Miniature motor with a frequency generator

• US 5,013,946 A
• Filed: 04/26/1989
• Issued: 05/07/1991
• Est. Priority Date: 05/11/1988
• Status: Expired due to Term

• Current Assignee: Mabuchi Motor Company Limited
• Original Assignee: Mabuchi Motor Company Limited
• Inventors: Sata, Nobuyuki
• Primary Examiner(s): Stephan, Steven L.
• Assistant Examiner(s): LABALLE, CLAYTON E
• Application Number:
  US07/343,790
• Time in Patent Office: 741 Days
• Field of Search: 310/40 MM, 310/48, 310/68 B, 310/68 R, 310/111, 310/113, 310/168, 310/169, 310/170, 310/171, 363/170, 363/175, 324/173, 324/174, 324/166
• US Class Current: 310/40.0MM
• CPC Class Codes: G01P 3/48 by measuring frequency of generated current or voltage in general G01R23/00
• CPC Class Codes: H02K 21/38 with rotating flux distributors, and armatures and magnets both stationary
• CPC Class Codes: H02K 23/66 Structural association with auxiliary electric devices influencing the characteristic of, or controlling, the machine, e.g. with impedances or switches
• 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 with a frequency generator comprising a motor portion having a stator with a permanent magnet for forming a magnetic field and a rotor with rotor windings wound on a rotor core; electric current being fed to the rotor windings via a commutator making sliding contact with brushes, and a frequency generator for detecting the revolution of the motor, in which the frequency generator comprises a frequency generator rotor, mounted on the motor rotor, having a disc-like rotor portion made of a soft magnetic material and equipped with a plurality of magnetic-pole teeth on the outer periphery thereof, an internal-gear core of an annular disc shape, made of a soft magnetic material, disposed in such a manner as to come in contact with the inside of a motor housing and face the outer circumferential surface of the rotor portion and equipped with a plurality of magnetic-pole teeth on the inner periphery thereof, a permanent magnet forming a magnetic field between the magnetic-pole teeth of the rotor portion and the magnetic-pole teeth of the inner-gear core, and a frequency generator stator having frequency-detecting coils which detect changes in magnetic flux in a magnetic circuit in which the magnetic fluxes caused by the permanent magnet pass, and generate an induced voltage proportional to the revolution of the rotor portion.

Claims

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

a bell-shaped housing portion;

an end plate portion connected to an open end of said bell-shaped housing;

a first motor shaft bushing connected to said bell-shaped housing;

a second motor shaft bushing connected to said end plate;

a motor shaft supported by said first housing and said second bushing for rotation;

a rotor core support on said rotor shaft;

a stator including a permanent magnet connected to said bell-shaped housing;

said stator being positioned radially outwardly of said rotor core;

rotor windings wound on said rotor core to form a rotor;

a commutator positioned on said rotor shaft within said bell-shaped housing;

brushes supported in said bell-shaped housing extending to engage said commutator by making sliding contact with said commutator;

a disk-shaped frequency generator rotor portion formed of soft magnetic material, said disk-shaped frequency generator rotor including magnetic-pole teeth on an outer periphery thereof;

an annular disk internal-gear core, formed of a soft magnetic material, an outer periphery of said annular-disk internal-gear core being connected to and supported by said bell-shaped housing, said annular-disk internal gear core having an inner periphery defining a plurality of magnetic-pole teeth, said annular-disk internal gear core magnetic-pole teeth being positioned facing said disk-shaped frequency generator rotor magnetic-pole teeth, said annular-disk internal gear core magnetic-pole teeth being spaced away from said disc-shaped frequency generator rotor magnetic-pole teeth to define a gap;

at least one frequency generator stator permanent magnet positioned adjacent said gap, said at least one frequency generator stator permanent magnet being connected to said end plate for defining a magnetic field between said disc-shaped frequency generator rotor and said annular-disc internal gear core magnetic-pole teeth; and

, a frequency generator stator including frequency-detecting coils for detecting the changes in magnetic flux and generating an induced voltage proportional to the revolution of the rotor, said frequency generator is disposed in a space defined by said brushes and said motor housing.

2. A miniature motor and frequency generator arrangement as set forth in claim 1, wherein said disc-shaped frequency generator rotor is disposed between said annular disc internal-gear core and said frequency generator stator permanent magnet.

3. A miniature motor and frequency generator arrangement as set forth in claim 1, wherein said disc-shaped frequency generator rotor magnetic pole teeth are positioned parallel to an axial direction of said shaft.

4. A miniature motor and frequency generator arrangement as set forth in claim 1, wherein said disc-shaped frequency generator rotor magnetic pole teeth and said annular-disc internal-gear core magnetic pole teeth face each other at an angle of 45 degrees.

5. A miniature motor and frequency generator arrangement as set forth in claim 1, wherein said frequency generator stator frequency-detecting coils are wound on the outer periphery of said frequency generator stator permanent magnet.

6. A miniature motor and frequency generator arrangement as set forth in claim 1, wherein said frequency generator stator frequency detecting coils are disposed in a groove formed on an outer periphery of a brush retainer, said brush retainer for retaining brushes and being positioned along an inner circumferential surface of a bell-shaped housing portion.