JPS5844937B2 - High frequency heating device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a high-frequency heating device having a control function to automatically properly heat an object to be heated.

In a high-frequency heating device that heats the object by supplying high-frequency power into a heating chamber that stores the object, the temperature of the object is determined by detecting the temperature of the air flowing out of the heating chamber or the temperature of the air inside the heating chamber. A high-frequency heating device has been invented that indirectly detects the heating time and automatically controls the heating time.

This type of high-frequency heating device has the advantage that it does not damage the heated object, compared to contact type devices that use a probe-shaped temperature sensing element to directly detect the temperature of the heated object. This is extremely useful.

The general structure of the above-mentioned high-frequency heating device of this type of invention will be explained using FIG.
This is an opening door for storing and discharging objects to be heated.

As is well known, this door 3 is designed to prevent the high-frequency power supplied to the heating chamber 1 from leaking to the outside through the opening, and allows the inside of the heating chamber 1 to be observed if necessary. In this way, a finder is formed using a perforated metal plate, a transparent glass plate, etc.

4 is a plate on which the object to be heated 2 is placed.

Reference numeral 5 denotes an opening which shields the inside and outside of the heating chamber 1 using high-frequency waves to allow air to flow therethrough, and in this device, air flows in from here.

Reference numeral 6 denotes an opening which shields the interior and exterior of the heating chamber 1 using high-frequency waves, as described above, to allow air to flow therethrough, and in this device, air flows out from here.

Reference numeral 7 denotes a blow device that forcibly causes the above-mentioned air flow, and discharges the exhaust gas to the outside of the high-frequency heating device through an exhaust path 8.

A magnetron 9 that generates high-frequency power is installed in the exhaust path 8, and is cooled by the exhaust gas.

Reference numerals 10 and 11 are openings formed at the outermost side of the high-frequency heating device, corresponding to the opening 5 through which the air flows in and the opening 6 through which the air flows out, respectively, and are provided so as not to spoil the appearance of the other parts.

As shown in the figure, the antenna of the magnetron 9 is projected directly into the heating chamber 1, and a cover 12 made of a material with low high frequency power loss is provided around it.

Reference numerals 13 and 14 designate temperature sensing elements, such as a thermistor, installed outside the openings 5 and 6 of the heating chamber 1, in portions that are not exposed to high-frequency power.

These temperature sensing elements 13 and 14 are connected to a control device 15, and the control device 15 receives a temperature signal of the air flowing into the heating chamber 1 from the temperature sensing element 13 and a temperature signal from the temperature sensing element 14 when the high frequency heating device is activated. The temperature signal of the air flowing out from the heating chamber 1 is received and compared, and the power supply device 16 is controlled in a predetermined state, for example, when the difference between the signal values of the temperature detection elements 13 and 14 reaches a predetermined value. , thereby stopping the operation of the magnetron 9 and blower 7 and stopping high frequency heating.

Reference numeral 17 denotes a guide plate that guides the flow of air so that the air flowing into (into) the heating chamber comes into contact with the object to be heated 2 as much as possible and incorporates the steam generated from the object to be heated 2.

In this way, the high-frequency heating device that indirectly detects the temperature of the object to be heated 2 by detecting the temperature of the air flowing out of the heating chamber 1 during high-frequency heating and automatically controls the heating time eliminates the troublesome timer setting operation. Although this method is unnecessary and greatly improves the usability of the high-frequency heating device, it also has some undesirable drawbacks.

That is, the temperature of the air flowing into the heating chamber 1 during high-frequency heating and the temperature of the air flowing out from the heating chamber 1 rises due to both heat transfer from the heated object 2 and water vapor generated from the heated object 2. Since it is convenient for highly accurate automatic control to have as large a difference between the two temperatures as possible, the amount of air flowing through the heating chamber 1 must be minimized.

Therefore, the water vapor generated from the heated object 2 is no longer carried out of the heating chamber 1 along with the circulating air, and naturally the amount of water vapor in the atmosphere inside the heating chamber 1 and the exhaust passage 8 tends to reach the saturation point. Put it away.

If the above saturation point is reached, condensation water immediately forms and adheres to the walls of the heating chamber 1 and the finder of the door 3, impeding the see-through function of the finder, and also accumulates as water inside the heating chamber. .

