JP2006244896A - Flash discharge tube - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a flash discharging tube capable of securing durability and reliability at continuous lighting even if a glass tube and a cathode are miniaturized. <P>SOLUTION: One end part of a cathode supporting member 14 is fixed to a first glass bead 20, and the other end 26 penetrates a cathode main body 18 and protruded toward an anode 16. The length of the protrusion against an end face 19 of the cathode main body is made 0.1 mm to 0.3 mm, and outer diameter of the cathode supporting member 14 is made 0.45 mm or less. The inner diameter of the cathode main body 18 is made larger than the outer diameter ϕ<SB>e</SB>of the cathode supporting member 14 and 0.45 or smaller, and the outer diameter ϕ<SB>ko</SB>of the cathode main body is made larger than the outer diameter ϕ<SB>e</SB>and smaller than 0.8 mm, and the length of the cathode main body L<SB>k</SB>is made 0.5 mm to 1.0 mm. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a flash discharge tube in which both ends of a glass tube are sealed with a glass bead for fixing a cathode and an anode. More specifically, the present invention is suitably used as a light source in a strobe device such as a digital camera or a cellular phone. A flash discharge tube.

  Conventionally, in a flash discharge tube, a cathode disposed at one end of a glass tube is fixed with a first glass bead, and an anode disposed at the other end of the glass tube is fixed with a second glass bead. The inside of the glass tube is hermetically sealed by thermally fusing the glass bead and the glass tube. In this case, the cathode includes a cathode body that emits electrons and a cathode support member that supports the cathode body (see Patent Documents 1 and 2).

  Here, when the flash discharge tube is downsized and applied as a light source in a strobe device such as a digital camera or a mobile phone, the glass tube is shortened to reduce tube resistance between the cathode and the anode. At the same time, it is preferable to reduce the diameter of the glass tube to suppress an increase in tube current due to shortening, and to protect the electronic components constituting the drive circuit of the flash discharge tube. It is possible to reduce the inner diameter of the glass tube to 1.0 mm and the outer diameter of the cathode body to 0.8 mm.

JP-A-6-243824 JP 2004-47252 A

  However, in the flash discharge tubes disclosed in Patent Documents 1 and 2 described above, when the inner diameter of the glass tube and the inner diameter of the cathode main body are further reduced, the electric discharge of the flash discharge tube depends on the support position of the cathode main body with respect to the cathode support member. As a result, there is a problem that durability and reliability of light emission cannot be ensured in the case of continuous light emission in the flash discharge tube.

  The present invention has been made to solve the above-described problems, and is a flash that can ensure durability in the case of continuous light emission and reliability of light emission even if the glass tube and the cathode are miniaturized. An object is to provide a discharge tube.

  The flash discharge tube according to the present invention has a cathode fixed to one end of a glass tube via a first glass bead, an anode fixed to the other end of the glass tube via a second glass bead, and the glass tube A flash discharge tube in which both ends of the glass tube and the first and second glass beads are heat-sealed to hermetically seal the inside of the glass tube, the cathode includes a cylindrical cathode body, and one end portion of the glass tube A cathode support member fixed to the first glass bead and having the other end penetrating the cathode body and projecting toward the anode, and a projection length of the cathode support member with respect to the cathode body is 0.1 mm to 0 mm The outer diameter of the cathode body is larger than the outer diameter of the cathode support member and less than 0.8 mm.

  In the flash discharge tube according to the present invention, the cathode is fixed to one end portion of the glass tube by thermal fusion, and the anode is fixed to the other end portion of the glass tube by thermal fusion, so that the inside of the glass tube is evacuated. In the hermetically sealed flash discharge tube, the cathode has a cylindrical cathode body, one end is fixed to one end of the glass tube, and the other end penetrates the cathode body and projects toward the anode. The cathode support member has a protruding length of 0.1 mm to 0.3 mm with respect to the cathode body, and the outer diameter of the cathode body is larger than the outer diameter of the cathode support member and is 0. It is characterized by being less than 8 mm.

