Power electronics for an electric drive axle

Abstract

The invention relates to power electronics (140) for an electric drive axle (100), comprising a printed circuit board (200), at least one busbar (205), and a fastening element (215) arranged one above the other in a planar arrangement, wherein the fastening element (215) in the assembled state is guided through aligned openings (245, 246) in the printed circuit board (200) and the at least one busbar (205), is arranged at a first end (260) to a housing-fixed component (220) in a rotationally and axially fixed manner, and has at a opposite second end (261) a thread (265) for receiving a screw nut (235) in order to fix the printed circuit board (200) and the at least one busbar (205) between the screw nut (235) and the housing-fixed component (220). The invention further relates to an electric drive axle (100) for a motor vehicle (105).

Description

[0001] The present invention relates to power electronics for an electric drive axle of a motor vehicle, comprising a printed circuit board and at least one, preferably two, busbars.

[0002] A first busbar can be an AC busbar and a second busbar can be a DC busbar, or vice versa. An AC busbar is a conductive component that carries alternating current (AC) from the inverter stage to the electric machine. It serves as the central connection for energy transport in the AC section of the system and ensures the distribution of AC current to the appropriate phases of the machine. A DC busbar is a conductive component that carries direct current (DC) from the energy source, typically an energy storage device such as a battery or rectifier, to the DC inputs of the inverter. This busbar represents the central connection for energy transport in the DC section and enables the inverter stage, which converts the DC current into alternating current, to be powered.

[0003] Up to now, power electronics have had one or more fixing pins for positioning components, particularly the circuit board and the busbar(s). The respective fixing pin is typically pressed into the housing or a housing-mounted component from above or from a side facing the circuit board and secured. The power electronics components are arranged with some play relative to each other along the length of the fixing pin. Due to this play, the components are not, or only partially, secured against vibrations in the fixing area or along the length of the fixing pin.

[0004] One object of the invention is to provide power electronics in which the components are not only fixed to one another but also protected against vibrations. The invention achieves this object by means of the subject matter of the independent claims. Dependent claims describe preferred embodiments.

[0005] A power electronics system according to the invention for an electric drive axle comprises a printed circuit board and at least one busbar, which are arranged one above the other in a plane, as well as a fastening element. In the assembled state, the fastening element is guided through aligned openings in the printed circuit board and the at least one busbar, is arranged at one end on a housing-mounted component in a rotationally and axially fixed manner, and has a thread at the opposite second end for receiving a screw nut in order to fix the printed circuit board and the at least one busbar between the screw nut and the housing-mounted component. In other words, during assembly of the power electronics system, the printed circuit board and the at least one busbar are positioned relative to each other without play and, after the fastening element has been guided through the openings, are clamped and held by the screw nut.The nut is located on the side of the circuit board opposite the first end. This prevents vibration of the components at the mounting point.

[0006] The fastening element is bolt-shaped, resembling a fixing pin, and essentially consists of a carrier section with a substantially constant cross-section and two opposing distal ends. Preferably, in its simplest and most cost-effective form, the fastening element has a circular cross-section with a diameter that is substantially constant along the axial length of the carrier section. In principle, the cross-sectional shape of the fastening element can be selected arbitrarily and adapted to the requirements. In particular, the cross-section can be adapted to integrate additional functions, such as anti-rotation protection on the housing-mounted component. For example, the carrier section can have an elliptical, particularly oval, cross-section, thus providing anti-rotation protection when mounted on the housing-mounted component.

[0007] The distal ends of the mounting element are designed, on the one hand, for connection to the housing-mounted component, i.e., for axially and rotationally fixed positioning, and on the other hand, for screwing the nut onto the thread to fix the circuit board and the at least one busbar to the housing-mounted component without play or vibration. The clamping effect increases the further the nut is screwed onto the thread of the mounting element. With such a mounting element, secure positioning of the clamped components and vibration damping can be achieved. This allows for a more reliable operation of the power electronics.

[0008] The fixed component can be part of a power electronics housing. The fixed component can form the housing of the power electronics. Alternatively, the fixed component can be another component that is fixed to the housing part and / or the housing of the power electronics.

