JP2659766B2 - Slip control device for four-wheel drive vehicle - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a slip control device for a four-wheel drive vehicle that performs control to suppress each wheel from slipping on a road surface in a vehicle driven by four wheels.

(Prior Art) When the slip of the wheels on the road surface is large when the vehicle is traveling, grip traveling is not performed, and proper traveling characteristics cannot be obtained. In such a case, 2. Description of the Related Art There has been known a slip control device that performs control to suppress a slip of a drive wheel on a road surface by operating a brake device provided in a vehicle or reducing an output of an engine.

With such a slip control device, when the slip of the drive wheel on the road surface is suppressed, it is possible to detect a state in which the drive wheel is slipping on the road surface by a predetermined amount or more, or to detect the slip on the road surface by a predetermined amount or more. In order to set a target slip ratio or the like for the generated drive wheels, it is required to detect a vehicle speed. In a two-wheel drive vehicle in which only the front wheels or the rear wheels are driven, the vehicle speed can be relatively easily detected based on the peripheral speed of a driven wheel that rarely causes slip on the road surface. In a four-wheel drive vehicle in which both the rear wheel and the rear wheel can be driven, when the four-wheel drive vehicle is in the four-wheel drive state, there is no wheel to be a driven wheel. It will be difficult.

In order to eliminate the inconvenience associated with such a four-wheel drive vehicle, for example, Japanese Patent Laying-Open No. 62-289429 discloses a method in which a peripheral acceleration of each wheel in a four-wheel drive vehicle is obtained, and based on the peripheral acceleration, A four-wheel drive in which a state in which each wheel is slipping by a predetermined amount or more with respect to a road surface is detected, and a vehicle speed is estimated based on a minimum peripheral speed of each wheel. A vehicle slip control device has been proposed.

As described above, in the slip control device of the four-wheel drive vehicle in which the state in which each wheel is slipping on the road surface is detected and the vehicle speed is estimated, the slip of the wheel with respect to the road surface is detected at a predetermined level or more. When the control is performed, the control for reducing the driving torque acting on the wheel in which the slip is detected to be equal to or more than a predetermined value is usually performed so that the slip ratio or the slip amount of the wheel in which the slip is detected is made to coincide with a predetermined target value. Is performed, but the target value in such control is set irrespective of the number of wheels in which a predetermined or more slip is detected.

(Problems to be Solved by the Invention) Generally, in a four-wheel drive vehicle, the number of wheels whose slip on the road surface is detected depends on the running state of the vehicle and the road surface condition (road surface friction coefficient, etc.). The larger the number of wheels having the above-mentioned slip, the greater the effect on the running stability of the vehicle is. It is desired that the target value of the slip ratio or the slip amount at the time of the control be set low, and that the running stability of the vehicle be prioritized. It is desirable that the target value of the slip rate or the slip amount during the slip control be set high and that the priority is given to securing the vehicle's running characteristics such as acceleration and running performance. However, there is no slip control device for a four-wheel drive vehicle in which a target value of a slip rate or a slip amount in slip control is set so as to satisfy such a demand.

In view of such a point, the present invention sets a slip rate or a slip amount for a wheel that is causing a detected slip when a predetermined or more slip on a road surface is detected for each wheel in a four-wheel drive vehicle. Control to change the driving torque acting on the wheels in order to make them coincide with the target value, and in this case, the target value of the slip ratio or the slip amount for the controlled wheels is determined by the running state of the vehicle or the road surface condition. It is an object of the present invention to provide a four-wheel-drive vehicle slip control device which is set in accordance with the following conditions and achieves desired traveling characteristics while substantially maintaining the traveling stability of the vehicle. .

(Means for Solving the Problems) In order to achieve the above-mentioned object, a slip control device for a four-wheel drive vehicle according to the present invention has a structure as shown in FIG. A slip detecting means for detecting slip on the road surface of the vehicle, and when a slip exceeding a predetermined value is detected by the slip detecting means, a slip rate or a slip amount of a specific wheel for which the predetermined slip or more is detected is specified. A drive torque control means for changing the drive torque acting on the wheels to match a preset target value, and a target value setting means. Depending on the number of wheels on which the above-described slip has been detected, the slip ratio or slip on the wheel on which a predetermined or more slip has been detected. It is assumed that the target value for the quantity is changed.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 2 conceptually shows an example of a slip control device for a four-wheel drive vehicle according to the present invention, together with a vehicle to which the slip control device is applied.

In FIG. 2, the vehicle is a four-wheel drive vehicle, and an engine 12 is mounted on a front portion of a vehicle body 10. The engine 12 has, for example, four cylinders 11 and the cylinders 11
Each is supplied with an air-fuel mixture formed by fuel supplied from a fuel supply system and intake air through an intake passage 16 provided with a throttle valve 14 which is opened and closed by a throttle actuator 13. The air-fuel mixture supplied into each cylinder 11 is combusted by the operation of the ignition system and discharged to the exhaust passage 17. The combustion of the air-fuel mixture causes the engine 12 to rotate, and the generated torque is transmitted to the transmission 2.
2, a center differential mechanism 23, a front wheel propeller shaft 24 and a differential mechanism 25, and a rear wheel propeller shaft 26 and a differential mechanism 27.
L, the right front wheel 20R, the left rear wheel 21L, and the right rear wheel 21R.

A brake control unit 30 is provided in association with the left front wheel 20L, the right front wheel 20R, the left rear wheel 21L, and the right rear wheel 21R. The brake control unit 30 includes a left front wheel 20L, a right front wheel 20R, and a left rear wheel.
The disc brakes 35A to 35D each include a disc 32 attached to each of the right rear wheel 21R and the right rear wheel 21R, and a caliper 34 provided with a brake pad for pressing the disc 32. Caliper in each of the disc brakes 35A to 35D
Each of the wheel cylinders 36 includes a conduit 37a extending from the hydraulic pressure adjusting unit 40.
To 37d are connected respectively. When brake fluid pressure is supplied to the wheel cylinder 36 from the fluid pressure adjusting unit 40 via the conduits 37a to 37d, the respective calipers 34 disc brake pads with a pressing force corresponding to the supplied brake fluid pressure.
32, the left front wheel 20L, the right front wheel 20R, the left rear wheel 21L, and the right rear wheel 21R are braked.

Hydraulic pressure according to the depression operation of the brake pedal 41 is supplied to the hydraulic pressure adjusting section 40 from the power cylinder 43 provided along with the brake pedal 41 through the conduits 42a and 42b, and the pump 44 and the pressure regulating valve. The hydraulic pressure formed by 45 is supplied through conduit 46. Hydraulic pressure adjustment section 40
During normal braking in which the slip control is not performed, a brake fluid pressure corresponding to the depression operation of the brake pedal 41 is formed, and the brake fluid pressure is formed through the conduits 37a to 37d.
To perform the operation of supplying the brake fluid to the disc brakes 35A to 35D in accordance with the operation states of the built-in solenoid on-off valves 51 to 58. The operation of selectively supplying the respective data is performed.

