Stator for an electric machine with slot insulation ring and compensation ring

Abstract

The invention relates to a stator (1) for an electric machine, comprising: - a stator body (2) for holding and conducting a magnetic flux of stator windings (9), the stator body comprising a plurality of stator slots (5), respectively separated by stator teeth (6) and extending between end faces (7) of the stator body (2), for receiving winding conductors (8) of the stator windings (9) and the stator body comprising, in end portions (11) adjoining the end faces (7), material-removed portions in the form of reduced-cross-section tooth ends (13) of the stator teeth (6) and increased-cross-section slot ends (12) of the stator slots (5), - at least one slot insulation ring (14) for electrically insulating the winding conductors (8) with respect to the slot ends (12), the at least one slot insulation ring having at least one annular carrier (15) abutting against one of the end faces (7), and having a plurality of slot lining elements (17) which are arranged on the carrier (15) and are respectively separated by plug-on elements (18), wherein the plug-on elements (18) are plugged onto the tooth ends (13) and the slot lining elements (18) thus protrude axially into the slot ends (12) and are arranged flush with slot surfaces (19) of the stator slots (5) in a central portion of the stator body (2), and - at least one magnetizable compensation ring (21) for guiding magnetic flux, the at least one compensation ring being arranged so as to radially overlap the stator body (2) at least in the region of the end portion (11) in order to compensate for the removal of material from the stator body (2).

Description

[0001] Stator for an electrical machine with slot insulation ring and compensation ring

[0002] The invention relates to a stator for an electric machine of a motor vehicle. The stator has a stator body for holding and conducting a magnetic flux of stator windings. The stator body comprises a plurality of stator slots distributed in the circumferential direction, each separated by a stator tooth, and extending between axially opposite end faces of the stator body for receiving winding conductors of the stator windings. Furthermore, the stator body comprises material removals in the form of reduced-cross-section tooth ends of the stator teeth and increased-cross-section slot ends of the stator slots in the end sections adjacent to the end faces. The stator also has at least one slot insulation ring for electrically insulating the winding conductors from the slot ends.The at least one slot insulation ring comprises an annular support applied to one of the end faces and a plurality of slot lining elements arranged circumferentially distributed on the support and separated by a respective plug-in element. The plug-in elements are plugged onto the tooth ends, thereby axially inserting the slot lining elements into the slot ends and forming an axially constant slot cross-section, flush with the slot surfaces in a central portion of the stator body. The invention also relates to an electric machine for a motor vehicle.

[0003] In this case, the focus is on electrical machines for electrified motor vehicles, such as electric or hybrid vehicles. Such electrical machines comprise a stationary stator with energizable stator windings and a rotor mounted rotatably relative to the stator, which includes a magnetic field-generating component, such as energizable rotor windings or permanent magnets. The stator comprises a stator body, such as a laminated core. Winding conductors, such as shaped bars or hairpins with a U-shape, are inserted into stator slots of the stator body, forming winding heads on axially opposite end faces of the stator body.To electrically insulate the stator body from the winding conductors, the stator slots are typically lined with slot insulation papers, which protrude axially from the end faces of the stator body to provide predetermined clearance and creepage distances between the live winding conductors and the grounded stator body. To prevent damage to the protruding slot insulation papers, the winding conductors must be axially oriented in the area where the slot insulation papers protrude. This undesirably increases the height of the winding overhang and thus the axial installation space of the stator. Furthermore, increased material usage is required for the winding conductors, resulting in cost disadvantages.

[0004] For this purpose, DE 102022 102 838 A1 proposes providing the stator body with slot insulation rings on the end faces. These are arranged in an end section within the stator body, which has the slot ends of the stator slots and the tooth ends of the stator teeth. The slot insulation rings have plug-in elements that are plugged onto the tooth ends and slot lining elements that are inserted into the slot ends. This displaces the electrical insulation partially into the interior of the stator, eliminating the need for the slot insulation paper to protrude from the end faces and thus the axial protrusion of the winding conductors from the stator slots. This allows the height of the winding overhangs to be reduced.However, the stator according to DE 102022 102 838 A1 has the disadvantage that the stator body exhibits material removal in the end sections, so that the stator slots, when the stator body is equipped with slot insulation rings, have a constant slot cross-section in the axial direction. The reduction of magnetic material in the stator body in the end sections undesirably reduces the magnetic flux density in the air gap of the electrical machine, and thus the torque and continuous power of the electrical machine.

