JPH06273429A - Fault detection apparatus of rotary sensor and rotary sensor equipped with fault detection function - Google Patents

Abstract

PURPOSE:To surely detect a fault even when a rotor is stopped because a voltage at a terminal in a normal operation is different from that in the fault even when the rotor is stopped. CONSTITUTION:By detecting a change in a magnetic field due to the rotation of a rotor with a Hall IC-type sensor 31, the rotation can be detected. A sensing part 30 which includes the Hall IC-type sensor 31 and a signal processing circuit 40 which includes a microcomputer 41 are connected by a power supply line 51, a signal line 52 and a grounding conductor 53. The Hall IC-type sensor 31 is provided with a power supply terminal 31b which is connected to the power supply line 51, with an output terminal 31b from which an output signal is extracted and with a grounding terminal 31c which is connected to the grounding conductor 53. A resistance R1 is connected in series between the output terminal 1a and the signal line 52. In addition, resistances R2, R3 are connected between the power supply terminal 31b and the output terminal 31a as well as between the output terminal 31a and the grounding terminal 31c, respectively.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotation sensor failure detection device and a rotation sensor with a failure detection function, which are applied to a rotation sensor used for detecting a wheel speed of a vehicle.

[0002]

2. Description of the Related Art Conventionally, a so-called anti-lock braking system has been mounted on a vehicle and used in order to prevent the wheels from being locked during a braking operation. The antilock brake system detects the wheel speed, which is the rotation speed of each wheel. Then, the frictional state between each wheel and the road surface is determined based on the wheel speed of each wheel, and the brake pressure of each wheel is controlled based on the determination result.

To detect the wheel speed, a rotation sensor is used which detects the rotation of the rotor to which the rotation of the axle is transmitted. Conventionally, as a rotation sensor, one having a configuration in which an electromagnetic detector having a permanent magnet and a voltage generating coil is opposed to a gear-shaped rotor having periodic irregularities formed on its peripheral portion is widely used. However, recently, a semiconductor type sensing device such as a Hall IC type sensor has been used. A semiconductor type sensing device has higher sensitivity than an electromagnetic detector and can detect over a wide speed range.

FIG. 6 is a block diagram showing an electrical configuration for detecting a wheel speed using a Hall IC type sensor.
The Hall IC type sensor 10 is arranged in the vicinity of a rotor (not shown) to which the rotation of the axle is transmitted, and detects the fluctuation of the magnetic field caused by the rotation of the rotor. The sensing unit 11 including the Hall IC type sensor 10 and the like is connected to the signal processing circuit 12 that is several meters away by the wire harness 5. In the signal processing circuit 12, there is provided a microcomputer 13 as a control center of the antilock brake system.

In the wire harness 5, a power supply line 1 for supplying a power supply voltage Vcc (for example, 12 V) to the Hall IC type sensor 10 and an output signal of the Hall IC type sensor 10 are transmitted to the signal processing circuit 12. A signal line 2 and a ground line 3 for giving a ground potential are included. Some semiconductor-type sensing devices can connect the sensing section and the signal processing circuit by a two-wire method, but this is disadvantageous from the viewpoint of noise immunity and the degree of freedom of power supply design, For this, connection by a three-wire system as shown in FIG. 6 is recommended.

In the signal processing circuit 12, the power supply line 1 is connected to the terminal t.
1, the signal line 2 is connected to the terminal t2, and the ground line 3 is connected to the terminal t3. The power supply voltage Vcc is supplied to the line 14 connected to the terminal t1, and the resistor R10 is interposed between the line 14 and the line 15 connected to the terminal t2. The signal appearing on the line 15 is input to the input port P11 of the microcomputer 13 via the buffer circuit 16. In FIG. 6, C10 is a capacitor for removing a noise component caused by vibration of the vehicle body.

