JP2790519B2 - Anti-skid control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Overview An anti-skid control system that determines at least a coefficient of friction between a road surface and a wheel based on a detection result of an acceleration sensor, and controls a braking force of the wheel according to the determination result. When the amount of change in the vehicle speed per predetermined time is equal to or greater than a predetermined value, or during a period from the start to the end of the anti-skid control, or within a predetermined time from the start of the pressure reduction control, the acceleration sensor When no change is detected in the output of, it is determined that the acceleration sensor is abnormal.

Thus, the abnormality of the acceleration sensor is determined early and accurately, and the fail-safe function is expanded.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an anti-skid control method for determining at least a friction coefficient between a wheel and a road surface using an acceleration sensor and controlling the braking force to an optimum braking force based on the determination result.

2. Description of the Related Art An anti-skid control device including an acceleration sensor has been put to practical use for determining a coefficient of friction between a wheel and a road surface and detecting a vehicle speed. In such an anti-skid control device, when a failure occurs in the acceleration sensor, a change in the acceleration of the vehicle body is not detected in spite of the fact that braking is being performed, so that excessive pressure reduction control is performed and the braking force is significantly increased. Problems such as dropping or locking of all wheels due to excessive pressure increase control occur.

In a typical conventional technique, a switch-type acceleration sensor configured using a pendulum, mercury, or the like is used.
Further, the abnormality determination of the acceleration sensor is performed based on whether or not the output of the acceleration sensor changes during a predetermined number of times, for example, 20 times or more, for stopping the motor from a predetermined speed or more. I have.

According to the above-described related art, since the abnormality determination is not performed until the number of stops from the speed reaches the predetermined number, it takes a relatively long time to complete the determination. Also,
Repeated stoppages with gentle brakes can lead to erroneous determinations.

On the other hand, in a configuration in which the vehicle speed or the acceleration is obtained based on the wheel speed, if all the wheels are locked, the detection becomes impossible. In addition, due to the slip between the wheels and the road surface, the detection accuracy is poor.

An object of the present invention is to provide an anti-skid control method that can quickly and accurately determine abnormality of an acceleration sensor.

Means for Solving the Problems The present invention detects an acceleration in the traveling direction of a vehicle body using an acceleration sensor, and based on the detection result, determines at least a coefficient of friction between a road surface and a wheel. In the anti-skid control method of controlling the braking force of the wheels in accordance with the following, when the amount of change per unit time of the vehicle speed obtained based on the wheel speed is equal to or greater than a predetermined value, the output of the acceleration sensor changes. If not detected,
The anti-skid control system is characterized in that it is determined that the acceleration sensor is abnormal, and the determination of the friction coefficient based on the detection result of the acceleration sensor is prohibited.

Further, the present invention detects acceleration in the traveling direction of the vehicle body using an acceleration sensor, determines at least a coefficient of friction between the road surface and the wheels based on the detection result, and controls the wheels according to the determination result. In the anti-skid control method for controlling the power, when no change is detected in the output of the acceleration sensor between the start time and the end time of the anti-skid control, it is determined that the acceleration sensor is abnormal, and the detection result of the acceleration sensor is determined. The anti-skid control system is characterized in that the determination of the friction coefficient based on the control is prohibited.

Furthermore, the present invention detects acceleration in the traveling direction of the vehicle body using an acceleration sensor, determines at least a coefficient of friction between the road surface and the wheel based on the detection result, and determines the friction coefficient of the wheel according to the determination result. In the anti-skid control method for controlling the braking force, when no change is detected in the output of the acceleration sensor within a predetermined time from the start of the pressure reduction control,
The anti-skid control system is characterized in that it is determined that the acceleration sensor is abnormal, and the determination of the friction coefficient based on the detection result of the acceleration sensor is prohibited.

In the anti-skid control system according to the present invention, the acceleration in the traveling direction of the vehicle body is detected by using an acceleration sensor, and the friction coefficient between the road surface and the wheels is determined based on the detection result. Is calculated. The braking force of the wheel is controlled during the anti-skid control in accordance with the determination result and the calculation result.

On the other hand, in performing the above-described anti-skid control, when the amount of change per unit time of the vehicle speed obtained from the wheel speed is equal to or more than a predetermined value, or from the start to the end of the anti-skid control. If no change is detected in the output of the acceleration sensor during the predetermined time or within a predetermined time after the start of the pressure reduction control, it is determined that the acceleration sensor is abnormal.

