JP2976712B2 - Anti-skid braking method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an anti-skid braking method suitably applied to a brake device of an automobile, and more particularly to an anti-skid braking method for appropriately controlling a brake fluid pressure at the time of sudden steering.

[0002]

2. Description of the Related Art Anti-skid braking that can prevent slipping of wheels, secure steering stability, and stop a vehicle at a short braking distance when braking on a low μ road such as a running road wet with rainwater. A method (referred to as an ABS control method) is known. In this ABS control method, the rotational speed of each wheel is detected to determine each wheel speed, and the slip ratio of each wheel is determined based on the deviation between the wheel speed and the reference vehicle speed. The brake pressure of each wheel is controlled to increase and decrease so that the coefficient is maintained near the optimum slip ratio at which the coefficient is maximized.

[0003] In the conventional ABS control, the highest priority is given to obtaining an optimum braking force, so that the steering performance during steering of the steering wheel is deteriorated. FIG. 19 shows the relationship between the range in which the optimum braking force is obtained and the maneuverability with respect to the slip ratio.
Regarding the maneuverability, the lower the slip ratio, the better. Therefore, it is clear from FIG. 19 that the maneuverability deteriorates at the slip ratio in the range where the optimum braking force can be obtained. However, from the viewpoint of the mechanical characteristics of the tire, the control for improving the braking force and the control for improving the maneuverability are incompatible with each other, so one of the two must be sacrificed.

[0004]

However, there are cases where it is desired to avoid obstacles by sudden steering while operating the brake in an emergency. In such a case, it may be preferable to secure the maneuverability at the expense of some braking force. The present invention has been made in response to such a demand, and when a driver has a will to make a sharp turn, anti-skid braking with improved maneuverability and improved ability to avoid obstacles is provided. The aim is to provide a method.

[0005]

In order to achieve the above-mentioned object, in the present invention, a slip ratio of a wheel is calculated from a deviation between a reference vehicle speed and a wheel speed of a wheel, and a brake device forming a pair with the wheel is calculated. In the anti-skid braking method of controlling the hydraulic pressure supplied to the wheel cylinder according to the calculated slip ratio, a steering angle and a steering speed are detected, and the detected steering angle is larger than a predetermined value, and the steering speed is higher than a predetermined value. When the steering speed is larger than the predetermined value, the slip ratio is corrected in a direction in which the hydraulic pressure of the wheel cylinder is reduced according to the detected steering angle, and during this correction , even if only the steering speed falls below the predetermined value. , A predetermined delay time from this point
An anti-skid braking method is provided, wherein the correction is continued until the lapse of time .

The correction of the slip ratio may be performed at least for the outer wheels of the front wheels that are the steered wheels.

[0007]

The driver's intention to steer sharply is detected based on the steering angle and the steering speed. If the driver's sudden steering is detected, the slip ratio is reduced according to the steering angle, and the hydraulic pressure of the wheel cylinder is reduced. In this case, the hydraulic pressure in the wheel cylinder is reduced, and the maneuverability is improved. In addition, the above-described correction of the slip ratio is continued until a predetermined delay time elapses even if only the steering speed becomes equal to or less than a predetermined value, and the effect of improving the controllability is maintained.

[0008]

Embodiments of the present invention will be described below with reference to the accompanying drawings. System Overview Figure 1 is an anti-skid braking system for a vehicle (hereinafter "AB
S ”), the front, rear, left and right wheels 1L, 1L,
A motor direct-acting hydraulic unit (HU) 10 is interposed between each of the R, 2L, and 2R brake devices 3 to 6 and a master cylinder 9 driven by a brake pedal 8, and each wheel 1L, 1R , 2L, 2R, wheel speed sensors 21, 22, 23, 24, the steering wheel 7 has a steering wheel angle sensor 25, and the vehicle body has an acceleration sensor (front and rear G sensor) 26 for detecting longitudinal acceleration. Is provided. The sensors 21 to 26 and the hydraulic unit 10 are connected to the electronic control unit 30.
(ECU). The ABS of the present embodiment
Applies to front-wheel drive vehicles, and the rear wheels are non-drive wheels.

