for run. The diagram for demonstrating the change of the temperature rise of IGBT when starting the uphill road based on the rotational speed of the motor for the said driving | running | working.

Hereinafter, the present invention will be described based on a first embodiment shown in FIGS.
FIG. 1 shows a schematic configuration of an electric vehicle (electric vehicle). The main parts of the electric vehicle will be described. In FIG. 1, 1 is a vehicle body of the electric vehicle, 3 is a front wheel disposed at the front of the vehicle body 1, 5 is a rear wheel disposed at the rear of the vehicle 7) has a traveling motor (for example, composed of a synchronous AC three-phase motor), 9 has a battery, and 11 has multiple phase IGBTs 11a (corresponding to switching elements) such as U phase, V phase and W phase An inverter 13 is configured by an ECU (composed of a microcomputer: corresponding to a control unit). An output portion of the traveling motor 7 is connected to the rear wheel 5 via a drive shaft 15 (made of a steel shaft member).

The battery 9 is connected to the traveling motor 7 via the inverter 11, converts the direct current output of the battery 9 into an alternating current output, and outputs the alternating current output to the traveling motor 7. As a result, the rear wheels 5 are driven by the power of the battery 9.
The ECU 13 switches the IGBT 11a according to the state of the traveling motor 7 (signals from the motor rotational speed sensor 21 and the motor rotational phase sensor 23) based on preset control information, or a signal from the accelerator sensor 17, ie, The generated alternating current is output to the traveling motor 7 in accordance with the accelerator opening signal of the accelerator pedal 19. That is, the traveling motor 7 is driven by the ECU 13, that is, torque is applied to the traveling motor 7.

This electric vehicle is provided with an uphill starting motor control device 29 that performs control related to starting up an uphill road. The uphill start motor control device 29 has, for example, the ECU 13 of a function of protecting the IGBT 11a from an excessive temperature rise, and a function of enhancing the uphill start performance using a phenomenon generated by the protection function.
The protection function (IGBT protection unit) of the IGBT 11a sets in the ECU 13 an allowable temperature for protecting the IGBT 11a in advance. The inverter 11 is provided with a temperature sensor 14 that detects the temperature of the IGBT 11a. When the temperature of the IGBT 11a detected by the temperature sensor 14 rises to the upper limit value t (FIGS. 3 and 4) of the allowable temperature (for example, 1-phase IGBT 11a). When the current is concentrated and the IGBT 11a is overheated, the control function is provided to temporarily stop the energization of the IGBT 11a. That is, the torque applied to the traveling motor 7 is suppressed by stopping the energization of the IGBT 11a. By this torque suppression, the temperature of the IGBT 11a is lowered, and an excessive temperature rise in the IGBT 11a is suppressed. Incidentally, the temperature drop of the IGBT 11a is performed in an extremely short time unit such as several tens of ms.

The function of increasing the limit of the starting performance of the electric vehicle is performed by utilizing the damping vibration of the drive shaft 15 generated immediately after the torque suppression is performed.
That is, immediately after the torque suppression control of the traveling motor 7 is executed, the drive shaft 15 (running motor 7: non-energized) is twisted from the initial positive drive direction as seen in the motor rotation phase of FIG. It is known that torsional vibration is alternately repeated in the circumferential direction, that is, it is twisted in the drive direction, twisted in the positive drive direction, and further twisted in the reverse drive direction (damped with a short period of ms). This vibration is called a damped vibration S.

  The function of increasing the limit of the starting performance is resonance control that applies torque to the traveling motor 7 in accordance with the period of the damped vibration. Specifically, in the same control, a detection function (corresponding to a vibration cycle detection unit) for detecting the cycle of the damped vibration S generated on the drive shaft 15 immediately after torque suppression and the cycle of the detected damped vibration S Again, a re-torque application function (corresponding to a re-torque application unit) for switching the IGBT 11a so that torque is applied to the traveling motor 7 is provided.

  The detection function of the present embodiment uses a method of detecting the cycle of the damped vibration S based on the cycle time set based on the natural frequency of the drive shaft 15. For example, when the natural frequency of the drive shaft 15 is “10 Hz”, one cycle of the damping vibration S is “approximately 100 ms”. Therefore, by detecting that the same time has elapsed after torque suppression, the drive shaft 15 It is possible to detect the period of damping vibration of

  Further, the re-torque application function is such that the torsional torque when the twist of the drive shaft 15 is released is most effectively transmitted as the starting torque to the rear wheel 5, and the damped vibration shown by the motor rotation phase and motor rotation speed in FIG. Return timing (y) when S is phased in the counter driving direction and then in the positive driving direction (here, half of “100 ms”, for example, when “50 ms” has elapsed after torque suppression) The AC generated according to the state (stopped state) of the motor 7 is controlled to output to the traveling motor 7.

