JPH08273824A - Microwave oven - Google Patents

Abstract

PURPOSE: To prevent burning from being extended to a panel sash even in the case dust accumulated on a substrate is burned due to the spark generated between the dust and a part to which 100V is applied near an electric power transformer. CONSTITUTION: A cover 17 made of a flame retardant material is so installed as to surround a high voltage region A of a substrate near an electric power transformer 11 and a cap 18 made of a metal is put on a boss part 15 projected integrally with a panel sash 5. Consequently, the boss part 15 and the front face part of the panel sash 5 can be prevented by extended burning which occurs due to a spark generated in the high voltage region A of the printed substrate 8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention arranges a high-voltage component such as a power transformer to which a relatively high voltage is applied inside a main body, and an electric component with a switching contact provided with a contact for opening and closing in a plastic case. Regarding microwave oven.

[0002]

2. Description of the Related Art Conventionally, in a microwave oven, a panel sash forming an operation panel is provided on the front surface of a main body, and a printed circuit board is provided inside the panel sash. Then, the printed circuit board is mounted with electronic components constituting a microcomputer and its peripheral circuits, and is provided with a DC power source for supplying DC power to these electronic components.
A power transformer for stepping down the 0V commercial AC power supply and supplying it to the rectifier circuit is mounted. Also, on the printed circuit board,
A relay for controlling the oscillating operation of the magnetron, a relay for controlling the grill heater or the oven heater is provided.

[0003]

There is a commercial AC power supply voltage in the vicinity of the power transformer of the printed circuit board.
There is a portion to which 00V is applied. For this reason, part 1
If, for example, dust accumulates in or near the region where the 00V is applied and the dust contains moisture,
It is conceivable that a spark will be generated between the 100V applied portion and the dust and the dust will burn.

By the way, since the power transformer is considerably heavy,
A boss portion is integrally provided on the panel sash, and the power transformer is fixed to the boss portion so that the weight of the power transformer is received by the boss portion. Panel sash is usually A
Although BS resin is made to contain bromine and the like so as to have a certain degree of flame retardancy, it is inferior in flame retardancy to flame retardant plastics containing a large amount of bromine, and therefore, as described above, When burned, the fire may spread to the front surface portion, the peripheral surface portion, or the boss portion of the panel sash. In order to prevent such fire spread, conventionally, the 100V area and the boss portion or the 100V area and the panel sash are separated by a certain distance or more, but this requires a large space, The panel part becomes larger.

If the panel sash is made of flame-retardant plastic, it is possible to prevent the spread of fire to the panel sash.
However, if a large amount of bromine or the like is added to make the flame-retardant plastic, the luster will be lost, so it becomes unattractive to use the panel sash that constitutes a part of the front surface of the microwave oven as the flame-retardant plastic, Sex becomes low.

On the other hand, the relay is constructed by providing a contact, which is opened and closed by an exciting coil, in a plastic case. The relay case is usually made of flame-retardant plastic, but if abnormal heat is generated due to poor connection of the lead wire to the terminal, the plastic case melts due to the heat generation, and the melting creates holes. The open / close contact (switch) may be exposed. Then
When a spark occurs between the contacts, the spark may reach outside and, in the worst case, the panel sash may ignite.

Further, even though the case is made of flame-retardant plastic, it does not burn easily.
Since it is not nonflammable, it is possible that the case ignites due to the abnormal heat generation as described above, and the fire spreads to the panel sash. The same thing can be said for a micro switch that constitutes, for example, a door switch.

The present invention has been made in view of the above circumstances, and an object thereof is to make a panel sash without forming a panel sash or the like from a flame-retardant plastic or setting a long distance to a high voltage region. It is possible to prevent the spread of fire to non-flame-retardant members such as, and even if the plastic case of the electrical parts with switching contacts provided with the contacts to open and close in the plastic case is ignited, or due to the sparks emitted by the electrical parts with switching contacts, An object of the present invention is to provide a microwave oven in which a member made of a non-incombustible material such as a panel sash, which is present in the vicinity thereof, does not burn.

[0009]

In order to achieve the above object, a microwave oven according to a first aspect of the invention is provided with a plastic panel sash constituting an operation panel on the front surface of the main body, and is arranged inside the panel sash. A high-voltage component to which a relatively high voltage is applied is provided on the printed circuit board, a non-flame-retardant member is difficult to be provided between the high-voltage region where the relatively high-voltage application part of the board exists. It is characterized in that a barrier made of a combustible material or a non-combustible material is provided.

The microwave oven according to a second aspect of the invention is characterized in that the barrier is arranged along the peripheral surface of the panel sash which is a member made of a non-flame retardant material and surrounds the high voltage region from the outside of the substrate. In the microwave oven according to a third aspect of the present invention, the barrier is made of a metal plate material, and the metal plate material barrier is integrally formed with a mounting portion by bending.

According to a fourth aspect of the microwave oven of the present invention, the panel sash is integrally provided with a boss portion for fixing high-voltage components,
The boss, which is a non-flame-retardant member, is covered with a metal cap that constitutes a barrier. In the microwave oven according to claim 5, the plate-shaped barrier is also disposed between the front surface of the panel sash, which is a non-flame-retardant member, and the high voltage region of the substrate, and is pressed and fixed to the boss by the cap. It is characterized by that. A microwave oven according to a sixth aspect of the present invention is characterized in that the barrier is a cover attached to the substrate so as to cover the high voltage region.

