JP2014102205A - Sensor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect abnormality due to the short circuit of mutual sensors even in a sensor device having an I/F circuit with simple configurations.SOLUTION: The sensor device is configured to compare a sensor signal to be output by each of a plurality of wheel speed sensors 10 with a first threshold which is larger than a middle level potential by a first comparator 32, and to compare the sensor signal to be output by each of the plurality of wheel speed sensors 10 with a second threshold which is smaller than the middle level potential by a second comparator 33 which is equivalent to a second signal detection circuit, and to detect the occurrence of abnormality due to short-circuit on the basis of whether or not the output signals of the first and second comparators 32 and 33 are coincident, for example, whether or not timings when the potential levels of the output signals change are coincident. Thus, it is possible to detect abnormality due to the short circuit of the mutual wheel speed sensors 10 even in a sensor device having an I/F circuit 20 with simple configurations without providing any complicate logic circuit.

Description

  The present invention relates to a sensor device having an abnormality detection function for detecting a short circuit between sensors based on sensor signals (detection signals) of a plurality of sensors, and is particularly suitable when applied to a wheel speed sensor mounted on a vehicle.

  The wheel speed sensor detects a change in magnetoresistance according to the unevenness of the teeth of the gear-shaped rotor rotated together with the wheel, and outputs high-level and low-level current pulses. An interface (hereinafter referred to as I / F) circuit provided in the sensor device of the wheel speed sensor detects the rotation of the wheel using a signal obtained by converting the current pulse into a voltage as a sensor signal.

  FIG. 3 is a block diagram of a conventional wheel speed sensor 100 and an I / F circuit 110 provided in the sensor device. The wheel speed sensor 100 includes a hall element and a transistor connected in parallel, and the hall element repeatedly turns the transistor on and off in accordance with the change in magnetoresistance, so that the current path from the power source to the hall element and the transistor is changed to the hall. It is changed between a case where current is passed only through the element and a case where current is passed through the Hall element and the transistor. As a result, the current output from the wheel speed sensor 100 changes in magnitude and becomes a current pulse. This is converted into a voltage by a pull-down resistor built in the signal detection circuit 120 in the I / F circuit 110 to be a sensor signal having a rectangular pulse waveform. Then, a comparator is provided in the signal detection circuit 120 to form a pulse by comparing the sensor signal with a detection threshold value, input the result to the calculation unit 130, and the calculation unit 130 calculates the number of pulses. The wheel rotation is detected, that is, the rotation speed and rotation angle are detected.

  The signal detection circuit 120 provided with such a pull-down resistor and a comparator is provided for each sensor, and detects the rotation of each wheel by comparing the sensor signal of each wheel speed sensor 100 with a threshold voltage.

  However, when a plurality of sensors are provided in this manner, the wheel speed sensors 100 may be short-circuited, such as a short circuit between the wirings of the wheel speed sensors 100. In this case, the sensor signal output from each wheel speed sensor 100 is not a normal pulse signal, and the signal detection circuit 120 cannot output a normal shaping pulse.

  FIG. 4 is a waveform diagram showing the sensor signals 1 and 2 of the two wheel speed sensors 100 before the short circuit, the sensor signal at the time of the short circuit, and the shaping pulse at the time of the short circuit.

  As shown in FIG. 4, when normal, the sensor signals 1 and 2 of each wheel speed sensor 100 have a rectangular pulse waveform corresponding to the rotation of the wheel. For this reason, a normal shaping pulse can be output by comparing the sensor signals 1 and 2 with the detection threshold.

  On the other hand, at the time of a short circuit, the sensor signal output from each wheel speed sensor 100 becomes a stepped signal. That is, since the low-level current output from the two wheel speed sensors 100 flows to the pull-down resistors corresponding to the wheel speed sensors 100 when the transistors of both wheel speed sensors 100 are off, the sensor signals 1, Both are at a low level potential. Further, when the transistors of both wheel speed sensors 100 are on, a high level current output from the two wheel speed sensors 100 flows to pull-down resistors corresponding to the wheel speed sensors 100, so that the sensor signal 1, 2 are both at a high level potential. When the transistor of one wheel speed sensor 100 is turned on and the transistor of the other wheel speed sensor 100 is turned off, a current obtained by adding the high level and low level currents output from each wheel speed sensor 100 is Since the current flows through the pull-down resistor corresponding to the speed sensor 100, the sensor signals 1 and 2 are both at the middle level potential.

