High-pressure mercury discharge lamp

The present invention relates to a mercury high pressure discharge lamp having an anode in which at least a part of the region is made of a material containing a tungsten component.

Conventional technology In mercury high-voltage discharge lamps, the impact of the anode electrode leads to heating. This vaporizes the anode material and deposits it inside the discharge tube of the lamp. The deposits thus formed on the inside are perceived as fogging or blackening of the tube, causing the resulting arc to decay and the available luminous flux to decrease. The effect is exacerbated as the useful life of the discharge lamp elapses. As the useful life of the discharge lamp progresses, the luminous flux decreases due to vaporization from the anode material.

In addition to the vaporization of the anode material, high-voltage discharge lamps also have a phenomenon that causes a decrease in the light used by the user. Such phenomena include the burning of the cathode and the expansion of the cathode plane. Approximately 1 mg / cm³~ 8mg / cm³In mercury high-pressure discharge lamps with a mercury filling amount, vaporization of the anode material is a significant cause of degradation and greatly affects the service life of the lamp.

When the mercury high pressure discharge lamp has a high rare gas filling pressure, especially a cold pressure higher than 3 bar, the vaporization of the anode material is enhanced. The rare gas to be filled, typically argon, krypton or a mixture thereof with xenon, has the effect of reducing the width of the arc. When the discharge lamp is used in an optical device, the action of the rare gas increases the available light, and the optical device has a high light intensity. Such an optical device is a so-called high-intensity lamp. A strong load is applied to the anode due to the high rare gas pressure, and wear of the anode surface also occurs under predetermined driving conditions. As a result, the vaporization of the anode material is further strengthened.

Normally, a mercury high voltage discharge lamp is driven by a constant power of direct current. However, there are some applications where it is advantageous to modulate the power periodically. However, in this way, the vaporization of the anode material is strengthened, and the degree of light reduction is increased.

In order to actually reduce the vaporization of the anode material, it is necessary to lower the anode temperature, which is achieved by increasing the energy radiation of the anode. Two techniques are used for this. The first technique is to increase the anode area or anode size. In particular, it is advantageous to increase the diameter of the anode. Compared to this, extending the length of the anode is less effective. In known discharge lamps, the diameter of the anode generally increases as the lamp output increases. The second technique is to coat or pattern the anode to increase its permeability. For example, coarse tungsten or dendritic rhenium is used as the coating material.

In a mercury high-pressure discharge lamp with a high rare gas filling pressure, when the cold pressure exceeds a predetermined value based on the type of rare gas and the lamp geometry, the vaporization rate of the anode material is practical even if the above two techniques are used. Above There is a problem that the required allowable value does not decrease. In this case, the rare gas filling pressure must be reduced. However, when the rare gas filling pressure is lowered, the effect of narrowing the arc is reduced, and when a lamp is used in the optical device, a decrease in light intensity is perceived. Although it is possible to selectively reduce the power and the lamp current, these means also lead to a decrease in the light intensity of the lamp.

From the prior art, discharge lamps with an anode made of tungsten with a flux are known. The flux is, for example, potassium, the component of which is 15 ppm to 300 ppm. Such a configuration is known from German Patent No. 3036746.

Further, from German Publication No. 19852703, a discharge lamp having an anode made of potassium-doped tungsten or alloy is known. The concentration of the doping substance is less than 100 ppm.

Further, from German Publication No. 119738574, a discharge lamp having an anode having a cylindrical base body is known. The cylindrical base body of this anode includes a conical tip, which is formed primarily by radial deformation. The number and density of particles at the tip portion typically differ by a coefficient of 2 or more compared to the number and density of particles at the shaft portion.

Disclosure of invention An object of the present invention is to provide a mercury high-pressure discharge lamp capable of reducing vaporization of an electrode material during driving.

This problem is solved by a mercury high pressure discharge lamp having the characteristics described in claim 1.

