Oven

Abstract

To provide an oven having a heating mechanism for improving heating efficiency.SOLUTION: An oven of the present invention includes: a plurality of linear burners which are placed inside the over or aligned in a horizontal direction above a food that moves inside the oven, and which have a burning port in one horizontal direction; and a plurality of far-infrared radiation generating plates which are made of thin metal plates having a ceramic coating layer only on a lower surface, and are provided so as to cover each of the burners and a flame blown out in one horizontal direction of the burner and a heating zone in front of the flame at a position away from a burner above each of the burners and a ceiling surface of the oven.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to an oven, and particularly to an oven having a heating structure for enhancing heating efficiency by providing a far-infrared generating plate based on a thin metal plate so as to cover a burner and a heating zone at the tip of a flame from the burner above the burner which is an upper heat source.

Background Art

[0002] In an oven for heat-treating food, particularly an industrial oven for heat-treating a large amount of food, heating devices such as gas burners are usually provided above and below the food, and food conveyed between the upper and lower heating devices by a stationary or conveying device or the like is heated from above and below. When the heating device is a burner, on the lower side of the food, heat is transmitted to a tray or a conveyor belt supporting the food by radiation from the flame of the burner and the upward flow of high-temperature exhaust gas generated by combustion and heated ambient air. On the other hand, on the upper side of the food, the food is mainly heated by radiant heat from the flame of the burner. Since the high-temperature exhaust gas generated by the upper burner and the heated ambient air rise, a part of them is discharged outside the oven, and the rest contributes to the heating of the food by convection in the oven, but it is not efficient in terms of heat utilization. In addition, since the effect of radiant heat is different between directly below the location where the flame is generated by the burner and a portion not covered by the flame such as a gap between the burners, unevenness in the heating state of the food is likely to occur. Therefore, a structure that combines a far-infrared generating plate with the upper burner to achieve uniformity has also been put into practical use.

[0003] Patent Document 1 describes a tunnel oven having a firing furnace, a radiation panel that can emit radiant heat when heated and has a large number of ventilation holes, and that divides the inside of the firing furnace vertically, a firing chamber provided below the radiation panel, a combustion chamber provided above the radiation panel and having a burner inside, and a conveyor for conveying an object to be fired to the firing chamber.

[0004] Patent Document 2 describes a tunnel oven that can use superheated steam or heated air in combination with a burner, in which a plurality of burner units are arranged above and below a conveyor that conveys a tray on which baked confectionery is placed, and a far-infrared radiation plate is provided above the burner units corresponding to the burner units and closer to the upper side between the burner units.

[0005] According to the tunnel oven of Patent Document 1, since the baking chamber in which the object to be baked such as confectionery dough is conveyed is almost uniformly covered by the radiation panel on the upper surface, it is possible to appropriately apply radiant heat to the object to be baked, and an effect of being able to bake products with uniform quality is expected. However, since the radiation panel of the tunnel oven of Patent Document 1 is located between the upper burner and the object to be baked, the heat generated by the upper burner is once blocked by the radiation panel, and the object to be baked is heated by the radiant heat emitted from the radiation panel that has been heated mainly by the radiant heat of the upper burner. Therefore, the heat efficiency is not necessarily good.

[0006] Also, according to the tunnel oven of Patent Document 2, since the far-infrared radiation plate is provided closer to the upper side between the burner units, the far-infrared radiation plate does not block the heat radiation from the burner units to the baked confectionery, and since it is provided between the burner units where there are no burner units, a reduction in the variation of the radiant heat radiated to the baked confectionery is expected. However, there is a gap between the burner unit and the far-infrared radiation plate, and the heat from the burner unit escapes upward through this gap, leaving a problem that the heat generated by the burner unit is not necessarily used effectively.

