JP2005042579A - Laser igniting engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laser igniting engine having, at a plurality of targets installed on the surfaces of the combustion chambers of a plurality of cylinders, a multi-point laser supply system capable of distributing laser beam from a laser transmission device to a plurality of cylinders and selectively using a plurality of targets according to an engine load. <P>SOLUTION: In this laser igniting engine, an air-fuel mixture is ignited by plasma generated by radiating the laser beam to the targets in the combustion chamber. The targets are formed so as to be fixed to the multiple positions of a combustion chamber component member and the laser beam is radiated to the targets through optical fibers of the same quantity as that of the targets. The laser igniting engine also comprises a rotating mirror which reflects the laser beam from the laser transmission device and distributes the laser beam to the plurality of cylinders. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention is mainly applied to a premixed combustion engine such as a gas engine, and is filled in the combustion chamber by plasma generated by irradiating a target provided in the combustion chamber with laser light transmitted from a laser transmission device. The present invention relates to a laser ignition engine configured to ignite a mixed gas.
[0002]
[Prior art]
In a premixed lean combustion gas engine, in order to promote ignition combustion of the lean mixed gas in the main combustion chamber, normally, the ignition is performed by igniting and igniting the rich mixture ratio gas in the sub chamber with a spark plug mounted in the sub chamber. “Ignition plug ignition method” in which a flame is injected into a lean air-fuel mixture in the main combustion chamber and main combustion is performed, or pilot fuel is injected into the mixed gas in the sub chamber by a pilot fuel injection valve installed in the sub chamber. In many cases, a “pilot fuel injection ignition system” is used in which an ignition flame is injected into a lean air-fuel mixture in the main combustion chamber to cause main combustion.
[0003]
However, the spark plug ignition system has a problem that the spark plug gap increases as the operation time elapses, so that the ignition performance is liable to be lowered, and the increase in the in-cylinder effective average pressure is limited. On the other hand, the pilot fuel injection ignition method can solve the above-mentioned problems of the addition plug method, but requires a high-pressure pilot fuel injection system, which makes the structure complicated and expensive, and near TDC (top dead center). Since the pilot fuel is injected and burned, the amount of NOx generated increases.
[0004]
Therefore, in the premixed lean combustion gas engine, as an ignition method that replaces the spark plug ignition method and the pilot fuel injection ignition method, a laser light is irradiated to a target fixed on the surface of the combustion chamber to generate plasma ignition. "Method" has been proposed. As a premixed lean combustion gas engine using such a laser ignition system, for example, techniques of Patent Document 1 (Japanese Patent Laid-Open No. 7-217521) and Patent Document 2 (Japanese Patent Laid-Open No. 9-42138) have been proposed.
[0005]
In the technique of Patent Document 1, the piston surface of the engine is used as a target, and by rotating a plurality of wedge substrates provided in the optical path of the laser light at different rotational speeds, the laser light transmitted from the laser transmission device is obtained. The laser beam is oscillated over a wide range on the piston surface.
Further, in the technique of Patent Document 2, a variable focus device is provided in the laser beam path between the laser transmission device and the target provided on the piston surface so that strong laser light can be always irradiated onto the target. is doing.
[0006]
[Patent Document 1] JP-A-7-217521 [Patent Document 2] JP-A-9-42138
[Problems to be solved by the invention]
However, in the technique of Patent Document 1, wear of the piston surface is reduced by causing the laser beam to oscillate in a wide range of the piston surface with the piston surface as a target. In the technique of Document 2, the focus is changed so that a strong laser beam can always be irradiated to the target provided on the piston surface, and a plurality of targets are separately provided on the piston surface of a plurality of cylinders. No means for distributing laser light from a single laser transmission device to a plurality of cylinders is disclosed.
[0008]
In view of the problems of the prior art, the present invention makes it possible to distribute laser light from a single laser transmission device to a plurality of cylinders on a plurality of targets provided separately from pistons on the combustion chamber surfaces of the plurality of cylinders. It is an object of the present invention to provide a laser ignition type engine equipped with a multi-point laser supply system capable of properly using the plurality of targets depending on engine load.
