EP1050067B1 - Electric incandescent lamp with infrared reflecting layer - Google Patents

Abstract

Electrical incandescent lamp, in particular a halogen incandescent lamp (4) having a lamp bulb (5) which has a coating (9) that reflects IR radiation, and having a flat luminous body (10) which defines a fictional plane of the light and is arranged inside the lamp bulb (5). The shape of the lamp bulb (5) with respect to those axes which lie in the plane of the light have no rotational symmetry, but the lamp bulb (5) in fact has a shape which differs from rotational symmetry but is matched to the flat geometry of the luminous body (10), that is to say a flattened shape, in particular the shape of an ellipsoid, whose shortest half-axis is oriented at right-angles to the fictional plane of the light of the luminous body (10).

Description

Technical field

The invention is based on an electric light bulb, in particular one Halogen incandescent lamp, with IR reflection layer according to the preamble of Claim 1.

It is in particular an incandescent lamp with a flat one Luminous body, a so-called flat core filament. The cross section of Flat core filaments have not, like the filament of incandescent for General lighting, a circular cross section, but rather an elongated cross section. The reason for this is the adjustment of the Geometry of the spiral shape to the preferred for the respective main area of application Radiation characteristics of the lamp or filament. The difference for rotationally symmetrical radiation characteristics of conventional Incandescent lamps are made possible by the flat luminous body of the aforementioned Lamp types emphasize areal radiation, such as for technical-scientific lighting purposes as well as in photo optics, especially for projection purposes. Typical electrical Power values are in the range of approx. 50 to 400 watts.

The one applied to the inside and / or outside surface of the lamp bulb Coating reflecting IR radiation - hereinafter shortened as an IR layer designated - causes a large part of the radiated from the filament IR radiation power is reflected back on it. The result achieved increase in lamp efficiency can be constant electrical power consumption for a temperature increase of the Luminous body and consequently an increase in luminous flux. on the other hand can be a predetermined luminous flux with lower electrical power consumption achieve - an advantageous "energy saving effect". Another desirable effect is that due to the IR layer significantly less IR radiation power radiated through the lamp bulb and so that the environment, e.g. an optical projection device, less is heated than with conventional light bulbs.

Because of the inevitable absorption losses in the IR layer increases the power density of the IR radiation components within the lamp bulb with the number of reflections and consequently also the efficiency of the Light bulb. Crucial for the actually achievable increase in efficiency it is therefore necessary for the return of the individual IR rays to minimize the number of reflections required on the filament. For this purpose, the shape of the one provided with the IR layer Lamp bulb specially matched to the shape of the filament.

State of the art

GB-A 2 082 383 discloses a lamp with an ellipsoidal bulb an annular filament is arranged in the circular focal line is. An IR layer is applied to the piston wall.

EP-A 0 470 496 discloses a lamp with a spherical bulb, in the center of which is a cylindrical filament. This font teaches that the loss of efficiency due to the deviation of the filament from the ideal spherical shape to an acceptable one under the following conditions Dimension can be limited. Either have piston diameters and filament diameter or length within a tolerance range be carefully coordinated, or the diameter of the Luminous body must be significantly smaller (small factor 0.05) than that of Lamp bulb. There is also a lamp with an ellipsoidal bulb specified, in the focal line an elongated filament axially arranged is.

Presentation of the invention

The invention has for its object a light bulb with a flat core filament to be specified as a flat filament, characterized by an efficient Returning the emitted IR radiation to the luminous element and consequently, a high level of efficiency. Another aspect is that Distribution of the returned IR radiation on the filament. Moreover should enable compact lamp dimensions with high luminance are being striven for, especially for low-voltage halogen incandescent lamps becomes.

This object is achieved by the characterizing features of claim 1 solved. Find particularly advantageous configurations themselves in the dependent claims.

The invention proposes to specifically shape the lamp bulb so that the Lamp bulb with respect to lying in the light plane of the flat filament Axes has no rotational symmetry, but that the lamp bulb rather, a deviation from the rotational symmetry on the flat geometry of the filament, i.e. flattened shape having. If necessary, the shape of the base of the flat Luminous body on the actually irradiated by the reflected IR radiation Coordinate surface of the filament.

