JPH0317428A - Electric oven - Google Patents

Abstract

PURPOSE:To obtain a heat insulating construction to prevent an outer surface of a casing from rising in temperature by a method wherein a surface preparation of high reflection rate is applied on the surface of a reflection plate on the heating element side, two or more layers of porous heat-insulation materials each having a thin metallic reflection film are provided closely in contact with the outside of the reflection plate, and the outermost insulation material is in contact with the inner face of the casing. CONSTITUTION:Insulation materials 9 and 10 mainly composed of glass fiber are provided on the outside of plate having elements 4 and 5, and the heat insulating materials 9 and 10 and the plate heating elements 4 and 5 are respectively integrated on a heat-insulating plates 11 and 12. The heat-insulating plate 11 and 12 are made of metal, and a surface preparation of a high-reflecting rate is applied on the inner surface of the heat-insulating plate. A glass tube heater 6 is located in a heating compartment and its ceiling serves for a reflecting plate 13, too. The reflecting plate 13 has a nearly parabolic shape focused on around an object to be heated. The inside surface of the parabolic face is applied with surface preparation of a high reflecting rate. A piece of aluminum foil 15, etc., is stuck on glass fiber heat-insulating material 16, and brought in close contact with the outer surface of the reflector 13, thereby the shielding of radiating heat waves and thermal decomposition due to conduction are carried out.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to electric heating devices such as electric open ovens and open microwave ovens.

Conventional technology In an electric heating device in which electric heating elements are arranged on the upper and lower walls of a heating chamber to heat an object to be heated housed inside the heating chamber, insulation treatment is usually applied to the outer surface of the heating element. The structure of the electric heating element varies depending on the structure of the electric heating element, but a relatively soft and flexible insulating material such as glass wool or asbestos is provided on the outside of the heating element, and a metal Generally, a presser foot is provided outside of the presser foot. When the electric heating element is a planar heating element, the insulation material is provided so as to be in close contact with the heat generation source and cover the entire surface of the electric heating element so that no part is exposed, and on the other hand, it is enclosed or inserted into the glass tube. In the case of a coil heating element, it is common to provide a metal reflector on the outside of the glass tube with a necessary gap between the metal reflector and the heat insulating material on the outside of the metal reflector. The above-mentioned heat insulating materials usually have an air layer between the fibers or materials that make up the material, and this air layer plays the role of heat insulation. Generally, air itself has extremely effective insulating properties, but it is prone to convection, which increases heat loss. Therefore, in order to prevent convection from occurring, the air is confined in a small space, or obstacles made of fine fibers are placed here and there to prevent convection, so that only the insulating properties of the air are utilized. It is an insulator.

On the other hand, the wiring connections and lead wires of these electric heating elements should be electrically insulated, and since not only the heating element but also the insulation material on the outside or the metal holding plate that presses it becomes high temperature, the leads should be Wires and wiring connections must be heat resistant enough to withstand contact with them, or rigid enough to avoid contact. Normally, a portion of the wiring passes above the upper heating element, and below it when the lower heating element is connected, and is led to the control room where the heater control device is housed.

In wiring that spans such a heating element, a highly heat-resistant material is often used to cover the copper wire. Furthermore, these are supported by a plurality of resin holders or the like so as not to come into contact with the temporary metal presser.

Alternatively, as shown in Japanese Utility Model Publication No. 62-30300, a metal relay plate may be used.

Problems to be Solved by the Invention In the above configuration, electric heating elements are provided above and below the heating chamber, and furthermore, a heat insulating material, metal fittings for fixing the heat insulating material, etc. are provided in a laminated manner on the outside thereof. In addition, there is an outer shell material that covers these, and the outer shell material is usually made of metal, and electrical insulation must be ensured for both the metal of the heating chamber and the outer shell material. It would be good if there was enough space here, but if this were done, the effective size of the heating chamber would be relatively small compared to the overall size of the device, which would be disadvantageous in terms of installation area and product price, making it uneconomical. There was a drawback. Furthermore, even though they have fine and large air spaces, fibrous materials such as glass wool and asbestos themselves have the role of heat transfer. Therefore, if the distance between the outer shell material and the heating chamber wall surface is narrow and the heat insulating structure of the heating element is in contact with the outer shell material, heat will be transferred directly to the outer shell material by conduction.
The surface temperature of the outer shell material may become rather high. Additionally, when most of the space between the heat insulating structure and the outer shell material is occupied by the heat insulating structure, it becomes difficult to secure sufficient insulation distance for the electrical wiring of the heating element. Insulating materials such as glass wool are particularly electrically insulating, but they are highly hygroscopic, and if moisture comes out when the heated object is heated, the moisture will adhere to this area and reduce its electrical insulation properties. There was a problem in that it was highly dangerous to run electrical wiring near the insulation material because the heat insulation material could be extremely degraded.

