Method for obtaining fire detection signal of cylinder of engine with speed sensor arranged in front

Abstract

The present invention discloses a method for obtaining a fire detection signal of each cylinder of an engine with a speed sensor arranged in the front, which comprises the following steps: calculating the difference of segment time of adjacent cylinders caused by a torsion torque according to the segment time of each cylinder of the engine detected by the speed sensor and the pre-calibrated torsion characteristic value of the adjacent cylinders of the engine, deducting the segment time of the adjacent cylinders caused by the torsion torque from the total difference of the segment time of the adjacent cylinders, and respectively calculating and outputting the fire detection signal of each cylinder of the engine. By adopting the method, the accurate fire detection signal can still be provided when the signal wheel of the speed sensor is arranged at the end of a belt pulley, the quality of the fire detection signal is improved in a project with the speed sensor arranged in the front of the engine, and the operating reliability of the fire detection function is improved.

Description

technical field [0001] The invention relates to an on-board diagnostic system (OBD) of an automobile electronic injection system, in particular to a method for obtaining misfire detection signals of each cylinder of an engine when a rotational speed sensor is in front. Background technique [0002] According to the definition of on-board diagnostic system (OBD) in my country's current light-duty vehicle pollutant emission limits and measurement methods (GB18352.3-2005), misfire detection is an important part of the OBD system. When an automobile manufacturer applies for vehicle type certification It is necessary to declare and determine the misfire rate when the emission exceeds the standard and the misfire rate that causes irreversible damage to the exhaust catalyst due to misfire. It is necessary to determine the misfire rate set during type certification. On the other hand, it is necessary to ensure that the vehicle cannot be misjudged as a misfire when the vehicle is runni...

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Problems solved by technology

[0003] Regarding the installation position of the speed sensor, it is usually installed at the flywheel end of the engine (power output end). The reason is that the signal wheel of the speed sensor is installed on the side of the flywheel and is close to the flywheel. Because the flywheel has an energy storage function, it will increase the speed of the signal wheel of the speed sensor. Stability, and if it is installed at the front end of the engine, that is, at the pulley end, due to the torsional vibration of the engine and transmission system, its stability will decrease compared with that installed at the flywheel end, which will affect the matching quality of misfire detection

[0004] However, as the engine and transmission system become more and more complex, due to space constraints, the signal wheel of the speed sensor of more and more models has to be installed at the end of the engine pulley, so that the torsional vibration of the engine and transmission system will The quality of the misfire detection signal will cause great disadvantages, and the quality of the misfire detection signal will decline, especially at high speeds and related self-learning (signal gear tooth deviation self-learning, fuel supply self-learning, that is, self-learning of the combustion uniformity of each cylinder) Good misfire detection signal quality cannot be guaranteed without sufficient

[0005] At present, many car models with the signal wheel of the speed sensor installed at the end of the engine pulley generally reduce the impact of the torsional vibration of the engine and transmission system on the quality of the misfire detection signal by controlling the machining accuracy, thereby improving the quality of the misfire detection, but it still cannot fundamentally Eliminate the interference to the operation of the signal wheel of the speed sensor due to the torsional vibration of the shaft system

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