The same applies to the inside of the exhaust path 8.

Furthermore, even if the amount of water vapor in the atmosphere within the heating chamber 1 has not reached the saturation point, if the temperature of the finder or the wall of the heating chamber 1 is lower than the ambient temperature, the saturation point will be reached at the portions in contact with those walls. , dew condenses and impedes the finder function as described above, and also accumulates in the heating chamber 1 as water.

Needless to say, the same thing will happen in the exhaust path 8 in this case as well.

If this situation continues, a large amount of water may overflow from the heating chamber 1 and enter the power supply section, leading to an extremely dangerous situation.

This is a serious defect as a product and must be eliminated.

However, from the standpoint of improving the accuracy of automatic control by detecting air temperature, condensation and improving accuracy are in a contradictory relationship, and it is therefore extremely difficult to achieve mutual satisfaction with both.

The relationship between the amount of air that flows into the heating chamber 1, circulates and flows out during high-frequency heating, and the temperature difference between the temperature of the inflowing air and the temperature of the air heated by the object to be heated 2 and then discharged is The situation tends to be as shown in Figure 2.

That is, if an attempt is made to prevent condensation of water vapor by increasing the air volume, a large temperature difference cannot be achieved, resulting in a decrease in detection accuracy.

On the other hand, if an attempt is made to increase the detection accuracy by reducing the air volume and increasing the temperature difference, dew condensation will occur in the heating chamber 1 and the like.

However, there is a cooking method called reheating food in the field where the high frequency heating device that automatically controls the heating time by temperature detection as described above is used for cloth. Even if there is a large amount of water vapor from the food to be heated, it will not cause a serious problem because the automatic control device will activate and stop high-frequency heating before the atmosphere reaches the saturation point or before dew condenses on the walls of the heating chamber. However, when it is desired to maintain a certain temperature of heated food for a certain period of time, condensation becomes a serious problem.

So, let's explain such a case using an actual example.

In other words, most of the potatoes are heated and the temperature rises, and the temperature is kept at about 60℃ to 70℃ for a while, and then it is raised to about 100℃ and kept at that temperature for a while. It is known that the most effective cooking method is to complete the alpha conversion of beta starch.

Therefore, the temperature detection mechanism of the high-frequency heating device is set so that the temperature of the potato, which is the object to be heated, is kept constant at a certain value of 60°C to 70°C, and high-frequency heating is started, and the automatic control device operates. If the magnetron is repeatedly turned on and off in accordance with the temperature, if the amount of water vapor generated from the potatoes is so large that it exceeds the saturation point of the heating chamber atmosphere, or even if it is not so large, the first wall of the heating chamber or the viewfinder surface may be If it is quite cold, the water vapor in the atmosphere will quickly condense on the wall surface, leading to the aforementioned problem.

Figure 3 conceptually shows how the temperature of the potato changes at this time.

In this Figure 3, T1 is the temperature at the start of heating the potato, T
3 is the upper limit of the temperature to be maintained, and T2 is the lower limit.

Among these, the upper limit and the lower limit are values controlled by the automatic control device 15 detecting the temperature of the heating chamber outflow air corresponding to each temperature.

As shown in this figure, the potatoes are first heated and then heated by the automatic control device 15.
When the first operating point T3 is reached, the automatic control device 15 operates to stop the operation of the magnetron 9, and the temperature of the rear end decreases for a while, so the temperature of the air flowing out from the heating chamber 1 also decreases, and the automatic control When the second operating point T2 of the device 15 is reached, the magnetron 9 is operated again to heat up to the first operating point T3, and this cycle is repeated thereafter.

The present invention was made in view of the above-mentioned circumstances, and
The above-mentioned drawbacks can be satisfied even when a certain predetermined temperature is held for a certain period of time (hereinafter referred to as temperature holding).

To this end, the present invention occasionally increases the amount of air flowing through the heating chamber 1 during temperature maintenance, and exhausts the heating chamber air, which is convenient for temperature detection but is prone to condensation, to the outside. Prevents condensation.

Specifically, if the amount of circulating air is alternately changed as shown in FIG. 3, dew condensation within the heating chamber 1 can be prevented.

