1. Field of the Invention
The present invention relates mainly to an automobile steering apparatus including a power steering apparatus using an electric motor and to a rotational angle detecting apparatus and a torque detecting apparatus therefor.
More particularly, the present invention relates to a rotational angle detecting apparatus wherein one or more targets are provided on a rotating member so that first detecting means outputs a detection signal as the rotating member rotates, second detecting means outputs a detection signal having a phase different from that of the detection signal of the first detecting means, and the rotational angle of the rotating member is detected on the basis of the detection signals outputted by the first detecting means and the second detecting means, to a torque detecting apparatus for detecting torque applied to a first shaft depending on a torsional angle generating in a connecting shaft for connecting the first shaft and a second shaft, and to a steering apparatus for generating a steering-assisting force on the basis of the detection result of the torque detecting apparatus.
2. Description of Related Art
The so called electric power steering apparatus wherein an electric motor is driven to assist steering in an automobile steering apparatus and to reduce a load on the driver is known. This apparatus comprises an input shaft connected to a steering wheel, an output shaft connected to wheels to be steered via a rack and a pinion and a connecting shaft for connecting the input shaft to the output shaft. In the apparatus, a torque detecting apparatus detects steering torque applied to the input shaft depending on a torsional angle generating in the connecting shaft, and a steering-assisting electric motor connected to the output shaft is driven and controlled on the basis of the steering torque detected by the torque detecting apparatus.
The applicant of this application in Japan has proposed, in U.S. Patent Publication No. US-2002-0124663-A1, a rotational angle detecting apparatus wherein one or more targets are provided on a rotating member so that first detecting means outputs a detection signal as the rotating member rotates, second detecting means outputs a detection signal having a phase different from that of the detection signal of the first detecting means, and the rotational angle of the rotating member is detected on the basis of the detection signals outputted by the first detecting means and the second detecting means; a torque detecting apparatus wherein the input shaft and the output shaft thereof are each provided with the rotational angle detecting apparatus, and torque applied to the input shaft is detected depending on a torsional angle generating in a connecting shaft for connecting the input shaft and the output shaft; and a steering apparatus for generating a steering-assisting force on the basis of the detection result of the torque detecting apparatus.
Since the above-mentioned rotational angle detecting apparatus cannot specify which target is detected by each of the detecting means, the apparatus detects only a relative rotational angle. The apparatus is sufficient to detect torque applied to the input shaft. However, the apparatus has a problem of being unable to detect an absolute rotational angle required to control the steering apparatus for generating a steering assisting force.