JPH01237251A - Trouble detecting device for wheel speed sensor - Google Patents

Abstract

PURPOSE:To correctly detect trouble by detecting the cycle of the output voltage and the amplitude of the voltage value of a wheel speed sensor and judging the trouble of the wheel speed sensor on the basis of the dispersion of the amplitude for the cycle. CONSTITUTION:A wheel speed sensor 5 is equipped with a rotor 2 and a speed sensor 4, and outputs an ac voltage proportional to the wheel speed. A control means 6 is equipped with a cycle detecting means 7, amplitude detecting means 8, calculation means 9, and a judging part 10, and the cycle detecting means 7 detects the cycle of the output voltage of the wheel speed sensor 5, and the amplitude detecting means 8 detects the amplitude of the output voltage. The calculating means 9 calculates the wheel speed on the basis of the detected cycle, and the judging means 10 judges the trouble of the wheel speed sensor 5, i.e., the rotor 2 or the speed sensor 4 on the basis of the cycle and amplitude. Therefore, trouble is judged on the basis of the dispersion of the amplitude for the cycle without installing a trouble judging means separately, and trouble can be correctly detected.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a device for detecting a failure of a wheel speed sensor that detects the rotational speed of a wheel using a rotor and a speed sensor.

[Conventional technology]

Conventionally, there has been a wheel speed sensor 5 that detects the rotational speed (wheel speed) of the wheel hub 1 as a sensor for performing anti-skid Il1wJ, and this wheel speed sensor 5 has a second
As shown in the figure, the vehicle includes a rotor 2 fixed to a wheel hub 1 of a wheel, and a speed sensor 4 fixed to a vehicle body 3 side. As shown in FIG. 3, the rotor 2 has a plurality of teeth 2a carved along its outer circumference, and as shown in FIG. 4, the sensor 4 has a permanent magnet 6 and a coil 7 inside.
and a pole piece 8 for an electromagnetic pickup that projects outside the sensor 4.

Here, the operation of the wheel speed sensor 5 will be explained.

The magnetic flux generated from the permanent magnet 6 changes as the rotor 2 rotates, and this change induces an AC voltage in the coil 7 via the pole piece 8.

That is, as shown in FIG. 3, when one of the teeth 2a approaches the pole piece 8 due to the rotation of the rotor 2, the voltage induced in the coil 7 increases accordingly, and conversely, when it moves away from the pole piece 8, the induced voltage decreases. Become. As a result, 111!
An alternating current voltage is induced in the coil 7, with one cycle being the time from when the previous tooth 2a approaches the pole piece 8 to when the next tooth 2a approaches, and this cycle changes as the rotational speed of the rotor 2 increases. , will be proportionately shorter. That is, as shown in FIG. 5, the period when the rotor 2 rotates at a high speed is shorter as shown by the solid line, compared to the period when the rotor 2 rotates at a low speed as shown by the broken line 1i1B.

In this manner, by detecting the period of the alternating current voltage induced in the coil 7, the rotational speed of the wheel hub 1 can be detected, and the wheel speed sensor 5 is configured to output this alternating voltage.

However, due to deterioration of the rotor 2 or pole piece 8 due to chains, adhesion of dust, rotor 2 or speed sensor 4
The waveform of the AC voltage is disturbed due to insufficient rigidity, gap fluctuations, lack of m2a of the rotor 2, etc., and the normal rotational speed of the wheel hub 1 cannot be detected, resulting in incorrect anti-clockwise detection. Skid control was sometimes used. In other words, the AC voltage of the wheel speed sensor 5 fluctuates extremely from the period during high speed rotation to the period during low speed rotation,
When this fluctuation is detected, it is determined that the wheel hub 1 is on the verge of locking, and anti-skid t, 1ltll is performed to prevent locking and perform stable &lJ movement.

As a countermeasure for this erroneous anti-skid control, some vehicles are equipped with a failure detection device for the wheel speed sensor 5, and others are configured with a failure detection device using a software program to simplify the configuration. That is, when determining the period of the output voltage, if the degree of fluctuation is outside the normal range and occurs repeatedly, the program determines that there is an abnormality. 5 failures were detected.