The electromagnetic on-off valves 51 to 58 include electromagnetic on-off valves 51 and 52, electromagnetic on-off valves 53 and 54, electromagnetic on-off valves 55 and 56, and an electromagnetic on-off valve 57.
And 58, each of which is involved in adjusting the brake fluid pressure for the disc brakes 35A to 35D provided on the left front wheel 20L, the right front wheel 20R, the left rear wheel 21L and the right rear wheel 21R. Is done. One solenoid on-off valve of each set 51, 53, 55
And 57 are opened and the other solenoid valves 52, 54, 56 and 58 are closed, the disc brake 35A
3535D is increased respectively, and conversely, one of the solenoid on-off valves 51, 53, 55 and
When the 57 is closed and the other solenoid on-off valves 52, 54, 56 and 58 are opened, the brake fluid pressure supplied to the disc brakes 35A to 35D is reduced respectively, and any of the sets is reduced. When closed, the disc brakes 35A-3
The brake fluid pressure supplied to 5D is maintained at the state at that time.

In addition to the above-described configuration, a control unit 100 for controlling the opening and closing of the electromagnetic on-off valves 51 to 58 and controlling the operation of the throttle actuator 13 is provided. The control unit 100 includes a front left wheel 20L, a front right wheel 20R, and a rear left wheel 21L.
And speed sensors 6 provided in relation to the right rear wheel 21R, respectively.
Detection signals S _{1 to} S corresponding to the peripheral speeds of the left front wheel 20L, the right front wheel 20R, the left rear wheel 21L, and the right rear wheel 21R obtained from 1 to 64, respectively.
₄ , a detection signal St corresponding to the throttle opening obtained from a throttle opening sensor 65 provided in connection with the throttle valve 14, and an accelerator opening sensor 67 provided in connection with the accelerator pedal 66. A detection signal Sa corresponding to the amount of depression of the accelerator pedal 66 and a steering wheel 68
And a detection signal Sd corresponding to the steering angle of the left front wheel 20L and the right front wheel 20R, which is obtained from the steering angle sensor 69 provided in association with the control signal.

Control unit 100 takes in the detection signal S ₁ to S ₄ with a predetermined cycle, the left front wheel 20L to the detection signal S ₁ to S ₄ which incorporated the preparative is expressed, the right front wheel 20R, left rear wheel 21L and the right rear wheel 21R The value of the estimated vehicle speed and the value of the peripheral acceleration are calculated based on the value of the peripheral speed, and the left front wheel 20L, the right front wheel 20R, the left rear wheel 21L, and the right rear wheel 21R are calculated.
Each of the calculated values of the circumferential acceleration is compared with a predetermined value Aa to determine whether or not a slip of a predetermined value or more has occurred. Then, among the left front wheel 20L, the right front wheel 20R, the left rear wheel 21L, and the right rear wheel 21R, those for which the value of the peripheral acceleration is determined to be equal to or more than the value Aa are regarded as having a predetermined slip or more, and the slip control is performed. To the front left wheel 20L, front right wheel 20R, rear left wheel
When it is determined that the value of each of the peripheral accelerations of the 21L and the right rear wheel 21R is less than the value Aa, the normal throttle opening control is performed.

When the control unit 100 performs the normal throttle opening control, the normal target throttle opening is set according to the depression amount of the accelerator pedal 66 represented by the detection signal Sa, and the throttle valve 14 represented by the detection signal St.
The throttle valve drive signal Ct corresponding to the difference between the normal target throttle opening and the opening of the throttle valve 14 is formed so that the opening of the throttle valve approaches the normal target throttle opening, and is supplied to the throttle actuator 13. You. As a result, the throttle valve 14 is driven to be opened and closed by the throttle actuator 13, and the opening thereof is controlled so as to match the normal target throttle opening. The normal target throttle opening is set to increase in a predetermined proportional relationship as the depression amount of the accelerator pedal 66 increases.

When the slip control is performed by the control unit 100, the left front wheel 20L, the right front wheel 20R, the left rear wheel 21L
And the value of the peripheral acceleration of each of the right rear wheel 21R is used to detect which of the four wheels is a wheel (hereinafter, referred to as a slip wheel) in which a predetermined or more slip on the road surface has occurred. , And, the number of slip wheels is detected, and further, when the number of detected slip wheels is plural, the number of slip wheels that have become the slip wheels substantially simultaneously among the plurality of slip wheels is detected. The calculation of the estimated vehicle speed and the setting of the slip control mode used when setting the target slip ratio are performed based on the detection result.

In estimating the vehicle speed setting by the control unit 100, a left front wheel 20L of 1 cycle before the detection signal S ₁ to S ₄ of the captured represent, right front wheel 20R, the peripheral velocity of the values of the left rear wheel 21L and the right rear wheel 21R The value of the estimated vehicle speed V _n-1 (where n is a positive integer) calculated at the time of high-speed running is equal to or more than a predetermined value Vh, and the value of the calculated estimated vehicle speed V _n-1 is a value. Vh and the left front wheel 20L and the right front wheel 2 represented by the detection signal Sd.
During low-speed straight running where the steering angle of 0R is less than the predetermined value θa, the predetermined correction is made to the lowest of the peripheral speed values of the left front wheel 20L, the right front wheel 20R, the left rear wheel 21L and the right rear wheel 21R. Coefficient α
₀ (<1) is multiplied, and the value Vn of the estimated vehicle speed at that time is calculated. Further, when the estimated vehicle speed value V _n-1 is less than the value Vh, and the steering angle of the left front wheel 20L and the right front wheel 20R is lower than or equal to the value θa, at the time of low-speed turning traveling, according to the detected slip wheels and the number thereof, The estimated vehicle speed is set in different setting modes based on the peripheral speeds of the wheels on which the slip on the road surface does not exceed a predetermined level (hereinafter, referred to as non-slip wheels).

In setting the estimated vehicle speed during low-speed turning,
When it is detected that the number of slip wheels is zero or one, when the left turning state of the vehicle is detected based on the steering angles of the left front wheel 20L and the right front wheel 20R, the left front wheel 20L and the right front wheel 2
If 0R are each non-slip wheels, is multiplied by the correction coefficient alpha ₁ predetermined for the mean value of the peripheral speed of the peripheral speed and the right rear wheel 21R of the left front wheel 20L, the value Vn of the estimated vehicle speed Calculated, and based on the detection that at least one of the left front wheel 20L and the right rear wheel 21R is a slip wheel, when the left turn of the vehicle is detected, the right front wheel 20R that is a non-slip wheel peripheral speed and is multiplied by the correction coefficient alpha ₁ to the average value of the peripheral speed of the left rear wheel 21L, the value Vn of the estimated vehicle speed is calculated. On the other hand, when it is detected that the number of slip wheels is zero or one and the right turning state of the vehicle is detected, when the right front wheel 20R and the left rear wheel 21L are non-slip wheels, respectively, the right and the correction coefficient alpha ₁ is multiplied by the mean value of the peripheral speed of the peripheral speed and the left rear wheel 21L of the front wheels 20R, the calculated value Vn of the estimated vehicle speed, also at least one of the right front wheel 20R and the left rear wheel 21L When it is detected that one of the wheels is a slip wheel and a right turn of the vehicle is detected, a correction is made to an average value of a peripheral speed of the left front wheel 20L and a peripheral speed of the right rear wheel 21R which are non-slip wheels. coefficient alpha ₁ is multiplied by the value Vn of the estimated vehicle speed is calculated.

