EP1477654B1 - Method to stop an internal combustion engine at a desired stand-by position - Google Patents

Description

The invention relates to a method for stopping an internal combustion engine - in particular an internal combustion engine with direct injection and spark ignition - in a desired rest position by influencing the discharge movement of the internal combustion engine, wherein the rest position is set based on current operating data, and adapted to influence the outflow due to the current operating data becomes. Furthermore, the invention relates to an internal combustion engine which is designed for carrying out such a method.

In order to improve fuel economy in internal combustion engine vehicles, complete engine shutdown rather than idling often occurs when no drive power is needed. The engine must then be restarted when its power is needed again. For starting, conventional internal combustion engines have special auxiliary units such as a starter motor or a generator which can be used as a motor (so-called starter generator). These are relatively large and expensive devices, since a high electrical power is required for starting the internal combustion engine.

Moreover, it is known to start an internal combustion engine by triggering combustion. This is possible in particular with internal combustion engines with spark ignition and direct injection. The injected directly into the combustion chamber fuel is thereby ignited by a spark, and the subsequent explosion of the air-fuel mixture moves the piston and starts the engine without the crankshaft would have to be moved by an additional auxiliary unit. Alternatively, even in conventional starting an internal combustion engine by a starter motor early or from the beginning injection and combustion take place in the cylinders to assist the starter.

Starting the engine by fuel ignition requires certain constraints in order to be successful. In particular, it is necessary or advantageous that the crankshaft is in or near a certain position at the beginning of cranking. In this regard, from DE 100 30 001 A1 various methods and devices are known with which the assumption of a desired rest position of the internal combustion engine to be ensured at standstill. By the methods and the facilities, it should be possible that a direct injection internal combustion engine can start without a starter is needed. For this purpose, it is provided that certain means are designed so that special ignition and injection pulses are generated such that the internal combustion engine is brought into a desired position. The next startup should then be a desired engine position. For this purpose, the angular position of the crankshaft and the camshaft and thus the cylinder position is monitored. However, how to always achieve exactly the desired rest position is not specified. Due to varying influences, however, the actually achieved rest positions of the internal combustion engine fluctuate considerably, which has a correspondingly negative effect on the conditions for a starterless starting of the internal combustion engine.

In EP 1 113 169 A1, the control of a stopping process of an internal combustion engine is described. The internal combustion engine described there requires an electric drive system both for starting and for the discharge process. By a sensor, the current speed, a crankshaft angle and an engine temperature is detected and transmitted to a powertrain control. It takes into account the rotational moment of inertia of the electric drive system, ie an electric machine, as well as other rotational moments of inertia. In The internal combustion engine integrated adjusting means can run controlled by setting of desired values by means of the drive train control in this way the stopping process. To achieve this, a clutch connected to the starter drive is opened in a controlled manner. However, since this solution requires an electric starter, it can be seen that no accurate positioning of the cylinder piston is achieved.

Against this background, it was an object of the present invention to provide means for stopping an internal combustion engine in a defined rest position, which allow a more accurate achievement of the desired rest position. In particular, it should be possible to start an internal combustion engine without a starter motor.

This object is achieved by a method having the features of claim 1 and by an internal combustion engine with the features of claim 7. Advantageous embodiments are contained in the subclaims.

• a) Aufgrund aktueller Betriebsdaten der Brennkraftmaschine bzw. des Fahrzeugs wird zu Beginn bzw. während der Auslaufbewegung die voraussichtliche Ruheposition der Brennkraftmaschine vorhergesagt.
• b) Die Einflußnahme auf die Auslaufbewegung wird aufgrund der genannten vorhersagten Ruheposition angepaßt, so daß die tatsächlich erreichte Ruheposition näher bei der gewünschten Ruheposition liegt oder diese im Idealfall exakt trifft.

