Electric furnace

Abstract

To provide an electric furnace allowing easy control of temperature in the furnace during burning.SOLUTION: An electric furnace 1 has a lower wall 20, a left wall 22, a right wall 24, a rear wall 26, an upper wall 28 and a lid 30 forming a furnace inner space FS, heaters 21 and refrigerant pipes 34 provided in the furnace inner space FS, and a refrigerant supply part 6 supplying refrigerant into the refrigerant pipes 34. Each heater 21 is arranged at a lower part of the furnace inner space FS, each refrigerant pipe 34 is arranged at an upper part of the furnace inner space FS. The furnace walls include fireproof bricks 20A-30A.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an electric furnace for firing ceramic products and the like.

Background Art

[0002] As a ceramic firing kiln, the one described in Japanese Utility Model Laid-Open No. 5-94696 (Patent Document 1) is known. In this ceramic firing kiln, an air cooling layer that is forcibly blown by a blower is provided on the outer wall of the firing kiln that fires ceramics with the heat source of an electric heater, and the discharged air from the air cooling layer is introduced into the electric furnace.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the above ceramic firing kiln, by forcibly blowing air into the air cooling layer by a blower, the kiln wall is rapidly cooled after firing, and the cooling time after firing is shortened to about 1 / 2 to 2 / 3. Also, if the air heated in the air cooling layer is introduced into the inside of the kiln, the cooling rate after firing can be further increased. Furthermore, if the heated air of the air cooling layer is sent into the furnace during the initial heating in the electric furnace kiln, the gas generated from the glaze and the product fabric is forcibly exhausted by the heating air with a small temperature difference from the temperature inside the furnace, and the quality of the fired product is improved. However, in the above ceramic firing kiln, an air cooling layer is provided on the outer wall of the firing kiln, and the air cooling layer is not used for adjusting the temperature inside the furnace during firing. That is, in the above ceramic firing kiln, the temperature adjustment inside the furnace during firing is solely performed by an electric heater. Therefore, there is room for improvement in the temperature adjustment inside the furnace during firing.

[0005] Therefore, the main object of the present invention is to provide an electric furnace in which the temperature adjustment inside the furnace during firing can be more accurately performed.

Means for Solving the Problems

[0006] The invention according to claim 1 is comprising a plurality of refractory bricks, a furnace wall forming an inner furnace space, and an electric heater provided on at least one of the inner furnace space and the furnace wall a heater, and a refrigerant pipe disposed at the upper part of the furnace interior space, and a refrigerant supply unit for supplying a refrigerant into the refrigerant pipe, and is wherein the refrigerant pipe passes between the refractory bricks forming the upper part of the furnace interior space and the refractory bricks forming the side part of the furnace interior space and extends outside the furnace interior space characterized by this. Claim 2 The invention according to is, in the above invention, characterized in that the electric heater is an infrared heater having a carbonaceous heating element that emits infrared rays when energized. Claim 3 The invention according to is, in the above invention, characterized in that the carbonaceous heating element has a meandering shape. Claim 4 The invention according to is, in the above invention, characterized in that the infrared heater has a quartz glass tube. Claim 5 The invention according to is, in the above invention, further characterized by comprising a control unit for controlling the calorific value of the electric heater and the supply amount of the refrigerant. Claim 6 The invention according to is, in the above invention, characterized in that the control unit has an input unit for inputting temperature transition setting information which is information related to the transition of a set temperature, and based on the input temperature transition setting information, controls at least one of the calorific value of the electric heater and the supply amount of the refrigerant.

Effects of the Invention

[0007] The main effect of the present invention is that an electric furnace in which the temperature adjustment inside the furnace during firing can be more accurately performed is provided.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Embodiments for Carrying Out the Invention

[0009] Hereinafter, examples of embodiments according to the present invention, together with their modified examples, will be described as appropriate based on the drawings. Note that the present embodiment is not limited to the following examples and modified examples.

