Ignition device for heat treatment furnace burner and maintenance method for the ignition device

Abstract

To simplify maintenance work in the ignition system of a burner for a heat treatment furnace when ignition failure occurs. [Solution] The ignition device 10 for a heat treatment furnace burner is provided with an ignition rod 13, a spark rod 14 fixed in a position where a spark discharge is possible between it and the ignition rod 13, and an ignition rod moving mechanism 20 that moves the ignition rod 13 along the extension direction of the ignition rod 13.

Description

Technical Field

[0001] The present invention relates to an ignition device for a burner for a heat treatment furnace and a maintenance method for the ignition device.

Background Art

[0002] As a burner used in a heat treatment furnace such as a carburizing furnace or a nitriding furnace, for example, a radiant tube burner is known. This radiant tube burner is composed of, for example, a double tube consisting of an inner tube and an outer tube, and is ignited by generating a spark (spark discharge) in the mixed gas of the combustible gas and air supplied to the inner tube.

[0003] As an ignition device for a burner, Patent Document 1 discloses a device having a rod-shaped electrode penetrating an insulator on the base end side, a rod-shaped ground, and a rod-shaped ignition sensor. In this device, a spark is generated between the rod-shaped electrode and the rod-shaped ground to ignite the combustible gas.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In a heat treatment furnace, the ignition and extinguishing of the burner are repeated to keep the temperature in the furnace within a predetermined range. However, when the heat treatment furnace is continuously used for a long time, poor ignition of the burner may occur. When poor ignition occurs, it is necessary to stop the operation of the heat treatment furnace and perform maintenance work on the burner. Since stopping the operation of the heat treatment furnace leads to a decrease in productivity, it is desired to simplify the maintenance work when poor ignition occurs in order to shorten the operation stop time of the heat treatment furnace.

[0006] This invention has been made in view of the above circumstances, and aims to simplify maintenance work in the event of ignition failure in an ignition device for a heat treatment furnace burner. [Means for solving the problem]

[0007] The inventors investigated the causes of burner ignition failure. As a result, they found that burner ignition failure is caused by changes in the distance between the tip of the rod-shaped power supply electrode (ignition rod) and the rod-shaped ground (spark rod) due to repeated spark generation, or by the coating of oxides on the surface of the tip of the ignition rod. A detailed explanation follows below.

[0008] The spark generated between the tip of the ignition rod and the spark rod occurs at the timing of the burner ignition, so the number of sparks increases in proportion to the operating time of the heat treatment furnace. Repeated sparks around the tip of the ignition rod can cause burning, bending, or coating of the tip of the ignition rod with oxides and soot that form on its surface.

[0009] Normally, the distance between the tip of the ignition rod and the spark rod (hereinafter referred to as the "spark gap") is pre-adjusted to an appropriate distance for easy spark generation. However, if the length of the ignition rod is shortened due to burning of the tip of the ignition rod, the spark gap changes. Also, for example, if the tip of the ignition rod is bent or deformed, the spark gap will change. Therefore, when burning or bending deformation occurs at the tip of the ignition rod, the pre-adjusted spark gap will no longer be the appropriate distance for easy spark generation, which will make it difficult to generate a spark at the ignition timing and cause burner ignition failure.

[0010] Furthermore, if the tip surface of the ignition rod becomes covered with oxides or soot, the conductivity of that tip decreases. Since the spark gap is pre-adjusted to take into account the original conductivity of the ignition rod, when the conductivity of the tip of the ignition rod decreases as described above, even if there is no change in the spark gap, it becomes difficult to generate a spark, which will cause burner ignition failure.

[0011] Considering that burner ignition failures, as described above, are caused by changes in the spark gap or changes in the conductivity of the ignition rod surface, the inventors have found a means to simplify the maintenance work on the ignition rod when ignition failures occur.

