JPS58106332A - Electronic range - Google Patents

Abstract

PURPOSE:To effectively prevent the excess scorch of food by raising a heater for heating grill to the prescribed temperature when the grill is heated by microwave heating and then lowering it to come to the prescribed height to the food. CONSTITUTION:When a grill heating key 3 is depressed to start cooking, a transistor Tr12 is first conducted by a microcomputer 8, and when a relay 19 is energized, its contact 23 is closed, thereby energizing a microwave heater 18. Thus, heating is advanced, and the output of a gas sensor 5 reaches the prescribed detecting level. Then, the Tr 12 is interrupted, while the Tr 11 is conducted, thereby stopping the heater 18. Subsequently, the energization of the heater 13 is started. Thereafter, when the time TS that the heater 13 is heated to become red hot is elapsed, the Tr 10 is conducted, the relay 16 is energized, its contact 21 is then closed, thereby moving downwardly the heater 13 by the operation of a motor 14 at the position where the heater 13 approaches the food.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a microwave oven that discriminates food based on the temporal change in terminal voltage of a gas sensor and determines when to automatically cook the food.

Traditionally, heaters used for heating grills have a large thermal time constant because the outer sheath of the heater is covered with an iron pipe to prevent it from being affected by microwave electric fields, etc. For example, it takes about 1 to 2 minutes for the grill to become red hot. there were. Therefore, when transitioning from microwave heating to grill heating, the heater is lowered onto the food,
If an abnormal situation such as contact with food occurs, the outer surface of the heater has not reached a sufficiently high temperature, so the amount of gas, smoke, etc. generated by contact with food in this state will be relatively small. In other words, there has been a drawback that it takes time to reach the level of the gas sensor at the time of abnormality, which is stored in advance in the ROM.

This state will be explained with reference to FIGS. 1 and 2. FIG. 1 is a general characteristic diagram of a gas sensor that shifts from microwave heating to grill heating, and FIG. FIG. 6 is an explanatory diagram of the operation of the gas sensor when the heater comes into contact with food.

In the figure, the horizontal axis shows the heating time, the microwave heating time is TI + the grill heating time is T1 + the time to energize the motor that drives the heater to lower when transitioning from microwave heating to grill heating, and the vertical axis is is the terminal voltage V of the gas sensor. The detection level at the end of microwave heating is set as VS, and the abnormal state level VP is set to detect a large amount of smoke, gas, etc. generated when the heater comes into contact with food.

Here, when the heater comes into contact with the food at position A after the motor drive time TM has elapsed in Fig. 2, the amount of burnt food is small because the heater has not heated it sufficiently, and the amount of smoke and gas generated is small, so the level of the gas sensor is The rise of t is also poor, and after the motor drive time TM has elapsed. If the abnormal state level reaches the abnormal state level A-'J p or more after taking a time of , the food is pressed down by the heater and loses its shape, resulting in excessive scorching.

The present invention has been made in view of the above points, and when shifting from microwave heating to grill heating, the heater for heating the grill is not lowered immediately, but the heating is continued until the heater reaches a predetermined temperature. After heating, the heater is moved closer to the food.

Hereinafter, one embodiment of the present invention will be described based on the drawings.

Fig. 3 is a characteristic diagram of a gas sensor showing an embodiment of the present invention, Fig. 4 is an explanatory diagram of the operation of the gas sensor when the heater comes into contact with food, and Fig. 5 is a microwave oven of an embodiment of the present invention. FIG. 2 is a schematic electrical circuit diagram of FIG.

In the figure, 1 is the keyboard of the operation panel of the microwave oven, and microwave heating keys 2. A grill heating key, heating start key 4, etc. are arranged.

5 is a gas sensor that is disposed at an open exhaust port (not shown) and whose resistance value changes depending on the concentration of exhaust gas consisting of evaporative components such as odors, smoke, and smoke from the food being heated; It is connected to a DC power supply Vc via a load resistor. The output of the gas sensor 5 is sent to the interface 7 via the A/II converter 6, and also to the microwave heating key 2 in the keyboard 1. Grill heating key 3. The respective outputs of the heating start key 4 and 4 are connected to the interface 7 and introduced into a microcomputer 8 consisting of ROM, RAM, CPU, etc. The microcomputer 8 stores heating cooking sequences, measurement data, and the like. 9,10
．． 11.12 is N connected to the above interface 7
PN) A normal rotation relay 15 which is a transistor and rotates the motor 14 which drives the heater 13 up and down on the collector side in the normal direction. Reversing relay 16. A heater relay 17 that controls energization to the heater 13 and a microwave heating relay 19 that controls energization to the microwave heating device 18 are connected. 20, 21, 22.23 are the forward rotation relays 15. Reversing relay 16. These are relay contacts of the heater relay 17 and the microwave relay 19.

