Heater plate assembly

Abstract

Provided is a heater plate assembly in which a plate with which an object to be heated comes into contact and a film heater which generates heat by energization are integrally formed, said heater plate assembly comprising: a plate (20); a film heater (33); two insulation sheets (32, 34); a power supply connection part (40); a heater holder (50); and a plate cover (60). The plate is formed of a thermally conductive metal and has a heating surface (21) with which the object to be heated comes into contact and an assembly surface (24). The heater holder is formed of a thermally conductive metal and covers the film heater on the opposite side to the plate with respect to the film heater. The heater holder holds the film heater between a holding surface (51) and the assembly surface of the plate via the insulation sheets and radiates heat from a radiation surface (53). The plate cover is formed of a metal and covers the heater holder on the opposite side to the plate with respect to the heater holder. The plate cover forms an air chamber (66) between a reflection surface (65) and the radiation surface of the heater holder.

Description

Heater Plate Assembly

[0001] The present disclosure relates to a heater plate assembly.

[0002] Heater plate assemblies used as cooking hot plates and the like are known. For example, the cooking hot plates disclosed in Patent Documents 1 and 2 include a cooking plate body with a top plate on its upper surface. The cooking plate body includes a film heater that generates heat when electricity is applied to the bottom side of the top plate, and a back plate disposed below the film heater. The back plate reflects radiant heat from the film heater.

[0003] The film heater, which has insulating sheets on both sides, is sandwiched between a front plate and a back plate together with a pressure plate for adjusting the thickness.

[0004] Utility Model Registration No. 3232687 Utility Model Registration No. 3233768

[0005] The cooking hot plates of Patent Documents 1 and 2, unlike hot plates that use a sheath heater to heat a large space, have no space between the film heater and the surface plate, which reduces heat loss caused by heating a large space. Also, because heat is generated widely and evenly on the back of the surface plate, temperature variations on the heating surface of the surface plate are reduced.

[0006] However, in the conventional technologies of Patent Documents 1 and 2, the back plate that holds the film heater is directly exposed to the outside, so heat flows out from the back plate to the outside. Therefore, there is room for improvement in the thermal efficiency of heating the front plate with the heat generated by the film heater.

[0007] It is an object of the present disclosure to provide a heater plate assembly that improves thermal efficiency.

[0008] The heater plate assembly according to the present disclosure is an integral assembly of a plate that comes into contact with an object to be heated and a film heater that generates heat when energized. The heater plate assembly includes the plate, the film heater, two insulating sheets, a power supply connector, a heater holder, and a plate cover.

[0009] The plate is made of a thermally conductive metal and has a heating surface that comes into contact with the object to be heated and an assembly surface that is the back surface of the heating surface. The plate of the present disclosure corresponds to the “surface plate” of Patent Documents 1 and 2.

[0010] The film heater is located on the mounting surface of the plate. Two insulating sheets sandwich the film heater to insulate both sides of the film heater. The power supply connector is connected to the film heater.

[0011] The heater holder is made of a thermally conductive metal and covers the film heater on the side opposite the plate. The heater holder holds the film heater with an insulating sheet between the holding surface, which is the surface facing the film heater, and the assembly surface of the plate, and radiates heat from the radiation surface, which is the surface opposite the holding surface.

[0012] The plate cover is made of metal and covers the heater holder on the opposite side of the heater holder from the plate. The plate cover has a reflective surface facing the radiation surface of the heater holder, and forms an air chamber between the reflective surface and the radiation surface of the heater holder.

[0013] The heater plate assembly of the present disclosure differs from the "back plate" of Patent Documents 1 and 2 in that it has a dual structure of a heater holder and a plate cover, forming an air chamber between them. The radiating surface of the heater holder is not directly exposed to the outside, and the air layer inside the air chamber functions as a heat insulating layer. In addition, the reflective surface of the plate cover reflects radiant heat, allowing heat to be efficiently transferred to the plate side. This improves the thermal efficiency of heating the plate using heat generated by the film heater.

