JP2016033334A - Engine with laser spark plug - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an engine capable of suppressing a reduction in output of a laser for a long period of time.SOLUTION: An engine comprises: a main chamber defined between a piston and a cylinder head; and a sub-chamber communicating with the main chamber via an injection hole, and further comprises: a laser spark plug including a laser transmission window provided at a position facing the sub-chamber and transmitting a laser beam, and configured to emit the laser beam to ignition fuel gas supplied to the sub-chamber via the laser transmission window; and a first gas supply passage configured to inject first gas toward the laser transmission window of the laser ignition plug.SELECTED DRAWING: Figure 1

Description

  The present disclosure relates to an engine with a laser spark plug.

A sub-chamber gas engine is used as one of engines used for power generation and the like. The sub-chamber gas engine includes a main chamber defined between a piston and a cylinder head, and a sub-chamber communicating with the main chamber via an injection hole, and an ignition fuel supplied to the sub-chamber. The gas is ignited by an ignition device. The combustion gas generated in the sub chamber is ejected as a fire type (torch) from the nozzle hole of the sub chamber, and the mixed gas in the main chamber is combusted. As a result, even if the mixed gas in the main chamber is a lean mixed gas, it is combustible and low fuel consumption is realized. The combustion of the lean mixture gas in the main chamber are the relatively low temperature of combustion, to reduce the generation amount of such NO _X, can achieve low pollution.

  By the way, when a laser spark plug is used as an ignition device for such a sub-chamber type gas engine, the laser output is reduced due to deposit (deposits) adhering to a laser transmitting window provided at a position facing the sub-chamber. May be a problem. This deposit is carbonized when oil mist contained in the intake gas flowing from the main chamber to the sub chamber in the compression stroke adheres to the laser transmission window, and the adhered oil mist is exposed to the combustion gas generated by laser ignition. It is thought to be a thing.

  In Patent Document 1, in a laser spark plug for an internal combustion engine, in order to suppress accumulation of a specific component of exhaust gas such as oil ash or soot on a laser transmission window, a casing provided in the laser spark plug is provided. It is described that an aperture is provided to reduce the number of particles of fluid reaching the laser transmission window.

Special table 2013-527376 gazette

  When the laser spark plug described in Patent Document 1 described above is applied to a sub-chamber gas engine, it is possible to reduce oil mist that arrives at the laser transmission window by providing a throttle in a casing provided in the laser spark plug. Although it is possible, oil mist and the like adhering to the laser transmission window cannot be removed. For this reason, when the laser spark plug is used for a long period of time, the amount of deposit deposited on the laser transmission window gradually increases, and the output of the laser cannot be avoided.

  In view of the above circumstances, at least one embodiment of the present invention can suppress a decrease in laser output over a long period of time in an engine that uses a laser spark plug to ignite an ignition fuel gas supplied to a sub chamber. Aims to provide a simple engine.

  (1) An engine according to at least one embodiment of the present invention includes a sub-chamber gas comprising a main chamber defined between a piston and a cylinder head, and a sub-chamber communicating with the main chamber via an injection hole. An engine is provided with a laser transmission window that transmits a laser at a position facing the sub chamber, and is configured to irradiate the fuel gas for ignition supplied to the sub chamber through the laser transmission window. A laser ignition plug; and a first gas supply path configured to inject a first gas toward the laser transmission window of the laser ignition plug.

  According to the engine described in (1) above, the first gas collides with the oil mist adhering to the surface of the laser transmission window, and the oil mist can be removed. In addition, since the surface of the laser transmission window and the oil mist adhering to the surface can be cooled, carbonization of the oil mist accompanying combustion in the sub chamber is suppressed, and the oil mist adheres to the surface of the laser transmission window. Can be suppressed. Thereby, the laser output fall of a laser spark plug can be suppressed over a long period of time.

  (2) In some embodiments, in the engine according to (1), the first gas is the ignition fuel gas.

  According to the engine described in the above (2), the ignition fuel gas supply path inherently provided in the sub-chamber gas engine is configured to inject the ignition fuel gas toward the laser transmission window. The above-described oil mist removal effect and oil mist carbonization and sticking suppression effect can be obtained without providing a special additional configuration.

(3) In some embodiments, in the engine according to the above (1) or (2), the sub-chamber base forming the sub-chamber includes a small-diameter cylindrical portion having an inner diameter r ₁ and the inner diameter r ₁ . and a large-diameter tubular portion provided on a side opposite to the injection hole with respect to the small diameter cylinder portion has an inner diameter larger r _2, wherein the laser transmission window of the laser spark plug, the larger-diameter tubular portion Is provided.

  According to the engine described in the above (3), the oil mist that has flowed into the sub chamber through the nozzle hole is unlikely to reach the laser transmission window, so that a reduction in laser output can be effectively suppressed.

  (4) In some embodiments, in the engine according to the above (2) or (3), the first gas supply path extends from a side circumferential surface of a sub chamber base forming the sub chamber to the sub chamber. It is provided through.

  According to the engine described in (4) above, even when the laser spark plug is disposed on the upper surface of the sub chamber, the above-described oil mist removal effect, An effect of suppressing carbonization and sticking can be obtained.

  (5) In some embodiments, in the engine according to (2) to (4) above, the first gas supply path has a bent portion or a curved portion.

  According to the engine as described in said (5), the freedom degree of the layout of the 1st gas supply path (ignition fuel gas supply path) can be raised. For example, even when a laser spark plug is disposed on the upper surface of the sub chamber, the first gas supply path is configured to inject the first gas guided from above the sub chamber base forming the sub chamber toward the laser transmission window. 22 can also be configured.

  (6) In some embodiments, in the engine according to (1), the first gas is a gas different from the ignition fuel gas, and the ignition fuel gas as the second gas is used as the gas. A second gas supply path for supplying to the sub chamber is further provided.

