METHOD FOR OPERATING AN ENGINE AND ENGINE

Description

[0001] The invention relates to a method for operating an internal combustion engine with a reciprocating piston engine, which can be operated in partial operation.

[0002] Multi-cylinder reciprocating internal combustion engines are known that can be temporarily operated in a so-called partial operation mode, in which some of the cylinders are deactivated, so that no thermodynamic cycles take place in them. Instead, the deactivated cylinders are driven along by the remaining active cylinders. This is done with the aim of increasing the efficiency of the internal combustion engine operation, because deactivating some of the cylinders with essentially the same drive power leads to the remaining active cylinders operating at a significantly higher load, which is associated with a higher specific efficiency of the thermodynamic cycles carried out in these cylinders.To minimize the reduction in efficiency achievable for the active cylinders due to the reduced efficiency of the deactivated cylinders, the gas exchange valves assigned to the deactivated cylinders are generally kept closed during partial operation. This causes the gas within the combustion chambers formed by these cylinders to be cyclically compressed and expanded, but not expelled. In this way, power losses resulting from the compression of gases that would subsequently be expelled through open exhaust valves are avoided.

[0003] To achieve the greatest possible driving comfort in a vehicle powered by such an internal combustion engine, switching between operating modes (full operation and partial operation) should be implemented as smoothly as possible, without torque transfer and thus without any drive jerking. This requires compensating, in the most optimally coordinated way possible, for the decreasing load on the cylinders being deactivated during the switchover by increasing the load on the cylinders that remain active.

[0004] From DE 10 2011 086 344 A1, an internal combustion engine with a two-cylinder engine is known, in which one of the cylinder banks can be deactivated for partial operation. The cylinders of the cylinder bank to be deactivated are deactivated sequentially in order to achieve a transition from full operation, in which both cylinder banks are activated, to partial operation with as little torque as possible.

[0005] DE 10 2012 017 275 A1 also describes a reciprocating internal combustion engine with several cylinders, some of which can be deactivated during partial operation. To achieve a switching operation from full to partial operation with minimal torque impact, it is proposed that a switchable compressor, in particular an electrically driven compressor, be briefly activated during the throttling of the cylinders to be deactivated over several cycles to increase the filling of the cylinders that remain actively operated.

[0006] US 2016 / 032846 A1 discloses an internal combustion engine that can be operated in full operation, first partial operation, and second partial operation, with at least one combustion chamber of the engine being deactivated in the first and second partial operation. Full operation of the engine is intended particularly for use under very high loads. When these loads decrease to medium values, the engine switches to first partial operation. Conversely, when the loads decrease to relatively low values, the engine switches to second partial operation. The first and second partial operations differ in that the intake valves of the remaining active combustion chambers are actuated by different cams, with the intake valves of the remaining active combustion chambers having a longer opening duration and a greater valve lift in the first partial operation.A larger overall valve opening is achieved than in the second operating phase. In full operation, the intake valves are actuated by the same cams used in the first operating phase. Therefore, the intake valves are also opened with a relatively long duration and a relatively large lift during full operation.

[0007] US Patent 2009 / 0007866 A1 describes an internal combustion engine capable of operating in full and partial modes. When switching from full to partial operation, the valve lift of the intake valves that remain active during partial operation is increased to achieve a transition with minimal torque. For this purpose, the engine's valve train features fully variable valve lift for these intake valves, meaning the lift can be adjusted arbitrarily between a minimum and maximum value. Furthermore, the engine's operation allows for adjustment of the intake valve lift within each operating mode.to vary depending on the load within a first full operating range (with low loads and operating speeds), within a partial operating range (with medium loads) and within a second full operating range (with high loads and operating speeds).

[0008] A method as defined in the preamble of claim 1 is disclosed in US 2015 / 0152756 A1.

[0009] The invention was based on the objective of achieving, in an advantageous manner, a switching from full operation to partial operation in an internal combustion engine that is as torque-neutral as possible.

[0010] This problem is solved by means of a method according to claim 1. An internal combustion engine suitable for carrying out such a method is the subject of claim 6. Advantageous embodiments of the method according to the invention and preferred configurations of the internal combustion engine according to the invention are the subject of further claims and will become apparent from the following description of the invention.