[0007] A far-infrared generation plate, also referred to as a radiation panel or far-infrared radiation plate that generates far-infrared rays, emits stronger radiant heat as the temperature rises. Therefore, it is effective for improving the heat efficiency to increase the temperature as much as possible using the heat generated by the burner. Therefore, it is desired to provide an industrially useful oven having a uniform and highly efficient heating structure that uses a far-infrared ray generating plate to effectively utilize the heat generated by a burner without blocking the heat generated from the burner.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0009] The present invention has been made in view of the problems in the above-described conventional ovens, and an object of the present invention is to provide an oven having a heating structure that improves heating efficiency by providing a far-infrared ray generating plate based on a thin metal plate so as to cover a burner and a heating zone at the tip of a flame from the burner above the burner which is an upper heat source.

Means for Solving the Problems

[0010] An oven according to the present invention made to achieve the above object is horizontally juxtaposed above food placed in the oven or moving in the oven, and includes a plurality of linear burners having a combustion port in one horizontal direction, and is composed of a thin metal plate having a ceramic coating layer only on the lower surface, and is provided at a position separated from the burners above each burner and the ceiling surface of the oven so as to cover each burner, a flame blowing out in one horizontal direction of the burner, and a heating zone at the tip of the flame.

[0011] The far-infrared ray generating plate is preferably rectangular in shape and has a shape in which two end faces parallel to the longitudinal direction of the burner are bent to the lower surface side. It is preferable that the thickness of the metal plate of the far-infrared ray generating plate is 2 ± 0.5 mm.

Advantages of the Invention

[0012] According to the oven of the present invention, the far-infrared ray generating plate is provided above the burner above the food and covers the burner, the flame blown out in one horizontal direction of the burner, and the heating zone at the tip of the flame. In addition, since the two end faces parallel to the longitudinal direction of the burner are installed in a shape bent downward on the lower surface side, heat transfer to the far-infrared ray generating plate is facilitated. As a result, the far-infrared ray generating plate becomes hot, and it is possible to efficiently generate radiant heat. Since the far-infrared ray generating plate is installed so as to widely cover the area above the burner, it is also effective in equalizing the radiant heat in the oven. At the same time, since there is nothing to block the space between the burner and the food to be heated, the convective heat in the oven generated by the heat of the burner unit can be sent to the food without loss, and the heat generated as in Patent Document 1 can be effectively utilized without loss. Therefore, not only radiant heat but also the heat in the oven can be efficiently used for heating.

[0013] Further, according to the oven of the present invention, the far-infrared ray generating plate can be made thinner to 2 ± 0.5 mm by forming the two end faces in a shape bent downward on the lower surface side. Therefore, the heat capacity of the far-infrared ray generating plate can be kept low, and it can be efficiently heated to a high temperature by the heat generated by the burner. However, since the heat storage of the plate itself is kept small, the loss of heat that wants to be used for food heating being stored in the plate is reduced. The far-infrared ray generating plate is formed of a thin metal plate provided with a ceramic coating layer only on the lower surface. Therefore, heat radiation mainly occurs on the lower surface side of the far-infrared ray generating plate at a high temperature, and radiation to the upper surface, which is a metal surface, is suppressed. Therefore, food heating can be performed more efficiently, and it is possible to bake food well even if the burner flame is reduced.

[0014] Furthermore, according to the oven of the present invention, since the far-infrared ray generating plate has a low heat capacity and is suppressed, the time from temperature change to temperature stabilization is shortened. Even when changing the setting of the temperature distribution of the oven, it is possible to shorten the time required for the setting change. Generally, when an oven heats foods with multiple different temperature settings, the time required for setting switching becomes long, leading to a decrease in production efficiency and energy loss. Being able to significantly shorten the time also has the effect of increasing production efficiency and energy saving, and these are also linked to reducing CO 2 emission reduction and reducing running costs, which are great merits in industrial applications. And furthermore, according to the oven of the present invention, there is no obstruction between the burner disposed under the carrier and the carrier, and it is possible to efficiently use heat to heat the food. Even without providing an obstruction between the burner and the carrier, due to the heat insulation structure of the oven body, the intake and exhaust adjustment function, and the internal structure that controls the heat flow generated by the lower burner, it is possible to heat the carrier so that the heat generated from the burner unit is uniformly transmitted to the food.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Embodiments for Carrying Out the Invention

[0016] Next, specific examples of embodiments for implementing the oven according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram schematically showing the overall structure of an oven according to an embodiment of the present invention. Referring to FIG. 1, an oven 1 according to an embodiment of the present invention is a tunnel oven 2 for baking food, and has an upper baking section 14 that heats from above the food, a lower baking section 15 that heats from below, and a conveying device 11.

