TWI900336B - oven - Google Patents

Abstract

An oven having a heating structure that improves heating efficiency is provided. The oven of the present invention comprises: a plurality of linear burners, mounted in the oven or arranged horizontally side by side above food moving in the oven, each having a combustion port on one horizontal side; and a plurality of far-infrared ray generating plates, each made of a thin metal plate having a ceramic coating only on its lower surface. The plates are positioned above each burner, away from the burner and the oven ceiling, and cover each burner, the flames that are blown horizontally toward one side of the burner, and the heating area at the flame front.

Description

oven

The present invention relates to an oven, and more particularly to an oven having a heating structure, wherein the heating structure has a far-infrared generating plate based on a thin metal plate above a burner serving as an upper heat source, so as to cover the burner and the heating area of the flame front generated by the burner, thereby improving heating efficiency.

Ovens that heat food, particularly commercial ovens used to heat large quantities of food, typically have heating devices such as gas burners located above and below the food. These devices heat the food from above and below, either stationary between the upper and lower heating devices or transported between them via a conveyor. In the case of burners, heat is transferred from below the food to the trays, conveyors, and other devices supporting the food via radiation from the burner flame, high-temperature exhaust gases from combustion, and the upwelling of heated ambient air. Meanwhile, heat is primarily generated above the food by radiant heat from the burner flame. The high-temperature exhaust gas generated by the upper burners and the heated surrounding air rise, partially exhausting the oven. The remaining heat contributes to food heating through convection within the oven, but is not effectively utilized as heat. Furthermore, the effect of radiant heat differs between areas not covered by the flames, such as directly below the burner flames and in the gaps between burners. This can lead to uneven heating of the food. Therefore, a structure that combines far-infrared emitting plates with the upper burners to achieve uniform heating has been implemented.

Patent Document 1 describes a tunnel oven having a baking furnace and comprising: a radiation panel that emits radiant heat when heated and has a plurality of ventilation holes that divide the baking furnace into upper and lower parts; a baking chamber disposed below the radiation panel; a combustion chamber disposed above the radiation panel and having a burner therein; and a conveyor for conveying the baked goods to the baking chamber.

Patent Document 2 describes a tunnel oven that can use superheated steam or heated air in conjunction with a burner. Multiple burner units are arranged above and below a conveyor that transports trays carrying baked cakes. Within the burner units arranged above the conveyor, far-infrared radiation panels are provided above and between the burner units, corresponding to the burner units.

According to the tunnel oven of Patent Document 1, the upper surface of the baking chamber, which transports baked goods such as pastry dough, is roughly evenly covered by the radiation panel. This allows the radiant heat to properly act on the baked goods, and is expected to result in products of uniform baking quality. However, the radiation panel of the tunnel oven of Patent Document 1 is located between the upper burner and the baked goods. Therefore, the heat generated by the upper burner is temporarily blocked by the radiation panel, and the baked goods are mainly heated by the radiant heat emitted by the radiation panel. The radiation panel is heated by the radiant heat from the upper burner. Therefore, the thermal efficiency cannot be guaranteed to be good.

Furthermore, in the tunnel oven of Patent Document 2, the far-infrared radiating plate is positioned above the burner units. Therefore, the far-infrared radiating plate does not block the heat radiation from the burner units to the baked cakes. Furthermore, since it is positioned between burner units where no burner units are present, it is expected that the variation in the radiated heat radiated to the baked cakes will be reduced. However, due to the gap between the burner units and the far-infrared radiating plate, heat from the burner units is dissipated upward through this gap, which may not necessarily allow for the efficient use of the heat generated by the burner units.

Far-infrared radiation panels, also called far-infrared radiating panels, radiate more intense heat as their temperature increases. Therefore, using the heat generated by the burner to raise the temperature as much as possible is effective in improving thermal efficiency.

