DE102011076854A1 - Optical splitter for laser ignition system of internal combustion engine for distribution of laser radiation, has laser source for providing laser radiation and optical output level for uncoupling of laser radiation - Google Patents

Abstract

The optical splitter (100) has a laser source (110) for providing laser radiation, an optical output level (120-1) for uncoupling of laser radiation and a distribution system (130) for selective distribution of the laser radiation on one of the optical output levels. The laser source has a vertically emitting semiconductor laser. The distribution system has a movable mirror (132) or a movable lens. The movable mirror is rotatably arranged around an axis. An independent claim is included for a method for operating an optical splitter.

Description

State of the art

The invention relates to an optical distributor for distributing laser radiation, in particular for a laser ignition system of an internal combustion engine, wherein the optical distributor comprises a laser source for providing laser radiation, at least two optical output stages for coupling out laser radiation, and a distributor system for selectively distributing the laser source provided by the laser source Laser radiation on at least one of the optical output stages.

The invention further relates to an operating method for such an optical distributor.

An optical distributor of the type mentioned is, for example, from US Pat. No. 7,421,166 B1 known.

Disclosure of the invention

It is an object of the present invention to improve an optical distributor of the aforementioned type and a corresponding operating method in that a flexible and reliable operation of the optical distributor is possible.

This object is achieved according to the invention in the optical distributor of the aforementioned type in that the laser source has at least one vertically emitting surface-emitting laser (VCSEL).

According to the invention, it has been recognized that, in particular when using a plurality of VCSEL laser elements (vertical emitters) as the laser source, a highly collimated laser radiation is obtained, which advantageously makes it possible to bridge relatively large optical path lengths between the individual components of the optical distributor, without the Significantly change the beam properties of the laser radiation produced. This results in advantageous degrees of freedom with respect to the spatial structure or the arrangement of components of the optical distributor.

In addition, the VCSEL laser elements, which are also referred to as surface-emitting semiconductor lasers, usually have higher duty cycles or uninterrupted turn-on times, up to continuous operation, which is not achievable, for example, in the case of semiconductor lasers designed as edge emitters. As a result, it is advantageously possible to use the optical distributor according to the invention for supplying a plurality of target systems, for example laser spark plugs of an internal combustion engine.

Another advantage over the use of edge emitters is that a cross-sectional transducer is not necessarily required to form a beam cross-section of the laser radiation produced.

In a further advantageous embodiment, it is provided that the laser source has a multiplicity of vertically emitting semiconductor lasers arranged substantially flat, preferably within a common virtual plane. Other configurations are also conceivable.

According to a further embodiment, the distribution system has at least one movable mirror and / or a movable lens, which is designed to deflect laser radiation emitted by the laser source optionally onto at least one of the optical output stages.

In a further variant of the invention, it is provided that the movable mirror is arranged to be rotatable about at least one axis. Alternatively or additionally, a translation of the mirror is conceivable.

Combinations of rotation and translation for the mirror and / or the lens or generally a laser radiation deflecting optics are also conceivable.

In a further advantageous embodiment, the mirror is associated with an optic, in particular a focusing optic, which is movable together with the mirror, which advantageously only relatively small positioning movements for the mirror or its associated optics are required for the laser radiation provided by the laser source Assign different output levels of the optical distributor.

In a further advantageous embodiment, it is provided that the laser source is designed to be rotatable about at least one axis, and that the distributor system has drive means for driving the laser source. This advantageously eliminates further movable elements, and it can be a very small-sized configuration can be achieved.

Since the vertical emissive semiconductor lasers of the laser source used in the present invention usually require relatively low supply currents (e.g., to edge emitters), an arrangement for providing electrical power to a rotatable laser source is relatively easy to implement, for example by means of sliding contacts.

In a further advantageous embodiment it is provided that the laser source is associated with an optical system, in particular a focusing optical system, which is movable together with the laser source. The integration of the focusing optics on the movably arranged laser source advantageously ensures that laser radiation with a relatively small beam cross-section is already emitted by the system laser source / focusing optics, so that relatively small actuating movements of the movable laser source are required for distributing the laser radiation onto the different optical output stages. For example, in the case of a rotatably arranged laser source, the adjustment of the laser source by relatively small angles of rotation can be sufficient to redirect the irradiation of the laser radiation from a first optical output stage to a further optical output stage.