Therefore, even if the gentle braking operation is continued, the abnormality of the acceleration sensor can be accurately detected. When the determination result is abnormal, the use of the detection result of the acceleration sensor is prohibited by, for example, determining the friction from the wheel speed by determining the acceleration.

Embodiment FIG. 1 is a block diagram showing an electric configuration of an anti-skid control device according to an embodiment of the present invention, and FIG. 2 is a piping diagram of control hydraulic pressure of the anti-skid control device.
Wheel speed sensors 1a to 1d provided for each wheel 34a to 34d
Detects the rotational speeds of the wheels 34a to 34d, respectively.

These wheel speed sensors 1a to 1d are provided, for example, in the circumferential direction of a ferromagnetic detection plate fixed to a wheel shaft, with a number of notches and projections at equal intervals, and provided near the periphery of the detection plate. An electromagnetic pickup or an optical sensor is used to derive a wheel speed signal having a frequency proportional to the rotational speed of the wheel. The wheel speed signals from the wheel speed sensors 1a to 1d are applied to waveform shaping circuits 5a to 5d in the anti-skid control circuit 4, and after being shaped into pulse signals,
Input to the processing circuit 2.

The acceleration sensor 3 outputs an analog signal having a level corresponding to the acceleration as described later. The output signal from the acceleration sensor 3 is supplied to an analog / digital conversion circuit 6 and converted into a digital value, and then supplied to the processing circuit 2, where a digital filter process for removing unnecessary components is performed. The processing circuit 2 includes these wheel speed sensors 1a to 1a.
An arithmetic operation is performed based on 1d and the output from the acceleration sensor 3 to perform anti-skid control.

After the output from the switch 7 for detecting that the brake pedal 30 is depressed is converted to a suitable voltage level in the anti-skid control circuit 4 by the level conversion circuit 8, the processing circuit 22 receives the input signal. Is done. Each circuit in the anti-skid control circuit 4 has a power switch.
The voltage from the battery 11 input through the power supply 10 is supplied after being stabilized by the power supply circuit 9.

The processing circuit 2 drives and controls the actuators 13a to 31d composed of the three-position electromagnetic control valves 32a to 32d and the wheel cylinders 33a to 33d, based on the input result input as described above, Perform anti-skid control operation. That is, the relay coil 15a of the relay 15 is excited via the solenoid relay drive circuit 14, whereby the relay switch 15b is turned on. This Relace Switch 15b
, A high-level voltage is commonly applied to one input of each of the actuators 13a to 13d. Control outputs from the processing circuit 2 are given to the other inputs of these actuators 13a to 13d via solenoid driving circuits 12a to 12d, respectively. This allows a three-position solenoid control valve
32a to 32d control the brake hydraulic pressure to one of the pressure increasing, reducing, and holding states, as described later.

Further, the processing circuit 2 derives an output to the relay coil 16a of the relay 16 via the motor relay drive circuit 18, whereby the motor 17 for generating the braking oil pressure connected to the relay switch 16b of the relay 16 is driven. Controlled. Furthermore, when an abnormality occurs in the anti-skid control, the processing circuit 2 turns on the warning lamp 19 via the lamp driving circuit 20.

Referring to FIG. 2, when the brake pedal 30 is depressed, a braking oil pressure is generated in the master cylinder 31, and the braking oil pressure is transmitted through the pipes P1 to P4 to the three-position electromagnetic control valve 32.
a to 32d, and further supplied to wheel cylinders 33a to 33d via pipelines P5 to P8. As a result, the wheels 34
a to 34d are braked and the vehicle speed decreases.

When the anti-skid control circuit 4 determines that the conditions for starting the anti-skid control are satisfied, the motor 17
The braking hydraulic pressure generated by the three-position electromagnetic control valve is supplied to the master cylinder 31 via a pipeline P9.
32a to 32d are controlled to increase, decrease, or maintain pressure, and brake hydraulic pressures of the wheel cylinders 33a to 33d are controlled.
As a result, the slip ratio of the wheels 34a to 34d is controlled so that a high friction control force acts on the road surface.

