JP2008280922A - Sub-chamber engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To attain a sub-chamber engine maintaining a stable combustion state even when intake pressure decreases as is in starting or in low load and discharging fuel gas existing in a valve chamber of a sun-chamber fuel supply valve to a blow-by gas path through a leak gas path without leaking it to the outside. <P>SOLUTION: When the leak gas path 35 is provided for connecting a leak part 34 formed in a gap between a valve stem 11 and a valve guide 12 of the sub-chamber fuel supply valve 15, an operation valve means 36 is provided in the leak gas part 35 and operates in a mode of blocking a gas flow from a blow-by gas path 40 side to a leak part 34 side and allowing a gas flow from the leak part 34 side to the blow-by gas path 40 side. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

According to the present invention, fresh air compressed by the rise of the piston in the main chamber is caused to flow into the sub chamber through the nozzle hole, and the fresh air that has flowed in the sub chamber and the fuel gas supplied from the sub chamber fuel supply valve The air-fuel mixture is configured such that a spark plug is actuated to spark-ignite and burn, and a flame jet is injected from the sub chamber into the main chamber through the nozzle hole.
The present invention relates to a sub-chamber engine including a leak gas passage that connects a leak portion provided in a gap between a valve stem of the sub-chamber fuel supply valve and a valve guide that guides and inserts the valve stem to a blow-by gas passage.

In the sub-chamber engine as described above, in the sub-chamber, fresh air such as a lean air-fuel mixture compressed in the main chamber flows from the nozzle hole, and the fuel gas supplied to the valve chamber of the sub-chamber fuel supply valve Supplied through a valve portion that is opened and closed every cycle, the mixture of the fresh air and the fuel gas is ignited by a spark plug and burned, and a flame jet is injected into the main chamber through the nozzle hole. (For example, refer patent document 1).
Further, such a sub-chamber engine can achieve high efficiency because lean combustion in which fuel is burned in a state where the fuel is lean relative to air in the entire combustion chamber can be realized as compared with a single-chamber engine. In particular, it has been introduced into cogeneration systems and the like that require improved efficiency.

Further, in such a sub-chamber engine, the pressure in the valve chamber of the sub-chamber fuel supply valve becomes very high particularly in the compression stroke in which the valve portion of the sub-chamber fuel supply valve is switched from the open state to the closed state. As the pressure in the valve chamber rises, the fuel gas existing in the valve chamber is transferred to the outside through the gap between the valve stem of the sub-chamber fuel supply valve and the valve guide that guides the valve stem. There is concern about leakage.
Therefore, a leak portion may be formed in the gap between the valve stem of the sub chamber fuel supply valve and the valve guide, and the leak portion may be connected to the blow-by gas passage through the leak gas passage. Therefore, the fuel gas that is about to leak through the gap as the pressure in the valve chamber rises flows into the leak portion, and then is discharged to the blow-by gas path through the leak gas path. As a result, the fuel gas discharged into the blow-by gas can be returned to the intake passage together with the blow-by gas and burned in the combustion chamber.
In addition, in such a sub-chamber engine, fresh air is passed to the main chamber by rotating the turbine by the kinetic energy of the exhaust gas flowing through the exhaust passage and rotating the compressor provided in the intake passage. A turbocharger such as a turbocharger may be provided.

JP 2005-133664 A JP 2003-278548 A

However, as described above, in the sub-chamber engine provided with the leak gas passage, the intake pressure becomes relatively low particularly at the start when the supercharger does not operate or at the time of low load where the opening of the throttle valve is reduced. In some cases, misfires occurred or the combustion state became unstable. In particular, at the time of start-up in which the supercharger does not operate because exhaust gas is not circulating in the exhaust passage, misfire occurs remarkably and the combustion state becomes unstable. Further, the sub-chamber fuel supply valve and the spark plug provided in the sub-chamber frequently cause malfunction due to, for example, solid substances attached, and the combustion state may become unstable.
And in the sub-chamber engine provided with the leak gas passage, the clear cause of the instability of the combustion state as described above has not been known.

