Heating furnace

Abstract

Improved durability of the furnace body. [Solution] The heating furnace 1 has a furnace body 10, conveying rollers 20, and a lower heater 33. The furnace body 10 has a bottom wall 11. The bottom wall 11 is located lower than the conveying rollers 20. The bottom wall 11 is made of brick. The bottom wall 11 has a first through hole 13a connecting the outside of the furnace body 10 with the conveying space 10a. The lower heater 33 heats the workpiece 5 being conveyed in the conveying space 10a. The lower heater 33 is inserted into the first through hole 13a. The portion of the bottom wall 11 facing the conveying space 10a is made of dense refractory brick. The portion of the bottom wall 11 not facing the conveying space 10a is made of insulating refractory brick.

Description

[Technical Field]

[0001] The present invention relates to a heating furnace. [Background technology]

[0002] Japanese Patent Application Publication No. 2023-130741 discloses a continuous heating furnace equipped with a tunnel-shaped furnace body that defines a transport space within which workpieces are transported along a transport direction, and a heater that heats the workpieces. The furnace body has a ceiling located above the transport space and a pair of side walls located on both sides of the furnace body in the width direction and supporting the underside of the ceiling. The underside of the ceiling has side portions located on both sides of the width direction, a central portion protruding downward from the side portions, and a pair of wall portions located at the boundary between the central portion and the side portions. At least the portion of the pair of side walls facing the transport space has multiple plate-shaped first insulating materials stacked along the transport direction. The multiple first insulating materials support the underside of the ceiling. According to Japanese Patent Application Publication No. 2023-130741, by configuring the furnace body in this way, the durability of the furnace body can be improved. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2023-130741 Summary of the Invention [Problem to be solved by the invention]

[0004] The present inventors aim to further improve the durability of the furnace body. [Means for solving the problem]

[0005] The heating furnace disclosed herein includes a furnace body forming a transport space within which workpieces are transported along a transport direction, a plurality of transport rollers arranged along the transport direction, a drive device for rotating the plurality of transport rollers, and a heater for heating the workpieces transported in the transport space. The furnace body is located below the transport rollers and includes a bottom wall made of bricks, a pair of side walls extending upward from both sides of the bottom wall in the width direction, and a ceiling wall supported by the pair of side walls. The bottom wall has a first through hole connecting the outside of the furnace body to the transport space. The heater is inserted into the first through hole. The portion of the bottom wall facing the transport space is made of dense refractory bricks. The portion of the bottom wall not facing the transport space is made of insulating firebricks. This heating furnace can improve the durability of the furnace body. [Brief explanation of the drawings]

[0006] [Figure 1] FIG. 1 is a side cross-sectional view that schematically shows a heating furnace. [Figure 2] FIG. 2 is a cross-sectional view taken along line II-II of FIG. [Figure 3] FIG. 3 is an enlarged schematic view showing the vicinity of the lower heater in FIG. [Figure 4] FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. [Figure 5] FIG. 5 is a view of FIG. 4 as seen from the direction of arrow V. [Figure 6] FIG. 6 is a schematic enlarged view showing the vicinity of the lower heater during replacement work of the lower heater. DETAILED DESCRIPTION OF THE INVENTION

[0007] An embodiment of the technology disclosed herein will be described below with reference to the drawings. The embodiment described herein is, of course, not intended to limit the present invention. Furthermore, members and parts performing the same function are appropriately designated by the same reference numerals, and redundant explanations will be omitted where appropriate. The reference numerals F, Rr, L, R, U, and D in the drawings represent front, rear, left, right, top, and bottom, respectively. The left-right direction is perpendicular to the front-rear direction. The up-down direction is perpendicular to the front-rear direction and the left-right direction. However, the directions defined here are merely for the convenience of description and do not limit the present invention unless otherwise specified.

[0008] FIG. 1 is a side cross-sectional view schematically illustrating a heating furnace 1. FIG. 2 is a cross-sectional view taken along line II-II of FIG. 1. The heating furnace 1 is a continuous heating furnace that continuously heats the workpiece 5 while transporting the workpiece 5 on rollers, a so-called roller hearth kiln. The type and shape of the workpiece 5 are not particularly limited. The workpiece 5 may be plate-shaped, sheet-shaped, or powder-like. If the workpiece 5 is powder-like, the workpiece 5 may be contained in a container. In this case, the container containing the powder-like workpiece 5 is transported on rollers, and the workpiece 5 is heated. As shown in FIGS. 1 and 2, the heating furnace 1 includes a furnace body 10, multiple transport rollers 20, a drive mechanism 25, a preheater 31, a ceiling heater 32, and a lower heater 33.

[0009] The furnace body 10 is formed in a tunnel shape. A transfer space 10a is formed inside the furnace body 10. In the transfer space 10a, the workpiece 5 is transferred along a transfer direction. In the embodiment shown in FIG. 1, the transfer direction is the front-rear direction, and the workpiece 5 is transferred from the rear to the front. In FIG. 1, the transfer direction of the workpiece 5 is indicated by an arrow. Note that, as shown in FIG. 2, the furnace body 10 may be provided on, for example, a base 6. A carry-in port 10a1 is formed at the rear of the furnace body 10. The carry-in port 10a1 is an opening for carrying the workpiece 5 into the furnace body 10. A carry-out port 10a2 is formed at the front of the furnace body 10. The carry-out port 10a2 is an opening for carrying the workpiece 5 out of the furnace body 10.

