Housing for accommodating an electric motor, in particular a rotor-stator arrangement, for a motor vehicle

Abstract

The invention relates to a housing for accommodating an electric motor, in particular a rotor-stator arrangement, for a motor vehicle. The invention also relates to a casting tool for producing such a housing, as well as to an electric motor and a motor vehicle.

Description

[0001] Description

[0002] Housing for accommodating an electric motor, in particular a rotor-stator arrangement, for a motor vehicle

[0003] The present invention relates to a housing for receiving an electric motor, in particular a rotor-stator assembly, for a motor vehicle. The invention further relates to a casting tool for manufacturing such a housing, as well as an electric motor and a motor vehicle.

[0004] A large number of housings for accommodating an electric motor, in particular a rotor-stator arrangement, for a motor vehicle are known from the prior art.

[0005] The known housings are usually thin-walled hollow cast structures, which are manufactured in a casting process, in particular in a die casting process.

[0006] Such housings typically have an outer shell surface with a non-directional surface structuring, which is formed from cross-shaped elevations or extensions, in particular a waffle grid structure.

[0007] The housing and the electric motor are usually connected to each other by means of a press fit, in particular a transverse press fit, so that very high forces are at work during or after the press fit.

[0008] The known non-directional lattice structures have essentially two major disadvantages. Firstly, the known non-directional lattice structures exhibit very poor notch properties, in particular a very poor notch efficiency factor, so that stress peaks due to transverse compression cannot be avoided by the known non-directional lattice structures.

[0009] Secondly, due to the disadvantageous lattice structure, only hollow cast structures with a wall thickness above 5 mm are feasible.

[0010] This results in particular from the surface tension of the molten metal and the oxide layer that forms on the melt front, especially over longer flow paths.

[0011] As a result, the existing housings have greater wall thicknesses than strictly necessary due to casting limitations. This leads to increased material usage and a higher weight, which is particularly disadvantageous with regard to lightweight construction.

[0012] It is therefore an object of the present invention to at least partially overcome the disadvantages described above. In particular, it is an object of the present invention to create, in a simple and cost-effective manner, a thin-walled hollow casting structure, especially a housing for receiving the stator of an electric motor, with a surface structuring optimized for strength and casting. It is further an object of the invention to provide a casting tool for producing such a housing, as well as an electric motor and a motor vehicle.

[0013] The foregoing problem is solved by a housing having the features of claim 1 and by a casting tool having the features of claim 6. With regard to the electric motor, the problem is solved by the subject matter of dependent claim 9 and with regard to the motor vehicle by the subject matter of dependent claim 10.

[0014] Further features and details of the invention will become apparent from the dependent claims, the description, and the drawings. Features and details described in connection with the housing according to the invention naturally also apply in connection with the casting tool according to the invention, and vice versa, so that the disclosure regarding the individual aspects of the invention always refers, or can refer, to each other.

[0015] According to a first aspect of the invention, a housing for receiving a stator of an electric motor, in particular a rotor-stator arrangement, for a motor vehicle is proposed.

[0016] The housing has a longitudinal axis and an outer surface, wherein the housing and the electric motor can be connected along the longitudinal axis by means of a press fit, in particular a transverse press fit.

[0017] The housing according to the invention is characterized in particular by the fact that the outer surface of the housing has a directed surface structuring in certain areas, wherein the directed surface structuring is formed from a plurality of wave-shaped structural elements.

[0018] The structurally required strength and rigidity of the housing are process-dependent. The reason for these restrictions is a limitation on the flow length of the molten metal, which results from the surface tension of the melt and the oxide layer that forms on the melt front.

[0019] During the production of the housing according to the invention, an impermeable oxide layer, in particular an air layer or air cushion, forms at the interface between the structured surface of the mold and the molten metal due to differing wetting behavior. This layer has an insulating effect and prevents the thermal energy of the molten metal from being reduced by direct contact with the surface structure of the casting tool. The impermeable oxide layer increases the surface tension, preventing thin-walled areas from being filled with molten metal.

[0020] This can be prevented by the directed surface structuring according to the invention, i.e., the wave-shaped structural elements. In particular, the directed surface structuring according to the invention can increase the local velocity of the molten metal based on local turbulent flows, so that the oxide layer forming on the melt front is increasingly torn apart.

