JPH11193720A - Structure of combustion chamber in gas engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a structure of combustion chamber for gas engines that lowers the fuel consumption by forming a circular recess in the piston on the vector of flame from the sub chamber to the main chamber in order to improve the combustion in the main chamber, while suppressing generation of NOx and hydrocarbon, thus increasing the thermal efficiency. SOLUTION: A control valve 4 is located at the center of the cylinder and arranged to a through passageway 13. A piston 15 is composed of a central projection 11 with a flat top 45 of a piston head 46 corresponding to a flat bottom 49 of a valve head 23, a circular recess 12 formed around the central projection 11, and an outer periphery 62 formed around the circular recess 12. The circular recess 12 is located on the line extended from the gas passage that is formed by a valve face 60 of the control valve 4 and a valve seat 31 of the through passageway 13. The flame is blown out from a sub chamber 2 to the swirl in the circular recess 12, which helps mixing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustion chamber structure of a gas engine, and more particularly, to a gas chamber such as a natural gas, which supplies gas fuel to a sub-chamber, supplies intake air to a main chamber, and supplies a gas near a top dead center of a compression stroke. The present invention relates to a combustion chamber structure of a gas engine for igniting and burning by mixing compressed air and gas fuel.

[0002]

2. Description of the Related Art Conventionally, in a gas engine, the combustion chamber is separated into a main chamber and a sub chamber in order to send the gas fuel into a combustion chamber without causing the pressure of the gas fuel such as natural gas to rise extremely, thereby performing diesel combustion. A control valve is disposed in a communication hole communicating the main chamber and the sub-chamber, gas fuel is supplied to the sub-chamber, air is introduced into the main chamber without gas fuel, and the air is compressed. Near the top dead center of the compression stroke, the gas fuel and compressed air are mixed and burned, enabling good operation.

A gas engine using a gas such as natural gas as a fuel is disclosed in, for example, Japanese Patent Application Laid-Open No. 7-158448. In the gas engine, a sub-chamber formed in a cylinder head and a main chamber formed in a cylinder side communicate with each other through a communication hole, and a control valve is arranged in the communication hole. In addition, the gas chamber and the sub-chamber communicate with the head portion through a constricted portion, a gas inlet is formed in the gas chamber to supply natural gas to the sub-chamber through the gas passage, and a communication hole is formed near the end of the compression stroke. A control valve that opens is provided, and a gas introduction valve that opens when the communication hole is closed is provided at a gas introduction port formed in the gas chamber.

In the sub-chamber type gas engine disclosed in Japanese Patent Application Laid-Open No. 9-256849, a sub-chamber structure constituting a sub-chamber is arranged on a cylinder head, a main chamber is formed on a cylinder side, and an intake system is formed. A fuel supply valve for supplying gaseous fuel to the passage or the main chamber is provided, and a part of the gaseous fuel is supplied to the main chamber to generate in advance a lean mixture that does not self-ignite. The valve is opened to introduce compressed air in the main chamber into the sub-chamber, ignite and burn in the sub-chamber with an equivalence ratio of 1 or less, and then rapidly burn as a lean mixture in the main chamber by the combustion gas jet from the sub-chamber. To shorten the combustion period,
The purpose is to prevent the generation of C and the like and to prevent the unburned gas from staying in the sub chamber.

[0005]

In a gas engine of the type described above, natural gas in the sub-chamber enters the main chamber in the first half of the compression stroke, and the natural gas mixes with air to form an ultra-lean mixture. In this case, if the mixed flame in the sub-chamber ignites and diffuses into the main chamber, the combustion proceeds evenly, the heat generation rate is biased near top dead center, fuel efficiency is improved, and the combustion gas is lean. to become a premixed state, results in generation of the NO _X is suppressed has been confirmed experimentally.