As shown in FIG. 2, a cylinder 12 is formed in a housing 11 of the hydraulic unit 10, and a piston 13 is slidably fitted in the cylinder 12. In the upper part of the housing 11, the cylinder 1
2, passages 11 a to 11 c are provided, an ABS check valve 14 is provided between the passages 11 a and 11 c, and a passage 11 b juxtaposed to the check valve 14 is provided.
Is provided with an ABS cut valve 15. The check valve 14 allows the flow of brake fluid from the passage 11c to the passage 11a, and the cut valve 15 opens and closes the passage 11b. When the piston 13 reaches the upper limit position, the check valve 14 is opened against a spring force by a projection 13a provided on the upper end surface of the piston 13.

The housing 11 is provided with a motor 16, and the driving force of the motor 16 is transmitted to the piston 13 via a gear mechanism 17 and a feed mechanism 18 to drive the piston 13. When the motor 16 rotates forward, the feed mechanism 18 is rotated via the gear mechanism 17 to rotate the piston 1.
3 is moved upward, and when the rotation is reversed, the piston 13 is moved downward. The passage 11a of the housing 11 is connected to the master cylinder 9, and the passage 11c is connected to the wheel cylinder 3a of the brake device 3. The hydraulic unit 10 is shown only between the brake device 3 of the front wheel 1L on one side and the master cylinder 9.

The electronic control unit 30 takes in signals from the wheel speed sensors 21 to 24, the steering wheel angle sensor 25, and the front and rear G sensor 26 at the time of braking, and outputs signals from the wheels 1L, 1R,
The slip conditions of 2L and 2R are predicted, the ABS cut valve 15 and the motor 16 are controlled so that these wheels are not locked, and the braking forces of the brake devices 3 to 6 are controlled. That is, when the wheels are in the locking direction, the piston 13 is moved downward, the brake fluid pressure is reduced to avoid wheel lock, and when the risk of wheel lock is avoided, the piston 13 is moved upward to increase the brake fluid pressure. Is increased again, and such control is repeated to control the brake fluid pressure applied to the wheel cylinder. ABS control procedure Next, ABS control executed by the electronic control unit 30 of the ABS is performed.
The BS control procedure will be described.

FIGS. 3 and 4 are functional block diagrams corresponding to the ABS control executed by the electronic control unit 30, which will be described with reference to the flowchart of the ABS main routine shown in FIG. ABS Main Routine First, input signals detected by various sensors are processed by the sensor signal processing means shown in FIG. 3 (step S).
1). The wheel speed signals from the wheel speed sensors 21 to 24 are amplified, waveform processed, sampled,
After the processing such as A / D conversion is completed, the high frequency component is cut by the filter means 31a and output from the sensor signal processing means as the wheel speed FVx of each wheel. The output from the filter means 31 a calculates the wheel acceleration of each wheel by the differentiating circuit 32, and the high-frequency components of these values are cut by the low-pass filter means 33. The correction signal is corrected by the longitudinal acceleration FGS detected by the longitudinal G sensor 26 described later, and output from the sensor signal processing means as the wheel acceleration FGx of each wheel. Here, the suffix "x" when representing the wheel speed FVx and the wheel acceleration FGx (the same applies to the slip ratio Sx of each wheel described later).
Represents each of the right front wheel 1R, the left front wheel 1L, the right rear wheel 2R, and the left rear wheel 2L. When the wheel speeds and the like are indicated with a suffix “x”, the value of each wheel is individually Is calculated.

The detection signal from the longitudinal G sensor 26 is subjected to processing such as amplification, waveform processing, and sampling by an input processing means 35 and output as raw data GS of longitudinal acceleration, while high-frequency components are cut by a low-pass filter means 36. Is output as the filtered filter value FGS.
The detection signal from the handle angle sensor 25 is subjected to filtering processing by a low-pass filter means 38 after processing such as amplification, waveform processing, and sampling by an input processing means 37, and is output as a handle angle Fθh.
Further, the steering wheel angle Fθh is time-differentiated by the differentiating circuit 39, and then filtered by the low-pass filter means 40, and is output as the steering speed FDθh.

