JPH09210369A - Microwave oven - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the irregularity of cooking and to attempt to reduce the manufacturing cost by providing means for regulating the output value of a gas sensor so as to fall within a predetermined range before the cooking is started to vary the control constant for automatic cooking based on the value of the regulated sensor output. SOLUTION: A gas sensor 18 for sensing the concentration of gas such as steam contained in the air in an exhaust passage 17 is disposed in the bottom wall of the passage 17. The sensor 18 senses the gas such as the steam generated from material 7 to be cooked. A control circuit 20 regulates the initial value of the sensor output from the sensor 18 so as to fall within a predetermined range. When heating cooking is automatically controlled based on the sensor data value from the sensor 18, a constant α is used as a control constant to control it. The circuit 20 is mainly constituted by a microcomputer to correct to vary the constant α based on the initial sensor data value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention includes a gas sensor for detecting gas generated from a food product, and an electronic device configured to automatically control cooking based on a sensor output output from the gas sensor. Regarding the range.

[0002]

2. Description of the Related Art A gas sensor has a characteristic that its resistance value changes according to the concentration of gas. Therefore, in a microwave oven, the resistance value of the gas sensor (specifically, the voltage between the terminals of the gas sensor) is measured to detect the amount of gas generated from the cooked food.

[0003]

The initial resistance value of the gas sensor before the start of cooking in which almost no gas is generated from the food is a value that varies in the range of about 10 kΩ to 100 kΩ, which is a considerable variation. There is. For this reason, it is necessary to provide a plurality of adjusting resistors switchably connectable to the gas sensor and adjust the value of the voltage between the terminals of the gas sensor, that is, the value of the sensor output to be a substantially constant value.
In this case, in the conventional configuration, the gas sensor is provided with various resistances, for example, about 5 adjusting resistors that can be connected in various combinations so that the initial value of the sensor output falls within a predetermined range. I try to fit it.

On the other hand, in the microwave oven, when the cooking is automatically controlled based on the value of the sensor output from the gas sensor, conventionally, constants α and β are used as control constants. These constants α and β are set so that optimum cooking is executed when the initial value of the sensor output is the median value of the above-mentioned predetermined range. Thereby, generally good cooking can be performed even in the microwave oven having the conventional configuration. However, when the initial value of the sensor output is close to the minimum value or the maximum value in the above predetermined range,
When the so-called α-decrease detection time is optimum (when the initial value of the sensor output is the median value of the predetermined range), it becomes much later or much earlier than the detection time.
For this reason, there is a drawback that overheating may occur or underheating may occur, and the finished state of cooking may vary.

As a structure for solving such a drawback, it is easy to consider narrowing the width of the predetermined range in which the initial value of the sensor output is contained. To realize this, the number of adjusting resistors is increased. It is necessary to use a variable resistor. However, in the case of such a configuration, there is a problem that the number of parts is increased, the configuration is complicated, the cost of parts is increased, and the manufacturing cost is considerably increased, which is difficult to realize. It was

Therefore, an object of the present invention is to control cooking based on the sensor output from the gas sensor,
It is possible to prevent variations in the completion of cooking as much as possible,
Moreover, it is to provide a microwave oven capable of preventing the manufacturing cost from increasing.

[0007]

The microwave oven according to the present invention comprises:
A gas sensor that detects the gas generated from the food, a cooking control unit that controls cooking based on the sensor output that is output from the gas sensor, and a value of the sensor output that is output from the gas sensor before the start of cooking are A feature is that it is provided with an adjusting means for adjusting so as to be within a predetermined range, and a control constant correcting means for changing a control constant for automatic cooking based on the value of the sensor output adjusted by the adjusting means. Have.

According to the above configuration, the control constant for automatic cooking is varied based on the value of the sensor output adjusted by the adjusting means. Therefore, the value of the sensor output (initial value)
Is a value close to the minimum or maximum of the specified range,
The so-called α-decrease detection time can be made approximately the same as the optimum detection time (when the sensor output value is the median value of the predetermined range). Therefore, the heating and cooking can be optimally performed without excess or deficiency, and the finished state of cooking is uniform. In the case of this configuration, since it is only necessary to change the control constant for automatic cooking based on the adjusted sensor output value, the number of parts does not increase, the configuration does not become complicated, and the manufacturing cost is reduced. Can be prevented from increasing.

