FUEL GAS INJECTION VALVE, DUAL-FUEL GAS ENGINE, AND FUEL GAS INJECTION METHOD

A fuel gas injection valve according to the present invention includes: a holder including a first injection hole through which fuel gas is injected to produce premixed fuel, and a second injection hole through which fuel gas is injected to produce diffusion fuel; a first needle valve that slidably reciprocates in the holder along an axial direction to open and close the first injection hole and the second injection hole; and a second needle valve having a sealing face on the top thereof and a through-hole provided along the axial direction at the central portion in a radial direction of the second needle valve, the sealing face being brought into contact with a needle valve seat provided in the holder, the first needle valve being slidably inserted into the through-hole, and the second needle valve reciprocating in the holder along the axial direction to prevent fuel gas from circulating to the first injection hole and the second injection hole when the sealing face is in contact with the needle valve seat, and to allow the fuel gas to circulate to the first injection hole or the second injection hole when the sealing face is separated from the needle valve seat.

FIELD

The present invention relates to a fuel gas injection valve, a dual fuel gas engine, and a method for injecting fuel gas, applicable to a (dual fuel two-stroke) gas engine capable of burning both fuel oil and fuel gas by using high-pressure injection.

BACKGROUND

Conventionally, there is publicly known a gas engine in which fuel gas such as natural gas is used as main fuel, and fuel oil such as light oil having high compression ignitability is used as pilot fuel, in order that the fuel oil such as light oil is injected into a combustion chamber in a high temperature atmosphere to be burned by self-ignition to burn the fuel gas serving as the main fuel.

For example, Patent Literature 1 (PTL 1 below) discloses a dual fuel diesel engine in which low cetane number fuel having low compression ignitability, such as fuel gas is used as main fuel, and fuel oil having high compression ignitability is used as pilot fuel. The engine disclosed in Patent Literature 1 (PTL 1) includes a fuel gas injection valve and a pilot fuel injection valve, provided in a cylinder head, and is configured to inject the fuel gas and the pilot fuel into a combustion chamber through the fuel gas injection valve and the pilot fuel injection valve so that the pilot fuel (fuel oil) is burned in the combustion chamber at high temperature by self-ignition to burn the main fuel (fuel gas).

In addition, for example, Patent Literature 2 (PTL 2 below) discloses a gas engine in which fuel gas having low compression ignitability is used as main fuel, and diesel fuel such as light oil and kerosene, having high compression ignitability, is used as pilot fuel. The gas engine disclosed in Patent Literature 2 (PTL2) includes an intake port and a diesel fuel injection device, provided in a cylinder head, and a fuel gas injection device provided in a cylinder circumferential wall. During an intake stroke in which a piston falls, air is introduced into a combustion chamber from the intake port, and the fuel gas injection device is configured to inject the fuel gas into the combustion chamber at proper timing between a later stage of the intake stroke and a later stage of a compression stroke. In addition, the diesel fuel injection device is configured to inject the diesel fuel into the combustion chamber at a time when the piston rises close to top dead center to allow the diesel fuel to burn in the combustion chamber by self-ignition, thereby burning the fuel gas serving as the main fuel.

SUMMARY

In the engine above described in PTL 1, since the main fuel and the pilot fuel are supplied into the combustion chamber almost at the same time when the piston is close to the top dead center, the main fuel injected into the combustion chamber is immediately burned without agitation. Thus, a combustion form of the main fuel is diffusion combustion. In the case of the diffusion combustion, uniform combustion is difficult as compared with premixed combustion, so that there is a problem in which NOx (nitrogen oxide) tends to easily occur in a combustion zone at high temperature.

In addition, the gas engine above described in PTL 2 is the invention made for increasing the amount of air to be sucked in the combustion chamber. That is, the invention described in PTL 2 is configured to suck only air from an intake port and to be separately provided with a fuel gas injection device while conventionally, a gaseous mixture of fuel gas and air is introduced from an intake port. The fuel gas injection device injects fuel gas into the combustion chamber by shifting the timing of injection with respect to an intake stroke to increase the amount of air to be sucked in the combustion chamber from the intake port, thereby improving engine output.

In PTL 2, there is disclosed no technical idea of reducing occurrence of NOx (nitrogen oxide) by promoting premixing.

The present invention is made in light of the problem of the conventional art as described above, and an object of the present invention is to provide a fuel gas injection valve, a dual fuel gas engine, and a method for injecting fuel gas, capable of reducing occurrence of NOx (nitrogen oxide) by promoting premixing of fuel gas and air.

A fuel gas injection valve in accordance with the present invention is applicable to a dual fuel gas engine capable of burning both fuel oil and fuel gas by using high-pressure injection, and the fuel gas injection valve includes: a holder including a first injection hole through which fuel gas is injected to produce premixed fuel when a piston included in the dual fuel gas engine is positioned between 40° and 100° before top dead center, and a second injection hole through which fuel gas is injected to produce diffusion fuel when the piston is positioned about 5° before the top dead center; a first needle valve that slidably reciprocates along an axial direction in the holder to close the second injection hole when the first injection hole is opened, and to open the second injection hole when the first injection hole is closed; and a second needle valve having a sealing face on the top thereof and a through-hole provided along the axial direction at the central portion in a radial direction of the second needle valve, the sealing face being brought into contact with a needle valve seat provided in the holder, the first needle valve being slidably inserted into the through-hole, and the second needle valve reciprocating in the holder along the axial direction to prevent fuel gas from circulating to the first injection hole and the second injection hole when the sealing face is in contact with the needle valve seat, and to allow the fuel gas to circulate to the first injection hole or the second injection hole when the sealing face is separated from the needle valve seat.

In addition, a method for injecting fuel gas in accordance with the present invention is applicable to a dual fuel gas engine capable of burning both fuel oil and fuel gas by using high-pressure injection, and the method includes: injecting fuel gas to produce premixed fuel when the piston included in the dual fuel gas engine is positioned between 40° and 100° before top dead center, and injecting fuel gas to produce diffusion fuel when the piston is positioned about 5° before the top dead center.

In accordance with the fuel gas injection valve and the method for injecting fuel gas according to the present invention, it is possible to promote premixing of fuel gas and air so that occurrence of NOx (nitrogen oxide) can be reduced.

