JP3850753B2 - Discharge lamp - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a high-intensity discharge lamp that can be lit at a low breakdown voltage by providing a trigger line.
[0002]
[Prior art]
Currently, high-intensity discharge lamps, such as high-pressure mercury lamps, are frequently used as light sources for liquid crystal projectors. Hereinafter, the problems of the conventional high-intensity discharge lamp will be briefly described with reference to FIGS. FIG. 5 shows a high-intensity discharge lamp (B1) of Conventional Example 1, which is made of quartz glass and has an arc tube portion (1) projecting sealing portions (3a) and (3b) on both sides thereof, and the sealing portion. (3a) Molybdenum metal foil (4a) (4b) embedded in an airtight manner in (3b), and disposed in the arc tube portion (1) facing each other, one end of the molybdenum metal foil (4a) ( 4b) are welded to the pair of electrodes (2a) (2b) and the sealing portions (3a) (3b), respectively, and one end thereof is welded to the molybdenum metal foil (4a) (4b), respectively. External lead rods (5a) and (5b). The pair of electrodes (2a) and (2b) become an anode electrode (2a) and a cathode electrode (2b), respectively, in the case of direct current lighting.
[0003]
In the arc tube portion (1), an inert gas such as argon gas, mercury, and a metal halide suitable for each use are sealed for starting. When the conventional example 1 (B1) is to be turned on, it is necessary to cause a dielectric breakdown between the electrodes (2a) and (2b), so that a high starting voltage must be applied by an igniter. This high-voltage starting voltage becomes a noise to the control circuit of the optical device on which the discharge lamp (B1) is mounted, and causes a malfunction. Therefore, it is currently required to make the starting voltage as low as possible. In addition, optical devices themselves are also becoming smaller, and there is a strong demand for smaller lighting devices.
[0004]
FIG. 5 shows Conventional Example 2 (B2), which is an improvement of Conventional Example 1 (B1). In the conventional example 2 (B2), the trigger wire (6c) connected to the external lead rod (5a) on the anode electrode (2a) side is along the outer surface of the arc tube part (1) in the conventional example 1 (B1). It is arranged and wound around the neck of the sealing part (3b) on the cathode electrode (2b) side. When this conventional example 2 (B2) is dc-lit, an electric field is formed between the electrodes (2a) (2b) and the trigger wire (6c), and the influence of this electric field causes the argon gas of the electrodes (2a) (2b) to Dielectric breakdown is advantageous, and the breakdown voltage is lower than that of Conventional Example 1 (B1).
[0005]
According to an experiment of a high-pressure mercury lamp having an arc length of 1.3 mm [Conventional Example 2 (B2)], a high-pressure pulse of about 10 kV (pulse width = about 0.1 μsec) was almost the minimum value that could be started. On the other hand, in the case of Conventional Example 1 (B1), since there is no trigger line (6c), the minimum voltage for starting was approximately 12 kV. FIG. 6 shows Conventional Example 3 (B3), which is the opposite of Conventional Example 2 (B2). In this case as well, as in Conventional Example 2 (B2), the minimum starting voltage was about 10 kV. .
[0006]
[Problems to be solved by the invention]
An object of the present invention is to turn on the starting high-voltage pulse voltage so as to be 10 kV or less in accordance with the recent demands for downsizing optical devices such as projectors and further noise reduction requirements for control circuits. There has been a demand for a discharge lamp that can achieve downsizing of an igniter constituting a part of the apparatus.
[0011]
[Means for Solving the Problems]
The invention according to “Claim 1 (see FIG. 4)” is the following: “A sealed container (10) having sealing portions (3a) and (3b) protruding from both sides of the arc tube portion (1); (3a) An anode electrode (2a) and a cathode whose one end is welded to the metal foil (4a) (4b) embedded in (3b) and the other end is disposed facing the arc tube section (1) an electrode (2b), the metal foil (4a) (4b) on its one end is welded, at the other end an external lead rod led to the outside (5a) (5b) and de-configured discharge lamp (A4) ,
The main trigger wire (6a) connected to the external lead rod (5a) on the anode electrode (2a) side extends to the outside of the arc tube portion (1) and the tip (61) of the main trigger wire (6a) Placed outside the arc tube (1),
Connect one end of the secondary trigger wire (6d) to the external lead rod (5b) on the cathode electrode side (2b) and wind the other end of the secondary trigger wire (6d) around the cathode side sealing portion (3b) . Further, the discharge lamp is characterized in that a slack and curved portion of the sub trigger line (6d) is disposed along the outer surface of the arc tube portion (1) .