[0021] In other words, the multitude of wave-shaped structural elements according to the invention can create a directed surface structuring that breaks up the oxide layer that forms during the flow of the melt front. Furthermore, the directed surface structuring according to the invention selectively reduces the surface tension of the melt front.

[0022] This makes it possible to increase the flow length of the melt while maintaining the same housing wall thickness, or conversely, to decrease the housing wall thickness while maintaining the same flow length. Naturally, a combination of increasing the flow length and decreasing the wall thickness is also possible.

[0023] This results in a reduction of the required melt, and the manufactured housing can also have thin walls of less than 5 mm. This reduces the overall weight of the housing and optimizes it for lightweight construction without negatively affecting its structural properties, particularly its strength.

[0024] Furthermore, the directed surface structuring according to the invention with a plurality of wave-shaped structural elements is suitable for the production of hollow cast structures made of light metal, preferably aluminum, in die casting, especially in gravity die casting.

[0025] According to a preferred embodiment of the invention, a housing may be provided in such a way that the wave-shaped structural elements each have a rounded tip that is aligned parallel or substantially parallel to the longitudinal axis of the housing. This ensures that the wave-shaped structural elements are aligned orthogonally or substantially orthogonally to a principal load direction of the transverse press fit. As a result, the directional surface structuring according to the invention exhibits very good notch properties, in particular a very good notch efficiency factor, so that stress peaks resulting from the transverse press fit can be avoided by the directional surface structuring according to the invention.

[0026] According to a preferred further development of the invention, a housing can be provided in such a way that the plurality of wave-shaped structural elements are arranged at regular intervals from one another and are connected to one another, so that the plurality of wave-shaped structural elements together form linear wave structures.

[0027] According to a preferred further development of the invention, a housing can be provided in such a way that the linear wave structures are arranged parallel to each other and interlock, so that the linear wave structures together form a wave pattern.

[0028] According to a preferred further development of the invention, a housing may be provided in such a way that the linear wave structures have interruptions in the area of ​​the radii of load-critical points.

[0029] Furthermore, according to a preferred embodiment of the invention, a housing may be provided in such a way that the housing, in particular the directional surface structuring of the outer surface of the housing, is manufactured in a casting process, especially a die casting process. Preferably, the die casting process is a gravity die casting process. It is also conceivable that the die casting process is a tilt casting, CPC casting (counter-pressure casting), low-pressure casting, or a pressure casting process.

[0030] According to a second aspect of the invention, a casting tool for manufacturing such a housing is proposed to solve the problem.

[0031] The casting tool according to the invention comprises:

[0032] - at least one tool part that defines a cavity,

[0033] - at least one feed channel for filling the cavity with a molten metallic alloy, - wherein the tool part has a tool surface that shapes the housing,

[0034] - wherein the shaping tool surface has in some areas an embossed structure with a multitude of wave-shaped negative structural elements for producing the directed surface structure of the outer shell surface of the housing to be manufactured.

[0035] The casting tool described according to the second aspect of the invention offers all the advantages that have already been described for a housing according to the first aspect of the invention.

[0036] According to a preferred further development of the invention, a casting tool may be provided in such a way that the embossing structure, in particular the plurality of wave-shaped negative structural elements, is formed by a milling process, in particular a micro-milling process, and / or a machining process and / or embossing process and / or a laser process.

[0037] According to a third aspect of the invention, an electric motor, in particular a rotor-stator assembly, for a motor vehicle, with such a housing is proposed. As already explained, the housing of the electric motor can be manufactured with thinner walls, and thus lighter and more cost-effectively, due to the strength- and casting-optimized surface structuring of the housing.

[0038] According to a fourth aspect of the invention, a motor vehicle is proposed comprising a drivetrain for propelling the motor vehicle and at least one electrical consumer, wherein the motor vehicle has an electric motor according to the invention, the electric motor according to the invention being configured with the drivetrain of the motor vehicle for propelling the motor vehicle and / or for generating electrical current for the at least one electrical consumer. The optimized electric motor also allows the motor vehicle to be manufactured more easily and cost-effectively. A housing according to the invention for receiving an electric motor, in particular a rotor-stator assembly, for a motor vehicle is explained in more detail below with reference to the drawings. The drawings schematically show:

[0039] Figure 1 shows a perspective view of a housing according to an embodiment of the present invention and

[0040] Figure 2 shows a top view of a housing according to an embodiment of the present invention.

