Miniature motor having a frequency generator

• US 5,070,269 A
• Filed: 01/16/1990
• Issued: 12/03/1991
• Est. Priority Date: 01/21/1989
• Status: Expired due to Term

• Current Assignee: Mabuchi Motor Company Limited
• Original Assignee: Mabuchi Motor Company Limited
• Inventors: Tamaki, Jun, Sata, Nobuyuki
• Primary Examiner(s): Stephan, Steven L.
• Assistant Examiner(s): LaBalle, C.
• Application Number:
  US07/465,459
• Time in Patent Office: 686 Days
• Field of Search: 310/40 MM, 310/67 R, 310/71, 310/89, 310/168, 310/169, 310/170, 310/171, 310/238, 310/239
• US Class Current: 310/171
• CPC Class Codes: G01P 3/465 by using dynamo-electro tachometers or electric generator
• CPC Class Codes: G01P 3/487 delivered by rotating magnets
• CPC Class Codes: H02K 21/38 with rotating flux distributors, and armatures and magnets both stationary
• CPC Class Codes: H02K 7/20 Structural association with auxiliary dynamo-electric machines, e.g. with electric starter motors or exciters

Abstract

A miniature motor having a frequency generator comprising a miniature motor consisting of a stator equipped with a permanent magnet for forming a magnetic field, and a rotor having windings wound on a rotor core, constructed so as to feed electric current to the rotor windings through a commutator which makes sliding contact with current-feeding brushes held by a brush holder fixedly fitted to a small motor case. A frequency generator is provided consisting of a rotor for detecting revolution, a stator disposed in such a manner as to face the rotor, a permanent magnet for forming a magnetic field between the rotor and the stator, and a frequency-detecting coil generating an induced voltage proportional to the revolution of the rotor. The frequency generator is incorporated in the miniature motor, in which the stator of the frequency generator has a cylindrical portion which comes in contact with the inner circumferential surface of the motor housing and a plurality of stator engaging portions, on the open-end edge of the cylindrical portion, for engaging with the open-end edge of the motor housing. The frequency generator stator is fitted to the motor housing in a state where the frequency generator stator cylindrical portion is press-fitted to the motor housing and the stator engaging portions are fitted to the open-end edge of the motor housing, and the brush holder on the small case is provided on the inner circumferential surface of the stator.

Claims

1. A miniature motor and frequency generator assembly, comprising:

a stator equipped with a motor permanent magnet for forming a magnetic field;

a rotor including rotor windings wound on a rotor core, said rotor core being mounted on a shaft for rotation;

a housing part surrounding said stator and said rotor, said housing part including a housing part open end;

a small case supporting part of a frequency generator including a frequency generator permanent magnet and a frequency-detecting coil for receiving changes in magnetic field, said small case also supporting a brush holder with current-feeding brushes;

a frequency generator rotor mounted to said rotor on said shaft, said frequency generator rotor being formed of soft magnetic material including a plurality of magnetic pole serations on an outer periphery thereof;

a frequency generator stator including a cylindrical portion contacting an inner circumferential surface of said motor housing, said frequency generator stator including a plurality of stator engaging portions, formed on an open end of said cylindrical portion, said plurality of stator engaging portions engaging an open-end edge formed on said motor housing, said frequency generator stator being fitted to said motor housing such that said stator cylindrical portion is press fit to said motor housing and said stator engaging portions engage with said motor housing open-end edge with said stator cylindrical portion surrounding a portion of said small case, said frequency generator stator having an inner periphery with a plurality of magnetic-pole serrations disposed facing said frequency generator rotor magnetic-pole serrations, said frequency-detecting coil being positioned adjacent said frequency generator stator for receiving changes in magnetic field between said frequency generator rotor and said frequency generator stator magnetic-pole serrations and generating an induced voltage proportional to rotor revolution, brush holder being provided on an inner circumferential surface of said stator cylindrical portion; and

, a commutator mounted adjacent said rotor for making sliding contact with said current-feeding brushes held by said brush holder, said brush holder being formed in a columnar shape with said frequency detecting coil wound around a columnar portion of said brush holder, said second frequency generator permanent magnet being installed on an inside wall of said small case.

2. A miniature motor having a frequency generator as set forth in claim 1 wherein a shouldered portion is provided on said motor housing open-end edge, and said stator engaging portions engage with said shouldered portion.

3. A miniature motor having a frequency generator as set forth in claim 1 wherein small case notched portions are provided on the outer periphery of said small case, and said frequency generator stator engaging portions and said shouldered portion provided on said motor housing open-end edge engage with each other at positions where said small case notched portions exist.

4. A miniature motor having a frequency generator as set forth in claim 1 wherein said frequency generator stator has notched portion to avoid interference with frequency generator terminals.

5. A miniature motor and frequency generator assembly, comprising:

a first miniature motor sub-assembly including a cylindrical housing with an open-end edge and with an inner circumferential surface, a motor shaft positioned in said housing, a miniature motor stator including a permanent magnet for forming a magnetic field, said permanent magnet being positioned in said housing, a rotor core mounted on said shaft, a rotor including rotor windings wound on said rotor core, a commutator mounted on said shaft, a frequency generator rotor mounted on said shaft adjacent said rotor, said frequency generator rotor being formed of a soft magnetic material and including a plurality of magnetic-pole serrations provided on an outer periphery of said frequency generator rotor;

a second sub-assembly consisting of a frequency generator stator formed as a cylindrical portion having an inner periphery with a plurality of magnetic-pole serrations, said cylindrical portion including an open-end edge with stator engaging means for engaging with said open-end edge of said motor housing and an inner cylindrical surface;

a third miniature motor sub-assembly with a cup-shaped portion for receiving said shaft, said third minature motor sub-assembly including an inner circumferential surface adjacent said cup-shaped portion, a brush holder positioned on said inner circumferential surface for holding current-feeding brushes in contact with said commutator, a frequency generator permanent magnet for forming a magnetic field between said frequency generator rotor magnetic-pole serrations and said frequency generator stator magnetic-pole serrations, said frequency generator permanent magnet being positioned held by said third miniature motor sub-assembly installed on said inner circumferential surface of said third miniature motor sub-assembly, said brush holder being formed in a columnar shape with a column portion, a frequency detecting coil wound on said column portion of said brush holder for generating an induced voltage proportional to rotor revolution, said first, second and third miniature motor sub-assemblies being connected positioned coaxially, with said frequency generator stator cylindrical portion surrounding said third miniature motor sub-assembly and said stator cylindrical portion being press-fit to said motor housing with said stator engaging portions engaging said motor housing open-end edge.