[0011] The invention is based on the idea of ​​achieving a switching from full operation to partial operation of an internal combustion engine with a multi-cylinder design that is as torque-neutral as possible. This is accomplished by compensating for the loss of torque due to the deactivation of the cylinder(s) designated for this purpose by the cylinder(s) remaining in operation. This compensation is achieved by increasing the volumetric efficiency (i.e., the ratio of the mass of fresh gas actually contained in the cylinder after completion of a charge cycle to the theoretically maximum possible mass) for these cylinders during the switchover, and in particular by setting it as high as possible. This allows the amount of fuel that can be metabolized in the combustion chambers of the cylinders remaining in operation, and thus the drive torque generated by them, to be increased, regardless of any increase in intake manifold pressure.A particular advantage of increasing the volumetric efficiency is that, especially compared to increasing the intake manifold pressure (particularly when using a relatively inexpensive exhaust gas turbocharger), this can be achieved relatively quickly by adjusting the valve timing of the intake valves of the cylinders that remain active. A particularly rapid adjustment of the valve timing can be accomplished by changing the cams that actuate these intake valves using a suitable switching device, such as those also used for deactivating the gas exchange valves of the cylinders to be deactivated.

[0012] Accordingly, a method for operating an internal combustion engine is provided, wherein the internal combustion engine comprises at least one combustion engine forming at least two combustion chambers, which are delimited by cylinders formed in a cylinder housing and pistons cyclically moved up and down therein, and in which thermodynamic cycles can be carried out during the operation of the internal combustion engine, wherein a gas exchange in the combustion chambers is then controlled by means of at least one intake valve and exhaust valve, which are actuated by means of cams, and wherein A first operating state is provided in which the thermodynamic cycles are carried out in both a first combustion chamber and a second combustion chamber (full operation), and a second operating state is provided in which the thermodynamic cycles are carried out in the first combustion chamber and the thermodynamic cycles are not carried out in the second combustion chamber (partial operation), by at least preventing the supply of fuel to the second combustion chamber and / or preventing ignition of fuel, and preferably also by not actuating the inlet and outlet valves assigned to the second combustion chamber and thus keeping them closed.

[0013] To switch from the first operating state to the second operating state, the use of a first intake cam is changed to the use of a second intake cam for actuating the intake valve assigned to the first combustion chamber.

[0014] In order to advantageously increase the volumetric efficiency by changing the intake cams for the intake valve assigned to the first combustion chamber, which is also actively used in the second operating state, it should preferably be provided that the volumetric efficiency for this combustion chamber (and preferably also for the second combustion chamber) is not maximized in the first operating state by providing a relatively early or a relatively late intake valve closing time for the intake valve(s) assigned to this or these combustion chambers. Such a procedure is regularly implemented in modern internal combustion engines and is known as the Miller or Atkinson cycle.This enables a relatively high efficiency to be achieved when operating an internal combustion engine at low to medium loads, due to a comparatively pronounced expansion of the relatively small amount of gas enclosed in the combustion chambers during the power stroke. According to the invention, it is therefore further provided that at least the intake valve of the first cylinder is closed when actuated by the first intake cam before bottom dead center (BDC) - 60° crank angle (CA) or after BDC + 100° CA (BDC + 100° CA). Since switching from full to partial operation of the internal combustion engine is often only practical if the engine has previously been operated (in full operation) essentially at a steady state with low to medium loads, it is also advantageous to operate this (full) operation according to a Miller cycle in order to achieve the best possible efficiency.According to the invention, after switching to partial operation, the volumetric efficiency in the still actively operated first combustion chamber should be increased compared to full operation in order to at least partially compensate for the loss of drive power to the combustion chamber. In particular, it can be provided that the highest possible volumetric efficiency is achieved, whereby limitations, such as the avoidance of knocking, should be taken into account. For this purpose, within the framework of the method according to the invention, it is provided that at least the intake valve of the first cylinder is closed in partial operation of the internal combustion engine and thus when actuated by the second intake cam in the range between bottom dead center (BDC) - 50° crank angle (CDC) and BDC + 50° CDC, preferably between BDC - 20° CDC and BDC + 30° CDC.

[0015] To achieve the most advantageous partial operation of the internal combustion engine, the inventive method further provides that, for switching from the first operating state to the second operating state, a valve overlap, i.e., a simultaneous opening of the inlet and exhaust valves assigned to the first combustion chamber, is adjusted. This can be achieved in particular by advancing at least the exhaust valve closing or the exhaust valve timing overall (i.e., also the exhaust valve opening) for the corresponding exhaust valve, for example by between 0°CA and 20°CA.

