Patent Publication Number: US-2023158881-A1

Title: Hybrid drive system comprising a multi-speed transmission device; and motor vehicle

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is the U.S. National Phase of PCT Appln. No. PCT/DE2021/100245 filed Mar. 10, 2021, which claims priority to DE 10 2020 109 237.7 filed Apr. 2, 2020, the entire disclosures of which are incorporated by reference herein. 
    
    
     TECHNICAL FIELD 
     The disclosure relates to a drive system for a hybrid motor vehicle, such as a car, truck, bus or other utility vehicle, comprising an internal combustion engine, a first electric machine, the rotor shaft of which is permanently rotationally coupled to an output shaft of the internal combustion engine and is arranged coaxially to said output shaft, a second electric machine, the rotor shaft of which is also arranged coaxially to the output shaft and can be uncoupled from the rotor shaft of the first electric machine via a clutch, and at least one differential transmission that has two outputs. Furthermore, the disclosure relates to a motor vehicle comprising this drive system. 
     BACKGROUND 
     Generic drive systems are already sufficiently known in the prior art. In this respect, WO 2007/004356 A1, for example, discloses a drive device for hybrid vehicles with two electric motors. Further prior art is known from EP 2 284 030 B1 and U.S. Pat. No. 8,894,525 B2. 
     However, regarding the drive systems known from the prior art, it has been shown that these are often relatively large in size and complex in structure. In particular, shift transmissions with higher complexity are usually used, which, apart from the fact that they take up additional installation space, also have a detrimental effect on the effort required to assemble the drive system. 
     SUMMARY 
     It is therefore the object of the present disclosure to eliminate the disadvantages known from the prior art and, in particular, to provide an efficiently operating drive system which has the simplest structure possible and saves installation space. 
     According to the disclosure, this is achieved in that the rotor shaft of the second electric machine is (rotationally) coupled/connected to an input of the at least one differential transmission via a two-speed transmission device (i.e. having no more or less than two gears). 
     Thus, on the one hand, the connection between the rotor shaft of the second electric machine and the differential transmission is realized using a transmission device that is as simple as possible as well as compact, and, on the other hand, the transmission device for utilizing different gear ratios can be switched to several operating modes for efficient operation of the drive system. 
     Further embodiments are claimed and explained in more detail below. 
     Accordingly, it is further advantageous if the fixed transmission stage is designed as a planetary transmission stage. This allows a particularly compact axial design. 
     In this context, it is also expedient if a planetary carrier of the fixed transmission stage is permanently connected to the output shaft of the internal combustion engine and/or a sun gear of the fixed transmission stage is connected to the rotor shaft of the first electric machine. A ring gear of the fixed transmission stage is further preferably supported fixed to the housing. This results in a transmission stage that is as simple as possible and sufficiently robust for the torque to be transmitted. 
     The fixed transmission stage is advantageously designed in such a way that it gears a speed to be transmitted from the output shaft of the internal combustion engine to the rotor shaft of the first electric machine into high. This means that the most efficient structure possible has been selected. 
     Furthermore, it is advantageous if the clutch is spatially arranged between rotors of the two electric machines. This also allows the clutch to be mounted in the most space-saving manner possible. 
     It is also useful if the transmission device is designed as a planetary transmission and preferably has two planetary transmission stages. This allows an even more compact axial design. 
     The transmission device is advantageously designed in such a way that it gears a speed to be transmitted from the rotor shaft of the second electric machine to an output shaft of the transmission device (in both gears) to low. This means that the most efficient structure possible has been selected. 
     It is also advantageous if a first switching element of the transmission device is designed as a brake and/or is operatively inserted between a support region fixed to the housing and a ring gear of one of the planetary transmission stages. This allows the first switching element to be made as compact as possible and to be arranged in a manner that saves installation space. 
     In this context, it is also useful if a second switching element of the transmission device is designed as a clutch and/or is operatively inserted between an input shaft and a ring gear of one of the planetary transmission stages. This allows the second switching element to be made as compact as possible and to be arranged in a manner that saves installation space. 
     It is also advantageous if an output shaft of the transmission device is rotationally coupled/connected to an input of a first differential transmission via a cardan shaft. This type of coupling results in further savings in installation space. 
