WO2018046523A1

WO2018046523A1 - Electrical machine comprising a structural unit and a cooling jacket

Info

Publication number: WO2018046523A1
Application number: PCT/EP2017/072310
Authority: WO
Inventors: Erich COSIC
Original assignee: Magna powertrain gmbh & co kg
Priority date: 2016-09-08
Filing date: 2017-09-06
Publication date: 2018-03-15
Also published as: DE102016217120A1

Abstract

The invention relates to an electrical machine that comprises a structural unit and a cooling jacket that surrounds at least some sections of said structural unit and that has at least one depression on its outer side, said cooling jacket being connected, particularly bonded, in the region of the depression, to a component of said structural unit that lies against the inner side of the cooling jacket.

Description

Electric machine with a structural unit and a cooling jacket

The present invention relates to an electrical machine having a structural unit and a cooling jacket surrounding the structural unit at least in sections.

Electrical machines of this type are already known. The assembly may in particular comprise a stator and a rotatably mounted rotor in the stator (electric motor). For various reasons familiar to the person skilled in the art, the operational waste heat of the machine must be removed as efficiently and reliably as possible. For this purpose - not necessarily exclusively - the cooling jacket is provided which surrounds the unit in sections, in particular circumferentially. However, the connection between the cooling jacket and the electric machine has proved problematic. On the one hand, the connection must be particularly reliable and robust, i. especially insensitive to temperature variations and mechanical stresses (e.g., operational vibration). On the other hand, the connection must be such that waste heat can be removed as efficiently as possible. For example, the cooling jacket with the electric machine, in particular with the assembly should be in the best possible thermally conductive contact. A large contact surface can have a particularly favorable effect on the efficiency of the heat conduction. The simultaneous fulfillment of both requirements - robust connection and good thermal conductivity - represents a special challenge.

The cooling jacket can be frictionally connected to the unit by means of interference fit. Although the stated requirements can then be met to a certain extent, the cooling jacket must be made relatively thick be so that it does not come to cracks in the cooling jacket at low temperatures and the cooling jacket is still stable and reliable connected to the unit at high temperatures. However, a thick-walled cooling jacket leads to a larger design of the electric machine and to a reduced heat dissipation efficiency. In general, the size of the entire electrical machine, ie inclusive cooling jacket, given, so that the use of the thick-walled cooling jacket undesirably limits the maximum size of the electrical machine, such as the rotor diameter, and consequently the achievable power density.

From DE 1746614U an electric machine with a cooling structure is known. In this case, cooling channels in the form of corrugated sheets are welded directly onto the laminated stator core. The cooling jacket consists of a metal jacket and from the cooling channels formed by pipes or corrugated metal which are interrupted by longitudinal ribs. End is the construction completed by end shields.

From JP 2010178598A an electric machine is known whose metallic cover plate is connected to the stator by friction stir welding.

From DE 102015006904, DE 102015006526 A1 and DE

102015006348 A1 cooling jackets are known, which form a gap as a closed jacket, are arranged in the cooling fins. The cooling fins are designed such that they have a recess in which rests the outer covering of the cooling jacket on the inner cooling jacket.

It is therefore an object of the invention to provide an improved electrical machine of the above type, in which the problems described are eliminated. The object is achieved by an electric machine having the features of claim 1.

The cooling jacket of the machine according to the invention has on its outer side at least one recess. Further, the cooling jacket in the region of the recess with a voltage applied to the inside of the cooling jacket component of the assembly, in particular cohesively connected.

In principle, the cooling jacket in the region of the depression can be provided with any means, e.g. Screws to be connected to the component of the assembly. Preferably, however, a cohesive connection is provided. As a result, on the one hand, the requirements for mechanical robustness can be met particularly well. On the other hand, the cooling jacket can be reliably sealing against coolant flowing along the cooling jacket, in particular coolant liquids. The connection may be a welded connection, in particular a friction stir welding connection.