[0016] Such an adjustment of the exhaust timing could be achieved by means of a phase adjuster, which allows the phase position of the exhaust cam(s), or optionally of the entire camshaft integrating the exhaust cam(s), to be rotated relative to a drive wheel that causes the exhaust cam(s) to rotate. However, since such phase adjusters generally operate relatively slowly, the inventive method provides for switching from the use of a first exhaust cam to the use of a second exhaust cam for actuating the exhaust valve associated with the first combustion chamber in order to achieve a corresponding adjustment of the exhaust timing. It is provided that the second exhaust cam causes a relatively early exhaust valve closure compared to the first exhaust cam.

[0017] An internal combustion engine according to the invention, comprising at least one combustion engine forming at least two combustion chambers, which are bounded by cylinders formed in a cylinder housing and pistons cyclically moved up and down therein, and in which thermodynamic cycles can be carried out during operation of the internal combustion engine, wherein a gas exchange in the combustion chambers can be controlled by means of an intake valve and an exhaust valve, which are actuated by means of cams, and wherein two intake cams are provided for the intake valve assigned to a first combustion chamber and two exhaust cams are provided for the exhaust valve assigned to the first combustion chamber, between the use of which it can be switched by means of a switching device, is characterized by a control device which is programmed in such a way that it can carry out a method according to the invention.

[0018] An increase in the volumetric efficiency for the cylinders that remain actively operated, as provided for switching from full to partial operation of an internal combustion engine according to the invention, is fundamentally applicable independently of any possible adjustment of the pressure in an intake manifold of the internal combustion engine, as can be achieved, for example, by turbocharging. The internal combustion engine according to the invention can therefore, in principle, also be a naturally aspirated internal combustion engine, i.e., one in which the combustion engine is designed as a naturally aspirated engine.Preferably, however, it can be provided that after switching from the first operating state to the second operating state, the pressure in an intake manifold of the internal combustion engine is increased, so that compensation for the lost proportion of drive power due to the deactivation of one or more cylinders in partial operation is achieved not only by increasing the delivery rate for the cylinder(s) that continue to be actively operated, but also by increasing the cylinder filling as a result of an increased intake manifold pressure and thus by the possibility of converting a larger quantity of fuel.

[0019] An internal combustion engine according to the invention can therefore include means for increasing the pressure in an intake manifold of the internal combustion engine. These means can, in particular, be a compressor integrated into a fresh gas stream of the internal combustion engine. Preferably, the compressor can be part of an exhaust gas turbocharger, which further comprises a turbine integrated into an exhaust stream of the internal combustion engine, by which the compressor can be driven. Such an exhaust gas turbocharger can also be equipped with a variable turbine geometry (VTG) device, which enables relatively rapid and effective control of the pressure in the intake manifold of the internal combustion engine.

[0020] The term "intake manifold" refers to the final section of the fresh gas stream of the internal combustion engine, in which the fresh gas flow is divided into partial flows that are supplied to the individual combustion chambers of the internal combustion engine, for which purpose the intake manifold forms a number of gas flow channels corresponding to the number of combustion chambers of the internal combustion engine.

[0021] A variable turbine flow (VTG) device can, in a known manner, comprise a plurality of guide vanes arranged in an inlet of a turbine of the exhaust gas turbocharger. These guide vanes are individually rotatable and can be adjusted collectively by means of an adjustment device. Depending on the rotational positions of the guide vanes, they narrow the free flow cross-section in the turbine inlet to a greater or lesser extent and also influence the section of the primary flow approaching the turbine impeller and the direction of this flow.

[0022] Influencing the pressure in the intake manifold of the internal combustion engine will generally require a relatively long time to reach a target value intended for partial operation, starting from an initial value intended for full operation. This time can be significantly longer than the time required for the intake valve associated with the first combustion chamber to switch from the first intake cam to the second intake cam. Therefore, particularly when influencing the pressure in the intake manifold is intended, it may be preferably provided that, after switching from the first operating state to the second operating state, the timing for the intake valve associated with the first combustion chamber is adjusted, particularly by means of a phaser. The inlet should be adjusted towards early if an inlet closure before UT was planned for the first operating state, or towards late if an inlet closure after UT was planned for the first operating state.

