Electric machine with housing and cooling structure, traction drive

Abstract

The invention relates to an electric machine (10) for an at least partially electrically driven motor vehicle, comprising a housing (14), a rotor (16) arranged in the housing (14) and mounted so as to be rotatable about an axis of rotation (18) of the rotor (16), wherein the housing (14) has a wall and at least one cooling fin (24) is formed on an inner side (22) of the wall, which faces the rotor (16), and an air flow generated by the rotor (16) within the housing (14) can be guided at least partially past the cooling fin (24).

Description

The invention relates to an electric machine for an at least partially electrically driven motor vehicle, wherein the electric machine has a rotor and a housing surrounding the rotor, and at least one cooling fin is formed on an inner side of the housing, which inner side faces the rotor. The invention also relates to a traction drive having the electric machine according to the invention.Electric machines for at least partially electrically driven motor vehicles are known in principle. These usually have a housing which surrounds the rotor and stator. As a rule, a cooling channel through which a liquid flows is formed in the housing in order to cool the stator and / or the rotor. By cooling the rotor and / or stator, the performance of the electric machine can be increased.It is an effort to increase the performance of the electric machine. For this purpose, it can be provided that the rotation of the rotor is increased, as a result of which heat generation within the electric machine can increase. An increased generation of heat is to be reduced.An object of the invention is to increase the cooling effect of an electric machine for a traction drive of an at least partially electrically driven motor vehicle.The object is achieved by the subject matter of the independent claims. Preferred developments of the invention are the subject matter of the dependent patent claims, the following description and / or the drawings. Each disclosed feature may represent an aspect of the invention both individually and in combination, unless the description explicitly gives a somewhat opposite result.According to a first aspect of the invention, an electric machine for an at least partially electrically driven motor vehicle is provided, having a housing, a rotor which is arranged in the housing and is mounted rotatably about an axis of rotation of the rotor, wherein the housing has a wall, and at least one cooling fin is formed on an inner side of the wall which faces the rotor, and an air flow generated by the rotor within the housing can be at least partially guided past the cooling fin.In other words, according to the first aspect of the invention, it is provided that an electric machine is provided for an at least partially electrically driven motor vehicle. The electric machine is preferably a component of a traction drive of the motor vehicle. It is provided that the electric machine has a housing. A rotor is arranged within the housing. The rotor has an axis of rotation which preferably corresponds to a longitudinal axis of the rotor. The rotor is designed to be rotatably mounted about the axis of rotation within the housing. In other words, the rotor can rotate about the axis of rotation or longitudinal axis. The housing surrounds the rotor partially and / or in sections. Furthermore, it is provided that the housing has at least one cooling fin on an inner side facing the rotor. A rotation of the rotor about its longitudinal axis generates an air flow within the housing. The air flow is guided past the cooling fin within the housing, such that heat from the air flow can be absorbed by the cooling fin, whereby the air within the housing of the electric machine can be cooled. By cooling the air or the air flow within the electric machine, the performance of the electric machine can be increased.In principle, the cooling fin can be arranged on the inner side of the housing in such a way that the air flow generated by the rotor flows against it inside the housing.An advantageous further development of the invention is that the cooling fin is formed on a bearing plate of the housing. In other words, the inner side of the housing having the cooling fin is an inner side of the bearing shield. An end face of the rotor oriented in the axial direction of the rotor is formed at a distance from the cooling fin. A rotation of the rotor about its axis of rotation generates an air flow which acts both in the axial direction of the rotor and in the radial direction of the rotor. Due to the cooling fin formed on the bearing plate at a distance from the end face of the rotor, the air flow can thus flow against it.It is conceivable for the cooling fin to have a height, wherein the height of the cooling fin is aligned substantially parallel to the longitudinal direction of the rotor. Essentially means that the cooling fin does not have to be aligned exactly parallel to the longitudinal direction over its height, but can be designed to be inclined to the longitudinal direction of the rotor. The inclination is preferably at an angle α= + / - 20°, preferably at an angle α= + / - 15°, and most preferably at an angle α= + / - 10°, with respect to the longitudinal direction of the rotor. The limits are included. Thus, depending on the generated air flow inside the housing, the cooling fin can be acted upon accordingly in order to generate the greatest cooling effect. However, it is particularly advantageous if the cooling fin extends over its height parallel to the longitudinal direction of the rotor.It is conceivable for the cooling fin to be designed to taper in sections or over its entire height, starting from the bearing plate in the direction of the rotor or rotor end face. This can entail manufacturing advantages, in particular when the cooling fin is formed parallel to the longitudinal direction of the rotor. If the housing is then preferably formed as a cast part and the cooling fin is preferably formed integrally with the housing, the housing can be more easily removed from the casting mold in this region.It is likewise conceivable for the housing to be produced in an additive production process. Thus, structures of the cooling fin inclined over the height of the cooling fin are also conceivable and can be produced easily.In a preferred development of the invention, it is provided that the cooling fin is formed in a circumferential manner, in particular in the shape of a circular ring or a helical ring. In this way, the cooling fin may form a larger surface area on the inner side of the housing, whereby the cooling effect of the electric machine may be increased.In the case of a helical course of the cooling fin on the inner side of the housing, the air flow can additionally be directed outwards in a targeted manner in the radial direction, for example to a wall region of the housing cooled with a liquid, in order to further cool the air flow.An advantageous embodiment of the invention is that a plurality of cooling fins spaced apart from one another are provided. By the plurality of cooling fins, which are preferably formed on the inner side of the housing at a distance in the radial direction of the rotor, the surface area of the housing inner side can be deliberately increased. When the cooling fins are impinged, the cooling fins may absorb the heat from the air, whereby the cooling effect within the electric machine may be increased.According to a preferred embodiment of the invention, it is provided that the cooling fin formed in the circumferential direction is formed without interruptions. In other words, the cooling fin, which is of circular ring-shaped or helical design, is formed continuously over an angle of β=3600°. A center point of the cooling fin, which is circular or helical, is located on the longitudinal axis of the rotor. A large surface area can be achieved with a continuously formed cooling fin, whereby the cooling effect of the electric machine can be increased.Alternatively or in addition, it can be