JP5598103B2 - Electric vehicle motor lock countermeasure control device - Google Patents

Description

  The present invention is an overheated state even when the electric motor in an electric vehicle such as an electric vehicle using only the electric motor as a power source or a hybrid vehicle that travels using energy from the engine and the electric motor tends to be rotationally locked. The present invention relates to a motor lock countermeasure control device for an electric vehicle that is not to become.

  In electric vehicles, when running with electricity (EV) using only an electric motor, for example, when an operation that depresses the accelerator pedal in a braking state in which the brake pedal is depressed, the electric motor requires a heavy load by depressing the accelerator pedal. In such a state, the motor rotation speed may be reduced or the motor may be locked.

  In this case, although the motor rotation speed is low or the motor rotation speed is 0, a large current corresponding to the depression of the accelerator pedal (large load) is supplied to the electric motor. As a result of a large current flowing to each phase of the motor (U phase, V phase, W phase) or a specific phase over a relatively long time, the electric motor may be overheated and its durability may be reduced. is there.

  As a motor lock countermeasure technique for such an electric vehicle, generally, for example, as described in Patent Document 1, when the motor rotation speed becomes less than a set value, the magnitude of the motor output torque (motor driving force) is limited, It is common to prevent overheating of the electric motor by suppressing the supply current to the electric motor.

JP 2007-331646 A

  However, since the limit value of the motor output torque (motor driving force) is a constant value as specified in Patent Document 1, conventionally, this limit value is used to prevent overheating of the electric motor in all rotation speed ranges. Since it is necessary to determine a small torque value (driving force) that can be reliably realized by the above, that is, it is necessary to apply a large torque limit, the following problems arise.

In other words, in the conventional technology, when the motor rotation speed is determined to be less than the set value, the magnitude of the motor output torque (motor driving force) is reduced at once from the current value to the above small constant limit value. It becomes.
Therefore, when the motor lock is determined, the driving force is suddenly reduced, causing a problem that the occupant feels a sudden and large deceleration to give an uncomfortable feeling.

In view of the above situation, the present invention is less likely to cause motor overheating while the vehicle speed is still relatively high even at the time of motor lock determination, and the motor driving force limit value for preventing overheating when the electric motor is locked is large. Based on the fact that it ’s good,
By varying the driving force limit value for preventing overheating when the motor is locked, depending on the vehicle speed, the driving force does not drop suddenly when taking measures against motor locking, and the driver feels sudden and large deceleration. An object of the present invention is to provide a motor lock countermeasure control device for an electric vehicle that can solve the above-mentioned problem of giving a pleasant feeling.

For this purpose, the motor lock countermeasure control device for an electric vehicle according to the present invention is:
For an electric vehicle that can travel by transmitting the driving force of the electric motor to the wheels,
Motor lock condition establishment determination means for determining that the rotation lock condition of the electric motor is established;
Motor driving force limiting means for limiting the driving force of the electric motor so that the driving force of the electric motor does not exceed the motor driving force upper limit when the motor lock condition is determined by the means;
The upper limit value of the motor driving force is set to a value that increases as the vehicle speed increases.

According to the motor lock countermeasure control apparatus for an electric vehicle according to the present invention,
In order to limit the driving force of the electric motor so that the driving force of the electric motor does not exceed the upper limit value of the motor driving force that is larger at higher vehicle speeds when the motor lock condition is established,
When the motor lock is taken, the driving force will gradually decrease as the vehicle speed decreases.Therefore, the drive force will not drop suddenly to the required limit value at the time of stopping when the motor lock is taken. It is possible to eliminate the above-described problem that the passenger feels the deceleration and feels uncomfortable.

1 is a schematic system diagram showing a vehicle drive system including a motor lock countermeasure control device according to an embodiment of the present invention and a control system thereof. 2 is a flowchart showing a motor lock countermeasure control program executed by the motor controller in FIG. FIG. 3 is an operation time chart when the motor lock countermeasure control program of FIG. 2 is executed when the electric motor is rotationally locked by a brake operation and an accelerator operation. FIG. FIG. 3 is a change characteristic diagram of a motor driving force upper limit value for motor lock countermeasure used in the motor lock countermeasure control program of FIG. 2;

Hereinafter, embodiments of the present invention will be described in detail based on examples shown in the drawings.
<Configuration>
FIG. 1 shows a vehicle drive system including a motor lock countermeasure control device according to an embodiment of the present invention and a control system thereof.
In the present embodiment, the vehicle in FIG. 1 is an electric vehicle that can drive by driving left and right front wheels (or left and right rear wheels) 1L and 1R.
When driving these left and right wheels 1L and 1R, the left and right wheels 1L and 1R are driven by an electric motor (traveling power source) 2 via a reduction gear 3 including a differential gear device.

