Abstract: The present invention is an exhaust emission control device for a diesel engine that is small and simple, and can efficiently reduce and eliminate NO.sub.x in exhaust gas. To this end, the device includes a reforming catalyst (12) for reforming either a mixture of diesel fuel and water, or a mixture of diesel fuel, water, and air to an oxygen-containing compound and for supplying the same into an exhaust pipe (2); and a NO.sub.x catalyst (3) is disposed in the exhaust pipe (2), at a position downstream from the supplying position, for reducing and controlling NO.sub.x in the exhaust gas from the diesel engine.

Abstract: A method and system for controlling the temperature of an exhaust system having a variable length exhaust pipe including a short path and a long path and an exhaust valve positioned in the exhaust pipe for regulating the flow of exhaust gas between the short path and the long path utilizes control logic for estimating a plurality of exhaust temperatures at various locations on the exhaust system. A plurality of maximum temperatures are also determined. The plurality of estimated exhaust temperatures are then compared with the plurality of maximum temperatures, and if a preselected number of the plurality of exhaust temperatures exceed the plurality of maximum temperatures, the exhaust valve is controlled so that the exhaust gas flows through the long path of the exhaust pipe so as to aid in cooling the exhaust gas.

Abstract: A method and system for estimating the midbed temperature of a catalytic converter in an exhaust system of an internal combustion engine utilizes a sensor for a rotational speed of the engine and generating a corresponding speed signal. A control logic determines whether the exhaust gas is flowing through the short path or the long path, determines an instantaneous temperature of exhaust gas at a first point on the exhaust pipe based on the speed signal, and determines an instantaneous temperature at a midbed point of the catalytic converter based on the instantaneous temperature of exhaust gas at the first point on the exhaust pipe and which path the exhaust gas is flowing.

Abstract: A method and system for controlling the amount of secondary air introduced into a vehicle's exhaust gases in order to maintain a desired catalyst air/fuel ratio for a predetermined engine air/fuel ratio. First, a quantity of primary air flow necessary to maintain the predetermined engine air/fuel ratio is determined. Next, a quantity of secondary air flow necessary to maintain the desired catalyst air/fuel ratio is determined. Finally, a controller controls the amount of secondary air introduced into the vehicle's exhaust gases based on the determined quantity of secondary air flow.

Abstract: An apparatus is disclosed for purifying the exhaust gas of a diesel engine by reducing the contents of soluble organic fractions which are particulates. The apparatus comprises a catalyzer provided on an exhaust pipe, a cooler provided around either a portion of the pipe between the catalyzer and the engine or the catalyzer in itself for cooling the gas flowing through the pipe, a temperature sensor for detecting the temperature of the gas flowing through the pipe, a tachometer for detecting the rotating speed of the engine, a load sensor for detecting the load on the engine, a controller for controlling the cooler on the basis of the respective detection outputs from the sensors.

Abstract: A secondary air control apparatus constituted by an exhaust gas purifier 32 of an engine 21, a feed quantity control valve 29 for feeding secondary air, a secondary air heating device 31, and a controller 35 for controlling the feed quantity of secondary air and the secondary air heating device 31. The quantity of secondary air to be fed is set in accordance with the operation conditions of an engine, and the secondary air to be fed is modulated in quantity and heated, so that it is possible to utilize the purifying effect of a catalyst efficiently.

Abstract: An internal combustion engine 12 in which liquid fuel is introduced prior to the charge entering the combustion chambers is mounted in a vehicle having an air scoop 34 which acts as a source of ram air pressurised by the movement of the vehicle. The ram air is fed into the exhaust system by way of an isolation valve 36 which is opened only during engine deceleration modes and serves to reduce emissions of unburnt hydrocarbons and carbon monoxide caused by the fuel wetting the intake manifold.

