JP4731952B2 - Laser ignition device and method - Google Patents

Description

  The present invention relates to an ignition device and method for an internal combustion engine in which a fuel / air mixture is forcibly ignited and burnt in a combustion chamber, such as a gasoline engine. Specifically, the fuel / air mixture injected from the injection valve in the combustion chamber formed by the cylindrical cylinder, piston, and cylinder head is irradiated with the laser beam from the laser generator to ignite and burn the mixture. The present invention relates to a laser ignition device and method.

  In a premixed combustion engine such as a gasoline engine, generally, an air-fuel mixture is ignited by spark discharge of a spark plug. However, when the compression ratio is increased, it is near the inner wall of the cylinder far from the ignition position. The so-called end gas may self-ignite and cause knocking. In addition, since the spark plug is directly exposed to the combustion chamber, carbon may adhere to the electrode of the plug, making discharge difficult. Furthermore, it takes time and the thermal efficiency is poor until the flame ignited by the plug spreads over the entire combustion chamber.

  Therefore, as an ignition device that replaces the ignition by the spark plug, for example, a laser ignition device shown in FIG. 16 has been developed (see, for example, Patent Document 1). This is because the laser beam 52 from the laser generator 51 is divided into three beams by the beam splitters 60a and 60b and the reflecting mirrors 71a and 71b, and the lens 90 provided in the passage 81 of the cylinder head 80 is divided into three parts in the combustion chamber. It concentrates and ignites.

However, the laser ignition device that divides into three beams at the upper right of the cylinder head and collects light at three locations from the direction in which the cylinder extends (the direction in which the piston moves up and down) has several problems. That is, the three ignition positions are biased to the right side of the combustion chamber, and even if knocking due to self-ignition of the end gas can be avoided, the optimum ignition position can be obtained during stratified operation when the concentration distribution of the air-fuel mixture changes greatly in the combustion chamber Unable to drive, resulting in worse emissions and fuel consumption due to misfire. In addition, there are many and complicated elements of the optical system that divides light into three beams to collect light, and it is difficult to maintain the initial performance by continuous operation. Furthermore, the cylinder head is provided with an intake pipe, an intake valve, an exhaust pipe, an exhaust valve, etc. (not shown), and there are many restrictions on arranging the laser ignition device as shown in the figure. Therefore, it is difficult to set three ignition positions in the end gas, and knocking avoidance has a problem that lacks certainty.
JP-A-9-303244

  The present invention has been made in view of the problems of the above-described conventional laser ignition device, and realizes highly robust combustion by enabling reliable ignition independent of the mixture distribution and mixture concentration distribution in the combustion chamber. It is an object of the present invention to provide a laser ignition device and method. Another object of the present invention is to provide a laser ignition device and method capable of shortening the combustion time, improving fuel efficiency and reliably avoiding knocking.

The invention according to claim 1 which has been made to solve the problems, cylindrical cylinder, a piston, and the fuel injected from the injector in the combustion chamber formed in a cylinder head, a laser generator or is Zabimu a laser ignition device for igniting the combustion front Symbol fuel irradiation shines, the direction extending the laser beam of the cylinder (z-axis) perpendicular to the plane (x-y plane) the combustion chamber of a predetermined in Incidence means for incidence at an incidence angle, and the laser beam incident on the incidence means are sequentially reflected on the wall surface of the cylinder perpendicular to the xy plane, and from incident or reflected to the next reflected the laser and the multi-pass means for the beam to each other to cross at a plurality of points on the the x-y plane, the fuel only the intensity of the laser beam incident at the incident means by the plurality of cross points It is characterized by having a strength control means for controlling the intensity you ignition combustion.

  Ignition combustion is performed at multiple cross points in a plane orthogonal to the direction in which the cylinder extends in the combustion chamber, enabling reliable ignition without being affected by the mixture distribution or mixture concentration distribution in the combustion chamber. Highly combustible combustion can be realized. In addition, the combustion time can be shortened to improve fuel consumption and avoid knocking.

