JPH0255906B2 - - Google Patents

Description

[Detailed description of the invention]

[Object of the Invention] (Industrial Application Field) The present invention relates to a metal vapor discharge lamp with improved restart characteristics. (Prior Art) Generally, high-pressure sodium lamps have higher luminous efficiency than high-pressure mercury lamps and the like, so they are used in a wide range of fields as various light sources. However, high-pressure sodium lamps have a higher starting voltage than the above-mentioned high-pressure mercury lamps, so they cannot be lit with a ballast for high-pressure mercury lamps, and they require an expensive dedicated ballast. In order to improve this, a proximal conductor is provided close to the arc tube, and this proximal conductor is connected to one electrode in the arc tube so that it has the same polarity, and a normally closed resistance heating element such as a filament is connected inside the outer bulb. A structure has been proposed in which a starting voltage generating circuit formed by connecting bimetallic switches (first bimetallic switches) in series is connected and housed in parallel with the arc tube. According to this method, when the lamp is started, electricity is supplied to the resistance heating element through the first bimetallic switch to generate heat, and this heat causes the first bimetallic switch to open, causing the generation of electricity at this moment. A high kick voltage based on the inductance of the ballast is applied between the adjacent conductors and the other electrode, creating a large potential gradient between the adjacent conductors and the other electrode, which causes an arc discharge within the arc tube. It is something that causes According to this, it is possible to light the lamp using the same ballast used in high-pressure mercury lamps.
It has advantages such as being cheaper. By the way, in devices equipped with the above-mentioned starting device, sodium ions in the arc tube are attracted to the nearby conductor during lighting and react with the materials that make up the arc tube, causing early blackening of the arc tube. There is. To prevent this, conventionally, after lighting, the adjacent conductor is electrically disconnected from one electrode.
A bimetal switch (second bimetal switch) for disconnecting the adjacent conductor was provided in a circuit that electrically connected the adjacent conductor and one electrode. (Problem to be Solved by the Invention) However, in the above-mentioned lamp, the first and second bimetal switches are housed in the outer bulb, and it is possible to turn off the lamp while it is on. If the engine was restarted without being completely cooled, a kick voltage much higher than the designed value would occur, which could burn out the ballast, cause a short circuit in the socket, or cause insulation breakdown. When the cause of this was investigated, it was found that during the cooling process of the lamp after extinguishing the lamp, the first bimetal switch sometimes returns earlier than the second bimetal switch, resulting in the above-mentioned problem. In other words, the kick voltage that occurs at the moment the first bimetallic switch is opened has the potential to reach a considerably high voltage, but this kick voltage generates a discharge between the adjacent conductor and the other electrode. Therefore, no voltage higher than the discharge starting voltage is generated between these adjacent conductors and the other electrode. When starting from room temperature, power supply starts with both the first bimetallic switch and the second bimetallic switch closed, so first the first bimetallic switch is opened by the heat of the resistance heating element. A discharge begins, after which heat from the arc tube causes the second bimetallic switch to open, electrically disconnecting the adjacent conductor from one electrode. Therefore, in this case, no kick voltage higher than the discharge starting voltage is generated between the adjacent conductor and the other electrode. However, at the time of restart, the first bimetal switch and the second bimetal switch, which were in the open state due to the heat from the arc tube, return as the light goes out, the first bimetal switch switches to the second bimetal switch. If the bimetal switch returns before the bimetal switch, the resistance heating element is energized in this state, so the first bimetal switch opens without the second bimetal switch returning. In this case, since the adjacent conductor is still cut off from one electrode, it cannot perform its original function, and therefore requires a discharge starting voltage between the two electrodes in the arc tube, which is extremely A high kick voltage will be generated. This caused problems such as ballast burnout and insulation breakdown. It is also known that the starting voltage of an arc