FIG. 3 is a block diagram showing the configuration of the acceleration sensor 3, and FIG. 4 is a diagram for explaining the principle of acceleration measurement by the acceleration sensor 3. As shown in FIG. The acceleration detector 41 of the acceleration sensor 3 is composed of three metal plates 41a, 41b, 41c arranged in parallel with each other in a direction intersecting with the running direction of the vehicle body indicated by the arrow A. Therefore, two capacitors 4 are formed by the adjacent metal plates 41a and 41c: 41c and 41b.
1ac and 41cb are configured.

The metal plates 41a and 41b are fixed, and the metal plate 41c is configured to be displaceable in the arrow A direction. Therefore, when the metal plate 41c is displaced by the acceleration in the arrow A direction,
The capacitance Cac of the capacitor 41ac and the capacitance Ccb of the capacitor 14ab change as shown in FIG.

Therefore, the acceleration can be detected from the change in the capacitances Cab and Ccb. A rectangular wave pulse as shown in FIG. 6 (1) is applied from the oscillator 42 to one capacitor 41ac of the acceleration detecting unit 41 configured as described above, and the other capacitor 41cb receives the rectangular wave pulse. The pulse is applied after being inverted by the inverting buffer 43 as shown in FIG. 6 (2).

The output of the acceleration detection unit 41 is derived from a connection point 41e of the capacitors 41ac and 41cb, amplified by, for example, about 20 dB in an amplifier 44, and then from a switch 45 via a low-pass filter (abbreviation: LPF) 46 to the analog / It is derived to the digital conversion circuit 6.

The switch 45 includes the oscillator shown in FIG.
A square wave pulse from 42 is given and the switch 45
Conducts when this pulse is at a high level and shuts off when it is at a low level.

Therefore, as shown in FIG. 6 (3), before time t0 when no acceleration is applied, a zero-level output is derived from the connection point 41e, and time t0 when acceleration is applied.
Thereafter, an output of a level corresponding to the acceleration is derived. This output is output from the switch 45 during a period when no pulse is derived from the oscillator 42,
After the level output is cut off, the output is smoothed by the LPF 46 and output.

FIG. 7 is a timing chart for explaining an abnormality detection operation of the acceleration sensor 3. A timer is built in the processing circuit 2, and the timer is shown in FIG.
As shown by, a clocking operation is performed for a predetermined time W1, for example, 1 second.

When the clocking operation of the timer is started at time t1, the seventh
As shown in FIG. 2B, a change detection flag F2 indicating whether or not the output of the acceleration sensor 3 has changed is once set to 1. This fluctuation detection flag F2 is
Is reset to 0 when the output fluctuates (time t
2).

The timer performs a clocking operation until the time W1 elapses, and at a time t3 when the count value CT elapses the time W1, the change amount ΔV of the estimated vehicle body speed obtained from the wheel speed, as described later, When it is equal to or greater than the predetermined threshold V1, the inspection of the acceleration sensor 3 is permitted. In this way, the inspection of the acceleration sensor 3 is performed. If the acceleration sensor 3 is normal, the fluctuation detection flag F2 is set to 1, and the abnormality flag F1 indicating whether the acceleration sensor 3 is abnormal is set in FIG. 7 (3). Is reset to 0 as shown by

After being reset at time t3, the timer restarts the clocking operation.At time t4 when the time W1 has elapsed from the time t3, the change amount ΔV of the estimated vehicle speed is equal to or greater than the threshold value V1. At some point, the fluctuation detection flag F2 is checked again.

At this time, as shown in FIG. 7 (2), when the fluctuation detection flag F2 remains at 1 set at the time t3, that is, when the output of the acceleration sensor 3 has not fluctuated, the acceleration It is determined that an abnormality has occurred in the sensor 3, and the abnormality flag F1 is set to 1 as shown in FIG. 7 (3).

FIG. 8 is a flowchart for explaining the abnormality detecting operation of the acceleration sensor 3 described above. In step m1,
It is determined whether or not the abnormality flag F1 is 1, and if not, the process proceeds to step m2, where the count value of the timer is set.
The count operation is performed by adding 1 to CT. Step
At m3, it is determined whether or not the predetermined time W1 has elapsed from the count result at step m2, and if not, the process proceeds to step m4.

In step m4, the previous output value G of the acceleration sensor 3
It is determined whether (n- ₁ ) is equal to the current output value G (n). If not, that is, if the output of the acceleration sensor 3 fluctuates as shown at time t2 in FIG. If it is detected, the fluctuation detection flag is set in step m5.
After F2 is reset to 0, the operation ends, and if so, the operation ends directly.

