Abstract:
A drive train ( 1 ) for a motor vehicle, comprising a combustion engine ( 2 ), an electric machine ( 29 ) and an automatic shift transmission ( 6 ) having a transmission input shaft ( 5 ) and a transmission output shaft ( 12 ), with a shifting actuator for selecting gear trains ( 7, 8, 9, 10, 11 ) situated between the transmission input shaft ( 5 ) and the transmission output shaft ( 12 ), acting as gears (I, II, III, IV, R), as well as a single automated friction clutch ( 4 ) situated between a crankshaft ( 3 ) of the combustion engine ( 2 ) and the transmission input shaft ( 5 ) of the shift transmission ( 6 ), wherein the electric machine ( 29 ) is switchable alternatively between the crankshaft ( 3 ) and the shift transmission ( 6 ).

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is filed under 35 U.S.C. §120 and §365(c) as a continuation of International Patent Application No. PCT/DE2010/000690 filed Jun. 17, 2010, which application claims priority from German Patent Application No. DE 10 2009 031 513.6 filed Jul. 2, 2009, which applications are incorporated herein by reference in their entireties. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The invention relates to a hybrid drive train comprising an internal combustion engine, an electric machine, an automatic shift transmission and a single automated friction clutch situated between a crankshaft of the internal combustion engine and the transmission input shaft of the transmission. 
       BACKGROUND OF THE INVENTION 
       [0003]    Drive trains of this species have already been proposed for use in motor vehicles. For example, electric machines connected to the crankshaft, with the friction clutch disengaged, are able to start the internal combustion engine and make a boost mode possible, in which the electric machine supports the internal combustion engine in particular during an acceleration of the motor vehicle. Purely electrical operation or recuperation, i.e., conversion of the kinetic energy of the motor vehicle during deceleration while it is being braked, is possible only to a limited degree, since the drag torque of the internal combustion engine interferes and reduces efficiency. Furthermore, replenishment of the propulsive power is not possible during shifting of the transmission. 
         [0004]    A drive train for a motor vehicle is known from DE 199 60 621 A1, in which a single friction clutch is situated between an internal combustion engine and the transmission. An electric machine that is optionally connectible with the transmission input shaft or the transmission output shaft of the transmission is engaged with the transmission, so that when the friction clutch is disengaged and the internal combustion engine is possibly shut down it is possible to drive or to drive off electrically using the electric machine. At the same time, switching between transmission input shaft and transmission output shaft enables better utilization of the properties of the electric machine, optionally with or without use of the transmission ratio of the transmission and addition of another gear ratio between electric machine and transmission output shaft. To start the internal combustion engine, the electric machine must be connected to the transmission input shaft, all of the gears in the transmission must be disengaged, and the friction clutch must be engaged. In particular at low temperatures, the drag losses of the transmission input shaft increase the efficiency of the electric machine, and the efficiency of the battery is also low at these temperatures. Furthermore, driving off again may be poor, that is, delayed, in particular in stop-and-go situations, for example in traffic jams or at traffic lights, because a start-up gear must still first be engaged after the internal combustion engine is started. 
       SUMMARY OF THE INVENTION 
       [0005]    The present invention broadly comprises a drive train ( 1 ) for a motor vehicle, comprising a combustion engine ( 2 ), an electric machine ( 29 ) and an automatic shift transmission ( 6 ) having a transmission input shaft ( 5 ) and a transmission output shaft ( 12 ), with a shifting actuator for selecting gear trains ( 7 ,  8 ,  9 ,  10 ,  11 ) situated between the transmission input shaft ( 5 ) and the transmission output shaft ( 12 ), acting as gears (I, II, III, IV, R), as well as a single automated friction clutch ( 4 ) situated between a crankshaft ( 3 ) of the combustion engine ( 2 ) and the transmission input shaft ( 5 ) of the shift transmission ( 6 ), wherein the electric machine ( 29 ) is switchable alternatively between the crankshaft ( 3 ) and the shift transmission ( 6 ). 
         [0006]    The object of the invention is therefore to propose a hybrid drive train in particular for a motor vehicle, having a single friction clutch situated between the internal combustion engine and the transmission, whose electric machine makes possible the functions of starting the internal combustion engine, recuperation, driving electrically, boost mode and electrical replenishment of the propulsion power with high efficiency during shifting of the transmission. 