[0012] In other words, the present invention, which solves the aforementioned problems, is an ignition device for a burner for a heat treatment furnace, characterized by comprising: an ignition rod; a spark rod fixed in a position where a spark discharge is possible between it and the ignition rod; and an ignition rod moving mechanism for moving the ignition rod along the extension direction of the ignition rod.

[0013] In another view, the present invention relates to a maintenance method for an ignition device, comprising an ignition rod, a spark rod fixed in a position where a spark discharge is possible between the ignition rod and the ignition rod, and an ignition rod moving mechanism for moving the ignition rod along the extension direction of the ignition rod, characterized in that when a failure to ignite the heat treatment furnace burner occurs, the ignition rod is moved along the extension direction of the ignition rod. [Effects of the Invention]

[0014] In the ignition system for burners used in heat treatment furnaces, maintenance work can be simplified in the event of ignition failure. [Brief explanation of the drawing]

[0015] [Figure 1] This figure shows a schematic configuration of a burner for a heat treatment furnace equipped with an ignition device according to an embodiment of the present invention. [Figure 2]It is a diagram showing a schematic configuration of an ignition device according to an embodiment of the present invention. [Figure 3] It is a perspective view for explaining an ignition rod moving mechanism. [Figure 4] It is a view of FIG. 3 seen from the positive X direction. [Figure 5] It is a diagram for explaining the attachment / detachment operation of a stopper provided in the ignition rod moving mechanism. [Figure 6] It is a diagram showing the ignition device with all stoppers attached and detached. [Figure 7] It is a diagram showing an example in which a plurality of spark rods are arranged. [Figure 8] It is a view of the ignition device of FIG. 7 seen from slightly below and obliquely. [Figure 9] It is a diagram showing a state in which a single spark rod is deformed. [Figure 10] It is a diagram showing a state in which one of the plurality of arranged spark rods is deformed.

Mode for Carrying Out the Invention

[0016] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the present specification and drawings, elements having substantially the same functional configuration are denoted by the same reference numerals, and redundant description is omitted.

[0017] <Burner for heat treatment furnace> FIG. 1 is a diagram showing a schematic configuration of a burner for a heat treatment furnace (hereinafter, may be simply referred to as "burner") to which the ignition device according to the present embodiment is attached. The burner 1 according to the present embodiment is a radiant tube burner. The burner 1 is composed of a double tube including an inner tube 2 and an outer tube 3, and an ignition device 10 is inserted inside the inner tube 2. A cap 4 for closing the upper opening of the inner tube 2 is attached to the upper end portion of the inner tube 2, and the posture of the ignition device 10 is maintained by fixing the ignition device 10 to the cap 4.

[0018] In the above burner 1, the ignition device 10 ignites the mixed gas of combustible gas and air introduced into the inner pipe 2, and the exhaust gas generated by combustion is discharged from the lower end of the inner pipe 2 to the outer pipe 3. The exhaust gas discharged into the outer pipe 3 rises between the inner pipe 2 and the outer pipe 3 and is discharged. The exhaust gas is at a high temperature due to the heat generated by the combustion of the combustible gas, and the heat generated here is transmitted to the heat treatment furnace 50 through the surface of the outer pipe 3 exposed in the heat treatment furnace 50, thereby increasing the furnace temperature of the heat treatment furnace 50. When the furnace temperature rises to the desired temperature, the supply of the combustible gas is stopped to extinguish the fire, and the furnace temperature decreases with the passage of time. The burner 1 repeats ignition and extinguishing so that the temperature in the heat treatment furnace 50 is maintained in a predetermined temperature range, and the ignition device 10 generates a spark at the ignition timing.