  According to the engine described in the above (6), the oil mist adhering to the laser transmission window of the laser spark plug by injecting the first gas at an arbitrary timing regardless of the supply timing of the ignition fuel gas can thereby be obtained. Can be removed.

  (7) In some embodiments, in the engine according to (6), the second gas supply path is configured to inject the ignition fuel gas toward the laser transmission window of the laser spark plug. Is done.

  According to the engine described in (7) above, the ignition fuel gas injected from the ignition fuel gas supply path (second gas supply path) inherently provided in the engine and the first gas (ignition fuel). The gas mist removal effect and the oil mist carbonization and sticking suppression effect can be obtained using both of the gas and the gas. Also in this case, the oil mist adhering to the laser transmission window of the laser spark plug can be removed by injecting the first gas at an arbitrary timing regardless of the timing of supplying the ignition fuel gas.

  (8) In some embodiments, in the engine according to (6) or (7), the first gas is air or nitrogen.

  According to the engine described in (8) above, oil mist adhering to the laser transmission window of the laser plug can be effectively removed without using a special cleaning agent or the like.

  (9) In some embodiments, the engine according to (6), further including a gas supply control unit configured to control injection of the first gas through the first gas supply path, and the gas supply The control unit is configured to be able to execute a normal mode in which the first gas supply path injects the first gas in a period including at least a part of the compression stroke in the combustion cycle.

  In the compression stroke of the engine, oil mist flows from the main chamber into the sub chamber as the piston rises. Therefore, as in the engine described in (9) above, the first gas supply path injects the first gas during a period including at least a part of the compression stroke in accordance with the timing when the oil mist flows in, By changing the direction in which the oil mist flows, it is possible to effectively suppress adhesion to the surface of the laser transmission window.

  (10) In some embodiments, in the engine according to (9), the gas supply control unit is configured such that the first gas supply path is in a combustion cycle over a period longer than an execution period of the normal mode. The cleaning mode for injecting the first gas is configured to be executable.

  According to the engine described in (10) above, oil mist adhering to the laser transmission window can be removed more effectively than in the normal mode.

  (11) In some embodiments, in the engine according to (10), the gas supply control unit executes the normal mode based on output state information regarding a laser output state of the laser spark plug. Or to execute the cleaning mode.

  According to the engine described in (11) above, for example, when it is estimated that the output of the laser is equal to or higher than a predetermined level, the normal mode is executed, and it is estimated that the output of the laser is lower than the predetermined level. In such a case, by executing the cleaning mode, the execution of the cleaning mode can be minimized. For this reason, the above-described oil mist removal effect and oil mist carbonization and sticking suppression effect can be obtained without shifting the air-fuel ratio from the optimum range more than necessary.

  (12) In some embodiments, the engine according to (11) further includes a misfire cycle determination unit that determines whether or not a misfire cycle has occurred, and the output state information is determined by the misfire cycle determination unit. Including the result, the gas supply control unit is configured to execute the cleaning mode when the misfire cycle determination unit determines that a misfire cycle has occurred.

  According to the engine described in (12) above, the oil mist can be removed at an effective timing because the cleaning mode is executed when there is a high possibility that the laser output state is lowered.

  (13) In some embodiments, in the engine according to (11) or (12), the engine further includes a variation coefficient calculation unit that calculates a variation coefficient of the pressure in the main chamber in a predetermined cycle, and the output state information Includes a calculation result of the variation coefficient calculation unit, and the gas supply control unit executes the cleaning mode when the variation coefficient of the pressure of the main chamber calculated by the variation coefficient calculation unit exceeds a threshold value. Configured to do.

  According to the engine described in (13) above, since the cleaning mode is executed when there is a high possibility that the output state of the laser is lowered, the oil mist can be removed at an effective timing.

  (14) In some embodiments, in the engine according to (11) to (13), the gas supply control unit does not continuously perform the cleaning mode for a plurality of cycles regardless of the output state information. It is configured as follows.

  According to the engine as described in said (14), the continuous generation | occurrence | production of a misfire cycle can be suppressed.

  (15) The engine according to some embodiments is the engine according to (12), wherein the engine includes a plurality of cylinders, and the gas supply control unit includes two or more cylinders of the plurality of cylinders. When the misfire cycle determination unit determines that the misfire cycle has occurred, the cleaning mode execution periods for the two or more cylinders determined to have generated the misfire cycle do not overlap. Is configured to perform the cleaning mode.

  According to the engine as described in said (15), it can suppress that misfire occurs simultaneously in two or more cylinders.

(16) The engine according to some embodiments is the sub-chamber type gas engine according to (13), wherein the sub-chamber type gas engine includes a plurality of cylinders, and the gas supply control unit includes the plurality of cylinders. When the variation coefficient calculated by the variation coefficient calculation unit for two or more cylinders out of the cylinders exceeds a threshold, the in-cylinder pressure variation coefficient exceeds the threshold in the cleaning mode of the two or more cylinders. The cleaning mode is configured to execute so that the execution periods do not overlap.

  According to the engine as described in said (16), it can suppress that misfire generate | occur | produces simultaneously in two or more cylinders.

(17) In some embodiments, in the engine according to the above (1) or (2), the first gas supply path is formed from the side surface of the casing to which the laser spark plug is attached, from the laser transmission window. The first gas is configured to be injected along the surface of the first gas.

  According to the engine described in (17) above, since the flow rate of the first gas is fast, the effect of peeling and removing the deposit can be enhanced. Further, since the concentration of the air-fuel mixture is high, the ignitability can be improved. Further, since the first gas flows along the surface of the laser transmission window, the surface of the laser transmission window and the oil mist adhering to the surface can be cooled by the first gas. Thereby, carbonization of the oil mist accompanying combustion in the sub chamber can be effectively suppressed, and the oil mist can be prevented from sticking to the surface of the laser transmission window. Therefore, it is possible to suppress a decrease in laser output of the laser spark plug over a long period of time.

