Abstract:
A method for controlling a hybrid drivetrain in a motor vehicle having an internal combustion engine, which has a crankshaft and an electric machine which can be operated as a motor and generator, having a rotor operatively connected to the crankshaft, having a torsional vibration damper operatively connected to the crankshaft, having a battery device for exchanging electrical energy with the electric machine, and having a control unit for controlling the battery device and the electric machine, and a corresponding battery device. To operate the electric machine with rapidly changing motor and generator operation without damaging the battery device, the electric machine is operatively connected to at least first and second electric batteries of the battery device, where at least part of the time one of the batteries is charged in the rhythm of occurring residual vibrations of the torsional vibration damper, while the other is discharged.

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/DE2012/000243 filed Mar. 12, 2012, which application claims priority from German Patent Application No. 10 2011 016 012.4 tiled Apr. 4, 2011, which applications are incorporated herein by reference in their entireties. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The invention relates to a method for controlling a hybrid drivetrain in a motor vehicle having an internal combustion engine, which has a crankshaft and an electric machine which can be operated as a motor and a. generator, having a rotor operatively connected to the crankshaft, having a torsional vibration damper operatively connected to the crankshaft, having a battery device for exchanging electrical energy with the electric machine, and having a control unit for controlling the battery device and the electric machine, and a corresponding battery device. 
       BACKGROUND OF THE INVENTION 
       [0003]    Hybrid drivetrains are known from series applications in motor vehicles. These hybrid drivetrains employ, for example, an electric machine, which serves as a starter for the combustion engine, as an additional or part-time solitary drive, and for recovering the kinetic energy of the motor vehicle, as a motor and generator; the electric machine being operatively connected to a battery device, which stores and emits electrical energy. 
         [0004]    A device for reducing non-uniformities of rotation of a combustion engine is also known from German Patent No, 197 09 299 A1, where half-waves from the electric machine switched to generator operation which lie above a mean torque of the combustion engine are damped and the released energy is stored in the battery unit, and the electric machine is driven to fill out half-waves lying below a mean torque, energy being taken from the battery device. All-in-all, the charging and discharging currents which occur here at the battery device in the rhythm of the non-uniformities of rotation of the combustion engine are high, so that the battery device may not have sufficient recharging kinetics and is damaged in the course of time due to the recharging. 
         [0005]    Furthermore, the non-uniformities of rotation, such as torsional vibrations in modem combustion engines are so high, for example, due to downsizing and the like, that traditionally employed torsional vibration dampers meet their capacity limits. 
       BRIEF SUMMARY OF THE INVENTION 
       [0006]    The object of the invention is therefore to operate a hybrid drivetrain in such a way that, on the one hand, the torsional vibrations of the combustion engine are damped in a satisfactory manner, and, on the other hand, the battery device is spared. The object of the invention is also to design a corresponding battery device so that it has longer and better functionality, for example, with high-frequency recharging processes between charging and discharging. 
         [0007]    The object is fulfilled by a method for controlling a hybrid drivetrain in a motor vehicle, having an internal combustion engine, which has a crankshaft and an electric machine, which can be operated as a motor and generator, having a rotor operatively connected to the crankshaft, having a torsional vibration damper operatively connected to the crankshaft, having a battery device for exchanging electrical energy with the electric machine, and having a control unit for controlling the battery device and the electric machine, the electric machine being operatively connected to at least first and second electric batteries of the battery device, and at least part of the time being charged in the rhythm of occurring residual vibrations of the torsional vibration damper of one of the batteries, while the other is being discharged. For example, to damp the residual vibrations of the torsional vibration damper through the alternating operation of the electric machine in motor and generator mode, the recharging currents, which occur with high frequency at the battery device, can be controlled such that one battery is only charged and the other is only discharged. Such an operating mode helps to conserve the batteries in the battery device, thereby prolonging their service life. 
         [0008]    To take account of a charge or discharge state of the batteries, there is also a provision to switch them to a charging or discharging mode, independent of their charged condition, by the control unit, whose function may be provided in one or more physical control devices and control units, in this connection, technically known devices, for example, devices that are already present in the batteries in an advantageous manner to determine the charged condition, can be conveyed to the control unit, which controls in particular the charging and discharging currents for operating the electric machine which damps the residual vibrations. It is understood that during the operating states of the electric machine, for example, during the start, a recovery or the like, both batteries may also be simultaneously charged or discharged. 
