JP2005008089A - Vehicle traction control device - Google Patents

Abstract

An object of the present invention is to prevent accidental continuation of traction control even when extremely small-diameter tires with different diameters are mounted on drive wheels.
A required driving torque of a driving wheel is calculated by a required driving torque calculating means, a friction coefficient of a road surface is estimated by a friction coefficient estimating means, and a correction permission determining means is calculated by a required driving torque calculating means. It is determined whether or not the calculated required driving torque is smaller than a torque threshold that changes in accordance with the friction coefficient estimated by the friction coefficient estimating means 6, and when the required driving torque is smaller than the torque threshold, the driving torque control means 3 While the traction control is executed, a signal for permitting correction of the calculated speed difference by the speed difference calculating means 2A, 2B is output.
[Selection] Figure 1

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a traction control device for a vehicle.
[0002]
[Prior art]
When the wheel speed difference obtained by subtracting the wheel speed of the driven wheel from the wheel speed of the driving wheel is greater than or equal to a predetermined value, the wheel speed of the driving wheel is corrected assuming that a different tire diameter such as a temporary tire is mounted on the driving wheel. Such an arrangement is already known (for example, see Patent Document 1).
[0003]
On the other hand, in a state where the wheel speed of the driving wheel greatly exceeds the wheel speed of the driven wheel, traction control is performed so as to reduce the driving torque by operating the wheel brake for the driving wheel because the driving wheel is slipping excessively. This is also well known from the past.
[0004]
[Patent Document 1]
JP-A-8-244593
[Problems to be solved by the invention]
By the way, the traction control is started when the wheel speed difference obtained by subtracting the wheel speed of the driven wheel from the wheel speed of the driving wheel becomes equal to or larger than the first set value, and the wheel speed difference is more than the first set value. In general, the wheel speed correction of the drive wheels is executed in response to a small second set value or more. However, when a different diameter tire having an extremely small diameter is mounted, the wheel speed difference is reduced. There is a possibility that the state where the value becomes equal to or greater than the first set value continues and the traction control continues to be executed by mistake.
[0006]
The present invention has been made in view of such circumstances, and even when an extremely small-diameter tire having a different diameter is mounted on a drive wheel, the traction of the vehicle is prevented from being erroneously continued to be executed. An object is to provide a control device.
[0007]
[Means for Solving the Problems]
To achieve the above object, the present invention provides a speed difference calculating means for calculating a wheel speed difference obtained by subtracting a wheel speed of a driven wheel from a wheel speed of a driving wheel, and a speed difference calculated by the speed difference calculating means is a set value. In a traction control device for a vehicle, comprising a drive torque control means for executing traction control for reducing drive torque during acceleration operation according to the above, driving based on accelerator pedal opening, engine speed, and transmission gear ratio Required drive torque calculating means for calculating the required drive torque of the wheel, friction coefficient estimating means for estimating the friction coefficient of the traveling road surface based on actual drive torque and drive wheel speed during traction control, and the required drive torque calculating means Is the required drive torque calculated in step (b) smaller than a torque threshold that changes according to the friction coefficient estimated by the friction coefficient estimation means? Correction permission determination means for outputting a correction permission signal when the required drive torque is smaller than the torque threshold during execution of traction control by the drive torque control means, and the speed difference calculation means includes the speed difference calculation means, The speed difference calculated by the speed difference calculating means is corrected in accordance with a correction permission signal output from the correction permission determining means.
[0008]
According to such a configuration, the accelerator pedal is preset by setting a torque threshold corresponding to the friction coefficient as a driving torque that does not cause excessive slip of the driving wheel on the road surface of the friction coefficient estimated by the friction coefficient estimating means. In a state where the required torque of the driving wheel calculated based on the opening degree, the engine speed and the transmission gear ratio is smaller than the torque threshold value, even if the speed difference calculated by the speed difference calculating means is greater than or equal to the set value, It is possible to determine that excessive slip has not occurred, and by correcting the calculated speed difference during execution of the traction control according to the correction permission determination means permitting correction of the wheel speed, an extremely small diameter different diameter tire It is possible to prevent the erroneous execution of the traction control by the drive torque control means from being continued even when the is attached to the drive wheel.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below based on one embodiment of the present invention shown in the accompanying drawings.
[0010]
1 to 4 show an embodiment of the present invention, FIG. 1 is a block diagram showing the configuration of a brake control device, FIG. 2 is a diagram showing a relationship between a friction coefficient and a torque threshold, and FIG. 3 is a speed difference. FIG. 4 is a flowchart showing a procedure of correction permission determination processing.
