JP2003048529A - Anti-skid controller for four wheel drive vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an anti-skid controller for a four wheel drive vehicle capable of performing predetermined fail-safe processings for various processings executed based on the contents of inference of a road surface friction coefficient inference means even if it is fixed in a low friction coefficient judging condition due to a failure of the road surface friction coefficient inference means. SOLUTION: This anti-skid controller for the four wheel drive vehicle is provided with an abnormality judging timer for counting the time when a wheel speed VW returns to a speed above a pseudo-vehicle body speed VI from the pressure reduction control start time by a control unit 40, an abnormality judging means for judging that an acceleration switch G- SW is in an abnormal condition in which it is fixed in a low μ road judging condition when count TSWLO of the abnormality judging timer exceeds a predetermined abnormality judging time, 1 sec, and a fail-safe means for setting a speed reduction limiter value of a speed reduction limiter VID of vehicle body deceleration VIK and the pseudo-vehicle body speed VI to 1.3 g which is a limiter value equivalent to a high μ road when it is judged that an abnormal condition occurs.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an anti-skid control device for a four-wheel drive vehicle that prevents wheel lock by increasing / decreasing a hydraulic pressure during braking of a wheel cylinder provided in each wheel of the vehicle. In particular, the present invention relates to a failure-safe technique at the time of abnormality determination and an abnormality determination of an acceleration switch (road surface friction coefficient estimation means) for estimating a road surface friction coefficient.

[0002]

2. Description of the Related Art In a conventional four-wheel drive anti-skid control device, the wheel speed of each wheel detected by a wheel speed sensor is a predetermined control target speed (pressure reduction threshold value).
When the following occurs, the pressure reduction control that reduces the hydraulic pressure in the wheel cylinder is executed to prevent the braking force from being weakened and the wheels from locking, and the wheel acceleration is reduced to zero by executing the pressure reduction control as described above. When the wheel acceleration becomes less than or equal to or below a certain value, the braking force is increased by switching to the pressure increase control state and executing the pressure increase control to increase the hydraulic pressure of the wheel cylinder. It is designed to prevent the occurrence of a shortage condition.

Further, the control target speed of each wheel, which is the target for starting pressure reduction control, is set to a value in consideration of a predetermined slip ratio based on the pseudo vehicle body speed, and the pseudo vehicle body speed is the maximum value of the wheel speed of each wheel. And calculated based on the vehicle deceleration. The vehicle body deceleration is calculated based on the wheel speed detected by the wheel speed sensor, and the vehicle body deceleration is subjected to a predetermined deceleration limiter according to the road surface friction coefficient estimated by the acceleration switch. Processing is performed. The value of the deceleration limiter is set to the value at the time of estimating the high friction coefficient road surface (about 1.3 g) at the initial setting, but when the low friction coefficient road surface is estimated by the acceleration switch, the low friction coefficient road surface is set. Estimated value (0.
The setting is changed to about 6 g), so that it is possible to prevent the wheels from entering the early lock state during traveling on a low friction coefficient road surface, particularly in a four-wheel drive vehicle in which four wheels are synchronized.

[0004]

However, in the anti-skid control device for the conventional four-wheel drive vehicle, as described above, when the low friction coefficient road surface is estimated by the acceleration switch, the low friction coefficient road surface is estimated. Since the structure is provided with the deceleration limiter means for applying the deceleration limiter to the estimated value (about 0.6 g), if the state is fixed to the low friction coefficient determination state due to the failure of the acceleration switch, the vehicle is kept in this state. 12 shifts to a high friction coefficient road surface, as shown in FIG. 12, although the actual vehicle body speed is decelerated, the deceleration of the pseudo vehicle body speed is limited by the deceleration limiter when estimating the low friction coefficient road surface. There is a problem in that the pseudo vehicle body speed may increase and, as a result, the vehicle may be over-decompressed and the vehicle may be in a state of insufficient deceleration.

The present invention has been made by paying attention to the above-mentioned conventional problems. When the acceleration switch (road surface friction coefficient estimating means) fails, the low friction coefficient determination state is fixed. Also in the above, it is an object of the present invention to provide an anti-skid control device in a four-wheel drive vehicle that can perform a predetermined fail-safe process for various processes executed based on the estimation content of the road surface friction coefficient estimating means, and At least, it is an additional object to provide an anti-skid control device in a four-wheel drive vehicle that can prevent a vehicle deceleration insufficient state due to the occurrence of an over-reduced pressure state in the fail-safe processing.

[0006]