[0009]
[Means for Solving the Problems]
The present invention achieves such an object, and ignites the mixed gas filled in the combustion chamber by the plasma generated by irradiating the target provided in the combustion chamber with the laser beam transmitted from the laser transmission device. In the laser ignition type engine configured as described above, the target is fixed to a plurality of locations on the surface of a combustion chamber constituent member including a piston, a cylinder head, and a cylinder liner, and the target is irradiated with the laser light through the same number of optical fibers as the target. And a rotating mirror that reflects the laser light from the laser transmission device and separates it into a plurality of cylinders.
[0010]
Preferably, in addition to the above-described configuration, each of the rotating mirrors is set according to an engine speed detector that detects the engine speed, a detected value of the engine speed from the engine speed detector, and an ignition order of the engine. And a first control means for transmitting the laser beam from the laser transmitting device in synchronization with the rotating mirror while rotating to the irradiation position of the cylinder.
[0011]
According to this invention, the first control means sets the rotating mirror in accordance with a preset engine ignition order at a pulse interval corresponding to the engine speed according to the detected value of the engine speed from the engine speed detector. Rotate the laser beam from the laser transmitter to the position where it irradiates the optical fiber entrance to each cylinder, and synchronize the laser beam with the rotating mirror at a pulse interval corresponding to the detected value of the engine speed from the laser transmitter. To make a call.
As a result, the laser light is split into the plurality of optical fiber inlets of each cylinder by the rotation according to the engine ignition order and the engine rotation speed of the rotating mirror, and is applied to the plurality of targets of each cylinder through the optical fiber for each cylinder. Irradiated.
[0012]
Therefore, according to this invention, the rotating mirror is rotated in accordance with the engine ignition order and the engine speed, and the laser beam is transmitted in synchronization with the rotating mirror at a pulse interval corresponding to the detected value of the engine speed. Thus, it is possible to easily divide and irradiate a plurality of targets with each laser beam for each cylinder, and as described above, divide and irradiate a plurality of targets with each laser beam for each cylinder. As a result, plasma in the combustion chamber can be formed at multiple locations, so that even if the mixed gas in the combustion chamber is lean and the mixed gas flow is somewhat turbulent, it can be ignited and burned easily and without problems. This allows further lean combustion conditions to be set, further increasing engine thermal efficiency. It is possible to above may achieve further reduction of the NOx in the exhaust gas (nitrogen oxides).
[0013]
In addition, since the laser light input to each cylinder is split and irradiated onto a plurality of targets provided for each cylinder, the laser light energy per target is applied to each cylinder as in the prior art. This is smaller than the engine provided for each one, and thus the wear of the target can be prevented and the life of the target can be extended.
[0014]
In addition to the invention, a condensing lens that condenses the laser light at the exit of each optical fiber, and deflects the laser light that has passed through the condensing lens in the direction of each target and between the combustion chamber and the outside. It is preferable to provide a sealing glass for performing the gas sealing.
If comprised in this way, while setting the deflection | deviation angle of a sealing glass according to each target, while being able to irradiate each target with a laser beam accurately, using this sealing glass also as a seal of combustion gas Can do.
[0015]
Preferably, in addition to such an invention, a second rotating mirror for splitting the reflected laser light from the rotating mirror into each of the optical fibers is provided.
Further, in addition to the above configuration, an engine load detector for detecting the engine load, the laser beam energy corresponding to the detected value of the engine load from the engine load detector, and the number of irradiation targets corresponding to the amount of the laser beam energy And the second rotating mirror is rotated in the direction of the optical fiber inlet connected to the irradiation target so that laser light can be input from the second rotating mirror to the optical fiber inlet and the second rotation is performed. It is preferable to provide second control means for transmitting laser light in synchronization with the mirror.
Specifically, the second control means reduces the number of irradiation targets as the engine load increases, and rotates the second rotating mirror in the direction of the optical fiber inlet corresponding to the irradiation target. Configure to squeeze.
[0016]
If comprised in this way, a 2nd control means will calculate the laser beam energy corresponding to the said load according to the detected value of the engine load from an engine load detector, and the irradiation target corresponding to the quantity of this laser beam energy The number is calculated, the second rotating mirror is rotated in the direction of the optical fiber inlet connected to the irradiation target calculated by the above, and laser light is transmitted in synchronization with the second rotating mirror to transmit the first rotating mirror. Laser light is introduced into the optical fiber inlet for the irradiation target via the two rotating mirrors.