[0017] The conveying device 11 includes a carrier 12 that circulates in the tunnel oven 2 so as to be turned back by turning sections 13 provided on the entrance side and the exit side of the tunnel oven 2, respectively, and conveys food such as dough from the entrance to the exit of the tunnel oven 2 by the carrier 12. The carrier 12 may be a caterpillar-shaped one driven by a chain that circulates a plurality of baking plates, or an endless steel belt-shaped one. The conveying speed of the conveying device 11 can be adjusted by an operation panel 10.

[0018] The upper baking section 14 and the lower baking section 15 each include a plurality of burners 16 along the conveying direction of the conveying device 11. In the embodiment of FIG. 1, the plurality of burners 16 are divided into three zones A, B, and C from the entrance side to the exit side of the tunnel oven 2, and are configured to be temperature-adjusted for each zone. A viewing window 19 is provided in each zone so that the heating state of the food can be confirmed. In the embodiment, the burner 16 is a gas burner. The food is placed on the carrier 12 and is heated by the upper baking section 14 and the lower baking section 15 while being conveyed from upstream to downstream, and baking is performed.

[0019] An exhaust fan 18 is provided above the tunnel oven 2 to discharge the burned gas generated by the burner 16 as exhaust. Although not shown in FIG. 1, an air inlet with an automatic opening and closing shutter is provided at the lower part of the tunnel oven 2. By controlling the intake air volume from the air inlet and the exhaust air volume of the exhaust fan 18 by a control device, not only the burned exhaust gas is exhausted, but also convection can be generated in the tunnel for transporting food, and the temperature variation depending on the location in the tunnel can be reduced.

[0020] As will be described next with reference to FIG. 2, the oven 1 according to the embodiment of the present invention is characterized by a heating structure. Not limited to the tunnel oven 2, as another embodiment, a batch type oven without the conveying device 11 may be used. However, in this specification, the tunnel oven 2 will be described as a representative.

[0021] FIG. 2 is a diagram schematically showing the heating structure of the oven according to the embodiment of the present invention. Referring to FIG. 2, the food 60 to be baked is placed at regular intervals on the circulating carrier 12 and conveyed through the tunnel oven 2 from the upstream right side to the downstream left side in the x-axis direction in the figure, and is heated by the upper baking section 14 and the lower baking section 15 during that time to show the state of baking.

[0022] Both the upper baking section 14 and the lower baking section 15 include linear gas burners 20 that each extend in the y-axis direction orthogonal to the conveying direction of the food 60 and a plurality of which are arranged along the conveying direction of the food 60. Each gas burner 20 is placed horizontally, but on one side of the gas burner 20, that is, in one horizontal direction, a plurality of combustion ports 21 are provided along the longitudinal direction of the gas burner 20, and the combustion gas supplied from one end of the gas burner 20 is burned while being ejected from the plurality of combustion ports 21 to generate a flame 22 in the horizontal direction. For this reason, on the tip side of the flame 22, there is a heating zone 23 where high-temperature exhaust gas generated by the gas burner 20 and heated surrounding air exist.

[0023] In the upper firing section 14 and the lower firing section 15, the gas burner 20 itself remains common and unchanged. However, in the upper firing section 14, an infrared ray generating plate 30 is provided so as to cover each gas burner 20, the flame 22 blown out in one horizontal direction of the gas burner 20, and the heating zone 23 at the tip of the flame 22.

