JP2669687B2 - Acceleration sensor abnormality detection device of anti-skid control device with acceleration sensor - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an acceleration sensor abnormality detection of an anti-skid control device that determines a friction coefficient of a road surface using an acceleration sensor and generates an optimum braking force based on the determination result. Related to the device.

2. Description of the Related Art An anti-skid control device is a device that generates a braking force for a wheel so as to increase a friction coefficient between the wheel and a road surface, and controls a slip ratio of the wheel. Assuming that the rotational speed of the wheels (hereinafter referred to as "wheel speed") is VW and the running speed of the vehicle (hereinafter referred to as "vehicle speed") is VS, the slip ratio S is defined by the following equation (1).

The wheel speed VW can be obtained from an output from a wheel speed sensor attached to a wheel shaft. The vehicle speed VS can be obtained by integrating the output of the acceleration sensor. Therefore, in order to obtain the slip ratio S, an anti-skid control device including an acceleration sensor has been put to practical use.

However, if an abnormality occurs in the acceleration sensor and, for example, the same output as during steady running is derived even during acceleration / deceleration, even if the driver depresses the brake pedal to perform a braking operation, deceleration (negative acceleration) Is not detected, the braking force is lost, and the original anti-skidding control cannot be realized.

For this reason, it is necessary to monitor whether or not an abnormality has occurred in the acceleration sensor.In a typical conventional technology, the vehicle speed is, for example, from a running state equal to or higher than a predetermined value of about 20 km / h to a stop state until the vehicle stops. The output of the acceleration sensor is sampled during the period, and when a state in which the output does not fluctuate continues for a predetermined number of times or more, it is determined that an abnormality has occurred in the acceleration sensor.

According to the related art described above, when an abnormality occurs so that the output from the acceleration sensor becomes constant, it is possible to detect the occurrence of the abnormality as described above. When an abnormality occurs such that the output fluctuates, the abnormality cannot be detected.

An object of the present invention is to provide an acceleration sensor abnormality detection device for an anti-skid control device with an acceleration sensor, which is capable of surely detecting an abnormality in the acceleration sensor and preventing the malfunction of the anti-skidding control.

Means for Solving the Problems The present invention detects acceleration in a traveling direction of a vehicle body by using an acceleration sensor, and based on the detection result, the slip ratio of a wheel increases a friction coefficient between a road surface and the wheel. In the anti-skidding control device with an acceleration sensor for controlling the braking force as described above, in a state in which anti-skidding control is not performed, in response to the output of the variation detecting means and the variation detecting means that detects the variation frequency of the output signal of the acceleration sensor And an abnormality determination device for an anti-skid control device with an acceleration sensor, comprising: abnormality determination means for determining that the acceleration sensor is abnormal when the variation frequency of the output signal is equal to or higher than a predetermined frequency. It is.

Further, the present invention is characterized in that the vehicle is traveling on a rough road when the fluctuation frequency of the wheel acceleration is larger than a predetermined value in response to an output of the wheel speed detecting means for detecting the wheel speed. An anti-skid control device with an acceleration sensor, comprising: a rough road judging means for judging; and an activating means responsive to an output of the rough road judging means for activating the abnormality judging means except when the vehicle is traveling on a rough road. It is an acceleration sensor abnormality detection device.

According to the present invention, the output signal of the acceleration sensor is given to the fluctuation detecting means, and the fluctuation detecting means detects the fluctuation frequency of the output signal. The output of the fluctuation detecting means is given to the abnormality judging means, and the abnormality judging means determines whether the fluctuation frequency is equal to or higher than a predetermined frequency during the period when the anti-skidding control is not performed. Is determined.

That is, during steady running with a small acceleration or deceleration, when the output signal from the acceleration sensor, which should have little fluctuation, has a fluctuation of the predetermined frequency or more, it is determined that an abnormality has occurred in the acceleration sensor. .

Further, according to the present invention, from the wheel speed detected by the wheel speed detecting means, the rough road determining means determines whether or not the fluctuation frequency of the wheel acceleration is greater than a predetermined value.
Determine whether the road you are driving is a bad road. As a result of the determination, during a period other than when the vehicle is traveling on a rough road, the abnormality determining means is activated by the activating means to perform an abnormality determining operation of the acceleration sensor. Therefore, when the vehicle is traveling on a rough road where an error due to vehicle body vibration tends to be superimposed on the output of the acceleration sensor, the abnormality determination operation is not performed.

