JPH04110267A - Acceleration sensor anomaly detecting device for anti-skid controller equipped with acceleration sensor - Google Patents

Abstract

PURPOSE:To previously prevent the malfunction of anti-skid control by judging the anomaly of an acceleration sensor if the output level of the acceleration sensor is over a previously determined level, when the calculated acceleration of a car body is less than a previously determined value, and the detected road surface state is not bad. CONSTITUTION:Clock signals are inputted into a bad road judging part 56 from an anti-skid control part 54 through a line 58, and during the period when a bad road judgment flag is reset 0, the anomaly judgement operation for acceleration sensors 3a and 3b is carried out. An anomaly judgement 57a turns ON an alarm lamp 19, and informs a driver of the generation of anomaly, in correspondence with the wheel speed signal, if the acceleration in the longitudinal direction of a car body is within a previously determined value, in other words when the acceleration in the longitudinal direction of the car body which is detected by a longitudinal acceleration sensor 3a is over a previously determined value, in the stationary traveling, during the period when antiskid control is not carried out, and the road surface state is not bad.

Description

[Detailed Description of the Invention] Overview In detecting an abnormality in an acceleration sensor used for anti-skid control, the output from the acceleration sensor is
It is determined whether there is an abnormality based on the output of each wheel speed sensor.

As a result, even if an abnormality occurs in the acceleration sensor in either direction, the direction in which the output is no longer derived from the acceleration sensor or the direction in which the output is derived, the abnormality is reliably detected.

Industrial Application Field The present invention determines the friction coefficient between the wheels and the road surface and calculates the vehicle speed based on the detection results of the acceleration sensor, and then calculates the vehicle speed based on the results of the determination and calculation. The present invention relates to an acceleration sensor abnormality detection device for an anti-skid control device that generates optimal braking force.

A conventional anti-skid control device is a device that controls the braking force of a wheel so as to increase the coefficient of friction between the wheel and the road surface, thereby controlling the slip rate of the wheel. This slip rate is determined from the rotational speed of the wheels and the running speed of the vehicle body.
Further, the traveling speed can be determined by integrating the acceleration of the vehicle body in the traveling direction. For this reason, anti-skid control devices using acceleration sensors have been put into practical use.

However, if an abnormality occurs in the acceleration sensor and, for example, the same output is derived during acceleration and deceleration as during normal driving, even if the driver depresses the brake pedal and performs a braking operation, the deceleration (negative acceleration) is not detected, and the amount of pressure reduction reaches its maximum, resulting in a no-brake condition.

Therefore, it is possible to determine whether an abnormality has occurred in the acceleration sensor or not.
It is necessary to monitor the speed of the vehicle, and in typical conventional technology, the output of the acceleration sensor is sampled and linked from the time when the vehicle speed exceeds a predetermined value of, for example, 20 km/h until the vehicle stops. It is determined that an abnormality has occurred in the acceleration sensor when there is no fluctuation in the output or when the sampling continues for a predetermined number of times.

Problems to be Solved by the Invention In the conventional technology as described above, if an abnormality occurs in a direction in which the output from the acceleration sensor is constant, it is possible to detect the abnormality, but the output fluctuates. If an abnormality occurs in the direction of

Furthermore, in recent years, a configuration has been proposed in which the lateral acceleration of the vehicle body is detected to improve control accuracy when driving around curves such as when turning. As described above, it is impossible to detect an abnormality in an acceleration sensor that detects lateral acceleration using the method described above.

It is a second object of the present invention to provide an abnormality detection device for an anti-skid control device with an acceleration sensor, which can reliably detect abnormalities in an acceleration sensor and prevent malfunctions of anti-skid control.

Means for Solving the Problems The present invention uses the acceleration in the running direction of the vehicle body detected by an acceleration sensor and the speed of each vehicle 1A detected by a wheel speed sensor to determine the coefficient of friction between the wheels and the road surface. An anti-skid control device with an acceleration sensor that controls braking force so that the braking force increases, comprising: a calculation means for calculating an acceleration in a running direction of a vehicle body based on each wheel speed detected by the wheel speed sensor; a rough road determining means for determining whether or not a road surface condition is a rough road; When the acceleration of the vehicle body is below a predetermined value and the road surface condition detected by the rough road determining means is not a bad road, and the output level of the acceleration sensor is above a predetermined level, the acceleration sensor is abnormal. The present invention is an acceleration sensor abnormality detecting device for an acceleration sensor-equipped assist kit control device, characterized in that the device includes a determining means for determining whether the acceleration sensor is abnormal or not.

