JP2006242034A - Laser ignition device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laser ignition device for an internal combustion engine preventing knocking, reducing NOx and coping with operation conditions of stratified combustion and swirl gas flow. <P>SOLUTION: The laser ignition device is provided with a plurality of laser irradiating means 33a-33d arranged in a combustion chamber 15 of the internal combustion engine, irradiating laser to air fuel mixture and igniting the same, a first map storing ignitable positions in the combustion chamber, position change means 35, 37 changing focus position of laser of a plurality of the laser irradiating means based on the first map, and a timing control means 42 controlling irradiation timing of laser of a plurality of the laser irradiating means based on a second map storing ignition timing of ignition position. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a laser ignition device for an internal combustion engine, and more particularly, to a device capable of changing the focal position of a plurality of laser light irradiation means.

  2. Description of the Related Art In an internal combustion engine such as a vehicle engine, a laser ignition device that ignites a combustible air-fuel mixture (air mixture) in a combustion chamber with a laser beam is known. That is, the fuel supplied by the fuel injection valve is mixed with air in the combustion chamber, and an air-fuel mixture is formed in the combustion chamber. After the air-fuel mixture in the combustion chamber is compressed by the piston, the air-fuel mixture is ignited by the laser light emitted from the laser oscillator of the laser ignition device and condensed by the lens. The air-fuel mixture explodes and expands by ignition, and its thermal energy is used as power.

  Immediately before ignition by the laser ignition device, there are cases where a rich region with a high fuel ratio and a lean region with a low fuel ratio are unevenly distributed in the combustion chamber. In this case, the combustion speed is different between the rich area and the lean area, and knocking may occur in an area where the combustion speed is low (lean area). The occurrence of knocking reduces the engine output. In order to improve the thermal efficiency of the internal combustion engine, it is desirable to improve the combustion speed of the air-fuel mixture, for example, to drive a plurality of ignition means simultaneously. However, if the combustion rate is rapidly increased, heat is generated, the amount of NOx generated increases due to the temperature rise of the combustion gas, and exhaust emission deteriorates.

  Various techniques have been developed in the past to deal with such problems. In a conventional ignition device (see Patent Document 1), the propagation behavior of a flame after igniting an air-fuel mixture with a laser light oscillator is observed. That is, the flame propagation behavior is observed with a fiber arranged in the peripheral region of the combustion chamber, and the ignition position by the laser light oscillator is adjusted according to the result, so that the flame propagates evenly into the combustion chamber. This reduces the temperature difference in each region of the combustion chamber and prevents knocking.

Moreover, in the conventional ignition timing control apparatus (refer patent document 2), the ignition timing of the several ignition plug arrange | positioned in a combustion chamber is shifted. That is, a plurality of spark plugs are installed in the central region and the peripheral region of the combustion chamber, and the spark plugs in the peripheral region are ignited first, and the spark plugs in the central region are ignited later. In this way, rapid heat generation is avoided without lengthening the combustion period, and NOx generation is reduced.
JP-A-5-33755 JP-A-6-323230

  The first conventional example and the second conventional example have room for improvement in the following points. First, in the first conventional example, when the air-fuel mixture is heated from one place with one ignition means at the center of the combustion chamber, the combustion temperature is likely to rise rapidly, NOx is generated, and it is difficult to improve exhaust emission. . In the second conventional example, the positions of a plurality of spark plugs arranged in the periphery of the combustion chamber are fixed. For this reason, for example, under operating conditions in stratified combustion (the air-fuel mixture is concentrated in the center of the combustion chamber and the periphery is lean to the non-ignitionable region), there is a risk that the ignition plug may misfire in the lean periphery. In addition, when a swirl air flow is generated in the circumferential direction in the peripheral portion of the combustion chamber, there is a risk that the ignition means in the peripheral portion may misfire depending on the strength of the swirl air flow.

  The present invention has been made in view of the above circumstances, and provides a laser ignition device for an internal combustion engine that can prevent occurrence of knocking, reduce NOx, and can cope with the case where the operation condition is stratified combustion or swirl airflow. With the goal.

  (B) As a result of extensive research and trial and error, the present inventor has conducted a plurality of laser light irradiation means at optimal positions and times according to the mixture distribution state and engine operating state. The present invention has been completed with the idea of enabling ignition. According to a first aspect of the present invention, there is provided a laser ignition device as set forth in claim 1, wherein a plurality of laser light irradiation means are disposed in a combustion chamber of an internal combustion engine for irradiating a mixture with laser light and ignited; Laser light based on the first map storing the position, position changing means for changing the focal position of the laser light irradiation means based on the first map, and the second map storing the ignition timing at the ignition position Timing control means for controlling the irradiation time of the laser light of the irradiation means.

