JP2003232515A - Flame rod - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a durable flame rod capable of accurately detecting firing and misfiring for a long time. <P>SOLUTION: The flame rod 2 comprises a rod substrate 8 made of a heat- resistant alloy containing Fe, Cr and Al and a coating 18 of electrically conductive ceramics provided on a surface of the rod substrate 8. The coating 18 is formed in a region including a flame insertion portion 20 at a front end of the rod substrate 8 and at least part of a flame non-insertion portion 22 lying closer to a proximal end than the flame insertion portion. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a flame rod for detecting whether a gas combustion device is ignited or misfired by measuring a flame current in a state where the gas combustion device is inserted in a flame of the gas combustion device.

[0002]

2. Description of the Related Art A gas combustion device typified by an oil fan heater and a water heater has a member called a frame rod. Usually, this kind of frame rod is made of iron (F
e) and chromium (Cr) are used as components and are made of an electrically conductive metal material, and are used in a state of being installed on the top of a metal burner. An AC power supply for applying an AC voltage of about 100 V and an ammeter for measuring the value of a minute current flowing in the flame are connected in series between the flame rod and the burner.

When the gas combustion equipment is used, the tip of the frame rod is inserted into the flame of the burner. When the gas combustion device is operating normally and a flame is present, the value of the flame current is high because the amount of ions existing around the flame rod is large. on the other hand,
When the gas combustion device is not operating normally and sufficient flame is not present, the amount of ions existing around the flame rod is small, and thus the flame current value is low. That is, by measuring the value of the flame current, it is possible to recognize whether ignition or misfire has occurred.

By the way, when the frame rod is used,
Exposed to high temperature of 00 ° C or higher. For this reason, the surface of the portion of the rod base that is inserted into the flame is gradually oxidized to form an insulating film, and as a result, the flame current cannot be accurately detected. Therefore, as shown in FIG. 5, the surface oxidation of the rod base 32 is prevented by covering only the portion 40 of the rod base 32 that is inserted into the flame 34 with the coating film 36 made of an electrically conductive ceramic material. A frame rod 38 has been proposed. A similar conventional technique is also disclosed in, for example, Japanese Utility Model Laid-Open No. 2-7455.

[0005]

However, in the case where the metal forming the rod base 32 contains aluminum, even if the above-mentioned structure is adopted, the flame insertion portion 40 of the flame insertion portion 40 is not used during long-term use. Oxidation occurs on the surface, resulting in the alumina insulating film 42. That is, the ceramic insulating film 36 is interposed by the alumina insulating film 42.
The insulation resistance between the rod base 32 and the rod base 32 increases, and it becomes difficult for current to flow.

Here, when a high temperature of 500 ° C. or higher is reached after a certain time has elapsed after ignition, a crack is formed in the alumina insulating film 42, so that an electric current can flow through the gap between the cracks. Therefore, in this case, the value measured by the ammeter is almost the same as that when the alumina insulating film 42 is not provided, and no particular inconvenience occurs. On the other hand, in the low temperature state immediately after ignition, the presence of the crack-free alumina insulating film 42 causes the current value measured by the ammeter to drop, and the current value serves as a threshold for determining ignition / misfire. It will fall below the value. Therefore, the ignition / misfire detection circuit connected to the ammeter is "misfiring".
There was a problem that the safety device, which was mistakenly recognized as being in a state and actuated in response to that, completely extinguished the fire.

[0007] Therefore, an object of the present invention is to provide a frame rod excellent in durability which can accurately detect ignition / misfire over a long period of time.

[0008]

Means for Solving the Problems, Actions and Effects The frame rod of the present invention comprises a rod base made of a heat-resistant alloy containing Fe, Cr and Al as components, and an electrically conductive ceramics provided on the surface of the rod base. And the covering body. Then, a region including at least a part of the flame insertion portion at the tip of the rod base body and the flame non-insertion portion located at the base end side thereof (in other words, the alumina insulating film forming portion at the tip end of the rod base body). , And the coating is formed on a region including at least a part of the alumina insulating film non-forming portion located on the base end side thereof (claim 1,
2).

