Cooling device for cooling stator of electric machine

Abstract

The invention relates to a cooling device for cooling a stator of an electric machine, comprising a hollow cylindrical cooling jacket and an annular channel axially adjacent to the cooling jacket, the annular channel is provided with an annular channel bottom plate, an annular channel outer wall and two annular channel axial walls, wherein the annular channel bottom plate limits an inner space of the annular channel on the radial inner side, the annular channel outer wall limits the inner space on the radial outer side, and the two annular channel axial walls are axially opposite to each other and limit the inner space in the axial direction. The inner space is fluidically connected to the outside of the annular channel via an annular channel inlet and an annular channel outlet, characterized in that the annular channel inlet is arranged offset by at least 30 DEG to at most 90 DEG with respect to an upper vertex perpendicular of the cooling device, the annular channel base plate has an azimuthally encircling rib in the axial central region thereof, said rib having an interruption which lies opposite the annular channel inlet in mirror symmetry with respect to an axially perpendicular mirror plane.

Description

Technical Field

[0001] This invention relates to a cooling device for cooling the stator of an electric motor. The cooling device includes: a hollow cylindrical cooling jacket, which, without considering the cooling jacket inlet and outlet, has a closed cooling channel device, and an annular channel axially adjacent to the cooling jacket. The annular channel has an annular channel bottom plate that defines an internal space of the annular channel on its radially inner side, an annular channel outer wall that defines the internal space on its radially outer side, and two annular channel axial walls that define the internal space axially opposite each other. The internal space is fluidly connected to the outside of the annular channel through the annular channel inlet and the annular channel outlet. Background Technology

[0002] Such a cooling device is known from document WO 2010 / 049204 A2.

[0003] When an electric traction motor operates in a motor vehicle, it generates a high current, which inevitably leads to heat loss. Therefore, it is necessary to efficiently dissipate this heat so that it can be used for heating in other locations when necessary. For this purpose, a cooling jacket is typically wrapped around the stator of the traction motor, which is usually designed as an internal rotor motor. This is essentially a double-walled sleeve that is thermally conductively in contact with the radial outer wall of the stator and can be flushed by a cooling medium, typically cooling oil or cooling water, or flushed during operation. The cooling medium flows into the substantially closed cooling channel of the cooling jacket through the cooling jacket inlet and then flows out through the cooling jacket outlet. Many specific methods of guiding such cooling channels are known to those skilled in the art, designed to achieve the most efficient and uniform cooling possible, but play only a secondary role in this invention. For example, a multi-stranded helical channel guide is known in the aforementioned representative document WO 2010 / 049204 A2. Document DE10 2021 121 031 S1 discloses a substantially axial channel guide. Document US 2023 / 0268795 A1 discloses a channel guide that is substantially along the azimuth angle. Document DE 10 2013 222 697 A1 discloses a method that simplifies the arrangement of cooling channels into radially extending columnar structures, with the cooling medium finding a flow path between these columnar structures.

[0004] As is known from representative document WO 2010 / 049204 A1, an annular channel, acting as a distribution ring, is axially arranged on one side of the cooling jacket. This annular channel has an inlet at the upper apex of the cooling device, designed as an inclined inlet pipe. Those skilled in the art should understand that the terms "upper" and "lower" used in this description always refer to the intended final installation location of the corresponding cooling device in the vehicle. This annular channel is directly connected to the cooling channel assembly of the cooling jacket via multiple axially extending connecting channels, which are essentially designed as through holes. These connecting channels or through holes collectively form the annular channel outlet and simultaneously constitute the cooling jacket inlet. The ratio of connecting channels or through holes to the annular channel inlet is designed such that the cooling medium flowing in through the annular channel inlet accumulates in the annular channel, thereby ensuring that the hydrostatic pressure from all connecting channels or through holes to the cooling jacket is substantially the same. Therefore, the annular channel acts as a distribution ring, ensuring that the cooling medium is evenly distributed along the circumference of the cooling jacket, even though the position of the annular channel inlet is very fixed. In known cooling devices, the axially opposite sides of the cooling jacket are provided with a collection ring similar to a distribution ring. This collection ring receives and collects the cooling medium flowing out of the cooling jacket and discharges it through a discharge pipe.

