WO2007118757A1

WO2007118757A1 - Method for operating an internal combustion engine

Info

Publication number: WO2007118757A1
Application number: PCT/EP2007/052786
Authority: WO
Inventors: Hans Schlembach; David Moessner; Christoph Zuelch; Andreas Lechler
Original assignee: Robert Bosch Gmbh
Priority date: 2006-04-12
Filing date: 2007-03-23
Publication date: 2007-10-25
Also published as: DE102007001119A1

Abstract

An internal combustion engine (10) serves to drive an automobile. Fuel is inserted at least intermittently into a combustion chamber (14) and ignited, thereby driving the piston (16). It is suggested that, during a storage stage in a combustion chamber (14), compressed fluid be led into a pressure reservoir (35).

Description

description

title

Method for operating an internal combustion engine

The invention relates to a method for operating an internal combustion engine according to the preamble of claim 1. The present invention is further a computer program, an electrical storage medium, a control and / or regulating device and an internal combustion engine according to the independent claims.

State of the art

A method of the type mentioned is known from DE 199 55 857 Al. Thereafter, at standstill of the crankshaft in the combustion chamber of that cylinder whose piston is in the compression stroke, fuel is injected and ignited, so that the crankshaft moves backwards. In this way, the air in that combustion chamber, the piston is meanwhile in the working stroke, compressed. If the compression in this combustion chamber reaches its maximum or ends the rearward movement, fuel is injected into the combustion chamber located in the working stroke and ignited, whereby the forward rotation of the crankshaft of the internal combustion engine is set in motion. Also known from the market are internal combustion engines with a pressure accumulator, which is fed by a separate compressor.

Object of the present invention is to develop a method of the type mentioned so that the cost of manufacturing the internal combustion engine are minimized. Disclosure of the invention

This object is achieved by a method having the features of claim 1. Further solutions are specified in the independent patent claims, which relate to a computer program, an electrical storage medium, a control and / or regulating device and an internal combustion engine. Advantageous developments of the invention are specified in subclaims. Furthermore, for the invention essential features in the following description and the drawings. The features may also be essential in very different combinations for the invention.

Advantages of the invention

When using the method according to the invention can be dispensed with a separate compressor, since the internal combustion engine itself is temporarily used as a compressor. This simplifies the manufacture of the internal combustion engine and reduces its costs. At the same time, however, compressed fluid is available in the pressure accumulator, which can be used for very different applications in the operation of the internal combustion engine. An existing ignition system is normally not in operation during the storage phase.

In this case, the use of the stored and pressurized fluid in the pressure accumulator depends on the type of fluid, which is passed during the storage phase in the pressure accumulator. For example, during the storage phase, the introduction of fuel into the combustion chamber can be interrupted, so that the fluid is at least substantially pure air. This is then available for example for the actuation of pneumatic devices.

It is also proposed that, prior to the storage phase, exhaust gas be retained in the combustion chamber and / or returned to it, so that the fluid comprises exhaust gas. In this way, a special type of exhaust gas recirculation can be realized by which the emission behavior of the internal combustion engine can be improved.

However, it is also possible for fuel to continue to be introduced into the combustion chamber during the storage phase, so that the fluid is a fuel / air mixture. Such stored in the pressure accumulator fuel / air mixture can be used, for example, for heating a catalyst system, to improve the emission behavior at low temperatures, etc.

However, the process according to the invention is very particularly advantageous in the

Connection with the direct start of an internal combustion engine. In such a direct start, the internal combustion engine is started without the aid of a starter by introducing and igniting fuel in a combustion chamber located in the working cycle. If the fluid stored in the pressure accumulator is pure air and this is introduced for a direct start in at least one combustion chamber, preferably in that combustion chamber in which the very first combustion takes place, the mixture preparation is significantly improved because it by the air injection to a Air movement comes in the combustion chamber, which supports the mixing of air and fuel.

This leads to an increase in torque, which increases the reliability in a direct start, and to a reduction in emissions. In addition, by such an air injection, the pressure in the combustion chamber is increased when the crankshaft is stationary, whereby more air mass can be trapped in the combustion chamber, which is then subsequently available during combustion. Thus, the torque generated in the first combustion during a direct start can be increased, which in turn increases the reliability of the direct start method because the crankshaft is accelerated more by the first combustion.

