JPH06160428A - Revolution sensor and method for detecting its fault - Google Patents

Abstract

PURPOSE:To surely detect the fault of a revolution sensor even during the stopping time of an automobile so as to improve the reliability of the sensor by providing magnetism sensitive elements in the main bodies of the sensor counterposed on both side of a center rotor and coils for generating magnetic fields around the elements for detecting faults. CONSTITUTION:In order to transmit magnetic fluxes to magnetic reluctance elements 1a and 1b, a magnetic pole 3 is formed in a U-shape and a coil 4 for generating magnetic fields is wound around one leg section of the pole 3. Power supply to the elements 1a and 1b is made through a cable 5 and the outputs of the elements 1a and 1b are lead to the outside through the cable 5. When a rotor 8 rotates, a differential output voltage is generated across the elements 1a and 1b and a voltage signal having the frequency corresponding to the rotating speed of the rotor 8 is outputted. During the stopping time of the rotor 8, no signal is generated, but, when an AC current having a sine waveform is applied to the coil 4, a differential output is generated across the elements 1 similarly to the case where the rotor 8 is rotated. The waveform of the differential output becomes the same as that of the applied voltage when the elements 1 are normal and different when the elements 1 are faulty. Therefore, the fault of this sensor can be detected even during the stopping time of an automobile.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotation sensor for detecting the rotation speed of an automobile wheel or the like and a method for detecting the rotation sensor.

[0002]

2. Description of the Related Art A rotation sensor used in an anti-lock system for braking the rotation of the wheels of an automobile is required to have extremely high reliability due to its nature. As such a rotation sensor for automobiles, there are an electromagnetic induction type rotation sensor having a coil for generating an electromagnetic power generation signal in a sensor detection unit, and a magnetic sensitive element type rotary sensor to which a magnetic sensitive element of a semiconductor or a metal thin film is applied. Examples of the latter include those disclosed in Japanese Utility Model Laid-Open No. 3-46820 or Japanese Utility Model Laid-Open No. 3-46821.

When any one of the above rotation sensors is used as a part of the configuration of an electronic control circuit such as an antilock system, extremely high reliability is required, and therefore, is the rotation sensor generally broken? A function is provided for self-diagnosis by an electronic control circuit before traveling. An example having such a self-diagnosis function is disclosed in, for example, Japanese Patent Laid-Open No. 3-25.
It is disclosed in Japanese Patent No. 8645.

[0004]

By the way, when an electromagnetic induction type rotation sensor is used in the electronic control circuit of the above publication, since the failure mode of this type of rotation sensor is concentrated in the disconnection of the coil, the electromagnetic power generation is performed. If the power supply coil is always energized, disconnection, that is, failure can be detected. However, in the magnetic sensitive element type rotation sensor, the failure mode is complicated not only with disconnection but also with various failure modes. Therefore, it is not sufficient to detect the failure by energizing the detection element section and checking the state thereof. As such, it is not commonly used in systems that require high reliability, such as antilock systems, because it is difficult to perform self-diagnosis of failures and its reliability is lower than that of electromagnetic induction type. It was.

The present invention has been made in consideration of the current state of the conventional rotation sensor and its failure detection method described above, and a rotation sensor having a structure in which it is easy to detect a failure by using a magnetic sensitive element, and an automobile using the rotation sensor. An object of the present invention is to provide a failure detection method capable of reliably and easily detecting a failure even when stopped.

[0006]

As a means for solving the above problems, the present invention provides a magnetic sensitive element for detecting a change in a magnetic field as a change in an electric signal in a case body of a rotation sensor which is arranged to face a sensor rotor. The rotation sensor is provided with a magnetic field generating coil for detecting a failure provided around the magnetic sensing element.

In this case, two magnetic sensing elements are provided, and the magnetic field generating coil is incorporated in the periphery of one of the two element groups in an offset state so as to obtain a rotation signal by the differential output of the two element groups. It is preferable to configure. Alternatively, two magnetic sensitive elements may be provided, and the magnetic field generating coils may be installed around the two element groups to obtain a rotation signal by the differential output of the two element groups.

In any case, it is preferable that a magnetic pole piece is arranged on the rear end face side of the magnetic sensing element, and the magnetic field generating coil is wound around the magnetic pole piece. Further, it is preferable that a waveform forming means for generating a voltage waveform applied to the coil is incorporated in the sensor.

