Gas metering valve for a dual fuel engine

Abstract

The invention relates to a gas metering valve (1) for a dual fuel engine (17), which has a displaceable closing body (6) which, in a position of resting against a valve seat (5), closes the gas metering valve (1) and, in a position of being lifted off from the valve seat (5), opens the gas metering valve (1). The gas metering valve (1) is actuatable in a gas operating mode, in which the gas metering valve (1) meters combustion gas via a gas channel (13) into an intake manifold (15) of the dual fuel engine (17), and in a liquid fuel operating mode, in which the gas metering valve (1) remains sealingly closed against the pressure prevalent in the intake manifold (15). The valve seat (5) is movably situated along a valve seat guide (4), the valve seat (5), owing to the combustion gas pressure in the gas channel (13), in the gas operating mode being pressed away from the closing body (6) against a stop (20) in the gas metering valve (1) and is kept in its operating position, and the valve seat (5) in the liquid fuel operating mode being sealingly pressed by the pressure from the intake manifold (15) against the closing body (6).

Claims

1. A gas metering valve for dual fuel engines and operable in a gas operating mode or a liquid fuel operating mode, said valve comprising: a housing which provides a gas inlet opening at a first end, a gas channel and a gas outlet opening, a seat sleeve at said gas outlet opening providing a seat guide and a seat stop, a valve seat positioned within said seat sleeve, said valve seat being movable along said seat guide, and a closing body in an interior of the housing and movable toward and away from the valve seat, the valve seat being movably mounted along the seat guide and is pressed against the stop to close the device by gas in the interior of the housing when in the gas operating mode, and wherein the valve seat is sealingly pressed against the closing body in the liquid fuel operating mode.

2. The valve according to claim 1, wherein said closing body includes a hole therethrough and said valve seat includes a body guide which extends into said hole, said closing body being moveable along said body guide toward and away from the valve seat.

3. The valve according to claim 1, wherein said valve seat comprises a plurality concentric circular slots.

4. The valve according to claim 1, including a electromagnet and an armature plate in the interior of the housing, the closing body being connected to the armature plate.

5. The valve according to claim 4, including a magnet base centrally positioned in the gas channel, said electromagnet being positioned in the magnet base.

6. The valve according to claim 1, including separate sealing elements within the seat sleeve respectively located on opposite sides of said stop.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present invention is subsequently described in more detail in reference to FIGS. 1 through 3, which show advantageous embodiments of the present invention in an exemplary, schematic and non-limiting manner.

(2) FIG. 1 shows the gas metering valve according to the present invention in a sectional view along the main axis;

(3) FIG. 2 shows a schematic illustration of one cylinder of a dual fuel engine equipped with the gas metering valve; and

(4) FIG. 3 shows a schematic illustration of the cylinders of a dual fuel engine equipped with the gas metering valve.

DETAILED DESCRIPTION

(5) Gas metering valve 1 according to the present invention and shown in FIG. 1 has a housing 2 in which a gas channel 13 is provided being through-flown by the metered combustion gas. The combustion gas enters gas metering valve 1 through a gas inlet 12, through-flows gas channel 13 and enters by way of a gas outlet 14 an intake manifold 15 which leads to combustion chamber 16 of a dual fuel engine 17 (FIG. 3). In the region of gas outlet 14, a valve seat 5 is located, which has a plurality of circular, concentric slots 8, which can be selectively closed or unblocked by a closing body 6. Closing body 6 has a corresponding number of concentric rings 25 which are connected to one another by radial webs distributed about the circumference and which are, for closing the valve, pressed against the concentric slots 8 of valve seat 5 and which are sealing said concentric slots.

(6) In order to actuate gas metering valve 1 illustrated in FIG. 1, a magnet-base 18, in which an electromagnet 7 is located, is situated in the gas channel 13. Upon activation, electromagnet 7 pulls an armature plate 11 and closing body 6 connected to armature plate 11 against the force of a return spring 9 into the opened valve position. A stop ring 21 is provided at closing body 6 which, in the open valve position, is deposited at a stop surface 22 of magnet-base 18. As soon as electromagnet 7 is deactivated, the unit made of armature plate 11, stop ring 22 and closing body 6 is pushed away from electromagnet 7 by return spring 9 and closing body 6 is deposited against valve seat 5. In a valve seat guide 4, valve seat 5 is movably mounted and is pressed against a stop 20 by the pressure of the combustion gas so that the position of valve seat 5 is always defined during the gas operating mode of dual fuel engine 17. Valve seat guide 4 and stop 20 are configured at the interior wall of a valve seat sleeve 3 which is connected to housing 2.

(7) The position illustrated in FIG. 1 corresponds with the closed valve position in the gas operating mode, the distance between stop ring 21 and stop surface 22 of magnet-base 18 corresponding with valve clearance x.

(8) The relationship of the surface of valve seat 5 facing closing body 6 to the surface of valve seat 5 facing intake manifold 15 is selected in such a manner that the pressure of the combustion gas acting from gas channel 13 upon valve seat 5 during the gas operating mode always exerts a greater force onto valve seat 5 in the axial direction than the force exerted by the maximum pressure in intake manifold 15 onto valve seat 5 in the opposite direction. In doing so, it is ensured that valve seat 5 during the gas operating mode is always kept in the position defined by stop 20 so that the function of valve seat 5 corresponds to that of a fixed valve seat in a generic gas metering valve. An additional tensioning device or spring which pretensions valve seat 5 in the direction of stop 20 is thus not required.

(9) A conical closing body guide 10 is provided in the center of valve seat 5, which is fixedly connected to valve seat 5 and projects from valve seat 5 in the direction of the armature plate. When opening and closing gas metering valve 1, closing body 6 slides on closing body guide 10 which positions, centers and guides said closing body during the opening and closing movement.

