JPH11295330A - Vehicle speed sensor - Google Patents

Abstract

(57) [Summary] [Problem] An arbitrary output pulse can be obtained only by two-pole magnetization,
To provide a vehicle speed sensor with improved detection accuracy and durability. SOLUTION: This vehicle speed sensor has a rotating magnet 4 that rotates in opposition to a magnetoelectric conversion element 7a. The rotating magnet 4 is composed of a magnet main body 4a and a magnetic cover 4b attached to the surface thereof. Body cover 4
The b is provided with a plurality of through holes 8 along the circumferential direction so that a pulse output can be obtained from the through holes 8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle speed sensor for detecting a vehicle speed by converting the rotation of a transmission of an automobile into an electric signal, and more particularly, a vehicle speed sensor for detecting a change in magnetic flux due to the rotation of a rotating magnet with a magnetoelectric conversion element. It is about.

[0002]

2. Description of the Related Art FIG. 4 shows a conventional rotary magnet type vehicle speed sensor. A bearing metal 2 is fixed in a case 1, and a drive shaft 3 is rotatably supported by the bearing metal 2, and a rotating magnet 4 is fixed to a tip of the drive shaft 3. A thrust washer 5 facing the braking magnet 9 attached to the front part of the bearing metal 2 is fixed to the rear part of the rotating magnet 4. A housing 6 is attached to a front portion of the case 1, and a magnetoelectric conversion element 7 a attached to the housing 6 is arranged so as to face the rotating magnet 4. The magnetoelectric conversion element 7a is embedded in the detection unit 7 together with the circuit board.

[0003] Drive shaft 3 connected to the transmission
A change in magnetic flux of the rotating magnet 4 rotating together with the rotating magnet 4 is detected by the magneto-electric conversion element 7a, and a rectangular wave is output as a pulse through an amplification and waveform shaping circuit.

As shown in FIG. 5, the rotating magnet 4 has a magnetized surface 10 formed by multi-polarizing N and S poles along a circumferential direction. In the drawing, the inner and outer magnetized members 10a and the outer magnetized member 10b have two inner and outer magnetized members.
There are various types of magnetized surfaces.

[0005]

SUMMARY OF THE INVENTION The magneto-electric conversion element 7a
Output pulse number from the magnetized surface 10 of the rotating magnet 4
Therefore, when a large number of pulse outputs are required (a device requiring high resolution), it is necessary to increase the number of magnetized poles. In such a multi-pole magnetized structure, when the outer shape is restricted, the pitch of the magnetized magnet becomes narrow, so that the durability of the magnetized yoke is reduced, and the production time of the magnet is increased and the yield is deteriorated. Further, as the pitch increases, the magnetic force of the magnetized surface 10 decreases, so that the detection gap between the magnetism conversion element 7a and the magneto-electric conversion element 7a must be minimized.

The present invention has been made in view of the above points, and it is an object of the present invention to provide a vehicle speed sensor capable of obtaining an arbitrary output pulse only by two-pole magnetization and improving detection accuracy and durability. I do.

[0007]

According to one aspect of the present invention, there is provided a vehicle speed sensor having a rotating magnet that rotates in opposition to a magnetoelectric conversion element, wherein the rotating magnet is a magnet main body. And a magnetic cover attached to the surface of the magnet main body. The magnet main body is magnetized in two poles in front and back directions, and the magnetic cover includes a plurality of magnetic transmission means along the circumferential direction. It is characterized by having been provided.

For this reason, in the first aspect of the present invention, since a magnetic flux is generated from the rotating magnet through the magnetic transmission means, a change in magnetic flux due to the rotation of the rotating magnet is detected by the magnetoelectric conversion element. The number of output pulses is determined by the number of magnetic transmission means, and the rotating magnet needs only two-pole magnetization in the axial direction (front and back directions), which simplifies the magnetizing yoke structure, increases durability and improves the yield of magnet production. I do. To increase the number of pulses, it is only necessary to increase the number of magnetic transmission means, and the minimum number of magnet poles is two, so that the magnetic force can be increased. Therefore, the detection gap with the magnetoelectric conversion element can be increased. As a result, the detection accuracy can be improved.

According to a second aspect of the present invention, there is provided the vehicle speed sensor according to the first aspect, wherein a thrust washer is provided between a bearing metal that supports a drive shaft of the rotating magnet and the rotating magnet. The thrust washer is smaller in diameter than the rotating magnet and the bearing metal, and magnetic braking is applied between the rotating magnet and the bearing metal.

For this reason, in the second aspect of the present invention, the rotating magnet is attracted to the bearing metal and is subjected to magnetic braking. Since a braking magnet is not required, workability in assembling is improved.

According to a third aspect of the present invention, there is provided the vehicle speed sensor according to the first or second aspect, wherein the magnetic permeable means is constituted by a through hole.

Therefore, according to the third aspect of the present invention, an arbitrary number of magnetic transmission means can be formed by forming the through holes in the magnetic cover.

According to a fourth aspect of the present invention, there is provided the vehicle speed sensor according to the first or second aspect, wherein the magnetic permeable means is constituted by a notch.

Therefore, according to the fourth aspect of the present invention, any number of magnetic transmission means can be formed by forming the notch in the magnetic material cover.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. 4 and 5 are denoted by the same reference numerals.

FIGS. 1 to 3 show a vehicle speed sensor according to an embodiment of the present invention.

In FIG. 1, a bearing metal 2 is provided in a case 1.
The drive shaft 3 is rotatably supported by the bearing metal 2, and a rotary magnet 4 is fixed to the tip of the drive shaft 3. A thrust washer 5 located at the front of the bearing metal 2 is fixed to the rear of the rotating magnet 4. A magnetoelectric conversion element 7 a is attached to the front of the case 1 so as to face the rotating magnet 4. Drive shaft 3
A change in magnetic flux of the rotating magnet 4 rotating together with the rotating magnet 4 is detected by the magneto-electric conversion element 7a, and a rectangular wave is output as a pulse through an amplification and waveform shaping circuit. Magnetoelectric conversion element 7
a is buried in the detection unit 7 together with the circuit board.