  According to a second aspect of the present invention, there is provided a laser light igniter according to a second aspect of the present invention, wherein a plurality of laser light irradiating means are disposed in a combustion chamber of an internal combustion engine for irradiating a mixture with laser light and ignited; Laser light based on a second map in which the measurement means for measuring the distribution, the position changing means for changing the focal position of the laser light of the laser light irradiation means based on the measurement result of the measurement means, and the ignition timing at the ignition position are stored. Timing control means for controlling the irradiation time of the laser light of the irradiation means.

  (B) Next, various aspects of the components of the laser ignition device of the present invention will be described. The fuel injection location may be an intake pipe or a combustion chamber. In the latter (in-cylinder direct injection type), the concentration of the air-fuel mixture often varies depending on the position in the combustion chamber, and this tendency is particularly noticeable in the stratified operation. It is desirable that two or more laser beams emitted from a plurality of laser beam irradiating means are focused on the periphery of the combustion chamber and one on the center by the changing means described later. It is not essential to focus on the center. Specifically, the laser beam irradiation means comprises a laser beam oscillator.

  a. The position changing means changes the focal point (ignition) position of the laser light emitted from each of the plurality of laser irradiation means based on the first map or the measurement result of the measurement means in the combustion chamber. The change in position includes both a change on the optical axis of the laser beam and a change in the direction perpendicular to the optical axis of the laser beam. Note that the optimal ignition position changes with time. The first map is created through an experiment, and memorizes positions in the combustion chamber that can be ignited according to the operating state of the internal combustion engine. The ignition position may not be a position that is too rich than the appropriate concentration, or a position that is too lean.

  Specifically, the region where the equivalence ratio in the combustion chamber is 0.5 to 2.0 is the ignitable position. The optimum position is an area where the equivalence ratio is 0.8 to 1.2. The “equivalent ratio” is the stoichiometric air-fuel ratio of the air-fuel mixture with respect to the actual air-fuel ratio of the air-fuel mixture, and the air-fuel mixture at the position where the equivalence ratio is 1 is in the stoichiometric air-fuel ratio. A region where the equivalence ratio is 1 is the optimum position, but such a region is very narrow. Therefore, the equivalence ratio is set to 0.5 to 2.0 with a certain width.

  Further, the concentration distribution of the air-fuel mixture may be measured based on the intensity of the concentration measurement laser light irradiated into the combustion chamber. For example, if the concentration measurement laser light has a wavelength near the absorption wavelength of the fuel, the intensity of the concentration measurement laser light varies depending on the fuel concentration in the combustion chamber, and the concentration distribution of the air-fuel mixture can be measured. The position changing means includes, for example, a condenser lens and driving elements, and the number thereof is the same as the number of laser light irradiation means.

  b. The timing control means determines the irradiation timing at each ignition position by the laser beams of the plurality of laser irradiation means. It is desirable to operate the laser light irradiation means at the peripheral portion first and the laser light irradiation means at the central portion later. The plurality of peripheral laser beam irradiation means may irradiate the laser beam at the same time, or may irradiate the laser beam at different times (timing). The different timing includes sequential ignition at a plurality of ignition positions and arbitrary ignition according to rich / lean or the like.

  The irradiation timings of the plurality of laser beam irradiation means in the central portion and the peripheral portion can be determined based on the second map in which the relationship between the operating state of the internal combustion engine and the ignition timing at the ignition position is stored. This second map was created through experiments, and the appropriate ignition timing at the ignitable position is memorized in consideration of the engine speed, rich lean in the combustion chamber, stratified combustion and swirl airflow, etc. Yes.

  According to the laser ignition device of the first invention, the mixture is ignited by irradiating the mixture with the laser beam at the optimum timing based on the first map and the second map from the plurality of laser beam irradiation means, so that knocking is performed. Can be prevented and NOx can be reduced. According to the laser ignition device of the second invention, in addition to the effect of the first invention, it is possible to accurately measure the distribution of the air-fuel mixture in the combustion chamber, so that the ignition position and timing become more accurate.