In the fuel gas injection valve described above, it is further preferable that the first needle valve serves as a slide valve that is reciprocated in the holder along the axial direction by pressure inside cylinder of the dual fuel gas engine.

In accordance with the fuel gas injection valve, only applying the pressure inside cylinder to the first needle valve (slide valve) allows the first needle valve (slide valve) to move to a side opposite to the inside of the cylinder.

Accordingly, it is possible to remove components for moving the first needle valve (slide valve) to the side opposite to the inside of the cylinder, such as a first electromagnetic valve41, a first flow channel switching valve42, and a first hydraulic oil pipe43, shown inFIG. 4, so that a configuration can be simplified.

In the fuel gas injection valve described above, it is further preferable that the nozzle includes oil reservoirs provided in a portion in which the second needle valve slides and in the through-hole, respectively, and the oil reservoir provided in the portion in which the second needle valve slides and the oil reservoir provided in the through-hole communicate with each other through a communication hole provided in the nozzle along a radial direction thereof.

In accordance with the fuel gas injection valve, it is possible to apply lubricant to a sliding portion so that abrasion and fastening of the sliding portion can be prevented.

The fuel gas injection valve in accordance with the present invention is applicable to a dual fuel gas engine capable of burning both fuel oil and fuel gas by using high-pressure injection, and the fuel gas injection valve includes: a holder including a first injection hole through which fuel gas is injected to produce premixed fuel when a piston included in the dual fuel gas engine is positioned between 40° and 100° before the top dead center, and a second injection hole through which fuel gas is injected to produce diffusion fuel when the piston is positioned between 10° before the top dead center and 15° after the top dead center; a first needle valve that slidably reciprocates along an axial direction in the holder to close the second injection hole when the first injection hole is opened, and to open the second injection hole when the first injection hole is closed; and a second needle valve having a sealing face on the top thereof, the sealing face being brought into contact with a needle valve seat provided in the holder, and the second needle valve reciprocating in the holder along the axial direction to prevent fuel gas from circulating to the first injection hole and the second injection hole when the sealing face is in contact with the needle valve seat, and to allow the fuel gas to circulate to the first injection hole or the second injection hole when the sealing face is separated from the needle valve seat.

In accordance with the fuel gas injection valve, it is possible to promote premixing of fuel gas and air so that occurrence of NOx (nitrogen oxide) can be reduced. In addition, in accordance with the fuel gas injection valve, as shown inFIG. 8, for example, the first needle valve and the second needle valve are not required to be formed concentrically with each other. As a result, manufacturing processes can be simplified, so that manufacturing cost can be reduced.

In the fuel gas injection valve described above, it is further preferable that the nozzle includes oil reservoirs provided in a portion in which the first needle valve slides and a portion in which the second needle valve slides, respectively.

In accordance with the fuel gas injection valve, it is possible to apply lubricant to a sliding portion so that abrasion and fastening of the sliding portion can be prevented.

The dual fuel gas engine according to the present invention includes any one of the fuel gas injection valves described above.

In accordance with a dual fuel gas engine according to the present invention, the dual fuel gas engine includes a fuel gas injection valve capable of promoting premixing of fuel gas and air to reduce occurrence of NOx (nitrogen oxide). As a result, it is possible to reduce NOx (nitrogen oxide) discharged from the dual fuel gas engine so that performance of the dual fuel gas engine can be improved.

In accordance with the fuel gas injection valve, there is achieved an effect in which premixing of fuel gas and air can be promoted so that occurrence of NOx (nitrogen oxide) can be reduced.

DESCRIPTION

Hereinafter, the first embodiment of the fuel gas injection valve according to the present invention will be described with reference toFIGS. 1 to 5.

The scope of the present invention, however, is not limited to the embodiments below. Although there are described size, material, shape, relative arrangement, and the like of components in the embodiments below, the scope of the present invention does not intend to be limited to them, but they are only examples unless otherwise specified.

FIG. 1is a schematic view for describing a basic configuration of a (dual fuel two-stroke) gas engine to which a fuel gas injection valve according to the present invention is applied.FIG. 1(a) is a top view showing a piston that is positioned about 5° before top dead center, andFIG. 1(b) is a sectional view showing the piston that is positioned about 5° before the top dead center.FIG. 2is a schematic view for describing a basic configuration of a gas engine to which a fuel gas injection valve according to the present invention is applied.FIG. 2(a) is a top view showing a piston that is positioned between 4° before the top dead center and 40° after the top dead center, andFIG. 2(b) is a sectional view showing the piston that is positioned between 4° before the top dead center and 40° after the top dead center.FIG. 3is a schematic view for describing a basic configuration of a gas engine to which a fuel gas injection valve according to the present invention is applied.FIG. 3(a) is top and sectional views showing a piston that is positioned between 40° and 100° before the top dead center,FIG. 3(b) is top and sectional views showing the piston that is positioned about 5° before the top dead center, andFIG. 3(c) is top and sectional views showing the piston that is positioned between 4° before the top dead center and 40° after the top dead center.FIG. 4shows a section and a hydraulic system of a fuel gas injection valve according to a first embodiment of the present invention.FIG. 5includes an upper half that shows operation of the fuel gas injection valve according to the first embodiment of the present invention, and a lower half that includes graphs showing a relationship among opening/closing of the first needle valve, opening/closing of the second needle valve, pressure inside the cylinder, and a crank angle.

As shown inFIGS. 1 to 3, a gas engine1to which the fuel gas injection valve according to the present invention is applied includes a cylindrical cylinder2, a cylinder head3joined to an upper end of the cylinder2, and a piston4accommodated inside the cylinder2so as to be movable back and forth. In addition, a combustion chamber “c” is defined by a circumferential wall2aof the cylinder2, the cylinder head3, and a top face4aof the piston4.

In the drawings, a reference numeral5indicates a piston ring.

