Cooler for a power electronics assembly, and power electronics assembly

Abstract

The invention relates to a cooler (1) for a power electronics assembly, having a housing (2) which encloses a cavity (12), said cavity (12) having an inlet (6), an outlet (8), and a cooling duct (19) through which a coolant can flow from the inlet (6) to the outlet (8). Flow-guiding elements (3, 4, 10) are arranged in the cooling duct (19) in such a way that a plurality of flow zones (15, 16, 17) and a number of mixing zones (7) are provided one behind the other in the flow direction, the flow zones (15, 16, 17) being formed by bypass zones (5), which are arranged next to one another transversally to the flow direction, and by heat exchange zones (14).

Description

[0001] Description

[0002] Cooler for a power electronic arrangement and power electronic arrangement

[0003] The invention relates to a cooler for a power electronic arrangement, for example an inverter of an electric motor, comprising a housing enclosing a cavity, wherein the cavity has an inlet and an outlet and a cooling channel through which a liquid coolant can flow from the inlet to the outlet. It further relates to a power electronic arrangement r with such a cooler.

[0004] An inverter for an electric motor comprises multiple power semiconductor modules that generate high power losses during operation and therefore require cooling. In a typical design, the power semiconductor modules are mounted directly on a liquid-cooled cooler housing, either directly or via an electrically insulating layer or substrate, with the modules arranged sequentially in the direction of coolant flow.

[0005] During operation, the temperature difference between the coolant and the power semiconductor modules decreases in the direction of flow, and the power semiconductor module furthest downstream receives the least cooling. Therefore, this least cooled power semiconductor module of the inverter determines both the maximum possible performance and the maximum lifespan of the entire inverter.

[0006] It is therefore a task to specify a cooler for a power electronic assembly that enables improved performance and a longer lifespan for the power electronic assembly.

[0007] This problem is solved by the subject matter of the independent patent claim. Advantageous embodiments and further developments are the subject matter of the dependent claims.

[0008] According to one aspect of the invention, a cooler for a power electronic arrangement is provided, comprising a housing enclosing a cavity, the cavity having an inlet and an outlet and a cooling channel through which a liquid coolant flows from the inlet to the outlet. Flow-guiding elements are arranged in the cooling channel such that a plurality of flow zones and a number of mixing zones are arranged one after the other in the flow direction, the flow zones being formed by bypass zones and heat transfer zones arranged side by side transversely to the flow direction. The flow zones and the bypass zones are, in particular, arranged in one plane.

[0009] The cooling channel of the cooler is thus divided into zones both in the direction of flow and perpendicular to the flow direction, which differ by the flow-guiding elements arranged within them. Perpendicular to the flow direction are bypass zones, which are characterized by the fact that they have no or essentially no flow-guiding elements, allowing the coolant to flow through them quickly and with reduced heat absorption. The flow in the bypass zones can, in particular, be laminar.

[0010] In contrast, the heat transfer zones arranged perpendicular to the flow direction next to the bypass zones are characterized by increased heat transfer. This is achieved by incorporating more flow-guiding elements into these zones, which allow the coolant flow to pass through at a reduced velocity and with increased heat absorption. The flow in the heat transfer zones can be laminar and / or turbulent.

[0011] For example, bypass zones can be arranged at the edge of the cooling channel with a heat transfer zone in between, or vice versa. Depending on the dimensions of the cooling channel, more heat transfer zones and bypass zones can also be provided side by side, perpendicular to the flow direction.

[0012] The bypass zones and heat transfer zones are arranged in the flow zones of the cooling channel. A multiple of these flow zones are arranged sequentially in the direction of flow and may be separated from each other by mixing zones.

