Sensor magnet device, gear mechanism and speed reducing electric motor
AssigneeAsmo Co., Ltd.
InventorsMasumi Tsuchida, Akio Oshiro
Life of this patent
Estimating the term…
Abstract
In a speed reducing electric motor, a speed reducing gear unit has a sensor magnet device, which is fixed to a worm wheel and includes an inner ring magnet, an outer ring magnet and connecting portions. The inner ring magnet is placed along a predetermined first imaginary circle. The outer ring magnet is placed along a predetermined second imaginary circle, which is coaxial with the first imaginary circle and has a diameter that is smaller or larger than that of the first imaginary circle. The connecting portions connect between the inner ring magnet and the outer ring magnet. The sensor magnet device is fixed to the worm wheel by a magnet fixing structure.
Claims14
A gear mechanism comprising:
- a gear that transmits rotation to an output shaft;
- a sensor magnet device that is placed at one axial end side of the gear, wherein the sensor magnet device includes
- at least one primary magnet portion that includes a magnetic material and is magnetized to have a predetermined magnetizing pattern, wherein the at least one primary magnet portion is placed along a predetermined first imaginary circle, a center of which coincides with a rotational axis of the gear,
- at least one secondary magnet portion that includes a magnetic material and is magnetized to have a predetermined magnetizing pattern, which is different from the predetermined magnetizing pattern of the at least one primary magnet portion in a circumferential direction, wherein the at least one secondary magnet portion is placed along a predetermined second imaginary circle, which is coaxial with the first imaginary circle along a common axis that is coaxial with the rotational axis of the gear and has a diameter that is smaller or larger than that of the first imaginary circle, and the at least one secondary magnet portion and the at least one primary magnet portion are arranged at different radial distances from the common axis, and
- at least one connecting portion that is formed integrally with and connects between the at least one primary magnet portion and the at least one secondary magnet portion, wherein
- the sensor magnet device is formed such that an external magnet sensor outputs a signal corresponding to a rotational state of the output shaft based upon a sensing by the external magnet sensor of at least one of the at least one primary magnet portion and the at least one secondary magnet portion;
- and
- a fixing means for fixing the sensor magnet device to the gear at the at least one connecting portion.
Dependencies are inferred from the claim text.