JPH0361317B2 - - Google Patents

Description

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

(b) Prior Art Generally, in a microwave oven equipped with an infrared detector, as shown in Japanese Patent Publication No. 56-42808,
The infrared detector is placed outside the heating chamber, and is configured to receive infrared rays from the food through an opening formed in the wall of the heating chamber and heat the food with microwaves while detecting the temperature of the food. The above-mentioned opening is closed by a shutter serving as an opening/closing means except when heating the food to such a temperature, so that water vapor, oil, etc. generated from the food in the heating chamber during heating are prevented from entering the above-mentioned opening at least after the microwave heating is completed. The light does not pass through and contaminate the infrared detector.

(c) Problems to be Solved by the Invention However, in such a microwave oven, when heating the food with microwaves while detecting the temperature, the opening remains open, and therefore the infrared detector No measures have been taken to prevent contamination.

(d) Means for Solving the Problems The present invention provides a heating chamber, a microwave supply means for supplying microwaves for heating food into the heating chamber, and a microwave supply means for supplying microwaves for heating food into the heating chamber, and a microwave supply means for supplying microwaves to the food through an opening formed in a wall of the heating chamber. an infrared detector for detecting food temperature by receiving infrared rays from the opening, an opening/closing means for opening and closing the opening, and controlling the opening/closing drive of the opening/closing means;
In the microwave oven, the microwave oven includes a control unit that controls driving of the microwave generation means depending on whether the temperature detected by the infrared detector reaches a desired temperature, and each time a desired time point arrives, the control unit controls the microwave generation means. The present invention is characterized in that the driving of the wave generating means is stopped, and after a predetermined period of time has elapsed, the opening/closing means is opened and the temperature of the food is detected by the infrared detector.

(E) Effect The opening formed in the heating chamber to allow the infrared detector to receive infrared rays from the food is opened by the opening/closing means at each desired time and after a predetermined period of time has elapsed after the microwave generation means has been stopped. I am forced to do it.
In this case, in the heating chamber, when a predetermined period of time has elapsed since the microwave generation means stopped driving, the amount of water vapor, oil, etc. generated from the food has eased, and therefore even if the opening is opened as described above, the amount of water vapor, oil, etc. Very little water vapor, oil, etc. reach the infrared detector through the opening. Furthermore, since this condition occurs only at each limited desired point in time, that is, only for a short period of time, contamination of the infrared detector is significantly suppressed. Further, after the opening is opened, the temperature of the food is detected by the infrared detector, but in this case, the microwave generation means is stopped;
Therefore, the food temperature can be detected without being affected by microwave noise.

(f) Examples The drawing shows a microwave oven according to an embodiment of the present invention.

1 and 2, 1 is an exterior, 2 is a heating chamber, 3 is a magnetron that oscillates microwaves for heating food 4, 5 is an opening formed in the upper wall of the heating chamber 2, and 6 7 is a microwave blocking ring attached to the opening and allows infrared rays to pass through but blocks microwaves from passing; 7 is a microwave shielding ring for receiving infrared rays from the food 4 through the opening 5 and ring 6 to detect the temperature of the food; 8 is an infrared detector; 8 is a shutter serving as an opening/closing means for opening and closing the upper end opening of the ring 6, that is, the opening 5; and 9 is a drive unit for driving the shutter. In the drive section,
10 is a support shaft that rotatably supports the shutter 8; 11 is a spring that biases the shutter 8 to rotate in the counterclockwise direction (FIG. 2) so that the shutter 8 closes the opening 5; and 12 is a spring In order for the shutter 8 to open the opening 5, the shutter 8 is moved clockwise (second direction) against the biasing force of the spring 11.
Solenoids 13 and 14 that bias the rotation of the shutter 8 in FIG. 1 are stoppers that restrict rotation of the shutter 8. 15
is a storage chamber in which the ring 6, the infrared detector 7, the shutter 8, and the drive section 9 are housed.

FIG. 3 shows the circuit of the microwave oven, where 16 is a microcomputer (hereinafter referred to as microcomputer) that controls the microwave oven, 17 is a setting unit for setting heating time, heating temperature, etc., and 18 is the infrared detection unit. A-D (analog-digital) converter, 19, which converts the detection signal from the device 7 into a digital signal;
2 is a commercial power supply, 20 is a high voltage supply circuit that supplies high voltage to the magnetron 3, and 21 is the microcomputer 16.
A first switching circuit 22 inputs power from the power source 19 to the high voltage supply circuit 20 in response to a heating signal H from the microcomputer 16; This is a second switching circuit for inputting the signal.