[0005] It is an object of the present invention to provide a stator for an electric machine of a motor vehicle which is improved compared to the prior art.

[0006] This object is achieved according to the invention by a stator and an electric machine having the features according to the respective independent patent claims. Advantageous embodiments of the invention are the subject of the dependent patent claims, the description, and the figures.

[0007] A stator according to the invention for an electric machine of a motor vehicle has a stator body for holding and conducting a magnetic flux of stator windings. The stator body comprises a plurality of stator slots distributed in the circumferential direction, separated by a stator tooth each, and extending between axially opposite end faces of the stator body for receiving winding conductors of the stator windings. Furthermore, the stator body comprises material removals in the form of reduced-cross-section tooth ends of the stator teeth and increased-cross-section slot ends of the stator slots in the end sections adjacent to the end faces. The stator also has at least one slot insulation ring for electrically insulating the winding conductors from the slot ends.The at least one slot insulation ring comprises an annular support applied to one of the end faces and a plurality of slot lining elements arranged circumferentially distributed on the support and separated by a respective plug-in element. The plug-in elements are plugged onto the tooth ends, thereby axially inserting the slot lining elements into the slot ends and forming an axially constant slot cross-section, flush with the slot surfaces in a central portion of the stator body. Furthermore, the stator has at least one magnetizable compensation ring for magnetic flux guidance, which is arranged radially overlapping the stator body to compensate for the material removal of the stator body, at least in the region of the end portion.

[0008] An electrical machine according to the invention comprises a stator according to the invention and a rotor which is mounted at a distance from and rotatably relative to the stator, forming an air gap. The electrical machine is used in particular as a drive machine for an electrified motor vehicle. The electrical machine can, for example, be an external rotor machine in which the rotor radially surrounds the stator and is thus arranged outside the stator. Preferably, the electrical machine is an internal rotor machine in which the rotor is arranged in an axially continuous receiving space within the hollow cylindrical stator body and the stator thus radially surrounds the rotor. The stator body or stator core is designed in particular as a laminated core made of axially stacked electrical steel laminations.A side of the stator body facing the air gap has the axial stator slots, which are arranged equidistant from one another in the circumferential direction. In the case of external rotor machines, the stator is externally slotted, so that an outer side of the stator body has the stator slots. In the case of internal rotor machines, the stator is internally slotted, so that an inner side of the stator body has the stator slots. An axially continuous stator tooth is arranged between each two adjacent stator slots. The slots have slot surfaces in the form of an axially and tangentially extending slot base and two axially and radially extending slot flanks. The slot flanks are identical to the tooth flanks of the adjacent stator teeth. In other words, the slot flanks of a stator slot each form a tooth flank of the adjacent stator teeth.Tooth fronts of the stator teeth extend in axial and tangential directions and form the side of the stator facing the air gap.

[0009] The stator body has two axially opposite end sections which, starting from the associated end face, extend axially into the stator body over a predetermined extent. A central section of the stator body is arranged between the end sections, wherein an axial extent of the central section is greater than an axial extent of the end sections. The slot ends of the stator slots and the tooth ends or tooth tips of the stator teeth are located in the end sections of the stator body. The tooth tips have a reduced cross-section compared to the stator teeth in the central section. In particular, the tooth tips are designed as radially and axially extending pins and have a reduced tangential width and a reduced radial depth compared to the central section. As a result, the tooth flanks in the region of the tooth tips are tangentially set back compared to the tooth flanks in the central section.Likewise, the tooth fronts are set back radially relative to the tooth fronts in the central section. Due to the reduction in cross-section, the slot ends have an increased cross-section. Due to the reduced tangential width of the adjacent tooth ends, the slot flanks are tangentially offset outwards, so that the tangential width of the slot ends is increased compared to the central section. In addition, the slot base of the slot ends is set back radially relative to the central section, so that the radial slot depth in the area of ​​the slot ends is also greater than in the central area. The cross-sectional changes of the tooth ends and the slot ends are formed particularly in both end sections of the stator body. The cross-sectional changes are formed by removal or free cuts of the stator body material in the end sections.

