DE102020202963A1 - DC link capacitor and manufacturing process - Google Patents

Abstract

An intermediate circuit capacitor (40, 70) for an inverter of a motor vehicle is proposed. The intermediate circuit capacitor has at least one capacitive element (46), which is arranged in a receiving space (44) of a housing arrangement (42), and a first and a second busbar (50, 52) each leading out of the receiving space (44) for the electrical connection of the capacitive element (46). At least one two-layer wall (56) delimiting the receiving space (44) is formed by the first busbar (50) as the inner layer and a thermally conductive and electrically insulating outer layer (54) arranged thereon on the outside. A corresponding manufacturing method is also proposed.

Description

Technical area

The present application relates to an intermediate circuit capacitor for an inverter of a motor vehicle, a method for producing an intermediate circuit capacitor and a method for producing an inverter.

• 1 zeigt beispielsweise ein erstes bekanntes Konzept zum Kühlen eines Zwischenkreiskondensators 10. Der Zwischenkreiskondensator 10 weist beispielsweise zwei oder mehr kapazitive Elemente 12 auf, welche in einem Gehäuse 14 eingehüllt sind. Vorliegend sind in der Ansicht von 1 zwei kapazitive Elemente 12 zu erkennen. Zum elektrischen Verbinden des Zwischenkreiskondensators 10 sind jeweilige Stromschienen 16 aus dem Gehäuse 14 herausgeführt. Unterseitig an dem Gehäuse 14 ist ein Kühler 18 angeordnet. Eine Kühlung ist bei diesem Konzept jedoch wenig effizient, da eine Entwärmung der wärmeerzeugenden kapazitiven Elemente 12 durch das Gehäuse 14 nur sehr unzureichend erfolgt.
• 2 zeigt beispielsweise ein zweites bekanntes Konzept zum Kühlen eines Zwischenkreiskondensators 20. Auch dieser Zwischenkreiskondensator 20 weist kapazitive Elemente 22 auf, welche in einem Gehäuse 24 eingehüllt sind. Zum elektrischen Verbinden des Zwischenkreiskondensators 20 sind ebenfalls jeweilige Stromschienen 26 aus dem Gehäuse 24 herausgeführt. Bei diesem Konzept ist ein Kühler 28 unterseitig an den Stromschienen 26 angeordnet. Zwischen dem Kühler 28 und den Stromschienen 26 ist eine Isolationsschicht 27 angeordnet. Üblicherweise sind Stromschienen 26 aus einem metallischen Werkstoff gebildet und thermisch gut leitend. Damit kann Wärme aus einem Gehäuseinneren gut nach außen abgeführt werden. Allerdings ist eine Kontaktfläche mit dem Kühler 28 gering. Außerdem gibt es einen Spalt 30 zwischen einem Kühlerbereich, welcher nicht mit den Stromschienen 26 kontaktiert ist, und einer Unterseite des Gehäuses 24. Eine Wärmeübertragung und damit Kühlung ist in diesem Bereich äußerst gering. Der Spalt 30 isoliert den Kühler 28 thermisch von dem Gehäuse 24. Auch die thermische Effizienz des zweiten Konzepts ist damit unbefriedigend.

Drive inverters, for example for electric motors in motor vehicles, usually have an intermediate circuit capacitor. This intermediate circuit capacitor can be sensitive to temperature. For example, film capacitors age faster at higher temperatures. Intermediate circuit capacitors are usually cooled accordingly.

• 1 shows, for example, a first known concept for cooling an intermediate circuit capacitor 10 . The intermediate circuit capacitor 10 has, for example, two or more capacitive elements 12th on which in a housing 14th are enveloped. The present are in the view of 1 two capacitive elements 12th to recognize. For the electrical connection of the intermediate circuit capacitor 10 are respective busbars 16 out of the case 14th led out. On the underside of the housing 14th is a cooler 18th arranged. With this concept, however, cooling is not very efficient because the heat-generating capacitive elements are cooled 12th through the housing 14th only very inadequately done.
• 2 shows, for example, a second known concept for cooling an intermediate circuit capacitor 20th . Also this intermediate circuit capacitor 20th has capacitive elements 22nd on which in a housing 24 are enveloped. For the electrical connection of the intermediate circuit capacitor 20th are also respective busbars 26th out of the case 24 led out. With this concept there is a cooler 28 on the underside of the busbars 26th arranged. Between the cooler 28 and the busbars 26th is an insulation layer 27 arranged. Usually busbars are 26th made of a metallic material and has good thermal conductivity. This allows heat to be dissipated from the inside of the housing to the outside. However, there is a contact surface with the cooler 28 small amount. There is also a crack 30th between a cooler area that is not connected to the busbars 26th is contacted, and an underside of the housing 24 . Heat transfer and thus cooling is extremely low in this area. The gap 30th insulates the radiator 28 thermally from the housing 24 . The thermal efficiency of the second concept is therefore also unsatisfactory.

