JP2007327673A - Microwave oven - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem with a microwave oven using a magnetron and a sheath heater, and provided with electronic components such as a circuit board for driving the magnetron on its bottom portion, and the sheath heater for the oven at a bottom portion side and a top face side in a heating chamber, wherein it is necessary to increase the capacity of a cooling fan for cooling all of the electronic components by the cooling fan of a back face portion, as the temperature of the electronic components disposed on the bottom portion is raised by the heat generated from the sheath heater in heating as the oven. <P>SOLUTION: The temperature of the electronic components is lowered without additionally installing a cooling fan by applying a part of the cooling air used exclusively for the magnetron as the cooling air for the electronic components, by operating the cooling fan 20 for cooling the magnetron even in operating the oven without using the magnetron 29, when the microwave oven is operated as the oven. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a microwave oven in which a magnetron and a sheathed heater are mounted and the temperature of the mounted electronic component is cooled using a part of cooling air used for cooling the magnetron.

What is cooled in a device equipped with a magnetron such as a microwave oven is disclosed in JP-A-2005
No. 26184 (Patent Document 1). Further, cooling of electronic components in a high-frequency heating apparatus such as a microwave oven is described in Japanese Patent Laid-Open No. 2003-203755 (Patent Document 2).

JP 2005-26184 A JP 2003-203755 A

  A microwave oven using a magnetron and a sheathed heater has a circuit board for driving the magnetron and a weight sensor for detecting the weight at the bottom. Also, there are sheathed heaters for the oven on the bottom side and top surface. When heated as an oven, the heat generated from the sheathed heater increases the temperature of these electronic components placed on the bottom, so that it is used for cooling. Fans are mounted on the rear.

  A cooling fan for cooling the magnetron is also attached to the rear surface. During oven operation, it is necessary to install additional cooling fans to secure the ventilation path in order to cool all the electronic parts on the front side and diagonal parts with only the cooling fan on the rear side. There were problems such as an increase in drive circuit cost and an increase in installation space.

  In view of the above-described problems, an object of the present invention is to provide a microwave oven that cools electronic components without adding a cooling fan.

  In the present invention, the temperature of the electronic components in each part is highest when the microwave oven is operated as an oven, that is, when the upper and lower sheathed heaters are used, but at this time, the magnetron is not used. Therefore, the temperature of the cooling air that cools the magnetron is low.

  In addition, a magnetron is used during the range, but the temperature of the electronic component is lower than when a sheathed heater is used.

  For this reason, the cooling fan that cools the magnetron is moved even in an oven that does not use the magnetron, and a part of the cooling air that was used exclusively for the magnetron is used as the cooling air for the electronic parts, so that the cooling fan can be expanded. Without reducing the temperature of electronic components.

  According to the present invention, since a part of the cooling air that cools the magnetron exclusively is used as the cooling air for the substrate, the electronic component can be cooled without adding a cooling fan.

  FIG. 1 is a perspective view of a product main body according to an embodiment of the present invention. There is a door 2 with a handle 1 on the front, and a transparent glass window 3 can be used to look inside. The door 2 can be opened horizontally by a hinge mechanism (not shown) with the lower part as a fulcrum by pulling the handle 1 forward. An operation panel 4 is disposed below the door 2, and a display device 5 is disposed in the center. The operation time can be quickly set by rotating the dial 6 provided on the operation panel. A plurality of exhaust ports 8 are provided on the side surface of the outer frame 7. The exhaust port 8 is also provided on the opposite side surface and the rear side.

  FIG. 2 relates to an embodiment of the present invention, and shows a front view as seen from the bottom. The electronic component cooling fan 20 is disposed on the lower surface on the right side of the back surface. Most of the cooling air by the electronic component cooling fan 20 passes through the air passage of the ventilation A, cools the electronic components of the inverter board 22 on which the high-voltage transformer 21 is mounted, and separates the power board 23 into the ventilation B and C. Cooling.

Ventilation C is exhausted from the side to the outside, and ventilation B passes through the power supply board 23 to the weight sensor 24b and is exhausted from the side. Since the position of the weight sensor 24b is far from the electronic component cooling fan 20, the cooling efficiency is very poor. For this reason, temperature becomes high compared with two other weight sensors. Although the weight sensor 24a is under the power supply board 23, it is cooled by the ventilation B, and therefore the distance from the electronic component cooling fan 20 is short, so that the cooling efficiency is relatively good.

Further, the cooling air flow D by the electronic component cooling fan 20 is cooled by efficiently applying the cooling air by the weight sensor 24 c by the ventilation guide 25. A turntable motor 27 for driving the turntable in the cabinet is arranged at the center. The magnetron cooling fan 28 is arranged on the lower surface on the left side of the back surface opposite to the electronic component cooling fan 20.

Ventilation E by the magnetron cooling fan 28 cools the magnetron 29, most of which is exhausted to the outside from the side surface, and part of the ventilation air 30 becomes cooling air from the ventilation port 30 to cool the weight sensor 24b. By setting the positions of the electronic component cooling fan 20 and the vent 30 to a rectangular diagonal position, the weight sensor 24b, which is an electronic component that cannot be cooled only by the electronic component cooling fan 20, can be cooled.

  FIG. 3 relates to an embodiment of the present invention, and shows a partially enlarged view of the vent 30. Since the automatic opening and closing is performed according to the temperature of the ventilation F, when the temperature of the ventilation F is low by using the shape memory alloy plate 31 or the bimetal plate, that is, in this embodiment, the shutter 32 is opened at 70 ° C. or less. When the air temperature is high, that is, when the air temperature is higher than 80 ° C., the weight sensor 24b is prevented from hitting.