Abstract: A motor-driven air pump operates when an engine is starting so that warming-up of an exhaust gas purifying catalyst may be expedited. The air pump has a low ventilation resistance to pass secondary air therethrough even when the pump is not driven by the motor. A high-response, low pressure-loss check valve is disposed in a passage connecting the catalyst in the exhaust gas passage and the air pump. When the engine is decelerating, the pump is not driven. However, the secondary air is introduced to the catalyst through the high-response, low pressure-loss check valve from the pump under the negative pressure caused by pulsation of the exhaust gas pressure. Thus, a bad smell from the catalyst may be prevented without increasing the size of the air pump and the motor.

Abstract: An apparatus for introducing fresh air into an exhaust pipe of an internal combustion engine for purification of exhaust gas includes an air introducing means disposed between an intake pipe and an exhaust pipe of an internal combustion engine for introducing a fresh air into the exhaust pipe and hence to a catalytic converter, and a heater for heating the fresh air introduced through the air introducing means, wherein the heated air is fed to an catalytic converter via the exhaust pipe. Conversion of noxious components contained in the exhaust gas into harmless components is attained with the enhanced efficiency owing to heating of the fresh air by the heating means.

Abstract: A supercharger system for an internal combustion engine in a vehicle driveline that includes a catalytic converter for oxidizing undesirable exhaust gas emissions including a single, dual-purpose air pump for establishing combustion airflow for the engine as well as for the catalytic converter including an automatic control valve system having an electronic microprocessor that monitors varying engine operating conditions for establishing optimum airflow for fuel combustion purposes and for oxidizing exhaust gas emissions throughout a range of operating conditions for the engine, the system including a variable ratio mechanical drive between the engine and the air pump.

Abstract: A composite check valve and positively closing electromagnetic solenoid valve, particularly such a valve for regulating the introduction of secondary air into the exhaust stream of an internal combustion engine at selected times during the operation of the engine. The valve comprises an inlet port, an outlet port, a first valve element movable between open and closed positions for nominally regulating the flow of a fluid between the inlet and outlet ports, and an electromagnetic solenoid having a closure element for overriding the first element. The rigid disk or closure element can function by seating against the same seat as the first element, or by "latching" the first element in its closed position. The disclosed embodiment is a flap valve which is modified by superimposing a rigid, movable valve disk over the flap. The rigid disk is connected to the solenoid armature and is movable between an override (closed) position and a disengaged (open) position when the solenoid is energized.

Abstract: An apparatus for monitoring a system for delivering secondary air to an exhaust tube of an internal combustion engine. In the method and apparatus, a secondary air pump is switched on and builds up a pressure on the inlet side of a blocking valve which is normally closed and not being acted upon. The blocking valve has a valve closing member that is acted upon by a predetermined closing force of an elastic element. If the secondary air quantity pumped by the secondary air pump reaches a certain minimum air quantity and pressure, then with the then-opened blocking valve, a lambda sensor disposed in an exhaust tube detects a change in the lambda value in the exhaust tube that exceeds a predetermined threshold value. The apparatus is suitable for monitoring the function of a system for delivering secondary air to the exhaust tube of an internal combustion engine.

Abstract: In case of trouble of a secondary air supply system, supply of an additional amount of fuel to an intake system and supply of secondary air to an exhaust system at the time of a particular engine operating condition such as an idling condition are stopped for regulating an air-fuel ratio closer to a stoichiometric value.

Abstract: A diagnostic apparatus for use in an exhaust system of an internal combustion engine is disclosed. The system has a catalyst for purifying the exhaust gas in the exhaust gas passage and an oxygen sensor for detecting an air-fuel ratio in a combustion chamber, wherein fuel injection volume is controlled for optimizing the air-fuel ratio and the catalyst activation when the engine is operated under normal conditions, and wherein secondary air is supplied to the exhaust gas passage from a secondary air supply mechanism for forcibly adjusting the air-fuel ratio when the engine is operating under extreme conditions. The apparatus has a computing device which computes an actual volume of the secondary air supplied to the exhaust gas passage from the secondary air supply mechanism.

Abstract: A small engine emissions control system with a float bowl carburetor minimizing CO emissions by tailoring fuel delivery to engine demand over a broad range of operating speeds and conditions, an exhaust gas recirculation valve to reduce NO.sub.x emissions and a pulse valve mixing fresh air with hot exhaust gases to reduce HC and CO emissions.

