Method for operating an internal combustion engine and internal combustion engine

Abstract

Method for operating an internal combustion engine with an internal combustion motor that forms at least three combustion chambers in which thermodynamic cycles can be carried out during the operation of the internal combustion engine, wherein - full operation may be planned in which the thermodynamic cycles are carried out in both a first combustion chamber and a second combustion chamber and - a partial operation can be 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, wherein fuel is supplied to the combustion chambers by means of a fuel pump (20) actuated by a cam drive shaft (18) with several pump cams (36, 38) for the execution of the thermodynamic cycles, and wherein a supply of fuel to the second combustion chamber is terminated for switching from full operation to partial operation, characterized in that for switching from full operation to partial operation, the use of a first pump cam (36) is changed to the use of a second pump cam (38) for actuating the fuel pump (20).wherein the specific delivery rate of the fuel pump (20) effected by the second pump cam (38) is less than the specific delivery rate effected by the first pump cam (36) and wherein the ratio of the number of cam projections (58) of the first pump cam (36) to the number of cam projections (58) of the second pump cam (38) corresponds to the ratio of the number of all combustion chambers to the number of first combustion chambers.

Description

[0001] The invention relates to a method for operating an internal combustion engine that can be operated in partial mode. The invention further relates to an internal combustion engine suitable for carrying out such a method.

[0002] Multi-cylinder internal combustion engines are known that can be temporarily operated in a so-called partial mode, in which a portion of the combustion chambers is deactivated, so that no thermodynamic cycles take place in them. Instead, the pistons assigned to the then deactivated combustion chambers are dragged along by the pistons of the still active combustion chambers. This is done with the aim of increasing the efficiency of the internal combustion engine operation, because deactivating a portion of the combustion chambers, with essentially constant drive power, leads to the operation of the remaining active combustion chambers at a significantly higher load, which is associated with a higher specific efficiency of the thermodynamic cycles taking place in these combustion chambers.In order to minimize the achievable efficiency increase for the active combustion chambers due to the dragging of the pistons of the deactivated combustion chambers, it is generally intended to keep the gas exchange valves assigned to the deactivated combustion chambers closed during partial operation when fuel injection is interrupted. This causes the gas within these combustion chambers to be cyclically compressed and expanded but not expelled. This avoids power losses due to the compression of gas quantities that would subsequently be expelled through open exhaust valves.

[0003] High-pressure fuel pumps are used to supply direct-injection internal combustion engines with the fuel required for operation. The fuel is delivered to the individual injectors, through which the fuel is injected into the combustion chambers of the internal combustion engine, at relatively high pressure in order to achieve the best possible distribution of the fuel in the combustion chambers and the best possible mixing with the fresh gas introduced into the combustion chambers via the intake valves. The pressure at which the fuel is delivered to the injectors is currently between approximately 200 bar and 400 bar for gasoline engines and around 2000 bar for diesel engines. To generate such high pressures, high-pressure fuel pumps are used. These are designed as positive displacement pumps and, in particular, as piston pumps.Since such piston pumps are often not sufficiently self-priming, they are preceded by pre-feed pumps designed as flow pumps.

[0004] High-pressure fuel pumps are usually driven directly by a shaft of the internal combustion engine, whereby it can be provided in particular that the number of delivery strokes performed by them corresponds to the number of injections into the combustion chambers of the internal combustion engine. For example, if a (4-stroke) internal combustion engine with four cylinders and thus four combustion chambers is provided with a high-pressure fuel pump in the form of a simple piston pump, it can be provided that the piston pump performs four delivery strokes and thus four pump pressure pulses for every two revolutions of the internal combustion engine's crankshaft in order to synchronize the cyclical increase in fuel pressure caused by the pump pressure pulses in a fuel distributor upstream of the injection valves with the pressure-reducing injections.If a cam drive shaft intended for actuating the piston pump is directly driven by the crankshaft, the pump cam of the cam drive shaft, which is operatively connected to the piston of the piston pump, can have two cam lobes. Alternatively, for example, the piston pump can be actuated directly by a camshaft primarily intended for actuating gas exchange valves of the internal combustion engine, in which case the pump cam of the camshaft, which is operatively connected to the piston of the piston pump, can have four cam lobes.