  According to the laser ignition device of the third aspect, since the first map is created based on the operating state of the engine, the ignition position is accurately determined. According to the laser ignition device of the fourth aspect, since one ignition position is arranged in the central portion of the combustion chamber and a plurality of ignition positions are arranged in the peripheral portion, various rich regions and lean regions in the combustion chamber can be dealt with. According to the laser ignition device of the fifth aspect, since the air-fuel mixture is first ignited at the peripheral ignition position and then ignited later at the central ignition position, the temperature rise of the entire combustion chamber becomes moderate.

  According to the laser ignition device of the sixth aspect, since the air-fuel mixture is first ignited at the peripheral ignition position and then ignited later at the central ignition position, the temperature increase in the entire combustion chamber is moderated. In addition, since the air-fuel mixture is ignited at different timings at the peripheral ignition position, it is advantageous when the rich region and the lean region are unevenly distributed in the circumferential direction or when a swirl airflow is applied. According to the laser ignition device of the seventh aspect, since the second map is determined by the relationship between the operating state of the internal combustion engine and the ignition timing at the ignition position, the air-fuel mixture can be ignited at the optimal position and at the optimal timing.

  The best mode in which the laser ignition device of the present invention is applied to an in-cylinder direct injection internal combustion engine for automobiles will be described below with reference to the drawings.

<First best mode>
(Constitution)
FIG. 1 shows an in-cylinder direct injection internal combustion engine (hereinafter referred to as “engine”). In this engine, a piston 13 is slidably engaged with a cylinder bore 11 of a cylinder block 10. A cylinder head (not shown) covers the cylinder block 10 and defines a combustion chamber 15. An intake pipe 21, an exhaust pipe 24, a fuel injection valve 27, and a laser beam irradiator 30 are attached to the cylinder head 10. The fuel injection valve 27 is disposed in the vicinity of the intake valve 22, and the laser beam irradiator 30 is disposed between the intake valve 22 and the exhaust valve 25.

  The intake port of the intake pipe 21 that sucks in air is opened and closed by the intake valve 22, and the exhaust port of the exhaust pipe 24 that exhausts combustion gas (exhaust gas) is opened and closed by the exhaust valve 25. A fuel injection valve 27 connected to the fuel tank directly injects fuel into the combustion 15 chamber. The laser beam irradiator 30 irradiates the gas mixture in the combustion chamber 15 with a laser beam and ignites it.

  Next, the laser beam irradiator 30 shown in FIG. 2 is provided in a cylindrical housing 31 with four laser beam generators 33a, 33b, 33c and 33d, four condensing lenses 35, four sets of driving elements 37 and protection. Glass 36 is built in. The housing 31 is fixed to the cylinder head such that a cylindrical tip portion (lower end portion in FIGS. 1 and 2) 32 protrudes into the combustion chamber 15. The laser light generators 33a to 33d are controlled by a control device (not shown) to generate laser light. A condensing lens 35 made of a convex lens is fixed to the distal end portion 32 of the housing 31 and is independently driven by a drive element 37 to change each condensing position.

  One drive element 37 composed of a piezo element or the like is disposed on each of one side and the other side of the condenser lens 35. Specifically, one end side of the drive element 37 is in contact with the condensing lens 35 and the other end side is in contact with a part of the housing 31, and the condensing lens 35 is moved by driving of the driving element 37 controlled by the control device. . When the condenser lens 35 moves, the focal position of the laser beam condensed by the condenser lens 35 moves. The laser beam irradiator 30 and the control device constitute the laser ignition device of the present invention.

(Function)
Next, the operation of the laser ignition device will be described. After an air-fuel mixture is formed by the air sucked from the intake pipe 21 and the fuel injected from the fuel injection valve 27, the laser light is condensed from the laser light irradiator 30 into the combustion chamber 15 and ignited. That is, as shown in FIG. 3, four laser light generators 33a to 33d, four condensing lenses 35 and four sets of drive elements 37 cause four focal positions (ignition points) from four irradiation windows 38 to the combustion chamber 15. Position) a, b, c and d are formed. The optimum focus position is determined by the first map of the control device, and the condensing lens 35 is driven by the drive element 37 so that the focus position of the laser beam coincides with the optimum focus position. Here, one focal position a is disposed at or near the center 16a of the combustion chamber 15, and three focal positions b, c, and d are disposed circumferentially away from the peripheral section 16b.

  First, the air-fuel mixture is ignited simultaneously at the ignition positions b, c, and d of the peripheral portion 16b, and the air-fuel mixture is ignited at the ignition position a of the central portion 16a after a predetermined time has elapsed. The air-fuel mixture in the combustion chamber 15 is combusted by ignition, the piston 13 is reciprocated by the thermal energy, and a crankshaft (not shown) that is an output shaft of the engine rotates. The exhaust gas after the air-fuel mixture burns is exhausted from the exhaust pipe 24.