[0010] The transfer space 10a is divided into multiple areas by partitions 8. In the embodiment shown in FIG. 1, the transfer space 10a is divided into a preheating area 10b, a heating area 10c, and a cooling area 10d. In the preheating area 10b, the workpiece 5 is heated by gradually increasing the temperature toward the heating area 10c until it reaches the highest temperature in the heating area 10c. The heating area 10c is located in front of the preheating area 10b. In the heating area 10c, the workpiece 5 preheated in the preheating area 10b is heat-treated according to predetermined heat treatment conditions. The temperature of the heating area 10c is higher than that of the preheating area 10b. The cooling area 10d is located in front of the heating area 10c. In the cooling area 10d, the workpiece 5 heat-treated in the heating area 10c is cooled to a predetermined temperature before being transported outside the furnace body 10. The temperature of the cooling area 10d is lower than that of the heating area 10c. In the embodiment shown in FIG. 1, the preheating area 10b, the heating area 10c, and the cooling area 10d are further divided into a plurality of areas by partitions 8b, 8c, and 8d, respectively.

[0011] As shown in Figures 1 and 2, the furnace body 10 has a bottom wall 11, a pair of side walls 15 and 16, and a ceiling wall 17. The thickness of each wall of the furnace body 10 is set to a thickness that provides sufficient thermal insulation for the transfer space 10a. As shown in Figure 2, the periphery of the furnace body 10 may be covered with a metal outer wall 18. The metal material used for the outer wall 18 may be, for example, a stainless steel material.

[0012] The bottom wall 11 is a portion that constitutes the lower part of the furnace body 10. In FIG. 2, hatching representing a cross section is omitted, and only the portion of the furnace body 10 that corresponds to the bottom wall 11 is hatched. The bottom wall 11 is located below the conveying roller 20. In the embodiment shown in FIG. 2, the bottom wall 11 is formed so as to have a U-shape when viewed from the front-to-rear direction. In this embodiment, the bottom wall 11 has a bottom portion 12, a left portion 13, and a right portion 14. The bottom portion 12 is a portion that constitutes the lower part of the bottom wall 11. In FIG. 2, the bottom portion 12 is a portion of the bottom wall 11 that is located below the vertical position indicated by the dashed dotted line AA. The bottom portion 12 is placed on the base 6. The left portion 13 is placed on the upper left of the bottom portion 12 and extends in the vertical direction. The right portion 14 is placed on the upper right of the bottom portion 12 and extends in the vertical direction. 2, the left side portion 13 and the right side portion 14 are portions of the bottom wall 11 that are located above the vertical position indicated by the dashed line AA. Note that a heat insulating member 19 made of a ceramic fiber board or the like may be provided on both the left and right sides of the bottom wall 11.

[0013] FIG. 3 is an enlarged schematic diagram of the vicinity of the lower heater 33 in FIG. 2. As shown in FIG. 3, the bottom wall 11 has a first through hole 13a and a second through hole 13b. The first through hole 13a and the second through hole 13b connect the outside of the furnace body 10 to the transfer space 10a. The first through hole 13a and the second through hole 13b are formed in a plurality of rows along the transfer direction. In this embodiment, the first through hole 13a and the second through hole 13b connect the outside of the furnace body 10 to the heating area 10c. The first through hole 13a is formed in the left side portion 13 and extends in the left-right direction. In this embodiment, the first through hole 13a is a rectangular hole. The second through hole 13b is formed in the left side portion 13 and extends in the left-right direction. The second through hole 13b is positioned higher than the first through hole 13a. In this embodiment, the second through-hole 13b is a circular hole.

[0014] As shown in FIG. 2 , a pair of side walls 15, 16 extend upward from both sides of the bottom wall 11 in the width direction. In this specification, the width direction refers to a direction perpendicular to the conveying direction and the vertical direction. In this embodiment, the width direction is the left-right direction. The side wall 15 extends upward from the left side portion 13 of the bottom wall 11. The side wall 16 extends upward from the right side portion 14 of the bottom wall 11. The ceiling wall 17 is provided on top of the pair of side walls 15, 16. The ceiling wall 17 is supported by the pair of side walls 15, 16. In this embodiment, the pair of side walls 15, 16 and the ceiling wall 17 are made of a board material having a predetermined heat resistance. For example, a ceramic fiber board can be used as this board material. The ceramic fiber board is, for example, formed into a plate shape by adding an inorganic filler and an inorganic / organic binder to so-called bulk fiber.

[0015] As shown in FIG. 1, multiple conveying rollers 20 are arranged along the conveying direction. In the embodiment shown in FIG. 1, the multiple conveying rollers 20 are arranged along the front-rear direction at predetermined intervals. In this embodiment, the conveying rollers 20 are formed in the shape of hollow cylinders. The conveying rollers 20 may be made of a highly heat-resistant ceramic material such as alumina. However, the conveying rollers 20 may also be made of a metal material such as heat-resistant cast steel or stainless steel. As shown in FIG. 2, the conveying rollers 20 are inserted into a pair of side walls 15 and 16. In the embodiment shown in FIG. 2, both left and right ends of the conveying rollers 20 are supported by support columns 22 arranged outside the furnace body 10.

