JP7539352B2 - Gas engine - Google Patents

Description

This disclosure relates to gas engines.

Patent Document 1 describes a gas engine that runs on natural gas as fuel gas. The gas engine described in this patent document 1 has a pre-chamber in the cylinder head that has a smaller capacity than the main combustion chamber. A mixture of fuel gas and air is supplied from the main combustion chamber through a nozzle to the pre-chamber of this gas engine. When this mixture is ignited, it burns, the pressure inside the pre-chamber increases, and the high-temperature gas inside the pre-chamber is ejected into the main combustion chamber as a torch jet due to the pressure difference between the main combustion chamber and the pre-chamber. The mixed gas in the main combustion chamber is then combusted by this torch jet, and the gas engine is operated in combustion mode.

JP 2018-66369 A

In a gas engine such as that described in Patent Document 1, the greater the ejection force of the torch jet, the more fires are generated in the main combustion chamber. Such an increase in the ejection force of the torch jet is expected to improve efficiency by shortening the combustion period and reduce combustion fluctuations by stabilizing ignition in the main combustion chamber.
For example, to strengthen the torch jet, it is necessary to increase the energy inside the pre-chamber or to increase the rate of pressure rise inside the pre-chamber.However, simply increasing the pre-chamber volume poses the problem that unburned gas inside the pre-chamber is pushed out into the main combustion chamber during flame propagation, making it impossible to effectively utilize the energy inside the pre-chamber, and the ejection force of the torch jet is not as large as desired.
This disclosure has been made in consideration of the above circumstances, and has an object to provide a gas engine that is capable of increasing the ejection force of the torch jet by effectively utilizing the energy inside the auxiliary chamber.

In order to solve the above problems, the following configuration is adopted.
According to a first aspect of the disclosure, the gas engine is a sub-chamber type gas engine in which an ignition plug burns an air-fuel mixture in a sub-chamber and ejects the mixture as a torch jet into a main combustion chamber, and includes: a first sub-chamber forming portion forming a first sub-chamber connected to the main combustion chamber, a nozzle hole forming portion forming a nozzle hole connecting the first sub-chamber and the main combustion chamber, a second sub-chamber forming portion formed on the opposite side of the first sub-chamber to the nozzle hole and forming a second sub-chamber connected to the first sub-chamber, and a throat forming portion forming a throat connecting the first sub-chamber and the second sub-chamber. The throat forming portion forms the throat at a throat angle such that the ignition portion of the ignition plug is not located on an extension of the throat.

The gas engine described above can effectively utilize the energy inside the auxiliary chamber to increase the ejection force of the torch jet.

1 is a cross-sectional view showing a schematic configuration of a gas engine according to this embodiment. FIG. 2 is a cross-sectional view taken along the central axis of a cylinder, showing the configuration of the auxiliary chamber and its surroundings of the gas engine according to this embodiment. FIG. 11 is a cross-sectional view perpendicular to the cylinder central axis in an auxiliary chamber forming portion according to a second embodiment of the present disclosure. FIG. 5 is a cross-sectional view corresponding to FIG. 3 in a modified example of the second embodiment of the present disclosure.

First Embodiment
Next, a gas engine according to a first embodiment of the present disclosure will be described with reference to the drawings.
FIG. 1 is a cross-sectional view showing a schematic configuration of a gas engine according to this embodiment.
As shown in FIG. 1, the gas engine 10 is a pre-chamber type gas engine, and includes at least a cylinder block 20, a cylinder head 30, and a pre-chamber forming portion 40.

A cylindrical cylinder 21 is formed in the cylinder block 20. A piston 22 is housed in the cylinder 21 so that it can move linearly back and forth along the central axis C of the cylinder 21. The piston 22 is connected to a crankshaft 24 housed in a crankcase (not shown) via a connecting rod 23. One end of the connecting rod 23 is rotatably connected to the piston 22 via a pin 25. The other end of the connecting rod 23 is rotatably connected to the crankshaft 24. As a result, when the piston 22 moves linearly in the cylinder 21 in a direction along the central axis C, the movement of the piston 22 is converted into the rotational movement of the crankshaft 24 by the connecting rod 23.

