JPH04328035A - Slit control device for vehicle - Google Patents

Abstract

PURPOSE:To perform proper slip control in accordance with a road surface condition, in the case of a vehicle in which a driving power distributing means for distributing an engine output to right/left drive wheels is provided. CONSTITUTION:By an ECU40 for controlling action of opening/closing valves 26, 27, 31, 32 and relief valves 33, 34 in a brake control system 15 and action of a throttle opening adjusting actuator 38 for adjusting an opening of a subthrottle valve 29 based on signals from wheel speed sensors 41 to 44 for detecting a rotational speed of each wheel 1 to 4, a spin condition of the right/ left rear wheels 3, 4, which are drive wheels, is periodically detected and also performing decision in accordance with a split decision map preset based on the spin condition. Till a difference between brake pressures, supplied to brake devices 13, 14 of the right/left rear wheels 3, 4, exceeds a predetermined value while a timer 15 of starting a count up after the decision reaches a predetermined lower limit value, execution of split control is restricted.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] This invention relates to a slip control device for a vehicle, particularly a vehicle equipped with a driving force distribution means such as a differential device that distributes engine output to a power transmission path from an engine to left and right drive wheels. The present invention relates to a slip control device that controls driving force according to the slip state of a wheel.

0002

[Prior Art] In recent years, vehicles have been equipped with traction control that suppresses the driving force when the driving wheels slip, in order to prevent the driving wheels from slipping due to excessive drive torque and reducing starting performance or acceleration. There is something I decided to do. This traction control is started, for example, when the rotational speed difference between the driving wheel and the driven wheel exceeds a predetermined value based on a signal from a wheel speed sensor that detects the rotational speed of the wheel. The driving force acting on the drive wheels is reduced by feedback-controlling the engine output or braking force so that it converges to a target value.

By the way, on a slippery road surface such as a snowy road, if excessive torque is transmitted to the drive wheels when starting or accelerating, the rotational speed of the drive wheels will increase due to the difference in the coefficient of friction between the drive wheels and the road surface on which they touch the ground. This difference may cause the vehicle to slip into a skidding state. This phenomenon is particularly noticeable in vehicles equipped with a drive force distribution means such as a differential in the power transmission path from the engine to the left and right drive wheels.

[0004] To solve this problem, for example, as disclosed in Japanese Patent Application Laid-Open No. 128028/1980, power from the power plant is distributed to the left and right drive wheels via a differential gear. In the vehicle,
Some systems detect the rotation speeds of the left and right drive wheels individually, and reduce the drive torque output from the power plant while the rotation speeds of these drive wheels are different. According to this, when there is a difference in rotational speed between the left and right drive wheels, the engine output is reduced, so that excessive driving force is not transmitted to the left and right drive wheels, and the above-mentioned inconvenience is avoided. That will happen.

[0005]

By the way, in cold regions and the like, there are many opportunities to drive on a so-called split road surface where the friction state of the road surface is different for the left and right drive wheels. In that case, if the drive torque is uniformly reduced when the rotational speeds of the left and right drive wheels are different, as in the prior art described in the above publication, for example, if the road surface on which one wheel touches the ground is a hindrance to normal driving. Even if there is sufficient grip force, if the grip force of the road surface that the other wheel contacts is somewhat insufficient, the drive torque will be reduced due to the rotational speed difference between both drive wheels. Even if the driver has the will to drive, sufficient starting or acceleration performance will not be obtained against that will.

Therefore, in normal conditions, normal traction control (hereinafter referred to as normal control) is performed to simply suppress the driving force when the driving wheels are in a spin state, and on split road surfaces, the driving wheels with a small degree of slip are controlled. The idea of switching to control that increases the transmitted drive torque (hereinafter referred to as split control) has been attracting attention, but the issue is the conditions for starting split control when it is determined that a split road surface is present. In other words, in this type of split control, by applying braking force to one drive wheel with a high degree of slip, the drive torque transmitted to the other drive wheel with a low degree of slip is relatively increased. However, for example, if split control is started in a state where braking pressure is insufficient, problems will arise in terms of control reliability, such as increasing the slippage of the drive wheels with a large degree of slippage.

