JPH07336807A - Drive control apparatus for electric car - Google Patents

Abstract

PURPOSE:To obtain a drive control apparatus in which a gentle reverse is realized when a torque is released from a stall state in the case of using a synchronous motor as a drive motor. CONSTITUTION:A torque instruction T*q is computed on the basis of an accelerator opening Acc (100), a stall is detected on the basis of the torque instruction T*q and a vehicle velocity (v) (102, 104), and the torque instruction T*q is reduced when the stall is detected (114). Since the reduction amount of the torque instruction T*q is set according to the deviation of the (v) with reference to a set vehicle velocity (v*), the speed of the reverse of a vehicle due to a reduction in the torque instruction T*q can be limited. Since the reduction in the torque instruction T*q is started by the passage of the stall permissible time TMO which is set according to the torque instruction Tq, the frequency of a torque reduction control operation can be suppressed. Since it is not required to detect the temperature, it is not required to install a temperature sensor so as to correspond to every power element.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive control device for an electric vehicle which is mounted on a vehicle equipped with a synchronous motor as a drive motor and which controls the drive of the drive motor.

[0002]

2. Description of the Related Art FIG. 3 shows an example of the structure of an electric vehicle. In this configuration, a three-phase AC motor is used as the traveling motor 10, and its driving power is supplied from the battery 14 via the inverter 12. That is, the discharge power of the battery 14 is converted into three-phase AC power by the inverter 12 and supplied to the traveling motor 10 as drive power. The inverter 12 includes a pair of power switching elements corresponding to each phase coil of the traveling motor 10, and performs the above-described power conversion by switching these switching elements. U in the figure
The switching elements corresponding to the phase coil are represented by U ⁺ and U ⁻ , the switching elements corresponding to the V phase coil are represented by V ⁺ and V ⁻ , and the switching elements corresponding to the W phase coil are represented by W ⁺ and W ⁻ , respectively. ing.

The output of the traveling motor 10 is controlled by the controller 16. That is, the control unit 16 includes the motor opening 1 which indicates the required output and the motor 1 which is detected by the rotation sensor attached to the traveling motor 10.
The rotation speed N of 0 is input, and the control unit 16 generates a torque command based on these. The torque command is the traveling motor 10
Output torque required by the control unit 16 to generate a PWM (pulse width modulation) signal based on the output torque.
2 is supplied to each switching element. As a result, alternating three-phase AC currents flow through the coils of the respective phases of the traveling motor 10, and the traveling motor 10 is provided with an output torque having a value according to the accelerator opening Acc and the like.

As the traveling motor 10, for example, a permanent magnet type synchronous motor can be used. Since the permanent magnet type synchronous motor has a large field magnetomotive force per unit volume, it is suitable for making the traveling motor 10 small and large in capacity. However, it should be noted that in a synchronous motor such as a permanent magnet type synchronous motor, heat is generated in a stopped state.
That is, unlike a motor such as an induction motor that does not stop unless an alternating magnetic field corresponding to the slip frequency is generated,
In a synchronous motor, current is concentrated in the switching element and coil related to any one phase in the stopped state,
Fever occurs.

For example, switching elements U ⁺ , V ⁻ and W
It is assumed that the traveling motor 10 is stopped in the state where ⁻ is on and U ⁻ , V ^+, and W ⁺ are off. In this case, since no slippage occurs in the permanent magnet type synchronous motor, as shown in FIG. 4, the current flowing through the switching element in the inverter 12 and each phase coil of the traveling motor 10 is DC. Further, among them, the current (I) flowing through the switching element U ⁺ and the U-phase coil is twice the current (I / 2) flowing through the switching elements V ⁻ and W ⁻ and the V-phase and W-phase coils. Therefore, the switching element U ⁺ and the U-phase coil generate heat more remarkably than other switching elements and coils. Thus, in the stopped state, local heat is generated in the inverter 12 and the traveling motor 10. Local heat generation due to such a stop may occur particularly when a stall occurs, that is, when the vehicle stops due to a large slope in an uphill condition.