According to a seventh aspect of the present invention, there is provided a microwave oven according to claim 7, wherein a substrate or a mounting member made of plastic is provided inside the main body, and an electric component with an opening / closing contact is provided on the substrate or the mounting member, the contact being opened / closed in a plastic case. In this case, a barrier is provided between the electric component with switching contacts and the non-combustible material member, and the barrier is provided with a distance between the electrical component with switching contacts and the non-combustible material member and the plastic case. It is characterized by being formed of a flame-retardant material or a non-combustible material depending on the forming material and the forming material of the mounting member or the substrate.

In the microwave oven according to the present invention, when the distance between the electric component and the non-combustible material is 100 mm or less and the non-combustible material is a non-flammable material corresponding to UL standard 94HB, the barrier is provided. Is formed of a UL standard 94V-0 flame-retardant material or a non-combustible material such as a metal, an inorganic material, or an inorganic compound.

According to a ninth aspect of the present invention, in the microwave oven, the distance between the electric component with switching contacts and the non-combustible member is 100 mm.
In the following, when the non-combustible material is a flame-retardant material having a self-extinguishing property of 94V-2 or more of UL standard and 94V-0 or less, the barrier is 94V-2 or more of UL standard 94V-2 or more.
It is characterized by being formed of a flame retardant of 0 or less.

[0015]

According to the means of claim 1, a barrier made of a flame-retardant material or a non-combustible material is provided between the non-flame-retardant member and the high voltage region of the substrate where a high voltage is applied. As a result, there is no risk of fire spreading from the substrate side to the non-flame-retardant member.

According to the second to fifth aspects, since the barrier prevents the spread of fire from the substrate side to the peripheral surface of the panel sash, it is not necessary to form the panel sash with flame-retardant plastic, and the commercial property is maintained. It can be made of high gloss plastic material.

In this case, particularly in the means described in claim 3,
Since the attachment portion is formed on the barrier, the barrier can be easily attached. Further, according to the means described in claim 5, the plate-shaped barrier arranged between the front portion of the panel sash and the substrate is fixed by the cap fitted on the boss portion, thereby simplifying the mounting structure. . Further, according to the means of the sixth aspect, since the region of the commercial power supply voltage is covered with the cover, the spread of fire to the non-flame-retardant member can be more reliably prevented.

According to the means of claim 7, since there is a barrier made of a flame-retardant material or an incombustible material between the electric component with switching contacts and the member made of non-combustible material, the electrical connection with switching contacts is improved. Even if the plastic case of the part catches fire,
Alternatively, even if the spark is blown from the electric component with the switching contacts, the non-combustible material member is not likely to burn out.

In this case, the material for forming the barrier is added to the distance between the electrical component with switching contacts and the non-combustible material, the material for forming the plastic case of the electrical component with switching contacts, the mounting member or the substrate. The distance between the electric component and the non-combustible member is 100 mm or less, and the non-combustible member is non-flame retardant equivalent to UL standard 94HB. In the case of a material, the barrier is formed of a UL standard 94V-0 flame-retardant material or a non-combustible material such as a metal, an inorganic material, or an inorganic compound.
As described above, the self-extinguishing characteristic that the distance between the electric component with switching contacts and the non-combustible material is 100 mm or less, and the non-combustible material is UL standard 94V-2 or higher and 94V-0 or lower. If the flame retardant material has
By forming the flame-retardant material of 94V-2 or more and 94V-0 or less of the standard, it is possible to obtain a good flame spread prevention effect at the lowest cost.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to FIGS. As shown in FIG. 6, the microwave oven includes an outer box 1 which houses an inner box (not shown) constituting a heating chamber to form a main body 2, and a door for opening and closing the heating chamber on the front surface of the main body 2. 3 is pivotally mounted and an operation panel 4 is attached. Then, although not shown, this microwave oven is a magnetron for heating the food stored in the heating chamber by microwaves, a heater for grilling for directly heating by radiant heat, and heating by sending hot air into the heating chamber. It is equipped with a heater for the oven.

The operation panel 4 is made of a non-flame-retardant material, for example, a flame-retardant plastic, specifically, an ABS resin panel to which a relatively small amount of an additive such as bromine that does not lose the gloss is added. It comprises a sash 5 and a front panel 6 mounted on the front surface of the panel sash 5. Inside the panel sash 5, two substrates, for example, printed boards 7 and 8 are arranged so as to face each other in the front and rear direction. The printed boards 7 and 8 are provided on the front surface and the back surface of the panel sash 5 so as to project therefrom. It is fixed to two types of protrusions (not shown) having different lengths. Both printed boards 7 and 8 are made of a flame-retardant material.

