JPH05125970A - Vehicle slip control device - Google Patents

Abstract

PURPOSE:To enhance the acceleration property of a vehicle equipped with a limited slip differential not only when the vehicle travels on a normal road surface but also when the vehicle travels on a split road surface using a slip control unit provided in the vehicle to perform traction control (engine control). CONSTITUTION:At the step S3, split judgement processing is executed to see whether or not a vehicle travels on a split road surface according to the spin patterns of right and left driving wheels. If the vehicle does not travel on a split road surface (split control flag FS is not set) at the step S4, normal control is executed at the step S5. If the vehicle travels on a split road surface, the control shifts to the step 6, at which split control is executed(traction control whereby a target control value is corrected by increasing it more than during normal control so that driving wheel slippage is permitted). Thereby limiting of engine output more than required due to the slip of one of the driving wheels is prevented and the acceleration property of the vehicle is held at its maximum by the other driving wheel having sufficient gripping forces against the road surface.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle slip control device, and more particularly to a slip control device provided in a vehicle provided with a so-called limited slip differential.

[0002]

2. Description of the Related Art When a vehicle is accelerated, the driving wheels may slip due to an excessive driving force, which may deteriorate the acceleration performance. Further, in the power transmission path from the engine to the left and right drive wheels, a differential device that allows a difference in rotational speed between the two drive wheels is generally provided, but the split road surface (the friction coefficient of the road surface contacting each drive wheel is When driving on different road surfaces between the two drive wheels, the differential function of the above-mentioned differential device causes the rotational speed of the drive wheel on the side with the smaller road surface friction coefficient to become abnormally high, resulting in a one-wheel slip condition. As a result, the behavior of the vehicle may become unstable.

Therefore, conventionally, when the slip ratio of the drive wheels with respect to the road surface exceeds a predetermined value, so-called traction control is performed to control the drive force of the drive wheels so that the slip ratio approaches a predetermined target slip ratio. A slip control device has been proposed. As a specific example of such a slip control device, there is known a device that performs driving force control by limiting an engine output (engine control) and applying a braking force to driving wheels (brake control).

[0004]

Among the above-mentioned driving force control, the brake control is individually performed for each driving wheel, but the engine control is uniformly performed for both driving wheels. The following problems occur when the control is performed. That is, when the vehicle travels on the split road surface, one driving wheel slips largely, but at that time, the other driving wheel hardly slips in many cases. In such a case, when the engine control is started and the engine output is limited due to a large slip of the one driving wheel, the other driving wheel has a sufficient gripping force on the road surface, Since the supply of the driving force to the other driving wheel is also uniformly limited, there arises a problem that the acceleration performance is unduly hindered.

By the way, in a vehicle with a limited slip differential equipped with differential limiting means for limiting the rotational speed difference permissible operation by the differential device when the rotational speed difference between both drive wheels exceeds a predetermined value, both drive Since the rotational speed difference of the wheels does not become extremely large, the driving force control can be performed only by the engine control, and the brake control can be abolished, but it is a vehicle with a limited slip differential. However, since the difference in rotational speed between the two driving wheels is not eliminated, it is not possible to solve the above-mentioned problem that the acceleration performance is impaired during traveling on the split road surface due to engine output limitation.

The present invention has been made in view of the above circumstances, and in a vehicle equipped with a limited slip differential, slip can be improved not only when traveling on a normal road surface but also when traveling on a split road surface. An object is to provide a control device.

It should be noted that, in Japanese Patent Publication No. 58-50902, in ABS (antilock brake system), when there is a large difference between the braking hydraulic pressures for the left and right braking wheels, the higher one is used. There is disclosed a technique in which the behavior of the vehicle is stabilized during traveling on a split road surface by lowering the hydraulic pressure.

[0008]

A vehicle slip control device according to the present invention achieves the above object by increasing and correcting a control target value or a control start threshold in driving force control during traveling on a split road surface. It is the one.