Presentation of the invention

The present invention relates to an intermediate circuit capacitor, a method for producing an intermediate circuit capacitor and a method for producing an inverter, the invention being defined by the subjects of the independent claims. Refinements with expedient developments are specified in the respective subclaims.

A first aspect relates to an intermediate circuit capacitor for an inverter of a motor vehicle. An intermediate circuit capacitor can be an electrical capacitor in an intermediate circuit of an inverter. The intermediate circuit capacitor can, for example, energetically couple several electrical networks and / or smooth respective voltages. An inverter can be an electrical device that converts DC voltage into AC voltage. For example, the inverter can convert a DC battery voltage into AC voltage for an electric motor. For example, a motor vehicle can be a vehicle with a drive, such as a car, truck, or bus. The drive can be designed as an electric drive, for example.

The intermediate circuit capacitor can have at least one capacitive element which is arranged in a receiving space of a housing arrangement. The capacitive element can be a passive electrical component which can statically store an electrical charge and the associated energy in an electrical field. A capacitive element can have two electrodes and a dielectric arranged between them. The capacitive element can be a capacitor in the narrower sense without components such as a housing, for example a capacitor winding. An example of a capacitive element is a wound capacitor, in particular a plastic film capacitor. The housing arrangement can have one or more housing parts which define the receiving space and, for example, serve to protect the respective capacitive elements. The receiving space can be delimited by respective walls, in particular respective housing parts. The receiving space can be a closed space or it can also have passages to an outside.

The intermediate circuit capacitor can have a first and a second each from the Have receiving space led out busbar for electrically connecting the capacitive element. In particular, an associated pair of busbars can be provided for each capacitive element. For example, a busbar can be connected to each pole of each capacitive element. The respective busbars can pass an outer boundary of the receiving space with a section leading out. For example, the respective busbars can be arranged at least partially in through openings of housing parts. The electrical connection allows the respective capacitive element to receive and release electrical energy via the busbars, in particular to a further electrical component connected via the busbars. The busbars can be designed as electrical conductors and made of a metallic material. The busbars can, for example, be designed as rigid elements, in particular in contrast to a cable. For example, the busbars can have a shape of a flat band.

In the case of the intermediate circuit capacitor, it can be provided that at least one two-layer wall delimiting the receiving space is formed as an inner layer to improve the heat dissipation through the first busbar and a thermally conductive and electrically insulating outer layer arranged thereon on the outside. The two-layer wall can be a structural section delimiting the receiving space, in particular a structural section extending over an area. The housing assembly can include the wall. The two-layer wall is preferably free of further layers. In particular, the wall can be free of an intermediate layer between the busbar and the outer layer. Further layers can also be provided, which are arranged on the outside and alternatively or additionally on the outside of the two-layer wall. The outer layer can be in direct contact with the busbar. Thermally conductive can mean that the outer layer is designed in terms of construction and material selection in such a way that the greatest possible heat transfer via the outer layer is possible. The outer layer can, for example, have a high thermal conductivity. The two-layer wall with the busbar and the outer layer forms a cooling surface, for example. The construction can also include a thickness, for example. For example, the outer layer can be more thermally conductive than the rest of the housing parts and, alternatively or additionally, walls that delimit the receiving space. Electrically insulating can mean, for example, that when the intermediate circuit capacitor is used as intended, no current can flow from the busbar via the outer layer to other components. The outer layer can be formed from an electrically non-conductive solid, for example. The outer layer can, for example, comprise a plastic, in particular silicone. The silicone can be enriched with a filler, such as a ceramic filler. For example, the outer layer can be approximately 1 to 2 mm thick. In the case of a plurality of first busbars, a common or in each case an assigned outer layer can be arranged thereon. In the case of a common outer layer, the outer layer can also be arranged in the case of a gap between first busbars, for example arranged on a potting material that fills the gap. One side of the receiving space can be formed in some areas by the two-layer wall and in areas only by an electrically insulating layer, such as a potting material. An inside of the intermediate circuit capacitor can be defined as pointing towards the respective capacitive elements and, alternatively or additionally, the receiving space. An outside of the intermediate circuit capacitor can be defined as pointing away from the respective capacitive elements and alternatively or additionally from the receiving space.

