Electric starter motor with holder for permanent magnets

Details Electric starter motor with holder for permanent magnets Electric starter motor with holder for permanent magnets

1982-08-11

1984-04-24

Miller, J. D.

Electrical generator or motor structure

Dynamoelectric

Rotary

310 42, H02K 1500, H02K 2126

Patent

active

044450605

DESCRIPTION:

BRIEF SUMMARY
The invention relates to an electric motor, and more particularly to a motor suitable as a starter for an internal combustion engine.


BACKGROUND

An electric motor is already known in which two pairs of permanent magnets are received in a housing in such a manner that two adjacent magnets lie on one long side similar to a spring-and-groove connection, while the arms of a yielding holder element rest on the other long side of the two adjacent magnets. The holder element, protruding beyond either end of the permanent magnets, has flaps formed thereon in the circumferential direction, which are bent over the ends of each of two adjacent magnets. The magnets are more or less firmly clamped into place between the flaps; this does not permit any compensation for manufacturing tolerances in the length of the magnets, and may result in damage to the permanent magnets. The holder parts also protrude beyond the flap resting on one end of the permanent magnets and terminate in a holder section having lateral slits for receiving the brush holder of the electric motor. The motor requires special means on the housing for longitudinally securing the permanent magnets in the housing. The connection of the brush holder with the holder parts for the permanent magnets is not sufficiently vibration-resistant for the rough operation conditions existing in motor vehicles.


THE INVENTION

It is an object to provide a holding arrangement for field permanent magnets of a motor, typically a starter motor for an automotive-type internal combustion engine, which is reliable, simple, and contributes to ease of assembly of the starter motor structure.
Briefly, the magnets are part-cylindrical elements fitted against the inside of a cylindrical shell of the motor. To position the magnets in place, a plurality of elongated strip-like holder elements are fitted between the arched part-cylindrical magnets, resiliently engaging neighboring side walls of respective neighboring permanent magnet elements. The strip-elements have a spacer portion which is supported at one end against an end cap or end bell of the motor. Oppositely directed springy flaps project from the strip-like elements and engage against the end faces of the magnets. The other end faces of the magnets are retained in position by projecting elements, for example projecting from a bearing support structure, or a transverse plate across the cylindrical housing shell of the motor. If the motor is a starter motor, the transverse plate may hold an intermediate bearing.
Preferably, the strip-like elements include elongated plastic portions which have a central opening. The central opening is used to guide tension bolts which hold the end caps or end bells of the motor, or motor-and-starter gear assembly, together.
The electric motor has the advantage that the holder parts of the permanent magnets simultaneously fix the magnets both in the longitudinal and circumferential direction in the housing. The magnets are no longer clamped firmly between rigid flaps of the holder parts but instead are yieldingly supported, and thus compensate for tolerances, on the parts which close the ends of the housing; the permanent magnets are securely held in place during rough motor vehicle operating conditions independently of the effects of temperature or acceleration and vibration.
It is particularly advantageous to make at least the holder parts of elastic plastic material, through which the fastening elements are guided, with which the bearing cap and the drive bearings are secured to the housing of the electric motor.
The tension bolts which hold the entire motor structure together, typically, are made of steel. Since the permanent magnet structures used for fields of starter motors have substantial magnetic force, it is difficult to thread steel rods between the magnets. Use of plastic holder parts has the additional advantage that the plastic holder elements will function as guide sleeves for the tension bolts, insuring placement of the tension bolts between the magnets, and permitting ea

REFERENCES:
patent: 2971107 (1961-02-01), Jin
patent: 3258622 (1966-06-01), Gillespie
patent: 3790830 (1974-02-01), Bonfiglio
patent: 4071794 (1978-01-01), Schoen
patent: 4219752 (1980-08-01), Katou

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