The present invention provides a slip control device for a vehicle in which a drive force distribution means for distributing the engine output to the left and right drive wheels is provided in the power transmission path from the engine to the left and right drive wheels. The purpose is to enable slip control.

[0008]

[Means for Solving the Problem] That is, the slip control device for a vehicle according to the invention of claim 1 of the present application (hereinafter referred to as the first invention) has a system that extends from the engine to the left and right drive wheels, as shown in FIG. In a vehicle, the power transmission path is provided with a driving force distribution means that distributes the engine output to the left and right driving wheels, and the driving force control means A that controls the driving force according to the slip state of the driving wheels. First and second spin detection means B and C periodically detect the spin state of the drive wheels, and the spin states of the left and right drive wheels detected by the first and second spin detection means B and C, respectively. a split determination means D that performs a split determination on the road surface on which each of the driving wheels touches the ground according to a preset split determination rule based on the split determination rule; and a small slip degree that is controlled by the driving force control means A until a prescribed condition is satisfied after the split determination. The present invention is characterized in that a split control regulating means E is provided for regulating the execution of split control that increases the drive torque transmitted to the drive wheels.

[0009] In addition, the invention of claim 2 of the present application (hereinafter referred to as the second invention)
The slip control device for a vehicle according to the present invention is similar to the invention of claim 1, in which a driving force distribution means for distributing the engine output to the left and right driving wheels is provided in the power transmission path from the engine to the left and right driving wheels. , and a vehicle equipped with a driving force control means A that controls the driving force according to the slip state of the drive wheels, first and second spin detection means B that periodically detect the spin states of the left and right drive wheels, respectively. , C, and split determination for the road surface on which each of the drive wheels touches the ground according to a split determination rule set in advance based on the spin states of the left and right drive wheels respectively detected by the first and second spin detection means B and C. a split determination means D that performs the split determination, and a split control that restricts the execution of the split control that increases the drive torque transmitted to the drive wheels with a small degree of slip by the driving force control means A until a predetermined time has elapsed after the split determination. It is characterized by providing a regulating means E'.

[0010]The slip control device for a vehicle according to the invention of claim 3 of the present application (hereinafter referred to as the third invention) is similar to the invention of claim 1, in which a slip control device for a vehicle according to the invention of claim 3 of the present application is provided with A vehicle provided with a driving force distribution means for distributing the engine output to the left and right driving wheels, and a driving force control means A for controlling the driving force according to the slip state of the driving wheels, the same as in claim 1 above. , first and second spin detection means B and C that periodically detect the spin states of the left and right drive wheels, respectively, and left and right drive wheels that are detected by these first and second spin detection means B and C, respectively. and a split determination means D for determining a split on the road surface on which each of the drive wheels touches the ground according to a preset split determination rule based on the spin state of the drive wheel.
A differential pressure detection means F detects a differential pressure between the braking pressures supplied to the braking devices that respectively brake the left and right drive wheels, and a predetermined differential pressure between the braking pressures detected by the differential pressure detection means F after the split determination is made. The present invention is characterized by the provision of a split control regulating means E" for regulating the execution of split control for increasing the drive torque transmitted by the drive force control means A to the drive wheels with a small degree of slip until the slip level exceeds the value.

[0011]

[Operation] First, according to the first invention, even if it is determined that the road surface on which the left and right drive wheels touch the ground is in a split state, split control is not actually performed until a predetermined execution condition is satisfied. Therefore, malfunctions are prevented and control reliability is improved.

According to the second aspect of the invention, execution of the split control is restricted until a predetermined time has elapsed after the split determination, so that malfunctions such as when the left and right drive wheels are spinning alternately can be avoided. This will be prevented.