  Therefore, even if the middle level potential is compared with the detection threshold, a normal shaping pulse cannot be obtained. For this reason, for example, the calculation unit 130 detects the rotation of the wheel by the rising edge of the shaping pulse. However, there is a problem that even if the shaping pulse is not a normal shaping pulse, it is erroneously recognized as a normal pulse.

  On the other hand, Patent Document 1 proposes a configuration in which a comparison unit including a comparator and an exclusive OR circuit is provided between the signal detection circuit and the calculation unit, and hysteresis is provided in the threshold value of the comparator. ing. In such a configuration, when an abnormal sensor signal at the time of a short circuit is output, the output of the comparator of the signal detection circuit and the output of the comparator of the comparison unit do not match, so the high level is output from the exclusive OR circuit. Is output. Based on this output, it is possible to detect that an abnormality due to a short circuit has occurred in the arithmetic unit.

Japanese Patent Laid-Open No. 9-318641

  However, in the configuration including the comparator and the exclusive OR circuit as in Patent Document 1, the circuit configuration is complicated. In particular, a logic circuit such as an exclusive OR circuit has a complicated circuit configuration. For this reason, there is a problem that the probability of failure is high due to a complicated hardware configuration and reliability is poor.

  In view of the above points, an object of the present invention is to enable detection of an abnormality caused by a short circuit between sensors even as a sensor device including an I / F circuit having a simple configuration.

  In order to achieve the above object, according to the first aspect of the present invention, the sensor signals of the plurality of sensors (10) are divided into a high level potential and a low level output as sensor signals when the plurality of sensors (10) are short-circuited. A first pulse (VrefA) that is larger than the middle level potential between the level potentials and smaller than the high level potential is compared with the first threshold value (VrefA), and an output signal of a shaping pulse whose potential level is changed according to the comparison result is output. One signal detection circuit (32) and a sensor signal are compared with a second threshold value (VrefB) smaller than the middle level potential and larger than the low level potential, and the potential level is changed according to the comparison result. A second signal detection circuit (33) for outputting a pulse output signal, and the abnormality detection means (40) outputs the output signal and the second signal of the first signal detection circuit (32). If the output signal of the circuit (33) out mismatch, detects that an abnormality has occurred due to a short circuit.

  Thus, it can be detected that an abnormality due to a short circuit has occurred based on whether or not the output signals of the first and second signal detection circuits (32, 33) match. Therefore, even if it does not have a complicated logical circuit such as an exclusive OR circuit as in Patent Document 1, even a sensor device having an I / F circuit with a simple configuration can detect an abnormality caused by a short circuit between sensors. It becomes possible to detect.

  For example, as described in claim 2, the abnormality detection means (40) includes the timing of the rising edge at which the output signal of the first signal detection circuit (32) switches from the low level potential to the high level potential, and the second signal detection circuit. When the rising edge timing at which the output signal (33) switches from the low level potential to the high level potential is inconsistent, it is possible to detect that an abnormality due to a short circuit has occurred.

  In addition, the code | symbol in the bracket | parenthesis of each said means shows an example of a corresponding relationship with the specific means as described in embodiment mentioned later.

It is the block diagram which showed the structure of the I / F circuit 20 with which the wheel speed sensor 10 concerning 1st Embodiment of this invention and the sensor apparatus are equipped. It is the wave form diagram which showed the sensor signal and shaping | molding pulse of the wheel speed sensor 10 at the time of a short circuit. It is a block diagram of the sensor apparatus in the conventional wheel speed sensor 100. FIG. It is the wave form diagram which showed the sensor signals 1 and 2 of the two wheel speed sensors before a short circuit, the sensor signal at the time of a short circuit, and the shaping pulse at the time of a short circuit.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following embodiments, parts that are the same or equivalent to each other will be described with the same reference numerals.

