WO2007048439A1 - Method for injecting fuel into a cylinder, cylinder unit for implementing such a method and internal combustion engine comprising such a unit - Google Patents

Method for injecting fuel into a cylinder, cylinder unit for implementing such a method and internal combustion engine comprising such a unit Download PDF

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Publication number
WO2007048439A1
WO2007048439A1 PCT/EP2005/013366 EP2005013366W WO2007048439A1 WO 2007048439 A1 WO2007048439 A1 WO 2007048439A1 EP 2005013366 W EP2005013366 W EP 2005013366W WO 2007048439 A1 WO2007048439 A1 WO 2007048439A1
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WO
WIPO (PCT)
Prior art keywords
cylinder
piston
center position
dead center
fuel
Prior art date
Application number
PCT/EP2005/013366
Other languages
French (fr)
Inventor
Nicolas Dronniou
Marc Lejeune
Original Assignee
Renault Trucks
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Renault Trucks filed Critical Renault Trucks
Priority to PCT/EP2005/013366 priority Critical patent/WO2007048439A1/en
Priority to EP05820637A priority patent/EP1943416A1/en
Publication of WO2007048439A1 publication Critical patent/WO2007048439A1/en

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Classifications

    • 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
    • F02F1/00—Cylinders; Cylinder heads 
    • F02F1/18—Other cylinders
    • 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
    • F02B23/0603—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 at least part of the interior volume or the wall of the combustion space being made of material different from the surrounding piston part, e.g. combustion space formed within a ceramic part fixed to a metal 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
    • F02B23/02—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
    • 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
    • F02B23/0696—W-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 wall
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M45/00—Fuel-injection apparatus characterised by having a cyclic delivery of specific time/pressure or time/quantity relationship
    • F02M45/02—Fuel-injection apparatus characterised by having a cyclic delivery of specific time/pressure or time/quantity relationship with each cyclic delivery being separated into two or more parts
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M61/00—Fuel-injectors not provided for in groups F02M39/00 - F02M57/00 or F02M67/00
    • F02M61/16—Details not provided for in, or of interest apart from, the apparatus of groups F02M61/02 - F02M61/14
    • F02M61/18—Injection nozzles, e.g. having valve seats; Details of valve member seated ends, not otherwise provided for
    • F02M61/1806—Injection nozzles, e.g. having valve seats; Details of valve member seated ends, not otherwise provided for characterised by the arrangement of discharge orifices, e.g. orientation or size
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2430/00—Influencing exhaust purification, e.g. starting of catalytic reaction, filter regeneration, or the like, by controlling engine operating characteristics
    • F01N2430/08—Influencing exhaust purification, e.g. starting of catalytic reaction, filter regeneration, or the like, by controlling engine operating characteristics by modifying ignition or injection timing
    • F01N2430/085—Influencing exhaust purification, e.g. starting of catalytic reaction, filter regeneration, or the like, by controlling engine operating characteristics by modifying ignition or injection timing at least a part of the injection taking place during expansion or exhaust stroke
    • 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
    • F02F1/00—Cylinders; Cylinder heads 
    • F02F2001/006—Cylinders; Cylinder heads  having a ring at the inside of a liner or cylinder for preventing the deposit of carbon oil particles, e.g. oil scrapers
    • 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