The cylinder head 30 is connected to the end surface 20a of the cylinder block 20 where the cylinder 21 opens, and closes the opening of the cylinder 21. The surface of the cylinder head 30 facing the cylinder block 20 has a flat, hemispherical, or curved roof surface 31 formed in the area facing the cylinder 21, which is perpendicular to the central axis C of the cylinder 21. The cylinder block 20, cylinder head 30, and piston 22 define a main combustion chamber 33.

The cylinder head 30 is formed with an intake port 34 and an exhaust port 35. One end 34a of the intake port 34 and one end 35a of the exhaust port 35 are located so as to open to the roof surface 31 and face the main combustion chamber 33. A mixed gas supply source (not shown) is connected to the end (not shown) of the intake port 34 opposite the main combustion chamber 33. In other words, a mixed gas G of air and combustion gas can be supplied from the mixed gas supply source to the intake port 34. An intake valve 36 is provided at the end 34a on the main combustion chamber 33 side of the intake port 34. The intake valve 36 can be displaced from a closed position to an open position by a valve drive mechanism (not shown), and the mixed gas G supplied from the mixed gas supply source flows from the intake port 34 to the main combustion chamber 33 when the intake valve 36 is in the open position.

An exhaust gas flow path (not shown) is connected to the end (not shown) of the exhaust port 35 opposite the main combustion chamber 33. An exhaust valve 37 is provided at the end 35a of the exhaust port 35 facing the main combustion chamber 33. The exhaust valve 37 can be displaced from a closed position to an open position by a valve drive mechanism (not shown), and exhaust gas in the main combustion chamber 33 is discharged from the main combustion chamber 33 to the exhaust port 35 when the exhaust valve 37 is in the open position.

FIG. 2 is a cross-sectional view taken along the central axis of the cylinder, showing the configuration of the auxiliary chamber and its surroundings of the gas engine according to this embodiment.
As shown in Figs. 1 and 2, the auxiliary chamber forming portion 40 in this embodiment is provided in the cylinder head 30. This auxiliary chamber forming portion 40 is fixed to the cylinder head 30. The auxiliary chamber forming portion 40 includes a first auxiliary chamber forming portion 41, a nozzle hole forming portion 42, a second auxiliary chamber forming portion 43, and a throat forming portion 44. The auxiliary chamber forming portion 40 in this embodiment is further provided with an ignition plug fixing portion 46 to which an ignition plug 45 is fixed. In the following description, the direction in which the central axis C of the cylinder 21 extends is referred to as the axial direction Da, and the main combustion chamber 33 side based on the position of the first auxiliary chamber 51 is referred to as the axial direction first side Da1, and the opposite side is referred to as the axial direction second side Da2. In addition, the direction perpendicular to the axial direction Da is referred to as the roof surface direction Dh, and the side closer to the central axis C is referred to as the roof surface direction inner side Dhi, and the opposite side is referred to as the roof surface direction outer side Dho.

The first auxiliary chamber forming portion 41 forms a first auxiliary chamber 51 that is connected to the main combustion chamber 33. The first auxiliary chamber 51 is provided so as to protrude from the center of the roof surface 31 of the cylinder head 30 toward the main combustion chamber 33. The first auxiliary chamber forming portion 41 has a first surface portion 52, a first peripheral surface portion 53, and a second surface portion 54 that define the first auxiliary chamber 51.

The first surface portion 52 is formed so as to be located on the second axial side Da2 and to extend in the roof surface direction Dh. The first peripheral surface portion 53 extends from the outer edge of the first surface portion 52 toward the first axial side Da1. The second surface portion 54 is formed so as to close the first axial side Da1 of the first peripheral surface portion 53, and is located closer to the main combustion chamber 33 than the roof surface 31. The first surface portion 52 has an opening of a through hole 46h for inserting the ignition portion 45s of the spark plug 45. The ignition portion 45s of the spark plug 45 is disposed on the second axial side Da2 of the first auxiliary chamber 51 through this through hole 46h.

