JPH04134267A - Rotary sensor - Google Patents

Abstract

PURPOSE:To provide possibility of sensing in a wide gap range by installing a magneto resistance element with its axis dislocated by a certain dimension from the axis in the direction across the width of the magnetized surface of a rotor. CONSTITUTION:A rotary sensor is arranged so that the axis Ct of a magneto resistance element 11 is dislocated for the axis Cr in the direction across the width l of the cylindrical magnetized surface of a rotor 10, and thereby a gauge 6 can be left unsaturated while gauges 5,7,8 be saturated. Therefore, the output therefrom assumes a gradual curve, and the gap (g) between the rotor 10 and magneto resistance element 11 may also be OK even between g3 and g4, and the serviceable gap range can be set off wider than between g1 and g2 which is the serviceable gap range according to the conventional arrangement.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a rotation sensor used for detecting wheel speed, engine rotation speed, etc. of a vehicle.

[Prior Art] To detect the rotational speed of a wheel or the like, a multi-pole magnetized rotor is rotated, and changes in the magnetic flux density are detected using a ferromagnetic magnetoresistive element.

The ferromagnetic magnetoresistive element has a structure as shown in FIG.

In FIG. 3, 1 to 4 indicate electrodes, and 5 to 8 indicate gauges.

Gauges 5 to 8 are attached to substrate 9 by sputtering or vapor deposition.
It is formed as a thin film on top and then patterned by etching. Gauges 5 to 8 are made by forming a thin film of material such as nickel cobalt (NiCo) or nickel iron (NiFe) on an insulating substrate such as glass. The film has a thickness of 500 to 2000 angstroms, and is formed on the substrate 9 in a meandering shape, for example. Further, a silicon oxide (St(la)) layer is formed as a protective film on the gauges 5 to 8.
8. Electrodes 1 to 4 are configured as a bridge as shown in FIG. In this bridge, cage 5 shows the same change in resistance as gauge 7, and gauge 6 shows the same change in resistance as gauge 8.

The magnetoresistive element 11 and the magnetized rotor 10 are arranged as shown in FIG. In the figure, 12 is a rotor shaft.

The resistance value of the magnetoresistive element 11 changes as shown in FIG. 7 when a magnetic flux is applied to the gauges 5 to 8 in the direction of arrow a as shown in FIG. 6. That is, as the magnetic flux is gradually increased from O, the resistance values of gauges 5 to 8 decrease. However, as the applied magnetic field increases further and becomes larger than H6, the change in resistance value becomes saturated.

Therefore, if the gauge is placed in a place where the magnetic flux changes are large as shown in Figure 8, the output voltage ■PP can be increased as shown in Figure 9, but the waveform is a sine wave (Figure 11).
The waveform is not close to .

The period of this waveform changes significantly when the median level changes. That is, as shown in FIG. 10, the values for periods T+ and T2 are significantly different.

[Problem to be Solved by the Invention] In such a conventional technique, if the gap g (FIG. 12) between the magnetized rotor 10 and the magnetoresistive element 11 is removed and all the gauges are used in a non-saturated state, the gap becomes When it becomes larger than the numerical value, the output suddenly decreases as shown in FIG.

That is, when the gap becomes smaller, the waveform becomes as shown in FIG. 10, and when the gap becomes larger, the output suddenly becomes smaller. For this reason, the usable gap becomes narrower, and assembly precision must be controlled.

The present invention was made in view of the above circumstances, and by arranging some of the plurality of gauges to be saturated and the remaining gauges to be non-saturated, the waveform is not saturated and the output voltage is as large as possible. However, it is an object of the present invention to provide a rotation sensor that can be used over a wide range of gaps.

[Means for Solving the Problems] In order to achieve the above object, the present invention disposes a magnetoresistive element at a predetermined gap from the cylindrical magnetized surface of a multipolar magnetized rotor, and Detects the magnetic flux density of the magnetized rotor,
The rotation sensor for detecting the number of rotations is characterized in that the center axis of the magnetoresistive element is shifted by a predetermined dimension from the center line of the width of the magnetized surface of the magnetized rotor.

[Function] Since some of the gauges are arranged in saturation and the rest in non-saturation, the output voltage does not change suddenly even if the gap between the magnetic rotor and the magnetic resistance element changes. That is, the curve of change in output voltage with respect to change in gap becomes gentle.