Further, in the above construction, a plurality of adjusting means are connected to the gas sensor, and a plurality of adjusting resistors for adjusting the value of the sensor output and a plurality of adjusting resistors are provided so that the level of the sensor output falls within a predetermined range. It is preferable that the adjusting resistor is composed of a switching means for switching and connecting the adjusting resistor.

Furthermore, after the level of the sensor output from the gas sensor reaches the peak value Vmax, the function of detecting the time point of α decrease, which is decreased by α · Vmax obtained by multiplying the peak value Vmax by a constant α, is provided as a cooking control means. In case of the above, the control constant correcting means may change the constant α as a control constant. Also, after the value of the sensor output from the gas sensor reaches the peak value Vmax, a constant α is added to this peak value Vmax.
Detects the time point of α decrease when it is decreased by α · Vmax multiplied by
When cooking is finished after a predetermined time T1 from this time point, or the time T from the start of cooking to the time point of α decrease is measured, and the remaining cooking time β · T is obtained by multiplying this time T by a constant β.
A function to continue cooking from the point when α decreases and finish cooking,
When the cooking control means is provided, it is preferable that the control constant correcting means varies the constant β or the time T1 as a control constant.

On the other hand, when the value of the sensor output adjusted by the adjusting means is larger than the upper limit value for sensor abnormality determination,
Alternatively, it is a more preferable configuration to include a notification unit that notifies that the sensor is abnormal when the value of the sensor output is smaller than the lower limit value for sensor abnormality determination. Furthermore, when the cooking control means has a function of controlling cooking based on a value obtained by multiplying the sensor output by the constant K, the control constant correction means is preferably configured to vary the constant K as a control constant.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION A first embodiment of a microwave oven with a heater will be described below with reference to FIGS. 1 to 7. First, in FIGS. 2 and 3 showing a schematic overall configuration of a microwave oven with a heater, a heating chamber 2 is provided inside a range main body 1. The front opening of the heating chamber 2 serves as a loading / unloading port for the food and is opened / closed by the door 3. An operation panel 4 is provided on the right end of the front surface of the range main body 1, and various display devices 5 and various operation switches 6 are provided on the operation panel 4.

At the inner bottom of the heating chamber 2, there is rotatably provided a rotary plate 7 on which the food A is placed. The rotary plate 7 is configured to be rotationally driven by an RT motor 8 via a rotary shaft 9. In the vicinity of the RT motor 8, a weight sensor 10 (see FIG. 4) that detects the weight of the food A placed on the rotary dish 7 via the rotary shaft 9 is provided.

Further, a machine room 11 is provided on the right side of the heating room 2 in the range main body 1. This machine room 1
Inside the unit 1, a magnetron 12, electric components such as a high-voltage transformer and a control circuit, and a fan device for cooling these components are arranged. The magnetron 12 supplies high frequency (microwave) into the heating chamber 2 through the waveguide 13 to heat the cooking food A in the heating chamber 2 by high frequency (range heating). The fan device includes a fan and a fan motor 14 (see FIG. 4) that rotationally drives the fan. A part of the cooling air blown by the fan device is supplied to the heating chamber 2 after cooling the magnetron 12.

On the other hand, in the upper part of the left side wall 15 of the heating chamber 2,
As shown in FIG. 3, an exhaust port 16 including a large number of small holes is provided. The exhaust port 16 communicates with the outside of the range main body 1 via an exhaust passage 17. In this case, when the fan motor 14 is energized and cooling air is supplied into the heating chamber 2 by the fan device, the air in the heating chamber 2 is discharged to the outside of the machine through the exhaust port 16 and the exhaust passage 17. It is configured to be.

A gas sensor 18 for detecting the concentration of gas such as water vapor contained in the air in the exhaust passage 17 is provided on the inner bottom wall of the exhaust passage 17. The gas sensor 18 is a sensor that detects gas such as water vapor generated from the cooked food 7.

An upper heater and a lower heater, which are flat heaters, are provided on the ceiling and bottom of the heating chamber 2. Further, a hot air heater that circulates hot air into the heating chamber 2 is provided at the rear of the heating chamber 2. The upper heater, the lower heater and the hot air heater constitute a heater device 19 (see FIG. 4) for oven cooking.

