Patent Publication Number: US-2012043316-A1

Title: High-frequency heating equipment

Description:
TECHNICAL FIELD 
     The present invention relates to a high-frequency heating equipment that can sense fast a temperature of a magnetron and halt operation of the high-frequency heating equipment in a case of no load running, i.e. no object to be heated exists in a heating chamber of the high-frequency heating equipment. 
     BACKGROUND ART 
     A conventional high-frequency heating equipment includes multiple cooling fins provided to a magnetron, and a temperature sensor is mounted to an outside cooling fin of the multiple cooling fins. This conventional example is disclosed in, e.g. Patent Literature 1, and is described hereinafter with reference to  FIG. 11-FIG .  13 . 
     High-frequency heating equipment  1  has heating chamber  2 , and magnetron  3  oscillates electromagnetic waves, thereby heating object to be heated  5  placed on tray  4  in heating chamber  2 . 
     High-frequency heating equipment  1  comprises the following structural elements:
         power supply  6  that supplies a high voltage to magnetron  3  for driving magnetron  3 ;   cooling fan  7  for cooling magnetron  3  and power supply  6 ;   controller  8  for transmitting electric signals to magnetron  3  and power supply  6 ; and   air guide  9  mounted to magnetron  3  for introducing airflow generated by cooling fan  7  into heating chamber  2 .       

     Multiple cooling fins  3 B are provided to magnetron  3 . Temperature sensor  10  is mounted to outside cooling fin  3 C of multiple cooling fins  3 B. The temperature sensed by temperature sensor  10  is transmitted to controller  8 , and when temperature sensor  10  senses a temperature not lower than a threshold temperature, controller  8  stops the operation of high-frequency heating equipment  1 . 
     The foregoing structure allows the conventional high-frequency heating equipment to work in a regular way, namely, a user puts object to be heated  5  on tray  4  in heating chamber  2 , and inputs a heating method and other conditions through operating section  8 , and then starts heating. This operation prompts power supply  6  to supply a high voltage to magnetron  3 , thereby supplying electromagnetic waves into heating chamber  2  for heating object to be heated  5 . 
     Motor  11  starts rotating at the same time when power supply  6  starts supplying the high voltage to magnetron  3 , and cooling fan  7  mounted on the shaft of motor  11  thus generates airflow to cool magnetron  3  and power supply  6 . Temperature sensor  10  senses a temperature of cooling fins  3 B of magnetron  3 . However, most of the electromagnetic waves are absorbed into object to be heated  5  in heating chamber  2 , and only a little amount of the electromagnetic waves are reflected to anode  3 A of magnetron  3 . The temperature of magnetron  3  thus stays lower than a given temperature, and the heating is kept going. 
     Starting the heat without object to be heated  5  in heating chamber  2  allows most of the electromagnetic waves to reflect and return to magnetron  3 , so that anode  3 A of magnetron  3  is heated, and this heat travels to cooling fins  3 B, thereby raising a temperature of temperature sensor  10 . When the temperature of temperature sensor  10  reaches a given temperature, controller  8  cuts off power supply  6 . Magnetron  3  thus halts its oscillation, so that an abnormality, e.g. thermal runaway or thermal deformation in resin components can be prevented. 
     Another conventional high-frequency heating equipment uses a temperature sensor that senses an ambient temperature of a magnetron (high frequency generator), and a sensed signal is transmitted to a controller. This example is disclosed in, e.g. Patent Literature 2, and is described hereinafter with reference to  FIG. 14 . 
     High-frequency heating equipment  12  comprises the following structural elements: heating chamber  13  for accommodating an object to be heated, magnetron  3  for supplying electromagnetic waves into heating chamber  13 , power supply  14  for driving magnetron  3 , cooling fan  15  for cooling magnetron  3  and power supply  14 , temperature sensor  16  for sensing an ambient temperature of magnetron  3 , and a controller (not shown) for controlling electric components with a sensed signal supplied from temperature sensor  16 . 
     The foregoing structure allows temperature sensor  16  to sense the ambient temperature of magnetron  3  during a no-load running, i.e. no object to be heated existing in heating chamber  13 . When the ambient temperature of magnetron  3  exceeds a given temperature, magnetron  3  halts its oscillation or lowers its output, so that an abnormality, e.g. a breakdown of magnetron  3  due to a thermal runaway or a thermal deformation in resin components, can be prevented. 
