Operating method for a hybrid vehicle

0001The invention relates to a method for operating a hybrid motor vehicle with a Internal combustion engine and at least one electric machine, wherein the transition from a first operating state with a first drive torque into a second Operating state with a lower second drive torque before switching to second mode drive torque of the internal combustion engine through a reduction of Cylinder filling and / or closing a throttle valve is decreased in accordance with the Preamble of claim 1.

0002To the highest possible ride comfort in vehicles with internal combustion engines reach, it is necessary in particular in unsteady operating phases, no Torque jumps to produce in the drive train, as this vehicle jerking or a Vibration can generate in the drivetrain, which the driver as very unpleasant is perceived. Thus, in today's control of internal combustion engines partly implemented very comprehensive functions to ensure that such Torque jumps are avoided.

0003A well-known at an engine problem are bucking the Transition from the fired operation in the unfired operation (fuel cut). Here, the fuel injection and possibly also the ignition can not be stopped abruptly be substituted by the driver starting from a torque demand (accelerator partially or fully depressed) on the engine drag torque (fuel cut or Accelerator pedal is changed in position equal to zero percent). The the the difference between Engine torque resulting in gefeuertem operation and the engine drag torque Torque step increases before the fuel cut at a higher torque.

0004To reduce this torque jump is executed in today motor controls in the Generally implements a dashpot function which through a gradual torque reduction gefeuertem engine in accordance with a predetermined time profile, for example by Cylinder charge degradation (closing the throttle valve, gasoline engine directly or indirectly injecting in homogeneous operation) and / or reduce the injection quantity (direct injection gasoline engine in shifts or diesel engine) initially the moment to the minimum possible value is lowered, and then from the lowest possible torque at gefeuertem operating in the to switch fuel cut.

0005Since the discharge of the accelerator by the driver in most driving conditions very quickly is completed, a corresponding rapid torque reduction is expected by the driver. During a rapid adjustment of the moment when on the injection mass Torque reduction is possible because the injection quantity from one to the next cycle can be changed, the torque reduction on the charge path requires a larger Time (slow path), as well as in the currently used electronic Throttle only finite adjustment speeds are achieved and which also includes the located between the throttle valve and intake valve intake manifold volume to be evacuated have to be. For this reason, often in parallel with gasoline engines in homogeneous operation to Filling degradation worked with Zündwinkeleingriffen (fast path) to the driving torque to degrade (dashpot function) according to the predetermined desired course. These However Zündwinkelverspätungen have a fuel consumption prejudiced in consequence as the optimal efficiency operating points are left.

0006The minimal presentable moment in fired operation (during the dashpot sequence and immediately before the fuel cut) at a homogeneously operated gasoline engine in the Usually by the minimum permissible filling in combination with the associated spätest possible ignition angle determined. set are lower cylinder fillings and / or the Ignition timing further delayed, the combustion limit is not reached, that is, the combustion in the Cylinder then runs only insufficient or they are not from. If in a direct-injection gasoline engine in shifts (or even the diesel engine) the moment decreases over the injection mass, the limit is in this case either by the minimal possible injection mass of the injectors, as too short in solenoid valve injectors lead actuation periods usually means that the nozzle needle is no longer the end stop achieved what undefined nozzle needle positions and thus undefined injection masses leads, or by a maximum allowable combustion air ratio (flammable limit) certainly. Due to the principle thus is always maintained a residual torque jump.

0007Due to the moment reduction over the filling and the limitation of the Ignition retard arise particularly when homogeneously operated SI engine Disadvantages even when executing the dashpot function.

0008From DE 198 39 315 A1 discloses a propulsion system for a motor vehicle having a Internal combustion engine, an electric machine and a device for fuel cut the internal combustion engine is known, wherein the electrical machine to the internal combustion engine with a torque applied such that a ruckvermindernde effect brought becomes. For a reduction in the damage caused by terminating the fuel cut Acceleration jerk is the electric machine by means of active and controlled deactivation signal of the fuel cut. In this way, the electrical counteract the pending machine acceleration jerk prematurely, before these for the passengers is noticeable or possibly load change oscillations leads. To avoid shock, the electric machine can advantageously be used as a motor and as Generator act, depending on whether the damping to jerk from activation or Deactivation of the fuel cut stems.