[0010] FIG. 1 is a front view of an electric furnace 1 (open lid state) according to the present invention. FIG. 2 is a sectional view taken along line A-A of the furnace 4 portion in FIG. 1 (however, in the closed lid state). FIG. 3 is a sectional view taken along line C-C of FIG. 2. FIG. 4 is a sectional view taken along line B-B of FIG. 3. The electric furnace 1 includes a base 2, a furnace 4, a refrigerant supply unit 6, a shelf plate 8, and a control unit 9. Note that in FIGS. 1 and 3, the top is the top of the electric furnace 1, and the left is the left of the electric furnace 1. Also, in FIG. 2, the top is the rear of the electric furnace 1, and the right is the right of the electric furnace 1. Such a direction of the electric furnace 1 is defined for convenience of explanation and may change depending on the movement and installation modes of various members and parts.

[0011] The base 2 has a plurality (four) of casters 10. The rolling of each caster 10 can be locked. The base 2 is movable when the locking of each caster 10 is released. Note that in FIGS. 2 to 4, part or all of the base 2 is omitted.

[0012] The furnace 4 is installed on the base 2. The furnace 4 includes a lower wall 20, a plurality (8) of heaters 21, a left wall 22, a right wall 24, a rear wall 26, an upper wall 28, a lid 30, a plurality (2) of lid retainers 32, a plurality (8) of refrigerant pipes 34, and a temperature sensor 36.

[0013] The lower wall 20 includes a plurality of refractory bricks 20A. Each refractory brick 20A is arranged on the top surface of the base 2 adjacent to each other. Each refractory brick 20A is held by the base 2.

[0014] Each heater 21 is provided on the lower wall 20. Each heater 21 is installed on a series of upper surfaces by each refractory brick 20A. Each heater 21 extends in the left - right direction and is arranged in the front - rear direction on the said upper surface. Incidentally, each heater 21 may be 7 or less, or may be 9 or more. Also, each heater 21 does not have to be arranged on the upper surface of each refractory brick 20A. For example, each heater 21 may be embedded in each refractory brick 20A or may be arranged in a hole provided in each refractory brick 20A. FIG. 5(A) is a top view of the heater 21 in FIG. 4. FIG. 5(B) is a front view of the heater 21 in FIG. 4. Each heater 21 is an electric heater that generates heat electrically. Each heater 21 has a quartz glass tube 40, a carbonaceous heating element 42, a plurality (2) of insulators 44, a plurality (2) of internal conductors 46, and a plurality (2) of heater conductors 48.

[0015] The quartz glass tube 40 is tubular and extends left - right, and more specifically, is cylindrical. An inert gas (for example, argon gas) is enclosed in the quartz glass tube 40. The quartz glass tube 40 passes infrared rays.

[0016] The carbonaceous heating element 42 is arranged in the quartz glass tube 40. The carbonaceous heating element 42 has the same length as the quartz glass tube 40. The carbonaceous heating element 42 is formed from a carbonaceous plate. The carbonaceous heating element 42 is in a horizontal posture. Incidentally, the posture of the carbonaceous heating element 42 may be other than horizontal. For example, when each heater 21 is arranged in a "U" shape in side view along the virtual curved surface as in the above-described modification example, the posture of the carbonaceous heating element 42 may be along the virtual curved surface. The carbonaceous plate has slits of the same length alternately and at equal intervals from both the left and right sides over the entire body except for the ends. Therefore, the carbonaceous heating element 42 has a meandering shape. The carbonaceous heating element 42 radiates infrared rays when energized.

[0017] Each insulator 44 is in the shape of a rectangular parallelepiped. Each insulator 44 has heat resistance and insulation properties. The first insulator 44 is provided at the left end of the quartz glass tube 40. The second insulator 44 is provided at the right end of the quartz glass tube 40. Each insulator 44 is a heating element support portion that supports the carbonaceous heating element 42. Also, each insulator 44 is a heater wire support portion that supports the heater wire 48.

