Stator

Abstract

The invention relates to a stator (2) of an electric machine (1), comprising a plurality of stator laminations (5), wherein the stator laminations (5) are arranged in a stack (6) relative to one another, wherein the stator laminations (5) have first bores (9) for passing through screws (10) for tensioning the stack (6) of stator laminations (5), wherein screws (10) are provided which are passed through the first bores (9) and screwed in to generate a preload of the stack (6), wherein a spring ring element (11) is arranged in or on the stack (6) to increase the preload of the stack (6), wherein the spring ring element (11) has second bores (12) for passing through the screws (10), wherein the screws (10) are passed through the second bores (12).

Description

[0001] The invention relates to a stator of an electric machine and an electric machine with a stator, in particular as a drive machine for a motor vehicle.

[0002] Electrical machines have a rotor and a stator. The stator has a laminated core consisting of a large number of iron sheets stacked on top of each other.

[0003] It is known in the art that a stator, with its laminated cores, is pressed into a housing with an oversize. Due to the compression within the housing, this leads to considerable stresses in the laminated core or in the stator laminations. The compression also creates the necessary clamping force in the housing, as the torque delivered by the rotor is supported by the stator. The stresses caused by the compression have a negative impact on the power consumption of the electric motor, which is undesirable.

[0004] Furthermore, due to material differences between the steel stator laminations and stator cores and an aluminum housing, the oversize of the stator laminations and stator cores must be increased to compensate for the different thermal expansion coefficients of the various materials. Only in this way can the full torque be transmitted with the required safety, even at the highest temperatures. This excessive oversize leads to additional undesirable losses.

[0005] To avoid the stresses described in the stator lamination stack, it is common practice to clamp the stator lamination stack axially using long screws. However, since the stator lamination stack consists of many individual stator laminations, usually around 500 to 1000, this results in a large number of joints for the screw connection. These joints lead to settlement over the service life due to fluctuations in time, temperature, and torque, which significantly reduces the preload of the screws used and thus also the transmittable torque.

[0006] The loss of preload force is amplified by the structure of the individual laminations in the laminated core. An electrical lamination used as a stator lamination consists of the sheet itself, which is additionally coated with a thin layer of varnish for insulation purposes. Above a certain temperature, the glass transition temperature, the varnish expands significantly due to thermal expansion, causing the individual lamination and thus the stator lamination core to grow axially relative to the screw. This growth plastically elongates the screw, resulting in a lower preload force after the cooling process. The previously described effect is extreme in stator lamination cores with self-bonding varnish. These cores are held together by an electrical lamination with an adhesive coating. Because the adhesive is thicker than normal insulating varnish, the effect of the thermal expansion of the varnish is particularly pronounced here.Laboratory tests show that the loss of preload force after 3 temperature cycles for these packages is 50-70% compared to the initial value.

[0007] The objective is to create a stator for an electric machine that exhibits neither stresses due to press-fitting nor significant losses in preload force, while also being simple and efficient to manufacture. The objective is also to create an electric machine that is improved over the state of the art.

[0008] The problem of the stator is solved with the features of claim 1.

[0009] An embodiment of the invention relates to a stator of an electric machine, with a plurality of stator laminations, wherein the stator laminations are arranged in a stack relative to one another, wherein the stator laminations have first bores for the passage of screws for bracing the stack of stator laminations, wherein screws are provided which are passed through the first bores and screwed in to generate a preload of the stack, wherein a spring ring element is arranged in or on the stack to increase the preload of the stack, wherein the spring ring element has second bores for the passage of the screws, wherein the screws are passed through the second bores.The arrangement of the spring washer element allows it to apply a preload to all screws simultaneously, sufficient to clamp the stator laminations reliably and securely. At the same time, the spring washer element allows the preload to be maintained across a large length difference between the stator laminations and screws. The length difference does not have to be applied solely by the screws; the spring washer element also contributes to the creation of the length difference.

[0010] In one embodiment, it is expedient if the stator laminations are arranged in stator packages.

[0011] It is also advisable for the stator laminations and / or stator cores to be completely or at least partially coated with an insulating varnish. This ensures that the individual stator laminations can be electrically insulated from one another.

