Pulse inverter having a cooling device and automobile having a pulse inverter

Abstract

To provide a pulse inverter for operating an electric machine of a motor vehicle, capable of achieving efficient cooling of the pulse inverter, and a motor vehicle.SOLUTION: A pulse inverter (3) includes a power module (4) for converting DC current provided by a motor vehicle battery into AC current, and a cooling device for cooling components of the pulse inverter (3) by an electrically insulating cooling fluid flowing through the cooling device. The cooling device includes a fluid-tight housing, and a cooling fluid flowing through the fluid-tight housing is in direct contact with at least one of the components to be cooled. The cooling device includes a cooling channel (10). The power module (4) is thermally connected to an outer surface of the cooling channel (10). An outflow port (11) of the cooling channel (10) opens into the fluid-tight housing, so that the cooling fluid flowing through the cooling device first flows through the cooling channel (10) and subsequently flows through the fluid-tight housing.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a pulse inverter with a cooling device and to a vehicle with a pulse inverter. The pulse inverter is used to convert DC current into AC current in order to operate an electric machine with the AC current. Thus, in an electric or semi-electrically operated vehicle, the DC current provided by the vehicle battery, usually a high-voltage battery, is converted into AC current by an inserted pulse inverter. The reverse direction, i.e. from AC current to DC current, can also be provided, i.e. for example when the electric machine is operating in generator mode. [Background technology]

[0002] A pulse inverter typically has a plurality of phase systems with at least one power module each having a semiconductor structural component. By means of the semiconductor structural components, in particular semiconductor switches, for example, the external conductors of the respective phase systems can be periodically switched for conversion of DC current to AC current, so that AC current is applied to the external conductors. For example, the semiconductor structural components can be FETs (field effect transistors) or IGBTs (insulated gate bipolar transistors). However, JFETs (junction gate field effect transistors) or MOSFETs (metal oxide semiconductor field effect transistors) are also envisaged.

[0003] The semiconductor components of the power supply module have an ohmic resistance, which in the case of a current leads to waste heat and thus an increase in temperature. To protect the power supply module from overheating, a cooling device is usually provided. Further components of the pulse inverter, such as DC link capacitors or contact bars, also have an ohmic resistance, so that these components of the pulse inverter are also heated during the operation of the pulse inverter.

[0004] For example, it is known from DE 10 2016 218 451 A1 to mount a power supply module on a heat sink, which is configured as an extruded profile. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] DE 102016218451(A1) Summary of the Invention [Problem to be solved by the invention]

[0006] The problem addressed by the invention is to specify a pulse inverter with an improved cooling device, which ensures particularly efficient cooling of the pulse inverter. It is a further problem of the invention to specify a motor vehicle having such a pulse inverter.

[0007] These problems are solved by the subject matter of the independent claims. Advantageous embodiments are the subject matter of the dependent claims. [Means for solving the problem]

[0008] The pulse inverter according to the invention is used for operating an electric machine of a motor vehicle, in particular for operating an electric motor. The pulse inverter comprises at least one power supply module, which serves to convert a DC current provided by a motor vehicle battery into an AC current. The pulse inverter comprises a cooling device for cooling components of the pulse inverter by means of an electrically insulating cooling fluid flowing through the cooling device. The cooling device comprises a fluid-tight housing through which the electrically insulating cooling fluid flows, the cooling fluid flowing through the fluid-tight housing being in direct contact with one of the components of the pulse inverter to be cooled. The cooling device further comprises a cooling channel, the power supply module being thermally connected to an outer surface of the cooling channel, the cooling channel comprising an outlet, the outlet opening into the fluid-tight housing such that the cooling fluid flowing through the cooling device flows first through the cooling channel and then through the fluid-tight housing.