     In this respect, it is also useful if the cardan shaft is connected to the input of the first differential transmission via a gearing stage. The gearing stage is preferably implemented as a bevel gearing stage. 
     If the output shaft of the transmission device is connected to an input of a second differential transmission via at least one gearing stage as an alternative or in addition to its coupling to the first differential transmission, either a front-wheel drive, rear-wheel drive or all-wheel drive can be realized in a simple manner. 
     In this respect, it is further expedient if the output shaft of the transmission device is rotationally coupled via a first gearing stage to an intermediate shaft arranged parallel thereto, which intermediate shaft is further connected to the input of the second differential transmission. This results in a drive system that is as simple as possible and saves installation space. 
     It is also advantageous if the intermediate shaft is connected to the input of the second differential transmission via a second gearing stage. The second gearing stage is further preferably implemented as a bevel gearing stage. This in turn results in a drive system that is as simple as possible and saves installation space. 
     Furthermore, it has proven advantageous if the output shaft of the internal combustion engine is connected to the rotor shaft of the first electric machine via a torsional vibration damper, which is preferably implemented as a dual-mass flywheel. This cleverly couples the internal combustion engine to the rest of the drive train in a damped manner in the particular operating mode. 
     Furthermore, the disclosure relates to a motor vehicle with a drive system according to the disclosure according to at least one of the embodiments described above, wherein the output shaft of the internal combustion engine is arranged parallel or coaxial to a vehicle longitudinal axis of the motor vehicle. 
     In this regard, it is also advantageous if each output of the first differential transmission is connected to a rear wheel (of the motor vehicle) for conjoint rotation and/or each output of the second differential transmission is connected to a front wheel (of the motor vehicle) for conjoint rotation. This results in the most direct possible coupling of the drive system with the wheels of a front axle or a rear axle. 
     If the internal combustion engine is arranged in front of the front wheels along the vehicle longitudinal axis and as seen in a main direction of travel of the motor vehicle, this results in an efficient application of the drive system with a front-longitudinal design of the internal combustion engine. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The disclosure will now be explained in more detail with reference to figures, in which context various exemplary embodiments are also shown. 
       In the figures: 
         FIG.  1    shows a schematic longitudinal sectional view of a drive system according to the disclosure according to a first embodiment, in which an output shaft of an internal combustion engine and two rotor shafts of two electric machines are arranged coaxially to one another and one of the rotor shafts is coupled to the output shaft of the internal combustion engine via a fixed transmission stage and the other of the rotor shafts is coupled to a rear wheel differential via a two-speed transmission device and a cardan shaft, and 
         FIG.  2    shows a schematic longitudinal sectional view of a drive system according to the disclosure according to a second embodiment, in which an output shaft of the transmission device is coupled both to the cardan shaft and, with the interposition of two gearing stages, to a second differential transmission. 
     
    
    
     DETAILED DESCRIPTION 
     The figures are only schematic in nature and serve only for understanding the disclosure. The same elements are provided with the same reference signs. 
       FIG.  1    illustrates the structure of a drive system  1  according to the disclosure in accordance with a first exemplary embodiment. The drive system  1  is implemented as a hybrid drive system  1  and is consequently used in a preferred area of application in a hybrid motor vehicle  2 , which is schematically indicated in  FIG.  1   . 
     The drive system  1  has an internal combustion engine  3 , for example in the form of a petrol or diesel engine, which is oriented with its output shaft  5  (crankshaft) along, i.e. parallel or coaxial to, an imaginary vehicle longitudinal axis  22 /vehicle centerline of the motor vehicle  2 . In addition, in this embodiment, the internal combustion engine  3  is arranged in front of a front axle with front wheels  25  (i.e. on a side of a front axle facing away from a rear axle with rear wheels  24 ) as viewed along the vehicle longitudinal axis  22 . 
     In the first exemplary embodiment according to  FIG.  1   , the drive system  1  serves to drive two rear wheels  24  of the rear axle of the motor vehicle  2 , as described in more detail below. In further exemplary embodiments, as described below in conjunction with  FIG.  2   , this drive system  1  is designed alternatively for driving two front wheels  25  of a front axle of the motor vehicle  2  or even as an all-wheel drive, i.e., for driving all wheels  24 ,  25  of the motor vehicle  2 . 