[0013] The mixing zones are characterized by the fact that coolant, which has previously flowed through a bypass zone, mixes with coolant, which has previously flowed through a heat transfer zone. This is achieved by appropriately directing the coolant flow. For example, a mixing zone can be free of flow-guiding elements, while in successive flow zones, the arrangement of bypass zones and heat transfer zones is reversed, so that no two bypass zones or two heat transfer zones follow each other in the flow direction. This directs the coolant flow perpendicular to the flow direction and promotes the mixing of coolant from previous bypass zones and heat transfer zones. The flow in the mixing zones can be turbulent or exhibit high turbulent components.

[0014] The cooler has the advantage of a more uniform distribution of cooling capacity in the direction of flow. This is achieved by allowing relatively cool coolant in the bypass zones to reach downstream flow zones without increased heat absorption. This results in a greater temperature difference between the coolant and the housing at the outlet, which can be used to cool the power semiconductor modules of the power electronic assembly mounted on the housing. The more homogeneous distribution of cooling capacity leads to more efficient cooling of the power semiconductor modules, an increased service life of the power electronic assembly, and / or a reduced coolant pressure drop.

[0015] According to one embodiment, the total cross-sectional area of ​​the cooling channel, i.e., the clear width of the cavity minus the flow-guiding elements arranged within it, decreases in the flow direction from the inlet to the outlet. This reduces the flow velocity of the coolant in the flow direction from the inlet to the outlet and increases the heat transfer.

[0016] The reduction of the cross-sectional area in the flow direction can be achieved, for example, by increasing the proportion of flow-guiding elements in the cross-section of the cooling channel in the flow direction. Alternatively or additionally, the cross-sectional area of ​​the cavity enclosed by the housing can decrease in the flow direction.

[0017] By reducing the overall cross-sectional area of ​​the cooling channel in the flow direction, cooling capacity is shifted from inlet-side flow zones to outlet-side flow zones, thus distributing the cooling capacity more homogeneously. The flow-guiding elements can be, for example, column-shaped, cuboid-shaped, rhomboid-shaped, or elliptical. However, other shapes for the flow-guiding elements are also conceivable. The shape and arrangement of the flow-guiding elements influence the flow velocity and thus the heat transfer in the flow zones as desired.

[0018] According to one embodiment, the cooler has first flow-guiding elements extending from areas of the housing cover to be cooled into the cooling channel, and second flow-guiding elements extending from the base of the housing into the cooling channel. The areas to be cooled are, in particular, areas in close thermal contact with power semiconductor modules. During operation, heat is dissipated from these areas by the first flow-guiding elements and transferred to the coolant. The second flow-guiding elements, on the other hand, have the function of guiding the flow of the coolant and, in particular, reducing the flow velocity in the heat transfer zones. Since they do not need to serve for heat transport, the second flow-guiding elements can, for example, be made of plastic.

[0019] According to one embodiment, the second flow-conducting elements are designed as sections of an insert shelf. In this embodiment, a plurality of second flow-conducting elements are connected to one another in a single component. The insert shelf can, for example, be made of plastic in a cost-effective and lightweight manner.

[0020] According to one embodiment, bypass zones of flow zones arranged one behind the other in the flow direction are alternately located in a peripheral region and in a central region of the cooling channel. This embodiment has the advantage that the alternating arrangement improves the mixing of coolant that has passed through the heat transfer zone with cooler coolant that has passed through the bypass zone in a mixing zone between the flow zones, because a bypass flow passing through several flow zones is prevented.

[0021] According to one embodiment, three flow zones are arranged sequentially in the cooling channel in the direction of flow. In this arrangement, the arrangement of the flow zones corresponds to the arrangement of the power semiconductor modules of an inverter. In particular, the number of flow zones corresponds to the number of power semiconductor modules, and each power semiconductor module is arranged on a region of the cooler's surface facing away from the cooling channel, opposite the respective flow zone, and is also thermally contacted with it.

[0022] Alternatively, it is also possible to provide only two flow zones or more than three flow zones.

