EP2935864B1 - Method and device for cranking an internal combustion engine - Google Patents

Description

The invention relates to a method for starting an internal combustion engine.

The DE 10 2009 033 544 A1 discloses a method for starting an internal combustion engine of a motor vehicle, wherein the internal combustion engine exerts a drive torque in a preferred direction of the internal combustion engine to a crankshaft. A starter motor applies a starting torque to the crankshaft in a starting operation to achieve a minimum speed of the internal combustion engine, with a control unit controlling the starting torque. Here, the control unit in the starting process controls the starting torque time-dependent between a positive maximum starting torque and a negative minimum starting torque, with a positive starting torque in the direction and a negative starting torque against the preferred direction acts on the crankshaft.

1. 1. Das einzige rotierende Element des Anlassmotors, nämlich der Rotor, kann eine Sekundärmasse eines Zweimassenschwungrades (ZMS) ersetzen. Hierdurch kann sich für das mechanische Gesamtsystem aus Kurbelwelle und Anlassvorrichtung ein kleineres Trägheitsmoment ergeben, welches wiederum höhere Drehzahlgradienten bei Drehzahl-Änderungen erlaubt und somit eine höhere Dynamik im Betrieb des Kraftfahrzeugs ermöglicht.
2. 2. Durch geeignete Ansteuerung des Anlassmotors können Dreh-Ungleichförmigkeiten der Kurbelwelle vollständig oder teilweise kompensiert werden. Die Anordnung erlaubt somit eine aktive Schwingungstilgung oder -dämpfung.
3. 3. Da zur Ansteuerung des Anlassmotors in der Regel ein elektrischer Rotorwinkel erforderlich ist, kann dieser mit wenig mehr Aufwand in einen mechanischen Rotorwinkel umgerechnet werden. Ist auch ein Kurbelwellenwinkel bekannt, so kann aus der Differenz zwischen dem Kurbelwellenwinkel und dem mechanischen Rotorwinkel ein Verdrehwinkel eines elastischen Kopplungselements, beispielsweise einer Drehfeder, bestimmt werden. In Abhängigkeit dieses Verdrehwinkels kann ein aktuell übertragenes Drehmoment zwischen Rotor und Kurbelwelle bestimmt werden. Somit ergibt sich vorteilhaft, dass keine direkte Messung des Drehmoments erforderlich ist.
4. 4. Ist, wie vorhergehend erläutert, der Drehwinkel bekannt, so kann in Abhängigkeit des Drehwinkels eine verbesserte Lastwechselregelung erfolgen, bei der trotz des sich elastisch verhaltenen Triebstrangs schnelle und komfortable Laständerungen ausgeregelt werden können.
5. 5. In Abhängigkeit des Drehwinkels kann ebenfalls eine Regelung des Anlassvorgangs derart erfolgen, dass ein maximaler Betrag des Verdrehwinkels nicht überschritten wird. Hierdurch kann z.B. eine mechanische Beanspruchung von Endanschlägen verhindert werden. Als Stellgröße für eine solche Regelung kann beispielsweise das von dem Anlassmotor erzeugte Anlassmoment, das von der Verbrennungskraftmaschine erzeugte Moment oder, bei einem Automatikgetriebe, eine Kupplungskapazität als Stellgröße verwendet werden.
6. 6. Es fällt bei einer solchen Triebstrang-Anordnung kein Verschleiß von z.B. Riemen an.
7. 7. Weiter werden in einer solchen Anordnung keine Riemen-Verluste erzeugt.

The document also discloses a drive train arrangement in which the rotor of the electric motor designed as a starter motor is rotationally connected to the crankshaft of the internal combustion engine. Such an arrangement offers a number of advantages:

1. 1. The only rotating element of the starter motor, namely the rotor, can replace a secondary mass of a dual mass flywheel (DMF). This can result in a smaller moment of inertia for the overall mechanical system comprising the crankshaft and the starting device, which in turn permits higher rotational speed gradients with changes in rotational speed and thus allows greater dynamics in the operation of the motor vehicle.
2. 2. By suitable control of the starter motor rotational non-uniformities of the crankshaft can be fully or partially compensated. The arrangement thus allows active vibration damping or damping.
3. 3. Since an electric rotor angle is usually required to control the starter motor, it can be converted into a mechanical rotor angle with little effort. If a crankshaft angle is also known, then the difference between the Crankshaft angle and the mechanical rotor angle, a twist angle of an elastic coupling element, such as a torsion spring, are determined. Depending on this angle of rotation, a currently transmitted torque between the rotor and the crankshaft can be determined. Thus, it is advantageous that no direct measurement of the torque is required.
4. 4. Is, as previously explained, the rotation angle known, it can be done depending on the angle of rotation an improved load change control, in spite of the elastically behaved drive train fast and comfortable load changes can be compensated.
5. 5. Depending on the angle of rotation can also be a control of the starting process done in such a way that a maximum amount of the rotation angle is not exceeded. As a result, for example, a mechanical stress on end stops can be prevented. As a control variable for such a control, for example, the starting torque generated by the starter motor, the torque generated by the internal combustion engine or, in an automatic transmission, a clutch capacity can be used as a control variable.
6. 6. It falls in such a drive train arrangement no wear of eg belts.
7. 7. Further, no belt losses are generated in such an arrangement.

A disadvantage of such an arrangement, however, is that in particular for the cold start of the internal combustion engine high torques must be generated by the starter motor, especially when there is no torque ratio between the crankshaft and the rotor.

Will that be in the DE 10 2009 033 544 A1 As applied to methods disclosed in such a drive train arrangement, the crankshaft of the internal combustion engine will move even before reaching a maximum allowable angle of rotation of the torsionally flexible coupling element, ie resonate. Due to the particular at low temperatures high friction torque of the crankshaft, including coupled to the crankshaft other components, such as the piston and the camshaft, the arrangement energy is withdrawn, which should be desirable for starting available. In particular, it may come to an equilibrium, in which by the Anchor torque supplied energy of the discharged friction energy corresponds. In this case, starting the internal combustion engine would not be possible.

The DE 10 2012 201 102 A1 discloses a vehicle with an internal combustion engine and an electric machine, which is kinematically coupled to the internal combustion engine for starting the internal combustion engine and which is kinematically decoupled from the internal combustion engine during operation of the internal combustion engine. Furthermore, the vehicle comprises an energy recuperation and storage device, wherein the energy recuperation and storage device is kinematically coupled to the internal combustion engine during shutdown or during the expiration of the internal combustion engine and receives at least a portion of the kinetic energy stored in the internal combustion engine at the moment of switching off the internal combustion engine and stores. The EP 1 106 823 A1 describes that when starting an internal combustion engine before the ignition of the first rotor of an electric machine is driven by electric drive against the subsequent operating direction of rotation of the internal combustion engine such that a, in particular designed as Torsionsdämpferelement, elastic element is biased at, in particular due to its Ruhereibung, stationary crankshaft and then reversing the driving rotational direction, igniting the internal combustion engine and electrically driving the crankshaft by the electric machine.