[0019] Note that the heat treatment furnace 50 to which the burner 1 is attached is, for example, a carburizing furnace for performing carburizing treatment of steel materials or a nitriding furnace for performing nitriding treatment, but the heat treatment furnace to which the burner 1 is applicable is not particularly limited. Further, the burner 1 may be any combustion device that requires ignition by a spark (spark discharge) for combustible gas or liquid fuel, and is not limited to a radiant tube burner. In addition, although the burner 1 according to the present embodiment is arranged to be inserted from the top surface of the heat treatment furnace 50 and extend vertically downward, the burner 1 and the ignition device 10 may be arranged to be inserted from the side wall of the heat treatment furnace 50 and extend horizontally.

[0020] <Ignition device> FIG. 2 is a diagram showing a schematic configuration of the ignition device 10 according to the present embodiment. The ignition device 10 according to the present embodiment includes a flame holder 11 surrounding the periphery of the spark generation portion, a tubular flame holder holder 12 holding the flame holder 11, an ignition rod 13, and a spark rod 14.

[0021] The flame holder 11 has an inner diameter at its lower end that is larger than the inner diameter at its upper end, and has a large diameter section, a reduced diameter section, and a small diameter section from the lower end to the upper end. The flame holder 11 is attached to the lower end of the flame holder holder 12, and the upper end of the flame holder holder 12 is fixed in a state where it is inserted into a through hole 5 formed in the center of the cap 4 of the burner 1. The ignition rod 13 passes through the through hole 5 of the cap 4 and the inside of the flame holder holder 12, and is fixed so that its ignition side end (lower end in this embodiment) is located inside the flame holder 11. The spark rod 14 is attached to the reduced diameter section of the flame holder 11, and the length of the spark rod 14 exposed inside the flame holder 11 is pre-adjusted so that a spark discharge is possible between it and the ignition rod 13 when power is supplied.

[0022] The ignition device 10 includes a power supply unit (not shown), and by connecting the ignition rod 13 to the power supply unit side and the spark rod 14 to the ground side and supplying power, a spark is generated between the lower end of the ignition rod 13 and the spark rod 14.

[0023] (Ignition rod relocation mechanism) The ignition device 10 according to this embodiment includes an ignition rod moving mechanism 20 that moves the ignition rod 13 along the extension direction of the ignition rod 13 (vertical direction in this embodiment) as a mechanism for adjusting the length of the ignition rod 13 exposed inside the flame holder 11.

[0024] The ignition rod moving mechanism 20 has a movable pipe 21 and a fixed pipe 22 that surround the ignition rod 13. Both the movable pipe 21 and the fixed pipe 22 are arranged parallel to the extension direction of the ignition rod 13. In this embodiment, the inner diameter of the movable pipe 21 is larger than the inner diameter of the fixed pipe 22, and the movable pipe 21 is slidably mounted to the fixed pipe 22. The fixed pipe 22 is fixed to the cap 4 with its lower end inserted into the upper end of the through hole 5 of the cap 4. The cap 4 is an example of a fixing member for maintaining the mounting position of the fixed pipe 22.

[0025] The ignition rod 13 is fixed to the movable pipe 21. On the other hand, the ignition rod 13 is not fixed to the fixed pipe 22, so the ignition rod 13 is able to move vertically in conjunction with the vertical movement (Z direction) of the movable pipe 21. Therefore, when the movable pipe 21 rises, the ignition rod 13 also rises, and when the movable pipe 21 lowers, the ignition rod 13 also lowers. In other words, the position of the ignition end of the ignition rod 13 also changes in conjunction with the vertical movement of the movable pipe 21. This makes it possible to adjust the length of the ignition rod 13 that is exposed inside the flame holder 11.

[0026] The ignition rod moving mechanism 20 has three stoppers 23-25 ​​between the lower end surface of the movable pipe 21 and the upper surface of the cap 4 that restrict the vertical position of the movable pipe 21. The details of the stoppers 23-25 ​​will now be described with reference to Figures 3 and 4.