It is understood that any number of wells can be provided. The depressions do not all have to be the same.

As mentioned, the assembly may comprise a stator and a rotor, ie the essential parts of an electric motor, which heat up during operation and must be cooled accordingly. The component of the structural unit, which bears against the inside of the cooling jacket and is connected to the cooling jacket in the region of the depression, can in particular be an element or a section of the stator. This can rest in sections flat on the inside of the cooling jacket. The cooling of the electric machine can thus be accomplished particularly well. Inn the recess of the cooling jacket is thinner than outside this area. A cohesive connection provided in this thinner area can have particularly favorable properties, since, for example, it is ensured that a weld extends sufficiently far into the component resting against the cooling jacket, without an excessively large heat input being required.

The fact that the cooling jacket is made thinner in the region of the depression does not mean that the cooling jacket per se is made thick. On the contrary, the cooling jacket can have a thinner wall than with the conventionally used press fit, in which, moreover, the thickness of the cooling jacket must be determined consuming with regard to the press fit. In the invention, a comparatively thin-walled cooling jacket can be used without any problem, which improves both the achievable power density (for example, by a larger rotor diameter) and the heat dissipation, and the mechanical stresses due to temperature fluctuations are reduced.

The cooling jacket is preferably connected to the component in the region of the depression by friction stir welding. In this case, the precisely defined spatial extent of the connection and the comparatively low heat input are advantageous. However, other welding methods may also be used. The recess is preferably adapted so that a welded connection with the desired properties can be formed without problems. The cohesive connection can be carried out continuously, in sections or even selectively.

The cooling jacket may for example be made in one piece by means of pressure or continuous casting. Alternatively or additionally, the cooling jacket can be made by milling. Advantageous embodiments of the invention are apparent from the drawings, the description and the dependent claims.

According to the invention, the recess extends substantially in the axial direction of the cooling jacket. In particular, the recess may extend axially parallel and e.g. to be a long-necked The requirements for the stability and robustness of the connection between the cooling jacket and the component as well as a large contact surface can be met in this way particularly well. This applies in particular to the case of a typically cylindrically extending electrical machine which is to be cooled along its axial length by the cooling jacket. It has been found that a compound extending in the axial direction is well suited to reliably absorb the forces occurring during operation between the component and the cooling jacket connected to it. For this purpose, the recess may extend more than 50%, preferably more than 75% or even substantially completely over the axial length of the cooling jacket, in order to minimize the partial loading of the connection. Axial end portions of the cooling jacket may be free from the recess.

It is understood that the connection preferably extends corresponding to the recess, i. The size of the recess can be adapted to the dimensions of the cohesive connection.

It is further understood that the recess or the cohesive connection need not necessarily extend only in the axial direction, for example in the direction of the longitudinal axis of the electrical machine. There are also recesses or connecting courses conceivable, which extend (in sections) transversely or obliquely to the axial direction, in particular (partially) in the circumferential direction of the cooling jacket. According to a further embodiment, the cooling jacket has a symmetrical cross-sectional shape. In particular, the cooling jacket is formed substantially hollow cylindrical. According to a further embodiment, the thickness or thickness of the cooling jacket in the region of the depression - substantially continuously or in sections - is substantially constant. The recess can thus be easily manufactured, for example by means of a milling process. Furthermore, the material connection produced, for example, by means of friction stir welding does not have to be arranged exactly, at least with regard to the thickness of the cooling jacket in the depression. Thus, unless the connection with respect to the voltage applied to the inside of the cooling jacket component is not provided only at a well-defined location, the position of the adhesive connection within the well can be varied without problems, which reduces the requirements of the manufacturing process.

The recess may have a substantially rectangular cross-section. The depression defining surfaces are preferably smooth. As an alternative to a rectangular depression, a concave shape can also be provided for the depression, in which case the thickness of the cooling jacket in the region of the depression can vary.

According to the invention, a complementary formed to the recess insert is arranged in the recess. Such an insert may close the recess and cover the area of the connection so as to make it e.g. to protect against external influences, in particular against contact with coolant liquid.

