JP3686626B2 - Control device for electric motor for vehicle - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a control device for a vehicle motor having an electric motor as a prime mover for driving a drive wheel of the vehicle.
[0002]
[Prior art]
Vehicles that use an electric motor as a prime mover include electric vehicles that use only the electric motor as a prime mover, and hybrid vehicles that have an internal combustion engine in addition to the electric motor. In a four-wheel drive hybrid vehicle, the front wheels are driven by the internal combustion engine, and the rear wheels Is driven by an electric motor. In a vehicle equipped with an electric motor, that is, an electric motor, such as an electric vehicle or a hybrid vehicle, a differential device, that is, a differential device, is used between the electric motor and the left and right drive wheels to absorb the rotational difference between the left and right drive wheels during turning. And the output of the electric motor is transmitted to the left and right drive wheels via a differential device.
[0003]
On the other hand, in a hybrid vehicle, for example, as disclosed in Japanese Patent Application Laid-Open No. 5-131858, an electric motor is controlled using a torque corresponding to a deviation between an engine output torque and a target torque as a control torque, or As disclosed in Japanese Patent Laid-Open No. 11-318001, the driving force of the front and rear wheels is distributed by controlling the power generation of the alternator according to the rotation difference between the front and rear wheels.
[0004]
When a four-wheel drive hybrid vehicle runs on a low-μ road such as a frozen road surface or a snowy road, if the output of the motor for driving the rear wheels becomes excessive, either the left or right of the rear wheels will idle, and the driving force May be transmitted to the idle wheel, and the driving force of the other wheel may become almost zero. For this reason, problems arise in terms of running performance and running performance as a four-wheel drive vehicle and durability of the differential. That is, firstly, the driving force of the rear wheels is lost, so the running performance deteriorates. Second, when the gripping force of the idling wheel is restored, such as when returning from a low μ road to the normal road surface, the vehicle behavior is It is assumed that it becomes unstable, and thirdly, the differential device burns.
[0005]
In order to solve such problems, conventionally, a rotational speed sensitive differential limiting device having a viscous coupling, a preload differential limiting device having a wet multi-plate clutch, and the like are used. When such a differential limiting device is not used, a technique for calculating the rotational change rate of the differential case and limiting the output of the electric motor is disclosed in, for example, Japanese Patent Laid-Open No. 10-75506.
[0006]
[Problems to be solved by the invention]
When the output of the motor is transmitted to the drive wheels via the differential device, especially in the case of a four-wheel drive vehicle, the driving force of the front and rear wheels is optimized to ensure the vehicle's running performance or traveling performance. In order to improve the durability of the moving device, it is necessary to mount the differential limiting device as described above on the vehicle. However, if the differential limiting device is mounted, there is a problem that the manufacturing cost of the vehicle increases.
[0007]
An object of the present invention is to improve the running performance of a vehicle without using a differential limiting device.
[0008]
Another object of the present invention is to improve the running performance of a hybrid vehicle in which rear wheels are driven by an electric motor.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, a first aspect of the present invention is a control device for a vehicle motor having a motor and a differential device that differentially distributes the output of the motor to left and right drive wheels. A wheel speed sensor for detecting the respective rotation speeds, an accelerator opening sensor for detecting the depression amount of an accelerator pedal operated by a driver, and the accelerator opening when the difference between the rotation speeds of the left and right drive wheels is equal to or less than a specified value Control means for controlling the electric motor based on a driving force value calculated from a signal from a sensor, and energizing the electric motor in a reverse direction when the difference in the rotation speed is equal to or greater than a predetermined value. .
