JPH10132834A - Wheel speed measuring equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable surely diagnosing whether there is abnormality of an interconnection from a wheel speed sensor and a waveform shaping circuit which shapes the waveform of a wheel speed pulse. SOLUTION: A signal line 5 which connects a wheel speed sensor 2 with a waveform shaping circuit 3 which slices the output of the wheel speed sensor 2 is connected with a DC power supply Vcc via a variable resistor Rv. At the time of diagnosing, a resistance value of the variable resistor Rv is changed, and the output amplitude of the waveform adjusting circuit 3 is watched. When change is not observed in the output amplitude, abnormality warning is outputted considering the state that abnormality is generated in the signal line 5 or the waveform shaping circuit 3. When the signal line 5 which connects the wheel speed sensor 2 with the waveform shaping circuit 3 generates abnormality such as disconnection and ground shortcircutting, or the waveform shaping circuit 3 which slices the output of the wheel speed sensor 2 and shapes the waveform generates abnormality, and the waveform shaping output vanishes, the fact that the cause of generation of abnormality is in the signal line 5 or the waveform shaping circuit 3 can be delivered with an abnormality alarm, by changing the resistance value of the variable resistor Rv, according to a command from an operating equipment 12 as a diagnosing means.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wheel speed measuring device capable of surely diagnosing a connection from a wheel speed sensor and an abnormality of a waveform shaping circuit for shaping a wheel speed pulse.

[0002]

2. Description of the Related Art In an anti-lock brake system or a four-wheel steering system, it is necessary to measure the rotational speed of each of four wheels supporting a vehicle. As a wheel speed sensor for detecting the rotation speed of such a wheel, for example, a wheel speed sensor that magnetically detects the rotation of a rotating disk that rotates integrally with the wheel is often used.

A conventional wheel speed measuring device 1 shown in FIG. 4 slices an output pulse of this kind of wheel speed sensor 2 by a waveform shaping circuit 3 and shapes the waveform, for example, anti-lock brake control or four-wheel steering control. Is supplied to the arithmetic unit 4 which is the center of the system. Wheel speed sensor 2 and waveform shaping circuit 3
Is formed of a two-core wire bundled with a wire harness. The waveform shaping circuit 3 includes a signal detection unit 3a
And a signal output unit 3b. A comparator (not shown) disposed in the signal detection unit 3a slices the input wheel speed pulse on the basis of a preset threshold value to remove a DC offset, thereby removing a waveform. The shaped wheel speed pulse is inverted in polarity at the signal output unit 3 b and supplied to the arithmetic unit 4. The arithmetic unit 4 includes a signal input unit 4 for receiving a wheel speed pulse.
a, a CPU 4b for comparing the wheel speed signal with the vehicle speed signal to calculate a wheel slip ratio and the like, and outputting a control signal to an operation unit (not shown) such as a brake mechanism or a steering mechanism; And a signal input unit 4c to which the diagnostic voltage detected by the above is input.

A signal line 5 connecting the wheel speed sensor 2 and a signal detecting section 3a in the waveform shaping circuit 3 has a resistance R
Is connected to the DC power supply Vcc. This resistor R is a pull-up resistor, and has an appropriate resistance value so as to apply a predetermined DC bias to the output pulse of the wheel speed sensor 2. However, the resistor R is necessary for monitoring a poor connection or abnormal connection with the wheel speed sensor 2. An appropriate resistance value is set in consideration of the magnitude of the diagnostic voltage. The signal line 5 has a branch line 6 branching from the middle thereof, and a voltage detection circuit 7 disposed on the branch line 6 detects the voltage of the signal line 5 via the branch line 6 to calculate the voltage of the signal line 5. To the signal input unit 4c.

