JP7423558B2 - heating cooker - Google Patents

Description

The present invention relates to a cooking device equipped with a temperature sensor that detects the temperature inside the oven during heating.

Some heating cookers with an oven function adjust the output of the heater based on the internal temperature detected by a temperature sensor, and cook at the optimal temperature range depending on the food and cooking menu. However, if there is a problem with the temperature sensor or its peripheral circuitry, it will not be possible to accurately detect the temperature inside the refrigerator, which may lead to problems such as not being able to cook at the optimal temperature range.

As a conventional technique for dealing with this problem, for example, there is a microwave oven described in Patent Document 1. The solution section of the abstract of the same document states, ``Based on the temperature detected by the thermistor 8, the temperature rise ΔT within the cooking chamber during a predetermined time is obtained and compared with the abnormality detection level ΔS. If this is the case, the heater heating continues until the preset heating time is reached.If the temperature rise ΔT is smaller than ΔS, it is determined that there is a heating abnormality, relays RL3 and RL4 are turned off, and the heaters 9a and 9b are turned off. The supply of current to is stopped.Therefore, since abnormal heating of the heater is detected based on the temperature detected by the thermistor 8 for controlling the temperature inside the cooking chamber, the configuration is simple and does not require a large increase in cost. ”.

In this way, in the microwave oven of Patent Document 1, in order to detect heating abnormalities in the oven with a simple configuration, the increase value (ΔT) of the temperature detected by the thermistor (temperature sensor) during a predetermined time is set to a preset threshold value. (ΔS) or less, it is determined that a heating abnormality (insufficient heating) has occurred in which the temperature inside the refrigerator does not reach the temperature that should originally be reached.

Japanese Patent Application Publication No. 9-213473

Cooking appliances with an oven function not only have a function to detect underheating to ensure cooking performance, but also take safety into consideration, and if overheating is detected inside the refrigerator, further heating is suppressed. Functionality is also required.

However, although the microwave oven of Patent Document 1 can detect insufficient heating, if the temperature detected by the thermistor rises sufficiently during a predetermined period, it will not be judged as abnormal heating. Even if a malfunction occurred, the current supply to the heater would continue, potentially causing overheating inside the refrigerator.

Therefore, it is an object of the present invention to provide a heating cooker that can detect a malfunction in a temperature sensor or its peripheral circuit that causes excessive heating in the refrigerator.

The heating cooker of the present invention has been made to solve the above problems, and includes a heating chamber for storing an object to be heated, an operation section for setting the heating temperature of the heating chamber, and a heating chamber for heating the heating chamber. a temperature sensor that detects the temperature of the heating chamber; and a control device that controls the heater based on a set heating temperature and the output of the temperature sensor, and determines whether there is an abnormality in the heater or the temperature sensor. The control device energizes the heater for a first period, generates a first temperature code based on the output of the temperature sensor at the time when the first period elapses, and controls the first temperature. If the code is smaller than the first threshold, it is determined that the temperature sensor is disconnected ; if the first temperature code is greater than or equal to the first threshold, the heater is further energized for a second period. and generate a second temperature code based on the output of the temperature sensor at the time point when the second period elapses, and if the increase value of the second temperature code from the first temperature code is greater than the second threshold value, the If it is determined that the temperature sensor is normal and the increase value is less than or equal to the second threshold value, and if the second temperature code is greater than or equal to the preheating end value corresponding to the set heating temperature, the temperature It was assumed that the sensor was determined to be normal .

According to the heating cooker of the present invention, if a malfunction occurs in the temperature sensor or its peripheral circuit that causes excessive heating in the refrigerator, the malfunction can be detected. This makes it possible to detect abnormal conditions step by step, and to determine countermeasures for various failure modes.

FIG. 2 is a perspective view of the heating cooker according to the embodiment as viewed from the door side. AA sectional view of the heating cooker in FIG. 1. FIG. 2 is a functional block diagram of a heating cooker according to an embodiment. Table (excerpt) showing the relationship between the current value of the current sensor and the current code. A table showing the relationship between the set heating temperature and control value. A graph showing changes in the temperature around the temperature sensor during oven heating. A graph showing the temperature detected by the temperature sensor when the temperature is normal, when the wire is disconnected, and when the detected temperature is abnormal. 5 is a flowchart of temperature sensor abnormality determination processing.

EMBODIMENT OF THE INVENTION Hereinafter, one Example of the cooking device of this invention is demonstrated using FIGS. 1-8.