In order to prevent such a problem, each switching element of the inverter 12 and the traveling motor 10
The temperature of each phase coil may be detected, and the torque command may be reduced when the temperature becomes equal to or higher than a predetermined value.
6599). That is, by reducing the torque command value, the value of the current flowing through the motor is reduced to suppress the heat generation of the motor coil.

[0007]

However, in the case where a motor torque is applied to an uphill road such that the vehicle does not move backward due to the driver's adjustment of the accelerator,
If you simply remove the torque to protect the motor with the above method,
There was a risk that the vehicle would suddenly move backwards, deteriorating the driver's feeling. This will not hinder safe operation, but will cause the driver's anxiety.

The present invention has been made to solve the above problems, and it is necessary to limit the reverse speed when performing the torque command value reduction control and to estimate the occurrence of local heat generation. Accordingly, it is an object of the present invention to provide an electric vehicle that can prevent local heat generation without providing a large number of temperature sensors, and that can steer a vehicle more securely without a sudden retreat of the vehicle.

[0009]

In order to achieve such an object, the present invention provides a drive control device for an electric vehicle which is mounted on a vehicle equipped with a synchronous motor as a traveling motor and which drives and controls the traveling motor. , Means for detecting a stall condition in which the traveling motor is almost stopped despite the torque being applied, and when the above condition is detected, the backward speed or acceleration of the vehicle becomes equal to or lower than a predetermined speed. And means for reducing and controlling the torque of the traveling motor.

The present invention further provides means for setting an allowable time for continuation of the above state based on the torque applied to the traveling motor, and a case where the above state continues beyond the set allowable time. And means for executing the above-mentioned reduction control.

[0011]

In the present invention, the stall state is detected. When the stall state is detected, the torque of the traveling motor is reduced and controlled accordingly. Therefore, in the present invention, when the stall condition occurs on the uphill road, the vehicle is retreated by the torque reduction control. But,
This setback is not a sudden one. That is, since the torque reduction control is performed so that the reverse speed or acceleration of the vehicle becomes equal to or lower than the predetermined speed, the reverse speed and acceleration are limited, and the driver does not feel anxious. Further, when the torque reduction control is performed, the electric current begins to alternate in the traveling motor configured as the synchronous motor, so that one-phase concentration of the electric current is prevented. Therefore, even if a stalled state occurs, no significant local heat is generated in the electric motor for traveling and other electric circuits. Also, the stall condition is
Since the speed is almost zero even though the torque is applied to the traveling motor, it can be detected regardless of the temperature. Therefore, in the present invention, local heat generation is prevented without providing a temperature sensor.

Further, according to the present invention, the torque reduction control is executed only when the stall state continues for a time longer than the permissible time. In addition, since this allowable time is set based on the torque applied to the traveling motor, it is estimated by the value of the torque current flowing in the traveling motor or the like, that is, the degree of local heat generation that is likely to occur. However, the torque reduction control is started. Therefore, if the time during which the stall state continues is short enough that local heat generation does not cause a problem, the torque reduction control is executed and the vehicle does not move backward.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to the drawings. Since the present invention can be carried out under the device configuration shown in FIG. 3, the device configuration shown in FIG. 3 is assumed in the following embodiments. However, the present invention does not need to limit the details of the apparatus configuration of FIG.

FIG. 1 shows a flow of operation of the control unit 16 in one embodiment of the present invention. The operation flow shown in this figure includes the control operation at the time of stall occurrence according to the feature of the present invention.

In the operation of this figure, first, the control unit 1
Reference numeral 6 denotes the accelerator opening Acc and the rotation sensor 1 that are input.
A torque command is calculated based on the rotation speed N of the traveling motor 10 detected by 8 (100). This torque command is a torque command calculated based on the accelerator opening Acc, and may not be actually output as the torque command T ^* _q , so it will be referred to as T ^* _qa below. Step 100
In, the torque command T ^* _qa calculated based on the accelerator opening Acc is substituted into the torque command T ^* _q .