In step m3, when the time W1 has elapsed, that is, at the timings t3 and t4 in FIG. 7, the process proceeds to step m6. In step m6,
Whether the difference ΔV between the previous estimated vehicle speed stored in the buffer _VSB and the current estimated vehicle speed _Vsi is equal to or greater than the predetermined threshold value V1, for example, 3.5 km / h / sec (0.1 G). If it is, that is, if the vehicle speed per unit time fluctuates and abnormality of the acceleration sensor 3 can be determined, the process proceeds to step m7.

At step m7, it is determined whether or not the fluctuation detection flag F2 is set to 1. If so, that is, if it is indicated at time t4 in FIG. 7, the process proceeds to step m8, and the abnormality flag F1 is set. Is set to 1,
Further, after the count value CT of the counter is reset to 0 in step m9, the operation ends.

In contrast, when the estimated vehicle speed V _si has not changed at step m6, and when the variation detection flag F2 at step m7 is reset to 0 step
moved to m10, the current estimated vehicle speed V _si are stored in buffer V _SB, further is reset to the count value CT 0 of the timer at step m11, after change detection flag F2 is excisional to 1 at step m12, End the operation.

FIG. 9 is a flow chart for explaining the anti-skid control operation. At step n1, an initialization process is performed, and at step n2, it is determined whether or not a predetermined operation timing, for example, every 5 msec, has been reached. At the time when the operation timing has come, the process proceeds to step n3.

In step n3, each wheel speed is calculated from the detection results of the wheel speed sensors 1a to 1d. At step n4, it is determined from the output of the switch 7 whether or not the brake pedal 30 is depressed. If so, the process proceeds to step n5, and the maximum value of the wheel speeds obtained at step n3 is estimated. The vehicle speed is set to the vehicle speed _Vsi . Otherwise, the process proceeds to step n6, and the minimum value among the wheel speeds is set to the estimated vehicle speed _Vsi .

In the step N4 to N6, after estimated vehicle speed V _si the influence of slips is removed between the wheel and the road surface is obtained proceeds to step n7, an output of the acceleration sensor 3 is an analog / digital converter 6 It is converted to a digital value and read. In step n8, the friction coefficient μ between the wheel and the road surface is determined based on the acceleration obtained in step n7, and in step n9, the vehicle speed Vs is determined based on the acceleration.
Is required.

When the parameters for the anti-skid control are obtained in steps n7 to n9 in this way, the process proceeds to step n10, where the control of the brake oil pressure as described later is performed. In step n11, the above-described abnormality determination of the acceleration sensor 3 is performed. When the determination result is abnormal, the warning light 19 is turned on to notify the driver, and the vehicle speed Vs is reduced. A fail-safe process such as substituting the estimated vehicle speed V _si is performed.

FIG. 10 is a flowchart for explaining in detail the control operation of the braking oil pressure in step n10. When the anti-skid control operation is performed, it is determined in step s1 whether or not the anti-skid control is currently being performed. If not, in step s2, it is determined whether or not the condition for starting the anti-skid control is satisfied. Is done. This control start condition is, for example, the wheel 34a
.. 34d is locked, or the wheel speed falls below a predetermined lock determination criterion.

When the anti-skid control start condition is satisfied, the process proceeds to step s3, a pressure reducing flag for causing the wheel cylinders 33a to 33d to perform a pressure reducing operation is set in a predetermined memory area of the processing circuit 2, and the process proceeds to step s4. If the anti-skid control has already been performed in step s1, the process directly proceeds to step s4. At step s4, it is determined whether or not the condition for terminating the anti-skid control is satisfied. The control termination condition is, for example, when the operation of the brake pedal 30 is released, or when the vehicle speed Vs becomes 5 km / h or less.

When the anti-skid control end condition is satisfied in step s4, and when the anti-skid control start condition is not satisfied in step s2, the process proceeds to step s18, where the three-position electromagnetic control valves 32a to 32d of the actuators 13a to 13d increase the pressure. The position is set and the anti-skid is not controlled. Accordingly, the braking oil pressure generated in the master cylinder 31 by the depression of the brake pedal 30 is transmitted to the wheel cylinders 33a to 33d, and a normal braking operation is performed.

