Internal-combustion engines – Charge forming device – Fuel flow regulation between the pump and the charge-forming...
Reexamination Certificate
2003-03-04
2004-03-09
Gimie, Mahmoud (Department: 3747)
Internal-combustion engines
Charge forming device
Fuel flow regulation between the pump and the charge-forming...
C123S461000
Reexamination Certificate
active
06701900
ABSTRACT:
TECHNICAL FIELD
The present invention relates generally to fuel systems for internal combustion engines, and more particularly to fuel systems with features to encourage quick priming.
BACKGROUND
In one class of fuel systems, most or all of the fuel system needs to be primed before fuel injectors will operate properly to start an engine. The difficulty and time consumed in priming a fuel system can sometimes be harmful to the fuel system and/or engine components, and is usually annoying to an operator. Long priming times can sometimes create new situations in which damage can occur. For instance, when a fuel filter is changed, there are sometimes attempts to refill the filter before attaching the filter canister to its head assembly. Maintaining the filter canister full of fuel during attachment to a head assembly is difficult and may result in debris entering the filter opening. In addition, the new filter is sometimes filled with the contents of the old filter, which can also introduce contaminates into the clean side of the filter. This debris can potentially be pushed toward fuel injectors without being filtered.
Hand pumps are sometimes provided for priming an engine after servicing, such as after replacement of a fuel filter or fuel injector. Although these pumps can be effective, an operator does not always have the knowledge or the patience to pump a number of strokes necessary to properly prime the engine before attempting to start the same.
Diesel engines are typically hard to start if any vapor or air is entrained in the fuel system. After changing a fuel filter, it is typical for an operator to bleed the air out of the system by loosening some fittings (injectors or lines). This is almost always a messy and time consuming process, and often requires manual operation by a skilled mechanic. In many diesel systems, there are several potential parts that could fail and therefore leak air into the system causing hard or no start conditions. Among these might be fuel injector O rings, pressure regulating check valves, bypass check valves, hand priming fuel pumps, transfer fuel pumps, fuel fitting seals, other fittings and seals, etc. Problems associated with air in fuel lines has sometimes been approached in the past by an arguably excessive use of check valves intended to keep fuel in the system, and thereby keep air out. Unfortunately, this approach to the problem can sometimes cause system failure from air leaks. In addition, the system might also be sensitive to the check valve seal wearing out.
Over the years, engineers have incorporated various features in fuel systems in order to assist in priming the same. For instance, it is known to include a bypass passage around a pressure regulating valve in the hopes of hastening the time needed to evacuate air or vapor from a fuel system. This bypass passageway typically includes a flow restriction or orifice that allows gas to pass without restriction, but is relatively restrictive to liquid flow. This restriction to liquid flow serves to prevent the bypass passage from undermining system pressure. Another known strategy is to include a bypass passage that circumvents both the fuel injectors and the pressure regulating valve. In this known system, the bypass passageway is fluidly connected on the upstream side of the fuel system between the fuel filter and the fuel injectors and connected on the downstream side between the pressure regulating valve and the fuel tank. The bypass passage includes a hand manipulated valve that is only opened when the engine is off and being primed via a hand priming pump. The manual valve has an intentional leaking feature such that an operator can determine that the system is primed when fuel begins to squirt out of the leakage opening. Upon noticing this, the operator then closes the manual valve and cranks the engine to start in a conventional manner. In still another strategy, a bleed valve is positioned in a bypass passage around a pressure regulating valve. the bleed valve has a relatively low opening pressure threshold. The bypass passage also includes a flow restriction or orifice that passes gas without restriction but passes liquid with restriction, so as not to undermine the system pressure and the functioning of the pressure regulating valve. Although these systems have performed satisfactorily, there remains room for improvement.
The present invention is directed to real and/or perceived priming problems in fuel systems.
SUMMARY OF THE INVENTION
In one aspect, a fuel system includes a supply pump positioned between a fuel tank and at least one fuel injector. A pressure regulating valve is fluidly positioned between the fuel injector and the fuel tank. A first bypass passageway circumvents the fuel injector(s), and a second bypass passageway circumvents the pressure regulating valve.
In another aspect, a method of priming a fuel system includes a step of circumventing gas around at least one fuel injector via a first bypass passageway. Circumventing gas around a pressure regulating valve via a second bypass passageway.
In still another aspect, a common housing for a fuel system includes an adapter having a supply passage and a return passage disposed there through. A first bypass passageway is disposed in the adapter and fluidly connects the supply passage to the return passage. A second bypass passageway is disposed in the adapter and fluidly connects an upstream portion to a downstream portion of the return passage.
REFERENCES:
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patent: 4617116 (1986-10-01), Seiler
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patent: 5731515 (1998-03-01), Tominaga et al.
patent: 5795995 (1998-08-01), Shimaoka et al.
patent: 6021763 (2000-02-01), Yoshihara et al.
patent: 1359466 (1987-12-01), None
Millar James S.
Thompson Lloyd
Caterpillar Inc.
Gimie Mahmoud
Liell & McNeil
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