JP2504506Y2 - Electromagnetic induction type rotation sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an electromagnetic induction type rotation sensor for detecting a rotation speed of a vehicle wheel or the like.

[Conventional technology]

2. Description of the Related Art Conventionally, an electromagnetic induction type sensor has been known as a sensor for detecting a rotation speed of a wheel of an automobile or the like. This electromagnetic induction type rotation sensor integrates a magnet, a magnetic pole and a coil for generating voltage in an outer frame case made of metal, resin, etc., and integrates the magnetic gear as a magnetic rotating body close to the magnetic pole. The unevenness causes a change in the amount of magnetic flux in the magnetic pole portion, thereby generating an AC voltage at both ends of the winding coil. The AC voltage generated in this manner is almost proportional to the rotation speed of the magnetic material gear, and its frequency is exactly proportional to the rotation speed of the magnetic material gear. Can be detected.

FIG. 3 is a sectional view showing a schematic configuration of a conventional electromagnetic induction type rotation sensor. In the figure, 1 is a rotation sensor, 2
Is a magnet, 3 is a magnetic pole, 4 is a coil, 5 is a bobbin, 6 is a housing, 6a is a bracket for mounting a sensor, 7 is an output lead wire, 9 is a potting agent, and a is an outer peripheral portion of a magnetic gear. ing. The magnetic gear is mounted on a drive shaft of a car or the like, and is provided so as to rotate as the wheels rotate.

The magnetic flux generated from the magnet 2 passes through the magnetic pole piece 3, and the amount of the magnetic flux is modulated by the proximity of the unevenness of the outer peripheral portion a of the magnetic body gear provided facing the magnetic pole piece 3. An output voltage is generated at both ends of the coil 4 depending on the rate of change of the amount of magnetic flux with respect to time, and the rotational speed of the magnetic gear, and thus the rotational speed of the wheel, can be detected from the variation frequency of the output voltage.

The detection of the rotational speed of the wheel is important in brake control of the wheel such as antilock, and it is necessary to stably detect the rotational speed of the wheel from low speed to high speed under various road surface conditions. Electromagnetic induction type rotation sensors are often used in automobiles and the like because of their advantages such as being relatively inexpensive and resistant to temperature changes.

In the conventional rotation sensor, a method of joining the housing 6 and the magnetic pole piece 3 by laser beam roasting or the like is adopted so that water or the like does not enter from the gap between the housing 6 and the pole piece 3.

[Problems to be solved by the device]

For example, in FIG. 3, if the front wall of the stainless steel housing is removed and the end of the bobbin 5 is also used as the tip surface of the rotation sensor, the sensor structure is simplified and the economy is excellent. However, since the entire bobbin is not covered by the housing, water and the like enter between the bobbin and the housing, resulting in poor waterproofness. When water or the like enters the sensor and reaches the coil or the terminal, the output voltage of the sensor decreases.

The present invention seeks to provide a sensor structure effective as a solution to this problem.

[Means for solving the problem]

In order to solve the above-mentioned problems, the electromagnetic induction type rotation sensor of the present invention embeds a pole piece and a magnet inside the bobbin, with the tip of the pole piece enclosed in the bobbin near the bobbin end. The housing for housing the bobbin is formed of the same resin as that of the bobbin, and the outer peripheral portion of the collar at the end of the bobbin is joined to the tip of the housing for housing the bobbin.

When a yoke of a magnetic material is installed behind the magnet in contact with the rear surface of the magnet in order to improve the output, it is desirable that at least a part of the yoke is also embedded in the bobbin and integrated with the bobbin.

The pole piece is completely enclosed inside the bobbin, and the outer circumference of the collar at the end of the bobbin is watertightly joined to the housing that houses the bobbin, so there is no interface entrance, so it is possible to prevent water from entering. You can

[Embodiment] FIG. 1 is a sectional view showing a schematic configuration of an embodiment of the present invention. As shown in the figure, the pole piece 3 and the magnet 2 are embedded in the bobbin 5 at the time of forming the bobbin so as to be integrated with the bobbin, and at the same time, the mutual positions are fixed.
There is no gap between the tip of the magnetic pole piece 3 and the bobbin 5 at a position slightly retracted from the end surface 5b of the bobbin, and it is completely enclosed in the bobbin.

The coil 4 is wound around the bobbin 5,
Both ends of this coil 4 are connected to terminals 8 press-fitted into a bobbin. The sensor output signal is taken out through the lead wire 7 through the terminal 8.

On the other hand, the flange 5a at the end of the bobbin 5 has its outer peripheral edge joined to the end 6b of the housing 6 over the entire circumference. The upper opening of the housing is sealed and fixed by a potting agent 9. In this embodiment, the housing 6 and the bobbin 5 are made of nylon reinforced with an inorganic material.

In the present embodiment, as can be seen from the drawing, the portion excluding the tip of the pole piece 3 and the magnet 2 are completely covered by the bobbin 5, and the outer circumference of the collar at the end of the bobbin and the opening of the housing 6 are entirely covered. Since it is joined over the circumference, water or the like does not enter the sensor, and high waterproof airtightness can be secured.

FIG. 2 is a sectional view showing a schematic structure of another embodiment of the present invention. In this case, the yoke 10 is provided at the rear stage of the magnet 2, and the terminal 8 is integrally formed by being inserted into the bobbin in advance when the bobbin 5 is formed. The other structure is almost the same as that of the embodiment shown in FIG. In this embodiment, the bobbin 5 and the housing 6 are PBT.
The materials were molded, and these were joined by resin welding.

Although only the case where the end face of the bobbin forms the end face on the detection side of the sensor is illustrated here, the present invention is not limited to this structure, and the rotary unit has a structure in which water enters from the periphery of the pole piece. It is generally applied to sensors.

〔effect〕

As described above, in the present invention, up to the tip of the pole piece is enclosed inside the bobbin, and the outer periphery of the collar at the end of the bobbin is joined to the tip of the housing. Can be stabilized.

Therefore, the electromagnetic induction type rotation sensor of the present invention is particularly effective when used as a wheel speed sensor or the like which is mounted on a wheel portion of an automobile or the like having a bad environment to detect the rotation speed of the wheel speed.

[Brief description of drawings]

FIG. 1 is a sectional view showing a schematic structure of one embodiment of the electromagnetic induction type rotation sensor of the present invention, FIG. 2 is a sectional view showing a schematic structure of another embodiment, and FIG. 3 is a conventional electromagnetic induction type sensor. It is sectional drawing which shows schematic structure of a rotation sensor. 1 ... rotation sensor, 2 ... magnet, 3 ... magnetic pole, 4 ...
Coil, 5 ... Bobbin, 6 ... Housing, 7 ... Lead wire, 8 ... Terminal, 9 ... Potting agent, 10 ... Yoke.

Claims (2)

(57) [Scope of utility model registration request] Claim: What is claimed is: 1. An electromagnetic device comprising: a magnet contacting a magnetic pole piece and a rear end surface thereof; a coil for generating an AC output according to a change in the magnetic flux amount of the magnetic pole piece; and a bobbin around which the coil is wound. In the induction type rotation sensor, the magnetic pole and the magnet are embedded inside the bobbin such that the tip of the magnetic pole is sealed in the bobbin near the bobbin end, and the outer periphery of the collar at the bobbin end is used for storing the bobbin. An electromagnetic induction type rotation sensor characterized by being joined to the tip of a resin housing. 2. An electromagnetic induction type rotation sensor according to claim 1, wherein a yoke is provided in contact with the rear surface of the magnet and behind the magnet, and at least a part of the yoke is embedded in the bobbin.