EP0167608B1 - Internal combustion engine with ignition by high energy rays introduced into the combusion changer - Google Patents

Abstract

A substantially instantaneous ignition of an ignitable fuel mixture during the compression phase in the volume of the combustion chamber of an alternating or rotary piston machine may be obtained together with a combination of a lean mixture and a reduction of noxious product emission by introducing high energy rays in the form of a plurality of unfocused laser rays (30) into the combustion chamber so as to generate in the combustion chamber at least at the ignition time a layer traversed by a plurality of those rays (30), the arrangement being such that the wall of the combustion chamber, and during the compression phase, the front surface of the piston facing said walls are close to the layer and that, at the ignition moment, at least in a surface area of the layer, elementary ignition processes are triggered so that the flame fronts providing from the neighbouring elementary ignition processes meet before a displacement of the front surface of the piston during the expansion stroke.

Description

The invention relates to an internal combustion engine in which an ignitable fuel mixture is compressed during a compression phase by means of a reciprocating piston or a rotary piston in a combustion chamber space, with light guides opening into this combustion chamber space, via which high-energy radiation in the form of a plurality of beams, in particular laser beams, emanating from a light source arrangement Combustion chamber is insertable.

It is already known to ignite an ignitable fuel mixture enclosed in a combustion chamber space at the time of ignition by means of radiation which is focused by means of suitable optics on a point within the combustion chamber space containing the compressed ignitable fuel mixture. This focal point corresponds to the arc or spark between the electrodes of the spark plug of a conventional ignition system and forms the starting point for flame fronts which spread through the ignitable fuel mixture to the combustion chamber walls and to the piston end face adjacent to them. It has been shown that when the flame fronts spread from a point within the combustion chamber space, comparatively rich, ignitable fuel mixtures are a prerequisite for proper functioning, these rich mixtures in turn being the cause of a comparatively high pollutant emission by the exhaust gases of the internal combustion engine in question.

If, however, the flame front spreads more slowly when leaner ignitable fuel mixtures are used or if the flame front extinguishes in some areas, complete ignition of the compressed ignitable fuel mixture can be disturbed and sometimes the piston runs away from the flame front at the start of the expansion stroke, as a result of which the performance the internal combustion engine is reduced and in turn increases the pollutant emissions.

From US Pat. No. 4,314,530, an internal combustion engine of the type described in the introduction is known, in which laser beams are introduced into the combustion chamber chamber containing the compressed ignitable fuel mixture with the aim of using several light guides from several light sources, at several points along the laser beams in their Line up the section passing through the combustion chamber space to trigger elementary ignition processes in order to be able to trigger a more complete combustion by the high-energy radiation. In this known system, however, it can happen that, especially when using lean ignitable fuel mixtures, only certain surface areas of the cross-section of the cylinder are preferably covered with points in which elementary ignition processes are triggered, so that a highly irregular loading of the piston and the cylinder walls occurs and a desired uniform ignition of the compressed ignitable fuel mixture is not achieved.

Furthermore, it is known from Japanese patent application 56-173934 to introduce laser beams into a combustible chamber containing an ignitable fuel mixture and to guide them within the combustion chamber space in such a way that the laser beams are focused at a plurality of focal points within the combustion chamber space. This known type of radiation ignition also does not enable an essentially uniform ignition of the compressed ignitable fuel mixture and moreover has the disadvantage of considerable technical outlay.

From Japanese patent application 58-162 773 it is also known to introduce laser beams into a swirl chamber adjacent to the cylinder space of an internal combustion engine and connected to the cylinder space by means of a light guide and to focus on a point in the swirl chamber, in the direction of at this point the fuel injection also takes place. The progress of the ignition process and the speed of the propagation of the flame front in this known construction depend on the fuel injection process, the ignition again starting from the point of focusing of the laser radiation and the piston face not being hit directly by the expansion wave.

The invention is intended to achieve the object of designing an internal combustion engine of the general type briefly described at the outset in such a way that, even when using lean and very lean ignitable fuel mixtures, high efficiency, low pollutant emissions from the exhaust gases and a comparatively simple structure of the internal combustion engine can be achieved.

