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
  • F02B23/02—Other engines characterised by special shape or construction of combustion chambers to improve operation with compression ignition
  • F02B23/06—Other engines characterised by special shape or construction of combustion chambers to improve operation with compression ignition the combustion space being arranged in working piston
  • F02B23/0618—Other engines characterised by special shape or construction of combustion chambers to improve operation with compression ignition the combustion space being arranged in working piston having in-cylinder means to influence the charge motion
  • F02B23/0624—Swirl flow
• • 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
  • F02B23/02—Other engines characterised by special shape or construction of combustion chambers to improve operation with compression ignition
  • F02B23/06—Other engines characterised by special shape or construction of combustion chambers to improve operation with compression ignition the combustion space being arranged in working piston
  • F02B23/0645—Details related to the fuel injector or the fuel spray
  • F02B23/0648—Means or methods to improve the spray dispersion, evaporation or ignition
  • F02B23/0651—Means or methods to improve the spray dispersion, evaporation or ignition the fuel spray impinging on reflecting surfaces or being specially guided throughout the combustion space
• • 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
  • F02B23/02—Other engines characterised by special shape or construction of combustion chambers to improve operation with compression ignition
  • F02B23/06—Other engines characterised by special shape or construction of combustion chambers to improve operation with compression ignition the combustion space being arranged in working piston
  • F02B23/0645—Details related to the fuel injector or the fuel spray
  • F02B23/066—Details related to the fuel injector or the fuel spray the injector being located substantially off-set from the cylinder centre axis
• • 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
  • F02B23/02—Other engines characterised by special shape or construction of combustion chambers to improve operation with compression ignition
  • F02B23/06—Other engines characterised by special shape or construction of combustion chambers to improve operation with compression ignition the combustion space being arranged in working piston
  • F02B23/0672—Omega-piston bowl, i.e. the combustion space having a central projection pointing towards the cylinder head and the surrounding wall being inclined towards the cylinder center axis
• • 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 an internal combustion engine with direct injection, comprising a piston, the combustion bowl of which has a boss of complex geometry.
• Such improvements can in particular be obtained by acting on the quality of the mixture between the intake gases and the fuel, that is to say by producing a substantially homogeneous mixture in the combustion chamber of the engine cylinder, more particularly in the piston combustion bowl.
• the main phenomena which combine and which make it possible to obtain a substantially homogeneous mixture are essentially the atomization of the fuel and the air movements of the "swirl" type of the gas charge d admission around an axis substantially coincident or parallel to the axis of the cylinder, and also the air movement caused by the injection of fuel.
• FIG. 1 shows a cylinder of an internal combustion engine with direct injection of the type described in document FR-A-2,844,012 illustrating an example of the state of the art.
• the internal combustion engine 10 comprises at least one cylinder 12 of vertical axis XX in which axially slides a piston 14 which comprises, in its upper face 16, a combustion bowl 18 delimiting the lower part of a combustion chamber 20 of which the upper part is delimited by a portion opposite the lower face 22 of a cylinder head 24, a injector 26 which is eccentric relative to the axis XX of the cylinder 12 and which sprays the fuel in the form of an injection ply 28, substantially conical with apex S, which is formed of several asymmetrical jets 30 which travel lengths before coming into contact with the internal wall 32 of the combustion bowl 18 which is constituted by a lateral annular groove 34 centered on a main axis of symmetry AA which is connected with a substantially horizontal bottom 36 from which a boss 38 s 'extends vertically over a determined total height H.
