DISPLACEMENT SENSOR HAVING A RETURN CORE IN A HOUSING CAVITY
A displacement sensor for sensing a distance, including an excitation coil for exciting an electromagnetic alternating field, a receiver device for inductively receiving the electromagnetic alternating field and for outputting an output signal which is dependent on the received electromagnetic alternating field. The receiver device has a functional core which is surrounded by at least one receiving coil, and a return core. The return core is designed to shield the functional core from an external electromagnetic field, and the receiver device has a housing with a cavity in which the return core is arranged.
1 . A displacement sensor for sensing a distance, comprising:
an excitation coil for exciting an electromagnetic alternating field, and
a receiver device for inductively receiving the electromagnetic alternating field and for outputting an output signal which is dependent on the received electromagnetic alternating field,
wherein the receiver device has a functional core which is surrounded by at least one receiving coil, and a return core, wherein the return core is designed to shield the functional core from an external electromagnetic field, and wherein the receiver device has a housing with a cavity in which the return core is arranged.
2 . The displacement sensor as claimed in claim 1 , wherein at least one holding element for holding the return core is arranged in the cavity or on a cover of the cavity, the return core being fastened to said holding element at a distance from one or more walls of the cavity.
3 . The displacement sensor as claimed in claim 1 , wherein the housing is formed by an injection molding compound which lies against the functional core and envelops the latter.
4 . The displacement sensor as claimed in claim 3 , wherein the injection molding compound comprises a thermosetting material.
5 . The displacement sensor as claimed in claim 3 , wherein the functional core comprises an amorphous, magnetostriction-free, alloy.
6 . The displacement sensor as claimed in claim 1 , wherein the return core contains or is composed of a crystalline alloy.
7 . The displacement sensor as claimed in claim 1 , wherein the displacement sensor is designed to use an inductive coupling between the excitation coil and the receiver device to sense the distance covered by an encoder, wherein the encoder influences the inductive coupling depending on the distance by local magnetic saturation of the functional core.
8 . The displacement sensor as claimed in claim 1 , further comprising a circuit on a wiring carrier for receiving the output signal from the receiver device.
9 . A method for producing a displacement sensor as claimed in claim 1 , comprising:
providing the functional core and the return core,
enveloping the functional core with the housing,
winding the excitation coil and the receiving coil around that part of the housing which contains the functional core,
introducing the cavity ( 86 ) into the housing outside that part of the housing around which the excitation coil and the receiving coil are wound, and
inserting the return core ( 77 ) into the cavity ( 86 ) of the housing.
10 . The method as claimed in claim 9 , wherein the housing is formed by injection molding or transfer molding, wherein the cavity ( 86 ) is introduced into the housing by a molding tool.
11 . The method as claimed in claim 9 , further comprising overmolding the functional core ( 76 ) at least partially with a protective compound ( 64 ) to form the housing.
12 . The method as claimed in claim 9 , further comprising connecting the receiving coil ( 5 ) to electrical connections ( 74 ) for outputting the output signal.
13 . The displacement sensor as claimed in claim 2 , wherein the housing is formed by an injection molding compound which lies against the functional core and envelops the latter.
14 . The displacement sensor as claimed in claim 4 , wherein the functional core comprises an amorphous, magnetostriction-free, alloy.
15 . The method as claimed in claim 10 , further comprising overmolding the functional core at least partially with a protective compound to form the housing.