Embodiment FIG. 1 is a functional block diagram for explaining the principle of an embodiment of the present invention. An output signal from the acceleration sensor 3 is supplied to an abnormality determining unit 43, which is a variation detecting unit and an abnormality determining unit, via an input unit 42, and the determination result is led to an anti-skid control unit 41. Speed sensor
The outputs from 1a to 1d are calculated by the calculation unit 44 into the wheel speed and the wheel acceleration, and are given to a rough road determination unit 45, which is a rough road determination unit and an activation unit. The bad road determination unit 45 determines that the road is a bad road when the fluctuation frequency of the input wheel acceleration signal is larger than a predetermined value, and
A signal for prohibiting the abnormality determination operation is derived at 43, and the anti-skid control unit 41 sets a road surface friction coefficient, which will be described later.

That is, based on the clock signal input from the anti-skidding control unit 41 via the line 46, the signal shown in FIG.
As indicated by, the built-in timer performs a time counting operation for a predetermined time W1. Within the clocking time W1, the wheel acceleration signals from the wheel speed sensors 1a to 1d via the calculation unit 44 as shown in FIG. 2A are, for example, + 2G (G is the gravitational acceleration).
The number of times the level exceeds a predetermined level L1, that is, the fluctuating frequency is counted as shown in FIG. 2 (3). When the count value K1 becomes equal to or more than the predetermined value KN1, the rough road determination flag F1 is set to 1 as shown in FIG. 2 (4).

When the rough road determination flag F1 is set to 1, the abnormality determination unit 43 does not perform the abnormality determination operation, and during the period when the rough road determination graph F1 is reset to 0, the acceleration sensor as shown below is displayed. The abnormality determination operation 3 is performed. On the basis of the clock signal input via the line 46, the built-in timer performs a time counting operation as shown in FIG. 3 (2). During the period until the counted time reaches the predetermined time W2, the output signal from the acceleration sensor 3 via the input unit 42 as shown in FIG.
The number of times the predetermined level L2 of about 2G is exceeded, that is, the fluctuating frequency is counted as shown in FIG. 3 (3). When the count value K2 becomes equal to or more than the predetermined value KN2, the abnormality determination flag F2 is set to 1 as shown in FIG. 3 (4).

Based on the abnormality determination graph F2 set as described above, the anti-skidding control unit 41 performs the anti-skidding control based on the output signal from the acceleration sensor 3 when the abnormality determination flag F2 is 0, and the abnormality determination flag F2 Is 1
If, the anti-skid control based on the output signal of the acceleration sensor 3 is prohibited, and the occurrence of abnormality is notified to the driver as described later.

FIG. 4 is a flowchart for explaining the rough road determination operation shown in FIG. At step n1, the built-in timer in the rough road determination unit 45 starts counting operation, and at step n2, the number of times that the wheel acceleration exceeds the predetermined level L1 is counted based on the wheel speed signal from the wheel speed sensors 1a to 1d. Is done. In step n3, the count value of the built-in timer is the predetermined time W1, for example, 0.
It is determined whether or not it has been 2 seconds or more. If not, the operation is terminated, and if it is, the timer is reset at step n4 and then the process proceeds to step n5.

In step n5, it is determined whether or not the count value K1 of the number of changes in the wheel acceleration in step n2 is the predetermined value KN1, for example, two or more times.
If so, in step n6, the rough road determination flag F1 is 1
Then, the operation is terminated. Otherwise, the count value K1 is reset to 0 in step n7, and the operation is terminated.

FIG. 5 is a flowchart for explaining the abnormality determination operation of the acceleration sensor 3 shown in FIG. At step n11, the built-in timer in the abnormality judging section 43 starts counting, and at step n12, the number of times that the output signal from the acceleration sensor 3 exceeds the predetermined level L2 is counted. In step n13, it is determined whether or not the count value of the built-in timer is equal to or longer than the predetermined time W2, for example, 1 sec, and if not, the operation is terminated, and if so, in step n14, the built-in timer is It is reset and moves to step n15.

In step n15, it is determined whether or not the count value K2 of the number of times of fluctuation of the output signal of the acceleration sensor 3 in the step n12 is the predetermined value KN2, for example, 10 times or more, and if so, in step n16. The abnormality determination flag F2 is set to 1 and the operation is terminated. Otherwise, the count value K2 is reset to 0 in step n17 and the operation is terminated.