Because the first busbar forms a layer of the two-layer wall, a large area can be provided for cooling the capacitor for dissipating thermal energy from the receiving space, in particular from the capacitive element, to an outside, in particular to a cooler arranged on the outside . There is no need for a complicated arrangement of the busbar outside the housing arrangement for thermal connection to the cooler. In addition, the cooler does not have to be electrically isolated from the power rail, as this is already done by the outer layer of the wall. The combination of busbar and thermally conductive outer layer can withstand loads similar to those of a housing, for example in FIG 1 shown, but at the same time allow a much better heat dissipation. The first busbar can be understood in the area of the two-layer wall as a reinforcement of the outer layer, so that it can be made particularly thin and can therefore conduct heat particularly well. Film capacitors in particular as capacitive elements can be temperature-critical and age faster at high temperatures. The intermediate circuit capacitor makes it possible to reliably avoid a critical temperature range, which means that its service life can be particularly long.

In one embodiment of the intermediate circuit capacitor, it is provided that the outer layer is designed as a film which is glued onto the first busbar. Production and assembly can thus be particularly simple. The film can, for example, be used as an adhesive film be trained. The adhesive film can be self-adhesive. An adhesive film can have a substrate, in particular a plastic film, and an adhesive applied to it. The adhesive side of the adhesive film is, for example, facing the first busbar when it is glued on. Alternatively, the film can be free of adhesive and adhesive can also be attached to the film or the first busbar before the film is glued on. In the present case, glue is not regarded as an additional layer. If the adhesive would be viewed as an additional layer, the wall can have three layers and, for example, free of further layers.

In one embodiment of the intermediate circuit capacitor, it is provided that the receiving space is at least partially delimited by a housing element of the housing arrangement of the intermediate circuit capacitor which has an opening in the area of the two-layer wall. A housing element can be a structural component. The housing element can have at least one wall delimiting the receiving space. For example, the housing element can be open on the side of the two-layer wall. The housing element can be shaped like a trough. For example, respective capacitive elements and partial sections of the first and second busbars can be accommodated in the housing element. The housing element can for example be designed as a plastic element

In one embodiment of the intermediate circuit capacitor, it is provided that the receiving space is filled with a potting material. The potting material can fix the capacitive element and, alternatively or additionally, respective busbars in the receiving space, in particular on the housing element. Other electronic components can also be encapsulated as an option. For example, the two-layer wall is supported on the inside by the potting material. The potting material preferably ends in front of an outside of the outer layer on the two-layer wall. The potting material can laterally enclose the two-layer wall. For example, a step is provided between an outside of the two-layer wall and the potting material adjoining it, the two-layer wall protruding from the potting material, for example. This makes it easier for a cooler to rest evenly against the two-layer wall. The potting material can be epoxy resin, PU or silicone, for example. The potting material can also form a wall in some areas which delimits the receiving space. Optionally, further electrical components can be provided in the receiving space, which can also be arranged in the potting material. The outer layer preferably has a higher thermal conductivity than the potting material.

In one embodiment, the potting material can completely enclose the second busbar in the receiving space, at least in some areas. For example, a horizontally aligned area of the second busbar can be completely enclosed by the potting material. Alternatively or additionally, an entire area of the second busbar, which is enclosed in the receiving space, can be completely enclosed by the potting material. In one embodiment, the potting material can completely enclose the first busbar in the receiving space, at least in some areas. In particular, the first busbar can be completely enclosed by the potting material in an area outside the two-layer wall.

In one embodiment of the intermediate circuit capacitor, it is provided that the outer layer of the two-layer wall is designed to arrange a cooler thereon. The cooler can be arranged on the outer layer of the two-layer wall. The intermediate circuit capacitor can include the cooler. Alternatively, the inverter can also have the intermediate circuit capacitor and the cooler. The cooler can be designed, for example, as a passive or active heat exchanger. Heat from the receiving space of the intermediate circuit capacitor, in particular generated by the busbars and the respective capacitive elements, can be given off by the cooler to a cooling medium, such as air or a cooling liquid, for example water. The cooler can reliably prevent the intermediate circuit capacitor from overheating. The two-layer wall can provide a large and flat contact surface. In particular, the two-layer wall can be significantly flatter compared to a surface formed by the potting material, since the two-layer wall, in contrast to an injection-molded compound, does not experience any shrinkage after manufacture.