  That is, at the start of a steep slope as restricted by the allowable temperature, the torque from the driving motor 7 and the twisting torque generated in the drive shaft 15 are applied to the rear wheel 5. The assist by the torsional torque allows the traveling motor 7 that was originally impossible to start moving. Of course, in order to protect the IGBT 11a from overheating, the retorque application is performed when the temperature of the IGBT 11a falls below the upper limit of the allowable temperature.

Next, the operation of the uphill starting motor control device 29 will be described. The flow chart shown in FIG. 2, the time chart shown in FIG. 4, and the perspective view schematically showing the electric vehicle (vehicle) stopped on the uphill road shown in FIG. 5 will be described.
For example, when an electric vehicle stopping an uphill road as shown in FIG. 5 starts up as an example, the driver releases the side brake (not shown) and depresses the accelerator pedal 19. As a result, the plurality of IGBTs 11 a of the inverter 11 are switched according to the state (stopped) of the traveling motor 7, and three-phase alternating current with a period corresponding to the traveling motor 7 is generated. Then, as shown in step S1 of FIG. 2, the generated torque is applied to the traveling motor 7 as the accelerator pedal 19 is depressed. The applied torque is transmitted to the drive shaft 15 as shown in FIG. 5, and the drive shaft 15 is first twisted in the positive drive rotational direction. When the drive shaft 15 finishes twisting, torque is transmitted to the rear wheel 5 as indicated by an arrow A in FIG. 5, and the electric vehicle is started (moved forward).

At this time, it is assumed that the motor lock occurs because the slope θ of the uphill road shown in FIG. 5 is steep. Then, current concentrates in one phase of the IGBT 11a, and the one-phase IGBT 11a generates excessive heat, and the temperature of the IGBT 11a detected by the temperature sensor 14 is the upper limit value t of the allowable temperature as shown in FIG. To reach.
In the following step S3 of FIG. 2, it is determined whether the temperature of the IGBT 11a is the upper limit value t. When the IGBT temperature reaches the upper limit value t, the process proceeds to step S5, where IGBT protection control for protecting the drive motor 7 from overheating, that is, torque suppression control for suppressing the torque applied to the drive motor 7 is performed.

Specifically, control for stopping energization of the IGBT 11a is performed. As a result, the temperature of the IGBT 11a decreases as shown in FIG.
Furthermore, since the traveling motor 7 is free and the twist of the drive shaft 15 is released, the motor rotation phase (detection signal of the motor rotation phase sensor 23) of FIG. A damped vibration S as shown in the signal of the rotation speed sensor 21 occurs. That is, the damping vibration S twists in the positive drive direction of the drive shaft 15, twists in the reverse drive direction, twists again in the positive drive direction, and further twists in the reverse drive direction. However, it is a vibration that attenuates (short period of ms unit).

In the next step S7, as shown in FIG. 4, the natural frequency (e.g. 10 Hz) of the drive shaft 15 is a predetermined time which is an elapsed time after the torque suppression as shown in FIG. It is determined whether or not one cycle time set based on the above, “50 ms” has elapsed.
The timing of “50 ms” is a return timing in which the drive shaft 15 twisted in the counter driving direction is phased in the positive driving direction as shown in the motor rotation phase in FIG. At the same timing (y), the process proceeds to step S9, and according to this timing, the three-phase AC output generated by the IGBT 11a is added to the traveling motor 7 again as shown by the motor torque in FIG. Torque is applied to the traveling motor 7 (resonance).

  As a result, as shown in FIG. 5, the torque A applied to the rear wheel 5 is excessive by adding the torsional torque A2 in the positive drive direction of the drive shaft 15 caused by the damping vibration S to the torque A1 from the traveling motor 7. Since the torque is applied, the traveling motor 7 can start to move even if the vehicle cannot start due to the overheating of the IGBT 11a, that is, it is not allowed to continue to stop on the uphill road.

In the following step S11, it is determined whether or not the traveling motor 7 has started to move. If the traveling motor 7 has started to move, it is determined that an excessive temperature rise of the IGBT 11a does not occur, and the process proceeds to step S13. Thus, the traveling motor 7 is controlled by the switching of the IGBT 11a according to the normal motor state, and the electric vehicle starts while accelerating on the uphill road.
As described above, even when the torque of the traveling motor 7 is suppressed for protection of the IGBT 11a at the start of the uphill road of the electric automobile, the traveling motor 7 generates the torsional torque generated by the damping vibration S of the drive shaft 15. Start moving with support.