  Since the laser beam is incident on the wall surface from the direction of removing the center of the cylinder and is subjected to multiple reflection on the wall surface of the cylinder to form and ignite a plurality of cross points, it is not necessary to add a complicated optical system.

The invention according to claim 2 is the laser ignition device according to claim 1, wherein the multi-pass means includes an angle-controllable mirror disposed along a wall surface of the cylinder. It is said.

  Since the multi-pass means controls the angle of the mirror disposed along the wall surface of the cylinder to cross at a plurality of points, it can be crossed at any position. Therefore, a cross point can be formed according to the mixture distribution and the concentration distribution of the mixture in the combustion chamber, enabling more reliable ignition and realizing highly robust combustion.

The invention according to claim 3 is the laser ignition device according to claim 1 or 2 , wherein the piston has a spherical cavity on a surface forming the combustion chamber, and fuel injected from the injection valve is It is characterized by a hollow cone shape.

  When the piston has a spherical cavity and the injection valve injects fuel in a hollow cone shape, the mixture distribution is divided into multiple parts in the plane perpendicular to the direction in which the cylinder extends. Therefore, the probability of matching with the air-fuel mixture distribution increases, and more reliable ignition becomes possible.

The invention according to claim 4 is the laser ignition device according to claim 3 , wherein the incident angle is determined by the laser beam incident by the incident means and the incident point of the laser beam on the wall surface of the cylinder. The predetermined incident angle of the incident means is {90 × (1−4 / 4) when n is an integer equal to or greater than 5, that is, n = 5, 6, 7,. n)} °.

The incident angle θ is θ = {90 × (1−4 / n)} ° (1)
In this case, the polygon connecting the cross points becomes a regular n-gon, and the probability of matching the cross points can be further increased even when the mixture distribution is divided into a plurality. Note that derivation of equation (1) will be performed later.

Invention, cylindrical cylinder, a piston, and the laser generator or is Zabimu the irradiation shines in front Symbol fuel to the fuel in the combustion chamber formed in a cylinder head according to claim 5 which has been made to solve the problem Is a laser ignition method for igniting and burning the laser beam , wherein the laser beam is incident at a predetermined incident angle into the combustion chamber in a plane (in the xy plane) orthogonal to the direction in which the cylinder extends (z axis). And sequentially reflecting the laser beams incident in the incident step on the inner wall surface of the cylinder perpendicular to the xy plane, and the laser beams from the incident or reflected to the next reflected x-y and multipath step of cross at a plurality of points on a plane, said fuel only the intensity of the laser beam incident at the incident step by the plurality of cross spotting It is characterized by having a strength control step of controlling the intensity you burn.

The invention according to claim 6 is the laser ignition method according to claim 5 , wherein the multi-pass step includes controlling an angle of a mirror disposed along a wall surface of the cylinder. It is characterized by that.

Here, the above equation (1) is derived using FIG. FIG. 9 is a redraw of FIG. 8C described later. That is, the laser beam incident in the direction from P ₀ to P ₁₁ is subjected to multiple reflections on the wall surface 41 of the cylinder and multipaths in the combustion chamber 7 to form cross points Q _{11 to} Q ₁₅ , and polygons connecting the cross points Is a case of a regular pentagon.

The apex angle θ ′ of a regular n-gon is from simple geometry θ ′ = 180 × (n−2) / n = 90 × (2−4 / n)
It can be seen that In the case of n = 5, θ ′ = 108 °. In FIG. 9, ∠Q ₁₁ Q ₁₂ Q ₁₃ is θ ′, the incident angle of the laser beam is ∠OP ₁₁ P ₀ is θ, and ∠P ₁₁ Q ₁₂ Q ₁₃ is α.
α = 180−θ ′ = 90 × 4 / n
And
θ = 90−α = 90 × (1−4 / n)
Thus, equation (1) is derived.