The Hall IC type sensor 10 changes the magnitude of the current flowing from the signal line 2 to the inside according to the fluctuation of the magnetic field accompanying the rotation of the rotor. This change in current causes the resistance R
It appears as a variation of the voltage drop at 10, and as a result,
The voltage of the signal line 2 changes. Therefore, the cycle of the pulse signal output from the buffer circuit 16 corresponds to the rotation speed of the rotor, that is, the wheel speed. Therefore, the microcomputer 13 counts the number of output pulses of the buffer circuit 16 within a fixed time, and
The wheel speed can be known by detecting the pulse width of the output pulse of.

By the way, since the antilock brake system prevents the wheels from being locked by attenuating the brake pressure, if a signal corresponding to the wheel speed is not input to the microcomputer 13, a failure occurs. If so, the brake pressure will not be properly controlled. For example, if a disconnection occurs in any of the power supply line 1, the signal line 2 and the ground line 3 between the sensing unit 11 and the signal processing circuit 12 or a short circuit occurs between the wirings, the microcomputer 13 is The pulse signal corresponding to the wheel speed will not be input.
In this case, the microcomputer 13 erroneously recognizes that the wheels are locked and attenuates the brake pressure.
Therefore, when the brake pedal is operated, a sufficient brake pressure may not be obtained.

In order to solve this problem, a disconnection failure or a short circuit failure of the wiring between the sensing section 11 and the signal processing circuit 12 is detected, and when these failures are detected, the antilock control by the microcomputer 13 is performed. It is necessary to cancel. FIG. 6 shows one technique for detecting the above disconnection failure and short circuit failure. That is, the signal from the terminal t2 is input to the analog / digital (A / D) converter 18 through the smoothing circuit 17,
The output of the analog / digital converter 18 is input to the input port P12 of the microcomputer 13.

When none of the failures occurs, the power supply voltage Vcc and the ground potential alternately appear at the terminal t2 as the wheels rotate. Therefore, the output voltage of the smoothing circuit 17 becomes approximately Vcc / 2, and the data corresponding to this voltage is input to the microcomputer 13. on the other hand,
When the power supply line 1 breaks, the signal line 2 breaks, the ground line 3 breaks, and a short circuit occurs between the power supply line 1 and the signal line 2, the potential of the terminal t2 is fixed to the power supply voltage Vcc. In addition, when a short circuit occurs between the signal line 2 and the ground line 3 and a short circuit occurs between the power line 1 and the ground line 3, the potential of the terminal t2 is fixed to the ground potential.

As described above, when any failure occurs, the output of the smoothing circuit 17 becomes the power supply voltage Vcc or the ground potential, and has a value different from the voltage Vcc / 2 at the normal time. Therefore, the microcomputer 13 can detect a failure by monitoring the output data of the analog / digital converter 18.

[0012]

However, in the above-mentioned technique, although the failure can be detected when the wheels are rotating, the failure cannot be detected when the wheels are not rotating. There is. This will be described in detail below. The Hall IC sensor 10 is a sensor that detects the intensity of the surrounding magnetic field rather than detecting the fluctuation of the magnetic field. Therefore, for example, when the Hall IC sensor 10 and the teeth of the gear-shaped rotor face each other, the output of the Hall IC sensor 10 becomes high level (for example, Vcc = 12V), and the Hall I
When the C-type sensor 10 faces the groove portion of the rotor, the output of the Hall IC type sensor 10 becomes a low level (for example, 0.1 V).

Therefore, if the Hall IC type sensor 10 faces the teeth or grooves of the rotor when the rotation of the wheels stops and the rotor stops, the Hall IC type sensor 1
The output of 0 is fixed at high level or low level. That is, the voltage of the terminal t2 is fixed to the above-mentioned high level or low level, so that the smoothing circuit 17
Output is 12V or 0.1V. Therefore, the data input from the analog / digital converter 18 to the input port P12 of the microcomputer 13 is almost the same as the data at the time of the above-mentioned failure.

Table 1 below shows that the terminal t
The voltage appearing at 2 is shown for the case of normal operation and the failure occurrence of each mode. In Table 1, "when stopped in a high state" means that the rotor is stopped while the output of the Hall IC sensor 10 is at a high level, and "when stopped in a low state" is an output of the Hall IC sensor 10. Shows the case where the rotor is stopped in the state where is at the low level. The unit of the numerical value is V (volt).