Abstract: In an internal combustion engine having a catalytic converter incorporated in an exhaust passage thereof, there is provided a secondary air control system. The control system comprises an electric air pump by which secondary air is fed to the exhaust passage. An intake air amount detecting device is provided for detecting the amount of air fed to the engine through an intake passage of the engine. A control unit is provided for controlling the voltage applied to the air pump in accordance with the amount of air detected by the intake air amount detecting device. The control is so made that the amount of secondary air fed to the exhaust passage by the air pump is substantially proportional to the amount of air detected by the intake air amount detecting device.

Abstract: An evaporative emission control system controls emission of evaporative fuel from an internal combustion engine having an intake system, an exhaust system, a catalytic converter arranged across the exhaust system, and a fuel tank. A charcoal canister is connected to the fuel tank for collecting evaporative fuel generated from the fuel tank. An exhaust purging passage is disposed to connect between the charcoal canister and the exhaust system for introducing evaporative fuel from the cansister together with purging air into the exhaust system at a location upstream of the catalytic converter. Load on the engine is detected. The exhaust purging passage is opened when the load on the engine detected is below a predetermined value.

Abstract: An evaporative emission control system for an internal combustion engine having an exhaust passage, an exhaust secondary air supply system connected to the exhaust passage for supplying secondary air thereto, has an ECU which detects an amount of evaporative fuel generated in a fuel tank, e.g., from an output from a tank internal pressure sensor which detects pressure within the fuel tank. An evaporative fuel passage connects between the fuel tank and the secondary air supply means. A control valve is arranged across the evaporative fuel passage for controlling an amount of the evaporative fuel flowing the evaporative fuel passage. The ECU is responsive to an output from the tank internal pressure sensor for causing the control valve to open when the amount of the evaporative fuel exceeds a predetermined value.

Abstract: A catalytic converter for use in the exhaust system of an internal combustion engine having a rigid outer canister with a catalyst support disposed therein for movement between a first position adjacent in inlet end of the canister and a second position located in spaced relationship with said inlet end. In its first position, the substrate seals the inlet thereby forcing the entire exhaust flow through the fluid flow passages within the catalyst support which are in axial alignment with the converter inlet. The effect of forcing the totality of flow reduced volume of the substrate to the entire thermal energy of the exhaust stream thereby assisting in a reduction in the catalyst light-off time. Following catalyst light-off, the catalyst support is moved to its second, spaced position in which the entire frontal area of the converter is exposed to the exhaust flow thereby lowering backpressure of the converter and preventing converter overtemperature problems.

Abstract: A method of detecting failure in a secondary air supply system for an internal combustion engine comprises the steps of (1) causing the secondary air supply system to operate when the engine is in a predetermined decelerating condition, (2) detecting a first value of concentration of an exhaust gas ingredient, from an output from a first exhaust gas ingredient concentration sensor arranged in the exhaust passage at a location upstream of the secondary air supply system when the engine is in the predetermined decelerating condition, (3) detecting a second value of concentration of the exhaust gas ingredient, from an output from a second exhaust gas ingredient concentration sensor arranged in the exhaust passage at a location downstream of the secondary air supply system when the engine is in the predetermined decelerating condition, (4) determining whether or not the first value of concentration of the exhaust gas ingredient is lower than a first predetermined value, (5) determining whether or not the second v

Abstract: A method for heating an exhaust gas catalyst of an internal combustion engine to an operating temperature during a warmup phase includes establishing an enriched mixture as a function of an engine operating state, with a control system. A sensor signal corresponding to a rich or lean mixture is output from a lambda sensor in an exhaust gas system. A quantity of secondary air is blown downstream of outlet valves and upstream of the lambda sensor in the exhaust gas system, from a secondary air pump. A feed quantity of the secondary air pump is pilot-controlled to a stoichiometric exhaust gas ratio, as a function of engine operating parameters, with the control system. The pilot control is corrected with a superimposed closed-loop control in accordance with the sensor signal, starting with operational readiness of the lambda sensor.

