WO2012069376A2

WO2012069376A2 - Operating method

Info

Publication number: WO2012069376A2
Application number: PCT/EP2011/070443
Authority: WO
Inventors: Christian BÜCKER; Martin Helmis
Original assignee: Mahle International Gmbh
Priority date: 2010-11-24
Filing date: 2011-11-18
Publication date: 2012-05-31
Also published as: WO2012069376A3; DE102010061858A1; EP2643570A2

Abstract

The invention relates to a method for operating an internal combustion engine (1), in particular of a motor vehicle, wherein the internal combustion engine (1) comprises a plurality of cylinders (3) controlled by gas exchange valves (5, 6) and an intake air system (7) feeding intake air to the cylinders (3) in an engine block (2), said intake air system comprising at least one auxiliary valve (30) disposed upstream of the associated gas exchange valves (5, 6) in an intake air channel (8', 8") leading to at least two cylinders (3), wherein the respective auxiliary valve (30) is operated so that open phases (A) in which the auxiliary valve (30) opens the intake air channel (8', 8") alternate with closed phases (B) in which the respective auxiliary valve (30) closes the air intake channel (30), wherein the respective auxiliary valve (30) is further operated so that a separate opening phase (A) is generated for each associated cylinder (3). An improved efficiency can be achieved if the respective auxiliary valve (30) is operated so that opening phases (A) of different sizes are generated for the associated cylinders (3) that follow directly one after the other.

Description

operating procedures

The present invention relates to a method for operating an internal combustion engine, in particular a motor vehicle.

Internal combustion engines come stationary, e.g. in emergency generators or combined heat and power plants, or in mobile applications such as e.g. in aircraft, watercraft and land vehicles, in particular road vehicles and off-road vehicles.

Usually, an internal combustion engine comprises an engine block which contains a plurality of cylinders, in each of which a piston is arranged such that it can be adjusted in terms of stroke, so-called piston engine or reciprocating engine. Gas exchange processes of these cylinders are controlled by means of gas exchange valves, ie with inlet valves and exhaust valves. To supply the cylinders with fresh air, the internal combustion engine is usually equipped with a fresh air system which comprises at least one fresh air duct, which simultaneously supplies several cylinders with fresh air. By way of example, such a fresh air duct comprises a fresh air distributor, from which individual connecting pipes exit to one cylinder each.

In order to improve the fresh air loading of the cylinder and to control a return of exhaust gas, it is basically possible to arrange in the fresh air system upstream of the gas exchange valves, so in addition to the gas exchange valves at least one additional valve in the fresh air system, with the help of the respective fresh air duct can be opened and closed. Such an additional valve operates dynamically and thus differs in principle from a throttle valve, which may be provided in conventional internal combustion engines in the fresh air system to at low loads the Restrict fresh air supply. With the help of such additional valves, it is in principle possible to generate pressure pulsations in the air flow leading to the cylinders or to intensify existing pressure pulsations due to the gas exchange processes. In this case, positive pressure pulses, which lead to pressure increases, can be used to supply the individual cylinders more air mass, so-called impulse charging. It is likewise possible to generate negative pressure pulses which lead to pressure drops in order to improve exhaust gas recirculation or specifically to set an exhaust gas recirculation rate.

Additional valves for controlling the exhaust gas recirculation are known, for example, from DE 10 2006 028 146 A1, from DE 10 2006 037 934 A1 and from US Pat

DE 10 2007 004 264 A1.

Furthermore, it is known, for example from DE 10 2008 036 494 A1, to coordinate such additional valves with intake valves of the cylinders in such a way that the temperature during the combustion process, ie the respective process temperature, is reduced in order to reduce pollutant emissions, in particular NOX emissions. For example, the so-called Miller process or the so-called Atkinson process can be carried out with the aid of the additional valves. In the Miller process, the loading process of the respective cylinder is terminated earlier than usual, namely before the bottom dead center of the associated piston. In the Atkinson process, the loading process is prolonged, namely until after the bottom dead center of the respective piston. In both cases, the total amount of fresh air supplied to the cylinder is reduced, which leads to a reduction in pressure in the combustion process and thus to a drop in temperature.

From WO 2010/007026 A1 another additional valve is known, which is equipped with a phase divider, by means of which the phase position between the drive and the valve member can be varied. According to DE 10 2009 020 171 it is also known to use the respective additional valve to optimize an environmental parameter of the internal combustion engine in individual operating points of the internal combustion engine or to set an optimized compromise for at least two environmental parameters of the internal combustion engine. This is achieved in that a phase angle of the respective additional valve relative to the rotation of a crankshaft of the internal combustion engine or relative to its Ku rbelwellenwinkel is varied.

In order to be able to generate the different flow dynamic effects, the respective additional valve is usually operated such that opening phases in which the additional valve opens the fresh air duct and closing phases in which the additional valve closes the fresh air duct alternate. If such an additional valve is assigned to a plurality of cylinders, that is to say arranged in a fresh-air duct which leads to a plurality of cylinders, the additional valve is expediently operated such that it generates separate opening phases for each assigned cylinder. For example, the respective fresh air duct lead to three cylinders of the internal combustion engine, so that the additional valve is then assigned to three cylinders. In a six-cylinder engine, which operates on the four-stroke principle, the firing order of the individual cylinders can be tuned so that the respective additional valve associated three cylinders are sequentially clocked in phase, so with respect to the crankshaft angle to each other, in particular the Suction cycles of the cylinder are separated in time and occur in succession. This makes it possible that with the help of an additional valve for each associated cylinder, a separate opening phase can be generated.

