Exhaust Emission Control Device For Internal Combustion Engines

Abstract

An exhaust emission control device comprising an inner core for causing unburned and nozious contained in exhaust gas from the internal combustion engine to undergo an oxidation reaction therein to convert to the innoxious gas, inlet tubes connected at one end thereof to said exhaust ports of the internal combustion engine and at the other end thereof to the cylindrical wall of the inner core tangentially with respect thereto so as to indroduce exhaust gas from the exhaust valve into the inner core, and exhaust gas outlet ports from inner core formed at opposite end walls concentrically in inner core and axially spaced apart from each other.

Description

This invention relates to exhaust emission control devices for internal combustion engines in general. More particularly, it is concerned with an exhaust emission control device of the type generally referred to as an exhaust manifold reactor which is effective on the exhaust emission by causing unburned gas components of exhaust gas to undergo an oxidation reaction.

A main object of this invention is to provide an exhaust emission control device for internal combustion engines which receives exhaust gas which contains unburned gas components so as to prevent such exhaust gas from mixing with exhaust gas that has undergone a reaction, which permits utilization of the space in the reaction chamber effectively, which provides sufficient residence time in the reaction chamber for oxidation reaction, and which can prevent a marked rise in reaction temperature locally in the reaction chamber.

Another object is to provide a device of the type described which can be produced easily.

Known types of manifold reactors are operative to introduce exhaust gas into a reaction chamber or an inner core in such a manner that the exhaust gas blows on the inner core wall, so that the kinetic energy of exhaust gas is suddenly converted into thermal energy. The devices of this type have a disadvantage that exhaust gas which has not undergone an oxidation reaction yet is mixed in the reaction chamber with exhaust gas which has already undergone an oxidation reaction. These phenomena prevent the effective utilization of the space in the reaction chamber for an oxidation reaction of exhaust gas. Besides, the unburned exhaust gas flows out from the manifold reactor before sufficient reaction. Another disadvantage of the above mentioned reactor is that mixing the exhaust gas with the air is not uniform in the reaction chamber, so that the temperature rise in the reactor goes locally and the device gets readily damaged.

To the accomplishment of the foregoing and related ends, this invention provides the features that inlet tubes for exhaust gas from the exhaust valve open tangentially with respect to the cylindrical reaction chamber and outlet ports are formed on opposite end of the reaction chamber. There is also provided the feature that a perforated tube of small diameter or a plurality of tubes of small length concentric with the cylindrical reaction chamber are mounted therein to extend between the opposite ends thereof or inwardly from the opposite ends, so as to permit exhaust gas that has undergone an oxidation reaction to be vented through this tube or tubes whereby the objects of the invention can be accomplished positively.

Additional objects as well as features and advantages of this invention will become evident from the description set forth hereinafter when considered in conjunction with the accompanying drawing, in which:

FIG. 1 is a longitudinal sectional view of the device comprising one embodiment of this invention;

FIG. 2 is a view in section taken along the line II--II of FIG. 1; and

FIGS. 3 and 4 are longitudinal sectional views of the device comprising other embodiments of this invention.

Embodiments of the invention will now be described. FIG. 1 illustrates one embodiment of the device according to this invention. The exhaust emission control device or manifold reactor 1 is retained to the cylinder head by a flange 2. The manifold reactor 1 comprises an outer shell formed in a plurality of layers including an outer plate 3, heat insulator 4 and inner plate of high temperature alloy 5, and a reaction chamber or inner core 7 enclosed by a radiation shield 6 and disposed in the outer shell. Spacers 12 are interposed between the inner core 7 and radiation shield 6 so as to maintain a small clearance between them.

The inner core 7 is connected to an exhaust port of the internal combustion engine through exhaust gas inlet tube 8 which are connected such that they open tangentially with respect to the inner core 7 as shown in FIG. 2. Outlet ports 9 are formed on opposite end walls of the inner core 7 in the central portion thereof.

An exhaust passage 10 is provided between the radiation shield 6 and the inner plate of the outer shell 5. The exhaust passage 10 is maintained in communication with the interior of the inner core 7 through the outlet ports 9. Formed in the peripheral wall of the reactor main body is an outlet pipe 11 which is connected to an exhaust pipe provided with a muffler.

Exhaust gas discharged from a combustion chamber of the internal combustion engine is mixed with air delivered under pressure by an air pump and this exhaust gas is introduced through the inlet tube 8 into the inner core 7. The exhaust gas introduced into the inner core 7 moves in currents along the inner peripheral surface of the inner core 7 in the direction of the arrow and gradually moves nearer to the central portion of the inner core.

During its movement along the inner peripheral wall of the inner core 7, the exhaust gas gets a large quantity of thermal energy from the heated inner wall of the inner core 7 and from the gas that has undergone an oxidation reaction already, so that unburned components of the exhaust gas undergo an oxidation reaction. This reaction is completed before the mixture of exhaust gas and air reaches the central portion of the inner core, and then exhaust gas that has been burned perfectly flows out from the outlet ports 9 into the exhaust passage 10, and discharged through the outlet pipe 11 out of the manifold reactor 1.