The technical problem is to provide a method for starting an internal combustion engine, which enables a reliable starting of the internal combustion engine, wherein requirements for a height of a maximum to be generated starting torque can be reduced.

The solution of the technical problem results from the subject matter with the features of claim 1. Further advantageous embodiments of the invention will become apparent from the dependent claims.

It is a basic idea of the invention to prevent a crankshaft of the internal combustion engine from rotating until a rotary oscillator formed from the crankshaft, a rotor of the starter motor and a mechanically coupling elastic coupling element reaches a state in which a stored energy in the rotary oscillator, which is composed of a potential energy of the torsionally elastic coupling element and a kinetic energy of the rotor of the starter motor, sufficient to start the internal combustion engine. In particular, the energy stored in the rotary oscillator is sufficient to produce e.g. overcome by a static friction of the internal combustion engine required breakaway torque and compression and Gleitreibungsmomente the internal combustion engine.

Proposed is a method for starting an internal combustion engine, wherein a crankshaft is rotationally elastically coupled to a rotor of an electric machine, for example via an elastic coupling element. In a starting process, the starter motor generates a Starting torque, which is transmitted via the torsionally flexible coupling to the crankshaft. The starter motor can be designed here as an electric machine.

At a starting time of the starting process, a negative or positive starting torque is generated. Here, a positive starting torque denotes a starting torque, which acts in a preferred direction of rotation of the crankshaft to the crankshaft. Correspondingly, a negative starting torque refers to a torque which acts counter to the preferred direction of rotation on the crankshaft. The preferred direction of rotation of the crankshaft corresponds to the direction of rotation of the crankshaft during operation of the internal combustion engine. Thus, the starting operation can begin either with a torque acting in the preferred direction of rotation or a torque acting counter to the preferred direction of rotation. During the starting process, at least one sign change of the starting torque takes place. Thus, after the start time, the starting engine is controlled in such a way that, following a negative starting torque at the starting time, a positive starting torque or, following a positive starting torque generated at the starting time, a negative starting torque is generated. Preferably, several sign changes of the starting torque occur during the starting process. This can also be described as a modulation of the starting torque. The modulation of the starting torque thus describes a control of the starting torque, the starting torque alternating between a positive starting torque and a negative starting torque. A sign change of the starting torque may e.g. time-dependent, so after a predetermined period of time. Preferably, a sign change of the starting torque takes place at a time or shortly after a point in time at which a change of sign of the rotary movement of the rotor takes place.

In this case, a control device may be provided which regulates the starting torque according to the previously described modulation of the starting torque. In particular, the starting torque between a positive maximum starting torque and a negative minimum starting torque can be controlled, with only the positive maximum starting torque or the negative minimum starting torque is generated by the starter motor.

Corresponds to a sign of the starting torque always the sign of the rotational movement of the rotor of the starter motor, it is operated exclusively in a motor operating mode.

According to the invention, a rotation of the crankshaft is mechanically blocked before or at the start time. The mechanical blockage can in this case be carried out, for example, by a blocking agent. For example, For example, rotation of the crankshaft with a crankshaft brake, i. be blocked by a frictional connection between the crankshaft and the blocking means. Alternatively, the crankshaft may be rotated by a crankshaft lock, i. a positive connection between the crankshaft and the blocking means to be blocked.

The rotation of the crankshaft is released again when or after energy stored in a torsional vibration system reaches a maximum allowable energy or energy necessary to start the internal combustion engine. Thus, the rotation of the crankshaft can be released precisely at the moment when the energy stored in the torsional vibration system reaches the maximum permissible energy or the energy required to start the internal combustion engine. Alternatively, the rotation of the crankshaft can be released in time after the time at which the energy stored in the torsional vibration system has reached the maximum allowable energy or the energy required to start the internal combustion engine. The time difference between reaching the maximum or necessary energy and the release may, for example, be a predetermined period of time, e.g. a period of time needed to achieve a desired phase of torsional vibration.

When the crankshaft is blocked, the torsionally flexible coupling and the rotor of the starter motor and optionally further parts mechanically connected to the rotor form a torsional vibration system or a so-called rotary oscillator. During the starting process, potential energy stored in torsionally elastic coupling is converted into kinetic energy of the rotor of the starter motor and vice versa. Thus, in each period between two similar sign changes of the rotor speed, there are two times when the potential energy is maximum and the kinetic energy is zero, and two times when the potential energy is zero and the kinetic energy is maximum. During cranking, when the crankshaft is locked, the energy stored in the torsional vibration system will increase because the energy supplied by the starter motor is greater than the energy essentially dissipated by friction.

The energy required to start the internal combustion engine may be less than the maximum allowable energy. The maximum allowable energy may be, for example, a potential Energy in a state amount of maximum torsions, wherein in the corresponding state, the torsionally flexible coupling is not damaged.

Preferably, the crankshaft rotation is released when the potential energy is zero and the kinetic energy of the torsional vibration system is maximum. In time, this may be the case a quarter of a period after passing through a minimum angle of rotation.

For example, the rotation of the crankshaft can be released even if or after a potential energy stored in the torsionally flexible coupling of the rotary vibrator reaches a maximum permissible energy or the potential energy stored in the torsionally flexible coupling of the rotary vibrator reaches a power necessary for starting the internal combustion engine. A maximum allowable energy in this case is e.g. achieved when a twist angle reaches a magnitude maximum twist angle. The angle of rotation describes the rotation of the rotor relative to the crankshaft. An energy required for starting the internal combustion engine can be achieved, for example, if a predetermined angle of rotation is achieved which is smaller in magnitude than the maximum permissible angle of rotation. As a result, a power required for the starting process can be reduced in an advantageous manner. In particular, in cold internal combustion engines, higher starting power is required than with warm internal combustion engines.

The proposed method thus describes a swinging or swinging of the existing of the elastic coupling element and the rotating mass of the rotor mechanical system against a braked crankshaft. If the crankshaft is released again, the energy stored in the oscillated system can be used to drive the crankshaft.

It is also possible that a change in sign of the starting torque takes place in such a time that a resonant frequency of the rotary oscillator is excited. Here, the sign change, for example, occur in time according to the resonance frequency.

It is possible that the blockage of the crankshaft is already at a previous shutdown or issue of the internal combustion engine, for example when parking the vehicle takes place. Thus, in a subsequent turn on or when activating the ignition described the starting process immediately.

The proposed method advantageously makes it possible to use an electric motor with a very low maximum starting torque which can be generated as the starting motor, since no friction losses of the crankshaft during starting by the starter motor have to be compensated for by preventing the rotation of the crankshaft.

