Exhaust gas purifying apparatus

Abstract

A throttle unit placed in an exhaust gas passage controls an opening-ratio of each of first and second valve members to control a gas-flow sectional area of the exhaust gas passage. When the temperature of a three-way catalyst is low, the throttle unit introduces the exhaust gas flow into a part of an outer-periphery of the three-way catalyst. This control can rapidly increase the temperature of the three-way catalyst from an early period of starting an internal combustion engine within a short period of time. The throttle unit increases the gas-flow sectional area of the exhaust gas passage according to increasing the temperature of the three-way catalyst. When the three-way catalyst reaches its activation temperature, the throttle unit instructs the first and second valve members to fully open. This decreases a pressure loss of the exhaust gas because the exhaust gas is supplied into the entire of the three-way catalyst.

Description

CROSS-REFERENCE TO RELATED APPLICATION[0001]This application is related to and claims priority from Japanese Patent Application No. 2008-8305 filed on Jan. 17, 2008, the contents of which are hereby incorporated by reference.BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]The present invention relates to an exhaust gas purifying apparatus using a catalyst such as a three way catalyst capable of purifying an exhaust gas emitted from an internal combustion engine such as a diesel engine under a low temperature of the catalyst in the early period of starting the internal combustion engine.[0004]2. Description of the Related Art[0005]Internal combustion engines such as diesel engines and gasoline engines include a problem of increasing the amount of specified materials such as hydro carbon (HC), carbon monoxide (CO), and nitrogen oxide (NOx) contained in an exhaust gas emitted from such an internal combustion engine mounted to a vehicle when the temperature of catalyst p...

AI Technical Summary

Benefits of technology

[0008]It is an object of the present invention to provide an exhaust gas purifying apparatus capable of rapidly increasing the temperature of a catalyst placed therein for a short period of time without increasing the pressure loss of an exhaust gas and without increasing the size of the exhaust gas purifying apparatus. The catalyst such as a three way catalyst placed in the exhaust gas purifying apparatus according to the present invention is capable of capturing specified materials such as hydro carbon (HC), carbon monoxide (CO), and nitrogen oxide (NOx) contained in an exhaust gas emitted from an internal combustion engine such as a diesel engine and a gasoline engine. The purified exhaust gas containing a smaller amount of those specified materials is then discharged from the exhaust gas purifying apparatus to outside.

[0010]When observed from the flowing direction of the exhaust gas in the exhaust gas passage formed in the exhaust gas pipe, the throttle unit is placed on at least one of the upstream side and the downstream side thereof. The throttle unit locally introduces the exhaust gas into a part of the catalyst placed in the catalyst unit when the temperature of the catalyst is lower than its activation temperature. That structure allows the exhaust gas emitted from an internal combustion engine to be introduced into the part of the catalyst when the temperature of the catalyst is low, namely, in the early period of starting the internal combustion engine. This allows the temperature of the part of the catalyst to locally and rapidly rise, through which the exhaust gas is concentrated in flow to the part of the catalyst such as the central part or the outer peripheral part of the catalyst. On the other hand, when the temperature of the catalyst reaches or is over its activation temperature, the throttle unit supplies the exhaust gas into the entire of the catalyst without closing the gas-flow sectional area of the exhaust gas passage. Accordingly, without causing the pressure loss of the exhaust gas and without increasing the size of the exhaust gas purifying apparatus, it is possible to rapidly increase the temperature of the catalyst such as a three way catalyst placed in the catalyst unit within a short period of time after the internal combustion engine starts or re-starts. Still further, the structure and function of the exhaust gas purifying apparatus of the present invention can efficiently eliminate specified materials, for example, hydro carbon (HC), carbon monoxide (CO), and nitrogen oxide (NOx) contained in the exhaust gas emitted from the internal combustion engine.

Problems solved by technology

Internal combustion engines such as diesel engines and gasoline engines include a problem of increasing the amount of specified materials such as hydro carbon (HC), carbon monoxide (CO), and nitrogen oxide (NOx) contained in an exhaust gas emitted from such an internal combustion engine mounted to a vehicle when the temperature of catalyst placed in an exhaust gas purifying apparatus mounted to the vehicle is low, for example, during early period of starting the internal combustion engine.

For this reason, the catalyst placed in the exhaust gas purifying apparatus does not adequately reach its optimum temperature, namely, its activation temperature to activate the function of the catalyst.

However, from the viewpoint of strength, it is in general difficult to use a usual ceramics support as the exhaust gas purifying apparatus having the low pressure-loss part formed at the central part thereof.

Still further, it is hard to concentrate the exhaust gas flow using a pressure difference between the central part and the remaining part of the exhaust gas purifying apparatus.

However, such a conventional solution will cause another problem from the viewpoint of miniaturization.

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