The heating cooker 1 of this embodiment is a microwave oven that uses microwaves, heater heat, etc. to heat and cook food (an object to be heated) stored in a heating chamber 11. As shown in the sectional view, a door 2 is provided at the front, an operation panel 3 is provided below the door 2, the upper surface and left and right sides are covered with an outer frame 4, and the back surface is covered with a rear plate 5.

The door 2 is opened and closed when taking food in and out, and by closing the door 2, the heating chamber 11 can be sealed, preventing leakage of microwaves used for cooking and sealing in heater heat.

The operation panel 3 is provided with an operation section 31 and a display section 32, as shown in FIG. The operation unit 31 includes a microwave heating setting key 31a, a heater heating setting key 31b, a setting dial 31c for inputting the heating temperature and heating time when heater heating is selected, a start key 31d for starting cooking, etc. is provided. The display section 32 displays the contents input from the operation section 31 and the progress state of heating.

As shown in FIG. 2, a machine room 12 is provided below the heating chamber 11, and includes a magnetron 12a, a rotating antenna 12b, a control device 12c, a cooling fan device 12d, a current sensor 12e, etc. (not shown), etc. is installed. The control device 12c includes a calculation section such as a CPU that controls each section in the heating cooker 1 according to input from the operation section 31, and a storage such as a semiconductor memory that stores tables shown in FIGS. 4 and 5, which will be described later. It is a computer equipped with a power supply section that supplies power to each section.

The heating cooker 1 of this embodiment includes a grill heater 13a and an oven heater 13b as heaters 13 for heating the heating chamber 11, as shown in FIG.

The grill heater 13a is, for example, a heater with a power consumption of 650 W, which is attached to the back side of the top surface of the heating chamber 11. This grill heater 13a is formed into a flat shape by winding a heating wire around a mica plate, and is pressed and fixed to the back side of the top surface of the heating chamber 11, heating the top surface of the heating chamber 11 and radiating heat to the food inside the refrigerator. It is baked by

The oven heater 13b is, for example, a heater with a power consumption of 680 W, which is provided in the hot air unit 11a on the back side of the heating chamber 11. When the oven heater 13b is used, the hot air fan of the hot air unit 11a rotates, so that the air circulating in the heating chamber 11 can be heated by the oven heater 13b.

Furthermore, a temperature sensor 11b is provided above the rear part of the heating chamber 11. Since this temperature sensor 11b is provided at a position that is not directly affected by the radiant heat from the grill heater 13a or the hot air blown out from the hot air unit 11a, it is possible to accurately detect the temperature inside the refrigerator. Note that although a thermistor whose resistance value decreases as the temperature increases is used as the temperature sensor 11b, other types of temperature sensors may be used.

<Functional block diagram>
Next, a functional block diagram of the heating cooker 1 of this embodiment will be explained using FIG. 3. As shown here, the control device 12c is connected to the operation panel 3, the hot air unit 11a, the temperature sensor 11b, the current sensor 12e, and the heater 13. In addition to these, a magnetron 12a, a rotating antenna 12b, a cooling fan device 12d, etc. are also connected to the control device 12c, but since the control executed during oven heating will be explained below, FIG. The illustration of the configuration used during wave heating is omitted.

As shown in the figure, a current (bold line) is supplied from the commercial power source to the control device 12c via the current sensor 12e. This current sensor 12e is, for example, a current transformer that outputs a detected current value, and the control device 12c detects a change in current based on the detected current value from the current sensor 12e when the voltage of the commercial power source fluctuates. It is detected and adjusted so that the output of the heater 13 becomes a desired output. Note that the control device 12c converts the detected current value from the current sensor 12e into a digital current code using the table (excerpt) of FIG. 4, and then uses it for various controls.

The temperature sensor 11b is a thermistor whose resistance value changes depending on the temperature inside the refrigerator, and converts the resistance value into a voltage and outputs it as a temperature detection value. The control device 12c converts the temperature detection value from the temperature sensor 11b into a digital temperature code, and detects the temperature inside the refrigerator and controls the heater 13 based on the temperature code.

<Heating process for oven heating with preheating>
Next, oven heating with preheating by the heating cooker 1 of this embodiment will be explained using FIGS. 5 and 6.

Before starting oven heating with preheating, when the cook uses the operation dial 31c or the like to set a desired heating temperature in the range of 100 to 300°C in 10°C increments, the control device 12c registers the temperature in advance in the storage unit. Based on the table illustrated in FIG. 5, the control values (preheating end value H, reference value T) corresponding to the set heating temperature are determined. Note that the control values shown in FIG. 5 are control values that have been experimentally confirmed to cause the heating temperature set by the cook and the ambient temperature of the temperature sensor 11b to match if these control values are used.

