JPH11108943A - Device for diagnosing failure in waveform shaping circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device for diagnosing a failure in a waveform shaping circuit capable of diagnosing a failure in the waveform shaping circuit reliably even in a single waveform shaping circuit. SOLUTION: Wheel velocity signals detected by four wheel velocity sensors FLS, FRS, RLS, and RRS each provided for a wheel are waveform-shaped by a waveform shaping circuit 14. In the case that output from the waveform shaping circuit 14 is absent for a predetermined period of time, a CPU 15 monitors the presence or absence of changes in the waveforms of the wheel velocity sensors inputted to an A/D converting part 17 at a frequency twice higher than a maximum wheel velocity frequency or more. Then on the basis whether there is a change by a predetermined value or more from a central value within a predetermined period of time in the voltage of a signal inputted to the A/D converting part 17, the waveform shaping circuit of wheel velocity is diagnosed. In the case that there is a change in the voltage by a predetermined value or more from the central value within a predetermined period of time, it is determined that the waveform shaping circuit 14 is faulty.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a failure diagnosis apparatus for a waveform shaping path, and more particularly to a failure diagnosis apparatus for a waveform shaping circuit such as a wheel speed sensor.

[0002]

2. Description of the Related Art Conventionally, a failure diagnosis device 21 for a waveform shaping circuit such as a wheel speed sensor of this kind, as shown in FIG. 3, has a wheel speed sensor FLS (left front wheel) for detecting the wheel speed of each wheel. FRS (right front wheel), RLS (left rear wheel), RRS (right rear wheel), and these wheel speed sensors F
Wheel speed sensor filter circuit 22 for filtering wheel speed signals detected by LS, FRS, RLS, RRS
And a first waveform shaping circuit 24 for shaping the 2ch output from the front wheel among the outputs from the wheel speed sensor filter circuit 22, and the first waveform shaping circuit 24 from the output from the wheel speed sensor filter circuit 22, for example, from the rear wheel. 2ch
A second waveform shaping circuit 25 for shaping the output, and calculating the wheel speed from the waveform shaping output input from the first waveform shaping circuit 24 and the second waveform shaping circuit 25 via the input capture 27. , Wheel speed sensor FL
S, FRS, RLS, RRS, first waveform shaping circuit 24
And a CPU 26 for diagnosing a short-circuit / disconnection of the second waveform shaping circuit 25 and a protection circuit 23 for applying DC and protecting the A / D converter 28 of the CPU 26 when diagnosing the short-circuit / disconnection of each wheel speed sensor. Have been.

The operation of the fault diagnosis device 21 for a waveform shaping circuit having such a configuration will be described.

[0004] Four wheel speed sensors FLS, FRS, R
By shaping the output of the LS and RRS with one waveform shaping circuit for each two wheels, one waveform shaping circuit such as the first
Even if the waveform shaping circuit 24 does not produce a waveform shaping output due to a complete failure, the waveform shaping circuit 25 outputs the waveform shaping output. That is, it is determined that the state where the waveform shaping output of one waveform shaping circuit 24 is present and the waveform shaping output of the other waveform shaping circuit 25 is absent is abnormal. An abnormality of the shaping circuit 25 was detected.

Further, four wheel speed sensors FLS, FR
When the waveforms of the outputs of S, RLS, and RRS are shaped by a single waveform shaping circuit, a method is employed in which the probability that the waveform shaping output does not appear due to a total failure of the waveform shaping circuit is determined, and the presence or absence of a failure is determined according to the probability. Was.

[0006]

However, in the case of the former fault diagnosis apparatus, if the waveform shaping output is not output due to a total fault of one of the waveform shaping circuits, the fault can be detected. You have to provide two,
There was a problem that the device became expensive.

Further, when the outputs of the four wheel speed sensors are shaped by one waveform shaping circuit from the viewpoint of price as in the latter case, the total failure of the waveform shaping circuit is determined by probability. There is a problem that the accuracy of detecting a failure is not good.

SUMMARY OF THE INVENTION An object of the present invention is to provide a failure diagnosis apparatus for a waveform shaping circuit that can reliably diagnose a failure of even one waveform shaping circuit.

[0009]

SUMMARY OF THE INVENTION Accordingly, the present invention provides
In order to achieve the above object, a wheel speed sensor provided on each wheel to detect the wheel speed, a waveform shaping circuit for shaping a wheel speed signal detected by the wheel speed sensor, and a waveform shaping circuit If there is no waveform shaping output from the controller for a certain period of time, the presence of a change in the input waveform to the A / D converter of the wheel speed sensor is monitored at a frequency twice or more the maximum wheel speed frequency, and a failure in the waveform shaping circuit is detected. And control means for performing the control.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of a fault diagnosis apparatus for a waveform shaping circuit according to the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of a failure diagnosis apparatus for a waveform shaping circuit according to the present invention, and FIG.
FIG. 3 is a signal waveform diagram illustrating an output waveform of a waveform shaping circuit and an input waveform of a CPU.