FIG. 4 is a diagram showing the electrical configuration of the above microwave oven in a combination of functional blocks. In FIG. 4, the control circuit 20 is mainly composed of a microcomputer, has a function of controlling the entire cooking operation of the microwave oven, and stores a control program therefor. The control circuit 20 constitutes cooking control means and control constant correction means.

The control circuit 20 includes various indicators 5 and R.
The T motor 8, the magnetron 12, and the heater device 19 are configured to be drive-controlled via a drive circuit 21. Further, the control circuit 20 is configured to receive the detection signal from the weight sensor 10 and the switch signals from the various operation switches 6, and the detection signal from the gas sensor 18 of the sensor circuit 22. The control circuit 20 is configured to switch and control the resistance switching circuit 23 of the sensor circuit 22 as described later.

Now, a specific structure of the sensor circuit 22 will be described with reference to FIG. As shown in FIG. 5, the resistance switching circuit 23 of the sensor circuit 22 includes five adjusting resistors 24, 25, 26, 27 and 28, and five switching elements 29 and 30, which include transistors and the like.
31, 32, and 33 are connected as shown in the figure. Specifically, a series circuit in which the adjustment resistor 24 and the switching element 29 are connected in series, and the adjustment resistor 25
And a switching element 30 connected in series, an adjustment resistor 26 and a switching element 31 connected in series, an adjustment resistor 27 and a switching element 32 connected in series, Adjustment resistor 28
And a switching element 33 connected in series to a series circuit connected in parallel. The adjusting resistor 24 is, for example, 5.6 kΩ, the adjusting resistor 25 is, for example, 13 kΩ, the adjusting resistor 26 is, for example, 39 kΩ, and the adjusting resistor 27 is, for example, 5 kΩ.
1 kΩ, and the adjustment resistor 28 is, for example, 68 kΩ.

Then, for example, a DC constant voltage terminal 34 of 5V
The resistor switching circuit 23 having the above-mentioned parallel circuit configuration and the gas sensor 18 are connected in series between the above and the ground. Further, the intermediate connection point between the resistance switching circuit 23 and the gas sensor 18 is connected to the input terminal I of the control circuit 20. Thereby, the control circuit 20 is configured to input the inter-terminal voltage of the gas sensor 18, that is, the sensor output (detection signal) output from the gas sensor 18 from the input terminal I.

The control terminals of the five switching elements 29 to 33 of the resistance switching circuit 23 are connected to the control circuit 20.
Are connected to the five output terminals SENC1 to 5, respectively. In this case, the control circuit 20 controls each output terminal SENC.
By setting 1 to 5 to low level (L), for example, each switching element 29 to 33 is turned on, and each output terminal S
Each of the switching elements 29 to 33 is turned off by setting ENC1 to 5 at a high level (H). As a result, the control circuit 20 causes the gas sensor 1 to
5 adjustment resistors 24 to 28 for 8 are shown in Table 1 below.
As shown in (specifically, 19 types of connection modes from NO1 to NO19), switching connection is possible. In this case, the control circuit 20 and the resistance switching circuit 23 constitute the adjusting means 35.

[0023]

[Table 1]

Next, the operation of the above configuration will be described with reference to FIGS.
Also, reference will be made to FIG. The flow chart of FIG. 1 schematically shows the content of the control of the control program stored in the control circuit 20 at the start of the cooking operation of the automatic cooking based on the sensor output from the gas sensor 18. Hereinafter, description will be given according to the flowchart of FIG.

Here, a case will be described in which, for example, warm cooking of rice is executed as automatic cooking. In this case, first, the user stores the cooked food A (rice) in the heating chamber 2 and operates the operation switch 6 in the operation panel 4 to set the cooking menu corresponding to the warming of the rice. After that, the start switch in the operation switch 6 is operated to start the cooking operation. Then, the control circuit 20 executes a process of adjusting the initial value of the sensor output output from the gas sensor 18 so as to be within a predetermined range.

