JPS6260804B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to improvements in pulse generators used to start high pressure metal vapor discharge lamps, such as high pressure sodium lamps. High-pressure metal vapor discharge lamps such as high-pressure sodium lamps generally have a high starting voltage and are difficult to start with normal commercial power supply voltage.
A pulse generator is installed inside a discharge lamp, and the pulse generator generates a high voltage pulse, which is applied together with a power supply voltage to the discharge lamp to start and light it. FIG. 1 shows an example of the circuit configuration of the above-described high-pressure metal vapor discharge lamp. This circuit consists of an AC power source 1 and an inductive element 2 such as a chiyoke coil.
A parallel circuit of a semiconductor switching element 4 and a diode 5 and a nonlinear capacitor element 6 are connected in parallel with the arc tube 3 through the arc tube 3.
A starting circuit 8 is connected in which a thermally responsive switch 7 and a starting circuit 8 are connected in series. Reference numeral 9 indicates an outer sphere housing the arc tube 3 and the starting circuit 8. In this circuit, when the AC power supply 1 is turned on, the nonlinear capacitor element 6 is charged in a half cycle of the power supply voltage frequency, and in the next half cycle, the semiconductor switching element 4 breaks over and the charge charged in the nonlinear capacitor element 6 is induced. A sudden discharge occurs through the magnetic element 2 and the capacitor 10. At this time, relaxation oscillation accompanied by a piezoelectric effect occurs due to the nonlinear characteristics of the nonlinear capacitor element 6, and a high voltage pulse is generated in the inductive element 2, which is applied to the arc tube 3 together with the power supply voltage, thereby starting the discharge lamp. After the discharge lamp is started, only a low voltage is applied to the starting circuit 8 and the thermally responsive switch 7 is also opened, so the generation of high voltage pulses is stopped. As is clear from the above operation, the nonlinear capacitor element 6 and the inductive element 2 constitute a pulse generator. By the way, the type of nonlinear capacitor element currently considered most suitable for use in the above-mentioned pulse generator is a ferroelectric ceramic capacitor mainly made of barium titanate. When used as a built-in device, a practical pulse generator is not possible unless various structural improvements are made, such as the selection of the constitutive material of the capacitor board, the connection structure of the lead wires to the capacitor board, and the exterior of the capacitor element. I can't get it. This is because these greatly affect the magnitude of the generated high voltage pulse, the heat resistance, pressure resistance, mechanical strength, etc. of the capacitor element. For example, ceramic capacitors, which have traditionally been used as general electronic components, have silver film electrodes coated on both sides of a ceramic substrate, lead wires connected to these with lead-tin alloy solder, and the entire body made of resin. Many have overcoats. However, this type of structure has a heat resistance of only about 150 degrees Celsius at most, so it cannot be used in a high-pressure metal vapor discharge lamp. In addition, since the lead wires are connected directly to the electrodes on the ceramic substrate, vibrations caused by the piezoelectric effect of the capacitor element cannot be sufficiently absorbed, and as a result, the generation of high voltage pulses is suppressed. The problem was that it was very tiring. The present invention has been made in view of the above points, and
In a pulse generator consisting of an inductive element and a nonlinear capacitor element, by improving and devising the structure of the nonlinear capacitor element, it is possible to generate a high voltage pulse that can reliably start a high pressure metal vapor discharge lamp. On the other hand, heat resistance,
It is an object of the present invention to provide a pulse generator which has sufficiently high pressure resistance and mechanical strength, and which can be incorporated into a discharge lamp for practical use. The inventors first focused on the fact that the connection structure of the lead wire to the ceramic substrate constituting the capacitor element has a particularly large relationship with the height of the high voltage pulse, mechanical strength, etc., and developed the following method. I conducted an experiment. A powder made by adding several mol% of barium zirconate (BaZrO ₃ ) and strontium titanate (SrTiO ₃ ) to barium titanate (BaTiO ₃ ) and a trace amount of rare earth metal oxide as a material for ferroelectric ceramic substrates. Polyvinyl alcohol was added as a binder, stirred, and press-molded, followed by baking in the air at a temperature of 1400°C for 2 hours to produce a disc-shaped substrate with a diameter of 26 mm and a thickness of 0.5 mm. Silver paste was applied to both sides of this substrate by screen printing to a diameter of 25.7 mm, and after drying, it was baked in air at a temperature of 750°C to form electrodes. Then, a terminal plate 12 equipped with a lead wire 11 as shown in Fig. 2 was adhered to this electrode part with a paste made of silver powder and low melting point glass powder, and fired in the air at a temperature of about 500°C. Fixed. Lead wire 11 has a diameter of 0.5
mm nickel wire is used, and the terminal board is iron - nickel -
A cobalt-chromium alloy was used, with a thickness of 0.3 mm, and various diameters ranging from 1 mm to 5 mm. As shown in FIG. 3, such a capacitor element is connected to an AC power source 1 via a parallel circuit of a semiconductor switching element 4, a diode 5, a resistor 13, and an inductive element 2, and the nonlinear capacitor 6 is held in Freon liquid,
The pulse peak voltage at room temperature was measured by applying AC 200V, 50Hz input. Table 1 shows the relationship between the diameter of the lead wire terminal plate and the pulse peak voltage at this time.