During the aforementioned oxidation operation, the mixture of exhaust gas and air introduced into the inner core 7 moves in currents along the inner peripheral surface of the inner core and reaches nearer to the central portion of the inner core. When it reaches the central portion, it is diffused axially of the inner core. According to the present invention, the gas current in the inner core is unidirectional, so that exhaust gas that has undergone an oxidation reaction is prevented from mixing with exhaust gas containing unburned components. It will be appreciated that this invention ensures that the space in the inner core is effectively utilized to permit exhaust gas to undergo an oxidation reaction. The reaction time corresponds to the residence time in the inner core. The smaller ratio of the diameter of outlet ports 9 to the inside diameter of inner core 7 results in the longer reaction time.

FIG. 3 shows a second embodiment of this invention. A tube 18 which has a lot of small openings 19 in its wall is mounted concentrically in the inner core and disposed between the outlet ports 15 and 16 made in the central portion of opposite end walls 13 and 14 respectively of the inner core 17, so that exhaust gas which moves nearer to the center of the inner core 17 after oxidation reaction can be discharged from the inner core through the small openings 19, outlet ports 15 and 16 to the exhaust passage 10. The provision of the perforated tube 18 permits the uniform discharge of exhaust gas from the inner core 17 along its full length. That is, the gas that has undergone a reaction concentrated in the central portion of the inner core 17 can be discharged uniformly from the inner core through the perforated tube.

FIG. 4 shows, in a longitudinal sectional view, a left half portion of a third embodiment of this invention. A short tube 22 is disposed concentrically with the inner core, and attached to each of the outlet ports made in the central portion of opposite end walls 20 of the inner core 27 and extended inwardly thereinto. The provision of such short tubes facilitates discharge of reacted exhaust gas from the central portion of the inner core in which temperature is maximized, thereby preventing local concentration of reaction heat.

Further, in the embodiment shown in FIG. 4, the short tubes 22 provided oppositely may be made unequally in length depending on the large variation of the engine exhaust gas pressure or fix position of the exhaust pipe.

From the foregoing description, it will be appreciated that the provision of an inlet tube opening tangentially with respect to the reaction chamber according to this invention permits the mixture of exhaust gas and air which has not undergone an oxidation reaction yet to move in currents along the inner peripheral surface of the reaction chamber without mixing with exhaust gas which has undergone an oxidation reaction and to gradually move nearer to the central portion of the reaction chamber. This permits effective utilization of the space in the reaction chamber so that exhaust gas may get sufficient residence time for reaction. At the same time, the exhaust gas is exposed to the heat of inner wall of the reaction chamber of elevated temperature and to the heat of exhaust gas undergoing an oxidation reaction, thereby increasing the efficiency of purifying exhaust gas.

The provision of a perforated tube or a plurality of short tubes mounted in the reaction chamber concentrically therewith according to this invention is effective to prevent local concentration of reaction temperature and a rise in temperature locally because exhaust gas that has undergone an oxidation reaction is discharged directly from the central portion of the reaction chamber.

The aforementioned results can be achieved by simply altering the position of the exhaust gas inlet tubes and the position of the outlet ports in conventional devices. The change in positions can also be effected readily.

Claims

What is claimed is:

1. An exhaust emission control device for use with an internal combustion engine, comprising a housing, an inner core means disposed in said housing, inlet pipe means carrying exnaust gas from said internal combustion engine to said inner core means, said inner core means having a generally cylindrical configuration, said inlet pipe means being tangentially disposed relative to said inner core means, outlets on the longitudinal ends of said inner core means, said outlets being disposed at a radially central location spaced from the outer peripheral boundary of said inner core means, said inner core means being disposed in said housing to form an annular space between the outer surface of said inner core means and the inside of said housing, and exhaust means on said housing, whereby gas entering said inner core means through said tangentially disposed inlet pipe means undergoes an oxidation reaction in said inner core means in passing radially inwardly for exit through said outlets on said inner core means, said gas thereafter passing through said annular space and thence through said exhaust means in said housing.

2. An exhaust emission control device according to claim 1, further comprising a tube coaxially disposed in said inner core means and extending between said two outlets, said tube having means defining a plurality of openings whereby exhaust gases having undergone an oxidation reaction in said inner core means pass from said inner core means through said openings in said tube and thence through said two outlets.

3. An exhaust emission control device according to claim 1 further comprising a tube coaxially disposed in said inner core means and connected to each of said outlets, each of said tubes having an outer diameter smaller than the inner diameter of said inner core means and having a longitudinal length less than one-half the longitudinal length of said inner core means, said pair of tubes receiving the gas in said inner core means which has undergone an oxidation reaction whereby such gas passes from said two tubes to the annular space between the outer surface of said inner core means and the inside surface of said housing.

4. An exhaust emission control device according to claim 1 wherein said inner core means comprises an inner core cylinder and a cylindrical radiation shield concentrically spaced about said inner cylinder, and spacer means disposed between said inner core cylinder and said radiation shield for maintaining said concentric spacing.

5. An exhaust emission control device according to claim 1 wherein said exhaust means is generally, centrally disposed relative to the longitudinal length of said housing.