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EP1519038B1 - Laser ignition device for combustion engine - Google Patents

Laser ignition device for combustion engine Download PDF

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Publication number
EP1519038B1
EP1519038B1 EP03021446A EP03021446A EP1519038B1 EP 1519038 B1 EP1519038 B1 EP 1519038B1 EP 03021446 A EP03021446 A EP 03021446A EP 03021446 A EP03021446 A EP 03021446A EP 1519038 B1 EP1519038 B1 EP 1519038B1
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EP
European Patent Office
Prior art keywords
laser
ignition device
cooling
resonator
laser crystal
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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EP03021446A
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German (de)
French (fr)
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EP1519038A1 (en
Inventor
Ernst Dipl.-Ing.Dr. Winklhofer
Georg Dipl.-Ing. Franz
Gerhard Dipl.-Ing. Kroupa
Volker Mannheim
Alfred Dipl.Ing. Binder
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AVL List GmbH
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AVL List GmbH
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Publication date
Application filed by AVL List GmbH filed Critical AVL List GmbH
Priority to DE50304768T priority Critical patent/DE50304768D1/en
Priority to EP03021446A priority patent/EP1519038B1/en
Priority to AT03021446T priority patent/ATE337486T1/en
Priority to EP03450285A priority patent/EP1519039A1/en
Priority to US10/573,115 priority patent/US7499477B2/en
Priority to PCT/AT2004/000320 priority patent/WO2005028856A1/en
Priority to JP2006527218A priority patent/JP4477636B2/en
Publication of EP1519038A1 publication Critical patent/EP1519038A1/en
Application granted granted Critical
Publication of EP1519038B1 publication Critical patent/EP1519038B1/en
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02P—IGNITION, OTHER THAN COMPRESSION IGNITION, FOR INTERNAL-COMBUSTION ENGINES; TESTING OF IGNITION TIMING IN COMPRESSION-IGNITION ENGINES
    • F02P23/00—Other ignition
    • F02P23/04—Other physical ignition means, e.g. using laser rays
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
    • F02B23/00—Other engines characterised by special shape or construction of combustion chambers to improve operation
    • F02B23/08—Other engines characterised by special shape or construction of combustion chambers to improve operation with positive ignition