Specifically, first, in step S1 of FIG. 1, the control circuit 20 sets the output terminals SENC1 to SENC1 to "H".
In addition, the output terminals SENC4 and 5 are set to "L", and the circuit in which the two adjusting resistors 27 and 28 are connected in parallel is connected to the gas sensor 18 in series to set the initial state.
Then, the control circuit 20 reads the sensor voltage (terminal voltage) output from the gas sensor 18, and switches the connection mode of the adjustment resistors 24 to 28 according to the read voltage value (step S2). Specifically, the control circuit 20
The sensor voltage of the gas sensor 18 is A / D converted to “0 to
It is converted into a sensor data value (1 byte data value) in the range of "255".

Then, according to the sensor data value, the connection mode of the five adjusting resistors 24 to 28 is switched as shown in Table 1 above. That is, when the sensor data value is 0 to 48, the state is switched to the connection mode number 1 (step S301), and when the sensor data value is 49 to 52, the state is switched to the connection mode number 2 (step S30).
2) If the sensor data value is 53 to 57, switch to the state of connection mode number 3 (step S303). If the sensor data value is 58 to 62, switch to the state of connection mode number 4 (step S303). S304), ..., When the sensor data value is 193 to 204, the state is switched to the connection mode number 18 (step S318), and when the sensor data value is 205 to 255, the connection mode number 19 is controlled. (Step S319).

By switching the resistance connection in this manner, the initial value of the sensor voltage (sensor data value) output from the gas sensor 18 is within a predetermined range, for example, "162-".
178 "(step S4).
Here, the relationship between the initial resistance value of the gas sensor 18 and the initial sensor data value (sensor output) after the resistance connection switching is adjusted as described above is shown in the graph of FIG. From this graph, the initial value of the sensor data value is "162-17
It can be seen that it is within the range of "8".

When the cooking is automatically controlled based on the sensor data value (value of the sensor output) from the gas sensor 18, conventionally, the constant α is used as the control constant. This constant α is a constant for detecting the time point at which the value of the sensor output from the gas sensor 18 has dropped to the peak value Vmax and then decreased by α · Vmax, which is the peak value Vmax multiplied by the constant α. .

The constant α is, for example, 0.1.
The value is set, which corresponds to the case where the rate of change of the resistance value of the gas sensor 18 (the amount of change) is 0.75. Here, the rate of change of the resistance value is defined by Rs1 / Rs0. Incidentally, Rs1 is a resistance value during heating and cooking, and Rs0 is an initial resistance value (peak resistance value). The constant α set to 0.1 is such that the initial sensor data value of the gas sensor 18 is within the predetermined range "1.
When the median value (for example, 170) in the range of 62 to 178 ”is set, it is set so that appropriate heating cooking (ideal heating cooking) is executed.

For this reason, the initial sensor data value is "1".
62 to 178 ”, which is close to the minimum or maximum value, the so-called α-decrease detection time is optimum (the initial sensor data value is the median value of the above“ 162 to 178 ”range). In some cases), there is a possibility that a problem will occur that will be much slower or much faster than the detection time. The graph of FIG. 7 shows how such a problem occurs.

In FIG. 7, a curve P1 is a graph showing the relationship between the resistance value change rate Rs1 / Rs0 and the constant α when the initial sensor data value is the median value in the range of "162-178". The curve P2 has an initial sensor data value of "162
Is a graph showing the relationship between the resistance value change rate Rs1 / Rs0 and the constant α when the minimum value 162 is in the range of ˜178 ″.
The curve P3 is the resistance value change rate Rs1 / R when the initial sensor data value is the maximum value 178 in the range of "162-178".
6 is a graph showing the relationship between s0 and a constant α.

According to FIG. 7, if the constant α is fixed to 0.1, the resistance value change rate Rs1 / Rs0 becomes larger than 0.75 when the initial sensor data value is 162. It can be seen that the detection time at the time point of α decrease is considerably later than the detection time at the optimum time. On the contrary, when the initial sensor data value is 178, the resistance value change rate Rs1 / Rs0 is 0.
It becomes smaller than 75, and it can be seen that the detection time at the time point of α decrease becomes considerably earlier than the detection time at the optimum time. Therefore, if it is left as it is, it may be overheated or insufficiently heated, and there is a possibility that the finished state of cooking may vary.