In one embodiment of the intermediate circuit capacitor, it is provided that the first and the second busbar are led to the outside on the side of the two-layer wall. The side can be a surface of the housing arrangement, in particular of the housing element, and alternatively or additionally the potting material, which essentially points in the same direction as an outside of the two-layer wall. The side can also have the two-layer wall. As a result of the arrangement described, the intermediate circuit capacitor and in particular its housing arrangement can be particularly compact. The first In this way, the busbar can have particularly few curves or angles in its course.

In one embodiment of the intermediate circuit capacitor, it is provided that the first and the second busbar are arranged in a bifilar manner, at least in some areas outside the receiving space. As an alternative or in addition, the first and the second busbar can be arranged in a bifilar manner at least in regions within the receiving space. In particular, it can be an electrically bifilar arrangement. For example, the first and the second busbar can be arranged in a non-bifilar manner in the area of a connection to an electrical component, such as a power module. A bifilar arrangement can mean that in the event of a current flow in opposite directions, the two resulting magnetic fields in the busbars almost cancel each other out in this area. In the simplest form, the first and the second busbar for a bifilar arrangement can be arranged closely aligned parallel to one another.

In one embodiment of the intermediate circuit capacitor, it is provided that an electrical insulation layer is arranged at least in some areas between the first and the second busbar. As a result, the busbars can be arranged closer together, as a result of which the intermediate circuit capacitor can be particularly compact. In particular, an insulation layer can be arranged at least in the area of the bifilar arrangement. The insulation layer can be formed, for example, by an insulation film or an insulation paper. The electrical insulation layer is preferably designed to prevent a current flow between the first busbar and the second busbar in the area of the insulation layer when the intermediate circuit capacitor is used as intended.

In one embodiment of the intermediate circuit capacitor, it is provided that the intermediate circuit capacitor has a connection area which is designed for connection to a power module. In particular, it can be a connection area of the first and second busbars. The first and the second busbar can have a connection area for connection to the power module. The connection can be electrical and, alternatively or additionally, mechanical. For example, respective busbars from the capacitive element can be connected to respective busbars of the power module in the connection area. The connection area is preferably designed for an integral connection, in particular by means of welding. For example, a laser welding process can be used for the connection. Alternatively or additionally, the connection area can also be, for example, a connection area in the housing element, such as a threaded hole for screwing the power module. The intermediate circuit capacitor can comprise the power module, wherein the power module can be connected to the busbars. Alternatively, the inverter can also have the intermediate circuit capacitor and the power module, the power module being connected to the intermediate circuit capacitor. The power module can be designed to control charging and discharging of the capacitive elements. The power module can have transistors, for example.

In one embodiment of the intermediate circuit capacitor, it is provided that a distance between the first and second busbars in the connection area for connection to the power module is greater than in an adjoining area. The distance can be, for example, a distance from a flat side of the first busbar to a flat side of the second busbar in the direction orthogonal to at least one of the flat sides. The flat sides are preferably aligned parallel to one another. The greater distance enables better electrical insulation in the connection area and, alternatively or additionally, simpler connection. For example, the connection area can thus be free of an insulation layer between the two busbars without a current flow occurring between the two busbars in this area. For example, insulation can be provided by the potting material instead. In this way, for example, the line module can be welded or soldered on without the insulation layer possibly being damaged by the high local temperatures. The adjoining area can in particular be an area in which the first and second busbars are arranged in a bifilar manner and in which, alternatively or additionally, the electrical insulation layer is provided between the first and second busbars.

In one embodiment of the intermediate circuit capacitor, it is provided that the housing arrangement has a cover element which encloses the two-layer wall together with the housing element. The cover element can thus protect the two-layer wall. The cover element can be a plastic element and, alternatively or additionally, can be designed in the form of a trough. In particular, the cover element with the housing element can define a housing interior space in which the receiving space with the capacitive element and the two-layer wall is arranged. The cover element can also protect the cooler and the power module. For example, this can Power module, and alternatively or additionally the cooler, can be arranged in the housing interior. The power module can, however, also be arranged in the cover element itself. In particular, the cover element can form a housing for the power module. For example, the cover element can be fastened to the housing element, in particular with a screw connection. The housing element can also protect respective subregions of the busbars protruding from the receiving space. The busbars can, for example, be arranged completely within the interior of the housing. The housing arrangement can completely enclose the interior of the housing, but have passages for maintenance and further connections.