• a piston 14 which comprises, in its upper face 16, a combustion bowl 18 delimiting the lower part of a combustion chamber 20 of which the upper part is delimited
• the invention relates more particularly to engines in which the fuel injector is arranged in an eccentric position relative to the vertical axis XX of the cylinder, such as generally internal combustion engines comprising two valves per cylinder in order to allow the implantation in each cylinder of an intake valve and an exhaust valve of large diameter.
• the various fuel jets are injected asymmetrically, which in particular affects the quality of the mixture which is not as homogeneous as desired throughout the combustion bowl 18.
• the different fuel jets 30 are asymmetrical in that they travel through different lengths, also called “free lengths", before coming into contact with the internal wall 32 of the bowl. combustion 18. More precisely, a first part of the jets, called long jets 30a, travel a path or a length "L”, while a second part of the jets 30b, called short jets 30b, travel a length "I" and finally a third part of the jets 30c, called intermediate jets 30c, travel an average length of between L and I, before all the fuel jets 30a, 30b and 30c respectively come into contact with the internal wall 32 of the groove 34.
• the combustion bowl 18 comprises on the one hand a first zone A predominantly rich in fuel attributable to the fact that the short jets 30b of length I are confined and roll up on themselves after coming into contact with the wall 32 thereby causing an overlap of the jets and, on the other hand, a second zone B close to the bottom 36 into which the long jets 30a of length L penetrate little and which is thus mainly rich in air and poor in fuel.
• a non-homogeneous air-fuel mixture in particular causes the appearance of fumes.
• the boss 38 generally has a form of revolution centered on the main axis of symmetry AA of the combustion bowl 18 so that there is then a significant risk of interference between the asymmetrical jets 30, particularly between the long jets. 30a and means 30c, and the top part of the boss 38.
• the object of the invention is to remedy these drawbacks and to propose an internal combustion engine comprising a piston whose combustion bowl has a boss of complex geometry making it possible in particular to obtain a homogeneous air-fuel mixture throughout bowl and without interference between the fuel jets and the top of the boss.
• the invention provides an internal combustion engine for a motor vehicle of the type described above, characterized in that the boss consists:
• the exchange between the injected fuel and the intake gases of the internal combustion engine is improved and the performance of the engine is increased while reducing the formation of pollutants, such as nitrogen oxides (NOx ), soot and other unburnt hydrocarbons constituting black smoke at the exhaust outlet.
• pollutants such as nitrogen oxides (NOx ), soot and other unburnt hydrocarbons constituting black smoke at the exhaust outlet.
• the lower truncated cone of the boss has a lower external wall of continuously variable convexity comprising at least:
• the first portion of the lower wall has a rectilinear inclined profile whose slope, called the first slope, is in line with the horizontal bottom and is determined so to prevent the jets of shorter lengths from rolling up on themselves towards the internal wall of the groove;
• the second portion of the lower wall has a rectilinear inclined profile whose slope, known as the second slope, is greater than the first slope so that the volume of the groove lateral is at least in the second angular sector less than the volume of the lateral groove in the first angular sector;
• the upper truncated cone of the boss has an upper external wall having a continuously variable convexity determined so as to avoid interference between the jets of the injection ply and the upper external wall of the boss;
• the height (h) of the upper horizontal face of the lower truncated cone is equal to half the total height of the boss from the bottom of the bowl to the top of the boss; - The total height of the boss is determined so that, during the injection, there is no interference between the jets and the top of the boss;
• the boss is produced by at least one operation of milling the piston
• the main axis of symmetry of the combustion bowl is coincident with the vertical axis X-X of the cylinder;
• the piston includes angular indexing means to allow the mounting of the piston in the engine in a determined operating position which is indexed according to the parameters of the associated injection ply of the injector.