In a further embodiment, the rotation of the crankshaft is released after a minimum allowable twist angle or a predetermined twist angle has been reached and / or a change in sign of the starting torque has occurred during the application of a negative starting torque. The modulation of the starting torque can thus take place until a minimum permissible angle of rotation is reached, and preferably not exceeded, and a sign change of the negative starting torque to a positive starting torque takes place. In this case, the stored in the rotary oscillator potential energy is transmitted to the crankshaft so that a rotation of the crankshaft takes place in the preferred direction of rotation. Thus, the internal combustion engine can be started in an advantageous manner in the preferred direction of rotation.

Preferably, the release of the rotation of the crankshaft occurs after a minimum allowable twist angle or a predetermined minimum twist angle has been reached during a negative torque application, a sign change of the cranking torque occurred and during the subsequent exercise of a positive cranking moment an amount of a difference between a current twist angle and a zero angle falls below a predetermined threshold. Thus, the release occurs in the vicinity of the zero crossing of the rotation angle.

Further preferably, after release of the rotation of the crankshaft, only a positive starting torque can be generated by the starter motor and transmitted to the crankshaft via the elastic coupling element.

As a result, a torque acting on the released crankshaft is maximized in an advantageous manner, as a result of which the above-explained static friction of the internal combustion engine as well as compression and sliding friction torques of elements of the internal combustion engine can be overcome.

In a further embodiment, after the rotation of the crankshaft has been released, ignition of a fuel-air mixture takes place in a combustion chamber of at least one cylinder of the internal combustion engine. Preferably, an ignition occurs when a Piston of the internal combustion engine during a rotation of the crankshaft in the preferred direction of rotation reaches a top dead center in or after a compression stroke.

The ignition can be a spark ignition or auto-ignition. In spark ignition, for example, an ignition timing of at least one of the at least one cylinder associated spark plug can be adjusted accordingly. In a spark ignition, for example, a temperature and / or pressure in the combustion chamber can be adjusted accordingly.

By the ignition, which takes place in particular at the time of reaching the top dead center in or after a compression stroke, another, acting in the preferred direction, torque is generated on the crankshaft, which supports the starting process. In this way, a maximum producible torque of the starter motor can be further reduced.

In another embodiment, before the blockage of the rotation of the crankshaft, a starting torque curve of the starting torque is generated such that a rotation of the crankshaft takes place. Here, the rotation of the crankshaft is mechanically released. In particular, a starting torque curve can be generated such that a static friction torque of the crankshaft and of elements, e.g. Piston, the internal combustion engine is overcome and a breakaway of the crankshaft takes place. For example, For example, the starting torque in the starting torque curve may be generated such that the crankshaft is positioned at a predetermined crankshaft position. The predetermined position may for example be a blocking position, wherein the crankshaft is mechanically blocked only in the blocking position. The starting torque curve can be generated such that it has at least one change of sign (modulation of the starting torque).

Alternatively or cumulatively, the starting torque curve, z. B. with at least one change of sign of the starting torque, carried out such that the crankshaft is pre-positioned in a predetermined crankshaft position. In this way, advantageously, a starting cylinder and / or a volume of the combustion chamber of the starting cylinder can be adjusted before the starting operation. A starting cylinder here describes a cylinder of the internal combustion engine, which reaches its upper compression dead center in a (shared) rotation of the crankshaft in the preferred direction of rotation as the first of several cylinders, wherein the upper compression dead center describes the top dead center in or after a compression stroke.

Also, the starting torque curve can be generated such that a predetermined fuel pressure is built up. For this purpose, the crankshaft can be mechanically directly or indirectly, e.g. via a camshaft, drive a pump of a fuel injection system. This is the case in particular in so-called common rail Otto or common rail diesel engines. Thus, advantageously by rotation of the crankshaft before the start of the actual starting process, a desired fuel pressure can be built up, which is necessary for subsequent injection and ignition, in particular in diesel internal combustion engines.

This is so even before a mechanical blockage of the rotation of the crankshaft, z. B. generated by a modulation of the starting torque a rotational movement of the crankshaft. However, this rotation does not serve to start the internal combustion engine, but a pressure build-up and / or a pre-positioning of the crankshaft.

In a preferred embodiment, the crankshaft is positioned at a predetermined blocking position prior to the starting time. Here, the blocking position may designate a position of the crankshaft in which rotation of the crankshaft may be blocked.

In particular, the blocking position can be predetermined by a mechanical design of the blocking agent. Preferably, therefore, the blocking means is designed such that it can mechanically block the rotation of the crankshaft in more than one crankshaft position.

The blocking position can also be adjusted depending on a desired start cylinder. Here, the crankshaft can be positioned such that, starting from the current position of the crankshaft, a desired cylinder during a rotation of the crankshaft in the preferred direction of rotation as the first of a plurality of cylinders reaches the upper compression dead center.

Also, the blocking position can be adjusted depending on a desired volume of a combustion chamber of the (start) cylinder. For example, a small volume of the (start) cylinder at the beginning of the starting process makes it easier to overcome the following upper compression dead center, but possibly an ignition of the fuel-air mixture is made difficult, thereby complicating a labor contribution to overcome the second upper compression dead center becomes. On the other hand, a large volume of the combustion chamber at the start of the tempering process requires a higher energy to overcome the first following upper compression dead center, however, facilitates the first combustion and thus the further starting process due to the higher working contribution due to the ignition.

Positioning of the crankshaft in a predetermined blocking position can also be achieved with a previous shutdown or shutdown of the internal combustion engine, e.g. by a suitable deceleration of the rotation of the crankshaft. As a result, rotational energy of the crankshaft which is still present when the engine is switched off can advantageously be used to set the desired blocking position.

In another embodiment, a regenerative operation mode of the starter motor is activated when a termination condition of the cranking operation is satisfied after the rotation of the crankshaft is blocked. In the generator operating mode, kinetic energy generated by the rotary oscillator is converted into electrical energy by the starter motor, which can also be operated as a generator. As a result, the rotational oscillator energy can be withdrawn in an advantageous manner.

If a termination condition of the starting operation is fulfilled, then the blockage of the rotation of the crankshaft can be released immediately or upon reaching a predetermined counter-torque, wherein the counter-torque designates the torque exerted by the crankshaft on the elastic coupling torque. As a result, an amplitude of the torsional vibration can be reduced as quickly as possible in an advantageous manner. Alternatively, the mechanical blockade can be solved upon reaching a lower threshold value of a fuel pressure, wherein the lower threshold value defines a fuel pressure, which no longer allows a start of the internal combustion engine safely. Further alternatively, the release of the blockade only at the beginning of a renewed starting operation, but before the proposed start time, take place, for example, when the internal combustion engine is reactivated after a previous shutdown of the internal combustion engine.

A regenerative operation mode of the starter motor may also be activated when the condition (s) for releasing the blockage of the crankshaft is / are satisfied, but the release does not occur due to a malfunction. As a result, the rotary oscillator can be actively deprived of energy, whereby operational reliability is increased.

An abort condition of the starting process can be met, for example, if a defect of the blocking agent and / or its activation is detected.