  • This invention concerns a method for injecting fluid into a cylinder of an internal combustion engine.
  • This invention also concerns a cylinder unit for implementing such a method and an internal combustion engine including such a cylinder unit.
  • JP-A-04191413 discloses a diesel engine where injection takes place in a combustion cavity formed on the front surface of a piston, this cavity being partly defined by a heat insulating material layer mounted on said piston.
  • Other heat insulating members are provided in the upper part of the cylinder. These heat insulating members are supposed to reduce heat losses in the metallic part and thus to increase engine efficiency.
  • it might be necessary to inject fuel when the piston is far from its top dead center position which is not possible with this structure where injection must take place when the piston is at or near this position.
  • This invention aims at proposing an optimized method for injecting fuel which result in a high overall efficiency of an internal combustion engine.
  • the invention concerns a method for injecting fuel into a cylinder of an internal combustion engine, said cylinder including a piston movable between a top dead center position and a bottom dead center position and equipped with at least a piston ring sliding against an internal surface of such cylinder, said cylinder being provided with a layer of heat insulating material near its head, said ring being kept away from said layer when said piston is in its top dead center position.
  • This method is characterized in that fuel injection within the cylinder starts when the piston is in its upward movement from its bottom dead center position to its top dead center position and in that the injected fuel is directed, upon injection, towards the layer of heat insulating material.
  • TDC top dead center position of a piston in the corresponding cylinder
  • BDC bottom dead center position of such a piston
  • the fuel which is injected before the piston reaches its TDC can be quickly evaporated because the surface of the insulating layer can be at a high temperature since this surface is thermally insulated with respect to the outside environment of the cylinder. This quick evaporation lowers the chances of a formation of a film or residues of fuel on this surface.
  • the piston rings will not interferer with the internal surface of the insulating layer so that no question arises with respect to the friction coefficient between these rings and this layer. Since the sliding ring is kept away from the insulating layer, no lubricating agent like oil must be spread on this layer, so that no dilution between fuel and lubricating agent is likely to occur. Since the volume within which fuel is injected is not limited to a cavity formed on the front face of the piston, the mixture of fuel and air can be homogenous, which improves combustion and lowers the pollutant emission of the engine.
  • such a method might incorporate the following features:
  • Fuel injection starts when the crank angle of the piston is between 180° and 20° before its angle at TDC; alternatively, fuel injection starts when the crank angle of the piston is between 0° and 180° after its angle at TDC;
  • An internal surface of the layer of insulating material which receives at least a part of the injected fuel is at a temperature above the temperature of the internal surface of the cylinder on which the piston ring slides.
  • the invention also concerns a cylinder unit for implementing the above mentioned method, where the front face of the piston has a convex cross-section.
  • the invention concerns a cylinder unit for implementing the above mentioned method, where the front face of the piston defines a cavity for the reception of a part of the injected fuel.
  • the front face of the piston has advantageously a globally frustroconical or conical portion. The central angle of said portion can be equal or substantially equal to the average central opening angle of the fuel injection within the cylinder.
  • the invention also concerns an internal combustion engine including at least a cylinder unit as mentioned here above.
  • FIG. 1 is schematic longitudinal cross-section of a cylinder unit according to the invention with its piston moving from BDC to TDC,
  • figure 2 a cross-section similar to figure 1 when the piston is in TDC
  • - figure 3 is an enlarged view of part III of figure 2
  • - figure 4 is a diagram showing the operation of a fuel injector of the cylinder unit of figures 1 to 3 depending on the crank angle
  • figure 5 is a cross-section similar to figure 3 for a cylinder unit according to a second embodiment of the invention, whose piston is about to reach TDC,
  • figure 6 is a diagram similar to figure 4 for an alternative method according to the invention.
  • figure 7 is a diagram similar to figure 4 for an alternative method according to the invention.
