JPH04366766A - Device and method for monitoring fault of wheel speed sensor - Google Patents

Abstract

PURPOSE:To provide a device and method for monitoring faults of a wheel speed sensor by which faults can be always detected not only when a vehicle runs and which can distinguish disconnection of wires from shortcircuiting. CONSTITUTION:A wheel speed sensor 1 which provides information about wheel speeds to the electronic controller of a vehicle is comprised of a means for feeding electricity to the wheel speed sensor 1 via a resistance R2 and a monitoring means which constantly monitors the divided potential values of both of the resistance R2 and a sensor resistance R1 and which when the divided potential values of both of the resistances are below a set low voltage value or above a set high voltage value detects faults of the wheel speed sensor 1.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wheel speed sensor failure monitoring device and method for constantly monitoring wheel speed sensor failures due to disconnection or short circuit.

0002

[Prior Art] In a vehicle electronic control device that uses wheel speed information, such as an anti-lock braking system (ABS) that aims to prevent wheel locking during braking, a wheel speed sensor is attached to each wheel. Obtaining wheel speed information. The rear wheel speed sensor is sometimes attached to the output shaft of the transmission or the propeller shaft side of the differential gear. Since the wheel speed sensor and the sensor cable are exposed to the outside, they are susceptible to failures such as short circuits and disconnections. Short-circuit failures occur due to dielectric breakdown failure of the coil inside the sensor, or the sensor cable gets caught in the vehicle body, and disconnection failures occur due to disconnection of the coil inside the sensor or the sensor cable. Conventionally, a constant current circuit a and a short circuit detection circuit b are added to the electronic control unit (ECU) as shown in FIG. 3, and a constant current is passed from the constant current circuit a to the wheel speed sensor c. A short-circuit detection circuit b monitors the voltage across the resistance of the wheel speed sensor c, and when the monitoring voltage of the wheel speed sensor c detected by the short-circuit detection circuit b differs from the reference voltage, the output of the wheel speed pulse is stopped, and the wheel speed It is determined that sensor a is malfunctioning. When a wire is disconnected, a sensor abnormality is determined within the waveform shaping circuit. Further, another conventional method for detecting a disconnection failure of a wheel speed sensor is shown in FIG. This detection method adds a comparator d in the electronic control unit (ECU), and resistor R1
The change in the partial pressure value V of the internal resistance R2 of the wheel speed sensor c is monitored by the comparator d, and the wheel speed sensor c
Detects the presence or absence of a disconnection fault. In addition, in the detection method of FIG. 4, the short-circuit failure of the wheel speed sensor c is detected by the CPU calculating each wheel speed based on the signal passed through the waveform shaping circuit.
The calculated wheel speed is compared with other wheel speeds, and when the speed difference exceeds a certain value, the CPU determines that a short-circuit failure has occurred in the wheel speed sensor c.

0003

Problems to be Solved by the Invention The conventional wheel speed sensor failure monitoring technology described above has the following problems.

<A> In the detection technique shown in FIG. 3, the CPU can determine that the sensor is abnormal due to the disappearance of the pulse output from the waveform shaping circuit, but it is difficult to determine whether the abnormality is a short-circuit failure or a disconnection failure. I can't tell which one is.

<B> Furthermore, in the detection technique shown in FIG. 3, the addition of the constant current circuit a and the short circuit detection circuit b complicates the overall circuit, which is one of the causes of rising product costs.

<C> Furthermore, the detection technology shown in FIGS. 3 and 4 responds to changes in resistance value when the resistance value of wheel speed sensor c changes due to new development of wheel speed sensor c or change to a sensor with different specifications. Therefore, it is necessary to replace the components inside the ECU.

<D> With the detection technique shown in FIG. 4, disconnection faults can be constantly monitored. However, short-circuit failures in wheel speed sensors can be detected while driving, but when the wheel speeds drop below a certain value due to low-speed driving or stopping, the speed difference falls within the set value, making it impossible to detect short-circuit failures in the sensors at all. Can not.

[0008]

OBJECTS OF THE INVENTION It is an object of the present invention to provide the following failure monitoring device and failure monitoring method for wheel speed sensors.

<A> A wheel speed sensor failure monitoring device and failure monitoring method that can detect failures at all times, not only while the vehicle is running.

<B> A failure monitoring device and failure monitoring method for a wheel speed sensor that can distinguish between a disconnection and a short circuit.

<C> A failure monitoring device and failure monitoring method for wheel speed sensors, which can reduce product costs.

0012

[Means for Solving the Problems] The present invention provides a wheel speed sensor that provides wheel speed information to an electronic control unit of a vehicle. The present invention is characterized by comprising monitoring means that constantly monitors the partial pressure values of both resistors and detects a failure of the wheel speed sensor when the partial pressure values of both resistors are below a set low voltage value or above a set high voltage value. Furthermore, the present invention provides a failure monitoring method for a wheel speed sensor that provides wheel speed information to an electronic control device of a vehicle, in which a partial pressure value of a resistance provided in the electronic control device and a resistance of the wheel speed sensor is determined by an A/D function of a microprocessor. It is characterized by being monitored by.

