EP0294092B1 - Heat-insulating engine structure - Google Patents
Heat-insulating engine structure Download PDFInfo
- Publication number
- EP0294092B1 EP0294092B1 EP19880304742 EP88304742A EP0294092B1 EP 0294092 B1 EP0294092 B1 EP 0294092B1 EP 19880304742 EP19880304742 EP 19880304742 EP 88304742 A EP88304742 A EP 88304742A EP 0294092 B1 EP0294092 B1 EP 0294092B1
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- EP
- European Patent Office
- Prior art keywords
- heat
- structure according
- piston
- engine structure
- insulating
- Prior art date
- Legal status (The legal status 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 status listed.)
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- 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
- F02F3/0015—Multi-part pistons
- F02F3/003—Multi-part pistons the parts being connected by casting, brazing, welding or clamping
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- 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
- F02B77/00—Component parts, details or accessories, not otherwise provided for
- F02B77/11—Thermal or acoustic insulation
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- 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
- F02F3/10—Pistons having surface coverings
- F02F3/12—Pistons having surface coverings on piston heads
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- 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
- F02B3/00—Engines characterised by air compression and subsequent fuel addition
- F02B3/06—Engines characterised by air compression and subsequent fuel addition with compression ignition
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
- F05C—INDEXING SCHEME RELATING TO MATERIALS, MATERIAL PROPERTIES OR MATERIAL CHARACTERISTICS FOR MACHINES, ENGINES OR PUMPS OTHER THAN NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES
- F05C2251/00—Material properties
- F05C2251/04—Thermal properties
- F05C2251/042—Expansivity
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
- F05C—INDEXING SCHEME RELATING TO MATERIALS, MATERIAL PROPERTIES OR MATERIAL CHARACTERISTICS FOR MACHINES, ENGINES OR PUMPS OTHER THAN NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES
- F05C2251/00—Material properties
- F05C2251/04—Thermal properties
- F05C2251/048—Heat transfer
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
- F05C—INDEXING SCHEME RELATING TO MATERIALS, MATERIAL PROPERTIES OR MATERIAL CHARACTERISTICS FOR MACHINES, ENGINES OR PUMPS OTHER THAN NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES
- F05C2253/00—Other material characteristics; Treatment of material
- F05C2253/16—Fibres
Description
- The present invention relates to a heat-insulating engine structure.
- A heat-insulating engine which makes use of heat-insulating members and heat-resistant members both made of a ceramics material has heretofore been known and is disclosed, for example, in Japanese Un-Examined Patent Publication No. 59-122, 765. This heat-insulating engine will be described with reference to Fig. 5 of the accompanying drawings. This heat-
insulating engine 50 includes acylinder head 53 of a cast metal and aliner head 51 of a ceramics material fitted into the cylinder head withpositioning rings liner head 51 constitutes a cylinder headbottom wall portion 63 and an integral cylinder linerupper portion 64 both of which are exposed to combustion gases at the highest temperature and pressure levels during each cycle of engine operation and from which heat is removed most during the engine operation. Acylinder block 69 is disposed under the bottom end of theliner head 51 with agasket 65 interposed therebetween. Thecylinder block 69 is fitted with acylinder liner 52 which accommodates a reciprocating piston having a piston head 54 of silicon nitride. The piston head is recessed in its central area, as shown atnumeral 55, to provide a combustion chamber 62 and has an inwardlystepped bottom end 56 which serves as means for positioning and preventing the piston head 54 from being moved relative to apiston body 57 when the piston head is assembled with the piston body. Abolt hole 68 is formed in and extends through the bottom wall of therecess 55. The outer periophery of the top of thepiston body 57 is shaped to provide anannular projection 58 which is snugly engaged with the inwardly stepped bottom end of the piston head 54. The upper face of the piston body has an upwardly projectingcentral portion 59 having a top face engaged with the bottom face of the piston head 54. The piston head andbody 54 and 57 are secured together by abolt 60 extending through thebolt hole 68 in the piston head and through a similar bolt hole in thepiston head 57. Intake andexhaust valves 61, only one of which is shown, are disposed adjacent to the cylinder head bottom wall portion and axially of thecylinder liner 52. - The heat-insulating
engine 50 is not of a structure which is suited to reduce the thermal capacity as much as possible, because the ceramics piston head 54 is formed therein with therecess 55 and, therefore, is required to have a substantial thickness so as to assure a sufficient mechanical strength. The intake andexhaust valves 61 are disposed axially of thecylinder liner 52 in compliance with the structure of the piston head 54. The cylinder headbottom wall portion 63 is of a flat design, with the result that air sucked into the engine cylinder flows radially outwardly of the intake valve and, accordingly, is apt to receive heat from the upper part of thecylinder liner 64 as well as from the cylinder headbottom wall portion 63. Thus, the cylinder head bottom wall portion is not so structured as to swirl the air for the purpose of agitating the air. - It is very difficult to fully obtain the heat-insulating characteristics of a heat-insulating engine which makes use of ceramics material as heat-insulating or heat-resistant material. The engine is of the structure which exposes the ceramics members to combustion gases at a high temperature, so that the ceramics members are subjected to thermal shocks, which raises a problem in terms of mechanical strength. In the case where the thickness of a ceramics member is increased for the purpose of heat-insulation, the thermal capacity of the member is increased, with a disadvantageous result that air sucked into an engine cylinder during an intake stroke of the cylinder receives heat much from the ceramics member and is heated and expanded to greatly decrease the suction efficiency.
