Inverter

Abstract

An inverter (1), in particular for an electrically powered vehicle (100), comprises a housing (10) and a printed circuit board (12) which is accommodated in the housing (10) and has a plurality of electrical components (14) of a power electronics system. A direct current connection (16) comes from at least one energy cell (3) of the vehicle (100). An alternating current connection (18) leads to at least one electric motor (5) of the vehicle (100). A heat sink (22) is connected to the printed circuit board (12). An elastic membrane (13) is connected to the heat sink (22) and the housing (10). A coolant cavity (20) for coolant and an air cavity (21) are defined by the heat sink (22) and the elastic membrane (13) connected to the heat sink and the housing (10).

Description

[0001] The invention relates to an inverter, in particular for an electrically powered vehicle. The invention particularly relates to an inverter for an electrically powered vehicle, comprising a housing, a circuit board accommodated in the housing and having a plurality of electrical components of a power electronics system, a direct current connection coming from at least one energy cell of the vehicle, and an alternating current connection leading to at least one electric motor of the vehicle. State of the art

[0002] Modern electric vehicles require power electronics units to convert the direct current from the battery (or fuel cell) into multi-phase alternating current to drive the vehicle's electric motor. These power electronics units typically comprise a main printed circuit board (PCB) containing the switching components (IGBTs (insulated-gate bipolar transistors), FETs (field-effect transistors)) and other auxiliary components. This circuit board is usually housed in a casing to protect it from environmental influences. The components, especially the switches, generate unwanted heat under load. The circuit board is therefore usually cooled either by air or by a water channel.

[0003] The components are typically attached to the circuit board using a soldering process. The circuit board is then bonded to the housing. This transfers most of the potential vibrations (oscillations), which are particularly common in automotive applications, from the chassis to the housing and beyond to the circuit board, the solder joints, and the components. The problem with this design is that it can weaken the solder joints, increase electrical resistance, or even lead to the failure of solder joints and components.

[0004] Currently, there are many different types of inverters available in the state of the art. Typically, a circuit board with components is housed in a plastic or metal housing. The circuit board has at least one heat sink. For higher power ratings, active air cooling can be added. For the highest performance requirements, water cooling is attached to one side (usually the back) of the circuit board using a water-cooled heat spreader made of a thermally conductive material, such as aluminum. The heat spreader is thus attached to one side of the circuit board. The coolant, possibly a dielectric, is passed through a cavity on the side of the heat spreader.

[0005] In all of these known designs, the PCB assembly is firmly bonded to the housing, creating a mechanically rigid connection that leads to the vibration problems described above. One currently practiced solution is the use of a casting resin after the soldering process, which provides additional strength to the solder joint between components and the PCB. However, this known casting resin approach leads to the following two disadvantages: The desired heat dissipation to the ambient air is significantly reduced, which is particularly critical for air-cooled PCBs. Furthermore, component-level repair is made virtually impossible, as the components are virtually inaccessible due to the casting resin encapsulation of the solder joints.

[0006] Other known options for mitigating the vibration-related problems described above include reducing the rated lifetime of components or specifying more restrictive vibration tolerances, both of which, however, limit the application range of these inverters, which is also detrimental. The main problem, therefore, is the weakening of solder joints and the failure of electrical components due to constant small vibrations and mechanical shocks. These vibrations and shocks occur in all types of vehicles, with the vibrations generally becoming more severe the larger the vehicle and the more difficult the application.

[0007] US 2004 / 0 124 332 A1 discloses a vibration-damping device for a control unit, in which a control unit portion of a drive unit provided with an electric motor is attached to the drive unit for connection thereto. The control unit portion comprises a drive unit and a control unit. The power unit is immovably attached to the drive unit, and the control unit is movably mounted on the drive unit by means of a vibration-damping mechanism. The drive unit comprises an inverter unit in a housing. The inverter unit is connected to the electric motor of the drive unit via a connecting element. The connecting element is immovably attached to the drive unit and the power unit.

