JP2005241128A - Cooker - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cooker capable of accurately judging the presence or absence of a heated matter in a heating chamber, properly heating the heated matter, preventing the heating in a non-load state, and preventing the deterioration and damage of components. <P>SOLUTION: In this cooker 1, a temperature of a magnetron 15b is detected by a thermistor 29 in heating the heated matter in a heating chamber by microwaves by driving the magnetron 15b, and a humidity in the heating chamber is detected by a humidity sensor 37. A control part 38 judges the presence or absence of the heated matter in the heating chamber on the basis of the temperature detected by the thermistor 29 and the humidity detected by the humidity sensor 37. For example, the control part 38 stops the microwave heating by judging the absence of the heated matter in the heating chamber when the detected temperature t of the thermistor 29 is more than a set temperature t0, and an output voltage value of the humidity sensor 37 is hardly changed for a specific time from the start of heating. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention is a cooker for heating an object to be heated stored in a heating chamber by microwaves, and damage that may occur when microwave heating is performed in a so-called no-load state in which there is no object to be heated in the heating chamber. The present invention relates to a cooker having a protective function for preventing the above.

  A cooker equipped with a magnetron oscillates a magnetron and supplies microwaves into a heating chamber to cook an object to be heated in the heating chamber. In this cooker, if microwave heating is performed in a no-load state where there is no object to be heated in the heating chamber, a large amount of microwaves that are not consumed in the heating chamber return to the magnetron, causing the temperature of the magnetron to rise, causing deterioration and damage. In some cases, microwaves concentrate on a portion of the tray installed in the heating chamber, and only that portion is heated and damaged, or resin parts in the heating chamber are melted and damaged.

  Therefore, a cooking device having a protective function for preventing damage that may occur when microwave heating is performed in a no-load state where there is no object to be heated in the heating chamber has been developed. A cooker having such a protection function is described in Patent Document 1, for example. In the cooker described in Patent Document 1, when the temperature detection element is attached to the cooling fin of the magnetron to detect the temperature of the magnetron, and an abnormal temperature rise of the magnetron is detected, there is no object to be heated in the heating chamber. Judgment is made to stop the oscillation of the magnetron and prevent the cooker from being damaged.

  FIG. 7 is a flowchart for explaining a no-load state detection process in a conventional cooking device. In step b1, the user operates the control key of the operation unit to input the heating time Ta (seconds), and when the user presses the start key of the operation unit in step b2, microwave heating is started. In step b3, the controller of the cooking device sets the flag Ft to 0. The flag Ft is a flag indicating whether or not the measured temperature of the thermistor that is a temperature detection element attached to the magnetron is equal to or higher than the set temperature, and is set to 0 when the measured temperature is lower than the set temperature. Is set to 1 when the temperature is equal to or higher than the set temperature.

  In subsequent step b4, the control unit measures the elapsed time T (seconds), and in step b5, it is determined whether or not T <Ta. If the elapsed time T has not reached the heating time Ta, the process proceeds to step b6 to determine whether or not the flag Ft = 0. When the flag Ft = 0, the process proceeds to step b7, and the thermistor temperature t (° C.) is measured.

  In the subsequent step b8, it is determined whether or not the measured temperature t ≧ thermistor set temperature t0. If the measured temperature t is lower than the thermistor set temperature t0, the process returns to step b4 and the processes of steps b4 to b7 are repeated. On the other hand, if the measured temperature t is equal to or higher than the thermistor set temperature t0 in step b8, the process proceeds to step b9 and the flag Ft is set to 1.

  In the subsequent step b10, it is determined whether or not the elapsed time T ≧ 120. If the elapsed time T is less than 120 seconds, the process returns to step b4, and the processes of steps b4 to b9 are repeated. In step b6, if the flag Ft is not 0, that is, if the flag Ft = 1, the process proceeds to step b10 without measuring the temperature of the thermistor.

  On the other hand, if the elapsed time T is 120 seconds or longer in step b10, the process proceeds to step b11, where the control unit determines that there is no object to be heated in the heating chamber and stops heating. An error message is displayed on the display unit and the process is terminated. That is, when the flag Ft = 1 (measured temperature t is equal to or higher than the thermistor set temperature t0) before 120 seconds have elapsed from the start of heating, microwave heating is continued until 120 seconds have elapsed, and 120 seconds have elapsed since the start of heating. After that, when the flag Ft = 1, the microwave heating is stopped at that time.

In step b5, when the elapsed time T is equal to or longer than the heating time Ta, the microwave heating for the heating time Ta set by the user is completed, so the process proceeds to step b13 to stop the heating and process Exit.
Japanese Patent No. 2823312

  In a cooker equipped with a protective function, depending on how the cooker is used, even if there is an object to be heated in the heating chamber, if there is no object to be heated because an abnormal temperature rise exceeding the set temperature is detected, the measured temperature of the thermistor is detected. As a result, the oscillation of the magnetron stops and the heating of the object to be heated may be insufficient.

  For example, when cooking such as cooking food, the heating time is relatively long, and a relatively large amount of water in the food evaporates. At this time, the oven impedance of the cooking device changes greatly with the evaporation of the moisture of the food, and the anode temperature of the magnetron rapidly rises due to this change, and an abnormal temperature rise may be detected. Such a phenomenon may also occur when frozen food is thawed and further cooked.

  In addition, in a commercial cooker used in a convenience store, a restaurant, or the like, cooking such as cooking food or thawing / cooking frozen food may be performed a plurality of times. At this time, after the cooking, the next cooking is performed before the temperature of the magnetron sufficiently decreases, so the temperature of the magnetron gradually rises and finally the measured temperature of the thermistor exceeds the set temperature. And may be detected as an abnormal temperature rise.