This object is achieved in that, at least at the time of ignition in the combustion chamber, a layer-shaped space penetrated by a plurality of the rays in the form of a fan beam can be generated, which is enclosed in a small space by the combustion chamber walls and the piston end face opposite them, and in that the arrangement is made in this way is that at the time of ignition, at least in a substantial cross-sectional area of the layered space, elementary ignition processes can be triggered in such a way that the flame fronts emanating from neighboring elementary ignition processes meet before the piston end face is substantially displaced in the expansion cycle.

This means that according to the invention in the the compressed ignitable fuel mixture containing combustion chamber volume in the form of a flat, for example disk-shaped spatial structure, a layer is created which is interspersed in a network-like or lattice-like manner by a large number of high-energy rays, so that at the time of ignition in this layer an essentially extending over the entire cylinder cross section or combustion chamber cross section Ignition layer can be generated, from which flame fronts corresponding to the combustion chamber cross section, on the one hand toward the combustion chamber walls and on the other hand towards the piston end face, spread stable flame fronts before a substantial movement of the piston end face has taken place in the expansion phase.

According to the invention, the generation of the ignition layer in the aforementioned sense can be supported by a number of measures.

One of these measures provides that a particularly high compression of the ignitable fuel mixture takes place, so that the molecular movement within the combustion chamber space containing the compressed ignitable fuel mixture with high statistical probability drives a sufficiently large number of molecule combinations causing the ignition into the large number of high-energy jets within the combustion chamber space .

Another way of supporting the formation of the ignition layer is to add radiation absorbents to the ignitable fuel mixture, with the corresponding absorbents being specified in detail below.

In addition, an improvement in the triggering of the ignition processes can be achieved by pulsing the ignition-triggering radiation. Depending on the fuel mixture used and the speed of the internal combustion engine, pulse frequencies in the range from 500 Hz to 1 MHz can be used.

Furthermore, it is important for an improved mode of operation of the internal combustion engine of the type proposed here if the combustion chamber walls and the piston end face are shaped in such a way that they run parallel, at least in regions, to the layer penetrated by the rays at a short distance. The shape of the combustion chamber is therefore preferably selected such that it is optimally adapted to the layer of the combustion chamber space penetrated by rays, so that the walls of the combustion chamber enclose the igniting light rays on a small scale. The arrangement can also be such that the igniting light beams sweep the combustion chamber space to fill the space in the compression phase. In this way you get a reliable ignition with lean air-fuel mixtures, for. B. to X approximately equal to 1.7 and also in super-lean air-fuel mixtures, for. B. up to about 2.0.

As already mentioned, the beams can be introduced in large numbers into the combustion chamber space by means of light guides, the light guides leading away from a common light source, in particular a laser, outside the combustion chamber space. Special cooling devices expediently protect both the light guide and the light source from the effect of temperature due to the heat which is transmitted from the engine block by radiation or heat conduction. The light guides can be guided in fixed or replaceable light guide housings.

A particularly expedient embodiment for reciprocating internal combustion engines provides that the individual light guides are guided in a light guide housing in the form of a light guide ring, a common light source being located at a point on the outer circumference of the light guide ring and the light guides starting from the light source and finally being distributed circumferentially extend radially inwards in the direction of the bore of the light guide ring which corresponds to the cylinder cross section, in order to finally open into the bore inner wall of the light guide ring from all sides at a multiplicity of points.

Another embodiment, which is suitable both for reciprocating piston internal combustion engines and for rotary piston internal combustion engines, contains as the light guide housing a rotationally symmetrical body with a beam entry surface and a beam exit surface, of which due to a diverging profile of the individual light guides in the rotationally symmetrical body, a radiation fan in the combustion chamber space exits.