That is, as described in claim 1 and as shown in FIG. 1, the difference is provided in the power transmission path from the engine to the left and right driving wheels and allows the difference in rotational speed between these two driving wheels. Differential limiting means (B) for limiting the rotational speed difference permissible operation by the differential device (A) when the rotational speed difference between the drive device (A) and the two drive wheels exceeds a predetermined value.
A slip control device provided in a vehicle including: and limiting an engine output so that the slip ratio approaches a predetermined target slip ratio when the slip ratio of the drive wheels with respect to the road surface becomes a predetermined value or more. In the slip control device for a vehicle including the driving force control means (C) for controlling the driving force of the driving wheels, the difference between the two driving wheels in the friction coefficient of the road surface contacting the driving wheels is equal to or more than a predetermined value. When it is determined that the vehicle is traveling on the split road surface, the split determination means (D) determines that the vehicle is traveling on the split road surface, and when the split determination means (D) determines that the vehicle is traveling on the split road surface, the driving force control means (C ) Is provided with a correction means (E) for increasing and correcting the control target value or the control start threshold value.

The "split judging means" is adapted to "determine that the vehicle is traveling on the split road surface when the difference in friction coefficient between the two driving wheels on which the driving wheels come into contact is equal to or larger than a predetermined value." However, whether or not the difference in friction coefficient exceeds a predetermined value depends on, for example, whether the difference between the slip rates of the two drive wheels with respect to the road surface or the rotational speed difference between the two drive wheels exceeds a predetermined value. Can be judged. When this determination is made based on whether or not the rotational speed difference between both drive wheels is equal to or greater than a predetermined value, the rotational speed of each drive wheel is detected, and the rotational speed difference is calculated based on the detection result. Of course, it may be determined whether or not the difference between the friction coefficients is equal to or more than a predetermined value based on the calculation result. However, the "differential limiting means" limits the "rotational speed difference allowable operation". It is also possible to provide a means for detecting that the "Yes" operation has been performed, and determine that the difference in the friction coefficient has become equal to or greater than a predetermined value based on the detection.

The above-mentioned "increasing correction" means a correction to the side where the "slip ratio of the driving wheels with respect to the road surface" increases.

[0012]

As described above, according to the first aspect of the present invention, when the split determining means determines that the vehicle is traveling on the split road surface, the correcting means controls the driving force control means. Since the target value or the threshold for control start is increased and corrected, during split road surface engine control will not start until a larger slip occurs on the drive wheels than during normal road surface travel, or during normal road surface travel Larger slip will be tolerated during engine control. That is, even if one driving wheel slips when traveling on a split road surface, the correction means allows a larger slip than when traveling on a normal road surface, so that an excessive engine output limit is prevented. As a result, the acceleration of the vehicle can be maximized by the other drive wheel that has a sufficient grip on the road surface.

Therefore, according to the present invention, the acceleration performance can be improved not only when the vehicle is traveling on the normal road surface but also when the vehicle is traveling on the split road surface.

The correction amount in the increase correction may be calculated according to claim 2.
As described above, if the friction coefficient is changed according to the size of the difference, it becomes possible to control the driving force in a more detailed manner, thereby further improving the acceleration performance during split road traveling. it can.

Further, since the turning performance is more important than the accelerating property from the viewpoint of importance of running stability during the vehicle turning traveling, as described in claim 3, during the vehicle turning traveling by the correction limiting means. It is preferable to limit the increase correction.

[0016]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 2 is a schematic configuration diagram showing an embodiment of a vehicle slip control device according to the present invention.

As shown in FIG. 2, in a vehicle provided with this slip control device, the left and right front wheels 1 and 2 are driven wheels, and the left and right rear wheels 3 and 4 are drive wheels. From transmission 6 to propeller shaft 7 and differential 8
And the left and right rear wheels 3, 4 via the left and right drive shafts 9, 10.
To be transmitted to.