     Conventional high-frequency heating equipment  1  disclosed in Patent Literature 1; however, has the following problem: If the heating starts with no object to be heated  5  in heating chamber  2 , most of the electromagnetic waves traveling into chamber  2  reflects and returns to magnetron  3 , so that anode  3 A of magnetron  3  is heated and the temperature rise of anode  3 A is conveyed to ambient subjects by means of, e.g. the heat conduction to cooling fins  3 B, the heat radiation from the surface of anode  3 A, the heat convection from the surface of anode  3 A and the surface of cooling fins  3 B. The temperature of temperature sensor  10  mounted to outside cooling fin  3 C of magnetron  3  rises only due to the heat convection. 
     A temperature rise during the no-load state or a temperature rise during a light-load state, e.g. a slice of bacon or some pop-corns, should be determined with a ratio of a quantity of heat produced by the heat convection vs. the total quantity of heat produced by the heat convection, heat conduction and heat radiation. However, the temperature rise per se disperses because there are dispersion factors such as dispersion in the mounting state of temperature sensor  10 , deformation of cooling fins  3 B, and dispersion in the rpm of cooling fan  7 . It can be thus concluded that it is very difficult to accurately detect and control the no-load state based on a small difference in temperatures. 
     If the temperature rise of magnetron  3  cannot be sensed accurately, magnetron  3  encounters a thermal runaway and breaks down, or resin components, e.g. air guide  9 , are deformed. Broken-down magnetron  3  thus needs to be replaced with a new one, so that this high-frequency heating equipment has a disadvantage in view of resource saving. 
     On top of that, since temperature sensor  10  is placed outside cooling fins  3 B, it is subjected to the airflow supplied from cooling fan  7  or the room temperature. Temperature sensor  10  thus tends to malfunction. For instance, anode  3 A of magnetron  3  stays at a high temperature during the no-load running even if the room temperature stands at 0(zero)° C. However, outside cooling fin  3 C is cooled by the airflow at 0(zero)° C. supplied from cooling fan  7 , so that a detection of the temperature rise is delayed, and magnetron  3  falls in danger of breaking down. 
     On the other hand, the temperature of temperature sensor  10  rises faster when the room temperature stands at as high as 30° C., and a halting signal is transmitted to controller  8 . As a result, even in a light-load running, magnetron  3  stops its oscillation and a cooking might be halted halfway. 
     High-frequency heating equipment  12  disclosed in Patent Literature 2 is formed of temperature sensor  16  that senses an ambient temperature of magnet  3  and a controller that controls electric components with a sensed signal supplied from temperature sensor  16 . Temperature sensor  16  determines whether a temperature rise is caused by a no-load running or a light-load running based on a ratio of a quantity of heat produced by the heat convection vs. the total quantity of heat produced by the heat convection, conduction and radiation. However, a mounting state of temperature sensor  16 , deformation of cooling fan  15 , and dispersion of the rpm of cooling fan  15  cause dispersion of the temperature rise of temperature sensor  16 . It can be thus concluded that it is very difficult to accurately detect and control the no-load state based on a small difference in temperatures. 
     Conventional high-frequency heating equipment  12  employs bulky temperature sensor  16  which occupies a rather large area, so that temperature sensor  16  senses a temperature rise with a time delay from an actual temperature rise of anode  3 A of magnetron  3 . The follow-up action of temperature sensor  16  thus becomes insubstantial due to dispersion in performance of magnetron  3  or when magnetron  3  encounters a sharp temperature rise caused by an inadequate matching between heating chamber  13  and magnetron  3 . The foregoing factors might induce a thermal runaway of magnetron  3 , which then breaks down, or invite melt-down of resin components near magnetron  3 .
         1. Unexamined Japanese Patent Application Publication No. 2002-260841   2. Unexamined Japanese Patent Application Publication No. 2004-265819       

     DISCLOSURE OF INVENTION 
     The present invention determines accurately whether a temperature of a magnetron is raised by a no-load running in a heating chamber or a light-load running, e.g. a slice of bacon or popcorn in the heating chamber, and reduces a risk of break down of the magnetron due to the temperature rise or a risk of melt-down of resin components. In other words, a malfunction, such as a light-load running is erroneously determined as a no-load running, and thereby halting a cooking operation halfway, can be prevented. The present invention thus can provide a high-frequency heating equipment that can be handled by a user with more ease and more safety and has an advantage in view of resource saving. 
