DE102022102408A1 - Electrical System and Electric Drive Unit - Google Patents

Abstract

The invention relates to an electrical system with optimized heat dissipation and an electrical drive unit that includes the electrical system. The electrical system includes a busbar (1), a machine element (20) and a heat-conducting element (40) that makes thermally conductive contact with the busbar (1). , wherein the machine element (20) on a side facing the conductor rail (1) comprises at least in regions a shaped element (30) which protrudes from an outer extension plane (21) and forms a contact surface (31), and wherein the heat-conducting element (40) has a bottom-side contact element (41) bears against the contact surface (31) in a thermally conductive manner and encases the protruding shaped element (30) with a encasing element (42). With the electrical system proposed here and the electric drive unit equipped with it, devices are made available which optimize heat dissipation guarantee with little space requirement.

Description

The invention relates to an electrical system with optimized heat dissipation and an electrical drive unit that includes the electrical system.

In electrical systems, in particular in those that are operated with high voltage, current rails, also known as busbars, are often used as current conductors.

Due to the high currents present, resistance-related heating often occurs, including the busbars. In order to reduce resistance-related losses and/or to protect the busbar itself or also other adjacent components, it is often necessary or appropriate for safety reasons to dissipate heat from the busbar. However, particularly in configurations in which the busbar is electrically conductively coupled to a module which itself has a plastic housing or a plastic casing on its outside, heat transfer to such a module is only possible to a reduced extent or is also dangerous damage to the plastic of the module.

To dissipate heat, there are, for example, so-called gap pads, that is to say essentially two-dimensional bodies which consist of thermally conductive material in order to create thermal interfaces between electronic components and heat sinks in air gaps.

However, such gap pads must meet the electrical requirements with regard to a sufficient clearance and creepage distance. In the case of two-dimensionally shaped gap pads, this is only possible if the gap pad has expansive areas which protrude beyond a contact surface on which the gap pad bears in a thermally conductive manner. However, this embodiment requires a large amount of installation space, since the edge area of the gap pad must be arranged sufficiently far from an adjacent current-carrying part due to the need to maintain a sufficient air gap. However, particularly in the case of adjacent busbars of different polarity, there is often not enough installation space available to arrange gap pads on both busbars with protruding edge regions, since these are often arranged relatively close together.

In addition, with a gap pad designed in this way, there is a risk that such a protruding edge region will vibrate and thereby generate acoustic emissions and/or hit neighboring components.

To eliminate the disadvantages mentioned, contact surfaces on machine elements into which heat is to be conducted from the respective busbar could be made smaller in order to lead the projecting areas of a respective gap pad sufficiently far beyond. This in turn results in a reduced area over which heat can be transferred, correspondingly reducing the heat dissipation effect.

Proceeding from this, the object of the present invention is to provide an electrical system and an electrical drive unit equipped therewith, which ensure optimized heat dissipation with a small installation space requirement.

This object is achieved by the electrical system according to claim 1 and by the electrical drive unit according to claim 10. Advantageous configurations of the electrical system are specified in dependent claims 2 to 9.

The features of the claims can be combined in any technically meaningful way, with the explanations from the following description and features from the figures also being able to be used for this purpose, which include supplementary configurations of the invention.

The invention relates to an electrical system with optimized heat dissipation, which comprises a busbar, a machine element and a heat-conducting element that makes thermally conductive contact with the busbar. On a side facing the conductor rail, the machine element comprises, at least in regions, a shaped element which protrudes from an outer plane of extension and which forms a contact surface. The heat-conducting element bears with a base-side contact element on the contact surface in a thermally conductive manner and encases the protruding shaped element with a sheathing element.

The outer extension plane of the machine element is a plane in which the outside of a boundary wall facing the busbar runs, outside of the respective protruding shaped element.

In one embodiment, it is provided that the conductor rail, also known as a busbar, electrically conductively connects a power module and a capacitor.

The power module and the capacitor can be components of power electronics that form a high-voltage intermediate circuit between a battery or an electrical Ener giespeicher and an electric drive machine, in particular an electrically driven motor vehicle. In this case, the capacitor can be an element of a converter which is set up to quickly feed direct current or direct current provided by the battery to the power module via the busbar, which converts this into alternating current.

Heat from the busbar is correspondingly transferred from the busbar to the machine element via the heat-conducting element. Such a heat-conducting element is also referred to as a gap pad or thermal interface material (TIM).