  In addition, commercial cookers may be used in two stages because of installation space. If the upper and lower cooking devices are operated simultaneously in this state, the cooling air passage of the lower cooking device becomes complicated due to the presence of the upper cooking device, so the heat released from the lower cooking device is The temperature rises easily in the upper cooking device.

  As a measure to prevent malfunctions that cause heating to stop despite the presence of an object to be heated in the heating chamber as described above, the reference temperature for determining that there is no object to be heated in the heating chamber, that is, the set temperature of the thermistor is increased. It is conceivable to set to However, with this measure, the measured temperature of the thermistor is set without reaching the set temperature even though the object to be heated is in a no-load state due to variations in the temperature of the anode part of the magnetron. The microwave heating is continued until the heating time is over, and part of the cooker may be damaged. This is likely to occur in commercial cookers with high output.

  The present invention has been made paying attention to such problems in the prior art, accurately determining the presence or absence of the object to be heated in the heating chamber, appropriately heating the object to be heated, and in an unloaded state It is an object of the present invention to provide a cooking device that can prevent the deterioration and damage of the component parts by avoiding heating in the oven.

  A cooker according to the present invention includes a heating chamber in which an object to be heated is stored, a magnetron that supplies microwaves to the heating chamber, a cooling fan that supplies cooling air for cooling the magnetron, Based on the temperature detection element for detecting temperature, the humidity detection element for detecting the humidity in the heating chamber, and the detected values of the temperature detection element and the humidity detection element, the presence / absence of an object to be heated in the heating chamber is determined. And control means for stopping microwave heating by the magnetron when it is determined that there is no object to be heated in the heating chamber.

  Further, in the cooking device, the control means is that the amount of increase in humidity with respect to the start of heating after the elapse of a predetermined time from the start of heating is less than a predetermined reference amount, and the detected temperature is equal to or higher than a predetermined reference temperature. The microwave heating is stopped when the three conditions that a predetermined average heating time has elapsed from the start of heating are satisfied.

  In the cooking device, the control means detects the humidity in the heating chamber from the start of heating until a predetermined time elapses, and when the detected humidity is equal to or higher than a predetermined initial value, the initial value is set. If the detected humidity is less than the initial value, the detected humidity is set as the reference humidity, and the difference between the detected humidity and the reference humidity after the lapse of a predetermined time is calculated to obtain the amount of increase in humidity. Features.

  In the cooking device, the control means outputs an error message after determining that there is no object to be heated in the heating chamber and stopping the microwave heating.

  In the cooking device, the humidity detecting element is a resistance element type humidity sensor using two thermistors, and one thermistor is arranged in a sealed space.

  In the cooking device, the humidity detecting element is attached in the vicinity of an exhaust duct that exhausts the air in the heating chamber to the outside.

  Moreover, the said cooking device WHEREIN: The said temperature detection element is attached to the position which adjoins or contacts the anode part of the said magnetron, It is characterized by the above-mentioned.

  Moreover, the said cooking device WHEREIN: The said temperature detection element is attached to the position where the cooling air from the said cooling fan does not blow directly.

  Moreover, the said cooking device WHEREIN: The said temperature detection element is attached to the cooling fin of the said magnetron located in the leeward side of the said cooling air, It is characterized by the above-mentioned.

  According to the cooking device of the present invention, the presence or absence of an object to be heated in the heating chamber is determined based on the temperature of the magnetron that is the detection value of the temperature detection element and the humidity in the heating chamber that is the detection value of the humidity detection element. The For example, when the object to be heated is heated, moisture evaporates from the object to be heated. Therefore, if microwave heating is performed with the object to be heated in the heating chamber, the humidity in the heating chamber increases. From this, when the humidity in the heating chamber does not increase, it can be determined that there is no object to be heated in the heating chamber. When microwave heating is performed in a state where there is no object to be heated in the heating chamber, a large amount of microwaves not consumed in the heating chamber returns to the magnetron, and the temperature of the magnetron increases rapidly. From this, when the temperature of the magnetron is abnormally rising, it can be determined that there is no object to be heated in the heating chamber.

  As described above, in the present invention, since the presence / absence of an object to be heated in the heating chamber is determined based on the temperature of the magnetron and the humidity in the heating chamber, it is more accurate than in the case where the determination is based only on the temperature of the magnetron as in the prior art. In addition, the presence or absence of an object to be heated in the heating chamber can be determined. Therefore, it is possible to prevent the heating from stopping in the middle even though there is an object to be heated in the heating chamber as in the prior art, and the object to be heated can be cooked appropriately. In addition, when it is determined that there is no object to be heated in the heating chamber, by stopping the heating, the cooker such as damage or deterioration of the magnetron, deformation due to melting of resin parts in the heating chamber or damage to the tray due to red heat Can be prevented from being damaged.

  Further, according to the cooker of the present invention, the amount of increase in humidity based on the start of heating after the elapse of a predetermined time from the start of heating is less than the predetermined reference amount, the detected temperature is equal to or higher than the predetermined reference temperature, Microwave heating is stopped when the three conditions that a predetermined average heating time has elapsed from the start of heating are satisfied.

