JPWO2004099584A1 - Subchamber gas engine combustion chamber structure and subchamber gas engine - Google Patents

Abstract

The sub-combustion chamber 4 of the sub-chamber type gas engine is formed with a concave portion having a substantially rectangular cross section, and the opening position of the fuel supply passage 68 for supplying the sub-chamber fuel gas to the sub-combustion chamber 4 is defined as the above-mentioned substantially square cross section. Set to the top corner of. On the other hand, the supply direction of the sub-chamber fuel gas into the sub-combustion chamber 4 is set to a direction along the diagonal line of the substantially square cross section. When a part of the lean air-fuel mixture in the main combustion chamber 3 flows into the sub-combustion chamber 4 as the piston 5 moves during the compression stroke, the sub-chamber fuel gas is pushed into the vicinity of the spark plug 7 and the ignition point of the spark plug 7 is reached. The gas concentration around S is kept high. Further, as the distance from the ignition point increases, the mixing ratio of the lean air-fuel mixture to the sub chamber fuel gas gradually increases. Thereby, it is possible to optimize the pressure and temperature around the spark plug at the time of ignition while obtaining good ignitability and flame propagation.

Description

  The present invention relates to a sub-chamber type gas engine used as a drive source for GHP (Gas Heat Pump), a generator, and the like, and a combustion chamber structure of the sub-chamber type gas engine. In particular, the present invention relates to a measure for extending the life of a spark plug (a spark plug).

Conventionally, a sub-chamber type gas engine (hereinafter referred to as a sub-chamber type gas engine) that uses natural gas, propane gas, or the like as a fuel and is used as a drive source for a GHP, a generator, or the like is known. This sub-chamber type gas engine includes a main combustion chamber (hereinafter referred to as a main chamber) and a sub-combustion chamber (hereinafter referred to as a sub chamber), as disclosed in, for example, Japanese Patent Laid-Open No. 10-47165. While supplying high-concentration fuel gas (for example, 100% concentration fuel gas) into the room, an ultra-lean air-fuel mixture, which is a low-concentration air-fuel mixture, is supplied into the main chamber, and this is ignited by ignition of a spark plug facing the sub chamber The fuel gas in the sub chamber is combusted and the flame is propagated to the ultra-lean mixture in the main chamber to perform the expansion stroke.
Further, the sub chamber is generally formed of a substantially cylindrical space as disclosed in the above publication, and a throat and a nozzle for propagating a flame generated in the sub chamber to the main chamber. Communicate. The throat is formed by a small-diameter passage extending from the sub chamber toward the main chamber. On the other hand, the nozzle hole is formed as a plurality of passages for injecting the flame propagating through the throat radially into the main chamber in a plurality of directions. As a result, the flame is propagated at a high speed over a wide range in the main chamber. As a result, ignition stability and rapid combustion are achieved, and ultra lean combustion can be realized.
By the way, the conventional sub-chamber type gas engine has the following problems (1) and (2), and at present, sufficient measures have not yet been taken for these problems.
(1) In the sub chamber, high-concentration fuel gas is ignited by a spark plug, and the nozzle hole comprising a small-diameter passage communicating the sub chamber and the main chamber acts as a throttle for flame propagation. The temperature and pressure in the sub chamber are much higher than the temperature and pressure in the main chamber. For this reason, the electrode of the spark plug is exposed to a high temperature and high pressure environment for a long time, the deterioration with time is remarkable, and there is a limit to extending the life of the spark plug.
(2) The combustion speed of the flame (also called torch combustion) generated in the sub chamber is extremely rapid, and in order to prevent knocking, the ignition timing of the spark plug is set to combustion TDC (Top Dead Center). In other words, the ignition timing delay margin is small, and the ignition advance is actually less than 10 °. Accordingly, the ignition timing of the spark plug is set at a point in time when the internal pressures of the main chamber and the sub chamber are considerably increased, so that the voltage value required to ignite the spark plug becomes high. This is because the air-fuel mixture density at the time of ignition is high, and in this state, a very high voltage is required for ignition by causing dielectric breakdown between the electrodes of the spark plug. As a result, there is a possibility that the wear of the electrode is rapidly progressed, and there is a risk of causing misfire.
The present invention has been made in view of the above points, and an object of the present invention is to provide a combustion chamber structure and a sub-chamber gas capable of extending the life of the spark plug with respect to the sub-chamber gas engine. To provide an institution.

In order to achieve the above object, the present invention aims to optimize the shape of the sub-combustion chamber of the sub-chamber type gas engine, or by appropriately setting the supply direction of the fuel gas for the sub-chamber into the sub-combustion chamber. Without requiring special control operation, the temperature and pressure in the sub-combustion chamber can be kept low, and the ignition advance angle can be increased, so that the voltage value required for ignition of the ignition plug (ignition plug) can be reduced. This lowers the life of the spark plug.
1. Specifically, the combustion chamber structure of the sub-chamber type gas engine of the present invention includes a main combustion chamber formed in a cylinder, a sub-combustion chamber communicating with the main combustion chamber, and an ignition plug facing the sub-combustion chamber. A fuel supply valve that supplies the sub-chamber fuel gas to the sub-combustion chamber, and a fuel supply passage that guides the sub-chamber fuel gas from the fuel supply valve to the sub-combustion chamber. Combustion chamber structure in a sub-chamber type gas engine that performs an expansion stroke by propagating a flame generated by supplying fuel gas for the sub-chamber to the sub-combustion chamber and igniting a spark plug through the sub-combustion chamber to the main combustion chamber Assuming With respect to this combustion chamber structure, the sub-combustion chamber is formed by a recessed portion whose one end opens to the main combustion chamber. Further, the ratio of the total volume of the sub-combustion chamber and the fuel supply path to the total volume of the main combustion chamber, the sub-combustion chamber and the fuel supply path when the piston in the cylinder is at the top dead center is 1.5. It is set to ~ 2.6%.
When the volume ratio (hereinafter referred to as the sub chamber volume ratio) is less than 1.5, the combustion fluctuation rate increases rapidly as the sub chamber volume ratio decreases. When the sub chamber volume ratio exceeds 2.6, the NOx generation amount increases rapidly as the sub chamber volume ratio increases (see FIG. 3). Therefore, by setting the sub chamber volume ratio in the range of 1.5 to 2.6%, it is possible to realize a sub chamber engine capable of satisfactorily obtaining both suppression of the combustion fluctuation rate and low NOx. .
In addition, in the conventional combustion chamber structure in which a flame jet is ejected from the sub-combustion chamber to the main combustion chamber through the nozzle, the ignition advance must be reduced because the lean mixture in the main combustion chamber burns rapidly due to the ejected flame jet. However, since the auxiliary combustion chamber according to the present invention is open to the main combustion chamber and there is no high-speed jet of flame jet, it is necessary to increase the ignition advance angle in order to reproduce the same good combustion as before. There is. In other words, by obtaining a large ignition timing delay margin, the ignition timing of the spark plug can be set at a time when the sub-combustion chamber is at a relatively low pressure. Therefore, the voltage value required to ignite the spark plug is reduced. This makes it possible to suppress electrode wear and prevent misfire. As a result, it is possible to extend the life of the spark plug. Further, in the present invention, as described above, an open-type subcombustion chamber that does not include a throat or a nozzle is adopted, so that a flame generated in the subcombustion chamber at the time of ignition easily propagates to the main combustion chamber side. The period during which the electrode is exposed to a high-temperature and high-pressure environment is extremely short, and this can also extend the life of the spark plug.