[0012]
Since the tip (61) of the main trigger wire (6a) is arranged outside the arc tube portion (1) in this way, it is between the tip (61) and the tip (21b) of the cathode electrode (2b) at the time of starting. An extremely unequal electric field was formed, and the dielectric breakdown between the electrodes (2a) and (2b) was likely to occur. As a result, the starting voltage could be lowered as compared with the conventional case.
In addition to the main trigger line (6a), the sub trigger line (6d) is provided, so that the main trigger line (6a) and the sub trigger line (6d) cooperate to form a more unequal electric field. As a result, dielectric breakdown between the electrodes (2a) and (2b) was more likely to occur, and as a result, the starting voltage could be minimized.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described using preferred examples (A1) to (A4). FIG. 1 is a sectional view of a double-ended high intensity discharge lamp (A1) according to a first embodiment of the present invention. The sealed container (10) is made of quartz glass that hardly undergoes thermal expansion and contraction.The sealed container (3a) (3b) extends straight from both ends of the arc tube (1) in the shape of a hollow sphere. It is configured. Molybdenum metal foils (4a) and (4b) are respectively embedded in the sealing portions (3a) and (3b) in an airtight manner by shrink seals, and anode and cathode electrodes (2a) and (2b) are formed at one ends thereof. The base end portions (22a) and (22b) of the outer lead rods (5a) and (5b) are welded to the other ends, and the other ends of the outer lead rods (5a) and (5b) are welded to the other ends. It is derived outside. The tip portions (21a) and (21b) of the anode and cathode electrodes (2a) and (2b) are opposed to each other with a predetermined interval (0.8 to 1.5 mm).
[0014]
The distal end portion (21a) of the anode electrode (2a) has a larger diameter than the proximal end portion (22a), and the distal end surface (21c) is formed in a flat circular shape. In contrast, the cathode electrode (2b) is thinner than the anode electrode (2a), and the tip thereof is sharp. The above configuration is common to Examples 1 to 4, and the above description is incorporated in Examples 2 to 4.
[0015]
The main trigger wire (6a) is composed of a thin wire or a slightly stiff bar (Fe-Cr, Ni, Pt, etc. is used), one end of which is connected to the anode external lead rod (5a) It is wound and extends along the anode side sealing portion (3a) and the arc tube portion (1), and its end (61) is disposed on the outer surface of the arc tube portion (1). Yes. The end portion (61) disposed on the outer surface of the arc tube portion (1) is preferably pointed to concentrate the electric field.
[0016]
In general, in order to start a discharge lamp, a high voltage is applied between the electrodes to cause dielectric breakdown (a region called townsend discharge), which is a continuous discharge that does not disappear even if the external high-pressure energy is cut off. There is a need to grow. This is thought to develop from a local sustained discharge called a corona discharge that occurs when the electric field distribution is extremely unequal (a phenomenon in which an ionizing action is performed in a part of the arc tube). If the tip of the electrode is sharp like a cathode electrode, the electric field concentrates on the sharp tip and corona discharge tends to develop, but if the tip surface is flat like the anode electrode, the concentration of the electric field is hindered and corona discharge occurs. It is considered to be disadvantageous to the development of. The tip of the anode electrode cannot be sharpened because of high heat capacity due to continuous inflow of electrons during lighting, and is usually flat.
[0017]
When the discharge lamp (A1) in the first embodiment is turned on, a high voltage for starting is applied between the electrodes (2a) and (2b) at the start, but the sharp tip (61) of the main trigger line (6a) and An extremely unequal electric field was formed between the cathode electrode (2b), dielectric breakdown could occur even with a starting high-pressure pulse much lower than before, and corona discharge could be easily generated. In this case, corona discharge could be generated with a starting voltage as low as 5-9 kV. On the other hand, as described above, in the case of the conventional example 2 (B2) in FIG. 5, the other end of the trigger wire (6c) is wound around the cathode side sealing portion (3b) to form a loop. The sharp tip as in Example 1 (A1) no longer exists, and although the trigger line (6c) is present, its starting voltage drop effect is small, and a starting voltage of about 10 kV is required.