[0023] According to one embodiment, the proportion of the bypass zones to the cross-sectional area on the inlet side is at least 10%, for example up to 30%. On the outlet side, it can be, for example, a maximum of 10%. In particular, no bypass zone at all may be provided on the outlet side. As it turns out, such a dimensioning of the bypass zones is advantageous for a more uniform distribution of the cooling capacity in the flow direction.

[0024] According to a further aspect, a power electronic arrangement is provided, comprising the described cooler and power semiconductor modules arranged one behind the other on the cooler housing in the direction of flow. The power semiconductor modules are distributed along the flow direction, each at the level of the respective flow zones.

[0025] In particular, the arrangement features power semiconductor modules, the number of which corresponds to the number of flow zones. In this case, each power semiconductor module is located on a specific area of ​​the cooler's surface facing away from the cooling channel, opposite the respective flow zone, and is also thermally contacted with it.

[0026] The power electronic arrangement is characterized by improved performance and a longer lifespan and / or reduced pressure loss.

[0027] According to a third aspect, an inverter, in particular a power inverter, is provided for supplying phase currents for an electric motor, e.g., in a motor vehicle. The inverter has at least one previously described power electronic arrangement and a control circuit for controlling the power semiconductor modules of the arrangement, wherein the control circuit is connected to the power semiconductor modules via control signal connections.

[0028] Embodiments of the invention are described below by way of example with reference to schematic drawings.

[0029] Figure 1 shows a cross-section through an inverter with a cooler according to an embodiment of the invention,

[0030] Figure 2 shows a longitudinal section through a cooler according to a first embodiment of the invention for the inverter according to Figure 1 ,

[0031] Figure 3 shows a longitudinal section through a cooler according to a second embodiment of the invention for the inverter according to Figure 1.

[0032] Figure 4 shows a longitudinal section through a cooler according to a third embodiment of the invention and

[0033] Figure 5 shows a cross-section through an inverter with a cooler according to the third embodiment.

[0034] Fig. 1 shows a cross-section through an inverter 30 of an electric motor with a cooler 1 according to one embodiment of the invention. The inverter 30 has a plurality of power semiconductor modules 9 arranged on the top surface 24 of an electrically insulating substrate or insulating layer 18. The substrate or insulating layer 18 is arranged with its underside 25 on a housing 2 of the cooler 1. The housing 2 is made of metal, for example, die-cast aluminum, and has a base 20, a cover 21, side walls 22, and end faces (not shown in Fig. 1). The housing 2 encloses a cuboid cavity 12 with a cooling channel 19, through which a coolant flows during operation.

[0035] In the illustrated embodiment, the cooler 1 is designed as a closed unit, meaning that the one-piece housing 2 essentially constitutes the cooler 1. Alternatively, however, an open design can also be chosen, in which, for example, the cover 21 is formed separately from the side walls 22, the end faces, and the base 20, but the cover 21 is placed on the rest of the housing structure to form a fluid-tight cavity 12. Flow-guiding elements 3 are arranged in the cooling channel 19, extending from the cover 21 towards the base 20 and made of the same material as the housing 2. In particular, they can be formed integrally with the housing 2. The flow-guiding elements 3 serve to transfer heat from the power semiconductor modules 9 to the coolant and also to direct the coolant flow in such a way that heat transfer is particularly efficient.The flow-guiding elements 3 are arranged in a central region of the cooling channel 19, also referred to as the heat transfer zone 14, as shown in Figure 1. Adjacent to the side walls 22, bypass zones 5 are formed which are free of flow-guiding elements 3. In other sections of the cooling channel 19 not shown in Figure 1, the arrangement of bypass zones 5 and heat transfer zones 14 differs transversely to the flow direction, as described in connection with Figures 2 and 3.