A front panel 6 is provided on the front of the operation panel 4.
A plurality of operating members 9 (shown as 1
(Only one is shown) is provided, and both printed circuit boards 7 and 8 are provided.
Among them, the printed circuit board 7 on the front side (hereinafter, referred to as “previous printed circuit board”) is provided with tactile switches 10 which are operated by being pressed by the operating member 9, and electronic parts (not shown) such as a microcomputer constituting a control device. It is installed.
Further, a printed circuit board 8 on the rear side (hereinafter, referred to as a rear printed circuit board) is connected between a commercial AC power source and a heater for a grill and a heater for an oven, and a triac (not shown) for controlling the ON / OFF of the heaters. No.), a power transformer 11 for stepping down a commercial AC power source, and an AC voltage which is connected to the secondary side of the power transformer 11 and rectified the AC voltage stepped down by the power transformer 11 to form an electronic component mounted on the front printed circuit board 7. An electric component (not shown) that constitutes a rectifying circuit or the like for supplying DC power is mounted. Therefore, the electric components such as the power transformer 11 and the triac are relatively high voltage, in this case, the voltage of the commercial AC power source 100.
It is a high-voltage component to which V is applied, and a relatively high voltage (10) is applied to the primary side of the rear printed circuit board 8 and the lower side part where the triac or the like is mounted.
This is a high voltage region in which a portion to which 0 V is applied (hereinafter, a high voltage application portion) exists. This area is shown in FIG.
Enclosed in brackets.

The power transformer 11 is the rear printed circuit board 8
The primary side terminals 11b and the secondary side terminals 11c are arranged on the rear surface side of the rear printed circuit board 8 and are soldered to the conductive paths 12 (only part of which is shown). Other electric components such as triacs are similarly soldered to the energization path 12, so that the high voltage region A exists on both front and rear surfaces of the rear printed circuit board 8.

Since the power supply transformer 11 has a considerable weight, if the weight of the transformer 11 is applied to the rear printed circuit board 8, if a fall accident occurs during transportation of the microwave oven, the rear printing is performed. A large impact force may act on the substrate 8 and damage it. Therefore, a pair of boss portions 15 are integrally provided on the back side of the front surface of the panel sash 5 so as to face each other in the vertical direction, and the power transformer 11
The pair of upper and lower mounting portions 11a of the self-tapping screw 16 are inserted into the through holes 13 and 14 formed in the front and rear printed circuit boards 7 and 8 and project toward the rear surface side of the rear printed circuit board 8. It is fixed by. As a result, the weight of the power transformer 11 is reduced by the boss portion 15.
The rear printed circuit board 8 will not be damaged in the event of a fall accident or the like. Since the lower side of the front printed circuit board 7 is cut off as will be described later, the lower boss portion 15 passes through the cut portion, and therefore, the front printed circuit board 7 has a lower boss portion 15 for the lower side. No through hole is formed. Reinforcing ribs 15a extending in the front-rear direction are integrally provided on the outer peripheral portion of the boss portion 15 so as to project.

Although the panel sash 5 has flame retardancy as described above, it is made of a non-flame retardant material which is inferior in flame retardance to flame retardant plastic containing a large amount of additives such as bromine. It is a member. Therefore, the dust accumulated near the high voltage area A of the rear printed circuit board 8 becomes moist, and sparks fly between the moistened dust and the high voltage application portion in the high voltage area A to generate dust. If it burns, there is a risk that the boss portion 12 integrated with the panel sash 5 will spread the fire. Also, as shown in FIG. 5, the lower side of the front printed circuit board 7 is in a form in which a portion of the rear printed circuit board 8 facing the high voltage region A is partially cut away, and the rear printed circuit board 8 is cut through the cut portion B. High voltage area A and panel sash 5 made of non-flame retardant material
Since it directly faces the front surface of the panel sash 5, the front surface of the panel sash 5 may spread.

In order to prevent the boss 12 and the front surface of the panel sash 5 from spreading, the space between the boss 12 and the high voltage areas A on the front and rear surfaces of the rear printed circuit board 8 and the front surface of the panel sash 5 are prevented. A barrier is provided between the high voltage region A on the front side of the rear printed circuit board 8 and the rear printed circuit board 8. That is, as shown in FIGS. 1, 3 and 4, a cover 17 as a barrier is attached to the front side of the rear printed circuit board 8 so as to surround the high voltage region A. The cover 17 is made of a flame-retardant plastic (flame-retardant material) containing a large amount of an additive such as bromine. After that, the cover 1 is mounted on the printed circuit board 8 as shown in FIG.
The elastic engagement means is used to elastically engage the elastic claw 17a integrally projecting with 7 with the engagement hole 8a formed in the rear printed circuit board 8.

Further, a cap 18 is covered on the front portion of the boss portion 12 as a barrier. This cap 18
Is formed into a cylindrical shape with one end face closed by drawing a non-combustible material such as a metal plate, and a through hole 18a for the self-tapping screw 16 is formed in the closed end face portion. The cap 18 is fitted into the boss portion 15 in advance, and the power transformer 1 is inserted from above the cap 18.
By fixing the mounting portion 11a of No. 1 with the self-tapping screw 16, the power supply transformer 11 and the boss portion 1
It is fixed at 5.

As described above, according to this embodiment, the high voltage region A on the front side of the rear printed circuit board 8 is covered with the cover 17 made of flame-retardant plastic. Even if ignition occurs due to sparks generated between the high-voltage application portion and the ignited portion, it does not spread to the cover 17 made of flame-retardant plastic, and therefore the boss portion 15 and the panel sash 5 which are members made of non-flame-retardant material. The cover 17 can prevent the spread of fire to the front surface.