Since the portion of the rod base located closer to the base end side than the flame insertion portion is not inserted into the flame, the temperature is not as high as that of the flame insertion portion, and the alumina insulating film is hardly formed on the surface. Therefore, if the coating is formed over the portion (flame non-insertion portion, alumina insulating film non-forming portion), it is possible to secure an electric conduction path between the coating and the rod base. Therefore, according to the frame rod of the first or second aspect, it is possible to solve the problem that the current value drops immediately after ignition due to the interposition of the alumina insulating film. Therefore, it is possible to accurately detect ignition / misfire over a long period of time, and it is possible to provide a frame rod having excellent durability.

In the frame rod according to claim 1 or 2, it is preferable that the coating body is a coating film made of ceramics having an electric conductivity higher than that of alumina, and further, the oxide ceramics having the above-mentioned characteristics. It is preferable that the coating film is composed of (claim 3).

Ceramics having electrical conductivity equal to or lower than that of alumina are not suitable conductors. For this reason, even if the covering body is formed by using the ceramics as a material, the energization path between the covering body and the rod base cannot be secured. On the other hand, according to the third aspect of the invention, since it is relatively easy to secure the energization path, it is possible to eliminate the drop in the current value immediately after ignition.

Moreover, the oxide-based ceramics have the advantage that they are more stable than the non-oxide-based ceramics. The non-oxide type includes, for example, carbide type ceramics, nitride type ceramics, boride type ceramics, silicide type ceramics, and the like. Non-oxide ceramics do not contain oxygen atoms in their molecular structure. Therefore, it is easily oxidized by being placed in a high temperature / oxidizing atmosphere for a long time. Therefore, suitable physical properties such as heat resistance and electric conductivity are likely to be impaired. Therefore, it may not be possible to achieve the object of the present invention to accurately detect ignition / misfire over a long period of time. On the other hand, oxide-based ceramics are originally formed in a state where oxygen atoms are included in their molecular structure. Therefore, even if it is placed in a high temperature / oxidizing atmosphere for a long period of time, it is unlikely to undergo chemical change. Therefore, suitable physical properties such as heat resistance and electric conductivity can be maintained for a long period of time. Therefore, it is possible to accurately detect ignition / misfire over a long period of time.

In the frame rod according to any one of claims 1 to 3, it is preferable that the covering is formed so as to be in direct contact with the surface of the rod base (claim 4).

If an intermediate layer or the like is interposed between the cover and the rod base, the layer structure becomes complicated and the manufacturing cost increases. In addition, depending on the selected material, the insulation resistance between the cover and the rod base increases, which may make it difficult to secure the current-carrying path. On the contrary,
If the coating is formed so as to be in direct contact with the surface of the rod base as in the fourth aspect of the present invention, an electric current can be directly and efficiently passed from the coating to the rod base. Therefore, it becomes easy to secure the energization path, and it is possible to more reliably eliminate the drop in the current value immediately after ignition. Moreover, since the layer structure is simple, the manufacturing cost is not increased.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The main features of the embodiments of the present invention described below will be described. (Mode 1) The electrically conductive ceramics has a temperature of -20 ° C to 14 ° C.
The electrical conductivity at 00 ° C. (particularly the electrical conductivity at 50 ° C. to 500 ° C.) is 10 ⁻⁴ Scm ⁻¹ or more, and the frame rod according to claim 1. According to this mode, the value of the flame current does not significantly decrease, and suitable conductivity can be obtained. (Feature 2) When the insulating member is provided at the base end portion of the frame rod, a region where the covering is not formed is left between the insulating member and the covering by a predetermined length. Item 1. The frame rod according to any one of items 1 to 4 and form 1. According to this aspect, it is possible to easily secure the insulation and maintain the appearance of the frame rod. Also,
The amount of electrically conductive ceramics used can be reduced compared to the case where the covering is formed up to the position where the insulating member is present. Therefore, cost reduction can be achieved.

[0016]

Embodiment FIG. 1 schematically shows a main part of a gas combustion device equipped with a frame rod 2 according to an embodiment of the present invention. The frame rod 2 is horizontally arranged in the upper region of the burner 4 made of a conductive metal, that is, in the region where the flame 6 is to be formed at the time of ignition. The tip side of the frame rod 2 (Fig. 1
Then, the right end side) is located directly above the burner 4. On the other hand, the base end side (the left end side in FIG. 1) of the frame rod 2 is at a position largely displaced from the position directly above the burner 4. An insulating insulator 10 is attached to the outer peripheral portion of the rod base 8 constituting the frame rod 2 on the base end side. A lead wire 12 is electrically connected to the base end surface of the rod base 8. An AC power supply 14 for applying an AC voltage of about 100 V and an ammeter 16 for measuring the value of a minute current flowing in the flame 6 are connected in series between the frame rod 2 and the burner 4. It is connected to the.

