WO2009033591A2 - Internal combustion engine for a motor vehicle and method for operating an internal combustion engine - Google Patents

Abstract

The invention relates to a method for operating an internal combustion engine comprising a spark-ignition engine for a motor vehicle. According to said method, in a first partial load range (1) of the internal combustion engine, the spark-ignition engine is operated using a charge compression combustion method and in a spark-ignition operating range (4) of the internal combustion engine, the spark-ignition engine is operated in the conventional manner. According to the invention, the internal combustion engine also comprises an electric drive and the spark-ignition engine is operated using a charge compression combustion method in another partial load range (2, 3) with the electric drive (ISG) activated in said other partial load range (2, 3). The invention also relates to an internal combustion engine for carrying out said method.

Description

 Daimler AG Brandstetter

25/08/2008

Internal combustion engine for a motor vehicle and method for operating a

Internal combustion engine

The invention relates to a method for operating an internal combustion engine having a gasoline engine for a motor vehicle, wherein in a first part load range of the internal combustion engine of the gasoline engine is operated in a Raumzündverbrennungsverfahren and operated in a gasoline operating range of the internal combustion engine of the gasoline engine as a conventional gasoline engine. The invention further relates to an internal combustion engine for carrying out the method.

From US 7 104 349 B2 an internal combustion engine is known, which is operated in a Raumzündverbrennungsverfahren (HCCI operation). A coupled to the internal combustion engine generator is used to generate electricity. The power can be supplied to an electric drive. A torque generated in the electric drive is transmitted via a drive train to the drive wheels of the motor vehicle, wherein the electric drive is the essential drive source of the vehicle. Optionally, a further mechanical connection is provided between the internal combustion engine and the drive wheels, so that part of the drive power of the internal combustion engine can be transmitted directly to the drive wheels. The US 7 104 349 B2 provides to operate the internal combustion engine continuously in an efficiency-optimized range, rates of change of the speed are limited. Load changes during driving are realized via the electric drive. At a low load request, a power surplus of the internal combustion engine is converted via the generator into electrical energy, which is stored in a battery and is available again for a subsequent high load request for operating the electric drive.

From DE 10 2006 041 467 A1 an internal combustion engine is known, which in a first operating range in a Raumzündverbrennungsverfahren (Homogeneous compression ignited combustion) and is operated in a second operating range as a conventional gasoline engine. The aim of DE 10 2006 041 467 A1 is to make the second operating range as large as possible by influencing various control parameters, so that the internal combustion engine can be operated as long as possible in the room ignition combustion method. For this purpose, various methods for controlling the start of combustion and the heat release are proposed.

The invention has for its object to provide a method for operating an internal combustion engine with gasoline engine for a motor vehicle, which is characterized by high efficiency and allows operation of the gasoline engine in Raumzündverbrennungsverfahren in a wide operating range. The invention is further based on the object to provide an internal combustion engine for carrying out the method.

The object is achieved by a method with the method steps specified in claim 1 and by an internal combustion engine having the features specified in claim 9.

In the method according to the invention, the internal combustion engine comprises an electric drive, and the gasoline engine is operated in a further partial load range of the internal combustion engine in a Raumzündverbrennungsverfahren, wherein the electric drive is connected in the further part load range. A resulting from the driving load of the internal combustion engine is thus distributed to the gasoline engine and the electric drive. By the connection of the electric drive a attributable to the gasoline engine portion of the load is variable, so that the gasoline engine itself can be operated longer in an advantageous for the Raumzündverbrennungsverfahren partial load range.

In one embodiment of the method, the electric drive is designed as an integrated starter generator (ISG). Such a starter-generator can be operated both in a charging operation for charging an electrical storage as well as in a boost operation. Thus, for example, at a constant load of the internal combustion engine in a simple manner a load applied to the gasoline engine load proportion both increase (integrated starter generator in the charging mode) and reduce (integrated starter generator in boost mode). The Integrated Starter Generator also fulfills a function as a starter of the internal combustion engine and as a generator. In this way, a variety of functions are combined in a space-saving manner in one component, which contributes to an increase in efficiency.

In a further embodiment of the method, a further partial load range is designed as a second partial load range in which a greater load resulting from a driving operation is applied to the internal combustion engine than in the first partial load range, and the electric drive is operated in the second partial load range in a boost mode. In boost mode, electrical energy supplied from an electrical storage is converted into in-torque and thus in-drive power for a vehicle. A load from the driving operation of the motor vehicle is thus distributed to the gasoline engine and the electric drive, so that applied to the gasoline engine in comparison to an operation of an internal combustion engine without electric drive reduced load. As a result, the gasoline engine can continue to be operated in the room ignition combustion method at a comparatively high load applied to the internal combustion engine from the driving operation.