  Ignition combustion is performed at multiple cross points in a plane orthogonal to the direction in which the cylinder extends in the combustion chamber, enabling reliable ignition without being affected by the mixture distribution or mixture concentration distribution in the combustion chamber. Highly combustible combustion can be realized. In addition, the combustion time can be shortened to improve fuel consumption and avoid knocking.

  The best mode for carrying out the present invention will be described with reference to the drawings.

(Embodiment 1)
Embodiment 1 of the laser ignition device according to the present invention will be described with reference to the drawings. 1 is a schematic configuration diagram of a laser ignition device for an engine according to the first embodiment, FIGS. 2 and 3 are AA cross-sectional views of FIG. 1, and FIG. 4 is a diagram for explaining an incident unit, FIG. These are enlarged views of intensity control means.

  In FIG. 1, 4 is a cylindrical cylinder, 5 is a piston, 6 is a cylinder head, 7 is a combustion chamber formed by an upper surface having a wall surface 41 of the cylinder 4 and a spherical cavity 51 of the piston 5 and a lower surface of the cylinder head 6, 8 Is a fuel injection valve. In FIG. 1, an intake pipe, an intake valve, an exhaust pipe, an exhaust valve, and the like are omitted.

  1 is a laser generator for generating a laser beam L, 2 is an intensity control means for controlling the intensity of the laser beam L to a predetermined intensity, and 3 is an in-plane orthogonal to the extending direction (z axis) of the cylinder 4 ( an incident means that is incident on the combustion chamber 7 at a predetermined incident angle in the xy plane).

In the laser ignition device configured as described above, the laser beam L generated from the laser generator 1 has a hole 3 or 3 ′ (see FIG. 3) formed in the cylinder 4 so that the incident angle is θ ₁ or θ ₂ . 4), and enters the intensity control means 2. That is, in this embodiment, the incident means that enters the combustion chamber at a predetermined incident angle is the hole 3 or 3 ′ formed in the cylinder 4 so that the incident angle is θ ₁ or θ ₂ .

In the laser ignition device of the present invention, it is necessary to control the laser beam intensity so that it is not ignited except at the cross point but only at the cross point. As shown in FIG. 5, the intensity control means 2 of this embodiment is a Galileo telescope comprising a convex lens 21, a concave lens 22, and a lens barrel 23. The intensity can be changed by reducing the beam diameter by the magnification. For example, if the ignition threshold intensity I _{th in} the case of thermal ignition is I _th = 6 MW / cm ² , it is necessary to control so that it becomes I _th or more at the cross point. In this embodiment, for example, a laser generator 1 that generates a laser beam L having a beam diameter of 10 mm, a power of 25 KW, and a laser beam intensity of 32 KW / cm ² is used. When a Galileo telescope having a magnification of 10 to reduce the beam diameter to 1/10 is used as the intensity control means 2, a laser beam L having a beam diameter of 10 mm, power of 25 KW, and beam intensity of 32 KW / cm ² has a beam diameter of 1 mm, power The laser beam L ′ is 25 KW and the beam intensity is 3.2 MW / cm ² . For example, if the laser beam L ′ having a beam diameter of 1 mm, a power of 25 KW, and a beam intensity of 3.2 MW / cm ² can be generated directly from the laser generator 1, the intensity control means 2 can be omitted. In that case, for example, the laser generator 1 may be disposed directly in the hole 3 or 3 ′ of the incident means.