FIG. 6 is a flowchart for explaining the operation timing of the rough road determination operation shown in FIG. 4 and the abnormality determination operation of the acceleration sensor 3 shown in FIG. At step n21, it is determined whether or not anti-skid control is being performed. If not, step n22 is performed.
Then, the rough road determination operation shown in FIG. 4 is performed, and the routine goes to Step n23.

At step n23, it is judged from the judgment result at step n22 whether or not the road is a bad road. If not, that is, when the bad road judgment flag F1 is 0, the acceleration sensor 3 shown in FIG. The abnormality determination operation is performed and the operation ends. When the anti-skidding control is being performed in step n21 and when it is determined that the road is a bad road in step n23, the abnormality determining operation of the acceleration sensor 3 is not performed and the direct operation is ended.

In this way, when the number of times that the output signal from the acceleration sensor 3 exceeds the predetermined level L2 is the predetermined value KN2 or more in the steady running state where the anti-skidding control is not performed, the output signal that the acceleration sensor 3 changes. It is possible to determine that an abnormal state has occurred in which is derived. Further, when the output signal is not derived during the anti-skid control, it can be determined that the acceleration sensor 3 is in an abnormal state with the constant output signal being derived. In this way, it is possible to reliably detect that an abnormality has occurred in the acceleration sensor 3.

Further, the abnormality determination operation in a state in which the acceleration sensor derives a fluctuating output signal is not performed when the vehicle is traveling on a rough road where vehicle body vibrations are frequent, so that abnormality detection can be performed more reliably. it can.

FIG. 7 is a block diagram showing the electrical configuration of the anti-skidding control device in which the present invention is implemented. Wheel speed sensors 1a to 1d provided on wheels 34a to 34d shown in FIG. 8 to be described later detect rotation speeds of 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, where they are shaped into pulse signals and then input to the processing circuit 2.

The acceleration sensor 3 is, for example, a strain gauge type acceleration sensor, and is fixed to a vehicle body. The output signal from the acceleration sensor 3 is used as an analog / digital conversion circuit 6
Is applied to the processing circuit 2 and is subjected to digital filter processing for removing unnecessary components. The processing circuit 2 performs a calculation operation based on the output from the acceleration sensor 3, and the processing circuit 2 shown in FIGS.
The abnormality detection of the acceleration sensor 3 shown in the figure and the anti-skid control described later are performed.

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, 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 13d formed by 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 a relay coil 16a of the relay 16 via a motor relay drive circuit 18, whereby the motor 17 for generating braking oil pressure is connected to the relay switch 16b of the relay 16. Is drive-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.

FIG. 8 is a block diagram for explaining a piping path of a braking hydraulic pressure of the anti-skid control device with an acceleration sensor having the above-described abnormality detecting function. When the brake pedal 30 is depressed, braking hydraulic pressure is generated in the master cylinder 31,
The braking oil pressure is supplied to the three-position electromagnetic control valves 32a to 32d via pipelines P1 to P4, and further supplied to the wheel cylinders 33a to 33d via pipelines P5 to P8. By this,
The wheels 34a to 34d are braked and the vehicle speed is reduced.

The rotation speeds of the wheels 34a to 34d are detected by wheel speed sensors 1a to 1d, respectively.
Is input to Further, the output signal representing the vehicle body acceleration detected by the acceleration sensor 3 fixed to the vehicle body is also
It is input to the anti-skidding control circuit 4.

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.
Accordingly, the slip ratio S of the wheels 34a to 34d is a value at which a high friction braking force acts on the road surface, for example, 10 to 20%.
Is controlled.

FIG. 9 is a flow chart for explaining the control operation of the anti-skidding control device configured as described above. When the anti-skid control operation is executed in the processing circuit 2, it is determined in step s1 whether or not the anti-skid control is currently being executed. It is determined whether or not. The control start condition is, for example, when the wheels 34a to 34d are locked, or when the wheel speed is lower than a predetermined value and the wheel deceleration is higher than the predetermined deceleration.

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-skidding control has already been performed in step s1, the process directly goes 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 becomes 5 km / h or less.