The present invention is concerned with the problem of providing an improved embodiment for an operating method of the type mentioned at the outset. ben, which is characterized in particular by the fact that the energy efficiency of the internal combustion engine is improved, in particular pollutant emissions to be reduced.

This problem is solved according to the invention by the subject-matter of the independent claim. Advantageous embodiments are the subject of the dependent claims.

The invention is based on the general idea of using the additional valve to optimize the opening phases individually in terms of their length or in terms of their duration for the respective cylinder. This is achieved, in which the additional valve is operated so that it generates different sized opening phases for the associated cylinder, which follow one another directly. Thus, if the respective additional valve, for example, three cylinders are assigned, the additional valve generates during a complete cycle of the internal combustion engine, ie during two complete revolutions of the crankshaft, ie within 720 ° crankshaft angle (short "KWW" or "KW") exactly three opening phases are spaced apart by closing phases, wherein these three opening phases are different in size, so extend over different angular ranges of crankshaft rotation.

The invention takes into account the knowledge that within the fresh air channel for each associated cylinder, a separate flow path is present, which leads from the common auxiliary valve to the respective cylinder or to the combustion chamber. Due to design needs, these flow paths are not identical. For example, one flow path may be longer than another. Additionally or alternatively, one flow path may contain more flow deflections than another. Additionally or alternatively, a flow path may contain more flow obstacles and / or flow resistances. as another. This leads in the end to equal opening times of the additional valve to different loads or - depending on the purpose of the additional valve - lead to different exhaust gas recirculation rates in the individual cylinders. It has thus been shown that identical opening phases of the common additional valve at the associated cylinders lead to an inhomogeneous supply of fresh air or recirculated exhaust gas. The proposal according to the invention of selecting the opening phases differently for the different cylinders now results in the possibility of homogenizing the supply of the associated cylinders with fresh air or with recirculated exhaust gas. For example, a smaller opening phase can be selected for a cylinder which is coupled to the additional valve via a shorter fresh air path, while a larger opening phase can be selected for a cylinder which is coupled to the additional valve via a fresh air path provided with a plurality of flow deflections , Through experiments, the optimum opening phases for the different cylinders can be determined in order to more or less compensate for the design-related deviations of the fresh air paths.

The achievable with the aid of the operating method according to the invention homogenization of the supply of individual cylinders with fresh air or with recirculated exhaust gas can reduce the pollutant emissions and / or fuel consumption.

According to an advantageous embodiment, the respective additional valve may have a permanently rotating valve member which at least completes a closing angle range forming such a closing phase and at least one opening angle range forming such an opening phase, wherein the rotational speed of the valve member is changed to change successive opening phases. With others In order to be able to vary the successive opening phases in terms of their duration with an additional valve with a permanently rotating valve member, the additional valve is designed so that the rotational speed at which the valve member rotates, can be changed dynamically, ie during one revolution of the valve member, in particular between two consecutive closing phases and in particular within an opening phase. This can be realized in particular by means of an electric motor drive, for example by means of a brushless DC motor.

According to another advantageous embodiment, the respective additional valve can be actuated so that the opening phases have a predetermined phase position to the crankshaft angle of a crankshaft of the internal combustion engine in a stationary operating state of the internal combustion engine. For example, it may be important for the respective positive or negative pressure pulse to arrive in the region of a predetermined crankshaft angle at the respective cylinder, for example immediately before the closing of the associated intake valve or the associated intake valves. The changing of the opening phases can then take place in such a way that the predetermined phase position relative to the crankshaft angle of the crankshaft is maintained during a stationary operating state of the internal combustion engine. For example, an opening phase can be increased by reducing the preceding and / or the subsequent closing phase, in such a way that a period duration remains constant. In the event that an opening phase is to be reduced, the preceding and / or the subsequent closing phase can be increased, such that the period duration remains constant. The respective period is defined by the time interval between the centers of two successive opening phases. In another advantageous embodiment, the respective additional valve can be used to control an exhaust gas recirculation rate. In the closing phases, a negative pressure can be generated or increased at a downstream of the additional valve inlet point for recirculated exhaust gas, whereby the amount of recirculated exhaust gas can be influenced. The exhaust gas recirculation rate behaves antiproportional to the opening phase of the additional valve. The larger the opening phase, the greater the exhaust gas recirculation rate and vice versa.

According to another advantageous embodiment, the fresh air passage from the respective additional valve to the associated cylinders may have different flow paths which would lead to differences in the fresh air filling and / or exhaust gas recirculation rate at the respective cylinder, wherein the different opening phases are adapted to the different flow paths, that the mentioned differences are reduced, in particular eliminated. In this embodiment, the potential of the present invention is optimally utilized to homogenize the supply of the individual cylinders with respect to fresh air and / or recirculated exhaust gas.

According to a particularly advantageous embodiment, the respective additional valve can be actuated by means of an electric motor, e.g. a brushless DC motor, permanently rotating driven valve member, wherein the electric motor for generating varying rotational speeds during a revolution of the valve member is driven with a continuous drive function. The use of a continuous drive function reduces the load on the electric motor and allows reliable control times.

The control function used in this case can be the product of at least two continuous sub-functions according to an advantageous embodiment. Suitably, the respective subfunction may each include a sine function. In particular, a first partial function may be a sine function of the first power, while a second partial function may be a sine function of the third power. Suitably, the zero crossing of the first partial function with negative derivative can be set to the middle of the opening phase of the additional valve. It is particularly advantageous to set the maximum of the second partial function to the middle of the opening phase of the additional valve. It has been shown that such a drive function leads to a particularly favorable course of the rotational movement of the valve member, with which the varying opening times can be represented in a particularly simple and reliable manner.

