Kabushiki Kaisha Toyota Chuo Kenkyusho, Toyota Jidosha Kabushiki Kaisha
대리인 / 주소
Oblon, Spivak, McClelland, Maier & Neustadt, P.C.
인용정보
피인용 횟수 :
40인용 특허 :
20
초록▼
A state of combustion in a combustion chamber is controlled by stratifying an intake gas charge within the combustion chamber, so as to reduce amounts of harmful substances left in exhaust gas. A direct-injection type internal combustion engine in which a fuel is injected into the combustion chamber
A state of combustion in a combustion chamber is controlled by stratifying an intake gas charge within the combustion chamber, so as to reduce amounts of harmful substances left in exhaust gas. A direct-injection type internal combustion engine in which a fuel is injected into the combustion chamber and which is arranged to stratify the intake gas charge within the combustion chamber ( 1 ) such that intake gases of different compositions exist in a central portion ( 13 ) of the combustion chamber including a position of the fuel injection, and in a peripheral portion of the combustion chamber, upon initiation of combustion of the fuel at a point of time near a terminal period of a compression stroke. The intake gases of different compositions may be intake gases having different concentrations of a specific component such as recirculated exhaust gas and the fuel.
대표청구항▼
1. A method of stratifying an intake gas charge within a combustion chamber of a direct-injection type internal combustion engine, comprising the steps of:injecting a fuel into the combustion chamber; andintroducing intake gases into the combustion chamber such that intake gases of different composi
1. A method of stratifying an intake gas charge within a combustion chamber of a direct-injection type internal combustion engine, comprising the steps of:injecting a fuel into the combustion chamber; andintroducing intake gases into the combustion chamber such that intake gases of different compositions exist in a central portion of the combustion chamber, which is a region inside a generally hemispherical or generally flat hemispherical plane having a center at a position of injection of the fuel, and in a peripheral portion of the combustion chamber, which is a region outside the generally hemispherical or generally flat hemispherical plane, upon initiation of combustion of the fuel at a point of time near a terminal period of a compression stroke. 2. A method according to claim 1, wherein said intake gases of different compositions are intake gases having different concentrations of a specific component contained therein. 3. A method according to claim 2, wherein a pattern of stratification of the intake gas charge within the combustion chamber is changed depending upon operating conditions of said internal combustion engine, to a selected one of:a normal stratification pattern in which the concentration of the specific component of the intake gas in said central portion is lower than that of the intake gas in said peripheral portion;a reverse stratification pattern in which the concentration of the specific component of the intake gas in said central portion is higher than that of the intake gas in said peripheral portion; anda homogeneous pattern in which the concentration of the specific component of the intake gas in said central portion is equal to that of the intake gas in said peripheral portion. 4. A method according to claim 3, wherein said internal combustion engine is a compression-ignition internal combustion engine. 5. A method according to claim 2, wherein a ratio of the concentration of the specific component of the intake gas in said peripheral portion to that of the intake gas in said central portion is changed depending upon operating conditions of said internal combustion engine. 6. A method according to claim 5, wherein said internal combustion engine is a compression-ignition internal combustion engine. 7. A method according to claim 1, wherein said internal combustion engine is a compression-ignition internal combustion engine. 8. A device for stratifying an intake gas charge within a combustion chamber of a direct-injection type internal combustion engine in which a plurality of intake ports are provided to form a plurality of swirl flows of intake gases in a same direction of rotation in the combustion chamber and in which a fuel is injected into the combustion chamber, from a center portion of a top surface of the combustion chamber opposed to a top face of a piston, toward a peripheral part of a cavity formed in a central portion of the top face of the piston, said device comprising:an arrangement for forming, in an intake stroke, a swirl flow of a first intake gas in an upper portion of the combustion chamber, along a cylindrical wall of the combustion chamber, and a swirl flow of a second intake gas in a lower portion of the combustion chamber, along the cylindrical wall of the combustion chamber, and for maintaining a state of vertical stratification of the intake gas charge consisting of the swirl flows of the first and second intake gases within the combustion chamber, up to a point of time within an intermediate period of a compression stroke;an arrangement for causing the first intake gas to flow into a central region of the cavity in the central portion of the top face of the piston, while the second intake gas remains in a peripheral region and a bottom region of the cavity, in a latter half of a compression stroke in which a squish flow is created; andan arrangement for stratifying the intake gas charge within the combustion chamber at a point of time near a terminal period of the compr ession stroke in which the combustion of the fuel is initiated, such that the first intake gas exists primarily in a region inside a generally hemispherical or generally flat hemispherical plane having its center at a position of injection of the fuel into the combustion chamber, while the second intake gas exists primarily in a region outside the generally hemispherical or generally flat hemispherical plane. 