JPH0294352A - High pressure sodium lamp - Google Patents

Abstract

PURPOSE:To improve the starting characteristic and enhance the lumer maintainance factor by meeting the specific relationship between the lamp current at the time of stable lighting, shortcircuiting current in a stabilizer, protruding length of an electrode shaft from the electrode coil part, section area of the electrode shaft, and the section area of the electrode incl. electrode coil part. CONSTITUTION:D (mm) represents the dia. of an electrode coil part 13, Scoil (mm<2>) the section area of this electrode coil part 13, d (mm) the dia. of an electrode shaft 12, Swel (mm<2>) the section area of this electrode shaft 12, and h (mm) the protruding length of the electrode shaft 12 from the electrode coil part 13 to the discharge space side. If the lamp current IL (ampere) when the lamp is in stable lighting is so condition as 1.7<=IL<3.5, and the shortcircuiting current of a stabilizer Ish (ampere) is 2.5<=Ish<5.6, it shall be so related that 0.3<=h<=0.9, 3.9<=Ish/Swel<=12.2, 0.15<=IL/Scoil<=0.39. This makes the electrode shaft thin relatively and heightens the current density relatively. This improves the starting characteristic and enhances the lumer maintainance factor.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a high-pressure sodium lamp that has a starter device built into the outer bulb and is used in a general-purpose ballast for high-pressure mercury lamps.

(Prior art) A high-pressure sodium lamp has a ceramic arc tube sealed with electrodes consisting of an electrode shaft and an electrode coil at both ends, and inside the arc tube are sodium as a luminescent substance, mercury as a buffer gas metal, and a starting material. It is attracting attention as an energy-saving lamp because it is filled with a rare gas and its luminous efficiency is about twice as high as that of a mercury lamp.

However, this type of high-pressure sodium lamp has poor starting performance compared to mercury lamps, and requires a special ballast with a built-in high-pressure pulse generator to start it, but a dedicated ballast is expensive. This was the biggest reason why this type of high-pressure sodium lamp was not popularized in the past.

For this reason, in recent years, the restriking voltage has been lowered by using xenon gas as a rare gas for starting, and a nearby conductor has been attached to the outside of the arc tube to which a potential is applied at the time of starting to promote discharge. A thermally responsive switch such as a bimetallic switch is built into the tube, and the kick voltage (4KV or less) generated by this thermally responsive switch is superimposed on the secondary voltage of the ballast and applied to the lamp. High-pressure sodium lamps have been developed that can be used with general-purpose ballasts for mercury lamps, such as single choke coil ballasts.

(Problem to be Solved by the Invention) However, even if the high-pressure sodium lamp has a built-in starting device as described above to improve startability, the electrodes are the same size as conventional high-pressure sodium lamps for dedicated ballasts. The lamp may be difficult to start if used.

In other words, in the case of a dedicated ballast, the short-circuit current of the ballast can be made relatively large, so the diameter d of the electrode shaft is made thicker, and the electrode shaft is made to protrude more than the electrode coil part (the protrusion height h big) can be done.

On the other hand, when a general-purpose ballast is used, the short-circuit current of the ballast is smaller than that of a dedicated ballast, and the current density is therefore smaller. becomes relatively large.

In general, when the electrode shaft is made thicker, the arc spot becomes unstable and tends to disappear, whereas when the electrode shaft is made thinner, the arc spot is stabilized and starting performance is improved.

In addition, if the protruding length h of the electrode shaft from the electrode coil section is increased, the heat capacity will increase and the energy concentration at the time of starting will be reduced, making the arc spot unstable and easy to disappear.On the contrary, if it is shortened, the arc spot will be stabilized. Starting performance improves.

However, during stable lighting, if the electrode shaft is thin, the temperature at the tip of the electrode shaft and the electrode coil becomes too high.
The electrodes and emitters scatter and adhere to the tube wall, causing blackening and reducing the luminous flux maintenance factor.

Furthermore, if the protrusion length h of the electrode shaft from the electrode coil section is made too small, the temperature of the electrode shaft and electrode coil section will become too high, and the electrode and emitter will scatter and adhere to the tube wall, resulting in blackening. As a result, the luminous flux maintenance rate decreases.

Furthermore, if the cross-sectional area of the electrode including the coil part is large, the arc spot will move around the coil part and the electrode axis during startup and become unstable, and if the cross-sectional area is small, the temperature of the electrode will easily rise. Scattering of electrodes, emitters, etc. occurs.

Despite this general tendency, high-pressure sodium lamps with a built-in starter retain the same size as conventional electrodes, resulting in relatively thick electrodes and poor starting performance. There is a problem that is not good.

The present invention has been made based on the above circumstances, and an object thereof is to provide a high-pressure sodium lamp with a built-in starting device that improves starting performance and does not reduce the luminous flux maintenance factor.

