Stator for an electric machine with improved cooling, electric machine and motor vehicle

Abstract

Stator (1) for an electric machine (100) comprising a plurality of stator laminations (3) stacked in an axial direction (A) to form a stator lamination stack (2), characterized in that the stator laminations (3) have a plurality of strip-shaped inserts (4) extending in a radial direction (R), wherein the inserts (4) have a higher thermal conductivity than the remaining stator lamination (3), wherein the stator laminations (3) are rotated relative to each other in an azimuthal direction (U) by an angle of rotation (D) such that the inserts (4) of directly adjacent stator laminations (3) are not arranged one above the other in the axial direction (A).

Description

[0001] The present invention relates to a stator for an electrical machine, an electrical machine, a motor vehicle and a method for producing a stator.

[0002] The performance of electrical machines is usually limited by their thermal limits. The focus here is on the stator, whose electrical wires typically generate the most heat due to ohmic resistance and, together with the stator iron of the stator core, become the power-limiting component of an electrical machine due to magnetization and eddy current losses. In addition to the heat tolerance of the installed components, cooling plays a crucial role. The dissipation of heat from stators using cooling elements arranged on the outside of the stator is widespread. However, this requires the heat to be conducted outward through the stator yoke to the cooling elements.

[0003] Silicon steel, less commonly cobalt and nickel alloys, often simply called stator iron, is commonly used to manufacture the stator yoke. The thermal conduction of the stator iron from the stator slots to the cooling elements is severely limited due to the low thermal conductivity of the materials used. A thinner stator yoke, i.e., a smaller stator outer diameter, would be thermally advantageous, but would have significant disadvantages regarding the magnetic flux through the stator. A stator yoke that is too thin would saturate, and the magnetic flux could not be maintained.

[0004] To increase the thermal conductivity of the stator yoke, a stator for an electrical machine is known from the generic document EP 2 793 375 B1, which comprises heat conductors. The heat conductors improve heat transfer from the interior of the stator to the exterior of the stator.

[0005] The problem here, however, is that heat conductors typically do not have good magnetic conductivity and thus impede the magnetic flux in the stator. The result is high power losses.

[0006] It is therefore an object of the present invention to provide a stator which does not have the disadvantages of the prior art described above, but rather enables very good heat conduction through the stator yoke from the inside of the stator to the outside of the stator and at the same time minimizes obstruction of the magnetic flux in the stator.

[0007] This object is achieved by a stator for an electrical machine comprising a plurality of stator laminations stacked in an axial direction to form a stator lamination stack, wherein the stator laminations have a plurality of strip-shaped inserts extending in a radial direction, wherein the inserts have a higher thermal conductivity than the remaining stator lamination, characterized in that the stator laminations are rotated relative to one another in an azimuthal direction by an angle of rotation such that the inserts of directly adjacent stator laminations are not arranged one above the other in the axial direction.

[0008] The stator according to the invention makes it possible for the magnetic flux flowing in the azimuthal direction to be unhindered by the inserts, but to switch to an adjacent stator lamination where an insert is arranged. This creates the opportunity for the magnetic flux to flow through the stator in a kind of slalom with minimal obstruction in the azimuthal direction. The individual stator laminations are of the same design. This makes sense because tools for manufacturing the stator laminations are expensive and thus money can be saved by standardizing the stator components. To ensure that the inserts of directly adjacent stator laminations do not lie directly on top of one another, the stator laminations are stacked rotated relative to one another. This means that a second stator lamination is placed on top of a first stator lamination, centered but rotated by the angle of rotation in the azimuthal direction.A third stator lamination is then centered on the second stator lamination and placed in the azimuthal direction, again rotated by the rotation angle. This process is repeated until all stator laminations are stacked to form the stator lamination stack. For the purposes of the present invention, the azimuthal direction refers to the circumferential direction of the stator. Rotation in the azimuthal direction is thus a rotation within the main extension plane of the stator lamination around the geometric center of the stator lamination. For the purposes of the present invention, all angles mentioned are understood as angles within the main extension plane of the stator lamination. It is conceivable for a stator lamination to have 10 or more, preferably 15 or more, particularly preferably 20 or more inserts.

