US-12618731-B2 - Magnetostrictive torque sensor and method for manufacturing magnetostrictive torque sensor

US12618731B2US 12618731 B2US12618731 B2US 12618731B2US-12618731-B2

Abstract

A magnetostrictive torque sensor that is configured to be attached around a rotating shaft exhibiting a magnetostrictive effect and detects torque transmitted by the rotating shaft in a predetermined operating temperature range. The magnetostrictive torque sensor is provided with a molded resin body including a cylinder portion with a hollow cavity in a center through which the rotating shaft is inserted, a flexible substrate that is wrapped around an outer circumference of the cylinder portion of the molded resin body and includes a plurality of detection coils composed of a wiring pattern, a cylindrical magnetic ring that houses the flexible substrate between the magnetic ring and the cylinder portion, and a filler composed of a curable resin filled between the cylinder portion, the flexible substrate, and the magnetic ring. A linear expansion coefficient of the molded resin body is higher than a linear expansion coefficient of the magnetic ring, and the filler is cured in a state in which temperatures of the cylinder portion, the flexible substrate, and the magnetic ring are elevated to higher than an upper limit temperature of the operating temperature range.

Inventors

Takashi Onimoto
Kei Kawano
Akitoshi FUJIMORI

Assignees

PROTERIAL, LTD.

Dates

Publication Date: 20260505
Application Date: 20231222
Priority Date: 20230119

Claims (8)

