Internal-combustion engines – Spark ignition timing control – Electronic control
Reexamination Certificate
1999-10-21
2001-12-04
Argenbright, Tony M. (Department: 3747)
Internal-combustion engines
Spark ignition timing control
Electronic control
C123S406450, C123S687000, C123S703000
Reexamination Certificate
active
06325046
ABSTRACT:
PRIORITY INFORMATION
This application is based on and claims priority to Japanese Patent Application No. 10-300217 filed Oct. 21, 1998, the entire contents of which is hereby expressly incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an engine feedback control system and method, and more particularly to such a system and method wherein the feedback control adjusts the air/fuel mixture of the engine.
2. Description of the Related Art
Various control methodology and systems have been employed in conjunction with internal combustion engines so as to improve their performance, particularly in the areas of fuel economy and exhaust emission control. One of the more effective types of controls is a so-called “feedback” control. With this type of control, a basic air/fuel ratio is set for the engine for given engine running parameters. The final adjustment in the air/fuel ratio is made from a sensor that senses the air/fuel ratio in the combustion chamber. Adjustments are then made from the basic setting in order to bring the air/fuel ratio into the desired range.
Normally, the type of sensor employed for such feedback controls is an oxygen (O
2
) sensor. By determining the amount of oxygen in the exhaust gases from the combustion chamber, it is possible to fairly accurately measure the actual fuel ratio that was delivered to the combustion chamber.
The system operates on a feedback-control principle, continuously making corrections to accommodate deviations from the desired ratio. Adjustments are made in stepped intervals until the sensor output goes to the opposite sense from its previous signal. For example, if the mixture was running rich, then lean adjustments are made until the mixture strength is sensed to be lean. Adjustments are then made back into the rich direction in order to try to maintain the desired ratio.
These systems have the drawback that adjustments to the air/fuel ratio affect the power output of the engine differently depending on the air/fuel ratio at which the adjustment is made. For example, the same quantitative increase in the air/fuel ratio made to a lean air/fuel mixture as compared to a rich air/fuel mixture will decrease engine power by a greater degree. Adjustments which greatly affect engine power are generally undesirable.
When the air/fuel ratio of the engine shifts the engine torque and especially engine speed also fluctuate. This is particularly noticeable in engine employing lean or fast burn combustion chamber technology. Thus, even if an operator tries to keep a steady throttle position, the engine speed fluctuates. These fluctuations are undesirable as they give the operator an uneasy feeling.
SUMMARY OF THE INVENTION
The present invention related to an engine for an outboard motor in which engine speed and torque are keep relatively constant despite changes in an air/fuel ratio as the air/fuel ratio is adjusted. The engine comprises an oxygen sensor which detects a current air/fuel ratio and an engine speed sensor for detecting the engine speed. A throttle angle sensor detects the current position of the throttle and a control compares the current air/fuel ratio with a predetermined air/fuel ratio. The control adjusts the ignition timing of the engine to maintain engine speed and torque generally constant. The control also adjust the air/fuel ratio toward the desired predetermined air/fuel ratio.
The present invention includes a control which adjusts the ignition timing based on the current air/fuel ratio. When the current air/fuel ratio is within a lean air/fuel ratio range, the control advances the ignition timing if the predetermined air/fuel ratio is greater than the current air fuel ratio and delays the ignition timing if the predetermined air/fuel ratio is less than the current air fuel ratio. These adjustments occur as the control also adjusts the fuel and air ratio toward the predetermined air/fuel ratio for the then existing engine condition. When the current air/fuel ratio is within a rich air/fuel ratio range, the control advances the ignition timing if the predetermined air/fuel ratio is less than the current air fuel ratio and delays the ignition timing if the predetermined air/fuel ratio is greater than the current air fuel ratio, which the control adjusts the air/fuel ratio toward the predetermined ratio.
The present invention also includes an oxygen sensor positioned within a recess within the exhaust manifold or in the alternative a protective element positioned proximate the oxygen sensor.
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Argenbright Tony M.
Knobbe Martens Olson & Bear LLP
Sanshin Kogyo Kabushiki Kaisha
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