The differential 8 allows the difference in rotational speed between the rear wheels 3 and 4 and the differential 8
Is a so-called limited slip differential (LSD), which has a built-in clutch 25 (differential limiting means) that operates when the difference in rotational speed between the rear wheels 3 and 4 exceeds a predetermined value to lock the differential device 8. Is configured as.

The wheels 1 to 4 are provided with disks 11a to 14a which rotate integrally with the wheels 1 to 4, respectively.
In response to the supply of the braking pressure, these disks 11a-14
and brake devices 11 to 14 including calipers 11b to 14b for braking the rotation of a, respectively.
Further, a brake control system 15 is provided for performing a braking operation on these brake devices 11-14.

The brake control system 15 includes a booster 17 for increasing the stepping force of a brake pedal 16 by a driver, and a master cylinder 18 for generating a braking pressure according to the stepping force increased by the booster 17. And have. The front wheel braking pressure supply lines 19 and 20 guided from the master cylinder 18 are the calipers 11b and 12 of the brake devices 11 and 12 on the left and right front wheels 1 and 2.
b respectively. Then, the braking pressure corresponding to the depression force of the brake pedal 16 generated in the master cylinder 18 is applied to the braking devices 11, 1 on the left and right front wheels 1, 2 via the braking pressure supply lines 19, 20 for the front wheels.
The front wheels 1 and 2 are respectively braked by the braking force corresponding to these braking pressures.

The booster 17 is connected to a working pressure supply line 22 for supplying a working pressure from the pump 21 and a return line 23 for returning excess brake oil generated in the booster 17 to a reservoir tank. Further, the first braking pressure supply line 24 guided from the booster 17 is branched at a point X, and the left and right rear wheels 3, 4 are branched from the branch point X.
Calipers 13b, 1 of the brake devices 13, 14 in
Rear wheel braking pressure supply lines 29 and 30 are led to 4b.

On the other hand, in the intake passage 35 of the engine 5, a main throttle valve 37 connected to an accelerator pedal 36 operated by a driver and a sub throttle valve 39 connected to a throttle opening adjusting actuator 38 are installed. The intake air amount of the engine 5 is variably controlled and the engine output is adjusted by adjusting the opening amounts of the throttle valves 37 and 39.

The slip control device comprises an electronically controlled control unit (hereinafter referred to as "ECU") 40, and the ECU 40 is adapted to perform traction control. In the traction control, when the slip ratios of the rear wheels 3 and 4 which are the driving wheels with respect to the road surface become equal to or more than a predetermined value, the driving force of each of the rear wheels 3 and 4 is set so that the slip ratio approaches a predetermined target slip ratio. The control of the driving force is specifically performed by limiting the engine output (engine control).

The ECU 40 is provided with signals from wheel speed sensors 41 to 44 for detecting the rotation speeds of the wheels 1 to 4,
A signal from the engine speed sensor 45 that detects the engine speed, a signal from the accelerator position sensor 48 that detects the depression amount of the accelerator pedal 36, and a signal from the steering angle sensor 49 that detects the steering angle. The ECU 40 controls the operation of the throttle opening adjustment actuator 38 for adjusting the opening of the sub-throttle valve 29 based on these signals.

The ECU 40 is also adapted to perform a friction coefficient estimation process necessary for determining a control target value and a control start threshold value in traction control.

The friction coefficient estimating process will be briefly described. For example, the left rear wheel 3 is performed as follows. That is, the ECU 40 uses the wheel speed sensor 41,
The average front wheel speed V _F obtained from the rotational speeds of the left and right front wheels 1 and 2 indicated by the signal from the reference numeral 42 is a predetermined lower limit value V _O (for example, 5 k
m / h), and when the average front wheel speed V _F is equal to or higher than the lower limit value V _O , the road surface friction coefficient μ is estimated by the average front wheel speed V _F and the front wheel acceleration A _F obtained from the average front wheel speed V _F. ..

