Abstract:
In a drive train assembly for a motor vehicle, which includes successively arranged an internal combustion engine, a starter clutch, an electrical machine a drive clutch, and an automatic transmission, preferably an automated manual transmission, a common double clutch positioner is assigned to the two clutches, which enables a selective setting of the applicable status (open or closed) of the clutches by assumption of a corresponding switching position.

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to a drive train assembly for a motor vehicle and to a method for controlling it. 
     From the prior art, drive train assemblies are known in which in succession an internal combustion engine, a starter clutch, an electrical machine, a drive clutch, and an automatic transmission, preferably an automated manual transmission, are disposed. The electrical machine can be used, among other purposes, as a starter-generator. Typically, the components listed are adapted to the various situations that occur during operation of the motor vehicle in a coordinated way in terms of their operating states. Usually, such control is effected via a central engine control unit, which specifies set-point variables to final control elements assigned to the various components of the drive train assembly. For instance, the starter clutch and the drive clutch have separate clutch positioners, with which a status (open or closed) of the clutches can be set selectively. Reducing the number of parts in the components present in the drive train assembly is a goal for manifold reasons. On the one hand, fewer parts means reduced material costs and reduced effort and expense for assembly, so that production costs can be reduced. On the other hand, the attendant space saving makes it possible to optimize the installation space, and the reduced weight then reduces fuel consumption on the part of the motor vehicle. 
     SUMMARY OF THE INVENTION 
     An additional reduction in the number of parts is possible as a result of the drive train assembly according to the invention and the method for controlling its operation. Because a common double clutch positioner is assigned to the two clutches, which enables a selective setting of the applicable status (open or closed) of the clutches by assumption of a corresponding switching position, one of the two usual clutch positioners can be dispensed with. 
     In a preferred embodiment of the invention, a control unit for specifying the switching positions is assigned to the double clutch positioner. The specification of the switching positions is effected as a function of the operating states and/or operating parameters of the assemblies present in the motor vehicle. In many operating situations, recourse can be had to time-tested control mechanisms. 
     The double clutch positioner preferably has up to four switching positions, whose location can be defined by the specification of different disengagement paths for the double clutch positioner, in which 
     both clutches are closed (coupling status Z 1 ), or 
     the starter clutch is open and the drive clutch is closed (coupling status Z 2 ), or 
     both clutches are open (coupling status Z 3 ), or 
     the starter clutch is closed and the drive clutch is open (coupling status Z 4 ). 
     In a further preferred embodiment of the invention, only three switching positions in the double clutch positioner are implemented, and either the aforementioned clutch status Z 3  or the clutch status Z 4  is dispensed with. In operating situations of the motor vehicle in which the aforementioned clutch statuses would be necessary, this is compensated for by a control of the operating states of the assemblies present in the motor vehicle. To that end, it is for instance possible, via the control unit, to actuate means with which the manual transmission can be shifted into a neutral position. 
     The present invention furthermore discloses especially preferred embodiments for the case where the clutch status Z 4  is dispensed with. In at least the following operating situations, 
     starting of the engine; 
     the shifting operation in the transmission; 
     a static mode of the engine; and 
     hard braking, for example ABS braking, with drive effected via the engine, 
     the missing clutch status Z 4  is compensated for in that the clutch status Z 1  and a neutral position of the transmission are set. To change gears, the transmission must be shifted without load and synchronized by means of controlling the engine and the electrical machine. It is also preferred that with the clutch status Z 4  dispensed with, the startup of the motor vehicle be designed such that the clutch status Z 1  and a gear are selected in the transmission, and the drive takes place via a sliding starter clutch. 
     In a further preferred embodiment of the invention, in which the clutch status Z 3  has been dispensed with, a pulsed start of the engine can be realized by providing that at least intermittently, the clutch status Z 2  and the neutral position of the transmission are specified to the double clutch positioner. If the clutch status Z 3  is dispensed with, hard braking, such as ABS braking, with drive via the electrical machine, can be designed such that shifting is done first into the clutch status Z 1  and then into the clutch status Z 4 . The closure of the clutch K 2  can be delayed via additional elements, until the status Z 1  is attained. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be described in further detail below in terms of exemplary embodiments in conjunction with the associated drawings. Shown are: 
     FIG. 1, a first variant for a drive train assembly, which has a double clutch positioner with three switching positions; and 
     FIG. 2, a second variant for this kind of double clutch positioner, with three switching positions. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In FIGS. 1 and 2, drive train assemblies  10  for a motor vehicle are shown schematically. The drive train assembly  10  includes, among other elements, in succession an internal combustion engine  12 , a starter clutch K 2 , an electrical machine  14 , a drive clutch K 1 , and an automatic, preferably automated manual transmission  16 . The electrical machine  14  can be designed as a starter-generator and in that case, with the starter clutch K 2  closed, transmits a torque required to start the engine  12 . The electrical machine  14  can also be designed as an asynchronous machine and optionally used to drive the motor vehicle and to recharge a battery. The required means or control sequences for defining such functionalities are well known and will therefore not be described further at this point. 
