JP4326316B2 - Vehicle traction control device - Google Patents

Description

  The present invention relates to a traction control device for a vehicle, and more particularly to a device for forcibly reducing engine torque in accordance with a slip state of a drive wheel.

Conventionally, Patent Document 1 discloses a traction control device that performs acceleration / declination determination at the time of vehicle start and corrects a lower limit torque according to the determination result to ensure acceleration while suppressing excessive slip. Yes.
Patent Document 2 discloses a configuration for increasing the target engine torque for traction control in order to prevent engine stall when starting uphill.
Japanese Patent Laid-Open No. 07-077080 Japanese Patent Publication No. 2002-513112

  By the way, in the case of the configuration for correcting the target of torque reduction according to the slip state as described above, in order to surely avoid the occurrence of engine stall with respect to various condition changes such as the gradient, a high target engine with a margin is provided. Although the torque needs to be set, in this case, there is a possibility that the slip suppression performance may be lowered, and there is a problem that it is difficult to achieve both the engine stall avoidance performance and the slip suppression performance at a high level.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a vehicle traction control device that can reliably prevent the occurrence of engine stall while avoiding the occurrence of excessive slip even when the gradient condition changes. To do.

Therefore, in the present invention, the speed at which the engine torque is reduced to the engine required torque determined according to the slip state of the drive wheels is set to a speed lower than the limit speed that becomes slower as the uphill slope becomes steep according to the slope of the traveling road surface. The configuration is limited.

According to such a configuration, the speed at which the engine torque is reduced to the required torque of the engine corresponding to the slip state is limited to a speed limit that is slower as the uphill slope becomes steeper according to the slope, so that the slope is gentle and the slope While it is possible to prevent the reduction rate of engine torque from being excessively limited under the condition of low resistance and prevent slip suppression performance from decreasing, when the gradient is steep and the gradient resistance is large, engine stall occurs due to a sudden decrease in engine torque. Can be avoided.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a system configuration diagram of a vehicle engine in the embodiment.
In FIG. 1, air is sucked into the engine 1 through a throttle valve 2, and fuel is injected by a fuel injection valve (not shown), whereby an air-fuel mixture is formed in the combustion chamber.

The air-fuel mixture is ignited and combusted by spark ignition of the spark plug 3, and the piston is reciprocated by combustion and explosion of the air-fuel mixture to obtain a driving force of the vehicle.
The throttle valve 2 is opened and closed by a throttle motor 4, while the opening degree of the throttle valve 2 is detected by a throttle sensor 5.
The throttle motor 4 and the spark plug 3 are controlled by an engine control unit 11 incorporating a microcomputer.

The engine control unit 11 includes a throttle opening signal from the throttle sensor 5, a vehicle speed signal from the vehicle speed sensor 12, an engine rotation signal from the engine rotation sensor 13, a gradient signal from the gradient sensor 14, and a traction control unit. The torque down request value signal from 15 is input.
The gradient sensor 14 may be a sensor that detects the gradient of the road surface as the inclination of the vehicle body, but is not limited to a sensor that directly detects the gradient. For example, the gradient sensor 14 is linked to a navigation system and is based on vehicle position information. A configuration for detecting the gradient, a configuration for receiving gradient information from the outside using a communication means, and a configuration in which the engine control unit 11 calculates the gradient resistance from the driving force of the vehicle, acceleration resistance, etc. All known methods can be adopted as a method for detecting the road surface gradient.

The traction control unit 15 receives wheel speed signals from wheel speed sensors 16a to 16d provided on the wheels.
Then, the front wheel average rotation speed and the rear wheel average rotation speed are calculated based on the wheel speed signal, and the wheel spin of the drive wheel (rear wheel or front wheel) is compared by comparing the front wheel average rotation speed and the rear wheel average rotation speed. Detects the occurrence of

When the wheel spin of the drive wheel is detected, a torque down request torque (target engine torque for reducing the wheel spin amount) is determined according to the wheel spin state (slip state) of the drive wheel, and the engine control unit 11 Output.
In the engine control unit 11 to which the torque down request value signal has been input, the wheel spin amount is reduced by reducing the engine torque to the required torque by the throttle valve 2 being throttled or fuel cut.

Here, the engine control unit 11 limits the torque reduction request torque from the traction control unit 15 and performs engine torque down control. Details of such control are shown in FIG. It demonstrates according to a flowchart.
In the flowchart of FIG. 2, first, in step S1, the gradient of the traveling road surface is detected.

Next, in step S2, based on the gradient detected in step S1, a limit value A (limit speed) of the engine torque decrease change speed by traction control is set.
The limit value A is set as the maximum value of the step change amount of the target engine torque per this routine execution cycle (10 ms).
As shown in FIG. 3, the limit value A (target torque inclination limit) is set to a smaller value as the uphill gradient becomes steeper, and as shown in FIG. A rapid decrease change is allowed, and when the uphill slope is steep, the decrease change of the engine torque is limited to be more gradual.