However, in a sub-chamber engine,
Gas such as flame and unburned mixture is blown out from the sub-chamber to the main chamber and the flame reaches the cylinder periphery. Since the ejection vector is directed downward from the shapes of the control valve and the communication hole, there is a phenomenon that the flame cannot easily reach the periphery, that is, the outer periphery of the cylinder. In a gas engine, when a control valve disposed in a communication hole communicating the main chamber and the sub chamber opens the communication hole near the top dead center of the compression stroke,
First, the compressed air in the main chamber flows into the sub-chamber, ignites and burns in the sub-chamber, and the pressure in the sub-chamber rises. Then, the combustion gas such as flame, unburned mixture, etc. is jetted from the sub-chamber into the main chamber. . At this time, the shape of the main chamber greatly affects the secondary combustion in the main chamber,
In the secondary combustion of the main chamber, how much the combustion flame diffuses into the main chamber, increases the combustion speed and shortens the combustion period,
O _X, the generation of HC is suppressed, there is one problem can improve the thermal efficiency to improve the fuel economy.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems, and a control valve disposed in a communication hole communicating a main chamber and a sub-chamber is provided near a top dead center of a compression stroke. When the main chamber is opened and ignited and burned, and then the combustion gas such as flame and unburned air-fuel mixture blows out from the sub-chamber to the main chamber, the main chamber is structured so that diffusion combustion can be satisfactorily achieved. Another object of the present invention is to provide a combustion chamber structure of a gas engine having a feature in a structure of a combustion gas passage formed between a communication hole and a control valve.

According to the present invention, a combustion chamber member is provided in a cylinder head and has a main chamber and a sub-chamber communicating with the main chamber through a communication hole, and reciprocates in a cylinder constituting a part of the main chamber. An engine comprising: a piston; a control valve disposed on the cylinder head for opening and closing the communication hole; and a fuel valve for opening and closing a fuel supply passage communicating with the sub-chamber for supplying gaseous fuel to the sub-chamber. The control valve comprises a valve stem located at the center axis of the cylinder and a valve head integrally formed with the valve stem. The valve head is seated on a valve seat on the outer periphery of the communication hole formed at the center of the sub chamber. A central projection having a flat upper surface corresponding to a flat lower surface of the valve head, an annular recess formed around the central projection and forming a part of the main chamber, and the annular recess; Combustion chamber structure of the gas engine, characterized in that it comprises a peripheral portion that faces the lower surface of the cylinder head is formed around.

The annular recess is located on an extension of a streamline of gas flow from a gas passage formed by a valve face of the control valve and a valve seat of the communication hole.

In the combustion chamber structure of this gas engine,
The clearance between the flat lower surface of the valve head and the flat upper surface of the central projection of the piston when the control valve is open at the piston top dead center is configured to be as small as possible. Have been. Further, the outer peripheral portion is formed around the annular concave portion so that the squish flow flows in a direction substantially perpendicular to the streamline of the fire flame from the sub-chamber.

[0011] In the combustion chamber structure of this gas engine, the opening of the communication hole of the control valve causes the vector of the blow-out from the sub-chamber to the main chamber to be directed downward. In order to eliminate the need for air to exist and to prevent the temperature of the control valve from rising due to combustion, an annular recess is formed in the piston head and a protrusion is formed in the center of the piston head to reduce the gap. It is advantageous. Also, if the above clearance near the top dead center of the piston is reduced, gas such as flame and unburned mixture does not flow into the area hidden by the control valve, so that the temperature of the control valve does not increase.
There is no ignition point of the control valve. Then, since the piston central portion by lowering the piston reverse squish occurs, the flame flows into the central portion, uniform combustion is diffused in the main chamber, can reduce the occurrence of NO _X, it is possible to improve the thermal efficiency it can.

In order to minimize the gap between the flat lower surface of the valve head of the control valve and the flat upper surface of the central projection of the piston at the top dead center of the piston, The shape of the piston head may be determined by the design of the arrangement of the communication hole of the control valve. For example, if the control valve protrudes from the lower surface of the cylinder head with the communication hole closed, the upper surface of the protrusion of the piston head should be The upper surface of the protruding portion of the piston head can be raised above the surface of the outer peripheral portion if the control valve is recessed below the lower surface of the cylinder head with the communication hole closed. (See FIG. 5).

