JPS6133450Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a microwave oven equipped with an infrared detector that detects infrared rays emitted from food and outputs a signal according to the temperature of the food.

Recently, microwave ovens have appeared that are equipped with an infrared detector, detect the temperature of the food by detecting infrared rays emitted from the food, and control the heating of the food based on the detected temperature. In such a microwave oven, the infrared detector is placed outside the heating chamber, and an opening is formed in the wall of the heating chamber to guide infrared rays emitted from the food in the heating chamber to the infrared detector. . Further, the infrared detector is cooled by cooling air, and this cooling air is then sent into the heating chamber through the opening. By blowing air into the heating chamber, steam emitted from the food is prevented from reaching the infrared detector through the opening, thereby preventing contamination of the infrared detector.

On the other hand, generally during microwave heating, a large amount of air is used to cool the magnetron, and then the air is supplied into the heating chamber to prevent the transparent window of the door for food entry and exit of the heating chamber from fogging up. The airflow is also used to exhaust steam, oil droplets, etc. from the heating chamber. In such a microwave oven, the amount of cooling air that cools the infrared detector is large, and this cooling air overcomes the pressure of the wind after cooling the magnetron and is sent into the heating chamber. The wind along with steam etc. will not reach the infrared detector side through the opening.

The microwave oven is further provided with an external heating device for externally heating the food using a heater or the like. During external heating using this device, magnetron cooling air is prevented from flowing into the heating chamber in order to increase external heating efficiency. However,
Such a microwave oven still has the drawback that air for cooling the infrared detector flows into the heating chamber, thereby reducing heating efficiency. However, since the air volume is large, this reduction in heating efficiency becomes even more noticeable.

The present invention has been devised in view of these points, and embodiments of the present invention will be described in detail below with reference to the drawings.

1 is a heating chamber that stores the food 2; 3 is a magnetron that oscillates microwaves for microwave heating the food 2; 4 is a first blower that generates a large amount of cooling air to cool the magnetron; 5 is a first blower that generates a large amount of cooling air to cool the magnetron; A duct 6 normally guides the wind after cooling the magnetron 3 into the heating chamber 1, and 6 is a damper. When the damper is in the position indicated by the solid line, the wind after cooling the magnetron 3 passes through the small hole group 7 into the heating chamber 1. This introduced air prevents the transparent window (not shown) of the food access door of the heating chamber 1 from fogging up, and also prevents the heating chamber 1 from fogging up.
It is used to exhaust steam, oil droplets, etc. On the other hand, when the damper 6 is at the position indicated by the broken line,
The wind after cooling the magnetron 3 is directly discharged to the outside of the heating chamber 1 through the opening 8. 9 is a hot air generating section for externally heating the food 2; in the generating section,
Reference numerals 10 and 11 designate a group of intake and discharge small holes formed in the upper wall 12 of the heating chamber, respectively, and 13 a hot air duct containing a heater 14 and disposed across both of the small hole groups. 15
is a hot air fan, which sucks the air in the heating chamber 1 through the intake hole group 10 and discharges the air heated by the heater 14 into the heating chamber 1 from the discharge hole group 11. Hot air circulates between the heating chamber 1 and the hot air duct 13. Reference numeral 16 indicates a microwave blocking ring that is attached to an opening 17 formed in the upper wall 12 of the heating chamber and allows infrared rays emitted from the food 2 to pass through, while blocking the passage of microwaves; 18 indicates the food that has passed through the ring; an infrared detector that detects infrared rays from 2 and outputs a signal according to the temperature of the food 2; 19 is a metal case that houses the detector;
The upper end opening of the ring 16 faces the bottom wall 20 of the case, and a large number of small holes 21, 21 are bored therein. 22 supplies cooling air for cooling the detector 18 to the case 1 through a duct 23.
9, the blower is powered by a motor 24.
The number of revolutions is controlled in two stages: large and small. 25
is a shutter that is driven by an electromagnet 26 to open and close the opening of the ring 16, and the shutter and the ring 16
There is a gap of about 1 mm between the shutter 25 and the ring 16, so that the shutter 25 is smoothly driven without any friction between the shutter 25 and the ring 16.

Therefore, when heating by microwave alone, damper 6
is at the position indicated by the solid line, and since the wind after cooling the magnetron 3 is sent to the heating chamber 1, fogging of the transparent window of the door is prevented and steam, oil droplets, etc. in the heating chamber 1 are exhausted. Further, the shutter 25 opens the opening of the ring 16, whereby the infrared rays from the food 2 are detected by the infrared detector 18, the temperature of the food 2 is detected, and the microwave heating is controlled based on this temperature. be done.

After cooling the infrared detector 18, the cooling air from the second blower 22 is discharged to the outside of the case 19 through the small holes 21, 21, . Furthermore, at this time, the rotation speed of the motor 24 of the second blower 22 increases and the rotation speed of the motor 24 of the second blower 22 increases.
The amount of cooling air from the blower 22 is large, so the air after cooling the detector 18 overcomes the wind pressure in the heating chamber 1 due to the magnetron 3 cooling air and is sent into the heating chamber 1 through the opening of the ring 16.

When heating with hot air alone, the damper 6 is at the position indicated by the broken line, and the shutter 25 closes the opening of the ring 16. This closure prevents steam, oil droplets, etc. in the heating chamber 1 from leaking to the detector 18 side.
However, there is a gap of about 1 mm between the shutter 25 and the ring 16 in order to smooth the drive of the shutter 25, and there is a risk that steam, oil droplets, etc. may leak from this gap due to the pressure of hot air. Regarding this point, since the air after cooling the infrared detector 18 overcomes the pressure of the hot air and is sent into the heating chamber 1 through the gap, there is no risk of steam, oil droplets, etc. leaking.

At this time, the hot air is circulating between the heating chamber 1 and the hot air duct 13 without introducing outside air, so the wind pressure inside the heating chamber 1 is small, and therefore the air volume after cooling the infrared detector 18 is also heated. It is made small enough to overcome the wind pressure inside room 1. That is, the second blower 2
The number of rotations of the second motor 24 is switched to a smaller value. This allows the infrared detector 18 to
Even if the cooling air is sent into the heating chamber 1, the amount of this air is extremely small, so the hot air heating efficiency hardly decreases. In this case, a desired time is set in advance and hot air heating is performed during this time. Furthermore, since the inside of the heating chamber 1 is at a high temperature due to hot air heating, the transparent window of the door hardly fogs up.

The case where microwave heating and hot air heating are alternately repeated is similar to the case where hot air heating is used alone.

Thus, according to the microwave oven of the present invention, at least during external heating by the external heating means, almost no cold air enters the heating chamber, so it is possible to significantly suppress a decrease in external heating efficiency.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a microwave oven according to an embodiment of the present invention, and FIG. 2 is a sectional view taken along line A--A in FIG. DESCRIPTION OF SYMBOLS 1... Heating chamber, 3... Magnetron, 9... Hot air generation part, 17... Opening, 18... Infrared detector, 22... Second blower.

Claims (1)

[Scope of utility model registration request] A heating chamber that stores food, a magnetron that oscillates microwaves to microwave food,
External heating means such as a heater for externally heating the food, an opening bored in the wall of the heating chamber, and arranged outside the heating chamber to detect infrared rays emitted from the food through the opening to control food heating. an infrared detector that outputs a signal according to the temperature of the food; cooling air generating means that cools the infrared detector and then generates cooling air that is sent into the heating chamber from the opening; A microwave oven characterized in that during external heating, the amount of cooling air from the cooling air generating means is reduced.