JPH074283A - Traction control method - Google Patents

Abstract

PURPOSE:To perform traction control to the maximum possible even on a road surface on which a relatively large rotation resistance is applied on a non-drive wheel such as an uphill slope, a deep snow road, or a muddy road, and enable a vehicle to run on such a road surface as a driver desires. CONSTITUTION:As parameters for determining an engine speed reduction instruction value to a slip ratio, a parameter (1) at the normal time, and a small engine speed reduction parameter (2) are set. When a vehicle runs from a flat road to an uphill slope, with wheel speed of front wheels 1, 2 reduced, and an apparent slip ratio increased up to (b'-a')/a', an engine speed reduction instruction value for traction control is set at e2 in accordance with the small engine speed reduction parameter (2), and this value e2 is much smaller than an engine speed reduction value e3 to a slip ratio (b'-a')/a' determined by the parameter (1) at the normal time. Large engine speed reduction can thus be avoided in this case.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a traction control method for preventing the drive wheels from idling when a vehicle such as an automobile starts or suddenly accelerates. The present invention relates to a traction control method capable of controlling the idling of drive wheels to be suppressed as accurately as possible when the vehicle speed becomes lower than the vehicle speed at the start of traction control.

[0002]

2. Description of the Related Art In recent years, in automobiles, the power loss of the engine is reduced as much as possible when the drive wheels tend to idle, and the drive force of the drive wheels is more effectively transmitted to the road surface to effectively propel the vehicle. Traction control (hereinafter, TRC) that adjusts the driving force of the driving wheels
System) is being developed.

As such a TRC system, for example, there is an ABS / TRC system as shown in FIG. 3. This ABS / TRC system is an anti-skid brake which adjusts a braking force in order to prevent locking of braking wheels during braking. Control (hereinafter also referred to as ABS) system and TR
This is a system in which C and C are integrated together.

The ABS / TRC system comprises wheel speed sensors 3 and 4 for detecting wheel speeds of left and right front wheels 1 and 2 which are non-driving wheels, a modulator 5 for adjusting brake pressure of the front wheels 1 and 2, and front wheels 1 and 2 Brake chamber 6 that generates braking force, wheel speed sensors 9 and 10 that detect the wheel speeds of the left and right rear wheels 7 and 8 that are drive wheels, and modulators 11 and 12 that adjust the brake pressure of the rear wheels 7 and 8, respectively. , Brake chambers 13 and 14 that generate braking forces on the rear wheels 7 and 8, respectively.
A dual brake valve 16 that is controlled to open and close by a brake pedal 15, and a traction solenoid valve that is a solenoid valve that is opened during traction control to send the compressed air in the air tank 17 to the modulators 11 and 12 of the left and right rear wheels 7 and 8, respectively. (Hereinafter, also referred to as TRC valve) 18,19, motor 21, which is a governor actuator, which operates the governor link for changing and setting the lower limit value of the rotational speed of the engine 20, each modulator 5, 11, 12,
Each traction electromagnetic valve 18, 19 and motor 21
An ABS / TRC control unit (hereinafter, also referred to as ABS / TRC ECU) 22 for controlling the In the figure, 23 is an accelerator pedal.

The ABS / TRC system shown in FIG.
Wheel speed sensors 3, 4, 9 and 10 are provided for each of the left and right front and rear wheels, and a modulator 5 is provided to the left and right front wheels 1 and 2.
For one in total and one for each of the left and right rear wheels 7, 8 for a total of 3
It is a 4-sensor, 3-channel control system provided individually.

In the ABS / TRC system thus constructed, the wheel speed signals from the wheel speed sensors 3, 4, 9 and 10 are sent to the ABS / TRC ECU 22. When the ABS / TRC ECU 22 makes a calculation on the basis of these wheel speed signals during the brake operation and judges that the wheels are in a skid tendency based on the calculation result, the ABS / TRC ECU 22
The TRC ECU 22 outputs a control signal to the modulators 5, 11, 12 corresponding to the skid-prone wheels. As a result, the modulators 5, 11, 12 adjust the brake pressure in the brake chambers 6, 13, 14 so as to eliminate the skid tendency of the wheels. Thus, A
The BS / TRC ECU 22 performs anti-skid brake control so that the wheel lock tendency is eliminated when the wheel lock tendency tends to occur during braking.