Since the upper limit T3 of the temperature of the heated object is determined, the above-mentioned repeated cycle stops the operation of the magnetron 9 when this upper limit T3 is reached, and immediately increases the amount of circulating air from Ql to Q2, and then waits for a while. This continues for a while to exhaust the atmosphere in the heating chamber that is prone to condensation, and then, just before the temperature of the heated object reaches the lower limit T3, the amount of circulating air is returned to the original amount convenient for temperature detection, and the air flow in the heating chamber is reduced. The flow is changed to a steady flow, the lower limit T2 of the temperature of the heated object is detected, and the automatic control device 15 controls the power supply device 16 again to operate the magnetron 9.

In the above-mentioned cycle, while the amount of circulating air is increasing, and after the amount of circulating air returns to the original state until the flow settles to a steady state, heating corresponding to the lower limit T2 of the temperature of the heated object is performed. The mechanism that detects the temperature of the air flowing out of the room must be temporarily turned off.

In this case, the interlocking may be such that, for example, when changing the rotational speed of the blower γ to increase or decrease the amount of circulating air, it may be turned OFF and ON in accordance with the device that performs the switching.

However, it is necessary to devise a delay operation so that the ON operation of the temperature detection mechanism is performed after waiting for the air flow in the heating chamber to reach a steady state.

In this way, the present invention detects the temperature of the air flowing out from inside the heating chamber 1, indirectly detects the temperature of the object to be heated, and automatically controls the heating time. Even when the temperature of the object to be heated is maintained at a predetermined value for a certain period of time, no condensation occurs on the inner wall of the heating chamber or on the viewfinder, and various types of prohibited writing can be almost completely removed.

In the above embodiment, the amount of air flowing through the heating chamber is increased or decreased by changing the rotation speed of the blower, but in this case, the performance of the magnetron cooled by the air discharged from the blower is Needless to say, it is designed so that it does not deteriorate.

When it is necessary to cool the magnetron with a steady flow, a dedicated blower may be provided and controlled to scavenge the air in the heating chamber.

Moreover, instead of changing the rotational speed of the blower, it is of course possible to provide a damper or the like in the air flow opening of the heating chamber and control the opening degree of the damper or the like.

Furthermore, the amount of air may be adjusted by using a heating chamber bypass air path or the like in accordance with an increase or decrease in the amount of circulating air.

In addition, when increasing the amount of circulating air to exhaust the atmosphere in the heating chamber that is prone to condensation, some air is heated using a heating element such as a magnetron or a dedicated heating device in order to lower the saturation point of the atmosphere as much as possible. It may be mixed.

When this is done, the saturation point of the atmosphere can be lowered favorably without increasing the absolute amount of circulating air, and good scavenging can be achieved.

In this case, if too much hot air is mixed in, it will warm up the heating chamber walls, finder, etc., as well as the temperature detection element, etc., which will have an adverse effect on the temperature control of the heated object, so take appropriate measures to prevent this from happening. It is necessary to limit it.

Incidentally, by mixing a portion of the warm air in this way, even if condensation does occur on the walls of the heating chamber, it is effective to remove a small amount of condensation.

In addition, in the explanation of the embodiment, when the temperature of the heated object reaches the upper limit of the set value, the operation of the magnetron is stopped and the high frequency heating is completely stopped. The magnetron may be operated by lowering the high frequency power to an extent that does not cause a rise in temperature or a sudden drop in temperature.

In addition, in the description of the embodiment, the upper and lower limits of the temperature of the air flowing out of the heating chamber corresponding to the temperature of the heated object are detected,
Although the temperature of the object to be heated is maintained within a predetermined range, the present invention is not limited to this, and the magnetron operation, the amount of circulating air is increased/decreased, and the temperature detection mechanism is turned off by capturing only the upper limit.

It is also possible to control ON.

In this case as well, when turning on the temperature detection mechanism, it is necessary to provide an appropriate delay operation means as described above so that the operation is carried out after the air flow in the heating chamber becomes a steady flow convenient for temperature detection.

Also, if you try to maintain the temperature of the heated object at a relatively high temperature of 80°C or 90°C, depending on the amount of the heated object, too much water vapor may be generated even when high-frequency heating is stopped. , or may easily become susceptible to condensation.