[0011]
First, in FIG. 1, for example, in a brake control device 1 provided in a four-wheeled vehicle having a pair of left and right drive wheels and a pair of left and right driven wheels, a portion for performing traction control calculates a speed difference corresponding to the left and right drive wheels individually. Means 2A, 2B, drive torque control means 3 for executing traction control for reducing the drive torque by operating the wheel brake for drive wheels, required drive torque calculation means 5 for calculating the required drive torque of the drive wheels, and travel Friction coefficient estimating means 6 for estimating the friction coefficient of the road surface, correction permission determining means 7 for determining whether or not correction of the calculated speed difference in the speed difference calculating means 2A and 2B is permitted during execution of the traction control, And averaging means 8 for averaging the left and right driven wheel speeds.
[0012]
The brake control device 1 includes driving wheel speed detectors 9A and 9B for detecting the wheel speeds of the left and right driving wheels, driven wheel speed detectors 10A and 10B for detecting the wheel speeds of the left and right driven wheels, respectively. The detection values of the accelerator pedal opening detector 11, the engine speed detector 12, and the transmission gear ratio detector 13 are input.
[0013]
The driven wheel speeds detected by the driven wheel speeds 10A and 10B are input to the averaging means 8 and averaged, and the speed difference calculating means 2A and 2B are detected by the driving wheel wheel speed detectors 9A and 9B. The driving wheel speed is input, and the driven wheel speed averaged by the averaging means 8 is input. Thus, the speed difference calculating means 2A, 2B respectively execute a calculation for subtracting the driven wheel speed averaged by the averaging means 8 from the driving wheel speed, and the calculation result is parallel to the driving torque control means 3. input.
[0014]
The drive torque control means 3 is the drive in which the calculated speed difference becomes greater than or equal to the set value during the acceleration operation in response to the calculated speed difference becoming greater than or equal to the set value in at least one of the speed difference calculating means 2A and 2B. In order to reduce the driving torque of the wheels, the operation of the brake actuator 14 for driving wheels is controlled, and the operation of the brake actuator 14 for driving wheels depends on the calculated speed difference obtained by the speed difference calculating means 2A and 2B. The corresponding brake fluid pressure is controlled to act on the wheel brake for the drive wheel.
[0015]
The speed difference calculating means 2A and 2B execute correction so that the calculated speed difference becomes small when a permission signal is input from the correction permission determining means 7 during execution of traction control by the drive torque control means 3.
[0016]
The required drive torque calculation means 5 is configured such that the accelerator pedal opening detected by the accelerator pedal opening detector 11, the engine speed detected by the engine speed detector 12, and the speed change detected by the transmission gear ratio detector 13. The required drive torque of the drive wheels is calculated based on the gear ratio, and the required drive torque obtained by the required drive torque calculation means 5 is input to the correction permission determination means 7.
[0017]
The friction coefficient estimating means 6 estimates the friction coefficient of the traveling road surface based on the actual driving torque and driving wheel speed at the time of traction control. In this embodiment, the brake of the wheel brake for driving wheels at the time of traction control is estimated. The coefficient of friction of the road surface is estimated based on the hydraulic pressure and the driving wheel speed. Thus, the control amount of the driving wheel brake actuator 14 corresponding to the brake fluid pressure of the driving wheel wheel brake is input from the driving torque control means 3 to the friction coefficient estimating means 6, and the driving wheel speed is detected as the driving wheel wheel speed detector. The friction coefficient estimating means 6 is input to the friction coefficient estimating means 6 from 9A and 9B. The friction coefficient estimating means 6 enters the traction control, the brake fluid pressure acting on the wheel brake for the drive wheels, and the drive wheel that changes by the action of the brake fluid pressure. The friction coefficient of the road surface is estimated from the relationship with the wheel speed.
[0018]
As shown in FIG. 2, the correction permission judgment means 7 has a torque threshold value corresponding to the friction coefficient as a drive torque that does not cause excessive slip of the drive wheels on the road surface of the friction coefficient estimated by the friction coefficient estimation means 6 as shown in FIG. The correction permission determination means 7 is set, and it is determined whether or not the required drive torque calculated by the required drive torque calculation means 5 is smaller than a torque threshold corresponding to the friction coefficient estimated by the friction coefficient estimation means 6. When the required drive torque is smaller than the torque threshold value, a signal for permitting correction of the calculated speed difference by the speed difference calculating means 2A and 2B is output during execution of the traction control by the drive torque control means 3.
[0019]