The nozzle hole forming portion 42 forms a nozzle hole 56 that connects the first auxiliary chamber 51 and the main combustion chamber 33. A plurality of nozzle holes 56 are provided. Each of these nozzle holes 56 is inclined so as to move toward the outer side Dho in the roof surface direction as it moves toward the first axial side Da1. The nozzle hole 56 illustrated in this embodiment is formed with a constant hole diameter. In addition, the nozzle hole 56 in this embodiment extends toward the main combustion chamber 33 from a corner portion 55 where the first peripheral surface portion 53 and the second surface portion 54 of the first auxiliary chamber forming portion 41 intersect.

The second sub-chamber forming portion 43 forms a second sub-chamber 57 that is connected to the first sub-chamber 51. This second sub-chamber 57 is located on the opposite side of the first sub-chamber 51 to the injection hole 56, i.e., on the second axial side Da2 of the first sub-chamber 51. In this embodiment, the volume of the second sub-chamber 57 is smaller than the volume of the first sub-chamber 51. This second sub-chamber 57 is formed on the outer side Dho of the roof surface direction of the spark plug 45.

In this embodiment, the dimension of the second auxiliary chamber 57 in the axial direction Da is smaller than the dimension of the first auxiliary chamber 51 in the axial direction Da, and the dimension of the second auxiliary chamber 57 in the roof surface direction Dh is smaller than the dimension of the first auxiliary chamber 51 in the roof surface direction Dh. In addition, the second auxiliary chamber 57 in this embodiment is formed in a substantially cubic shape, and its aspect ratio is 1:1 or close to 1:1.

In this embodiment, the second auxiliary chamber 57 includes a third surface portion 61 extending in the roof surface direction Dh on the first axial side Da1, a second peripheral surface portion 62 extending from the edge of the third surface portion 61 in the roof surface direction Dh toward the second axial side Da2, and a fourth surface portion 63 connected to the edge of the second peripheral surface portion 62 on the second axial side Da2 and extending in the roof surface direction Dh. Note that in order to smoothly generate a swirling flow, which will be described later, the second auxiliary chamber 57 may be provided with a concave curved surface 63a on the fourth surface portion 63 located on the side opposite to the first auxiliary chamber 51, i.e., the second axial side Da2.

The throat forming portion 44 forms a throat 65 that connects the first sub-chamber 51 and the second sub-chamber 57. The throat 65 is a flow path through which the mixed gas G and the burned gas pass, and in this embodiment, the throat 65 has a constant hole diameter. In addition, the throat 65 in this embodiment is formed to extend from the first surface portion 52 that defines the first sub-chamber 51 to the third surface portion 61, which is the surface on the axial first side Da1 that defines the second sub-chamber 57.

More specifically, the first end 65a of the throat 65 on the axial first side Da1 is connected to a portion of the first surface 52 that is closer to the first circumferential surface 53 than the electrode of the spark plug 45 in the roof surface direction Dh. Furthermore, the second end 65b of the throat 65 on the axial second side Da2 is connected to a portion of the third surface 61 of the second auxiliary chamber 57 that is closer to the second circumferential surface 62 than the center of the third surface 61 in the roof surface direction Dh. The opening area of the throat 65 on the third surface 61 is set to be at least smaller than half the surface area of the third surface 61.

In this embodiment, the throat 65 is inclined so as to move toward the outside Dho in the roof surface direction from the first sub-chamber 51 toward the second sub-chamber 57.
The throat forming portion 44 forms the throat 65 at a throat angle such that the electrode of the spark plug 45 is not located on an extension of the throat 65. For example, when the combustion gas flows from the second auxiliary chamber 57 to the first auxiliary chamber 51 through the throat 65, the combustion gas does not directly collide with the electrode. In this embodiment, the flow passage cross-sectional area of the throat 65 is set to be equal to the flow passage cross-sectional area of the injection hole 56.

