Cooling device for an inverter and inverter with such a cooling device

Abstract

The invention relates to a cooling device (300) for a fluid-cooled inverter (130), comprising a base body (305) and heat sinks (310) arranged thereon and thermally connected thereto. The cooling device (310) is characterized in that the respective heat sink (310) is rib-shaped and, extending from the base body (305), has a substantially oval cross-sectional shape in its longitudinal extension with part-circular grooves (410) on its outer surface (415). Furthermore, the invention relates to an inverter (130) and an electric drive axle (100), comprising an electric machine (125) and such an inverter (130).

Description

[0001] The present invention relates to a cooling device for a fluid-cooled inverter and to an inverter having at least one such cooling device. The cooling device is configured to cool heat-generating components of the inverter or to absorb and dissipate heat from these components or to transfer it to a cooling fluid. Such components can be, for example, power modules or chips of half-bridges of an inverter. The invention further relates to an electric drive axle having such an inverter.

[0002] Inverters are an essential component in electric vehicles, where power modules or switching devices are used to convert direct current into alternating current. The heat generated in the chips during power conversion must be dissipated to prevent their function from being impaired. Cooling devices are typically used for this purpose. These devices are thermally coupled to the chips on the one hand and come into contact with the cooling fluid on the other, for example, in fluid temperature control. Heat sinks are typically arranged on the side of the cooling device facing the fluid to increase the contact area between the cooling device and the cooling fluid and thus improve heat transfer. Pin-fin or elliptical fin plates are currently used to dissipate heat to the coolant.

[0003] US 2023 / 050599 A1 discloses a heat exchanger configured to transfer heat between a heat medium conveyed in a heat medium flow passage and an electronic component. The heat exchanger comprises a plurality of fins positioned in the heat medium flow passage. The plurality of fins are spaced apart from one another and arranged in a predetermined direction, defined as a fin arrangement direction, to divide the heat medium flow passage into a plurality of narrow passages. The heat medium flow passage extends in a passage longitudinal direction, which is a direction intersecting the fin arrangement direction. Each of the plurality of fins includes a plurality of thick wall portions and a plurality of thin wall portions arranged alternately along an entirety or a portion of the fin in the passage longitudinal direction.A plate wall thickness of each of the plurality of thick wall sections is relatively large and a plate wall thickness of each of the plurality of thin wall sections is relatively small.

[0004] One object of the invention is to provide a cooling device for a fluid-cooled inverter that improves the temperature control of thermally coupled components of the inverter. The invention achieves this object by means of the subject matter of the independent claims. Subclaims specify preferred embodiments.

[0005] In a first aspect of the invention, a cooling device for a fluid-cooled inverter comprises a base body and heat sinks arranged thereon and thermally connected thereto, wherein the respective heat sink is rib-shaped and, starting from the base body, has a substantially oval cross-sectional shape with part-circular grooves on its outer surface in its longitudinal extent.

[0006] The specific design of the fin-shaped heat sinks improves the heat transfer efficiency of the cooling device. In other words, heat dissipation can be made more efficient, especially compared to other known variants of heat sink designs. Furthermore, the maximum and average junction temperatures in heat-generating components of the inverter, particularly in power modules of the inverter's semiconductor packages, can be reduced. Furthermore, a pressure drop in the cooling fluid in the contact area between the cooling device and the cooling fluid can be reduced. This, in turn, results in improved inverter performance and a reduction in the capacity of a pump conveying the cooling fluid.

[0007] In relation to the heat sink, "oval" is understood to mean an elongated basic shape of the heat sink that has no corners or edges. In plan view, the heat sink has an imaginary rectangular shape with rounded corners. The corners are formed as part-circular with a radius. Preferably, the heat sink is designed so narrow that a semicircular outer contour is formed on the narrow sides of the heat sink. Between the two semicircular outer contours arranged on the opposite sides, the grooves are formed on the long sides of the heat sink. These grooves are also formed as part-circular, preferably semicircular, in a plan view of the heat sink. In this sense, the grooves are preferably arranged on the side surfaces, in particular the long side surfaces, of the heat sink. "Part-circular" means that the grooves are formed with a radius, preferably a constant radius.The grooves have no edges or corners, allowing the cooling fluid to flow freely along the heat sink without negatively impacting the flow and heat transfer. Preferably, the transitions between the grooves and the outer contour of the heat sink are also rounded and thus free of edges. The grooves increase the contact area between the heat sink and the cooling fluid.

