Gas separation – With separating media bypass or system gas pressure relief
Reexamination Certificate
2002-09-18
2004-07-27
Hopkins, Robert A. (Department: 1724)
Gas separation
With separating media bypass or system gas pressure relief
C055S343000, C055S418000, C055S482000, C055S484000, C055SDIG003
Reexamination Certificate
active
06767378
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an exhaust gas purifying system for an internal combustion engine and, more particularly, to an exhaust gas purifying system provided in an exhaust passage of the internal combustion engine to purify exhaust gas.
2. Description of Related Art
Conventionally, it is known that an exhaust gas purifying system is provided in an exhaust passage of an internal combustion engine to collect particulates (particulate substances) in exhaust gas emitted from the internal combustion engine such as a diesel engine or to reduce NOx content.
As an exhaust gas purifying system for collecting particulates, a system provided with an exhaust emission after-treatment device consisting of a diesel particulate filter (hereinafter referred to as a DPF) has been developed.
As an exhaust gas purifying system for reducing NOx content, a system provided with an exhaust emission after-treatment device consisting of a NOx reduction catalyst (DeNOx catalyst) or a NOx occlusion reduction catalyst has been developed.
In both cases, the exhaust emission after-treatment device of the exhaust gas purifying system uses, for example, a columnar carrier (core) formed of a ceramic material such as cordulite and silicon carbide or a metal. This carrier has a construction such that a large number of small holes are formed in the axial direction in a honeycomb shape.
In the exhaust emission after-treatment device provided with the DPF, the carrier has a function as a filter. Specifically, exhaust gas flows into the carrier from one end face of the carrier, passing through a porous wall (boundary wall) separating the small holes, and flows out of the other end face. When the exhaust gas passes through the wall, particulates in the exhaust gas are collected.
Also, in the exhaust emission after-treatment device provided with the NOx reduction catalyst or the NOx occlusion reduction catalyst, various types of catalysts have been carried in advance in the carrier, and NOx is reduced during the time when exhaust gas flows in the carrier.
Such a carrier has many limitations in manufacturing, so that it is difficult to manufacture a carrier having a remarkably large cross-sectional shape. Therefore, the capacity of the whole carrier must be increased. That is, in order to increase the collecting efficiency of the DPF or to increase the reducing efficiency of the catalyst, a plurality of carriers must be arranged in parallel to increase the capacity of the whole carrier.
However, if a plurality of carriers are arranged in parallel, the cross-sectional area of the whole carrier increases, so that a large space for arranging the carriers must be secured in an engine room, which presents a problem of hindering the downsizing of equipment.
To solve this problem, a system as described below can be thought. In this system, a pair of carriers are arranged in series with a clearance provided therebetween, and exhaust gas is caused to flow into between the carriers, by which a half of the exhaust gas is caused to flow into one carrier and the remaining half of the exhaust gas is caused to flow in the reverse direction so as to flow into the other carrier. Thereby, the capacity of the whole carrier can be doubled without arranging a pair of carriers in parallel.
In this system, however, although a large cross-sectional area is restrained, the flow direction of exhaust gas in each of the carriers is reverse, so that two outlet pipes are needed, and some consideration is still needed for the arrangement space. Therefore, there still remains a problem to be solved.
SUMMARY OF THE INVENTION
The main object of the present invention is to provide an exhaust gas purifying system for an internal combustion engine in which the inherent function can be improved by increasing the capacity of the whole of carriers and a large installation space is made unnecessary.
The present invention provides an exhaust gas purifying system for an internal combustion engine, which is provided in an exhaust flow path of the internal combustion engine, including a plurality of carriers for exhaust emission after-treatment arranged in series along the flow direction of exhaust gas; a distribution flow path for distributing exhaust gas to each of the carriers to cause the exhaust gas to flow in the carrier; and a combined flow chamber in which the exhaust gases having passed through the distribution flow paths are combined.
In the above-described exhaust gas purifying system, although the carriers are arranged in series, the exhaust gas passing through a different distribution flow path flows in each of the carriers. Therefore, the capacity of the whole of the carriers increases substantially a plurality of times as in the case of the carriers arranged in parallel, so that the inherent function as an exhaust gas purifying system is improved.
Also, since the exhaust gases having passed through the distribution flow paths are combined in the combined flow chamber, only one outlet pipe communicating with the combined flow chamber has only to be provided. Therefore, an increase in cross-sectional area is restrained because the carriers are arranged in series, and a large installation space is unnecessary because the number of outlet pipes need not be increased.
The present invention provides an exhaust gas purifying system for an internal combustion engine, which is provided in an exhaust flow path of the internal combustion engine, including a plurality of carriers for exhaust emission after-treatment arranged in series along the flow direction of exhaust gas; and a distribution flow path for distributing exhaust gas to each of the carriers to cause the exhaust gas to flow in the carrier; the flow direction of the exhaust gas being set in one direction.
In the above-described exhaust gas purifying system, as in the case of the before-mentioned construction, the capacity of the whole of the carriers increases substantially a plurality of times as in the case of the carriers arranged in parallel, so that the inherent function as an exhaust gas purifying system is improved.
Also, since the flow direction of the exhaust gas flowing in each of the carriers is the same, the exhaust gases having passed through the distribution flow paths are combined easily at one place, so that only one outlet pipe has only to be provided in this combined flow portion. In this case as well, therefore, an increase in cross-sectional area is restrained because the carriers are arranged in series, and a large installation space is unnecessary because the number of outlet pipes need not be increased.
In the present invention, it is preferable that two of the carriers be arranged in series on the upstream side and the downstream side; a bypass flow path be provided on a concentric circle of each of the carriers; between the carriers, there be provided a split flow portion provided with an outlet space in which the exhaust gas having passed through the upstream-side carrier flows, an inlet space in which the exhaust gas to be caused to flow in the downstream-side carrier flows, and a wall portion for partitioning the spaces; a first distribution flow path for the upstream-side carrier be formed so as to include the outlet space of the split flow portion and the downstream-side bypass flow path communicating with the outlet space; and a second distribution flow path for the downstream-side carrier be formed so as to include the upstream-side bypass flow path and the inlet space of the split flow portion communicating with the upstream-side bypass flow path.
According to the above-described exhaust gas purifying system, since two carriers are provided, the capacity is substantially doubled as compared with the case where one carrier is provided.
Further, since the bypass flow path of the first and second distribution flow paths for each carrier is provided on a concentric circle of the carrier, the cross section thereof is formed so as to be annular, fan-shaped, or cylindrical, so that there is no fear of extreme
Emori Nobuhiko
Nishiyama Toshihiko
Wakamoto Koutarou
Hopkins Robert A.
Komatsu Ltd.
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