In this case, the cover 17 is the rear printed circuit board 8
Since the high voltage region A on the front side of the rear printed circuit board is covered and isolated from the outside, it is possible to more reliably prevent the spread of fire from the front side of the rear printed circuit board 8 to the front surface portion of the panel sash 5 and the boss portion 15. It is possible. By the way, the cover 17
Since there is a low voltage application portion suitable for application to electronic components, even if dust is deposited on a portion of the front surface of the rear printed circuit board 8 outside the cover 17, the low voltage application portion is outside. There is no danger of sparks flying between and, so there is no danger of the dust burning out.

Further, the front portion of the boss portion 15 which is a non-flame-retardant member, that is, the portion which projects rearward from the rear printed circuit board 8 is covered with the cap 18 made of non-combustible material, so that the rear printed circuit board 8 is covered. Even if the dust accumulated on the rear surface is burned by the spark generated between the rear surface side and the high voltage applying portion on the rear surface side of the same, there is no possibility that the boss portion 15 is spread.

Then, as described above, the spread of heat from the rear printed circuit board 8 side to the boss portion 15 is performed by the cover 17 and the cap 1.
8 can be prevented, so the mounting portion 1 of the power transformer 11
It is not necessary to project 1a for a long time so as to project the boss portion 15 at a position separated from the high voltage region A by a predetermined distance or more, and thus the space for disposing the power transformer 11 can be reduced. Further, since the cover 17 can prevent the spread of heat from the rear printed circuit board 8 side to the front surface of the panel sash 5, the distance between the rear printed circuit board 8 and the front surface of the panel sash 5 can be shortened, and the operation panel The thickness in the front-rear direction of 4 can be reduced.

7 and 8 show a second embodiment of the present invention. The same parts as those of the first embodiment described above are designated by the same reference numerals and only different parts will be described. In this embodiment, the cover 17 of the first embodiment is not provided, but instead of the front printed circuit board 7 and the rear printed circuit board 8, a noncombustible material such as a mica plate is used as a plate-shaped barrier. A shield plate 19 is arranged. This shield plate 19 has a boss 1
5, a through hole 20 for passing through 5 is formed.
Is a receiving portion provided on the boss portion 15, and in this embodiment, a rear end of a reinforcing rib 15a protruding from the outer periphery of the boss portion 15 is used as a receiving portion and abutted on the rear end of the rib 15a. Further, the cap 21 covered with the boss portion 15 is longer in the axial direction than the cap 18 of the first embodiment, and covers the portion of the boss portion 15 protruding rearward from the shield plate 19. . The cap 21 is secured to the rib 15 by tightening the self-tapping screw 16.
It is pressed and fixed to the rear end of a.

In the case of such a configuration, the boss portion 15
The portion of the cap 2 that projects rearward of the shield plate 19 is the cap 2
Since the dust is accumulated on the front surface and the rear surface of the rear printed circuit board 8 even if it is burned by the sparks generated between the front and rear surfaces of the high voltage region A on the front and rear surfaces, the boss portion 15 is covered. There is no spread of fire. Further, since the shielding plate 19 is arranged between the high voltage area A on the front side of the rear printed board 8 and the front portion of the panel sash 5, the dust accumulated on the front side of the rear printed board 8 burns. Even if
The front surface of the panel sash 5 does not spread.

9 to 11 show a third embodiment of the present invention. The same parts as those in the first embodiment described above are designated by the same reference numerals, and the description thereof will be omitted. Only different parts will be described. In this embodiment as well, the cover 17 of the first embodiment is not provided, and instead the cap (not shown) put on the front end of the boss portion 15 is the same as the cap 21 of the second embodiment in the axial direction. A long one is used to cover the portion of the boss portion 15 that projects rearward from the front printed circuit board 7.
As a result, even if dust accumulated on both front and rear surfaces of the rear printed circuit board 8 burns, the boss portion 15 will not be spread.

Further, as shown in FIG. 11, a shield plate 22 as a barrier formed in a substantially U shape is arranged along the inner surface of the peripheral surface portion of the panel sash 5. In this case, the shield plate 22 is provided at the approximate center of the width in the front-rear direction.
Are arranged so that the shielding plate 22 is located in the high voltage area A on both front and rear surfaces of the rear printed circuit board 8 due to this positional relationship.
After that, the printed circuit board 8 is surrounded from the outside.

The shield plate 22 is made of a non-combustible material such as a metal plate, and has mounting portions 22a,
22b is integrally formed by bending. The mounting portions 22a and 22b are fixed to the front printed board 7 by self-tapping screws 23 and 23.
The self-tapping screws 23, 23 are for fixing the front printed circuit board 7 to a protrusion (not shown) provided on the back side of the front surface of the panel sash 5, and accordingly, the shield plate 22.
Is the self-tapping screw 2 at the same time as the front printed circuit board 7.
It will be clamped and fixed to the protrusion by 3, 23.

In the present embodiment provided with such a shield plate 22, even if dust accumulated on the front and rear surfaces of the rear printed circuit board 8 burns, it is possible to prevent the panel sash 5 from spreading to the peripheral surface portion. Moreover, the shield plate 22 is the rear printed circuit board 8
Since it is arranged on the outer side of the panel sash 5, the one shield plate 22 can shield between the high voltage regions A on the front and rear surfaces of the rear printed circuit board 8 and the peripheral surface portion of the panel sash 5, and an increase in the number of components can be suppressed. . In addition, the shielding plate 22 is made of a metal plate material, and the mounting portion 2
Since 2a and 22b are integrally formed by bending, the shield plate 22 can be easily attached.

