SUMMERY OF THE UTILITY MODEL
Against this background, it is an object of the invention to improve the usability of a drive system.
This object is achieved by a drive system for a motor vehicle, having: an electric machine; a rectifier connected to the electric machine, the rectifier having one or more semiconductor switches; and a common cooling device for cooling the electric machine and the rectifier, wherein the cooling device has a coolant guide, by means of which coolant can be first guided through the rectifier and from there through the electric machine, wherein the coolant guide has
-a first rectifier coolant path for cooling a top side of semiconductor switches of the rectifier, wherein the semiconductor switches are covered by a protective layer or protective material, and the first rectifier coolant path is designed such that the coolant can make direct contact with the protective layer or protective material when flowing through the first rectifier coolant path; and
-a second rectifier coolant path arranged in parallel with the first rectifier coolant path for cooling a bottom side of the rectifier opposite the top side, the second rectifier coolant path extending through a cooling body of the rectifier.
According to the utility model provides a: the rectifier, in particular the semiconductor switches of the rectifier, are cooled from a plurality of sides. The top side of the semiconductor switch may be cooled via the first rectifier coolant path. The semiconductor switch is covered by a protective layer or protective material, so that the electrically conductive surface of the semiconductor switch is effectively protected from adhesion by particles carried in the coolant. The bottom side of the semiconductor switch can be cooled via a second rectifier coolant path extending through the cooling body. On the one hand, the cooling body can shield the semiconductor switches from the coolant, so that even particles carried in the coolant on the underside cannot reach the electrically conductive surfaces of the semiconductor switches. On the other hand, the cooling body may additionally form a holding element for the semiconductor switch. In summary, in the drive system according to the invention, the occurrence of undesired short circuits due to particle deposition is prevented, thereby improving the usability of the drive system.
The heat sink is preferably connected to a conductor track plate, in particular a circuit board, on which the semiconductor switch is arranged.
According to one advantageous embodiment, it is provided that: the protective layer or material is provided with an epoxy resin. The epoxy may form a thermally conductive, electrically insulating protection for the semiconductor switch. Preferably, the protective layer or the protective material is formed by a casting method, so that the effort for protecting the semiconductor components can be kept low.
It is advantageous to have a design of the first valve which can be controlled for regulating the volume flow in the first rectifier coolant path and the second rectifier coolant path. The first valve may have an adjustable flow cross section for the first rectifier coolant path and the second rectifier coolant path. Alternatively, it is possible to provide: the drive system has two first valves, wherein the volume flow in the first rectifier coolant path can be regulated by one of the valves and the volume flow in the second rectifier coolant path can be regulated by the other of the valves. Further alternatively, the first rectifier coolant path and the second rectifier coolant path may originate from branch positions designed without valves. In such a configuration, the volume flow may not be regulated, but rather may be regulated by itself.
According to an advantageous embodiment of the invention, it is provided that: the first rectifier coolant path and the parallel second rectifier coolant path are connected with a third rectifier coolant path at a connection location such that coolant flowing through the first rectifier coolant path and the second rectifier coolant path can be directed into the third rectifier coolant path. In the third rectifier coolant path, the coolant may converge together and be directed collectively in the direction of the electric machine. Such a design with a connection point at which the first rectifier coolant path and the second rectifier coolant path converge brings the following advantages: the distribution of the coolant in the first and second rectifier coolant paths can be designed independently of the design of the coolant guiding device in the region of the electric machine, in particular independently of the distribution of the coolant guiding device in the region of the electric machine in the form of parallel paths.
In a preferred embodiment, the coolant conducting device has a first machine coolant path for cooling a stator of the electric machine and a second machine coolant path arranged in parallel with the first machine coolant path for cooling a rotor of the electric machine. In this way, not only the rectifier but also the stator and the rotor of the electric machine can be cooled by the same cooling device. Preferably, the stator coolant path is designed such that coolant can flow around the windings of the stator. Such cooled windings are also referred to as directly cooled windings.
In this connection, it has proven advantageous: the drive system includes a second valve that can be controlled for regulating the volumetric flow in the first machine coolant path and the second machine coolant path. The second valve may have adjustable flow cross-sections for the first machine coolant path and the second machine coolant path. Alternatively, it is possible to provide: the drive system has two second valves, wherein the volume flow in the first machine coolant path can be regulated by one of the valves and the volume flow in the second machine coolant path can be regulated by the other of the valves. Further alternatively, the first machine coolant path and the second machine coolant path may originate from branch positions designed without valves. In such a configuration, the volume flow may not be regulated, but rather may be regulated by itself.