In step s4, when the anti-skid control end condition is not satisfied, the process proceeds to step s5, where a flag for controlling the increase / decrease of the brake hydraulic pressure of the wheel cylinders 33a to 33d is determined. At the start of the anti-skid control, as indicated by the step s3, since the pressure reduction flag is set, the process proceeds to the step s6. In step s6, it is determined whether or not the pressure reduction control should be terminated. If not, in step s7, the pulse width control of the pressure reduction pulse is performed, the ratio between the pressure reduction output and the hold output is changed, and the operation ends.

When the pressure reduction control should be terminated in step s6, that is, when the wheel speed starts to recover, step
The process proceeds to s8, where a holding flag for keeping the brake oil pressure of the wheel cylinders 33a to 33d constant is set, and the process proceeds to step s9. Such an anti-skid control operation is repeatedly performed, and even when the holding flag has already been set in step s5, the process proceeds to step s9. Step
In s9, it is determined whether the retention end condition is satisfied, and
Otherwise, in step s10, the three-position solenoid control valve 32a
After ~ 32d is set to the holding position and holding control is performed,
End the operation.

In step s9, if the hold termination condition for determining that the wheel speed has been recovered is satisfied, in step s11, a pressure increase flag for increasing the brake oil pressure of the wheel cylinders 33a to 33d is set, and in step s12. Move on. If the pressure increase flag has already been set in step s5, the process directly proceeds to step s12. This step s12
In step s13, it is determined whether the pressure increase termination condition has been satisfied. If not, the control proceeds to step s13.
After 2a to 32d are set to the pressure increasing position and the pressure increasing control is performed, the operation ends.

This pressure increase control is performed based on the peak value of the wheel acceleration recovered by the pressure reduction control and the friction coefficient μ set in the step n8. The friction coefficient μ is high and the acceleration peak value is large. As the pressure increases, the pressure increase amount increases. The pressure increase termination condition is, for example, when a pressure increase time determined by the wheel acceleration obtained when the wheel speed is recovered has elapsed.

When the pressure increase ending condition is satisfied in step s12, the process proceeds to step s14, where the wheel cylinder 33a
The pulse pressure increasing flag for gradually increasing the braking oil pressure within the range .about.33d is set, and the routine proceeds to step s15. If the pulse pressure increase flag has already been set in step s5, the process directly proceeds to step s15. In this step s15, it is determined whether or not the end condition of the pulse pressure increase control is satisfied.
In s16, the pulse pressure increasing control of the three-position electromagnetic control valves 32a to 32d is continued, and the operation is ended. If the condition for terminating the pulse pressure increase control is satisfied in step s15, the pressure reduction flag is set in step s17, and then the flow proceeds to step s7 where the pressure reduction control is performed.

FIG. 11 is a timing chart for explaining the operation of another embodiment of the present invention. In this embodiment, as shown in FIG. 11 (1), during the period when the anti-skid control is being performed, as shown between times t11 and t12, the determination timing flag F3 is set as shown in FIG. 11 (2). If the output of the acceleration sensor 3 does not change while the determination timing flag F3 is set to 1, it is determined that the acceleration sensor 3 is abnormal.

That is, the time at which the anti-skid control is started
At time t11, as shown in FIG. 11 (3), the fluctuation detection flag F2 is set to 1, and when a fluctuation occurs in the output of the acceleration sensor 3 between the time t11 and the time t12, At time t13, the fluctuation detection flag F2 is reset to 0 as indicated by a virtual line in FIG. 11 (3).

When there is no fluctuation, the flag F2 remains set to 1 even after the time t12, so that after the time t12, as shown in FIG. Is set to 1.

FIG. 12 is a flowchart for explaining the operation of the embodiment shown in FIG. At step i1, it is determined whether or not the anti-skid control is being performed. If not, the process proceeds to step i2, where it is determined whether or not the determination timing flag F3 is 0. If so, that is, before the time t11 Then, the operation is directly terminated.

In step i1, when the anti-skid control is being performed, the process proceeds to step i3, and the determination timing flag F3
Is determined to be 1; otherwise, the process proceeds to step i4 at the time t11 when the anti-skid control is started. In step i4, the determination timing flag F3 is set to 1, and in step i5, the change detection flag F2 is set to 1, and then the operation proceeds to step i6. If the determination timing flag F3 is 1 in step i3, the process directly proceeds to step i6.

At step i6, the previous output value G (n- ₁ ) of the acceleration sensor 3 and the current output value G are obtained in the same manner as at step m4.
It is determined whether or not (n) is equal. If so, the operation is directly terminated. If not, that is, if there is a change as shown at the time t13, the change detection flag is set at step i7. After resetting F2 to 0, the operation ends.

