JPH06241467A - Microwave oven provided with tableware drying function - Google Patents

Abstract

PURPOSE:To prevent the electric discharge of metallic tablewares, the no-load operation of a magnetron and/or the sofetening and melting of a cage for drying the tablewares by a method wherein the operation of the microwave oven is stopped forcibly when the fluctuating width of the frequency of oscillation of an output signal from a weight sensor has exceeded a predetermined value, in the microwave oven provided with tableware drying function. CONSTITUTION:A weight sensor 8 detects whether materials to be heated are existing on a turn table 20 or not when foods on the turn table 20 are heated by microwave through a magnetron 12. When there is no material to be heated, a microcomputer stops the operation of the microwave oven. A tableware drying cage 22, receiving table wares 23, is put on a water receiving tray 24, then, these are inserted into a heating chamber 19 and the water receiving tray 24 is set under a condition that it is levitated from the turn table 20. Then, a drying key is operated to circulate hot air in the heating chamber 19 and dry the tablewares. When the fluctuating width of the frequency of oscillation of the output signal of the weight sensor 8 has exceeded a predetermined value, the operation of the oven is stopped forcibly.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microwave oven with a tableware drying function, which is obtained by adding a tableware drying function to a microwave oven for microwave heating an object to be heated such as food.

[0002]

2. Description of the Related Art In recent years, microwave ovens with heaters have become widespread due to multifunctionalization of microwave ovens. This has enabled grilled and oven dishes that were previously impossible. Recently, from the viewpoint of more effective utilization of microwave oven with heater, microwave heating,
The idea of drying dishes when not heating the grill or the oven has been proposed.

In order to dry the dishes, first, the dishes are placed in a basket for drying dishes, the basket for drying dishes is placed on a tray for receiving water, and the basket for drying dishes and the tray for receiving water are heated together. Put in the refrigerator. The water tray has legs,
The legs are supported on the bottom surface inside the oven outside the turntable, so that the water receiving tray floats from the turntable. The tray for receiving water has a role of receiving the water drained by the dish-drying basket, and a role of preventing the dish-drying basket from being unintentionally rotated on the turntable, that is, the dish-drying basket and the basket. Has the role of separating from the turntable.

Next, when the dry key on the operation panel is operated, the heater is energized, the blower motor is energized, and the air heated by the heater is circulated as hot air in the oven chamber by the fan blower, thereby Dry the dishes in the drying basket. The microwave is not heated when the dishes are dried, and the turntable is not rotated.

By the way, a basket for drying tableware is usually made of a resin such as polypropylene (PP), and may be softened and melted by high temperature heating such as grill heating or oven heating. There are various types of tableware, including metal spoons, forks, knives, and teacups with gold leaf. If such a metallic object is mistakenly microwave-heated, an electric discharge will occur and burnout will occur. Therefore, when the tableware is dried, even if the grill key, the oven key, or the range key is mistakenly operated, it is necessary to prohibit the operation corresponding to the operation.

Generally, a microwave oven is provided with a weight sensor attached to a turntable. This is for detecting that the object to be heated is placed on the turntable during microwave heating. If the weight sensor detects that the object to be heated is not placed on the turntable when the range key is operated, the microcomputer stops driving the magnetron and microwave heating is automatically prohibited. is there. In addition, if microwaves are radiated in an oven without any object to be heated (more specifically, water) and no load is applied, the microwaves reflected by each part are guided because there is nothing that absorbs the microwaves. There is a possibility that the magnetron is reversely incident through the tube to burn out the magnetron to shorten its life, or the temperature of each electric component is abnormally increased to cause deterioration, resulting in deterioration of reliability. A weight sensor is provided to prevent such inconvenience.

This weight sensor is also used for ensuring safety when tableware is dried. When the tableware is dried, the correct operation is to place the tableware drying basket storing the tableware on the water receiving tray as described above, and put the tableware drying basket and the water receiving tray together in the heating chamber. This allows
The weight of the basket for drying dishes (including the weight of the dishes in the basket) is not applied to the weight sensor via the turntable. Suppose you accidentally press the range key on the control panel when you try to dry the dishes and you are in microwave heating mode. However, since the weight sensor does not detect the load, the microcomputer forcibly prohibits microwave heating.

