Method for starting an internal combustion engine of a motor vehicle and internal combustion engine

Abstract

The invention relates to a method for starting an internal combustion engine (1) of a motor vehicle, in which method the internal combustion engine (1) has an output shaft (3) which rotates in a first direction of rotation (20) relative to a housing (2) of the internal combustion engine (1) during fired operation of the internal combustion engine (1), via which output shaft the motor vehicle can be driven by the internal combustion engine (1). The internal combustion engine (1) has an inlet tract (7) through which air can flow, by means of which the air can be introduced into at least one combustion chamber (4) of the internal combustion engine (1).After deactivation of the internal combustion engine (1), which was transferred from its fired operation to its unfired operation by the deactivation, a starting process is carried out by which the deactivated internal combustion engine (1) is activated and thereby transferred from its unfired operation to its fired operation.

Description

The invention relates to a method for starting an internal combustion engine of a motor vehicle according to the preamble of claim 1.DE 10 2009 001 317 A1 discloses a device for starting an internal combustion engine. DE 10 2015 208 456 A1 discloses a device for adjusting the relative angular position between at least one camshaft and a crankshaft of an internal combustion engine. Furthermore, DE 10 2004 006 337 A1 discloses a device for detecting the angle of a crankshaft of an internal combustion engine. Furthermore, DE 10 2014 014 279 A1 discloses a camshaft adjusting device for an internal combustion engine of a motor vehicle as known. Furthermore, DE 10 2017 207 905 A1 discloses a camshaft phase adjuster.It is an object of the present invention to provide a method for starting an internal combustion engine and an internal combustion engine for a motor vehicle, so that the internal combustion engine can be started particularly advantageously.This object is achieved according to the invention by a method having the features of patent claim 1 and by an internal combustion engine having the features of patent claim 8. Advantageous embodiments of the invention are the subject of the dependent claims.A first aspect of the invention relates to a method for starting an internal combustion engine, which is in particular initially deactivated and is also referred to as an engine, internal combustion engine or internal combustion engine, of a motor vehicle, which is also referred to simply as a vehicle and is preferably designed as a motor vehicle, in particular as a passenger car, and can be driven by means of the internal combustion engine. The internal combustion engine is very preferably designed as a reciprocating piston engine, and therefore as a reciprocating piston engine. In the method, the internal combustion engine has an output shaft which rotates relative to a housing of the internal combustion engine during a fired operation of the internal combustion engine in a first rotational direction and via which the motor vehicle can be driven by the internal combustion engine. In particular when the internal combustion engine is a reciprocating piston engine, and therefore a reciprocating piston engine, the output shaft is designed as a crankshaft. The internal combustion engine can provide drive torques for driving the motor vehicle via its output shaft. The internal combustion engine has at least one combustion chamber and an intake tract through which air can flow, also referred to as the intake tract, by means of which the air flowing through the intake tract can be introduced into the at least one combustion chamber of the internal combustion engine. For example, the output shaft is mounted on the housing such that it can rotate about an output shaft rotational axis relative to the housing. If the internal combustion engine is operated in its fired operation, the output shaft rotates in the first rotational direction about the output shaft rotational axis relative to the housing during the fired operation. Thus, in particular, when the motor vehicle is driven by the internal combustion engine, the output shaft rotates in the first rotational direction about the output shaft rotational axis relative to the housing. The housing is preferably an engine housing, which is also referred to as an engine block. The housing is very preferably a cylinder housing, in particular a cylinder crankcase. In this case, for example, the housing has at least one cylinder, by means of which the combustion chamber is partially delimited. For example, a piston is accommodated in the cylinder so as to be movable in translation, wherein the at least one combustion chamber is partially delimited by the piston. For example, the cylinder that is translationally movable relative to the housing is connected in particular via a connecting rod in an articulated manner to the output shaft, so that translatory movements of the piston that take place relative to the housing can be converted into a rotatory movement of the output shaft and vice versa.During the fired operation of the internal combustion engine, combustion processes take place in the combustion chamber. In particular, it is provided that within a respective working cycle of the internal combustion engine, exactly one of the combustion processes proceeds into the combustion chamber. The respective working cycle of the internal combustion engine preferably comprises exactly two complete revolutions of the output shaft and thus in particular, preferably exactly, 720 degrees crank angle. During the respective combustion process, a fuel-air mixture, also referred to simply as a mixture, is burned, in particular ignited and burned, in the combustion chamber, the mixture comprising the air introduced into the combustion chamber by means of the inlet tract and a preferably liquid fuel. The fuel is introduced into the combustion chamber, for example during the fired operation and in particular within the respective working cycle of the internal combustion engine which takes place during the fired operation, in particular is injected directly into the combustion chamber.In the method, after deactivation of the internal combustion engine, wherein the internal combustion engine has been transferred from its fired operation to its non-fired operation by the deactivation, a starting process is carried out, by means of which the initially deactivated internal combustion engine is activated and is thereby transferred, that is to say brought, from its non-fired operation to its fired operation. In the non-fired operation of the internal combustion engine, combustion processes in the combustion chamber are omitted, so that during the non-fired operation of the internal combustion engine, no combustion processes take place in the combustion chamber, in particular in the internal combustion engine as a whole. In particular, it is provided that after the deactivation of the internal combustion engine and before the starting process, i.e. before its start, the output shaft comes to a standstill, so that preferably at the start of the starting process, i.e. only when the starting process begins, the output shaft is stationary relative to the housing, thus a rotation of the output shaft taking place relative to the housing is omitted. In particular, it is provided that the starting process lies temporally between the deactivation