Further, as another means for solving the above-mentioned problems, in a rotation sensor in which a magnet is bonded to a magnetic sensitive element in the case body of the rotational sensor and a magnetic field generating coil is provided around the magnetic sensitive element. On the other hand, a rotation sensor that is provided so as to face this and energizes the coil in a stationary state and detects a signal generated from the magnetic sensitive element to detect normality or abnormality of the magnetic sensitive element and its associated electric circuit. It is also possible to adopt the failure detection method of.

In this case, an alternating current or a rectangular wave current is applied to the magnetic field generating coil, a signal corresponding to rotation is generated by a change in the generated magnetic field, and the magnetic sensitive element and its associated electric circuit are normally or normally operated. It is better to detect an abnormality.

Alternatively, two magnetic field generating coils are provided, an alternating current or a rectangular wave current is applied to one of the coils, and an alternating current or a rectangular wave current having a 180 ° phase shift is applied to the other coil to generate the magnetic field. A signal corresponding to rotation may be generated by a change in magnetic field to detect normality or abnormality of the magnetic sensing element and its associated electric circuit.

Further, two magnetic field generating coils are provided, and each of them is energized once for a fixed time.
It is also possible to detect the normality or abnormality of the magnetic sensing element and its associated electric circuit by using the sensor signal that changes according to the change of the generated magnetic field.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view of the rotation sensor of the first embodiment. The magnetoresistive element 1 is composed of two elements 1a and 1b, and is provided by being joined to a magnetic pole piece 3 that transmits the magnetic flux generated from a magnet 2 provided behind the magnetoresistive element 1 to the magnetoresistive element 1.

The pole piece 3 includes two magnetoresistive elements 1a and 1a.
In order to transmit a magnetic flux to each of b, it is formed in a two-forked U shape, and one of the legs (left side in the drawing) is wound with a field generating coil 4. The magnetoresistive elements 1a and 1b include
The power supply Vcc is supplied through the cable 5, and its output signal is also led out through the cable 5. or,
As shown in FIG. 2, fixed resistors 1c and 1d are provided to form a bridge circuit in combination with the magnetoresistive elements 1a and 1b (not shown in FIG. 1). A current for failure detection is also applied to the coil 4 through the cable 5.

The sensor components 1 to 4 are molded and fixed in the case body 6 by the potting material 7. 8 is a gear-shaped rotating rotor made of a magnetic material,
The rotation sensor is arranged to face the rotation rotor 8.

In the rotation sensor of this embodiment constructed as described above, when the rotary rotor 8 rotates in a normal state where no failure occurs, a differential output voltage is generated from the magnetoresistive elements 1a and 1b, and the speed of the rotating body changes. A voltage signal having a corresponding frequency is generated. The detection signal is obtained as follows. When the rotating rotor 8 is rotating, the magnetoresistive element 1a
If the crests of the rotary rotor 8 face each other and the valleys face the 1b side, a large magnetic flux density is generated on the 1a side and the resistance is large. At this time, the magnetic flux density is small and the resistance is small on the 1b side.

The rotation of the rotary rotor 8 progresses, and a valley is formed on the 1a side.
When the peaks are in the opposite phase to the 1b side, the state opposite to that described above occurs, and an AC voltage is generated at the output terminals 5a and 5b as the rotary rotor 8 rotates.

As described above, the rotation sensor can obtain information on the rotation speed, and the failure detection is performed as follows. Although no signal is generated when the rotation is stopped, when an alternating current having a voltage waveform as shown in FIG. 3A is applied to the coil 4 when the rotation is stopped, the magnetic pole is generated by the alternating current as in the case where the rotating rotor 8 rotates. A differential output is generated in the magnetoresistive element 1 by the action of the change in the magnetic flux generated in the child 3.

If the magnetoresistive element 1 is normal, the waveform of this differential output is the same as the waveform of the voltage applied to the coil 4, as shown in FIG. 3 (b). However, if the magnetoresistive element 1 has a failure such as a wire break or a defect of sensitivity abnormality, the above voltage waveform is not the same as the applied voltage waveform, so that the failure of the magnetoresistive element 1 is detected. can do.

FIG. 4 shows a cross section of the rotation sensor of the second embodiment. The rotation sensor of this embodiment has the same basic configuration as that of the first embodiment, but an electric circuit for processing the output signal of the magnetoresistive element 1 is provided by providing two coils 4a and 4b as magnetic field generating coils. The difference is that 9 is provided. The other same functional members are designated by the same reference numerals, and the description thereof will be omitted.