Next, the control unit 16 performs stall detection (102, 104). Here, the stall state is a state in which the vehicle is not traveling even though torque is applied to the traveling motor 10. Therefore, the stall state can be detected by detecting that the torque command T ^* _q is larger than a certain level and the vehicle speed is almost zero. Therefore, the control unit 16 controls the torque command T
A determination (102) is made as to whether ^* _q is greater than the allowable static torque value T _M0 and a determination (104) is made as to whether the vehicle speed v is substantially zero. Here, the allowable static torque value T _M0 is the allowable current I when the traveling motor 10 is stationary.
Corresponds to _M0 . Permissible current I _M0, the permissible even if the traveling motor 10 is stationary current I _M0
The value is set so that special control corresponding to the stall does not need to be performed unless a current exceeding 10 flows. Further, the vehicle speed v is calculated based on the rotation speed N of the traveling motor 10 detected by the rotation sensor 18. Control unit 1
6 executes the control corresponding to the stall only when the torque command T ^* _q is larger than the static torque allowable value T _M0 and the vehicle speed v is almost 0, and is calculated in step 100 otherwise. The torque of the traveling motor 10 is controlled based on the torque command T ^* _qa (106).

When the stall state is detected in steps 102 and 104, the control section 16 first executes step 108. In step 108, the stall allowable time T ₀ is calculated based on the torque command T ^* _q , that is, the torque command T ^* _qa calculated based on the accelerator opening Acc. The relation T ₀ = f (T
^* _Q ) has a relationship as shown in FIG. 2, for example. That is, as the torque command T ^* _q increases, the allowable time T
₀ is set short. This is because the stall state cannot be allowed for a long time when the torque command T ^* _q is large and a large amount of current is flowing through the traveling motor 10. The control unit 16 counts the passage of time by the built-in timer (110) and determines whether the counted time t exceeds the set stall allowable time T ₀ (112). When the time t does not exceed the stall allowable time T ₀ , the transition to the torque reduction control described below is temporarily suspended and the torque control of the traveling motor 10 based on the torque command T ^* _q is executed (106). .

When it is determined in step 112 that the time t exceeds the stall allowable time T ₀ , the control unit 1
6, T ^* _qa- k (v ^* -v) is used as the torque command T ^* _q
(114). Here, v ^* is a control target of the vehicle speed v, and k is a constant. Step 116 to be described later
When the torque control based on the torque command T ^* _q is performed via 120, the output torque of the traveling motor 10 is k (v
^* -V) Since the current is reduced by a considerable amount, the current flowing through each phase coil of the traveling motor 10 and each switching element of the inverter 12 starts to alternate, and the current does not concentrate in one phase. This prevents local heat generation of the traveling motor 10 and the inverter 12 due to the stall. Further, the reduction amount of the torque command at that time is determined by the error of the actual reverse vehicle speed v with respect to the set vehicle speed v ^* . Therefore, the backward movement of the vehicle caused by the reduction of the torque command T ^* _q in step 114, and consequently the reduction of the output torque of the traveling motor 10, does not become abrupt. That is, since the reverse speed v is controlled and limited to the set vehicle speed v ^* , the vehicle operator does not feel anxiety due to a sudden reverse.

Step 116 executed after execution of step 114 is a judgment as to whether or not the torque command T ^* _q is less than zero. This step is executed to prevent reverse running of the traveling motor 10. That is, when the torque command T ^* _q has a negative value as a result of the reduction of the torque command T ^* _q in step 114, if this torque command T ^* _q is directly used for the motor torque control in step 106, The motor 10 runs in reverse rotation. In order to prevent such a situation, it is determined in step 116 whether or not the torque command T ^* _q is negative, and if it is negative, 0 is set in the torque command T ^* _q in the following step 118. Then, step 106 is executed.