In order to achieve the above-mentioned object, in the anti-skid control device according to the first aspect of the present invention, the master cylinder that generates the braking fluid pressure and the wheels of the vehicle are respectively arranged. A braking cylinder that is provided and that generates a braking force by supplying hydraulic pressure, a depressurization control state that reduces the hydraulic pressure of the braking cylinder, a holding control state that holds the hydraulic pressure, and an increase pressure that increases the hydraulic pressure. Switching control means capable of switching drive control to any one of the control states, wheel speed detecting means for detecting the wheel speed of each wheel, and vehicle body deceleration based on the wheel speed detected by the wheel speed detecting means A vehicle body deceleration calculating means, a road surface friction coefficient estimating means for estimating whether the road surface friction coefficient is at least a low friction coefficient state or a high friction coefficient state from the change state of the longitudinal acceleration, and the road surface friction coefficient Of the wheels detected by the wheel speed detecting means, and a deceleration limiter means for applying a predetermined deceleration limiter to the vehicle body deceleration calculated by the vehicle body deceleration calculating means according to the road surface friction coefficient estimated by the number estimating means. A pseudo vehicle body speed calculating means for calculating a pseudo vehicle body speed based on the wheel speed and the vehicle body deceleration calculated by the vehicle body deceleration calculating means, and a predetermined vehicle body speed based on the pseudo vehicle body speed calculated by the pseudo vehicle body speed calculating means. Control target speed calculating means for calculating the control target speed of the wheel in consideration of the slip ratio, wheel acceleration calculating means for calculating the acceleration of each wheel from the wheel speed detected by the wheel speed detecting means, and the wheel speed detecting means. When the wheel speed of each wheel detected by the means reaches the control target speed calculated by the control target speed calculation means, the switching control means is switched to the pressure reduction control state. When the pressure reduction control for reducing the hydraulic pressure of the braking cylinder is executed, and thereafter, the wheel acceleration of each wheel calculated by the wheel acceleration calculating means becomes zero or less or becomes a wheel acceleration of a certain value or more. The braking fluid pressure control means for executing the pressure increase control for increasing the fluid pressure of the braking cylinder by switching the switching control means to the pressure increase control state, and the wheel speed from the time point when the pressure reduction control by the braking fluid pressure control means is started. An abnormality determination timer that counts the time to return to the pseudo vehicle body speed, and when the mass count of the abnormality determination timer is equal to or longer than a predetermined abnormality determination time, the road surface friction coefficient estimation means is fixed in a low friction coefficient determination state. And an abnormality determining means for determining an abnormal state.

In the anti-skid control device for a four-wheel drive vehicle according to a second aspect, in the anti-skid control device for a four-wheel drive vehicle according to the first aspect, the abnormality determination means determines that the road surface friction coefficient estimation means is in an abnormal state. When the vehicle is decelerated, the deceleration limiter means determines the vehicle body deceleration calculated by the vehicle body deceleration calculation means based on the road surface friction coefficient content according to the high friction coefficient estimation regardless of the estimation content of the road surface friction coefficient estimation means. The means provided with a fail-safe means for applying the deceleration limiter of.

[0008]

Since the anti-skid control device according to the first aspect of the present invention is configured as described above, in the braking hydraulic pressure control means, the wheel speed of each wheel detected by the wheel speed detection means is a predetermined control target. When the speed is reached, the switching control means is switched to the pressure reducing control state to execute the pressure reducing control for reducing the hydraulic pressure of the braking cylinder, thereby weakening the braking force and preventing the wheels from locking. After that, if the wheel deceleration calculated by the wheel deceleration calculating means becomes zero or less or the wheel acceleration becomes a certain value or more by executing the pressure reducing control as described above, the switching control means is switched to the pressure increasing control state. By executing the pressure increase control for increasing the hydraulic pressure of the braking cylinder, the braking force is strengthened and the deceleration insufficient state of the vehicle body is prevented from occurring.

As described above, the control target speed of each wheel which is the target for starting pressure reduction control is calculated in consideration of a predetermined slip ratio based on the pseudo vehicle body speed, and the pseudo vehicle body speed is the wheel speed of each wheel and the vehicle body. It is calculated based on the deceleration.
Then, the vehicle body deceleration is calculated based on the wheel speed detected by the wheel speed detecting means in the vehicle body deceleration calculating means, and also in accordance with the road surface friction coefficient estimated by the road surface friction coefficient estimating means in the deceleration limiter means. A process of applying a predetermined deceleration limiter to the vehicle body deceleration is performed.

Further, the abnormality determination timer counts the time for the wheel speed to return to the vicinity of the pseudo vehicle body speed from the start of the pressure reduction control by the braking fluid pressure control means, while the abnormality determination means counts the count of the abnormality determination timer. Is determined to be equal to or greater than a predetermined abnormality determination time, and if the count is equal to or greater than the predetermined abnormality determination time, the road surface friction coefficient estimation means is fixed in a low friction coefficient determination state. Is determined. Therefore, by determining the abnormal state of the road surface friction coefficient estimating means, it is possible to perform predetermined fail-safe processing for various processing executed based on the estimation content of the road surface friction coefficient estimating means.

In the anti-skid control device according to the second aspect of the present invention, as described above, when the road surface friction coefficient estimating means is judged to be in the abnormal state by the abnormal state judging means, the vehicle body reduction is performed by the deceleration limiter means in the fail safe means. When applying a predetermined deceleration limiter to the speed, regardless of the estimation content of the road surface friction coefficient estimating means, the process of applying the deceleration limiter based on the road surface friction coefficient content according to the high friction coefficient estimation is performed. Even when the road surface friction coefficient estimation means is in a fixed abnormal state in the low friction coefficient determination state, at least the vehicle deceleration insufficient state due to excessive pressure reduction is prevented.

[0012]

Embodiments of the present invention will be described in detail below with reference to the drawings. First, a configuration of an anti-skid control device in a four-wheel drive vehicle according to an embodiment of the present invention is shown in FIG.
In the four-wheel drive vehicle, a wheel speed sensor (wheel speed sensor) that generates a wheel speed pulse according to the rotation of the right front wheel 10 and the left front wheel 14, which are steered wheels (driven wheels), will be described. Speed detection means) 12 and 1
6, wheel speed sensors (wheel speed detecting means) 24 and 26 that generate wheel speed pulses in response to the rotation of the right rear wheel 20 and the left rear wheel 22, which are driving wheels, and the friction coefficient of the traveling road surface. An acceleration switch G_SW (road surface friction coefficient estimating means) is provided, and these sensors are connected to a control unit (hereinafter referred to as ECU) 40 including a microcomputer (CPU).