In the mercury high-pressure discharge lamp of the present invention, at least a part of the anode is made of a material containing a tungsten component, and the anode material is 200 pieces / mm.²Larger particle number and 19.05 g / cm³Has a higher density. As a result, a significant reduction in vaporization of the electrode material is achieved. The above-mentioned advantages are that it has a rated output larger than 1.5kW for DC current operation, the diameter of the anode in the discharge tube is 25mm to 70mm, and the filling gas in the discharge tube is 0.5mg / cm.³~ 7mg / cm³200 pieces / mm of anode material in a mercury high pressure discharge lamp containing a filling amount of mercury and at least one rare gas with a cold pressure greater than 0.8 bar.²Larger particle number and 19.05 g / cm³Achieved by having a higher density. However, when only one of the two parameters is satisfied, the effect obtained is smaller than when both ranges are satisfied.

<figref num="1">It is a figure which shows the Example of the mercury high pressure discharge lamp of this invention.</figref><figref num="2">It is a figure which shows the 1st Example of an anode.</figref><figref num="3">It is a figure which shows the 2nd Example of an anode.</figref><figref num="4">It is a graph which shows the relationship between the relative light intensity and the driving time of the mercury high-voltage discharge lamp which has the 1st lamp parameter.</figref><figref num="5">It is a graph which shows the relationship between the relative light intensity and the driving time of the mercury high-voltage discharge lamp which has a 2nd lamp parameter.</figref>

The diameter of the anode is the maximum diameter of the anode. When the anode normally has a cylindrical portion followed by a conical portion, the diameter of the cylindrical portion is the diameter of the anode.

Currently known, the arc causes thermal stress, which causes the anode plane to warp in lamps that operate in direct current. In this case, the arc stays at the warped location, which causes local overheating. As this progresses, it can even reach temperatures locally above the melting point of tungsten, 3400 ° C. In that case, tungsten is excessively vaporized and the discharge tube is blackened, resulting in a significant decrease in luminous flux.

Advantageously, the density of the anode material is 19.15 g / cm³That is all.

Advantageously, the number of particles in the anode material is 350 / mm²That is all. With such a configuration, the vaporization characteristics can be further lowered.

The number of particles in the anode before driving the lamp is defined by ASTM E112 as the average number of particles. As the lamp is used, the structure may become coarser and the anode may have locally coarse particles.

To reduce grain coarsening, the material is advantageously doped with potassium. The maximum potassium content is 100 μg / g, usually less than 50 ppm, preferably 8 ppm to 45 ppm. Particularly advantageous, the potassium component is 10 ppm to 40 ppm.

The anode is advantageously formed at least partially cylindrically. The distal end side of the anode is advantageously formed in a conical shape. However, the anode may have a different geometric shape.

The cylindrical portion of the anode has a diameter greater than 28 mm, preferably more than 30 mm. Particularly advantageous, the diameter of the cylindrical portion is 34 mm or more. This achieves a significant reduction in vaporization of the electrode material at that portion. Regarding the function of the anode, vaporization of the material becomes a problem, but this is remarkably reduced by the configuration of the present invention.

The mercury high pressure discharge lamp of the present invention is 0.5 mg / cm.³~ 7mg / cm³Has a mercury filling amount of. Especially, the filling amount of mercury is 1mg / cm.³~ 3mg / cm³If so, vaporization is significantly reduced. Further, when the mercury high-pressure discharge lamp is driven by a constant electric power, the cold gas pressure of the rare gas is larger than 3.5 bar, which is preferably 4 bar or more. When the mercury high pressure discharge lamp is driven by modulated power, the cold gas cold pressure is greater than 0.8 bar, preferably greater than 1.5 bar. The structure of the rare gas cold pressure and the anode of the present invention is particularly advantageous for preventing vaporization of the electrode material.

As the type of rare gas, xenon, argon, krypton or a mixture of these rare gases is preferably used.

In order to prevent vaporization of the electrode material, particularly the anode material, a lamp having a rated output larger than 1.5 kW is required, and a lamp having a rated output of 4 kW, particularly preferably about 5 kW or more is used. The reduction of vaporization of the electrode material is achieved regardless of the properties of the electrode surface, that is, regardless of the pattern or coating condition.

The final molding of the electrodes is performed by striking, cutting, milling, water cleaning and heat cleaning. Further, the plane of the electrode may be forged in the axial direction.

According to the present invention, a mercury high-pressure discharge lamp having an anode made of the above-mentioned material is formed at least partially, and a decrease in luminous flux is significantly alleviated as compared with a conventional mercury high-pressure discharge lamp having an anode made of a tungsten material. To. This is particularly advantageous when driving at high rare gas filling pressures or at periodic modulated powers.