(10) During the liquid fuel operating mode of dual fuel engine 17, electromagnet 7 is deactivated and return spring 9 presses closing body 6 against valve seat 5 so that gas metering valve 1 remains closed. When the combustion gas supply is closed, the gas pressure in gas channel 13 declines. For this reason, closing body 6 is pressed against valve seat 5 exclusively by the force of return spring 9, the pressure in intake manifold 15 continuously being maintained when operating dual fuel engine 17 with liquid fuel. Pressure differences between the intake manifold pressure and the gas pressure in the interior of the valve and pressure peaks arising when operating the turbo charger can then for generic valves result in that the pressure force acting upon the closing body through the slots of the valve seat exceeds the force of the return spring which, for a generic charge cycle valve, would lead to that the closing body lifts off the valve seat and charge air having therein contained pollutants would penetrate into the gas metering valve, as a result of which said gas metering valve can be damaged. Since a stronger spring tension of the return spring would also require a stronger dimensioning of the electromagnet, one, is intended to keep the spring tension as low as possible to minimize costs and the dimensions of the gas metering valve. For this reason, an increase in spring tension is generally not desired.

(11) In contrast, in the case of gas metering valve 1 according to the present invention and illustrated in FIG. 1, stop 20 safeguards valve seat 5 only against a movement in the direction of intake manifold 15. Since the pressure in intake manifold 15 does not only act upon the surfaces of rings 25 of closing body 6, which are exposed by the slots of valve seat 5, but also upon the much greater surface of movable valve seat 5, which is oriented towards intake manifold 15, the pressure in intake manifold 15 cannot lift off closing body 6 from valve seat 5, even when the spring tension of return spring 9 is rather low, because valve seat 5 would be continuously pressed against closing body 6 and because valve seat 5, together with closing body guide 10 and closing body 6, as a unit moves axially in the direction of the valve interior until stop ring 21 abuts at stop surface 22 of magnet-base 18. When the pressure in intake manifold 15 declines again, the return spring pushes the unit out of closing body 6, valve seat 5 and closing body guide 10 back into the starting position, in which valve seat 5 abuts stop 20. The sealing function of the gas metering valve is ensured for the entire deflection movement of the unit out of closing body 6, valve seat 5 and closing body guide 10 during the liquid fuel operating mode.

(12) Valve seat guide 4 is sealed vis--vis valve seat 5 by way of two sealing elements 23, 24, which are respectively situated above and below the step of stop 20. Sealing elements 23, 24 are preferably O-rings, which are situated in annular grooves at the circumferential surface of valve seat 5. In addition to the sealing function, sealing elements 23, 24 also act as scrapers for pollutants during the movements of the valve seat, which have penetrated into the gap between valve seat 5 and valve seat sleeve 3. In order to ensure the sealing function, a single sealing element would suffice; however, it is advantageous to protect stop 20 from both sides from pollutants because, when dirt accumulates on stop 20, the resting position of valve seat 5 (that is, the position during the gas operating mode) is no longer accurately defined, and the distance between closing body 6 and the valve seat would, during a complete lifting-off of the closing body, be altered or even, seen in the radial direction, be uneven if the valve seat were obliquely situated in valve seat guide 4.

(13) FIG. 2 shows a schematic illustration of a cylinder 31 of a dual fuel engine 17 equipped with a gas metering valve 1 according to the present invention. Gas metering valve 1 is situated in the intake manifold just upstream of charge cycle valve 19. In FIG. 2, gas metering valve 1 is schematically illustrated, the potential technical configurations of the gas supply, which, for example, can be implemented in intake manifold 15 as an annular channel having openings and enclosing intake manifold 15, are known to the skilled person. In a known manner, charge cycle valve 19 opens and closes the inlet to combustion chamber 16 of cylinder 31 during the intake stroke according to the position of piston 27. Charge cycle valve 19 is operated by a camshaft 28. A second camshaft 28 operates a second charge cycle valve 19 to discharge during the exhaust stroke the exhaust gases into an exhaust gas line 29. During the liquid fuel operating mode, in which gas metering valve 1 is deactivated, liquid fuel is injected in a known manner via a direct injection 29 directly into combustion chamber 16.

(14) FIG. 3 shows a schematic illustration of a dual fuel engine 17 equipped with the gas metering valve, having six cylinders, each of which are configured according to FIG. 2. The charge air is supplied to the cylinders via a joint charge air supply 30 by way of individual intake manifolds 15. One gas metering valve 1 is situated at each intake manifold 15 which, in the gas operating mode, supplies the cylinder 31 with combustion gas, and each cylinder is, furthermore, provided with a direct injection 26 for the liquid fuel operation.

LIST OF REFERENCE CHARACTERS

(15) 1 Gas metering valve

(16) 2 Housing

(17) 3 Valve seat sleeve

(18) 4 Valve seat guide

(19) 5 Valve seat

(20) 6 Closing body

(21) 7 Electromagnet

(22) 8 Slots

(23) 9 Return spring

(24) 10 Closing body guide

(25) 11 Armature plate

(26) 12 Gas inlet

(27) 13 Gas canal

(28) 14 Gas outlet

(29) 15 Intake manifold

(30) 16 Combustion chamber

(31) 17 Dual fuel engine

(32) 18 Magnet-base

(33) 19, 19 Charge cycle valve

(34) 20 Stop

(35) 21 Stop ring

(36) 22 Stop surface

(37) 23 Gas channel sided sealing element

(38) 24 Intake manifold sided sealing element

(39) 25 Rings

(40) 26 Direct injection

(41) 27 Piston

(42) 28, 28 Camshaft

(43) 29 Exhaust gas line

(44) 30 Charge air supply

(45) 31 Cylinder