In step i2, when the determination timing flag F3 is not 0, that is, at the end timing of the anti-skid control indicated by the time t12, the process proceeds to step i8.
At step i8, it is determined whether or not the fluctuation detection flag F2 has been reset to 0.
At i9, the abnormality flag F1 is set to 1, and the process proceeds to step i10. If so, the process directly proceeds to step i10. In step i10, the operation ends after the determination timing flag F3 is reset to 0.

FIG. 13 is a timing chart for explaining the operation of still another embodiment of the present invention. In this example,
A period during which the anti-skid control is started as shown at time t21 in FIG. 13 (1), and further the pressure reduction control of the control oil pressure is performed as shown at times t22 and t23 in FIG. 13 (2). In the meantime, as shown in FIG. 13 (3), the count value CT of the counter is set to a predetermined value KT, for example, 0.5 sec, and from the time t23 when the pressure reduction control is released, the count value CT is increased. The subtraction is started, and when the count value CT becomes 0, abnormality determination of the acceleration sensor 3 is performed.

That is, at the time t22 when the pressure reduction control is suspicious,
As shown in FIG. 13 (4), the determination timing flag F3
Is set to 1, and the fluctuation detection flag F2 is set to 1 as shown in FIG. 13 (5). The determination timing flag F3 is reset to 0 at time t24 when the count value CT of the counter becomes 0.

On the other hand, similarly to the above-described embodiment, the determination timing flag
If a change is detected in the output of the acceleration sensor 3 during the time t22 to t24 when F3 is set to 1, the time t2
At 5, the change detection flag F2 is reset to 0 as indicated by the imaginary line in FIG. 13 (5). Therefore, the acceleration sensor 3 is set within the determination timing between the times t22 and t24.
When no fluctuation is detected in the output of
At time t24 when CT becomes 0, the abnormality flag F1 is set to 1 as shown in FIG. 13 (6).

FIG. 14 is a flowchart for explaining the operation of the embodiment shown in FIG. In step k1,
It is determined whether or not the anti-skid control is being performed. If not, that is, before the time t21, the process proceeds to step k2, the count value CT is reset to 0, and the process proceeds to step k2.
After the determination timing F3 is reset to 0 at k3, the operation ends.

If the anti-skid control is being performed in step k1, the process proceeds to step k4, and the determination timing flag F3
Is determined to be 1, and if not, that is, between the times t21 and t22, the process proceeds to step k5. Step
At k5, it is determined whether or not the pressure reduction control of the brake hydraulic pressure is being performed.If not, that is, the operation is directly terminated between the times t21 and t22, and if so, that is, the time
The process moves to step k6 at the timing of t22.

In step k6, the predetermined value KT is substituted for the count value CT, and in step k7, the determination timing flag F3 is set to 1
Is set to Further, a change detection flag is set in step k8.
After F2 is set to 1, the operation ends.

In step k, when the determination timing flag F3 is 1, that is, during the time t22 to t24, the process proceeds to step k9, the count value CT is decremented by 1, and the process proceeds to step k10. At step k10, it is determined whether or not the count value CT has become 0, and if not, the process proceeds to step k10.
At k11, it is determined whether the current output value G (n) of the acceleration sensor 3 is larger than a predetermined threshold value KG, for example, 0.5G, and if so, the process proceeds to step k12.

At step k12, it is determined whether or not the current output value G (n) is equal to the previous output value G (n-1). If so, that is, if there is no change in the output of the acceleration sensor 3, the direct operation is performed. To end. In step k12, when the output of the acceleration sensor 3 fluctuates, and in step k11, the current output G of the acceleration sensor 3 is changed.
When (n) is equal to or smaller than the threshold value KG, the process proceeds to step k13, where the fluctuation detection flag F2 is reset to 0, and the operation is terminated.

At step k10, when the count value CT is 0, that is, at the timing of the time t24, step k is performed.
The process proceeds to step 14, where it is determined whether the abnormality detection flag F2 is 0. If not, the abnormality flag F1 is determined in step k15.
Is set to 1 and the process proceeds to step k16. If so, the process directly proceeds to step k16. At step k16, the operation ends after the decision timing flag F3 is reset to 0.