         [0009]    Furthermore, damping of the residual vibrations by means of the electric machine may also be suspended if the charge state or operating condition of the batteries falls below a specified residual charge or residual capacity, for example, at very low temperatures, during long drives with the support of the electric machine or the like. 
         [0010]    In this connection, besides controlling the battery unit, the control unit controls the electric machine, while the battery switched to the charging state is charged by means of half-waves that lie above a mean torque of the residual vibrations, which are converted to electrical energy by driving the electric machine, and the battery switched to the discharging state drives the electric machine by half-waves that lie below a mean torque of the residual vibrations to compensate. The operating data for controlling the electric machine and the battery device are provided by corresponding sensor devices for detecting rotational characteristics such as angles of rotation and their temporal derivatives from shafts such as the crankshaft of the combustion engine, the transmission input shaft(s) of a gear unit, the rotor shaft of the electric machine, inner variables of the engine controller of the combustion engine such as engine characteristics, upper dead-center position and the like. 
         [0011]    The object is also fulfilled by a battery device for carrying out the proposed method in a hybrid drivetrain which has first and second batteries which are alternately connectible by means of current-direction-sensitive switches and a control unit for connecting the switch, as well as a frequency converter. In this case, the minus pole is preferably grounded and the plus pole is connected by means of the switch, Alternatively, the grounding paths of the batteries can be connected by means of the proposed switches. To this end, the control unit issues a control signal in a preferred manner to two alternately switching logic switches, which switch the switches themselves, where in a preferred embodiment a switch for the charging current and a switch for the discharging current are provided at each plus pole, and these are alternately switched contrary to each other. In order to damp the residual vibrations of the torsional vibration damper, the switches are switched alternately with reference to the batteries, so that only one battery is charged and the other is discharged. If the electric machine is to start the combustion engine in motor mode or to deliver additional drive torque in a boost mode, the discharge switches of both batteries can be switched and the charge switches deactivated. In the case of recovery with the motor vehicle in deceleration mode, on the other hand, the charge switches of both batteries can be switched and the discharge switches deactivated. It is understood that the connection layout of the switches can be designed so that, for example, for simultaneous discharging or simultaneous charging of both batteries the switches can be switched accordingly, for example, the charge switches and the discharge switches can be connected simultaneously. 
         [0012]    In an embodiment of a battery device, devices may be provided in each of the batteries to ascertain the charge state, which have a signal connection to the control unit and report the present charge state of the batteries, right down to individual charge states of the battery cells. The control unit registers the charge states and determines a charging plan for the various operating states of the motor vehicle, for example, for damping the residual vibrations of the torsional vibration damper by means of the electric machine. The control unit registers and/or obtains for this purpose data for appraising the operating states, for example, starting the combustion engine, shifting the transmission, compression and acceleration modes of the motor vehicle and the like. 
         [0013]    The switches may be made, for example, of active electronic components, e.g., MOSFETs (metal-oxide-semiconductor field-effect transistors). However, IGBTs (insulated-gate bipolar transistors) have proven to be advantageous, which, in contrast to MOSFETs, block completely against the switching direction due to the absence of suppressor diodes. 
         [0014]    Lead storage batteries and the like may be used, for example, as the batteries. However, lithium-ion batteries have proven advantageous due to their favorable power-to-weight ratio and their time-dependent charging and discharging behavior. Connecting the latter by means of the switches prevents damage, which can occur, for example, due to subjecting them to micro-cycles, as are necessary when damping residual vibrations by means of the electric machine, Due to the currents that are directed through the converter and the switches into the corresponding battery in only one direction of flow, long charging cycles are produced, which can he set as macro-cycles for each battery, from a low charge state up to a prescribed charge state. When the batteries are designed with the same capacity, each battery may be charged alternately to approximately the maximum capacity. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]    The nature and mode of operation of the present invention will now be more fully described in the following detailed description of the invention taken with the accompanying drawing figures, in which: 
           [0016]      FIG. 1  is a circuit diagram for controlling the charge states of batteries of a. battery device; 
           [0017]      FIG. 2  is a depiction of charging processes of a conventional battery device having a battery and the battery device of the present invention, over time; 
           [0018]      FIG. 3  is a depiction of the currents appearing in a hybrid drivetrain during a compensation of residual vibrations of a torsional vibration damper at a conventional battery device and the battery device of the present invention, over time; and, 
           [0019]      FIG. 4  is a circuit diagram similar to the circuit diagram of Figure I for controlling the charge state of batteries of a battery device. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0020]    At the outset, it should be appreciated that like drawing numbers on different drawing views identify identical, or functionally similar, structural elements of the invention. While the present invention is described with respect to what is presently considered to be the preferred aspects, it is to be understood that the invention as claimed is not limited to the disclosed aspects. 