According to the third invention, split control is not performed until sufficient braking pressure is supplied to the brake device of the drive wheel in the slipping state, thereby preventing the vehicle from accidentally slipping. It turns out.

[0014]

[Examples] Examples of the present invention will be described below.

As shown in FIG. 2, in the vehicle according to this embodiment, the left and right front wheels 1 and 2 are driven wheels, and the left and right rear wheels 3 and 4 are driving wheels, and the output torque of the engine 5 is The power is transmitted from the transmission 6 to the left and right rear wheels 3 and 4 via a propeller shaft 7, a differential device 8, and left and right drive shafts 9 and 10.

Each of the wheels 1 to 4 has disks 11a to 14a that rotate integrally with the wheels 1 to 4,
These discs 11a to 14 are supplied with braking pressure.
Brake devices 11 to 14 each including calipers 11b to 14b are provided to brake the rotation of the vehicle a, and a brake control system 15 is provided to perform a braking operation on these brake devices 11 to 14.

This brake control system 15 includes a booster 17 that increases the force with which the driver depresses the brake pedal 16, and a master cylinder 18 that generates braking pressure in accordance with the increased force with which the brake pedal 16 is depressed by the booster 17. and has. Front wheel braking pressure supply lines 19 and 20 led from this master cylinder 18 are connected to calipers 11b and 12b of brake devices 11 and 12 for left and right front wheels 1 and 2, respectively. The braking pressure generated in the master cylinder 18 according to the depression force of the brake pedal 16 is directly transmitted to the braking devices 11 and 12 of the left and right front wheels 1 and 2 via the braking pressure supply lines 19 and 20 for each front wheel. The front wheels 1 and 2 are braked with braking forces corresponding to these braking pressures.

On the other hand, the booster 17 has an operating pressure supply line 22 that supplies the operating pressure from the pump 21, and a return line 23 that returns excess brake oil generated in the booster 17 to the reservoir tank. A first braking pressure supply line 24 connected and led from the booster 17
and a second braking pressure supply line 25 branched from the pump discharge side of the working pressure supply line 22, an electromagnetic first
, second on-off valves 26 and 27 are installed, respectively. A check valve 28 for preventing backflow is installed in the first braking pressure supply line 24 in parallel with the first on-off valve 26 . Further, the first and second braking pressure supply lines 24 and 25 are merged at a point
Brake pressure supply lines 29 and 30 for the rear wheels are led to b, and on these brake pressure supply lines 29 and 30,
Electromagnetic on-off valves 31, 32 and relief valves 33, 34 are installed, respectively.

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

[0020] Then, an electronic control unit (hereinafter referred to as ECU) 40 performs traction control.
This ECU 40 receives signals from wheel speed sensors 41 to 44 that detect the rotation speed of each wheel 1 to 4, and an engine rotation speed sensor 45 that detects the engine rotation speed.
A first pressure that is installed downstream of the on-off valve 31 in the rear wheel braking pressure supply line 29 leading to the brake device 13 of the left rear wheel 3 and detects the braking pressure supplied to the brake device 13. sensor 46 and a second pressure sensor that is installed downstream of the on-off valve 32 in the rear wheel braking pressure supply line 30 leading to the brake device 14 of the right rear wheel 4 and detects the braking pressure supplied to the brake device 14. 47, a signal from an accelerator position sensor 48 that detects the amount of depression of the accelerator pedal 36, and a signal from a steering angle sensor 49 that detects the steering angle, and based on these signals, the brake control system 15 On-off valve 26,2 in
7.31, 32 and relief valves 33, 34, and the throttle opening adjustment actuator 38 that adjusts the opening of the sub-throttle valve 29 are controlled. In other words, with the control signal from the ECU 40,
As shown in the figure, the first on-off valve 24 on the first braking pressure supply line 24 is opened, the second on-off valve 27 on the second braking pressure supply line 25 is closed, and the braking pressure supply lines 29 and 30 for rear wheels are closed. When the on-off valves 31 and 32 are open, braking pressure corresponding to the depression force of the brake pedal 16 generated by the booster 17 is applied to the left and right rear wheels via the first braking pressure supply line 24. 3, 4 to the brake devices 13, 14,
The rear wheels 3 and 4 are respectively braked with braking forces corresponding to these braking pressures.