In this case, especially when the fluid is a fuel / air mixture, a

Direct start can also be performed in an internal combustion engine with intake manifold injection. This significantly expands the scope of the direct start procedure and even with internal combustion engines with intake manifold injection can be dispensed with a starter with the corresponding advantages.

The aforementioned storage phase can be carried out, for example, during normal operation of the internal combustion engine. For example, it is conceivable that at individual working cycles of a cylinder no ignition and optionally also no introduction of fuel into the combustion chamber and specifically during these individual working cycles, the compressed fluid in the combustion chamber is passed into the pressure accumulator.

However, it is more comfortable for the user of the internal combustion engine if the storage phase is carried out during a coasting operation of the internal combustion engine. During such an overrun operation no ignition takes place anyway and generally also no introduction of fuel into the combustion chamber, so that during the overrun operation the internal combustion engine can operate without loss of comfort as a compressor for feeding the pressure accumulator.

It is also possible that the storage phase is performed during a run-out of the internal combustion engine after a previous shutdown instruction. Also in this case, the comfort in the operation of the internal combustion engine is not affected.

In an internal combustion engine suitable for the above-mentioned method, the pressure accumulator can be thermally insulated and / or heated and / or cooled. This can influence the combustion chamber temperature.

drawing

Hereinafter, particularly preferred embodiments of the present invention will be explained in more detail with reference to FIG.

Description of the embodiments In FIG. 1, an internal combustion engine bears the reference numeral 10 as a whole. It serves to drive a motor vehicle (not shown) and comprises a plurality of cylinders, of which only one is shown by the reference numeral 12 in FIG. The cylinders 12 are, however, constructed identically. The cylinder 12 has a combustion chamber 14 which is delimited by a reciprocating piston 16. The cylinder 12 is provided with two gas exchange valve devices: on the one hand an inlet valve device 18, through which the combustion chamber 14 can be connected to an intake pipe 20, and on the other with an outlet valve device 22, through which the combustion chamber 14 can be connected to an exhaust pipe 24.

Fuel is injected in the internal combustion engine 10 into the combustion chamber 14 directly from an injector 26 associated therewith. An existing in a combustion chamber 14 fuel-air mixture is ignited by a spark plug 28. The pistons of the cylinders are connected in the usual way to a common crankshaft 30 whose angular position and angular velocity are detected by a sensor 32. In addition, the combustion chamber 14 is still associated with a valve device 34 which is connected to a pressure accumulator 36. This is, what is not shown in the drawing, provided with a thermal insulation. In an embodiment not shown, the pressure accumulator also has a heating and / or cooling device.

The operation of the internal combustion engine 10 is controlled and regulated by a control and regulating device 38. This is provided with a memory on which a computer program for controlling and regulating the internal combustion engine 10 is stored. The control and regulating device 38 receives signals from various sensors of the internal combustion engine 10, so also from the sensor 32 and a lambda sensor, not shown, which detects a mixture composition, an accelerator pedal 34, with which a user of the motor vehicle, in which the internal combustion engine 10 is installed, can express a torque request, etc. are controlled by the control and Control device 38, among other things, the injectors 26, the spark plugs 28, and the valve device 34th

The internal combustion engine 10 can be operated in different modes. In a first operating mode, the so-called "shift operation", the fuel is injected from the injector 26 into the combustion chamber 14 during a compression phase caused by a piston 16, locally into the immediate vicinity of the spark plug 28 and immediately before a top dead center OT of the corresponding piston 16 or before the ignition. Then, with the aid of the spark plug 28, the fuel is ignited, so that the piston 16 is driven in the now following power stroke by the expansion of the ignited fuel and thereby the crankshaft 30 is placed in a forward movement over which ultimately the wheels of the motor vehicle are driven.

In a second operating mode, the "homogeneous operation", the fuel is injected from the injector 26 into the combustion chamber 14 during an intake stroke caused by the piston 16. By simultaneously sucked air, the injected fuel is swirled and thus in the combustion chamber 14 substantially evenly, so homogeneously distributed. Thereafter, the fuel / air mixture is compressed during the subsequent compression stroke to then be ignited by the spark plug 28. Due to the expansion of the ignited fuel turn the piston 16 and ultimately the crankshaft 30 are driven.