(effect)
According to this best mode, the three ignition positions b, c, and d of the outer peripheral portion 16b of the combustion chamber 15 can be selected as the optimum positions by the first map. Further, after igniting simultaneously at the ignition positions b, c and d of the outer peripheral portion 16b, ignition is performed at the ignition position a of the central portion 16a, and the flame is centered from the peripheral portion of the combustion chamber 15 as shown in FIG. Since it progresses toward the direction, the flame area decreases as time elapses. As a result, the combustion period is shortened and the peak of the heat generation rate can be suppressed. That is, the heat generation rate becomes smooth as indicated by i in FIG. 4A, thereby making it possible to achieve both prevention of knocking and reduction of NOx.

  On the other hand, in the first conventional example, the spark plug or the like ignites the air-fuel mixture at one location in the center of the combustion chamber. In this case, as shown in FIG. 4C, flame propagation proceeds from the central portion of the combustion chamber 15 to the peripheral portion, so that the flame area increases as time elapses. As a result, the heat generation rate becomes partly steep as indicated by j in FIG.

<Second best mode>
(Constitution)
In the second best mode, the laser beam irradiation timing at the peripheral portion 16b of the combustion chamber 15, that is, the ignition timing of the air-fuel mixture is shifted as compared with the first best mode. Hereinafter, the first best mode and common parts will be described briefly, and different configurations will be mainly described.

  In the actual air-fuel mixture in the combustion chamber 15, there are cases where a rich region where the fuel ratio is large and a lean region where the fuel ratio is small are unevenly distributed in the circumferential direction of the peripheral portion due to the engine speed and load. . In this case, if ignition is performed simultaneously at the ignition positions b, c, and d of the peripheral portion 16b, the combustion speed at each ignition position varies depending on the degree of rich / lean, resulting in a decrease in thermal efficiency or in a region where the combustion speed is slow. There is a risk of knocking.

  Further, as in the stratified combustion shown in FIG. 5, the concentration of the air-fuel mixture is different between the central portion 16a and the peripheral portion 16b of the combustion chamber 15, and the rich region and the lean region are unevenly distributed in the peripheral portion 16b. Furthermore, as shown in FIG. 6, when a circumferential air flow is forcibly generated in the combustion chamber 15 by a swirl or the like, the flow velocity increases as the air travels from the central portion 16a to the peripheral portion 16b.

  Considering these, in the second best mode, the ignition timing for the air-fuel mixture at the plurality of ignition positions of the outer peripheral portion 16b is shifted. First, the control device 40 for controlling the laser beam irradiator 30 will be described with reference to FIG. The control device 40 includes a timing control unit 42 and a position control unit 45. The timing control unit 42 determines the ignition timing based on the operating state of the engine and controls the generation timing of the laser beam from the laser beam generator 30. "Operating state" refers to engine speed, stratified operation mode on / off, oil / water temperature, injection timing or swirl valve opening, intake pipe negative pressure or intake air amount to determine engine load, The throttle opening.

  The position control unit 45 controls driving of the drive element 37, and stores an information input unit 46 to which information related to the operating state of the engine is input, a first map related to the optimum focal position of the laser beam, and a second map related to the optimum time. A map storage unit 47, a position determining unit 48 for determining the optimum focal position of the laser beam, and a movement control unit 49 for moving the focal position of the laser beam.

  The first map and the second map stored in the map storage unit 47 will be described in detail. As described above, the state of the air-fuel mixture in the combustion chamber 15 immediately before ignition varies greatly depending on the operating condition of the engine, and a lean region or a rich region is generated in the combustion chamber 15 depending on the operating condition. Therefore, the relationship between the engine operating conditions and the air-fuel mixture concentration distribution is measured in advance by experiments or the like, and the first map and the second map are created by mapping the position and timing that can be ignited with respect to the rotational speed, and stored in the map. Stored in the unit 47. For example, as shown in FIG. 8A, if the equivalence ratio of the air-fuel mixture is different, the combustion rate changes. Further, when an air flow such as a swirl flow is forcibly generated in the combustion chamber 15 using a swirl valve or the like, the flame may blow out depending on the ignition position, as shown in FIG. Therefore, the map storage unit 47 stores the ignition position and timing relative to the swirl valve opening.