[0008] The dimensions and shape of the cooling device are adapted to the shape and design of the inverter components to be cooled. Typically, the semiconductor packages of the power module's half-bridges are flat components, so it is advantageous if the base body is complementarily flat or plate-shaped. In one embodiment, the base body is a base plate. Thus, the cooling device is preferably a cooling plate with heat sinks arranged thereon. The heat sinks are preferably formed integrally with the base body. The heat sinks and the base body are made of aluminum or copper to optimize the thermal conductivity.

[0009] Preferably, a plurality of heat sinks are arranged on the base body. The heat sinks are preferably evenly distributed over the surface of the base body. Furthermore, all heat sinks are preferably designed essentially identically. This simplifies the manufacture and design of the cooling device. The heat sinks also preferably extend perpendicular to the base body. In other words, a longitudinal extension of the heat sink is oriented perpendicular to the surface of the base body on which the heat sink is arranged. The side of the base body opposite the heat sink is configured to be thermally coupled to the heat-generating component.

[0010] According to one embodiment, the heat sinks are arranged in a staggered pattern on the base body. The term "staggered" or "staggering" refers to a non-perfectly parallel, uniform arrangement of the heat sinks in the longitudinal and transverse directions on the surface of the base body. Instead, the heat sinks or cooling fins are arranged offset from one another on the surface of the base body. The staggered arrangement of the heat sinks serves to prevent or reduce the collision of fluid flows and thus improve the heat transfer efficiency of the cooling plate.

[0011] According to one embodiment, the grooves are arranged on the side surfaces of the heat sink such that the thickness of the heat sink does not fall below a certain threshold. The threshold is selected so that sufficient cooling performance is achieved with the heat sink. Preferably, and to further optimize the thermal conduction properties, the grooves are arranged on the side surfaces of the heat sink such that the thickness of the heat sink is essentially constant. This ensures constant heat transfer across the entire heat sink while simultaneously avoiding heat hotspots.

[0012] Preferably, the grooves of the heat sink are arranged evenly spaced from one another on the respective side surface of the heat sink and run parallel. The grooves of the heat sink preferably have the same radius. This simplifies the manufacture of the heat sink and ensures uniform heat transfer across the entire height of the heat sink. By optionally rounding the transitions from the grooves to the normal outer contour of the heat sink, a wave-shaped surface or a serpentine outer contour can be created on the respective side surface of the heat sink by appropriately spacing the grooves from one another.

[0013] In a further aspect of the invention, an inverter comprises a cooling device proposed herein, wherein the cooling device is thermally coupled to a heat-generating component of the inverter. An inverter is a power converter that converts direct current (DC) into alternating current (AC). The inverter is preferably a fluid-temperature-controlled, in particular fluid-cooled, inverter whose cooling device comes into contact with a temperature-control fluid, in particular a cooling fluid, at least in some regions or sections. The cooling device can be coupled to the heat-generating component via a heat-conducting compensating layer or the like.

[0014] The heat-generating component of the inverter is a component of the inverter that needs to be cooled. The inverter is designed to control the motor vehicle's engine and to control an electric machine of the motor vehicle. The inverter, in particular a power module of the inverter, can have one or more half-bridges, each comprising semiconductor packages. For example, two semiconductor packages form a half-bridge of the power module, with several half-bridges being separately controllable to operate an electric machine of the electric drive axle. The respective semiconductor package is used to switch current, in particular for consumers in the several tens of kW range, in particular for electric machines, e.g., for a motor vehicle. The semiconductor packages are to be understood as heat-generating components of the inverter that must not exceed certain temperatures for optimal functioning.Accordingly, the semiconductor packages can be thermally coupled to the cooling device directly or via an optional compensation layer.

[0015] In a further aspect of the invention, an electric drive axle according to the invention, also called an E-axle, comprises an electric machine and an inverter proposed herein. The electric machine is a three-phase electric machine. The preferably fluid-cooled inverter forms a motor controller that controls the electric machine. The inverter is therefore designed in particular to control a three-phase electric machine. In addition to the electric machine, the electric drive axle can comprise an optional transmission to provide a torque and a speed for driving a drive wheel of the motor vehicle. The electric machine is supplied with electrical energy from an energy storage device.

[0016] The electric drive axle, the inverter, and / or the cooling device can be advantageously used in a motor vehicle. The motor vehicle can, in particular, comprise a motorcycle, a passenger car, a truck, or a bus. The motor vehicle comprises at least two axles. Preferably, two axles are provided, with at least one of the axles being an electric drive axle and being drivable by at least one electric motor.

[0017] The above definitions and explanations regarding technical effects, advantages, and advantageous embodiments of the heat sinks according to the invention also apply mutatis mutandis to the inverter according to the invention according to the second aspect of the invention, to the electric drive axle according to the invention according to the third aspect of the invention, and to the aforementioned motor vehicle, and vice versa. It is understood that the features mentioned above and those to be explained below can be used not only in the respective combinations specified, but also in other combinations or on their own, without departing from the scope of the present invention.