[Structure of the Invention] (Means for Solving the Problem) The present invention makes the protruding height and diameter of the electrode shaft relatively small compared to a lamp using a dedicated ballast.
In this type of high-pressure sodium lamp using a general-purpose ballast, the lamp current IL (ampere) during stable operation is
is 1.7≦IL<3.5, and the short-circuit current I of the ballast is
The situation is such that the lamp is lit in the range of sh (ampere) 2.5≦Ish<5.6, and under these conditions, the protrusion length of the electrode shaft from the electrode coil part is h(ff1
m), the cross-sectional area of the electrode axis is Swel (m+++”)
, the cross-sectional area of the electrode including the electrode coil portion is S co
When il (arm2), 0.3≦h≦0.9 3.9≦I sh/ S wel ≦12.20, 15
≦I L /5coff≦0.39.

(Function) According to the configuration of the present invention, the current density (Ish/Svθl) also becomes relatively high as the electrode axis becomes relatively thin, so starting performance is improved, and the heat capacity due to the electrode axis becoming thinner. The reduction in the electrode coil portion is borne by a relatively large heat capacity due to the electrode coil portion having the same size as the conventional one, and therefore, scattering of the electrode material can be prevented and the luminous flux maintenance factor can be increased.

(Example) The present invention will be described below based on an example shown in the drawings.

In the figure, 1 is an outer tube made of hard glass or the like, and houses an arc tube 2.

The arc tube 2 is made of ceramic such as polycrystalline alumina or single crystal alumina, and contains a predetermined amount of sodium, mercury as a buffer gas metal, and 50~
It is filled with xenon gas of about 300 torr.

This arc tube 2 is supported by support wires 4a, 4b via holders 3a, 3b.

On the outside of the arc tube 2, a starting proximity conductor 5 made of molybdenum wire or the like is arranged along the tube axis in contact with or close to the outer wall surface of the arc tube 2, and the lower end of this proximity conductor 5 is It is mechanically and electrically connected to one of the support wires 4a by a bimetal piece 6, and its upper end is loosely passed through a retaining ring 7 attached to the one of the support wires 4a.

When the ambient temperature is low, the adjacent conductor 5 is in contact with or close to the outer wall surface of the arc tube 2, and when the lamp is lit and the ambient temperature rises, the bimetal piece 6 is thermally deformed and warped, so that the adjacent conductor 5 is spaced apart from the outer wall surface of the arc tube 2.

The outer tube 1 houses a starter device consisting of a thermally responsive switch 8 such as a bimetallic switch and a coil heater 9. These thermally responsive switches 8 and heaters 9
are mounted on an insulating base 10 in close proximity to each other, and the thermally responsive switch 8 and heater 9 form a series circuit as shown in the circuit diagram shown in FIG. And such a series starting device has support wire 4 a s 4
b, and is therefore connected in parallel to the arc tube 2.

An electrode 11 is sealed at the end of the arc tube 2, as shown in FIG.

That is, an end cap 15 made of a ceramic tube such as polycrystalline alumina or single crystal alumina is attached to the end of the two bulbs of the arc tube made of a ceramic tube made of polycrystalline alumina or single crystal alumina, etc., using glass solder or the like. A conductor 16 made of, for example, niobium is passed through the end cap 15 in an airtight manner.

The electrode 11 is connected to the end of the conductor 16 inside the arc tube 2 . The electrode 11 includes an electrode shaft 12 made of, for example, tungsten, an electrode coil 13 made of, for example, tungsten wound in two layers around this electrode shaft 12, and a Ba2Ca (not shown) held by this electrode coil 13.
It is composed of an emitter such as WO6 or BaO.

Here, the diameter of the electrode coil portion 13 is D (am), and the cross-sectional area of the electrode coil portion 13 is S coil (111 m2).
, the diameter of the electrode shaft 12 is d (IIIl), the cross-sectional area of the electrode shaft 12 is 5 vel (am2), and the length of the electrode shaft 12 protruding from the electrode coil part 13 toward the discharge space is h (a
m), and the lamp current when the lamp is stably lit is IL (A
- ampere), and the short-circuit current of the high-pressure mercury lamp choke coil type ballast 18 (see Figure 2) to which the lamp is connected is defined as l5h (A- ampere), then the lamp is formed so as to satisfy the following relationship. ing.

That is, in the case of this type of starting device, which is lit using a choke coil type ballast for high-pressure mercury lamps, a high-pressure sodium starting device of 50 to 300 to improve starting performance.
It is filled with xenon gas of about rr, and the lamp current IL (ampere) during stable lighting is 1.7≦lL<3
．． 5, and the short circuit current of the ballast is 1sh (ampere)
is turned on in the range of 2.5≦Ish<5.6.