[0005] DE 10 2013 212 302 A1 discloses an internal combustion engine with a high-pressure fuel pump in which two piston pump assemblies are actuated by means of the same multiple cam of a camshaft. For partial load operation, which may also be partial operation with partially deactivated combustion chambers of an internal combustion engine, one of the two piston pump assemblies can be deactivated by keeping the associated intake valve permanently open. This is intended to adapt, among other things, the delivery capacity of the high-pressure fuel pump to the reduced fuel requirement of the internal combustion engine during partial load operation.

[0006] DE 10 2014 106 425 A1 also describes an internal combustion engine with a high-pressure fuel pump designed as a piston pump. Its piston is actuated by a cam drive shaft, with a switching device provided to bring one of three different pump cams into operative connection with the piston of the piston pump as needed. The three pump cams differ in the piston strokes they cause, with the stroke caused by one of the pump cams being zero, thus leading to deactivation of the fuel pump.

[0007] DE 10 2015 105 735 A1 discloses a method for operating a fuel pump for an internal combustion engine, in which the stroke of a piston of the fuel pump is increased for starting the internal combustion engine. For this purpose, the fuel pump, designed as a piston pump, is actuated by a cam drive shaft comprising two different pump cams, which lead to different strokes of the fuel pump pistons.

[0008] DE 103 52 769 A1 describes a fuel pump for an internal combustion engine in which the number of working cycles of the high-pressure fuel pump is increased when the internal combustion engine is started compared to normal operation.

[0009] DE 10 2008 061 628 A1 discloses the selective actuation of a fuel pump of an internal combustion engine by means of different cams of a camshaft in order to adapt the delivery capacity of the fuel pump to a varying fuel requirement of the internal combustion engine.

[0010] The object of the invention was to achieve the greatest possible efficiency in an internal combustion engine that can also be operated in partial mode.

[0011] This object is achieved by means of a method according to patent claim 1. An internal combustion engine designed to carry out such a method is the subject of patent claim 4. Advantageous embodiments of the method according to the invention and preferred embodiments of the internal combustion engine according to the invention are the subject of the further patent claims and / or emerge from the following description of the invention.

[0012] According to the invention, a method is provided for operating an internal combustion engine with an internal combustion engine, preferably a spark-ignition internal combustion engine and in particular a gasoline engine, wherein the internal combustion engine forms at least two combustion chambers in which thermodynamic cycles can be carried out during operation of the internal combustion engine, wherein - full operation can be provided in which the thermodynamic cycles are carried out in one or more first combustion chambers as well as in one or more second combustion chambers, and - partial operation can be provided in which the thermodynamic cycles are carried out in the first combustion chamber(s) and the thermodynamic cycles are not carried out in the second combustion chamber(s).

[0013] To carry out the thermodynamic cycles, fuel is introduced into the combustion chambers by means of a fuel pump (preferably in the form of a positive displacement pump and in particular a piston pump) which is actuated by a cam drive shaft having a plurality of pump cams, wherein a supply of fuel to the second combustion chamber(s) is terminated for switching from full operation to partial operation. Furthermore, it is provided that for switching from full operation to partial operation, a switch is made from using a first of the pump cams to using a second of the pump cams for actuating the fuel pump, wherein the specific delivery rate of the fuel pump caused by the second pump cam is lower than the specific delivery rate caused by the first pump cam.The “specific delivery rate” is understood to mean the delivery rate of the fuel pump per revolution of the camshaft.

