Power plants – Internal combustion engine with treatment or handling of... – Material from exhaust structure fed to engine intake
Reexamination Certificate
1999-11-24
2001-08-14
Denion, Thomas (Department: 3748)
Power plants
Internal combustion engine with treatment or handling of...
Material from exhaust structure fed to engine intake
C060S279000, C060S605200, C123S568170, C123S184240
Reexamination Certificate
active
06272851
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to an exhaust recirculation system in an internal combustion engine such as a diesel engine of an automobile.
BACKGROUND OF THE INVENTION
In regard to an exhaust recirculation system (EGR system) wherein a part of the exhaust is recirculated into the intake air to perform combustion control of an internal combustion engine, various devices have been proposed to promote mixing of intake air and recirculated exhaust gas.
Jikkai Hei 3-114563 published by the Japanese Patent Office in 1991 discloses a system wherein an insulator is gripped between a throttle case and surge tank in the intake passage of the engine, a pair of exhaust inlets are provided at an 180-degree interval in the insulator towards the center of the intake passage, and exhaust gas is mixed with intake air through these exhaust gas inlets.
Jikkai Hei 3-114564 published in 1991 by the Japanese Patent Office discloses a device wherein an annular passage for leading exhaust gas surrounds the intake passage, and exhaust gas is led into the intake air via plural holes connecting the annular passage and intake passage.
Tokkai Hei 5-106519 published by the Japanese Patent Office in 1993 discloses a system wherein a minute throughhole connecting an exhaust port and intake port of an engine.
Further, this prior art discloses that the air-fuel mixture of fuel injected into the intake port and intake air is heated by the exhaust gas led to the intake port, and a swirl promoted by the throughhole arranged on a tangential line of the cross-section of the inlet port accelerates evaporation of the fuel adhering to the wall of the inlet port.
SUMMARY OF THE INVENTION
When exhaust gas is introduced from a right-angled direction as in Jikkai Hei 3-114563 and Jikkai Hei 3-114564 towards the center of the intake passage of a multi-cylinder engine, the exhaust gas forms an uneven flow in the passage due to the flow of intake air in the intake passage, and this causes unevenness in the exhaust concentration in each part of the cross-section of the passage. As a result, the exhaust gas concentration in the intake air will vary greatly depending on the cylinder. In general, in diesel engines which do not have a throttle, the flow of intake air is close to laminar flow, so this phenomenon is very pronounced, and as a result, a difference easily arises in the exhaust recirculation rate depending on the cylinder.
On the other hand, when the exhaust gas is supplied to the intake air through a minute throughhole formed in the cylinder head as in Tokkai Hei 5-106519, the exhaust recirculation rate is limited, and as the exhaust gas is mixed with the intake air just before the combustion chamber, the exhaust gas and intake air are aspirated into the combustion chamber without being properly mixed, and a variation in the running conditions of the engine has a direct effect on the exhaust recirculation rate (EGR rate). Such characteristics may makes the EGR rate of the engine unstable.
It is therefore an object of this invention to make the EGR rate of each cylinder of a multi-cylinder engine uniform, while preventing the variation of the running conditions of the engine from affecting the EGR rate.
In order to achieve the above object, this invention provides a exhaust recirculation system for a multi-cylinder internal combustion engine, wherein intake air aspirated to a collector from an intake passage of circular cross-section is provided to cylinders via branch pipes connected to the collector, and part of exhaust gas of the engine is recirculated to the intake passage from an exhaust passage. The exhaust recirculation system comprises an exhaust recirculation pipe which branches off from the exhaust passage and is connected to the intake passage, and an exhaust gas inlet which leads a recirculated exhaust gas of the exhaust recirculation pipe into the intake passage along a tangent line of the circular cross-section of the intake passage.
The details as well as other features and advantages of this invention are set forth in the remainder of the specification and are shown in the accompanying drawings.
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Patent Abstracts of Japan, vol. 017, No. 671 (M-1525), Dec. 10, 1993 & JP 05 223016 A (Toyota Motor Corp), Aug. 31, 1993 (Abstract).
Patent Abstracts of Japan, vol. 1998, No. 08, Jun. 30, 1998 & JP 10 077913 A (Aisin Seiki Co. Ltd.), Mar. 24, 1998 (Abstract).
Matayoshi Yutaka
Mori Kouji
Noda Yasushi
Denion Thomas
Foley & Lardner
Nissan Motor Co,. Ltd.
Tran Binh
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