Exhaust emission control device

Abstract

An exhaust emission control device includes an adsorbent trapper having an adsorbent for adsorbing and desorbing hydrocarbon in exhaust gas, a catalytic converter, a main exhaust gas passage with a first valve, a bypass exhaust gas passage with a second valve and a control unit. The bypass exhaust gas passage bypassing the first valve is connected with the adsorbent. The control unit controls the first and second valves to desorb the hydrocarbon from the adsorbent when a condition is satisfied. The condition is that the catalyst converter is in active, an oxygen adsorption amount of the catalyst converter is not less than a first predetermined amount and an exhaust gas amount is not more than a second predetermined amount. The first valve is opened and the second valve is closed when the condition is not satisfied during desorption of the hydrocarbon from the adsorbent.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The present invention relates to an exhaust emission control device that controls exhaust emission discharged from an internal combustion engine.[0003]2. Description of the Related Art[0004]A conventional exhaust emission control device of this kind is disclosed in Japanese Patent Application Laid-Open Publication NO. 06-229235. This conventional exhaust emission control device has a main exhaust gas passage and a bypass exhaust gas passage that are arranged in parallel to each other at an upstream side of an exhaust emission control catalytic converter. The bypass exhaust gas passage is provided with an adsorbent that can adsorb hydrocarbon (HC) contained in an exhaust gas at a low temperature and desorb the HC adsorbed thereon at a high temperature. The conventional exhaust emission control device further has a valve for opening and closing the bypass exhaust gas passage. The valve is controlled by a control unit acco...

AI Technical Summary

Benefits of technology

[0008]According to a first aspect of the present invention there is provided an exhaust emission control device including an adsorbent trapper, a catalytic converter, a main exhaust gas passage, a first valve, a bypass exhaust gas passage, a second valve and a control unit. The adsorbent trapper has an adsorbent that can adsorb hydrocarbon in exhaust gas discharged from an internal combustion engine on the adsorbent a low temperature thereof and desorb the hydrocarbon from the adsorbent at a high temperature thereof. The catalytic converter is arranged at a downstream side of the adsorbent trapper and has catalyst for purifying the exhaust gas. The main exhaust gas passage is arranged between the internal combustion engine and the catalytic converter so that the main exhaust passage can flow the exhaust gas discharged from the internal combustion engine to the catalytic converter. The first valve is arranged in the main exhaust gas passage and it is capable of opening and closing to flow the exhaust gas through the main exhaust gas passage and shut the main exhaust gas passage. The bypass exhaust gas passage has an upstream portion connected with an upstream portion of the main exhaust gas passage to bypass the first valve and have the adsorbent trapper in the bypass exhaust gas trapper. The second valve is arranged in the bypass exhaust gas passage and it is capable of opening and closing to flow the exhaust gas through the bypass exhaust gas passage and shut the bypass exhaust gas passage. The control unit controls the first valve and the second valve to open so that the exhaust gas flow through the main exhaust gas passage and the bypass exhaust gas passage so as to desorb the hydrocarbon from the adsorbent when a condition is satisfied, where the condition is that the catalyst converter is in active, an oxygen adsorption amount of the catalyst converter is not less than a first predetermined amount and an exhaust gas amount is not more than a second predetermined amount, while the control unit controls the first valve to open and the second valve to close when the condition is not satisfied during desorption of the hydrocarbon from the adsorbent.

[0009]According to a second aspect of the present invention there is provided an exhaus...

Problems solved by technology

However, in the above known conventional exhaust emission control device, there are a problem in that the purification performance of the catalytic converter is deteriorated due to lack of the oxygen adsorption amount of the catalytic converter because a large amount of the HC adsorbed on the adsorbent rapidly desorbs from the adsorbent when the exhaust gas flows into the bypass exhaust gas passage when the valve is controlled to open to flow the exhaust gas through the bypass exhaust gas passage.

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