Electric motor and radiator fan

Abstract

An electric motor including a rotor rotatably mounted about a rotational axis extending in the axial direction, and a stator including stator teeth widened in a T shape at the tooth-base side to form pole tabs and extending in the circumferential direction. The pole tabs may form a bearing shoulder. A respective stator slot for receiving coils of a stator winding is formed between adjacent stator teeth and a slot opening formed between mutually facing pole tabs. A reinforcing element may be inserted into a slot opening. The reinforcing element are held on mutually facing pole tabs of adjacent stator teeth by the bearing shoulders. The reinforcing element includes a contour that engages a bearing region to reduce a contact area with the bearing shoulders.

Claims

1. An electric motor comprising: a rotor rotatably mounted about a rotational axis extending in an axial direction; and a stator provided with a laminated core, forming a stator yoke, a number of stator teeth extending radially from the stator yoke, and a number of reinforcing elements, wherein each of the stator teeth are T shaped and include a tooth-base side forming pole tabs extending in a circumferential direction defined by the stator, wherein the stator defines a stator slot and a slot opening, wherein the stator slot is disposed between a first stator tooth and a second stator tooth, adjacent to the first stator tooth and configured to receive coils of a stator winding, wherein the slot opening is formed between a first pole tab and a second pole tab facing the first pole tab, wherein the first pole tab forms a first bearing shoulder and the second pole tab forms a second bearing shoulder, wherein a reinforcing element of the number of reinforcing elements includes a narrow side and a wider side, the wider side wider than the narrow side, the narrow side facing the first pole tab and defining a cutout forming a contour, and wherein the reinforcing element is inserted into the slot opening and the contour engages the first bearing shoulder to hold the reinforcing element between the first pole tab and the second pole tab, wherein the contour is configured to minimize a contact area between reinforcing element and the first bearing shoulder.

2. The electric motor of claim 1, wherein the reinforcing elements is coated with a coating configured to increase electrical resistance of the reinforcing element.

3. The electric motor of claim 1, wherein the laminated core is formed by a number of individual laminations each including an annular yoke portion and lamination teeth, wherein the lamination teeth are T-shaped and extend in a radial direction to form lamination tabs extending in the circumferential direction, wherein the stator yoke is formed by the yoke portions of each of the individual laminations, the stator teeth are formed by the lamination teeth, and the pole tabs are formed by the lamination tabs.

4. The electric motor of claim 1, wherein the first pole tab includes a number of slot walls defining a slot facing towards the circumferential direction and extending in the axial direction, and wherein the first bearing shoulder is formed by a wall of one of the slot walls.

5. The electric motor of claim 4, wherein the stator includes a plastic over molding that forms at least one of the slot walls.

6. The electric motor of claim 1, wherein the reinforcing element is rectangular.

7. The electric motor of claim 6, wherein the reinforcing element is formed by a non-magnetic material.

8. The electric motor of claim 7, wherein the reinforcing element is formed by X5CrNi18-10.

9. The electric motor of claim 1, wherein the reinforcing element includes at least one end-face narrow side defining a joining contour configured to engage the first pole tab to form a form fit connection between the first pole tab and the reinforcing element in the axial direction.

10. The electric motor of claim 9, wherein the reinforcing element includes a peg, wherein the peg forms the joining contour.

11. The electric motor of claim 1, wherein the reinforcing element defines at least one through-opening facing the stator slot.

12. A radiator fan for use in a motor vehicle, including the electric motor of one claim 1.

13. The electric motor of claim 1, wherein the reinforcing element defines a longitudinal axis and the reinforcing element is bilaterally symmetric with respect to the longitudinal axis.

14. An electric motor comprising: a rotor configured to rotate about a rotational axis and extending in an axial direction; and a stator circumferentially surrounding the rotor and including, a stator yoke, a first stator tooth and a second stator tooth each radially extending from the stator yoke, wherein a distal end of the first stator tooth forms a first pole tab and a distal end of the second stator tooth forms a second pole tab, adjacent to the first pole tab, wherein the first pole tab defines a bearing shoulder, and a reinforcing element including a narrow side and a wider side, the wider side wider than the narrow side, the narrow side facing the first pole tab and defining a cutout forming a contour that engages the first pole tab, wherein the contour is configured to minimize a contact area between reinforcing element and the bearing shoulder.