[0005]

In the conventional wheel speed measuring device 1, if it is found that the output of the waveform shaping circuit 3 does not exist for more than a predetermined period of time, first, the voltage detecting circuit 7
Read the output voltage of. The CPU 4b, which has received the output voltage of the voltage detection circuit 7 via the signal input unit 4c, determines whether the read diagnostic voltage is within an allowable range between the upper threshold voltage and the lower threshold voltage. If the threshold value is discriminated and the value deviates from the permissible range, an abnormality alarm is issued assuming that the signal line 5 connecting the wheel speed sensor 2 and the waveform shaping circuit 3 is abnormal. That is, the connection abnormality is determined by monitoring the output of the voltage detection circuit 7 of a different system from the waveform shaping circuit 3. Therefore, even if the waveform shaping circuit 3 becomes abnormal, the wheel speed sensor 2 operates normally. If there is no abnormality in the branch line 6, the output of the voltage detection circuit 7 does not indicate an abnormality, so that an abnormality of the wheel speed detection system cannot be detected. There is a problem that the fact that no output is obtained is easily misunderstood as an abnormality of the signal line 5.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has as its object to provide a wheel speed measuring device capable of detecting a failure in connection between a waveform shaping circuit and a wheel speed sensor with a simple circuit configuration. Is what you do.

[0007]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a wheel speed sensor for detecting wheel rotation to generate a wheel speed pulse, and outputs an output of the wheel speed sensor to a predetermined threshold value. A waveform shaping circuit for slicing on the basis of, a variable resistor connecting a signal line connecting the waveform shaping circuit and the wheel speed sensor to a DC power supply, and switching the resistance value of the variable resistor during diagnosis to output the waveform shaping circuit. Diagnostic means for monitoring the amplitude and issuing an abnormality alarm when there is no change in the output amplitude, assuming that there is an abnormality in either the signal line or the waveform shaping circuit. It is.

The present invention also provides a wheel speed sensor for detecting wheel rotation to generate a wheel speed pulse, a waveform shaping circuit for slicing the output of the wheel speed sensor on the basis of a predetermined threshold value, A variable resistor connecting a signal line connecting the waveform shaping circuit and the wheel speed sensor to a DC power supply; a voltage detection circuit connected to a branch line branched from the signal line to detect a voltage of the branch line; The output voltage of the detection circuit is determined as a threshold value, and if the output voltage is less than a predetermined voltage, a line abnormality alarm is issued assuming that the signal line or the branch line is abnormal, and abnormality is detected in both the signal line and the branch line. If not, the output value of the waveform shaping circuit is monitored by switching the resistance value of the variable resistor, and when no change is found in the output amplitude, a circuit abnormality alarm is issued assuming that the waveform shaping circuit is abnormal. It is characterized in that it comprises a cross section.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a circuit diagram showing an embodiment of a wheel speed measuring device according to the present invention, and FIG. 2 is a signal waveform diagram of each part of the circuit shown in FIG.

The wheel speed measuring device 11 shown in FIG. 1 eliminates the branch line 6 and the voltage detection circuit 7 that have been branched from the signal line 5 connecting the wheel speed sensor 2 and the waveform shaping circuit 3, and eliminates the resistance R. The resistance value is replaced by a variable resistance Rv that can be switched in two stages, and this variable resistance Rv is
The switching control is performed based on the output of the signal output unit 12c. That is, the abnormality diagnosis system is not formed separately from the waveform shaping circuit 3, but a circuit abnormality is found by observing the response of the output waveform of the waveform shaping circuit 3 when the input voltage of the waveform shaping circuit 3 is switched. It was a configuration. The variable resistor Rv is a common resistor Ra having a small resistance value.
And a diagnostic resistor Re having a large resistance value are connected in parallel with each other, and these resistors Ra and Re are switched in response to a switching command from the signal output unit 12c.
The signal line 5 can be selectively switched and connected. The arithmetic unit 12, which is a diagnostic unit, includes a signal input unit 1 for receiving wheel speed pulses, in addition to the signal output unit 12c.
2a, and a CPU 12b that compares the wheel speed signal with the vehicle speed signal to calculate a wheel slip ratio or the like and outputs a control signal to an operation unit such as a brake mechanism or a steering mechanism.
The CPU 12b issues a diagnosis command to the signal output unit 12c.