[0009] The circuit board and at least one busbar are clamped axially and at least indirectly between a first contact surface in the area of ​​the housing-mounted component and a second contact surface of the screw nut, with the screw nut pressing the parts together axially during assembly. "At least indirectly" means that further components may be provided, which can also be arranged between the screw nut and the housing-mounted component and clamped in the assembled state. These could be, for example, spacers such as a clamping sleeve, or further power electronics components such as another busbar.

[0010] In this sense, the power electronics have multiple busbars, specifically at least one DC busbar as the first and one AC busbar as the second. Everything previously stated regarding "at least one busbar" applies accordingly to two or more busbars, which can be fixed to the circuit board between the screw nut and the housing-mounted component and secured against vibrations.

[0011] The term "surface-mounted" describes an arrangement of power electronics elements or components in which they are stacked in layers or planes. In this arrangement, the elements cover an area without necessarily having to make contact with each other at specific points or only at a few locations. Instead, they are stacked on top of each other across a surface, resulting in a continuous coverage. The arrangement sequence of the printed circuit board and the busbar(s) is, in principle, arbitrary and can be adapted to the spatial and structural conditions.

[0012] To prevent any interaction, particularly electrical, between the components, the respective busbar is encased in plastic, at least in the area of ​​the opening for the mounting element and at the respective contact surface with components immediately adjacent to the mounting element in the axial direction. The circuit board may be made of plastic, particularly in the area of ​​the opening for the mounting element. Alternatively or additionally, the circuit board is not electrically connected to the mounting element.

[0013] Preferably, the fastening element has a pressing area at its first end, where an anti-rotation device is arranged or formed. The pressing area is the axial section of the fastening element that, after the fastening element is installed, bears against the material of the housing-mounted component and creates the press fit. In this sense, the fastening element is pressed into a through-hole in the housing-mounted component at its first end.

[0014] The anti-rotation device ensures that the fastener cannot rotate around its longitudinal axis after installation. Preferably, the anti-rotation device has a collar that bears against the housing-mounted component, at least in the circumferential direction. The collar can have several surfaces that bear against the housing-mounted component in the installed, particularly pressed-in, state. In its simplest form, the collar is square or hexagonal. Depending on the design of the fastener and its connection to the housing-mounted component, the collar can also provide axial locking against the housing-mounted component. Thus, the collar can also bear axially against the housing-mounted component, so that the fastener is axially secured to the housing-mounted component.

[0015] Alternatively or additionally, the anti-rotation device has knurling on the outer circumference of the fastening element, which is in operative contact with the housing-mounted component. Within the scope of the present invention, knurling is understood to mean a circumferential deviation in the surface shape produced by knurling, pressing, thread cutting, turning, milling, or embossing, which has been pressed into the metal fastening element. The knurling is advantageously formed over the axial length of the pressing area and over the entire outer circumference of the fastening element. The through-hole of the housing-mounted component can also be prepared to improve the press fit.

[0016] The power electronics preferably include a cooling element which, in the assembled state, is positioned between the housing-mounted component and the screw nut. The cooling element is, for example, a pin-fin cooling element. The cooling element is, for example, made of copper or another material with good thermal conductivity. If a cooling element is provided, the fastening element can also be pressed into a through-hole or opening in the cooling element at its first end. Thus, the pressing area of ​​the fastening element extends over the area that, after the joining process, is in press contact with both the housing-mounted component and the cooling element.

[0017] Preferably, the power electronics further comprise a spacer for distancing components between the screw nut and the housing-mounted component. The spacer can be designed as a clamping sleeve, which allows the necessary clamping effect to be generated even when there is a large distance between the housing-mounted component and the components to be clamped. The spacer is preferably a cylindrical or tubular component, or a section of another component, which serves to bridge a defined distance between two components and simultaneously enable a secure connection in the assembled or clamped state. This is to be understood as "spacer mounting."

[0018] The spacer can be a separate component that is installed when the components are threaded onto the mounting element. Alternatively, the spacer can be an injection-molded plastic component of a busbar, particularly one facing the housing-mounted component. Another alternative is that the spacer can be part of the housing-mounted component. It is also conceivable that several spacers are provided, which could be formed from a combination of the examples mentioned here. Thus, the spacer can also be integrated into an adjacent part.