     The high-frequency heating equipment of the present invention comprises the following structural elements:
         a heating chamber for accommodating an object to be heated;   a magnetron including multiple cooling fins and radiating electromagnetic waves into the heating chamber;   a power supply for driving the magnetron;
 
a cooling fan for cooling the magnetron and the power supply;
   a temperature sensor for sensing a temperature of the magnetron;   a mounting bracket holding the temperature sensor;   an air guide for guiding an airflow supplied by the cooling fan; and   a controller for controlling the power supply, the magnetron, and the cooling fan.       

     The temperature sensor is mounted with the mounting bracket such that the temperature sensor is pressed by a lateral face of the cooling fins, and an end of the temperature sensor points to an anode of the magnetron on the downwind side of the cooling fan. 
     The structure discussed above allows the temperature sensor to sense a temperature close to the temperature of the anode of the magnetron, so that dispersing factors, e.g. a mounting state of the mounting bracket, deformation of the cooling fan, and dispersion in the rpm of the cooling fan, are excluded from causing the temperature sensor to delay sensing a temperature rise. As a result, a risk of thermal runaway which may break down the magnetron as well as a risk of melt-down of the resin components near the magnetron can be reduced. Replacements of the broken-down magnetron or melt-down components with new ones can be thus reduced, so that the high-frequency heating equipment of the present invention is advantageous in view of resource saving. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a sectional view of a high-frequency heating equipment in accordance with a first embodiment of the present invention. 
         FIG. 2  is a plan view of an essential part of the high-frequency heating equipment in accordance with the first embodiment. 
         FIG. 3  is a front view of an essential part of the high-frequency heating equipment in accordance with the first embodiment. 
         FIG. 4  is a plan view of a temperature sensor in accordance with the first embodiment. 
         FIG. 5  is a front view of a temperature sensor in accordance with the first embodiment. 
         FIG. 6A  shows variations in temperature during a no-load running in accordance with the first embodiment. 
         FIG. 6B  is a graph of the variations in temperature during the no-load running. 
         FIG. 7A  shows variations in temperature during a light-load running in accordance with the first embodiment. 
         FIG. 7B  is a graph of the variations in temperature during the light-load running. 
         FIG. 8A  shows differences in temperature between the no-load running and the light-load running in accordance with a first embodiment of the present invention. 
         FIG. 8B  is a graph of the differences in temperature between the no-load running and the light-load running. 
         FIG. 9  is a lateral view cutaway in part of a mounting bracket in accordance with a second embodiment of the present invention. 
         FIG. 10  is a lateral view of a mounting bracket in accordance with a third embodiment of the present invention. 
         FIG. 11  is a lateral view illustrating a structure of a conventional high-frequency heating equipment. 
         FIG. 12  is a plan view illustrating an essential part of the conventional high-frequency heating equipment. 
         FIG. 13  is a front view illustrating an essential part of another conventional high-frequency heating equipment. 
         FIG. 14  is a lateral view illustrating a structure of the another conventional high-frequency heating equipment. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Exemplary embodiments of the present invention are demonstrated hereinafter with reference to the accompanying drawings. The present invention is not limited to these embodiments. 
     Exemplary Embodiment 1 
       FIG. 1  is a perspective view of a high-frequency heating equipment in accordance with the first embodiment of the present invention.  FIG. 2  and  FIG. 3  are a plan view and a front view of an essential part, i.e. a structure of a magnetron, of the present.  FIG. 4  and  FIG. 5  are a plan view and a front view of a temperature sensor in accordance with the first embodiment.  FIG. 6  shows variations in temperature during a no-load running in accordance with the first embodiment.  FIG. 7  shows variations in temperature during a light-load (water 100 cc) running in accordance with the first embodiment.  FIG. 8  shows differences in temperature between the no-load running and the light-load (water 100 cc) running in accordance with a first embodiment of the present invention. 
