Valves and valve actuation – Fluid actuated or retarded – Pilot or servo type motor
Reexamination Certificate
2002-08-09
2004-04-27
Hirsch, Paul J. (Department: 3754)
Valves and valve actuation
Fluid actuated or retarded
Pilot or servo type motor
C123S446000, C251S129070
Reexamination Certificate
active
06726172
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a valve for bringing gaseous fuel into the combustion chamber of gas engines including a solenoid valve controlling the fuel supply and an adjoining check valve designed as a poppet valve (disk valve), which is closed by the force of a spring and which opens in the direction of the combustion chamber through the pressure of gas flowing from the opened solenoid valve.
2. The Prior Art
Valves of this type are known from JP 58-128 588 or EP 0 425 327 B1, for example, which make possible direct metering of gaseous fuels into the combustion chamber of reciprocating engines. The pressurized gaseous fuel is guided through the electrically controlled solenoid valve to the check valve, which is closed by the force of a spring, designed as a poppet valve, and disposed on the side of combustion chamber. The check valve is subsequently opened through the existing gas pressure after overcoming the closing force of the spring. After closing of the solenoid valve, the gas located in the space between the solenoid valve and the poppet valve escapes further into the combustion chamber until the closing force of the pull-back spring of the poppet valve becomes effective again against the decreasing gas pressure and it thereby closes the poppet valve.
In the disclosed arrangements with its described simple concept it has been shown—especially from examination of the combustion exhaust fumes—that under some operational conditions undesirably high emissions of unburned hydrocarbon occur that originate obviously from the fuel that reaches the combustion chamber even after the completion of the actual combustion process.
To avoid these disadvantages, there is according to an earlier invention (see U.S. patent application Ser. No. 09/876 030) the closing element of the poppet valve connected to a step piston on the side that faces away from the valve head (disk) whereby the step piston's larger upper side facing away from the head and the opposite smaller lower side are biased by the fuel pressure existing in the space located between the solenoid valve and the valve head, and whereby the step piston's step area corresponds to the difference in diameter between the two step piston areas, is influenced by an essentially constant pressure, and whereby the step area of the step piston is significantly larger than the actuation space of the check valve that remains between the stem and the seat area of the valve head. Thereby there is determined the force balance (the spring force and the gas pressure at both sides) effecting the poppet valve at first only through the spring force and the pressure differential on the step piston. The pressure forces, which naturally engage the substantially smaller valve head like before and thereby also the above-mentioned influence of the pressure reduction caused by the flow, are now of secondary significance whereby a sufficiently large closing force surplus may be ensured without difficulties and re-opening of the poppet valve is strictly prevented at the end of the working stroke under the described conditions.
With this earlier design, the fact was taken into consideration that the possibly largest surplus in closing force must exist toward the end of the closing phase of the check valve on the side of the combustion chamber so that the re-opening of the valve is prevented with certainty after the completed combustion. For the achievement of this object, there is additionally the difficulty that during the flow of the gaseous fuel around the disk head, a pressure develops that lies below the static pressure of the otherwise local pressure in the space. The local pressure is caused on the side facing the stem through the high flow velocity of the gaseous fuel, which lies in order of magnitude at the speed of sound whereby the force balance initiating the closing movement is reached only at a higher pressure differential between the first space and the working chamber compared to the transferred closing force of the spring of the disk valve onto the pressure-biased surface of the poppet valve. The surplus of closing force at the end of the closing phase of the disk valve is thus significantly reduced. It is thereby practically impossible to avoid under all circumstances the re-opening of the disk valve at the end of the working stroke simply by suitable balancing structural conditions of the known valve.
It has been shown in various specific designs and operational conditions of the valve in a previous application that, under certain circumstances, fuel may obviously still enter the combustion chamber even after completion of the actual combustion process. An effort has been made to achieve the stated object in a better and more reliable way to avoid these disadvantages.
SUMMARY OF THE INVENTION
This is achieved according to the present invention in that the first space defined by the step area on the step piston is connected via a passageway to the fuel supply line, on one hand, and to the second space between the step piston and the valve head, on the other hand, whereby these passageways are selectively opened and closed according to the movement of the step piston by a respective switching member.
In this simply way, it can be achieved that the step piston—and thereby the poppet valve—is kept in a closed position by an assisting pressure after completion of the injection of fuel into the combustion chamber whereby the corresponding assisting pressure is controlled by the step piston itself at the start of the next opening movement of the step piston. The assisting pressure in the first space underneath the step piston is released and then it is again directly made available for [continued] operation without additional arrangements. The respective switching times for opening and closing of said passageways, leading to or away from the first space defined by the step area on the step piston, may be determined or varied very simple through mutual positioning of the corresponding members so that the design of the valve may be simply adjusted to the respective requirement.
In an additional embodiment of the invention it is proposed that the first switching member on the passageway between the fuel supply line and the step area and the step piston is provided with a sealing member at the larger circumference of said step piston whereby said sealing member opens or closes the piston-side opening of this passage according to the movement of the step piston, and whereby the delivery of the pressurized gaseous fuel is actively guided to the first space defined by the step area of the step piston. In addition, the alternative opening and closing of the fuel delivery could also be achieved through constructive influence of flow resistance in the path of the gaseous fuel from the delivery side to the outlet side in the direction of the second space between the step piston and the valve disk since a sufficiently large flow resistance the same effect as the actual active blocking and opening of the flow path during specific times of the dynamically occurring flow action.
According to an additional preferred embodiment of the invention, the switching member of the passageway between the first space defined by the step area on the step piston and the second space between the step piston and the valve head is provided with a sealing member at the smaller circumference of the step piston, which opens and closes an opening of the passageway arranged in the housing to the second space between the step piston and the valve head according to the movement of the step piston. As mentioned above, the pressurized gaseous fuel used to keep the valve head in a closed position is again guided thereby in an especially advantageous manner to the gaseous fuel flowing into the combustion chamber so that no other arrangements are necessary in this regard.
The required pressure conditions in the step area on the step piston may be very simply achieved through mutual positioning of the juxtaposed ope
Malicke Dustin A.
Mathews Hans F.
Racaniello Jerry
Steinrück Peter
Dykema Gossett PLLC
Hirsch Paul J.
Hoerber Kompressortechnik Services GmbH
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