Further, when the propulsive force of the vehicle is increasing at the time of starting the vehicle or during sudden acceleration, the ABS / TRC ECU 22 calculates based on the wheel speed signals from the wheel speed sensors 3, 4, 9 and 10, and If it is determined from the calculation result that the rear wheels 7 and 8 that are the drive wheels tend to idle, this ABS / TRC ECU
Reference numeral 22 denotes modulators 11 and 12 and traction electromagnetic valves (hereinafter,
The control signal is also output to the TRC valves 18 and 19 and the control signal is output to the motor 21 that operates the governor link.

In this case, the determination of the slipping tendency of the rear wheels 7, 8 which is the basis of the output timing of the control signal from the ABS / TRC ECU 22 to the TRC valves 18, 19 is made by the difference between the wheel speeds of the left and right rear wheels 7, 8. Is greater than a predetermined value, it is determined that the rear wheel having the higher wheel speed tends to idle. That is, when the difference between the wheel speeds of the left and right rear wheels 7, 8 becomes larger than a predetermined value, the rear wheel 7, 8 having the larger wheel speed is used.
It is judged that there is a tendency to slip. Actually, the wheel speed selected by the select high of the wheel speeds of the left and right front wheels 1 and 2 which are non-driving wheels is determined as the vehicle body speed (hereinafter, also referred to as vehicle speed),
The idling tendency of one of the rear wheels 7, 8 is determined based on the difference between the vehicle speed and the wheel speed of the rear wheel on the low μ side of the road friction coefficient (μ) of the left and right rear wheels 7, 8.

The determination of the slipping tendency of the rear wheels 7 and 8 which is the basis of the output timing of the control signal from the ABS / TRC ECU 22 to the motor 21 is based on the vehicle speed and the wheel speeds of the left and right rear wheels 7 and 8 described above. When the difference from the average exceeds a predetermined value, it is determined that the left and right rear wheels 7, 8 tend to slip.

The TRC valves 18, 19 are turned on and opened by a control signal from the ABS / TRC ECU 22, and compressed air from the air tank 17 is transferred to the TRC valves 18, 19,
Double check valves 24 and 25 and modulator 1
It is supplied to the brake chambers 13 and 14 through 1 and 12 to brake the rear wheels 7 and 8 which tend to slip. By the braking of the rear wheels 7 and 8, the rotational driving force of the rear wheels 7 and 8 is suppressed, and as a result, the idling tendency of the rear wheels 7 and 8 which tends to slip is eliminated.

A TRC shown in FIG. 4 is an example of the TRC for braking the driving wheels. In FIG. 4, at time t ₀ , TRC is in a non-controlled state, brake pressure is not generated, and rear wheels 7 and 8 are not braked. At time t ₁ , the ABS / TRC ECU 22 determines that the wheel speed of the rear wheels 7 and 8 on the low μ side becomes higher than the set threshold value with respect to the vehicle speed, and the rear wheels 7 and 8 on the low μ side idle. When it is determined that the tendency has occurred, a control signal is output to the TRC valves 18 and 19. By this control signal from the ABS / TRC ECU 22, the TRC valves 18, 19 of the rear wheels 7, 8 on the low μ side are turned on.
Then, the brake is applied to the rear wheels 7, 8 on the low μ side, that is, the wheels that tend to idle. Thus, TRC by braking is started. For a certain period after the start of braking, a relatively long build pulse is output to the holding solenoid valves (not shown) of the modulators 11 and 12 to remove the hysteresis of the braking system, and the holding solenoid valves are turned on / off. Repeat off.
At time t ₂ , the pressure gradually increases. Several types of this slow pressure increase rate are set according to the idling amount of the drive wheels, that is, the size of the road surface μ. When the idling tendency is decreasing, the holding solenoid valves of the modulators 11 and 12 are turned on at time t ₃ , and the exhaust solenoid valves of the modulators 11 and 12 (not shown) are turned on.
The brake pressure is maintained or reduced by turning on or off for a short time to monitor the degree of wheel recovery. The vehicle starts in this state. When the idling amount becomes considerably small, the brake pressure is further reduced at time t ₄ , and when the idling amount of the rear wheels 7 and 8 gradually increases again due to the reduction of the brake pressure, after the time t _5, this idling tendency Adjust the brake pressure by slowly increasing the pressure. Subsequently, it carried out, the reduced pressure of the same brake pressure at time t ₄ in the holding or reduced and the time t ₇ the same brake pressure at time t ₃ at time t ₆ according to slipping tendency state of the drive wheels. When the slipping tendency of the rear wheels 7 and 8 is eliminated, time t ₈
Then, the TRC valves 18 and 19 are turned off, and the supply of air from the air tank 17 is stopped. In that case, the modulators 11 and 12 are continuously operated to discharge the residual pressure in the piping system. The modulators 11 and 12 at time t ₉ after the elapse of a certain time
Is turned off and the TRC is ended.