[0018] The invention will now be described in more detail with reference to the accompanying figures, in which: Fig. 1 is a highly schematic view of a motor vehicle with an electric drive axle; Fig. 2 a highly simplified representation of a structure of an inverter according to the invention of the electric drive axle according to Fig. 1, Fig. 3 a schematic perspective view of a - only partially shown - cooling device according to the invention of the inverter according to the invention according to Fig. 2; Fig. 4 a schematic plan view of a heat sink of the cooling device according to the invention according to Fig. 3; wherein identical or similar components or elements are provided with the same reference numerals.

[0019] Fig. 1 shows an electric drive axle 100 in a motor vehicle 105. The motor vehicle 105 may additionally include an internal combustion engine 110 connected to a drive wheel 120 of the motor vehicle 105 via a transmission 115. In this case, the motor vehicle 105 would be a hybrid vehicle.

[0020] The electric drive axle 110 comprises an electric machine 125, which can also act on the drive wheel 120, preferably by means of the transmission 115. Furthermore, an inverter 130 is provided, which can be supplied with electrical energy from an electrical energy storage device 135. The electrical energy storage device 135 is preferably electrochemically constructed, but a fuel cell or another power source can also be used, for example. The inverter 130 is preferably configured to provide phase-shifted alternating currents to the electric machine 125. The machine 125 is implemented, for example, as a permanent-magnet synchronous machine, but other embodiments are also possible. The voltages and frequencies of the alternating currents provided can be determined such that the electric machine 125 converts a predetermined torque or rotates at a predetermined speed.A field-oriented control system can be implemented to control the direction of rotation and speed. The nominal voltage of the electrical energy storage device 135 is typically several hundred to over 1000 V. The current through the electrical machine 125 can be several hundred A.

[0021] Fig. 2 shows the inverter 130 as a motor controller with a power module 200, comprising three half-bridges 205, which can be controlled, for example, by means of a common control device 210. The motor controller 200 is configured to control the rotational behavior of the electric machine 125 and typically operates digitally using a microcomputer. Each half-bridge 205 comprises two semiconductor packages 215, 220, wherein the semiconductor packages 215, 220 are connected in series between DC voltage potentials of the energy storage device 135 as shown. A DC link capacitor 225 is preferably provided between the potentials. A center tap 230 between the semiconductor packages 215, 220 is connected to an associated phase of the electric machine 125.The upper semiconductor package 215 lies between a high potential of the energy storage device 135 and the center tap 230, and the lower semiconductor package 220 lies between the center tap 230 and a low potential of the energy storage device 135.

[0022] After Fig. 3 in conjunction with Fig. 2, the inverter 130 comprises a cooling device 300 for cooling the power module 200, in particular the half-bridges 205. The cooling device 300 is only partially shown here. The semiconductor packages 215, 220, in particular - in Fig. 2 power modules of the semiconductor packages 215, 220 (not shown) are heat-generating components of the inverter 130, which are cooled by means of the cooling device 300 and a cooling fluid that partially contacts the cooling device 300. Thus, the inverter 130 is a fluid-cooled, in particular liquid-cooled, inverter 130. The cooling fluid can be supplied via a pump (not shown here) that supplies a cooling fluid circuit with cooling fluid.

[0023] After Fig. 3 in conjunction with Fig. 4, the cooling device 300 comprises a base body 305 in the form of a substantially flat base plate or base plate, wherein heat sinks 310 in the form of cooling fins are arranged on a side of the base body 305 facing the cooling liquid and are thermally connected thereto. The heat sinks 310 are identically designed and arranged perpendicular to the base body 305 in their longitudinal extent. The heat sinks 310 therefore have the same spatial dimensions and specific structural features. Each heat sink 310 has a substantially oval cross-sectional shape with respect to its longitudinal extent in cross-section, wherein part-circular, here semicircular, grooves 410 are arranged on the long side surfaces 400, 405 of the heat sink 310 on the outer surface 415 of the heat sink 310, which give the heat sink a groove shape. The grooves 410 have the same radius.

[0024] In the Fig. 4, the specific design and arrangement of the grooves 410 results in a wave-shaped or serpentine shape of the heat sink 310 with rib-shaped or bead-shaped elevations with bead-shaped grooves 410 in between, wherein the Fig. 4, the upper and lower ends of the heat sink 310 are rounded. This keeps the entire outer contour of the heat sink 310 free of corners and edges, thus ensuring efficient heat transfer.