Further, the brake hydraulic circuit configuration diagram (1
(Wheel only), a wheel cylinder (braking cylinder) 50 arranged on each wheel and a master cylinder 52 that generates a brake fluid pressure when a driver depresses a brake pedal are connected to the main fluid passage. An actuator unit 60 for controlling the fluid pressure of each wheel cylinder 50 is provided in the middle of the main fluid passage 54.
Is installed. Although not shown in FIG. 2 and only one system of brake fluid pressure circuit and one wheel is illustrated, two systems of brake fluid pressure circuit are connected to the master cylinder 50, and one system of brake fluid pressure circuit is connected. The right front wheel 10 and the left rear wheel 22 wheel cylinders 50, 50 are connected to the circuit, and the left front wheel 14 and the right rear wheel 20 wheel cylinders 50, 50 are connected to the other brake hydraulic circuit. There is.

In this actuator unit 60, a switching control valve (switching control means) 62 for switching and controlling the increase / decrease in the hydraulic pressure of each wheel cylinder 50, and the brake fluid is stored when the pressure reduction of the wheel cylinder 50 is controlled. A reservoir 64 and a hydraulic pump 66 for returning the brake fluid stored in the reservoir 64 to the main fluid passage 54 are provided. The reservoir 64 is provided in each of the two brake hydraulic circuits.

Next, the basic control contents of the anti-skid control in the ECU 40 will be explained based on the control flow chart of FIG. First, in step S1, the right front wheel 10, the left front wheel 14, the right rear wheel 20, and the left rear wheel 22 are output according to the outputs from the wheel speed sensors 12, 16, 24, 26.
The wheel acceleration VWD is calculated by calculating each wheel speed VW and differentiating each wheel speed VW.

In the following step S2, the above step S1
A pseudo vehicle speed, that is, a pseudo vehicle body speed VI is calculated from the wheel speeds VW calculated in step 1. The details of the calculation of the pseudo vehicle body speed VI will be described later with reference to the flowchart of FIG.

In the following step S3, the above step S2
The control target speed (pressure reduction determination threshold value) VWS is calculated from the pseudo vehicle body speed VI calculated in. The details of the calculation of the control target speed VWS will be described later based on the flowchart of FIG. 7.

In the following step S4, PI control calculation processing is performed. That is, the target increase / decrease pulse time PB indicating the target pressure increase / decrease control time of the brake fluid is calculated. The details of the PI control calculation process will be described later with reference to the flowchart of FIG.

In the following step S5, the step S1
The wheel speed VW of each wheel calculated in step S3 is the same as that in step S3.
It is determined whether or not the control target speed VWS calculated in step 2 is less than 1 and the pressure increase execution flag ZFLAG (a flag indicating that pressure increase control is being executed) is set to 1 and YES (VW <VWS , And ZFLAG = 1)
If it is, it is necessary to execute the pressure reduction control, and therefore the process proceeds to step S7.

In this step S7, after the processes listed below are performed, the process proceeds to step S8 where the brake fluid pressure reduction control is executed.・ Set the decompression control execution time AS to the predetermined time A.・ Holding control time THOJI is reset to 0.・ Set the decompression flag GFLAG to 1.

In step S8, brake fluid pressure reduction control is performed. That is, the switching signal is output from the ECU 40 to the switching control valve 62 of the actuator unit 60, and the master cylinder 52, the wheel cylinder 50, and the reservoir 6 are output.
4 is communicated with. The details of this pressure reduction control will be described later based on the flowchart of FIG.

The determination in step S5 is NO (VW ≧ V
If WS or ZFLAG = 0), the process proceeds to step S6. This step S6 is a step of determining the necessity of the brake fluid pressure reduction control. Specifically, the holding control time THOJI exceeds the predetermined time Bms, and the target increase / decrease pulse time PB-depressurization time timer DECT is set. Either the predetermined time T ₁ ms (T1 <) is exceeded, or the hold control time THOJI exceeds the predetermined time Cms (B <C),
Further, the time obtained by subtracting the decompression time timer DECT from the target increase / decrease pulse time PB is a predetermined time T2ms (T2 <T
It is determined whether or not 1) is exceeded, and even if YES (either one of the conditions is satisfied), it is necessary to perform the pressure reduction control, so the process proceeds to step S7.

When the determination in step S6 is NO (none of the conditions is satisfied), the process proceeds to step S9 to determine the necessity of increasing the brake fluid pressure or holding control.
Determine the need for brake fluid pressure increase control. Specifically, from the target increase / decrease pulse time PB to the increase time timer I
The time obtained by subtracting NCT is less than the predetermined time −T ₁ ms,
At the same time, it is determined whether the holding control time THOJI exceeds Cms. If the determination in step S9 is YES (both conditions are satisfied), it can be determined that the wheels have not slipped yet, so the process proceeds to step S10.

In step S10, the pressure reduction execution flag GFLAG (a flag indicating that the pressure reduction control is being executed) is set to 1 and the wheel acceleration V is also increased.
It is determined whether or not WD exceeds 0 g, and if NO (at least one of the conditions is not satisfied), the hydraulic pressure in the wheel cylinder 50 is insufficient, so step S
After proceeding to step 11 and resetting the holding control time THOJI to 0, the procedure proceeds to step S12 for executing the brake fluid pressure increase control.

In step S12, brake fluid pressure increase control is performed. That is, in this case, the switching control valve 62 of the actuator unit 60 is
2 and the wheel cylinder 50 are driven so as to be in communication with each other. The details of this pressure increase control will be described later with reference to the flowchart of FIG. Then, in the subsequent step S13, the pressure increase execution flag ZFLAG is set to 1.

The determination in step S9 is NO (P
B is ≦ −T ₁ ms, or THOJI ≦ C ms), or the determination in step S10 is YES (GFLAG = 0,
Alternatively, when VWD ≦ VIK), step S14
After incrementing the holding control time THOJI, the process proceeds to step S15 in which the brake fluid pressure holding control is performed.