[0009] The advantage of the aforementioned design of the cooling device is that the relatively cold cooling fluid first flows through the cooling channel, thereby cooling the power module, particularly efficiently, since the power module is in thermal contact with the cooling channel and thereby cools the power module using the relatively cold cooling fluid flowing through the cooling channel. The power module is typically the component of the pulse inverter with the highest cooling demand. Meanwhile, the cooling demand of further components, for example the contact bars and / or the DC link capacitors, is usually smaller than the cooling demand of the power module. Only after following the cooling channel does the cooling fluid then flow through the waste heat of the power module into the fluid-tight housing, so that it comes into direct contact with other components and / or the power module to cool them, which then continue to heat up. In the design according to the invention, the relatively cold cooling fluid is intentionally directed towards the power module, and only afterwards does the cooling fluid then permeate the fluid-tight housing, so that it comes into direct contact with further components of the pulse inverter to be cooled, which then continue to heat up. A particularly efficient and sufficient cooling of the power module can be achieved, since in the design according to the invention the relatively cold cooling fluid is deliberately directed towards the power module, and only afterwards does the cooling fluid then permeate the fluid-tight housing, and thus only afterwards does it come into direct contact with further components of the pulse inverter to be cooled. If all components, especially the power modules, were only cooled in the same manner, for example by permeating the fluid-tight pulse inverter housing, i.e. without targeted conduction of a relatively cool cooling fluid to the power modules, insufficient cooling of the respective power modules may not be guaranteed, or the cooling fluid may need to have a lower temperature for sufficient cooling, or the flow rate would need to be increased, which would increase the power demand of the cooling system.

[0010] It is considered to be particularly advantageous when the pulse inverter comprises a plurality of power supply modules, the plurality of power supply modules being thermally connected to the outer surface of the same cooling channel, in which case the same cooling channel serves to cool the plurality of power supply modules.

[0011] This is considered to be particularly advantageous when the power module is in direct contact with the cooling fluid flowing in the fluid-tight housing, in which in the flow direction of the cooling fluid, firstly indirect cooling of the power module takes place via the cooling channels, followed by direct cooling of the power module via direct contact with the cooling fluid.

[0012] As such, it is considered particularly advantageous when the power module then has a fluid-tight power module housing in which the semiconductor components or semiconductor devices are placed, which ensures that the semiconductor components do not come into direct contact with the cooling fluid, thereby avoiding damage to the power electronics or semiconductor components from conductive contaminants of the cooling fluid.

[0013] Preferably, the power supply module is disposed within a fluid-tight housing of the pulse inverter.

[0014] Preferably, the fluid tight housing forms a pulse inverter housing which encloses all components of the pulse inverter.

[0015] It is considered to be particularly advantageous when the cooling channels are arranged in a fluid-tight housing such that the cooling fluid flowing through the housing is in contact with one or all of the outer surfaces of the cooling channels. It is considered to be particularly advantageous when the cooling channels are arranged in the fluid-tight housing such that the cooling fluid flowing through the housing flows around the cooling channels. In this regard, the cooling channels are surrounded by the cooling fluid on their outside and inside. Preferably, the cooling fluid flowing in the fluid-tight housing flows around the cooling channels in the opposite flow direction of the cooling fluid in the cooling channels. By reversing the flow direction, it is possible to achieve cooling that is as homogeneous as possible.

[0016] The electrically insulating cooling fluid is in particular a dielectric cooling fluid, preferably a cooling oil.

[0017] In a preferred embodiment, a plurality of power modules, a plurality of DC link capacitors, and a plurality of live contact bars connected to the power modules are disposed within a fluid-tight housing, and a cooling fluid flowing through the housing is provided in direct contact with the plurality of power modules, the plurality of DC link capacitors, and the plurality of live contact bars.

[0018] The cooling channels are preferably configured as extruded profiles, and it is certainly contemplated that cooling structures may be introduced into the cooling channels, e.g., contracted or compressed, to provide targeted guidance or conduction of cooling fluid into the cooling channels.

[0019] In a preferred embodiment, the respective power supply module is connected to the outer surface of the cooling channel in a material-locking manner, for example by soldering or gluing. It is considered to be particularly advantageous when the power supply module comprises an external cooling plate, for example made of copper, which contacts the outer surface of the cooling channel. As a result, a particularly efficient indirect cooling can be achieved. In this regard, it is considered to be particularly advantageous when the power supply module housing of the power supply module fluid-tightly encloses the internal space of the power supply module, where the cooling plate is exposed and contacts the cooling channel.

[0020] This is considered to be particularly advantageous when a cooling channel is formed between the power supply module and the DC link capacitor.

[0021] In a preferred embodiment, it is provided that the cooling device comprises a further cooling channel, the DC link capacitor is thermally connected to an outer surface of the further cooling channel, the further cooling channel comprises an outlet, the outlet of the further cooling channel opens into the one cooling channel, so that the cooling fluid flowing through the cooling device flows first through the further cooling channel, then through the one cooling channel and then through the fluid-tight housing.