The operation of the microwave oven will now be explained. First, when a desired heating time is set in the setting section 17 and a heating start operation is performed, the microcomputer 16 outputs a heating signal H during the heating time, thereby executing microwave heating for the desired heating time. Ru. In this case, the opening 5 is closed by the shutter 8.

Next, when performing microwave temperature heating, in this case, reference is made to the flowchart of the program of the microcomputer 16 shown in FIG. 4 and the heating temperature characteristic chart of the food 4 shown in FIG. 5.

When the desired heating end temperature TE is set in the setting section 17 and a heating start operation is performed, the program starts.
Reaching S1 step. In this step, output of the shutter signal S is started, so that the solenoid 12 is driven, the shutter 8 is rotated clockwise (FIG. 2), and the opening 5 is opened. In the next step S2, the infrared rays from the food 4 are received by the infrared detector 7 through the open opening 5, so that the current food temperature TF (temperature shown in Figure 5) is detected.
) is detected. In the following step S3, it is determined whether the food temperature TF is lower than the heating end temperature TE. In this case, since heating has not yet started, the food temperature TF is lower than the heating end temperature TE, so the program is then
Proceed to step. In this step, the shutter signal S
is stopped, the shutter 8 is rotated counterclockwise (FIG. 2) by the force of the spring 11, and the opening 5 is closed. In the following step S5, a heating signal H is output and microwave temperature heating is started. next
In step S6, it is determined whether the value obtained by subtracting the current food temperature TF from the heating end temperature TE is greater than a predetermined constant temperature difference ΔTM, for example, 5°C. The value subtracted above is the constant temperature difference △
If it is greater than TM, then △ for a certain period of time
The opening 5 is closed for tM ₁ (for example, 20 seconds). During this time, microwave heating is of course performed.

That is, the program then proceeds to step S7.
In this step, the counter Δt in the microcomputer 16
Timing starts at . In the following step S8, it is determined whether the time count of the counter Δt has reached the predetermined time _ΔtM1 . In this case, this has not been reached since the time has just started, and the program therefore remains at step S8. and,
The time measurement content of the above counter Δt is the above fixed time ΔtM ₁
When reaching , the program moves from step S8 to step S9. In this step, the time measurement of the counter Δt is stopped and its contents are cleared. Continue
In step S10, the output of the heating signal H is stopped and the microwave heating is stopped. In the next step S11, the counter Δt' in the microcomputer 16 starts counting time. The program then reaches step S12. In this step, it is determined whether the time measured by the counter Δt' has reached a certain time ΔtN (for example, 5 seconds). In this case, this has not been reached since the time has just started, and the program therefore remains at step S12. Then, the time measurement content of the counter Δt′ is the constant time ΔtN
When reached, the program starts from step S12.
Reaching step S13. In this step, the counter Δt' stops counting and its contents are cleared.

Here, at present, ΔtN time (5 seconds) after microwave heating is stopped at step S10.
In this case, the amount of water vapor, oil, etc. generated from the food 4 has eased considerably, so even if the opening 5 is opened immediately thereafter, it will still reach the infrared detector 7 through the opening 5. The amount of water vapor, oil, etc. that can be produced is extremely small.

The program then returns from step S13 to step S1, and the opening 5 is opened. After that, the food temperature TF (temperature shown in Figure 5) is detected sequentially.
As long as the value obtained by subtracting T2, T3, etc.) from the heating end temperature TE is greater than the constant temperature difference ΔTM, the program cycles through steps S1 to S13.
During such circulation, microwave heating is performed with the opening 5 closed, and the food temperature is maintained at the above-mentioned temperature.
Sequential detection of TF is ΔtN from microwave heating stop.
Of course, the opening 5 is opened after a period of time has elapsed.