By the way, the lower surface of the shield plate 22 has a width in the front-rear direction narrower than the left and right side surfaces, and the lower surface surrounds the high voltage area A on the rear surface of the rear printed circuit board 8, but the high voltage area on the front surface side. Although A is excluded from being enclosed by the lower surface of the shield plate 22, the high voltage area A on the front surface side of the rear printed circuit board 8 is narrower than the high voltage area A on the rear surface side and the high voltage area A on the front surface side and the panel. 10m from the lower surface of the peripheral surface of the sash 5
Since they are separated by at least m, the spread distance prevents the panel sash 5 from spreading below the peripheral surface portion.

The present invention is not limited to the embodiments described above and shown in the drawings, and the following modifications and expansions are possible. As a high-voltage component, a heater for a grill,
There is a triac that controls the heater for the oven. However, when the location of the triac is far from the location of the power transformer 11, both the power transformer 11 and the high-voltage electrical components such as the triac are as described above. A barrier should be provided. The shield plate 22 may be attached to the rear printed board 8 or the panel sash 5. The shield plate 22 may be formed of mica and attached to the inner surface of the peripheral surface portion of the panel sash 5. The shield plate 22 may be fixed to the rear printed circuit board 8.

In the second embodiment shown in FIGS. 7 and 8, FIG.
The shielding plate 22 of the third embodiment shown in FIG. 11 may be provided. In this case, the front portion of the panel sash 5,
It is possible to prevent fire spread to the peripheral surface portion and the boss portion 15. When a member made of a non-flame-retardant material other than the panel sash 5 is present inside or on the rear side of the operation panel 4, a barrier may be provided between this member and the high voltage region. The member forming the barrier may be made of ceramics. Further, the applied voltage of the high voltage application portion is not limited to 100V, and may be a voltage at which a spark may occur between the dust accumulated on the substrate and the high voltage application portion, for example, a voltage of about 30V.

12 to 14 show a fourth embodiment of the present invention. Hereafter, the same functional portions as those in FIG. 1 are designated by the same reference numerals, detailed description thereof will be omitted, and different portions will be described. Inside the panel sash 5, two boards, for example, a front printed board 24 and a rear printed board 25 are arranged in the same mounting structure as the two printed boards 7 and 8 of the first embodiment.

The front printed circuit board 24 is provided with, for example, a tact switch 26 for selecting a cooking menu which is operated by a pressing portion 5a formed on the front surface of the panel sash 5 so as to be flexibly deformable. Also, the rear printed circuit board 25
In addition to a plurality of relays 27 as electric parts with open / closed contacts arranged therein, a microcomputer 28 constituting a control device, other electronic parts 29, a buzzer 30, a display tube 31, and the power source of the first embodiment. A power transformer (not shown) similar to the transformer 11 is arranged. In addition,
A transparent or translucent display window member 32 is provided at a portion of the front surface of the panel sash 5 that faces the display tube 31.

The relay 27 is a plastic case 2.
An exciting coil in 7a and a relay switch which is an opening / closing contact opened / closed by the exciting coil (neither is shown)
Is provided in the lower part of the rear surface of the rear printed circuit board 25. And the terminal 27 of each relay 27
b is connected to the excitation coil drive circuit, the AC power supply, and the load side via a lead wire or a faston terminal (not shown). These relays 27 are for controlling the oscillating operation of a magnetron (not shown), which is a load, and the on / off switching of the grill heater or the oven heater.

A substantially U-shaped shield plate 33 is sandwiched and fixed between the lower portions of the front and rear printed boards 24 and 25 and the inner surface of the panel sash 5. Here, as shown in FIGS. 13 and 14, the relay 27 is connected to the rear printed circuit board 2
Although they are arranged vertically side by side on the left and right of the lower portion of 5, the left and right side surface portions of the shield plate 33 are arranged from the rear because four are arranged vertically on the left side and two on the right side when viewed from the rear. The left side surface portion 33a is extended (higher) than the right side surface portion 33b, and the distance L1 from the upper end of the left side surface portion 33a and the left uppermost relay 27 and the right side surface The distance L1 from the upper end of the portion 33b and the rightmost uppermost relay 27 is set to be equal. The distance L1 is set to 100 mm or more, which is about 100 mm in this embodiment.

Further, a small hole 34 is formed on the bottom surface of the outer box 1 for discharging the air sent from the fan unit for cooling the magnetron to the outside. This small hole 34
Is 30 mm or more from the lowermost relay 27 (L in Fig. 12
(Distance indicated by 2) are formed apart.

Now, the shielding plate 33 is located between the relay 27 and the panel sash 5 as a non-combustible material member,
It functions as a barrier for preventing the spread of fire from the relay 27 side to the panel sash 5. Here, in order to explain the material for forming the shield plate 33, first, the combustion class defined in the UL standard of the United States will be described for the sake of understanding the following description.

