JPH05205932A - Magnet body for rotary sensor - Google Patents

Abstract

PURPOSE:To manufacture the title magnet body for rotary sensor hardly demagnetized while hardly developing the defects such as cracking, breaking off, etc., when the magnet body is force-fitted into a rotary axle by a method wherein multiple thin ring type plates are laminated through the intermediary of elastic bonding agent layers to be force-fitted into the rotary axle for fixation. CONSTITUTION:A ring type magnet body 11 comprising Fe-31Cr-23Co magnets is composed of thin ring type magnet plates 12 laminated through the intermediary of bonding agent layers 13 comprising elastic bonding agent. Next, this magnet body 11 is force-fitted into a rotary axle to be fixed. Through these procedures, the operating point of magnetized magnet part can be shifted to the stabilized side resultantly making it to be hardly demagnetized. Furthermore, the defects such as cracking, breaking off, etc., can be diminished.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotation sensor magnet body which generates a magnetic signal by relative displacement with a detection head.

[0002]

2. Description of the Related Art Conventionally, in order to detect the number of rotations of a rotary shaft with high accuracy, a magnet body magnetized in multiple poles is used as a rotor as disclosed in, for example, Japanese Patent Application Laid-Open No. 62-218814. There is known a magnetic signal detection sensor which is mounted on a rotary shaft and has a detection head provided on the fixed portion side in the vicinity of the rotor.

In such a rotation sensor, the rotor for detecting the rotational speed of a shaft rotating at high speed has a mechanical strength sufficient to withstand tensile stress caused by a centrifugal force and an excellent impact resistance against vibration. In addition, FeCrCo-based permanent magnets have been conventionally used.

[0004]

However, since this magnet material has a low coercive force by nature, when iron powder or the like adheres to this magnet material, it causes a significant demagnetization, and there is a problem that the signal output decreases. ..

Further, since the above-mentioned magnet material has a mechanically fragile property, when it is press-fitted into the rotating shaft, cracks,
Occasionally, defects such as chipping occurred.

In view of such a problem, the present invention has an object to provide a magnet body for a rotation sensor, which is less likely to cause demagnetization, and is less likely to cause defects such as cracking and chipping when press-fitting into a rotary shaft. To do.

[0007]

A magnet for a rotation sensor according to the present invention comprises a plurality of thin ring-shaped magnet plates laminated with an adhesive layer having elasticity, and is press-fitted onto a rotary shaft. It is characterized by being fixed.

[0008]

According to the present invention, since the rotation sensor magnet body is formed by laminating a plurality of thin ring-shaped magnet plates with the adhesive layer having elasticity, the magnetized magnet portion. Since the operating point of can be moved to the stable side, demagnetization is less likely to occur.

Further, when the magnet body is pressed into the rotary shaft, the tensile stress generated in the magnet body can be released by the adhesive layer, and defects such as cracking and chipping can be reduced.

[0010]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view of an axle portion of an automobile equipped with a magnet body according to the present invention as a rotor of a rotation sensor.
In FIG. 1, 1 is an axle, 2 is a knuckle that rotatably supports the axle 1 via a bearing 3, 4 is a ring-shaped permanent magnet rotor press-fitted to the axle 1, and 5 is opposed to the rotor 4. Sensor head fixed to the knuckle 2 and 6
Is a brake disc mounting portion fixed to the axle.

FIG. 2 is a plan view of the ring-shaped magnet body 11 used in the permanent magnet rotor 4, and FIG. 3 is a sectional view taken along line III-III of FIG. 4 is a partially enlarged view of FIG.

The ring-shaped magnet body 11 is made of Fe-31Cr-23C.
Made of magnet, outer diameter 70mm, inner diameter 60mm, thickness 0.1-0.5m
A thin ring-shaped magnet plate 12 with a thickness of 5 m with a thickness of 5
It is constructed by laminating to mm. The adhesive layer 13 is made of an elastic adhesive such as a fluorine resin.

The magnet body 11 is alternately magnetized S and N at an interval of about 2.5 mm on the outer circumference, and the magnetized depth is 3 mm.

In order to study the influence of the thickness of the thin ring-shaped magnet plate 12 on the magnetic characteristics of the magnet body 11 having such a structure, the specifications shown in Table 1 below are provided.
Ten samples were made.

[0016]

[Table 1]

The surface of each sample was sprinkled with iron powder (particle size: 200 μm or less) and allowed to stand for one month, and the decrease rate of the signal output before the iron powder was adhered was measured using the apparatus shown in FIG. The result is shown in FIG.