Definitions

  • the invention relates to a laser ignition device for an internal combustion engine, according to the preamble of patent claim 1.
  • US 6,514,069 B1 discloses a laser ignition device which consists of an ignition laser and an excitation laser having a pump light source. Only the ignition laser is housed in a cylindrical tube, which corresponds to a spark plug well. The excitation laser, however, is spatially separated from the ignition laser and connected to this via optical fiber.
  • a laser ignition device for an internal combustion engine wherein the resonator of the laser including photo-optical focusing device is screwed into a cylinder head bore so that the ignition device opens directly into the combustion chamber.
  • the laser ignition device uses the principle of a solid-state laser with a pulsed pump light source. This has the advantage that high pulse energies can be achieved with relatively little expenditure of energy.
  • a pump light source while a flash lamp is used.
  • an actively switchable Q-switch is used. In the so-called "Q-switching", the energy is stored during the pumping of the active medium in the laser cavity and released during a very short emission time. This results in an extremely high-energy laser pulse.
  • the photo-optical device of the known laser ignition device has three lenses. Together with the active Q-switch and by a flash lamp formed pump light source results in the most serious disadvantage that the device can not be housed entirely in a screwed into a spark plug shaft component. About the required for pumped solid state lasers cooling the laser crystal and the light source of the document no information can be found.
  • US Pat. No. 6,413,077 B1 describes a laser ignition device in which a plurality of lasers, namely an excitation laser and an ignition laser, are used. By means of a Q-switch, the pulses of the excitation laser and the ignition laser are added up and thus the energy density required for an ignition is provided.
  • This known ignition device has the disadvantage of a very high design effort and requires too much space to be used instead of a spark plug in an internal combustion engine can.
  • the use of laser ignition instead of spark ignition offers a number of advantages.
  • the relatively freely selectable location of the ignition plasma does not require any material structure which could disturb the combustion process.
  • the choice of the ignition location allows an optimization of the combustion process, possibly also a multiple ignition.
  • the high ignition pressures, such as occur in gas engines, are contrary to the laser ignition, since the required pulse energy decreases at higher pressures.
  • the laser ignition ignites even lean mixtures, resulting in very low NO x emissions.
  • the object of the invention is to provide a suitable for practical use in internal combustion engine laser ignition device, which takes up little space and which can be used with little design effort in internal combustion engines.
  • the pump diodes used as a pump light source have the advantage of higher efficiency compared to flash lamps.
  • the laser diodes are operated pulsed with a pulse energy of a few mJ and about 100-200 ⁇ s, whereby the power per diode is limited to a few 10W.
  • High-power laser diodes consist of an array of many single diodes and thus achieve a very high pulse energy. Due to the large emission area and the non-continuous distribution (low quality), the laser beam can only be focused very badly. Due to the long resonator, a much higher beam quality and thus a smaller focus diameter can be achieved with a solid-state laser
  • the pulsed solid-state laser used for the laser ignition device according to the invention is composed of the four main components pump diode, crystal rod, resonator with Auskoppelapt, Q-switch and focusing device.
  • the radiation of the pump diodes stimulates metastable energy levels in the laser crystal and thus stores the energy. Due to a low spontaneous emission, the laser crystal begins to emit light at the laser wavelength (1064nm).
  • the laser crystal is embedded in an optical resonator whose quality is increased in a pulse-like manner with the Q-switch when the desired power density is reached.
  • the geometry of the resonator results from the requirement that the pump diodes must be arranged at the upper end of the spark plug well. To achieve a high quality, the largest possible distance between the laser crystal and the output mirror is necessary. This results in the elongated design, with the head area with laser crystal at one end and the output mirror at the other end of a tube.
  • the pump diodes Since the wavelength of the pump diodes changes with the temperature of the laser substrate and the laser crystal has only a very narrow absorption line, the pump diodes must be thermally stabilized. Investigations have shown that at least two, preferably three different cooling systems for thermal stabilization of the resonator are advantageous. For at least one cooling system, the temperature-controlled cooling water of the internal combustion engine offers. However, since the pump diodes must be operated at a much lower temperature level than the cooling water temperature, the use of thermoelectric cooling elements (Peltier cooling elements) is required in this case. At least one cooling system therefore has at least one Peltier cooling element. It is provided that for cooling the laser crystal and / or the pump diodes, the resonator has a first inner coolant circuit.
  • the heat of the inner circuit is derived via a heat spreader to at least one Peltier cooling element. It is particularly advantageous if the resonator has at least one outer second coolant circuit for heat removal from the Peltier cooling element. At least one of the cooling systems can also be designed to warm the pump diodes. It is particularly advantageous if, during a cold start, the pump diodes can be heated by the Peltier cooling element to the operating temperature.
  • the laser crystal can consist of either ND: YAG (neodymium: YAG) or ND: YVO 4 (neodymium: vanadate).
  • ND: YAG is widely used, inexpensive and mechanically strong, but has a much narrower absorption line than ND: YVO 4 .
  • the use of ND: YAG laser crystals thus requires a particularly good cooling device.
  • a very effective heat removal from the laser crystal is achieved when the laser crystal is surrounded by at least one preferably annular first cooling channel.
  • a plurality of pump diodes are arranged concentrically around the laser crystal, wherein preferably at least three, more preferably at least six pump diodes are arranged uniformly around the laser crystal.
  • the pump diodes are advantageously connected in series.
  • the laser crystal is thus pumped laterally by the pump diodes, that is radially.
  • several rings of pump diodes can also be arranged concentrically one behind the other around the laser crystal.
  • water can be used at least for the second outer cooling circuit.
  • the laser ignition device 1 consists of the main components laser crystal 2, pump light source 30, passive Q-switch 4, tube 5, Auskoppelapt 6 and focusing 7 with a focus lens 8, and a cooling device 11th
  • a high efficiency can be achieved if the pump light source 30 is formed by pump diodes 3.
  • the laser crystal 2 Via the irradiation of the pump diodes 3 (808nm), metastable energy levels in the laser crystal 2 are excited and the energy is thus stored. Due to a low spontaneous emission, the laser crystal 2 emits light at the laser wavelength (1064nm).
  • the laser crystal 2 is embedded in an optical resonator 9 whose quality is increased in a pulse-like manner with the passive Q-switch 4 when the desired power density is reached.
  • a short, strong laser pulse 26 is obtained at the outcoupling mirror 6.
  • Individual pump diodes 3 are connected in series and arranged annularly laterally around the laser crystal 2.
  • the pump diodes 3 must be operated at relatively low temperature of about 30 ° C due to greatly reduced lifetime at higher operating temperature. In addition, the wavelength of the pump diodes 3 changes with the temperature. Since the rod-shaped laser crystal 2 consisting of neodymium: YAG (ND: YAG) has only a very narrow absorption line, the pump diodes 3 must be thermally stabilized. For this purpose, the cooling device 11 is provided in the head region 10 of the laser ignition device 1.
  • the cooling device 11 includes three different cooling systems A, B, C.
  • the first cooling system A has annularly distributed around the heat spreader 28 Peltier cooling elements 12.
  • further cooling systems B, C with two liquid cooling circuits 13, 14 are provided.
  • the coolant of the cooling circuit 13 flows through the head part 10 substantially in the direction of the axis 1 a of the laser ignition device 1.
  • the first cooling circuit 13 has the task to thermally stabilize the laser crystal 2 and to transfer its heat loss to the heat spreader 28.
  • the laser crystal 2 is surrounded by at least one first cooling channel 16, which may be formed as an annular channel, as can be seen from Fig.7. Instead of an annular channel, a plurality of first inlet channels 16 may be arranged around the laser crystal 2. Via at least one inlet opening 19a and one distributor ring space 19, the coolant is supplied to the first cooling channel 16, and discharged again via a collecting ring space 20 and outlet openings 20a.
  • the heat loss of the laser crystal 2 is at least partially transmitted when flowing through the annular spaces 19, 20 to the flange plate 17 and the connection plate 23, these in turn transmit the heat by heat conduction to the heat spreader 28th
  • the heat spreader 28 may have axial cooling channels 15, as indicated in Fig. 4 and 6 by dashed lines.
  • the cooling medium enters through the access openings 19a in the Verteilerringraum 19, flows through the first cooling channels 15 of the heat spreader 28 and is passed via the transfer channel 18 in the cooling channel 16. Thereafter, it flows through the collecting ring space 20 and outlet openings 20a to an external pump.
  • the second cooling circuit 14 has inlet openings 21 in the outer heat exchanger 29, which lead to second cooling channels 24 and on to outlet openings 22.
  • the coolant formed for example by water passes through the inlet openings 21 into the second cooling channels 24, flows through the outer heat exchanger 29 and leaves the laser ignition device 1 again in the region of the outlet openings 22. Cooling elements 12 discharged via the outer heat exchanger 29.
  • the three cooling systems A, B, C - namely Peltier cooling elements 12, the first cooling circuit 13 and second cooling circuit 14 - existing cooling device 11, it is possible, as a material for the laser crystal 2, the widely used, inexpensive and mechanically strong neodymium: YAG and to use pump diodes 3 as the pump light source.
  • the pump diodes 3 can be thermally stabilized to about 30 ° C, which has an advantageous effect on their life.
  • it can be achieved by the thermal stabilization that the wavelength of the pump diodes 3 always remains within the narrow absorption line of the laser crystal 2.
  • the laser crystal 2 is mirrored in the area of the end-side connection plate 23 for the laser wavelength (1064 nm) and antireflective coated on the other end.
  • the shape of the laser ignition device 1 results from the requirement that it should be mounted instead of a spark plug in the spark plug well 31 of a cylinder head 32 and from the boundary condition that the pump diodes 3 in the head region 10 of the laser ignition device 1 must be arranged.
  • the Auskoppelspiegel 6 is therefore arranged in the foot region 25 of the laser ignition device 1 near the combustion chamber.
  • the focusing device 7 Shortly after the Auskoppelspiegel 6 is the focusing device 7 with a single focus lens 8, which simultaneously forms the window to the combustion chamber and is designed as a plano-spherical lens.
  • sapphire is suitable.
  • the second cooling circuit 14 may be coupled to the existing water cooling of the engine.
  • For the first cooling circuit higher optical, qualitative and thermal conditions have to be fulfilled, so that a separate coolant is required here.
  • the pump diodes 3 must be operated at a higher operating temperature at about 30 ° C due to greatly reduced lifetime.
  • the waste heat flow is derived via a heat spreader 28, which consists of copper, to the Peltier cooling elements 12, which transform the heat flow to the temperature level of the engine cooling water and deliver it via the outer heat exchanger 29 thereto.
  • the wavelength of the pump diodes 3 shifts with temperature and the absorption band of the laser crystal 2 is extremely narrow, a fast and accurate temperature control must be provided.
  • the temperature on the cold side should deviate by a maximum of +/- 1.5 ° C from the nominal value. To this To reach the Peltier cooling elements 12 are operated with at least one temperature sensor and a power source in a closed loop.
  • the laser crystal 2 Via the preferably six pump diodes 3 arranged around the laser crystal 2, light pulses are supplied to the laser crystal 2. Via the irradiation of the pump diodes 3 (808nm), metastable energy levels in the laser crystal 2 are excited and the energy is thus stored. Due to a low spontaneous emission, the laser crystal 2 emits light at the laser wavelength (1064nm). For amplification and coherence of the light, the laser crystal 2 is embedded in an optical resonator 9 whose quality is increased in a pulse-like manner with the passive Q-switch 4 when the desired power density is reached. As a result, a high, short laser pulse 26, which is focused via the focusing lens 8 in a focal point 27, is obtained at the outcoupling mirror 6.
  • the laser ignition device 1 can be arranged entirely in the spark plug shaft 31 of a cylinder head 32 of an internal combustion engine.
  • the laser ignition device 1 is thus suitable for use in existing conventional cylinder head concepts for spark-ignition internal combustion engines.
  • the focusing lens 8 is flush with the cylinder head cover surface 34 toward the combustion chamber 33.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Lasers (AREA)
  • Combustion Methods Of Internal-Combustion Engines (AREA)

Abstract

The device has a switched pumped solid laser with a light source, and a solid laser crystal enclosed in a resonator (9). A quality switch (4) increases power density, and a focusing device (7) focuses a laser beam into a combustion chamber. The source, resonator, crystal, switch, focusing device, an output mirror and a cooling device (11) that cools the resonator, are integrated into a single unit in a spark plug shaft of an engine.

