Honda Motor Co., Ltd.

Yukiya Kashimura

Hitoshi Harata

Tomohiro Hoshi

Yuichi Fukuda

Nobuhiko Yoshimoto

Mizuho Doi

Hitoshi Karasawa

Takuya Yamamura

A magnestostrictive torque sensor detects rotating torque applied to a rod-shaped rotating shaft to work around the rotating shaft based on a change in magnetic characteristics of a magnetostrictive film formed on a surface the rotating shaft so as to extend around a full circumference thereof in a circumferential direction. The magnetostrictive film is formed continuously in an axial direction at a portion on the rotating shaft in the axial direction thereof. The magnetostrictive film has on the continuously formed area a first magnetostrictive film portion and a second magnetostrictive film portion having magnetic anisotropies which are opposite to each other and a third magnetostrictive film portion which is formed between the first and second magnetostrictive film portions. A first detection coil, a second detection coil and a third detection coil are provided for the first magnetostrictive film portion, the second magnetostrictive film portion and the third magnetostrictive film portion, respectively.

Magnestostrictive torque sensor and manufacturing method thereof, and electric power steering system

This magnetostrictive torque sensorincludes a rotating shaftused to rotate according to an input torque and provided with magnetostrictive filmsA andB, an excitation coilconfigured to apply an alternating magnetic fieldto the magnetostrictive film, and detection coilsA andB each of which detects a change in the magnetic characteristic of an associated one of the magnetostrictive films. The magnetostrictive torque sensor is configured so that a bias magnetic field is added to the alternating magnetic field from a bias power supplyso as to satisfy the following conditions:H&#x3c;H&#x3c;H; and&#x2212;where H(&#x3e;0) is an applied magnetic field corresponding to a maximum magnetic permeability obtained according to a magnetic hysteresis curveof the magnetostrictive film, which shows magnetization caused by the alternating magnetic field, H(&#x3e;0) is an applied magnetic field corresponding to an end of a range in which a discontinuous magnetization is performed, and H(&#x3e;0) is an applied magnetic field that determines a sensitivity range to be set on a magnetostrictive sensitivity curve representing a magnetostrictive sensitivity exhibited by the magnetostrictive film.

Magnetostrictive torque sensor and electric power steering apparatus

A method for manufacturing a magnetostrictive torque sensor having low nonuniformity of sensitivity characteristics. The residual austenite content in the rotating shaft of the torque sensor is measured first. A magnetic film is subsequently subjected to a heat treatment under heat treatment conditions that are different for each of the measured residual austenite contents, and magnetic anisotropy is imparted.

Method for manufacturing magnetostrictive torque sensor

A magnetostrictive torque sensor includes a rotating shaft that is rotated by an applied torque, magnetostrictive films formed around the entire circumferential periphery of a surface of the rotating shaft in at least one location, sensor coils for sensing a change in impedance of the magnetostrictive films, and a torque calculation unit for calculating the torque applied to the rotating shaft on the basis of a signal relating to the change in impedance outputted from the sensor coils. In this magnetostrictive torque sensor, a width of the magnetostrictive films in the axial direction of the rotating shaft and a width of the sensor coils in the axial direction of the rotating shaft are set so as to fulfill the relationship 1&#x3c;(W/W)&#x3c;1.35.

Magnetostrictive torque sensor and electrically powered steering apparatus using same

A magnetostrictive torque sensor comprising a first magnetostrictive film, a second magnetostrictive film, and a third magnetostrictive film formed over the entire circumferential periphery of a surface of a rotating shaft. A first sensor coil, a second sensor coil, and a third sensor coil for sensing changes in impedance are provided for the first, second, and third magnetostrictive films, respectively. Signals according to the changes in impedance outputted from the first through third sensor coils are inputted to a torque calculating unit. The torque calculating unit calculates the torque applied to the rotating shaft on the basis of the output signal from the first sensor coil and the output signal from the second sensor coil. Furthermore, the output signals from the first through third sensor coils are compared, and failures in the first magnetostrictive film or the second magnetostrictive film are detected by a failure detector.

Growing community of inventors

Haga-machi, Japan

Yukiya Kashimura