Abstract: A secondary air supply system for a supercharged engine includes a control valve which controls a diaphragm-operated valve. The control valve with solenoid is electrically controlled according to various engine operating conditions. The diaphragm-operated valve tightly closes the secondary air supply passage to prevent exhaust gas from flowing into the intake passage through the secondary air supply passage under a high engine load and high engine speed condition. The diaphragm-operated valve opens the secondary air supply passage to allow air to be supplied into the exhaust gas under a low engine load and low engine speed condition.

Abstract: A metal support catalyst is inserted into the exhaust pipe of a reciprocating piston engine. The catalyst comprises two monoliths spaced away from one another and surrounded by jacket tubes which are centered coaxially with respect to one another with a sliding fit in beads and crimpings of the outer jacket. At an air feeding point between the beads of the outer jacket, air is introduced between the two monoliths in the lower rotational speed range of the engine in order to achieve an afterreaction of the exhaust gases.

Abstract: An air flow/check valve for an exhaust emission system combines flow and check functions into a single valve which is especially well-suited for use with an electric motor driven air pump. The valving mechanism is operated by a fluid actuator, and pressure conditions in the actuator are controlled by sensing the pressure differential across the valving mechanism to close the valving mechanism when exhaust back pressure is indicative of causing potentially damaging backflow to the air pump. Several embodiments of the invention are disclosed.

Abstract: In an exhaust emission control system for an internal combustion engine, a secondary air is selectively introduced into an exhaust passage at a first position upstream of a catalytic converter. A failure detection system utilizes a plurality of temperatures of an exhaust gas for detecting a failure of the exhaust emission control system. A first temperature is derived at a second position between the first position and the catalytic converter when the secondary air is introduced into the exhaust passage at the first position. A second temperature is derived at the second position when no secondary air is introduced into the exhaust passage at the first position. By comparing the first and second temperature, it is detected whether the exhaust emission control system includes a failure. Third and fourth temperatures may also be derived at a third position located inside or downstream of the catalytic converter, which respectively correspond to the first and second temperatures.

Abstract: In a supercharged engine, a part of the pressurized air pressurized by a supercharger is introduced into the exhaust system as secondary air in a predetermined operating range of the engine. The supercharging pressure is controlled to be lower when introduction of secondary air is effected than when it is not effected.

Abstract: Admission of secondary air is effected to remove a portion of exhaust gases staying in components of a secondary air supply system, particularly, a one-way valve with a pair of lead valves. The scavenging with the secondary air is carried out when the fuel supply to the engine is suspended under a predetermined deceleration condition. When the predetermined deceleration condition is satisfied, a secondary air shut off valve is opened even when a coolant temperature of the engine is so high that the secondary air is not required by a catalyst in the exhaust system.

Abstract: An electronic control circuit for actuating a solenoid-operated air-diverter valve or valves connected with the exhaust manifold of an internal combustion engine, to supply supplemental air thereto. The supplemental air reacts with some of the hot exhaust gases, producing other gases which are in general less toxic than those coming directly from the engine. The circuit responds to engine speed in such a manner that, after a predetermined period of operation has elapsed during which the speed was continuously above a predetermined value, the normally energized solenoids are shut off to thus close the diverter valves and thereby interrupt the flow of supplemental air to the exhaust manifold. This prevents overheating of the exhaust system at high engine speeds.

Abstract: An apparatus for controlling the supply of air to a burner used to recombust diesel particulates trapped in a ceramic filter. The inventive control apparatus includes an exhaust bypass line that bypasses the filter, an air supply line leading to a burner associated with the filter, a flow control valve that adjusts the cross-sectional area for the air flow in the air supply line, a relief valve that maintains a constant difference between pressures at points upstream and downstream of the flow control valve, and a control unit that controls the degree of opening of the flow control valve. With the invention, precise control over the flow rate of secondary air is ensured.

Abstract: A device for controlling the supply of secondary air in an internal combustion engine, having a secondary air control valve and a reed valve provided in the secondary air supply path and having a control circuit for receiving the output signal of an O.sub.2 sensor and producing a control signal for air-bleeding control valves of a carburetor for the engine. The secondary air control valve is controlled in accordance with the opening degree of a throttle valve of the carburetor.