Description

Die Erfindung betrifft eine Laser-Zündeinrichtung für eine Brennkraftmaschine, gemäß dem Oberbegriff von Patentanspruch 1.The invention relates to a laser ignition device for an internal combustion engine, according to the preamble of patent claim 1.

Die US 6,514,069 B1 offenbart eine Laserzündeinrichtung, welche aus einem Zündlaser und einer eine Pumplichtquelle aufweisenden Anregungslaser besteht. Nur der Zündlaser ist in einem zylindrischen Rohr unterbringbar, welches einem Zündkerzenschacht entspricht. Der Anregungslaser hingegen ist räumlich getrennt vom Zündlaser angeordnet und mit diesem über Lichtleiter verbunden.US 6,514,069 B1 discloses a laser ignition device which consists of an ignition laser and an excitation laser having a pump light source. Only the ignition laser is housed in a cylindrical tube, which corresponds to a spark plug well. The excitation laser, however, is spatially separated from the ignition laser and connected to this via optical fiber.

Weiters ist es aus der Veröffentlichung XP 002304489, Walter KÖCHNER, "Solid State Laser Engineering", 1992, Sringer-Verlag, Germany, 3rd Edition, ISBN 0-387-53756-2 (Seite 337, Absatz 6.3.1 - Seite 352) bekannt, Kühleinrichtungen im Zusammenhang mit Festkörperlasern einzusetzen, um die Temperatur zu stabilisieren. Die beschriebenen und gezeigten seitlich gepumpten und gekühlten Festkörperlaser eignen sich auf Grund ihrer Baugröße und Komplexität aber nicht ohne weiteres für den Einsatz als in einem Zündkerzenschaft unterbringbare Laserzündeinrichtung für eine Brennkraftmaschine.It is further known from the publication XP 002304489, Walter Koechner, "Solid State Laser Engineering", 1992, Sringer-Verlag, Germany, 3 rd Edition, ISBN 0-387-53756-2 (page 337, paragraph 6.3.1 - Page 352 ) known to use cooling devices in connection with solid-state lasers to stabilize the temperature. The described and laterally pumped and cooled solid-state lasers are due to their size and complexity but not readily suitable for use as housed in a spark plug shaft laser ignition device for an internal combustion engine.

Aus der US 4,416,226 ist eine Laser-Zündeinrichtung für eine Brennkraftmaschine bekannt, wobei der Resonator des Lasers samt fotooptischer Fokussiereinrichtung in eine Zylinderkopfbohrung so eingeschraubt ist, dass die Zündeinrichtung direkt in den Brennraum einmündet. Die Laser-Zündeinrichtung wendet dabei das Prinzip eines Festkörperlasers mit einer gepulsten Pump-Lichtquelle an. Dies hat den Vorteil, dass mit relativ geringem Energieaufwand hohe Pulsenergien erreicht werden können. Als Pump-Lichtquelle wird dabei eine Blitzlampe verwendet. Zur Erhöhung der Leistungsdichte wird ein aktiv schaltbarer Güteschalter ("Q-Switch") eingesetzt. Beim sogenannten "Q-switching" wird die Energie während des Pumpvorganges des aktiven Mediums in der Laser-Kavität gespeichert und während einer sehr kurzen Emissionszeit freigesetzt. Hieraus resultiert ein extrem energiereicher Laserpuls. Aktiv schaltbare Güteschalter haben aber den Nachteil, dass für die Steuerung ein erheblicher Schaltungsaufwand erforderlich ist, und dass sie für schnelle Impulsfolgen weniger gut geeignet sind. Die fotooptische Einrichtung der bekannten Laserzündvorrichtung weist drei Linsen auf. Zusammen mit dem aktiven Güteschalter und der durch eine Blitzlampe gebildeten Pump-Lichtquelle ergibt sich der gravierendste Nachteil, dass die Einrichtung nicht zur Gänze in einem in einen Zündkerzenschacht einschraubbaren Bauteil untergebracht werden kann. Über die bei gepumpten Festkörperlasern erforderliche Kühlung des Laserkristalls und der Lichtquelle sind der Druckschrift keine Informationen zu entnehmen.From US 4,416,226 a laser ignition device for an internal combustion engine is known, wherein the resonator of the laser including photo-optical focusing device is screwed into a cylinder head bore so that the ignition device opens directly into the combustion chamber. The laser ignition device uses the principle of a solid-state laser with a pulsed pump light source. This has the advantage that high pulse energies can be achieved with relatively little expenditure of energy. As a pump light source while a flash lamp is used. To increase the power density, an actively switchable Q-switch is used. In the so-called "Q-switching", the energy is stored during the pumping of the active medium in the laser cavity and released during a very short emission time. This results in an extremely high-energy laser pulse. However, actively switchable Q-switches have the disadvantage that a considerable amount of circuitry is required for the controller, and that they are less well suited for fast pulse sequences. The photo-optical device of the known laser ignition device has three lenses. Together with the active Q-switch and by a flash lamp formed pump light source results in the most serious disadvantage that the device can not be housed entirely in a screwed into a spark plug shaft component. About the required for pumped solid state lasers cooling the laser crystal and the light source of the document no information can be found.

Die US 6,413,077 B1 beschreibt eine Laserzündeinrichtung, bei der mehrere Laser, und zwar ein Anregungslaser und ein Zündlaser zum Einsatz kommen. Mittels eines Güteschalters werden die Pulse des Anregungslasers und des Zündlasers aufsummiert und somit die für eine Zündung erforderliche Energiedichte bereitgestellt. Diese bekannte Zündeinrichtung hat den Nachteil eines sehr hohen konstruktiven Aufwandes und benötigt zu viel Bauraum, um anstelle einer Zündkerze in einer Brennkraftmaschine eingesetzt werden zu können.US Pat. No. 6,413,077 B1 describes a laser ignition device in which a plurality of lasers, namely an excitation laser and an ignition laser, are used. By means of a Q-switch, the pulses of the excitation laser and the ignition laser are added up and thus the energy density required for an ignition is provided. This known ignition device has the disadvantage of a very high design effort and requires too much space to be used instead of a spark plug in an internal combustion engine can.