- The present invention seeks to provide a heat-insulating engine which is structured to improve the suction efficiency and the cycle efficiency of the heat-insulating engine as well as to assure that fuel injected from a fuel injection nozzle is immediately and uniformly mixed with intake air, thereby to solve the problems pointed out above.
- Accordingly, it has been desired to improve the suction efficiency and the cycle efficiency of heat-insulating engines. In addition, it has also been demanded in Diesel engines to assure that a fuel injected from a fuel injection nozzle is quickly and uniformly mixed with air by virtue of swirl formed in a combustion chamber.
- According to the present invention there is provided a heat-insulating engine structure comprising;
a piston reciprocatingly movable in a cylinder liner;
a cylinder liner upper portion of a ceramic material disposed above said cylinder liner;
a cylinder head bottom wall portion integral with said cylinder liner upper portion; and
a cylinder head including a tubular section accommodating said integral cylinder liner upper portion and said cylinder head bottom wall portion;
characterised in that said cylinder head bottom wall portion and said cylinder liner upper portion together define a combustion chamber;
the piston has a surface to be exposed to combustion gases facing said combustion chamber which is planar;
said cylinder head bottom wall portion is formed with, at least on the side facing the combustion chamber, a raised outer peripheral portion and a lowered central portion, with an inclined surface thereof extending radially upwardly from said central portion to said outer peripheral portion;
a fuel injection nozzle is disposed substantially centrally of said cylinder head bottom wall portion and has radially outwardly directed injection orifices;
and in that intake and exhaust valve seats are formed in the inclined surface of the cylinder head bottom wall portion having intake and exhaust valves associated with said intake and exhaust valve seats, respectively. - More specifically, in order to improve the suction efficiency and the cycle efficiency, the top face portion of a piston head of the engine which is exposed to combustion gases is formed of a wall of a ceramics material having as small a thickness as possible to minimize the thermal capacity of the piston top face portion. Reduction in the thicknesses of the ceramics wall portions exposed to combustion gases and the resultant decrease in the thermal capacities thereof assure that walls defining a combustion chamber can better follow variation in combustion gas temperature. As compared with the case in which the combustion chamber walls have greater thicknesses, the amplitude of the temperature variation in the combustion chamber walls having smaller thicknesses is increased to advantageously decrease the difference in temperature between the combustion gases and the ceramics material of the combustion chamber walls with a resultant decrease in the heat transfer to thereby reduce the heat transferred from the combustion chamber walls to the air introduced into the combustion chamber. The reduction in the heat transfer to the intake air is effective to prevent undue expansion of the intake air and, thus, assure a smooth flow of air into the combustion chamber, whereby the suction efficiency and the cycle efficiency are greatly improved.
- By providing a heat-insulating engine structure in which the top wall portion of a piston, which is exposed to combustion gases, is of a planar design that portion does not define any combustion chamber and, instead, a combustion chamber is defined in the bottom wall portion of a cylinder head. This is because, in order to reduce the thickness of the top wall portion of the piston, it is most preferred for the top wall portion of the piston to have such a planar configuration.
- In order that a combustion chamber may be formed on the side of the cylinder head, rather than on the side of the piston, the bottom wall portion of the ceramics cylinder head is shaped to have the lowered central portion and raised outer peripheral portion and cooperates with an integral ceramics cylinder liner upper portion to define the combustion chamber, as described above. The above-mentioned combustion chamber is shaped to accommodate the pattern of jets of fuel injected by the fuel injection nozzle. Thus, the injected fuel can be immediately agitated with intake air and thus uniformly mixed therewith due to an agitating flow produced in the combustion chamber.