[Table] As is clear from Table 1, the diameter of the terminal plate is 2
When it exceeds mm, the pulse peak voltage tends to decrease rapidly. This is thought to be because the terminal plate and the conductive glass adhesive suppress vibrations in the diametrical direction of the ferroelectric ceramic plate, and for this reason it is desirable to make the area of the lead wire terminal plate as small as possible. However, reducing the area of the terminal plate leads to a reduction in the connection strength of the lead wires to the ferroelectric ceramic plate and the electrodes. When considering incorporation into a discharge lamp, the diameter of the terminal plate needs to be at least 3 mm or more. In the above experiment, when the diameter of the terminal plate was 3 mm, the pulse peak value was 2000 V, as is clear from Table 1, and it was possible to start the high pressure sodium lamp. However, when a capacitor element equipped with such a terminal plate was actually incorporated into the outer bulb of a discharge lamp and used, an inconvenient phenomenon occurred that was not observed when operating in Freon liquid. That is, sparks frequently occurred between the terminal plates bonded to both sides of the board due to poor voltage resistance. The reason for this is that the ferroelectric ceramic capacitor substrate itself does not have a medium to resist mechanical vibrations, so stress concentrates on the bonded area of the terminal board that suppresses vibrations, causing cracks in that area and sparks. This is considered to occur. Also,
If the inside of the outer bulb in which the capacitor element is installed is in a vacuum, discharge will occur on the edge of the capacitor element, and the high temperatures associated with lighting a discharge lamp will eat away the oxygen in the capacitor base, reducing the specific resistance of the capacitor element. Other inconveniences may also occur. Therefore, the inventors devised the structure of the capacitor element as follows. First, similarly to the experiment described above, a substrate having a diameter of 26 mm and a thickness of 0.5 mm was formed from a material mainly consisting of barium titanate. Next, silver paste was applied to both sides of this substrate by screen printing to a diameter of 25.7 mm, and then baked in air at a temperature of 750°C to form electrodes. Then the fourth
As shown in the figure, the base 14 and electrodes 15a, 15
The circumference of b is the diameter 2 of the center of electrodes 15a and 15b.
The substrate was completely overcoated with the low melting point glass paste 16, except for only the mm, and after drying, baking was performed in air at a temperature of 550° C. to cover the periphery of the substrate with inorganic glass. Next, as shown in FIG. 5, terminal plates 12a and 12b having a structure as shown in FIG. 2 and having an area larger than the area of the non-coated portion of the inorganic glass are placed on the outside of the non-coated portion of the inorganic glass, and this is made conductive. The electrodes 15a and 15b were adhered to each other using glass pastes 17a and 17b, and then baked in air at a temperature of about 500° C. to fix them. The capacitor element constructed in this way was connected to the circuit shown in Figure 3 in the same way as in the previous experiment, and an input of AC 200 V and 50 Hz was applied in Freon liquid.
Pulse peak voltage was measured at room temperature. Second
The table shows the relationship between the diameter of the lead wire terminal plate and the pulse peak voltage at that time.

[Table] As is clear from Table 2, if the structure shown in Figure 5 is used, the diameter of the lead wire terminal plate will be 2.5 mm.
In the range of ~5 mm, the value of the pulse peak voltage is extremely stable, and even if the terminal plate diameter is increased, a higher pulse peak value can be obtained compared to when the terminal plate is directly bonded to the capacitor substrate. This means that the connection strength of the lead wires can be increased without reducing the pulse peak value. Incidentally, according to the above structure, the pulse peak value is 2500V when the diameter of the lead wire terminal plate is 3 mm in consideration of incorporation into a discharge lamp, and this value is sufficient to reliably start a high-pressure sodium lamp. It is a sufficient value. In addition, according to the above structure, the base of the capacitor element is completely covered with inorganic glass, so even when it is incorporated into the outer bulb of a discharge lamp, it has great heat resistance, and the edge surface discharge Furthermore, it is possible to prevent the occurrence of oxygen in the capacitor substrate and a decrease in specific resistance. A pulse generator with a nonlinear capacitor element configured as described above was used in a 360W high-pressure sodium lamp to perform a flashing test, and the lamp started reliably after more than 5,000 starts, and the connection of the capacitor element was No discharge damage occurred in the terminal portion, and the vibration resistance was sufficient. As is clear from the above description, the present invention provides a pulse generator comprising an inductive element and a nonlinear capacitor element, in which an electrode is adhered to the surface of a ferroelectric ceramic substrate as the nonlinear capacitor element, and is completely covered with inorganic glass except for the current-carrying part to the electrode, and a terminal plate having an area larger than the area of the non-covered part is installed in the non-covered part of the inorganic glass, and this is connected to the electrode with conductive glass. It is characterized by the use of a structure in which lead wires are connected to the terminal board in addition to bonding, and thereby the various effects described above can be obtained.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram of a high-pressure metal vapor discharge lamp equipped with a pulse generator according to the present invention, Fig. 2 is a perspective view of a lead wire terminal plate used for a capacitor element of the pulse generator, and Fig. 3 is a circuit diagram of a high-pressure metal vapor discharge lamp equipped with a pulse generator according to the present invention. A test circuit diagram of the generator, FIG. 4 is a cross-sectional view of a capacitor element used in the pulse generator according to the present invention during completion, and FIG. 5 is a cross-sectional view of the capacitor element after completion.

Claims (1)

[Claims] 1. In a pulse generator consisting of an inductive element and a nonlinear capacitor element, the nonlinear capacitor element has electrodes made of a metal film adhered to both sides of a ferroelectric ceramic substrate, and the entire structure is made of a ferroelectric ceramic substrate, except for the current-carrying part to the electrode. At the same time, a terminal plate having an area larger than the area of the uncoated part is installed outside the uncoated part of the inorganic glass, and this is adhered to the electrode with conductive glass. A pulse generator characterized by having a structure in which a lead wire is connected to a plate.