Next, the wheel speed FVx, the wheel acceleration FGx and the steering wheel angle Fθh, which have been processed as described above, are used.
Is supplied to the reference vehicle speed calculating means 41 shown in FIG. 4, and the reference vehicle speed Vref is calculated (step S2). At this time, at the time of a sharp turn in which the absolute value of the steering wheel angle Fθh is large, the inner wheel difference is corrected, and the reference vehicle speed Vrefo of the outer wheel and the reference vehicle speed Vrefi of the inner wheel are calculated. The vehicle speed on the outer wheel side and the vehicle speed on the inner wheel side differ depending on the inner wheel difference, and the slip ratio of each wheel can be accurately obtained by correcting the inner wheel difference in vehicle speed.

The reference vehicle speed Vref (Vrefo and Vrefi) calculated by the reference vehicle speed calculating means 41 is supplied to the slip ratio calculating means 42, and the wheel speed FVx of each wheel and the reference vehicle speed Vref are used for each wheel. The slip ratio Sx is calculated based on the following equation (S1) (step S3). Sx = (Vref−FVx) / Vref × 100 (S1) The slip ratio correcting means 44 is composed of an initial correcting means 44a, a rough road correcting means 44b, a steering correcting means 44c, and an adding means 44d. Correction means 44a-44
The correction value calculated in step c is added by the adding means 44d, and the above-mentioned slip ratio Sx is corrected using the added value HSR (step S4). These corrections are performed in order to prevent the operation of the ABS due to riding over a protrusion, improve the braking force and directional stability on a rough road, and improve the maneuverability at the time of sudden steering.

The pressure increase / decrease determination means 46 includes a slip rate SRx corrected by the slip rate correction means, an integrated value ISRx of the slip rate SRx, and a wheel acceleration FGx of each wheel.
, And its differential value Jx are supplied, and a brake pressure increase / decrease determination is executed by fuzzy inference (step S5). The calculation of the integrated value ISRx is performed by the slip rate integrating means 4.
According to 8, the operation of the differential value Jx is executed by the differentiating means 49, respectively.

FIG. 6 shows the relationship between the slip ratio S and the friction coefficient μ. As a general method of the ABS control, the relationship between the slip ratio S and the friction coefficient μ, and the wheel acceleration FGx
From equation (1), the slip ratio S becomes the value S1 at which the friction coefficient μ becomes maximum.
If the value is smaller or smaller than the value S1, the brake fluid pressure is increased. If the value is larger than the value S1 or larger than the value S1, the pressure is reduced. However, with only the wheel acceleration FGx, the termination of the pressure reduction control may be delayed due to the phase delay of the sensor filter system. To prevent this, the recovery tendency of the wheel speed is determined by the differential value (jerk) Jx of the wheel acceleration FGx. We try to detect it early. Further, the extremely low μ road is detected by the integrated value ISRx of the slip ratio SRx, and the transition from the low μ road to the high μ road is detected at an early stage to optimize the brake fluid pressure.

The result of the pressure increase / decrease determination by the pressure increase / decrease determination means 46 is output to the motor current command value calculation means 50 as a motor drive target value II, and the calculation means 50 calculates the motor drive current IMTR by a predetermined procedure. Further, the motor drive processing means 52 outputs a drive current IOUT of the motor 16 of the hydraulic unit (HU) 10 based on the calculated value IMTR (step S6). The motor drive processing means 52 controls the current value IOUT to be supplied to the motor 16 to an optimum value according to the change of the calculated value IMTR and the sign. The next correction of the slip ratio, according to the present invention method, the procedure for correcting a slip ratio performed by the electronic control unit 30 with reference to FIG. 7 will be described in detail.

The electronic control unit 30 starts with step S4
At 0, it is determined whether or not the ABS control is being performed. If the result of the determination is negative, the steering correction value HSTR is set to a value of 0 in step S41, and then an initial correction value HOFF is calculated (step S42). When the vehicle goes over a protrusion or the like, the wheel speed temporarily decreases and the wheels tend to lock. To prevent the ABS control from operating in such a case, an initial correction value HOFF corresponding to the reference vehicle speed Vref is set, and the initial correction value HOF is set.
F, the slip ratio S calculated by the above equation (S1)
The start of pressure reduction control of the brake fluid pressure is delayed by correcting x in the negative direction.

FIG. 8 shows the relationship between the reference vehicle speed Vref and the initial correction value HOFF set according to the value. When the wheel passes over the protrusion, there is a drop of about 2 to 3 km / hr in the wheel speed. When the reference vehicle speed Vref is lower than the predetermined speed, the correction amount for the drop is set to be larger than the correction amount at high speed, and the predetermined speed is set. When the value exceeds, the influence of over-projection can be almost ignored, so the value is set to a small value of about 3%.