When the anti-skidding control ending condition is satisfied in step s4, and when the anti-skidding control starting condition is not satisfied in step s2, the process proceeds to step s18, and the three-position solenoid control valves 32a-32d of the actuators 13a-13d increase in pressure. Set to position. As a result, the brake hydraulic pressure generated in the master cylinder 31 due to the depression of the brake pedal 30 is applied to the wheel cylinders 33a to 33d.
Is transmitted to

When the anti-skidding control ending condition is not satisfied in the step s4, the process proceeds to step s5, and a flag for controlling the increase / decrease in the braking hydraulic pressure of the wheel cylinders 33a to 33d is determined. At the start of the anti-skidding control, as shown in the step s3, since the pressure reduction flag is set, it moves to step s6, it is judged whether or not the pressure reduction control should be ended, and if not so, the pressure reduction pulse is sent in step s7. Pulse width control is performed and the operation ends. The pulse width control of the pressure reducing pulse in step s7 is performed by setting the friction coefficient of the road surface used for the anti-skid control to be relatively high when it is determined by the above-described rough road determination operation that the vehicle is traveling on a rough road. .

Further, when it is not necessary to end the pressure reduction control in step s6, that is, when the wheel speed starts to increase, the process proceeds to step s8, and the holding flag for keeping the braking hydraulic pressure of the wheel cylinders 33a to 33d constant is set, Step s9
Move on to 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. In step s9, it is judged whether or not the holding end condition is satisfied, and if not, in step s10, the three-position electromagnetic control valves 32a to 32d are set to the holding positions to perform the holding control, and then the operation is ended.

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 12
In step s13, it is determined whether the pressure increase ending condition is satisfied.
After 2a to 32d are set to the pressure increasing position and the pressure increasing control is performed, the operation ends. 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.

EFFECTS OF THE INVENTION As described above, according to the present invention, during steady-state running with small acceleration or deceleration in which anti-skidding control is not performed, the output signal from the acceleration sensor, which should have little fluctuation, has fluctuations of a predetermined frequency or more. When is detected, it is determined that an abnormality has occurred in the acceleration sensor, so that it is possible to reliably detect that the acceleration sensor has entered an abnormal state in which it continues to derive a fluctuating output signal. The malfunction of the anti-skidding control can be prevented in advance.

Further, according to the present invention, when traveling on a rough road where an error due to vehicle body vibration is likely to be superimposed on the output of the acceleration sensor, the abnormality determination operation is not performed, so that abnormality determination can be performed with high accuracy. It is possible to prevent malfunction of the anti-skidding control.

[Brief description of the drawings]

FIG. 1 is a functional block diagram for explaining the principle of one embodiment of the present invention, FIG. 2 is a waveform diagram for explaining a rough road judging operation, and FIG. 3 is a diagram for explaining an abnormal judging operation of the acceleration sensor 3. FIG. 4 is a flowchart for explaining the rough road determination operation shown in FIG. 2, FIG. 5 is a flowchart for explaining the abnormality determination operation shown in FIG. 3, and FIG. FIG. 6 is a flowchart for explaining the operation timing of the detection operation shown in FIGS. 4 and 5, and FIG.
FIG. 8 is a block diagram showing an electric configuration of an anti-skid control device with an acceleration sensor according to the present invention. FIG. It is a flowchart for explaining an operation. 1a to 1d wheel speed sensor, 2 processing circuit, 3 acceleration sensor, 4 anti-skid control circuit, 13a to 13d
… Actuator, 41… Anti-skid control unit, 42…
... input unit, 43 ... abnormality determination unit, 44 ... calculation unit, 45 ... bad road determination unit

Claims (2)

(57) [Claims] 1. An acceleration sensor is used to detect an acceleration in a traveling direction of a vehicle body, and the braking force is controlled on the basis of the detection result so that a slip ratio of a wheel increases a friction coefficient between a road surface and the wheel. In the anti-skid control device with an acceleration sensor, a fluctuation detection means for detecting a fluctuation frequency of the output signal of the acceleration sensor, and a response to the output of the fluctuation detection means, in a state where anti-skid control is not performed, Abnormality detecting means for judging that the acceleration sensor is abnormal when the fluctuation frequency is equal to or higher than a predetermined frequency. An acceleration sensor abnormality detecting device for an anti-skid control device with an acceleration sensor. A wheel speed detecting means for detecting a wheel speed; responsive to an output of the wheel speed detecting means, traveling on a rough road when a fluctuation frequency of wheel acceleration is larger than a predetermined value. 2. The method according to claim 1, further comprising: determining a rough road determining means; and activating means responsive to an output of the rough road determining means to activate the abnormality determining means except when the vehicle is traveling on a rough road. Acceleration sensor abnormality detection device for anti-skidding control device with acceleration sensor.