The gas combustion device further includes an ignition / misfire detection circuit and a safety device (both not shown). The ignition / misfire detection circuit is electrically connected to the ammeter 16 and receives the output signal of the ammeter 16 (that is, the current value obtained by the measurement). The ignition / misfire detection circuit has in advance information on the threshold value of the current that serves as a criterion for determining ignition / misfire, and compares the threshold value with the measured current value at that time. The ignition / misfire detection circuit recognizes that it is in the "ignition" state when the measured current value is larger than the threshold value, and recognizes that it is in the "misfire" state when it is below the threshold value. The safety device operates only when the ignition / misfire detection circuit recognizes that it is in the "misfire" state. And, for example, burner 4
Mechanically shut off the gas supply to. As a result, the fire is completely extinguished within a few seconds.

Next, the structure of the frame rod 2 will be described in more detail. Rod base 8 of frame rod 2
Is a rod-shaped body having a circular cross section. This rod base 8 is F
It is made of a heat-resistant alloy conductive material containing e, Cr and Al as components. In the present embodiment, among these alloys, the Fe-Cr-Al-Y alloy having excellent high temperature heat resistance is used. Of course, as long as it has suitable heat resistance and conductivity, a material containing another metal instead of Y may be selected as the heat resistant alloy for forming the rod base 8.

The frame rod 2 has a coating (coating film 18) on its surface. The coating film 18 in this embodiment
Is made of a ceramic material having electrical conductivity. Here, “having electrical conductivity” means having electrical conductivity higher than at least alumina (Al ₂ O ₃ ). This is because it is difficult to say that ceramics having an electric conductivity equal to or lower than that of alumina is a suitable conductor, and there is no practical benefit to select it as a material for forming the coating film 18.

As shown in FIG. 1, such a coating film 18
Is formed in a region including the flame insertion portion 20 at the tip of the rod base 8 and a part of the flame non-insertion portion 22 located on the base end side thereof. To put it another way,
The coating film 18 is formed in a region including the alumina insulating film forming portion at the tip portion of the rod base 8 and a part of the alumina insulating film non-forming portion located at the base end side thereof.

The "alumina insulating film forming portion" means the flame 6
Since the temperature of the rod rod 8 becomes high when the frame rod 2 is used, the alumina insulating film 24 is formed on the surface of the rod base 8 after the frame rod 2 is used. On the other hand, the “alumina insulating film forming portion” does not reach a temperature higher than that of the alumina insulating film forming portion because it is not inserted into the flame 6, and the alumina insulating film is not formed on the surface of the rod base 8 even after the frame rod 2 is used. It refers to a region where the film 24 is not formed or is hardly formed.

The coating film 18 in the present embodiment is formed so as to be in direct contact with the surface of the rod base 8 without interposing an intermediate layer or the like. The coating film 18 covers the entire flame insertion portion 20 and a part of the flame non-insertion portion 22 over the entire circumference of the rod.

The average thickness of the coating film 18 is preferably 0.1 mm or more and a fraction of the diameter of the rod substrate 8 or less. In particular, it is more preferably about 0.5 mm to 3 mm. The reason is that if the coating film 18 is too thin, the effect of the coating may not be sufficiently expected, while if it is too thick, a large amount of ceramic material is required and the manufacturing cost increases.

The electrically conductive ceramic material that can be used for the coating film 18 has at least higher electrical conductivity than alumina, and the operating temperature range of the frame rod 2 (-2
It is sufficient if it has heat resistance at 0 ° C to 1400 ° C. Therefore, various ceramic materials can be selected regardless of whether they are non-oxide ceramics or oxide ceramics. Examples of non-oxide ceramics that can be used for the coating film 18 include TiC, HfC,
Carbide-based ceramics typified by B ₄ C, β-SiC and the like, nitride-based ceramics typified by Si ₃ N _{4 and the} like,
Examples thereof include boride-based ceramics and silicide-based ceramics represented by ZrB ₂ , B ₄ C and the like.