Preferably, the second valve is adjusted in such a way that the volume flow through the first machine coolant path for cooling the stator is greater than the volume flow through the second machine coolant path for cooling the rotor. Such a regulation of the second valve is advantageous in electric machines in which a greater power loss is released in the stator than in the rotor. Since the volume flow in the region of the stator is greater, more heat can be removed from the stator.
According to an alternative preferred embodiment, the coolant guide has a common coolant path for cooling the stator and the rotor in the region of the electric machine. The common coolant path may be designed such that the coolant may flow first through the rotor and then through the stator. However, the common coolant path is preferably designed such that the coolant can flow first through the rotor and then through the stator, so that it flows first through the region of the electric machine (here the rotor) in which less power loss is released.
Another subject of the invention is a motor vehicle having a drive system as described above.
The same advantages as already described in connection with the drive system can be achieved in this motor vehicle.
Preferably, the drive system forms a traction drive of the motor vehicle, in particular a front wheel drive, a rear wheel drive, an all-wheel drive or a hub drive.
According to one advantageous embodiment, the motor vehicle comprises a transmission coupled to the rotor of the electric machine. In the design of a motor vehicle with a transmission, the cooling device of the drive train is preferably designed independently of the cooling device of the transmission. Further, the transmission may be coupled with the combustion engine. In the design of a motor vehicle with a combustion engine, the cooling device of the drive train is preferably designed independently of the cooling circuit of the combustion engine.
Another subject of the invention is a method for cooling a drive system of a motor vehicle, the drive system having: an electric machine; a rectifier connected to the electric machine, the rectifier having one or more semiconductor switches; and a common cooling device for cooling the electric machine and the rectifier, wherein the cooling device has a coolant guide by which coolant is first guided through the rectifier and from there through the electric machine, wherein the coolant in the coolant guide is caused to flow
-is guided in a first rectifier coolant path for cooling the top side of the rectifier, wherein the semiconductor switches are covered by a protective layer or protective material and the first rectifier coolant path is designed such that the coolant makes direct contact with the protective layer or protective material when flowing through the first rectifier coolant path; and
-is guided in a second rectifier coolant path arranged in parallel with the first rectifier coolant path for cooling a bottom side of the rectifier opposite the top side, the second rectifier coolant path extending through a cooling body of the rectifier.
In this way the same advantages as already described in connection with the drive system can be achieved.
According to an advantageous embodiment of the method, it is provided that: the coolant in the coolant guiding device is guided in a first machine coolant path for cooling a stator of the electric machine and in a second machine coolant path for cooling a rotor of the electric machine, which is arranged in parallel with the first machine coolant path. By thus conducting the coolant through the rotor and the stator in parallel, the disadvantages of a series-connection conducting can be avoided. That is, if the coolant is first directed through the stator and then through the rotor, a relatively large coolant temperature is generated in the rotor, thereby possibly reducing the efficiency of the machine. Conversely, if the same coolant flows first through the rotor and then through the stator, it may lead to an increase in pressure on the radial shaft seal ring, with a consequent increased risk of frictional losses and damage to the seal.
In this connection, it is advantageous: the first volume flow in the first machine coolant path is set to be greater than the second volume flow in the second machine coolant path, in particular by means of a valve that can be controlled. Since the volume flow in the region of the stator is greater, more heat can be removed from the stator.
In addition to the advantageous embodiments described above, the advantageous embodiments described in conjunction with the drive system according to the invention can alternatively or additionally also be used individually or in combination in the method.
Detailed Description
Fig. 1 shows a motor vehicle 1 designed as an electric vehicle, which has a drive system 2 according to the invention. The drive system 2 is designed as a traction drive of the motor vehicle 1 and drives one or more wheels of the motor vehicle. One component of the drive system 2 is an energy store 3, which can be designed, for example, as a battery, a rechargeable battery or an ultracapacitor (super capacitor). The drive system 2 further comprises a rectifier 4 and an electric machine 5.
The rectifier 4 is designed as an inverter and has a dc voltage side and an ac voltage side. The rectifier 4 is connected on its dc voltage side to the energy store 3. The rectifier 4 is connected on its ac voltage side to an electric machine 5. The rectifier 4 comprises an intermediate circuit capacitor 4.1 on the direct voltage side. The rectifier further comprises a plurality of semiconductor switches 4.2, which can be designed, for example, as MOSFETs, IGBTs or bipolar transistors. A freewheeling diode 4.3 is arranged in parallel with these semiconductor switches 4.2.