On the other hand, when performing traction control using brake control, the ECU 40 closes the first on-off valve 26 and opens the second on-off valve 27. Therefore, the working pressure generated by the pump 21 does not go through the booster 17 and is used as braking pressure in the rear wheel braking pressure supply line 2.
Supplied on 9,30.

When the spin state of the left rear wheel 3 is detected, for example, by the signals from the respective wheel speed sensors 41 to 44, that is, the average front wheel speed VF is determined by averaging the rotational speeds of the front wheels 1 and 2, which are driven wheels. When it is detected that the rotational speed of the rear wheel 3, which is the driving wheel, is high with reference to A braking force is applied to the rear wheel 3 with a braking pressure according to the state of the brake. Note that when a spin state of the right rear wheel 4 is detected, the on-off valve 32 and the relief valve 34 on the braking pressure supply line 30 for the other rear wheel are opened and closed by duty control, and braking is performed according to the slip state. pressure on the rear wheel 4
braking force will be applied to. That is, in this embodiment, the braking forces applied to the left and right rear wheels 3 and 4 are independently controlled.

In particular, in this embodiment, the above ECU
Reference numeral 40 performs split determination of road surface conditions based on 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 drive wheels, based on the signals input from the respective wheel speed sensors 41 to 44 for each control cycle, and also determines the spin patterns of the left and right rear wheels 3, 4, which are the drive wheels, based on the signals inputted from the wheel speed sensors 41 to 44, and also determines the spin patterns of the left and right rear wheels 3, 4, which are drive wheels, based on the signals inputted from the respective wheel speed sensors 41 to 44, and A split determination is made by comparing the previous spin pattern and the current spin pattern with a split determination map stored in a ROM in advance. The split control flag FS is set to 1 when other predetermined execution conditions are satisfied, and the split control flag FS is reset to 0 when a predetermined release condition is satisfied.

Note that a timer 51 for managing split control is connected to the ECU 40.

Next, the traction control in this embodiment will be explained. This traction control is performed as follows according to the flow chart of FIG.

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

[0027] Here, an outline of the friction coefficient estimation process will be explained. For example, for the left rear wheel 3, it is performed as follows. That is, the ECU 40 controls the wheel speed sensor 41,
The average front wheel speed VF obtained from the rotational speeds of the left and right front wheels 1 and 2 indicated by the signal from
m/h), and when the average front wheel speed VF exceeds the lower limit value V0, the road surface friction coefficient μL is estimated from the front wheel acceleration AF obtained from this average front wheel speed VF and the average front wheel speed VF. .

[0028] Here, the road surface friction coefficient μ is selected from one of five numerical values, from 1 indicating an extremely low μ road to 5 indicating a high μ road.

On the other hand, when the ECU 40 determines that the average front wheel speed VF is smaller than the lower limit value V0, the rear wheel acceleration ARL determined from the left rear wheel speed VRL indicated by the signal from the sensor 43 is set to a predetermined reference value A0. (for example, 2G), and when the determination is YES, the starting μ estimation flag FMS is set to 1, and then the engine speed N indicated by the signal from the engine speed sensor 45 is set. Accordingly, the road surface friction coefficient μL for the left rear wheel 3 is estimated.

[0030] Also, the rear wheel acceleration ARL is equal to the above reference value A0.
When it is determined that the road friction coefficient μL is smaller than , a fixed value (for example, 3) is selected as the road surface friction coefficient μL.

Note that the road surface friction coefficient μR for the right rear wheel 4 is estimated in the same manner.