Further, when it is detected that the number of slip wheels is two, the non-slip wheels are the left front wheel 20L and the right front wheel 20R,
Alternatively, in the case of the left rear wheel 21L and the right rear wheel 21R, the average value of the peripheral speed of the left front wheel 20L and the peripheral speed of the right front wheel 20R, or the peripheral speed of the left rear wheel 21L and the right rear wheel 21R. peripheral speed average value in advance correction coefficient alpha ₂ defined is multiplied by the value Vn of the estimated vehicle speed is calculated. Also, the non-slip wheel is the left front wheel
20L and left rear wheel 21L, or right front wheel 20R and right rear wheel 21R
, The correction coefficient α is set to the peripheral velocity of the wheel that takes the locus closest to the locus of the center of gravity of the vehicle among the non-slip wheels.
_By multiplying by ₂ , the value Vn of the estimated vehicle speed is calculated. Specifically, when the non-slip wheels are the left front wheel 20L and the left rear wheel 21L, when the vehicle is turning right, the left front wheel 20L
The speed correction coefficient alpha ₂ is multiplied by the circumferential, when the vehicle is turning left state, the peripheral speed of the left rear wheel 21L correction coefficient alpha ₂ is multiplied, while non-slip wheels, right front wheel 20R and the right when a rear wheel, if the vehicle is turning right, the correction coefficient alpha ₂ is multiplied by the circumferential speed of the right front wheel 20R, when the vehicle is turning left state, the peripheral speed of the right rear wheel 21R correction coefficient alpha ₂ is multiplied, the estimated vehicle speed in each case the value Vn
Is calculated.

On the other hand, if the non-slip wheels are the left front wheel 20L and the right rear wheel 21R, or the right front wheel 20R and the left rear wheel 21L, the average value of the peripheral speed of the left front wheel 20L and the peripheral speed of the right rear wheel 21R, or the average value of the peripheral speed of the peripheral speed and the left rear wheel 21L of the right front wheel 20R, the correction coefficient alpha ₂ is multiplied by the value Vn of the estimated vehicle speed is calculated.

In shall be slipping wheels is three is detected by the peripheral speed correction coefficient alpha ₃ multiplied for the remaining one being a non-slip wheels, the value Vn of the estimated vehicle speed is calculated.

Under the assumption that all of the front left wheel 20L, the front right wheel 20R, the rear left wheel 21L and the rear right wheel 21R are detected as slip wheels, the value Vn of the estimated vehicle speed calculated immediately before such slip wheels are detected is , The value of the estimated vehicle speed Vn at that time.

The above-mentioned correction coefficients α ₁ , α ₂ and α ₃ are set to 1> α ₁ > α ₂ > α _{3 in} consideration of the fact that the vehicle is in an unstable state as the number of slip wheels increases. It is desirable to set so that

As described above, under the setting mode according to which of the four wheels is the slip wheel and the number of the slip wheels,
By setting the estimated vehicle speed, the estimated vehicle speed is calculated based on the actual vehicle speed in a relatively simple configuration without using an expensive ground speed sensor or the like, in consideration of the running state of the actual vehicle. It will be set to something that does not greatly deviate.

With the estimated vehicle speed set as described above, the control unit 100 performs the slip control on the slip wheels according to the combination of the number of slip wheels and two or more of the four wheels in the vehicle. The control is performed as follows in accordance with a control mode predetermined in advance.

In the slip control by the control unit 100, the left front wheel 20L, the right front wheel 20R, the left front wheel 20R, the left front wheel 20R, the left front wheel 20R, the left front wheel 20R, and the left front wheel 20 Rear wheel
Brake control for applying a braking force to each of the rear wheel 21R and the right rear wheel 21R and throttle control for reducing the output of the engine by reducing the opening of the throttle valve 14 are selectively performed. At the same time, the target slip rate TGBR in the brake control is set to the smallest value TG1 of three predetermined values TG1 to TG3 (0 <TG1 <TG2 <TG3), and the target slip rate TGBR in the throttle control is set. The slip ratio TGTR is set by selecting one of the values TG1 to TG3.

Then, the target slip TGBR in the set brake control and the target slip ratio TGTR in the throttle control
Are multiplied by the correction coefficient γ preset for each number of slip wheels and stored in the built-in memory according to the number of slip wheels at that time, and the target slip rates TGBR and TGTR Is corrected. In this case, the correction coefficient γ multiplied by each of the target slip rate TGTR and the target slip rate TGTR is set to 1 when the number of slip wheels is one, and is set to a smaller value as the number of slip wheels increases. .

Thus, as the number of slip wheels increases, the correction coefficient γ
Is set to a smaller value, the values of the target slip rates TGBR and TGTR corrected and multiplied by the correction coefficient γ are
It depends on the running state of the vehicle and the road surface condition.

In performing the brake control and the throttle control, the estimated vehicle speed value Vn calculated as described above is used, and the left front wheel 20L, the right front wheel 20R, the left rear wheel 21L, and the right rear wheel 2 are used.
Actual slip ratio SFL, SFR, SRL and SRR in each of 1R
Are, respectively, the formula; SFL = (VFLn−Vn) / VFLn, SFR = (VFRn−V
n) / VFRn, SRL = (VRLn−Vn) / VRLn, and SRR = (VRRn
−Vn) / VRRn (VFLn, VFRn, VRLn and VRR)
n (where n is a positive integer) is the left front wheel 20L and the right front wheel 20, respectively.
R, the value of the peripheral speed of the left rear wheel 21L and the right rear wheel 21R).

Then, when the brake control is performed, the control is performed based on a comparison between the calculated actual slip ratios SFL, SFR, SRL, and SRR and the corrected target slip ratio TGBR multiplied by the correction coefficient γ. Drive signal Ca by unit 100
~ Ch are selectively formed and supplied to the solenoid on-off valves 51-58. Thereby, the front left wheel 20L, the front right wheel 20R, and the rear left wheel
Disc brakes 35A-3 attached to 21L and right rear wheel 21R
The brake fluid pressure for 5D is adjusted, and the slip ratio of the slip wheel is controlled to match the value of the target slip ratio TGBR corrected by multiplying by the correction coefficient γ.

