JPH0953829A - Cooking apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable setting of a proper initial value by a method wherein a means is provided to adjust the initial value of a sensor output by switching and connecting a plurality of resistors for adjusting the sensor output sequentially so that the sensor output is held within an application range and a fan device is stopped during the adjusting of the initial value. SOLUTION: A microcomputer 21 performs adjustment and control of an initial value of a moisture detection signal as sensor output to be outputted from a moisture detection circuit 34 containing two thermistors 18 and 19 of a moisture sensor 17 while receiving the moisture detection signal outputted from the moisture detection circuit 34. The microcomputer 21 is also so arranged to allow the setting of output ports D0-D7 connected to eight resistors 45-52 for adjusting the sensor output to a high level or a low level by switching. A fan device is stopped during the adjustment of the initial value of the sensor output of the moisture sensor 17. The resistors 45-52 for adjusting the sensor output are connected by switching sequentially thereby reducing changes in the moisture even when the time required to adjust the initial value is prolonged.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heating cooker which includes a sensor for detecting water vapor generated from food and is configured to control heating based on a sensor output from the sensor.

[0002]

2. Description of the Related Art In a microwave oven which is a heating cooker of this type, an air blower for blowing air into the heating chamber is provided, and a gas sensor is provided in an exhaust passage for exhausting the air in the heating chamber to the outside. There is a sensor configured to detect water vapor generated from food. In this configuration, when the water vapor is detected by the gas sensor, the air blower is driven to make the water vapor distribution (that is, humidity) in the heating chamber and the exhaust passage uniform.

The gas sensor has a characteristic that its resistance value changes in accordance with the amount of water vapor generated. A predetermined voltage is applied in a state where the gas sensor and the resistor are connected in series, and between the terminals of the gas sensor. The voltage is used to detect the amount of water vapor generated. Here, since the initial resistance value of the gas sensor varies, if the series resistance is kept constant, the initial value of the sensor output of the gas sensor will not fall within a predetermined range. Therefore, a plurality of resistors having different resistance values are switchably provided to the gas sensor, and at the start of heating and cooking, a process of adjusting the initial value of the sensor output by connecting a resistor having an appropriate resistance value (referred to as calibration) ) Is configured to do. And
The blower is also driven when the initial value adjustment processing is executed.

In the case of this configuration, specifically, at the beginning of the initial value adjustment processing, the reference resistance is connected to the gas sensor to detect the sensor output, and the resistance having an appropriate resistance value is based on the detected sensor output. Select to connect. Therefore, the switching connection of the resistor is required only once or twice,
The initial value adjustment process was completed in a short time of about 0.5 to 1 second.

[0005]

By the way, as a sensor for detecting water vapor generated from food, a humidity sensor is known in addition to the above gas sensor. Therefore, the inventor of the present invention considered a configuration for detecting water vapor generated from food by using a humidity sensor. In the case of this configuration, there is a characteristic that the initial value of the sensor output of the humidity sensor fluctuates considerably, as in the case of the gas sensor. For this reason, a plurality of sensor output adjusting resistors for adjusting the level of the sensor output are provided so as to be switchably connectable, and the plurality of sensor output adjusting resistors are sequentially connected for switching during the initial value adjustment processing.
In this case, in order to make the humidity in the heating chamber uniform, the blower was driven. However, when the initial value of the sensor output of the humidity sensor is adjusted as described above, it may not be possible to set an appropriate initial value, and the detection accuracy of the humidity sensor may deteriorate. Therefore, the present inventor has sought the cause of the above problems. This revealed the following.

That is, since the fluctuation of the initial value of the sensor output of the humidity sensor is considerably larger than that of the gas sensor, a plurality of resistors for adjusting the sensor output having considerably different resistance values are prepared, and the initial value of the sensor output is set. The operation of sequentially switching and connecting the plurality of sensor output adjusting resistors must be repeated until the value falls within a predetermined range. Therefore, for example, when eight sensor output adjusting resistors are prepared, it is necessary to switch and connect at most eight times. Since it takes about 0.5 seconds to switch once, the processing requires a relatively long time of about 4 to 5 seconds at maximum. Here, if the air blower was continuously driven for the above 4 to 5 seconds, the humidity in the heating chamber tended to change considerably during the above time. Therefore, if the initial value of the sensor output is adjusted as described above, it may not be possible to set an appropriate initial value.