The incident angles θ ₁ and θ ₂ of the laser beam L ′ are angles formed by a line connecting the center O of the cylinder 4 and the incident point P ₁ and the incident laser beam, and the incident laser beam does not pass through the center O of the cylinder 4. In this case, the laser beam reflected by P _{1 on} the wall surface 41 of the cylinder 4 is sequentially reflected by P ₂ , P ₃ , P ₄ , or P ₂ ′, P ₃ ′, P ₄ ′, and the laser beam L ′ is x− Multipass in the y plane. Therefore, in this embodiment, the multipath means is the wall surface 41. Since multipath is performed in the xy plane, cross points Q ₁ , Q ₂ , Q ₃ , Q ₄ , Q ₅ , or Q ₁ ′, Q ₂ ′, Q ₃ ′, Q ₄ ′, Q ₅ ′ Form.

As described above, since the beam intensity of the laser beam L ′ is 3.2 MW / cm ² , the cross points Q ₁ , Q ₂ , Q ₃ , Q ₄ , Q ₅ , or Q ₁ ′, Q ₂ ′, Q _{3 ', Q 4', Q} 5 ' at 6.4 mW / cm ^2, and the since the ignition threshold intensity I _th = 6MW / cm ² or more, to start the ignition combustion only at the cross point.

  When fuel is injected from the fuel injection valve 8 during the compression stroke and the stratified operation is performed, the mixture of the injected fuel and air is greatly influenced by the engine conditions, the airflow caused by the combustion chamber shape, and so on, so An air-fuel mixture with the optimum concentration is not formed at the position. The ignition position is preferably a region where the equivalence ratio of the air-fuel mixture is 0.5 to 2, particularly 0.8 to 1.2.

  Since it is ignited and combusted at five points crossing in the xy plane perpendicular to the z-axis perpendicular to the extending direction of the cylinder in the combustion chamber 7, it is not affected by the mixture distribution or mixture concentration distribution in the combustion chamber. Reliable ignition is possible and combustion with high robustness can be realized. In addition, the combustion time can be shortened to improve fuel consumption and avoid knocking.

As can be seen by comparing FIG. 2 and FIG. 3, when the incident angle is small (in the case of θ ₁ ), a cross point is formed near the center of the combustion chamber, and when the incident angle is large (in the case of θ ₂ ), the cross point is burned. Formed around the chamber. Therefore, when the fuel / air mixture distribution that changes depending on the fuel shape and operating conditions injected from the injection valve 8 is distributed, for example, near the center of the combustion chamber, a laser ignition device having an incident angle θ ₁ is provided. Use it.

  Note that the application of the laser ignition device of the present embodiment is not limited to a so-called spray guide, and may be applied to, for example, switch-to-burn combustion.

(Embodiment 2)
Embodiment 2 of the laser ignition device according to the present invention will be described with reference to the drawings. FIG. 6 is a schematic configuration diagram of an engine laser ignition device according to the second embodiment, FIG. 7 is an enlarged view of an intensity control unit, and FIG. 8 is a mixture when a piston has a spherical cavity and fuel is injected into a hollow cone shape. FIG. 10 is a schematic configuration diagram of a modification of the second embodiment, and is a diagram for explaining the behavior of the gas concentration distribution pattern and the correspondence between the mixture concentration distribution pattern and the cross point of the laser beam.

In FIG. 6, 4 is a cylindrical cylinder having an inner diameter R = 50 mm, 5 is a piston having a spherical cavity 51 having a radius R _c = 25 mm, 6 ′ is a cylinder head, 7 ′ is a wall surface 41 of the cylinder 4 and the piston 5 A combustion chamber, 8 ', formed by the upper surface and the lower surface of the cylinder head 6', is a fuel injection valve. In FIG. 6, the intake pipe, the intake valve, the exhaust pipe, the exhaust valve, etc. are omitted.