  In controlling the driving force of the electric motor 2, the motor controller 4 converts the power of the battery 5 as a power source into DC-AC conversion by the inverter 6, and supplies this AC power to the electric motor 2 under the control of the inverter 6. Thus, the driving force of the electric motor 2 is controlled so that the torque of the electric motor 2 matches the calculation result (a target motor torque tTm described later) in the motor controller 4.

In addition, when the calculation result (target motor torque tTm) in the motor controller 4 has a negative polarity that requires the electric motor 2 to perform a regenerative braking action, the motor controller 4 applies a power generation load to the electric motor 2 via the inverter 6. give.
At this time, the electric power generated by the electric motor 2 due to the regenerative braking action is AC-DC converted by the inverter 6 to charge the battery 5.

In the motor controller 4, as information for calculating the target motor torque tTm,
A signal from a vehicle speed sensor 7 that detects a vehicle speed VSP that is a ground speed of the electric vehicle;
A signal from an accelerator opening sensor 8 that detects an accelerator opening APO (electric motor required load) that is an accelerator pedal depression amount by a driver;
A signal from the current sensor 9 that detects the current of the electric motor 2 (in FIG. 1, the currents iu, iv, and iw are three-phase alternating current composed of the U phase, V phase, and W phase)
The range selected by the shift operation performed by the driver to command the vehicle travel mode is the forward travel (D) range, the motor speed limit (B) range (corresponding to the engine brake range in a vehicle equipped with an automatic transmission), A signal from the range sensor 11 that detects whether the vehicle is in the reverse travel (R) range, the stop (N) range, or the parking (P) range,
Input the signal from the brake switch 12 that is turned on during braking by depressing the brake pedal.

The motor controller 4 generates a PWM signal for controlling the electric motor 2 according to the input information, and generates a drive signal for the inverter 6 through the drive circuit according to the PWM signal.
The inverter 6 includes, for example, two switching elements (for example, power semiconductor elements such as IGBT) for each phase, and the DC current supplied from the battery 5 is turned on / off according to the drive signal. Is converted into alternating current and reversely converted, and the electric motor 2 is supplied with a current corresponding to the target motor torque.

The electric motor 2 generates a driving force (torque) according to the alternating current supplied from the inverter 6 and transmits the driving force to the left and right wheels 1L and 1R through the speed reducer 3.
Also, when the electric motor 2 is driven by the left and right wheels 1L, 1R during vehicle travel, the vehicle motion is achieved by applying a regenerative braking action to the electric motor 2 by applying a power generation load to the electric motor 2. The energy is regenerated and stored in the battery 5.

<Motor lock countermeasure control>
The motor controller 4 executes the control program shown in FIG. 2 and performs motor lock countermeasure control to obtain the target motor torque tTm, and instructs the inverter 6 to control the driving force of the electric motor 2.

In step S11 of FIG. 2, it is checked whether or not the accelerator opening APO (motor required load) is equal to or greater than the set accelerator opening A1 (set load). In step S12, the brake switch 12 is ON (during braking). Check whether or not.
The set accelerator opening A1 is an accelerator opening for determining whether or not the motor lock condition is satisfied, which is used to determine whether or not the rotation lock condition of the electric motor 2 is satisfied.
Therefore, step S11 corresponds to the motor lock condition establishment determining means in the present invention.

If it is determined in step S11 that APO <A1, or if it is determined in step S12 that the brake switch 12 is OFF (not braking),
When the accelerator pedal is depressed while the brake pedal is depressed, that is, the rotation lock of the electric motor 2 due to the brake operation and the accelerator operation (hereinafter referred to as “two-operation motor lock”) does not occur, and the two-operation motor lock condition is satisfied. Because there is no
In step S13, the timer TM for measuring the elapsed time from when the two-operation motor lock condition is satisfied is reset to zero.

If it is determined in step S11 that APO ≧ A1, and it is determined in step S12 that the brake switch 12 is ON (braking),
There is a possibility that the two-operation motor lock of the electric motor 2 will occur by depressing the accelerator pedal while depressing the brake pedal, and the two-operation motor lock condition is satisfied,
In step S14, the elapsed time from when the two-operation motor lock condition is satisfied is measured by incrementing the timer TM.
Therefore, step S12 also corresponds to the motor lock condition establishment determination means in the present invention, as in step S11.