Here, the road surface friction coefficient μ is extremely low μ
Any one of the numerical values divided into 5 stages from 1 indicating a road to 5 indicating a high μ road is selected.

On the other hand, when the ECU 40 determines that the average front wheel speed V _F is smaller than the lower limit value V _{O, the} rear wheel speed V _RL , V _RR obtained from the signals from the sensors 43, 44 is calculated. It is determined whether or not any of the accelerations A _RL and A _RR exceeds a predetermined reference value A _O (for example, 2G).
The road friction coefficient μ corresponding to the engine speed N indicated by the signal from No. 5 is estimated. On the other hand, when it is determined that both the rear wheel accelerations A _RL and A _RR are smaller than the reference value A _O , a fixed value (for example, 3) is selected as the road surface friction coefficient μ.

Traction control by the ECU 40 is performed as follows.

That is, first, the ECU 40 determines from the table in which the road surface friction coefficient μ is set in advance as a parameter.
Engine control start threshold value S _EO and engine control target value S _E
And read out.

Table 1 shows the relationship between the road surface friction coefficient μ and the engine control start threshold value S _EO and the target value S _E.
become that way. In this embodiment, the engine control start threshold value S _EO is set to the same value as the engine control target value S _E.

[0033]

[Table 1]

In Table 1 above, the control start threshold value S _EO and the control target value S _E are set as values corresponding to the slip ratios of the rear wheels 3, 4 with respect to the road surface.

The ECU 40 uses the wheel speed sensors 43, 4 and 4 described above.
From the rear wheel speeds V _RL and V _RR indicated by the signal from No. 4 and the average front wheel speed V _F from the signals from the wheel speed sensors 41 and 42, the following equations (1) and (2) are applied to the road surface of the left rear wheel 3. The first slip rate S ₁ and the second slip rate S ₂ for the road surface of the right rear wheel 4 are calculated.

S ₁ = (V _RL −V _F ) / V _RL (1) S ₂ = (V _RR −V _F ) / V _RR (2) The ECU 40 controls the first and second slip ratios S ₁ ,
As shown in FIG. 3, when any one of S ₂ exceeds the engine control start threshold value S _EO (t ₁ ), engine control is started and the throttle opening is adjusted so that the engine control target value S _E is obtained. The sub-throttle valve 39 is feedback-controlled via the adjusting actuator 38. As a result, the output torque of the engine 5 is controlled so as to converge to the engine control target value S _E.

Since the engine control is uniformly performed on both the rear wheels 3 and 4, if the engine control is carelessly performed, the following problems occur. That is, when traveling on a split road surface, one driving wheel (for example, the rear wheel 3) largely slips, but at that time, the other driving wheel (the rear wheel 4 in the above example) hardly slips in many cases. In such a case, when the engine control is started and the engine output is limited due to a large slip of the one driving wheel, the other driving wheel has a sufficient gripping force on the road surface, Since the supply of the driving force to the other driving wheel is also uniformly limited, there arises a problem that the acceleration performance is unduly hindered.

For this reason, in the present embodiment, when the road surface is split, the split control (which will be described later) is performed instead of the normal control so that the control target value S _E in the engine control is increased and corrected. It has become. By this split control, the acceleration performance is improved not only during normal road surface traveling but also during split road surface traveling.

In order to perform the split control, the EC
The U40 makes a split determination of the road surface condition based on the signals input from the wheel speed sensors 41 to 44. That is, the ECU 40 sequentially determines the spin patterns of the left and right rear wheels 3 and 4, which are the driving wheels, based on the signals input from the wheel speed sensors 41 to 44 for each control cycle, and stores them in the memory 50 the previous time. The split determination is performed by comparing the spin pattern of No. 1 and the spin pattern of this time with the split determination map stored in ROM in advance. Then, the split control flag F _S is set to 1 when other predetermined execution conditions are satisfied, and the split control flag F _S is reset to 0 when the predetermined release condition is satisfied. There is.

