CN-115371530-B - Magnet unit and method for manufacturing the same

Abstract

A magnet unit includes a tubular holder having a central axis, and a magnet formed in an inner region of a side where one end of the tubular holder is located, wherein the magnet includes a protruding portion at a corner portion where an end surface of the magnet in a central axis direction intersects an outer peripheral surface of the magnet, the outer peripheral surface of the magnet is disposed along the inner peripheral surface of the tubular holder, and the protruding portion protrudes in the central axis direction.

Inventors

• Taketaro Taniguchi
• Usui Kangying
• Hamada and tree
• All build filial regulations
• Great Bridge History

Assignees

• 株式会社大同电子
• 株式会社爱信

Dates

Publication Date

20260508

Application Date

20220518

Priority Date

20210519

Claims (8)

1. 1. A magnet unit comprising: A tubular holder having a central axis, and A magnet formed in an inner region of a side of one end of the tubular holder, Wherein the magnet includes a protruding portion at a corner portion where an end surface of the magnet in a central axis direction intersects an outer peripheral surface of the magnet, the outer peripheral surface of the magnet is disposed along an inner peripheral surface of the tubular holder, and the protruding portion protrudes in the central axis direction, Wherein the protruding portion includes an outer surface extending in the central axis direction and facing outward in a direction perpendicular to the central axis direction in a cross-sectional view along the central axis direction, and the protruding portion contacts the tubular holder only on the outer surface, and Wherein the protruding portion further comprises a tapered inner surface that separates from the central axis as proceeding from the end surface toward the front end of the protruding portion.
2. 2. The magnet unit according to claim 1, wherein the protruding portion has an endless loop shape along an inner peripheral surface of the tubular holder.
3. 3. The magnet unit according to claim 1, wherein the tubular holder includes a groove extending in the direction of the central axis and opening at a side where the other end of the tubular holder is located.
4. 4. The magnet unit according to claim 1, wherein the tubular holder includes a plurality of grooves each extending in the central axis direction and opening at a side where the other end of the tubular holder is located.
5. 5. The magnet unit according to any one of claims 1 to 4, wherein the tubular holder includes a protruding portion that protrudes radially inward from the inner peripheral surface of the magnet at a substantially middle portion in the central axis direction.
6. 6. The magnet unit according to claim 5, wherein the protruding portion has an endless loop shape along an inner peripheral surface of the tubular holder.
7. 7. The magnet unit according to any one of claims 1 to 4, wherein the tubular holder includes a plurality of protruding portions each protruding radially inward from the inner peripheral surface of the magnet at a substantially middle portion in the central axis direction.
8. 8. A method of manufacturing a magnet unit as claimed in claim 1 or 2, the method comprising: Inserting a die into the tubular holder to define a cavity in the tubular holder, and Injecting the material of the magnet into the cavity to obtain a magnet molded body, Wherein the die includes a tapered portion corresponding to the protruding portion of the magnet at a tip corner portion of a portion inserted into the tubular holder.

Description

Magnet unit and method for manufacturing the same Technical Field The present invention relates to a magnet unit for measuring a rotational position of a rotating body or the like, and a method of manufacturing the same. Background Magnetic field detection devices (magnetic sensors) having magnets are widely used for measuring the rotational position of a rotating body or the like. The magnetic field detection device includes a magnet fixed to the rotating body and a magnetic field detector that measures the magnetic field intensity from the magnet fixed to the rotating body. As a method of fixing the magnet to the rotating body, for example, as described in patent document 1 below, a cylindrical, non-magnetic holder (hereinafter, cylindrical holder) is used to fix the magnet to the rotating body. Prior to assembly, the magnets are placed in the interior region of the cylindrical holder. Patent document 1 Japanese patent application No. 2016-153765 Disclosure of Invention The relative position between the magnetic field detector and the magnet fixed to the rotating body is very important to accurately measure the rotational position of the rotating body. In the case where the rotating body is a part of an automobile component, engine vibration or driving vibration may be an external force and stress factor to both the cylindrical holder and the magnet for a long time. Therefore, sufficient strength is required between the cylindrical holder and the magnet to prevent deformation or rattling due to long-term stress. On the other hand, in some cases, it is considered difficult to secure sufficient strength due to requirements such as size limitation, miniaturization, and cost reduction. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a magnet unit that can increase the adhesive strength between a holder and a magnet formed in an inner region of the holder, and a manufacturing method thereof. As a result of intensive studies to solve the above problems, the present inventors have conceived the following. (1) A magnet unit comprising: A tubular holder having a central axis, and A magnet formed in an inner region of a side where one end of the tubular holder is located, Wherein the magnet includes a protruding portion at a corner portion where an end surface of the magnet in the central axis direction intersects an outer peripheral surface of the magnet, the outer peripheral surface of the magnet being disposed along an inner peripheral surface of the tubular holder, and the protruding portion protruding in the central axis direction. According to the magnet unit of this aspect, the contact area between the holder and the magnet can be increased without greatly changing the shapes of the holder and the magnet constituting the magnet unit, and the bonding (bonding) strength between the holder and the magnet can be increased. (2) In the magnet unit defined in (1), the protruding portion may include an outer surface extending in the direction of the central axis and contacting the tubular holder, and a tapered inner surface separated from the central axis as proceeding from the end surface toward the front end of the protruding portion, in a sectional view along the direction of the central axis. This form of protruding portion can be achieved by using a mold having a tapered portion corresponding to the protruding portion, the tapered portion being provided at a tip corner portion of a portion of the mold inserted into the holder during injection molding. The tapered portion also functions as a guide when the mold is inserted into the holder, and interference between the mold and the holder can be prevented to improve manufacturability of the magnet unit during injection molding. (3) In the magnet unit defined in (1) or (2), the protruding portion may have an endless loop shape along an inner peripheral surface of the tubular holder. According to the magnet unit of this aspect, the contact area between the holder and the magnet can be maximized in the circumferential direction. (4) In the magnet unit defined in any one of (1) to (3), the tubular holder may include a groove that extends in the direction of the central axis and that opens at the side where the other end of the tubular holder is located. According to the magnet unit of this aspect, when the rotating body is fitted into the holder, the groove functions as a vent that discharges air in the holder to the outside. (5) In the magnet unit defined in any one of (1) to (3), the tubular holder may include a plurality of grooves each extending in the central axis direction and opening at the side where the other end of the tubular holder is located. According to the magnet unit of this aspect, when the rotating body is fitted into the holder, the groove functions as a vent port that more effectively discharges air in the holder to the outside. (6) In the magnet unit defined in any one