2. Further, as another invention for extending the life of the spark plug, the following configuration is listed. That is, a main combustion chamber formed in the cylinder, a sub-combustion chamber communicating with the main combustion chamber, a spark plug facing the sub-combustion chamber, and a fuel supply valve for supplying sub-chamber fuel gas to the sub-combustion chamber And a fuel supply passage for guiding the subchamber fuel gas from the fuel supply valve to the subcombustion chamber, and supplying the subchamber fuel gas from the fuel supply valve to the subcombustion chamber via the fuel supply passage. A combustion chamber structure in a sub-chamber type gas engine that performs an expansion stroke by propagating a flame generated by igniting the gas from the sub-combustion chamber to the main combustion chamber is assumed. In contrast to this combustion chamber structure, the sub-combustion chamber is formed by a substantially cylindrical bottomed recessed portion having one end opened to the main combustion chamber. Further, the ratio of the depth dimension (L) to the inner diameter (D) of the auxiliary combustion chamber is set to 0.9 to 1.5.
When the ratio (hereinafter referred to as “L / D”) is less than 0.9, the combustion fluctuation rate increases rapidly as “L / D” decreases. When “L / D” exceeds 1.5, the combustion fluctuation rate increases rapidly as “L / D” increases, and the thermal efficiency also deteriorates rapidly (see FIG. 4). Furthermore, by setting “L / D” within the above range, it is possible to make the fuel gas of an appropriate concentration exist only in the vicinity of the spark plug and to obtain stable engine rotation.
In addition, in the conventional combustion chamber structure in which a flame jet is ejected from the sub-combustion chamber to the main combustion chamber through the nozzle, the ignition advance must be reduced because the lean mixture in the main combustion chamber burns rapidly due to the ejected flame jet. However, since the auxiliary combustion chamber according to the present invention is open to the main combustion chamber and there is no high-speed jet of flame jet, it is necessary to increase the ignition advance angle in order to reproduce the same good combustion as before. There is. That is, even if the ignition advance angle of the spark plug is made larger than that of the conventional one, it is possible to obtain a stable engine rotation in which knocking hardly occurs. Therefore, even with this solution, the retarding margin of the ignition timing can be increased, and the ignition plug can be ignited at a time when the subcombustion chamber is at a relatively low pressure. The required voltage value can be lowered, electrode wear can be suppressed, and misfire can be prevented. Also in the present invention, since an open subcombustion chamber having no conventional throat or nozzle is adopted, flames generated in the subcombustion chamber at the time of ignition easily propagate to the main combustion chamber side, and the spark plug The period during which the electrode is exposed to a high-temperature and high-pressure environment is extremely short, and this can also extend the life of the spark plug.
3. It is also possible to have the two solution means described above. The configuration is as follows. A main combustion chamber formed in the cylinder, a sub-combustion chamber communicating with the main combustion chamber, a spark plug facing the sub-combustion chamber, a fuel supply valve for supplying sub-chamber fuel gas to the sub-combustion chamber, A fuel supply passage for guiding the subchamber fuel gas from the fuel supply valve to the subcombustion chamber, and supplying the subchamber fuel gas from the fuel supply valve to the subcombustion chamber through the fuel supply passage to ignite the spark plug It is premised on a combustion chamber structure in a sub-chamber type gas engine that performs an expansion stroke by propagating a flame generated by this process from the sub-combustion chamber to the main combustion chamber. In contrast to this combustion chamber structure, the sub-combustion chamber is formed by a substantially cylindrical bottomed recessed portion having one end opened to the main combustion chamber. Further, the ratio of the total volume of the sub-combustion chamber and the fuel supply path to the total volume of the main combustion chamber, the sub-combustion chamber and the fuel supply path when the piston in the cylinder is at the top dead center is 1.5. It is set to ~ 2.6%. Moreover, the ratio of the depth dimension to the inner diameter of the auxiliary combustion chamber is set to 0.9 to 1.5.
According to this specific matter, the effects of the above-mentioned two solving means (optimization of “sub-chamber volume ratio” and “L / D”) can be exhibited together, and the life of the spark plug can be extended. Can be realized more reliably.
4). Further, a sub-chamber type gas engine having a combustion chamber structure according to each of the above-described solutions is also within the scope of the technical idea of the present invention. That is, a sub-chamber type gas engine having a combustion chamber structure according to any one of the above solutions, wherein the sub-chamber fuel gas is supplied from the fuel supply valve to the sub-combustion chamber through the fuel supply path. Then, the flame generated by igniting the spark plug is propagated from the auxiliary combustion chamber to the main combustion chamber to perform the expansion stroke.
5). Further, the following can be listed as means for optimizing the pressure and temperature around the spark plug at the time of ignition by appropriately setting the supply direction of the fuel gas for the sub chamber into the sub combustion chamber. A main combustion chamber formed in the cylinder, a sub-combustion chamber communicating with the main combustion chamber, a spark plug facing the sub-combustion chamber, a fuel supply valve for supplying sub-chamber fuel gas to the sub-combustion chamber, A fuel supply passage for guiding the subchamber fuel gas from the fuel supply valve to the subcombustion chamber, and supplying the subchamber fuel gas from the fuel supply valve to the subcombustion chamber through the fuel supply passage to ignite the spark plug A sub-chamber type gas engine that performs an expansion stroke by propagating a flame generated by the operation from the sub-combustion chamber to the main combustion chamber is assumed. With respect to this sub-chamber type gas engine, the sub-combustion chamber is formed by a recessed portion whose one end opens to the main combustion chamber. The supply direction of the sub-chamber fuel gas into the sub-combustion chamber is set such that the linear movement distance of the sub-chamber fuel gas in the sub-combustion chamber space is the longest.
Due to this specific matter, the fuel gas for the sub chamber supplied from the fuel supply valve to the sub combustion chamber through the fuel supply passage is ejected from the fuel supply passage into the sub combustion chamber and then the axis of the blowing direction (for example, fuel supply) (Substantially coincides with the axial direction of the road) and flows (moves) in the subcombustion chamber space. Thus, in the stage where the sub chamber fuel gas is moving in the sub combustion chamber, the compression stroke is started in the sub chamber type gas engine, and the piston moves from the bottom dead center toward the top dead center. As the piston moves, a part of the lean air-fuel mixture in the main combustion chamber flows from the main combustion chamber into the sub-combustion chamber. In this solution, since the supply direction of the sub chamber fuel gas is set in the direction in which the linear movement distance of the sub chamber fuel gas in the sub combustion chamber space becomes the longest, the sub chamber fuel gas is supplied to the sub combustion chamber. Part of the lean mixture before reaching the wall surface or changing the flow direction of the sub-chamber fuel gas under the influence of the wall surface of the sub-combustion chamber (the directivity changes from the blowing direction to the other direction). It becomes possible to start the operation of flowing into the auxiliary combustion chamber. The lean air-fuel mixture flowing into the sub-combustion chamber causes the sub-chamber fuel gas in the sub-combustion chamber to be pushed toward the vicinity of the spark plug, and the boundary between the sub-chamber fuel gas and the lean air-fuel mixture. These two kinds of gases are appropriately stirred in the part and its periphery. That is, the directivity of the blowout is in a certain direction (the blowout direction from the fuel supply path) (the directivity of the blowout has not changed). The gas is pushed in and moderately mixed between the gas at the boundary portion and its periphery. For this reason, in the local region in the vicinity of the ignition point (electrode) of the spark plug, a high concentration state is maintained due to the pushing-in of the sub-chamber fuel gas, and as the distance from the ignition point increases, the sub-chamber fuel gas becomes leaner. The mixture ratio of the air-fuel mixture gradually increases (the fuel gas concentration gradually decreases). Since the ignition plug is ignited in this state, the initial combustion (ignition) in the vicinity of the ignition plug is favorably performed due to the presence of the high-concentration sub-chamber fuel gas, and from the sub-combustion chamber to the main combustion chamber. The flame propagation toward the direction can be smoothly performed by the air-fuel mixture whose concentration gradually decreases.
