JPH0437336B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a microwave oven that detects the temperature of food and controls microwave heating based on the detected temperature.

(b) Prior art In a conventional microwave oven as seen in Utility Model Application No. 10072/1980, microwaves oscillated from a magnetron as a microwave supply means are supplied into a heating chamber via a waveguide. The food on the turntable is heated by such microwaves. on the other hand,
An infrared sensor is provided outside the heating chamber as a temperature detection means for detecting the temperature of the food by receiving infrared rays from the food. The microwave oscillation of the magnetron is controlled based on the detected temperature signal from the sensor.

In this case, although the structure is designed to prevent the microwaves supplied into the heating chamber from leaking to the outside as much as possible, leakage of such microwaves cannot be completely suppressed, and such leakage occurs. The noise caused by this gets on the output of the above sensor, and the sensor's SN
There is a disadvantage that the ratio decreases significantly, thus making it impossible to perform heating control at an accurate temperature, and resulting in poor cooking results.

(c) Problems to be Solved by the Invention The object of the present invention is to provide a microwave oven that can control heating at an accurately detected temperature without being affected by noise, and that provides good cooking results.

(d) Means for solving the problems The present invention provides a heating chamber for storing food, a microwave supply means for supplying microwaves for microwave heating into the heating chamber, and a means for detecting the temperature of the food. In a microwave oven, the microwave oven includes a temperature detecting means for detecting the temperature, and a control section that controls driving of the microwave supply means based on the temperature detected by the temperature detecting means,
The control unit includes a first stop step of stopping the driving of the microwave supply means when the temperature detected by the temperature detection means reaches a temperature lower than the desired temperature by a predetermined temperature after the start of microwave heating, and a first stop step after which a first time elapses. a first determination step for determining whether or not the temperature detected by the temperature detection means at the time reaches the desired temperature and the desired heating is achieved; a driving step of driving the microwave supplying means; a second stopping step of stopping the driving of the microwave supplying means when the temperature detected by the temperature detection means reaches the desired temperature and a second time has elapsed; a second determination step for determining whether the temperature detected by the temperature detection means after three hours has reached the desired temperature and the desired heating has been achieved; If it is determined, the control section repeats the driving step, the second stopping step, and the second determining step.

(c) Effect In the present invention, heating can be controlled at an accurate detected temperature without being affected by noise caused by microwaves.

(F) Embodiment A microwave oven according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a cross section of the same microwave oven. Microwaves oscillated from a magnetron 1 as a microwave supply means are supplied to a heating chamber 4 in a main body 3 via a waveguide 2. The food 6 on the turntable 5 is heated. On the other hand, an infrared sensor 7 is provided outside the heating chamber 4 as a temperature detection means for receiving infrared rays from the food 6 and detecting the temperature of the food.

FIG. 2 shows the circuit of such a microwave oven, and is provided with a control section, that is, a microcomputer 8, which controls the microwave oven. Inputting desired information from a keyboard 9 having menu keys etc., and inputting temperature information detected by the infrared sensor 7 via an A/D converter 10,
The output of the heating signal H is controlled based on both of these pieces of information. When such a heating signal H is output, the switching circuit 11 consisting of a bidirectional thyristor is turned on, and the commercial power supply 12 is turned on.
Electric power is supplied to the high voltage circuit 13, which applies high voltage to the magnetron 1, oscillates microwaves, and performs heating.

Now, in such a microwave oven, the structure is such that the microwaves supplied into the heating chamber 4 do not leak to the outside as much as possible, but the leakage of such microwaves cannot be completely suppressed. Some of the microwaves leak out of the heating chamber 4.

Therefore, in such microwave ovens, differences naturally occur between individual products even if they are of the same model, and in some products, noise caused by leaked microwaves always becomes a positive value in the output of the sensor 7. In other products, a situation occurs in which such noise always appears on the output of the sensor 7 in a negative manner.

Here, the microwave oven is configured to be able to cope with microwave noise regardless of whether the microwave noise is on the plus or minus side in the same model.

Next, first of all, regarding what to do when microwave noise is on the negative side, the operation of the microwave oven described above will be explained using the flowchart of the program of the microcomputer 8 shown in FIG. This will be explained based on the output characteristic diagram. Fourth
In figure a, the horizontal axis is the cooking time and the vertical axis is the sensor 7.
Indicates the detected temperature of food.

