Internal-combustion engines – Charge forming device – Fuel injection system
Reexamination Certificate
1999-11-16
2001-11-27
Moulis, Thomas N. (Department: 3747)
Internal-combustion engines
Charge forming device
Fuel injection system
C123S184310
Reexamination Certificate
active
06321720
ABSTRACT:
PRIORITY INFORMATION
This application is based on and claims priority to Japanese Patent Application Nos. 10-324301, 10-330086, and 10-330087, filed Nov. 16, 1998, Nov. 20, 1998, and Nov. 20, 1998, respectively.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a four-cycle engine for powering an outboard motor, and in particular, relates to an induction system for such engine.
2. Description of the Related Art
Engines used to power outboard motors are typically water-cooled. The cooling water is usually drawn from the body of water in which the motor is operating through an inlet port in the lower unit of the outboard motor.
The cooling water is pumped from the lower unit to the power head, where it is circulated through various coolant passages formed in the cylinder blocks and cylinder heads to cool the engine. Because the cooling water is drawn from below the engine, it is typically circulated through the coolant passages from the bottom of the engine to the top of the engine. As a result, the bottom cylinders of the engine are generally cooler than the top cylinders.
Fuel tends not to mix with induction air as readily at lower temperatures. As a result, the combustion efficiency of the cooler bottom cylinders is generally lower than the top cylinders. This results in an unbalanced power output between the top and bottom cylinders of the engine.
Induction systems for outboard motors typically include an air intake chamber located within the motor cowling and intake pipes leading from the intake chamber to intake passages formed in the cylinder heads. A throttle valve is usually provided in the intake chamber for regulating the air flow through the intake pipes.
The manufacture and assembly of the intake chamber and intake pipes must be precise so that, during operation of the motor, external air does not leak into the induction system at the junctions between the intake chamber and intake pipes. Because the throttle is located upstream of the junctions between the intake chamber and intake pipes, external air leaking through the junctions can result in unstable engine output.
SUMMARY OF THE INVENTION
An aspect of the present invention involves an engine comprising at least first and second combustion chambers. The first combustion chamber is arranged above the second combustion chamber. An induction system selectively communicates with the combustion chambers to supply a fuel/air charge thereto, and includes a first intake passage that leads to the first combustion chamber. A first fuel injector communicates with the first intake passage. A second intake passage leads to the second combustion chamber, and a second fuel injector communicates with the second intake passage. A length of the second intake passage from the second fuel injector to second combustion chamber is greater than a length of the first intake passage from the first fuel injector to the first combustion chamber. Thus, it takes less time for the fuel injected from the first injector to reach the first combustion chamber as compared to the second fuel injector and second combustion. Because the temperature in the engine is higher at the top than at the bottom, the fuel more quickly vaporizes in the first intake passage. Thus, the diffusion rate per unit time is greater in the first (upper) intake passage than in the second (lower) intake passage. The greater length of the second passage, however, compensates for the slower diffusion rate associated with the second passage. As a result, the output powers of the cylinders better approximate each other, i.e., a smaller differential of the power outputs between the combustion chambers occurs.
Another aspect of the present invention involves an engine comprising at least first and second combustion chambers, wherein the first combustion chamber is arranged above the second combustion chamber. An induction system selectively communicates with the combustion chambers to supply a fuel/air charge thereto. The induction system includes a first intake passage leading to the first combustion chamber and having a first fuel injector communicating therewith, and a second intake passage leading to the second combustion chamber and having a second fuel injector communicating therewith. The second intake passage descends from the second fuel injector toward the second combustion chamber by a greater degree than the first intake passage descends from the first fuel injector toward the first combustion chamber. This orientation tends to produce differing degrees of swirl within each combustion chamber, with greater swirl in the fuel/air charge occurring in the second (lower) combustion chamber. The increased swirl enhances flame propagation within the combustion chamber, and thus, improves combustion efficiency. This arrangement therefore improves the combustion efficiency of the second (lower) combustion chamber vis-a-vis the first (upper) combustion chamber, to compensate for the differential in combustion efficiency that occurs between the combustion chambers due to the cooler operating temperature of the second (lower) combustion chamber.
In accordance with another aspect of the present invention, an engine includes an improved induction system to simplify the assembly of the engine and to reduce the girth of the engine. In one mode, the induction system, which selectively communicates with at least one combustion chamber of the engine, includes an air intake chamber, a throttle device, and a first intake passage that extends between the intake chamber and the throttle device. A second intake passage extends between the throttle device and the combustion chamber. A fuel injector communicates with the induction system upstream of the second intake passage. The fuel injector also can be mounted upstream of the second intake passage.
In another mode, the induction system includes a first intake passage that extends between the intake chamber and the throttle device, and the second intake passage that extends between the throttle body and the combustion chamber. The second intake passage has a curvilinear portion that transitions from a direction along a side of the engine to a direction leading into the combustion chamber. The fuel injector communicates with the induction system upstream of the curvilinear portion of the second intake passage. The fuel injector also can be mounted upstream of the curvilinear portion.
In an additional mode, a first intake passage of the induction system extends outwardly from the intake port of the combustion chamber and then curves back inwardly toward the engine. The first intake passage communicates with a second intake passage that extends along a side of the engine and communicates with the air intake chamber. The fuel injector communicates with the second intake passage and is oriented to spray toward the first intake passage. This arrangement reduces the girth of the engine.
In another mode, a first intake passage extends outwardly from the intake port of the combustion chamber and a second intake passage communicates with the first intake passage. The second intake passage is curved and extends inwardly along a side of the engine, and also communicates with the air intake chamber. A fuel injector communicates with the second intake passage and is oriented to spray toward the first intake passage. In this manner, the first and second intake passages define an induction path that leads from the air intake chamber, bows outwardly along the side of the engine, and then curves back toward the engine and around to communicate with the intake port. This shape can generally approximate the curved shape of a side of a protective cowling which surrounds the engine in an outboard motor application of the invention.
Further aspects, features, and advantages of the present engine will become apparent from the detail description of the preferred embodiments which follow.
REFERENCES:
patent: 4922876 (1990-05-01), Mizoguchi et al.
patent: 4924834 (1990-05-01), Bonfiglioli et al.
patent: 4932368 (1990-06-01), Ab
Knobbe, Martens, Olson & Bear Llp.
Moulis Thomas N.
Sanshin Kogyo Kabushiki Kaisha
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