On the other hand, the control signal from the ABS / TRC ECU 22 rotates the motor 21 to adjust the governor link of the engine 20, and the engine 20 is decelerated. Due to the deceleration of the engine 20, the rotational driving force of the rear wheels 7, 8 is suppressed, and as a result, the rear wheels 7, 8 which tend to idle.
The tendency of slipping will be eliminated. Also, the rear wheels 7,8
Even during TRC due to braking of the engine 20, the deceleration control of the engine 20 is performed, and the lower limit value of the rotational speed of the engine 20 is set to a slightly larger lower limit value during TRC so that engine stall does not occur during TRC due to braking of the rear wheels 7 and 8. Change and adjust.

As a TRC based on such engine deceleration, there is a TRC shown in FIG. In the TRC by engine deceleration shown in FIG. 5, when the rear wheels 7 and 8 tend to idle after the start of the vehicle at time t ₀ , the ABS / TR
The C ECU 22 detects this and outputs a control signal to the motor 21 at time t ₁ . As a result, the deceleration of the engine 20 starts with a slow deceleration. However, at time t
_When the average drive shaft speed of the left and right rear wheels 7 and 8 exceeds a permissible level at 2, the engine 20 is decelerated at full deceleration. When the idling tendency decreases, the engine 2 starts at time t _3.
Release the 0 deceleration gradually. That is, the engine 20 is accelerated by gentle acceleration. In that case, the engine 20 is rapidly accelerated according to the amount of idling and the deceleration of the drive shaft (the average of the deceleration of the left and right rear wheels 7, 8). In this state, the rear wheels 7,
When the idling tendency of only one side of 8 rises again, T at time t ₄
One of RC18 and 19 is turned on and the rear wheel 7, which tends to idle,
The brake is applied to one of the Nos. 8 and the engine deceleration is started. As a result, the tendency of one of the rear wheels 7, 8 which tends to slip is reduced, but when the tendency of the other of the rear wheels 7, 8 also becomes less, the engine 20 is abruptly accelerated at time t ₅ to avoid engine stall. To do. When the idling tendency of the rear wheels 7, 8 increases again due to the sudden acceleration of the engine 20, time t ₆
Then, the engine 20 is rapidly decelerated again. In that case, the engine 20 is slowly decelerated depending on the acceleration of the drive shaft (the average of the accelerations of the left and right rear wheels 7, 8) and the idling amount. When the wheel speeds of the rear wheels 7 and 8 tend to decrease, the vehicle gradually accelerates at time t ₇ . This slow acceleration is calculated based on the internal integrated value of the deceleration instruction value, and the internal integrated value is calculated by the wheel behavior and the previous deceleration instruction value. Thus, TRC is performed until the tendency of the rear wheels 7, 8 to slip is eliminated.

In this way, the ABS / TRC ECU
The reference numeral 22 performs TRC by braking and TRC by engine control so that the idling tendency of the rear wheels 7 and 8 as driving wheels is eliminated. Also, ABS / TRC
The ECU 22 lights the traction pilot lamp 26 during the TRC to notify the driver that the TRC is being performed.

[0015]

By the way, when a vehicle travels on a road surface such as an uphill road, a deep snow road or a bad mud road, the front wheels receive resistance to one or two rotations. 2 may slow down. When the front wheels 1 and 2 decelerate in this way, the following problems occur.