  First, one of the conditions is that the amount of increase in humidity based on the start of heating after the elapse of a predetermined time from the start of heating is less than the predetermined reference amount. This is because almost no water evaporates. In addition, one of the conditions that the detected temperature is equal to or higher than a predetermined reference temperature is that if the microwave heating is performed in a state where there is no object to be heated in the heating chamber, the temperature of the magnetron rises above the predetermined reference temperature. Because it does. The predetermined reference temperature is set to a value higher than the temperature of the magnetron at the time of normal microwave heating in a state where the object to be heated is in the heating chamber, for example.

  Furthermore, one of the conditions is that a predetermined average heating time has elapsed since the start of heating, when determining the presence or absence of an object to be heated based on the temperature of the magnetron and the amount of increase in humidity in the heating chamber This is because the object to be heated can be heated even when an erroneous determination occurs. That is, the temperature of the magnetron may vary greatly depending on the use state of the cooker, and the humidity in the heating chamber may hardly increase depending on the type and state of the object to be heated. Therefore, even when there is an object to be heated in the heating chamber, it may be determined that there is no object to be heated. In this case, if microwave heating is stopped immediately, the object to be heated is not sufficiently heated, and it is necessary to heat the object to be heated again, which is troublesome. Therefore, in the present invention, the object to be heated is heated only for a predetermined average heating time. As a result, the object to be heated can be prevented from being insufficiently heated, and sufficient cooking can be performed.

  Moreover, according to the cooking device of the present invention, it is possible to accurately set the reference humidity that is a reference for obtaining the amount of increase in humidity. This improves the accuracy of detecting the amount of increase in humidity in the heating chamber, and makes it possible to more accurately determine the presence or absence of an object to be heated in the heating chamber.

  Further, according to the cooking device of the present invention, when it is determined that there is no object to be heated in the heating chamber and the microwave heating is stopped, an error message is output. Thereby, the user of the cooker can check the error message and take an appropriate action. For example, when there is no object to be heated in the heating chamber, it is considered that the user has forgotten to put the object to be heated. Therefore, the object to be heated may be put in the heating chamber again and heated. In addition, when there is an object to be heated in the heating chamber, it is considered that the heating has been continuously performed a plurality of times. Therefore, the cooker may be used after resting for a while. At this time, if the object to be heated in the heating chamber is not sufficiently heated, the object to be heated may be heated again.

  According to the cooking device of the present invention, the humidity detecting element is a resistance element type humidity sensor using two thermistors, and one thermistor is arranged in a sealed space, and is a dry and wet hygrometer. The humidity is detected by the same principle. Since the resistance element type humidity sensor using two thermistors is relatively inexpensive, the manufacturing cost of the cooker can be reduced.

  Further, according to the cooker of the present invention, the humidity detecting element is attached in the vicinity of the exhaust duct that exhausts the air in the heating chamber to the outside, so that the humidity in the heating chamber can be accurately detected.

  Moreover, according to the cooking device of the present invention, the temperature detecting element is attached at a position close to or in contact with the anode portion of the magnetron, so that the temperature of the magnetron can be accurately detected.

  Moreover, according to the cooking device of the present invention, since the temperature detecting element is attached at a position where the cooling air is not directly blown, the temperature of the magnetron can be accurately detected without being influenced by the cooling air.

  Further, according to the cooking device of the present invention, since the temperature detecting element is attached to the cooling fin of the magnetron located under the cooling air, the temperature of the magnetron can be accurately detected without being affected by the cooling air. .

  FIG. 1 is a block diagram showing a basic electrical configuration of a cooking device 1 according to an embodiment of the present invention, FIG. 2 is a perspective view showing an appearance of the cooking device 1, and FIG. FIG. 4 is a cross-sectional view of the cooking device 1 as seen from the section line IV-IV in FIG. 3.

  As shown in FIG. 2, the cooking device 1 has a heating chamber 3 in a substantially rectangular parallelepiped casing 2, and an openable / closable door 4 that opens and closes the heating chamber 3 is provided on the front surface of the cooking device 1. Is provided. An operation unit 5 is provided on the right side of the door 4, and the operation unit 5 includes a display unit 6 and a key input unit 7.

  The heating chamber 3 includes a cavity top plate 8 corresponding to the top surface, a cavity bottom plate 9 corresponding to the bottom surface, a cavity rear surface plate 10 corresponding to the rear surface, a cavity left side plate 11 corresponding to the left side, and a cavity right side plate 12 corresponding to the right side. It is installed and configured inside. The casing 2 includes a substantially flat bottom plate 13 and a substantially rectangular parallelepiped frame 14. A space is formed between the cavity rear plate 10 and the back surface portion of the casing 2, and magnetrons 15 a and 15 b serving as heating means are disposed in the space, that is, behind the heating chamber 3.

  The magnetron 15 a is attached to the cavity top plate 8 corresponding to the top surface of the heating chamber 3, and the magnetron 15 b is attached to the cavity bottom plate 9 corresponding to the bottom surface of the heating chamber 3. The cavity top plate 8 and the cavity bottom plate 9 are provided with waveguides 16a and 16b, respectively. The magnetrons 15a and 15b are attached so that the microwave output portion is located on one end side of the waveguides 16a and 16b, and the other ends of the waveguides 16a and 16b are formed on the cavity top plate 8. The feeding opening 17a and the feeding opening 17b formed in the cavity bottom plate 9 are communicated with each other. With this configuration, the microwaves from the magnetrons 15a and 15b are supplied to the heating chamber 3 through the waveguides 16a and 16b.

