Abstract: There is provided a multicylinder internal combustion engine. Branches of an exhaust manifold are connected to a common exhaust gas sensor via respective exhaust communication passages. The exhaust gas sensor detects the exhaust air-fuel ratio of each cylinder. The distance from exhaust ports of the engine to the exhaust gas sensor is set to be shorter than the distance from the exhaust ports to a catalyst disposed in an exhaust pipe.

Abstract: There is provided an exhaust pressure-adjusting valve that is brought into a closed position due to a biasing force of a resilient body and is opened against the biasing force of the resilient body due to the exhaust pressure in an exhaust channel, which is raised in response to the closing of a throttle valve, in which valve-opening area is increased or decreased according to the displacement of the resilient body, to thereby adjust the exhaust pressure. The exhaust pressure-adjusting valve has a unit for changing the growth rate of the valve-opening area, which gradually heightens the growth rate of the valve-opening area with respect to the displacement of the resilient body in a valve-opening direction.

Abstract: The air/fuel ratio of exhaust flowing into a catalytic converter is forcibly modulated, between a lean air/fuel ratio leaner than a target average air/fuel ratio and a rich air/fuel ratio richer than the target average air/fuel ratio, with a specific period, a specific amplitude, a specific modulation ratio and a specific waveform. During the forcible modulation (S10, S12), the ratio of a time for which the output of an oxygen sensor is greater than a standard value Sb for the output set between the maximum and minimum values of the output (“rich” output time), or of a time for which it is smaller than the standard value Sb (“lean” output time), in a predetermined period of time, or a value correlating with this ratio is obtained (S14), and the air/fuel ratio of the exhaust is controlled on the basis of this ratio or the value correlating with this ratio (S16, S18).

Abstract: Normally, at the time of cold-start of an internal combustion engine or the like, the flow of exhaust in an exhaust passage of the internal combustion engine is suppressed or two-stage combustion is carried out so as to promote exhaust purification in an exhaust system. However, when a correlation value of a braking force required to be generated by a vacuum type brake booster is greater than a correlation value of a braking force that can be actually generated by the vacuum type brake booster, a restricting device restricts the suppression of the exhaust flow or a two-stage combustion prohibiting device prohibits the two-combustion.

Abstract: The air/fuel ratio of exhaust flowing into a catalytic converter is forcibly modulated, between a lean air/fuel ratio leaner than a target average air/fuel ratio and a rich air/fuel ratio richer than the target average air/fuel ratio, with a specific period, a specific amplitude, a specific modulation ratio and a specific waveform. During the forcible modulation (S10, S12), the ratio of a time for which the output of an oxygen sensor is greater than a standard value Sb for the output set between the maximum and minimum values of the output (“rich” output time), or of a time for which it is smaller than the standard value Sb (“lean” output time), in a predetermined period of time, or a value correlating with this ratio is obtained (S14), and the air/fuel ratio of the exhaust is controlled on the basis of this ratio or the value correlating with this ratio (S16, S18).

Abstract: There is provided a failure diagnostic system which includes an intake channel and an exhaust channel in communication with cylinders of an internal combustion engine; the exhaust pressure increasing device that increases the exhaust system pressure of the exhaust channel; an intake system pressure detecting device provided in the intake channel, for detecting the intake system pressure; and an exhaust pressure increase failure diagnostic section that determines whether the exhaust pressure increasing device has failed or not according to intake system pressure information obtained by the intake system pressure detecting device and a predetermined failure diagnosis reference range.

Abstract: An exhaust emission control device for internal combustion engine comprising air-fuel ratio modulating means and air-fuel ratio modulation adjusting means. The air-fuel ratio modulation adjusting means adjusts a lean period to be longer or the degree of leaning to be higher, during which the air-fuel ratio of exhaust gas is a lean air-fuel ratio, compared with when an oxygen storage (S10) of a three-way catalyst exceeds a first given value X1 if the oxygen storage is not higher than the first given value X1 (S16, S18), and adjusts a rich period to be longer or the degree of enriching to be higher, during which the exhaust air-fuel ratio is a rich air-fuel ratio, compared with when a reducing agent storage (S12) exceeds a second given value Y1 if the reducing agent storage is not higher than the second given value Y1 (S20, S22).

Abstract: There is provided a multicylinder internal combustion engine. Branches of an exhaust manifold are connected to a common exhaust gas sensor via respective exhaust communication passages. The exhaust gas sensor detects the exhaust air-fuel ratio of each cylinder. The distance from exhaust ports of the engine to the exhaust gas sensor is set to be shorter than the distance from the exhaust ports to a catalyst disposed in an exhaust pipe.

Abstract: When a NOx-releasing unit is operated to change an air-fuel ratio to a rich side to thereby establish a low-oxygen-concentration atmosphere of an exhaust gas such that NOx is released from a NOx catalyst, a reducer-supplying unit additionally supplies a reducer during an operating period of the NOx-releasing unit for reducing NOx released into an exhaust path such that release of NOx balances with reduction of NOx, thereby reducing NOx released from the NOx catalyst and thus suppressing worsening of an exhaust gas performance.

Abstract: There is provided an exhaust emission control apparatus for an internal combustion engine, which includes a failure diagnostic device that fixes three parameters selected from the group consisting of the engine speed detected by an engine speed detecting device, the fuel quantity controlled by a fuel quantity control device, the ignition timing controlled by an ignition timing control device, and the intake air volume controlled by an intake air control device at respective predetermined values, and finds values of the remaining one parameter, and compares the values of the remaining one parameter with each other to determine whether an exhaust flow control apparatus has failed or not.

