Abstract: The fuel pump control system includes an electronic control unit (ECU) for controlling the discharge capacity of a plunger type high pressure fuel pump driven by a driving cam connected to the camshaft of an engine. The engine is provided with a variable valve timing device for controlling valve timing of the engine by adjusting the rotation phase of the camshaft relative to the crankshaft. The pump is provided with a suction valve. When the open/close timing of the suction valve changes, the effective discharge stroke of the pump and, thereby the discharge capacity of the pump changes. The ECU estimates the change in the valve timing of the engine during the effective discharge stroke of the pump before the effective discharge stroke starts, and adjusts the open/close timing of the suction valve in accordance with the estimated change in the valve timing so that the discharge capacity of the pump becomes a target discharge capacity regardless of the change in the valve timing of the engine.

Abstract: A direct-fuel-injection-type internal combustion engine is equipped with an injector for injecting fuel directly into a combustion chamber of a cylinder. A controller controls the degree of opening of a throttle valve for adjusting the amount of air drawn into the combustion chamber and sets the throttle valve to a closed valve state by setting the degree of opening of the throttle valve to a degree of opening that is on the closed valve side of a post-engine start target degree of opening, when the engine is to be started. After it is determined that a start of the engine has been accomplished, the controller opens the throttle valve by gradually increasing the degree of opening of the throttle valve from the degree of opening of the closed valve state to the post-engine start target degree of opening.

Abstract: A fuel pressure control apparatus and method controls a pressure of fuel that is delivered from a fuel pump to a fuel pipe in an internal combustion engine of a vehicle. A controller of the fuel pressure control apparatus calculates a controlled variable based on at least an integral term that is updated in accordance with a difference between an actual fuel pressure in the fuel pipe and a target value thereof; and controls an amount of the fuel delivered from the fuel pump in a feedback manner, using the controlled variable, so that the actual fuel pressure approaches the target value. During the control of the fuel pressure, the controller inhibits updating of the integral term to a value that results in an increase in the amount of the fuel delivered from the fuel pump, when the amount of the fuel delivered is approximate to or equal to a maximum value thereof.

Abstract: A direct-injection internal combustion engine can smoothly switch and transition between a first operation mode and a second operation mode according to an operating condition of the engine. An engine control amount in the first operation mode is calculated differently from an engine control amount in the second operation mode. However, even if the engine control amount requires correction only in the second operation mode, calculation of a correction amount is made during the first operation mode as well. During a transition from the first operation mode to the second operation mode, the correction amount calculated during the first operation mode is taken into account in calculating an engine control amount. As the correction amount is already available at the time of transition, a suitable engine control amount can be immediately obtained.

Abstract: A flow control device comprising an EGR control valve arranged in an EGR passage. The pressure control chamber of the EGR control valve is connected to a pressure control valve in a conduit, and a volume chamber is arranged in the conduit. The vibration of the valve body and the diaphragm of the EGR valve is prevented by the reflecting wave of the pressure wave which is produced in the pressure control chamber due to such vibrations.

Abstract: This fuel injection control apparatus consists of a calculating device for calculating an air-fuel ratio correction factor FAF, a learning device for learning an air-fuel ratio learning factor KG in accordance with the deviation of FAF from the reference value, and a controller for controlling the amount of injected fuel in accordance with FAF and KG. When the start enrichment FASE and the warm-up enrichment FWL are added, KG is learned in accordance with the corrected deviation which is the deviation of FAF corrected by the correction factor f(FASE+FWL) which is concerned with FASE and FWL. The learning accuracy is improved because KG is learned at each region of FWL which is divided into plural regions in accordance with the engine driving conditions.

Abstract: An air-fuel ratio control device including an O.sub.2 sensor arranged in the exhaust passage downstream of a three-way catalyst. In the lean air-fuel ratio operating state such as at a fuel cut, when a large amount of oxygen is introduced to the three-way catalyst, air-fuel ratio feedback control by the O.sub.2 sensor output is stopped. Next, after the end of the lean air-fuel ratio operating state, the resumption of the air-fuel ratio feedback control by the O.sub.2 sensor output is delayed for a predetermined time T and, during the delay period, the air-fuel ratio upstream of the catalyst is made rich.

Abstract: In an air-fuel ratio feedback control system including at least one air-fuel ratio sensor downstream of a catalyst converter provided in an exhaust gas passage, an actual air-fuel ratio is controlled in accordance with the output of the downstream-side air-fuel ratio sensor. When at least one of the air-fuel ratio feedback control conditions for the downstream-side air-fuel ratio sensor is not satisfied the controlled air-fuel ratio is made an air-fuel ratio by an open loop control, while all the air-fuel ratio feedback control conditions for the downstream-side air-fuel ratio sensor are satisfied the controlled air-fuel ratio is made the stoichometric ratio (.lambda.=1) in accordance with the output of the downstream-side air-fuel ratio sensor.

Abstract: In an air-fuel ratio feedback control system including at least one air-fuel ratio sensor downstream of a catalyst converter provided in an exhaust gas passage, an actual air-fuel ratio is controlled in accordance with the output of the downstream-side air-fuel ratio sensor. When at least one of the air-fuel ratio feedback control conditions for the downstream-side air-fuel ratio sensor is not satisfied the controlled air-fuel ratio is made an air-fuel ratio by an open loop control, while all the air-fuel ratio feedback control conditions for the downstream-side air-fuel ration sensor are satisfied the controlled air-fuel ratio is made the stoichiometric ratio (.lambda.=1) in accordance with the output of the downstream-side air-fuel ratio sensor.

Abstract: In a double air-fuel sensor system including two air-fuel ratio sensors upstream and downstream of a catalyst converter provided in an exhaust gas passage, an air-fuel ratio correction amount is calculated in accordance with the outputs of the upstream-side and downstream-side air-fuel ratio sensors, thereby obtaining an actual air-fuel ratio. When all of the feedback control conditions for the downstream-side air-fuel ratio sensor are satisfied, a speed of renewal of the air-fuel ratio correction amount in accordance with the output of the downstream-side air-fuel ratio sensor is lowered before the output of the downstream-side air-fuel ratio sensor is reversed or for a predetermined time period.

Abstract: In a double air-fuel sensor system including two air-fuel ratio sensors upstream and downstream of a catalyst converter provided in an exhaust gas passage, an air-fuel ratio correction amount is calculated in accordance with the outputs of the upstream-side and downstream-side air-fuel ratio sensors, thereby obtaining an actual air-fuel ratio. The speed of renewal of the air-fuel ratio correction amount is higher when output of the downstream-side air-fuel ratio sensor indicates a lean state than when the output of the downstream-side air-fuel ratio sensor indicates a rich state.

Abstract: An average air-fuel ratio detection circuit for generating a signal which indicates the average value of a detection signal from an air-fuel ratio sensor, and a reference value control circuit are provided in the air-fuel ratio control apparatus. The reference value control circuit controls the reference value of a comparison circuit which compares the value of the detection signal from the air-fuel ratio sensor with the reference value, in accordance with the generated signal from the average air-fuel ratio detection circuit.

Abstract: The output of an exhaust gas sensor disposed in the exhaust system of an engine is amplified by a variable gain amplifier circuit. The gain of the amplifier circuit is controlled so that the peak output voltage thereof is kept constant irrespective of changes in the output of the exhaust gas sensor due to, for example, its deterioration. The output of the exhaust gas sensor is integrated and compared with a reference value by a comparator circuit which generates a reference voltage variable with the output waveform of the exhaust gas sensor whereby a stable feedback control is realized even though the air-fuel ratio of the mixture produced from a carburetor is greatly changed.