[0015]

[Table 1]

As can be seen from Table 1, even in the normal state, the voltage of the terminal t2 is 12V when the high state is stopped, and the voltage of the terminal t2 is 0.1V which is a value near 0V when the low state is stopped. . Therefore, in the above-described technique of detecting a failure by monitoring whether the output of the smoothing circuit 17 has a value near Vcc / 2, there is a possibility that the failure cannot be detected when the rotor is stopped.

Not only that, as is apparent from Table 1, the voltage at the terminal t2 is the same in "normal state" and "at the time of failure" in "at the time of stopping in the high state". Therefore, it is impossible to detect the failure based on the voltage of the terminal t2. Further, when the “low state is stopped”, and with respect to the failure of and, the voltage appearing at the terminal t2 does not change much between the normal time and the failure time, and thus it is difficult to detect the presence or absence of the failure.

Therefore, an object of the present invention is to solve the above-mentioned technical problems and to provide a failure detecting device for a rotation sensor capable of surely detecting a failure even when the rotation is stopped. Another object of the present invention is to provide a rotation sensor having a failure detection function that enables reliable failure detection even when rotation is stopped.

[0019]

According to another aspect of the present invention, there is provided a failure detecting device for a rotation sensor, which is provided with a rotating body capable of varying a magnetic field in the vicinity by rotation and a power supply voltage. A power supply terminal, an output terminal for outputting an output signal and a ground terminal to which a ground potential should be given, and a sensing unit including a sensor for outputting a signal corresponding to a magnetic field in the vicinity of the rotating body to the output terminal, A signal processing unit for processing the output signal of the sensor to obtain rotation information, a power supply line for supplying a power supply voltage from the signal processing unit to the power supply terminal of the sensor, and an output terminal of the sensor. A signal line for transmitting the signal to the signal processing unit, a ground line for supplying a ground potential from the signal processing unit to the ground terminal of the sensor, and a ground line in or above the sensing unit. In the vicinity of the sensing unit, in the middle of the signal line or in the first resistor interposed in series between the signal line and the output terminal of the sensor, and in the sensing unit or in the vicinity of the sensing unit, A second resistor connected between any position on the signal path from the sensor to the first resistor and the middle portion of the power supply line or the power supply terminal of the sensor, and in the sensing unit or the sensing unit. A third resistor connected between any position on the signal path from the sensor to the first resistor in the vicinity of the sensor and the middle portion of the ground line or the ground terminal of the sensor, and the signal. It is characterized by including a determination means for monitoring the voltage of the signal line in the vicinity of the processing unit and determining the presence or absence of a failure based on the voltage.

According to another aspect of the rotation sensor failure detecting device of the present invention, the determining means detects the average voltage of the signal line in the vicinity of the signal processing part, and the detected average voltage deviates from a predetermined range. And a means for determining that a failure has occurred when the value is According to another aspect of the present invention, there is provided a rotation sensor with a failure detection function, which includes a rotating body capable of varying a magnetic field in the vicinity by rotation, a power supply terminal to which a power supply voltage is applied, an output terminal to which an output signal is output, and a ground potential. Having a ground terminal to which a signal corresponding to the magnetic field in the vicinity of the rotating body is output, a first resistor connected in series to the output terminal of the sensor, and the power supply terminal And a second resistor connected between the output terminal and the output terminal, and a third resistor connected between the output terminal and the ground terminal.

[0021]

[Function] Between the sensing unit and the signal processing unit, a power line,
In the configuration connected by the signal line and the ground line,
There is a possibility that a disconnection failure of each of these wirings or a short circuit failure between the wirings may occur. According to the present invention, the first resistance, the second resistance, and the third resistance work to transmit the signal to the signal processing unit via the signal line in the normal state even when the rotating body is stopped. The voltage and the voltage appearing on the signal line near the signal processing unit when a failure occurs can be made different. Therefore, the determination unit monitors the voltage of the signal line near the signal processing unit and determines the presence or absence of a failure based on the voltage.