[0014] Accordingly, it is intended to reduce the specific delivery rate of the fuel pump for the partial operation of the internal combustion engine and thus to adapt it to the lower fuel requirement in partial operation compared to the full operation planned before the change (with essentially identical power generation of the internal combustion engine) by reducing the amount of fuel delivered by the fuel pump per revolution of the camshaft and thus the specific delivery rate, which offers relevant advantages over alternative measures for influencing the delivery rate, in particular speed control and control by diverting part of the fuel already delivered.Compared to speed control, the method according to the invention enables, in particular, the delivery rate of the fuel pump to be influenced independently of the drive speed (of the cam drive shaft), thereby making it possible, in particular, to have the drive shaft advantageously driven directly by a crankshaft of the internal combustion engine or another shaft of the internal combustion engine driven by the crankshaft, in particular a camshaft primarily intended for actuating gas exchange valves, or to integrate the cam drive shaft into the crankshaft or other shaft, in particular the camshaft, of the internal combustion engine. Compared to diverting part of the fuel already delivered, the method has a particular advantage in terms of efficiency because essentially only the amount of fuel is delivered that is actually intended to be used for introduction into the combustion chambers.

[0015] An internal combustion engine which is structurally suitable for carrying out such a method comprises at least one internal combustion engine, preferably a spark-ignition internal combustion engine, in particular a gasoline engine, which forms at least two combustion chambers in which thermodynamic cycles can be carried out, wherein, for carrying out the thermodynamic cycles, fuel can be introduced into the combustion chambers by means of a fuel pump (preferably a positive displacement pump and in particular a piston pump) which can be actuated by a camshaft drive shaft with a plurality of pump cams, wherein a partial operation of the internal combustion engine can be achieved in which the introduction of fuel into some of the combustion chambers is terminated, as a result of which this combustion chamber or these combustion chambers are deactivated.Furthermore, a switching device is provided by which the use of a first pump cam can be switched to the use of a second pump cam for actuating the fuel pump, wherein the specific delivery rate of the fuel pump caused by the second pump cam is lower than the specific delivery rate caused by the first pump cam. Preferably, such an internal combustion engine according to the invention further comprises a control device that is programmed such that it can execute a method according to the invention in an automated manner.

[0016] The specific delivery rate of the fuel pump caused by the second pump cam, which is relatively low compared to the specific delivery rate caused by the first pump cam, is achieved by reducing the number of delivery strokes performed by the fuel pump per revolution of the cam drive shaft, for which purpose the number of cam lobes of the second pump cam is smaller than the number of cam lobes of the first pump cam. It can be provided that the pump cams differ only in the number of cam lobes and thus not in the height of the cam lobes and thus in the size of the piston strokes caused by them. In this way, relatively small piston strokes caused by the second pump cam can be avoided, which can be associated with relatively low efficiency in the operation of the fuel pump.In addition, however, it can also be provided that the stroke of one or more pistons of the fuel pump caused by the second pump cam is (at least on average) smaller than the stroke of the piston(s) caused by the first pump cam, so that the height of the cam lobes of the second pump cam is reduced compared to the height of the cam lobes of the first pump cam.

[0017] Specifically, the method according to the invention provides for at least three combustion chambers, wherein the ratio of the number of cam lobes of the first pump cam to the number of cam lobes of the second pump cam corresponds to the ratio of the number of all combustion chambers to the number of first combustion chambers. Similarly, for an internal combustion engine according to the invention, at least three combustion chambers are provided, wherein the ratio of the number of cam lobes of the first pump cam to the number of cam lobes of the second pump cam corresponds to the ratio of the number of all combustion chambers to the number of combustion chambers to continue to be operated in partial operation.In this way, the delivery capacity of the fuel pump and the pressure pulsation caused by the fuel pump in a high-pressure section of a fuel supply system of the internal combustion engine, located between the fuel pump and the internal combustion engine, in particular in a fuel distributor, can be adapted as optimally as possible to the partial operation of the internal combustion engine.

