FLOW LIMITING VALVE, IN PARTICULAR FOR A DUAL FUEL INJECTION SYSTEM

Abstract

A flow limiting valve, comprising a valve body adjustable between a closed position and an open position, wherein in the open position a flow channel for a conveying fluid is opened in the flow limiting valve and in the closed position the flow channel is closed, whereby the adjustment of the valve body is subject to conveying fluid pressure; wherein a control valve is integrated into a housing of the flow limiting valve through which the valve body is adjustable between open and closed positions, regardless of the conveying fluid.

Claims

1. A flow limiting valve, comprising: a housing; a valve body adjustable between a closed position and an open position, wherein in the open position a flow channel for a conveying fluid is opened in the flow limiting valve and in the closed position the flow channel is closed, whereby the adjustment of the valve body is subject to conveying fluid pressure; and a control valve integrated into the housing of the flow limiting valve through which the valve body is adjustable between open and closed positions, regardless of the conveying fluid.

2. The flow limiting valve according to claim 1, wherein the flow limiting valve is used in a dual-fuel injection system.

3. The flow limiting valve according to claim 1, wherein a control element of the control valve operates the valve body and is adjustable by a control fluid.

4. The flow limiting valve according to claim 3, wherein the control element is an adjusting piston and is located within a piston housing supplied by the control fluid.

5. The flow limiting valve according to claim 3, wherein end faces of the control element or of a component connected with the control element are supplied by the control fluid at different pressures.

6. The flow limiting valve according to claim 5, wherein a throttle is integrated into a control line for conveying the control fluid.

7. The flow limiting valve according to claim 6, wherein opposite end faces of the control element or of components connected with the control element are supplied with the control fluid upstream and downstream of the throttle.

8. The flow limiting valve according to claim 3, wherein the valve body and the control element of the control valve are arranged coaxially.

9. The flow limiting valve according to claim 1, wherein the valve body is force-actuated into the open position by a spring element.

10. The flow limiting valve according to claim 3, wherein the control element of the control valve is force-actuated by a spring element into a non-functional position.

11. The flow limiting valve according to claim 1, wherein the conveying fluid is a burnable gas.

12. The flow limiting valve according to claim 3, wherein the control fluid is a liquid fuel.

13. A dual-fuel injection system, comprising: a flow limiting valve, including: a control valve integrated into a housing, the control valve including: a valve body adjustable between a closed position and an open position, the adjustment operable by pressure of a conveying fluid or in the absence of the conveying fluid; and a flow channel in the valve body for passage of the conveying fluid, the flow channel being opened in the open position and closed in the closed position; a burnable gas injector unit; and a liquid fuel injector unit.

14. The dual-fuel injection system according to claim 13, wherein the flow limiting valve is allocated to the burnable gas injector unit.

15. The dual-fuel injection system according to claim 13, further comprising an adjustable pilot valve located in a control line connected with the liquid fuel injector unit, wherein control fluid is operable to be supplied to the flow limiting valve downstream from the pilot valve.

16. A method of operating a dual-injection system, comprising: providing a flow limiting valve, including: a control valve integrated into a housing, the control valve including: a valve body adjustable between a closed position and an open position, the adjustment operable by pressure of a conveying fluid or in the absence of the conveying fluid; and a flow channel in the valve body for passage of the conveying fluid, the flow channel being opened in the open position and closed in the closed position; a burnable gas injector unit; and a liquid fuel injector unit; providing a liquid fuel used as a control fluid; and adjusting the control valve with pressure of the control fluid.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention will be better understood by reference to the following description of an embodiment of the invention taken in conjunction with the accompanying drawings, wherein:

[0020] FIG. 1 is a schematic illustration of a dual fuel injection system for an internal combustion engine according to the invention; and

[0021] FIG. 2 is a longitudinal sectional view of a flow limiting valve according to the invention.

[0022] Corresponding reference characters indicate corresponding parts throughout the several views. The exemplification set out herein illustrates one embodiments of the invention, in one form, and such exemplification is not to be construed as limiting the scope of the invention in any manner.

