JPS6032766B2 - High frequency heating device - Google Patents

Description

[Detailed Description of the Invention] The present invention provides two heating methods: microwave heating that utilizes the self-heating of the food itself due to microwaves generated by a magnetron, and a general heating method that uses an electric heater to raise the temperature inside the heating chamber. This invention relates to an improvement in a microwave oven equipped with an electric heater that can perform both functions at the same time.

This will be explained below with reference to the accompanying drawings. FIG. 1a is a top sectional view schematically showing a conventional microwave oven, and FIG. 1b is a side sectional view thereof.

Microwaves generated by the magnetron 1 are guided to a heating chamber 4 through a waveguide 3. A door 6 is provided in the front of the heating chamber 4 so as to be openable and closable, and the door 6 is used to take food in and out. An electric heater 10 is disposed within the heating chamber 4, and is used when raising the temperature within the heating chamber 4 to heat food. The magnetron 1 is cooled by a motor fan 2, and the air guide 7 is for guiding the cooling air generated by the motor fan 2 to the magnetron 1. Now, when operating only the magnetron 1 in this microwave oven, move the shutter 9 provided in the exhaust guide 8 that guides the cooling air after cooling the magnetron 1 to the position shown in the figure by the imaginary dashed line. The magnetron 1 is moved and the air after cooling the magnetron 1 is introduced into the heating chamber 4.

The reason why the exhaust gas that has cooled the magnetron 1 is introduced into the heating chamber 4 is because water vapor from the food during microwave heating condenses on the window of the door 6 and forms water droplets, causing the window of the door 6 to fog up. The main purpose is to prevent the inside of the heating chamber 4 from becoming visible from the outside. Now, when heating by the electric heater 10 and microwave heating by the magnetron 1 are performed simultaneously, it is necessary to keep the overall electric capacity small.

Therefore, the most practical way to achieve simultaneous heating is to
For example, 1. When the temperature in the heating chamber 4 reaches a predetermined temperature, the power consumption of the electric heater 10 is reduced to 0.7 W, and the remaining power of 0.4 W is used to power the magnetron. There is a way to operate on output. In any case, heating with electric heater 10 and magnetron 1
When simultaneously performing microwave heating at a small output of Therefore, it is clear that if such air is introduced into the heating chamber 4, the temperature inside the heating chamber 4 will drop. Therefore, conventionally, the shutter 9
The magnetron 1 was moved to the position shown by the solid line in FIG. 1, the magnetron 1 was cooled, and the exhaust gas was discharged to the outside of the heating chamber 4. However, even if the flow of air is changed by such a shutter 9, the motor fan 2 naturally cools the magnetron 1 by sucking in cold outside air from outside the body 5, and the motor fan 2 constitutes the power source of the magnetron 1. It also serves to cool the transformer 11 and condenser (not shown) with the air sucked into the motor fan 2, and in many cases, an air intake vent a is opened in the body 5 near the bottom of the transformer 11. . Therefore, even if the exhaust gas after cooling the magnetron 1 is directly discharged from the body 5 through the exhaust port b by the exhaust guide 8, a flow of cold air exists as shown by the arrow ↑ in FIG. The outer wall of the heating chamber 4 is cooled due to the air sucked into the heating chamber 4.
The temperature inside the motor fan 2 is lowered, and the heating efficiency of the electric heater 01 is significantly lower than when the motor fan 2 is not driven. However, when heating by the open-air heater 10 and microwave heating by the magnetron 1 are performed at the same time as we are currently considering, it is necessary to keep the power consumed by both the electric heater 10 and the magnetron 1 as small as possible in terms of power capacity. Therefore, it is desired that the thermal efficiency be higher than when heating with the electric heater 10 alone. The present invention solves the problems of the prior art and relates to a method for realizing a microwave oven that drives the motor fan 2 and sufficiently cools the magnetron 1 without reducing the thermal efficiency of heating by the electric heater 1.

Embodiments of the present invention will be described with reference to the drawings.

FIG. 2 shows an embodiment of the microwave oven according to the present invention, and corresponds to FIG. 1, and parts common to those in FIG. 1 are given the same numbers. Now, in the case of the configuration shown in FIG. 2 according to the present invention, when heating is performed using both the electric heater 0 and the small output of the magnetron 1, the shutter 9 is set at the position shown by the solid line in FIG. The passage of cooling air coming out of the is closed.