  • the cylinder unit 1 represented on figures 1 to 3 belongs to a multi- cylinder internal combustion diesel type engine according to the invention and includes a piston 2 movable, as shown by arrow Fi between a bottom dead center position, or BDC, represented in dashed lines on figure 1 and a top dead center position, or TDC, represented on figure 2. Piston 2 is also movable from TDC to BDC. Cylinder unit 1 also includes a cylinder body 3 and a cylinder head 4 fixed onto the cylinder body 3. Cylinder body 3 and head 4 are metallic, preferably made of iron. In figures 1 to 3, piston 2 is not cut for an easier reading of the drawings. Cylinder head 4 is equipped with one or several fuel injectors, one of which is shown with reference 5. Cylinder head 4 might also include one or several air intake and exhaust valves which are not represented.
  • Piston 2 is equipped with two piston rings 21 and 22 which are adapted to slide against the internal surface 31 of body 3, while piston 2 moves as shown by arrow F- ⁇ .
  • Piston 2 might be equipped with more than two sliding rings, e.g. three such rings.
  • a ring 6 of heat insulating material e.g. ceramic, is mounted within body 3 close to cylinder head 4. Ring 6 lies against head 4 and is received in an internal housing made in surface 31.
  • the internal surface 61 of unit 6 is aligned with internal surface 31 and centred on the central axis Xi of unit 1 , as surface 31.
  • the diameter of surface 61 might be larger than the diameter of surface 31 , which prevents fuel from flowing directly from surface 61 to surface 31 since a shoulder is provided at the bottom of the internal housing where ring 6 is received.
  • the diameter of surface 61 might be smaller th ⁇ n the diameter of surface 31 , which also avoids direct flow of fuel between these surfaces.
  • a layer of insulating material might be deposited, e.g. by spraying, on the upper part of surface 31 , with the same function as ring 6.
  • the operating state S of injector 5 changes from 0 to 1 up to when crank angle reaches a first value ⁇ - ⁇ . Then it stays at 1 up to when crank angle ⁇ equals its value at TDC, that is 0. Then, this operational state switches from 1 to 0.
  • operating state S can be kept at 1 for a while after piston 2 reaches TDC.
  • operating state S can be switched to 0 before piston 2 reaches TDC.
  • # 1 is chosen between 20° and 180° prior to 0. In other words, injection is piloted in order to start before piston 2 reaches TDC, while it is moving from BDC, and to last up to when piston 2 reaches TDC.
  • ring 6 is made of heat insulating material
  • surface 61 can be at a very high temperature due to the previous combustions which took place in cylinder unit 1 , the temperature of surface 61 being higher than the temperature of surface 31.
  • the temperature T 6 i of surface 61 can be of about 300 0 C
  • the temperature T 3 i of surface 31 is of about 200 0 C since body 31 dissipates heat towards the outside environment.
  • Front face 24 includes a globally conical portion 241 and an annular portion
  • Front face 24 has a convex cross-section.
  • a the center angle of portion 241.
  • ⁇ the average central opening angle of the fuel jet F 2 coming out of valve 5, that is the average center angle of jet F 2 which is roughly conical.
  • a is chosen equal or similar to ⁇ , which means that when piston 2 is in TDC, the flow of fuel coming out of valve 5 is roughly parallel to portion 241 of front face 24.
  • piston 2 bears three rings 21 , 22 and 23 which slide against the internal surface 31 of the cylinder body 3. All rings are kept below insulating ring 6 when piston 2 is in TDC.
  • the front face 24 of piston 2 comprises a globally frustroconical portion 243, a convex curved portion 244 and an outer ring portion 245 which define together a cavity 25 where fuel is injected when piston 2 is in TDC.
  • piston 2 When injection starts, piston 2 is below ring 6 with respect to cylinder head 4, so that the jet or flow of fuel F 2 is directed towards internal surface 61 of ring 6 which is made of the same heat insulating material as in the first embodiment. Then, when piston 2 moves towards TDC, the flow F 2 of fuel is progressively retained into the cavity 25.
  • the center angle 7 of portion 243 is advantageously similar to the average central opening angle ⁇ of the jet F 2 of fuel coming out of injector 5.
  • combustion takes place mainly within cavity 25.
  • front face 24 of piston 2 are very advantageous, other shapes might be considered.
  • front face 24 might be planar and perpendicular to axis X 1 .
  • operations of injector 5 can be stopped between two crank angles 0 2 and ⁇ 3 comprised between ⁇ - ⁇ and 0.
  • injection can take place in two phases, a first phase between angles ⁇ - ⁇ and ⁇ 2 and a second phase between angles O 2 , and 0.
  • the invention can also be used for late past injection, that is in order to feed fuel to a catalytic exhaust pipe or a particulate filter.
  • fuel injection starts and ends when the piston as in its downwardly oriented movement between TDC and BDC, that is when the crank shaft angle is between 0° and 180°.
  • fuel is injected towards insulating ring or layer 6.
  • the exhaust valve(s) of the cylinder unit is (are) left, as shown by curve LE, and fuel can be directed to the exhaust pipe or filter.
  • the invention is also applicable to a mono cylinder engine. LIST OF REFERENCES