A timer 51 for managing split control is connected to the ECU 40.

Next, the traction control in this embodiment will be described. This traction control is performed as shown in the flow chart of FIG.

That is, the ECU 40 reads various data in step S1, executes the friction coefficient estimation process in step S2, and executes the split determination process in step S3. Then, in step S4, it is determined whether or not the split control flag F _S is set to 1, and if it is not set to 1, normal control is executed in step S5. On the other hand, if the flag F _S is set to 1, the process proceeds to step S6 to execute a predetermined split control.

The above-mentioned split determination processing will be specifically described as shown in the flowchart of FIG.

That is, the ECU 40 reads various data in step T1 and then determines the spin pattern P _SP for the left and right rear wheels 3 and 4 in step T2. That is, the ECU 40 sets the first spin flag F ₁ to 1 when the first slip value S ₁ obtained from the left rear wheel speed V _RL and the average front wheel speed V _F exceeds, for example, the engine control target value S _E. , The second slip value S ₂ obtained from the right rear wheel speed V _RL and the average front wheel speed V _F is the engine control target value S 2.
_{When E} is exceeded, the second spin flag F ₂ is set to 1. Then, these first and second spin flags F ₁ ,
By comparing F ₂ with the spin pattern map in which the spin flag is set as a parameter in advance, the present spin pattern P _SP is sequentially determined. Here, as the spin pattern map, as shown in FIG. 6, when both the _first and second spin flags F ₁ and F ₂ are 0, the value of the current spin pattern P _SP is 0 and the first spin flag F _{1 is} Is 1
When the second spin flag F ₂ is 0, the value of the current spin pattern P _SP is 1, and when the first spin flag F ₁ is 0 and the second spin flag F ₂ is 1, the current spin pattern P _{SP is}
Is 2, and both the first and second spin flags F ₁ and F ₂ are 1, the value of the current spin pattern P _SP is set to 3.

[0045] Then, ECU 40 the previous spin pattern P _SP which is stored in the current spin pattern P _SP and the memory 50 determined at Step T3 'and advance both patterns P _SP as shown in FIG. 7, P _SP' , Is set as a parameter, and the split control is performed by comparing the split determination map (step T3).

Here, as shown in FIG. 7, when the present spin pattern P _SP indicates that the left and right rear wheels 3 and 4 are in the non-spin state, the split determination map basically indicates the value of the split determination flag F _SP . Is set to 0 indicating a non-split state, but when either one of the left and right rear wheels 3 and 4 indicates the spin state last time, the flag F is set.
_{The SP} value is set to 2 indicating the split continuation state. This is to improve responsiveness when re-spin occurs. Further, when the present spin pattern P _SP indicates that one of the left and right rear wheels 3 and 4 indicates the spin state, the value of the split determination flag F _SP is basically set to 1 indicating the split state. However, when the other rear wheels 3 and 4 indicate the spin state last time, the value of the flag F _SP is 0 indicating the non-split state.
Is set to be This is to prevent an erroneous determination as a split state when the left and right drive wheels alternately enter the spin state when traveling on a low μ road such as an ice pattern. Then, when the present spin pattern P _SP indicates that both the left and right rear wheels 3 and 4 are in the spin state, the split determination flag F _SP is set to 0, which indicates the non-split state.

[0047] Then, ECU 40 proceeds to step T4 in the flowchart of FIG. 5, the split determination flag F _SP
Is determined to be 2, and if NO is determined, step T
'While replacing the previous spin pattern P _SP branches to step T6 when it is determined that YES' 5 at this spin pattern P _SP last spin pattern P _SP to hold.

Then, the ECU 40 determines in step T7 whether or not the value of the split determination flag F _SP is 0, and the result is YES.
If it is determined that the count value T _M of the timer 51 is reset, the value of the split control flag F _S is set to 0, which indicates that split control is not executed, in step T9.

