Power plants – Internal combustion engine with treatment or handling of... – By means producing a chemical reaction of a component of the...
Reexamination Certificate
2002-01-31
2004-11-23
Nguyen, Tu M. (Department: 3748)
Power plants
Internal combustion engine with treatment or handling of...
By means producing a chemical reaction of a component of the...
C060S297000, C060S324000
Reexamination Certificate
active
06820416
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an exhaust emission control system of an internal combustion engine for cleaning exhaust gases discharged from the internal combustion engine by adsorbing unburned constituents included in the exhaust gases with an adsorbent material.
2. Description of the Related Art
An exhaust emission control system disclosed in Japanese Patent Unexamined Application Hei. 9-324621 is known as a conventional exhaust emission control system of this type. This exhaust emission control system has an adsorbing device for adsorbing hydrocarbons which are unburned constituents. This adsorbing device is disposed downstream of a three-way catalyst in an exhaust pipe, and provided in the adsorbing device are two exhaust passages which branch from each other in the vicinity of an entrance and join together in the vicinity of an exit of the adsorbing device. An adsorbent material is provided in one of the exhaust passages (hereinafter, referred to as an “adsorbent material side passage”) which is adapted to adsorb hydrocarbons and to release the hydrocarbons so adsorbed thereto as temperature increases. Additionally, a switchable recirculation pipe for recirculating part of exhaust gas to an induction side of an engine is connected to the adsorbent material side passage downstream of the adsorbent material. Furthermore, a switching valve is provided where the adsorbent material side passage and the other exhaust passage (hereinafter, referred to as “the other passage”) join together which is adapted to open one of the exhaust passages while closing the other thereof. This switching valve is driven to open the adsorbent material side passage when a vacuum is provided which is generated when the engine is in operation.
The switching valve of the adsorbing device keeps the other passage open before the engine is started. The switching valve is controlled to open the adsorbent material side passage once the engine is started, whereby exhaust gases which have not been cleaned by the three-way catalyst which has not yet been activated are allowed to flow into the adsorbent material side passage, and hydrocarbons included in the exhaust gases are adsorbed by the adsorbent material. The exhaust gases so cleaned by adsorbing the hydrocarbons to the adsorbent material are then discharged to the outside via an exhaust pipe connected to the exit of the adsorbing device.
Thereafter, when the three-way catalyst is activated, the switching valve then opens the other passage. As this occurs, the recirculation pipe connected to the adsorbent material side passage is also opened, whereby most of the exhaust gases which have been cleaned by the three-way catalyst are allowed to flow through the other passage for discharge to the outside, whereas part of the exhaust gases flows through the adsorbent material side passage. Then, when the adsorbent material is heated by the exhaust gases which flow through the adsorbent material side passage the hydrocarbons which are now adsorbed to the adsorbent material are then released from the adsorbent material for recirculation to the induction side of the engine via the recirculation pipe. Thereafter, when the hydrocarbons have been completely released from the adsorbent material the recirculation pipe is closed, whereby exhaust gases are then allowed to flow through only the other passage to be discharged to the outside.
Additionally, in this exhaust emission control system, the switching valve is controlled as follows in order to remove from the adsorbent material deposits such as soot which are deposited to the adsorbent material while hydrocarbons are adsorbed and/or released. Namely, the switching valve is controlled to open the adsorbent material side passage when a fuel cut is executed while the engine is in operation or when the engine is in deceleration with the air-fuel ratio of exhaust gas being in lean conditions even while fuel is being supplied, whereby exhaust gases containing therein much oxygen are allowed to flow into the adsorbent material side passage so as to promote the combustion of deposits deposited in the adsorbent material to thereby remove the deposits from the adsorbent material. Thus, the recovery of the adsorbing performance of the adsorbent material and improvement of the durability thereof are attempted to be attained by removing the deposits from the adsorbent material.
As has been described above, in the conventional exhaust emission control system, the special control is required that the switching valve is driven when the predetermined conditions are established such as the fuel cut while the engine is in operation in order to remove the deposits from the adsorbent material. Moreover, since the driving of the switching valve occurs frequently while the engine is in operation, the durability of the switching vale and hence the exhaust emission control system becomes deteriorated. In addition, since the switching valve is driven by a vacuum generated by the operation of the engine, it is not possible to drive the switching valve which closes the adsorbent material side passage before the engine is started. To cope with this, in order for exhaust gases initially generated when the engine is started to be allowed to flow into the adsorbent material side passage, the switching valve needs to be controlled to be operated by estimating timing at which the switching valve is driven from the layout of the adsorbing device.
SUMMARY OF THE INVENTION
It is an object of the invention to provide an exhaust emission control system which can ensure that deposits in an adsorbent material are removed and also can improve the durability thereof without implementing any special control for switching a flow path of exhaust gases.
According to an aspect of the invention, there is provided an exhaust emission control system for an internal combustion engine provided along an exhaust system
2
having a main exhaust passage
13
connected to an internal combustion engine
1
and a bypass exhaust passage
14
which branches off and joins back to the main exhaust passage
13
for cleaning exhaust gases discharged from the internal combustion engine, the exhaust emission control system comprising
5
a switching device (an exhaust passage switching device
9
in an embodiment (hereinafter, referred to as the same when discussions are made as to the aspect of the invention)) for switching an exhaust gas flow path to either of the main exhaust passage and the bypass exhaust passage, an adsorbent material of zeolite (an HC adsorbent material
16
) disposed within the main exhaust passage for adsorbing unburned constituents present in exhaust gases introduced into the main exhaust passage and releasing the unburned constituents so adsorbed as temperature increases, and a control device (an ECU
21
) for controlling the switching device such that the exhaust gas flow path is switched to the main exhaust passage when the unburned constituents in the exhaust gases are allowed to be adsorbed by the adsorbent material, that the exhaust gas flow path is switched to the bypass exhaust passage when the unburned constituents so adsorbed by the adsorbent material are allowed to be released from said adsorbent material, and that the exhaust gas flow path is switched to the main exhaust passage when the release of the unburned constituents from the adsorbent material is completed.
According to the construction, the switching device is controlled such that the exhaust gas flow path is switched to the main exhaust passage when the unburned constituents in the exhaust gases are allowed to be adsorbed by the adsorbent material disposed within the main exhaust passage, that the exhaust gas flow path is switched to the bypass exhaust passage when the unburned constituents so adsorbed by the adsorbent material are allowed to be released from the adsorbent material, and that the exhaust gas flow path is switched to the main exhaust passage when the release of the unburned constituents from the adsorbent mater
Machida Kei
Takakura Shiro
Ueno Masaki
Arent & Fox PLLC
Honda Giken Kogyo Kabushiki Kaisha
Nguyen Tu M.
LandOfFree
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