Therefore, it is desired to provide a commercially useful oven that uses a far-infrared ray generating plate to effectively utilize the heat generated by the burner, does not block the heat generated by the burner, and has a uniform and thermally efficient heating structure.

Prior Art Documents Patent Documents Patent Document 1: Japanese Patent Application Publication No. 2012-000033 Patent Document 2: Japanese Patent Application No. 5545422

The present invention has been developed in view of the above-mentioned problems in conventional ovens. An object of the present invention is to provide an oven having a heating structure having a far-infrared generating plate based on a thin metal plate above a burner serving as an upper heat source, so as to cover the burner and the heating area of the flame front generated by the burner, thereby improving heating efficiency.

The oven of the present invention, which was completed to achieve the above-mentioned purpose, is characterized in that it has: a plurality of straight burners, which are placed in the oven or arranged horizontally in parallel above the food moving in the oven, and have burning ports in the horizontal direction on one side; and a plurality of far-infrared ray generating plates, which are composed of metal plates with a ceramic coating only on the lower surface, and are arranged above each burner, away from the burner and the top surface of the oven, covering each burner and the flame blown horizontally toward one side of the burner and the heating area of the flame front, and the far-infrared ray generating plates are rectangular in shape, with two end surfaces parallel to the long side direction of the burner bent toward the lower surface.

The thickness of the metal plate of the far-infrared ray generating plate is preferably 2±0.5 mm.

According to the oven of the present invention, the far-infrared ray generating plate is positioned above the burner above the food, covering the burner, the flame that blows horizontally toward one side of the burner, and the heating area of the flame's front. Furthermore, the plate is designed with its two end surfaces, parallel to the burner's longitudinal direction, bent laterally toward the bottom. This facilitates heat transfer to the far-infrared ray generating plate, resulting in a higher temperature and efficient generation of radiant heat. The far-infrared ray generating plate's wide coverage above the burner also effectively distributes radiant heat evenly within the oven. At the same time, since there are no components blocking the burner and the food being heated, the convection heat in the oven generated by the heat generated by the burner unit can be transferred to the food without loss, and the heat generated as in Patent Document 1 can be effectively utilized without loss, thereby achieving a heating effect that effectively utilizes not only radiant heat but also the heat in the oven.

Furthermore, the oven of the present invention reduces the thickness of the far-infrared emitting plate to 2±0.5 mm by bending both end surfaces toward the bottom surface. This minimizes the heat capacity of the far-infrared emitting plate, effectively raising the temperature using heat generated by the burner. Furthermore, since the plate's own heat storage is minimized, the heat loss from heating food, which is stored within the plate, is reduced. The far-infrared emitting plate is formed of a thin metal plate with a ceramic coating only on its bottom surface. Therefore, the heated far-infrared emitting plate radiates heat primarily from the bottom surface, suppressing radiation to the metal top surface. Therefore, food can be heated more efficiently, and food can be baked well even if the burner power is reduced.

Furthermore, the oven of the present invention minimizes the heat capacity of the far-infrared emitting plate, shortening the time it takes for the temperature to stabilize in response to temperature fluctuations. This shortens the time required to change the oven's temperature profile. Generally, when heating food at multiple different temperature settings, the time required to switch settings increases, leading to reduced production efficiency and energy loss. Significantly reducing this time not only increases production efficiency but also saves energy. This, in turn, reduces CO2 emissions and lowers operating costs, offering significant advantages for commercial use.

Furthermore, the oven of the present invention eliminates any obstruction between the burner located below the conveyor and the conveyor, effectively utilizing heat to heat food. Even without a shielding member between the burner and the conveyor, the oven's oven's thermal insulation, air intake and exhaust adjustment functions, and internal mechanisms that control the flow of heat generated by the lower burner allow the conveyor to be heated, evenly transferring heat from the burner unit to the food.

Next, a specific example of a method for implementing the oven according to the present invention will be described in detail with reference to the accompanying drawings.

FIG1 is a diagram schematically showing the overall structure of an oven according to an embodiment of the present invention.