[0041] Fig. 1 shows a perspective view of a housing 10 for receiving an electric motor 20 (not shown), in particular a rotor-stator arrangement, for a motor vehicle 200 (not shown) according to an embodiment of the present invention.

[0042] As can be clearly seen in Fig. 1, the housing 10 is designed as a thin-walled hollow cast structure.

[0043] The housing 10 has a longitudinal axis L and an outer surface 15, wherein the housing 10 and the electric motor 20 (not shown) can be connected along the longitudinal axis L by means of a press fit, in particular a transverse press fit.

[0044] The outer surface 15 of the housing 10 has a directed surface structuring 30 in certain areas, wherein the directed surface structuring 30 is formed from a plurality of wave-shaped structural elements 31.

[0045] As can be clearly seen in Fig. 2, the wave-shaped structural elements 31 each have a rounded tip 32, which is aligned parallel or substantially parallel to the longitudinal axis L of the housing 10. This ensures that the wave-shaped structural elements 31 are aligned orthogonally or substantially orthogonally to a principal load direction H of the transverse press fit. The multiple wave-shaped structural elements 31 are arranged at regular intervals and connected to one another, so that the multiple wave-shaped structural elements 31 together form linear wave structures 33.

[0046] The linear wave structures 33 are arranged parallel to each other and interlock, so that the linear wave structures 33 together form a wave pattern 34.

[0047] The linear wave structures 33 have interruptions in the area of ​​radii 35 of load-critical points or taper off in this area.

[0048] It is conceivable that individual wave-shaped structural elements 31 are arranged at irregular intervals from one another. In other words, it is conceivable that the wave-shaped structural elements 31 are not connected to each other in certain areas.

[0049] The housing 10 according to the invention, in particular the directed surface structuring 30 of the outer shell surface 15 of the housing 10, is produced in a casting process, in particular in a die casting process.

[0050] It is generally known that flowability and mold-filling capacity are crucial factors in the manufacture of the housing 10 according to the invention. For example, flowability indicates how far the metallic melt can flow within the predetermined mold before the flow stagnates due to progressive solidification, whereas mold-filling capacity is defined as the ability of a melt to conform to the contours of the mold.

[0051] The two parameters that influence flowability and mold filling ability can usually be divided into two categories.

[0052] The first category includes metallurgical parameters, such as the chemical composition of the melt, heat of solidification, viscosity, and surface tension. The second category includes parameters of the mold and casting process used, such as mold material, surface finish, and mold temperature.

[0053] In other words, surface tension is particularly crucial for mold filling capacity. The surface tension of, for example, molten aluminum is influenced by the proportion of alloying elements and the temperature. Surface tension is especially important to consider for thin-walled hollow casting structures with wall thicknesses of less than 5 mm.

[0054] The housing 10 according to the invention is preferably made of an aluminum-silicon alloy. For example, AISi7MgCu0.5. Other AISi10, AISi13 or AISi17 alloys are also conceivable.

[0055] It is generally known that in AISi alloys, the silicon content, as well as the proportions of iron and manganese, primarily determine the flow properties. It is generally known that at a silicon content of approximately 3%, the flow length decreases and then increases until it reaches the eutectic point. It is generally known that the maximum flow length is reached at a silicon content of approximately 18%. At silicon contents above this level, the flow length decreases.

[0056] The core idea of ​​the invention is to effectively weaken the oxide layer at the melt front by means of a directed surface structuring 30, in particular by means of a plurality of wave-shaped structural elements 31 to form a wave pattern 34, through frequent contact with the edges of the wave-shaped structural elements 31, in order to thus achieve higher flow paths.

[0057] The wave-shaped structural elements 31 according to the invention break up the oxide layer that forms during the flow of the melt front. Breaking up the oxide layer specifically reduces the surface tension of the melt front.