Even if the grill key or the oven key is operated by mistake, the corresponding operation is prohibited because the weight sensor does not detect the load.

[0009]

However, even if the weight sensor is devised such that it functions during the drying of the tableware in this way, the table for drying the tableware is placed directly on the turntable without the tray for receiving the water. When attempting to dry the tableware in, there is a possibility that the following inconvenience may occur. That is, since the weight of the tableware drying basket is applied to the weight sensor via the turntable, the microcomputer determines that food is placed on the turntable. If the range key is accidentally pressed, metal dishes are discharged and burned, and if the grill key or oven key is mistakenly pressed, the resin tableware drying basket is softened or melted. If heating is continued without noticing it, there is a risk that the water will be lost and the magnetron will deteriorate, or the tableware drying basket will ignite.

The present invention was devised in view of such circumstances, and when the tableware is dried,
Even if you do not accidentally use the water tray and accidentally press a key other than the dry key, the metal dishes will be discharged, the magnetron will become unloaded and deteriorate,
The purpose of the present invention is to prevent the basket for drying dishes from being softened, melted or ignited.

[0011]

A microwave oven with a tableware drying function according to the present invention irradiates microwaves to an object to be heated placed on a turntable in a heating chamber to heat the object to be heated,
The tray for receiving water is placed above the turntable while being supported on the bottom of the heating chamber outside the turntable, and the table for drying dishes containing the dishes is placed on the tray for receiving water. It is configured to dry the tableware by circulating hot air, and provided with a weight sensor for detecting the load of the object placed on the turntable, microwave heating is performed when the weight sensor does not detect the load during microwave heating. In a microwave oven with a tableware drying function configured to stop, a means for obtaining a fluctuation range of the oscillation frequency of the output signal from the weight sensor, and a means for forcibly stopping the operation when the fluctuation range exceeds a predetermined value. It is characterized by having and.

[0012]

[Function] When the dishes are dried by mistake, without using the tray for receiving water, the basket for drying dishes is put in the heating cabinet and placed directly on the turntable, and when a key other than the dry key is accidentally pressed, Even if the turntable rotates, the tableware drying basket does not rotate because it comes into contact with the wall surface of the heating cabinet, so the fluctuation range of the oscillation frequency of the weight sensor exceeds a predetermined value, and incorrect operation is automatically stopped. .

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a microwave oven with a tableware drying function according to the present invention will be described in detail below with reference to the drawings.

1 (a) and 1 (b) are circuit diagrams showing the electrical construction of the main part of a microwave oven with a tableware drying function.
In FIG. 1, reference numeral 1 denotes an operation panel, which includes a liquid crystal display unit 2, a start key 3, a range key 4,
A grill key 5, an oven key 6, a drying key 7, etc. are provided. A weight sensor 8 is connected to the microcomputer 9 together with the operation panel 1. Relay coils Y ₁ , Y ₂ , Y ₃ are connected to the collectors of the transistors Q ₁ , Q ₂ , Q ₃ connected to the output port of the microcomputer 9, respectively. Reference numeral 10 is a power supply circuit, 11 is an oscillation transformer, 12 is a magnetron, 13 is a turntable motor, 14 is a heater, and 15 is a blower motor. y ₁ , y ₂ and y ₃ are relay contacts corresponding to the relay coils Y ₁ , Y ₂ and Y ₃ , respectively.

FIG. 2 shows a specific circuit configuration of the weight sensor 8. The amplifiers 16, 17 and 18 are connected in three stages, the input / output terminals of the amplifier 16 and the amplifier 18 are feedback-connected with a resistor R, and the input / output terminals of the amplifier 16 and the amplifier 17 have electrostatic capacitances according to the load. Variable capacitor V that changes
It is connected by feedback at C. Therefore, as for the weight sensor 8 itself, the oscillation frequency of its output signal varies depending on the load.