As an alternative to a rotatably arranged laser source, a laser source can also be provided, which can perform a translation in order thereby to radiate the laser radiation to different ones of a plurality of available optical output stages. In this embodiment as well, an optic, in particular a focusing optic, can again be arranged movably together with the laser source. A combination of rotation and translation for the laser source and the system laser source / focusing optics is also conceivable.

A carrier element accommodating the movable laser source is particularly advantageously used simultaneously as a heat sink, so that efficient heat dissipation is also possible in those variants of the invention in which the laser source is movably arranged.

As a drive means for a rotatably or longitudinally displaceably or otherwise movably arranged laser source are in particular a stepper motor or a linear drive, for example having piezoelectric elements or solenoids or the like, into consideration.

In a further advantageous embodiment, it is provided that the distribution system has a plurality of, in particular in a beam path of the laser source, linearly arranged mirror, wherein at least one first mirror is movable, in particular rotatable about at least one axis, preferably such that the at least one mirror can be moved out of a connecting line between the laser source and at least one further mirror. Such a series arrangement of a plurality of mirrors in the beam path of the laser source can be realized particularly advantageously with semiconductor lasers (VCSEL) designed as vertical emitters, because VCSEL or VCSEL arrays emit laser radiation with a relatively low divergence. As a result, the entire beam path, which comprises a plurality of mirrors, can be made geometrically relatively long.

For example, a distance between the laser source and the first mirror and / or between two adjacent mirrors may be at least about two centimeters, preferably at least about five centimeters, or more.

It is also conceivable to arrange the optical distributor with the distributor system in the region of a cylinder head of the internal combustion engine such that the plurality of movable mirrors in the beam path of the laser source are spatially associated with a respective cylinder of the internal combustion engine. In this case, therefore, the distance between adjacent mirrors is determined by the distance between the cylinders of the internal combustion engine in the cylinder head to each other.

In a further advantageous embodiment, it is provided that drive means for driving at least one mirror are provided which a) comprise at least one stepping motor or a linear drive (eg piezoelectric element, solenoid) or the like and / or b) the drive of at least one mirror by an external Enable component. For example, the optical distributor according to the invention can be arranged on an internal combustion engine with a laser-based ignition system such that an adjustment mechanism for the individual mirrors of the distributor system can be actuated, for example, by means of a camshaft of the internal combustion engine or of another valve drive.

In a further advantageous embodiment, it is provided that at least one optical output stage has an optical interface for the optical connection of the optical distributor to a further system, in particular a laser spark plug. The optical interface can be made for example by means of conventional optical connectors or by the production of a permanent optical-mechanical connection.

Furthermore, it can be provided that at least one optical output stage has an optical system for influencing laser radiation distributed by means of the distributor system, in particular for focusing. Due to the provision of individually optics assigned to each of the different optical output stages, according to another embodiment it is advantageously possible to carry out different measures with regard to the beam shaping of the laser radiation distributed by the distributor system for different optical output stages hold true. For example, a first plurality of optical output stages may be provided with optics of a first focal length while a second plurality of optical output stages are each provided with optics having a second focal length other than the first focal length.

As a further solution to the object of the present invention, a method for operating an optical distributor according to claim 15 is given.

Other features, applications and advantages of the invention will become apparent from the following description of embodiments of the invention, which are illustrated in the figures of the drawing. All described or illustrated features, alone or in any combination form the subject matter of the invention, regardless of their summary in the claims or their dependency and regardless of their formulation or representation of the description or in the drawing.

In the drawing shows:

1 a schematic representation of a laser-based ignition system of an internal combustion engine,

2 A first embodiment of an optical distributor according to the invention for use in the ignition system according to 1 .