<Action and effect>
The gas engine 10 of the first embodiment described above comprises a first sub-chamber forming section 41 which forms a first sub-chamber 51 connected to the main combustion chamber 33, a nozzle hole forming section 42 which forms a nozzle hole 56 which connects the first sub-chamber 51 with the main combustion chamber 33, a second sub-chamber forming section 43 which is formed on the opposite side of the first sub-chamber 51 from the nozzle hole 56 and which forms a second sub-chamber 57 which connects with the first sub-chamber 51, and a throat forming section 44 which forms a throat 65 which connects the first sub-chamber 51 with the second sub-chamber 57.
Therefore, during the compression stroke of the piston 22, the mixed gas G in the main combustion chamber 33 flows from the main combustion chamber 33 into the first auxiliary chamber 51 through the injection hole 56. Furthermore, a part of the mixed gas G that flows into the first auxiliary chamber 51 flows into the second auxiliary chamber 57 through the throat 65. The mixed gas G that flows into the second auxiliary chamber 57 through the throat 65 becomes a swirling flow in the second axial side Da2 in the second auxiliary chamber 57 from the outer side Dho in the roof surface direction to the inner side Dhi in the roof surface direction. When the mixed gas G in the first auxiliary chamber 51 is ignited by the spark plug 45, the flame propagates to the second auxiliary chamber 57 through the throat 65. Since the mixed gas G in the second auxiliary chamber 57 becomes a swirling flow, the combustion speed of the mixed gas G increases compared to when the mixed gas G is not a swirling flow. Furthermore, since the combustion speed in the second auxiliary chamber 57 is increased, the pressure rise rate dp/dt in the second auxiliary chamber 57 is also increased, so that the pressure rise rate dp/dt in the first auxiliary chamber 51, which is connected to the second auxiliary chamber 57 by the throat 65, can also be increased. Then, the high-temperature gas in the first auxiliary chamber 51 can be ejected as a torch jet into the main combustion chamber 33 due to the pressure difference between the first auxiliary chamber 51 and the main combustion chamber 33. In addition, since the second auxiliary chamber 57 is disposed on the opposite side of the first auxiliary chamber 51 from the main combustion chamber 33, it is possible to prevent the unburned gas in the second auxiliary chamber 57 from flowing out to the main combustion chamber 33. Therefore, the energy in the auxiliary chamber can be effectively utilized to increase the ejection force of the torch jet. Furthermore, since the ejection force of the torch jet can be increased, it is possible to improve the efficiency of the gas engine 10 and reduce the combustion fluctuation.

The throat forming portion 44 in the gas engine 10 of the first embodiment described above further forms the throat 65 at a throat angle such that the ignition portion 45 s of the spark plug 45 is not positioned on an extension of the throat 65 .
With this configuration, it is possible to prevent the high-temperature gas flowing from the second sub-chamber 57 into the first sub-chamber 51 through the throat 65 from coming into contact with the ignition portion 45s, thereby reducing the heat input to the ignition portion 45s and extending the life of the spark plug 45.

Second Embodiment
Next, a gas engine according to a second embodiment of the present disclosure will be described with reference to the drawings. The gas engine according to the second embodiment differs from the gas engine 10 according to the first embodiment described above only in the configuration of the nozzle hole and the throat formed by the sub-chamber forming portion. Therefore, the same parts as those in the first embodiment will be described with the same reference numerals, and duplicated explanations will be omitted. The overall configuration of the gas engine will be described with reference to FIG. 1.

FIG. 3 is a cross-sectional view perpendicular to the central axis of the cylinder in the auxiliary chamber forming portion according to the second embodiment of the present disclosure.
As shown in FIG. 3, the auxiliary chamber defining portion 140 in the second embodiment comprises a first auxiliary chamber defining portion 41, an injection hole defining portion 42, a second auxiliary chamber defining portion 43, and a throat defining portion 44, similar to the auxiliary chamber defining portion 40 in the first embodiment described above.

