JPH0227497Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a high-pressure discharge lamp having an arc tube made of translucent ceramic.

Incidentally, high-pressure sodium lamps are attracting attention as lamps suitable for the energy-saving era because they have high efficiency and a high luminous flux maintenance rate. The arc tube of this lamp is made of translucent ceramic that is resistant to alkali. Normally, end rings made of translucent ceramic are sealed at both ends of the tubular luminous tube envelope made of translucent ceramic with cement or the like. The end ring is sealed, and the electrode conductor is hermetically sealed with cement or the like, passing through the center of the end ring.

However, the above structure has a problem in that leaks and cracks are likely to occur in the sealing portion between the end ring and the arc tube envelope.

Therefore, recently, a translucent ceramic arc tube having a shape in which an arc tube envelope and an end ring are integrated has been proposed. However, in this type of arc tube, the electrode conductor must be sealed with cement as before, and depending on the angle the electrode conductor makes with the wall of the arc tube, the lamp characteristics, especially the lamp voltage. There was a problem that the values varied widely.
This was because the cement did not remain in a fixed position during such sealing.

The present invention provides a high pressure discharge lamp that can obtain a predetermined lamp voltage.

The present invention will be explained below with reference to the drawings.

In FIG. 1, an arc tube 1 is made of translucent ceramic and has a shape in which the ends of the tube are narrower than the center of the tube. An electrode conductor 3 having an electrode 2 at its tip is hermetically sealed to this end with cement 4. Further, the angle θ between the tube wall of the arc tube 1 and the electrode conductor 3 is 50 to 85 degrees (see FIG. 2). The arc tube 1 is filled with excess sodium, mercury, and rare gas.

According to the above configuration, when the electrode conductor 3 is sealed to the end of the arc tube 1 with the cement 4, the angle θ of the tube wall of the arc tube 1 with the electrode conductor 3 is 50 to 85 degrees. Therefore, the flow of cement 4 does not spread unnecessarily, and the position of cement 4 remains constant.As a result, the temperature of the coldest point of arc tube 1 remains constant between lamps, and as a result, the lamp voltage also remains constant. be.

Next, an experimental example in which the present invention was implemented will be described.

The arc tube is made of polycrystalline alumina, has an inner diameter of 5.4 mm at the center of the tube, a wall thickness of 0.75 mm, and a diameter of 3.1 mm through which the electrode conductor passes. The electrode conductor has an outer diameter of 3.0 mm, and an electrode to which an electron radioactive substance is attached is provided at the tip. The angle θ between the wall of the arc tube and the electrode conductor is 55 degrees. The distance between both electrodes is 41 mm. 3.7mg of sodium in the tube,
It contained 16.3 mg of mercury and 30 Torr of xenon.
When we prototyped 10 such lamps and turned them on with an input of 150W, the lamp voltage was 84V compared to the rated voltage of 90V.
The variation was small at ~93V.

Furthermore, the angle θ is set to 20, 30, 40, 50, 60,
70, 80, 85 degrees, and use the same arc tube as above for each
When 10 lamps were prototyped and tested, the lamp voltage of each lamp was as shown in Figure 3. As is clear from this, when the angle θ was 20, 30, and 40 degrees, the lamp voltage varied greatly. The main reason for this is thought to be that when the electrode conductor is sealed to the end of the arc tube, the flow of cement spreads unnecessarily and does not stop at a predetermined location. Regarding this,
Further explanation will be given with reference to FIGS. 4 and 5.

Figure 4 shows the spread length l (mm) of the cement in the arc tube by cutting the arc tube of the lamp with the experimental data shown in Figure 3 along the tube axis direction, and Figure 5 shows the relationship between the angle θ and the same length l. As is clear from FIG. 5, when the angle θ is between 50 and 85 degrees, the length l of the spread of the cement into the arc tube becomes extremely small, 0.3 mm or less. Furthermore, if the angle θ exceeds 85 degrees,
Although the length l is small, it not only becomes difficult to manufacture, but also causes problems such as a longer ramp-up time. Therefore, the angle θ needs to be in the range of 50 to 85 degrees.

The present invention can be applied not only to high-pressure sodium lamps in which excess sodium is sealed in a ceramic arc tube, but also to metal halide lamps in which a metal halide is similarly sealed in the arc tube.

As explained above, the present invention is a high-voltage arc tube in which an electrode conductor with an electrode at the tip is sealed with cement at the end of a ceramic arc tube whose end is constricted compared to the center of the tube. In a discharge lamp, the tube wall angle of the arc tube that forms the electrode conductor is
By setting the angle in the range of 50 to 85 degrees, it is possible to provide a high-pressure discharge lamp with a small variation in lamp voltage without requiring special parts or special processing.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing an example of the arc tube of the high-pressure discharge lamp according to the present invention, Fig. 2 is an enlarged sectional view of the main part thereof, and Fig. 3 is the angle between the electrode conductor and the wall of the arc tube and the lamp. A diagram showing the relationship with voltage variation,
Figure 4 is a diagram showing how the cement spreads inside the arc tube by cutting the arc tube of the lamp with the experimental data shown in Figure 3 along the tube axis direction, and Figure 5 shows the angle θ and the spread of cement into the arc tube. It is a figure which shows the relationship with spread length l. 1... Arc tube, 2... Electrode, 3... Electrode conductor,
4...Cement.

Claims (1)

[Scope of utility model registration request] The electrode conductor having an electrode at the tip is sealed with cement to both ends of a ceramic arc tube having a shape where both ends of the tube are constricted compared to the center part of the tube, and the electrode conductor is A high-pressure discharge lamp characterized in that the arc tube wall angle is in the range of 50 to 85 degrees.