JPH0527833Y2 - - Google Patents

Description

[Detailed description of the invention] (a) Industrial application field The present invention relates to a microwave oven that can heat the oven using a heater.

(B) Prior Art Microwave ovens equipped with heaters are known that not only heat food using dielectric heating, but also include a heater and can perform oven cooking of toasts and the like.

When making toast, this microwave oven automatically adjusts the heating time according to the desired degree of doneness.
However, when using the microwave after a while,
The residual heat inside the refrigerator is different when used continuously, so the heating time may be shorter when used continuously.

Conventionally, when a microwave oven is started, the temperature inside the oven is detected using a thermistor or the like, and the heating time is determined based on the detected temperature.

(c) Problems that the invention aims to solve However, even if you actually make toast by determining the heating time using the conventional method described above, after using the microwave once, the time it takes to leave it in the microwave until the next use is Also, there was a problem in that the state of the baked food differed depending on whether the door for taking food in or out was opened or closed during the time the food was left standing.

An object of the present invention is to solve the above problems and provide a microwave oven with a heater that can always bake food in the same desired state.

(d) Means for solving the problem In the present invention, the heating time for heating the heater by supplying electricity to it is determined based on the initial temperature detected by the thermistor and the rate of temperature increase after the heating starts. This is what I did.

(E) Effect The residual heat state of the equipment can be accurately determined by taking into account not only the initial temperature but also the temperature rise rate, so the above method allows setting an appropriate heating time and baking the food to the desired state. I can do it.

(F) Embodiments Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

FIG. 1 is a perspective view showing the schematic structure of a microwave oven with a heater according to the present invention. In the figure, inside the housing frame 1 is a cavity 2 for storing food.
is formed. A heater 3 and a heater 4 are fixed above and below the cavity 2, respectively. In addition, a shelf support 6 with a grid 5 fixed to the side surface of the cavity 2 is provided at the center position between the heaters 3 and 4.
Supported by

A thermistor 7 for detecting temperature is fixed to the upper outer surface of the cavity 2, and a magnetron 8 for generating microwaves during dielectric heating is disposed at the outer upper end of the cavity 2. An operating section 9 equipped with operation buttons and the like is provided on the front surface of the lower housing frame 1, and further lower the housing frame 1.
Inside is a control unit 1 that is made up of electronic circuits and controls each part.
0 is placed.

Although not shown, a door is attached to the front of the cavity 2 in the figure, and the door is opened to take food in and out. In addition, various switches are installed that are turned on and off by opening and closing the door.

FIG. 2 shows a circuit configuration diagram of the control section 10. In the figure, one line of the commercial power supply is connected to one end of each of the primary winding of the high voltage transformer 11, the cooling fan ₁₂ , and the heaters 3 and ₄ via a safety fuse F, latch switch S1, and door switch S2. has been done. In addition, the other line of the commercial power supply is connected to the high voltage transformer 11 through one contact from the contacts of relay RL ₁ and the common terminal of relay RL ₂ .
The other end of the primary winding of is connected to the contacts of relay RL ₃ . Further, the other line is connected to the contacts of relays RL ₄ and RL ₅ via the other contact of relay RL ₂ . The monitor switch _S3 is connected from the door switch _S2 side of the latch switch _S1 to the other line of the commercial power supply.

Here, the latch switch S ₁ , the door switch S ₂ and the monitor switch S ₃ are all switches that are turned on and off by opening and closing the door. High voltage transformer 1
1 generates high voltage to drive the magnetron 8, and the diode D and capacitor C constitute a voltage doubler rectifier circuit, and the high voltage transformer 1
The high voltage induced on the secondary side of the magnetron 1 is rectified and applied to the magnetron 8. Further, the high voltage transformer 11 has a secondary winding for energizing the filament of the magnetron 8, and the filament is energized from this winding.

The cooling fan 12 cools the high voltage transformer 11 and magnetron 8. Relay RL ₁ ~ _{RL 5}
is used to turn on/off or switch the power supply to each part. The control circuit 13 has a built-in microcomputer and operates the relay according to the control program.
RL ₁ to RL ₅ are appropriately controlled to perform a predetermined heat treatment. The transformer 14 is the control circuit 1
This is to supply power to 3.

The microwave oven with a heater of this embodiment is configured as described above, and relays oven heating by the heaters 3 and 4 and dielectric heating by the magnetron 8.
You can select and cook food using RL ₂ .

First, when performing dielectric heating, open the door and
Place food in cavity 2.

Here, when the door is opened, the latch switch S ₁
and door switch _S2 are both turned off and turned on when the door is closed. This is because it is dangerous if the magnetron 8 is activated when the door is opened, so the power must be turned off at this time. Also, the monitor switch S ₃ turns on when the door is opened, and the latch switch S ₁ turns on when the door is closed.
It's starting to turn off earlier. This is because it is dangerous if latch switch _S1 fails and remains on when the door is opened, so in this case, when monitor switch _S3 closes, the power line is shorted and fuse F is blown. , the operation is stopped.