In other words, if the sub-chamber fuel gas amount supplied from the fuel supply valve to the sub-combustion chamber is set to a predetermined amount, if the gas concentration becomes uniform over the entire sub-combustion chamber, ignition will occur. Insufficient gas concentration in the vicinity of the ignition point of the plug will impede ignitability and make combustion unstable. Conversely, if the high concentration region of the sub chamber fuel gas in the vicinity of the spark plug is large, the gas concentration is too low in other regions, resulting in deterioration of flame propagation. Further, in this case, there are concerns about defects such as generation of soot and burning of the spark plug. In this solution, the gas concentration in a relatively narrow region only near the ignition point of the ignition plug is appropriately obtained by appropriately pushing the sub chamber fuel gas into the vicinity of the ignition plug and stirring and mixing the lean mixture with the sub chamber fuel gas. The gas concentration can be gradually set lower as the distance from the ignition point increases. For this reason, it is avoided that the pressure and temperature in the auxiliary combustion chamber rises immediately after ignition, and the pressure and temperature around the spark plug at the time of ignition are optimized while achieving good ignitability and flame propagation. Therefore, the life of the spark plug can be extended. In addition, there is no inconvenience such as generation of soot and burning of the spark plug.
6). As described above, a specific configuration for setting the direction in which the sub chamber fuel gas is supplied to the sub combustion chamber in such a direction that the linear movement distance of the sub chamber fuel gas in the sub combustion chamber space is longest is as follows. Are listed. The sub-combustion chamber is formed of a recessed portion having a substantially rectangular longitudinal section. And the opening position of the fuel supply path with respect to a subcombustion chamber is set to the upper-end corner part of the said substantially square cross section. On the other hand, the supply direction of the fuel gas for the sub chamber toward the sub combustion chamber connects the upper end corner portion and the lower end edge portion of the sub combustion chamber opening side that forms a diagonal with the upper end corner portion. The direction is set along the diagonal line of the rectangular cross section.
By performing such a sub-chamber fuel gas blowing operation, a part of the sub-chamber fuel gas supplied to the sub-combustion chamber stops in the sub-combustion chamber, and other sub-chamber fuel gases are sub-combusted. It will be in the state which flows out from a chamber to the main combustion chamber. In the compression stroke of the sub chamber type gas engine, as the piston moves from the bottom dead center toward the top dead center, the sub chamber fuel gas flowing into the main combustion chamber is diluted with the lean mixture in the cylinder. It flows from the main combustion chamber into the sub-combustion chamber while being mixed with gas. By this flow, the sub-chamber fuel gas that has stopped in the sub-combustion chamber is pushed toward the vicinity of the spark plug. Then, these two kinds of gases are moderately agitated at and around the boundary portion between the high-concentration fuel gas being pushed in and the relatively low-concentration fuel gas flowing from the main combustion chamber into the sub-combustion chamber. Therefore, in the local region near the ignition point of the spark plug, the high concentration state of the sub chamber fuel gas is maintained, and as the distance from the ignition point increases, the mixture ratio of the lean mixture to the sub chamber fuel gas increases. The state gradually increases (the fuel gas concentration gradually decreases). Since the ignition plug is ignited in this state, the initial combustion in the vicinity of the ignition plug is favorably performed due to the presence of the high-concentration sub-chamber fuel gas, and flame propagation from the sub-combustion chamber to the main combustion chamber is achieved. It will be smooth. In other words, in the case of this solution, it is possible to optimize the pressure and temperature around the spark plug at the time of ignition while obtaining good ignitability and flame propagation, and to extend the life of the spark plug. Can be planned.
7). In the above solution, the following can be listed as a configuration for ensuring a high concentration of the sub-chamber fuel gas in the sub-combustion chamber, particularly in the vicinity of the ignition point of the spark plug. That is, the throttle part which reduces the cross-sectional area of the surface orthogonal to the propagation direction of the flame from the subcombustion chamber to the main combustion chamber is provided in the vicinity of the open side end of the subcombustion chamber which opens to the main combustion chamber. According to this, the throttle portion can prevent the sub-chamber fuel gas that is supplied toward the sub-combustion chamber and should stop in the sub-combustion chamber from flowing into the main combustion chamber. For this reason, the amount of the fuel gas for the sub chamber can be sufficiently secured, and the high concentration state of the fuel gas for the sub chamber can be reliably maintained in the local region near the ignition point of the spark plug, so that the ignitability can be maintained. Can be obtained satisfactorily.
8). Moreover, the following is mentioned as a structure for enabling smoothly returning the mixed gas of the sub-chamber fuel gas flowing out from the sub-combustion chamber to the main combustion chamber and the lean mixture into the sub-combustion chamber. That is, an enlarged portion is provided in the vicinity of the open side end of the sub-combustion chamber that opens to the main combustion chamber, and the cross-sectional area of the surface orthogonal to the direction of flame propagation from the sub-combustion chamber to the main combustion chamber is enlarged. According to this, the gas from the main combustion chamber to the sub-combustion chamber (the gas in which the sub-chamber fuel gas that has flowed out to the main combustion chamber and the lean mixture is stirred and mixed) flows along with the movement of the piston in the compression stroke It is possible to create a state in which the mixture ratio of the lean air-fuel mixture to the subchamber fuel gas gradually increases as the distance from the ignition point of the spark plug increases, ensuring good flame propagation. can do.
9. Further, the following is listed as a configuration for favorably performing the agitation when the mixed gas of the sub-chamber fuel gas flowing out from the sub-combustion chamber to the main combustion chamber and the lean mixture is smoothly returned to the sub-combustion chamber. It is done. That is, the opening shape of the surface perpendicular to the flame propagation direction at the open side end of the sub-combustion chamber that opens to the main combustion chamber is eccentric with respect to the opening shape of the surface perpendicular to the flame propagation direction at the back side portion of the auxiliary combustion chamber. I am letting. As a result, the mixed gas of the sub-chamber fuel gas and the lean air-fuel mixture flowing from the main combustion chamber into the sub-combustion chamber is stirred and mixed in the sub-combustion chamber as a swirling flow (tumble flow) around the horizontal axis. Thereby, it can stir moderately and can aim at optimization of the gas concentration in a subcombustion chamber.
10. Specific examples of the fuel supply valve include the following. That is, the fuel supply valve is operated by an automatic valve that opens and closes according to the pressure difference between the back pressure of the built-in valve body and the cylinder internal pressure, and supplies the sub chamber fuel gas to the sub combustion chamber through the fuel supply path when opened. Is configured.