Further, the present invention uses at least the lateral acceleration of the vehicle body detected by an acceleration sensor and the wheel speed detected by a wheel speed sensor to increase the braking force so as to increase the coefficient of friction between the wheels and the road surface. An anti-skid control device with an acceleration sensor for controlling the vehicle, comprising: a calculation means for calculating the difference between the respective wheel speeds detected by the wheel speed sensor; a rough road determining means that determines whether the difference between the wheel speeds calculated by the calculating means is within a predetermined value in response to the outputs of the calculating means and the rough road determining means; and
and determining means for determining that the acceleration sensor is abnormal when the road surface condition determined by the rough road determining means is not a rough road and the output level of the acceleration sensor is equal to or higher than a predetermined level. There is an acceleration sensor abnormality detection device for an anti-skid control device with an acceleration sensor.

Furthermore, the rough road determining means of the present invention is characterized in that it performs the rough road determination when the amount of variation per predetermined time in each wheel speed detected by the wheel speed sensor is greater than or equal to a predetermined value.

Further, the present invention uses at least the lateral acceleration of the vehicle body detected by an acceleration sensor and the wheel speed detected by a wheel speed sensor to increase the braking force so as to increase the coefficient of friction between the wheels and the road surface. In an anti-skid control device with an acceleration sensor, the calculation means calculates a difference in wheel speed between a left wheel and a right wheel based on each wheel speed detected by the wheel speed sensor; In response to the output, the acceleration is determined when the output level of the acceleration sensor is below a predetermined level while the difference in wheel speed calculated by the calculation means is above a predetermined value while the anti-skid control is not being controlled. This is an acceleration sensor abnormality detecting device for an anti-skid control device with an acceleration sensor, characterized in that it includes a determining means for determining whether the sensor is abnormal.

According to the present invention, the calculation means calculates the acceleration of the vehicle body in the traveling direction based on the wheel speed detected by each wheel speed sensor, and responds to the calculation result and the judgment result of the rough road judgment means. Then, the determining means determines whether the acceleration sensor that detects the acceleration of the vehicle body in the running direction is abnormal. The rough road determining means determines the rough road when the amount of variation of each wheel speed per predetermined time is greater than or equal to a predetermined value, that is, when the acceleration/deceleration of the wheels is greater than or equal to a predetermined value.

That is, the determining means determines that, while the anti-skid control is not being performed, the acceleration of the vehicle body calculated by the calculating means is equal to or less than a predetermined value, and the road surface condition detected by the rough road determining means is not a rough road; That is, in a steady running state, when the output level of the acceleration sensor is below a predetermined level, it is determined that the acceleration sensor is abnormal.

Thereby, even if an abnormality occurs in the acceleration sensor in a direction in which the output from the acceleration sensor fluctuates, the determination means can reliably detect the abnormality.

Further, according to the present invention, the determining means determines that the difference between the respective wheel speeds determined by the calculating means is within a predetermined value, and the road surface condition determined by the rough road determining means is not a bad road. When the output level of the acceleration sensor that detects the lateral acceleration of the vehicle body is equal to or higher than a predetermined level while the anti-skid control is not being performed, it is determined that the acceleration sensor is abnormal.

This makes it possible to reliably detect that an abnormality has occurred in the acceleration sensor that detects lateral acceleration in a direction in which the output from the acceleration sensor fluctuates.

Furthermore, according to the present invention, the determining means, in response to the difference in wheel speed between the left wheel and the right wheel determined by the calculation means based on the respective wheel speeds, performs the following during the non-control of anti-skid control: When the difference is greater than a predetermined value, that is, when the output of an acceleration sensor that detects the lateral acceleration of the vehicle body is lower than or equal to a predetermined level while driving on a curve, it is determined that the acceleration sensor is abnormal. .

This makes it possible to reliably detect the occurrence of an abnormality in either the acceleration sensor that detects the lateral acceleration of the vehicle body or the direction in which no output is derived.

Embodiment FIG. 1 is a functional block diagram for explaining the principle of an embodiment of the present invention. The output from the longitudinal acceleration sensor 3a that detects the longitudinal acceleration of the vehicle body is sent to the input processing section 51.
It is input to the vehicle body speed calculating section 52 and the friction coefficient determining section 53 via a.

Similarly, the output from the lateral acceleration sensor 3b that detects the lateral acceleration of the vehicle body is input to the vehicle speed calculation section 52 and the friction coefficient determination section 53 via the input processing section 51b.

The vehicle speed calculating unit 52 and the friction coefficient determining unit 53 calculate the sum of the acceleration in the longitudinal direction of the vehicle body and the acceleration in the lateral direction of the vehicle body. Further, the vehicle speed calculating section 52 calculates the vehicle speed by integrating the sum of accelerations thus obtained, and outputs the result to the anti-skid control section 54 .

On the other hand, wheel speed sensors 1a to 1d are provided to each of the wheels 34a to B4d, which will be described later.The wheel speed pulses from each of these wheel speed sensors 1a to 1d are processed by a wheel speed calculation unit 55 to determine the wheel speed and After being converted into a wheel speed signal representing wheel acceleration, the anti-skid control section 54
is input.