By doing this, it goes without saying that no cooling air will enter the heating chamber 4, but what is important is that the motor fan 2 itself basically loses its air outlet and no longer takes in air. The relationship between the air volume and wind pressure of a motor fan 2 such as the Sirotsko fan, which is commonly used in fin ranges, is a P-Q curve as shown in FIG. Now, when the shutter 9 is at the pupil of the imaginary line shown by the dashed-dotted line in FIG. Provides the most stable and efficient cooling performance. Now, when the shutter 9 is placed in the position shown by the solid line in FIG. 2, that is, in the closed state, the exhaust path from the magnetron 1 is closed, so the wind pressure increases and the operating point moves from P to P2. The reason why the air volume Q is not completely zero here is because the current /' configuration cannot completely close off the air outlet from the motor fan 2 and there is a part where it leaks, or vice versa. It is also conceivable that a portion of the magnetron 1 is intentionally leaked due to the cooling of the magnetron 1, which will be described next, but in any case, when the shutter 9 is closed, the wind pressure P increases considerably and the air volume Q decreases considerably. Now, it goes without saying that when such a shutter 9 is closed, no air flows into the heating chamber 4, but the fact that the storm volume Q falls during the middle of the day means that the motor fan 2 absorbs almost no air. It will have to be cancelled. That is, while the shutter 9 was open, cold air was sucked in from outside the body 5, and the air was sucked into the motor fan 2 while cooling the side wall of the heating chamber 4. However, when the shutter 9 is closed, As a result, the inflow of cold outside air into the body 5 is almost stopped, and therefore, heat is no longer lost from the outer wall of the heating chamber 4. on the other hand,
Looking at the cooling of magnetron 1, of course when the output of magnetron 1 is high (generally 500W to 600W)
The shutter 9 is open and is designed to provide sufficient cooling.

On the other hand, when the electric heater 10 and the magnetron 1 are operated simultaneously at a small output, the shutter 9 is closed and the exhaust duct 8 is closed as explained above.
At this time, the output of the magnetron 1 is about 1/2 to 1/3, and of course the calorific value of the magnetron 1 is also 1/2 to 1/3, and even if the shutter 9 is closed, the air has both compressibility and fluidity. Even if the total subtraction of the air passing through the magnetron 1 is zero because it is a certain gas, the drive of the motor fan 2 causes the magnetron's heat dissipation plate (generally composed of 4 to 5 aluminum plates parallel to the cooling air) to be )
If you look at the area nearby, there is a flow of air, which creates a considerable cooling effect even if the amount of air exhausted from magnetron 1 is zero.There are two reasons why the temperature rise of magnetron 1 is lower than the output. It is possible to suppress the value to a low value equivalent to that of Otoki. And if the output of magnetron 1 is relatively large when the output is small, and if the exhaust passage is blocked, cooling will not be sufficient, it is natural to consider leaving some exhaust port to secure the air volume by, for example, 1/2. However, it goes without saying that the above explanation and the effects of this aircraft can be expected. In addition, in the above explanation, it was considered that the magnetron 1 is operated continuously at a small output to heat with both the electric heater 10 and the magnetron 1, but this can be done by intermittent high output operation to generate an equivalent output (low output). In that case, it is common to operate when the electric heater 10 is off, but if the cycle of on-off time is short enough, the above-mentioned continuous operation can also be used for cooling the magnetron 1. It goes without saying that this is exactly the same machine as in the case of , and the configuration of the present invention is valid as is.

As described above, according to the present invention, when microwave heating at a low output of the magnetron 1 and heating of the electric heater 10 are performed simultaneously, the magnetron is heated while the magnetron cooling air passage is closed on the exhaust side of the magnetron 1. Since the cooling motor fan 2 is driven, it is possible to remove heat from the outer wall of the heating chamber 4 and prevent cold outside air from being sucked in by the motor fan 2, thereby cooling the magnetron 1 without reducing the thermal efficiency of the electric heater 10. This makes it possible to realize a microwave oven that can perform simultaneous heating using an electric heater and microwave heating, which was previously difficult to realize due to electric capacity.

[Brief explanation of the drawing]

1a in FIG. 1 is a top sectional view schematically showing a high-frequency heating chamber device with a conventional structure, FIG. 1b is a side sectional view thereof, and FIG. FIG. 2B is a schematic top sectional view, FIG. 2B is a side sectional view, and FIG. 3 is a diagram showing an example of the motor fan air volume, wind pressure characteristics, and operating points of the high-frequency heating device according to the present invention. 1...Magnetron, 2...Motor fan, 8...Exhaust guide, 9...Shutter, a...Intake port. Figure 3 Figure 1 Figure 2

Claims (1)

[Scope of Claims] 1. In a microwave oven equipped with a magnetron, a motor fan that cools the magnetron, a switching mechanism that switches the magnetron output between high and low levels, and an electric heater, when heating is performed simultaneously with the low output of the magnetron and the electric heater. A high-frequency heating device configured to drive a motor fan with the magnetron cooling air passage closed on the side where the cooling air exits the magnetron, that is, on the exhaust side. 2. In a microwave oven equipped with a magnetron, a motor fan that cools the magnetron, and an electric heater, when the magnetron and the electric heater are alternately energized and the magnetron and electric heater heat at the same time, the magnetron cooling air causes cooling air to pass through the passage. Close the magnetron on the exit side, that is, the exhaust side, or reduce it to a large width, and reduce the intake air volume of the motor fan to about 1/2 of that of the magnetron at high output.
High frequency heating equipment as below.