In one embodiment of the intermediate circuit capacitor, it is provided that the cover element is designed to seal an area in which the busbars are led out of the receiving space. Sealing can be, for example, a fluid-tight and, alternatively or additionally, a gas-tight enclosure. For example, this area can be enclosed by the cover element together with the potting material and, alternatively or additionally, the housing element. For example, the sealing can take place by the cover element resting against the housing element and, alternatively or additionally, the potting material. A contact area can be sealed. The housing element can have a seal. With the seal, the housing element can rest against the housing element and, alternatively or additionally, the potting material. The seal can be designed, for example, as an elastomer seal. The seal is preferably carried out outside an area which is formed by the two-layer wall. The seal can prevent or at least reduce the penetration, in particular creeping, of liquids into the receiving space with the capacitive element in the area in which the busbars are led out.

In one embodiment of the intermediate circuit capacitor, it is provided that the connection area for connection to the power module is filled with a potting material at least in the area of the first and second busbars. In this way, penetration of moisture, in particular moisture creeping into the receiving space, can be reliably prevented or greatly reduced there. In addition, the busbars and in particular the connection area can be supported and protected. The potting material preferably envelops the busbars. Production is particularly simple if the cover element seals the area in which the busbars are led out of the receiving space. The potting material can then be filled in there, for example through a filling opening. The filling opening can be closed by the potting material after it has hardened. For example, the same potting material can be used as in the receiving space in which, for example, the capacitive element is potted.

A second aspect relates to a method for producing an intermediate circuit capacitor for an inverter of a motor vehicle. The method can be designed to produce the intermediate circuit capacitor according to the first aspect.

The method can have the step of providing at least one capacitive element with a first and a second busbar, the two busbars being designed to electrically connect the capacitive element. The capacitive element can be or can be electrically connected to a power module, for example. The method can furthermore have the step of arranging the capacitive element in a receiving space of a housing arrangement, the first busbar forming an outside of the receiving space at least in some areas. The receiving space can for example be defined by a housing element and does not have to be completely closed off. The method can have a step of applying a heat-conducting and electrically insulating layer on the outside of the first busbar in order to form a two-layer wall delimiting the receiving space. The thermally conductive and electrically insulating layer can form an outer layer of the receiving space. The application can take the form of gluing, in particular if an adhesive film is provided to form the outer layer. The outer layer is applied in particular in the area in which the first busbar previously delimited the receiving space at least in certain areas. The steps mentioned can be carried out, for example, in the order outlined.

In addition, the method can have the step of filling a potting material into the receiving space. This step takes place, for example, after the application of the heat-conducting and electrically insulating layer on the first busbar. The potting material can frame the two-layer wall, in particular up to an upper edge or below. After the potting material has been filled in, it can be cured in a further step. The hardening takes the potting material, for example, from a liquid state to a solid state. Curing can be started, for example, by UV light or by adding a hardener to a resin. The curing can also be brought about by heating, for example in an oven.

A third aspect relates to a method for manufacturing an inverter. The method can result in an intermediate circuit capacitor as an intermediate product. The method can have the steps of the method for producing an intermediate circuit capacitor according to the second aspect. The method can result in the intermediate circuit capacitor according to the first aspect as an intermediate product.

The method can include the step of filling potting material into the receiving space. Furthermore, the method can have a step of electrically connecting the first and second busbars to a power module. For example, busbars of the power module can be welded to busbars of the capacitive element, in particular by means of a laser. Furthermore, the method can have a step of housing a connection area of the first and second busbars with the power module up to an area in which the first and second busbars are led out of the receiving space. For example, a cover element for this purpose can form a wall around the busbars from a delimitation of the receiving space to at least the connection area with the power module. This wall with a housing element and, alternatively or additionally, the potting material can rest in the receiving space. The connection area can be the area in which the busbars are connected to the power module. The cover element can have a seal with which it rests against the housing element and, alternatively or additionally, the potting material in the receiving space. Furthermore, the method can have a step of filling further potting material into the enclosed area. As a result, the inverter can be protected from environmental influences and structurally reinforced. The mentioned steps of the method for producing the inverter take place, for example, in the order outlined.

Further features emerge from the claims, from the exemplary embodiments and on the basis of the drawings. The features and combinations of features mentioned above in the description and the features and combinations of features mentioned below in the exemplary embodiment can be used not only in the respectively specified combination, but also in other combinations. The features and advantages resulting from the respective aspects also represent the respective features and advantages of other aspects.