[Example code] Hereinafter, the present invention will be described in detail based on the accompanying drawings.

Fig. 1 is an explanatory diagram showing the positional relationship between the magnetized surface of the magnetic rotor and the magnetoresistive element according to an embodiment of the present invention, and Fig. 2 is a characteristic showing the gap between the magnetic rotor and the magnetoresistive element and the output voltage. It is a diagram.

As shown in FIG. 1, the rotation sensor of the present invention has a magnetized rotor 1.
By arranging the center line Ct of the magnetoresistive element 11 at a position shifted from the center line C1 of the width β of the cylindrical magnetized surface of 0, the gauge 6 is unsaturated and the gauges 5 and 7.8 are saturated. be able to.

Therefore, this output becomes a gentle curve as shown in Fig. 2, and therefore the gap g (Fig. 12) between the magnetizing rotor lO and the magnetoresistive element 11 can be between g3 and g4, which is the conventional method. The usable gap range can be wider than the usable gap range between g+ and gz (FIG. 13) due to the arrangement of (FIG. 8).

This means that if we take approximately the same usable output voltage range,
The conventional rotation sensor has a steep curve as shown in Fig. 13, so the usable gap range is narrow between gl and gz, but the rotation sensor of the present invention has a gentle curve as shown in Fig. 2. Therefore, the usable gap range is g
, and g4, which is wider than before.

Note that similar results can be obtained by using gauges 5 and 6.7 in a non-saturated state and gauge 8 in a saturated state.

[Effects of the Invention] The rotation sensor of the present invention described in detail above has the output voltage generated by arranging the central axis of the magnetoresistive element offset with respect to the center line of the width of the magnetized surface of the magnetized rotor. The waveform is sinusoidal, and even if the gap between the magnetized rotor and the magnetoresistive element becomes large, the output voltage does not drop significantly unlike in conventional rotation sensors, so detection is possible over a wide gap range.

Therefore, the rotation sensor is resistant to vibrations of the magnetized rotor, and therefore the mounting accuracy can be lowered and the mounting can be simplified.

Furthermore, unlike conventional rotation sensors, the period of the output waveform does not change significantly and is stable, so it can be applied to systems that measure the period and perform control, such as vehicle ABS systems, to achieve highly accurate control. It is.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing the positional relationship between the magnetized surface of the magnetic rotor and the magnetoresistive element of a rotation sensor showing one embodiment of the present invention;
Fig. 2 is a characteristic diagram showing the relationship between the gap between the magnetic rotor and the magnetoresistive element and the output voltage, Fig. 3 is a front view of the magnetoresistive element, Fig. 4 is a bridge configuration circuit diagram, and Fig. 5 is the magnetoresistive element. Figure 6 is a perspective view of the element and rotor, Figure 6 is a perspective view of the magnetoresistive element, Figure 7 is a characteristic diagram showing the resistance value change of the magnetoresistive element, Figure 8 is the positional relationship between the magnetoresistive element and the magnetized rotor. Explanatory diagrams, Figures 9 and 10 are characteristic diagrams showing signals output by conventional magnetoresistive elements, Figure 11 is a waveform showing a sine wave, and Figure 12 shows the relationship between the magnetic rotor and the magnetoresistive element. The explanatory diagram, FIG. 13, is a characteristic diagram showing the relationship between the output voltage and the gap between the magnetic rotor and the magnetoresistive element of a conventional rotation sensor. 10... Magnetized rotor, 11... Magnetoresistive element, 10
a... Magnetized surface, g... Gap, Ct... Central axis of the magnetoresistive element, Or... Center line of the width of the magnetized surface of the magnetized rotor. Patent Applicant: Aisin Seiki Co., Ltd. Figure 2: Figure 4: Figure 8

Claims (1)

[Claims] (1) Rotation in which a magnetic resistance element is arranged at a predetermined gap from the cylindrical magnetized surface of a multi-pole magnetized rotor, and the magnetic flux density of the magnetized rotor is detected to detect the number of rotations. A rotation sensor, wherein the center axis of the magnetoresistive element is shifted by a predetermined dimension from the center line of the width of the magnetized surface of the magnetized rotor.