Next, a desired heating time is set using the operating section 9. Then, the control circuit 13 switches the relay RL ₂ to the high voltage transformer side and turns on the relay RL ₁ . As a result, commercial power is input to the primary side of the high voltage transformer 11, and the magnetron 8 is excited by the voltage induced on the secondary side. As a result, microwaves are irradiated from the magnetron 8 onto the food set above, and dielectric heating is performed. When the set heating time has elapsed, the control circuit 13 turns off the relay RL ₁ and ends its operation.

Next, the case of making toast by oven heating will be explained based on the operation flowchart of the control circuit 13 shown in FIG.

First, open the door, place bread on the grill 5, and close the door. Next, after placing it there and closing the door, the user uses the operation button on the operation unit 9 to specify "toast". In addition, there is a baking specification button that allows you to specify whether you want to bake on a ``strong'' setting with a longer heating time or ``lower'' with a shorter heating time. do.
Next, press the "Start" button.

When "toast" is designated (Y in process 21 in FIG. 3), the control circuit 13 determines the designated content if toasting is designated next, and if it is not designated, determines it as standard. The baked state is stored (process 22). Then, when the "Start" button is pressed (Y in process 23), the thermistor 7
Read the initial temperature t ₀ detected by (Process 2
4).

Next, relay RL ₂ is switched so that the power line is connected to heaters 3 and 4, and relays RL ₁ and
The contacts RL ₄ and RL ₅ are turned on to start energizing the heaters 3 and 4 (process 25).

After this, after a preset period of time Tc, such as 30 seconds, (processing 2
6), the temperature t ₁ is read again by the thermistor 6 (process 27).

By the way, in order to determine the heating time for the set bread, it is necessary to determine the residual heat state of the equipment. The required heating time differs greatly between when the oven is heated by the heaters 3 and 4 for the first time and there is no residual heat, and when the oven is heated for the second time or later and there is considerable residual heat. Therefore, the presence or absence of residual heat and its magnitude are roughly determined based on the initial temperature t ₀ detected above.

In addition, when we actually conducted the experiment, we found that the initial temperature
Even if t ₀ is the same, the difference will be different after oven heating by heaters 3 and 4 and after dielectric heating by magnetron 8, or after being left with the door closed and left with the door open. The rate of increase in detected temperature is different. It can be seen that the setting of the heating time necessary to bake the bread to the same state is required depending on whether the rate of increase in the detected temperature is high or low.

Therefore, in this example, the initial temperature t ₀ and the constant time
Temperature deviation t ₁ − between temperature t ₁ after Tc and initial temperature t ₀
The heating time T is set based on _t0 .

For example, the possible temperature range of initial temperature t ₀ is 40℃.
Below, we divide the temperature into three temperature ranges: 40°C to 120°C and 120°C or higher, and compare the temperature deviation t ₁ − _{t 0} when a certain period of time has elapsed after starting heating from each temperature range with each reference value. , the heating time T is set corresponding to the size. In this case, the heating time T is
Taking into account the specified baking conditions of "standard", "high", and "weak", each heating time T corresponding to the above temperature range and the size of the temperature deviation is determined in advance from experimental results, and this is calculated using a microcomputer. The corresponding information is stored in the memory of , and the corresponding one is selected from among them (process 28).

Next, after heating for the set heating time T (process 29), the relays RL ₁ , RL ₄ , and RL ₅ are turned off to cut off the power to the heaters 3 and 4 (process 30).

As described above, in this embodiment, the heating time T is set by taking into account not only the initial temperature t ₀ but also the temperature deviation t ₁ -t ₀ after a certain period of time from the start of heating. As a result, the residual heat state can be determined more accurately, and the set bread can always be toasted to the desired state to make toast, regardless of the temperature state inside the refrigerator.

In the above embodiments, the case of making toast was explained, but it goes without saying that the same applies to other cases of oven cooking. Also,
In addition to oven cooking, when dielectric heating is performed using a magnetron, the residual heat state in the refrigerator may be determined in a similar manner and an appropriate heating time may be set.

(g) Effects of the invention As described above, according to the invention, the heating time for oven heating by the heater is set based on the detected initial temperature inside the refrigerator and the rate of increase in temperature after heating starts. Therefore, since an appropriate heating time is set according to the preheating state of the device, it is possible to always bake the food to the desired state.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing a schematic configuration of a microwave oven with a heater according to an embodiment of the present invention, FIG. 2 is a circuit configuration diagram of a control circuit, and FIG. 3 is a flow chart showing the operation of the control circuit during toast cooking. It is. 1... Housing frame, 2... Cavity, 3, 4...
Heater, 5...grill, 6...shelf support, 7...thermistor,
8...Magnetron, 9...Operation unit, 10...Control unit,
11...High voltage transformer, 12...Cooling fan, 13...
Control circuit, 14...Transformer, _S1 ...Latch switch, _S2 ...Door switch, _S3 ...Monitor switch,
RL ₁ to _{RL 5} ...Relay.

Claims (1)

[Scope of utility model registration request] In a microwave oven equipped with a heater for heating the oven, a temperature sensor is attached to the wall of the heating chamber and detects the temperature inside the oven, and the temperature is detected by the temperature sensor when electricity starts to be applied to the heater. The heating time determining means determines the heating time based on the determined initial temperature and the rate of increase of the temperature, and the controlling means controls energization to the heater according to the determined heating time. Microwave with heater.