CN1111436A - Plane Heator for heating cooker - Google Patents

Abstract

The planar heater 17 of heating cooker comprises metal housing 21, the metal insulation board 22 that places in this housing 21 and the plate-shaped heat source 23 that is supported on the opening top of housing 21 by dividing plate 22, The housing is installed on the heating surface of the heating cooker, and the plate-shaped heat source is pushed against the heating surface. The heat insulating sheet is provided with a plurality of stabs 30 obliquely upward and a conical protrusion 33 formed by drawing downward. The heat insulation board is placed on the bottom surface of the shell with the protrusion 33 as a supporting foot, and the plate-shaped heat source is supported by the spines 30, so the contact area between the heat insulation plate 22 and the shell and the plate-shaped heat source can be reduced, and the heat transferred to the outside can be reduced. Improve thermal insulation.

Description

The present invention relates to a flat heater used as a heat source of a heating cooker such as a microwave oven.

An exterior-mounted flat heater is used in a microwave oven as a lower heater for heating food from the lower side, and the bottom surface of an inner box serving as a heating chamber is used as a heat radiation surface.

The planar heater takes a plate-shaped heat source as its main body. In order to insulate this plate-shaped heat source from other components, it is made of a structure in which two insulating mica plates sandwich a mica core plate wound with nickel-chromium heating wires. A planar heater installed close to the outer bottom surface of the inner box heats the bottom surface, and the food placed in the heating chamber is heated with radiant heat from the bottom surface of the inner box.

Existing planar heaters have structures as shown in Figure 12 and Figure 13, and two structures as shown in Figure 14 and Figure 15. The planar heater 1 shown in Fig. 12 and Fig. 13 is installed in a rectangular container-shaped housing 4 through a heat insulator 3 made of glass fiber through a plate-shaped heat source 2, and then the housing 4 is fixed on the inner box, and the plate-shaped The heat source 2 is pushed and pressed on the bottom surface of the inner box. In addition, the structure of the planar heater 5 shown in Fig. 14 and Fig. 15 is that the plate-shaped heat source 2 is installed in the casing 4 through the heat insulating plate 6 made of metal, and then the casing 4 is fixed on the bottom surface of the inner box. , the plate heat source 2 is pushed on the bottom surface of the inner box.

In addition, the heat insulator 3 and the heat insulation plate 6 have functions of blocking heat conduction to the casing 4 and pressing the plate-shaped heat source 2 against the bottom surface of the inner box.

The planar heater 1 shown in Fig. 12 and Fig. 13 is excellent in heat insulation because the heat insulating member 3 is made of glass fiber. However, because the heat insulating member 3 is made of glass fiber accumulation, its thickness and dimension error is large. When the plate-shaped heat source 2 is pushed to the bottom surface of the inner box, the pushing force will be different, so that the plate-shaped heat source 2 will be transferred to the bottom surface of the inner box. The heat varies. Furthermore, when the planar heater 1 is disassembled and discarded, the insulator 3 made of glass fiber is difficult to reuse as a resource, and it is non-combustible, and cannot be burned, and eventually becomes non-combustible garbage.

On the other hand, for the plane heater 5 shown in Fig. 14 and Fig. 15, because the heat insulating plate 6 does not have the dimensional error like the glass fiber heat insulator 3, so the plate heat source 2 is pushed to the bottom surface of the inner box. There is no difference in the pushing force, therefore, the difference in heat transfer from the plate heat source 2 to the bottom surface of the inner box is small, and it is easy to reuse as resources. However, the heat insulating board 6 made of metal has a thermal conductivity more than 100 times higher than that of the heat insulating material 3 made of glass fiber. The amount of heat transfer to the heat insulating board 6 increases, and the heat insulating performance is poor.

As mentioned above, although the heat insulating body 3 made of glass fiber is good in heat insulation, it will eventually become non-combustible garbage, which is harmful to the environment. 6. However, if the heat insulating board 6 made of a conventional metal is used, the heat insulating property is poor. Therefore, there is an urgent need for the development of a planar heater that uses a heat shield made of a metal plate and has good heat insulation.

In view of the above circumstances, it is an object of the present invention to provide a flat heater for a cooking device that can ensure good heat insulation while using a metal heat insulating plate.

