Inductor devices – With supporting and/or spacing means between coil and core – Preformed insulation between coil and core
Reexamination Certificate
2003-06-19
2004-10-05
Nguyen, Tuyen T. (Department: 2832)
Inductor devices
With supporting and/or spacing means between coil and core
Preformed insulation between coil and core
C336S090000, C336S221000, C324S207160
Reexamination Certificate
active
06801113
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a high frequency oscillation type proximity sensor and, more particularly, to a proximity sensor having a feature in that a positioning structure for a coil spool and a core is characteristic. The present invention also relates to an assembling method of the coil spool and the core of the proximity sensor.
2. Description of the Related Art
In a high frequency oscillation type proximity switch, it is necessary to set deviations in detection characteristic, typically represented by the detection distance, between products to a value not more than a specific value. In order to make the deviations in detection characteristic smaller, in most cases, circuit adjustments are carried out by using a variable resistor or the like during the assembling processes of the product; however, by making deviations in the positions of the members on the periphery of the detection coil such as a coil spool, a core and a coil case smaller, it is possible to narrow the adjusting range of the circuit or to eliminate the adjustments of the circuit.
The core is formed by sintering ferrite powder that has been molded, and since the powder shrinks by 10 to 20% during the sintering, it is difficult to improve the dimension precision. Therefore, in the case when positioning is carried out by using a simple fitting structure between the core and the coil spool or between the core and the coil case, since it is necessary to provide a gap-fitting structure with a margin, it is not possible to achieve positioning between members on the periphery of the detection coil with high accuracy. In addition, with respect to the members on the periphery of the detection coil, it is desirable not only to simply provide a positioning process with high accuracy, but also to provide a preferable assembling workability. The following documents relate to the positioning and the assembling workability of the members on the periphery of the detection coil of a proximity switch.
In the proximity switch disclosed in Japanese Unexamined Utility Model Publication No. 64-21939, in order to ensure the mechanical coupling between a bobbin (coil spool) and a core and also to provide an attaching device that achieves excellent workability and makes deformation of the bobbin smaller, an elastic bridge portion is formed on the cylinder portion of the bobbin, and a protrusion that is elastically brought into contact with the center portion of the core is formed at the intermediate portion of the bridge portion. However, in the embodiment shown in the figure, since two-point contacts are made between the protrusion of the bridge portion and the center portion of the core, it is not possible to ensure a coaxial structure between the bobbin and the core, and the bobbin axis tends to tilt from the core axis. Moreover, no consideration is given to the positioning in the axial direction with high accuracy.
With respect to the assembling method for a proximity switch, Japanese Unexamined Utility Model Publication No. 3-99305 has disclosed a method in which the flange face of a coil bobbin is placed on a flat plate and this is covered with a ferrite magnetic core (core), so that the flange face of the coil bobbin and the end face of the ferrite magnetic core are placed onto the same face. In this method, however, it is not possible to ensure the coaxial property between the coil bobbin and the ferrite magnetic core, and the assembling uses a bonding agent that is placed with a volume, and cured, thereby failing to provide a method with high productivity.
In the proximity switch disclosed in Japanese Unexamined Utility Model Publication No. 1-152431, an extended portion that is extended in the diameter direction is formed on the flange of the detection end side of the coil spool, and a step portion that is the same as the thickness of the extended portion is formed on the end face of the core side leg portion (circumferential wall portion); thus, the end face of the detection-end side of the coil spool and the end face of the core side leg portion are positioned on the same face. In this arrangement, however, it is not possible to ensure the coaxial property of the coil spool and the core as well as the coaxial property of the core and the coil case.
In none of the above-mentioned conventional techniques, it is not possible to simultaneously ensure the mutual coaxial property of the core, coil spool and coil case and the positioning in the axial direction thereof with sufficiently high accuracy.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide: a high-frequency oscillation type proximity sensor having small deviations among products in detection property and having excellent assembling workability because of small mutual positional deviations of at least a core and coil spool, more preferably, small mutual positional deviations among members including a coil case in addition to these; a detection end module used therefor; and an assembling method of a coil spool a core used therefor.
A proximity sensor according to the present invention includes: a detection coil; a detection circuit including an oscillation circuit having the detection coil as a resonance circuit element; a coil spool including a hollow cylindrical wire-winding drum around which a lead wire of the detection coil is wound, a detection-side flange provided on a detection side end of the wire-winding drum, and a circuit side flange provided on the detection circuit side end of the wire-winding drum; a core, made of a magnetic member, including a shaft inserted into the wire-winding drum of the coil spool, and a plate-shaped base located between the coil spool and the detection circuit; a cylindrical coil case housing the coil spool and the core and having a bottom on the detection side end; and a main body case, fitted to the coil case, for housing the detection circuit, wherein the wire-winding drum of the coil spool includes protrusions that protrude toward the center from not less than three points distributed in the range exceeding a semi-circle on the circumference of the wire-winding drum and that are elastically brought into contact with a shaft of the core, respectively, thereby coaxially positioning the coil spool and the shaft of the core.
According to the present invention, the elastic contact between the protrusion of the coil spool and the shaft of the core makes it possible to coaxially position the coil spool and the core. It is preferable to position all the coil spool, core and the main body case (or the coil case to be fitted to the main body case) mutually without deviations; however, since the coaxial property of the coil spool and the core gives more influences to the detection property of the proximity sensor rather than to the positional relationship between these and the main body case, even achieving only the coaxial property makes it possible to limit deviations in detection characteristics among the products to a considerably small range. In addition, even combining only the coil spool and the core through an elastic contact makes it possible to achieve the coaxial property, and this position-determined state is maintained even until the time at which it has been finally cured by resin; therefore, it becomes possible to eliminate the coating process of an adhesive agent and the stand-by process for the curing so as to maintain the position-determined state, and consequently to provide a superior assembling workability.
In addition to a proximity switch for outputting a binary signal corresponding to the presence or absence of object detection, the proximity sensor herein includes of which outputs an analog signal corresponding to the intensity of the object detection and a digital signal formed by encoding this signal, and those which outputs the resulting signal obtained by subjecting these to any signal treatment. The intensity of the object detection varies when any of the distance to an object, the size of the object and the material of t
Hatada Mitsuo
Kitajima Koro
Nakazaki Takao
Tsuchida Hiroyuki
Foley & Lardner LLP
Nguyen Tuyen T.
Omron Corporation
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