1 , an oven 1 according to an embodiment of the present invention is a tunnel oven 2 for baking food, comprising an upper baking section 14 for heating the food from above, a lower baking section 15 for heating the food from below, and a conveying device 11.

The conveyor device 11 includes a conveyor body 12. This conveyor body 12 circulates within the tunnel oven 2, turning back at turning sections 13 provided at the entrance and exit of the tunnel oven 2. This conveyor body 12 transports food, such as dough, from the entrance to the exit of the tunnel oven 2. The conveyor body 12 can be a caterpillar-shaped conveyor driven by chains that circulate multiple baking plates, or it can be an endless steel belt. The conveying speed of the conveyor device 11 can be adjusted using the operating panel 10.

The upper baking section 14 and the lower baking section 15 are respectively provided with a plurality of burners 16 along the conveying direction of the conveying device 11 .

In the embodiment shown in Figure 1 , multiple burners 16 are divided into three zones, A, B, and C, from the entrance to the exit of the tunnel oven 2. Temperature control is performed for each zone. Observation windows 19 are provided in each zone to verify the heating status of the food. In this embodiment, the burners 16 are gas burners.

The food is placed on the conveyor 12 and is heated and toasted by the upper toasting section 14 and the lower toasting section 15 while being conveyed from upstream to downstream.

An exhaust fan 18 is installed at the top of the tunnel oven 2 to exhaust the post-combustion gases generated by the burner 16 as exhaust gas. Although not shown in Figure 1, an air intake with an automatically opening and closing shutter is installed at the bottom of the tunnel oven 2. A control device controls the air intake volume from the intake port and the air discharge volume of the exhaust fan 18. This system not only exhausts post-combustion exhaust gases but also generates convection within the food transport tunnel, reducing temperature fluctuations caused by the tunnel's internal environment.

As will be described below with reference to FIG. 2 , the oven 1 of the embodiment of the present invention has characteristics in its heating structure and is not limited to the tunnel oven 2. As another embodiment, a batch oven without the conveyor 11 may also be used. However, in this specification, the tunnel oven 2 is used as a representative example for explanation.

FIG2 is a diagram schematically showing a heating structure of an oven according to an embodiment of the present invention.

Referring to FIG. 2 , the following situation is shown: food items 60 to be baked are placed at regular intervals on a circulating conveyor 12 and are conveyed in the tunnel oven 2 from the upstream right side to the downstream left side along the x-axis in the figure, while being heated and baked by the upper baking section 14 and the lower baking section 15.

The upper baking section 14 and the lower baking section 15 each include a linear gas burner 20 , which extends in a y-axis direction perpendicular to the conveying direction of the food 60 , and a plurality of the gas burners 20 are arranged along the conveying direction of the food 60 .

Each gas burner 20 is mounted horizontally and has multiple combustion ports 21 on one side of the gas burner 20, i.e., along one horizontal direction, along the longitudinal direction of the gas burner 20. Combustion gas supplied from one end of the gas burner 20 is ejected from the multiple combustion ports 21 while burning, generating a horizontal flame 22. Therefore, a heating zone 23 exists at the leading end of the flame 22. This heating zone 23 contains the high-temperature exhaust gas generated by the gas burner 20 and the heated surrounding air.

In the upper baking section 14 and the lower baking section 15, the gas burners 20 themselves are the same and unchanged, but a far-infrared generating plate 30 is provided in the upper baking section 14. The far-infrared generating plate 30 covers each gas burner 20 and the flame 22 blown horizontally toward one side of the gas burner 20 and the heating area 23 at the front end of the flame 22.