[0036] Fig. 2 shows a longitudinal section through the cuboid cavity 12. The two end faces 23 of the housing 2 are also shown in this view. The cooler 1 has an inlet 6 and an outlet 8 for the coolant, which flows through the cooling channel 19 formed in the cavity 12 in the flow direction indicated by arrow 11, from the inlet 6 to the outlet 8. In the embodiment shown, the inlet 6 and the outlet 8 are arranged in the two opposing end faces 23 of the housing 2. However, they can also be arranged, for example, in the same end face 23 or in the side walls 22. In this case, the coolant flow is deflected in the housing 2 and flows back in the original direction, for example, in a second plane.

[0037] In the embodiment shown, the cooling channel 19 has three flow zones 15, 16 and 17, which are arranged one behind the other in the direction of flow and are each separated from each other by a mixing zone 7.

[0038] Flow zones 15 and 16 are further subdivided into zones arranged side by side transversely to the flow direction, which are either designed as bypass zones 5 or as heat transfer zones 14. Flow zone 17 does not have a bypass zone 5.

[0039] In the cooling channel 19, a number of differently shaped, exemplary flow-guiding elements 3, 4 and 10 are arranged. As described with reference to Figure 1, the flow-guiding elements 3, 4 and 10 extend from the cover 21 towards the base 20. In an embodiment not shown in this figure, flow-guiding elements 3, 4 and 10 extend from both the base 20 and the cover 21 into the cavity 12.

[0040] In the first flow zone 15, closest to the inlet 6, two bypass zones 5 are arranged at the edge of the cooling channel 19 on the side walls 22. These bypass zones are free of flow-conducting elements 3, 4, and 10 and are traversed by the coolant in the direction of arrow 13. A heat transfer zone 14 is arranged between the bypass zones 5 in the central region of the cooling channel 19. A plurality of flow-conducting elements 3, arranged in a columnar configuration with a circular cross-section, are located in the heat transfer zone 14. The flow-conducting elements 3 are traversed by the coolant, as indicated by arrow 26.

[0041] The distances between the individual flow-conducting elements 3 are chosen such that the flow velocity of the coolant in this heat transfer zone 14 is reduced compared to that in the bypass zone 5, so that the heat transfer from the flow-conducting elements 3 to the coolant is particularly good.

[0042] The bypass zones 5 are dimensioned in their cross-section such that the coolant flows through them at a relatively high velocity and absorbs relatively little heat. For example, in the embodiment shown, each of the two bypass zones 5 can extend over, for example, 3-20% of the cross-sectional area of ​​the cooling channel 19.

[0043] A mixing zone 7 is arranged between the first two flow zones 15 and 16. In the mixing zone, relatively cool coolant that has passed through the bypass zones 5 mixes with warmer coolant that has passed through the heat transfer zone 14. This mixing is promoted by the placement of flow-guiding elements 4 in the mixing zone 7, which direct the cooler coolant from the bypass zones 5 into the central area of ​​the cooling channel 19, as indicated by arrow 27.

[0044] The mixing zone 7 is followed in the direction of flow by the second flow zone 16. In the second flow zone 16, the heat transfer zone 14 with column-shaped flow-guiding elements 3 is arranged in the edge regions of the cooling channel 19 near the side walls 22, while the bypass zone 5, as indicated by the arrows 13, runs in the central region of the cooling channel 19.

[0045] The second flow zone 16 is followed in the direction of flow by another mixing zone 7 with flow-guiding elements 4, in which coolant that has passed through the bypass zone 5 mixes with warmer coolant that has passed through the two heat transfer zones 14.

[0046] The third flow zone 17 adjoins the further mixing zone 7, in which flow-guiding elements 3 and 10 are again arranged. The flow-guiding elements 3 are column-shaped, while the flow-guiding element 10 is essentially cuboid-shaped.

[0047] The outlet 8 follows the third flow zone 17 in the direction of flow.

[0048] The flow-guiding elements 3 in the first flow zone 15 result in a more turbulent flow of the coolant and a reduced flow velocity in the heat transfer zone 14, thus leading to increased heat absorption. In the bypass zones 5, the higher flow velocity is utilized to minimize the heating of the coolant. In the subsequent mixing zone 7, the cooler coolant is directed by the flow-guiding elements 4 into the central area of ​​the cooling channel 19, where it mixes with the more heated coolant.

