Exhaust gas purification system of internal combustion engine

Details Exhaust gas purification system of internal combustion engine Exhaust gas purification system of internal combustion engine

2000-02-07

2001-09-11

Denion, Thomas (Department: 3748)

Power plants

Internal combustion engine with treatment or handling of...

By means producing a chemical reaction of a component of the...

C060S286000, C060S289000

Reexamination Certificate

active

06286306

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an exhaust gas purification system of an internal combustion engine having a catalyst or an adsorbent stored in a bypass exhaust gas passage (branched from the exhaust pipe and opened/closed by a switch-over valve) which adsorbs unburned components such as hydrocarbons (HC) of the exhaust gas generated by the engine to enhance exhaust gas purification. More particularly it relates to a system for controlling the operation of opening the switch-over valve at high engine speeds and loads to reduce noise and to introduce heated exhaust gas to burn cloggy material, such as soot away from the adsorbent, to prevent the adsorbent from deteriorating and regenerating the same.
2. Description of the Related Art
Internal combustion engines are ordinarily provided with a catalyst (a three-way catalytic converter) in the exhaust system which removes HC, NOx and CO components in the exhaust gas generated by the engine. However, when the engine is cold started, for example, and the catalyst is not activated, unburned components of the exhaust gas, in particular, unburned hydrocarbons (HC) are immediately released into the atmosphere. An exhaust gas purification system is therefore proposed, in which the exhaust pipe is branched out at a location downstream of the catalyst and the bypass exhaust gas passage is provided with a lightoff catalyst with an electric heater (for speedily activating the catalyst) or an adsorbent (a kind of catalyst made of a zeolite material or some similar materials) which adsorbs unburned components such as the HC content when the catalyst is not activated and desorbs the same to be recirculated into the engine intake system and burned again in the combustion chambers after the catalyst has been activated. A switch-over valve is provided at the branching point to regulate the introduction of exhaust gas into the bypass exhaust gas passage.
When the exhaust system is configured to have such a bypass exhaust gas passage branching from the exhaust pipe, the switch-over valve may sometimes chatter due to the pulsation of exhaust gas pressure and makes noise.
In order to solve this problem, Japanese Laid-Open Patent Application No. Hei 9 (1997)-72, 210 proposes a switch-over valve installed at the branching point of the exhaust pipe in such manner that, the disc of the valve is faced, at one surface, to the exhaust pipe through a first opening (exhaust pipe inner wall defining the main exhaust gas passage), and is faced, at the other surface, to the bypass exhaust gas passage through a second opening. In this prior art, the area of the second opening is configured to be smaller than that of the first opening in such a way that the difference between the pressures acting on the valve discs becomes less, thereby suppressing the valve disc chattering and hence, reducing noise due to the chattering.
However, this prior art is disadvantageous, in that it requires a complicated valve structure design to suppress the chattering.
Moreover, in this kind of internal combustion engine having the main exhaust gas passage and bypass exhaust gas passage, opening/closing of the intake and exhaust valves generates a pulsatory sound which may sometimes be amplified by the resonance in the main exhaust gas passage and the bypass exhaust gas passage. However, the aforesaid prior art does not cope with the reduction of this kind of noise.
SUMMARY OF THE INVENTION
The first object of this invention is therefore to provide an internal combustion engine having a bypass exhaust gas passage branched from the exhaust pipe defining a main exhaust gas passage and a switch-over valve for opening/closing the bypass exhaust gas passage, which reduces noise due to the chattering of the switch-over valve and the resonance of the pulsatory sound generated by the opening/closing of the intake and exhaust valves.
Further, when the engine is provided with an exhaust gas purification system having an adsorbent installed at the bypass exhaust gas passage which adsorbs the unburned component such as the unburned HC component of the exhaust gas at the time of the engine starting, since the operation of the exhaust gas purification system is conducted by operating the switch-over valve, this would cause an interference between the operation of the switch-over valve for noise reduction. Therefore, it becomes necessary to avoid any interferences between the operation of the switch-over valve for exhaust gas purification and that for noise reduction.
The second object of this invention is therefore to provide an exhaust gas purification system of an internal combustion engine having an adsorbent, which adsorbs unburned components of the exhaust gas generated by the engine, installed at a bypass exhaust gas passage branched from the exhaust pipe defining a main exhaust gas passage and a switch-over valve for opening/closing the bypass exhaust gas passage, which reduces noises due to the chattering of the switch-over valve and due to the resonance of the pulsatory sound generated by the opening/closing of the intake and exhaust valves, without causing any interference with the switch-over valve operation of the exhaust gas purification.
Also, cloggy material such as soot, adheres to the adsorbent as the repetition of the exhaust gas purification increases and clogs the adsorbent. This deteriorates and degrades the performance of the adsorbent.
In view of the above, Japanese Laid-Open Patent Application No. 9 (1997)-324,621 teaches detecting the engine operating condition such as the time when the fuel supply is cut off or the air/fuel ratio is controlled to a lean value where the oxygen concentration in the exhaust gas is relatively high and introduces the exhaust gas into the bypass exhaust gas passage by operating the switch-over valve to open the passage so as to burn away the adhered cloggy material from the adsorbent and to regenerate or renew the adsorbent.
More specifically, this prior art system is configured to introduce the exhaust gas to heat and raise the temperature of the adsorbent such that the temperature rise will promote the oxygen to react with the cloggy material to burn it away from the adsorbent.
However, in order to determine the engine operating condition where the exhaust gas temperature becomes high enough to regenerate the adsorbent, the prior art system does not detect the exhaust gas temperature directly. Rather, the prior art system simply detects the engine operating conditions where the fuel cutoff is in progress or the air/fuel ratio is controlled to a lean value and conducts the adsorbent regeneration. With this, the prior art system can not always achieve the regeneration of adsorbent to a satisfactory extent.
The third object of this invention is therefore to provide an exhaust gas purification system of an internal combustion engine having an adsorbent, which adsorbs unburned components of the exhaust gas generated by the engine, installed at a bypass exhaust gas passage branched from the exhaust pipe defining a main exhaust gas passage and a switch-over valve for opening/closing the bypass exhaust gas passage, which detects the exhaust gas temperature and when the detected exhaust gas temperature is greater or equal to a predetermined temperature, introduces the exhaust gas to burn away the cloggy material from the adsorbent, thereby regenerating the adsorbent to a satisfactory extent.
This invention achieves this object by providing a system for purifying exhaust gas generated by an interal combustion engine having a bypass exhaust gas passage branching from an exhaust pipe and is opened or closed by a switch-over valve, and at least one of a catalyst and an adsorbent which adsorbs unburned components in the exhaust gas installed at the bypass exhaust passage, comprising: engine operating condition detecting means for detecting operating conditions of the engine including at least engine speed and engine load; high engine speed and load region determining means for comparing the detected engine spe

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