On the other hand, when the ECU 40 determines in step T7 that the value of the split determination flag F _SP is not 0, it determines in step T10 whether the value of the split determination flag F _SP is 2 and determines NO. Sometimes the process proceeds to step T11 and the count value T of the timer 51 is
It is determined whether _M exceeds a predetermined upper limit value T ₀ (for example, 10 seconds), and if NO is determined, step T12
After adding the count value T _M in step T13, it is determined in step T13 whether or not the count value T _M is 0. If NO is determined, the process proceeds to step T14, in which the count value T _M is set to a predetermined lower limit value T _M. It is determined whether or not it exceeds ₁ (for example, 0.5 seconds), and if YES is determined in this step T14, the process proceeds to step T15 and the split control flag F _S
Set 1 to execute split control.

When the ECU 40 determines in step T10 that the value of the split determination flag F _SP is 2, the ECU 40 branches to step T16 and subtracts the count value T _M of the timer 51, and then returns to step T13. To do. Then, at that time, when the count value T _M is 0, the process proceeds to step T9 and the value of the split control flag F _S is set to 0. As a result, the split control is released and the control shifts to the normal control.

When the ECU 40 makes a negative determination in step T14, the ECU 40 proceeds to step T17 and determines whether or not the start μ estimation flag F _MS is set to 1. That is, it is determined whether or not the road surface friction coefficient is estimated at the time of starting. Then, the flag F
When _{the MS} is set to 1, the flow advances to step T18 left and right road surface friction coefficient mu _L, mu _R of the deviation [Delta] [mu (= |
μ _L −μ _R |) exceeds a predetermined reference value μ ₀ , and when YES is determined, the process returns to step T15 and the split control flag F _S is set to 1,
Split control will be performed.

In the split control, the ECU 40
Performs a predetermined rough road determination processing to determine whether or not the traveling road surface is a rough road. That is, the ECU 40
For example, if the number of times the deceleration or acceleration of the rear wheels 3 and 4 exceeds a predetermined upper limit value or lower limit value within a fixed time is less than a set value, it is determined that the road surface is not a bad road, and the bad road flag F _A Is maintained at 0 while the values indicating the acceleration and deceleration exceed the upper limit value and the lower limit value within a certain period of time or more, it is determined that the road surface is a bad road and the bad road flag is determined. F _A is set to 1.

Next, the contents of the split control will be described as shown in the flowchart of FIG.

That is, the ECU 40 reads various data in step U1, and then determines in step U2 whether or not the steering angle θ indicated by the signal from the steering angle sensor 49 is larger than a predetermined value θ _0. If it is determined, step U
In step 3, it is determined whether or not the rough road flag F _A is set to 1, which indicates a rough road condition. When the result is NO, the routine proceeds to step U4, where the accelerator depression rate A is set in advance as shown in FIG.
The engine control target value S _E is corrected based on the map set as the parameter. Here, accelerator depression rate A
Is expressed as a percentage with respect to the total depression amount of the accelerator pedal 36. When the depression amount is small when the accelerator depression ratio is 50%, the engine control target value correction coefficient K is set.
₁ becomes 1.5, and the engine control target correction coefficient K ₁ is set to 2.0 when the depression amount is large. That is, the engine control target value S _E is corrected to a greater extent as the accelerator depression amount increases.

Then, the ECU 40 proceeds to step U5 to set the basic throttle gain G ₀ . In other words, EC
As shown in FIG. 10, U40 uses the gain label table in which the deviation of the drive wheel speed with respect to the engine control target value S _E and the drive wheel speed change amount are set as parameters, and the actual drive wheel speed deviation and the drive wheel speed are set. Call the gain label of the throttle opening corresponding to the speed change amount. Then, the basic throttle gain G ₀ corresponding to the gain label thus called is called from the table set in accordance with the gain raven as shown in FIG. Here, the basic throttle gain G ₀ is set as a value expressed as a percentage with respect to the total rotation angle from the fully closed state to the fully opened state of the sub throttle valve 39. That is, when the above-mentioned gain label is NB indicating the maximum gain on the − side, −10%
The throttle gain of will be obtained. Note that the above gain label indicates the minimum gain when NS is −,
Is set to indicate an intermediate gain on the − side, the maximum gain on the PB + side, PS is the maximum gain on the + side,
PM is set to show an intermediate gain between the two. And, ZO indicates a throttle gain of 0%.