Further, the output from the wheel speed calculating section 55 is input to the friction coefficient determining section 53, and the friction coefficient determining section 53 calculates the sum of the accelerations obtained from the outputs of the acceleration sensors 3a and 3b and the wheel speed. , determines the coefficient of friction between the wheels and the road surface, and outputs the determination result to the anti-skid control section 54.

The anti-skid control section 54 calculates, for example, the vehicle speed determined by the vehicle speed calculation section 52 and the friction coefficient determination section 53.
A slip standard is set in accordance with the friction coefficient determined in , and when the wheel speed becomes equal to or less than this slip standard, a pressure reduction signal is output to actuators 13a to 13d, which will be described later, to perform pressure reduction control of the braking oil pressure. Anti-skid control is thus achieved.

The wheel speed signal from the wheel speed calculating section 55 is also given to a rough road determining section 56. This rough road determining section 56 determines that the road is bad when the fluctuation frequency of the input wheel speed signal is larger than a predetermined value, and provides abnormality determining sections 57a and 57b (described later) with a function for prohibiting a determining operation. While deriving the signal, the anti-skid control section 54 sets the friction coefficient μ between the wheels and the road surface used for control to medium μ.

The anti-skid control unit 54 also receives a detection result from a switch 7 that detects that a brake pedal 30 (described later) has been depressed. The anti-skid control unit 54 controls sensors la to ld, 3a, 3b and actuators 13a to
When an abnormality occurs in the controller 13d and correct control cannot be performed, a warning light 19 is turned on to notify the driver.

FIG. 2 is a diagram for explaining the rough road judgment operation. The rough road judgment section "56t\" is the anti-skid control section 54.
In response to this clock signal, a built-in timer performs a timed operation for a predetermined time W 1 , for example 0.5 seconds, as shown in FIG. 2(2). I do.

As shown in FIG. 2 (1) within the time limit Wl,
The number of times that the wheel speed signal from the wheel speed calculation unit 55 is 1 or more on a predetermined level such as +IG (G is gravitational acceleration), that is, the fluctuation frequency is shown in FIG. 2 (3).
It is counted as shown in . 1 to that count value
When the value KNI exceeds the predetermined value KNI, as shown in Figure 2 (4
), the rough road determination flag F1 is set to 1.

When the rough road determination flag F1 is set to 1, the abnormality determination units 57a and 57b do not perform abnormality determination operations, and during the period when the rough road determination flag F1 is reset to O, the following operations are performed. An abnormality determination operation for the acceleration sensors 3a and 3b is performed.

The abnormality determination unit 57a determines whether the longitudinal acceleration αsa of the vehicle body is within a predetermined value ΔV in response to the wheel speed signal during a period when anti-skid control is being performed and the road surface is not in bad condition. At a certain time, that is, when the longitudinal acceleration αa of the vehicle body detected by the longitudinal acceleration sensor 3a is equal to or higher than a predetermined value KG, for example 0.2G during steady driving, the warning light 19 is turned on and the vehicle is driven. Notify the person of the occurrence of an abnormality.

FIG. 3 is a flowchart for explaining the abnormality determination operation of the longitudinal acceleration sensor 3a described above.

In step m1, the maximum value of each wheel speed detected by the wheel speed sensors 1a to 1d is determined by the estimated vehicle body speed Vsi.
Stored as . In step m2, each wheel 34a
~34d wheel acceleration αFL, αFF+αKL, αl(
(Hereinafter, when they are referred to collectively, they are indicated by the reference symbol αW) are calculated.

In step m3, it is determined from the detection result of the switch 7 whether or not the brake pedal 30, which will be described later, is being depressed and braking is in progress. If so, in step m21, the estimated vehicle speed Vsi is stored in the register M1. Stored as the previous estimated vehicle speed. In step m22, the count value CT of the counter in the rough road determining section 56 is reset to zero, and in step m23, the rough road determining flag F1 is reset to zero, and then the operation is ended.

In step m3, if braking is not in progress, the process moves to step m4, where it is determined whether or not the count value CT of the counter in the rough road determining section 56 is zero. If so, the process moves to step m5, where the count value The time W1 is substituted into CT. In step m6, the rough road determination flag F1 is reset to zero.

In step m7, the previous estimated vehicle speed stored in the register M1 and the current estimated vehicle speed Vs
It is determined whether the difference from i, that is, the longitudinal acceleration αsa of the vehicle body determined from the wheel speed, is larger than a predetermined value Δ■, for example, 0.5 km/h, and if so, In other words, when there is a change in vehicle speed,
The process moves to step m21, where the estimated vehicle speed in the register M1 is updated; otherwise, when there is no variation in vehicle speed, the estimated vehicle speed in the register M1 is updated in step m8, and then the process moves to step m9. .

Further, in step m4, when the count value CT of the counter is not zero, that is, during the counting operation, the process directly moves to step m9. In step m9, the count value CT
is subtracted by 1 and a counting operation is performed.

In step mlo, it is determined whether at least one of the wheel accelerations αW obtained in step m2 is greater than or equal to 1 on the predetermined level, and if so, in step m11, the rough road judgment Flag F
After 1 is set to 1, the process moves to step m12; otherwise, the process moves directly to step m12.

