Sensor for detecting magnetic powders in a lubricant

1. A sensor for sensing reduction of electric resistance between a first electrode and at least one second electrode, a magnetic field being applied between the first electrode and said at least one second electrode to accumulate magnetic powder floating in a lubricant between the first electrode and said at least one second electrode,

wherein the first electrode comprises a magnet producing the magnetic field;

wherein at least one sensing region in which the magnetic powder is to be accumulated is provided in at least a part of a region between the first electrode and said at least one second electrode, and

wherein the magnetic powder is inhibited from being accumulated in a non-sensing region constituted by a space around the first electrode and said at least one second electrode other than the at least one sensing region.

2. The sensor of claim 1 ,

wherein at least one gap is provided between the first electrode and the at least one second electrode, and

wherein the at least one gap includes the at least one sensing region to which the magnetic field is applied.

3. The sensor of claim 2 , further comprising a magnet producing the magnetic field.

4. The sensor of claim 1 , further comprising a covering member that covers the first electrode and said at least one second electrode to inhibit the magnetic powder from being accumulated in the non-sensing region.

5. The sensor of claim 1 , wherein an entire periphery of the magnet is covered with a magnet covering member.

6. The sensor of claim 1 , wherein the magnetic field is selectively applied to the at least one sensing region.

7. The sensor of claim 1 , wherein the at least one sensing region comprises a plurality of sensing regions.

8. The sensor of claim 7 , wherein the plurality of sensing regions comprise a first sensing region and a second sensing region,

wherein the first sensing region is provided adjacent to an N-pole of the magnet, and

wherein the second sensing region is provided adjacent to an S-pole of the magnet.

9. The sensor of claim 7 , wherein the at least one second electrode comprises a plurality of second electrodes,

wherein the at least one gap comprises a plurality of gaps provided between the first electrode and each of the plurality of second electrodes, and

wherein each of the plurality of gaps includes one of the plurality of sensing regions.

10. The sensor of claim 9 , wherein the plurality of sensing regions have different gap lengths.

11. The sensor of claim 7 , further comprising a plurality of pairs of the first and second electrodes,

wherein the plurality of pairs of the first and second electrodes have different gap lengths.

12. The sensor of claim 1 , wherein a narrow recess is provided in an outer periphery of the sensor, and

wherein the at least one sensing region is provided deep in the recess.

13. The sensor of claim 1 , further comprising a filter member disposed between the at least one sensing region and an outer space, the filter member blocking foreign matter having a large particle diameter.

14. The sensor of claim 1 , wherein the sensor is configured such that magnetic flux is prevented from leaking out of the at least one sensing region.

15. The sensor of claim 14 , wherein the at least one sensing region is interposed between a first plane formed on the first electrode and a second plane formed on the at least one second electrode and opposed in parallel to the first plane, and

wherein the magnetic flux intersects the first plane and the second plane perpendicularly in the at least one sensing region.