For example, as shown in FIG. 6, when the vehicle speed of the rear wheels 7, 8 is higher than the vehicle speed by a predetermined value when the vehicle is traveling on a flat road while accelerating, the rear wheels 7, 8 are Then, the TRC is started, and the wheel speeds of the rear wheels 7 and 8 and the vehicle body speed are controlled to be substantially constant. When the vehicle enters an uphill road while traveling on a flat road at a constant vehicle speed a and a constant wheel speed b of the rear wheels 7 and 8, the wheel speeds of the front wheels 1 and 2 decrease as described above. In such a case, since the wheel speeds of the front wheels 1 and 2 are low, it is used to judge the idling tendency of the rear wheels 7 and 8.
The body speed determined by the select high of the wheel speeds of the front wheels 1 and 2 is apparently low. Therefore, for example, as shown in FIG. 6, the slip ratio is (ba) / a when traveling on a flat road, whereas it is (b′−a ′) / a ′ when traveling on an uphill road.
Therefore, considering that a> a 'and b≈b', (b'-a ') / a'> (ba) / a, and the slip ratio on the apparent uphill road becomes large. Will end up.

Since the apparent slip ratio increases in this way, the ABS / TRC ECU 22 is
When it is determined that the slip of 8 has become larger, the engine is further decelerated, and the braking pressure applied to the rear wheels 7 and 8 is further increased. For this reason,
On a front wheel heavy load road surface such as a deep snow road or a bad muddy road, there is a problem that not only the wrong TRC is carried out, but also the driver may not be able to travel as he / she intends and the travel may be hindered.

The present invention has been made in view of the above problems, and an object thereof is even on a road surface such as an uphill road, a deep snow road or a bad mud road where a relatively large rotational resistance acts on a non-driving wheel. , TRC can be performed as accurately as possible, and a traction control method by which a vehicle can travel on such a road surface as the driver intends.

[0019]

In order to solve the above-mentioned problems, the invention of claim 1 detects each wheel speed of a non-driving wheel and a driving wheel of a vehicle, and determines the wheel speed of the non-driving wheel. Based on the body speed and the wheel speed of the drive wheels, it is determined whether or not the drive wheels have a tendency to idle, and the drive wheels are When it is judged that it is occurring, in the traction control method that adjusts the rotational driving force of the drive wheel so that the idling tendency is eliminated, after the traction control is started, the current vehicle speed at the time when the traction control starts When it is determined that the current vehicle speed is lower than the vehicle speed at the start of the traction control by a predetermined value or more than the vehicle speed, Is characterized by that the larger the capacity of the idle trend.

According to a second aspect of the present invention, the rotational driving force of the idling tendency drive wheel is adjusted by decelerating the engine, and the parameter for determining the instruction value of the engine deceleration with respect to the idling amount is a normal parameter. And a small engine deceleration parameter that reduces the instruction value of the engine deceleration from the normal time parameter is set, and in setting the allowable amount of the idling tendency of the drive wheels to be large, based on the small engine deceleration parameter. The instruction value of the engine deceleration with respect to the idling amount is determined.

Further, the invention of claim 3 adjusts the rotational driving force of the idling tendency driving wheel by braking the driving wheel, and sets a parameter for determining the braking force of the driving wheel for the idling amount. In setting a normal time parameter and a small braking force parameter that reduces the braking force of the driving wheel to be smaller than this normal time parameter, and setting the allowable amount of the idling tendency of the driving wheel to be large, The braking force for braking the drive wheels with respect to the idling amount is determined based on the braking force parameter.

[0022]

According to the present invention thus constructed, after the traction control is started, if it is determined that the current vehicle speed is lower than the vehicle speed at the start of the traction control by a predetermined value or more, the drive wheels tend to idle. The allowable amount of is set to a large value. Accordingly, when such a determination is made, the rotational driving force of the drive wheels is not significantly reduced by TRC. Therefore, during traction control, the road surface at which the current vehicle speed is lower than the vehicle speed at the start of traction control by a predetermined value or more,
That is, even when the vehicle is traveling on a road surface such as an uphill road, a deep snow road, or a bad muddy road where the rotational load of the non-driving wheels is large, the TRC is more appropriately performed and the vehicle is operated by the driver. You will be able to drive according to your will.

In that case, as a method for preventing the rotational drive force of the drive wheels from being greatly reduced by the TRC, a method of controlling the rotational drive force of the drive wheels by reducing the engine deceleration amount is adopted in the invention of claim 2. In the third aspect of the invention, a method of controlling the rotational driving force of the driving wheels by reducing the braking force of the driving wheels is adopted.