When the throttle control is performed, the control unit notices a comparison between the calculated actual slip ratios SFL, SFR, SRL and SRR and the corrected target slip ratio TGTR multiplied by the correction coefficient γ. 100 forms a throttle valve drive signal Ct, which is supplied to the throttle actuator 13. As a result, the opening of the throttle valve 14 is adjusted, and the slip ratio of the slip wheel is reduced by the correction coefficient γ.
Is controlled so as to be equal to the corrected target slip ratio TGTR. However, during such throttle control, the opening of the throttle valve 14 is
When the throttle opening is set to be larger than the normal target throttle opening set according to the stepping amount of the throttle valve, the throttle control is stopped and the normal throttle control is started.

As described above, the brake control and the throttle control are selectively performed in accordance with the number of slip wheels and the combination of the slip wheels. However, when it is detected that the number of slip wheels is one, only the brake control is performed. Is performed. In addition, when it is detected that the number of slip wheels is two, one of the control modes predetermined according to each of the six combinations of two of the four wheels is used. That is, when the left rear wheel 21L and the right rear wheel 21R are slip wheels, only the brake control is performed,
If the left front wheel 20L and the right front wheel 20R are slip wheels, the effect on the running stability of the vehicle thereby,
Since the rear left wheel 21L and the right rear wheel 21R are likely to be larger than when they are slip wheels, in addition to the brake control, the target slip ratio TGTR is corrected by multiplying the value TG3 by a correction coefficient γ. Throttle control is performed under the setting of, and further, the slip wheel is a left front wheel 20L and a right rear wheel 21L,
Alternatively, in the case of the right front wheel 20R and the right rear wheel 21R, since the yaw motion may occur in the vehicle, in addition to the brake control, the target slip ratio TGTR is multiplied by the correction coefficient γ to the value TG2. When the throttle control under the corrected value is performed and the slip wheels are the left front wheel 20L and the right rear wheel 21R, or the right front wheel 20R and the left rear wheel 21L, only the brake control is performed. Done.

As described above, under the condition that the number of slip wheels is two, the influence on the running stability of the vehicle is relatively small by setting the slip control mode according to the combination of the slip wheels. In this case, only the brake control is performed, so that the output of the engine is not reduced and the driving torque of the wheels is not reduced more than necessary, and the traveling characteristics required for the vehicle such as acceleration and running performance are required. Is suppressed. In addition, when the influence on the running stability of the vehicle is likely to be large, throttle control is performed in addition to the brake control. Be avoided.

On the other hand, if the number of detected slip wheels is three, and the slips of which are equal to or more than a predetermined value occur almost simultaneously, the vehicle is in an extremely unstable running state, and the target slip rate TGTR is , The throttle control is performed only when the value TG2 is multiplied by the correction coefficient γ and set to a corrected value. If the three slip wheels do not slip more than a predetermined amount at substantially the same time, the target slip ratio TGTR is set to a value in addition to the brake control.
The throttle control is performed under the condition that TG2 is multiplied by the correction coefficient γ and set to a corrected value.

Furthermore, when it is detected that there are four slip wheels, the brake control is stopped, the target slip ratio TGTR is set to zero, and the throttle control for bringing the throttle valve 14 into the fully closed state is performed. Then, in order to determine whether or not each of the four wheels is in a state in which substantially no slip occurs, with the throttle valve 14 fully closed.
The average peripheral speed VAV is given by the formula; VAV = (VFLn + VFRn + VRLn + VRR)
n) / 4, and using the calculated peripheral velocity average value VAV, the total deviation ε is calculated by the following equation: ε = (VFLn−VAV) ² +
(VFRn-VAV) ² + (VRLn-LAV) ² + (VRRn-VAV) ²
Is calculated, and the calculated total deviation value ε is a predetermined value.
It is determined whether or not Za or less. The total deviation ε is the value Za
If it is determined that the value is larger, the four wheels are not in a slip-free state, so that the fully closed state of the throttle valve 14 is maintained, and it is determined that the total deviation value ε is equal to or less than the value Za. In this case, the slip control is resumed, assuming that the four wheels are in a state where there is substantially no slip.

When the slip control is restarted, the brake control is not performed and the target slip ratio TGTR is not performed until a predetermined period Tx elapses from the time when the total deviation value ε becomes equal to or less than the value Za.
However, only the throttle control under the condition that the value TG1 is multiplied by the correction coefficient γ and set to a corrected value is performed. However, when such throttle control is being performed, when the opening of the throttle valve 14 is set to be larger than the normal target throttle opening set in accordance with the depression amount of the accelerator pedal 66, such throttle control is performed. The operation is stopped, and the normal throttle opening control is started.

As described above, when it is detected that all four wheels have slipped on the road surface by a predetermined amount or more, the brake control is stopped and the four wheels are substantially in a slip-free state. Since the throttle valve 14 is maintained in the fully closed state and the output of the engine is rapidly reduced, a situation that affects the running stability of the vehicle is avoided. A state in which slip does not substantially occur is set. Therefore, even if slippage of the four wheels with respect to the road surface exceeds a predetermined value, a running state in which the estimated vehicle speed becomes equal to or substantially equal to the actual vehicle speed can be obtained in a very short time. Also, after the four wheels have been substantially free of slip,
Until Tx elapses, there is a great possibility that the four wheels will again slip more than a predetermined amount on the road surface,
As described above, during such a period, only the throttle control is performed to suppress the occurrence of slippage exceeding a predetermined level. Therefore, the vehicle immediately after the four wheels are substantially in a state of substantially no slippage Running stability is ensured.

When the slip control is performed as described above,
Target slip ratio TGBR and TG according to the number of slip wheels
Since the value of TR is corrected so that the slip ratio of the slip wheel is made to match the corrected target slip ratio TGBR and TGTR, appropriate slip control according to the running state of the vehicle and the road surface condition is performed. Will be performed, and the running stability of the vehicle can be substantially secured,
Desired driving characteristics can be obtained.

The slip control as described above is mainly performed based on the operation of a microcomputer built in the control unit 100. For an example of a program executed by the microcomputer, refer to the flowcharts of FIGS. 3 to 10. I will explain.

In the main program shown in the flowchart of FIG. 3 performs initialization at the start after the process 101, the detection signal S ₁ to S ₄ in the process 102, St, Sa
And Sd are taken in to create necessary data, and in the following processes 103 to 108, a slip determination program, an estimated vehicle speed setting program, a control mode setting program, a target slip rate correction program,
The program for throttle control and the program for brake control are executed, and the process returns to the process 102.

As shown in the flowchart of FIG. 4, the slip determination program executed in the process 103 of the flowchart of FIG. 3 sets the simultaneous slip count flag SFS to zero in the process 111 after the start, and The value of the peripheral speed of the left front wheel 20L one cycle before
VFL _n-1 is set to the value VWO, the value of the peripheral speed VFLn of the left front wheel 20L at that time is set to the peripheral speed value VWN, the slip wheel determination flag SFQ is set to the left front wheel slip flag SFFL, and the process 113 is executed. , A slip detection program as shown in FIG. 5 is executed.