In such a case, the supply humidity and relative humidity of the air flowing out from or into the heating chamber may be detected, and the air may be discharged based on the detected signal.

In this case, the above-mentioned discharge may be performed several times while the operation of the magnetron is stopped.

In addition, as mentioned above, if a means is provided to detect the humidity of the heating chamber or the air flowing out from the heating chamber and to discharge the atmosphere of the heating chamber when the humidity reaches a predetermined level, that is, a condition where dew condensation is likely to occur. By performing scavenging at the last moment without worrying about the temperature of the object to be heated, high-frequency heating can be performed while preventing dew condensation.

As a result, without causing various prohibited documents due to condensation,
High frequency heating of the object to be heated can be terminated.

Note that the steam generated from the heated object may contain various oils other than water,
It goes without saying that the present invention can be effectively applied to alcohols and other cases.

As described above, as an example of the present invention, the heating time is controlled by detecting the temperature of the heating chamber or the air flowing out from the heating chamber.However, by detecting the humidity of the heating chamber or the air flowing out from the heating chamber, It goes without saying that the heating time can also be controlled.

Furthermore, when detecting temperature or humidity in a heating chamber, it is necessary to prevent the detection element from being exposed to high frequency power.

If the device is to be exposed to high-frequency power, it is necessary to take measures to prevent the high-frequency power from having an adverse effect on users and equipment outside the heating chamber.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view of a general temperature sensing type high-frequency heating device including the present invention, and FIG. 2 is a relationship diagram between the amount of circulating air and the temperature difference between air flowing in and out of the heating chamber when temperature sensing is performed. Third
The figure is an example of a conceptual diagram of temperature changes when the object to be heated is maintained at a predetermined temperature, and Figure 4 shows the interlocking of increases and decreases in the amount of air circulating in the heating chamber when the temperature of the object to be heated is controlled as shown in Figure 3. It is an explanatory diagram showing a state. 1... Heating chamber, 2... Heated object, 3.
...Door, 5゜6...Opening, 7...
・Prower, 8... Exhaust path, 9... Magnetron, 13, 14... Temperature detection element, 15
...Following control device, 16...Power supply device.

Claims (1)

[Claims] 1. In a high-frequency heating device that heats an object by supplying high-frequency power into a heating chamber housing an object to be heated, a temperature detection mechanism detects the temperature of the heating chamber or the air flowing out from the heating chamber. A high-frequency heating device that detects the temperature and controls high-frequency power when the temperature reaches a preset value, and increases or decreases the amount of air flowing through the heating chamber, thereby preventing dew condensation due to the atmosphere of the heating chamber. 2. In claim 1 above, the amount of air flowing in the heating chamber increases when the supply of high-frequency power is stopped, and after the atmosphere in the heating chamber is exhausted, it decreases again to return to the original state. Features of high-frequency heating equipment. 3 In claim 1, the flow rate of the air flowing inside the heating chamber is reduced sufficiently before the high frequency power returns to the original high frequency power after the high frequency power is controlled, and when the temperature detection mechanism operates, the flow rate of the air is reduced sufficiently before the high frequency power returns to the original high frequency power again, and when the temperature detection mechanism operates, A high frequency heating device characterized by a good steady flow. 4. The high-frequency heating device according to claim 1, characterized in that the air flowing through the heating chamber at an increased flow rate is appropriately mixed with warm air. 5. A high-frequency heating device according to claim 1, characterized in that the air flowing through the heating chamber is appropriately warmed by increasing the flow rate.6. This high-frequency heating device is characterized in that the amount of air being heated increases and decreases multiple times while the high-frequency power is controlled. 1. In a high-frequency heating device that heats an object by supplying high-frequency power into a heating chamber housing an object to be heated, the temperature of the heating chamber or the air flowing out from the heating chamber is detected by a temperature detection mechanism, and the temperature is detected. The humidity of the heating chamber or the air flowing out from the heating chamber is detected by the humidity detection mechanism until the high frequency power is controlled when the high frequency power reaches a preset value, and the humidity is set to the preset value. A high-frequency heating device characterized by increasing the amount of air flowing through the heating chamber when the temperature reaches a certain value, thereby scavenging the atmosphere in the heating chamber that tends to cause dew condensation.