[0024]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram for explaining an embodiment of a traction control method according to the present invention, and FIG. 2 is a diagram for explaining a processing flow in this embodiment. In addition,
Since the ABS / TRC system used in this embodiment is the same as the above-mentioned conventional ABS / TRC system, this embodiment will be described using the same reference numerals as in this conventional ABS / TRC system.

In the present embodiment, as shown in FIG. 1, as a parameter for determining the engine deceleration instruction value with respect to the slip ratio, the normal parameter (1) and a parameter smaller than the normal parameter (1), The small engine deceleration parameter (2) when the front wheels are running on a heavily loaded road surface is set.

Therefore, the engine deceleration instruction value of the TRC due to the engine deceleration at the normal time is set according to the parameter (1) at the normal time. For example, in FIG. 1, when the slip ratio is (ba) / a, the engine deceleration instruction value is e ₁ according to the parameter (1) at the normal time.
Is set to. The ABS / TRC ECU 22 drives and controls the governor motor 21 so that the governor decelerates and controls the engine so as to obtain the instruction value e ₁ . On the other hand, as described above, when the vehicle shifts from a flat road to an uphill road, the wheel speeds of the front wheels 1 and 2 decrease, and the apparent slip ratio becomes (b
When it becomes large as'-a ') / a', the engine deceleration instruction value of the TRC is set to e ₂ in accordance with the small engine deceleration parameter (2) when traveling on a road with a large front wheel.
This engine deceleration instruction value e ₂ is a slip ratio (b′−a) determined according to the normal parameter (1).
It is considerably smaller than the engine deceleration value e ₃ for ′) / a ′. Therefore, in this case, the engine is not significantly decelerated, erroneous TRC is prevented from being performed, and the traveling of the vehicle on the uphill road is not hindered. As a result, the vehicle can be driven on the uphill road according to the driver's intention.

The processing of the engine deceleration control at the time of traveling on a road with a large load of front wheels such as an uphill road will be described. As shown in FIG. 2, first, in step ST1, the engine E
Is performing the TRC operation. When it is determined that the engine E is not performing the TRC operation, the process of step ST1 is performed again after a predetermined time. If it is determined in step ST1 that the engine E is operating TRC, the current vehicle speed is set to TR in step ST2.
It is determined whether the vehicle speed is lower than the vehicle speed at the start of C. When it is determined that the current vehicle speed is lower than the vehicle speed at the start of TRC, it is determined in step ST3 whether or not a predetermined time has elapsed since it was determined that the current vehicle speed was lower than the vehicle speed at the start of TRC. When it is determined that the predetermined time has elapsed, it is determined in step ST4 whether or not the difference between the current vehicle body speed and the vehicle body speed at the start of TRC is greater than or equal to a certain amount, and it is determined that this difference is greater than or equal to the certain amount. And step ST5
At step ST6, the timer is cleared and the current vehicle speed is set to the vehicle speed at the start of TRC, and then the slip allowable amount is increased at step ST6. That is, the parameter shown in FIG. 1 is switched from the normal parameter (1) to the front wheel heavy load road surface parameter (2). As a result, the engine deceleration instruction value for the same slip ratio is set small.

With the parameter (2) switched in this way, the TRC control routine by decelerating the engine is executed in step ST7. Therefore,
Even if the apparent slip ratio becomes large, the engine will not be significantly decelerated, and TR due to engine deceleration
The wrong C is avoided.

At step ST3, the current vehicle speed is TR
When it is determined that a certain time has not elapsed since it was determined that the vehicle speed was lower than the vehicle speed at the start of C, and step ST4
If it is determined that the difference between the current vehicle speed and the vehicle speed at the start of TRC is not equal to or more than a certain value, the step S
The process proceeds to the TRC control routine of T7. When it is determined in step ST2 that the current vehicle speed is not lower than the vehicle speed at the start of TRC, the current vehicle speed is set to the vehicle speed at the start of TRC in step ST8, and then the TRC control routine of step ST7 is performed.

In the above-described embodiment, the case where the present invention is applied to the TRC based on engine deceleration is described, but the present invention can also be applied to the TRC based on braking of the driving wheels. In that case, a parameter for determining the braking force for braking the driving wheels with respect to the idling amount is a normal parameter, and a small braking force parameter for making the braking force for braking the driving wheels smaller than the normal parameters. Try to set it. Further, when setting the allowance of the idling tendency of the drive wheels to be large, the braking force for braking the drive wheels with respect to the idling amount is determined based on the small braking force parameter.