In particular, the invention proposes that the shape of the lamp bulb essentially corresponds to an ellipsoid with three semiaxes, of which are at least two different lengths and the filament is arranged within the lamp bulb such that the shortest of the three semiaxes of this ellipsoid perpendicular to the light plane of the filament is oriented. In this way, the lamp bulb receives with viewing direction in the light plane looks at the desired flat shape.

To further explain the inventive concept, reference is made in the following taken on Figures 1a-1c. They show a schematic representation of the basic connections and lead some for the further Understanding the invention essential sizes.

Among other things, three sections are shown through an ellipsoid 1 with the three Semi-axes a, b and c. The cuts correspond to the viewing directions in the three Cartesian spatial axes x, y and z, which are also collinear with the three Semi-axes a, b and c are selected. The semiaxis c is shorter than the others two semiaxes a and b. Inside the ellipsoid 1 is a stylized one flat filament 2 with two mutually parallel rectangular bases 3 or 3 'centered. These two base areas 3 and 3 ' correspond to those of a real flat filament Luminous surfaces that essentially generate the luminous flux of the lamp.

For the sake of simplicity, a fictional lighting level is referred to below taken as parallel and centered between the two bases 3, 3 'is defined to run.

The luminous element 2 is now oriented within the ellipsoid 1 in such a way that its fictional light plane is perpendicular to the semiaxis c. So get lost the semiaxes a and b in the light plane and consequently parallel to the two base areas 3, 3 'of the luminous element 2.

The specific values for the three semi-axes are in the individual case on the shape and to specifically coordinate the dimensions of the filament, that the most efficient possible return of the emitted IR radiation the filament is reached. With a view to a long life of the Lampe can weight the voting criteria for the three semi-axes also more towards a distribution that is as uniform as possible the returned IR radiation can be shifted on the filament. In particular local IR radiation power maxima, so-called "hot spots", are usually detrimental to the long life of the filament and should therefore be avoided.

Improvement in distribution uniformity can also be achieved by a targeted adjustment of the outer shape of the filament to the shape of the retroreflective spot can be achieved on the filament. It has For example, it was found that, in the case of the maximum return of the emitted IR radiation, the retroreflective spot is substantially oval. For this reason, it can be advantageous for the filament as well choose an oval shape and also its outer dimensions to largely adapt those of the reflection spot.

In the case of rotationally symmetrical light bodies, i.e. Luminous bodies with a circular base and for lighting fixtures that are at least rough Approximation can be considered circular, e.g. Filament with square base, it can be advantageous to use the semiaxes a and b of the ellipsoid to be of equal length.

The targeted matching of the three ellipse half axes to the luminous element can be supported with so-called ray tracing methods. there light rays emanating from the flat core helix are tracked and the Ellipse semi-axes determined such that maximum return efficiency or an optimal uniformity of the distribution of the returned Rays of light on the. Helix or whatever Compromise is achieved.

Description of the drawings

Figur 1a

eine schematische Darstellung des Prinzips der Erfindung anhand eines Ellipsoiden und eines rechteckförmigen flachen Leuchtkörpers mit Blick in der z-Richtung,

Figur 1b

eine schematische Darstellung des Ellipsoiden mit Leuchtkörper aus Figur 1a mit Blick in der x-Richtung,

Figur 1c

wie Figur 1b, aber mit Blick in der y-Richtung,

Figur 2

eine NV-Halogenglühlampe mit IR-Schicht und einer Flachkernwendel sowie einer erfindungsgemäßen Kolbenform,

Figur 3a

eine schematische Darstellung einer Seitenansicht der Flachkemwendel aus Figur 2,

Figur 3b

eine Schnittdarstellung der Flachkernwendel aus Figur 3a entlang der Linie AA.