In step S15, it is checked whether or not the above-described timer TM (elapsed time from when the two-operation motor lock condition is satisfied) has reached the set time TM1 or more.
Here, the set time TM1 corresponds to a limit time in which the electric motor 2 is not overheated when the accelerator pedal is depressed so that APO ≧ A1 while the brake pedal is depressed.
Therefore, step S15 also corresponds to the motor lock condition establishment determination means in the present invention, as in steps S11 and S12.

  Until it is determined in step S15 that the timer TM ≧ TM1 is satisfied, that is, before the electric motor 2 is in a state immediately before overheating due to the two-operation motor lock by the brake operation and the accelerator operation, the control proceeds to step S17.

  This step S17 is a step that is selected even after step S13 is executed. In this step S17, the motor request for the electric motor 2 obtained as follows according to the operating state is set as the target motor torque tTm. The driving force vTm is set, and this target motor torque tTm = vTm contributes to the driving force control of the electric motor 2.

  When calculating the motor required driving force vTm, first, the driving of the vehicle requested by the driver from the selection range detected by the sensor 11 of FIG. 1, the vehicle speed VSP and the accelerator opening APO detected by the sensors 7 and 8 is performed. The driving force of the electric motor 2 required to realize the driving force of the vehicle requested by the driver is determined as the motor required driving force vTm from the obtained force and the gear ratio of the reduction gear 3.

  When it is determined in step S15 that the timer TM ≧ TM1 is satisfied, that is, when the electric motor 2 is in a state immediately before overheating due to the two-operation motor lock, the control is sequentially advanced to step S18 and step S19.

In step S18, the timer TM is held at the set time TM1 so as not to become longer than this.
In step S19, first, a motor driving force upper limit value uTm for preventing motor lock is calculated, and this motor driving force upper limit value uTm for preventing motor lock and a motor required driving force vTm obtained in the same manner as described above for step S17. Min (vTm, uTm) is the target motor torque tTm, and this target motor torque tTm = Min (vTm, uTm) contributes to the driving force control of the electric motor 2.
Therefore, step S19 corresponds to the motor driving force limiting means in the present invention.

  The motor driving force upper limit value uTm for motor lock countermeasure in step S19 is determined as follows.

That is, since there is a motor driving force limit value for each vehicle speed VSP so that the electric motor 2 is not overheated even when the two-operation motor is locked by the brake operation and the accelerator operation described above,
In this embodiment, in order to determine the motor driving force limit value for each vehicle speed VSP as the motor locking force upper limit value uTm for motor locking measures, for example, based on the map shown in FIG. 4, the motor driving force upper limit value for motor locking measures from the vehicle speed VSP. The value uTm (the vehicle speed VSP in FIG. 4 is an absolute value) is obtained by searching.

Of course, the motor driving force upper limit value uTm for motor lock countermeasures determined in this way is larger as the vehicle speed VSP is higher.
The motor lock countermeasure motor driving force upper limit value uTm preferably increases monotonously as the vehicle speed VSP increases.
Note that the vehicle speed VSP = V1 in FIG. 4 corresponds to a limit vehicle speed at which the electric motor 2 is rotationally locked and overheated, for example, 7 km / h, when the accelerator pedal is depressed so that APO ≧ A1.

<Effect>
According to the motor lock countermeasure control according to FIG. 2 of the present embodiment, the following operational effects can be obtained when described representatively based on the time chart of FIG.

  In Fig. 3, the accelerator opening APO is increased from the instant t1 as shown in the figure, the set opening A1 is made at the instant t2, and after the instant t3, the accelerator operation is performed to maintain a constant value larger than the set opening A1. However, as is apparent from the ON / OFF signal of the brake switch 12, it is a time chart when the vehicle speed VSP changes in time series as shown in the figure by braking by the brake pedal operation at the instant t4 to t7.

  During this time, the required motor driving force vTm used in step S17 and step S19 is obtained as shown in FIG. 3 according to the accelerator opening APO and the vehicle speed VSP, and the motor driving force upper limit value uTm for motor lock countermeasure used in step S19 is According to the vehicle speed VSP, it is required as shown in Fig. 3.

  Since the accelerator opening APO is less than the set opening A1 between the instants t1 and t2 in FIG. 3, the control program in FIG. 2 selects a loop including step S11, step S13, and step S17, and the timer in step S13. TM is set to 0, and the motor required driving force vTm is set to the target motor torque tTm in step S17.

  Therefore, between t1 and t2, as shown in FIG. 3, the required motor driving force vTm is set to the target motor torque tTm, and this target motor torque tTm = vTm is used for driving force control of the electric motor 2. Become.

Between the instants t2 and t4, since the accelerator opening APO is equal to or greater than the set opening A1, step S11 selects step S12, but since it is still in the non-braking state, step S12 sequentially controls step S13 and step S13. Proceed to step S17.
In step S13 (TM = 0) is executed, and in step S17, the motor required driving force vTm is set to the target motor torque tTm.