[Problem to be solved by the invention]

In this type of wheel speed sensor failure detection device, it is determined whether there is an abnormality only based on the cycle of the output voltage of the wheel speed sensor, so whether the output cycle is disturbed due to a failure of the wheel speed sensor or not. Alternatively, there is a problem in that it is difficult to determine whether the wheel speed sensor is normal but the cycle is disturbed due to repeated locking and unlocking of the wheels.

In addition, in order to solve the above problem, if the deceleration of the cycle from high speed rotation to low speed rotation is more than a predetermined value, and the fluctuation of the cycle occurs more than a predetermined number of times within a predetermined time, the wheel speed sensor will malfunction. Even if the setting is made so that the predetermined value, the predetermined time, or the predetermined number of times (hereinafter simply referred to as predetermined values, etc.) are not set properly, an incorrect failure judgment will be made, and further erroneous judgments will occur. If the predetermined value or the like is set excessively (leniently) in order to prevent this, there is a problem that even if the wheel speed sensor is actually malfunctioning, it will be determined that the vehicle is on the verge of locking, and erroneous anti-skid control will be performed.

The present invention detects the cycle of the output voltage of a wheel speed sensor and the amplitude of the voltage value, determines a failure of the wheel speed sensor based on the variation in amplitude with respect to the cycle, and provides a wheel speed sensor that can perform accurate failure detection. The present invention aims to provide a sensor failure detection device.

(Means for Solving the Problems) In order to achieve the above object, the present invention includes a rotor fixed to a wheel, a rotor fixed to a vehicle body side, and generating an alternating current voltage with a frequency proportional to the rotational speed of the rotor. In a wheel speed sensor failure detection device comprising a speed sensor and a control means for calculating a wheel speed based on a periodic change in the alternating current voltage, the υ control means is configured to control the rotation speed of the rotor based on the period and amplitude of the alternating voltage. Alternatively, it is equipped with a determination unit that determines whether the speed sensor is malfunctioning.

[Effect]

According to the failure detection device for a wheel speed sensor having the above configuration, a failure of the wheel speed sensor is detected based on the period and amplitude of the output voltage of the wheel speed sensor, so that variations in the amplitude with respect to the period of the output voltage can be detected. By doing this, it is possible to accurately identify and detect whether the disturbance in the cycle of the output voltage of the wheel speed sensor is due to a state where the wheels are on the verge of locking, or whether it is due to a malfunction of the wheel speed sensor due to a chain, tooth loss in the rotor, etc. can do.

〔Example〕

FIG. 1 shows a block configuration according to an embodiment of the present invention.

In the same figure, the wheel speed sensor +J5 is
It is equipped with a rotor 2 and a speed sensor 4 having the same configuration as shown in FIG. 4, and outputs an alternating current voltage proportional to the wheel speed. The control means 6 includes a period detection means 7, an amplitude detection means 8, a calculation means 9, and a determination section 10. The period detection means 7 detects the period of the output voltage of the wheel speed sensor 5, and the amplitude detection means 8 detects the amplitude of the output voltage. Further, the calculating means 9 calculates the wheel speed based on the above-mentioned cycle, and the determining unit 10 judges whether the wheel speed sensor 5, that is, the rotor 2 or the speed sensor 4 is malfunctioning, based on the above-mentioned cycle and the width. be.

Further, the anti-skid control section 11 performs anti-skid control based on signals from the X-only means 9 and the determining section 10, and the display section 12 indicates that the determining section 10 indicates that the wheel speed sensor 5 is malfunctioning. Once determined, it is displayed.

Next, the operation of detecting the period of the period detecting means 7 will be explained using FIG. 6.

First, when the output voltage of the wheel speed sensor 5 is input to the period detection means 7, the period detection means 7 compares the output voltage with a preset voltage value 0, and the output voltage is determined to be 1.
! If it is larger than the voltage value Vo, it outputs a high voltage (displayed as "H" in Fig. 6), and if it is smaller than the voltage value Vo, it outputs a low voltage (displayed as "°" in Fig. 6).As a result, As shown in FIG. 6, the cycle detection means 7 outputs a pulse train with a cycle T corresponding to the cycle of the output voltage of the wheel speed sensor 5.