Also, regarding the normal control, the left and right rear wheels 3,
For example, the left rear wheel 3 is performed in the following manner. That is,
The ECU 40 reads out the engine control target reference value and the brake control target reference value from a map preset with the road surface friction coefficient μL as a parameter, and also corrects these values according to the average front wheel speed VF, etc., which represents the vehicle speed. As a result, the final engine control target value SE and brake control target value SB are obtained.

Then, the average front wheel speed VF indicated by the signals from the wheel speed sensors 41 and 42 is subtracted from the left rear wheel speed VRL indicated by the signal from the wheel speed sensor 43 to obtain a first slip value S1 for the left rear wheel 3. is calculated, and this first slip value S1 becomes the engine control target value SE as shown in FIG.
At the time (t1) when the target value SE is exceeded, engine control is started, and the sub-throttle valve 39 is feedback-controlled via the throttle opening adjustment actuator 38 so that this target value SE is obtained. Thereby, the output torque of the engine 5 is controlled so as to converge to the engine control target value SE.

Even with this engine control, the slip condition is not resolved and the left rear wheel speed VRL continues to increase, and at the time when the first slip value S1 exceeds the brake control target value SB (
At t2), braking pressure is supplied to the brake device 13 in the rear wheel 3, and control using both engine control and brake control is performed. Note that the braking pressure is the first slip value S1
is feedback-controlled so that it becomes the brake control target value SB.

[0035] Then, at the time (t3) when the first slip value S1 has decreased to the brake control target value SB, the brake control is stopped and the braking pressure is reduced. Note that engine control is performed until a predetermined termination condition is satisfied.

[0036] Normal control is also performed for the right rear wheel 4 in the same manner. That is, the ECU 40 subtracts the average front wheel speed VF from the right rear wheel speed VRR indicated by the signal from the wheel speed sensor 44, and calculates the second
Calculate the slip value S2. Then, when this first slip value S2 exceeds the engine control target value SE set in the same manner as above, engine control is started, and the throttle opening adjustment actuator 38 is adjusted so that this target value SE is obtained. The sub-throttle valve 39 is feedback-controlled via the sub-throttle valve 39. Even with this engine control, the slip condition is not resolved and the right rear wheel speed VRR continues to increase, and when the second slip value S2 exceeds the brake control target value SB as described above, both engine control and brake control are stopped. A combined control is performed. Then, when the second slip value S2 decreases to the brake control target value SB, the brake control is stopped and the braking pressure is reduced.

On the other hand, in the above split control, for example, the engine control target value SE is set higher than in normal times. In other words, for example, if the right rear wheel 4 is in a situation where it is more likely to slip than the left rear wheel 3, when the second slip value S2 for the right rear wheel 4 exceeds the brake control target value SB, the braking pressure for the rear wheel is supplied. Braking pressure is supplied to the brake device 14 via the line 30, which causes the right rear wheel 4 to
braking force is applied to. In this case, when the first slip value S1 for the left rear wheel 3, which is less likely to slip relative to the right rear wheel 4, does not reach the brake control target value SB, no braking pressure is supplied to the brake device 13, so the left rear No braking force acts on wheel 3. Therefore, the distribution ratio of the driving force to the left rear wheel 3 increases, and the function of the differential device 8 appears to be restricted. As a result, the engine output increased by the amount that the engine control target value SE is set higher than normal is preferentially transmitted to the left rear wheel 3, which improves starting performance or acceleration on this type of split road surface. This will improve your sexuality.

Next, the split determination process, which is a characteristic part of the present invention, will be explained in detail according to the flowchart shown in FIG.