  Accordingly, the present invention has been made in view of the above circumstances, and its purpose is a leak gas that connects a leak portion provided in a gap between a valve stem and a valve guide of a sub-chamber fuel supply valve to a blow-by gas path. When a passage is provided, a stable combustion state is maintained even when the intake pressure decreases at the time of starting or at a low load, and the fuel gas existing in the valve chamber of the sub chamber fuel supply valve is leaked to the outside. The purpose is to realize a sub-chamber engine that can be discharged to a blow-by gas passage through a leak gas passage.

In order to achieve the above object, a sub-chamber engine according to the present invention is configured to cause fresh air compressed by a piston ascending in a main chamber to flow into a sub-chamber through a nozzle hole and to flow into the sub-chamber. And the fuel gas supplied from the sub-chamber fuel supply valve are ignited and burned by operating a spark plug, and a flame jet is injected from the sub-chamber into the main chamber through the nozzle hole. Configured as
The sub-chamber engine is provided with a leak gas passage that connects a leak portion provided in a gap between a valve stem of the sub-chamber fuel supply valve and a valve guide that guides and inserts the valve stem to a blow-by gas passage. The characteristic configuration is an operation that operates in a form that prevents the gas flow from the blow-by gas path side to the leak part side and allows the gas flow from the leak part side to the blow-by gas path side in the leak gas path. The valve means is provided.

As a result of earnest research, the inventors of the present application have misfired particularly when the intake pressure becomes relatively low, such as at the time of starting when the turbocharger does not operate or at the time of low load where the opening of the throttle valve is reduced. In the intake stroke in which the valve part of the sub chamber fuel supply valve is switched from the closed state to the open state, the main cause of the unstable combustion state is the valve chamber of the sub chamber fuel supply valve as the intake pressure decreases. As a result, the blow-by gas existing in the blow-by gas passage is caused to flow into the sub chamber through the leak gas passage and the valve chamber, and the present invention is completed. It was.
That is, when the pressure in the valve chamber of the sub-chamber fuel supply valve becomes very low, blow-by gas existing in the blow-by gas passage flows into the sub-chamber through the leak gas passage and the valve chamber, thereby forming the sub-chamber. It becomes difficult to ignite the air-fuel mixture with the spark plug, and misfires occur, or oil ash from the oil contained in the blow-by gas adheres to the sub-chamber fuel supply valve and spark plug, resulting in malfunctions. It was found to be.

Therefore, according to the above characteristic configuration, even when the pressure in the valve chamber of the sub chamber fuel supply valve becomes very low, the operating valve means prevents gas flow from the blow-by gas path side to the leak portion side in the leak gas path. Therefore, blow-by gas existing in the blow-by gas passage can be prevented from flowing into the sub chamber through the leak gas passage and the valve chamber, and the combustion state can be stabilized.
Conversely, the operating valve means is provided even when the pressure of the valve chamber of the sub chamber fuel supply valve becomes very high, particularly in the compression stroke in which the valve portion of the sub chamber fuel supply valve is switched from the open state to the closed state. Since the gas flow from the leak portion side to the blow-by gas path side is allowed, the fuel gas that has flowed into the leak portion provided in the gap between the valve stem and the valve guide from the valve chamber is allowed to leak out without leaking outside. It can be discharged to the blow-by gas passage through the leak gas passage.
Therefore, according to the present invention, the fuel gas existing in the valve chamber of the sub-chamber fuel supply valve is not leaked to the outside while maintaining a stable combustion state even when the intake pressure is reduced at the time of starting or at a low load. A sub-chamber engine that can be discharged into the blow-by gas path can be realized.

  A further characteristic configuration of the sub-chamber engine according to the present invention is that the operating valve means is closed when a pressure difference with respect to the blow-by gas path side on the leak portion side is a predetermined value or less, and the pressure difference is a predetermined value or more. It is in the point comprised by the non-return valve which will be in an open state at the time of.