and the fired operation, in particular immediately following the deactivation, in which the internal combustion engine is transferred by the starting process, such that the starting process is carried out, for example, between the deactivation and the fired operation of the internal combustion engine immediately following the deactivation. The feature that the fired operation, in which the initially deactivated internal combustion engine is transferred by the starting process, directly follows the deactivation of the internal combustion engine, is to be understood to mean that the fired operation of the internal combustion engine does not occur between the deactivation and the fired operation of the internal combustion engine directly following the deactivation.In order to be able to start the initially deactivated internal combustion engine in a particularly advantageous manner, it is provided in the method according to the invention that during the starting process the output shaft is rotated relative to the housing by means of an electric motor in a second rotational direction opposite the first rotational direction, in particular about the output shaft rotational axis, whereby air absorbed in the at least one combustion chamber is conveyed out of the at least one combustion chamber and conveyed into the intake tract, i.e. is pushed out into the intake tract, for example, whereupon the output shaft is rotated relative to the housing by means of the electric motor or by means of a further electric motor in the first rotational direction and the fired operation is started, i.e. activated. The rotation of the output shaft in the second rotational direction and relative to the housing and in particular about the output shaft rotational axis during the starting process is also referred to as reverse rotation or reverse rotation of the output shaft. The invention thus provides that the output shaft is rotated backwards after deactivation of the internal combustion engine and before the fired operation of the internal combustion engine that follows immediately after the deactivation and is effected by the starting process, i.e. activated. For example, due to or due to the above-described, in particular articulated, coupling of the piston to the output shaft, the piston is moved translationally into the cylinder and in particular relative to the housing by the rearward rotation of the output shaft in such a way that air accommodated in the combustion chamber is pushed out of the combustion chamber and pushed out into the intake tract. Thereupon, i.e. after the reverse rotation of the output shaft and thus after the ejection of the air initially taken up in the combustion chamber into the intake tract caused by the reverse rotation of the output shaft, the output shaft is rotated forward, i.e. in the first rotational direction, by means of the electric motor or by means of the further electric motor, in particular in such a way or until the output shaft rotates, in particular about the output shaft rotational axis and relative to the housing, in the first rotational direction at a rotational speed which corresponds, for example, to an in particular predetermined or predeterminable starting rotational speed. When the starting rotational speed is reached or when the starting rotational speed is reached by the rotational speed of the output shaft rotating in the first rotational direction and in particular about the output shaft rotational axis relative to the housing, that is to say in particular when the output shaft rotates in the second rotational direction at a rotational speed which is greater than or equal to the starting rotational speed, the initially deactivated, fired operation of the internal combustion engine is activated, that is to say started, for example. The change to the fired operation can be variable and can be dependent on whether support of the internal combustion engine is necessary for the desired rotational speed ramp-up if a battery power is not sufficient for this purpose.In particular, it is provided, for example, that the starting process ends with a beginning of the fired operation immediately following the deactivation of the internal combustion engine, which begins, for example, by starting the fired operation. In particular, the start can be ended when the desired starting rotational speed, also referred to as the target rotational speed, is reached or is reached. Whether or not the fired operation is already in effect is subject to various influencing factors. In other words again, for example, the fired operation is started at an activation time at which, for example, the starting operation ends and the fired operation begins, wherein, for example, at the activation time, the rotational speed of the output shaft, which rotates in particular about the output shaft rotational axis and relative to the housing in the first rotational direction, is greater than or equal to the starting rotational speed. The fired operation or its start does not necessarily have to be a criterion for the end of the starting process. For example, the starting process is ended when the starting rotational speed is reached. It can be seen that the reverse rotation and thus after the deactivation and before the fired operation of the internal combustion engine immediately following the deactivation is carried out, with the result that, for example, the fired operation of the internal combustion engine is omitted between the deactivation and the fired operation of the internal combustion engine immediately following the deactivation, that is to say no fired operation of the internal combustion engine takes place. In particular, it is provided that during the, in particular entire, reverse rotation of the internal combustion engine taking place during the starting process and during at least a part of the rotation of the crankshaft effected by means of the electric motor or by means of the further electric motor, also referred to as forward rotation, in the first rotational direction and in particular about the output shaft rotational axis, also referred to simply as rotational axis, and relative to the housing, effected during the starting process, the fired operation of the internal combustion engine, in particular continuously, is omitted.As a result of the forward rotation of the output shaft, the output shaft or its starting rotational speed, with which the output shaft rotates in the first rotational direction during the starting process, in particular about the output shaft rotational axis and relative to the housing, is dragged to the starting rotational speed, from which an ignition for igniting the respective mixture and / or the introduction of the fuel into the combustion chamber is activated and / or begins, as a result of which the fired operation is started, that is to say is activated. This means in particular that at the activation time the ignition and / or the introduction of the fuel into the combustion chamber is activated and / or begins, so that at the activation time the fired operation of the internal combustion engine is started and thus begins. In particular, it is provided that during the in particular entire reverse rotation and during at least a part of the forward rotation of the output shaft effected by means of the electric motor or by means of the further electric motor, the fired operation of the internal combustion engine, in particular continuously, is omitted.Because, in the method