JPH0668849A - High pressure discharge lamp of horizontal lighting type - Google Patents

Abstract

PURPOSE:To start and restart a discharge lamp at a low voltage by providing electrode protruding parts diagonally under upper forward end parts of a pair of electrodes, and composing them in such a way that a distance between the protruding parts is shorter than a distance between the forward end parts. CONSTITUTION:In a discharge lamp, the axis of a light emitting tube 1 is put to be horizontal to position electrode protruding parts 4 under electrode upper forward end parts 3. A high voltage pulse is applied between electrode leads 6, 6 in starting or restarting, electric breakdown occurs between the protruding parts 4, 4 of the shortest distance between electrodes 2, 2 for transition to arc discharge to make a lighting condition. During lighting, arc floats up by convection to hold the arc discharge at the forward end parts 3 of a conventional electrode distance. The voltage in starting and restarting can thus be reduced, and thereby insulation design for a discharge lamp, its lighting device, and peripheral devices can be formed simple and compact.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a horizontal lighting type high pressure discharge lamp such as a high pressure mercury lamp or a metal halide lamp which is lit by arc discharge between a pair of electrodes.

[0002]

2. Description of the Related Art In recent years, horizontal lighting type high pressure discharge lamps have been attracting attention for applications such as in-vehicle light sources because of their brightness, high reliability and long life.

A conventional horizontal lighting type high pressure discharge lamp will be described below with reference to the drawings. FIG. 5 shows the structure of a conventional horizontal lighting type high pressure discharge lamp. As shown in FIG. 5, the arc tube 21 is sealed with a pair of electrodes 22 and 22, and the electrode tips 23 and 23 are closest to each other. The electrode 22 is connected to an electrode lead wire 26 via a metal foil 25.

The operation of the horizontal lighting type high pressure discharge lamp configured as described above will be described below. First, the central axis of the arc tube 21 is arranged substantially horizontally. When a high voltage pulse is applied between the pair of electrode lead wires 26, 26 from an external high voltage pulse generating circuit at the time of starting / restarting, the pair of electrode tip portions 23, 2
A dielectric breakdown phenomenon occurs between the three. After that, electrode lead wire 2
When electric power is supplied from an external AC power source between 6 and 26, the arc discharge starts and the lighting state occurs.

In such a conventional discharge lamp, starting /
Various measures have been taken in order to reduce the applied voltage at the time of restart and to sustain the discharge stably. For example, Japanese Patent Laid-Open No. 3-2
As disclosed in Japanese Patent No. 25742, the tips of the pair of electrodes are formed in a conical shape to reduce power consumption.

[0006]

However, in such a conventional horizontal lighting type high pressure discharge lamp, the gas pressure inside the arc tube is high and the distance between the electrodes during lighting is the distance between the electrodes during starting and restarting. Therefore, it is necessary to apply a high voltage between the electrode lead wires in order to cause dielectric breakdown between the electrodes at the time of starting and restarting. Therefore, it is necessary to take sufficient insulation measures against the generation of high voltage in the horizontal lighting type high pressure discharge lamp, the lighting device, the peripheral equipment and the like.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a horizontal lighting type high pressure discharge lamp which is started and restarted at a low voltage.

[0008]

DISCLOSURE OF THE INVENTION The present invention proposes a specific structure of a horizontal lighting type high pressure discharge lamp which is started and restarted at a low voltage.

In order to solve the above-mentioned problems, the horizontal lighting type high pressure discharge lamp of the present invention is such that at least one electrode of a pair of electrodes sealed in an arc tube has a relative electrode tip portion or a portion in the vicinity of the electrode tip portion. When projecting downwards to the side of the electrodes that are opposite to each other and projecting downwards to the side of the electrodes facing each other, the shortest distance between the electrodes is formed between the tips of the projecting portions of both electrodes, and only one of the electrodes faces each other. When projecting downward to the electrode side, the shortest distance to the opposing electrode is formed between the tip ends of the projecting portions of the electrode.

Further, at least one of the pair of electrodes sealed in the arc tube has at least one electrode when the electrode tip portion or the vicinity of the electrode tip portion projects downward and both electrodes project downward. The sharpness of the tip of the protruding part of the electrode is maximized at the tip of the electrode and in the vicinity of the tip, and when only one electrode projects downward, the sharpness of the protruding part of the electrode is , The maximum at the tip of the electrode and in the vicinity of the tip.