- The present invention further seeks to provide a heat-insulating engine structure in which a cylinder head bottom wall section and cylinder liner upper portion which cooperates therewith to define a combustion chamber are thermally insulated from the cylinder head by an heat insulating layer, the surface of a piston which is exposed to combustion gases, i.e., a thin-walled piston top wall portion, is thermally insulated from a piston head by a heat insulating layer, and the cylinder liner upper portion, the cylinder head bottom wall portion and the piston top surface portion are designed to have as small thicknesses as possible to minimize their heat capacities as well as to provide the engine with highly improved heat-resisting characteristic, heat-insulation characteristic, anti-deformation characteristic and anti-corrosion characteristic.
- Preferably, the intake and exhaust valve seats are formed in radially upwardly inclined surfaces of cylinder head bottom wall section such that intake and exhaust valves are disposed in an inverted-V arrangement and, more particularly, the primary flow of air introduced into the combustion chamber when the intake valve is opened is disposed substantially centrally of the combustion chamber and, thus, of a cylinder bore to reduce the possibility that the air flowing into the combustion chamber is brought into contact with the inner surface of a heated upper portion of a cylinder liner whereby the transfer of heat from the cylinder liner upper portion to the air is decreased to minimize the expansion of the air to thereby improve the suction efficiency of the engine.
- Preferably, the cylinder liner upper portion has a tubular upper portion having an inner surface of substantially square cross-section and a lower portion having an inner surface of substantially circular cross-section, whereby said combustion chamber includes a substantially square portion defined by said tubular upper portion of said cylinder liner upper portion, the non-circular inner peripheral configuration being effective to destroy the swirl formed in the combustion chamber to cause an agitation which is effective to assure that the fuel injected by a fuel injection nozzle is immediately and uniformly mixed with intake air in a zone adjacent to the piston top dead center.
- The present invention further seeks to provide a heat-insulating engine structure in which the primary flow of intake air is disposed centrally of a combustion chamber and, thus, of a cylinder with a resultant increase in the quantity of intake air that is brought into contact with a thin-walled portion disposed on a piston head through the intermediary of a heat insulating material and exposed to combustion gases, and in which the thin-walled portion is structured to have a very small thermal capacity so as to eliminate decrease in the suction efficiency whereby the suction efficiency and the cycle efficiency of the engine are improved.
- Preferably, the fuel injection nozzle is disposed substantially centrally of a cylinder head bottom wall portion and a combustion chamber is shaped to accommodate the loci or pattern of jets of fuel injected from a fuel injection nozzle to reduce the transfer of heat to the injected fuel and the intake air in the combustion chamber so that expansion of the air can be suppressed and the injected fuel can be well mixed with the air to ensure a good combustion.
- The piston may have a piston head portion of cermet and a thin-walled portion of a ceramics material having a coefficient of thermal expansion substantially equal to that of cermet to provide a reliable connection between the two portions, in which the piston head portion of cermet is highly rigid and hardly deformed even by a high level of pressure to assure a stable connection between the piston head portion and the piston thin-walled portion, to establish a reliable gas-seal at the boundary therebetween and to avoid any strength problem which would otherwise be adversely affected by thermal shock, in which the heat-resisting characteristic, anti-deformation characteristic and anti-corrosion characteristic and so forth of the piston are improved, and in which the pressure exerted to the thin-walled portion of the piston in each combustion stroke can be borne through a heat-insulating material by the piston head portion.
- A heat-insulating material interposed between a thin-walled portion of a piston and a piston head portion may be made of potassium titanate whisker, zirconia fiber or of a mixture of these materials and glass fiber to provide a highly efficient heat-insulator against the heat produced in an associated combustion chamber to eliminate leakage of thermal energy from the combustion chamber through the piston whereby the thermal energy is trapped inside the combustion chamber to assure that the thermal energy can be collected by means of an energy-collector disposed at a downstream point of the flow of engine exhaust gases.
- Embodiments of the invention will be described, by way of example only, with reference to the following drawings in which:
- Fig. 1 is an axial sectional view of an embodiment of a heat-insulating engine according to the present invention;
- Fig. 2 is a cross-sectional view of the engine taken along line II-II in Fig. 1;
- Fig. 3 is an axial sectional view of another embodiment of the heat-insulating engine according to the present invention;
- Fig. 4 is similar to Fig. 3 but illustrates a flow of air in a combustion chamber; and
- Fig. 5 is an axial sectional view of the prior art heat-insulating engine discussed hereinabove.