DETAILED DESCRIPTION OF THE INVENTION

[0023] The dual fuel injection system 1 illustrated in FIG. 1 is equipped for operation in the pilot injection method with liquid fuel, for example diesel fuel or heavy oil or bio-oil, as well as for operation with burnable gas, for example natural gas or bio-gas. Dual fuel injection system 1 includes a dual fuel injector system 2, a high-pressure gas tank 3 for storage of pressurized burnable gas, a burnable gas flow limiting valve 4 that is supplied by the high-pressure gas storage tank 3, two pumps 5 and 6 that are located in series in the fuel section, and a liquid fuel tank 7. Dual fuel injector system 2 includes a liquid fuel injector unit 8, as well as a burnable gas injector unit 9 through which the liquid fuel or burnable gas can be injected into the combustion chamber of an internal combustion engine.

[0024] High pressure tank 10 for the liquid fuel is associated with dual fuel injector system 2; said tank being supplied via in-series connected pumps 5 and 6 with the liquid fuel that is under high pressure. High pressure tank 10 is located either in the injector unit or is arranged as a common-rail high pressure tank outside the injector unit. Following high pressure tank 10, a liquid fuel flow limiting valve 11 is located in a high pressure line 12 that leads to liquid fuel injector unit 8. From this high pressure line 12, supply control lines 13 and 14 each branch to a throttle for activation of liquid fuel injector unit 8 or burnable gas injector unit 9. The fuel supplied via supply control lines 13, 14 represents the control fluid for activation of injector units 8,9.

[0025] The control fluid supplied to liquid fuel injector unit 8 flows via a return control line 15 in which a pilot valve 16 is located, to liquid fuel tank 7. Pilot valve 16 is designed for example as a 2/2-way valve. A throttle 17 is located in the control line segment between pilot valve 16 and fuel tank 7; throttles are also located in supply control lines 13 and 14 to the injector units 8, 9 and in return control line 15 upstream of pilot valve 16.

[0026] On the gas side, the burnable gas flows from high-pressure fuel tank 3 to burnable gas flow limiting valve 4 and onward via line 18 to burnable gas injector unit 9. Activation of injector unit 9 occurs via the liquid fuel that is supplied via supply control line 14. On the outlet side, the control fluid is discharged from supply control line 14 via return line 19 into which a throttle and downstream a control or pilot valve 20 is integrated. Downstream of valve 20, return control line 19 runs into return control line 15 of liquid fuel injector unit 8, upstream of throttle 17.

[0027] During the starting procedure of the internal combustion engine, the dual fuel injection system 1 operates preferably exclusively with fuel injection via liquid fuel injector unit 8. At higher speeds, changeover to gas operation in the pilot injection method can occur, whereby a pilot injection occurs via liquid injector unit 8.

[0028] Now referring to FIG. 2 with continued reference to FIG. 1, a longitudinal section of burnable gas flow limiting valve 4 is illustrated. Flow limiting valve 4 includes a housing 21, as well as flange piece 22 facing the injector inlet and which is connected with housing 21 by way of a cap nut 23.

[0029] In housing 21 a gas chamber 24 is established into which gas flows from the high pressure gas tank 3, through a connecting element 25 located on the opposite side of flange piece 22 as indicated by the arrow. In gas chamber 24 a piston shaped valve body 26 can move axially, whereby into its wall an axially progressing overflow channel 27 is incorporated through which the gas travels from gas chamber 24 to an outlet channel 28 in flange piece 22, from where the gasas indicated by the arrowis diverted out of the burnable fuel flow limiting valve 4 and is moved along in the direction of the injector unit.

[0030] Valve body 26 is force-actuated into its open position by a spring element 29. Valve body 26 is located in a housing space 30 and can be axially moved inside housing space 30. As a result of the force of spring element 29, valve body 26 is held in its open position where valve body 26 protrudes partially into gas chamber 24 and whereby gas from gas chamber 24 gets into outlet channel 28 via overflow channel 27. In the event that valve body 26 is completely or almost completely pushed into housing space 30, overflow channel 27 will be located outside the flow connection with gas chamber 24, so that the flow connection is interrupted; the valve body is thus in a closed position wherein the flow through flow limiting valve 4 is interrupted.

