Patent ID: 7259695
Filing Date: 2007-08-21
Classification: H03M

Abstract:
1. A capacitive-type displacement sensing device for determining a relative rotational position between two members along a measuring axis direction, the displacement sensing device comprising: a transmitter member having a first transmitter member surface, the transmitter member comprising at least a first transmitter element configuration comprising at least two transmitter electrode elements, at least some of the transmitter electrode elements located on the first transmitter member surface; a receiver member having a first receiver member surface, the receiver member comprising at least a first receiver element configuration comprising at least one receiver electrode element, at least some of the receiver electrode elements located on the first receiver member surface, the first receiver element configuration fixed relative to the first transmitter element configuration and capacitively coupled to the first transmitter element configuration across an operating gap located between the first receiver element configuration and the first transmitter element configuration; at least a first scale member, the first scale member comprising at least a first capacitive-coupling modulation pattern, the first capacitive-coupling modulation pattern located in the operating gap located between the first receiver element configuration and the first transmitter element configuration, the first capacitive-coupling modulation pattern movable along a rotational direction relative to the first transmitter element configuration and the first receiver element configuration to modulate the capacitive coupling between the first transmitter element configuration and the first receiver element configuration, and the first capacitive-coupling modulation pattern capacitively coupled to the first transmitter element configuration to provide a first modulator-transmitter capacitive coupling configuration; a primary member configured to be coupled to and rotate with an input shaft; and a gear-reduction configuration providing at least a first level of gear-reduction between the rotation of the primary member and the rotation of the first scale member, wherein: the at least two transmitter electrode elements of the first transmitter element configuration are respectively operable to provide respective time-varying transmitter voltage signals during a measurement period; the at least one receiver electrode element of the first receiver element configuration is respectively operable to provide at least one respective receiver signal at least during at least one time during the measurement period, the at least one respective receiver signal varying in a manner that depends on the relative rotational position between the first capacitive-coupling modulation pattern and the first transmitter element configuration along the rotational direction; the first scale member is driven such that one rotation of the first scale member corresponds to a plurality of a rotations of primary member according to the first level of gear-reduction; and the elements of the gear reduction configuration that provide at least the first level of gear reduction are located entirely between the plane of the first transmitter member surface and the plane of the first receiver member surface.