KR101500172B1 - Method for controlling driving power for 4 wheel drive vehicle - Google Patents

Abstract

Disclosed is a method for controlling the driving force of a four-wheel drive vehicle. The method comprises: a wheel speed detecting step of detecting the rotation speed of each of the wheels of the vehicle; an average value calculating step of calculating a front wheel average value as the average wheel speed value of two front wheels and a rear wheel average value as the average wheel speed value of two rear wheels; a difference value calculating step of calculating a difference value between two calculated average values; a difference value distinguishing step of determining to which section the calculated difference value belongs among multiple predetermined difference value sections; and a control step of applying a predetermined torque value to rear axle shafts when the predetermined torque value corresponds to the section determined in the difference value distinguishing step. The method according to the present invention is capable of determining the current attachment of a different kind of a tire in the vehicle through the divided steps, and is capable of differently controlling a torque input to the rear wheels according to the steps, thereby preventing the component of a driving system from being damaged when excessive torque is applied to the rear wheels.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a four-wheel drive vehicle,

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a driving force control method for a four-wheel drive vehicle in which a tire having a different radius is mounted on a four-wheel drive (4WD) vehicle.

A four-wheel drive vehicle generally refers to a vehicle that is capable of driving all four wheels unlike a two-wheel drive vehicle that drives only a front wheel or a rear wheel. Compared to a two-wheel drive vehicle, four wheels are driven at the same time, which means that the driving performance is superior, and the driving performance is excellent for rough roads such as unpaved roads, roads where slopes are very urgent, and slippery roads.

However, the above-mentioned four-wheel-drive vehicle may cause problems such as deterioration of fuel efficiency and generation of high noise when the vehicle is traveling on a general road, that is, on a road which does not take much load in running. Therefore, in general, a four-wheel drive vehicle is driven by two wheels during normal driving, and is driven by four wheels in a section requiring a rough road, a slippery road surface, and a high thrust, thereby improving fuel economy and reducing noise and vibration.

As described above, in the past, when the driving force distribution of the four-wheel-drive vehicle is considered, all four-wheel-drive to two-wheel-drive conversions have been performed mechanically by the driver's operation.

However, in recent years, the driving force distribution of such a four-wheel drive vehicle is electronically performed, and it is possible not only to switch from the four-wheel drive to the two-wheel drive but also to vary the driving force distribution ratio of the front wheel and the rear wheel depending on the situation. It may be controlled so that the driving force distribution varies depending on the degree of slip.

Conventional KR10-2012-0103938A "Torque distribution control device and control method for four-wheel drive vehicle" describes "a torque distribution control device and a control method for a four-wheel drive vehicle " in which the stall opening degree is less than 50% in the city driving mode, However, when the rotational aberrations of the front wheels and the rear wheels are larger than the allowable values, the four-wheel drive controller controls the actuator unit in the front and rear wheel driving force distribution determining unit to automatically change the torque of the front wheels and the rear wheels in the four- The AUTO mode controls the driving force of the front wheel and the rear wheel to be distributed to a maximum of 50:50, and the engine torque and the NVH (Noise, Vibration, and Harshness) input from the engine torque sensor are distributed, And so on. "It is suggested that the driving force distribution may be changed according to the degree of slip of the actual wheel .

However, there is a problem with such a four-wheel drive control system. In the case where a heterogeneous tire having a different tire radius is provided on either the front wheel or the rear wheel, the rotation speed of the other wheels is relatively higher than that of the wheel provided with the different- The rotational speed of the rear axle shaft is different from the rotational speed of the rear axle shaft, thereby causing a slip in the clutch inside the coupling which controls the transmission of the driving force from the propeller shaft to the rear axle shaft.

The coupling does not overheat because the clutch maintains the noncontact state when the vehicle is traveling in a two-wheel drive state. However, when a different type of tire is installed in the vehicle and the wheel speeds of the front wheel and the rear wheel become different from each other, The slip of the clutch occurs in a state in which the clutch is frictionally contacted and frictionally contacted due to the different rotational speeds between the propeller shaft and the rear axle shaft.

If the state in which the four-wheel drive mode is entered, that is, the state in which the clutch in the coupling is frictionally contacted and the driving force is transmitted to the rear wheel is performed for a short time, a large problem may not occur. However, The clutch is kept in a frictional contact state continuously for a long time, for example, in a constant speed running state of 60 to 100 kph. As a result, the clutch slips for a long time and the clutch is overheated, There has been a problem that parts are overheated and damaged.