[0031] The pressure of the introduced burnable gas prevailing in gas chamber 24 acts upon the face side of valve body 26 and actuates same against the force of spring element 29 into the closed position. At the same time, a gas pressure that force-actuates valve body 26 into the open position also prevails in housing space 30 where valve body 26 can move. Provided that the gas pressure is approximately equal at both end faces of valve body 26, valve body 26 is held in the open position by the force of the spring element acting upon it. However, if the gas pressure drops on the side facing away from gas chamber 24, then valve body 26 is moved into the closed position by the pressure in gas chamber 24.

[0032] A control valve 31 is integrated into housing 21 of flow limiting valve 4, whose control element 32 is in the embodiment of an adjusting piston that is arranged coaxially as well as coaxially offset relative to valve body 26. The adjusting piston is accommodated axially adjustable in an enclosed piston housing space 33 and is force actuated by a spring element 34 in a direction of a functional position, where adjusting piston 32 moves valve body 26 axially into the closed position. Adjusting piston 32 is connected with a head 35 that divides piston housing space 33 into two chambers, whereby spring element 34 engages on head 35 on the side opposite adjusting piston 32.

[0033] Piston housing space 33 is connected on both sides of head 35 via control channels 36 and 37 with control lines 38 and 39 (FIG. 1) that branch immediately upstream and downstream of throttle 17 in return control line 15 that leads to liquid fuel tank 7. Control channels 36 and 37 are provided in flange plate 22 or respectively housing 21. Sealing rings 40, 41 and 42 that seal control channels 36 and 37 radially are located between flange plate 22 and housing 21.

[0034] Via first control channel 36 that is connected with control line 38, liquid fuel is supplied as the control fluid under relatively high pressure into the chamber of piston housing space 33 with adjusting piston 32. The opposite chamber of piston housing space 33 in which spring element 34 is arranged is connected via second control channel 37 with control line 39 downstream from throttle 17 where a lower pressure prevails. This pressure differential actuates the control element with the adjusting piston and the head against the force of spring element 34 into the retracted non-functional position. If the pressure difference drops below a threshold value, the resulting force of the hydraulic differential pressure upon head 35 drops below the spring force of spring element 34, and adjusting piston 32 is moved axially from the non-functional position into the functional position in which the front face of the adjusting piston presses against valve body 26 and moves valve body 26 into its closed position.

[0035] During the fuel injection operation, pilot valve 16 opens and closes in sequence with the injection. An average pressure results hereby in return control line 15, downstream of pilot valve 16 that is conveyed via control line 38 and control channel 36 into the chamber of piston housing space 33 with adjusting piston 32. In regular operation, the average pressure exceeds the threshold value that is relevant for maintaining the non-function position, so that the control element of control valve 31 is held in the non-functional position.

[0036] If on the other hand, for example due to a malfunction, the average pressure immediately upstream of throttle 17 drops below the threshold valuewhich is the case for example during permanent closing of pilot valve 16the pressure in the chamber of piston housing space 33 with the adjusting piston drops accordingly, so that spring element 34 presses the adjusting piston into the functional position and said piston closes valve body 26.

[0037] If pilot valve 20 that is allocated to burnable fuel injector unit 9 remains open due to a malfunction and at the same time, pilot valve 16 that is allocated to liquid fuel injector unit 8 is closed due to a malfunction, valve body 26 of flow limiting valve 4 is also moved into the closed position, whereas control valve 31 remains in its non-functional position.

[0038] If pilot valve 20 that is allocated to burnable fuel injector unit 9 remains open, then liquid fuel flow limiting valve 11 closes advantageously, so that flow limiting valve 4 closes subsequently.

[0039] While this invention has been described with respect to at least one embodiment, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.