Therefore, an object of the present invention is to provide a heating cooker capable of setting an appropriate initial value when adjusting the initial value of the sensor output and increasing the detection accuracy of the humidity sensor.

[0008]

The cooking device according to the present invention comprises:
Heating means for heating the food contained in the heating chamber, a blowing device for blowing air into the heating chamber, a humidity sensor provided in an exhaust passage for exhausting the air in the heating chamber to the outside, and from this humidity sensor Heating control means for controlling the heating means on the basis of the output sensor output, a plurality of sensor output adjusting resistors connected to the humidity sensor for adjusting the level of the sensor output, and the sensor output An initial value adjusting means for adjusting an initial value of the sensor output by sequentially switchingly connecting the plurality of sensor output adjusting resistors so that the value is within a use range, and
It is characterized in that the air blower is stopped during the adjustment of the initial value of the sensor output.

According to the above-mentioned means, the air blower is stopped during the adjustment of the initial value of the sensor output. Therefore, when the plurality of sensor output adjusting resistors are sequentially switched and connected, the initial value is adjusted relatively. Even if it takes a long time, the humidity in the heating chamber hardly changes. Therefore, an appropriate initial value can be set, and the detection accuracy of the humidity sensor can be increased.

Further, in the case of the above construction, the heating means is stopped during the adjustment of the initial value of the sensor output, the heating means is driven after the adjustment of the initial value, and the air blower is driven as necessary. Is preferred. Further, it is also possible to drive the blower for several seconds to several tens of seconds immediately after starting the cooking and then stop the blower to adjust the initial value of the sensor output. Furthermore, it is a preferable configuration that the humidity sensor includes a thermistor housed in a metal container in a sealed state and a thermistor housed in an open state in the metal container.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment in which the present invention is applied to a microwave oven with a heater will be described below with reference to the drawings. First, in FIGS. 3 and 4 showing the overall structure of the microwave oven, a heating chamber 2 is provided in a main body 1 of the microwave oven. A door 3 for opening and closing a front opening of the heating chamber 2 is provided on the front surface of the main body 1, and an operation panel 4 is provided at the right end. At the inner bottom of the heating chamber 2, a turntable 6 on which the food 5 is placed is rotatably provided. The turntable 6 is rotationally driven by an RT motor 7 (see FIG. 5) via a rotary shaft 8.

A machine room 9 is provided on the right side of the heating room 2 in the main body 1, and a magnetron 10 as a heating means is provided in the machine room 9. The magnetron 10 supplies microwaves to the heating chamber 2 through a waveguide (not shown) to cook the food 5 in the heating chamber 2. Further, a fan unit 11 for cooling the magnetron is arranged in the machine room 9. The fan device 11 is composed of a fan 11a and a fan motor 11b.

The fan unit 11 includes a rear wall 12 of the main body 1.
The outside air is sucked in through the intake port 12a formed by a large number of small holes formed in the air outlet, and the outside air (cooling wind) is blown onto the magnetron 10 to cool it, and then the front portion of the right side wall 13 of the heating chamber 2 is The gas is supplied into the heating chamber 2 through the vent hole 13a formed by a large number of small holes formed in the. In this case, the fan device 11 constitutes a blower device.

On the other hand, in the rear portion of the left side wall 14 of the heating chamber 2,
An exhaust port 14a including a large number of small holes is formed, and the exhaust port 14a is configured to communicate with the outside of the main body 1 through an exhaust passage 15. In this case, when the fan device 11 is energized and air is supplied into the heating chamber 2, the air in the heating chamber 2 is discharged to the outside of the machine through the exhaust port 14a and the exhaust passage 15. .

Here, on the inner wall surface 16 of the exhaust passage 15,
A humidity sensor 17 is provided. This humidity sensor 17
As shown in FIG. 6, the two thermistors 18 and 1
9 is a humidity sensor for detecting absolute humidity (water content in a unit volume). In this case, one of the two thermistors, the thermistor 18, is housed in a metal container in a sealed state together with dry air. The other thermistor 19 is housed in a metal container in an open state, and the air whose humidity is desired to be detected (air in the exhaust passage 15) can freely enter the metal container. There is. The specific configuration of the humidity detecting circuit including the thermistors 18 and 19 will be described later.

