JPH095345A - Electromagnetic pickup for rotation sensor and bearing fixed with pickup - Google Patents

Abstract

PURPOSE: To obtain a highly sensitive electromagnetic pickup for rotation sensor which can produce a high signal voltage. CONSTITUTION: A sensing rotor 9 comprises a ferromagnetic body and an annular ferrite magnet 2 is disposed on the side or outer circumferential side of an annular coil 4. One side of an L-shaped annular ferromagnetic body 5 is arranged on the inner circumferential side of an annular bobbin 3 applied with the annular coil 4. The L-shaped annular ferromagnetic body 5 and the annular ferrite magnet 2 are arranged to form a U-shape opening toward the sensing rotor 9 and the annular bobbin 3 applied with the annular coil 4 is disposed in the U-shape.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic pickup device used in a rotation sensor for detecting the number of rotations and the rotation speed of a rotating body such as a wheel of an automobile, and a bearing device to which the device is attached.

[0002]

2. Description of the Related Art A rotation sensor in which a sensing rotor having a magnet is attached to a rotating portion of a wheel bearing device of an automobile, and an electromagnetic pickup having an annular ferromagnetic material is fixedly arranged so as to face the sensing rotor, is disclosed in Japanese Patent Laid-Open No. Hei 5 (1999) -5. -2645
No. 62 publication. In the magnetic pickup used in this rotation sensor, the annular ferromagnetic material has a U-shape, and the opening of the U-shape is arranged at a position facing the sensing rotor, so that the magnetic path is a closed loop. And high output characteristics are obtained.

Further, as shown in FIG. 5, an example in which the magnet 22 is provided in the fixed portion of the electromagnetic pickup 20 instead of the rotating portion, and a ferromagnetic material is used for the sensing rotor 23 attached to the axle 25 can be considered.

[0004]

However, in the rotation sensor described in the above publication, since a magnet is used for the sensing rotor of the rotating part, the mass production processability is poor depending on the type of magnet, or the sensing rotor is press-fitted onto the axle 25. Since damage or the like may occur at the time of mounting by a construction method, etc., there is expected to be a problem of poor workability and mountability.

Further, in the electromagnetic pickup device for a rotation sensor of FIG. 5, a magnet 22 is provided on the inner peripheral side of an annular coil 21 of the electromagnetic pickup 20, a ferromagnetic material is used for the sensing rotor 23, and a surface thereof is used. It has uneven portions 23a having a constant pitch in the circumferential direction. In this case, as the sensing rotor 23 rotates, the electromagnetic pickup 20
The magnetic field formed by the sensing rotor 23 reciprocates between points a and b as shown by the magnetization curve (B-H curve) in FIG. 6, and causes a change ΔH ₁ in the magnetic field (H). As a result, the magnetic flux density (B) also changes ΔB ₁ .

The output voltage e in the electromagnetic induction type sensor is
Formula e = -dΦ / dt = -d (BS) / dt (Φ: magnetic flux inside coil, S: cross-sectional area, B: magnetic flux density,
t: time). That is, the output voltage e increases in proportion to the temporal change of the magnetic flux density B. However, in this case is clear from Figure 6, the .DELTA.B ₁ for [Delta] H ₁ for the slope of the magnetization curve is small small, has a problem that the output voltage obtained by the change in the magnetic field is small.

Therefore, an object of the present invention is to improve the workability of the sensing rotor, increase ΔB ₁ with respect to the change ΔH ₁ of the magnetic field generated by the electromagnetic pickup and the sensing rotor due to the rotation of the sensing rotor, and obtain the obtained output voltage e. It is to provide an electromagnetic pickup device for a rotation sensor having high sensitivity by increasing the size.

[0008]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention relates to a rotating body composed of a ferromagnetic sensing rotor and an electromagnetic pickup having an annular coil and an annular magnet wound around an annular bobbin. In the sensor electromagnetic pickup device, the annular magnet made of a ferrite magnet is arranged on the outer peripheral side or the side of the annular coil, and the cross section is formed on the inner peripheral side of the annular bobbin around which the annular coil is wound. L-shaped 1 of the L-shaped annular ferromagnet
Since the sides are arranged, and the annular ferromagnetic material and the annular magnet are arranged so as to surround the bobbin in a U shape, the opening of the U shape faces the sensing rotor. is there.

