Rotation angle detecting device
View Patent ↗A rotation angle detecting device includes a housing, a rotating shaft rotatably held by the housing, a driving gear fixed to the rotating shaft, a driven gear engaged with the driving gear, a magnetic field generating part fixed in the driven gear, having a permanent magnet, and configured to generate a magnetic field, a magnetic sensor element configured to detect a change in the magnetic field due to a rotational movement of the magnetic field generating part, and a signal processor configured to process a signal from the magnetic sensor element for detecting a rotation angle of the rotating shaft. Each of teeth of the driving gear has a first circumferential width, each of teeth of the driven gear has a second circumferential width, and the second circumferential width is greater than the first circumferential width.
1. A rotation angle detecting device comprising:
a housing;
a rotating shaft rotatably held by the housing;
a driving gear having a plurality of teeth and fixed to the rotating shaft;
a driven gear having a plurality of teeth and engaged with the driving gear;
a magnetic field generating part fixed in the driven gear, having a permanent magnet, and configured to generate a magnetic field;
a magnetic sensor element configured to detect a change in the magnetic field due to a rotational movement of the magnetic field generating part;
a signal processor configured to process a signal from the magnetic sensor element for detecting a rotation angle of the rotating shaft, and
a screw receiver held by the housing and screwed with the driven gear, wherein:
each of the teeth of the driving gear has a first circumferential width on an addendum circle that connects radial-outside surfaces of the teeth of the driving gear;
each of the teeth of the driven gear has a second circumferential width on an addendum circle that connects radial-outside surfaces of the teeth of the driven gear;
the second circumferential width is greater than the first circumferential width;
the screw receiver has a female screw surface;
each of the radial-outside surfaces of the teeth of the driven gear has a male screw surface screwed with the female screw surface; and
the rotating shaft is a steering shaft of a vehicle.
2. The rotation angle detecting device according to claim 1 , wherein:
the magnetic field generating part is configured to generate the magnetic field on an axis of the driven gear;
the magnetic sensor element is located on the axis of the driven gear and is fixed to the housing;
the driven gear is rotatably moved by the driving gear and is moved in an axial direction of the driven gear biased by the screw receiver; and
the signal processor detects a rotation angle of the rotating shaft over 360 degrees based on a change in the magnetic field in a direction perpendicular to the axial direction due to the rotational movement of the magnetic field generating part and a change in a strength of the magnetic field due to a movement of the driven gear in the axial direction.
3. The rotation angle detecting device according to claim 1 , wherein the second circumferential width is from two times to three times greater than the first ircumferential width.