[0010]
The invention according to claim 2 is a control device for a motor for a vehicle having a motor and a differential device that differentially distributes the output of the motor to the left and right drive wheels, and detects the rotational speeds of the left and right drive wheels, respectively. A speed sensor, an accelerator opening sensor that detects the amount of depression of the accelerator pedal operated by the driver, and a signal from the accelerator opening sensor when the difference between the rotation speeds of the left and right drive wheels is equal to or less than a first specified value. The motor is controlled on the basis of the driving force value calculated by the formula (1), while the difference between the rotation speeds of the left and right drive wheels is between the first specified value and a second specified value that is larger than the first specified value. Control means for stopping energization of the electric motor when in the middle, and energizing the electric motor in the reverse direction when the difference in rotational speed between the left and right drive wheels is greater than the second specified value. .
[0012]
In the control device for a motor for a vehicle according to the present invention, it is driven by a signal from a wheel speed sensor without using a differential limiting device as a differential device for transmitting the output of the motor to the left and right drive wheels. Since the output of the electric motor can be limited when the wheel is idling, it is possible to prevent an overload from being applied to the differential device. Thereby, the lubrication of the differential device can be simplified and the durability can be improved. Since it is possible to immediately detect that the idling of the driving wheel has been eliminated by the wheel speed sensor, it is possible to quickly return to the normal control state when the idling is eliminated.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic perspective view showing a drive system of a hybrid vehicle, and FIG. 2 is a skeleton diagram showing the rear wheel drive device shown in FIG.
[0014]
The hybrid vehicle shown in FIG. 1 is a four-wheel drive vehicle that drives left and right front wheels 11a and 11b and left and right rear wheels 12a and 12b. The vehicle includes an internal combustion engine 13 that drives front wheels 11a and 11b, and a rear wheel. An electric motor for driving 12a and 12b, that is, an electric motor 14 is provided. The power of the internal combustion engine 13 is transmitted to the left and right front wheels via a transmission 15 having a transmission and a differential. On the other hand, the power of the electric motor 14 is transmitted to the left and right rear wheels via the differential 16.
[0015]
As shown in FIG. 2, the differential gear 16 for the rear differential, that is, the rear wheel has a differential case 18 provided with a final reduction gear 17 and is connected to the rear wheel via a drive shaft 19a. A side gear 22a fixed to the axle shaft 21a connected to 12a and a side gear 22b fixed to the axle shaft 21b connected to the rear wheel 12b via the drive shaft 19b are rotatably incorporated, and these side gears 22a. , 22b face each other. A pinion shaft 23 is attached to the differential case 18 in a direction perpendicular to the axle shafts 21a and 21b. The pinion shaft 23 opposes the pinion gears 23a and 22b, and meshes with the side gears 22a and 22b. 24b is rotatably mounted.
[0016]
The differential device 16 is a normal differential device that does not include a differential limiting device, and is incorporated in a gear case 25 that is attached to the vehicle body. An electric motor 14 is installed in a motor case 26 that is attached to the gear case 25. Is incorporated. The final reduction small gear 27 fixed to the main shaft of the electric motor 14 meshes with the final reduction large gear 17, and the power of the electric motor 14 is transmitted to the left and right rear wheels 12 a and 12 b via the differential device 16. When the vehicle turns, the differential device 16 absorbs the rotational difference between the rear wheels 12a and 12b as the left and right drive wheels. In FIG. 2, the electric motor 14 is arranged at right angles to the axle shafts 21a and 21b. However, the electric motor 14 may be arranged parallel to the axle shafts 21a and 21b. The differential device 16 and the electric motor 14 may be incorporated in one case.
[0017]
FIG. 3 is a block diagram showing a control circuit of the electric motor, and a detection signal from an accelerator opening sensor 32 for detecting the depression amount of an accelerator pedal operated by a driver is sent to an electronic control unit (ETC) 31. At the same time, signals corresponding to the rotational speeds of the left and right rear wheels are sent from the first and second wheel speed sensors 33a and 33b. A control signal is sent from the electronic control unit 31 to a motor control unit 34 having an inverter circuit, and the operation of the electric motor 14 is controlled by a signal from the motor control unit 34. As each wheel speed sensor 33a and 33b, the sensor used for ABS (anti-lock brake system) can be used. Therefore, in an ABS-equipped vehicle, a signal from an ABS wheel speed sensor can be shared for controlling the electric motor.