It should be understood that the foregoing description of the background art is merely for the purpose of promoting an understanding of the background of the present invention and is not to be construed as an admission that the prior art is known to those skilled in the art.

KR10-2012-0103938A

SUMMARY OF THE INVENTION The present invention has been proposed in order to solve such a problem, and it is an object of the present invention to determine whether a vehicle is currently attached with a different kind of tire by dividing it into a plurality of steps and control the torque inputted to the rear wheel differently according to the step, The present invention is directed to a driving force control method for a four-wheel drive vehicle that prevents damage to a driveline component that may be generated as a result of being applied.

According to an aspect of the present invention, there is provided a driving force control method for a four-wheel drive vehicle, including: a wheel speed detection step of detecting a rotation speed of each vehicle wheel; An average value calculating step of calculating a front wheel average value which is the average wheel speed value of the two wheels provided on the front wheel and an average rear wheel value which is the average wheel speed value of the two wheels provided on the rear wheel; A difference value calculating step of calculating a difference value between the two calculated average values; A difference value classifying step of determining in which interval of the plurality of difference value intervals the calculated difference value belongs to; And a control step of applying a set torque value corresponding to an interval determined in the difference value dividing step to a rear wheel axle shaft.

And determining whether the vehicle speed is included in the set vehicle speed range before the wheel speed detection step.

And determining whether the accelerator pedal opening amount is equal to or less than a predetermined opening amount for each vehicle speed within the set vehicle speed range before the wheel speed detecting step.

And a braking determining step of determining whether the brake is operated before the wheel speed detecting step.

And a steering angle determination step of determining whether the steering angle is included in the set steering angle range before the wheel speed detection step.

The difference value may be calculated as an equation (front wheel average value - rear wheel average value) / rear wheel average value * 100.

The determining step may further include a setting time holding step of determining whether the difference value is included in a difference value interval of the difference value interval for a set time period.

The difference value interval may include a first interval, a second interval, and a third interval, and each difference value interval may be continuous, and the third interval may include a larger difference value than the first interval.

The set torque value of the first section may be greater than the set torque value of the second section and the set torque value of the second section may be greater than the set torque value of the third section.

The set torque value of the third section may be zero.

In the control step, the clutch slip ratio of the coupling provided on the propeller shaft may be controlled to apply the set torque value to the rear axle shaft.

On the other hand, the present invention comprises a wheel speed detecting step of detecting a wheel speed of each vehicle wheel; An error value calculating step of calculating an error value by comparing any two values among the detected wheel speed values; An error value classifying step of determining in which interval of the plurality of error value intervals the calculated error value belongs; And a control step of applying a set torque value corresponding to an interval determined in the error value dividing step to a rear wheel axle shaft.

Either of the two values may be a maximum wheel speed value and a minimum wheel speed value among the detected wheel speed values.

The difference value can be calculated as an equation (maximum wheel speed value-minimum wheel speed value) / minimum wheel speed value * 100.

According to the driving force control method of the four-wheel drive vehicle having the above-described structure, when a different type of tire is mounted on the vehicle, the vehicle is recognized as a slip state and repeatedly applied with strong frictional force to the coupling, .

The control for the coupling protection can be performed only under the condition that the coupling is damaged by performing the condition search for judging whether or not the plurality of different types of tires are mounted before performing the control, Can be reduced.

1 is a flowchart of a driving force control method of a four-wheel drive vehicle according to a first embodiment of the present invention.
2 is a flowchart of a driving force control method of a four-wheel drive vehicle according to a second embodiment of the present invention.

Hereinafter, a driving force control method for a four-wheel drive vehicle according to a preferred embodiment of the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a flowchart of a driving force control method of a four-wheel drive vehicle according to a first embodiment of the present invention, which comprises a wheel speed detecting step (S200) of detecting the rotational speed of each vehicle wheel; An average value calculation step (S210) of calculating a front wheel average value, which is an average wheel speed value of the two wheels provided on the front wheel, and a rear wheel average value, which is an average wheel speed value of the two wheels provided on the rear wheel; A difference value calculation step (S220) of calculating a difference value between the calculated two average values; A difference value classifying step (S230) of determining in which interval of the plurality of difference value intervals that the calculated difference value belongs to; And a control step (S310) of applying a set torque value corresponding to the interval determined in the difference value sorting step S230 to a rear wheel axle axis.

