Abstract: An exhaust pipe of an internal combustion engine is equipped with a three-way catalytic converter. Provided upstream and downstream the converter are an A/F sensor and a downstream O2 sensor, respectively. A CPU executes air-fuel feedback control according to the readings from the A/F sensor. When the period of air-fuel ratio inversion by the downstream O2 sensor has exceeded a predetermined time, the CPU determines that the three-way catalytic converter is activated. At that point, the CPU estimates the quantity of heat required from the start-up of the engine up to catalyst activation. The quantity of heat is obtained by accumulating the intake air quantity from the start of the engine up to catalyst activation (i.e., accumulated intake air quantity). Given the accumulated quantity of heat calculated, the CPU determines accordingly whether the three-way catalytic converter has deteriorated.

Abstract: In an apparatus for controlling the introduction of air into an exhaust pipe of an internal combustion engine in which air is introduced from the intake side to the exhaust side to improve the efficiency of purifying exhaust gases, to prevent a decline in the purification efficiency of a catalyst in a state in which the exhaust gas temperature immediately after starting is low. A control valve 11 is provided in an air introducing pipe 9 for introducing air from the intake side to the exhaust side, and the control valve 11 is set in a shut-off state during starting or during starting and a predetermined time duration immediately after starting.

Abstract: A method and apparatus for inferring and controlling the temperature of a NO.sub.x trap located downstream from a three-way catalyst that employs a temperature sensor to correct a temperature estimation model under relatively steady-state conditions to provide a more accurate estimate of NO.sub.x trap temperature and three-way catalyst temperature. In a second embodiment, the three-way catalyst also includes a temperature sensor for improving the instantaneous catalyst temperature estimation.

Abstract: The present invention relates generally to an exhaust gas back pressure attenuator for truck exhaust stacks. In particular, the present invention is directed toward an improved exhaust gas deflector that reduces the back pressure within the vertical tubular exhaust stacks of over-the-road type tractor-trailer trucks. At highway speeds a number of factors may operate to make it difficult for the engine to force exhaust gas out of the system and into the atmosphere. The present invention is attached to the top of the stack and is designed to create an aerodynamic low-pressure condition that in effect pulls the exhaust gas from the stack, thereby reducing back pressure buildup, decreasing the load on the engine, and increasing the fuel efficiency. A first embodiment of the present invention employs an air wedge to divide a first ambient air volume and cause it to pass on either side of the exhaust stack, thereby creating a pressure differential which operates to pull the exhaust gases thereout.

Abstract: The efficiency of a catalyser is evaluated starting from output signals of two lambda probes disposed upstream and downstream respectively of the catalyser. In particular, a signal obtained by calculating the difference between the time averages obtained by integration and subsequent division for the duration of an integration window of output signals of these probes is used as the signal indicative of efficiency.

Abstract: A method for monitoring the starting behavior of a catalytic conversion system by placing an apparatus in the exhaust-gas pipe of an internal combustion engine. The conversion power of the starting region can be determined from the temperature which results when an air/fuel mixture is fed to the catalytic conversion system.

Abstract: There is provided a catalyst deterioration-detecting system for an internal combustion engine having at least one catalyst arranged in the exhaust passage, for purifying noxious components present in exhaust gases emitted from the engine, and an exhaust gas component concentration sensor arranged in the exhaust passage at a location downstream of the catalyst, for detecting concentration of a specific component in the exhaust gases. An ECU of the system controls the ignition timing of the engine, and detects the degree of deterioration of the catalyst, based on an output value from the exhaust gas component concentration sensor. The ignition timing of the engine is retarded in dependence on the detected degree of deterioration of the catalyst.

Abstract: An exhaust gas-purifying device for an internal combustion engine has an adsorbing device arranged in an exhaust passage of the engine for adsorbing unburnt fuel components in exhaust gases from the engine, a catalytic converter arranged in same at a location downstream of the adsorbing device for purifying the exhaust gases, and a heater for electrically heating the catalytic converter. The temperature of the adsorbing device is detected. The heater is controlled to be operated at least on condition that the temperature of the adsorbing device is above a predetermined value. In another form of the invention, the temperature of the catalytic converter is detected. A rate of a rise of the temperature of the catalytic converter is determined. A deterioration state of the adsorbing device is determined based on the rate of the rise of the temperature of the catalytic converter.

Abstract: Non-thermal plasma gas treatment is combined with selective catalytic reduction to enhance NO.sub.x reduction in oxygen-rich vehicle engine exhausts.

Abstract: A number of embodiments of feedback control systems for two-cycle, internal combustion engine management systems. Each embodiment employs an exhaust system sensor which senses the exhaust gases by drawing exhaust gases from the exhaust of the engine. In some instances this is done directly from the cylinder and in others it is done in the exhaust system. In each embodiment, the sensor is provided in an accumulator chamber so as to provide an accurate signal of instantaneous engine running conditions. The use of the accumulator chamber insures that the combustible gases will not be diluted with fresh air charge, but will be able to purge from cycle to cycle so as to provide cycle-by-cycle information. Various arrangements are provided for protecting the sensor including serpentine flow paths, shields, the direction in which the exhaust gases are delivered and combinations of these features.