Due to the fact that the machine element is a large-volume component of greater mass, especially if it is a housing element or housing, its specific heat capacity is high and its surfaces to the ambient air are large, so that the machine element can absorb a lot of heat and / or over the surfaces can give off to the environment via convection. If the machine element is connected to other units in a thermally conductive manner, this effect is further intensified. According to the invention, it is thus achieved that the heat of the busbar does not have to remain in the busbar or does not have to be dissipated via a slightly thermally conductive plastic housing.

This results in a constructively optimized heat dissipation of the busbar.

The heat-conducting element not only covers the protruding shaped element on the contact surface, in particular completely, but also covers the protruding shaped element on the lateral boundary surfaces of the protruding shaped element if this forms a polygon in cross section, or on one lateral boundary surface if it is round has cross section.

Only the area or the side of the protruding shaped element in which or on which the protruding shaped element is connected to the machine element is not covered by the heat-conducting element.

A lateral boundary surface of the protruding shaped element is a surface that realizes the connection in the machine element between the plane in which the outside of a boundary wall facing the busbar runs and the contact surface of the machine element on which the heat-conducting element rests.

Accordingly, it is provided that the heat-conducting element is shaped three-dimensionally, essentially like a pot or bowl, with a contact element on the bottom side as the bottom of the pot, and with the casing element as the pot wall. The encasing element can likewise rest in a thermally conductive manner on one lateral boundary surface or on a plurality of lateral boundary surfaces of the protruding shaped element. In an alternative embodiment, a minimum distance is realized between the encasing element and the one lateral boundary surface or multiple lateral boundary surfaces. The machine element can in particular be a housing element, or also a complete housing of a structural unit.

The protruding shaped element can also be referred to as a cooling plateau, which is surrounded by the casing element of the heat-conducting element. The heat-conducting element forms a base-side contact element lying against the contact surface, which contact element is firmly and thermally conductively connected to the casing element. In particular, the base-side contact element and the encasing element are integral components of the heat-conducting element. The three-dimensionality of the heat-conducting element serves to enlarge the surface for the purpose of dissipating heat to the environment by means of convection, as well as to improve the heat transfer to the machine element and to extend the creepage distance without significantly using the installation space.

In a simple embodiment, the heat-conducting element can be produced by means of injection molding, although production by means of additive manufacturing processes, such as 3D printing, is not ruled out.

In one embodiment of the electrical system, it is provided that at least one lateral delimiting surface of the protruding shaped element is arranged at an angle of 60° to 120° in relation to the contact surface.

In an advantageous embodiment it is provided that the contact surface is flat. Accordingly, the protruding shaped element essentially forms the shape of a projection with a front contact surface and the cross section of a polygon or also with a round cross section, with the casing element of the heat conducting element around a longitudinal axis of the protruding shaped element, which runs essentially perpendicular to the contact surface, around the protruding molding is formed around.

The machine element can consist of a material which has thermal conductivity of at least 40 W/mK. In particular, the machine element can be made of a metallic material, such as cast steel or cast iron.

The heat-conducting element can consist of a material which has a thermal conductivity of at least 1.6 W/mK.

In particular, a silicone with ceramic and/or glass fiber additives comes into consideration as a material for the heat-conducting element.

At the same time, the material of the heat-conducting element should have an electrically insulating effect due to a dielectric strength of at least 12 kV/mm. In one embodiment of the electrical system, it is provided that the distance As between the busbar and the contact surface of the protruding shaped element is at most 3 mm.

The intermediate, bottom contact element of the heat conducting element is designed to be correspondingly thick, it being possible for the bottom contact element to be arranged with a slight press fit between the busbar and the contact surface. In an advantageous embodiment it is provided that the distance is not more than 2 mm, optionally not more than 1 mm. This means that a respective protruding shaped element, which forms a so-called plateau as a contact surface, reaches up to a minimal distance from the busbar.

The ratio of a distance aE of the outer extension plane of the machine element to the busbar to the distance aS between the busbar and the contact surface of the protruding shaped element is aE/aS > 4 in an advantageous embodiment.

This means that a protruding shaped element protrudes relatively far from the outer extension plane in the direction of the conductor rail. In this embodiment, it can be provided that a protruding shaped element is also formed through the machine element only at the points of the machine element at which a heat-conducting element is to be arranged.

The protruding shaped element can be designed with an open cavity on the side facing the busbar.