     In  FIG. 1-FIG .  5 , high-frequency heating equipment  17  in accordance with this first embodiment includes heating chamber  18  for accommodating object to be heated  5 , magnetron  3  having multiple cooling fins  3 B and radiating electromagnetic waves into heating chamber  18 , power supply  19  for driving magnetron  3 , and cooling fan  20  for cooling magnetron  3  and power supply  19 . High-frequency heating equipment  17  further includes temperature sensor  21  for sensing a temperature of magnetron  3 , mounting bracket  22  for holding temperature sensor  21 , air guide  23  for guiding an airflow supplied from cooling fan  20 , and controller  24  for controlling power supply  19 , magnetron  3  and cooling fan  20 . High-frequency heating equipment  17  in accordance with this first embodiment still further includes temperature sensor  21  is mounted with mounting bracket  22  such that temperature sensor  21  can be pressed by a lateral face of cooling fins  3 B and an end of temperature sensor  21  points to anode  3 A of magnetron  3  on the downwind side of cooling fan  20 . As shown in  FIG. 2  and  FIG. 3 , temperature sensor holding section  22 A of mounting bracket  22  restricts airflow  25  (indicated with arrows) from cooling fan  20  toward temperature sensor  21   
     To be more specific, temperature sensor  21  is held by temperature sensor holding section  22 A at approx. center (inside of the both ends at the sides of cooling fins  3 B) of multiple cooling fins  3 B. Lateral face  21 A of temperature sensor  21  touches cooling fins  3 B and is pressed by cooling fins  3 B, and end  21 B of temperature sensor  21  is held by mounting bracket  22  such that end  21 B can be headed for anode  3 A on the downwind side of cooling fan  20 . Air guide  23  is often formed of resin material. Multiple cooling fins  3 B are fixed at each of their both ends with yokes  3 D. 
     In the case of no-load running, i.e. no object to be heated in heating chamber  18 , the foregoing structure allows most of the electromagnetic waves radiated from magnetron  3  to reflect on chamber  18  and returns to magnetron  3 , thereby raising the temperature of anode  3 A of magnetron  3 . The heat of anode  3 A raises the temperature of temperature sensor  21  by means of radiation, conduction to cooling fins  3 B, and convection to the ambient air. The temperature of temperature sensor  21  thus rises close to that of anode  3 A. 
     When temperature sensor  21  senses a given threshold temperature, controller  24  halts the operation, thereby preventing magnetron  3  from falling in a thermal runaway which may result in breaking down magnetron  3 . 
     Since temperature sensor  21  is excellent in the follow-up action, high-frequency heating equipment  17  can determine without fail whether the operation is a no-load running or a light-load running. High-frequency heating equipment  17  thus invites fewer malfunctions and expects stable performance, and the user can handle high-frequency heating equipment  17  with more ease and with safety. 
     The temperature variation characteristics in accordance with this first embodiment are shown in  FIG. 6A-FIG .  8 B. For instance,  FIGS. 6A and 6B  show variations in temperature and the graph thereof during the no-load running in accordance with the first embodiment. As shown in  FIGS. 6A and 6B , the temperature of anode  3 A of high-frequency heating equipment  17  rises to 271° C. in 10 minutes after the start of no-load running, i.e. no object to be heated  5  in heating chamber  18 , and temperature sensor  21  senses a temperature of 247° C. 
     In the case of conventional example  1  disclosed in Patent Literature  1 , the temperature sensor is mounted to outside cooling fin  3 C, and the temperature sensor senses the temperature of 157° C. In the case of conventional example 2 disclosed in Patent Literature 2, the temperature sensor senses a temperature of 212° C. as the ambient temperature of magnetron  3 . These comparisons prove that temperature sensor  21  in accordance with the first embodiment can sense the temperature close to that of anode  3 A of magnetron  3 , so that temperature sensor  21  can positively measure the anode temperature of magnetron  3 . 
       FIGS. 7A and 7B  show variations in temperature and the graph thereof during the light-load running in accordance with the first embodiment. In this instance, the temperature variation of water 100 cc in 10 minutes is measured. The anode temperature of magnetron  3  shows 177° C. in 10 minutes after the light-load running starts, and temperature sensor  21  senses 168° C. Conventional example 1 disclosed in Patent Literature 1 senses 123° C., while conventional example 2 disclosed in Patent Literature 2 senses 151° C. These comparisons prove that temperature sensor  21  in accordance with this first embodiment can sense the temperature close to the temperature of anode  3 A of magnetron  3 , so that it can be concluded that temperature sensor  21  can positively sense the anode temperature of magnetron  3 . 
       FIGS. 8A and 8B  show differences in temperature and the graph thereof between the no-load running and the light-load running. The temperature difference between the no-load running and the light-load running (water 100 cc) exhibits the following facts: in the case where anode  3 A of magnetron  3  has a difference of (271-177)=94 degrees, temperature sensor  21  in accordance with this embodiment has a difference of (247-168)=79 degrees, and conventional example 1 disclosed in Patent Literature 1 has a difference of (157-123)=34 degrees, and conventional example 2 disclosed in Patent Literature 2 has a difference of (212-151)=61 degrees. 