  In addition, radio wave stirring blades 18a and 18b are rotatably attached to the cavity top plate 8 and the cavity bottom plate 9 in the vicinity of the power supply openings 17a and 17b. The radio wave agitating blades 18a and 18b are fixed to the respective rotation shafts of the guard motors 19a and 19b by fixing pins 20a and 20b, and are rotationally driven by the guard motors 19a and 19b. The microwaves from the power supply openings 17a and 17b are agitated by the rotation of the radio wave agitating blades 18a and 18b.

  Furthermore, the inside air duct 21 and the outside air duct 22 are attached to the cavity top plate 8. The inside exhaust duct 21 and the outside exhaust duct 22 are connected, the opening of the inside exhaust duct 21 communicates with the heating chamber 3, and the opening of the outside exhaust duct 22 is a space outside the casing 2. Communicating with With this configuration, air containing water vapor in the heating chamber 3 can be exhausted to the outside of the cooking device 1.

  A protective cover 23 is provided on the top surface side of the heating chamber 3 so as to cover the radio wave stirring blade 18a. The protective cover 23 is made of a material that transmits microwaves. Further, a tray 24 is provided on the bottom side of the heating chamber 3 so as to cover the radio wave stirring blade 18b. The tray 24 is made of a material that transmits microwaves, for example, a ceramic material. An object to be heated 25 is placed on the upper surface of the tray 24. In FIG. 3, the object to be heated 25 is placed on the upper surface of the tray 24 while being placed on a plate or the like.

  As shown in FIG. 4, high-voltage transformers 26 a and 26 b are attached to the bottom plate 13 of the casing 2 in the space behind the heating chamber 3. The high voltage transformers 26a and 26b supply high voltages to the magnetrons 15a and 15b, respectively. Cooling fans 27 a and 27 b are attached to the cavity top plate 8 in the space behind the heating chamber 3. A duct 28a is provided between the cooling fan 27a and the magnetron 15a, and a duct 28b is provided between the cooling fan 27b and the magnetron 15b. Cooling air from the cooling fans 27a and 27b is supplied to the magnetrons 15a and 15b through the ducts 28a and 28b, whereby the magnetrons 15a and 15b are cooled. In addition, by sending the cooling air from the cooling fans 27 a and 27 b into the heating chamber 3, the air in the heating chamber 3 is exhausted to the outside through the internal exhaust duct 21 and the external exhaust duct 22. This exhaust operation is performed while the object to be heated 25 is heated.

  A thermistor 29, which is a temperature detection element, is attached to the magnetron 15b. 5A and 5B are diagrams showing the shape of the magnetron 15b, where FIG. 5A is a front view, and FIG. 5B is a cross-sectional view as seen from the cutting plane line bb in FIG. As shown in FIG. 5A, the magnetron 15 b generates a magnetic field in an anode 30 having a resonant cavity, a donut-shaped permanent magnet 31 provided at both ends of the anode 30, and an electron action space in the anode 30. A yoke 32 forming a magnetic circuit to be driven, a microwave output antenna 33, an anode cooling fin 34, a filter box 35 provided in the cathode portion, and a cathode connection terminal 36 are provided.

  As shown in FIG. 5B, the thermistor 29 is attached to the cooling fin 34 so as to be in contact with or close to the anode 30 portion. The thermistor 29 is a resistance element whose resistance value changes with temperature change, and is 63.26 k ohm when the detected temperature is 100 ° C., and 4 k ohm when the detected temperature is 200 ° C. The thermistor 29 is preferably attached to the cooling fin 34 of the magnetron 15b located at a position where the cooling air is not directly blown, for example, leeward of the cooling air.

  Further, the outside exhaust duct 22 is provided with a humidity sensor 37 which is a humidity detecting element. The humidity sensor 37 is a resistance element type using two thermistors, one of the thermistors is arranged in a sealed space, and detects humidity on the same principle as a dry-wet hygrometer. That is, the detection temperature of the thermistor disposed in the sealed space is the dry bulb temperature, and the detection temperature of the other thermistor exposed to the air in the heating chamber 3 that is the detection target is the wet bulb temperature. Based on the bulb temperature, the humidity of the air in the heating chamber 3 is determined. In this embodiment, the output voltage of the humidity sensor 37 before microwave heating is about 1 to 1.5 V, and the increase amount of the output voltage of the humidity sensor 37 when 1 liter of water is heated to 90 ° C. is , About 2.5V.

  As shown in FIG. 1, the magnetron 15b is driven by a drive voltage supplied via a high voltage transformer 26b. The magnetron 15a is driven by a driving voltage supplied via the high-voltage transformer 26a. Since the circuit configuration for driving is the same as that of the magnetron 15b, the magnetron 15b will be described with reference to FIG.

  The two terminals of the cathode MK of the magnetron 15b are connected to the two terminals of the heater winding TH of the high voltage transformer 26b, respectively, and the anode MA of the magnetron 15b is grounded. One terminal of the cathode MK of the magnetron 15b is connected to one terminal of the high voltage capacitor C and to the anode of the high voltage diode D. The other terminal of the high voltage capacitor C is connected to one terminal of the secondary winding T2 of the high voltage transformer 18b, and the other terminal of the secondary winding T2 of the high voltage transformer 26b is grounded. The cathode of the high voltage diode D is grounded. The high voltage capacitor C and the high voltage diode D constitute a half-wave voltage doubler rectifier circuit RC.

  One terminal of the primary winding T1 of the high-voltage transformer 26b is connected to one terminal of the magnetron drive control relay R, and the other terminal of the magnetron drive control relay R is connected to the AC power source V via the first door switch DS1. One terminal is connected. A control signal from the control unit 38 is input to the control terminal of the magnetron drive control relay R. On the other hand, the other terminal of the primary winding T1 of the high-voltage transformer 26b is connected to the other terminal of the AC power supply V via the second door switch DS2. Further, a monitor switch MS is interposed between the other terminal of the primary winding T1 of the high voltage transformer 26b and the other terminal of the magnetron drive control relay R.