In a further embodiment of the method, a further partial load range is designed as a third load range, in which a smaller load resulting from a driving operation is applied to the internal combustion engine than in the first partial load range, and the electric drive is operated in the third partial load range in a charging mode. In charging operation, an electrical energy is generated in the electric drive, which can be stored in suitable energy storage units and fed back into the electric drive at a subsequent high load request. The load applied to the gasoline engine in this case is composed of the load required for the driving operation of the motor vehicle and of a load from the charging operation of the electric drive. In particular, at low loads from driving, it is possible to operate the gasoline engine in an extended operating range in the space ignition combustion method.

In a further embodiment of the method, a change of operating mode is made from the first partial load range to the second partial load range and subsequently to the Otto operating range as the load requirement increases. In a full load range of the internal combustion engine of the gasoline engine must be operated in the rule in a conventional Otto process. By the connection of the electric drive before the However, switching the gasoline engine from a room ignition combustion method to a conventional gasoline combustion method provides additional power for driving the motor vehicle, so that the gasoline engine can be operated longer in the space ignition combustion method.

In a further embodiment of the method, a change of operating mode from the first part-load range to the third part-load range and subsequently to the Otto operating range is carried out as the load requirement decreases. In a low-load range, the gasoline engine usually also has to be operated in a conventional Otto process, since only little fuel is injected and the temperature of the fuel-air mixture after compression is not sufficient for ignition. However, by the connection of the electric drive in charging operation before switching the gasoline engine of a Raumzündverbrennungsverfahren to a conventional gasoline combustion process, an additional load on the gasoline engine, so that more fuel must be injected, whereby the gasoline engine operated longer in the Raumzündverbrennungsverfahren can be.

In a further embodiment of the method, switching between the second or third partial load ranges and the Otto operating range is at least largely torque-neutral with the aid of the electric drive. Large changes in the torque due to a mode change from an operation with room ignition combustion to a gasoline operation or vice versa are thus mitigated by a connection of the electric drive.

In a further embodiment of the method, the gasoline engine has a variable compression, with the help of which an increased compression is set in an operation of the internal combustion engine in a partial load range. Thus, another manipulated variable is available with which a load of the gasoline engine varies and thus an operating range of the gasoline engine with room ignition combustion can be extended.

An internal combustion engine according to the invention for a motor vehicle having a gasoline engine which can be operated in a room ignition combustion method comprises a switchable electric drive. Depending on a load request from the driving operation can be applied to the gasoline engine load by switching the vary so that the gasoline engine is operable in an extended operating range in a space ignition combustion method.

In one embodiment of the invention, the electric drive is designed as an integrated starter generator. The integrated starter generator fulfills several functions. On the one hand, the integrated starter-generator is operable as an electric motor and serves in this function in a conventional manner for starting the internal combustion engine from standstill. On the other hand, with the aid of the integrated starter-generator while driving, in particular when braking the motor vehicle, mechanical energy can be converted into electrical energy, which can be stored in a downstream energy store. Moreover, with the aid of the integrated starter-generator, the load of the gasoline engine can be varied so that the gasoline engine as a whole is operable in an extended operating range in the space-burning combustion process. Thus, the integrated starter generator fulfills a multitude of functions in a compact component.

In a further embodiment of the invention, the gasoline engine to a variable compression, by means of which the load can be further varied. This results in a further enlarged operating range in which the gasoline engine can be operated in a Raumzündverbrennungsverfahren.

Advantageous embodiments of the invention are illustrated in the drawings. In this case, the features mentioned above and those yet to be explained below can be used not only in the respectively specified combination of features, but also in other combinations or alone, without departing from the scope of the present invention.

Showing:

Fig. 1 in an overview of possible technologies for further development of a conventional gasoline engine; Fig. 2 shows schematically different operating ranges of an internal combustion engine with a gasoline engine and an integrated starter-generator.

The requirements for future internal combustion engines, starting from diesel and gasoline internal combustion engines, can be summarized as follows: Diesel engines are to be as emission-poor as gasoline engines and gasoline engines are to be as fuel-efficient as diesel engines. An exemplary internal combustion engine for meeting future fuel consumption regulations (CO 2 emissions) is formed from a combination of a gasoline engine and various technologies, some of which are already known per se. The combination creates synergies that enable engines with high specific power and high specific torque with very low fuel consumption (CO2 emissions). So far, these two requirements were difficult to meet, since in particular high performance was usually associated with measures to reduce the tendency to knock (for example, ignition timing adjustment, enrichment, low compression ratio).