That is, the ECU 40 reads various data in step T1, and then determines the spin pattern PSP for the left and right rear wheels 3 and 4 in step T2. That is, when the first slip value S1 obtained from the left rear wheel speed VRL and the average driven wheel speed VF exceeds the engine control target value SE, the ECU 40 sets the first spin flag F1 to 1.
Also, when the second slip value S2 obtained from the right rear wheel speed VRL and the average front wheel speed VF exceeds the engine control target value SE, the second spin flag F2 is set to 1. Then, by comparing these first and second spin flags F1 and F2 with a spin pattern map in which the spin flags are set in advance as parameters, the current spin pattern PSP is sequentially determined. Here, as shown in FIG. 6, the spin pattern map is as follows:
When both the first and second spin flags F1 and F2 are 0, the value of the current spin pattern PSP is 0, and when the first spin flag F1 is 1 and the second spin flag F2 is 1, the value of the current spin pattern PSP is 1. , first spin flag F1
is 0 and the second spin flag F2 is 0, the value of the current spin pattern PSP is 2, and the first and second spin flags F1
, F2 are both 1, the current spin pattern PSP
The value of is set to 3.

Next, the ECU 40 converts the current spin pattern PSP determined in step T3 and the previous spin pattern P'SP stored in the memory 50 into parameters in advance, as shown in FIG. A split determination is made by comparing the split determination map set as (step T3).

Here, as shown in FIG. 7, the above split determination map basically indicates that when the current spin pattern PSP indicates that the left and right rear wheels 3 and 4 are in a non-spin state, the value of the split determination flag FSP is non-spin. It is set to 0, which indicates a split state, but the previous left and right rear wheels 3,
4 indicates a spin state, the value of the flag FSP is set to 2, which indicates a split continuation state. This is to improve responsiveness when re-spin occurs. Additionally, when the current spin pattern PSP indicates that either the left or right rear wheels 3, 4 are in a spin state, the value of the split determination flag FSP is basically set to 1, which indicates a split state. When the other rear wheels 3 and 4 indicate a spin condition last time, the value of the flag FSP is set to 0, which indicates a non-split condition. This is to prevent erroneously determining that the vehicle is in a split state when the left and right drive wheels are alternately in a spin state when driving on a low μ road such as an icy road. When the current spin pattern PSP indicates that both the left and right rear wheels 3 and 4 are in a spin state, the value of the split determination flag FSP is set to 0, which indicates a non-split state.

Next, the ECU 40 proceeds to step T4 of the flowchart of FIG. 5, and sets the split determination flag FS.
It is determined whether the value of P is 2 or not, and if the determination is NO, the current spin pattern PSP is replaced with the previous spin pattern P'SP in step T5, and if the determination is YES, the process branches to step T6 and the previous spin pattern P' is replaced. SP
hold.

Then, the ECU 40 determines whether or not the value of the split determination flag FSP is 0 in step T7, and if the determination is YES, the ECU 40 proceeds to step T8, resets the count value TM of the timer 51, and then proceeds to step T9. Set the value of the split control flag FS to 0, which indicates that split control will not be executed.

On the other hand, when the ECU 40 determines in step T8 that the value of the split determination flag FSP is not 0, it determines in step T10 whether the value of the split determination flag FSP is 2 or not. Proceeding to step T11, it is determined whether the count value TM of the timer 51 exceeds a predetermined upper limit T0 (for example, 10 seconds), and when the determination is NO, step T11 is performed.
After adding the count value TM in step 12, it is determined in step T13 whether or not the count value TM is 0. When the determination is NO, the process proceeds to step T14, and this time the count value TM is added.
It is determined whether or not exceeds a predetermined lower limit value T1 (for example, 0.5 seconds), and when the determination is YES, the process proceeds to step T15, and the first and second pressure sensors 46, 4
It is determined whether the differential pressure δp of the brake oil pressure indicated by the signal from 7 exceeds a predetermined reference value p0, and when the determination is YES, the process proceeds to step T16 and the split control is performed based on the value of the split control flag FS. Set 1 to execute.