On the other hand, if the determination result in step S40 is affirmative, that is, if the ABS control is being performed, step S40 is executed.
After setting the initial correction value HOFF to a value 0 in 43,
Calculation of the steering correction value HSTR is performed (step S4).
4). FIG. 10 shows a calculation procedure of the steering correction value HSTR. The electronic control unit 30 first determines whether the steering speed FDθh is equal to or higher than a predetermined determination value XDθ, that is, whether the steering is suddenly performed due to obstacle avoidance or the like. Yes (Step S44)
1). The discrimination value XDθ is set to an appropriate value that can discriminate the driver's intention of sudden steering. In addition, it is preferable to set the discrimination value XDθ to a different value between when the steering speed FDθh is increasing and when the steering speed FDθh is decreasing, and to provide a hysteresis characteristic. Hunting can be prevented.

If the decision result in the step S441 is negative, the count value of the delay timer TDθ is set to a predetermined value XTθ.
(For example, a value corresponding to one second) is determined (step S443), and the determination result is affirmative.
Only after that, in step S444, the correction value HST
R is set to 0, and the flag FL is set at step S445.
STR is reset to a value of 0, and the routine ends.
The flag FLSTR is a program control variable for storing the rapid steering and the large steering angle.

On the other hand, if the decision result in the step S441 is affirmative, in a step S442, the delay timer T
After resetting the count value of Dθ to 0, step S4
Proceed to 43. If the rapid steering state continues, the positive determination result continues in step S441, and each time, the delay timer TDθ in step S442.
Is reset to 0.

If the decision result in the step S443 is negative, that is, if the count value of the delay timer TDθ has not reached the predetermined value XTθ (1 second), the process proceeds to the step S443.
At 446, the count value TDθ is advanced by 1 and the process proceeds to step S447. In this step, the steering wheel angle F
It is determined whether or not the absolute value of θh is equal to or greater than a predetermined determination value XFθ, that is, whether or not the steering wheel is largely steered. The discrimination value XFθ is set to an appropriate value capable of discriminating the driver's large steering angle operation, and this discrimination value XFθ is also different when the steering wheel angle Fθh is increasing and when it is decreasing. May be set to give a history characteristic.

If the determination result in step S447 is negative, the correction value HSTR is obtained in step S444.
Is set to the value 0, and the flag FL is set in step S445.
STR is reset to a value of 0, and the routine ends. If the determination result in step S447 is affirmative, that is, if the steering is sharp and the steering angle is large, the process proceeds to step S448, and the correction value HSTR is set to the electronic control unit. The data is read from the map of the storage device built in 30. FIG. 9 shows the steering wheel angle F
The relationship between θh and the correction value HSTR read according to the value is shown. The correction value HSTR is set to a value corresponding to the steering wheel angle Fθh in a region where the absolute value of the steering wheel angle Fθh is larger than a predetermined determination value XFθ. . Then, step S4
Proceeding to 49, set flag FLSTR to value 1 and end the routine.

If the count value of the delay timer TDθ reaches the predetermined value XTθ (1 second) in step S443, or if the absolute value of the steering wheel angle Fθh becomes smaller than the predetermined determination value XFθ in step S447, the above-described steps S444 and S445 are performed. Is executed again and the correction value HST
R is set to the value 0 and the flag value FLSTR is reset to 0. Note that the flag FLSTR is also used in calculating a rough road correction value described later.

The steering correction value HSTR calculated as described above
The brake fluid pressure is loosened and controlled arbitrarily by pseudo-correcting each slip ratio Sx of the front and rear wheels by using the above, thereby improving the turning performance. Since the generation of the lateral force during steering is mainly performed by the outer wheels of the front wheels, which are the steered wheels, the above-described correction of the slip ratio by the steering correction value HSTR may be performed only on at least the front outer wheels.