according to the invention, the output shaft is rotated backwards before the start and thus before the start of the fired operation, whereby air absorbed in the combustion chamber is pushed out of the combustion chamber and conveyed into the intake tract, an excessive compression work to be performed by the internal combustion engine during the forward rotation of the output shaft following the reverse rotation of the output shaft can be avoided, so that the fired operation can be activated particularly advantageously and thus the initially deactivated internal combustion engine can be started particularly advantageously. The expulsion of the air from the combustion chamber into the intake tract caused by the reverse rotation of the output shaft is thus, as it were, a decompression, so that in the invention the starting process is embodied as a decompression start or can be referred to as a decompression start.For example, it is provided that the electric motor and / or the further electric motor is arranged coaxially with respect to the output shaft. It is in particular conceivable for the electric motor and / or the further electric motor to be arranged on the output shaft. As a result, the output shaft can be rotated forwards and backwards in a particularly advantageous manner during the starting process. It is furthermore conceivable for the electric motor and / or the further electric motor to be arranged off-axis with respect to the output shaft, such that, for example, a machine rotation axis about which a rotor of the electric motor or of the further electric motor is rotatable relative to a stator of the electric motor or of the further electric motor runs parallel to the output shaft rotation axis and is spaced apart from the output shaft rotation axis.The invention is based in particular on the following findings and considerations: in conventional internal combustion engines, a so-called engine shake of the respective internal combustion engine can occur when the respective conventional internal combustion engine is started, wherein this engine shake can be perceived by occupants who are in the interior of a respective motor vehicle having the respective internal combustion engine. This can lead to comfort impairment if no corresponding countermeasures are taken. This engine shake was attributed to a compression work to be performed by the internal combustion engine at its start, in particular in a respective combustion chamber of the respective internal combustion engine. As a result of the method according to the invention, excessive compression work to be performed by the internal combustion engine during the starting process can be avoided or at least advantageously kept low, excessive shaking of the internal combustion engine during its start can be avoided, so that the method according to the invention enables particularly high starting comfort of the internal combustion engine. The compression work at the start of the internal combustion engine, also referred to as engine start, is primarily dependent on an amount of air absorbed in the combustion chamber, specifically at a point in time when the combustion chamber changes in its compression stroke. For the first combustion chambers, which come into their compression stroke during starting, the air mass cannot usually be adjusted, since no defined intake stroke follows a previous exhaust stroke, in which air mass could be limited by a throttle valve or an intake stroke of the intake valve, for example. Thus, the compression work or the compression work in the first combustion chambers of air mass can usually be influenced only by a shut-down position of the output shaft. By virtue of a favorable shut-down position, the compression work can be reduced at best per combustion chamber or distributed over a plurality of combustion chambers, but not reduced overall. Against this background, the method now makes it possible to expel air initially taken up in the combustion chamber back into the intake tract and thus to be able to keep the compression work advantageously low.In an advantageous embodiment of the invention, the internal combustion engine has at least one inlet valve assigned to the combustion chamber, via which the air can be introduced into the combustion chamber. In particular, the inlet valve is movable translationally relative to the housing between a closed position and at least one open position. Preferably, the closed position and the open position are respective end positions of the inlet valve, which relative to the housing can be moved in particular translationally into the respective end position but not beyond the respective end position. Thus, the open position is preferably the maximum, and thus the largest possible, open position of the inlet valve, which is also referred to simply as a valve, so that the inlet valve in its open position has or assumes its maximum stroke, which is also referred to as an inlet stroke. In other words, the inlet valve is preferably opened to the maximum extent in its open position. It is conceivable that the inlet valve is movable at least one or more intermediate positions lying between the closed position and the open position, wherein in the respective intermediate position the inlet valve is opened further than in the closed position less far than in the open position. It is in particular conceivable for the inlet valve to be movable from the closed position into the open position and from the open position into the closed position. It is furthermore conceivable for the inlet valve to be movable from the closed position into the respective intermediate position and, moreover, from the respective intermediate position back into the closed position without the inlet valve reaching the open position. This is possible, for example, by means of a variable valve drive of the internal combustion engine, by means of the variable valve drive of which the inlet valve can be actuated and can thereby be moved between the closed position and the open position and very preferably between the closed position and the respective intermediate position.In order to realize a particularly advantageous, in particular particularly comfortable, start of the internal combustion engine, also referred to as engine start, it has proven particularly advantageous if, at least during a part of the rotation of the output shaft that takes place in the second rotational direction during the starting process, in particular during the entire rotation of the output shaft that takes place in the second rotational direction during the starting process, the inlet valve is opened to the maximum extent, in particular continuously and thus without interruptions, and is therefore located in its open position. As a result, during the backward rotation of the output shaft taking place during the starting process, a particularly high quantity or mass of air initially taken up in the combustion chamber can be pushed out of the combustion chamber into the intake tract in a short time, so that the internal combustion engine can be started particularly advantageously, and can therefore be transferred in particular to subsequent fired operation.A further embodiment is characterized in that during the starting process, the inlet valve is opened, in particular at a maximum, before the output shaft rotates in the second rotational direction. This is to be understood as meaning that at the beginning of the starting process the inlet valve is not yet opened to