There is opened a scavenging port6in the circumferential wall2aon a lower side of the cylinder2. The scavenging port6is formed at a position above the top face4a(indicated by a dash-dot-dot line in the drawing) of the piston4positioned close to bottom dead center. When the piston4is positioned close to the bottom dead center, air is supplied to the combustion chamber “c” from the scavenging port6. In addition, in a top of the cylinder head3, an exhaust port is opened and an exhaust valve7for opening and closing the exhaust port is provided. The exhaust valve7is opened until the piston4reaches a position about 100° before top dead center during a scavenging stroke in which the piston4is in a rising stroke. Then, the air supplied to the combustion chamber “c” from the scavenging port6scavenges exhaust gas of the previous stroke, staying in the combustion chamber “c”.

The cylinder head3is provided with a fuel gas injection valve (fuel gas injection device)8for injecting fuel gas8ainto the combustion chamber “c”, as well as with a fuel oil injection valve (fuel oil injection device)10for injecting fuel oil10ahaving high compression ignitability into the combustion chamber “c”. The fuel gas injection valve8and the fuel oil injection valve10are provided one by one, 180° apart in a circumferential direction in which the center “o” of the cylinder center serves as the center of rotation.

In the present embodiment, each of the fuel gas injection valve8and the fuel oil injection valve10is provided with four injection holes. In the present invention, installed number of the fuel gas injection valve8and the fuel oil injection valve10, described above, is not limited, so that the installed number may be one, for example. However, in the present embodiment in which the exhaust valve7is provided at the top of the cylinder head3, it is preferable that each of a plurality of fuel gas injection valves8and fuel oil injection valves10is arranged in the circumferential direction at equal intervals.

As shown inFIGS. 1 and 2, the fuel gas injection valve8and the fuel oil injection valve10are connected to an engine control unit (ECU)12through a cable14. The ECU12is connected to a crank angle sensor15for detecting a rotation angle of a crankshaft17through a cable16, and receives a signal on the rotation angle of the crankshaft17from the crank angle sensor15to detect a phase of the piston4. In addition, the fuel gas injection valve8and the fuel oil injection valve10inject the fuel gas8aand the fuel oil10ainto the combustion chamber “c”, respectively, at predetermined timing on the basis of the signal transmitted from the ECU12.

That is, the ECU12constitutes a fuel gas injection timing control unit in the present embodiment, as well as constitutes an ignition timing control unit in the present embodiment which allows the fuel oil injection valve10to ignite fuel gas in the combustion chamber “c” when the piston4is positioned between 4° before the top dead center and 40° after the top dead center.

In addition, as shown inFIG. 3(a), when the piston4is in a rising stoke, and is positioned between 40° and 100° before the top dead center, the fuel gas injection valve8injects the fuel gas8binto the combustion chamber “c” on the basis of a signal transmitted from the ECU12(fuel gas injection timing control unit). As above, when the fuel gas8bis injected into the combustion chamber “c” while the piston4is positioned between 40° and 100° before the top dead center, the fuel gas8binjected and air inside the combustion chamber “c” are mixed in a process in which the piston4further rises close to the top dead center, thereby promoting premixing.

Next, as shown inFIGS. 1 and 3(b), when the piston4reaches about 5° before the top dead center, the fuel gas injection valve8injects the fuel gas8a, as well as the fuel oil injection valve10injects the fuel oil10a, on the basis of a signal transmitted from the ECU12(fuel gas injection timing control unit and ignition timing control unit), so that the fuel oil10ahaving high compression ignitability is burned by self-ignition in the combustion chamber “c” in a high temperature atmosphere. As a result, the fuel gas8ainjected is burned almost at the same time, so that combustion flame “f” is produced inside the combustion chamber “c” as shown inFIGS. 2 and 3(c), and then the combustion flame “f” is propagated to the gaseous mixture20described above to cause occurrence of explosive combustion in the whole of the combustion chamber “c”.

As above, the gas engine1according to the present embodiment is configured to inject the fuel gas8bwhen the piston4is positioned between 40° and 100° before the top dead center, and to inject the fuel gas8aand the fuel oil10awhen the piston4is positioned about 5° before the top dead center. Thus, premixing of the fuel gas8binjected when the piston4is positioned between 40° and 100° before the top dead center, and air, is promoted, so that the gaseous mixture20is produced to cause a part of combustion form to be premixed combustion. As a result, occurrence of NOx (nitrogen oxide) can be reduced as compared with a conventional gas engine in which the whole of combustion form is diffusion combustion.

In addition, the gas engine1according to the present embodiment is configured to control injection timing of the fuel gas injection valve8by using only the fuel gas injection timing control unit composed of the ECU12. Thus, it is possible to easily promote premixing in an existing gas engine without requiring a new additional device and the like.

As shown inFIG. 4, the fuel gas injection valve8according to the present embodiment includes a nozzle holder21, a nozzle22, a first needle valve23, a first needle valve pressing spring24, a second needle valve25, and a second needle valve pressing spring26.

The nozzle holder21includes: a recessed portion32for slidably accommodating a first enlarged diameter portion31provided at one end (apex) of the first needle valve23that extends along an axial direction (a vertical direction inFIG. 4), and that reciprocates along the axial direction; a first communication hole34that extends in a radial direction (a lateral direction inFIG. 4) to introduce hydraulic oil that moves the first needle valve23in an opening direction (an upper direction inFIG. 4) to a lower face (bottom face)33of the first enlarged diameter portion31, the lower face being a pressure receiving face; and a second communication hole36that extends along the radial direction to introduce hydraulic oil pushed out by an upper face (top face)35of the first enlarged diameter portion31when the first needle valve23is moved in the opening direction, to the outside of the nozzle holder21.

The hydraulic oil pushed out by the upper face35of the first enlarged diameter portion31is leaked through a sliding portion, namely a clearance between an outer peripheral face of the first enlarged diameter portion31and an inner peripheral face of the recessed portion32.

The first communication hole34is connected to the first flow channel switching valve42in which a flow channel is switched by the first electromagnetic valve41, through the first hydraulic oil pipe43. The first flow channel switching valve42is connected to a downstream end of a first hydraulic oil supply pipe44, and an upstream end of a first hydraulic oil return pipe45. The upstream end of the first hydraulic oil supply pipe44is arranged so as to be positioned inside a hydraulic oil tank46as well as close to a bottom face of the hydraulic oil tank46, and a hydraulic oil pump47is connected to the middle of the first hydraulic oil supply pipe44. The downstream end of the first hydraulic oil return pipe45is arranged so that hydraulic oil returned through the first hydraulic oil pipe43and the first hydraulic oil return pipe45is recovered inside the hydraulic oil tank46.