     These comparisons prove that temperature sensor  21  can determine with ease whether the operation is a no-load running or a light-load running within the wider temperature range of 79 degrees, while the conventional examples are obliged to determine with difficulty within the smaller temperature range of 34 degrees or 61 degrees. 
     As discussed above, this first embodiment allows temperature sensor  21  to sense a temperature close to that of anode  3 A of magnetron  3 . The dispersion factors, such as the mounting state of temperature sensor  21 , deformation of cooling fan  20 , dispersion in the rpm of cooling fan  20 , are thus excluded from causing temperature sensor  21  to delay sensing a temperature rise. As a result, high-frequency heating equipment  17  in accordance with this embodiment can prevent magnetron  3  from falling into a thermal runaway which may result in break down of magnetron  3 , and can prevent the resin components, such as air guide  23 , from melting down. On top of that, replacements of the broken down magnetron  3  or the melt-down resin components with new ones can be reduced, so that high-frequency heating equipment  17  is advantageous in view of resource saving. 
     Exemplary Embodiment 2 
       FIG. 9  is a lateral view cutaway in part of a mounting bracket in accordance with the second embodiment of the present invention ( FIG. 9  is a profile viewed from the right side of  FIG. 3 ). As shown in  FIG. 9 , mounting bracket  22  restricts airflow  25  from cooling fan  20  to temperature sensor  21  (refer to arrows). To be more specific, mounting bracket  22  shuts off airflow  25  so that temperature sensor  21  cannot be cooled by cooling fan  20 . 
     The foregoing structure allows holding section  22 A of mounting bracket  22  to shut off the airflow blown from cooling fan  20  to temperature sensor  21  which shows a temperature rise due to the heat from anode  3 A of magnetron  3 . Airflow  25  around temperature sensor  21  thus stagnates as arrows indicate, so that airflow  25  less cools temperature sensor  21 . 
     Temperature sensor  21  senses the temperature rise caused by the heat from anode  3 A of magnetron  3 ; however, the airflow supplied from cooling fan  20  suppresses this temperature rise. The structure discussed above allows suppressing the temperature rise, thereby preventing temperature sensor  21  to delay sensing the given temperature. As a result, the risk of breaking down magnetron  3  or the risk of melting down the resin components, e.g. air guide  23 , can be reduced. 
     Replacements of the broken magnetron  3  or melted air-guide  23  with new ones can be thus reduced, so that high-frequency heating equipment  17  is advantageous in view of resource saving. 
     Exemplary Embodiment 3 
       FIG. 10  is a lateral view illustrating a structure in accordance with the third embodiment. As shown in  FIG. 10 , mounting bracket  22  for holding temperature sensor  21  is clamped between yokes  3 D of magnetron  3  and air guide  23  placed on downwind side of airflow  25  supplied from cooling fan  20 . 
     The foregoing structure allows airflow  25  supplied from cooling fan  20  to less affect mounting bracket  22  because mounting bracket  22  is covered by air guide  23 , so that mounting bracket  22  can prevent the temperature of temperature sensor  21  from lowering. The third embodiment thus can prevent temperature sensor  21  from the delay of sensing the given temperature, thereby reducing the risk of breaking down magnetron  3  or the risk of melting down the resin components, e.g. air guide  23 . On top of that, replacements of broken magnet  3  or melted air guide  23  with new ones can be reduced. The high-frequency heating equipment in accordance with the third embodiment is thus advantageous in view of resource saving. 
     As discussed previously, the high-frequency heating equipment of the present invention comprises the following structural elements:
         a heating chamber for accommodating an object to be heated;   a magnetron including multiple cooling fins and radiating electromagnetic waves into the heating chamber;   a power supply for driving the magnetron;   a cooling fan for cooling the magnetron and the power supply;   a temperature sensor for sensing a temperature of the magnetron;   a mounting bracket holding the temperature sensor;   an air guide for guiding an airflow supplied by the cooling fan; and   a controller for controlling the power supply, the magnetron, and the cooling fan.       

     The temperature sensor is mounted with the mounting bracket such that the temperature sensor is pressed by a lateral face of the cooling fins, and an end of the temperature sensor points to an anode of the magnetron on the downwind side of the cooling fan. 