As shown in Figs. 1 and 3, the first auxiliary chamber forming portion 41 forms a first auxiliary chamber 51 that is connected to the main combustion chamber 33, as in the first embodiment. The first auxiliary chamber 51 is provided so as to protrude from the center of the roof surface 31 of the cylinder head 30 into the main combustion chamber 33, and includes a first surface portion 52, a first peripheral surface portion 53, and a second surface portion 54 that define the first auxiliary chamber 51. The first peripheral surface portion 53 is circular when viewed from the axial direction Da. A through hole 46h is formed in the first surface portion 52 for inserting the ignition portion 45s of the spark plug 45. The ignition portion 45s of the spark plug 45 is disposed on the axial second side Da2 in the first auxiliary chamber 51.

The nozzle hole forming portion 42 forms a nozzle hole 56 that communicates the first auxiliary chamber 51 and the main combustion chamber 33. A plurality of nozzle holes 56 are provided. In this second embodiment, the plurality of nozzle holes 56 are formed rotationally symmetrically with respect to the central axis (equal to the central axis C) of the first peripheral surface portion 53. In this second embodiment, four nozzle holes 56 are provided, and these four nozzle holes 56 are provided at equal intervals in the circumferential direction Dc centered on the central axis C of the first peripheral surface portion 53. Like the nozzle holes 56 in the first embodiment, these nozzle holes 56 are inclined toward the roof surface direction outer side Dho as they approach the axial first side Da1. The nozzle holes 56 in the second embodiment are also formed with a constant hole diameter and extend from the corner portion where the first peripheral surface portion 53 and the second surface portion 54 of the first auxiliary chamber forming portion 41 intersect toward the main combustion chamber 33.

The nozzle hole 56 is formed at an angle such that the central axis of the first peripheral surface portion 53 is not located on the extension of the nozzle hole 56 as viewed from the axial direction Da (see FIG. 3). In other words, for example, when one nozzle hole 56A is described as an example among the multiple nozzle holes 56, the position of the nozzle hole 56A in the direction Dv perpendicular to the direction D56A in which the nozzle hole 56 extends as viewed from the axial direction Da shown in FIG. 3 is between the central axis C of the first peripheral surface portion 53 in the direction Dv and the end portion 53t of the first peripheral surface portion 53. Furthermore, the nozzle hole 56A in this second embodiment is located on the side closer to the end portion 53t of the first peripheral surface portion 53 between the central axis C of the first peripheral surface portion 53 and the end portion 53t of the first peripheral surface portion 53 in the direction Dv perpendicular to the direction D56A in which the nozzle hole 56A extends as viewed from the axial direction Da.

By providing multiple injection holes 56 as described above, the mixed gas G that flows from the main combustion chamber 33 into the first auxiliary chamber 51 during the compression stroke of the piston 22 swirls in the same direction as shown by the arrows in FIG. 3 around the central axis C. This makes it possible to efficiently form a swirling flow within the first auxiliary chamber 51. Note that, although an example has been given in which four injection holes 56 are provided, only one injection hole 56 or five or more injection holes 56 may be provided.

The second subchamber forming portion 43, like the first embodiment, forms a second subchamber 57 that is connected to the first subchamber 51. This second subchamber 57 has the same configuration as the second subchamber 57 of the first embodiment, and is defined by a third surface portion 61, a fourth surface portion 63, and a second circumferential surface portion 62, and is located on the opposite side of the first subchamber 51 from the injection hole 56, i.e., on the second axial side Da2 of the first subchamber 51.

The throat forming portion 44 forms a throat 65 that connects the first sub-chamber 51 and the second sub-chamber 57. The throat 65 is a flow path through which the mixed gas G and the burned gas pass, and like the first embodiment, the throat 65 in this second embodiment is formed with a constant hole diameter and is formed to extend from the first surface portion 52 that defines the first sub-chamber 51 to the third surface portion 61, which is the surface on the axial first side Da1 that defines the second sub-chamber 57.