This results in an advantageous manner that an operational safety during the starting process is ensured even if energy is already stored in the rotary oscillator, but the starting process must be terminated. This energy can advantageously be converted back into electrical energy by a so-called recuperation, whereby e.g. a battery of the vehicle can be charged.

In a further embodiment, a target torque of the starter motor increases continuously with decreasing difference between a current twist angle and the minimum allowable or the predetermined negative twist angle. Here, a sign-sensitive consideration of both the setpoint torque and the difference takes place. This can be done in particular in a half-oscillation from a positive reversal angle to a negative reversal angle, wherein a reversal angle denotes a rotation angle at which a reversal of the direction of rotation of the rotor takes place. If the current angle of rotation approaches the minimum permissible angle of rotation, the difference described above decreases. At the same time, however, the nominal torque of the starter motor increases. Thus, the rotation of the rotor against the preferential direction of rotation, which is caused by a negative target torque, less supported with decreasing difference or, if the target torque is positive, this even counteracted.

As a result, a mechanical damage of the elastic coupling element can be avoided in an advantageous manner, as falling below the minimum allowable or the predetermined negative rotation angle is avoided. Alternatively, the target torque of the starter motor may gradually increase in one or more steps as the difference between the actual twist angle and the minimum allowable or the predetermined negative twist angle decreases. For example, e.g. conceivable that when falling below a predetermined difference, the target torque is suddenly set to a reference value of zero and when reversing the direction of rotation of the rotor or upon reaching the minimum allowable or predetermined negative rotation angle abruptly a positive target torque is set. Another alternative is conceivable that when falling below a predetermined difference, the target torque is suddenly set to a positive or negative target torque.

Alternatively or cumulatively, the nominal torque of the starter motor decreases continuously with decreasing difference between the maximum permissible twist angle or a predetermined positive twist angle and a current twist angle or in one or more Step by step. This can be done in particular in a half-oscillation from a negative angle of return to a positive angle of reversal.

The predetermined negative angle of rotation or the predetermined angle of rotation in this case denote angle of rotation, when it reaches enough energy is stored in the rotary oscillator to start the internal combustion engine.

This results in an advantageous manner an increased reliability in the excitation of the previously described rotary vibrator for starting the internal combustion engine, since permissible angle of rotation is not exceeded or exceeded.

In a further embodiment, a defect of the torsional vibration system is detected if a frequency of the sign change of the starting torque deviates from a predetermined resonance frequency by more than a predetermined amount. If the sign of the starting torque is always changed when a reversal of the direction of rotation of the rotor of the starter motor takes place, then times of the change of sign can be detected and from this a frequency of the change of sign can be determined. If this frequency deviates from a known resonant frequency of the torsional vibration system determined, for example, by tests or modeling, then a defect of the rotary vibrator can be detected.

Alternatively or cumulatively, a defect of the torsional vibration system may be detected when a difference between amounts of the reversing angle immediately following the starting operation, for example, the maximum positive and maximum negative rotational angles, exceeds a predetermined difference. During cranking, an amount of twist angle may increase continuously. However, this increase is limited by dynamic properties of the rotary oscillator in height. If the difference between the amounts of successive reversal angles exceeds a predetermined level, the angle of rotation actually achieved during the starting process thus increases or decreases disproportionately. Also in this case, a defect of the torsional vibration system can be detected.

Alternatively or cumulatively, a defect of the torsional vibration system can be detected if a temporal twist angle course deviates from an expected course by more than a predetermined amount. The expected course here refers to a time course of the angle of rotation, which will adjust due to the dynamic properties of the rotary vibrator. In a torsionally flexible coupling with linear properties, for example a linear torsion spring, for example, can set as sinusoidal course as expected course.

Alternatively or cumulatively, a defect of the torsional vibration system can be detected when an amount ratio between reversing angles immediately following each other during the starting operation exceeds or falls below a predetermined amount.

Further alternatively or cumulatively, a defect of the torsional vibration system can be detected if a ratio of the mechanical power generated by the starter motor exceeds the predetermined angle of rotation reaches a predetermined level. For this purpose, a current twist angle and the mechanical power generated by the starter motor can be detected or determined. The mechanical power generated by the starter motor can be determined, for example, as a function of an electric power required by the starter motor.

If a defect of the torsional vibration system is detected, then a termination condition of the starting operation can be fulfilled.

This results in an advantageous manner an increase in reliability during a starting operation, since the functionality of the rotary vibrator can be monitored.

Fig. 1

ein schematisches Blockschaltbild eines Antriebstranges,

Fig. 2

ein schematisches Schaubild eines Blockiermittels in einer ersten Ausführungsform,

Fig. 3

ein schematisches Schaubild eines Blockiermittels in einer zweiten Ausführungsform,

Fig. 4

ein schematisches Schaubild eines Blockiermittels in einer dritten Ausführungsform und

Fig. 5

einen schematischen zeitlichen Verlauf eines Anlassmoments, einer Drehzahl einer Verbrennungskraftmaschine, einer Drehzahl des Anlassmotors und eines Winkels eines drehelastischen Kopplungselements.

The invention will be explained in more detail with reference to an embodiment. The figures show:

Fig. 1

a schematic block diagram of a drive train,

Fig. 2

a schematic diagram of a blocking agent in a first embodiment,

Fig. 3

a schematic diagram of a blocking agent in a second embodiment,

Fig. 4

a schematic diagram of a blocking agent in a third embodiment and

Fig. 5

a schematic time course of a starting torque, a rotational speed of an internal combustion engine, a speed of the starter motor and an angle of a torsionally flexible coupling element.

Hereinafter, like reference numerals designate elements having the same or similar technical features.

In Fig. 1 a schematic block diagram of an inventive device 1 for starting an internal combustion engine 2 is shown. The device 1 comprises, in addition to the internal combustion engine 2, a crankshaft 3 of the internal combustion engine 2, a starter motor 4 and a torsionally elastic coupling element 5, by which the crankshaft 3 is mechanically connected to a rotor 6 of the starter motor 4. The torsionally flexible coupling element 5 in this case forms the inventive torsionally flexible coupling and may for example be a torsion spring. Furthermore, the device 1 comprises a blocking means 7, by which a rotation of the crankshaft 3 can be mechanically blocked or released. Also shown is a transmission 8, a drive shaft 9 and a rotatable wheel 10 of a motor vehicle which can be driven by the drive shaft 9.

