Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
  • F02B23/00—Other engines characterised by special shape or construction of combustion chambers to improve operation
  • F02B23/08—Other engines characterised by special shape or construction of combustion chambers to improve operation with positive ignition
  • F02B23/10—Other engines characterised by special shape or construction of combustion chambers to improve operation with positive ignition with separate admission of air and fuel into cylinder
  • F02B23/101—Other engines characterised by special shape or construction of combustion chambers to improve operation with positive ignition with separate admission of air and fuel into cylinder the injector being placed on or close to the cylinder centre axis, e.g. with mixture formation using spray guided concepts
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
  • F02B17/00—Engines characterised by means for effecting stratification of charge in cylinders
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02F—CYLINDERS, PISTONS OR CASINGS, FOR COMBUSTION ENGINES; ARRANGEMENTS OF SEALINGS IN COMBUSTION ENGINES
  • F02F3/00—Pistons 
  • F02F3/26—Pistons  having combustion chamber in piston head
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
  • F02B23/00—Other engines characterised by special shape or construction of combustion chambers to improve operation
  • F02B23/08—Other engines characterised by special shape or construction of combustion chambers to improve operation with positive ignition
  • F02B23/10—Other engines characterised by special shape or construction of combustion chambers to improve operation with positive ignition with separate admission of air and fuel into cylinder
  • F02B2023/103—Other engines characterised by special shape or construction of combustion chambers to improve operation with positive ignition with separate admission of air and fuel into cylinder the injector having a multi-hole nozzle for generating multiple sprays
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
  • F02B75/00—Other engines
  • F02B75/12—Other methods of operation
  • F02B2075/125—Direct injection in the combustion chamber for spark ignition engines, i.e. not in pre-combustion chamber
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
  • Y02T10/00—Road transport of goods or passengers
  • Y02T10/10—Internal combustion engine [ICE] based vehicles
  • Y02T10/12—Improving ICE efficiencies

