JP3211643B2 - Discharge lamp electrode - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge lamp electrode structure, and more particularly to a discharge lamp electrode for suppressing an increase in anode temperature.

[0002]

2. Description of the Related Art Conventionally, electrode life has been known as a factor for determining the life characteristics of a discharge lamp. Generally, deterioration of the electrode itself is observed as electrode deformation. This is because the electrode material melts and evaporates when the temperature of the electrode tip becomes high.

One factor that determines the electrode temperature is the collision of electrons in the discharge arc with the electrodes. When observing the behavior of electrons during lamp operation, the state differs between the anode and the cathode. The cathode in the discharge arc is a portion where thermoelectrons are emitted at a high density, and it is necessary to keep the temperature high enough to maintain the discharge current. In an arc discharge in which steady thermal electron emission is a main source of electrons, a decrease in the temperature of the cathode means that it becomes difficult to maintain the discharge, that is, it cannot be intentionally reduced. The reason why the cathode is kept at a high temperature is that the energy of the cations projected on the cathode is transferred, and the breakdown is the kinetic energy and the neutral atoms that are accelerated by the cathode fall voltage. The ionization potential energy.

On the other hand, the anode is a portion into which a high-density electron flow coming from a discharge arc flows. An anode drop occurs due to the space charge effect of only electrons on the front surface of the anode, and a local strong electric field is generated based on the drop. At the anode, kinetic energy and energy corresponding to the work function obtained while the flowing electrons pass through the anode descending portion are emitted at the anode. When the electrode material is a high melting point material such as carbon or tungsten, the temperature of the anode is higher than that of the cathode, particularly. This is because almost no cations are emitted from the anode, but a large amount of thermoelectrons are emitted from the cathode and heat is taken away. This also means that the electron current accounts for a large proportion at the cathode. That is, the anode only plays a role of collecting electrons, and therefore, the anode temperature has little to do with sustaining the discharge.

[0005] If the electrode temperatures of the anode and the cathode are different, the state of melting and evaporation of the electrode material is also different for each electrode. As can be seen from the above description, the anode temperature is generally higher than that of the cathode. In order to suppress melting and evaporation, it is sufficient to lower the electrode temperature. However, if the cathode temperature is intentionally lowered, it becomes difficult to maintain discharge. Rather, since the anode temperature has little to do with the maintenance of the discharge, the anode temperature may be lowered. A lamp in which the physical shape of the anode is made larger than that of the cathode based on such a concept has been reported.
This is shown as an example of a conventional lamp in FIG.
No.). The physical shape of the anode 104
By receiving the electron current flowing into the anode 104 with a larger surface area, the current density is reduced to suppress an increase in the anode temperature.

[0006]

The lamp configuration as shown in FIG. 3 is based on DC lighting and is not suitable for AC lighting. When AC lighting is performed using a lamp as shown in FIG. 3, a problem arises when the electrode having a larger shape becomes a cathode as compared with a lamp having both electrodes of the same shape. As described above, it is necessary to keep the temperature of the cathode high. However, as the shape becomes large and the surface area of the cathode becomes large, the temperature of the cathode decreases and it becomes difficult to maintain the discharge. In addition, the current density is large while the surface area of the anode remains small, and the anode temperature is high.

[0007] Even when both electrodes are normally AC-lit by a lamp having the same shape, the high temperature during the anode cycle promotes melting and evaporation of the electrode material and causes electrode deformation.

An object of the present invention is to provide an electrode structure for suppressing an increase in anode temperature during an anode cycle in lamp AC lighting.

[0009]

In order to achieve the above object, the present invention provides an electrode having a plurality of current conducting means;
The current drawer connected to each of the plurality of current conducting means.
And the power supply from the power supply via the current lead-out line.
Control means for supplying a current to the pole, wherein the control means
By selecting the current conducting means that supplies the current
A discharge lamp for controlling a current density flowing through the electrode.
You. The present invention also provides an electrode having a plurality of current conducting means.
And a power supply connected to each of the plurality of current conducting means.
A current draw line and a power supply through the current draw line
Control means for supplying a current to the electrode;
Means are more in the anodic cycle than in the cathodic cycle.
Select a large number of said current conducting means to reduce current density
It is a discharge lamp .