  The two door switches DS1, DS2 are switches that are turned on / off in conjunction with the opening / closing of the door 4, and are turned off when the door is opened and turned on when the door is closed. The monitor switch MS is also a switch that is turned on / off in conjunction with the opening / closing of the door 4, but is opposite to the door switches DS1, DS2 and is turned on when the door is opened and turned off when the door is closed. . When the door is closed, the monitor switch MS is turned off and then the door switches DS1 and DS2 are turned on. When the door is opened, the door switch DS1 and DS2 are turned off and then the monitor switch MS is turned on. ing.

  When the door 4 is closed, the monitor switch MS is turned off, and then the two door switches DS1 and DS2 are turned on. When the magnetron drive control relay R is turned on in this state, the AC voltage from the AC power supply V is supplied to the primary winding T1 of the high-voltage transformer 26b. As a result, in the high voltage transformer 26b, an AC voltage suitable for the cathode MK of the magnetron 15b is induced in the heater winding TH, and an AC voltage suitable for oscillation of the magnetron 15b is induced in the secondary winding T2. The AC voltage induced in the heater winding TH of the high-voltage transformer 26b is supplied to the cathode MK of the magnetron 15b, thereby heating the magnetron 15b. The AC voltage induced in the secondary winding T2 of the high-voltage transformer 26b is rectified by the half-wave voltage doubler rectifier circuit RC, and the rectified high voltage is supplied to one terminal of the cathode MK of the magnetron 15b. As a result, the magnetron 15b starts an oscillation operation. Microwaves are output by the oscillation operation of the magnetron 15b, and the output microwaves are supplied to the heating chamber 3, and the object to be heated 25 in the heating chamber 3 is heated.

  On the other hand, when the door 4 is opened, the two door switches DS1, DS2 are turned off, and then the monitor switch MS is turned on. In this state, even if the magnetron drive control relay R is turned on, the AC voltage from the AC power supply V is not supplied to the primary winding T1 of the high voltage transformer 26b, and the magnetron 15b does not operate.

  The monitor switch MS is provided to prevent malfunction of the magnetron 15b when the contacts of the door switches DS1 and DS2 are welded by heating and the door switches DS1 and DS2 remain on even when the door 4 is opened. Yes. That is, since the monitor switch MS is configured to be turned on when the door 4 is opened, even if the door switches DS1 and DS2 remain turned on due to welding of the contacts, the monitor switch MS is turned on. Therefore, a short circuit is formed with respect to the AC power source V, the AC voltage from the AC power source V is not supplied to the primary winding T1 of the high-voltage transformer 26b, and the magnetron 15b does not operate. Accordingly, it is possible to prevent the microwave from leaking to the outside of the cooking device 1 by operating the magnetron 15b with the door 4 opened.

  Further, each output signal from the key input unit 7, the thermistor 29, and the humidity sensor 37 is given to the control unit 38. The control unit 38 controls the operation of the cooking device 1, for example, the operation of the display unit 6 and the magnetron drive control relay R, based on output signals from the key input unit 7, the thermistor 29, and the humidity sensor 37. The control unit 38 is configured by a microcomputer, for example, and includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like. Is done.

  In the cooking device 1, based on the temperature of the magnetron 15 b that is the detection value of the thermistor 29 and the humidity in the heating chamber 3 that is the detection value of the humidity sensor 37, the presence or absence of the heated object 25 in the heating chamber 3 is determined. Is done. In general, when the object to be heated 25 such as food is heated, moisture is evaporated from the object to be heated 25. Therefore, if microwave heating is performed with the object to be heated 25 in the heating chamber 3, the inside of the heating chamber 3 Humidity will increase. From this, when the humidity in the heating chamber 3 does not increase, it can be determined that there is no object to be heated 25 in the heating chamber 3.

  Here, this inventor experimented about the generation | occurrence | production state of the water vapor | steam from a to-be-heated material. As the object to be heated, “pork grilled meat bowl” sold at a convenience store was used. The contents of the experiment are as follows: A1 with the pork yakiniku bowl covered and covered with a wrap, A2 with the pork yakiniku bowl just covered, and the pork yakiniku bowl Heating is performed using the cooker 1 in the three states A3 with the wrap and lid, the initial output voltage Emin of the humidity sensor 37 and the output voltage E after heating are measured, and the output voltage E-initial output Each heating time for voltage Emin ≧ 0.5 (V) was determined. The result was 1 minute 6 seconds in state A1, 44 seconds in state A2, and 19 seconds in state A3.

  The case where the container containing the food is covered and heated with the whole covered with a wrap is the case where water vapor is hardly generated. Even in this case, for example, for “pork yakinikudon”, when 1 minute and 6 seconds have elapsed from the start of heating, the detected humidity (output voltage) E−the minimum value of the detected humidity (initial output voltage) Emin ≧ 0.5, It can be determined that it occurred. Moreover, even when it heats in the state which covered the container which put the foodstuff, if 44 second passes from a heating start, it can be judged that it became E-Emin> = 0.5 and water vapor | steam generate | occur | produced. In addition, the other foods were confirmed to be the same as “Pork Yakiniku”. From this, the humidity can be used to determine the presence or absence of the object to be heated 25 in the heating chamber 3.