An upper heater and a lower heater 20 (see FIG. 4), which are, for example, flat heaters, are provided as heating means on the ceiling and bottom of the heating chamber 2. Further, a hot air heater, for example, is provided as a heating means on the back surface of the heating chamber 2, and the hot air heater circulates and supplies hot air into the heating chamber 2. The heaters are capable of oven-heating or grill-heating the food in the heating chamber 2. And
Inside the heating chamber 2, a temperature sensor for detecting the temperature inside the heating chamber 2 (internal temperature) is provided.

Further, FIG. 5 schematically shows an electrical configuration by combining functional blocks. In FIG. 5, the heating control means, for example, the microcomputer 21, has a reset signal from the reset circuit 23 connected to the AC power supply 22, a power supply synchronization signal from the power supply synchronization signal generation circuit 24 connected to the AC power supply 22, and It is configured to receive the clock signal from the clock signal generation circuit 25. Then, the microcomputer 21 drives and controls the magnetron 10 via the magnetron drive circuit 26, drives and controls the upper heater, the lower heater 20 and the hot air heater via the heater drive circuit 27, and drives the fan motor drive circuit 28. The fan motor 11b is drive-controlled, and the RT motor 7 is drive-controlled via the turntable motor drive circuit 29.

Further, the microcomputer 21 drives and controls various display devices 4a arranged on the operation panel 4 through the display drive circuit 30, drives and controls the buzzer 32 through the buzzer drive circuit 31, and It is configured to receive various key switch signals from a key switch circuit 33 including various key switches 4b (see FIG. 4) arranged on the operation panel 4. Then, the microcomputer 21 uses the two thermistors 18 of the humidity sensor 17,
The humidity detection circuit 34 including 19 adjusts and controls the initial value of the humidity detection signal as a sensor output, and receives the humidity detection signal output from the humidity detection circuit 34. In this case, the microcomputer 21 constitutes an initial value adjusting means.

The humidity detecting circuit 34 will be described in detail with reference to FIG. In FIG. 6, the two thermistors 18 and 19 of the humidity sensor 17 are the resistors 35 and 36.
Together with this, a bridge circuit 37 as shown is configured. In the bridge circuit 37, the intermediate connection point B1 between the thermistor 18 and the resistor 35 is, for example, 1 via the resistor 38.
It is connected to a 5V power supply terminal 39, and an intermediate connection point B2 between the thermistor 19 and the resistor 36 is connected to the ground. The intermediate connection point B3 between the resistors 35 and 36 is connected to the (+) side input terminal of the operational amplifier 41 of the buffer circuit 40, and the intermediate connection point B4 between the thermistor 18 and the thermistor 19.
Is connected to the (−) side input terminal of the operational amplifier 43 of the amplifier circuit 42 via the resistor 44.

The intermediate connection point B2 between the thermistor 19 and the resistor 36 (that is, the (+) side input terminal of the operational amplifier 41 of the buffer circuit 40) is provided at one end of each of a plurality of, for example, eight sensor output adjusting resistors 45 to 52. It is connected to the. The other ends of the eight sensor output adjusting resistors 45 to 52 are connected to the eight output ports D0 to D7 of the microcomputer 21, respectively.
It is connected to the. The microcomputer 21 is
Each of the eight output ports D0 to D7 can be set to a high level or a low level (earth level).

On the other hand, the operational amplifier 41 of the buffer circuit 40.
A power supply terminal 53 of, for example, 15V is connected to the.
The (−) side input terminal of the operational amplifier 41 is connected to the output terminal of the operational amplifier 41. Further, the output terminal of the operational amplifier 41 is connected to the (+) side input terminal of the operational amplifier 43 of the amplifier circuit 42 via the resistor 54. A resistor 55 is connected between the (+) side input terminal of the operational amplifier 43 and the ground. A resistor 56 is connected between the (−) side input terminal and the output terminal of the operational amplifier 43. Further, the operational amplifier 43 is connected to a power supply terminal 57 of 15V, for example.