[0010] This suppresses a rise in anode temperature during an anode cycle in lamp AC lighting.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In order to suppress a rise in anode temperature during an anode cycle in lamp AC lighting, the present invention provides:
At least two or more current conducting means, and control means for controlling the timing of conducting at least one or more of the current conducting means, wherein all of the current conducting means are electrically connected to one discharge support portion. The electrode structure is connected. According to the present invention, two or more current conducting means connected to the discharge supporting portion at the tip of the electrode are conducted more frequently in the anode cycle than in the cathode cycle by using a control means for controlling the timing of conducting. By doing so, the concentration of the electron flow in the discharge supporting portion during the anode cycle in which electrons flow is reduced, the current density is reduced, and the increase in anode temperature is suppressed. An embodiment of the electrode for a discharge lamp of the present invention will be described with reference to the drawings.

(Embodiment 1) FIG. 1 shows a first embodiment of an electrode for a discharge lamp according to the present invention. 1A and 1B show one-sided electrodes and a circuit in the case of a lamp. FIG. 1A is a top view of an electrode structure of a discharge lamp, and FIG.

As shown in the figure, the upper surface of the electrode serving as the discharge supporting portion 1 has a planar circular shape. The electrode shaft has a coaxial structure. The central cylindrical shaft is the current conducting means 2 and the peripheral cylindrical portion is the current conducting means 3. These are all electrically connected to the discharge support 1. I have. The shaft portion and the cylindrical portion are insulated from each other by the insulator 4. The current conducting means 2 is joined to the current lead wire at the joint 5 and is connected directly to the AC power supply 10.
Connected to. The current conducting means 3 is joined to the current drawing line at the junctions 6 and 7, and is connected to the AC power supply 10 via the switching element 8 whose conduction timing is controlled by the control means 9.

A description will be given of how the current flows through the electrodes during lamp AC lighting and how the rise in anode temperature during the anode cycle is suppressed accordingly. The control means 9 turns off the switching element 8 when the electrode is in the cathode cycle and turns on the switching element 8 when the electrode is in the anode cycle.

Since the switching element 8 is turned off when the electrode is in the cathode cycle, the discharge current flows only in the current conducting means 2. At this time, the current conducting means 2
The current flows intensively in the central part connected to At the time of this cathode cycle, the cathode must be heated for thermionic emission to maintain the discharge current, and thus the current intensively flows to a specific portion of the discharge support portion 1 and the current density increases, Heating is essential to the extent necessary. Since the temperature follows the increase or decrease of the current density, the diameter of the current conducting means 2, that is, the connection area between the discharge supporting portion 1 and the current conducting means 2 may be appropriately determined in order to obtain a necessary temperature.

When the electrode is in the anode cycle, the switching element 8 is turned on. The discharge current flows through the current conducting means 2 and the current conducting means 3. At this time, in addition to the portion connected to the current conducting means 2 on the discharge supporting portion 1, the current also flows to the portion connected to the current conducting means 3. Since the electrode during the anode cycle merely collects the inflowing electrons, it is necessary to reduce the current density by receiving the inflowing electrons over as large an area as possible on the discharge supporting portion 1 so as not to raise the temperature. By conducting the current conducting means 3 at the time of the anode cycle in this way, it is possible to receive the inflowing electrons in a wider discharge supporting area and suppress a rise in the temperature of the discharge supporting portion.

In this embodiment, a columnar electrode is assumed, but the shape is not limited to a columnar shape.

(Embodiment 2) In the first embodiment, one current conduction means for turning on / off the conduction by the switching element is used. However, the current density distribution on the discharge supporting portion at the time of ON is determined. It is also possible to provide two or more current conducting means for turning on / off for the purpose of controlling to a value of, and to provide control means for controlling the timing to all of them. FIG.
Fig. 2 shows a second embodiment. FIG. 2A is a top view of an electrode structure of a discharge lamp according to a second embodiment of the present invention,
(b) is the same circuit configuration diagram.