[0012] It is also advantageous if the stator laminations have a ring-shaped base body and the first holes for the screws are located radially on the outside of the base body. This places the holding function radially on the outside, which minimizes the disruption to the electrical properties of the stator laminations toward the rotor.

[0013] It is also advantageous if the first holes are distributed around the circumference of the base body, especially evenly distributed over the circumference. This allows for uniform clamping.

[0014] It is also advantageous if the spring washer element has an annular base body with second holes distributed therein. The base body is formed, for example, from a thin metal ring, preferably from a metal sheet, such as spring steel. The spring washer element is preferably designed as a bent sheet metal part. This allows the spring washer element to distribute the clamping force as evenly as possible across all screws.

[0015] The spring ring element preferably rests on one end face of the stack of stator laminations and the first holes of the stator laminations are aligned with the second holes of the spring ring element.

[0016] It is advantageous if the annular base body has first regions between the bores, with a bead arranged adjacent to the bores on both sides and a second region formed between each of the beads, with the bores formed in the second region. This results in a design of the spring ring element that allows elastic preloading of the screws.

[0017] It is also advantageous if the first areas and / or the second areas are flat. This results in a slim design that requires little installation space.

[0018] It is particularly advantageous if the second areas are axially offset from the first areas. This gives the second areas sufficient clearance to develop the preload of the screws.

[0019] The screw heads of the screws can accordingly rest on the second areas, with the first areas being supported on the front side of the stack of stator laminations.

[0020] The problem of the electric machine is solved with the features of claim 10.

[0021] An embodiment of the invention relates to an electric machine with a stator and with a rotor arranged in a recess of the stator, wherein the stator is designed according to the invention.

[0022] The invention will be explained in detail below using an exemplary embodiment with reference to the drawings. In the drawings: Fig. 1 a schematic representation of an embodiment of an electric machine according to the invention, Fig. 2 a schematic partial representation of the stator of the electric machine according to Fig. 1, Fig. 3 a schematic partial sectional view of the stator according to Fig. 2, and Fig. 4 a schematic representation of a spring ring element of the stator according to Fig. 2.

[0023] The Fig. Figure 1 shows a schematic representation of an electric machine 1, for example, of a motor vehicle, which can be used as the drive motor of the motor vehicle. The electric machine 1 has a stator 2 and a rotor 3, wherein the rotor 3 is rotatably arranged in a recess 4 of the stator 2. The rotor 3 is rotatably arranged about the rotation axis xx.

[0024] The stator 2 has a plurality of stator laminations 5, wherein the stator laminations 5 are arranged relative to one another in a stack 6. The stator laminations 5 can be configured as stator packs 7, which are combined to form the stack 6, or the stator laminations 5 can be stacked as such to form the stack 6.

[0025] The Fig. 2 shows that the stator laminations 5 have an annular base body 8 for forming the recess 4 for receiving the rotor 3.

[0026] In one embodiment, it is expedient if the stator laminations 5 and / or the stator cores 7 are completely or at least partially coated with an insulating varnish. This ensures that the individual stator laminations 5 can be electrically insulated from one another.

[0027] The Fig. 2 shows that stator laminations 5 have first bores 9 for the passage of screws 10 for clamping the stack 6 of stator laminations 5.

[0028] It is in Fig. 2 shows that the stator laminations 5 comprise the annular base body 8, and the first holes 9 for the passage of the screws 10 are arranged radially outward on the base body 8. This positions the holding function radially outward, which minimizes the disruption to the electrical properties of the stator laminations 5 toward the rotor 3.

[0029] It can also be seen that the first holes 9 are distributed over the circumference of the base body 8, in particular, they are evenly distributed over the circumference. This allows for uniform clamping of the stack 6.

[0030] Accordingly, screws 10 are provided which are passed through the first bores 9 and screwed in to generate a preload of the stack 6. For example, the screws 10 are screwed to a housing at the second end of the screws (not shown), which serves to support the torque.

[0031] Furthermore, a spring ring element 11 is arranged in or on the stack 6. The spring ring element 11 serves to increase the preload of the stack 6 and to even out the preload.

[0032] The spring ring element 11 has second bores 12 for the passage of the screws 10, wherein the screws 10 are Fig. 2 and Fig. 3 are also carried out through the second holes 12.