The planar heater of the heating cooker provided by the present invention comprises: a flat box-shaped metal housing; it is arranged in the housing and is pushed against the heating surface of the heating cooker by installing the housing on the heating surface of the cooking device. A plate-shaped heat source on the heating surface; a metal heat shield provided between the plate-shaped heat source and the bottom surface of the housing; and a support protrusion provided on the heat shield to support the plate-shaped heat source.

In this case, the supporting protruding part is formed by a slanted piece formed by obliquely cutting on the heat shield. The slit is elastically deformed in the direction of falling due to contact with the heating surface of the plate-shaped heat source, and is elastically deformed in the direction of erection due to contact with the heating surface of the plate-shaped heat source. The recovery elasticity can push the plate-shaped heat source to the heating surface. In addition, in order to increase the strength of the heat insulating board, it is preferable that the tabs constituting the supporting protrusions are cut and formed continuously in substantially the entire width direction of the heat insulating board.

In order to minimize heat transfer due to radiation from the plate heat source to the heat shield, electroplating can be performed on the heat shield. In addition, in order to minimize the heat transfer from the plate heat source to the heat shield due to radiation in a limited space, the distance between the heat shield and the bottom surface of the shell can also be set to be smaller than the distance between the plate heat source and the heat shield. interval size between.

Because the contact area of the heat shield relative to the plate heat source is small, even if the heat shield is made of metal with high thermal conductivity, the heat transfer from the plate heat source to the heat shield is small, which can improve the heat insulation.

Brief introduction to the drawings:

Fig. 1 is a longitudinal sectional side view showing part of a planar heater according to a first embodiment of the present invention.

Fig. 2 is a longitudinal sectional side view of the entire planar heater.

Fig. 3 is a longitudinal sectional side view along the line III-III in Fig. 2 .

Fig. 4 is an exploded perspective view of a plate-shaped heat source.

Fig. 5 is an exploded perspective view of a planar heater.

Fig. 6 is a longitudinal sectional view of a bakeable microwave oven.

Fig. 7 is a view corresponding to Fig. 1 showing a second embodiment of the present invention.

Fig. 8 is a diagram corresponding to Fig. 1 showing a third embodiment of the present invention.

Fig. 9 is a diagram corresponding to Fig. 1 showing a fourth embodiment of the present invention.

Fig. 10 is a view corresponding to Fig. 1 showing a fifth embodiment of the present invention.

Fig. 11 is a diagram corresponding to Fig. 1 showing a sixth embodiment of the present invention.

Fig. 12 is a view corresponding to Fig. 5 showing a conventional planar heater.

Fig. 13 is a view corresponding to Fig. 1 of the planar heater shown in Fig. 12 .

Fig. 14 is a view corresponding to Fig. 5 showing another conventional planar heater.

Hereinafter, a first embodiment of the ovenable microwave oven applicable to the present invention will be described with reference to FIGS. 1 to 6 .

The overall structure of a bakeable microwave oven is shown in FIG. 6 . In this figure, 11 is an outer box, 12 is an inner box, and the inside of this inner box 12 is a heating chamber 13. As shown in FIG. A magnetron 15 is arranged on the outer side of the inner box 12 to supply microwaves into the heating chamber 13 via the waveguide 14 . In addition, a lamp heater 16 is provided on the upper inner side of the inner box 12, and a planar heater 17 of the present invention is provided on the outer bottom surface. This planar heater 17 is configured to use the bottom surface of the inner box 12 as the heating surface 12a, and by heating the heating surface 12a, food is heated by radiant heat from the heating surface 12a.

At the bottom of the above-mentioned planar heater 17, a motor 19 is mounted via a mounting frame 18. As shown in FIG. A rotating shaft 19a of the motor 19 protrudes through the flat heater 17 into the inner case 12 (heating chamber 13), and a turntable 20 is mounted on the upper end of the rotating shaft 19a. The food to be heated is placed on the turntable 20 and driven by the turntable 20 to rotate, thereby preventing uneven heating of the food.