Abstract: An exhaust gas purification apparatus in an internal combustion engine comprising a control device for biasing the air-fuel ratio of the exhaust gas toward the rich side or the lean side from the theoretical perfect air-fuel ratio in accordance with an operating condition of the engine. The control device can include a control valve controlled to open and close according to the output signal of an exhaust gas sensor interposed in a secondary air introducing passage connected to the exhaust passage of the engine upstream of the catalyzer. The control device can also include a device for causing a delay in opening or a delay in closing of the control valve in accordance with the operating condition of the engine.

Abstract: An internal combustion engine having a supercharger utilizes a secondary air supply control system for purifying exhaust gas. A secondary air supply passage with a reservoir chamber is provided in the middle of an intake passage communicating with an exhaust gas passage. A check valve prevents the back flow of exhaust gas in the middle of the secondary air supply passage. The secondary air passage in another embodiment has the intake passage downstream of a compressor or reservoir chamber in communication with the exhaust passage. A suitable amount of air is supplied into the exhaust passage from the intake passage or reservoir, at high pressure via the secondary air passage and check valve.

Abstract: An improved internal combustion engine for use with motorcycles including an intake system, an exhaust system, a starting aid such as a choke valve in the intake system for expediting the engine starting, and an exhaust gas cleaning device adapted to supply secondary air to the exhaust system for cleaning the exhaust gas flowing therethrough. The exhaust gas cleaning device comprises a secondary-air supply passage communicated with the exhaust system, a secondary-air control valve gear disposed in the intermediate part of the secondary-air supply passage and adapted to regulate the flow rate of the secondary air flowing through the supply passage, and a controller connected to the valve gear and adapted to close the same on detecting the operation of the starting aid and a vehicle speed below a set value.

Abstract: An integrated three-component insulation wall assembly which can be used by itself as an insulation wall assembly, or which can be incorporated into a solid rocket motor case that is made of material fabricated using conventional layup construction methods, or which can provide the contour stability necessary to allow its functioning as a mandrel for filament-winding a solid rocket motor case, and which can be spliced and reinforced across the splice. The insulation wall assembly comprises, in an integrated condition, an inner wall component (i.e., a flame side wall component) which is laminated from woven reinforcements in an ablative matrix, a middle wall component of non-metallic honeycomb core material, and an outer wall (i.e., a pressure side wall component). The inner wall component provides a fire barrier; the middle wall component provides thermal insulation; and the outer wall component provides structural stability.

Abstract: A positive displacement air delivery system for an internal combustion engine having a multiple chamber positive displacement air pump and a control valve for directing the output of the air pump to either the engine's catalytic converter or to the engine's air intake for supercharging the engine. The control valve interconnects the individual input and output ports of the air pumps chamber in a predetermined arrangement for optimum efficiency of the pump under the various operational modes of the engine.

Abstract: An improvement in an exhaust gas purification apparatus wherein a detector senses the operation of a device for injecting additional intake air into the intake passage and triggers a timing unit. The timing unit produces a signal for a predetermined amount of time which holds open a control valve for introducing secondary air into the exhaust passage ahead of the catalytic converter. This structure enables the reduction of harmful components of the exhaust gas produced during a gear-change operation of the engine without greatly overheating the catalytic converter.

Abstract: Herein disclosed is a secondary air supply control device for use with an apparatus for purifying an exhaust gas of an internal combustion engine. In the exhaust gas purifying apparatus, a secondary air supply system is made to communicate with the exhaust system of the internal combustion engine so that secondary air may be supplied during the running operation of the internal combustion engine to said exhaust system thereby to oxidize and clear the unburned noxious content of said exhaust system. The secondary air supply control device comprises a vacuum-operated secondary air control valve which is disposed midway of said secondary air supply system for controlling the flow rate of the secondary air to be supplied to said exhaust system; and means for controlling said vacuum-operated secondary air control valve during the deceleration and the choking operation at the start of said engine so that the supply of the secondary air to said exhaust system is interrupted.