[0023] An internal combustion engine according to the invention can, in particular, include a phaser for changing the valve timing of the intake valve assigned to the first combustion chamber and / or the second combustion chamber. This advantageously enables a particularly smooth, torque-neutral switchover from full operation to partial operation, as the increase in the volumetric efficiency for the cylinder(s) still operating is compensated for by the relatively slow increase in the effect of the pressure increase in the intake manifold. Thus, it can be provided, in particular, that switching from the first intake cam to the second intake cam results in a volumetric efficiency increase that is greater than that which is provided for operation after an initial phase during which the effect of the pressure increase in the intake manifold is not yet fully realized.Starting from this initially relatively large increase in the volumetric efficiency, a corresponding change in the timing of the valves for the intake valve assigned to the first combustion chamber, which reduces the volumetric efficiency somewhat and in the opposite direction to the increase in pressure in the intake manifold, allows for an essentially constant drive torque during the initial phase and beyond.

[0024] If the switching from the first intake cam to the second intake cam is intended to maximize the volumetric efficiency of the intake valve associated with the first combustion chamber, this can cause the combustion processes occurring within the thermodynamic cycle in this combustion chamber to approach the knock limit, or even exceed it without countermeasures. To prevent this, a preferred embodiment of the method according to the invention provides for retarding the ignition timing when switching from the first to the second operating state. Preferably, this can be done simultaneously with switching the intake cams. Such a procedure is particularly feasible in a spark-ignition internal combustion engine, especially a gasoline engine.

[0025] The invention also relates to a control device with a memory, wherein a computer program is stored in the memory, in the execution of which a method according to the invention can be carried out.

[0026] The invention also relates to a computer program with program code for executing a method according to the invention when the computer program is executed on a computer.

[0027] The indefinite articles ("ein", "eine", "einer" and "eines"), particularly in the patent claims and in the description generally explaining the patent claims, are to be understood as such and not as numerals. Accordingly, components specified by these articles are to be understood as occurring at least once and potentially multiple times.

[0028] The present invention is explained in more detail below with reference to an embodiment illustrated in the drawings. The drawings show: Fig. 1: a schematic representation of an internal combustion engine according to the invention; Fig. 2: a schematic longitudinal section of the internal combustion engine of the internal combustion engine according to the Fig. 1 ; Fig. 3: a cam carrier for an internal combustion engine according to the Fig. 1 ; Fig. 4: a pair of cams of the cam carrier according to the Fig. 3 ; Fig. 5: a section of the cam carrier according to the Fig. 3 and a switching actuator in a schematic representation; Fig. 6: various stroke profiles for the gas exchange valves of an internal combustion engine according to the Fig. 2 ; and Fig. 7: in a diagram the quantitative trends of various operating parameters of an internal combustion engine according to the Fig. 1 before and after switching from full operation to partial operation.

[0029] In the Fig. 1 A schematic representation of an internal combustion engine according to the invention is shown. The internal combustion engine can, for example, power a motor vehicle (not shown).

[0030] The internal combustion engine includes a [details also in the] Fig. 2 The illustrated internal combustion engine 10, which can be operated according to the Otto cycle, comprises several (here: four) cylinders 16 in a cylinder crankcase 12 and cylinder head 14. The cylinders 16 are connected on the intake side to an intake manifold 18 of a fresh gas stream and on the exhaust side to an exhaust manifold 20 of an exhaust stream of the internal combustion engine. In a known manner, fresh gas (essentially air) is combusted with fuel in combustion chambers 22, which are bounded by the cylinders 16 together with the pistons 24 guided therein and the cylinder head 14. The fuel can be injected directly into the combustion chambers 22 by means of injectors 26. The exhaust gas produced during the combustion of the fuel-fresh gas mixture is discharged via the exhaust stream.

[0031] The supply of fresh gas to the combustion chambers 22 and the removal of exhaust gas from the combustion chambers 22 is controlled by four gas exchange valves, namely two intake valves 28 and two exhaust valves 30, per cylinder 16, which are operated by a [unclear] in the Fig. 1 The valve train of the internal combustion engine 10, not shown, is actuated. According to the... Fig. 2 A crankshaft 34 forming a crankpin 32, the crankpins 32 being connected to the pistons 24 via connecting rods 36. This translates the linear movements of the pistons 24 into a rotation of the crankshaft 34, the rotation of which in turn causes a periodic change in the direction of the linear movements of the pistons 24. The rotation of the crankshaft 34 is also transmitted via a timing gear, for example a toothed belt drive 38, to two camshafts 40, each of which actuates two gas exchange valves 28, 30 per combustion chamber 22 via, for example, rocker arms or tappets (not shown). One of the camshafts 40 is configured as an intake camshaft, i.e., it actuates all intake valves 28, while the other is configured as an exhaust camshaft and consequently actuates all exhaust valves 30.