[0018]
The electronic control unit 31 includes a microprocessor (CPU) that calculates a control signal sent to the motor control unit 34 based on a detection signal from the accelerator opening sensor 32 and the like, a control program, an arithmetic expression, map data, and the like. A memory (ROM) to be stored and a memory (RAM) to temporarily store data are included. The read-only memory (ROM) stores map data and tables indicating the relationship between the accelerator opening and the required torque, and the accelerator opening sensor 32 detects the amount of depression of the driver's accelerator pedal. Accordingly, the driver's required torque can be calculated. When the required torque is calculated, the driving force (Fr) of the electric motor 14 can be calculated based on the value of the required torque. FIG. 4A is a characteristic diagram showing an example of the relationship between the accelerator opening and the required torque.
[0019]
On the other hand, the rotation difference between the left and right rear wheels 12a and 12b can be calculated from signals from the respective wheel speed sensors 33a and 33b. When the vehicle turns, not only the left and right front wheels but also the left and right rear wheels generate a difference in rotation, but the differential device 16 absorbs the difference in rotation and ensures smooth running. On the other hand, when the vehicle is traveling on a low μ road such as a snowy road or a frozen road surface, one of the rear wheels may be idled. Compared to this, the rotation difference is large. Therefore, when a large rotational difference occurs, the electric power supplied to the electric motor 14 is limited to limit the motor output.
[0020]
FIG. 4B is a characteristic diagram showing a motor output restriction example when one of the left and right rear wheels idles and the rotational difference becomes a specified value or more. This characteristic diagram shows that the electric power to the electric motor 14 is stopped when the rotation difference becomes larger than the specified value A, and the reverse rotation direction with respect to the electric motor 14 when the rotation difference exceeds the specified value B larger than the specified value A. The control characteristics are shown in which the power in the reverse direction is increased in accordance with the rotation difference.
[0021]
In the vehicle having the control device shown in FIG. 2, a simple differential device 16 can be used without using a differential limiting device, and a signal is sent from a wheel speed sensor used for ABS. Since they can be shared, differential limiting of the differential device 16 can be performed at low cost without adding equipment. In addition, when a differential limiting device is used as the differential device 16, the idling cannot be suppressed unless the rotational difference is increased to some extent. The idling of the wheel can be quickly stopped by the signal, and the rotation difference for suppressing idling can be set to an arbitrary value.
[0022]
FIG. 5 is a flowchart showing an example of a motor control routine, and this routine is executed at a predetermined cycle. First, in step S1, a signal from the accelerator opening sensor 32 is read, and the driver's required torque is calculated from the depression amount of the accelerator pedal operated by the driver. Based on this calculation result, the driving force Fr of the rear wheels is calculated in step S2. On the other hand, the rotational speeds of the left and right rear wheels 12a and 12b are obtained from the signals sent from the wheel speed sensors 33a and 33b, and the rotational difference between both rear wheels is calculated in step S3 based on the respective rotational speeds. In step S4, it is determined whether or not the rotation difference is larger than a specified value. If it is determined that the difference has not reached the specified value, step S5 is executed and the electric motor 14 is calculated in step S2. The electric motor 14 is controlled using the motor output Fmot corresponding to the rear wheel driving force Fr as an output value.
[0023]
On the other hand, when it is determined in step S4 that the rotation difference is larger than the specified value, in step S6, the limit value Fstop corresponding to the rotation difference between the left and right rear wheels is set. If the rotation difference is between the first specified value A and the second specified value B larger than the first specified value A in FIG. Fstop = 0 is set so as to stop, and if the rotation difference is larger than the second specified value B, Fstop <0 is set so that the electric motor 14 is energized in the reverse direction. The energization amount in the reverse direction is set to be larger as the rotation difference is larger. In step S7, the electric motor 14 is controlled using the set limit value as an output value. When the rotation difference becomes equal to or less than the first specified value A and the idling is eliminated, the normal control is immediately resumed. As shown in step S6, the energization is stopped or the energization in the reverse direction is performed according to the rotation difference, so that feedback control according to the rotation difference is achieved in the control method shown in FIG.