[0018] According to a preferred embodiment of a method according to the invention or according to a preferred embodiment of an internal combustion engine according to the invention, it can be provided that, when carrying out the thermodynamic cycles, a gas exchange in the combustion chambers is controlled or can be controlled by means of gas exchange valves, wherein the gas exchange valves are preferably actuated or can be actuated by means of a camshaft. It can further be provided that, in order to achieve partial operation of the internal combustion engine, actuation of the gas exchange valves assigned to the second, deactivatable combustion chamber(s) is terminated, i.e., that these gas exchange valves are no longer opened. For this purpose, a corresponding internal combustion engine according to the invention can comprise a deactivation device by means of which, for the partial operation of the internal combustion engine, a part of the combustion chambers, i.e.for the second combustion chamber(s), at least one of the gas exchange valves can be deactivated. The deactivation device of such an internal combustion engine, in which the gas exchange valves are actuated by means of one or more camshafts, can in particular be based on switching between different valve cams of the camshaft(s) provided for actuating the gas exchange valves of at least the deactivatable combustion chambers, wherein one of these valve cams is a "zero cam" which has no cam lobe and thus does not lead to an opening of the gas exchange valve associated with it.

[0019] A preferred development of such a method according to the invention provides that, for full operation of the internal combustion engine, an actuation of at least one of the gas exchange valves of the individual (first and second) combustion chambers can be provided alternatively according to either a first valve lift curve or a second valve lift curve. When the gas exchange valves are actuated according to the first valve lift curve, the fuel pump is actuated by means of the first pump cam, and when the gas exchange valves are actuated according to the second valve lift curve, the fuel pump is actuated by means of a third pump cam of the cam drive shaft. For this purpose, an internal combustion engine according to the invention can comprise a switching device by means of which it is possible to switch from an actuation of at least one of the gas exchange valves of the combustion chambers according to a first valve lift curve to an actuation according to a second valve lift curve.The internal combustion engine can then further comprise a third pump cam, which can be switched to by means of the switching device for actuating the fuel pump. In this way, not only can the specific delivery rate of the fuel pump be adjusted for switching between full operation and partial operation by changing the pump cam actuating the fuel pump, but also the specific delivery rate can be adjusted when the valve lift curves used to actuate the gas exchange valves change during full operation, for example as a result of changed power requirements. This can also prevent or minimize the delivery of fuel by the fuel pump beyond its required level, which can have an overall beneficial effect on the operating efficiency of the internal combustion engine.

[0020] In particular, in such a configuration of an internal combustion engine according to the invention, it can be provided that the cam drive shaft of the fuel pump is driven directly (and in particular also at the same rotational speed) by the camshaft, or these shafts are formed integrally (in that the camshaft also forms the pump cams), which then makes it possible to switch the pump cams and change the valve lift curves (generated by valve cams) using the same adjusting device. The switching device and the changing device would then be identical or formed integrally in the form of the adjusting device. This makes it possible to realize a design of a corresponding internal combustion engine according to the invention that is as compact and cost-effective as possible.

[0021] The invention also relates to a computer program with a program code for carrying out a method according to the invention when the computer program is executed on a control device (computer) of an internal combustion engine according to the invention.

[0022] The indefinite articles ("a," "an," "one," and "another"), particularly in the patent claims and in the description generally explaining the patent claims, are to be understood as such and not as numerals. Components specified accordingly are thus to be understood as being present at least once and may be present multiple times.

[0023] The invention is explained in more detail below using an exemplary embodiment illustrated in the drawings. In the drawings: Fig. 1: a section of a perspective view of an internal combustion engine according to the invention; Fig. 2: the internal combustion engine according to the Fig. 1 in a partially sectioned view; Fig. 3: schematically a camshaft and an adjusting device of the internal combustion engine and Fig. 4: a sectional view according to the section plane IV - IV in the Fig. 3.