Der Einsatz einer Laserzündung anstelle einer Funkenzündung bietet eine Reihe an Vorteilen. Zum einen benötigt der relativ frei wählbare Ort des Zündplasmas keinerlei materielle Struktur, die den Verbrennungsvorgang stören könnte. Weiters lässt die Wahl des Zündortes eine Optimierung des Verbrennungsvorganges zu, gegebenenfalls auch eine Mehrfachzündung. Die hohen Zünddrücke, wie sie bei Gasmotoren auftreten, kommen der Laserzündung entgegen, da die benötigte Pulsenergie bei höheren Drücken abnimmt. Mit der Laserzündung lassen sich noch magere Gemische zünden, wodurch sich sehr niedrige NOx-Emissionswerte erzielen lassen.The use of laser ignition instead of spark ignition offers a number of advantages. On the one hand, the relatively freely selectable location of the ignition plasma does not require any material structure which could disturb the combustion process. Furthermore, the choice of the ignition location allows an optimization of the combustion process, possibly also a multiple ignition. The high ignition pressures, such as occur in gas engines, are contrary to the laser ignition, since the required pulse energy decreases at higher pressures. The laser ignition ignites even lean mixtures, resulting in very low NO x emissions.

Aus der Literatur ist es bekannt, dass ein fokussierter Laser auf einen hinreichend kleinen Fokusdurchmesser mit genügend Intensität zu einer Plasmabildung und zu einer lokalen Temperaturerhöhung und somit zu einer Zündung eines explosiven Gemisches führt. Für praktische Gasgemische wird vorwiegend der Lawineneffekt freier Elektronen für die Plasmabildung erklärt. Der Effekt ist dann praktisch unabhängig von der verwendeten Wellenlänge.From the literature it is known that a focused laser leads to a sufficiently small focus diameter with sufficient intensity to a plasma formation and to a local temperature increase and thus to an ignition of an explosive mixture. For practical gas mixtures, the avalanche effect of free electrons for plasma formation is mainly explained. The effect is then practically independent of the wavelength used.

In der US 5,673,550 A wird die Zündung von Kraftstofftröpfchen unter Plasmabildung innerhalb des Kraftstoff-Luftnebels mittels eines über eine kohärente Lichtquelle gepulsten Lasers beschrieben.In US 5,673,550 A, the ignition of fuel droplets under plasma formation within the fuel-air mist is described by means of a laser pulsed via a coherent light source.

Aufgabe der Erfindung ist es, eine für den praktischen Einsatz in Brennkraftmaschinen geeignete Laserzündeinrichtung zu schaffen, welche nur wenig Bauraum beansprucht und welche mit geringem konstruktiven Aufwand in Brennkraftmaschinen eingesetzt werden kann.The object of the invention is to provide a suitable for practical use in internal combustion engine laser ignition device, which takes up little space and which can be used with little design effort in internal combustion engines.

Erfindungsgemäß werden diese Aufgaben durch die Merkmale von Patentanspruch 1 gelöst.According to the invention, these objects are achieved by the features of claim 1.

Durch die Verwendung eines gütegeschalteten, gepumpten Festkörperlasers können hohe Pulsenergien erreicht werden. Die wesentlichsten Elemente sind kompakt in einem einzigen Bauteil zusammengefasst, welcher sich anstelle einer Zündkerze in den Zündkerzenschacht einer Brennkraftmaschine einschrauben lässt. Wesentlich ist weiters eine effiziente kühlung durch eine Kühleinrichtung, die einen kühlmittel kreislauf aufweist.By using a Q-switched, pumped solid state laser high pulse energies can be achieved. The most essential elements are compactly combined in a single component which can be screwed into the spark plug shaft of an internal combustion engine instead of a spark plug. It is also essential efficient cooling by a cooling device having a coolant circuit.

Die als Pump-Lichtquelle verwendeten Pumpdioden haben im Vergleich zu Blitz-lampen den Vorteil eines höheren Wirkungsgrades.The pump diodes used as a pump light source have the advantage of higher efficiency compared to flash lamps.

Die Laserdioden werden dabei mit einer Pulsenergie von einigen mJ und etwa 100-200µs gepulst betrieben, wodurch die Leistung pro Diode auf einige 10W beschränkt bleibt.The laser diodes are operated pulsed with a pulse energy of a few mJ and about 100-200μs, whereby the power per diode is limited to a few 10W.

Hochleistungslaserdioden bestehen aus einem Array von vielen Einzeldioden und erreichen dadurch eine sehr hohe Pulsenergie. Durch die große Emissionsfläche und die nicht kontinuierliche Verteilung (geringe Güte) kann der Laserstrahl allerdings nur sehr schlecht fokussiert werden. Durch den langen Resonator kann mit einem Festkörperlaser eine wesentlich höhere Strahlgüte und damit geringerer Fokusdurchmesser erreicht werdenHigh-power laser diodes consist of an array of many single diodes and thus achieve a very high pulse energy. Due to the large emission area and the non-continuous distribution (low quality), the laser beam can only be focused very badly. Due to the long resonator, a much higher beam quality and thus a smaller focus diameter can be achieved with a solid-state laser

Der für die erfindungsgemäße Laser-Zündeinrichtung verwendete gepulste Festkörperlaser ist aus den vier Hauptkomponenten Pumpdioden, Kristallstab, Resonator mit Auskoppelspiegel, Güteschalter (Q-Switch) und Fokussiereinrichtung aufgebaut. Über die Einstrahlung der Pumpdioden werden metastabile Energieniveaus im Laserkristall angeregt und die Energie damit gespeichert. Aufgrund einer geringen spontanen Emission beginnt der Laserkristall Licht auf der Laserwellenlänge (1064nm) zu emittieren.The pulsed solid-state laser used for the laser ignition device according to the invention is composed of the four main components pump diode, crystal rod, resonator with Auskoppelspiegel, Q-switch and focusing device. The radiation of the pump diodes stimulates metastable energy levels in the laser crystal and thus stores the energy. Due to a low spontaneous emission, the laser crystal begins to emit light at the laser wavelength (1064nm).

Zur Verstärkung und Kohärenz des Lichtes ist der Laserkristall in einen optischen Resonator eingebettet, dessen Güte mit dem Güteschalter bei Erreichen der gewünschten Leistungsdichte pulsartig erhöht wird. Dadurch erhält man am Auskoppelspiegel einen kurzen, hohen Laserpuls. Es wird dabei ein passiver Güteschalter verwendet, welcher einerseits eine hohe Verstärkung, andererseits kurze Energieimpulse ohne aufwändige Steuerung ermöglicht.For amplification and coherence of the light, the laser crystal is embedded in an optical resonator whose quality is increased in a pulse-like manner with the Q-switch when the desired power density is reached. This gives the output mirror a short, high laser pulse. It becomes a passive Q-switch used, which on the one hand a high gain, on the other hand allows short energy pulses without complex control.

Die Geometrie des Resonators ergibt sich aus der Forderung, dass die Pumpdioden am oberen Ende des Zündkerzenschachts angeordnet sein müssen. Zur Erzielung einer hohen Güte ist ein möglichst großer Abstand zwischen dem Laserkristall und dem Auskoppelspiegel nötig. Daraus ergibt sich die längliche Bauform, wobei sich der Kopfbereich mit Laserkristall an einem Ende und der Auskoppelspiegel am anderen Ende eines Tubus befinden.The geometry of the resonator results from the requirement that the pump diodes must be arranged at the upper end of the spark plug well. To achieve a high quality, the largest possible distance between the laser crystal and the output mirror is necessary. This results in the elongated design, with the head area with laser crystal at one end and the output mirror at the other end of a tube.