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

Abstract

A piston (2) is movable in a cylinder (3), between a top dead center position and a bottom dead center position, and equipped with at least a piston ring (21, 22) sliding against an internal surface (31) of the cylinder. The cylinder (3) is provided with a layer (6) of heat insulating material near the cylinder head (4). The ring (21, 22) is kept away from this layer (6) when the piston (2) is in its top dead center position. Fuel injection (F2) within the cylinder starts when the piston (2) is in its upward movement (F1) from its bottom dead center position to its top dead center position and the injected fuel (F2) is directed, upon injection, towards the heat insulating material layer (6).

Description

METHOD FOR INJECTING FUEL INTO A CYLINDER, CYLINDER UNIT FOR IMPLEMENTING SUCH A METHOD AND INTERNAL COMBUSTION ENGINE
COMPRISING SUCH A UNIT
TECHNICAL FIELD OF THE INVENTION
This invention concerns a method for injecting fluid into a cylinder of an internal combustion engine. This invention also concerns a cylinder unit for implementing such a method and an internal combustion engine including such a cylinder unit.
BACKGROUND OF THE INVENTION
In internal combustion engines, it is known that fuel injected within a cylinder might form a film or some residues on the internal surface of the cylinder, this film or these residues being scraped by the piston rings mounted onto a piston. In such a case, the piston rings become dirty and their lifetime is shortened.
JP-A-04191413 discloses a diesel engine where injection takes place in a combustion cavity formed on the front surface of a piston, this cavity being partly defined by a heat insulating material layer mounted on said piston. Other heat insulating members are provided in the upper part of the cylinder. These heat insulating members are supposed to reduce heat losses in the metallic part and thus to increase engine efficiency. However, for some advanced combustion schemes, it might be necessary to inject fuel when the piston is far from its top dead center position, which is not possible with this structure where injection must take place when the piston is at or near this position.
SUMMARY OF THE INVENTION
This invention aims at proposing an optimized method for injecting fuel which result in a high overall efficiency of an internal combustion engine.
The invention concerns a method for injecting fuel into a cylinder of an internal combustion engine, said cylinder including a piston movable between a top dead center position and a bottom dead center position and equipped with at least a piston ring sliding against an internal surface of such cylinder, said cylinder being provided with a layer of heat insulating material near its head, said ring being kept away from said layer when said piston is in its top dead center position. This method is characterized in that fuel injection within the cylinder starts when the piston is in its upward movement from its bottom dead center position to its top dead center position and in that the injected fuel is directed, upon injection, towards the layer of heat insulating material. Hereafter, the top dead center position of a piston in the corresponding cylinder is noted "TDC" and the bottom dead center position of such a piston is noted "BDC".
Thanks to the invention, the fuel which is injected before the piston reaches its TDC can be quickly evaporated because the surface of the insulating layer can be at a high temperature since this surface is thermally insulated with respect to the outside environment of the cylinder. This quick evaporation lowers the chances of a formation of a film or residues of fuel on this surface. Moreover, the piston rings will not interferer with the internal surface of the insulating layer so that no question arises with respect to the friction coefficient between these rings and this layer. Since the sliding ring is kept away from the insulating layer, no lubricating agent like oil must be spread on this layer, so that no dilution between fuel and lubricating agent is likely to occur. Since the volume within which fuel is injected is not limited to a cavity formed on the front face of the piston, the mixture of fuel and air can be homogenous, which improves combustion and lowers the pollutant emission of the engine.
According to further aspects of the invention, such a method might incorporate the following features:
- Fuel injection starts when the crank angle of the piston is between 180° and 20° before its angle at TDC; alternatively, fuel injection starts when the crank angle of the piston is between 0° and 180° after its angle at TDC;
- An internal surface of the layer of insulating material which receives at least a part of the injected fuel is at a temperature above the temperature of the internal surface of the cylinder on which the piston ring slides.
