JP2001303958A - Operation method for precombustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide operation technique sufficiently mixing a fuel for a prechamber and new air fed from a main combustion chamber 2 in the prechamber 7 and improving the efficiency in a precombustion engine feeding prechamber fuel to the prechamber 7 provided in a cylinder head 1, igniting the prechamber fuel fed to the prechamber 7 by an ignition plug 14, and jetting a flame torch from the prechamber 7 to the main chamber 2 via a plurality of jet holes 10. SOLUTION: Feeding of the prechamber fuel to the prechamber 7 is completed at the time lowering a piston in a suction stroke.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel supply system for a sub-combustion chamber provided in a cylinder head. The fuel for the sub-chamber supplied to the sub-combustion chamber is ignited by a spark plug.
The present invention relates to a method for operating a sub-chamber combustion type engine that ejects a flame torch from the sub-combustion chamber to a main combustion chamber through a plurality of injection holes.

[0002]

2. Description of the Related Art In such a sub-chamber combustion engine, fuel for a sub-chamber is supplied to a sub-combustion chamber via a sub-chamber valve, and fresh air such as an air-fuel mixture is mainly supplied via an intake valve in an intake stroke. The main combustion is performed by inhaling the fuel into the combustion chamber, igniting the fuel for the sub-chamber supplied to the sub-combustion chamber with an ignition plug, and burning the fuel. The air-fuel mixture in the chamber is burned to maintain the rotation of the crankshaft.

[0003] During the operation of the sub-chamber combustion engine, the fuel gas for the sub-chamber is adjusted by a gas pressure control device or the like so that the pressure becomes higher than the pressure of the intake manifold. , Flows into the gas chamber on the upstream side of the sub chamber valve provided in the sub combustion chamber. The sub-chamber fuel gas flows into the sub-combustion chamber when the sub-chamber valve is opened.

On the other hand, in order to realize high-efficiency, low-NOx combustion in the main combustion chamber, a mixture of fuel and air in a fuel-lean state is sucked as fresh air via an intake valve. When a high voltage is applied to the ignition plug by an ignition device linked to the rotational movement of the crankshaft, the sub-chamber fuel gas in the sub-combustion chamber is ignited and burned by spark discharge from the ignition plug. The ignited fuel gas for the sub-chamber is ejected from the injection hole into the main combustion chamber as a flame torch, and burns the lean mixture in the main combustion chamber.

In the sub-chamber combustion type engine, the sub-chamber valve is a reed valve provided with a spring member for generating an elastic force in a closing direction, or a valve which opens and closes by utilizing the rotation of a crankshaft by a cam mechanism. The opening / closing timing is set to an open state immediately before the TDC timing (timing at which the piston position reaches the top dead center) at which the exhaust process ends, and the auxiliary chamber fuel gas is supplied to the auxiliary combustion chamber during the intake stroke. When the pressure of the sub-combustion chamber becomes substantially equal to the gas pressure in the gas chamber after the BDC timing (the timing at which the piston position becomes the bottom dead center) at which the compression stroke starts, the sub-chamber is closed. Gas supply was complete.

[0006]

In such a sub-chamber combustion engine, in the sub-combustion chamber, the fuel gas for the sub-chamber and the lean air-fuel mixture flowing through the injection hole from the main combustion chamber in the compression stroke are sufficiently supplied. It is necessary to mix. If this mixing is not sufficient, uneven fuel concentration occurs in the sub-combustion chamber, which not only makes the combustion of the sub-chamber fuel gas unstable in the sub-combustion chamber, but also causes the main combustion to be performed by the flame torch from the sub-combustion chamber. The combustion of the air-fuel mixture in the room is also unstable, resulting in reduced engine efficiency.

Accordingly, the present invention has been made in view of the above circumstances,
It is an object of the present invention to obtain a driving technique of a sub-chamber combustion type engine that can sufficiently mix a fuel for the sub-chamber and fresh air supplied from the main combustion chamber in the sub-combustion chamber to achieve high efficiency. .

[0008]

According to a first aspect of the present invention, there is provided a method for operating a sub-chamber combustion engine according to the present invention, wherein the sub-combustion chamber is supplied with fuel for the sub-chamber. The supply of the fuel for the sub-chamber to the sub-combustion chamber is completed at a time when the piston is descending during the intake stroke.