(Function)
Next, the operation of the second best mode will be described. In the control flowchart shown in FIG. 9, first, engine operating conditions are read from the information input unit 46 in step S11. The operating conditions to be read are, for example, the rotational speed, stratified operation mode on / off, swirl valve opening, and the like. Next, in step S12, using the first map in the map storage unit 47, the position determination unit 48 calculates the optimum ignition position that can be ignited according to the engine operating conditions. Next, in step S <b> 13, the movement control unit 49 changes the focus position by changing the inclination of the condenser lens 35 by the driving element 37 of the laser beam irradiator 30.

  Subsequently, in step S14, the optimal ignition timing at each ignition position of the plurality of laser irradiators 30 is calculated from the second map of the map storage unit 47. Basically, the ignition ratio is advanced as the equivalence ratio is richer or leaner than the appropriate concentration, and as the flow rate of the swirl airflow is slower. Next, in step S15, the timing control unit 42 irradiates the laser beam from the laser beam generators 33a to 33d to the optimum focus position.

(effect)
According to the second best mode, the air-fuel mixture can be ignited by irradiating the optimum place with the laser light at the optimum time according to the operating state of the engine or the like. For example, in the case of stratified combustion shown in FIG. 5, the ignition is performed first at the outer peripheral portion 16b of the combustion chamber 15, and then ignited later at the central portion 16a. Is provided.

  Further, when the genuine concentration region, the rich region, and the lean region are unevenly distributed in the circumferential direction at the peripheral portion 16b of the combustion chamber 15 due to the engine speed and the load, the rich region or the lean region is more than the genuine concentration region. Ignite first. In the rich region and the lean region, the lean region is ignited first and the rich region is lit later. As a result, NOx reduction and knocking prevention can be realized.

  Furthermore, the ignition timing can be determined in consideration of the swirl airflow shown in FIG. That is, when the swirl flow forcibly applied to the peripheral portion 16b of the combustion chamber 15 by the swirl valve is ignited, the flame spreads along the swirl flow. Therefore, the ignition positions b, c, and d of the peripheral portion 16b are ignited in the order facing the swirl flow (d → c → b).

  In this way, by shifting the ignition timing at the three ignition positions b, c, and d of the peripheral portion 16b of the combustion chamber 15, the flame spread is not biased in the combustion chamber, and stable combustion is always obtained. At the same time, the occurrence of knocking can be suppressed. As a result, it is possible to ignite reliably even under engine operating conditions where there is a possibility that combustion cannot be performed at a fixed ignition position such as a plurality of spark plugs as in the second conventional example, and the effect of improving thermal efficiency and exhaust emission can be obtained.

<Third best mode>
The third best mode in which the method for measuring the concentration distribution of the air-fuel mixture at each ignition position is modified will be described below. In the first and second best modes, the measurement results measured in advance by experiments or the like are mapped. Instead, in the third best mode shown in FIGS. 10 and 11, the concentration distribution of the air-fuel mixture in the combustion chamber 15 is directly measured. More specifically, a measurement laser irradiator 80 is disposed radially inward of the combustion chamber 15 between the cylinder block 10 and the cylinder head, and irradiates a laser beam in a sheet shape on the upper portion of the combustion chamber 15. A measuring instrument 82 that receives the laser beam is arranged at a portion facing the laser beam irradiator 80 in the diameter direction.

  A control flowchart of this modification is shown in FIG. After capturing the engine operation information in step S21, measurement laser light is emitted from the laser light irradiator 80 in step S22. Based on this, the concentration distribution of the air-fuel mixture is calculated in step S23. That is, immediately before the ignition timing of the air-fuel mixture by the ignition laser beam irradiator 30, the laser beam near the absorption wavelength of the fuel is irradiated from the measurement laser beam irradiator 80 into the combustion chamber 15 in a sheet shape. Since the irradiated measurement laser beam is absorbed by the fuel, the intensity at the measuring instrument 82 changes according to the fuel concentration.

  Next, in step S24, the drive element 37 is controlled to change the focal position of the condenser lens 35, that is, the ignition position. Finally, in step S25, ignition timing at each ignition position is calculated based on the map. That is, the concentration distribution is taken into the measuring device 82, and the position and timing of the optimum fuel concentration for ignition are found based on the result, and ignition is performed. According to the third best mode, since the concentration distribution in the combustion chamber 15 is measured, the determination of the ignition position and the ignition timing becomes more accurate. In addition, since it is not necessary to create the first map and the second map in advance, it is possible to save labor.