According to the above characteristic configuration, the check valve can be caused to function as the above-described operating valve means only by providing a check valve having a very simple configuration in the leak gas passage.
That is, when the pressure in the valve chamber of the sub-chamber fuel supply valve becomes very low and the pressure difference with respect to the blow-by gas path side on the leak portion side in the check valve provided in the leak gas path becomes less than a predetermined value, the check Since the valve is closed and the gas flow from the blow-by gas path side to the leak portion side is blocked, it is possible to prevent the blow-by gas from flowing into the sub chamber.
On the other hand, when the pressure in the valve chamber of the sub-chamber fuel supply valve becomes very high and the pressure difference with respect to the blow-by gas path side on the leak side in the check valve provided in the leak gas path exceeds a predetermined value, the check Since the valve is opened and the gas flow from the leak portion side to the blow-by gas passage side is allowed, the fuel gas flowing into the leak portion can be discharged to the blow-by gas passage without leaking outside.

  A further characteristic configuration of the sub-chamber engine according to the present invention is a mode in which the compressor provided in the intake passage is driven to rotate by rotating the turbine by the kinetic energy of the exhaust gas flowing through the exhaust passage. It has a supercharger that supercharges fresh air.

  According to the above characteristic configuration, even when the intake pressure is relatively low at the start-up time when the supercharger does not operate because exhaust gas does not flow through the exhaust passage, as described above, the operating valve By means, it is possible to prevent blow-by gas existing in the blow-by gas passage from flowing into the sub chamber through the leak gas passage and the valve chamber, so that misfire can be prevented and the combustion state can be stabilized.

An embodiment of a sub-chamber engine according to the present invention will be described with reference to the drawings.
A sub-chamber engine 100 shown in FIG. 1 includes a piston 2 and a cylinder 3 that houses the piston 2 and forms a main chamber 1 together with the top surface of the piston 2, and reciprocates the piston 2 in the cylinder 3. The intake valve 6 and the exhaust valve 7 are opened and closed to perform intake, compression, combustion / expansion, and exhaust strokes in the main chamber 1, and the piston 2 is reciprocated by a connecting rod (not shown). (This is not shown in the figure) and is output as a rotary motion. Such a configuration is not different from a normal four-stroke internal combustion engine.
The sub-chamber engine 100 is normally configured to be rated so that the engine speed is a constant rated speed.

  The subchamber engine 100 uses city gas (13A), which is a gaseous fuel, as the fuel gas G. The intake valve 6 is opened in the intake stroke, and air is supplied from the intake port 5 to the main chamber 1. A mixture of a small amount of the fuel gas G, preferably a lean mixture, is sucked in the fresh air I, and the intake valve 6 and the exhaust valve 7 are closed in the compression, combustion and expansion strokes, and the sucked fresh air I is compressed. Then, the fuel gas G is combusted and expanded, and the exhaust valve 7 is opened in the exhaust stroke so that the exhaust gas E is discharged from the main chamber 1 to the exhaust port 8.

In addition, in the intake passage 4 leading to the upstream side of the intake port 5, the fuel gas G supplied from the fuel supply passage 25 is mixed with the air A taken into the intake passage 4, and the lean mixture as the fresh air I is mixed. A mixer 28 is formed to form a gas. The mixer 28 has a venturi structure in which the diameter of the intake passage 4 is reduced. The air A flowing through the intake passage 4 passes through the venturi structure at a high speed to generate a pressure drop, and uses this pressure drop. Thus, the fuel gas G supplied from the fuel supply passage 25 is supplied to the air A flowing through the intake passage 4 to form a lean air-fuel mixture in the intake passage 4.
Further, the fuel supply path 25 is provided with an adjustment valve 26 that can adjust the amount of fuel supplied to the mixer 28 and a governor 27 that maintains the fuel supply pressure to the mixer 28 constant.

  The intake passage 4 is provided with a supercharger 29 that supercharges fresh air I. This supercharger 29 is driven by the kinetic energy of the exhaust gas E that flows through the exhaust passage 9 that leads to the downstream side of the exhaust port 8. A turbo that rotates the turbine and supercharges the compressor provided in the intake passage 4 by the rotational force of the turbine, and supercharges the fresh air I flowing through the intake passage 4 by the rotational drive of the compressor. It is configured as a charger.