[0019] In one embodiment, the spacer is arranged axially along the mounting element between the circuit board and the at least one busbar on one side, and the housing-mounted component on the other. If a cooling element is provided, it is preferred that the cooling element be arranged axially along the mounting element between the spacer on one side and the housing-mounted component on the other.

[0020] According to a second aspect of the invention, an electric drive axle for a motor vehicle comprises power electronics as described above. The electric drive axle is, in particular, an electric drive train for an axle of a motor vehicle. The electric drive axle can include an electric motor and an optional transmission to provide torque for driving at least one drive wheel of the hybrid or electric vehicle. In addition to the electric motor, an electric control device and an energy storage device can also be included.

[0021] The electric drive axle according to the invention can be advantageously used in a motor vehicle, in particular an electric or hybrid vehicle, according to a fifth aspect of the invention. The motor vehicle comprises a first axle and at least one further axle, wherein at least one of the axles is designed as an electric drive axle in accordance with the invention. In the case of a hybrid vehicle, one of the axles is additionally or separately connected to an internal combustion engine. Preferably, the electric drive axle is arranged transversely to the longitudinal axis of the vehicle, such that the rotatable parts are arranged transversely to the longitudinal axis of the vehicle or parallel to the transverse axis of the vehicle. Depending on the design and the number of driven axles, the vehicle can also comprise two or more such drive axles. The motor vehicle is preferably an automobile, in particular a passenger car, a bus, or a truck, in particular a bus and a truck.

[0022] The above definitions, as well as the explanations regarding technical effects, advantages, and advantageous embodiments of the power electronics according to the first aspect of the invention, also apply mutatis mutandis to the electric drive axle according to the second aspect of the invention, and vice versa. It is understood that the features mentioned above and those to be explained below can be used not only in the combinations specified, but also in other combinations or individually, without departing from the scope of the present invention.

[0023] The invention will now be described in more detail with reference to the attached figures, in which: Fig. 1 a highly simplified representation of a motor vehicle according to the invention with an electric drive axle according to the invention; Fig. 2 a schematic perspective section view of a section of a power electronics of the drive axle according to the invention Fig. 1 to illustrate the structure and assembled state of an exemplary fastening element; Fig. 3 a schematic perspective view of the fastening element according to Fig. 2; Fig. 4 a schematic perspective section view of one end of the fastening element according to Fig. 2 and Fig. 3; Fig. 5 shows a schematic perspective view of the fastening element according to an alternative embodiment.

[0024] Fig. Figure 1 shows a drive train 100 in the form of an electric drive axle in a motor vehicle 105. The motor vehicle 105 can additionally include an internal combustion engine 110, which is 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. Furthermore, an electric machine 125 is provided, which can also act on the drive wheel 120, preferably via the transmission 115. An inverter 130 is also provided, which is supplied with electrical energy by the electrical energy storage device 135. Finally, power electronics 140 according to the invention are provided, which are electrically connected to the electric machine 125 and the inverter 130, and are supplied with electrical energy by the energy storage device 135.

[0025] After Fig. Figure 2 shows a section of the power electronics 140, which is intended to illustrate a vibration-proof fixing of a circuit board 200, a first busbar 205 in the form of an AC busbar and a second busbar 210 in the form of a DC busbar by means of an actuating element 215. Fig. Figure 2 shows the assembled state of the - only partially shown here - power electronics 140.

[0026] The circuit board 200 and the busbars 205, 210 are arranged one above the other in a housing of the power electronics 140, with only one housing-mounted component 220 of the housing being shown here. The first busbar 205 is spatially arranged between the circuit board 200 (located above) and the second busbar 210 (located below). Furthermore, a cooling element 225 in the form of an aluminum pin-fin cooling plate, which is associated with and attached to the housing-mounted component 220, and a sleeve-shaped, cylindrical spacer 230 in the form of a clamping sleeve for bridging the gap between the housing-mounted component 220 or the cooling element 225 on the one hand and a screw nut 235 on the other are provided. Thus, the spacer 230 provides a distance between components between the screw nut 235 and the housing-mounted component 220 or the cooling element 225.