In the UL standard, the following five classes are defined as the combustion class of the insulating material and the insulating system. 94HB 25.4mm flame length tested, burning speed 76m
Things that do not have to be extinguished even if the flame is removed at m / min or less. 94V-2 19mm flame length tested, after removing the flame,
Extinguish within 30 seconds. 94V-1 Tested with a flame length of 19 mm, after removing the flame,
Extinguish within 30 seconds and no flame drip. 94V-0 Tested with 19 mm flame length, after removing the flame,
Extinguish within 10 seconds without dripping flame. 94-5VA Tested with a flame length of 127 mm, extinguished within 5 seconds after removing the flame, and no flame dripping. However, since the concept of each class has been made easy to understand, it is not an accurate description of the specified content itself.

If the rear printed circuit board 25 burns due to the ignition of the relay 27, there is a risk that the panel sash 5 will eventually burn and burn to the house side. Therefore, in this embodiment, the relay 27 to the panel sash 5 are used.
The shielding plate 33 is provided to prevent the spread of fire, but the risk of the spread of fire depends on the distance between the relay 27 and the panel sash 5, the panel sash 5, the rear printed circuit board 25, and the relay 27. Plastic case 27a
However, the material for forming the shielding plate 33 is selected in consideration of them.

Now, the plastic case 27 of the relay 27
The combustion class of the forming material of a is 94V-0, and the combustion class of the forming material of the rear printed board 25 is also 94V-0.
And the combustion class of the material forming the panel sash 5 is 94HB.

In this case, the plastic case 27a of the relay 27 is 94V-0, which has a relatively high flame retardancy, but it is not nonflammable because it is difficult to burn. That is, in the case where a large current flows through the opening and closing contacts like the relay 27, it is safe to consider that it continuously has ignition energy during heating and cooking of the microwave oven. For example, the plastic case 27a has a relay switch. When it is carbonized by the sparks generated in 1) or it is heated due to poor connection with the lead wire of the terminal 27b or the faston terminal and carbonized or melted, the rear printed circuit board 25 or the panel sash in which the relay 27 is arranged. However, since the material for forming the rear printed circuit board 25 has a relatively high flame retardancy at 94V-0 as described above, it is formed of the material having the lowest flame retardancy of 94HB. The panel sash 5 that is formed will spread the fire first.

Here, it is generally said that the non-flame-retardant member will not burn out if the non-flame-retardant member is separated from the flame by a distance of more than 100 mm. Since the shortest distance between a certain relay 27 and the panel sash 5 which is a non-flame-retardant member is 100 mm or less, there is a possibility that the relay 27 may spread the fire to the panel sash 5. It should be noted that if the relay 27 and the panel sash 5 can be separated by a distance exceeding 100 mm, it can be said that the shielding plate 33 is not necessary, but it is difficult to secure such a distance in an actual microwave oven.

Therefore, in this case, that is, when the plastic case 27a of the relay 27 and the rear printed circuit board 25 are 94V-0 and the panel sash 5 is 94HB, the shortest distance between the relay 27 and the panel sash 5 is obtained. Is 100 mm or less, the material for forming the shielding plate 33 has the highest flame retardancy, combustion class 94-5VA.
Plastic or non-combustible material such as mica. As a result, fire spread from the relay 27 side to the panel sash 5 is prevented.

Further, in this embodiment, the side surface portion 3 of the shielding plate 33 is
Since 3a and 33b are extended upward from the relay 27 by about 100 mm, the fire spread from the relay 27 to the panel sash 5 can be prevented more effectively. That is, when the ignition source is close to the wall surface, even if the flame length is as short as about 5 to 15 mm, the air having a high temperature due to the flame violently rises, and the flame length also becomes longer due to this rising airflow. According to the experiment, when a flame of 20 mm was generated with the distance between the burner (ignition source) and the wall surface being 5 mm, the flame length on the wall surface reached 50 mm. Also, the ambient temperature of the flame is
Exceeding 300 ℃ at a distance of 50 mm from the flame, 10
Even at a point of 0 mm, the temperature becomes 150 ° C or higher.

Therefore, in this embodiment, the inner peripheral surface of the panel sash 5 has both side surface portions 33a, 3a of the shield plate 33.
Since it will be about 100 mm apart by 3b,
Even if the relay 27 ignites, and as a result, an ascending air current is generated and a long flame is generated, the flame does not directly touch the panel sash 5 and the panel sash 5 receives from the flame.
Since the temperature can be set to about 150 ° C. under the condition that spontaneous combustion does not occur, the fire spread from the relay 27 to the panel sash 5 can be more effectively prevented. Of course, both side surface portions 33a and 33b of the shield plate 33 are connected to the relay 27.
It is safer to keep the distance above 100 mm above.

Also, the plastic case 2 of the relay 27
7a is formed of 94V-0, the panel sash 5 and the rear printed circuit board 25 are made of a flame-retardant material having a self-extinguishing property (property of extinguishing when the flame is removed) of 94V-2 or more and 94V-0 or less. Since the panel sash 5 and the rear printed circuit board 25 have high flame retardancy, it is difficult to spread the fire from the relay 27 to the panel sash 5 and the rear printed circuit board 25. Therefore, in this case, the shield plate 33 is formed of a relatively inexpensive flame-retardant material having a self-extinguishing property of 94V-2 or more and 94V-0 or less, and if 94V-0 is used, Since the shield plate 33 becomes superior to the panel sash 5 in self-extinguishing property and flame retardancy, it is more preferable in preventing fire spread.