The output terminal of the operational amplifier 43 is connected to A / A of the microcomputer 21 via the resistor 58.
It is connected to the D conversion input terminal 59. Also, the above A /
A diode 61 having the illustrated polarity is connected between the D conversion input terminal 59 and the 5V power supply terminal 60, and a capacitor 62 is connected between the A / D conversion input terminal 59 and the ground. The specific values of the resistors in the humidity detecting circuit 34 are set as follows in this embodiment. That is, the resistance 35 is 2 kΩ, the resistance 36 is 2.2 kΩ,
The resistance 38 is 330Ω, the resistance 44 is 1 kΩ, and the resistance 45 is 2
0 kΩ, resistor 46 39 kΩ, resistor 47 82 kΩ, resistor 48 150 kΩ, resistor 49 300 kΩ, resistor 50
Is 620 kΩ, the resistance 51 is 1.2 MΩ, and the resistance 52 is 2.
The resistance is 4 MΩ, the resistance 54 is 1 kΩ, the resistance 55 is 300 kΩ, the resistance 56 is 300 kΩ, and the resistance 58 is 10 kΩ. Further, the amplification circuit 42 of the humidity detection circuit 34 has a function of amplifying the voltage level of the sensor output output from the humidity sensor 17 (that is, the bridge circuit 37) by about 300 times.

Next, the operation of the above structure will be described with reference to FIGS. 1, 2 and 7. First, the case of performing range cooking by the magnetron 10 will be described with reference to FIG. In this case, when range cooking is started at time t0,
The microcomputer 21 energizes only the fan device 11 for about 10 seconds after the start of cooking. As a result, fresh outside air is supplied into the heating chamber 2 and air (particularly residual gas) in the heating chamber 2 is exhausted to the outside.

Subsequently, the microcomputer 21 stops the fan device 11 and then starts the humidity sensor 1 from time t1.
7 (humidity detection circuit 34) adjusts the initial value of the sensor output (calibration). This initial value adjustment processing is executed according to the flowchart shown in FIG. Specifically, the microcomputer 21 first sets all the output ports D0 to D7 to the high level (that is, the e-active state), and sets the output port pointer to D.
It is set to 0 (step S1). In this state, the sensor output signal output from the humidity detection circuit 34, that is, the voltage level of the signal input to the A / D conversion input terminal 59 of the microcomputer 21 becomes maximum.

Then, in the above state, the microcomputer 21 reads the sensor output signal output from the humidity detecting circuit 34 (step S2). In this case, about 0.5 is required for analog signal processing in the humidity detection circuit 34 and A / D conversion processing of the built-in A / D conversion circuit of the microcomputer 21.
It takes about a second. Then, the voltage level of the read sensor output signal (ie, sensor data) is, for example, (1
It is determined whether or not it is within the range of ± 0.2) V (step S3). Here, if the voltage level of the sensor output signal is within the range of (1 ± 0.2) V, step S3
Then, the process proceeds to “YES” to end the initial value adjustment processing, restart the drive of the fan device 11, and
Oscillation driving of 0 is started (see FIGS. 1B and 1C).

On the other hand, the voltage level of the sensor output signal is (1
If it is not within the range of ± 0.2) V, step S
The process proceeds to "NO" in 3 and it is determined whether the voltage level of the sensor output signal is higher than (1 + 0.2) V or the voltage level is lower than (1-0.2) V (step S4). ). Here, the voltage level of the sensor output signal is (1
If it is larger than +0.2) V, the process proceeds to “large” in step S4, and the level (specifically, high level) of the output port (specifically, D0) currently pointed to by the pointer is maintained. Until then, the output port (specifically, D1) one level higher is switched to the low level, and the pointer is counted up so that the pointer indicates the switched output port (step S5).

If the voltage level is lower than (1-0.2) V in step S4, step S4 is performed.
Then, the process proceeds to "small" and it is determined whether or not all the output ports are at the high level (step S6). here,
If all the output ports are at the high level, the process proceeds to “YES” in step S6 and the humidity sensor 17 has some abnormality because the initial value of the sensor output cannot be adjusted. Is displayed (step S7). If all the output ports are not at the high level, proceed to “NO” in step S6,
The output port currently pointed to by the pointer is returned to the high level, the output port immediately above is switched to the low level, and the pointer is counted up so that the pointer points to the switched output port (step S).
8).