The far-infrared ray generating plate 30 is composed of a thin rectangular metal plate 32 with a ceramic coating 33 on its lower surface. Heat generated by the gas burner 20 increases the temperature of the plate, and far-infrared rays 34 are radiated from the ceramic coating 33 formed on its lower surface. Examples of ceramics include silicon carbide, silicon nitride, and titanium dioxide. Ceramic coating 33 can be formed by spraying the ceramic material or applying a ceramic coating agent and sintering it. The radiated far-infrared rays 34 strike the food 60 moving below, contributing to its heating as radiant heat.

The total heat energy Q radiated by radiation from a flat plate of area A on the radiation surface is expressed by the following formula (1). [Mathematical formula 1] Q = σεT ⁴ A (1) Here, σs is the Stefan-Boltzmann constant, ε is the emissivity of the radiation surface, and T is the absolute temperature of the radiation surface.

In this way, the higher the emissivity of the radiation surface and the higher the absolute temperature of the radiation surface, the greater the heat energy released.

Therefore, ceramic, a high emissivity material, is coated on the lower surface of the far-infrared ray generating plate 30 that faces the food 60 and contributes to heating the food 60. In contrast, the upper surface of the far-infrared ray generating plate 30 that does not contribute to heating the food 60 is not provided with the ceramic coating 33.

On the other hand, to increase the absolute temperature of the radiation surface, it is effective to minimize the heat capacity of the far-infrared ray generating plate 30 so that it can easily rise in temperature by receiving heat generated by the gas burner 20. Furthermore, to effectively utilize the heat generated by the gas burner 20, the far-infrared ray generating plate 30 is preferably shaped so as to easily retain the high-temperature exhaust gas and heated surrounding air.

FIG3 is a diagram showing the structure of a far-infrared ray generating plate according to an embodiment of the present invention.

3 , the far-infrared generating plate 30 of the embodiment of the present invention is rectangular in shape, with a length L in the y-axis direction and a width W aligned with the longitudinal direction of the gas burner 20. The two end surfaces parallel to the longitudinal direction of the gas burner 20 are bent to form a bent portion 31 with a height H.

The far-infrared generating plate 30 is formed by bending a metal plate 32 having a thickness of t. While FIG3 illustrates the lower surface facing the food 60 with the bent portion 31 facing upward, when installed in the oven 1, the bent portion 31 is actually formed into a downward-pointing U-shape. As mentioned above, the far-infrared generating plate 30 preferably has a low heat capacity, so reducing the thickness t of the metal plate 32 is effective. In the embodiment, the metal plate 32 is made of heat-resistant and high-strength stainless steel, with a thickness t of 2 ± 0.5 mm.

On the other hand, in the embodiment, the far-infrared ray generating plate 30 is sometimes used with a side exceeding several hundred millimeters. If a thin plate is used, it is easy to bend and deform in the longitudinal direction. However, by forming the bent portion 31 at the end in the width direction, the bending rigidity in the longitudinal direction is improved, which does not pose a practical problem. By using this shape to make the plate thinner, the far-infrared ray generating plate 30 has a low heat capacity, which makes it easier to increase the temperature even with the same amount of heat, and shortens the time it takes for the temperature to stabilize. Therefore, for example, after baking a food 60, even if the set temperature of the tunnel oven 2 is changed to switch to another food 60 with different baking conditions, the preparation time associated with the switch can be shortened.

The bend 31 effectively enhances the rigidity of the far-infrared generating plate 30. Furthermore, it also enhances interaction with the high-temperature exhaust gas and heated ambient air generated by the gas burner 20. As shown in Figure 2, the flame 22 extends horizontally from one side of the gas burner 20. At the leading end of the flame 22, a heated area 23, where the high-temperature exhaust gas and heated ambient air flow, expands. The bend 31 is bent to shield the high-temperature exhaust gas and heated ambient air, thereby enhancing interaction with the gas on the lower surface of the far-infrared generating plate 30. In this embodiment, the height H of the bend 31 is 30 to 50 mm, but this is not limited to this.