The nozzle22includes: a first recessed portion51that extends in the axial direction, and that accommodates the first needle valve pressing spring24and the second needle valve pressing spring26; a second recessed portion52that extends in the axial direction, and that slidably accommodates the second needle valve25that reciprocates along the axial direction; a third recessed portion54that slidably accommodates a second enlarged diameter portion53provided at the other end portion (tip portion) of the first needle valve23that reciprocates along the axial direction; a first communication hole57that extends in the radial direction to introduce hydraulic oil for moving the second needle valve25in the opening direction (upper direction inFIG. 4) to a lower face (bottom face)56of an enlarged diameter portion55of the second needle valve25, the lower face being a pressure receiving face; a second communication hole58that extends in the radial direction to introduce hydraulic oil pushed out by rising of the enlarged diameter portion55when the second needle valve25is moved in the opening direction, to the outside of the nozzle22; a third communication hole60that extends in the radial direction to introduce fuel gas into a chamber (annular space)59provided in a portion between the second recessed portion52and the third recessed portion54; a first injection hole61that introduces the fuel gas introduced into the chamber59and the third recessed portion54, into the combustion chamber “c” (refer toFIG. 1, etc.), at the time of injecting premixed fuel; and a second injection hole62that introduces the fuel gas introduced into the chamber59and the third recessed portion54, into the combustion chamber “c”, at the time of injecting diffusion fuel.

The first communication hole57is connected to a second flow channel switching valve72in which a flow channel is switched by a second electromagnetic valve71, through a second hydraulic oil pipe73. The second flow channel switching valve72is connected to a downstream end of a second hydraulic oil supply pipe74, and an upstream end of a second hydraulic oil return pipe75. The upstream end of the second hydraulic oil supply pipe74is connected to the middle of the first hydraulic oil supply pipe44positioned downstream the hydraulic oil pump47, and the downstream end of the second hydraulic oil return pipe75is connected to the middle of the first hydraulic oil return pipe45.

The third communication hole60is connected to a downstream end a fuel gas supply pipe76whose upstream end is connected to a fuel gas supply source (not shown).

The engine control unit12(refer toFIG. 1, etc.) transmits a command signal for energizing the first electromagnetic valve41and the second electromagnetic valve71, and a command signal for nonenergizing the first electromagnetic valve41and the second electromagnetic valve71, to an energization device63. The first electromagnetic valve41and the second electromagnetic valve71are energized or nonenergized on the basis of the command signals.

The first needle valve23includes the first enlarged diameter portion31at one end portion thereof in the axial direction, the second enlarged diameter portion53at the other end portion thereof in the axial direction, and a third enlarged diameter portion81on a side of the one end from the center thereof in the axial direction. The first needle valve is a solid cylindrical member, and is provided at its other end (tip) with a sealing face (seat face)83that is to be brought into contact with a first needle valve seat82. In addition, a top face of the third enlarged diameter portion81serves as a spring receiving face84that is brought into contact with a lower end of the first needle valve pressing spring24. The second enlarged diameter portion53is provided with a plurality of through-holes that penetrates through the second enlarged diameter portion53along the axial direction, that is, there is provided along the circumferential direction a plurality of communication holes85each of which allows top and lower faces of the second enlarged diameter portion53to communicate with each other.

The first needle valve pressing spring24urges the first needle valve23in a closing direction (urges so that the first needle valve seat82and the sealing face83are brought into contact with each other). Thus, in a state where the first hydraulic oil pipe43and the first hydraulic oil return pipe45communicate with each other, that is, in a state where hydraulic pressure of hydraulic oil is not applied to the lower face33of the first enlarged diameter portion31, the first needle valve23is urged in the closing direction.

The second needle valve25is a hollow cylindrical member in which there is provided along the axial direction a through-hole91through which the first needle valve23is slidably inserted, in its central portion in the radial direction. The second needle valve25includes a top face (apex face) serving as a spring receiving face92that is brought into contact with the lower end of the second needle valve pressing spring26, and a sealing face (seat face)94that is provided at the other end (tip) thereof, and that is brought into contact with the second needle valve seat93.

The second needle valve pressing spring26urges the second needle valve25in a closing direction (urges so that the second needle valve seat93and the sealing face94are brought into contact with each other). Thus, in a state where the second hydraulic oil pipe73and the second hydraulic oil return pipe75communicate with each other, that is, in a state where hydraulic pressure of hydraulic oil is not applied to the lower face56of the enlarged diameter portion55of the second needle valve25, the second needle valve25is urged in the closing direction.

Next, operation of the fuel gas injection valve8will be described with reference toFIGS. 4 and 5.

First, as shown inFIG. 4and the illustration at the first position from the left of the upper half ofFIG. 5, in a state where the first hydraulic oil pipe43and the first hydraulic oil return pipe45communicate with each other, as well as the second hydraulic oil pipe73and the second hydraulic oil return pipe75communicate with each other, a lift of each of the first needle valve23and the second needle valve25becomes 0 (zero) to close both of the first needle valve23and the second needle valve25.

Subsequently, the electromagnetic valve41shown inFIG. 4is energized to switch a flow channel of the first flow channel switching valve42to allow the first hydraulic oil pipe43and the first hydraulic oil supply pipe44to communicate with each other. Then, hydraulic oil introduced through the first communication hole34is applied to the lower face33of the first enlarged diameter portion31to lift up the first needle valve23(moves in the opening direction) as shown in the illustration at the second position from the left of the upper half ofFIG. 5. As a result, the outer peripheral face of the second enlarged diameter portion53closes the second injection hole62.

Next, the electromagnetic valve71shown inFIG. 4is energized to switch a flow channel of the second flow channel switching valve72to allow the second hydraulic oil pipe73and the second hydraulic oil supply pipe74to communicate with each other. Then, hydraulic oil introduced through the first communication hole57is applied to the lower face56of the enlarged diameter portion55of the second needle valve25to lift up the second needle valve25(moves in the opening direction) as shown in the illustration at the third position from the left of the upper half ofFIG. 5. As a result, the fuel gas introduced into the chamber59through the third communication hole60is introduced into the first injection hole61through the communication hole85so as to be injected as premixed fuel from the first injection hole61.

