Electric machine with direct stator cooling

Abstract

The invention relates to an electric machine with a radially outer stator (3) and a radially inner rotor (5) spaced apart from each other by an electromagnetic gap (4), wherein the stator (3) is formed from a laminated core (12) with electrical steel laminations (20) stacked one above the other in the axial direction and has at least one stator slot (9) in which electrical conductors (14) are arranged, with direct stator cooling by means of which a coolant can flow through the stator slot (9) in the axial direction, and with a coolant seal (21) by means of which the electromagnetic gap (4) is protected from coolant ingress. According to the invention, the coolant seal (21) is designed as a single, integral component of each of the electrical steel laminations (20).

Description

[0001] The invention relates to an electric machine with direct stator cooling according to the preamble of claim 1.

[0002] Such an electric motor can be part of a vehicle drive system and be designed as a wet-running electric motor with direct stator cooling. With direct stator cooling, the coolant is guided directly through the stator slots where the electrical conductors are located. This reduces the electrical resistance of the conductors, allowing them to handle higher current densities.

[0003] A typical electric machine comprises a radially outer, stationary stator and a radially inner, rotating rotor, separated by an electromagnetic gap. The stator consists of a laminated core with electrical steel laminations stacked axially. The stator also features at least one slot containing electrical conductors. Furthermore, the machine is equipped with direct stator cooling, allowing coolant to flow axially through the stator slot. It is important to keep the electromagnetic gap essentially free of coolant to prevent drag losses at the rotor, which would reduce the efficiency of the electric machine.

[0004] In the prior art, a coolant seal is provided to protect the electromagnetic gap from coolant ingress. However, in the prior art, this coolant seal is space-consuming, constructed from complex injection-molded components and / or CFRP / GFRP sleeves. These components increase the electromagnetic air gap, leading to electromagnetic disadvantages.

[0005] From DE 10 2021 210 277 A1, a direct cooling of the electrical conductors of a stator of an electric machine is known, in which the cooling medium is guided as close as possible to the electrical conductors and in which high mechanical stability of the electrical conductors in the stator slots is ensured. The electric machine has a stator with at least one stator slot, in which electrical conductors and spacers are arranged. The electrical conductors are positioned at a distance from one another in the stator slot by means of the spacers; the spacers are arranged between the electrical conductors in such a way that a cooling fluid can flow around the electrical conductors.

[0006] German patent application DE 10 2022 119 049 A1 describes a component for the electrical insulation of at least one stator slot of a stator. The component includes slot insulation for the stator slot. The slot insulation has side walls that cover the corresponding inner walls of the stator slot. The side walls of the slot insulation extend axially along the stator. At least one side wall of the slot insulation forms at least part of an axially extending coolant channel for receiving coolant to cool one or more stator windings. This provides direct cooling of the stator windings.

[0007] From DE 10 2021 210 278 A1, a direct cooling system for an electric machine is known, in which a stator with at least one stator slot is provided. A layer of sealing material is inserted into the stator slot. The sealing material layer is also applied to the outer wall of the stator slot. Subsequently, electrical conductors are inserted into the stator slot, and a stator slot opening is sealed by means of the sealing material layer.

[0008] From DE 10 2020 204 233 A1, a stator for an electric machine is known. This stator has the following features: a longitudinal axis and a stator body extending along the longitudinal axis, with a plurality of stator slots and a plurality of stator conductors arranged in stator windings within the slots. A cooling fluid channel for conveying a cooling fluid is formed between at least two immediately adjacent stator conductors of a stator winding in a stator slot.

[0009] The object of the invention is to provide an electric machine with direct stator cooling, the coolant sealing of which is structurally simple compared to the prior art.

[0010] The problem is solved by the features of claim 1. Preferred embodiments of the invention are disclosed in the dependent claims.

[0011] The invention relates to an electric machine with a radially outer stator and a radially inner rotor, which are spaced apart from each other by an electromagnetic gap. The stator consists of a laminated core with electrical steel laminations stacked one above the other in the axial direction. The stator has at least one stator slot in which electrical conductors are arranged. The electric machine is equipped with direct stator cooling, by means of which a coolant flows through the stator slot in the axial direction. Compared to other cooling concepts, direct stator cooling provides improved heat dissipation from the stator teeth. Furthermore, the electric machine has a coolant seal that protects the electromagnetic gap from coolant ingress.According to the characterizing part of claim 1, the coolant seal is designed with reduced component complexity compared to the prior art, namely as a single-material and / or one-piece component of each of the electrical steel laminations. In this way, a separate sealing element, such as a CFRP / GFRP sleeve or other complex injection-molded components, can be eliminated.