3 A second embodiment of an optical distributor according to the invention for use in the ignition system according to 1 , and

4 a further embodiment of an optical distributor according to the invention for use in the ignition system according to 1 ,

Description of the embodiments

1 schematically shows an internal combustion engine 10 that is not in to drive a 1 serves pictured motor vehicle. The internal combustion engine 10 this includes several cylinders, of which in 1 only one shown and with the reference numeral 12 is designated. A combustion chamber 14 of the cylinder 12 is from a piston 16 limited. Fuel enters the combustion chamber 14 directly through an injector 18 , to a designated as a rail or common rail fuel pressure accumulator 20 connected.

Alternatively, it may be in the internal combustion engine 10 also to a stationary engine, such as a large gas engine act.

In the 1 illustrated internal combustion engine 10 has a laser-based ignition system 27 on, one in the combustion chamber 14 injected fuel quantity 22 by means of a laser beam or a laser pulse 24 is ignited. The laser pulse 24 is by means of a cylinder 12 associated laser device 26 , For example, a laser spark plug, into the combustion chamber 14 radiated. The laser device 26 is part of the laser-based ignition system 27 , which in addition to other decentralized, ie different cylinders associated laser devices (not shown), also an optical distributor 100 with a laser light source (not shown) that generates laser light and to the decentralized laser devices 26 distributed.

A control of the laser-based ignition system 27 or the optical distributor 100 For example, via one of the internal combustion engine 10 associated control unit 40 carried out, in a known manner by driving the injector 18 also the metering of fuel 22 in the combustion chamber 14 of the cylinder 12 causes.

The laser device or laser spark plug 26 is via a light guide device 28 with that of the optical distributor 100 distributed laser light fed, which, for example, for optical pumping a locally in the laser spark plug 26 provided resonator, not shown, which in turn - excited by the pump laser light - the required for ignition laser pulse 24 generated.

Alternatively, one for igniting the amount of fuel 22 provided laser pulse 24 directly through the laser source of the optical distributor 100 generated and hereby and via the light guide device 28 to the laser spark plug 26 to get redirected.

In both cases, results from the application of the invention, in 2 schematically shown in a side view, optical distributor 100 a significant advantage because overall only one central laser source is to be provided and not every cylinder 12 the internal combustion engine 10 or an associated laser spark plug 26 For example, it must be equipped with its own semiconductor laser.

Through the use of the optical distributor according to the invention 100 it is also particularly advantageous possible, the distributor 100 or its associated laser source 110 ( 2 ) of an engine block of the internal combustion engine 10 To arrange away, so that they are not directly the high temperature fluctuations and vibration in an immediate environment of the internal combustion engine 10 is exposed.

2 shows a first embodiment of the optical distributor 100 , The optical distributor 100 has a laser source 110 for providing laser radiation L on which is like off 2 visible on a simultaneously acting as a heat sink carrier element 112 is arranged.

In the beam path of the laser source 110 is a distribution system 130 arranged for the distribution of the laser source 110 provided laser radiation L is formed on at least two optical output stages, of which in 2 for the sake of clarity, only a first optical output stage 120_1 is shown.

In the present case, the distribution system 130 a mirror arranged to be movable about a rotation axis A. 132 on, whose rotational movement by means of drive 134 is controlled. For the drive means 134 For example, it may be a stepper motor, as well as other components of the optical distributor 100 , through the control unit 40 ( 1 ) of the internal combustion engine is controllable.

With suitable orientation of the rotating mirror 132 with respect to the first optical output stage 120_1 becomes that of the laser source 110 provided laser radiation L in the in 2 mapped manner to the first optical output stage 120_1 distributed. Specifically, the on the rotating mirror 132 reflected laser radiation L 'on an optic 120b for influencing the distributed laser radiation L ', in particular for focusing, irradiated. After appropriate beam shaping by the optics 120b The focused distributed laser radiation is transformed into an optical fiber 120c blasted, which, for example, part of an optical interface 120a the optical output stage 120_1 can form.

About the fiber 120c , for example, with the light guide device 28 according to 1 can be connected to a laser spark plug 26 the internal combustion engine 10 the means of the optical distributor 100 ( 2 ) Distributed laser radiation L 'are supplied.

According to the invention, the laser source 110 at least one vertically emitting surface emitting laser (VCSEL). Particularly preferred is the laser source 110 however, formed by a so-called VCSEL array, that is, by a plurality of VCSEL semiconductor lasers. Particularly preferably, the multiplicity of VCSEL semiconductor lasers are arranged essentially flat, preferably within a common virtual plane. The common virtual plane is according to the embodiment 2 through a surface of the carrier element 112 or the heat sink defined.

