DE10242115A1 - Method, computer program and control and / or regulating device for operating an internal combustion engine, and internal combustion engine - Google Patents

Abstract

An internal combustion engine comprises at least one intake valve, the operation of which can be described at least by the parameters opening angle, closing angle, valve lift curve (H1, H2) and phase position (pn) of the valve lift curves (H1, H2,). At least one (pn) of the parameters can be continuously adjusted and at least one other parameter (H1, H2) can be switched in stages. In order to avoid jumps in the torque delivered by the internal combustion engine when switching, it is proposed that before switching (74) the step-by-step parameter (H1, H2) the continuously adjustable parameter (pn) is set (72) in such a way that when switching (74) of the step-by-step switchable parameter (H1, H2) does not change or does not significantly change at least one state variable (rl) of the combustion of a combustion chamber assigned to the intake valve.

Description

State of the art

The invention initially relates to a method for operating an internal combustion engine with at least one Inlet valve, the operation of which at least by the Parameters opening angle, closing angle, valve lift curve and Phase position of the valve lift curve can be described, and where at least one of the parameters is continuous adjusted and another parameter switched in stages can be.

Such a process is known from the market. A corresponding internal combustion engine has a so-called "variable valve timing". Such variable Valve controls have the advantage that especially when Internal combustion engines, which also with high speeds can be operated, the demand for low Exhaust emissions and low fuel consumption at both high Speeds (in the maximum power range) as well medium speeds (in the range of the best torque) and finally well fulfilled at low engine speeds can be.

Typically, the intake valves from Internal combustion engines actuated by a camshaft. By these are at a certain "opening angle" or a certain "closing angle" of the crankshaft Internal combustion engine opened the corresponding inlet valve or closed. The valve lift curve will, if that Inlet valve is actuated by a camshaft determines the shape of the cam. The phase position of the Valve lift curve is usually also on the cylinder - specific angle of the crankshaft Internal combustion engine related and depends on the angular position the camshaft from the crankshaft.

Various types of are known from the prior art variable valve control known. So it is possible that Camshaft during operation of the internal combustion engine Need around its longitudinal axis relative to the crankshaft twist. The rotation of the camshaft is infinitely variable possible between two end positions. This allows the Phasing of the valve lift curve continuously between two End positions are changed.

It is also possible to use a camshaft, which cam with one changing in the axial direction of the camshaft Profile has to move in the longitudinal direction. To this All of the above parameters can be changed in this way become.

There are also camshafts for which control of an intake valve not just a cam profile, but there are two cam profiles arranged in pairs, By shifting such a camshaft in its Longitudinal direction can be between the two by each Cams predetermined valve lift curves can be selected.

With such a switchover from a valve lift curve to Another problem arises that without appropriate countermeasures, various state variables the combustion in the combustion chamber and consequently also that Suddenly change the torque of the internal combustion engine can. For example, with a valve lift curve large valve lift on a valve lift curve with a small one Valve stroke switched, suddenly gets less Fresh air in the combustion chamber, which in turn corresponding "jerking" of the engine result Has.

So that no such sudden jump in torque Internal combustion engine occurs, so far Stroke switching, the control of a throttle valve Internal combustion engine, the output of an ignition angle and the Injection of fuel into the combustion chamber with high Effort synchronized.

Controlling this synchronization requires one as precise a knowledge as possible of the time of the changeover, which with a hydraulic adjustment system and here especially when compared to cold oil Actuation itself can be delayed. Beyond that the diagnosis of such a system is also very complex. she is necessary because of an incorrect switch position (for example, only one cylinder) to dropouts or unwanted acceleration or deceleration of the Internal combustion engine can lead. This is beyond that even possible at low and medium speeds.

The object of the present invention is a method of the type mentioned in such a way that the Synchronization and diagnostic effort can be reduced or even completely disappears.

This task is initiated in a procedure mentioned type in that before switching of the stepwise switchable parameter of the continuously adjustable parameters is set so that the Switching the stepwise switchable parameter at least one state variable of the combustion of a Inlet valve associated with combustion chamber not or not changes significantly.