[0027] In this embodiment, the stoppers 23 to 25 are flat plates made of steel, and multiple stoppers are arranged in a row with their planar portions perpendicular to the plate thickness direction parallel to the vertical direction (Z direction). Of the three stoppers 23 to 25, the upper end of the uppermost first stopper 23 is in contact with the ignition side end face (lower end face in this embodiment) of the movable pipe 21, the lower end of the first stopper 23 is in contact with the upper end of the second stopper 24 located directly below the first stopper 23, and the lower end of the second stopper 24 is in contact with the upper end of the third stopper 25 located directly below the second stopper 24.

[0028] A support column 15 is provided on the side of the movable pipe 21, extending parallel to the movable pipe 21. The lower end of the support column 15 is fixed to the cap 4, and three slit collars 26-28, which serve as stopper mounting members, are fitted onto the support column 15. A first stopper 23 is attached to slit collar 26, a second stopper 24 is attached to slit collar 27, and a third stopper 25 is attached to slit collar 28. Furthermore, each stopper 23-25 ​​and each slit collar 26-28 are joined to each other by joining means such as welding or industrial adhesive. The vertical position of each stopper 23-25 ​​is fixed by these slit collars 26-28. Note that the support column 15 does not have to be newly installed for the application of the ignition rod moving mechanism 20. For example, the support column 15 may be an existing structure such as a pipe for visual monitoring to check the state of the flame inside the burner 1, or for installing a flame detector.

[0029] Figure 5 is a diagram illustrating the operation of the first stopper 23, and is a view of the first stopper 23 from below. Figure 5(a) shows the state in which the movable pipe 21 is fixed by the first stopper 23 (hereinafter, the same state will be referred to as the "operated state"), and Figure 5(b) shows the state in which the movable pipe 21 is released from being fixed by the first stopper 23 (hereinafter, the same state will be referred to as the "released state").

[0030] As shown in Figure 5(a), when the first stopper 23 is in operation, the first stopper 23 and the lower end surface 21a of the movable pipe 21 are in contact, and the movable pipe 21 shown in Figure 2 cannot move downward.

[0031] On the other hand, as shown in Figure 5(b), when the slit collar 26 to which the first stopper 23 is attached rotates and the lower end surface 21a of the movable pipe 21 and the first stopper 23 are no longer in contact, the movable pipe 21 shown in Figure 2 becomes capable of moving vertically downward by the height of the first stopper 23, and the position restriction of the movable pipe 21 by the first stopper 23 is released. This allows the length of the ignition rod 13 exposed inside the flame holder 11 to be increased by the height of the first stopper 23.

[0032] Furthermore, when the position restriction of the movable pipe 21 by the first stopper 23 is released, the second stopper 24 and the lower end surface 21a of the movable pipe 21 come into contact, and the second stopper 24 restricts the vertical downward movement of the ignition rod 13.

[0033] Figure 6 illustrates the difference in the tip position of the ignition rod 13 with and without the three stoppers 23-25. Figure 6(a) shows the state with all stoppers 23-25 ​​installed, and Figure 6(b) shows the state with all stoppers 23-25 ​​removed. As shown in Figure 6, by switching between the activated and deactivated states of the stoppers 23-25, the ignition rod 13 can be moved along the extension direction of the ignition rod 13.

[0034] Next, we will explain the timing for removing stoppers 23-25. First, ignition of the flammable gas and air mixture is achieved by generating a spark between the ignition rod 13 and the spark rod 14. For example, ignition can be achieved by alternately repeating a spark generation process, in which a spark is generated between the ignition rod 13 and the spark rod 14 by supplying power for 3 seconds, followed by an interval process, in which the power supply is stopped for 12 seconds.

[0035] When the heat treatment furnace 50 is used continuously for a long period of time while repeating the spark generation process and interval process described above, the length of the ignition rod 13 may shorten due to burnout of the tip of the ignition rod 13 caused by the repeatedly generated sparks, or the conductivity may decrease due to the coating of oxides on the surface of the tip of the ignition rod 13. In such cases, burner ignition failure may occur due to poor spark generation.