the maximum extent, that is to say is not yet in its open position, but rather, for example, the inlet valve is closed at the beginning of the starting process, and therefore, for example, the inlet valve is in the closed position at the beginning of the starting process, or at the beginning of the starting process the inlet valve is, for example, in the intermediate position or in one of the intermediate positions. Due to the fact that during the starting process and before the rotation of the output shaft in the second rotational direction, the inlet valve is opened to the maximum extent, that is to say due to the fact that the inlet valve is opened to the maximum extent during the starting process and thus after the deactivation and before the reverse rotation of the output shaft begins, the inlet valve is already in the open position at the beginning of the reverse rotation, with the result that the inlet valve is already opened to the maximum extent at the beginning of the reverse rotation. As a result, a particularly large quantity of air initially taken up in the combustion chamber can be pushed out of the combustion chamber and pushed into the intake tract in a short time by the reverse rotation, so that a particularly advantageous start of the internal combustion engine can be ensured.Since it is preferably provided that during the starting process and before the reverse rotation of the output shaft the inlet valve is opened, in particular at a maximum, the inlet valve is already in the open position, in the intermediate position or in one of the intermediate positions at the beginning of the reverse rotation, so that particularly advantageously a particularly large amount of air initially taken up in the combustion chamber can be pushed out. Since the starting process is carried out after the above-mentioned deactivation of the internal combustion engine or the inlet valve is opened in the starting process in the described manner, the inlet valve is opened after the deactivation of the internal combustion engine and before the starting, that is to say before the activation of the fired operation of the internal combustion engine, the fired operation of the internal combustion engine remaining the case between this opening of the inlet valve and the deactivation of the internal combustion engine. A particularly advantageous start can thereby be realized.A further embodiment is distinguished in that the inlet valve is opened, in particular at a maximum, at least during a part of the rotation of the output shaft taking place in the second rotational direction during the starting process. This means that alternatively or additionally an opening of the inlet valve takes place at least during a part of the reverse rotation, so that the internal combustion engine can be started particularly comfortably and in a particularly short time.In a further, particularly advantageous embodiment of the invention, it is provided that the inlet valve is completely closed at least during a part of the rotation of the output shaft taking place in the first rotational direction during the starting process and also referred to as forward rotation or forward rotation. This makes it possible to prevent an excessively large amount of air from being conveyed, in particular sucked, back out of the intake tract again into the combustion chamber after air initially absorbed in the combustion chamber as a result of the reverse rotation and inserted into the intake tract, during the forward rotation of the output shaft following the reverse rotation, so that an excessive compression work to be performed by the internal combustion engine during the forward rotation can be prevented. The internal combustion engine can thus be started particularly comfortably.In order to realize a particularly comfortable start of the internal combustion engine, it has proven to be particularly advantageous if the inlet valve is closed, in particular completely, during a part of the rotation of the output shaft which takes place in the first rotational direction during the starting process. Thus, for example, the following is preferably provided: The inlet valve is preferably and / or, in particular, is opened at least during a first part of the rotation of the output shaft taking place in the second rotational direction during the starting process. In other words, it is preferably provided that the inlet valve is opened to the maximum, in particular in a particularly continuous manner, at least during a first part of the rotation of the output shaft taking place in the second rotational direction during the starting process. It is conceivable that, for example, within the first part of the rotation of the output shaft in the second rotational direction during the starting process, the inlet valve is opened, in particular at a maximum. In this case, it is preferably possible for the inlet valve to be closed, in particular completely, during a second part, which follows the first part in time, of the rotation of the output shaft taking place in the second rotational direction during the starting process, and thus moved into its closed position. This makes it possible to ensure that during the first part of the forward rotation, an advantageously large quantity of air initially taken up in the combustion chamber is pushed out of the combustion chamber and into the intake tract, and it is also possible to ensure that, during the forward rotation following the reverse rotation in time, it is prevented that an excessive quantity of air is conveyed from the intake tract into the combustion chamber or is sucked in, so that an excessive compression work to be performed by the internal combustion engine during the forward rotation can be prevented. In order to be able to activate the fired operation of the internal combustion engine in an advantageous manner, for example, it is conceivable that during a third part of the reverse rotation occurring during the starting process, which third part is temporally subsequent to the first part and temporally subsequent to the second part, and / or during a further part of the forward rotation of the output shaft, which further part is temporally subsequent to the first part and temporally subsequent to the second part, and for example also temporally subsequent to the third part, the inlet valve is opened, in particular completely or only partially, that is to say less far compared to a complete opening. This makes it possible to ensure that, in particular as a result of the forward rotation, a sufficient quantity of air is conveyed, in particular sucked, from the intake tract into the combustion chamber, as a result of which the fired operation of the internal combustion engine can advantageously be activated.It has furthermore been found to be particularly advantageous if, alternatively or additionally, the inlet valve is closed, in particular completely, at least during a part of the rotation of the output shaft which takes place in the first rotational direction during the starting process and / or between the rotation of the output shaft which takes place in the second rotational direction during the starting process and the rotation of the output shaft which takes place in the first rotational direction during the starting process. It is thus conceivable that between the reverse rotation of the output shaft occurring during the starting process and the reverse rotation of the output shaft occurring during the starting process, a