  Therefore, the electric vehicle can be started from a slope where it is difficult to start due to the upper limit of the allowable temperature until now, and the electric vehicle can be given a start performance on an uphill road exceeding the limit. In particular, since torque is applied to the traveling motor 7 at the timing when the damped vibration S is phased in the positive drive direction, the torsion torque of the damped vibration S generated in the drive shaft 15 is most effectively assisted by the traveling motor 7. Available to

Moreover, since the cycle time (50 ms in this case) based on the natural frequency of the drive shaft 15 is used to detect the cycle of the damped vibration S, the cycle of the vibration of the damped vibration S of the drive shaft 15 is simply controlled. In addition, torque can be applied to the traveling motor 7.
Moreover, since the retorque application of the traveling motor 7 is executed when the temperature of the IGBT 11a falls below the upper limit value t of the allowable temperature, stable control of the retorque application can be promised.

FIG. 6 shows a second embodiment of the present invention.
The detection of the period of the damped oscillation is not performed by an indirect method such as the detection of the period time based on the natural frequency of the drive shaft as in the first embodiment, but a sensor such as a motor rotational phase sensor 23 (or a motor speed The period of the damped vibration S of the drive shaft 15 is directly detected from the motor rotation phase shown in FIG. 4 using the sensor line 21).

  Specifically, as shown in the flow chart of FIG. 6, instead of step S7 in the flow chart of FIG. 2 (first embodiment), it is generated after torque suppression from the output signal of the motor rotational phase sensor 23 as step S6. Cycle of detecting the phase from the phase point (x) at the time of starting to return in the reverse drive direction in FIG. 4 to the phase point (y) heading in the positive drive direction among the damped vibrations S of the drive shaft 15 A detection process is provided, and in the next step S9, torque is applied to the traveling motor 7 in accordance with the cycle of the damped vibration S detected in step S6.

The re-torque application of the travel motor 7 may be performed not at the first cycle timing after torque suppression but at the second cycle timing.
However, the same reference numerals as in FIG. 2 (first embodiment) denote the same parts in FIG. 6 and a description thereof will be omitted.
Each configuration, combination, and the like in the embodiment described above is an example, and addition, omission, replacement, and other modifications of the configuration can be made without departing from the spirit of the present invention. Absent. Further, it is needless to say that the present invention is not limited by the above-described embodiment, and is limited only by the claims.

5 Rear wheels (drive wheels)
7 Traveling motor 11 Inverter 11a IGBT (switching element)
13 ECU (control unit, vibration period detection unit, re-torque application unit)
15 Drive shaft A Damped vibration

Claims (5)

An inverter having a plurality of switching elements that convert DC power into AC power;
A traveling motor connected to the inverter;
A drive shaft for transmitting the output of the traveling motor to drive wheels;
A controller that outputs an alternating current from the switching element by an accelerator pedal operation and applies a torque to the traveling motor;
An uphill start motor control apparatus for an electric automobile, which suppresses the torque applied to the traveling motor when the temperature of the switching element rises to the upper limit value of the allowable temperature at the start of the uphill road of the electric automobile.
The control unit
A vibration cycle detection unit that detects a cycle of damping vibration alternately vibrating in the reverse drive direction and the positive drive rotation direction of the drive shaft generated on the drive shaft immediately after suppression of the torque at the start of the uphill road of the electric vehicle When,
An uphill start motor control apparatus for an electric vehicle, comprising: a retorque application unit that applies a torque to the traveling motor in accordance with the detected period of the damping vibration of the drive shaft. The re-torque application unit is
The uphill starting motor control device for an electric vehicle according to claim 1, wherein torque is applied to the traveling motor at a timing when the damped vibration of the drive shaft is phased in the positive driving direction. The torque application of the traveling motor in the re-torque application unit is
It is performed when the temperature of the said switching element is less than the upper limit of allowable temperature. The climbing start motor control apparatus of the electric vehicle of Claim 1 or Claim 2 characterized by the above-mentioned. The period detection of the damped vibration in the vibration period detector is
The uphill start motor control apparatus for an electric automobile according to any one of claims 1 to 3, wherein the control system is based on a cycle time set according to the natural frequency of the drive shaft. The period detection of the damped vibration in the vibration period detector is
The climbing start motor control device for an electric vehicle according to any one of claims 1 to 3, wherein the motor control device is based on detection of a phase by a sensor.

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