Figure list

• 1 illustrates in a schematic sectional view an embodiment of a known intermediate circuit capacitor.
• 2 illustrates in a schematic sectional view a second embodiment of a known intermediate circuit capacitor.
• 3 illustrates an intermediate circuit capacitor in a schematic perspective view.
• 4th illustrates in a schematic sectional view the intermediate circuit capacitor according to FIG 3 .
• 5 illustrates in a schematic sectional view a second embodiment of an intermediate circuit capacitor with a cooler and power module connected to it.
• 6th illustrates in a schematic sectional view in detail a connection area of the intermediate circuit capacitor according to FIG 5 .
• 7th illustrates the connection area of the intermediate circuit capacitor according to 5 in a schematic perspective view without the cooler and the power module.

Detailed description of embodiments

3 shows an intermediate circuit capacitor in a schematic perspective view 40 . 4th illustrates the interior of the intermediate circuit capacitor in a sectional view 40 . The intermediate circuit capacitor 40 has a trough-shaped housing element 42 with one side open at the top 48 on which a recording room 44 Are defined. In the recording room 44 are capacitive elements 46 arranged, which in the present case are designed as wound film capacitors. On one of the open sides 48 facing pole of the capacitive elements 46 is a first power rail 50 tied together. With a pole facing away from it, there is a second busbar 52 tied together. The two power rails 50 , 52 are out of the recording room 44 led out, present in a lateral area of the open side 48 . This is especially good in 3 to recognize. The two power rails 50 , 52 are designed to use the capacitive elements 46 connect to another electrical component, such as a power module. The two power rails 50 , 52 connect all three capacitive elements in the present case 46 . The two power rails 50 , 52 are in a connection area with the capacitive elements 46 Cut out in such a way that they form associated pairs of fingers and can each be connected with half bridges.

The two power rails 50 , 52 are designed as flat metallic strips, which are in 3 extend in and out of the image plane in width. The housing element 42 is formed for example from a plastic.

The first power rail 50 extends on the open side 48 so this there is the recording room 44 limited. Outside the recording room 44 is turned away on the power rail 50 an outer layer in some areas 54 arranged. This outer layer 54 insulates the first busbar 50 electrical in this area compared to the environment. At the same time, the outer layer allows 54 a heat transfer, in particular to dissipate a heat transfer due to the operation of the intermediate circuit capacitor 40 and by charging and discharging the capacitive elements 46 generated heat. That's what the outer layer is for 54 more thermally conductive than the walls of the housing element 42 . The outer layer 54 is a thermally conductive and electrically insulating layer. The present is the outer layer 54 designed as a silicone adhesive film, which is attached to the first busbar 50 is glued on the outside. The silicone adhesive film is enriched with a ceramic filler.

The first power rail 50 and the outer layer disposed thereon 54 together form a two-layer wall 56 showing the recording room 44 in the area of the open side 48 of the housing element 42 limited at least in certain areas. The first power rail 50 forms an inner layer of the two-layer wall 56 . The two-layer wall 56 extends over almost the entire open side 48 and thus several capacitive elements 46 , as in 1 can be seen. The two-layer wall 56 Provides a large and flat surface for placing a cooler so that heat can be efficiently dissipated.

The recording room 44 is with a potting material 58 filled up. The potting material 58 attached the capacitive elements 46 in position and protects it from the environment, supports and fixes the two busbars 50 , 52 and closes the entire recording space 44 .

The potting material 58 protrudes on the open side 48 not all the way to an outside edge of the outer layer 54 approach. Between an outer surface of the outer layer 54 and an adjacent outside of the potting material 58 one stage is provided. This hinders the potting material 58 not the arrangement of the cooler on the two-layer wall 56 , whereby respective tolerances can be large. The potting material 58 frames the outer layer 54 a, whereby this also through the potting material 58 is held. The potting material 58 shrinks as it hardens. However, this does not result in a curvature of the two-layer wall 56 . By having the outer surface of the two-layer wall 56 through the first busbar 50 is supported, this surface is flat. The two-layer wall 56 , the potting material 58 and the housing element 42 together form a housing arrangement of the intermediate circuit capacitor 40 , which are the capacitive elements 46 completely encloses and protects.

