Rotor magnet and brushless motor

By setting specific thicknesses and shapes on the cylindrical portion and ribs of the rotor magnet, the problem of increased injection pressure during injection molding is solved, which improves productivity and reduces costs, while improving product quality.

CN120077552AActive Publication Date: 2025-05-30MABUCHI MOTOR CO LTD
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Patent Information

Application Number
CN202380076313.2
Authority / Receiving Office
CN · China
Patent Type
Applications(China)
Current Assignee / Owner
Filing Date
2023-05-15
Publication Date
2025-05-30
Estimated Expiration
2043-05-15

AI Technical Summary

Technical Problem

During the injection molding process, thin-walled rotor magnets are difficult to form, resulting in increased injection pressure, decreased productivity and increased cost.

Method used

By providing a specific thickness and shape on the cylindrical portion and rib portion of the rotor magnet, the injection pressure is reduced, and the number of rotor magnets that can be produced by a one-piece filling process is increased.

Benefits of technology

It realizes reducing injection pressure, improving productivity and reducing costs, while preventing the occurrence of poor forming and improving product quality.

✦ Generated by Eureka AI based on patent content.

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Abstract

The disclosed rotor magnet (2) is provided so as to be rotatable with respect to a substrate (8) to which a stator (5) or a rotation angle sensor (9) is fixed, is disposed so as to face the stator (5) or the rotation angle sensor (9), and is formed by injection molding a mixed material of a magnetic body and a resin through a pin gate (42). The rotor magnet (2) is provided with: a cylindrical part (21) which is formed in a cylindrical shape and on which a plurality of magnetic poles are arranged; and a rib (22) formed in a shape protruding in the radial direction at an axial end portion of the cylindrical portion (21). The thickness (T1) of the cylindrical part (21) is smaller than the inner diameter (D0) of the front end part of the pin-point gate (42), and the thickness (T2) of the rib (22) is larger than the inner diameter (D0) of the front end part of the pin-point gate (42).
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Claims

1. A rotor magnet is configured to be rotatable relative to a substrate to which a stator or a rotational angle sensor is fixed, and is disposed opposite to the stator or the rotational angle sensor. The rotor magnet is formed by injection molding a mixed material of a magnetic material and a resin through a pin point gate. Characterized in that: The rotor magnet includes: A cylindrical portion formed in a cylindrical shape and having a plurality of magnetic poles arranged thereon; and Ribs formed in a shape protruding radially at an axial end of the cylindrical portion. The thickness of the cylindrical portion is a dimension smaller than the inner diameter of the front end portion of the pin point gate. The thickness of the ribs is a dimension equal to or greater than the inner diameter of the front end portion of the pin point gate.

2. The rotor magnet according to claim 1, Characterized in that: The rotor magnet includes a trace portion that bulges on the axial end surface of the ribs, i.e., the rib end surface, as a trace of the injection molding of the rotor magnet, and is formed in a substantially circular shape corresponding to the inner diameter of the front end portion of the pin point gate. The thickness of the cylindrical portion is a dimension smaller than the outer diameter of the trace portion. The thickness of the ribs is a dimension equal to or greater than the outer diameter of the trace portion.

3. The rotor magnet according to claim 2, Characterized in that: The axial end surface of the cylindrical portion, i.e., the cylindrical portion end surface, has a shape protruding toward the substrate side in the axial direction compared to the rib end surface. And the step size between the rib end surface and the cylindrical portion end surface is equal to or greater than the height dimension of the trace portion.

4. The rotor magnet according to claim 1, Characterized in that: When viewed axially of the rotor magnet, the ribs are arranged so as to avoid the boundaries of the plurality of magnetic poles.

5. The rotor magnet according to claim 4, Characterized in that: When viewed axially of the rotor magnet, the ribs are arranged at the center of any of the magnetic poles.

6. The rotor magnet according to claim 5, Characterized in that: The rotor magnet is a magnetically anisotropic ring magnet.

7. A brushless motor includes a stator, a rotor magnet disposed opposite to the stator in the radial direction, and a rotor housing that holds the rotor magnet. The rotor magnet is formed by injection molding a mixed material of a magnetic material and a resin through a pin point gate. Characterized in that: The rotor magnet has a cylindrical portion formed in a cylindrical shape and having a plurality of magnetic poles arranged thereon, and ribs formed in a shape protruding radially at an axial end of the cylindrical portion and engaging with the rotor housing. The thickness of the cylindrical portion is a dimension smaller than the inner diameter of the front end portion of the pin point gate. The thickness of the ribs is a dimension equal to or greater than the inner diameter of the front end portion of the pin point gate.

Citation Information

Patent Citations

  • plastic magnet rotor

    JP1994002976U

  • Motor magnet, and motor

    JP2010273497A

  • Brushless motor and manufacturing method of rotor for brushless motor

    JP2015204638A

  • Magnet rotor, electric motor comprising the same, and method of manufacturing the same

    JP2016135043A