     For the sake of simplicity, no attempt has been made, either, to show a control unit (engine control unit) that can be used to coordinate the components of the drive train assembly  10 . By way of such a control unit, the operating states and/or operating parameters of the various components of the drive train assembly  10  can be varied, by the specification of suitable set-point variables to final control elements assigned to the various components. Especially the two clutches K 1 , K 2  can be actuated by a common double clutch positioner, not shown. An actuation of the clutches K 1 , K 2  leads to a respective change in the status of each of the clutches K 1 , K 2 . The status is then either “open” or “closed”. 
     The double clutch positioner should have a maximum of four switching positions, between which shifting can be done, for instance by the specification of different disengagement paths. The possible switching positions are as follows: 
     both clutches K 1 , K 2  are closed (coupling status Z 1 ), 
     the starter clutch K 2  is open and the drive clutch K 1  is closed (coupling status Z 2 ), 
     both clutches K 1 , K 2  are open (coupling status Z 3 ); and 
     the starter clutch K 2  is closed and the drive clutch K 1  is open (coupling status Z 4 ). 
     Theoretically, all four clutch statuses Z 1 , Z 2 , Z 3 , Z 4  are needed to control the operation of the motor vehicle. In the variants  1  and  2  shown in FIGS. 1 and 2, however, one of the clutch statuses Z 3  or Z 4  can be dispensed with in each case. 
     Via the control unit, the switching position to be set can be specified to the double clutch positioner. This specification is done as a function of the operating states and/or operation parameters of the assemblies present in the motor vehicle. Thus the prevailing peripheral conditions can be addressed flexibly in accordance with the operating situation, and a starting event, for instance, of the engine  12  or a startup of the motor vehicle can be controlled. 
     In variant  1  shown in FIG. 1, the clutch status Z 4 , in which the starter clutch K 2  is closed and the drive clutch K 1  is open, is dispensed with. At least in the following operating situations, it is then necessary, via the control unit, to make interventions into the operating states and/or parameters of the components of the drive train assembly  10 : 
     starting phase of the engine  12 ; 
     a shifting operation in the manual transmission  16 ; 
     a static mode of the engine  12 ; and 
     hard braking, for example ABS braking, with drive effected via the engine  12 . 
     In the cases listed, the clutch status Z 1  is specified to the double clutch positioner on the one hand and a neutral position N in the manual transmission  16  on the other are now specified by means of the control unit. In this way, the manual transmission  16  and the assemblies following it can be decoupled, for instance during the starting operation. 
     If the clutch status Z 4  is dispensed with, then startup of the motor vehicle can be controlled such that the clutch status Z 1  is set, a gear in the manual transmission  16  is specified, and the startup is effected via a sliding starter clutch K 2 . Optionally, an rpm adaptation of the engine  12  must be performed, for instance in order to assure a minimum rpm or to make an ensuing gear synchronization easier. 
     In the variant shown in FIG. 2, the clutch status Z 3  has been dispensed with, in which both clutches K 1 , K 2  are open. In the event that a pulsed start of the engine  12  is to be performed, then at least intermittently the clutch status Z 2  and a neutral position N of the manual transmission  16  must be specified. 
     If ABS braking is done while clutch status Z 3  is dispensed with and driving is effected via the electrical machine  14 , then a transition must be made from the clutch status Z 1  to the clutch status Z 4 , before the drive clutch K 1  can be opened in order to decouple the inertias of the engine  12  and of the electrical machine  14 . At the onset of hard braking, for example the ABS braking, not only the inertia in the drive train but also a surge in moment upon starting of the engine  12  have an effect. The closure of the starter clutch K 2  can be delayed optionally by means of suitable additional elements, such as a damper that switches over on its own.