For starting a so-called "direct start procedure" is used. For this purpose, various possibilities are known: In a first direct start method of the internal combustion engine 10 is at standstill internal combustion engine 10 in the combustion chamber of that cylinder 12 whose piston 16 is currently in a power stroke, injected a necessary amount of fuel for combustion by means of the injector 26 and ignited by the spark plug 28. As a result, the crankshaft 30 is accelerated in the forward direction. Thereafter, in each of those combustion chamber 14 of the cylinder 12, the piston 16 performs the next power stroke, fuel from Injector 26 is injected and ignited as soon as the corresponding piston 16 has reached its working position.

Another method for direct start of the internal combustion engine 10 is configured as follows: When the crankshaft 30 stops, fuel is injected and ignited in the cylinder 12 whose piston 16 is currently in a compression stroke, so that the crankshaft 30 initially moves backward. In this case, the injection and ignition is performed so that the piston 16 does not move beyond its rear bottom dead center, but that approximately in the region of the bottom dead center, the movement of the crankshaft 30 from the backward movement to a forward movement reverses.

At this reversal point or shortly after this reversal point, fuel is injected and ignited into cylinder 12 whose piston 16 is currently in a working stroke. This combustion leads to an acceleration of the crankshaft 30 in the forward direction, whereby the piston 16, which is in the compression stroke exceeds the top dead center. The combustion exhaust gases of the first combustion in the cylinder 12, whose piston 16 is in the compression stroke, are in this case compressed and then expanded, without resulting in a recombustion. Thereafter, in each case into the combustion chamber 14 of the cylinder or 12 whose piston 16 perform the next power stroke, fuel is injected and ignited as soon as the respective piston 16 have reached the working position.

However, with both of the described direct start methods, the fuel is completely closed

Start the start sequence injected into the combustion chamber 14, without this in a "natural" charge movement is present, which could be caused by the flowing from the intake manifold 20 via the inlet valve means 18 into the combustion chamber 14 air. Such an air flow does not exist at the very beginning. Nevertheless, a good mixture formation in the combustion chambers 14 at the very beginning of

To enable a direct start method, the following procedure is used in the present internal combustion engine 10: For example, during a coasting operation of the internal combustion engine 10, during which the crankshaft 30 is driven by the motor vehicle and therefore no fuel is injected into the combustion chambers 14 and no ignition takes place through the spark plug 28, a "storage phase" is initiated by the control and regulating device 38. During such a storage phase, the valve device 34 is opened during a compression stroke of a cylinder 12, so that the air compressed in the combustion chamber 14 by the piston 16 is conducted into the pressure reservoir 36. In this way, the pressure accumulator 36 is filled with air, wherein the maximum accumulator pressure in the pressure accumulator 36 corresponds to the maximum compression pressure in the combustion chamber 14. The internal combustion engine 10 is thus operated as a compressor during such a storage phase, with which the pressure accumulator 36 is filled with air. The storage phase ends at the latest when the overrun operation of the internal combustion engine 10 ends.

If, after a standstill of the internal combustion engine 10, these are started by one of the direct start methods described above, during the first injections of fuel through the injector 26 into the combustion chamber 14, the air stored in the pressure accumulator 36 is blown into the combustion chamber 14 by means of the valve device 34. This results in an air movement in the combustion chamber 14, which supports the mixing of air and fuel. In addition, this air injection increases the pressure in the combustion chamber 14 when the crankshaft 30 is stationary, as a result of which more air mass can be trapped in the combustion chamber 14, which is then subsequently available for combustion. Ultimately, this increases the torque at the first burns during a direct start, which improves the reliability of the direct start method. In addition, by better mixing of the air with the fuel emissions are reduced.

In the storage phase described above, there was no injection of fuel through the injector 26 into the combustion chamber 14, so that substantially pure air was conveyed via the valve device 34 into the pressure accumulator 36 during a compression stroke. It is also possible to continue during the storage phase To inject fuel through the injector 26 into the combustion chamber 14, and only omit the ignition of this fuel through the spark plug 28. This forms in the combustion chamber 14, a fuel / air mixture, which is then conveyed during the compression stroke via the then opened valve means 34 into the pressure accumulator 36. In such a storage phase, the internal combustion engine 10 also operates as a compressor, in the accumulator 36, however, not pure air, but a fuel / air mixture is stored under pressure. If, for a direct start, the fuel / air mixture stored in the pressure accumulator 36 is introduced into the combustion chamber 14, a very uniform distribution of the fuel in the combustion chamber 14 and thus an advantageous mixture formation for the direct start.