Next, the configuration of the amplitude detection means 8 and the operation for detecting the amplitude will be explained using FIGS. 7 and 8.

In addition, in FIG. 7, the amplitude detection means 8 is placed in a central processing unit (CPU
) 16 etc., FIG. 8 shows a sample hold circuit 13 and an A/D conversion circuit 1.
4 indicates an output signal obtained by analog-to-digital conversion of the output voltage of the wheel speed sensor 5.

In FIG. 7, a sample and hold circuit 13 samples the output voltage of the wheel speed sensor 5 (above log voltage signal) at a constant cycle using a sampling pulse from an interface circuit 15, which will be described later, and further converts the output voltage into an A/
The D conversion circuit 14 holds the signal for the time required for analog-to-digital conversion. As shown in FIG. 8, the A/D conversion circuit 14 performs analog-to-digital conversion on the output voltage of the wheel speed sensor 5 sampled at regular intervals, and converts these digital values through the interface circuit 15 as described below. It is output to the CPU 16. The interface circuit 15 is connected to the CPU 16
The digital value is output to the CPU 16 under the control of the CPU 16, and a start pulse for starting sampling and the sampling pulse are output to the sample hold circuit 13.

The CPU 16 controls the interface circuit 15, detects the maximum value within a predetermined period of time from among the digital values, and stores this maximum value in the storage section 17, which will be described later. The storage unit 17 includes a ROM that stores a program for controlling the CPU 16, a RAM that stores the maximum value, and the like.

Further, the CPU 16 does not have the functions of only the amplitude detecting means 8, but can also have the functions of the period detecting means 7, the calculating means 9, and the determining section 10.

In the above explanation, only one wheel speed sensor 5 is used, but in an actual vehicle, a wheel speed sensor 5 is installed for each wheel, and accordingly, a sample hold circuit 13 and an A are installed for each wheel speed sensor 5. By providing an A/D conversion circuit 14 and switching the output signal of this A/D conversion circuit 14 with an interface circuit 15, one CPU 16 can detect the maximum value of the output voltage of the wheel speed sensor 5 for each wheel. can do.

Next, the operation of this apparatus will be explained using the flowchart shown in FIG.

In the same flowchart, first, in step S1, the sample and hold circuit 13, storage unit 17, etc. are initialized, and in step S2, channel switching is performed. In order to detect the wheel speed, the output signal of the A/D conversion circuit 14 corresponding to each wheel is switched by the interface circuit 15. Next, step 33,
34, a sampling pulse and a start pulse for starting sampling are input to the sample hold circuit 13, and in step S5, a value obtained by analog-to-digital conversion of the output voltage of the wheel speed sensor 5 is output to the CPU 16. Then, in step S6, wheel speed calculation llNl0
The maximum value of the output voltage within a cycle (for example, set to 7-81S) is detected.

Next, in step 87, Sg, a value determined based on the period detected by the period detecting means 7 and the maximum value is compared with a preset map value, and the determined value is mapped. If it is outside the range set within the value, failure processing is performed in step S9. That is, if it is outside the range, the wheel speed sensor 5 is determined to be abnormal, the display unit 12 displays a failure, and the anti-skid control unit 11 does not perform anti-skid control.

On the other hand, if it is within the set range, in step Sm, it is determined whether the skid state (the wheels are on the verge of locking),
If it is in a skid state, that is, in a state where the cycle suddenly changes from a short cycle to a long cycle, the anti-skid control unit 11 performs anti-skid control in step S11, and if it is not in a skid state, it does not perform the process in step Sn. To,
Returning to step S2, the process from step 82 onwards is repeated.

Here, regarding the processing of steps S7 and Sa, the first
This will be explained in detail using examples shown in FIGS. 0 and 11.

Note that (A), (B), and (C) in FIG. 10 represent the output voltage of the wheel speed sensor 5, the pulse train output from the period detection means 7, and the analog-digital output voltage of the wheel speed sensor 5, respectively. The converted values are shown, and FIG. 11 shows a map value in which a normal range is set in advance based on the cycle and maximum value of the output voltage of the wheel speed sensor 5, and the shaded area B in the figure shows the normal range. If the period and maximum value of the output voltage are normal, they are all set to fall within the shaded area 8 (\).