The output signal of the weight sensor 8 thus constructed is guided to the microcomputer 9.

The microcomputer 9 not only determines whether the weight sensor 8 is loaded,
It is also determined whether or not the fluctuation range of the oscillation frequency of the signal input from the weight sensor 8 exceeds a predetermined threshold level f _th .

When the pressing operation of the dry key 7 is detected, the microcomputer 9 forcibly stops the heating operation when the fluctuation range of the oscillation frequency exceeds the threshold level f _th. It is configured.

FIG. 3 is a schematic sectional view of the microwave oven in a normal state for heating food. The magnetron 12 is arranged on the side of the heating chamber 19, the heater 14 is arranged on the upper portion of the heating chamber 19, and the turntable 20 is rotatably arranged on the lower portion. The turntable 20 is connected to the turntable motor 13, and the entire turntable 20 is mounted on the weight sensor 8. The zero point adjustment is performed so that the output of the weight sensor 8 becomes zero when nothing is placed on the turntable 20.

When the food 21 to be heated is placed on the turntable 20, the door is closed and the start key 3 of the operation panel 1 is pressed, and then the range key 4 is pressed, the microcomputer 9 turns on the transistor Q ₁ . Then, current is passed through the relay coil Y ₁ to turn on the relay contact y ₁ , so that the magnetron 12 is driven and the turntable motor 13 is driven. Therefore, the turntable 20 is rotated and the food 21 on the turntable 20 is rotated.
Are heated by the microwaves emitted from the magnetron 12. If the food 21 is not placed on the turntable 20 and the output of the weight sensor 8 is zero,
Even if the range key 4 is pressed, the microcomputer 9 does not drive the transistor Q ₁ , so microwave heating is prohibited.

FIG. 4 is a schematic sectional view of the microwave oven for drying tableware. The tableware 23 is put in the tableware drying basket 22, and the tableware drying basket 22 is placed on the water receiving tray 24. Water adhering to the tableware 23 and drained in the tableware drying basket 22 accumulates on the water receiving tray 24.

A basket 22 for drying dishes and a tray 24 for receiving water
And put together in the heating chamber 19. The legs 24a of the water receiving tray 24 are placed and supported on the bottom surface of the heating chamber 19 outside the turntable 20. As a result, the water receiving tray 24 is in a state of floating from the turntable 20. In this case, a tableware drying basket 2 containing the tableware 23
The weight of No. 2 is not applied to the weight sensor 8, and the output of the weight sensor 8 is zero.

As another procedure, the water receiving tray 24 is first placed in the heating chamber 19 and then the dishes 2
The tableware drying basket 22 containing 3 may be put in the heating chamber 19 and placed on the water receiving tray 24.

Close the door and start key 3 on the operation panel 1.
When the dry key 7 is pressed after pressing, the microcomputer 9 turns on the transistors Q ₂ and Q ₃ because the load detected by the weight sensor 8 is zero. Then, the relay coils Y ₂ , Y ₃ are excited and the relay contacts y ₂ , y
₃ is turned on, heater 14 and blower motor 1
Power is supplied from the power supply circuit 10 to 5. The heat generated by the heater 14 flows in the heating chamber 19 along with the air flow generated by the blower motor 15. Hot air heating chamber 1
By circulating it inside 9, the water adhering to the tableware 23 is evaporated and dried. The temperature of the hot air during the tableware drying is set to be lower than the temperature inside the refrigerator in the grill mode or the oven mode, and the resin tableware drying basket 22 is not softened.

It is assumed that the range key 4 is accidentally pressed in the tableware drying mode. However, the microcomputer 9
Since the load detected by the weight sensor 8 is zero,
The magnetron 12 and the turntable motor 13 are not driven because it is determined that the object to be heated is not placed on the turntable 20 (no load state). Therefore, even if the tableware 23 is mixed with metal, there is no danger of electric discharge. In addition, since there is no object to be heated, there is no fear that microwaves will enter the magnetron 12 backwards and deteriorate the magnetron 12. Similarly, when the grill key 5 or the oven key 6 is pressed by mistake, heating is prohibited.