[0049] Following the same principle, the coolant passes through the second flow zone 16 and the further mixing zone 7 and enters the third flow zone 17. The flow-guiding elements 3, 10 arranged there again reduce the flow velocity and thus improve heat absorption. The third flow zone 17 has no bypass zone because a bypass of cooler coolant is not desired in this last flow zone in order to achieve the highest possible heat transfer for the last power semiconductor module.

[0050] Figure 2 indicates the position of the power semiconductor modules 9 with dashed lines. In the embodiment shown, the power semiconductor modules are arranged in three assemblies 31, 32, and 33 in a sequential arrangement on the cooler 1 in the direction of flow, with the first assembly 31 being closest to the inlet 6. The position of the assemblies 31, 32, and 33 corresponds to the position of the three flow zones 15, 16, and 17. However, such an assignment of flow zones and assemblies is not necessary. In embodiments not shown, more or fewer flow zones than assemblies are provided.

[0051] The bypass zones 5, in which coolant can flow with reduced heat absorption, shift cooling power in the direction of flow and improve the cooling of the second and third assemblies 32, 33. This allows the heat capacity of the entire coolant to be used efficiently.

[0052] Fig. 3 shows a longitudinal section through a cooler 1 according to a second embodiment. This differs from the one shown in Fig. 2 in that, in this embodiment, the cross-section of the housing 2 decreases in the flow direction. In the embodiment shown, the cross-section decreases in steps, with a step 28 arranged between the first flow zone 15 and the second flow zone 16, and a step 29 between the second flow zone 16 and the third flow zone 17. The steps 28 and 29 also have a flow-guiding function, similar to the flow-guiding elements 4 shown in Fig. 2.

[0053] In an alternative embodiment not shown, the cross-section of the cooling channel 19 can decrease in the direction of flow without decreasing the cross-section of the housing 2 by increasing the thickness of the side walls 22 in the direction of flow.

[0054] Figures 4 and 5 show a longitudinal section and a cross-section, respectively, through a cooler 1 according to a third embodiment of the invention. This differs from those shown in Figures 1 to 3 in that part of the flow-guiding elements 3 are designed as parts of an insert 35. The insert 35, which is visible in cross-section in Figure 5, extends in length and width substantially over the entire base 20 of the housing 2. Flow-guiding elements 34 project from the insert 35 into the cooling channel 19.

[0055] While the flow-conducting elements 3 projecting from the cover 21 into the cooling channel 19 primarily serve to transfer heat from the power semiconductor modules 9 to the coolant, in addition to conducting the flow, the flow-conducting elements 34 are solely for flow conduction, as they do not come into contact with the areas of the housing 2 that heat up considerably in the region of the power semiconductor modules 9. They can therefore be made of a material with lower thermal conductivity. For example, the insert 35 can be manufactured cost-effectively and with low weight from plastic. It is also suitable for retrofitting existing coolers 1.

[0056] As can be seen in Figure 4, the flow-conducting elements 3, which are also provided for heat dissipation, are arranged in the area of ​​the power semiconductor modules 9, while the flow-conducting elements 34 are provided in other areas.

[0057] The flow-conducting elements 4 and 10 shown in Figures 2 and 3 also do not serve, or only serve to a subordinate extent, the purpose of heat dissipation and, in an embodiment not shown, can also be designed as flow-conducting elements 34 of an insert shelf 35.