In the combustion chamber structure of this gas engine, the squish flow generated from between the upper surface of the outer peripheral portion of the piston and the lower surface of the cylinder head to the annular recess as the piston approaches the vicinity of the piston top dead center and The squish flow generated into the annular recess from between the flat upper surface of the central projection of the piston and the flat lower surface of the valve head of the control valve flows into the annular recess and swirls at the annular recess. Is formed.

In the combustion chamber structure of this gas engine, a part of intake air of the annular concave portion flows into the sub-chamber when the control valve opens the communication hole near the piston compression top dead center. Then, the flame in the sub-chamber is jetted into the vortex existing in the annular recess through the communication hole to promote mixing with air, and the upper surface of the outer peripheral portion of the piston from the annular recess during the piston expansion stroke. The flame spreads and spreads over the entire cylinder due to the reverse squish flow generated between the lower surface of the cylinder head and the flat upper surface of the protrusion of the piston and the flat lower surface of the valve head of the control valve. , Completes the combustion period in a short time.

Since the combustion chamber structure of this gas engine is configured as a multi-stage combustion system as described above, the combustion gas such as flame and unburned mixture injected from the sub-chamber to the main chamber communicates with the communication hole and the control valve. Smoothly jets into the vortex in the annular recess of the main chamber through the passage between the main chamber and the vortex, generating a vortex, which promotes the mixing of the combustion gas, such as flame, unburned mixture, etc., with the ultra-lean mixture in the main chamber. You. In other words, the flame ejection vector from the sub chamber to the main chamber is directed downward along the valve face of the control valve, but the flame ejection force is injected into the vortex in the annular recess of the piston head, Mixing with a lean mixture is promoted. Next, in the expansion stroke, the gas flows on the reverse squish flow generated by the downward movement of the piston and diffuses also into the area below the control valve in the main chamber, increasing the air utilization rate in the main chamber and ensuring uniform secondary combustion. progresses, the combustion was complete to shorten the combustion period to up the combustion speed, NO _X,
The generation of HC is suppressed, the performance is improved, the thermal efficiency is improved, and the fuel efficiency can be improved.

[0016]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a gas engine according to an embodiment of the present invention;
The combustion chamber structure of this gas engine can be applied as a cogeneration system or an automobile engine. 1 is a sectional view showing an embodiment of a combustion chamber structure of a gas engine according to the present invention, and FIG. 2 is a sectional view showing an operation state of a control valve before a top dead center of a compression stroke in the combustion chamber structure of the gas engine of FIG. FIG. 3 is a sectional view showing the operation state of the control valve at the top dead center of the compression stroke in the combustion chamber structure of the gas engine of FIG. 1, and FIG. 4 is a control valve, fuel valve, intake valve and exhaust gas of the gas engine of FIG. FIG. 3 is a diagram illustrating a valve opening timing and a valve opening period.

In the gas engine incorporating the combustion chamber structure, the cylinder block 14, the cylinder head 7 mounted and fixed on the upper surface of the cylinder block 14 via the gasket 38, and the hole 37 formed in the cylinder block 14
Cylinder liner 2 that constitutes cylinder 28 fitted to
7, a combustion chamber member 10 forming the main chamber 1 and the sub-chamber 2 arranged in the cavity 9 of the cylinder head 7, and a piston 15 reciprocating in a cylinder 28 formed in the cylinder liner 27. The combustion chamber member 10 is composed of a head liner composed of a lower surface portion of a head and an upper portion of a liner integrally formed therewith. An intake port 20 in which the intake valve 16 is arranged and an exhaust port 21 in which the exhaust valve 18 is arranged are formed on the lower surface of the head of the combustion chamber member 10. The intake port 20 communicates with the intake port 17 formed in the cylinder head 7, and the exhaust port 21 communicates with the exhaust port 19 formed in the cylinder head 7.