After executing step S5 or step S8, it is determined whether or not all output ports have been switched (step S9). Here, when all the output ports are switched, the process proceeds to “YES” in step S9, and the humidity sensor 17 has some abnormality because the initial value of the sensor output cannot be adjusted. The sensor abnormality is displayed on (step S7). On the other hand, if all the output ports have not been switched, "NO" in step S9.
Then, the process returns to step S2 to read the sensor output signal (sensor data) output from the humidity detection circuit 34 with the output port switched. Hereinafter, the above-described processing is repeated.

By executing such an initial value adjustment process, the voltage level of the sensor output signal becomes (1 ± 0.2).
Adjusted to fall within the V range. As a result, the voltage level of the sensor output signal comes into the predetermined use range. In this case, if there is no abnormality in the humidity sensor 17, the voltage level of the sensor output signal is (1 ± 0.
2) The configuration is such that it can be adjusted to fall within the range of V. Therefore, the initial value adjustment is completed by executing the switching processing at the maximum for a total of 9 times including the switching processing performed once when all the output ports are set to the high level and the switching processing performed eight times. Since one switching process takes about 0.5 seconds, the initial value adjustment takes about 4.5 seconds at maximum. That is, the period of the initial value adjustment processing is within about 5 seconds.

Now, the voltage level of the sensor output signal is (1
After entering the range of ± 0.2) V and proceeding to “YES” in step S3 of FIG. 7 and ending the initial value adjustment processing, as shown in FIG. From t2, the fan device 11 is started to be driven again, and the magnetron 10 is started to be oscillated. Then, the microcomputer 21 is configured to drive and control the magnetron 10 based on the sensor output output from the humidity sensor 17 to automatically perform heating and cooking. After that, when the cooking end condition is reached, the time t
At 3, the magnetron 10 and the fan device 11 are stopped, and the buzzer 32 is sounded to notify the end of cooking and the range cooking is ended.

Next, the case of performing oven grill cooking (ie, heater cooking) with the upper heater, the lower heater 20 or the hot air heater will be described with reference to FIG. In this case, when the oven / grill cooking is started at time t0, the microcomputer 21 causes the fan device 1 to operate.
Only 1 is energized for about 10 seconds from the start of cooking. As a result, fresh outside air is supplied into the heating chamber 2 and air (particularly residual gas) in the heating chamber 2 is exhausted to the outside. Subsequently, after stopping the fan device 11, the microcomputer 21 performs a process of adjusting the initial value of the humidity sensor 17 (humidity detection circuit 34) from time t1. This initial value adjustment processing is executed according to the flow chart shown in FIG. 7, as in the case of the range cooking described above.

After this, when the initial value adjustment process is completed, as shown in FIG.
Oven and grill cooking is performed by starting 0 (one or two of them) as appropriate. The three heaters 20 (one or two of them) are drive-controlled based on the sensor output from the humidity sensor 17 to automatically perform cooking. Further, in the case of this heater cooking, the heating cooking is executed while the fan device 11 is stopped. After that, when the cooking end condition is reached, each heater 20 is stopped at that time t3, and the buzzer 32 is sounded to notify the end of cooking, and the cooking is ended.

According to this embodiment having such a configuration, the fan device 11 is stopped during the adjustment of the initial value of the sensor output of the humidity sensor 17, so that a plurality of sensor output adjusting resistors 45 to 45 are provided. Even if it takes a relatively long time (about 5 seconds at the maximum) to sequentially switch and connect 52 to adjust the initial value, the humidity in the heating chamber 2 and thus the humidity sensor 1 is increased.
The humidity in the vicinity of 7 hardly changes. For this reason,
An appropriate initial value can be set, and the detection accuracy of the humidity sensor 17 can be increased.