Here, the difference value may be calculated as a formula (front wheel average value-rear wheel average value) / rear wheel average value * 100, which is calculated as% relative to the rear wheel average value, so that there is a difference in wheel speed to some extent between the front wheel and the rear wheel Can be calculated.

It is important to determine whether the difference value occurring in the current vehicle is a difference value caused solely by the heterogeneous tire before performing the wheel speed detection step S200. This is because the difference value can be influenced not only by the heterogeneous tire but also by various driving environments such as a vehicle turning, rapid acceleration and sudden stopping. Therefore, it is necessary to first determine whether the current state of the vehicle is a condition in which the wheel speed difference does not occur between the front wheels and the rear wheels of the vehicle, that is, a condition in which the wheel will not slip. If a wheel speed difference occurs between the front wheel and the rear wheel (i.e., if the difference value is equal to or greater than 0%) as in the case where a slip occurs even though the wheel does not slip, It can be judged that the change in the wheel speed is caused by the attachment of the different kind of tire to the present vehicle and the torque applied to the rear axle shaft is controlled to prevent the clutch of the coupling from being continuously brought into frictional contact state can do. A method of controlling the torque will be described later.

Therefore, a vehicle speed determination step (S100) for detecting the vehicle speed and determining whether the detected vehicle speed is included in the set vehicle speed range before the wheel speed detection step (S200) can be further performed.

When the vehicle speed is lowered, the absolute value of the average value of the front wheel and the average value of the rear wheel are lowered, and the difference between the average value of the front wheel and the average value of the rear wheel naturally decreases.

For example, when a different kind of tire is installed on the rear wheel, the wheel speed is the number of revolutions per second of the wheel, the vehicle is traveling for one second, and the vehicle is traveling at a low vehicle speed, The rotation speed per second is lowered, so that the difference between the average value of the front wheel and the average value of the rear wheel is not large.

However, when the vehicle speed increases, the rotation speed per second increases because the distance that the vehicle can move for one second is long, and thus the difference between the average value of the front wheel and the value of the rear wheel becomes large.

Therefore, the set vehicle speed must be provided to perform the discrimination of the heterogeneous tire only when the difference value is sufficient to detect the wheel speed difference by the heterogeneous tire.

The set vehicle speed is also a preset value according to the vehicle type and driving environment through experiments. It is preferable that the vehicle speed is usually 10 kph or more and 120 kph or less.

Meanwhile, the ECU may further determine whether the amount of opening of the vehicle before the wheel speed detection step (S200) is equal to or less than a predetermined opening amount for each vehicle speed within the set vehicle speed range.

When the opening amount exceeding the limit opening amount corresponding to a vehicle speed within the set vehicle speed range is detected, the present vehicle acceleration is detected by a detection sensor that detects the depth at which the pedal is depressed by the pedal next to the accelerator pedal. It is preferable to set the limit opening amount so that it can be judged as the state. When the vehicle is in a rapid acceleration state, the wheel speeds of the front wheels and the rear wheels of the all-wheel drive vehicle are higher than those of the different tires in the difference value calculation step (S220) The difference value calculation can be performed.

Therefore, it is preferable to set the limit opening amount as an index for determining whether or not the vehicle is rapidly accelerated so that the wheel speed detection step (S200) is not performed at the time of a rapid acceleration.

Preferably, the limit opening amount is differently set for each vehicle speed, and the limit opening amount is preferably increased as the vehicle speed is increased.

In addition, it is preferable that the limit opening amount is a preset value according to the type of vehicle and the driving environment through experiments.

Meanwhile, a braking determination step (S120) may be performed to detect a brake pedal operation signal before the wheel speed detection step (S200) and determine whether the brake is operated according to the detected brake pedal operation signal. The difference between the average value of the front wheel and the average value of the rear wheel may occur due to the difference in the braking force between the front wheel and the rear wheel during the braking operation. Therefore, it may be considered that the difference value by the different type of tires may not be accurately calculated at the time of detecting the brake pedal operation signal In this case, it is preferable that the wheel speed detection step S200 is not performed.

Preferably, the steering angle determining step S130 is performed to detect the steering angle before the wheel speed detecting step S200 and to determine whether the detected steering angle is within the set steering angle range, it means.

As the steering angle increases, the difference in the turning radius between the wheels increases as the vehicle rotates, which increases the rotational speed difference between the wheels and the wheel speed difference between the generated wheels is reflected in the calculation of the difference value In the difference value sorting step S230, it is possible to influence the selection of the interval, which is not a selection of the interval by the different kind of tires. Therefore, in order to prevent the wheel speed detection step S200 from being performed at this time, It is preferable to perform the judgment step.