tube is related to the area of adjacent conductors, especially the area of the conductor located near the electrode with the opposite polarity to the potential of the adjacent conductor. When the area of the adjacent conductor was increased, there was a problem that the adjacent conductor blocked the emitted light from the arc tube. Therefore, in the present invention, it is possible to reliably prevent the generation of excessive kick voltage at the time of restarting, prevent malfunctions such as burnout of the ballast and dielectric breakdown, and furthermore, it is possible to increase the area of the adjacent conductor. An object of the present invention is to provide a metal vapor discharge lamp capable of effectively lowering the starting voltage without causing any damage. [Structure of the Invention] (Means for Solving Problems) The present invention provides an arc tube housing a pair of electrodes, an outer tube housing the arc tube, and an arc tube housed within the outer tube in parallel with the arc tube. A series circuit consisting of a resistive heating element connected to the resistive heating element and a bimetallic switch opened by heat from the resistive heating element, and a part proximate to the arc tube and connected to the same polarity as the one electrode. and a thermally responsive actuating means disposed near the other electrode for separating the proximate portion of the proximate conductor from the arc tube when the arc tube is turned on and returning it when the lamp is turned off, the thermally responsive means. The invention is characterized in that the return operation of the adjacent portion is faster than the closing operation of the bimetal switch. (Function) According to the present invention, during lighting, the portion of the proximal conductor that is close to the arc tube is separated from the arc tube by the thermally responsive operating means, so that sodium ions and the like in the arc tube are not attracted. Prevents early darkening. When the light goes out, the nearby conductor returns faster than the bimetal switch and comes close to the arc tube, so when restarting, a discharge is reliably started between the nearby part and the other electrode, creating a high kick voltage. It will not occur. in this case,
Even if the bimetal switch returns and generates a kick voltage when the adjacent conductor does not return completely but partially returns, the adjacent conductor will be electrically connected to one electrode via the thermally responsive operating means. Since the connection state is maintained, it functions as a proximal conductor even in the mid-return state, and there is no need to worry about generating an excessively high voltage as in the conventional case. This increases the tolerance range, giving you more freedom in design. In addition, thermally responsive operating means for separating adjacent conductors,
Since it is disposed in the vicinity of an electrode having a polarity opposite to that of the adjacent conductor, the thermally responsive operating means itself serves to reduce the starting voltage of the arc tube, effectively reducing the starting voltage. (Embodiment of the Invention) The present invention will be described below based on an embodiment shown in the drawings. This embodiment is applied to a 360W high-pressure sodium lamp, and in the figure, 1 is an outer tube, 2 is a stem, and 3 is a base. An arc tube 4 is housed within the outer tube 1. This arc tube 4 is made of a translucent alumina ceramic material, and end caps 5 and 6 made of niobium are sealed at both ends thereof, and electrodes 7 and 8 are attached to these end caps, respectively. The arc tube 4 is attached via holders 11 and 12 to support wires 9 and 10 that serve both as support and power supply. Support wire 9, 10
are welded to lead-in wires 13 and 14 sealed to the stem 2, respectively, and the tip of one support 9 wire is held at the top of the outer tube 1 by leaf springs 15 and 15. One electrode 7 of the arc tube 4 is connected to one support wire 9 via a holder 11, and the other electrode 8 is connected to the other support wire 9 via a holder 12. Note that the other holder 12 is electrically insulated from one support wire 9 by an insulating tube 16. Mercury and sodium are contained in the arc tube 4.
It is filled with 300Torr of xenon gas. A starting voltage generating circuit 17 is built in the outer tube 1, and this starting voltage generating circuit 17 is constructed by connecting in series a resistance heating element 18 made of a tungsten filament and a normally closed bimetallic switch 19. . This starting voltage generating circuit 17 is connected between the support wires 9 and 10 and in parallel with the arc tube 4. Note that 20 is a substrate that supports these resistance heating element 18 and bimetal switch 19, and this substrate 20 is made of an electrically insulating material.