The far-infrared emitting plate 30 of this embodiment of the present invention is formed by providing a bent portion 31 in a thin metal plate, resulting in a structure that easily retains heat and increases temperature. Furthermore, the far-infrared emitting plate 30 has a ceramic coating 33 on its lower surface with an emissivity ε of approximately 0.9, thereby more effectively radiating far-infrared rays 34.

On the other hand, the top surface of the far-infrared generating plate 30 is not provided with a ceramic coating 33, leaving the metal surface of the metal plate 32 exposed. The metal surface has an emissivity of approximately 0.1 or less, preventing heat from escaping from the top surface where heat radiation is not necessary. Even for the same metal, the emissivity differs between mirrored and roughened surfaces, with the roughened surface having a higher emissivity. Therefore, the metal plate 32 of the far-infrared generating plate 30 is a flat rolled metal plate. However, depending on the embodiment, a metal plate 32 with a mirrored top surface may also be used. In addition, the bend 31 does not face the food 60, so even if the ceramic coating 33 is provided on the bend 31, the far infrared rays 34 emitted from the bend 31 will not effectively contribute to heating the food 60, so the ceramic coating 33 may not be provided on the bend 31.

FIG4 is a diagram showing the mounting structure of the far-infrared generating plate according to an embodiment of the present invention.

4 , the frame 40 on which the far-infrared generating plate 30 according to an embodiment of the present invention is mounted comprises: two main frames 41 extending in the x-axis direction, which is the transport direction of the transport device 11; and a plurality of side frames 42, which are orthogonal to the main frames 41 and are arranged to connect the two main frames 41.

The side frames 42 have an L-shaped cross-section, with two adjacent side frames 42 positioned facing each other. The two main frames 41 and the two opposing side frames 42 form a rectangular frame 44 with upper and lower openings for mounting a far-infrared generating panel 30. The lower edges of the L-shaped side frames 42 form flanges 43 positioned below the bend 31 of the far-infrared generating panel 30.

In the embodiment shown in FIG4 , the housing 40 includes four side frames 42, which form two rectangular frames 44 for spacing and mounting the two far-infrared generating panels 30. The gap between the two rectangular frames 44 serves as a passage for exhausting the heated combustion gas to the exhaust fan 18 as exhaust. In other embodiments, the housing 40 may also be configured with more side frames 42 to accommodate three or more far-infrared generating panels 30.

The main frame 41 is equipped with support protrusions 45 that project toward the rectangular opening. These support protrusions 45 are located at two locations on each of the two opposing main frames 41, corresponding to each rectangular frame 44, for a total of four locations. These support protrusions 45 support the lower surface of the far-infrared generating plate 30. The position and arrangement of the support protrusions 45 are not limited to the example shown in Figure 4. Any variation is acceptable as long as it provides stable support for the far-infrared generating plate 30.

When the far-infrared generating plate 30 is placed from above within the rectangular frame 44, it is supported by the small support protrusions 45. Therefore, the amount of heat released from the far-infrared generating plate 30, heated by the heat generated by the gas burner 20, into the frame 40 is negligible. In Figure 4, the support protrusions 45 are shown as extending horizontally, but in other embodiments, they can also extend vertically in the yz plane. This ensures the strength required to support the far-infrared generating plate 30 while reducing the contact area with the far-infrared generating plate 30, further suppressing heat outflow from the far-infrared generating plate 30.

The frame 40, equipped with the far-infrared generating panels 30, is mounted on frame support rails 51 on the inner sidewall of the tunnel oven 2 and moved to a position corresponding to the gas burners 20 of the tunnel oven 2. The position corresponding to the gas burners 20 is where each far-infrared generating panel 30 covers the gas burner 20, the flame 22 generated by the gas burner 20, and the heating area 23 at the front of the flame 22. This allows the far-infrared generating panels 30 to effectively absorb the heat generated by the gas burner 20 and reach a higher temperature.