[0018] Each internal wire 46 has conductivity. Each internal wire 46 is disposed inside the quartz glass tube 40. The first internal wire 46 is electrically connected to the left end of the carbonaceous heating element 42. The second internal wire 46 is electrically connected to the right end of the carbonaceous heating element 42.

[0019] Each heater wire 48 has a covering portion and a wire portion disposed therein. Each wire portion has conductivity. The wire portion of the first heater wire 48 is electrically connected to the first internal wire 46. The first heater wire 48 passes through the first insulator 44 and extends downward (in the radial direction of the heater 21). The wire portion of the second heater wire 48 is electrically connected to the second internal wire 46. The second heater wire 48 passes through the second insulator 44 and extends downward (in the radial direction of the heater 21).

[0020] When the carbonaceous heating element 42 of each heater 21 receives power supply through each heater wire 48 and each internal wire 46, it lights up, emits infrared rays, and generates heat with a calorific value corresponding to the amount of electric power. The quartz glass tube 40, each abrasive grain 44, each internal wire 46, and each heater wire 48 are non-heating parts. That is, those other than the carbonaceous heating element 42 that actively generate heat by electric power indirectly generate heat by receiving heat from the carbonaceous heating element 42, but do not become heating parts.

[0021] The left wall 22 includes a plurality of refractory bricks 22A and a brick holding plate 22B. Each refractory brick 22A is formed in the same manner as the refractory brick 20A. The brick holding plate 22B is a metal plate. The brick holding plate 22B holds each refractory brick 22A. Each refractory brick 22A is disposed on the right side of the right surface, which is the inner surface of the brick holding plate 22B in the left-right direction. Incidentally, the brick holding plate may be included in the lower wall 20. Also, one or more heaters 21 may be provided on the left wall 22.

[0022] The right wall 24 includes a plurality of refractory bricks 24A and a brick holding plate 24B. Each refractory brick 24A is formed in the same manner as the refractory brick 20A. The brick holding plate 24B is formed in the same manner as the brick holding plate 22B. The brick holding plate 24B holds each refractory brick 24A. Each refractory brick 24A is disposed on the left side of the left surface of the brick holding plate 24B. Incidentally, one or more heaters 21 may be provided on the right wall 24.

[0023] The rear wall 26 includes a plurality of refractory bricks 26A and a brick holding plate 26B. Each refractory brick 26A is formed in the same manner as the refractory brick 20A. The brick holding plate 26B is formed in the same manner as the brick holding plate 22B. The brick holding plate 26B holds each refractory brick 26A. Each refractory brick 26A is disposed on the front side of the front surface of the brick holding plate 26B. Incidentally, one or more heaters 21 may be provided on the rear wall 26.

[0024] The upper wall 28 includes a plurality of refractory bricks 28A, a brick holding plate 28B, and a plurality of bolts 28C. Each refractory brick 28A is formed in the same manner as the refractory brick 20A. The brick holding plate 28B is formed in the same manner as the brick holding plate 22B. The brick holding plate 28B holds each refractory brick 28A. Each refractory brick 28A is disposed below the lower surface of the brick holding plate 28B. Each bolt 28C extends in the left - right direction and passes through each refractory brick 28A. Each bolt 28C connects the inside of each refractory brick 28A. In addition, one or more heaters 21 may be provided on the upper wall 28. Also, bolts 28C may be provided on the lower wall 20 or the like.

[0025] The lid 30 is rotatably attached about its lower side at the front side of the lower wall 20. The lid 30 includes a plurality of refractory bricks 30A, a brick holding plate 30B, and a plurality (two) of hinges 30C. Each refractory brick 30A is formed in the same manner as the refractory brick 20A. The brick holding plate 30B is made of metal and is box - shaped with an opening at the rear (above when the lid is opened). Inside the brick holding plate 30B, each refractory brick 30A is placed. The brick holding plate 30B holds each refractory brick 30A. Each hinge 30C is arranged left - right. Each hinge 30C is interposed between the lower wall 20 and the lid 30. In addition, one or more heaters 21 may be provided on the lid 30.