0009The invention is based on the object, a method of the aforementioned type with to provide improved dashpot function.

0010This task is accomplished by a method of the aforementioned type having the in claim 1 Features marked resolved. Advantageous embodiments of the invention are shown in additional claims described.

0011For this purpose, it is provided according to the invention in a method of the aforementioned type that during the Reducing the drive torque by means of reduction of cylinder filling and / or Closing of the throttle flap, an ignition angle in dependence on the instantaneous Cylinder filling and / or in dependence on the instantaneous position of the throttle to a value is set, which for this current cylinder charge and / or for that current position of the throttle optimal or nearly optimal Efficiency of the internal combustion engine results wherein in addition the drive torque via a the drive torque acting opposite counter-torque at least one of electrical machines is reduced.

0012This has the advantage that the quick but fuel consumption, pollutant and for catalysts aging unfavorable engagement via the ignition angle to reduce the drive torque of Internal combustion engine is replaced by an engagement means of the electric machine so that by means of the electric machine a continuous adjustment of the moment (as positive negative) during the reduction of the drive torque, for example for an Fuel cut-off, the entire operating range of the engine with a very high Dynamics is possible. This achieves optimization of the performance, for example in Switch to boost mode, operation with a minimum driving torque or automated Switching of a transmission with lower fuel consumption and reduced Catalyst aging.

0013Suitably, at least one of the electric motors to reduce the Drive torque operated as a generator, wherein an electric power thus generated in an energy storage device, such as a battery or a memory Capacitor memory is stored. As a result, this electrical energy in another During the journey for an electromotive drive support or the supply of Vehicle electrical system can be used. This part of the otherwise at least by Ignition retard in many phases of operation with no benefit in exhaust or Coolant heat used transformed energy, which increases the overall efficiency.

0014For example, the first operating state is a fired mode, the second operating state a ungefeuerter operation and the second drive torque an engine drag torque. in this connection A firing of the engine stopped and in a unfired operation passed if the cylinder charging wirkungsgradoptimalem with at least virtually Ignition angle reaches the combustion limit. Preference is given here just before the transition in the unfired operating the cylinder charge and the firing angle to respective values ​​with greater distance provided combustion limit. For example, just before the transition in the unfired operating the cylinder charge starting from a value at the combustion limit 0.5% to 6%, particularly 1% to 3%, increased and / or immediately before the transition in the unfired operation of the ignition angle, starting from a value at the combustion limit to at least 3 ° KW, preferably at least 6 ° KW adjusted to early.

0015A transition to the unfired operation without torque jump with correspondingly increased driving comfort is achieved by the fact that after the transition to the unfired Operating at least one of the electrical machines, a driving torque in such a Drive train of the internal combustion engine is generated so that a time course of Drive torque from the current drive torque at the time of switching to unfired operation up to an engine drag torque in unfired operation of Engine runs smoothly.

0016Alternatively, the first mode is a ride on a first gear ratio and second operating state a ride with a second, from the first gear ratio different gear ratios.

0017To obtain a jerk-free transition as possible in the second operating state, is the Transition to the second operating state for a predetermined period of, for example, 10 ms to 100 ms, the drive torque is reduced via an ignition angle.

0018Conveniently, to reduce the drive torque over time, a desired torque curve predetermined over time and generates the electrical machine during the Reducing the drive torque, such a counter torque, that an actual curve of the Drive torque over time follows the torque command history.

0019The invention is illustrated below with reference to the drawing. This shows in the single Fig., a graphical representation of time variation of accelerator pedal position, Cylinder charging, ignition, torque which is applied by an electric machine is, and entire drive torque in the drive train.