Definitions

• the invention relates to a direct-injection gasoline engine with an injector per cylinder for fuel injection into a combustion chamber of the type specified in the preamble of claim 1 and a method for operating such an internal combustion engine with the features of claim 10.
• the fuel / air mixture to be burned for driving the piston is formed in the combustion chamber of each cylinder from fuel injected directly into the combustion chamber with combustion air supplied separately through inlet channels.
• the fuel / air mixture is to be ignited by the ignition spark of a spark plug protruding into the combustion chamber and therefore an ignitable mixture is to be provided on the electrodes of the spark plug.
• stratified charge operation a layered mixture cloud with an ignitable fuel concentration can be formed by late fuel injection during the working cycle of the respective cylinder, with an overall lean mixture in the entire combustion chamber volume. Operation with a stratified mixture leads to a reduction in fuel consumption and pollutant emissions from the internal combustion engine.
• the fuel is usually injected into the combustion chamber in a cone jet, a cone-shaped fuel cloud with the combustion air is formed.
• a cone jet a cone-shaped fuel cloud with the combustion air is formed.
• the mixture formation strongly depends on the ignitable quality of the mixture of the fuel cloud in the area of the spark plug.
• so-called multi-hole injectors are known, the injection nozzle of which is provided with a plurality of injection holes distributed over its circumference.
• DE 198 04 463 A1 discloses such a multi-hole injector, in which at least one row of injection holes distributed over the circumference of the injection nozzle is provided, in order to implement a jet-guided combustion process by forming the mixture cloud by targeted injection of fuel via the injection holes.
• the geometric shape of the combustion chamber is influenced by a recessed piston recess in the piston crown of the piston.
• the piston bowl is located approximately opposite the injection nozzle and represents the remaining volume of the combustion chamber in which the injected fuel is located in the area of the top dead center of the piston movement.
• DE 199 22 964 AI discloses a geometric design of the piston bowl to improve the mixture formation with conically injected fuel.
• the geometric shape of the combustion chamber plays a key role in the quality of the mixture formation, particularly in the case of self-igniting diesel engines.
• the known combustion chamber design has a so-called omega piston bowl, in which the fuel is directed into the outer peripheral areas of the circular piston bowl by a central elevation at the bottom of the piston bowl, in order to contribute to the formation of the fuel / air mixture there.
• the present invention is based on the object of designing the internal combustion engine in such a way that fuel wetting of the piston during the injection is excluded even during operation with late fuel injection.
• the piston bowl is expanded with a plurality of radial cavities hollowed out in the piston crown in the radial direction of the piston.
• the radial cavities are distributed over the circumference of the piston recess in such a way that a cavity for receiving the respective fuel jet of this injection hole is assigned to each injection hole of the injector.
• the individual jets of the injected fuel which also emanate from the injector with radial components within the cone jet, are received in the radial cavities and are kept away from the surface of the piston crown.
• the inventive design of the piston bowl with additional radial cavities precludes wetting of the piston surface with fuel and thus reduces the pollutant emission of the internal combustion engine.
• the hollow of the piston crown with radial cavities for receiving the fuel jets of the multi-hole injector allows a free design of the fuel injection in the jet-guided mixture formation process and also allow larger opening angles of the cone jet. If necessary, the fuel can be injected at an opening angle of approximately 130 ° of the cone formed from the fuel jets of all injection holes of the multi-hole injector.
• the opening cone is preferably 75 ° to 85 °.
• the stratified fuel metering forms a stratified mixture with locally different fuel concentrations (stratified charge operation) at least in lower load areas of the internal combustion engine, with fuel metering being provided at a later point in time than approximately 50 ° crank angle before top dead center during the compression stroke.
• the fuel / air mixture is advantageously ignited at the latest 10 ° crank angle after the end of the fuel injection of the multi-hole injector.
• the radial cavities absorb the respective fuel jet from the individual injection holes of the injector and extend the distance of the piston bowl from the respective injection hole and therefore allow fuel injection at a high pressure of more than 80 bar.
• the fuel is preferably injected at more than 160 bar.
• a radial cavity is advantageously provided per injection hole of the injector, into which the fuel jet of the respective injection hole is directed and the injected fuel is mixed with the combustion air.
• the radial cavities are distributed in a rotationally symmetrical manner on the circumference of the piston recess.
• a piston with a piston recess designed in this way can interact with multi-hole injectors of different number of holes, which are evenly distributed around the circumference of the multi-hole nozzle and is an integral multiple of the number of rotationally symmetrical radial cavities.
• the number of injection holes on the circumference of the injection nozzle is coordinated with the number of radial cavities for expanding the piston recess, a radial cavity being assigned to each injection hole.
• an angle of rotation-oriented installation position of the injector can also be provided, for example with a locally different fuel concentration in the cone jacket of the cone jet for the purpose of enriching the fuel in the area of the spark plug, wherein a design of the radial cavities taking into account the angle of rotation orientation of the injector is possible ,
• the piston trough with the radial cavities in the piston is bulged radially beyond an edge of the piston trough lying at the level of the piston crown, as a result of which the radial cavities partially extend below the overlap of the piston crown in the manner of a cavern.
• the piston bowl is advantageously formed with a central elevation from its base, which can be conical in order to actively support the mixture formation in the radial cavities.
• the radial cavities diametrically opposite one another at the edge of the piston recess have an approximately omega-shaped cross section.
• FIG. 2 is a sectional view of an injection nozzle
• Fig. 3 is a plan view of a piston crown with a piston bowl formed thereon.
• the internal combustion engine 1 shown in section in FIG. 1 comprises a plurality of cylinders 2, in which a reciprocating piston 3 is arranged to move longitudinally in a manner known per se and delimits a combustion chamber 4 with its piston crown 5.
• the cylinder 2 is closed by a cylinder head 9, in which an injector 8 for the direct injection of fuel into the combustion chamber 4 is accommodated.
• an injector 8 for the direct injection of fuel into the combustion chamber 4 is accommodated.
• at least one inlet valve is also provided, through which fresh gas is led into the combustion chamber 4 when the charge is changed to form an ignitable fuel / air mixture with the fuel injected from the injector 8.
• the fuel / air mixture is ignited by a spark plug 10.