Further, in the above embodiment, the magnetron 10 or the heater 20 is stopped during the adjustment of the initial value of the sensor output, and the magnetron 10 or the heater 20 is started to be driven after the adjustment of the initial value. The food 5 is not heated by the magnetron 10 or the heater 20 during the adjustment. Therefore, the initial value adjustment can be performed in a state where the food 5 produces almost no steam,
The initial value can be set accurately. Further, when the heaters 20 are used to cook the heaters, the fan device 11 is stopped while the heaters 20 are being driven. Therefore, even when the amount of water vapor generated from the food 5 is small as in the heater cooking, The humidity sensor 17 can accurately detect the amount of water vapor generated from the food 5, and the heating and cooking can be controlled more appropriately.

Further, in the above-mentioned embodiment, the fan device 11 is driven for about 10 seconds immediately after starting the cooking, and then the fan device 11 is stopped and then the initial value of the sensor output is adjusted. . As a result, the initial value of the sensor output can be adjusted in a clean state in which the gas remaining in the heating chamber 2 is sufficiently exhausted, and in the state where the humidity in the heating chamber 2 is sufficiently uniform. The initial value can be set more accurately. Further, in the above embodiment,
Since the humidity sensor 17 is composed of the thermistor 18 which is hermetically housed in the metal container and the thermistor 19 which is housed in the metal container in an open state, the humidity sensor 17 for accurately detecting the humidity has a simple structure. It can be easily realized.

In the above embodiment, the fan device 11 is driven for about 10 seconds immediately after starting cooking, but the invention is not limited to this, and it is within a range of several seconds to several tens seconds. The fan device 11 may be driven only for an appropriate time. In the above embodiment, the fan unit 1 for cooling the magnetron is used as the air blower.
1 is used, but a dedicated fan device for blowing outside air into the heating chamber 2 may be provided.

[0037]

As is apparent from the above description, the present invention is configured so that the blower is stopped during the adjustment of the initial value of the sensor output, so that a plurality of sensor output adjusting resistors are sequentially switched and connected. Even if it takes a relatively long time to adjust the initial value, the humidity in the heating chamber hardly changes, and it is possible to set an accurate initial value and increase the detection accuracy of the humidity sensor. It has an excellent effect that

[Brief description of drawings]

FIG. 1 is a time chart of range cooking showing an embodiment of the present invention.

[Figure 2] Heater cooking time chart

FIG. 3 is a cross-sectional view of a microwave oven.

FIG. 4 is a perspective view of a microwave oven.

FIG. 5 is a block diagram.

FIG. 6 is an electric circuit diagram of a humidity detection circuit.

FIG. 7: Flow chart

[Explanation of symbols]

1 is a main body, 2 is a heating chamber, 4 is an operation panel, 5 is food, 1
0 is a magnetron (heating means), 11 is a fan device (blowing device), 15 is an exhaust passage, 16 is an inner wall surface, 17 is a humidity sensor, 18 and 19 are thermistors, 20 is a lower heater (heating means), and 21 is a micro. A computer (heating control means, initial value adjusting means), 34 is a humidity detecting circuit, 37 is a bridge circuit, 42 is an amplifying circuit, 45 to 52 are sensor output adjusting resistors, and 59 is an A / D conversion input terminal.

Claims (4)

[Claims] 1. A heating means for heating food contained in a heating chamber, an air blower for blowing air into the heating chamber, and a humidity sensor provided in an exhaust passage for exhausting air in the heating chamber to the outside. Heating control means for controlling the heating means based on a sensor output output from the humidity sensor, and a plurality of sensor output adjusting resistors connected to the humidity sensor for adjusting the level of the sensor output And an initial value adjusting means for adjusting the initial value of the sensor output by sequentially switching and connecting the plurality of sensor output adjusting resistors so that the sensor output falls within a use range, and the initial value of the sensor output The heating cooker characterized in that the air blower is stopped during the adjustment of the value. 2. The heating means is stopped during the adjustment of the initial value of the sensor output, the heating means is driven after the adjustment of the initial value, and the air blower is driven as necessary. Cooking device. 3. The initial value of the sensor output is adjusted after driving the air blower for several seconds to several tens of seconds immediately after starting the cooking and then stopping the air blower. Or the heating cooker according to 2. 4. The humidity sensor comprises a thermistor housed in a metal container in a sealed state and a thermistor housed in an open state in the metal container. The cooking device according to any one of the claims.