Abstract: An NO.sub.x absorber (18) is arranged in an exhaust passage of an internal combustion engine. The NO.sub.x absorber (18) absorbs the NO.sub.x when the air-fuel ratio of the exhaust gas flowing into the NO.sub.x absorber (18) is lean while releases the absorbed NO.sub.x when the air-fuel ratio of the exhaust gas flowing into the NO.sub.x absorber (18) becomes the stoichiometric air-fuel ratio or rich. An air-fuel ratio sensor (22) is arranged in the exhaust passage downstream of the NO.sub.x absorber (18). When the air-fuel ratio detected by the air-fuel ratio sensor (22) is switched from lean to rich after the air-fuel ratio of the exhaust gas flowing into NO.sub.x absorber (18) is switched from lean to rich, it is decided that the releasing action of NO.sub.x from the NO.sub.x absorber (18) is completed.

Abstract: A NO.sub.x absorbent (18) which absorbs the NO.sub.x when the air-fuel ratio of the exhaust gas flowing into the NO.sub.x absorbent (18) is lean and releases the absorbed NO.sub.x when the oxygen concentration of the exhaust gas flowing into the NO.sub.x absorbent (18) is lowered, is arranged in the exhaust passage of the engine. The amount of alkali metals, alkali-earth metals or rare-earth metals contained in the NO.sub.x absorbent (18) positioned on the downstream side, is made lower than the amount of alkali metals, alkali-earth metals or rare-earth metals contained in the NO.sub.x absorbent (18) positioned on the upstream side, to increase a reducing ability of the NO.sub.x absorbent (18) positioned on the downstream side as compared to the reducing ability of the NO.sub.x absorbent (18) positioned on the upstream side.

Abstract: An exhaust gas purification system for an internal combustion engine includes a dual passage portion having a first passage and a second passage which are connected in parallel to each other. In the first passage, a first catalyst constructed of lean NOx catalyst is located and further a second catalyst constructed of oxidizing catalyst or three-way catalyst is located downstream of the first catalyst. In the second passage, a third catalyst constructed of oxidizing or three-way catalyst is located. A flow switching valve is provided so as to switch the flow of exhaust gas between the first passage and the second passage. The flow switching valve is switched so that exhaust gas flows through the third catalyst when the engine is being warmed-up and flows through the first catalyst and the second catalyst after the engine has been warmed-up.

Abstract: A method for purifying an oxygen excess exhaust gas by catalytically reducing nitrogen oxides contained in the exhaust gas, which comprises bringing a catalyst comprising at least one noble metal supported on a carrier composed mainly of an oxide or a complex oxide of at least one metal selected from rare earth metals and metals of the group IV A of the periodic table of elements into contact the exhaust gas.

Abstract: An exhaust gas purification system for an internal combustion engine includes a dual passage portion having a first passage and a second passage which are connected in parallel to each other. In the first passage, a first catalyst constructed of lean NOx catalyst is located and further a second catalyst constructed of oxidizing catalyst or three-way catalyst is located downstream of the first catalyst. In the second passage, a third catalyst constructed of oxidizing or three-way catalyst is located. A flow switching valve is provided so as to switch the flow of exhaust gas between the first passage and the second passage. The flow switching valve is switched so that exhaust gas flows through the third catalyst when the engine is being warmed-up and flows through the first catalyst and the second catalyst after the engine has been warmed-up.

Abstract: An exhaust gas purification system for an internal combustion engine includes an engine 1 capable of fuel combustion at lean air-fuel ratios, a lean NOx catalyst 3 installed in an exhaust conduit 16 of the engine, an HC producing means for producing hydrocarbons of low boiling points utilizing fuel for the engine, and an HC supply means for supplying the hydrocarbons of low boiling points to the exhaust conduit upstream of the lean NOx catalyst 3. NOx reduction reaction needs hydrocarbons of low boiling points. The HC producing means produces hydrocarbons of low boiling points from diesel oil by cracking, fractional distillation, or both cracking and fractional distillation. The cracked and/or distilled fuel includes a large amount of hydrocarbons of low boiling points and increases NOx purification rate of the lean NOx catalyst when the hydrocarbons of low boiling points are introduced into the exhaust conduit by the HC supply means.