[0024] The Fig. 1 and Fig. 2 show an internal combustion engine according to the invention with an internal combustion engine designed as a reciprocating piston engine and operable in particular according to the Otto principle. This comprises, in a known manner, a cylinder crankcase 10, within which a plurality (here: four) of cylinders (not visible) are formed. Pistons (not visible) are movably guided within the cylinders and are connected to a crankshaft (not visible) via connecting rods (not visible). Sections of the cylinders and the top surfaces of the pistons, together with a cylinder head 12 of the internal combustion engine, each define a combustion chamber. In the combustion chambers, fuel injected directly by means of injectors (not visible) is mixed with fresh gas (essentially air drawn in from the environment), which is supplied to the combustion chambers via a fresh gas line 14, ignited, and thereby combusted. The resulting exhaust gas is discharged via an exhaust line (not visible).The supply of fresh gas into the combustion chambers and the removal of exhaust gas from the combustion chambers is carried out in a known manner via gas exchange valves 16 (cf. Fig. 3) which is controlled by means of at least one camshaft 18 (cf. Fig. 2, Fig. 3). The camshaft 18 is driven directly by the crankshaft, for example via a toothed belt, a timing chain, or a gear transmission (not visible), so that the rotational speeds of the crankshaft and camshaft 18 are proportional.

[0025] The fuel is supplied to the injectors at a relatively high pressure in order to achieve the finest possible atomization through injection and thus the best possible mixing with the fresh gas. This relatively high fuel pressure is generated by a (high-pressure) fuel pump 20, which is also actuated or driven by the camshaft 18. The (or one of the) camshafts 18 thus simultaneously represents a cam drive shaft of the fuel pump 20. The fuel pump 20 pumps the fuel into a high-pressure section of a fuel supply system of the internal combustion engine, into which a fuel distributor (not visible), also referred to as a "rail," is integrated, which represents a reserve volume for a relatively large quantity of the pressurized fuel.Such a fuel distributor serving as a pressure and fuel buffer enables injection of fuel by means of the injectors, which is, to a certain extent, independent of the delivery of the fuel by means of the fuel pump 20.

[0026] In the present embodiment, the fuel pump 20 is designed as a simple, single-cylinder piston pump. This comprises a housing 22 with a single piston 24 displaceably mounted within the housing 22. The housing 22 and the piston 24 define a pump chamber 26, the size of which can be cyclically varied by a reciprocating displacement of the piston 24.When the volume of the pump chamber 26 is reduced, the fuel pump 20 delivers fuel via an outlet 28 with an outlet valve integrated therein into the high-pressure section of the fuel supply system, while when the volume of the pump chamber 26 is increased, fuel is sucked in from a low-pressure section of the fuel supply system or is introduced into the pump chamber 26 by means of a pre-feed pump (not visible) integrated into the low-pressure section, wherein the fuel can flow into the pump chamber 26 via an inlet (not visible) with an integrated inlet valve.

[0027] The reciprocating movement of the piston 24, and thus a drive of the fuel pump 20, is effected by pump cams 36, 38 of (one) of the camshaft(s) 18 in interaction with a spring element 30. By means of the spring element 30, a piston rod 32 connected to the piston 24 is pressed against a roller cup 34, which in turn is pressed against one of the two pump cams 36, 38. Upon rotation of the camshaft 18, a roller 40 of the roller cup 34 thus rolls on the cam track formed by the corresponding pump cam 36, 38. The cyclically non-uniform course of the cam tracks of the pump cams 36, 38 with regard to the radial distance from the rotational axis 42 of the camshaft 18 leads to the cyclical reciprocating movement of the piston 24, which effects the delivery of the fuel.