0020The inventive method for operating a hybrid vehicle having Internal combustion engine and an example of a connected electric machine is in the single Fig. graphically illustrated. In the single Fig. Is on a vertical axis at 10 an angle of a pedal position in percent [%], at 12 a relative cylinder charge in percent [%] (Current value based on the maximum possible cylinder filling), at 14 a cylinder angle in degrees crank angle [° CA], at 16 a of the electric machine in the drive train Moment generated in Newton-meter [Nm] and at 18 an entire drive torque Powertrain applied in Newton-meter [Nm]. An arrow 20 indicates an adjustment the firing angle 14 by early and an arrow 22 indicates adjusting the ignition angle 14 retarded.

0021On a horizontal axis 24 the time is plotted. A graph 26 illustrates the Extending the pedal position 10 on the time 24, a graph 28 illustrates the course of the relative cylinder 12 through the filling time 24, a graph 30 illustrates the course of the Ignition angle 14 via the time 24, a graph 32 illustrates the course of the moment 16 the electric machine over time 24 and a graph 34 illustrates the course of the entire drive torque 18 over time 24th

0022At time t₁ 36 is a fuel cut-off, ie a ungefeuerter operation Internal combustion engine, due to the pedal position requested 0% and is followed by the reduction 18 the drive torque according to Graph 34 (dashpot function). At time t₂ 38 takes place then the fuel cut, for example, in that the fuel supply to the Internal combustion engine is interrupted. Of the graph 30, the time course of the 14 illustrates firing angle in accordance with the inventive method, in addition to the Compared with a dashed line 40, a time characteristic of the firing angle 14 in accordance with an in The prior art known methods for reduction of the drive torque 18 is shown.

0023According to the invention it is provided that with a reduction of the drive torque 18 according a predetermined time profile, as illustrated by graph 34, which as a "Dashpot" function is called, the drive torque 18 initially similar to previously over the dismantling of the cylinder charge 12 (Graph 28) and the closing of the Throttle valve (not shown) to reduce. The invention additionally another Adaptation of the actual torque to the desired course 34 via torque intervention of electric machine, said during the period of t₁ 36 to t₂ 38, the firing angle 14 (Graph 30) for the internal combustion engine at every operating point, ie especially when any Setting the cylinder charge and the throttle, optimum efficiency or is set approximately optimum efficiency.

0024In other words, the 40 depicted with dashed line conventional engagement on the firing angle 14, which is used for quick reduction of the drive torque, by the engagement of the electrical machine with a negative drive torque (Counter torque) in the period from t₁ 36 to t₂ 38 replaced. After time t₁ 36, ie, immediately after the request of the overrun mode generates an electric machine negative drive torque according to graph 32, while the cylinder charge 12 according to graph 28 is slowly degraded. At the same time, according to Graph 30, the firing angle 14 to one for the respective cylinder charging held 12 optimum efficiency level, ie, the firing angle 14 is adjusted with the gradual removal of the cylinder charge 12 by early (arrow 20). this happens in contrast to the conventional reduction of the drive torque 18, wherein the firing angle 14 is displaced greatly retarded (arrow 22), which with a dashed line 40 for comparison is illustrated. Through this combination of engagement in the cylinder charge 12 with the negative or counter-torque of the electric machine according to graph 32 it is achieved that the entire drive torque 18 in the period t₁ 36 to t₂ 38 according to the predetermined Dashpot function 34 is terminated.

0025After time t₂ 38, that is, after the start of fuel cut, has the dashpot function 34 have a value for the entire drive torque 18, which is higher than a Value of an engine drag torque 42, so that it is of the conventional method Fuel cut-off at 44 comes to a torque jump. According to the invention it is in addition optionally provided that the electric machine immediately after the time t₂ 38 positive, with time verringemdes drive torque is generated so that a stepless transition of the entire drive torque 18 at the time t₂ 38 on the Engine drag torque is achieved 42.

