| Title of Invention | IGNITION DEVICE FOR AN INTERNAL COMBUSTION ENGINE |
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| Abstract | The invention relates to an ignition device for an internal combustion engine, comprising at least one pump light source, which supplies a pump light. The device is equipped with a laser unit (26), which generates a laser pulse (24) that is emitted in a combustion chamber. An optical fiber (28) transmits the light (60) pumped by the pump light source to the laser unit (26). According to the invention, a laser-active solid body (44), a passive Q-switch (46), an input mirror (42) and an output mirror (48) of the laser device (26) are configured as an integrated monolithic part (50). |
| Full Text | Ignition device for an internal combustion engine State of the art of technology The invention relates to an ignition device for an internal combustion engine according to the generic description of the claim 1. An ignition device under the generic category is already known from the patent document WO 02/081904, in which on a cylinder of an IC engine a laser-ignition device is provided. The laser device proper is connected through a light conducting device formed by an optic fibre, with a light pumping source, which pumps the labour device optically. The task of the above invention is to further develop an ignition device of the type mentioned at the outset so further that it can be applied as price competitively as possible in large series. This task is achieved through an ignition device with the characteristics of claim 1. Advantageous further developments are indicated in sub -claims. Advantages of the Invention The monolithic component visualized according to the invention can well withstand the external conditions applicable to an internal combustion engine of an automobile such as accelerations, very low and very high temperatures as well as high temperature gradients, without any need for complex and expensive design measures such as for instance for fastening the inward coupling mirror and the outward coupling mirror. Already as a result of this, manufacturing cost would be substantially reduced. Furthermore, also the reliability in the operation of such an ignition device is enhanced as a result of this, because the individual elements cannot alter their positions to each other important for the operation of the ignition device despite the external stresses. Moreover, the assembly costs and assembly times are reduced, because lesser number of separate components must be handled. Further, such a monolithic component can be automatically manufactured, which similarly reduces the manufacturing costs. This is applicable especially then if the different mirrors can be produced through a corresponding coating of an end-surface of the area of the laser-active fixed-body and if the monolithic component is made of a Wafer. Additional cost-savings can be achieved if the resonator of the laser device is formed not only through the laser-active fixed-body, but additionally through a glass /optic body. In this case, the relatively expensive laser-active fixed-body can be considerably smaller. In this context, different arrangements /configurations of the optic bodies relative to the laser-active fixed-bodies of the laser device and relative to the Q-switch are possible, depending upon the individual assembly requirement. Radially around the laser-active fixed body, a reflection device, for instance, in shape of an optic body, can be arranged, in order that in this manner the pumped light radiated by the light conducting device passing the inward - coupling mirror, is injected in the laser-active fixed-body. Hereby, an ignition device which can be obtained with a short design without special inward coupling optic, but nevertheless working with a very high degree of effectiveness, can be realized. An improvement in the effectiveness degree is possible also through the use of an optical booster, which can be supplied by a light pumping source of its own or by the light pumping source of the labour device. The first variant facilitates the realization of higher efficiency whereas the last mentioned variant is very simple from the point of view of design. This is applicable especially then if the optical booster and the laser device are monolithic. Even here a monolithic unit consisting of the labour device, the optic bodies, reflection device and optical booster can be formed, where the reflection device can make available at least one reflection surface through which the pumped light is reflected not only to the labour active bodies of the laser device but also towards the booster. In this manner, very compact, sturdy units which can be manufactured in large series automatically are realizable. It is also possible that the pumped lights supplied from a single pumped light source can be divided through a bi-focal lens on the