In addition, according to the example of Publication No. 62-30300, there were difficulties in ensuring the strength of the relay metal plates and ensuring the insulation distance. Therefore, a first object of the present invention is to provide a heat insulation structure that does not increase the temperature of the surface of the outer shell even when the space between the surface of the heating chamber and the outer shell is narrow and an air insulation layer cannot be secured.

A second object of the present invention is to provide a connection method that can ensure electrical insulation distance and heat resistance when electrically wiring a heating element in such an extremely narrow space.

! Means for Solving IN In order to achieve the above-mentioned first object, the present invention includes a box-shaped heating chamber for storing and heating an object to be heated, a plurality of electric heating elements provided on the upper and lower surfaces of this heating chamber, and In the electrothermal heating device, a metal reflecting plate is provided on the outside of a part of the electric heating element with a necessary gap therebetween, and this reflecting plate covers at least the surface on the side of the heating element. In addition to applying a surface treatment with high reflectance, a plurality of layers of porous heat insulating material having a metal reflective thin film are provided on the outside in close contact with the reflective plate, and the outermost layer of the heat insulating material is in contact with the inner surface of the outer shell material. In order to achieve the second purpose, a box-shaped heating chamber for storing and heating an object to be heated, and a plurality of electric heating elements provided on the upper and lower surfaces of this heating chamber,
In an electric heating device that is disposed adjacent to the heating chamber and includes a control chamber that houses a control device that controls the electric heating element, and an outer shell that houses and covers the entirety of the control chamber, the heating device that is farthest from the control chamber and between the electrical connection terminal of the heating element provided on the metal insulation plate outside the heating element and the connection terminal near the entrance of the control room, approximately between the outer shell material and the metal insulation plate. A metal plate located in the middle and having a holding member made of an insulating material at the portion closest to each other due to the deformation of the outer shell material and the heating chamber wall material is used for relay connection.

Effect According to the first structure described above, when the heating element is a planar heating element, the thermal energy emitted from the heating element is first absorbed because the heating element is in close contact with the heating chamber wall surface (usually made of a metal plate). It is transmitted to the heating chamber by conduction and heats the inside of the heating chamber uniformly. This type of heating means that uniformly heats the entire heating chamber is applied to so-called open cooking. In the case of a planar heating element, a heat insulating material is usually provided on the outside of the heating element, and a reflective plate is further placed on top of the heat insulating material. At this time, the reflecting plate plays a role as a heat insulating plate that properly holds the heat insulating material rather than reflecting heat rays. Therefore, thermal energy directed in the direction opposite to the wall surface of the heating chamber, that is, toward the outside, is once blocked by the heat insulating material, reflected by the reflecting plate (insulating plate), and returned to the heating element again. Even so, the temperature on the outside of the reflector increases, and heat is radiated outward from here. On the other hand, in the case of a glass tube heater, there is a space between the tube heat and the reflector, and if the shape of the reflector is appropriately designed and processed, the heat rays heading toward the reflector will be irradiated toward the heated object. . However, since the reflector itself is also heated, its outer surface increases in temperature and dissipates heat further toward the outside, that is, the outer shell. In either case, by providing a porous heat insulating material having a metallic reflective thin film in close contact with the reflective plate, heat rays are reflected, shielded and diffused by the metallic reflective thin film, and then the heat rays are absorbed by the heat insulating material. Thermal insulation is achieved by Moreover, since this is provided over multiple layers, the temperature drop is significant. The outermost layer of this heat insulating material is in contact with the inner surface of the outer shell material, so that there is no air heat insulating layer that tends to generate natural convection.

Although the air heat insulating layer has effective heat insulating properties, it has the disadvantage that when accompanied by convection, the temperature of other parts increases.

Therefore, it is effective to insulate only by an air layer that does not cause convection in the heat insulating material.

Further, according to the second configuration, the wiring structure can ensure electrical insulation in an extremely narrow space, and there is no need to worry about heat resistance, and can sufficiently cope with changes in insulation distance due to deformation of the outer shell material or the heating chamber wall surface, etc. You can gain power. Embodiments Hereinafter, embodiments of the present invention will be explained based on the drawings.

In FIGS. 1 and 2, the ceiling surface 2 and bottom surface 3 of the heating chamber 1 are provided with planar heating elements 4 and 5 in close contact with each other, located outside the metal plates that constitute the heating chamber 1. In addition to the planar heating element 4, the ceiling surface 2 is also provided with a heating element 6 (hereinafter referred to as a glass tube heater) consisting of a coil heater inserted into a glass tube. The planar heating elements 4 and 5 are constructed by wrapping a band-shaped heating element made of an iron-chromium material around a thin plate made of an inorganic material such as mica, and then sandwiching thin plates of an inorganic material on both outer sides of the heating element. .

