Power plants – Internal combustion engine with treatment or handling of... – By means producing a chemical reaction of a component of the...
Reexamination Certificate
1999-05-05
2001-02-27
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...
C060S274000, C060S299000, C422S171000, C422S177000
Reexamination Certificate
active
06192679
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to purification of discharged hydrocarbons (HC) from an internal combustion engine.
BACKGROUND OF THE INVENTION
Tokkai Hei 5-57148 published by the Japanese Patent Office in 1993 regarding the purification of hydrocarbon (HC) in the exhaust of an internal combustion engine, discloses an arrangement wherein plural catalytic converters comprising hydrocarbon adsorbents (HC adsorbents) and catalysts which oxidize hydrocarbons are disposed in series in an exhaust passage of an engine. The HC adsorbents absorb hydrocarbons when the temperature is low, and discharge the hydrocarbons when the temperature is high. The catalyst is activated when the temperature rises, and then oxidizes the hydrocarbons.
When the catalyst activation temperature is higher than the temperature at which HC adsorbent starts to discharge hydrocarbons, a specific region will be created where hydrocarbons released from the HC adsorbent are not oxidized.
As the converter temperature generally decreases the further away the converter is from the engine, the HC adsorbent of the downstream converters will still not have reached the HC discharge start temperature even if the upstream converters reaches the aforesaid specific temperature region.
Therefore, hydrocarbons flowing out of the upstream converter are adsorbed by the HC adsorbent of the downstream converters.
In this case, during the interval from when the temperature of the converter situated furthest downstream reaches the aforesaid specific temperature region to when it rises above the specific temperature region, hydrocarbons will be discharged into the atmosphere.
However, the discharge amount is less than the discharge amount of hydrocarbons discharged by the upstream converter discharges, and the amount of hydrocarbons which is finally discharged is less the larger the number of converters connected in series.
SUMMARY OF THE INVENTION
In the aforesaid prior art, if the HC adsorbent of the downstream converter reaches a temperature at which hydrocarbons are no longer adsorbed before the HC adsorbent of the upstream converter has finished discharging hydrocarbons, the hydrocarbons discharged by the upstream converter thereafter cannot be adsorbed by the HC adsorbent of the downstream converter.
In such a case, even if plural converters are used, a temporary increase in the discharge amount of hydrocarbons cannot be avoided.
It is therefore an object of this invention to suppress the discharge amount of hydrocarbons across the whole range of temperature increase of an exhaust passage due to engine warmup.
In order to achieve the above object, this invention provides an exhaust purifying device, comprising a first and second converters respectively comprising a hydrocarbon adsorbent and a catalyst and an exhaust passage connecting the first and second converters.
The adsorbent adsorbs hydrocarbons at a temperature lower than a first temperature and discharging adsorbed hydrocarbons at a temperature higher than the first temperature. The catalyst oxidizes hydrocarbons discharged from the adsorbent at a temperature higher that a second temperature which is higher than the first temperature.
The exhaust passage connects the first and second converters such that the first converters are situated further upstream than the second converters with respect to the flow of exhaust,
The heat capacity of the exhaust passage is set so that the temperature of the absorbent of the second converter does not reach the first temperature before the temperature of the catalyst of the first converter rises to the second temperature.
This invention also provides an exhaust purifying method of an engine. The method comprises disposing a first and second converters in an exhaust passage of the engine such that the first converters are situated further upstream than the second converters with respect to the flow of exhaust of the engine. The converters respectively comprises a hydrocarbon adsorbent adsorbing hydrocarbons at a temperature lower than a first temperature and discharging adsorbed hydrocarbons at a temperature higher than the first temperature and a catalyst oxidizing hydrocarbons discharged from the adsorbent at a temperature higher that a second temperature which is higher than the first temperature. The method also comprises setting the heat capacity of the exhaust passage so that the temperature of the absorbent of the second converter does not reach the first temperature before the temperature of the catalyst of the first converter rises to the second temperature.
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.
REFERENCES:
patent: 5398503 (1995-03-01), Danno et al.
patent: 5501073 (1996-03-01), Miyashita et al.
patent: 5538697 (1996-07-01), Abe et al.
patent: 5606857 (1997-03-01), Harada
patent: 5649421 (1997-07-01), Wakabayashi et al.
patent: 5722363 (1998-03-01), Iida et al.
patent: 5804148 (1998-09-01), Kanesaka et al.
patent: 6047544 (2000-04-01), Yamamoto et al.
patent: 5-57148 (1993-03-01), None
Nakamura Takeshi
Nishizawa Kimiyoshi
Sato Ritsuo
Denion Thomas
Foley & Lardner
Nissan Motor Co,. Ltd.
Tran Binh
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