(First embodiment)
In the present embodiment, description will be made by taking as an example a wheel speed sensor that is provided on each wheel of the vehicle and outputs a pulse signal corresponding to each wheel speed as the plurality of sensors. FIG. 1 is a block diagram showing a configuration of a wheel speed sensor 10 and an I / F circuit 20 provided in the sensor device according to the present embodiment. FIG. 2 is a waveform diagram showing sensor signals and shaping pulses of the wheel speed sensor 10 at the time of a short circuit.

  As shown in FIG. 1, sensor signals from a plurality of wheel speed sensors 10 are input to an I / F circuit 20 provided in the sensor device, and the rotation of each wheel is detected by the I / F circuit 20, and the sensors are connected to each other. Detects abnormalities due to short circuit at.

  The wheel speed sensor 10 is disposed to face a gear-shaped rotor 11 that is rotated together with the wheels. Although not shown, the wheel speed sensor 10 is configured to include, for example, a Hall element and a transistor whose on / off is controlled by the Hall element and connected in parallel to the Hall element. When the Hall element repeatedly turns on and off the transistor according to the change in magnetoresistance based on the rotation of the gear-shaped rotor that rotates with the wheel, the current flows from the power source through the Hall element and the transistor only through the Hall element. , And when flowing through the Hall element and the transistor. As a result, high and low level current pulses are output from each wheel speed sensor 10. Since this is converted into a voltage by flowing through a pull-down resistor 31 in the I / F circuit 20 described later, a sensor signal represented by a rectangular pulse waveform of a high level potential and a low level potential is output from the wheel speed sensor 10. Will be.

  The I / F circuit 20 includes a signal processing circuit 30 and an arithmetic circuit 40.

  The signal processing circuit 30 includes a pull-down resistor 31 and first and second comparators 32 and 33 corresponding to the first and second signal detection circuits corresponding to the wheel speed sensors 10.

  The pull-down resistor 31 is connected to a wiring connecting the wheel speed sensor 10 and the non-inverting input terminals of the first and second comparators 32 and 33, and converts the current output from the wheel speed sensor 10 into a voltage. Specifically, the current output from the wheel speed sensor 10 flows to the pull-down resistor 31, and the potential of the sensor signal is set by the pull-down resistor 31. In the present embodiment, the potential of the sensor signal becomes the high side potential of the pull-down resistor 31. The high side potential of the pull-down resistor 31 changes according to the magnitude of the current flowing through the pull-down resistor 31. For this reason, when the current output from the wheel speed sensor 10 changes between high level and low level, the high side potential of the pull-down resistor 31 changes, and the sensor signal is a rectangular pulse of high level potential and low level potential as described above. It becomes a waveform.

  The first and second comparators 32 and 33 perform pulse shaping by comparing the potential of the sensor signal input to the inverting input terminal with the reference potentials VrefA and VrefB input to the inverting input terminal. The reference potentials VrefA and VrefB of the first and second comparators 32 and 33 correspond to the first and second threshold values, both of which are higher than when the sensor signal is at the low level potential and at the high level potential. The reference potential VrefA is set lower than the reference potential VrefB.

  As shown in FIG. 2, when a short circuit occurs between the wheel speed sensors 10, the sensor signals output from the wheel speed sensors 10 are stepped signals. Since the low-level current output from the two wheel speed sensors 10 flows to the pull-down resistor 31 corresponding to each wheel speed sensor 10 when the transistors of both of the short-circuited wheel speed sensors 10 are off, the sensor signal is Low level potential. In addition, when the transistors of both the wheel speed sensors 10 are on, the high level current output from the two wheel speed sensors 10 flows to the pull-down resistors 31 corresponding to the wheel speed sensors 10, so the sensor signal is High level potential. When the transistor of one wheel speed sensor 10 is turned on and the transistor of the other wheel speed sensor 10 is turned off, a current obtained by adding the high level current and the low level current output from each wheel speed sensor 10 is Since the current flows through the pull-down resistor 31 corresponding to the speed sensor 10, the sensor signal has a middle level potential. Therefore, the reference voltage VrefA serving as the first threshold is larger and the reference voltage VrefB serving as the second threshold is smaller than the middle level potential.