Subsequently, the electromagnetic valve41and the electromagnetic valve71shown inFIG. 4are nonenergized, so that the flow channel of the first flow channel switching valve42and the flow channel of the second flow channel switching valve72are switched to allow the first hydraulic oil pipe43and the first hydraulic oil return pipe45to communicate with each other, as well as to allow the second hydraulic oil pipe73and the second hydraulic oil return pipe75to communicate with each other, as shown inFIG. 4and the illustration at the fourth position from the left of the upper half ofFIG. 5, that is, both the first needle valve23and the second needle valve25are closed.

Next, the electromagnetic valve71shown inFIG. 4is energized to switch the flow channel of the second flow channel switching valve72to allow the second hydraulic oil pipe73and the second hydraulic oil supply pipe74to communicate with each other. Then, hydraulic oil introduced through the first communication hole57is applied to the lower face56of the enlarged diameter portion55of the second needle valve25to lift up the second needle valve25(moves in the opening direction) as shown in the illustration at the fifth position from the left of the upper half ofFIG. 5. As a result, the fuel gas introduced into the chamber59through the third communication hole60is introduced into the second injection hole62so as to be injected as diffusion fuel from the second injection hole62.

At this time, the electromagnetic valve41shown inFIG. 4is not energized, so that a lift of the first needle valve23becomes 0 (zero) to close the first needle valve23.

Subsequently, the electromagnetic valve71shown inFIG. 4is nonenergized, so that the flow channel of the second flow channel switching valve72is switched to allow the second hydraulic oil pipe73and the second hydraulic oil return pipe75to communicate with each other, as shown inFIG. 4and the illustration at the sixth position from the left of the upper half ofFIG. 5, that is, both the first needle valve23and the second needle valve25are closed.

The graphs in the lower half ofFIG. 5show a relationship among opening/closing of the first needle valve23, opening/closing of the second needle valve25, pressure inside the cylinder, and a crank angle.

In addition, the illustration at the third position from the left of the upper half ofFIG. 5corresponds toFIG. 3(a), and the illustration at the fifth position from the left of the upper half ofFIG. 5corresponds toFIGS. 1 and 3(b).

In accordance with the fuel gas injection valve8and the method for injecting fuel gas according to the present embodiment, it is possible to promote premixing of fuel gas and air so that occurrence of NOx (nitrogen oxide) can be reduced.

In accordance with the gas engine1provided with the fuel gas injection valve8according to the present embodiment, the gas engine includes the fuel gas injection valve8capable of promoting premixing of fuel gas and air to reduce occurrence of NOx (nitrogen oxide). As a result, it is possible to reduce NOx (nitrogen oxide) discharged from the gas engine1so that performance of the gas engine1can be improved.

Hereinafter, the second embodiment of the fuel gas injection valve according to the present invention will be described with reference toFIGS. 6 and 7.

FIG. 6shows a section and a hydraulic system of a fuel gas injection valve according to the second embodiment of the present invention.FIG. 7includes an upper half that shows operation of the fuel gas injection valve according to the second embodiment of the present invention, and a lower half that includes graphs showing a relationship among opening/closing of a needle valve, opening/closing of a slide valve, pressure inside the cylinder, and a crank angle.

As shown inFIG. 6, the fuel gas injection valve108according to the present embodiment includes a nozzle holder121, a nozzle122, a slide valve123, a slide valve pressing spring124, a needle valve125, and a needle valve pressing spring126.

The nozzle122includes: a first recessed portion151that extends in the axial direction, and that accommodates the slide valve pressing spring124and the needle valve pressing spring126; a second recessed portion152that extends in the axial direction, and that slidably accommodates the needle valve125that reciprocates along the axial direction; a third recessed portion154that slidably accommodates the other end portion (tip portion)153of the slide valve123that reciprocates along the axial direction; a first communication hole157that extends in the radial direction to introduce hydraulic oil for moving the needle valve125in an opening direction (upper direction inFIG. 6) to a lower face (bottom face)156of an enlarged diameter portion155of the needle valve125, the lower face being a pressure receiving face; a second communication hole158that extends in the radial direction to introduce hydraulic oil pushed out by rising of the enlarged diameter portion155when the needle valve125is moved in the opening direction, to the outside of the nozzle122, as well as to introduce hydraulic oil into the recessed portion151from the outside of the nozzle122when the needle valve125is moved in a closing direction (lower direction inFIG. 6); a third communication hole160that extends in the radial direction to introduce fuel gas into a chamber (annular space)159provided in a portion between the second recessed portion152and the third recessed portion154; a first injection hole161that introduces the fuel gas introduced into the chamber159and the third recessed portion154, into the combustion chamber “c” (refer toFIG. 1, etc.), at the time of injecting premixed fuel; and a second injection hole162that introduces the fuel gas introduced into the chamber159and the third recessed portion154, into the combustion chamber “c”, at the time of injecting diffusion fuel.

The first communication hole157is connected to a flow channel switching valve172in which a flow channel is switched by an electromagnetic valve171, through a hydraulic oil pipe173. The flow channel switching valve172is connected to a downstream end of a hydraulic oil supply pipe174, and an upstream end of a hydraulic oil return pipe175. The upstream end of the hydraulic oil supply pipe174is arranged so as to be positioned inside a hydraulic oil tank146as well as close to a bottom face of the hydraulic oil tank146, and a hydraulic oil pump147is connected to the middle of the hydraulic oil supply pipe174. The downstream end of the hydraulic oil return pipe175is arranged so that hydraulic oil returned through the hydraulic oil pipe173and the hydraulic oil return pipe175is recovered inside the hydraulic oil tank146.

The third communication hole160is connected to a downstream end of a fuel gas supply pipe176whose upstream end is connected to a fuel gas supply source (not shown).

The engine control unit12(refer toFIG. 1, etc.) transmits a command signal for energizing the electromagnetic valve171, and a command signal for nonenergizing the electromagnetic valve171, to an energization device163. The electromagnetic valve171is energized or nonenergized on the basis of the command signals.