However, as the ceramic material that can be used for the coating film 18, oxide ceramics are preferable to non-oxide ceramics. Non-oxide ceramics do not contain oxygen atoms in their molecular structure. Therefore, it is easily oxidized by being placed in a high temperature / oxidizing atmosphere for a long time. Therefore, suitable physical properties such as heat resistance and electric conductivity are likely to be impaired. On the other hand, oxide-based ceramics are originally formed in a state where oxygen atoms are included in their molecular structure. Therefore,
Even if it is left in a high temperature / oxidizing atmosphere for a long time, it is unlikely to undergo a chemical change. Therefore, it is physically stable in that suitable physical properties such as heat resistance and electric conductivity can be maintained for a long period of time.

As electrically conductive oxide ceramics
Are, for example, as follows. Perovskite type
As oxide-based ceramics, ReO_Three, M_xReO
_Three(M is metal), M_xWO_Three(M is metal), Na_xTa
_yW_1-yO_Three, M_xNbO_Three(M = Er), Na
_1-xSr_xNbO_Three, CaVO_Three, SrVO_Three, La
_1-xSr_xVO_Three, La₅SrCu₆O₁₅, La_Two
SrCu_Two2O_6.2, LaNiO_Three, LaCuO_Three，
SrRuO_Three, Ca_1-xMg_xRu_Three(X = 0.1,
0.3, 0.5), BaRuO_Three, L added with MgO
aCrO₃(La _1-xMg_xCrO_3-z), CaO
Added LaCrO₃(La_1-xCa _xCrO
_3-z, X = 0 to 0.6), Sr-added LaCrO
₃(La_1-xSr_xCrO_3-z, X = 0 to 0.
5), LaMnO with CaO added₃(La _1-xCa
_xMnO_3-z, X = 0 to 0.4), SrO was added
LaMnO₃(La_1-xSr_xMnO_3-z, X = 0
~ 1), LaFeO with SrO added ₃(La_1-xS
r_xFeO_3-z, X = 0.3-1), CaO is added
LaCoO₃(La_1-xCa_xCoO_3-z, X =
0.3), LaCoO with SrO added₃(La_1-x
Sr_xCoO_3-z, X = 0.3 to 0.5), MgO
LaCrO added₃(La_1-xMg_xCr
O_3-z, X = 0 to 0.5), CeO_TwoCa with added
MnO₃(Ca_1-xCe_xMnO_3-z, X = 0.
1) etc. can be mentioned.

Among the substances listed above, at least one selected from lanthanoid elements (La, Ce, etc.)
One), an alkaline earth metal (at least one selected from Mg, Ca, Sr, Ba, etc.) and a transition metal (V, C)
It is desirable to use an oxide containing at least one selected from r, Mn, Fe, Co, Ni, Cu and the like.
It is preferable to select La as the lanthanoid element. As alkaline earth metals, Mg, Ca,
It is preferred to select one of Sr. As the transition metal, it is preferable to select one of Cr, Mn, Fe, Co and Ni.

The reason is that the perovskite type oxide ceramics satisfying the above-mentioned conditions generally have suitable electric conductivity and heat resistance. “Having suitable electrical conductivity” means that, in consideration of the operating temperature range (−20 ° C. to 1400 ° C.) of the frame rod 2,
It means that the conductivity is high in the low temperature range (temperature range of about 500 ° C. or lower). More specifically, for example, 50 ° C
The electric conductivity at ˜500 ° C. is 10 ⁻⁴ Scm ⁻¹ or more,
It means preferably 10 ⁻³ Scm ⁻¹ or more, more preferably 10 ⁻² Scm ⁻¹ or more. This is because the flame current value does not significantly decrease and suitable conductivity can be obtained.

As spinel type oxide ceramics
Is LiTi_TwoO_Four, LiM_xTi _2-xO_Four(M = L
i, Al, Cr), Li_1-xM_xTiO_Four(M = M
g, Mn), LiV_TwoO_Four, Fe_ThreeO_FourMg with addition
Cr_TwoO_Four, Fe_ThreeO_FourAdded MgAl_TwoO_Four, F
e_ThreeO_FourCo added with_ThreeO_Four, Fe_ThreeO_FourEtc.
be able to. Rutile-MoO₂Type oxide ceramic
As a cous, VO_Two, CrO_Two, NbO_Two, Mo
O_Two, WO_Two, ReO_Two, RuO_Two, RhO_Two, OsO
_Two, PtO _Two, IrO_TwoEtc. can be mentioned.