(18) In some embodiments, in the engine according to (17), an ignition fuel gas supply path for supplying an ignition fuel gas, and a second gas different from the ignition fuel gas are provided. A second gas supply path for supplying, wherein the first gas supply path is connected to the ignition fuel gas supply path and the second gas supply path, and the ignition fuel gas and the second gas Is configured to inject at least one of them as the first gas.

  According to the engine as described in said (18), a piping path | route can be simplified. Moreover, since interference between gases can be avoided, the deposit removal effect can be enhanced.

(19) In some embodiments, in the engine according to any one of (1), (2), and (17), the sub-chamber base forming the sub-chamber has a small diameter having an inner diameter r _1. It includes a cylindrical portion, and said large-diameter portion to the small-diameter cylindrical portion has an inner diameter larger r ₂ than the inner diameter r ₁ is provided opposite the injection hole, the laser transmission of the laser spark plug A window is provided in the large-diameter cylindrical portion, and the first gas supply path is configured to inject the first gas in the axial direction of the large-diameter cylindrical portion along the surface of the laser transmission window.

  According to the engine as described in said (19), since the flow rate of 1st gas is quick, the effect of peeling and removing a deposit can be heightened. Further, since the concentration of the air-fuel mixture is high, the ignitability can be improved. Further, since the first gas flows along the surface of the laser transmission window, the surface of the laser transmission window and the oil mist adhering to the surface can be cooled by the first gas. Thereby, carbonization of the oil mist accompanying combustion in the sub chamber can be effectively suppressed, and the oil mist can be prevented from sticking to the surface of the laser transmission window. Therefore, it is possible to suppress a decrease in laser output of the laser spark plug over a long period of time.

  According to at least one embodiment of the present invention, in an engine that uses a laser spark plug to ignite an ignition fuel gas supplied to a sub chamber, it is possible to suppress a decrease in laser output over a long period of time.

It is a schematic diagram which shows schematic structure of the subchamber type gas engine which concerns on one Embodiment of this invention. It is a schematic diagram which shows the structure of the sub chamber vicinity of the sub chamber type gas engine which concerns on one Embodiment of this invention. It is a schematic diagram which shows the structure of the sub chamber vicinity of the sub chamber type gas engine which concerns on one Embodiment of this invention. It is a schematic diagram which shows the structure of the sub chamber vicinity of the sub chamber type gas engine which concerns on one Embodiment of this invention. It is a schematic diagram which shows the structure of the sub chamber vicinity of the sub chamber type gas engine which concerns on one Embodiment of this invention. It is a schematic diagram which shows the structure of the sub chamber vicinity of the sub chamber type gas engine which concerns on one Embodiment of this invention. It is a schematic diagram which shows the structure of the sub chamber vicinity of the sub chamber type gas engine which concerns on one Embodiment of this invention. It is a figure which shows the cylinder pressure with respect to the crank angle in the combustion cycle of the subchamber type gas engine shown in FIG.6 and FIG.7, and has shown the execution period (crank angle range) of normal mode and washing | cleaning mode. It is a figure which shows a mode that a 1st gas supply path (cleaning gas supply path) injects 1st gas in the period including at least one part of a compression process, and changes the direction through which oil mist flows. It is a figure which shows the flow which determines whether normal mode or cleaning mode is performed. It is a schematic diagram which shows the structure of the sub chamber vicinity of the sub chamber type gas engine which concerns on one Embodiment of this invention. It is a schematic diagram which shows the structure of the sub chamber vicinity of the sub chamber type gas engine which concerns on one Embodiment of this invention. It is a schematic diagram which shows the structure of the sub chamber vicinity of the sub chamber type gas engine which concerns on one Embodiment of this invention.

Hereinafter, some embodiments of the present invention will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of the components described in the embodiments or shown in the drawings are not intended to limit the scope of the present invention, but are merely illustrative examples. Absent.
For example, expressions expressing relative positional relationships such as “in a certain direction”, “along a certain direction”, “parallel”, “orthogonal”, “center”, “concentric”, “coaxial”, “coincidence”, etc. Not only such a relative arrangement relationship is strictly expressed, but also a state of relative displacement with a tolerance or an angle or a distance at which the same function can be obtained is also expressed.
The expression “comprising”, “comprising”, “comprising”, “including”, or “having” one constituent element is not an exclusive expression for excluding the presence of the other constituent elements.

FIG. 1 is a schematic diagram showing a schematic configuration of a sub-chamber gas engine according to an embodiment of the present invention.
The sub-chamber gas engine 100 includes a cylinder 2, a piston 11 that is housed in the cylinder 2 and reciprocates, an intake port 5 and an exhaust port 6 that are connected around a cylinder head 2 a of the cylinder 2, and an intake port 5. An intake valve 8 that opens and closes and an exhaust valve 10 that opens and closes the exhaust port 6 are provided. The sub-chamber gas engine 100 is provided with a main chamber 12 (main combustion chamber) defined between the cylinder head 2 a and the piston 11.

