JP2012207971A - Flame sensor and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flame sensor capable of inhibiting a so-called pseudo-discharge, in which a discharge is easily induced in a pair of surface electrodes disposed on a discharge tube for detection of UV rays (UV tube), the discharge starting from an outer circumferential portion where an electric field is particularly intense, although irradiation with UV rays is finished.SOLUTION: The flame sensor uses a UV tube including a pair of surface electrodes (an anode electrode 21 and a cathode electrode 22). The flame sensor is configured in such a manner that the distance between the electrodes in the center portion of the surface electrodes is shorter than the distance between the electrodes on an outer circumferential portion of the surface electrodes, and thereby, electric fields are substantially uniform in the center portion and the outer circumferential portion between electrodes, which can inhibit a pseudo-discharge that is easily induced starting from an outer circumferential portion of the surface electrodes where an electric field is particularly intense.

Description

  The present invention relates to a flame sensor that detects ultraviolet rays contained in a flame.

One type of flame sensor is a flame sensor that detects ultraviolet rays contained in a flame using a unitized ultraviolet ray detection discharge tube (UV tube). This UV tube is obtained by sealing a pair of discharge electrodes that generate discharge upon receiving ultraviolet rays in a cylindrical glass tube, and leading out the lead wires of the pair of discharge electrodes from one end of the glass tube.
The UV tube having such a structure plays a role of ensuring safety for reliably detecting that the fire is on, and is used, for example, as a flame sensor for monitoring a combustion state in a boiler (for example, , See Patent Document 1).

  FIG. 1 is a schematic diagram showing the structure of a conventional UV tube. In the glass tube 10, a mesh-like anode electrode 11 and a cathode electrode 12 are supported by lead wires 13 and 14, respectively, and a gas is sealed in the glass tube 10. The anode electrode 11 and the cathode electrode 12 have a parallel plane structure, and are arranged with a distance of about 0.5 mm between the electrodes. Then, ultraviolet rays incident from the end portion (upper end portion in FIG. 1) and the side portion of the glass tube 10 pass through the mesh of the anode electrode 11 and hit the cathode electrode 12 to discharge (for example, see Patent Document 2).

Japanese Patent Laid-Open No. 5-12581 Japanese Patent Publication No. 44-1039

  However, in the conventional flame sensor, as described above, since the pair of surface electrodes (anode electrode and cathode electrode) in the UV tube are arranged in parallel, the electric field in the outer peripheral portion rather than the center portion of the surface electrode is increased. Becomes stronger, and the outer peripheral portion of the surface electrode is in a state of being easily discharged. For this reason, the problem is that the fire is extinguished and so-called false discharge is likely to occur starting from the outer periphery of the surface electrode where the electric field is particularly strong even though the irradiation of ultraviolet rays has ended. was there. As a result, the flame was detected even though there was no flame, which was very dangerous.

  The present invention has been made to solve the above-described problems, and aims to provide a flame sensor that can suppress false discharge in a flame sensor using a UV tube having a pair of surface electrodes. Yes.

  In order to achieve the above object, the present invention provides a flame sensor using a UV tube having a pair of surface electrodes, wherein at least one of the pair of surface electrodes is curved. The distance between the electrodes at the center is shorter than the distance between the electrodes at the outer periphery of the surface electrode.

  Further, the present invention is characterized in that at least two lead wires for fixing the pair of surface electrodes are provided, and the surface electrodes are inclined at the connection portions between the surface electrodes and the lead wires. To do.

  The present invention is also a method of manufacturing a flame sensor using a UV tube having a pair of surface electrodes, wherein the step of bending at least one of the pair of surface electrodes includes the surface electrode to be curved In the connecting portion with the lead wire, the surface electrode is inclined so that the distance between the two electrodes at the center portion of the surface electrode is shorter than the distance between the two electrodes at the outer peripheral portion of the surface electrode. To do.

  Moreover, this invention is a flame sensor provided with the insulator which integrates said pair of surface electrode.