When installing the heating chamber, the wall material of the heating chamber is usually a metal plate, which has high heat conductivity, and conductive heat is the most efficient way to transfer heat, so the heating chamber is installed so that it is as close as possible. In other words, the planar heating element is used for heating by conduction heat.

The glass tube heater 6 has a linear heating element 7 made of an iron-chromium material in the form of a coil, which is inserted into a quartz tube or a crystallized glass tube 8, and an insulator or the like is connected to both ends of the coil. It is configured with a connection terminal. Since the glass tube heater 6 is used to irradiate the radiant heat of the red-hot coil onto the food in the heating chamber,
If this is installed outside the heating chamber, many small openings should be provided on the wall of the heating chamber so that radiant heat can be irradiated into the heating chamber through these openings. Generally, the VT terminal connected to the ceiling 4 of the heating chamber is drawn out to the outside, and the heat generating section itself is often provided inside the heating chamber.

In this way, the planar heating element 4.5 heats the wall surface of the heating chamber itself by conductive heat, and the glass tube heater 6 directly heats the object to be heated by radiant heat. These different heating methods are convenient and can be adapted to various types of cooking. Further, a heat insulating material 9.10 mainly made of glass fiber is provided on the outside of the planar heating elements 4, 5, and the heat insulating material 9.10 and the planar heating element 4.5 are integrated into a heat insulating plate 11. It is held at 12. This insulation board 11. 12 is made of metal, and the inner surface is treated with high reflectance. The glass tube heater 6 is located inside the heating chamber, and its ceiling portion also serves as a reflector plate 13 for the heater. The reflection plate l3 has a cross-sectional shape approximating a parabola whose focal point is near where the object to be heated is placed. The inside of this parabolic curved surface is subjected to high reflectance treatment, such as pride treatment.

As described above, the planar heating element 4.5 is attached to a relatively flat part of the wall of the heating chamber, whereas the glass tube heater 6 is attached to a part of the wall of the heating chamber (in this case, the ceiling 4) in a parabolic shape. Since it is attached by penetrating the inside of the shaped part, locally raised parts are created on the wall surface of the heating chamber.

Therefore, the distance between the locally raised portion and the outer shell member l4 becomes extremely close.

Therefore, the temperature of the outer shell l4 cannot be lowered by simply providing a normal heat insulating material for the insulation of this part. If the thickness of the insulation material is increased, the outer shell material 14 will be pushed up from the inside, which will affect the appearance, and the insulation material will be compressed, reducing the air layer in this area and increasing the conduction heat using the glass fiber itself as a medium. In some cases, the temperature of the outer shell material l4 may increase. Here, a glass fiber insulation material 16 with aluminum foil 15 etc. pasted is provided, and first the aluminum foil 15 side is attached to the reflective plate 1.
3, thereby blocking the radiant heat rays of the surface and performing thermal decomposition by conduction. The glass fiber insulation 16 acts as a poor conductor of heat. Furthermore, a glass fiber insulation material 16 to which aluminum foil 15 is similarly pasted is placed on top of the glass fiber insulation material 16. In this case, the glass fiber insulation material 16 may have aluminum foil 15 pasted on both sides. By stacking several layers of these, it is possible to reduce the amount of heat that reaches the outer shell material 14. Outermost layer insulation material 16
is aluminum′! The glass fiber insulation material itself, not 415, is made to directly touch the outer shell material 14. metal foil 15
If it touches the outer shell material l4, heat dispersion and conduction will be significant here, which may even increase the outer shell surface temperature.

With the above configuration, the thickness of the heat insulating material itself can be made relatively thin, and the problem of swelling the outer shell material 14 can be solved. Further, as shown in FIGS. 3 and 4, the glass tube heater 6 is located at the rear of the ceiling and is provided penetrating left and right, with wiring terminals 17 on both sides. It has 18.

Further, the upper heating element 4 is located in front of the ceiling of the heating chamber,
Again, there are connection terminals 19 on the left and right. It has 20.

In order to lead the electrical connections of these heating elements to the control room 21 on the right side, the connections on the left side are
An insulator 22 is attached on top, and one connection terminal 17 of each of the planar heating element 4 and the glass tube heater 6 is attached to this.
19, and an insulator 23 is also installed in the right control room.
Both insulators 22. 23 with a U-shaped or L-shaped cross section +yi. Attach 24. Electrical connection of the terminals is obtained by screwing directly to the relay metal plate 24 with metal screws.