[0017]
Since the laser light can be ignited with a small laser light energy as the engine load increases, the second control means transmits the number of laser beams transmitted from the laser transmitter as the engine load increases. (Specifically, the irradiation of the target near the outer periphery of the combustion chamber is cut off) to reduce the number of irradiation targets, and the second rotating mirror in the direction of the optical fiber inlet corresponding to the irradiation target. Rotate and irradiate only the irradiation target with laser light.
[0018]
Therefore, according to this invention, at the time of start-up or when the load is low, which is difficult to ignite and burn, it is possible to improve the ignition and combustion performance by irradiating laser light to all the targets provided in a plurality of locations in the combustion chamber, and to reduce the energy of the laser light. Thus, at high loads where laser light ignition is possible, the life of the target is extended by reducing the number of irradiation targets by reducing the number of laser light transmissions from the laser transmission device, and low laser light energy. Ignition combustion is possible.
This makes it possible to improve the ignition and combustion performance by irradiating all targets with laser light during startup and low load, and by irradiating the minimum number of targets that can be ignited and combusted during high loads. It is possible to extend the life of the target and realize reliable ignition combustion with less laser light energy.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the embodiments shown in the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the component parts described in this example are not intended to limit the scope of the present invention only to specific examples unless otherwise specified. Only.
[0020]
FIG. 1 is an overall configuration diagram of a laser ignition gas engine provided with a multipoint laser supply system according to an embodiment of the present invention, and FIG. 2 is a control block diagram. FIG. 3 is a diagram showing the laser energy distribution.
[0021]
In FIG. 1 showing an embodiment of the present invention, 31 is a cylinder head of a gas engine (hereinafter referred to as engine), 33 is a piston, 34 is a cylinder liner, 32 is defined by the cylinder head 31, piston 33 and cylinder liner 34. The combustion chamber, 35 is a connecting rod, and 36 is a crankshaft.
Further, 41 is an air supply port, 39 is an air supply valve that opens and closes the air supply port 41, 42 is an exhaust port, and 40 is an exhaust valve that opens and closes the exhaust port 42.
[0022]
A plurality of targets 8a, 8b, 8c, 8d are fixed to the surface of the piston 33. The targets 8a, 8b, 8c, and 8d are made of a small-diameter thin disk having a diameter of about 5 mm, preferably made of a stainless steel plate and fixed to the surface of the piston 33 by coating, and a plurality of the targets 8a, 8b, 8c, and 8d are installed in the radial direction of the piston 33 Has been. The structure of the targets 8a, 8b, 8c, 8d itself is known.
Reference numeral 7 (7a, 7b, 7c, 7d) is an optical fiber that propagates laser light 2 irradiated (transmitted) from a laser transmitting device 1 described later to the cylinder, and targets 8a, 8b, 8c, 8d for each cylinder. The same number is provided correspondingly.
[0023]
Reference numerals 10a, 10b, 10c, and 10d denote condensing lenses that condense the laser light 2 at the exits of the optical fibers 7a, 7b, 7c, and 7d. It is a seal glass that deflects the light 2 in the direction of the targets 8a, 8b, 8c, and 8d. The seal glass 9 is made of a transparent heat-resistant glass, and performs gas sealing between the inside of the combustion chamber 32 and the outside by cooperation with the gasket 43. Reference numeral 44 denotes a fixing screw for fixing the seal glass 9.
If comprised as mentioned above, the laser beam 2 is irradiated to each target 8a, 8b, 8c, 8d accurately by setting the deflection angle of the said seal glass 9 according to each target 8a, 8b, 8c, 8d. In addition, the seal glass 9 can be used as a seal for combustion gas.
[0024]
Reference numeral 1 denotes a laser transmitter that transmits a laser beam (laser pulse) 2. Reference numeral 3 denotes a first mirror (rotating mirror) that splits the laser beam 2 transmitted from the laser transmitter 1 into each cylinder. The first mirror 3 is rotationally driven by a first mirror driving device 4 so as to reflect a laser beam 2 from the laser transmission device 1 toward a second mirror 5 of each cylinder to be described later.