• Fig. 1 einen Längsschnitt durch eine Hubkolben-Brennkraftmaschine mit einem Zündsystem der hier angegebenen Art und in einer Bauart ohne Zylinderkopfdichtung,
• Fig. 2 einen Querschnitt durch die Brennkraftmaschine nach Figur 1 entsprechend der in Figur 1 angedeuteten Schnittlinie A-A,
• Fig. 3 einen Längsschnitt durch eine Hubkolben-Brennkraftmaschine in einer anderen Ausführungsform sowie in einer Bauart mit Zylinderkopfdichtung,
• Fig. 4 eine Hälfte eines Lichtleitereinsatzes zur Einleitung der zündenden Lichtstrahlen in den Brennkammerraum der Hubkolben-Brennkraftmaschinen nach den Figuren 1 und 3,
• Fig. 5 eine Stirnansicht zweier zusammengefügter Hälften des Lichtleiter-Einsatzes gemäß Figur 4,
• Fig. 6 einen Längsschnitt durch eine wiederum andere Ausführungsform einer Hubkolben-Brennkraftmaschine mit einem Lichtleitergehäuse in Gestalt eines Lichtleiterringes, der mit Hilfe eines Lichtleiterkabels an ein entfernt angeordnetes strahlenerzeugendes Gerät angeschlossen ist,
• Fig. 7 eine teilweise im Schnitt gezeichnete Ansicht des Lichtleiterringes der Brennkraftmaschine gemäß Figur 6 entsprechend der in dieser Zeichnungsfigur angedeuteten Schnittebene C-C,
• Fig. 8 einen Schnitt durch eine Kreiskolben-Brennkraftmaschine mit einem Zündsystem der hier angegebenen Art,
• Fig. 9 eine Schnittdarstellung durch die Brennkraftmaschine gemäß Figur 8 entsprechend der in dieser Zeichnungsfigur angedeuteten Schnittebene D-D,
• Fig. 10 eine Teilansicht des Kreiskolbens der Brennkraftmaschine gemäß Figur 8 entsprechend der in Figur 8 durch den Pfeil E angedeuteten Blickrichtung und
• Fig. 11 ein Doppeldiagramm zur Erläuterung der Zusammenhänge bei der Verbrennung supermagerer zündbarer Gemische.

Some exemplary embodiments are explained in more detail below with reference to the attached drawing. Show it :

• 1 shows a longitudinal section through a reciprocating piston internal combustion engine with an ignition system of the type specified here and in a type without a cylinder head gasket,
• 2 shows a cross section through the internal combustion engine according to FIG. 1 corresponding to the section line AA indicated in FIG. 1,
• 3 shows a longitudinal section through a reciprocating piston internal combustion engine in another embodiment and in a type with a cylinder head gasket,
• 4 shows a half of a light guide insert for introducing the igniting light beams into the combustion chamber space of the reciprocating piston internal combustion engines according to FIGS. 1 and 3,
• 5 shows an end view of two joined halves of the light guide insert according to FIG. 4,
• 6 shows a longitudinal section through yet another embodiment of a reciprocating piston internal combustion engine with an optical waveguide housing in the form of an optical waveguide ring, which is connected with the aid of an optical waveguide cable to a remotely located radiation-generating device,
• Fig. 7 is a partially sectioned view of the light guide ring of the internal combustion engine 6 according to the sectional plane CC indicated in this drawing figure,
• 8 shows a section through a rotary piston internal combustion engine with an ignition system of the type specified here,
• 9 shows a sectional view through the internal combustion engine according to FIG. 8 in accordance with the sectional plane DD indicated in this drawing figure,
• FIG. 10 shows a partial view of the rotary piston of the internal combustion engine according to FIG. 8 in accordance with the viewing direction indicated by the arrow E in FIG. 8 and
• 11 shows a double diagram to explain the relationships in the combustion of super-lean ignitable mixtures.

The internal combustion engine according to FIG. 1 has an engine cylinder 12, the cylinder head of which is connected in one piece to the cylinder block. The reciprocating piston 14, which is connected to the connecting rod 16 in the usual way, is guided within the cylinder. The reciprocating piston 14 has a flat end face which faces a corresponding flat combustion chamber wall, the valves located in the cylinder head part 17 opening into these planes, in a radial surface relative to the cylinder axis, which results in a very simple construction. Between the cylinder block and the cylinder head 17 there is a bore with a conical base that opens into the upper region of the cylinder space and is approximately radial to the cylinder axis, into which a light guide insert 1 having a frustoconical front end is inserted as a light guide housing via a conical ring seal 22, for example made of copper is. The light guide insert 1 is attached to the cylinder block 12 or the cylinder head 17 in the manner shown in FIG. 1 with the interposition of a pressure compensation ring 46, which avoids punctiform pressure concentrations on the light guide insert 1, by means of a holding flange 20 equipped with support legs 21. In the light guide insert 1, multiple light guides 31 run from a beam entry surface 38 of the light guide insert to a convexly curved beam exit surface 36 in the manner shown in FIG. 2 in such a way that the igniting light beams 30 running in the flat-disk-shaped combustion chamber or cylinder chamber pass through one of the light beams within the space mentioned thin layer.