         [0007]    The problem is solved by a drive train for a motor vehicle comprising an internal combustion engine, an electric machine and an automatic shift transmission, having a transmission input shaft and a transmission output shaft with a shifting actuator for engaging gear trains acting as gear ratios, situated between the transmission input shaft and the transmission output shaft, as well as a single automated friction clutch situated between a crankshaft of the internal combustion engine and the transmission input shaft of the shift transmission, the electric machine being switchable alternatively between the crankshaft and the transmission. The electric machine in this case may be switchably connected to the transmission input shaft and/or to the transmission output shaft, directly or by means of an additional shifting clutch. 
         [0008]    It has proven to be advantageous to execute the shifting of the electric machine independently of a shift state of the transmission, so that the electric machine may be connected to the crankshaft and the transmission input shaft as it were with each selected gear, and the electric machine may also be switched over during a gear change. In this case, advantageously no additional actuating system is provided, but rather the electric machine is switched using the shifting actuator. To this end appropriate switching means are provided, such as shifting clutches with sliding muff-type couplings, selector forks and selector rails, and are lined up with or between the shifting clutches to shift the gears. The connection to the transmission input shaft or the transmission output shaft may be accomplished via the gear wheel pairing of a gear ratio, so that in the event the electric machine is switched to the transmission, the electric machine is connected to the transmission input shaft if a gear is selected, and connected exclusively to the transmission output shaft if no gear is selected. 
         [0009]    According to one advantageous exemplary embodiment, a shifting of the gears and switching of the electric machine is accomplished by means of a two-dimensionally repositionable selector shaft driven for example by one or more electric motors, having at least one actuating element, for example a selector finger, and/or by a shifting actuator containing auxiliary actuating elements, wherein a first direction of motion of the selector shaft is selected, for example when the selector shaft is displaced longitudinally, a selector position is selected by the at least one actuating element and is switched to a second direction of motion of the selector shaft, running essentially perpendicular to the first direction of motion, for example when the latter is twisted, starting from a zero position such as a neutral position, by means of the at least one actuating element. In this case a first actuating element such as a selector finger may be moved back into the zero position after a gear is shifted, and may optionally switch the electric machine by changing the first direction of motion, while a second actuating element optionally stabilizes the engaged gear in its shifted position, or when a different gear is being engaged, disengages the latter during the same motion of the selector shaft. A shifting principle of this sort has become known under the designation active interlock, and is explained in greater detail for example in DE 102 065 61 A1. In this way, switching of the electric machine is possible independent of the shifting of the gears. Provision is made in this case to switch the electric machine by the first or one of the second actuating elements between the crankshaft, a zero position and the transmission, for example between the transmission input shaft and/or the transmission output shaft. 
         [0010]    According to one advantageous exemplary embodiment, an air conditioner compressor may be linked directly or detachably to the electric machine, so that the latter can preferably drive the air conditioner compressor in the event that it is not necessary to operate the electric machine. On the other hand, when the electric machine is not being operated, or is being operated only at partial load, the air conditioner compressor may be driven via the connection from the transmission, for example in non-recuperating drag mode. 
         [0011]    The proposed drive train is suitable for operation at high efficiency when starting the internal combustion engine, using the electric machine with the friction clutch disengaged and the electric machine connected to the crankshaft. An especially high degree of efficiency is achieved in this case due to the direct connection with the crankshaft and elimination of the drag torque of the transmission components. When the electric machine is connected to the transmission, with the friction clutch disengaged, the motor vehicle can be set in motion, driven and recuperated under deceleration in an ideal manner, independently of the internal combustion engine, using the electric machine, through conversion of the kinetic energy into electrical energy by the electric machine. In this case an appropriate gear with a suitable gear ratio is selected. At the same time, the internal combustion engine may be operated for example at idle or may be shut down. To decelerate the vehicle especially effectively, the friction clutch may in addition be at least partly engaged, accepting a reduction in the efficiency of the recuperation, in order to achieve a more rapid slow-down, by using the drag torque of the internal combustion engine—preferably not running—to this end. 