Reference numeral 5 denotes a second mirror (second rotating mirror) provided in each cylinder. The second mirror 5 is rotationally driven by a second mirror driving device 6 so that the reflected laser light from the second mirror 5 is split into the optical fibers 7a, 7b, 7c, and 7d.
[0025]
Reference numeral 20 denotes a laser control device that controls a pulse interval of laser light 2 emitted from the laser transmission device 1, laser light energy (laser light intensity), and the like.
Reference numeral 51 denotes a rotational speed detector that detects the rotational speed of the engine, and reference numeral 52 denotes a load detector that detects the load of the engine. Reference numeral 38 denotes a crank angle detection timing disk which is connected to the crankshaft 36 via a rotating shaft 37 to detect the crank angle.
Reference numeral 100 denotes a controller for performing a control operation, which will be described later. The detected value of the engine speed from the engine speed detector 51, the detected value of the engine load from the load detector 52, and the engine crank from the timing disk 38. The detected angle value is input, and a control operation signal is output to the first mirror driving device 4, the second mirror driving device 6, and the laser control device 20.
[0026]
Next, the operation of the laser ignition gas engine having the above-described configuration will be described with reference to FIG.
The detected value of the engine speed from the engine speed detector 51 and the detected value of the crank angle from the timing disk 38 are sent to the first mirror rotation angle calculator 54 and the laser pulse transmission interval calculator 55 of the controller 100. Entered. The detected value of the engine load from the load detector 52 is input to the laser energy calculation unit 56. Further, an engine ignition order setting signal is input from the ignition order setting unit 53 to the first mirror rotation angle calculation unit 54.
[0027]
In the first mirror rotation angle calculation unit 54, each cylinder of the first mirror 3 is matched with the pulse interval corresponding to the rotation speed according to the detected value of the engine rotation speed and according to the ignition order of the engine. The rotation angle is calculated and input to the laser / first mirror synchronization control unit 61.
Further, the laser pulse transmission interval calculation unit 55 calculates a laser pulse transmission interval corresponding to the detected value of the engine speed and inputs it to the laser / first mirror synchronization control unit 61.
In the laser / first mirror synchronization control unit 61, the rotation angle of each cylinder of the first mirror 3 and the laser pulse transmission interval are synchronized and input to the first mirror driving device 4, and the laser control device 20
[0028]
In the first mirror driving device 4, the first mirror 3 is rotated so that the laser beam 2 from the laser transmitting device 1 is irradiated to the entrance of the optical fiber 7 to each cylinder. In the laser control device 20, the laser beam 2 is transmitted from the laser transmission device 1 to the first mirror 3 at a pulse interval corresponding to the detected value of the engine speed.
Thereby, like the laser light pulses 2a, 2b, 2c, 2d, 2e, and 2f shown in FIG. 1, the laser light reflected by the first mirror 3 is incident on the second mirror 5 of each cylinder according to the firing order. Is done.
That is, the laser beam 2 from the laser transmission device 1 is incident on the second mirror 5 of each cylinder according to the engine ignition order and the engine speed of the first mirror 3.
[0029]
On the other hand, reference numeral 57 denotes a load to laser energy setting unit, in which the relationship between engine load and laser energy is set.
In such a gas engine, laser light ignition is possible with a small laser light energy as the engine load increases, so that the laser light energy decreases in the load to laser energy setting unit 57 as the engine load increases. Is set to
Then, the laser energy calculation unit 56 calculates the laser light energy corresponding to the load according to the detected value of the engine load, and inputs it to the laser control device 20 and the target selection unit 58.
[0030]
Reference numeral 59 denotes a laser light energy to use target setting unit in which the number of use targets 8 corresponding to the laser light energy (specifically, the targets 8c and 8d near the center of the combustion chamber are used preferentially) is set.
In the use target selection unit 58, the number of irradiation targets 8 corresponding to the amount of laser light energy calculated by the laser energy calculation unit 56 is selected from the laser light energy to use target setting unit 59. Input to the mirror rotation angle calculator 60.