The open cavity in the protruding mold element has technological advantages, particularly when the machine element is produced using casting technology, particularly when the machine element is removed from the mold. In addition, inclusions in the casting, such as pores or blowholes, can be reduced by wall thicknesses suitable for casting

Although a protruding molded element designed with a cavity has a reduced contact surface compared to a protruding molded element made of solid material and consequently causes increased thermal resistance when heat is conducted into the protruding molded element, the enlarged contact surface means that the encasing element can be used to reduce the heat-conducting element in turn bring about a reduction in the thermal resistance, so that ultimately a respective protruding shaped element can be optimized in terms of casting and nevertheless sufficient heat conduction into the protruding shaped element or into the machine element is ensured.

The electrical system can be designed in such a way that the heat-conducting element rests with at least one inner projection element on an inner side surface of the protruding shaped element, which delimits the cavity.

The electrical system may include a converter, with the machine element being the housing or a part of a housing of the converter.

Furthermore, the electrical system can have a plurality of protruding moldings, and the heat-conducting element can have a plurality of encasing elements and a plurality of base-side abutment elements, each of which encases and covers a protruding molding element, with the encasing elements and bottom-side abutment elements being mechanically connected to one another by respective transition regions.

This means that each of the encasing elements is mechanically, possibly indirectly, connected to each additional encasing element. The same applies to the floor-side contact elements.

A heat-conducting element thus forms a plurality of pot-like structures, each of which has a casing element and a base-side contact element.

The plurality of casing elements and the bottom contact elements associated with these casing elements can be arranged in series, with the electrical system being able to comprise a plurality of busbars which are aligned essentially parallel to one another. A longitudinal axis of the row arrangement can be transverse in relation to the longitudinal direction of the busbars run, so that in each case a bottom-side contact element of the heat-conducting element rests on at least two of the busbars.

The busbars can have different poles.

The transverse course of the direction can take place, for example, in an angular range of 30°-150° between the longitudinal axis of the row arrangement in relation to the longitudinal direction of the busbars.

The encasing or encasing of at least one protruding shaped element by a encasing element also fixes the heat-conducting element in relation to the machine element in at least two translatory degrees of freedom and two rotational degrees of freedom.

The length of a respective casing element, measured essentially perpendicularly to the base-side bearing element, can be adapted to the respective electrical system, so that the necessary long creepage distance through the casing element is ensured.

A further aspect of the present invention is an electric drive unit, which comprises at least one electric rotary machine and power electronics for controlling and/or power supply of the electric rotary machine, and has an electric system according to the invention as part of the power electronics.

• 1: das elektrische System in einer Schnittansicht,
• 2: das Wärmeleitelement 40 in einer ersten perspektivischen Ansicht, und
• 3: das Wärmeleitelement 40 in einer zweiten perspektivischen Ansicht.

The invention described above is explained in detail below against the relevant technical background with reference to the accompanying drawings, which show preferred embodiments. The invention is in no way limited by the purely schematic drawings, it being noted that the exemplary embodiments shown in the drawings are not limited to the dimensions shown. It is shown in

• 1 : the electrical system in a sectional view,
• 2 : the heat-conducting element 40 in a first perspective view, and
• 3 : the heat-conducting element 40 in a second perspective view.

This in 1 illustrated electrical system according to the invention comprises a busbar 1, which is composed of a first part 11 of the busbar 1 and a second part 12 of the busbar 1. In particular, these two parts 11,12 of the conductor rail 1 are welded together.

The conductor rail 1 connects a capacitor 70, which can have a plastic casing, for example, to a power module 60.

Below the conductor rail 1 is a machine element 20 which forms a housing or part of a housing of a converter 80 of the electrical system.

The machine element 20 comprises a shaped element 30 protruding from an outer extension plane 21, which generally forms an outer side of the machine element 20. The protruding shaped element 30 forms a contact surface 31, with which the protruding shaped element 30 rests on a heat-conducting element 40 in a thermally conductive manner. The heat-conducting element 40 in turn rests on the first part 11 of the busbar 1 in a thermally conductive manner.

Correspondingly, heat can be transferred from the conductor rail 1 via the heat-conducting element 40 into the protruding shaped element 30 or into the machine element 20, essentially along the outlined heat flow 90.

In order to improve the conduction of heat from the busbar 1 into the machine element 20 and to lengthen the creepage distance, the heat-conducting element 40 comprises a sheathing element 42 which extends from a base-side contact element 41 which is located between the busbar 1 and the machine element 20.

The encasing element 42 is in contact with an outer lateral boundary surface 34 of the protruding shaped element 30 . The bottom contact element 41 rests against the contact surface 31 of the protruding shaped element 30 . Heat can be transferred from the conductor rail 1 to the heat-conducting element 40 and from there to the machine element 20 both via the casing element 42 and via the contact element 41 on the bottom.