[0024] The infrared ray generating plate 30 is composed of a thin rectangular metal plate 32 having a ceramic coating layer 33 only on the lower surface. It receives heat generated by the gas burner 20 and becomes high in temperature, and emits infrared rays 34 from the ceramic coating layer 33 formed on the lower surface. Examples of the ceramic include silicon carbide, silicon nitride, titanium dioxide, etc. The ceramic coating layer 33 can be formed by methods such as thermal spraying of a ceramic material or applying and baking a ceramic coating agent. The radiated infrared rays 34 are irradiated onto the food 60 moving downward and contribute to the heating of the food 60 as radiant heat.

[0025] The total amount of thermal energy Q radiated by the radiation from a flat plate with a radiation surface area A is expressed by the following formula (1). 〔Equation 1〕 Q = σεT 4 A (1) Here, σ is the Stefan - Boltzmann constant, ε is the emissivity of the radiation surface T is the absolute temperature of the radiation surface

[0026] Thus, the higher the emissivity of the radiation surface and the higher the absolute temperature of the radiation surface, the greater the amount of thermal energy released. Therefore, the lower surface of the infrared ray generating plate 30 facing the food 60 and contributing to the heating of the food 60 is coated with a ceramic, which is a material with a high emissivity. Conversely, the ceramic coating layer 33 is not provided on the upper surface of the infrared ray generating plate 30 that does not contribute to the heating of the food 60.

[0027] On the one hand, in terms of increasing the absolute temperature of the radiation surface, it is effective to keep the heat capacity of the far-infrared ray generating plate 30 as low as possible so that the temperature can easily rise by receiving the heat generated by the gas burner 20. Further, the far-infrared ray generating plate 30 preferably has a shape that can easily retain high-temperature exhaust gas and heated ambient air in order to efficiently utilize the heat generated by the gas burner 20.

[0028] FIG. 3 is a diagram showing the structure of the far-infrared ray generating plate according to the embodiment of the present invention. Referring to FIG. 3, the far-infrared ray generating plate 30 according to the embodiment of the present invention has a rectangular shape with a length of L and a width of W in the y-axis direction that is the same as the longitudinal direction of the gas burner 20, and two end faces parallel to the longitudinal direction of the gas burner 20 are bent to form a bent portion 31 with a height of H.

[0029] The far-infrared ray generating plate 30 is formed by bending a metal plate 32 with a thickness of t. In FIG. 3, the lower surface facing the food 60 is shown facing upward, and the bent portion 31 is also shown facing upward. However, in the actual state of being installed in the oven 1, the bent portion 31 is formed in a downward U-shaped shape. As described above, it is preferable that the heat capacity of the far-infrared ray generating plate 30 is low, and for this purpose, it is effective to reduce the thickness t of the metal plate 32. In the embodiment, the metal plate 32 is made of heat-resistant and high-strength stainless steel, and the thickness t is 2 ± 0.5 mm.

[0030] On the one hand, in an embodiment, the far-infrared ray generating plate 30 may be used with a size where one side exceeds several hundred millimeters. When using a thin plate, bending deformation is likely to occur in the longitudinal direction, but by forming the bent portion 31 at the end in the width direction, the bending rigidity with respect to the longitudinal direction is improved, and there is no problem in practical use. The far-infrared ray generating plate 30 with a low heat capacity due to being thinned into such a shape is likely to have its temperature rise with the same amount of heat, and the effect that the time until the temperature stabilizes is shortened. Therefore, for example, even when switching the set temperature of the tunnel oven 2 to switch to another food 60 with different baking conditions after the baking of the food 60 is completed, it is possible to shorten the preparation time associated with the switching.

[0031] In this way, the bent portion 31 is effective in improving the rigidity of the far-infrared ray generating plate 30, and in addition, it has the effect of increasing the interaction with the high-temperature exhaust gas generated by the gas burner 20 and the heated surrounding air. As shown in FIG. 2, the flame 22 extends and spreads horizontally from one side of the gas burner 20, and a heating zone 23 where the high-temperature exhaust gas and the heated surrounding air flow is spreading at the tip of the flame 22. Since the bent portion 31 is bent so that the high-temperature exhaust gas and the heated surrounding air block the flow, the interaction with the gas is increased on the lower surface side of the far-infrared ray generating plate 30. In the embodiment, the height H of the bent portion 31 is 30 to 50 mm, but it is not limited to this.