In the slip detection program shown in FIG. 5, after the start, in the process 131, the peripheral speed value VWN is subtracted from the peripheral speed value VWN to calculate the peripheral acceleration ΔVW of the left front wheel 20L, and in the following decision 132 It is determined whether or not the circumferential acceleration ΔVW is equal to or more than the value Aa, and if it is determined that the circumferential acceleration ΔVW is equal to or more than the value Aa, it is determined that a slip of a predetermined amount or more has occurred in the left front wheel 20L, and in a process 133, The slip wheel determination flag SFQ is set to 1, the simultaneous slip count flag SFS is incremented by 1, a new simultaneous slip count flag SFS is set, and the program is terminated. If it is determined that the value is less than the value Aa, the program ends without going through the process 133.
After the program in FIG. 5 is completed, the process proceeds to process 115 in which the left front wheel slip flag SFFL is replaced with the slip wheel determination flag SFQ in the process 114 in the flowchart in FIG.

In the process 115, the value VFR _n-1 of the peripheral speed of the right front wheel 20R one cycle before is set as the value VWO, and the right front wheel 2
The value VFRn of the peripheral speed of 0R is set to the value VWN, the slip wheel determination flag SFQ is set to the right front wheel slip flag SFFR, and in the process 116, a program for slip detection as shown in FIG. At 117, the right front wheel slip flag SFFR is replaced with the slip wheel determination flag SFQ, and the routine proceeds to process 118. Process 118
, The peripheral velocity value VRL _n-1 of the left rear wheel 21L one cycle before
Is set to the value VWO, the value VRLn of the peripheral velocity of the left rear wheel 21L at that time is set to the value VWN, the slip wheel determination flag SFQ is set to the left rear wheel slip flag SFRL, and the process 119
After executing the slip detection program as shown in FIG. 5, in step 120, the left rear wheel slip flag SFRL is replaced with the slip wheel determination flag SFQ, and the process proceeds to process 122. In process 122, 1
Set the value VRR _n-1 of the peripheral speed of the right rear wheel 21R before the cycle as the value VWO,
Further, the value VRRn of the peripheral speed of the right rear wheel 21R at that time is set to the value VWN, the slip wheel determination flag SFQ is set to the right rear wheel slip flag SFRR, and the fifth
After executing the slip detection program as shown in the figure, in process 124, the right rear wheel slip flag SFR
Replace R with the slip wheel determination flag SFQ and proceed to process 12.
Go to 5.

In process 125, the left front wheel slip flag SFFL,
Right front wheel slip flag SFFR, Left rear wheel slip flag SFRL
And the right rear wheel slip flag SFRR is added to set the slip wheel count flag SF.
In step 6, it is determined whether or not the accelerator pedal 66 has been released.If it is determined that the accelerator pedal 66 has been released, the slip wheel count flag SF is set to zero in process 127. Thereafter, the program is terminated, and if it is determined in decision 126 that the accelerator pedal 66 is not released, the program is terminated without passing through the process 127.

On the other hand, the process 104 in the flowchart of FIG.
As shown in the flowchart of FIG. 6, the estimated vehicle speed setting program executed in
At 140, the estimated vehicle speed value V _n-1 set one cycle ago
There it is determined whether the value Vh or more, when the value V _n-1 of the estimated vehicle speed is determined to be the value Vh or more, in the process 141, the detection signal S ₁ ~ value Vn of the estimated vehicle speed left front wheel 20L to S ₄ are represented, right front wheel 20R, multiplying the correction coefficient alpha ₀ in the smallest of the peripheral speed of the value VFLn, VFRn, VRLn and VRRn for each of the left rear wheel 21L and the right rear wheel 21R This program is ended, and in decision 140, when it is determined that the value V _n-1 of the estimated vehicle speed is less than the value Vh, in decision 142, the left front wheel 20L representing the detection signal Sd and It is determined whether or not the steering angle θ of the right front wheel 20R is equal to or greater than the value θa, and if it is determined that the steering angle θ is less than the value θa, the process 141 is executed in the same manner as described above to execute this program. When it is determined that the steering angle θ is equal to or larger than the value θa, the process proceeds to decision 143.

In decision 143, it is determined whether or not the slip wheel count flag SF is zero or one, and if it is determined that the slip wheel count flag SF is zero or one, in decision 144, the steering angle θ is determined. It is determined whether or not the vehicle is in a right-turning state based on this.If it is determined that the vehicle is in a right-turning state, it is determined in decision 145 whether or not the right front wheel slip flag SFFR is zero. If it is determined that the right front wheel slip flag SFFR is zero, it is determined in decision 146 whether the left rear wheel slip flag SFRL is zero and the left rear wheel slip flag SFRL is zero. If it is determined that there is, in the process 147, the estimated vehicle speed value Vn is calculated by the following equation; Vn = ｛(VFRn + VR
Ln) / 2｝ × α ₁ and terminates the program. If it is determined in decision 145 or 146 that the right front wheel slip flag SFFR and the left rear wheel slip flag SFRL are not zero, respectively, the value Vn of the estimated vehicle speed at 148 expression; calculated by Vn = {(VFLn + VRRn) / 2} × α 1 ends this program.

On the other hand, when it is determined in decision 144 that the vehicle is not turning right, in decision 151, it is determined whether the left front wheel slip flag SFFL is zero, and the left front wheel slip flag SFFL is zero. If it is determined that the right rear wheel slip flag SFRR is zero in decision 152, the process is performed if the right rear wheel slip flag SFRR is zero.
In 153, the value of the estimated vehicle speed Vn is calculated by the following expression; Vn = ｛(VFLn + VRRn)
/ 2} is calculated by × alpha ₁ to exit this program, in decision 151 and 152, respectively, when the left front wheel slip flag SFFL and the right rear wheel slip flag SFRR is determined not to be zero, the process 154 , the value Vn of the estimated vehicle speed formula; calculated by Vn = {(VFRn + VRLn) / 2} × α 1 ends this program.

If it is determined in decision 143 that the slip wheel count flag SF is not zero or one,
At decision 155, the slip wheel counting flag SF
Is determined to be 2 and the slip wheel count flag SF
Is determined to be 2 in decision 156, it is determined whether or not the right front wheel slip flag SFFR is zero. If it is determined that the right front wheel slip flag SFFR is not zero, decision 157 is performed. It is determined whether or not the right rear wheel slip flag SFRR is zero.If it is determined that the right rear wheel slip flag SFRR is not zero, it is determined whether the vehicle is in a right turning traveling state at decision 158. Determine whether or not. When the vehicle is determined to be in the right turning traveling state, in the process 159, the value Vn of the estimated vehicle speed formula; calculated by Vn = VFLn × α ₂ terminates this program. If it is determined in decision 158 that the vehicle is not in the right-turning state, the process 160 calculates the estimated vehicle speed post-value Vn in the process 160;
It is calculated by ln × alpha ₂ terminates this program.