Further, in the above-mentioned embodiment, the present invention is applied to the air
The case where the present invention is applied to the over hydraulic brake has been described.
Any device that performs C can be applied to, for example, a full air brake system or a hydraulic brake control system.

Further, in the above-mentioned embodiment, the case where the ABS system and the TRC system are incorporated together has been described. However, the present invention describes that the TRC system is the ABS.
When provided separately from the system or T
It is also applicable when only RC is provided.

[0033]

As is apparent from the above description, according to the traction control method of the present invention, after the traction control is started, the current vehicle speed is lower than the vehicle speed at the start of the traction control by a predetermined value or more. If it is determined, the rotational driving force of the driving wheels is TRC.
Therefore, during traction control, the current vehicle speed is less than the vehicle speed at the start of traction control by more than a predetermined value, that is, uphill road, deep snow road or bad mud road. Even when the vehicle is traveling on a road surface in which the rotational load of the non-driving wheels is large, the TRC can be performed more appropriately, and the vehicle can be driven as the driver desires. become able to.

[Brief description of drawings]

FIG. 1 is a diagram illustrating an embodiment of a traction control method according to the present invention.

FIG. 2 is a diagram illustrating a processing flow in this embodiment.

FIG. 3 is a diagram showing a conventional ABS / TRC system.

FIG. 4 is a diagram illustrating a TRC using a conventional brake.

FIG. 5 is a diagram illustrating a conventional TRC due to engine deceleration.

FIG. 6 is a diagram illustrating that the idling amount of the drive wheels apparently increases when the wheel speed of the front wheels decreases on an uphill road.

[Explanation of symbols]

1, 2 ... left and right front wheels (non-driving wheels) 3, 4.9, 10 ... wheel speed sensors 5, 11, 12 ... modulators for anti-skid control 6, 13, 14 ... brake chambers 7, 8
... left and right rear wheels (driving wheels), 15 ... brake pedal, 16
… Dual brake valve, 17… Air tank, 18,
19 ... Traction electromagnetic valve (TRC valve), 20
... engine, 21 ... motor, 22 ... ABS / TRC control unit (ABS / TRC ECU), 23 ...
Accelerator pedal, 24,25 ... double check valve,
26 ... Traction pilot lamp

Claims (3)

[Claims] 1. A vehicle speed of each of a non-driving wheel and a driving wheel of a vehicle is detected, a vehicle speed is obtained based on the wheel speed of the non-driving wheel, and the vehicle speed and the wheel speed of the driving wheel are calculated. When it is determined whether the drive wheels have a slip tendency based on the set slip amount, and when it is determined that the drive wheels have a slip tendency, the spin driving tendency of the drive wheels is determined to be the slip tendency. In the traction control method for adjusting so that the current vehicle body speed is lower than the vehicle body speed at the start of traction control by a predetermined value or more after the traction control is started, the current vehicle body speed is adjusted by the traction control. When it is determined that the vehicle speed at the start is smaller than a predetermined value by a predetermined value or more, the allowable amount of the idling tendency of the drive wheels is set to be large. Lac Deployment control method. 2. The rotation driving force of the idling tendency drive wheels is adjusted by decelerating the engine, and a parameter for determining an instruction value of the engine deceleration for the idling amount is a normal parameter and a normal parameter. When setting a small engine deceleration parameter that makes the engine deceleration instruction value smaller than the parameter and setting the allowable amount of the idling tendency of the drive wheels to be large, the engine for the idling amount based on the small engine deceleration parameter The traction control method according to claim 1, wherein an instruction value for deceleration is determined. 3. The rotation driving force of the idling tendency drive wheel is adjusted by braking the drive wheel, and a parameter for determining a braking force of the drive wheel for the idling amount is a normal time parameter, Setting a small braking force parameter that reduces the braking force of the driving wheel from the normal time parameter, and setting the allowable amount of the idling tendency of the driving wheel to be large, based on the small braking force parameter. The traction control method according to claim 1, wherein a braking force for braking the drive wheels with respect to the idling amount is determined.