[0032] The far-infrared ray generating plate 30 according to the embodiment of the present invention has a structure in which heat is easily retained and the temperature is likely to rise by providing the bent portion 31 in a thin metal plate. In addition to this, since the far-infrared ray generating plate 30 is provided with a ceramic coating layer 33 having a high emissivity ε of approximately 0.9 on the lower surface, far-infrared rays 34 are radiated more efficiently.

[0033] On the upper surface side of the far-infrared ray generating plate 30, no ceramic coating layer 33 is provided, and the metal surface of the metal plate 32 is exposed as it is. The metal surface has an emissivity of approximately 0.1 or less, preventing the outflow of heat on the upper surface side where heat radiation is unnecessary. Even for the same metal, the emissivity differs between a mirror surface and a roughened surface, and the emissivity of the roughened surface is higher. Therefore, the metal plate 32 of the far-infrared ray generating plate 30 uses a rolled surface with a flat surface, but depending on the embodiment, a metal plate 32 polished to a mirror-like shape on the upper surface side may also be used. Since the bent portion 31 does not face the food 60, even if a ceramic coating layer 33 is provided on the bent portion 31, the far-infrared rays 34 emitted from the bent portion 31 do not contribute effectively to food 60 heating, so the ceramic coating layer 33 may not be provided on the bent portion 31.

[0034] FIG. 4 is a diagram showing an attachment structure of a far-infrared ray generating plate according to an embodiment of the present invention. Referring to FIG. 4, a frame body 40 for attaching the far-infrared ray generating plate 30 according to an embodiment of the present invention includes two main frames 41 extending in the x-axis direction, which is the conveyance direction of the conveyance device 11, and a plurality of side frames 42 provided orthogonally to the main frames 41 and connecting between the two main frames 41.

[0035] The side frame 42 has an L-shaped cross-section and is provided in a form where two adjacent side frames 42 face each other. The two main frames 41 and the two side frames 42 facing each other constitute a rectangular frame 44 that is open at the top and bottom for attaching one far-infrared ray generating plate 30. Thereby, the L-shaped lower surface side edge of the side frame 42 constitutes a flange 43 located below the bent portion 31 of the far-infrared ray generating plate 30.

[0036] In the embodiment of FIG. 4, the frame body 40 includes four side frames 42, thereby forming two rectangular frames 44 for mounting the two far-infrared ray generating plates 30 with a gap therebetween. The gap between the two rectangular frames 44 serves as a passage for allowing the burned gas using heat to escape to the exhaust fan as exhaust gas. In other embodiments, the frame body 40 may further include more side frames 42 and may be configured to mount three or more far-infrared ray generating plates 30.

[0037] The main frame 41 is provided with support protrusions 45 protruding toward the rectangular opening. The support protrusions 45 are provided at a total of four locations, two locations on each of the two opposing main frames 41 with respect to one rectangular frame 44. The lower surface of the far-infrared ray generating plate 30 is supported by the support protrusions 45. The position and arrangement of the support protrusions 45 are not limited to the example of FIG. 4 and can be changed as long as the far-infrared ray generating plate 30 is stably supported.

[0038] When the far-infrared ray generating plate 30 is placed from above so as to fit within the rectangular frame 44, it is supported by the small-area support protrusions 45. Therefore, the amount of heat escaping from the far-infrared ray generating plate 30, which has been heated to a high temperature by the heat generated by the gas burner 20, to the frame body 40 is negligibly small. In FIG. 4, the support protrusions 45 are shown in a shape that spreads in the horizontal direction. However, in other embodiments, they may be provided so as to spread in the yz plane along the vertical direction. By doing so, while ensuring the strength of supporting the far-infrared ray generating plate 30, the contact area with the far-infrared ray generating plate 30 can be reduced, and thus the outflow of heat from the far-infrared ray generating plate 30 can be further suppressed.