one side to the laser device and on the other, to the optical booster. A cost reduction can be achieved also through the monolithic structure of that optical device through which the laser beam is inward-coupled in the combustion chamber and focussed there on a specific spot. Drawings Specially preferred design examples of the above invention are further elucidated below under reference to the enclosed drawing. The drawings show: Figure 1 a schematic illustration of an IC engine with an ignition device; Figure 2 a schematic illustration of the ignition device of figure 1; Figure 3 an enlarged illustration of an area of figure 2; Figure 4-21 different design examples of the ignition device of figure 2; and Figure 22 an illustration of the front side of a composite lens of the design example of figure 21. Description of the design examples An IC engine carries in figure 1in its entirety the reference number 10. It serves to drive an automobile not illustrated. The IC engine 10 encompasses several cylinders, of which only one with reference number 12 is shown in figure 1. A combustion chamber 14 of the cylinder 12 is bordered / restricted by a piston 16. Fuel reaches the combustion chamber 14 direct through an injector 18, which is connected to a fuel ("rail") 20. The fuel 22 injected in the combustion chamber 14 is ignited by a laser impulse 24, which is radiated in the combustion chamber 14 by an ignition device 27 encompassing a laser device 26. For this purpose, the laser device 26, through a light conducting device 28, is supplied with a pumped light, which in turn is supplied by a pumped light source 30. The pumped light source 30 is controlled by a control-and regulating- device 32, which also triggers the injector 18. As can be seen from figure 2, the pumped light source 30 supplies several light conducting devices 28 for different laser devices 26. For this purpose, it makes use of several individual-light sources 34, which are connected with a pulse-current- supply 36. The laser device 26 includes a housing 38 in which, seen from the direction of the pump light, the following are arranged: to start with, a lens 40, then an inward coupling mirror 42, further a laser-active fixed-body 44, a passive Q-switch 46 and an outward coupling mirror 48 (compare also figures 4-7). The elements 42-48 are designed as a total monolithic component 50. In figure 2, left from the outward coupling mirror 48, a focusing optic 52 is available, which, as is evident from figure 3, is designed as a monolithic component with a concave entry surface 54 for beam expansion (dispersal lens) as well as a convex exit surface 56 for focusing (compacting lens). The focusing optic 52 is designed preferably non-spherical / aspherical. Further, a combustion chamber window 58 is visualized which is however advantageously designed as a single piece with the focusing optic 52. Now, based on figures 4-7, different principal designs of the laser device 26 are explained. For reasons of simplicity, for those elements and areas which have equivalent functions to elements and areas of design forms described earlier, the same reference numbers are applied. In this regard, the design examples shown in figure 4 somewhat corresponds to the arrangement illustrated in reduced scale in figure 2. The arrangements shown in figure 5 is very similar, all the same the pumped light 60 exits from the light conducting device 28 marginally divergent and reaches the inward coupling mirror 42. Under the arrangement as per figure 6, the pumped light is concentrated on the inward coupling mirror 42 at the laser-active fixed body 44 through a composite /compact lens 60 while under the design form of figure 7 and through a gradient - index - lens 40. Hereby, an optimum beam density of the pumped light 60 can be adjusted / set, and lesser pumped light 60 goes waste. Moreover, the optically critical border areas of the laser-active fixed-body 44 can be omitted. The principal method of function of the labour device 26 is as follows: Pumped light 60 leaves the light conducting device 28 and penetrates through the inward coupling mirror 42, which is transparent for the wave length of the pumped length 60, into the rod shaped laser active fixed bodies 44. The pumped light 60 is absorbed there, leading to an occupation inversion. Through the high losses of the passive Q-switch 46, laser oscillation is avoided. With increasing pumping duration, the beam density increases in the inner areas of the resonator 62. From a certain beam density, the passive Q-switch 46 fades, the boosting exceeds the total loss in resonator and the laser begins to oscillate. In this manner a "massive pulse" 24 occurs, a pulse with a very high peak performance. This amounts typically to a few Megawatt for a time duration of a few Nano-seconds. Prerequisite for this is that the inward-coupling mirror 42 has for the wave-length of the laser light 