Thereafter, in the above circulation state, when the newly detected food temperature TF (equal to the temperature TN in FIG. 5) is subtracted from the heating end temperature TE, it is assumed that the value becomes equal to or less than a certain temperature difference ΔTN. Then, the program exits the cycle of steps S1 to S13 at step S6 and reaches step S14, which is the same as step S7. In the following step S15, it is determined whether the time measured by the counter Δt has reached a certain time ΔtM ₂ (for example, 10 seconds). In this case, this has not been reached since it is just after the start of time measurement, and therefore the program remains at step S15. This fixed time ΔtM ₂ is smaller than the above fixed time ΔtM ₁ . and,
When the above is reached, the program exits step S15, returns to step S1 via steps S9 to S13, and thereafter cycles through steps S1 to S6, S14, S15, and S9 to S13. Therefore, in this case, the food temperature TF
It can be seen that the detection interval becomes more frequent than during the cycle of steps S1 to S13 described above. This is because the food temperature TF will soon reach the desired heating end temperature TE, that is, the food temperature will frequently reach the desired heating end temperature TE.
Detects TF and food temperature TF reaches end temperature TE
This is to know as soon as possible that the goal has been reached.

Then, when the food temperature TF reaches the heating end temperature TE, the program starts from S1 to S6, S14, S15, S9 to
The cycle of S13 step is exited at S3 step, and S16
Reaching the steps. Step S16 is similar to step S7, and the opening 5 is closed to complete the microwave temperature heating. The program then enters a standby state, and a signal from the setting section 17 for the next heating can be input.

Therefore, even during microwave temperature heating, the degree to which the aperture 5 is opened is extremely small, and moreover, the aperture 5 stops microwave heating at each desired time point when the temperature is detected by the infrared detector 7. The infrared detector 7 is opened after a period of ΔtN has elapsed, and therefore water vapor, oil, etc. hardly ever reach the infrared detector 7 as described above. Furthermore, the above temperature detection is
This is done after microwave heating has stopped and is therefore not affected by microwave noise.

Incidentally, instead of the above embodiment, as shown in FIG. 6,
The temperatures at two points A and B after a predetermined time has elapsed from the start of microwave temperature heating are detected in the same manner as described above, and from the temperature difference between these two points, the desired heating end temperature TE is determined. The approximate time point C at which the temperature reached by subtracting the above-mentioned constant temperature difference ΔTM is immediately determined based on a predetermined calculation formula, and after the heating time reaches the above-mentioned time point C, the above-described embodiment It may be controlled as follows.

(G) Effects of the Invention According to the present invention, the opening formed in the heating chamber to allow the infrared detector to receive infrared rays from the food is opened very rarely, and moreover, the opening does not stop microwave heating. Since this is carried out after a predetermined period of time has elapsed, the amount of water vapor, oil, etc. that reaches the infrared detector through the opening is extremely small, and contamination of the infrared detector is significantly suppressed, increasing the reliability of the infrared detector. performance is significantly improved. Furthermore, temperature detection by the infrared detector is performed after microwave heating has stopped and the opening has been opened, so it is not affected by microwave noise.
Therefore, the reliability of the infrared detector described above is significantly improved in this respect as well.

[Brief explanation of drawings]

The drawing shows a microwave oven according to an embodiment of the present invention.
The figure is a sectional view, Figure 2 is a plan view of the main part, Figure 3 is a circuit diagram, Figure 4 is a flowchart of a microcomputer program, Figure 5 is a diagram of heating temperature characteristics of food, and Figure 6 is a diagram of the present invention. FIG. 7 is a diagram of heating temperature characteristics of food in a microwave oven of another example. 2... Heating chamber, 3... Magnetron, 5... Opening, 7... Infrared detector, 8... Shutter, 16
...Microcomputer.

Claims (1)

[Claims] 1. A heating chamber, a microwave supply means for supplying microwaves for heating food into the heating chamber, and an infrared ray for detecting the temperature of the food by receiving infrared rays from the food through an opening formed in the wall of the heating chamber. A detector, an opening/closing means for opening and closing the opening, and control for controlling the opening/closing drive of the opening/closing means, and controlling the driving of the microwave generating means depending on whether the temperature detected by the infrared detector has reached a desired temperature. In the microwave oven equipped with a microwave oven, the control section stops driving the microwave generating means every time a desired time arrives, and after a predetermined period of time has elapsed, drives the opening/closing means to open the infrared detector. A microwave oven characterized by detecting the temperature of food.