Marine propulsion – Means to control the supply of energy responsive to a sensed...
Reexamination Certificate
2000-02-22
2001-04-10
Morano, S. Joseph (Department: 3617)
Marine propulsion
Means to control the supply of energy responsive to a sensed...
C440S002000, C440S087000
Reexamination Certificate
active
06213820
ABSTRACT:
PRIORITY INFORMATION
This application is based on and claims priority to Japanese Patent Application No. 11-44465 filed Feb. 23, 1999, the entire contents of which is hereby expressly corporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to alarm control systems for engines. More specifically, the present invention relates to alarm control systems for lubrication systems of engines of outboard motors.
2. Description of Related Art
Outboard motors pose unique challenges to engine designers due to their orientation and the rotation of the engines about a tilting and trimming axis during operation. One such challenge involves supplying lubricant to the moving components of the engine during a variety of operating conditions. Because the orientation of the engine changes during use, accurately sensing a level of lubricant remaining in an lubricant pan becomes difficult, if not impossible. Accurate monitoring of the lubricant is desirable to ensure that the engine is not run dry of lubricant because of a leak or a clogged passage.
In some outboard motors, the engine has a pressure sensor that detects a decrease in lubricant by evaluating the operating pressure within the lubrication system. If the pressure falls to a level indicative of a malfunction, then a buzzer or other alarm immediately sounds. One difficulty in such sensors is determining whether the low pressure is indicative of an actual problem or, rather, is indicative of a sudden change in operating conditions. For instance, due to the viscous nature of oil as a lubricant, the pressure of the lubricant does not vary as rapidly as engine speed. Accordingly, upon rapid acceleration, the lubricant pressure may incorrectly indicate a low pressure and a nonexistent malfunction.
Some engine designers have remedied these false alarm problems by setting the sensor to indicate a problem only when the pressure falls below a minimum pressure that corresponds to an adequate supply of lubricant during idle speed operation.
SUMMARY OF THE INVENTION
One aspect of the present invention includes the realization that when a lubrication alarm system of an outboard motor is configured trigger an alarm only when the oil pressure falls below a predetermined minimum oil pressure for idle speed operation, the engine may operate at higher speeds with inadequate lubrication, thereby reducing the durability and life span of the engine. For example, although an outboard motor may generate sufficient minimum oil pressure at idle so as to prevent a conventional oil pressure alarm system from being triggered, the engine may operate at higher speeds with an inadequate flow rate of oil. This condition may be produced by a number of various causes such as, for example but without limitation, a leak, or a partial or complete blockage of one of the lubricant galleries within the engine. Although the engine may generate sufficient oil pressure at idle, a leak or a blockage within the engine may cause the oil pressure to fall below the appropriate pressure for the corresponding engine speed above idle. Thus, conventional systems do not adequately address the problems associated with lubricant pressure irregularities at engine speeds above idle.
A need therefore exists for a lubrication system for an outboard motor which is able to better identify inadequate lubricant pressure at engine speeds above idle and emit appropriate alarms when the lubricant pressure falls below a desired pressure.
In accordance with one aspect of the present invention, a lubricant pressure alarm system for use in a marine engine, includes an engine speed sensor, a lubricant pressure sensor, and an alarm threshold calculator configured to calculate a threshold pressure based on the engine speed. The alarm system is configured to emit an alarm signal when a lubricant pressure within the engine falls below the alarm threshold. By providing a lubrication alarm system as such, the present invention ensures that an operator is adequately informed of inadequate lubrication flows during high speed operation.
According to another aspect of the invention, the lubrication alarm system is configured so as to emit an alarm if the lubricant pressure within the engine fluctuates above a predetermined fluctuation rate during operation. Thus, by configuring the lubrication alarm system as such, the lubrication system informs an operator of a potential malfunction of the lubrication system. For example, if a vehicle is operated in a rough manner, liquid lubricant in an lubricant pan of the engine may be violently sloshed within the lubricant pan. Such movement of the liquid lubricant may cause the pressure to fluctuate rapidly as the lubricant inlet in the lubricant pan becomes exposed and resubmerged in the liquid lubricant, allowing air to enter the lubricant inlet and the lubricant pump. As the inlet repeatedly becomes exposed above the level of liquid and resubmerged below the liquid lubricant, the pressure in the lubricant system fluctuates due to the air entering the system. Thus, by configuration the lubricant alarm system to emit an alarm when the pressure in the lubricant system fluctuates above a predetermined rate, the operator of the associated vehicle is informed of the interruption in lubricant delivery, and thus may stop the engine or slow the engine speed so as to prevent damage to the engine.
Further aspects, features and advantages of this invention will become apparent from the detailed description of the preferred embodiments which follow.
REFERENCES:
patent: 3893108 (1975-07-01), McBride, Jr. et al.
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patent: 5704819 (1998-01-01), Isogawa
patent: 5778848 (1998-07-01), Takahashi
patent: 5876188 (1999-03-01), Okamoto
patent: 5997371 (1999-12-01), Oishi
patent: 6086435 (2000-07-01), Hoshiba et al.
Knobbe Martens Olson & Bear LLP
Morano S. Joseph
Sanshin Kogyo Kabushiki Kaisha
Wright Andrew
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