[0005] As can be seen from the aforementioned document DE 10 2021 121 031 A1, the axially adjacent annular channels of the cooling jacket also serve as distribution rings or collection rings, but at the same time, there are radially inward openings through which the cooling medium can be directly sprayed onto the winding heads on the stator.

[0006] A drawback of known distribution ring designs is the potential for air bubbles to form on the upper part of the distribution ring, leading to uneven cooling. This uneven cooling primarily affects the stator region thermally connected to the distribution ring and / or the housing containing that region. Undesirable heating occurs, particularly in the bubble regions. Furthermore, in the direct connection between the distribution ring and the cooling jacket as described in the aforementioned literature, there is also the problem of uneven cooling medium supply to the cooling jacket. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to improve the cooling equipment of the aforementioned type in order to achieve a more uniform cooling effect.

[0008] This invention provides a cooling device for cooling the stator of a motor. The cooling device includes: a hollow cylindrical cooling jacket; without considering the cooling jacket inlet and outlet, the cooling jacket has a closed cooling channel arrangement; and an annular channel axially adjacent to the cooling jacket. The annular channel has an annular channel base plate defining an internal space radially inward, an annular channel outer wall defining the internal space radially outward, and two axially opposed annular channel axial walls defining the internal space axially. The technical problem is thus solved by the annular channel being fluidly connected to the outside of the annular channel through an annular channel inlet and an annular channel outlet. The annular channel inlet is arranged offset from the vertical line of the upper apex of the cooling device by at least 30° to at most 90°, and the annular channel base plate has ribs surrounding it along an azimuth angle in its axial central region. The ribs have interruptions that are mirror-symmetrically opposite the annular channel inlet with reference to an axially perpendicular mirror plane.

[0009] The preferred embodiment of the present invention is the technical solution of the present invention.

[0010] The basic idea of ​​this invention is to divide an annular channel into two sub-channels, also referred to as flow paths, by ribs, wherein these flow paths are interconnected in a defined manner. Preferably, the rib height is less than the total height of the channel, so that although the cooling medium is mainly guided along the flow paths, it can also overflow from one flow path to the other across the ribs. However, due to gravity, this mainly occurs in the lower region of the annular channel. In the upper region, it is mainly the air carried by the cooling medium that can be exchanged between the flow paths in this way.

[0011] The ribs are interrupted in at least one of the upper quadrants of the annular channel, creating a direct and complete connection between the two channels. This interruption is arranged mirror-symmetrically to the annular channel inlet, which is located in the other upper quadrant of the annular channel. This design of the ribs forces air contained in the annular channel, or air introduced with the cooling medium into the channel communicating with the annular channel inlet, into the other channel, particularly its upper top region. From there, the air is forced out by the cooling medium that subsequently flows in and may overflow between the channels, and compressed towards the annular channel outlet. Especially when the annular channel outlet is preferably designed as an azimuthally offset drain pipe relative to the annular channel inlet, the air is gradually and completely discharged from the annular channel through this drain pipe. The drain pipe can be connected to the inlet pipe of the cooling jacket via a heat exchanger. This arrangement is referred to as an indirect connection between the annular channel and the cooling jacket.

[0012] In the case of a direct connection between the annular channel and the cooling jacket, as described above in the discussion of the prior art, air is evenly distributed into the cooling jacket, passes through the cooling jacket, and is discharged from the cooling jacket outlet.

[0013] This design prevents persistent air buildup in the top area of ​​the annular channel under all circumstances, thus significantly balancing cooling performance.

[0014] In principle, it is conceivable that the ribs are interrupted at multiple locations along their extension direction. However, it is preferable that the ribs consist of only one rib body continuously surrounding most of the annular channel and two end segments defining the boundaries of the interruption. In other words, it is preferable that there is exactly one rib interruption.

[0015] Furthermore, it is preferably specified that the inlet of the annular channel is offset relative to the axial center of the channel. This allows the coolant to reliably flow into only one of the two sub-channels or one of the two flow paths. This arrangement ensures that the above process can be carried out reliably even when the vehicle equipped with the cooling device according to the invention is traveling unevenly.

