Patent Application
20090026874
The invention relates to a method for mounting a laminated armature core onto an armature shaft. Moreover, the invention relates to a laminated armature core for an armature shaft, and an armature shaft with pressed-on laminated armature core for an electric motor.
When pressing a laminated armature core onto an armature shaft, it is known to place the armature shaft into a press-cast mold with the loosely mounted laminated armature core, and to press an electrically-insulating plastic material between the armature shaft and armature laminated core. The method costs time and money, and it cannot be guaranteed to resist thermal expansion during operation of the electric motor in that a rising torque might cause the laminated armature core to rotate with respect to the armature shaft.
Even if armature cores of slightly smaller aperture dimension are pressed onto an armature shaft, a firm seat cannot be ensured for all torques, and also, this method is not proof against process failure, and is dependent on alterations to materials.
Per EP 0 299 100 A1, the armature shaft may be so deformed that it includes detents on its upper surface that engage complimentarily-formed lateral shoulder inclinations around the circumference of the aperture, thus forming a positive fit about the direction of rotation. Such a design is expensive, and it is difficult to mount the laminated armature core on the armature shaft.
In another very expensive method for insulated mounting of a laminated armature core onto an armature shaft per DE 44 32 356 A1, first a tube of deformable, electrically-insulating material is inserted into the aperture of the laminated armature core. Subsequently, the armature shaft prepared to have a slightly larger dimension than the tube is pressed into it, whereby the tube is stretched and forced into recesses of the laminated armature core where applicable.
Starting from these known methods, it is the task of the invention to provide a simple, low-cost, but reliable manufacturing process to mount a laminated armature core onto an armature shaft for an electric motor.
This task is solved by a method with the properties of patent claim 1.
The central aperture of armature cores with at least one projection is provided a dimension such that the armature cores, or a laminated armature core form of them in advance, are not loose, but rather may only be forced onto the armature shaft by pressing the projection into the surface of the plastic of the armature shaft. During this, plastic material is removed, i.e., plastic flakes or chips may be created as a result of compressing and displacing the plastic material by means of the projection or projections when the armature cores are pressed onto the armature shaft. By means of this, however, a positive fit may be simultaneously achieved in a simple fashion along the rotational direction between laminated armature core and armature shaft that may safely withstand the torque forces arising during operation. The excess plastic material thus drops away as a result of gravity upon pressing the armature cores onto the armature shaft, or it is extracted using a suitable partial-vacuum device.
At least two projections, and particularly three projections, are preferably provided that are preferably distributed evenly about the circumference.
It has proved to be particularly useful for the axially-positioned projections to gouge into the plastic to a depth of 0.05-0.4 mm, particularly from 0.1 mm-0.3 mm, and most particularly 0.1-0.25 mm.
Further, it has been shown to be advantageous if the armature cores are first assembled into a packet and then the armature core is pressed onto the armature shaft as a unit. The pressing force thus required is not significantly greater than the force required to press the first armature core onto the armature shaft.
Another subject of the invention is a laminated armature core with the properties of Claim 5.
The apertures in the armature cores (or in a laminated armature core formed of them) in the areas other than the projection(s) possess a diameter that is essentially the same as the outer diameter of the armature shaft; it is preferably very slightly less than the outer diameter of the armature shaft. For an outer diameter of the armature shaft of 5 to 15 mm, particularly from 8 to 12 mm, the diameter of the aperture of the armature cores (outside the projection) is about 5 to 10 μm less than the outer diameter of the armature shaft in order to achieve an even seat for the laminated armature core. Load-relief recesses may also be provided in the armature cores that prevent the arising of excess tension during pressing the armature cores [onto the armature shaft], or during operation of the electric motor, because of thermal expansion.
For an aperture diameter of from 5-15 mm, and preferably 8-12 mm, outside of the minimum of one projection, the laminated armature core is so formed per an advantageous embodiment [of the invention] that at least one projection extends inward radially from a concentric edge section adjacent to the aperture for 0.05-0.4 mm, particularly 0.1-0.3 mm, and most particularly 0.1-0.25 mm.
Further, it has proved to be useful for the projection projecting sharply outward possesses at its radial inner end a curvature radius of maximum 0.4 mm, particularly of maximum 0.3 mm, and most particularly of maximum 0.25 mm.
For this, the thickness of the armature cores is preferably 0.3-0.8 mm, particularly from 0.4-0.7 mm.
Further, protection is claimed for an armature shaft with pressed-on laminated armature core with the properties of Claim 9.
Further properties, details, and advantages of the invention result from the included Dependent Claims, and from the graphic representation and subsequent description of an advantageous embodiment of the invention, which show:
a-3f various views of an armature core.
a through 3f show various views of an armature core 12 formed per the invention.
The concentric edge sections 18 define an inner diameter that in this illustrated case is only a few μm smaller than the outer diameter of the plastic-mantled armature shaft 2.
The projections 20 in the illustrated case with an aperture diameter of 10 mm extend radially inward from the concentric edge sections 18 by 0.15 mm. An inscribed circle 22 that is limited or defined by the projections 20 projecting radially inward possesses an open cross-sectional surface that in the illustrated case is 9.7 mm less in diameter than is the outer diameter of the plastic-mantled armature shaft 2, which is 10 mm.
A recess 24 is provided along with each projection 20 which provides a tension-relief pocket to prevent that peak tension within the material of the armature core 12 occur during manufacture or during operation of the electric motor. They possess no direct relation to the achievement of a firm seat of the armature cores 12 or of a laminated armature core 6 made of them during pressing onto an armature shaft 2.
d shows a perspective view of an armature core 12.
The laminated armature core 6 is then forced onto the armature shaft 2 in an axial direction. During this, the projections 20 projecting sharply outward with curvature radius of 0.2 mm gouge into the surface of the mantle 8 of electrically insulating plastic 10. The outer diameter in the pertinent section 30 of the armature shaft 2 shown in
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP2005/004715 | 4/30/2005 | WO | 00 | 9/26/2007 |