- According to a first embodiment, the invention also concerns a cylinder unit for implementing the above mentioned method, where the front face of the piston has a convex cross-section. According to another embodiment, the invention concerns a cylinder unit for implementing the above mentioned method, where the front face of the piston defines a cavity for the reception of a part of the injected fuel. In these units, the front face of the piston has advantageously a globally frustroconical or conical portion. The central angle of said portion can be equal or substantially equal to the average central opening angle of the fuel injection within the cylinder.
Finally, the invention also concerns an internal combustion engine including at least a cylinder unit as mentioned here above.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will now be explained in correspondence with the annexed figures and as an illustrative example, without restricting the object of the invention. In the annexed figures:
- figure 1 is schematic longitudinal cross-section of a cylinder unit according to the invention with its piston moving from BDC to TDC,
- figure 2 a cross-section similar to figure 1 when the piston is in TDC,
- figure 3 is an enlarged view of part III of figure 2, - figure 4 is a diagram showing the operation of a fuel injector of the cylinder unit of figures 1 to 3 depending on the crank angle,
- figure 5 is a cross-section similar to figure 3 for a cylinder unit according to a second embodiment of the invention, whose piston is about to reach TDC,
- figure 6 is a diagram similar to figure 4 for an alternative method according to the invention, and
- figure 7 is a diagram similar to figure 4 for an alternative method according to the invention.
DETAILED DESCRIPTION OF SOME EMBODIMENTS The cylinder unit 1 represented on figures 1 to 3 belongs to a multi- cylinder internal combustion diesel type engine according to the invention and includes a piston 2 movable, as shown by arrow Fi between a bottom dead center position, or BDC, represented in dashed lines on figure 1 and a top dead center position, or TDC, represented on figure 2. Piston 2 is also movable from TDC to BDC. Cylinder unit 1 also includes a cylinder body 3 and a cylinder head 4 fixed onto the cylinder body 3. Cylinder body 3 and head 4 are metallic, preferably made of iron. In figures 1 to 3, piston 2 is not cut for an easier reading of the drawings. Cylinder head 4 is equipped with one or several fuel injectors, one of which is shown with reference 5. Cylinder head 4 might also include one or several air intake and exhaust valves which are not represented.
Piston 2 is equipped with two piston rings 21 and 22 which are adapted to slide against the internal surface 31 of body 3, while piston 2 moves as shown by arrow F-\. Piston 2 might be equipped with more than two sliding rings, e.g. three such rings.
A ring 6 of heat insulating material, e.g. ceramic, is mounted within body 3 close to cylinder head 4. Ring 6 lies against head 4 and is received in an internal housing made in surface 31. The internal surface 61 of unit 6 is aligned with internal surface 31 and centred on the central axis Xi of unit 1 , as surface 31.
According to further embodiments of the invention, the diameter of surface 61 might be larger than the diameter of surface 31 , which prevents fuel from flowing directly from surface 61 to surface 31 since a shoulder is provided at the bottom of the internal housing where ring 6 is received.
According to another embodiment, the diameter of surface 61 might be smaller thεn the diameter of surface 31 , which also avoids direct flow of fuel between these surfaces.
According to still another embodiment, a layer of insulating material might be deposited, e.g. by spraying, on the upper part of surface 31 , with the same function as ring 6.
As shown on figure 4, operation of fuel injector 5 varies as a function of the crank angle 6 of the engine. On figure 4, the "θ" axis corresponds to the crank angle of the engine and one considers that angle θ equals 0 when piston 2 reaches TDC where combustion takes place, as shown in figure 2. On this figure, LE represents the lift of the exhaust valve(s) of cylinder unit 1 , which is (are) not represented, and the "S" axis corresponds to the working conditions of fuel injector 5. Value 1 on this axis means that fuel injector 5 is active and delivers fuel to cylinder unit 1 , whereas value 0 means that fuel injector 5 is not active. The operating state S of injector 5 changes from 0 to 1 up to when crank angle reaches a first value θ-\. Then it stays at 1 up to when crank angle θ equals its value at TDC, that is 0. Then, this operational state switches from 1 to 0. According to a non represented embodiment, operating state S can be kept at 1 for a while after piston 2 reaches TDC. Alternatively, operating state S can be switched to 0 before piston 2 reaches TDC.
