Electricity: measuring and testing – Electrical speed measuring – Including speed-related frequency generator
Reexamination Certificate
2001-07-27
2003-04-01
Lefkowitz, Edward (Department: 2862)
Electricity: measuring and testing
Electrical speed measuring
Including speed-related frequency generator
C324S207250, C384S448000
Reexamination Certificate
active
06541958
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATION
This application is based upon Japanese Patent Application No. 2000-231651, filed on Jul. 31, 2000, the contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a rotation detecting device which electromagnetically detects the rotating state of a rotating body to be detected, by the use of a rotor in accordance with the rotation of the rotating body to be detected.
2. Description of Related Art
There has been conventionally known a rotation detecting device, as disclosed in Japanese Patent Laid-Open No. Hei 9-196948, which electromagnetically detects the state of rotation of a rotating body to be detected, on the basis of a rotor rotating in accordance with the rotation of the rotating body to be detected.
The rotation detecting device is for detecting the rotation of a rotor having a number of alternately arranged portions of different magnetic reluctance. This device has a sensor body comprising such components as a core and a permanent magnet forming a closed magnetic circuit including a part of the rotor in a part of a magnetic circuit, an electromagnetic coil which converts a change of magnetic flux quantity in the closed magnetic circuit to an alternating current, and a spool wound with the electromagnetic coil.
The sensor body is integrally formed by injection-molding each of these components and a terminal as an output terminal of the sensor after installation of each component (the core, the permanent magnet, and the spool wound with magnetic coil).
In forming the sensor body, however, the electromagnetic coil contacts a high-temperature and high-pressure resin during a secondary molding (injection molding) process, and therefore there arises such a problem that the electromagnetic coil may be damaged. That is, the electromagnetic coil may be broken by the resin pressure and the fluid pressure during the injection molding. Furthermore, after the secondary molding, the magnetic coil repetitively undergoes, with ambient temperature changes, a thermal stress resulting from a difference in the coefficient of linear thermal expansion between resin and copper as a coil material. Particularly, when the rotation detecting device is applied to a vehicle wheel speed sensor used in vehicle brake control, it is conceivable that an excessive stress will be repetitively applied to the electromagnetic coil because of a large change in an ambient temperature.
As methods for solving the above-described problem, the electromagnetic coil is coated with a silicone material or is covered with a soft material. These methods, however, separately require a winding protective material for covering the electromagnetic coil.
Besides, the resin molding process for molding the sensor body is needed at least two times, which will inevitably increase the cost.
SUMMARY OF THE INVENTION
In view of these and other problems associated with the prior art, an object of this invention is to prevent giving damage to the electromagnetic coil even when no winding protective member is needed. Another object of this invention is to provide a sensor structure which is capable of forming the sensor body by a single time of resin molding.
According to first aspect of this invention, the rotation detecting device includes a sensor body and a cover section. The sensor body comprises a magnetic path portion for changing, in response to the rotation of a rotating body to be detected, magnetic reluctance by a rotary switch section in which portions of different magnetic reluctance alternately change; a magnet which produces a magnetic flux in the path of magnetic flux; an electromagnetic coil which generates the electric current in accordance with a change in the magnetic flux in the path of magnetic flux; and an electrical connection portion for connection with the electromagnetic coil. The cover serves as a lid with a bottom face and holds the sensor body. The magnetic flux path, the magnet, and the output terminal are molded in a resin-molded section. The electromagnetic coil is wound in a slot section formed in the outer periphery of the resin-molded section. In a part of arrangement of an electrical connection portion between the electromagnetic coil and the output terminal, a recess is formed in the resin-molded section and the electrical connection portion is exposed out of the resin-molded section.
In the above-described configuration that the electromagnetic coil is wound in the slot section formed in the resin-molded section after molding the magnetic flux path, magnet, and output terminal in the resin-molded section, it is possible to dispense with molding to be performed after winding the electromagnetic coil and accordingly to dispense with the winding protective member without giving damage to the electromagnetic coil.
It is preferable that the magnetic flux path is composed of a first and second cores of a disk shape, thereby allowing the location of the slot section between the first and second cores.
It is preferable that a connector section formed partly projecting is provided in the resin-molded section; the output terminal is provided at the connector section; and in the part of formation of the connector section, a projecting portion projecting in a direction of insertion into the cover in the outer periphery of the resin-molded section is not formed at a portion where the connector section is formed in the resin-molded section, and a recess be formed in this portion.
Thus, the recess is formed at the portion in the part of the resin-molded section where the connector section is formed, it is possible to electrically connect the electromagnetic coil with the output terminal through the recess. Accordingly the components can be integrally formed by a single time of resin molding.
It is preferable that the sensor body is pressed and fixed in the cover. It is possible to thus press into and fix the sensor body to the cover.
It is preferable that the sensor body is pressed into the cover through a metal ring member provided in the outer peripheral portion of the resin-molded section. It is preferable that a flange-shaped portion is formed at the outer periphery of the resin-molded section, and is projecting in the direction of outer periphery of the resin-molded section, and the ring member is disposed in the flange-shaped portion.
It is preferable that a plurality of projections projecting in the direction of outer periphery of the flange-shaped portion are formed in the flange-shaped portion. On the plurality of projections are pressed ring members, thereby reducing the contact surface area of installation of the ring member to allow ring installation with a low pressure as compared with where no projection is formed on the outer periphery of the flange-shaped portion.
It is preferable that a taper portion which has a reduced inside diameter than the portion on the inlet side is provided on the bottom side of the cover. The ring member is pressed in on the bottom side from a position where the taper starts. Forming the taper portion on the bottom side of the cover can easily press the ring member into the cover.
Other objects and features of the present invention will become more readily apparent from a better understanding of the preferred embodiment described below with reference to the following drawings.
REFERENCES:
patent: 5547290 (1996-08-01), Ouchi et al.
patent: 5602335 (1997-02-01), Ouchi
patent: 5760576 (1998-06-01), Ouchi
patent: 5967669 (1999-10-01), Ouchi
patent: 6011388 (2000-01-01), Miyazaki et al.
patent: 6053046 (2000-04-01), Masaki et al.
patent: A-8-248049 (1996-09-01), None
patent: A-9-196948 (1997-07-01), None
patent: 09-311054 (1997-12-01), None
Aurora Reena
Denso Corporation
Law Offices of David G. Posz
Lefkowitz Edward
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