<Modification>
The first to third best modes can be modified as follows. For example, there are cases where ignition is performed only at the peripheral portion 16b of the combustion chamber 15 and not at the central portion 16a. In this case, the number of ignition positions can be changed in the range of 2 to 8. Further, when ignition is performed at the peripheral portion 16b and the central portion 16a of the combustion chamber 15, the number of ignition positions of the peripheral portion 16b can be changed to 2, 4, 5,. Can be changed to Further, as shown in FIG. 12, four ignition positions m are arranged on the outer peripheral portion 16b of the combustion chamber 15, and three ignition positions n are arranged on the radial intermediate portion 16c, thereby forming a double (concentric circle) shape. Also good.

  In either case, the same number of laser oscillators as the number of ignition positions are arranged, or the laser beams of the laser oscillators less than the number of ignition positions and the number are split into the same number of laser lights as the ignition positions by the optical system. Also good.

It is a whole explanatory view of the first best mode. (A) is a principal part longitudinal cross-sectional view of the laser beam irradiator of the 1st best form, (b) is a perspective view similarly. It is explanatory drawing of the ignition position by the laser beam irradiator of the 1st best form. (A) is a graph showing the relationship between time and calorific value in the first best mode and the conventional example, (b) is an explanatory diagram of flame propagation in the first best mode, and (c) is in the conventional example. It is explanatory drawing of propagation of a flame. It is explanatory drawing of the stratified combustion in the 2nd best form. It is explanatory drawing of the swirl airflow in the 2nd best form. It is a block diagram which shows the control apparatus of the 2nd best form. (A) is a graph which shows the relationship between the equivalence ratio in the 2nd best form, and combustion temperature, (b) is a graph which shows the relationship between the flow velocity of airflow, and combustion temperature. It is a flowchart explaining the effect | action of a 2nd best form. It is whole explanatory drawing of the 3rd best form. It is a flowchart explaining the effect | action of the 3rd best form. It is explanatory drawing of the ignition position in a modification.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10: Cylinder 15: Piston 16a: Center part 16b: Peripheral part 22: Intake valve 25: Exhaust valve 30: Laser beam irradiation device 33a to 33d: Laser beam generator 45: Condensing lens 37: Drive element 40: Control apparatus 42 : Time control unit 45: Position control unit 47: Map storage unit

Claims (7)

A plurality of laser light irradiation means (33a to 33d) disposed in the combustion chamber (15) of the internal combustion engine, for irradiating and igniting the mixture with laser light;
A first map in which the ignitable positions in the combustion chamber are stored;
Position changing means (35, 37) for changing the focal position of the laser beam of the laser beam irradiation means based on the first map;
A timing control means (42) for controlling the laser light irradiation timing of the laser light irradiation means based on the second map in which the ignition timing at the ignition position is stored;
A laser ignition device for an internal combustion engine, comprising: A plurality of laser light irradiation means (33a to 33d) disposed in the combustion chamber (15) of the internal combustion engine, for irradiating and igniting the mixture with laser light;
Measuring means (80, 82) for measuring the concentration distribution of the air-fuel mixture in the combustion chamber;
Position changing means (35, 37) for changing the focal position of the laser light of the laser light irradiation means based on the measurement result of the measuring means;
A timing control means (42) for controlling the laser light irradiation timing of the laser light irradiation means based on the second map in which the ignition timing at the ignition position is stored;
A laser ignition device for an internal combustion engine, comprising:   2. The laser ignition device according to claim 1, wherein the first map stores a position in the combustion chamber that can be ignited according to an operating state of the internal combustion engine.   3. The laser ignition according to claim 1, wherein the position changing means forms a single focal position in the central portion (16 a) of the combustion chamber and a plurality of focal positions separated in the circumferential direction in the peripheral portion (16 b). apparatus.   5. The laser ignition of the internal combustion engine according to claim 4, wherein the timing control unit simultaneously irradiates a laser beam from a plurality of the laser beam irradiation units in a peripheral portion and thereafter irradiates a laser beam from the laser beam irradiation unit in a central portion. apparatus.   5. The internal combustion engine according to claim 4, wherein the timing control unit irradiates the laser beams of the plurality of laser beam irradiation units in the peripheral portion at different timings, and thereafter irradiates the laser beams of the laser beam irradiation unit in the central portion. Laser ignition device.   The laser ignition device for an internal combustion engine according to claim 5 or 6, wherein the second map stores a relationship between an operating state of the internal combustion engine and an ignition timing at the ignition position.

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