[0016] Alternatively, preferably, and additionally, the annular channel body may be offset relative to the channel center in a direction opposite to the offset direction of the annular channel inlet, by an offset of 5% to 15% of the axial channel width. In other words, this means that the two sub-channels or flow paths have different widths, with the cooling medium injected into the wider of the two flow paths. Air is primarily forced into the top region above the narrower flow path through the interruption, and from there, it is forced through the subsequently flowing cooling medium to the annular channel outlet. The air remaining in the top region above the wider flow path is drawn out by the pressure difference generated by the flow in the annular channel according to the principle of a hose pump and sent back into the annular channel for a new circulation.

[0017] To simplify or reliably design the flow path transition between air and cooling medium, it is preferable that at least one of the end sections of the rib has an axial bend, with the annular channel inlet offset relative to the axial center of the channel along the axial direction. In particular, it can be specified that the end section of the rib closer to the annular channel inlet along the azimuth angle ends with an axial distance of 5% to 15% of the axial channel width relative to the axial wall of the annular channel closest to that end section, and this end section typically defines the end section of the interruption from above. This means that the sub-channel directly accessible from the annular channel inlet is almost, but not completely, closed in the region of the interruption, thereby enhancing the aforementioned hose pump effect to draw out air contained in the upper top region of the sub-channel. It is particularly advantageous that the corresponding end section of the rib is designed to extend in a straight line and with an inclined bend relative to the rib body. Therefore, this end section simultaneously forms an effective flow guide structure for supporting the flow path transition of the cooling medium. While the end section could also be designed in a curved shape, this design is currently less advantageous than the aforementioned straight and bent design. Those skilled in the art should understand that the term “bending” as used herein is a broader concept, encompassing both straight but bent designs and designs with curved shapes.

[0018] Alternatively or additionally, the end section of the rib that is further away from the inlet of the annular channel along the azimuth angle, i.e., the end section defining the interruption from below, ends relative to the rib body with an axial distance of 5% to 15% of the axial channel width. In other words, the narrower flow channel widens slightly towards the interruption, thereby avoiding the formation of backward-rotating vortices at the confluence of adjacent flow channels. The corresponding end sections of the rib are preferably designed with a curved shape.

[0019] In an improved embodiment of the invention, two directly adjacent annular channels may be provided, at least one, but preferably both, designed according to the invention. If two annular channels are provided, they may be fluidly interconnected. The annular channel inlet of the upstream annular channel may be designed as an externally connectable nozzle, and the annular channel outlet of the downstream annular channel may be directly or indirectly connected to a cooling jacket. In a particularly preferred embodiment, the upstream annular channel may have a branch leading to an external component requiring cooling, such as an electronic torque vectoring unit, and then rejoining the annular channel after the external component.

[0020] Regarding the sealing of one or more annular channels, these channels are preferably sealed on one side relative to the cooling jacket and on the other side relative to the environment surrounding the housing, where free oil is often present. The seal relative to the cooling jacket is desirable to prevent lateral flow between the cooling jacket and the annular channel, which could interfere with the aforementioned process. The seal relative to the environment surrounding the housing is necessary to prevent contamination of the cooling medium by external oil or dilution of the oil within the housing. The corresponding seal can be achieved by placing O-rings in appropriately sized annular grooves. It is advantageous to place two parallel O-rings in two parallel grooves for sealing with the oil passage structure. The sealing material of the O-rings may be unstable with oil over long periods. However, a double seal is generally sufficient to maintain adequate sealing during the normal service life of the vehicle.

[0021] For the special structures of cooling jackets and one or more annular channels, the so-called assembly-modification scheme is advantageous. Here, corresponding parts of different sleeves and channels are nested together to form a multi-walled cooling device. Which components are assigned to which sleeve layer is determined by the design engineers based on the specific requirements. Of course, in principle, a single-piece modification scheme, such as one achieved through casting, can also be considered. Attached Figure Description

[0022] Further features and advantages of the invention are obtained, in particular, from the following description and accompanying drawings.

[0023] In the attached diagram:

[0024] Figure 1 This shows a partially transparent view of the drive housing of an electric vehicle.

[0025] Figure 2 A side view of the inner sleeve of a preferred embodiment of the cooling device according to the invention is shown, and

[0026] Figure 3 Show Figure 2 A partially transparent side view of the annular channel region of the sleeve shown.

