Miniature electrical drive and magnetic return path element, and method for its production

• US 20090015093A1
• Filed: 07/15/2008
• Published: 01/15/2009
• Est. Priority Date: 07/13/2007
• Status: Active Grant

• Current Assignee: Dr. Fritz Faulhaber GmbH & Co.
• Original Assignee: Dr. Fritz Faulhaber GmbH & Co.
• Inventors: Teufel, Jurgen, Reutter, Kornelius
• Granted Patent: US 8,143,760 B2
• Time in Patent Office: Days
• US Class Current: 310/254.100
• CPC Class Codes: H02K 1/187 to inner stators
• CPC Class Codes: H02K 15/028 for fastening to casing or support, respectively to shaft or hub
• CPC Class Codes: H02K 5/04 Casings or enclosures characterised by the shape, form or construction thereof
• CPC Class Codes: Y10T 29/49009 Dynamoelectric machine

Abstract

The present invention relates to a miniature electrical drive (1), in particular a rotating field drive with permanent magnet excitation, having a stator (2) and a soft-magnetic return path element (6) which cylindrically surrounds the stator (2) and has a multiplicity of sheet-metal laminates (22) which are in the form of annular disks and are arranged in layers to form a cylindrical laminated core (20). The sheet-metal laminates (22) in the laminated core (20) are held prestressed exclusively with a force fit and in an interlocking manner in the axial and radial directions, and without adhesive or integral joint means such as this, in a supporting sleeve (24) which coaxially surrounds said sheet-metal laminates (22).

Claims

1. Miniature electrical drive (1), in particular a rotating field drive with permanent magnet excitation, having a stator (2) and a soft-magnetic return path element (6) which cylindrically surrounds the stator (2) and has a multiplicity of sheet-metal laminates (22) which are in the form of annular disks and are arranged in layers to form a cylindrical laminated core (20), characterized in that the sheet-metal laminates (22) in the laminated core (20) are held prestressed with a force fit exclusively in the radial direction, and are held axially prestressed in an interlocking manner in the axial direction, and without adhesive or integral joint means such as this, in a supporting sleeve (24) which coaxially surrounds said sheet-metal laminates (22).

2. Miniature drive according to claim 1, characterized in that the sheet-metal laminates (22) in the laminated core (20) make touching contact with the supporting sleeve (24) in the area of their external circumference just at least three, and in particular six, contact points (26) which are distributed around the circumference, and are therefore held at least with a force fit.

3. Miniature drive according to claim 1, characterized in that the supporting sleeve (24) has embossed areas (28), which are shaped radially inwards, in order to hold the laminated core (20).

4. Miniature drive according to one of claim 1, characterized in that the supporting sleeve (24) is formed from a thin stainless-steel sheet.

5. Miniature drive according to claim 1, characterized in that the sheet-metal laminates (22) are composed of magnetic sheet steel, preferably with each individual sheet-metal laminate (22) in its own right having an insulating coating.

6. Miniature drive according to claim 2, characterized in that the circumferential contact points (26) of the laminated core (20) are formed by at least three, and preferably six, longitudinal beads (30) on the supporting sleeve (24), which longitudinal beads (30) project like ribs pointing radially inwards and run in particular parallel to the axis, at least over the entire axial length of the laminated core (20), with the inner surface, located between the longitudinal beads (30), of the supporting sleeve (24) forming a clearance fit with the laminated core (20), and with the longitudinal beads (30) of said supporting sleeve (24) forming an interference fit with the laminated core (20).

7. Miniature drive according to claim 1, characterized in that the layered sheet-metal laminates (22) of the laminated core (20) are held axially between holding embossed areas (32) on the supporting sleeve (24), which are arranged distributed around the circumference on each axial face and project radially inwards.

8. Miniature drive according to claim 1, characterized in that the supporting sleeve (24) is stamped as a blank (34) from an originally flat sheet-metal material and is formed into its cylindrical shape, with two mutually adjacent longitudinal edges (36a, 36b) in the circumferential direction being connected via interlocking elements (38a, 38b) which engage in one another.

9. Miniature drive according to claim 8, characterized in that the longitudinal edges (36a, 36b) are in addition integrally connected at least at points, in particular by means of spot welds, to the interlocking elements (38a, 38b) which engage in one another.

10. Miniature drive according to claim 1, characterized in that an end frame (18a, 18b) is mounted on both axial faces of the supporting sleeve (24), to be precise preferably by a holding section on each end frame (18a, 18b) engaging axially in the supporting sleeve (24) and being attached by means of holding embossed areas (44) which are arranged distributed over the circumference, project radially inwards and each engage behind a holding edge on the end frame.

11. Miniature drive according to claim 10, characterized in that the end frames (18a, 18b) are centered by means of the longitudinal beads (30).

12. Miniature drive according to claim 10, characterized in that the end frames (18a, 18b) are fitted with a rotating bearing arrangement (16a, 16b) for a rotor shaft (14) of a rotor (4) which is arranged within the stator (2).

14. Magnetic return path element according to claim 13, characterized by the characterizing features of at least one of claims 2 to 12.

13. Soft-magnetic return path element (6) for a miniature drive (1), comprising a multiplicity of sheet-metal laminates (22) which are in the form of annular disks and are arranged in layers to form a cylindrical laminated core (20), characterized in that the sheet-metal laminates (22) are held prestressed with a force fit exclusively in the radial direction, and are held axially prestressed in an interlocking manner in the axial direction, and without adhesive or integral joint means such as this, in a supporting sleeve (24) which surrounds the laminated core (20).

15. Method for production of a magnetic return path element (6) for a miniature electrical drive (1), characterized in that a multiplicity of individual sheet-metal laminates (22) which are in the form of annular disks are arranged in layers to form a cylindrical laminated core (20) and, in order to hold them, are inserted into a supporting sleeve (24) such that the sheet-metal laminates (22) are held prestressed with a force fit exclusively in the radial direction, and are held axially prestressed in an interlocking manner in the axial direction, and without adhesive or integral joint means such as this.

16. Method according to claim 15, characterized by the following method steps:

a) a flat blank (34) for the supporting sleeve (24) is stamped out from a sheet-metal material, in particular from a stainless-steel sheet,

b) the flat blank (34) is provided with all the necessary embossed areas (28), to be precise with the longitudinal beads (30) and the holding embossed areas (32, 44) for the laminated core (20) and preferably for the end frames (18a, 18b),

c) the holding embossed areas (32, 44) are deformed back onto the plane of the flat blank (34) with the exception of those holding embossed areas (32) which are provided on an axial face in order to make contact with the laminated core (20),

d) the flat blank (34) is formed into the cylindrical shape of the supporting sleeve (24), with two longitudinal edges (36a, 36b) being connected via the interlocking elements (38a, 38b) which engage in one another, and preferably via additional spot welds,

e) a cylindrical laminated core (20) is formed by stacking one on top of the other a multiplicity of sheet-metal laminates (22) which have previously been stamped out individually in the form of annular disks and have preferably been individually coated with insulation,

f) the sheet-metal laminates (22) are pressed together with a specific pressure force,

g) the laminated core (20) is inserted axially into the supporting sleeve (24) in the compressed state, with the pressure force applied, of the sheet-metal laminates (22) and with a force-fitting contact with the longitudinal beads (30) until axial contact is made with the holding embossed areas (32),

h) the holding embossed areas (32) are once again stamped in radially on the other axial face of the laminated core (20),

i) the axial pressure force is released from the sheet-metal laminates (22), with the laminated core (20) making contact in an interlocking manner between the holding embossed areas (32) that are provided axially on both sides, by axial elastic expansion while maintaining axial prestressing.