subsequent forward rotation of the output shaft in time to the reverse rotation of the output shaft occurring during the starting process, the output shaft is stationary for a possibly only short period of time, so that during the period of time rotation about the axis of rotation relative to the housing of the internal combustion engine, in particular continuously, is omitted. It is furthermore conceivable that during the time interval during which the rotation of the output shaft following about the axis of rotation and relative to the housing is omitted, in particular continuously, the inlet valve is closed, in particular completely. This makes it possible to prevent an excessive amount of air from being conveyed or sucked into the combustion chamber from the intake tract during the forward rotation following the reverse rotation, whereby excessive compression work of the internal combustion engine can be prevented.A second aspect of the invention relates to an internal combustion engine for a motor vehicle, also referred to as an internal combustion engine, engine or internal combustion engine, wherein the internal combustion engine according to the second aspect of the invention is designed to carry out a method according to the first aspect of the invention. Advantages and advantageous configurations of the first aspect of the invention are to be regarded as advantages and advantageous configurations of the second aspect of the invention and vice versa.Further details of the invention will become apparent from the following description of a preferred exemplary embodiment with the associated drawings. The following shows: FIG. 1 shows a schematic illustration of an internal combustion engine of a motor vehicle; and FIG. 2 shows diagrams for illustrating a method for starting the internal combustion engine.In the figures, identical or functionally identical elements are provided with identical reference symbols.FIG. 1 shows a schematic illustration of an internal combustion engine 1, also referred to as an internal combustion engine, internal combustion engine or engine, of a motor vehicle, also referred to simply as a vehicle. This means that the motor vehicle has the internal combustion engine 1 and can be driven by means of the internal combustion engine 1. The internal combustion engine 1 has an engine housing 2, which is also referred to simply as a housing and is also referred to as an engine block. For example, the engine housing 2 is a cylinder housing, in particular a cylinder crankcase. For example, the internal combustion engine 1 is designed as a reciprocating piston engine, in particular as a reciprocating piston engine. The internal combustion engine 1 has an output shaft 3 via which the motor vehicle can be driven by the internal combustion engine 1. This means that the internal combustion engine 1 can provide drive torques for driving the motor vehicle via its output shaft 3. For example, the output shaft 3 is designed as a crankshaft. The internal combustion engine 1 also has at least one combustion chamber 4, in which combustion processes proceed during a fired operation of the internal combustion engine 1. In this case, it is provided in particular that within a respective working cycle of the internal combustion engine 1, in particular exactly, one of the combustion processes takes place in the combustion chamber 4. The internal combustion engine 1 is preferably designed as a four-stroke engine, so that the respective working cycle of the internal combustion engine 1 has exactly two complete revolutions of the output shaft 3 and thus, in particular when the output shaft 3 is designed as a crankshaft, exactly 720 degrees of crank angle. It can be seen that the output shaft 3 is mounted on the motor housing 2 such that it can rotate relative to the motor housing 2 about an output shaft rotational axis 5, also referred to simply as an axis of rotation. In the exemplary embodiment shown in FIG. 1, the engine housing 2 has at least one cylinder 6, by which the combustion chamber 4 is partially delimited. A piston, not visible in FIG. 1, is accommodated in the cylinder 6 so as to be movable in translation, which piston is movable in translation relative to the motor housing 2. The combustion chamber 4 is also partially delimited by the piston. The piston, in particular a connecting rod, is coupled in an articulated manner to the output shaft 3, such that translatory movements of the piston which take place in the cylinder 6 and relative to the motor housing 2 can be converted into a rotatory movement of the output shaft 3 which takes place about the output shaft rotational axis 5 and relative to the motor housing 2, which is also referred to simply as a housing, and is also referred to as a rotational movement, and vice versa.The internal combustion engine 1 has an inlet tract 7 through which air can flow, which is also referred to as the intake tract. By means of the intake tract 7, the air flowing through the intake tract 7 can be conducted to and into the combustion chamber 4. During the respective combustion process, a respective fuel-air mixture, also referred to simply as a mixture, is burned. The respective mixture comprises the air which is conducted by means of the intake tract (intake tract 7) to and into the combustion chamber 4. In addition, the respective mixture comprises a fuel, in particular a liquid fuel. Within the respective working cycle, the mixture in the combustion chamber 4 is ignited and thereby burned, resulting in exhaust gas of the internal combustion engine 1. In this case, the internal combustion engine 1 has an exhaust tract 8, also referred to as an exhaust system, through which the exhaust gas from the combustion chamber 4 can flow.Associated with the combustion chamber 4 is at least one inlet valve 9, which is illustrated particularly schematically in FIG. 1 and is designed, for example, as a poppet valve and via which the air flowing through the intake tract (inlet tract 7) can be introduced into the combustion chamber 4. The inlet valve 9 is movable in translation relative to the motor housing 2 between a closed position and an open position. The closed position and the open position of the inlet valve 9 are end positions of the inlet valve 9, which can be moved translationally relative to the motor housing 2 into the respective end position but cannot be moved beyond the respective end position. The internal combustion engine 1 has a variable valve drive, for example, by means of which the inlet valve 9 can be actuated and can thereby be moved between the closed position and the open position. In particular, the inlet valve 9 is opened to the maximum in the aforementioned open position, i.e. to the greatest possible extent, so that the inlet valve 9 is opened completely, i.e. to the maximum in its open position. This means that, for moving the inlet valve 9, the inlet valve 9 executes its largest possible, i.e. maximum stroke, so that, for example, the inlet valve 9 in its open position has the largest, i.e. largest possible and thus maximum stroke.A method for starting the initially deactivated internal combustion engine 1 is described below. For starting the internal combustion engine 1, the start of which is also referred to as engine start, an electric machine 10 provided additionally to the internal combustion engine 1 is used, which in the present case is arranged, for example, coaxially with the output shaft 3.FIG. 2 shows diagrams for illustrating the method. The time