[0039] The frame body 40 provided with the far-infrared ray generating plate 30 is placed on the frame body support rail 51 provided on the inner side wall of the tunnel oven 2, and is moved and installed at a position corresponding to the gas burner 20 of the tunnel oven 2. The position corresponding to the gas burner 20 is such that each far-infrared ray generating plate 30 covers the gas burner 20, the flame 22 generated by the gas burner 20, and the heating zone 23 at the tip of the flame 22. Thereby, the far-infrared ray generating plate 30 can efficiently receive the heat generated by the gas burner 20 and is likely to become high temperature.

[0040] The high-temperature exhaust gas and heated surrounding air generated by the gas burner 20 transfer heat to the far-infrared ray generating plate 30, and are then pushed out by the exhaust gas generated later and pass upward between the adjacent far-infrared ray generating plates 30, and finally most of them are discharged to the outside from the exhaust fan 18. However, since the exhaust gas and heated surrounding air still have a sufficiently high temperature even when passing upward between the adjacent far-infrared ray generating plates 30, this temperature can be used to maintain the high temperature of the far-infrared ray generating plate 30.

[0041] FIG. 5 is a diagram schematically showing a heating structure of an oven according to another embodiment of the present invention. Referring to FIG. 5, the food 60 to be baked is conveyed by the circulating carrier 12, and during this time, it is baked by the upper baking section 14 and the lower baking section 15 each provided with a gas burner 20, and the upper baking section 14 is provided with a far-infrared ray generating plate 30 that covers the upper part of the gas burner 20. The basic heating structure is the same as the heating structure described with reference to FIG. 2, but in the embodiment of FIG. 5, it is different in that a cover plate 37 is further provided at a certain interval above the far-infrared ray generating plate 30.

[0042] The cover plate 37 is provided so as to cover at least the gap between the adjacent far-infrared ray generating plates 30 from above. Further, the cover plate 37 is installed so as to partially or entirely cover at least the upper part of at least one of the adjacent far-infrared ray generating plates 30. With such a structure, the exhaust gas and the heated ambient air that escape upward between the adjacent far-infrared ray generating plates 30 are blocked from rising by the cover plate 37 and flow and spread horizontally along the cover plate 37. The cover plate 37 may be provided with a bent portion in which the end portions in the width direction are bent toward the lower surface side, similar to the far-infrared ray generating plate 30. The cover plate 37 may be common to the far-infrared ray generating plate 30 without being separately manufactured as a dedicated element.

[0043] By providing the above-described structure, a state is formed in which the space formed by the upper surface of the far-infrared ray generating plate 30 and the lower surface of the cover plate 37 is filled with relatively high-temperature exhaust gas and heated ambient air. Along with the combustion in the gas burner 20, relatively high-temperature exhaust gas and heated ambient air are continuously supplied to this space, so the temperature in this space is maintained at a relatively high temperature, and the upper surface of the far-infrared ray generating plate 30 can maintain a higher temperature than when there is no cover plate 37. When the temperature in this space is higher than the upper surface of the far-infrared ray generating plate 30, it also contributes to further increasing the temperature of the far-infrared ray generating plate 30.

[0044] Incidentally, in the tunnel oven 2, it is also known as a technical problem that when viewed in a direction orthogonal to the conveyance direction of the conveyance device 11, the temperature of the food 60 in the portion closer to the center is likely to be higher than the temperature of the food 60 at both end portions closer to both side walls of the tunnel oven 2. Therefore, a linear gas burner 20 installed so that its longitudinal direction comes in a direction orthogonal to the conveyance direction of the conveyance device 11 is divided into three sections: a central section and both end sections in the length direction, and a gas burner 20 that can adjust the firing power according to the section has also been put into practical use. However, even without using such a special gas burner 20, it is also possible to improve the problem of temperature distribution by using the far-infrared ray generating plate 30.