Next, the ECU 40 executes step U6 to judge whether or not the basic throttle gain G ₀ is larger than 0, and when it judges YES, executes step U7 to set the accelerator pedal depression rate as shown in FIG. First gain correction coefficient K obtained from a map in which A is set as a parameter
₂ is used to correct the basic throttle gain G ₀ and the final throttle amount T _H is calculated. Here, the first gain correction coefficient K ₂ is set when the accelerator depression rate A exceeds 50%.
It is set to be 2.0. That is, the gain in the opening direction of the sub-throttle valve 39 is corrected to be large. Then, ECU 40 outputs a control signal to the actuator 38 so that the throttle amount T _H is obtained.

When it is determined NO at step U6, the ECU 40 proceeds to step U8 and uses the second gain correction coefficient K ₃ obtained from the map in which the accelerator depression rate A is set as a parameter as shown in FIG. Then, the basic throttle gain G ₀ is corrected to calculate the final throttle amount T _H. Here, the second gain correction coefficient K ₃ is set to 0.5 when the accelerator depression rate exceeds 50%. That is, the sub throttle valve 39
Will be corrected so that the gain in the closing direction becomes smaller.

Next, the operation of this embodiment will be described.

First, as shown in FIG. 14, the left rear wheel speed V _RL
Is almost the same as the average front wheel V _F, and the rear right wheel speed V
The second spin flag F ₂ is set to 1 when _RR exceeds the engine control start threshold value S _EO (equal to the engine control target value S _E ) (t ₃ ). In this case, the rear left wheel speed V
_{Since RL} is stuck to the average front wheel speed V _F , the first spin flag F ₁ is maintained at 0. Therefore, the split determination flag F _SP is set to 1, and at the same time, the timer 51 starts counting up.

When the timer 51 counts up the predetermined lower limit value T ₁ (t ₄ ), the split control flag F _S is set to 1 and the normal control is switched to the split control. That is, the engine control target value S _E increases from the time t ₄ . In this case, when the accelerator depression rate A exceeds 50%, the engine control target value S _E is largely corrected accordingly.

Even if the split state is determined, the split control is not actually performed until the count value T _{M of the} timer 51 exceeds the predetermined lower limit value T ₁ , so that the left rear wheel 3 Becomes a spin state, the split determination flag F _SP switches to 0 indicating a non-split state, thereby preventing malfunction.

Then, at a time point (t ₅ ) when the accelerator depression rate A falls below 50% (t ₅ ), the engine control target value S _E is somewhat lowered.

As described above, the engine control target value S is determined by the depression amount of the accelerator pedal 36 operated by the driver.
_Since the correction amount of _E will be different, accelerator pedal 3
When the depression amount of 6 is small, the engine output is prevented from excessively increasing, and running stability is ensured.
When the amount of depression of the accelerator pedal 36 is large, the engine output is increased to reflect the driver's willingness to accelerate, and good acceleration is obtained.

As shown by the chain line in FIG. 9, the engine control target value correction coefficient K ₁ may be set to 1 when the accelerator depression rate A is smaller than 50%. In this case, the split control is performed when the accelerator depression rate A exceeds 50%.

Further, while the left rear wheel speed V _RL is stuck to the average front wheel speed V _F , the right rear wheel speed V _RR is the engine control target value S _E.
2 is set to the value of the split determination flag F _SP , and the timer 51 is switched from counting up to counting down while maintaining the split control flag F _S at 1 from the time t ₆ .
In this embodiment, the gain for the count-up of the timer 51 is set to 0.5. That is, for example, when the timer 51 counts up for 5 seconds, the count value T _M becomes 0 and the split control flag F _S is reset to 0 only when the countdown is continued for 10 seconds.