The high-temperature exhaust gas generated by the gas burner 20 and the heated ambient air transfer heat to the far-infrared generating panels 30. At the same time, they are squeezed out by the subsequently generated exhaust gas and discharged upward between adjacent far-infrared generating panels 30. Ultimately, most of the exhaust gas is exhausted to the outside through the exhaust fan 18. However, even during the stage of being discharged upward between adjacent far-infrared generating panels 30, the exhaust gas and heated ambient air still maintain a sufficiently high temperature, so this temperature can be used to maintain the high temperature of the far-infrared generating panels 30.

FIG5 is a diagram schematically showing a heating structure of an oven according to another embodiment of the present invention.

5 , the baked food 60 is transported by a circulating conveyor 12 and baked in an upper baking section 14 and a lower baking section 15, each equipped with a gas burner 20. The upper baking section 14 includes a far-infrared ray generating plate 30 covering the upper portion of the gas burner 20. The basic heating structure is the same as that described with reference to FIG2 , but the embodiment of FIG5 differs in that a cover plate 37 is provided above the far-infrared ray generating plate 30 at a certain distance.

The cover plate 37 is provided to cover at least the gap between adjacent far-infrared generating plates 30 from above. Furthermore, the cover plate 37 is provided to partially or entirely cover the upper portion of at least one of the adjacent far-infrared generating plates 30. With this structure, exhaust gas and heated ambient air emitted upward between adjacent far-infrared generating plates 30 are shielded by the cover plate 37 and rise, flowing horizontally along the cover plate 37 and expanding. Similarly to the far-infrared generating plates 30, the cover plate 37 may be provided with a bent portion, with its widthwise end bent toward the lower surface. The cover plate 37 may also be shared with the far-infrared generating plates 30, rather than being manufactured as a dedicated component.

With this structure, the space defined by the upper surface of the far-infrared generating plate 30 and the lower surface of the cover plate 37 is filled with relatively high-temperature exhaust gas and heated ambient air. As the gas burner 20 burns, relatively high-temperature exhaust gas and heated ambient air are continuously supplied to this space, maintaining a relatively high temperature within the space. This allows the upper surface of the far-infrared generating plate 30 to maintain a higher temperature than would be possible without the cover plate 37. Even if the temperature within this space is higher than that of the upper surface of the far-infrared generating plate 30, this contributes to further increasing the temperature of the far-infrared generating plate 30.

However, in tunnel oven 2, when viewed perpendicularly to the conveying direction of conveyor 11, the temperature of food 60 near the center tends to be higher than the temperature of food 60 near the ends of the tunnel oven 2's side walls, a known technical issue. Therefore, a linear gas burner 20, arranged with its longitudinal direction perpendicular to the conveying direction of conveyor 11, is divided into three sections along its longitudinal direction: the center and its two ends. A gas burner 20 capable of adjusting the heating power according to the section has also been put into practical use. However, even without using such a special gas burner 20, the problem of improving temperature distribution can be addressed by using far-infrared emitting plates 30.

FIG6 is a diagram schematically showing a modified example of the heating structure of an oven according to another embodiment of the present invention.

Referring to FIG6 , the cover plates 37 are positioned above the gaps between adjacent far-infrared generating plates 30 and extend across the adjacent far-infrared generating plates 30. The length of the cover plates 37 in the y-axis direction, i.e., the length in a direction perpendicular to the conveying direction of the conveyor device 11, is shorter than the y-axis length of the far-infrared generating plates 30. Two cover plates 37 are provided, sandwiching the center of the far-infrared generating plates 30 and positioned at both ends.

The exhaust gas and heated surrounding air emitted upward between adjacent far-infrared generating plates 30 are not blocked in the center of the far-infrared generating plates 30, where the cover 37 is not installed, and thus rise and are discharged directly. However, at the ends where the cover 37 is installed, the exhaust gas is blocked by the cover 37 and flows and expands in the space between the upper and lower surfaces of the far-infrared generating plates 30. As a result, when viewed along the y-axis, the temperature of the far-infrared generating plates 30 increases at the ends compared to the center, and the amount of radiated heat radiated from the ends increases compared to the center. The ends of the far-infrared generating plate 30 are close to the side walls of the tunnel oven 2, corresponding to the portion where the temperature of the food 60 flowing below is difficult to rise. However, by providing the cover plate 37, the radiant heat from this portion is increased, thereby reducing uneven baking of the food 60.