In order to solve the above-mentioned inconvenience, as is apparent from FIG. 7, when the initial sensor data value is 162,
Constant α when the resistance change rate Rs1 / Rs0 becomes 0.75
Is 0.115, the constant α may be set to be slightly larger than 0.1. The initial sensor data value is 17
In the case of 8, the constant α when the resistance change rate Rs1 / Rs0 becomes 0.75 is 0.085.
It may be set to be slightly smaller than 1.

Therefore, in this embodiment, step S in FIG.
In step 5, the control circuit 20 performs a correction process for changing the constant α based on the initial sensor data value. In particular,
When the initial value of the sensor data value adjusted by the adjusting means 35 is 160 to 165, the constant α is set to 0.12 (step S601), and the initial value of the sensor data value is 16.
When the value is 6 to 175, the constant α is set to 0.10 (step S602), and the initial value of the sensor data value is 176 to 1.
When it is 80, the constant α is set to 0.08 (step S603).

Subsequently, the magnetron 12 is driven to oscillate to start heating and cooking (step S).
7). Then, the heating and cooking control thereafter is configured to execute the same control as the conventionally known heating and cooking control (heating and cooking control based on constants α and β). Specifically, after the level (sensor data value) of the sensor output from the gas sensor 18 reaches the peak value Vmax, the peak point Vmax is multiplied by a constant α to decrease by α · Vmax. The time T from the start of cooking to the point of decreasing α is measured, and the control is performed to continue the heating and cooking from the point of decreasing α for the remaining cooking time β · T obtained by multiplying the time T by a constant β. Is configured to.

According to the present embodiment having such a configuration, the initial value of the sensor output (sensor data value) output from the gas sensor 18 by switching and connecting the five adjusting resistors 24 to 28 is within a predetermined range. After being adjusted to fall within the range of “162 to 178”, the constant α, for example, is changed as the control constant for automatic cooking based on the adjusted sensor output value. As a result, even when the initial value of the sensor output is close to the minimum value or the maximum value of the above-mentioned predetermined range, when the so-called α decrease time detection point is optimum (the initial value of the sensor output is the median value of the predetermined range, If there is)
It is almost the same as the detection time of Therefore, the heating and cooking can be optimally performed without excess and deficiency, and the finished state of cooking can be made as uniform as possible.

By the way, if the gas sensor 18 is normal, the initial value of the sensor data value output from the gas sensor 18 is "162 to 178" by switching and connecting the five adjusting resistors 24 to 28. It can be adjusted to fit in the range. However, when the gas sensor 18 deteriorates, the initial value of the sensor data value from the gas sensor 18 is "162 even if the five adjusting resistors 24 to 28 are switched and connected.
.About.178 ".

In such a case, if the initial value of the sensor data value is slightly out of the range of "162 to 178", automatic cooking based on the sensor output of the gas sensor 18 can be executed without much problem. (You can eat enough cooked food). However, if the initial value of the sensor data value deviates significantly from the range of “162 to 178”, automatic cooking may be inappropriately performed, and the cooked food may not be eaten.

Therefore, as in the second embodiment shown in FIG. 8, the process of determining whether the gas sensor 18 is normal or abnormal based on the adjusted initial value of the sensor data value is started. It may be configured to be executed before. Specifically, after adjusting the initial value of the sensor data value from the gas sensor 18 (that is, before starting heating), first, in step S801 of FIG. 8, the adjusted initial value of the sensor data value is for sensor abnormality determination. It is determined whether or not it is larger than the upper limit value of, for example, “220”. Here, if the initial value is larger than the upper limit value for sensor abnormality determination, step S8
At 01, the process proceeds to “YES”, and an error display indicating that the gas sensor 18 is abnormal is displayed on the display device 5 (step S8).
04). Then, the cooking operation is stopped.

If the initial value is not larger than the upper limit value for sensor abnormality determination, "N" is determined in step S801.
The process proceeds to "O", and it is determined whether or not the initial value of the sensor data value is smaller than the lower limit value for sensor abnormality determination, for example, "100" (step S803). Here, when the initial value is smaller than the lower limit value for sensor abnormality determination, step S
The process proceeds to “YES” at 803, and an error display indicating that the gas sensor 18 is abnormal is displayed on the display device 5 (step S8).
04), stop the cooking operation. On the other hand, when the initial value is not smaller than the lower limit value for sensor abnormality determination, the process proceeds to "NO" in step S803 to start heating (step S7). The configuration of the second embodiment other than that described above is the same as the configuration of the first embodiment.