[0027] The same reference numerals in the accompanying drawings denote the same or similar elements. Detailed Implementation

[0028] Figure 1A partially transparent schematic diagram of the drive housing 10 of an electric vehicle is shown to illustrate the positioning of the cooling device 12 according to the invention and the preferred cooling medium flow path through the cooling device 12. The cooling device 12 includes a cooling jacket 14 and an annular channel 16. The cooling jacket 14 is designed as a double-layered hollow cylinder containing a closed cooling channel assembly 141, which consists of cooling channels extending partially along the azimuth and partially along the axial direction. The annular channel 16 extends along the axial direction (… Figure 1 (Right side) is connected to the cooling jacket 14. Within the cylindrical internal space enclosed by the cooling jacket 14 and the annular channel 16, as... Figure 1 As shown in the diagram, the electric tractor is installed on the final assembled motor vehicle, and the outer surface of the stator of the electric tractor forms thermal contact with at least the inner wall of the cooling jacket 14.

[0029] Circular passage 16 in its upper region, Figure 1 In particular, its upper right quadrant has an annular channel inlet 161 through which the cooling medium flows into the annular channel 16. At another location within the annular channel 16, in... Figure 1 In the lower left quadrant of the cooling jacket 14, an annular channel outlet 162 is arranged, through which the cooling medium can flow out of the annular channel 16. In other embodiments, an axial connecting channel is provided that is connected to the cooling channel device 141 of the cooling jacket 14.

[0030] In the illustrated embodiment, an additional cooling device 18 is connected upstream of the cooling device 12 according to the invention. This is particularly relevant to cooling structures for power electronic devices, especially pulse inverters, which are necessary for supplying power to motors as needed. A heat exchanger 20 is connected downstream of the annular channel outlet 162, through which the cooling medium can release or absorb heat, depending on the specific circumstances, after the annular channel 16. After flowing through the heat exchanger 20, the cooling medium flows into the cooling channel device 141 through the cooling jacket inlet 142, and then exits through the cooling jacket outlet 143.

[0031] The cooling device 12 according to the present invention is preferably a so-called modular cooling device 12, which is composed of multiple sleeves assembled into a socket. Figure 2 The inner sleeve 121 is shown, with multiple rib structures protruding from its surface. These rib structures are particularly shown as ribs 24 of the annular channel 16 and additional ribs in the region of the cooling sleeve 14 that form the cooling channel assembly 141. Furthermore, a sealing structure 22 is provided, which axially defines the boundaries of the cooling sleeve 14 and the annular channel 16 and is configured as a protrusion with a slotted annular groove into which a sealing element, such as an O-ring, can be embedded.

[0032] In order to form a flow channel, the inner sleeve 121 is inserted into the outer sleeve (not shown), the inner wall of which is in close contact with the ridge of at least the ribs that constitute the cooling channel device 141, and forms a fluid-tight boundary with the sealing element arranged in the sealing structure 22.

[0033] Rib 24 almost completely surrounds the annular channel 16. Rib body 241 surrounds most of the circumferential portion of the annular channel 16, but... Figure 2 and Figure 3 As can be seen, the main body of the rib is interrupted at exactly one position. The area of ​​the rib 24 directly adjacent to this interruption is referred to herein as the first end segment 242 and the second end segment 243.

[0034] Especially Figure 3 As shown, the interrupted section is at approximately the same height as the annular channel entrance 161, and particularly at the same height as the point where the annular channel entrance enters the annular channel 16. Figure 3 As shown, the entrance to this annular channel is clearly located from the axial center of the channel ( Figure 3 Offset to the right (from center). In the illustrated embodiment, the rib body 241 extends slightly in the opposite direction from the axial center of the channel (offset to the right). Figure 3 The offset V1 in the middle.

[0035] In the illustrated embodiment, the end sections 242 and 243 of the rib 24 are designed in a special manner. The first end section 242 is designed to be straight, and the first end section is bent at an angle relative to the rib body 241. The first end section extends into one of the two flow channels separated by the rib body 241, and the annular channel inlet 161 also connects to this flow channel. However, the first end section is not completely closed as... Figure 3 The flow channel is shown on the right. Conversely, the first end section ends with an offset V2 before the axial boundary of the annular channel 16. This offset V2, along with the previously mentioned offset V1, is approximately 5% to 15% of the total width of the axial channel.

[0036] The second end segment 243 of the rib 24 is also curved and bends in the same direction as the first end segment 242. However, this bending is achieved by bending the end segment 243 itself, rather than bending the straight end segment as in the first end segment 242. The second end segment 243 terminates approximately at the axial center of the annular channel 16.