Although not shown in the figure, the electric circuit 9 includes, for example, a rectangular wave forming means for forming a predetermined rectangular wave from the current sent from the cable 5 by using a multivibrator or the like, and the magnetoresistive element 1. Another rectangular wave forming means for forming the output waveform of the rectangular wave by shaping the waveform of the detection signal detected by the sensor, for example, by a Schmitt circuit or the like.

In the rotation sensor of the second embodiment having the above structure,
During normal rotation, information on the rotation speed is obtained in the same manner as in the first embodiment. However, in this case, the output signal is output by the rectangular wave forming means as a rectangular wave signal having a cycle corresponding to the rotation speed.

When a failure is detected when the rotation is stopped, a rectangular wave voltage signal is applied to the coil 4 by the rectangular wave forming means of the electric circuit 9 by a current applied from the cable 5 based on an external self-diagnosis execution signal. In that case, FIG.
180 ° to coil 4a and coil 4b
Apply rectangular wave voltage signals with different phases.

When the voltage applied to the coil 4a is the maximum voltage, the resistance of the magnetoresistive element 1a is large, and when it is OV, the resistance is small. The same applies to the coil 4b,
Since the phases are different by 180 °, the resistance change of the magnetoresistive element 1b is opposite to that of 1a. Therefore, the waveform of the output signal obtained by the two magnetoresistive elements 1 becomes a rectangular wave shape as shown in FIG. 5B, and the failure is caused by judging the rectangular wave signal in the same manner as in the first embodiment. Can be detected. In addition,
Although the waveform applied to the coil 4 is a rectangular wave in this embodiment, it may be a sine wave.

As described above, since two coils are formed in this embodiment, a signal can be generated only by applying a positive voltage by shifting the phase of the applied voltage. When there is only one coil as in the first embodiment, +
This is because it is necessary to apply a negative voltage, but when there are two coils, the same effect as applying a negative voltage can be obtained by energizing only one of the coils.

In this embodiment, since only the positive voltage is required, the electric circuit can be easily constructed, and not only the failure of the sensor element but also the failure of the electric circuit 9 can be detected and the waveform applied to the coil. Since the means to generate
It is only necessary to input the self-diagnosis execution signal from the outside, and there is an advantage that the configuration of the external circuit is simple. Furthermore, it is only necessary to add one signal line (for self-diagnosis start command), and there are various advantages such as cost increase of the cable can be minimized.

6 and 7 show voltage waveforms of the third embodiment. The rotation sensor of this embodiment is basically the same as that of the second embodiment, except that the waveform of the voltage applied to the coil 4 is a single pulse waveform as shown. Therefore, the pulse forming means is used instead of the rectangular wave forming means. The detection of the normal rotation speed is exactly the same as in the case of the second embodiment.

When the rotation is stopped, the abnormality diagnosis is performed as follows. First, as the voltage applied to the coil 4, a pulse voltage is applied only once to each of the coil 4a and the coil 4b. At this time, (a) when the crest of the rotary rotor 8 corresponds to the magnetoresistive element 1a side, the symbol V _{L of the} output voltage waveform
During this period, only a higher magnetic flux density is generated in 1a, and there is no change in the output of the low-level signal voltage.

While the voltage is being applied to the coil 4b,
A magnetic field having a high magnetic flux density is generated at 1a corresponding to the crests of the rotating rotor 8, but since the coil 4b is energized, a higher magnetic flux density is generated at the 1b side, as if the crests of the rotating rotor 8 were at the 1b side. The signal voltage is low.
The (VL) level is switched to the High (VH) level. On the contrary, if there is a mountain of the rotating rotor 8 on the magnetic resistance element 1b side, the signal voltage is replaced with VL when the coil 4a is energized, as shown in (b).

Therefore, when a voltage having a pulse waveform is applied to the coils 4a and 4b once, the Low or High signal is always generated once regardless of the position of the crest of the rotor. When such a signal is detected, it is normal, but when it is not detected, the magnetoresistive element 1 has some abnormality, and the failure diagnosis can be performed by detecting this normal or abnormal signal.