Therefore, also in the second embodiment, it is possible to obtain substantially the same operational effect as that of the first embodiment. Especially,
According to the second embodiment, the gas sensor 18 is judged to be normal or not, and if the gas sensor 18 is abnormal, the abnormality is informed.
The abnormality of can be recognized promptly, and the countermeasure such as repair can be executed. This makes it possible to prevent the failure of automatic cooking.

FIG. 9 shows a third embodiment of the present invention, and the difference from the first embodiment will be described.
The same components as those in the first embodiment are designated by the same reference numerals. In the third embodiment, instead of changing the constant α, the constant β for automatic cooking is changed based on the adjusted initial value of the sensor data value (step S9).

Specifically, after adjusting the initial value of the sensor data value (that is, after executing step S4), when the adjusted initial value is 160 to 165, the constant β is 1.
2 (step S901), the initial value is 166 to 1
When it is 75, the constant β is set to 1.0 (step S9
02), the constant β is set to 0.8 when the initial value is 176 to 180 (step S903). In this case, the constant α is fixed at 0.1. Then, after correcting the constant β as described above, the magnetron 12
Is driven to oscillate to start heating and cooking (step S7). The configuration of the third embodiment other than the above is the same as the configuration of the first embodiment.

In the third embodiment, since the constant β for automatic cooking is made variable on the basis of the adjusted initial value of the sensor data value, the cooking time (remaining cooking time) after the time point α decreases. Is an appropriate time according to the initial value, and heating and cooking can be optimally executed without excess or deficiency. Therefore, also in the third embodiment, it is possible to obtain substantially the same effect as in the first embodiment.

In the third embodiment, the constant β for automatic cooking is made variable on the basis of the adjusted initial value of the sensor data value. However, instead of this, the constant β for automatic cooking is predetermined from the time point α decreases. In the case of automatic cooking in which the cooking is finished after the time T1, the time T1 may be changed to be long or short based on the adjusted initial value of the sensor data value. Also in the case of this configuration, it is possible to obtain substantially the same operational effects as the third embodiment.

FIG. 10 shows a fourth embodiment of the present invention, and the difference from the first embodiment will be described. still,
The same components as those in the first embodiment are designated by the same reference numerals. In the fourth embodiment, the heating cooking is controlled based on the value obtained by multiplying the sensor data value from the gas sensor 18 by the constant K, and instead of varying the constant α,
The constant K is configured to be variable based on the adjusted initial value of the sensor data value.

Specifically, after adjusting the initial value of the sensor data value from the gas sensor 18 (after executing step S4), the constant K is varied based on the adjusted initial value of the sensor data value ( Step S10). in this case,
When the adjusted initial value is 160 to 165, the constant K is set to 0.8 (step S1001), and the initial value is 16
The constant K is set to 1.0 when it is 6 to 175 (step S1002), and the constant β is set to 1.2 when the initial value is 176 to 180 (step S1003). The constant α is fixed at 0.1 and the constant β is fixed at 1.0.

Then, after the constant K is corrected as described above, the cooking is started (step S7). Then, during heating and cooking, K · V obtained by multiplying the sensor data value (sensor output) V output from the gas sensor 18 by the constant K is set as V ′ (step S11), and based on this V ′, the time point α decreases. Is configured to be detected (step S12).

After that, when the time point at which α has decreased is detected, the process proceeds to “YES” at step S12 to calculate the cooking remaining time β · T (step S13). Then, the cooking is finished after the heating cooking is continued from the time point when α is decreased by the calculated remaining cooking time β · T. The configuration of the fourth embodiment other than the above is the same as the configuration of the first embodiment.

In the fourth embodiment, since the constant K is made variable on the basis of the adjusted initial value of the sensor data value, the heating and cooking time (remaining cooking time) after the decrease of α is the initial value. Therefore, the cooking time can be optimally executed without excess or deficiency. Therefore,
Also in the above-mentioned fourth embodiment, almost the same effect as in the first embodiment can be obtained.