provided that the cooling fin of circumferential design has at least one interruption. In other words, the cooling fin is not continuous over its length, but rather has one or more interruptions formed at a distance from one another. As a result of the at least one interruption, preferably a turbulence can be generated in the air stream in a targeted manner, which can have an advantageous effect on the cooling effect of the electric machine.It is thus conceivable that, in the case of a plurality of cooling fins arranged spaced apart from one another in the radial direction, at least one cooling fin is designed without interruptions in the circumferential direction, while a further cooling fin has at least one interruption. Preferably, in particular the cooling fin located further outward in the radial direction of the rotor has at least one interruption.In a preferred embodiment of the invention, it is provided that a base between two spaced apart and / or adjacent cooling fins is designed in the shape of a fillet. Due to the fillet-shaped configuration of the base between the cooling fins, on the one hand, the air flow can be guided past the inner side of the housing with lower friction losses, which can have an advantageous effect on the cooling effect of the electric machine. In addition, the fillet-shaped configuration of the base can be advantageous during production, in particular when the housing is configured as a cast component. Due to the fillet shape of the base between two cooling fins, the housing can be more easily removed from the casting mold in this region.It is conceivable that the housing is made of a plastic. A particularly advantageous development of the invention is that the housing is formed from a metal. The metal is preferably an aluminum or at least partially comprises aluminum. Such a housing can be produced inexpensively and enables an advantageous heat dissipation of the heat generated within the housing.In a second aspect, the invention relates to a traction drive for a motor vehicle having the electric machine according to the invention.It is to be noted that all features described above and below with respect to one aspect of the present invention apply equally to every other aspect of the present invention. In particular, all features of the electric machine may equally apply to the traction drive. This also applies in reverse.Further features and advantages of the present invention are evident from the dependent claims and the exemplary embodiments below. The exemplary embodiments are not to be understood as restrictive, but rather as exemplary. They are intended to enable those skilled in the art to practice the invention. The applicant reserves the right to make individual and / or several of the features disclosed in the exemplary embodiments the subject matter of patent claims, or to include such features in existing patent claims. The exemplary embodiments are explained in more detail on the basis of drawings.In these show: FIG. 1 shows a longitudinal section through an electric machine; FIG. 2 shows a three-dimensional view of a housing of the electric machine.FIG. 1 shows a longitudinal section through an electric machine 10 of a traction drive 12 for an at least partially electrically driven motor vehicle.The electric machine 10 has a housing 14. A rotor 16 is arranged within the housing 14. The rotor 16 has an axis of rotation 18 which preferably corresponds to a longitudinal axis of the rotor 16. The rotor 16 is designed to be rotatably mounted about the axis of rotation 18 within the housing 14 via at least one bearing device 20. In other words, the rotor 16 can rotate about the axis of rotation 18 or longitudinal axis. The housing 14 surrounds the rotor 16 partially and / or in sections. Furthermore, it is provided that the housing 14 has at least one cooling fin 24 on an inner side 22 facing the rotor 16. A rotation of the rotor 16 about its axis of rotation 18 generates an air flow within the housing 14. The air flow is guided past the cooling fin 24 within the housing 14 so that heat from the air flow can be absorbed by the cooling fin 24, whereby the air or the air flow within the housing 14 of the electric machine 10 can be cooled. By cooling the airflow within the electric machine 10, the performance of the electric machine 10 may be increased.The cooling fin 24 is formed on a bearing shield 26 of the housing 14. An end face 28 of the rotor 16 oriented in the axial direction of the rotor 16 is formed at a distance from the cooling fin 14. A rotation of the rotor 16 about its axis of rotation 18 generates an air flow which acts both in the axial direction of the rotor 16 and in the radial direction of the rotor 16. The cooling fin 24 formed on the bearing plate 16 at a distance from the end face 28 of the rotor 16 can therefore be subjected to the flow of the air.In the exemplary embodiment, it is shown that the cooling fin 24 has a height in the longitudinal direction of the rotor 16, wherein the cooling fin 24 is formed over the height thereof parallel to the longitudinal direction of the rotor 16. It can be provided that the cooling fin 24 is designed to taper in sections or over its entire height, starting from the inside of the bearing shield 26 in the direction of the end face 28 of the rotor 16. This can entail manufacturing advantages if the housing 14 is preferably designed as a cast part and the cooling fin 24 is preferably designed as one piece with the housing 14. With a cooling fin 24 formed in this way, easier shelling out of the housing 14 from a casting mold is possible.In the present case, a plurality of cooling fins 24 spaced apart from one another are provided. By the plurality of cooling fins 24, which are preferably formed on the inner side 22 of the bearing shield 26 at a distance in the radial direction of the rotor 16, the surface area of the housing inner side 22 can be deliberately increased. When the cooling fins 24 are impacted, the cooling fins 24 may at least partially absorb the heat from the airflow, which may increase the cooling effect within the electric machine 10.It can also be seen that a base 30 between two cooling fins 24 spaced apart from one another is of fillet-shaped design. Due to the fillet-shaped configuration of the base 24 between the cooling fins 24, on the one hand, the air flow can be guided past the inner side 22 of the housing 14 with lower friction losses, which can have an advantageous effect on the cooling effect of the electric machine 10. In addition, the fillet-shaped configuration of the base 30 can be advantageous during the production of the housing, in particular when the housing 14 is configured as a cast component. Due to the fillet shape of the base 30 between two cooling fins 24, the housing 14 can be removed more easily from a casting mold in this region.FIG. 2 shows a three-dimensional view of the housing 14 of the electric machine 10. In this way, the cooling fin 24 or the cooling fins 24 may form a larger surface area on the inner side 22 of the housing 14, whereby the cooling effect of the electric machine 10 may be increased.It is provided that at least one cooling fin 24 formed in a circumferential manner is formed without interruptions. In other words, the cooling fin 24 formed in the shape of a ring is formed continuously over an angle of β=3600°. A center point of the cooling fin 24 formed in the shape of a ring or helix lies on the longitudinal axis of the rotor 16. a greater surface area can be achieved with a continuously formed cooling fin 24, as a result of which the cooling effect of the electric machine 10 can be increased.It can also be seen that a further cooling fin 24 has at least one interruption. In other words, the cooling fin 24 is not continuous over its length in the circumferential direction, but rather has an interruption or a plurality of interruptions formed at a distance from one another. As a result of the at least one interruption, preferably a turbulence can be generated in the air flow in a targeted manner, which can have an advantageous effect on the cooling effect.