In particular, it should be noted with regard to the light guide insert 1 that it can be made of technical ceramic or Invar steel, while the light guides can be made of quartz on the inside. As will be explained further below in connection with FIGS. 4 and 5, the light guide insert 1 is preferably made of two halves 33 which have grooves which are incorporated in their mutually facing contact surfaces for receiving the light guides 31. Preferably, two half-compartments of the light guides are formed, which emerge closely above one another in two planes. The jet exit surface 36 has a small diameter in order to achieve low heat absorption. The convex shape serves for easier cleaning. After assembly, the two halves 33 of the light guide insert 1 are processed, for example by gluing or soldering with silver solder, in particular on the sealing surfaces and the force introduction surfaces. The beam entry surface 38 and the beam exit surface 36 are finely machined. The mentioned ring seal 22, for example made of copper, brings about good heat dissipation from the light guide insert to the cooling water jacket of the internal combustion engine. The cooling is set in such a way that on the one hand the jet exit surface 36 is kept free of fuel droplets, but on the other hand prevents the jet exit surface 36 from glowing.

The holding flange 20 is preferably designed as a triangular flange with three holding screws and three support legs 21. A rear cylindrical extension of the light guide insert 1 extends through the central opening of the holding flange and the holding flange exerts a pressure holding force on the planar ring surface of the light guide insert 1 via the pressure compensation ring 46, which can be made of aluminum or copper. The depth of the tapered receiving bore for the light guide approach 1 from the support surface of the holding flange 20 is tolerated so that the ring seal 22 seals when the support legs 21 of the holding flange 20 positively sit against the support surface. In addition, the holding flange 20 has an outer centering collar 24, on which a centering cap 29 of a housing 25 with a sliding fit fits, the housing 25 enclosing a radiation-generating device 5, in particular a laser. A beam of rays emerges from the radiation-generating device 5 in the center and is centered on the entry ends of the light guides 31 in the middle of the beam entry surface 38 of the light guide insert 1.

The housing 25 for the radiation-generating device 5 has three cooling devices in order to keep the heat of the internal combustion engine away from the radiation-generating device 5 and also to effectively dissipate the heat generated in the radiation-generating device 5 itself. A cooling device forms the arrangement of outer cooling fins which can be seen in FIGS. 1 and 2 and ensures that the rear end of the housing to which the radiation-generating device 5 is connected is cooler than the front end of the housing 25 which is fastened to the internal combustion engine.

The second cooling device is created by designing the housing 25 in such a way that a cooling air flow occurs through the housing, which enters the housing at 26 at the rear end and exits at 28 at the front end of the housing on the engine side.

Finally, a third cooling device has the shape of a radiation protection ring and cooling air guide ring 27 with a polished surface, which the Prevents heat radiation of the holding flange 20 from the radiation-generating device 5 and directs the cooling air to the end of the device.

If the ignition system proposed here is applied to a reciprocating piston internal combustion engine which has a cylinder head gasket, the light guide insert 1 and the radiation-generating device 5 according to FIG. 3 can assume a different position from the vertical position with respect to the cylinder axis and the system can be in the off position the drawing can be seen connected to the cylinder head 17. The cylinder head gasket is designated 23 in FIG. For the rest, the same reference numerals are used in FIG. 3 as are entered in FIGS. 1 and 2 for corresponding components.

While in the embodiment according to FIGS. 1 and 2, the combustion chamber space in the compression phase has the shape of a flat disk, into which the fan of the igniting rays radially from the disk periphery. If the inside is introduced at half the height of the disc, a correspondingly narrow enclosure of the fan of radiation by the combustion chamber walls and the piston end face can be achieved in the embodiment according to FIG. 3 in that the piston crown receives a rotationally symmetrical cusp 18 which has a spherical crest and rounded transitions to the piston crown and whose axis to the piston axis has an eccentric distance indicated at 19.