Normally, a program cycles through S1 and S2 steps. In step S1, key information operated on the keyboard 9 is input into the computer 8, and in step S2, it is determined whether or not the operation relates to a menu key.

For example, if you operate the menu key related to sake cans on the keyboard 9, the information will be displayed.
Inputted into the computer 8 at step S1,
The program then exits the cycle of S1 and S2 steps and reaches step S3. In this step, information regarding the operated menu key, in this case the desired temperature for the sake can, ie, the cooking end temperature T ₀ (55° C. in this case), is read from the memory (ROM) in the computer 8. The program then
Cycle through S4 and S5 steps. S4 step is above
This is the same as step S1, and in step S5 it is determined whether the information input in step S4 is related to the start key.

Then, when the start key is operated, the program exits the cycle of steps S4 and S5 and reaches step S6. In this step, output of the heating signal H is started, and microwave heating is started. The program then cycles through steps S7 and S8. In step S7, the detected temperature _T1 of sensor 7 is input, and in step S8, this detected temperature is equal to the above-mentioned cooking end temperature.
It is determined whether a temperature lower than T ₀ by a predetermined temperature (for example, 5° C.) has been reached. Such predetermined temperature 5℃
is slightly smaller than the temperature that rises or falls under the influence of microwave noise. During the circulation of steps S7 and S8, the temperature _T1 detected by the sensor 7 gradually rises as the temperature increases. Such a detected temperature _T1 is a state in which microwave noise is on the negative side (range in FIG. 4a).

Thereafter, when the detected temperature reaches a predetermined temperature of 5°C lower than the cooking end temperature _T0 (point a in Figure 4), the program starts as the first stop step.
Proceed to step S9. In this step, the output of the heating signal H is stopped, and the microwave heating is stopped. In the following step S10, a first time, ie, 5 seconds, is set in the timer (TM) in the computer 8, and counting down is started from that time.
In the following step S11, it is determined whether the contents of the timer (TM) have become 0, that is, whether 5 seconds have elapsed. The program remains at the same step until 5 seconds have elapsed (range).

The next step S12 is the same as the above step S7, and the detected temperature _T1 is input. In this case, the detected temperature T ₁ is when the microwave heating is stopped and the microwave noise is not on the negative side, that is, the detected temperature T 1 is higher than during the microwave heating by the temperature related to the microwave noise (5 degrees Celsius or more). and accurately represents the food temperature (point a in Figure 4). Therefore, this detected temperature T ₁ is 5° C. or more higher than the temperature at the above point, and slightly exceeds the above cooking end temperature T ₀ .

The program then performs the first decision step.
Proceed to step S13. In this step, the detected temperature
It is determined whether T ₁ has reached the cooking end temperature T ₀ and it is time to end cooking. In this case, a termination determination is made, and the program thus reaches step S27. In this step, if the heating signal H is being output, it is stopped and cooking is completed, and a buzzer (not shown) is used to notify the completion of cooking. This is where the sake can is made.

Next, the operation of the microwave oven will be described with reference to the flowchart in FIG. 3 and the output characteristic diagram of the sensor 7 shown in FIG. Figure 4b
is a diagram similar to FIG. 4a.

In this case, when the menu key and start key related to the sake can are operated as described above, the program advances to step S13 as described above. However, in this case, during the circulation of steps S7 and S8, the detected temperature _T1 of the sensor 7 gradually increases as it heats up, but the detected temperature _T1 reaches a state where the microwave noise is on the positive side. (range in Figure 4b).

Also, in step S12, the detected temperature T ₁ is
When microwave heating is stopped, the microwave noise is not on the positive side, that is, the temperature is lower than during microwave heating by the amount related to the microwave noise (5 degrees Celsius or more), and the food temperature is not accurately represented. (point b in Figure 4). This detected temperature T ₁ is lower than the point temperature by 5° C. or more.

Therefore, in step S13, the detected temperature T ₁
If it is determined that the cooking end temperature _T0 has not been reached, the program proceeds to step S14. In this step, the counter (CT) in the computer 8 is reset to 0. The program then proceeds to step S15 as a driving step, which is the same as step S6, and microwave heating is resumed. The program then cycles through steps S16 and S17. These S16 and S17 steps are S12,
Same as S13 step. During such circulation, the detected temperature T ₁ gradually increases as it heats up,
In this case, the detected temperature T ₁ is in a state where microwave noise is on the plus side (range shown in FIG. 4b).