[0058] This prevents the formation of a cold start, ensuring that even thin-walled areas are filled with melt. This, in turn, significantly influences and improves the strength, particularly the effective wall thickness and surface roughness, of the housing 10 according to the invention. This makes it possible to increase the flow length of the melt while maintaining the same wall thickness of the housing 10, or conversely, to decrease the wall thickness of the housing 10 while maintaining the same flow length. Naturally, a combination of increasing the flow length and decreasing the wall thickness is also possible.

[0059] This results in a reduction of the required melt, and the manufactured housing 10 can also have thinner walls of less than 5 mm. This reduces the overall weight of the housing 10 and optimizes it for lightweight construction without negatively affecting its structural properties, particularly its strength.

[0060] Reference symbol list

[0061] 10 cases

[0062] 15 Outer surface area of ​​the housing

[0063] 20 electric motor

[0064] 30 directional surface structuring of the outer shell surface

[0065] 31 wave-shaped structural elements

[0066] 32 rounded tips of the wave-shaped structural elements

[0067] 33 linear wave structures

[0068] 34 wave patterns

[0069] 35 Radius range of critical stress points of the housing

[0070] 100 casting tools

[0071] 110 cavity

[0072] 120 tool parts

[0073] 130 feed channel

[0074] 140 shaping tool surface

[0075] 150 embossing structuring

[0076] 160 wave-shaped negative structural elements

[0077] 200 motor vehicles

[0078] L Longitudinal axis of the housing

Claims

Patent claims 1. Housing (10) for receiving an electric motor (20), in particular a rotor-stator assembly, for a motor vehicle (200), - wherein the housing (10) has a longitudinal axis (L) and an outer surface (15), - wherein the housing (10) and the electric motor (20) can be connected along the longitudinal axis (L) by means of a press fit, in particular a transverse press fit, characterized in that - that the outer surface (15) of the housing (10) has a directed surface structuring (30) in certain areas, - wherein the directed surface structuring (30) is formed from a plurality of wave-shaped structural elements (31 ).

2. Housing (10) according to claim 1 , characterized in that the wave-shaped structural elements (31) each have a rounded tip (32) which are aligned parallel or substantially parallel to the longitudinal axis (L) of the housing (10).

3. Housing (10) according to at least one of the preceding claims, characterized in that the plurality of wave-shaped structural elements (31 ) are arranged at regular intervals from each other and are connected to each other, such that the plurality of wave-shaped structural elements (31 ) together form linear wave structures (33).

4. Housing (10) according to claim 3, characterized in that the linear wave structures (33) are arranged parallel to each other and interlock, so that the linear wave structures (33) together form a wave pattern (34).

5. Housing (10) according to claim 4, characterized in that the linear wave structures (33) have interruptions in the area of ​​the radii (35) of load-critical points.

6. Housing (10) according to at least one of the preceding claims, characterized in that the housing (10), in particular the directed surface structuring (30) of the outer shell surface (15) of the housing (10), is manufactured in a casting process, in particular a die casting process.

7. Casting tool (100) for manufacturing a housing (10) according to at least one of the preceding claims 1 to 6 by means of a casting process, in particular a die casting process, the casting tool (100) comprising: - at least one tool part (120) defining a cavity (110), - at least one feed channel (130) for filling the cavity (110) with a molten metallic alloy, - wherein the tool part (120) has a tool surface (140) that shapes the housing (10), - wherein the shaping tool surface (140) has in some areas an embossed structure (150) with a multitude of wave-shaped negative structural elements (160) for producing the directed surface structure (30) of the outer shell surface (15) of the housing (10) to be produced.

8. Casting tool (100) according to claim 7, characterized in that the embossing structure (150), in particular the plurality of wave-shaped negative structural elements (160), is formed by a milling process, in particular a micro-milling process, and / or a machining process and / or embossing process and / or a laser process.

9. Electric motor (20), in particular a rotor-stator arrangement, for a motor vehicle (200), with a housing (10) according to any one of the preceding claims 1 to 6.

10. Motor vehicle (200) with a drive train for propelling the motor vehicle (200) and at least one electrical consumer, wherein the motor vehicle (200) has an electric motor (20) according to claim 9, wherein the electric motor (20) is configured with the drive train of the motor vehicle (200) for propelling the motor vehicle (200) and / or for generating electric current for the at least one electrical consumer.

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