     The output shaft  5  of the internal combustion engine  3  is arranged coaxially with a (first) rotor shaft  4  of a first electric machine  6 . The output shaft  5  is permanently rotationally coupled/connected to the first rotor shaft  4 . 
     In this embodiment, the output shaft  5  is connected to the first rotor shaft  4  via, among other things, a torsional vibration damper  21 , here in the form of a spring damper (for example a dual-mass flywheel). 
     Furthermore, the output shaft  5  is connected to the first rotor shaft  4  via a fixed transmission stage  42 . For this purpose, the fixed transmission stage  42  is connected on the input side to a connecting shaft  47 , wherein the connecting shaft  47  is further connected to a side of the torsional vibration damper  21  facing away from the output shaft  5 . On the output side, the fixed transmission stage  42  is directly connected to the first rotor shaft  4 . 
     The fixed transmission stage  42  is designed as a planetary transmission stage. One input of the fixed transmission stage  42  is formed as a (third) planetary carrier  43 . A plurality of (third) planetary gears  45  are rotatably supported on the planetary carrier  45  in a typical manner. The planetary gears  45  are in meshed engagement with both a (third) sun gear  44  and a (third) ring gear  46 . The sun gear  44  directly forms the output of the fixed transmission stage  42 , which is further connected to the first rotor shaft  4 . In this design, the ring gear  46  of the fixed transmission stage  42  is supported fixed to the housing. 
     The first electric machine  6  is further designed to be switchable as a generator machine in a first operating mode of the drive system  1 . The first electric machine  6  has a (first) stator  26  that is fixedly received in a housing  27 . Relative to the first stator  26 , a (first) rotor  28  of the first electric machine  6  is rotatably supported. The first rotor  28  is connected to the first rotor shaft  4  for conjoint rotation. The first rotor shaft  4  is supported in the housing  27 . 
     In addition to the first electric machine  6 , a second electric machine  9  is present. In the first operating mode of the drive system  1 , the second electric machine  9  serves as a drive machine/traction machine. The second electric machine  9  also has a (second) stator  37  received fixed to the housing and a (second) rotor  38  received rotatably relative to the second stator  37 . The second rotor  38  is directly connected to a second rotor shaft  7  associated with the second electric machine  9 . The second rotor shaft  7  is also supported in the housing  27 . The second rotor shaft  7  is arranged coaxially with the first rotor shaft  4  and the output shaft  5 . Accordingly, the output shaft  5 , the first rotor shaft  4  and the second rotor shaft  7  are arranged coaxially and in a row to one another. 
     A clutch  8 , preferably in the form of a friction clutch, is operatively inserted between the two rotor shafts  4 ,  7 . The clutch  8  is used to selectively couple or decouple the two rotor shafts  4 ,  7  to or from one another. In a closed position of the clutch  8 , the two rotor shafts  4 ,  7  are connected to one another for conjoint rotation; in an open position of the clutch  8 , the two rotor shafts  4 ,  7  are decoupled from one another/freely rotatable relative to one another. It can be seen that the clutch  8  is spatially arranged between the two rotors  28 ,  38  of the two electric machines  6 ,  9 . 
     In addition, the second rotor shaft  7  is permanently rotationally coupled/connected to an input  14  of a first differential gear  12  (here a rear wheel differential) via a two-speed transmission device  16 , which has exactly two gears (implementing different gear ratios). 
     In the first exemplary embodiment, a cardan shaft  23  is used to implement the rotary connection of an output shaft  36  of the transmission device  16  to the input  14  of the first differential transmission  12 . The cardan shaft  23  is connected to an end of the output shaft  36  facing away from the second electric machine  9 . The cardan shaft  23  is coupled to the input  14  of the first differential transmission  12  via a (third) gearing stage  19 . The input  14  is implemented in a typical manner as an input gear. In this embodiment, the input  14  is implemented as a bevel gear and the third gearing stage  19  is thus designed as a bevel gearing. 
     Two outputs  10   a ,  10   b  of the first differential transmission  12 , each connected to a rear wheel  24  in this first exemplary embodiment, are arranged obliquely, namely substantially perpendicularly, to the output shaft  5  of the internal combustion engine  3  and the rotor shafts  4 ,  7 . 