[0008] US 5,812,374 A discloses a thermally conductive device for a printed circuit board comprising a flexible, thermally conductive film with a damping layer on one side and a thermally conductive and elastic layer on the other side. A number of thermal contact pieces made of rigid material are arranged on the thermally conductive and elastic layer. Each of the contact pieces has a contour that allows close contact with an electrical component on the printed circuit board. The device is clamped between two printed circuit boards, with the damping layer in contact with the back of one of the cards, while the contact pieces of the same device are in close contact with the components of the other printed circuit board. The flexible film provides laterally arranged fastening sections for attaching the flexible film to mechanical supports, which also serve as heat sinks.In an alternative embodiment, the contact pieces can be part of a monolithic structure. DE 10 2011 085 169 A1 discloses a control unit for a motor vehicle, which has a circuit carrier (printed circuit board) with electrically conductively connected electrical and / or electronic components, and a cover structure connected to the circuit carrier in a fluid-tight manner. The circuit carrier and the cover structure delimit an interior space (air cavity), wherein the electrical and / or electronic components protrude into the interior space. The circuit carrier and at least one electrical and / or electronic component arranged outside the interior space can be electrically conductively connected to one another. The cover structure and / or the circuit carrier has at least one partial region, wherein the at least one partial region is reversibly deformable with essentially no resistance in at least one direction.The deformable portion of the cover structure and / or the circuit carrier ensures that a fluid enclosed in the interior can expand or contract due to pressure or heat. The cover structure and / or the circuit carrier can reversibly change the appearance. Overview of the invention

[0009] It is an object of the invention to provide an inverter, in particular for an electrically powered vehicle, which is resistant to vibrations and mechanical shocks and also enables the installation of components near an engine of the vehicle or as a unit with the engine.

[0010] This object is achieved by an inverter, in particular for an electrically powered vehicle, which inverter comprises the features of claim 1.

[0011] The current state of the art uses rigid or non-suspended inverters in passenger cars and light commercial vehicles. However, with future electrification in medium- and heavy-duty vehicles, the vibration resistance of the inverter should be increased to prevent premature failure of the electrical components. Instead of a fully suspended inverter housing with difficult mounting to various vehicle systems, a rigid housing (state of the art) is proposed, in which, according to the invention, the circuit board itself is suspended within the housing. This also reduces the length of the flexible high-voltage cables and enables the power electronics unit to be mounted close to the engine or as a single unit with it.

[0012] In one embodiment, the inverter, which is particularly suitable for an electrically powered vehicle, comprises a housing and a circuit board. The circuit board is housed in the housing and has a plurality of electrical components of a power electronics system. A DC connection comes from at least one energy cell of the vehicle. An AC connection leads to at least one electric motor of the vehicle. A heat sink is connected to the circuit board. An elastic membrane is connected to the heat sink and the housing. Furthermore, a coolant cavity for coolant and an air cavity are provided. The coolant cavity and the air cavity are defined by the heat sink and the elastic membrane connected to the heat sink and the housing.To prevent the transmission of vibrations to the circuit board and critical components, the circuit board itself is suspended in the inverter housing by means of an elastic membrane. The elastic membrane dampens the vibrations that act from outside on the housing and then on to the circuit board and the soldered components before they reach the circuit board, so that little or no vibration affects the circuit board and the soldered components. Furthermore, the coolant cavity with coolant ensures the urgently needed water cooling of the circuit board, even at higher power ratings. Additional casting of the components, for example, with cast resin, can be avoided, which increases the cooling effectiveness and the repairability of the inverter, as mentioned above.

[0013] According to another possible embodiment, the membrane could also be connected to the circuit board.

[0014] In one embodiment, wires for the DC connection, wires for the AC connection within the air cavity, and wires at the connection points of the wires to the circuit board are provided, with the wires being flexible. The flexible wires thus also absorb vibrations and do not break, so that less or no vibration reaches the circuit board and the soldered components, and the inverter remains functional.

[0015] In one embodiment, the coolant in the coolant cavity for the circuit board is water.

[0016] In one embodiment, the diaphragm connected to the heat sink and the housing acts as an elastic spring, and the coolant in the coolant cavity acts as a damper. The use of such a damping and spring-damping assembly can further improve vibration and shock damping for the circuit board and the soldered components, and ideally, only a few additional components are required. Mechanical damping can be achieved, for example, through a hydraulic design of the coolant cavity, and mechanical stiffness can be adjusted through the elasticity of the diaphragm. In particular, mechanical stiffness of the wires of the DC connection and the AC connection can contribute to the mechanical stiffness of the system consisting of the circuit board, the heat sink, and the diaphragm.

[0017] In another embodiment, a spring-damper element comprises an elastic spring and a damper. The spring-damper element connects the heat sink and the housing and / or connects the circuit board and the housing.

[0018] In one embodiment, the circuit board is thermally connected to the heat sink using thermal paste and additionally with screws or thermal adhesive. This also allows heat to be dissipated from the circuit board to the outside.

[0019] In one embodiment, a vehicle comprises an inverter according to one of the embodiments described above. The inverter connects at least one energy cell of the vehicle to at least one motor, for example, an electric motor, of the vehicle. Short description of the drawings

[0020] The invention and its advantages are described in more detail below with reference to the attached schematic drawings. Fig. 1 shows a vehicle with an embodiment of the drive unit in which the inverter is housed in a cooling housing. Fig. 2 shows an embodiment of the inverter according to the present invention.