9. A device according to claim 8, wherein said generally hemispherical or generally flat hemispherical plane is spaced from the position of injection of the fuel into the combustion chamber, in a direction of injection of the fuel, by a distance 1-1.5 times a spray breakup length of the injected fuel. 10. A device according to claim 8, wherein said internal combustion engine is a compression-ignition internal combustion engine. 11. A device according to claim 8, wherein a first intake valve in the intake port for forming the swirl flow of the first intake gas in the upper portion of the combustion chamber and a second intake valve in the intake port for forming the swirl flow of the second intake gas in the lower portion of the combustion chamber are opened for respective different periods, so that only the second intake valve is open to permit only the second intake gas to flow into the combustion chamber in an initial period of the intake stroke, so that the first and second intake valves are open to permit the first and second intake gases to flow into the combustion chamber in an intermediate period of the intake stroke, and so that only the first intake valve is open to permit only the first intake gas to flow into the combustion chamber in a terminal period of the intake stroke. 12. A direct-injection type internal combustion engine wherein a fuel is injected into a combustion chamber, said engine comprising:an arrangement for stratifying an intake gas charge such that an intake gas not containing a recirculated exhaust gas or having a low concentration of the recirculated exhaust gas exists in one of a central portion of the combustion chamber including a position of injection of the fuel and a peripheral portion of the combustion chamber, while an intake gas containing the recirculated exhaust gas or having a high concentration of the recirculated exhaust gas exists in the other of the central and peripheral portions of the combustion chamber, upon initiation of combustion of the fuel at a point of time near a terminal period of a compression stroke. 13. A direct-injection type internal combustion engine according to claim 12, wherein said internal combustion engine is a compression-ignition internal combustion engine. 14. A direct-injection type internal combustion engine according to claim 12, wherein the intake gas containing the recirculated exhaust gas or having the high concentration of the recirculated exhaust gas exists in said central portion of the combustion chamber, while the intake gas not containing or having the low concentration of the recirculated exhaust gas exists in said peripheral portion, upon initiation of combustion of the fuel at the point of time near the terminal period of the compression stroke, when the internal combustion engine is operated under a high load or at a high speed. 15. A direct-injection type internal combustion engine according to claim 14, wherein said internal combustion engine is a compression-ignition internal combustion engine. 16. A direct-injection type internal combustion engine according to claim 12, wherein a ratio of the concentration of the recirculated exhaust gas in said peripheral portion to the concentration of the recirculated exhaust gas in said central portion is changed depending upon operating conditions of the internal combustion engine. 17. A direct-injection type internal combustion engine in which a plurality of intake ports are provided to form a plurality of swirl flows of intake gases in a same direction of rotation in a combustion chamber and in which a fuel is injected into the combustion chamber, from a center portion of a top surface of the combustion chamber opposed to a top face of a piston, toward a peripheral part of a cavity formed in a central portion of the top face of the piston, said engine comprising:an arrangement for forming, in an intake stroke, a swirl flow of a first intake gas not containing a recirculated exhaust gas, along an upper portion of a cylindrical wall of the combustion chamber, and a swirl flow of a second intake gas containing the recirculated exhaust gas, along a lower portion of the cylindrical wall of the combustion chamber;an arrangement for causing the first intake gas to flow into a central region of the cavity in the central portion of the top face of the piston, while the second intake gas remains in a peripheral region and a bottom region of the cavity, in a latter half of a compression stroke in which a squish flow is created; andan arrangement for stratifying an intake gas charge within the combustion chamber at a point of time near a terminal period of the compression stroke in which the combustion of the fuel is initiated, such that the intake gas not containing the recirculated exhaust gas or having a low concentration of the recirculated exhaust gas exists in a region inside a generally hemispherical or generally flat hemispherical plane having its center at a position of injection of the fuel into the combustion chamber, while the intake gas containing the recirculated exhaust gas or having a high concentration of the recirculated exhaust gas exists in a region outside the generally hemispherical or generally flat hemispherical plane. 18. A direct-injection type internal combustion engine according to claim 17, wherein said internal combustion engine is a compression-ignition internal combustion engine. 