Magnetic rotational position sensor

摘要

A rotational position sensor having a compact and simple structure, in which a magnetic surface can be formed to have a more accurate shape, and an electronically controlled throttle device for an internal combustion engine, which employs the rotational position sensor. The rotational position sensor comprises a pair of substantially half disk-shaped magnetic cores (1, 2) disposed in an opposed relation to each other with a magnetic sensitive device interposed therebetween, a pair of substantially arc-shaped magnetic cores (41-47, 51-57) disposed in an opposed relation to each other along outer peripheries of the half disk-shaped magnetic cores (1, 2), and a permanent magnet (21, 22) fixed in contact with at least one of the arc-shaped magnetic cores (41-47, 51-57). Magnetic flux generating from the permanent magnet flows successively through one of the arc-shaped magnetic cores (41-47, 51-57), the half disk-shaped magnetic cores (1, 2), and the other of the arc-shaped magnetic cores (1, 2), followed by returning to the permanent magnet (21, 22). The half disk-shaped magnetic cores (1, 2) or the permanent magnet (21, 22) is rotatable, and the magnetic sensitive device detects an amount of the magnetic flux varying with rotation of the half disk-shaped magnetic cores (1, 2) or the permanent magnet (21, 22).