A control valve 4 for opening and closing the communication hole 13 formed at the center of the sub-chamber 2 is seated in a communication hole 13 formed in the combustion chamber member 10 and communicating the main chamber 1 and the sub-chamber 2. The valve seat 31 is formed. The control valve 4 includes a valve head 23 located at the center of the cylinder and a valve stem 24 integrally formed with the valve head 23. The valve head 23 of the control valve 4 is
Insertion hole 5 formed in cylinder head 7 and combustion chamber member 10
5 are arranged. The combustion chamber member 10 is made of Si
Is formed from heat-resistant material ₃ N ₄ or the like of ceramics or heat-resistant alloy, intervening gasket 51 so as to form a thermal barrier air layer 50 between the outer surface and the cavity 9 formed in the cylinder head 7 of the combustion chamber member 10 The main chamber 1 and the sub-chamber 2 are arranged in a cavity 9 of the cylinder head 7 so as to form a heat shielding structure. Further, the combustion chamber member 10 has a fuel supply port 54 communicating with a fuel supply passage 8 formed in the cylinder head 7 for supplying gaseous fuel to the sub-chamber 2. The fuel supply port 54 has a fuel valve 5 for opening and closing it.
Is arranged.

The piston 15 has a piston head 46 formed of a heat-resistant material such as ceramics such as Si ₃ N ₄ or a heat-resistant alloy, and a piston skirt 47 formed of a metal material such as an Al alloy fixed to the piston head 46. It is composed of Piston head 46 and piston skirt 4
7, a gasket 52 is interposed to form a heat shielding air layer 53.
Is formed, and the piston head 46 and the piston skirt 4 are formed.
7 is fixed by a connecting ring 48 by metal flow or the like. The main chamber 1 includes the combustion chamber member 10, the cylinder 28 of the cylinder liner 27, and the upper surface 35 of the piston head 46.
And the annular recess 12 formed in the piston head 46 of the piston 15.

The combustion chamber structure of this gas engine is, in particular,
The structure of the piston 15 and the structure formed between the control valve 4 and the communication hole 13 are characterized by the structure of the gas passage. The piston head 46 of the piston 15 has a central projection 11 having a flat surface 45 formed in the center of the cylinder, an annular recess 12 formed around the central projection 11 and an annular recess 1.
2 has an outer peripheral portion 62 formed around it. In the figure, the central protruding portion 11 is formed lower than the outer peripheral portion 62, and the lower surface 49 of the control valve 4 slightly protrudes from the lower surface 59 of the cylinder head 7. The annular recess 12 is located on an extension of a gas passage 63 (FIGS. 2 and 3) formed by the valve face 60 of the control valve 4 and the valve seat 31 of the communication 13. The flat surface 45 of the central projection 11 is located on the valve head 2 of the control valve 4.
3 corresponds to the flat lower surface 49. The outer peripheral portion 62
The upper surface 35 (the top surface of the piston head 46) is connected to the lower surface 59 of the cylinder head 7 (in FIG. 1, the intake valve 16 and the exhaust valve 1).
8 (the same plane as the lower surface of the lower surface 8).

The combustion chamber structure of this gas engine has a flat lower surface 49 of the valve head 23 of the control valve 4 and a flat upper surface 45 of the central projection 11 of the piston 15 at the top dead center of the piston.
Is designed to be as small as possible. In addition, this combustion chamber structure has a squish flow S generated from between the upper surface 35 of the outer peripheral portion 62 of the piston 15 and the lower surface 59 of the cylinder head 7 to the annular concave portion 12 as the piston approaches the piston compression top dead center. The squish flow S generated into the annular recess 12 from between the flat upper surface 45 of the central projection 11 of the piston 15 and the flat lower surface 49 of the valve head 23 of the control valve 4 flows into the annular recess 12 and enters the annular recess. A vortex is formed at 12.

