Internal-combustion engines – Charge forming device – Fuel injection system
Reexamination Certificate
2003-07-15
2004-11-02
Kwon, John T. (Department: 3747)
Internal-combustion engines
Charge forming device
Fuel injection system
C123S494000, C073S118040, C073S204110
Reexamination Certificate
active
06810859
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a control system of an internal combustion engine provided with a thermal type air flow sensor and more particularly to a control system of an internal combustion engine for correcting both surge voltage and warming-up characteristic of the thermal type air flow sensor when the air flow sensor starts so as to correct the intake air flow detected value according to the initial temperatures of both temperature sensing and heating resistors of the thermal type air flow sensor.
BACKGROUND OF THE INVENTION
It has been a conventional method that disposes a temperature sensing (thermal type) air flow meter in an intake air pipe of an internal combustion engine so as to detect the intake air flow in the engine. The temperature sensing (thermal type) air flow meter has such internal circuits as a temperature sensing resistor and a heating resistor used to detect the intake air flow respectively. In the temperature sensing (thermal type) air flow meter, the heating resistor is disposed in the intake air passage that receives a current and releases its heat at a constant temperature, thereby the temperature drop to be caused by the intake air is prevented with an increase of the supply of the current. The air flow meter calculates the intake air flow from the supplied current value.
However, such a temperature sensing (thermal type) air flow meter generates a detection error in a period between when the meter is powered and when the heating resistor reaches the normal control temperature. This is why the air flow meter detected value must be corrected for a predetermined time after the sensor is powered. And, to solve the conventional problem, there has been disclosed a technique (JP Patent Application No. 7-318118(1995) (JP Patent Publication (Kokai) No. 9-158758 (1997))) that calculates a warming-up correction factor for correcting an intake air flow signal according to an elapsed time after ignition switch ON and the warming-up characteristic of the temperature sensing (thermal type) air flow sensor using means for measuring a time elapsed after the ignition switch ON and means for estimating the warming-up characteristic of the temperature sensing (thermal type) air flow sensor from the water temperature at the starting time of the sensor.
There is also disclosed another technique (JP Patent Publication (Kokai) No. 6-33825(1994)) for correcting the starting time characteristic of such a thermal type air flow sensor according to the results of the measurements of the last power-on time, the last power-off time, and the current power-on time. Concretely, the correcting technique is employed as means for correcting the starting time characteristic of the thermal type air flow sensor described above when the sensor is powered soon after the power-off state so as to prevent the temperature of the heating resistor from falling nearly to the room temperature after the power-off.
There is disclosed proposed still another technique (JP Patent Publication (Kokai) No. 5-288113(1993)) for correcting the starting time characteristic of such a thermal type air flow sensor according to the results of measurements of the last power-off time and the current power-on time, as well as a time on which a predetermined voltage value of the thermal type air flow sensor is exceeded at starting time of the sensor.
Each of the conventional techniques described above, however, includes a problem that the detection accuracy is deteriorated when the equilibrium is lost from among the temperature of the engine water, the temperature of the temperature sensing resistor, and the temperature of the heating resistor of the thermal type air flow sensor. This is because the initial temperature of the thermal type air flow sensor is estimated from the temperature of the engine water at the starting time of the sensor. Concretely, the initial temperatures of the temperature sensing resistor and the heating resistor of the thermal type air flow sensor do not fall so much even when the engine water is low in temperature if the engine stops before it is warmed up, then it starts again soon. In that state, the equilibrium is lost. If the engine starts in such a state, a detection error occurs.
If the initial temperature of the thermal type air flow sensor is estimated from the power-on and power-off times, the last power-off time must always be measured. Thus, the CPU operation must be continued even at the power-off time of the engine, thereby the sensor needs time measuring means for such a measurement. The power consumption therefore comes to increase, since the CPU power cannot be turned off until the engine cools down completely after its power-off. The power wiring system must be checked.
Further, in the case of the conventional technique for correcting the warming-up characteristic of the thermal type air flow sensor according to the time on which the voltage of the air flow sensor at its starting time exceeds a predetermined voltage, the time depend strongly on the supply voltage. This is because falling of the supply voltage causes degradation in the heating performance of the heating resistor and the temperature sensing resistor, thereby the correction amount varies significantly according to the changes of the supply voltage to be caused by how much the battery is charged, the power consumption variation of each accessory member, a sudden fluctuation in the power source at the time of starter switch ON, etc. This has also been a problem.
Under such circumstances, it is an object of the present invention to provide a control system employed for an internal combustion engine provided with a thermal type air flow sensor. The control system is provided with means for correcting the output of the air flow sensor, which is capable of correcting a detected voltage error according to both of the surge voltage and the supply voltage of the sensor when the sensor is started.
SUMMARY OF THE INVENTION
In order to solve the above conventional problems, the control system of the present invention employed for an internal combustion engine is basically provided with means for correcting the output of the thermal type air flow sensor. The output correcting means includes surge time measuring means for measuring a surge time in a value detected by the thermal type air flow sensor when the air flow sensor is powered, as well as supply voltage detecting means. The thermal type air flow sensor output correcting means calculates a warming-up characteristic correction amount for the air flow sensor according to the values of the measured surge time and the detected supply voltage. Concretely, the output correcting means estimates the initial temperature of the thermal type air flow sensor element according to the values of the measured surge time and the detected supply voltage, then calculates the warming-up characteristic correcting amount of the thermal type air flow sensor from the estimated initial temperature.
In the control system of the present invention employed for an internal combustion engine and configured as described above, it is possible to correct an output error of the detected voltage properly according to a high voltage output (surge) caused by, for example, a temperature rise of the air flow sensor heating resistor to occur just after the air flow sensor is started. Consequently, the intake air amount of the engine is detected accurately when the engine is started. The starting time variation is thus reduced, thereby the CO and the hydrocarbon included in the exhaust gas is reduced at the starting time of the engine.
The high voltage output (surge) is detected in the temperature rising process of the heating resistor and the high voltage output (surge) time is measured by the surge time measuring means. The surge time of the heating resistor often depends on the supply voltage (ex., battery), so that it is possible to correct the surge time according to the value of the supply voltage so as to correct the output error of the thermal type air flow sensor, ther
Akagi Yoshihiko
Hirayama Hiroshi
Iwasaki Tetsuya
Miya Kazuhiko
Nagaishi Hatsuo
Hitachi , Ltd.
Kwon John T.
Mattingly Stanger & Malur, P.C.
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