[0011]

According to the above-mentioned structure, in the horizontal lighting high-pressure discharge lamp of the present invention, at least one of the electrodes has a tip portion or a portion near the tip portion projected downward toward the opposite electrode side, so that light is emitted during lighting. The arc floats due to the convection phenomenon inside the tube, and the position of the discharge point on the electrode also rises, so the arc length during lighting is the same as before. At the time of starting / restarting, the phenomenon of dielectric breakdown occurs in the shortest distance between the electrodes formed by the protruding portions of the electrodes, so that the voltage required for starting / restarting can be reduced.

Further, the tip of at least one of the electrodes or the vicinity of the tip is projected downward, and the sharpness of the tip of the protruding portion is maximized at the tip of the electrode and the vicinity of the tip. Since the electric field strength of the protruding part can be increased, the arc floats upward due to the convection phenomenon inside the arc tube during lighting, and the position of the discharge point formed on the electrode also rises. Is the same as before. However, at the time of starting / restarting, dielectric breakdown occurs in the protruding portion of the electrode, so that the voltage required for starting / restarting can be reduced.

[0013]

Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 shows the structure of a horizontal lighting type high pressure discharge lamp according to Embodiment 1, FIG. 2 shows the state of dielectric breakdown at the time of starting and restarting of this embodiment, and FIG. The arc during lighting of an Example is shown. 1 to 3, reference numeral 1 is a light emitting tube, 2 is an electrode, 3 is an electrode upper tip portion, and 4 is an electrode projecting portion, which are projected downward to opposite electrode sides so that the electrodes approach each other. There is. 5 is a metal foil, 6 is an electrode lead wire, 7
Is a discharge path at the time of dielectric breakdown. Reference numeral 8 is a discharge path of arc discharge during lighting, that is, an arc. Here, the distance between the pair of electrode upper tips 3, 3 is the same as the distance between the electrodes of the conventional horizontal lighting type high pressure discharge lamp, but the distance between the electrode protrusions 4, 4 is between the electrode upper tips 3, 3. It is configured to be shorter than the distance.

The operation of the horizontal lighting type high pressure discharge lamp of the first embodiment constituted by the above members will be described below. First, in the horizontal lighting high-pressure discharge lamp shown in FIG. 1, the central axis of the arc tube 1 is placed in a horizontal position so that the electrode protrusion 4 is located below the electrode upper tip 3. When a high voltage pulse is applied between the pair of electrode lead wires 6 and 6 from the external high voltage pulse generation circuit at the time of starting and restarting, the electrode protrusion 4 which minimizes the distance between the electrodes 2 and 2 as shown in FIG. , 4, the phenomenon of dielectric breakdown occurs. The discharge path at that time has a shape as shown in the discharge path 7 at the time of dielectric breakdown, for example. After that, when electric power is supplied from an external AC power source between the electrode lead wires 6 and 6, the arc discharge is started and the lamp is turned on.
During lighting, the arc 8 floats and curves upward as shown in FIG. 3 due to convection in the arc tube 1, and the discharge point on the power supply 2 also floats upward and is formed at the position of the electrode upper tip 3. . In this way, during lighting, the distance between the electrodes is the same as in the conventional example,
That is, the arc discharge is maintained with the arc length which is the same as the conventional example.

As described above, according to the horizontal lighting high-pressure discharge lamp of the first embodiment, the phenomenon of dielectric breakdown occurs between the electrode protrusions 4 and 4, which is the shortest distance between the electrodes 2 and 2, so that the dielectric breakdown voltage is reduced. It can be made lower than before, and the voltage applied between the electrode lead wires 6 and 6 at the time of starting and restarting, that is, starting
The restart voltage can be reduced. As a result, it is possible to simplify the insulation design of the horizontal lighting high-pressure discharge lamp and its lighting device and peripheral equipment, and to downsize the lighting equipment and peripheral equipment.

Further, since the electrode protrusion 4 is close to the wall of the arc tube 1 and the temperature of the coldest spot of the arc tube 1 can be raised by the heat radiation from the electrode protrusion 4, the luminous efficiency is improved. You can

In this embodiment, the structure in which both electrodes are projected downward to the opposing electrode side is described. However, if the shortest distance between the electrodes is formed between the electrode projecting portions, one of the electrodes is at a right angle. It may be projected downward, another structure may be projected downward, or it may be a straight rod shape as in the conventional example.

(Second Embodiment) Next, a horizontal lighting type high pressure discharge lamp according to a second embodiment of the present invention will be described with reference to FIG.