[0022] In a preferred embodiment, a pulse inverter is provided that comprises a first row of power modules and cooling channels associated with the first row of power modules, the first row of power modules being thermally connected to the outer surfaces of the associated cooling channels, and a pulse inverter is provided that comprises a second row of power modules and cooling channels associated with the second row of power modules, the second row of power modules being thermally connected to the outer surfaces of the associated cooling channels, the outlets of the two cooling channels opening into the same fluid-tight housing, such that the cooling fluid flowing through the cooling device first flows through the respective cooling channels and then through the housing.

[0023] The vehicle according to the invention comprises a vehicle battery, an electric machine and a pulse inverter for operating the electric machine. The pulse inverter comprises a power supply module for converting a DC current provided by the vehicle battery into an AC current. The pulse inverter comprises a cooling device for cooling components of the pulse inverter by means of an electrically insulating cooling fluid flowing through the cooling device. The cooling device comprises a fluid-tight housing, the cooling fluid flowing through the fluid-tight housing being in direct contact with one of the components to be cooled. The cooling device further comprises a cooling channel, the power supply module being thermally connected to an outer surface of the cooling channel, the cooling channel comprising an outlet, the outlet opening into the fluid-tight housing such that the cooling device flows first through the cooling channel and then through the fluid-tight housing.

[0024] It is considered to be particularly advantageous when the motor vehicle is equipped with a machine cooling system for cooling an electric machine, and the cooling fluid flowing out of the fluid tight housing flows into the machine cooling system.

[0025] In this context, it is considered to be particularly advantageous when the cooling fluid flowing from the cooling device to the machine cooling system directly contacts and thereby cools the contact bars electrically connecting the pulse inverter and the electric machine.

[0026] Advantageous embodiments described in relation to a pulse inverter may be applied to a motor vehicle as appropriate, and vice versa.

[0027] In the following figures, the invention is explained in more detail with reference to exemplary embodiments without being limited thereto. [Brief description of the drawings]

[0028] [Figure 1] 1 is a schematic, illustrative view of a propulsion system for an electric or semi-electric vehicle. [Diagram 2] FIG. 2 is an internal view of a pulse inverter in a schematic illustration. [Diagram 3] FIG. 2 is a perspective view illustrating an internal view of a pulse inverter. [Figure 4] 4 is an internal view of the pulse inverter according to FIG. 3, illustrating diagrammatically the flow direction of the cooling fluid; [Diagram 5] 1 illustrates an embodiment of a cooling channel of a cooling device in a perspective view. [Figure 6] 6 shows components of the cooling channel according to FIG. 5 in a perspective illustrative view. [Figure 7] 13 is a further embodiment of a cooling channel in a perspective illustrative view. [Figure 8] 1 is a first embodiment of a cooling circuit in a schematic, illustrative view; [Figure 9] 2 is a second embodiment of a cooling circuit in a schematic solution. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029] FIG. 1 shows the components of a propulsion system of an electric or semi-electric vehicle in a schematic illustration. The propulsion system comprises an electric machine 1, an automobile battery 2 and a pulse inverter 3 for converting the DC current provided by the automobile battery 2 into an AC current for operating the electric machine 1. The pulse inverter 3 comprises a number of power supply modules 4, which comprise power electronics in the form of semiconductor structural components. Furthermore, the propulsion system comprises a control unit 5, which drives the pulse inverter 3 in such a way that the DC voltage of the automobile battery 2 is converted into an AC voltage for driving the electric machine 1. During operation of the pulse inverter 3, very high currents flow through the semiconductor structural components of the power supply modules 4. The resulting ohmic losses lead to heating of the power supply modules 4. This heat must be dissipated. For this purpose, the power supply modules 4 are cooled by a cooling device 6, which is a component of a cooling circuit 16, through which a cooling fluid flows. The flow direction of the cooling fluid is indicated by an arrow in FIG. 1.

[0030] The configuration of the cooling device 6 of the pulse inverter 3 is shown in more detail in Figures 2 to 4, Figure 2 being merely a schematic illustration.