The throat 65 is inclined toward the outside Dho in the roof surface direction as it moves from the first sub-chamber 51 toward the second sub-chamber 57. Similarly to the throat forming portion 44 of the first embodiment, the throat 65 is formed at a throat angle such that the electrode of the ignition plug 45 is not located on the extension of the throat 65. In this embodiment, the flow passage cross-sectional area of the throat 65 is equivalent to the flow passage cross-sectional area of the injection hole 56.

The throat forming portion 44 in the second embodiment forms a throat 65 so as to follow the swirling direction of the mixture that becomes a swirling flow when it flows from the main combustion chamber 33 into the first auxiliary chamber 51 during the compression stroke of the piston 22. In other words, when viewed from the axial direction Da as shown in FIG. 3, the opening of the throat 65 on the first auxiliary chamber 51 side is positioned so as to face the upstream side of the flow direction of the swirling flow in the first auxiliary chamber 51.

<Action and effect>
According to the gas engine 10 of the second embodiment described above, the throat 65 is formed along the swirling direction of the air-fuel mixture that flows from the main combustion chamber 33 into the first auxiliary chamber 51 during the compression stroke of the piston 22 and becomes a swirling flow, so that the swirling flow in the first auxiliary chamber 51 can be smoothly introduced into the throat 65. This strengthens the swirling flow in the second auxiliary chamber 57 caused by the flow in the throat 65 during the compression stroke of the piston 22, thereby improving the combustion promotion effect in the second auxiliary chamber 57. This makes it possible to further increase the ejection force of the torch jet.

Furthermore, during the intake and exhaust stroke, the burnt gas that flows from the second auxiliary chamber 57 into the first auxiliary chamber 51 through the throat 65 becomes a swirling flow, and the burnt gas can be efficiently discharged into the main combustion chamber 33 from the nozzle holes 56 that are aligned with the swirling direction of this swirling flow. As a result, the burnt gas in the second auxiliary chamber 57 can be efficiently discharged from the exhaust port.

This disclosure is not limited to the configurations of the above-described embodiments, and design changes are possible without departing from the spirit of the disclosure.
For example, in each of the above-described embodiments, a so-called passive-type pre-chamber gas engine in which mixed gas G flows from the main combustion chamber 33 into the first pre-chamber 51 has been described as an example, but the engine may be an active-type pre-chamber gas engine in which fuel gas can be directly injected into the first pre-chamber 51.

In the above-mentioned second embodiment, the case where one second sub-chamber 57 and one throat 65 are provided has been described. However, a plurality of second sub-chambers 57 and throats 65 may be provided so as to be rotationally symmetrical, as in the modified sub-chamber forming portion 240 shown in FIG. 4. In this way, the volume of the entire sub-chamber can be further increased by the plurality of second sub-chambers 57, and the combustion speed can be increased by the swirling flow in each of the plurality of second sub-chambers 57, so that the energy in the sub-chamber can be increased while the increased energy can be effectively utilized. Therefore, the ejection force of the torch jet can be further increased.

Furthermore, in the second embodiment, the nozzle holes 56 are arranged at equal intervals in the circumferential direction Dc when viewed from the axial direction Da, and the nozzle holes 56 are rotationally symmetrical. However, the arrangement of the nozzle holes 56 is not limited to being at equal intervals or rotationally symmetrical.

In the second embodiment, a single throat 65 is provided for each second sub-chamber 57 . However, two or more throats 65 may be provided for each second sub-chamber 57 .
Furthermore, the shape and arrangement of the second auxiliary chamber 57 are not limited to those in the above-described embodiments. The shape of the second auxiliary chamber 57 may be any shape that can generate a swirling flow therein, and may be, for example, a cylindrical shape, a spherical shape, an annular shape, or various other shapes.

<Additional Notes>
The gas engine described in the embodiment can be understood, for example, as follows.