[0045] FIG. 6 is a diagram schematically showing a modification of the heating structure of the oven according to another embodiment of the present invention. Referring to FIG. 6, it is installed above the gap between the adjacent far-infrared ray generating plates 30 and straddling the adjacent far-infrared ray generating plates 30. The length of the cover plate 37 in the y-axis direction, that is, the length in the direction orthogonal to the conveyance direction of the conveyance device 11, is shorter than the length of the far-infrared ray generating plate 30 in the y-axis direction, and two cover plates 37 are provided so as to be positioned at both ends with the central portion of the far-infrared ray generating plate 30 left open.

[0046] The exhaust gas and the heated ambient air that pass upward between the adjacent far-infrared ray generating plates 30 rise and escape as there is nothing to block them at the central portion of the far-infrared ray generating plate 30 where the cover plate 37 is not provided. However, at both ends where the cover plate 37 is provided, they are blocked by the cover plate 37 and spread into the space between the upper surface of the far-infrared ray generating plate 30 and the lower surface of the cover plate 37. As a result, when the far-infrared ray generating plate 30 is viewed along the y-axis direction, the temperature at both ends rises compared to the central portion, and the radiant heat radiated from both ends increases compared to the central portion. Both ends of the far-infrared ray generating plate 30 are close to the side walls of the tunnel oven 2 and correspond to portions where the temperature of the product 60 flowing below is difficult to rise. However, by installing the cover plate 37, it becomes possible to reduce the uneven baking of the product 60 by increasing the radiant heat from this portion.

[0047] The variation in the temperature distribution when viewed in the direction orthogonal to the conveyance direction of the conveyance device 11 can also be reduced by changing the structure of the far-infrared ray generating plate 30 without using the cover plate 37 as shown in FIG. 6. FIG. 7 is a diagram showing the structure of the far-infrared ray generating plate according to another embodiment of the present invention.

[0048] Referring to Fig. 7, the basic shape of the far-infrared ray generating plate 35 according to another embodiment of the present invention is the same as that of the far-infrared ray generating plate 30 shown in Fig. 3, but the formation state of the ceramic coating layer 33 provided on the lower surface is different. In the far-infrared ray generating plate 30, it is shown that a uniform ceramic coating layer 33 is formed on the entire lower surface, but in the far-infrared ray generating plate 35, a metal exposed portion 36 is provided in a portion of the lower surface that is close to the center of the tunnel oven 2 where the temperature of the food 60 is likely to rise as described above, so that the ceramic coating layer 33 is not formed by masking or the like.

[0049] By providing a portion where the ceramic coating layer 33 is not formed partially by masking or the like, in the far-infrared ray generating plate 35, even if the temperature is the same near the center in the longitudinal direction and at both ends, the amount of far-infrared rays 34 radiated is different, and the temperature variation of the food 60 conveyed at both ends close to the both side walls of the tunnel oven 2 and the food 60 conveyed at the central portion where the temperature is likely to rise is reduced.

[0050] In Fig. 7, the metal exposed portion 36 where the ceramic coating layer 33 is not formed is shown as five thick lines along the longitudinal direction, but the shape of the portion where the ceramic coating layer 33 is not formed is not limited to this, and it may be a pattern shape perpendicular to the longitudinal direction, a pattern shape provided with an inclination with respect to the longitudinal direction, or a pattern shape provided in a lattice shape. Furthermore, the entire central portion in the longitudinal direction may be made such that the ceramic coating layer 33 is not formed.

[0051] Also, although the ceramic coating layer 33 is provided on the entire lower surface, the density of the ceramic to be attached may be changed to be low at the center so that the underlying metal plate 32 is partially exposed, and high at both ends. Also, after the ceramic coating layer 33 is provided on the entire lower surface, the ceramic coating layer 33 may be partially removed by mechanical grinding or the like on the ceramic coating layer 33 to form the metal exposed portion 36, and processed so that the amount of far-infrared rays 34 generated varies depending on the location.