As shown in FIG. 2A, the rotating magnet 4 is composed of a disk-shaped magnet main body 4a and a magnetic cover 4b attached to the surface of the magnet main body 4a. The magnet main body 4a has a magnetizing structure which is magnetized in the axial direction (front and back direction) 12, that is, has a two-pole magnetized structure in which the front side is N (or S) and the back side is S (or N).

As shown in FIG. 2 (b), the magnetic cover 4b is provided with magnetic transmission means comprising a plurality of through holes 8 at equal intervals along the circumferential direction. In the example shown,
The through hole 8 is composed of two bands, an inner peripheral through hole 8a and an outer peripheral through hole 8b, but the number of bands is arbitrary.

FIG. 3 shows a modification of the magnetic transmission means.
A notch 9b is provided on the outer periphery of the magnetic cover 4b in place of the outer peripheral hole 8b in FIG. 2, and a long hole 9 is used instead of the inner peripheral hole 8a.
b.

A magnetic flux is generated from the rotating magnet 4 through magnetic transmission means such as an inner peripheral through hole 8a, an outer peripheral through hole 8b or a long hole 9a, and a notch 9b. 7a, and outputs a rectangular wave pulse through an amplification and waveform shaping circuit. This number of pulses corresponds to the number of magnetic transmission means of the magnetic body cover 4b.

As described above, the number of output pulses is determined by the number of magnetic transmission means, and the rotating magnet 4 can be magnetized by two poles in the axial direction. Manufacturing yield is also improved. Also,
In order to increase the number of pulses, it is only necessary to increase the number of magnetic transmission means. Since the number of magnet poles is a minimum of two, the magnetic force can be increased. Therefore, the detection gap with the magnetoelectric conversion element 7a can be increased. Detection accuracy can be improved.

The diameter of the thrust washer 5 is preferably smaller than that of the rotating magnet 4 and the bearing metal 2, as shown in FIG. 1, and the thrust washer 5 does not exist between the rotating magnet 4 and the bearing metal 2. The braking gap 11 is formed. The rotating magnet 4 is attracted to the bearing metal 2 through the braking gap 11 and is subjected to magnetic braking. Therefore, the conventional braking magnet 9 becomes unnecessary, and the cost can be reduced by reducing the number of parts and improving the workability of assembling.

[0024]

As described in detail above, according to the first aspect of the present invention, the magnet body of the rotating magnet has two poles magnetized in the front and back directions, and the magnetic body cover has a plurality of magnets extending along the circumferential direction. Since the magnetic transmission means is provided, the magnet body can be magnetized in two poles in the axial direction, so that the magnetized yoke structure is simplified, the durability is enhanced, and the yield of magnet production is improved. To increase the number of pulses, it is only necessary to increase the number of magnetic transmission means, and the number of magnet poles is minimized, so that the magnetic force can be strengthened. Accuracy can be improved.

According to the second aspect of the present invention, the thrust washer is made smaller in diameter than the rotating magnet and the bearing metal to apply magnetic braking between the rotating magnet and the bearing metal. In addition to the effects described above, a braking magnet is not required, the number of parts is reduced, the assembling workability is improved, and the cost can be reduced.

According to the third aspect of the present invention, since the magnetic permeable means is constituted by a through hole, in addition to the effect of the first or second aspect of the present invention, a through hole is formed in the magnetic cover. Thus, any number of magnetic transmission means can be easily formed.

According to the fourth aspect of the present invention, the magnetic permeable means is constituted by a notch. In addition to the effect of the first or second aspect, the notch is formed in the magnetic material cover. Any number of magnetic transmission means can be easily formed.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional side view showing an embodiment of a vehicle speed sensor of the present invention.

FIGS. 2A and 2B show details of a rotating magnet applied to the vehicle speed sensor of FIG. 1, wherein FIG. 2A is a longitudinal side view and FIG. 2B is a plan view.

FIG. 3 is a plan view showing another modification of the magnetic material cover of the rotating magnet applied to the vehicle speed sensor of FIG. 1;

FIG. 4 is a longitudinal sectional side view of a conventional vehicle speed sensor.

FIG. 5 shows a conventional rotating magnet portion.
(A) is a plan view, (b) is a longitudinal sectional side view.

[Explanation of symbols]

 2 Bearing metal 3 Drive shaft 4 Rotating magnet 4a Magnet body 4b Magnetic cover 5 Thrust washer 7a Magnetoelectric conversion element 8 Through hole (magnetic transmission means) 9b Notch (magnetic transmission means)

Claims (4)

[Claims] 1. A vehicle speed sensor having a rotating magnet that rotates to face a magnetoelectric conversion element, wherein the rotating magnet includes a magnet main body and a magnetic body cover attached to a surface of the magnet main body, A vehicle speed sensor, wherein the magnet main body is magnetized in two poles in the front and back directions, and the magnetic body cover is provided with a plurality of magnetic transmission means along a circumferential direction. 2. A thrust washer is provided between a bearing metal for supporting a drive shaft of the rotating magnet and the rotating magnet, and the thrust washer is smaller in diameter than the rotating magnet and the bearing metal. 2. The vehicle speed sensor according to claim 1, wherein magnetic braking is applied between the bearing metals. 3. The vehicle speed sensor according to claim 1, wherein the magnetic transmission unit is formed by a through hole. 4. The vehicle speed sensor according to claim 1, wherein the magnetic transmission unit is formed by a notch.