The use of a VCSEL array for the laser source 110 offers the advantage that the radiated laser radiation L is almost completely collimated, so that relatively long beam paths for the laser radiation L in the optical distributor 100 can be realized without significantly deteriorating the beam quality of the laser radiation L or the distributed laser radiation L '.

Moreover, with VCSEL semiconductor lasers, significantly higher duty cycles are possible than with, for example, edge-emitting semiconductor lasers, and in particular a continuous operation of the laser source 110 is feasible. This can advantageously many, preferably all, cylinder of the internal combustion engine 10 from a single laser source 110 of the optical distributor 100 be supplied with pumping light.

Another particular advantage of VCSEL arrays as a laser source 110 is formed by the fact that an electric current required for the supply is relatively low, whereby corresponding drive stages for the laser source 110 less expensive to design and electrical losses can be reduced.

The optical distributor 100 according to 2 is thus in particular also for the supply of internal combustion engines 10 with a large number of cylinders or laser spark plugs 26 usable, for example, repetition rates of about 10 Hz to about 50 Hz per cylinder can be realized.

3 shows a further embodiment 100 ' the optical distributor according to the invention.

In contrast to the above with reference to 2 described embodiment, the optical distributor 100 ' according to 3 a movably arranged laser source 110 on. The distribution system 130 For example, it has a movable carrier unit which, in turn, advantageously at the same time serves as the heat sink 112 ( 2 ) satisfies the VCSEL array 110 is arranged. An electrical supply to the laser source 110 For example, by means of sliding contacts (not shown) in the region of the distribution system 130 respectively.

Exemplary are the distribution system 130 of the 3 a total of four optical output stages 120_1 . 120_2 . 120_3 . 120_4 assigned, in each case via unspecified optics and optical fibers for coupling the distributed laser radiation, for example to the spark plug 26 ( 1 ), serve.

Under drive of the distribution system 130 , For example by means of a stepping motor (not shown), the laser source 110 around one in 3 arranged perpendicular to the plane of the drawing Rotary axis A can be rotated, so that of the laser source 110 provided laser radiation L optionally, depending on the rotation angle of the laser source 110 , on one of the several optical output stages 120_1 . 120_2 . 120_3 . 120_4 is einstrahlbar.

It is also possible to use the laser source 110 and to arrange the output stages so that, for example, two output stages each are supplied with distributed laser radiation at the same time.

Furthermore, it is conceivable to associate with at least one output stage means for the diagnosis (for example photodiode) or for the feedback of the laser radiation to a remotely located diagnostic unit. The provision of a dedicated optical output stage for diagnostic purposes, in particular for determining whether the laser radiation L the required intensity and / or wavelength and / or a time course of the intensity, etc., is also possible.

Particularly preferably, the laser source 110 during an actuating movement, which includes a rotation of, for example, 90 °, are deactivated at least in those time ranges in which the of the rotatably arranged laser source 110 generated laser beam does not meet in an optimal manner to a corresponding optics of the optical output stages. This means an electrical control of the laser source 110 can be advantageous with an actuating movement of the drive means for the distribution system 130 be synchronized.

Alternatively to the in 3 pictured configuration, the rotatably arranged laser source 110 Also be associated with this rotatably arranged optics, in particular focusing optics, be assigned so that can be dispensed with the optical output stages, for example, the corresponding optics, or the corresponding optics can be designed less expensive. Due to the focusing of the laser source 110 produced laser radiation L by means of a co-moving focusing optics (not shown) results on the output side of this focusing optics already advantageously a relatively small beam cross-section, so relatively small actuating movements of the laser source 110 sufficient to switch the distribution of the generated laser radiation L between the individual optical outputs back and forth.

Alternatively to the above with reference to 2 . 3 described variants of the invention, it is also conceivable, the laser source 110 subject to translatory or mixed rotational / translational movement to allow adjustment to various optical output stages. For example, the laser source 110 along a longitudinal axis to be moved back and forth, preferably by means of a piezo-electric actuator or a solenoid or the like to supply each different optical output stages with the laser radiation.