[0036] Furthermore, during the burner ignition process, if, for example, the following conditions (1) or (2) are met, it is determined that an ignition failure has occurred. (1) If no flame is detected 5 seconds after the end of the spark generation process. (2) When the detected voltage at the flame detector falls below the standard value (1.5V)

[0037] As described above, in the ignition rod moving mechanism 20 according to this embodiment, stoppers 23 to 25 are detachably attached to the movable pipe 21, and by removing the stoppers 23 to 25 in order from top to bottom, the ignition rod 13 can be moved downward by a fixed amount. By adjusting the length of the ignition rod 13 exposed inside the flame holder 11 in this way, the undeformed portion of the ignition rod 13 that has not lost conductivity can be brought closer to the spark rod 14, and a state in which sparks can easily be generated between it and the spark rod 14 can be restored. In this way, when a failure to ignite the burner 1 occurs, the ignition rod moving mechanism 20 can be used to move the ignition rod 13 along the extension direction of the ignition rod 13, thereby suppressing the occurrence of failure to ignite the burner 1.

[0038] The removal of the stopper described above can be easily performed during maintenance work on the burner 1. Therefore, for example, if a failure to ignite the burner 1 occurs, the stopper can be removed in a short time while the heat treatment furnace 50 is still in operation, or even if the heat treatment furnace 50 is stopped. In other words, the ignition device 10 according to this embodiment simplifies maintenance work in the event of a failure to ignite and shortens the downtime of the heat treatment furnace 50, thereby improving productivity.

[0039] Furthermore, if ignition failure occurs due to a spark failure with all three stoppers 23-25 ​​removed, the ignition rod 13 cannot be moved further downward. In this case, the operation of the heat treatment furnace 50 should be stopped, and the ignition rod 13 should be replaced as part of the burner 1 maintenance work.

[0040] In the above example, a configuration with three stoppers 23-25 ​​was described, but the number of stoppers may be just one. Even with only one stopper, the ignition rod 13 can be moved downward by the height of one stopper when ignition failure occurs, simplifying maintenance compared to the conventional maintenance work that involved replacing the ignition rod 13. However, by providing multiple (two or more) stoppers, the position of the ignition rod 13 can be adjusted multiple times, so from the viewpoint of reducing the frequency of ignition rod 13 replacement, it is preferable to provide multiple stoppers. Furthermore, the distance the ignition rod 13 can be adjusted by one stopper and the number of stoppers to be installed can be arbitrarily set depending on the structure of the equipment and the size of the stopper member to be applied.

[0041] Furthermore, when multiple stoppers are provided, it is preferable to use different colors for the surfaces of each stopper 23-25, as illustrated in Figure 4, so that the installation status of each stopper 23-25 ​​can be visually identified. For example, if the first stopper 23 is colored blue, the second stopper 24 is colored yellow, and the third stopper 25 is colored red, field workers can easily recognize the stopper supporting the lower end surface of the movable pipe 21 (the stopper currently in use) and the number of remaining stoppers. This allows field workers to recognize that the time for replacing the ignition rod 13 is approaching and to make preparations in advance for replacing the ignition rod 13.

[0042] Possible methods for coloring each stopper 23-25 ​​include painting or applying colored tape, but the coloring method is not particularly limited as long as each stopper 23-25 ​​can be easily identified. Also, as long as each stopper 23-25 ​​can be easily identified, the colored area on the stopper surface does not have to cover the entire surface.

[0043] The ignition rod moving mechanism 20 of the ignition device 10 according to this embodiment has been described above. In this embodiment, stoppers 23 to 25 are attached to slit collars 26 to 28, and the slit collars 26 to 28 are rotated to realize stoppers 23 to 25 that can be attached to the movable pipe 21. However, the structure for realizing detachable stoppers is not limited to that described in this embodiment. Furthermore, the ignition rod moving mechanism 20 is not limited to a structure using stoppers 23 to 25, as long as the ignition rod 13 can be moved along the extension direction of the ignition rod 13.