In this way, it is determined in step m3 that the vehicle is not braking, and after the rough road determination and vehicle speed fluctuation determination are performed in steps m4 to mll, the process moves to step m12. In step 'm12, it is determined whether or not the rough road determination flag F1 is 1. If not, step 'm1
At step m14, it is determined whether the output αa of the longitudinal acceleration sensor 3a is greater than or equal to the predetermined value KG, and if so, at step m14, the warning light 19 is turned on to issue an alarm. Further, when the rough road determination flag F1 is zero in step m12, and when the output αa of the acceleration sensor 3a is normal, which is less than the value KGa, in step m13, the direct operation is ended.

In this way, the abnormality determination unit 57a determines that the output level αa of the longitudinal acceleration sensor 3a is set to a predetermined value while the anti-skid control is not being performed, the road surface is not rough, and the road surface is not rough, and the output level αa of the longitudinal acceleration sensor 3a is KG or more, the longitudinal acceleration sensor 3a is determined to be abnormal, so the longitudinal acceleration sensor 3a reliably detects that an abnormality has occurred in the direction in which the output of the longitudinal acceleration sensor 3a fluctuates or increases. can do. Furthermore, it is possible to prevent erroneous judgments while driving on rough roads.

The anti-skid control unit 4 reads the output αa of the longitudinal acceleration sensor 3a when the vehicle body is stopped, stores the read value as an offset value, and uses the offset value to set the output αa during anti-skid control. Corrected and used for control.

FIG. 4 is a flowchart for explaining the abnormality determination operation of the lateral acceleration sensor 3b by the abnormality determination section 57b.
The operation is similar to the operation of the abnormality determination unit 57a shown in the third column above, and corresponding parts are given the same reference numerals. Abnormality determination section 5
Similarly to the abnormality determining section 57a, 7b indicates the difference between the wheel speeds Vw detected by each of the wheel speed sensors 1a to 1d when anti-skid control is not being performed and the road surface condition is not bad. ΔVw is a predetermined value KVI
When the output αb from the lateral acceleration sensor 3b is within
However, when it exceeds the predetermined value KG, it is determined that an abnormality has occurred in the lateral acceleration sensor 3b in the direction in which the output of the lateral acceleration sensor 3b fluctuates.

That is, in step m31, the wheel speed VFL, FR; V*L+V-P of each wheel 34a to 34d
(Hereinafter, when collectively referred to as Vw), is calculated, and in step m2, the wheel acceleration αW is determined.

If braking is not being performed in step m3, step m32
Then, it is determined whether the difference ΔVw between the respective wheel speeds Vw is less than or equal to a predetermined value KVI, and if so, steps m4 to m6 and m9 to mll are performed.
The process moves on to the rough road judgment operation. Further, when braking is in progress in the step m3, and when the wheel speed difference ΔVw is larger than the value KVI in the step m32, the step m22. Moving to m23, the count value CT of the counter and the rough road determination flag Fl are reset to zero.

After the rough road determination is performed, if the rough road determination flag F1 is not 1 in step m12, the process moves to step m33;
The output αb of the lateral acceleration sensor 3b is equal to the predetermined value K.
It is determined whether or not it is equal to or higher than G. If so, the process moves to step m14 and an alarm is generated, and if not, the operation is ended.

In this way, the abnormality determination unit 57b determines that when the vehicle is not braking, the road surface is not rough, and the wheel speed difference Δ■W is less than a predetermined value, that is, the vehicle is traveling straight. When the output αb of the lateral acceleration sensor 3b is equal to or higher than a predetermined value KG, it is determined that an abnormality has occurred in the lateral acceleration sensor 3b and an alarm is issued. It is possible to reliably detect the occurrence of an abnormality in the direction of increasing size.

Note that the abnormality determination unit 57b performs the following operations as shown in FIG.
An abnormality in the acceleration sensor 3b may be detected.

That is, in step m31, each wheel speed Vw is calculated, and in step m3, when braking is not being performed, the process moves to step m41.

In step m41, the right non-drive wheel, for example 34a
It is determined whether the wheel speed VFP of the wheel is equal to or less than a predetermined speed KV11, for example, 100 km/h, and if so, step m42 is performed to similarly adjust the wheel speed of the left non-driving wheel, for example 34c. It is determined whether "FL is less than or equal to the speed .about.11", and if so, the process moves to step m43.

In step m4B, it is determined whether the wheel speed VFR is greater than or equal to a predetermined speed KV12, for example 10 km, . , speed KV12
It is determined whether or not the above is true, and if so, the process moves to step m45 and subsequent steps, and an abnormality determination of the lateral acceleration sensor 3b is performed.