[0016] The drive mechanism 25 is attached to the conveying rollers 20. In this embodiment, the drive mechanism 25 is provided on the left side of the furnace body 10. In the embodiment shown in FIG. 2, the drive mechanism 25 includes a plurality of driven sprockets 26, a chain 27, a drive sprocket 28, and a drive unit 29. The plurality of driven sprockets 26 are attached to the plurality of conveying rollers 20, respectively. The chain 27 is wound around the plurality of driven sprockets 26 and the drive sprocket 28. The drive unit 29 is attached to the drive sprocket 28. The drive unit 29 is a drive source for rotating the plurality of conveying rollers 20. The type of the drive unit 29 is not particularly limited. In this embodiment, the drive unit 29 is an electric motor. Note that the drive mechanism 25 may include, as necessary, a tension roller (not shown) for adjusting the slack of the chain 27 and a guide roller (not shown) around which the chain 27 is wound. Note that the configuration of the drive mechanism 25 is not particularly limited and is not limited to the embodiment shown in FIG. 2. The drive mechanism 25 may be provided on the right side of the furnace body 10, or on both the left and right sides of the furnace body 10.

[0017] The preheater 31, ceiling heater 32, and bottom heater 33 heat the workpiece 5 being transported in the transport space 10a. As shown in FIG. 1, the preheater 31 is provided in the preheating area 10b. The preheater 31 is positioned and its output is set so that the temperature reaches the maximum temperature of the heating area 10c from room temperature. The preheaters 31 are arranged at predetermined intervals above and below the transport roller 20 along the transport direction. The output of the preheater 31 is set so that the temperature of the preheating area 10b is lower than the temperature of the heating area 10c. In the embodiment shown in FIG. 1, the preheater 31 is formed in a cylindrical shaft shape. The preheater 31 may be, for example, a ceramic heater. However, the type and shape of the preheater 31 are not particularly limited, and various heaters can be used depending on the heating conditions.

[0018] The ceiling heater 32 and the lower heater 33 are provided in the heating area 10c. The ceiling heater 32 is inserted into the ceiling wall 17 at predetermined intervals along the conveying direction. The ceiling heater 32 is located above the conveying rollers 20. In this embodiment, a molybdenum disilicide heater folded back within the conveying space 10a is used as the ceiling heater 32. The ceiling heater 32 is inserted so as not to come into contact with the workpiece 5 being conveyed. However, the type and shape of the ceiling heater 32 are not particularly limited, and various heaters can be used depending on the heating conditions, etc.

[0019] The lower heaters 33 are arranged at predetermined intervals along the conveying direction. As shown in Fig. 3, in this embodiment, the lower heaters 33 are inserted into first through holes 13a formed in the left side portion 13 of the bottom wall 11. As shown in Fig. 2, the lower heaters 33 are disposed below the conveying rollers 20. In this embodiment, molybdenum disilicide heaters are used for the lower heaters 33. However, the lower heaters 33 may also be, for example, ceramic heaters or silicon carbide heaters.

[0020] FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. 1. However, FIG. 4 illustrates only a portion of the heating area 10c, and the remaining portions are omitted. The lower heater 33 includes a heat generating portion 33a and a terminal portion 33b. The heat generating portion 33a is disposed in the transfer space 10a. The heat generating portion 33a is formed in a cylindrical shape and is folded back multiple times within the transfer space 10a. As shown in FIG. 4, in this embodiment, the heat generating portion 33a is folded back five times within the transfer space 10a. The heat generating portion 33a generates heat when energized. In this embodiment, the heat generating portion 33a is made of molybdenum disilicide. The terminal portion 33b electrically connects the heat generating portion 33a to a power source (not shown). The terminal portion 33b is made of a material with a lower electrical resistivity than the heat generating portion 33a. In this embodiment, the terminal portion 33b is formed in a cylindrical shape.

[0021] The lower heater 33 deteriorates over time with use. Therefore, the lower heater 33 needs to be replaced periodically. The present inventors discovered that if the temperature of the lower heater 33 is sufficiently lowered before replacement, the lower heater 33 may crack and break. The present inventors attribute this to the following: Heaters such as molybdenum disilicide heaters used as the lower heater 33 develop a glass coating on their surfaces with use. If the temperature of the lower heater 33 is lowered in this state, the glass coating formed on the surface of the lower heater 33 may break. Breaking of the glass coating formed on the surface of the lower heater 33 may cause an internal wire break in the lower heater 33, which may cause the lower heater 33 to crack. In particular, in continuous heating furnaces such as roller hearth kilns, the lower heater 33 operates continuously for long periods without interruption. As a result, the glass coating formed on the surface of the lower heater 33 is likely to become thick. If the glass coating formed on the surface of lower heater 33 is thick, damage to the glass coating is likely to cause a disconnection inside lower heater 33, making lower heater 33 more likely to crack. For this reason, the present inventors would like to replace lower heater 33 while it is still in a high temperature state.