This eliminates the need for special control for supplying the sub-chamber fuel gas to the sub-combustion chamber, thereby realizing a low-cost and highly reliable fuel supply system. In particular, in the case of this fuel supply valve (automatic valve that uses the pressure difference as the driving force), the supply timing and supply amount of the sub chamber fuel gas cannot be arbitrarily controlled, and the supply of the sub chamber fuel gas starts. When the time from ignition to ignition of the spark plug becomes long, most of the sub-chamber fuel gas flows out to the main combustion chamber, and the sub-chamber fuel gas with an appropriate concentration exists in the sub-combustion chamber. There were cases where it was not possible. According to the present invention, as described above, ignitability can be achieved even when the automatic valve is used by pushing the sub chamber fuel gas into the vicinity of the spark plug and stirring and mixing the lean mixture with the sub chamber fuel gas. In addition, it is possible to realize the fuel gas concentration in the sub-combustion chamber that can obtain good flame propagation characteristics.

FIG. 1 is a diagram showing a schematic configuration of an engine combustion chamber, a peripheral portion of the combustion chamber, and a fuel supply system according to the first embodiment of the combustion chamber structure of the present invention.
FIG. 2 is a cross-sectional view showing the main chamber and the sub chamber in the state where the piston is at the top dead center in the combustion chamber structure of the present invention, and their surroundings.
FIG. 3 is a diagram showing experimental results of engine characteristics when the sub chamber volume ratio is changed in the range of 1.0 to 3.2% in the combustion chamber structure of the present invention. It is a figure which shows a combustion fluctuation rate, (b) shows the thermal efficiency of an engine, (c) shows the NOx amount which an engine emits, respectively.
FIG. 4 is a diagram showing experimental results of engine characteristics when the ratio “L / D” of the depth dimension to the inner diameter of the sub chamber is changed in the range of 0.6 to 1.8 in the combustion chamber structure of the present invention. Here, (a) shows the engine combustion fluctuation rate, (b) shows the engine thermal efficiency, and (c) shows the NOx amount emitted by the engine.
FIG. 5 is a longitudinal sectional view showing an auxiliary chamber of an engine according to the second embodiment of the present invention and its periphery.
FIG. 6 is a diagram showing a result of testing engine characteristics when the sub chamber fuel gas is supplied in a different direction in the second embodiment of the present invention, in which (a) shows the combustion fluctuation rate of the engine, ( (b) is a graph showing the amount of soot generated by the engine, and (c) is a graph showing the thermal efficiency of the engine.
FIG. 7A is a longitudinal sectional view showing a sub chamber and its periphery of an engine according to a third embodiment of the present invention, and FIG. 7B shows opening shapes in the lower end opening portion and the electrode peripheral portion of the sub chamber. FIG.
FIG. 8 is a diagram showing the combustion fluctuation rate of the engine when the throttle part is provided in the sub chamber and when the throttle part is not provided in the third embodiment of the present invention.
FIG. 9A is a longitudinal sectional view showing a sub chamber and its periphery of an engine according to a fourth embodiment of the present invention, and FIG. 9B shows an opening shape in a lower end opening portion and an electrode peripheral portion of the sub chamber. FIG.
FIG. 10 is a diagram showing the soot generation amount of the engine when the enlarged portion is provided in the sub chamber and when the enlarged portion is not provided in the fourth embodiment of the present invention.
FIG. 11A is a longitudinal sectional view showing a sub chamber and its periphery of an engine according to a fifth embodiment of the present invention, and FIG. 11B shows opening shapes in the lower end opening portion and the electrode peripheral portion of the sub chamber. FIG.
FIG. 12 is a graph showing the engine combustion fluctuation rate when the sub chamber opening is eccentric and when it is not eccentric in the fifth embodiment of the present invention.

Hereinafter, an embodiment of a combustion chamber structure of the present invention will be described based on the drawings. In this embodiment, the combustion chamber structure of the present invention is applied to a sub-chamber type gas engine provided with a so-called injector type fuel supply system that supplies fuel gas toward the main chamber by an injector provided on the downstream side of the supercharger. The case will be described.
(First embodiment)
-Configuration of the main parts of the engine-
First, a schematic configuration of a fuel supply system that is a main part of a sub-chamber gas engine (hereinafter simply referred to as an engine) according to the present embodiment will be described.
FIG. 1 is a diagram showing a schematic configuration of a combustion chamber of this engine, a peripheral portion of the combustion chamber, and a fuel supply system. As shown in this figure, the engine has a cylinder head 2 fastened to the top of a cylinder block 1 and is formed between a cylinder 11 formed in the cylinder block 1 and a lower surface 21 of the cylinder head 2. This space is configured as the main room 3. FIG. 1 shows a state where the piston 5 inserted into the cylinder 11 is located at the top dead center. In this state, a space 31 (so-called squish area) formed between the lower surface 21 of the cylinder head 2 and the top surface 51 of the piston 5 and a recessed portion 52 formed at the center of the top surface 51 of the piston 5. The main chamber 3 is constituted by the internal space 32.
The cylinder head 2 has an air supply port 22 and an exhaust port 23 communicating with the main chamber 3. The air supply port 22 has an air supply valve 24, and the exhaust port 23 has an exhaust valve 25. Is provided.
On the other hand, a sub chamber 4 is formed at the center of the lower surface 21 of the cylinder head 2. The sub chamber 4 is recessed in a cylindrical shape, and its lower end is open to the main chamber 3. The shape of the sub chamber 4 will be described later.
An automatic check valve 62 as a fuel supply valve and a spark plug 7 as a spark plug are disposed in the upper portion of the sub chamber 4.
Next, the fuel supply system of the engine will be described. In FIG. 1, the intake ports 22 are gathered in the intake manifold 8 via an intake pipe 26, and the intake manifold 8 communicates with a supercharger (not shown) via a throttle 9, which is provided for each cylinder of the engine. The intake pipe 26 is provided with an injector (not shown) for supplying fuel gas. Thereby, fuel gas is supplied from the injector to the air pressurized by the supercharger to generate an ultra-lean air-fuel mixture that is a low-concentration air-fuel mixture, and this air-fuel mixture is supplied from the air supply port 22 to the main chamber 3. To be supplied to
On the other hand, the fuel gas is supplied to the sub chamber 4 by the automatic check valve 62 using the diaphragm regulator 61. In this diaphragm regulator 61, as is well known, the first pressure chamber 63 having the same pressure as the intake pipe internal pressure communicating with the intake manifold 8 and the sub chamber supply gas pressure communicating with the fuel gas supply source and the check valve 62 are the same. The pressure second pressure chamber 64 is partitioned by a diaphragm 65, the balance spring 66 disposed in the automatic check valve 62, the pressure difference between the pressure chambers 63 and 64, and the set pressure of the regulator spring 67 Therefore, the fuel gas is supplied into the sub chamber 4 using the pumping loss of the engine as a driving force. Further, the automatic check valve 62 and the sub chamber 4 communicate with each other through a fuel supply path 68, and the 100% concentration fuel gas is automatically checked only at the timing when the automatic check valve 62 is opened by the driving force due to the pumping loss. The valve 62 is supplied to the sub chamber 4 through the fuel supply path 68.