In Fig. 1, various technologies for a gasoline engine 10 are shown, which allow depending on the use (vehicle, engine) by suitable combination fuel-efficient internal combustion engines 20. These include

• a first method for direct injection DE (λ = 1) with spark ignition and homogeneous mixtures with an air / fuel mixture λ = 1;

A second method for direct injection DE (λ> 1) with a spray-guided combustion method and an air / fuel mixture λ> 1;

• Room ignition combustion RZV, where an air-fuel mixture is ignited by compression and where combustion control technologies and combustion state information are required (for example, by measuring the flow of ions or monitoring combustion chamber pressure);

• channel injection KE for combustion processes with homogeneous mixtures;

Variable valve train by means of a camshaft positioner NWS and / or a valve lift switchover VHS or by means of a fully variable valve drive WS, which can be implemented mechanically, electromechanically or electrohydraulically;

• Turbo Charging TC, for example by means of variable turbocharger, rigid loader, mechanical supercharger and / or two-stage supercharger;

• Multi Displacement System (MDS);

• Variable compression VCR;

• direct start device DS;

• Integrated Starter Generator ISG.

By combining these technologies, the gasoline engine 10 of the internal combustion engine 20 can be operated in a wide operating range in a room ignition combustion process RZV. A room ignition combustion process RZV is a process in which a homogeneous gas-air mixture by autoignition is inflamed. The temperature required for this purpose can be achieved via appropriate compression, exhaust gas recirculation, exhaust gas retention, exhaust gas recirculation or intermediate injection of fuel. The

Raumzündverbrennungsverfahren RZV is a partial load method, that is, the gasoline engine 10 must be conventional, ie externally ignited, operated in higher load ranges. The load range is essentially limited by too low temperatures in the combustion chamber at low loads, by increased tendency to knock at high loads and in the case of exhaust gas recirculation, exhaust gas retention and / or exhaust gas recirculation due to insufficient oxygen (reduced air mass) in the combustion chamber.

A method for operating an internal combustion engine 20 with a gasoline engine 10 and an electric drive in the form of an integrated starter-generator ISG is explained in more detail below with reference to FIG. 2.

FIG. 2 shows various operating ranges of the internal combustion engine 20 as a function of a load L required during driving operation and a rotational speed n of the internal combustion engine 20. A first part-load range 1 is characterized by a mean load required during driving and a medium speed range. The gasoline engine 10 is operated in the first part-load range 1 of the internal combustion engine 20 in a room ignition combustion process RZV. The integrated starter-generator ISG contributes not or only slightly to the drive of the motor vehicle. The first operating region 1 is characterized by a low specific consumption of the internal combustion engine 20. In the direction of higher driving loads, the first operating range 1 would be limited without further measures by an upper limit load Lo, above which there would be knock-like phenomena in the gasoline engine 10 in the combustion of the fuel-air mixture. In the case of exhaust gas recirculation or retention combustion would be limited only possible without further measures above the limit load Lo due to lack of oxygen.

With the aid of the integrated starter-generator ISG, it is possible to shift the upper limit load L ₀ in the direction of an extended upper limit load LE _O ZU. For this purpose, part of the drive power of the internal combustion engine 20 is provided by the integrated starter-generator ISG in a second partial load range 2. The power provided by the gasoline engine 10 remains approximately constant with increasing load demand and approximately corresponds to the provided power of the internal combustion engine 20 when operating at an upper boundary line 5, through which the first part-load area 1 and the second part load area 2 are separated. In this way, the gasoline engine 10 also at a higher load requirement to the internal combustion engine in the second part-load range 2 continue to be operated in a consumption and low-emission Raumzündverbrennungsverfahren.

With a further increasing load demand on the internal combustion engine, the power supplied by the gasoline engine 10 operated in the space ignition combustion method and by the integrated starter-generator ISG is no longer sufficient. In this case, a mode change is made from the second part-load range 2 into an Otto operating range 4, in which the gasoline engine 10 is operated conventionally and the fuel-air mixture is ignited by means of an ignition device. The integrated starter-generator ISG can be operated supportive in a boost operation or even in a charging operation for charging an electrical storage unit. In a modified embodiment, the integrated starter-generator is deactivated at high loads.

With further increasing load requirements, operation of the internal combustion engine 20 is limited by a full load line 7 of the gasoline engine 10.

The first part-load range 1 of the internal combustion engine 20 is limited in the direction of low loads by a lower limit load Lu, below which without further measures operation of the gasoline engine 10 in the room ignition combustion process RZV would not or only to a limited extent possible, especially since the injected fuel does not lead to a safe self-ignition of Fuel-air mixture is sufficient and because the temperature in the combustion chamber of the gasoline engine 10 is too low.