  In addition, when microwave heating is performed in a state where there is no object to be heated 25 in the heating chamber 3, a large amount of microwaves that have not been consumed in the heating chamber 3 return to the magnetrons 15a and 15b, and the temperature of the magnetrons 15a and 15b is It rises rapidly. From this, when the temperatures of the magnetrons 15a and 15b are abnormally increased, it can be determined that there is no object to be heated 25 in the heating chamber 3. Hereinafter, an example of the control operation of the cooking device 1 will be described.

  FIG. 6 is a flowchart for explaining the control operation of the cooking device 1. In step a1, the user operates the control key of the key input unit 7 to input the heating time Ta (seconds). When the user presses the start key of the key input unit 7 in step a2, microwave heating starts.

  In step a3, the flag Ft is set to 0, in step a4, the flag Fe is set to 1, and in step a5, the initial value Emin of the output voltage of the humidity sensor 37 is set to 100 (V), for example.

  In step a6, the control unit 38 measures an elapsed time T (seconds) from the start of microwave heating, and in step a7, it is determined whether or not the elapsed time T <heating time Ta. When the elapsed time T has not reached the heating time Ta, the process proceeds to step a8, and the control unit 38 measures the output voltage E (V) of the humidity sensor 37.

  In step a9, it is determined whether or not the elapsed time T> 8. If the elapsed time T has not reached 8 seconds, the process proceeds to step a10, where it is determined whether or not the initial value Emin ≦ the measured output voltage E. When the initial value Emin is larger than the measured output voltage E, the process proceeds to step a11, and after the initial value Emin is set to the measured output voltage E, the process proceeds to step a14. On the other hand, if the initial value Emin is equal to or lower than the measured output voltage, the process proceeds to step a14.

  As described above, when the humidity in the heating chamber 3 immediately after the start of heating is lower than the initial value set in step a5 by the processing of steps a9 to a11, the measured humidity (output voltage E) is set as the initial value Emin. Is set. The initial value Emin is corrected in the cooking device 1 in order to discharge the water vapor generated in the previous heating and remaining in the heating chamber 3 to the outside. , 27b is supplied to the heating chamber 3 and the air in the heating chamber 3 is discharged to the outside of the cooker 1, so that the humidity may be lower than a predetermined initial value. It is. By correcting the initial value Emin in this way, it is possible to accurately determine the amount of increase in humidity described later.

  In step a9, when the elapsed time T becomes 8 seconds or more, the process proceeds to step a12, and it is determined whether or not the measured output voltage E−initial value Emin <0.5. This determination corresponds to whether or not the amount of increase in humidity based on the start of heating is less than a predetermined reference amount. If the difference between the measured output voltage E and the initial value Emin is 0.5 (V) or more, it can be determined that water vapor is generated, and thus the process proceeds to step a13 and the flag Fe is set to 0. The process proceeds to step a14. On the other hand, if the difference between the measured output voltage E and the initial value Emin is less than 0.5 (V), it can be determined that water vapor is not generated, and thus the process proceeds to step a14.

  It should be noted that, after 8 seconds have elapsed from the start of heating, whether or not the measured output voltage E−initial value Emin <0.5 is determined is that heating is performed for about 8 seconds from the start of heating. This is because water vapor is hardly generated even when an object is heated.

  In step a14, the control unit 38 measures the temperature t (° C.) of the thermistor 29. In step a15, it is determined whether or not the measured temperature t <the set temperature t0 of the thermistor 29. If the measured temperature t is equal to or higher than the set temperature t0 of the thermistor 29, the process proceeds to step a16. After the flag Ft is set to 1, the process proceeds to step a17. On the other hand, if the measured temperature t is lower than the set temperature t0 of the thermistor 29, the process proceeds directly to step a17. The set temperature t0 is set to a value higher than the temperature of the magnetrons 15a and 15b at the time of normal microwave heating with the article 29 to be heated in the heating chamber 3, for example. In this embodiment, it is set to 190 ° C.

  In step a17, it is determined whether or not the product Ft * Fe = 1 of the flags Ft and Fe. If Ft * Fe = 1, the process returns to step a6. The case where Ft * Fe is not 1 is a case where at least one of the flags Ft and Fe is 0, and this condition is satisfied when the measured temperature t of the thermistor 29 does not reach the set temperature t0. 3 is a case where water vapor is generated in the heating chamber 3, or a case where the measured temperature t of the thermistor 29 does not reach the set temperature t0 and the water vapor is generated in the heating chamber 3.

  On the other hand, if Ft * Fe = 1 in step a17, the process proceeds to step a18 to determine whether or not the elapsed time T ≧ 120. When the elapsed time T is less than 120 (seconds), which is a predetermined average heating time, the process returns to step a6 and heating is continued. On the other hand, when the elapsed time T is 120 (seconds) or longer, the process proceeds to step a19, where it is determined that there is no object to be heated 25 in the heating chamber 3, and the heating is stopped. An error message is displayed on the unit 6 and the process is terminated.

  The case where Ft * Fe = 1 is the case where both the flags Ft and Fe are 1, and this condition is satisfied when the measured temperature t of the thermistor 29 is equal to or higher than the set temperature t0 and in the heating chamber 3 This is a case where no water vapor is generated. Since this state is considered that there is no object to be heated 25 in the heating chamber 3, if heating is continued, damage to the magnetrons 15a and 15b, deformation due to melting of resin parts, and breakage due to red heat of the tray may occur. Very expensive.