[0009] Advantageous embodiments and further developments of the invention can be found in the dependent claims and the description with reference to the drawings.

[0010] According to a preferred embodiment of the invention, the length of the inserts in the radial direction is at least four times greater than the width of the inserts in the azimuthal direction. This enables highly directed and efficient heat conduction from the interior of the stator to its exterior.

[0011] According to a further preferred embodiment of the invention, the thickness of the inserts in the axial direction corresponds to the thickness of the stator laminations in the axial direction. This further improves thermal conduction and enables dense packing of the stator laminations. It is conceivable that the thickness of the stator laminations is between 100 µm and 1 mm, preferably between 200 µm and 400 µm.

[0012] According to a further preferred embodiment of the invention, the stator laminations have at least two, preferably four, recesses on their outer side, wherein the recesses are evenly distributed in the azimuthal direction, wherein the stator laminations are rotated relative to one another in the azimuthal direction such that the recesses of all stator laminations are arranged one above the other in the axial direction. The recesses of the stator laminations thus form registration recesses arranged axially along the length of the stator for securing the stator.

[0013] According to a further preferred embodiment of the invention, the stator laminations have n cutouts, wherein the cutouts and the inserts are arranged such that n-1 stator laminations are arranged between two stator laminations with inserts arranged one above the other in the axial direction, wherein the stator preferably has no inserts in the axial direction between the two stator laminations, which inserts are arranged one above the other in the axial direction with the inserts of the two stator laminations. This advantageously enables the stator laminations to be rotated such that the registration cutouts are continuous in the axial direction and, at the same time, the distance between two inserts lying one above the other in the axial direction is maximized, which further reduces disturbance of the magnetic flux. With n cutouts, the angle of rotation is thus α=360° / n.

[0014] According to a further preferred embodiment of the invention, the inserts are not evenly distributed in the azimuthal direction. This allows for advantageously wide and efficient spacing of the inserts.

[0015] According to a further preferred embodiment of the invention, the inserts are arranged in the azimuthal direction in groups of at least two inserts each, wherein the inserts of a group are spaced apart from one another in the azimuthal direction by an azimuthal angle, wherein the groups are spaced apart from one another in the azimuthal direction by group angles, wherein the azimuthal angles of all groups are the same. This enables a further improved arrangement of the inserts.

[0016] Preferably, it is provided that the azimuthal angle and the group angles are different from each other, wherein the group angles are preferably different from each other.

[0017] According to a further preferred embodiment of the invention, the inserts are made at least partially of aluminum and / or copper. These materials exhibit good thermal conductivity and are excellent for rolling as inserts.

[0018] According to a further preferred embodiment of the invention, the inserts have an electrically insulating coating, preferably an electrically insulating lacquer coating. This can further reduce interference with the magnetic flux.

[0019] According to a further preferred embodiment of the invention, the stator has a cooling element on its exterior, preferably a cooling jacket and / or cooling fins. This enables effective dissipation of heat from the exterior of the stator. Preferably, the cooling element is made at least partially of aluminum. It is conceivable that the cooling element is shrink-fitted.

[0020] A further object of the invention to solve the problem formulated at the outset is an electrical machine having a stator according to the invention.

[0021] A further object of the invention to solve the problem formulated at the outset is a motor vehicle having an electric machine according to the invention.

[0022] A further object of the invention to achieve the initially formulated problem is a method for producing a stator according to the invention, wherein a stator lamination advantage with slots is punched from a sheet metal, wherein the inserts are punched, wherein the inserts are subsequently rolled into the slots, wherein the stator lamination advantages with rolled-in inserts are stacked and packaged as stator laminations, rotated relative to one another. The stator laminations are preferably packaged to form the stator lamination package by punching, by means of a baked varnish, by gluing, or by welding.