24, a high degree of reflective property, the outward coupling mirror 48 however a partial reflective property for the wavelength of the laser light 24, and the passive Q-switch 46 a certain start/initial transmission. The laser devices 26 shown in figures 4-6 can be assembled very easily and therefore are especially price-competitive. The connection between the laser-active fixed-body 44 and the Q-switch 46 is ideally done through wringing or through thermal bonding. The inward coupling mirror 42 and the outward coupling mirror 48 are produced through a coating of the axial end-surface of the laser-active fixed-body 44 and /or of the Q-switch 46. Another basic principle is shown in Figures 8 and 9. There, the resonator 62 of the laser device 26 is formed through a combination of the laser-active fixed-body 44 and an optic-body 54. This allows keeping of the length of the laser-active fixed-body 44 comparatively small, which reduces the manufacturing cost. Another distinct advantage is that through a longer resonator, the beam quality of the laser device can be improved. Moreover, it is possible to control the pulse duration of the 'massive impulse' with the refraction index of the special glass/optic and the length of the glass-body. However, the prerequisite for this is that the pumped-light is completely absorbed in the laser-active fixed-body 44, despite its lesser/shorter length. In the laser-device shown in Figure 8, the Q-switch 46 is arranged between the laser-active fixed-body 44 and the glass-body 64, and the outward-coupling mirror 48 is located on the open axial end-surface of the glass-body 64. In the laser device 26 shown in figure 9 the glass body 64 is arranged in contrast between the Q-switch and the laser-active fixed-body 44, and the outward coupling mirror 48 is located on the axial end surface of the Q- switch 46, as in design examples of figures 4-7. Additionally, between the laser -active fixed body 44 and the glass body 64, there is a layer 66 highly reflective for the pumped light 60, but transparent for the laser light 24, so that the pumped light 60 not yet absorbed over the axial length of the laser-active fixed body 44, is re-reflected on this layer. In the design as per figure 10, a lens is dispensed with. Instead, the pumped light beam by-passing the laser active fixed body 44 is radiated on the reflection device, which is designed as a type of sleeve surrounding the glass body 69. On its radial outer reflection surface 67, which is equipped with a mirror coating where applicable, the pumped light 60 is reflected again towards the laser active fixed body 44, as for example illustrated through the beam 60a, and inward coupled in it transversely. The mirror coating can above all then be dispensed with if the glass body 69 does not have towards radial outer any optical contact to another medium. Otherwise, the mirror coating 67 can be realized even simply through an adhesive material with which the glass body 69 is attached to another body. It is understood that the glass body 69 or the reflection surface 67 need not have, only a cylindrical outer contour but even one which narrows itself conicaily or one with a bent outer contour. Even in the design form shown in figure 11, a reflection device in form of a glass body 69 is provided radially outer half of the laser active fixed body 44. Its radial inner border surface abuts however only in an area on the Q-switch 46; however, in contrast it is designed conicaily in the area of the radial outer half of the laser-active fixed body 44, as reflection surface 67, and equipped with a mirror coating 68. Pumped light 60 is reflected also on this (for example beam 60a and 60b), which cannot be inward coupled longitudinally in the laser-active fixed body 44 through the inward coupling layer 42, and inward coupled transversely in the laser active fixed body 44. The extractable energy of such a device is especially high, because a large volume of laser active fixed body 44 can be pumped. Alternatively, in case of the glass body 69 even a metal body can be used, which is equipped with a reflective, for instance polished, reflection surface. It is also conceivable to fill the intermediate space between light conducting device 28 and the laser device 26 with a transparent casting mass. In the devices shown in figures 8-11, the glass body 64 or 69 is connected with the laser device 26 firmly and represents to that extent a part and parcel of the monolithic component 50. In figures 12-21, again other variants of a laser device 26 are illustrated. In these devices, an optical booster 70 is visualized optically in series to the laser device 28. In figure 12, the optical booster 70 which is essentially formed through a laser active fixed body is arranged co-axially to the laser active fixed body 44 of the laser device 26. The optical booster 70 in this context makes use of a pumped light