Patent ID: 8922204

Claim:
A fail detecting device for a rotation angle sensor, comprising: a cam with a continuously formed cam surface having an actuating surface for reciprocating a push rod and a non-actuating surface that does not reciprocate the push rod, an angle sensor formed of an endless rotary potentiometer for detecting a rotation angle of the cam and having an output voltage increasing in proportion to the rotational angle in a range of 360 degrees, and a controller for detecting a fail state of the angle sensor, said cam is configured to be driven to rotate in one direction by an electric motor controlled by the controller and to reciprocate the push rod; the output voltage of the angle sensor detects: a first region equal to or lower than a first predetermined voltage from 0 degrees to an angle θ 1 , and a second region equal to or higher than a second predetermined voltage higher than the first predetermined voltage from 360 degrees to an angle θ 2 , said first and second regions being recognized as a dead zone; the controller is configured to drive the rotation of the cam to a predetermined position in the non-actuating surface at a constant speed in transition of the cam surface of the cam abutting against the push rod from a side of the actuating surface to a side of the non-actuating surface; and the angle sensor is configured wherein the dead zone is disposed at a position in the non-actuating surface of the cam and in an area in front of the predetermined position.