[0027] In this case, the spacer 230 is arranged in the axial direction of the bolt-like fastening element 215 between the package consisting of the circuit board 200 and busbars 205, 210 on the one hand and the cooling element 225 on the other.

[0028] The spacer 230 has a radially flared shoulder 240 on the busbar side to increase the contact area between the spacer 230 and the second busbar 210. On the opposite side, the spacer 230 rests on the cooling element 225.

[0029] The fastening element 215 is guided axially through aligned openings 245, 246, 247, 248 in the form of bores or through-holes in the circuit board 200, the busbars 205, 210, and the cooling element 225, as well as through the spacer 230. In this embodiment, during assembly, the fastening element 215 was pressed – from below – through a through-hole 250 in the insertion direction 255 into the housing-mounted component 220 and into the opening 248 of the cooling element 225. The through-hole 250 can then be closed from below, as shown here by way of example.

[0030] The fastening element 215 is designed in the form of a bolt and has two opposite ends 260, 261, wherein the first end 260 faces the housing-fixed component 220 and the second end 261 faces the circuit board 200 or the screw nut 235 or is associated with it.

[0031] By pressing the fastening element 215 into the housing-mounted component 220 and the cooling element 225, a press fit is created between the fastening element 215 and the housing-mounted component 220 at a pressing area 263 of the fastening element 215, so that the fastening element 215 is arranged rotationally and axially fixed on the housing-mounted component 220.

[0032] At its second end 261, the fastening element 215 has a thread 265, in this example designed as an external thread (here metric), which is complementary to an internal thread 270 of the nut 235. After the press fit between the fastening element 215 and the housing-mounted component 220 and the cooling element 225 is established, the aforementioned components are threaded onto the fastener: first the spacer 230, then the second busbar 210, then the first busbar 205, and finally the circuit board 200, with the axially adjacent components coming into contact with each other without axial play. The spacer 230, acting as a clamping sleeve, can be pressed onto the fastening element 215. Finally, the nut 235 is screwed onto the thread 265 of the fastening element 215 at its second end 261, thus positioning and clamping or fixing these components relative to each other.This ensures a vibration-resistant arrangement of the power electronics components 140. The screw nut 235 demonstrates... Fig. 2 in combination with Fig. 4 On a side axially opposite the internal thread 270, a receptacle 275, for example in the form of a Torx drive, for an assembly tool is provided. This enables at least a semi-automated assembly process.

[0033] The pressing area 263 is designed, at least in this case, to prevent the fastening element 215 from rotating. According to Fig. 2 in combination with Fig. 3 The fastening element 215 has a square collar 280 at its second end 261, the outer surfaces of which are supported on the housing-mounted component 220 to prevent rotation in the circumferential direction. The collar 280 is provided to prevent rotation relative to the housing-mounted component 220 and to secure the fastening element 215 in its longitudinal direction. Furthermore, according to Fig. 3. A knurling 300, shown here simplified as a dotted line, is provided on the outer circumference 285 of the fastening element 215 and in the area of ​​the pressing area 263 to further improve the anti-rotation effect. The knurling 300 creates a force-fit and form-fit connection between the fastening element 215 and the housing-mounted component 220. The knurling 300 is designed such that, in the assembled or pressed-in state, a higher rotational force is required to rotate the fastening element 215 relative to the housing-mounted component 220 than the torque required to tighten the nut 235. This alone achieves the anti-rotation effect.

[0034] Fig. Figure 4 shows the second end 261 of the fastening element 215 in detail. Accordingly, the fastening element 215 is designed such that it has a constant diameter over the entire height of the circuit board 200. For this purpose, a recess – not shown in detail here – can be provided within or on one side of the nut 235 facing the internal thread 270 to allow the nut 235 to be securely tightened. This improves the surface pressure between the fastening element 215 and the circuit board 200. Furthermore, the outer diameter of the fastening element 215 is also essentially constant over the entire height of the first and second busbars 205, 210.