Not shown is a control device which controls the starter motor 4 such that during a starting operation, the starting torque generated by the starter motor 4 AM (see Fig. 5 ) has at least one, but preferably several, sign changes. At a starting time of the starting operation or before the starting time, the blocking means 7 can be activated, whereby a rotation of the crankshaft 3 is mechanically blocked. Mechanically blocked here means that a rotation of the crankshaft 3 is not possible. At the start time, for example, a negative starting torque AM is generated by the starter motor 4. As a result, the rotor 6 of the starter motor 4 is rotated counter to a preferred direction of rotation, which is represented by an arrow 11. Since a rotation of the crankshaft 3 is blocked, the rotor 6 biases the torsionally flexible coupling element 5. Thus, the starting torque AM acts counter to the restoring torque generated by the torsionally flexible coupling element 5. This increases with a decreasing, ie increasing in magnitude, angle of rotation W (see Fig. 5 ). If the restoring torque exceeds the torque generated by the starter motor 4 in terms of magnitude, then a reversal of the rotational acceleration takes place. At this time or after this time, a reversal of the direction of rotation can also take place. At the time of reversal of rotation then takes place a sign change of the starting torque AM, the starter motor 4 generates from this point on a positive starting torque AM and the rotor 6 in the preferred direction of rotation 11 drives. Another change of sign to a negative starting torque AM takes place when a renewed reversal of the direction of rotation of the rotor 6 takes place from a direction of rotation in the preferred direction of rotation in a direction of rotation opposite to the preferred direction of rotation. Thus, a swinging of the rotational crankshaft formed by the blocked crankshaft 3, the torsionally flexible coupling element 5 and the rotor 6 takes place. During the excitation energy is stored in the rotary oscillator, wherein at the time of reversal of rotation of the rotor 6, the stored energy in the rotary oscillator is completely stored as potential energy.

If a minimum permissible angle of rotation W, that is to say a maximum permissible angle of rotation W, is attained in a rotation of the rotor 6 contrary to the preferential direction of rotation, a sign change of the starting torque AM takes place, as described above. In the following on this change of sign as temporally next zero crossing of the rotation angle W, the blocking means 7 is deactivated, so that the rotation of the crankshaft 3 is released. Thus, the stored in the rotary oscillator at this time as kinetic and potential energy energy at least partially cause a rotation of the crankshaft 3 in the preferred direction of rotation 11. The torque transmitted to the crankshaft 3 at this time may advantageously be greater than a breakaway torque and compression and sliding friction torques present in the internal combustion engine 2. Thus, the crankshaft 3 can be driven so that the internal combustion engine 2 can be started.

Even before the blocking of the crankshaft 3, the released crankshaft 3 can be positioned by generating a suitable course of the starting torque AM in a predetermined blocking position. For this purpose, for example, a modulation of the starting torque AM take place, that is to say a chronological progression of the starting torque AM is generated with at least one change of sign.

The described method for starting the internal combustion engine 2 may be combined with other methods of starting. Thus, it is possible to carry out a known towing start-up method in an operating internal combustion engine, the starter motor 4 without activating the blocking means 7 and without sign change a starting torque AM in the preferred direction of rotation 11, that is, a positive starting torque AM, and thus starts the internal combustion engine 2.

Also, the proposed method can be combined with a method in which energy of a rolling vehicle to start or to start the Internal combustion engine 2 is used by a torque-transmitting connection between a wheel 10 of the vehicle and the internal combustion engine 2 is activated. For example, a control device may determine which method of starting is carried out as a function of input variables such as a temperature of the internal combustion engine 2, a state of the blocking means 7, a vehicle speed, a pedal position and / or a selector lever position. The control device can also monitor the selected method and, if appropriate, stop it and subsequently carry out a different method.

It is also possible that prior to the blocking of the crankshaft 3 by the blocking means 7, a modulation of the starting torque generated by the starter motor 4 AM such that a desired fuel pressure is built up.

In order to store a maximum possible energy in the rotary oscillator, the starting torque AM is controlled such that in a last half period with a negative starting torque AM just a minimum allowable angle of rotation W is achieved, but not to damage the elastic coupling element 5, not is exceeded. If the minimum permissible angle of rotation W of the elastic coupling element 5 is reached, there is a change of sign of the starting torque AM, which is now positive. If, due to a malfunction, no deactivation of the blocking means 7 takes place, ie if the crankshaft 3 remains locked, then the starting torque AM can be changed to a minimum value immediately after detection of the malfunction and a generator operating mode of the starter motor 4 can be activated. Thus, the starter motor 4 is operated until reaching a maximum angle of rotation W as a generator, whereby the rotary oscillator is actively deprived of energy. In this case, for example, a predetermined number of further deactivation attempts of the blocking agent can take place or the starting process can be aborted.

If, for example, in the case of a failure of the rotary vibrator, the starter motor 4 or the blocking means 7, a minimum allowable or a predetermined negative angle of rotation W is not reached after a predetermined period of time, a termination condition of the starting operation can be met. An abort condition can also be met, for example, if an amount ratio of successive reversal angles is one or more times below a predetermined minimum value.

If the blocking means 7 is designed so that the crankshaft 3 can only be blocked in predetermined crankshaft positions, the number of cylinders that can be used as starting cylinders may be limited. In this case, a start cylinder is understood to mean that cylinder whose upper compression dead center is first overcome in a preferred direction of rotation 11 when the crankshaft 3 is rotated out of this predetermined crankshaft position. This can usually, but not necessarily, be the cylinder that is also ignited first. For a four-stroke engine with an even number of cylinders, the number of starting cylinders may be two, for a three-cylinder engine the number is usually one. Is, e.g. Due to an embodiment of the blocking means 7, not every cylinder can be used as a start cylinder, the crankshaft 3 can already be positioned in such a way that a desired start cylinder is set when the internal combustion engine 2 is switched off by a corresponding crankshaft position control.

Advantageously, the blocking means 7 is designed or designed such that it can block the rotation of the crankshaft 3 in more than one crankshaft position. For example, For example, the blocking means 7 may be designed in such a way that it can block the crankshaft 3 in 36 equidistant crankshaft positions, ie every 10 ° crankshaft angle. In this case, the blocking means 7 may be e.g. be formed by a fixed to a housing, not shown, the internal combustion engine 2 radially displaceable bolt which can be inserted into bores or recesses which are introduced into the crankshaft 3.

It is also possible that the blocking means 7 does not directly block a rotation of the crankshaft 3, ie interacts directly with the crankshaft 3, but instead acts on a further shaft, which is coupled to the crankshaft 3, of the internal combustion engine 2, e.g. on a camshaft, acts.

For a reliable cold start of diesel engines usually a preheating of sucked air and, for example, parts of a combustion chamber by appropriate heating or annealing, such as glow plugs, performed. The proposed method for starting the internal combustion engine 2 in this case advantageously allows a content of a combustion chamber of a cylinder, in contrast to conventional starting method before the first compression need not be replaced. This results in an advantageous manner that the heating or annealing means have a longer period over which they can act on the contents of the combustion chamber. Of course, it is conceivable that a cylinder-dependent control of the heating or annealing takes place, so that, for example, a preheating of the starting cylinder or in the combustion chamber of the Starting cylinder introduced air is more intense or starts earlier. In a spark-ignition engine, such as a gasoline engine, an ignition energy in an ignition of the starting cylinder can be increased to achieve a reliable ignition. Furthermore, compared to conventional starting methods, very early fuel pre-injections can take place in the starting cylinder, since, as explained above, the contents of the combustion chamber are no longer exchanged during the starting process and thus a longer time is available for vaporization of the fuel.