Further, when the ECU 40 determines that the value of the split determination flag FSP is 2 in step T10, the process branches to step T17, and after subtracting the count value TM of the timer 51, the process proceeds to step T13.
Return to. If the count value TM is 0 at this time, the process moves to step T9 and the value of the split control flag FS is set to 0. As a result, split control is canceled and a transition is made to normal control.

Note that when the ECU 40 determines NO in step T14, the process proceeds to step T18 and determines whether the starting μ estimation flag FMS is set to 1 or not. In other words, it is determined whether the road surface friction coefficient has been estimated at the time of starting. Then, when the flag FMS is set to 1, step T1
Proceed to step 9 and find the deviation δμ(
=|μL−μR|) exceeds a predetermined reference value μ0, and when the determination is YES, step T1
5, it is determined whether the differential pressure δp of the brake oil pressure detected by the first and second pressure sensors 46 and 47 exceeds a predetermined reference value p0. In this case, the above differential pressure δ
When p exceeds the predetermined reference value p0, the split control flag FS is set to 1 in the same way as above, and split control is performed.

Next, the operation of this embodiment will be explained.

First, as shown in FIG. 8, the left rear wheel speed VRL
When the right rear wheel speed VRR exceeds the engine control target value SE (t4) when there is almost no difference between the average front wheel speed VF and the average front wheel speed VF.
Then, the second spin flag F2 is set to 1. In this case, the first spin flag F1 is maintained at 0 because the left rear wheel speed VRL is stuck to the average front wheel speed VF. Therefore, the split determination flag FSP is set to 1, and at the same time, the timer 51 starts counting up. When the right rear wheel speed VRR continues to increase and exceeds the brake control target value SB, supply of braking pressure to the brake device 14 of the right rear wheel 4 is started at that time (t5).

Then, at the time (t6) when the timer 51 counts up a predetermined lower limit value T1, the differential pressure δp of the braking pressures supplied to the brake devices 13 and 14 between the left and right rear wheels 3 and 4 reaches the reference value. When it exceeds p0, the split control flag FS is set to 1 and normal control is switched to split control. In other words, the relevant time t6
The engine control target value SE increases by a predetermined amount. In this case, while the second slip value S2 for the right rear wheel 4 in the slip state exceeds the brake control target value SB, one rear wheel braking pressure supply line 20
Braking pressure is continuously supplied to the brake device 14 via the brake system 14, and braking force is applied to the right rear wheel 4, and the left rear wheel 3 whose first slip value S1 does not reach the brake control target value SB
Braking pressure is not supplied to the brake device 13 and no braking force is applied. As a result, the engine output whose suppressed state is relaxed by the amount that the engine control target value SE has increased is preferentially distributed to the left rear wheel 3, thereby improving starting performance or acceleration performance.

In this way, even if it is determined that the split state is present, split control is not actually performed until the count value TM of the timer 51 exceeds the predetermined lower limit value T1. When the spin state occurs, the split determination flag FSP switches to 0 indicating a non-split state, thereby preventing malfunctions.

Furthermore, in this embodiment, even if the count value TM of the timer 51 exceeds the predetermined lower limit T1, the brake devices 13 of the left and right rear wheels 3, 4
, 14, the split control is not performed until the differential pressure δp of the braking pressure supplied to the right rear wheel 4 exceeds the reference value p0.
The engine output will not increase when the braking pressure of the brake device 14 is insufficient, thereby preventing the vehicle from slipping unexpectedly.

[0052] Then, the left rear wheel speed VRL is equal to the average front wheel speed VF.
If the right rear wheel speed VRR falls below the engine control target value SE, the split judgment flag F
The value of SP is set to 2, and the timer 51 is switched from counting up to counting down from time t7 while maintaining the split control flag FS at 1. In this embodiment, the gain of the timer 51 for counting down is set to 0.5. That is, for example, when the timer 51 counts up for 5 seconds, the count value TM becomes 0 only when the countdown continues for 10 seconds, and the split control flag FS is reset to 0.