[0033] The spring washer element 11 is arranged such that it simultaneously exerts a preload on all screws 10, which is sufficient to clamp the stator laminations 5 reliably and securely. At the same time, the spring washer element 11 allows the preload to be ensured over a large length difference between the stator laminations 5 and the screws 10. The length difference does not have to be applied solely by the screws 10, but the spring washer element 11 also contributes to the effect of the length difference.

[0034] Fig. 4 shows an embodiment of a spring ring element 11, wherein the spring ring element 11 has an annular base body 13 with second bores 12 distributed therein.

[0035] The base body 13 is formed, for example, from a thin metal ring, preferably from a metal sheet, such as spring steel. The spring ring element 11 is preferably designed as a bent sheet metal part. As a result, the spring ring element 11 distributes the clamping force as evenly as possible across all screws 10.

[0036] The spring ring element 11 preferably rests on an end face of the stack 6 of the stator laminations 5 and the first bores 9 of the stator laminations 5 are aligned with the second bores 12 of the spring ring element 11.

[0037] The annular base body 13 is designed such that first regions 14 are provided between the bores 12, a bead 15 being arranged adjacent to the bores 12 on both sides and a second region 16 being formed between each of the beads 15, the bores 12 being formed in the second region 16.

[0038] In the illustrated embodiment, the first regions 14 and the second regions 16 are flat. Alternatively, the first regions 14 and / or second regions 16 can also be curved or otherwise structurally designed. This results in a slim design of the spring ring element 11 that requires little installation space.

[0039] The second regions 16 are axially offset from the first regions 14, so that the second regions 16 allow sufficient clearance to form the preload of the screws 10. The screw heads of the screws 10 rest against the second regions 16, with the first regions 14 resting against the end face of the stack 6 of stator laminations 5. This design of the spring ring element 11 allows for elastic preload of the screws 10. List of reference symbols 1 electric machine 2 Stator 3 Rotor 4 recess 5 Stator sheet 6 stacks 7 Stator package 8 basic bodies 9 first drilling 10 screw 11 Spring ring element 12 second hole 13 basic bodies 14 first area 15 bead 16 second area

Claims

[1] Stator (2) of an electric machine (1), with a plurality of stator laminations (5), wherein the stator laminations (5) are arranged in a stack (6) relative to one another, wherein the stator laminations (5) have first bores (9) for the passage of screws (10) for bracing the stack (6) of stator laminations (5), wherein screws (10) are provided which are passed through the first bores (9) and screwed in to generate a prestress of the stack (6), wherein a spring ring element (11) is arranged in or on the stack (6) to increase the prestress of the stack (6), wherein the spring ring element (11) has second bores (12) for the passage of the screws (10), wherein the screws (10) are passed through the second bores (12). [2] Stator (2) according to claim 1, characterized by that the stator laminations (5) are arranged in stator packages (7). [3] Stator (2) according to claim 1 or 2, characterized bythat the stator laminations (5) and / or the stator packages (7) are completely or at least partially coated with an insulating varnish. [4] Stator (2) according to claim 1, 2 or 3, characterized by that the stator laminations (5) have an annular base body (8) and the first bores (9) for passing the screws (10) are arranged radially on the outside of the base body (8). [5] Stator (2) according to claim 1, 2, 3 or 4, characterized by that the first bores (9) are arranged distributed over the circumference of the base body (8), in particular are arranged evenly distributed over the circumference. [6] Stator (2) according to one of the preceding claims, characterized by that the spring ring element (11) has an annular base body (13) with second bores (12) distributed therein. [7] Stator (2) according to claim 6, characterized bythat the annular base body (13) has first regions (14) between the bores (12), wherein a bead (15) is arranged adjacent to the bores (12) on both sides and a second region (16) is formed between each of the beads (15), wherein the bores (12) are formed in the second region (16). [8] Stator (2) according to claim 7, characterized by that the first regions (14) are flat and / or the second regions (16) are flat. [9] Stator (2) according to one of claims 7 or 8, characterized by that the second regions (16) are arranged axially offset from the first regions (14). [10] Electric machine (1) with a stator (2) and with a rotor (3) arranged in a recess (4) of the stator (2), wherein the stator (2) is designed according to at least one of the preceding claims.

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