The proposed method for starting the internal combustion engine 2 advantageously allows a maximum starting torque AM of the starter motor 4 to be generated to be as small as possible. Under these conditions, it may be advantageous for the internal combustion engine 2 to make its own torque contribution as early as possible during the starting process, if possible already by overcoming the first upper compression dead center.

To determine an injection or ignition timing is usually required that a crankshaft or camshaft angle is known. For example, (absolute) angle sensors can be used to detect such an angle. These can be improved at low resolution by existing incremental sensors. Maintaining conventional incremental sensors on the crankshaft 3 and / or camshaft, a number and location of signal edges can be optimized for early detection of injection angles or ignition angles. Such a detection can also take place in an opposite to the preferred direction of rotation 11 rotating starter motor 4. When parking the internal combustion engine 2, information present at this time, e.g. a present crankshaft angle, are used as initial values for a new startup, possibly even after a non-volatile storage when the controllers were switched off in the meantime. It is also possible for information present locally in a control unit to be transmitted via a bus system, e.g. a CAN bus, transmitted information from other control units are adjusted and used only as initial values, if there is no deviation.

If the blocking means 7 is already actuated when the internal combustion engine 2 is switched off and the blocking means 7 remains activated until the next starting of the internal combustion engine 2, the crankshaft angle set at the time of activation of the blocking means 7 can be used as the initial value at the next start.

A rotor angle of the rotor 6, together with a specific crankshaft angle, can be used to determine the angle of rotation W between the crankshaft 3 and the rotor 6 and thus to determine the rotation of the elastic coupling element 5. In this case, the angle of rotation W can be made plausible by predetermined and / or determined torques and / or detected rotational accelerations using mathematical models.

Further, it is possible that means for valve train, for example, camshaft phaser, a cylinder deactivation additionally or alternatively to set a predetermined crankshaft position with activated blocking means 7 such that a predetermined filling of a combustion chamber is set.

Furthermore, a defect of the blocking means 7 and / or its activation can be detected. Here, e.g. are detected, whether in an activated state of the blocking means 7 movements of the crankshaft 3 done. These movements may e.g. be detected by the aforementioned crankshaft or camshaft sensor. In this case, an impermissible movement of the crankshaft 3 can be detected when an amplitude of the movement is above a predetermined value, wherein the predetermined value takes into account an elasticity of the crankshaft 3 and the blocking means 7.

Alternatively, the blocking means 7 via a means for detecting a Einrückweges, for example of pins or a locking bar 18 (see, eg Fig. 2 ), wherein in an engaged state, the rotation of the crankshaft 3 is blocked. If an output signal of the means for detecting the engagement path does not change in a predetermined manner upon activation, a defect can be detected.

In the case of an electromagnet used as an actuator for the blocking means 7, a current waveform in windings of the electromagnet or a variation of an inductance of the electromagnet, e.g. in response to a current gradient at a given voltage jump, and a defect is detected when these quantities deviate from predetermined magnitudes.

In the case of an electric motor as an actuator for the blocking means 7 can be detected whether a rotation of the rotor of the electric motor corresponds to a desired rotation upon activation of the blocking means 7, whether a voltage is induced in the electric motor or a current consumption of the electric motor deviates from a predetermined current consumption. It is also possible to detect whether there is no commutation in the case of a BLDC motor.

A defect of the blocking means 7 can also be detected if, after a deactivation of the blocking means 7, no or only a slight movement of the crankshaft 3 occurs for a predetermined period of time.

Fig. 2 shows a schematic diagram of a blocking means 7 in a first embodiment. The blocking means 7 comprises a gear 12, which is rotatably mounted about a central axis of rotation 13. The gear 12 can on the crankshaft 3 (see Fig. 1 ) be fixed torsionally rigid. In this case, the gear 12 teeth 14, each having a rounded portion 15 and a straight portion 16. Here, the teeth 14 in a cross section with a sectional plane perpendicular to the central axis of rotation 13 a quarter-circle-shaped cross-section. The straight sections 16 in this case run in the radial direction with respect to a center 17 of the gear 12.

Next, the blocking means 7 comprises a locking bar 18 which is rotatably mounted about a rotation axis 19 of the locking bar 18. The latching bar 18 has at a gear-side end a latching lug 20, wherein the latching lug 20 can interact with the teeth 14. The rounded portions 15 of the teeth 14 are in this case designed such that when the gear 12 rotates in the counterclockwise direction, which is relative to the central axis of rotation 13 rotates, a tip 21 of the locking tooth 20 along the rounded tooth surface of the teeth 14 can slide without latching with your teeth. In this case, a rotational movement of the gear 12 and thus also the crankshaft 3 is released. The straight portions 16 of the teeth 14 are in this case designed such that when the gear 12 rotates clockwise, formed by the locking lug 20 abutment surface 22 abuts the straight portion 16, whereby the gear 12 is locked to the locking bar 18. In this case, a rotational movement of the gear 12 and thus also the crankshaft 3 is locked.

The blocking means 7 further comprises a first spring 23 and a further spring 24. In this case, the further spring 24 is attached to a latching nose side portion of the locking bar 18, wherein the first spring with respect to the axis of rotation 19 of the locking bar 18 on a detent side portion opposite portion of Rastbalkens 18 is attached. Furthermore, the blocking means 7 comprises an actuator 25, which can move the further spring 24 in or against a vertical direction, which is represented by an arrow 26. In a release position, the further spring 24 is positioned by the actuator 25 in a vertical direction 26 upper position. In this release position exercises, especially exclusively, the first spring 23, a force on the locking bar 18, so that the locking lug 20 due to the rotation of the locking bar about the rotation axis 19 against the in Fig. 3 shown vertical direction 26 moves upward and thus releases the rotational movement of the gear 12 in both directions of rotation.

In a blocking position, the further spring 24 is positioned by the actuator 25 in a lower position in the vertical direction 26. In this case, both the first spring 23 and the further spring 24 exerts a force in the vertical direction 26 on the latching bar 18. Since both forces, with respect to the axis of rotation 19, act on opposite sections of the locking bar 18, there is no rotation of the locking bar 18 and thus no release of the rotational movement in both directions of rotation. Rather, the rotational movement of the gear 12 is locked in the clockwise direction in this blocking position. Counterclockwise, the rotational movement, as previously described, against the spring force of the other spring 24 is possible.

Fig. 3 shows a schematic diagram of a blocking means 7 in a second embodiment. The blocking means 7 comprises a gear 12, which is rotatably mounted about a central axis of rotation 13. The gear 12 can on the crankshaft 3 (see Fig. 1 ) be fixed torsionally rigid. Here, the gear 12 teeth 14, wherein the teeth 14 in a cross section with a sectional plane perpendicular to the central axis of rotation 13 have a trapezoidal cross-section.