is plotted on the respective abscissa 11 of the respective diagram. On the ordinate 12 of a first of the diagrams, a rotational speed is plotted at which the output shaft 3 rotates about the output shaft rotational axis 5 relative to the motor housing 2. If the rotational speed has the value 0 shown in FIG. 2, the output shaft 3 is stationary relative to the motor housing 2, so that rotations of the output shaft 3 about the output shaft rotational axis 5 and relative to the motor housing 2 are omitted. On the ordinate 13 of a second of the diagrams, the lift of the intake valve 9, also referred to as valve lift, is plotted. On the ordinate 14 of a third of the diagrams, a torque is plotted which can be provided or is provided by the electric machine 10 via its rotor. On the ordinate 15 of a fourth of the diagrams, a rotational position of the output shaft 3 before the top dead center of ignition (ZZOT) of the piston is plotted in degrees of crank angle (° CA). A time profile 16 thus illustrates the rotational speed of the output shaft 3. a time profile 17 illustrates the valve lift, a time profile 18 illustrates the torque and a time profile 19 illustrates the rotational position of the output shaft 3, also referred to as the engine position, before the top dead center of ignition. In addition, the diagrams shown in FIG. 2 show points in time t 0, t 1, t 2, t 3, t 4, t 5 and t 6, wherein the points in time t 0- 6 are temporally successively and temporally spaced apart from one another.During the fired operation of the internal combustion engine 1, the output shaft 3 rotates about the output shaft axis of rotation 5 relative to the motor housing 2 in a first direction of rotation extending about the output shaft axis of rotation 5, which is illustrated in FIG. 1 by an arrow 20. A second rotational direction of the output shaft 3 extending about the output shaft rotational axis 5 and illustrated in the first rotational direction is illustrated by an arrow 21. This means that, when and preferably whenever the internal combustion engine 1 is in its fired operation and the internal combustion engine 1 drives the motor vehicle in its fired operation, the output shaft 3 rotates about the output shaft axis of rotation 5 in the first direction of rotation relative to the motor housing 2.In the method for starting the internal combustion engine 1, a starting process is carried out after deactivation of the internal combustion engine 1, which has been transferred from its fired operation to its non-fired operation by the deactivation. The starting of the internal combustion engine 1 and thus of the fired operation of the internal combustion engine 1 directly follows the mentioned deactivation, so that the fired operation of the internal combustion engine 1 is omitted between the deactivation and the starting of the internal combustion engine 1 that temporally immediately follows the deactivation of the internal combustion engine 1. In the non-fired operation of the internal combustion engine 1, that is to say during the non-fired operation of the internal combustion engine 1, combustion processes are omitted, in particular continuously, in the combustion chamber 4, in particular in the engine housing 2, so that no combustion processes run during the entire non-fired operation of the internal combustion engine 1 into the combustion chamber 4, in particular in the engine housing 2. As a result of the starting process immediately following the deactivation of the internal combustion engine 1, the deactivated internal combustion engine 1 is activated and is thus transferred from its non-fired operation to its fired operation. The feature that the starting process follows directly the deactivation is to be understood as meaning that the fired operation of the internal combustion engine 1 does not occur between the deactivation of the internal combustion engine 1 and the starting process that follows directly from the deactivation of the internal combustion engine 1 in terms of time.In order to be able to start the internal combustion engine 1 in a particularly comfortable and thus particularly advantageous manner, it is provided in the method that during the starting process the output shaft 3 is rotated by means of the electric machine 10 in the second rotational direction, opposite the first rotational direction, relative to the engine housing 2 about the output shaft rotational axis 5, whereby air absorbed in the combustion chamber 5 is conveyed out of the combustion chamber 4 and conveyed into the intake tract 7, whereupon the output shaft 3 is rotated by means of the electric machine 10 in the first rotational direction relative to the engine housing 2 about the output shaft rotational axis 5 and the fired operation of the internal combustion engine 1 is started. The rotation of the output shaft 3 in the second rotational direction occurring during the starting process and effected by means of the electric machine 10 is also referred to as reverse rotation or reverse rotation. The rotation of the output shaft 3 in the first rotational direction, which occurs during the starting process and follows the reverse rotation in time and is effected by means of the electric machine 10, is also referred to as forward rotation or as forward rotation of the output shaft 3. If the term "reverse rotation" or "reverse rotation" is used above and below, this is to be understood as meaning, unless otherwise stated, the reverse rotation of the output shaft 3 which takes place in the starting operation. If the term "forward rotation" or "forward rotation" is used above and below, this is to be understood as meaning, unless otherwise indicated, the forward rotation of the output shaft 3 which takes place in the starting operation. In order to effect the reverse rotation and the subsequent forward rotation of the output shaft 3 by means of the electric machine 10, the electric machine 10 is operated in each case in a motor mode and thus as an electric motor, so that the electric machine 10 is also referred to as an electric motor. Since, during the backward rotation of the piston, the piston is moved translationally relative to the engine housing 2 in such a way that air initially taken up in the combustion chamber 4 is conveyed out of the combustion chamber 4 and conveyed into the intake tract 7, in the exemplary embodiment shown in FIG. 1, the air initially taken up in the combustion chamber 4 is pushed by the backward rotation into the intake tract 7, that is to say pushed out of the combustion chamber 4 and into the intake tract 7. In other words, during the reverse rotation or as a result of the reverse rotation, the air initially absorbed in the combustion chamber 4 is conveyed out of the combustion chamber 4 via the open inlet valve 9 and conveyed into the inlet tract 7.It can be seen that the inlet valve 9 is thus opened at least during a part of the forward rotation following the reverse rotation in time, so that during this part of the forward rotation air is conveyed or sucked from the intake tract 7 via the opened inlet valve 9 into the combustion chamber 4.For example, at the time t 1, a so-called start notification is performed. For example, at time t 2, the reverse rotation starts, so that time t 2 coincides with a start of the reverse rotation. At the time t0preceeding the time t2, the inlet valve 9 is in its open position, so that, for example, at the time t0, the inlet valve 9 is fully, i.e., maximally, open. For example, the inlet valve 