As shown in Fig. 2 and Fig. 5, above-mentioned planar heater 17 comprises: be formed into the shell 21 of flat rectangular container shape, be arranged on the heat shield 22 in this shell 21, and be positioned at shell by the heat shield 22 support. The plate-shaped heat source 23 at the upper position of the opening of the body 21. The concrete structure of above-mentioned plate-like heat source 23 is as shown in Figure 4, and the mica core plate 25 of the heating wire 24 that is wound around nickel-chromium electric heating wire etc. A sheet of insulating mica board 26 sandwiches them therein. The housing 21 and the heat shield 22 are processed from a thin metal plate, and the surface has a coating that reflects the radiant heat (infrared rays) from the plate-shaped heat source 23, so as to prevent the housing 21 and the heat shield 22 from being damaged as much as possible. The radiant heat of the plate heat source 23 is heated.

The casing 21 , the heat shield 22 , and the plate-shaped heat source 23 as described above are connected to each other through the grommets 27 at four corners. At this time, as shown in FIG. 1 , in order to pass through the buttonhole 27, the inner diameter of the through holes 21a, 22a, 23a formed on the housing 21, the heat shield 22, and the plate heat source 23 should be larger than the outer diameter of the buttonhole 27. . In this way, the heat shield 22 and the plate heat source 23 can move freely relative to the housing 21 in the lateral direction, and can absorb the difference in thermal expansion between the shell 21, the heat shield 22 and the plate heat source 23 when the plate heat source 23 generates heat.

The above-mentioned planar heater 17 is installed by fastening the bottom surface of the casing 21 to the mounting base 28 with screws 29 , and the mounting base 28 is fixed on the lower side of the heating surface 12 a of the inner box 12 . When the housing 21 is installed on the mounting seat 28, the plate-shaped heat source 23 is pushed on the heating surface 12a of the inner box 12, and the heat emitted by the heating wire 24 is transferred to the heating surface 12a.

Here, the support structure of the plate-shaped heat source 23 using the heat insulation board 22 is demonstrated. On the heat shield 22, as shown in FIG. 5, a plurality of tabs 30 are formed as supporting protrusions by cutting and lifting, and the length between the elongated holes 31 produced by the cutting and lifting of the tabs 30 is A plurality of conical projections 33 protruding downward are formed on the bar portion 32 by deep drawing. At this time, the protruding height of the tab 30 is set higher than that of the protrusion 33 .

The above-mentioned spines 30 are continuously cut out substantially in the entire width direction of the heat insulating board 22, and the cut-out state is in an inclined state as shown in FIG. 1 . And, the upper end portion of the spine 30 is bent obliquely downward to form the bent piece 30 a, so the bent portion 30 b becomes the top portion of the spine 30 .

In this way, the heat insulating plate 22 is supported on the inner bottom surface of the housing 21 by making the protrusion 33 abut against the inner bottom surface of the housing 21, and the bent portion 30b, which is the top part of the spine 30, is connected to the plate-shaped heat source 23. The plate-shaped heat source 23 is supported in contact with it. In this case, as shown in FIG. 3 , both ends of the bent portion 30b in the longitudinal direction contact the lower insulating mica plate 26 at positions shifted from the positions where the heating wire 24 is placed.

Here, the distance _L1 between the inner bottom surface of the housing 21 and the upper side of the plate-shaped heat source 23 in the state before the housing 21 is mounted on the mounting seat 28 is set to be larger than the lower side and the inner surface of the mounting seat 28. The distance L ₂ between the heating surfaces 12a of the box 12 . Like this, when casing 21 is installed on mounting seat 28, blade 30 elastically deforms to the direction shown by arrow A in Figure 1 from the state shown in Figure 1 solid line, becomes the state shown in double-dot dashed line, and blade 30 30 generates a restoring elastic force to restore the original shape from the elastically deformed state, and pushes the plate-shaped heat source onto the heating surface 12 a of the inner case 12 . At this time, the tab 30 is not elastically deformed in the direction of the arrow A alone, but is elastically deformed in the form of rotating in the direction of the arrow A around the protrusion 33 together with the elongated portion 32 .

In addition, in FIG. 5 , 34 is a wire connected to both ends of the heating wire 24 .

If the planar heater 17 structured as above is used, the following effects can be obtained.

The heat shield 22 supports the plate-shaped heat source 23 by the spines 30, so that the heat shield 22 is opposite to the heat shield.