  According to each configuration described above, even if the flash discharge tube is miniaturized by reducing the outer diameter of the cathode body to less than 0.8 mm, the protruding length of the cathode support member is 0.1 mm to 0.00 mm. Since it is within the range of 3 mm, an increase in the minimum light emission voltage of the flash discharge tube is suppressed, and reliability of light emission is ensured, and an increase in non-light emission rate with respect to continuous light emission of the flash discharge tube is suppressed. Thus, durability in the case of continuous light emission is ensured.

  When the protrusion length is less than 0.1 mm, the electron emission surface is significantly damaged due to energy concentration at the electron emission surface of the cathode body that occurs when the flash discharge tube emits light. The non-light emission rate increases and the durability in the case of continuous light emission decreases. On the other hand, if the protrusion length exceeds 0.3 mm, the minimum light emission voltage of the flash discharge tube increases, and the reliability of light emission decreases.

  In the flash discharge tube described above, either the anode or the cathode may be fixed to the glass tube via a glass bead, and the other may be directly fixed to the glass tube.

  Furthermore, in the above-described configuration, the length of the cathode body is preferably 0.5 mm to 1.0 mm, and the outer diameter of the cathode support member is preferably 0.45 mm or less.

  According to the flash discharge tube of the present invention, even if the flash discharge tube is downsized by reducing the outer diameter of the cathode body to less than 0.8 mm, the protruding length of the cathode support member is 0.1 mm to 0 mm. Because it is within the range of 3 mm, the increase in the minimum light emission voltage of the flash discharge tube is suppressed, the reliability of light emission is ensured, and the increase in the non-light emission rate for the continuous light emission of the flash discharge tube is suppressed. Thus, durability in the case of continuous light emission is ensured.

  A preferred embodiment of a flash discharge tube according to the present invention will be described below and described in detail with reference to the accompanying drawings.

  FIG. 1 is a cross-sectional view showing a flash discharge tube 10 according to the present embodiment, and FIG. 2 is an enlarged cross-sectional view showing one end of the flash discharge tube 10.

  A flash discharge tube 10 shown in FIGS. 1 and 2 is used as a light source in a strobe device such as a digital camera or a mobile phone, for example, and includes a glass tube 12 and a cathode 13 disposed at one end of the glass tube 12, An anode 16 disposed at the other end of the glass tube 12, a first glass bead 20 that fixes the cathode 13 to one end of the glass tube 12, and the anode 16 at the other end of the glass tube 12 Basically, the second glass bead 22 is fixed.

The glass tube 12 is made of a glass material having substantially the same coefficient of thermal expansion as the cathode support member 14, the anode 16, the first glass bead 20, and the second glass bead 22 constituting the cathode 13. A rare gas 24 such as xenon is hermetically sealed in the space sealed by thermal fusion with the two glass beads 20 and 22. In this case, the inner diameter φ _gi of the glass tube 12 is less than 1.0 mm.

  The cathode 13 includes a cathode support member 14 and a cylindrical cathode body 18 supported by the other end portion 26 of the cathode support member 14.

The cathode support member 14 is a metal rod made of tungsten. One end of the cathode support member 14 is fixed to the first glass bead 20, and the other end 26 penetrates the cathode body 18 and protrudes toward the anode 16. In this case, the protruding length L of the other end portion 26 with respect to the end surface 19 on the anode 16 side of the cathode body 18 is 0.1 mm to 0.3 mm, and the outer diameter φ _e of the cathode support member 14 is 0.45 mm. The following.

The cathode body 18 is supported coaxially with the cathode support member 14 at the other end 26 of the cathode support member 14. In this case, the inner diameter φ _{ki of} the cathode body 18 is not less than the outer diameter φ _e of the cathode support member 14 and not more than 0.45 mm, and the outer diameter φ _ko exceeds the outer diameter φ _e and is 0. Less than 8 mm, and its length L _k is 0.5 mm to 1.0 mm. The end face 19 of the cathode body 18 is an electron emission surface from which a large amount of electrons are emitted when a voltage is applied between the cathode 13 and the anode 16.