1 'is a laser generator, 2' is intensity control means for controlling the intensity of the laser beam to a predetermined intensity, 10 is an optical fiber for propagating the laser beam generated from the laser generator 1 'to intensity control means 2', Reference numeral 3 ″ denotes an incident means for causing the laser beam L ″ to enter the combustion chamber 7 ′ at a predetermined incident angle in a plane (xy plane) orthogonal to the direction (z axis) in which the cylinder 4 extends. in projecting means 3 '' embodiment 1 and the hole 3 drilled in the same manner as the wall of the cylinder 4 '', a line segment with the incident laser beam intensity control means 2 'connecting the center O to the incident point P ₁₁ of the cylinder 4 angle between is what attached to a predetermined angle theta (see FIG. 8 (c)). that is, the hole 3 '', the direction coincides with the direction of the incident point P _11, perpendicular to the z-axis is doing.

In the laser ignition device of the present invention, it is necessary to control the laser beam intensity so that it is not ignited except at the cross point but only at the cross point. As shown in FIG. 7, the intensity control means 2 ′ according to the present embodiment includes a collimating lens 21 ′, an emission end 101 of the fiber 10, and a lens barrel 23 ′. The intensity can be changed by increasing the beam diameter. . For example, if the ignition threshold intensity I _th ′ in the case of photochemical ignition is I _th ′ = 60 KW / cm ² , it is necessary to control so that it becomes I _th ′ or more at the cross point. In the present embodiment, for example, a laser generator 1 that generates a laser beam with a power of 250 W is used and coupled to a quartz fiber 10 having a core diameter of 100 μm. Then, the intensity control means 2 ′ having a collimating lens 21 ′ that makes the beam diameter 10 times the core diameter produces a laser beam L ″ having a beam diameter of 1 mm, a power of 250 W, and a beam intensity of 32 KW / cm ² .

8A shows the relationship between the injection valve 8 ′ and the piston 5 in FIG. 6, and FIG. 8B shows the A′-A ′ cross section of FIG. 6A. From now on, when fuel is injected into a hollow cone shape, FIG. first it annularly, then the air-fuel mixture under the influence of the air flow is divided into four, it can be seen that distributed circular cavity inner radius R _c indicated by a dotted line.

  FIG. 8 (d) shows the behavior of the air-fuel mixture when the operating conditions are changed. Depending on the operating conditions, the air-fuel mixture is not divided, and an annular shape is maintained in the circular cavity.

In this embodiment, the incident angle θ = 18 ° = {90 × (1−4 / 5) so that the polygon formed by connecting the cross points is a regular pentagon and the cross point is located at r from the center O of the cylinder. } °. That is, the laser beam incident on P ₁₁ of the wall surface 41 of the cylinder 4 at an incident angle of 18 ° is sequentially reflected by P ₁₂ , P ₁₃ and P ₁₄ , and the laser beam multipaths in the xy plane. Since multipath is performed in the xy plane, cross points Q ₁₁ , Q ₁₂ , Q ₁₃ , Q ₁₄ , and Q ₁₅ are formed. Since the incident angle θ = 18 ° = {90 × (1−4 / 5)} °, the pentagon connecting Q ₁₁ , Q ₁₂ , Q ₁₃ , Q ₁₄ , and Q ₁₅ is a regular pentagon. Become. When attention is paid to the triangle OQ ₁₂ P ₁₄ , ∠OQ ₁₂ P ₁₄ = 54 ° and ∠OP ₁₄ Q ₁₂ = 18 °.
r / sin18 = R / sin54 (2)
It can be seen that this relationship holds. Therefore, for example, when R = 50 mm, r = 19 mm. Since r (= 19 mm) <R _c (= 25 mm), as shown in FIGS. 8C and 8E, an air-fuel mixture distribution in which most of the cross points are distributed within a circle indicated by a dotted line with a radius R _c. It matches the pattern, enables reliable ignition, and realizes robust combustion. In addition, the combustion time can be shortened to improve fuel consumption and avoid knocking.

  As described above, when the incident angle θ = {90 × (1−4 / n)} °, the polygon connecting the cross points becomes a regular n-gon, and a relational expression such as Expression (2) is obtained. Therefore, the mixture distribution pattern is measured in advance, and the incident angle can be determined so that the cross point matches the pattern as much as possible.