[0021] In the following, exemplary embodiments will explain the invention and its advantages in more detail with reference to the accompanying figures. The proportions in the figures do not always correspond to the actual proportions, as some shapes are simplified and others are shown enlarged relative to other elements for better illustration. Detailed description of the drawings and embodiments

[0022] Fig. Figure 1 shows an embodiment of a vehicle 100 with an embodiment of the drive unit in which the inverter 1 is housed in a cooling housing. The inverter 1 connects at least one energy cell 3 of the vehicle 100 to at least one motor, for example, an electric motor 5, of the vehicle 100.

[0023] Fig. 2 shows an embodiment of the inverter 1 for a vehicle 100 (see Fig. 1) according to the present invention. The inverter 1 is particularly suitable for an electrically powered vehicle 100 and comprises a housing 10 and a circuit board 12. The circuit board 12 is housed in the housing 10 and has a plurality of electrical components 14 of a power electronics system, for example, PE chips. A DC connection 16 comes from at least one energy cell 3 of the vehicle 100 (see Fig. 1). An AC connection 18 leads to at least one motor or electric motor 5 of the vehicle 100.

[0024] A heat sink 22 is connected to the circuit board 12. According to the invention, in this embodiment, an elastic membrane 13 is connected to the heat sink 22 and the housing 10. Instead of a fixed installation in the inverter housing 10, for example by means of screws and as known from the prior art, a cooling element is produced here with an attached elastic membrane 13, wherein a second end 132 of the elastic membrane 13 is connected to the heat sink 22. An opposite first end 131 of the membrane 13 is connected to the housing 10. Overall, this creates a coolant cavity 20 for a coolant (no reference number), which is used for cooling the (in Fig. 2) arranged above it. The circuit board 12 can then be attached to the suspended cooling element using a method with good thermal conductivity, for example using a thermal paste (not shown) and additionally using screws (not shown) or a thermally conductive adhesive (not shown).

[0025] On one side of the circuit board 12, the coolant cavity 20 is provided for coolant, and on the other side of the circuit board 12, an air cavity 21 is provided. The coolant cavity 20 and the air cavity 21 are defined by the heat sink 22 and the elastic membrane 13 connected to it and the housing 10. To prevent the transmission of vibrations to the circuit board 12 and the critical components, in particular the electrical components 14 of the power electronics, the circuit board 12 itself is suspended in the housing 10 of the inverter 1 by means of the elastic membrane 13.The elastic membrane 13 dampens the vibrations acting from outside on the housing 10 and further on the printed circuit board 12 and the soldered components, in particular the electrical components 14 of the power electronics, before they reach the printed circuit board 12, so that less or no vibrations act on the printed circuit board 12 and the soldered components, in particular the electrical components 14 of the power electronics. Furthermore, the coolant cavity 20 with coolant ensures the urgently needed water cooling of the printed circuit board 12, even at higher rated powers. Additional casting of the components, for example, with cast resin, can be avoided, which increases the effectiveness of the cooling and the repairability of the inverter 1, as mentioned above.

[0026] The coolant enters the coolant cavity 20 via a coolant inlet 24 and exits the coolant cavity 20 via a coolant outlet 25. The coolant in the coolant cavity 20 for the circuit board 12 can be water, for example.

[0027] The diaphragm 13 connected to the heat sink 22 and the housing 10 can be viewed as an elastic spring 32. The coolant in the coolant cavity 20 can be considered a damper 34. By using such a damping and spring-damping assembly, vibrations and shocks for the circuit board 12 and the soldered components, in particular the electrical components 14 of the power electronics, can be even more effectively dampened, and in the best case, only a few additional components are required. Mechanical damping can be adjusted, for example, by a hydraulic design of the coolant cavity 20, and mechanical stiffness can be adjusted by the elasticity of the diaphragm 13. In particular, the mechanical stiffness of the wires 7 of the DC connection 16 and the wires 7 of the AC connection 18 can contribute to the mechanical stiffness of the system comprising the circuit board 12, the heat sink 22, and the diaphragm 13.

[0028] The elastic membrane 13 and the coolant in the coolant cavity 20 can be considered a spring-damper element 30 comprising the elastic spring 32 and the damper 34. Such a spring-damper element 30 can function as a connection between the heat sink 22 and the housing 10 and / or as a connection between the circuit board 12 and the housing 10, depending on which side of the circuit board 12 is more easily accessible. This allows the inverter 1 according to the invention to be used in various environments with different vibration and shock profiles. In the embodiment according to Fig. 2, for example, two spring-damper elements 30 are provided, wherein a first spring-damper element 30 connects the heat sink 22 and the housing 10 and a second spring-damper element 30 connects the circuit board 12 and the housing 10.