[0026] A rectangular - parallelepiped - shaped furnace interior space FS is formed by the lower wall 20, the left wall 22, the right wall 24, the rear wall 26, the upper wall 28, and the closed lid 30. The lower wall 20, the left wall 22, the right wall 24, the rear wall 26, the upper wall 28, and the lid 30 are furnace walls. The furnace interior space FS is surrounded by the refractory bricks 20A - 30A. At the lower end of the furnace interior space FS, each heater 21 is disposed. The furnace space FS may have a shape other than a rectangular parallelepiped. For example, the furnace space FS may have a spherical or elliptical shape.

[0027] The lid holders 32 are disposed on the left and right sides of the front surface of the top wall 28. Each lid holder 32 pinches the top edge of the closed lid 30 between itself and the front surface of the top wall 28, thereby pressing the top edge of the lid 30 backward and maintaining the lid 30 in a closed state. Furthermore, when the clamping of each lid holder 32 is released, the lid 30 can be opened by rotating around each hinge 30C. The opened lid 30 can come into contact with the top surface of the base 2.

[0028] Each refrigerant pipe 34 is a metal pipe. Each refrigerant pipe 34 is installed on a continuous lower surface (upper surface of the furnace space FS) formed by each refractory brick 28A of the upper wall 28. Each refrigerant pipe 34 extends in the left-right direction and is aligned in the front-rear direction below the lower surface. That is, each refrigerant pipe 34 is arranged at the upper end of the furnace space FS. The right portion of each refrigerant pipe 34 passes between the right wall 24 and the upper wall 28 and protrudes outside the furnace space FS. To allow the right portion of each refrigerant pipe 34 to pass through, a downwardly recessed groove 24P is formed in the corresponding upper end firebrick 24A on the right wall 24. A total of two grooves 24P are formed, one in front of and one behind the temperature sensor 36, with multiple (17) refrigerant pipes 34 entering the front groove 24P and multiple (13) refrigerant pipes 34 entering the rear groove 24P. In addition, the brick holding plate 24B of the right wall 24 has holes extending left and right to allow each refrigerant pipe 34 to pass through. Similarly, the left portion of each refrigerant pipe 34 passes between the left wall 22 and the upper wall 28 (groove 22P) and protrudes outside the furnace space FS. The total number of refrigerant pipes 34 may be 29 or less, or 31 or more. The number of refrigerant pipes 34 inserted into the front and rear grooves 22P, 24P may also be changed in various ways, such as making the number of refrigerant pipes 34 equal in the front and rear grooves. The grooves 22P, 24P may be provided for each refrigerant pipe 34. Furthermore, each refrigerant pipe 34 does not have to be disposed on the lower surface of each refractory brick 28A. For example, the center portion of each refrigerant pipe 34 may be entirely embedded in each refractory brick 28A, or may be disposed in a hole provided in each refractory brick 28A.

[0029] The temperature sensor 36 is a sensor that detects the temperature of the furnace space FS (furnace temperature). The temperature sensor 36 is a thermocouple that extends vertically. The temperature sensor 36 penetrates the upper wall 28. A temperature detection unit is disposed at the lower end of the temperature sensor 36 disposed within the furnace space FS. On the other hand, a terminal for connecting to the control unit 9 is disposed at the upper end of the temperature sensor 36 disposed outside the furnace space FS.