[0023] All previously disclosed details, features and advantages relate to the stator according to the invention, the electrical machine according to the invention, the motor vehicle according to the invention, as well as to the method according to the invention.

[0024] Further details, features, and advantages of the invention will become apparent from the drawings and the following description of preferred embodiments with reference to the drawings. The drawings merely illustrate exemplary embodiments of the invention, which do not limit the scope of the invention. Fig. 1 (a) and (b) schematically illustrate a stator according to an exemplary embodiment of the present invention. Fig. 2 (a) to (d) each schematically illustrate a stator lamination of a stator according to an exemplary embodiment of the present invention. Fig. 3 schematically illustrates a section through a stator according to an exemplary embodiment of the present invention. Fig. 4 schematically illustrates a motor vehicle according to an exemplary embodiment of the present invention.

[0025] Fig. 1 (a) and (b) each schematically illustrate a stator 1 according to an exemplary embodiment of the present invention with a stator laminated core 2. The stator laminated core 2 has the stator laminations 3 stacked on top of one another in the axial direction A and welded together. During operation of the stator 1, heat is generated primarily in the interior of the stator 2. A cooling jacket made of aluminum (not shown) is shrunk onto the outside of the stator 1. A cooling liquid flows through the cooling jacket and cools the outside of the stator laminated core 2. The cooling jacket is fixed to the four registration recesses 5 that are evenly distributed in the azimuthal direction. In order to improve heat conduction from the inside of the stator laminated core 2 to the outside of the stator laminated core 2, the stator laminations 3 have strip-shaped inserts 4 arranged in the radial direction R.The inserts 4 are made of a material with good thermal conductivity, such as copper or aluminum. The radial arrangement of the highly thermally conductive inserts 4 allows the heat from the interior to be efficiently conducted to the cooling jacket.

[0026] Materials with good thermal conductivity often have poor conductivity for magnetic flux (see designator F in Fig. 3). The inserts 4 are therefore advantageous for thermal conductivity, but they hinder the magnetic flux in the azimuthal direction U during operation of the stator.

[0027] To reduce this interference, the stator laminations are rotated against each other by an angle D in the azimuthal direction U. For illustrative reasons, this is not shown in the Fig. 1 is not visible, but is shown in the Fig. 2 illustrated.

[0028] In the exemplary embodiments shown here, the inserts 4 are arranged in groups 6 of four inserts 4 each. Within each group 6, the inserts 4 are spaced apart from one another in the azimuthal direction U by the azimuthal angle φ. The azimuthal angle φ is the same for all groups 6. The groups 6 are in turn spaced apart in the azimuthal direction U by the group angle φ. G spaced from each other. The group angles φ G between the different groups 6 are of different sizes.

[0029] Fig. 2 (a) to (d) each schematically illustrate a stator lamination 3 of a stator 1 according to an exemplary embodiment of the present invention. For clarity, the details of the stator laminations 3 are not further designated here. Stator laminations 3 of a stator 1 according to one of the exemplary embodiments of Fig. 1. Fig. Figures 2 (a) to (d) show four stator laminations 3, each rotated by the angle of rotation D in the azimuthal direction U. The stator laminations 3 each have four registration recesses. To ensure that the registration recesses are aligned axially when the stator laminations 3 are stacked one above the other as a stator lamination stack, the stator laminations 3 are rotated relative to each other by the angle of rotation D = 360° / 4 = 90°. Thus, it is advantageously possible to use rotated stator laminations 3 to enable good heat conduction from the interior of the stator to its exterior, while still not obstructing the magnetic flux with barrier-like inserts that poorly conduct the magnetic flux.

[0030] Fig. 3 schematically illustrates a section through a stator 1 according to an exemplary embodiment of the present invention. The stator laminations 3 are stacked one above the other in the axial direction A and rotated relative to one another in the azimuthal direction. For the sake of clarity, only three stator laminations 3 are shown here. The inserts 4, for the sake of clarity, only four inserts 4 are shown, are not arranged one above the other in the axial direction A in a barrier-like manner, but are arranged offset in a stepped manner. This allows the magnetic flux F to flow relatively unhindered, as it can bypass the inserts 4 and switch to an adjacent stator lamination 3.