  As shown in FIG. 10, two intensity control means 2 'may be stacked in the z-axis direction. Then, the laser beam multipaths in two planes orthogonal to the z axis, and a regular pentagon connecting the cross points in FIG. 8C can be formed in two layers in the z axis direction, and laser ignition is performed at a total of 10 points. A more reliable ignition is possible and combustion with high robustness can be realized. In this case, for example, as the laser generator 1 '', one that generates a laser beam having a power of 500 W is used, and as the fiber 10 ′, one having a Y branch that divides the propagating laser power by half. Must be used.

  Note that the application of the laser ignition device of the present embodiment is not limited to a so-called spray guide, and may be applied to, for example, switch-to-burn combustion.

(Embodiment 3)
Embodiment 3 of the laser ignition device according to the present invention will be described with reference to the drawings. 11 is a schematic configuration diagram of an engine laser ignition device according to a third embodiment, FIG. 12 is a cross-sectional view taken along the line A′-A ′ of FIG. 11, and FIGS. 13 to 15 are schematic configuration diagrams of modifications of the second embodiment. It is.

  In the first embodiment, the multipath means is the wall surface 41. However, the present embodiment is different from the first embodiment only in that the multipath means is a mirror disposed along the wall surface.

  Reference numeral 42 denotes four mirrors arranged along the wall surface 41. The reflecting surface is arranged so that the reflection surface can be controlled to rotate around an axis parallel to the z axis. That is, the four mirrors 42 are fixed after adjusting their angles so as to form cross points at predetermined positions. Reference numeral 43 denotes a window that transmits the laser beam.

  Since the multi-pass means of the laser ignition device of the present embodiment controls the angle of the mirror disposed along the wall surface of the cylinder to cross at a plurality of points, it can be crossed at an arbitrary position. Therefore, a cross point can be formed according to the mixture distribution and the concentration distribution of the mixture in the combustion chamber, enabling more reliable ignition and realizing highly robust combustion.

  As shown in FIG. 13, for example, a variable angle mirror (incident unit) 30 whose reflection surface can be controlled to rotate around an axis parallel to the z axis is disposed after the intensity control unit 2, and the combustion chamber is interposed through the window 44. 7 may be incident at a predetermined incident angle. Even if there is no mirror 42 disposed along the wall surface, the multi-path indicated by the solid line can be changed to the multi-path indicated by the dotted line by rotating the variable angle mirror 30 in the direction of the arrow, for example, and the cross point (ignition point). ) The position can be changed. Further, a mirror 42 whose reflection surface can be controlled to rotate around an axis parallel to the z axis may be disposed on the wall surface on which the laser beam is incident and reflected. Further, the cross point position can be arbitrarily changed.

  Moreover, as shown in FIG. 14, in the laser ignition device of Embodiment 3 shown in FIG. 12, the number of mirrors 42 arranged along the wall surface may be one. Even by rotating one mirror 42 in the direction of the arrow, the multipath indicated by the solid line can be changed to the multipath indicated by the dotted line, and the position of the cross point (ignition point) can be changed.

  As shown in FIG. 15, a mirror 42 that can be controlled to rotate around an axis parallel to the z-axis is disposed on the wall surface of the cylinder, and the intensity control means 2 can be rotated in the direction of the arrow about the mirror 42. A rotary stage (incident unit) 30 ′ may be provided. By combining the control of the incident angle of the laser beam L ′ by the rotary stage 30 ′ and the control of the reflection angle by the mirror 42, the cross point position can be set to an arbitrary position.