[0010] These material removals are refilled, in particular by arranging a slot insulation ring at each of the end sections. The slot insulation rings are made of an electrically insulating material, for example plastic. The slot insulation rings can be produced, for example, by injection molding. The slot insulation rings each have an annular carrier, which is placed adjacent to the respective end face and on which an axially projecting collar is arranged. A ring width of the annular carrier is in particular significantly smaller than a ring width of the associated end face, such that the carrier does not completely cover the end face. The collar comprises a slot lining element for each stator slot and a slip-on element for each stator tooth.The slot lining elements and the slip-on elements are arranged on an inner side of the carrier in the case of an internally slotted stator and on an outer side of the carrier in the case of an externally slotted stator.

[0011] The slot lining elements each have two side wall parts for contact with the slot flanks at the slot end and a rear wall part for contact with the slot base at the slot end. Two adjacent side wall parts belonging to adjacent slot lining elements are also connected via a top part for contact with the end face. The side wall parts and the top part each form a slip-on element which has a slot-shaped receiving area for receiving the pin-shaped tooth tip. Due to the cross-sectional widening of the slot ends, the rear wall part is arranged flush with the slot base in the central section and the side wall parts are arranged flush with the slot flanks in the central section. Thus, each stator slot has a constant slot cross-section in the axial direction over the entire length of the stator body.By means of the slot insulation rings, the end insulation of the stator body, which is required to maintain predetermined clearance and creepage distances, is shifted into the stator slots and thus into the interior of the stator.

[0012] Preferably, an insulating paper is arranged in each stator slot, extending at most over the axial length of the respective stator slot and overlapping the respective slot lining element in the end sections, so that the stator slots in the end sections are insulated by both the slot lining elements and the slot insulating paper. The stator body is thus doubly insulated in the end section. The slot insulating papers are arranged entirely within the stator slots and do not protrude beyond the end surfaces of the stator body.

[0013] The winding conductors, which are held by the stator body, are designed in particular as shaped rods, in particular U-pins or hairpins with a U-geometry, which extend axially within the stator slots and emerge from the stator slots, forming a curve on the end face, where they form the winding overhang. By relocating the, in particular double, electrical insulation to the slot ends, the winding overhangs can be made significantly shorter, since an axial exit of the winding conductors from the stator slots and an axial projection of the winding conductors at the end faces are now no longer necessary. This advantageously reduces the axial installation space of the stator and thus the electrical machine, as well as the winding conductor material on the stator and thus the costs of the electrical machine.However, the material cutouts in the stator body in the area of ​​the end sections reduce the magnetic material and thus weaken the magnetic flux guided in the area of ​​the end sections. This also reduces the torque and the continuous power of the electric machine. In order to compensate for the material loss, or in particular to overcompensate for it, a magnetizable compensation ring is arranged radially overlapping with the end section. In particular, the compensation ring is arranged axially at least partially in the receiving space of the internally slotted stator on the inside of the stator body. The respective magnetizable compensation ring can, for example, be designed as a tubular hollow body in the form of a hollow cylinder, with a cylindrical wall extending parallel to the side of the stator facing the air gap. The hollow body has an axial length which is greater than its radial wall thickness.The compensation ring comprises a magnetizable material. It preferably consists of a composite material, in particular an electrically non-conductive metal powder bonded with casting resin.

[0014] Particularly preferably, the at least one compensation ring is arranged adjacent to the tooth fronts of the tooth ends and is thus arranged flush with the tooth fronts in the central section of the stator body, forming an axially constant stator diameter. In the case of an internally slotted stator, the compensation ring thus forms a constant inner diameter over the entire axial length of the stator body. In the case of an externally slotted stator, the compensation ring forms a constant outer diameter over the entire axial length of the stator body. The axially constant diameter on the side of the stator facing the air gap thus makes it possible to provide a constant air gap width over the length of the stator body.

[0015] The compensation rings can thus prevent the magnetic flux from being weakened in the area of ​​the end sections and thus reducing the torque and continuous power of the electrical machine.

[0016] In a preferred embodiment of the invention, the at least one compensation ring projects axially over the associated end face and radially overlaps with side regions of the respective winding overhang. In the internally slotted stator, the compensation ring thus projects axially into the annular winding overhang. This generates a rotating field across an active length of the stator, which corresponds to an axial extension of the stator between the tops of the winding overhangs. This rotating field provides the rotor with additional power and torque due to metallic components at the axial ends of the rotor, such as end covers, support disks, etc. The compensation rings can thus overcompensate for the torque and power loss caused by material removal.