  When such reference potentials VrefA and VrefB are set, when a normal sensor signal that is not short-circuited is output from the wheel speed sensor 10, the sensor signal has a normal rectangular pulse waveform. For this reason, the timing at which the potential of the sensor signal exceeds the reference voltage VrefA coincides with the timing at which the potential of the sensor signal exceeds the reference voltage VrefB, and the timing at which the outputs of the first and second comparators 32 and 33 become the high level potential. That is, the shaping pulses represented by the output signals of the first and second comparators 32 and 33 match.

  On the other hand, when a short circuit occurs, as shown in FIG. 2, the timing at which the potential of the sensor signal exceeds the reference voltage VrefA does not coincide with the timing at which the potential exceeds the reference voltage VrefB. Timings at which the outputs of 32 and 33 become high level potentials do not coincide. That is, the shaping pulse A represented by the output signal of the first comparator 32 and the shaping pulse B represented by the output signal of the second comparator 33 are inconsistent.

  Therefore, whether or not the output signal of the first comparator 32 matches the output signal of the second comparator 33 is determined depending on whether or not a short circuit has occurred. Indicates whether or not an abnormality has occurred due to a short circuit. Based on this, the calculation unit 40 detects an abnormality due to a short circuit.

  The calculation unit 40 is composed of a microcomputer or the like, and corresponds to the abnormality detection means of the present invention. In the calculation unit 40, the output signals of the first and second comparators 32 and 33 provided in each wheel speed sensor 10 are input, and the rotation speed and rotation speed of each wheel are determined based on the shaping pulse represented by the output signal. Rotation is detected, and abnormality due to short circuit is detected.

  For example, the arithmetic unit 40 detects the rising edge of the shaping pulse represented by the output signals of the first and second comparators 32 and 33, and detects the timing of the edge of each shaping pulse from the built-in operation clock. And if the timing of the edge of each shaping | molding pulse corresponds, since the abnormality by a short circuit has not generate | occur | produced, the calculating part 40 will detect rotation of each wheel based on one of output signals. That is, since the number of teeth of the rotor is determined, the rotation of the rotor, that is, the wheel can be detected from the number of edges.

  The rotation detection result can be used for brake control, for example. For example, the wheel speed is calculated from the rotational speed of each wheel and the estimated vehicle speed is calculated. Based on the slip ratio represented by the deviation between the estimated vehicle speed and the wheel speed, antilock brake (ABS) control and skid prevention control are performed. Etc. can be executed.

  On the other hand, if the timings of the edges of the shaping pulses do not match, the calculation unit 40 detects that an abnormality due to a short circuit has occurred. For example, if the rotation detection result is used for brake control, measures such as prohibiting execution of the brake control are taken. This makes it possible to prevent malfunctions in which brake control is executed based on erroneous wheel speeds.

  As described above, in the present embodiment, the sensor signals output from the plurality of wheel speed sensors 10 are compared in magnitude with the first threshold value larger than the middle level potential by the first comparator 32 corresponding to the first signal detection circuit. ing. The potential level of the output signal of the first comparator 32 is changed depending on whether the sensor signal is larger or smaller than the first threshold value. Similarly, the sensor signals output from the plurality of wheel speed sensors 10 are compared in magnitude with a second threshold value smaller than the middle level potential by a second comparator 33 corresponding to a second signal detection circuit. The potential level of the output signal of the second comparator 33 is changed depending on whether the sensor signal is larger or smaller than the second threshold value.

  With such a configuration, a short circuit is caused based on whether or not the output signals of the first and second comparators 32 and 33 match, for example, whether or not the timings at which the potential levels of the output signals change match. It is possible to detect that an abnormality has occurred. Therefore, even if it does not have a complicated logical circuit such as an exclusive OR circuit as in Patent Document 1, a sensor device having an I / F circuit 20 having a simple configuration can be used between the wheel speed sensors 10. An abnormality due to a short circuit can be detected.