15. The electric motor of claim 14, wherein the first pole tab extends in a circumferential direction from the first stator tooth and the second pole tab extends from the second stator tooth in the circumferential direction towards the first pole tab.

16. The electric motor of claim 15, wherein the first pole tab includes first wall and a second wall, wherein the second wall defines a cutout and is disposed closer to the stator yoke than the first wall, and wherein the cutout forms the bearing shoulder.

17. The electric motor of claim 16, wherein the reinforcing element includes a distal end and a peg extending therefrom, wherein the peg forms the contour.

18. The electric motor of claim 16, wherein the stator yoke is formed by a plurality of stamped laminations.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Exemplary embodiments of the invention are explained in more detail below, with reference to a drawing, which shows:

(2) FIG. 1 in an exploded illustration, a radiator fan with an electric motor, which has a rotor designed as an inner rotor, and a stator whereof the stator teeth extend radially to the rotor, wherein the stator teeth are widened at the free-end side to form pole tabs,

(3) FIG. 2a and FIG. 2b in a plan view and in an enlarged detail in a perspective view, the laminated core of the stator, which is formed from a number of individual laminations, wherein the individual laminations each have a yoke portion from which stator teeth, monolithically formed on the yoke portion, extend radially,

(4) FIG. 3 in a perspective view, the stator with the laminated core and with a plastic over molding, wherein a respective reinforcing element for reinforcing the stator is inserted into slot openings formed between the pole tabs and held by bearing shoulders formed by the pole tabs,

(5) FIG. 4 on an enlarged scale, the region IV of FIG. 3, wherein the reinforcing element has a respective joining contour on its transverse sides, which joining contours are formed as pegs and grip the pole tabs axially from behind in the assembled state.

(6) FIG. 5 the stator according to FIG. 4 with the reinforcing elements removed, wherein the stator has a circumferentially open slot in the region of the pole tabs for receiving the reinforcing element,

(7) FIG. 6a and FIG. 6b in a perspective view and in a plan view, the reinforcing element with through-openings incorporated in its broad side, with pegs extending perpendicularly outwards with respect to the transverse side and with longitudinal sides which adjoin these transverse sides and which have a contour for reducing a contact area with the bearing shoulders, and

(8) FIG. 7 a cross-section through the stator, with two further alternative configurations of the reinforcing element which are inserted into the corresponding slot openings, wherein the pole tabs of the stator teeth each serve as a bearing shoulder for the reinforcing elements.

DETAILED DESCRIPTION

(9) As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention that may be embodied in various and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention.

(10) Mutually corresponding parts are denoted by the same reference signs in all figures.

(11) In this case, the rotor and the stator can each be formed as a laminated core, in particular to prevent eddy current losses. For example, WO 2010/145841 A2 discloses an electric motor with a stator, which can be constructed from a laminated core with individual laminations stacked on top of one another. This has a circumferential yoke and an even number of stator teeth, which protrude radially inwards. In this case, every second stator tooth in the circumferential direction is without a winding. The stator teeth supporting a winding furthermore have pole tabs at the inner tooth end, which protrude in the circumferential direction.

(12) During operation of such an electric motor with a stator having a laminated core, a (natural) oscillation of the stator can be excited at certain rotational speeds. In other words, this refers to a resonance. This disadvantageously manifests itself as increased noise development, for example. Furthermore, as a result of these excited oscillations, an additional load and associated wear on the components which are in communication with the stator is increased.

(13) FIG. 1 shows, in an exploded illustration, a radiator fan 1, which may be configured for use in a motor vehicle (not illustrated further), with an electric motor 2, with a rotor 4 and with a stator 6. The rotor 4 is mounted to be rotatable about a rotational axis D by means of an axial pin 8, wherein the rotational axis D extends in an axial direction A. In this case, the axial pin 8 is mounted by means of bearings 10, which are arranged at the end face of the axial pin 8 in each case. In the drawing, the rotor 4 is designed as an inner rotor, i.e. the stator 6 surrounds the rotor 4 externally with respect to a radial direction R extending perpendicularly to the axial direction A. However, in a variant of the electric motor 2 which is not illustrated further, the rotor 4 is designed as an outer rotor. The explanations below apply analogously in this case.