The heat insulating board 22 supports the plate-shaped heat source 23 through the spines 30, so that the contact area of the heat insulating board 22 relative to the plate-shaped heat source 23 becomes extremely small. Therefore, the amount of heat transferred from the plate-shaped heat source to the heat shield 22 is small, and the heat transfer from the heat shield 22 to the casing 21 is also reduced, so that the heat insulation (heat insulation) of the heat shield 22 can be improved.

At this time, since the heat shield 22 is supported on the bottom surface of the housing 21 through the protrusion 33 , the contact of the heat shield 22 with respect to the housing 21 is in a state of approximately point contact. Therefore, the contact area of the heat shield 22 with respect to the casing 21 is also extremely small, and the heat transferred from the heat shield 22 to the casing 21 is also extremely small.

In addition, because the heat insulating plate 22 is set so that the distance H ₁ from the plate-shaped heat source 23 is greater than the distance H ₂ from the bottom surface of the casing 21 . Therefore, in a limited space, the heat transfer from the high-temperature plate heat source 23 to the heat shield 22 and the heat radiation from the heat shield 22 to the housing 21 can be minimized. At this time, since the thermal insulation board 22 is coated, and the radiant heat emitted by the plate-shaped heat source 23 is reflected by the coating, less heat is transmitted from the plate-shaped heat source 23 to the thermal insulation board 22 .

Moreover, the spine 30 is folded obliquely, and when the planar heater 17 is installed on the heating surface 12a, the spine 30 is elastically deformed in the direction of falling down, and the plate-shaped heat source 23 is pushed to the heating surface 12a due to its restoring elastic force. Therefore, the state in which the plate-shaped heat source 23 is pressed against the heating surface 12a with an appropriate pressing force can always be maintained. Therefore, the thermal conductivity from the plate-shaped heat source 23 to the heating surface 12a can be improved, and the heat transfer efficiency can be improved.

Moreover, the spines 30 are formed by continuous cutting in substantially the entire width direction of the heat shield 22, so the strength of the heat shield 22 is enhanced, and the number of protrusions 30 attached to one spine 30 can be at least within The entire length direction of the spines 30 pushes the plate-shaped heat source 23 to the heating surface 12a.

On the other hand, because the spine 30 abuts against the plate-shaped heat source 23 through the bent portion 30b, the contact portion of the spine 30 relative to the plate-shaped heat source 23 is an arc surface. Therefore, different from the situation where only the upper end of the sliced blade is brought into contact with the plate-shaped heat source 23, the insulating mica plate 26 on the lower side of the plate-shaped heat source 23 will not be damaged, and the thin insulating mica 26 (thickness: 0.3 mm) will not be damaged. -0.5mm) rupture, the contact between the stab 30 and the heating wire 24 and the occurrence of leakage accidents and other undesirable phenomena.

In addition, at both ends in the longitudinal direction of the bent portion 30b, there are cutting edges when the tabs 30 are cut. However, since the both ends in the longitudinal direction of the bent portion 30b are in contact with the plate-shaped heat source 23 at positions shifted from the locations where the heating wires 24 are disposed, even if the cut sides of the both ends in the longitudinal direction of the bent portion 30b are in contact with each other. The insulating mica plate 26 of the downside of the plate heat source 23 is broken, and the spines 30 will not be in contact with the heating wire 24 either.

7 to 11 show the second to sixth embodiments of the present invention. In these drawings, the same parts as in FIG. 1 are denoted by the same symbols for description.

In the second embodiment shown in FIG. 7 , on the heat shield 35 , there are formed tabs 37 and 36 which are vertically folded up and down alternately. The heat shield 35 is supported on the bottom surface of the housing 21 by making the downward stick 36 abut against the bottom surface of the housing 21, and the upward stick 37 is used as a supporting protrusion, and the plate is supported by the stick 37. Shaped heat source 23 .

In the third embodiment shown in FIG. 8 , on the heat insulating board 38 , the leg piece 39 is formed by bending its edge portion downward, and a plurality of spines as supporting protrusions are vertically folded upward. 40. The heat shield 38 is supported by the casing 21 by making the leg pieces 39 abut against the bottom surface of the casing 21 , and supports the plate-shaped heat source 23 by the spines 40 .