[0031]
The second mirror rotation angle calculation unit 60 calculates the rotation angle of the second mirror 5 up to the entrances of the optical fibers 7c and 7d connected to the irradiation target targets (for example, the targets 8c and 8d) selected as described above. And input to the laser / second mirror synchronization controller 62.
In the laser / second mirror synchronization control unit 62, the rotation of the second mirror 5 to the optical fiber (for example, 7c, 7d) entrance is synchronized with the transmission timing of the laser pulse, and the laser control device 20 and the second mirror driving device 6 are synchronized. To enter.
[0032]
Therefore, the second mirror driving device 6 rotates the second mirror 5 to the entrance of the optical fiber (for example, 7c, 7d) to be irradiated, and the laser control device 20 transmits the laser beam 2 in synchronization with the second mirror 5. To do. As a result, the laser beam 2 enters the optical fiber (for example, 7c, 7d) inlet for the target to be irradiated (for example, 8c, 8d) via the second mirror 5, and is irradiated through the optical fiber (for example, 7c, 7d). The target target (for example, 8c, 8d) is irradiated. The mixed gas filled in the combustion chamber 32 is ignited by the plasma generated by the irradiation of the laser beam 2.
[0033]
That is, as the engine load increases, laser light ignition can be performed with small laser light energy. That is, in this embodiment, as the engine load increases, the number of laser beams transmitted from the laser transmitter 1 is selectively cut off from the laser beam irradiation to the targets 8a and 8b near the outer periphery of the combustion chamber 32. And the number of the irradiation targets is decreased, and the second mirror 5 is rotated in the direction of the optical fibers 7c and 7d inlets corresponding to the irradiation targets 8c and 8d near the center of the combustion chamber 32, so that the irradiation targets 8c, It is also possible to irradiate only 8d with laser light.
[0034]
Therefore, at the time of start-up or low load where ignition combustion is difficult, the ignition combustion performance is obtained by irradiating all the targets 8a, 8b, 8c, 8d provided on the surface of the piston 33 in the combustion chamber 32 with the laser beam 2. To improve. On the other hand, at the time of high load in which laser light ignition is possible with small laser light energy, the number of laser beams 2 transmitted from the laser transmitter 1 is decreased to reduce the number of irradiation targets to only 8c and 8d closer to the center. As a result, the life of the target 8 can be extended and ignition combustion can be performed with a small amount of laser light energy.
[0035]
FIG. 3 shows the crank angle and time change of the laser irradiation energy E in the 6-cylinder gas engine. As shown in FIG. 3A, in the case of a 6-cylinder engine, a peak of laser irradiation energy E stands at 120 ° intervals.
Further, as shown in FIG. 3B, a plurality of targets 8 are provided, and the number of laser pulses is changed from one of C1 (E ₁ ) to two of C2 (E ₂₁ , E ₂₂ ), 3 of C3. The peak of each laser irradiation energy E decreases as the number increases (E, ₃₁ , E ₃₂ , E ₃₃ ) and four of C 4 (E ₄₁ , E ₄₂ , E ₄₃ , E ₄₄ ).
[0036]
Further, according to this embodiment, the first mirror 3 is rotated according to the engine ignition order and the engine speed, and the laser beam 2 is emitted from the laser transmission device 1 at a pulse interval corresponding to the detected value of the engine speed. By transmitting in synchronization with the mirror 3, the laser beam 2 can be easily split and irradiated onto the targets 8 a, 8 b, 8 c, 8 d provided for each cylinder. As a result, plasma in the combustion chamber 32 can be arbitrarily formed at a plurality of locations, so that even if the mixed gas in the combustion chamber 32 is dilute and the mixed gas flow is somewhat disturbed, there is no problem and easily. It can be ignited and burned.
Further, since the laser light 2 injected into each cylinder is split and irradiated onto a plurality of targets 8a, 8b, 8c, and 8d provided for each cylinder, as shown in FIG. The laser light energy per unit becomes smaller than that of an engine in which one target 8 is provided for each cylinder as in the prior art, thereby preventing the target 8 from being worn.