  According to the present invention, in the flame sensor using the UV tube provided with a pair of surface electrodes, the distance between both electrodes in the center portion of the surface electrode is shorter than the distance between both electrodes in the outer peripheral portion of the surface electrode. The electric field at the center part and the outer peripheral part between the pair of surface electrodes becomes substantially uniform, and the false discharge that is likely to occur from the outer peripheral part of the surface electrode where the electric field is particularly strong can be suppressed.

It is a schematic diagram which shows the structure of the conventional discharge tube for ultraviolet detection (UV tube). It is a figure which shows the manufacturing process of the discharge tube for ultraviolet rays (UV tube) in Embodiment 1 of this invention. It is an enlarged view which shows the connection part of the cathode electrode and Kovar wire in Embodiment 1 of this invention. It is a figure which shows the curved cathode electrode in Embodiment 1 of this invention. It is an enlarged view which shows the connection part of the anode electrode and Kovar line in Embodiment 1 of this invention. It is a figure which shows the curved anode electrode in Embodiment 1 of this invention. It is a schematic diagram which shows schematic relationship between the anode electrode and cathode electrode in Embodiment 1 of this invention. It is a figure which shows the anode electrode and cathode electrode in Embodiment 2 of this invention. It is a schematic diagram which shows schematic relationship between the anode electrode and cathode electrode in Embodiment 2 of this invention. It is a schematic diagram which shows the manufacturing method of the discharge tube for ultraviolet rays (UV tube) in Embodiment 3 of this invention. It is a schematic diagram which shows schematic relationship between the anode electrode and cathode electrode in Embodiment 3 of this invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
Embodiment 1 FIG.
The ultraviolet ray detection discharge tube (UV tube) of the flame sensor according to Embodiment 1 of the present invention is produced according to the manufacturing process shown in FIG. Here, the anode electrode 21 and the cathode electrode 22 used in the UV tube are both surface electrodes as in the conventional case, and only the anode electrode 21 is a mesh electrode.

  First, as shown in FIG. 2A, the exhaust pipe 26, the button glass 27, and the three Kovar lines 23 and 24 are sealed simultaneously to form the button stem 28. Next, as shown in FIG. 2B, the cathode electrode 22 is welded to the three Kovar wires (lead wires) 24 for the cathode electrode 22. After that, as shown in FIG. 2C, a predetermined distance (0.4 mm in this case) is maintained between the anode electrode 21 and the cathode electrode 22 even in the place where the distance between both electrodes is the shortest. In order to achieve this, the spacer 29 is temporarily arranged. In this state, as shown in FIG. 2D, the anode electrode 21 is welded to three kovar wires (lead wires) 23, and the spacer 29 is removed. Finally, as shown in FIG. 2 (e), a cup-shaped glass 20 having a space is covered and welded to the button stem 28, and gas is sealed inside and sealed. Note that the cup-shaped glass 20 having a space is made of ultraviolet-transmitting glass only at the end 25 (the upper end in FIG. 2E).

  Here, the procedure for welding the cathode electrode 22 in FIG. 2B and the result that the cathode electrode 22 bends will be described. The cathode electrode 22 is provided with a cutout at a position corresponding to the three kovar lines 23 so as not to contact the three kovar lines 23 for the anode electrode 21.

When welding the cathode electrode 22 in FIG. 2B, first, the cathode electrode 22 is disposed on the three Kovar wires 24 for the cathode electrode 22. In this state, only one of the three Kovar wires 24 is welded to the cathode electrode 22 by laser irradiation. As a result, the welded Kovar wire 24 is melted and shortened, the cathode electrode 22 is inclined at the connection portion with the Kovar wire 24, and only the vicinity of the Kovar wire 24 of the cathode electrode 22 is bent obliquely downward.
FIG. 3 is an enlarged view showing a connection portion between the cathode electrode 22 and the Kovar wire 24. Thus, welding is performed by irradiating a laser from the upper surface of the electrode plate of the cathode electrode 22 disposed on the Kovar wire 24 toward the end surface of the Kovar wire 24. At this time, the Kovar wire 24 is melted by about 0.01 to 0.03 mm and the entire length is reduced, the cathode electrode 22 is inclined at the connection portion with the Kovar wire 24, and only the vicinity of the Kovar wire 24 of the cathode electrode 22 is oblique. It will be in the state bent down.