In the fourth embodiment shown in FIG. 9 , on the heat insulating plate 41 , terrace-shaped protrusions 42 and 43 are alternately drawn downward and upward. The heat shield 41 is supported on the bottom surface of the housing 21 by making the downwardly protruding protrusion 42 contact the bottom surface of the housing 21, and the upward protruding protrusion 43 is used as a supporting protrusion. The plate-shaped heat source 23 is supported.

In the fifth embodiment shown in FIG. 10 , a corrugated portion 45 serving as an upwardly protruding support protrusion is formed by deep drawing on a heat insulating plate 44 . Furthermore, an upwardly protruding corrugated protrusion 46 is formed by deep drawing on the bottom surface of the housing 21 . In this way, the heat insulating plate 44 is supported by the casing 21 by being placed on the protrusion 46 , and the plate-shaped heat source 23 is supported by the corrugated portion 47 .

In the sixth embodiment shown in FIG. 10 , downwardly convex and upwardly convex corrugated portions 48 and 49 are alternately drawn and formed on a heat insulating plate 47 . Therefore, the section of the heat shield 47 is substantially corrugated. The heat insulating plate 47 is supported by the case 21 by making the corrugated portion 48 protruding downward contact the bottom surface of the case 21, and the corrugated portion 49 protruding upward is used as a supporting protrusion, and the plate is supported by the corrugated portion 49. Shaped heat source 23 .

Even if the structure of the second to sixth embodiments is made, the contact area of the heat insulating plates 35, 38, 41, 44, 47 relative to the plate heat source 23 and the housing 21 is very small, so it is different from the above-mentioned first embodiment. As in Example 1, the effect of improving heat insulation can be obtained. In particular, in the fourth embodiment shown in FIG. 9, since the plate-shaped heat source 23 is supported by the planar upper end surface of the protrusion 43, the insulating mica plate 26 on the lower side is not damaged.

At this time, in the second and third embodiments shown in FIGS. 7 and 8, the top ends of the spines 37, 40 may be bent to form a horizontal piece, and the plate-shaped heat source 23 may be supported by the horizontal piece.

In addition, in each of the above-mentioned embodiments, the application to the flat heater installed on the bottom surface of the inner box 12 (heating surface 12a) has been described, but it can also be applied to the flat heater installed on the upper side of the inner box. In addition, the grommet 27 may be replaced with a stepped shaft fixed to the casing, and the heat shield board may be supported by the stepped portion of the stepped shaft.

In addition, the present invention is not limited to the embodiments described above and shown in the drawings, for example, is not limited to a flat heater for a microwave oven, and can be widely applied to a flat heater for a general heating cooker, etc., without departing from It can be implemented with various changes within the scope of the gist.

As mentioned above, if the flat heater of the heating cooker of the present invention is adopted, since the member for heat insulation is made of a metal heat shield, it is different from the case of using a glass fiber heat insulator, and resources can be reused, which is not harmful to the environment. There will be adverse effects, and since the support protrusion is protruded from the metal heat shield, and the plate heat source is supported by the support protrusion, the contact area of the heat shield to the plate heat source becomes small, and the heat shield from the plate heat source The heat transfer to the heat shield is reduced, and as a result, the heat that escapes from the plate-shaped heat source to the housing through the heat shield is reduced, and excellent heat insulation can be obtained even though the heat shield is made of metal.

According to the planar heater of the heating cooker of the present invention, the heat shield plate and the plate-shaped heat source are connected to each other so as to be movable relative to the housing, so even if there is a difference in their respective thermal expansion coefficients, they can be absorbed, so there will be no conflict between the above three. Deformation or damage due to large thermal stress.

According to the planar heater of the heating cooker of the present invention, the supporting protrusion of the heat insulating plate is composed of a barbed piece folded in an inclined state, and the barbed piece is elastically deformed in the direction of falling due to the contact of the plate-shaped heat source with the heating surface. The restoring elastic force pushes the plate-shaped heat source to the heating surface, so the plate-shaped heat source is always pressed against the heating surface by a moderate pressure, and heat can be transferred to the heating surface well.

According to the planar heater of the heating cooker of the present invention, since the tabs constituting the supporting protrusions are formed in substantially the entire width direction of the heat insulating plate, the strength of the heat insulating plate can be maintained even if the thickness of the heat insulating plate is relatively thin. It can push the plate-shaped heat source well on the heating surface.