When the user wants to dry the tableware, the user forgets to use the water receiving tray 24 and the tableware drying basket 22 in which the tableware 23 is stored.
It is assumed that the above is put as it is in the heating chamber 19. In this case, the tableware drying basket 22 is placed directly on the turntable 20, and the weight sensor 8 is loaded.

Under such a condition, even if the dry key 7 is pressed, the microcomputer 9 still operates the weight sensor 8
Since the load is applied to the heater 14, the heater 14 and the blower motor 15 are not driven. That is, the dry mode is prohibited.

Further, it is assumed that the range key 4 is pressed by mistake. Then, since the load is applied to the weight sensor 8, the microcomputer 9 makes the transistor Q ₁ conductive, the relay coil Y ₁ is excited, the relay contact y ₁ is turned on, and the magnetron 12 and the turntable motor 13 are turned on. Will be driven. However, as described later, this is a short-time drive.

That is, when the turntable motor 13 is driven and the turntable 20 rotates, the tableware drying basket 22 on the turntable 20 also tries to rotate together, but it is only in the initial stage of rotation, and when it rotates a little,
As shown in FIG. 5, the tableware drying basket 22 rotates from the position indicated by the chain double-dashed line to the position indicated by the solid line, abuts against the wall surface of the heating chamber 19, and its rotation is stopped.

However, since the turntable 20 continues to rotate, the tableware drying basket 22 vibrates rattlingly. This vibration gives a large change to the load applied to the weight sensor 8. That is, the capacitance of the variable capacitor VC changes, and the oscillation frequency of the output signal output from the weight sensor 8 greatly changes. The oscillation frequency of the output signal of the weight sensor 8 is monitored by the microcomputer 9. This is shown in FIG.

In FIG. 6, the frequency characteristic a shown by the broken line
Is a characteristic of the tableware 23 shown in FIG. 3 in a normal microwave heating mode. The oscillation frequency of the weight sensor 8 at that time is, for example, a center frequency of 30 KHz,
It fluctuates slowly within the range of 100 Hz. Since the fluctuation of the oscillation frequency of the weight sensor 8 is within the predetermined range, the microcomputer 9 does not stop the driving of the transistor Q _{1 at} this time, but drives the magnetron 12 while rotating the turntable 20. Continue wave heating.

However, as described above, while the turntable 20 rotates, the tableware drying basket 22 moves in the heating chamber 19
When the rotation of the weight sensor 8 is stopped (see FIG. 5), the fluctuation of the oscillation frequency of the weight sensor 8 becomes large like the frequency characteristic b shown by the solid line in FIG. 6, and the maximum is ± 3 KH.
It also becomes z. For example, 500 Hz is set for both the plus side and the minus side as the threshold level f _th in the fluctuation detection of the oscillation frequency and is stored in the microcomputer 9.

In the microcomputer 9, the fluctuation of the oscillation frequency of the weight sensor 8 causes the threshold level f _th = 5.
When the frequency is within 00 Hz, the microwave oven heats the ordinary tableware 23 and continues to operate. However, when the threshold level f _th = 500 Hz is exceeded, the load on the weight sensor 8 causes the tableware drying basket 22 to turntable. The microwave heating is stopped when it is determined to be directly placed on 20. That is, the transistor Q ₁ is turned off, the relay contact y ₁ is turned off, and the magnetron 12 and the turntable motor 13 are forcibly stopped.

As a result, it is possible to prevent the metal tableware from being discharged and burned out, and also to prevent the deterioration of the magnetron 12 and other electric parts due to the no-load operation in the state where the water content is lost. You can

To detect the fluctuation range of the oscillation frequency of the weight sensor 8, for example, the turntable motor 13
The maximum value and the minimum value of the frequency when rotated can be stored, and the difference can be determined from the difference between the maximum value and the minimum value. The maximum value and the minimum value may be those during the rotation of the motor 13 a plurality of times. Alternatively, the frequency may be checked over a predetermined period, the average value during that period may be obtained, and the amount of deviation from the average value may be used as the fluctuation range.

