Device for reactivating catalyst of engine

Details Device for reactivating catalyst of engine Device for reactivating catalyst of engine

1998-07-31

2001-01-30

Chapman, Jeanette (Department: 3748)

Power plants

Internal combustion engine with treatment or handling of...

Having sensor or indicator of malfunction, unsafeness, or...

C060S295000, C060S287000, C060S288000, C060S289000, C060S286000, C060S303000, C060S277000

Reexamination Certificate

active

06178743

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a device for reactivating a catalyst of an engine.
2. Description of the Related Art
Typically, a catalyst arranged in an exhaust passage of an engine is provided with a porous carrier which has an adsorbing function. However, the exhaust gas discharged from the engine includes a soluble organic fraction (SOF) and the SOF is adsorbed in the porous carrier. However, if the SOF is adsorbed in the inner portion of the porous carrier which is spaced apart from the surface of the carrier, it is difficult for the SOF to be desorbed therefrom. Also, a porous carrier such as zeolite has a catalytic function by itself and, therefore, the SOF may be reformed in the porous carrier if the SOF stays in the porous carrier for a long time. If the reformed SOF covers the catalytic metal or blocks the micro pores of the porous carrier, NO
X
and the reducing agent cannot reach the catalytic metal and, therefore, the NO
X
can not be reduced sufficiently. In this way, the catalyst is poisoned by SOF.
However, the SOF will be burned when the temperature of the porous carrier becomes high in an oxidizing atmosphere. Therefore, Japanese Unexamined Patent Publication No. 6-200737 discloses a device for reactivating a catalyst of a diesel engine in which it is judged whether the catalyst is poisoned by SOF and, if the catalyst is judged to be poisoned, the catalyst is heated so that the SOF in the catalyst is burned, to thereby reactivate the catalyst.
In this device, the SOF existing on or near the surface of the porous carrier is relatively easily heated and thus burned. However, it is difficult to heat the SOF existing in the inner portion of the porous carrier to a temperature where the SOF can be burned. Namely, it is difficult for the catalyst to be reactivated sufficiently.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a device for reactivating a catalyst of an engine capable of reactivating the catalyst sufficiently from the poisoning thereof, to thereby purify the exhaust gas sufficiently.
According to the present invention, there is provided a device for reactivating a catalyst of an engine having an exhaust passage, the catalyst being housed in a catalyst casing arranged in the exhaust passage, the device comprising: heating means which is able to heat the catalyst; pressure reducing means which is able to reduce the pressure in the catalyst casing; and reactivating means for controlling the heating means and the pressure reducing means to heat the catalyst and reduce the pressure in the catalyst casing to reactivate the catalyst.
The present invention may be more fully understood from the description of the preferred embodiments of the invention as set forth below, together with the accompanying drawings.


REFERENCES:
patent: 5201802 (1993-04-01), Hirota et al.
patent: 5271906 (1993-12-01), Yuuki et al.
patent: 5331809 (1994-07-01), Takeshima et al.
patent: 5724808 (1998-03-01), Ito et al.
patent: 5934072 (1999-08-01), Hirota et al.
patent: 5953907 (1999-09-01), Kato et al.
patent: 5-288042 (1993-11-01), None
patent: 6-200737 (1994-07-01), None

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