According to the planar heater of the heating cooker of the present invention, since the top end of the blade constituting the supporting protrusion is bent, and the bent portion abuts against the plate-shaped heat source, the plate-shaped heat source will not be affected by the blade. And was damaged.

According to the planar heater of the heating cooker of the present invention, since the heat shield plate has the coating for light reflection, the heat shield plate receives less heat due to the radiation of the plate-shaped heat source, and the heat insulation performance is further improved.

According to the planar heater of the heating cooker of the present invention, because the distance between the plate-shaped heat source and the heat shield is set to be greater than the distance between the bottom surface of the housing and the heat Heat transmitted by radiation to the insulation panel.

According to the planar heater of the heating cooker of the present invention, since the both ends in the longitudinal direction of the supporting protrusion are in contact with the plate-shaped heat source at a position offset from the position where the heating wire is arranged, even if the longitudinal direction of the supporting protrusion is There are blades at both ends, and the blades damage the plate-shaped heat source, and the supporting protrusions do not touch the heating wire, so that electric leakage accidents do not occur.

Claims (13)

1. A plane heater for heating a cooker, characterized in that it comprises: A metal shell forming a flat box shape; A plate-shaped heat source provided in the housing and crimped on the heating surface of the heating cooker by installing the housing on the heating surface; a metal heat shield disposed between the plate-shaped heat source and the bottom surface of the housing; On the heat insulating plate, a support protrusion is protrudingly provided to contact the plate-shaped heat source and support the plate-shaped heat source. 2. The planar heater for heating cooker as claimed in claim 1, characterized in that the plate-shaped heat source and the heat insulating plate are connected to each other freely movable relative to the housing so as to absorb the difference in thermal expansion. 3. The planar heater for a heating cooker according to claim 1, wherein the supporting protrusion is formed by a slanted piece cut out on the heat insulating plate, and the thorny piece is shaped like a plate. The heat source abuts against the heating surface to produce elastic deformation in the falling direction, and the plate-shaped heat source is pushed against the heating surface by the restoring elastic force in the standing direction. 4. The planar heater for heating cookers according to claim 3, wherein the tabs constituting the supporting protrusions are formed by continuously cutting substantially the entire width direction of the heat insulating plate. 5. The planar heater for a heating cooker according to claim 1, wherein a protrusion is provided on the bottom surface of the housing to contact the heat insulating plate and support the heat insulating plate. 6. The planar heater for a heating cooker according to claim 1, wherein a plurality of protrusions are formed on the heat insulating plate to protrude toward the side opposite to the supporting protrusion, and the heat insulating plate passes through the protrusions. supported on the bottom of the housing. 7. The planar heater for heating cooker according to claim 1, characterized in that, a plurality of protruding tabs protruding to opposite sides are formed on the heat insulating plate, and the heat insulating plate passes through the protruding tabs protruding to one side. The spines are supported on the bottom surface of the casing, and the spines protruding to the other side are used as supporting protrusions to abut against the plate-shaped heat source. 8 . The planar heater for heating cooker according to claim 1 , wherein the portion of the support protrusion abutting against the plate-shaped heat source is a flat surface. 9. The planar heater for heating cooker according to any one of claims 3, 4, 6, 7, characterized in that the top end of the spine constituting the supporting protrusion is bent, and the bend for the bending is The part is in contact with the plate-shaped heat source. 10. The planar heater for heating cooker according to claim 1, characterized in that the distance between the heat shield and the plate-shaped heat source is set to be larger than the distance between the heat shield and the bottom surface of the casing. 11. The planar heater for heating cooker according to claim 1, characterized in that, the heat insulating plate is made to have a roughly corrugated cross-section, and is supported on the bottom surface of the casing by a protruding corrugated part on one side, and On the other side, the protruding corrugated portion is used as a supporting protrusion to be brought into contact with the plate-shaped heat source. 12. The flat heater for a heating cooker according to claim 1, wherein the plate-shaped heat source is formed by sandwiching a heating wire with an insulating plate such as a mica plate, and the two ends of the supporting protrusion in the longitudinal direction are at The part deviated from the part where the heating wire is arranged in the plate-shaped heat source is in contact with the plate-shaped heat source. 13. The planar heater for a heating cooker according to claim 1, wherein a plated layer for light reflection is provided on the plate-shaped heat source side surface of the heat insulating plate.

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