4 shows a further embodiment 100 '' the optical distributor according to the invention.

At the in 4 illustrated embodiment 100 '' is the laser source 110 formed stationary with their VCSEL array, that is stationary. Along an optical axis OA or the beam path of the laser radiation 110 is a substantially linear distribution system 130 arranged, which has a plurality of mutually linearly arranged mirrors 136_1 . 136_2 . 136_3 . 136_4 having. At least the first three mirrors 136_1 . 136_2 . 136_3 are movably arranged according to the invention such that they are under control by means of suitable drive means 134 ' from the beam path OA of the laser source 110 be moved out and moved back into it.

In this way it can be determined by appropriate control of the individual mirrors, which optical output stage of the distribution system 130 is supplied with laser radiation L.

The last mirror 136_4 the linear arrangement of the distribution system 130 does not have to be designed to be movable.

Instead of a rotational adjustment of the individual mirrors of the distribution system 130 according to 4 is also a translation or other movement conceivable, with the relevant mirror in the beam path OA of the laser source 110 be moved in and out again.

According to another embodiment, rotating mirrors can also be combined with mirrors arranged in a linear manner.

It is also conceivable, in a further embodiment, the laser source 110 movable, in particular rotatable, form, so that several benches of mirrors 136_1 , ..., 136_4 optionally with laser radiation through the laser source 110 can be acted upon.

Due to the VCSEL arrays used 110 relatively high beam quality, in particular low divergence, of the generated laser radiation L can advantageously relatively large geometric distances for the beam path of the distribution system 130 will be realized. Particularly preferred is a distance d1 between the laser source 110 and the first mirror 136_1 of the distribution system 130 at least about two inches, preferably at least about five inches. The same is preferably true for a distance d2 between adjacent mirrors 136_1 . 136_2 ,

In this way, the distribution system 130 according to 4 advantageous to the internal combustion engine 10 ( 1 ), that the entire beam path of the distribution system 130 For example, along a cylinder bank (not shown) of the internal combustion engine 10 extends. That means the individual mirrors 136_1 . 136_2 , ... of the distribution system 130 are arranged with such distances from each other, that they each directly to a cylinder assigned to them 12 ( 1 ) of the internal combustion engine 10 assigned. In this way, the optical distributor 100 '' particularly favorable in the internal combustion engine 10 to get integrated.

To protect the beam path OA from dirt particles can not in 4 imaged housing may be provided, which either contains a defined gas filling, for example with a protective gas or a vacuum.

Instead of individual drive means 134 for the mirrors of the distribution system 130 can also be an operating mechanism for the distribution system 130 be provided, which allows the movements of a camshaft or other valve train of the internal combustion engine 10 ( 1 ) on the individual mirrors 136_1 . 136_2 , ... transferred to. In this way, the individual mirrors of the distribution system 130 particularly advantageous while saving separate drive means 134 ' with an operating state of the internal combustion engine 10 be synchronized.

As an alternative or in addition to the provision of at least one vertically emitting semiconductor laser (VCSEL), at least one semiconductor laser of the VECSEL type (Vertical External Cavity Surface Emitting Laser) can advantageously also be used, wherein a further increased beam quality and thus lower divergence can be realized. Accordingly, the above-described embodiments can be realized with either VCSEL type or VECSEL type semiconductor lasers or with a laser source having both VCSEL semiconductor laser and VECSEL semiconductor laser.

A further reduction in the divergence of the radiation generated by the laser source can be realized by the provision of microlenses or microlens arrays, which can optionally also be integrated into the semiconductor laser.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• US 7421166 B1 [0003]

Claims (15)