The resistance heating element 18 made of the above-mentioned filament is erected on the substrate 20 in a meandering manner. The bimetal switch 19 is composed of a bimetal plate 21 and a movable contact 22 and a fixed contact 23 attached to the tip of the bimetal plate 21. It is configured to receive heat from this resistance heating element 18 and heat from the arc tube 4. Reference numeral 24 denotes a proximity conductor, which is formed from a wire made of a high melting point metal material such as molybdenum or tantalum, and is provided close to the outer peripheral surface of the arc tube 4 and along the longitudinal direction of the arc tube 4. It is being One end of this proximity conductor 24 is bent into a crank shape, and its tip is supported by a shaft support member 25 attached to one of the support wires 9 so as to be rotatable and slidable in the axial direction. . Also,
The other end of the proximity conductor 24 is connected to one support wire 9
An electrode 8 connected to the adjacent conductor 24 and having a polarity different from that of the adjacent conductor 24
It is welded to the tip of the thermally responsive actuating means for disconnecting the adjacent conductor, for example, the bimetallic piece 26, which is located near the bimetallic piece 26. Since the proximate conductor 24 is connected to one of the support wires 9 via the shaft supporting member 25 and the bimetallic piece 26 for separating proximal conductors, it is always electrically connected to the one electrode 7. . Furthermore, when the bimetal piece 26 is deformed by the heat from the arc tube 4, the proximal conductor 24 rotates around the shaft supporting member 25, causing the arc tube to
It is configured to be spaced apart from. The bimetal piece 26 for separating the adjacent conductor and the bimetal plate 21 of the bimetal switch 19 are made of a highly heat-resistant bimetal, such as TNY bimetal manufactured by Toshiba Corporation (high expansion coefficient side material: Ni-
Mn-Fe alloy, low expansion material: Ni-Fe alloy, maximum operating temperature 450℃) or HTY bimetal (high expansion material: Ni-Cr-Fe alloy, low expansion material: Cr- Fe-based alloy, maximum operating temperature 550
°C). The thickness t ₁ of the bimetallic piece 26 for separating adjacent conductors is formed thinner than the thickness t ₂ of the bimetal plate 21 of the bimetal switch 19, and the ratio of these thicknesses t ₁ /t ₂ is t ₁ /t ₂ ≦ 0.8, and both of these thicknesses t ₁ and t ₂ are
The diameter is 0.05 mm or more and 0.2 mm or less. One embodiment of the present invention configured as described above is the third embodiment of the present invention.
As shown in the figure, it is connected to a ballast A for a mercury lamp and turned on. In the low temperature state, the bimetallic piece 26 for separating the proximate conductor and the bimetal plate 21 of the bimetal switch 19 are both in the restored state, the proximal conductor 24 is close to the arc tube 4, and the bimetal switch 19 is closed. When power supply is started in order to start from this state, current flows through the resistance heating element 18 and generates heat, and this heat deforms the bimetal plate 21, causing the bimetal switch 1 to
9 opens. At this moment, a kick voltage is generated by the inductance of the ballast A, and this kick voltage is applied between the adjacent conductor 24 and the other electrode 8, causing a discharge in the space within the arc tube between them. . In this case, the proximity conductor 24 is close to the arc tube 4 and the distance from the other electrode 8 is small, so the discharge starting voltage between them is relatively low, and the above-mentioned kick voltage is the withstand voltage of the ballast A etc. For example, below
The voltage will be around 2500V. Also, a bimetal piece 26 that separates adjacent conductors
However, since it is located near the electrode 8 having the opposite polarity to the adjacent conductor 24, the area corresponding to the member (bimetal piece 26) having the same polarity as the adjacent conductor increases near the electrode 8. Therefore, the discharge starting voltage (starting voltage) can be effectively lowered without increasing the area of the adjacent conductor 24 itself. The discharge between the adjacent conductor 24 and the other electrode 8 causes ionization of the filling in the arc tube 4, and the electrode 7,
Arc discharge occurs for 8 hours and lighting starts. After lighting, the bimetal piece 26 for separating the adjacent conductor is deformed by the heat from the arc tube 4, and the adjacent conductor 2