As described above, the anti-skid control device according to the present invention includes:
Since the analog acceleration sensor 3 is used,
Even if all the wheels 34a to 34d are locked, the vehicle acceleration can be obtained, and the vehicle acceleration can be detected with higher accuracy than the switch-type acceleration sensor described in the section of the related art. . Accordingly, the vehicle speed and the friction coefficient between the wheels and the road surface can be accurately obtained, and the braking distance can be reduced.

Also, by using the analog acceleration sensor 3 as described above, the size can be reduced as compared with the switch type sensor using the pendulum or mercury, and the acceleration sensor 3 is integrated into the anti-skid control circuit 4. Can be incorporated with

Furthermore, abnormality of the acceleration sensor 3 can be detected by at least one anti-skid control operation, and abnormality can be detected in a short time. Furthermore, even if the stop with the gentle brake is repeated, the abnormality determination can be accurately performed.

Effect of the Invention As described above, according to the present invention, when performing anti-skid control based on the detection result of the acceleration sensor, the amount of change per unit time of the vehicle speed obtained from the wheel speed is equal to or more than the predetermined value. Is determined, or when no change is detected in the output of the acceleration sensor during a period from the start time to the end time of the anti-skid control or within a predetermined time from the start of the pressure reduction control, it is determined that the acceleration sensor is abnormal. Therefore, even in the case of a gentle braking operation in which the fluctuation of the acceleration is small, it is possible to accurately and early in the morning determine the abnormality of the acceleration sensor.

If the result of the determination indicates that the acceleration sensor is abnormal, the acceleration sensor does not perform the anti-skid control, for example, by switching to the acceleration obtained from the time change rate of the wheel speed, but from the detection result of the acceleration sensor. Since the control based on the detection result is prohibited, the fail-safe function can be expanded.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an electric configuration of an anti-skid control device according to one embodiment of the present invention, FIG. 2 is a piping diagram of a braking hydraulic pressure of the anti-skid control device, and FIG. FIG. 4 is a block diagram illustrating the measurement principle of the acceleration sensor 3, FIG. 5 is a graph illustrating the measurement principle of the acceleration sensor 3, and FIG. 6 is a graph illustrating the measurement principle of the acceleration sensor 3. FIG. 7 is a timing chart for explaining the operation of one embodiment of the present invention, FIG. 8 is a flowchart of the embodiment shown in FIG. 7, and FIG. 9 is an explanation of the anti-skid control operation. FIG. 10 is a flowchart for explaining in detail the control operation of the brake hydraulic pressure, FIG. 11 is a timing chart for explaining the operation of another embodiment of the present invention, and FIG. 11 Flow chart of the embodiment shown in, FIG. 13 timing Chiya over bets for further explaining the operation of another embodiment of the present invention, FIG. 14 is a flow chart of the embodiment shown in FIG. 13. 1a to 1d wheel speed sensor, 2 processing circuit, 3 acceleration sensor, 4 anti-skid control circuit, 13a to 13d
… Actuator, 41… Acceleration detector, 41ac, 41cb…
... capacitors, 42 ... oscillators

Claims (3)

(57) [Claims] An acceleration sensor detects acceleration in a traveling direction of a vehicle body, and based on the detection result, determines at least a friction coefficient between a road surface and a wheel. In the anti-skid control method for controlling power, when the amount of change per unit time of the vehicle speed obtained based on the wheel speed is equal to or more than a predetermined value, and when no change is detected in the output of the acceleration sensor, the acceleration sensor Is determined to be abnormal, and the determination of the friction coefficient based on the detection result of the acceleration sensor is prohibited. An acceleration sensor for detecting an acceleration of the vehicle body in a traveling direction, determining at least a friction coefficient between a road surface and a wheel based on the detection result; In the anti-skid control method for controlling the power, when no change is detected in the output of the acceleration sensor between the start time and the end time of the anti-skid control, it is determined that the acceleration sensor is abnormal, and the detection result of the acceleration sensor is determined. An anti-skid control method, wherein the determination of the friction coefficient based on the control is prohibited. 3. An acceleration sensor detects acceleration in the traveling direction of the vehicle body, and based on the detection result, determines at least a coefficient of friction between the road surface and the wheel. In the anti-skid control method for controlling power, when no change is detected in the output of the acceleration sensor within a predetermined time from the start of the pressure reduction control, it is determined that the acceleration sensor is abnormal, and the detection result of the acceleration sensor is determined. An anti-skid control method, wherein the determination of the friction coefficient based on the control is prohibited.