[0014] Preferably, the thickness of the plate is greater than the thickness of the heater holder, so that the heat generated by the film heater is transferred more efficiently to the plate, which has a relatively large heat capacity, thereby improving the thermal efficiency of heating the plate.

[0015] The above and other objects, features, and advantages of the present disclosure will become more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which Fig. 1 is a diagram of a cooking appliance using a heater plate assembly according to one embodiment, Fig. 2 is a plan view of the heater plate assembly according to one embodiment, Fig. 3 is a bottom view of the heater plate assembly according to one embodiment, Fig. 4 is a perspective view of the heater plate assembly according to one embodiment viewed from the bottom side, Fig. 5 is a front view of the heater plate assembly according to one embodiment, Fig. 6 is a schematic exploded view of the heater plate assembly according to one embodiment, Fig. 7 is a schematic cross-sectional view of the heater plate assembly according to one embodiment, Fig. 8 is an enlarged view of portion VIII of Fig. 7, and Fig. 9 is a schematic cross-sectional view of a heater plate assembly according to a comparative example.

[0016] (One embodiment) A heater plate assembly according to one embodiment will be described with reference to the drawings. The heater plate assembly is a heater that transfers heat to an object to be heated that is in contact with the plate, and is configured by integrating a plate and a film heater that generates heat when electricity is applied. For example, the heater plate assembly of this embodiment is used in a cooking device that heats and cooks food, which is the object to be heated.

[0017] 1 shows an example of a cooking device 90. In this cooking device 90, an object to be heated, such as bread, is sandwiched between a base 91 supported by a bottom case 92 and a cover 93, and heated from both the top and bottom. The cover 93 rotates around a hinge 98 as a fulcrum, and can be opened and closed relative to the base 91. A heater plate assembly 100 is attached to the top surface of the base 91 and the bottom surface of the cover 93.

[0018] When attached to the cooking appliance 90, the heating surface 21 of the plate 20 of the heater plate assembly 100 is exposed to the outside, and the other elements are hidden behind the plate 20. In this example, the heater plate assembly 100 on the base 91 side can be removed by simply lifting it up. The heater plate assembly 100 on the cover 93 side can be removed by disengaging the plate claws 28. The user can remove the heater plate assembly 100 and wash it with water.

[0019] The configuration of a heater plate assembly 100 according to one embodiment will be described with reference to Figures 2 to 8. Figures 2 to 5 show external views. Figures 2 and 3 correspond to views taken in the directions indicated by arrows II and III in Figure 4, respectively, and Figure 5 corresponds to a view taken in the direction indicated by arrow V in Figure 3. Figure 6 shows a schematic exploded view. Figure 7 shows a schematic cross-sectional view of one side relative to the central axis O, and Figure 8 shows an enlarged view of part VIII in Figure 7. In the schematic exploded views and schematic cross-sectional views, the thicknesses of particularly thin components are exaggerated.

[0020] First, the external structure will be described with reference to Figures 2 to 5. The heater plate assembly 100 of this embodiment is a generally rectangular plate having long sides corresponding to the front-to-rear direction of the cooking appliance 90 and short sides corresponding to the left-to-right direction of the cooking appliance 90. One side exposes the heating surface 21 of the plate 20, and the other side exposes the back surface 61 of the plate cover 60.

[0021] A plate flange 22 is formed on the outer periphery of the plate 20, surrounding the heating surface 21. Plate claws 28 are provided on each short side of the plate 20. The plate cover 60 has a height of several millimeters from the joint surface with the plate 20. This height ensures an internal air chamber 66 (see FIG. 7), which will be described later. Circular and arc-shaped reinforcing ribs 63 are formed on the back surface 61 of the cover. In addition, a check valve 68 is provided in one corner of the plate cover 60 to release the internal pressure of the air chamber 66.

[0022] A power supply connection portion 40, which connects power to the film heater 33 (see FIGS. 6 and 7), is provided inside the cover insertion hole 64 of the plate cover 60. A tubular housing portion 41 of the power supply connection portion 40 is formed of an insulating material such as resin. The power supply connection portion 40 of this embodiment has a cylindrical tubular housing portion 41 in the center of the plate cover 60, and is provided with multiple terminals 45 for power supply and temperature detection.