Abstract: An internal combustion engine is comprised of a gas injecting device injecting gas into the combustion chamber of the internal combustion engine, and a gas injection control device controlling the gas injecting device, wherein the gas injection control device provides control such that the gas is injected toward the combustion chamber for a period of time after flame extinguishing timing and before exhaust valve closing timing. Therefore, the internal combustion engine is capable of reliably combusting HC, CO, smoke, and so forth remained in a combustion chamber due to a quenching phenomenon or the like.

Abstract: A three-way catalyst (30) comprises a microporous catalyst element (30a) having a micropore group whose average pore opening size is smaller than molecular size of HC in a washcoat and a macroporous catalyst element (30b) having a macropore group whose average pore opening size is larger than the molecular size of HC in a washcoat.

Abstract: An exhaust emission control device of an internal-combustion engine comprises a three-way catalytic converter provided in an exhaust passage of the internal-combustion engine, and an air-fuel ratio varying element for forcedly varying an air-fuel ratio of exhaust flowing into the three-way catalytic converter, between a rich air-fuel ratio and a lean air-fuel ratio. A variation characteristic altering element for altering a characteristic of the air-fuel ratio variation is provided, and the three-way catalytic converter has a HC selective oxidizing component for selectively oxidizing HC rather than CO, and a CO storage component for storing CO in a reducing atmosphere. The variation characteristic altering element alters a characteristic of the air-fuel variation (such as an A/F variation period) depending on an stored CO quantity correlative value (such as a quantity of flowing-in CO) which correlates with a quantity of CO stored by the CO storage component (S12).

Abstract: There is provided an exhaust pressure-adjusting valve that is brought into a closed position due to a biasing force of a resilient body and is opened against the biasing force of the resilient body due to the exhaust pressure in an exhaust channel, which is raised in response to the closing of a throttle valve, in which valve-opening area is increased or decreased according to the displacement of the resilient body, to thereby adjust the exhaust pressure. The exhaust pressure-adjusting valve has means for changing the growth rate of the valve-opening area, which gradually heightens the growth rate of the valve-opening area with respect to the displacement of the resilient body in a valve-opening direction.

Abstract: A catalyst deterioration suppressing apparatus and method stops supply of fuel when an engine is decelerating, and prohibits the supply of fuel from being stopped when the catalyst temperature is equal to or higher than a predetermined temperature when the engine is decelerating. When the supply of fuel is prohibted from being stopped, the air-fuel ratio is prohibited from being feedback-controlled. As a result, it is possible to control the air-fuel ratio in a stable manner while suppressing deterioration of a catalyst.

Abstract: A catalyst deterioration detecting apparatus aims at accurately determining whether or not a catalyst deteriorates even if a strict standard for catalyst deterioration is established. The catalyst deterioration detecting apparatus includes catalyst temperature sensing means for obtaining temperature of a catalyst, including ceria (CeO2) serving as an oxygen storage agent, and deterioration detecting means for detecting a degree of deterioration of the catalyst if the temperature is obtained by the catalyst temperature sensing means is equal to or higher than an activation temperature at which the catalyst is activated and is in a particular temperature range causing NOX conversion efficiency of the catalyst to decrease.

Abstract: An exhaust emission control system for an internal combustion engine includes an exhaust air-fuel ratio changing device switching the exhaust air-fuel ratio of exhaust gas flowing into one of an upstream exhaust passages and the exhaust air-fuel ratio of exhaust gas flowing into the other one of the upstream exhaust passages to a rich air-fuel ratio and to a lean air-fuel ratio alternately on a predetermined cycle longer than each of combustion cycles of the internal combustion engine, to thereby determine whether upstream catalytic converters have deteriorated or not according to a change in the exhaust air-fuel ratio outputted by upstream exhaust sensors provided downstream of the upstream catalytic converters. Therefore, it is possible to surely determine whether catalytic converters have deteriorated even slightly or not while ensuring a high exhaust emission control performance.

Abstract: An exhaust emission control device for internal combustion engine comprising air-fuel ratio modulating means and air-fuel ratio modulation adjusting means. The air-fuel ratio modulation adjusting means adjusts a lean period to be longer or the degree of leaning to be higher, during which the air-fuel ratio of exhaust gas is a lean air-fuel ratio, compared with when an oxygen storage (S10) of a three-way catalyst exceeds a first given value X1 if the oxygen storage is not higher than the first given value X1 (S16, S18), and adjusts a rich period to be longer or the degree of enriching to be higher, during which the exhaust air-fuel ratio is a rich air-fuel ratio, compared with when a reducing agent storage (S12) exceeds a second given value Y1 if the reducing agent storage is not higher than the second given value Y1 (S20, S22).

Abstract: There is provided a failure diagnostic system which includes an intake channel and an exhaust channel in communication with cylinders of an internal combustion engine; the exhaust pressure increasing device that increases the exhaust system pressure of the exhaust channel; an intake system pressure detecting device provided in the intake channel, for detecting the intake system pressure; and an exhaust pressure increase failure diagnostic section that determines whether the exhaust pressure increasing device has failed or not according to intake system pressure information obtained by the intake system pressure detecting device and a predetermined failure diagnosis reference range.

Abstract: An exhaust purifying apparatus includes an exhaust throttle valve provided in an exhaust passage of the internal combustion engine for closing the exhaust passage to increase a pressure therein; a relief passage provided bypassing the exhaust throttle valve; a relief valve provided to be able to close the relief passage and to be open when receiving an increased pressure in the exhaust passage with closure of the exhaust throttle valve; fuel cut determining means for determining whether the engine is during fuel cut-off; and a relief-valve forcibly operating means for closing the exhaust throttle valve when the fuel cut determining means determines that the engine is during fuel cut-off, thereby removing condensed water accumulated in the relief passage to avoid faulty operations of the relief valve, and suppressing deteriorated fuel consumption upon operation of the relief valve.