1 is a schematic configuration diagram of a laser ignition device for an engine according to Embodiment 1. FIG. It is AA sectional drawing of FIG. It is AA sectional drawing of FIG. It is a figure for demonstrating the incident means of Embodiment 1. FIG. It is an enlarged view of the intensity | strength control means of Embodiment 1. FIG. 5 is a schematic configuration diagram of an engine laser ignition device according to a second embodiment. It is an enlarged view of the intensity | strength control means of Embodiment 2. It is a figure for demonstrating the response | compatibility of the mixture concentration distribution pattern when a piston is provided with a spherical cavity, and fuel is injected in a hollow cone shape, and the correspondence between the mixture concentration distribution pattern and the cross point of a laser beam. It is the figure which redrawn FIG.8 (c) for derivation | leading-out of (1) Formula. FIG. 6 is a schematic configuration diagram of a modification of the second embodiment. FIG. 6 is a schematic configuration diagram of an engine laser ignition device according to a third embodiment. It is A'-A 'sectional drawing of FIG. FIG. 10 is a schematic configuration diagram of a modified aspect of the third embodiment. FIG. 10 is a schematic configuration diagram of another modification of the third embodiment. FIG. 10 is a schematic configuration diagram of another modification of the third embodiment. It is a block diagram of the conventional laser ignition device.

Explanation of symbols

1, 1 ′, 1 ″... Laser generator 2, 2 ′... Intensity control means 3, 3 ′, 3 ″... Incident means)
4 ... Cylinder 5 ... Piston 6 ... Cylinder head 7 ... Combustion chamber 8, 8 '... Injection valve 30 ... Variable angle mirror (incident means)
30 '... Rotary stage (incident means)
41 ..... Wall surface (multi-pass means)
42 ········· Mirror
L, L ′, L ″,... Laser beam θ, θ ₁ , θ ₂ .. Incident angle

Claims (6)

Cylindrical cylinder, a piston, and the fuel injected from the combustion chamber of the injection valve is formed in the cylinder head, a laser ignition device for igniting the combustion front Symbol fuel shines a laser generator or is Zabimu irradiation And
An incident means for causing the laser beam to enter the combustion chamber at a predetermined incident angle in a plane (in the xy plane) perpendicular to the direction in which the cylinder extends (z axis);
The laser beams incident by the incident means are sequentially reflected by the wall surface of the cylinder orthogonal to the xy plane, and the laser beams from the incident or reflected to the next reflected are xy. Multi-pass means to cross at a plurality of points on the plane;
And intensity control means for the said fuel only the intensity of the laser beam incident at an incident means by the plurality of cross point control the intensity you ignition combustion
The laser ignition device characterized in that it comprises a.   2. The laser ignition device according to claim 1, wherein the multi-pass means includes an angle-controllable mirror disposed along a wall surface of the cylinder. Said piston comprises a spherical cavity in the surface forming the combustion chamber, a laser ignition device according to claim 1 or 2 fuel injected from the injection valve, characterized in that a hollow cone shape. The incident angle is an angle formed by the laser beam incident on the incident means and a normal line of the incident point of the laser beam on the wall surface of the cylinder, and the predetermined incident angle of the incident means is 5 for n. 4. The laser ignition device according to claim 3 , wherein the integer is {90 × (1−4 / n)} °, where n = 5, 6, 7,... Cylindrical cylinder, a piston, and a laser ignition method for igniting and burning the previous SL fuel a laser generator or is Zabimu irradiation shines the fuel in the combustion chamber formed in the cylinder head,
An incident step of causing the laser beam to enter the combustion chamber at a predetermined incident angle in a plane (in the xy plane) orthogonal to a direction in which the cylinder extends (z axis);
The laser beams incident in the incident step are sequentially reflected on the inner wall surface of the cylinder perpendicular to the xy plane, and the laser beams from the incident or reflected to the next reflected are reflected in the x−. a multi-pass step that crosses at multiple points on the y-plane;
And intensity control step of the said fuel only the intensity of the laser beam which is incident at step by the plurality of cross point control the intensity you ignition combustion
Laser ignition method characterized by having a. 6. The laser ignition method according to claim 5 , wherein the multipass step includes controlling an angle of a mirror disposed along a wall surface of the cylinder.

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