- Referring first to Fig. 1 showing the structure of a heat-insulating engine embodying the present invention, the
engine 50 is generally designated byreference numeral 10 and constituted mainly by apiston 20 which reciprocates within acylinder liner 34 fitted into acylinder block 38 and formed by apiston head portion 1 and apiston skirt portion 2 of a metal, aliner head 30 fitted in ametallic cylinder head 33 with a heat-insulating layer interposed therebetween and made of a ceramics material such as a silicon nitride or a silicon carbide, afuel injection nozzle 25 disposed centrally of theliner head 30, and anintake valve 21 and anexhaust valve 27 both disposed adjacent to the undersurface of theliner head 30. A flat or planar and thin-walled portion 5 of a ceramics material is mounted, via a heat-insulatingmaterial 3, on the side of thepiston head portion 1 which is adjacent to a combustion chamber to be described. The thin-walledportion 5 is shaped to provide a planar surface which is to be exposed to combustion gases. To accord with this planar surface of the thin-walledportion 5, theliner head 30 is shaped to define acombustion chamber 15 having a lowered part and a raised part which are disposed adjacent to the central and outer peripheral zones of the cylinder and thus will be termed "lowered central part" and "outer peripheral part", respectively. Theliner head 30 is constituted by a cylinder linerupper portion 23 disposed above thecylinder liner 34 and a cylinder headbottom wall portion 22 integral with the cylinder linerupper portion 23. The cylinder headbottom wall portion 22 is shaped to have a raised outer peripheral part and a lowered central part to provide an inclined surface extending radially upwardly from the lowered central part to the raised outer peripheral part. The heat-insulatingengine 10 equipped with theliner head 30 of the described structure is of the structure which is suited to insulate heat particularly during a heat-producing period when a combustion is most active. Thecombustion chamber 15, which is defined by the cooperation of theliner head 30 and the thin-walled element 5 of thepiston head portion 1, both having the structures described above, is most suited to a heat-insulating engine and presents a configuration or profile resembling the shape of a shallow dish providing a radially outwardly increasing volume. The piston is provided withpiston rings 39 received in piston ring grooves and has apin hole 41 for a piston pin. - Fig. 2 is a cross-sectional view taken along line II-II in Fig. 1. The cylinder liner
upper portion 23, which cooperates with the piston to define thecombustion chamber 15, has an uppertubular part 26 of a generally square cross-section and a lowercylindrical part 28 of a circular cross-section. The squaretubular part 26 is smaller in diameter than thecylindrical part 28. The squaretubular part 26 has corners each of which, from the view point of the flow of the fluid, is preferably rounded with a radius of curvature equal to about from 1/2 to 1/3 the radius of the cylindrical part. This design is effective to assure that the four sides of the square cross-section of the squaretubular part 26 are operative to destroy a swirl produced within thecombustion chamber 15, or in other words, to break the swirl to establish an agitation by which injected fuel and intake air are very quickly and uniformly mixed in a zone adjacent to the top dead center of the piston to thereby facilitate a good combustion. The outer surfaces of theliner head 30 are thermally insulated by a heat-insulatinggasket 29 of potassium titanate and by a heat-insulatinglayer 24. Thus, theliner head 30 itself can be designed to have a reduced wall thickness and, thus, a small thermal capacity. As will be clearly seen in Fig. 2, moreover, theintake valve 21 and theexhaust valve 27 are so disposed as to cooperate with intake and exhaust valve seats formed in the inclined surface of the cylinder headbottom wall portion 22 which surface extends between the central and outer peripheral portions thereof. More specifically, the cylinder headbottom wall portion 22 has its major part extending radially outwardly and upwardly to provide the above-mentioned inclined surface, as shown in Fig. 1, so that the intake andexhaust valves - Due to this inclined arrangement of the