Particularly advantageous is an embodiment in which the fresh air system downstream of the respective additional valve up to the gas exchange valves and upstream of the respective additional valve contains no controllable throttle. In other words, the fresh air system is operated unthrottled or throttle-free. The fresh air supply to the cylinders is controlled exclusively via the respective additional valve. In particular, thus, the loading control for the cylinder can be realized by means of the additional valve. In this case, an embodiment in which the respective additional valve is operated both for loading control of the associated cylinders and for controlling an exhaust gas recirculation rate to the individual cylinders is particularly expedient.

It has proven particularly advantageous if, in a 4-stroke engine for every three cylinders, a single additional valve is used which is assigned to these three cylinders. In particular, therefore, only a single additional valve can be provided in a 3-cylinder engine. In contrast, in the case of a 6-cylinder engine, precisely two such additional valves may be provided, which are then assigned to three cylinders each. According to another advantageous embodiment, it can be provided that the opening phases are varied depending on a current operating state of the internal combustion engine in order to adapt the opening phases to the current operating state of the internal combustion engine. It is expedient to vary the opening phases for adaptation to the current operating state of the internal combustion engine such that an opening duration of the respective opening phase measured in degrees crankshaft angle of a crankshaft of the internal combustion engine is varied, for which a closing time of the opening phase is varied with respect to its phase angle to the crankshaft angle during an opening time the opening phase remains constant with respect to its phase angle to the crankshaft angle.

This embodiment is based on the general idea, to vary the opening phases as part of the adaptation to different operating states of the internal combustion engine, to shift only the closing time and to keep the opening time constant. To increase the opening phases thus only the closing time is moved to late, while only the closing time is moved to shorten the opening phases to early. This measure is based on the surprising finding that, for an optimal compromise between fuel consumption and pollutant emissions, in particular NOX emissions, there is a time window in which the opening time for the opening phases must lie, this time window being independent of the operating state of the internal combustion engine and independent of the Size of the opening phase is, even if the size of the opening phase has a strong dependence on the operating condition of the internal combustion engine. However, the position of this time window may depend on the respective pursued operating strategy, according to which the internal combustion engine is to be operated, eg optimized for pollutants, optimized for consumption, optimized for performance, etc. According to an advantageous embodiment, the respective additional valve may have a permanently rotating valve member which at least completes a closing angle range forming such a closing phase and at least one opening angle range forming such an opening phase, the rotational speed of the valve member varying within a complete revolution to vary the closing time is so that during the opening phases other rotational speeds are present than during the closing phases.

For example, in order to shorten the opening duration, the rotational speed can then be increased during the opening phase and reduced in the closing phase, such that the phase position of the opening time to the crankshaft angle remains constant. By keeping constant the phase position of the opening time, the change in the opening period is based solely on a shift of the closing time. The same applies to increasing the opening duration, which is achieved by reducing the rotational speed during the opening phase and increasing it in the closing phase, such that the phase angle of the opening time to the crankshaft angle remains constant.

According to a specific embodiment, the opening time of the opening phase of the respective additional valve coincide regardless of the operating condition of the internal combustion engine with a controlled by the gas exchange valves inlet start for the respective cylinder or a maximum of 10 ° crankshaft angle or a maximum of 5 ° crankshaft angle. Such a relationship between the opening time and the beginning of the intake can be observed for a predetermined operating strategy, for example, to optimize a low fuel consumption with low Pollutant emissions. In another operating strategy, for example, should lead to a rapid warm-up of the internal combustion engine, of course, other relationships between the opening time and the beginning of intake can be selected. For example, other relationships between the opening time and the beginning of the intake may be relevant for the heat charge mentioned at the outset (Miller method or Atkinson method).

Other important features and advantages of the invention will become apparent from the dependent claims, from the drawings and from the associated figure description with reference to the drawings.

It is understood that the features mentioned above and those yet to be explained below can be used not only in the particular combination given, but also in other combinations or in isolation, without departing from the scope of the present invention.

Preferred embodiments of the invention are illustrated in the drawings and will be described in more detail in the following description, wherein like reference numerals refer to the same or similar or functionally identical components.

Show, in each case schematically,

Fig. 1 is a greatly simplified schematic diagram of a schematic

Internal combustion engine,

2 is an isometric view of an additional valve, 3a is a greatly simplified, schematic longitudinal section of the additional valve,

3b is a diagram for illustrating the opening behavior of

Additional valve depending on a rotation angle of a valve member,

4 shows a diagram for illustrating different opening phases of the additional valve,

5 shows a diagram for illustrating successive, different opening phases for three cylinders,

6 is a diagram illustrating successive different opening phases in a 6-cylinder engine,

Fig. 7 to 14 each have a simplified longitudinal section of the additional valve (a), a

Schematic representation of the internal combustion engine with three cylinders (b) and a course diagram for a four-stroke operation of the three cylinders, depending on the crankshaft angle (c), at different times or crankshaft angles,

15 shows several diagrams (a) to (f) for illustrating different opening phases in the case of different operating states of the internal combustion engine.