[0030] The refrigerant supply unit 6 has a supply tank 50, a supply pipe 52, a discharge tank 54, and a discharge pipe 56 (see FIG. 1). The supply-side tank 50 is box-shaped and extends forward and backward, and is connected to the right ends of each of the refrigerant pipes 34. The supply-side pipe 52 connects the refrigerant source CS to the supply-side tank 50. The supply-side pipe 52 is capable of supplying the refrigerant (water) from the refrigerant source CS to each of the refrigerant pipes 34 via the supply-side tank 50. The supply-side tank 50 may be omitted, in which case the supply-side pipe 52 may branch into each of the refrigerant pipes 34. The refrigerant may be something other than water, such as air. The discharge tank 54 is box-shaped and extends forward and backward, and is connected to the left ends of each refrigerant pipe 34. The discharge pipe 56 connects the supply tank 50 and the refrigerant source CS. The refrigerant circulates. The discharge pipe 56 can discharge the refrigerant from each refrigerant pipe 34 through the discharge tank 54. The discharge tank 54 may be omitted, in which case the refrigerant pipes 34 may be joined together to form the discharge pipe 56. The refrigerant may also be cooled by a cooling unit. Furthermore, the refrigerant does not have to circulate to the refrigerant source CS.

[0031] The shelf board 8 is heat-resistant and table-shaped, and can be placed in the furnace space FS with an object to be heated placed thereon. The object to be heated is a ceramic product (tile sample TL). Note that the object to be heated may be something other than a ceramic product (tile sample TL). The shelf board 8 may be plate-shaped. In this case, the shelf board 8 may be installed in the furnace interior space FS via one or more separate legs. Part or all of the legs may be made of refractory bricks or may be formed of refractory bricks.

[0032] The control unit 9 is provided outside the base 2. The control unit 9 is only shown in FIG. 1. Incidentally, the control unit 9 may be provided integrally with the base 2. Also, the control unit 9 may not be included in the components of the electric furnace 1. The control unit 9 controls at least one of various members and parts, and here it is a computer. The control unit 9 includes an arithmetic unit 60, a storage unit 62, an input unit 64, an output unit 66, and an interface 68. The arithmetic unit 60 (CPU) is connected to the other parts respectively and controls the other parts. The storage unit 62 (memory) stores various information. The input unit 64 (keyboard, pointing device) receives the input of various information. The output unit 66 (monitor) outputs various information. The interface 68 exchanges information with the outside. The heaters 21, the temperature sensor 36, and the refrigerant supply unit 6 are connected to the interface 68. Incidentally, the control unit 9 may be other than the above. For example, the output unit 66 may be a printer instead of or together with the monitor.

[0033] Based on the furnace interior temperature obtained from the temperature sensor 36, the control unit 9 controls at least one of the power to each heater 21 (heating by each heater 21) and the supply of the refrigerant from the refrigerant supply unit 6 (cooling by the refrigerant supply unit 6) to control the furnace interior temperature. Due to the convection caused by the heating of each heater 21 located at the bottom of the furnace space FS, the air at the bottom of the heated furnace space FS moves to the top, thereby uniformizing the temperature inside the furnace. When a refrigerant is passed through each refrigerant pipe 34 located at the top of the furnace space FS and the air at the top of the furnace space FS is cooled, an air flow opposite to the convection before cooling begins occurs within the furnace space FS, further promoting the uniformity of the temperature inside the furnace.

[0034] An example of the operation of such an electric furnace 1 will be described below. The user places the objects to be heated (tile samples TL before firing) on the shelf boards 8, places them in the furnace space FS, closes the lid 30, and fixes the lid 30 with each lid holder 32.