The insert may generally be positively and / or non-positively, in particular cohesively connected to the cooling jacket. Thus, the insert may be firmly connected to the cooling jacket, for example by welding, gluing or Terminals. In this case, a seal of the recess to prevent ingress of liquids and / or dirt can be realized in the recess. Alternatively, the insert may be loosely inserted into the recess or be connected by positive engagement with the cooling jacket. The insert can also be held in the depression by a jacket surrounding the cooling jacket.

The recess may be rounded at least at one axial end. The insert formed complementary to the depression can thereby be easily, i. without tilting, be inserted into the recess.

Preferably, the insert terminates substantially flush with the outside of the cooling jacket. The insert thus offers no special attack surface for dirt. Furthermore, a coolant liquid flow in the region of the insert without significant friction losses.

According to the solution according to the invention, the cooling jacket has at least one outer circumferential cooling rib, which is interrupted in the region of the depression. In this case, the insert has at least one cooling rib which connects the interrupted cooling rib of the cooling jacket "with itself", i. The cooling rib of the insert bridges the interruption of the cooling rib of the cooling jacket. A respective cooling rib can serve to delimit cooling channels through which a coolant liquid is passed. But the cooling fins can also be provided exclusively to increase the surface of the cooling jacket.

According to a further embodiment, the cooling jacket has at least two adjacent cooling ribs which circulate on the outside and which are each interrupted in the region of the depression. In this case, the insert part can have at least one cooling rib, which connects the two adjacent cooling ribs to one another. The cooling rib of the insert can therefore the adjacent cooling fins of the Bridge the cooling jacket at an angle over the recess or the insert part. In this way, cooling channels can be easily connected to each other. An elaborate production of thread-like arranged around the cooling jacket around cooling fins is thus not necessary to lead a coolant flow several times circumferentially along the cooling jacket.

The invention will now be described by way of example only with reference to the drawings, in which:

Fig. 1 is a cooling jacket for an electrical machine with an outside

Depression shows;

Fig. 2 shows an insert for the recess of the cooling jacket of Fig. 1;

Fig. 3 shows the cooling jacket of Fig. 1 with the insert part of Fig. 2;

Fig. 4 shows another insert for the recess of the cooling jacket of Fig. 1;

Fig. 5 shows the cooling jacket of Fig. 1 with the insert part of Fig. 4.

In Fig. 1 1, a cooling jacket 10 is shown, which has a hollow cylindrical basic shape with symmetrical cross-section. The cooling jacket 10 is intended to be connected to a not shown component of a structural unit of an electrical machine (not shown). In particular, the component may be a stator (not shown) of an electric motor, which is arranged inside the cooling jacket 10 and at least partially bears against the inside of the cooling jacket 10. The cooling jacket 10 is therefore preferably at least partially se formed inside complementary to the stator. To optimize the heat dissipation, it is applied over a large area to the stator.

On its outside, the cooling jacket 10 has an elongated recess 12 which extends in the axial direction, i. axially parallel to the longitudinal axis of the shell 10 extends. The recess 12 extends substantially completely over the axial length of the jacket 10 and is rounded at the axial ends in each case. The recess 12 has a substantially rectangular cross-section, wherein the thickness of the shell 10 in the region of the recess 12 is smaller. The recess 12 is not a passage or an opening of the cooling jacket 10.

In the region of the recess 12, a material connection with a voltage applied to the inside of the jacket 10 component of a structural unit (not shown) can be produced. Preferably, a friction stir welding process is used for this purpose.

The cooling jacket 10 also has on its outer side a plurality of circumferential cooling fins 14 in the circumferential direction; in the concrete example four equidistantly spaced cooling fins 14. The cooling fins 14 serve e.g. for limiting cooling channels, in which cooling liquid is passed for cooling the electrical machine.