Abstract: A catalyst for purifying an exhaust gas comprising a zeolite catalyst ion-exchanged with a transition metal, which is heat-treated in a gas stream containing a sulfur oxide, optionally followed by washing with a glycol.

Abstract: An engine control system having an oxygen density sensor arranged in an intake system at a position downstream of a throttle valve for detecting the amount of air newly introduced into the engine. The sensor is a limit electric current detection type capable of detecting a continuously changing density of the oxygen. An amount of fuel to be injected is calculated in accordance with the output level of the sensor by using mapped data of the output level of the sensor signal. A precise detection of new air is made possible while maintaining the advantages of the known D-J system. An ignition timing also may be calculated by the signal from the oxygen sensor.

Abstract: An exhaust emission gas control device having a first filter trapping particulates contained in an exhaust gas, and a second filter removing offensive odor components in the exhaust gas. The first filter is a honeycomb type having a cordierite substrate on which .tau.-alumina is coated. The second filter is provided downstream of the first filter, and is formed by an ion-exchange of copper on a synthetic zeolite rich in silica to form copper ions thereon.

Abstract: An exhaust gas purifying apparatus comprising a first and a second casings having expansion chambers, respectively, a third casing arranged between the first and second casings to form a passage therebetween, an inlet pipe introducing the exhaust gas into the first expansion chamber, and an outlet pipe discharging the exhaust gas from the second expansion chamber, whereby a muffler is constituted. The apparatus also comprises a filter arranged in the third casing to trap particulates in the exhaust gas, and a heater arranged adjacent to the filter on the side of the second expansion chamber to burn the particulates deposited on the filter, to regenerate the filter. A flow control unit, comprising a bypass and a valve therein, is arranged such that the exhaust gas normally flows through the filter and the heater, and when the filter is regenerated, at least a part of the exhaust gas flows in reverse through the heater and the filter. This exhaust gas purifying apparatus is built-in to the muffler.

Abstract: An engine control system having an oxygen density sensor arranged in an intake system at a position downstream of a throttle valve for detecting the amount of air newly introduced into the engine. The sensor is a limit electric current detection type capable of detecting a continuously changing density of oxygen. An amount of fuel to be injected is calculated in accordance with the output level of the sensor by using mapped data of the output level of the sensor signal. The sensitivity of the sensor is detected and multiplied by the output value of the sensor for obtaining a precise oxygen partial pressure. Instead of calculating the basic fuel amount from the output level of the oxygen density sensor, a normal intake pressure sensor with an intake pressure-engine speed map can be employed. In the latter case, the oxygen partial pressure from the oxygen density sensor is used for correcting the calculated basic fuel amount. The sensitivity of the sensor is also corrected.

Abstract: A method of reducing the amount of nitrogen oxides (NOx) in an internal combustion engine in which the air/fuel ratio is controlled higher than a theoreticl air/fuel ratio during normal operation of a vehicle, characterized in that the air/fuel ratio is controlled lower than the theoretical air-fuel ratio for a predetermined period of time during acceleration from the start of acceleration, the control being effected by means for detecting an accelerated state of the vehicle, means for measuring the lapse of time during acceleration from the start of acceleration and means for performing an acceleration increment correction upon detection of acceleration.

Abstract: A combustion process sensor for detecting combustion processes occurring in a combustion chamber of an engine has a generally tubular mounting casing to be screwed into a threaded hole in the combustion chamber wall and a quartz-glass rod axially extending in the mounting casing and held in position therein. The casing includes two axially aligned generally tubular members rigidly secured together at their own ends. The quartz-glass rod has a first portion remote from a sensing end thereof adapted to be exposed to combustion flame in the combustion chamber, and a second portion between the first portion and the sensing end. The first portion is secured to one of the two tubular members of the casing, while the second portion is supported from the casing only by a vibration damping material disposed in engagement with the outer peripheral surface of the quartz-glass rod and the inner peripheral surface of the casing.