[0031] Fig.4 schematically illustrates a motor vehicle 200 according to an exemplary embodiment of the present invention, having an electric machine 100 according to an exemplary embodiment of the present invention. The electric machine 100 has a stator (not shown or designated further here) according to an exemplary embodiment of the present invention.

Claims

[1] Stator (1) for an electrical machine (100) comprising a plurality of stator laminations (3) stacked in an axial direction (A) to form a stator lamination stack (2), characterized by in that the stator laminations (3) have a plurality of strip-shaped inserts (4) extending in a radial direction (R), wherein the inserts (4) have a higher thermal conductivity than the remaining stator lamination (3), wherein the stator laminations (3) are rotated relative to one another in an azimuthal direction (U) by an angle of rotation (D) such that the inserts (4) of directly adjacent stator laminations (3) are not arranged one above the other in the axial direction (A). [2] Stator (1) according to claim 1, wherein a length of the insert parts (4) in the radial direction (R) is at least four times as large as a width of the insert parts (4) in the azimuthal direction. [3] Stator (1) according to one of the preceding claims, wherein a thickness of the inserts (4) in the axial direction (A) corresponds to a thickness of the stator laminations (3) in the axial direction (A). [4] Stator (1) according to one of the preceding claims, wherein the stator laminations (3) have at least two, preferably four, recesses (5) on their outer side, wherein the recesses (5) are arranged uniformly distributed in the azimuthal direction (U), wherein the stator laminations (3) are rotated relative to one another in the azimuthal direction (U) such that the recesses (5) of all stator laminations (3) are arranged one above the other in the axial direction (A). [5] Stator (1) according to claim 4, wherein the stator laminations (3) have n recesses (5), wherein the recesses (5) and the inserts (4) are arranged such that n-1 stator laminations (3) are arranged between two stator laminations (3) with inserts (4) arranged one above the other in the axial direction (A), wherein the stator (1) preferably has no inserts (4) in the axial direction (A) between the two stator laminations (3) which are arranged one above the other in the axial direction (A) with the inserts (4) of the two stator laminations (3). [6] Stator (1) according to one of the preceding claims, wherein the insert parts (4) are not arranged uniformly distributed in the azimuthal direction (U). [7] Stator (1) according to claim 6, wherein the insert parts (4) are arranged in the azimuthal direction (U) in groups (6) of at least two insert parts (4) each, wherein the insert parts (4) of a group (6) are arranged spaced apart from one another in the azimuthal direction (U) by an azimuthal angle (φ), wherein the groups (6) are spaced apart in the azimuthal direction (U) by group angles (φ G ) are arranged at a distance from one another, the azimuthal angles (φ) of all groups (6) being the same. [8] Stator (1) according to claim 7, wherein the azimuthal angle (φ) and the group angles (φ G ) are different from each other, where the group angles (φ G ) are preferably different from each other. [9] Stator (1) according to one of the preceding claims, wherein the insert parts (4) are at least partially made of aluminum and / or copper. [10] Stator (1) according to one of the preceding claims, wherein the insert parts (4) have an electrically insulating coating, preferably an electrically insulating paint. [11] Stator (1) according to one of the preceding claims, wherein the stator (1) has a cooling element on its outer side, preferably a cooling jacket and / or cooling fins. [12] Electrical machine (100) comprising a stator (1) according to one of the preceding claims. [13] Motor vehicle (200) comprising an electric machine (100) according to claim 12. [14] Method for producing a stator (1) according to one of claims 1 to 11, wherein a stator sheet advantage with slots is punched from a sheet, wherein the inserts are punched, wherein the inserts are subsequently rolled into the slots, wherein the stator sheet advantages with rolled-in inserts are stacked and packaged as stator sheets rotated against one another.

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