[0028] The internal combustion engine further comprises an adjusting device by means of which, on the one hand, both the (or at least some of the) gas exchange valves 16 can be switched from actuation by means of a first valve cam 44 to actuation by means of a second valve cam 46 and, on the other hand (simultaneously) from actuation of the piston 24 of the fuel pump 20 by means of a first (36) of the pump cams 36, 38 to actuation by means of a second (38) of the pump cams 36, 38 - and vice versa. This adjusting device can be controlled by means of a control device (engine control; not visible) and in the Fig. 3 is shown only schematically. The function of the adjusting device is based on the longitudinal axial displacement of sleeve-shaped cam carriers 48, which are arranged in a rotationally fixed manner on a base shaft 50 of the camshaft(s), by means of an actuator 52 each. The cam carriers 48 have two different valve cams 44, 46 for each of the gas exchange valves 16 actuated by them, which interact alternatively with the associated gas exchange valves 16 depending on the set displacement positions of the cam carriers 48.

[0029] In the design example according to the Fig. 3, each of the cam carriers 48 comprises a total of four valve cam pairs, each of which is assigned to a gas exchange valve 16 of the internal combustion engine. By means of the valve cams 60, 62 formed by such a cam carrier 48, the gas exchange valves 16 of a total of two adjacent combustion chambers of the internal combustion engine, in which each combustion chamber is assigned two gas exchange valves 16 (in a configuration with one camshaft 18) or four gas exchange valves 16 (in a configuration with two camshafts 18), can be actuated. Between the two valve cam pairs assigned to the gas exchange valves 16 of a first combustion chamber and the two valve cam pairs assigned to the gas exchange valves 16 of a second combustion chamber, the cam carrier 48 forms a switching gate in the form of a Y-shaped guide groove 54.Through the interaction of this guide groove 54 with drivers 56 of the associated actuator 52, the cam carrier 48 can be displaced axially by the distance x, thereby bringing a selected valve cam 44, 46 of each valve cam pair into operative connection with the associated gas exchange valve 16. According to the . Fig. 3, for example, starting from the illustrated functional position in which the gas exchange valves 16 are each in operative connection with the right (first) valve cam 44 of each valve cam pair, the right driver 56 can be extended and the cam carrier 48 can thereby, in cooperation with its rotation (in the Fig. 3 upwards) to the right by the distance x. As a result of the Y-shaped guide groove 54 running out (ie it becomes continuously flatter) in the middle, in the Fig. 3 lower section, the right-hand driver 56 is thereby moved back into the retracted position. After such a displacement of the cam carrier 48 by the distance x, the left (second) valve cams 46 of each valve cam pair are then in operative connection with the associated gas exchange valve 16. Such a displacement of the cam carrier 48 by the distance x to the right further results in the left-hand driver 56 being brought into overlap with the left section of the Y-shaped guide groove 54, so that by extending this driver 56, the cam carrier 48 can again be displaced to the left by the distance x.

[0030] It is provided that for partial operation of the internal combustion engine, a subset and in particular half of the combustion chambers, specifically for example the two central ones of the four combustion chambers arranged in series, can be deactivated by interrupting the supply of fuel to the associated injectors and no longer actuating the gas exchange valves 16 assigned to them, i.e. no longer opening them. For this purpose, it is provided that each valve cam pair assigned to the gas exchange valves 16 of such a deactivatable combustion chamber has a second valve cam 46, which is designed in the form of a so-called zero cam and which accordingly has no cam lobe and thus does not lead to an opening of a gas exchange valve 16 assigned to it. In the cam carrier 48 according to Fig. 3, the second valve cams 46 shown on the left of the two valve cam pairs arranged to the right of the guide groove 54 are each designed as corresponding zero cams. The valve cam pairs arranged to the left of the guide groove 54, in contrast, have identically designed and aligned first and second valve cams 44, 46, since these are intended to actuate the gas exchange valves of those (first) combustion chambers that continue to be actively operated even during partial operation.