Under these conditions, the protrusion length of the electrode shaft from the electrode coil lip is h (IIIIl), and the cross-sectional area of the electrode shaft is S.
wel (am2), and the cross-sectional area of the electrode including the electrode coil portion is S coil (Inm2),
0.3≦h≦0.9 3.9≦I sh/ S vel≦12.20.15≦
IL/S coil≦0.39.

The starting operation of a high-pressure sodium lamp with such a configuration will be explained.

Before starting the lamp, the bimetallic piece 6 is deformed and restored because the ambient temperature is low, and therefore the proximal conductor 5 is in close contact with or close to the outer surface of the arc tube 2.

Further, in this case, the thermally responsive switch 8 is closed.

When a power supply voltage is applied through the single choke coil ballast 18 in this state, a potential difference is generated between the adjacent conductor 5 and the opposing electrode, and the heater 9 begins to generate heat.

When the thermally responsive switch 8 is heated to a predetermined temperature by the heat generated by the heater 9, the contacts of the thermally responsive switch 8 are opened, and at this time a kick voltage is generated, and this kick voltage becomes a pulse voltage and is applied to the electrodes 11 and 11. and is provided between the proximal conductor 5 and the counter electrode.

Therefore, a discharge is induced between the adjacent conductor 5 and the counter electrode, which transfers to an arc discharge between the electrodes 11.11 and the lamp is started.

Note that since the arc tube 2 is filled with xenon gas, the starting voltage is lowered to facilitate starting.

When the lamp lights up and the arc tube 2 warms up, the ambient temperature rises, and the bimetal piece 6 is thermally deformed and warped.
Therefore, the proximal conductor 5 is spaced apart from the outer wall surface of the arc tube 2. Therefore, the light emitted from the arc tube 2 is less likely to be blocked.

In this case, the thermally responsive switch 8 is also warmed up, and therefore the contacts of the thermally responsive switch 8 remain open.

It has been confirmed that in such a lamp, when the electrode structure is configured as described above, starting is ensured and the luminous flux maintenance rate is also improved.

That is, the present invention will be explained based on the results of experiments.

(Experiment 1) Inside the arc tube with an inner diameter of 7.25 m+a and a total length of 91.0 am,
sodium 3 rags mercury 27 mg, xenon gas 2
00 torr.

A proximate conductor made of a molybdenum wire with a diameter of 0.5a+i was placed on the outer wall of the arc tube so as to be in close contact with it over the entire length of the arc tube, and was set so as to be separated from the arc tube by a bimetallic piece during lamp lighting.

The starting device, which consists of a thermally responsive switch connected to a coil heater, regulates the current flowing through the thermally responsive switch to be less than IA due to the current suppression effect of the heater, and the kick voltage when the thermally responsive switch is opened. is set to a maximum of 4KV.

The diameter d of the electrode shaft 12 of the electrode 11 is 0.75 ma+.

In this case, the cross-sectional area S wet of the electrode shaft 12 is 0.441
1Il12, the diameter of the electrode coil part 13 is 3.75mm
The length h of the electrode shaft 12 protruding from the electrode coil portion 13 toward the discharge space is 0.3 mm.

The lamp current IL when the lamp is stably lit is 1.7A.

When such a lamp was connected to a single choke coil type ballast 18 with a short circuit current of 1 sh of 2.5 A and turned on, it started reliably even at 90% of the rated power supply voltage.

(Experiment 2) Next, using the single choke coil type ballast 18 with the short circuit current 1sh of 2.5A, the diameter d1 of the electrode shaft 12, the diameter of the electrode coil portion 13, and the protrusion length h of the electrode shaft 12 were determined. Table 1 shows the test results for arc tubes with different lamp currents IL of 1.7 A when lit at 90% of the rated power supply voltage.

The maximum kick voltage was 4 KV, and the luminous flux maintenance rate was determined to be good if the luminous flux maintenance rate was 85% or more when the lamp was rated for 12,000 hours.

From Table 1, when the short circuit current 1sh is 2.5 using the ballast 18 and the lamp current IL is 167A, the protrusion length h of the electrode shaft from the electrode coil part is 0.3≦h≦0. The short-circuit current of the ballast (I sh-
ampere) and cross-sectional area of the electrode axis (S wet -mm2)
The relationship is 3.9≦I sh/Swel, and the lamp current IL and the cross-sectional area of the electrode coil part (S coil -■2)
It has been confirmed that if the relationship 0.15≦IL/5coff is satisfied at the same time, starting is reliable and the luminous flux maintenance rate is high.

(Experiment 3) Next, the results of an experiment using high-pressure sodium lamps of different wattages will be explained.

Inner diameter 7.25mm, total length 112. In the in+ arc tube,
4.5 mg of sodium, 25.5 mg of mercury, and xenon gas were sealed at 200 torr.