[0032] The internal combustion engine also includes an exhaust gas turbocharger. This turbocharger has a turbine 42 integrated into the exhaust stream and a compressor 44 integrated into the fresh air stream. A rotating impeller of the turbine 42, driven by the exhaust gas flow, drives an impeller of the compressor 44 via a shaft 46. The resulting rotation of the impeller of the compressor 44 compresses the fresh air flow passing through it. A wastegate 48 allows boost pressure limitation by diverting a portion of the exhaust gas flow around the turbine 42 when the internal combustion engine 10 is operating at high speeds and / or loads. Furthermore, an exhaust aftertreatment device 50, for example in the form of a three-way catalytic converter, is integrated into the exhaust stream.

[0033] The internal combustion engine 10 further comprises a phase adjuster 54 for each of the camshafts 40, controlled by a control device 52 (engine control unit). The phase adjusters 54 enable the timing, and thus the opening phases, of the associated gas exchange valves 28, 30 to be changed or shifted. The phase adjusters 54 are integrated into a gear wheel 56 of each camshaft 40 in a known manner (see, for example, DE 10 2013 223 112 A1). Accordingly, each phase adjuster 54 of the camshafts 40 can have a vane rotor (not shown) that is rotationally fixed to the respective camshaft 40 and is rotatably arranged within limits within a stator (not shown) of the phase adjuster 54. The stator forms a tooth contour on its essentially cylindrical outer surface for the engagement of teeth of a toothed belt of the toothed belt drive 38.Between the vane rotor and the stator of the phase adjuster 54, several pressure chambers can be formed, which, controlled by a phase adjuster valve (not shown), can be selectively filled with a liquid, in particular an oil, in order to rotate the vane rotor within the stator in a defined manner, thereby changing the phase angle between the respective camshaft 40 connected to the vane rotor and the stator connected to the crankshaft 32 in a rotational driving manner, in accordance with the aim of changing the opening phase of the associated gas exchange valves 28, 30.

[0034] The internal combustion engine further includes a switching device 58, by means of which both the inlet valves 28 and the exhaust valves 30 can be switched from actuation by a first cam 60 to actuation by a second cam 62. This switching device 58 can also be controlled by the control device 52 and is located in the Fig. 2 only schematically indicated. The function of the switching device 58 is based on a longitudinal axial displacement of sleeve-shaped cam carriers 64 (see also Fig. 3 ), which are arranged non-rotatably on a basic shaft 66, by means of a switching actuator 68 each (see Fig. 4 ), wherein the cam carriers 64 have two different cams 60, 62 for each of the inlet valves 28 and exhaust valves 30 that can be actuated by them (cf. Fig. 3 and 4), which, depending on the set displacement positions of the cam carriers 64, interact alternatively with the associated inlet valves 28 and exhaust valves 30.

[0035] In the design example, as it appears in the Fig. 2 and 3 As shown, each of the cam carriers 40 comprises a total of four cam pairs, each of which is assigned to a gas exchange valve 28, 30 of the internal combustion engine. By means of the cams 60, 62 formed by such a cam carrier 64, either the intake valves 28 or the exhaust valves 30 of a total of two adjacent cylinders 16 of an internal combustion engine 10 are thus actuated according to the Fig. 1 und 2 , in which each cylinder 16 is assigned two inlet valves 28 and two exhaust valves 30, is actuated. Between the two pairs of cams assigned to the gas exchange valves 28, 30 of a first cylinder 16 and the two pairs of cams assigned to the gas exchange valves 28, 30 of a second cylinder 16, the cam in the Fig. 3 The cam carrier 64 shown also features a switching cam in the form of a Y-shaped guide groove 70. Through the interaction of this guide groove 70 with the drivers 72 of the associated switching actuator 68, the cam carrier 64 can be axially displaced by the distance x, thereby bringing a selected cam 60, 62 of each cam pair into operative contact with the associated gas exchange valve 28, 30. According to the Fig. 5 For example, starting from the illustrated functional position in which the gas exchange valves 28, 30 are each in operative connection with the right (first) cam 60 of each cam pair, the right driver 72 can be extended and the cam carrier 64 thereby, in conjunction with its rotation (in the Fig. 5 upwards) are shifted to the right by a distance x. As a result of the Y-shaped guide groove 70 ending in the middle, in the Fig. 5 In the lower section, the right driver 72 is moved back into its retracted position. After such a displacement of the cam carrier 64 by the distance x, the left (second) cams 62 of each cam pair are then in operative contact with the corresponding gas exchange valve 28, 30. Such a displacement of the cam carrier 64 by the distance x to the right also results in the left driver 72 being brought into contact with the left section of the Y-shaped guide groove 70, so that by extending this driver 72 the cam carrier 64 can again be displaced by the distance x to the left.

