Internal-combustion engines – Charge forming device – Including exhaust gas condition responsive means
Reexamination Certificate
2000-03-27
2001-09-11
Solis, Erick (Department: 3747)
Internal-combustion engines
Charge forming device
Including exhaust gas condition responsive means
Reexamination Certificate
active
06286492
ABSTRACT:
PRIORITY INFORMATION
This application is based on and claims priority to Japanese Patent Application No. 11-081111, filed Mar. 25, 1999.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is directed to a controller for an engine, and in particular, a controller for a fuel-injected engine which controls the fuel injectors based on a detected intake air pressure.
2. Description of Related Art
In all fields of engine design, there is an increasing emphasis on obtaining more effective emission control, better fuel economy, and at the same time, continued high or higher power output. This trend has resulted in the substitution of fuel injection systems for carburetors as the charge former for internal combustion engines. Typically, fuel injection systems for internal combustion engines receive input from a variety of sensors included on the engine which are configured to output data which reflect the operating conditions of the engine. For example, a fuel-injected engine may include an engine speed sensor, an air temperature sensor, a throttle position sensor, an engine temperature sensor, and an air flow sensor. The controller for the engine monitors each of these sensors to determine the appropriate fuel injection timing and duration corresponding to the detected conditions. Thus, as the accuracy of the sensors and the processing of the data from the sensors is increased, so is the accuracy of the fuel injection duration and timing calculations and the emissions and the fuel efficiency of the engine.
Among the various types of data monitored by the controllers of fuel-injected engines, accurate determination of air flow into the engine poses a unique challenge. Although the flow of induction air into an engine is controlled by a throttle valve, it is imperative to determine the mass flow rate of the induction air into the engine in order to determine the appropriate mass of fuel required to accurately produce the desired air/fuel ratio. In some applications, the mass flow rate of air into the engine is estimated by detecting the absolute pressure within the induction manifold (manifold absolute pressure or “MAP”) which is proportional to the total volume of air drawn into the engine. The absolute pressure is then used, in combination with other data collected from various other sensors, by the engine controller in order to calculate the mass air flow rate into the engine. Such calculations are known as volume-density computations or speed-density computations.
Recently, air flow meters have been used with fuel-injected engines which directly measure air flow rates of induction air into the engine. For example, known air flow meters include suspended-plate-type flow sensors, swinging-gate-type air flow sensors, and mass-flow sensors. However, these flow meters provide additional bulk and make engines more expensive to manufacture.
SUMMARY OF THE INVENTION
A need therefore exists for a less expensive fuel injection control system for an engine which accurately determines a flow rate of induction air into the engine.
One aspect of the present invention includes the realization that the timing during a combustion cycle, i.e., the crankangle position of a crankshaft, at which a minimum induction air pressure is generated within an internal combustion engine varies substantially in accordance with changes in engine speed and another engine operation characteristic. For example, in a four-cycle internal combustion engine, air is drawn into the respective cylinders when the intake valve is open and the piston moves downwardly within the cylinder, i.e., during the “intake stroke.” The intake stroke occurs once every two revolutions of the crankshaft. Thus, within the engine operation speeds between 1,000 rpm and 6,000 rpm, air is drawn through the induction system in pulses of a frequency from about 500 times per minute to 3,000 times per minute.
As induction air is drawn into the induction system, the absolute pressure generated in the induction system predictably falls in accordance with the vacuum generated by the downward movement of the piston. The actual mass flow rate attained by the induction air is affected by numerous conditions. For example, although the diameter of the cylinder and the stroke length of the piston of an internal combustion engine remain constant during operation, the atmospheric air pressure, temperature, and density may change in accordance with environmental conditions. Internal combustion engines having the same cylinder diameter and stroke length may also have differently configured induction systems with different aerodynamic resistance. Internal combustion engines also may incorporate variable valve timing for at least the intake valves, thus affecting the flow of induction air differently at different engine speeds. Accordingly, the minimum absolute pressure generated in the induction system is a result of numerous factors which can affect the mass flow rate of induction air through the induction system.
Significantly, it has been found that the timing at which the minimum pressure in the induction system is generated predictably varies according to the position of a throttle valve in the induction system, as well as engine speed. Thus, an outboard motor constructed in accordance with the first aspect of the present invention includes an engine having an engine body defining at least one combustion chamber therein. A crankshaft is rotatably journaled at least partially within the engine body. An induction system is configured to guide induction air into the combustion chamber and a pressure sensor is configured to detect a pressure in the induction system. A charge former is connected to the engine to supply a fuel charge to the combustion chamber. An engine speed sensor is connected to the engine to detect rotation of the crankshaft. The outboard motor also includes a controller connected to the pressure sensor, and the engine speed sensor, and includes a memory containing data regarding a relationship between a plurality of peak positions of the crankshaft, a plurality of engine speeds, and a plurality of values of an engine operation characteristic other than engine speed, wherein the peak positions correspond to a position of the crankshaft when an induction air pressure in the induction system is at a substantially minimum value. The controller is configured to sample the output from the pressure sensor when the crankshaft is approximately at the peak position corresponding to the engine speed and the engine operation characteristic.
Preferably, the engine includes a throttle valve positioned in the induction system and configured to regulate a flow of induction air through the induction system. Additionally, the engine preferably includes a throttle position sensor configured to detect a position of the throttle valve, wherein the engine operation characteristic is the throttle valve position. Thus, the data contained in the memory reflects a relationship between the peak positions of the crankshaft, engine speed, and throttle valve positions. The controller samples the output from the pressure sensor when the crankshaft is at the peak position corresponding to the engine speed and the throttle position.
As noted above, one aspect of the present invention includes the realization that the peak position of the crankshaft predictably varies according to throttle valve position as well as engine speed. Thus, by including a memory containing data regarding a relationship between peak positions of the crankshaft, engine speeds and throttle positions, the controller can more accurately determine the timing at which the output of the pressure sensor should be sampled, thus obtaining a more accurate minimum pressure reading in the induction system and a more accurate fuel injection duration calculation.
One advantage stemming from a more accurate timing for sampling the air pressure sensor is that the controller can be configured to sample the air pressure sensor only once per rotation of the crankshaft. As such, the cost and com
Knobbe Martens Olson & Bear LLP
Sanshin Kogyo Kabushiki Kaisha
Solis Erick
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