  Therefore, in this embodiment, when the measured temperature t of the thermistor 29 is equal to or higher than the set temperature t0 before 120 (seconds) elapses from the start of heating, and no steam is generated in the heating chamber 3, The microwave heating is continued, and the microwave heating is stopped when 120 (seconds) has elapsed from the start of heating. Further, when the measured temperature t of the thermistor 29 is equal to or higher than the set temperature t0 after 120 (seconds) from the start of heating, and no steam is generated in the heating chamber 3, the microwave is generated at that time. The heating is stopped.

  In step a7, when the elapsed time T becomes equal to or longer than the heating time Ta, the process proceeds to step a21, the heating is stopped, and the process is terminated.

  As described above, according to the present embodiment, the presence / absence of the object to be heated 25 in the heating chamber 3 is determined based on the temperature of the magnetron 15b and the humidity in the heating chamber 3, so that the temperature of the magnetron 15b is conventionally changed. Compared with the case where only the determination is made, it is possible to determine the presence or absence of the object to be heated 25 in the heating chamber 3 more accurately. Therefore, it is possible to prevent the heating from stopping in the middle of the heating chamber 3 in the heating chamber 3 as in the conventional case, and the heating target 25 can be cooked appropriately. . Further, when it is determined that there is no object to be heated 25 in the heating chamber 3, by stopping the heating, damage or deterioration of the magnetrons 15a and 15b, deformation due to melting of resin parts in the heating chamber 3, It is possible to prevent breakage of the cooking device 1 such as breakage due to red heat.

  In the cooking device 1, the difference between the output voltage E of the humidity sensor 37 and the initial output voltage Emin of the humidity sensor 37 after 8 seconds from the start of heating is less than 0.5 (V), and the detected temperature of the thermistor 29. Microwave heating is stopped when three conditions are satisfied, that is, t is equal to or higher than the set temperature t0 and 120 seconds, which is an average heating time, has elapsed since the start of heating.

  First, one of the conditions is that the difference between the output voltage E of the humidity sensor 37 and the initial output voltage Emin of the humidity sensor 37 after 8 seconds from the start of heating is less than 0.5 (V). This is because moisture hardly evaporates from the object to be heated 25 until 8 seconds have elapsed from the start. Further, one of the conditions that the detected temperature t of the thermistor 29 is equal to or higher than the set temperature t0 is that the temperature of the magnetrons 15a and 15b is obtained when microwave heating is performed without the heated object 25 in the heating chamber 3. This is because the temperature rises above the set temperature t0.

  Furthermore, one of the conditions that the average heating time of 120 seconds has elapsed since the start of heating is the presence or absence of the object to be heated 25 based on the temperature of the magnetron 15b and the amount of increase in humidity in the heating chamber 3. This is because the object to be heated 25 can be heated even when an erroneous determination occurs when determining the above. That is, the temperature of the magnetron 15b may vary greatly depending on the use state of the cooking device 1, and the humidity in the heating chamber 3 may hardly increase depending on the type and state of the object to be heated 25. Therefore, even when the object to be heated 25 is present in the heating chamber 3, it may be determined that there is no object to be heated 25. In this case, if the microwave heating is stopped immediately, the object to be heated 25 is not sufficiently heated. Therefore, it is necessary to heat the object to be heated 25 again, which is troublesome.

  Therefore, the cooker 1 is configured to heat the article to be heated 25 only for a predetermined average heating time of 120 seconds. As a result, the object to be heated 25 can be prevented from being insufficiently heated, and sufficient cooking can be performed. For example, when the cooking device 1 is used in a convenience store (that is, when the cooking device 1 is used for business purposes), the type of the heated object to be heated by the cooking device 1 is limited to a lunch box or a rice ball. And the optimal heating time for lunch boxes and rice balls is shorter than 120 seconds. The average heating time can be determined from these heating times.

  In the cooking device 1, microwave heating continues until 120 seconds elapses even when the measured temperature t of the thermistor 29 is equal to or higher than the set temperature t0 and no steam is generated in the heating chamber 3. Therefore, the measurement temperature t of the thermistor 29, that is, the temperature of the magnetrons 15a and 15b may rise to a temperature that greatly exceeds the set temperature t0, for example, 190 ° C. However, since the magnetron itself is not damaged even when it reaches a considerably high temperature (for example, 400 ° C.), there is no particular problem in continuing the heating at the set temperature t0 or higher. However, since the life of the magnetron is shortened when the temperature becomes high, it is not preferable to continue heating at the set temperature t0 or more for a long time. Therefore, microwave heating is stopped at 120 seconds, which is the average heating time, as described above.

  Moreover, in the cooking device 1, since the initial value Emin of the humidity sensor 37 can be set accurately, the determination accuracy of the presence / absence of water vapor generation in the heating chamber 3 is improved, and the presence / absence of the object 25 to be heated in the heating chamber 3 is improved. Can be judged more accurately.

  In addition, in the cooking device 1, when it is determined that there is no object to be heated 25 in the heating chamber 3 and the microwave heating is stopped, an error message is displayed on the display unit 6. Thereby, the user of the cooking device 1 can check the error message and take an appropriate response. For example, when there is no object to be heated 25 in the heating chamber 3, it is considered that the user forgot to put the object to be heated 25, and therefore, the object to be heated 25 may be put in the heating chamber 3 and heated again. Moreover, when the to-be-heated material 25 exists in the heating chamber 3, since it is thought that heating was performed continuously several times, what is necessary is just to use it, after making the cooker 1 rest for a while. At this time, when the object to be heated 25 in the heating chamber 3 is not sufficiently heated, the object to be heated 25 may be heated again.