[0025]
In the control method shown in FIG. 5 described above, even if the normal differential device 16 is used without using the differential limiting device, idling is prevented according to the rotational difference between the left and right drive wheels. The durability of the differential device can be improved without overloading the differential device.
[0026]
The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the invention. For example, the vehicle shown in FIG. 1 is a hybrid vehicle in which the front wheels are driven by the internal combustion engine 13 and the rear wheels are driven by the electric motor 14, but a hybrid vehicle or an internal combustion engine in which the front wheels are driven by the electric motor 14 is used. The present invention can also be applied to a vehicle in which the front wheels, rear wheels, and front and rear wheels are driven by the electric motor 14 without having them.
[0027]
【The invention's effect】
According to the present invention, when the idling of the drive wheel is detected by the wheel speed sensor, the output of the electric motor is limited, so that an overload can be prevented from being applied to the differential device, and the lubrication of the differential device is simplified. And durability can be improved. It is not necessary to use a differential limiting device as a differential device for transmitting the output of the electric motor to the left and right drive wheels, and a vehicle having an electric motor can be manufactured at low cost.
[0028]
Since it is possible to immediately detect that the idling of the driving wheel has been eliminated by the wheel speed sensor based on the signal from the wheel speed sensor, it is possible to quickly return to the normal control state when the idling is eliminated. As the wheel speed sensor, the ABS wheel speed sensor can be shared.
[Brief description of the drawings]
FIG. 1 is a schematic perspective view showing a drive system of a hybrid vehicle.
2 is a skeleton diagram showing the rear wheel drive device shown in FIG. 1; FIG.
FIG. 3 is a block diagram showing a control circuit of the electric motor.
FIG. 4A is a characteristic diagram showing an example of the relationship between the accelerator opening and the required torque, and FIG. 4B is a diagram in which one of the left and right rear wheels slips and the rotational difference becomes a specified value or more. It is a characteristic diagram which shows the example of a restriction | limiting of the motor output at the time.
FIG. 5 is a flowchart showing an example of a control routine for an electric motor.
[Explanation of symbols]
11a, 11b Front wheels 12a, 12b Rear wheels 13 Internal combustion engine 14 Electric motor 16 Differential device 31 Electronic control unit 32 Accelerator opening sensors 33a, 33b Wheel speed sensors

Claims (2)

A control device for a motor for a vehicle having a motor and a differential device that differentially distributes the output of the motor to left and right drive wheels,
A wheel speed sensor for detecting the rotational speeds of the left and right drive wheels respectively;
An accelerator opening sensor for detecting the amount of depression of the accelerator pedal operated by the driver;
When the difference between the rotation speeds of the left and right drive wheels is less than a specified value, the motor is controlled based on the driving force value calculated from the signal from the accelerator opening sensor, while the difference in rotation speed is greater than or equal to the specified value. And a control means for energizing the electric motor in the reverse direction . A control device for a motor for a vehicle having a motor and a differential device that differentially distributes the output of the motor to left and right drive wheels,
  A wheel speed sensor for detecting the rotational speeds of the left and right drive wheels respectively;
  An accelerator opening sensor that detects the amount of depression of the accelerator pedal operated by the driver;
When the difference between the rotation speeds of the left and right drive wheels is equal to or less than a first specified value, the motor is controlled based on a drive force value calculated by a signal from the accelerator opening sensor, while the rotation speeds of the left and right drive wheels When the difference between the first specified value and the second specified value larger than the first specified value is within the range, the energization to the motor is stopped, and the difference between the rotational speeds of the left and right drive wheels is And a control means for energizing the electric motor in the reverse direction when it is larger than the second specified value.

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