Initial correction value HOFF and steering correction value HS
When the calculation of TR is completed, step S45 in FIG. 7 is executed, and the rough road correction value HJDR is calculated this time. FIG.
Shows the procedure for calculating the slip ratio bad road correction value, which will be described in detail with reference to the functional block diagram of FIG.
It has been found that it is better to increase the slip ratio and control the wheels in a locked state in order to improve the braking force on a rough road. Further, the front-rear G sensor 26 can detect a large vertical vibration while detecting the longitudinal acceleration of the vehicle. Therefore, the vertical vibration during traveling on a rough road is detected by using the front and rear G sensor 26, and when the rough road is determined based on the detected vertical vibration, the slip ratio is controlled to 100%, the wheels are locked, and the braking is performed. Let it. However, the front-rear G sensor 26 may detect vertical vibration even at the beginning of deceleration, for example, even when the vehicle is not traveling on a rough road. In such a case, if the slip ratio is controlled to 100%, ABS control becomes impossible. Become. Therefore, when a bad road is detected by the front-rear G sensor 26, a filtering process is performed by the rear wheel acceleration FGx and the front-rear acceleration FGS to secure the detection accuracy. In order to secure directional stability and calculate the reference vehicle speed Vref, the slip ratio of the rear wheels that are not driven is limited to about 20%.

To explain this in more detail, the electronic control unit 30 first determines whether or not the flag FLSTR indicating the rapid steering and the large steering angle is set to a value of 1.
If the result of this determination is affirmative, it means that the switch means 78 in FIG. 12 has been opened (turned off). In such a case, the process proceeds to step S451, where the rough road correction value HJDR for the front wheels and the rear wheel The road rough road correction values HJDRR are set to 0, respectively, and the routine ends. No rough road correction is performed during sudden steering or turning with a large steering angle.

On the other hand, if the decision result in the step S450 is negative, the rear wheel acceleration FGr is amplified, signal processing such as filtering is performed (step S452), and the correction coefficient JD
Calculate R2. This will be described in more detail with reference to the functional block diagram of FIG. 12. Explaining in detail, the respective wheel accelerations FG detected from the left and right wheel speed sensors 24 and 23 of the rear wheels.
rr and FGrl are amplified by the amplification means 80a and 80b.
The gain used at this time is based on the reference vehicle speed Vref from FIG.
It is set according to. That is, when the reference vehicle speed Vref is low, the gain is set large. Next, only the high-frequency component is extracted by the high-pass filter means 81a and 81b, the absolute value of the signal extracted by the signal processing means 82a and 82b is obtained, and the absolute value is clipped at a predetermined upper limit, and the signal processing is performed in this manner. The selecting unit 83 selects the larger value of the left and right rough road vibration components. After the selected signal value is filtered (integrated) by the low-pass filter 84, the coefficient correction circuit 85 outputs a filter correction coefficient JD corresponding to the output value JDR 1 of the low-pass filter 84.
Calculate R2.

FIG. 14 shows the relationship between the output value JDR1 and the correction coefficient JDR2 calculated in accordance with the output value. When the output value JDR1 is equal to or less than a first predetermined value (for example, 0.3 g), the filter is set. The correction coefficient value JDR2 is set to a value 0, and when the correction coefficient value is equal to or more than a second predetermined value (for example, 0.8 g), the coefficient value is set to 1.0.
When taking a value between the first and second predetermined values, the output value JD
It is set to a value between 0 and 1.0 in proportion to R1.
When detecting a rough road from the high frequency component JDR1 of the wheel acceleration, when the output value JDR1 is equal to or less than the first predetermined value as described above, it is determined that the road is not a rough road, and the filter correction coefficient value JDR2 is set to 0. Set it. Then, the coefficient value JDR2 set in this way is supplied to the multiplying means 73 to multiply the signal value of the vertical vibration component detected by the front and rear G sensor 26, thereby obtaining the vertical vibration generated for a reason other than a rough road. Will be eliminated.

When the calculation of the correction coefficient JDR2 is completed, the process proceeds to step S454 in FIG. 11, where the raw data GS of the longitudinal acceleration detected by the longitudinal G sensor 26 is subjected to signal processing such as amplification and filtering. More specifically, the longitudinal acceleration GS detected by the longitudinal G sensor 26 is amplified by an amplifying unit 70 (FIG. 1).
Amplify by 2). The gain used at this time is set according to the reference vehicle speed Vref from FIG.
18 shows the output signal waveform of the front and rear G sensor 26 and the signal processing waveform at each point of the signal processing means shown in FIG. 12. (A1) to (A4) of FIG. And (B1) to (B4) show signal processing waveforms on a rough road, respectively. The output signal waveform of the amplifying means 70 is shown in (A1) and (B1) of FIG.