In step S3, the difference a between the latest torque-down request torque and the final target torque 10 ms before the execution cycle of this routine is calculated.
S3: Target torque before difference a = 10 ms−latest torque request torque In step S4, the limit value A is compared with the difference a. When the difference a is equal to or less than the limit value A, the process proceeds to step S5, where traction The torque reduction request torque from the control unit 15 is set as it is as the target torque in the engine torque control.

On the other hand, when the difference a exceeds the limit value A, that is, when there is a request to reduce the engine torque at a speed exceeding the limit value A according to the gradient at that time, the process proceeds to step S6, 10 ms before The result of subtracting the limit value A from the final target torque is set to the current target torque, so that the target torque is decreased and changed within the range of the limit value A or less.
S6: Target torque = target torque before 10 ms−limit value A
The engine control unit 11 controls throttle of the throttle valve 2, fuel cut, and the like according to the target torque.

  As described above, the engine torque decrease change rate by traction control is limited according to the uphill slope, and when the slope resistance is large due to a steep uphill slope, the engine torque decrease change speed is forcibly made gentle. With this configuration, it is possible to avoid a sudden torque reduction on a steep slope and a sudden decrease in engine stall or rotation speed (see FIG. 5).

On the other hand, on flat roads and gentle uphill slopes, resistance to torque down control is high, and therefore, a rapid decrease in wheel spin can be achieved by allowing a rapid torque down.
The flowchart of FIG. 6 shows a second embodiment of the torque down request torque restriction control. In the second embodiment, the torque down speed is restricted according to the uphill slope and the engine torque is restricted according to the slope. It is configured to limit to more than the value.

In the flowchart of FIG. 6, the processing of step S11 to step S13 is performed in the same manner as step S1 to step S3 of the flowchart of FIG.
In step S14, the torque lower limit B is set based on the gradient detected in step S11 and the engine speed.
As shown in FIG. 7, the torque lower limit value B is set higher as the uphill slope is steeper and higher as the engine speed is lower.

This is because the steeper slope and the lower the engine speed, the lower the resistance to torque-down control, and the higher the possibility of engine stall and sudden rotation drop.
In step S15, the limit value A is compared with the difference a. When the difference a is equal to or less than the limit value A, the process proceeds to step S16.

In step S16, the larger one of the torque down request torque from the traction control unit 15 and the lower limit B is selected, and the selected value is set as the target torque.
On the other hand, when the difference a exceeds the limit value A, the process proceeds to step S17.
In step S17, the larger of the target torque-limit value A 10 ms before and the lower limit B is selected, and the selected value is set as the target torque.

That is, the speed of torque reduction is limited to the limit value A or less, and the target torque is limited to the lower limit value B or more (see FIG. 8).
According to the above configuration, the speed of torque reduction is limited. Therefore, even if the lower limit value B is set to a relatively low value, occurrence of engine stall or sudden rotation drop can be avoided.
Accordingly, the slip suppression performance can be maintained high compared to the case where only the lower limit value B avoids the occurrence of engine stall and sudden rotation drop.

1 is a system configuration diagram of a vehicle engine in an embodiment. The flowchart which shows 1st Embodiment of torque down control. The diagram which shows the correlation with an uphill slope and the limit value of torque down speed. The time chart which shows the change of the engine torque restrict | limited according to an uphill slope. 3 is a time chart showing changes in accelerator opening, engine torque, engine speed, and vehicle speed in the first embodiment. The flowchart which shows 2nd Embodiment of torque down control. The diagram which shows the correlation with a gradient, an engine speed, and a torque lower limit. The time chart which shows the change of the accelerator opening degree, engine torque, engine speed, and vehicle speed in 2nd Embodiment.

Explanation of symbols

    DESCRIPTION OF SYMBOLS 1 ... Engine, 2 ... Throttle valve, 3 ... Spark plug, 4 ... Throttle motor, 5 ... Throttle sensor, 11 ... Engine control unit, 12 ... Vehicle speed sensor, 13 ... Engine rotation sensor, 14 ... Gradient sensor, 15 ... Traction control Unit, 16a to 16d ... Wheel speed sensor

Claims (5)

In a vehicle traction control device that detects a slip state of a drive wheel and determines a required torque of an engine according to the slip state,
A vehicle traction control characterized by detecting a gradient of a traveling road surface and limiting a speed at which the engine torque is reduced to the required torque to a speed lower than a limit speed that becomes slower as the slope is steep according to the slope. apparatus. The traction control device for a vehicle according to claim 1, wherein a speed at which the engine torque is reduced is limited according to the gradient, and the engine torque is limited to a limit value or more according to the gradient. The traction control device for a vehicle according to claim 2, wherein the limit value is set based on the gradient and the engine speed. 4. The vehicle traction control device according to claim 3, wherein the limit value is set higher as the engine speed is lower. The traction control device for a vehicle according to any one of claims 2 to 4, wherein the limit value is set higher as the climbing slope becomes steeper.

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