Electrical generator or motor structure – Dynamoelectric – Rotary
Patent
1987-07-01
1988-05-31
Budd, Mark O.
Electrical generator or motor structure
Dynamoelectric
Rotary
310254, H02K 2126
Patent
active
047483580
DESCRIPTION:
BRIEF SUMMARY
PRIOR ART
The invention is based on an electric machine, particularly for starting devices of internal combustion engines, which includes a cylindrical housing and, within the housing a plurality of arcuate permanent magnets each having a convex side in contact with the inner wall of the housing, an opposite concave side, two opposite longitudinal sides and front sides, and a plurality of magnetic flux conducting pieces arranged, respectively, in contact with a longitudinal side of assigned permanent magnets. An electric machine in which the permanent magnets are held in a housing by means of retaining springs is already known. The retaining springs are arranged between two adjacent permanent magnets in each instance and have resilliently contacting spring arms as well as fastening means at one front face of the permanent magnets in order to hold the permanent magnets in the correct position in the housing. By means of the deliberately produced dome effect, no additional fastening of the permanent magnets in the housing are required in this known arrangement. If in a known electric machine the permanent magnets are provided with magnetic flux conducting pieces, then radial forces act on the flux conducting pieces in the direction toward the armature, which radial forces are so great that the retaining springs must be additionally fastened in the housing with at least one rivet in order to hold the permanent magnets and flux conducting pieces in fixed position in the housing. Such a fastening of the permanent magnets with the assigned flux conducting pieces has the disadvantage that it requires numerous fastening parts in the form of retaining springs and rivets and, when taken with high assembly costs, is no longer economical.
SUMMARY OF THE INVENTION
The object of the invention is to provide an electric machine of the type named in the beginning in which the permanent magnets, together with the flux conducting pieces, can be securely, but detachably, arranged and fastened in the housing at low cost with simple means.
In keeping with this object and others which will become apparent hereafter, one feature of this invention resides in the provision of resilient retaining means for fastening the permanent magnets and conducting pieces in fixed, circumferential and longitudinal positions in the housing, the retaining means consisting of two facing rings each having a flangelike edge part matching the inner diameter of the housing and engaging assigned front sides of the permanent magnets and conducting pieces, a cylindrical part projecting at right angles from the edge part to contact assigned end portions of the concave sides of the permanent magnets and the conducting pieces, the edge parts being provided with retaining projections for engaging end portions of free longitudinal sides of respective permanent magnets and conducting pieces and the edge part of at least one of the rings being provided with axially directed projections for detacheably fastening the one ring to the inner wall of the housing. Preferably, at least one catch projection is formed on the inner wall of the housing, and at least one axially directed projection of the one ring can snap engage at the catch projection. At the other ring, there is provided at least one resilient projection, which is bent outwardly over the edge part of the other ring to engage an intermediate bearing or drive bearing arranged at an end side of the housing.
It is advantageous that only two retaining rings, which can be used regardless of the respective magnet length and clockwise or counterclockwise rotation of the electric machine, are required in order to securely hold the permanent magnets with the assigned flux conducting pieces. Moreover, the retaining rings make it possible to fix the permanent magnets and flux conducting pieces in a form-locking manner and to preassemble the magnet group. Moreover, the retaining rings form a mechanical protection for the magnets when.
Advantageous developments of the electric machine indicated in the main claim ar
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patent: 4580072 (1986-04-01), Morishita
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Kleindieck Peter
Kropp Manfred
Ruhle Walter
Zimmermann Kurt
Budd Mark O.
Robert & Bosch GmbH
Striker Michael J.
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