According to FIG. 1, an internal combustion engine 1, as can be used, for example, in a motor vehicle, for example, an engine block 2, which contains a plurality of cylinders 3, each enclosing a combustion chamber 4 and in which each one unspecified piston is arranged adjustable in stroke. Other engine configurations, such as the boxer engine, V-engine and W-engine, are a matter of course. In the example, by way of example only and without limiting the generality, exactly six such cylinders 3 are arranged in series. Each combustion chamber 4 and each cylinder 3 gas exchange valves, namely intake valves 5 and 6 associated exhaust valves, which are arranged in the engine block 2. In the example, per combustion chamber 4 or per cylinder 3 an inlet valve 5 and an outlet valve 6 are provided. It is clear that two or more intake valves 5 or two or more exhaust valves 6 per cylinder 3 may be provided. The internal combustion engine 1 is preferably for use as a vehicle drive for commercial vehicles and passenger cars, useful in heavy commercial vehicles, such as construction vehicles and off-road vehicles. In principle, however, a use of the internal combustion engine 1 in other vehicles, such as watercraft or in stationary facilities is conceivable.

The internal combustion engine 1 has a fresh air system 7, which serves for the supply of fresh air to the combustion chambers 4 and to the cylinders 3. For this purpose, the fresh air system 7 a fresh air line 8, which contains a fresh air path 9, which is indicated in Fig. 1 by arrows. In addition, the internal combustion engine 1 is equipped with an exhaust system 10, which serves to carry away exhaust gases from the combustion chambers 4. For this purpose, it has an exhaust pipe 1 1, which contains an exhaust path 12, which is indicated by arrows. In addition, the internal combustion engine 1 is equipped with an exhaust gas recirculation system 13, with which it is possible to recirculate exhaust gases from the exhaust system 10 to the fresh air system 7. For this purpose, the exhaust gas recirculation system 13 has at least one return line 14. In the example, two such return lines 14 are provided. Each return line 14 leads from a branch point 15 to a discharge point 16. At the respective branch point 15, the return line 14 is connected on the input side to the exhaust line. tion 1 1 connected. At the respective introduction point 14, the respective return line 14 is connected on the output side to the fresh air line 8.

In the example, the fresh air system 7 is designed to be double-flowed at least in a section adjoining the combustion chambers 4 to the cylinders 3, so that the fresh air line 8 in this area a first flood 8 'to supply the first three cylinders 3 and the first three combustion chambers 4 and a second flow 8 ", which serves to supply the second three cylinders 3 and the second three combustion chambers 4. The first flow 8 'and the second flow 8" each form a fresh air duct, which in the following also uses 8' or 8 ' 8 ".

Analogous to the fresh air system 7 and the exhaust system 10 is at least in a subsequent to the cylinder 3 and the combustion chambers 4 double-flow configured so that the exhaust pipe 1 1 at least in a subsequent to the cylinder 3 and the combustion chambers 4 a section the first three cylinders 3 associated first tide 1 1 'and the second three cylinders 3 associated second tide 1 1 "has.

The two exhaust gas recirculation lines 14 are accordingly each one of these floods 8 'and 8 "or 1 1' or 1 1" assigned. In particular, such an exhaust gas recirculation line 14 is connected to each fresh air duct 8 ', 8 ". In the example, each return line 14 is also equipped with an exhaust gas recirculation cooler 17.

Furthermore, the internal combustion engine 1 is charged in the illustrated example, so that at least one charging device is provided. In the example, two charging devices are provided, namely a first charging device 18 and a second charging device 19. Both charging devices 18, 19 are configured in the example as an exhaust gas turbocharger. Accordingly, the first loading facility tion 18, a first compressor 20 which is arranged in the fresh air line 8, and which is drive-connected via a first drive shaft 21 with a first turbine 22, which is arranged in the exhaust pipe 11. The second charging device 19 accordingly comprises a second compressor 23, which is arranged in the fresh air line 8 and is drive-connected via a second drive shaft 24 to a second turbine 25, which is arranged in the exhaust pipe 11. In this case, the second compressor 23 is arranged downstream of the first compressor 20, while the second turbine 25 is arranged upstream of the first turbine 22. Between the first compressor 20 and the second compressor 23, a first intercooler 26 is arranged in the fresh air line 8. Between the second compressor 23 and the cylinders 3, a second intercooler 27 is arranged in the fresh air line 8.

A corresponding exhaust gas recirculation flow is indicated by arrows 28. In the example of FIG. 1, an exhaust gas recirculation valve 29 is arranged in each return line 14, with the aid of which the respective return line 14 can be opened or closed and which can be used in particular for setting an exhaust gas recirculation rate.

The internal combustion engine 1 is also equipped with at least one additional valve 30. In the example, two such additional valves 30 are provided. The respective additional valve 30 is in the fresh air system 7 upstream of the gas exchange valves 5, 6, that is arranged here upstream of the intake valves 5. In the example, such an additional valve 30 is assigned to each of the two floods 8 ', 8 ", that is to say that in each fresh air channel 8', 8" such an additional valve 30 is arranged. Thus, in the example, each additional valve 30 is associated with three cylinders 3 and three combustion chambers 4, respectively. 2, such an additional valve 30 can have an electric motor 31 as a drive in order to be able to actuate the respective additional valve 30 for opening and closing the respective fresh-air duct 8 'or 8''In the example, the additional valve 30 comprises a line section 32 with which the additional valve 30 in the respective fresh air duct 8 'and 8 "of the fresh air system 7 can be integrated. The additional valve 30 includes in the associated channel portion 32, a valve member 33 which is formed in the example by a flap, which may be referred to in particular as a butterfly flap. The valve member 33 is rotatably mounted on a shaft 34 which is drivingly connected to the electric motor 31. The electric motor 31 is preferably designed such that it can drive the valve member 33 to a permanent rotation. The rotational speed of the drive 31 or of the valve member 33 may, for example, be in a substantially fixed relation to a rotational speed of a crankshaft 35 of the internal combustion engine 1 indicated in FIG. 1.

