Electricity: measuring and testing – Magnetic – Displacement
Patent
1994-07-08
1996-02-20
O'Shea, Sandra L.
Electricity: measuring and testing
Magnetic
Displacement
324173, 324262, 32420712, G01B 730, G01P 3488
Patent
active
054932173
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention is based on an inductive sensor with an electric coil. In commonly used sensors, the surrounding injection molding compound is injected directly onto the region of the current conductor on which the ends of the windings of the coil are wound. Owing to the different expansion coefficients between the injection molding compound and the copper wire, a relative movement takes place between these two materials. Since the coil wire is constantly exposed to alternating load during changes in temperature, a fatigue fracture may occur in extreme cases. This results in a complete failure of the inductive sensor.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an inductive sensor with an electrical coil of the above-mentioned type which does not have the above-mentioned disadvantages.
According to the invention, the inductive sensor comprises a housing; a coil body and at least one coil arranged on the coil body, the coil body with the at least one coil being located inside the housing and the at least one coil including a winding having winding end portions; current conductors having conductor end portions and arranged in the housing, the conductor end portions electrically contacting the winding end portions of the windings in a contact region inside the housing; a permanently elastic material enclosing the contact region between the conductor end portions and winding end portions; and a circumferential element made of a temperature-resistant material and enclosing the contact region between the conductor end portions of the current conductors and the winding end portions of the windings of the at least one coil.
The inductive sensor, according to the invention, has the advantage over the prior art that the contacting end portions of the current conductors are embedded in a permanently elastic material and are protected from the surrounding injection molding compound by a temperature-resistent circumferential element. This creates an open space within the injection molded housing for the alternating load of the coil wire. The coil wire can expand freely. The temperature change cycles can also be quadrupled. In this way, an inductive sensor is obtained which can withstand high loads and has a long useful life.
The permanently elastic material is advantageously gel-like or gelatinous. Silicone is particularly preferred for this material.
The circumferential element is advantageously an adhesive tape that surrounds or covers the region where electrical contact between the winding end portions and the current conductors occurs. A polyimide strip or tape is particular preferred for this circumferential element, however it can also be an adhesive tape. The circumferential element can also be a thin sleeve of heat-resistant material.
BRIEF DESCRIPTION OF THE DRAWING
An embodiment example of the invention is shown in the drawing and described more fully in the following description. The drawing shows a cross-sectional view of a sensor according to the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
In the drawing, a housing of a speed sensor 11 manufactured by an injection molding process is designated by 10. An elongated coil body 13 with a coil 14 having a winding is inserted in the housing 10. The winding of the coil 14 is connected electrically to two current conductors 15 (arranged one behind the other in the drawing). The upwardly projecting free ends of the current conductors 15 are contacted by, e.g. welded with, the two contacts 16 of a connector plug 17 for taking off signals. The conductor end portions 115 of the current conductors 15 on the coil end are bent and project away from the coil 14. However, the resulting bend of the current conductors 15 is as close as possible to the coil bounding portion 20 of the coil body 13. By coil bounding portion is meant the two bounding end pieces for the coil 14 which are included in the coil body 13. The respective winding end portions 114 of the coil 14 are fastened to the conductor end p
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patent: 4680543 (1987-07-01), Kohen
patent: 4847557 (1989-07-01), Saito et al.
patent: 5039942 (1991-08-01), Buchschmid et al.
patent: 5121056 (1992-06-01), Onishi et al.
patent: 5278496 (1994-01-01), Dickmeyer et al.
Katzenwadel Uwe
Stahl Ulrich
Edmonds Warren S.
O'Shea Sandra L.
Robert & Bosch GmbH
Striker Michael J.
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