         [0012]    With the friction clutch slipping or engaged, the electric machine and the internal combustion engine can propel the motor vehicle jointly in boost mode. 
         [0013]    Especially advantageous, with the electric machine connected or connectible to the transmission output shaft, is a drawing off of torque through a corresponding driving or driven state of the electric machine during shifting, depending on the driving situation under traction or drag, as well as when shifting up or down. 
         [0014]    The invention will be explained in further detail on the basis of the exemplary embodiment depicted in the single figure. This shows a hybrid drive train in a schematic depiction. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]    The present invention will be explained in greater detail below on the basis of preferred exemplary embodiments, in combination with the pertinent figures. These show the following: 
           [0016]      FIG. 1  shows drive train  1  in a schematic depiction, which for the sake of greater clarity of the transmission layout does not reproduce the actual geometric arrangement of the components. Drive train  1  contains a combustion machine  2 —here in the form of an internal combustion engine—having a crankshaft  3  to which automatically operated friction clutch  4  is firmly attached. The output part is firmly connected to the transmission input shaft  5  of automatic shift transmission  6 . Shift transmission  6  contains a plurality of gear trains  7 ,  8 ,  9 ,  10 ,  11  to form gears I, II, III, IV, R, gear R being the reverse gear, between transmission input shaft  5  and transmission output shaft  12 , which is connected to the drive wheels  14  through the differential  13 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0017]    Gear trains  7 ,  8 ,  9 ,  10 ,  11  are formed of one fixed gear  15 ,  16 ,  17 ,  18 ,  19  and one idler gear  20 ,  21 ,  22 ,  23 ,  24  each, and in the case of the gear R, in addition by a reversing gear  25 . When shifting of a gear is desired, idler gears  20 ,  21 ,  22 ,  23 ,  24  are each connected by a shifting clutch  26 ,  27 ,  28  to the appropriate shaft, such as the transmission input shaft  5  or transmission output shaft  12 . This is done by an actuation activator, which according to the H shifting principle moves to a corresponding shifting clutch  26 ,  27 ,  28  through longitudinal movement of a selector shaft by an actuating element in a selection gate and selects the appropriate gear by turning, where aside from the reverse gear R, which has a separate shifting clutch  28 , the other gears are engaged in pairs through selection of the direction of rotation of the selector shaft by a shifting clutch  26 ,  27 . The depicted exemplary embodiment shows shift transmission  6  with five gears I, II, III, IV, R. It goes without saying that a different number of gears and a different arrangement and distribution of the transmission ratios of the individual pairs of gear wheels  7 ,  8 ,  9 ,  10  among the shift clutches  26 ,  27 ,  28  and their arrangement on transmission input shaft  5  or transmission output shaft  12  are included by the invention. 
         [0018]    In the exemplary embodiment depicted, the electric machine  29  is connected to the auxiliary shaft  33  by means of an additional shifting clutch  30  operated by the shifting actuator, which connects the idler gears  31 ,  32  to the auxiliary shaft  33 , or sets a neutral position in which none of the idler gears  31 ,  32  are connected to the auxiliary shaft, and therefore the electric machine  29  is completely uncoupled from drive train  1 , and is optionally connectible to shift transmission  6  by means of fixed gear  34 , which is firmly connected to the input part of friction clutch  4  and thus to crankshaft  3 , or by means of idler gear  20  of gear I, which may be a start-up gear. Through the connection to the idler gear  20 , when idler gear  32  is shifted the electric machine  29  is always connected to transmission output shaft  12  in a rotationally locked connection via fixed gear  15  of gear I. If gear I is selected, a connection is also made to transmission input shaft  5 . Idler gear  32  is firmly connected to fixed gear  35 , which meshes with the fixed gear  37  situated on rotor shaft  36  and sets a predefined transmission ratio. Air conditioner compressor  38  is situated coaxially to rotor shaft  36  and is driven by the latter. Electric machine  29  is fed by accumulator  39  or feeds electrical energy into the latter, depending on the operating mode as a motor or generator. 
         [0019]    Shifting clutch  30  is arranged together with shifting clutches  26 ,  27 ,  28  to be operated jointly by the shifting actuator. In this case the shifting actuator, together with the corresponding actuating devices, is designed according to the active interlock principle, so that when one of the gears I, II, III, IV, R is selected, and independent of the shift state of the latter, electric machine  20  is connectible to crankshaft  3  or to transmission output shaft  12  by means of shifting clutch  30 . 