[0044] (Multiple spark rods) Next, a preferred configuration of the ignition device 10 will be described, in which multiple spark rods 14 are provided around the ignition rod 13. Figure 7 is an example of a configuration in which multiple spark rods 14 are provided, showing the area around the flame holder 11 in a configuration in which three spark rods 14 are provided, and Figure 8 is a view of the flame holder 11 from below at a slight angle.

[0045] In the examples shown in Figures 7 and 8, three spark rods 14 are arranged at intervals along the circumferential direction of the ignition rod 13, viewed from the tip side (ignition side) of the ignition rod 13. The distance (spark gap) between the ignition rod 13 and each of the spark rods 14a to 14c is adjusted to a distance suitable for spark generation, and a spark is generated between at least one of the spark rods 14a to 14c and the ignition rod 13 when power is supplied.

[0046] The spark rod 14 can burn out due to repeated spark generation, and its tip may bend as shown in Figure 9. In this case, the spark gap will deviate from the appropriate distance for spark generation. This makes it difficult to generate sparks during power supply, and ignition failures are more likely to occur. If ignition failure occurs due to deformation of the spark rod 14, the operation of the heat treatment furnace must be stopped and the spark rod 14 replaced.

[0047] On the other hand, if multiple spark rods 14 are provided, for example, as shown in Figure 10, even if one spark rod 14a is deformed due to burnout, if the other spark rods 14b are in a normal state, a spark can be generated between the spark rod 14b and the ignition rod 13. Therefore, ignition can be performed without replacing the deformed spark rod 14a, and the operation of the heat treatment furnace can be continued. Thus, from the viewpoint of reducing the frequency of ignition failures and continuing the operation of the heat treatment furnace, it is preferable to provide multiple spark rods 14.

[0048] Furthermore, if the number of spark rods 14 is excessively large, numerous small sparks may be generated between the ignition rod 13 and each spark rod 14, potentially leading to more unstable ignition than when the number of spark rods 14 is small. For this reason, when providing multiple spark rods 14, it is preferable to have 3 to 5 spark rods 14 to promote stable ignition.

[0049] Furthermore, when multiple spark rods 14 are provided, it is preferable that each spark rod 14 is arranged at equal intervals along the circumferential direction of the ignition rod 13, as viewed from the tip side of the ignition rod 13. For example, if the distance between two adjacent spark rods 14 is narrow when viewed from the tip side of the ignition rod 13, when bending deformation occurs in one spark rod 14, there is a possibility that the remaining spark rod 14 will also undergo similar bending deformation. However, by arranging each spark rod 14 at equal intervals along the circumferential direction of the ignition rod 13, the distance between two adjacent spark rods 14 can be maximized, thereby reducing the risk of multiple spark rods 14 deforming at the same time.

[0050] Although embodiments of the present invention have been illustrated above, the present invention is not limited to these examples. It will be obvious to those skilled in the art that various modifications or alterations can be conceived within the scope of the technical idea described in the claims, and these will naturally also fall within the technical scope of the present invention.

[0051] For example, the constituent elements of the above embodiments can be combined in any way. From such any combination, the functions and effects of each constituent element in the combination will naturally be obtained, as well as other functions and effects that will be obvious to those skilled in the art from the description herein.

[0052] Furthermore, the effects described herein are merely descriptive or illustrative and not limiting. In other words, the technology relating to this disclosure may produce other effects that will be apparent to those skilled in the art from the description herein, in addition to or instead of the effects described herein.