  Similarly, only one of the other Kovar wires 24 is welded to the cathode electrode 22 by laser irradiation. As a result, the cathode electrode 22 is also inclined at the connection portion with the second Kovar line 24 and bends obliquely downward in the vicinity of the Kovar line 24. Finally, the remaining Kovar wire 24 is also welded to the cathode electrode 22 by laser irradiation. As a result, the cathode electrode 22 also inclines at the connection portion with the last Kovar line 24 and bends obliquely downward in the vicinity of the last Kovar line 24. As a result, the vicinity of the center of the cathode electrode 22 swells upward (convexly), and the portions near the kovar lines 24 and between the line segments connecting the kovar lines 24 (that is, the outer periphery of the cathode electrode 22) are downward. It becomes a curved shape.

  FIG. 4 is a diagram showing the curved cathode electrode 22 obtained as described above. Note that the amount of bending of the cathode electrode 22 is determined by the amount of penetration during welding of the cathode electrode 22 and the Kovar wire 24.

  Next, when the spacer 29 is temporarily disposed on the cathode electrode 22 thus curved as shown in FIG. 2C, the anode electrode 21 in FIG. 2D is welded. And the result that the anode electrode 21 is bent will be described. The mesh-like anode electrode 21 is provided with holes for connecting the three Kovar wires 23 at locations corresponding to the three Kovar wires 23, respectively. The three Kovar wires 23 are made longer than the three Kovar wires 24 for the cathode electrode 22, and when the anode electrode 21 is welded to the Kovar wire 23, the anode electrode 21, the cathode electrode 22, Is set not to touch.

  When the anode electrode 21 in FIG. 2D is welded, first, the anode electrode 21 is arranged by aligning the positions of the three holes of the anode electrode 21 with the positions of the three Kovar wires 23. At this time, if the spacer 29 is not provided, the vicinity of the center of the anode electrode 21 comes into contact with the vicinity of the center of the cathode electrode 22. However, since the spacer 29 is interposed, the anode electrode 21 has a thickness corresponding to the thickness of the spacer 29. The electrode 22 is arranged at a distance. In this state, similarly to the cathode electrode 22 described above, the three Kovar wires 23 are welded to the anode electrode 21 by laser irradiation one by one in order.

  FIG. 5 is an enlarged view showing a connection portion between the anode electrode 21 and the Kovar wire 23. In this way, the Kovar wire 23 is melted by passing the Kovar wire 23 through the hole for connection with the Kovar wire 23 provided in the anode electrode 21 and directly irradiating the end surface of the Kovar wire 23 with a laser from above. I do. At this time, the distance between the two electrodes is determined by the thickness of the spacer 29 disposed between the cathode electrode 22 and the anode electrode 21. At this time, the Kovar wire 23 is melted by about 0.10 to 0.15 mm and the entire length is reduced, and the anode electrode 21 is inclined at the connection portion with the Kovar wire 23 and bent into a valley fold. Only the vicinity of the Kovar line 23 is bent downward. At this time, as shown in FIG. 2C, the spacer 29 is a portion between the line segments connecting the kovar wires 23 (the portion corresponding to the kovar wire 24 for the cathode electrode 22 in the outer peripheral portion of both electrodes). 5, the anode electrode 21 is further further than the right end portion of the anode electrode 21 shown in FIG. 5 in that portion, that is, the portion facing the vicinity where the cathode electrode 22 is welded to the Kovar wire 24. The outer peripheral portion is curved upward.