The casing element 42 extends from the plane of the contact surface 31 in the direction of the outer extension plane 21 of the machine element 20.

The protruding shaped element 30 is designed with a cavity 32 which forms an opening 33 in the contact surface 31 .

Correspondingly, alternatively or additionally, at least one projection element could also be used be present, which extends along and abuts the inner side surface 35 of the male mold element 30 to introduce heat into the male mold element 30 .

It can be seen that the distance aS between the busbar 1 and the contact surface 31 is much smaller than the distance aE between the busbar 1 and the outer extension plane 21 of the machine element 20. This means that the protruding shaped element 30 makes a significantly greater contribution to the Bridging the distance between the outer extension plane 21 of the machine element 20 provides as the heat conducting element 40.

The elements described here are components of power electronics, in particular power electronics for an electrically driven motor vehicle. 2 and 3 each show a heat-conducting element 40 with three casing elements 42 and three bottom-side contact elements 41 in a row arrangement. There is a transition area 43 between adjacent casing elements 42.

It can be seen that a respective base-side contact element 41 together with a respective casing element 42 essentially forms a pot shape, with the bottom-side contact element 41 forming the pot bottom and the casing element 42 forming the pot wall.

Furthermore, it can be seen that the bottom contact elements 41 and the casing elements 42 are integral parts of the same component or are made of the same material.

With the electrical system proposed here and the electrical drive unit equipped with it, devices are made available which ensure optimized heat dissipation with a small installation space requirement.

Reference List

1

power rail

11

First part of the power rail

12

Second part of the power rail

20

machine element

21

outer extension plane

30

prominent feature

31

contact surface

32

cavity

33

opening

34

lateral boundary surface outer side surface of the protruding shape element

40

heat conducting element

41

ground-side attachment element

42

sheathing element

43

transition area

60

power module

70

capacitor

80

converter

90

heat flow

aS

Distance between the conductor rail and the contact surface

aE

Distance between the conductor rail and the outer extension plane

Claims (10)

Electrical system with optimized heat dissipation, comprising a busbar (1), a machine element (20) and a heat-conducting element (40) which makes thermally conductive contact with the busbar (1), the machine element (20) on a side facing the busbar (1) at least partially comprises a shaped element (30) protruding from an outer extension plane (21), which forms a contact surface (31), and wherein the heat-conducting element (40) bears thermally conductively with a base-side contact element (41) on the contact surface (31) and with a sheathing element (42) encases the protruding mold element (30). Electrical system after claim 1 , characterized in that at least one lateral boundary surface (34) of the protruding shaped element (30) is arranged at an angle of 60° to 120° in relation to the contact surface (31). Electrical system according to one of the preceding claims, characterized in that the machine element (20) consists of a material which has a thermal conductivity of at least 40 W/mK. Electrical system according to one of the preceding claims, characterized in that the heat-conducting element (40) consists of a material which has a thermal conductivity of at least 1.6 W/mK. Electrical system according to one of the preceding claims, characterized in that the distance (aS) between the conductor rail (1) and the contact surface (31) of the protruding shaped element (30) is a maximum of 3 mm. Electrical system according to one of the preceding claims, characterized in that the protruding shaped element (30) is designed with an open cavity (32) on the side facing the conductor rail (1). Electrical system according to one of the preceding claims, characterized in that the electrical system has a converter (80) and that the machine element (20) is the housing or a part of a housing of the converter (80). Electrical system according to one of the preceding claims, characterized in that the electrical system has a plurality of projecting shaped elements (30), and the heat-conducting element (40) has a plurality of casing elements (42) and a plurality of base-side bearing elements (41), with each of which a projecting shaped element ( 30) is sheathed and covered, the sheathing elements (42) and bottom-side abutment elements (41) being mechanically connected to one another by respective transition regions (43). Electrical system after claim 8 , characterized in that the casing elements (42) and the base-side contact elements (41) assigned to these casing elements (42) are arranged in series, with the electrical system comprising a plurality of busbars (1) which are aligned essentially parallel to one another and have a longitudinal axis of the Row arrangement runs transversely with respect to the longitudinal direction of the busbars (1), so that a bottom-side contact element (41) of the heat-conducting element (40) rests on at least two of the busbars (1). Electrical drive unit, comprising at least one electrical rotary machine and power electronics for controlling and / or power supply of the electrical rotary machine, and an electrical system according to one of Claims 1 until 9 as part of the power electronics.

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