In addition to the embodiments according to FIGS. 1 and 2 and according to FIG. 3, it should be noted that a feed device 7 for acting on the radiation-generating device 5 is controlled via a feed line from the ignition contact on the camshaft. The power supply is designated 10 and the ignition switch on the ignition key is indicated at 11.

FIGS. 6 and 7 show a particularly expedient embodiment of the light guide housing for an internal combustion engine with a cylinder head 17 which is separate from the cylinder block 12. In this embodiment, the light guide housing has the shape of a light guide ring 2 which, as can be seen from FIG. 6, is composed of two halves 35 . These halves in turn have grooves on their mutually facing contact surfaces for receiving light guides 32 and the light guides accommodated therein lead from the beam entry surface 39 to the beam exit surface 37 adapted to the cylinder inner surface. The grooves designated 34 in the previously described embodiment according to FIG a depth corresponding to the diameter of the light guide, so that one half of the light guide body carries the light guide to form a fan, while the other half of the light guide body houses the light guide to form the second fan. In the light guide ring 2 35 half-grooves can be formed on the mutually facing surfaces of the halves, so that channels for laying out the light guide 32 are formed in a single plane after the assembly of the light guide ring halves. The light guide ring 2 has. a small overall height in order to realize a small jet exit surface 37 for the purpose of only a low heat absorption.

The two light guide ring halves 35 can in turn be made of technical ceramics or Invar steel and glued together or soldered with silver solder. The cylinder head seals 23 on both sides of the light guide ring 2 bring about an appropriate cooling of the ring by appropriate heat dissipation to the cooling water jacket of the internal combustion engine, with conditions similar to those described for the light guide insert 1 of the previously described embodiments.

It is also noteworthy that in the embodiment according to FIGS. 6 and 7, a radiation-generating device, for example a laser 6, which is acted upon by the supply device 7, is arranged at a distance from the internal combustion engine and is connected to the light guide ring 2 via a light guide cable 3 and a light guide coupling 4 is.

It should be pointed out, however, that this design can also be used in the embodiments according to FIGS. 1 and 2 or according to FIG. 3, while conversely the connection of the light guide insert 1 of the previously described embodiments to the radiation-generating device can also be carried out via optical fiber cables and optical fiber coupling, as in FIG 6 and 7 shown can be made.

As shown in FIGS. 8 to 10, the light guide insert 1 can also be used for Wankel rotary piston internal combustion engines, but has a greater length than in the case of reciprocating piston internal combustion engines, because the housing wall of the motor housing 13, which is provided with inlet and outlet channels, is shaped according to the epitrochoid requires a flat entrance angle for the light rays, as shown in FIG. 8. It is therefore expedient to provide an additional centering shoulder 47 on the holding flange 20, which is accommodated in a corresponding recess in the housing of the internal combustion engine with a narrow sliding fit. The centering approach can also be provided for shorter light guide inserts for reciprocating internal combustion engines.

The rotary piston 15, which is provided with circumferential sealing strips 41 and a flame retainer 42 in the form of additional sealing strips with a limited stroke, with retaining pieces 43 limiting the stroke of the flame retainers 42, is equipped on the rotary piston base with combustion chamber longitudinal grooves 40 which on each side of the triangular piston from reach approximately one peripheral sealing strip to the other peripheral sealing strip. In these longitudinal grooves 40, which form a flat rectangular combustion chamber with the trochoid wall, half of a rectangular side of the combustion chamber is formed from the central region Combustion chamber height initiated the igniting light beams 30.

A special feature of the Wankel rotary piston internal combustion engine shown is the additional flame retainer 42 in the form of the additional sealing strip, which seals only on the circumference and has a limited stroke, in front of the circumferential sealing strips 41, i. i.e., leading the peripheral sealing strips. Due to the stroke limitation, the flame retainers 42 do not touch the entire trochoidally shaped housing wall, but only the flattened parts of the trochoids.