An den Auskoppelspiegel schließt die aus einer einzigen Fokuslinse bestehende Fokussiereinrichtung an. Dies ermöglicht eine sehr kleine Bauweise.At the Auskoppelspiegel includes the existing of a single focus lens focusing device. This allows a very small construction.

Da die Wellenlänge der Pumpdioden sich mit der Temperatur des Lasersubstrats ändert und der Laserkristall eine nur sehr schmale Absorptionslinie besitzt, müssen die Pumpdioden thermisch stabilisiert werden. Untersuchungen haben gezeigt, dass zumindest zwei, vorzugsweise drei verschiedene Kühlsysteme für eine thermische Stabilisierung des Resonators von Vorteil sind. Für zumindest ein Kühlsystem bietet sich das temperaturgeregelte Kühlwasser der Brennkraftmaschine an. Da aber die Pumpdioden auf einem wesentlich niedrigeren Temperaturniveau als die Kühlwassertemperatur betrieben werden müssen, ist der Einsatz von thermoelektrischen Kühlelementen (Peltier-Kühlelementen) in diesem Fall erforderlich. Zumindest ein Kühlsystem weist daher zumindest ein Peltier-Kühlelement auf. Dabei ist vorgesehen, dass zur Kühlung des Laserkristalls und/oder der Pumpdioden der Resonator einen ersten inneren Kühlmittelkreislauf aufweist. Die Wärme des inneren Kreislaufes wird über einen Wärmeverteiler an zumindest ein Peltier-Kühlelement abgeleitet. Besonders vorteilhaft ist es, wenn zur Wärmeabfuhr vom Peltier-Kühlelement der Resonator zumindest einen äußeren zweiten Kühlmittelkreislauf aufweist. Zumindest eines der Kühlsysteme kann dabei auch zum Aufwärmen der Pumpdioden ausgelegt sein. Besonders vorteilhaft ist es, wenn bei Kaltstart die Pumpdioden durch das Peltier-Kühlelement auf die Betriebstemperatur erwärmbar sind.Since the wavelength of the pump diodes changes with the temperature of the laser substrate and the laser crystal has only a very narrow absorption line, the pump diodes must be thermally stabilized. Investigations have shown that at least two, preferably three different cooling systems for thermal stabilization of the resonator are advantageous. For at least one cooling system, the temperature-controlled cooling water of the internal combustion engine offers. However, since the pump diodes must be operated at a much lower temperature level than the cooling water temperature, the use of thermoelectric cooling elements (Peltier cooling elements) is required in this case. At least one cooling system therefore has at least one Peltier cooling element. It is provided that for cooling the laser crystal and / or the pump diodes, the resonator has a first inner coolant circuit. The heat of the inner circuit is derived via a heat spreader to at least one Peltier cooling element. It is particularly advantageous if the resonator has at least one outer second coolant circuit for heat removal from the Peltier cooling element. At least one of the cooling systems can also be designed to warm the pump diodes. It is particularly advantageous if, during a cold start, the pump diodes can be heated by the Peltier cooling element to the operating temperature.

Der Laserkristall kann prinzipiell entweder aus ND:YAG (Neodym:YAG) oder aus ND:YVO4 (Neodym :Vanadat) bestehen. ND:YAG ist weit verbreitet, kostengünstig und mechanisch gut belastbar, hat aber eine weit schmälere Absorptionslinie als ND:YVO4. Der Einsatz von ND:YAG-Laserkristallen bedingt somit eine besonders gute Kühleinrichtung.In principle, the laser crystal can consist of either ND: YAG (neodymium: YAG) or ND: YVO 4 (neodymium: vanadate). ND: YAG is widely used, inexpensive and mechanically strong, but has a much narrower absorption line than ND: YVO 4 . The use of ND: YAG laser crystals thus requires a particularly good cooling device.

Eine sehr effektive Wärmeabfuhr aus dem Laserkristall wird erreicht, wenn der Laserkristall von zumindest einem vorzugsweise ringförmigen ersten Kühlkanal umgeben ist.A very effective heat removal from the laser crystal is achieved when the laser crystal is surrounded by at least one preferably annular first cooling channel.

Um eine sehr kompakte Bauweise der Zündeinrichtung zu ermöglichen, ist im Rahmen der Erfindung vorgesehen, dass mehrere Pumpdioden konzentrisch um den Laserkristall angeordnet sind, wobei vorzugsweise mindestens drei, besonders vorzugsweise mindestens sechs Pumpdioden gleichmäßig um den Laserkristall herum angeordnet sind. Die Pumpdioden sind dabei vorteilhafter Weise in Serie geschaltet sind. Der Laserkristall wird somit durch die Pumpdioden seitlich, das heißt radial, gepumpt. Zur Erhöhung der Pulsenergie können auch mehrere Ringe von Pumpdioden konzentrisch hintereinander um den Laserkristall herum angeordnet sein.In order to enable a very compact design of the ignition device, it is provided in the invention that a plurality of pump diodes are arranged concentrically around the laser crystal, wherein preferably at least three, more preferably at least six pump diodes are arranged uniformly around the laser crystal. The pump diodes are advantageously connected in series. The laser crystal is thus pumped laterally by the pump diodes, that is radially. To increase the pulse energy, several rings of pump diodes can also be arranged concentrically one behind the other around the laser crystal.

Als Kühlmedium kann zumindest für den zweiten äußeren Kühlkreislauf Wasser zur Anwendung kommen.As the cooling medium, water can be used at least for the second outer cooling circuit.

Die Erfindung wird im Folgenden anhand der Figuren näher erläutert. Es zeigen

Fig. 1
eine erfindungsgemäße Laser-Zündeinrichtung in einer Schrägansicht,
Fig. 2
den Kopfteil der Laser-Zündeinrichtung im Detail in einer Schrägansicht,
Fig. 3
die Laser-Zündeinrichtung in einem Längsschnitt,
Fig. 4
den Kopfteil der Laser-Zündeinrichtung in einer geschnittenen Schrägansicht gemäß der Linie IV-IV in Fig. 1,
Fig. 5
den Fußteil der Laser-Zündeinrichtung in einer geschnittenen Schrägansicht,
Fig. 6
die Laser-Zündeinrichtung schematisch in einem Längsschnitt gemäß der Linie VI-VI in Fig. 7,
Fig. 7
die Laser-Zündeinrichtung in einem Schnitt gemäß der Linie VII-VII in Fig. 6 und
Fig. 8
einen Zylinderkopf mit einer eingebauten Laser-Zündeinrichtung.
The invention will be explained in more detail below with reference to FIGS. Show it
Fig. 1
a laser ignition device according to the invention in an oblique view,
Fig. 2
the head part of the laser ignition device in detail in an oblique view,
Fig. 3
the laser ignition device in a longitudinal section,
Fig. 4
the head part of the laser ignition device in a sectional oblique view along the line IV-IV in Fig. 1,
Fig. 5
the foot part of the laser ignition device in a sectional oblique view,
Fig. 6
the laser ignition device schematically in a longitudinal section along the line VI-VI in Fig. 7,
Fig. 7
the laser ignition device in a section along the line VII-VII in Fig. 6 and
Fig. 8
a cylinder head with a built-in laser ignition device.