Such a "blowing in" of a fuel / air mixture into the combustion chamber 14 for a direct start of the internal combustion engine 10 extends the scope of such a direct start method to internal combustion engines with intake manifold injection. In such a case, only for the very first ignition (s) the injection of a fuel / air mixture by means of the valve means 34 is used, immediately after, when the crankshaft 30 rotates, the injection by the usual injection valve (not in the figure shown) in the suction tube 20.

It goes without saying that the storage method described above can be carried out significantly more effectively if the inlet valve device 18 and the outlet valve device 22 can be actuated independently of the position of the crankshaft 30. In such a "fully variable valve train" namely not only the compression stroke, but also the exhaust stroke of a cylinder 12 for the compression and promotion of existing in the combustion chamber 14 fluid in the

Pressure accumulator 36 can be used. This may be air or a fuel / air mixture, but also a previously retained in the combustion chamber or recycled into this exhaust gas. The latter allows the realization of a particularly flexible variant of exhaust gas recirculation.

It has been described above that the storage phase is performed during a coasting operation of the internal combustion engine 10. But it is also possible that such Memory phase repeated and very briefly carried out in normal operation of the internal combustion engine 10, deliberately omitted in the individual cylinders 12 during a cycle ignition and instead the valve device 34 during the compression stroke of this cycle (and in a fully variable valve train during the exhaust stroke) As a result, the pressure accumulator 36 is filled.

A further opportunity for carrying out the storage phase is provided when the internal combustion engine 10 is switched off, while it is coasting after a previous shutdown instruction. Under certain circumstances, a few compression strokes are sufficient to fill the pressure accumulator 36 with an air or fuel / air mixture quantity sufficient for a subsequent direct start.

In the internal combustion engine 10 described above, all cylinders 12 are constructed identically. In principle, however, it is also conceivable to provide only one cylinder with a valve device 34 through which the pressure accumulator 36 can be filled during a storage phase and the stored fluid can be returned to the combustion chamber 14 for a direct start.

Claims

claims

1. A method for operating an internal combustion engine (10), preferably for driving a motor vehicle, in which at least temporarily introduced and ignited fuel into a combustion chamber (14) and thereby a piston (16) is driven, characterized in that during a storage phase in a combustion chamber (14) compressed fluid in a pressure accumulator (36) is passed.

2. The method according to claim 1, characterized in that before and / or during the storage phase, the introduction of fuel is interrupted, so that the fluid is at least substantially air.

3. The method according to claim 1, characterized in that prior to the storage phase, exhaust gas in the combustion chamber (14) retained and / or is returned to this, so that the fluid comprises exhaust gas.

4. The method according to claim 1, characterized in that before and / or during the storage phase further fuel is introduced, so that the fluid

Fuel / air mixture is.

5. The method according to any one of the preceding claims, characterized in that for a direct start in the pressure accumulator (36) stored fluid is introduced into at least one combustion chamber (14).

6. Process according to claims 4 and 5, characterized in that the internal combustion engine (10) operates with intake manifold injection.

7. The method according to any one of the preceding claims, characterized in that the storage phase is carried out during normal operation of the internal combustion engine (10).

8. The method according to any one of the preceding claims, characterized in that the storage phase during a pushing operation of the internal combustion engine (10) is performed.

9. The method according to any one of the preceding claims, that the storage phase is carried out during a run-out of the internal combustion engine (10) after a previous shutdown instruction.

10. Computer program, characterized in that it is programmed for use in a method according to one of the preceding claims.

11. An electrical storage medium for a control and / or regulating device (38) of an internal combustion engine (10), characterized in that a computer program for use in a method of claims 1 to 9 is stored on it.

12. Control and / or regulating device (38) for an internal combustion engine (10), characterized in that it is programmed for use in a method according to one of claims 1 to 9.

13. internal combustion engine (10), with at least one combustion chamber (14), a piston (16), an ignition device (28), and a fuel injection device (26), characterized in that it comprises a pressure accumulator (36), the over a valve device (34) can be connected directly to the combustion chamber (14) and can be stored in the fluid compressed in the combustion chamber (14).

14. Internal combustion engine (10) according to claim 13, characterized in that the pressure accumulator (34) is thermally insulated and / or heated and / or cooled.

15. Internal combustion engine (10) according to any one of claims 13 or 14, characterized in that it comprises a control and / or regulating device (38) which is programmed for use in a method according to one of claims 1 to 9.