The inventive method is used to stop an internal combustion engine in a desired rest position, the rest position can be clearly described, for example by the crankshaft angle. The internal combustion engine may in particular be an internal combustion engine with direct injection and spark ignition of the fuel. The stopping of the internal combustion engine in the desired rest position is carried out in the process by active and / or passive influence on the discharge movement of the internal combustion engine, ie the movement phase of the internal combustion engine from stopping (termination of the ignition and / or fuel supply) to its standstill. An active influence involves the immediate exercise of forces on the Movement of the internal combustion engine using external energy, while a passive influence is limited to the adjustment of operating parameters of the internal combustion engine, which indirectly affect the discharge movement. The method is characterized by the following steps:

• a) Based on current operating data of the internal combustion engine or the vehicle, the expected rest position of the internal combustion engine is predicted at the beginning or during the discharge movement.
• b) The influence on the discharge movement is adjusted due to the said predicted rest position, so that the actually achieved rest position is closer to the desired rest position or this meets in the ideal case exactly.

For the prediction of the anticipated rest position, a model of the outflow movement of the internal combustion engine is used according to the invention, which takes into account (a) the current kinetic energy of the drive train, (b) the friction losses and / or (c) the compression and expansion processes in the cylinders of the internal combustion engine. Such a model can be obtained on the basis of theoretical considerations and implemented in the form of mathematical equations. Preferably, however, the model is obtained entirely or at least partially empirically, i. by observing the engine behavior and conditioning the measurement data obtained (e.g., as a look-up table).

The model may optionally include parameters that are adapted based on a comparison between the model predicted and the actually assumed home position of the engine. In this way, the predictive power of the model can be constantly improved or adapted to changes in the behavior of the internal combustion engine. An adaptability of the model ensures that this is due to production-related tolerances in engine behavior and aging phenomena during the lifetime of a motor vehicle and therefore achieves a high prediction accuracy for each individual vehicle and at each point in time.

The method described has the advantage that it can be exercised very flexibly in conjunction with different methods of influencing the movement of an internal combustion engine. That is, virtually any special procedure for stopping an internal combustion engine in a desired rest position by the described method can be further improved. In particular, simple, inexpensive methods can be improved so that they achieve the precision and reliability of more complex methods.

The desired rest position of the internal combustion engine specified in the method can in particular be set so that the internal combustion engine is in an optimal initial configuration for a subsequent start-up solely by (or at least assisted by) fuel combustion. In this case, the above-described advantages of starting with fuel combustion can be achieved, ie the reduction in size of the required auxiliary equipment (starter motor) or the complete waiver thereof.

For the prediction of the rest position of the internal combustion engine can be used in principle all already measured and / or derived for the usual engine control data on the operating condition of the vehicle. In particular, operating data including engine speed, crankshaft angle, engine temperature (or temperature correlated therewith such as coolant temperature), and / or intake manifold intake pressure is used to predict the idle position. Experience has shown that the variables mentioned have the strongest influence on the outflow movement of the internal combustion engine.

• des Öffnungswinkels einer Drosselklappe;
• der Bremskraft, die auf eine mit der Bewegung der Brennkraftmaschine gekoppelte Einrichtung ausgeübt wird;
• der Lichtmaschine des Kraftfahrzeugs;
• der Ölpumpe des Kraftfahrzeugs;
• des Kompressors einer Klimaanlage des Kraftfahrzeugs;
• der Pumpe eines Lenkunterstützüngssystems;
• der Steuerkette und/oder des Zahnriemens zwischen der Kurbelwelle und der Nockenwelle
• der Kupplung zwischen Brennkraftmaschine und Getriebe.

As already mentioned, the influence on the discharge movement of the internal combustion engine can in principle be carried out with any known or yet to be developed methods. In particular, the influence on the discharge movement may include the control of at least one of the following quantities or devices:

• the opening angle of a throttle valve;
• the braking force exerted on a device coupled with the movement of the internal combustion engine;
• the alternator of the motor vehicle;
• the oil pump of the motor vehicle;
• the compressor of an air conditioner of the motor vehicle;
• the pump of a steering assisting system;
• the timing chain and / or the toothed belt between the crankshaft and the camshaft
• the clutch between the engine and transmission.

The invention further relates to an internal combustion engine with direct injection and spark ignition and a motor control unit, which is designed to carry out a method of the type described above. That is, the engine control unit can take advantage of the outflow movement of the internal combustion engine via suitable means to bring the latter in a desired rest position to a standstill. Furthermore, the engine control unit has means for predicting the anticipated rest position and is able to adjust the influence on the coasting movement due to such prediction, the prediction using a model of the coasting motion of the engine which determines the kinetic energy of the driveline, the friction losses and the Comprises compression and expansion processes of the internal combustion engine.