The cylinder head 2 a is provided with a sub chamber 14 (sub combustion chamber), and the main chamber 12 and the sub chamber 14 are communicated with each other by at least one injection hole 9. An ignition fuel gas supply path 16 for introducing an ignition fuel gas into the sub chamber 14 is connected to the sub chamber 14. The sub chamber 14 is provided with a laser spark plug 18 for igniting the air-fuel mixture containing the ignition fuel gas introduced into the sub chamber 14. The laser spark plug 18 includes a laser transmission window 20 that transmits laser at a position facing the sub chamber 14, and is configured to irradiate the ignition fuel gas supplied to the sub chamber 14 through the laser transmission window 20. Has been.
The combustion gas generated in the sub chamber is ejected as a fire type (torch) from the nozzle hole 9 in the sub chamber 14 and burns the mixed gas in the main chamber 12 as shown by the broken line in the vicinity of the nozzle hole 9 in FIG. As a result, even if the mixed gas in the main chamber 12 is a lean mixed gas, it can be burned and low fuel consumption is realized. The combustion of the lean mixture gas in the main chamber 12 are the relatively low temperature of combustion, to reduce the generation amount of such NO _X, can achieve low pollution.

  Next, several embodiments will be described with reference to FIGS. 2 to 7 for specific configuration examples in the vicinity of the sub chamber 14 of the sub chamber type gas engine 100 shown in FIG.

  FIG. 2 is a schematic diagram illustrating a configuration in the vicinity of the sub chamber 14 of the sub chamber type gas engine 100 according to the embodiment. FIG. 3 is a schematic diagram illustrating a configuration in the vicinity of the sub chamber 14 of the sub chamber type gas engine 100 according to the embodiment. FIG. 4 is a schematic diagram illustrating a configuration in the vicinity of the sub chamber 14 of the sub chamber type gas engine 100 according to the embodiment. FIG. 5 is a schematic diagram showing a configuration in the vicinity of the sub chamber 14 of the sub chamber type gas engine 100 according to the embodiment. FIG. 6 is a schematic diagram illustrating a configuration in the vicinity of the sub chamber 14 of the sub chamber type gas engine 100 according to the embodiment. FIG. 7 is a schematic diagram illustrating a configuration in the vicinity of the sub chamber 14 of the sub chamber type gas engine 100 according to the embodiment.

In some embodiments, for example, as shown in FIGS. 2-7, the subchamber gas engine 100 is configured to inject the first gas g ₁ toward the laser transmission window 20 of the laser spark plug 18. A first gas supply path 22 (16, 28) is provided.

Thus, it is possible to first gas g ₁ to the oil mist attached to the surface 20a of the laser transmitting window 20 collide, removing the oil mist. Further, since the surface 20a of the laser transmission window 20 and the oil mist adhering to the surface 20a can be cooled, carbonization of the oil mist accompanying combustion in the sub chamber 14 is suppressed, and the surface 20a of the laser transmission window 20 is suppressed. The oil mist can be prevented from sticking to the surface.

In some embodiments, for example, as shown in FIGS. 2 to 5, the first gas supply path 22 is an ignition fuel gas supply path 16. In this case, the first gas g ₁ is ignited fuel gas. That is, in the sub-chamber type gas engine 100 shown in FIGS. 2 to 5, the ignition fuel gas supply path 16 for introducing the ignition fuel gas into the sub-chamber 14 is directed toward the laser transmission window 20 of the laser spark plug 18. The fuel gas for ignition is injected.

  As described above, the ignition fuel gas supply path 16 inherently provided in the sub-chamber gas engine 100 is configured to inject the ignition fuel gas toward the laser transmission window 20, thereby providing a special additional feature. Without providing a configuration, the above-described oil mist removal effect and oil mist carbonization and sticking suppression effect can be obtained.

  In some embodiments, for example, as shown in FIG. 2, the first gas supply path 22 (ignition fuel gas supply path 16) extends from the side peripheral surface 24 a of the sub chamber base 24 that forms the sub chamber 14 to the sub chamber. 14 is provided. In the embodiment shown in FIG. 2, the first gas supply path 22 (ignition fuel gas supply path 16) is provided linearly through the side peripheral surface 24 a of the sub-chamber base 24. A laser transmission window 20 is provided on the straight line.

In some embodiments, for example, as shown in FIG. 3 or FIG. 4, the first gas supply path 22 (ignition fuel gas supply path 16) has a curved portion 16a or a bent portion 16b.
In the embodiment shown in FIG. 3, the first gas supply path 22 (ignition fuel gas supply path 16) extends from the upper surface 24 b of the large-diameter cylindrical portion 28 of the sub-chamber base 24 described later to the inside of the large-diameter cylindrical portion 28. The first straight portion 16c extends, and the curved portion 16a is connected to the first straight portion 16c and communicates with the sub chamber. In the embodiment shown in FIG. 4, the first gas supply path 22 (ignition fuel gas supply path 16) extends from the upper surface 24 b of the large-diameter cylindrical portion 28 of the sub-chamber base 24 described later to the inside of the large-diameter cylindrical portion 28. The first straight portion 16c extends, and the second straight portion 16d is connected to the first straight portion 16c and communicates with the sub chamber. A laser transmission window 20 is provided on the extended line of the second straight part 16d.

  As described above, by providing the curved portion 16a or the bent portion 16b in the first gas supply path 22 (ignition fuel gas supply path 16), the layout of the first gas supply path 22 (ignition fuel gas supply path 16) can be improved. The degree of freedom can be increased. For example, as shown in FIGS. 3 and 4, when the laser spark plug 18 is disposed on the upper surface 14 a of the sub chamber 14, the first is transferred from the side peripheral surface 24 a of the sub chamber base 24 that forms the sub chamber 14 to the sub chamber 14. Even if it is difficult to penetrate the gas supply path 22 (ignition fuel gas supply path 16), the first gas guided from the upper surface 24b of the sub-chamber base 24 forming the sub-chamber 14 is directed to the laser transmission window 20. The first gas supply path 22 can be configured so as to be injected. As described with reference to FIG. 3, when the first gas supply path 22 (ignition fuel gas supply path 16) is constituted by the first straight line portion 16 c and the second straight line portion 16 d, the upper surface 24 b of the sub chamber base 24. Since it can be easily drilled from the side and the inner circumference 24c side, there is a merit in terms of workability.