-Description of subchamber shape-
Next, the shape of the sub chamber 4 which is a characteristic part of this embodiment will be described. The sub chamber 4 is configured by a substantially cylindrical recess. In other words, the sub chamber 4 is formed with a concave portion having a substantially circular cross-sectional shape perpendicular to the propagation direction of the flame toward the main chamber 3 (downward direction in the figure), and is open toward the main chamber 3. The open shape of the communicating portion 41 is also substantially circular. In addition, a slight tapered surface 42 is formed at the opening edge of the communication portion 41 so that the cross-sectional area gradually increases toward the main chamber 3 (downward).
One of the features of this embodiment is that, as shown in FIG. 1, the space in the cylinder (the space serving as the main chamber 3), the internal space in the sub chamber 4, and the fuel supply when the piston 5 is at the top dead center. The ratio of the total volume of the internal space of the sub chamber 4 and the internal space of the fuel supply path 68 to the total volume of the internal space of the passage 68 is set to 1.5 to 2.6%. .
FIG. 2 is a cross-sectional view showing the main chamber 3 and the sub chamber 4 in the state where the piston 5 is at the top dead center, and their surroundings. In this figure, the cylinder inner space (the space serving as the main chamber 3) is shaded, while the internal space of the sub chamber 4 and the internal space of the fuel supply path 68 are blacked out. That is, the ratio of the volume of the space filled in black to the total volume of the space of the shaded portion and the space filled in black is set to 1.5 to 2.6%.
Moreover, this ratio is preferably set to 2.0 to 2.3%. More preferably, it is set to 2.15 to 2.25%.
As the shape of the sub chamber 4, the ratio of the depth dimension (L in FIG. 2) to the inner diameter (D in FIG. 2) is set to 0.9 to 1.5. That is, “L / D” in FIG. 2 is set to 0.9 to 1.5. This ratio is preferably set to 1.2 to 1.3. More preferably, it is set to about 1.2.
Next, the reason why the ratio of the space and the shape of the sub chamber 4 are set as described above will be described.
First, the reason for setting the space ratio will be described. FIG. 3 shows the sub chamber 4 with respect to the total volume of the cylinder inner space (the space serving as the main chamber 3), the inner space of the sub chamber 4, and the inner space of the fuel supply passage 68 in a state where the piston 5 is at the top dead center. Experimental results of engine characteristics when the ratio of the total volume between the internal space and the internal space of the fuel supply passage 68 (hereinafter referred to as the sub-chamber volume ratio) is changed in the range of 1.0 to 3.2%. It is. FIG. 3A shows the combustion fluctuation rate of the engine, FIG. 3B shows the thermal efficiency of the engine, and FIG. 3C shows the NOx amount generated by the engine.
As is apparent from FIG. 3, there is shown a characteristic in which a large inflection point appears when the sub chamber volume ratio is 1.5% and 2.6%. That is, as shown in FIG. 3A, when the sub chamber volume ratio is less than 1.5%, the combustion fluctuation rate increases rapidly as the sub chamber volume ratio decreases. Further, as shown in FIG. 3C, when the sub chamber volume ratio exceeds 2.6%, the NOx discharged increases rapidly as the sub chamber volume ratio increases. Therefore, by setting the sub chamber volume ratio in the range of 1.5 to 2.6%, both the suppression of the combustion fluctuation rate, the thermal efficiency (see FIG. 3B) and the low NOx can be obtained well. I understand. Further, when the sub-chamber volume ratio is in the range of 1.5 to 2.6%, the amount of NOx generated by the engine does not exceed the regulation value A (for example, 600 ppm) (see FIG. 3 (c)). The engine has little adverse effects.
Next, the reason why the shape of the sub chamber 4 is set in the above numerical range will be described. FIG. 4 shows experimental results of engine characteristics when the ratio “L / D” of the depth dimension to the inner diameter of the sub chamber 4 is changed in the range of 0.6 to 1.8. 4A shows the combustion fluctuation rate of the engine, FIG. 4B shows the thermal efficiency of the engine, and FIG. 4C shows the NOx amount generated by the engine.
As is apparent from FIGS. 4A and 4B, there is shown a characteristic in which a large inflection point appears when the “L / D” is 0.9 and 1.5. That is, when “L / D” is below 0.9, the combustion fluctuation rate increases rapidly as “L / D” decreases. Further, when “L / D” exceeds 1.5, the combustion fluctuation rate increases rapidly as “L / D” increases, and the thermal efficiency also deteriorates rapidly. From these facts, it can be seen that by setting “L / D” in the range of 0.9 to 1.5, both the combustion fluctuation rate and the thermal efficiency can be obtained satisfactorily. Further, when the “L / D” is in the range of 0.9 to 1.5, the amount of NOx generated by the engine does not exceed the regulation value A (for example, 600 ppm) (see FIG. 4C), and the environment The engine has little adverse effects.
-Effect of the embodiment-
As described above, in this embodiment, it is possible to realize an engine that can satisfactorily obtain both reduction in combustion fluctuation rate, thermal efficiency, and low NOx. Further, since the sub chamber 4 opens to the main chamber 3 and does not cause high-speed ejection of the flame jet, knocking is less likely to occur even if the ignition advance angle of the spark plug 7 is larger than that of the conventional one. Stable engine rotation can be obtained. Therefore, the ignition timing retard margin can be increased, and the spark plug 7 can be ignited at a time when the pressure in the sub chamber 4 is relatively low. As a result, the voltage value required to ignite the spark plug 7 can be lowered, electrode wear can be suppressed, and misfire can be prevented. As a result, the life of the spark plug 7 can be extended. In addition, since the engine includes the open sub chamber 4 that does not include the conventional throat and nozzle, the flame generated in the sub chamber 4 during ignition easily propagates to the main chamber 3 side. The electrode is not exposed to a high-temperature and high-pressure environment, so that the life of the spark plug 7 can be extended.
(Second Embodiment)
Next, a second embodiment will be described. In this embodiment, by appropriately setting the supply direction of the sub chamber fuel gas into the sub chamber 4, the temperature and pressure in the sub chamber 4 are kept low, and the life of the spark plug 7 is extended. . Therefore, here, only the supply direction of the fuel gas for the sub chamber into the sub chamber 4 will be described, and description of other configurations (substantially the same configurations as those of the first embodiment described above) will be omitted.
FIG. 5 is a longitudinal sectional view showing the sub chamber 4 and its periphery. In this figure, the supply direction of the fuel gas for the sub chamber toward the sub chamber 4 is indicated by a dashed arrow.
As shown in FIG. 5, in this embodiment, the supply direction of the sub chamber fuel gas into the sub chamber 4 is the direction in which the linear movement distance of the sub chamber fuel gas in the sub chamber 4 space is the longest. Is set. More specifically, the sub chamber 4 is formed by a concave portion having a substantially rectangular cross section, and the opening position of the fuel supply passage 68 with respect to the sub chamber 4 is set at the upper corner ( Set to point X) in FIG. On the other hand, the direction in which the fuel gas for the sub chamber is supplied into the sub chamber 4 is divided into the upper end corner (point X) and the sub chamber open side lower end edge that forms a diagonal with the upper end corner (see FIG. 5 is set in a direction along a diagonal line (Z indicated by a one-dot chain line in the drawing) of the substantially rectangular cross section connecting the point Y). That is, the fuel supply path 68 is formed so that the axial direction of the fuel supply path 68 extends in a direction passing through the upper end corner (point X) and the sub chamber open side lower end edge (point Y). Has been.