[0017] In a further development of the invention, the at least one slot insulation ring and the at least one compensation ring are arranged concentrically to one another and mechanically, in particular materially, connected. For example, the slot insulation ring and the associated compensation ring can be adhesively bonded before or after assembly on the stator body. The slot insulation ring and the associated compensation ring can also be mechanically connected by encapsulating the fully assembled stator with a potting compound. It can also be provided that the at least one compensation ring has radial through-openings distributed in the circumferential direction, through which injection molding compound flows and hardens during injection molding of the slot insulation ring. The compensation ring can, for example, be inserted into the injection molding tool for producing the slot insulation ring.When manufacturing the slot insulation ring, the injection molding compound, for example liquid plastic, flows through the through openings and thus creates a mechanical connection between the slot insulation ring and the compensation ring after curing.

[0018] The embodiments presented with reference to the stator according to the invention and their advantages apply accordingly to the electrical machine according to the invention.

[0019] Further features of the invention emerge from the claims, the figures, and the description of the figures. The features and combinations of features mentioned above in the description, as well as the features and combinations of features mentioned below in the description of the figures and / or shown alone in the figures, can be used not only in the respective specified combination, but also in other combinations or on their own.

[0020] The invention will now be explained in more detail using a preferred embodiment and with reference to the drawings. They show:

[0021] Fig. 1 is a perspective view of an embodiment of a stator of an electrical machine; and Fig. 2 is an exploded view of the stator according to Fig. 1 without winding conductors.

[0022] In the figures, identical and functionally identical elements are provided with the same reference numerals.

[0023] Fig. 1 and Fig. 2 show a stator 1 for an electric drive motor of a motor vehicle. The stator 1 has a hollow cylindrical stator body 2, in the receiving space 3 of which a rotor (not shown here) of the electric drive motor can be rotatably mounted relative to the stator 1. On an inner side 4, the stator body 2 has stator slots 5, which are arranged at a distance from one another in the circumferential direction and are each separated by a stator tooth 6 and extend axially between two end faces 7 of the stator body 2. In the stator slots 5, as is only shown in Fig. 1, winding conductors 8 of stator windings 9 of the stator 1 are arranged, which project beyond the end faces 7 on both sides and form winding overhangs 10 there.

[0024] The stator slots 5 and the stator teeth 6 have cross-sectional changes in axially opposite end sections 11 of the stator body 2, which border the end faces 7. Slot ends 12 of the stator slots 5 have a wider cross-section, while the tooth ends 13 of the stator teeth 6 have a reduced cross-section. As a result, the tooth ends 13 are designed in a peg-like manner. A slot insulation ring 14 made of an electrically insulating material is arranged at each end section 11. Each slot insulation ring 14 has an annular carrier 15 and an annular collar 16 projecting axially from the carrier 15. The respective collar 16 has a number of slot lining elements 17 corresponding to the number of stator slots 5 and a number of slip-on elements 18 corresponding to the number of stator teeth 6. The groove lining elements 17 and the plug-in elements 18 are arranged alternately on the carrier 15 in the circumferential direction.The slip-on elements 18 are placed onto the tooth ends 13, and the slot lining elements 17 are arranged in the slot ends 12. The slot lining elements 17 are arranged flush with the slot surfaces 19 of the stator slots 5 in the central section 20 of the stator body 2, which is arranged axially between the end sections 11, so that the slot cross-section of the stator slots 5 remains constant over an axial length L of the stator body 2. The slot insulation rings 14 electrically insulate the end sections 11 of the stator body 2 from the live winding conductors 8. Slot insulation papers are also arranged in the stator slots 5 and extend over the slot lining elements 17, so that the stator slots 5 are doubly insulated in the end sections 11.