Thereafter, when the detected temperature _T1 reaches the cooking end temperature _T0 , the program reaches step S18, and it is determined whether the content of the counter (CT) has reached 2 or not. Since it is 0 in this case, the program then proceeds to step S19. In this step, a second time, ie, 5 seconds, is set in the timer (TM) and a down count is started from that time.
The following step S20 is the same as the step S11 above, and the program remains at this step until 5 seconds have elapsed (range of Figure 4b).

S21 as the second stop step after that
The step is the same as step S9, and microwave heating is stopped. In the following step S22, the timer (TM) is set to a third time, that is, 5 seconds, and starts counting down from that time.
The following step S23 is the same as the step S11 above, and the program remains at this step until 5 seconds have elapsed (range of Figure 4b).

Therefore, the next step S24 is the same as the above step S7, and the detected temperature _T1 is input. In this case, the detected temperature T ₁ is when the microwave heating is stopped and the microwave noise is not on the positive side.
That is, compared to during microwave heating, the temperature is lowered by the amount associated with microwave noise (5° C. or more), and the food temperature is accurately represented (point in FIG. 4b). and,
It is now assumed that this detected temperature T ₁ is lower than the cooking end temperature T ₀ .

Therefore, in step S25, which is the second judgment step, the detected temperature _T1 is equal to the cooking end temperature _T0.
It is determined whether or not the cooking time has reached the end of cooking.
In this case, a non-termination determination is made, and the program then proceeds to step S26. In this step, the contents of the counter (CT) are incremented by one, and the contents become one.

The program then returns to step S15 and returns to step S15~
After passing through the S24 step, the process returns to the S25 step. Here, the detected temperature T ₁ (which accurately represents the food temperature) input in step S24 is the cooking end temperature.
Assuming that T ₀ has been reached (point b in Figure 4), the program reaches step S27, and the can of sake has been completed.

If it is assumed that the detected temperature T ₁ has not yet reached the cooking end temperature T ₀ at step S25, the program returns to step S26, and in this case the content of the counter (CT) becomes 2. The program is
After that, the process returns to step S15, but when it reaches step S18, the content of the counter (CT) in this case is 2.
Therefore, the process reaches step S27, which means that the cooking is complete and the can of sake is completed.

In the above embodiment, the desired temperature that the food should reach is the cooking end temperature, but it may be any temperature during cooking. In this case, the above-mentioned step S27 is a step for executing the next heating and ending the cooking.

(g) Effects of the Invention According to the present invention, it is possible to provide a practical microwave oven that can accurately detect the temperature of food without being affected by microwave noise, thereby improving the cooking quality.

[Brief explanation of drawings]

The drawing shows a microwave oven according to an embodiment of the present invention.
2 is a circuit diagram, FIG. 3 is a flowchart of a microcomputer program, and FIGS. 4a and 4b are output characteristic diagrams of the infrared sensor. 1... Magnetron, 4... Heating chamber, 7... Infrared sensor, 8... Microcomputer.

Claims (1)

[Claims] 1. A heating chamber for storing food, a microwave supply means for supplying microwaves for microwave heating into the heating chamber, a temperature detection means for detecting the temperature of the food, and a temperature detection means for detecting the temperature of the temperature detection means. In the microwave oven, the control section controls the operation of the microwave supply means when the temperature detected by the temperature detection means reaches a temperature lower than the desired temperature by a predetermined temperature after the start of microwave heating. a first stop step of stopping the driving of the microwave supply means; and a step of determining whether or not the temperature detected by the temperature detection means after a first time period has reached the desired temperature and the desired heating has been achieved. 1 judgment step, and if the first judgment step is negative, a driving step of driving the microwave supply means, and then a second time period when the detected temperature of the temperature detection means reaches the desired temperature. a second stop step of stopping the driving of the microwave supply means after the elapse of the third stop step;
and a second determination step for determining whether or not the temperature detected by the temperature detection means after the elapse of time has reached the desired temperature and the desired heating has been achieved, and if the second determination step determines that the temperature has not reached the desired temperature. In the microwave oven, the control section repeats the driving step, the second stopping step, and the second determining step.