[0022] Furthermore, the heat generating portion 33a of the lower heater 33 is located inside the furnace body 10. It is difficult for an operator who replaces the lower heater 33 to perform the work while directly visually observing the inside of the furnace body 10, and it is difficult for the operator to perform the work while accurately grasping the position of the heat generating portion 33a. Therefore, when the operator attempts to remove the lower heater 33 from the first through-hole 13a, the heat generating portion 33a in a high temperature state may collide with the bottom wall 11 (particularly the left side portion 13). The heat generating portion 33a in a high temperature state is particularly likely to collide with the portion of the bottom wall 11 (particularly the left side portion 13) that faces the transfer space 10a.

[0023] In the heating furnace 1 proposed herein, the bottom wall 11 is made of bricks. The bottom wall 11 is formed by stacking bricks in multiple layers. In the embodiment shown in FIG. 2, the bottom portion 12 is formed by stacking six layers of bricks. The left side portion 13 and the right side portion 14 are formed by stacking three layers of bricks. In the embodiment shown in FIG. 2, the bottom wall 11 is made of six types of bricks 11a, 11b, 11c, 11d, 11e, and 11f. In FIG. 2, bricks of the same type are marked with the same hatching, and bricks of different types are marked with different hatching. In addition, in FIGS. 3 and 4, the boundaries between the bricks that make up the bottom wall 11 are not shown. In the embodiment shown in FIG. 2, bricks 11a, 11d, and 11e are arranged in order from the inside of the furnace body 10 in the first layer of the left side portion 13. In the embodiment shown in FIG. 2, bricks 11a and 11d are arranged in the first row of the right side portion 14 in this order from the inside of the furnace body 10.

[0024] 2 shows a simplified shape of the bottom wall 11. Regardless of the shape shown in FIG. 2, the bottom 12, left side 13, and right side 14 may be constructed using so-called Dutch or English bond. By offsetting the brick joints, it is possible to prevent heat from leaking from the transfer space 10a to the outside.

[0025] The portion of the bottom wall 11 facing the transfer space 10a is made of bricks 11a. In this embodiment, the bricks 11a are high-alumina bricks. In the embodiment shown in FIG. 2, among the bricks 11a to 11f used in the bottom wall 11, the bricks 11a, at least a portion of which faces the transfer space 10a, are made of high-alumina bricks. High-alumina bricks have a high alumina content and are excellent in fire resistance and mechanical strength. The alumina content of the high-alumina bricks used here is preferably 95% or more, and more preferably 99% or more. For example, bricks conforming to JIS R2305 can be used as the high-alumina bricks used here.

[0026] The portion of the bottom wall 11 that does not face the transfer space 10a is composed of bricks 11b to 11f. The bricks 11b to 11f are insulating firebricks. The insulating firebricks have low thermal conductivity. For example, bricks conforming to JIS R2611 can be used as the insulating firebricks used here. The insulating firebricks used here preferably have a lower thermal conductivity than the high-alumina bricks used in the portion of the bottom wall 11 that faces the transfer space 10a. The insulating firebricks used here may have a thermal conductivity of, for example, 0.45 W / (m·K) or less, 0.43 W / (m·K) or less, 0.36 W / (m·K) or less, 0.28 W / (m·K) or less, or 0.22 W / (m·K) or less. The thermal conductivity values ​​listed here are those measured at 600°C by the hot wire method specified in JIS R2616. In the following description, when the thermal conductivity values ​​of insulating firebricks are mentioned, they refer to values ​​measured at 600°C by the above method unless otherwise specified.

[0027] Furthermore, in this embodiment, the portion of the bottom wall 11 that does not face the transfer space 10a is configured so that the thermal conductivity decreases toward the outside of the furnace body 10. In this embodiment, the thermal conductivity of brick 11b is 0.45 W / (m·K), the thermal conductivity of brick 11c is 0.43 W / (m·K), the thermal conductivity of brick 11d is 0.36 W / (m·K), the thermal conductivity of brick 11e is 0.28 W / (m·K), and the thermal conductivity of brick 11f is 0.22 W / (m·K). Also, in this embodiment, the thermal conductivity of brick 11a is 1.65 W / (m·K). Note that the thermal conductivity values ​​of brick 11a shown here are values ​​at 800°C measured by the hot wire method specified in JIS R2616.

[0028] Incidentally, the present inventors wish to improve the electrical insulation between the bricks 11a to 11f used in the bottom wall 11 and the lower heater 33. Furthermore, according to the knowledge of the present inventors, since the first through-holes 13a communicate with the inside and outside of the furnace body 10, some of the heat generated from the heat generating portion 33a of the lower heater 33 can be transmitted to the outside of the furnace body 10 through the first through-holes 13a.