Advantages of the invention

According to the invention, it was recognized that the large number of Parameters that determine the actuation of the intake valve describe similar or even the same Combustion states in the combustion chamber with different Parameter combinations can be achieved. Subsequently enables the continuous adjustment of the a parameter to set it so that a Change of the switchable parameter none or none significant impact on one or more state variables of combustion in the combustion chamber.

If the torque-relevant combustion parameters in the However, the combustion chamber does not or does not switch can be significantly affected on an elaborate Synchronization of the ignition timing, for example Injection point and the throttle valve position with the Switching process of the switchable parameter and to the Diagnosis of this synchronization can be dispensed with. The The internal combustion engine can therefore be manufactured more cheaply become.

Advantageous developments of the invention are in Subclaims specified.

A first further training proposes that the State variable of the combustion of a fresh air filling and / or a focus of combustion. This both parameters have a particularly important one Influence on the torque of the internal combustion engine.

It is also suggested that it is gradual switchable parameter is the valve lift curve, such that the different valve lift curves distinguish at least by the respective maximum stroke, and that it's the continuously adjustable Parameter is the phase position of the valve lift curves.

On the one hand, these two parameters are those parameters that have a particularly strong impact on have the combustion in the combustion chamber and with which therefore the general advantages of variable valve timing can be realized particularly well. Furthermore these parameters can be technically comparatively simple. to be changed.

It when the closing angle of the Inlet valve with the same phase position for all Valve lift curves is approximately the same and the switching of Valve lift curve only takes place at low speeds.

The basic idea of this training is the fact that the closing time, especially at low speeds or closing angle of the inlet valve on the Fresh air filling in the combustion chamber has a major impact. Consequently can then, if the switching of the valve lift curve only at low speeds, this largely independent from the phase position of the valve lift curve. This The process is therefore particularly easy to implement.

It is very advantageous if at the time of Switching the valve lift curve no or no significant Valve overlap between the intake valve and one Exhaust valve is present. This causes the The valve lift curve switches on due to a internal exhaust gas recirculation in the combustion chamber Residual gas content does not change significantly. Given a Ignition angle changes the focus of combustion and as a result, the torque of the internal combustion engine only little.

In an advantageous embodiment of the invention It is also proposed that a Valve stroke curve with a smaller maximum stroke approximately in the middle within a valve curve with a larger maximum stroke is arranged, and that switching from one Valve lift curve to another at a late phase the valve lift curves takes place with both Valve lift curves in approximately the same fresh air filling in the Combustion chamber is reached.

This takes into account the fact that at an equation of the closing angle of the individual Inlet valve lift curves u. May not be sufficient Early displacement of the stroke curve with a small maximum stroke is possible. Often, however, such a strong can only Early shift the fuel saving potential, which resulting from the corresponding dethrottling, optimal be used. However, there is an early shift a valve lift curve due to the risk of collision with the There are limits to the number of pistons moving in the combustion chamber: if erroneously from a stroke curve with a small maximum stroke be switched to a stroke curve with a large maximum stroke would and the stroke curves would be shifted strongly to "early", could cause such a risk of collision with the intake valve the piston exist, which inevitably causes damage would lead to the internal combustion engine.

The proposed design of the invention The method enables the phase position of the valve lift curve with a small maximum stroke sufficiently after "early" shift, and at the same time the phase position of the Valve lift curve with a large maximum lift at "late" leave. So the danger of a collision of the Intake valve with the piston in the case of a false one Switch to a valve stroke curve with a large maximum stroke reduced. To none when switching To generate a torque jump, this takes place at a comparatively late phase and at such Crank angle at which with both valve lift curves approximately the same fresh air filling is achieved in the combustion chamber.

It is also possible for a plurality of intake valves is available per combustion chamber and one of the valve lift curves at least one of these intake valves the maximum stroke Has zero. Basically, through such Valve lift curve corresponding intake valve switched off.