Die Laser-Zündeinrichtung 1 besteht aus den Hauptkomponenten Laserkristall 2, Pumplichtquelle 30, passiver Güteschalter 4, Tubus 5, Auskoppelspiegel 6 und Fokussiereinrichtung 7 mit einer Fokuslinse 8, sowie einer Kühleinrichtung 11.The laser ignition device 1 consists of the main components laser crystal 2, pump light source 30, passive Q-switch 4, tube 5, Auskoppelspiegel 6 and focusing 7 with a focus lens 8, and a cooling device 11th

Ein hoher Wirkungsgrad lässt sich erzielen, wenn die Pumplichtquelle 30 durch Pumpdioden 3 gebildet ist.A high efficiency can be achieved if the pump light source 30 is formed by pump diodes 3.

Über die Einstrahlung der Pumpdioden 3 (808nm) werden metastabile Energieniveaus im Laserkristall 2 angeregt und die Energie damit gespeichert. Aufgrund einer geringen spontanen Emission beginnt der Laserkristall 2 Licht auf der Laserwellenlänge (1064nm) zu emittieren.Via the irradiation of the pump diodes 3 (808nm), metastable energy levels in the laser crystal 2 are excited and the energy is thus stored. Due to a low spontaneous emission, the laser crystal 2 emits light at the laser wavelength (1064nm).

Zur Verstärkung und Kohärenz des Lichts ist der Laserkristall 2 in einen optischen Resonator 9 eingebettet, dessen Güte mit dem passiven Güteschalter 4 bei Erreichen der gewünschten Leistungsdichte pulsartig erhöht wird. Dadurch erhält man am Auskoppelspiegel 6 einen kurzen, starken Laserpuls 26.For amplification and coherence of the light, the laser crystal 2 is embedded in an optical resonator 9 whose quality is increased in a pulse-like manner with the passive Q-switch 4 when the desired power density is reached. As a result, a short, strong laser pulse 26 is obtained at the outcoupling mirror 6.

Einzelne Pumpdioden 3 sind in Serie geschaltet und ringförmig seitlich um den Laserkristall 2 angeordnet.Individual pump diodes 3 are connected in series and arranged annularly laterally around the laser crystal 2.

Die Pumpdioden 3 müssen aufgrund stark eingeschränkter Lebensdauer bei höherer Betriebstemperatur bei relativ niedriger Temperatur von etwa 30°C betrieben werden. Darüber hinaus ändert sich die Wellenlänge der Pumpdioden 3 mit der Temperatur. Da der aus Neodym:YAG (ND:YAG) bestehende stabförmige Laserkristall 2 eine nur sehr schmale Absorptionslinie besitzt, müssen die Pumpdioden 3 thermisch stabilisiert werden. Dazu ist im Kopfbereich 10 der Laser-Zündeinrichtung 1 die Kühleinrichtung 11 vorgesehen.The pump diodes 3 must be operated at relatively low temperature of about 30 ° C due to greatly reduced lifetime at higher operating temperature. In addition, the wavelength of the pump diodes 3 changes with the temperature. Since the rod-shaped laser crystal 2 consisting of neodymium: YAG (ND: YAG) has only a very narrow absorption line, the pump diodes 3 must be thermally stabilized. For this purpose, the cooling device 11 is provided in the head region 10 of the laser ignition device 1.

Die Kühleinrichtung 11 beinhaltet drei verschiedene Kühlsysteme A, B, C. Das erste Kühlsystem A weist ringförmig um den Wärmeverteiler 28 verteilte Peltier-Kühlelemente 12 auf. Zur besseren Wärmeabfuhr sind weiters die Kühlsysteme B, C mit zwei Flüssigkeits-Kühlkreisläufen 13, 14 vorgesehen. Das Kühlmittel des Kühlkreislaufs 13 durchströmt den Kopfteil 10 im Wesentlichen in Richtung der Achse 1a der Laser-Zündeinrichtung 1.The cooling device 11 includes three different cooling systems A, B, C. The first cooling system A has annularly distributed around the heat spreader 28 Peltier cooling elements 12. For better heat dissipation further cooling systems B, C with two liquid cooling circuits 13, 14 are provided. The coolant of the cooling circuit 13 flows through the head part 10 substantially in the direction of the axis 1 a of the laser ignition device 1.

Der erste Kühlkreislauf 13 hat die Aufgabe, den Laserkristall 2 thermisch zu stabilisieren und dessen Verlustwärme an den Wärmeverteiler 28 zu übertragen. Der Laserkristall 2 ist dabei von zumindest einem ersten Kühlkanal 16 umgeben, welcher als Ringkanal ausgebildet sein kann, wie aus Fig.7 hervorgeht. An Stelle eines Ringkanals können auch mehrere erste Einlasskanäle 16 rund um den Laserkristall 2 angeordnet sein. Über zumindest eine Eintrittsöffnung 19a und einen Verteilerringraum 19 wird das Kühlmittel dem ersten Kühlkanal 16 zu-, und über einen Sammelringraum 20 und Austrittsöffnungen 20a wieder abgeführt. Die Verlustwärme des Laserkristalls 2 wird zumindest teilweise beim Durchströmen der Ringräume 19, 20 an die Flanschplatte 17 und die Anschlussplatte 23 übertragen, diese wiederum übertragen die Wärme durch Wärmeleitung an den Wärmeverteiler 28.The first cooling circuit 13 has the task to thermally stabilize the laser crystal 2 and to transfer its heat loss to the heat spreader 28. The laser crystal 2 is surrounded by at least one first cooling channel 16, which may be formed as an annular channel, as can be seen from Fig.7. Instead of an annular channel, a plurality of first inlet channels 16 may be arranged around the laser crystal 2. Via at least one inlet opening 19a and one distributor ring space 19, the coolant is supplied to the first cooling channel 16, and discharged again via a collecting ring space 20 and outlet openings 20a. The heat loss of the laser crystal 2 is at least partially transmitted when flowing through the annular spaces 19, 20 to the flange plate 17 and the connection plate 23, these in turn transmit the heat by heat conduction to the heat spreader 28th

Gegebenenfalls kann auch der Wärmeverteiler 28 axiale Kühlkanäle 15 aufweisen, wie in Fig. 4 und 6 durch strichlierte Linien angedeutet ist. Das Kühlmedium tritt dabei durch Zutrittsöffnungen 19a in den Verteilerringraum 19 ein, durchströmt die ersten Kühlkanäle 15 des Wärmeverteilers 28 und wird über den Übertrittskanal 18 in den Kühlkanal 16 geleitet. Danach strömt es durch den Sammelringraum 20 und Austrittsöffnungen 20a zu einer externen Pumpe.Optionally, the heat spreader 28 may have axial cooling channels 15, as indicated in Fig. 4 and 6 by dashed lines. The cooling medium enters through the access openings 19a in the Verteilerringraum 19, flows through the first cooling channels 15 of the heat spreader 28 and is passed via the transfer channel 18 in the cooling channel 16. Thereafter, it flows through the collecting ring space 20 and outlet openings 20a to an external pump.