In particular, the engine control unit may include engine speed, crankshaft angle, intake pressure, and / or engine temperature sensor inputs. In this way, it is ensured that these variables, which are particularly relevant for the outward movement of the internal combustion engine, can currently be detected with their actual values.

The internal combustion engine also optionally includes a braking device, with which a braking force can be exerted on the outlet movement of the internal combustion engine. The braking device may be e.g. attach directly to the crankshaft, to the camshaft or to a piston. It allows stopping in a desired rest position without the energy of the movement of the internal combustion engine should be actively supplied from the outside.

The invention will be explained in greater detail below by way of example with reference to the FIGURE. The single figure shows schematically the components of a direct injection internal combustion engine and a motor control unit for carrying out the method according to the invention.

In the illustrated in the figure internal combustion engine 10 is a combustion engine with spark ignition and direct injection of gasoline over the leading into the cylinder 3 fuel supply 4. Such a direct injection engine has the advantage that this by spark ignition of the air-fuel mixture can be started directly in the cylinders 3, without an additional starter motor must drive the crankshaft 11 during a cranking phase. Alternatively, the (external or self) ignition of an air-fuel mixture during the start phase, but only to support a starter (starter motor) done in order to accelerate the starting process ("Quick Start") to be able to interpret the starter smaller , and to improve the comfort of the conventional launch. In such a supported start, fuel is injected and ignited already from the first revolution or from the first expansion stroke of a piston.

The internal combustion engine 10 further includes an intake manifold 2 for supplying fresh air, wherein the supply rate can be adjusted via a throttle valve 1. Downstream of the throttle valve 1, a pressure sensor for the suction pressure is arranged, whose signal p _{man is passed} to a motor control unit 7, which may be realized for example by a microprocessor. Further, on the crankshaft 11 of the internal combustion engine 10, a sensor for the crankshaft angle φ or the rotational speed n and on the internal combustion engine 10, a sensor for the engine temperature T is provided, which both transmit their signals to the engine control unit 7. Other sensor inputs are generally designated by x. The engine control unit 7 receives said sensory information and calculates therefrom control commands for various components of the internal combustion engine such. B. a fuel injection system.

The exhaust gases from the cylinders 3 of the internal combustion engine 10 are passed from an exhaust manifold 5 in an exhaust system. Of course, the internal combustion engine od with other known components such as an exhaust gas recirculation, an exhaust gas turbocharger, a catalyst. Like. Be equipped, which are not shown in detail in the figure.

In order to successfully start the internal combustion engine 10 directly after a standstill (ie without auxiliary unit) or to be able to support a start by early ignitions in the starting phase, compliance with a number of boundary conditions is required. To these boundary conditions in particular the most accurate compliance with an optimal rest position (corresponding to an optimal crankshaft angle φ _opt ), in which the piston of at least one cylinder ("working cylinder") is in the position of an expansion stroke, so that there when starting the internal combustion engine Ignition of an air-fuel mixture can take place as efficiently as possible.

In order to ensure the assumption of a desired rest position, various influencing measures can be exerted by the engine control unit 7. In particular, a control of the throttle valve 1 can take place with control signals TP in order to influence the change in the pumping work of the internal combustion engine 10 to take on the reached end position of the crankshaft and to ensure the largest possible amount of fresh air in the cylinders.

Furthermore, a braking device 6 is shown schematically in the figure, which can exert a directly or indirectly predetermined by the engine control unit 7 braking force F _B on the crankshaft 11 of the internal combustion engine 10. Alternatively, the braking device could also act on another part coupled to the engine rotation, such as the camshaft (not shown) or a piston.

Furthermore, an alternator 9 is indicated whose electrical load L is transmitted from the engine control unit 7, e.g. can be controlled by turning on power consumers. Further, not shown in the figure, devices whose control can be used to influence the outflow movement of the internal combustion engine 10, an oil pump, an air conditioning compressor, a pump for a steering assist system, a timing chain or a timing belt for coupling crankshaft and camshaft and located between the engine and transmission friction clutch, but the vehicle brake should be activated.