[0023] Next, the internal structure of the heater plate assembly 100 will be described with reference to Figures 6 to 8. Assuming the assembly process of the heater plate assembly 100, the heater plate assembly 100 is illustrated with the cover rear surface 61 facing up and the heating surface 21 facing down. In the following description, up and down are indicated according to the orientation shown in Figures 6 to 8. In Figure 6, the heater plate assembly 100 is configured by assembling, from bottom to top, the plate 20, the plate-side insulating sheet 32, the film heater 33, the holder-side insulating sheet 34, the power supply connection portion 40, the waterproof ring 70, the heater holder 50, and the plate cover 60. The power supply connection portion 40 and the waterproof ring 70 may be first assembled to the heater holder 50 to form a subassembly.

[0024] The plate 20 is made of a thermally conductive metal and has a heating surface 21 that comes into contact with the object to be heated, and an assembly surface 24 that is the back surface of the heating surface 21. In this embodiment, aluminum is used as the material for the plate 20 because of its thermal conductivity, weldability, and light weight. A film heater 33 and two insulating sheets 32 and 34 are arranged on top of each other on the assembly surface 24 side of the plate 20. As shown by the dashed lines in Figures 2 and 3 , the rectangular shapes of the film heater 33 and the insulating sheets 32 and 34 are the same size.

[0025] The film heater 33 is a thin-film heater with a zigzag conductive path formed therein, and is also called a circuit heater. The film heater 33 has less heat loss than a sheathed heater, which heats a large surrounding space, and can uniformly heat the entire heating surface 21 of the plate 20. Two insulating sheets 32 and 34 are provided on either side of the film heater 33 to insulate both sides of the film heater 33.

[0026] The power supply connection part 40 is placed on the holder-side insulating sheet 34 and has a tubular housing part 41 made of an insulating material. An outer peripheral wall 43 of the tubular housing part 41 is inserted into the holder insertion hole 54 of the heater holder 50 and the cover insertion hole 64 of the plate cover 60. A flange part 42 protruding radially outward is provided at the end of the tubular housing part 41 facing the holder-side insulating sheet 34. A terminal seat 44 on which a plurality of terminals 45 are erected is formed inside the tubular housing part 41. In this embodiment, four terminals 45 are provided: two power supply terminals and two temperature detection terminals.

[0027] 8, the insulating sheets 32 and 34 are formed with relief holes for electrically connecting the power supply connection portion 40 and the film heater 33. For example, a temperature sensor 48 such as an NTC thermistor biased by a spring 47 is pressed against the temperature detection portion of the film heater 33 at the location of the relief hole.

[0028] Next, before describing the waterproof ring 70, the heater holder 50 and the plate cover 60 will be described. The heater holder 50 is formed of a thermally conductive metal and covers the film heater 33 on the side opposite the plate 20 (the upper side in the figure). In this embodiment, like the plate 20, aluminum is used as the material for the heater holder 50 because of its thermal conductivity, weldability, and light weight.

[0029] The surface of the heater holder 50 facing the film heater 33 (lower side in the figure) is called the holding surface 51, and the surface opposite to the holding surface 51 (upper side in the figure) is called the radiation surface 53. The heater holder 50 holds the film heater 33 between the holding surface 51 and the assembly surface 24 of the plate 20 via insulating sheets 32 and 34. More specifically, holes for preventing misalignment are formed in the film heater 33 and the insulating sheets 32 and 34, and protrusions for preventing misalignment that correspond to the holes are formed on the holding surface 51 of the heater holder 50.