[Function and Effect] As in the present configuration, the fuel for the sub-chamber is supplied to the sub-combustion chamber, and the timing of completing the supply is determined by the timing during which the piston is descending during the intake stroke, that is, the crank angle during the intake stroke. By setting the timing before 180 ° ATDC, it is possible to increase the time from the completion of the supply of the fuel for the sub-chamber to the ignition of the fuel for the sub-chamber by the ignition plug at the end of the compression stroke. Until the time, the fuel for the sub-chamber can be sufficiently mixed by the lean mixture flowing into the sub-combustion chamber from the injection hole. Therefore, in the sub-chamber combustion engine, the mixing of the sub-combustion chamber is improved, the combustion in the sub-combustion chamber and the combustion in the main combustion chamber are stabilized, and high efficiency operation can be realized.

When the supply of the fuel for the sub chamber is completed, the crank angle is set at 60 ° ATDC during the intake stroke.
The later timing is preferable, and if it is completed at a timing before 60 ° ATDC, it is difficult to secure the supply amount of the fuel for the sub-chamber to the sub-combustion chamber and obtain sufficient performance. If is set high, the supply amount of the fuel for the sub-chamber can be secured, but the compression power of the fuel for the sub-chamber increases, and the advantage of high efficiency is offset. Further, when the supply of the fuel for the sub chamber is completed, the crank angle is set at 150 degrees during the intake stroke.
The timing after ATDC is more preferable. Even if the supply pressure of the sub-chamber fuel is set relatively low, the sub-combustion chamber can be sufficiently supplied with the sub-chamber fuel.

[Structure 2] According to a second aspect of the present invention, there is provided a method for operating a sub-chamber combustion engine according to the present invention. A sub-chamber valve for supplying fuel for the sub-chamber to the sub-combustion chamber is opened and closed by a cam which is opened and closed and whose closing timing is a timing during which the piston is descending during the intake stroke.

[Effects] As in the present configuration, the intake valve and the sub-chamber valve are opened and closed by the same cam mechanism, and both valves are moved during the lowering of the piston during the intake stroke, that is, the crank angle during the intake stroke is reduced. By closing at a time before 180 ° ATDC, there is no need to provide a dedicated cam mechanism for operating the sub-chamber valve. Further, by closing the intake valve at a time when the piston is descending during the intake stroke, the sub-chamber is closed. The combustion engine can be operated in a Miller cycle system. The Miller cycle method is a method of reducing the in-cylinder compression temperature and pressure by lowering the actual compression ratio depending on the timing of closing the intake valve to avoid knocking. As a result, a large expansion ratio can be obtained,
Thermal efficiency can be improved. Therefore, a high-efficiency sub-chamber combustion engine with an inexpensive and simple structure can be realized.

In the present application, TDC indicates the position of the top dead center of the piston, BDC indicates the position of the bottom dead center of the piston, and the crank angle is indicated by an early or late angle with respect to the TDC. BTDC is shown for an angle, and ATDC is shown for a retard.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a method for operating a sub-chamber combustion engine according to the present invention will be described with reference to the drawings. FIG. 1 is a sectional view of a main part showing a combustion chamber and a fuel supply system of a sub-chamber combustion type engine, wherein 1 is a cylinder head, 2 is a main combustion chamber, and the main combustion chamber 2 is a piston 3. , The inner surface of the cylinder 4, and the lower surface of the cylinder head 1. A lean mixture of fuel gas, which is natural gas-based city gas 13A, and air is introduced into the main combustion chamber 2 through an intake valve 5.

Reference numeral 7 denotes a sub-combustion chamber. The sub-combustion chamber 7 is formed substantially at the center of the cylinder head 1 and has a cylindrical shape having an axial direction in the cylinder axis direction. A sub-chamber upper metal part 8 is provided at an upper part of the sub-combustion chamber 7, and a sub-chamber base 9 is provided at a lower part thereof. One or a plurality of injection holes 10 are drilled at the tip of the sub-chamber base 9. Reference numeral 11 denotes a gas chamber formed in the sub-chamber upper metal part 8. The gas chamber 11 controls a gas pressure of a sub-chamber fuel gas, which is a natural gas-based city gas 13A, through a gas passage 12. It is connected to a control device (not shown). Reference numeral 13 denotes a sub-chamber valve provided in the sub-chamber upper metal part 8 so as to be slidable back and forth, and opens and closes a space between the gas chamber 11 and the sub-combustion chamber 7. 14 is the auxiliary combustion chamber 7
It is a spark plug for igniting the fuel gas inside.