In the electrode 11, the diameter i of the electrode shaft 12 is 0.9 ma+, the cross-sectional area 5vel of the electrode shaft 12 in this case is 0.64 cm2, the diameter of the electrode coil portion 13 is 3.3 cm, and the electrode shaft 12 is an electrode coil. The length h protruding from the portion 13 toward the discharge space is 0.
It is said to be 5ml1.

The lamp current ■L when the lamp is stably lit is 3.3A.

When such a lamp was connected to a single choke coil type ballast 18 with a short circuit current of 1 sh of 5.4 A and turned on, it started reliably even at 90% of the rated power supply voltage.

(Experiment 4) Next, using the single choke coil type ballast 18 with the short circuit current 1sh of 5.4A, the diameter d1 of the electrode shaft 12, the diameter of the electrode coil portion 13, and the protrusion length h of the electrode shaft 12 were determined. Regarding the arc tube with different lamp current IL of 3.3A,
Table 2 shows the test results when the lamp was lit at 90% of the rated power supply voltage.

In this case as well, the maximum kick voltage was 4 KV, and the evaluation of the luminous flux maintenance rate was determined to be a good product if the luminous flux maintenance rate was 85% or more after rated lighting for 12,000 hours.

From Table 2, when using the single choke coil type ballast 18 with short circuit current 1sh of 5.4A, lamp current 1 is 3.3A.
For the arc tube, the protrusion length h of the electrode shaft from the electrode coil portion falls within the range of 0.3≦h≦0.9. The relationship between the short circuit current of the ballast (Ish - ampere) and the cross-sectional area of the electrode shaft (S vel = am2) is
sh/S wet ≦12.2, and lamp current IL
and the cross-sectional area of the electrode coil (S coil = ms+2)
It has been confirmed that if the relationship 0.14≦IL/5coll≦0.39 is satisfied at the same time, starting is reliable and the luminous flux maintenance rate is also high.

From (Experiment 1) or Experiment 4), using a single choke coil type ballast 18 with short circuit current Ish of 2.5≦Ish<5.6A, lamp current IL is 1.7≦IL<3.5.
In the case of the arc tube designated as A, the protrusion length h of the electrode shaft from the electrode coil portion is 0. The range may be 3≦h≦0,9.

This is illustrated in the shaded range in the characteristic diagram shown in FIG.

Also, the relationship between the short circuit current of the ballast (I sh - ampere) and the cross-sectional area of the electrode shaft (Swel = mI112) is 3.9≦
It is confirmed that it is sufficient to satisfy I sh/S wet≦12.2.

Furthermore, the lamp current ■L and the cross-sectional area of the electrode coil section (S
coil - arm”) is 0.15≦IL/S
It can also be seen that m only needs to satisfy coil≦0.39.

[Effects of the Invention] As explained above, according to the present invention, the electrode shaft becomes relatively thin and the current density (Ish/5vel) also becomes relatively high, so starting performance is improved. The reduction in heat capacity due to thinning is borne by the relatively large heat capacity of the electrode coil portion, which is the same size as the conventional electrode coil portion, which has the advantage of preventing scattering of the electrode material and increasing the luminous flux maintenance factor.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention; FIG. 1 is a front view of a high-pressure sodium lamp, FIG. 2 is a circuit diagram, FIG. 3 is an enlarged sectional view of the end of the arc tube, and FIG. It is a characteristic diagram. DESCRIPTION OF SYMBOLS 1... Outer tube, 2... Luminous tube, 3a, 3b... Holder 4a, 4b... Support wire, 5... Proximity conductor for starting, 6... Bimetal piece, 8... Thermal response switch, 9... Heater, 11... Electrode, 12... Electrode shaft, 13... Electrode coil. Applicant's representative Patent attorney Takehiko Suzue

Claims (1)

[Scope of Claims] An arc tube comprising an outer tube, electrodes housed in the outer tube and consisting of an electrode shaft and an electrode coil portion at both ends, and filled with sodium, buffer gas metal, and xenon gas;
The lamp is equipped with a starting proximity conductor attached to the outside of the arc tube and to which a potential is applied at the time of starting, and a starting device housed in the outer tube that generates a kick voltage by opening and closing a thermally responsive switch. Current I_L (ampere) is 1.7
In a high-pressure sodium lamp that is lit in a range where ≦I_L<3.5 and the short-circuit current Ish (ampere) of the ballast is in the range of 2.5≦Ish<5.6, the protrusion length of the electrode shaft from the electrode coil part is h (mm), the cross-sectional area of the electrode axis is Swel (mm^2), and the cross-sectional area of the electrode including the electrode coil part is Scoli (
mm^2), 0.3≦h≦0.9 3.9≦Ish/Swel≦12.2 0.15≦I_L/Scoli≦0.39.