The set steering angle range is a value set in advance according to the vehicle type and the driving environment through an actual vehicle test or the like. When the steering angle range is larger than 0 degrees and smaller than 90 degrees, the difference value A segment selection can be made.

When the vehicle speed is included in the set vehicle speed range as described above and the amount of excavation is less than or equal to the limit opening amount preset for the vehicle speed within the set vehicle speed range and the brakes are operated and the steering angle is within the set steering angle range, Is considered to have been generated by the different kind of tire, it is preferable to perform the wheel speed detection step (S200).

Meanwhile, the difference value interval may include a first interval, a second interval, and a third interval, and each difference value interval may be consecutively connected, and the third interval may be set to include a larger difference value than the first interval .

For example, if the first section has a difference value interval of 1.5% or more and less than 2.5%, the second section is 2.5% or more and less than 4.5%, and the third section is 4.5% And a difference value interval.

If the difference value is low enough that the difference value is not included in the first section, it is determined that the different tire is not mounted on the current vehicle, and the control step S310 is not performed.

Further, the method may further include a step S300 of determining whether or not the difference value is included in one of the difference value intervals for a set time period so that the difference value is stored in the first to third The control unit 310 determines that the difference value is not the difference value generated by the heterogeneous tire, and the control step S310 is performed when the difference value is not the difference value generated by the heterogeneous tire It does not.

The reason why the setup time holding step (S300) is performed is that there may occur a situation in which a slip may instantaneously occur even when the vehicle is running. That is, even in a constant-speed running condition that satisfies all the conditions for performing the wheel speed detection step S200, for example, a running condition of 60 to 100 kph per hour, an external factor such as unevenness of the road surface instantaneously causes slip between the tire and the road surface The wheel speed may instantaneously be increased. If the set time holding step S300 is not performed, the selection of the difference value interval may be changed even when the instantaneous road surface changes as described above The set time holding step S300 is necessary.

Also, for the reason that the set time holding step (S300) is necessary, it is for checking whether the current vehicle is in the constant speed running state.

That is, when the coupling is overheated and the coupling is damaged, the clutch provided in the coupling is maintained in a frictional contact state for a long time to continuously transmit power. In a case where a heterogeneous tire is mounted on the vehicle in a constant- The slip does not actually occur but the slip occurs due to the difference in the wheel speeds of the front wheels and the rear wheels. Therefore, the clutch is maintained in the frictional contact state for a long period of time at constant speed, Which may be overheated and damaged.

On the other hand, if the clutch is kept in friction contact only for a short time, there is almost no occurrence of overheating to such an extent that the coupling is damaged because contact and non-contact are repeated.

Accordingly, it is possible to determine whether the current vehicle is in the constant-speed running state, that is, in a state where the coupling can be overheated to such an extent that the coupling is damaged when the different-type tire is mounted on the vehicle, It is preferable that the control step (S310) can be performed only in one case.

If the corresponding difference value interval is selected according to the difference value, it is preferable that the control step S310 is performed. At this time, the set torque value of the first section is set to be greater than the set torque value of the second section And the set torque value of the second section is set to be larger than the set torque value of the third section.

Also, in the control step S310, the clutch slip ratio of the coupling provided on the propeller shaft is controlled to apply the set torque value to the rear axle shaft.

More specifically, for example, if the first section is selected, the wheel speed difference between the front wheel and the rear wheel of the vehicle is relatively low compared to the second section and the third section, so that the rotational speed of the propeller shaft, The difference in the rotational speed of the shaft is not large and the occurrence of the slip of the clutch in the coupling is relatively less than in the case where the difference value is located in the second and third sections. In this case, therefore, the clutch slip ratio is controlled so that only a part of the input torque transmitted from the propeller shaft, for example, 70%, is transmitted to the rear wheel axle shaft, and the input torque is only 70% .

Here, the clutch slip ratio refers to the degree to which the clutch slips when the clutch is in a fully engaged state and 0% when the clutch is completely separated. When the slip ratio is low, the torque applied to the rear axle shaft is And approaches the input torque. That is, the power transmission rate approaches 100%. Of course, as the clutch slip ratio decreases, the clutch is strongly contacted, so that the load applied to the clutch increases and the amount of heat generated by the load also increases.