On the other hand, when it is determined in decision 157 that the right rear wheel slip flag SFRR is zero, it is determined in decision 161 whether the left front wheel slip flag SFFL is zero and the left front wheel slip flag SFFL is determined. If it is determined to be zero, in the process 162, the value Vn of the estimated vehicle speed formula; calculated by Vn = {(VFLn + VRRn) / 2} × α 2 exit this program, at decision 161, the left If it is determined that the front wheel slip flag SFFL is not zero, in the process 163, the estimated vehicle speed value Vn
Equation; calculated by Vn = {(VRRn + VRLn) / 2} × α 2 terminates this program.

If it is determined in decision 156 that the right front wheel slip flag SFFR is zero, it is determined in decision 170 whether the left front wheel slip flag SFFL is zero and the left front wheel slip flag SFFL is zero. If it is determined that, in the process 164, the value Vn of the estimated vehicle speed formula; calculated by Vn = {(VFRn + VFLn) / 2} × α 2 exit this program, at decision 170, the left front wheel If it is determined that the slip flag SFFL is not zero, it is determined in decision 165 whether the left rear wheel slip flag SFRL is zero. And
If it is determined that the left rear wheel slip flag SFRL is zero, in a process 166, the value of the estimated vehicle speed Vn is calculated by the formula;
{(VFRn + VRLn) / 2 } is calculated by × alpha ₂ terminates this program. On the other hand, if it is determined in decision 165 that the left rear wheel slip flag SFRL is not zero, it is determined in decision 167 whether or not the vehicle is in a right turn traveling state. If it is determined not to, in process 168, the value Vn of the estimated vehicle bundle formula; calculated by Vn = VRRn × α ₂ exit this program, at decision 167, the vehicle is right-turning traveling state If so, process 169
The value Vn of the estimated vehicle speed formula in; calculated by Vn = VFRn × α ₂ terminates this program.

Further, when it is determined in decision 155 that the slip wheel count flag SF is not 2, it is determined in decision 171 whether the slip wheel count flag SF is 3 or not. If so, a decision is made at decision 172 as to whether the right front wheel slip flag SFFR is zero, and if it is determined that the right front wheel slip flag SFFR is zero, an estimate is made at process 173, at step 173. Formula of vehicle speed value Vn; Vn = VF
Is calculated by Rn × α ₃ to end the program. In decision 172, when it is determined that the right front wheel slip flag SFFR is not zero, it is determined in decision 174 whether the right front wheel slip flag SFFL is zero, and that the left front wheel slip flag SFFL is zero. If it is determined, at process 175, the value Vn of the estimated vehicle speed formula; calculated by Vn = VFLn × α ₃ terminates this program. When it is determined in decision 174 that the left front wheel slip flag SFFL is not zero, it is determined in decision 176 whether the right front wheel slip flag SFRR is zero, and the right rear wheel slip flag SFRR is zero. when it is determined, at process 177, the value Vn of the estimated vehicle speed formula; calculated by Vn = VRRn × α ₃ to exit this program, and in decision 176, the right rear wheel slip flag SFRR zero If not, the process 178 calculates the estimated vehicle speed value Vn in the process 178;
It is calculated by ln × alpha ₃ terminates this program.

On the other hand, if it is determined in decision 171 that the number of slip wheel count flags SF is not three, the program is terminated.

Then, the process 10 in the flowchart of FIG.
As shown in FIG. 7, after the start, the control mode setting program executed in step 5 determines in decision 179 whether or not a four-wheel slip control flag CF4 described later is zero indicating a steady state. If it is determined that the four-wheel slip control flag CF4 is zero, it is determined in decision 180 whether the slip wheel count flag SF is 1 and the slip wheel count flag SF is 1 If so, in process 181 the brake control execution flag EBF is set to 1 and the throttle control execution flag ETF is set to zero. In process 182, the target slip ratio TGTR for throttle control is set to the value TG2.
In the process 183, the target slip ratio TGBR for brake control is set to the value TG1, and the program ends.

When it is determined in decision 180 that the slip wheel count flag SF is not 1, it is determined in decision 184 whether the slip wheel count flag SF is 2 or not. If it is determined that there is, in decision 185, it is determined whether or not the right slip flag SFFR is zero.
When it is determined that the right front wheel slip flag SFFR is zero, it is determined in decision 186 whether the left front wheel slip flag SFFL is zero and the left front wheel slip flag SFFL is determined to be zero. In this case, since the left rear wheel 21L and the right rear wheel 21R are slipping by a predetermined amount or more with respect to the road surface, the brake control execution flag EBF is set to 1 in the process 187, and the throttle control execution flag ETF is set to zero. Set each and proceed to process 182,
The processes after 182 are sequentially executed in the same manner as described above, and the program ends.

On the other hand, when it is determined in decision 186 that the left front wheel slip flag SFFL is not zero, it is determined whether or not the left rear wheel slip flag SFRL is zero in decision 188, and the left rear wheel slip flag SFRL is set to zero. If not, the left front wheel 20L and the left rear wheel 21L have slipped more than a predetermined amount with respect to the road surface.
At 189, the target slip rate TGTR is set to the value TG2 and the process proceeds to 194. When it is determined in decision 185 that the right front wheel slip flag SFFR is not an example, in decision 190, the right rear wheel slip flag S
It is determined whether or not FRR is zero, and the right rear wheel slip flag S is determined.
If FRR is determined to be zero, decision 191
It is determined whether or not the left front wheel slip flag SFFL is zero, and if it is determined that the left front wheel slip flag SFFL is not zero, the left front wheel 20L and the right front wheel 20R cause slippage of a predetermined amount or more with respect to the road surface. Process 192
In, the target slip ratio TGTR is set to the value TG3 and the process proceeds to the process 194. Further, when it is determined in the decision 190 that the right rear wheel slip flag SFRR is not zero, the right front wheel 20R and the right rear wheel 21R have slipped by more than a predetermined amount with respect to the road surface.
The target slip ratio TGTR is set to the value TG2 and the process proceeds to the process 194. In the process 194, the brake control execution flag E
Both the BF and the throttle control execution flag ETF are set to 1, and in the following process 183, the target slip ratio TGBR is set to the value TG1, and the program ends. further,
If it is determined in decision 188 that the left rear wheel slip flag SFRL is zero, the left front wheel 20L and the right rear wheel 2
1R has a predetermined slip or more, and when it is determined in decision 191 that the left front wheel slip flag SFFL is zero, the right front wheel 20R and the left rear wheel 21L have a predetermined slip or more. Therefore, in such a case, the process proceeds to the process 187, and the processes after the process 187 are executed in the same manner as described above, and the program ends.