Next, the operation of the embodiment of the present invention having the above configuration will be explained.

First, when you press the grill heating key 3 and the heating start key 4, the microcomputer 8 sends the
A high level signal is output to the base of P1'l transistor 12, and this NPN) U/raster 12 and relay 1
9 turns on. Therefore, when the relay contact 23 of the relay 19 is closed, the microwave heating device 18 starts to be energized and microwave heating is performed. Above microwave power 1
When 1 heat crab is executed, the microcomputer 8 calculates the terminal voltage of the gas sensor 5 and its rate of change over time, determines the type of food, and sets the gas sensor detection level 5 corresponding to the food. And now, the time T when the gas sensor level of the food in the car reaches the above detection level■
Once 1 has passed, the microwave power mouth fever ends.

At this time, a low level signal is sent to the NPN run raster 120 pace through the microcomputer 875 and the interface 7, and a low level signal is sent to the pace I of the NPN transistor 1.
/CHi g A h level signal is output. Therefore, the relay 19 is turned off, but the relay 17 is turned on, the relay contact 23 is opened, and the relay contact 22 is closed, so that the power supply to the microwave heating device 18 is stopped.
Power supply to the heater 3 is started. In this case, since the motor 4 is not energized, the heater 3 does not move and heats up at a predetermined position well above the food. The time T is the time required for the heater 3 to heat up to a sufficiently high temperature, and is stored in the preparatory microcomputer 8. Then, when this red-hot time Ts has elapsed, the microcomputer 8 connects the NPN transistor via the interface 7.

Since a high level signal is output at the pace of , relay 16 is turned on, relay contact 21 is closed, and motor
starts rotating the heater 3 so that it descends. For example, the motor 4 continues to rotate for a time TM until the heater 3 stops at a position 3 cm above the food, and when the time TM has elapsed, the NPN transistor o
Then, the microcomputer 8 outputs a low level signal via the interface 7, the relay 16 is turned off, the relay contact 2o for controlling the downward drive of the motor 4 is opened, and the electric motor 13 is stopped.

In this way, the heater 3 is energized after the microwave heating is completed and is fixed at a predetermined position above the food until it reaches a predetermined temperature, and after the time Ts has passed and the temperature has reached a certain level, the heater 3 is heated. 4, and stops at a position approximately 3c+11 above the food, and grill heating continues in this state.

Therefore, if an abnormal situation occurs in which the heater 13 comes into contact with the food while descending, the heater will be at a sufficiently high temperature during the descent, so gas, smoke, etc. will be rapidly generated from the food. 4 Heater 1 at B as shown in Figure 4
3 and food, the terminal voltage Va of the gas sensor 5 suddenly decreases due to the effect of the rapidly increasing exhaust gas concentration, becomes below the abnormal state level Vp in a very short time, and the microcomputer 8 causes the interface 7 to A Low level signal is output to the NPN transistor 10 through the NPN transistor 10, and a High level signal is output to the NPN transistor 9. The relay 16 is turned off and the relay 15 is turned on, so the relay contact 21 is opened and the relay contact 20 is closed. The motor 14 is driven to rotate so that the heater 13 moves upward. Therefore, when the abnormal state level vP is reached, the heater 13 immediately moves upward and away from the food. In this case, the abnormal state level VP
Since the time it takes to reach this point is extremely short, the time that the heater 13 is in contact with the food can also be significantly shortened.

As explained above, the present invention provides for a microwave oven that automatically determines the completion of cooking by determining the type of food based on the time change of the terminal voltage of a gas sensor, when switching from microwave heating to grill heating. The heater for heating the grill is equipped with a control means that raises it to a predetermined temperature and then lowers it to a certain height relative to the food, so if the heater approaches or comes into contact with the food, the motor can be quickly turned on. Since the heater can be rotated in the opposite direction to raise the heater and move it away from the food, it is possible to efficiently prevent the food from being overcooked.

[Brief explanation of the drawing]

Fig. 1 is a general characteristic diagram of a gas sensor that shifts from microwave to grill heating, Fig. 2 is an explanatory diagram of the operation of the gas sensor when the heater comes into contact with food, and Fig. 3 is a diagram showing the implementation of the present invention. A characteristic diagram of a gas sensor, Fig. 4, shows an example of a gas sensor in which a heater comes into contact with food. 15...Forward rotation relay, 16...Reverse rotation relay, 17
・Heater relay, 18...Microwave heating device. 19 Microwave heating relay. Agent Patent Attorney Aihiko Fukushi

Claims (1)

[Claims] 1. In a microwave oven that automatically determines the completion of cooking by determining the type of food based on time changes in the terminal voltage of a gas sensor, when switching from microwave heating to grill heating, the grill heating heater is set to a predetermined temperature. A microwave oven characterized in that it is equipped with a control means for raising the food to a certain height and then lowering it to a certain height relative to the food.