[0018]
Next, the second embodiment (A2) will be described. In this case as well, as described above, the main trigger wire (7) is wound around the coil on the tip portion (21a) of the flat anode electrode (2a) on the tip surface (21c), and the sharp tip (71) is the tip. Since the high voltage is applied to the electrodes (2a) and (2b), the main trigger wire wound around the tip portion (21a) of the anode electrode (2a) ( As described above, an extremely unequal electric field is formed between the sharp tip (71) of 7) and the tip (21b) of the cathode electrode (2b), and dielectric breakdown occurs even with a starting high-pressure pulse that is much lower than before. The generation of corona discharge can be facilitated. Also in this case, corona discharge could be generated with a starting voltage as low as 5 to 9 kV.
[0019]
Next, a third embodiment (A3) will be described. In this case, one end of the cathode electrode (2b) side is wound around the external lead rod (5b), and the outer end of the arc tube portion (1) is wound around the neck portion of the anode side sealing portion (3a). The attached secondary trigger wire (6d) and one end thereof are wound around the anode-side external lead rod (5a), and are extended to the outside of the arc tube portion (1) and the sharp tip (61) emits light. A main trigger wire (6a) arranged on the outer surface of the pipe section (1), the sub trigger wire (6d) and the main trigger wire (6a) cooperate to lower the starting voltage, and as a result The generation of corona discharge could be achieved with the lowest high voltage pulse of 4-8 kV.
[0020]
Finally, the fourth embodiment (A4) will be described. In this case, the sub trigger line (6e) is provided in the first embodiment (A1). One end of the secondary trigger wire (6e) is wound around the cathode-side external lead rod (5b), the other end is wound around the neck of the cathode-side sealing portion (3b), and the middle portion (6e1) emits light It arrange | positions along the outer surface of a pipe part (1). When starting lighting in this state, as described above, between the tip (61) of the main trigger line (6a) and the tip (21b) of the cathode electrode (2b) and the middle part (6e1) of the sub trigger line (6e) As a result, a significantly unequal electric field is formed between the tip surface (21c) of the anode electrode (2a) and, as a result, the lowest high-pressure pulse of 4 to 8 kV, as in the third embodiment (A3). The generation of corona discharge could be achieved. The advantage of the third embodiment (A3) is that the distance between the main trigger line (6a) and the sub trigger line (6e) can be increased, and the main trigger line (6a) and the sub trigger line can be taken. It is possible to prevent discharge at start-up in (6e).
[0021]
【The invention's effect】
As described above, in the discharge lamp according to the first and second embodiments of the present invention, the sharp tip of the main trigger line connected to the anode side external lead rod is disposed on the outer surface of the arc tube portion. Alternatively, the main trigger wire is wound around the tip of the anode electrode, and the tip thereof is placed close to the tip surface of the anode electrode, so that the sharp tip of the main trigger wire and the cathode electrode A significantly unequal electric field is formed between the tip and the corona discharge can be generated at a much lower starting voltage than before.
[0026]
In addition to this, as shown in the third and fourth embodiments, by providing a sub trigger line in addition to the main trigger line, the two trigger lines cooperate to generate a corona discharge with a lower starting voltage. Can now be achieved. As a result, it was possible to reduce the size and noise of the igniter.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a first embodiment of a high-intensity discharge lamp according to the present invention.
FIG. 2 is a cross-sectional view of a second embodiment of the high-intensity discharge lamp of the present invention.
FIG. 3 is a cross-sectional view of a third embodiment of the high-intensity discharge lamp of the present invention.
FIG. 4 is a cross-sectional view of a fourth embodiment of the high intensity discharge lamp of the present invention.
5 is a cross-sectional view of Conventional Example 1. FIG.
6 is a cross-sectional view of Conventional Example 2. FIG.
7 is a cross-sectional view of Conventional Example 3. FIG.
[Explanation of symbols]
(A1) to (A3) Discharge lamp of the present invention
(1) Arc tube
(2a) (2b) Sealing part
(3a) (3b) Sealing part
(5a) (5b) External lead rod
(6a) (7) Main trigger wire
(6d) (6e) Sub trigger line
(10) Enclosure container

Claims (1)

A sealed container with sealing portions projecting from both sides of the arc tube portion, and an anode having one end welded to a metal foil embedded in the seal portion and the other end disposed opposite the arc tube portion In a discharge lamp composed of an electrode and a cathode electrode, and an external lead rod having one end welded to the metal foil and the other end led to the outside,
Extending the main trigger line connected to the external lead rod on the anode electrode side to the outside of the arc tube portion and disposing the tip of the main trigger line on the outside of the arc tube portion ,
One end of the sub trigger line is connected to the external lead rod on the cathode electrode side, and the other end of the sub trigger line is wound around the cathode side sealing portion. A discharge lamp characterized by being disposed along the outer surface of the arc tube portion .

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