[0012] The stator slot is bounded by two circumferentially adjacent stator teeth. In one technical implementation, the coolant seal can be an axially extending sealing rib that connects the upper surfaces of the two stator teeth in a coolant-tight and continuous manner. The stator slot is therefore completely closed on its rotor-facing side, preventing coolant from entering the electromagnetic gap. The sealing rib is preferably made of non-magnetic steel, thus preventing unwanted electromagnetic interference.

[0013] In a specific embodiment, the sealing rib can be constructed from sealing rib segments. Each of these sealing rib segments is a single, integral component of the respective electrical steel lamination. For example, the electrical steel lamination can consist of an electrical steel base body and a sealing rib segment. The sealing rib or sealing rib segment can be bonded to the stator, i.e., to the respective electrical steel base body, in a joining step, particularly a sintering step.

[0014] A possible sintering process for bonding the sealing web segment to the electrical steel base body is described in WO 2023 / 208674 A1. Explicit reference is made to the process steps disclosed in WO 2023 / 208674 A1.

[0015] The stator according to the invention can be manufactured in a process sequence with the following process steps: a stamping step in which electrical steel base bodies are produced; a joining step, in particular a sintering step, in which sealing web segments are joined to the electrical steel base bodies, forming the electrical steel laminations; and a stacking step in which the electrical steel laminations are stacked to form the stator lamination stack.

[0016] In the completed stator, the upper surfaces of the two adjacent stator teeth facing the rotor may be exposed by the coolant seal, meaning they are not covered by it. In this case, the electromagnetic air gap between the stator and rotor does not need to be increased to provide sufficient space for the coolant seal.

[0017] Each stator tooth's upper surface can be fitted with a tooth shoe, which, together with a groove flank, forms an internal corner area acting as an undercut. The two tooth shoes of the stator teeth, facing each other circumferentially, can be spaced apart by a tooth gap. This gap is bridged by the sealing rib in a coolant-tight manner. Preferably, the sealing rib transitions flush with the upper surfaces of the two adjacent stator teeth.

[0018] In a first embodiment, the sealing rib can engage behind the undercut formed between the groove flank and the tooth shoe. In a further development of the invention, the sealing rib can have a T-shaped cross-section, with a circumferentially wide transverse leg that engages behind the undercuts of the two stator teeth, and with a circumferentially narrow central leg that projects into the tooth gap between the tooth shoes of the two stator teeth.

[0019] In another embodiment, the coolant seal can be a hollow cylindrical sealing body, in particular a sintered body, which covers not only the tooth gaps of the stator slots, but also the upper surfaces of the stator teeth.

[0020] Exemplary embodiments of the invention are described below with reference to the accompanying figures. These show: Fig. Figures 1 to 9 show different views illustrating the structure of the stator according to the invention.

[0021] In the Fig. Figure 1 shows a roughly schematic representation of an electric machine, insofar as this is necessary for understanding the invention. Accordingly, the electric machine has a stator housing 1 in which a radially outer, stationary stator 3 and a radially inner, rotating rotor 5 interacting with it are arranged. The stator 3 and the rotor 5 are spaced apart from each other by an electromagnetic gap 4. The rotor shaft 6 is located in the Fig. 1 rotatably mounted on axially opposite housing walls 8 of the stator housing 1 in bearing openings.

[0022] Stator 3 exhibits a [feature] in the partial view of the Fig. Figure 2 shows an enlarged laminated core 12 with a plurality of electrical steel laminations 20 stacked one behind the other in the axial direction. The stator 3 also has a plurality of stator windings, of which in the Fig. 1 only two stator windings 7 are roughly schematically indicated. Each of the stator windings 7 is axially formed on both sides with a winding head 9, which projects into an end-face winding head space 11 of the stator housing 1. The stator windings 7 consist of electrical conductors 14, which are guided axially through stator slots 9, as can be seen from the Fig. 2 or Fig. 3 emerges. The stator slots 9 are formed circumferentially distributed in the stator lamination stack 12.