[0029] FIG. 5 is a view of FIG. 4 as viewed from the direction of arrow V. The terminal portion 33b is sandwiched between a pair of boards 40 and 41 made of a ceramic material. In this embodiment, the terminal portion 33b is sandwiched between the pair of boards 40 and 41. As shown in FIG. 4, the pair of boards 40 and 41 are configured to be fitted into the first through hole 13a. The pair of boards 40 and 41 may be, for example, ceramic fiber boards. Ceramic fiber boards are formed by adding inorganic filler and inorganic / organic binders to so-called bulk fiber and molding them into a plate shape. In this embodiment, the boards 40 and 41 are ceramic fiber boards using alumina fiber as the ceramic fiber. The boards 40 and 41 may be ceramic fiber boards having a thermal conductivity lower than that of the bricks 11a to 11f used in the bottom wall 11. For example, the board materials 40, 41 may be ceramic fiber boards having a thermal conductivity of 0.18 W / (m·K) or less at 600°C. The thermal conductivity values ​​of the board materials 40, 41 shown here are values ​​at 600°C measured by the hot wire method specified in JIS R2616. The board materials 40, 41 may be made of the same material as that used for the pair of side walls 15, 16, or may be made of a different material. The pair of board materials 40, 41 have the same shape. The pair of board materials 40, 41 are arranged symmetrically in the vertical direction. The pair of board materials 40, 41 each have a main body portion 40a, 41a and a stopper portion 40b, 41b.

[0030] The main bodies 40a, 41a are portions that sandwich the terminal portion 33b. The main bodies 40a, 41a are fitted into the first through hole 13a. In this embodiment, the main bodies 40a, 41a are each formed in a substantially rectangular parallelepiped shape. The main bodies 40a, 41a may be configured such that, when the main bodies 40a, 41a are fitted into the first through hole 13a, a gap of, for example, about 5 mm to 10 mm is formed between the first through hole 13a and the main bodies 40a, 41a. For example, the length of the main bodies 40a, 41a in the front-rear direction may be about 5 mm to 10 mm shorter than the length of the first through hole 13a in the front-rear direction. For example, the length of the main bodies 40a, 41a in the up-down direction may be about 5 mm to 10 mm shorter than the length of the first through hole 13a in the up-down direction.

[0031] The stopper portions 40b, 41b protrude from the main body portions 40a, 41a, respectively. In this embodiment, the stopper portion 40b protrudes left, right, and downward from the main body portion 40a. The stopper portion 41b protrudes left, right, and upward from the main body portion 40a. When the main body portions 40a, 41a are fitted into the first through-hole 13a, the stopper portions 40b, 41b are pressed against the furnace body 10. In this embodiment, the stopper portions 40b, 41b are pressed against the left side portion 13 of the bottom wall 11.

[0032] As shown in FIG. 5, grooves 40c and 41c into which the terminal portions 33b are fitted are formed in the pair of board materials 40 and 41. In this embodiment, two grooves 40c are formed in the main body portion 40a of the board material 40, and two grooves 41c are formed in the main body portion 41a of the board material 41. The grooves 40c and 41c extend in the left-right direction and are formed linearly. The two grooves 40c are formed parallel to each other with a predetermined gap in the front-rear direction. Similarly, the two grooves 41c are formed parallel to each other with a predetermined gap in the front-rear direction. In this embodiment, the grooves 40c and 41c are formed semicircularly when viewed from the left-right direction. Note that in FIG. 4, the illustration of the board material 41 is partially omitted by adding broken lines, and only the board material 40 is shown in some places.

[0033] As shown in FIG. 3, the heating furnace 1 includes a tray 50 and a heat insulating material 55. The tray 50 is placed on the bottom wall 11. The tray 50 is preferably made of a highly heat-resistant material such as alumina. In this embodiment, the tray 50 is rectangular in plan view. The tray 50 has a mounting portion 52 on which the heat insulating material 55 is placed, and a peripheral portion 54 provided around the mounting portion 52. The peripheral portion 54 rises from the mounting portion 52. The upper end of the peripheral portion 54 is located above the mounting portion 52.

[0034] The heat insulating material 55 is placed on the placement portion 52 of the tray 50. The heat insulating material 55 is made of granular alumina. The heat insulating material 55 is arranged so as to overlap the heat generating portion 33a of the lower heater 33 when viewed from above. The heat insulating material 55 is preferably placed evenly on the tray 50 and arranged so as to overlap the entire heat generating portion 33a of the lower heater 33. Note that the heat insulating material 55 is not shown in FIG. 4.

[0035] As shown in FIG. 3, the heating furnace 1 includes a pipe 60 and a thermocouple 65. The pipe 60 and the thermocouple 65 are arranged at a predetermined interval along the conveying direction. The pipe 60 is made of an alumina material. The pipe 60 is formed in a cylindrical shape. The pipe 60 is inserted into the second through-hole 13b. The pipe 60 is arranged above the lower heater 33. The pipe 60 is arranged below the conveying rollers 20. A flange may be attached to the pipe 60. The outer diameter of the flange is preferably larger than the diameter of the second through-hole 13b. This makes it easier to attach the pipe 60 to the furnace body 10.

[0036] The thermocouple 65 is inserted into the pipe 60. The thermocouple 65 measures the temperature in the transfer space 10a. Here, the thermocouple 65 measures the temperature in the heating area 10c. The heating furnace 1 is preferably configured to control the output of the lower heater 33 based on the result of the temperature measurement by the thermocouple 65. The type of thermocouple 65 is not particularly limited, and any conventionally known thermocouple can be used as appropriate depending on the heating conditions, etc.