With this configuration, the voltage of the signal line in the vicinity of the signal processing unit can be made different between the normal time and the failure time, regardless of whether the rotating body is rotating or stopped. Therefore, the determination unit can reliably detect the presence or absence of a failure even when the rotating body is stopped. It should be noted that, in the determination means, if the average voltage of the signal line is detected and whether the detected average voltage is a value deviating from a predetermined range is monitored, a signal is output when the rotating body rotates. Even if the voltage of the line fluctuates, it is possible to determine the presence or absence of a failure by eliminating the influence of this voltage fluctuation.

Further, the first resistor, the second resistor and the third resistor
If the resistance of is connected to each terminal of the sensor that detects the magnetic field in the vicinity of the rotating body, the failure detecting function can be added to the rotation sensor.

[0024]

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 is a block diagram showing the configuration of a failure detection device for a rotation sensor according to an embodiment of the present invention.
This device has a sensing unit 30 including a Hall IC type sensor 31 that detects the rotation of each wheel of the vehicle, and a signal processing circuit 40 including a microcomputer 41 that serves as a control center of the antilock brake system. ing. The sensing unit 30 and the signal processing circuit 40 are connected by a wire harness 50. The wiring length from the sensing unit 30 to the signal processing circuit 40 is about several meters.

The sensing section 30 has a Hall IC type sensor 31 for detecting the strength of the surrounding magnetic field, a first resistor R1 connected in series to an output terminal 31a from which the output signal of the sensor 31 is output, A second resistor R2 connected between the output terminal 31a and the power supply terminal 31b to which the power supply voltage should be applied, and a third resistor R2 connected between the output terminal 31a and the ground terminal 31c to which the ground potential is applied. Resistor R3,
It has a capacitor C1 for removing a noise component caused by vehicle vibration and the like.

In the wire harness 50, the power supply line 51 for supplying the power supply voltage Vcc (for example, 12 V) from the signal processing circuit 40 to the sensing section 30 and the output signal of the Hall IC type sensor 31 are sent to the signal processing circuit 40. A signal line 52 for transmitting and a ground line 53 for giving a ground potential from the signal processing circuit 40 are included. Power line 5
1 is connected to the power supply terminal 31b of the Hall IC type sensor 31, the signal line 32 is connected to the output terminal 31a of the Hall IC type sensor 31 with the resistor R1 interposed in series, and the ground line 53. Is connected to the ground terminal 31c of the Hall IC sensor 31. In addition, the power supply line 51,
The signal line 52 and the ground line 53 are connected to the terminals T1, T2, T3 of the signal processing circuit 40, respectively.
The power supply voltage Vcc is applied to the terminal T1, and the terminal T3
A ground potential is applied to.

The signal processing circuit 40 includes a microcomputer 41 and a resistor R connected between terminals T1 and T2.
11, a buffer circuit 42 that adjusts the level of the signal applied to the terminal T2 from the signal line 52, a smoothing circuit 43 that smoothes the signal applied to the terminal T2, and a smoothing circuit 43.
And an analog / digital (A / D) converter 44 for converting the output voltage V _{M of the above} into digital data. The output signal of the buffer circuit 42 is the microcomputer 4
1 and the output signal of the analog / digital converter 44 is applied to the input port P2 of the microcomputer 41.

In the smoothing circuit 43, a series circuit of a resistor R12 and a capacitor C12 is provided between the terminal T2 and a terminal T3 to which a ground potential is applied, and a connection point 45 between the resistor R12 and the capacitor C12 is provided. It is composed of an integrating circuit adapted to apply the voltage V _M to the analog / digital converter 44. FIG. 2 is an illustrative view for explaining the principle of rotation detection by the Hall IC type sensor 31. The Hall IC type sensor 31 is arranged near the rotor 35 to which the rotation of the axle is transmitted. More specifically, the rotor 35 has teeth 35a periodically formed on the peripheral edge thereof, and rotates around the axis 36 as the axle rotates. The Hall IC type sensor 31 is arranged so as to face the peripheral portion of the rotor 35.
Is arranged, and a permanent magnet 37 is arranged behind the Hall IC type sensor 31.