The illustration in fig. 2 shows a drive system 2, which can be used, for example, in the vehicle 1 according to fig. 1. The drive system 2 comprises a cooling device 6 which is designed as a common cooling device for the rectifier 4 and the electric machine 5. The cooling device 6 comprises a coolant guiding device 7, by means of which coolant can be first guided through the rectifier 4 and from the rectifier 4 through the electric machine 5. Preferably, a poorly or non-conductive cooling medium (e.g., oil) is used as the coolant.
The coolant guide has a first rectifier coolant path 11 in the region of the rectifier 4 for cooling the top side of the semiconductor switch 4.2. In order to protect the semiconductor switches 4.2 from undesired contamination, they are covered by a protective layer 9 or protective material. The protective layer 9 is formed of epoxy resin. The semiconductor switch 4.2 is fastened to the heat sink 8. The first rectifier coolant path 11 is designed such that the coolant can come into direct contact with the protective layer 9 or the protective material when flowing through the first rectifier coolant path 11.
A second rectifier coolant path 12 is arranged in parallel with the first rectifier coolant path 11, which second rectifier coolant path serves to cool a bottom side of the rectifier 4 (in particular the semiconductor switch 4.2) opposite the top side. The second rectifier coolant path 12 extends through the cooling body 8 of the rectifier 4, so that even the coolant flowing in the coolant path 12 may not come into direct contact with the semiconductor switches. The flow of coolant is indicated in fig. 2 by arrows within the respective rectifier coolant paths 11, 12. The second rectifier coolant path 12 thus enables indirect cooling of the rectifier 4 above the cooling body 8.
For regulating the volume flow in the first rectifier coolant path 11 and the second rectifier coolant path 12, the cooling device 6 has a first valve 16 which can be controlled. The first rectifier coolant path 11 and the parallel second rectifier coolant path 12 open into the third rectifier coolant path 13 at a connection point 18. Thus, the coolant flowing through the first rectifier coolant path 11 and the second rectifier coolant path 12 is mixed and guided through the third rectifier coolant path 13 in the direction of the electric machine 5.
The coolant guide 7 also has two parallel coolant paths 14, 15 in the region of the electric machine 5. The first machine coolant path 14 is provided in the region of the stator for cooling the stator 5.1 of the electric machine 5. A second machine coolant path 15, which is arranged in parallel with the first machine coolant path 14, extends through the rotor 5.2 of the electric machine and enables independent cooling of the rotor 5.2. The first machine coolant path 14 is designed such that coolant can flow through the windings of the stator, in particular of the stator 5.1. In this regard, there is direct cooling of the stator windings.
The distribution of the volume flow in the first machine coolant path 14 and the second machine coolant path 15 can be adjusted independently of the distribution of the volume flow in the first rectifier coolant path 11 and the second rectifier coolant path 12. For regulating the volume flow in the first machine coolant path 14 and the second machine coolant path 15, the drive system 2 comprises a second valve 17 which can be controlled. According to this embodiment, the first volume flow in the first machine coolant path 14 is adjusted to be greater than the second volume flow in the second machine coolant path 15.
The illustration in fig. 3 shows a section through the drive system 2 along the section line III-III' according to fig. 2. It can be seen that the stator 5.1 and the rotor 5.2 are separated by a sleeve 19. The sleeve is designed in a fluid-tight manner and seals the stator 5.1, through which the coolant flows, against the rotor 5.2.
In the drive system 2 shown above, a method for cooling the drive system 2 may be used in which the coolant in the coolant guiding device 7 is caused to: is guided in a first rectifier coolant path 11 for cooling the top side of the rectifier 4, wherein the semiconductor switches 4.2 are covered by a protective layer 9 or protective material, and the first rectifier coolant path 11 is designed such that the coolant makes direct contact with the protective layer 9 or protective material when flowing through the first rectifier coolant path 11; and in a second rectifier coolant path 12 arranged in parallel with the first rectifier coolant path 11 for cooling a bottom side of the rectifier 4 opposite the top side, which extends through the cooling body 8 of the rectifier 4. The occurrence of undesired short circuits due to particle deposition is prevented in the drive system 2, thereby improving the usability of the drive system 2.