The reason why the clutch slip ratio is controlled to keep the slip state in a state where the clutch slip has already been generated by the different kind of tires is to keep the vehicle in the four-wheel drive state as much as possible. If you enter into the wheel drive mode, you may not be able to use the strengths of a four-wheel drive vehicle if you are faced with situations where you need four-wheel drive, for example when you are accelerating or entering some ice roads to be.

That is, when the difference value belongs to the first section, the difference between the rotational speed of the propeller shaft and the rotational speed of the rear axle shaft is not relatively large as described above. Therefore, even if some slip occurs, By setting the set torque value of the first section to such an extent that the vehicle is not burned, the vehicle can maintain the four-wheel drive state without burn-out of the coupling.

Therefore, it is preferable to set the set torque value of the first section to such an extent that the coupling of the vehicle is not burned even when the difference value belongs to the first section through repeated experiments.

And the set torque value of the first section is set to have a value between 70% and 90%.

When the difference value belongs to the second section, the difference between the rotational speed of the propeller shaft and the rotational speed of the rear axle shaft is larger than that of the difference value belonging to the first section, The slip rate of the clutch is increased and the set torque value is controlled so as to be controlled to be lower than the clutch slip rate corresponding to the set torque value of the first section by increasing the slip ratio of the clutch, 1 is set to be lower than the set torque value.

In the second section, the power transmission rate decreases due to the increase of the clutch slip ratio. As a result, the amount of torque transmitted to the rear axle shaft of the input torque decreases as compared with when the difference value belongs to the first section. It is possible to reduce the amount of heat generated by the clutch due to the slippage of the clutch due to the difference between the rotational speed of the propeller shaft and the rotational speed of the rear axle shaft, It is possible to maintain the four-wheel drive state without burn-out of the coupling and the clutch due to overheating even in a situation where the vehicle can be increased.

Therefore, it is preferable that the set torque value of the second section has such a value that the coupling and the clutch are not damaged by the overheat even if the difference value belongs to the second section.

For example, the set torque value of the second section may be any value between 30% and less than 70%.

Meanwhile, when the difference value belongs to the third section, it is preferable that the set torque value of the third section is set to be zero.

Specifically, when the difference value falls within the third section, the slip of the clutch due to the difference between the rotational speed of the propeller shaft and the rotational speed of the rear axle shaft is very large, so that when the clutch is contacted and rubbed, In this case, the clutch slip ratio is set to 100%, that is, the clutch is completely released from contact and the vehicle is controlled to be in the two-wheel drive state, It is possible to prevent burn-out.

The range of the first section, the second section and the third section and the set torque value of each difference value section as described above are set such that when the difference value between the front wheel and the rear wheel occurs, Value should be set so that the coupling is overheated even if the set torque value is applied to the rear axle axis during a predetermined time, and the state in which the combustion does not occur is maintained.

Meanwhile, FIG. 2 is a flowchart of a driving force control method of a four-wheel drive vehicle according to a second embodiment of the present invention, which includes a wheel speed detection step (S200) of detecting the rotational speed of each vehicle wheel; An error value calculation step (S211) of calculating an error value by comparing any two values among the detected wheel speed values; An error value classifying step (S212) of determining in which interval of the plurality of error value intervals the calculated error value belongs to; And a control step (S311) of applying a set torque value corresponding to an interval determined in the error value dividing step to a rear wheel axle axis.

The error value may be calculated as an equation (maximum wheel speed value-minimum wheel speed value) / minimum wheel speed value * 100, and each section has an error value range as described above. Of course, the range of the error value interval may be different from the range of the difference value interval. For example, the first error value interval of the error value interval may range from 2.4% to less than 4.5% A range of 4.5% or more to less than 7%, and a third error value range of 7% or more.

As described above, by comparing the maximum wheel speed value and the minimum wheel speed value, it is possible to determine the difference between the wheel speeds of the front wheel and the rear wheel and how much the difference occurs. For example, The maximum wheel speed value is detected at the wheel speed, the minimum wheel speed value is detected at the right wheel speed or the left wheel speed of the rear wheel, or the maximum wheel speed value is detected at the right wheel speed or the left wheel speed of the rear wheel, When the minimum wheel speed value is detected at the wheel speed, it can be determined that a difference occurs between the average wheel speeds of the front wheel and the rear wheel by calculating the error value, so that a necessary set torque value according to the error value is determined through repeated experiments And thus the range of the error value interval can be determined.