In some embodiments, for example, as shown in FIGS. 5 and 13, the auxiliary chamber cap 24 for forming the sub-chamber 14, a small-diameter cylindrical portion 26 having an inner diameter r _1, a large inner diameter r ₂ than the inner diameter r ₁ A large-diameter cylindrical portion 28 located on the opposite side of the injection hole 9 in the extending direction d ₁ (vertical direction) of the sub chamber 14 with respect to the small-diameter cylindrical portion 26, and the laser transmitting window 20 is a large-diameter cylinder. The unit 28 is provided. The small-diameter cylindrical portion 26 and the large-diameter cylindrical portion 28 are arranged concentrically, and the small-diameter cylindrical portion 26 and the large-diameter cylindrical portion 28 are located between the small-diameter cylindrical portion 26 and the large-diameter cylindrical portion 28. A transition section 37 is provided in which the inner diameter uniformly increases from r ₁ to r ₂ . The laser transmitting window 20 is provided on the inner peripheral surface 28 a of the large diameter cylindrical portion 28 so as to be positioned on the outer peripheral side with respect to the inner peripheral surface 26 a of the small diameter cylindrical portion 26.

In some embodiments, for example, as shown in FIGS. 6 and 7, the first gas supply path 22 (cleaning gas supply path 28) is different from the ignition fuel gas (hereinafter referred to as cleaning gas). The first gas g ₁ is injected toward the laser transmission window 20 of the laser spark plug 18. In this case, pre-combustion chamber gas engine 100 includes a second gas supply passage 30 (ignition fuel gas supply passage 16) for supplying the ignition fuel gas as the second gas g ₂ to the auxiliary chamber 14 . That is, the sub-chamber type gas engine 100 shown in FIGS. 6 and 7 uses a cleaning gas for cleaning the laser transmission window 20 separately from the ignition fuel gas supply path 16 that the engine 100 originally has. A first gas supply path 22 (cleaning gas supply path 28) configured to inject toward the laser transmission window 20 of the laser spark plug 18 as the first gas is provided. For example, air or nitrogen may be used as the cleaning gas.

Thus, the oil mist adhering to the laser transmission window 20 of the laser spark plug 18 can be removed by injecting the first gas g ₁ (cleaning gas) at an arbitrary timing regardless of the timing of supplying the ignition fuel gas. it can.

In some embodiments, for example, as shown in FIG. 7, the first gas supply path 22 (cleaning gas supply path 28) supplies a first gas (cleaning gas) different from the ignition fuel gas to the laser spark plug 18. The second gas supply path 30 (ignition fuel gas supply path 16) is configured to inject toward the laser transmission window 20, and the second gas g ₂ ( The fuel gas for ignition is injected.
In the embodiment shown in FIG. 7, the first gas supply path 22 (cleaning gas supply path 28) and the second gas supply path 30 (ignition fuel gas supply path 16) are provided at positions facing each other in the circumferential direction. It has been. In the illustrated embodiment, both the first gas supply path 22 (cleaning gas supply path 28) and the second gas supply path 30 (ignition fuel gas supply path 16) are connected to the sub chamber from the side peripheral surface 24a of the sub chamber base 24. 14 is provided so as to penetrate linearly to 14, but may be configured to have a curved portion 16a or a bent portion 16b as shown in FIGS.

  Thereby, using both the ignition fuel gas injected from the ignition fuel gas supply passage 16 inherently provided in the sub-chamber gas engine 100 and the cleaning gas, the oil mist removal effect described above, An effect of suppressing carbonization and sticking of oil mist can be obtained. Also in this case, it is possible to remove the oil mist adhering to the laser transmission window 20 of the laser spark plug 18 by injecting the cleaning gas at an arbitrary timing.

  Here, the injection control of the first gas (cleaning gas) in some embodiments shown in FIGS. 6 and 7 will be described. In some embodiments shown in FIGS. 6 and 7, the sub-chamber gas engine 100 includes a gas supply control unit 32 and an in-cylinder pressure sensor 34. The gas supply control unit 32 is configured as a microcomputer including a central processing unit (CPU), a random access memory (RAM), a read only memory (ROM), an I / O interface, and the like.

Gas supply control unit 32, the first gas supply passage 22 (the cleaning gas supply path 28) the first gas _{g 1} injection by a second gas supply passage 30 (ignition fuel gas supply passage 16) the second gas by _{g 2} Is controlled to be injected. The gas supply control unit 32 includes, for example, a valve 29 provided in the first gas supply path 22 (cleaning gas supply path 28) and a valve 31 provided in the second gas supply path 30 (ignition fuel gas supply path 16). closing by controlling the valve control unit 33 may control the injection first gas g ₁ and the injection second gas g _2.

  In some embodiments shown in FIGS. 6 and 7, the gas supply control unit 32 causes the first gas supply path 22 (cleaning gas supply path 28) to pass the first gas (cleaning gas) through the laser spark plug 18. As a mode for spraying toward the window 20, a normal mode and a cleaning mode can be executed. The gas supply control unit 32 is configured to execute the normal mode during normal operation of the sub-chamber gas engine 100, and to execute the cleaning mode when the necessity of cleaning the laser transmission window 20 of the laser spark plug 18 is high. Yes. The normal mode and the cleaning mode differ in the execution period (first gas injection period) in the combustion cycle of the sub-chamber gas engine 100.

  Here, the execution period of the normal mode and the cleaning mode in the combustion cycle of the sub-chamber gas engine 100 shown in FIGS. 6 and 7 will be described with reference to FIG. 8 by taking the case of a 4-stroke / 1-cycle engine as an example.