19. A direct-injection type internal combustion engine according to claim 17, wherein a first intake valve in the intake port for forming the swirl flow of the first intake gas in the upper portion of the combustion chamber and a second intake valve in the intake port for forming the swirl flow of the second intake gas in the lower portion of the combustion chamber are opened for respective different periods, so that only the second intake valve is open to permit only the second intake gas to flow into the combustion chamber in an initial period of the intake stroke, so that the first and second intake valves are open to permit the first and second intake gases to flow into the combustion chamber in an intermediate period of the intake stroke, and so that only the first intake valve is open to permit only the first intake gas to flow into the combustion chamber in a terminal period of the intake stroke. 20. A direct-injection type internal combustion engine according to claim 19, wherein said internal combustion engine is a compression-ignition internal combustion engine. 21. A direct-injection type internal combustion engine according to claim 17, wherein said generally hemispherical or generally flat hemispherical plane is spaced from the position of injection of the fuel into the combustion chamber, in a direction of injection of the fuel, by a distance 1-1.5 times a spray breakup length of the injected fuel. 22. A direct-injection type internal combustion engine of compression-ignition or spark-ignition type in which a fuel is injected into an intake gas within a combustion chamber or to the intake gas within the combustion chamber and an intake gas within an intake passage and in which combustion of the fuel is initiated at a point of time near a terminal period of a compression stroke, said engine comprising:a cavity formed in a central portion of a top face of a piston;a spuish area over a peripheral portion of the top face of the piston;an arrangement for stratifying an intake gas charge within the combustion chamber such that an intake gas containing a fuel or having a high concentration of the fuel exists in a central portion of the combustion chamber including a center portion of a top surface of the combustion chamber, while an intake gas not containing the fuel or having a low concentration of the fuel exists in the squish area and near wall surfaces of the cavity, upon initiation of combustion of the fuel. 23. A direct-injection type internal combustion engine according to claim 22, wherein a ratio of the concentration of the fuel in the intake gas existing upon initiation of combustion of the fuel in the peripheral portion of the combustion chamber, to the concentration of the fuel in the intake gas existing in the central portion of the combustion chamber including the center portion of the top surface is changed depending upon operating conditions of the internal combustion engine. 24. A direct-injection internal combustion engine of compression-ignition or spark-ignition type in which a plurality of intake ports are provided to form a plurality of swirl flows of intake gases in a same direction of rotation in the combustion chamber and in which a premixing amount of a fuel is injected into the combustion chamber or an intake passage, at a premixing fuel-injection timing before 30° BTDC in an intake or compression stroke, and in which combustion of the fuel is initiated at a point of time near a terminal period of a compression stroke, said engine comprising:a cavity formed in a central portion of a top face of a piston;a squish area over a peripheral portion of the top face of the piston;an arrangement for injecting the premixing amount of the fuel into a swirl flow of a specific intake gas within the combustion chamber, or into an intake gas in a specific intake port or an intake passage including the specific intake port,and an arrangement for stratifying an intake gas charge within the combustion chamber upon initiation of combustion of the fuel, such that an intake gas containing the fuel or having a high concentration of the fuel exists in a central portion of the combustion chamber including a center portion of a top surface of the combustion chamber, while an intake gas not containing the fuel or having a low concentration of the fuel exists in the squish area and near wall surfaces of the cavity. 25. A direct-injection internal combustion, engine according to claim 24, comprising:an arrangement for forming, in an intake stroke, a swirl flow of a first intake gas along an upper portion of the combustion chamber, and a swirl flow of a second intake gas along a lower portion of the combustion chamber, and for injecting the premixing amount of the fuel into the first intake gas; andan arrangement for causing the first intake gas to flow into a central region of a cavity in a central portion of a top face of a piston, while the second intake gas remains in a peripheral region and a bottom region of the cavity, in a latter half of the compression stroke in which a squish flow is created. 26. A direct-injection internal combustion engine according to claim 24,wherein said premixing amount of the fuel is injected from a fuel injector disposed on a top surface of the combustion chamber, into the intake gas within the combustion chamber,said fuel injector is a variable type fuel injector which is variable in its fuel injecting characteristics such as a direction of injection of the fuel, an angle of spraying of the fuel and a penetration force of the fuel; andsaid fuel injecting characteristics are controlled to be suitable for permitting a most of the fuel injected at said premixing fuel-injection timing, to be mixed with only the swirl flow of the intake gas which exists, upon initiation of combustion of the fuel, primarily in a central portion of the combustion chamber including a center portion of the top surface of the combustion chamber.
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