  The shape memory alloy plate 31 is fixed by screws 33. Although a plate is used for the shape memory alloy, the directivity cannot be restricted if it is linear, so that it can be easily fixed with screws 33 or the like.

  FIG. 4 shows a circuit block diagram according to the embodiment of the present invention. The power supply 40 is connected to a commercial power supply of AC100V50 / 60Hz. The power switch 41 is turned on and the power switch 41 is turned on.

  The magnetron 29 cuts power line noise and aerial radio noise by the filter circuit 42, supplies the power converted into the DC power by the rectifier circuit 43 to the inverter circuit 44, increases the frequency, and connects to the temporary side of the high voltage transformer 21. As a result, a high voltage is generated on the secondary side, and the magnetron drive circuit 45 operates the magnetron 29.

  A signal from the operation panel 4 is controlled by the microcomputer 47 via the display circuit 46. There are a total of three weight sensors 24, two on the front side and one on the rear side, thereby detecting the weight of the heated object on the pan placed on the weight sensor 24.

  Further, a temperature sensor 48 for detecting the temperature in the cabinet and a buzzer circuit 49 for notifying the end or abnormality are connected to the microcomputer 47. Various electrical components are connected to the microcomputer 47 via the drive circuit 50.

  As main electrical components, an electronic component cooling fan 20, a magnetron cooling fan 28, an upper heater 51, a lower heater 52, a hot air motor 53, a hot air heater 54, and a boiler heater 55 are connected.

  FIG. 5 relates to the embodiment of the present invention, and shows the operation timing of each electrical component. When the range is used, the magnetron 29 mainly operates. At this time, the electronic component cooling fan 20 and the magnetron cooling fan 28 are on. The upper and lower heaters, that is, the upper heater 51 and the lower heater 52 are in an off state. When using the oven, the upper and lower heaters are mainly used.

  At this time, the electronic component cooling fan 20 and the magnetron cooling fan 28 are also turned on. The magnetron 29 is in an off state. That is, the magnetron cooling fan 28 is operated regardless of the operation of the magnetron 29, thereby cooling the weight sensor 24 b, which is an electronic component, through the vent hole 30. When the vent hole 30 remains open, the exhaust gas is used for cooling by lowering the exhaust temperature from the vent hole 30 to 85 ° C., which is the allowable temperature of the electronic components.

  Hereinafter, the present invention will be described in detail. In this embodiment, the continuous range output of the microwave oven with an oven function is 700 W at the maximum. (The maximum output for a short time is 1,000 W) On the other hand, the heater power consumption when using the oven is 1,390 W.

  As for the heater, an upper heater 51 is disposed on the upper surface of the chamber, and a lower heater 52 is disposed on the lower surface. Various electronic components are arranged below the lower heater 52 and insulated by glass fiber, but the temperature easily rises due to heat conduction.

  Further, the temperature in the cabinet is 250 ° C. when using the oven and is higher than 220 ° C. when using the range. For this reason, since the temperature of the weight sensor 24b increases when the oven is used than when the range is used, it is necessary to reduce the temperature rise when the oven is used.

  When the vent 30 is not used, this temperature difference is as large as about 30 ° C., but when it is used, it is about 15 ° C., which is half, because the amount of heat conducted by heat conduction is large. The cooling fan 28 for the magnetron has a cooling air volume that can withstand the maximum output for a short time.

  In addition, when both the range and the oven are used, the duty of the range, that is, the energization rate of the magnetron 29 is small. Therefore, when the oven is used, the duty of the magnetron 29 is small. The cooling capacity of the magnetron cooling fan 28 used has a considerable margin.

  The exhaust temperature after cooling the magnetron 29 is 100 ° C. when the maximum output is 1,000 W for a short time, 70 ° C. when the continuous range output is 700 W, and 30 ° C. (room temperature) when the magnetron 29 is not used. Further, since the exhaust temperature when using the continuous range is about 70 ° C., there is a margin for the upper limit of 85 ° C. of the heat resistance temperature of the electronic component, so the exhaust after cooling the magnetron 29 is used as it is for the cooling air of the weight sensor 24b which is an electronic component. Even so, there is no problem and it can be cooled.

  In this embodiment, since the temperature of the weight sensor 24a, which is an electronic component when using the oven, is significantly higher than that when using the range, the magnetron cooling fan 28 when using the range is used in the oven without increasing the cooling fan 20 for electronic components. The weight sensor 24a, which is remote from the mounting position of the electronic component cooling fan 20 by being turned on during use, is cooled by guiding a part of the cooling exhaust of the magnetron 29 through the air vent 30.

FIG. 4 is a perspective view of a product main body according to an embodiment of the present invention. The front view which concerns on the Example of this invention and was seen from the bottom face part is shown. It concerns on the Example of this invention, and the fragmentary enlarged view of the ventilation port is shown. FIG. 2 is a circuit block diagram according to an embodiment of the present invention. It concerns on the Example of this invention, and the operation timing of each electric component is shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 20 ... Cooling fan for electronic components, 28 ... Cooling fan for magnetron, 29 ... Magnetron, 30 ... Ventilation opening, 31 ... Shape memory alloy plate, 32 ... Shutter.

Claims (3)

  In a microwave oven having a function of an oven and a range provided with a cooling fan for an electronic component and a cooling fan for a magnetron for cooling an electronic component provided at the bottom, a ventilation opening is provided in a part of the cooling air ventilation path for cooling the magnetron. A microwave oven characterized in that a part of cooling air from the magnetron cooling fan is used for cooling the electronic component.   The microwave oven according to claim 1, wherein a shutter using a plate-shaped shape memory alloy or bimetal is provided at the vent hole. 3. The microwave oven according to claim 1, wherein the position of the ventilation port is located at a diagonal position with respect to the cooling fan for electronic components. 4.

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