Such wheel speed correction of the drive wheel by the brake control device 1 is executed according to the procedure shown in FIG. 3, the vehicle body speed is equal to or higher than a certain value, and the wheel acceleration of the drive wheel is within a certain value, In addition, after confirming that the vehicle is traveling straight in steps S1, S2, and S3, if it is confirmed in step S4 that traction control is not being executed, the speed difference between the driving wheel and the driven wheel is corrected in step S5. When it is confirmed in step S4 that traction control is being executed, it is confirmed in step S6 whether correction is permitted.
[0020]
The correction permission determination in step S6 is executed according to the procedure shown in FIG. 4. In step S12 after confirming that the non-traction control is being performed in step S11, a torque threshold value based on the estimated friction coefficient is searched. When it is confirmed in step S13 that the driving torque of the driving wheel is equal to or lower than the torque threshold, a lapse of a fixed time after the driving torque of the driving wheel becomes equal to or lower than the torque threshold by passing through steps S14 and S15. Is confirmed, the correction during the traction control is permitted in step S16, and the speed difference is corrected in step S5 of FIG. 3 according to the correction permission.
[0021]
Next, the operation of this embodiment will be described. The friction coefficient estimating means 6 estimates the friction coefficient of the traveling road surface based on the brake fluid pressure and the driving wheel speed of the wheel brake for driving wheels at the time of traction control. The correction permission determining means 7 determines whether or not the required driving torque calculated by the required driving torque calculating means 5 is smaller than a torque threshold that changes according to the friction coefficient estimated by the friction coefficient estimating means 6. When the required drive torque is smaller than the torque threshold value, a signal permitting correction of the calculated speed difference in the speed difference correction means 2A, 2B is output during the traction control by the drive torque control means 3.
[0022]
Therefore, by setting in advance the torque threshold value corresponding to the friction coefficient as the driving torque that does not cause excessive slip of the driving wheel on the road surface of the friction coefficient estimated by the friction coefficient estimating means 6, the accelerator pedal is set. In a state where the required torque of the drive wheel calculated by the required drive torque calculation means 5 based on the opening degree, the engine speed and the transmission gear ratio is smaller than the torque threshold, the speed difference calculated by the speed difference calculation means 2A, 2B is It can be determined that an excessive slip of the drive wheels does not occur even if the set value is exceeded. As a result, the correction by the drive torque control means 3 is corrected by correcting the speed difference calculated by the speed difference calculation means 2A, 2B during execution of the traction control in response to the correction permission judgment means 7 permitting correction of the wheel speed. It is possible to prevent the execution of the traction control from continuing.
[0023]
Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various design changes can be made without departing from the present invention described in the claims. It is.
[0024]
For example, in the above embodiment, the traction control for reducing the drive torque is performed by controlling the brake pressure of the drive wheel. The present invention can also be applied to a traction control device that uses both brake pressure control and throttle control of drive wheels.
[0025]
【The invention's effect】
As described above, according to the present invention, it is possible to prevent erroneous traction control from being continuously performed by the drive torque control means even when extremely small diameter tires are mounted on the drive wheels. Can do.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a brake control device.
FIG. 2 is a diagram showing a relationship between a friction coefficient and a torque threshold value.
FIG. 3 is a flowchart showing a procedure for correcting a speed difference.
FIG. 4 is a flowchart illustrating a procedure of correction permission determination processing.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Brake control apparatus 2A, 2B ... Speed difference calculation means 3 ... Drive torque control means 5 ... Request drive torque calculation means 6 ... Friction coefficient estimation means 7 ... Correction permission judgment means

Claims (1)

Speed difference calculating means (2A, 2B) for calculating the wheel speed difference obtained by subtracting the wheel speed of the driven wheel from the wheel speed of the driving wheel, and the speed difference calculated by the speed difference calculating means (2A, 2B) being equal to or greater than a set value In a traction control device for a vehicle comprising drive torque control means (3) for executing traction control for reducing drive torque during acceleration operation according to the above, based on accelerator pedal opening, engine speed, and transmission gear ratio Requested drive torque calculating means (5) for calculating the required drive torque of the drive wheel, friction coefficient estimating means (6) for estimating the friction coefficient of the traveling road surface based on the actual drive torque and the drive wheel speed during traction control, and The required drive torque calculated by the required drive torque calculation means (5) changes according to the friction coefficient estimated by the friction coefficient estimation means (6). Correction permission judging means (7) for determining whether or not the required driving torque is smaller than the torque threshold during execution of traction control by the driving torque control means (3). The speed difference calculating means (2A, 2B) corrects the speed difference calculated by the speed difference calculating means (2A, 2B) according to the correction permission signal output from the correction permission determining means (7). A traction control device for a vehicle.

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