intake valve 21 and due to the shape of anintake port 31 extending radially inwardly and obliquely from outside thecombustion chamber 15 to the cylinder headbottom wall portion 22, the intake air sucked into the combustion chamber has its primary flow directed substantially vertically of the engine towards the center of the combustion chamber (refer to the air flow shown by arrows A in Fig. 4 and described later). Accordingly, the intake air is hardly brought into contact with the inner surface of theliner head 30 which is at a high temperature during each intake stroke of the engine, with a result that the heat transfer from the liner head to the intake air is advantageously reduced to minimize the thermal expansion of the air and, thus, to eliminate reduction in the suction efficiency which would otherwise be caused. In this case, the amount of intake air would be increased which is brought into contact with the thin-walled portion 5 of thepiston head 1, i.e., the top face of the piston. Such increase, however, will not give rise to decrease in the suction efficiency because the thin-walled portion 5 of thepiston 20 is structured to have a very small thermal capacity. On the other hand, because theintake valve 21 and theexhaust valves 27 are disposed in thecombustion chamber 15, these valves do not interfere with thepiston 20 even if the valves were accidentally opened when thepiston 20 is in its top dead center, thereby to assure a reliable and safe engine operation. In addition, thefuel injection nozzle 25 has its injection orifices directed radially outwardly. Thus, the jets of fuel injected through the injection orifices are directed in parallel with and radially outwardly of the thin-walled portion 5 of thepiston head 1. It will therefore be appreciated that thecombustion chamber 15, which is partly defined by theliner head 30, is shaped to accommodate the loci of the jets of fuel injected by the fuel injection nozzle 25 (see the pattern of the jets of fuel shown by arrows B in Fig. 1). - Then, the
piston 20 will be described. Thispiston 20 is constituted mainly by apiston skirt 32 having anupper end wall 32, the above-mentionedpiston head portion 1 which has a mountinghub 4 by which the piston head portion is mounted on the skirtupper end wall 32, aring 6 of a ceramics material secured to the upper face of theskirt 2 in pressure-contact therewith, the above-mentioned thin-walled portion 5 of a ceramics material having an outer periphery bonded to thering 6 and providing a surface to be exposed to combustion gases, and a layer of a heat-insulatingmaterial 3 interposed between thepiston head portion 1 and the thin-walled portion 5. Thepiston head portion 1 has the mountinghub 4 in its center and is made of a material, such as, for example, cermet or a metal, which has a thermal expansion coefficient substantially equal to that of a ceramics material, a high strength and a relatively high Young's modulus. Thepiston head 1 itself is not formed therein with any combustion chamber and is planar or flat in its side adjacent to thecombustion chamber 15. Theupper end wall 2 of thepiston skirt 2 is formed therein with a central mountinghole 12 for receiving the mountinghub 4 of thepiston head portion 1. The pistonhead mounting hub 4 is fitted into the mountinghole 12 in the piston skirtupper end wall 32 with ametallic ring 11 press-fitted into and interconnecting anannular groove 14 in the outer peripheral surface of the mountinghub 4 and anannular groove 13 in the inner peripheral surface of the mountinghole 12 so that thepiston head portion 1 is secured to thepiston skirt 2. Ashock absorbing member 8 formed of a heat-insulating material is interposed and pressed between thepiston head portion 1 around the mountinghub 4 and thepiston skirt 2 around the central mountinghole 12 and acts also as a heat-insulator. A heat-insulatingair chamber 9 is defined by the cooperation of the undersurface of thepiston head portion 1, the upper surface of thepiston skirt 2 and the inner peripheral surface of thering 6. It is to be understood that the thin-walled portion 5 of thepiston 20 is so disposed on thepiston head portion 1 as to face thecombustion chamber 15, i.e., exposed to combustion gases, with theheat insulating material 3 interposed between the thin-walled portion 5 and thepiston head portion 1. The thin-walled portion 5 is made of a ceramics material such as silicon nitride or silicon carbide and has a thickness of about 1 mm or less. - The outer periphery of the thin-
walled portion 5 is bonded to thering 6 which is made of a similar material. The bonding between the thin-walled portion 5 and thering 6 is achieved by, for example, a chemical vapor deposition of a ceramics material at ajunction 18 therebetween. The inner peripheral surface of thering 6 is formed thereon with an annular shoulder orstep 16. Thepiston head 1 has anouter periphery 17 which is fitted into thering 6 and disposed in engagement with theannular step 16. The upper surface of thepiston head portion 1, the undersurface of the thin-walled portion 5 and a part of the inner peripheral surface of the ring cooperate together to define a space which is filled with the heat-insulatingmaterial 3. This heat-insulatingmaterial 3 is made from potassium titanate whisker, zirconia fiber or the like and acts not only as a heat-insulating layer but also as a structural member which bears the pressure exerted to the thin-walled portion 5 and produced when a combustion takes place in thecombustion chamber 15. - Because the