Der zweite Kühlkreislauf 14 weist Eintrittsöffnungen 21 im äußeren Wärmetauscher 29 auf, welche zu zweiten Kühlkanälen 24 und weiter zu Austrittsöffnungen 22 führen. Das beispielsweise durch Wasser gebildete Kühlmittel gelangt über die Eintrittsöffnungen 21 in die zweiten Kühlkanäle 24, durchströmt den äußeren Wärmetauscher 29 und verlässt die Laser-Zündeinrichtung 1 wieder im Bereich der Austrittsöffnungen 22. Über die zweiten Kühlkanäle 24 wird also vor allem Wärme aus den Peltier-Kühlelementen 12 über den äußeren Wärmetauscher 29 abgeführt.The second cooling circuit 14 has inlet openings 21 in the outer heat exchanger 29, which lead to second cooling channels 24 and on to outlet openings 22. The coolant formed for example by water passes through the inlet openings 21 into the second cooling channels 24, flows through the outer heat exchanger 29 and leaves the laser ignition device 1 again in the region of the outlet openings 22. Cooling elements 12 discharged via the outer heat exchanger 29.

Durch die aus drei Kühlsystemen A, B, C - nämlich Peltier-Kühlelemente 12, erstem Kühlkreislauf 13 und zweitem Kühlkreislauf 14 - bestehende Kühleinrichtung 11 ist es möglich, als Material für den Laserkristall 2 das weit verbreitete, kostengünstige und mechanisch gut belastbare Neodym :YAG und als Pumplichtquelle Pumpdioden 3 zu verwenden. Durch die Kühleinrichtung 11 können die Pumpdioden 3 thermisch auf etwa 30°C stabilisiert werden, was sich vorteilhaft auf deren Lebensdauer auswirkt. Andererseits kann durch die thermische Stabilisierung erreicht werden, dass die Wellenlänge der Pumpdioden 3 stets innerhalb der schmalen Absorptionslinie des Laserkristalls 2 bleibt.By the three cooling systems A, B, C - namely Peltier cooling elements 12, the first cooling circuit 13 and second cooling circuit 14 - existing cooling device 11, it is possible, as a material for the laser crystal 2, the widely used, inexpensive and mechanically strong neodymium: YAG and to use pump diodes 3 as the pump light source. By the cooling device 11, the pump diodes 3 can be thermally stabilized to about 30 ° C, which has an advantageous effect on their life. On the other hand, it can be achieved by the thermal stabilization that the wavelength of the pump diodes 3 always remains within the narrow absorption line of the laser crystal 2.

Der Laserkristall 2 ist im Bereich der stirnseitigen Anschlussplatte 23 für die Laserwellenlänge (1064nm) verspiegelt und am anderen Ende antireflektierend beschichtet.The laser crystal 2 is mirrored in the area of the end-side connection plate 23 for the laser wavelength (1064 nm) and antireflective coated on the other end.

Die Form der Laser-Zündeinrichtung 1 ergibt sich aus der Forderung, dass diese anstelle einer Zündkerze in den Zündkerzenschacht 31 eines Zylinderkopfes 32 montierbar sein soll und aus der Randbedingung, dass die Pumpdioden 3 im Kopfbereich 10 der Laser-Zündeinrichtung 1 angeordnet sein müssen. Zur Erzielung einer hohen Strahlgüte ist ein möglichst großer Abstand zwischen dem Laserkristall 2 und dem Auskoppelspiegel 6 nötig. Der Auskoppelspiegel 6 ist daher im Fußbereich 25 der Laser-Zündeinrichtung 1 brennraumnahe angeordnet. Kurz nach dem Auskoppelspiegel 6 befindet sich die Fokussiereinrichtung 7 mit einer einzigen Fokuslinse 8, die gleichzeitig das Fenster zum Brennraum bildet und als plano-spherische Linse ausgebildet ist. Als Material für die Fokussierlinse 8 eignet sich beispielsweise Saphir.The shape of the laser ignition device 1 results from the requirement that it should be mounted instead of a spark plug in the spark plug well 31 of a cylinder head 32 and from the boundary condition that the pump diodes 3 in the head region 10 of the laser ignition device 1 must be arranged. To achieve a high beam quality, the largest possible distance between the laser crystal 2 and the output mirror 6 is necessary. The Auskoppelspiegel 6 is therefore arranged in the foot region 25 of the laser ignition device 1 near the combustion chamber. Shortly after the Auskoppelspiegel 6 is the focusing device 7 with a single focus lens 8, which simultaneously forms the window to the combustion chamber and is designed as a plano-spherical lens. As a material for the focusing lens 8, for example, sapphire is suitable.

Der zweite Kühlkreislauf 14 kann mit der vorhandenen Wasserkühlung des Motors gekoppelt sein. Für den ersten Kühlkreislauf sind höhere optische, qualitative und thermische Bedingungen zu erfüllen, sodass hier ein eigenes Kühlmittel erforderlich ist.The second cooling circuit 14 may be coupled to the existing water cooling of the engine. For the first cooling circuit, higher optical, qualitative and thermal conditions have to be fulfilled, so that a separate coolant is required here.

Die Pumpdioden 3 müssen aufgrund stark eingeschränkter Lebensdauer bei höherer Betriebstemperatur bei etwa 30°C betrieben werden. Der Verlustwärmestrom wird über einen Wärmeverteiler 28, welcher aus Kupfer besteht, an die Peltier-Kühlelemente 12 abgeleitet, die den Wärmestrom auf das Temperaturniveau des Motorkühlwassers transformieren und über den äußeren Wärmetauscher 29 an dieses abgeben.The pump diodes 3 must be operated at a higher operating temperature at about 30 ° C due to greatly reduced lifetime. The waste heat flow is derived via a heat spreader 28, which consists of copper, to the Peltier cooling elements 12, which transform the heat flow to the temperature level of the engine cooling water and deliver it via the outer heat exchanger 29 thereto.

Da sich die Wellenlänge der Pumpdioden 3 mit der Temperatur verschiebt und das Absorptionsband des Laserkristalls 2 extrem schmal ist, muss eine schnelle und genaue Temperaturregelung vorgesehen sein. Die Temperatur auf der kalten Seite sollte dabei maximal um etwa +/- 1,5°C vom Sollwert abweichen. Um dies zu erreichen, werden die Peltier-Kühlelemente 12 mit mindestens einem Temperatursensor und einer Stromquelle in einem geschlossenen Regelkreis betrieben.Since the wavelength of the pump diodes 3 shifts with temperature and the absorption band of the laser crystal 2 is extremely narrow, a fast and accurate temperature control must be provided. The temperature on the cold side should deviate by a maximum of +/- 1.5 ° C from the nominal value. To this To reach the Peltier cooling elements 12 are operated with at least one temperature sensor and a power source in a closed loop.