Next, the high-pass filter means 71 extracts only high-frequency components. This filtering removes the DC component, that is, the longitudinal acceleration component, from the signal GS (see (A2) and (B2) in FIG. 18). Then, the absolute value of the high-frequency component extracted by the high-pass filter unit 71 is obtained by the signal processing unit 72 (see (A3) and (B3) in FIG. 18). After the multiplication unit 73 multiplies the correction coefficient value JDR2 described above, the low-pass filter unit 74 performs a filtering process (integration process) (see (A4) and (B4) in FIG. 18) to obtain a signal JD1 (step S455). .

Next, the process proceeds to step S456 in FIG. 11, and based on the multiplication value JD1, the rough road degree JD is calculated from the following equation (H1).
2 is calculated (bad road degree calculating means 75 in FIG. 12). JD2 = GJD × JD1 (H1) Here, GJD is a gain set according to the longitudinal acceleration FGS, and the gain GJD−the longitudinal acceleration FG in FIG.
It is determined from the S map. Front and rear G sensor 2 on rough road
The longitudinal acceleration FGS observed by 6 is, for example, 0.3
0.80.8 g, the detected longitudinal acceleration FG
When S is a value within this range, the gain GJD is set to a value of 1.
On the other hand, the gain GJD is set low in other ranges to identify a rough road.

When the degree of bad road JD2 is obtained, step S4
Then, the process proceeds to 57, where a rough road correction value HJDR for the front wheels according to the rough road degree JD2 is obtained (calculating means 76 in FIG. 12), and this is filtered (low-pass filter means 7 in FIG. 12).
7). Vertical vibration may not be detected for a moment even on a rough road. In such a case, if the pressure reduction control is started immediately, a feeling of idling occurs, which is not preferable. Therefore, a sudden change in the rough road correction value HJDR is prevented by the above-described filtering processing.

Then, the determined rough road correction value HJDR of the front wheels is obtained.
The rough road correction value HJDRR for the rear wheels according to
Calculation means 79). FIG. 16 shows the relationship between the degree of rough road JD2 and the rough road correction value HJDR of the front wheels set according to this value. When the rough road degree JD2 is equal to or more than a predetermined value (for example, 0.4 g), the rough road correction value HJDR is set to 100%.
Since the rough road correction value HJDR is negatively corrected with respect to the slip ratio Sx, the slip ratio SRx corrected with this correction value becomes a very small value when the rough road correction value HJDR is set to 100%. On a rough road, the front wheel brake hydraulic pressure is reliably controlled to increase to the locked state.

On the other hand, the rough road correction value HJDRR for the rear wheels is suppressed to at most 20% of the rough road correction value HJDR for the front wheels. FIG. 17 shows the relationship between the rough road correction value HJDR for the front wheels and the rough road correction value HJDRR for the rear wheels set according to this correction value, and the rough road correction value HJDR for the front wheels is a predetermined value (for example, 20). %), The rough road correction value HJDRR for the rear wheels is set in proportion thereto, but when the rough road correction value HJDR for the front wheels exceeds a predetermined value (20%), the predetermined value (20%) is set.
%) Held constant. This ensures the directional stability and avoids the inconvenience that the calculation of the reference vehicle speed Vref becomes impossible.

When the calculation of the rough road correction values HJDR and HJDRR is completed, the process proceeds to step S46 in FIG. 7, and the slip ratio correction amount HSR is calculated by the following equation (H2). HSR = −HOFF−HJDR + HSTR (H2) Then, the slip ratio Sx calculated by the slip ratio calculation unit 42 and the correction amount HSR calculated by the slip ratio correction unit 44 are added by the addition unit 45 (Step S).
48), and ends the slip ratio correction routine.

The anti-skid braking method of the present invention is characterized by the correction of the slip ratio, and how the brake fluid pressure is controlled to increase or decrease using the slip ratio calculated by the method of the present invention. It is needless to say that various methods can be applied and the method is not limited to the method based on fuzzy inference as in the embodiment. Further, in this embodiment, a motor direct-acting hydraulic unit (HU) 10 is provided in an oil passage between the wheel cylinder and the master cylinder, and the brake fluid pressure is controlled by this unit 10. The application of the invention is not limited to the hydraulic unit (HU) 10 as a matter of course.

