JPH04245191A - Electronic oven - Google Patents

Abstract

PURPOSE:To provide an electronic oven, which can improve the reliability by leaps and bounds while reducing manufacturing cost. CONSTITUTION:This is provided with a detection circuit 6, which detects the magnitude of the reflected wave from a cavity, and an output control circuit 7, which increases or decreases the output of a magnetron 1, according to the magnitude of the reflected wave, based on this detection output. Or, it is provided with a control circuit, which turns off the output from the magnetron 1 when the magnitude of the reflected wave gets over the specified value.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microwave oven that applies microwaves from a magnetron to a cavity through a waveguide to raise the temperature of food inside the cavity.

0002

2. Description of the Related Art Conventional microwave ovens have a microwave oven of 2,000 cc, regardless of the amount of food (load) to be cooked in the cavity.
The microwaves emitted from the magnetron were applied to the cooking food inside the cavity with approximately the same intensity regardless of whether the load was high or there was almost no load.

0003

[Problem to be Solved by the Invention] However, with the above configuration, there is no problem when the load is large, but when there is almost no load, a strong standing wave is formed in the cavity. As a result, parts of the cavity or waveguide may become excessively heated. Therefore, if the waveguide or the like is made of plastic or glass, it will melt, but if it is made of metal, discharge or oxidation will occur. Furthermore, since a large reflected wave is sent from the cavity to the magnetron, there is a risk that it will be difficult to cool the magnetron or that it will be destroyed. For these reasons, there have been problems such as a decrease in the reliability of the microwave oven.

The present invention has been made in view of the current situation, and it is an object of the present invention to provide a microwave oven that can dramatically improve reliability while reducing manufacturing costs.

[0005]

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a microwave oven that applies microwaves from a magnetron to a cavity through a waveguide to raise the temperature of the food being cooked in the cavity. a detecting means for detecting the magnitude of the reflected wave from the cavity; and based on the detection result of the detecting means, the output of the magnetron is reduced when the reflected wave is large, while the output of the magnetron is reduced when the reflected wave is small. It is characterized by comprising a control means for keeping the output constant or increasing the output.

[0006] The present invention also provides a microwave oven in which microwaves from a magnetron are applied to a cavity via a waveguide to raise the temperature of food in the cavity. and a control means for turning off the output from the magnetron when the magnitude of the reflected wave exceeds a set value based on the detection result of the detection means. do.

[0007]

[Operation] As in the first invention, the magnitude of the reflected wave from the cavity is detected by the detection means, and based on the detection result, the output of the magnetron is increased or decreased according to the magnitude of the reflected wave, or According to the second invention, if the output from the magnetron is turned off when the magnitude of the reflected wave exceeds a set value based on the detection result, a strong standing wave is formed within the cavity. can be prevented. Therefore, a part of the cavity or the waveguide is not heated excessively, so that it is possible to prevent the waveguide and the like from melting, discharging, and oxidizing.

[0008] Furthermore, since large reflected waves from the cavity are prevented from being applied to the magnetron, and the internal loss of the magnetron can also be suppressed, the magnetron can be easily cooled. In addition, since the output of the magnetron can be prevented from always being at a high level, it is possible to suppress a large load from being applied to each component such as the magnetron.

[0009]

[Example] (First Example) The first example of the present invention is shown in FIG.
The following is an explanation based on the following. FIG. 1 is a block diagram showing the configuration of a microwave oven according to a first embodiment of the present invention, which includes a magnetron 1, a waveguide 2, a cavity 3,
It has a stirrer 4, a directional coupler 5, a detection circuit 6, an output control circuit 7, and a magnetron drive circuit 8.

The magnetron 1 generates microwaves using drive power supplied from the magnetron drive circuit 8. The waveguide 2 guides the microwave to the cavity 3. The cavity 3 has a space into which food to be cooked is loaded. The stirrer 4 stirs the radio waves to prevent uneven cooking of the food.

The directional coupler 5 receives reflected waves (microwaves) guided from the cavity 3 through the waveguide 2.
is detected and a detection signal is output to the detection circuit 6. As the directional coupler 5, it is possible to use a differential path type, a series-parallel type, a cross type, or the like. In the detection circuit 6,
After rectifying the reflected wave with a microwave diode, a rectified signal is output to the output control circuit 7.

The output control circuit 7 sends a control signal to the magnetron drive circuit 8 based on the rectified signal. The magnetron drive circuit 8 supplies the magnetron 1 with drive power according to the control signal. Here, the microwave oven having the above structure operates as follows.

First, when the microwave oven is turned on by a switch (not shown), microwaves generated from the magnetron 1 are applied to the cavity 3 via the waveguide 2. At this time, if there are many foods to be cooked in the cavity 3, most of the microwaves will be absorbed by the foods, so the reflected waves from the cavity 3 will be small. On the other hand, when the amount of food to be cooked in the cavity 3 is small, the microwaves are not absorbed by the food so much that the reflected waves from the cavity 3 become large.