The combustion chamber structure of this gas engine is
As shown in FIG. 2, the control valve 4 close to the piston compression top dead center.
By opening the communication hole 13, a part of the intake air of the annular concave portion 12 flows into the sub-chamber 2 and ignites and burns in the sub-chamber 2, and then the flame in the sub-chamber 2 is controlled as shown in FIG. Through the gas passage 63 of the communication hole 13 formed by the valve face 60 of the valve 4 and the valve seat 31 of the communication 13, the gas is blown into the vortex existing in the annular recess 12 to promote mixing with air, and the annular shape is increased during the piston expansion stroke. It is generated from the recess 12 between the upper surface 35 of the outer peripheral portion 62 of the piston 15 and the lower surface 59 of the cylinder head 7, and the flat upper surface 45 of the central projection 11 of the piston 15 and the flat surface of the valve head 23 of the control valve 4. Lower surface 4
The flame is diffused and burned over the entire area of the cylinder by the reverse squish flow generated to 9, and the combustion period can be completed in a short time.

The control valve 4 is opened and closed by a cam valve mechanism 6, which is the same as a cam valve mechanism for opening and closing the intake valve 16 and the exhaust valve 18, and a hydraulic valve mechanism 3 provided separately therefrom. Driven. The cam type valve operating mechanism 6 includes an intake valve 16.
Shaft 4 which is the same as the cam shaft for driving the opening and closing of the exhaust valve 18
4 includes a cam 56, a rocker arm 61 that swings according to the rotation of the cam 56, a cam cap 43 that moves up and down according to the swing of the rocker arm 61, and a valve return spring 42 that returns the cam cap 43.

The hydraulic valve gear 3 lifts the control valve 4 independently of the cam valve gear 6. The controller 3 responds to the engine load from the load sensor 57.
Controlled by 0. The hydraulic valve gear 3 includes a control valve 4
Plunger 29 for lifting the valve stem 24 of the valve, and the hydraulic chamber 2 containing the hydraulic pressure for operating the hydraulic plunger 29
6, a hydraulic passage 58 for supplying hydraulic pressure from the high-pressure hydraulic chamber 33 of the hydraulic pressure source to the hydraulic chamber 26, and an electromagnetic valve 32 controlled by the controller 30 to open and close the hydraulic passage 58. The hydraulic pressure in the high-pressure hydraulic chamber 33 is constantly raised by an oil pump. In the multi-cylinder gas engine, the solenoid valve 32 is provided for each cylinder. The high-pressure hydraulic chamber 33 is provided with a plunger 36 driven by the operation of the drive solenoid valve 34.

When the plunger 36 is driven by the operation of the drive electromagnetic valve 34, the hydraulic pressure in the high-pressure hydraulic chamber 33 is supplied to the hydraulic chamber 26 through the hydraulic passage 58 by the operation of the electromagnetic valve 32, and the hydraulic plunger 29 is operated. Hydraulic plunger 2
9 operates, the control valve 4 is lifted via the rocker arm 61 against the spring force of the valve return spring 42, the control valve 4 opens the communication hole 13, and the gas fuel in the sub-chamber 2 is released from the main chamber 1 Supplied to The hydraulic chamber 26 in the hydraulic valve train 3 is opened more than necessary if the hydraulic pressure leaks when the control valve 4 is opened by lifting the hydraulic plunger 29 by a predetermined amount. Thus, a predetermined amount of gas fuel is supplied from the sub chamber 2 to the main chamber 1.

The control valve 4 is reciprocated by the cam type valve operating mechanism 6 to open the communication hole 13 near the end of the compression stroke, to establish a communication state between the sub-chamber 2 and the main chamber 1, and to close at the latest at the end of the exhaust stroke. The main chamber 1 and the sub-chamber 2 are set to operate so as to be shut off. The fuel valve 5 is set so as to open when the communication hole 13 is closed and supply gaseous fuel from the fuel supply passage 8 to the sub-chamber 2. The fuel valve 5 is a control valve 4
Is operated to open the gas fuel inlet when the communication hole 13 is closed. Therefore, when the fuel valve 5 opens the gas fuel inlet from the intake stroke to the compression stroke, the gas fuel is supplied to the sub-chamber 2 through the gas fuel supply passage 8.