[0025] The grooves 410 on the respective side surfaces 400, 405 of the heat sink 310 are arranged at equal distances from one another and run as beads or depressions parallel to one another and to the longitudinal extent of the heat sink 310. The grooves 410 of one side surface 400 are arranged with respect to the grooves 410 of the opposite side surface 405 such that a thickness 420 of the heat sink 310 does not fall below a limit value in order not to negatively influence heat transfer. Furthermore, the grooves 410 of one side surface 400 are arranged with respect to the grooves 410 of the opposite side surface 405 such that the thickness 420 of the heat sink 310 is essentially constant. In other words, one groove 410 of one side surface 400 is arranged centrally between two adjacent grooves 410 of the other side surface 405, and vice versa.The spacing between adjacent grooves 410 can be selected and the transitions to the outer contour of heat sink 310 can be rounded such that the material of heat sink 310 located between grooves 410 is formed in the shape of a bead whose radius corresponds to the radius of groove 410. A groove 410 on one side surface 400 of heat sink 310 is thus aligned with a bead between two grooves 410 on the other side surface 405, and vice versa. The alternating arrangement of grooves 410 and the beads located therebetween on both side surfaces 400, 405 of heat sink 310 results in a wave-shaped cross-sectional shape of heat sink 310 with a substantially constant thickness 420.

[0026] As in Fig.3, the heat sinks 310 are arranged on the base body 305 in several parallel rows 315, 320, 325, wherein the heat sinks 310 of the respective row 315, 320, 325 are arranged flush with one another and spaced from one another. A heat sink 310 of a first row 315 is arranged exactly parallel to a laterally offset heat sink 310 of a second row 320. Thus, the heat sinks 310 of the first and second rows 315, 320 are arranged exactly parallel and evenly spaced from one another. The heat sinks 310 of a third row 325 arranged between the first and second rows 315, 320 are arranged longitudinally offset with respect to the heat sinks 310 of the first and second rows 315, 320, respectively, so that a staggered arrangement of the heat sinks 310 on the base body 305 is realized. The so-called “staggering” of the heat sinks 310 prevents flows of the cooling fluid or heat transfer paths from directly colliding with each other.Instead, the heat is better distributed across the entire surface of the cooling device 300 that comes into contact with the cooling fluid. This can help avoid hot spots and optimize overall cooling performance. In this case, the heat sinks 310 of each directly adjacent row are arranged offset from one another, with the heat sinks 310 of every other row being arranged exactly parallel. Reference symbol 100 electric drive axles 105 Motor vehicle 110 combustion engine 115 gearboxes 120 drive wheel 125 electric machine 130 inverters 135 energy storage 200 power module 205 Half Bridge 210 Control device 215 Upper semiconductor package of the semiconductor bridge 220 Lower semiconductor package of the semiconductor bridge 225 DC link capacitor 230 center tap 300 cooling device 305 basic body 310 heat sink 315 First Row 320 Second Row 325 Third Row 400 First side surface of the heat sink 405 Second side surface of the heat sink 410 groove 415 Outer surface of the heat sink 420 Heatsink thickness QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] US 2023 / 050599 A1

[0003]

Claims

[1] Cooling device (300) for a fluid-cooled inverter (130), comprising a base body (305) and heat sinks (310) arranged thereon and thermally connected thereto, characterized by that the respective heat sink (310) is rib-shaped and, starting from the base body (305), has a substantially oval cross-sectional shape in its longitudinal extent with part-circular grooves (410) on its outer surface (415). [2] Cooling device (300) according to claim 1, wherein a plurality of heat sinks (310) are arranged on the base body (305). [3] Cooling device (300) according to claim 1, wherein the heat sinks (310) are arranged staggered on the base body (305). [4] Cooling device (300) according to one of the preceding claims, wherein the grooves (410) are arranged on the side surfaces (400, 405) of the heat sink (310). [5] Cooling device (300) according to claim 4, wherein the grooves (410) are arranged on the side surfaces (400, 405) of the heat sink (310) such that a thickness (420) of the heat sink (310) does not fall below a limit value. [6] Cooling device (300) according to claim 5, wherein the grooves (410) are arranged on the side surfaces (400, 405) of the heat sink (310) such that a thickness (420) of the heat sink (310) is substantially constant. [7] Cooling device (300) according to one of the preceding claims, wherein the grooves (410) of the heat sink (310) on the respective side surface (400, 405) are arranged at equal distances from one another and run parallel. [8] Cooling device (300) according to one of the preceding claims, wherein the grooves (410) of the heat sink (310) have the same radius. [9] Inverter (130) comprising a cooling device (300) according to one of the preceding claims, wherein the cooling device (300) is thermally coupled to heat-generating components of the inverter (130). [10] Electric drive axle (100) comprising an electric machine (125) and an inverter (130) according to claim 9.

Images