Note that when braking is in progress in step m3, and in step m41. Wheel speed V FR, V at m42
When FL is higher than said speed KVII, and step m44. When the wheel speeds VFR and VFL are less than the speed KV12 at m45, the operation is ended. That is, when the wheel speed is less than the speed KV12 or exceeds the speed KV11, where errors are likely to occur, the determination operation is not performed in step m45.

The difference from the predetermined value ΔKVI1. For example, 2km7・
It is determined whether or not it is greater than or equal to 'h. If so, it is determined that the vehicle is in a turning state and the process moves to step m46. In step m46, as will be described later, it is determined whether the value obtained by subtracting the offset value stored in the register M11 during normal driving from the output αb of the lateral acceleration sensor 3b is less than or equal to a predetermined value KG11. If this is the case, it is determined that an abnormality has occurred in the lateral acceleration sensor 3b, and the warning light 19 is turned on in step m14. If not, that is, if the lateral acceleration sensor 3b is normal, the direct operation is terminated. do.

In step m45, the wheel speed Vpp.

When the difference in VFL is less than the value ΔKVl1, that is, in a non-turning state, the process moves to step m47, and the difference between the wheel speeds VFR and VFL is set to a predetermined value Δ.
KV12. For example, it is determined whether the speed is 0.5 km/h or less, and if so, it is determined that the vehicle is traveling in a straight line, and in step m48, the output αb of the lateral acceleration sensor 3b is
Otherwise, the operation is directly terminated.

In this way, when the output αb of the lateral acceleration sensor 3b is less than or equal to the predetermined value KGII during a turn in which the left and right wheel speeds differ in the non-braking state, it is determined that an abnormality has occurred in the lateral acceleration sensor 3b. By doing so, it is possible to reliably detect that an abnormality has occurred in the direction in which the lateral acceleration sensor 3b does not derive an output.

FIG. 6 is a block diagram showing the electrical configuration of an anti-skid control device in which the present invention is implemented, and FIG. 7 is a piping route diagram for braking oil pressure in the anti-skid control device. Wheel speed sensor 1 provided on each wheel 34a to 34d
a to 1d detect the rotational speeds of the wheels 34a to 34d, respectively.

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

The acceleration sensors 3a and 3b (hereinafter collectively referred to as reference numeral 3) output analog signals of a level corresponding to acceleration, as will be described later. The output signals from these acceleration sensors 3 are respectively given to analog/digital conversion circuits 6a and 6b (indicated by reference numeral 6 when referred to collectively), converted into digital values, and then given to the processing circuit 2. Digital filter processing is performed to remove unnecessary components. The processing circuit 2 processes these acceleration sensors 3
A calculation operation is performed based on the outputs from the wheel speed sensors 1a to 1d to perform anti-skid control.

The processing circuit 2 also includes an output from the switch 7 that detects that the brake pedal 30 has been depressed, or a voltage level that is converted into a suitable voltage level in the anti-skid control port F#14 by the level conversion circuit FI118. is input. Each circuit in the anti-skid control circuit 4 is supplied with voltage from the battery 11 that is input via the power switch 10 after being stabilized by the power supply circuit.

The processing circuit 2 drives and controls actuators 13a to 13d constituted by three-position electromagnetic control valves 32a to 32d and wheel cylinders 33a to 33d, which will be described later, based on the input results input as described above, and performs anti-skid control. Perform control actions. That is, the relay coil 15a of the relay 15 is connected via the solenoid relay drive circuit 14.
is excited, thereby making the relay switch 15b conductive. A high level voltage is commonly applied to one input of each of the actuators 13a to 13d via this relay switch 15b. These actuators 1
The control output from the processing circuit 2 is given to the other inputs of the inputs 3a to 13d via the solenoid drive circuits 12a to 12d, respectively.

As a result, the three-position electromagnetic control valves 32a to 32d control the braking oil pressure to be increased, decreased, or maintained as described later.

The processing circuit 2 also outputs an output to the relay coil 16a of the relay 16 via the motor relay drive circuit 18, thereby causing the motor 17 for generating braking oil pressure connected to the switch 16kj of the relay 16 to Drive controlled. Furthermore, the processing circuit 2 turns on the warning light 19 via the lamp drive circuit 20 when an abnormality occurs in the anti-skid control.

Referring to FIG. 7, when the brake pedal 30 is depressed, braking oil pressure is generated in the master cylinder 31, and the braking oil pressure is transmitted through the three-position electromagnetic control valves 32a to 32a through the pipes P1 to P4. 32d, and further supplied to wheel cylinders 33a to 33d via pipes P5 to P8.

As a result, the wheels 34a to 34d are braked, and the vehicle speed is reduced.

The rotational speed of the wheels 34a to 34d is determined by the wheel speed sensor 1a.
~1d, respectively, and inputted to the anti-skid control circuit 4. Further, an output signal representing the vehicle body acceleration detected by the acceleration sensor 3 fixed to the vehicle body is also input to the anti-skid control circuit 4.