[0009]

According to the present invention, since the magnet is provided in the electromagnetic pickup, a ferromagnetic material can be used for the sensing rotor, which is excellent in mass production workability, and the sensing rotor can be attached by press fitting or the like. Therefore, the workability and the mountability are improved.

Further, the annular magnet made of a ferrite magnet is arranged on the outer peripheral side or the side surface side of the annular coil, and the L of the annular ferromagnetic material is formed on the inner peripheral side of the bobbin around which the annular coil is wound. By taking an arrangement with one side of the letter,
Since the relationship between the magnetic field and the magnetic flux density after the magnetic field has passed through the ferromagnetic body draws a magnetization curve (B-H curve) having a large gradient as shown in FIG. 4, the change in magnetic flux density ΔB with respect to the change in magnetic field ΔH ₁ . ₂ becomes large, a large output voltage can be obtained, and a highly sensitive electromagnetic pickup device for a rotation sensor can be obtained.

As described above, when the ferrite magnet is used as a large magnet having a ring shape like the sensor of the present invention, it is excellent in economic efficiency, but the magnetic flux density derived from the small gradient of the magnetization curve. The problem that the small change in the output has a bad influence on the output side can be solved by adopting the structure of the present invention, and a detector excellent in both economical efficiency and output characteristics can be obtained. be able to.

Also, facing the sensing rotor,
By providing the L-shaped end face of the annular ferromagnet or the end face of the annular magnet with irregularities at a constant pitch, a larger change in the magnetic field occurs, so that a higher output voltage can be obtained. Further, when the electromagnetic pickup having the structure of the present invention is attached to the bearing device, the electromagnetic pickup is formed compact, so that the bearing device itself can be miniaturized in the axial direction.

[0013]

Embodiments of the present invention will be described below with reference to the accompanying drawings. As shown in FIG. 1, the bearing device comprises an electromagnetic pickup 1 and a wheel bearing 11.
Is composed of an outer ring 12, an inner ring 14, a rolling element 16 and the like.
The vehicle axle 13 penetrates the inner ring 14, and the sensing rotor 9 is attached to the tip of the inner ring 14 via a sleeve 17. The sensing rotor 9 is made of a ferromagnetic material, and has a mountain-shaped uneven portion 9a having a constant pitch in the circumferential direction on the surface facing the electromagnetic pickup 1. Since the sensing rotor 9 also rotates with the rotation of the axle 13,
The uneven portion 9 a can change the magnetic field between the sensing rotor 9 and the electromagnetic pickup 1. The electromagnetic pickup 1 is fixed by a holding member 6 at a position facing the sensing rotor 9 with a required gap.
It is formed as an electromagnetic pickup device for a rotation sensor. As the axle 13 rotates, the sensing rotor 9 rotates, and the rotation speed can be detected by the electromagnetic pickup 1.

As shown in the enlarged view of FIG. 2, the electromagnetic pickup 1 is provided with an annular bobbin 3 having a U-shaped cross section and an open portion of the U-shaped outside, and a coil is provided therein. The coil 4 is wound to form an annular coil 4. An annular magnet 2 made of a ferrite magnet is arranged on the outer peripheral side of the annular coil 4. By using a ferrite magnet as this magnet, the magnet can be made thin, which can contribute to downsizing of the electromagnetic pickup 1.

On the inner peripheral side of the annular bobbin 3 around which the annular coil 4 is wound, one side of the L-shaped annular ferromagnetic body 5 having an L-shaped cross section is arranged. L of magnetic body 5
The U-shape and the annular magnet 2 are arranged so as to form a U-shape, and the U-shaped opening is installed so as to face the sensing rotor 9. And the resin 7
Thus, the electromagnetic pickup 1 is formed and protected as an integral assembly.

By disposing one side of the L-shape of the annular ferromagnetic material on the inner peripheral side of the bobbin 3 around which the annular coil 4 is wound, the magnetic field passes through the magnetic pole piece of the ferromagnetic material. , The relationship between the magnetic flux density and the magnetic field draws a magnetization curve (BH curve) having a larger gradient as shown in FIG. 4, and the change ΔB _{2 in the} magnetic flux density with respect to the change ΔH _{1 in} the magnetic field is ΔB described above.
_Greater than ₁ . Therefore, a larger output voltage can be obtained.