In step S15, the brake fluid pressure holding control is performed. That is, in this case, the switching control valve 62 is driven to a position where the wheel cylinder 50 disconnects the communication with the master cylinder 52 and the reservoir 64, respectively.

After any of the steps S8, S13, S15 is performed, the process proceeds to step S16.
It is determined whether or not ms has elapsed. If less than 10 ms (NO), the determination in step S16 is repeated, and 1
If 0 ms has elapsed (YES), the process proceeds to step S17. In other words, the control routine is executed every 10 ms.

In the following step S17, after the pressure reduction control execution time AS is decremented, the one-time flow is ended, and the process returns to the step S1.

Next, the specific contents of the pseudo vehicle body speed calculation processing control of step S2 in FIG. 3 will be described with reference to the flowchart of FIG. First, in step S21, the wheel speed V of the four wheels is set as the select high wheel speed VFS.
After setting the maximum value of W, the process proceeds to step S22.

In this step S22, it is judged whether or not the non-decompression control is being performed depending on whether or not the decompression control execution time AS is 0. If YES (AS = 0, the non-decompression control is being executed), After proceeding to step S23 and setting the maximum value of the wheel speed VW of the driven wheels as the select high wheel speed VFS, the process proceeds to step S24, and when NO (AS ≠ 0 is being under pressure reduction control), it is as it is. It proceeds to step S24.

In step S24, the pseudo vehicle body speed VI
Is greater than or equal to the select high wheel speed VFS, and if YES (VI ≧ VFS), step S2
After proceeding to 5, the pseudo vehicle body speed VI at the time of vehicle deceleration is obtained by the following equation, and then one flow is ended. VI = VI-VID * k VID is a deceleration limiter of the pseudo vehicle body speed VI (absolute value of a value obtained by adding a predetermined offset value (0.3 g) to the vehicle body deceleration VIK). The details of the calculation of the vehicle body deceleration VIK will be described later with reference to the flowchart of FIG.

In step S24, NO (VI <VF
If it is S), it is determined that the vehicle is accelerating and the routine proceeds to step S26, where the deceleration limiter constant x is set to 2 km / h, and then the routine proceeds to step S27. This step S2
At 7, it is judged again whether or not the non-decompression control is being performed by whether or not the decompression control execution time AS is 0, and YES (A
When S = 0 and the non-pressure reduction control is being performed), the process proceeds to step S28, the deceleration limiter constant x is set to 0.1 km / h, and then the process proceeds to step S29, or NO (pressure reduction control when AS ≠ 0). If it is "medium", the process directly proceeds to step S29.

Then, in this step S29, the pseudo vehicle body speed VI is obtained by the following equation, and then one flow is ended. VI = VI + x

Next, the specific contents of the vehicle body deceleration calculation used in step S25 of FIG. 4 will be described with reference to the flowchart of FIG. First, in step S251, it is determined whether or not the state during non-pressure reduction control (AS = 0) is switched to during pressure reduction control (AS ≠ 0). If YES, the process proceeds to step S252, and pressure reduction control is performed. Is set at the pseudo vehicle body speed VI, that is, the vehicle speed when the vehicle pressure reduction control start vehicle speed VO is set at the pseudo vehicle body speed VI.
After resetting O to 0, the process proceeds to step S253. If NO (during non-depressurization control (AS = 0)), the process proceeds directly to step S253. Then, in step S253, the vehicle deceleration generation timer TO is incremented, and then the process proceeds to step S254.

At step S254 (spin-up determination), the select high wheel speed VFS is the pseudo vehicle speed V.
It is determined whether or not it has returned to I, and YES (VI <VFS →
If VI ≧ VFS), the process proceeds to step S255, and the vehicle body deceleration VIK is calculated by the following equation, and then step S255.
Proceed to 256. VIK = (VO-VI) / TO

Further, the determination in step S254 is NO.
If (VI <VFS), step S25 is performed as it is.
Go to 6. In this step S256, of the abnormal states of the acceleration switch G_SW that determines whether the road surface friction coefficient (μ) is high μ or low μ, a G_SW abnormality determination that detects a fixed state in the low μ road determination state is performed. Is done.
The specific contents of this G_SW abnormality determination will be described later in detail with reference to the flowchart of FIG.

In a succeeding step S257 (determination of low μ road), it is determined whether or not the traveling road surface is a low μ road by determining whether the depressurization time timer DECT is Dms or more, and YES (DECT If ≧ Dms = low μ road), the process proceeds to step S258, the low μ flag LouF is set to 1, and then one flow is ended, and NO (DECT <Dms = high μ road). ), The flow ends once.

Next, step S256 in FIG.
The specific contents of the G_SW abnormality determination / control of the above will be described based on the flowchart of FIG. First, step S56
At 1, it is determined whether or not the abnormality determination flag GSENF is set to 1. If NO (GSENF = 0), it is determined that the acceleration switch G_SW is operating normally. The process proceeds to step S562 to perform processing based on

In this step S562, it is determined whether or not the output of the acceleration switch G_SW is in the high μ road determination state Hi, and if it is NO (low μ road determination state Lo), the process proceeds to step S563 to reduce the vehicle body. The speed VIK is set to the smaller value of the low μ road equivalent limiter value of 0.6 g and the vehicle body deceleration VIK calculated in step S255 of FIG. 5, and the deceleration limiter of the pseudo vehicle body speed VI is set. VI
D is the smaller of 0.6 g which is a low μ road equivalent limiter value and the absolute value of the value obtained by adding a predetermined offset value (0.3 g) to the vehicle body deceleration VIK calculated in step S255 of FIG. After setting the other value, the process proceeds to step S564.