When the grill key 5 or the oven key 6 is mistakenly pressed in a state where the tableware drying basket 22 is placed in the heating cabinet 19 without using the water receiving tray 24, the heater is processed in the same manner as described above. 14 and the turntable motor 13 are forcibly stopped. As a result, it is possible to prevent the resin tableware drying basket 22 from softening, melting, or igniting.

When the microwave heating is stopped halfway due to incorrect handling as described above, it is preferable to display a warning on the liquid crystal display section 2 of the operation panel 1. You may sound a buzzer to warn you.

The user put the basket 22 for drying dishes in the heating cabinet 19 without using the tray 24 for receiving water by a forced stop or a warning simultaneously therewith, and mistakenly pressed another key other than the dry key 7. You will be informed that you have pressed it, and you will perform the correct operation again.

Even in the case of heating ordinary foods, because the foods are too large, for example, when one whole sea bream is used, or too many foods are put in, the heating chamber 19
When only the turntable 20 rotates on the wall surface of the weight sensor 8, the fluctuation width of the oscillation frequency of the weight sensor 8 exceeds the threshold level f _th by the same operation as described above, so that heating in an abnormal state is forced. It can be stopped.

Needless to say, when the tableware drying operation is properly performed, that is, the tableware drying basket 22 is stored in the heating chamber 19 together with the water receiving tray 24, and the drying key 7 is pressed. If pressed, turntable 2
0 is non-rotating, and since the load of the tableware drying basket 22 is not applied to the weight sensor 8, the oscillation frequency of the weight sensor 8 does not change. At this time, the microcomputer 9 does not need to monitor the fluctuation of the oscillation frequency.

[0041]

As described above, according to the present invention, when the table tray for water is dried and the tray for receiving water is not used by mistake, and when a key other than the dry key is pressed by mistake, the oscillation frequency of the weight sensor fluctuates greatly. Since it was configured to automatically stop the erroneous operation based on the detection of the width, it is possible to prevent problems such as discharge of metal tableware, no-load operation of magnetron and softening and melting of a tableware drying basket. It is possible to improve safety.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an electrical configuration of a microwave oven with a tableware drying function according to an embodiment of the present invention.

FIG. 2 is a circuit diagram showing a specific configuration of the weight sensor in the embodiment.

FIG. 3 is a schematic cross-sectional view of a microwave oven in a normal state where food is heated in an example.

FIG. 4 is a schematic cross-sectional view of a microwave oven for drying tableware in an example.

FIG. 5 is a schematic plan view of the microwave oven in a state where the turntable is rotated and the tableware drying basket is stopped in the embodiment.

FIG. 6 is a characteristic diagram showing temporal changes in the oscillation frequency of the weight sensor in the normal and abnormal states in the example.

[Explanation of symbols]

 1 ... Operation panel 4 ... Range key 5 ... Grill key 6 ... Oven key 7 ... Drying key 8 ... Weight sensor 9 ... Microcomputer 12 ... Magnetron 13 ... Turntable motor 14 ... Heater 15 ... ... Blower motor 19 ... Heating cabinet 20 ... Turntable 21 ... Food 22 ... Tableware drying basket 23 ... Tableware 24 ... Water tray 24a ... Leg VC ... Variable capacitor

Claims (1)

[Claims] 1. A state in which an object to be heated placed on a turntable in the heating cabinet is irradiated with microwaves to be heated and a water receiving tray is supported on the bottom surface of the heating cabinet outside the turntable. Is arranged above the turntable to be placed above, and a tableware drying basket containing the tableware is placed on the tray for receiving water, and the tableware is dried by circulation of hot air. In a microwave oven with a tableware drying function configured to stop the microwave heating when the weight sensor does not detect the load during microwave heating by providing a weight sensor for detecting the load of the placed object, the weight sensor from the weight sensor A food characterized by comprising means for obtaining a fluctuation range of the oscillation frequency of the output signal and means for forcibly stopping the operation when the fluctuation range exceeds a predetermined value. Microwave oven with a drying function.