(14) The rotor 4 is in driving communication with a fan impeller 11. On its outer circumference, this latter has air guide vanes 12, which are only illustrated in part for better clarity. The fan impeller 11 has a central cap 13, which is secured to the rotor 4 of the electric motor 2.

(15) A motor mount 14 with flanges 15 for securing the radiator fan is arranged on the end face of the electric motor 2 which is remote from the fan impeller 11. The motor mount 14 furthermore has, on its side remote from the fan impeller 11, an electronics compartment 16 for motor electronics 17, which is covered by an electronics compartment cover 18 in the assembled state.

(16) The stator 6 has a substantially hollow-cylindrical stator yoke 19. From this, the stator teeth 20 thereof extend radially to the rotor 4. In this case, the stator teeth are widened at their free-end side, i.e. at the end facing the rotor 4, in a circumferential direction U with respect to the stator 6, in other words perpendicularly to the axial direction A and perpendicularly to the radial direction R, to form pole tabs 21. The stator teeth 20 therefore form a T shape in a plane perpendicular to the axial direction A, the horizontal T limb of which is formed by the pole tabs 21.

(17) In this case, the stator 6 has a laminated core 22, which is illustrated in FIG. 2a and FIG. 2b, and a plastic over molding 23 (plastic sheath) comprising the laminated core 22. In this case, the stator teeth 20 are not provided with the plastic over molding 23 on the side facing the rotor 4. The widened stator teeth 20 are designed as pole shoes.

(18) In this case, a respective stator slot 24, in which a coil 25 of a stator winding is received, is formed between adjacent stator teeth 20. In this case, the stator winding is energized accordingly by means of connections 26 for generating a rotating field. The slit-like opening, which is formed between the pole tabs 21 and, in the radial direction R, connects the corresponding stator slot 24 to an air gap formed between the rotor 4 and the stator 6, is referred to as slot opening 30 here. In other words, a respective slot opening 30 is formed between mutually facing pole tabs 21.

(19) FIGS. 2a, b show the laminated core 22 of the stator 6. This is formed by a number of individual laminations 32. In this case, each of the individual laminations has an annular yoke portion 34 and lamination teeth 36 formed in one piece, i.e. monolithically, therewith, which extend radially from the yoke portion 34 to the center, in other words towards the inside of the yoke portion 34. On the tooth-base side (free-end side, inner side), the lamination teeth 36 are widened in the circumferential direction U of the stator 6 to form lamination tabs 38, so that the lamination teeth 36 are formed in a T shape. The individual laminations 32 are joined together to form the laminated core 22, wherein the stator yoke 19 is formed from the yoke portions 34 of the individual laminations 32, the stator teeth 20 are formed from the lamination teeth 36 and the pole tabs 21 are formed from the lamination tabs 38.

(20) In FIG. 3, the stator 6 is illustrated with the laminated core 22 and the plastic over molding 23 surrounding the laminated core 22. In this case, a respective reinforcing element 42 is inserted into each of the slot openings 30. In this case, the pole tabs 21 each form a bearing shoulder 43 for the reinforcing elements 42. In other words, these are held on mutually facing pole tabs 21 of adjacent stator teeth 20 in the radial direction R by means of the bearing shoulders 43, wherein the bearing shoulders 43 are formed by the corresponding pole tabs 21. The acoustic properties of the stator 6 are altered as a result of the reinforcing elements 42. As an example, an oscillation excitation of the stator 6 is reduced, a possibly excited oscillation is damped to a comparatively great extent and/or a (natural) frequency of the oscillation of the stator 6 is shifted to a range in which oscillation excitation is not to be expected.