#1 is chosen between 20° and 180° prior to 0. In other words, injection is piloted in order to start before piston 2 reaches TDC, while it is moving from BDC, and to last up to when piston 2 reaches TDC.
The flow of fuel coming out of injector 5 during injection is directed toward surface 61 as a jet, as shown by arrows F2 on figures 1 , 2 and 3.
Because ring 6 is made of heat insulating material, surface 61 can be at a very high temperature due to the previous combustions which took place in cylinder unit 1 , the temperature of surface 61 being higher than the temperature of surface 31. For example, the temperature T6i of surface 61 can be of about 3000C, whereas the temperature T3i of surface 31 is of about 2000C since body 31 dissipates heat towards the outside environment.
Since temperature T6i is high, vaporisation of fuel takes place very quickly so that no deposit or residues of fuel particles appear on surface 31.
Since fuel injection F2 starts before piston 2 reaches TDC, fuel injection occurs within a relatively large volume in unit 1 , which induces that the mixture of fuel and air is relatively homogenous when combustion takes place.
One notes 21 the piston ring closer to the front face 24 of piston 2. At TDC, the distance d, taken in a direction parallel to axis Xi, between ring 21 and cylinder head 4 is larger than the height h6 of ring 6 taken in the same direction. This induces that ring 21 never scraps surface 61 , so that its lifetime is increased. Moreover, the material of ring 21 can be chosen independently of the friction coefficient between this ring and surface 61 and of temperature T6i. Front face 24 includes a globally conical portion 241 and an annular portion
242, portion 242 surrounding portion 241. Front face 24 has a convex cross-section. One notes a the center angle of portion 241. One notes β the average central opening angle of the fuel jet F2 coming out of valve 5, that is the average center angle of jet F2 which is roughly conical. a is chosen equal or similar to β, which means that when piston 2 is in TDC, the flow of fuel coming out of valve 5 is roughly parallel to portion 241 of front face 24. in the embodiment of figure 5, the same elements as the one of the first embodiment have the same reference numbers. In this embodiment, piston 2 bears three rings 21 , 22 and 23 which slide against the internal surface 31 of the cylinder body 3. All rings are kept below insulating ring 6 when piston 2 is in TDC. The front face 24 of piston 2 comprises a globally frustroconical portion 243, a convex curved portion 244 and an outer ring portion 245 which define together a cavity 25 where fuel is injected when piston 2 is in TDC.
When injection starts, piston 2 is below ring 6 with respect to cylinder head 4, so that the jet or flow of fuel F2 is directed towards internal surface 61 of ring 6 which is made of the same heat insulating material as in the first embodiment. Then, when piston 2 moves towards TDC, the flow F2 of fuel is progressively retained into the cavity 25.
The center angle 7 of portion 243 is advantageously similar to the average central opening angle β of the jet F2 of fuel coming out of injector 5. When piston 2 of this embodiment reaches TDC, combustion takes place mainly within cavity 25.
Although the conical or frustroconical shapes of front face 24 of piston 2 are very advantageous, other shapes might be considered. For instance, front face 24 might be planar and perpendicular to axis X1. As shown on figure 6, operations of injector 5 can be stopped between two crank angles 02 and Θ3 comprised between θ-\ and 0. In other words, injection can take place in two phases, a first phase between angles θ-\ and θ2 and a second phase between angles O2, and 0.
As shown on figure 7, the invention can also be used for late past injection, that is in order to feed fuel to a catalytic exhaust pipe or a particulate filter. In a such a case, fuel injection starts and ends when the piston as in its downwardly oriented movement between TDC and BDC, that is when the crank shaft angle is between 0° and 180°. Here again, fuel is injected towards insulating ring or layer 6. After fuel has been injected, the exhaust valve(s) of the cylinder unit is (are) left, as shown by curve LE, and fuel can be directed to the exhaust pipe or filter.
The invention is also applicable to a mono cylinder engine. LIST OF REFERENCES
1 cylinder unit
2 piston
21 piston ring 22 piston ring
23 piston ring
24 front face
241 conical portion
242 annular portion 243 frustroconical portion
244 curved portion
245 outer ring portion
25 cavity
3 cylinder body 31 internal surface
4 cylinder head
5 fuel injector
6 ring
61 internal surface
Fi arrow (movement of piston 2).
Fa arrows (jet of fuel)
Xi central axis of unit 1
LE lift of exhaust valve(s) T31 temperature at 31
Tei temperature at 61 d distance he height of ring 6 θ crank angle a center angle of portion 241 β εverage angle of fuel jet γ center angle of portion 243
S state of injector 5