In step S564, the wheel speed VW
Is determined to be equal to or higher than the pseudo vehicle body speed VI, the result of the pressure reduction control is that the wheel speed VW is the pseudo vehicle body speed VI.
If NO (VW <VI), the acceleration switch G_SW has an abnormality, that is, a high μ
Even if the road is a road, it may be fixed in the low μ road judgment state.
Proceed to.

In this step S565, first, it is determined whether the count TSWLO of the abnormality determination timer is 1 sec or more to determine whether the acceleration switch G_SW is abnormal, and if YES (TSWLO ≧ 1 = abnormal). Proceeds to step S566 to set the vehicle speed when the pressure reduction control is first performed, that is, the pressure reduction control start vehicle speed VO to the pseudo vehicle body speed VI, reset the vehicle deceleration generation timer TO to 0, and The vehicle body deceleration VIK is set to an initial setting value 1.3 g for high μ in order to prevent the occurrence of a vehicle deceleration insufficient state due to excessive decompression, and the abnormality determination flag GSENF is set to 1 in the following step S567, and the subsequent step In S568, the deceleration limiter VID for the pseudo vehicle body speed VI
Is set to 1.3 g, the process proceeds to step S572.

The determination in step S565 is NO (TS
When WLO <1), the process proceeds to step S569, the count TSWLO of the abnormality determination timer is incremented, and then the process proceeds to step S572.

The determination in step S564 is YES (V
When W ≧ VI), the acceleration switch G_SW is operating normally, or at least the high μ road determination state is set. Therefore, the process proceeds to step S570, and the count TSWLO of the abnormality determination timer is reset to 0. Then, it progresses to step S572.

If the determination in step S562 is YES (high μ road determination state Hi), the flow advances to step S571 to set the vehicle body deceleration VIK to 1.3 g, which is the limiter value corresponding to the high μ road, as shown in FIG. The deceleration limiter VID of the pseudo vehicle body speed VI is set to the smaller one of the vehicle body deceleration VIK calculated in step S255 and 1.3 g which is the limiter value corresponding to the high μ road and the step of FIG. S25
After setting the vehicle deceleration VIK calculated in step 5 to the absolute value of the value obtained by adding a predetermined offset value (0.3 g), whichever is smaller, the process proceeds to step S572.

The determination in step S561 is YES (G
When SENF = 1), it is determined that the output of the acceleration switch G_SW is fixed in the low μ road determination state Lo despite the high μ road. In order to avoid the occurrence of the vehicle deceleration insufficient state due to the pressure reduction, the process proceeds to step S571, and the vehicle body deceleration VIK is set to the high μ road equivalent limiter value of 1.3 g.
And the vehicle body deceleration VI calculated in step S255 of FIG.
K, whichever is smaller, and the deceleration limiter VID of the pseudo vehicle body speed VI is 1.3 g, which is the limiter value corresponding to the high μ road, and the vehicle body deceleration VIK calculated in step S255 of FIG. Predetermined offset value (0.3g)
Is set to the smaller of the absolute value of the added value and the smaller value, and the process proceeds to step S572.

In this step S572, it is determined whether or not the anti-skid control is being performed by determining whether or not the pressure reducing control execution time AS is reset to 0, and when YES (AS = 0) is determined. For step S573
After resetting the abnormality determination flag GSENF to 0, the flow ends once, and when NO (AS ≠ 0), the flow ends immediately.

Next, the specific contents of the control target speed calculation of step S3 in FIG. 3 will be described with reference to the flowchart of FIG. First, in step S31, the offset value XX of the control target speed VWS is first set to 8 km /
After setting to h, the process proceeds to step S32.

In step S32, the vehicle body deceleration VI
By determining whether K is less than the predetermined value E and the low μ flag LouF is set to 1, it is determined whether or not the traveling road surface is a low μ road, and YES (low μ road (Determination), the process proceeds to step S33, the offset value XX is changed and set to 4 km / h, and then step S3
4. If NO (high μ road determination), go to step S3 (without changing XX = 8 km / h).
Go to 4.

In step S34, the control target speed VWS is calculated based on the following equation based on the pseudo vehicle body speed VI calculated in the flow chart of FIG. 4 and the offset value XX, and then the process proceeds to step S35. VWS = 0.95 × VI-XX

In step S35, the pressure reduction flag GF is set.
LAG is set to 1, the wheel acceleration VWD exceeds a predetermined value F, and the wheel speed VW is equal to the control target speed V.
It is determined whether or not WS is exceeded, and if YES,
In step S36, the target slip vehicle speed VWM is set to the pseudo vehicle body speed VI, and if NO, the process proceeds to step S37 to set the target slip vehicle speed VWM to the control target speed VWS. End the flow.

Next, P in step S4 in FIG.
Specific contents of the I control calculation process will be described with reference to the flowchart of FIG. First, in step S41, the deviation ΔVW is calculated based on the following equation. ΔVW = VWM-VW

In the following step S42, PI is calculated by the following equation.
The proportional PP of control is obtained. PP = KP × ΔVW (KP: Proportional gain) In the following step S43, the integral IP of PI control is obtained by the following equation. IP = 10 ms before IP + KI × ΔVW (KI: integral gain)

In the following step S44, the target increase / decrease pulse time PB is obtained from the following equation, and one flow is ended. PB = PP + IP

Next, the specific contents of the pressure reducing control in step S8 in FIG. 3 will be described with reference to the flowchart in FIG. First, in step S81, the pressure increase time counter INCT is reset to 0, and then in step S82, the depressurization pulse time GAW is set to the target increase / decrease pulse time P.
After setting to B, the process proceeds to step S83.