9 is completely, i.e. maximally opened, at the time t 0, and is therefore moved into the open position. This is to be understood in particular as meaning that, for example, at the time t 0, the inlet valve 9 starts to open, which is moved into the open position during the opening and is thus opened to the maximum extent, that is to say completely. In this case, it is preferably provided that this opening of the inlet valve 9 takes place while the output shaft 3 is stationary relative to the motor housing 2, in particular continuously, that is to say while a rotation of the output shaft 3, in particular continuously, that is to say without interruption, takes place about the output shaft rotation axis 5 and relative to the motor housing 2. It can be seen from FIG. 2 that, for example, at the time t 1 temporally following the time t 0 and preceding the time t 2, the inlet valve 9 is closed, i.e. closing of the inlet valve 9 is started. The aforementioned opening of the intake valve 9 is also referred to as first opening, and the aforementioned closing of the intake valve 9 is also referred to as first closing of the intake valve 9. During or by the first closing, for example, the inlet valve 9 is moved from its open position in the direction of its closed position and in the process is moved, for example, into a first intermediate position lying between the open position and the closed position and is held, for example, at least temporarily in the first intermediate position relative to the motor housing 2, wherein, for example, the first closing of the inlet valve 9 takes place, while the output shaft 3 is stationary, in particular continuously, relative to the motor housing 2. At time t 2, for example, the reverse rotation starts. At the time t 3 temporally preceding the time t 2 subsequent to the time t 2, the rotational position of the output shaft 3 has, for example, a first value at or from which an in particular further, second closing of the inlet valve 9 takes place, so that, for example, at the time t 3, the mentioned, second closing of the inlet valve 9 takes place, which during the second closing is moved from the first intermediate position in particular further in the direction of the closed position and is thus further closed. The second closing extends, for example, from the third point in time t 3 to the fourth point in time t 4 following the third point in time t 3 and preceding the fifth point in time, at which the inlet valve 9 reaches its closed position and is thus fully closed, i.e. maximally closed. For example, the reverse rotation ends at time t 4 such that time t 4 coincides with an end of the reverse rotation. It can thus be seen that the inlet valve 9 is already open at the beginning of the reverse rotation, in the present case already at the time t 2. It can also be seen that the inlet valve 9 is open during the entire reverse rotation. In general terms, it is thus preferably provided that the inlet valve 9 is opened at least during a part, in particular at least during a predominant part and thus during at least more than half of the reverse rotation of the inlet valve 9.It can also be seen that the inlet valve 9 is closed, in particular completely closed, during a part of the reverse rotation and is thereby moved into the closed position. For example, it is provided that during a first part of the reverse rotation, the inlet valve 9 is opened. It is conceivable that during the first part of the reverse rotation the inlet valve 9, in particular continuously, is in a position of the inlet valve 9, which is open in the mentioned position, wherein movement of the inlet valve 9 relative to the engine housing 2 is preferably omitted and so that preferably during the first part of the reverse rotation the inlet valve 9 remains continuously, i.e. without interruption, in the mentioned position. The position of the inlet valve 9 can be the open position, so that, for example, during the first part of the reverse rotation, the inlet valve 9 is continuous, that is to say uninterruptedly at its maximum and thus completely open. In the exemplary embodiments shown in the figures, however, in the present case, for example, the said position of the inlet valve 9 is the said first intermediate position of the inlet valve 9, which in the first intermediate position is open but is further closed compared to the open position and is further open compared to the closed position. Preferably and in the present case, it is provided that the first part of the reverse rotation starts at the beginning of the reverse rotation and in the present case at the time t 2. Furthermore, it is provided in the present case and preferably that during a second part of the reverse rotation that temporally adjoins the first part of the reverse rotation, the inlet valve 9 is closed, in particular starting from the position and is thus moved in the direction of the closed position, for example and in the present case in such a way that during the second part of the reverse rotation, the inlet valve 9 is maximally, that is to say completely closed and is thus moved into the closed position. In the exemplary embodiments shown in the figures, it is provided that during the second part of the reverse rotation, the inlet valve 9 is moved from the first intermediate position in the direction of the closed position into the closed position in the present case and is thus completely closed.It can be advantageous if the inlet valve 9 is closed but not fully closed, so that during the intake stroke a significantly reduced air mass is present in the cylinder compared to the initial state before the reverse rotation. Complete closing is of great advantage, but partial strokes during suction are also advantageous for achieving decompression compared to the initial state.For example and in the present case, the second part begins at a point in time at which the first part ends, such that an end of the first part coincides with a beginning of the second part. In the present case, the second part ends at the time t 4 such that an end of the second part coincides with an end of the reverse rotation. At the time t 4, the rotational position or the motor position has, for example, a second value at or from which the forward rotation can advantageously begin and in the present case begin. Thus, in the exemplary embodiments shown in FIGS. 1 and 2, it is provided that the forward rotation of the output shaft 3 temporally following the reverse rotation begins at the time t 4 at which the inlet valve 9 is completely closed. Thus, it is preferably provided that at the beginning of the forward rotation, the inlet valve 9 is maximally, i.e. completely closed. The inlet valve 9 is continuous, i.e. without interruption, in the closed position from the time t 4 at least up to the time t 5 temporally subsequent to the time t 4 and temporally preceding the time t 6. During or through the forward rotation, the output shaft 3 is driven by means of the electric machine 10 as strongly or as long as and thereby rotated in the first rotational direction about the output shaft rotational axis 5 relative to the motor housing 2 until the rotational speed of the output shaft 3 illustrated by the temporal profile 16 corresponds to a predetermined or predeterminable starting rotational speed, for example, and therefore has a predetermined or predetermined starting value, for example. This is the case at the time t 6. This means that at the time t 6, the rotational speed at which the