The deviation in temperature distribution when viewed in a direction perpendicular to the conveying direction of the conveyor 11 can be reduced by changing the structure of the far-infrared generating plate 30 even without using the cover plate 37 shown in Figure 6. Figure 7 shows the structure of a far-infrared generating plate according to another embodiment of the present invention.

Referring to FIG. 7 , the basic shape of a far-infrared generating plate 35 according to another embodiment of the present invention is the same as that of the far-infrared generating plate 30 shown in FIG. 3 , but the ceramic coating 33 provided on the lower surface is different. While the far-infrared generating plate 30 shows a uniform ceramic coating 33 formed across the entire lower surface, the far-infrared generating plate 35 has a metal exposed portion 36 on the lower surface where the ceramic coating 33 is not formed, provided by masking or the like, in a portion located near the center of the tunnel oven 2, where the temperature of the food 60 tends to rise, as described above.

By providing a portion where the ceramic coating 33 is not formed, such as by partial shielding, the far-infrared ray generating plate 35 emits different amounts of far-infrared rays 34 near the center and at both ends in the long-side direction, even at the same temperature. This reduces the temperature deviation between the food 60 transported at the end portions close to the side walls of the tunnel oven 2 and the food 60 transported in the center portion where the temperature is more likely to rise.

In FIG7 , the exposed metal portion 36 without the ceramic coating 33 is shown as five thick lines along the longitudinal direction. However, the shape of the portion without the ceramic coating 33 is not limited to this. It can be a pattern perpendicular to the longitudinal direction, a pattern inclined relative to the longitudinal direction, or a pattern arranged in a grid pattern. Furthermore, the ceramic coating 33 need not be formed on the entire surface of the central portion in the longitudinal direction.

Furthermore, while the ceramic coating 33 is applied to the entire lower surface, the density of the applied ceramic can be varied so that it is low in the center, to the extent that the base metal plate 32 is partially exposed, while being high at the ends. Furthermore, after applying the ceramic coating 33 to the entire lower surface, the ceramic coating 33 can be partially removed by mechanical grinding or the like to form exposed metal portions 36, thereby processing the ceramic coating 33 so that the amount of far-infrared radiation 34 generated varies depending on the location.

In either case, by providing the ceramic coating 33 in the above-described manner, the amount of far-infrared radiation 34 generated is varied according to the temperature of the tunnel oven 2, depending on the areas where the temperature is likely to rise and the areas where it is less likely to rise. This allows for a far-infrared radiation generating plate 35 that suppresses temperature variations caused by the location of the food 60, even when using a conventional linear gas burner 20. The far-infrared radiation generating plate 35 can also be used in combination with the modified heating structure shown in FIG6 .

FIG. 8 is a diagram showing the baking state of food caused by different heating structures.

FIG8(a) shows the baking state of food 60 when the food 60 is baked in the tunnel oven 2 of the prior art heating structure A described in Patent Document 2, and FIG8(b) shows the baking state of food 60 when the food 60 is baked in the tunnel oven 2 of the heating structure B of the embodiment of the present invention.