However, there may be a case where the maximum wheel speed value and the minimum wheel speed value are both outputted from the left and right sides of the front wheel or the rear wheel. Even if this happens, a difference occurs between the average wheel speeds of the front wheel and the rear wheel. The difference between the average wheel speed of the rear wheels and the average wheel speed of the rear wheels also increases. Therefore, even when the maximum wheel speed value and the minimum wheel speed value are both outputted from the right and left sides of the front wheel or rear wheel, It is desirable to set the range of the error value interval through repeated experiments so that it can be determined.

The remaining steps except for the error value calculation step (S211) are all performed in the same manner as described in the first embodiment.

That is, the error value dividing step S212 has the same interval number as the difference value interval and the interval of each interval, and after the error value dividing step S212, in the setting time holding step S300 of the first embodiment, (S301) having the same set time as the control time (S301), and the control step (S311) performs the control for each section in the same manner as the control step (S310) of the first embodiment.

Since the effects and methods of the second embodiment are the same as those of the first embodiment, a detailed description of the second embodiment will be omitted.

According to the driving force control method of the four-wheel drive vehicle having the above-described structure, when a different type of tire is mounted on the vehicle, the vehicle is recognized as a slip state and repeatedly applied with strong frictional force to the coupling, .

The control for the coupling protection can be performed only under the condition that the coupling is damaged by performing the condition search for judging whether or not the plurality of different types of tires are mounted before performing the control, Can be reduced.

While the present invention has been particularly shown and described with reference to specific embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the following claims It will be apparent to those of ordinary skill in the art.

S100: Steering angle determination step S110: Excel opening amount determination step
S120: Break determination step S130: Steering angle determination step
S200: Wheel speed detection step S210: Average value calculation step
S211: Error value calculation step S212: Error value classification step
S220: Difference value calculating step S230: Difference value dividing step
S300, S301: Preset time holding step S310, S311: Control step

Claims (14)

A wheel speed detecting step of detecting a rotational speed of each of the vehicle wheels;
An average value calculating step of calculating a front wheel average value which is the average wheel speed value of the two wheels provided on the front wheel and an average rear wheel value which is the average wheel speed value of the two wheels provided on the rear wheel;
A difference value calculating step of calculating a difference value between the two calculated average values;
A difference value classifying step of determining in which interval of the plurality of difference value intervals the calculated difference value belongs to; And
And a control step of applying a set torque value corresponding to an interval determined in the difference value dividing step to a rear wheel axle shaft,
Wherein the difference value interval comprises a first interval, a second interval and a third interval, each difference value interval continuing, and the third interval including a larger difference value than the first interval. A driving force control method for a vehicle. The method according to claim 1,
And determining whether the vehicle speed is within a set vehicle speed range prior to the wheel speed detection step. The method according to claim 1,
And determining whether or not the amount of opening of the accelerator is equal to or less than a predetermined opening amount for each vehicle speed within the set vehicle speed range prior to the wheel speed detecting step. The method according to claim 1,
And a braking determining step of determining whether or not the brake is operated before the wheel speed detecting step. The method according to claim 1,
And a steering angle determination step of determining whether or not the steering angle is included in the set steering angle range before the wheel speed detection step. The method according to claim 1,
Wherein the difference value is calculated as an equation (front wheel average value - rear wheel average value) / rear wheel average value * 100. The method according to claim 1,
Wherein the dividing step further comprises a setting time holding step of determining whether the difference value is included in a difference value interval of the difference value interval for a preset time period Control method. delete The method according to claim 1,
Wherein the set torque value of the first section is greater than the set torque value of the second section and the set torque value of the second section is greater than the set torque value of the third section. The method of claim 9,
And the set torque value of the third section is zero. The method according to claim 1,
Wherein the control step controls the clutch slip ratio of the coupling provided on the propeller shaft to apply the set torque value to the rear wheel axle shaft. A wheel speed detecting step of detecting a rotational speed of each of the vehicle wheels;
An error value calculating step of calculating an error value by comparing any two values among the detected wheel speed values;
An error value classifying step of determining in which interval of the plurality of error value intervals the calculated error value belongs; And
And a control step of applying a set torque value corresponding to an interval determined in the error value dividing step to a rear wheel axle shaft,
Wherein the error value interval is comprised of a first interval, a second interval and a third interval, each error value interval continuing continuously, and the third interval including a larger error value than the first interval. A driving force control method for a vehicle. The method of claim 12,
Wherein the two values are the maximum wheel speed value and the minimum wheel speed value among the detected wheel speed values. 14. The method of claim 13,
Wherein the error value is calculated as an expression (maximum wheel speed value - minimum wheel speed value) / minimum wheel speed value * 100.

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