JP2002181037A - Bearing with rotary sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a bearing with a rotary sensor capable of reducing unevenness of amplitude of a limited wave output by using isotropic magnetic powder if an encoder output is analog output. SOLUTION: A pulser ring 4 is fixed to an inner race 3, a magnetic sensor 5 is fixed to an outer race 1 through a sensor case 6, and a magnetic encoder is formed in the pulser ring 4. If encoder output is analog output, isotropic magnetic powder is used, and if encoder output is a rectangular wave signal, anisotropic magnetic powder is used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bearing with a rotation sensor, and more particularly to a bearing with a rotation sensor having a function of detecting a rotation speed or a rotation direction.

[0002]

2. Description of the Related Art FIG. 3 is a sectional view of a conventional bearing with a rotation sensor. In FIG. 3, a bearing with a rotation sensor is a rolling bearing including an outer ring 1, an inner ring 3 and a rolling element 2. The magnetic sensor 5 is fixed via a sensor case 6. A magnetic encoder is formed on the surface of the pulsaring 4. Such a bearing with a rotation sensor is small in size, does not require assembly adjustment, has characteristics such as robustness, and is used as a motor support bearing or the like.

[0003] In some cases, the outer ring 1 is on the rotating side and the inner ring 3 is on the non-rotating side. As the sensor output of such a bearing with a rotation sensor, there are two types, an analog output as shown in FIG. 4A and a rectangular wave output as shown in FIG. 4B. Since the analog output type requires reproducibility of a sinusoidal waveform, it is important for a magnetic encoder to have uniform magnetization strength. In the rectangular wave output type, since the output signal is used with a saturated waveform, the magnetization intensity is required to be larger than the magnetization intensity uniformity. This is because the higher the magnetization strength, the sharper the rise of the waveform, the better the pitch accuracy, or the larger the sensor gap.

[0004]

Conventionally, regardless of the output signal, anisotropic magnetic powder has been used for the magnetic encoder. However, when the encoder output is an analog output, the use of anisotropic magnetic powder has a disadvantage that the amplitude of the sine wave output varies greatly.

[0005] Therefore, a main object of the present invention is to provide a bearing with a rotation sensor that can use an isotropic magnetic powder in the case of an analog output and can reduce the variation in the amplitude of the limited wave output.

[0006]

SUMMARY OF THE INVENTION The present invention provides a bearing with a rotation sensor having an inner ring, an outer ring, and a plurality of rolling elements housed between the inner ring and the outer ring, and having a built-in sensor for detecting the rotation speed of the rotating body. Wherein one of the inner ring and the outer ring constitutes a rotating raceway, the other constitutes a fixed raceway, and a pulsar ring mounted on one end of the rotating raceway and fixed opposite the pulsar ring. The pulsaring is a magnetized encoder made of an elastomer mixed with magnetic powder.If the encoder output is an analog signal, the isolator is used for the magnetic powder and a rectangular wave is used. In the case of a signal, the magnetic powder is characterized by using anisotropy.

As a result, variations in the magnetization strength can be reduced, and thus variations in the amplitude of the sensor output can be reduced.

Further, when the encoder output is an analog signal, an MR element is used as a sensor.

Further, the magnetic powder is a ferrite.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, there are two types of magnetic powder, one having an isotropic magnetization property and the other having an anisotropic magnetization property when magnetized.
The isotropic one has a defect that the magnetization strength (magnetization strength) is low while the magnetization strength in any direction is uniform. On the other hand, in the case of an anisotropic material, if it is aligned in one direction, the magnetization strength is increased, but if the directions are not uniformly aligned, the magnetization strength tends to vary.

As an example, isotropic ferrite magnetic powder can be regarded as forming a polycrystal, and has a particle size of several μm. On the other hand, anisotropic ferrite is a single crystal in the shape of a hexagonal prism or a hexagonal plate, and its size is about 1 μm.

FIG. 1 and FIG. 2 show the results of measuring the variation in the magnetization strength of the isotropic ferrite used in the present invention and the anisotropic ferrite. As is clear from the comparison between FIGS. 1 and 2, when the isotropic ferrite shown in FIG. 1 is used, the variation in the magnetization strength can be suppressed to about 1/2 as compared with the anisotropic ferrite shown in FIG. We see what is possible. Therefore, when the isotropic ferrite is adopted, the fluctuation of the sensor output can be reduced.

As shown in Table 1, the magnetization strength of isotropic ferrite is reduced by about 30% as compared with anisotropic ferrite, and a high-sensitivity sensor such as an MR element is used as a magnetic sensor. In this case, it is not necessary for the magnetization strength to be the strongest, which is preferable.

[0014]

[Table 1]

The embodiments disclosed this time are to be considered in all respects as illustrative and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

[0016]

As described above, according to the present invention, one of the inner race and the outer race constitutes the rotating race, and the other constitutes the fixed race, and one end of the rotating race is provided at one end of the rotating race. Including a pulsar ring to be mounted and a sensor to be mounted on the fixed side bearing ring facing the pulsar ring, the pulsar ring is a magnetized encoder made of an elastomer mixed with magnetic powder, and when this encoder output is an analog signal,
By using isotropic magnetic powder and using anisotropic magnetic powder in the case of a rectangular wave signal, the variation in magnetization strength can be reduced. Thereby, the variation of the amplitude of the sensor output can be reduced.

Further, in the case of an MR element having a high sensor output, it is more preferable because the weak magnetizing strength does not become a disadvantage.

[Brief description of the drawings]

FIG. 1 is a view showing a result of measuring a variation in magnetization strength of an isotropic ferrite used in the present invention.

FIG. 2 is a view showing a result of measuring a variation in magnetization strength of an anisotropic ferrite used in the present invention.

FIG. 3 is a cross-sectional view of a conventional bearing with a rotation sensor.

FIG. 4 is a diagram showing a sensor output waveform of a bearing with a rotation sensor.

[Explanation of symbols]

1 outer ring, 2 rolling element, 3 inner ring, 4 pulsaring,
5 Magnetic sensor, 6 sensor case.

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Takashi Koike 1578 Higashikaizuka, Iwata City, Shizuoka Prefecture (72) Inventor Kazuyuki Iguchi 1578 Higashikaizuka, Iwata City, Shizuoka Prefecture F Term (in reference) 2F077 AA11 CC02 NN04 NN24 PP14 QQ03 VV02 VV11 VV13 3J101 AA02 AA42 AA62 FA23 GA24 5H611 AA01 BB01 PP05 QQ01 QQ02 RR03 UA05

Claims (3)

[Claims] 1. A bearing with a rotation sensor, comprising: an inner ring, an outer ring, and a plurality of rolling elements housed between the inner ring and the outer ring, the sensor having a built-in sensor for detecting a rotation speed of the rotating body. Alternatively, one of the outer rings constitutes a rotating raceway, the other constitutes a fixed raceway, and a pulsar ring attached to one end of the rotating raceway; and the fixed side facing the pulsar ring. A sensor mounted on a bearing ring, wherein the pulsar ring is a magnetized encoder made of an elastomer mixed with magnetic powder, and when the encoder output is an analog signal, the magnetic powder is isotropic and rectangular. A bearing with a rotation sensor, wherein the magnetic powder uses anisotropy when the signal is a wave signal. 2. The bearing with a rotation sensor according to claim 1, wherein when the encoder output is an analog signal, an MR element is used as the sensor. 3. The bearing with a rotation sensor according to claim 1, wherein the magnetic powder is ferrite.