  When the cathode body 18 is formed, first, a binder is added to a metal powder such as Ni, Ta, Nb, Ti, Zr and the like, and after being molded into a cylindrical shape by a molding apparatus not shown, The cylindrical molded body is heated to a predetermined temperature to remove the binder, and the molded body from which the binder has been removed is sintered at a higher temperature. Next, the cylindrical sintered body obtained by the sintering process is impregnated with an aqueous solution or an alcohol solution containing cesium carbonate or the like serving as an emitter that emits electrons, and the impregnated sintered body is dried. Thus, the cathode body 18 is formed. The cathode body 18 is fixedly supported on the cathode support member 14 by caulking the cathode body 18 thus completed with a tool (not shown) while being coaxially attached to the cathode support member 14. .

  The anode 16 is a metal rod made of tungsten, the center portion is fixed to the second glass bead 22, and the tip portion on the glass tube 12 side protrudes toward the cathode support member 14.

  The first glass bead 20 and the second glass bead 22 are made of the same glass material as that of the glass tube 12 and are heat-fused with the cathode support member 14 and the anode 16 and then cooled and solidified to thereby form the cathode support member 14 and The anode 16 is fixedly supported, and the inside of the glass tube 12 is hermetically sealed by heat-sealing with both ends of the glass tube 12.

  The flash discharge tube 10 according to the present embodiment is configured as described above. Next, the function and effect of the flash discharge tube 10 will be described with reference to FIGS.

  FIG. 3 shows an inspection circuit 30 used for the inspection of the flash discharge tube 10 described above. In FIG. 3, the first and second glass beads 20 and 22 (see FIGS. 1 and 2) are omitted from the flash discharge tube 10.

  In the inspection circuit 30, a series circuit of a resistor 34 and a trigger capacitor 36, a flash discharge tube 10, and a main capacitor 44 are connected in parallel to a power source 32. The trigger capacitor 36 includes a trigger coil 38. A series circuit of a primary winding 38 a and a switch 40 is connected in parallel, and a trigger electrode 42 disposed in the vicinity of the flash discharge tube 10 is connected to the switch 40 via a secondary winding 38 b of the trigger coil 38. Yes.

  When a power switch (not shown) of the power source 32 is turned on while the switch 40 is in an off state, a DC voltage of several hundred volts is applied from the power source 32 to the main capacitor 44 to charge the main capacitor 44. Next, when the switch 40 is turned on, a pulse voltage of several kV is generated in the secondary winding 38b of the trigger coil 38 by the discharging action of the main capacitor 44. When this pulse voltage is applied to the trigger electrode 42, electrons are emitted from the end face (electron emission face) 19 of the cathode body 18 to induce discharge inside the glass tube 12, and as a result, the flash discharge tube 10 emits light. . The flash discharge tube 10 emits light repeatedly by alternately switching the on and off states of the switch 40. Then, by placing a light receiving element (not shown) near the flash discharge tube 10, the amount of light emitted from the flash discharge tube 10 is measured.

FIG. 4 is a list showing the sizes of glass tubes and cathodes in three types of flash discharge tubes inspected by the inspection circuit 30 (see FIG. 3). The flash discharge tubes according to the examples are related to this embodiment. The flash discharge tube 10 (see FIGS. 1 to 3), while the flash discharge tubes according to Comparative Examples 1 and 2 are flash discharge tubes according to the prior art. In the embodiment, the inner diameter φ _gi of the glass tube 12 is 0.85 mm and the outer diameter φ _ko of the cathode body 18 is 0.7 mm, whereas in the comparative examples 1 and 2, the inner diameter φ _gi is 1 0.0 mm or more and the outer diameter φ _ko is 0.8 mm or more.

  FIG. 5 shows the inspection results of the minimum light emission voltage of each flash discharge tube (Example, Comparative Examples 1 and 2) when the protrusion length L is changed in the range of 0 mm to 0.6 mm. Here, the minimum light emission voltage is a minimum value of the voltage applied to the flash discharge tube when the flash discharge tube emits light.