Abstract: A system for supplying secondary air for an emission control system of an internal combustion engine having a catalytic converter. The system comprises a secondary air conduit communicated with an exhaust port of the engine, a reed valve provided in the secondary air conduit for preventing the counterflow. The inlet of the reed valve is communicated with the atmosphere for inducting secondary air into the exhaust passage. A valve is provided for opening the inlet of the reed valve, and a valve actuator for actuating the valve. An engine temperature sensor is provided for producing an output signal when the temperature of the engine is below than a predetermined temperature. An electric circuit is operated in response to the output signal of the engine temperature sensor.

Abstract: An exhaust gas cleaning system for an internal combustion engine is provided which has an exhaust system including a TWC catalyst. The exhaust gas cleaning system comprises a secondary air supply passage coupled to the exhaust system on the upstream side of the ternary catalyst for supplying secondary air to the exhaust system. A secondary air control valve is positioned in the secondary air supply passage for regulating the flow of secondary air therethrough. The secondary air control valve comprises a unitary valve casing, a valve passage in the valve casing coupled to the secondary air supply passage, and first and second control valves for separately opening and closing the valve passages. The first control valve is closed when the engine is decelerating and the second control valve is closed when the engine is accelerating or operating at high speed, thereby maintaining the TWC catalyst as a reducing atmosphere.

Abstract: An air/fuel ratio control system for use with an internal combustion engine, which includes a three-way catalyst arranged in the exhaust system of the engine, an electrical circuit operatively connecting an O.sub.2 sensor with fuel quantity adjusting means in a manner effecting feedback control of the air/fuel ratio of a mixture produced by the fuel quantity adjusting means and being supplied to the engine, in response to an output signal produced by the O.sub.2 sensor, and secondary air supply means for supplying atmospheric air into the exhaust system at a zone upstream of the O.sub.2 sensor. The secondary air supply means is adapted to operate only during open loop control of the air/fuel ratio.

Abstract: An exhaust gas cleaning system for an internal combustion engine having an exhaust system leading to an exhaust port of an engine body. The exhaust gas cleaning system comprises a TWC catalyst disposed in the exhaust system for simultaneously cleaning HC, CO and NO.sub.X in exhaust gas flowing through the exhaust system. A secondary-air supply passage is connected to the exhaust system on the upstream side of the TWC catalyst and coupled to the atmosphere.

Abstract: An exhaust gas purification apparatus is provided for an internal combustion engine which comprises an intake passage means, an exhaust passage means, a catalyzer for exhaust gas purification which is coupled to an exhaust passage, and an external air introducing passage for introducing external air. The external air introducing passage is coupled to the exhaust passage on the upstream side of the catalyzer. A control valve is positioned in the external air introducing passage and a detecting device is coupled to said control valve for detecting a deceleration of the engine and for opening the control valve in response thereto. External air flows through the external air introducing passage and the control valve into the catalyzer for cooling said catalyzer.

Abstract: A motorcycle having an internal combustion engine mounted on a main frame and including suction and exhaust systems, an exhaust gas cleaning means adapted to supply secondary air to the exhaust system for cleaning an exhaust gas flowing therethrough, a carburetor provided in the suction system and provided with a throttle valve therein, and a throttle opener provided on the carburetor and adapted to open the throttle valve slightly while the internal combustion engine is decelerated. A secondary air supply passage is connected to the exhaust system, and a flow rate of the secondary air flowing through the passage is controlled by a secondary air control valve. When a vehicle speed of the motorcycle has decreased to a level not higher than a predetermined level, the secondary air control valve is closed to stop supplying the secondary air to the exhaust system, and the operation of the throttle opener is rendered ineffective simultaneously. This prevents the temperature of the exhaust gas from increasing.

Abstract: At least one electrical signal which indicates an operating condition of an internal combustion engine is generated, and then a first air-fuel ratio feedback control system which controls a carburetor air-fuel ratio and a second air-fuel ratio feedback control system which controls the amount of secondary air supplied into the exhaust system is selectively energized so as to function in accordance with the generated electrical signal.