The NaCl type oxide ceramics include TiO, VO, NbO, LaO, NdO, SmO,
EuO _1-x, can be cited LiVO ₂ and the like. As the oxide ceramic which do not fall into the type described above, include NiO added with Li ₂ O, CoO added with Li ₂ O, MnO was added Li ₂ O, the _Cr 2 _{O 3} or the like added with MgO be able to. Thus, an alkali metal (at least one selected from Li, Na, K, etc.) and a transition metal (V, Cr, Mn, Fe, Co, N)
An oxide containing at least one selected from i, Cu and the like may be used. In addition to such oxides, for example, BaTiO ₃ with La ₂ O ₃ , ZnO with Al ₂ O ₃ and SnO ₂ with Sb ₂ O ₅ can be used.

By the way, it is preferable that the electrically conductive ceramic material for forming the coating film 18 has a coefficient of thermal expansion close to that of the heat-resistant alloy forming the rod base 8. Specifically, it is 8 × 10 ⁻⁶ / K or more, preferably 10 × 10 ⁻⁶ / K or more, more preferably 12 × 1.
It is good is to be set to more than 0 ^-6 / K. By setting the value of the coefficient of thermal expansion in this way, even if the frame rod 2 repeatedly encounters a heat cycle,
It is possible to avoid generation of large stress due to thermal expansion / contraction. Therefore, the occurrence of cracks in the coating film 18 can be prevented in advance. As a result, the formation of the alumina insulating film 24 can be prevented.

Next, a method of manufacturing the frame rod 2 will be described. When manufacturing the frame rod 2, first, the rod base 8 must be manufactured. The rod base 8 can be obtained by processing a material made of a heat resistant alloy into a predetermined shape. Of course, the method is not limited to such a method, and the rod base 8 may be manufactured by another method (for example, casting). The insulating insulator 10 is mounted on the rod base 8 in advance. The insulating insulator mounting step may be performed after the covering body forming step described below.

The covering 18 is formed by the following procedure.
First, it is desirable to wash the entire surface of the rod base 8 on the tip side of the insulator 10 with an acidic solution and then with an alkaline solution. The reason why such cleaning is performed is that impurities (metal oxide film, organic matter, etc.) adhering to the surface of the rod substrate 8 are removed in advance so that the coating film 18 formed later has high adhesion and This is because it imparts high conductivity. After the acid cleaning or the alkali cleaning, it is desirable that the rod substrate 8 is once washed and dried to sufficiently remove the acidic solution or the alkaline solution.

Then, a coating material for forming a coating is prepared by adding a solvent or the like to the powder of the ceramic material having electric conductivity and mixing the powder with a predetermined length from the tip of the rod base 8. Soak only for a minute. By such a dip coating method, the coating material is uniformly attached to the entire circumference of the predetermined length portion. At this time, the immersion depth extends to a portion of the rod base 8 which is not inserted into the flame during normal use (a portion which is not directly touched by the flame). However, a method other than the dip coating method (for example, curtain coating method) may be adopted as the coating method for the rod base 8. Furthermore, it is also possible to adopt a method other than coating (for example, a CVD method, a plating method, etc.). However, among these, the dip coating method has an advantage that it is the simplest and the cost is low.

When performing dip coating,
It is preferable to provide a region (non-immersed region) which is not immersed in the paint of a certain length between the region immersed in the paint (immersion region) and the insulating insulator 10. The reason is that if no non-immersion area is provided, the possibility that the coating material will adhere to the surface of the insulating insulator 10 during immersion increases, so from the viewpoint of maintaining the appearance as well as from the viewpoint of maintaining the appearance. Is also not preferable. Further, as compared with the case where the coating film 18 is formed up to the position where the insulating insulator 10 is present, the amount of the electrically conductive ceramic material used is small, and thus there is an advantage that the cost can be surely reduced. Because there is.

After carrying out the coating process as described above,
Dry at a temperature of 100 ° C. or higher to sufficiently remove the solvent in the paint. Further, by baking at a temperature of several hundreds of degrees Celsius or higher, the powder of the ceramic material is completely fixed on the surface of the rod base 8, and the formation of the coating film 18 is completed. As a result, the frame rod 2 having the structure shown in FIG. 1 can be obtained.