  Accordingly, as shown in FIG. 3, the motor required driving force vTm is set to the target motor torque tTm between t2 and t4, and this target motor torque tTm = vTm is used for driving force control of the electric motor 2. .

Between the instant t4 and t7, the accelerator opening APO is equal to or greater than the set opening A1, and the brake switch 12 is ON (braking state), that is, the two-operation motor lock condition is established by the accelerator operation and the brake operation. Therefore, step S11 selects step S12, and step S12 advances the control to steps S14 and S15 sequentially.
Note that during braking from the instant t4 to t7, the vehicle speed VSP decreases with the time series change of FIG. 3 due to this braking.

In step S14, the elapsed time from the moment t4 when the two-operation motor lock condition is established by the accelerator operation and the brake operation is measured as shown in FIG.
In step S15, it is checked whether or not the timer TM (elapsed time from the instant t4) indicates the set time TM1, that is, whether or not the instant t5 has been reached.

  If the timer TM (elapsed time from the instant t4) is before the set time TM1 (between the instants t4 and t5), step S15 advances the control to step S17. In step S17, the motor required driving force vTm is set to the target motor torque tTm.

  Therefore, also during the instant t4 to t5, as shown in FIG. 3, the motor required driving force vTm is set to the target motor torque tTm, and this target motor torque tTm = vTm is used for driving force control of the electric motor 2. Become.

As a result of step S15 proceeding to step S18 and step S19 sequentially at the instant t5 when the set time TM1 has elapsed from the instant t4 when the two-operation motor lock condition is established by the accelerator operation and the brake operation,
As shown in FIG. 3, the timer TM is held at the set time TM1 (step S18), and the smaller one of the target motor torque tTm and the motor driving force upper limit value uTm for motor lock countermeasure and the motor required driving force vTm Min (vTm, uTm) Is set (step S19).

  However, between t5 and t6, as shown in FIG. 3, the motor drive force upper limit uTm for motor lock countermeasure is larger than the motor required drive force vTm even if the vehicle speed decreases, so the motor required drive is still driven to the target motor torque tTm. The force vTm is set, and this target motor torque tTm = vTm is used for driving force control of the electric motor 2.

However, after the instant t6 when the motor driving force upper limit value uTm for motor lock countermeasure becomes smaller than the motor required driving force vTm due to further decrease in the vehicle speed VSP,
In step S19, the smaller value Min (vTm, uTm) = uTm of the motor driving force upper limit value uTm for motor lock prevention and the motor required driving force vTm is set to the target motor torque tTm. This target motor torque tTm = uTm This is used for driving force control of the electric motor 2.

When the brake switch 12 is turned OFF at the instant t7 by stopping the braking, step S12 sequentially selects step S13 and step S17.
In step S13, the timer TM is set to 0 as shown in FIG.
In step S17, the motor required driving force vTm is set to the target motor torque tTm, and this target motor torque tTm = vTm is used for driving force control of the electric motor 2.

For this reason, the target motor torque tTm = vTm is supposed to return from the motor driving force upper limit value uTm for motor lock countermeasure to the motor required driving force vTm at a moment at the instant t7.
In this embodiment, the target motor torque tTm is not shown in FIG. 2, but from a motor lock countermeasure motor driving force upper limit uTm at a predetermined time change rate shown in FIG. The motor is gradually returned to the required motor driving force vTm so that no shock is generated.

  When braking is stopped at the instant t7, the vehicle speed VSP increases as shown in FIG. 3 after the instant t7.

According to the motor lock countermeasure control described above with reference to FIGS. 2 and 3, the accelerator opening APO is equal to or greater than the set opening A1, and the brake switch ON state that brakes the vehicle continues for the set time TM1. At t5, it is determined that the two-operation motor lock condition is satisfied (step S11, step S12, step S14, step S15), and from this time t5 when the motor lock condition is satisfied, it is determined that the non-braking state is established in step S12. In order to limit the driving force of the electric motor 2 so that the target motor torque tTm of the electric motor 2 does not exceed the driving force upper limit value uTm for motor lock countermeasures until
The electric current supplied to the electric motor 2 is limited so that it does not exceed the current value corresponding to the driving force upper limit value uTm for motor lock measures, and the electric motor 2 becomes overheated due to the tendency of rotation lock. Can be reliably prevented.