• the injector 8 is arranged in the central position of the combustion chamber 4 on a cylinder axis 7 of the cylinder 2 and, with its injection nozzle protruding into the combustion chamber 4, conically injects the fuel into the combustion chamber.
• a cone-shaped mixture cloud 14 is formed with the combustion air, the electrodes of the spark plug 10 being located in the jacket region of the cone-shaped fuel cloud 14.
• Stratified charge operation is provided in the lower load ranges of the internal combustion engine, the fuel being injected at a late point in time shortly before the mixture is ignited. There are local differences in the fuel concentration in the combustion chamber, and if the mixture is lean overall, a fuel-rich and ignitable mixture can be provided on the electrodes of the spark plug 10.
• the injection nozzle 11 of the injector 8 is equipped with a plurality of injection holes on its circumference, through which individual fuel jets enter the combustion chamber 4 during an injection process.
• the injection nozzle 11 is preferably designed as a so-called seat hole nozzle, as shown in FIG. 2.
• the injector 8 has an inwardly opening valve needle 18.
• the Valve member 18 closes the fuel chamber, which has access to the outside through injection holes 12 on the circumference of nozzle 11.
• fuel is made available for injection under a high pressure of preferably more than 160 bar.
• the injection holes 12 are designed as channels in the wall of the injection nozzle 11 such that each fuel jet from an injection hole is emitted at an angle to the longitudinal axis 7.
• the individual fuel jets form the cladding of a cone jet.
• FIG. 2 shows an injector 8, on the injector tip 19 of which a conically tapered injection nozzle 11 is formed, on the circumference of which there are provided evenly distributed injection holes 12.
• injection holes 12 preferably have a diameter of less than 140 ⁇ m.
• a ratio of the length of the injection holes L to the diameters D of L / D ⁇ 3 is considered advantageous; the ratio preferably relates to approximately 2.
• the internal mixture formation and fuel distribution can be supported by suitable air movement in the combustion chamber.
• the intake air can be controlled by swirling about the cylinder axis by appropriate design of the intake ducts 7 or tumble movements in the plane of the injector axis 7 can be controlled.
• a piston recess 6 is provided in the piston crown 5 of the piston 3 shown in section in FIG. 1, which is recessed in a central position opposite the injection nozzle 11.
• the piston recess 6 is expanded with radial cavities 16, as shown in FIG. 3.
• the radial cavities 16 hollowed out in the piston crown 5 are distributed over the circumference of the piston recess 6 such that a cavity 16 for receiving the respective fuel jet 13 is assigned to each injection hole 12 of the injector 8.
• each cavity 16 is provided for an injector with eight injection holes, which, according to the uniform arrangement of the injection holes on the circumference of the nozzle, are arranged rotationally symmetrically on the circumference of the piston recess 6.
• the radial cavities 16 extend in the radial direction up to a common radius 22, the radius R ⁇ of which is approximately 0.6 to 0.9 times, preferably 0.8 times the radius R z of the piston 3 or the cylinder 2.
• the radial cavities 16 widen the piston recess 6, which extends on the circumference 21, in sections in the area of the fuel jets of the injector, as a result of which a longer distance is available for each fuel jet 13 even when the piston is near the injector and counteracts wetting of the piston surface.
• the radial cavities 16 are preferably bulged in the piston 3 such that the piston recess 6 extends radially in the area of the cavities within the piston 3 beyond an edge 17 located at the level of the piston crown 5.
• the radial cavities for receiving the respective fuel jets lie inside the piston in the manner of a cavern 3 below the piston surface.
• the piston bowl 6 is advantageously designed with a depth of at least 5 mm and has a central elevation 15, which conically shapes the base of the piston bowl 6 and contributes to guiding the mixture cloud during the mixture formation into the radial cavities 16.
• the radial cavities 16 of the piston recess 6 according to the invention on the one hand prevent the wetting of the piston surface with fuel, so that even very late fuel injections in stratified charge operation are possible and the quality of the mixture formation can be increased.
• the radial cavities 16 according to the invention contribute in the radial direction to the beam propagation of the injector cone beam to maintain the compression ratio of the respective internal combustion engine, which is required by design.
• the compression ratio is advantageously between 10 and 13 for naturally aspirated engines and between 8.5 and 11 for supercharged internal combustion engines.
• the formation of the piston surface with radial cavities in the piston recess allows a free choice of the opening angle of the cone jet of the injector 8 with regard to the quality of combustion to be achieved.
• a beam angle between the individual steel axes of the fuel jets measured in the injector axis of 60 ° to 130 ° can be freely selected, an opening angle of the cone beam of 75 ° to 85 ° being seen as advantageous.
• the injector can be equipped with heating elements for preheating fuel or also have devices for supplying different types of fuel (bi-fuel valve), for example for supplying volatile starting fuel for the cold start.
• bi-fuel valve supplying different types of fuel
• a ratio of the diam. water of the injection valve for the cylinder bore from 0.3 to 0.38 and a ratio of the diameter of the exhaust valve to the cylinder bore from 0.28 to 0.32 for expedient.
• the inlet valves and the outlet valves are advantageously in a ratio of 1.02 to 1.1 to one another.
• a high injection pressure of advantageously more than 160 bar, an exact and very late fuel metering can take place, since the radial cavities according to the invention prevent wetting of the piston surface even at a high pressure.
• the diametrically opposed cavities 16 in the piston recess 6 form an omega shape, which contributes to the preparation of the fuel jet injected into the respective radial cavity 6.
• a ratio of the channel length of the injection holes 12 shown in FIG. 2 to the injection pressure should be less than 0.25 x 10 "9 / Pa.
• the spark plug is expediently positioned between two fuel jets 13 of the injector.
• the spark plug should be between the exhaust valves.
• the spark plug can be installed with an angle-oriented mass electrode, and several spark plugs and in particular an AC voltage ignition system with variable spark duration can also be used to stabilize the ignition.
• the combustion chamber geometry according to the invention with radial cavities for expanding the piston bowl and receiving the individual fuel jets 13 of a multi-hole injector 8 allows a very late fuel injection and rapid ignition of the fuel / air mixture at the latest 10 ° crank angle after the end of the fuel injection without wetting the piston.

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Combustion Methods Of Internal-Combustion Engines (AREA)
• Fuel-Injection Apparatus (AREA)

Applications Claiming Priority (3)

Publications (1)

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• 2002
  • 2002-12-20 DE DE10261185A patent/DE10261185A1/de not_active Withdrawn
• 2003
  • 2003-11-14 WO PCT/EP2003/012732 patent/WO2004059153A1/de not_active Application Discontinuation
  • 2003-11-14 JP JP2004562547A patent/JP4280928B2/ja not_active Expired - Lifetime
  • 2003-11-14 EP EP03779929A patent/EP1573191A1/de not_active Withdrawn
• 2005
  • 2005-06-20 US US11/157,165 patent/US7143738B2/en not_active Expired - Lifetime

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