The gap g between the permanent magnet 37 and the rotor 35 is small when the tooth portion 35a faces the Hall IC type sensor 31 as shown in FIG. 2 (a), but as shown in FIG. 2 (b). It is large when the groove portion 35b between the tooth portions 35a faces the Hall IC type sensor 31. This gap g
The density of the magnetic flux penetrating the Hall IC type sensor 31 changes depending on the magnitude of.

The Hall IC type sensor 31 outputs a voltage according to the surrounding magnetic flux density to the output terminal 31a. Therefore, if the positional relationship between the rotor 35 and the Hall IC type sensor 31 is in the state shown in FIG. 2 (a), the potential of the output terminal 31a, for example, becomes high level (= Vcc), and these positional relationships are shown in FIG. 2 (b). In this state, the potential of the output terminal 31a becomes low level (a value close to the ground potential, for example, 0.1 V). Therefore, when the rotor 35 rotates, a signal which changes its height between high and low appears at the output terminal 31a in a cycle corresponding to the rotation speed.

The change in the potential at the output terminal 31a appears at the terminal T2 as a change in the voltage drop across the resistor R11. Therefore, the output signal of the buffer circuit 42 becomes a pulse signal having a cycle corresponding to the rotation speed of the rotor 35.
The microcomputer 41 obtains the rotation speed of the rotor 35, for example, by counting the number of output pulses of the buffer circuit 42 within a certain time or measuring the pulse width of the output pulse.

The rotor 35 is made of a magnetic material such as iron or a material having a high magnetic permeability such as ferrite. Also,
Even if the material is normal copper or sintered alloy, the gap g
Any material having a magnetic permeability that allows the magnetic flux density in the vicinity of the Hall IC type sensor 31 to be changed in accordance with the change can be applied as the constituent material of the rotor 35.

Next, the sensing section 30 and the signal processing circuit 4
A process for detecting a failure related to the wiring between 0 and 0 will be described. The type of failure is practically sufficient considering the case of one wire disconnection or two wire short circuit. These faults cover all cases in six ways, which are shown in simplified form in FIGS. 3 and 4. Specifically, Fig. 3 (a), (b)
, (C) show the case where a disconnection failure occurs in the power supply line 51, the signal line 52, and the ground line 53, respectively. Further, FIG. 4 (d) shows a case where a short-circuit failure occurs between the power supply line 51 and the signal line 52, and FIG. 4 (e) shows a case where a short-circuit failure occurs between the signal line 52 and the ground line 53. Figure 4 (g) shows the power line 51
Shows a case where a short-circuit failure occurs between the ground line 53 and the ground line 53.

For example, the power supply voltage Vcc is 12V,
It is assumed that the resistance values of the resistors R11, R1, R2, R3 are as follows. R11 ・ ・ ・ ・ ・ ・ 1.1 kΩ R1 ・ ・ ・ ・ ・ ・ 0.2 kΩ R2 ・ ・ ・ ・ ・ ・ 10 kΩ R3 ・ ・ ・ ・ ・ ・ 10 kΩ In this case, either In a normal state where no failure occurs, when the output of the Hall IC type sensor 31 is at a high level, the voltage of the terminal T2 (that is, the voltage of the signal line 52 near the signal processing circuit 40) V _B is 11.0V. Becomes That is, the current does not flow into the Hall IC sensor 31, but the current from the power supply is divided into the series circuit of the resistors R11 and R1 and the resistor R2, and further flows into the ground line 53 through the resistor R3. Therefore, the potential of the output terminal 31a of the Hall IC sensor 31 is approximately equal to the following
It is given by equation (1). Strictly speaking, since a minute current is flowing in order to make the discrimination circuit and the amplification circuit of the Hall IC function, a strict value cannot be obtained by the following formula (1). It should be noted that each of the mathematical expressions shown below does not consider the minute current described above, and is therefore an approximate expression.