Next, the blocking means 7 comprises a locking bar 18 which is rotatably mounted about a rotation axis 19 of the locking bar 18. The latching bar 18 has at a gear-side end on a locking lug 20 with also trapezoidal cross-section, wherein the latching lug 20 can interact with the teeth 14. The blocking means 7 further comprises a first spring 23 and a further spring 24. In this case, the further spring 24 is attached to a latching nose side portion of the locking bar 18, wherein the first spring 23 with respect to the axis of rotation 19 of the locking bar 18 on a detent side portion opposite section of the locking bar 18 is attached. Furthermore, the blocking means 7 comprises an actuator 25, which can move the further spring 24 in a vertical direction, which is represented by an arrow 26. In a release position, the further spring 24 is positioned by the actuator 25 in a vertical direction 26 upper position. In this release position exercises, in particular exclusively, the first spring 23 a force on the locking bar 18, so that the locking lug 20 due to the rotation of the locking bar 18 about the rotation axis 19 against the in Fig. 3 shown Vertical direction 26 moves upward and thus releases the rotational movement of the gear 12 in both directions of rotation.

In a blocking position, the further spring 24 is positioned by the actuator 25 in a lower position in the vertical direction 26. In this blocking position, both the first spring 23 and the further spring 24 exert a force in the vertical direction on the latching bar 18. Since both forces act on, with respect to the axis of rotation 19, opposite portions of the locking bar 18, there is no rotation of the locking bar 18 and thus no release of both rotational movement. Rather, the rotational movement of the gear 12 is locked in both directions of rotation in this blocking position.

Fig. 4 shows a schematic diagram of a blocking means 7 in a third embodiment. The blocking means 7 comprises two brake pads 27, which on opposite sides of the crankshaft 3 (see Fig. 1 ) are arranged. Furthermore, the blocking means 7 comprises an actuator 25, which can be moved in and against a longitudinal direction, which is symbolized by an arrow 28. Furthermore, the blocking means 7 comprises the respective brake pads 27 associated lever arms 29 which are each rotatably mounted about rotation axes 30. Here, the rotation axes 30 are perpendicular to the longitudinal direction 28. In Fig. 4 It is shown that the lever arms 29 have two arm portions. A first arm portion 31 extends from the rotation axis 30 to the corresponding brake pad 27. A second arm portion 32 extends away from the brake pad 27 and encloses an angle α with the first arm portion. At a free end of the second arm portion 32 of the lever arm 29 is mechanically connected to the actuator 25, for example via a pull rope. Furthermore, the blocking means 7 comprises a spring 33 which is arranged between the brake pads 27. In an initial position of the spring 33, in which the spring is not biased, the brake pads 27 are not in mechanical contact with the crankshaft 3. If now the actuator 25 moved in the longitudinal direction 28, the brake pads 27 due to the mechanical connection of the actuator 25th pressed with the lever arms 29 and due to the formation and storage of the lever arms 29 against the spring force generated by the spring 33 to the crankshaft 3, whereby a mechanical contact between the brake pads 27 and the crankshaft 3 is made and the crankshaft 3 is braked. In this blocking state, a rotational movement of the crankshaft 3 is not possible. If the actuator 25 is moved counter to the longitudinal direction 28, the brake pads are moved away from the crankshaft 3 by the spring force generated by the spring 33. As a result, a release state is achieved in which a rotational movement of the crankshaft 3 is released.

Fig. 5 shows a schematic course of a starting torque AM by a solid line, a rotational speed DV of an internal combustion engine 2 (see Fig. 1 ) by a dashed line, a rotational speed DA of the starter motor 4 by a dash-dot line and a rotation angle W of a torsionally flexible coupling element 5 by a dotted line over a time t.

In a first phase P1, a modulation of the starting torque AM takes place such that the crankshaft 3 breaks loose. This takes place at the end time E_P1 of the first phase P1. In a second phase P2, the starting torque AM is modulated in such a way that the crankshaft 3 is moved in a predetermined angular range in such a way that a fuel pump coupled to the crankshaft 3 can build up a desired injection pressure. From the end time E_P2 of the second phase P2, the starting torque AM is controlled such that the crankshaft 3 is positioned in a crankshaft position in which a blockage of the crankshaft 3 is possible. At a blocking time B, the rotational movement of the crankshaft 3 is blocked. In a fourth phase P4 energy is now accumulated in the above-explained rotary oscillator, with maximum and minimum amplitudes of the speed DA and the angle W increase. After an end time E_P4 of the fourth phase P4 takes place in a fifth phase P5, a release of the blockade, which at a release time L, the speed DV of the internal combustion engine 2 temporally fast, e.g. jumpy, increased.

It is also possible to control the blocking means 7 before the blocking time 3 and / or before the release time L.

Thus, side surfaces of the teeth 14 and the locking lug 20 (see Fig. 2 and Fig. 3 ) be frictionally connected when a force acts on these surfaces, for example, during a blockage of the crankshaft 3. This force is essentially dependent on a twist angle W of the elastic coupling element 5. In particular, the frictional force generated by the frictional connection can prevent release, for example when the frictional force is greater than the lifting force exerted by the springs 23, 24 on the detent bar 18. However, the frictional force will be low when the elastic coupling element 5 is relaxed, that is, has a magnitude small angle of rotation W.

Thus, the time interval in which the blocking means 7 should release the rotation of the crankshaft 3 is small. During the fourth phase P1, a period duration, that is to say a time duration between two successive identical sign changes of the direction of rotation, can be for example approximately 120 ms. Thus, they are also temporally consecutive following maximum maxima of the twist angle W only about 60ms apart. As a result, a time interval for release can include periods of time from 0 ms to 20 ms.

In general, the cost and the installation space requirements of an adjusting device, eg of the in Fig. 2 and Fig. 3 illustrated actuator 25, the blocking means 7 with increasing maximum power, which is determined from the product of force and distance per operating time. Thus, if a positioning time, which in this case corresponds to the duration of the release of the rotation, increased, so costs and space can be reduced.

In an advantageous design of the blocking means 7, instead of a direct mechanical coupling of the actuator 25 with the locking bar 18, a mechanical coupling via the further spring 24 is realized. This further spring 24 serves as a temporary storage for a generated by the actuator 25 point energy.

If the actuator 25 is e.g. designed as an electric motor, possibly with a gear, so this actuator 25 can be controlled even before the release time L, at the latest to the release time L, a movement of the locking bar 18 should be made. This control can be maintained until the end of the movement of the locking bar 18 or even beyond.