As an alternative to the solution mentioned at the beginning according to the invention also proposed that the closing angle of the intake valve is approximately the same for all valve lift curves and switching from a valve lift curve to others only at low speeds. This Variant of the method according to the invention is special simple and inexpensive to implement.

The invention also relates to a computer program which is suitable for performing the above method if it is running on a computer. It becomes special preferred if the computer program is on a memory, is stored in particular on a flash memory.

The invention also relates to a control and / or regulating device for operating an internal combustion engine. It will be special preferred if the control and / or regulating device a Includes memory on which a computer program of the above Type is stored.

The invention further relates to an internal combustion engine, which is a control and / or regulating device of the above type includes.

drawing

The following are particularly preferred Embodiments of the present invention under Reference to the attached drawing in detail explained. The drawing shows:

Figure 1 is a schematic representation of an internal combustion engine with an intake valve which is controlled by a switchable and adjustable camshaft.

FIG. 2 shows two cams of a pair of cams of the camshaft from FIG. 1 at different angular positions of the camshaft and the associated position of a tappet of the intake valve from FIG. 1;

Fig. 3 is a diagram showing the lift curves of the intake valve of Fig. 1 caused by the two cams of Fig. 2;

FIG. 4 shows a diagram in which the valve lift curves of FIG. 2 are plotted against the crankshaft at different phase positions of the camshaft;

Fig. 5 is a diagram similar to Figure 4 of a variant of the valve lift.

Figure 6 is an expanded view of a portion of the curves of Figure 5;

Fig. 7 is a diagram in which a valve lift caused by the filling of Figure 6 air is illustrated at different phase angles of the camshaft. and

Fig. 8 is a flow diagram illustrating a method for switching from one to the other cam of the camshaft, Fig.

Description of the embodiments

In Fig. 1, an internal combustion engine is identified overall by reference numeral 10. It comprises several cylinders, of which only one is shown in FIG. 1, which comprises a combustion chamber 12 . Combustion air is supplied to this via an inlet valve 14 and an intake pipe 16 . An injector 18 injects fuel into the intake pipe 16 . The fuel is provided by a fuel system 20 . A throttle valve 22 enables the cross section of the intake pipe 16 to be narrowed. The air mass, which is sucked in by the intake pipe 16 , is detected by an HFM sensor 24 .

The combustion exhaust gases are discharged from the combustion chamber 12 into an exhaust pipe 28 via an exhaust valve 26 . A fuel-air mixture located in the combustion chamber 12 is ignited by a spark plug 30 , which in turn is controlled by an ignition system 32 . A piston, not shown, is connected to a symbolically represented crankshaft 34 via a connecting rod, also not shown. Their angular position and speed is picked up by a sensor 36 .

The intake valve 14 is actuated by an intake camshaft 38 and the exhaust valve 26 by an exhaust camshaft 40 . The actuators 42 and 44 can be used to adjust the camshafts 38 and 40 in a manner which is still to be explained in more detail. The current angular position of the intake camshaft 38 is detected by a sensor 46 . The current angular position of the exhaust camshaft 40 is detected by a sensor 48 .

The operation of the internal combustion engine 10 is controlled or regulated by a control and regulating device 50 . This is connected on the input side to the HFM sensor 24 , the crankshaft sensor 36 and the camshaft sensors 46 and 48 . On the output side, the control and regulating device 50 is connected to the injector 18 , the throttle valve 22 , the ignition system 32 and the actuators 42 and 44 of the camshafts 38 and 40 .

FIG. 2 shows the intake camshaft 38 from FIG. 1 and a tappet 52, not shown in FIG. 1, of the intake valve 14 . Fig. 2 a total of five individual representations includes the intake camshaft 38 at different angles. For the sake of simplicity, only one of the images shown is provided with corresponding reference numerals.

