Inductive sensor for shock absorber
An inductor sensor assembly for determining to position of object includes a layer of ferrite overlaying exciting and receiving coils formed on a substrate. A magnet attached to the target produces a virtual coupler in an area of ferrite overlaying the coils. An application for a shock absorber includes a sensor module mounted in a recess in a dust cover and a magnet mounted to a cylinder tube of the shock absorber.
1. An inductive sensor assembly for determining a position of a target on an object, the inductive sensor assembly comprising:
a substrate having at least one transmitting coil and at least one receiving coil mounted to the substrate;
a resonator connected to the at least one transmitting coil;
a processing module connected to the at least one receiving coil, the processing module measuring eddy currents produced in the receiving coil;
a layer of ferrite having magnetic permeability greater than 10 covering the at least one transmitting coil and the at least one receiving coil;
a magnet mounted to a movable object spaced apart from the layer of ferrite, the magnet producing a magnetic field acting on an area of the ferrite layer to inductively couple the at least one transmitting coil with the at least one receiving coil in a region adjacent the area.
2. The sensor assembly of claim 1 , wherein the substrate is a printed wiring board having a top surface.
3. The sensor assembly of claim 1 , wherein the layer of ferrite has one side having an adhesive.
4. The sensor assembly of claim 2 , wherein the layer of ferrite is mounted to the top surface of the printed wiring board.
5. The sensor assembly of claim 1 , wherein the layer of ferrite is flexible.
6. The sensor assembly of claim 1 , wherein the object is formed of aluminum non-magnetic material.
7. A sensor assembly for sensing a position of a shock absorber, the sensor assembly comprising:
a housing;
a sensor module mounted to the housing, the module having at least one transmitting coil and at least one receiving coil, the module further having a layer of ferrite covering the at least one transmitting coil and at least one receiving coil;
a magnet mounted to the shock absorber, the magnet spaced apart from the ferrite layer, the magnet having a magnetic field action on the ferrite layer to inductively couple the at least one transmitting coil to the at least one receiving coil to produce a signal indicative of the position of the magnet and object relative to the housing.
8. The sensor assembly of claim 7 , wherein the housing has a generally circular cross section defining a center cavity.
9. The sensor assembly of claim 7 , wherein the housing has a recess for housing the sensor module.
10. The sensor assembly of claim 7 , wherein the shock absorber has an aluminum tube movable with respect to a rod.
11. The sensor assembly of claim 7 , wherein the sensor module includes a connector.
12. The sensor assembly of claim 7 , wherein the sensor module includes a printed wire board and a printed wire assembly.
13. The sensor assembly of claim 12 , wherein the printed wire assembly includes a resonator.
14. The sensor assembly of claim 13 , wherein the printed wire board includes at least one exciting coil and at least one receiving coil.