(21) FIGS. 4 and 5 show, in an enlarged detail according to FIG. 3, adjacent stator teeth 20 with the slot opening 30 formed between their pole tabs 21. In this case, the reinforcing element 42 is not illustrated further in FIG. 5 in order to more clearly illustrate the free end with respect to the circumferential direction U of the pole tabs 21. In the free-end-side region of the pole tabs 21, the stator 6 has a slot 44 which is open in the circumferential direction U and extends in the axial direction A. In this case, the slot walls 46 of the slot 44, which extend along the circumferential direction U, each form a bearing shoulder 43 for the reinforcing element 42. In the course of assembling the electric motor 2, the reinforcing elements 42 are each inserted into the corresponding slot 44 so that the reinforcing element 42 is consequently held in the slot opening 30 with form fit in the radial direction R by means of the bearing shoulders 43 formed by the slot walls 46.

(22) To form the slot 44, the laminated stack 22 has, on the pole tabs 21, a notch on the free-end side with respect to the circumferential direction U, on the side facing the stator yoke 19. In this case, that side of the notch of the pole tabs 21 which is opposite the stator yoke 19 forms the slot wall 46 which is closer to the air gap and therefore the corresponding bearing shoulder 43. As illustrated comparatively clearly in FIG. 5, the plastic over molding 23 in this case forms the slot wall 46 which is closer to the stator yoke 19, whilst the slot wall 46 which is closer to the air gap formed between the stator 6 and the rotor 4 is formed by the laminated core of the corresponding stator tooth 20. In this case, the slots 44 are not continuous in the axial direction A. On one of its end sides, the slot has a further slot wall, referred to below as bearing portion 48, which extends in a plane perpendicular to the axial direction A. This establishes a form fit with the reinforcing element 42 to prevent the reinforcing element 42 from being released in the axial direction from the open end face of the slot 44 towards the bearing portion 48.

(23) The planar sides (referred to as broad sides 50) of the reinforcing element 42 designed as a rectangular plate adjoin sides of the plate which are referred to as longitudinal sides 52 or as transverse sides 54. The reinforcing element 42 in FIGS. 6a and 6b is illustrated on an enlarged scale in a perspective view and in a plan view of the broad side 50. In this case, the reinforcing element 42 has an extent (thickness) perpendicularly to the broad side 50, which corresponds to the spacing between the slot walls 46. The wide side 50 and the longitudinal sides 52 also referred to as first narrow sides furthermore have an extent (length) which corresponds substantially to the extent of the slot 44 in the axial direction A. Both transverse sides 54, which are also referred to as end-face narrow sides, and which adjoin the longitudinal sides 52 and the broad sides 50, each have a joining contour 56 which is in turn designed as two pegs. The pegs reach behind the pole tabs 21 of the corresponding stator teeth 16 in the assembled state so that a form fit is established with respect to the axial direction A.

(24) The reinforcing element 42 is made from a metal or from an alloy, for example from a non-magnetic stainless steel here. Prior to the initial assembly, the pegs protrude perpendicularly to the end-face narrow side 54. In the course of the assembly procedure, the pegs are bent to produce the form fit in the circumferential direction U.

(25) The reinforcing element 42 here is designed in one piece and symmetrically. In this case, the reinforcing element 42 is mirror-symmetrical with respect to a plane which extends through the perpendicular bisector of the broad side 50 and parallel to the transverse side 54, and likewise mirror-symmetrical with respect to a plane which is formed by the perpendicular bisector of the broad side 50 and parallel to the longitudinal side 52.

(26) The reinforcing element 42 furthermore has through-openings 58, which are designed as continuous bores incorporated in the broad side 50. In the assembled state, these lead into the corresponding stator slot 44. Eddy current losses are reduced by the through-bores 58. The through-bores 58 furthermore enable air circulation, such as for cooling.

(27) The reinforcing elements 42 furthermore each have a contour 59 in the corresponding bearing region for reducing a contact area with the bearing shoulders 43 and therefore for reducing a contact area with the laminated core 22. In this case, the contour 59 is formed by two recess 59a in the respective longitudinal side 52. In other words, the recesses 59a are incorporated in the respective longitudinal sides 52 of the reinforcing element 42.

(28) According to an alternative (not illustrated further) of the reinforcing element 42, this is additionally provided with a coating 70 which increases the electrical resistance of the reinforcing element 42.