FIGS. 2 and 3a show an expedient example of an additional valve 30, which has a permanently rotating valve member 33. Fig. 3b illustrates the course of the valve member 33 controlled by flow Baren cross section of the fresh air channel 8 'and 8 "depending on the rotation angle φ of the valve member 33. The respective opening phase A is designated within the curve A, while the closing phases adjacent thereto with B are designated.

During a complete revolution of this valve member 33, this passes through at least one closing angle range β and at least one opening angle range a. The respective closing angle range β defines a closing phase B of the additional valve 30, while the respective opening angle range α forms an opening phase A of the additional valve 30. During the opening phases A, the additional valve 30 or its valve member 33 opens the fresh air duct 8 'or 8 ". During the closing phases B, the additional valve 30 or its valve member closes In the example shown, the additional valve 30 has a complete revolution of the valve member 33 exactly two opening phases A and two closing phases B, which alternate.

For the formation of significant closing angle ranges ß has a channel wall 36 recesses 37, in which the valve member 33 is immersed in its rotation. The depressions 37 are, for example, profiled in the manner of a circle segment and have a diameter D which is greater than a height H of the respective channel 8 'or 8 "or 32 and which essentially corresponds to a width of the valve member 33 measured transversely to the axis of rotation.

With the aid of a controller 38 indicated in FIG. 1, which is connected in a suitable manner to the respective additional valve 30, the respective additional valve 30 can be operated such that it generates a separate opening phase A for each associated cylinder 3.

This means that the respective additional valve 30 is adapted to the gas exchange operations according to the four-stroke principle of the associated three cylinders 3 so that in each case an intake stroke of the respective cylinder 3, an opening phase A can be assigned.

The respective additional valve 30 is now operated with the aid of the controller 38 so that it can generate different sized opening phases A for the associated cylinder 3, wherein these differently sized or differently long opening phases A can follow one another directly.

By way of example, FIG. 4 shows two examples of opening phases A of different sizes. A shorter or smaller opening phase Ai is apparent, which develops in a crankshaft angle range from approximately 60 ° KWW to approximately 180 ° KWW. stretches. Furthermore, a larger or longer opening phase A _{2 can be seen} , which extends for example in a crankshaft angle range from about 40 ° KVWV to about 200 ° KVWV. As a comparison, a sinusoidal curve E of an inlet valve 5 is entered in the diagram of FIG. 4, whose opening time window ranges from about 0 ° KVWV to about 240 ° KVWV.

FIG. 5 now shows how differently sized opening phases A follow one another during the successive loading phases of the successive cylinders 3 located in the intake stroke. For example, the three associated with the respective additional valve 30 cylinder 3 can differ from each other due to their distance from the additional valve 30. For example, a first cylinder 3i has the greatest distance to the additional valve 30, a second cylinder 3 ₂ has a mean distance to the additional valve 30, and a third cylinder 3 ₃ has the smallest distance to the auxiliary valve 30. For orientation, the indicated reference numbers are also in FIG registered to characterize the individual cylinder 3 with respect to their distance from the respective additional valve 30.

According to FIG. 5, the three cylinders 3-i, 3 ₂ and 3 _{3 are} each assigned a separate opening phase A with the aid of a common additional valve 30, wherein the successive opening phases A differ from one another with respect to their length or time duration. Thus, the first cylinder 3i receives the largest opening phase Ai while the third cylinder 3 _{3 is} the smallest opening phase A _{3 is} metered. The second cylinder 3 ₂ receives a medium opening phase A ₂ . It is noteworthy that while the opening time window E of the intake valves 5 remain the same size.

6 shows, purely by way of example, the sequence of the different opening phases A in the six cylinders of the six-cylinder engine of FIG. 1. The one shown in FIG. 1 lower auxiliary valve 30 generates the shown in Fig. 6 below. th three different, successive opening phases Ai, A ₂ and A ₃ for the three in Fig. 1 arranged below cylinder 3-i, 3 ₂ and 3 ₃ , while the other shown in FIG. 1 upper auxiliary valve 30 for in Fig. 1 above shown three cylinders 3-I, 3 ₂ and 3 _3, the different opening phases Ai, A ₂ and A ₃ generated. Visible results between the opening phases A of the one additional valve 30 and the opening phases A of the other auxiliary valve 30, a phase shift of about 120 ° KWW, which is due to the firing order of the six-cylinder four-stroke engine.

FIGS. 7 to 14 now illustrate the interaction of the different working cycles of the three cylinders 3, which are assigned to the one additional valve 30. In this case, the sub-figures 7a to 14a each show the auxiliary valve 30 in a longitudinal section in a simplified representation, in which case it is essential here to distinguish the closing phases B and the opening phases A from one another. The subfigures 7b to 14b illustrate the gas flow. The subfigures 7c to 14c illustrate the relation of the respective state with respect to the rotation of the crankshaft 35. Two complete revolutions of the crankshaft 35, ie 720 ° KWW or KW correspond to a duty cycle or cycle of the internal combustion engine. 1

In the sub-figures 7c to 14c, the different clocks of the individual cylinders 3 are listed according to the four-stroke principle, namely as "suction" for the intake stroke, "compression" for the compression stroke, "combustion" for the combustion cycle and "pushing out" for the Ausschiebetakt.

