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Further improved reversing flow catalytic converter for internal combustion enginesRelated Patent Categories: Power Plants, Internal Combustion Engine With Treatment Or Handling Of Exhaust Gas, Methods, Anti-pollutionFurther improved reversing flow catalytic converter for internal combustion engines description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20060283173, Further improved reversing flow catalytic converter for internal combustion engines. Brief Patent Description - Full Patent Description - Patent Application Claims
[0001] The present invention relates to catalytic converters for internal combustion engines, and in particular, to a further improved reversing flow catalytic converter over that disclosed in U.S. patent application Ser. No. 11/218,608 filed Aug. 29, 2005 in the name of some of the inventors herein for treating exhaust gases from internal combustion engines. BACKGROUND OF THE INVENTION [0002] A problem relating to catalytic converters for internal combustion engines, such as the prior art reversing flow catalytic converter for internal combustion engines disclosed in U.S. Pat. No. 6,148,613, is overheating Lean burn combustion systems for fuel-efficient vehicles are particularly hard on exhaust after-treatment systems because excessive oxygen is always present in the exhaust. For example, the exhaust of diesel dual fuel (DDF) engines, which is one type of diesel engine, normally contains more than 5% volumetric oxygen after combustion. Under partial load the surplus of oxygen in the exhaust may be higher than 10% by volume. Under such circumstances, any engine management problems that result in excessive fuel in the exhaust, will generally damage exhaust after-treatment system due to overheating. [0003] If a fuel management problem occurs, a large amount of the excess fuel delivered to the engine can pass through it and into the engine exhaust. That fuel will burn inside the catalyst if sufficient oxygen is available and the catalyst has reached catalytic temperature. For example, the complete burning of 2% of methane in the exhaust, can raise the temperature of exhaust gases by about 420.degree. C., in addition to the 600.degree. C. temperature of the exhaust as it is ejected from the engine. Consequently, the rate of temperature rise in the catalyst can reach 20 to 30.degree. C./second, if the monoliths are metallic. Besides the catalytic burning of methane, any combustible matter such as soot accumulated on the catalyst surface, will also be rapidly oxidized under such high temperatures. The burning of accumulated soot will escalate and prolong the temperature rise. The thermal wave oscillation produced by the reverse flow process will also expedite the rise of the peak temperature of the catalyst substrate. Once the catalyst temperature reaches 1200.degree. C., a metallic substrate will begin to soften and subsequently lose mechanical strength. Further temperature rise will cause collapse of the substrate and eventual melt-down will occur when it is heated to 1400-1450.degree. C. A detrimental uncontrolled temperature rise can damage a catalyst in less than 20 seconds. [0004] In the prior art, when a catalyst protection mode is required for a gasoline engine, an extremely rich fuel/air mixture is delivered to the engine. Since all oxygen is basically consumed inside the engine during the over-rich combustion process, the engine exhaust contains no oxygen. The large amount of excessive fuel from the engine pulls down the catalyst temperature. In this type of catalyst protection mode, however, the carbon monoxide content of the exhaust gas is undesirably very high. [0005] However, for lean burn systems such as diesel or dual fuel engines, the excessive fuel will not cool down the catalyst temperature because of the presence of a high concentration of oxygen in the exhaust. Furthermore, lean burn systems cannot burn stoichiometric fuel/air mixtures because of knocking restrictions. For knock-free operation of a dual fuel engine, the original compression ratio of the baseline diesel engine requires the pre-mixed natural gas/air mixture to be generally leaner than .lamda.=1.5. [0006] As well, the concept of the reversing flow catalytic converter has been found to offer nearly continuous oxidation of exhaust components, mainly unburned hydrocarbons and carbon monoxide, when used after natural gas or dual fuel engines, in a 13 mode test cycle. For this reason, such a catalytic converter will likely not require supplementary heat added to the converter to maintain oxidation temperature. However, for a diesel engine there are fewer hydrocarbons and CO in the exhaust stream providing less fuel in the emissions. Engine fuel will need to be added to the exhaust stream during idle and low power operation of the engine in order to maintain an oxidation temperature sufficient to convert CO and hydrocarbons (including particulates), however, a considerably lesser