     With the clutch  8  closed, the internal combustion engine  3  thus drives the motor vehicle  2  directly in a second operating mode (with optional drive assistance from the second electric machine  9 ) and by shifting one of the two gears of the transmission device  16 . 
     With regard to the transmission device  16 , it can further be seen that it has two planetary transmission stages  29 ,  30 . A first planetary transmission stage  29  of the transmission device  16  directly forms an input shaft  35  of the transmission device  16 . The input shaft  35  is connected to the second rotor shaft  7  for conjoint rotation. In addition, the input shaft  35  is directly connected to a (first) sun gear  39   a  of the first planetary transmission stage  29 . 
     The first planetary transmission stage  29 , in a typical manner, has a plurality of (first) planetary gears  40   a  arranged distributed in the circumferential direction in meshed engagement with the first sun gear  39   a  in addition to the first sun gear  39   a , which first planetary gears  40   a  are further in meshed engagement with a first ring gear  33   a . The first planetary gears  40   a  are also rotatably supported on a first planetary carrier  41   a.    
     The second planetary transmission stage  30 , which also directly forms the output shaft  36  of the transmission device  16 , also has a (second) sun gear  39   b , a plurality of (second) planetary gears  40   b  arranged distributed in the circumferential direction and in meshed engagement with the second sun gear  39   b , and a (second) ring gear  33   b  in turn in meshed engagement with the second planetary gears  40   b . Also, the second planetary gears  40   b  are rotatably supported on a (second) planetary carrier  41   b.    
     In this embodiment, the first planetary carrier  41   a  is connected to the second sun gear  39   b  for conjoint rotation. The second planetary carrier  41   b  again transitions directly into the output shaft  36  or is directly connected to this output shaft  36  for conjoint rotation. 
     Two switching elements  31 ,  34  are provided for switching the transmission device  16  between its two different gears. In this embodiment, a first switching element  31  is designed as a brake and is thus operatively inserted between a support region  32  fixed to the housing and a component of the transmission device  16 . In this embodiment, the first switching element  31  is operatively inserted between the support region  32  fixed to the housing and the first ring gear  33   a . In an activated position/state of the first switching element  31 , the first ring gear  33   a  is thus supported fixed to the housing, whereas in a deactivated position/state of the first switching element  31 , it is free to rotate relative to the housing  27 . 
     In this embodiment, a second switching element  34  is implemented as a clutch, which is realized as a friction clutch, for example. The second switching element  34  is operatively inserted between the input shaft  35  and the first ring gear  33   a . Consequently, in a closed position of the second switching element  34 , the input shaft  35  and the first ring gear  33   a  are coupled for conjoint rotation so that the first planetary transmission stage  29  rotates in the block. In an open position of the second switching element  34 , the first ring gear  33   a  and the input shaft  35  are free to rotate relative to one another. 
     Furthermore, it can be seen that in this embodiment the second ring gear  33   b  is permanently connected to the housing  27 /the support region  32  fixed to the housing. 
     In the second exemplary embodiment shown in  FIG.  2   , an alternative design of the drive system  1  according to the disclosure can be seen. The basic structure of this second exemplary embodiment is the same as that of the first exemplary embodiment, so for reasons of brevity only the differences between these two exemplary embodiments are described below. 
     In  FIG.  2   , the output shaft  36  of the transmission device  16  is coupled to a further second differential transmission  13  (front wheel differential), implementing an all-wheel drive. In this context, it should be noted that in a further embodiment of the drive system  1  according to the disclosure, there is also only the second differential transmission  13 , i.e. without the first differential transmission  12 , implementing a front-wheel drive. 
     In  FIG.  2   , the output shaft  36  of the transmission device  16  is rotationally connected to an intermediate shaft  20  via a first gearing stage  17  (in the form of a spur gear gearing stage). The intermediate shaft  20  is arranged parallel to the rotor shafts  4 ,  7 . The intermediate shaft  20  is connected to an input  15  of the second differential transmission  13  via a further second gearing stage  18 , here in the form of a bevel gearing. Consequently, the input  15  is realized as a bevel gear. Thus, there is also a permanent rotational coupling of the second rotor shaft  7  with the input  15  of the second differential transmission  13 . The rotary connection of the second rotor shaft  7  with the input  15  of the second differential transmission  13  is thus implemented via the transmission device  16 , the intermediate shaft  20  and the two first and second gearing stages  17 ,  18 . 