It is noteworthy that in the present case, the respective additional valve 30 is used to control an exhaust gas recirculation rate. Accordingly, in FIGS. 7a to 14a, the point of introduction 16 can be recognized, via the recirculated exhaust gas into the respective fresh air duct 8 'or 8 "or into the line section 32. can be directed. Accordingly, the respective return line 14 can also be seen in FIGS. 7b to 14b.

In the state according to FIG. 7, the consideration starts at 0 ° CA. The additional valve 30 is at a rotational angle φ of 0 ° and generates a closing phase B. The first cylinder 3i is in the intake stroke, the second cylinder 3 ₂ is in the compression stroke and the third cylinder 3 ₃ is in the combustion cycle. In this state, exhaust gas is increasingly supplied to the first cylinder 3i because the supply of fresh air is interrupted by the closing phase B of the auxiliary valve 30.

Fig. 8 shows a state at 120 ° KW. Now the additional valve 30 is at a rotational angle φ of 90 ° and generates an opening phase A, so that the first cylinder 3i is now increasingly supplied with fresh air. The second cylinder 3 ₂ is here at the transition to the combustion cycle. The third cylinder 3 ₃ is in the Ausschiebetakt.

Fig. 9 now shows the state at 240 ° KW. The additional valve 30 is at a rotational angle φ of 180 ° and generates a closing phase B. Consequently, it is now about the supply of the third cylinder 3 ₃ with exhaust gas.

In Fig. 10, the system is at 360 ° KW. The additional valve 30 shows a rotation angle φ of 270 ° and is open. This is thus about the supply of the third cylinder 3 ₃ with fresh air.

In Fig. 1 1 is now supplied at 480 ° KW and φ = 360 °, the second cylinder 3 ₂ with exhaust gas. According to FIG. 12, the second cylinder 3 _{2 is} supplied with fresh air at 600 ° CA and φ = 90 °.

In Fig. 13, the system is in the state of 720 ° KW (φ = 180 °), so that now two complete revolutions of the crankshaft 35 are completed. The state according to FIG. 13 therefore corresponds identically to the state according to FIG. 7.

Another 120 ° CA (φ = 270 °) later shows the state of FIG. 14, which corresponds to the state of FIG. 8.

It is noteworthy that the speeds of crankshaft 35 and valve member 33 to move in accordance with a ratio of 4: 3 to each other.

In order to vary the opening phases A in terms of their size or in terms of their duration, the rotating valve member 34 is provided to change the rotational speed of the valve member 34, namely dynamically, ie within a single revolution of the valve member 33. If the valve member 33 as in the examples shown here during a complete revolution, two opening phases A and two closing phases B, the rotational speed of the valve member 33 can be varied so that two different opening phases A can be realized within a single revolution.

As can be seen in FIGS. 4 to 6, the respective additional valve 30 can be suitably actuated such that the opening phases A have a predetermined phase position relative to the crankshaft angle of the crankshaft 35. For example, in FIG. 4 the vertex of the respective progression curve of the opening phase A is in each case at approximately 120 ° KWW and in FIG. 5 approximately in the center of the elevation curve E of the respective inlet valve. Also Fig. 6 can be seen, that successive opening phases A each have the same distance with respect to their vertices or their centers or centers, namely 240 ° KWW.

The changing of the opening phases A can thus preferably be carried out so that the predetermined phase angle to the crankshaft angle is maintained.

To increase the opening phase A, it is therefore possible to reduce both the preceding and the subsequent closing phase B, in such a way that a period remains constant. The respective period is measured, for example, by the time interval or the crankshaft angle between the centers of two successive opening phases A. In the examples shown here, this period is approximately

240 ° KWW. If the opening phase A is to be reduced, it may be expedient to increase the preceding and the subsequent closing phase B, such that the period duration remains constant.

As mentioned, in the example shown, the respective additional valve 30 is used to control the exhaust gas recirculation rate. The longer the closing phase B lasts, the more exhaust gas can be sucked in or returned. If the respective additional valve 30 is used for controlling the exhaust gas recirculation rate, basically the recirculation valves 29 shown in FIG. 1 can be dispensed with.

The different opening phases A take into account the different flow paths from the respective additional valve 30 to the respective cylinder 3-i, 3 ₂ , 3 ₃ and reduce resulting asymmetries with respect to the supply of the respective cylinder 3 with fresh air or with recirculated exhaust gas. If, as in the example shown, the respective additional valve 30 is driven by means of an electric motor 31, it can be provided according to a particularly advantageous embodiment to actuate the electric motor 31 with a continuous control function f (x). This drive function f (x) is expediently the product of at least two continuous subfunctions g (x) and h (x). The two subfunctions g (x) and h (x) are in particular sine functions. The first partial function g (x) is for example a sine function of the first power, while the second partial function h (x) can be, for example, a sine function of the third power. Particularly advantageous is now a design in which the zero crossing of the first partial function g (x) is set with a negative derivative to the center of the opening phase A of the additional valve 30. At the same time, the maximum of the second partial function h (x) is set to the middle of the opening phase A of the additional valve 30. Due to the proposed design of the drive function f (x), a particularly harmonic curve for the valve member 33 can be realized.

As can be seen from Fig. 1, the fish air system 7 downstream of the respective additional valve 30 to the gas exchange valves 5, 6 and upstream of the respective additional valve 30 has no controllable throttle. In that regard, the fresh air system 7 is designed unthrottled or throttle-free. The loading control of the individual cylinders 30 can be realized by means of the respective additional valve 30, namely by the appropriate dimensioning of the opening phases A.