With the aid of the integrated starter-generator ISG, the lower limit load Lu can be shifted in the direction of an extended lower limit load L _E u. For this purpose, in a third part-load range 3, the integrated starter-generator is operated in a charging mode and the generated electrical energy is stored in an energy store. The load applied to the gasoline engine 10 corresponds approximately to a load during operation of the internal combustion engine 20 at a lower boundary line 6 between the first part-load range 1 and the third part-load range 3. The power provided by the gasoline engine 10 exceeds in the third part-load range 3 necessary for driving Power and excess power can be used to drive the Integrated Starter Generator ISG. In this way, the gasoline engine 10 can continue to be operated even in a low load request to the engine 20 in the third part load range 3 in the space ignition combustion process RZV. In a modified operating method, not shown, the power provided by the gasoline engine is greater than the sum of the power required for the driving operation and the maximum power required for driving the integrated starter generator with a further decrease in load request. In this case, a mode change is made from the third part load range to an Otto operating range in which the gasoline engine is conventionally operated at low load. The integrated starter-generator ISG is preferably deactivated. In another modified operating method, the power required for driving operation is provided exclusively by the integrated starter-generator or other electric drive, and the gasoline engine is deactivated.

In addition to the application shown, the integrated starter-generator ISG can be used to make switching between operating areas in which the gasoline engine 10 is operated in the room ignition combustion method RZV, and operating areas in which the gasoline engine 10 is operated conventionally, torque neutral. For this purpose, a correction intervention to compensate for momentary jumps via the integrated starter-generator ISG is made. Furthermore, a hysteresis 8 when switching the operating modes by the integrated starter-generator ISG can be influenced such that the first partial load range 1 is restricted as little as possible by the hysteresis 8.

In a modified, not shown embodiment, instead of an integrated starter-generator any electric drive (electric motor) is provided, for example, as it comes in a hybrid vehicle used.

In a further, modified embodiment, the internal combustion engine comprises a gasoline engine with a variable compression. This makes it possible to operate the gasoline engine in a partial load range with very high compression ratios. In this way, a required amount of residual gas can be reduced and an oxygen content of the charge can be increased. This leads to a further reduction of the tendency to knock with increasing load requirements to the drive unit, since the fuel-air mixture is emaciated, so that the first operating range of the internal combustion engine can be further expanded in the direction of higher loads.

Claims

Daimler AG Brandstetter25.08.2008Patent claims 1. A method for operating an internal combustion engine (20) with a gasoline engine (10) for a motor vehicle, in which - In a first part load range (1) of the internal combustion engine (20) of the gasoline engine (10) in a Raumzündverbrennungsverfahren (RZV) is operated and - In a gasoline operating range (4) of the internal combustion engine (20) of the gasoline engine (10) is operated as a conventional gasoline engine, characterized in that the internal combustion engine (20) comprises an electric drive (ISG) and that the gasoline engine (10) in one another partial load range (2, 3) of the internal combustion engine (20) in a Raumzündverbrennungsverfahren (RZV) is operated, wherein the electric drive (ISG) in the further part load range (2, 3) is switched on. 2. The method according to claim 1, characterized in that the electric drive is designed as an integrated starter-generator (ISG). 3. The method according to any one of claims 1 or 2, characterized in that a further partial load range as a second partial load range (2) is configured in which a greater from a driving operation resulting load on the internal combustion engine (20) as in the first part-load range (1 ), and that the electric drive (ISG) in the second partial load range (2) is operated in a boost mode. 4. The method according to any one of claims 1 to 3, characterized in that a further part-load range is designed as a third part-load range (3) in which a smaller resulting from a driving load on the internal combustion engine (20) is applied as in the first part-load range (1 ), and that the electric drive (ISG) in the third part-load range (3) is operated in a charging operation. 5. The method according to any one of claims 3 or 4, characterized in that with increasing load request a Betriebsartenwechsel_von_den the first part load range (1) to the second part load range (2) and subsequently to the Otto operating range (4) is made. 6. The method according to any one of claims 4 or 5, characterized in that with decreasing load request, a mode change from the first part-load range (1) to the third part-load range (3) and subsequently to the Otto operating range (4) is made. 7. The method according to any one of claims 1 to 6, characterized in that switching between the second or third part-load range (2, 3) and the Otto operating range (4) by means of the electric drive (ISG) is at least largely independent of torque. 8. The method according to any one of claims 1 to 7, characterized in that the gasoline engine (10) has a variable compression (VCR), with their help in an operation of the internal combustion engine (20) in a partial load range (1, 2, 3) a increased compression of the gasoline engine (10) is adjustable. 9. internal combustion engine (20) for a motor vehicle, with a gasoline engine (10) which is operable in a Raumzündverbrennungsverfahren (RZV), characterized in that the internal combustion engine (20) a switchable electric drive (ISG) includes. 10. Internal combustion engine according to claim 9, characterized in that the electric drive is designed as an integrated starter-generator (ISG). 11. Internal combustion engine according to any one of claims 9 or 10, characterized in that the gasoline engine (10) has a variable compression (VCR).