[0035] 6, the user inputs any (desired) temperature transition setting information to the control unit 9 via the input unit 64. In addition, based on the display on the output unit 66 as shown in FIG. That is, the calculation unit 60 receives the input of the temperature transition setting information, and causes the output unit 66 to display a temperature transition setting information input screen TM. The temperature trend setting information input screen TM has a step display section 70, a process time display section 72, a cumulative time display section 73, a set temperature display section 74, a scroll bar 75, an operating status display section 76, a menu symbol display section 77, an add button 78, a delete button 79, and a set button 80. In the step display section 70, serial numbers relating to steps (process numbers) are displayed from top to bottom. The process time display section 72 displays the process time for each step. The cumulative time display section 73 displays the total process time. The set temperature display section 74 displays the set temperature for each step. A scroll bar 75 is displayed to change the display range if not all steps fit. The operating state display section 76 displays the operating state of the electric furnace 1 . In the menu symbol display unit 77, a symbol corresponding to the currently displayed menu is displayed. The menu is the type of temperature transition setting information. Also, the menu is switched by input to the menu symbol display unit 77. The add button 78 is displayed to receive an input for adding a step. The delete button 79 is displayed to receive an input for deleting a step. The setting button 80 is displayed to receive an input for finalizing the temperature transition setting information.

[0036] The user adjusts the number of steps by input to the add button 78 and the delete button 79. Furthermore, the user inputs the duration of the step by input to the process time display unit 72. Also, the user inputs the set temperature for the step by input to the set temperature display unit 74. When the user has completed input of the temperature transition setting information related to this menu, the user makes an input to the setting button 80. The temperature transition setting information is stored in the storage unit 62. The temperature transition setting information is information related to the transition of the set temperature. In addition, when the set temperature transition setting information is in a predetermined mode or not in a specific mode, the control unit 9 can display an error and prompt for input correction. For example, when the control unit 9 does not reach a predetermined temperature or lower, such as room temperature, at the final step, it can display an error. Also, when an error exists, the control unit 9 does not have to start the operation related to the temperature transition setting information.

[0037] Then, the user issues a command to start the operation to the control unit 9 through the input unit 64. Then, the control unit 9 starts the operation of the electric furnace 1 based on the temperature transition setting information related to the selected menu. Also, the calculation unit 60 outputs an operation-time screen DM, which is a display during operation as shown in FIG. 7, at the output unit 66. During operation, the operation screen DM includes a current temperature display unit 82, a temperature change graph display unit 83, a left movement button 84, a right movement button 85, a magnification button 86, and a reduction button 87. Further, on the operation screen DM, following the temperature change setting information input screen TM, an operation state display unit 76, a menu symbol display unit 77, and a setting button 80 are displayed. In the current temperature display unit 82, the current temperature inside the furnace is displayed. The control unit 9 stores, in the storage unit 62, the temperature change information during operation, which is the temperature inside the furnace every predetermined time (for example, 5 minutes) from the start of operation. In the temperature change graph display unit 83, a temperature change graph is displayed. The vertical axis of the temperature change graph is temperature. The horizontal axis of the temperature change graph is the elapsed time (operation time) from the start of operation. In the temperature change graph display unit 83, the temperature change (broken line L1) of the temperature change setting information and the temperature change (broken line L2) of the temperature change information during operation up to the current time are displayed. The left movement button 84 and the right movement button 85 are displayed to move the display on the temperature change graph display unit 83 left and right based on an input. The magnification button 86 and the reduction button 87 are displayed to perform magnification and reduction of the display on the temperature change graph display unit 83 based on an input.