Although the relay metal plate 24 is on the heat insulating plate 11 of the planar heating element, the surrounding environment temperature is that of the heater! Since the temperature is high at time t, the material must have sufficient heat resistance, the structure itself must have little heat accumulation, and the position must have good heat dissipation. In this example, a stainless steel plate is used,
It is shaped so that it has a downward U-shaped cross section, and has an outer shell l4.
and the heat insulating plate 1l, and is arranged so as to touch the surrounding air layer. In addition, since it is a metal plate, in order to ensure insulation distance even when the intermediate part is bent or thermally deformed, or when the outer shell material 14 is dented due to external force, the relay metal plate is used as shown in Figure 5. A heat-resistant insulating support member 25 is provided in the middle of the plate 24, passing through it vertically.

This insulating support member 25 is in contact with the heat insulation vi11 and the outer shell member 14.

As shown in FIG. 4, the insulator 22 provided on the heat insulator 22 partially forms a protrusion 22a, the top of which is connected to the relay metal plate 24.
It protrudes upward from the head of the metal screw that fixes connection terminals such as metal screws and heaters, etc., and even if the outer shell l4 is recessed and approaches it, the protrusion 22a will hit first and the screw or connection terminal will be damaged. An insulating distance can be secured between the

Further, even when the temporary heat insulating plate 11 and the upper surface 2 of the heating chamber are thermally expanded and deformed upward, the insulator 22 itself is also lifted up, so that the insulation distance between the heat insulating plate 11 and the relay metal plate 24 is kept constant. Effects of the Invention As described above, according to the present invention as described in claim (1), the following effects can be obtained.

(11) The inner surface of the reflector is treated with a highly reflective surface, and a highly thermally conductive metal foil is provided in contact with the outer surface, so radiant heat is shielded and diffused, increasing the temperature of the outer shell material surface. can be lowered.

(2) By providing multiple layers of heat insulating material and arranging the heat insulating material so as to be in contact with the inner surface of the outer shell material, an air layer that does not generate convection can be obtained, and the surface temperature of the outer shell material can be lowered.

(3) By arranging the heat insulating material so that it is in contact with the inner surface of the outer shell, the thickness of the air insulation layer does not change due to the deformation of the outer shell, so it is possible to always maintain a constant surface temperature, and It is less likely to deform even if an abnormal external force is applied.

Further, according to the present invention as described in claim (2), the following effects can be obtained.

(1) By bridging and electrically connecting the relay metal plate in the narrow space between the outer shell material and the heat insulating plate, the insulation distance can be kept constant and risks such as short circuits can be avoided.

(2) By providing an insulating support member between the relay metal plates, an insulating distance can be ensured even when the outer shell material is deformed.

(3) By arranging the connecting part between the relay metal plate and the heating element on the heat insulation plate, the insulation distance between the relay metal plate and the heat insulation plate can be kept constant due to thermal deformation of the heat insulation plate.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of an electric heating device according to an embodiment of the present invention, FIG. 2 is an enlarged cross-sectional view of the glass tube heater portion of FIG. 1, and FIG.
The figure shows a top view of the electric heating device according to the embodiment of the present invention, FIG. 4 shows a partial cross-sectional view of the vicinity of the insulator 22a in FIG. 3, and FIG. 5 shows a partial cross-sectional perspective view of the vicinity of the support member 25 in FIG. . 4.5...Sheet heating element, 6...Glass tube heater, 9.10...Insulating material, 11. 12
...Insulation plate, 13...Reflector plate, 14.
...Outer shell material, 15...Metal reflective thin film,
16...Insulation material, 2l...Control room, 2
2. 23... Insulator, 24... Relay metal plate, 25... Support member.

Claims (2)

[Claims] (1) Consisting of a box-shaped heating chamber that houses and heats objects to be heated, a plurality of electric heating elements provided on the upper and lower surfaces of this heating chamber, and an outer shell that houses and covers these, some of the electric heating elements A metal reflective plate is installed on the outside of the
This reflective plate has at least the surface on the side of the heating element subjected to a surface treatment with a high reflectance, and further has a porous heat insulating material having a highly thermally conductive metal reflective thin film on at least one side of the reflective plate in close contact with the reflective plate on the outside thereof. An electric heating device comprising a plurality of layers, and the outermost layer on the non-metal side of the heat insulating material is in contact with the inner surface of the outer shell material. (2) A box-shaped heating chamber that houses and heats an object to be heated, a plurality of electric heating elements provided on the upper and lower surfaces of this heating chamber, and arranged adjacent to the heating chamber to control the electric heating elements. An electrical connection for a heating element, which consists of a control room that houses a control device and an outer shell that houses and covers the whole, and is provided on a metal heat insulating plate at the farthest position from the control room and outside the heating element. The connection between the terminal and the connection terminal near the entrance of the control room is located approximately midway between the outer shell material and the metal heat insulating plate, and is located closest to each other due to deformation of the outer material and the heating chamber wall material. An electric heating device configured to be relay-connected by a metal plate having a holding member made of an insulating material.