[0025] Due to the modified cross-section of the slot ends 12 and tooth ends 13, a magnetic material of the stator body 2 is reduced in the end sections 11 compared to the central section 20. This also reduces the magnetic air gap flux density, which arises from the superposition of a stator magnetic field excited by the stator windings 9 and a rotor magnetic field. To prevent this reduction, the material loss of the stator body 2 is compensated by means of magnetizable compensation rings 21. The compensation rings 21 consist of a magnetizable, electrically non-conductive material and are arranged at least in the end sections 11 of the stator body 2. The compensation rings 21 therefore cover at least the slot insulation rings 14 in the radial direction. In particular, the compensation rings 21 project axially beyond the end faces 7 of the stator body 2 and protrude into the winding overhangs 10.Thus, they even overcompensate for the material loss of the stator body 2. The compensation rings 21 have a cylindrical wall 22 extending in the axial direction. The compensation rings 21 are attached, for example, by adhesive bonding, to the corresponding slot insulation ring 14. For example, a slot insulation ring 14 and a compensation ring 21 can be mechanically connected before being arranged on the stator body 2 and mounted on the stator body 2 by slipping the slip-on elements onto the tooth ends 13.

Claims

Patent claims 1. Stator (1) for an electric machine of a motor vehicle, comprising: - a stator body (2) for holding and conducting a magnetic flux of stator windings (9), which has a plurality of stator slots (5) distributed in the circumferential direction, separated by a stator tooth (6) each and extending between axially opposite end faces (7) of the stator body (2) for receiving winding conductors (8) of the stator windings (9), and which has material removals in the form of tooth ends (13) of the stator teeth (6) with a reduced cross-section and slot ends (12) of the stator slots (5) with an increased cross-section in end sections (11) adjacent to the end faces (7), - at least one slot insulation ring (14) for electrically insulating the winding conductors (8) from the slot ends (12), with at least one annular support (15) applied to one of the end faces (7) and with a plurality of slot lining elements (17) arranged distributed in the circumferential direction on the support (15) and separated by a respective plug-in element (18), wherein the plug-in elements (18) are plugged onto the tooth ends (13) and wherein the slot lining elements (18) are thereby axially immersed in the slot ends (12) and are arranged flush with slot surfaces (19) of the stator slots (5) in a central section of the stator body (2) to form an axially constant slot cross-section, characterized by - at least one magnetizable compensation ring (21) for magnetic flux guidance, which is arranged radially overlapping with the stator body (2) at least in the region of the end section (11) to compensate for the material removal of the stator body (2).

2. Stator (1) according to claim 1, characterized in that the at least one compensation ring (21) is made of a composite material, in particular from an electrically non-conductive metal powder and casting resin.

3. Stator (1) according to claim 1 or 2, characterized in that the stator body (2) is hollow-cylindrical and the stator slots (5) are formed on an inner side (4) which encloses a receiving space (3) for a rotor of the electrical machine, wherein the at least one compensation ring (21) is arranged at least partially in the receiving space (3).

4. Stator (1) according to one of the preceding claims, characterized in that the at least one compensation ring (21) is arranged adjacent to tooth fronts of the tooth ends (13) and is thereby arranged flush with the tooth fronts in the central section of the stator body (2) to form an axially constant stator diameter.

5. Stator (1) according to one of the preceding claims, characterized in that a slot insulation paper is arranged in each stator slot (5), which extends at most over an axial length of the respective stator slot (5) and is arranged in the end sections (11) overlapping with the respective slot lining element (17), so that the stator slots (5) are insulated in the end sections (11) both by the slot lining elements (17) and by the slot insulation paper.

6. Stator (1) according to claim 5, characterized in that the winding conductors (9) are designed as shaped bars which extend axially within the stator slots (5) and emerge from the stator slots (5) forming a curvature on the end face (7).

7. Stator (1) according to one of the preceding claims, characterized in that the at least one slot insulation ring (14) and the at least one Compensation ring (21) are arranged concentrically to one another and are mechanically connected, in particular by a material bond.

8. Stator (1) according to claim 7, characterized in that the at least one compensation ring (21) has radial through-openings distributed in the circumferential direction, through which injection molding compound flows and hardens during injection molding of the slot insulation ring (14).

9. Stator (1) according to one of the preceding claims, characterized in that the at least one compensation ring (21) projects axially on the associated end face (7) and is arranged radially overlapping with side regions of a winding head (10) of the stator windings (9), which is formed by winding conductor sections of the stator windings (9) projecting on the end face (7).

10. An electric machine for a motor vehicle comprising a stator (1) according to one of the preceding claims and a rotor which is arranged at a distance from a side of the stator (1) having the stator slots (5) to form an air gap and is rotatably mounted with respect to the stator (1).

Images