  The cylinder head 30 of the sub-chamber engine 100 is provided as a combustion chamber together with the main chamber 1, and is provided with a sub-chamber 17 communicating with the main chamber 1 through the injection hole 18. The structure of the chamber mechanism 10 will be described below.

Above the sub chamber 17, an ignition plug 19 and a sub chamber fuel supply valve 15 are provided.
The spark plug 19 is configured to spark-ignite the air-fuel mixture formed in the sub chamber 17 by generating a spark every cycle.

On the other hand, the sub-chamber fuel supply valve 15 opens and closes the valve portion 14 for each cycle, so that the fuel gas G supplied from the sub-chamber fuel supply passage 22 to the valve chamber 13 passes through the valve portion 14 to the sub chamber. 17 is configured to be supplied intermittently.
The sub-chamber fuel supply path 22 has a supply pump 20 for increasing the supply pressure of the fuel gas G to the valve chamber 13 to about 0.2 MPa (Gauge), and the fuel gas supply amount to the valve chamber 13 can be adjusted. A control valve 21 is provided.

Hereinafter, the operation state of one cycle in the sub-chamber engine 100 will be described below.
In the sub-chamber engine 100, first, the intake valve 6 is opened, and the intake stroke in which the fresh air I is drawn from the intake port 5 into the main chamber 1 is performed by the lowering of the piston 2 from TDC (top dead center). Is called.
At this time, the sub chamber fuel supply valve 15 installed in the sub chamber 17 is supplied to the valve chamber 13 by changing the valve portion 14 from the closed state to the open state substantially simultaneously with the opening timing of the intake valve 6. The supply of the fuel gas G to the sub chamber 17 is started.

Later, the intake valve 6 and the valve portion 14 of the sub-chamber fuel supply valve 15 are closed at substantially the same time, and a so-called compression stroke is performed in which the fresh air I sucked into the main chamber 1 is compressed by the rise of the piston 2. Is called.
In addition, when the sub chamber 17 in the initial stage of the compression stroke is still in a low pressure state, the valve portion 14 of the sub chamber fuel supply valve 15 may be opened to supply the fuel gas G to the sub chamber 17.

In this compression stroke, as the piston 2 moves up, the volume of the main chamber 1 decreases, and the fresh air I in the main chamber 1 flows into the sub chamber 17 through the nozzle holes 18. When the gas flows due to the inflow, the fresh air I and the fuel gas G are mixed, and an air-fuel mixture having an equivalent ratio within the spark ignition possible range (for example, about 1) is formed.
That is, at the end of the compression stroke, the sub-chamber 17 has a mixture with a relatively high equivalence ratio, whereas the main chamber 1 has fresh air I with a relatively low equivalence ratio. become.

Next, the sub-chamber engine 100 operates the spark plug 19 immediately before top dead center, for example, near 8 ° BTDC, and sparks and burns in the upper portion of the sub-chamber 17.
Then, the combustion proceeds in the sub chamber 17, and the flame jet F is jetted into the main chamber 1 through the nozzle hole 18 together with the fuel gas G not burned in the sub chamber 17.
Further, a plurality of nozzle holes 18 communicating with the sub chamber 17 and the main chamber 1 are distributed at equal intervals in the circumferential direction around the central axis X of the main chamber 1 and extend radially. The flame jets F are configured to be ejected radially from the respective nozzle holes 18 into the main chamber 1.

On the other hand, in the main chamber 1, since the lean air-fuel mixture sucked as fresh air I is stably burned by the flame jets F ejected radially from the respective nozzle holes 18, combustion with high efficiency and low NOx is performed. Done.
Although the combustion state in the main chamber 1 is a state close to that of a normal SI engine, knocking does not occur even when the compression ratio is set high, so that the thermal efficiency can be improved.