The slide valve123is a solid cylindrical member that is provided at its one end in the axial direction with a first enlarged diameter portion131, and is provided in its outer peripheral face of the other end portion with peripheral grooves182and183along a circumferential direction, in order from an end face181that is to be a pressure receiving face of gas (gas inside the cylinder) in the combustion chamber “c”. In addition, the peripheral groove182and the peripheral groove183communicate with each other through a first hole (vertical hole)184penetrated along the axial direction through a central portion of the other end portion of the slide valve123in the radial direction, and second holes (horizontal holes)185penetrated along the radial direction through respective both ends of the first hole184. Further, a top face of the first enlarged diameter portion131serves as a spring receiving face186that is brought into contact with a lower end of the slide valve pressing spring124.

The slide valve pressing spring124urges the slide valve123in the closing direction.

The needle valve125is a hollow cylindrical member in which there is provided along the axial direction a through-hole191through which the slide valve123is slidably inserted, in its central portion in the radial direction. The second needle valve25is provided with a top face (apex face) that serves as a spring receiving face192that is brought into contact with the lower end of the needle valve pressing spring126, and is provided at its other end (tip) with a sealing face (seat face)194that is brought into contact with the needle valve seat193.

The needle valve pressing spring126urges the needle valve125in the closing direction (urges so that the needle valve seat193and the sealing face194are brought into contact with each other). Thus, in a state where the hydraulic oil pipe173and the hydraulic oil return pipe175communicate with each other, that is, in a state where hydraulic pressure of hydraulic oil is not applied to the lower face156of the enlarged diameter portion155of the needle valve125, the needle valve25is urged in the closing direction.

Next, operation of the fuel gas injection valve108will be described with reference toFIGS. 6 and 7.

First, as shown inFIG. 6and the illustration at the first position from the left of the upper half ofFIG. 7, in a state where gas pressure (gas pressure inside the cylinder) in the combustion chamber “c” is not applied to the end face181, and the hydraulic oil pipe173and the hydraulic oil return pipe175communicate with each other, a lift of each of the slide valve123and the needle valve125becomes 0 (zero) to close both of the slide valve123and the needle valve125.

Subsequently, the electromagnetic valve171shown inFIG. 6is energized to switch a flow channel of the flow channel switching valve172to allow the hydraulic oil pipe173and the hydraulic oil supply pipe174to communicate with each other. Then, hydraulic oil introduced through the first communication hole157is applied to the lower face156of the enlarged diameter portion155to lift up the needle valve125(moves in the opening direction) as shown in the illustration at the second position from the left of the upper half ofFIG. 7. As a result, the fuel gas introduced into the chamber159through the third communication hole160is introduced into the first injection hole161through the peripheral groove183, the second hole185, the first hole184, the second hole185, and the peripheral groove182, in order, so as to be injected as premixed fuel from the first injection hole161.

At this time, the second injection hole162is closed by an outer peripheral face of the other end portion153positioned between the peripheral groove182and the peripheral groove183.

Subsequently, the electromagnetic valve171shown inFIG. 6is nonenergized, so that the flow channel of the flow channel switching valve172is switched to allow the hydraulic oil pipe173and the hydraulic oil return pipe175to communicate with each other, as well as to allow gas pressure (gas pressure inside the cylinder) in the combustion chamber “c” to be applied to the end face181, as shown in the illustration at the third position from the left of the upper half ofFIG. 7, that is, the needle valve125is closed, and the slide valve123is lifted up (opened).

Next, the electromagnetic valve171shown inFIG. 6is energized to switch a flow channel of the flow channel switching valve172to allow the hydraulic oil pipe173and the hydraulic oil supply pipe174to communicate with each other. Then, hydraulic oil introduced through the first communication hole157is applied to the lower face156of the enlarged diameter portion155of the needle valve125to lift up the needle valve125(moves in the opening direction) as shown in the illustration at the fourth position from the left of the upper half ofFIG. 7. As a result, the fuel gas introduced into the chamber159through the third communication hole160is introduced into the second injection hole162through the peripheral groove183, the second hole185, the first hole184, the second hole185, and the peripheral groove182, in order, so as to be injected as premixed fuel from the second injection hole162.

At this time, the first injection hole161is closed by the outer peripheral face of the other end portion153positioned between the peripheral groove182and the end face181.

Subsequently, the electromagnetic valve171shown in FIG.6is nonenergized, so that the flow channel of the flow channel switching valve172is switched not to allow the gas pressure (gas pressure inside the cylinder) in the combustion chamber “c” to be applied to the end face181, as well as to allow the hydraulic oil pipe173and the hydraulic oil return pipe175to communicate with each other, as shown inFIG. 6and the illustration at the fifth position from the left of the upper half ofFIG. 7, that is, both the slide valve123and the needle valve125are closed.

The graphs in the lower half ofFIG. 7show a relationship among opening/closing of the slide valve123, opening/closing of the needle valve125, pressure inside the cylinder, and a crank angle.

In addition, the illustration at the second position from the left of the upper half ofFIG. 7corresponds toFIG. 3(a), and the illustration at the fourth position from the left of the upper half ofFIG. 7corresponds toFIGS. 1 and 3(b).

In accordance with the fuel gas injection valve108and the method for injecting fuel gas according to the present embodiment, it is possible to promote premixing of fuel gas and air so that occurrence of NOx (nitrogen oxide) can be reduced.

In accordance with the fuel gas injection valve108according to the present embodiment, only applying the pressure inside cylinder to the slide valve123allows the slide valve123to move to a side opposite to the inside of the cylinder.

Accordingly, it is possible to remove components for moving the slide valve123(first needle valve23) to the side opposite to the inside of the cylinder, such as the first electromagnetic valve41, the first flow channel switching valve42, and the first hydraulic oil pipe43, shown inFIG. 4, so that a configuration can be simplified.

In addition, in accordance with the gas engine1provided with the fuel gas injection valve8according to the present embodiment, the gas engine includes the fuel gas injection valve8capable of promoting premixing of fuel gas and air to reduce occurrence of NOx (nitrogen oxide). As a result, it is possible to reduce NOx (nitrogen oxide) discharged from the gas engine1so that performance of the gas engine1can be improved.

Hereinafter, the third embodiment of the fuel gas injection valve according to the present invention will be described with reference toFIG. 8.