In this case, if the right rear wheel speed VRR exceeds the engine control target value SE again before the count value TM of the timer 51 reaches 0, the split determination flag FS
P is set to 1, and the timer 51 restarts counting up from time t8. This improves the responsiveness of the split control when the right rear wheel 4 spins again.

[0054]

As described above, according to the present invention, even if it is determined that the road surface on which the left and right drive wheels touch the ground is in a split state, split control is not actually performed until a predetermined execution condition is satisfied. Since this is not performed, malfunctions are prevented and control reliability is improved.

Further, according to the second invention, the execution of split control is restricted until a predetermined time has elapsed after the split determination, so that malfunctions such as when the left and right drive wheels are spinning alternately can be avoided. This will be prevented.

According to the third invention, the split control is not performed until sufficient braking pressure is supplied to the brake device of the drive wheel in the slipping state, so that the vehicle is prevented from inadvertently slipping. become.

[Brief explanation of the drawing]

FIG. 1 is a functional block diagram showing the basic configuration of a first invention.

FIG. 2 is a diagram of the vehicle control system.

FIG. 3 is a flowchart showing basic control of traction control.

FIG. 4 is a time chart diagram showing a control mode of normal traction control.

FIG. 5 is a flowchart showing split determination processing.

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

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

FIG. 8 is a time chart diagram showing the operation of this embodiment.

[Explanation of symbols]

1, 2 Front wheels 3, 4 Rear wheels 5 Engine 8 Differential device 40 ECU 41 to 44 Wheel speed sensor 46 First pressure sensor 47
Second pressure sensor 51
timer

Claims (3)

[Claims] Claim 1: A drive system in which a drive force distribution means for distributing the engine output to the left and right drive wheels is provided in a power transmission path from the engine to the left and right drive wheels, and the drive force is controlled in accordance with the slip state of the drive wheels. A slip control device for a vehicle equipped with a force control means, comprising first and second spin detection means for periodically detecting the spin states of left and right drive wheels, and the first and second spin detection means. a split determination means for determining a split on a road surface on which each of the drive wheels touches the ground according to a preset split determination rule based on the respective detected spin states of the left and right drive wheels; A slip control device for a vehicle, comprising a split control regulating means for regulating the execution of split control for increasing the drive torque transmitted to drive wheels with a small degree of slip by the driving force control means. 2. A drive system in which a drive force distribution means is provided in the power transmission path from the engine to the left and right drive wheels to distribute the engine output to the left and right drive wheels, and the drive force is controlled in accordance with the slip state of the drive wheels. A slip control device for a vehicle equipped with a force control means, comprising first and second spin detection means for periodically detecting the spin states of left and right drive wheels, and the first and second spin detection means. a split determination means for determining a split on the road surface on which each of the drive wheels touches the ground according to a preset split determination rule based on the detected spin states of the left and right drive wheels; 1. A slip control device for a vehicle, comprising: split control regulating means for regulating execution of split control for increasing drive torque transmitted to drive wheels with a small degree of slip by the driving force control means. 3. A drive system in which a power transmission path from the engine to the left and right drive wheels is provided with a drive force distribution means for distributing the engine output to the left and right drive wheels, and the drive force is controlled in accordance with the slip state of the drive wheels. A slip control device for a vehicle equipped with a force control means, comprising first and second spin detection means for periodically detecting the spin states of left and right drive wheels, and the first and second spin detection means. a split determination means for determining a split on a road surface on which each of the drive wheels touches the ground according to a preset split determination rule based on the detected spin states of the left and right drive wheels; and a brake for braking the left and right drive wheels, respectively. A differential pressure detecting means detects a differential pressure between braking pressures supplied to the device, and the driving force controlling means operates until the differential pressure between the braking pressure detected by the differential pressure detecting means after the split determination reaches a predetermined value or more. 1. A slip control device for a vehicle, comprising: split control regulating means for regulating execution of split control that increases drive torque transmitted to drive wheels with a low slip degree.