source of its own (not illustrated) which conveys the pumped light 74 through its own light conducting device 72 to the optical booster 70. In this context, the pumped light 74 is inward coupled longitudinally in the optical booster 70, in that it is radiated through a lens 76 and two deflection mirrors 78a and 78b on the front side 79 of the optical booster 70 facing the Q-switch 46. The mirror 78b arranged between the laser active fixed body 44 of the laser device 26 and the optical booster 70 is highly reflective for the wave length of the pumped light 74 for the booster 70, but transparent for the laser light 80 radiated from the laser device 26 to the booster 70. The design form illustrated in figure 13 works similarly, where laser device 26 and optical booster 70 are monolithic in this case. In order to achieve this, the pumped light 74 from the light conducting device 72 is pumped to the optical booster 70 from "around the rear", that is, at that front side from which the boosted laser beam 24 exits. This denotes that the mirror 78b is highly reflective for the pumped light 74 but transparent for the laser impulse 24. Yet another design form is shown in figure 14. In this, a multiple passage of the laser light 80 through the optical booster 70 is realized. Advantageously, the dosage of the optical booster 70 is so selected that the energy of the pumped light 74 is only absorbed at the end of the optical booster 70. The multiple passage of the laser light 80 in optical booster 70 is achieved thereby that the laser beam 80 meets not perpendicular on the axial end surface 79 of the optical booster 70, but slanted /inclined. For this purpose, the longitudinal axis of the optical booster 70 is tilted as against the respective laser active fixed body 44. A further advantage of this configuration is that for inward coupling of the pumped light 74 in the optical booster 70 only one single deflection mirror 78 is required; where applicable even no such deflection mirror at all. In figures 15-21, design forms are shown with which an optical booster 70 is provided, and an additional light conducting device can however be dispensed with. The arrangement shown in figure 15 is similar to that of figure 10. All the same, seen in the direction of the optical axis, immediately at the rear of the Q-switch 46 with the outward coupling mirror 48 the optical booster 70 is arranged. A sleeve-type reflection device in form of an optical /glass body 69 extends itself again radially towards the outer from laser - active fixed body 44, from Q-switch 46 and also from optical booster 70. With the diameter of the sleeve type glass body 69 is so selected that pumped light 74a, 74b and 74c exiting from the light conducting device 28 and by-passing the inward coupling mirror 42 of the laser active fixed body 44 of the laser device 26 reflects on the radial outer reflection surface 67 of the sleeve type glass-body 69, which is provided with a mirror coating where applicable, and is inward coupled transversely in the optical booster 70. In this context, the laser device 26, the optical booster 70 and the glass body 69 can be designed altogether as a monolithic part. The device shown in figure 16 is-similarly built, in total however short because the radial outer circumferential surface of the glass body 69 narrows itself conically, seen in beam direction. The design shown in figure 17 is again similar to that of figure 14. However, the laser device 26 as against the axis of the light conduction device 28 is arranged with somewhat of an offset. Further, the mirror 78 is designed as a collective mirror, which concentrates the pump light rays 74 exiting divergently from the light conducting device 28 on the axial entry surface 79 of the optical booster 70. An extremely simple arrangement is shown in figure 18. In this, the optical booster 70 directly joins the Q-switch 46 and /or the outward coupling mirror 48 provided on it, and it is supplied by the pumped light (without reference number) which penetrates from the light conducting device 28 through the laser-active fixed-body 44, that is, what is not fully absorbed by it. This means that the Q-switch 46 for the wave length of the pumped light for the optical booster 70 is transparent and also the outward coupling mirror 48 must be transparent for the wave length of the pumped light for the optical booster 70. Moreover, the pumped light radiation for the optical booster 70 should have a lesser divergence. Even here, the booster 70 is part of the monolith 50. In the device shown in figure 19 again the pumped light 74 for the booster 70 comes from the light conducting device 28 direct to the optical booster 70. The pumped light 60 for the laser active fixed body 44 of the laser device 26 penetrates through the optical booster 70 and only then arrives at the laser active fixed-body 74. The mirrors 42' and 48' are correspondingly