During the operation of the sub-chamber combustion type engine, the pressure of the sub-chamber fuel gas is set by the gas pressure control device to a set pressure higher than the pressure on the upstream side of the intake manifold (not shown). After being adjusted to
The gas flows into the gas chamber 11 through the gas passage 12 in the inside.
The sub-chamber fuel gas flows into the sub-combustion chamber 7 when the sub-chamber valve 13 is opened.

On the other hand, in order to realize high-efficiency and low-NOx combustion, a mixture of fuel and air having a lean amount of fuel is sucked into the main combustion chamber 2 via the intake valve 5 as fresh air.
When a high voltage is applied to the ignition plug 14 by an ignition device (not shown) interlocked with the rotational movement of a crankshaft (not shown), spark discharge from the ignition plug 14 causes the sub-combustion chamber 7 The fuel gas ignites and burns. The ignited sub-chamber fuel gas is used as a flame torch in the
The fuel gas is injected into the main combustion chamber 2 from 0 to burn the lean mixture in the main combustion chamber 2.

The sub-chamber combustion engine is, for example, a four-stroke engine that completes one cycle through an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke. Note that, in the present application, each process is defined as TDC and BDC.
For example, the intake stroke indicates a period from TDC when the intake valve is opened to BDC when the next compression stroke is started when the intake valve is closed.

The above is the description of the basic configuration of the sub-chamber combustion type gas engine. Hereinafter, the characteristic configuration of the present invention will be described. In the sub-chamber combustion engine, the sub-chamber valve 13, the intake valve 5, and the exhaust valve 6 are each configured as a valve that is opened and closed by the cam mechanism A using the rotational movement of the crankshaft. As shown in FIG. 2, the cam mechanism A includes a camshaft 24 that makes one rotation per cycle due to the rotation of the crankshaft, cams 21, 22, 23 provided on the camshaft 24, and respective cams 21. , 22,
Push rods 25, 26, 27 that reciprocate in the axial direction according to the surface shape of 23, an intake rocker arm 28 that swings around a rocker arm axis 31 by the push rod 25 to open and close the intake valve 5, and a push rod 26.
Swings around the rocker arm shaft 31 by the exhaust valve 6.
And a sub chamber rocker arm 30 that swings around a rocker arm axis 31 by a push rod 27 to open and close the sub chamber valve 13.

The opening / closing timings of the intake valve 5 and the exhaust valve 6 are the same as those of the conventional engine, but the opening / closing timing of the sub-chamber valve is shown in FIG. Thus, when the crank angle during the exhaust stroke is 30
° BTDC at the time of opening, the crank angle during the intake stroke before BDC is closed at the time of about 165 ° ATDC, and the supply of the sub-chamber fuel gas to the sub-combustion chamber 7 is completed before the end of the intake stroke. Will be completed. In this way, the supply of the sub-chamber fuel gas to the sub-combustion chamber 7 and the completion of the supply are set to the timing during which the piston is descending during the intake stroke, whereby the supply of the sub-chamber fuel gas is completed. After that, the ignition plug at the end of the compression stroke can increase the time required to ignite the fuel for the sub-chamber by the spark plug. Until the ignition timing, the lean air-fuel mixture flowing from the injection hole 10 into the sub-combustion chamber 7 can sufficiently increase the time. The fuel for the sub-chamber can be mixed.

Further, in the sub-chamber combustion type engine in which the supply completion timing of the sub-chamber fuel gas is set to a timing where the crank angle before BDC during the intake stroke is about 165 ° ATDC as in the present method, The thermal efficiency when the gas supply pressure is changed and the supply pressure of the fuel gas for the sub-chamber are changed in the sub-chamber combustion type engine in which the completion of the supply of the fuel gas for the sub-chamber is set at the time after BDC as in the conventional case. FIG. 4 shows the thermal efficiency when this is performed. As can be seen from FIG. 4, in this method, high thermal efficiency can be maintained even when the supply pressure of the fuel gas for the sub-chamber is changed. When closed, the heat exchange rate is low overall, and when the supply pressure of the sub-chamber fuel gas is set high, the heat exchange rate further deteriorates. This is because, in the conventional sub-chamber combustion type engine, the fuel gas for the sub-chamber is supplied halfway through the compression stroke, so that the mixing time until ignition is short and the combustion in the sub-combustion chamber 7 is unstable. It can be said that.