[0031] The cooling device 6 comprises a fluid-tight housing 7, through which the cooling fluid flows in direct contact with the components to be cooled. In the present case, the components of the pulse inverter 3 around which the cooling fluid flows directly are the power modules 4, the DC link capacitors 8 and the contact bars 9. The cooling fluid is a dielectric cooling fluid, for example cooling oil. Direct contact of the live components by the cooling fluid can therefore be made without risk of short circuits or of current flow through the cooling fluid. Isolation of the live components, which would adversely affect the cooling effect, can therefore be omitted.

[0032] The cooling device 6 comprises a cooling channel 10, which is configured as an extruded profile. The power module 4 is soldered directly to the outer surface of the cooling channel 10. An outlet 11 of the cooling channel 10 opens into the fluid-tight housing 7, such that the cooling fluid flowing through the cooling device 6 first flows through the cooling channel 10 and then through the fluid-tight housing 7. In other words, the cooling oil leaving the cooling channel 10 at the outlet 11 is distributed throughout the interior of the pulse inverter 3, which is surrounded by the fluid-tight housing 7.

[0033] In the embodiment of the pulse inverter 3 shown in Figs. 2-4, a cooling channel 10 is arranged between the DC link capacitor 8 and the power module 4. Furthermore, the cooling device 6 comprises a further cooling channel 12, which is used for indirect cooling of the DC link capacitor 8. For this purpose, the DC link capacitor 8 is thermally connected to the outer surface of the further cooling channel 12. The further cooling channel 12 is provided with an inlet 13 for a cooling fluid and opens into one of the cooling channels 10, which serves to cool the power module 4. The cooling fluid flowing through the cooling device 6 therefore flows through the further channel 12, then the one of the cooling channels 10 and then through the fluid-tight housing 7.

[0034] As can be seen in particular in Figures 3 and 4, the pulse inverter 3 comprises a first string 19a of power modules 4 and a second string 19b of power modules 4. Each string 19a, 19b of power modules 4 is associated with an associated DC link capacitor 8 having a separate cooling channel 10 and a further cooling channel 12. The two aforementioned arrangements are arranged in the same housing 7, which is not shown in greater detail in Figures 3 and 4.

[0035] In Fig. 5 the cooling channels 10 in which the power modules 4 are arranged are shown in more detail. The power modules 4 each comprise a closed, fluid-tight power module housing 14, which is directly surrounded by the cooling fluid flowing in the housing 6. The power module housing 14 prevents the cooling fluid from coming into direct contact with the semiconductor structural components. The power modules 14 are soldered to the cooling channels 10 in the area of ​​the bottom of the respective power module 4. For better heat conduction, each power module 4 comprises a heat-conducting cooling plate made of copper at its bottom.

[0036] To improve heat transfer from the power modules 4 to the cooling fluid flowing within the cooling channels 10, contoured cooling structures 15 are introduced into the cooling channels 10. Such cooling structures 15 may also be attached to the outer surface of the cooling channels 10, as illustrated in FIG.

[0037] FIG. 8 shows an exemplary cooling circuit 16 of a motor vehicle with a pulse inverter 3 according to the invention. In the cooling circuit 16, a dielectric cooling oil circulates, the cooling circuit 16 comprises a heat exchanger 17 and a pump 18, in which the pulse inverter 3 is arranged upstream of the electric machine 1 in the flow direction of the cooling fluid. The pulse inverter 3 is therefore first flowed through and then the electric machine 1. In this context, it is considered to be particularly advantageous when the cooling fluid is supplied from the housing 7 of the electric machine 1 or of the machine cooling system of the electric machine 1, so that the contact bars 9 electrically connecting the pulse inverter 3 and the electric machine 1 are in direct contact with the cooling fluid and are cooled in this manner. FIG. 9 shows a further embodiment of the cooling circuit 16, which differs substantially from the embodiment according to FIG. 8 in that the vehicle battery 2 is also flowed through by the cooling fluid to cool the vehicle battery 2, which is arranged in front of the pulse inverter 3 in the flow direction of the cooling fluid. The cooling fluid flowing from the high-voltage battery 2 in the direction of the pulse inverter 3 comes into direct contact with the contact bars 9 electrically connecting the high-voltage battery 2 and the pulse inverter 3 in order to cool them. [Explanation of symbols]