  FIG. 6 is a diagram showing the curved anode electrode 21 obtained in this manner. Similar to the welding of the cathode electrode 22, the bending amount of the anode electrode 21 is determined by the amount of penetration when the anode electrode 21 and the Kovar wire 23 are welded.

  FIG. 7 is a schematic diagram showing a schematic relationship between the anode electrode 21 and the cathode electrode 22 in the UV tube according to Embodiment 1 of the present invention. This figure is a figure which shows only the part corresponding to the anode electrode 11 and the cathode electrode 12 among the structures of the conventional UV tube shown in FIG. As can be seen from comparison with FIG. 1, in the past, both electrodes are arranged in parallel, and there is no difference in the distance between the electrodes at the center portion and the outer peripheral portion of the surface electrode. Each of the anode electrode 21 and the cathode electrode 22 is curved so that the distance between the two electrodes at the center of the surface electrode is shorter than the distance between the two electrodes at the outer peripheral portion of the surface electrode.

  According to the flame sensor using the UV tube thus created, ultraviolet rays due to the occurrence of the flame are incident from the end portion 25 of the cup-shaped glass 20 having a space, pass through the mesh of the anode electrode 21, and the cathode. A flame can be detected by discharging against the electrode 22, and when the fire is extinguished and ultraviolet light is not irradiated, a false discharge that is likely to occur from the outer periphery of the anode electrode 21 and the cathode electrode 22, particularly where the electric field is strong, is generated. Since it can suppress, a combustion state can be detected reliably.

In the first embodiment, the distance between the two electrodes at the center of the surface electrode is 0.4 mm, but this can be adjusted as appropriate depending on the thickness of the spacer 29.
In addition, the number of Kovar wires connected to each surface electrode is three, but may be changed as appropriate as long as it is at least two and can support the surface electrode.

Embodiment 2. FIG.
The anode electrode 31 and the cathode electrode 32 used in the ultraviolet ray detection discharge tube (UV tube) of the flame sensor according to the second embodiment of the present invention are both surface electrodes as in the conventional and the first embodiment. Although only 31 is a mesh electrode, unlike the prior art and the first embodiment, holes 33 and 34 having the same diameter are formed at the center of the anode electrode 31 and the center of the cathode electrode 32, respectively.

  In the second embodiment, the UV tube first seals the exhaust pipe 26, the button glass 27, and the three Kovar wires (lead wires) 23 and 24 at the same time as in the first embodiment. Thus, the button stem 28 is formed. Next, the cathode electrode 32 is welded to the three Kovar wires 24 for the cathode electrode 32. At this time, the cathode electrode 32 is not bent like the cathode electrode 22 in the first embodiment, and the cathode electrode 32 is connected to the three kovar lines 24 while maintaining the planar state as in the conventional case. Thereafter, the anode electrode 31 is welded to the three kovar wires 23. Also at this time, the cathode electrode 31 is not bent like the anode electrode 21 in the first embodiment, and the cathode electrode 31 is connected to the three kovar lines 23 while maintaining the planar state as in the conventional case.

  After that, the anode electrode 31 and the cathode electrode 32 are both in the central portion of the surface electrode as in the schematic diagram (FIG. 7) showing the schematic relationship between the anode electrode 21 and the cathode electrode 22 of the UV tube in the first embodiment. The anode electrode 31 and the cathode electrode 32 are curved so that the distance between the electrodes is shorter than the distance between the two electrodes on the outer periphery of the surface electrode. This process will be described with reference to FIGS.

  FIG. 8 is a diagram showing an anode electrode 31 and a cathode electrode 32 according to Embodiment 2 of the present invention. Holes 33 and 34 having the same diameter are formed in the center of the anode electrode 31 and the center of the cathode electrode 32, respectively. Further, an insulating ring 35 having the same inner diameter as that of the holes 33 and 34 is inserted between both electrodes, and the insulating rod 36 is passed through the hole 33, the insulating ring 35 and the hole 34, and the upper and lower portions of the insulating rod 36 are inserted. The anode electrode 31, the insulating ring 35, and the cathode electrode 32 are integrated by, for example, melting them.