Fig. 2 shows a complementary to the recess 12 of the shell 10 of FIG. 1 formed insert 16a. The insert 16a has on its upper side - analogous to the cooling ribs 14 of the shell 10 - four equidistant from each other arranged cooling fins 18. The insert 16a is disposed in the recess 12 or inserted into the recess 12, so that the state shown in Fig. 3 results. A respective cooling rib 18 of the insert 16a now bridges a respective cooling rib 14 of the jacket 10, so that the cooling ribs 14 are closed in each case completely circumferentially. Here is an advantage of the invention in that In the region of the depression 12, a continuous cohesive connection can be formed over the axial length of the jacket 10, without the cooling fins 14 having an obstructive effect. Although they are interrupted in the region of the recess 12, but are closed by the insert 16a again.

The insert 16a can thus compensate for the "interruption" of the outer contour of the shell 10 caused by the recess 12, the cohesive connection being covered and protected on the outside. The insert 16a may be e.g. be integrally connected to the cooling jacket 10 at its axial ends, or completely along its outer contour. As mentioned above, but other types of connections are conceivable.

FIG. 4 shows a further insert part 16b which, as an alternative to the insert part 16a of FIG. 2, can be arranged in the recess 12. The insert 16b has four equidistantly spaced and inclined to the longitudinal axis of the insert 16b extending cooling fins 20. The cooling fins 20 have at their ends a respective kink, which is followed by a respective end section which runs perpendicular to the longitudinal axis of the insert 16b. Due to the cooling ribs 20, the insert 16b is adapted to connect two neighboring cooling ribs 14 of the jacket 10 bridging each other (see FIG. 5). In this way, coolant liquid can be diverted from a limited by two cooling fins 14 channel to an adjacent channel.

Reference number list cooling jacket

deepening

cooling fin

a, 16b insert

, 20 cooling rib

Claims

claims

1 . Electric machine with a structural unit and a cooling jacket (10) surrounding the structural unit at least in sections, which has at least one recess (12) on its outside, wherein the cooling jacket (10) in the region of the recess (12) with a on the inside of the cooling jacket (10 ) adjoining component of the assembly is materially connected, characterized in that the recess (12 in the axial direction of the cooling jacket (10), wherein the recess is an axially parallel recess (12) or long groove, and a complementary to the recess (12) in the recess (12) is arranged and the cooling jacket (10) has at least one outer circumferential cooling rib (14) which is interrupted in the region of the recess (12), wherein the insert part (16a) at least one Cooling fin (18) which bridges the interrupted cooling rib (14) of the cooling jacket (10).

2. Electrical machine according to claim 1, characterized in that extending the recess (12) over more than 50%, preferably more than 75% and in particular substantially completely over the axial length of the cooling jacket (10).

3. Electrical machine according to at least one of the preceding claims, characterized in that the thickness or thickness of the cooling jacket (10) in the region of the recess (12) is substantially constant.

4. Electrical machine according to at least one of the preceding claims, characterized in that the insert part (16a, 16b) is fixedly connected to the cooling jacket (10).

5. Electrical machine according to at least one of the preceding claims, characterized in that the insert part (16a, 16b) is substantially flush with the outside of the cooling jacket (10).

6. Electrical machine according to at least one of the preceding claims, characterized in that the cooling jacket (10) has at least two circumferentially adjacent adjacent cooling ribs (14) which are each interrupted in the region of the recess (12),

wherein the insert part (16b) has at least one cooling rib (20) which connects the two adjacent cooling ribs (14) to each other.

7. Electrical machine according to at least one of the preceding claims, characterized in that the cooling jacket (10) has a symmetrical cross-sectional shape.

8. Electrical machine according to at least one of the preceding claims, characterized in that the structural unit comprises a stator and a rotor, wherein the component is an element or a portion of the stator.

9. Electrical machine according to at least one of the preceding claims, characterized in that the connection between the cooling jacket (10) and the component in the region of the recess (12) is a welded connection, in particular a friction stir welding connection.