The gas engine has a valve guide member 22 made of a porous material fixed to the cylinder head 7 for guiding the valve stem 24 of the control valve 4, and oil supply means for passing oil through the valve guide member 22. have. The valve stem 24 is made of a ceramic material such as SiC or Si ₃ N ₄ . The oil supply means includes an oil reservoir 40 provided in the cylinder head 7 on the outer periphery of the valve guide member 22, an oil passage 41 provided in the cylinder head 7 for supplying oil to the oil reservoir 40, and an oil supply source through the oil passage 41. It comprises a pump 39 for supplying oil to the reservoir 40. Here, the oil functions as a lubricating oil and a coolant. The oil supply means allows oil to pass through the porous material of the valve guide member 22 to increase the heat transfer rate, and dissipates heat generated in the control valve 4 through the valve stem 24 and the valve guide member 22 to cause the control valve 4 to operate. Cooling can be performed, and wear and damage of the control valve 4 can be reduced. Further, a sheath member 25 made of a material having a higher thermal conductivity than a ceramic material can be attached to the outer periphery of the valve stem 24 forming a sliding surface with respect to the cylinder head 7 and the combustion chamber member 10.
3 can be dissipated to the valve guide member 22 through the sheath member 25. For example, the valve stem 24 Si ₃
When the sheath member 25 is made of N ₄ , the sheath member 25 can be made of a coating member made of SiC or diamond or a fitting member made of SiC.

The gas fuel of natural gas is accommodated in a gas fuel supply source such as a gas fuel tank or a gas fuel accumulator (not shown) for accumulating gas fuel. Since the temperature of the communication hole 13 becomes high due to the combustion gas, the control valve 4 disposed in the communication hole 13 is preferably made of ceramics such as silicon nitride and silicon carbide having high temperature strength and excellent heat resistance. By opening the gas inlet, the fuel valve 5 supplies gas fuel from the gas fuel supply source to the sub-chamber 2 by a required amount.
It is configured to be introduced.

Next, the operation of the gas engine having the combustion chamber structure of the gas engine according to the present invention will be described with reference to FIGS. This gas engine is operated by sequentially repeating four strokes of an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke. First, in the intake stroke, as shown in FIG. Port 1
With the control valve 4 closing the communication hole 13 and the fuel valve 5 opening the gas fuel supply path 8, the gas is supplied through the gas fuel supply path 8 while the control valve 4 closes the communication hole 13. Gas fuel is supplied from the fuel inlet to the sub chamber 2.

Next, the gas engine shifts to a compression stroke. In the first half of the compression stroke, in which the compressed air pressure of the main chamber 1 formed by the cylinder 28 is low, the control valve 4 controls the hydraulic valve gear 3 to operate. The lift is slightly lifted by the operation, the communication hole 13 is opened, and a part of the gas fuel stored in the sub chamber 2 is removed.
That is, an amount of gaseous fuel that does not self-ignite is supplied to the main chamber 1 through the communication hole 13, and an ultra-lean mixture is generated in the main chamber 1, where the control valve 4 closes the communication hole 13. Next, when the piston 15 rises and the ultra-lean mixture in the main chamber 1 reaches the vicinity of the top dead center of the compression stroke in which the compressed air is highly compressed, the control valve 4 is lifted again by the operation of the cam type valve operating mechanism 6, and the communication hole is opened. 13 opens. Therefore, as shown in FIG. 2, the high-compression ultra-lean mixture in the main chamber 1 immediately passes through the communication hole 13 and becomes
The fuel gas enters the sub-chamber 2 and is ignited and combusted with the gas fuel in the sub-chamber 2 to increase the pressure in the sub-chamber 2. Next, as shown in FIG. 3, the process proceeds to the expansion stroke, and gas such as flame and unburned mixture in the sub-chamber 2 is blown out to the main chamber 1 through the communication hole 13, and the gas flows into the main chamber 1. The existing super-lean mixture is entrained to promote mixing and increase the secondary combustion speed, shorten the combustion period and complete the combustion.