designed. The axial length surface 79 of the optical booster facing the light conducting device 28 is designed with a slant and is equipped with a mirror coating 84 which is transparent for the pumped light 60, 74, but reflective for the wave length of the laser beam 24. In this manner, the laser variation 80 radiated from the laser active fixed body 44 in the optical booster 70 as an inclined /slant reflection and exits as laser beam 24 with a slant from the optical booster 70. The arrangement as per figure 20 has a still greater effectiveness degree. In this, the pumped light 60 exiting from the light conducting device 28 is collected by a bi-focal Fresnel lens 40 and is beamed in the shape of two discreet beams through a mirror arrangement 84 on the laser active fixed body 44 and the optical booster 70 arranged adjacent to it. The laser active fixed body 44 of the laser device 26 and the laser active fixed body of the optical booster 70 is designed in this case as a monolithic single piece 50. The mirror arrangement 84 encompasses two mirror surfaces 84a and 84b positioned in a right angle to each other, which are transparent for the pumped light 60 emanating from the light conducting device 28 but however reflective for the laser light 80 exiting from the laser active fixed body 44 of the laser device 26. In this manner, the laser beam 80 reversing from the laser device 26 is deflected side-wards and back to the optical booster 70. The arrangement illustrated in figure 21 works similarly, where the laser active fixed body 44 of the laser device 26 and the optical booster 70 are designed as separate components and where the pumped light 60, 74 is generated through a non-rotation-symmetric bifocal collective lens 40, corresponding to figure 22 with two lens centres 40a and 40b. The device illustrated in figure 21 has the advantages, similar to that in figure 20, that only one light conducting device 28 is required, that laser device 26 and optical booster 70 are longitudinally pumped with corresponding high efficiency, that the laser beam 24 exits axially, and that the total dimensions are relatively small. Needless to say the devices shown in figures 12-21 in which a laser device 26 is coupled with an optical booster 70 can be combined with the design forms shown in figures 8-11, in which additionally a glass / optic body 64 is provided. Further, even if not illustrated, an outward coupling surface of the optical booster 70 (fo instance surface 86 is figure 20) can be equipped with a partial mirroring, whereby a "coupled resonator" comes into being. In this manner, a partial multiple-passage is obtained through the optical booster 70. Claims 1. Ignition device for an internal combustion engine (10), especially of an automobile, with minimum one pumped light source (30) which makes available a pumped light (60), with a laser device (26) which generates a laser impulse (24) for beaming in a combustion chamber (14), and with a light conducting device (28) which transmits the pumped light (60) from the light source (30) to the laser device (26), is thereby characterized that a laser-active fixed body (44) and a passive Q-switch (46) ideally also an inward coupling mirror (42) and an outward coupling mirror (48) of the laser device (26) are together designed as a monolithic component /unit (50). 2. Ignition device according to claim 1 is thereby characterized that the laser active fixed body (44) and the passive Q-switch (46) are jointed with one another through wringing, through thermal bonding or through a sinter-process. 3. Ignition device according to one of the claims 1 or 2 is thereby characterized that inward coupling mirror (42) and /or the outward coupling mirror (48) are produced through a die-electric coating. 4. Ignition device according to one of the above claims is thereby characterized that the monolithic unit (50) is produced as a Wafer. 5. Ignition device according to one of the claims is thereby characterized that a resonator (62) of the laser device (26) is formed through the laser active fixed body (44) and minimum one glass / optic body (64). 6. Ignition device according to claim 5 is thereby characterized that the glass body (64) is arranged serially to the laser active fixed body (44) and is longer than it. 7. Ignition device according to one of the claims 5 or 6 is thereby characterized that the glass body (64) and the laser active fixed body (44) are monolithic. 8. Ignition device according to one of the claims 5 to 7 is thereby characterized that the glass body (64) is arranged between passive Q-switch (46) and the laser active fixed body (44) and that between the laser active fixed body (44) and the glass body (64) a transparent layer (66) is provided which is highly reflective for the pumped light (60) but transparent for the laser light (24). 