1 . A magnetostrictive torque sensor that is configured to be attached around a rotating shaft exhibiting a magnetostrictive effect and detects torque transmitted by the rotating shaft in a predetermined operating temperature range, the magnetostrictive torque sensor comprising: a molded resin body comprising a cylinder portion with a hollow cavity in a center through which the rotating shaft is inserted; a flexible substrate that is wrapped around an outer circumference of the cylinder portion of the molded resin body and comprises a plurality of detection coils composed of a wiring pattern; a cylindrical magnetic ring that houses the flexible substrate between the magnetic ring and the cylinder portion; and a filler comprising a curable resin filled between the cylinder portion, the flexible substrate, and the magnetic ring, wherein a linear expansion coefficient of the molded resin body is higher than a linear expansion coefficient of the magnetic ring, and wherein the filler is cured in a state in which temperatures of the cylinder portion, the flexible substrate, and the magnetic ring are elevated to higher than an upper limit temperature of the operating temperature range.
2 . The magnetostrictive torque sensor according to claim 1 , wherein a linear expansion coefficient of the filler is lower than the linear expansion coefficient of the molded resin body and higher than the linear expansion coefficient of the magnetic ring.
3 . The magnetostrictive torque sensor according to claim 1 , wherein the filler comprises a thermosetting resin with a curing temperature higher than the upper limit temperature.
4 . The magnetostrictive torque sensor according to claim 1 , wherein the flexible substrate comprises a band-shaped portion extending in a circumferential direction of the cylinder portion, and both longitudinal ends of the band-shaped portion are fastened with a tape.
5 . The magnetostrictive torque sensor according to claim 1 , wherein the filler comprises a locking portion to stop the magnetic ring from coming off.
6 . A method for manufacturing a magnetostrictive torque sensor that is configured to be attached around a rotating shaft exhibiting a magnetostrictive effect and detects torque transmitted by the rotating shaft in a predetermined operating temperature range, the method comprising: preparing a molded resin body comprising a cylinder portion with a hollow cavity in a center through which the rotating shaft is inserted, a flexible substrate comprising a plurality of detection coils composed of a wiring pattern, and a cylindrical magnetic ring having a lower linear expansion coefficient than the molded resin body; arranging the flexible substrate and the magnetic ring by wrapping the flexible substrate around an outer circumference of the cylinder portion and placing the magnetic ring around the outer circumference of the cylinder portion and the flexible substrate; and curing a filler comprising a curable resin filled between the cylinder portion, the flexible substrate, and the magnetic ring in a state in which temperatures of the cylinder portion, the flexible substrate and the magnetic ring are elevated to higher than an upper limit temperature of an operating temperature range.
7 . The method according to claim 6 , wherein the filler comprises a thermosetting resin with a curing temperature higher than the upper limit temperature, and wherein in the curing, after filling between the cylinder portion, the flexible substrate and the magnetic ring with the filler in liquid form before curing, the filler is cured by raising temperature thereof to higher than the upper limit temperature.
8 . The method according to claim 6 , wherein the flexible substrate comprises a band-shaped portion extending in a circumferential direction of the cylinder portion, and wherein in the arranging, both longitudinal ends of the band-shaped portion of the flexible substrate are fastened with a tape.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS The present application is based on Japanese patent application No. 2023-006852 filed on Jan. 19, 2023, the entire contents of which are incorporated herein by reference. TECHNICAL FIELD The present invention relates to a magnetostrictive torque sensor to detect torque transmitted by a rotating shaft, and a method for manufacturing the same. BACKGROUND OF THE INVENTION Conventionally, magnetostrictive torque sensors are used to detect torque of, e.g., an output rotating shaft of an automobile engine. Magnetostrictive torque sensors are configured to detect torque applied to a rotating shaft based on changes in the inductance of a detection coil placed around the rotating shaft, using the magnetostrictive effect in which the magnetic permeability of the rotating shaft changes due to stress. The present applicant has proposed magnetostrictive torque sensors which have a flexible substrate having plural detection coils formed thereon and placed around a rotating shaft, and detect torque applied to the rotating shaft based on changes in the inductances of the plural detection coils (see Patent Literatures 1 and 2). The torque sensors described in Patent Literatures 1 and 2 have a cylindrical bobbin through which a rotating shaft is inserted at the center thereof, a flexible substrate curved and wrapped around the outer surface of the bobbin, and a cylindrical magnetic ring that covers a periphery of the flexible substrate. The bobbin is made of a non-magnetic material such as resin. The flexible substrate has plural detection coils composed of wiring patterns formed across plural wiring layers. The magnetic ring described in Patent Literature 1 is composed of a magnetic material such as a powder magnetic core or amorphous soft magnetic material. The magnetic ring described in Patent Literature 2 is configured by wrapping an amorphous tape composed of a Fe-based or Co-based amorphous soft magnetic material around the flexible substrate. The magnetic ring serves to reduce the magnetic resistance of a magnetic circuit and suppress a decrease in sensitivity due to leakage of magnetic flux generated by the plural detection coils to the outside. Citation List Patent Literature 1: JP2022-110970A Patent Literature 2: JP2022-117292A SUMMARY OF THE INVENTION Torque sensors installed in automobiles are used in high-temperature environments of, e.g., not less than 100° C. in some cases. If the bobbin thermally expands at a higher rate than the magnetic ring at such high temperatures, the flexible substrate is strongly pressed toward the magnetic ring due to the thermal expansion of the bobbin. If the flexible substrate is pressed, the spaces between the wiring layers in the thickness direction of the flexible substrate are narrowed and this causes changes in capacitance, which may adversely affect torque detection accuracy. Therefore, it is an object of the invention to provide a magnetostrictive torque sensor that has a flexible substrate having plural detection coils formed by wiring patterns and in which the flexible substrate is placed between a cylinder portion of a molded resin body and a magnetic ring located on the outer side and strong pressing of the flexible substrate in a thickness direction when at high temperatures can be suppressed, and a method for manufacturing such a magnetostrictive torque sensor. To solve the problem described above, the invention provides a magnetostrictive torque sensor that is configured to be attached around a rotating shaft exhibiting a magnetostrictive effect and detects torque transmitted by the rotating shaft in a predetermined operating temperature range, the magnetostrictive torque sensor comprising: a molded resin body comprising a cylinder portion with a hollow cavity in a center through which the rotating shaft is inserted;a flexible substrate that is wrapped around an outer circumference of the cylinder portion of the molded resin body and comprises a plurality of detection coils composed of a wiring pattern;a cylindrical magnetic ring that houses the flexible substrate between the magnetic ring and the cylinder portion; anda filler comprising a curable resin filled between the cylinder portion, the flexible substrate, and the magnetic ring,wherein a linear expansion coefficient of the molded resin body is higher than a linear expansion coefficient of the magnetic ring, andwherein the filler is cured in a state in which temperatures of the cylinder portion, the flexible substrate, and the magnetic ring are elevated to higher than an upper limit temperature of the operating temperature range. Advantageous Effects of the Invention According to the magnetostrictive torque sensor and the method for manufacturing the same of the invention, it is possible to suppress strong pressing of the flexible substrate in the thickness direction when at high temperatures. BRIEF DESCRIPTION OF DRAWINGS FIGS. 1A and 1B are perspective views showing a m