In this example, various test samples of frame rods were actually manufactured by the following procedure, and comparative tests were conducted on them. (Production of Comparative Test Sample) A procedure for producing the test sample 1 will be described with reference to the flowchart of FIG. First, the rod substrate 8 with the insulator 10 was prepared. As a material for forming the rod base 8, an Fe-Cr-Al-Y-based alloy (Hitachi Metals Ltd., trade name "YSS-SYTT")
Was used. After that, the insulating insulator 1 in the rod base 8
5% of 60 ° C for the entire surface of the part on the tip side of 0
It was washed with a sulfuric acid solution for 1 minute. After that, it was washed with running water and then degreased by washing with a 5% sodium hydroxide solution for 1 minute. Then, it was washed again with running water and dried.

Also, so-called LSM powder (La _0.7 Sr), which is a kind of ceramic material having electrical conductivity, is used.
_A predetermined amount of terpineol, which is a solvent, was added to _0.3 MnO ₃ ) and mixed to prepare a coating material for forming a coating. Then, a dip coating method was performed to immerse the coating material in a predetermined length from the tip of the rod substrate 8. The immersion depth is the rod base 8
At the time of normal use, it was set so as to extend to the part that would not be inserted into the flame. That is, in the test sample 1, the coating film 18 was formed in the region including the entire flame insertion site 20 and a part of the flame non-insertion site 22 at the tip of the rod substrate 8. Then, the test sample 1 was obtained by performing drying at 120 ° C. and baking at 1050 ° C.

A test sample 2 was obtained by forming a coating film 18 using NiO added with Li ₂ O as a ceramic material. Basically, the manufacturing method, conditions, etc. for test sample 1 were followed except that the ceramic materials were different. A test sample 3 was obtained by forming the coating film 18 using SnO ₂ with Sb ₂ O ₅ added as a ceramic material. Basically, the manufacturing method, conditions, etc. for test sample 1 were followed except that the ceramic materials were different. In addition to the test samples 1 to 3 of the above examples, a test sample 4 as a comparative example (conventional example) was also prepared. In the test sample 4, the coating film 18 was formed using LSM powder, but the forming range was set to be narrower than that of the others. That is, in the test sample 4, unlike the other three test samples, the coating film 18 was formed only on the flame insertion site 20.

(Test Method and Results) These four test samples were actually mounted on a gas combustion device and continuously operated for 3400 hours. Then, in order to investigate the response at the initial stage of ignition at this point, the value of the flame current immediately after ignition was measured with time. The graph in FIG. 3 shows the result. In this graph, the horizontal axis represents time (seconds) and the vertical axis represents the flame current value (μA).

As to the test sample 4 which is a comparative example,
It was found that the flame current value once reached a peak value (about 8 μA) 0.3 to 0.4 seconds after ignition, then drastically dropped to about 1 μA after 1 to 5 seconds, and then gradually increased. It was Therefore, it was found that the responsiveness was considerably lowered. Also, the ignition connected to the ammeter 16
The misfire detection circuit mistakenly recognized that it was in the "misfire" state, and the safety device that actuated in response to that accident completely extinguished the fire, which was also likely to occur. That is, the flame rod of Test Sample 4 could not accurately detect ignition / misfire for a long period of time, and had poor durability.

On the other hand, regarding the test samples 1 to 3 included in the scope of the present invention, it was confirmed that the flame current value generally increases within a short time, and all of them have excellent responsiveness. I understood. In addition, there was no drop in the flame current value, or even if it did exist, it was negligible, so there was no risk of misrecognition by the ignition / misfire detection circuit. That is, since the flame rods 2 of the test samples 1 to 3 can accurately detect ignition / misfire over a long period of time, they were excellent in durability.

Further, these four test samples were removed and cut in parallel with the axial direction of the rod, and the cut surface was observed and investigated by a conventionally known method. As a result, in all of them, the thin alumina insulating film 24 was formed on the surface of the rod substrate 8. Regarding the test sample 4 in which the coating film 18 is formed only on the flame insertion site 20, the energization path between the coating film 18 and the rod base 8 is
It was completely cut off by the interposition of the alumina insulating film 24. On the other hand, for the test samples 1 to 3, the alumina insulating film 24 is present at the flame insertion site 20, but
It was not present in the flame non-insertion site 22. Therefore,
The energization path between the coating film 18 and the rod base 8 was secured.