[0038] 1 Electrical machinery 2 Car Batteries 3-pulse inverter 4 Power Module 5. Controller 6 cooling device 7 Housing 8 Intermediate Circuit Capacitor 9 Contact Bar 10 Cooling Channels 11 Outlet 12 additional cooling channels 13 inlet 14 Power Module Housing 15 cooling structure 16 cooling circuits 17 heat exchanger 18 Pump 19 rows

Claims

1. A pulse inverter (3) for operating an electric machine (1) of a motor vehicle, said pulse inverter (3) comprising a power supply module (4) for converting a DC current provided by a motor vehicle battery (2) into an AC current, said pulse inverter (3) comprising a cooling device (6) for cooling components of said pulse inverter (3) by means of an electrically insulating cooling fluid flowing through said cooling device (6), said cooling device (6) comprising a fluid-tight housing (7) and a cooling fluid flowing through said fluid-tight housing (7).

1. A pulse inverter (3), wherein a cooling fluid is in direct contact with at least one of the components to be cooled, wherein the cooling device (6) comprises a cooling channel (10), wherein the power module (4) is thermally connected to an outer surface of the cooling channel (10), wherein the cooling channel (10) comprises an outlet (11), wherein the outlet (11) opens into the fluid-tight housing (7), so that the cooling fluid flowing through the cooling device (6) first flows through the cooling channel (10) and then through the fluid-tight housing (7).

2. 2. The pulse inverter (3) of claim 1, wherein the pulse inverter (3) comprises a plurality of power supply modules (4), the plurality of power supply modules (4) being thermally connected to the outer surface of the cooling channel (10).

3. 2. A pulse inverter (3) according to claim 1, wherein the power module (4) is in direct contact with the cooling fluid flowing through the fluid-tight housing (7).

4. 2. The pulse inverter according to claim 1, wherein the cooling channel (10) is arranged in the fluid-tight housing (7) such that the cooling fluid flowing through the fluid-tight housing (7) flows around the cooling channel (10).

5. 2. The pulse inverter of claim 1, wherein a plurality of power supply modules (4), a plurality of DC link capacitors (8), and a plurality of live contact bars (9) connected to the power supply modules (4) are arranged in the housing (7), and the cooling fluid flowing through the housing (7) is in direct contact with the plurality of power supply modules (4), the plurality of DC link capacitors (8), and the plurality of live contact bars (9).

6. 6. A pulse inverter according to claim 5, wherein the cooling device (6) comprises a further cooling channel (12), the DC link capacitor (8) is thermally connected to an outer surface of the further cooling channel (12), the further cooling channel (12) comprises an outlet, the outlet opening into the one cooling channel (10), and the cooling fluid flowing through the cooling device (6) flows first through the further cooling channel (12), then through the one cooling channel (10) and then through the fluid-tight housing (7).

7. 2. The pulse inverter of claim 1, wherein the power module (4) comprises a fluid-tight power module housing (14), and the semiconductor components of the power module (4) are arranged in the power module housing (14).

8. A motor vehicle, An automobile battery (2); An electric machine (1); a pulse inverter (3) for operating the electric machine, 1. A motor vehicle, comprising: a pulse inverter (3) comprising a power supply module (4) for converting a DC current provided by the vehicle battery (2) into an AC current; the pulse inverter (3) comprising a cooling device (6) for cooling components of the pulse inverter (3) by means of an electrically insulating cooling fluid flowing through the cooling device (6), the cooling device (6) comprising a fluid-tight housing (7), the cooling fluid flowing through the fluid-tight housing (7) being in direct contact with at least one of the components to be cooled; the cooling device (6) comprising a cooling channel (10), the power supply module (4) being thermally connected to an outer surface of the cooling channel (10), the cooling channel (10) comprising an outlet (11), the outlet (11) opening into the fluid-tight housing (7), so that the cooling fluid flowing through the cooling device (6) flows first through the cooling channel (10) and then through the fluid-tight housing (7).

9. 9. The vehicle according to claim 8, wherein the vehicle comprises a machine cooling system for cooling the electric machine (1), and the cooling fluid leaving the housing (7) flows into the machine cooling system.

10. 10. The vehicle according to claim 9, wherein the cooling fluid flowing from the cooling device (6) to the machine cooling system is in direct contact with contact bars (9) electrically connecting the pulse inverter and the electric machine.

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