Internal-combustion engines – Intake manifold
Reexamination Certificate
1999-12-22
2001-10-09
Argenbright, Tony M. (Department: 3747)
Internal-combustion engines
Intake manifold
Reexamination Certificate
active
06298815
ABSTRACT:
PRIORITY INFORMATION
This application is based on and claims priority to Japanese Patent Application No. 10-363985 filed Dec. 22, 1998.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is directed to an induction system for an engine and more particularly to an improved induction system for a V-type, four-cycle outboard motor engine.
2. Description of the Related Art
As is known in the art, the configuration of the induction system of an engine is determinative of the performance of the engine. By appropriately configuring the induction system and designing its volume and the length of the intake runners, the performance of the engine can be optimized.
This design parameter, however, is often balanced with space restrictions. That is, the induction system in some applications must be configured to fit within a defined space, sometimes sacrificing the optimal induction system design for top-end engine performance. A prime example of such compromise occurs in outboard motors. In an outboard motor, the engine is contained within a cowling which together form the uppermost portion or “powerhead” of the outboard motor.
During operation of an outboard motor with a watercraft, the powerhead may be exposed above the watercraft, thus affecting the overall aerodynamics of the watercraft. The powerhead typically includes a protective cowling that fits over the engine, in order to protect the engine and enhance the aerodynamics of the outboard motor. The protective cowling is designed to be as close fitting as possible with the engine, thus minimizing the size of and hence the aerodynamic drag caused by the powerhead.
There is an additional problem in conjunction with outboard motors related to separating water, which often is present in the surrounding air about the outboard motor during use, out of the air inducted into the induction system of the engine. For this reason, outboard motor cowling systems employ various types of devices that separate water from the inducted air. These separating systems, however, obviously reduce the air flow, and accordingly, can adversely affect engine performance.
These problems become particularly acute in conjunction with the utilization of four-cycle engines with outboard motors. Four-cycle engines are desirable for use in outboard motors because they improve emission control and better performance throughout a wider range of engine speed. However, because each cylinder in a four-cycle engine fires only once for every two revolutions of the crankshaft, the specific output of a four-cycle engine is lower than a two-cycle engine. Thus, it is desirable that high performance alternatives are used to ensure that four-cycle engines remain competitive with two-cycle engines in outboard motor construction.
Induction systems have been known to include two vertically extending plenum chambers positioned within the valley of a V-type outboard motor engine. The plenum chambers of such known induction systems are connected to the combustion chambers of the engine via a plurality of intake runners. The plenum chambers are also connected to a common intake. A throttle body is disposed downstream from the inlet to control the flow of air into the plenum chambers. In this known induction system, the inlet and the throttle body are arranged above the crankcase of the engine and facing the crankshaft. An example of such induction system is disclosed in U.S. Pat. No. 5,765,519.
SUMMARY OF THE INVENTION
A need therefore exists for a tuned induction system for a four-cycle, V-type outboard motor engine which is compact in shape and effectively utilizes the available space within the cowling of the outboard motor powerhead.
According to one aspect of the invention, an outboard motor includes a four-cycle, V-type internal combustion engine arranged such that its crankshaft is oriented vertically. The engine includes an induction system having a pair of vertically extending plenum chambers which are positioned within the valley between the cylinder banks of the engine and which communicate with the combustion chambers of a respective cylinder bank via a plurality of intake runners. The induction system also includes an induction passage extending from an air inlet to the plenum chambers. A throttle device is provided in the induction system downstream of the inlet, so as to control a flow of air into the plenum chambers. Downstream from the throttle device, a branch portion is provided for connecting the induction passage to each of the plenum chambers. The throttle device is positioned at least partially below the upper surface of the crankcase of the engine
By arranging the throttle device at least partially below the upper surface of the crankcase of the engine, the present invention allows for a more compact arrangement of a dual plenum chamber induction system for an engine of an outboard motor engines.
An aspect of the present invention includes a realization that when the throttle device of an induction system is arranged above the crankcase, the overall height of the engine is unnecessarily large. The height of the engine is reduced with the present construction and thus the cowling can be shorter to reduce the portion of the outboard motor exposed above the associated watercraft. There are several positions where the throttle device can be positioned within the cowling of an outboard motor to allow a shorter cowling to be used.
The air inlet preferably includes a silencing device positioned below the upper end of the engine. By arranging the silencing device with the air inlet below the upper end of the engine, the present aspect of the invention allows the inclusion of an additional bulky device without raising the overall height of the engine. Additionally, because there is typically dead space (i.e., unused space) within the cowling of an outboard motor having a V-type engine, the present induction system arrangement allows for additional quieting and improved performance of the engine without increasing the overall size of the cowling used to cover the engine.
Further aspects, features, and advantages of the present invention will become apparent from the Detailed Description of the Preferred Embodiment which follows.
REFERENCES:
patent: 4827879 (1989-05-01), Ohmi et al.
patent: 5476402 (1995-12-01), Nakai et al.
patent: 5630390 (1997-05-01), Tsunoda et al.
patent: 5657727 (1997-08-01), Uchida
patent: 5765519 (1998-06-01), Watanabe
patent: 5904604 (1999-05-01), Suzuki et al.
patent: 5911211 (1999-06-01), Uchida
patent: 5941205 (1999-08-01), Hiraoka et al.
Iwata Yoshibumi
Kashima Yukinori
Onoue Akihiro
Takahashi Masanori
Ali Hyder
Argenbright Tony M.
Knobbe Martens Olson & Bear LLP
Sanshin Kogyo Kabushiki Kaisha
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