         [0020]    This arrangement results below, among other things, in the following operating modes: 
         [0021]    Starting combustion engine  2 : 
         [0022]    Actuating shifting clutch  30  and thereby connecting idler gear  31  to fixed gear  34 , so that electric machine  29  is connected to crankshaft  3 . Disengaging friction clutch  4 . Supplying electricity to electric machine  29  and thereby starting combustion engine  2 . In this case a start-up gear, for example gear II, may already be selected, so that friction clutch  4  merely needs to be engaged to drive off immediately. 
         [0023]    Driving with electric machine  29 : 
         [0024]    Actuating shifting clutch  30  to connect idler gear  32  to idler gear  20  of gear I. Supplying electricity to electric machine  29 . The motor vehicle is propelled directly via fixed wheel  15 . 
         [0025]    Driving with combustion engine  2  supported by electric machine  29 : 
         [0026]    Actuating shifting clutch  30  to connect idler gear  32  to idler gear  20  of gear I. Supplying electricity to electric machine  29 . Engaging friction clutch  4 . In addition, another gear II, III, IV can be selected by means of shifting clutches  26 ,  27 . When a predefined speed of rotor shaft  36  is reached with increasing speed of crankshaft  3  or transmission input shaft  5  during an acceleration process, the speed of rotor shaft  36  can be limited for example by a motor intervention into the control of combustion engine  2 . 
         [0027]    Recuperation: 
         [0028]    Actuating shifting clutch  30  to connect idler gear  32  to idler gear  20  of gear I. Disengaging friction clutch  4 . Operation of electric machine  29  in generator mode. Optionally, to increase the deceleration effect of the shut-down or idling combustion machine  2 , friction clutch  4  may be at least partially engaged and its drag torque be used for deceleration. 
         [0029]    Electric machine  29  in operation uncoupled from the shift transmission  6 : Shifting of shifting clutch  30  into neutral position. Operation of air conditioner compressor  38  insofar as necessary. It goes without saying that in urgent cases air conditioner compressor  38  can also be driven in motor or generator mode. Alternatively, when electric machine  29  is not active, air conditioner compressor  38  can be driven with friction clutch  4  and idler gear  31  selected with a gear engaged or not engaged, or in deceleration mode with friction clutch  4  disengaged, by drive wheels  14  with idler gear  32  connected to auxiliary shaft  33 , by turning rotor shaft  36  with electric machine  29  short-circuited. 
         [0030]    Torque equalization by electric machine  29  while changing gears: 
         [0031]    If the intention is to shift up or down from a gear I, II, III, IV into a different gear, during the gear change during upshifting or downshifting processes a loss of traction power occurs under traction and a torque overload occurs during a downshift under deceleration. To compensate, torque is fed accordingly into transmission input shaft  12  by means of electric machine  23 , and is drawn off by generator operation in the event of a downshift under deceleration. To this end, shifting clutch  30  is actuated to connect idler gears  20 ,  32 , and torque is fed in or drawn off. 
       REFERENCE LABELS 
       [0000]    
       
           1  drive train 
           2  combustion engine 
           3  crankshaft 
           4  friction clutch 
           5  transmission input shaft 
           6  shift transmission 
           7  gear train 
           8  gear train 
           9  gear train 
           10  gear train 
           11  gear train 
           12  transmission output shaft 
           13  differential 
           14  driving wheel 
           15  fixed gear 
           16  fixed gear 
           17  fixed gear 
           18  fixed gear 
           19  fixed gear 
           20  idler gear 
           21  idler gear 
           22  idler gear 
           23  idler gear 
           24  idler gear 
           25  reversing gear 
           26  shifting clutch 
           27  shifting clutch 
           28  shifting clutch 
           29  electric machine 
           30  shifting clutch 
           31  idler gear 
           32  idler gear 
           33  auxiliary shaft 
           34  fixed gear 
           35  fixed gear 
           36  rotor shaft 
           37  fixed gear 
           38  air conditioner compressor 
           39  accumulator 
         I gear 
         II gear 
         III gear 
         IV gear 
         R gear