  In this case, the flash discharge tube shown in FIG. 4 is arranged instead of the flash discharge tube 10 shown in FIG. 3, and the switch 40 is turned off after the DC voltage is applied from the power source 32 to the main capacitor 44 and the flash discharge tube. Even when the pulse voltage is applied to the trigger electrode 42 (hereinafter also referred to as a trigger) even when the trigger electrode 42 is changed to an ON state, if the flash discharge tube does not emit light, the DC voltage is boosted and the trigger operation is performed again.

  In FIG. 5, in the case of Comparative Examples 1 and 2, even if the protrusion length L changes within the range of 0 mm to 0.6 mm, there is no significant variation in the minimum light emission voltage. On the other hand, in the example, when the protrusion length L exceeds 0.3 mm, the minimum light emission voltage increases rapidly. That is, in the flash discharge tube 10 according to the embodiment (see FIGS. 1 to 3), when L> 0.3 mm, light is not emitted unless the voltage applied to the cathode 13 and the anode 16 is increased.

  FIG. 6 is a test result showing the non-light emission rate of each flash discharge tube when the protrusion length L is changed in the range of 0 mm to 0.6 mm. Here, the non-light emission rate means a ratio of the number of times of non-light emission (non-light emission number) when a predetermined voltage is continuously applied a predetermined number of times to a predetermined number of flash discharge tubes {non-light emission rate. (%) = 100 × number of non-light emission / (number of flash discharge tubes × number of times of voltage application)}. FIG. 6 shows a case in which 20 flash discharge tubes are prepared for each of the example, comparative example 1 and comparative example 2, and a 300 V DC voltage is continuously applied to each flash discharge tube 5000 times. The test result of rate is shown.

  In the case of Comparative Examples 1 and 2, even if the protrusion length L changes in the range of 0 mm to 0.6 mm, the non-light emission rate is 0%. On the other hand, in the example, the protrusion length L is 0.1 mm and the non-light emission rate is 0.002%, and 0.2 mm and 0.3 mm are 0%, but 0 mm increases to 0.005%. At 0.4 mm, it rises to 0.016%, and at 0.6 mm, it rises to 0.12%. This is because when the projection length L is less than 0.1 mm, energy concentration occurs on the end face 19 which is the electron emission surface of the cathode body 18 every time the flash discharge tube 10 (see FIGS. 1 to 3) emits light, and the end face. This is because the damage 19 becomes remarkable, and as a result, the non-light emission rate increases. On the other hand, when the protrusion length L exceeds 0.3 mm, the minimum light emission voltage (see FIG. 5) of the cathode body 18 increases and the non-light emission rate increases.

Thus, according to the flash discharge tube 10 according to the present embodiment, even if the flash discharge tube 10 is downsized by reducing the outer diameter φ _ko of the cathode body 18 to less than 0.8 mm, the cathode support Since the protrusion length L at the other end portion 26 of the member 14 is in the range of 0.1 mm to 0.3 mm, an increase in the minimum light emission voltage of the flash discharge tube 10 is suppressed, and the light emission reliability is ensured. In addition, an increase in the non-light emission rate with respect to continuous light emission of the flash discharge tube 10 is suppressed, and durability in the case of continuous light emission is ensured.

Further, in the flash discharge tube 10, even when the outer diameter φ _ko of the cathode body 18 is reduced to less than 0.8 mm, the cathode body 18 can be formed using the conventional technique, and the cathode body 18 The cathode support member 14 can be fixed and supported by caulking. That is, the cathode body 18 is formed while maintaining the same level as in the prior art with respect to variations in blending the metal powder to be the cathode body 18, the strength of the mold forming the molded body, and the strength of the sintered body. be able to. As a result, the cathode body 18 free from defects such as cracks and chips is formed, and the cathode body 18 is caulked and fixedly supported on the cathode support member 14 to form the cathode 13. For example, the outer diameter φ _go is 1 It is possible to arrange the cathode 13 in a glass tube 12 having a reduced diameter of 3 mm and an inner diameter φ _gi of 0.85 mm.

