Proximity sensor

The present invention relates to a proximity sensor of induction type for detecting the approach of a metal object or the like in a contactless fashion, through a magnetic field, or in particular to a proximity sensor and modules used for theproximity sensor realized in a wealth of production lines while reducing the production cost.

The basic component elements of a proximity sensor include a detection coil assembly having a coil and a core, an oscillation circuit unit, an output circuit unit and an outer shell case for accommodating these elements. In order to meet theusers' demand for a wide range of product specifications in versatile way, the makers are required to reduce the cost by concentrating the basic component parts as far as possible.

With regard to the magnetic circuit, for example, the cost reduction by the concentration of component parts poses the following problems in respect of the characteristics and structure of the detection coil assembly.

The proximity sensor of induction type has a detection coil assembly responsive to the approach of a metal. This detection coil assembly includes a coil and a ferrite core. The approach of a metal is detected utilizing the change in thecharacteristic of the detection coil assembly. The body case (outer shell case) of the proximity sensor is formed of any of various materials including brass, stainless steel and resin due to the variety of the operating environments. The detectionperformance of the proximity sensor changes also with the outer diameter of the detection coil assembly. For this reason, many variations of the detection coil assembly of cylindrical type having different outer diameters are prepared including M8(about 8 mm in outer diameter), M12 (about 12 mm in outer diameter) and M30 (about 30 mm in outer diameter).