[0035]

[Equation 1]

Therefore, the voltage V _B applied to the output terminal T2 becomes 11.0 V as shown in the following expression (2).

[0037]

[Equation 2]

On the other hand, when the output of the Hall IC type sensor 31 is at a low level (for example, 0.1 V) in a normal state where no failure occurs, as shown in the following expression (3), the terminal T2 is The voltage V _B becomes 1.93V.

[0039]

[Equation 3]

During the period when the vehicle is traveling and the rotor 35 is rotating, the voltage V _B takes the above-mentioned two values alternately, so the smoothing circuit 43 for smoothing the voltage V _B.
Output voltage V _M is expressed by the following equation (4).

[0041]

[Equation 4]

Table 2 below shows the voltage V _B appearing at the terminal T2 when the vehicle stops and the rotor 35 stops rotating.
In the normal state and in FIGS. 3 (a) to (c) and FIGS. 4 (d) to (f)
In the case of failure occurrence of each aspect shown in FIG. In Table 2, "when stopped in a high state" means that the rotor 35 is stopped while the output of the Hall IC sensor 31 is at a high level, and "when stopped in a low state".
Indicates that the rotor 35 is stopped while the output of the Hall IC sensor 10 is at a low level. The unit of the numerical value is V (volt).

[0043]

[Table 2]

When the rotor 35 is stopped, the ho
Do not change the potential of the output terminal 31a of the IC sensor 31.
Yes. Therefore, if neither failure has occurred,
Pressure V _BIs obtained by the equation (2) above when the high state is stopped.
It becomes 11.0V, which is high when the low level is stopped.
It becomes 1.93V obtained by the equation (3). That
Voltage V_BDoes not change, so V_B= V_MBecomes

First, a disconnection failure of the power supply line 51 (see FIG. 3).
Corresponds to (a). ) Will be described. When the power supply line 51 is broken, the Hall IC sensor 30 does not operate, so that no current flows into the output terminal 31a. for that reason,
The voltage V _B has the same value when the high state is stopped and when the low state is stopped, and the value is given by the following equation (5).

[0046]

[Equation 5]

That is, both the normal value of 11.0 V when the high state is stopped and the normal value of 1.9 when the low state is stopped.
The value is different from 3V. It is also different from the normal value of 6.47 (V) in the rotating state. The difference in the voltage when the high state is stopped is that the current from the power supply is mainly due to the resistance R2.
It is due to the fact that it is no longer shunted. Next, the disconnection failure of the signal line 52 (corresponding to FIG. 3B) will be described. At this time, since no current flows into the resistor R11, no voltage drop occurs in the resistor R11, and the voltage V _B is equal to the power supply voltage Vcc 12.0.
It is fixed at V. Therefore, the voltage V _M is the normal value 1
The value is 12.0V, which is a value different from any of 1.0V, 1.93V, and 6.47V.

In the case of the disconnection failure of the ground line 53 (corresponding to FIG. 3 (c)), the Hall IC type sensor 31 cannot operate and its output terminal 31
No current flows into a. Further, since the terminal of the resistor R3 on the side of the ground line 53 is opened, the current does not flow into the resistor R3 either, and eventually the resistors R11 and R3.
No current flows through 1. Therefore, the voltage V _B becomes 12.0V equal to the supply voltage Vcc. Therefore, the output voltage V _M of the smoothing circuit 43 has normal values of 11.0 V and 1.93.
12.0V which is a value different from both V and 6.47V
Becomes

When a short circuit failure (corresponding to FIG. 4D) between the power supply line 51 and the signal line 52 occurs, the voltage V _B naturally becomes equal to the voltage Vcc, and the voltage V _M is
It takes a value (12.0 V) different from any normal value. On the other hand, in the case of, that is, the signal line 52 and the ground line 53.
When a short-circuit failure (corresponding to FIG. 4 (e)) occurs with, the voltage V _B naturally becomes 0V. Therefore, the output voltage V _M of the smoothing circuit 43 is 0 V, but this value is different from any of the normal values 11.0 V, 1.93 V, and 6.47 V.