Next, the operation of setting the supply direction of the sub chamber fuel gas into the sub chamber 4 will be described with reference to FIGS. 5 and 1.
When the sub-chamber fuel gas is supplied into the sub-chamber 4 through the fuel supply path 68 as the automatic check valve 62 is opened, the supply direction (blowing direction) is the upper corner (the point X ) To the lower end edge (point Y) on the sub-chamber opening side. Due to this blowing, a part of the sub chamber fuel gas stops in the sub chamber 4, and the other sub chamber fuel gas flows out from the sub chamber 4 to the main chamber 3. Thus, in the stage where the sub chamber fuel gas is moving, the compression stroke is started in the sub chamber type gas engine, and the piston 5 moves from the bottom dead center toward the top dead center.
As the piston 5 moves, the sub chamber fuel gas flowing into the main chamber 3 flows into the sub chamber 4 from the main chamber 3 while being agitated and mixed with the lean air-fuel mixture in the cylinder 11 (in the main chamber 3). (See arrow C in FIG. 5). That is, the sub chamber fuel gas once flowing into the main chamber 3 is returned to the sub chamber 4 while being stirred and mixed with the lean air-fuel mixture. In this case, in this embodiment, the supply direction of the sub chamber fuel gas is set in the direction in which the linear movement distance of the sub chamber fuel gas in the space in the sub chamber 4 is the longest. Before reaching the inner wall surface of the sub chamber 4 or under the influence of the inner wall surface of the sub chamber 4, the flow direction of the fuel gas for the sub chamber changes (directivity changes from the blowing direction to another direction). In addition, the operation of flowing part of the lean air-fuel mixture into the sub chamber 4 (arrow C) can be started.
By the flow of the lean air-fuel mixture into the sub chamber 4, the sub chamber fuel gas that has stopped in the sub chamber 4 is pushed toward the ignition point S of the spark plug 7. Then, these two kinds of gases are appropriately agitated at and around the boundary portion between the pushed high concentration fuel gas and the relatively low concentration fuel gas flowing from the main chamber 3 into the sub chamber 4. For this reason, in the local region (relatively narrow region) in the vicinity of the ignition point S (near the electrode) of the spark plug 7, a high concentration state of the sub chamber fuel gas is maintained, and as the distance from the ignition point S increases, The mixture ratio of the lean air-fuel mixture to the sub-chamber fuel gas gradually increases (the fuel gas concentration gradually decreases).
Since the ignition plug 7 is ignited in this state, the initial combustion in the vicinity of the ignition plug 7 is good due to the presence of the high concentration sub chamber fuel gas (the high concentration sub chamber fuel gas existing in the narrow region). In addition, flame propagation from the sub chamber 4 to the main chamber 3 can be performed smoothly. Thereby, it is avoided that the pressure and temperature in the sub chamber 4 increase excessively immediately after ignition. That is, by setting the sub chamber fuel gas supply direction into the sub chamber 4 as in the present embodiment, the pressure around the spark plug 7 at the time of ignition is obtained while obtaining good ignitability and flame propagation. In addition, the temperature can be optimized and the life of the spark plug 7 can be extended.
The sub chamber fuel gas supply direction may be slightly shifted from the upper end corner (point X) toward the sub chamber open side lower end edge (point Y). It is possible to obtain the above effect (optimization of pressure and temperature around the spark plug 7 at the time of ignition). That is, the above-described effect can be obtained even when the supply direction is shifted by about 5 ° with respect to the supply direction indicated by the dashed arrow in FIG. 5 (see angle α in FIG. 5).
FIG. 6 shows that the sub-chamber fuel gas is supplied in a different direction in a state where the opening position of the fuel supply passage 68 with respect to the sub-chamber 4 is set to the upper corner (point X in FIG. 5) of the substantially rectangular cross section. It is the result of having tested the engine characteristic in the case. Here, the supply direction (the supply direction of the fuel gas for the sub chamber with respect to the horizontal direction and the angle θ in FIG. 5) is 55 ° from the upper end corner (point X) to the lower end of the sub chamber opening side. This corresponds to a balloon in the direction toward the part (point Y). In this test, the test was performed for the case where the supply direction (the angle θ) was changed to 40 °, 55 °, and 70 °. That is, when the angle θ is 40 °, the sub chamber fuel gas is blown out in a direction toward the inner wall surface of the sub chamber 4, and when the angle θ is 70 °, the sub chamber fuel gas is directed toward the main chamber 3. Will be blown out. FIG. 6A shows the combustion fluctuation rate of the engine, FIG. 6B shows the soot generation amount of the engine, and FIG. 6C shows the thermal efficiency of the engine.
As can be seen from FIG. 6, by setting the supply direction to 55 °, it is possible to minimize the combustion fluctuation rate of the engine (see FIG. 6 (a)), and to maximize the thermal efficiency of the engine. It is possible to obtain high (see FIG. 6C). Further, by setting the supply direction to 50 ° or more, the amount of soot generated by the engine does not exceed the regulation value E (see FIG. 6B), and the engine has little adverse effect on the environment.
(Third embodiment)
Next, a third embodiment will be described. In this embodiment, the shape in the vicinity of the open side end of the sub chamber 4 that opens to the main chamber 3 is changed, and other configurations are substantially the same as those in the first and second embodiments described above. Therefore, only the shape near the open side end of the sub chamber 4 will be described here.
FIG. 7A is a longitudinal sectional view showing the sub chamber 4 and the periphery thereof, and FIG. 7B is an opening shape in the lower end opening portion (solid line in the drawing) and the electrode peripheral portion (broken line in the drawing) of the sub chamber 4. FIG. Further, in FIG. 7A, the supply direction of the sub chamber fuel gas into the sub chamber 4 is indicated by a dashed arrow.
As shown in FIG. 7, in this embodiment, in the vicinity of the open side end of the sub chamber 4 that opens to the main chamber 3, the flame propagates from the inside of the sub chamber 4 to the main chamber 3 (downward direction in the figure). On the other hand, there is provided a throttle portion 43 that reduces the cross-sectional area of the surface orthogonal to the surface. That is, a throttle part 43 bulging in an annular shape toward the inner peripheral side of the sub chamber 4 is provided at a position slightly above the open end of the sub chamber 4, and the opening area in this portion is reduced.
By providing such a throttle portion 43, it is possible to prevent the fuel gas for the sub chamber supplied to the sub chamber 4 and stopping in the sub chamber 4 from flowing into the main chamber 3. A sufficient amount of fuel gas can be secured. For this reason, the high concentration state of the sub chamber fuel gas in the local region near the ignition point S of the spark plug 7 can be reliably maintained, and the ignitability can be obtained satisfactorily.
FIG. 8 shows the results of testing engine characteristics when the throttle part 43 is provided in the sub chamber 4 and when the throttle part 43 is not provided. Here, various types of shapes of the throttle portion 43 (the amount of protrusion into the sub chamber 4) were tested. In FIG. 8, the sectional ratio of the opening when the throttle 43 is not provided is “1.0”, and in the case where the throttle 43 is provided, the larger the amount of protrusion into the sub chamber 4, the larger the section of the opening. The ratio is expressed as small. For example, the opening area at the aperture 43 forming portion (shown by a solid line in FIG. 7B) with respect to the opening area at the electrode peripheral portion of the spark plug 7 (opening area shown by a broken line in FIG. 7B). When the (opening area) is ½, the opening section ratio is set to “0.5”. Here, a test was performed with the opening section ratio set to “0.4”, “0, 6”, “0.7”, and “1.0”.