(29) FIG. 7 shows a plan view of a cross-section through the stator 6, with a section plane which extends perpendicularly to the axial direction A. In this case, two further alternative configurations of the reinforcing elements 42 are illustrated, which are held in the radial direction by means of the bearing shoulders 43 formed by the pole tabs 32. In this case, the first of these two variants has a web 60, which extends in the radial direction R and abuts against the stator yoke 19. The reinforcing element 42 in this variant therefore has a T-shaped cross-section, whereof the horizontal T limb 62 abuts against the bearing shoulders 43 formed by the pole tabs 32 and the vertical T limb 64 is supported on the stator yoke 19. This reinforcing element 42 is pressed into the corresponding stator slot 24 and connected there with material fit, for example by (ultrasonic) welding.

(30) The second alternative variant of the reinforcing element 42 of FIG. 7 has, in the section plane shown, a substantially H-shaped cross-section. The vertical H limbs 66 of the reinforcing element 42 of this variant surround the bearing shoulders 43, formed by the pole tabs 32, of adjacent stator teeth 20. In this case, the spacing between the vertical H limbs 66 is selected such that a press-fitting dimension is permitted. In other words, the reinforcing element 42 is held against the bearing shoulders 43 with force fit by press-fitting. In addition, this is joined to the bearing shoulders 43 with material fit by an adhesive or alternatively by (ultrasonic) welding. In this case, compared to the other vertical H limb 66, the vertical H limb 66 projecting into the air gap has a smaller extent in a direction along the horizontal H limb, i.e. in the radial direction R in the assembled state.

(31) The dotted lines furthermore show the course of the surface 68 of the respective reinforcing element 42 in the region of the bearing shoulders 43 in a section plane which is parallel to, and spaced from, the section plane of FIG. 7. In this case, the reinforcing elements 42 do not abut against the pole tabs 21 or against the bearing shoulders 43 in this section plane. Therefore, in this plane, contact between the reinforcing element 42 and the laminated core 22 is prevented. As a result, contact (a contact area) with the laminated core 22 of the stator 6 is reduced, along with eddy currents which may be produced during operation of the electric motor 2.

(32) The invention is not restricted to the exemplary embodiments described above. Rather, the person skilled in the art is also able to derive other variants of the invention from these without deviating from the subject matter of the invention. As an example, all individual features which are described in association with the exemplary embodiments can furthermore be combined with one another in a different manner without deviating from the subject matter of the invention.

(33) The following is a list of reference numbers shown in the Figures. However, it should be understood that the use of these terms is for illustrative purposes only with respect to one embodiment. And, use of reference numbers correlating a certain term that is both illustrated in the Figures and present in the claims is not intended to limit the claims to only cover the illustrated embodiment.

LIST OF REFERENCE SIGNS

(34) 1 Radiator fan

(35) 2 Electric motor

(36) 4 Rotor

(37) 6 Stator

(38) 8 Axial pin

(39) 10 Bearing

(40) 11 Fan impeller

(41) 12 Air guide vane

(42) 13 Cap

(43) 14 Motor mount

(44) 15 Flange

(45) 16 Electronics compartment

(46) 17 Motor electronics

(47) 18 Electronics compartment cover

(48) 19 Stator yoke

(49) 20 Stator tooth

(50) 21 Pole tab

(51) 22 Laminated core

(52) 23 Plastic over molding

(53) 24 Stator slot

(54) 25 Coil

(55) 26 Connections

(56) 30 Slot opening

(57) 32 Individual lamination

(58) 34 Yoke portion

(59) 36 Lamination tooth

(60) 38 Lamination tab

(61) 42 Reinforcing element

(62) 43 Bearing shoulder

(63) 44 Slot

(64) 46 Slot wall

(65) 48 Bearing portion

(66) 50 Broad side or Wider side

(67) 52 Longitudinal side/first narrow side

(68) 54 Transverse side/second narrow side

(69) 56 Joining contour, peg

(70) 58 Through-openings

(71) 59 Contour

(72) 59a Recess

(73) 60 Web

(74) 62 Horizontal T-limb

(75) 64 Vertical T-limb

(76) 66 Vertical H-limb

(77) 68 Surface

(78) 70 Coating

(79) D Rotational axis

(80) R Radial direction

(81) U Circumferential direction

(82) While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention. Additionally, the features of various implementing embodiments may be combined to form further embodiments of the invention.