Über die vorzugsweise sechs rund um den Laserkristall 2 angeordneten Pumpdioden 3 werden Lichtimpulse dem Laserkristall 2 zugeführt. Über die Einstrahlung der Pumpdioden 3 (808nm) werden metastabile Energieniveaus im Laserkristall 2 angeregt und die Energie damit gespeichert. Aufgrund einer geringen spontanen Emission beginnt der Laserkristall 2 Licht auf der Laserwellenlänge (1064nm) zu emittieren. Zur Verstärkung und Kohärenz des Lichtes ist der Laserkristall 2 in einen optischen Resonator 9 eingebettet, dessen Güte mit dem passiven Güteschalter 4 (Q-Switch) bei Erreichen der gewünschten Leistungsdichte pulsartig erhöht wird. Dadurch erhält man am Auskoppelspiegel 6 einen hohen, kurzen Laserpuls 26, welcher über die Fokussierlinse 8 in einem Brennpunkt 27 fokussiert wird.Via the preferably six pump diodes 3 arranged around the laser crystal 2, light pulses are supplied to the laser crystal 2. Via the irradiation of the pump diodes 3 (808nm), metastable energy levels in the laser crystal 2 are excited and the energy is thus stored. Due to a low spontaneous emission, the laser crystal 2 emits light at the laser wavelength (1064nm). For amplification and coherence of the light, the laser crystal 2 is embedded in an optical resonator 9 whose quality is increased in a pulse-like manner with the passive Q-switch 4 when the desired power density is reached. As a result, a high, short laser pulse 26, which is focused via the focusing lens 8 in a focal point 27, is obtained at the outcoupling mirror 6.

Wie aus Fig. 8 ersichtlich ist, kann die Laser-Zündeinrichtung 1 zur Gänze im Zündkerzenschacht 31 eines Zylinderkopfes 32 einer Brennkraftmaschine angeordnet werden. Die Laser-Zündeinrichtung 1 eignet sich somit für den Einsatz in bestehende konventionelle Zylinderkopfkonzepte für fremdgezündete Brennkraftmaschinen. Um Verunreinigungen der Fokussiereinrichtung möglichst gering zuhalten schließt die Fokussierlinse 8 zum Brennraum 33 hin plan an die Zylinderkopfdeckfläche 34 an.As can be seen from FIG. 8, the laser ignition device 1 can be arranged entirely in the spark plug shaft 31 of a cylinder head 32 of an internal combustion engine. The laser ignition device 1 is thus suitable for use in existing conventional cylinder head concepts for spark-ignition internal combustion engines. In order to minimize contamination of the focusing device, the focusing lens 8 is flush with the cylinder head cover surface 34 toward the combustion chamber 33.

Claims (11)

  1. Laser ignition device (1) for an internal combustion engine, comprising a Q-switched, pumped solid-state laser with a pulsed pump-light source (30), a solid laser crystal (2) embedded in a resonator (9), a Q-switch (4) for increasing power density, at least one output mirror (6) and a focussing device (7) which serves to focus the laser ray (26) into a combustion chamber, with the pump-light source (30), the resonator (9) including the laser crystal (2), the Q-switch (4), the output mirror (6) and the focussing device (7) forming an integrated unit, characterized in that the pump-light source (30) consists of pumping diodes, the Q-switch (4) is of the passive type, and that a cooling assembly (11) for cooling the resonator (9) is provided, which has at least one coolant circuit (13, 14), and which is also integrated in said unit, said unit being configured as a single element that may be inserted into the spark plug bore (31) of the internal combustion engine.
  2. Ignition device (1) according to claim 1, characterized in that the focussing device (7) has a single focussing lens (8).
  3. Ignition device (1) according to claim 1 or 2, characterized in that the cooling assembly (11) comprises at least two, preferably three cooling systems (A,B,C).
  4. Ignition device (1) according to any of claims 1 to 3, characterized in that the resonator (9) is furnished with at least one Peltier cooling element (12) for cooling the pumping diodes (3).
  5. Ignition device (1) according to any of claims 1 to 4, characterized in that the resonator (9) has a first inner coolant circuit (13) for cooling the laser crystal (2).
  6. Ignition device (1) according to claim 4 or 5, characterized in that the resonator (9) has at least one outer, second coolant circuit (14) for draining heat from the Peltier cooling element (12).
  7. Ignition device (1) according to any of claims 1 to 6, characterized in that the laser crystal (2) is surrounded by at least one, preferably annular, first cooling channel (16).
  8. Ignition device (1) according to any of claims 1 to 7, characterized in that several pumping diodes (3) are placed concentrically around the laser crystal (2).
  9. Ignition device (1) according to claim 8, characterized in that at least three, preferably at least six, pumping diodes (3) are placed uniformly around the laser crystal.
  10. Ignition device (1) according to any of claims 1 to 9, characterized in that in the cold start situation the pumping diodes (3) can be heated to operating temperature by the Peltier cooling element (12).
  11. Ignition device (1) according to any of claims 1 to 10, characterized in that the pumping diodes (3) are connected in series.
EP03021446A 2003-09-23 2003-09-23 Laser ignition device for combustion engine Expired - Lifetime EP1519038B1 (en)

Priority Applications (7)

Application Number Priority Date Filing Date Title
DE50304768T DE50304768D1 (en) 2003-09-23 2003-09-23 Laser ignition device for an internal combustion engine
EP03021446A EP1519038B1 (en) 2003-09-23 2003-09-23 Laser ignition device for combustion engine
AT03021446T ATE337486T1 (en) 2003-09-23 2003-09-23 LASER IGNITION DEVICE FOR AN INTERNAL COMBUSTION ENGINE
EP03450285A EP1519039A1 (en) 2003-09-23 2003-12-23 Q-switched pumped solid-state laser
US10/573,115 US7499477B2 (en) 2003-09-23 2004-09-23 Internal combustion engine
PCT/AT2004/000320 WO2005028856A1 (en) 2003-09-23 2004-09-23 Internal combustion engine
JP2006527218A JP4477636B2 (en) 2003-09-23 2004-09-23 Laser ignition device for internal combustion engine

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
EP03021446A EP1519038B1 (en) 2003-09-23 2003-09-23 Laser ignition device for combustion engine

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EP1519038A1 EP1519038A1 (en) 2005-03-30
EP1519038B1 true EP1519038B1 (en) 2006-08-23

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AT508801B1 (en) * 2009-10-07 2011-09-15 Ge Jenbacher Gmbh & Co Ohg BRENNKRAFTMASCHINENZÜNDVORRICHTUNG
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EP2522842A1 (en) * 2011-05-13 2012-11-14 GE Jenbacher GmbH & Co. OHG Cylinder head for a combustion engine
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DE102013226119A1 (en) 2013-02-11 2014-08-14 Robert Bosch Gmbh laser ignition system
DE102013212065A1 (en) 2013-06-25 2015-01-08 Robert Bosch Gmbh Method for mounting a laser spark plug
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