FIG. 8shows a section and a hydraulic system of a fuel gas injection valve according to the third embodiment of the present invention.

As shown inFIG. 8, the fuel gas injection valve308according to the present embodiment includes a nozzle holder321, a nozzle322, a first needle valve323, a first needle valve pressing spring324, a second needle valve325, and a second needle valve pressing spring326.

The nozzle holder321includes: a recessed portion332for slidably accommodating a first enlarged diameter portion331provided at one end (apex) of the first needle valve323that extends along an axial direction (a vertical direction inFIG. 8), and that reciprocates along the axial direction; a first communication hole334that extends in a radial direction (a lateral direction inFIG. 8), and that introduces hydraulic oil that moves the first needle valve323in an opening direction (an upper direction inFIG. 8) to a lower face (bottom face)333of the first enlarged diameter portion331, the lower face being a pressure receiving face; and a second communication hole336that extends along the radial direction, and that introduces hydraulic oil pushed out by an upper face (top face)335of the first enlarged diameter portion331when the first needle valve323is moved in the opening direction, to the outside of the nozzle holder321.

The hydraulic oil pushed out by the upper face335of the first enlarged diameter portion331is leaked through a sliding portion, namely a clearance between an outer peripheral face of the first enlarged diameter portion331and an inner peripheral face of the recessed portion332.

The first communication hole334is connected to a first flow channel switching valve342in which a flow channel is switched by a first electromagnetic valve341, through a first hydraulic oil pipe343. The first flow channel switching valve342is connected to a downstream end of a first hydraulic oil supply pipe344, and an upstream end of a first hydraulic oil return pipe345. The upstream end of the first hydraulic oil supply pipe344is arranged so as to be positioned inside a hydraulic oil tank346as well as close to a bottom face of the hydraulic oil tank346, and a hydraulic oil pump347is connected to the middle of the first hydraulic oil supply pipe344. The downstream end of the first hydraulic oil return pipe345is arranged so that hydraulic oil returned through the first hydraulic oil pipe343and the first hydraulic oil return pipe345is recovered inside the hydraulic oil tank346.

The nozzle322includes: a first recessed portion351that extends in the axial direction, and that accommodates the first needle valve pressing spring324and the second needle valve pressing spring326; a second recessed portion352that slidably accommodates the first needle valve323that reciprocates along the axial direction; a third recessed portion353that slidably accommodates the second needle valve325that reciprocates along the axial direction; a fourth recessed portion355that slidably accommodates a second enlarged diameter portion354provided at the other end portion (tip portion) of the first needle valve323that reciprocates along the axial direction; a first communication hole358that extends in the radial direction to introduce hydraulic oil for moving the second needle valve325in the opening direction (upper direction inFIG. 8) to a lower face (bottom face)357of an enlarged diameter portion356of the second needle valve325, the lower face being a pressure receiving face; a second communication hole359that extends in the radial direction to introduce hydraulic oil pushed out by rising of the enlarged diameter portion356when the second needle valve325is moved in the opening direction, to the outside of the nozzle322; a third communication hole361that extends in the radial direction to introduce fuel gas into a chamber (annular space)360provided in a portion below the third recessed portion353; a first injection hole363that introduces the fuel gas introduced into the chamber360, the fourth recessed portion355, and a communication passage362, into the combustion chamber “c” (refer toFIG. 1, etc.), at the time of injecting premixed fuel; and a second injection hole364that introduces the fuel gas introduced into the chamber360, the fourth recessed portion355, and the communication passage362, into the combustion chamber “c”, at the time of injecting diffusion fuel.

The first communication hole358is connected to a second flow channel switching valve372in which a flow channel is switched by a second electromagnetic valve371, through a second hydraulic oil pipe373. The second flow channel switching valve372is connected to a downstream end of a second hydraulic oil supply pipe374, and an upstream end of a second hydraulic oil return pipe375. The upstream end of the second hydraulic oil supply pipe374is connected to the middle of the first hydraulic oil supply pipe344positioned downstream the hydraulic oil pump347, and the downstream end of the second hydraulic oil return pipe375is connected to the middle of the first hydraulic oil return pipe345.

The third communication hole361is connected to a downstream end of a fuel gas supply pipe376whose upstream end is connected to a fuel gas supply source (not shown).

The engine control unit12(refer toFIG. 1, etc.) transmits a command signal for energizing the first electromagnetic valve341and the second electromagnetic valve371, and a command signal for nonenergizing the first electromagnetic valve341and the second electromagnetic valve371, to an energization device377. The first electromagnetic valve341and the second electromagnetic valve371are energized or nonenergized on the basis of the command signals.

The first needle valve323includes the first enlarged diameter portion331at one end portion thereof in the axial direction, the second enlarged diameter portion354at the other end portion thereof in the axial direction, and a third enlarged diameter portion381on a side of the one end from the center thereof in the axial direction. The first needle valve is a solid cylindrical member, and is provided at its other end (tip) with a sealing face (seat face)383that is to be brought into contact with a first needle valve seat382. In addition, a top face of the third enlarged diameter portion381serves as a spring receiving face384that is brought into contact with a lower end of the first needle valve pressing spring324. The second enlarged diameter portion354is provided with a plurality of through-holes that penetrates through the second enlarged diameter portion354along the axial direction, that is, there is provided along the circumferential direction a plurality of communication holes385each of which allows top and lower faces of the second enlarged diameter portion354to communicate with each other.

The first needle valve pressing spring324urges the first needle valve323in a closing direction (urges so that the first needle valve seat382and the sealing face383are brought into contact with each other). Thus, in a state where the first hydraulic oil pipe343and the first hydraulic oil return pipe345communicate with each other, that is, in a state where hydraulic pressure of hydraulic oil is not applied to the lower face333of the first enlarged diameter portion331, the first needle valve323is urged in the closing direction.

The second needle valve325is a solid cylindrical member in which a one end portion in the axial direction is formed so as to be fitted to a lower end portion of the second needle valve pressing spring326. The second needle valve325includes a spring receiving face392that is provided along a circumferential direction in one end portion thereof, and that is brought into contact with the lower end of the second needle valve pressing spring326, and a sealing face (seat face)394that is provided at the other end (tip) thereof, and that is brought into contact with the second needle valve seat393.