If the output of the waveform shaping circuit 3 is not observed for a certain period of time, the CPU in the arithmetic unit 12
12b issues a diagnosis command to the signal output unit 12c.
The signal output unit 12c that has received the diagnosis command issues a switching command shown in FIG. 2A to the changeover switch S in the variable resistor Rv, so that the variable resistor Rv switches from the regular resistor Ra to the diagnostic resistor Re. The variable resistor Rv is the regular resistor R
When the diagnostic resistance is switched from “a” to “Re”, the resistance value naturally increases, so that the signal voltage supplied to the signal detection unit 3a of the waveform shaping circuit 3 decreases as shown in FIG. Since the threshold value of the comparator in the signal detector 3a is fixed, the wheel speed sensor 2 and the waveform shaping circuit 3
Is not broken or short-circuited to the ground, and if there is no abnormality in the waveform shaping circuit 3, the peak value of the signal whose polarity is inverted and output from the signal output unit 3b of the waveform shaping circuit 3 is: It will change as shown in FIG.
Therefore, when this change is observed, it is understood that there is no abnormality in the above-mentioned diagnosis location.

However, even if the resistance value of the variable resistor Rv is switched, if the signal output from the output section 3b of the waveform shaping circuit 3 is zero as shown in FIG. Either the signal line connecting the waveform shaping circuit 3 and the signal shaping circuit 3 is broken or short-circuited to the ground, or an abnormality occurs in the waveform shaping circuit 3. The occurrence of such an abnormality is notified from the CPU 12b of the arithmetic unit 12 by an abnormality alarm. Be informed.

As described above, according to the wheel speed measuring device 11, the signal line 5 connecting the wheel speed sensor 2 and the waveform shaping circuit 3 for slicing its output is connected to the DC power supply Vcc via the variable resistor Rv. Then, at the time of diagnosis, the resistance value of the variable resistor Rv is switched to monitor the output amplitude of the waveform shaping circuit 3, and when no change is found in the output amplitude, an abnormality is detected in either the signal line 5 or the waveform shaping circuit 3. Since the configuration is such that an abnormal alarm is issued, the signal line 5 connecting the wheel speed sensor 2 to the waveform shaping circuit 3 may cause an abnormality such as disconnection or ground short-circuit, or the output of the wheel speed sensor 2 may be sliced to generate a waveform. When the waveform shaping circuit 3 for shaping causes an abnormality and the waveform shaping output disappears, the resistance value of the variable resistor Rv is switched by a command from the arithmetic unit 12 as a diagnostic means. Can know with alarming that cause the normally is at the signal line 5 or the waveform shaping circuit 3. Further, by replacing the resistor R connecting the signal line 5 to the DC power supply Vcc with a variable resistor Rv,
Since the abnormality diagnosis can be performed without the voltage detection circuit 7 that detects the voltage of the signal line 5, the abnormality diagnosis target can be extended from the signal line 5 to the waveform shaping circuit 3 after simplifying the circuit configuration.

In the above embodiment, the wheel speed sensor 2
It is not possible to determine whether there is an abnormality in the connection with the signal or the waveform shaping circuit 3. However, as in the case of the wheel speed measuring device 21 shown in FIG. Can be determined. In the wheel speed measuring device 21, a voltage detection circuit 7 is connected to a branch line 6 branched from a signal line 5, and first, the output voltage of the voltage detection circuit 7 is determined as a threshold value, and the output voltage is less than a predetermined voltage. In this case, a line abnormality alarm is issued assuming that the signal line 5 or the branch line 6 has an abnormality. However, when there is no abnormality in both the signal line 5 and the branch line 6, the output value of the waveform shaping circuit 3 is monitored by switching the resistance value of the variable resistor Rv, and when no change is found in the output amplitude, the waveform shaping is performed. A circuit abnormality alarm is issued assuming that the circuit 3 has an abnormality. For this reason, when the signal line 5 connecting the wheel speed sensor 2 to the waveform shaping circuit 3 has an abnormality such as disconnection or ground short circuit, a line abnormality alarm is issued, and the output of the wheel speed sensor 2 is sliced to form a waveform. When the waveform shaping circuit 3 for shaping has an abnormality, a circuit abnormality alarm is issued, for example, a different alarm is issued in accordance with the content of the generated abnormality, and the location of the abnormality can be specified. Anomalies occurring in the detection system can be finely analyzed and reported. Note that the signal output unit 1 provided in the arithmetic unit 12 in the above-described embodiment is used.
2c is abolished, and in the present embodiment, the signal detector 12
A signal input / output unit 12d is provided in place of c.