When using the table in FIG. 5, for example, if the heating temperature set by the cook is 180° C., the control device 12c sets the reference value T in hexadecimal notation as the control value that is the reference for the energization control of the heater 13. [8D] is determined, and a preheating end value H[88] in hexadecimal notation is determined as a control value for transitioning from the preheating process to the main process. In addition, in FIG. 5, the higher the heating temperature, the larger the reference value T and preheating end value H are registered.

FIG. 6 is a graph illustrating the transition of the internal temperature (temperature around the temperature sensor 11b) after the start of oven heating with preheating, when the heating temperature is set to 180°C and the heating time is set to 20 minutes. It shows the change in temperature inside the refrigerator.

When using this setting, the control device 12c first obtains [8D] as the reference value T from the table of FIG. 5, and also obtains [88] as the preheating end value H. Thereafter, when the cook inputs the start key 31d, oven heating with preheating, which consists of a preheating process and a main process, is started. Each step will be explained in detail below.

<Preheating process>
When the cook inputs the start key 31d without putting food (item to be heated) into the heating chamber 11 after setting the heating temperature, etc., the control device 12c first starts a preheating process. In the preheating process, the control device 12c energizes the grill heater 13a and the oven heater 13b at a high energization rate, and at the same time energizes the hot air motor of the hot air unit 11a to rotate the hot air fan. When the heat of the oven heater 13b is circulated by the rotating hot air fan, the entire heating chamber 11 is heated, and the internal temperature rises rapidly. In addition, since the temperature inside the refrigerator immediately after the start of the preheating process is the same as the room temperature, the temperature detection value outputted by the temperature sensor 11b is a small value indicating that the temperature inside the refrigerator is low, and the control to which the temperature detection value is input is The device 12c generates a small temperature code indicating that the internal temperature is low.

When the temperature inside the refrigerator further rises due to the heating of the heater 13 and the temperature code generated by the control device 12c reaches the preheating end value H[88] corresponding to the heating temperature of 180°C, the control device 12c turns off the power supply to the heater 13. is turned off, and the cook is notified of the completion of preheating using the display unit 32, buzzer, etc.

<Main process>
When the completion of preheating is notified, the cook opens the door 2, places the square plate on which the food (item to be heated) is placed in the heating chamber 11, closes the door 2, and then inputs the start key 31d again. do. This starts the main process of heating the heater 13 at a lower energization rate than the preheating process in order to prevent an overshoot of the internal temperature. In addition, in FIG. 6, illustration of the period from the end of the preheating process until the start of the main process is omitted.

Also in this step, the control device 12c sequentially generates temperature codes using the temperature detection value of the temperature sensor 11b. Then, during a period in which the generated temperature code is smaller than the reference value T[8D] of the heating temperature of 180° C., the control device 12c turns on the power supply to the heater 13 and heats the heating chamber 11. Thereafter, when the internal temperature further rises and the generated temperature code reaches [8E], which is one code larger than the reference value T[8D], the control device 12c turns off the power supply to the heater 13. When the generated temperature code drops to [8C], which is one code smaller than the reference value T [8D], as the temperature inside the refrigerator decreases, the control device 12c turns on the power supply to the heater 13 again and turns on the heating chamber 11. Reheat. By repeating such ON/OFF control of the heater 13, the control device 12c can maintain the internal temperature of the refrigerator at the set heating temperature of about 180°C. Then, when 20 minutes have passed through this process, the control device 12c turns off the heater 13 and uses a buzzer or the like to notify the cook that the cooking is complete.

<Temperature sensor abnormality determination>
Although FIG. 6 shows the change in temperature inside the refrigerator when the temperature sensor 11b and its peripheral circuits are normal, if there is an abnormality in the temperature sensor 11b, etc., the temperature inside the refrigerator can be maintained at the set heating temperature. Therefore, it is necessary to detect abnormalities early and notify the cook. Therefore, below, a method for determining an abnormality of the temperature sensor 11b, etc., and a control operation when an abnormality is determined will be explained using FIGS. 7 and 8.

FIG. 7 shows a case where the temperature sensor 11b and the peripheral circuit are normal (solid line), a case where the temperature sensor 11b and the peripheral circuit are disconnected and there is no output (dotted line), and a case where there is an abnormality in the temperature sensor 11b and the peripheral circuit and an abnormal value is generated. This is a graph in which the temperature code generated by the control device 12c is converted into the temperature inside the refrigerator for each case where the temperature code is output (broken line).