In addition, the intervals tO to t1 and yA from t1 to t2 in FIG. 10 respectively indicate the period of the wheel speed control cycle °C, and the wheel speed is constant during the period to-t2, and the period to- The disturbance in the output voltage waveform at t1 is due to the chisel, the tooth loss in rotor 2, etc., and the difference between lff1tt and t2 is
It is assumed that the output voltage waveform of is normal.

That is, as shown in FIG. 11, Iao calculated from the period fmto-tt and the maximum digital value ma is outside the shaded area B, and furthermore, this state is irregularly repeated several times. It is determined that the failure has occurred.

On the other hand, Ibo determined from the period 11 to t20 and the maximum value is within the shaded area B, and in this state, it is always determined to be normal.

In this way, wheel speed meter II 1lill m cycle t
By determining the failure based on the period of the output voltage of the wheel speed sensor 5 and the degree of variation in the maximum value during the period, it is possible to accurately detect the failure of the wheel speed sensor 5.

In the above description, a case has been described in which the device of the present invention is used for anti-skid control, but this device may be used for other than the anti-skid 111111.

That is, for example, the present invention may be used in a vehicle having a four-wheel steering (4WS) function. In other words, the four-wheel steering function determines the steering ratio of the front wheels to the front wheels based on the vehicle speed, etc., and if the vehicle speed is detected based on the wheel speed, incorrect four-wheel steering can be prevented. Accurate wheel speed sensor failure detection is necessary to achieve this goal. Furthermore, even in the case of a four-wheel steering function that changes the setting of steering ratio characteristics depending on the road surface condition, it is necessary to accurately distinguish between a failure of the wheel speed sensor and an output signal of the wheel speed sensor depending on the road surface condition.

Even in these cases, this device can accurately identify the failure of the first speed sensor, allowing accurate four-wheel steering function to be performed.

[Effects of the Invention] Since the present invention determines a failure based on the cycle of the output voltage of the wheel speed sensor and the degree of variation in the maximum value, it is possible to detect dust adhesion, rust, etc. without providing a separate failure determination means. Although it is a low-cost configuration, it is possible to detect failures in the system, and sudden changes in wheel speed due to wheels on the verge of locking can be detected! It is possible to accurately determine whether the change is due to a failure or a sudden change due to a failure, and it is possible to prevent erroneous anti-skid control.

[Brief explanation of the drawing]

FIG. 1 is a block configuration diagram according to an embodiment of the present invention, and FIG.
The figure shows the layout of the wheel speed sensor in a vehicle, Figure 3 shows the layout relationship between the speed sensor and the rotor, Figure 4 shows the internal configuration of the speed sensor υ, and Figure 5 shows the output voltage waveform of the wheel speed sensor. , FIG. 6 is a diagram explaining the operation of the period detection means, FIG. 7 is a configuration diagram of an embodiment using a CPU or the like as the amplitude detection means, and FIG. 8 is a diagram explaining the operation of the period detection means, and FIG. - a diagram showing the signal of the digitally converted output;
Fig. 9 is a flowchart showing the operation of this device, and Fig. 10 explains the relationship between the output voltage of the wheel speed sensor, the pulse train output from the period detection means, and the value obtained by analog-to-digital conversion of the output voltage of the wheel speed sensor. Figure 411 is a diagram showing a map in which a normal range is set in advance based on the period and maximum value of the output voltage of the wheel speed sensor. 1...Wheel hub of the wheel, 2...Rotor, 3...
- Vehicle body, 4... Speed sensor, 5... Wheel speed sensor, 6... Control means, 7... Period detection means, 8...
- Amplitude detection means, 9... Calculation means, 10... Judgment section.

Claims (1)

[Claims] 1. A rotor fixed to a wheel, a speed sensor fixed to a vehicle body side and generating an alternating current voltage with a frequency proportional to the rotational speed of the rotor, and a control means for calculating a wheel speed based on a periodic change in the alternating voltage. A failure detection device for a wheel speed sensor, characterized in that the control means includes a determination unit that determines failure of the rotor or speed sensor based on the cycle and amplitude of the AC voltage. Fault detection device.