In the following, the invention will be explained in more detail using an exemplary embodiment. Show it:

Figure 1a

1 shows a schematic representation of the principle of the invention using an ellipsoid and a rectangular flat luminous element with a view in the z direction,

Figure 1b

1 shows a schematic illustration of the ellipsoid with the luminous element from FIG. 1 a, looking in the x direction,

Figure 1c

like FIG. 1b, but with a view in the y direction,

Figure 2

a low-voltage halogen incandescent lamp with an IR layer and a flat-core filament and a bulb shape according to the invention,

Figure 3a

2 shows a schematic illustration of a side view of the flat core helix from FIG. 2,

Figure 3b

a sectional view of the flat core helix from Figure 3a along the line AA.

FIG. 2 shows an exemplary embodiment of a lamp 4 according to the invention shown schematically. It is a halogen light bulb with a nominal voltage of 24 V and a nominal power of 250 W or in a variant for 150 W. The following values refer to unless stated otherwise, to both types of services. For both types deviating values is first the value for the 250 W lamp type and the corresponding value for the 150 W lamp type specified.

The lamp has a lamp bulb 5 which is pinched on one side and which its first end merges into a neck 6, which is in a pinch seal 7 ends. At its opposite end, the lamp bulb 5 has one Pump tip 8 on. The position of the pump tip 8 and the pinch seal 7 define a longitudinal axis LA of the lamp 4.

An IR layer 9, consisting of an interference filter with more than 20 layers of TiO ₂ and SiO _{2, is} applied to the outer surface of the lamp bulb 5. Instead of TiO ₂ , Ta ₂ O ₅ is also suitable. The IR layer also covers about half of the pinch seal 7. In this way, a particularly dimensionally stable shape of the IR layer 9 is achieved, since when the lamp bulb 5 is manufactured, the outer surface of the calculated contour of the ellipsoid is embossed. On the other hand, due to the expansion of the IR layer 9 over part of the pinch seal 7, the individual layers in the region of the piston surface are particularly uniform. This reduces color errors.

The length of the lamp neck 6 is approximately 2 mm with a maximum width of approx.9.6 mm. The lamp bulb 5 is made of quartz glass with a wall thickness of approx. 1 mm.

With the exception of the pinch seal 7 and the pump tip 8, the lamp bulb 5 shaped as an ellipsoid. The respective length of the three semiaxes a, b and c of this ellipsoid are 8.4 mm, 9 mm and 8 mm (8.2 mm, 8.5 mm, respectively) or 8 mm) for maximum efficiency and 9 mm, 9.6 mm and 8 mm for optimal Uniformity of the radiation return with the 250 W lamp type.

A luminous element 10 is arranged centrally within the lamp bulb 5. The luminous element 10 consists of a simple flat core filament (shown here only schematically, but see Figures 3a and 3b). The spiral axis is oriented perpendicular to the longitudinal axis LA of the lamp 9 and extends in that spanned by the semiaxes a and b of the ellipsoid Level. For further details on the flat core helix 10, see FIGS. 3a and 3b and the associated description of the figures.

The current leads 11a, b are formed directly by the spiral wire and connected with molybdenum foils 12a, b in the pinch seal 7. The Molybdenum foils 12a, b are in turn connected to outer socket pins 13a, b.

Inside the lamp bulb 5 there is a filling of approx. 3990 hPa Xenon (Xe) nitrogen (N) mixture in the ratio Xe: N = 88: 12 with an admixture of 0.7% (0.4%) hydrogen bromide (HBr).

The lamp 4 has a color temperature of approximately 3400 K. The luminous flux is 12230 lm (6750 lm) with a power consumption of 265 W (158 W), accordingly a luminous efficacy of approx. 46 lm / W (42.7 lm / W). With a comparable one conventional lamp will use the same electrical power only achieved a luminous flux of 9150 lm (5050 lm), accordingly a luminous efficacy of approx. 34.4 lm / W (32 lm / W). Hence can in comparison with the lamp according to the invention an increase in efficiency of up to 34% (33.7%) can be achieved.

FIGS. 3a and 3b show the flat core coil 10 from FIG. 2 in one Side view or in a section along the line AA. The Flachkemwendel 10 is made of a tungsten wire with a diameter of approx. 292 µm and wound a total of 17 turns (20 turns). The length L of the Helix 10 in the direction of the helix axis WA is approximately 7.4 mm (6.9 mm). The height H and width B are approx. 4 mm (3.26 mm) and 1.4 mm (1.15 mm). In the sectional view in Figure 3b is one in the sectional plane essentially elongated oval turn 14 of the flat core coil 10 and the gate 15 can be seen.