FIG. 9 is a schematic diagram showing a schematic relationship between the anode electrode 31 and the cathode electrode 32 created as described above. In the second embodiment, the anode electrode 31 and the cathode electrode 32 are maintained at a predetermined distance (here, 0.4 mm) at a place (center portion) where the distance between the electrodes is the shortest. Thus, the thickness of the insulating ring 35 is set. At this time, the difference in length between the three Kovar wires 23 for the anode electrode 31 and the three Kovar wires 24 for the cathode electrode 32 is set to be equal to or greater than the thickness of the insulating ring 35. Thus, when the anode electrode 31, the insulating ring 35, and the cathode electrode 32 are integrated by the insulating rod 36 as shown in FIG. 9, the anode electrode 31 and the cathode electrode 32 have a distance between the electrodes at the center of the surface electrode. Each of them is curved so as to be shorter than the distance between both electrodes in the outer peripheral portion of the surface electrode.
Finally, a cup-shaped glass 20 having a space is covered and welded to the button stem 28, and after sealing the gas inside, it is sealed.

Embodiment 3 FIG.
The anode electrode 41 and the cathode electrode 42 used in the ultraviolet ray detection discharge tube (UV tube) of the flame sensor according to the third embodiment of the present invention are both surface electrodes as in the conventional and the first embodiment. Only 41 is a mesh-like electrode. However, in order to bend the electrode in a flat state, when the glass stem 20 having a space is covered and welded to the button stem 28 in the process shown in FIG. Tool 43 is used.

  As in the first embodiment, the UV tube according to the third embodiment first seals the exhaust pipe 26, the button glass 27, and the three Kovar wires (lead wires) 23 and 24 at the same time. A button stem 28 is formed. Next, the cathode electrode 42 is welded to the three Kovar wires 24 for the cathode electrode 42. At this time, the cathode electrode 42 is not curved like the cathode electrode 22 in the first embodiment, and the cathode electrode 42 is connected to the three Kovar lines 24 while maintaining the planar state as in the conventional case. Thereafter, the anode electrode 41 is welded to the three kovar wires 23. Also at this time, the cathode electrode 41 is not curved like the anode electrode 21 in the first embodiment, and the cathode electrode 41 is connected to the three kovar lines 23 while maintaining the planar state as in the conventional case.

Thereafter, when a glass cup 20 having a space is covered and welded to the button stem 28, a UV tube is manufactured by the method of the schematic diagram shown in FIG.
First, as described above, the button stem 28 in which the anode electrode 41 and the cathode electrode 42 are welded together is fixed to the jig 43. The jig 43 includes a stepped portion 44 that covers the exhaust pipe 26 and is fixed so that the lower part of the Kovar wire 24 for the cathode electrode 42 is slightly expanded. In addition, fingers 45 that respectively hold the three kovar wires 24 for the cathode electrode 42 are provided for each kovar wire 24. In this state, a cup-shaped glass 20 having a space is covered, and a joint portion with the button stem 28 is welded with a burner. At this time, by applying a force in a direction in which the upper portion of the finger 45 is pushed inward, a force is easily applied to the Kovar wire 24 in the vicinity of the joint portion softened by welding by the burner, and the cathode electrode 42 is as shown in FIG. The outer peripheral portion is curved downward (the central portion is upward).

  FIG. 11 is a schematic diagram showing a schematic relationship between the anode electrode 41 and the cathode electrode 42 of the UV tube according to Embodiment 3 of the present invention. In the third embodiment, unlike the first and second embodiments, the anode electrode 41 remains a flat electrode that is not curved, and only the cathode electrode 42 rises upward in the vicinity of the center. The distance between the two electrodes at the center of the surface electrode is shorter than the distance between the two electrodes at the outer periphery of the surface electrode.