[0053] Furthermore, the following configuration examples also fall within the technical scope of this disclosure. (1) Ignition device for a burner in a heat treatment furnace, Ignition rod and A spark rod fixed in a position where it can discharge a spark between itself and the ignition rod, An ignition device characterized by comprising an ignition rod moving mechanism for moving the ignition rod along the extension direction of the ignition rod. (2) The ignition rod moving mechanism is A movable tube, which surrounds the ignition rod and is movable along the extension direction of the ignition rod, It has a removable stopper that contacts the ignition-side end face of the movable pipe and restricts the movement of the movable pipe, The ignition device according to (1), characterized in that the ignition rod is fixed to the movable pipe. (3) The ignition device according to (2), characterized in that a plurality of stoppers are arranged along the extension direction of the ignition rod. (4) The ignition device according to (3), characterized in that the surface colors of each stopper are different from each other. (5) The ignition rod moving mechanism is A fixed pipe provided inside the aforementioned movable pipe, The ignition-side end of the fixed pipe is fixed to a fixing member, The movable pipe is slidably mounted relative to the fixed pipe. The ignition device according to any one of (2) to (4), characterized in that the stopper is disposed between the ignition-side end face of the movable pipe and the fixing member. (6) The ignition device according to any one of (1) to (5), characterized in that a plurality of spark rods are arranged around the ignition rod. (7) The ignition device according to (6), characterized in that, when viewed from the tip side of the ignition rod, each spark rod is arranged at equal intervals in the circumferential direction of the ignition rod. (8) The ignition device according to any one of (1) to (7), characterized in that the burner for the heat treatment furnace is a radiant tube burner. [Industrial applicability]

[0054] This invention can be applied to ignition devices for burners in heat treatment furnaces. [Explanation of Symbols]

[0055] 1. Burner for heat treatment furnace 2 Inner tube 3 outer tube 4 caps 5 Through hole 10 Ignition device 11 Flame holder 12 Flame holder 13 Ignition rod 14 Spark Rod 15 Posts 20 Ignition rod relocation mechanism 21 Movable tube 22 Fixed pipe 23 First Stopper 24 Second Stopper 25. Third Stopper 26 Slit Collar 27 Slit collar 28 Slit Collar 50 Heat treatment furnaces

Claims

1. An ignition device for a burner in a heat treatment furnace, Ignition rod and A spark rod fixed in a position where it can discharge a spark between itself and the ignition rod, An ignition device characterized by comprising an ignition rod moving mechanism for moving the ignition rod along the extension direction of the ignition rod.

2. The ignition rod moving mechanism is, A movable tube, which surrounds the ignition rod and is movable along the extension direction of the ignition rod, It has a removable stopper that contacts the ignition-side end face of the movable pipe and restricts the movement of the movable pipe, The ignition device according to claim 1, characterized in that the ignition rod is fixed to the movable pipe.

3. The ignition device according to claim 2, characterized in that a plurality of stoppers are arranged along the extension direction of the ignition rod.

4. The ignition device according to claim 3, characterized in that the surface colors of each stopper are different from each other.

5. The ignition rod moving mechanism is, A fixed pipe provided inside the aforementioned movable pipe, The ignition-side end of the fixed pipe is fixed to a fixing member, The movable pipe is slidably mounted relative to the fixed pipe. The ignition device according to any one of claims 2 to 4, characterized in that the stopper is disposed between the ignition-side end face of the movable pipe and the fixing member.

6. The ignition device according to claim 1, characterized in that a plurality of spark rods are arranged around the ignition rod.

7. The ignition device according to claim 6, characterized in that, when viewed from the tip side of the ignition rod, each spark rod is arranged at equal intervals in the circumferential direction of the ignition rod.

8. The ignition device according to claim 1, characterized in that the burner for the heat treatment furnace is a radiant tube burner.

9. An ignition device for a burner in a heat treatment furnace comprises an ignition rod, a spark rod fixed in a position where a spark discharge is possible between it and the ignition rod, and an ignition rod moving mechanism for moving the ignition rod along the extension direction of the ignition rod, A maintenance method for an ignition device, characterized by moving the ignition rod along the extension direction of the ignition rod when a failure to ignite occurs in the burner for the heat treatment furnace.

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