As described above, the gas engine provided with the control valve cooling device according to the present invention has a structure in the first half of the compression stroke.
Since a part of the gas fuel in the auxiliary chamber 2 are previously supplied to the main chamber 1, there is no gas fuel becomes unburned staying in subchamber 2, HC, is possible to reduce the occurrence of NO _X it can. The amount of gas fuel previously supplied to the main chamber 1 is
It is controlled by the controller 30 according to the engine load. For example, when the engine load is low,
The amount of gaseous fuel supplied to the sub-chamber 2 is reduced, and the mixture formed in the sub-chamber 2 has a sufficient air equivalent ratio. The hydraulic valve train 3 is not operated, the control valve 4 is not lifted in the first half of the compression stroke, and the communication hole 13 is not opened. When the engine load is a medium load (1/2 load), the amount of gas fuel supplied to the sub-chamber 2 is moderate, and the air-fuel mixture formed in the sub-chamber 2 slightly increases the amount of gas fuel. Since there is no air equivalent ratio, the hydraulic valve system 3 is operated to lift the control valve 4 in the first half of the compression stroke to open the communication hole 13 in order to supply the gaseous fuel to the main chamber in advance. About 10% of the gas fuel amount (opening indicated by a solid line in the compression stroke of FIG. 2) is supplied to the main chamber 1 to generate an ultra-lean mixture in the main chamber 1.
When the engine load is high (full load), the amount of gas fuel supplied to the sub-chamber 2 is large, and the air-fuel mixture formed in the sub-chamber 2 does not have a sufficient air equivalent ratio. In order to supply the gaseous fuel to the main chamber in advance, the hydraulic valve system 3 is operated to lift the control valve 4 in the first half of the compression stroke to open the communication hole 13 and to supply the gaseous fuel amount of 10 to the main chamber 1. % To 2
About 0% (opening indicated by a solid line and a dotted line in the compression stroke of FIG. 2) is supplied to generate an ultra-lean mixture in the main chamber 1.

Next, a second embodiment of the combustion chamber structure of the gas engine according to the present invention will be described with reference to FIGS. FIG. 5 is a sectional view showing a second embodiment of the combustion chamber structure of the gas engine according to the present invention, and FIG. 6 is an enlarged sectional view showing a state where the control valve in the combustion chamber structure of FIG. 5 is lifted. The second embodiment is the same as the first embodiment except that the shape of the piston, the communication hole formed in the cylinder head, and the state of the control valve disposed in the communication hole are different. Since they have the same function, the same components are denoted by the same reference numerals, and redundant description will be omitted.

In the combustion chamber structure of the gas engine according to the second embodiment, the communication hole 13 formed in the cylinder head 7 has a main chamber 1.
The lower surface 49 of the control valve 4 is formed so as to be located in the communication hole 13. The central protruding portion 11 formed on the piston head 46 of the piston 15 is configured to protrude by an amount corresponding to the recess of the control valve 4 from the lower surface 59 of the cylinder head 7. Therefore, the piston head 4
6 shows that the upper surface 45 of the central projecting portion 11 is the upper surface 3 of the outer peripheral portion 62.
It is configured in a shape higher than 5. When the control valve 4 of this embodiment is lifted, as shown in FIG. 6, the lower surface 59 of the cylinder head 7 and the lower surface 49 of the control valve 4 are located on substantially the same plane. Since the structure of the combustion chamber of the gas engine of the second embodiment has substantially the same operation and effect as those of the first embodiment, a description thereof will be omitted here.

[0034]

Since the combustion chamber structure of the gas engine according to the present invention is constructed as described above, the combustion gas such as the flame and the unburned mixture injected from the sub chamber into the main chamber is connected to the communication hole and the control valve. Smoothly blows out into the vortex in the main chamber through the passage between the two to generate a vortex, which promotes the mixing of the combustion gas such as a flame, an unburned mixture, and the air in the main chamber. Next, in the expansion stroke, the fuel spreads on the reverse squish flow generated by the downward movement of the piston, diffuses into the main chamber, increases the air utilization rate in the main chamber, promotes secondary combustion uniformly, and increases the combustion speed. To shorten the combustion period to complete the combustion,
_X and HC generation can be suppressed, fuel efficiency can be improved, and thermal efficiency can be improved.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of a combustion chamber structure of a gas engine according to the present invention.