Starting in a corner area next to one of the capacitive elements 46 , still covered by the potting material 58 , are the two power rails 50 , 52 arranged parallel to each other. The two power rails 50 , 52 are also arranged parallel and close to each other from the recording room 44 out of the potting material 58 out. The arrangement of the two busbars 50 , 52 in the area in which it is arranged in parallel, it is bifilar. This enables a low-inductance DC link connection. Between the conductor rails 50 , 52 is an insulation layer in this area 60 arranged, which is formed by an insulating paper or an insulating film. As a result, the two busbars are reliably electrically isolated from one another in this area as well.

An adjoining connection area 62 of the two busbars 50 , 52 , which their respective end outside of the recording space 44 is designed so that there is a distance between the first and the second busbar 50 , 52 is bigger. This area is free of an insulation layer. There is correspondingly in the connection area 62 a crack 64 between the two busbars 50 , 52 . Due to the greater distance, a current flow from one to the other busbar is nevertheless generated when the device is used as intended 50 , 52 prevents, which could occur if the distance is too small, for example by an electric arc. The greater distance also enables potting material to be introduced 58 in the gap 64 . Also the potting material 58 insulates the two busbars 50 , 52 electrically from each other. By having the connection area 62 If the insulation layer is free, the busbars can 50 , 52 can be easily connected to other electrical components using a thermal process such as laser beam welding.

5 shows a further embodiment of an intermediate circuit capacitor in a schematic sectional view 70 . This intermediate circuit capacitor 70 is in 7th shown partially in a perspective view. In 6th is a fragmentary perspective sectional view of the intermediate circuit capacitor 70 shown.

The basic structure of the intermediate circuit capacitor 70 is the same as that of the intermediate circuit capacitor 40 identical. Correspondingly, the same reference numerals are given for the same components or components with the same function and their further description is dispensed with.

The intermediate circuit capacitor 70 additionally has a cooler 72 on which is the outside on the two-layer wall 56 is arranged. The cooler 72 has respective cooling structures in the form of ribs 74 on so the cooler 72 can be at least partially flowed through by water-glycol as a coolant.

In addition, the intermediate circuit capacitor 70 a cover element 76 on which with the housing element 42 is screwed and on its open side 48 is arranged. The cover element 76 so closes the cooler 72 , the two-layer wall 56 and the recording room 44 together with the housing element 42 in a housing interior.

In the cover element 76 is a - not shown - added power module. The combination of cover element 76 and power module is also referred to as a power module. The power module is with respective busbars 78 with the two assigned busbars 50 , 52 in the connection area 62 laser welded. The intermediate circuit capacitor 70 with the power module connected to it forms an inverter.

The cover element 76 has a wall area 82 on which the area of the busbars 50 , 52 where this from the recording room 44 protrude, umwandet. This wall area 82 is particularly good at 7th to recognize in which the intermediate circuit capacitor 70 without the cooler 72 and the rest of the cover element 76 is shown. There are also the busbars 50 , 52 partially cut, creating the insulation layer 60 is visible.

The wall area 82 points on its the open side 48 or the housing element 42 facing side an elastomer seal 80 on. The elastomer seal 80 is in 6th shown. In the embodiment shown, the elastomer seal is located 80 on the potting material 58 and seals an area there where the busbars 50 , 52 from the recording room 44 are led out from. In an alternative embodiment, the elastomer seal 80 also partially or completely on the housing element 42 rest and seal there.

The area sealed in this way is covered with additional potting material 84 filled up. The potting material 84 can for example through an upper opening in the wall area 82 limited space with the busbars inside 50 , 52 , 78 be filled. Through the further potting material 84 in the area of the electrical connection of the busbars 50 , 52 with the busbars 78 of the power module, the required clearances and creepage distances can be maintained.

In one embodiment of a manufacturing method for the intermediate circuit capacitor 40 and 70 first the capacitive elements 46 in the recording room 44 arranged, the first busbar 50 at least in some areas an outside of the receiving space 44 on the open side 48 of the housing element 42 forms. Before or after the outer layer can 54 on the first busbar 50 be applied. This application takes place in one embodiment by gluing. Then the potting material 58 filled and hardened. In one embodiment of the manufacture of the intermediate circuit capacitor 70 becomes the cooler 72 on the two-layer wall 56 on the outer layer 54 arranged. Arranging the cooler 72 can be before or after filling, and alternatively or additionally hardening, of the potting material 58 take place. After the potting material has hardened 58 is used to manufacture the intermediate circuit capacitor 70 the cover element 76 on the housing element 42 attached and the busbars 78 with the busbars 50 , 52 tied together. Then more potting material is used 84 in the through the walls 82 limited area filled and cured.