The effect of the flame retainer is illustrated in FIG. 10. When the circumferential sealing strips 41 pass through the combustion chamber slot 44 to introduce the igniting light beams, the slot being wider than the so-called firing opening in the case of spark-electric ignition, the combustion gases 45 flow around the flame retainer strips on both sides, then the narrow gap between the rotary piston and trochoid between the two sealing strips 41 and 42 to the inside and finally reach outside the peripheral sealing strip 41 and along the width of the slot 44 into the fresh gas of the subsequent chamber. The fuel gases are cooled by the cool machine parts and especially by the trochoid wall and the flame is extinguished. At the same time, the fresh gas is blown back into the subsequent chamber from the space between the two sealing strips and, in the further course of the rotary piston process, can no longer reach the unburned hydrocarbon fraction in the exhaust gases, as a result of which the hydrocarbon emissions in the exhaust gases are reduced. The flame retardant strips 42 can be made from coal or from technical ceramics.

The relationships of the super-lean combustion concept are shown in FIG. 10 with the aid of known internal combustion engine diagrams and with moderate turbulence in the combustion chamber. The ignition limit is 62, the knock limit at z. B. RON = 92 with 63. In addition, the emaciation limit for electrical single-point spark ignition is indicated at 64 and the working range for electrical single-point spark ignition at 65. The area 66 is the working area in the case of light beam ignition with the realization of a multiplicity of points with elementary ignition processes. The arrow 67 indicates the shift of the lean limit 64 by the light beam ignition. At 68, a construction point for a light-ignited internal combustion engine is entered, for example. With 69, 70, 71 and 72, the characteristic curves of the hydrocarbon emission in the case of ignition with one ignition spark or with two ignition sparks or with three ignition sparks or with five ignition sparks are shown in the diagram.

FIG. 10 is a double diagram which shows the known relationships between the air-fuel ratio \ and the compression ε in the upper part and the relationship between the air-fuel ratio and the exhaust gas emissions CO in the lower part , NO and CH illustrates. Since the air-fuel ratio λ is arranged on the horizontal axes in both partial diagrams, its value can be transferred directly from the upper part to the lower part, and vice versa.

The super-lean combustion concept due to the construction specified here is located in the right half of both part diagrams, to the right of the leanness limit 64.

In this area, conventional single-point spark ignition can no longer be used advantageously because the very lean air-fuel mixture extinguishes the burn-off front prematurely, a lot of unburned hydrocarbons remain as residual gases, and increases CH emissions. An improvement by burning the entire cylinder charge can only be achieved by multiple ignition, which ignites the mixture at many points at the same time. For this would, for. B. ten or more spark plugs useful, but which can not be accommodated in the cylinder head, and whose power supply would be very expensive and difficult.

In order to achieve the same effect with significantly simpler means, the light beam ignition is proposed, which is the mechanical engineering basis for the super-lean combustion concept.

The light beam ignition is designed from the outset to generate many ignition points that are also spatially distributed in the combustion chamber. Comparable to this is e.g. B. a spatial distribution of the ignition points in spark plugs is not possible.

In particular, a light beam ignition with a beam fan is suitable for successively striking the small and very small fuel droplets in the combustion chamber caused by spatial turbulence in the whirling movements in the igniting light beams and for their individual combustion or combustion with several small combustion fronts cause. It is important that the temperature increase required to achieve ignition in the light beams is not great, since the ignition temperature of the air-fuel mixture is already around 250 ° C. with increased compression, and the temperature Increases due to the compression. Due to the spatial multi-point ignition with a medium turbulence in the combustion chamber, unburned hydrocarbons can essentially not remain as residual gases, so that, as indicated at 74 and 73, the CH emission of this area 66 can be effectively reduced.

On this basis, a construction point 68 for a light-beam ignited internal combustion engine is entered in both partial diagrams, with z. B. Air-fuel ratio X of - 1.9; a compression ₈ of - 13 and a CH emission of - 1.5 g / KWh. It is assumed that even higher leanings and densifications can be achieved, as entered at 75.