  As shown in FIG. 8, the normal mode is executed in a period including at least a part of the compression stroke in the combustion cycle of the sub-chamber gas engine 100. The execution period of the normal mode illustrated in FIG. 8 is from the suction process to the compression process. In the normal mode, the first gas (cleaning gas) and the second gas (ignition gas) are supplied from the first gas supply path 22 (cleaning gas supply path 28) and the second gas supply path 30 (ignition fuel gas supply path 16). Fuel gas) may be injected at the same time.

  As shown in FIG. 8, the cleaning mode is executed over a period longer than the execution period of the normal mode in the combustion cycle of the sub-chamber gas engine 100. Thereby, the removal effect of the above-mentioned oil mist, the carbonization of oil mist, and the suppression effect of sticking can be heightened. The execution period of the cleaning mode illustrated in FIG. 8 is an exhaust process to a compression stroke (until ignition timing), and includes at least a part of the compression stroke in the combustion cycle of the sub-chamber gas engine 100.

In the embodiment shown in FIGS. 6 and 7, as the normal mode, the first gas supply path 22 (cleaning gas supply path 28) is in a period including at least a part of the compression stroke in the combustion cycle of the sub-chamber gas engine 100. By injecting the first gas g ₁ (cleaning gas), the effects described below with reference to FIG. 9 can be obtained. As shown in FIG. 9, in the compression stroke, oil mist flows from the main chamber 12 into the sub chamber 14 as the piston 11 (see FIG. 1) rises. Thus, the oil mist that injection period into the first gas supply passage 22 (the cleaning gas supply path 28) a first gas g _1, comprising at least part of the compression stroke in accordance with the timing coming flow, oil mist It is possible to effectively prevent the laser beam from adhering to the surface 20a of the laser transmission window 20 by changing the flow direction of the laser beam.

  The gas supply control unit 32 is configured to determine, by the mode determination unit 35, whether to execute the normal mode or the cleaning mode based on the output state information regarding the laser output state of the laser spark plug. The gas supply control unit 32 may execute the normal mode during normal operation and execute the cleaning mode only when output state information indicating that the output of the laser is reduced is obtained. Here, in view of the fact that the oil mist attached to the laser transmission window 20 is deposited as the engine operating time is longer, the output state information regarding the laser output state is simply from the previous cleaning of the laser transmission window 20. It is also possible to set as the operation time. Further, as will be described in detail below, the laser output state may be estimated based on the in-cylinder pressure measured by the in-cylinder pressure sensor 34.

  The gas supply control unit 32 includes a misfire cycle determination unit 36 and a variation coefficient calculation unit 38 in order to estimate the output state of the laser. The misfire cycle determination unit 36 is configured to determine whether or not a misfire cycle has occurred based on the pressure in the main chamber 12 (in-cylinder pressure) measured by the in-cylinder pressure sensor 34. The variation coefficient calculation unit 38 is configured to calculate a variation coefficient (COV, Coefficient of variation) of the pressure in the main chamber 12 in a predetermined cycle measured by the in-cylinder pressure sensor 34. In this case, the output state information related to the laser output state includes the determination result of the misfire cycle determination unit 36 and the calculation result of the variation coefficient calculation unit 38, and the mode determination unit 35 of the gas supply control unit 32 determines the output state information based on the output state information. Whether to execute the normal mode or the cleaning mode is determined as follows.

  The mode determination unit 35 of the gas supply control unit 32 determines whether to execute the normal mode or the cleaning mode according to the flow shown in FIG. In the flow shown in FIG. 10, first, in S11, the in-cylinder pressure sensor 34 measures the in-cylinder pressure in the main chamber 12. Next, based on the in-cylinder pressure measured by the in-cylinder pressure sensor 34 in S11, the misfire cycle determination unit 36 determines whether or not a misfire cycle has occurred in S12. The presence or absence of the misfire cycle is determined by comparing, for example, the maximum in-cylinder pressure in one combustion cycle measured by the in-cylinder pressure sensor 34 with a threshold value, and when the measured maximum in-cylinder pressure falls below the threshold value, misfire occurs in the combustion cycle. It can be determined that it has occurred. If the misfire cycle determination unit 36 determines that a misfire cycle has occurred in S12, the gas supply control unit 32 executes the cleaning mode in S13 because there is a high possibility that the laser output state has decreased. If the misfire cycle determination unit 36 determines that no misfire cycle has occurred in S12, the coefficient of variation in the predetermined cycle of the maximum in-cylinder pressure of the main chamber 12 calculated by the coefficient of variation calculation unit 38 exceeds the threshold value in S14. It is determined whether or not. A large variation coefficient of the maximum in-cylinder pressure in a predetermined cycle means that a change in the maximum in-cylinder pressure is large. If it is determined in S14 that the coefficient of variation exceeds the threshold value, there is a high possibility that the laser output state has decreased, and in S13, the gas supply control unit 32 executes the cleaning mode. If it is determined in S14 that the coefficient of variation does not exceed the threshold value, the gas supply control unit 32 executes the normal mode in S15.

When the cleaning mode is executed, a cleaning gas different from the fuel gas is introduced into the sub chamber 14, so that the air-fuel ratio in the sub chamber 14 may deviate from the optimum value. For example, when the cleaning gas is nitrogen, introducing nitrogen into the sub chamber 14 may cause a risk of misfire due to a decrease in the O ₂ concentration or the excess air ratio in the sub chamber 14. Therefore, the gas supply control unit 32 shown in FIGS. 6 and 7 may impose the constraint conditions described below for the execution of the cleaning mode.