9. Ignition device according to one of the above claims is thereby characterized that a reflection device (69), especially an optic body, is arranged parallel to the laser active fixed body (44), especially surrounds it radially from the outer, and that the reflection device (69) has a reflection surface (67) from which pumped light (60) is reflected transversely in the laser active fixed body (44). 10. Ignition device according to claim 9 is thereby characterized that the reflection surface (67) is inclined /tilted or conical. 11. Ignition device according to one of the above claims is thereby characterized that it encompasses an optical booster (70), in which pumped light (74) is inward coupled and is arranged optically in series to the laser device (26). 12. Ignition device according to claim 11 Is thereby characterized that the laser device (26) is supplied by a first light conducting device (28) and the booster (70) by a second light conducting device (72). 13. Ignition device according to one of the claims 11 or 12 is thereby characterized that the laser device (26) and the booster (70) is supplied by the same light conducting device (28). 14. Ignition device according to claim 13 is thereby characterized that the pumped light (74) is divided through a bi-focal composite /collective lens arrangement (40) on the laser device (26) and the booster (70). 15. Ignition device according to claims 11 to 14 is thereby characterized that the booster (70) is supplied transversely through reflection on a reflection device surrounding it, especially a reflection surface (67) of an optical body (69). 16. Ignition device according to claim 15 is thereby characterized that the reflection device (69) narrows itself conically, seen in beam direction. 17. Ignition device according to claims 11 to 16 is thereby characterized that the booster (70) is supplied longitudinally through reflection on a reflection device (78). 18. Ignition device according to one of the claims 11 to 17 is thereby characterized that the passive Q-switch (46) and the outward coupling mirror (48) of the laser device (26) are transparent for the wave length of the booster - pumped light (74), that the pumped light (60) from laser active body (74) of the laser device (26) is not fully absorbed and that the booster (70) is located on the side f the laser device (26) opposite to the light conducting device (28). Ignition device according o one of the claims 11 to 18 is thereby characterized that the booster (70) is arranged optically between the light conducting device (28) and the laser device (26), a reflector (42)' optically behind the passive Q-switch (46) and the outward coupling mirror (48)' between booster (70) and laser active fixed body (44) of the laser device (26), where the area (82) of the booster (70) in which the pumped light (60,74) is inward coupled is designed with a tilt / incline, and the booster (70) includes a side outward coupling area (86). Ignition device according to claims 11 to 18 is thereby characterized that a reflector (42') is arranged optically behind the Q-switch (46) and the outward coupling mirror (48') on the side of the laser active fixed body (44) of the laser device (26), and that it includes a deflection direction (84) which deflects the laser beam (80) to the booster (70). Ignition device according to claim 20 is thereby characterized that the booster (70) and the laser active fixed body (44) of the laser device (46) are arranged side by side, and are preferably monolithic. Ignition device according to claims 11 to 21 is thereby characterized that the outward coupling surface (86) of the booster (70) has a partial mirroring. Ignition device according to one of the above mentioned claims is thereby characterized that it includes a focusing optic /lens (52) for the laser beam (24), which in turn encompasses a dispersal lens (54) and a collective / composite lens (56) which are incorporated in a monolithic unit. Ignition device according to claim 23 is thereby characterized that the monolithic unit (52) includes a combustion chamber window (58) or is itself the window. |
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| Patent Number | 272452 | |||||||||||||||
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| Indian Patent Application Number | 5445/CHENP/2007 | |||||||||||||||
| PG Journal Number | 15/2016 | |||||||||||||||
| Publication Date | 08-Apr-2016 | |||||||||||||||
| Grant Date | 01-Apr-2016 | |||||||||||||||
| Date of Filing | 27-Nov-2007 | |||||||||||||||
| Name of Patentee | ROBERT BOSCH GMBH | |||||||||||||||
| Applicant Address | POSTFACH 30 02 20 D-70442 STUTTGART | |||||||||||||||
Inventors:
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| PCT International Classification Number | F02P 23/04 | |||||||||||||||
| PCT International Application Number | PCT/EP06/61049 | |||||||||||||||
| PCT International Filing date | 2006-03-27 | |||||||||||||||
PCT Conventions:
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