piston head 1 is urged against and connected to thepiston skirt 2, theouter periphery 17 of thepiston head portion 1 is urged against theannular step 16 on thering 6 which in turn is urged against the outer periphery of the upper surface of thepiston skirt 2. The junction between thering 6 and thepiston skirt 2 is sealed by a gasket formed by acarbon seal 7 interposed therebetween. An axial sealing force is exerted to and acts on thecarbon seal 7 because thepiston head portion 1 is urged against and secured to thepiston skirt 2. It is a requirement for the structure of thepiston 20 that the heat-insulatingmaterial 3 uniformly receives a compression force produced by a combustion. So as to comply with this requirement, the surface of thepiston head 1 adjacent to the combustion chamber and the thin-walled ceramics portion 5 are designed to be planar. - Another or second embodiment of the heat-insulating engine according to the present invention will be described with reference to Figs. 3 and 4. The heat-insulating engine of the second embodiment is distinguished from the heat-insulating engine of the embodiment described with reference to Fig. 1 only in the shape of the liner head constituted by the cylinder head bottom wall portion and the cylinder liner upper portion. The portions of the second embodiment which are the same as those of the first embodiment are designated by the same reference numerals and thus are not described hereinunder for the purpose of simplification of the description. The heat-insulating engine of the second embodiment is generally designated by
reference numeral 40 and has aliner head 35 which constitutes a cylinder headbottom wall portion 37 and an integral cylindrical linerupper portion 36. The cylinder headbottom wall portion 37 of the heat-insulatingengine 40 is shaped to provide a raised outer peripheral portion and a lower central portion as in the cylinder headbottom wall portion 22 of the heat-insulatingengine 10 of the first embodiment. Thus, the cylinder headbottom wall portion 37 provides an inclined surface extending radially outwardly and upwardly from the central portion to the outer peripheral portion. Accordingly, thecombustion chamber 15 which is defined by the cooperation of the cylinder head bottom wall portion of the described shape and the flat thin-walled portion 5 of thepiston head 1 is most suited for a heat-insulating engine and resembles the shape of a shallow dish providing a radially outwardly increasing volume. With respect to theintake valve 21, thefuel injection nozzle 25 and thepiston 20, theengine 40 of the second embodiment is entirely the same as theengine 10 of the first embodiment. The flow of air introduced in each intake stroke of the heat-insulatingengine 40 is shown by arrows A in Fig. 4. The flow of intake air into thecombustion chamber 15 and the directions of the jets of fuel injected from afuel injection nozzle 25 into the combustion chamber are also entirely the same as those in the first embodiment.
Claims (30)
- A heat-insulating engine structure comprising;
a piston (20) reciprocatingly movable in a cylinder liner (34);
a cylinder liner upper portion (23,36) of a ceramic material disposed above said cylinder liner (34);
a cylinder head bottom wall portion (22,37) integral with said cylinder liner upper portion (23,36); and
a cylinder head (33) including a tubular section accommodating said integral cylinder liner upper portion (23,36) and said cylinder head bottom wall portion (22,37);
characterised in that said cylinder head bottom wall portion (22,37) and said cylinder liner upper portion (23,36) together define a combustion chamber (15);
the piston (20) has a surface to be exposed to combustion gases facing said combustion chamber which is planar;
said cylinder head bottom wall portion (22,37) is formed with, at least on the side facing the combustion chamber, a raised outer peripheral portion and a lowered central portion, with an inclined surface thereof extending radially upwardly from said central portion to said outer peripheral portion;
a fuel injection nozzle (25) is disposed substantially centrally of said cylinder head bottom wall portion (22,37) and has radially outwardly directed injection orifices;
and in that intake and exhaust valve seats are formed in the inclined surface of the cylinder head bottom wall portion (22,37) having intake and exhaust valves (21,27) associated with said intake and exhaust valve seats, respectively. - A heat-insulating engine structure according to claim 1, wherein said cylinder liner upper portion (23) has a tubular upper portion (26) having an inner surface of substantially square cross-section and a lower portion (28) having an inner surface of substantially circular cross-section, whereby said combustion chamber (15) includes a substantially square portion defined by said tubular upper portion (26) of said cylinder liner upper portion (23).
- A heat-insulating engine structure according to claim 2, wherein the inner dimension across said tubular upper portion (26) is smaller than the inner diameter of said lower portion (28).
- A heat-insulating engine structure according to claim 2 or 3, wherein said tubular upper portion (26) has rounded corners.