(1) The gas engine 10 according to the first embodiment is a sub-chamber type gas engine 10 that burns an air-fuel mixture in a sub-chamber using an ignition plug 45 and ejects the mixture as a torch jet into the main combustion chamber 33. The gas engine 10 includes a first sub-chamber forming section 41 that forms a first sub-chamber 51 that is connected to the main combustion chamber 33, a nozzle hole forming section 42 that forms a nozzle hole 56 that connects the first sub-chamber 51 to the main combustion chamber 33, a second sub-chamber forming section 43 that is formed on the opposite side of the first sub-chamber 51 from the nozzle hole 56 and that forms a second sub-chamber 57 that is connected to the first sub-chamber 51, and a throat forming section 44 that forms a throat 65 that connects the first sub-chamber 51 to the second sub-chamber 57.

With this configuration, during the compression stroke of the piston 22, the mixed gas G in the main combustion chamber 33 flows from the main combustion chamber 33 into the first auxiliary chamber 51 through the nozzle hole 56. Furthermore, a part of the mixed gas G that flows into the first auxiliary chamber 51 flows into the second auxiliary chamber 57 through the throat 65. The mixed gas G that flows into the second auxiliary chamber 57 through this throat 65 becomes a swirling flow in the second auxiliary chamber 57. Then, when the mixed gas G in the first auxiliary chamber 51 is ignited by the spark plug 45, the flame propagates to the second auxiliary chamber 57 through the throat 65. Since the mixed gas G in the second auxiliary chamber 57 becomes a swirling flow, the combustion speed of the mixed gas G increases compared to when the mixed gas G is not a swirling flow. In addition, since the combustion speed in the second auxiliary chamber 57 increases, the pressure rise rate dp/dt inside the second auxiliary chamber 57 also increases, so that the pressure rise rate dp/dt in the first auxiliary chamber 51 connected to the second auxiliary chamber 57 by the throat 65 can also be increased. The pressure difference between the first auxiliary chamber 51 and the main combustion chamber 33 allows the high-temperature gas in the first auxiliary chamber 51 to be ejected as a torch jet into the main combustion chamber 33. In addition, since the second auxiliary chamber 57 is disposed on the opposite side of the first auxiliary chamber 51 from the main combustion chamber 33, it is possible to prevent unburned gas in the second auxiliary chamber 57 from flowing into the main combustion chamber 33. Therefore, the energy inside the auxiliary chamber can be effectively utilized to increase the ejection force of the torch jet. Furthermore, since the ejection force of the torch jet can be increased, it is possible to improve the efficiency of the gas engine 10 and reduce combustion fluctuations.

(2) A gas engine 10 according to a second aspect is the gas engine 10 of (1), wherein the throat forming portion 44 forms the throat 65 at a throat angle such that the ignition portion of the spark plug 45 is not located on an extension of the throat 65.
With this configuration, it is possible to prevent the high-temperature gas flowing from the second sub-chamber 57 into the first sub-chamber 51 through the throat 65 from coming into contact with the ignition portion, thereby reducing the heat input to the ignition portion and extending the life of the spark plug 45.

(3) A gas engine 10 according to a third aspect is the gas engine 10 of (1) or (2), wherein the throat forming portion 44 forms the throat 65 so as to follow the swirling direction of the air-fuel mixture that flows from the main combustion chamber 33 to the first auxiliary chamber 51 during the compression stroke of the piston 22 and becomes a swirling flow.
With this configuration, the throat 65 is formed along the swirling direction of the air-fuel mixture that flows from the main combustion chamber 33 into the first auxiliary chamber 51 during the compression stroke of the piston 22 and becomes a swirling flow, thereby strengthening the swirling flow inside the second auxiliary chamber 57 caused by the flow inside the throat 65 during the compression stroke, and improving the combustion promotion effect inside the second auxiliary chamber 57. Therefore, it is possible to further increase the ejection force of the torch jet.