[0035] Fig. Figure 5 shows an alternative embodiment of the fastening element 215. Accordingly, the collar 280 is attached to a design that differs from that shown in Figure 5. Fig. 2 in conjunction with Fig. 3 alternative axial positions of the fastening element 215 or the pressing area 263. In this case, the collar 280 can be arranged axially between a first section 500, which has the knurling 300, and a second section 505, which is to be understood as a support section between the ends 260, 261 of the fastening element 215. In this case, the fastening element 215 can be arranged with respect to the illustration in Fig. 2 from the top, i.e., opposite to the one in Fig.The fastening element 215 is pressed into the through-hole 250 in the direction 255 shown in Figure 2. Alternatively or additionally, the fastening element 215 can be secured longitudinally or in the Z-direction by screwing the cooling element 225 to the housing-mounted component 220, whereby the cooling element 225 rests axially against the collar 280 and thus holds it in its axial position between the cooling element 225 and the housing-mounted component 220. This prevents the fastening element 215 from being pulled out of the housing-mounted component 220 when the nut 225 is tightened.

[0036] It is of course conceivable to provide a fastening element 215 that has only a collar 280 or only a knurling as described above. Furthermore, several such fastening elements 215 can be provided for the power electronics 140. Reference sign 100 Electric drive axle 105 motor vehicles 110 internal combustion engine 115 gearbox 120 drive wheel 125 Electric Machine 130 Inverter 135 energy storage 140 Power Electronics 200 circuit boards 205 First busbar 210 Second busbar 215 Fastening element 220 Housing-mounted component 225 Cooling element 230 spacers 235 Screw nut 240 Shoulder of the spacer 245 Opening 246 Opening 247 Opening 248 Opening 250 through holes 255 Press-fit direction 260 First end of the fastener 261 Second end of the fastener 263 Pressing area 265 thread 270 internal threads 275 recording 280 Bund 285 mm external circumference 300 knurling 500 First Section 505 Second Section

Claims

[1] Power electronics (140) for an electric drive axis (100), comprising a printed circuit board (200) and at least one busbar (205) arranged one above the other in a planar arrangement, and a fastening element (215), wherein the fastening element (215) in the assembled state is passed through aligned openings (245, 246) in the printed circuit board (200) and the at least one busbar (205), is arranged at a first end (260) on a housing-fixed component (220) in a rotationally and axially fixed manner, and has at an opposite second end (261) a thread (265) for receiving a screw nut (235) in order to fix the printed circuit board (200) and the at least one busbar (205) between the screw nut (235) and the housing-fixed component (220). [2] Power electronics (140) according to claim 1, wherein the fastening element (215) has a pressing area (263) at the first end (260) on which an anti-rotation device is arranged or formed. [3] Power electronics (140) according to claim 2, wherein the anti-rotation device has a collar (280) which is supported at least in the circumferential direction on the housing-fixed component (220). [4] Power electronics (140) according to claim 2 or claim 3, wherein the anti-rotation device has a knurling (300) on the outer circumference (285) of the fastening element (215) which is in operative contact with the housing-fixed component (220). [5] Power electronics (140) according to one of the preceding claims, wherein the fastening element (215) is pressed into a through-hole (250) of the housing-mounted component (220) in the region of the first end (260). [6] Power electronics (140) according to one of the preceding claims, further comprising a cooling element (225) which, in the assembled state, is arranged between the housing-fixed component (220) and the screw nut (235). [7] Power electronics (140) according to one of the preceding claims, further comprising a spacer (230) for spacing components between the screw nut (235) and the housing-mounted component (220). [8] Power electronics (140) according to claim 7, wherein the spacer (230) is arranged in the axial direction of the fastening element (215) between the printed circuit board (200) and the at least one busbar (205) on the one hand and the housing-mounted component (220) on the other. [9] Power electronics (140) according to claim 8 in conjunction with claim 6, wherein the cooling element (225) is arranged in the axial direction of the fastening element (215) between the spacer (230) on the one hand and the housing-fixed component (220) on the other hand. [10] Electric drive axle (100) for a motor vehicle (105), comprising power electronics (140) according to any of the preceding claims.

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