As is apparent from FIG. 8, the engine combustion fluctuation rate can be kept small by setting the opening cross-sectional ratio to less than “1.0”. However, when the opening cross-sectional ratio is less than “0.6”, the engine combustion fluctuation rate slightly increases. Therefore, it is preferable that the opening section cross-sectional ratio in the case of providing the throttle section 43 is “0.6” or more.
In addition, the formation position of the throttle part 43 may be the open side edge of the sub chamber 4, or the back side position (upper position in the figure) than the vicinity of the open side end of the sub chamber 4. Also good. In any case, the throttle portion 43 can prevent the sub chamber fuel gas from flowing into the main chamber 3.
(Fourth embodiment)
Next, a fourth embodiment will be described. In this embodiment, the shape of the vicinity of the open side end of the sub chamber 4 that opens to the main chamber 3 is changed, and other configurations are substantially the same as those of the first and second embodiments described above. Therefore, only the shape near the open side end of the sub chamber 4 will be described here.
9A is a longitudinal sectional view showing the sub chamber 4 and its periphery, and FIG. 9B is an opening shape in the lower end opening portion (solid line in the drawing) and the electrode peripheral portion (broken line in the drawing) of the sub chamber 4. FIG. In FIG. 9A, the supply direction of the sub chamber fuel gas into the sub chamber 4 is indicated by a dashed arrow.
As shown in FIG. 9, in this embodiment, in the vicinity of the open side end of the sub chamber 4 that opens to the main chamber 3, the flame propagates from the inside of the sub chamber 4 to the main chamber 3 (downward direction in the figure). An enlarged portion 44 is provided for enlarging the cross-sectional area of the orthogonal surface. An enlarged portion 44 having a curved surface whose opening cross-sectional area gradually increases from a position slightly above the open side end of the sub chamber 4 toward the open side (lower side in the figure) is provided. It is expanding.
By providing such an enlarged portion 44, the gas from the main chamber 3 to the sub chamber 4 accompanying the movement of the piston 5 in the compression stroke (the fuel gas for the sub chamber flowing out to the main chamber 3 and the lean mixture) (Mixed gas) can be smoothly flowed in, and a state in which the mixing ratio of the lean air-fuel mixture to the sub-chamber fuel gas gradually increases as the distance from the ignition point S of the spark plug 7 increases. It is possible to ensure good flame propagation.
FIG. 10 is a result of testing engine characteristics when the enlarged portion 44 is provided in the sub chamber 4 and when the enlarged portion 44 is not provided. Here, various types of shapes (expansion dimensions) of the enlarged portion 44 were tested. In FIG. 10, when the enlarged portion 44 is not provided, the opening section ratio is set to “1.0”, and in the case where the enlarged section 44 is provided, the larger the diameter expansion dimension, the larger the opening section ratio. Represents. For example, the opening area at the portion where the enlarged portion 44 is formed (shown by a solid line in FIG. 9B) relative to the opening area at the electrode peripheral portion of the spark plug 7 (opening area indicated by a broken line in FIG. 9B). When the opening area is double, the opening section ratio is set to “2.0”.
As is apparent from FIG. 10, when the opening cross-sectional ratio is set to a value exceeding “1.0”, the soot generation amount of the engine does not exceed the regulation value E even if the opening cross-sectional ratio increases. The engine has little negative impact on the environment. However, it was confirmed from the test results that the combustion fluctuation rate of the engine slightly increased when the opening cross-sectional ratio exceeded “1.2”. Therefore, the upper limit value of the opening section ratio is preferably “1.2” or less.
(Fifth embodiment)
Next, a fifth embodiment will be described. In this embodiment, the opening shape of the surface orthogonal to the flame propagation direction at the open side end of the sub chamber 4 opened to the main chamber 3 is compared with the opening shape of the surface orthogonal to the flame propagation direction at the back side portion of the sub chamber 4. Is eccentric. Other configurations are substantially the same as those of the first and second embodiments described above. Therefore, only the opening shape at the open end of the sub chamber 4 will be described here.
FIG. 11A is a longitudinal sectional view showing the sub chamber 4 and its periphery. FIG. 11B is a view showing the opening shape in the lower end opening part (solid line in the figure) and the electrode peripheral part (broken line in the figure) of the sub chamber 4. As shown in FIG. 11, in this embodiment, the opening shape of the surface orthogonal to the flame propagation direction at the open side end of the sub chamber 4 that opens to the main chamber 3 is set in the flame propagation direction at the back side portion of the sub chamber 4. It is decentered with respect to the opening shape of the orthogonal surface. Specifically, one of the side walls of the sub chamber 4 (the left side wall in FIG. 11A) is swelled to the vicinity of the axis of the sub chamber 4, and the bulging portion 45 is connected to the main chamber 3. It hangs down to the opening. For this reason, the axis L2 of the opening portion is eccentric to the side where the bulging portion 45 is not formed with respect to the axis L1 in the back side portion of the sub chamber 4 (for example, the electrode peripheral portion of the spark plug 7). It has become. In the present embodiment, the shape of the opening portion of the sub chamber 4 is an oval shape (see FIG. 11B), but it is formed at a position that is eccentric with respect to the axis L1 in the back side portion of the sub chamber 4. As long as it is made, a perfect circle shape may be sufficient and shapes other than a circle may be sufficient.
In the sub-chamber structure of this embodiment, the sub-chamber fuel gas is supplied into the sub-chamber 4 in the direction along the plane of FIG. 11A, that is, from the upper corner of the sub-chamber 4. The direction toward the upper surface of the portion 45 may be the upper end corner of the sub chamber 4 in the direction orthogonal to the paper surface of FIG. 11A, that is, in the plane orthogonal to the bulging direction of the bulging portion 45. The direction from the corner portion toward the lower end edge of the sub chamber opening side may be used.
According to the configuration of the present embodiment, the mixed gas of the sub-chamber fuel gas and the lean air-fuel mixture flowing from the main chamber 3 into the sub-chamber 4 becomes a swirling flow (tumble flow) around the horizontal axis in the sub-chamber 4. And mixed. Thereby, optimization of the gas concentration in the sub chamber 4 can be achieved.
FIG. 12 shows the results of testing engine characteristics when the opening of the sub chamber 4 is not decentered (symmetric type) and when decentered as shown in FIG. 11 (asymmetric type). As is apparent from FIG. 12, when the opening of the sub chamber 4 is eccentric, the combustion fluctuation rate of the engine is smaller than when the opening is not eccentric.
-Other embodiments-
In the above embodiment, the case where the present invention is applied to the sub-chamber type gas engine provided with the injector type fuel supply system has been described. The present invention is not limited to this, and can also be applied to a sub-chamber gas engine having a so-called mixer-type fuel supply system in which air and fuel gas are mixed by a mixer and supplied to the main chamber. The present invention can also be applied to a sub-chamber type gas engine not provided with a supercharger.
The fuel supply valve is not limited to the automatic check valve 62, and an electromagnetically driven gas injector may be applied.
Further, the cross section of the sub chamber 4 when the direction of supply of the sub chamber fuel gas into the sub chamber 4 is set to the direction in which the linear movement distance of the sub chamber fuel gas in the sub chamber 4 inner space is the longest. The shape (cross-sectional shape orthogonal to the flame propagation direction) is not limited to a perfect circle shape, and may be an oval shape or a polygonal shape.