In the case of the frame rod 2 of the present embodiment configured as described above, since the current-carrying path between the coating film 18 and the rod base 8 is secured, it is caused by the interposition of the alumina insulating film 24. The problem of current drop immediately after ignition is solved. Therefore, it is possible to accurately detect ignition / misfire over a long period of time, and it is possible to provide the frame rod 2 having excellent durability.

Further, in this embodiment, the coating film 18 made of oxide ceramics having higher electric conductivity than alumina is formed. Therefore, it is relatively easy to secure the energization path, and the drop in the current value immediately after ignition can be reliably eliminated. Moreover, since the coating film 18 is resistant to chemical change and has high stability, suitable physical properties such as heat resistance and electrical conductivity can be maintained for a long period of time.
Therefore, it is possible to accurately detect ignition / misfire over a long period of time.

Further, in this embodiment, the coating film 8 is formed so as to directly adhere to the surface of the rod substrate 8. Therefore, a current can be directly and efficiently passed from the coating film 18 to the rod base 8. Therefore, it becomes easy to secure the energization path, and the drop in the current value immediately after ignition can be reliably eliminated. Moreover, since the layer structure is simple, there is an advantage that the manufacturing cost is not increased.

Specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.

(1) For example, as shown in FIG. 4, a frame rod 2 obtained by modifying the above embodiment may be used.
In the above-described embodiment, the coating film 18 is formed over the entire circumference of the flame non-insertion portion 22, but in this modification, the coating film 18 is formed only on a part of the flame non-insertion portion 22 (only the lower portion).
Are formed. Of course, this may be formed only in the upper portion. (2) The entire region from the tip of the rod base 8 to the location where the insulating insulator 10 is present can be used as the formation region of the coating film 18. (3) The insulating insulator 10 is not an essential component in the present invention, and thus may be omitted. (4) The covering does not necessarily have to be a film-like material as in the embodiment, but may be, for example, a cap-like material that can be fitted to the tip side of the rod base 8. However, considering the adhesion with the rod base 8 and the ease of formation,
After all, it can be said that the film-shaped covering body as in the above embodiment is more preferable.

The technical elements described in this specification or the drawings are
The technical usefulness is exerted alone or in various combinations, and is not limited to the combinations described in the claims at the time of filing. Further, the technique illustrated in the present specification or the drawings can simultaneously achieve a plurality of purposes, and achieving the one purpose among them has technical utility.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a main part of a gas combustion device equipped with a frame rod according to an embodiment of the present invention.

FIG. 2 shows a flowchart for explaining a procedure for producing a test sample 1 included in an example of the present invention.

FIG. 3 is a graph showing the results of time-dependent measurement of flame current values immediately after ignition for four test samples.

FIG. 4 shows a schematic cross-sectional view of a frame rod of another modification.

FIG. 5 shows a schematic sectional view of a conventional frame rod.

[Explanation of symbols]

2: Frame rod 8: Rod base 18: Coating film (coating body) 20: Flame insertion site 22: Flame non-insertion site 24: Alumina insulating film

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Akio Tanaka             2-26, Fukuzumi-cho, Nakagawa-ku, Nagoya, Aichi Prefecture             Inside Nanai Co., Ltd. (72) Inventor Takeshi Fukaya             2-26, Fukuzumi-cho, Nakagawa-ku, Nagoya, Aichi Prefecture             Inside Nanai Co., Ltd. F term (reference) 3K005 WB02 WC01 XB01 XB02 XB07

Claims (4)

[Claims] 1. A rod base made of a heat-resistant alloy containing Fe, Cr and Al as components, and a coating body made of electrically conductive ceramics provided on the surface of the rod base. And a frame rod in which a cover is formed in a region including at least a part of a flame non-insertion site located on the base end side thereof. 2. An alumina insulating film at the tip of the rod base, comprising a rod base made of a heat-resistant alloy containing Fe, Cr and Al as components, and a coating made of electrically conductive ceramics provided on the surface of the rod base. A frame rod, characterized in that a coating is formed in a region including at least a part of a formation portion and a portion of the alumina insulating film non-formation portion located on the base end side thereof. 3. The frame rod according to claim 1, wherein the coating body is a coating film made of oxide-based ceramics having higher electrical conductivity than alumina. 4. The frame rod according to claim 1, wherein the cover is formed so as to be in direct contact with the surface of the rod base.