  Moreover, in the cooking device 1, the humidity sensor 37 is a resistance element type humidity sensor using two thermistors, and one thermistor is arranged in a sealed space, and is based on the same principle as a dry-wet humidity meter. Detect humidity. Since the resistance element type humidity sensor 37 using two thermistors is relatively inexpensive, the manufacturing cost of the cooking device 1 can be reduced.

  Moreover, in the cooking appliance 1, since the humidity sensor 37 is attached in the vicinity of the outside exhaust duct 22 that exhausts the air in the heating chamber 3 to the outside, the humidity in the heating chamber 3 can be accurately detected.

  In the cooking device 1, the thermistor 29 is attached at a position close to or in contact with the anode 30 portion of the magnetron 15b, so that the temperature of the magnetron 15b can be accurately detected.

  In addition, in the cooking device 1, the thermistor 29 is attached to the cooling fin 34 of the magnetron 15b that is not directly blown by the cooling air, for example, the lee of the cooling air, so that the magnetron 15b is not affected by the cooling air. The temperature can be accurately detected.

  The present invention can be applied to a cooking device provided with a magnetron. The present invention can also be applied to a cooker provided with an electric heater in addition to a magnetron. Furthermore, it is preferable to apply this invention to the cooker for business which is used in a convenience store. This is because commercial cookers are often used in harsh conditions, such as being used in two stages, or being heated several times in succession. This is because judgment is likely to occur.

It is a block diagram which shows the basic electric constitution of the cooking appliance 1 which is one Embodiment of this invention. It is a perspective view which shows the external appearance of the cooking appliance. 2 is a cross-sectional view illustrating a schematic configuration of the cooking device 1. FIG. It is sectional drawing of the cooking device 1 seen from the cut surface line IV-IV of FIG. It is a figure which shows the shape of the magnetron 15b, (a) is a front view, (b) is sectional drawing seen from the cut surface line bb of (a). It is a flowchart for demonstrating the control action of the cooking appliance. It is a flowchart for demonstrating the no-load state detection process in the conventional cooking appliance.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cooker 2 Casing 3 Heating chamber 4 Door 5 Operation part 6 Display part 7 Key input part 8 Cavity top plate 9 Cavity bottom plate 10 Cavity rear plate 11 Cavity left side plate 12 Cavity right side plate 13 Bottom plate 14 Frame 15a Magnetron 15b Magnetron 16a Guide Wave tube 16b Waveguide 17a Feed opening 17b Feed opening 18a Radio wave agitating blade 18b Radio wave agitating blade 19a Gard motor 19b Gard motor 20a Fixed pin 20b Fixed pin 21 Inside exhaust duct 22 Outside exhaust duct 23 Protective cover 24 Tray 25 Heated object 26a High voltage transformer 26b High voltage transformer 27a Cooling fan 27b Cooling fan 28a Duct 28b Duct 29 Thermistor 30 Anode 31 Permanent magnet 32 Yoke 33 Microwave output antenna 34 Anode cooling fan 35 Filter box 36 Cathode connection terminal 37 Humidity sensor 38 Control unit C High voltage capacitor D High voltage diode DS1 First door switch DS2 Second door switch MA Anode MK Cathode MS Monitor switch R Magnetron drive relay RC Half-wave voltage doubler rectifier circuit T1 Primary winding T2 Secondary winding TH Heater winding V AC power supply

Claims (9)

  A heating chamber in which an object to be heated is stored, a magnetron that supplies microwaves to the heating chamber, a cooling fan that supplies cooling air for cooling the magnetron, and a temperature detection element that detects the temperature of the magnetron A humidity detection element for detecting the humidity in the heating chamber, and the presence or absence of an object to be heated in the heating chamber based on the detected values of the temperature detection element and the humidity detection element, and the object to be heated in the heating chamber A cooking device comprising: control means for stopping microwave heating by the magnetron when it is determined that there is not.   2. The cooking device according to claim 1, wherein the controller is configured such that the amount of increase in humidity with respect to the start of heating after the elapse of a predetermined time after the start of heating is less than a predetermined reference amount, and the detected temperature is a predetermined reference temperature. A cooker characterized in that microwave heating is stopped when three conditions are satisfied, that is, a predetermined average heating time has elapsed from the start of heating.   The cooker according to claim 2, wherein the control means detects the humidity in the heating chamber from the start of heating until a predetermined time elapses, and when the detected humidity is equal to or higher than a predetermined initial value, When the initial value is the reference humidity and the detected humidity is less than the initial value, the detected humidity is set as the reference humidity, and the difference between the detected humidity and the reference humidity after the lapse of a predetermined time is calculated to increase the humidity. A cooking device characterized by seeking.   The cooker according to any one of claims 1 to 3, wherein the control means outputs an error message after determining that there is no object to be heated in the heating chamber and stopping microwave heating. Cooking device.   The cooker according to any one of claims 1 to 4, wherein the humidity detection element is a resistance element type humidity sensor using two thermistors, and one thermistor is arranged in a sealed space. A cooking device characterized by being.   The cooker according to any one of claims 1 to 5, wherein the humidity detecting element is attached in the vicinity of an exhaust duct that exhausts the air in the heating chamber to the outside.   The cooker according to any one of claims 1 to 6, wherein the temperature detection element is attached to a position close to or in contact with an anode portion of the magnetron.   8. The cooking device according to claim 7, wherein the temperature detecting element is attached at a position where the cooling air from the cooling fan is not directly blown.   9. The cooker according to claim 8, wherein the temperature detecting element is attached to a cooling fin of the magnetron located on the leeward side of the cooling air.

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