Abstract: An internal combustion engine of a lean burn type, wherein the air-fuel ratio is feedback controlled to a predetermined fixed value which is higher than a theoretical air-fuel ratio. The ignition timing is changed when the air-fuel ratio as detected by a lean sensor is off from the target air-fuel ratio, enabling quick control of the engine when the air-fuel ratio is off from the target air fuel ratio.

Abstract: An air intake device comprising a main air intake passage and an auxiliary air intake passage. The main air intake passage interconnects the air cleaner to the engine cylinders. The auxiliary air intake passage is connected to the air cleaner at one end thereof and to the main air intake passage at the other end thereof. The equivalent pipe lengths of the main air intake passage and the auxiliary air intake passage are almost the same. A control valve actuated in response to the engine speed is arranged in the other end of the auxiliary air intake passage. The valve body of the control valve has a conically-shaped convex front face and a conically-shaped convex rear face.

Abstract: An air intake device comprising a main air intake passage and an auxiliary air intake passage, in which the main air intake passage interconnects the air cleaner to the engine cylinders and the auxiliary air intake passage is connected to the air cleaner at one end thereof and to the main air intake passage at the other end thereof. The equivalent pipe lengths of the main air intake passage and the auxiliary air intake passage are almost the same. An air pulsation control valve actuated in response to the engine load and the engine speed is arranged in the other end of the auxiliary air intake passage. The engine has a helically-shaped intake port comprising a helical portion, an inlet passage portion, and a bypass passage branched off from the inlet passage portion and connected to the helix terminating portion of the helical portion. A flow path control valve actuated in response to the engine load is arranged in the bypass passage.

Abstract: A fuel injection quantity is calculated on the basis of an engine speed and an engine load and is corrected by an output incremental value determined in accordance with acceleration and deceleration of an engine, at least. The position of an intake throttle valve is detected with regard to whether it is located within a small-opening region, an intermediate-opening region or a large-opening region. When the intake throttle valve is switched over from the small-opening region to the large-opening region, the output incremental value is increased to its maximum value. When the intake throttle valve is switched over from the small-opening region to the intermediate-opening region, the output incremental value is increased such as to gradually approach the maximum value. When the intake throttle valve is switched over from the large-opening region to the small-opening region, the output incremental value is decreased to almost zero.

Abstract: A piston assembly for an internal combustion engine is made up from a piston main body and a lubricant reservoir defining member. The piston main body has a cup-shaped structure including a crown portion and a hollow cylindrical wall portion joining thereto, two piston pin bosses being formed at opposite sides of the wall portion. The lubricant reservoir defining member is made from a shelf plate main body portion which provides a central lubricant reservoir and two openings on its opposite sides, and two major legs extending from the shelf plate main body portion and each formed with a hole surrounded by an annular portion. Each of the annular portions is engaged with an inner end portion of a corresponding one of the bosses and surrounds the piston pin hole thereof.

Abstract: A piston assembly for an internal combustion engine is made up from a piston main body and a lubricant reservoir defining member. The piston main body has a cup shaped structure including a crown portion and a hollow cylindrical wall portion joining thereto. The lubricant reservoir defining member includes a shelf plate main body portion formed with first and second depressions which define first and second lubricant reservoirs, and is securely mounted within the cup shaped piston structure with the shelf plate portion generally to and opposing the piston crown. The ratio of the surface area of the first lubricant reservoir to the surface area of the second lubricant reservoir is less than the ratio of the volume of the first lubricant reservoir to the volume of the second lubricant reservoir. Lubricant is supplied more towards the first lubricant reservoir and is drained more from the second reservoir.

Abstract: An engine comprising an intake port which has a separating wall projecting downwardly from the upper wall of the intake port. The separating wall defines a helical portion, an inlet passage portion tangentially connected to the helical portion, and a bypass passage interconnecting the inlet passage portion and the helical portion. The separating wall has an upstream end portion centrally located between the opposed side walls of the intake port. A rotary valve is arranged in the bypass passage and is actuated by a vacuum-operated diaphragm apparatus. The rotary valve is opened when the amount of air fed into the cylinder of the engine is increased beyond a predetermined value.