Chemical apparatus and process disinfecting – deodorizing – preser – Analyzer – structured indicator – or manipulative laboratory... – Means for analyzing gas sample
Reexamination Certificate
2000-05-10
2003-08-05
Warden, Jill (Department: 1743)
Chemical apparatus and process disinfecting, deodorizing, preser
Analyzer, structured indicator, or manipulative laboratory...
Means for analyzing gas sample
C422S068100, C422S083000, C073S023310, C436S139000
Reexamination Certificate
active
06602471
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an adsorption amount sensor for detecting an amount of hydrocarbons and/or an amount of water adsorbed by a zeolite of a hydrocarbon adsorber that adsorbs hydrocarbons or hydrocarbons and water in exhaust gases by using the zeolite as well as a coking sensor for an internal combustion engine, which is employed for detecting an amount of coke deposition (amount of coke or soot deposited) on inner surfaces of a pipe used in the engine.
2. Description of the Prior Art
Generally, in an exhaust system of a gasoline engine or the like, a three-way catalyst is arranged in an intermediate portion of an exhaust pipe in order to purify harmful substances (hydrocarbons, carbon monoxide and nitrogen compounds) in exhaust gases the amount of which can not be reduced sufficiently by engine modifications or EGR (exhaust gas recirculation). The three-way catalyst is heated by exhaust gasses or by using additional means, and activated at temperatures equal to or higher than a predetermined temperature (300° C., for instance), thereby purifying harmful substances flowing through the exhaust pipe by oxidation-reduction catalytic actions thereof. However, e.g. when the engine is started in a cold condition, before approximately 30 to 40 seconds have passed after the cold start of the engine, the temperature of the three-way catalyst is lower than the predetermined temperature, and the catalyst remains inactive, so that among the harmful substances, particularly hydrocarbons are emitted from the engine as they are as unburned combustible components. Therefore, in order to prevent emission of hydrocarbons into the air, there has been proposed an engine which incorporates not only the three-way catalyst but also a hydrocarbon adsorber arranged in an exhaust pipe thereof.
This hydrocarbon adsorber includes a zeolite as an adsorbent arranged therein along a direction of flow of exhaust gases. When the exhaust gases are passing through the hydrocarbon adsorber, molecules of hydrocarbons are caused to enter small pores of the zeolite, whereby hydrocarbons are adsorbed by the zeolite. Further, when the zeolite is heated by the exhaust gases to a temperature equal to or higher than a predetermined temperature (e.g. 100 to 250° C.), the zeolite desorbs hydrocarbons once adsorbed thereby. The desorbed hydrocarbons are circulated by the EGR and oxidized by the heated three-way catalyst.
As described above, in the hydrocarbon adsorber, although adsorption and desorption of hydrocarbons are repeatedly carried out by the zeolite, the amount of undesorbed hydrocarbons remaining or depositing in the zeolite by a long-term use thereof progressively increases, which results in the degradation of the zeolite, that is, a lowered adsorbing capacity of the zeolite for adsorbing hydrocarbons. If the engine is repeatedly started in such a state, an increasing amount of unadsorbed hydrocarbons is emitted into the air. Therefore, to carry out engine control for desorbing hydrocarbons (e.g. by elevating the temperature of the hydrocarbon adsorber) to cope with the degraded state of the zeolite, or to notify the driver of the degradation of the zeolite, it is required to detect an amount of hydrocarbons adsorbed by the zeolite.
Among methods of detecting the amount of hydrocarbons adsorbed by the zeolite or detecting the degradation of the zeolite, there are a method (1) using a hydrocarbon sensor, a method (2) using temperature sensors, and a method (3) based on measurement of a weight of the zeolite.