As shown by the solid line, if the temperature sensor 11b etc. is normal, the temperature code will follow and increase as the temperature inside the refrigerator increases, so during this process described above, the set heating temperature (for example, 180 ° C.) will not be maintained. The heater 13 can be appropriately controlled to maintain the following.

On the other hand, as shown by the dotted line, if the temperature sensor 11b is disconnected and there is no valid output from the temperature sensor 11b, the generated temperature code will continue to be zero even if the temperature inside the refrigerator is actually rising. Therefore, according to the heater control during the main process described above, it is not possible to turn off the electricity to the heater 13, and as a result, there is a possibility that the heating chamber 11 is overheated.

Furthermore, as shown by the broken line, even if there is a valid output from the temperature sensor 11b, if the temperature code generated based on the output is an abnormal value, even if the temperature inside the refrigerator is actually rising, Since the temperature code obtained does not reflect the temperature inside the refrigerator, the heater control during this process described above cannot turn off the power to the heater 13, resulting in overheating of the heating chamber 11. there is a possibility.

Therefore, in the heating cooker 1 of this embodiment, when the temperature sensor 11b is disconnected and there is no valid output (dotted line in FIG. 7), or when there is a valid output from the temperature sensor 11b, an abnormal temperature code is generated. Even in the case of a failure (as shown by the broken line in FIG. 7), the failure mode can be detected and overheating can be prevented. Hereinafter, the abnormality determination process of the temperature sensor 11b by the heating cooker 1 of this embodiment will be described in detail using the flowchart of FIG.

First, in step S1, the cook operates the heater heating setting key 31b to select the oven or grill cooking menu, and further operates the setting dial 31c to adjust the finish, heating temperature, heating time, etc. Set conditions. At this time, the control device 12c acquires the control values (preheating end value H, reference value T) corresponding to the set heating temperature from the table in FIG.

In step S2, when the cook operates the start key 31d, the control device 12c starts supplying power to the heater 13, and oven heating and grill heating are started.

In step S3, the control device 12c continues to energize the heater 13 for, for example, 5 minutes. During this time, if the heater 13 is normal, the temperature inside the refrigerator increases, and if the temperature sensor 11b is normal, the temperature code generated by the control device 12c also increases.

In step S4, the control device 12c determines whether or not the temperature sensor 11b is disconnected. Specifically, the control device 12c checks the temperature code of the temperature sensor 11b five minutes after the start of heating, and determines whether the temperature code is equal to or higher than the first threshold value. If the temperature code is less than the first threshold, the process proceeds to step S5, and if the temperature code is greater than or equal to the first threshold, the process proceeds to step S6. Note that the first threshold value is, for example, a temperature code [03] equivalent to room temperature, and a temperature code less than the first threshold value is, for example, a temperature code [00] that means that the temperature sensor 11b has no output. be.

In step S5, the control device 12c determines that there is no valid output from the temperature sensor 11b, stops power supply to the heater 13 to prevent overheating, and displays a disconnection of the temperature sensor 11b on the display unit 32. Display an error message indicating.

On the other hand, in step S6, the control device 12c continues to energize the heater 13 for an additional 10 minutes, for example. Note that if the heater 13 is normal by energizing the heater for 5 minutes in step S3 and energizing the heater for 10 minutes in step S6, the temperature inside the refrigerator has sufficiently reached the preheating end temperature or the set heating temperature. There is.

In step S7, the control device 12c determines whether the output of the temperature sensor 11b is normal. Specifically, the control device 12c checks the temperature code at the time when heating continues for another 10 minutes, and determines whether the amount of increase from the temperature code at the time of step S2 is less than or equal to the second threshold value. Then, if the amount of increase is larger than the second threshold (if the temperature sensor 11b can detect a sufficient temperature rise), the process proceeds to step S8, and if the amount of increase is less than the second threshold (if the temperature sensor 11b can detect a sufficient temperature rise) (If no rise is detected), proceed to step S9. Note that the second threshold value is, for example, "7", which corresponds to a temperature increase of about 50°C.

In step S8, the control device 12c determines that the temperature sensor 11b is normal and continues cooking until the set heating time elapses.

In step S9, the control device 12c determines whether the temperature code generated in step S7 is equal to or greater than the preheating end value H. If the temperature code has reached the preheating end value H, the process proceeds to step S8, where it is determined that the temperature sensor 11b is normal; if the temperature code has not reached the preheating end value H, the process proceeds to step S10. The reason for providing the determination in step S9 after step S7 is that, as in the case of continuous oven cooking, there is a difference between the temperature code when 5 minutes have elapsed from the start of cooking and the temperature code when another 10 minutes have elapsed. If it is small, there is a possibility that the normal temperature sensor 11b will be determined to be abnormal only by the determination in step S7, so this is to enable appropriate diagnosis of abnormalities in the temperature sensor 11b assuming various usage conditions. .