As described above, since it depends on the distance between the relay 27 and the panel sash 5 and the forming material of the panel sash 5, the rear printed board 25, and the plastic case 27a of the relay 27, the shielding plate 33 is taken into consideration.
Since the forming material is selected, the shielding plate 33 can be made of a material with the lowest cost depending on the case and a good effect of preventing spread of fire can be obtained. As will be understood from this, when the rear printed circuit board 25 is made of a material having a high degree of flame retardancy, the shield plate 33 is made of the material forming the plastic case 27a and the panel sash 5.
What is necessary is just to determine the forming material.

When the relay 27 is ignited, the heat may cause the plastic case 27a to melt and drop while burning. In this case, since the small hole 34 on the bottom surface of the outer box 1 does not exist directly below the relay 27, there is no possibility that the plastic dropping while burning will fall out from the small hole 34. Therefore, a plate in which the microwave oven is easily burned. Even if they are placed on a cloth or cloth, there is no danger of them burning out.

Further, when abnormal heat is generated due to a defective connection of the lead wire or the faston terminal to the terminal of the relay 27, the generated heat causes the plastic case 27 to be heated.
It is also conceivable that a melts and the melting causes a hole to be exposed to expose the relay switch. Then, a spark may occur between the contact of the relay switch and the shield plate 33.

In consideration of this, it is preferable that the shielding plate 33 is formed of an electrically insulating material such as plastic, and functions as an insulator for the relay switch of the relay 27. Then, as described above, the relay switch and the shield 3
In order to prevent a spark from being generated between the shield plate 33 and the electric shield plate 3 and to prevent the shield plate 33 from being ignited by the spark, the shield plate 33 has a comparative tracking index of 174 V or more (U
It is made of a material of L standard class 3 or higher). The comparative tracking index of the UL standard defines the deterioration of the insulating property due to the contamination of the insulating material, and conforms to the test method of IEC112.

Further, it is known that the spark generated by the relay switch due to the voltage applied to the relay 27 does not fly to a place separated by 30 mm or more. Therefore, the small hole 34 on the bottom surface of the outer box 1 is made into the relay 27. 30mm or more away from (L
The distance (indicated by 2) prevents the spark generated in the relay switch from protruding from the small hole 34 to the outside, thereby improving electrical safety.

When the relay 27 is arranged in the main body 2 through a plastic mounting member, a switch such as a door switch for opening / closing the magnetron or heater by opening / closing the door 3 is used as a substrate or plastic. Also in the case of arranging it on the main body 2 via a mounting member made of metal, the material of the barrier provided between the member made of non-combustible material in the vicinity of the main body 2 is selected according to the degree of danger in the same way as the fourth embodiment. Is something that can be done.

[0062]

As described above, according to the present invention, the following effects can be obtained. In the microwave oven according to claim 1, a barrier made of a flame-retardant material or a non-combustible material is provided between the non-flame-retardant member and the high-voltage region of the substrate where a relatively high voltage is applied. Therefore, there is no risk of fire spreading from the substrate side to the non-flame-retardant member. Therefore, the distance between the high voltage region and the non-flame-retardant member can be shortened.

In the microwave oven according to the present invention, the barrier is arranged along the inner surface of the peripheral surface portion of the panel sash so as to surround the high voltage region from the outside of the substrate. Since it is possible to prevent the spread of flame to the surface portion, the distance between the high voltage region and the peripheral surface portion of the panel sash can be shortened. Moreover, when there are high voltage regions on both sides of the substrate, it is possible to block between the high voltage regions on both sides and the peripheral surface portion of the panel sash with one barrier,
It is possible to suppress an increase in the number of parts.

In the microwave oven according to the third aspect, the barrier is made of a metal plate material, and the mounting portion is formed integrally with the barrier by bending, so that the barrier can be easily fixed. In the microwave oven according to claim 4, since the boss portion for fixing the high-voltage component is covered with the cap, the spread of heat from the substrate side to the boss portion can be prevented, and the distance between the high-voltage region and the boss portion can be shortened. .

In the microwave oven according to the present invention, the plate-shaped barrier is arranged between the front portion of the panel sash and the high voltage region of the substrate and is fixed to the boss portion by the cap, so that the substrate side. From this, it is possible to prevent the spread of fire to the front surface of the panel sash, and it is possible to easily fix the barrier without using a fixture dedicated thereto. In the microwave oven according to the sixth aspect of the present invention, since the barrier is composed of the cover covering the high voltage region of the substrate, it is possible to more reliably prevent the substrate from spreading to the non-flame-retardant member.

In the microwave oven according to the present invention, since a barrier made of a flame-retardant material or a non-combustible material exists between the electric component with switching contacts and the non-combustible material member, the electric oven with switching contacts is assumed. Even if the plastic case of the component is ignited or the electric component with switching contacts emits a spark, the non-combustible member is not likely to burn out. In this case, the barrier forming material is determined by taking into consideration the distance between the electrical component with switching contacts and the non-combustible material, the forming material of the plastic case of the electrical component with switching contacts, the mounting member or the substrate. Therefore, depending on the case, it is possible to obtain the effect of preventing the spread of fire from the electric component with switching contacts to the non-combustible material member at the lowest cost.