[0029] The DC terminal 16 and the AC terminal 18 are preferably located in a fixed position on the DC protection 15 on the housing 10 and on the AC protection 17 on the housing 10, respectively, so that the inverter 1 according to the invention can be used in the same packaging as previous inverters 1. The high-voltage wires 7 should preferably be flexible within the housing 10 and at the connection points 19 to the circuit board 12. The wires 7 are the only metal parts exposed to alternating stress and must therefore be carefully designed. As shown in Fig.2, in particular, the wires 7 of the DC connection 16, the wires 7 of the AC connection 18 within the air cavity 21, and the wires 7 at the fixed connection points 19 of the wires 7 to the circuit board 12 can be flexible. The flexible wires 7 thus also absorb vibrations and do not break, so that fewer or no vibrations reach the circuit board 12 and the soldered components, and the inverter 1 remains functional.

[0030] Optionally, the stiffness of the high-voltage connections 16, 18 can be used to change the overall stiffness of the system and save additional spring-damper system components.

[0031] It is believed that the present disclosure and many of the advantages recited therein will be understood from the foregoing description. It will be apparent that various changes in form, construction, and arrangement of components may be made without departing from the disclosed subject matter. The form described is merely illustrative, and it is the intent of the appended claims to encompass and embrace such changes. Accordingly, the scope of the invention should be limited only by the appended claims. List of reference symbols 1 inverter 3 energy cells 5 Electric motor 7 wire 10 housings 12 Printed circuit board (PCB) 13 Membran 131 first membrane end 132 second membrane end 14 electrical components 15 DC protection 16 DC connection 17 AC protection 18 AC power connection 19 connection point 20 Coolant cavity 21 Air cavity 22 heat sink 24 Coolant inlet 25 Coolant drain 30 spring-damper element 32 elastic spring 34 dampers 100 vehicles 102 Body

Claims

[1] An inverter (1), in particular for an electrically driven vehicle (100), comprising a housing (10), a printed circuit board (12) which is accommodated in the housing (10) and has a plurality of electrical components (14) of a power electronics system, a direct current connection (16) coming from at least one energy cell (3) of the vehicle (100), and an AC connection (18) leading to at least one electric motor (5) of the vehicle (100), characterized by a heat sink (22) connected to the circuit board (12); an elastic membrane (13) connected to the heat sink (22) and the housing (10); a coolant cavity (20) for coolant; and an air cavity (21), wherein the coolant cavity (20) and the air cavity (21) are defined by the heat sink (22) and the elastic membrane (13) connected thereto and to the housing (10). [2] The inverter (1) according to claim 1, wherein wires (7) of the DC terminal (16), wires (7) of the AC terminal (18) within the air cavity (21) and wires (7) at connection points (19) of the wires (7) to the circuit board (12) are flexible. [3] The inverter (1) according to any one of the preceding claims, wherein the coolant in the coolant cavity (20) for the circuit board (12) is water. [4] The inverter (1) according to any one of the preceding claims, wherein the membrane (13) connected to the heat sink (22) and the housing (10) acts as an elastic spring (32) and the coolant in the coolant cavity (20) acts as a damper (34). [5] The inverter (1) according to claim 4, wherein a mechanical damping is adjustable by a hydraulic design of the coolant cavity (20) and a mechanical stiffness is adjustable by the elasticity of the membrane (13). [6] The inverter (1) according to claim 5, wherein a mechanical rigidity of the wires (7) of the DC terminal (16) and the wires (7) of the AC terminal (18) contributes to the mechanical rigidity of the system comprising the circuit board (12), the heat sink (22) and the membrane (13). [7] The inverter (1) according to any one of claims 4 to 6, wherein a spring-damper element (30) comprising an elastic spring (32) and a damper (34) connects the heat sink (22) and the housing (10), and / or a spring-damper element (30) comprising an elastic spring (32) and a damper (34) connects the circuit board (12) and the housing (10). [8] The inverter (1) according to one of the preceding claims, wherein the circuit board (12) is connected to the heat sink (22) in a thermally conductive manner via a thermal paste and additionally with screws or a thermally conductive adhesive. [9] A vehicle (100) comprising an inverter (1) according to one of the preceding claims, wherein the inverter (1) connects at least one energy cell (3) of the vehicle (100) to at least one electric motor (5) of the vehicle (100).

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