When the anti-skid control circuit 4 determines that the conditions for starting anti-skid control are met, the anti-skid control circuit 4 controls the motor 17.
The braking hydraulic pressure generated by is applied to the master cylinder 31 via the pipe P9, and the three-position electromagnetic control valves 32'a to 32d are controlled to increase, decrease, or maintain the pressure, and the brake hydraulic pressure is applied to the wheel cylinder 33a. ~33d braking oil pressure is controlled. Thereby, the slip ratios of the wheels 34a to 34d are controlled to a value at which a high frictional braking force acts on the road surface.

FIG. 8 is a block diagram showing the electrical configuration of the acceleration sensor 3, and FIG. 9 is a diagram for explaining the principle of acceleration measurement by the other acceleration sensor 3. , is composed of three metal plates 41a, 41c, and 41b that are arranged parallel to each other in a direction that intersects the traveling direction of the vehicle body shown by arrow A. Previously adjacent metal plates 41a, 41c: 41
two capacitors 41ac, 41c by c41b
b is constructed.

The metal plates 41a and 41b are fixed, and the metal plate 41c
is configured to be movable in the direction of the arrow A. Therefore, when the metal plate 41c is displaced due to acceleration in the direction of arrow A, the capacitance Cac of the capacitor 41ac and the capacitance CCb of the capacitor 41cb change as shown in FIG. 10.

Therefore, acceleration can be detected from changes in the capacitances Cac and Cab. A rectangular wave pulse as shown in FIG. 11(1) is applied from the oscillator 42 to one capacitor 41ac of the acceleration detection section 41 configured as described above, and the rectangular wave pulse as shown in FIG. 11(1) is applied to the other capacitor 41cb. The pulse is inverted in the buffer 43, as shown in Fig. 1'1 (2).
It is applied after being inverted as shown in .

Acceleration detection section 41g) Output is from capacitor 41ac41
After being amplified by the amplifier 44 by, for example, about 20 dB, the signal is led out from the switch 45 to the analog/digital conversion circuit 6 via the low-pass filter (abbreviated as LPF) 46.

The switch 45 is given a rectangular wave pulse from the oscillator 42 shown in FIG. 11(1), and the switch 45 is conductive when this pulse is at a high level.
Shuts off when the level is low.

Therefore, as shown in FIG. 11(3), before the time to when no acceleration is applied, the connection point 41e
An output of O level is derived from , and after time 10 when acceleration is applied, an output of a level corresponding to the acceleration is derived. This output is output at the switch 45 during a period when no pulse is derived from the oscillator 42;
That is, after the 0 level output is cut off, the signal is smoothed by the LPF 46 and output.

- Therefore 1. ■Since it is a turn, when a sudden braking turn is performed, the acceleration in the rear direction of the vehicle body force detected by the longitudinal acceleration sensor 3a is the force at the time when braking is started? It increases to the negative side from then on, starts to recover at the start of a turn, and reaches its minimum value when the attitude of the vehicle body is displaced by 90 degrees. After that, it increases again until the turn ends, and then recovers.

On the other hand, the lateral acceleration of the vehicle body detected by the lateral acceleration sensor 3b increases from the time when the turn starts, reaches its maximum value when the vehicle body posture shifts by 90 degrees, and then the turn ends. decreases until

Therefore, the friction coefficient μ is determined only by the longitudinal acceleration of the vehicle body.
If this determination is made, even if there is a road with a high friction coefficient, it will be incorrectly determined to be medium μ or low μ during turning. For this reason, in this embodiment, the friction coefficient μ is determined based on the acceleration of the sum of the accelerations in the longitudinal direction and the lateral direction of the vehicle body, and the friction coefficient μ is accurately determined.
Make a judgment.

In this way, by sudden braking on a road with a high friction coefficient, it is possible to prevent erroneous determination of the friction coefficient μ during turning, realize highly accurate anti-skid control, and shorten the braking distance.

FIG. 12 is a flowchart for explaining the anti-skid control operation. In step n1, an initialization process is performed, and in step n2, it is determined whether or not a predetermined calculation operation timing, for example every 5 m5ec, has arrived, and when the calculation operation timing has arrived, step n3
Move to.

In step n3, each wheel speed Vw is calculated from the detection results of the respective wheel speed sensors 1a to 1d. In step n4, it is determined whether or not the brake pedal 30 is depressed based on the output of the switch 7, and if so, the process moves to step n5, and the maximum value of each wheel speed Vw determined in step n3 is estimated. If not, the process moves to step n6, where the minimum value of the respective wheel speeds is set as the estimated vehicle speed Vsi.

In steps n4 to n6, after the estimated vehicle speed Vsi, which has been removed from the effects of slippage caused by the wheels and the road surface, is determined, the process moves to step n7, where the output αa of the longitudinal acceleration sensor 3a is calculated using analog/digital conversion. The circuit 6a converts it into a digital value and reads the longitudinal acceleration.Similarly, in the Ste Noah n8, the output αb of the lateral acceleration sensor 3b
The lateral acceleration is read after tesital conversion. Step n9 and step n7. As described above, it is determined whether the friction coefficient is 7.7 from the acceleration of the sum of the respective accelerations obtained in step n8, and in step nlo, the sum of the accelerations is integrated to obtain the vehicle speed Vs.