On the other hand, when it is determined in decision 184 that the slip wheel count flag SF is not 2, it is determined in decision 196 whether the slip wheel count flag SF is 3 or not. If it is determined that there is, in decision 197, 3
It is determined whether or not the simultaneous wheel slip occurrence flag CF3 is zero. If it is determined that the simultaneous three wheel slip occurrence flag CF3 is zero, it is determined whether the simultaneous slip count flag SFS is 3 in decision 198. If it is determined that the simultaneous slip count flag SFS is not 3, the process proceeds to step 199 where the target slip rate TGTR is set to the value TG2.
, The brake control execution flag EBF and the throttle control execution flag ETF are both set to 1, and in the process 183, the target slip ratio TGBR is set to the value TG1 and the program is terminated. Further, when it is determined in decision 197 that the three-wheel simultaneous slip occurrence flag CF3 is not zero, and when it is determined in decision 198 that the simultaneous slip count flag SFS is 3, the target slip ratio is determined in process 200. TGTR value TG2
, The brake control execution flag EBT and the throttle control execution flag ETF are both set to 1, and the simultaneous three-wheel slip occurrence flag CF3 is set to 1, and the process 183
Is executed in the same manner as described above, and the program ends.

In decision 196, slip wheel counting flag S
When it is determined that F is not 3, it is determined in decision 201 whether or not the slip wheel count flag SF is 4, and when it is determined that the slip wheel count flag SF is 4, the decision is made. Proceed to 202. Also, when it is determined in decision 179 that the four-wheel slip control flag CF4 is not zero, the process proceeds to decision 202,
At decision 202, the four-wheel slip control flag CF4
Is determined to be 2, which represents the slip convergence state. When it is determined that the four-wheel slip control flag CF4 is not 2, the decision 203 determines whether or not the four-wheel slip control flag CF4 is zero indicating a steady state. Is determined to be zero, in process 204, the target slip ratio TGTR is set to zero, the brake control execution flag EBF is set to zero, the throttle control execution flag ETF is set to 1, and the four-wheel slip control flag CF4 is set to the slip convergence process. Set to 1 and go to process 205. On the other hand, in decision 203,
When it is determined that the four-wheel slip control flag CF4 is not zero, the process directly proceeds to the process 205.

In the process 205, the peripheral speed values VFLn, VFRn, VRLn
And VRRn are added and divided by 4 to obtain the average peripheral speed VA
Calculate V and calculate the sum deviation value ε in the following process 206; ε = (VFLn−VAV) ² + (VFRn−VAV) ² + (VRLn−
VAV) ² + (VRRn−VAV) ²
At 207, it is determined whether or not the total deviation value ε is equal to or less than a predetermined value Za. If it is determined that the total deviation value ε is not less than or equal to the value Za, the process directly proceeds to the process 183 and proceeds to the process 183.
Is executed in the same manner as described above, and the program ends. When it is determined in the decision 207 that the total deviation value ε is equal to or smaller than the value Za, in a process 208, the target slip ratio TGTR is set to the value TG1, the four-wheel slip control flag CF4 is set to 2, and the built-in timer is set. To start measuring the elapsed time T. And the decision that follows
At 210, it is determined whether or not the elapsed time T is equal to or greater than a predetermined time length Tx. When the program is terminated and it is determined that the elapsed time T is equal to or longer than the time length Tx, in process 213, the brake control execution flag EBF and the throttle control execution flag ET
F, the three-wheel simultaneous slip occurrence flag CF3, the four-wheel slip control flag CF4, and the slip wheel count flag SF are set to zero,
After resetting the built-in timer and executing process 183 as described above, the program ends. Also, when it is determined in the process 201 that the slip wheel count flag SF is not 4, the process 213 and the process 183 are executed in the same manner as described above, and the process returns to the original.

On the other hand, in the program for correcting the target slip ratio in the process 106 in the flowchart shown in FIG. 3, as shown in FIG.
At 215, the slip wheel count flag S
Correction coefficient γ corresponding to the number of slip wheels represented by F
Is read, in a process 216, a new target slip ratio TGBR is set by multiplying the target slip ratio TGBR by the correction factor γ read in the process 215, and in a process 217, the correction factor read in the process 215 is set. γ is multiplied by the target slip rate TGTR to set a new target slip rate TGBR, and the program ends.

As shown in FIG. 9, the throttle control program of the process 107 in the flowchart of FIG. 3 determines whether or not the throttle control execution flag ETF is zero at the decision 220 after the start, as shown in FIG. Is determined to be zero, in a process 221, a normal throttle opening control program is executed, and the program is terminated.
If it is determined in 220 that the throttle control execution flag ETF is not zero, it is determined in decision 222 whether the target slip rate TGTR is zero, and it is determined that the target slip rate TGTR is zero. If the process
At 224, a throttle valve drive signal Ct is sent to the throttle actuator 13 in order to fully close the throttle valve 14, and this program ends.

In decision 222, the target slip rate TGT
If it is determined that R is not zero, in decision 225, the opening degree Th of the throttle valve 14
Normal target throttle opening TK set according to the amount of depression
It is determined whether or not the following is true.If it is determined that the opening Th of the throttle valve 14 is larger than the normal target throttle opening TK, a normal throttle opening control program is executed in process 221. Terminate the leverage program.
If it is determined in the decision 225 that the opening Th of the throttle valve 14 is equal to or smaller than the normal target throttle opening TK, in the process 226, the left front wheel 20L and the right rear The average slip ratio SAV of the 20R, the left rear wheel 21L, and the right rear wheel 21R that has caused a slip of a predetermined amount or more with respect to the road surface is calculated, and the difference is obtained by subtracting the average slip ratio SAV from the target slip ratio TGTR in process 227. Calculate ΔS. And the following process 228
In order to make the average slip ratio SAV equal to the target slip ratio TGTR, the throttle valve drive signal Ct corresponding to the difference ΔS
And sends it to the throttle actuator 13 to end this program.