List of reference symbols

10

DC link capacitor

12th

capacitive element

14th

casing

16

Busbar

18th

cooler

20th

DC link capacitor

22nd

capacitive element

24

casing

26th

Busbar

27

Insulation layer

28

cooler

30th

gap

40

DC link capacitor

42

Housing element

44

Recording room

46

capacitive element

48

open side

50

first busbar

52

second busbar

54

outer layer

56

two-layer wall

58

Potting material

60

Insulation layer

62

Connection area

64

gap

70

DC link capacitor

72

cooler

74

Ribs

76

Cover element

78

Busbar

80

Elastomer seal

82

Wall area

84

Potting material

Claims (15)

Intermediate circuit capacitor (40, 70) for an inverter of a motor vehicle, having at least one capacitive element (46) which is arranged in a receiving space (44) of a housing arrangement, and a first and a second busbar (50) each leading out of the receiving space (44) , 52) for electrically connecting the capacitive element (46), characterized in that at least one two-layer wall (56) delimiting the receiving space (44) to improve the dissipation of heat through the first busbar (50) as an inner layer and a thermally conductive wall arranged on the outside and electrically insulating outer layer (54) is formed. Intermediate circuit capacitor (40, 70) after Claim 1 , characterized in that the outer layer (54) is designed as a film which is glued onto the first busbar (50). Intermediate circuit capacitor (40, 70) after Claim 1 or 2 , characterized in that the receiving space (44) is at least partially delimited by a housing element (42) of the housing arrangement of the intermediate circuit capacitor (40, 70) which has an opening in the area of the two-layer wall (56). Intermediate circuit capacitor (40, 70) according to one of the preceding claims, characterized in that the receiving space (44) is filled with a potting material (58). Intermediate circuit capacitor (40, 70) after Claim 4 , characterized in that the potting material (58) ends in front of an outside of the outer layer (54) on the two-layer wall (56). Intermediate circuit capacitor (40, 70) according to one of the preceding claims, characterized in that a cooler (72) is arranged on the outer layer (54) of the two-layer wall (56). Intermediate circuit capacitor (40, 70) according to one of the preceding claims, characterized in that the first and second busbars (50, 52) are arranged in a bifilar manner, at least in some areas outside the receiving space (44). Intermediate circuit capacitor (40, 70) according to one of the preceding claims, characterized in that an electrical insulation layer (60) is arranged at least in some areas between the first and second busbars (50, 52). Intermediate circuit capacitor (40, 70) according to one of the preceding claims, characterized in that the intermediate circuit capacitor (40, 70) has a connection area (62) which is designed for connection to a power module. Intermediate circuit capacitor (40, 70) after Claim 9 , characterized in that a distance between the first and the second busbar (50, 52) in the connection area (62) for connection to the power module is greater than in an adjoining area. Intermediate circuit capacitor (40, 70) after Claim 3 , characterized in that the housing arrangement has a cover element (76) which encloses the two-layer wall (56) together with the housing element (42). Intermediate circuit capacitor (40, 70) after Claim 11 , characterized in that the cover element (76) is designed to seal an area (62) in which the busbars (50, 52) are led out of the receiving space (44). Intermediate circuit capacitor (40, 70) according to one of the preceding claims, characterized in that the connection area (62) for connection to the power module is filled with a potting material (84) at least in the area of the first and second busbars (50, 52). Method for producing an intermediate circuit capacitor (40, 70) for an inverter of a motor vehicle, comprising the steps: - Providing at least one capacitive element (46) with a first and a second busbar (50, 52), the two busbars (50, 52 ) are designed to electrically connect the capacitive element (46); - Arranging the capacitive element (46) in a receiving space (44) of a housing arrangement, the first busbar (50) forming an outside of the receiving space (44) at least in some areas; - Application of a heat-conducting and electrically insulating layer (54) on the outside of the first busbar (50) to form a two-layer wall (56) delimiting the receiving space (44). A method for producing an inverter, which comprises the steps of the method according to Claim 14 and additionally has the following steps: - Filling potting material (58) into the receiving space (44); - electrically connecting the first and second busbars (50, 52) to a power module; - Housing a connection area (62) of the first and second busbars (50, 52) with the power module up to an area in which the first and second busbars (50, 52) lead out of the receiving space (44); and - Filling further potting material (84) into the enclosed area.

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