0026The by the regenerative operation of the electric machine in the period between t₁ 36 and t₂ 38 generated electric energy is preferably (with the appropriate Efficiencies) stored in an electric energy storage device and can then in the further course of the journey for an electromotive drive assistance or Supply the vehicle electrical system can be used. The electrical energy storage is , for example, a battery storage and / or a capacitor storage. This at least a portion of otherwise by the retardation of the ignition angle in many 14 Operating phases useless used converted energy in the exhaust heat or coolant heat, which increases the overall efficiency of the drive system. This Energy conversion process during the regenerative operation of the electric machine typically lasts for 200 ms to 800 ms, so that the use of the generated electrical energy offers a capacitor storage because these with the electric power good efficiencies and store in this short phase with high performances can so that the realizable by the electric machine generating torque or Counter-torque is not limited by the performance of the energy storage.

0027Is or are the energy storage exceptionally charged to 100%, can further in the conventional methods for the torque reduction be used. On the other hand, for these short-term transactions also always a small Einspeicherreserve be retained without the overall system performance by significant changes.

0028In an advantageous embodiment of the inventive method can also Torque reduction to the engine drag torque 42 by means of the electric machine take place, as previously explained and shown in the single Figure. in circuit 46 so that a Transition from fired into the unfired operation at time t₂ 38 no carried torque jump more what the ride comfort compared to the present state, where applicable, in direct injection gasoline engines in the stratified charge mode or at Diesel engines further improved. The time t₂ 38, in which the firing of the Internal combustion engine is interrupted, corresponds to that point in time at which the Cylinder filling at 12 (at least almost) optimal ignition angle reaches the combustion limit. At this point 38 switches to the electric machine from a negative generator a positive (motor) torque. Here, in order at the time t₂ 38 a jumpy to make the transition, it is optionally provided only here a very short transition period carried out by, for example, 10 ms to 100 ms, within which ignition angle by derogation allowed by optimum efficiency values ​​to the combustion-engine torque 18 according to graph abzusteuern 34 and the electric motor aufzusteuern torque according Graph 32nd In this procedure, the desired torque curve 34 are also adapted so that the entire dashpot function 34 in the same Time as in the conventional process expires.

0029In a particularly advantageous embodiment of the invention, filling cylinder 12 and Ignition 14 immediately before the transition to the fuel cut-off at the time t₂ 38 Values ​​set that a homogeneous driven a greater distance from the internal border Gasoline engine exhibit. For example, the relative cylinder charge is 12 by 0.5 to 6 percent, preferably increased by 1 to 3 percent, and / or - if the ignition angle is adjusted here by late is - the ignition angle by at least 3 crank angle degrees, preferably by at least 6 Degree crank angle by adjusting early (compared to today's standard exported parameterization or proceeding before the latest possible ignition angle immediately the time t₂ 38). This ensures that even in unfavorable Boundary conditions, such as inaccuracies in the fuel metering or air and possibly resulting air ratio deviations, an almost complete Combustion in the cylinder occurs, so that a downstream catalyst system, for example, consisting of one or more catalysts, in particular also Precatalyzer plus downstream NO_xStorage catalyst, in this transient phase no additional exposure to unburned fuel portions learns. At the same time a cause this advance a decrease in the exhaust or catalytic converter temperature, so that a total of a reduced aging of the exhaust gas aftertreatment system is achieved.

0030The novel implementation of the dashpot function 34 can also be employed if subsequently, that is at time t₂ 38, no fuel cut Segregate z. B. due to low engine speed or component protection reasons the fired operation with minimal Driving torque is maintained.

0031The method described above can in principle even during shifting of automatic transmissions, such as torque converters, transmissions or direct are dual clutch transmissions used. The switching times of automatic transmissions must be carried out extremely briefly to an appropriate ride comfort Guarantee. At the same time, the motor torque must be reduced for the switching operation and the Engine and the transmission speed are synchronized. For these interventions is the moment Filling path of the internal combustion engine is usually not fast enough, so that here at yet worked high cylinder charges with partly extremely retarded ignition angles needs to be in order according to the drive torque generated by the internal combustion engine to reduce. The resulting exhaust gas temperature increases lead to a strong Catalyst loading. In order to counteract this, the mixture must be enriched partially be, which means an increase of fuel consumption. Again, the electrical Machine instead of Zündwinkelverspätungen for the torque reduction and the Speed ​​reduction (for engine speed enhancement during downshifts) in an analogous Forms are as used in the dashpot function described above. Since, in this Case, in addition, the catalyst loading or the fuel consumption by sacrificing a Mixture enrichment is reduced with still high air mass flows, arising more significant benefits for the interpretation of the exhaust gas aftertreatment system or the Overall efficiency of the drive.