Claims

Electric machine (10) for an at least partially electrically driven motor vehicle, having a housing (14), a rotor (16) which is arranged in the housing (14) and is mounted rotatably about an axis of rotation (18) of the rotor (16), wherein the housing (14) has a wall and at least one cooling fin (24) is formed on an inner side (22) of the wall which faces the rotor (16), and an air stream which is generated by the rotor (16) within the housing (14) can be at least partially guided past the cooling fin (24).Electric machine according to Claim 1, characterized in that the cooling fin (24) is arranged and / or formed on a bearing shield (26) of the housing (14).Electric machine according to one of the preceding claims, characterized in that the cooling fin (24) has a height, wherein the height of the cooling fin (24) is aligned substantially parallel to the longitudinal direction of the rotor (16).Electric machine according to one of the preceding claims, characterized in that the cooling fin (24) is formed so as to be circumferential, in particular in the form of a circular ring or helical ring.Electric machine according to one of the preceding claims, characterized in that a plurality of mutually spaced cooling fins (24) is provided.Electric machine according to one of the preceding claims, characterized in that the cooling fin (24), which is formed in a circumferential manner, is formed without interruptions.Electric machine according to one of the preceding claims, characterized in that the cooling fin (24), which is formed in a circumferential manner, has at least one interruption.Electric machine according to one of the preceding claims, characterized in that a base (30) between two cooling fins (24) spaced apart from one another is of fillet-shaped design.Electric machine according to one of the preceding claims, characterized in that the housing (14) is formed from a metal.Traction drive (12) for a motor vehicle having an electric machine (10) according to one of the preceding claims.

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