  Furthermore, in order to detect a failure of the four comparators 32 provided corresponding to each wheel speed sensor 10, it is conceivable to include a fifth comparator having the same configuration. Then, the sensor signals are sequentially input to the fifth comparator based on the switch switching, and the output of the fifth comparator is input to the calculation unit 40, and the outputs of the four comparators 32 and 5 Compare the output of the first comparator in order. By this comparison, a failure of the comparator 32 can be detected. However, it is necessary to provide a switch that may cause a failure so that each sensor signal is sequentially input to the fifth comparator. Further, in the case of a short circuit between the wheel speed sensors 10, the comparator 32 does not fail, so the outputs of the four comparators 32 and the fifth comparator match, and an abnormality due to the short circuit cannot be detected. For this reason, it can be said that it is effective to adopt the configuration of the present embodiment.

(Other embodiments)
In the above embodiment, the wheel speed sensor 10 is exemplified as a plurality of sensors. However, the present invention can be applied to a sensor device that performs sensing by processing a sensor signal of a sensor that outputs a sensor signal of a rectangular pulse wave. .

  In the above embodiment, the occurrence of an abnormality due to a short circuit is detected based on whether the timings of the rising edges of the output signals of the first and second comparators 32 and 33 match. However, this is merely an example of a method for confirming the coincidence of the output signals, and is based on whether the timings of the falling edges coincide and whether the times from the rising edge to the falling edge coincide. Thus, it may be detected that an abnormality has occurred due to a short circuit.

  In addition, when detecting the rotation direction, the sensor signal does not have an accurate rectangular pulse waveform, and may have a potential for detecting forward / reverse rotation higher than the high-level potential at the time of rising and falling, for example. . Even in that case, since the outputs of the first and second comparators 32 and 33 are the same as those in the above embodiment, it can be detected that an abnormality due to a short circuit has occurred without any problem.

  In the above embodiment, the reference voltages VrefA and VrefB are input to the inverting input terminals of the comparators 32 and 33 and the sensor signal is input to the non-inverting input terminal. However, this may be reversed. . In that case, the comparators 32 and 33 output the relation between the high level and the low level reversed.

  DESCRIPTION OF SYMBOLS 10 ... Wheel speed sensor, 11 ... Rotor, 20 ... I / F circuit, 31 ... Pull-down resistor, 32 ... 1st comparator (1st signal detection circuit), 33 ... 2nd comparator (2nd signal detection circuit), 40 ... Calculation unit

Claims (2)

The high sensor signal output from a plurality of sensors (10) that output a sensor signal composed of a high level potential and a low level potential at normal time is output as a sensor signal when the plurality of sensors (10) are short-circuited. Compared with a first threshold (VrefA) that is larger than the middle level potential that is between the level potential and the low level potential and smaller than the high level potential, the potential level is changed according to the comparison result. A first signal detection circuit (32) for outputting an output signal of the shaping pulse;
The sensor signal is compared with a second threshold value (VrefB) that is smaller than the middle level potential and larger than the low level potential, and an output signal of a shaping pulse in which the potential level is changed according to the comparison result is output. A second signal detection circuit (33) for
If the output signal of the first signal detection circuit (32) and the output signal of the second signal detection circuit (33) do not match, an abnormality detection means (40) for detecting that an abnormality has occurred due to the short circuit. And a sensor device comprising an interface circuit. The first signal detection circuit (32) outputs a high level potential if the sensor signal is greater than the first threshold (VrefA), and outputs a low level potential if the sensor signal is smaller than the first threshold (VrefA).
The second signal detection circuit (33) outputs a high level potential if the sensor signal is larger than the second threshold (VrefB), and outputs a low level potential if the sensor signal is smaller than the second threshold (VrefB).
The abnormality detection means (40) is configured such that the rising edge timing at which the output signal of the first signal detection circuit (32) switches from a low level potential to a high level potential and the output signal of the second signal detection circuit (33) are low. 2. The sensor device according to claim 1, wherein an abnormality due to the short circuit is detected if timings of rising edges at which the level potential is switched to a high level potential are inconsistent.

Images