In step S10, the control device 12c turns off the heater 13 for several seconds.

In step S11, the control device 12c turns on the heater 13 again. This stabilizes the output of the current sensor 12e.

In step S12, the control device 12c determines whether the current code generated from the output of the current sensor 12e is greater than or equal to a third threshold value. If the current code is less than the third threshold and it is considered that there is no power consumption in any of the heaters 13, the process proceeds to step S13, where the current code is greater than or equal to the third threshold and power is consumed in both heaters 13. If it can be determined that it has been consumed, the process advances to step S14. Note that the third threshold value is, for example, a value [24] smaller than the current code corresponding to the current value when only one of the grill heater 13a and the oven heater 13b is used.

In step S13, the control device 12c determines that one of the heaters 13 is disconnected, displays the error of the disconnection of the heater 13 on the display unit 32, and stops cooking.

In step S14, the control device 12c determines that the output of the temperature sensor 11b is abnormal and that the temperature code generated based on the output does not reflect the actual temperature inside the refrigerator, and displays the temperature sensor on the display unit 32. 11b is displayed, and the cooking is stopped.

In this way, by the determination in step S12, it is determined from the value of the current code whether the cause of no increase in the temperature code is a malfunction in the temperature sensor 11b or its peripheral circuit, or a disconnection of the heater 13, and the cause is isolated. be able to.

According to the heating cooker of the present embodiment described above, if a malfunction occurs in the temperature sensor 11b or its peripheral circuit that causes excessive heating in the refrigerator, the malfunction can be detected. This makes it possible to detect abnormal conditions step by step and to discriminate between various failure modes.

Note that the present invention is not limited to the embodiments described above, and includes various modifications. The embodiments described above are described in detail to explain the present invention in an easy-to-understand manner, and the present invention is not necessarily limited to those having all the configurations described.

1 Cooking device 11 Heating chamber 11a Hot air unit 11b Temperature sensor 12 Machine room 12a Magnetron 12b Rotating antenna 12c Control device 12d Cooling fan device 12e Current sensor 13 Heater 13a Grill heater 13b Oven heater 2 Door 3 Operation panel 31 Operation section 31a Microwave heating setting key 31b Heater heating setting key 31c Setting dial 31d Start key 32 Display section 4 Outer frame 5 Rear plate

Claims (5)

a heating chamber that stores an object to be heated;
an operation unit that sets the heating temperature of the heating chamber;
a heater that heats the heating chamber;
a temperature sensor that detects the temperature of the heating chamber ;
A heating cooker comprising: a control device that controls the heater based on a set heating temperature and the output of the temperature sensor, and determines an abnormality of the heater or the temperature sensor,
The control device includes:
energizing the heater for a first period, generating a first temperature code based on the output of the temperature sensor at the time when the first period elapses, and if the first temperature code is smaller than a first threshold; , determining that the temperature sensor is disconnected ;
If the first temperature code is equal to or higher than the first threshold, the heater is further energized for a second period, and a second temperature code is generated based on the output of the temperature sensor at the time when the second period elapses. and determining that the temperature sensor is normal if the increase value of the second temperature code from the first temperature code is greater than a second threshold;
If the increase value is less than or equal to the second threshold, the temperature sensor is determined to be normal if the second temperature code is greater than or equal to the preheating end value corresponding to the set heating temperature. A heating cooker with special features. The heating cooker according to claim 1,
The heating cooker, wherein the first threshold value is a value of a temperature code corresponding to room temperature. The heating cooker according to claim 1 ,
Equipped with a current sensor that detects the current supplied from the commercial power supply,
If the second temperature code is less than the preheating end value,
The control device generates a current code based on the output of the current sensor when the heater is operated, and determines that the output of the temperature sensor is abnormal if the current code is equal to or higher than a third threshold. A heating cooker featuring: In the heating cooker according to claim 3 ,
The heating cooker, wherein the control device determines that the heater is disconnected if the current code is less than the third threshold value. In the heating cooker according to any one of claims 1 to 4 ,
The heating cooking device is characterized in that the control device stops power supply to the heater when determining a disconnection of the temperature sensor, an abnormality in the output of the temperature sensor, or a disconnection of the heater.

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