• FIG. 1 is a schematic view in axial section of an internal combustion engine cylinder comprising a piston provided with a combustion bowl according to the prior art;
• FIG. 2 is a schematic view in axial section of an internal combustion engine cylinder similar to that of Figure 1 comprising a piston provided with a combustion bowl comprising a boss of complex geometry according to the invention;
• FIG. 3 is a schematic view in axial section of the combustion bowl of the piston according to FIG. 2 which illustrates the theoretical construction cones corresponding respectively to the lower truncated cone and to the upper lower truncated cone, the superposition of which makes it possible to obtain the boss according to the invention;
• FIG. 4 is a schematic perspective view which shows in detail the conical sheet of complementary injection of the boss of complex geometry according to the invention.
• Figure 2 which represents a part of the internal combustion engine 10 of the direct injection type and more particularly one 12 of the engine cylinders 10 .
• the cylinder 12 extends axially along a vertical axis of symmetry X-X and delimits an internal bore in which the piston 14 slides axially in a reciprocating movement.
• the piston 14 comprises axially an upper head 40 and a lower skirt 42, the external cylindrical wall 44 of the head 40 comprising peripheral annular grooves 46 which receive segments 48.
• the piston 14 has in its upper horizontal face 16 the combustion bowl 18, also called cavity, which axially delimits the lower part of the combustion chamber 20, the upper part of which is delimited by a portion of the lower face 22 of the cylinder head 24 of the motor.
• the cylinder head 24 comprises at least one air intake duct which opens out through an inlet orifice closed by an intake valve (not shown) in the combustion chamber 20, and at least one gas exhaust duct burned out which opens through an outlet orifice intended to be closed by an exhaust valve (not shown) in the combustion chamber 20.
• the cylinder head 24 carries at least one fuel injector 26 which is eccentric relative to the vertical axis XX of the cylinder 12 so as to allow in particular the installation of large diameter valves.
• the injector 26 is provided with an injection nozzle 50 which opens directly into the combustion chamber 20 of the engine and has injection holes 52 for spraying the fuel towards the combustion bowl 18.
• the holes 52 are for example arranged axially on a single row and distributed annularly with respect to the main axis C-C of the injector around the injection nozzle 50.
• the number of holes 52 is greater than or equal to 6 and the holes 52 are preferably distributed angularly in a regular manner around the main axis C-C of the injector 26.
• the nozzle 50 of the injector 26 is here brought closer to the axis XX of the cylinder, in tilting the main axis CC of the injector 26 relative to the vertical axis XX of the cylinder 12.
• the fuel is sprayed through the holes 52 in the form of a substantially conical injection ply 28.
• the conical injection ply 28 is defined by an apex S which is in particular determined as a function of the injection holes 52 and which here corresponds to a fictitious point of origin approximately situated at the end of the nozzle 50 of the injector 26.
• the set of asymmetrical fuel jets 30 extends from the apex S at a solid ply angle ( ⁇ ) determining the opening of the injection ply 28.
• the combustion bowl 18 has a lateral annular groove 34 which is centered on a main axis of symmetry A-A.
• the main axis of symmetry A-A here extends vertically, that is to say coaxially with the axis X-X of the cylinder 12.
• the main axis of symmetry AA of the combustion bowl 18 is coincident with the vertical axis XX of the cylinder 12 so that the combustion bowl 18 is centered relative to the cylinder 12 and to the piston 14 of the engine 10.
• the combustion bowl 18 has a substantially horizontal bottom 36, of constant depth, from which the boss 38 extends vertically, or even axially, over a determined total height H.
• depth is understood here to mean the axial coast between the bottom 36 and the upper horizontal surface 16 of the piston 14 comprising the upper circular edge 54 which delimits the inlet opening of the bowl 18.
• the upper circular edge 54 also sometimes called the "lip" of the combustion bowl 18, here has a circular profile which is centered on the main axis of symmetry A-A.
• the upper circular edge 54 has an asymmetrical profile of the type described in French patent application No. 0550156 filed by the applicant on January 19, 2005 and not yet published to date.