In this way, when the parameters for anti-skid control are obtained in steps n7 to nlO, step nl
1, the braking oil pressure is controlled as described later.

In step n12, abnormality determination of the acceleration sensor 3 as shown in FIGS. 3 to 5 described above is performed, and
If the determination result is abnormal, one warning light is turned on to notify the driver, and a fail-safe process is performed in which the estimated vehicle speed \si is not substituted for the vehicle speed Vs.

FIG. 13 is a flowchart for explaining in detail the braking oil pressure control operation in step nll.

When the anti-skid control motion is executed, step ”s
In step 1, it is determined whether anti-skid control is currently being executed, and if not, in step s2, it is determined whether or not the conditions for starting anti-skid control are satisfied. The control start condition is, for example, when the wheels 34a to 34d are locked, or when the wheel speed Vw becomes equal to or lower than a predetermined slip reference.

When the anti-skid control start condition is satisfied, the process moves to step s3, where a pressure reduction flag for causing the wheel cylinders 33a to 33d to perform a pressure reduction operation is set in a predetermined memory area of the processing circuit 2, and the process proceeds to step s3.
Move on to 4. If anti-skid control has already been performed in step s1, step s4 is performed directly.
Move to.

In step 's4, it is determined whether the conditions for terminating the anti-skid control are satisfied.

The control termination condition is, for example, when the operation of the flake belt 30 is released, or when the vehicle body speed \'S becomes 5 km,'h or less.

When the anti-skid control end condition is satisfied in step S4, or when the anti-skid control start condition is not satisfied in step S2, the process moves to step s18, and the actuators 13a to 13d
The three-position electromagnetic control valves 32a to 32d are set to the pressure increasing position, and anti-skid is not controlled. Therefore, by depressing the brake pedal 30, the master syringe 3
The braking oil pressure generated in wheel cylinders 33a to 3
3d, and a normal braking operation is performed.

In step s4, if the anti-skid control end condition is not satisfied, the process moves to step s5, and a flag for controlling the increase/decrease of the braking oil pressure of the wheel cylinders 33a to 33d is determined. At the start of the skit control, the pressure reduction flag is set as shown in step s3, so the process moves to step s6. In step s6, it is determined whether or not to end the pressure reduction control. If not, in step s7, the pulse width of the pressure reduction pulse is controlled, the ratio between the pressure reduction output and the holding output is changed, and the operation is ended. do.

Further, when the pressure reduction control should be ended in step S6, that is, when the wheel speed starts to recover, the process moves to step s8, and a holding flag is set to keep the braking oil pressure of the wheel cylinders 33a to 33d constant. The process moves to step s9. Even when such anti-skid control operation is repeated and the holding flag has already been set in step s5, the process moves to step s9. In step s9, it is determined whether the holding end condition is satisfied, and if not, in step slo, the three-position electromagnetic control valves 32a to 32d are set to the holding position, holding control is performed, and then the operation is ended.

In step S9, if the holding end condition for determining that the wheel speed has recovered is satisfied, a pressure increase flag for increasing the braking oil pressure of the wheel cylinders 33a to 33d is set in step sll, and the process proceeds to step s12. Move. Further, if the pressure increase flag is already set in step s5, the process moves directly to step SL2. In this step 312, it is determined whether the pressure increase end condition is satisfied, and if not, step s13
After the three-position electromagnetic control valves 32a to B2d are set to the pressure increase position and pressure increase 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 step n9. , the amount of pressure increase is increased. The pressure increase end condition is, for example, when the pressure increase time determined by the wheel acceleration obtained when the wheel speed is restored has elapsed.

If the pressure increase end condition is satisfied in step s12, the process moves to step s14, where a pulse pressure increase flag for gradually increasing the brake oil pressure in the wheel cylinders 33a to 33d is set, and the process moves to step s15. Further, when the pulse pressure increase flag is completely set in the step 's5, the pulse pressure increase flag is directly set in the step s15.
Move to.

In this step s15, it is determined whether or not the conditions for ending the pulse pressure increase control are satisfied, and if not, in step s16, the three-position electromagnetic control valves 32a to 32a to 32b are
The pulse pressure increase control of d is continued and the operation is completed. If the conditions for ending the pulse pressure increase control are satisfied in step s15, the pressure reduction flag is set in step s17, and then the process moves to step S7, where pressure reduction control is performed.

As described above, the anti-skid control device according to the present invention is provided with the longitudinal acceleration sensor 3a that detects the longitudinal acceleration αa of the vehicle body and the lateral acceleration sensor 3b that detects the lateral acceleration αb of the vehicle body. Since anti-skid control is performed using the acceleration that is the sum of the accelerations detected by the acceleration sensor 3, highly accurate control can be achieved even when turning. In addition, each acceleration sensor 3 is judged to be abnormal by the above-mentioned operations shown in FIGS. There are two things that can be done and improve safety.