[0031] When the internal combustion engine switches from full operation, in which all of the combustion chambers are operated at particularly low to medium loads, to partial operation, half of the combustion chambers are deactivated within a short period of time, corresponding roughly to one revolution of the crankshaft, and can therefore no longer contribute to the generation of drive power by the internal combustion engine. In order to compensate for this share of the drive power provided by the deactivated (second) combustion chambers in the full operation preceding partial operation, the still actively operated (first) combustion chambers must be operated at essentially twice the load compared to the previous full operation. This increased load is associated with an increased efficiency of the thermodynamic processes carried out therein, resulting in an overall higher efficiency for the operation of the internal combustion engine.A correspondingly increased efficiency is associated with a reduced specific fuel consumption, which means that only a reduced amount of fuel needs to be pumped by the fuel pump 20 in the partial operation compared to the previous full operation, wherein the output speed of the internal combustion engine and thus the drive speed of the camshaft (drive) 18 driving the fuel pump 20 has remained substantially the same.

[0032] For a corresponding adjustment of the specific delivery capacity of the fuel pump due to the change in the operating mode of the internal combustion engine from full operation to partial operation, it is provided to switch from the use of the first pump cam 36 to the use of the second pump cam 38 for the actuation or movement of the piston 24 of the fuel pump 20, whereby these differ in that the first pump cam 36 has four cam lobes 58 arranged at an equal pitch (with respect to the circumferential directions around the rotation axis 42), whereby during one revolution of the pump cams 36, 38 or during one revolution of the camshaft 18 comprising the pump cams 36, 38, the piston 24 of the fuel pump 20 performs a total of four delivery strokes, corresponding to the number of (first and second) combustion chambers actively operated during full operation of the internal combustion engine.while the second pump cam 38 has two equally spaced cam lobes 58, which accordingly only lead to two delivery strokes of the piston 24 of the fuel pump 20 during one revolution of the pump cams 36, 38. As a result, the number of delivery strokes of the piston 24 of the fuel pump 20 is also adapted for the partial operation of the internal combustion engine to the (first) combustion chambers that are still actively operating at that time. Although the specific fuel consumption in the partial operation is generally not halved compared to the preceding full operation, the fundamental halving of the delivery capacity of the fuel pump 20 by halving the number of pump cams 36, 38 advantageously takes into account the fact thatthat partial operation is regularly only provided for at partial load of the internal combustion engine and that by halving the delivery capacity of the fuel pump 20, a better adaptation to the actual fuel consumption of the internal combustion engine is achieved than in the preceding full operation, in which the delivery capacity of the fuel pump 20 (as a result of a design of the fuel pump 20 when actuated by means of the first pump cam 36, which must ensure a sufficient fuel supply even at full load of the internal combustion engine) may have been significantly higher than the actual fuel consumption, which could lead to a part of the fuel delivered by the fuel pump 20 having to be diverted again, i.e. returned to the low-pressure side of the fuel pump 20.

[0033] The change between the pump cams 36, 38, which are each in operative connection with the piston 24 of the fuel pump 20, takes place simultaneously with the change of the valve cams 44, 46 assigned to the gas exchange valves 16, in that one of the cam carriers 48 (according to the Fig. 3) has a lateral extension in comparison to the other cam carrier(s) 48 of the internal combustion engine, into which the two pump cams 36, 38 are integrated, so that the effect of the associated actuator 52 not only changes the valve cams 44, 46 operatively connected to the associated gas exchange valves 16 to achieve either full or partial operation of the internal combustion engine, but also changes the pump cams 36, 38 provided for the individual operating modes and provided for actuating the fuel pump 20. LIST OF REFERENCE SYMBOLS 10 cylinder crankcases 12 cylinder head 14 Fresh gas line 16 Gas exchange valve 18 Camshaft (drive) 20 Fuel pump 22 housings 24 pistons 26 Pump room 28 Outlet 30 spring element 32 piston rod 34 roller cup 36 first pump cam 38 second pump cam 40 rolls 42 Rotation axis 44 first valve cam 46 second valve cam 48 cam carriers 50 Basic camshaft shaft 52 Actuator 54 guide groove 56 drivers 58 cam elevation