[0030] The heater holder 50 has a holder flange 52 located outside the outer periphery of the film heater 33 and the insulating sheets 32, 34. The holder flange 52 is formed so as to bend in a step from the holding surface 51 toward the plate 20. The height of the step corresponds to the thickness of the film heater 33 and the insulating sheets 32, 34 stacked together. The holder flange 52 is welded to the inner frame region 25 on the assembly surface 24 of the plate 20. By welding the holder flange 52 to the plate 20, the film heater 33 and the insulating sheets 32, 34 are fixed integrally with the plate 20 and the heater holder 50. In addition, a holder insertion hole 54 is formed in the center of the heater holder 50, through which the power connection part 40 can be inserted.

[0031] When the film heater 33 generates heat due to the passage of electricity through the terminals 45 of the power connection portion 40, the heat is transferred to both the plate 20 and the heater holder 50. Here, the thickness of the plate 20 is greater than the thickness of the heater holder 50. Therefore, more of the heat generated by the film heater is transferred to the plate, which has a relatively larger heat capacity. The heat transferred to the heater holder 50 is radiated from the radiation surface 53 toward the plate cover 60.

[0032] The plate cover 60 is made of metal and covers the heater holder 50 on the side opposite the plate 20 (upper side in the figure) of the heater holder 50. In this embodiment, aluminum is used as the material for the plate cover 60 because of its radiant heat reflectivity, weldability, and light weight. Alternatively, SUS304, which is used for the back plate in the prior art disclosed in Patent Documents 1 and 2, may be used because of its radiant heat reflectivity, although it is less lightweight than aluminum.

[0033] The surface of the plate cover 60 facing the radiation surface 53 of the heater holder 50 is called the reflective surface 65, and the exposed surface on the opposite side of the reflective surface 65 (the upper side in the figure) is called the cover back surface 61. The reflective surface 65 reflects radiant heat from the radiation surface 53 of the heater holder 50 toward the heater holder 50, suppressing the outflow of heat from the cover back surface 61 to the outside. The plate cover 60 forms an air chamber 66 between the reflective surface 65 and the radiation surface 53 of the heater holder 50. The air inside the air chamber 66 has a lower thermal conductivity than metal, and therefore functions as a heat insulating layer.

[0034] When the air inside the air chamber 66 expands due to a rise in temperature, the internal pressure increases. Reinforcement ribs 63 formed on the cover back surface 61 prevent deformation of the cover back surface 61. Also, a check valve 68 is provided in one corner of the plate cover 60. The check valve 68 has a vent function that opens when the internal pressure of the air chamber 66 increases, releasing the internal pressure to the outside. The check valve 68 is made of an elastic material such as rubber, and is attached to a check valve attachment hole 67 formed in the plate cover 60.

[0035] When the pressure difference between the internal pressure and the external pressure is equal to or less than a predetermined value, the umbrella portion of the check valve 68 abuts against the cover rear surface 61 due to its elastic force. When the pressure difference between the internal pressure and the external pressure exceeds a predetermined value, the force of the air flow passing through the gap between the check valve mounting hole 67 and the check valve 68 pushes up the umbrella portion of the check valve 68, causing air to flow out. Note that, as will be described later, there is a possibility that water may enter the air chamber 66. In that case, steam generated by heating the water will escape to the outside through the open check valve 68.

[0036] The plate cover 60 has a cover flange 62 located outside the outer periphery of the heater holder 50. The cover flange 62 is formed so as to bend in a step from the reflecting surface 65 toward the plate 20. The height of the step is approximately the height of the air chamber 66. The cover flange 62 is welded to the outer frame region 26, which is located outside the inner frame region 25 to which the holder flange 52 is welded, on the assembly surface 24 of the plate 20. In addition, a cover insertion hole 64 is formed in the center of the plate cover 60, through which the power connection part 40 can be inserted.

[0037] The waterproof ring 70 is made of, for example, silicone rubber and is provided along the outer peripheral wall 43 of the tubular housing portion 41. The lower end of the waterproof ring 70 faces the flange portion 42 of the tubular housing portion 41. The waterproof ring 70 prevents water from entering through gaps between the outer peripheral wall 43 of the tubular housing portion 41 and the holder insertion hole 54 and the cover insertion hole 64. The inner peripheral wall of the waterproof ring 70 is formed with protrusions (not shown) that increase the contact surface pressure with the outer peripheral wall 43 of the tubular housing portion 41. Because the heater plate assembly 100 is washed with water, waterproof performance is required to prevent short circuits and corrosion, especially in electrical components.

