Abstract: An engine has variable timing mechanisms, which are controlled in starting an engine to set valve opening overlap of an intake valve and an exhaust valve around 30° CA. In this case, internal EGR is actively conducted and fuel burning velocity within a cylinder becomes relatively slow and unburned fuel within the cylinder is emitted to an exhaust pipe to be post-burned by itself. Temperature of exhaust gas is maintained high and catalyst converters in the cold state may be activated quickly by actively implementing the post-burning within the exhaust pipe. Further, ignition timing is retarded, an air-fuel ratio is controlled at a slightly lean ratio and the exhaust valve is advanced. The effect of raising the temperature of exhaust gas by the post-burning may be realized more reliably by combining each of these controls.

Abstract: An engine has variable valve timing mechanisms, which are controlled in starting an engine to set valve opening overlap of an intake valve and an exhaust valve around 30° CA. In this case, internal EGR is actively conducted and fuel burning velocity within a cylinder becomes relatively slow and unburned fuel within the cylinder is emitted to an exhaust pipe to be post-burned by firing by itself. Temperature of exhaust gas is maintained high and catalyst converters in the cold state may be activated quickly by actively implementing the post-burning within the exhaust pipe. Further, ignition timing is retarded, an air-fuel ratio is controlled at a slightly lean ratio and the exhaust valve is advanced. The effect of raising the temperature of exhaust gas by the post-burning may be realized more reliably by combining each of these controls.

Abstract: An engine variable valve timing mechanism is controlled during engine starting to set valve opening overlap of intake and exhaust valves around 30° CA. In this case, internal EGR is actively conducted, fuel burning velocity within a cylinder becomes relatively slow and unburned fuel within the cylinder is emitted to an exhaust pipe to be post-burned. The temperature of exhaust gas is maintained high and catalyst converters in the cold state may be activated quickly by actively implementing such post-burning within the exhaust pipe. Further, ignition timing is retarded, the air-fuel ratio is controlled to a slightly lean ratio and the exhaust valve is advanced. The effect of raising the temperature of exhaust gas by post-burning may be realized more reliably by combining each of these controls.

Abstract: A fuel injector comprises an injector body and an air assisting adapter. The adapter is attached to the injector body and has a fuel passage for guiding spray of injected fuel. The fuel passage is divided into two directions. A plurality of air introduction holes are communicated with the fuel passage, so that pressurized air is introduced into the fuel passage to atomize the injected fuel. The air introduction holes open to the passage at a position where the particle size of the injected fuel starts to reduce. This position is 4 mm to 5 mm away in the downstream direction from an injection port plate of the injector body.

Abstract: A fuel injection control system for an engine enhances efficiency for charging suctioned air into a cylinder stabilizes a fuel combustion state. An engine intake pipe is provided with an air-assisted injector. Fuel injected by the injector flows into a combustion chamber within the cylinder via an intake valve. An ECU controls the injector drive so that injected fuel flows into the cylinder about 1/3 of the time at the beginning of the valve opening period. This arrangement allows a large amount of fuel supplied into the cylinder to be vaporized quickly and completely before the intake value is closed. At this time, because temperature of air drops due to heat of vaporization of the fuel, weight (density) of air suctioned into the cylinder per unit volume increases, thus enhancing the charging efficiency of suctioned air.

Abstract: An air-assisted type injector injects a fuel into an intake port toward the face part of an intake valve, and its injection port has multiple holes to atomize the injected fuel into a predetermined fuel particle diameter (e.g., SMD=about 50 microns). An air feed pump supplies pressurized air to the injector to atomize the gas particle size of about 10 microns in a low/medium speed and low/medium load region where the face of the intake valve is at low temperatures. In a high speed or high load region where the face temperature is high, the air assistance by the air feed pump is stopped. When the fuel atomization by the air assistance is stopped, the gas particle diameter of the injected fuel is about 50 microns, but the fuel atomization is promoted by the valve face at a high temperature. Thus, the fuel flowing into the cylinder is atomized to a diameter as small as that at the time when the air assistance is executed.

Abstract: An air-fuel ratio control system comprises a comparator circuit for comparing a predetermined reference level with an output signal of a first oxygen sensor disposed upstream of a three-way catalyst for purifying the exhaust gas in the exhaust system of an internal combustion engine, the comparator circuit producing a signal indicative of whether the output signal of the first oxygen sensor is higher (lean) or lower (rich) than a predetermined air-fuel ratio, a delay circuit for delaying at least one of the output signals of the comparator circuit, and a delay time adjusting circuit for adjusting the delay time of the signal delayed by the delay circuit, in accordance with the value of the output signal of a second oxygen sensor disposed downstream of the three-way catalyst.