Power plants – Internal combustion engine with treatment or handling of... – By means producing a chemical reaction of a component of the...
Reexamination Certificate
2000-11-20
2001-12-25
Denion, Thomas (Department: 3748)
Power plants
Internal combustion engine with treatment or handling of...
By means producing a chemical reaction of a component of the...
C060S313000, C060S322000, C060S323000, CD12S194000
Reexamination Certificate
active
06332314
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a catalyzer arrangement in an exhaust system of a multi-cylinder internal combustion engine, particularly relates to an improvement of a catalyzer arrangement in an exhaust system of a multi-cylinder internal combustion engine for raising output of the internal combustion engine while lowering emission.
Hitherto, an exhaust system of a multi-cylinder internal combustion engine having a catalyzer arranged midway of an exhaust pipe has been known by Japanese Laid-Open Patent Publication Hei 6-10146. This exhaust system comprises an exhaust manifold, a catalyzer provided on a downstream side of the exhaust manifold and an exhaust pipe provided on the downstream side of the catalyzer. The catalyzer is so formed that exhaust gas discharged from the exhaust manifold flows in parallel with an output shaft of the engine, and the exhaust pipe is directed in a predetermined direction so as to discharge the exhaust gas into the atmosphere.
In the above-mentioned exhaust apparatus, an exhaust manifold having an exhaust pipe length (single pipe length) effective for the output and a catalyzer for purification of exhaust gas are provided in a limited space of an engine room to raise output of the engine while lowering emission.
However, according to the above exhaust apparatus, in case of an exhaust system in which a plurality of exhaust pipes (four exhaust pipes for example) connected to exhaust ports of an engine are collected into a collective exhaust pipe (exhaust system of 4-1 construction), it is difficult to ensure an exhaust pipe length sufficient for reducing exhaust gas interference accompanying high output of the engine within a space limited by breadth of the engine.
If it is intended to ensure a sufficient exhaust pipe length, it becomes difficult to ensure a space for arranging the catalyzer or to ensure a sufficient catalyzer capacity. In addition, since a distance between the exhaust port of the engine and the catalyzer becomes long, the catalyzer takes much time to reach the minimum active temperature and emission is increased.
The above circumstance is similar about an exhaust system in which a plurality of exhaust pipes (four exhaust pipes for example) connected with exhaust ports of an engine are collected into intermediate collective exhaust pipes every two pipes then the intermediate collective exhaust pipes are collected into a final collective exhaust pipe (exhaust system of 4-2 construction). Anyway, until now, it was difficult that high output and low emission are made compatible in an internal combustion engine.
SUMMARY OF THE INVENTION
A subject of the present invention is to solve the above-mentioned problem of the customary catalyzer arrangement in an exhaust system of a multi-cylinder internal combustion engine and provide a novel catalyzer arrangement in an exhaust system of a multi-cylinder internal combustion engine in which exhaust pipe length of an exhaust manifold can be set freely, a sufficient space for arranging a catalyzer can be ensured, performance of the catalyzer can be maintained highest always, and therefore high engine output and low emission can be made compatible.
The present invention provides a catalyzer arrangement in an exhaust system of a multi-cylinder internal combustion engine having a plurality of exhaust pipes connected with exhaust ports of the engine, wherein each of the exhaust pipes has a first exhaust pipe section extending away from a main body of the engine; a second exhaust pipe section contiguous to the first exhaust pipe section having a first curved portion for turning the second exhaust pipe section to the main body of the engine; and a third exhaust pipe section contiguous to the second exhaust pipe section having a second curved portion for turning the third exhaust pipe section away from the main body of the engine, and the catalyzer is connected to a downstream side of the third exhaust pipe section and disposed within a space surrounded by the first, second and third exhaust pipe sections.
According to the invention, since the catalyzer is disposed within a space surrounded by the first exhaust pipe section, the second exhaust pipe section having the first curved portion, and the third exhaust pipe section having the second curved portion, pipe lengths of the exhaust pipes can be set freely within a space limited by breadth of the engine, by suitably selecting curvatures of the curved portions. Therefore, the exhaust pipe length can be matched with valve timing or the like easily, an exhaust pipe length sufficient for reducing exhaust gas interference accompanying high output of the engine can be ensured easily so that output of the engine can be made high. In addition, the construction of the exhaust pipe around the catalyzer can be simplified and made compact.
The catalyzer can be disposed within the space limited by breadth of the engine utilizing a dead space with high space efficiency and a sufficient catalyzer capacity can be ensured easily by adjusting curvature of the curved portion. Therefore, emission can be lowered easily, and emission deterioration characteristic is improved because thermal load per one catalyzer is reduced.
The distance from the exhaust port of the engine to the catalyzer becomes long, but since the catalyzer is surrounded by the exhaust pipes and receives heat from the exhaust pipes, time required for the catalyzer to reach the minimum active temperature is not prolonged even if the engine is started at a low temperature. Therefore, exhaust emission can be reduced.
The exhaust pipes may be divided into one group positioned near one end of a row of cylinder of the engine and another group positioned near another end of the row of cylinder, the catalyzer may be divided into one unit catalyzer positioned near one end of the row of cylinder and another unit catalyzer positioned near another end of the row of cylinder, the one group of cylinders may be connected to the one unit catalyzer, and the another group of cylinders may be connected to the another unit catalyzer.
As the result, since the both unit catalyzers deteriorate equally and each unit catalyzer deteriorates uniformly, endurance of the catalyzer is improved to enable to utilize the catalyzer effectively.
At least one of the first and second exhaust pipe sections may have a portion contacted with at least one of a connecting portion of the third exhaust section to the catalyzer and the catalyzer itself.
As the result, since the catalyzer receives heat from exhaust gas on an upstream side of the catalyzer more efficiently by thermal conduction through the contacted portion, active temperature of the catalyzer can be maintained surly, time required for the catalyzer to reach the minimum active temperature is shortened, and exhaust emission is further lowered.
The exhaust pipes may be divided into one group positioned near one end of a row of cylinder of the engine and another group positioned near another end of the row of cylinder, and in each of the group, two exhaust pipes may be collected into a collective exhaust pipe at a portion extending over the second and third exhaust pipe sections or at the third exhaust pipe section.
As the result, length of each exhaust pipe can be set freely by changing the position where the two exhaust pipes are collected into the one collective exhaust pipe. Therefore, the exhaust pipe length can be matched with valve timing or the like more easily, and exhaust gas interference accompanying high output of the engine can be further reduced, so that output of the engine can be made higher.
The catalyzer may be divided into one unit catalyzer positioned near one end of the row of cylinder and another unit catalyzer positioned near another end of the row of cylinder, the collective exhaust pipe in the one group may be connected to the one unit catalyzer, and the collective exhaust pipe in the another group may be connected to the another unit catalyzer.
As the result, since the both unit catalyzers deteriorate equally and each unit cataly
Kurotobi Takeshi
Maeda Fumihiko
Nakade Junichi
Sakanushi Masahiro
Armstrong Westerman Hattori McLeland & Naughton LLP
Denion Thomas
Honda Giken Kogyo Kabushiki Kaisha
Tran Binh
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