FIG. 4 shows the structure of the horizontal lighting type high pressure discharge lamp of the second embodiment. In FIG. 4, reference numeral 12 is an electrode, 13 is an electrode upper tip portion, and 14 is an electrode protrusion portion. The difference from the first embodiment in structure is that the sharpness of the tip portion of the electrode protrusion portion 14 is as shown in FIG. This is to be larger than the sharpness of the electrode upper tip portion 13. The operation differs from that of the first embodiment in that the sharpness of the electrode projecting portion 14 is large, so that the electric field strength of the electrode projecting portion 14 is large, and therefore, the phenomenon of dielectric breakdown between the electrode projecting portions 14 and 14 at the time of starting and restarting. Happens. Further, while the arc is lit, the arc and the electrode 12 are the same as in the first embodiment.
The upper discharge point floats, and the arc discharge is maintained with the arc length that is the same as the conventional example.

As described above, according to the discharge lamp of the second embodiment, since the tip of the electrode protrusion 14 is sharp, the electric field strength of the electrode protrusion 14 can be increased.
Since the electrode protrusion 14 is more likely to cause dielectric breakdown than the discharge lamp of No. 1, the voltage applied between the electrode lead wires 6 at the time of starting and restarting can be further reduced as compared with the discharge lamp of the first embodiment. Therefore, the insulation design of the horizontal lighting high-pressure discharge lamp and its lighting device and peripheral equipment can be further simplified, so that the lighting equipment and peripheral equipment can be further downsized.

In this embodiment, the discharge lamp having a structure in which both electrodes project downward on the opposite electrode side is described, but the range in which the electric field strength between both electrodes is larger than the electric field strength between the electrodes in the conventional example. If so, another downward projecting structure may be used, and one of the electrodes may have a straight rod shape as in the conventional example.

In Examples 1 and 2, the discharge path and the discharge point on the electrode were assumed to float at the time of arc discharge.
The discharge may float in the process of reaching arc discharge such as dielectric breakdown or glow discharge. For example, even if discharge starts at the electrode protrusion at the beginning of the dielectric breakdown, the dielectric breakdown phenomenon may occur near the electrode upper tip during application of the high voltage pulse.In that case, at the beginning of arc discharge transition. An arc and a discharge point are formed at a position which is levitated from.

Further, although the electrode tips are projected in the first and second embodiments, it goes without saying that they may be projected from the vicinity of the electrode tips.

Further, as the horizontal lighting type high pressure discharge lamp described in Embodiments 1 and 2, any high pressure discharge lamp such as a high pressure mercury lamp, a metal halide lamp, a high pressure sodium lamp and a xenon lamp may be used. Further, in the first and second embodiments, the AC lighting discharge lamp is described as the horizontal lighting type high pressure discharge lamp, but it goes without saying that it may be a DC lighting discharge lamp. Further, in the first and second embodiments, the double-sealed horizontal lighting high-pressure discharge lamp is described, but it goes without saying that a single-sealed lamp may be used.

[0026]

The horizontal lighting type high pressure discharge lamp of the present invention is
With the configuration as described above, the tip or the vicinity of the tip of at least one of the electrodes is made to project downward to the opposite electrode side, and the tip or the vicinity of the tip of at least one of the electrodes is By projecting downward and making the tip of the projecting portion sharp, the start and restart voltages can be reduced. With this configuration, the horizontal lighting high-pressure discharge lamp, the lighting device for the same, and the insulating design of the peripheral device can be easily designed, and the lighting device and the peripheral device can be downsized. Further, since the tip of the electrode approaches the lower wall of the arc tube and the heat from the tip of the electrode can raise the coldest spot temperature of the arc tube, the vapor pressure inside the arc tube increases and the luminous efficiency is improved. Can be increased.

[Brief description of drawings]

FIG. 1 is a sectional view showing a configuration of a horizontal lighting type discharge lamp according to a first embodiment of the present invention.

FIG. 2 is a sectional view showing a state of dielectric breakdown at the time of starting the same.

FIG. 3 is a sectional view showing a state of an arc during lighting.

FIG. 4 is a cross-sectional view showing the configuration of a horizontal lighting high pressure discharge lamp according to the second embodiment.

FIG. 5 is a cross-sectional view showing the structure of a conventional horizontal lighting type high pressure discharge lamp.

[Explanation of symbols]

 1 arc tube 2 electrode 3 electrode upper tip 4 electrode protrusion 5 metal foil 6 electrode lead wire

Claims (2)

[Claims] 1. An arc tube surrounding an arc discharge, and a pair of electrodes sealed in the arc tube, the tip of at least one electrode of the pair of electrodes or a portion near the tip of the electrode. Horizontally-lit high-pressure discharge lamp in which the two electrodes project diagonally downward toward the opposite electrodes, and the shortest distance between the two electrodes is formed at the projecting portion. 2. A tip of at least one of the pair of electrodes or a portion near the tip of the electrode projects downward,
The horizontal lighting high-pressure discharge lamp according to claim 1, wherein the protruding portion has the highest sharpness at the tip of the electrode or in the vicinity of the tip of the electrode.