[0058] Reference symbol list

[0059] 1 cooler

[0060] 2 cases

[0061] 3 Flow-guiding element

[0062] 4 Flow-guiding element

[0063] 5 Bypass zone

[0064] 6 Coolant inlet

[0065] 7 Mixing zone

[0066] 8 Coolant outlet

[0067] 9 Power semiconductor module

[0068] 10 Flow-guiding element

[0069] 11 Arrow

[0070] 12 Cavity

[0071] 13 Arrow

[0072] 14 Heat transfer zone

[0073] 15 first flow zone

[0074] 16 second flow zone

[0075] 17 third flow zone

[0076] 18 electrically insulating substrate or electrical insulating layer

[0077] 19 Cooling channel

[0078] 20 floor

[0079] 21 lids

[0080] 22 side wall

[0081] 23 Front

[0082] 24 Top

[0083] 25 Underside

[0084] 26 Arrow

[0085] 27 Arrow

[0086] 28th level

[0087] 29th level

[0088] 30 Inverter

[0089] 31 power semiconductor modules in the first assembly

[0090] 32 power semiconductor modules in a second assembly

[0091] 33 power semiconductor modules in the third assembly

[0092] 34 flow-conducting element

[0093] 35 shelves

Claims

Patent claims 1. Cooler (1) for a power electronic arrangement, comprising a housing (2) enclosing a cavity (12), wherein the cavity (12) has an inlet (6) and an outlet (8) and a cooling channel (19) through which a coolant flows from the inlet (6) to the outlet (8), wherein flow-guiding elements (3, 4, 10) are arranged in the cooling channel (19) such that a plurality of flow zones (15, 16, 17) and a number of mixing zones (7) are formed one after the other in the direction of flow, wherein the flow zones (15, 16, 17) are formed by bypass zones (5) and heat transfer zones (14) arranged next to each other transversely to the direction of flow.

2. Cooler (1 ) according to claim 1 , wherein the total cross-sectional area of ​​the cooling channel (19) decreases in the direction of flow from the inlet (6) to the outlet (8).

3. Cooler (1 ) according to one of claims 1 or 2, wherein the proportion of the flow-guiding elements (3, 4, 10) in the cross-section of the cooling channel (19) increases in the direction of flow.

4. Cooler (1 ) according to one of claims 1 to 3, wherein the cross-sectional area of ​​the cavity (12) enclosed by the housing (2) decreases in the direction of flow.

5. Cooler (1 ) according to one of claims 1 to 4, wherein the flow-guiding elements (3) are column-shaped and / or cuboid-shaped and / or rhomboid-shaped and / or elliptical-shaped.

6. Cooler (1 ) according to one of claims 1 to 5, comprising first flow-guiding elements (3) extending from areas to be cooled of a cover (21 ) of the housing (2) into the cooling channel (19), and second flow-guiding elements (34) extending from a bottom (20, 35) of the housing (2) into the cooling channel (19).

7. Cooler (1 ) according to claim 6, wherein the second flow-guiding elements (34) are designed as areas of an insert (35).

8. Cooler (1) according to one of claims 1 to 7, wherein bypass zones (5) of flow zones (15, 16, 17) arranged one behind the other in the direction of flow are arranged alternately in a peripheral region and in a central region of the cooling channel (19).

9. Cooler (1) according to one of claims 1 to 8, wherein three flow zones (15, 16, 17) are arranged one after the other in the cooling channel (19) in the direction of flow.

10. Cooler (1 ) according to one of claims 1 to 9, wherein a proportion of the bypass zones (5) on the cross-sectional area on the inlet side is at least 3%.

11. Cooler (1) according to one of claims 1 to 10, wherein a proportion of the bypass zones (5) on the cross-sectional area on the outlet side is at most 3%.

12. Power electronic arrangement comprising a cooler (1) according to one of claims 1 to 11 and power semiconductor modules (9) arranged one behind the other in the direction of flow on the housing (2) of the cooler (1), wherein the power semiconductor modules (9) are arranged distributed in the direction of flow at the level of the respective flow zones (15, 16, 17).

13. Inverter (30) comprising a power electronic arrangement according to claim 12, and a control circuit for controlling the power semiconductor modules (9) of the arrangement, wherein the control circuit is connected to the power semiconductor modules (9) by means of control signal connections.

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