Abstract: A residual fuel quantity measuring device for automobiles has a fuel flow rate sensor provided in a filler neck of a fuel tank for measuring the flow rate of liquid fuel supplied to a fuel tank. A computer computes the quantity of liquid fuel remaining in the fuel tank from a previously stored residual quantity of liquid fuel, the measured fuel flow rate, the injection rate of fuel from fuel injection valves, and the purge quantity of fuel evaporated in the fuel tank. A fuel meter visually displays the thus computed residual quantity of liquid fuel in the fuel tank.

Abstract: To perform leak diagnosis, when it is determined (during engine idling) that leakage exists in the purge system air is reintroduced into a purge system. Then, determination of leakage existence is stopped. Accordingly, erroneous diagnosis caused by opening the filler cap during engine idling is prevented, and reliability of leakage diagnosis is improved.

Abstract: A leakage diagnosing apparatus for an evaporated gas purge system, which executes purge system leakage diagnosis based on a detected pressure change amount and an introduced pressure which is introduced into a part of the purge system including at least a fuel tank and a canister. The detected pressure change amount is obtained by detecting pressure in the part of the purge system after such part of the purge system is hermetically sealed. Accordingly, the reliability of the leakage diagnosis is improved because an erroneous diagnosis caused by the introduced pressure is prevented. The detected pressure change amount may be compensated based on the introduced pressure into the sealed gas purge system. Accordingly, an erroneous leakage determination is prevented, and the reliability of leakage determination is improved.

Abstract: When a diagnosis execution condition is established, a canister closure valve is closed, thereafter, a purge control valve is opened, a purge control valve is closed in a state where negative pressure is introduced into an evaporated gas system to thereby maintain the evaporated gas system in a hermetically-sealed state and the hermetically-sealed state is continued until abnormality diagnosis is finished. Time period for maintaining the evaporated gas system in the hermetically-sealed state is divided into three time periods of a pressure change determining time period at a first time, an awaiting time period and a pressure change determining time period at a second time.

Abstract: An air/fuel ratio controller for an internal combustion engine that obtains stabilized air-fuel ratio controllability even when an air-fuel ratio is changed during purge execution. In purge control to discharge fuel vapor adsorbed in a canister to an intake-air side of an internal combustion engine, the controller controls a purge ratio, by controlling operation of the purge solenoid valve, even when an air-fuel ratio is changed. A fuel-injection quantity from an injector is then compensated in correspondence thereto. Thus, stabilized air-fuel ratio controllability can be obtained by correction with a fuel-injection quantity, or purge correction by a control duty of the purge solenoid valve as a purge control parameter, even when an air-fuel ratio .lambda. is changed during purge execution, taking a predetermined ratio as the purge ratio.

Abstract: An antidissipation apparatus for evaporated fuel vapor for an internal combustion engine. A purge passage connects the intake manifold and the fuel tank. A canister is installed in the purge passage and adsorbs evaporated fuel vapor generated in the fuel tank. A purge pump is installed in the purge passage and delivers the adsorbed evaporated fuel vapor to the intake manifold. Since the purge pump is driven by at least a part of a fuel flow in the fuel passage, the purge pump can change its discharge amount of the adsorbed evaporated fuel vapor to the intake manifold according to an amount of the fuel flow in the fuel passage. Therefore, the evaporated fuel vapor which is adsorbed at the canister can be supplied (purged) to the intake manifold by the purge pump forcibly even if the engine is a lean-burn type which can not employ large negative pressure of the intake manifold.

Abstract: Electric current to a fuel pump in an engine fuel supply system is controlled so that a deviation in the number of pump rotations between a predetermined reference number of rotations of the fuel pump and an actual number of rotations thereof is within a predetermined range. When the deviation exceeds a predetermined range, it is determined that the fuel supply system is abnormal and at this time the operation of the fuel pump is limited. In this manner, the electric power consumed by the fuel pump is reduced because excess fuel is not circulated in the fuel supply system, thus accomplishing an improved reliability.

Abstract: In a fuel pump control, until a rotational speed of an electrically-driven fuel pump rises to a predetermined speed, an electric current supplied to the fuel pump at an engine starting is increased higher than that normally supplied after engine starting thereby causing fast build-up of the fuel pressure. After the fuel pump reaches the predetermined speed, the electric current is decreased to a normal after-start current thereby suppressing a fuel pressure overshoot and resulting overrich mixture. Alternatively, a fuel pump speed is raised by the voltage control first at an engine starting operation, while switching the voltage control to the current control intermittently to detect the voltage applied to the fuel pump. When the detected voltage reaches a first predetermined voltage, the fuel pump speed is controlled exclusively by the current control.

Abstract: In a fuel supply system employing a returnless fuel pipe arrangement, a relief valve is provided at a discharge side of a fuel pump. The relief valve is opened when fuel pressure in the fuel pipe arrangement becomes no less than a system protective pressure, so as to relieve the fuel pressure to protect the system. The relief valve is also arranged to be open when the fuel pressure in the fuel pipe arrangement becomes higher than a target fuel pressure by a predetermined value or when the fuel cut is performed. Thus, the fuel pressure in the fuel pipe arrangement is lowered. Thereafter, when the fuel pressure in the fuel pipe arrangement is lowered to a pressure near the target fuel pressure, the relief valve is arranged to be closed so that the fuel pressure in the fuel pipe arrangement is held substantially at the target fuel pressure.