[0038] When the current temperature inside the furnace is equal to or lower than the set temperature at the same elapsed time in the temperature change setting information, the control unit 9 supplies power to each heater 21 to heat the furnace space FS. The control unit 9 determines the amount of electric power (heat amount of each heater 21) to each heater 21 according to the temperature difference between the temperature inside the furnace and the set temperature. In this case, the control unit 9 stops the supply of the refrigerant into each refrigerant pipe 34. Further, when the temperature inside the furnace exceeds the set temperature, the control unit 9 supplies power to each heater 21 to heat the furnace interior space FS, and supplies refrigerant into each refrigerant pipe 34 to cool the furnace interior space FS. The control unit 9 determines the amount of power supplied to each heater 21 (the amount of heat of each heater 21) and the supply amount of refrigerant into each refrigerant pipe 34 (the cooling amount by each refrigerant pipe 34) according to the temperature difference between the temperature inside the furnace and the set temperature. Here, unlike the electric furnace 1, when the cooling of the furnace interior space FS is performed by blowing cold air into the furnace interior space FS, even if the arrangement of the air outlets or the like is changed in various ways, temperature unevenness will occur in the furnace interior space FS for a relatively long period. In contrast, in the electric furnace 1, the cooling of the furnace interior space FS is performed by supplying refrigerant into each refrigerant pipe 34, so temperature unevenness in the furnace interior space FS is suppressed. Also, in the electric furnace 1, since the cooling by supplying refrigerant into each refrigerant pipe 34 can be performed simultaneously with the heating by each heater 21, fine adjustment of the furnace temperature is easy to perform. Furthermore, when the temperature inside the furnace exceeds the set temperature by a predetermined degree or more, the control unit 9 supplies refrigerant into each refrigerant pipe 34 to cool the furnace interior space FS. In this case, the control unit 9 stops the power supply to each heater 21. In addition, the control unit 9 may perform other controls. For example, when the temperature inside the furnace exceeds the set temperature for a predetermined time or more, cooling by each refrigerant pipe 34 may be used in combination. Also, the cooling by each refrigerant pipe 34 in a state where heating by each heater 21 is not performed may be performed only when the slope of the temperature transition in the temperature transition setting information is a predetermined value or more. Furthermore, when a hold for a predetermined time or more at a predetermined temperature is set in the temperature transition setting information, the control unit 9 may basically supply a predetermined amount of power to each heater 21 and a predetermined amount of refrigerant to each refrigerant pipe 34, and perform fine adjustment according to the temperature inside the furnace at the current time. In addition, the control unit 9 may divide each heater 21 into a plurality of parts and perform independent control for each of those parts, and similarly divide each refrigerant pipe 34 into a plurality of parts and perform independent control for each of those parts.

[0039] By the control by such a control unit 9, the temperature inside the furnace changes according to the temperature transition setting information. In particular, since heating by the heaters 21 and cooling by the refrigerant pipes 34 can be used in combination, the temperature inside the furnace can be controlled more precisely than when the temperature inside the furnace is controlled only by controlling the amount of heat generated by the heaters 21. In this example, a maximum of 1550 W (watts) of power is applied to each heater 21 from a three-phase 200V commercial power supply, and the eight heaters 21 generate heat equivalent to 12.4 kW. The efficiency of power-to-heat conversion in each heater 21 is extremely good, approaching 100%, due to the use of a carbonaceous heating element 42, etc. Furthermore, the use of a carbonaceous heating element 42, etc., allows each heater 21 to reach its maximum heat output in an extremely short time after power supply begins. Furthermore, the use of a quartz glass tube 40 and a carbonaceous heating element 42, etc., makes each heater 21 less susceptible to overshooting, which is common with sheathed heaters, and it is lighter than sheathed heaters. Therefore, the temperature inside the furnace can easily reach about 1300°C. When the temperature inside the furnace reaches about 1000°C or higher, the refractory bricks 20A to 30A become red hot. Each of the refractory bricks 20A to 30A accumulates and slowly releases heat, thereby contributing to maintaining the temperature inside the furnace.

[0040] The control unit 9 stops the operation when all steps of the temperature transition setting information are completed. Note that the control unit 9 may stop the operation midway based on a predetermined input to the input unit 64. The user confirms that the temperature inside the furnace has cooled to about room temperature, or that the specified standing time has elapsed, then operates each lid holder 32 to open the lid 30 and removes the shelf 8 on which the baked object to be heated is placed.