In step S83, it is determined whether or not the pressure boosting execution flag ZFLAG is set to 1, and Y
When ES (ZFLAG = 1), the process proceeds to step S84, the depressurization pulse time GAW is calculated by the following equation, and GAW = VWD × α / VIK (α: coefficient) pressure boosting execution flag ZFLAG is reset to 0. After that, the process proceeds to step S85. If NO (ZFLAG = 0), the process proceeds directly to step S85.

In step S85, the port pressure reducing output process is performed, and the pressure reducing time timer DECT is incremented, and then the process proceeds to step S86.

In step S86, it is determined whether the depressurization time timer DECT is equal to or longer than the depressurization pulse time GAW or the wheel acceleration VWD exceeds the predetermined value F, and YES (DECT ≧ GAW, or, VWD) is determined. >
If it is F), the process proceeds to step S87, the holding control output process is performed, the depressurization time timer DECT is decremented, and then one flow is ended, and N
If O (DECT <GAW, and, VWD ≦ F), this ends the flow once.

Next, the specific contents of the pressure increase control of step S12 in FIG. 3 will be described with reference to the flowchart of FIG. 10. First, in step S121, the pressure reduction time counter DECT is reset to 0, and the subsequent step S12.
In 2, the pressure increasing pulse time ZAW is set to the target pressure increasing / depressurizing pulse time PB, and then the process proceeds to step S123.

In a succeeding step S123, it is determined whether or not the depressurization execution flag GFLAG is set to 1.
If YES (GFLAG = 1), step S12.
4, the pressure reduction pulse time GAW is obtained by the following equation, and GAW = VWD × β × VIK (β: coefficient) After the pressure reduction execution flag GFLAG is reset to 0, the flow proceeds to step S125, and NO (GFLAG = If it is 0), the process directly proceeds to step S125.

In step S125, the port pressure increase output process is performed, and the pressure increase time timer INCT is incremented. Then, the process proceeds to step S126. In step S126, it is determined whether the pressure increase time timer INCT is equal to or longer than the pressure increase pulse time ZAW, and YES (IN
If CT ≧ ZAW), the process proceeds to step S127, the port hold output process is performed, and the pressure increase time timer INCT is decremented. Then, one flow is ended, and NO (INCT <ZAW). ),
This completes one flow.

Next, the operation and effect of the embodiment of the present invention will be described based on the time chart of FIG. (A) Antiskid basic control Since the antiskid control device according to the embodiment of the present invention is configured as described above, each wheel 10 detected by the wheel speed sensors 12, 16, 24, 26 in the ECU 40, 1
When the wheel speeds VW of 4, 20, 21 become less than the control target speed VWS obtained from the pseudo vehicle body speed VI, the wheels may be locked. Therefore, the switching control valve 62 is switched to the pressure reducing control state and the wheel cylinder 50 is operated. The braking force is weakened by executing depressurization control for depressurizing the hydraulic pressure. By executing this pressure reduction control, the wheel speed VW changes from the deceleration direction to the acceleration direction,
The wheels are prevented from locking.

After that, when the wheel acceleration VWD becomes 0 g or less by executing the pressure reducing control as described above, the switching control valve 62
Is switched to the pressure increasing control state to execute the pressure increasing control for increasing the hydraulic pressure of the wheel cylinder 50, thereby increasing the braking force and preventing the deceleration of the vehicle body from being insufficient.

(B) Setting of deceleration limiter value As described above, the control target speed VWS of each wheel which is the target of pressure reduction control is calculated in consideration of a predetermined slip ratio based on the pseudo vehicle body speed VI (FIG. 7), The pseudo vehicle body speed is selected high wheel speed VFS and vehicle body deceleration VI.
It is calculated based on the deceleration limiter VID of the pseudo vehicle body speed VI obtained by adding a predetermined offset value (0.3 g) to K (step S25 in FIG. 4).

Then, the vehicle body deceleration VIK is calculated by the vehicle wheel deceleration calculation means (FIG. 5) by the wheel speed sensors 12, 1.
The processing is performed based on the wheel speed VW detected at 6, 24, and 26, and a process of applying a predetermined limiter to the vehicle body deceleration VIK and the deceleration limiter VID according to the road surface μ estimated by the acceleration switch G_SW is performed. . That is, when the estimated output of the acceleration switch G_SW is in the high μ road judgment state Hi, the deceleration limiter value of the deceleration limiter VID of the vehicle body deceleration VIK and the pseudo vehicle body speed VI becomes 1.3 g which is the high μ road equivalent limiter value. When the estimated output of the acceleration switch G_SW is in the low μ road determination state Lo, a process for setting the low μ road equivalent limiter value to 0.6 g is performed.

(C) Acceleration Switch Abnormality Judgment In the abnormality judgment timer, the wheel speed VW becomes the pseudo vehicle body speed VI from the time when the pressure reduction control by the control unit 40 starts.
While the time for returning to (VW ≧ VI) is counted, the abnormality determination means of the acceleration switch G_SW determines whether the count TSWSO of the abnormality determination timer is equal to or longer than a predetermined abnormality determination time (1 sec). Done,
If the count TSWSO is less than 1 second, it is determined that the acceleration switch G_SW is operating normally.
Based on the road surface μ judgment content of the acceleration switch G_SW,
The deceleration limiter values of the deceleration limiter VID for the vehicle body deceleration VIK and the pseudo vehicle body speed VI are set.