4 away from the arc tube 4. Further, the bimetal plate 21 of the bimetal switch 19 receives heat from the arc tube 4 and is maintained in a deformed state, and the bimetal switch 19 is maintained in an open state. When the lamp is turned off, the entire lamp gradually cools down, and correspondingly, the bimetal plate 21 of the bimetal switch 19 and the bimetal plate 26 for separating the adjacent conductor gradually return to its original state. In this case, since the thickness t ₁ of the bimetallic piece 26 for separating adjacent conductors is formed to be thinner than the thickness t ₂ of the bimetal plate 21 of the bimetal switch 19, the heat capacity relative to the surface area is smaller than that of the bimetal plate 21. The cooling rate is faster than that of the bimetal plate 21. Therefore, the bimetal piece 26 for separating the adjacent conductor will surely return first. Therefore, when the bimetal plate 21 returns to its original position and the bimetal switch 19 is closed during the cooling process of the lamp, the proximal conductor 24 always approaches the arc tube 4. Therefore, as in the conventional case, the problem that the resistive heating element 18 is energized and the bimetal switch 19 is opened while the proximity effect due to the adjacent conductor 24 is not yet obtained, resulting in an excessive kick voltage, can be avoided. It can definitely be prevented. Moreover, since the proximal conductor 24 is always electrically connected to one electrode 7 through the bimetal piece 26 and the support wire 9, the proximal conductor 24 can produce the proximity effect even while returning to a predetermined position. That is, when the proximal conductor 24 is returned halfway, compared to when it is completely returned to its original proximate position, the starting performance is inferior due to the distance from the other electrode 8 being longer, but the bimetal switch 19 When it is opened after closing, a kick voltage is definitely applied between the proximal conductor 24 and the other electrode 8, so that discharge starts. Although the kick voltage at this time is slightly higher than when the adjacent conductor 24 is completely restored, the voltage does not become so excessive as to cause burnout or dielectric breakdown of the ballast. From this, although the bimetal piece 26 for separating adjacent conductors needs to return earlier than the return of the bimetal switch 19, some variation is allowed within this range. Therefore, strict thermal response is no longer required, and the degree of freedom in design increases.
Manufacturing becomes easier. On the other hand, in a conventional switch equipped with a first and second bimetal switch, a potential is not applied to the adjacent conductor unless the second bimetal switch is closed. Moreover, it is necessary to restore the switch before the first bimetal switch. For this reason, it is necessary to strictly select the thermal response accuracy of the second bimetal switch, and it is also necessary to adjust the contact points, resulting in a problem that manufacturing conditions and adjustment conditions become stricter. And this bimetal 2 for separating the adjacent conductor
6 and bimetal plate 21 of bimetal switch 19
Since the order of return is given by varying their thickness, the order of return is reliably regulated. That is, in order to regulate the order of these returns, it is sufficient to vary their cooling rates, so it is also possible to vary their cooling rates by, for example, varying their placement locations. However, when these parts are housed in the outer tube 1, the light from the arc tube 4 must not be blocked and other conditions require that their placement is limited to the vicinity of the neck of the outer tube 1 in practice. Under these limitations, even if the placement location is slightly different, there will not be a large difference in the cooling rate, and since the usage conditions of the lamp vary widely, the cooling conditions for the entire lamp will not be constant either. , it is difficult to reliably regulate the return order simply by selecting the placement location. However, if the thicknesses of the bimetallic piece 26 for separating adjacent conductors and the bimetallic plate 21 of the bimetal switch 19 are made different as in this embodiment, a clear difference can be caused in the cooling rate, and the cooling conditions may be slightly changed. However, the order in which they return can be reliably regulated. In order to confirm such an effect, the bimetal piece 26 for separating the adjacent conductor of the lamp of the above embodiment was used.
We made many prototypes with various thicknesses t ₁ and t ₂ of the bimetal plate 21 of the bimetal switch 19, turned on these lamps for a certain period of time, then turned them off, and then restarted them by restarting the power supply during the cooling process. We investigated the kick voltage at restart. Table 1 shows an example of the experimental results, and this example was obtained when the lamp was lit bare at room temperature.

