Torque sensor and motor-driven power steering apparatus using thereof

• US 20040159488A1
• Filed: 02/12/2004
• Published: 08/19/2004
• Est. Priority Date: 07/25/2002
• Status: Abandoned Application

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Yamada, Masamichi, Matsumoto, Masahiro
• Application Number:
  US10/776,257
• Publication Number:
  US 20040159488A1
• Time in Patent Office: Days
• US Class Current: 180/443
• CPC Class Codes: G01L 3/104 involving permanent magnets
• CPC Class Codes: G01L 3/105 involving inductive means G01L3/102, G01L3/104 take precedence
• CPC Class Codes: G01L 3/109 involving measuring phase difference of two signals or pulse trains
• CPC Class Codes: G01L 5/221 to steering wheels, e.g. for power assisted steering

Abstract

A torque sensor includes input and output axes coupled through a torsion bar, magnetic media attached to the input and output axes and having magnetic tracks magnetized at a predetermined pitch and magnetic detection elements disposed opposite to the magnetic media to be sensitive to the magnetic tracks. At least two magnetic tracks for detection of torque are formed with a magnetic phase difference in each of the magnetic media attached to the input and output axes.

Claims

1. A motor-driven power steering apparatus which transmits rotation of a steering wheel to wheels through a rotational axis and detects at least torque of said rotational axis so that a motor for assisting operation of the steering wheel is controlled on the basis of the detected signal, wherein

said detection of said torque is performed by providing a plurality of magnetic tracks each having a phase difference in a plurality of magnetic drums provided in two rotational axes coupled through a torsion bar and by means of a contactless magnetic encoder system.

2. A motor-driven power steering apparatus which transmits rotation of a steering wheel to wheels through a rotational axis and detects at least torque of said rotational axis so that a motor for assisting operation of the steering wheel is controlled on the basis of the detected signal, wherein

said detection of said torque is performed by detecting distortion of said rotational axis and taking out the detected signal by means of electromagnetic induction from a moving coil provided in said rotational axis to at least two fixed coils disposed around said rotational axis.