Effects of the Invention As described above, according to the present invention, in detecting an abnormality in an acceleration sensor used for anti-skid control, it is possible to determine whether the output from the acceleration sensor is abnormal based on the output of each wheel speed sensor. To ensure that an abnormality is detected even if an abnormality occurs in an acceleration sensor in either direction, the direction in which the output is no longer derived from the acceleration sensor, or the direction in which the output is derived. I can do it.

[Brief explanation of drawings]

Fig. 1 is a functional block diagram for explaining the principle of an embodiment of the present invention, Fig. 2 is a waveform diagram for explaining rough road judgment operation, and Fig. 3 (21 is an abnormality judgment operation of longitudinal acceleration sensor 3a). FIG. 4 is a flowchart for explaining one embodiment of the abnormality determination operation of the lateral acceleration sensor 3b, and FIG. 5 is a flowchart for explaining another embodiment of the abnormality determination operation of the lateral acceleration sensor 3b. Nano flow chart,
FIG. 6 is a block diagram showing the electrical configuration of the anti-skid control device in which the present invention is implemented, FIG. 7 is a piping route diagram for the braking oil pressure of the anti-skid control device, and FIG. 8 is the electrical configuration of the acceleration sensor 3. 9 is a diagram for explaining the measurement principle of the acceleration sensor 3. FIG. 10 is a graph for explaining the measurement principle of the acceleration sensor 3.
The figure is a waveform diagram to explain the measurement principle of the acceleration sensor 3, Figure 12 is a flowchart to explain the anti-skid control operation, and Figure 13 is a flowchart to explain the brake oil pressure control operation in detail. be. 1a to 1d...Wheel speed sensor, 2...Processing circuit,
3a, 3b... Acceleration sensor, 4... Anti-skid control circuit, 13a-13d... Actuator, 1
9... Warning light, 51a, 51b... Input processing unit, 52 Vehicle speed calculation unit, 53... Friction coefficient determination unit, 54 Anti-skid control unit, 55 Wheel speed calculation unit, 56… Rough road determination unit, 57a, 57b Abnormality Judgment Department Agent Patent Attorney Number of strokes

Claims (4)

[Claims] (1) Using the acceleration of the vehicle body in the running direction detected by the acceleration sensor and the speed of each wheel detected by the wheel speed sensor, the coefficient of friction between the wheels and the road surface is increased. In an anti-skid control device with an acceleration sensor that controls braking force, a calculation means calculates an acceleration in a running direction of a vehicle body based on each wheel speed detected by the wheel speed sensor; and a road surface condition on which the vehicle body is traveling. a rough road determining means for determining whether or not the road is a rough road; and in response to the outputs of the calculating means and the rough road determining means, the acceleration of the vehicle body calculated by the calculating means is calculated in advance while the anti-skid control is not being performed. a determination that determines that the acceleration sensor is abnormal when the output level of the acceleration sensor is equal to or higher than a predetermined level and the road surface condition detected by the rough road determining means is not a rough road; An acceleration sensor abnormality detection device for an anti-skid control device with an acceleration sensor, comprising: means. (2) At least the lateral acceleration of the vehicle body detected by the acceleration sensor and the wheel speed detected by the wheel speed sensor are used to increase the coefficient of friction between the wheels and the road surface. An anti-skid control device with an acceleration sensor that controls braking force, comprising: a calculation means for calculating the difference between the respective wheel speeds detected by the wheel speed sensor; and a calculation means for calculating the difference between the respective wheel speeds detected by the wheel speed sensor; a rough road determining means for determining whether or not the vehicle is on a rough road; within the value,
and determining means for determining that the acceleration sensor is abnormal when the road surface condition determined by the rough road determining means is not a rough road and the output level of the acceleration sensor is equal to or higher than a predetermined level. An acceleration sensor abnormality detection device for an anti-skid control device with an acceleration sensor. (3) The rough road determining means performs the rough road determination when the amount of variation per predetermined time in each wheel speed detected by the wheel speed sensor is equal to or greater than a predetermined value. An acceleration sensor abnormality detection device for an anti-skid control device with an acceleration sensor according to items 1 and 2. (4) At least the lateral acceleration of the vehicle body detected by the acceleration sensor and the wheel speed detected by the wheel speed sensor are used to increase the coefficient of friction between the wheels and the road surface. An anti-skid control device with an acceleration sensor that controls braking force, comprising: a calculation means for calculating a difference in wheel speed between a left wheel and a right wheel based on each wheel speed detected by the wheel speed sensor; In response to the output of the calculation means, when the output level of the acceleration sensor is below the predetermined level while the difference in wheel speed calculated by the calculation means is above the predetermined value while anti-skid control is not being performed. and determining means for determining whether the acceleration sensor is abnormal.