[0037] FIG. 6 is a schematic diagram showing an enlarged view of the vicinity of the lower heater 33 during replacement work for the lower heater 33. Note that FIG. 6 does not illustrate the boundaries between the bricks that make up the bottom wall 11. As shown in FIG. 6, a worker replacing the lower heater 33 removes the lower heater 33 by pulling the lower heater 33 together with the pair of board materials 40, 41 out of the first through-hole 13a. The worker then sandwiches the terminal portion 33b of the new lower heater 33 between the pair of board materials 40, 41. The worker installs the new lower heater 33 by fitting the pair of board materials 40, 41, with the terminal portion 33b of the new lower heater 33 sandwiched between them, into the first through-hole 13a.

[0038] According to the embodiment described above, the heating furnace 1 includes a furnace body 10, a plurality of conveying rollers 20, a drive unit 29, and a lower heater 33. A conveying space 10a is formed inside the furnace body 10, through which the workpiece 5 is conveyed along the conveying direction. The furnace body 10 includes a bottom wall 11, a pair of side walls 15 and 16, and a ceiling wall 17. The bottom wall 11 is located below the conveying rollers 20. The bottom wall 11 is made of brick. The bottom wall 11 has a first through hole 13a connecting the outside of the furnace body 10 with the conveying space 10a. The lower heater 33 is inserted into the first through hole 13a. The portion of the bottom wall 11 facing the conveying space 10a is made of high-alumina brick. The portion of the bottom wall 11 not facing the conveying space 10a is made of refractory insulating brick.

[0039] According to this heating furnace 1, the portion of the bottom wall 11 facing the transfer space 10a is made of high-alumina bricks, which have excellent heat resistance and mechanical strength. Therefore, even if the lower heater 33 collides with the bottom wall 11 during replacement work of the lower heater 33, the bottom wall 11 is unlikely to be damaged. This improves the durability of the furnace body 10.

[0040] On the other hand, high-alumina bricks are relatively expensive, so constructing the entire bottom wall 11 from high-alumina bricks would increase the cost of the heating furnace 1. However, according to the above-described embodiment, the portion of the bottom wall 11 that does not face the transfer space 10a is constructed from insulating firebricks. Insulating firebricks are relatively cheaper than high-alumina bricks. Therefore, the portion that is less likely to be hit by the lower heater 33 can be constructed relatively inexpensively. This makes it possible to improve the durability of the furnace body 10 while suppressing an increase in the cost of the heating furnace 1.

[0041] According to the above-described embodiment, the portion of the bottom wall 11 that does not face the transfer space 10a is configured so that the thermal conductivity decreases toward the outside of the furnace body 10. This configuration can improve the thermal insulation of the furnace body 10.

[0042] According to the above-described embodiment, the bottom 12 of the bottom wall 11 is made of bricks stacked with the brick joints offset, which prevents the temperature in the transfer space 10a from leaking to the outside and provides good thermal insulation. In addition, a stable stacked structure of the bottom 12 is achieved.

[0043] According to the embodiment described above, half of the area surrounding the first through hole 13a is made of high-alumina bricks. This configuration further reduces damage to the bottom wall 11 during the replacement work of the lower heater 33.

[0044] According to the embodiment described above, the lower heater 33 has a heat generating portion 33a and a terminal portion 33b. The heat generating portion 33a is disposed in the transfer space 10a. The heat generating portion 33a generates heat when energized. The terminal portion 33b electrically connects the heat generating portion 33a to a power source. The terminal portion 33b is sandwiched between a pair of board members 40, 41 made of a ceramic material. This prevents the terminal portion 33b from coming into direct contact with the bricks that form the bottom wall 11, thereby improving electrical insulation between the terminal portion 33b and the bricks that form the bottom wall 11.

[0045] According to the above-described embodiment, grooves 40c, 41c into which the terminal portion 33b is fitted are formed in the pair of board materials 40, 41, respectively, which allows the terminal portion 33b to be stably sandwiched.

[0046] According to the above-described embodiment, the pair of boards 40, 41 are configured to be fitted into the first through hole 13a. Thus, by fitting the pair of boards 40, 41 into the first through hole 13a, the lower heater 33 can be inserted into the first through hole 13a. Therefore, the lower heater 33 can be easily replaced. Furthermore, according to the above-described configuration, the lower heater 33 can be removed from the first through hole 13a by pulling out the pair of boards 40, 41 fitted into the first through hole 13a. Therefore, when removing the lower heater 33 from the first through hole 13a, the lower heater 33 is less likely to move in the front-to-back or up-to-down directions, and the lower heater 33 is prevented from colliding with the bottom wall 11. Furthermore, because the pair of boards 40, 41 block the first through hole 13a, heat transfer from the first through hole 13a to the outside of the furnace body 10 can be suppressed.

[0047] According to the above-described embodiment, the pair of board materials 40, 41 each have a main body portion 40a, 41a and a stopper portion 40b, 41b. The main body portions 40a, 41a sandwich the terminal portion 33b and are fitted into the first through-hole 13a. The stopper portions 40b, 41b protrude from the main body portions 40a, 41a, respectively. When the main body portions 40a, 41a are fitted into the first through-hole 13a, the stopper portion 41b is pressed against the furnace body 10. This prevents a worker replacing the lower heater 33 from over-fitting the pair of board materials 40, 41 into the first through-hole 13a. This makes it easier to position the lower heater 33 appropriately during replacement. Furthermore, since the entrance of the first through hole 13a is closed by the stopper portions 40b and 41b, the heat insulation of the furnace body 10 can be further improved.