output shaft 3 is rotated about the output shaft rotational axis 5 and relative to the motor housing 2 by means of the electric machine 10 during the forward rotation corresponds to the starting rotational speed, thus has the starting value.The aforementioned position of the intake valve 9 is also referred to as the first position. It can be seen on the basis of the profile 17 that after the time t 5 and shortly before the time t 6 the inlet valve 9 is opened again and in the process moved from the closed position in the direction of its open position, in particular by carrying out a second opening of the inlet valve 9. In the case of the second opening of the inlet valve 9 taking place temporally after the first opening, the first closing and the second closing of an inlet valve 9, the inlet valve 9 is opened and in the process moved translationally from the closed position in the direction of the open position relative to the engine housing 2, such that the one inlet valve 9 is opened at the time t 6, in the present case such that the inlet valve 9 is in a second position at the time t 6. The second position may be the aforementioned first position or a position of the intake valve 9 different from the first position, which is opened in the second position. This means that the second position can be the open position. Alternatively, the second position may be the first intermediate position. In the present case, the second position is a second intermediate position which is situated between the open position and the closed position and is different from the first intermediate position, in which the inlet valve 9 is open but is open to a lesser extent than in the open position and is open further than in the closed position. For example, at the time t 6 or at a first intermediate time lying between the time t 5 and t 6 or at a second intermediate time following the time t 6, an ignition in the combustion chamber 4 and / or an introduction, in particular a direct injection of the fuel into the combustion chamber 4, are started, i.e. activated, so that, for example, at the time t 6, at the first intermediate time or at the second intermediate time, the fired operation of the internal combustion engine 1 is activated. This activation of the fired operation of the internal combustion engine 1 preferably takes place at the time t 6 or at the intermediate time, since at the time t 6 or at the second intermediate time, the rotational speed of the output shaft 3 is greater than or equal to the starting rotational speed, wherein, for example, before the time t 6, the rotational speed of the output shaft 3 is, in particular, still lower than the starting rotational speed.Since air taken into the combustion chamber 4 by the reverse rotation is conveyed out of the combustion chamber 4 and conveyed into the intake tract 7, compression work to be performed by the internal combustion engine 1 during the forward rotation can be advantageously kept low, so that excessive shaking of the internal combustion engine 1 occurring during the starting of the internal combustion engine 1 and also referred to as engine shaking can be avoided. As a result, the internal combustion engine 1 can be started particularly comfortably.List of reference characters1 Internal combustion engine 2 engine housing 3 output shaft 4 combustion chamber 5 output shaft axis of rotation 6 cylinder housing 7 intake tract 8 exhaust tract 9 intake valve 10 electric machine 11 abscissa 12 ordinate 13 ordinate 14 ordinate 15 ordinate 16 temporal profile 17 temporal profile 18 temporal profile 19 temporal profile 20 arrow 21 arrow t 0 time t 1 time t 2 time t 3 time t 4 time t 5 time t 6 timeReferences included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedDE 10 2009 001 317 A1

[0002] DE 10 2015 208 456 A1

[0002] DE 10 2004 006 337 A1

[0002] DE 10 2014 014 279 A1

[0002] DE 10 2017 207 905 A1

[0002]

Claims

Method for starting an internal combustion engine (1) of a motor vehicle, in which: - the internal combustion engine (1) has an output shaft (3) which rotates relative to a housing (2) of the internal combustion engine (1) in a first rotational direction (20) during a fired operation of the internal combustion engine (1) and via which the motor vehicle can be driven by the internal combustion engine (1); - the internal combustion engine (1) has an inlet tract (7) through which air can flow, by means of which the air can be introduced into at least one combustion chamber (4) of the internal combustion engine (1); and - after deactivation of the internal combustion engine (1), which was transferred from its fired operation to its non-fired operation by the deactivation, a starting operation is carried out, by means of which the deactivated internal combustion engine (1) is activated and is thereby transferred from its non-fired operation to its fired operation; characterized in that, during the starting operation, the output shaft (3) is rotated relative to the housing (2) by means of an electric motor (10) in a second rotational direction (21) which is opposite to the first rotational direction (20), as a result of which air absorbed in the at least one combustion chamber (4) is conveyed out of the at least one combustion chamber (4) and fed into the inlet tract (7), whereupon the output shaft (3) is rotated relative to the housing (2) by means of the electric motor (10) or by means of a further electric motor in the first rotational direction (20), and the fired operation is started.Method according to Claim 1, characterized in that the internal combustion engine (1) has at least one inlet valve (4) which is assigned to the combustion chamber (4) and via which the air can be introduced into the combustion chamber (4).Method according to Claim 2, characterized in that the inlet valve (9) is opened to the maximum extent at least during part of the rotation of the output shaft (3) which takes place in the second rotational direction (21) during the starting operation.Method according to Claim 2 or 3, characterized in that, during the starting process, the inlet valve (9) is opened before the output shaft (3) is rotated in the second rotational direction (21).Method according to one of Claims 2 to 4, characterized in that the inlet valve (9) is opened at least during part of the rotation of the output shaft (3) which takes place in the second rotational direction (21) during the starting operation.Method according to one of Claims 2 to 5, characterized in that the inlet valve (9) is completely closed at least during part of the rotation of the output shaft (3) which takes place in the first rotational direction (20) during the starting operation.Method according to one of Claims 2 to 6, characterized in that the inlet valve (9) is closed during part of the rotation of the output shaft (3) which takes place in the second rotational direction (21) during the starting operation and / or at least during part of the rotation of the output shaft (3) which takes place in the first rotational direction (20) during the starting operation and / or between the rotation of the output shaft (3) which takes place in the second rotational direction (21) during the starting operation and the rotation of the output shaft (3) which takes place in the first rotational direction (20) during the starting operation.Internal combustion engine (1) for a motor vehicle, wherein the internal combustion engine (1) is designed to carry out a method according to one of the preceding claims.

Images