The second needle valve pressing spring326urges the second needle valve325in a closing direction (urges so that the second needle valve seat393and the sealing face394are brought into contact with each other). Thus, in a state where the second hydraulic oil pipe373and the second hydraulic oil return pipe375communicate with each other, that is, in a state where hydraulic pressure of hydraulic oil is not applied to the lower face357of the enlarged diameter portion356of the second needle valve325, the second needle valve325is urged in the closing direction.

Next, operation of the fuel gas injection valve308will be described.

First, in a state where the first hydraulic oil pipe343and the first hydraulic oil return pipe345communicate with each other, as well as the second hydraulic oil pipe373and the second hydraulic oil return pipe375communicate with each other, a lift of each of the first needle valve323and the second needle valve325becomes 0 (zero) to close both of the first needle valve323and the second needle valve325.

Subsequently, the electromagnetic valve341is energized to switch a flow channel of the first flow channel switching valve342to allow the first hydraulic oil pipe343and the first hydraulic oil supply pipe344to communicate with each other. Then, hydraulic oil introduced through the first communication hole334is applied to the lower face333of the first enlarged diameter portion331to lift up the first needle valve323(moves in the opening direction). As a result, the outer peripheral face of the second enlarged diameter portion354closes the second injection hole364.

Next, the electromagnetic valve371is energized to switch a flow channel of the second flow channel switching valve372to allow the second hydraulic oil pipe373and the second hydraulic oil supply pipe374to communicate with each other. Then, hydraulic oil introduced through the first communication hole358is applied to the lower face357of the enlarged diameter portion356of the second needle valve325to lift up the second needle valve325(moves in the opening direction). As a result, the fuel gas introduced into the chamber360through the third communication hole361is introduced into the first injection hole363through the communication passage362and the communication hole385so as to be injected as premixed fuel from the first injection hole363.

Subsequently, the electromagnetic valve341and the electromagnetic valve371are nonenergized, so that the flow channel of the first flow channel switching valve342and the flow channel of the second flow channel switching valve372are switched to allow the first hydraulic oil pipe343and the first hydraulic oil return pipe345to communicate with each other, as well as to allow the second hydraulic oil pipe373and the second hydraulic oil return pipe375to communicate with each other, that is, both the first needle valve323and the second needle valve325are closed.

Next, the electromagnetic valve371is energized to switch a flow channel of the second flow channel switching valve372to allow the second hydraulic oil pipe373and the second hydraulic oil supply pipe374to communicate with each other. Then, hydraulic oil introduced through the first communication hole358is applied to the lower face357of the enlarged diameter portion356of the second needle valve325to lift up the second needle valve325(moves in the opening direction). As a result, the fuel gas introduced into the chamber360through the third communication hole361is introduced into the second injection hole364through the communication passage362so as to be injected as diffusion fuel from the second injection hole364.

At this time, the electromagnetic valve341is not energized, so that a lift of the first needle valve323becomes 0 (zero) to close the first needle valve323.

Subsequently, the electromagnetic valve371is nonenergized, so that the flow channel of the second flow channel switching valve372is switched to allow the second hydraulic oil pipe373and the second hydraulic oil return pipe375to communicate with each other, that is, both the first needle valve323and the second needle valve325are closed.

In accordance with the fuel gas injection valve308and the method for injecting fuel gas according to the present embodiment, it is possible to promote premixing of fuel gas and air so that occurrence of NOx (nitrogen oxide) can be reduced.

In addition, in accordance with the fuel gas injection valve308according to the present embodiment, the first needle valve323and the second needle valve325are not required to be formed concentrically with each other. As a result, manufacturing processes can be simplified, so that manufacturing cost can be reduced.

Further, in accordance with the gas engine1provided with the fuel gas injection valve308according to the present embodiment, the gas engine includes the fuel gas injection valve8capable of promoting premixing of fuel gas and air to reduce occurrence of NOx (nitrogen oxide). As a result, it is possible to reduce NOx (nitrogen oxide) discharged from the gas engine1so that performance of the gas engine1can be improved.

Hereinafter, the fourth embodiment of the fuel gas injection valve according to the present invention will be described with reference toFIG. 9.

FIG. 9shows a section and a hydraulic system of a fuel gas injection valve according to the fourth embodiment of the present invention.

There is a difference between a fuel gas injection valve208according to the present embodiment and the fuel gas injection valve according to the first embodiment described above in that the fuel gas injection valve208includes a nozzle222and a second needle valve225instead of the nozzle22and the second needle valve25.

The same member as that of the first embodiment described above is indicated by the same reference numeral, and hereinafter description of the member is omitted.

As shown inFIG. 9, the nozzle222according to the present embodiment includes a fourth communication hole232that is positioned in a portion between the first communication hole57and the third communication hole60, and that extends along a radial direction to introduce lubricant into an oil reservoir (annular space)231. The fourth communication hole232is connected to a downstream end of a lubricant supply pipe233whose upstream end is connected to a lubricant tank (not shown), and a lubricant pump234is connected to the middle of the lubricant supply pipe233.

The second needle valve225includes a through-hole91provided with an oil reservoir (annular space)235that extends in a circumferential direction, and a communication hole236that extends along the radial direction to allow the oil reservoir231and the oil reservoir235to communicate with each other.

In accordance with the fuel gas injection valve208according to the present embodiment, it is possible to apply lubricant to a sliding portion so that abrasion and fastening of the sliding portion can be prevented.

In addition, in a state where lubricant with pressure higher than gas pressure of fuel gas is supplied through the lubricant supply pipe233, the fuel gas is to be sealed in the oil reservoir231. As a result, blow-by (gas leak) of the fuel gas upward from the oil reservoir231can be prevented.

Since other effects are the same as those of the first embodiment described above, hereinafter description of the effects is omitted.

The present invention is not limited to the embodiments described above, but can be appropriately modified or varied if necessary.

For example, the configuration described in the fourth embodiment is also applicable to the second and third embodiments.

In addition, numeric values indicated in, between 40° and 100° before top dead center, about 5° before top dead center, and between 4° before top dead center and 40° after top dead center, described in the first embodiment, are examples for describing the embodiment. Thus, the numeric values can be appropriately changed depending on maximum power of the gas engine1, and the like.