[0048] According to the embodiment described above, the heating furnace 1 includes a tray 50 and a heat insulating material 55. The tray 50 is placed on the bottom wall 11. The heat insulating material 55 is placed on the tray 50. The heat insulating material 55 is made of granular alumina. The heat insulating material 55 is arranged so as to overlap the heat generating portion 33a of the lower heater 33 when viewed from above. This configuration can prevent the heat generating portion 33a from coming into direct contact with the bottom wall 11, thereby further preventing damage to the bottom wall 11 and disconnection of the lower heater 33.

[0049] According to the embodiment described above, the tray 50 has the mounting portion 52 on which the insulating material 55 is placed, and the peripheral portion 54 provided around the mounting portion 52. The peripheral portion 54 stands upright from the mounting portion 52. This prevents the insulating material 55 from spilling off the tray 50.

[0050] According to the embodiment described above, the bottom wall 11 has a second through hole 13b that connects the outside of the furnace body 10 with the transfer space 10a. A pipe 60 made of an alumina material is inserted into the second through hole 13b. A thermocouple 65 that measures the temperature of the transfer space 10a is inserted into the pipe 60. With this configuration, the thermocouple 65 is protected by the pipe 60. Furthermore, the thermocouple 65 can be attached and detached by inserting and removing the pipe 60 into the second through hole 13b, which makes it easy to replace the thermocouple 65.

[0051] Although one embodiment of the technology proposed here has been described above, the above embodiment is merely an example and the technology can be implemented in other modes.

[0052] In the above embodiment, the transfer space 10a is divided into the preheating area 10b, the heating area 10c, and the cooling area 10d. However, the transfer space 10a does not necessarily have to be divided into multiple areas. The transfer space 10a may be entirely composed of the heating area 10c.

[0053] In the above-described embodiment, the lower heater 33 is inserted in the left side portion 13 of the bottom wall 11. However, the lower heater 33 may be inserted in the right side portion 14 of the bottom wall 11. Also, the lower heater 33 may be inserted in both the left side portion 13 and the right side portion 14 of the bottom wall 11. Also, in the above-described embodiment, the thermocouple 65 is inserted in the left side portion 13 of the bottom wall 11. However, the thermocouple 65 may be inserted in the right side portion 14 of the bottom wall 11, or may be inserted in both the left side portion 13 and the right side portion 14 of the bottom wall 11.

[0054] In the above-described embodiment, the stopper portion 40b of the board material 40 protrudes to the left, right, and downward. However, the stopper portion 40b may protrude only to the left, only to the right, or only downward. Also, in the above-described embodiment, the stopper portion 41b of the board material 41 protrudes to the left, right, and upward. However, the stopper portion 40b may protrude only to the left, only to the right, or only upward.

[0055] In the above-described embodiment, the grooves 40c, 41c are formed in both of the pair of board materials 40, 41. However, the groove into which the terminal portion 33b of the lower heater 33 is fitted may be formed in at least one of the pair of board materials 40, 41. For example, the groove 40c may be formed in the board material 40, but the groove 41c may not be formed in the board material 41. Conversely, the groove 40c may not be formed in the board material 40, but the groove 41c may be formed in the board material 41.

[0056] In the above embodiment, the portion of the bottom wall 11 facing the transfer space 10a is made of high-alumina bricks. However, the portion of the bottom wall 11 facing the transfer space 10a may be made of a type of brick other than high-alumina bricks as long as it is made of dense refractory bricks. The portion of the bottom wall 11 facing the transfer space 10a may be made of, for example, a brick made of a zirconia-based electrocast refractory. Dense refractory bricks include high-alumina bricks and bricks made of a zirconia-based electrocast refractory. The dense refractory brick refers to a brick having a dense and stable crystalline phase. Here, the dense refractory brick has a bulk specific gravity of 1.0 or more as measured by the method specified in JIS R2205. The dense refractory brick does not include the insulating refractory bricks used in the portion of the bottom wall 11 not facing the transfer space 10a. Here, the insulating firebrick has a bulk specific gravity of less than 1.0 as measured by the method specified in JIS R2205.

[0057] The technology disclosed herein has been described in various ways. Unless otherwise specified, the embodiments and the like described herein do not limit the present invention. Furthermore, the technology disclosed herein can be modified in various ways, and as long as no particular problems arise, each component and each process described herein can be omitted or combined as appropriate. Furthermore, this specification includes the disclosures described in the following sections.