Optical distributor ( 100 ) for the distribution of laser radiation (L), in particular for a laser ignition system of an internal combustion engine ( 10 ), wherein the optical distributor ( 100 ) a laser source ( 110 ) for providing laser radiation (L), at least two optical output stages ( 120_1 . 120_2 ) for decoupling laser radiation (L '), and a distribution system ( 130 ) for selectively distributing by the laser source ( 110 ) provided laser radiation (L) on at least one of the optical output stages ( 120_1 . 120_2 ), characterized in that the laser source ( 110 ) has at least one vertically emitting semiconductor laser (VCSEL). Optical distributor ( 100 ) according to claim 1, wherein the laser source ( 110 ) has a plurality of substantially vertically, preferably within a common virtual plane, arranged vertically emitting semiconductor lasers (VCSEL). Optical distributor ( 100 ) according to any one of the preceding claims, wherein the distribution system ( 130 ) at least one movable mirror ( 132 ) and / or a movable lens which is adapted to be moved by the laser source ( 110 ) radiated laser radiation (L) optionally on at least one of the optical output stages ( 120_1 . 120_2 ) distract. Optical distributor ( 100 ) according to claim 3, wherein the movable mirror ( 132 ) is arranged rotatably about at least one axis. Optical distributor ( 100 ) according to claim 4, wherein the mirror ( 132 ) an optics, in particular a focusing optics ( 132a ), associated with the mirror ( 132 ) is movable. Optical distributor ( 100 ) according to one of the preceding claims, wherein the laser source ( 110 ) is rotatable about at least one axis, and wherein the distribution system ( 130 ) Drive means ( 134 ) for driving the laser source ( 110 ) having. Optical distributor ( 100 ) according to claim 6, wherein the laser source ( 110 ) an optics, in particular a focusing optics ( 134a ), which together with the laser source ( 110 ) is movable. Optical distributor ( 100 ) according to one of claims 6 to 7, wherein the laser source ( 110 ) on one together with the laser source ( 110 ) rotatable heat sink ( 112 ) is arranged. Optical distributor ( 100 ) according to one of claims 6 to 8, wherein the drive means ( 134 ) have at least one stepper motor or a linear drive. Optical distributor ( 100 ) according to any one of the preceding claims, wherein the distribution system ( 130 ) a plurality of, in particular in a beam path (OA) of the laser source ( 110 ), mutually linearly arranged mirrors ( 136_1 , ..., 136_4 ), wherein at least one first mirror ( 136_1 ) is movable, in particular about at least one axis rotatable, is formed, preferably such that the at least one mirror ( 136_1 ) from a connecting line between the laser source ( 110 ) and at least one further mirror ( 136_2 ) is movable out. Optical distributor ( 100 ) according to claim 10, wherein drive means ( 134 ' ) for driving at least one mirror ( 136_1 , ..., 136_4 ) are provided which have a) at least one stepper motor or a linear drive or the like and / or b) the drive of at least one mirror ( 136_1 , ..., 136_4 ) by an external component, in particular by a camshaft of an internal combustion engine, the optical distributor ( 100 ) assigned. Optical distributor ( 100 ) according to one of claims 10 to 11, wherein a distance (d1, d2) between the laser source ( 110 ) and the first mirror ( 136_1 ) and / or between two adjacent mirrors ( 136_1 . 136_2 ) is at least about two centimeters, preferably at least about five centimeters. Optical distributor ( 100 ) according to one of the preceding claims, wherein at least one optical output stage ( 120_1 ) an optical interface ( 120a ) for the optical connection of the optical distributor ( 100 ) with another system ( 200 ), in particular a laser spark plug ( 26 ), having. Optical distributor ( 100 ) according to one of the preceding claims, wherein at least one optical output stage ( 120_1 ) an optic ( 120b ) for influencing by means of the distribution system ( 130 ) has distributed laser radiation (L '), in particular for focusing. Method for operating an optical distributor ( 100 ) for the distribution of laser radiation (L), in particular for a laser ignition system of an internal combustion engine ( 10 ), wherein the optical distributor ( 100 ) a laser source ( 110 ) for providing laser radiation (L), at least two optical output stages ( 120_1 . 120_2 ) for decoupling laser radiation (L '), and a distribution system ( 130 ) for selectively distributing by the laser source ( 110 ) provided laser radiation (L) on at least one of the optical output stages ( 120_1 . 120_2 ), characterized in that the laser source ( 110 ) has at least one vertically emitting semiconductor laser (VCSEL) whose Laser radiation (L) through the distribution system ( 130 ) optionally on at least one of the optical output stages ( 120_1 . 120_2 ) is distributed.

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