• the solid ply angle ( ⁇ ) of the injection ply 28 with apex S is in particular determined as a function of the geometric parameters of the associated combustion bowl 18, such as the diameter or the depth, and vice versa.
• the asymmetrical jets 30 travel for example a path or a length I for the short jets 30b and a longer length L for the long jets 30a, that is to say different lengths before coming into contact with the internal wall 32 of the annular groove 34 of the combustion bowl 18.
• the asymmetrical jets 30 of an eccentric injector 26 are generally called long jets 30a when the length L which they travel is greater than the radius of the bowl 18, so-called short jets 30b when the length I they travel is less than the radius of the combustion bowl 18 and said medium jets 30c when they travel an intermediate length between L and I substantially equal to the radius R of the combustion bowl 18.
• the boss 38 consists on the one hand of a lower truncated cone 38A whose base is included in the horizontal plane of the bottom 36 and is centered on the main axis of symmetry AA and whose apex S 'is the symmetrical point of the vertex S of the injection ply 28 with respect to the main axis of symmetry AA and, on the other hand, of an upper truncated cone 38B whose base 56 is formed by the face upper horizontal of the lower truncated cone 38A and the apex of which corresponds to the apex S of the injection ply 28 through which a vertical reference axis BB passes.
• boss 38 of complex geometry according to the invention and illustrated the theoretical cones of construction of vertex S 'and S corresponding to each of the truncated cones 38A and 38B forming the boss 38.
• the lower truncated cone 38A of the boss 38 has a lower external wall 58 of continuously variable convexity comprising at least:
• a second portion 62 of the lower wall extending over a second angular sector ( ⁇ ) determined corresponding substantially to the angular sector of the injection ply 28 formed of jets 30a of greater lengths.
• the angular sectors ( ⁇ ) and ( ⁇ ) are centered on the vertical reference axis B-B passing through the apex S of the conical injection ply 28.
• the first portion 60 of the lower wall 58 has, in section through a vertical section plane passing through the main axis AA, an inclined profile whose slope, called the first slope, is in line with the horizontal bottom 36 and which is determined so as to prevent the jets 30b from being over short lengths do not wind on themselves towards the internal wall 32 of the lateral annular groove 34.
• the second portion 62 of the lower wall has, in section through a vertical section plane passing through the main axis AA, an inclined profile whose slope, known as the second slope, is greater than the first slope so that the volume of the lateral groove 34 or, at least in the second angular sector ( ⁇ ), less than the volume of the lateral groove 34 in the first angular sector ( ⁇ ).
• the respective inclined profiles of the first portion 60 and of the second portion 62 of the bottom wall 58 are, in section, advantageously rectilinear and obtained by milling.
• the upper truncated cone 38B of the boss 38 has an upper external wall 64 having a continuously variable convexity, that is to say in section by successive vertical cutting planes following a rotation about the axis A- A , the wall has an inclined profile whose slope varies continuously, in particular according to the angular sector in which one is.
• the convexity of the upper external wall 64 is determined so as to avoid interference between the jets 30 of the injection ply 28 and said upper external wall 64 of the boss 38.
• the upper external wall 64 of the upper truncated cone 38B is advantageously entirely included inside the volume of the cone formed by the asymmetrical jets 30 of the injection ply 28 in order to avoid any interference between any of the asymmetrical jets 30a, 30b and 30c and the upper external wall 64 of the boss 38.
• the upper external wall 64 of the upper truncated cone 38B of continuously variable convexity comprises at least:
• a first portion 66 of upper wall 64 extending over a determined primary angular sector ( ⁇ ) which corresponds substantially at the angular sector of the injection ply 28 formed of jets 30b of shorter lengths, and
• a second portion 68 of upper wall 64 extending over a determined secondary angular sector ( ⁇ ) which corresponds substantially to the angular sector of the injection ply 28 formed of jets 30a of greater lengths.