amount of fuel than would be required by a conventional uni-directional oxidation catalyst. For this reason, addition of fuel can also result in overheating of the catalyst, if too much fuel is added. [0007] U.S. Pat. No. 6,148,613 discloses a prior art reversing flow catalytic converter for internal combustion engines. Such device 10 includes a valve housing 14 which reversibly directs exhaust gases through a "U" shaped passage having a catalytic material therein. A valve disk 42 having two openings 48 therein rotates around a central axis, wherein in a first position of such rotatable valve disk 42 the exhaust gases enter the exhaust cavity from an exhaust pipe and pass through one of the openings in valve disk 42 into the "U" shaped passage. In the second position of the rotatable valve disk 42, the disk 42 and corresponding openings 48 therein are rotated 90.degree. so that each opening 48 communicates with the same cavity within the valve housing 14, but a different one of the ports communicating with the U-shaped passage, so that gas flow through the u-shaped passage is thereby able to be reversed. [0008] Disadvantageously, prior art devices such as the type disclosed in U.S. Pat. No. 6,148,613 lack a safeguard system to protect such reversing flow catalytic converter from overheating, as may arise under any one or more of the conditions explained above. [0009] Further, there exists a need for a continuously oxidizing filter particulate trap for diesel engine exhausts. [0010] An improved patent application Ser. No. 11/212,608 addresses the above problems and disadvantages and presents solutions and improvements. [0011] The improved patent however, suffers from use of a rotating compact valve that is prone to having a high degree of friction drag due to its design and requirement for low leakage of exhaust gas across the valve. For each percent of exhaust gas leakage across the valve, the effectiveness of the destruction of exhaust methane or exhaust particulates diminishes by about one percentage point. Leakage and drag at the valve are reduced in this new invention by a re-configuration of the valve rotor and stator ports from being rotated as a sliding assembly perpendicular to and rotated about a shaft, to the rotor now being a symmetrical flapper and four stator ports now being fixed in the two conjoined inner valve walls parallel to the shaft intersecting each other at the center of the valve at the shaft area, and the rotor flapper being rotated about the shaft between two stator walls with four ports. The improved valve is divided into four cavities separated from each other by the internal valve walls The valve cavities extending from container chambers one and two and constrained between valve bottom ports one and two, the two valve inner walls, the outer wall and the cover plate are now better described as extended cavities to chambers one and two of the container. The valve cavities extending from the inlet and outlet piping ports and constrained by the valve top and bottom covers and between two valve walls are now better called inlet and outlet cavities through which the flapper moves to redirect flow as directed by the controller, actuator, spring return and rotor The rotor is now better described as a symmetrical flapper without ports and the stator is now better described as two pairs of conjoined walls intersecting at the center of the valve housing, each wall section having a valve port which the flapper covers two at a time while leaving the other two completely uncovered on a cyclic basis This type of valve action occurs with very little drag even at operating temperature, and the flapper is able to cover valve ports effectively and in this manner improve exhaust component destruction efficiency. The valve action of the flapper alternately covering two ports and uncovering the other two ports on a cyclic basis, is controlled by a temperature control system and has the effect of reversing the flow of exhaust gas cyclically flowing through the monolith in the container. [0012] The improved patent application also suffers from a neutralizing spring return design with two compressed springs such that the spring return is not force-balanced at the shaft and therefore prone to shaft wear. Therefore an improvement is made to create a force-balanced spring return with the use of four compressed springs mounted in such a way as to balance out forces on the shaft that were prevalent with the original two spring design. [0013] The improved patent application used diesel injection as required into the inlet pipe taking exhaust gases from the diesel engine into the valve and oxidation or filter monolith and also mentioned that injection of diesel was alternately possible into the space at the central core of the monolith. It is preferred to add diesel fuel within the central core since the heat in this area is prevalently greater than in the inlet to the monolith, giving greater opportunity for complete diesel vaporization within