[0013]

[Operation of the present invention] The malfunction of the wheel speed sensor is constantly monitored by the analog-to-digital conversion function of the microprocessor (CPU) between the internal resistance provided in the ECU and the partial pressure value of the wheel speed sensor resistance. When the monitored voltage is lower than the set low voltage value, it is determined that there is a short-circuit failure in the wheel speed sensor, and when the monitored voltage is higher than the set high voltage value, it is determined that there is a disconnection failure in the wheel speed sensor cable.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained with reference to the drawings. <A> System configuration FIG. 1 is a block diagram of a wheel speed sensor failure detection circuit according to the present invention. In FIG. 1, 1 is a wheel speed sensor that detects the speed of each wheel, and has an internal resistance R2. A waveform shaping circuit 2 shapes the wheel speed signal from the wheel speed sensor 1 so that it can be processed by the microcomputer (CPU) 4. R1 is an internal resistance built into the ECU 3, and 5 is a filter that smoothes the voltage across the voltage dividing resistors R1 and R2. A monitoring reference voltage, which will be described later, is set in the CPU 4, and the voltage V of the voltage dividing resistor of both resistors R1 and R2 is monitored by the A/D function. Both resistors R1,
Power is continuously supplied to R2 when the ignition switch is turned on, regardless of whether the vehicle is stopped or running.

<B> Voltage dividing resistor value The monitoring voltage V of the voltage dividing resistor is determined by the following equation. Therefore, for example, V0 = 5V, R1 = 1K,
Based on the premise that R2 = 1K, the voltage value V of each voltage dividing resistor when the wheel speed sensor 1 is normal, short-circuited, and disconnected is as follows.

<C> Monitoring voltage The monitoring range of the voltage V of the voltage dividing resistor by the CPU 4 is shown in FIG. The setting values for low voltage value VL and high voltage value VH are as follows:
It is set in consideration of the resistance R1 of the wheel speed sensor 1, the internal resistance R2, etc. In the present invention, when the resistance R2 is changed due to a change in the wheel speed sensor 1, it is only necessary to change the set values of the low voltage value VL and the high voltage value VH of the monitoring voltage V, respectively. Therefore, when the voltage value V of the voltage dividing resistor by the CPU 4 is lower than the low voltage value VL, it is determined to be a short circuit failure, and when it exceeds the high voltage value VH, it is determined to be a disconnection failure. If it is determined that wheel speed sensor 1 is malfunctioning,
Distinguish between short circuits and disconnections and notify the driver with a lamp or alarm sound. Further, when the CPU 4 determines that the wheel speed sensor 1 has a short-circuit failure or a disconnection failure, normal braking is restored. The return to normal braking follows a known control method. Further, when it is determined that the wheel speed sensor 1 has a short-circuit failure or a disconnection failure, the corresponding failure code is stored.

[0017]

[Effects of the Invention] Since the present invention is as explained above, the following effects can be obtained.

<A> A short-circuit failure or disconnection failure of the wheel speed sensor can be detected at all times, not only when the vehicle is running but also when the vehicle is stopped.

<B> Since failure codes can be stored separately according to the details of the failure of the wheel speed sensor (disconnection, short circuit), the location and cause of the failure can be easily identified.

<C> Even if the resistance value of the sensor changes due to a change in the wheel speed sensor, this can be easily handled by simply changing the monitoring voltage range of the software on the CPU side. Therefore, the conventional problem of replacing hardware parts can be solved.

<D> The structure of the monitoring circuit is simpler than that of the conventional one, and the product cost can be reduced and the monitoring circuit can be made smaller.

[Brief explanation of the drawing]

[Fig. 1] Block diagram of a failure detection circuit for a wheel speed sensor according to the present invention

[Figure 2] Model diagram of monitoring voltage range

Claims (2)

[Claims] 1. A wheel speed sensor that provides wheel speed information to an electronic control unit of a vehicle; means for supplying power to the wheel speed sensor via a resistor; and constant monitoring of a partial pressure value of both the resistor and the sensor resistor. and a monitoring means for detecting a failure of the wheel speed sensor when the partial pressure value of both resistors is below a set low voltage value or above a set high voltage value. . 2. A failure monitoring method for a wheel speed sensor that provides wheel speed information to an electronic control device of a vehicle, in which a partial pressure value of a resistance provided in the electronic control device and a resistance of the wheel speed sensor is calculated by an A/V of a microprocessor. A failure monitoring method for a wheel speed sensor, characterized in that monitoring is performed using a D function.