In the fourth embodiment, K'V obtained by multiplying the sensor data value V by the constant K is defined as V ', and this V'
However, instead of this, K · α obtained by multiplying α by the constant K is defined as α ′, and the α decrease point at which α ′ becomes 0.1 is detected. The same effect can be obtained in this configuration as well.

[0053]

As is apparent from the above description, the present invention has a structure in which the control constant for automatic cooking is varied based on the initial value of the sensor output adjusted by the adjusting means. Even if the value is close to the minimum value or the maximum value in the predetermined range, it is almost the same as the detection time when the so-called α decrease time point is optimum (when the initial value of the sensor output is the median value of the predetermined range). Since they are the same, the cooking effect can be optimally performed without excess or deficiency, and the excellent effect that the cooked state can be made uniform can be achieved.

[Brief description of drawings]

FIG. 1 is a flowchart showing a first embodiment of the present invention.

FIG. 2 is a perspective view of the entire microwave oven.

FIG. 3 is a schematic vertical sectional front view of a microwave oven.

FIG. 4 is a block diagram.

FIG. 5 is an electric circuit diagram around the sensor circuit.

FIG. 6 is a graph showing the relationship between the initial resistance value of the gas sensor and the initial value of the sensor data value after adjustment of resistance connection switching.

FIG. 7: Resistance value change rate Rs1 / Rs0 of gas sensor and constant α
Graph showing the relationship with

FIG. 8 is a flowchart showing a second embodiment of the present invention.

FIG. 9 is a flowchart showing a third embodiment of the present invention.

FIG. 10 is a flowchart showing a fourth embodiment of the present invention.

[Explanation of symbols]

1 is a range main body, 2 is a heating chamber, 4 is an operation panel, 5 is an indicator, 6 is an operation switch, 11 is a machine room, 12 is a magnetron, 16 is an exhaust port, 17 is an exhaust passage, 18 is a gas sensor, 20 Is a control circuit (cooking control means, control constant correction means), 22 is a sensor circuit, 23 is a resistance switching circuit, 24,
Reference numerals 25, 26, 27 and 28 denote adjustment resistors, and 35 an adjustment means.

Claims (6)

[Claims] 1. A gas sensor for detecting gas generated from cooked food, cooking control means for controlling cooking based on a sensor output from the gas sensor, and a gas sensor output before the start of cooking. An adjusting means for adjusting the value of the sensor output to fall within a predetermined range, and a control constant correcting means for changing the control constant for automatic cooking based on the value of the sensor output adjusted by the adjusting means are provided. A microwave oven. 2. The adjusting means is connected to a gas sensor and has a plurality of adjusting resistors for adjusting the level of the sensor output, and the plurality of adjusting resistors so that the value of the sensor output falls within a predetermined range. The microwave oven according to claim 1, further comprising a switching unit that switches and connects the adjustment resistor. 3. The function of the cooking control means for detecting an α-decreasing point when the value of the sensor output from the gas sensor reaches the peak value Vmax and then decreases by α · Vmax obtained by multiplying the peak value Vmax by a constant α. The microwave oven according to claim 1 or 2, wherein the control constant correcting means varies the constant α as a control constant. 4. The cooking control means detects a time point at which the sensor output from the gas sensor has decreased by α · Vmax, which is obtained by multiplying the peak value Vmax by a constant α, after the value reaches a peak value Vmax. When the cooking is finished after a predetermined time T1 from this point, or when the time T from the start of cooking to the point of decreasing α is measured, and the remaining cooking time β · T is obtained by multiplying the time T by a constant β. The electronic device according to claim 1 or 2, wherein the control constant correcting means varies the constant β or the time T1 as a control constant when a function of continuing the cooking from the time point of α decrease and ending the cooking is provided. range. 5. The sensor abnormality when the value of the sensor output adjusted by the adjusting means is larger than the upper limit value for sensor abnormality determination, or when the sensor output value is smaller than the lower limit value for sensor abnormality determination. The microwave oven according to any one of claims 1 to 4, further comprising a notifying unit for notifying that the microwave oven. 6. When the cooking control means has a function of controlling cooking based on a value obtained by multiplying a sensor output by a constant K, the control constant correction means varies the constant K as a control constant. The microwave oven according to claim 1 or 2.