[0038] A fitting groove 75 into which the inner peripheral edge 55 of the holder insertion hole 54 of the heater holder 50 fits is formed in the middle of the outer peripheral wall of the waterproof ring 70 in the height direction. The bottom and upper and lower walls of the fitting groove 75 abut against the inner peripheral edge 55 from three sides, ensuring high waterproofing performance against water intrusion into the area housing the electrical components.

[0039] The inner peripheral wall of the cover insertion hole 64, which is bent so as to extend in the axial direction, abuts against the outer peripheral wall of the upper end of the waterproof ring 70. Even if water seeps into the air chamber 66 through the gap between the waterproof ring 70 and the cover insertion hole 64, it will not directly affect the electrical components, so a higher level of waterproofing is not required compared to the gap with the holder insertion hole 54. However, there is a possibility that the water that has seeped into the air chamber 66 will be heated and generate steam, which will increase the internal pressure of the air chamber 66. Therefore, as described above, the plate cover 60 is provided with a check valve 68.

[0040] (Comparison with Comparative Example) As a comparative example to be compared with this embodiment, Fig. 9 shows a schematic cross-sectional view of a heater plate assembly 110 corresponding to the prior art disclosed in Patent Documents 1 and 2. In the heater plate assembly 110 of the comparative example, an upper insulating sheet 13, a film heater 14, and a lower insulating sheet 15 are stacked and held between a front plate 11 and a back plate 17. The back plate 17 is fastened to the connecting protrusions of the front plate 11 with screws 19. Waterproof gaskets 12 are provided on the outer edges between the front plate 11 and the back plate 17 and in the seats of the screws 19.

[0041] In the heater plate assembly 110 of the comparative example, when the film heater 14 generates heat, the heat is transferred to both the front plate 11 and the back plate 17, as indicated by the block arrows. Because the back plate 17 is directly exposed to the outside, heat flows out from the back plate 17. Therefore, of the total heat generated by the film heater 14, a relatively large proportion is not used to heat the front plate 11, leaving room for improvement in thermal efficiency.

[0042] Furthermore, fastening the back plate 17 and the front plate 11 with multiple screws 19 requires a large number of parts and increases the number of labor hours. The front plate 11 requires thicker metal to accommodate the connecting protrusions, increasing the weight. Furthermore, variations in the work involved in assembling the waterproof packing 12 between the back plate 17 and the front plate 11 make it difficult to ensure stable waterproof performance.

[0043] In contrast, the heater plate assembly 100 of this embodiment, unlike the back plate 17 of the comparative example, has a double structure consisting of the heater holder 50 and the plate cover 60, which forms an air chamber 66 between them. The radiation surface 53 of the heater holder 50 is not directly exposed to the outside, and the air layer inside the air chamber 66 functions as a heat insulating layer. In addition, the reflective surface 65 of the plate cover 60 reflects radiant heat, allowing the heat to be efficiently transferred to the plate 20 side. Therefore, the thermal efficiency of heating the plate 20 by the heat generated by the film heater 33 is improved.

[0044] The heater holder 50 and the plate cover 60 are welded to the plate 20 without using screws 19, thereby reducing the number of parts. Furthermore, no connecting protrusions for screw fastening are required, and the plate 20 and the heater holder 50 are made of aluminum, thereby reducing weight. In addition, the heater holder 50 and the plate cover 60 are welded to the inner frame region 25 and the outer frame region 26 on the assembly surface 24 of the plate 20, thereby improving waterproofing by sealing with a double frame.

[0045] (Other embodiments) (a) The heater plate assembly of the present disclosure is not limited to use in cooking appliances for food preparation, but may also be used in heaters for any purpose in which heat is transferred to an object in contact with the plate, such as for crafts, arts and crafts, or medical purposes.