the core thereby effecting a greater oxidation efficiency of the added fuel. SUMMARY OF THE INVENTION [0014] It is accordingly an object of the present invention to provide a further improved reversing flow catalytic converter system for treating exhaust gases from an internal combustion engine, which system includes an improved compact valve structure incorporated in the converter as well as an improved safeguard system to protect the catalyst and converter from overheating and including an improved method for monolith heat addition by diesel injection into the central core of the monolith. [0015] Another object of the present invention is to provide a further improved reversing flow catalytic converter system for treating exhaust gases from an internal combustion engine which has a compact structure for efficient performance, minimal heat loss, and mechanical simplicity. [0016] Yet another object of the present invention is to provide an improved three-way valve for a further improved reversing flow catalytic converter which overcomes the shortcomings of the prior art discussed above. [0017] A further object of the present invention is to provide a further improved reversing flow catalytic converter having an improved bypass system to protect the further improved reversing flow catalytic converter from overheating. [0018] A still further object of the present invention is to provide an improved three-way valve for a further improved reversing flow catalytic converter that is maintained in a neutral position to permit exhaust gases to bypass the further improved catalytic converter when the improved valve is not actuated. [0019] A further object of the present invention is to optionally provide a further improved reversing flow catalytic converter with an oxidizing filter trap that may or may not be coated with catalytic material, to trap, hold and oxidize particulates, in place of the oxidation catalytic substrate within the further improved reversing flow catalytic converter. [0020] A further object of the present invention is to provide a further improved reversing flow catalytic converter with an improved means of injecting a controlled amount of diesel engine fuel within the core of the further improved reversing flow catalytic converter, when required to maintain a continuous oxidation temperature. The catalytic converter monolith may or may not be coated with catalytic material, depending on the application and upon the amount of fuel normally present in the exhaust stream and additionally injected into the middle of the further improved reversing flow catalytic converter. [0021] A still further object of the present invention is the provision of an improved force-balanced spring return design component such that the improved valve can be reliably and quickly returned to a neutral or bypass position upon detection of damaging impending temperatures within the monolith of the further improved reversing flow catalytic converter. [0022] Accordingly, in one broad aspect of the invention, a further improved reversing flow catalytic converter for treating exhaust gases from an internal combustion engine is provided, comprising: [0023] a container having a gas flow passage therein and a top end having a first chamber and a second chamber that respectively communicate with the gas flow passage; [0024] a catalytic material in the gas flow passage adapted for contacting the exhaust gases that flow through the gas flow passage; [0025] an improved valve for reversing an exhaust gas flow through the gas flow passage, including an improved valve housing with two extended valve cavities connecting to chambers one and two of the container and mounted to the top end of the container, an improved intake cavity and an improved exhaust cavity, the improved intake cavity adapted for connection to an exhaust gas pipe from said engine and the improved exhaust cavity adapted for connection to a tail pipe for egress of said exhaust gas from said converter; and [0026] an improved valve component for reversing gas flow operably mounted to the improved valve housing, adapted to move between a first position in which the intake cavity communicates with the first valve opening and container chamber and the exhaust cavity communicates with the second valve opening and container chamber, a second position in which the intake cavity communicates with the second valve opening and container chamber and the exhaust cavity communicates with the first valve opening and container chamber, and a third position which allows the intake cavity to communicate with the exhaust cavity; and [0027] a controller for controlling movement of the improved valve component between the first and second positions during normal operating temperatures for the further improved reversing flow catalytic converter and otherwise permitting movement of the improved valve component to the third position for abnormal operating temperatures. 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