         [0021]    Furthermore, it is understood that this invention is not limited to the particular methodology, materials and modifications described and, as such, may, of course, vary. it is also understood that the terminology used herein is for the purpose of describing particular aspects only, and is not intended to limit the scope of the present invention, which is limited only by the appended claims. 
         [0022]    Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood to one of ordinary skill in the art to which this invention belongs. Although any methods, devices or materials similar or equivalent to those described herein can be used in the practice or testing of the invention, the preferred methods, devices, and materials are now described. 
         [0023]      FIG. 1  shows circuit diagram  2  of battery device  1 , having first and second batteries  3 ,  4  with the same or different capacity, control unit  5  and converter  6 , which are connected to each other by means of grounding line  7 . Converter  6  forms the interface to the electric machine (not shown), and transforms the direct current of batteries  3 ,  4  into a plurality of alternating current phases, of which only one phase w is depicted here symbolically, to drive the electric machine, 
         [0024]    Situated between converter  6  and batteries  3 ,  4  in each case are two parallel-switched switches  8 ,  9 ,  10 ,  11  in the form of IGBTs connected oppositely in regard to their switch position, so that with gates of switches  8 ,  9 ,  10 .  11  connected in each case with the same signal level through logic switches  12 ,  13 , in each case one switch of battery  3 ,  4  is switched to conductive and the other to non-conductive. in this case, the gates are connected so that, for example, at battery  3 , when a positive level is present at output Out 1  of control unit  5 , switch  8  of battery  3  and switch  11  of battery  4  are switched so that when an AC signal is present at access line  14  only battery  3  receives charging Current through dosed switch  8 , while switch  10  which is responsible for the charging current of battery  4  remains open. In regard to discharge current, switch  9  of battery  3  is open, and a discharge current is able to flow from battery  4  through closed switch  11 . 
         [0025]    If the level at output Out 1  is set to Low, inversely switched logic switches  12 ,  13  issue a level to the gates of switches  9 ,  10 , so that the discharge current from battery  3  and the charge current for battery  4  are switched through switch  9 , while switches  8 ,  11  remain open. 
         [0026]    The connection of output Out! of control unit  5  is dependent on the charge states ascertained in batteries  3 ,  4  by devices  15 ,  16 , which are made up of the charge states of the individual cells and are fed to inputs In 1 , In 2  of control unit  5  by means of signal lines  17 ,  18 . 
         [0027]      FIG. 2  shows Diagram  19 , in which curves  20 ,  21 ,  22  represent the charge states of batteries against time in the range of, for example, several minutes to several hours, where these charge states may vary and depend among other things on the capacity of the batteries and their electrode kinetics. The actual excitations of the drivetrain, which the torsional vibration damper in the drivetrain does not damp adequately, cause small waves in the range of approximately 100 Hz in the DC section which is downline from the converter. The depiction of the long-term charging process and the depiction of the AC portion of the excitations are shown overdrawn in Diagram  19  to explain the effects. 
         [0028]    Curve  22 , identified using the symbols ‘+,’ shows a conventional battery device having a charge state of approximately 30% during a compensation of residual vibrations of a torsional vibration damper by means of an electric machine, which is connected to the single battery of the battery device. The battery is charged and discharged here using micro-cycles, which may lie within the range of the frequency of the occurring residual vibrations of the torsional vibration damper. The battery may be damaged by such micro-cycles and have a short service life. 
         [0029]    Curves  20 ,  21 , identified using the symbols ‘o’ and ‘x’ respectively, show the charge states of battery device  1  of  FIG. 1 , first and second batteries  3 ,  4  having different capacities—as is evident from  FIG. 2 . The connection of batteries  3 ,  4  in accordance with circuit diagram  2  results in the uniform charging and discharging of the batteries over macro-cycles, which can be made to approximate the charging and discharging processes recommended. by the manufacturer. In this case, the battery with curve  20  has the smaller capacity, so that it determines the macro-cycles, which may range from a few minutes to a few hours in length. The charge states are measured at the batteries and are registered by control unit  5 , which controls the switching of switches  8 ,  9 ,  10 ,  11  to adjust the macro-cycles. In one embodiment, the battery with curve  20  is charged up to a charge state of 80% of the total capacity and discharged to 20% thereof, which results in a recharging of between 20% and 32% of its total capacity for the battery having the greater capacity. 