If the adjusting device of the blocking means 7, that is, for example, the actuator 25, via a spring, for example the further spring 24, coupled to a release element, eg the locking bar 18, the actuator 25 at a drive time, a predetermined period of time, eg 70ms , before the desired release time L is controlled such that an actuator-side end of the further spring 24 in a release direction, which is oriented in this case against the vertical direction 26, is moved. From this point on, for example, a motor of the actuator 25 is accelerated. The spring force which builds up during this movement in the release direction, which accelerates the release element, that is to say the latching bar 18, likewise in the release direction, does not exceed the previously explained frictional force until a further point in time, which is later than the actuation time and before the release time L, which is generated by the angle of rotation W of the elastic coupling element 5 dependent frictional connection between the teeth 14 and the locking tooth 20. Here, the Ansteuerzeitpunkt and the driving force generated by the actuator 25 is selected in such a function of a time course of the angle of rotation W of the elastic coupling element 5, that for the previously explained further time the spring force exceeds the frictional force and thus the locking bar 18 in the release direction accelerated and consequently moved. In such a method, the release time L is thus set virtually automatically.

In this case, only the locking bar 18 and a part of the other spring 24 must be accelerated, and in the case of a direct mechanical coupling of the actuator 25 with the locking bar 18 also has an optionally connected via a gear with the other spring 24 rotor of the actuator 25 and accelerate thus a comparatively larger moment of inertia would have to be overcome. This would require a higher performance of the actuator 25.

At the in Fig. 3 shown trapezoidal cross-sections of the teeth 14 and the locking lug 20 increases with increasingly traveled path of the locking bar 18 in the release direction, the distance between a tooth 14 and the locking lug 20 continuously, so that after the beginning of the movement of the locking bar 18, the probability of unwanted renewed contact of the side surfaces , which would cause a frictional force-based braking of the locking bar 18, decreases. The locking bar 18 is thus accelerated unrestrained. The spring force hardly decreases here, since the actuator 25 now moves the actuator-side end of the further spring 24 correspondingly faster.

Accordingly, a control of the blocking means 7 take place before the blocking time B, wherein the frictional force when moving the latching lug 20 against the release direction, ie in the vertical direction 26, is overcome.

The increasing angle of rotation W of the elastic coupling element 5 causes an increasing torque on the crankshaft 3, which is accelerated. The locking bar 18 is now so far moved in the release direction 18 that no mechanical contact between the teeth 14 and the locking lug 20 may occur more.

After this, the activation of the actuator 25 can be switched off.

Previously, the method of premature activation of an actuator of the blocking means 7 for the in Fig. 2 and Fig. 3 illustrated embodiments explained. Of course, the described method is also executable for further embodiments of the blocking means 7, in particular for embodiments in which the adjusting device of the blocking means 7 is connected via an elastic element with a release element. In this case, in time before a blocking time B and / or before a desired release time L, the adjusting device can be controlled such that a the device-side end of the elastic element is moved in a release direction. In this case, a control time and / or the force generated by the adjusting device can be selected depending on a time profile of the angle of rotation W of the elastic coupling element 5, that at a further time the force of the elastic element on the release element a frictional force between the release element and a crankshaft side corresponding element of the blocking agent exceeds.

LIST OF REFERENCE NUMBERS

1

contraption

2

Internal combustion engine

3

crankshaft

4

starter motor

5

elastic coupling element

6

rotor

7

blocking agent

8th

transmission

9

drive shaft

10

wheel

11

Preferred direction of rotation

12

gear

13

rotation axis

14

tooth

15

rounded section

16

straight section

17

Focus

18

Rest bar

19

axis of rotation

20

locking lug

21

top

22

stop surface

23

first spring

24

another spring

25

actuator

26

vertical direction

27

brake pads

28

longitudinal direction

29

lever arm

30

axis of rotation

31

first arm section

32

another arm section

33

feather

AT THE

starting torque

THERE

Speed of the starter motor

DV

Speed of the internal combustion engine

W

angle of twist

P1

first phase

P2

second phase

P3

third phase

P4

fourth phase

P5

fifth phase

E_P1

End time of the first phase

E_P2

End time of the second phase

B

Blocking time

E_P4

End time of the fourth phase

L

Release time

t

Time

Claims (8)

1. Method for starting an internal combustion engine (2), wherein a crankshaft (3) is coupled in a rotationally elastic fashion to a rotor (6) of a starter motor (4), wherein in a starting process the starter motor (4) generates a starting torque (AM) which is transmitted to the crankshaft (3) via the rotationally elastic coupling, wherein a negative or positive starting torque (AM) is generated at a starting time of the starting process, wherein at least one change of sign of the starting torque (AM) takes place during the starting process,
   characterized in that
   before or at the starting time rotation of the crankshaft (3) is mechanically blocked, wherein the rotation of the crankshaft (3) is enabled if or after energy stored in a torsional oscillation system reaches a maximum permissible amount of energy or an amount of energy which is necessary to start the internal combustion engine (2), wherein the torsional oscillation system is composed at least of the rotationally elastic coupling and the rotor (6) of the starter motor (4).
2. Method according to Claim 1, characterized in that the rotation of the crankshaft (3) is enabled after a minimum permissible rotational angle (W) or a predetermined negative rotational angle (W) has been reached and/or a change of sign of the starting torque (AM) has taken place, while a negative starting torque (AM) is being applied.
3. Method according to one of Claims 1 or 2, characterized in that after rotation of the crankshaft (3) has been enabled, a fuel-air mixture in a combustion chamber of at least one cylinder of the internal combustion engine (2) is ignited.
4. Method according to one of Claims 1 to 3, characterized in that before the blocking of the rotation of the crankshaft (3), a starting torque profile of the starting torque (AM) is generated in such a way that the crankshaft (3) rotates.
5. Method according to one of Claims 1 to 4, characterized in that before the starting time the crankshaft (3) is positioned in a predetermined blocking position.
6. Method according to one of Claims 1 to 5, characterized in that if an abort condition of the starting process is satisfied after the rotation of the crankshaft (3) has been blocked, a generator operating mode of the starter motor (4) is activated.
7. Method according to one of Claims 1 to 6, characterized in that a target torque of the starter motor (4) increases continuously or increases incrementally in one or more steps as the difference between a current rotational angle (W) and the minimum permissible or the predetermined negative rotational angle (W) decreases, and/or in that the target torque of the starter motor (4) decreases continuously or decreases incrementally in one or more steps as the difference between the maximum permissible rotational angle (W) or a predetermined positive rotational angle (W) and a current rotational angle (W) decreases.
8. Method according to one of Claims 1 to 7, characterized in that a defect of the torsional oscillation system is detected if a frequency of the change of sign of the starting torque (AM) deviates from a predetermined resonance frequency by more than a predetermined amount and/or a difference between the absolute values of the positive and negative reversal angles, which follow one another immediately during the starting process, exceeds a predetermined difference and/or a deviation of a chronological rotational angle profile from an expected profile exceeds a predetermined amount and/or an absolute value ratio between positive and negative reversal angles which follow one another immediately during the starting process undershoots or exceeds a predetermined absolute value and/or a ratio of the mechanical power which is generated by the starter motor exceeds a predetermined amount at the rotational angle (W) which is reached.

Images