In heating structure A, the basic structure of food 60 being transported between upper and lower gas burners 20 is similar to the heating structure shown in Figure 2. However, unlike the far-infrared generating plates 30 of the present embodiment, the far-infrared generating plates 70 in heating structure A do not cover the gas burners 20 or the horizontal flames 22 generated by them, but are instead positioned between adjacent gas burners 20. Furthermore, the far-infrared generating plates 70 are formed by bending a metal plate, but in the opposite direction of the far-infrared generating plates 30, upward. The metal plate has a thickness of 3 ± 0.5 mm and is coated with a ceramic coating 33 not only on the bottom surface but also on the top surface. Therefore, far infrared rays 34 are also emitted toward the upper surface side as well as the lower surface of the far infrared ray generating plate 70. In the heating structure A, a cap 71 is provided on the upper gas burner 20, but the cap 71 is not provided with a ceramic coating 33, so that almost no far infrared rays used for heating food are emitted.

The heating structure B is a structure having the far infrared ray generating plate 30 of the embodiment of the present invention described with reference to FIG. 2 .

In the example shown in FIG8 , croissant dough was used as food 60 in tunnel ovens 2 using the aforementioned heating structures A and B, respectively, and the baking completion status of food 60 was compared when baked at the same conveying speed and the same set temperature. It was confirmed that the croissant dough was significantly more baked when baked in heating structure B than when baked in heating structure A. This result demonstrates improved thermal efficiency and that the use of the thin far-infrared ray generating plate 30 of an embodiment of the present invention allows the desired baking completion to be achieved even at a lower set temperature.

As mentioned above, the embodiment of the present invention has been described in detail with reference to the accompanying drawings. However, the present invention is not limited to the above-mentioned embodiment, and various modifications can be made within the scope of the technical scope of the present invention.

1: Oven 2: Tunnel Oven 10: Control Panel 11: Conveyor 12: Conveyor Body 13: Turning Section 14: Upper Baking Section 15: Lower Baking Section 16: Burner 17: Turbine Blower 18: Exhaust Fan 19: Observation Window 20: Gas Burner 21: Burner Port 22: Flame 23: Heating Zone 30, 35, 70: Far-Infrared Generator Plate 31: Bend 32: Metal Plate 33: Ceramic Coating 34: Far-Infrared 36: Exposed Metal Section 37: Cover 40: Frame 41: Main Frame 42: Side Frame 43: Flange 44: Rectangular frame 45: Support protrusion 50: Top surface 51: Frame support rail 60: Food 71: Cover

Figure 1 schematically illustrates the overall structure of an oven according to an embodiment of the present invention. Figure 2 schematically illustrates the heating structure of an oven according to an embodiment of the present invention. Figure 3 schematically illustrates the structure of a far-infrared ray generating plate according to an embodiment of the present invention. Figure 4 schematically illustrates the mounting structure of a far-infrared ray generating plate according to an embodiment of the present invention. Figure 5 schematically illustrates the heating structure of an oven according to another embodiment of the present invention. Figure 6 schematically illustrates a modified example of the heating structure of an oven according to another embodiment of the present invention. Figure 7 schematically illustrates the structure of a far-infrared ray generating plate according to another embodiment of the present invention. Figure 8 illustrates the different states of food being baked depending on the heating structure.

1: Oven 2: Tunnel Oven 12: Conveyor 14: Upper Baking Section 15: Lower Baking Section 20: Gas Burner 21: Burner Port 22: Flame 23: Heating Zone 30: Far-Infrared Generator 31: Bend 32: Metal Plate 33: Ceramic Coating 34: Far-Infrared 40: Frame 50: Top 60: Food

Claims (2)

An oven comprises: A plurality of linear burners, mounted in the oven or arranged horizontally side by side above food moving in the oven, each having a combustion port on one horizontal side; and A plurality of far-infrared ray generating plates, each formed of a metal plate having a ceramic-coated thin plate on its lower surface. The plates are positioned above each burner, away from the burner and a top surface of the oven, and cover each burner, a flame that blows horizontally toward one side of the burner, and a heating area at the front end of the flame. The far-infrared ray generating plates are rectangular in shape, with two end surfaces parallel to the longitudinal direction of the burner bent laterally toward the lower surface. An oven as described in claim 1, wherein the thickness of the metal plate of the far-infrared ray generating plate is 2±0.5 mm.