• a) der Abgas-Katalysator ist überflüssig und kann weggelassen werden, wobei die super-magere Verbrennung für geringe schädliche Abgas-Emissionen sorgt, die noch günstiger ausfallen dürfen als bei Verwendung eines Katalysators. Dadurch wird die Brennkraftmaschine billiger in der Herstellung und in der Wartung ;
• b) das Kraftfahrzeug kann (vorübergehend) auch mit verbleiten Kraftstoffen betrieben werden, ohne einen Schaden zu erleiden ;
• c) der Kraftstoff-Verbrauch sinkt weiter ab, weil das Luft-Kraftstoff-Gemisch noch einmal abgemagert wird ;
• d) die klopfende Verbrennung wird gänzlich wegfallen, weil durch die gleichzeitige räumliche Vielpunkt-Zündung bei mittlerer Turbulenz keine Gemisch-Restbereiche übrig bleiben, die durch die Zündungs-Druckerhöhung in der Brennkammer von selbst zünden ;
• e) der Oktan-Zahl-Bedarf der Brennkraftmaschine wird gesenkt (ersichtlich im oberen Teil-Diagramm der Figur 10), wodurch man im Kraftstoff kein Bleietraäthyl und vielleicht auch kaum andere Klopfbremsen benötigt :
• f) die leichtstrahlgezündete Brennkraftmaschine kann bei z. B. Einspritzung des Kraftstoffes auch mit Dieselöl oder mit Kerosin betrieben werden.

Light beam ignition also offers the following operational options:

• a) the exhaust gas catalytic converter is superfluous and can be omitted, the super-lean combustion ensuring low harmful exhaust gas emissions, which may be even cheaper than when using a catalytic converter. This makes the internal combustion engine cheaper to manufacture and to maintain;
• b) the motor vehicle can also (temporarily) be operated with leaded fuels without suffering any damage;
• c) the fuel consumption drops further because the air-fuel mixture is emaciated again;
• d) the knocking combustion will be completely eliminated, because due to the simultaneous spatial multi-point ignition with medium turbulence, no residual mixture areas remain which ignite automatically due to the ignition pressure increase in the combustion chamber;
• e) the octane number requirement of the internal combustion engine is reduced (as can be seen in the upper part diagram of FIG. 10), as a result of which no lead ethyl and possibly hardly any other knocking brakes are required in the fuel:
• f) the light beam ignited internal combustion engine can be at z. B. Fuel injection can also be operated with diesel oil or with kerosene.

As already noted, dyes can be added to the fuel, which increase the radiation absorption and thereby improve the readiness to ignite and which brighten when burned in order to open the way for further, still unburned mixture areas for the igniting light beam. Examples of such dyes are cryptocyamine-methanol solutions in combination with ruby lasers as the radiation source or phthalocyanine nitrobenzene solutions in combination with Nd gas lasers or explosives such as picric acid for lasers in the yellow spectrum range or for broadband lasers. In addition, as already mentioned, the ignition processes can be improved by pulsing the laser beams in the frequency range from 500 Hz to 1 MHz.

Claims (13)

1. Internal combustion engine, in which an ignitable fuel mixture is compressed during a compression phase in a combustion chamber space by means of a reciprocating piston (14) or a rotary piston (15), with optical fibres (31, 32) which lead into this combustion chamber space and through which high-energy radiation, in particular laser radiation, emanating from a light source arrangement (5, 6) can be introduced in the form of a plurality of beams (30) into the combustion chamber, characterized in that, at least at the ignition time, a layershaped space can be generated in the combustion chamber, which space is penetrated by a multiplicity of the beams (30) in the form of a fan of beams and which is surrounded as a small space by the combustion chamber walls and the piston endface opposite the latter, and that the arrangement is made such that, at least in a substantial cross-sectional region of the layer-shaped space, elementary ignition processes can be triggered at the ignition time in such a way that the flame fronts emanating from adjacent elementary ignition processes meet before the piston endface is significantly displaced during the expansion stroke.

2. Internal combustion engine according to Claim 1, characterized by a compression of more than 1 :10, especially more than 1 :13.

3. Internal combustion engine according to Claim 1 or 2, characterized in that a lean air/fuel mixture of 1.7to more than 2.0 can be introduced into the combustion chamber space.

4. Internal combustion engine according to one of Claims 1 to 3, characterized by means for the admixture of dyestuffs to the fuel, especially for the admixture of cryptodyanine/methanol solutions or phthalocyanine/nitrobenzene solutions or of liquid fuels, for example of picric acid.