Abstract: An engine includes a three way catalytic converter in its exhaust system, and a carburetor whose throttle valve has a normal and an idle up idling position, selected between by an idle up device. A device for weakening the air/fuel ratio of the mixture in the engine intake system only functions when no oxygen is detected in the engine exhaust system by an oxygen sensor. A means for supplying enough secondary air into the exhaust system upstream of the oxygen sensor to make the exhaust gases leaner than stoichiometric functions according to supply of a controlling vacuum. A first vacuum take out port is provided in the throat of the carburetor at a position downstream of the throttle valve when it is in the normal idling position and upstream of it when it is opened a little from the normal idling position.

Abstract: An internal combustion engine has an exhaust manifold, an inlet manifold, and a carburetor which has a fuel jet. An oxygen sensor is mounted within the exhaust manifold, and produces an output signal according to the oxygen present within the exhaust gases. A computing means computes a corrective signal according to the oxygen sensor output signal. This corrective signal is fed as an input signal both to a means for supplying secondary air into the exhaust manifold, and also to a means for supplying bleed air to the jet of the carburetor. In a particular embodiment, a secondary air signal cutoff device selectively intercepts supply of the corrective signal to the secondary air supply means, and an air bleed signal cutoff device selectively intercepts the supply of the corrective signal to the air bleed supply means. These cutoff devices may be controlled according to vehicle road speed, engine temperature, engine rotational speed, inlet manifold vacuum, and the temperature of a catalytic converter.

Abstract: An air-fuel ratio discrimination signal, having two voltage levels depending upon whether the air-fuel ratio of the engine is rich or lean in comparison with a predetermined air-fuel ratio, is generated in accordance with the sensed signal from a sensor which detects the concentration of a particular component in the exhaust gas. Then, the amount of secondary air supplied into the exhaust system of the engine is gradually increased or decreased in accordance with the level of the air-fuel ratio discrimination signal. Furthermore, the amount of secondary air supplied into the exhaust system is additionally increased or decreased in accordance with the average value of the air-fuel ratio discrimination signal.

Abstract: An air by-pass valve (1) has an air inlet (5), an air outlet (7), a relief port (11), and a relief valve (37) responsive to excessive air pressure for opening the relief port and dumping air to atmosphere. The relief valve comprises a valve member (39) mounted on a stem (23) and movable relative thereto. One side of the valve member is acted on by a spring (41) biasing the valve member to close the relief port. Air pressure acts on the opposite side of the valve member to move the valve member against the spring and open the relief port. The side of the valve member against which the spring acts is contoured so the spring force is unevenly applied to the valve member over the surface on which the spring acts.

Abstract: In an exhaust gas cleaning system for an internal combustion engine in which additional air is injected from outside into an engine exhaust manifold by an on-off-duty solenoid valve under control of a microcomputer operating on the partial oxygen pressure in the exhaust gas as detected by an oxygen sensing element, the engine r.p.m. and the exhaust gas temperature, a vacuum control valve adapted to add vacuum signals responsive to variations in the intake manifold vacuum of the engine and throttle opening to the output vacuum signals of the solenoid valve commanding the air injection.

Abstract: An air-fuel ratio control apparatus for an internal combustion engine comprises a carburetor for controlling the air-fuel ratio of the fuel-air mixture supplied to the engine, a thermal reactor in which the exhaust gas from engine is caused to undergo reaction with secondary air supplied to the reactor, an oxygen sensor disposed in an exhaust gas passage between the reactor and three-way catalyst, a negative pressure generator for producing a negative pressure corresponding to the output from the oxygen sensor, a detector for detecting a low and a high speed operation region of the engine, and means for controlling a low speed fuel system and a main fuel system, respectively, of the carburetor in response to the negative pressure in such a manner that the fuel-air mixture is enriched with the secondary air supply being concurrently increased in the low speed operation region of the engine, while in the high speed operation range the fuel-air mixture having an approximately stoichiometric air-fuel ratio is sup