Claims

[1] Method for operating an internal combustion engine with an internal combustion engine which forms at least three combustion chambers in which thermodynamic cycles can be carried out during operation of the internal combustion engine, wherein - full operation can be provided in which the thermodynamic cycle processes are carried out in both a first combustion chamber and a second combustion chamber, and - a partial operation can be 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, wherein for the implementation of the thermodynamic cycles, fuel is introduced into the combustion chambers by means of a fuel pump (20) which is actuated by a cam drive shaft (18) with a plurality of pump cams (36, 38), and wherein for switching from full operation to partial operation, a supply of fuel to the second combustion chamber is terminated, characterized bythat for switching from full operation to partial operation, a switch is made from using a first pump cam (36) to using a second pump cam (38) for actuating the fuel pump (20), wherein the specific delivery rate of the fuel pump (20) brought about by the second pump cam (38) is lower than the specific delivery rate brought about by the first pump cam (36), and wherein the ratio of the number of cam lobes (58) of the first pump cam (36) to the number of cam lobes (58) of the second pump cam (38) corresponds to the ratio of the number of all combustion chambers to the number of first combustion chambers. [2] Method according to claim 1, characterized by that the height of the cam lobes (58) of the second pump cam (38) is reduced compared to the height of the cam lobes (58) of the first pump cam (36). [3] Method according to one of the preceding claims, characterized bythat when carrying out the thermodynamic cycles, a gas exchange in the combustion chambers is controlled by means of gas exchange valves (16) and that for full operation, an actuation of at least one of the gas exchange valves (16) of the individual combustion chambers can be provided according to either a first valve lift curve or a second valve lift curve, wherein when the gas exchange valves (16) are actuated according to the first valve lift curve, the fuel pump (20) is actuated by means of the first pump cam (36) and when the gas exchange valves (16) are actuated according to the second valve lift curve, the fuel pump (38) is actuated by means of a third pump cam. [4] Internal combustion engine with an internal combustion engine which forms at least three combustion chambers in which thermodynamic cycles can be carried out, wherein, for carrying out the thermodynamic cycles, fuel can be introduced into the combustion chambers by means of a fuel pump (20) which can be actuated by a cam drive shaft (18) with a plurality of pump cams (36, 38), wherein a partial operation of the internal combustion engine can be achieved in which the introduction of fuel into some of the combustion chambers is interrupted, whereby this combustion chamber or these combustion chambers are deactivated, characterized bya switching device by means of which it is possible to switch from the use of a first pump cam (36) to the use of a second pump cam (38) for actuating the fuel pump (20), wherein the specific delivery capacity of the fuel pump (20) brought about by the second pump cam (38) is lower than the specific delivery capacity brought about by the first pump cam (36), and wherein the ratio of the number of cam lobes (58) of the first pump cam (36) to the number of cam lobes (58) of the second pump cam (38) corresponds to the ratio of the number of all combustion chambers to the number of combustion chambers to be continued to be operated in the partial operation. [5] Internal combustion engine according to claim 4, characterized by a control device programmed to carry out a method according to any one of claims 1 to 3. [6] Internal combustion engine according to claim 4 or 5, characterized bythat a gas exchange in the combustion chambers can be controlled by means of gas exchange valves (16) and a deactivation device is provided by which at least one of the gas exchange valves (16) can be deactivated for the partial operation of the internal combustion engine for a part of the combustion chambers. [7] Internal combustion engine according to one of claims 4 to 6, characterized by - a changeover device by means of which, in full operation, it is possible to change from an actuation for at least one of the gas exchange valves (16) of the combustion chambers according to a first valve lift curve to an actuation according to a second valve lift curve, and - a third pump cam, which can be switched to using the switching device.

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