Internal-combustion engines – Charge forming device – Fuel flow regulation between the pump and the charge-forming...
Reexamination Certificate
2000-01-04
2001-09-18
Miller, Carl S. (Department: 3747)
Internal-combustion engines
Charge forming device
Fuel flow regulation between the pump and the charge-forming...
C123S514000, C123S557000
Reexamination Certificate
active
06289879
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to fuel systems for internal combustion engines.
BACKGROUND OF THE INVENTION
Most fuel systems for internal combustion engines include a tank for holding a supply of fuel, an engine where the fuel is converted into energy, and a filter between the tank and the engine to separate particles and contaminants that could cause adverse effects to the engine. In certain engines, for example diesel engines, the fuel can wax or plug the filter during cold operation. This is a well-known problem, and many devices have been developed in an attempt to solve this. For example, a heater can be provided internally of the filter housing to heat the fuel and the media as the fuel passes through the filter (see, e.g., Richard, U.S. Pat. No. 4,091,265).
Another technique which can be used alternatively or in addition to a filter heater, is to use excess fuel from the engine. Excess fuel that is not burned in the engine is normally recirculated back to the tank. Since the fuel is warmed when it passes through the engine, the fuel can be directed back through the filter to warm the filter. It is believed that prior techniques have included a simple valve that opens under cold temperature operating conditions, and redirects at least a portion of the excess heated fuel back into the filter element. The valve then closes after the engine is warm to direct all the excess fuel back to the tank. While this technique provides some relief from the problem of waxing and plugging of the filter, it is believed that the prior techniques have also recirculated any excess air received back from the engine. The engine supplies air particularly during its priming, and the air is simply fed back with the fuel through the filter to the engine. Recirculating the air with the fuel, however, can effect the combustion characteristics of the engine, which is undesirable from an efficiency standpoint.
As such, applicants believe there is a demand in the industry for a fuel system which recirculates excess warm fuel from the engine so as to at least reduce waxing and plugging problems in the filter during cold start, but which can also differentiate between fuel and air, such that only the warm fuel is directed back to the filter during cold star-up, and any air is directed back to the tank.
SUMMARY OF THE PRESENT INVENTION
The present invention provides a novel and unique valve for a fuel system which directs excess heated fuel back through the filter during cold operation, and which directs any air from the engine directly back to the tank.
According to the present invention, the recirculation valve has a body including a fuel supply passage which receives fuel from the tank and directs the fuel to the filter and then on to the engine; and a fuel return passage which receives excess fuel and air from the engine. The fuel return passage includes an enlarged air separation chamber, and a fixed orifice at the downstream end of the air separation chamber to a fuel return outlet port. The orifice has a restricted diameter that allows air to pass to the outlet port, and then back to the tank, but which causes a pressure drop when fuel enters the chamber.
A pressure valve is located in a valve passage interconnecting the air separation chamber and the fuel supply passage. The pressure valve includes a spring biased valve head with a valve seal. The pressure valve is normally in a closed condition when only air is present in the air separation chamber. When fuel enters the air separation chamber, the pressure in the chamber increases, and moves the pressure valve into an open condition. When the valve is in an open condition, the excess fuel in the chamber flows into the fuel supply passage, and then back the filter, where the warm fuel warms the filter to prevent waxing and plugging. The orifice in the air separation chamber is located toward the upper portion of the chamber such that the air continues to pass directly to the tank, while the fuel, in the bottom portion of the chamber, is directed through the pressure valve and recirculates back to the engine.
A thermal actuator can also be provided with the pressure valve to maintain the pressure valve in the closed condition when the fuel through the fuel supply passage is above a predetermined temperature, such as after engine warm-up. In this case, all excess fuel and air is directed through the orifice back to the tank.
A relief valve can alternatively be provided in the fuel return outlet port instead of the fixed orifice. The relief valve includes a valve head with a restrictive orifice, where the valve head is spring-biased against an opening into the air separation chamber. The orifice in the relief valve functions in the same manner as the fixed orifice to direct air in the chamber back to the tank, and to cause a pressure drop when fuel is present in the chamber. After the engine warms up and the thermal actuator closes the pressure valve, the relief valve opens to allow excess fuel to easily pass back to the tank with minimal pressure drop.
As such, as described above, the present invention provides a novel and unique recirculating valve which effectively differentiates between air and fuel, and allows excess heated fuel to recirculate through the fuel system during cold operation to prevent plugging and waxing of the filter, and which directs any air from the engine directly back to the tank. The recirculation valve is simple in construction, and operates effectively to reduce, if not eliminate, any air recirculated back to the engine.
Further features of the present invention will become apparent to those skilled in the art upon reviewing the following specification and attached drawings.
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Clausen Michael D.
Knight Steven R.
Hunter Christopher H.
Miller Carl S.
Parker-Hannifin Corp.
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