[0036] According to the invention, for so-called partial operation of the internal combustion engine, a subset, and in particular half, of the combustion chambers 22, specifically the two central combustion chambers, can be deactivated by interrupting the fuel supply to the corresponding injectors 26 and no longer actuating, i.e., opening, the gas exchange valves 28, 30 associated with them. For this purpose, it is provided that each cam pair associated with the gas exchange valves 28, 30 of such a deactivatable combustion chamber 22 forms a second cam 62 in the form of a so-called zero cam, which has no cam profile and thus does not lead to the opening of an associated gas exchange valve 28, 30. In the cam carrier 64 according to the Fig. 3 The left cams of each of the two cam pairs arranged to the right of the guide groove 70 are designed as corresponding zero cams.

[0037] When switching from full operation of the internal combustion engine, in which all cylinders 16 are operated at low to medium loads, to partial operation, half of the cylinders 16 are deactivated within a very short period, approximately one revolution of the crankshaft 32. These deactivated cylinders can therefore no longer contribute to generating drive power from the internal combustion engine 10. On the contrary, since the pistons 24 assigned to these cylinders 16 must be driven by the cylinders 16 that remain actively operating, these deactivated cylinders 16 change their function from power generators to power consumers.

[0038] Since such a switch from full to partial operation is intended to occur regularly during a constant operating phase of the internal combustion engine, the drive power should consequently remain essentially constant before and after the switchover. Therefore, the failure of the deactivated cylinders 16 as power generators must be compensated for by the cylinders 16 that remain actively operating. The load with which these cylinders operate after a switchover must be significantly increased, and in particular, approximately doubled. For this to occur, a considerably larger quantity of fuel must be converted within one cycle of the thermodynamic cycles carried out in the cylinders 16 that remain actively operating, which requires a correspondingly increased quantity of fresh gas.

[0039] This increased quantity of fresh gas is to be achieved, on the one hand, by increasing the pressure in the intake manifold 18 using standard turbocharger boost pressure control measures. Through higher compression of the fresh gas, more fresh gas can then be introduced into the combustion chambers 22, thus enabling a correspondingly increased amount of fuel to be used.

[0040] Furthermore, it is planned that the delivery rate, and thus the ratio of the mass of fresh gas actually contained in the cylinders 16 after completion of a charge exchange to the theoretically maximum possible mass, will also be increased and, in particular, maximized. Both measures in combination lead to a significant increase in the amount of fresh gas supplied to the cylinders 16, which remain actively operated, within a cycle during partial operation compared to the full operation preceding the switchover.

[0041] The effect of the increased delivery rate is particularly pronounced because the internal combustion engine is designed to operate in a so-called Miller cycle during full operation, which precedes a switch to partial operation. According to the present embodiment, the intake valves 28 are closed relatively early and therefore significantly (e.g., approximately 50°) before bottom dead center (BDC), resulting in incomplete filling of the combustion chambers. This is in the Fig. 6 This is shown based on the stroke profile 74 provided for all inlet valves 28 in full operation of the internal combustion engine. After switching to partial operation, for which not only the cams 60, 62 assigned to the gas exchange valves 28, 30 of the cylinders 16 to be deactivated are changed (each to a zero cam) but also (at least partially) the cams 60, 62 assigned to the gas exchange valves 28, 30 of the cylinders 16 to continue to be operated actively are changed, the inlet valves 28 of these cylinders 16 to continue to be operated actively no longer close relatively early but with regard to maximizing the volumetric efficiency at and specifically a few degrees after bottom dead center (BDC), as shown based on the in the Fig. 6 The stroke progression shown in section 76a is illustrated.

[0042] In the Fig. 7 In summary, the measures provided according to the invention are shown in order to make switching the internal combustion engine from full operation to partial operation as torque-neutral as possible and consequently without a noticeable short-term reduction in the drive power generated by the internal combustion engine.