In this case, if the right rear wheel speed V _RR exceeds the engine control target value S _E again before the count value T _{M of the} timer 51 reaches 0, the split determination flag F _SP is set to 1. At the same time, the timer 51 restarts counting up from the time t ₇ . This improves the responsiveness of split control when the right rear wheel 4 re-spins.

When the vehicle shifts to the turning state during the split control, the split control is switched to the normal control and the engine control target value S _E is lowered. This prevents the vehicle from becoming unstable in running.

Further, even when it is determined that the road is rough, the control is switched to the normal control. Therefore, excessive rotation of the rear wheels 3 and 4 on a bad road where the road surface condition is unstable is prevented, and malfunction due to erroneous determination is also avoided.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of a vehicle slip control device according to the present invention.

FIG. 2 is a schematic configuration diagram showing an embodiment of a vehicle slip control device according to the present invention.

FIG. 3 is a time chart showing the operation of the above embodiment (basic control of traction control).

FIG. 4 is a flowchart showing the operation of the above embodiment.

FIG. 5 is a flowchart showing split determination processing in the above embodiment.

FIG. 6 is an explanatory diagram showing an example of a spin pattern map used in the split determination process.

FIG. 7 is an explanatory diagram showing an example of a split determination map used in the split determination processing.

FIG. 8 is a flowchart of the split control process.

FIG. 9 is an explanatory diagram showing an example of a map of an engine control target value correction coefficient with an accelerator depression rate as a parameter.

FIG. 10 is an explanatory diagram showing an example of a table used for calling a gain label.

FIG. 11 is an explanatory diagram showing an example of a table used for setting a basic throttle gain.

FIG. 12 is an explanatory diagram showing an example of a map of a first gain correction coefficient with an accelerator depression rate as a parameter.

FIG. 13 is an explanatory diagram showing an example of a map of a second gain correction coefficient with the accelerator depression rate as a parameter.

FIG. 14 is a time chart showing the operation of this embodiment.

[Explanation of symbols]

1, 2 front wheels 3, 4 rear wheels (driving wheels) 5 engine 8 differential device 13, 14 brake device 15 brake control system 25 clutch (differential limiting means) 36 accelerator pedal 38 throttle opening adjusting actuator 39 sub-throttle valve 40 ECU (driving force control means, split determination means, correction means, correction restriction means) 41 to 44 wheel speed sensor 46 first pressure sensor 47 second pressure sensor 48 accelerator position sensor 49 steering angle sensor

Claims (3)

[Claims] 1. A differential device provided in a power transmission path from an engine to left and right drive wheels and allowing a difference in rotation speed between these drive wheels, and a difference in rotation speed between the both drive wheels being a predetermined value or more. And a slip limiting device for limiting the rotational speed difference allowable operation by the differential device, the slip control device being provided in a vehicle, wherein the slip ratio of the drive wheels with respect to the road surface is a predetermined value or more. In the slip control device for a vehicle, the drive control means controls the drive force of the drive wheels by limiting the engine output so that the slip rate approaches a predetermined target slip rate. Split determination means for determining that the vehicle is traveling on a split road surface when the difference between the two driving wheels in the friction coefficient of the road surface with which the wheels come into contact is equal to or greater than a predetermined value; When it is determined that the traveling on a split road surface, a slip control device for a vehicle, characterized in that the control target value or the control start threshold and a correction means for correction of increasing the driving force control means. 2. The vehicle slip according to claim 1, wherein the correction means is configured to change a correction amount in the increase correction according to a magnitude of a difference between the friction coefficients. Control device. 3. The slip control device for a vehicle according to claim 1, further comprising correction limiting means for limiting the increase correction while the vehicle is turning.