[0023] As from the Fig. As further shown in Figure 1, the radially outer winding headspace 11 is separated from a radially inner rotor chamber 15 by a coolant-tight partition 13. The electric machine is equipped with direct stator cooling, in which each of the winding headspaces 11 is integrated into a coolant circuit comprising a circulation pump 17 and an oil sump 19. The circulation pump 17 circulates the coolant, i.e., an electrically non-conductive cooling oil, into the chambers located in the Fig. 1 left winding head space 11 of the stator housing 1 and from there further in axial direction through the stator slots 9 to the one in the Fig. 1 right winding head chamber 11. From there the coolant is returned to the oil sump 19.

[0024] To avoid drag losses at the rotating rotor 5, the stator 3 is designed with a coolant seal 21 that prevents coolant from entering radially from the stator slots 9 towards the electromagnetic gap 4. A key aspect of the invention is that the coolant seal 21 is not installed as a separate sealing element between the stator 3 and the rotor 5, but rather is designed as a single, integral component of the electrical steel laminations 20 of the stator lamination stack 12.

[0025] In the Fig. Figure 3 shows an enlarged view of one of the stator slots 9. Accordingly, the stator slot 9 is bounded by two circumferentially adjacent stator teeth 23. Their slot flanks 24 extend radially outwards into a stator slot base. On the upper surfaces 18 of the stator teeth 23 facing the rotor 5, mutually facing tooth shoes 25 are formed, which are connected via a tooth gap 27 (only in the Fig. 4 or Fig. 7 shown) are spaced apart from each other.

[0026] Between each of the toothed shoes 25 and the groove flank 24, an internal corner area forming an undercut is spanned. In the Fig. 3. The tooth gap 27 between the two facing tooth shoes 25 is closed by means of a sealing rib 21, which acts as a coolant seal. The sealing rib 21 connects the two tooth shoes 25 together in a closed, coolant-tight manner, so that the stator slot 11 is completely closed on its side facing the rotor 5. The sealing rib 21 is made of non-magnetic steel using a sintering process.

[0027] As from the Fig. As the 3 continues, the upper surfaces 18 of the stator teeth 23 remain free of a coolant seal. The sealing rib 21 transitions flush into the two upper surfaces 18 of the stator teeth 23.

[0028] The following is based on the Fig. 4 and Fig. 5. A manufacturing process of the stator 3 is indicated: Accordingly, a stamping step is performed first ( Fig. 4), in which electrical steel sheet base bodies are produced from electrical steel sheets not shown, of which in the Fig. Figure 4 shows an electrical steel sheet base body 29. The electrical steel sheet base body 29 then undergoes a sintering step ( Fig. 5) is subjected to a sealing rib segment 31, in which a sealing rib segment 31 is joined to the electrical steel base body 29. The sealing rib segment 31 connects the two toothed shoes 25 formed in the electrical steel base body 29. After the sintering step has been completed, the electrical steel lamination 20 ( Fig. 5) completed. In the next step of the process, a stacking step follows, in which a large number of such electrical steel laminations 20 are stacked to form the stator lamination stack 12. The sealing web segments 31 of the electrical steel laminations 20 form the sealing web 21 in the stator lamination stack 12.

[0029] In the Fig. Figures 6 to 9 illustrate further embodiments of the stator 3 according to the invention. Fig. 6. The sealing web 21 is a single, integral component of each of the electrical steel laminations 20. This means that each of the sealing web segments 31 is also a single, integral component of the respective electrical steel lamination 20, which is completed in a single stamping step. In the exemplary embodiment of the Fig. The 6 sheet metal lamellae 20 used can be completed in the stamping step without an additional sintering process. In the exemplary embodiment of Fig. However, 6 very high leakage flux occurs, which makes the stator 3 electromagnetically very inefficient.

[0030] In the Fig. Figure 7 shows another embodiment variant in which the sealing rib 21 engages behind the undercut formed between the groove flank 24 and the toothed shoe 25. Alternatively, in the Fig. 8 The sealing rib 21 has a T-shaped cross-section, with a circumferentially wide transverse leg 33 and a narrow central leg 35. The transverse leg 33 of the sealing rib 21 engages behind the undercuts of the two stator teeth 23, while the narrow central leg 35 of the sealing rib 21 projects into the tooth gap 27 between the tooth shoes 25 of the two stator teeth 23.