In one variant (not shown) the flat core filament of the lamp is off FIG. 2 shaped in such a way that the side view of the flat core helix is an oval, has a contour matched to the shape of the IR reflection spot. To for this purpose, the respective height H of the individual turns on one first end of the helix small, then grows in the middle of the helix on it maximum height (in the example of the lamp from FIG. 2 to approx. 4 mm at 250 W Type) and decreases to the other end of the coil.

The following tables 1, 2 and 3 use a ray tracing program to find the ellipse half axes a, b, c found suitable for three power types, namely 150 W, 250 W and 400 W. The ellipse semi-axis c was specified in each case and the other two ellipse semi-axes a, b were determined. In practice, the maximum value for the semiaxis c is often predetermined, depending on the area of use, for example in projectors by the intended installation depth. The wall thickness was assumed to be constant at 0.8 mm. The dimensions of the flat core helix provided for the respective power type in the plane spanned by the ellipse half axes a, b are also given.

According to the results shown in the tables above and the current state of knowledge regarding the most compact bulb shapes as well as the tuning options with regard to maximum efficiency or optimal uniformity, the following ratios of the three semi-axes a, b, c of an ellipsoid essentially forming the lamp bulb have been found turned out to be advantageous:
0.9 ≤ c / a ≤ 0.99, in particular 0.95 ≤ c / a ≤ 0.98 and
0.8 c c / b 0,9 0.97, in particular 0.85 c c / b wobei 0.95, the two semi-axes a, b being in the plane of the flat-core coil and the semi-axis c being perpendicular to the light level of the flat-core coil.

Claims (8)

1. Electrical incandescent lamp, in particular a halogen incandescent lamp (4) having a lamp bulb (5) which has a coating (9) that reflects IR radiation, and having a flat luminous body (10) which defines a fictional plane of the light, is a flat-core element, is arranged inside the lamp bulb (5) and is held by means of two electricity supply leads (11a, 11b), with the two electricity supply leads (11a, 11b) being routed to the exterior in a gastight manner, characterized in that the shape of the lamp bulb (5) with respect to those axes which lie in the plane of the light have no rotational symmetry, but in that the lamp bulb (5) in fact has a shape which differs from rotational symmetry but is matched to the flat geometry of the luminous body (10), that is to say a flattened shape.
2. Incandescent lamp according to Claim 1, with the shape of the lamp bulb (5) essentially corresponding to an ellipsoid (1) having three half-axes (a, b, c), at least two of which are of different lengths, and with the luminous body (2; 10) being arranged inside the lamp bulb (5) in such a manner that the shortest (c) of the three half-axes of this ellipsoid (1) is oriented at right-angles to the fictional plane of the light of the luminous body (2; 10).
3. Incandescent lamp according to Claim 1 or 2, with the following value range applying to the relationships of the half-axes a, c:
   0.9≤ c / a≤0.99, in particular 0.95≤ c / a≤0.98.
4. Incandescent lamp according to Claim 1, 2 or 3, with the following value range applying to the relationships of the half-axes b, c:
   0.8 ≤ c / b≤ 0.97, in particular 0.85 ≤ c / b≤ 0.95.
5. Incandescent lamp according to one of the preceding claims, with the outline of the luminous body (10) having a rectangular shape parallel to the fictional plane of the light.
6. Incandescent lamp according to one of the preceding claims, with the outline of the luminous body having an oval shape parallel to the fictional plane of the light.
7. Incandescent lamp according to one of the preceding claims, with the outline of the luminous body having a circular shape, or at least a roughly approximately circular shape, parallel to the fictional plane of the light, in particular also the shape of a square or a regular polygon.
8. Incandescent lamp according to one of the preceding claims, characterized in that the lamp bulb (5) has a lamp neck (6) at at least one end, which lamp neck (6) surrounds at least one electricity supply lead (11a, 11b) as closely as possible, and whose end (8) remote from the bulb is closed in a gastight manner.

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