     The two outputs  11   a ,  11   b  of the second differential transmission  13  are also aligned obliquely, specifically substantially perpendicularly, to the rotor shafts  4 ,  7  and the output shaft  5  of the internal combustion engine  3 . In this context, it should be noted for the sake of completeness that the illustration according to  FIG.  2    is to be understood in such a way that the first output  11   a  of the second differential transmission  13  crosses the first rotor shaft  4  below or above the drawing plane, so that of course the first rotor shaft  4  is not directly connected to the first output  11   a.    
     In other words, a two-speed dedicated hybrid transmission for power shifting is thus implemented according to the disclosure for a drive train in front-longitudinal configuration. In particular, the internal combustion engine  3  is installed longitudinally. In addition, a clutch  8  is inserted between the E-machines  6 ,  9 . 
     Furthermore, the first electric machine  6  is geared to a higher speed via a stationary gear ratio  42  (e.g. planetary stage). The first electric machine  6  is directly connected to the second electric machine  9  via the clutch  8 . The second electric machine  9  is geared back to low speeds via a combination of stationary gear ratios (e.g. planetary stages  29 ,  30 ). A gearing from the internal combustion engine  3  to the differential  12 ,  13  is thus directly implemented, i.e. about 5.9 and 2.8. The two gears are made possible by actuating the brake  31  or the clutch  34 . The two gears allow the second electric machine  9  to be dimensioned smaller (torque and speed). This is an advantage for vehicles with high requirements in terms of Vmax and start-up performance. 
       FIG.  1    shows a structure according to the disclosure in which the first electric machine  6  is also geared to higher speeds. This can also be advantageous in order to increase the performance with the same installation space or to require less installation space for the same performance. The clutch  8  is located directly between the electric machines  6 ,  9  and only has to transmit a low torque due to the high drive. 
     A gearing of the three machines ( 3 ,  6 ,  9 ) to the wheel  24  is defined/fixed only by the two planetary sets  29  and  30  with the switching elements  31  and  34  and a fixed differential gear ratio. 
       FIG.  2    shows another possible configuration level with a longitudinal installation of the internal combustion engine  3  and front-wheel drive; optionally, all-wheel drive can also be represented by retaining the cardan shaft  23  and the rear-wheel differential  12 . For front-wheel drive, torque is transmitted on a shaft  20  to the differential  13  via a transmission stage. For all-wheel drive, the gearing must be selected in any case such that the output speeds of both differentials  12 ,  13  are the same. 
     LIST OF REFERENCE NUMBERS 
     
         
         
           
               1  Drive system 
               2  Motor vehicle 
               3  Internal combustion engine 
               4  First rotor shaft 
               5  Output shaft of the internal combustion engine 
               6  First electric machine 
               7  Second rotor shaft 
               8  Clutch 
               9  Second electric machine 
               10   a  First output of the first differential transmission 
               10   b  Second output of the first differential transmission 
               11   a  First output of the second differential transmission 
               11   b  Second output of the second differential transmission 
               12  First differential transmission 
               13  Second differential transmission 
               14  Input of the first differential transmission 
               15  Input of the second differential transmission 
               16  Transmission device 
               17  First gearing stage 
               18  Second gearing stage 
               19  Third gearing stage 
               20  Intermediate shaft 
               21  Torsional vibration damper 
               22  Vehicle longitudinal axis 
               23  Cardan shaft 
               24  Rear wheel 
               25  Front wheel 
               26  First stator 
               27  Housing 
               28  First rotor 
               29  First planetary transmission stage 
               30  Second planetary transmission stage 
               31  First switching element 
               32  Support region fixed to housing 
               33   a  First ring gear 
               33   b  Second ring gear 
               34  Second switching element 
               35  Input shaft 
               36  Output shaft of the transmission device 
               37  Second stator 
               38  Second rotor 
               39   a  First sun gear 
               39   b  Second sun gear 
               40   a  First planetary gear 
               40   b  Second planetary gear 
               41   a  First planetary carrier 
               41   b  Second planetary carrier 
               42  Fixed transmission stage 
               43  Third planetary carrier 
               44  Third sun gear 
               45  Third planetary gear 
               46  Third ring gear 
               47  Connecting shaft