From Fig. 2 it can be seen that the intake camshaft 38 is provided per intake valve 14 in pairs with two spaced cams 54 and 56. By displacing the inlet camshaft 38 in its longitudinal direction, which can be brought about by one of the actuators 42 , either the cam 54 or the cam 56 works on the tappet 52 . The stroke curve of the cam 54 is denoted by H1 in FIG. 3, the stroke curve of the cam 56 in FIG. 3 by H2. The position of the plunger 52 , which is caused by the cam 54 , is shown in solid lines in FIG. 2, and the position which is caused by the cam 56 is shown in broken lines.

It can be seen from FIG. 3 that the maximum stroke hmax1 of the tappet 52 , which is caused by the cam 54 , is approximately twice as large as the maximum stroke hmax2, which is caused by the cam 56 . It can also be seen that the inlet valve 14 , when the tappet 52 is acted upon by the cam 56 , opens later than in the case in which the tappet 52 is acted upon by the cam 54 . Finally, it can be seen from FIG. 3 that the closing angle of the inlet valve 14 is always the same for both stroke curves H1 and H2. This is based on the following consideration:

Variable valve timing has the advantage that the demands for successful exhaust emissions and low fuel consumption can be better met in all speed ranges than with non-variable valve timing. A simple possibility to change the control times of the inlet valve 14 is that the tappet 52 is actuated either by the cam 54 or the cam 56 and the different stroke curves H1 and H2 of FIG. 3 can be realized in this way. However, care must be taken to ensure that when switching from one stroke curve to another, the torque does not change suddenly due to the changeover.

It has now been recognized that, at low engine speeds, the air charge entering combustion chamber 12 is approximately the same even with different stroke curves if the closing time of the valve stroke curves is the same. However, the air charge present in the combustion chamber 12 is a decisive parameter for the torque which the internal combustion engine 10 produces. If, as is the case with the two stroke curves H1 and H2 in FIG. 3, the closing time of the intake valve 14 is approximately the same for both valve stroke curves H1 and H2, it can be assumed that at least at low speeds when switching from one Valve lift curve to the other no sudden change in the torque produced by the internal combustion engine 10 occurs.

A simultaneous closing time of the inlet valve 14 can be realized in that the two cams 54 and 56 , as can be seen from FIG. 2, are designed and arranged rigidly with respect to one another such that the corresponding valve lift curves H1 and H2 always correspond to one of the selected lift curve H1 or H2 lead independent and same closing angle of the intake valve 14 . Even a slightly later closing of the inlet valve 14 when using the stroke curve H2 (smaller maximum stroke) can have an advantage compared to using the stroke curve H1 (larger maximum stroke). In this way, the filling loss, which is present due to the smaller stroke at a certain speed, can be compensated for.

The simultaneity of the closing angles of the inlet valve 14 in the two valve lift curves H1 and H2 in the embodiment shown in FIGS. 2 and 3 has a disadvantage in certain cases, as can be seen from FIG. 4. In certain cases it is advantageous to vary the timing of the intake valve 14 not only by switching from one valve lift curve to another, but also to change the phase position of the valve lift curves with respect to the crankshaft angle. This phase shift can be carried out in a technically simple manner in a continuous manner, that is to say without intermediate stages, by rotating the intake camshaft 38 with respect to the crankshaft 34 . Such a rotation thus leads to a phase shift of the camshaft 38 with respect to the crankshaft 34 .

In order to be able to utilize the full fuel saving and emission optimization potential of a variable valve control, for example, if the valve lift curve H2 is used with a small maximum lift, the timing of the opening of the inlet valve 14 should be as close as possible to the top dead center of the piston, that is to say approximately at 360 °. Crankshaft angle wk. In order to achieve this, the phase position of the intake camshaft 38 is shifted to "early" (see FIG. 4; in this the valve stroke curves with a late phase position with solid (H1) or dash-dot lines (H2) lines, the valve stroke curves H1 and H2 with earlier phasing, and a valve lift curve of the exhaust valve 26 is shown with a double line).