While the above description is largely based on stationary operating states of the internal combustion engine 1, in which in particular constant rotational speeds and / or the same performances are required by the internal combustion engine 1, the following description relates to the behavior of the controller 38 and the adaptation of the opening phases A at different Operating conditions. Depending on the operating condition, it may be necessary to Opening phase A change in terms of their length, for example, to achieve optimal fuel consumption and pollutant emission for the respective operating state. In principle, the above individualization of the opening phases A for the individual cylinders 3 can be disregarded. However, an embodiment is preferred in which, during a steady-state operating state, different opening phases are allocated to the cylinders 3 associated with the same additional valve 30 and in which the opening phases A can be varied when changing over between two stationary operating states.

In other words, the cylinder-specific or local variation of the opening phases A serves to homogenize the supply of fresh air or of recirculated exhaust gas with respect to the individual cylinders 3. The general or global variation of the opening phases A serves to adapt the opening phases A of all cylinders 3 to changing ones Operating States of the Internal Combustion Engine 1. These two different variations (global or local) can basically be considered separately. However, a combined consideration is preferred, so that the respective controller 38 realizes the local variation for homogenizing the supply of the individual cylinders 3 with fresh air or recirculated exhaust gas by corresponding adaptation of the opening phases A even with changing operating states and associated globally varied different opening phases A. ,

In order to be able to vary the opening phases A for adaptation to the current operating state of the internal combustion engine 1, as explained, the opening duration of the respective opening phase A can be changed. In principle, an opening time and a closing time of the additional valve 30 can be shifted. Particularly useful, however, is a procedure in which to vary the opening phases A in terms of their opening duration only the closing time of the opening phase A is varied with respect to its phase angle to the crankshaft angle, while the opening time of the opening phase A is kept constant with respect to its phase angle to the crankshaft angle. It has been found that this procedure is particularly advantageous with regard to the achievable values for fuel consumption and pollutant emissions.

FIGS. 15a to 15f show elevation curves E for inlet valves 5 and elevation curves V for outlet valves 6. Furthermore, the closing phases B and the opening phases A of the additional valve 30 can be seen. Furthermore, each diagram 15 a to 15 f includes a vertical line 39 representing the opening timing of the opening phase A associated with the intake stroke of the respective cylinder 3. Further, a vertical line 40 defines the closing timing at which the respective opening phase A is completed. An opening period 41 then results from the difference between closing time 40 and opening time 39.

FIGS. 15a to 15f now show a sequence of different operating states of the internal combustion engine 1, each requiring different opening durations 41. In the sequence of the diagrams of FIGS. 15a to 15f, said opening duration 41 decreases. For this purpose, the closing time 40 is shifted in the direction of smaller crankshaft angles, while the opening time 39 remains constant.

According to an advantageous embodiment, the respective additional valve 30 may have a permanently rotating valve member 33, which at least one closing phase B forming such a closing phase B and at least one opening angle A forming such an opening phase A passes through a complete revolution, wherein for varying the closing time 40, the rotational speed the valve member 33 within a full revolution is varied, so that during the opening phase A different rotational speeds than during the closing phases B.

For example, to shorten the opening period 41, the rotational speed during the opening phase A can then be increased and reduced in the closing phase B such that the phase angle of the opening time point 39 to the crankshaft angle remains constant. By keeping constant the phase position of the opening time 39, the change in the opening period 41 is based solely on a shift of the closing time 40. The same applies to increasing the opening duration 41, which is achieved by reducing the rotational speed during the opening phase A and increasing it in the closing phase B. is such that the phase angle of the opening timing 39 remains constant to the crankshaft angle.

According to a specific embodiment, for the respective cylinder 3, the opening time 39 of the opening phase A of the respective additional valve 30 can coincide with a controlled by the gas exchange valves 5, 6 inlet start (start of the elevation curve E of the intake valve 5) or a maximum distance regardless of the operating condition of the internal combustion engine 1 of 10 ° crankshaft angle or at most a distance of 5 ° crankshaft angle have. Such a relationship between opening time 39 and start of intake can be maintained for a predetermined operating strategy, for example to optimize low fuel consumption with low pollutant emissions. In another operating strategy, which is to lead, for example, to a rapid warming of the internal combustion engine 1, of course, other relationships between opening time 39 and the beginning of intake can be selected. For example, other relationships of opening time 39 and inlet beginning may be relevant for the heat charge mentioned at the outset (Miller method or Atkinson method). The variation of the opening phases A proposed here for adaptation to changing operating states by shifting the closing time 40 and keeping the opening time 39 constant can be carried out in fresh air systems 7 which have a separate additional valve 30 for each cylinder 3.

According to the embodiment shown here, the respective fresh air duct 8 ', 8 ", in which the respective additional valve 30 is arranged, lead to a plurality of cylinders 3, so that respective additional valve 30 is assigned to a plurality of cylinders 3, for which it generates separate opening phases A, respectively. Since such an additional valve 30 can operate and be driven with high dynamics, it may be sufficient to allocate a single additional valve 30 to a plurality of cylinders 3 in order to be able to provide separate opening phases A for the cylinders 3. In particular, provision can be made for the respective additional valve 30 to be so operate that it generates different sized opening phases A for the associated cylinder 3, which follow each other directly.

Claims

claims

1 . Method for operating an internal combustion engine (1), in particular a motor vehicle,

wherein the internal combustion engine (1) in an engine block (2) a plurality of gas exchange valves (5, 6) controlled cylinder (3) and the cylinders (3) supplying fresh air fresh air system (7), which has at least one additional valve (30) in a to at least two cylinders (3) leading fresh air duct (8 ', 8 ") upstream of the associated gas exchange valves (5, 6) is arranged,

in which the respective additional valve (30) is operated such that opening phases (A), in which the additional valve (30) opens the fresh air duct (8 ', 8 "), and closing phases (B), in which the additional valve (30) the fresh air channel (8 ', 8 ") closes, alternating,

in which the respective additional valve (30) is operated such that it generates a separate opening phase (A) for each associated cylinder (3), in which the respective additional valve (30) is operated in such a way that it is responsible for the associated cylinders (3). different sized opening phases (A) generated, which follow each other directly.

