Slotless stators and methods for manufacturing such stators

1 . A stator for use in a slotless electric motor, the stator comprising:

a winding body in the form of a hollow cylinder, consisting of three or more coils, and having a working section located between two winding heads at two longitudinal ends of the winding body; and

a cylindrical stator lamination stack, close-fittingly encompassing said working section of the winding body;

wherein said two winding heads consist of the longitudinal ends of the three or more coils;

wherein said two winding heads positively lock the stator lamination stack along a longitudinal axis of the winding body by form-fit;

wherein said two winding heads have the shape of a circular flange with an inner radius (r wh ) essentially or almost equal to an inner radius (r ws ) of the working section of the winding body; and

wherein the two winding heads of the winding body have an outer radius (R wh ) essentially or almost equal to an outer radius (R sls ) of the stator lamination stack.

2 . The stator according to claim 1 ,

wherein a longitudinal front face of the two winding heads facing outward is oriented perpendicular to the longitudinal axis of the winding body.

3 . The stator according to claim 1 ,

wherein the coils forming the winding body are made with multi-strand wire.

4 . The stator according to claim 3 , wherein the multi-strand wire comprises a multi-strand copper wire.

5 . The stator according to claim 1 ,

wherein connecting wires of the different coils protrude in an axial direction in the middle of a longitudinal front face of the winding heads.

6 . The stator according claim 1 ,

wherein the ratio (R wh -r wh )/L wh of the thickness (R wh -r wh ) of a winding head and the axial length L wh of said winding head lies between 0.5 and 1.

7 . The stator according to claim 1 ,

wherein the ratio (R sls -r sls )/L wh of the thickness (R sls -r sls ) of the stator lamination stack and the length L wh of each of the winding heads lies between 0.2 and 0.7.

8 . A slotless electric motor with a stator according to claim 1 and a rotor arranged within the interior compartment of said stator.

9 . The electric motor according to claim 8 , wherein a bearing and/or an encoder element and/or a balancing element of the rotor are positioned at least partially located within a winding head of the stator.

10 . The stator according to claim 1 , wherein the slotless electric motor comprises an electronically commutated motor.

11 . The stator according to claim 1 , wherein the ratio (R sls -r sls )/L wh of the thickness (R sls -r sls ) of the stator lamination stack and the length L wh of each of the winding heads lies between 0.35 and 0.6.

12 . A tool for manufacturing a stator for use in a slotless electric motor, wherein the tool comprises:

a tool body with a central bore and a multitude of hook pins;

wherein said hook pins can be moved between a first, operative configuration and a second, retracted configuration;

wherein in said operative configuration of the hook pins, the inner ends of the hook pins protrude into the central bore of the tool body; and

wherein in said retracted configuration of the hook pins, the inner ends of the hook pins are retracted, such that the distance of the inner ends of the hook pins from the longitudinal axis is larger than in the operative configuration.

13 . The tool according to claim 12 , wherein the slotless electric motor comprises an electronically commutated motor.

14 . A method for manufacturing a stator for use in a slotless electric motor, comprising the steps:

providing a stator lamination stack of the stator, the stator lamination stack having the form of a hollow cylinder with an outer radius (R sls ) and a bore with an inner radius (r sls );

providing a multitude of hook pins on one or both longitudinal ends of said stator lamination stack in a first configuration, the multitude of hook pins protruding toward a longitudinal axis of the stator lamination stack, and the inner ends of said hook pins having a distance from said longitudinal axis that is smaller than the outer radius (R sls ) of the stator lamination;

winding three or more wire coils across the bore of the stator lamination stack, the individual wires inside the bore being oriented essentially parallel to the longitudinal axis, and the individual wires on the longitudinal ends of the coils outside the stator lamination stack being placed on the multitude of hook pins;

moving the multitude of hook pins in a second configuration, in which said multitude of hook pins no longer support the individual wires; and

compressing the wires on the longitudinal ends of the coils outside the stator lamination stack in a toroidally shaped winding head with an inner radius (r wh ) that is essentially equal to the inner radius (r ws ) of the coils inside the stator lamination stack.

15 . The manufacturing method of claim 14 , wherein the compressing step of the wires on the longitudinal ends of the coils outside the stator lamination stack of the stator is carried out with a toroidal press mould formed by a longitudinal front face of the stator lamination stack and one or more tool elements.

16 . The manufacturing method of claim 14 , wherein the wires inside the stator lamination stack of the stator are radially compressed against the inner surface of the stator lamination stack.

17 . The manufacturing method of claim 14 wherein the wires coated with a heat curable prepolymer are used for winding the coils; and wherein after winding the coils and compressing the wires, said prepolymer is heat-cured, to form a mechanically stable winding body of the stator.

18 . The manufacturing method of claim 14 , wherein a manufacturing tool according to claim 10 is applied.

19 . The method according to claim 14 , wherein the slotless electric motor comprises an electronically commutated motor.