[0040]

As is apparent from the above description, according to the anti-skid braking method of the present invention, when the steering angle and the steering speed are both steeper than a predetermined value, the detected steering angle is determined. The slip ratio is corrected in the direction in which the hydraulic pressure of the wheel cylinder is reduced in accordance with the above, so that the maneuverability during emergency steering is improved and the ability to avoid obstacles and the like is improved. Then, the correction of the slip ratio depends on the steering speed .
Even if the value falls below the specified value, the specified delay time elapses.
In because continues, improving the improved steerability and avoidance capability is maintained.

[Brief description of the drawings]

FIG. 1 is a block diagram schematically showing an overall configuration of an ABS device to which a method of the present invention is applied.

FIG. 2 shows a hydraulic unit (HU) 1 shown in FIG.
FIG. 3 is a hydraulic circuit diagram showing a more detailed configuration of a hydraulic circuit.

FIG. 3 is a functional block diagram of input signal processing of the electronic control device 30 shown in FIG.

FIG. 4 is a functional block diagram of ABS control of the electronic control device 30 shown in FIG.

FIG. 5 is a flowchart of a main routine showing a control procedure of ABS control executed by electronic control device 30 shown in FIG.

FIG. 6 is a graph showing a relationship between a slip ratio S and a friction coefficient μ.

FIG. 7 is a flowchart showing a procedure for calculating a slip ratio correction value, which is executed by the electronic control unit 30 shown in FIG. 1;

FIG. 8 is a graph showing a relationship between a reference vehicle speed Vref and an initial correction value HOFF set thereby.

FIG. 9 is a graph showing a relationship between a steering wheel absolute value Fθh and a steering correction value HSTR set thereby.

FIG. 10 is a flowchart showing a procedure of calculating a slip ratio steering correction value, which is executed by the electronic control device 30 shown in FIG. 1;

11 is a flowchart showing a procedure of calculating a slip ratio bad road correction value, which is executed by the electronic control device 30 shown in FIG. 1.

FIG. 12 is a functional block of the electronic control unit 30 shown in FIG. 1 for calculating a slip ratio bad road correction value.

FIG. 13 is a graph showing a relationship between a reference vehicle speed Vref and a gain set by the reference vehicle speed Vref, which is used for calculating a slip ratio bad road correction value.

FIG. 14 is a graph showing a relationship between an output value JDR1 and a correction coefficient JDR2 used for calculating a slip ratio bad road correction value.

FIG. 15 is a graph showing a relationship between a wheel acceleration FGS and a gain set thereby.

FIG. 16 is a graph showing a relationship between a bad road degree JD2 and a front road side bad road correction value HJDR set thereby.

FIG. 17 is a graph showing the relationship between the front wheel side rough road correction value HJDR and the rear wheel side rough road correction value HJDRR set thereby.

18 is a graph showing a signal waveform at each point of the functional block diagram shown in FIG.

FIG. 19 is a graph showing a relationship between a braking force and operability with respect to a change in a slip ratio.

[Explanation of symbols]

 3-6 Brake device 7 Handle 8 Brake pedal 9 Master cylinder 10 Motor direct-acting hydraulic unit 21-24 Wheel speed sensor 25 Handle angle sensor 26 Acceleration sensor 30 Electronic control device

Claims (2)

(57) [Claims] 1. A slip ratio of a wheel is calculated from a difference between a reference vehicle speed and a wheel speed of a wheel, and a hydraulic pressure supplied to a wheel cylinder of a brake device paired with the wheel is controlled in accordance with the calculated slip ratio. Detecting the steering angle and the steering speed, and when the detected steering angle is larger than a predetermined value and the steering speed is larger than a predetermined value, the slip ratio is determined according to the detected steering angle. Is corrected in the direction in which the hydraulic pressure of the wheel cylinder is reduced.During this correction, even if only the steering speed falls below the predetermined value, a predetermined delay time elapses from this time.
Wherein the correction is continued during the period . 2. The anti-skid braking method according to claim 1, wherein the slip ratio is corrected for at least a front outer wheel.