In the sub-chamber engine 100 described above, in order to minimize the thermal energy of the flame jet F and suppress abnormal combustion such as knocking in the main chamber 1 during high-load operation, the main chamber 1 and the sub-chamber 17 are The volume ratio of the sub chamber 17 is several percent (for example, about 2% to 3%) with respect to the minimum volume of the combustion chamber that is included, that is, the volume of the combustion chamber that is minimum when the position of the piston 2 is the top dead center position. ) And designed to be very small.
In FIG. 1, in order to make it easy to recognize the internal structure of the sub chamber mechanism 10, the ratio of the size of the sub chamber mechanism 10 to the whole is drawn larger.

The above is the description of the basic configuration of the sub-chamber engine 100. The characteristic configuration of the sub-chamber engine 100 will be described below.
As described above, in the sub-chamber engine 100 provided with the sub-chamber fuel supply valve 15, the sub-chamber fuel supply valve particularly in the compression stroke in which the valve portion 14 of the sub-chamber fuel supply valve 15 is switched from the open state to the closed state. The pressure in the 15 valve chambers 13 becomes very high. As the pressure in the valve chamber 13 rises, the fuel gas G present in the valve chamber 13 is inserted into the valve stem 11 of the sub chamber fuel supply valve 15 and the valve stem 11 to guide the valve guide 12. There is a concern of leaking outside through the gap.
Therefore, a leak part 34 is formed in the gap between the valve stem 11 of the sub chamber fuel supply valve 15 and the valve guide 12, and the leak part 34 is connected to the blow-by gas path 40 via the leak gas path 35. ing.
The blow-by gas passage 40 recirculates the blow-by bus BG leaked from the main chamber 1 to the crank chamber (not shown) through the gap between the piston 2 and the inner surface of the cylinder 3 to the intake passage 4, thereby This is for burning unburned gas contained in the gas BG in the main chamber 1.
Further, such a blow-by gas passage 40 is connected to the upstream side of the supercharger 29 that has a relatively low pressure, preferably a negative pressure, in the intake passage 4. Therefore, the blow-by gas BG flowing through the blow-by gas 40 is satisfactorily supplied to the intake passage 4 and is sucked into the main chamber 1 together with the fresh air I.

In particular, the pressure in the intake passage 4 (intake pressure) is relatively low, such as during startup when the turbocharger 29 does not operate or during low load when the opening of a throttle valve (not shown) provided in the intake passage 4 is reduced. As a result, the pressure in the valve chamber 13 of the sub-chamber fuel supply valve 15 that is opened in the intake stroke becomes very low. Therefore, when the leak gas passage 35 is connected to the blow-by gas passage 40 as it is, the blow-by gas BG existing in the blow-by gas passage 40 is leaked along with the pressure drop in the valve chamber 13 of the sub-chamber fuel supply valve 15. In addition, there is a concern of flowing into the sub chamber 17 through the leak portion 34 and the valve chamber 13.
When the blow-by gas BG flows into the sub chamber 17, it becomes difficult to ignite the air-fuel mixture formed in the sub chamber 17 with the spark plug 19, and misfire occurs, or the oil by the oil contained in the blow-by gas BG. Ash may adhere to the valve portion 14 of the sub-chamber fuel supply valve 15, the spark plug 19, and the like, causing them to malfunction.

In view of this, the leak gas passage 35 is actuated valve means that operates in such a manner as to prevent the gas flow from the blow-by gas passage 40 side to the leak portion 34 side and allow the gas flow from the leak portion 34 side to the blow-by gas passage 40 side. A check valve 36 is provided that is closed when the pressure difference between the leak portion 34 and the blow-by gas passage 40 is equal to or less than a predetermined value, and is open when the pressure difference is equal to or greater than a predetermined value.
That is, even when the pressure in the valve chamber 13 of the sub chamber fuel supply valve 15 becomes very low during the intake stroke, the check valve 36 is closed and the leak gas passage 35 is closed from the blow-by gas passage 40 side to the leak portion 34 side. Gas flow to is blocked. Therefore, the blow-by gas BG existing in the blow-by gas path 40 is prevented from flowing into the leak portion 34, the valve chamber 13 and further the sub chamber 17 through the leak gas path 35, and as a result, the combustion state is stabilized.