[0041] Such an electric furnace 1 provides the following effects. That is, the electric furnace 1 includes a lower wall 20, a left wall 22, a right wall 24, a rear wall 26, an upper wall 28, and a lid 30 that form an interior space FS, a heater 21 and a refrigerant pipe 34 that are provided in the interior space FS, and a refrigerant supply unit 6 that supplies refrigerant into the refrigerant pipe 34. Thus, an electric furnace 1 is provided that makes it easier to more accurately adjust the temperature inside the furnace 4 during firing. In addition, each heater 21 is disposed at the lower part of the furnace interior space FS, and each refrigerant pipe 34 is disposed at the upper part of the furnace interior space FS. Therefore, temperature unevenness in the furnace interior space FS is suppressed. Furthermore, the furnace wall includes refractory bricks 20A to 30A. Therefore, the furnace interior temperature can be maintained more appropriately.

[0042] In addition, each heater 21 is an infrared heater having a carbonaceous heating element 42 that emits infrared rays when energized. Further, the carbonaceous heating element 42 has a meandering shape. Therefore, heating required for firing ceramic products or the like can be obtained more easily. Furthermore, each heater 21 has a quartz glass tube 40. The melting point of the quartz glass tube 40 is approximately 1600°C. Therefore, each heater 21 that can sufficiently withstand high temperatures, and thus the electric furnace 1, are provided.

[0043] Moreover, the electric furnace 1 includes a control unit 9 that controls the calorific value of each heater 21 and the supply amount of the refrigerant. Therefore, the furnace interior temperature is controlled even more accurately. In addition, the control unit 9 has an input unit 64 that inputs temperature transition setting information, which is information related to the transition of the set temperature, and controls at least one of the calorific value of each heater 21 and the supply amount of the refrigerant to each refrigerant pipe 34 based on the input temperature transition setting information. Therefore, the furnace interior temperature is controlled according to the transition of the set temperature desired by the user.

[0044] Note that the above-described embodiment or modification example of the present invention may further appropriately have the following modification examples. Instead of the heater 21, or together with the heater 21, an electric heater that heats by radiation other than infrared rays or the like may be used. The material of various members or parts may be changed, such as the base 2 being made of heat-resistant plastic. It is also possible to change at least one of the number and arrangement of various members or parts, such as arranging some or all of each heater 21 to extend in the front-rear direction, arranging some or all of each refrigerant pipe 34 to extend in the front-rear direction, or arranging the refractory bricks 20A to 30A only on the lower wall 20. The change in the number of various members or parts may include setting it to zero, that is, omitting various members or parts.

Explanation of Signs

[0045] 1··Electric furnace, 6··Refrigerant supply section, 9··Control section, 20··Lower wall (furnace wall), 21··Heater (electric heater), 22··Left wall (furnace wall), 24··Right wall (furnace wall), 26··Rear wall (furnace wall), 28··Upper wall (furnace wall), 30··Lid (furnace wall), 20A to 30A··Refractory bricks, 34··Refrigerant pipe, 40··Quartz glass tube, 42··Carbonaceous heating element, 64··Input section, FS··Furnace interior space.

Claims

Claim 1: An electric furnace comprising a plurality of refractory bricks and a furnace wall forming a furnace interior space, an electric heater provided in at least one of the furnace interior space and the furnace wall, a refrigerant pipe disposed at an upper portion of the furnace interior space, a refrigerant supply unit for supplying a refrigerant into the refrigerant pipe, wherein the refrigerant pipe passes between the refractory bricks forming the upper portion of the furnace interior space and the refractory bricks forming the side portion of the furnace interior space and extends outside the furnace interior space. Claim 2: The electric heater is an infrared heater having a carbonaceous heating element that emits infrared rays upon energization. Claim 3: The carbonaceous heating element has a meandering shape. Claim 4: The infrared heater has a quartz glass tube. Claim 5: The electric furnace according to any one of Claims 1 to 4, further comprising a control unit configured to control a calorific value of the electric heater and a supply amount of the refrigerant. Claim 6: The control unit has an input unit configured to input temperature transition setting information, which is information related to a transition of a set temperature, and controls at least one of the calorific value of the electric heater and the supply amount of the refrigerant based on the input temperature transition setting information. ​ ​ ​ ​ ​ ​ ​

Images