JPS6214640Y2 - - Google Patents

Description

[Detailed explanation of the idea] The present invention relates to a discharge lamp starting device.

BACKGROUND ART Discharge lamps that have a high starting voltage and require a high voltage on the order of kilovolts for starting, such as high-pressure sodium lamps and metal halide lamps, require a starting device in addition to a discharge lamp lighting circuit. Discharge lamps in which such a starter device is built into the outer bulb of the discharge lamp are currently commercially available.

In order to improve a discharge lamp with a built-in starter device, the applicant previously proposed a technique using a ceramic thick-film resistor in the starter device in Japanese Patent Application No. 54386/1983.
Although a discharge lamp incorporating such a starting device exhibits excellent electrical and mechanical properties and is excellent in practical use, it has been found that there is room for further improvement in starting characteristics.

The object of the present invention is to improve the starting characteristics of a discharge lamp incorporating a starting device using a ceramic thick film resistor.

The present invention will be explained below with reference to the drawings. FIG. 1 shows a circuit diagram of a discharge lamp circuit in which the starting device of the present invention is used. In FIG. 1, an arc tube 1 is connected to a light current power source via a choke coil 2. A starting device is connected to the arc tube 1 in parallel thereto. The starting device consists of a bimetal switch 4, a filament heater 5 for heating it, and a ceramic thick film resistor 6 connected in series.
to form a discharge lamp. It should be noted here that the filament heater 5 is a bimetal switch 4.
The ceramic thick film resistor 6 is used to limit the switching current to a predetermined value.

Briefly describing the operation of the circuit shown in FIG. 1, when the power source 3 is turned on, a switching current flows through a normally closed contact type bimetal switch 4 which is closed at room temperature. This switching current is mainly determined by the value of the ceramic thick film resistor 6. When the switching current flows for several seconds, the filament heater 5 is heated, and in response to the heat, the bimetal switch 4 is opened, and as a result, the switching current is cut off. At that moment, a high voltage pulse is induced at both ends of the chiyoke coil 2, which is superimposed on the power supply voltage and applied to the arc tube 1, starting and lighting the discharge lamp.

There is no problem if the discharge lamp lights up with just one high-voltage pulse, but if the amplitude of the high-voltage pulse or its energy is insufficient, or due to the usage conditions of the discharge lamp, a single high-voltage pulse may ignite the discharge lamp. is not limited. Even if the chattering of the bimetal switch 4 is taken into consideration, it is not guaranteed that the discharge lamp will be lit in one starting operation. If the discharge lamp does not light up after one starting operation, the starting operation is repeated again after waiting for the return of the bimetal switch 4. It is left open for conduction and radiation. Therefore, the number of starting operations of the bimetal switch 4 is limited, and if the discharge lamp does not light up within the number of operations, the discharge lamp will malfunction. Experimentally, it has been found that unless the bimetal switch is started at least 20 times, it is difficult to keep the failure rate close to zero during shipping tests of discharge lamps.

The present invention aims to minimize the failure rate by improving the starting characteristics of a discharge lamp, and FIG. 2 shows an outline of a discharge lamp incorporating the starting device of the present invention. In FIG. 2, the arc tube 1 is positioned approximately on the center line of the outer sphere 7 in the conventional manner by means of struts 9 and other supports. The starting device of the present invention is disposed concentrically with the arc tube 1 at the lower end of the arc tube 1, that is, on the base side, and is shown as an assembly 10.

The starting device comprising assembly 10 is shown in perspective view in FIG. The ceramic thick film resistor 6 has a toroidal shape, and is composed of a thick film resistor made of a hardly soluble metal such as tungsten or molybdenum (schematically indicated by a dotted line 11 in the drawing) interposed in the ceramic in the form of a sandwich. This ceramic thick film resistor 6 is supported by support pins 12 and 13 as shown in FIG.
mounted on. Note that the support pin 12 serves as one terminal of the starter device.

Two conductive posts 14 and 15 are placed on the ceramic thick film resistor 6, and the filament heater 5 is stretched over the upper end thereof. As shown in the figure, one end of the resistor 11 is connected to the fixed end of the conductive post 14. On the other hand, a bimetal strip 4A forming the bimetal switch 4 is fixed to the free end of the conductive post 15, and a contact member 4B is attached to the free end. The other contact member 4C which is to be in contact with this contact member 4B is fixed to the free end of a terminal member 16 attached to the ceramic thick film resistor 6.