  Conversely, in the compression stroke in which the valve portion 14 of the sub chamber fuel supply valve 15 is switched from the open state to the closed state, even when the pressure of the valve chamber 13 of the sub chamber fuel supply valve 15 becomes very high, the check valve The gas flow from the leak portion 34 side to the blow-by gas path 40 side is allowed with 36 open. Therefore, the fuel gas G flowing from the valve chamber 13 into the leak portion 34 provided in the gap between the valve stem 11 and the valve guide 12 is discharged to the blow-by gas passage 40 through the leak gas passage 35 without leaking outside. The main chamber 1 is combusted together with the blow-by gas BG.

[Another embodiment]
(1) In the above embodiment, in the leak gas passage 35, the gas flow from the blow-by gas passage 40 side to the leak portion 34 side is prevented and the gas flow from the leak portion 34 side to the blow-by gas passage 40 side is allowed. Although the check valve 36 is provided as the actuating valve means that operates, the actuating valve means includes an on-off valve that can interrupt the gas flow in the leak gas passage 35, and a control means that controls opening and closing of the on-off valve, The control means is configured to close the on-off valve when the pressure difference between the leak portion 34 side and the blow-by gas passage 40 side is less than a predetermined value, and to open when the pressure difference is greater than the predetermined value. It doesn't matter.

(2) As described in the above embodiment, the sub-chamber engine according to the present invention exhibits an excellent effect when a gaseous fuel gas such as city gas is used. Such a fuel gas In addition to the city gas, there are gaseous fuels other than hydrocarbons mainly composed of carbon monoxide and hydrogen such as hydrogen and propane.

  The sub-chamber engine according to the present invention includes a leak gas passage that connects the leak portion provided in the gap between the valve stem and the valve guide of the sub-chamber fuel supply valve to the blow-by gas passage, and is started at a low load. A stable combustion state can be maintained even when the intake pressure is reduced, such as during the time, and the fuel gas present in the valve chamber of the sub chamber fuel supply valve can be discharged to the blow-by gas passage through the leak gas passage without leaking outside. It can be effectively used as a sub-chamber engine.

Partial sectional view of sub-chamber engine

Explanation of symbols

1: Main chamber 4: Intake passage 9: Exhaust passage 11: Valve stem 12: Valve guide 13: Valve chamber 14: Valve portion 15: Sub chamber fuel supply valve 17: Sub chamber 18: Injection hole 34: Leak portion 35: Leak gas Path 36: Check valve (actuating valve means)
100: Sub-chamber engine I: Fresh air E: Exhaust gas G: Fuel gas BG: Blow-by gas

Claims (3)

Fresh air compressed by the rise of the piston in the main chamber is caused to flow into the sub chamber through the nozzle hole, and a mixture of fresh air that has flowed in the sub chamber and fuel gas supplied from the sub chamber fuel supply valve is formed. The spark plug is operated to ignite and burn, and is configured to inject a flame jet from the sub chamber to the main chamber through the nozzle hole.
The sub-chamber engine is provided with a leak gas passage that connects a leak portion provided in a gap between a valve stem of the sub-chamber fuel supply valve and a valve guide that guides and inserts the valve stem to a blow-by gas passage. And
A sub-chamber provided in the leak gas passage with operating valve means that operates in a form that prevents a gas flow from the blow-by gas passage side to the leak portion side and allows a gas flow from the leak portion side to the blow-by gas passage side. Expression engine.   The actuating valve means is constituted by a check valve that is closed when a pressure difference between the leak portion side and the blow-by gas path side is a predetermined value or less and is opened when the pressure difference is a predetermined value or more. The sub-chamber engine according to claim 1.   2. A supercharger that supercharges fresh air to the main chamber in a form in which a turbine is rotated by kinetic energy of exhaust gas flowing through an exhaust passage to rotate a compressor provided in the intake passage. Or the sub-chamber engine according to 2.

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