According to the eighth aspect of the present invention, there is provided a microwave oven in which the distance between the electric component and the non-combustible material member is 100 mm or less, and the non-combustible material member is a non-flammable material equivalent to UL standard 94HB. Is formed of a UL standard 94V-0 flame-retardant material or a non-combustible material such as a metal, an inorganic material, or an inorganic compound, it is possible to obtain a good flame spread prevention effect even if the non-combustible material is relatively easily combusted. it can.

According to a ninth aspect of the microwave oven, the distance between the electric component with switching contacts and the non-combustible member is 100 mm.
In the following, when the non-combustible material member is a flame-retardant material having a self-extinguishing property of 94V-2 or more of UL standard and 94V-0 or less, the barrier is formed of ULV 94V-0 flame retardant material. By doing so, it is possible to obtain a good effect of preventing spread of fire at low cost.

[Brief description of drawings]

FIG. 1 is a vertical sectional side view of a main part showing a first embodiment of the present invention.

FIG. 2 is a perspective view of a main part

FIG. 3 is a vertical sectional side view of an operation panel portion.

FIG. 4 is a cross-sectional view as seen from the direction of the arrow along the line A-A in FIG.

FIG. 5 is a cross-sectional view as seen from the direction of the arrows along the line EE in FIG.

FIG. 6 is a perspective view of a microwave oven.

FIG. 7 is a diagram corresponding to FIG. 3 showing a second embodiment of the present invention.

FIG. 8 is a cross-sectional view seen from the direction of the arrow of the woo line in FIG.

FIG. 9 is a view corresponding to FIG. 3 showing a third embodiment of the present invention.

FIG. 10 is a cross-sectional view as seen from the direction of arrow A-A in FIG.

FIG. 11 is a perspective view of a shield plate.

FIG. 12 is a vertical cross-sectional side view of essential parts showing a fourth embodiment of the present invention.

[Fig. 13] Longitudinal section rear view

FIG. 14 is an exploded perspective view

[Explanation of symbols]

2 is a main body, 4 is an operation panel, 5 is a panel sash, 7 is a front printed circuit board, 8 is a rear printed circuit board (board), 11 is a power transformer (high voltage component), 15 is a boss portion, 17 is a cover (barrier). , 18 is a cap (barrier), 19 is a shield plate (barrier), 21 is a cap, 22 is a shield plate (barrier), 24 is a front printed circuit board, 25 is a rear printed circuit board (substrate), and 27 is a relay (with open / close contact) Electrical parts), 2
7a is a plastic case, and 33 is a shielding plate (barrier).

Claims (9)

[Claims] 1. A plastic panel sash constituting an operation panel is provided on a front surface of a main body, and a high voltage component for applying a relatively high voltage is provided on a substrate arranged inside the panel sash. In the microwave oven, a barrier made of a flame-retardant material or a non-combustible material is provided between the high-voltage region where the relatively high voltage application portion exists and the non-flame-retardant material member of the substrate. 2. The microwave oven according to claim 1, wherein the barrier is arranged along a peripheral surface portion of the panel sash which is a non-flame-retardant member and surrounds the high voltage region from the outside of the substrate. 3. The microwave oven according to claim 2, wherein the barrier is made of a metal plate, and the barrier made of the metal plate is integrally formed with a mounting portion by bending. 4. The panel sash is integrally provided with a boss portion for fixing a high-voltage component, and the boss portion, which is a non-flame-retardant material member, is covered with a metal cap that constitutes a barrier. The microwave oven according to claim 1. 5. A plate-shaped barrier is also disposed between the front surface of the panel sash, which is a non-flame-retardant member, and the high-voltage region of the substrate, and is pressed and fixed to the boss by a cap. The microwave oven according to claim 4. 6. The barrier is a cover attached to the substrate so as to cover the high voltage region.
The microwave oven as described. 7. An opening / closing contact, wherein a board or a plastic mounting member is provided inside the main body, and an electric component with a switching contact provided with a contact for opening / closing in a plastic case is arranged on the board or mounting member. A barrier is provided between the attached electric component and the non-combustible material member, and the barrier is provided with a distance between the electric component with switching contacts and the non-combustible material member, and the plastic case forming material and the mounting member or A microwave oven, which is formed of a flame-retardant material or a non-combustible material according to a material for forming a substrate. 8. The distance between the electric component and the non-combustible material is 100 mm or less, and the non-combustible material is UL standard 94.
In case of non-flame retardant material equivalent to HB, the barrier is UL standard 9
The microwave oven according to claim 7, wherein the microwave oven is formed of a 4V-0 flame-retardant material or a non-combustible material such as a metal, an inorganic material, or an inorganic compound. 9. The non-combustible material member is U and the distance between the electric component with switching contacts and the non-combustible material member is 100 mm or less.
In the case of a flame-retardant material having a self-extinguishing property of 94V-2 or more in the L standard and 94V-0 or less, it is necessary to form the barrier with a flame retardant material in the UL standard of 94V-2 or more and 94V-0 or less. The microwave oven according to claim 7, wherein the microwave oven is a microwave oven.