In some embodiments, the gas supply control unit 32 shown in FIGS. 6 and 7 relates to output state information (determination result of the misfire cycle determination unit 36 and calculation result of the variation coefficient calculation unit 38) regarding the output state of the laser. Alternatively, the cleaning mode may not be performed continuously for a plurality of cycles. For example, when the sub-chamber gas engine 100 shown in FIGS. 6 and 7 includes a plurality of cylinders 2 (cylinders), the cleaning mode execution interval is several cycles or more for each cylinder 2 regardless of the output state information. It may be vacant (see Table 1). Thereby, the risk that misfire cycles occur continuously can be suppressed.

  Table 1 shows an example of the execution timing of the cleaning mode when the sub-chamber gas engine 100 shown in FIGS. 6 and 7 includes a plurality of cylinders 2. In Table 1, when the laser output falls below the allowable level in the cylinders C and D among the plurality of cylinders 2 (cylinder A to cylinder D) (the misfire cycle determination unit 36 determines that a misfire cycle has occurred). Or when the fluctuation coefficient calculated by the fluctuation coefficient calculation unit 38 exceeds a threshold value), “e” is written in a cycle in which the cleaning mode is executed among the subsequent combustion cycles, and “ * ”.

  In some embodiments, when the sub-chamber gas engine 100 shown in FIGS. 6 and 7 includes a plurality of cylinders 2, the gas supply control unit 32 includes two or more cylinders among the plurality of cylinders 2. When the misfire cycle determination unit 36 determines that a misfire cycle has occurred for 2, the execution periods of the cleaning mode for two or more cylinders 2 that have been determined to have a misfire cycle do not overlap. It may be configured to perform a cleaning mode (see Table 1). Thereby, the risk of misfire occurring simultaneously in two or more cylinders 2 can be suppressed.

  In some embodiments, when the sub-chamber gas engine 100 shown in FIGS. 6 and 7 includes a plurality of cylinders 2, the gas supply control unit 32 includes two or more cylinders among the plurality of cylinders 2. When the variation coefficient calculated by the variation coefficient calculation unit 38 for 2 exceeds a threshold value, the cleaning mode is set so that the execution periods of the cleaning modes of two or more cylinders 2 whose in-cylinder pressure variation coefficient exceeds the threshold value do not overlap. It may be configured to execute (see Table 1). Thereby, it is possible to suppress the misfire from occurring in two or more cylinders 2 at the same time.

In some embodiments, for example, as shown in FIGS. 11 to 13, the first gas supply path 22 extends from the side surface 50 a of the holder 50 (housing) to which the laser ignition plug 18 is attached to the surface of the laser transmission window 20. configured to inject the first gas _{g 1} along 20a. In this case, the opening 22 a of the first gas supply path 22 is provided on the side of the surface 20 a of the laser transmission window 20, and the first gas supply path 22 is substantially parallel to the surface 20 a of the laser transmission window 20. Inject gas.
In the embodiment shown in FIGS. 11 and 13, the first gas supply path 22 may be configured as an ignition fuel gas supply path 16 configured to inject the ignition fuel gas as the first gas.
As shown in FIG. 13, when the laser transmission window 20 is provided on the inner peripheral surface 28 a of the large-diameter cylindrical portion 28, the first gas supply path 22 is connected to the first gas in the axial direction of the large-diameter cylindrical portion 27. May be configured to be injected. In this case, the opening of the first gas supply path 22 is attached in parallel to the axis of the large-diameter cylindrical portion 27, and the laser ignition plug 18 is substantially parallel to the gas flow direction of the opening of the first gas supply path 22. A laser transmission window 20 may be provided.

  According to the above configuration shown in FIGS. 11 to 13, since the flow rate of the first gas is fast, the effect of peeling and removing the deposit can be enhanced. Further, since the concentration of the air-fuel mixture is high, the ignitability can be improved. Further, since the first gas flows along the surface 20a of the laser transmission window 20, the surface 20a of the laser transmission window 20 and the oil mist attached to the surface 20a can be cooled by the first gas. Thereby, the carbonization of the oil mist accompanying combustion in the sub chamber 14 can be effectively suppressed, and the oil mist can be prevented from sticking to the surface 20a of the laser transmission window 20. Therefore, it is possible to suppress a decrease in the laser output of the laser spark plug 18 over a long period of time.

  In some embodiments, for example, as shown in FIG. 12, an ignition fuel gas supply path 16 for supplying an ignition fuel gas and a cleaning gas (second gas) different from the ignition fuel gas are supplied. And a cleaning gas supply path 28 (second gas supply path 30). In this case, the first gas supply path 22 is connected to the ignition fuel gas supply path 16 and the cleaning gas supply path 28, and is configured to inject at least one of the ignition fuel gas and the cleaning gas as the first gas.

  In the embodiment shown in FIG. 12, the first gas supply path 22 is ignited by adjusting the valve 31 provided in the ignition fuel gas supply path 16 and the valve 29 provided in the cleaning gas supply path 28. And at least one of the cleaning gas is injected as the first gas. The ignition fuel gas supply path 16 and the cleaning gas supply path 28 are connected to a collective pipe 51 (connecting member), and the collective pipe 51 is screwed into a holder 50 and fixed. The first gas supply path 22 is connected to the ignition fuel gas supply path 16 and the second gas supply path 30 via the collecting pipe 51.

  According to the above configuration shown in FIG. 12, the piping path can be simplified. Moreover, since interference between gases can be avoided, the deposit peeling effect can be enhanced as compared with the configuration shown in FIG.

  The present invention is not limited to the above-described embodiments, and includes forms obtained by modifying the above-described embodiments and forms obtained by appropriately combining these forms. Although the present invention has been described by taking a gas engine as an example, it can also be applied to other engines (including external combustion engines such as jet engines, rocket engines, and the like).