Furthermore, during the intake and exhaust stroke, the burnt gas that flows from the second auxiliary chamber 57 into the first auxiliary chamber 51 through the throat 65 becomes a swirling flow, and the burnt gas can be efficiently discharged into the main combustion chamber 33 from the nozzle holes 56 that are aligned with the swirling direction of this swirling flow. As a result, the burnt gas in the second auxiliary chamber 57 can be efficiently discharged from the exhaust port.

(4) A gas engine 10 according to a fourth aspect is any one of the gas engines 10 of (1) to (3), wherein the second sub-chamber forming portion 43 forms a plurality of second sub-chambers 57, and the throat forming portion 44 forms a plurality of throats 65 that respectively connect the plurality of second sub-chambers 57 to the first sub-chamber 51.
With this configuration, the volume of the entire sub-chamber can be further increased by the multiple second sub-chambers 57, and the combustion speed can be increased by the swirling flow in each of the multiple second sub-chambers 57. This increases the energy in the sub-chamber and makes effective use of the increased energy, thereby further increasing the ejection force of the torch jet.

10...Gas engine 20...Cylinder block 20a...End surface 22...Piston 23...Connecting rod 24...Crankshaft 30...Cylinder head 31...Roof surface 33...Main combustion chamber 34...Intake port 34a...End 35...Exhaust port 35a...End 36...Intake valve 37...Exhaust valve 40, 140, 240...Auxiliary chamber forming portion 41...First auxiliary chamber forming portion 42...Injection hole forming portion 43...Second auxiliary chamber forming portion 44...Throat forming portion 45...Spark plug 45s...Ignition portion 46...Spark plug fixing portion 51...First auxiliary chamber 52...First surface portion 53...First circumferential surface portion 54...Second surface portion 55...Corner portion 56...Injection hole 57...Second auxiliary chamber 61...Third surface portion 62...Second circumferential surface portion 63...Fourth surface portion 65...Throat C...Central axis G...Mixed gas

Claims (4)

A gas engine with a pre-chamber in which an air-fuel mixture is burned in the pre-chamber by an ignition plug and ejected as a torch jet into the main combustion chamber,
a first sub-chamber forming portion that forms a first sub-chamber that is in communication with the main combustion chamber;
a nozzle hole forming portion that forms a nozzle hole that communicates the first auxiliary combustion chamber and the main combustion chamber;
a second sub-chamber forming portion that is formed on the opposite side of the injection hole with respect to the first sub-chamber and that forms a second sub-chamber that is in communication with the first sub-chamber;
a throat forming portion that forms a throat that communicates the first sub-chamber and the second sub-chamber,
The throat forming portion forms the throat at a throat angle such that the ignition portion of the ignition plug is not located on an extension of the throat.
Gas engine. The throat forming portion is
The throat is formed so as to follow the swirling direction of the air-fuel mixture that flows from the main combustion chamber to the first auxiliary chamber during the compression stroke of the piston and becomes a swirling flow.
2. A gas engine as claimed in claim 1. A gas engine with a pre-chamber in which an air-fuel mixture is burned in the pre-chamber by an ignition plug and ejected as a torch jet into the main combustion chamber,
a first sub-chamber forming portion that forms a first sub-chamber that is in communication with the main combustion chamber;
a nozzle hole forming portion that forms a nozzle hole that communicates the first auxiliary combustion chamber and the main combustion chamber;
a second sub-chamber forming portion that is formed on the opposite side of the injection hole with respect to the first sub-chamber and that forms a second sub-chamber that is in communication with the first sub-chamber;
a throat forming portion that forms a throat that communicates the first sub-chamber and the second sub-chamber,
The throat forming portion is
a throat formed along a swirling direction of the air-fuel mixture that flows from the main combustion chamber into the first auxiliary chamber during a compression stroke of a piston, the air-fuel mixture forming a swirling flow. The second sub-chamber forming portion forms a plurality of the second sub-chambers,
4. The gas engine according to claim 1, wherein the throat forming portion forms a plurality of the throats that respectively connect the second sub-chambers to the first sub-chamber.

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