In order to use the above enumerated possibilities of influencing the discharge movement of the internal combustion engine 10 as effectively as possible, is within the engine control unit 7 according to the invention a model 8 for the outlet movement of the engine 10, ie their movement from stopping the ignition or the fuel supply to standstill (speed Zero). This model may predict the anticipated resting position of the engine 10 based on the current engine operating parameters. When there is a deviation between the predicted rest position and the desired rest position, the engine control unit 7 can adjust its influence on the coasting movement so that the actually achieved rest position is closer to the desired rest position than predicted by the model (assuming an unmatched influence).

The engine idle position prediction model implemented in the engine control unit 7 preferably calculates the kinetic energy E _kin = θω ^{2/2 of} the entire powertrain (with the moment of inertia θ) moved with the engine 10 as a function of the measured value or derived from other quantities current engine speed n or the angular velocity ω.

Furthermore, the model calculates the friction acting on the motor movement, the z. B. can be expressed as a frictional force F _R. This friction is estimated on the basis of the loss of kinetic energy between two times t ₁ and t ₂ during the coasting movement of the internal combustion engine 10. Furthermore, the compression and expansion processes are modeled in the engine 10, as these also have a significant influence on the discharge movement. Based on an energy balance between the current energy of the engine and the energy losses, the expected resting position can then be predicted. If this is not within the desired target range, the influence measures available to the engine control unit 7 can be adapted accordingly.

Preferably, the model 8 of the engine control unit 7 is adapted to learn. In particular, the model may contain for this purpose learning subsystems, for. In the form of neural networks. By adapting the corresponding parameters, good predictions can be guaranteed during the entire service life of the motor vehicle or over the entire range of variation of a mass production. The model can be refined by considering all relevant engine parameters such as engine wear, production tolerances, oil viscosity and the like.

Claims (9)

1. Method for stopping an internal combustion engine, in particular an internal combustion engine (10) with direct injection and spark ignition, in a desired position of rest by influencing its running down movement, wherein the position of rest is set on the basis of current operating data (ϕ, ω, T, p_man, x), and the influencing of the running down movement is adapted on the basis of the current operating data.
   characterized in that
   the position of rest is set based on a prediction by a model (8) of the running down movement of the internal combustion engine (10) which takes into account the kinetic energy (E_kin) of the drive train, the frictional losses (F_R) and the compression processes and expansion processes of the internal combustion engine.
2. Method according to Claim 1,
   characterized in that
   the desired position of rest is suitable for starting the internal combustion engine (10) solely by means of, or with support from, the combustion of fuel.
3. Method according to Claim 1 or 2,
   characterized in that
   the operational data which is used to predict the position of rest comprises the engine speed (n), the crank shaft angle (ϕ), the engine temperature (T) and/or the intake pressure (p_man).
4. Method according to at least one of Claims 1 to 3,
   characterized in that
   the influencing of the running down movement of the internal combustion engine (10) comprises checking at least one of the following variables or devices:

   - the angle of aperture of a throttle valve (1);

   - the combustion force (F_B), which is exerted on a device coupled to the movement of the internal combustion engine;

   - the dynamo of the motor vehicle;

   - the oil pump of the motor vehicle;

   - the compressor of an air conditioning system of the motor vehicle;

   - the pump of a power steering system;

   - the control chain and/or the toothed belt between the crank shaft and the cam shaft;

   - the clutch between internal combustion engine and transmission.
5. Method according to at least one of Claims 1 to 4,
   characterized in that
   the model (8) is acquired empirically, at least to a certain extent.
6. Method according to Claim 5,
   characterized in that
   the model (8) contains parameters which are adapted to the internal combustion engine (10) on the basis of a comparison between the predicted and virtual position of rest.
7. Internal combustion engine (10) with direct injection and spark ignition, characterized by an engine control unit (7) which is designed to carry out a method according to at least one of Claims 1 to 6.
8. Internal combustion engine according to Claim 7,
   characterized in that
   the engine control unit (7) has sensor inputs for the engine speed (n), the crank shaft angle (ϕ), the intake pressure (p_man) and/or the engine temperature (T).
9. Internal combustion engine according to Claim 7 or 8,
   characterized in that
   said engine contains a brake device (6) for exerting a braking force (F_B) on the running down movement of the internal combustion engine (10).

Images