In addition, the driving force upper limit value uTm for motor lock measures is set as a motor driving force limit value that does not cause the electric motor 2 to be overheated even if the motor lock condition is satisfied, and the higher the vehicle speed according to the vehicle speed VSP. Because it was something like that shown in Figs.
As is apparent from the change over time in the target motor torque tTm immediately after the instant t6 when the driving force limitation of the electric motor 2 is started, the driving force of the electric motor 2 is gradually changed as the vehicle speed changes.

  For this reason, the motor driving force does not decrease stepwise at a time when the motor lock is taken, and it is possible to solve the above-mentioned problem of causing the passengers to feel a sudden and large change in the vehicle speed when the motor lock is taken. .

  In addition, at the instant t7 when the driving force limit of the electric motor 2 ends, the target motor torque tTm is gradually increased from the motor driving force upper limit value uTm for motor lock countermeasures to the motor required driving force vTm at a predetermined time change rate by rate limit processing. No shock will occur because it is restored.

  In this embodiment, since the motor driving force upper limit value uTm for motor lock countermeasures is monotonically increased with respect to the increase in the vehicle speed VSP as described above and as shown in FIG. Can be a thing.

Further, in this embodiment, the two-operation motor lock condition is established only when the accelerator opening APO is equal to or larger than the set opening A1 (step S11) and only the brake switch ON state (step S12) that brakes the vehicle is established. In order to determine that the two-operation motor lock condition is satisfied at the instant t5 when it is determined that these two requirements are aligned over the set time TM1 without determining,
Immediately before the electric motor is overheated, it can be determined that the two-operation motor lock condition is satisfied, and the driving force limit of the electric motor 2 for motor lock countermeasure can be minimized.

In addition, when the two-operation motor is locked, overheating protection of the electric motor 2 by the inverter 6 can be considered. However, as described above, the accelerator opening APO is not less than the set opening A1 (step S11) and the vehicle is braked. In order to determine that the two-operation motor lock condition has been satisfied when the brake switch ON state (step S12) is continued for the set time TM1 or longer,
Overheating protection of the electric motor 2 can be performed by the integrated controller of the vehicle at a higher level than the inverter 6 and with a high degree of freedom, and the uncomfortable feeling to the driver can be reduced.

  In addition, in the present embodiment, the set time TM1 is a time corresponding to a limit time in which the electric motor 2 is not overheated under the condition that the two-operation motor lock condition is satisfied as described above. The above-described effects can be made more remarkable.

<Other examples>
In the above-described embodiment, the motor driving force upper limit value uTm for motor lock measures is set to the motor driving force limit value for each vehicle speed VSP so that the electric motor 2 is not overheated even when the two-operation motor is locked. But
The motor driving force upper limit uTm for motor lock countermeasures is not limited to this, and gradually decreases as the vehicle speed VSP decreases from the substantial start of motor driving force limitation at the instant t6 in FIG. Any device may be used as long as it can be used to prevent overheating when the motor is locked.

1L, 1R left and right drive wheels
2 Electric motor
3 Reducer
4 Motor controller
5 Battery
6 Inverter
7 Vehicle speed sensor
8 Accelerator position sensor
9 Current sensor
11 Range sensor
12 Brake switch

Claims (5)

In an electric vehicle that can travel by transmitting the driving force of an electric motor to wheels,
Motor lock condition establishment determination means for determining that the rotation lock condition of the electric motor is established;
Motor driving force limiting means for limiting the driving force of the electric motor so that the driving force of the electric motor does not exceed the upper limit value of the motor driving force when the motor lock condition is determined by the means;
The motor lock countermeasure control device for an electric vehicle, wherein the motor driving force upper limit value is set to a value that increases as the vehicle speed increases. In the motor lock countermeasure control device for the electric vehicle according to claim 1,
The motor lock countermeasure control device for an electric vehicle, wherein the motor driving force upper limit value increases monotonously with an increase in vehicle speed. In the motor lock countermeasure control device for an electric vehicle according to claim 1 or 2,
The motor driving force upper limit value is a motor driving force limit value corresponding to a vehicle speed, which does not cause the electric motor to be overheated even if the motor lock condition is satisfied, and is a motor lock measure for an electric vehicle. Control device. In the motor lock countermeasure control device for an electric vehicle according to any one of claims 1 to 3,
The motor lock condition satisfaction determining means determines that the motor lock condition is satisfied when the required load on the electric motor is equal to or greater than the set load and the vehicle is being braked for a set time. A motor lock countermeasure control apparatus for an electric vehicle. In the motor lock countermeasure control device for the electric vehicle according to claim 4,
The electric vehicle characterized in that the set time is a limit time in which the electric motor does not become overheated when the required load on the electric motor is equal to or greater than the set load and the vehicle is being braked. Motor lock countermeasure control device.

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