[0037]
【The invention's effect】
As described above, according to the present invention, the rotating mirror is rotated according to the engine ignition order and the engine speed, and the laser beam is synchronized with the rotating mirror at a pulse interval corresponding to the detected value of the engine speed from the laser transmission device. By transmitting the laser beam, it is possible to easily divide and irradiate laser light to a plurality of targets provided for each cylinder.
As described above, the plasma in the combustion chamber can be formed at a plurality of locations by spectroscopically irradiating a plurality of targets on each cylinder with laser light, so that the mixed gas in the combustion chamber is dilute and mixed. Even under conditions where the gas flow is somewhat disturbed, it can be ignited and burned without any problems, which makes it possible to set further lean combustion conditions, thereby improving the thermal efficiency of the engine. In addition, further reduction of NOx (nitrogen oxide) in the exhaust gas can be realized.
[0038]
In addition, according to the present invention, at the time of start-up or low load where ignition combustion is difficult, the laser beam is irradiated to all targets provided in a plurality of locations in the combustion chamber to improve the ignition combustion performance, and the small laser beam At high loads where laser light ignition is possible with energy, the life of the target is extended by reducing the number of irradiated targets by reducing the number of laser beams transmitted from the laser transmitter, and the amount of laser light is reduced. Ignition combustion with energy becomes possible.
As a result, the ignition and combustion performance can be improved by irradiating all targets with laser light during startup and low load, and the minimum target that can be ignited and combusted during high loads is irradiated with laser light. As a result, the life of the target can be extended, and reliable ignition and combustion can be realized with less laser light energy.
[Brief description of the drawings]
FIG. 1 is an overall configuration diagram of a laser ignition gas engine including a multipoint laser supply system according to an embodiment of the present invention.
FIG. 2 is a control block diagram in the embodiment.
FIG. 3 is a diagram showing a laser energy distribution.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Laser transmitter 2 Laser beam 3 1st mirror 4 1st mirror drive device 5 2nd mirror 6 2nd mirror drive device 7a, 7b, 7c, 7d Optical fiber 8a, 8b, 8c, 8d Target 9 Seal glass 10a, 10b, 10c, 10d Condensing lens 20 Laser control device 31 Cylinder head 32 Combustion chamber 33 Piston 34 Cylinder liner 36 Crankshaft 38 Timing disk 51 Rotation speed detector 52 Load detector 100 Controller

Claims (6)

In a laser ignition engine configured to ignite a mixed gas filled in a combustion chamber by plasma generated by irradiating a target provided in the combustion chamber with laser light transmitted from a laser transmission device,
While fixing the target to a plurality of locations on the surface of the combustion chamber constituent member including the piston, cylinder head, cylinder liner,
The target is irradiated with the laser beam through the same number of optical fibers as the target,
A laser ignition engine characterized by further comprising a rotating mirror that reflects the laser beam from the laser transmitting device and separates it into a plurality of cylinders. 2. The laser ignition engine according to claim 1, further comprising a second rotating mirror that splits and reflects the reflected laser light from the rotating mirror to each of the optical fibers. A condensing lens that condenses the laser light at the exit of each optical fiber, and a seal glass that deflects the laser light that has passed through the condensing lens in the direction of each target and performs a gas seal between the combustion chamber and the outside. The laser ignition type engine according to claim 1, comprising: The engine speed detector for detecting the engine speed, the detected value of the engine speed from the engine speed detector and the ignition order of the engine, and the rotating mirror is rotated to the irradiation position of each cylinder. 2. The laser ignition type engine according to claim 1, further comprising first control means for transmitting laser light in synchronization with the rotating mirror from the laser transmitting device. An engine load detector for detecting an engine load; a laser beam energy corresponding to a detected value of the engine load from the engine load detector; and an irradiation target number corresponding to the amount of the laser beam energy; The rotating mirror is rotated in the direction of the optical fiber inlet connected to the irradiation target so that laser light can be input from the second rotating mirror to the optical fiber inlet, and the laser light is synchronized with the second rotating mirror. The laser ignition type engine according to claim 2, further comprising second control means for transmitting The second control means is configured to reduce the number of irradiation targets as the engine load increases and to rotate the second rotating mirror toward the optical fiber inlet corresponding to the irradiation target. 6. The laser ignition engine according to claim 5, wherein:

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