Patent ID: 7420363
Filing Date: 2008-09-02
Classification: G01D

Abstract:
1. A rotation angle detection apparatus for deriving a current value of shaft rotation angle of a rotary shaft within a range which exceeds 360°, said apparatus comprising: a housing having said rotary shaft rotatably mounted therein, a magnet fixedly attached to said rotary shaft, a first magnetic sensor and a second magnetic sensor respectively fixedly mounted with respect to said housing and each located on an axis of rotation of said rotary shaft, for producing respective sensor signals varying in accordance with levels of magnetic flux flowing in directions at right angles to one another and at right angles to said axis of rotation, and signal processing circuitry for processing said sensor signals; said signal processing circuitry being configured to: derive a current value of said first calculation amount and a current value of a second calculation amount based on respective values of said first sensor signal and second sensor signal, with said first calculation amount varying monotonically in a predetermined relationship to said shaft rotation angle throughout said range of values of said shaft rotation angle, said second calculation amount varying periodically between a minimum to a maximum value in accordance with successive increase of said shaft rotation angle, and with a predetermined integral number of variation periods of said second calculation amount occurring within a range of 360° variation in said shaft rotation angle, and obtain said current value of the shaft rotation angle by a calculation utilizing said current values of the first calculation amount and second calculation amount.