5. Internal combustion engine according to one of Claims 1 to 4, characterized in that substances of higher light absorption, which are bleached by the combustion, can be admixed to the fuel.

6. Internal combustion engine according to one of Claims 1 to 5, characterized in that the optical fibres are accommodated in an optical fibre housing which has the shape of a ring (2) of small overall height and of an internal diameter corresponding to the cylinder diameter of the reciprocating-piston internal combustion engine, the ring being arranged between the engine block (12) and the cylinder head (17) with interposed cylinder head gaskets (23), the optical fibres running from a beam inlet surface (39) located on the periphery of the ring in a radial central plane to the beam outlet surface (37) on the inner wall of the bore of the ring (2).

7. Internal combustion engine according to Claim 6, characterized in that the ring (2) forming the optical fibre housing is composed of two identical halves (35) and half-grooves for receiving the optical fibres are cut into the mutually adjoining surfaces of the halves, the two halves being made, in particular, of technical ceramics or of invar steel and being glued together and soldered together with silver solder.

8. Internal combustion engine according to one of Claims 1 to 5, characterized in that the optical fibres are accommodated in an optical fibre housing which has the shape of a rotationally symmetrical body fitted in as an insert (1) and having a beam inlet surface (38) which is adjoined by a cylindrical peg part and a conically tapering section providing a conical sealing surface with a beam outlet surface (36), the optical fibres running within the insert from the beam inlet surface to the beam outlet surface (36) from which the beams emanate as a fan of diverging ignition beams.

9. Internal combustion engine according to Claim 8, characterized in that the insert (1) is composed of two halves, grooves being cut into one surface, adjoining the parting surface between the halves, of one half of the insert for receiving optical fibres for generating one half-fan, and grooves being cut into the surface, adjoining the parting surface, of the other half of the insert for receiving optical fibres for generating a second half-fan, and the two halves (33) of the insert being made of technical ceramics or of invar steel and being glued together or soldered together with silver solder.

10. Internal combustion engine according to Claim 8 or 9, characterized in that, for sealing and appropriate cooling of the insert (1), conical ring gaskets (22), especially of copper, are used, which bear against the conically tapering sealing surface of the insert (1), and that the insert is fixed by means of a holding flange (20) which is joined to the internal combustion engine by means of three holding bolts and three support legs distributed on the periphery and which, especially in the case of long optical fibre inserts, is also provided with a centering adaptor (47) which fits with narrow sliding seating into a corresponding recess in the housing of the internal combustion engine, the cylindrical peg of the optical fibre insert passing through the central orifice of the holding flange, and the holding flange exerting a holding thrust force on the plane ring surface of the optical fibre insert by means of a thrust- compensating ring (46), and the holding flange additionally having an outer centering collar (24) for the housing (25) of the radiation-generating apparatus.

11. Internal combustion engine according to Claim 10, characterized in that the housing (25) for the radiationgenerating apparatus has a centering cap (29) which fits with narrow sliding seating onto the centering collar (24), and the housing additionally has three cooling devices :

1. external air cooling fins,

2. a cooling-air stream through the housing, with the cooling-air inlet (26) at the outer housing end and the cooling-air outlet (28) near to the internal combustion engine, and

3. a radiant-heat protection ring and cooling-air guide ring (27) around the end of the radiation generating apparatus (5 ; 60) on the side of the internal combustion engine.

12. Internal combustion engine with reciprocating pistons according to one of Claims 1 to 11, characterized in that, in the case of a cylinder head oriented at an angle to the cylinder axis, the piston endface is provided with a protrusion (18) which preferably is rotationally symmetrical and has a spherical cap and rounded transitions to the remaining parts of the piston endface and is located eccentrically to the piston axis and close to the inlet point of the beam fan.

13. Internal combustion engine according to one of Claims 1 to 11, with rotary pistons, characterized in that the rotary piston is provided with a shallow longitudinal groove (40) which extends on each side of the triangular rotary piston from approximately one peripheral sealing strip to approximately another peripheral sealing strip, the longitudinal groove having the same depth across its entire width.

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