  In the embodiment described above, the cathode 13 is fixed to one end of the glass tube 12 via the first glass bead 20, and the anode 16 is fixed to the other end of the glass tube 12 via the second glass bead 22. Yes. Instead of such a configuration, as shown in FIG. 7, the cathode 13 is directly fixed to one end portion of the glass tube 12 by heat fusion, and the anode 16 is directly fixed to the other end portion of the glass tube 12. However, it goes without saying that the above-described effects can be obtained. In this case, since the flash discharge tube 10 does not include the first glass bead 20 and the second glass bead 22, it is suitable for further reducing the diameter of the glass tube 12.

  Furthermore, as shown in FIG. 8, the cathode 13 is fixed to the other end of the glass tube 12 via the first glass bead 20 and the anode 16 is directly fixed to one end of the glass tube 12 as described above. Needless to say, an effect can be obtained. In this case, since the flash discharge tube 10 does not include the second glass bead 22, it is possible to further reduce the diameter of the glass tube 12.

  Of course, the flash discharge tube according to the present invention is not limited to the above-described embodiment, and various configurations can be adopted without departing from the gist of the present invention.

It is sectional drawing of the flash discharge tube which concerns on this embodiment. It is an expanded sectional view which shows the one end part of the flash discharge tube of FIG. It is a circuit diagram of the test | inspection circuit which test | inspects the flash discharge tube of FIG. It is a table | surface which shows the size of the glass tube and cathode of a flash discharge tube test | inspected by the test | inspection circuit of FIG. 5 is a table showing the inspection results of the minimum light emission voltage when the protrusion length L is changed in each flash discharge tube of FIG. 5 is a table showing the non-light emission rate test results when the protrusion length L is changed in each flash discharge tube of FIG. 4. It is sectional drawing of the flash discharge tube which fixed the cathode and the anode directly to the glass tube. It is sectional drawing of the flash discharge tube which fixed the cathode to the glass tube via the 1st glass bead, and fixed the anode directly to the said glass tube.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Flash discharge tube 12 ... Glass tube 13 ... Cathode 14 ... Cathode support member 16 ... Anode 18 ... Cathode main body 19 ... End surface 20, 22 ... Glass bead 24 ... Noble gas 26 ... Other end part

Claims (5)

A cathode is fixed to one end of the glass tube via a first glass bead, an anode is fixed to the other end of the glass tube via a second glass bead, and both ends of the glass tube and the first and first In a flash discharge tube in which the inside of the glass tube is hermetically sealed by thermally fusing two glass beads,
The cathode includes a cylindrical cathode body, and a cathode support member having one end fixed to the first glass bead and the other end penetrating the cathode body and projecting toward the anode.
The protruding length of the cathode support member relative to the cathode body is 0.1 mm to 0.3 mm,
The external diameter of the said cathode main body is larger than the outer diameter of the said cathode support member, and is less than 0.8 mm. The flash discharge tube characterized by the above-mentioned. In a flash discharge tube in which the cathode is fixed to one end portion of the glass tube by heat fusion, and the anode is fixed to the other end portion of the glass tube by heat fusion, and the inside of the glass tube is hermetically sealed.
The cathode includes a cylindrical cathode body, and a cathode support member having one end fixed to one end of the glass tube and the other end penetrating the cathode body and projecting toward the anode.
The protruding length of the cathode support member relative to the cathode body is 0.1 mm to 0.3 mm,
A flash discharge tube characterized in that an outer diameter of the cathode main body is larger than an outer diameter of the cathode supporting member and less than 0.8 mm. The flash discharge tube of claim 2,
The flash discharge tube, wherein the anode or the cathode is fixed to the glass tube through a glass bead. The flash discharge tube according to any one of claims 1 to 3,
The length of the said cathode main body is 0.5 mm-1.0 mm. The flash discharge tube characterized by the above-mentioned. In the flash discharge tube of any one of Claims 1-4,
A flash discharge tube characterized in that an outer diameter of the cathode support member is 0.45 mm or less.

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