The structure of the assembly 10 thus far described is essentially the same as that previously proposed by the present applicant and disclosed in Japanese Patent Application No. 54386/1983. Let us examine the starting characteristics when a discharge lamp is lit using an assembly with such a structure. FIG. 4 is an experimental example in which changes in the current flowing through the starter device are plotted on the time axis after the power is turned on. FIG. 4a shows the starting characteristics of a discharge lamp incorporating a starting device using the assembly disclosed at the top above.
As can be seen from FIG. 4a, when such a starting device is used, several starting operations are required to start the engine, and the high-voltage pulse generating circuit correspondingly generates only a few pulses. Therefore, there is a high probability that the discharge lamp will fail.

Incidentally, the number of operations of the bimetal switch of the starting device is related to the starting characteristics of the discharge lamp. Figure 5 shows the number of switch operations and the lighting rate of the discharge lamps.
The lighting ratio (%) shown on the vertical axis of FIG. 5 is determined as follows using the number of switch operations as a parameter.

Lighting ratio = Cumulative number of discharge lamps started / Number of test discharge lamps As can be seen from Figure 5, the number of times the switch must be operated until the discharge lamps are completely started, that is, the lighting ratio reaches 100%. Approximately 20 times are required. However, in a discharge lamp with a built-in starting device that has the starting characteristics shown in Figure 4a, the number of switch operations is 5.
Since the lighting rate is about 70%, the failure rate is high.

According to the present invention, in order to improve the starting characteristics of the discharge lamp, a heat sink 20 is attached to the post 15 on which the heater 5 is stretched, as shown in FIG. This reduces or slows down the conduction of heat.

An iron-nickel alloy material is used as the heat sink 20,
The experiment was conducted using two types of heat sinks: one in a rectangular shape with a length of 7 mm, a width of 15 mm, and a thickness of 0.7 mm, and a rectangular shape with a length of 10 mm, a width of 20 mm, and a thickness of 0.7 mm. Figure 4b shows the intermittent state of switching current when the former and latter heat sinks are spot welded to the post 15.
and c are shown respectively. It can be seen from this that when the mass and surface area of the heat sink are small, the switching current is intermittent 15 times, but when it is large, the switching current reaches 25 times. What can be inferred from this is that from heater 5 to post 15
The heat conducted to the bimetallic strip 4A is absorbed and dissipated by the heat sink, and becomes difficult to be transferred to the bimetal strip 4A.
On the other hand, the heat radiated from the heater 5 is received by the bimetal strip, but the heat is transferred to the heat radiator and the temperature of the bimetal strip decreases, which shortens the time the bimetal contact is open, resulting in the number of operations of the bimetal switch. increases, and as a result, the number of intermittent switching currents increases.

Next, use a heat sink made of the same material and of the same dimensions (width 7
mm, width 15mm, thickness 0.7mm) and post 1.
5 is soldered with silver solder.The experimental results are shown in 4th.
Shown in Figure d. As can be seen from this, although the dimensions are the same as those of FIG. 4b, the number of interruptions is comparable to that of the larger dimension of FIG. 4c. It is presumed that this is because brazing improves heat conduction to the heat sink.

As is clear from the above, the larger the mass and surface area of the heat sink, the greater the effect, and brazing provides better heat conduction and is more effective than spot welding. Note that the shape of the heat radiator is not limited to the above example, and may be arbitrarily selected depending on the space of the mounting position.

As described above, according to the present invention, the thermal coupling relationship between the bimetal switch and the heater can be adjusted and maintained appropriately by the heat radiator, thereby improving the starting characteristics of the discharge lamp and reducing the failure rate of the discharge lamp. can be minimized.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram of a discharge lamp circuit in which the starting device of the present invention is used, Fig. 2 is a schematic front view of a discharge lamp incorporating the starting device of the present invention, and Fig. 3 is an assembly of the starting device of the present invention. FIG. 4 is a waveform diagram showing the intermittent state of the switching current flowing through the starter when starting the discharge lamp, and FIG. 5 is a graph diagram showing the lighting characteristics of the discharge lamp. Explanation of the symbols of the main parts: Arc tube...1, York coil...2, Bimetal switch...4, Heater...5, Ceramic thick film resistor...6, Outer bulb...7.

Claims (1)

[Claims for Utility Model Registration] 1. A bimetal switch, a heater for heating the bimetal switch, and a ceramic thick film resistor connected in series to the heater, which are connected in series, and the series circuit is In a discharge lamp starting device connected in parallel to the arc tube of an electric lamp and housed inside the outer bulb of the discharge lamp, the bimetal switch and heater are heated on the ceramic thick film resistor positioned inside the outer bulb of the discharge lamp. A discharge lamp starting device characterized in that a heat radiator is provided which is arranged in a responsive relationship and relieves the thermal coupling relationship of the heater to the bimetal switch. 2 Utility Model Registration The device according to claim 1, characterized in that a heat radiator is attached to a post embedded in a ceramic thick film resistor that stretches a heater and fixes one end of a bimetal strip of a bimetal switch. discharge lamp starting device.