FIG. 2 is an enlarged sectional view showing an operation state of a control valve before a top dead center of a compression stroke in the combustion chamber structure of the gas engine of FIG.

FIG. 3 is an enlarged sectional view showing an operation state of a control valve at a top dead center of a compression stroke in a combustion chamber structure of a gas engine according to the present invention.

FIG. 4 shows a control valve, a fuel valve,
FIG. 4 is a diagram illustrating valve opening timings and opening periods of an intake valve and an exhaust valve.

FIG. 1 is a sectional view showing another embodiment of the combustion chamber structure of the gas engine according to the present invention.

FIG. 6 is an enlarged sectional view showing a state in which a control valve in the combustion chamber structure of FIG. 5 is lifted.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Main chamber 2 Sub chamber 4 Control valve 5 Fuel valve 7 Cylinder head 8 Fuel supply path 10 Combustion chamber member 11 Center projected part 12 Annular concave part 13 Communication hole 15 Piston 23 Valve head 24 Valve stem 28 Cylinder 31 Valve seat 35 Peripheral part Upper surface 45 Upper surface of central projecting portion 46 Piston head 49 Lower surface of control valve 59 Lower surface of cylinder head 60 Valve face 62 Outer peripheral portion 63 Gas passage 64 Gap

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI F02M 21/02 F02M 21/02 L

Claims (6)

[Claims] A combustion chamber member disposed in a cylinder head and having a main chamber and a sub-chamber communicating with the main chamber through a communication hole; a piston reciprocating in a cylinder; and a piston disposed in the cylinder head and connected to the cylinder head. In an engine provided with a control valve for opening and closing a hole and a fuel valve for supplying gaseous fuel to the sub-chamber, the control valve comprises a valve stem located on a cylinder central axis and a valve head integrated with the valve stem;
The valve head is seated in a valve seat of the communication hole formed in the center of the sub-chamber, and the piston has a central projection having a flat upper surface corresponding to a flat lower surface of the valve head;
A gas engine comprising: an annular concave portion formed around the central projecting portion and constituting a part of the main chamber; and an outer peripheral portion formed around the annular concave portion and facing a lower surface of the cylinder head. Combustion chamber structure. 2. The method according to claim 1, wherein the annular recess is located on an extension of a streamline of a gas flow from a gas passage formed by a valve face of the control valve and a valve seat of the communication hole. Item 2. The combustion chamber structure of the gas engine according to Item 1. 3. The gap between the flat lower surface of the valve head and the flat upper surface of the central projection of the piston with the control valve open at a piston top dead center is as small as possible. The combustion chamber structure of a gas engine according to claim 1, wherein: 4. The method according to claim 1, wherein the outer peripheral portion is formed around the annular concave portion so that a squish flow flows in a direction substantially perpendicular to a streamline of the flame emitted from the sub-chamber. The combustion chamber structure of the gas engine described. 5. A squish flow generated from between an upper surface of the outer peripheral portion of the piston and a lower surface of the cylinder head to the annular concave portion as the piston approaches the vicinity of the piston compression top dead center and the central protrusion of the piston. The squish flow generated into the annular recess from between the flat upper surface of the portion and the flat lower surface of the valve head of the control valve flows into the annular recess and forms a vortex in the annular recess. The combustion chamber structure of a gas engine according to claim 1, wherein 6. When the control valve opens the communication hole near the piston compression top dead center, a part of intake air of the annular concave portion flows into the sub-chamber and ignites and burns in the sub-chamber. The flame in the sub-chamber is blown into the vortex existing in the annular recess through the communication hole to promote mixing with air, and the upper surface of the outer peripheral portion of the piston and the lower surface of the cylinder head from the annular recess during the piston expansion stroke. The flame diffuses and burns throughout the cylinder due to the reverse squish flow generated between the flat upper surface of the central projection of the piston and the flat lower surface of the valve head of the control valve. 6. The combustion chamber structure of a gas engine according to claim 5, wherein is completed in a short time.