Power steering apparatus

A power steering apparatus comprising:

• a steering mechanism arranged to steer a steered wheel in accordance with an operation of a steering wheel;
• an electric motor arranged to provide a steering force to the steering mechanism;
• a sensor housing provided to the steering mechanism, and including a first gear supporting portion and a second gear supporting portion which are formed within the sensor housing;
• a first gear which is rotatably held on the first gear supporting portion, which includes a plurality of first tooth portions integrally formed on an outer circumference side, and a first magnetic member in which an N pole and an S pole are magnetized around a rotation axis that is a center, and which is arranged to be rotated in accordance with a rotation of the steering wheel;
• a first sensed portion which is provided to the first gear, and which is arranged to permit sensing of a position of one of the N pole and the S pole that are magnetized in the first magnetic member, by a sensing device;
• a second gear which is rotatably held on the second gear supporting portion, which includes a plurality of second tooth portions integrally formed on an outer circumference side, and arranged to be directly or indirectly engaged with the first tooth portions, which includes a second magnetic member in which an N pole and an S pole are magnetized around a rotation axis that is a center, and which is arranged to be rotated in accordance with the rotation of the first gear;
• a second sensed portion which is provided to the second gear, which is arranged to permit sensing of a position of one of the N pole and the S pole that are magnetized in the second magnetic member, by a sensing device, and which is in a predetermined position relationship with the first sensed portion in an initial state where the first gear and the second gear are received on the gear supporting portions;
• a first detector arranged to sense a rotation angle of the first gear based on a variation of a magnetic field generated by the first magnetic member;
• a second detector arranged to sense a rotation angle of the second gear based on a variation of a magnetic field generated by the second magnetic member;
• an absolute steering angle calculating circuit configured to calculate an absolute steering angle of the steering wheel from an neutral position of the steering wheel at which the steered wheel directs in a straight direction, by a combination between the rotation angle of the first gear and the rotation angle of the second gear;
• and
• a control section configured to drive and control the electric motor based on the absolute steering angle.

A power steering apparatus comprising:

• a steering mechanism arranged to steer a steered wheel in accordance with an operation of a steering wheel;
• an electric motor arranged to provide a steering force to the steering mechanism;
• a sensor housing provided to the steering mechanism, and including a first gear supporting portion and a second gear supporting portion which are formed within the sensor housing;
• a first gear which is rotatably held on the first gear supporting portion, which includes a plurality of first tooth portions integrally formed on an outer circumference side, and a first magnetic member in which an N pole and an S pole are magnetized around a rotation axis that is a center, and which is arranged to be rotated in accordance with a rotation of the steering wheel;
• a second gear which is rotatably held on the second gear supporting portion, which includes a plurality of second tooth portions integrally formed on an outer circumference side, and arranged to be directly or indirectly engaged with the first tooth portions, which includes a second magnetic member in which an N pole and an S pole are magnetized around a rotation axis that is a center, and which is arranged to be rotated in accordance with the rotation of the first gear;
• a first detector arranged to sense a rotation angle of the first gear based on a variation of a magnetic field generated by the first magnetic member;
• a second detector arranged to sense a rotation angle of the second gear based on a variation of a magnetic field generated by the second magnetic member;
• a storage circuit configured to store a correction value for correcting an output of the first detector or an output of the second detector;
• a correction value abnormality sensing circuit configured to sense an abnormality of the correction value;
• and
• an absolute steering angle calculating circuit configured to calculate an absolute steering angle of the steering wheel from an neutral position of the steering wheel at which the steered wheel directs in a straight direction, based on the output of the first detector, the output of the second detector, and the correction value when the abnormality of the correction value is not sensed,
• the first gear and the second gear being disposed, respectively, on the gear supporting portions so that a direction of a magnetic pole of the first magnetic member and a direction of a magnetic pole of the second magnetic member are in a predetermined position relationship, and
• the absolute steering angle calculating circuit being configured to calculate the absolute steering angle based on the output of the first detector and the output of the second detector when the correction value abnormality sensing circuit senses the abnormality.