0032With the invention described above, it is further possible to make the precious metal content of lower catalysts. Vehicles with lean runnable engine, which in New European Driving Cycle with thermally undamaged catalysts (with a stored sulfur mass less 0.2g / l of catalyst volume) and a time fired lean operation Share (without coasting phases) with lambda> 1.15 of at least 250 Seconds (in particular at least 350 seconds) a HC emissions of less 0.07 g / km and NO_xachieve emissions of less than 0.05 g / km, are now in the prior Technology equipped with catalysts, the noble metal content of greater than or equal to 100 g / ft³exhibit.

0033With the use of catalyst systems consisting of at least one NOx storage catalytic converter and possibly at least an upstream pre-catalyst, the precious metal content at least a catalyst, to values ​​below 100 g / ft³, And in particular less than or equal 80 g / ft³ and preferably to less than or equal 60/40/20/10 g / ft³ When lowered, without that the emissions in the NEDC with increasing vehicle mileage over the original version with higher precious metal content and without the invention Process deteriorate.

0034Even with conventional gasoline engines is to use the method described above, Possibility the precious metal content of the catalysts based on the standard today executed values ​​and 10%, preferably 20% and most preferably by 30% lower, without the emissions in the NEDC with increasing vehicle mileage compared with the original version with higher precious metal content and without the The method according to the invention deteriorate. In particular, the precious metal content can to less than or equal 40/30/20/10/5 g / ft³ be lowered.

0035It is also possible to proceed with dynamic positive load change in a similar way. Here often the problem occurs that during strong acceleration, sudden by Torque change oscillations are induced in the drive line, which subsequently by Ignition angle are damped again. It provides in particular from Fuel consumption reasons, which damping at least one of the electrical making machinery and the electrical energy generated in regenerative electric Energy storage cache.

LIST OF REFERENCE NUMBERS

0036<dl tsize="2" compact="compact"><dt>10</dt><dd>Angle of a pedal position in percent [%]</dd><dt>12</dt><dd>relative cylinder charge in percent [%]</dd><dt>14</dt><dd>Cylinder angle in degrees crank angle [° CA]</dd><dt>16</dt><dd>a signal generated by the electric machine in the drive train torque in Newton-meters [Nm]</dd><dt>18</dt><dd>an entire drive torque in the drive train in Newton-meter [Nm]</dd><dt>20</dt><dd>Arrow: the ignition angle 14 by early</dd><dt>22</dt><dd>Arrow: the ignition angle 14 by late</dd><dt>24</dt><dd>timeline</dd><dt>26</dt><dd>Graph: Evolution of pedal position 10 over time 24</dd><dt>28</dt><dd>Graph: Evolution of relative cylinder filling 12 over time 24</dd><dt>30</dt><dd>Graph: History of the firing angle 14 about the time 24</dd><dt>32</dt><dd>Graph: History of the moment 16 of the electric machine over time 24</dd><dt>34</dt><dd>Graph: the course of the entire drive torque 16 over time 24</dd><dt>36</dt><dd>time t₁: Requirement of fuel cut</dd><dt>38</dt><dd>time t₂: Implementation of fuel cut</dd><dt>40</dt><dd>Dashed line: the course of the firing angle 14 over time (conventional method)</dd><dt>42</dt><dd>Engine drag torque</dd><dt>44</dt><dd>Torque jump (conventional method)</dd><dt>46</dt><dd>circle</dd></dl>