         [0030]      FIG. 3  shows Diagram  23 , with currents occurring cyclically at battery devices during the compensation of residual vibrations of a torsional vibration damper by means of an electric machine connected to the batteries of the battery devices, over time. Here curve  24 , identified using the symbols ‘x,’ shows the currents of a conventional battery device having a single battery, which is recharged micro-cyclically at the frequency of the alternating currents. The batteries connected in accordance with circuit diagram  2  of  FIG. 1 , on the other hand, are only charged or discharged, so that over a relatively long macro-cycle they undergo only positive or negative current cycles, as may be seen from curves  25 ,  26  identified using the symbols ‘o’ and respectively, which each show the current of one battery. 
         [0031]      FIG. 4  shows circuit diagram  2   a  of first and second batteries  3   a,    4   a  with the same or different capacity, control unit  5   a  and converter  6   a,  which are connected to each other by means of grounding line  7   a  and access line  14   a . Converter  6   a  forms the interface to electric machine  27 , and converts the DC current of batteries  3   a,    4   a  to a plurality of AC phases u, v, w to drive electric machine  27 . At the same time, phase-selective commutation currents or commutation voltages in the range from 100 Hz to 1 kHz are output, while the voltage modulations recovered by electric machine  27  to damp the vibration of the drivetrain, which are transmitted via converter  6   a  to the DC network, i.e., via access line Ha and grounding line  7   a  to the batteries, lie within the range from approximately 60 to 100 Hz. Switches  8   a,    9   a,    10   a,  Ha. are addressed directly by control unit  5   a  by means of control lines  28 ,  29 ,  30 ,  31 , and are thereby placed in a through-connected or open state. 
         [0032]    Because of the free design of the connection of switches  8   a,    9   a,    10   a,    11   a  by control unit  5   a,  one of batteries  3   a,    4   a  can be charged while the other is being discharged. To this end, for example, switch  8   a  is connected through in the direction of battery  3   a  and switch Ha is connected through in the direction of converter  6   a,  while switches  9   a,    10   a  are open. This causes battery  3   a  to be charged and battery  4   a  to be discharged. By closing switches  8   a,    10   a  in the same direction, both batteries  3   a,    4   a  are charged, for example, during recovery of the drivetrain while the motor vehicle is decelerating, and by closing switches  9   a,    11   a  in the same direction both batteries  3   a,    4   a  are discharged simultaneously, for example, while starting the combustion engine or when the drivetrain is in boost mode. 
         [0033]    Control unit  5   a  has a signal connection to batteries  3   a,    4   a  and converter  6   a  by means of signal lines  17   a,    18   a,    32 , and thereby controls the charging of the batteries and the commutation of electric machine  27 . 
         [0034]    Thus, it is seen that the objects of the present invention are efficiently obtained, although modifications and changes to the invention should be readily apparent to those having ordinary skill in the art, which modifications are intended to be within the spirit and scope of the invention as claimed. It also is understood that the foregoing description is illustrative of the present invention and should not be considered as limiting. Therefore, other embodiments of the present invention are possible without departing from the spirit and scope of the present invention. 
       LIST OF REFERENCE NUMBERS 
       [0000]    
       
           1  battery device 
           2  circuit diagram 
           2   a  circuit diagram 
           3  battery 
           3   a  battery 
           4  battery 
           4   a  battery 
           5  control unit 
           5   a  control unit 
           6  converter 
           6   a.  converter 
           7  grounding line 
           7   a  grounding line 
           8  switch 
           8   a  switch 
           9  switch 
           9   a.  switch 
           10  switch 
           10   a  switch 
           11  switch 
           11   a  switch 
           12  logic switch 
           13  logic switch 
           14  access line 
           14   a  access line 
           15  device 
           16  device 
           17  signal line 
           17   a  signal line 
           18  signal line 
           18   a  signal line 
           19  diagram 
           20  curve 
           21  curve 
           22  curve 
           23  diagram 
           24  curve 
           25  curve 
           26  curve 
           27  electric machine 
           28  control line 
           29  control line 
           30  control line 
           31  control line 
           32  signal line 
         In 1  input 
         In 2  input 
         Out 1  output 
         u phase 
         v phase 
         w phase