Advantageously, the method for producing an electrode of the present invention does not need to be changed as compared with an electrode having a known tungsten material.

Hereinafter, the present invention will be described in detail with reference to the illustrated examples.

Advantageous examples of the present invention In the figure, the same reference numerals are given to the same components or the components having the same action.

FIG. 1 shows a schematic view of a discharge lamp 1 configured as a mercury high-pressure discharge lamp. This high-voltage discharge lamp has a discharge tube 2, and a cathode 3 and an anode 4 extend in the inner chamber 21 of the discharge tube 2. The anode 4 is configured to be substantially cylindrical as shown in FIGS. 2 and 3.

FIG. 2 shows the first anode 4 having a diameter d1 of about 35 mm. The length in the direction of the axis A is about 65 mm. Correspondingly, FIG. 3 shows a second anode 4'with a diameter d2 of about 35 mm. Like the first anode 4, the second anode 4'extends in the direction of axis B over a length of about 65 mm.

In the first configuration shown in FIG. 2, the front side of the anode 4, that is, the side close to the cathode 3, is formed in a conical shape so as to be tapered. The conical part extends over a length of l1. A conical part is also formed on the front side of the second anode 4'in FIG. 3, which has a length l2 smaller than a length l1.

In the configurations of FIGS. 2 and 3, the first anode 4 and the second anode 4'are arranged in the discharge lamp 1 of FIG.

In this embodiment, the anode 4 arranged in the discharge lamp 1 is made of a tungsten material, and the number of particles of this tungsten material is 350 particles / mm.²Is. Advantageously, the density of the anode material is 19.15 g / cm³That is all. Further, the material of the first anode 4 is doped with potassium, and the potassium component is 10 ppm to 40 ppm.

The discharge lamp is driven by a direct current, and the rated output of the discharge lamp is 5 kW or more. Mercury filling amount is 0.5mg / cm³~ 5mg / cm³Is. Advantageously the mercury filling is 1 mg / cm³~ 3mg / cm³Is. The cold gas cold pressure of the inner chamber 21 is larger than 4 bar when the mercury high-pressure discharge lamp is driven by a constant power. When the mercury high-pressure discharge lamp is driven by modulated power, the cold gas pressure of the rare gas is 1.5 bar or more. Power modulation is done at amplitudes up to 15% and frequencies from 0.5Hz to 5Hz.

In this embodiment, the first anode 4 is uniformly composed of the above-mentioned density and the above-mentioned particle number from the doped tungsten material. However, the only partial region of anode 4 can be constructed from such materials. In this way, the anode 4 can also be composed of a plurality of parts. Particularly advantageous, the conical region of at least near the cathode 3 or a portion thereof of the anode 4 is made of a tungsten material and has the aforementioned number of particles and a corresponding density and / or a corresponding potassium doping concentration. Similarly, of the anodes 4, 4', only the pin-shaped partial region centered on the axes A and B can be composed of the above-mentioned material.

FIG. 4 shows the relationship between the relative light intensity of the discharge lamp 1 and the driving time. Here, the parameter of the discharge lamp 1 is the cold pressure of krypton, which is a rare gas. The discharge lamp 1 is driven by a constant power of 5.5 kW. In this graph, the luminous flux characteristics of the discharge lamp provided with the anode of the present invention are shown by the solid curve I. In contrast, the luminous flux characteristics of a conventional discharge lamp with an anode are shown by the dashed curve II.

FIG. 5 shows the relationship between the relative light intensity of the discharge lamp 1 and the driving time in another case. Here, a xenon krypton mixture is used as the rare gas to be filled, and the cold pressure of the rare gas, which is a lamp parameter, is 1.9 bar. In this case, the discharge lamp is driven by power that is periodically modulated between 4.5kW and 5kW. In FIG. 5, the luminous flux characteristics of the discharge lamp with the anode of the present invention are shown by the solid line curve III, and the luminous flux characteristics of the conventional discharge lamp with the anode are shown by the curved line IV.

From FIGS. 4 and 5, it can be seen that the anode of the present invention achieves remarkably high light intensity as the service life progresses. In the known discharge lamp, the light intensity decreases as the driving time increases as shown in the characteristic curves II and IV, but the discharge lamp of the present invention hardly decreases.