Embodiment 4 FIG.
The anode electrode 51 and the cathode electrode 52 used in the ultraviolet ray detection discharge tube (UV tube) of the flame sensor according to the fourth embodiment of the present invention are curved in advance by bending the same surface electrode as in the conventional and the first embodiment. Electrode. In addition, what is necessary is just to produce a curved electrode by a well-known method, such as making it match with a spherical support member.

  In the fourth embodiment, the UV tube first seals the exhaust pipe 26, the button glass 27, and the three Kovar wires (lead wires) 23 and 24 at the same time as in the first embodiment. Thus, the button stem 28 is formed. Next, the cathode electrode 52 is arranged and welded to the three Kovar wires 24 for the cathode electrode 52 in such a direction that the center portion of the curved cathode electrode 52 is raised. Thereafter, the three kovar wires 23 for the anode electrode 51 are arranged and welded so that the center portion of the curved anode electrode 51 protrudes downward. Finally, a cup-shaped glass 20 having a space is covered and welded to the button stem 28, and after sealing the gas inside, it is sealed.

Also in the fourth embodiment, the anode electrode 51 and the cathode electrode 52 have the same structure as the schematic diagram (FIG. 7) showing the schematic relationship between the anode electrode 21 and the cathode electrode 22 of the UV tube in the first embodiment. can do.
Further, if only one of the electrodes is curved as in the third embodiment, a schematic diagram showing a schematic relationship between the anode electrode 41 and the cathode electrode 42 of the UV tube in the third embodiment (FIG. 11). ).
In order to maintain a predetermined distance (0.4 mm in this case) between the electrodes at the center of the anode electrode 51 and the cathode electrode 52, the lengths of the kovar lines 23 and 24 and the kovar lines are used. What is necessary is just to adjust the amount of penetration by laser irradiation at the time of welding to the electrode.

  As described above, according to the first to fourth embodiments of the present invention, in a flame sensor using a UV tube provided with a pair of surface electrodes, the distance between both electrodes at the center of the surface electrode is set to the outer periphery of the surface electrode. Since the distance between the electrodes at the center is shorter than the distance between the electrodes, the electric field at the center and outer periphery of the pair of electrodes is almost uniform, and the false discharge that tends to occur from the outer periphery of the surface electrode, which has a particularly strong electric field, is suppressed can do.

  In the present invention, within the scope of the invention, any combination of the embodiments, or any modification of any component in each embodiment, or omission of any component in each embodiment is possible. .

10 Glass tube 11, 21, 31, 41, 51 Anode electrode 12, 22, 32, 42, 52 Cathode electrode 13, 14, 23, 24 Kovar wire (lead wire)
20 Glass-shaped glass with space 25 End of glass-shaped glass 20 with space 26 Exhaust pipe 27 Button glass 28 Button stem 29 Spacer 33, 34 Electrode center hole 35 Insulating ring 36 Insulating rod 43 Jig 44 Jig 43 steps 45 fingers

Claims (4)

In a flame sensor using a UV tube with a pair of surface electrodes,
The distance between the two electrodes at the center of the surface electrode is shorter than the distance between the two electrodes at the outer periphery of the surface electrode because at least one of the pair of surface electrodes is curved. A flame sensor. At least two lead wires for fixing the pair of surface electrodes,
The flame sensor according to claim 1, wherein the surface electrode is inclined at a connection portion between the curved surface electrode and the lead wire. A method of manufacturing a flame sensor using a UV tube having a pair of surface electrodes,
In the step of bending at least one of the pair of surface electrodes, the surface electrode is inclined at the connection portion between the surface electrode to be bent and the lead wire, thereby, between the two electrodes at the center portion of the surface electrode. The flame sensor is made shorter than the distance between the two electrodes on the outer periphery of the surface electrode.   The flame sensor according to claim 1, further comprising an insulator for integrating the pair of surface electrodes.

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