According to the method (1) using a hydrocarbon sensor, the hydrocarbon sensor is arranged at a location close to and upstream of a zeolite, and concentrations of hydrocarbons in exhaust gases flowing into the hydrocarbon adsorber are detected to thereby indirectly detect an amount of hydrocarbons adsorbed by the zeolite. According to the method (2) using temperature sensors, as proposed e.g. by Japanese Laid-Open Patent Publication (Kokai) No. 11-2115, the temperature sensors are arranged at locations upstream and downstream of the zeolite, and an amount of displacement between peaks of temperatures of the respective temperature sensors is detected, thereby detecting the degradation of the zeolite. According to the method (3) based on measurement of a weight of the zeolite, the hydrocarbon adsorber is removed from the exhaust pipe after stopping the engine, and the weight of the hydrocarbon adsorber is directly measured, whereby an amount of hydrocarbons adsorbed by the zeolite is detected based on the difference between the thus measured weight of the hydrocarbon adsorber and a weight of the same before use.
The above methods suffer from the following problems: In the method (1) using the hydrocarbon sensor, an amount of hydrocarbons adsorbed by the zeolite is indirectly detected, so that a detecting error is liable to occur with respect to an actual amount of hydrocarbons adsorbed by the zeolite. Moreover, a hydrocarbon sensor in general use has a limitation of detecting a concentration of a hydrocarbon up to approximately 100 ppm. To obtain a more accurate amount, it is required to provide a high-precision hydrocarbon sensor capable of detecting a concentration of approximately 20 ppm. However, such a high-precision hydrocarbon sensor is expensive, resulting in an increase in manufacturing costs of the whole exhaust system.
Further, in the method (2) using the temperature sensors, not the amount of hydrocarbons adsorbed by the zeolite but the degradation of the zeolite is detected, and hence it is impossible to detect an accurate amount of adsorbed hydrocarbons. In the method (3) based on measurement of a weight of the zeolite, although it is possible to accurately detect an amount of hydrocarbons adsorbed by the zeolite, as described above, it is required to remove the hydrocarbon adsorber from the exhaust pipe when the amount of adsorbed hydrocarbons is detected, which makes the detecting operation troublesome. Moreover, it is impossible to detect an amount of adsorbed hydrocarbons when the engine is in operation.
Depending on the temperature of exhaust gases, the amount of water contained in the exhaust gases is larger than the amount of hydrocarbons contained in the same. The zeolite of the hydrocarbon adsorber usually adsorbs water as well. Therefore, it is possible to detect the degradation of the zeolite by detecting the amount of water adsorbed by the zeolite. However, conventionally, similarly to the method (3), the detection of adsorbed water is carried out by measuring the weight of the zeolite. Hence, the operation for detecting the amount of adsorbed water is troublesome, and moreover it is impossible to detect an amount of adsorbed water when the engine is in operation.
In an internal combustion engine, when fuel is burned, coke or soot of the fuel contained in exhaust gases deposits on the inner wall of the exhaust pipe. When the temperature of the exhaust gases is higher than a predetermined temperature, the coke or soot is burned by the heat of the exhaust gases. However, when the temperature of exhaust gases is low, e.g. immediately after a cold start of the engine, the coke is not burned, and deposits on the inner wall of the exhaust pipe. If the engine is repeatedly started in such a condition, the coke deposits on a three-way catalyst arranged in the exhaust pipe to cause degradation of the performance of the three-way catalyst or increase the flow resistance of the exhaust pipe and the three-way catalyst to exhaust gases. Further, when a hydrocarbon adsorber is arranged in the exhaust pipe, for adsorbing unburned hydrocarbons contained in the exhaust gases, the coke can clog small pores of zeolite of the hydrocarbon adsorber used therein as an adsorbent, to cause degraded performance of the hydrocarbon adsorber. Therefore, to carry out engine control such that the temperature of the hydrocarbon adsorber is elevated to cause the deposited coke to burn, or indirectly determine the degree of degradation of the performance of
Endo Tetsuo
Haga Takashi
Iwaki Yoshihisa
Sato Masahiro
Ueno Masaki
Arent Fox Kinter Plotkin & Kahn
Honda Giken Kogyo Kabushiki Kaisha
Sines Brian
Warden Jill
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