In principle, however, the case must always be taken into account that an error in control unit 50 results in an erroneous switchover from the small valve lift curve H2 with a small maximum lift to the valve lift curve H1 with a large maximum lift. In the early phase position of the valve lift curve H2 shown in dashed lines in FIG. 4 and with a simultaneous closing angle of both valve lift curves H1 and H2, such an erroneous switchover could lead to a collision of the intake valve 14 with the piston (the lift curve of the piston carries this in FIG. 4 Reference numeral 62 ).

In order to avoid such a collision of the valve element of the inlet valve 14 with the piston of the combustion chamber 12 in the event of an erroneous changeover from one stroke curve to the other, it is more advantageous if the two stroke curves H1 and H2 have the phase position shown in FIG. 5 with respect to one another. This "relative" phase position of the valve lift curves H1 and H2 is selected such that the lift curve H2 with a small maximum lift is approximately central to the lift curve H1 with a large maximum lift.

Even in the case of an early "absolute" phase position of the stroke curve H2 with a small maximum stroke, which is related to the crank angle wk - this corresponds to an opening angle in the area of the top dead center of the piston - an erroneous changeover from the stroke curve H2 with a small maximum stroke to the stroke curve H1 With a large maximum stroke, the valve element of the intake valve 14 does not collide with the piston of the internal combustion engine 10 (curve 62 in FIG. 5).

However, since the closing angle of the stroke curve H2 with a small maximum stroke differs from the closing angle of the stroke curve H1 with a large maximum stroke, another way must be found to ensure that when switching from one stroke curve to the other there is no undesirable change in the torque of the internal combustion engine 10 occurs. For this purpose, reference is now made to FIGS. 6 and 7:

In FIG. 6, the angle range between 360 ° and 540 ° of the crankshaft angle wk of the diagram of Fig. 5 is shown enlarged. The valve lift curves H1 and H2 are shown in dotted lines at a phase angle of the intake camshaft 38 ; which corresponds to a value pn0. This is a phase angle of the intake camshaft 38 , which corresponds to a clear "early" adjustment of the intake camshaft 38 .

FIG. 7 shows the air filling R1 of the combustion chamber 12 , which is achieved with the different stroke curves H1 and H2 at different phase angles of the intake camshaft 38 . The air filling curve which is achieved with the lifting curve H1 is denoted by reference numeral 64 in FIG. 7 and is shown as a solid line, that air filling curve which is achieved with the lifting curve H2 (small maximum stroke) is denoted by the reference symbol 66 in FIG. 7 and is dash-dotted shown.

It can be seen that with an "absolute" phase position pn0 of the intake camshaft 38, the air charge in the combustion chamber 12 , which is achieved with the stroke curve H1 (large maximum stroke), is significantly greater than that air charge with the same phase position pn0 with the stroke curve H2 (smaller Maximum stroke) can be achieved. The difference of this air filling rl is designated as drl in FIG. 7. Such a difference drl in the air charge rl would, however, lead to an undesirable torque jump in the internal combustion engine 10 .

However, it can also be seen from FIG. 7 that if the phase position pn of the intake camshaft 38 is adjusted to "late", the air charge achievable with the stroke curve H2 (small maximum stroke) in the combustion chamber 12 increases, whereas that air charge which is achieved with the stroke curve H1 (larger Maximum stroke) in the. Combustion chamber 12 can be introduced, decreases. The air charge curve 64 intersects the air charge curve 66 at a phase position of the intake camshaft 38 that has the value pn1. This means that if the phase position pn of the intake camshaft 38 is set to the value pn1 before switching from one stroke curve to the other, when switching from one stroke curve to another despite an unequal closing angle of the two stroke curves H1 and H2, this is undesirable Torque jump of the engine 10 does not occur.