[0052] In any case, by providing the ceramic coating layer 33 so that the amount of far-infrared rays 34 changes corresponding to the parts in the tunnel oven 2 where the temperature rises easily and the parts where the temperature rises hardly, even when using the normal linear gas burner 20, it is possible to realize the far-infrared ray generation plate 35 that suppresses the temperature variation depending on the location of the food 60. The far-infrared ray generation plate 35 may be used in combination with the modification of the heating structure shown in Fig. 6.

[0053] Fig. 8 is a diagram showing the baking state of food depending on the difference in heating structure. Fig. 8(a) shows the baking state of food when baking food in the tunnel oven with the heating structure A according to the prior art as described in Patent Document 2, and Fig. 8(b) shows the baking state of food when baking food in the tunnel oven with the heating structure B according to the embodiment of the present invention.

[0054] In the heating structure A, the basic configuration in which the product 60 is conveyed between the gas burners 20 provided above and below is the same as the heating structure shown in Fig. 2. However, unlike the far-infrared ray generation plate 30 according to the embodiment of the present invention, the far-infrared ray generation plate 70 in the heating structure A does not cover the gas burner 20 and the flame generated horizontally from the gas burner 20, and is provided between the adjacent gas burners 20. Further, the far-infrared ray generation plate 70 is formed by bending a metal plate, but the bending direction is bent upward contrary to the far-infrared ray generation plate 30. The thickness of the metal plate is 3 ± 0.5 mm, and the ceramic coating layer 33 is formed not only on the lower surface but also on the upper surface. Therefore, the far-infrared rays 34 are also emitted to the upper surface side as well as the lower surface of the far-infrared ray generation plate 70. In the heating structure A, a cover cap 71 is provided above the upper gas burner 20, but the ceramic coating layer 33 is not provided on the cover cap 71, and hardly emits far-infrared rays for food heating. The heating structure B is a structure including the far-infrared ray generation plate 30 according to the embodiment of the present invention described with reference to Fig. 2.

[0055] In the example shown in FIG. 8, the baking states of the food 60 when baking a croissant dough as the food 60 at the same conveyance speed and the same set temperature are compared by the tunnel ovens 2 having the heating structures A and B as described above. It was confirmed that the baking state of the croissant dough was clearly stronger when baked by the heating structure B than when baked by the heating structure A. This result indicates that the efficiency of heat has been improved, and shows that by using the far-infrared ray generating plate 30 with a thin plate thickness according to the embodiment of the present invention, the required baking state can be obtained even when the set temperature is lowered.

[0056] As described above, the embodiments of the present invention have been described in detail with reference to the drawings. However, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the technical scope of the present invention.

Explanation of Reference Numerals

[0057] 1 Oven 2 Tunnel Oven 10 Operation Panel 11 Conveying Device 12 Carrier 13 Folding Part 14 Upper Baking Part 15 Lower Baking Part 16 Burner 17 Turbo Blower 18 Exhaust Fan 19 Peephole 20 Gas Burner 21 Combustion Port 22 Flame 23 Heating Zone 30, 35, 70 Far-Infrared Ray Generating Plate 31 Bent Part 32 Metal Plate 33 Ceramic Coating Layer 34 Far-Infrared Ray 36 Metal Exposed Part 37 Cover Plate 40 Frame 41 Main Frame 42 Side frame 43 Flange 44 Rectangular frame 45 Support projection 50 Ceiling surface 51 Frame support rail 60 Food 71 Cover cap

Claims

1. A plurality of linear burners having a combustion port in one horizontal direction, placed in an oven or horizontally juxtaposed above food moving in the oven; An oven characterized by comprising a plurality of far-infrared generating plates made of a thin metal plate having a ceramic coating layer only on the lower surface, and provided so as to cover each burner, the flame blown out in one horizontal direction of the burner, and the heating zone at the tip of the flame at a position separated from the burner and the ceiling surface of the oven.

2. The oven according to claim 1, wherein the far-infrared generating plate has a rectangular shape, and two end faces parallel to the longitudinal direction of the burner are bent to the lower surface side.

3. The oven according to claim 1, wherein the thickness of the metal plate of the far-infrared generating plate is 2 ± 0.5 mm.

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