From FIG. 6, the ratio of (thickness / magnetization depth) is 0.17.
Under the following conditions, it can be seen that the output is hardly reduced.

Next, FIG. 7 shows the signal output of each sample. Figure 7
From the above, it can be seen that when the ratio of (thickness / magnetization depth) is smaller than 0.03, the output is significantly reduced.

From the above results, it is appropriate to set the ratio (thickness / magnetization depth) in the range of 0.03 to 0.17 in order to enhance the demagnetization resistance without lowering the signal output.

Further, the rotation sensor magnet body 11 according to the present invention.
Since a plurality of thin ring-shaped magnet plates 12 are laminated via an adhesive layer 13 having elasticity, when the magnet body 11 is press-fitted onto the rotating shaft, the tension generated in the magnet body 11 The stress is released by the adhesive layer 13, and defects such as cracks and chips are reduced. By the way, the conventional ring-shaped magnet with a single structure is 4% (n = 100) when it is pressed into the rotating shaft.
However, the defect rate of the magnet body having the same specifications as the sample No. 6 in Table 1 was reduced to 1% (n = 100).

By the way, when a rotor made of a FeCrCo type magnet is used as a suspension member of an automobile as shown in FIG. 1, there is a problem that the signal output is lowered due to environmental corrosion.

Therefore, the nitriding treatment for improving the corrosion resistance of the FeCrCo type magnet rotor will be described below.

First, an alloy of Fe-31Cr-23Co was prepared by a melting method to prepare a test piece. After subjecting this test piece to a heat treatment at a temperature of 1300 ° C., as a magnetic property treatment, it was held at a temperature of 640 ° C. for 0.5 hour and cooled. Then, for the purpose of improving corrosion resistance and magnetic properties, salt bath nitriding treatment (tuftride) was performed at a temperature of 600 ° C. for 2 hours to form a nitride layer on the surface of the test piece. After cooling, temperature lower than nitriding temperature (500 ℃)
The strain was removed in an unoxidized atmosphere for 1.5 hours and then gradually cooled. Incidentally, bath composition of salt bath nitriding treatment, CNO ^- potassium cyanate or sodium cyanate. 26 as an ion
39%, 0-6% sodium cyanide or potassium cyanide as CN ^- ions, the remainder sodium carbonate or potassium carbonate.

FIG. 8 shows the results of comparing the corrosion resistances of the test pieces thus nitrided and those not nitrided, respectively, by subjecting them to a salt water fog test for 1000 hours. As is clear from FIG. 8, the corrosion weight loss of the test piece subjected to the nitriding treatment was only 3 mg, whereas the corrosion weight loss of the comparative example reached 80 mg.

FIG. 9 is a comparison of the magnetic properties after a 1000-hour salt water mist test. From Figure 9,
It can be seen that the holding power is improved by performing the nitriding treatment.

Since the FeCrCo alloy is extremely brittle, the nitriding treatment may easily cause surface defects. In order to prevent this, after the nitriding treatment, strain relief treatment is performed at a temperature (500 ° C.) lower than the nitriding treatment temperature (600 ° C.) to prevent the toughness of the FeCrCo magnet from being lowered by the nitriding treatment.

[Brief description of drawings]

FIG. 1 is a sectional view of an axle portion of an automobile provided as a rotor of a rotation sensor for a magnet body according to the present invention.

FIG. 2 is a plan view of a rotation sensor magnet body.

FIG. 3 is a sectional view taken along line III-III in FIG.

FIG. 4 is a partially enlarged sectional view of FIG.

FIG. 5 is a schematic diagram of a sensor output measuring device.

FIG. 6 is a characteristic diagram showing the relationship between the thickness of magnet thin plate / magnetization depth and the output reduction rate.

FIG. 7 is a characteristic diagram showing the relationship between the thickness / magnetization depth of a magnet thin plate and the holding force.

[Figure 8] Characteristic diagram comparing corrosion resistance

FIG. 9 is a characteristic diagram comparing magnetic characteristics.

[Explanation of symbols]

 1 axle 2 knuckle 3 bearing 4 permanent magnet rotor 5 detection head 11 ring-shaped magnet body 12 ring-shaped magnet plate 13 adhesive layer

Claims (1)

[Claims] 1. A rotation sensor comprising a ring-shaped magnet body and a detection head for detecting a magnetic signal, wherein the magnet body comprises a plurality of thin ring-shaped magnet plates with an elastic adhesive layer interposed therebetween. A magnet body for a rotation sensor, which is made of a plurality of laminated layers and is press-fitted and fixed to a rotation shaft.