- A heat-insulating engine structure according to any preceding claim, wherein said fuel injection nozzle (25) is arranged to inject a fuel radially outwardly through said injection orifices into said combustion chamber (15).
- A heat-insulating engine structure according to any preceding claim, wherein said cylinder head bottom wall portion (22,37) and said cylinder liner upper portion (23,36) are of an integral thin-walled structure of a ceramics material.
- A heat-insulating engine structure according to any preceding claim, wherein said cylinder head bottom wall portion (22,37) and said cylinder liner upper portion (23,36) are of an integral structure of silicon nitride.
- A heat-insulating engine structure according to any one of claims 1 to 6, wherein said cylinder head bottom wall portion (22,37) and said cylinder liner upper portion (23,36) are of an integral structure of silicon carbide.
- A heat-insulating engine structure according to claim 1, wherein a heat-insulating layer (24) is disposed between an outer surface of said integral cylinder head bottom wall portion (22) and said cylinder liner upper portion (23), and an inner surface of said cylinder head (33).
- A heat-insulating engine structure according to claim 9, wherein said heat-insulating layer (24) includes a heat-insulating material made of potassium titanate or the like.
- A heat-insulating engine structure according to any preceding claim, wherein said intake and exhaust valves (21,27) are disposed in a generally inverted-V arrangement.
- A heat-insulating engine structure according to claim 11, wherein said cylinder head (33) is formed therein with an intake port (31) extending obliquely and radially inwardly to said intake valve seat.
- A heat-insulating engine structure according to claim 12, wherein, in use, intake air introduced through said intake port (31) into said combustion chamber (15) in each suction stroke of the engine includes a primary flow disposed substantially vertically centrally of said combustion chamber (15).
- A heat-insulating engine structure according to any one of claims 2 to 4, wherein, in use, sprays of fuel injected into said combustion chamber (15) and intake air form a swirl, the sides of said tubular upper portion (26) of substantially square inner cross-section serving to agitate said swirl whereby the fuel and the air are immediately and uniformly mixed.
- A heat-insulating engine structure according to claim 1, wherein said piston (20) includes a piston skirt (2) having an upper end wall (32), a piston head portion (1) having a mounting portion by which said piston head portion (1) is mounted on said upper end wall (32), a ring of a ceramics material urged against and secured to an upper surface of said piston skirt (2), a thin-walled portion (5) constituting said planar surface of said piston and having an outer periphery bonded to said ring (6), said piston head portion (1) having an upper surface defining with an undersurface of said thin-walled portion (5) and with a part of an inner peripheral surface of said ring (6) a space, a heat-insulating material disposed within and filling up said space.
- A heat-insulating engine structure according to claim 15, wherein said thin-walled portion (5) constitutes said planar surface to be exposed to combustion gases, which portion is made of a ceramics material having as thin a wall thickness as possible.
- A heat-insulating engine structure according to claim 15 or 16, wherein the outer periphery of said thin-walled portion (5) is bonded to an upper portion of said ring (6) by a chemical vapor deposition (18) of a ceramics material.
- A heat-insulating engine structure according to any one of claims 15 to 17, wherein said piston head (1) has a planar upper surface.
- A heat-insulating engine structure according to any one of claims 15 to 18, wherein said heat-insulating material (3) filling the space defined by the piston head (1), thin-walled portion (5) and ring (6) acts as a structural member which bears a pressure acting on said thin-walled portion (5).
- A heat-insulating engine structure according to any one of claims 15 to 19, wherein said thin-walled portion (5) and said ring (6) are made of silicon nitride.
- A heat-insulating engine structure according to any one of claims 15 to 19, wherein said thin-walled portion (5) and said ring (6) are made of silicon carbide.
- A heat-insulating engine structure according to any one of claims 15 to 21, wherein the inner peripheral surface of said ring (6) is formed thereon with a step with which said piston head (1) engages at its outer periphery, and wherein said piston head portion (1) is secured to said piston skirt (2) whereby a lower end of said ring (6) is urged against an upper end face of said piston skirt (2).
- A heat-insulating engine structure according to claim 22, wherein a sealing gasket (7) is interposed between said lower end of said ring (6) and said upper end face of said piston skirt (2).
- A heat-insulating engine structure according to any one of claims 15 to 23, wherein said mounting portion of said piston head portion (1) is a mounting hub (4) formed substantially centrally of said piston head portion (1), and wherein said mounting hub (4) is fitted into a central mounting hole (12) formed in said piston skirt (2).