Further, process 10 in the flowchart of FIG.
After the start, as shown in FIG. 10, the brake control program of FIG. 8 determines whether or not the brake control execution flag EBF is zero at decision 230, and determines that the brake control execution flag EBF is zero. In the case where the disc brakes 35A to 35D are released in the process 231 to stop the transmission of the drive signals Ca to Ch,
After ending this program, at decision 230,
If it is determined that the brake control execution flag EBT is not zero, it is determined in decision 232 whether the left front wheel slip flag SFFL is zero. If it is determined that the left front wheel slip flag SFFL is not zero, in process 233, the left front wheel 20L is calculated using the estimated vehicle speed value Vn.
The actual slip ratio SFL is calculated by the formula; SFL = (VFLn−Vn) / VFLn, and in a subsequent process 234, the actual slip ratio SFL and the target slip ratio TGBR are made to coincide with each other. The drive signals Ca and Cb are selectively sent to the solenoid valves 51 and 52 based on the comparison with the slip ratio TGBR, and the process proceeds to decision 235. Also, when it is determined in decision 232 that the left front wheel slip flag SFFL is zero, the process proceeds to decision 235. In decision 235, it is determined whether or not the right front wheel slip flag SFFR is zero.If it is determined that the right front wheel slip flag SFFR is not zero, the process 236 uses the estimated vehicle speed value Vn to determine whether the right front wheel slip flag SFFR is not zero. The actual slip ratio SFR of the front wheel 20R is calculated by the formula; SFR = (VFRn−Vn) / VFRn, and in the following process 237, the actual slip ratio SF is set so that the actual slip ratio SFR matches the target slip ratio TGBR.
The drive signals Cc and Cd are selectively sent to the solenoid valves 53 and 54 based on the comparison between R and the target slip ratio TGBR, and the process proceeds to decision 238. The process also proceeds to decision 238 when it is determined in decision 235 that the right front wheel slip flag SFFR is zero. In the decision 238, it is determined whether or not the left rear wheel slip flag SFRL is zero.If it is determined that the left rear wheel slip flag SFRL is not zero, in the process 239, the estimated vehicle speed value Vn is used. And the actual slip ratio SRL of the left rear wheel 21L is calculated by; SRL = (VRLn
−Vn) / VRLn, and in a subsequent process 240,
To match the actual slip ratio SRL with the target slip ratio TGBR, the actual slip ratio SRL and the target slip ratio TGBR
Drive signals Ce and Cf based on the comparison with the solenoid on-off valve 55 and
Selectively sent to 56 and proceed to decision 241. In decision 238, the left rear wheel slip flag S
If the FRL is determined to be zero, decision 241
Proceed to. In the decision 241, it is determined whether or not the right rear wheel slip flag SFRR is zero, and if it is determined that the right rear wheel slip flag SFRR is not zero, the process
In step 242, the actual slip ratio SRR of the right rear wheel 21R is calculated using the estimated vehicle speed value Vn according to the formula; SRR = (VRRn−Vn) / VRRn. In the subsequent process 243, the actual slip ratio SRR is calculated.
The drive signals Cg and Ch are selectively sent to the solenoid valves 57 and 58 based on a comparison between the actual slip rate SRR and the target slip rate TGBR so that the actual slip rate SRR and the target slip rate TGBR match. I do. Also, Decision 24
When it is determined in step 1 that the right rear wheel slip flag SFRR is zero, the process 231 is executed in the same manner as described above, and the program ends.

In the above-described example, when the number of slip wheels is two, the slip control is performed in the first control mode in which only the brake control is performed and the throttle control in addition to the brake control in accordance with the combination of the slip wheels. Is performed, and in the second control mode, in particular, the left or right front and rear wheels or the left and right rear wheels that easily affect the running stability with respect to the vehicle are slip wheels. The control mode in which the target slip ratio is different between the time and when the other two wheels are slip wheels is set to be different. However, the slip control device of the four-wheel drive vehicle according to the present invention is not necessarily required. It is not necessary to do so, for example, when the target slip ratios in the brake control and the throttle control are set to the same value, the brake control and the slot And the ratio between the brake control and the throttle control of the reduction in the driving torque acting on the slip wheels differs according to the combination of the two slip wheels. The slip control may be performed according to the assumed control mode.

Further, in the above-described example, the slip ratio of the specific wheel in which the slip is detected to be equal to or more than the predetermined value is calculated, and the specific wheel is actuated so that the calculated slip ratio matches the set target value. However, the four-wheel driver's slip control device according to the present invention is not necessarily required to change the drive torque. For example, a specific wheel in which a slip equal to or more than a predetermined value is detected. By subtracting the value of the estimated vehicle speed from the value of the peripheral speed of the vehicle, the slip amount for the specific wheel is calculated, and the drive torque acting on the specific wheel is adjusted so that the calculated slip amount matches the target value. It may be made to change.

Further, in the above-described example, the output of the engine during the slip control is adjusted by changing the throttle opening, but it is not always necessary to do so. Air-fuel ratio,
The adjustment may be made by changing the ignition timing, the exhaust gas recirculation amount, the intake / exhaust valve opening / closing timing, the supercharging pressure, the fuel injection timing, and the like.

Furthermore, the above-described example is applied to a full-time type four-wheel drive vehicle that is always in a four-wheel drive state, but the present invention is not limited thereto, and the four-wheel drive state and the two-wheel drive state are not limited thereto. The present invention is also applicable to a part-time type four-wheel drive vehicle in which the state can be selectively selected.

(Effects of the Invention) As is clear from the above description, according to the slip control device for a four-wheel drive vehicle according to the present invention, when the slip control is performed, the target of the slip rate or the slip amount is determined according to the number of slip wheels. The drive torque acting on the slip wheels is reduced in order to make the slip rate or the slip amount of the slip wheels coincide with the set target value, so that the slip control adapted to the running condition of the vehicle and the road surface condition is set. As a result, desired traveling characteristics can be obtained while the traveling stability of the vehicle is substantially ensured.

[Brief description of the drawings]

FIG. 1 is a basic configuration diagram showing a slip control device for a four-wheel drive vehicle according to the present invention according to the claims, and FIG. 2 is an example of a slip control device for a four-wheel drive vehicle according to the present invention.
Conceptual diagram showing the vehicle to which it is applied, FIGS.
FIG. 10 is a flowchart showing an example of a program executed by the microcomputer when the microcomputer is used in the control unit of the example shown in FIG. In the figure, 5 is a vehicle, 12 is an engine, 13 is a throttle actuator, 14 is a throttle valve, 20L is a front left wheel, 20R is a front right wheel, 21L is a rear left wheel, 21R is a rear right wheel, 30 is a brake control section, 35A ~ 35D is a disc brake, 40 is a hydraulic pressure adjustment unit, 61 to 64 are speed sensors, 65 is a throttle opening sensor,
67 is an accelerator opening sensor, and 100 is a control unit.

Continued on the front page (72) Inventor Mitsuru Nagaoka 3-1 Shinchi, Fuchu-cho, Aki-gun, Hiroshima Mazda Corporation (72) Inventor Kenichi Watanabe 3-1 Shinchi, Fuchu-cho, Aki-gun, Hiroshima Mazda Corporation (56) References JP-A-62-15127 (JP, A) JP-A-60-12337 (JP, A) JP-A-62-16831 (JP, A)

Claims (2)

(57) [Claims] 1. A slip detecting means for detecting a slip of each wheel with respect to a road surface in a four-wheel drive vehicle, and when the slip detecting means detects a slip greater than a predetermined value, identification of the detection of the slip value exceeding the predetermined value. A drive torque control means for changing a drive torque acting on the specific wheel so that a slip ratio or a slip amount of the wheel coincides with a preset target value; A target value setting means for changing a target value for a slip ratio or a slip amount of a wheel in which the slip of the predetermined level or more is detected, in accordance with the number of wheels in which the detection is performed. Driving vehicle slip control device. 2. The method according to claim 1, wherein the target value setting means sets the slip ratio or the slip rate of the wheel in which the slip greater than the predetermined value is detected, as the number of wheels detected as slip greater than the predetermined value by the slip detector is increased. The slip control device for a four-wheel drive vehicle according to claim 1, wherein a target for the amount is set low.