2. The method according to claim 1,

characterized,

that the respective additional valve (30) has a permanently rotating valve member (33), the at least one such a closing phase (B) forming closing angle range (ß) and at least one a such opening phase (A) forming opening angle range (a) passes, wherein for varying successive opening phases (A), the rotational speed of the valve member (33) is changed.

3. The method according to claim 1 or 2,

characterized,

the respective additional valve (30) is actuated such that the opening phases (A) have a predetermined phase angle relative to the crankshaft angle of a crankshaft (35) of the internal combustion engine (1),

in that the changing of the opening phases (A) takes place in such a way that the predetermined phase position is maintained relative to the crankshaft angle of the crankshaft (35).

4. The method according to claim 3,

characterized,

that in the event that such an opening phase (A) is increased, the preceding and / or the subsequent closing phase (B) is / are reduced, such that a period remains constant, and / or in the event that such Opening phase (A) is reduced, the preceding and / or the subsequent closing phase (B) is / are increased, so that a period remains constant,

wherein the respective period duration is formed by the time interval between the centers of two successive opening phases (A).

5. The method according to any one of claims 1 to 4,

characterized,

the respective additional valve (30) is used to control an exhaust gas recirculation rate, the exhaust gas recirculation rate being proportional to the size of the opening phase (A).

6. The method according to any one of claims 1 to 5,

characterized,

that the fresh air duct (8 ', 8 ") from the respective additional valve (30) to the associated cylinders (3) has different flow paths which at the respective cylinder (3) at equal opening phases (A) to differences in the fresh air filling and / or Exhaust gas recirculation rate would lead, the different opening phases (A) are tuned to the different flow paths, that said differences are reduced, in particular eliminated.

7. The method according to any one of claims 1 to 6,

characterized,

in that the respective additional valve (30) has a valve member (33) permanently driven by an electric motor (31), wherein the electric motor (31) generates varying rotational speeds during one revolution of the valve member (33) with a continuous drive function (f (x )) is driven.

8. The method according to claim 7,

characterized,

the drive function (f (x)) is the product of at least two continuous subfunctions (g (x), h (x)),

wherein in particular it can be provided

that the respective subfunction (g (x), h (x)) in each case contains a sine function,

a first subfunction (g (x)) is a sine function of first power, that a second subfunction (h (x)) is a sine function of third power, that the zero crossing of the first subfunction (g (x)) with negative derivative to the center the opening phase (A) of the additional valve (30) is set, the maximum of the second partial function (h (x)) is set to the middle of the opening phase (A) of the additional valve (30).

9. The method according to any one of claims 1 to 8,

characterized,

that the fresh air system (7) downstream of the respective additional valve (30) up to the gas exchange valves (5, 6) and upstream of the respective additional valve (30) contains no controllable throttle, and / or

the respective additional valve (30) is operated for loading control of the associated cylinders (3).

10. The method according to any one of claims 1 to 9,

characterized,

that in a four-stroke engine for each three cylinders (3) a single, these three cylinders (3) associated additional valve (30) is provided, in particular in a four-stroke engine with exactly three cylinders (3) exactly one such additional valve (30) is provided or in a four-stroke engine with exactly six cylinders (3) exactly two such additional valves (30) are provided, which are each associated with three cylinders (3).

1 1. Method according to one of claims 1 to 10,

characterized,

the opening phases (A) are varied as a function of a current operating state of the internal combustion engine (1) in order to adapt the opening phases (A) to the current operating state,

in that the varying of the opening phases (A) for adaptation to the current operating state of the internal combustion engine (1) takes place such that an opening duration (41) of the opening phase (A) measured in degrees crankshaft angle of a crankshaft (35) of the internal combustion engine (1) is varied, what for Closing time (40) of the opening phase (A) is varied with respect to its phase angle to the crankshaft angle, while an opening time (39) of the opening phase (A) remains constant with respect to its phase angle to the crankshaft angle.

12. The method according to claim 1 1,

characterized,

in that the respective additional valve (30) has a permanently rotating valve member (33) which, during one complete revolution, passes through at least one closing angle range (β) forming such a closing phase (B) and at least one opening angle range (a) forming such an opening phase (A), wherein, for varying the closing time (41), the rotational speed of the valve member (33) is varied within one complete revolution so that there are different rotational speeds during the opening phases (A) than during the closing phases (B).

13. The method according to claim 12,

characterized,

in that, in order to shorten the opening period (41), the rotational speed is increased during the opening phase (A) and reduced in the closing phase (B), such that the phase angle of the opening time (39) to the crankshaft angle remains constant, and / or

in that, in order to increase the opening duration (41), the rotational speed is reduced during the opening phase (A) and increased in the closing phase (B), such that the phase angle of the opening time point (39) to the crankshaft angle remains constant.

14. The method according to any one of claims 1 1 to 13,

characterized, in that for the respective cylinder (3) the opening time (39) of the opening phase of the respective additional valve (30) and an inlet beginning controlled by the gas exchange valves (5, 6) coincide or at most a distance of 10 ° crankshaft angle or at most a distance of 5 ° crankshaft angle exhibit.