Further, when the end surface 5a of the annular ferromagnetic body 5 facing the sensing rotor 9 is provided with a mountain-shaped uneven portion having the same constant pitch as the uneven portion 9a of the sensing rotor 9, a larger change in magnetic field occurs. As a result, a higher output voltage can be obtained in combination with the change ΔB _{2 in the} magnetic flux density. A similar uneven portion may be provided on the end surface 2a of the magnet 2.

FIG. 3 shows another embodiment of the electromagnetic pickup device for the rotation sensor. In this case, the sensing rotor 9 having the concavo-convex portion 9a is the electromagnetic pickup 1
It is installed on the outer periphery of. In the electromagnetic pickup 1 in this case, a piece of an annular ferromagnetic body 5 having an L-shaped cross section is arranged on the inner peripheral side of the annular coil 4. However, the annular magnet 2 is arranged not on the outer peripheral side of the annular coil 4 but on the side surface side, and an uneven portion 2 a is provided at the end of the magnet facing the sensing rotor 9. Of course, the concavo-convex portion 5a can be formed on the ferromagnetic body 5, and even in this case, the same result as in the case of FIG. 1 can be obtained.

[0019]

As described above, according to the present invention, the coil of the electromagnetic pickup is surrounded by the magnet and the ferromagnetic material in a U shape, and its opening is opposed to the sensing rotor, so that a high output voltage is obtained. It is possible to provide an electromagnetic pickup device for a rotation sensor with higher sensitivity,
Further, since the workability of the sensing rotor is good, it is easy to attach to the axle of an automobile or the like, and can be used as an electromagnetic pickup device for a rotation sensor for automobiles.

[Brief description of drawings]

FIG. 1 is a sectional view of an embodiment of a vehicle bearing according to the present invention.

FIG. 2 is a sectional view of an embodiment of an electromagnetic pickup device for a rotation sensor according to the present invention.

FIG. 3 is a sectional view of another embodiment of an electromagnetic pickup device for a rotation sensor according to the present invention.

FIG. 4 is a diagram showing a magnetization curve (BH curve) of a ferromagnetic material.

FIG. 5 is a sectional view showing a conventional electromagnetic pickup device for a rotation sensor.

FIG. 6 is a chart showing a magnetization curve (BH curve) of a magnet.

[Explanation of Codes] 1 Electromagnetic pickup 2 Annular magnet 2a Uneven portion 3 Annular bobbin 4 Annular coil 5 Annular ferromagnetic body 5a Uneven portion 6 Holding member 7 Resin 8 Sensor signal line 9 Sensing rotor 9a Uneven portion 11 Vehicle Bearing 12 Outer ring 13 Axle 14 Inner ring 16 Rolling element 17 Sleeve 18 Cager 20 Electromagnetic pickup 21 Annular coil 22 Annular magnet 23 Sensing rotor 23a Uneven portion 24 Annular bobbin 25 Axle 26 Sleeve

Claims (3)

[Claims] 1. An electromagnetic pickup device for a rotation sensor, comprising: a ferromagnetic sensing rotor; and an electromagnetic pickup having an annular coil and an annular magnet wound on an annular bobbin. An outer peripheral side or a side surface of the annular coil. Arrange the annular magnet made of ferrite magnet on the side,
One side of an L-shape of an annular ferromagnetic body having an L-shaped cross section is arranged on the inner peripheral side of the annular bobbin around which the annular coil is wound, and the annular ferromagnetic body and the annular ring. An electromagnetic pickup device for a rotation sensor, wherein a magnet is arranged so as to surround the bobbin in a U-shape, and the U-shaped opening faces the sensing rotor. 2. The L-shaped end surface of the annular ferromagnet or the end surface of the annular magnet facing the sensing rotor is provided with irregularities at a constant pitch. Electromagnetic pickup device for rotation sensor. 3. A bearing device to which the electromagnetic pickup device for a rotation sensor according to claim 1 is attached.