The control means 11 includes a predetermined number of current conducting means on the discharge supporting portion, each of which is a current conducting means for conducting in the anode cycle and a current conducting means for conducting in the cathode cycle. However, it is possible to control the conduction according to the lamp output rising time at the time of starting or the lamp lighting elapsed time.

With this configuration, the current density distribution on the discharge supporting portion can be appropriately adjusted by the plurality of current conducting means as the excessive current at the start of lighting gradually decreases from the start of discharge to the stable discharge. By performing the control, it is possible to suppress an increase in the electrode temperature due to a high current density at the start of lamp lighting. In addition, according to the lamp lighting elapsed time, by sequentially changing the portions of the current conducting means that conducts also at the time of the cathode cycle, it is possible to sequentially move the portions of the high electrode temperature due to the bright spots generated at the time of the cathode cycle. In addition, deterioration due to concentration for a long time can be reduced.

Although the present embodiment has been described on the premise of AC lighting, the current conducting means on the anode side is also ON in DC lighting, and the present invention is applicable.

[0022]

As described above, the present invention has an electrode structure for suppressing an increase in anode temperature during an anode cycle during discharge lamp AC lighting. Melting and evaporation can be suppressed.

The deformation of the electrode is suppressed by suppressing the melting of the electrode material. The electrode deformation causes irregularities on the electrode surface.
In this case, a bright point is easily formed on the convex portion, and the bright point moves on the plurality of convex portions, causing a flicker in optical characteristics. In the present invention, since there is no unevenness in the discharge supporting portion, it is difficult for a bright spot to be spontaneously formed due to the shape, and the position of the bright spot can be intentionally controlled. Reduced.

By suppressing the evaporation of the electrode material, a change in the distance between the electrodes is suppressed. If the electrode material evaporates, the distance between the electrodes becomes longer. The distance between the electrodes affects the lamp voltage, and the longer the distance, the higher the lamp voltage. If the change in the distance between the electrodes is suppressed by the present invention, the rise in the lamp voltage is reduced, and it is not necessary to increase the allowable lamp voltage value in the lighting circuit design, which is advantageous.

The suppression of the evaporation of the electrode material suppresses the blackening of the inner wall of the arc tube. Although the blackening is one of the main causes of the decrease in the luminous flux, if the blackening phenomenon is suppressed by the present invention, an increase in the luminous flux maintenance rate is expected, which leads to a longer lamp life.

Further, the role of the current conducting means for turning on / off in the present invention is to capture a part of the electrons flowing into the electrode and to suppress the rise of the electrode temperature, in other words, to dissipate the heat of the coil of the generally used coil electrode. It can be said to be an alternative.
According to the present invention, the coil electrode generally used can be made coilless.

[Brief description of the drawings]

FIG. 1 is a diagram showing an upper surface and a circuit configuration of an electrode structure of a discharge lamp according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a top view and a circuit configuration of an electrode structure of a discharge lamp according to a second embodiment of the present invention.

FIG. 3 is a diagram showing an electrode structure of a conventional discharge lamp.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Discharge support part 2 Current conduction means 3 Current conduction means 4 Insulator 5 Joint part 6 Joint part 7 Joint part 8 Switching element 9 Control means 10 AC power supply 11 Control means

Continuation of the front page (56) References JP-A-64-50359 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01J 61/067 H01J 61/56

Claims (2)

(57) [Claims] An electrode having a plurality of current conducting means;
Current drawer connected to each of the plurality of current conducting means
And the electrode from a power supply through the current lead-out line.
Control means for supplying a current to the control means, and the control means selects a current conducting means for supplying the current.
Controlling the current density flowing through the electrode by
A discharge lamp . 2. An electrode having a plurality of current conducting means,
Current drawer connected to each of the plurality of current conducting means
And the electrode from a power supply through the current lead-out line.
Control means for supplying current to the anode cycle during the anode cycle rather than the cathode cycle.
Then, the current density is selected by selecting more current conducting means.
Discharge lamp characterized by being lowered .