US-12625018-B2 - Load sensor

Abstract

A load sensor is provided with a pressure-receiving core made of a magnetostrictive material on which a load to be detected acts, a non-pressure-receiving core made of a magnetic material concentrically arranged with the pressure-receiving core and on which the load to be detected does not act, a detection coil that generates a magnetic flux that passes through the pressure-receiving core by energizing, and a reference coil that, when energized, generates a magnetic flux that does not pass through the pressure-receiving core but passes through the non-pressure-receiving core.

Inventors

• Yuta Sugiyama

Assignees

• PROTERIAL, LTD.

Dates

Publication Date

20260512

Application Date

20231114

Priority Date

20221116

Claims (7)

1. 1 . A load sensor, comprising: a pressure-receiving core made of a magnetostrictive material on which a load to be detected acts; a non-pressure-receiving core made of a magnetic material concentrically arranged with the pressure-receiving core and on which the load to be detected does not act; a detection coil that generates a magnetic flux that passes through the pressure-receiving core by energizing; and a reference coil that, when energized, generates a magnetic flux that does not pass through the pressure-receiving core but passes through the non-pressure-receiving core, wherein at least one of the pressure-receiving core and the non-pressure-receiving core is located between adjacent coils in a radial direction of a plurality of coils constituting the detection coil and the reference coil and has a yoke formed with both magnetic fluxes generated by energizing the adjacent coils respectively.
2. 2 . The load sensor according to claim 1 , wherein a magnetic permeability of the yoke is not less than a magnetic permeability of the pressure-receiving core and the non-pressure-receiving core, except the yoke.
3. 3 . The load sensor according to claim 1 , wherein the load to be detected acts axially on a receiving surface at one end of the pressure-receiving core in the axial direction.
4. 4 . The load sensor according to claim 3 , wherein the receiving surface is located on an opposite side to a mounting object with respect to the non-pressure-receiving core when mounted on the mounting object.
5. 5 . The load sensor according to claim 4 , wherein an axial length of the pressure-receiving core is longer than an axial length of the non-pressure-receiving core.
6. 6 . The load sensor according to claim 1 , wherein the detection coil and the reference coil are covered from at least one side in an axial direction by a shield member having a magnetic shield effect.
7. 7 . The load sensor according to claim 1 , wherein the detection coil comprises a first detection coil and a second detection coil, and the reference coil comprises a first reference coil and a second reference coil, the first detection coil and the first reference coil are connected in series, the second reference coil and the second detection coil are connected in series, the first reference coil and the first detection coil are connected in parallel with the second reference coil and the second detection coil to form a bridge circuit.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS The present application is based on Japanese patent application No. 2022-183120 filed on Nov. 16, 2022, the entire contents of which are incorporated herein by reference. TECHNICAL FIELD The present invention relates to a load sensor. BACKGROUND OF THE INVENTION Patent Literature 1 and Patent Literature 2 disclose a load sensor that uses a magnetostrictive material whose magnetic permeability changes according to the magnitude of an externally applied load, thereby detecting the magnitude of the externally applied load. Each of the load sensors described in Literature 1 and 2 includes a detection shaft portion made of a magnetostrictive material on which a load acts, a reference shaft portion on which no load acts, and a plurality of load-detecting coils wound around the detection shaft portion and the reference shaft portion. In the load sensor described in Patent Literature 1, the detection shaft and reference shaft portions are aligned in the axial direction of the plurality of coils. In the load sensor described in Patent Literature 2, the detection shaft and reference shaft portions are aligned in the direction perpendicular to the axial direction of the plurality of coils. CITATION LIST Patent Literature 1: JP2020-91222APatent Literature 2: JP2020-176879A SUMMARY OF THE INVENTION In the load sensors described in Patent Literature 1 and Patent Literature 2, respectively, they may become larger in the arrangement direction of the detection shaft portion and the reference shaft portion. The present invention was made in view of the aforementioned circumstances, and it is an object to provide a load sensor that can be downsized. For the purpose of solving the above problem, one aspect of the present invention provides a load sensor, comprising: a pressure-receiving core made of a magnetostrictive material on which a load to be detected acts;a non-pressure-receiving core made of a magnetic material concentrically arranged with the pressure-receiving core and on which the load to be detected does not act;a detection coil that generates a magnetic flux that passes through the pressure-receiving core by energizing; anda reference coil that, when energized, generates a magnetic flux that does not pass through the pressure-receiving core but passes through the non-pressure-receiving core. Advantageous Effects of the Invention According to the present invention, it is possible to provide a load sensor that can be downsized. BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a cross-sectional view of a load sensor in the first embodiment of the present invention. FIG. 2 is an enlarged view of an area shown by the double-dotted line in FIG. 1. FIG. 3 is an exploded view of the load sensor in the first embodiment. FIG. 4 is a circuitry diagram of the load sensor in the first embodiment. FIG. 5 is a cross-sectional view of the load sensor in the second embodiment. FIG. 6 is a cross-sectional view of the load sensor in the third embodiment. FIG. 7 is a cross-sectional view of the load sensor in the fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION First Embodiment The first embodiment of the present invention will be described with reference to FIGS. 1 to 4. The embodiments described below are shown as suitable concrete examples for implementing the invention, and although there are parts that specifically illustrate various technically preferred technical matters, the technical scope of the invention is not limited to concrete aspects. FIG. 1 is a cross-sectional view of the load sensor 1 in this embodiment. FIG. 2 is an enlarged view of an area shown by the two-dotted line of FIG. 1. FIG. 3 is an exploded view of the load sensor 1. The load sensor 1 includes a pressure-receiving core 2, first and second non-pressure-receiving cores 3a, 3b, first and second detection coils 51, 52 wound around a detection bobbin 4, and first and second reference coils 71, 72 wound around a reference bobbin 6. The pressure-receiving core 2 is made of a magnetostrictive material and is the core on which the load to be detected (i.e., detection target) acts. The first and second non-pressure-receiving cores 3a, 3b are made of a magnetic material (specifically, soft magnetic material), are concentrically arranged with the pressure-receiving core 2, and are cores on which the load to be detected does not act. The first and second detection coils 51, 52 are coils that generate a magnetic flux φ1 that passes through the pressure-receiving core 2 when energized. The first and second reference coils 71, 72 are coils that, when energized, generate a magnetic flux φ2 that does not pass through the pressure-receiving core 2 but passes through the first and second non-pressure-receiving cores 3a, 3b. The load sensor 1 is provided with, in order from an inner-periphery, the first non-pressure-receiving core 3a, the first and second reference coils 71, 72 wound around the reference bobbin 6, the second non-pressu