[0043] In the diagram according to the Fig. 7 The graph qualitatively depicts the course of various operating parameters of the internal combustion engine, specifically the opening time (line 78) for the intake valves 28 of those cylinders 16 that are also actively operated during partial operation, the closing time (line 80) for the exhaust valves 30 of the same cylinders 16, the pressure in the intake manifold (line 82), and the ignition angle (line 84), as a function of time t (horizontal axis). The left half of the diagram, divided by a vertical line, shows the corresponding operating parameters for full operation of the internal combustion engine, while the right half shows the course of the operating parameters during an initial phase of partial operation.The position of the vertical line thus corresponds to the switching point or the switching process, which is carried out relatively quickly, namely within one revolution of the camshafts 40 and becomes effective within one revolution of the crankshaft 34.

[0044] The increase in delivery rate also takes effect during the same short period, which is achieved by switching between the two cams 60, 62 which are offset with respect to their timing (cf. Fig. 5 ), by means of which the inlet valves 28 of the cylinders 16, which continue to be operated actively, can be actuated, while the effect of increasing the pressure in the intake manifold 18 only increases relatively slowly to a predetermined level.

[0045] This delayed effect of the pressure increase in the intake manifold 18 is compensated for by the rapidly acting increase in volumetric efficiency. This is achieved by means of the (second) cams 62, which are assigned to the cylinders 16 that are also active during partial operation, and initially provide a lift profile designed for maximum volumetric efficiency. However, immediately following the switching operation, this lift profile is advanced slightly by means of the phase adjuster 54 of the internal combustion engine, which is assigned to the intake camshaft 40. This continues until the pressure in the intake manifold 18 reaches the intended value (see lift profile 76b in the Fig. 6 ).

[0046] Since the stroke profile 76a for the inlet valves 28 assigned to the cylinders 16 that remain actively operated in partial operation, which is designed with regard to a maximum volumetric efficiency, would lead to a significantly increased tendency to knock without countermeasures, according to the Fig. 7 (cf. curve 84) Simultaneously with the switching, a retardation and thus an advancement of the ignition timing is also provided to counteract such an increase in the tendency to knock. The initially relatively strong retardation of the ignition timing is continuously and partially reversed as long as the stroke profile 76a, 76b of the intake valves 28 is advanced by means of the phase adjuster 54.

[0047] In the Fig. 7 It is further shown (see curve 80) that simultaneously with the switch from full operation to partial operation, the closing of the exhaust valves 30 assigned to the still actively operated cylinders 16 is advanced, thereby achieving the most optimal possible adjustment of the valve overlaps of the intake valves 28 and exhaust valves 30. Fig. 6 Figure 86 shows the corresponding stroke profile 86 as it is provided for the exhaust valves 30 in full operation before switching, as well as the stroke profile 88 as it is provided for the exhaust valves 30, which are still actuated, after the influence by the phase adjuster 54 has ended in partial operation.

[0048] This early adjustment of the valve timing of the exhaust valves 30 of the cylinders 16, which remain actively operated in partial operation, could, as in the Fig. 7 As shown, this is achieved by means of the phase adjuster 54. According to the invention, however, the advance adjustment of the valve timing of the exhaust valves 30 is also achieved by switching between two cams 60, 62 with different cam tracks for the exhaust valves 30, which are also actuated in partial operation, as shown in the Fig. 7 as shown by the dashed line 80. Bezugszeichenliste

[0049] 10 Internal combustion engine 12 Cylinder crankcase 14 Cylinder head 16 Cylinder 18 Intake manifold 20 Exhaust manifold 22 Combustion chamber 24 Piston 26 Injector 28 Gas exchange valve / Intake valve 30 Gas exchange valve / Exhaust valve 32 Crankpin 34 Crankshaft 36 Connecting rod 38 Timing belt drive 40 Camshaft 42 Turbine 44 Compressor 46 Shaft 48 Wastegate 50 Exhaust aftertreatment device 52 Control device 54 Phaser 56 Pulley 58 Switching device 60 First cam 62 Second cam 64 Cam carrier 66 Main shaft 68 Switching actuator 70 Guide groove 72 Driver 74 Lift profile of the intake valves in full operation 76a Lift profile of the valves actuated in partial operation Intake valves before a phase shift 76b Lift profile of the intake valves actuated in partial operation after a phase shift 78 Opening timing profile of the intake valves actuated in partial operation 80 Closing timing profile of the exhaust valves actuated in partial operation 82 Intake manifold pressure profile 84 Ignition angle profile 86 Exhaust valve lift profileIn full operation, the stroke profile of the exhaust valves actuated in partial operation after a phase shift is shown.