[0058] Section 1: a furnace body that defines a transport space therein through which the workpiece is transported along a transport direction; a plurality of conveying rollers arranged along the conveying direction; a drive device that rotates the plurality of conveying rollers; a heater that heats the object to be processed that is transported in the transport space; Equipped with The furnace body is a bottom wall made of bricks and located below the conveying roller; a pair of side walls extending upward from both sides of the bottom wall in the width direction; a ceiling wall supported by the pair of side walls; and the bottom wall has a first through hole connecting the outside of the furnace body and the transfer space, the heater is inserted into the first through hole, a portion of the bottom wall facing the transfer space is made of dense refractory bricks, a portion of the bottom wall that does not face the transfer space is made of insulating firebricks;

[0059] Section 2: Item 2. The heating furnace according to item 1, wherein a portion of the bottom wall facing the transfer space is made of high-alumina bricks.

[0060] Section 3: The portion of the bottom wall that does not face the transfer space is Item 3. The heating furnace according to item 1 or 2, wherein the furnace body is configured so that the thermal conductivity decreases toward the outside.

[0061] Section 4: The heater is a heat generating portion that is disposed in the transfer space and generates heat when energized; a terminal portion that electrically connects the heat generating portion to a power source; and Item 4. The heating furnace according to any one of items 1 to 3, wherein the terminal portion is sandwiched between a pair of board materials made of a ceramic material.

[0062] Section 5: Item 5. The heating furnace according to item 4, wherein at least one of the pair of boards has a groove formed therein into which the terminal portion is fitted.

[0063] Item 6: Item 6. The heating furnace according to item 4 or 5, wherein the pair of board materials are configured to be fitted into the first through holes.

[0064] Section 7: The pair of board materials are: a main body portion that sandwiches the terminal portion and is fitted into the first through hole; a stopper portion protruding from the main body portion; and Item 7. The heating furnace according to item 6, wherein the stopper portion is pressed against the furnace body when the main body portion is fitted into the first through hole.

[0065] Section 8: a tray placed on the bottom wall; a heat insulating material made of granular alumina placed on the tray; Equipped with The heater is a heat generating portion that is disposed in the transfer space and generates heat when energized; a terminal portion that electrically connects the heat generating portion to a power source; and 8. The heating furnace according to any one of items 1 to 7, wherein the heat insulating material is arranged so as to overlap the heat generating portion when viewed from above.

[0066] Section 9: the bottom wall has a second through hole connecting the outside of the furnace body and the transfer space, a pipe made of an alumina material is inserted into the second through hole; Item 9. The heating furnace according to any one of items 1 to 8, wherein a thermocouple for measuring the temperature of the transfer space is inserted into the pipe. [Explanation of symbols]

[0067] 1 Furnace 5. Material to be processed 10 Furnace body 10a Transfer space 11 Bottom wall 13a 1st through hole 13b 2nd through hole 20 Conveyor roller 29 Drive unit 33 Lower heater (heater) 33a Heat generating part 33b Terminal section 40, 41 Board material 40a, 41a Main body 40b, 41b Stopper part 40c, 41c groove 50 trays 55 Insulation 60 Pipe 65 Thermocouple

Claims

1. a furnace body that defines a transport space therein through which the workpiece is transported along a transport direction; a plurality of conveying rollers arranged along the conveying direction; a drive device that rotates the plurality of conveying rollers; a heater that heats the object to be processed that is transported in the transport space; Equipped with The furnace body is a bottom wall made of bricks and located below the conveying roller; a pair of side walls extending upward from both sides of the bottom wall in the width direction; a ceiling wall supported by the pair of side walls; and the bottom wall has a first through hole connecting the outside of the furnace body and the transfer space, the heater is inserted into the first through hole, a portion of the bottom wall facing the transfer space is made of dense refractory bricks, a portion of the bottom wall that does not face the transfer space is made of insulating firebricks;

2. 2. The heating furnace according to claim 1, wherein a portion of said bottom wall facing said transfer space is made of high-alumina bricks.

3. The portion of the bottom wall that does not face the transfer space is The heating furnace according to claim 1 , wherein the furnace body is configured so that the thermal conductivity decreases toward the outside.

4. The heater is a heat generating portion that is disposed in the transfer space and generates heat when energized; a terminal portion that electrically connects the heat generating portion to a power source; and 2. The heating furnace according to claim 1, wherein the terminal portion is sandwiched between a pair of board members made of a ceramic material.

5. The heating furnace according to claim 4 , wherein at least one of the pair of boards has a groove formed therein into which the terminal portion is fitted.

6. The heating furnace according to claim 4 , wherein the pair of board materials are configured to be fitted into the first through holes.

7. The pair of board materials are: a main body portion that sandwiches the terminal portion and is fitted into the first through hole; a stopper portion protruding from the main body portion; and The heating furnace according to claim 6 , wherein the stopper portion is pressed against the furnace body when the main body portion is fitted into the first through hole.

8. a tray placed on the bottom wall; a heat insulating material made of granular alumina placed on the tray; Equipped with The heater is a heat generating portion that is disposed in the transfer space and generates heat when energized; a terminal portion that electrically connects the heat generating portion to a power source; and The heating furnace according to claim 1 , wherein the heat insulating material is arranged so as to overlap the heat generating portion when viewed from above.

9. the bottom wall has a second through hole connecting the outside of the furnace body and the transfer space, a pipe made of an alumina material is inserted into the second through hole; 2. The heating furnace according to claim 1, wherein a thermocouple for measuring a temperature of the transfer space is inserted into the pipe.

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