     The foregoing structure allows mounting the temperature sensor such that the cooling fins can press the temperature sensor on the lateral face and the end of the temperature sensor points to the anode of the magnetron on the downwind side of the cooling fan. In the case of a no-load running, i.e. no object to be heated in the heating chamber, most of the electromagnetic waves radiated from the magnetron reflect on the heating chamber and returns to the magnetron, thereby raising the temperature of the anode of the magnetron. The heat of the magnetron raises the temperature of the temperature sensor by means of radiation, conduction to the cooling fins, and convection to the ambient air, so that the temperature sensor senses a temperature close to that of the anode of the magnetron. This mechanism allows the temperature sensor to sense a given threshold temperature for the controller to perform control operation, e.g. halting the operation of the high-frequency heating equipment. The magnetron thus can be prevented without fail from falling into a thermal runaway which may result in a breakdown of the magnetron. 
     The temperature sensor is excellent in follow-up action, and it can determine without fail whether the operation is a no-load running or a light-load running, so that the high-frequency heating equipment with stable quality and fewer malfunctions is obtainable. The users thus can use this high-frequency heating equipment with ease. 
     The temperature sensor can sense a temperature close to the anode temperature of the magnetron. Therefore, dispersing factors, e.g. a mounting state of the mounting bracket, deformation of the cooling fan, and dispersion in the rpm of the cooling fan, are excluded from causing the temperature sensor to delay sensing a temperature rise. As a result, a risk of thermal runaway which may break down the magnetron as well as a risk of melt-down of the resin components, e.g. the air guide near the magnetron, can be reduced. Replacements of the broken-down magnetron or melt-down components with new ones can be thus reduced, so that the high-frequency heating equipment of the present invention is advantageous in view of resource saving. 
     The present invention includes the mounting bracket that provides a structure of restricting the airflow from the cooling fan to the temperature sensor. This structure allows mitigating the suppression of the temperature rise of the temperature sensor. Because the heat from the anode of the magnetron anode raises the temperature of the temperature sensor; however, the airflow from the cooling fan suppresses this temperature rise, and this suppression causes the temperature sensor to delay sensing the threshold temperature. As a result, the mitigation of the suppression prevents the magnetron from falling into a breakdown or the resin components from melting down. The replacements of the broken magnetron or the melted components with new ones can be reduced, so that the high-frequency heating equipment is advantageous in view of resource saving. 
     The mounting bracket of the present invention is clamped between the yoke of the magnetron and the air guide disposed on the downwind side of the cooling fan. This structure allows the mounting bracket to be covered with the air guide, so that the cooling air supplied from the cooling fan less affects the temperature sensor, and the mounting bracket suppresses the reduction in temperature of the temperature sensor. This mechanism prevents the temperature sensor from delaying a sense of the threshold temperature, so that a risk of breaking down the magnetron or melting down the resin components can be reduced. 
     The mounting bracket of the present invention is mounted inside of both the ends at one side of the cooling fins. This structure allows the temperature sensor to be placed near the center of the cooling fins, so that the temperature sensor can sense a temperature close to the anode temperature of the magnetron in a faster and a more reliable manner. The no-load running or the light-load running can be thus determined in a more reliable manner, so that stable performance and fewer malfunctions can be expected. The magnetron can be prevented more positively from falling into the thermal runaway which may result in a breakdown of the magnetron. 
     INDUSTRIAL APPLICABILITY 
     A high-frequency heating equipment of the present invention is excellent in follow-up action, so that it can determine whether the operation is no-load running or a light-load running in a reliable manner. The high-frequency heating equipment with stable performance and fewer malfunctions is thus obtainable. The high-frequency heating equipment can prevent without fail the magnetron from falling into a thermal runaway that invites a breakdown of the magnetron. The high-frequency heating equipment is thus useful not only for home use but also for various applications including professional use. 
     DESCRIPTION OF REFERENCE SIGNS 
       3  magnetron 
       3 A anode 
       3 B cooling fin 
       3 D yoke 
       5  object to be heated 
       17  high-frequency heating equipment 
       18  heating chamber 
       19  power supply 
       20  cooling fan 
       21  temperature sensor 
       21 A lateral face 
       21 B end 
       22  mounting bracket 
       22 A holding section 
       23  air guide 
       24  controller 
       25  airflow