• the first portion 66 of the upper wall 64 has an inclined profile whose slope, called the third slope, is determined so as to be generally in line with the continuity of the first slope of the first portion 60 of the lower wall 58 in order to allow the short jets 30b to develop from the internal wall 32 of the groove 34 towards the top of the boss 38.
• the second portion 68 of the upper wall 64 has an inclined profile whose slope, called the fourth slope, is determined so as to avoid interference with the jets 30, in particular with the long jets 30a and with the medium jets 30c of intermediate length.
• the respective inclined profiles of the first portion 66 and of the second portion 68 of the upper external wall 64 are advantageously rectilinear and obtained by milling.
• the distribution of the volume throughout the bowl 18 is optimized as a function in particular of the parameters of the injection ply 28 so as to obtain an optimal compression ratio for a total volume of the bowl of combustion 18 given.
• the boss 38 of complex geometry allows for the same volume, that is to say isovolume, to obtain an optimal mixture. air and fuel.
• the boss 38 has centrally around the axis XX a greater volume of material so that the volume the bowl is advantageously distributed radially and mainly consisting of the volume of the lateral annular groove 34 in which the air and the fuel are mixed.
• the complex geometry of the boss 38 makes it possible to reduce, in the second zone B, the volume of air present relative to the fuel and thus rebalance the air-fuel ratio in order to obtain a more homogeneous air-fuel mixture .
• the volume of the lateral annular groove 34 is greater in the first angular sector ( ⁇ ) of the first portion 60 of the lower external wall 58 which corresponds to the first zone A of FIG. 1 which is radially generally opposite the second zone B.
• the complex geometry of the boss 38 conversely makes it possible to increase the volume of air present in this first zone A which is generally predominantly rich in fuel so as to obtain a more homogeneous mixture by rebalancing the ratio between the air and fuel.
• the height h of the upper horizontal face 56 of the lower truncated cone 38A forming the base of the upper truncated cone 38B is substantially equal to half the total height H of the boss 38, that is to say half of the axial rib in the vertical direction of the boss 38 from the bottom 36 of the bowl 18 to the top part 70 of the boss 38.
• the top part of the boss 38 is machined by milling so as to form an upper face 70 preferably generally horizontal, as a variant of convex shape.
• the upper horizontal face 70 thus determines the total height H of the boss 38 so that, during injection, there is no interference between the fuel jets 30 and the top part of the boss 38, which is vertically at a determined minimum distance from the top S of the injection ply 28.
• combustion bowl 18 and the boss 38 are produced by milling the piston 14, in particular by means of a numerically controlled milling machine.
• the main axis of symmetry A-A of the combustion bowl 18 being coincident with the vertical axis of symmetry X-X of the cylinder 12, the combustion bowl 18 and the lower truncated cone 38A are advantageously centered relative to the cylinder 12 and to the piston
• AA of the combustion bowl 18 is eccentric relative to the axis XX of the cylinder 12 so as to reduce the distance between the axis AA of the bowl 18 and the vertical reference axis BB passing through the apex S of the sheet of injection 28.
• the piston 14 includes angular indexing means (not shown) to allow the mounting of the piston 14 in the engine 10 in a determined operating position which is capable of being indexed as a function of the parameters of the injection ply. 28 of the associated injector 26.
• the engine 10 comprises means for producing on admission an ordered swirl movement of the "swirl" type in the cylinder 12 so as to promote the formation of a homogeneous air-fuel mixture.

Landscapes

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

Applications Claiming Priority (2)

Publications (1)

Family

ID=36952598

Family Applications (1)

Country Status (5)

Families Citing this family (12)

Family Cites Families (15)

• 2005
  • 2005-12-08 FR FR0553779A patent/FR2894614B1/fr not_active Expired - Fee Related
• 2006
  • 2006-11-29 EP EP06842055A patent/EP1957772A1/de not_active Withdrawn
  • 2006-11-29 JP JP2008543874A patent/JP2009518574A/ja not_active Withdrawn
  • 2006-11-29 US US12/094,658 patent/US20090205607A1/en not_active Abandoned
  • 2006-11-29 WO PCT/FR2006/051244 patent/WO2007066027A1/fr active Application Filing

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events