[0015]

As described above, according to the present invention,
A signal line connecting the wheel speed sensor and a waveform shaping circuit that slices the output is connected to a DC power supply via a variable resistor, and at the time of diagnosis, the resistance value of the variable resistor is switched to monitor the output amplitude of the waveform shaping circuit. When the output amplitude does not change, an alarm is issued assuming that there is an abnormality in either the signal line or the waveform shaping circuit. Therefore, the signal line connecting the wheel speed sensor to the waveform shaping circuit is broken. When the waveform shaping circuit for shaping the waveform by slicing the output of the wheel speed sensor causes an abnormality such as a short circuit or a ground short circuit, and the waveform shaping output disappears, the variable resistor Rv is instructed by the diagnostic means. By switching the resistance value, it is possible to know with an abnormality alarm that the cause of the abnormality is in the signal line or the waveform shaping circuit, and to connect the signal line to the DC power supply. By replacing the resistor that was connected to the variable resistor with a variable resistor, it is possible to diagnose abnormalities without a voltage detection circuit that detects the voltage of the signal line. It has excellent effects such as being able to be extended to.

Further, according to the present invention, a voltage detection circuit is connected to a branch line branched from a signal line, and the output voltage of the voltage detection circuit is firstly determined as a threshold value. Or, if there is no abnormality in both the signal line and the branch line, monitor the output amplitude of the waveform shaping circuit by switching the resistance value of the variable resistor. When no change is observed, the waveform shaping circuit is assumed to be abnormal and a circuit abnormality alarm is issued, so if the signal line connecting the wheel speed sensor to the waveform shaping circuit has an abnormality such as disconnection or ground short circuit When a waveform shaping circuit that issues a line abnormality alarm and slices the output of the wheel speed sensor to shape the waveform is abnormal, it issues a circuit abnormality alarm. Flip to be able to identify an abnormal occurrence location emit different alarm, an effect such as can be informed by detailed analysis of the abnormality occurring in the wheel speed pulse detection system.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an embodiment of a wheel speed measuring device according to the present invention.

FIG. 2 is a signal waveform diagram of each section of the circuit shown in FIG.

FIG. 3 is a circuit configuration diagram showing another embodiment of the wheel speed measuring device of the present invention.

FIG. 4 is a circuit diagram showing an example of a conventional wheel speed measuring device.

[Explanation of symbols]

 Reference Signs List 2 wheel speed sensor 3 waveform shaping circuit 3a signal detection unit 3b signal output unit 5 signal line 6 branch line 7 voltage detection circuit 11, 21 wheel speed measurement device 12 diagnostic means (arithmetic device) 12a signal input unit 12b CPU 12c signal output unit 12d signal input / output unit Rv variable resistor Ra working resistor Re diagnostic resistor S switch

Claims (2)

[Claims] 1. A wheel speed sensor for detecting rotation of a wheel to generate a wheel speed pulse, a waveform shaping circuit for slicing an output of the wheel speed sensor on the basis of a predetermined threshold value, and a waveform shaping circuit. A variable resistor that connects a signal line connecting the wheel speed sensor to a DC power supply, and the resistance value of the variable resistor is switched during diagnosis to monitor the output amplitude of the waveform shaping circuit, and when no change is observed in the output amplitude. A wheel speed measuring device, further comprising: a diagnosis unit that issues an abnormality alarm when there is an abnormality in either the signal line or the waveform shaping circuit. 2. A wheel speed sensor for detecting rotation of a wheel to generate a wheel speed pulse, a waveform shaping circuit for slicing an output of the wheel speed sensor on the basis of a predetermined threshold value, and a waveform shaping circuit. A variable resistor connecting a signal line connecting the wheel speed sensors to a DC power supply; a voltage detection circuit connected to a branch line branched from the signal line to detect a voltage of the branch line; and an output of the voltage detection circuit. When the voltage is determined as a threshold value and the voltage is less than a predetermined voltage, a line abnormality alarm is issued assuming that the signal line or the branch line is abnormal, and if there is no abnormality in the signal line or the branch line, Diagnostic means for monitoring the output amplitude of the waveform shaping circuit by switching the resistance value of the variable resistor, and issuing a circuit abnormality alarm on the assumption that the waveform shaping circuit has an abnormality when no change is observed in the output amplitude. Preparation A wheel speed measuring device.