Abstract: The invention includes an on-board diagnostic system for monitoring exhaust gas from an automotive combustion engine and includes a sample port connected to the exhaust piping, preferably downstream from the catalytic converter. The exhaust port leads to a sample cell to which an infrared spectrometry system is operably connected to measure the concentration of hydrocarbons in the sample cell. An air pump is connected to the exhaust port and communicates with the sample cell. The air pump is operated to continuously purge the sample cell by pushing small amounts of clean air through the sample cell into the exhaust.

Abstract: An exhaust system for an internal combustion engine includes an exhaust turbocharger, and exhaust emission control with 3-way catalysts. In order to shorten the delay until emission control begins after the engine is started, a first catalytic converter is located in the exhaust line downstream from the turbocharger which is always traversed by the exhaust. Downstream of the turbocharger, a second catalytic converter is arranged that is traversed by exhaust only temporarily, with the second catalytic converter being traversed only until the exhaust system has reached a predetermined temperature.

Abstract: A thin-walled double pipe exhaust manifold comprises a double pipe consisting of a comparatively thin inner tube and a comparatively thick outer tube, both spaced apart from each other adiabatically through an aperture defined between these tubes. The inner tube is formed with at least one bead portion for relieving thermal stresses induced in the inner tube. To effectively reduce thermal stresses by way of thermal expansion or contraction, the bead portion is provided around each heat spot similarly to the temperature distribution of each heat spot.

Abstract: A method for regenerating a particulate collection filter by the use of a regenerative gas according to the present invention comprises a step for causing particulate combustion in only the downstream part of said filter in the flow of the regenerative gas by the use of the regenerative gas, and a step for causing the particulate combustion in the downstream part of the filter to propagate toward the upstream part of the filter in the flow of the regenerative gas. Therefore, the direction of propagation of the combustion is opposite to the direction of the flow of the regenerative gas so that only part of the particulate combustion heat in each part of the filter is transferred upstream. Accordingly, each part of the filter will not become too hot.

Abstract: The invention relates especially to an exhaust piping for a catalytic gas exhaust system including a gas manifold and a catalyzer, said piping (4) being situated between said manifold and said catalyzer and provided with a composite tube (8) which consists of an internal tube and of an external tube defining between them a substantially annular space.Advantageously, said composite tube (8) is housed inside said exhaust piping (4), the external tube coming substantially into contact with said piping, and said internal tube (10) and external tube (11) exhibit thin walls (10A, 11A), the thickness of which is less than 0.3 millimeter.

Abstract: An electronic concentration control system in which a first exhaust gas composition sensor located in an exhaust pipe downstream from a catalytic converter is connected to an input to a P.I. circuit which generates a control output signal comprising a succession of opposing triangular ramps. The system includes a second exhaust gas composition sensor located in the exhaust pipe upstream from the catalytic converter generating a signal which is fed to a proportional integral circuit whose integrating and multiplying coefficients are altered on the basis of the control signal. The system includes a diagnostic circuit which checks the efficiency of the first and second sensors.

Abstract: An exhaust system of an internal combustion engine has an exhaust gas inlet tube extending from the engine. A muffler is connected at its inlet side to the exhaust gas inlet tube. The muffler includes first and second exhaust gas flowing passages. First and second exhaust gas outlet tubes are respectively connected to the first and second exhaust gas flowing passages and extend from the muffler independently. A flow controller steplessly varies the flow passage area of the second exhaust gas outlet tube in accordance with the pressure of the exhaust gas discharged from the engine. The flow controller continuously increases the flow passage area with increase of the magnitude of the exhaust gas pressure.

Abstract: A pollutant reducing exhaust manifold for an internal combustion engine incorporating a catalytic converter therein. The manifold has a plurality of header pipes connected to and receiving exhaust gases from respective ones of a plurality of exhaust ports of an internal combustion engine. The header pipes are connected to a single chamber with an outlet therefrom connected to an exhaust pipe as well as a catalytic converter structure having a catalyst disposed on a supporting substrate disposed in the chamber between the inlet(s) and the outlet so that all exhaust gases from the engine must pass through the catalytic converter structure. The catalytic converter operates at higher temperatures for increased efficiency and comes to operating temperature virtually immediately.

Abstract: In an exhaust gas system comprising a hydrocarbon trap (28) and a downstream catalyst zone (30), a heat exchange catalyst member (10) is incorporated into the system to provide heat exchange between the exhaust gas and air that is pumped through the heat exchange catalyst member (10). The heated air is injected into the exhaust gas stream to facilitate the oxidation of hydrocarbons in the downstream catalyst zone. The heat exchange catalyst member (10) defines two separate flow paths therethrough, one of the flow paths containing a catalyst zone for the exhaust gas. In an alternative embodiment, the injected air is heated by a heat exchange trap (28') or by a separate heating element (62).

Abstract: A method is described for operating an engine having an afterburner and a catalytic converter downstream of the afterburner. Sufficient excess fuel is introduced into the engine to produce in the exhaust gases fuel constituents including unburnt hydrocarbons, carbon monoxide and hydrogen. Unburnt hydrocarbons are intercepted upstream of the afterburner so as to allow substantially only carbon monoxide and hydrogen to reach the afterburner. Sufficient additional air is introduced into the exhaust system to bring the composition of only the carbon monoxide, hydrogen and air to stoichiometry or leaner than stoichiometry, the resulting concentration of hydrogen and oxygen in the mixture reaching the afterburner being sufficient for ignition immediately after a cold start.By removing the hydrocarbons temporarily before the exhaust gases reach the afterburner, reliable cold ignition can be achieved with lower levels of fuel enrichment.