In the case of, that is, when a short-circuit failure between the power supply line 51 and the ground line 53 (corresponding to FIG. 4 (f)) occurs, the voltage V _B becomes 0 V and the voltage V _M becomes any. It becomes 0V which is a value different from the normal value. in this way,
In the event of any of the above failures, the output voltage V _M of the smoothing circuit 43 takes a value different from the normal value. Therefore, in the microcomputer 31, is the voltage V _M within the predetermined range set near the normal values 11.0V, 1.93V and 6.47V based on the value given to the input port P2? It may be determined whether or not any failure has occurred when it is detected that the voltage V _M has a value outside the predetermined range.
After it is determined that a failure has occurred, the microcomputer 31 stops the antilock control.
However, with respect to the above-mentioned failure, an excessive current will flow into the power supply line 51, so the failure can be detected by detecting this overcurrent.

In this way, the microcomputer 3
In No. 1, not only when the vehicle is traveling, based on the voltage obtained by averaging the voltage of the terminal T2 by the smoothing circuit 43,
The failure can be reliably detected even when the vehicle is stopped. As a result, the safety of the anti-lock braking system can be significantly improved. In addition, the voltage V _M when the disconnection failure of the power supply line 51 occurs
Value of 10.8V and normal value when stopped in high state 11.
The voltage difference from 0V is 0.2V, which is relatively small,
This failure is considered to be the most difficult to detect. However, if there is a voltage difference of about 0.2 V between the normal state and the fault state, the microcomputer 31 can perform the fault determination with sufficiently high accuracy. Further, this voltage difference can be increased by reducing the resistance value of the resistor R2 connected between the output terminal 31a and the power supply terminal 31b. Therefore, for example, when the resolution of the analog / digital converter 44 is low, a resistor having a low resistance value may be applied as the resistor R2.

In the cases of and, the difference between the value 11.0V of the voltage V _M in the normal state when stopped in the high state and the value 12.0V in the case of failure is 1.0V. As can be seen from Table 1 above, the corresponding voltage difference in the conventional configuration is 0V. Therefore, in the present embodiment, it is possible to have a failure that could not be done by the conventional technique. Such a voltage difference of 1.0 V can be generated because the signal line 52 is connected to the ground line 53 via the resistor R3.
Because it is connected to. That is, even when the output of the Hall IC sensor 31 is at a high level, the resistance R1
Since a current can be passed to the terminal 1, the voltage V of the terminal T2 when the output of the Hall IC sensor 31 is at a high level
_B can be made lower than the power supply voltage Vcc.

Further, in the cases (1) and (2), the difference between the normal voltage V _M of 1.93 V when the low state is stopped and the fault value 0 V is 1.93 V. As can be seen from Table 1 above, the corresponding voltage difference in the conventional configuration is 0.1V. Therefore, it is understood that the detection of each of the short-circuit faults of and can be performed significantly better in this embodiment as compared with the conventional technique. It is Hall I that can generate such a large voltage difference of 1.93V.
Terminal T when the output of the C-type sensor 31 is at low level
This is because the voltage V _B of 2 is raised by the resistor R1.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments. For example, as shown in FIG. 5, a disc-shaped rotor 60 whose peripheral portion is alternately magnetized into N poles and S poles can be applied to the rotor to which the rotation of the axle is transmitted. In this case, it is not necessary to dispose a permanent magnet behind the Hall IC sensor 31.

In the above embodiment, the sensing unit 3
Although the resistors R1, R2, and R3 are provided inside 0, these resistors R1, R2, and R3 may be connected to the outside of the sensing unit 30 in the vicinity of the sensing unit 30. That is, the resistor R1 may be provided in the middle of the signal line 52. The resistor R2 is connected to any position on the signal path from the Hall IC sensor 31 to the resistor R1 and the power supply line 51.
Power supply terminal 31 of Hall IC type sensor 31 in the middle of
It suffices if it is connected to b. Furthermore, the resistor R3
Need only be connected between any position on the signal path from the Hall IC type sensor 31 to the resistor R1 and the middle portion of the ground line 53 or the ground terminal 31c of the Hall IC type sensor 31.