2 Cylinder 2a Cylinder head 5 Intake port 6 Exhaust port 8 Intake valve 9 Injection hole 10 Exhaust valve 11 Piston 12 Main chamber 14 Sub chamber 14a Upper surface of sub chamber 16 Fuel gas supply path for ignition 16a Bending portion 16b Bending portion 16c First straight line Portion 16d Second linear portion 18 Laser spark plug 20 Laser transmission window 20a Laser transmission window surface 22 First gas supply path 22a First gas supply path opening 24 Sub chamber base 24a Sub chamber base side peripheral surface 24b Sub chamber Upper surface 26 of the base 26 Small diameter cylindrical portion 27 Large diameter cylindrical portion 28 Cleaning gas supply path 29 Valve 30 Second gas supply path 31 Valve 32 Gas supply control section 33 Valve control section 34 In-cylinder pressure sensor 35 Mode determination section 36 Misfire cycle determination section 38 Fluctuation coefficient calculation unit 50 Holder 51 Collective piping 100 Sub chamber type gas engine

Claims (19)

An engine comprising a main chamber defined between a piston and a cylinder head, and a sub chamber communicating with the main chamber via a nozzle hole,
A laser ignition plug configured to irradiate the ignition fuel gas supplied to the sub chamber through the laser transmission window with a laser transmission window that transmits a laser at a position facing the sub chamber;
A first gas supply path configured to inject a first gas toward the laser transmission window of the laser spark plug;
Further equipped with an engine.   The engine according to claim 1, wherein the first gas is the ignition fuel gas. The sub chamber base forming the sub chamber has a small diameter cylindrical portion having an inner diameter r ₁ and an inner diameter r ₂ larger than the inner diameter r ₁ and is provided on the opposite side to the injection hole with respect to the small diameter cylindrical portion. A large-diameter cylindrical portion,
The engine according to claim 1 or 2, wherein the laser transmission window of the laser spark plug is provided in the large-diameter cylindrical portion.   The engine according to any one of claims 1 to 3, wherein the first gas supply path is provided so as to penetrate from the side peripheral surface of a sub chamber base forming the sub chamber to the sub chamber.   The engine according to any one of claims 1 to 4, wherein the first gas supply path has a bent portion or a curved portion. The first gas is a gas different from the ignition fuel gas,
The engine according to claim 1, further comprising a second gas supply path for supplying the ignition fuel gas as the second gas to the sub chamber.   The engine according to claim 6, wherein the second gas supply path is configured to inject the ignition fuel gas toward the laser transmission window of the laser ignition plug.   The engine according to claim 6 or 7, wherein the first gas is air or nitrogen. A gas supply control unit configured to control injection of the first gas through the first gas supply path;
The gas supply control unit according to claim 6 or 7, wherein the gas supply control unit is configured to be able to execute a normal mode in which the first gas supply path injects the first gas in a period including at least a part of a compression stroke in a combustion cycle. The listed engine.   The said gas supply control part is comprised so that execution of the washing | cleaning mode in which the said 1st gas supply path injects the said 1st gas over a period longer than the execution period of the said normal mode in a combustion cycle is possible. Engine.   The gas supply control unit is configured to determine whether to execute the normal mode or the cleaning mode based on output state information related to a laser output state of the laser spark plug. Engine. A misfire cycle determination unit for determining whether or not a misfire cycle has occurred,
The output state information includes a determination result of the misfire cycle determination unit,
The engine according to claim 11, wherein the gas supply control unit is configured to execute the cleaning mode when the misfire cycle determination unit determines that a misfire cycle has occurred. A fluctuation coefficient calculating unit for calculating a fluctuation coefficient of the pressure in the main chamber at a predetermined number of cycles;
The output state information includes a calculation result of the coefficient of variation calculation unit,
The gas supply control unit is configured to execute the cleaning mode when a variation coefficient of the pressure of the main chamber calculated by the variation coefficient calculation unit exceeds a threshold value. engine.   The engine according to any one of claims 11 to 13, wherein the gas supply control unit is configured not to continuously perform the cleaning mode for a plurality of cycles regardless of the output state information. The engine includes a plurality of cylinders,
The gas supply control unit determines that the misfire cycle has occurred when the misfire cycle determination unit determines that the misfire cycle has occurred for two or more cylinders of the plurality of cylinders. The engine according to claim 12, wherein the engine is configured to execute the cleaning mode such that execution periods of the cleaning mode for the two or more cylinders are not overlapped. The engine includes a plurality of cylinders,
The gas supply control unit, when the variation coefficient calculated by the variation coefficient calculation unit for two or more cylinders of the plurality of cylinders exceeds a threshold, the variation coefficient of the in-cylinder pressure exceeds the threshold The engine according to claim 13, wherein the engine is configured to execute the cleaning mode such that execution periods of the cleaning mode of two or more cylinders do not overlap.   3. The engine according to claim 1, wherein the first gas supply path is configured to inject the first gas along a surface of the laser transmission window from a side surface of the housing to which the laser ignition plug is attached. Furthermore, an ignition fuel gas supply path for supplying an ignition fuel gas, and a second gas supply path for supplying a second gas different from the ignition fuel gas,
The first gas supply path is connected to the ignition fuel gas supply path and the second gas supply path, and is configured to inject at least one of the ignition fuel gas and the second gas as the first gas. The engine according to claim 17. The sub chamber base forming the sub chamber has a small diameter cylindrical portion having an inner diameter r ₁ and an inner diameter r ₂ larger than the inner diameter r ₁ and is provided on the opposite side to the injection hole with respect to the small diameter cylindrical portion. A large-diameter cylindrical portion,
The laser transmission window of the laser spark plug is provided in the large-diameter cylindrical portion,
The said 1st gas supply path is comprised so that the said 1st gas may be injected in the axial direction of the said large diameter cylinder part along the surface of the said laser transmission window. The listed engine.

Images