[0031] In the preceding embodiments, a sealing rib 21 is provided for each of the stator slots 9. Instead, in the Fig. 9 The coolant seal 21 is formed from a hollow cylindrical sealing body, in particular a sintered body. This covers both the stator tooth tops 18 and the tooth gaps 27. Reference symbol list 1 Stator housing 3 Stator 4 electromagnetic gap 5 Rotor 6 Rotor shaft 8 Housing wall 9 Stator slot 10 winding head 12 sheet metal packages 11. Changing head space 13 Coolant partition 14 electrical conductors 15 coolant-free rotor chamber 17 Circulation pump 18 upper tooth 19 Coolant sump 20 electrical steel lamellae 21 Coolant sealing 23 Stator tooth 24 groove flank 25 Tooth shoe 27 tooth gaps 29 Electrical sheet metal base bodies 31 Sealing web segment 33 wide transverse leg 35 narrow mid-thigh QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2021 210 277 A1

[0005] DE 10 2022 119 049 A1

[0006] DE 10 2021 210 278 A1

[0007] DE 10 2020 204 233 A1

[0008] WO 2023 / 208674 A1

[0014]

Claims

[1] Electric machine with a radially outer stator (3) and a radially inner rotor (5) spaced apart from each other by an electromagnetic gap (4), wherein the stator (3) is formed from a laminated core (12) with electrical steel laminations (20) stacked one above the other in the axial direction and has at least one stator slot (9) in which electrical conductors (14) are arranged, with direct stator cooling by means of which the stator slot (9) can be cooled by an axial flow of coolant, and with a coolant seal (21) by means of which the electromagnetic gap (4) is protected from coolant ingress, characterized by , that the coolant seal (21) is designed as a materially uniform and / or one-piece component of each of the electrical sheet lamellae (20), so that in particular the provision of a separate sealing element is eliminated. [2] Electric machine according to claim 1, characterized by, that the stator slot (9) is bounded by two circumferentially adjacent stator teeth (23), and that in particular the coolant seal (21) is an axially extending sealing rib that connects the upper surfaces (18) of the two stator teeth (23) together in a coolant-tight and closed-surface manner, so that in particular the stator slot (9) is completely closed on its slot side facing the rotor (5). [3] Electric machine according to claim 2, characterized by , that the sealing rib (21) is composed of sealing rib segments (31), each of which is a materially uniform and / or one-piece component of the respective electrical sheet lamination (20). [4] Electric machine according to any one of the preceding claims, characterized by, that each of the electrical steel laminations (20) is formed from an electrical steel base body (29) and from a sealing web segment (31), and / or that the sealing web (21) can be joined to the stator (3) in a joining step, in particular a sintering step. [5] Electric machine according to any one of the preceding claims, characterized by , that the stator (3) can be manufactured in a process sequence, with - a stamping step in which a large number of electrical steel base bodies (29) can be produced; - a joining step, in particular a sintering step, in which sealing web segments (31) can be joined to the electrical steel base bodies (29), forming the electrical steel laminations (20); and - a stacking step in which the electrical steel laminations (20) can be stacked to form the stator lamination stack. [6] Electric machine according to any one of the preceding claims, characterized by, that the stator tooth surfaces (18) of the two adjacent stator teeth (23) facing the rotor (5) are exposed by the coolant seal (21), i.e., are not covered by the coolant seal (21), and / or that a tooth shoe (25) is formed on each stator tooth surface (18), which together with a groove flank (24) of the stator groove (9) forms an undercut, and / or that the tooth shoes (25) of the two stator teeth (23) facing each other in the circumferential direction are spaced apart from each other by a tooth gap (27), and that in particular the tooth gap (27) is bridged by the sealing rib (21). [7] Electric machine according to claim 6, characterized by , that a flush transition is formed between the upper surfaces (18) of the two stator teeth (23) and the sealing rib (21). [8] Electric machine according to claim 6 or 7, characterized by, that the sealing rib (21) engages behind the undercut formed between the groove flank (24) and the toothed shoe (25). [9] Electric machine according to any one of claims 6 to 8, characterized by , that the sealing rib (21) is T-shaped in cross-section, with a circumferentially wide transverse leg (33) that engages behind the undercuts of the two stator teeth (23), and with a circumferentially narrow central leg (35) that projects into the tooth gap (27) between the tooth shoes (25) of the two stator teeth (23). [10] Electric machine according to any one of the preceding claims, characterized by , that the coolant seal (21) is a particularly sintered hollow cylindrical sealing body which is in contact with the stator tooth tops (18) and bridges the tooth gaps (27).

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