Claims

1. Method for operating an internal combustion engine having an IC engine (10) which forms at least two combustion chambers (22) which are delimited by cylinders (16) formed in a cylinder housing (12) and pistons (24) guided cyclically up and down therein and in which thermodynamic cyclic processes can be carried out during operation of the internal combustion engine, wherein a gas exchange in the combustion chambers (22) is then controlled, in each case, by means of at least one intake valve (28) and an exhaust valve (30), which are actuated by means of cams (60, 62), and wherein - a first operating state is provided in which the thermodynamic cyclic processes are carried out both in a first combustion chamber (22) and in a second combustion chamber (22), and - a second operating state is provided in which the thermodynamic cyclic processes are carried out in the first combustion chamber (22) and the thermodynamic cyclic processes are not carried out in the second combustion chamber (22), wherein, for switching from the first operating state to the second operating state, a change is made from using a first intake cam (60) to using a second intake cam (62) for actuating the intake valve (28) associated with the first combustion chamber, characterized in that - at least the intake valve (28) associated with the first combustion chamber (22) is closed when actuated by means of the first intake cam (60) before BDC - 60° crankshaft angle or after BDC + 100° crankshaft angle and by means of the second intake cam (62) in the range between BDC - 50° crankshaft angle and BDC + 50° crankshaft angle, and - for switching from the first operating state to the second operating state, a valve overlap of the intake and exhaust valves associated with the first combustion chamber (22) is adapted, wherein a change is made from using a first exhaust cam (60) to using a second exhaust cam (62) for actuating the exhaust valve (30) associated with the first combustion chamber (22), wherein the second exhaust cam (62) brings about a relatively early exhaust closure in comparison with the first exhaust cam (60).

2. Method according to claim 1, characterized in that at least the intake valve (28) associated with the first combustion chamber (22) is closed when actuated by means of the second intake cam (62) in the range between BDC - 20'°crankshaft angle and BDC + 30'°crankshaft angle.

3. Method according to any of the preceding claims, characterized in that, after switching from the first operating state to the second operating state, the pressure in an intake manifold (18) of the internal combustion engine is increased.

4. Method according to any of the preceding claims, characterized in that, for switching from the first operating state to the second operating state, an ignition angle is adjusted in the direction of retard for the first combustion chamber (22).

5. Method according to any of the preceding claims, characterized in that, after switching from the first operating state to the second operating state, the control times for the intake valve (28) associated with the first combustion chamber (22) are - adjusted in the direction of advance if, for the first operating state, an intake closure was provided before BDC, or - adjusted in the direction of retard if, for the first operating state, an intake closure was provided after BDC.

6. Internal combustion engine having an IC engine (10) which forms at least two combustion chambers (22) which are delimited by cylinders (16) formed in a cylinder housing (12) and pistons (24) guided cyclically to and fro therein and in which thermodynamic cyclic processes can be carried out during operation of the internal combustion engine, wherein a gas exchange in the combustion chambers (22) can be controlled, in each case, by means of an intake valve (28) and an exhaust valve (30), which are actuated by means of cams (60, 62), and wherein, for the intake valve (28) associated with a first combustion chamber (22), two intake cams (60, 62) are provided and, for the exhaust valve (30) associated with the first combustion chamber (22), two exhaust cams (60, 62) are provided, between the use of which it is possible to switch by means of a switching device (58), characterized by a control device (52) programmed in such a way that it can carry out a method according to any of the preceding claims.

7. Internal combustion engine according to claim 6, characterized by two exhaust cams (60, 62) for the exhaust valve (30) associated with the second combustion chamber (22), between the use of which it is possible to switch by means of a switching device (58).

8. Internal combustion engine according to claim 6 or 7, characterized by means for influencing the pressure in an intake manifold (18) of the internal combustion engine.

9. Internal combustion engine according to any of claims 6 to 8, characterized by a phase adjuster (54) for changing the control times for the intake valve (28) associated with the first combustion chamber (22) and / or the second combustion chamber (22).

10. Internal combustion engine according to any of claims 6 to 9, characterized by a phase adjuster (54) for changing the control times for the exhaust valve (30) associated with the first combustion chamber (22) and / or the second combustion chamber (22).