[0037] For information on the effectiveness of this design, please refer to the implementation details in the general section of this specification.

[0038] Of course, the embodiments discussed in the detailed description and shown in the figures are merely exemplary embodiments of the present invention. Those skilled in the art can discover a wide range of variations based on this disclosure. In particular, alternatives can be made... Figure 1 and Figure 2 The figure shows only one annular channel 16, but multiple, especially two, annular channels 16 are provided, wherein the first annular channel can be used for additional cooling structures not shown in the figure.

[0039] List of reference numerals

[0040] 10 drive housing

[0041] 12 Cooling Equipment

[0042] 121 Inner Sleeve

[0043] 14 Cooling jacket

[0044] 141 Cooling Channel Device

[0045] 142 Cooling jacket inlet

[0046] 143 Cooling jacket outlet

[0047] 16-ring channel

[0048] 161 Circular Passage Entrance

[0049] 162 Circular Tunnel Exit

[0050] 18. Additional cooling equipment

[0051] 20 heat exchangers

[0052] 22 Sealing Structure

[0053] 24 ribs

[0054] 241 ribs main body

[0055] End section of rib 242

[0056] End section of rib 243

Claims

1. Cooling device (12) for cooling a stator of an electrical machine, the cooling device comprising: - a hollow-cylindrical cooling jacket (14) having closed cooling channel means (141) disregarding a cooling jacket inlet (142) and a cooling jacket outlet (143), and - an annular channel (16) axially adjacent to the cooling jacket (14), the annular channel having an annular channel floor radially inside defining an inner space of the annular channel, an annular channel outer wall radially outside defining the inner space, and two axially opposite annular channel axial walls axially defining the inner space, wherein the inner space is fluidically connected to the outside of the annular channel (16) by an annular channel inlet (161) and an annular channel outlet (162), characterized in that the annular channel inlet (161) is arranged offset by at least 30° and at most 90° with respect to a perpendicular of an upper vertex of the cooling device (12), and in that the annular channel floor has in its axially central region a rib (24) circumferentially in azimuth, the rib having a discontinuity which is oppositely mirrored symmetrically with respect to the annular channel inlet (161) with reference to an axially vertical mirror plane.

2. Cooling device (12) according to claim 1, characterized in that The rib (24) is composed of a rib body (241) continuously circumferentially surrounding a major portion of the annular channel (16), and two end sections (242, 243) delimiting the discontinuity.

3. Cooling device (12) according to one of the preceding claims, characterized in that The annular channel inlet (161) is offset with respect to an axial center of the annular channel (16).

4. Cooling device (12) according to claim 3, characterized in that The rib body (241) is arranged offset by 5% to 15% of an axial channel width with respect to the axial center of the annular channel (16) in a direction opposite to a direction of the offset of the annular channel inlet (161).

5. Cooling device (12) according to claim 3 or 4 and claim 2, characterized in that At least one of the end sections (242, 243) of the rib (24) has a curvature in an axial direction in which the annular channel inlet (161) is offset with respect to the axial center of the annular channel (16).

6. Cooling device (12) according to claim 5, characterized in that The end section (242) of the rib (24) closer in azimuth to the annular channel inlet (161) ends with an axial distance of 5% to 15% of the axial channel width with respect to the annular channel axial wall closest to this end section.

7. Cooling device (12) according to claim 5 or 6, characterized in that The end section (242) of the rib (24) closer in azimuth to the annular channel inlet (161) itself extends linearly and obliquely bent with respect to the rib body (241).

8. Cooling device (12) according to one of claims 5 to 7, characterized in that The end section (243) of the rib (24) farther in azimuth from the annular channel inlet (161) ends with an axial distance of 5% to 15% of the axial channel width with respect to the rib body (241).

9. Cooling device (12) according to one of claims 5 to 8, characterized in that The end section (243) of the rib (24) farther in azimuth from the annular channel inlet (161) itself is designed curved.

10. Cooling device (12) according to one of the preceding claims, characterized in that The annular channel outlet (162) is designed as a discharge nozzle arranged angularly offset relative to the annular channel inlet (161) or as a connecting channel or a plurality of connecting channels axially extending, which communicates with the cooling channel means (141) of the cooling jacket (14).

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