- A heat-insulating engine structure according to claim 24, wherein said piston head portion (1) and said piston skirt (2) are secured together by a metallic ring (11) forcibly engaged into and interconnecting annular grooves (14,13) respectively formed in an outer peripheral surface of said mounting hub (4) and an inner peripheral surface of said central mounting hole (12).
- A heat-insulating engine structure according to claim 24, wherein a portion of said piston head portion (1) adjacent to said mounting hub (4) and a portion of said piston skirt (2) adjacent to said central mounting hole (12) are urged toward each other with a shock absorbing member (8) interposed therebetween, said shock absorbing member (8) also providing a heat-insulating function.
- A heat-insulating engine structure according to any one of claims 15 to 26, wherein said piston head portion (1) has an undersurface cooperating with an upper surface of the upper end wall (32) of said piston skirt (2) and a portion of an inner peripheral surface of said ring (6) to define a heat-insulating air chamber (9).
- A heat-insulating engine structure according to any one of claims 15 to 27, wherein said piston head (1) is made of a material having a coeffecient of thermal expansion substantially equal to that of a ceramics material of cermet or metallic material, a high strength and a high Young's modulus.
- A heat-insulating engine structure according to any one of claims 15 to 28, wherein said heat-insulating material (3) filling the space defined by the piston head, thin-walled portion (5) and ring (6), is a heat-resisting material of a high porosity such as potassium titanate whisker, zirconia fiber and so forth.
- A heat-insulating engine structure according to any one of claims 15 to 29, wherein said piston skirt (2) has an outer peripheral surface with a piston ring groove (39) formed therein and provided with a piston pin hole (41) extending diametrically of said piston skirt (2).
Applications Claiming Priority (4)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP62133301A JPH066891B2 (en) | 1987-05-30 | 1987-05-30 | Insulation engine structure |
JP133302/87 | 1987-05-30 | ||
JP62133302A JPH066892B2 (en) | 1987-05-30 | 1987-05-30 | Insulation engine structure |
JP133301/87 | 1987-05-30 |
Publications (3)
Publication Number | Publication Date |
---|---|
EP0294092A2 EP0294092A2 (en) | 1988-12-07 |
EP0294092A3 EP0294092A3 (en) | 1989-10-25 |
EP0294092B1 true EP0294092B1 (en) | 1992-07-29 |
Family
ID=26467689
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP19880304742 Expired - Lifetime EP0294092B1 (en) | 1987-05-30 | 1988-05-25 | Heat-insulating engine structure |
Country Status (3)
Country | Link |
---|---|
EP (1) | EP0294092B1 (en) |
CA (1) | CA1331119C (en) |
DE (2) | DE3873184T2 (en) |
Families Citing this family (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2526947B2 (en) * | 1987-12-14 | 1996-08-21 | いすゞ自動車株式会社 | Insulation engine structure |
US5282411A (en) * | 1989-08-10 | 1994-02-01 | Isuzu Motors Limited | Heat-insulating piston with middle section of less dense but same material |
JPH0668257B2 (en) * | 1989-08-10 | 1994-08-31 | いすゞ自動車株式会社 | Structure of adiabatic piston |
DE10261181A1 (en) * | 2002-12-20 | 2004-07-01 | Daimlerchrysler Ag | Internal combustion engine with auto-ignition |
Family Cites Families (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE3126028A1 (en) * | 1981-07-02 | 1983-01-20 | Klöckner-Humboldt-Deutz AG, 5000 Köln | CERAMIC WALL FOR LINING COMBUSTION SPACES |
DE3420571C1 (en) * | 1984-06-01 | 1986-01-09 | Alcan Aluminiumwerk Nürnberg GmbH, 6000 Frankfurt | Component for internal combustion engines and method for its production |
-
1988
- 1988-05-25 DE DE19883873184 patent/DE3873184T2/en not_active Expired - Fee Related
- 1988-05-25 EP EP19880304742 patent/EP0294092B1/en not_active Expired - Lifetime
- 1988-05-25 DE DE1988304742 patent/DE294092T1/en active Pending
- 1988-05-27 CA CA 567987 patent/CA1331119C/en not_active Expired - Fee Related
Also Published As
Publication number | Publication date |
---|---|
DE294092T1 (en) | 1989-04-20 |
DE3873184D1 (en) | 1992-09-03 |
EP0294092A3 (en) | 1989-10-25 |
EP0294092A2 (en) | 1988-12-07 |
DE3873184T2 (en) | 1993-03-04 |
CA1331119C (en) | 1994-08-02 |
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