In step 116, the torque command T ^* _q
When it is determined that is not negative, it is determined in step 120 whether the vehicle speed v is substantially zero. That is, it is determined whether or not the vehicle speed v is substantially 0, and whether or not the vehicle is flat is determined. When it is determined that the vehicle is flat, the process proceeds to step 118 and 0 is set to the torque command T ^* _q . In other cases, the process proceeds to step 106, and control based on the torque command T ^* _q set in step 114 is executed.

As described above, according to this embodiment, since the stall state is detected and the torque reduction control of the traveling motor 10 is performed, a permanent magnet type synchronous motor is used as the traveling motor 10. Regardless, the traveling motor 10 and the inverter 12 are not provided with many temperature sensors.
It is possible to prevent local heat generation. Further, in the torque reduction control, the torque command reduction amount is determined based on the error of the vehicle speed v with respect to the set vehicle speed v ^* . Therefore, when the vehicle moves backward as the output torque of the traveling motor 10 is reduced, the backward movement is performed. Since the speed v is limited by the set vehicle speed v ^* , the vehicle operator is not anxious. In addition, the stall allowable time T ₀ is set according to the value of the torque command T ^* _q , and the torque reduction control is executed after the set stall allowable time elapses, so the frequency of executing the torque reduction control is suppressed. can do.

Although the torque reduction control is executed with reference to the stall time T ₀ in the above description, the temperature of the motor 10 or the inverter 12 may be referred to. It is also possible to perform control so as to change at an extremely slow change rate (acceleration) at the initial stage of this control, that is, from the vehicle speed of 0 to v ^* . Further, not only the constant speed control as in the present embodiment, but the torque may be reduced so as to be equal to or less than a predetermined acceleration (nearly zero).

[0023]

As described above, according to the present invention,
Since the stall condition is detected and the torque of the traveling motor is controlled to be reduced so that the reverse speed or acceleration of the vehicle is equal to or lower than the predetermined speed, the reverse movement of the vehicle due to the torque reduction control does not become abrupt. The driver no longer feels anxious. Further, it is possible to prevent remarkable local heat generation from occurring in the traveling motor and other electric power circuits without providing a temperature sensor.

According to the present invention, further, the permissible time is set based on the torque applied to the traveling motor, and the torque reduction control is executed only when the stall state continues beyond the permissible time. Therefore, it is possible to prevent the vehicle from moving backward due to the torque reduction control executed for a short time in which local heat generation does not pose a problem.

[Brief description of drawings]

FIG. 1 is a flowchart showing a flow of control operation in an embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between a torque command and a stall allowable time in this embodiment.

FIG. 3 is a diagram showing an example device configuration of an electric vehicle.

FIG. 4 is a circuit diagram showing a motor current state in a stopped state.

[Explanation of symbols]

10 running motor 12 inverter 14 battery 16 control unit 18 rotates the sensor ^{U +, U -, V +} , V -, W +, W - is computed based on the switching element Acc accelerator opening N rpm T ^* _qa accelerator opening Torque command T ^* _q Torque command used for control T _M0 Allowable static torque v Vehicle speed T ₀ Allowable stall time v ^* Set vehicle speed

Claims (2)

[Claims] 1. A drive control device for an electric vehicle, which is mounted on a vehicle equipped with a synchronous motor as a running motor and which controls the driving of the running motor, wherein the running motor is substantially stopped even though torque is applied. And a means for reducing the torque of the traveling motor so that the reverse speed or acceleration of the vehicle becomes equal to or lower than a predetermined speed when the above condition is detected. And a drive control device for an electric vehicle. 2. The drive control device for an electric vehicle according to claim 1, further comprising means for setting an allowable time for continuation of the state based on a torque applied to the traveling motor, and exceeding the set allowable time. A drive control device for an electric vehicle, comprising: means for executing the reduction control only when the above state continues.