[Table] As is clear from this result, if the thickness t ₁ of the bimetallic piece 26 for separating adjacent conductors is made thinner than the thickness t ₂ of the bimetal plate 21 of the bimetal switch 19, the bimetal switch 19 will open after returning. When the kick voltage is generated, the proximal conductor 24 is already completely close to the arc tube 4, so the generated kick voltage is stabilized at 2500V. On the other hand, when the thicknesses of t ₁ and t ₂ are made equal, the kick voltage increases to 3000V, and this 3000V is the limit of the withstand voltage of a ballast, etc. When t ₁ becomes thicker than t ₂ , the kick voltage becomes 3000 V or more, which exceeds the withstand voltage limit of a stabilizer or the like. Therefore, to prevent the kick voltage from exceeding 3000V, at least t ₁
must be smaller than t ₂ . In addition, as a result of experiments with various lighting conditions for such a lamp, it was found that the cooling rate was slowest when the lamp was housed in a sealed floodlight, and the bimetal plate 21 of the bimetal plate 21 for separating adjacent conductors and the bimetal switch 19 It was found that there was little difference in the recovery speed. The experimental results in this case are shown in Table 2.

【table】

[Table] As is clear from this result, even when the light is turned on in a sealed type floodlight under the worst conditions, the kick voltage can be reduced.
In order to reduce the voltage to 3000V or less, the ratio t ₁ /t ₂ of t ₁ and t ₂ should be set to 0.8 or less. In addition, the bimetal 2 for separating these adjacent conductors
6 and bimetal plate 21 of bimetal switch 19
As a result of examining the thickness from other points, it was found that if the thickness is less than 0.05 mm, permanent deformation etc. will occur during use and it will not be suitable for practical use. Further, when the relationship between the thickness of the bimetal plate 21 of the bimetal switch 19 and the time required for it to recover and restart, the results shown in FIG. 4 were obtained. In addition, the solid line in FIG. 4 shows the case of naked lighting, and the broken line shows the case of being housed in a closed type floodlight. Since the restart time of this type of lamp usually needs to be 10 minutes or less, the thickness t ₂ of the bimetal plate 21 needs to be at least 0.2 mm or less. If all of the above conditions are satisfied, it is possible to reliably prevent the generation of excessive voltage under any usage conditions, and the restart time can be made equal to or less than that of conventional products. be. Note that the present invention is not limited to the above embodiment. As a method for regulating the return order of the bimetal for disconnecting adjacent conductors and the bimetal switch, for example, the surface of the bimetal for disconnecting adjacent conductors may be made rough or black to increase heat dissipation, and the cooling rate may be increased to control the return order. may be regulated. Therefore, depending on the case, the thickness of the bimetal plate of the bimetal switch or the bimetal for separating adjacent conductors may not necessarily be within the above range. Furthermore, the present invention is applicable not only to high-pressure sodium lamps but also to other metal vapor discharge lamps such as metal halide lamps. [Effects of the Invention] As explained above, according to the present invention, when the light is turned off, the adjacent part of the adjacent conductor returns to its original state before the bimetal switch, so that when restarting, the adjacent conductor and the other electrode are reliably discharged. This prevents excessive kick voltage from being generated. In addition, since the thermally responsive operating means for separating the adjacent conductors is located near the electrode with the opposite polarity to that of the adjacent conductors, the discharge starting voltage (starting voltage) can be increased without increasing the area of the adjacent conductors themselves. can be effectively reduced.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention; FIG. 1 is a longitudinal sectional view, FIG. 2 is a view taken along the - line in FIG. 1, FIG. 3 is a circuit diagram, and FIG. FIG. 3 is a characteristic diagram showing the relationship with starting time. 1... Outer tube, 4... Arc tube, 7, 8... Electrode,
17... Starting voltage generation circuit, 18... Resistance heating element, 19... Bimetal switch, 21... Bimetal plate, 24... Proximity conductor, 26... Bimetal for separating proximal conductor (thermal response operating means), A...
…stabilizer.

Claims (1)

[Claims] 1. An arc tube that houses a pair of electrodes, an outer tube that houses this arc tube, a resistance heating element that is housed within this outer tube and is connected in parallel with the arc tube, and is released by heat from this resistance heating element. a series circuit consisting of a bimetallic switch connected to the arc tube; a nearby conductor having a portion close to the arc tube and connected to the same polarity as the one electrode; and a thermally responsive actuating means disposed near the other electrode that is moved away from the arc tube when the lamp is turned on and reset when the lamp is turned off. A metal vapor discharge lamp that is characterized by being faster to produce.