Abstract: A fuel filter having a filter element and fuel pump in a housing is disposed in a fuel tank. The filter element has a partition in contact with the fuel outlet side of the element. Fuel filtered by the element is divided into two stream passages, one of which is a return passage to the fuel tank and the other is a supply passage to fuel injectors of a common rail mounted on an engine. The amount of the stream returning to the tank is larger than the amount of the other stream so that a substantial amount of foreign particles in the fuel tank are carried by the returning stream and filtered. As a result, foreign particles may not so thickly accumulate on the filter portion in the supply passage.

Abstract: Throttle valve opening and engine rotational speed are detected to estimate intake air pressure. Fuel consumption Q is estimated from the estimated intake air pressure. Fuel pump drive voltage is calculated from estimated intake air pressure and estimated fuel consumption through a data map. This map is set in advance from data measured experimentally. By thus driving the fuel pump, it can be controlled at an earlier (i.e., advanced) relative time by taking the response time delay of the control system and the fuel pump into consideration.

Abstract: An abnormality detecting apparatus for use in a fuel-transpiration preventing mechanism can eliminate effects of changes in operating conditions and variations in equipment to increase the accuracy of abnormality detection. Fuel gas generated in a fuel tank and then absorbed by an absorbing material accommodated in a canister is discharged to an intake pipe by opening and closing a purge control valve. A change in pressure at a negative-pressure holding time after introduction of a negative pressure to the fuel-transpiration preventing mechanism and a change in pressure at an atmosphere-air introduction time after the negative-pressure holding time are calculated and the changes in pressure are used as a basis for determining the existence of an abnormality. As a result, effects of changes in operating conditions and effects of variations in purge control valves and canister closing valves can be eliminated, thus allowing the detection accuracy to be improved.

Abstract: In a fuel supply system for an internal combustion engine, a feedback correction amount relative to a reference control value for a fuel pump is derived based on a deviation between an actual fuel pressure detected by a pressure sensor and a target fuel pressure. Since the feedback correction amount is controlled to be around zero during normal operation of the system, it is checked whether the feedback correction amount is within a given range. If negative, an occurrence of abnormality in the system is determined when a residual fuel amount in a fuel tank is no less than a criterion value and further when a vehicle is not running on a rough road. When the occurrence of abnormality is determined, a failure flag is set to ON while a failure determination enabling flag is reset to OFF so as to prohibit execution of a given other failure determination process such as a misfire detection process.

Abstract: In a fuel supply system of an internal combustion engine, an actual fuel pressure Pf is measured by a differential pressure sensor and the actual fuel pressure Pf is averaged in a different degree to determine two kinds of values Pfs and Pft. The value Pfs is used to control the fuel pressure, while the value Pft is used to correct a pulse width. Then, a correction value Vfpci is determined according to the load applied to the engine and used in a feedback control to adjust a fuel discharge pressure of a fuel pump.

Abstract: A fuel cut-off operation is delayed until a predetermined delay time period elapses after a fuel cut-off condition is satisfied. During the delay period, the voltage for driving a fuel pump is gradually dropped to decrease the rotation speed of the fuel pump gradually. Thus, the discharge pressure of the fuel pump is low and hence the rise of a fuel pressure immediately after the fuel cut-off operation starts can be prevented. After the fuel cut-off condition, updating of a fuel pressure feedback correction amount is prohibited until the fuel cut-off operation terminates. In this manner, a feedback control immediately after the fuel cut-off operation terminates is executed by using the feedback correction amount used immediately before the fuel cut-off condition to prevent the drop of the fuel pressure immediately after the fuel cut-off operation terminates. Thus, the fuel pressure can be maintained at a target fuel pressure.

Abstract: A fuel supplying apparatus controls fuel pressure according to engine operating conditions to prevent blow-through of injected fuel into the exhaust system and hyper-vaporization of fuel. When the engine is being started and the fuel temperature is high, or when the engine has just started and the fuel temperature is high, a target fuel pressure is determined according to the fuel temperature. When a predetermined time has elapsed following the starting of the engine, or when the fuel temperature is not high (even if the predetermined time has not elapsed), it is determined whether fuel vapor is being purged from a canister into an intake pipe. The canister traps fuel vapor from a fuel tank. If the fuel purging is being performed, the apparatus determines whether the current engine operation is in a low-load region. If the fuel purging is being performed and the engine operation is in the low-load region, the apparatus computes a target fuel pressure according to the fuel purging conditions.

Abstract: A loop back method for a network including a plurality of node units connected in loop by duplexed transmission lines in the opposite directions with each other, wherein the respective node units have a function of detecting failure on the duplexed transmission lines and a loop back function for returning data received from one of the transmission lines to one of the other in the opposite direction, one of the node units commands loop back to all other node units upon detecting failure on the transmission lines, and the one node unit commands the determination of a loop back state to all other node units to thereby perform a loop back operation for the whole network.

Abstract: A phase-locked-loop (PLL) circuit comprising a phase comparator, a current-variable charge pump, a voltage-controlled oscillator, a low-pass filter, and frequency dividers. The charge pump drive current is controlled in steps or continuously depending on the operating mode.