Claims

1. A method for injecting fuel into a cylinder (3) of an internal combustion engine, said cylinder including a piston (2) movable between a top dead center position and a bottom dead center position, and equipped with at least a piston ring (21 , 22) sliding against an internal surface (31 ) of said cylinder, said cylinder being provided with a layer (6) of heat insulating material near cylinder head (4), said ring being kept away (d/hβ) from said layer when said piston is in its top dead center position characterized in that fuel injection within said cylinder starts when said piston (2) is in its upward movement (F-i) from its bottom dead center position to its top dead center position and in that injected fuel (F2) is directed, upon injection, towards said layer (6) of heat insulating material.
2. The method of claim 1 wherein fuel injection starts when the crank angle (θ) of said piston (2) is between 180° to 20° before its angle (0) in said top dead center position.
3. The method of claim 1 wherein fuel injection starts when the crank angle (0) of said piston (2) is between 0° and 180° after its angle (0) in said top dead center position.
4. The method of one of claims 1 to 3 wherein an internal surface (61) of said layer of said insulating material (6) which receives at least a part of the injected fuel
(F2) is at a temperature above the temperature of the internal surface (31) of said cylinder (3) on which said piston ring (21) slides.
5. A cylinder unit (1 ) for implementing the method of one of claims 1 to 4 characterized in that the front face (24) of said piston has a convex cross-section.
6. A cylinder unit (1 ) for implementing the method of one of claims 1 to 4 characterized in that the front face (24) of said piston defines a cavity (25) for the reception of a part of the injected fuel (F2).
7. A cylinder unit according to one of claims 5 or 6 wherein said front face (24) has a globally frustroconical or conical portion (241 , 243).
8. A cylinder unit according to claim 7 wherein the center angle (a, γ) of said frustroconical or conical portion (241 , 243) is equal or substantially equal to the average central opening angle (β) of the fuel injection stream (F2) within said cylinder.
9. An internal combustion engine characterized in that it includes at least a cylinder unit (1) according to one of claims 5 to 8.
PCT/EP2005/013366 2005-10-24 2005-10-24 Method for injecting fuel into a cylinder, cylinder unit for implementing such a method and internal combustion engine comprising such a unit WO2007048439A1 (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
PCT/EP2005/013366 WO2007048439A1 (en) 2005-10-24 2005-10-24 Method for injecting fuel into a cylinder, cylinder unit for implementing such a method and internal combustion engine comprising such a unit
EP05820637A EP1943416A1 (en) 2005-10-24 2005-10-24 Method for injecting fuel into a cylinder, cylinder unit for implementing such a method and internal combustion engine comprising such a unit

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/EP2005/013366 WO2007048439A1 (en) 2005-10-24 2005-10-24 Method for injecting fuel into a cylinder, cylinder unit for implementing such a method and internal combustion engine comprising such a unit

Publications (1)

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WO2007048439A1 true WO2007048439A1 (en) 2007-05-03

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Cited By (3)

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Publication number Priority date Publication date Assignee Title
JP2014088863A (en) * 2012-10-31 2014-05-15 Isuzu Motors Ltd Internal combustion engine
JP2016084713A (en) * 2014-10-23 2016-05-19 マツダ株式会社 Heat insulation layer formation method of cylindrical hole inner peripheral surface, heat insulation layer formation structure, and engine including heat insulation layer formation structure
WO2021166278A1 (en) * 2020-02-18 2021-08-26 三菱重工エンジン＆ターボチャージャ株式会社 Heat-insulating film member

Citations (4)

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Publication number Priority date Publication date Assignee Title
DE3331579A1 (en) * 1983-09-01 1985-03-21 Klöckner-Humboldt-Deutz AG, 5000 Köln Piston internal combustion engine
FR2596808A1 (en) * 1986-04-04 1987-10-09 Rech Machines Thermiqu Centre Direct injection diesel engine piston
EP0363190A2 (en) * 1988-10-07 1990-04-11 Ngk Insulators, Ltd. Direct injection-type diesel engines
JPH04191413A (en) 1990-11-27 1992-07-09 Toyota Central Res & Dev Lab Inc Diesel engine

Patent Citations (4)

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Publication number Priority date Publication date Assignee Title
DE3331579A1 (en) * 1983-09-01 1985-03-21 Klöckner-Humboldt-Deutz AG, 5000 Köln Piston internal combustion engine
FR2596808A1 (en) * 1986-04-04 1987-10-09 Rech Machines Thermiqu Centre Direct injection diesel engine piston
EP0363190A2 (en) * 1988-10-07 1990-04-11 Ngk Insulators, Ltd. Direct injection-type diesel engines
JPH04191413A (en) 1990-11-27 1992-07-09 Toyota Central Res & Dev Lab Inc Diesel engine

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2014088863A (en) * 2012-10-31 2014-05-15 Isuzu Motors Ltd Internal combustion engine
JP2016084713A (en) * 2014-10-23 2016-05-19 マツダ株式会社 Heat insulation layer formation method of cylindrical hole inner peripheral surface, heat insulation layer formation structure, and engine including heat insulation layer formation structure
WO2021166278A1 (en) * 2020-02-18 2021-08-26 三菱重工エンジン＆ターボチャージャ株式会社 Heat-insulating film member
US11840981B2 (en) 2020-02-18 2023-12-12 Mitsubishi Heavy Industries Engine & Turbocharger, Ltd. Thermal barrier coating member

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