[0046] (b) The plate 20 and heater holder 50 may be formed of a heat-conductive metal other than aluminum. The plate cover 60 may be formed of a metal that reflects radiant heat, other than aluminum or SUS304. When welding the flanges 52, 62 to the mounting surface 24 of the plate 20 as in the above embodiment, good weldability is also a requirement. However, one or both of the heater holder 50 and the plate cover 60 may be joined to the plate 20 by a method other than welding, such as by screwing. In this case, the heater holder 50 or the plate cover 60 may be formed of a metal that has poor weldability.

[0047] (c) In the above embodiment, the power supply connection unit 40 having a cylindrical housing tube portion 41 is provided in the center of the plate cover 60, but the shape and arrangement of the housing of the power supply connection unit are not limited to this. For example, a power supply connection unit having a rectangular prism-shaped housing may be provided on one edge of the plate cover. Furthermore, the shape of the waterproof ring and the structure of the check valve are not limited to those in the above embodiment, and shapes and structures that provide the desired waterproofing and venting functions can be selected as appropriate.

[0048] (d) Of the multiple terminals 45 of the power supply connection portion 40, the terminal for power supply is essential, but the terminal for temperature detection is not necessary if a sensorless system is adopted. In the sensorless system, the temperature is estimated by calculating the resistance from the current value based on the resistance-temperature characteristics of the film heater 33.

[0049] As described above, the present disclosure is not limited to the above-described embodiments, and can be embodied in various forms without departing from the spirit of the present disclosure.

[0050] The present disclosure has been described based on the embodiments. However, the present disclosure is not limited to the embodiments and structures. The present disclosure also encompasses various modifications and variations within the scope of equivalents. Furthermore, various combinations and forms, as well as other combinations and forms including only one element, more than one element, or less than one element, are also within the scope and spirit of the present disclosure.

Claims

1. A heater plate assembly in which a plate that comes into contact with an object to be heated and a film heater that generates heat when current is applied are integrally formed, comprising: a plate (20) made of thermally conductive metal and having a heating surface (21) that comes into contact with the object to be heated and an assembly surface (24) that is the back surface of the heating surface; a film heater (33) that is arranged on the assembly surface side of the plate; two insulating sheets (32, 34) that are provided on either side of the film heater and insulate both surfaces of the film heater; a power supply connection part (40) to which a power supply to the film heater is connected; a heater holder (50) made of thermally conductive metal that covers the film heater on the side opposite the plate from the film heater, holds the film heater between a holding surface (51) that is the surface on the film heater side and the assembly surface of the plate via the insulating sheet, and radiates heat from a radiation surface (53) that is the surface opposite the holding surface; a plate cover (60) formed of metal, covering the heater holder on the opposite side of the heater holder from the plate, having a reflective surface (65) facing the radiation surface of the heater holder, and forming an air chamber (66) between the reflective surface and the radiation surface of the heater holder.

2. The heater plate assembly according to claim 1, wherein the thickness of said plate is greater than the thickness of said heater holder.

3. A heater plate assembly as described in claim 1 or 2, wherein the heater holder has a holder flange (52) positioned outside the outer periphery of the film heater and the insulating sheet, and the holder flange is welded to the mounting surface of the plate.

4. A heater plate assembly as described in claim 3, wherein the plate cover has a cover flange (62) located outside the outer periphery of the heater holder, and the cover flange is welded to an outer frame area (26) located outside the inner frame area (25) to which the holder flange is welded on the assembly surface of the plate.

5. A heater plate assembly as described in claim 1 or 2, wherein the power connection portion is formed of an insulating material and has a tubular housing portion (41) that is inserted into the holder insertion hole (54) of the heater holder and the cover insertion hole (64) of the plate cover, and a waterproof ring (70) is provided along the outer peripheral wall (43) of the tubular housing portion to prevent water from entering through the gap between the holder insertion hole and the cover insertion hole.

6. A heater plate assembly according to claim 1 or 2, wherein the plate cover is provided with a check valve (68) that opens when the internal pressure of the air chamber rises and releases the internal pressure to the outside.

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