It should be noted that the present invention can be implemented in various other forms without departing from the spirit or main features thereof. Therefore, the above-mentioned embodiment is only a mere illustration in all points, and should not be interpreted limitedly. The scope of the present invention is indicated by the scope of claims, and is not restricted by the text of the specification. Further, all modifications and changes belonging to the equivalent scope of the claims are within the scope of the present invention.

  As described above, in the present invention, by optimizing the shape of the sub chamber of the sub chamber type gas engine, or by appropriately setting the supply direction of the fuel gas for the sub chamber into the sub chamber, The pressure can be kept low, and the ignition advance angle can be increased to reduce the voltage value required for ignition of the spark plug (ignition plug), thereby extending the life of the spark plug. In particular, even a sub-chamber type gas engine using an automatic valve that uses a pressure difference as a driving force is useful because it can obtain good ignitability and flame propagation.

Claims (10)

A main combustion chamber formed in the cylinder, a sub-combustion chamber communicating with the main combustion chamber, a spark plug facing the sub-combustion chamber, a fuel supply valve for supplying sub-chamber fuel gas to the sub-combustion chamber, A fuel supply passage for guiding the subchamber fuel gas from the fuel supply valve to the subcombustion chamber, and supplying the subchamber fuel gas from the fuel supply valve to the subcombustion chamber through the fuel supply passage to ignite the spark plug A combustion chamber structure in a sub-chamber type gas engine that performs an expansion stroke by propagating a flame generated by performing from the sub-combustion chamber to the main combustion chamber,
The sub-combustion chamber is formed with a recessed portion whose one end opens to the main combustion chamber,
The ratio of the total volume of the auxiliary combustion chamber and the fuel supply path to the total volume of the main combustion chamber, the auxiliary combustion chamber and the fuel supply path when the piston in the cylinder is at the top dead center is 1.5 to A combustion chamber structure of a sub-chamber type gas engine characterized by being set to 2.6%. A main combustion chamber formed in the cylinder, a sub-combustion chamber communicating with the main combustion chamber, a spark plug facing the sub-combustion chamber, a fuel supply valve for supplying sub-chamber fuel gas to the sub-combustion chamber, A fuel supply passage for guiding the subchamber fuel gas from the fuel supply valve to the subcombustion chamber, and supplying the subchamber fuel gas from the fuel supply valve to the subcombustion chamber through the fuel supply passage to ignite the spark plug A combustion chamber structure in a sub-chamber type gas engine that performs an expansion stroke by propagating a flame generated by performing from the sub-combustion chamber to the main combustion chamber,
The sub-combustion chamber is formed of a substantially cylindrical bottomed recessed portion whose one end opens to the main combustion chamber,
A combustion chamber structure of a sub-chamber type gas engine, wherein a ratio of a depth dimension to an inner diameter of the sub-combustion chamber is set to 0.9 to 1.5. A main combustion chamber formed in the cylinder, a sub-combustion chamber communicating with the main combustion chamber, a spark plug facing the sub-combustion chamber, a fuel supply valve for supplying sub-chamber fuel gas to the sub-combustion chamber, A fuel supply passage for guiding the subchamber fuel gas from the fuel supply valve to the subcombustion chamber, and supplying the subchamber fuel gas from the fuel supply valve to the subcombustion chamber through the fuel supply passage to ignite the spark plug A combustion chamber structure in a sub-chamber type gas engine that performs an expansion stroke by propagating a flame generated by performing from the sub-combustion chamber to the main combustion chamber,
The sub-combustion chamber is formed of a substantially cylindrical bottomed recessed portion whose one end opens to the main combustion chamber,
The ratio of the total volume of the auxiliary combustion chamber and the fuel supply path to the total volume of the main combustion chamber, the auxiliary combustion chamber and the fuel supply path when the piston in the cylinder is at the top dead center is 1.5 to 2.6% is set,
A combustion chamber structure of a sub-chamber type gas engine, wherein a ratio of a depth dimension to an inner diameter of the sub-combustion chamber is set to 0.9 to 1.5. A sub-chamber type gas engine comprising the combustion chamber structure according to any one of claims 1 to 3, wherein the sub-chamber fuel gas is supplied from the fuel supply valve to the sub-combustion chamber through a fuel supply path. A sub-chamber gas engine configured to perform an expansion stroke by propagating a flame generated by supplying and igniting a spark plug from a sub-combustion chamber to a main combustion chamber. A main combustion chamber formed in the cylinder, a sub-combustion chamber communicating with the main combustion chamber, a spark plug facing the sub-combustion chamber, a fuel supply valve for supplying sub-chamber fuel gas to the sub-combustion chamber, A fuel supply passage for guiding the subchamber fuel gas from the fuel supply valve to the subcombustion chamber, and supplying the subchamber fuel gas from the fuel supply valve to the subcombustion chamber through the fuel supply passage to ignite the spark plug In the sub-chamber type gas engine that performs the expansion stroke by propagating the flame generated by performing from the sub-combustion chamber to the main combustion chamber,
The sub-combustion chamber is formed with a recessed portion whose one end opens to the main combustion chamber,
The sub-chamber type is characterized in that the supply direction of the sub-chamber fuel gas into the sub-combustion chamber is set in a direction in which the linear movement distance of the sub-chamber fuel gas in the sub-combustion chamber space is the longest. Gas engine. In the sub-chamber type gas engine according to claim 5,
The sub-combustion chamber is formed with a recessed portion having a substantially rectangular cross section, and the opening position of the fuel supply passage with respect to the sub-combustion chamber is set at the upper corner of the substantially square cross section,
The direction of supply of the auxiliary chamber fuel gas into the auxiliary combustion chamber is the substantially square shape connecting the upper end corner and the lower end edge of the auxiliary combustion chamber opening side that forms a diagonal with the upper end corner. A sub-chamber gas engine characterized by being set in a direction along a diagonal line of the cross section. In the sub-chamber type gas engine according to any one of claims 4 to 6,
In the vicinity of the open side end of the sub-combustion chamber that opens to the main combustion chamber, there is provided a constriction that reduces the cross-sectional area of the surface perpendicular to the flame propagation direction from the sub-combustion chamber to the main combustion chamber. Characteristic sub-chamber gas engine. In the sub-chamber type gas engine according to any one of claims 4 to 6,
In the vicinity of the open side end of the sub-combustion chamber that opens to the main combustion chamber, there is provided an enlarged portion that enlarges the cross-sectional area of the surface orthogonal to the propagation direction of the flame from the sub-combustion chamber to the main combustion chamber. Characteristic sub-chamber gas engine. In the sub-chamber type gas engine according to any one of claims 4 to 6,
The opening shape of the surface orthogonal to the flame propagation direction at the open side end of the sub-combustion chamber opening to the main combustion chamber is decentered with respect to the opening shape of the surface orthogonal to the flame propagation direction at the back side portion of the sub-combustion chamber. A sub-chamber gas engine characterized by In the subchamber type gas engine according to any one of claims 4 to 9,
The fuel supply valve automatically opens and closes according to the pressure difference between the back pressure of the built-in valve body and the cylinder internal pressure, and automatically supplies the auxiliary chamber fuel gas to the auxiliary combustion chamber via the fuel supply path when opened. A sub-chamber type gas engine comprising a valve.

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