However, as shown in FIG. 11, when the count TSWSO of the abnormality determination timer is 1 sec or more, the pseudo vehicle body speed VI is higher than the actual vehicle body speed Vcar, and the wheel speed VW is increased. Is an abnormal state in which the reduced pressure is excessive without returning to the pseudo vehicle body speed VI. Therefore, in such a case, the actual road surface has a high μ
It is determined that the acceleration switch G_SW is in an abnormal state fixed in the low μ road determination state Lo regardless of whether the road is a road.

(D) Failsafe processing at the time of acceleration switch abnormality determination When the abnormality determination is made as described above, the vehicle body deceleration VIK and the pseudo vehicle body speed VI are performed as the abnormality state determination processing.
The fail-safe process of setting the deceleration limiter value of the deceleration limiter VID of No. 3 to 1.3 g which is the high μ road equivalent limiter value corrects the up-shift state of the pseudo vehicle body speed VI with respect to the actual vehicle body speed Vcar. Therefore, although the actual road surface is a high μ road, the acceleration switch G_S
Even when W is in the abnormal state that is fixed in the low μ road determination state Lo, at least the effect of being able to prevent the vehicle deceleration insufficient state due to excessive decompression can be obtained.

Although the embodiments of the present invention have been described in detail above with reference to the drawings, the specific configuration is not limited to the embodiments of the present invention, and design changes and the like within the scope not departing from the gist of the present invention. Even so, it is included in the present invention. For example, in the embodiment of the invention, the pressure increase is performed again when the wheel acceleration VWD becomes 0 g or less, but in addition, when the wheel acceleration VWD becomes a predetermined value (5 g) or more, the pressure is promptly increased. By starting the repressurization,
The pseudo vehicle body speed VI can be made fine.

Further, in the embodiment of the invention, the select high wheel speed VFS which is the maximum value of each wheel speed is used in the calculation of the pseudo vehicle body speed VI.
The second or third highest wheel speed may be selected and used according to the running state of the vehicle. Further, in the embodiment of the invention, the example in which the acceleration switch G_SW is used as the road surface friction coefficient estimating means is shown, but a longitudinal acceleration sensor may be used in addition to the above.

Further, in the embodiment of the invention, an example in which the abnormality determination timer count TSWLO is set to 1 sec has been shown, but the invention is not limited to this, and for example, 0.5 se.
By setting the value within the range of c to 2.0, it is possible to prevent erroneous determination when traveling on a low μ road surface, and prevent the braking failure state from becoming long.

In the embodiment of the invention, the predetermined deceleration limiter value applied to the vehicle body deceleration VIK in the low μ road determination state Lo is set to 0.6 g, but the present invention is not limited to this. No, for example, 0.3 g to 0.7 g
By setting it within the range, it is possible to prevent the braking distance from becoming long and to prevent the early locking from occurring.

Further, in the embodiment of the invention, an example in which the predetermined deceleration limiter value applied to the vehicle body deceleration VIK in the high μ road judgment state Hi is set to 1.3 g has been shown, but the present invention is not limited to this. No, for example, 0.85 g to 1.5
By setting it within the range of g, it is possible to prevent the braking distance from becoming long and prevent the occurrence of early locking.

Further, in the embodiment of the invention, the predetermined deceleration limiter value applied to the vehicle body deceleration VIK is set to 1.3 g based on the content of the road friction coefficient conforming to the high μ road judgment state Hi in the fail-safe processing. However, the present invention is not limited to this. For example, 0.85
By setting it within the range of g to 1.5 g, it is possible to prevent the braking distance from becoming long and prevent the occurrence of early locking.

[0075]

As described above, in the anti-skid control device for a four-wheel drive vehicle according to claim 1 of the present invention, the wheel speed is close to the pseudo vehicle body speed from the time when the pressure reduction control by the braking hydraulic pressure control means is started. An abnormality determination timer that counts the time to return to, and when the mass count of the abnormality determination timer is equal to or longer than a predetermined abnormality determination time, the road surface friction coefficient estimating means determines that the abnormal state is fixed in the low friction coefficient determination state. By using the means for determining abnormality of determining the friction coefficient of the road surface, the estimated content of the friction coefficient estimating means of the road surface can be estimated even when the road friction coefficient estimator is in a state of being fixed to the low friction coefficient judgment state due to a failure of the hand. There is an effect that it is possible to perform a predetermined fail-safe process for various processes executed based on the above.

In an anti-skid control device for a four-wheel drive vehicle according to a second aspect of the present invention, in the first aspect, when the abnormality determination means determines that the road friction coefficient estimating means is in an abnormal state, the road friction coefficient estimating means operates. Includes fail-safe means for applying a predetermined deceleration limiter to the vehicle body deceleration calculated by the vehicle body deceleration calculation means based on the road surface friction coefficient content according to the high friction coefficient estimation in the deceleration limiter means regardless of the estimation content. Even if the acceleration switch (road surface friction coefficient estimation means) fails and the low friction coefficient determination state is fixed, at least the vehicle deceleration is insufficient due to the over-decompression state. The effect of being able to prevent falling is obtained.

[Brief description of drawings]

FIG. 1 is a system schematic diagram showing an anti-skid control device according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of a brake hydraulic circuit in the anti-skid control device according to the embodiment of the invention.

FIG. 3 is a control flowchart showing basic control contents in the ECU of the anti-skid control device according to the embodiment of the present invention.

FIG. 4 is a flowchart showing a pseudo vehicle speed calculation content of the control content in the ECU of the anti-skid control device according to the embodiment of the present invention.

FIG. 5 is a flowchart showing a vehicle deceleration calculation content of the control content in the ECU of the anti-skid control device according to the embodiment of the present invention.

FIG. 6 is a flowchart showing an abnormality determination / control content of an acceleration switch among the control content in the ECU of the anti-skid control device according to the embodiment of the present invention.