Furthermore, in the above embodiment, the case of detecting the wheel speed has been described as an example, but the present invention can be widely applied to a rotation sensor for detecting rotation information such as a rotation speed and a rotation angle. Is something that can be done. In addition, various design changes can be made without changing the gist of the present invention.

[0057]

As described above, according to the present invention, even when the rotating body is stopped, the voltage transmitted to the signal processing unit via the signal line in the normal state and the occurrence of the failure The voltage appearing on the signal line near the signal processing unit can be made different. Therefore, it is possible to reliably detect the failure by monitoring the voltage of the signal line regardless of whether the rotating body is rotating or stopped.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a failure detection device for a rotation sensor according to an embodiment of the present invention.

FIG. 2 is an illustrative view for explaining a principle of rotation detection by a Hall IC type sensor.

FIG. 3 is an electric circuit diagram for explaining a failure mode, where (a) shows a disconnection failure of a power supply line, (b) shows a disconnection failure of a signal line, and (c) shows a disconnection of a ground line. Indicates a failure.

FIG. 4 is an electric circuit diagram for explaining a mode of failure, where (d) shows a short circuit failure between a power supply line and a signal line, (e) shows a short circuit failure between a signal line and a ground line, (f) shows a short-circuit fault between the power line and the ground line.

FIG. 5 is a simplified perspective view showing another configuration example of the rotation sensor.

FIG. 6 is a block diagram showing a configuration for obtaining rotation information using a Hall IC type sensor.

[Explanation of symbols]

 30 sensing unit 31 Hall IC type sensor 31a output terminal 31b power supply terminal 31c ground terminal 35 rotor R1 first resistance R2 second resistance R3 third resistance 40 signal processing circuit 41 microcomputer 42 buffer circuit 43 smoothing circuit 44 analog / Digital converter 50 Wire harness 51 Power line 52 Signal line 53 Ground line 60 Rotor

Claims (3)

[Claims] 1. A rotating body capable of varying a magnetic field in the vicinity by rotation, a power supply terminal to which a power supply voltage is applied, an output terminal to which an output signal is output, and a ground terminal to which a ground potential is applied. A sensing unit including a sensor that outputs a signal corresponding to a magnetic field near the rotating body to an output terminal, a signal processing unit that processes the output signal of the sensor to obtain rotation information, and from this signal processing unit A power supply line for supplying a power supply voltage to the power supply terminal of the sensor, a signal line for transmitting the signal output to the output terminal of the sensor to the signal processing unit, and a grounding of the sensor from the signal processing unit. A ground line for supplying a ground potential to the terminal, and a part of the signal line or the output of the sensor in the middle of the sensing part or near the sensing part. A first resistor interposed in series between the terminal and a terminal, and in the sensing unit or in the vicinity of the sensing unit, any position on a signal path from the sensor to the first resistor and the power supply line A second resistor connected between the sensor and the power supply terminal of the sensor, and either on the signal path from the sensor to the first resistor in the sensing unit or in the vicinity of the sensing unit. A third resistor connected between the position and the middle portion of the ground line or the ground terminal of the sensor, and the voltage of the signal line near the signal processing unit are monitored, and a failure is detected based on the voltage. A failure detection device for a rotation sensor, comprising: 2. The determining means is means for detecting an average voltage of the signal line in the vicinity of the signal processing part, and a failure has occurred when the detected average voltage has a value deviating from a predetermined range. The failure detection device for a rotation sensor according to claim 1, further comprising: 3. A rotating body capable of varying a magnetic field in the vicinity by rotation, a power supply terminal to which a power supply voltage should be applied, an output terminal to output an output signal, and a ground terminal to which a ground potential should be applied. A sensor that outputs a signal corresponding to a magnetic field near the rotating body to an output terminal, a first resistor connected in series to the output terminal of the sensor, and a power source terminal and an output terminal A rotation sensor with a failure detecting function, comprising a second resistor and a third resistor connected between the output terminal and the ground terminal.