A waveform diagnosing circuit fault diagnostic apparatus 11 according to the present invention.
Are wheel speed sensors FLS (left front wheel), FRS (right front wheel), RLS (left rear wheel), RRS (right rear wheel) for detecting the wheel speed of each wheel, as shown in FIG.
These wheel speed sensors FLS, FRS, RLS, RRS
A filter circuit 12 for filtering the wheel speed signal detected in the above, a 4cH input waveform shaping circuit 14 for shaping all the outputs from the filter circuit 12, and a signal input from the waveform shaping circuit 14 via the input capture 16. While calculating the wheel speed from the waveform shaping output,
CPU 15 as control means for diagnosing short-circuit / disconnection of the wheel speed sensors FLS, FRS, RLS, RRS and the waveform shaping circuit 14; And a protection circuit 13 for protecting.

The protection circuit 13 outputs a signal detected by a wheel speed sensor to the A / D converter 17 in order to diagnose a short circuit or a failure of the waveform shaping circuit 13.

The operation of the fault diagnosis device 11 for a waveform shaping circuit having such a configuration will be described with reference to the drawings.

When the wheel speed is detected by the wheel speed sensor, the signal is output to the waveform shaping circuit 14 via the protection circuit 13 and the filter circuit 12.

When the above signal is output from the waveform shaping circuit 14 to the input capture 16, the CPU 15
Determines that all wheel speed sensors are normal,
The diagnosis of the input waveform of the A / D converter 17 of U15 is not performed. Therefore, the software processing time of the CPU 15 is not affected.

If the signal is not output from the waveform shaping circuit 14 to the input capture 16, the CPU 1
5 confirms the minimum detectable cycle time at a normal control speed from the waveform of the signal output from the wheel speed sensor to the A / D converter 17 via the protection circuit 13, and averages the center value of the voltage of the signal. And diagnose the disconnection / short circuit of the wheel speed sensor.

The diagnosis of the waveform shaping circuit at the time of low wheel speed is made based on whether or not the voltage of the signal input to the A / D converter 17 at that time has changed from the center value by a certain value within a certain period. When the voltage changes from the center value by a certain value or more within a certain period, it is determined that the waveform shaping circuit 14 has failed.

Here, when the wheel speed is high, A / D
Since the diagnosis may not be performed due to the sampling timing in the conversion unit 17, the voltage of the signal input to the A / D conversion unit 17 is monitored at a frequency twice or more the maximum wheel speed frequency. Diagnoses the waveform shaping circuit when the wheel speed is high, based on whether or not the voltage has changed by more than a certain value within a certain period from the center value.If the voltage has changed by more than a certain value within a certain period from the center value, the waveform is shaped The circuit 14 is determined to have failed.

By the way, when there is no waveform shaping output, the microcomputer does not perform the wheel speed calculation processing, so that the software processing time is short. Therefore, since the input waveform to the A / D converter 17 is checked when there is no wheel speed input, even if the software processing time of the microcomputer increases, it can be performed within a prescribed processing loop time.

[0021]

As described above, according to the present invention,
Diagnosis of the waveform shaping circuit of the wheel speed sensor determines that the A of the wheel speed sensor is not less than twice the maximum wheel speed frequency if the waveform shaping output from the waveform shaping circuit is not present for a certain period.
Since the presence or absence of a change in the input waveform to the / D conversion unit is monitored and a failure of the waveform shaping circuit is detected, the failure can be reliably detected even with one waveform shaping circuit.

Further, the effect on the software processing time of the microcomputer can be reduced by checking the input waveform to the A / D converter when there is no wheel speed input.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a method for diagnosing a waveform shaping circuit of a wheel speed sensor according to the present invention.

FIG. 2 is a signal waveform diagram of a wheel speed output of a waveform shaping circuit of a wheel speed sensor according to the present invention.

FIG. 3 is a block diagram showing a diagnostic method of a conventional waveform shaping circuit of a wheel speed sensor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Fault diagnosis apparatus 12 Filter circuit 13 Protection circuit 14 Waveform shaping circuit 15 CPU (control means)

Claims (1)

[Claims] 1. A wheel speed sensor provided on each wheel for detecting a wheel speed thereof, a waveform shaping circuit for shaping a waveform of a wheel speed signal detected by the wheel speed sensor, and a waveform shaping from the waveform shaping circuit. If there is no output for a certain period of time, the A /
A failure diagnosis device for a waveform shaping circuit, comprising: a control unit for monitoring the presence or absence of a change in an input waveform to a D conversion unit and detecting a failure of the waveform shaping circuit.