[Another Embodiment] In the cam mechanism section A of the above embodiment, the intake valve 5 and the sub-chamber valve 13 are driven by different cams. It can also be driven by a cam. That is,
As shown in FIG. 5, a camshaft 24 that makes one rotation per cycle by the rotation of the crankshaft,
And two cams 32 and 22 provided on the
Two push rods 33, 26 reciprocating in the axial direction according to the surface shapes of the rocker arms 2, 22, and a rocker arm 34 swinging around the rocker arm shaft 31 by the push rod 33 to open and close both the intake valve 5 and the sub-chamber valve 13.
And an exhaust rocker arm 29 that swings around a rocker arm shaft 31 by a push rod 26 to open and close the exhaust valve 6.

Further, in the present method, the sub-chamber valve 1
3 is configured to close at the time when the piston is descending during the intake stroke, so that the intake valve 5 is also closed at the time when the piston is descending during the intake stroke.
The sub-chamber combustion engine can be operated in a so-called Miller cycle system, and the efficiency can be further improved with a simple configuration.

The gaseous fuel that can be used in the sub-chamber combustion engine of the present invention includes propane,
Any hydrocarbon gaseous fuel, such as hydrogen, can be used.

[0025]

According to the present technique, in the sub-chamber combustion engine, even if the supply pressure of the sub-chamber fuel is set to be high, the supply amount does not become excessively large. A good mixed state can be obtained. For this reason, the efficiency of the engine can be greatly improved, the variation in the supply amount of the fuel for the sub-chamber can be suppressed, and stable operation can be maintained for a long period of time.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part showing a combustion chamber and a fuel supply system of a sub-chamber combustion engine.

FIG. 2 is a cam mechanism section A of the sub-chamber combustion type engine shown in FIG.
Perspective view of

FIG. 3 is a graph showing a change in a lift amount of a sub chamber valve 13;

FIG. 4 is a graph showing changes in thermal efficiency when the supply pressure of the fuel gas for the sub-chamber is changed in the sub-chamber combustion engine.

FIG. 5 is a perspective view showing another configuration of the cam mechanism section A of the sub-chamber combustion engine.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cylinder head 2 Main combustion chamber 3 Piston 4 Cylinder 5 Intake valve 6 Exhaust valve 7 Subcombustion chamber 10 Injection hole 13 Subchamber valve 14 Spark plug 32 Cam A Cam mechanism

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) F02D 19/02 F02D 19/02 Z F02M 21/02 F02M 21/02 Q (72) Inventor Shinichi Adachi Osaka-shi, Osaka Osaka Gas Co., Ltd. 4-1-2, Hirano-cho, Ward (72) Inventor Yoshitaka Tsunohama 3000 Tana, Sagamihara-shi, Kanagawa Prefecture Mitsubishi Heavy Industries, Ltd. 5-7-1, Machi Nagasaki R & D Co., Ltd. F-term (reference) 3G018 AB06 AB19 BA01 CA01 DA03 EA25 EA32 FA08 FA27 GA07 3G023 AA02 AA07 AB01 AC03 AC07 AD07 AD24 3G092 AA01 AA05 AA07 AA08 AA09 AB02 AB07 AB12 BB DD03 DF01 EA02 FA22 FA24 HA13X HA14Z HB02X HE03Z

Claims (2)

[Claims] An auxiliary chamber fuel is supplied to an auxiliary combustion chamber provided in a cylinder head, and the auxiliary chamber fuel supplied to the auxiliary combustion chamber is ignited by an ignition plug. A method for operating a sub-chamber combustion engine in which a flame torch is ejected to a main combustion chamber through a hole, wherein the sub-combustion chamber is supplied with fuel for the sub-chamber. Method for operating a sub-chamber combustion type engine in which the supply of air is completed during a period when the piston is descending during the intake stroke. 2. A sub-chamber valve for supplying fuel for the sub-chamber to the sub-combustion chamber by means of a cam which opens and closes an intake valve and sets a closing timing to a timing when the piston is descending during an intake stroke. An operating method of the sub-chamber combustion engine according to the above.