Next, the reflected wave passes through the waveguide 2 again and is applied to the magnetron 1 and the directional coupler 5. The reflected wave detected by the directional coupler 5 is rectified by the detection circuit 6 and then given to the output control circuit 7 as a rectified signal. Next, the output control circuit 7 outputs a control signal to the magnetron drive circuit 8 based on the rectified signal. This control signal changes the amount of power supplied to the magnetron 1 to change the microwave output from the magnetron 1. Specifically, when the reflected wave is small, the output from the magnetron 1 changes to 100%. %, and when the reflected wave is large, the output from the magnetron 1 is controlled to be 50%. Note that it is preferable to use a structure in which the output changes continuously, such as in an inverter power supply.

[0015] In this way, when the amount of food to be cooked in the cavity 3 is small and the reflected wave from the cavity 3 becomes large, the output from the magnetron 1 is reduced while the amount of food inside the cavity 3 is reduced. If the reflected wave from the cavity 3 is small due to the presence of food to be cooked, maintaining the output from the magnetron 1 can prevent the formation of strong standing waves within the cavity. It will be possible.

The electrolytic distribution (impedance) inside the cavity 3 changes from time to time due to the stirrer 4, a turntable (not shown), and the like. In particular, when the load is small, the electrolytic distribution changes significantly, so if the output of the magnetron 1 is made to completely follow this change, normal oscillation may become difficult. Therefore, for example, it is desirable to use an average value over a long period of time (several seconds) as the magnitude of the reflected wave, and to control the output of the magnetron 1 based on this average value. In this case, it is desirable to incorporate such a circuit into the output control circuit 7, but it may be incorporated into other circuits.

Further, in the detection circuit 6, the reflected wave is rectified by a microwave diode, but the structure is not limited to this. For example, the microwave can be absorbed by a thermistor and the resistance change can be output. Control circuit 7
It may be a structure that gives Furthermore, in the above embodiment,
Although the minimum value of the output from the magnetron 1 is specified to be 50%, it is not limited to this value.

(Second Embodiment) A second embodiment of the present invention will be described below with reference to FIG. It should be noted that members having the same functions as those in the first embodiment are given the same reference numerals and their explanations will be omitted. FIG. 2 is a block diagram showing the configuration of the microwave oven of the present invention, which includes a magnetron 1, a waveguide 2, a cavity 3, a stirrer 4, a directional coupler 5, and a magnetron drive circuit 8. , a detection circuit 9,
It has a display circuit 10.

The detection circuit 9 has a function of rectifying the reflected wave using a microwave diode like the detection circuit 6 of the first embodiment, and also has a built-in comparator. and,
When the reflected wave becomes larger than a preset value, a drive stop command signal is output to the magnetron drive circuit 8 in order to prevent the magnetron 1 from generating microwaves. Furthermore, by sending a display command signal to the display circuit 10,
Since the display section (not shown) displays a message indicating that the device is in a no-load operating state, even if the operation stops, the user can be prevented from mistaking it for failure. Note that this display is preferably configured to be reset when the user opens the door of the microwave oven.

With the above configuration, it is possible to obtain the same effects as in the first embodiment. Note that, as in the first embodiment, when the load is small, the electrolytic distribution changes significantly, so for example, the magnitude of the reflected waves is integrated in units of several seconds to calculate an average value, and this average value is used to calculate the magnitude of the magnetron 1. It is desirable to turn on/off the output. In this case, it is desirable to incorporate such a circuit into the detection circuit 9.

[0021]

Effects of the Invention As explained above, according to the present invention, it is possible to prevent the formation of strong standing waves in the cavity, thereby preventing melting of the waveguide, electrical discharge, oxidation, etc. It is possible to prevent this from happening. Furthermore, the magnetron can be easily cooled, and a large load can be suppressed from being applied to each component of the magnetron and the like.

[0022] From the above, the reliability of the microwave oven can be dramatically improved while reducing the manufacturing cost.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a microwave oven according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing the configuration of a microwave oven according to a second embodiment of the present invention.

[Explanation of symbols]

1 Magnetron 3 Cavity 6 Detection circuit 7 Output control circuit 9 Detection circuit

Claims (2)

[Claims] Claim 1: In a microwave oven in which microwaves from a magnetron are applied to a cavity via a waveguide to raise the temperature of food in the cavity, the magnitude of reflected waves from the cavity is detected. a detection means; and a control means for reducing the output of the magnetron when the reflected wave is large, and keeping the output of the magnetron constant or increasing the output when the reflected wave is small, based on the detection result of the detection means. A microwave oven characterized by: 2. In a microwave oven in which microwaves from a magnetron are applied to a cavity via a waveguide to raise the temperature of food in the cavity, the magnitude of reflected waves from the cavity is detected. a detection means; and based on the detection result of the detection means, the output from the magnetron is turned off when the magnitude of the reflected wave exceeds a set value.
A microwave oven characterized by comprising: a control means for controlling F.