Also in this embodiment, since the applied voltage need only be the voltage on the plus side, an electric circuit can be easily formed, and the circuit configuration is simple because it is sufficient to input only one pulse to the coil. is there. In the case of Examples I and II, an AC or rectangular wave pulse train signal is generated regardless of the rotor position. Further, in the above embodiment, the case where the magnetoresistive element is used as the magnetic sensitive element has been described, but the present invention is also applicable to other magnetic sensitive elements such as Hall elements.

[0032]

As described above in detail, in the present invention, the magnetic sensor is provided in the rotation sensor, and the magnetic field generating coil is provided around the magnetic sensor, so that the magnetic sensor can be used. It is possible to obtain a rotation sensor which is easy to detect a failure and has a simple structure.

Further, when the coil is energized in a stationary state with respect to this rotation sensor, the normal or abnormal state of the magnetic sensitive element and its associated electric circuit can be detected by detecting the signal obtained from the magnetic sensitive element. There is an advantage that a method capable of detecting a failure even when stopped is obtained.

Therefore, the reliability of the rotation sensor according to the present invention is remarkably improved by this, and anti-lock system etc.
It is effective when applied to a system that requires high reliability for the rotation sensor.

[Brief description of drawings]

FIG. 1 is a sectional view of a rotation sensor according to a first embodiment.

FIG. 2 Same as above Electric circuit in rotation sensor

FIG. 3 is a waveform diagram of the applied voltage and the output voltage of the same as above.

FIG. 4 is a sectional view of a rotation sensor according to a second embodiment.

FIG. 5 is a waveform diagram of applied voltage and output voltage of the same as above.

FIG. 6 is a waveform diagram of the voltage applied to the rotation sensor of the third embodiment.

FIG. 7 is a waveform diagram of the rotation sensor output voltage according to the third embodiment.

[Explanation of symbols]

 1, 1a, 1b Magnetoresistive element 2 Magnet 3 Magnetic pole piece 4, 4a, 4b Magnetic field forming coil 5 Cable 6 Case body 7 Potting material 8 Rotating rotor 9 Electric circuit

Claims (9)

[Claims] 1. A magnetic sensor for detecting a change in a magnetic field as a change in an electric signal is provided in a case body of a rotation sensor arranged to face a sensor rotor, and a magnetic field for detecting a failure is provided around the magnetic sensitive element. A rotation sensor provided with a generating coil. 2. A magnetic field generating coil is provided in a state of being offset to the periphery of one of two element groups so that a rotation signal is obtained by a differential output of the two element groups. The rotation sensor according to claim 1, wherein the rotation sensor is provided. 3. Two magnetic sensing elements are provided, and the magnetic field generating coils are incorporated around each of the two element groups,
The rotation sensor according to claim 1, wherein a rotation signal is obtained by a differential output of two element groups. 4. A magnetic pole piece is arranged on the rear end face side of the magnetic sensing element, and the magnetic field generating coil is wound around the magnetic pole piece. Rotation sensor. 5. The rotation sensor according to claim 1, wherein a waveform forming means for generating a voltage waveform applied to the coil is incorporated in the sensor. 6. A rotating body, which is provided in a case body of a rotation sensor by bonding a magnet to a magnetic sensing element, and a magnetic field generating coil is provided around the magnetic sensing element so as to face the rotation sensor. A failure detection method for a rotation sensor, which energizes the coil in a stationary state, detects a signal generated from the magnetic sensitive element to detect normality or abnormality of the magnetic sensitive element and its associated electric circuit. 7. An alternating current or a rectangular wave current is applied to the magnetic field generating coil to generate a signal corresponding to rotation by a change in the generated magnetic field, so that the magnetic sensing element and its associated electric circuit are normal or abnormal. The failure detection method of the rotation sensor according to claim 6, wherein 8. The two magnetic field generating coils are provided, and an alternating current or a rectangular wave current is applied to one of them, and an alternating current or a rectangular wave current with a phase difference of 180 ° is applied to the other coil to generate the magnetic field. The failure detection method for a rotation sensor according to claim 6, wherein a signal corresponding to rotation is generated by a change in the magnetic field to detect normality or abnormality of the magnetic sensing element and its associated electric circuit. 9. The magnetic field generating coil is provided with two magnetic field generating coils, each of which is energized once for a certain period of time, and a sensor signal which changes according to a change of a generated magnetic field is used. 7. The rotation sensor failure detection method according to claim 6, wherein normality or abnormality of the electric circuit is detected.