FIG. 7 is a flowchart showing a control target speed calculation content of the control content in the ECU of the anti-skid control device according to the embodiment of the present invention.

FIG. 8 is a flow chart showing PI control calculation processing contents of the control contents in the ECU of the anti-skid control device according to the embodiment of the present invention.

FIG. 9 is a flowchart showing a pressure reducing control content of the control content in the ECU of the anti-skid control device according to the embodiment of the present invention.

FIG. 10 is a flowchart showing a pressure increasing control content of the control content in the ECU of the anti-skid control device according to the embodiment of the present invention.

FIG. 11 is a time chart showing the abnormality determination / control contents of the acceleration switch among the control contents in the ECU of the anti-skid control device according to the embodiment of the present invention.

FIG. 12 is a time chart showing an operating state of the conventional anti-skid control device when an acceleration switch is abnormal.

[Explanation of symbols]

10 right front wheel 12 Wheel speed sensor (wheel speed detecting means) 14 left front wheel 16 Wheel speed sensor (wheel speed detecting means) 20 right front wheel 22 left front wheel 24 Wheel speed sensor (wheel speed detecting means) 26 Wheel speed sensor (wheel speed detecting means) 40 ECU (braking hydraulic pressure control means) 50 wheel cylinder (braking cylinder) 52 Master cylinder 54 Main liquid passage 60 actuator unit 62 Switching control valve (switching control means) 64 reservoir 66 hydraulic pump VI pseudo vehicle speed VW wheel speed VWS control target speed ZFLAG booster execution flag GFLAG decompression implementation flag AS decompression control execution time THOJI hold control time PB target increase / decrease pulse time VFS select high wheel speed LoμF Low μ flag VIK body deceleration VID Pseudo vehicle speed deceleration limiter value G_SW Acceleration switch TSWLO abnormality determination timer count GSENF abnormality judgment flag x Deceleration limiter constant Vehicle speed at the start of VO pressure reduction control TO Vehicle deceleration timer DECT decompression time timer XX offset value VWD Wheel acceleration (differential value of wheel speed VW) VWM target slip vehicle speed INCT Pressure boosting time timer GAW decompression pulse α coefficient ZAW boost pulse β coefficient ΔVW deviation (deviation between target slip vehicle speed and wheel speed) Proportional to PP deviation KP proportional gain IP deviation integral KI integral gain

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Nobuyuki Otsu             1370 Onna, Atsugi, Kanagawa             Nissia Jex F-term (reference) 3D046 AA01 BB01 BB23 BB28 CC02                       EE01 HH23 HH26 HH36 HH39                       HH46 JJ06 KK00 KK03 KK11                       MM06 MM13

Claims (2)

[Claims] 1. A master cylinder that generates a braking hydraulic pressure, a braking cylinder that is disposed on each wheel of a vehicle and that generates a braking force by supplying a hydraulic pressure, and a hydraulic pressure of the braking cylinder is reduced. Switching control means capable of switching drive control to any one of a pressure reduction control state, a holding control state for holding the hydraulic pressure, and a pressure increase control state for increasing the hydraulic pressure, and a wheel for detecting the wheel speed of each wheel. Speed detecting means, vehicle deceleration calculating means for calculating the vehicle deceleration based on the wheel speed detected by the wheel speed detecting means, and the road surface friction coefficient is at least a low friction coefficient state or high from the change state of the longitudinal acceleration. A road surface friction coefficient estimating means for estimating whether the vehicle is in a friction coefficient state, and a predetermined vehicle body deceleration calculated by the vehicle body deceleration calculating means according to the road surface friction coefficient estimated by the road surface friction coefficient estimating means. Deceleration limiter means for applying the deceleration limiter, and a pseudo vehicle body speed for calculating a pseudo vehicle body speed based on the wheel speed of each wheel detected by the wheel speed detecting means and the vehicle body deceleration calculated by the vehicle body deceleration calculating means. Calculating means, control target speed calculating means for calculating a control target speed of a wheel in consideration of a predetermined slip ratio based on the pseudo vehicle body speed calculated by the pseudo vehicle body speed calculating means, and detection by each wheel speed detecting means When the wheel acceleration calculating means for calculating the acceleration of each wheel from the determined wheel speed, and the wheel speed of each wheel detected by the wheel speed detecting means becomes the control target speed calculated by the control target speed calculating means. Switches the switching control means to the pressure reduction control state to execute pressure reduction control for reducing the hydraulic pressure of the braking cylinder, and then calculates by the wheel acceleration calculation means. Pressure increasing control for changing the switching control means to the pressure increasing control state to increase the hydraulic pressure of the braking cylinder when the wheel acceleration of each wheel becomes zero or less or becomes a wheel acceleration of a certain value or more. A braking fluid pressure control means, an abnormality determination timer that counts the time for the wheel speed to return to near the pseudo vehicle body speed from the time point when the pressure reduction control by the braking fluid pressure control means is started, and the abnormality count timer has a predetermined count. In the four-wheel drive vehicle, when the abnormality determination time is longer than or equal to, the road surface friction coefficient estimating means includes an abnormality determining means that determines that the road surface friction coefficient is fixed in a low friction coefficient determining state. Anti-skid control device. 2. When the abnormality determining means determines that the road surface friction coefficient estimating means is in an abnormal state, the deceleration limiter means performs the road surface friction according to the high friction coefficient estimation regardless of the estimation content of the road surface friction coefficient estimating means. The anti-skid control for a four-wheel drive vehicle according to claim 1, further comprising fail-safe means for applying a predetermined deceleration limiter to the vehicle body deceleration calculated by the vehicle body deceleration calculation means based on the content of the coefficient. apparatus.