A corresponding method is shown as a flowchart in FIG. 8: after a start block 68 , a block 70 checks whether a switch is to be made from one lift curve H1 to another lift curve H2. If this is the case, the phase position pn of the intake camshaft 38 is adjusted in block 72 . During the adjustment 72 it is checked in block 73 whether at the current operating point of the internal combustion engine 10 with the set phase position pn the air charge rl of the stroke curve H1 is equal to the air charge rl of the stroke curve H2. If so, a switch is made in block 74 from one stroke curve to the other. The method ends in block 76 .

It goes without saying that the phase position of the intake camshaft 38 , at which the air fillings rl of the two stroke curves H1 and H2 are the same at the current operating point of the internal combustion engine 10 , could also be determined directly from one or more characteristic maps, and the corresponding phase position could thus be approached immediately.

Claims (12)

1. Method for operating an internal combustion engine ( 10 ) with at least one inlet valve ( 14 ), the operation of which can be described at least by the parameters opening angle, closing angle, valve lift curve (H1, H2), and phase position (pn) of the valve lift curve (H1, H2) , and in which at least one (pn) of the parameters is continuously adjusted and another parameter (H1, H2) can be switched in stages, characterized in that before a switchover ( 74 ) of the gradually switchable parameter (H1, H2) the continuously adjustable parameter (pn) is set ( 72 ) in such a way that when switching ( 74 ) the stepwise switchable parameter (H1, H2) at least one state variable (rl) of the combustion of a combustion chamber ( 12 ) assigned to the inlet valve ( 14 ) does not change or does not change significantly , 2. The method according to claim 1, characterized in that that the state quantity of the combustion is a Fresh air filling (rl) and / or one Combustion focus includes. 3. The method according to any one of claims 1 or 2, characterized characterized that it is gradual switchable parameters around the valve lift curve (H1, H2) acts in such a way that the different Valve lift curves (H1, H2) at least through the respective Maximum stroke differ, and that it is continuously adjustable parameters around the phase position (pn) of the valve lift curves (H1, H2). 4. The method according to claim 3, characterized in that the closing angle of the inlet valve ( 14 ) with the same phase position (pn) is approximately the same for all valve lift curves (H1, H2) and the changeover ( 74 ) of the valve lift curve (H1, H2) only at low and / or medium speeds. 5. The method according to any one of claims 3 or 4, characterized in that at the time of switching ( 74 ) of the valve lift curve (H1, H2) there is no or no significant valve overlap between the inlet valve ( 14 ) and an outlet valve ( 26 ). 6. The method according to any one of claims 3 to 5, characterized in that a valve lift curve (H2) with a smaller maximum lift is arranged approximately centrally within a valve lift curve (H1) with a larger maximum lift, and that the switchover ( 74 ) from a valve lift curve (H1 , H2) to another (H2, H1) with a late phase position (pn1) of the valve lift curves (H1, H2), in which with both valve lift curves (H1, H2) approximately the same fresh air charge (rl) in the combustion chamber ( 12 ) is achieved. 7. The method according to any one of the preceding claims, characterized in that a plurality of Intake valves per combustion chamber is present and one of the Valve lift curves of at least one of these intake valves has maximum stroke zero. 8. Method for operating an internal combustion engine ( 10 ) with at least one inlet valve ( 14 ), the operation of which can be described at least by the parameters opening angle, closing angle, and valve lift curve (H1, H2), and in which at least one valve lift curve (H1, H2 ) to another (H2, H1) can be switched in stages, characterized in that the closing angle of the inlet valve ( 14 ) is approximately the same for all valve lift curves (H1, H2) and the switchover from one valve lift curve (H1, H2) to the other (H2, H1) only at low and / or medium speeds. 9. Computer program, characterized in that it is used for Carrying out the method according to one of the preceding Claims is appropriate when it is on a computer is performed. 10. Computer program according to claim 9, characterized characterized it on a store, in particular on a flash memory. 11. Control and / or regulating device ( 50 ) for operating an internal combustion engine, characterized in that it comprises a memory on which a computer program according to one of claims 9 or 10 is stored. 12. Internal combustion engine ( 10 ), characterized in that it comprises a control and / or regulating device ( 50 ) according to claim 11.