Patent Publication Number: US-6909079-B2

Title: Microwave oven having an internal components cooling structure

Description:
This application claims the benefit of the Korean Application No. P2002-0072423 filed on Nov. 20, 2002, which is hereby incorporated by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to microwave ovens, and more particularly, to a structure of a microwave oven, which can cool down various components of the microwave oven, smoothly. 
     2. Background of the Related Art 
     In general, the microwave oven (MWO) cooks food with heat from friction between molecules caused by disturbance of the molecular arrangement of the food made with a microwave (approx. 2,450 MHz). The microwave oven may have one or more than one magnetrons. 
     The microwave oven with one magnetron is used as domestic use where the microwave oven is not used frequently, and the microwave oven with more than one magnetrons is used as commercial use for convenience store and the like where the magnetron is used frequently. 
     FIGS.  1 ˜ 5  illustrate inside structures of related art microwave ovens each with two magnetrons schematically, referring to which the microwave oven will be described. 
     Referring to  FIG. 1 , the related art commercial microwave oven is provided with an outer case  11 , a base plate  12 , an inner case  13  of a cooking chamber, a front panel  14 , a rear panel  15 , and an outfit room. 
     The front panel  14  is mounted in a front part of the base plate  12 , and, as shown in  FIG. 2 , the base plate  12  has a plurality of inflow holes  12   a  for drawing external air. 
     The inner case  13  has a plurality of outflow holes  13   a . The rear panel  15  is mounted in a rear part of the base plate  12 , and, as shown in  FIG. 3 , has discharging holes  15   a  and  15   b  for discharging air. 
     Referring to  FIGS. 4 and 5 , in the outfit room, there are one pair of transformers  16   a , and  16   b , one pair of magnetrons  17   a , and  17   b , a fan  18   a , and a fan motor  18   b  provided thereto. 
     The one pair of transformers  16   a  and  16   b  are mounted on the base plate  12  side by side. The one pair of the magnetron  17   a  and  17   b  are mounted in an upper part and a lower part of the inner case  13 , respectively. A microwave from the magnetrons  17   a  and  17   b  propagates to an upper space and a lower space of the inner case  13  through guide ducts (not shown). 
     The fan  18   a  is mounted in a space between the transformers  16   a  and  16   b , and the magnetrons  17   a  and  17   b  in the outer case  11 , and connected to the fan motor  182   b  in a state protected with a fan housing  18   c.    
     The fan housing  18   c  has a suction side facing a lower space. The fan housing  18   c  is in communication with an air duct  19  for guiding air flow to the magnetrons  17   a  and  17   b . An end of the air duct  19  is in communication with the discharging holes  15   a  and  15   b  in the rear panel  15 . 
     A process for cooling the components of the microwave oven will be described in detail. 
     When the microwave oven is put into operation, the fan  18   a  rotates as the fan motor  18   b  is driven, to draw external air. The external air is introduced into the microwave oven through the inflow holes  12   a  in the base plate  12 , and cools the one pair of transformers  16   a  and  16   b  as the external air moves toward the fan  18   a . Then, the external air cools the magnetrons  17   a  and  17   b  through the air duct  19  in communication with the fan housing  18   c.    
     In this instance, a portion of the air passed through the magnetrons  17   a  and  17   b  is discharged through the discharging holes  15   a  in the upper part of the rear panel  15  via the outflow holes  13   a . Rest of the air passed through the magnetrons  17   a  and  17   b  is discharged through the discharging hole  15   b  in a lower part of the rear panel  15 . 
     However, the related art microwave oven has the following problems. 
     First, the one pair of magnetrons in the related art microwave oven, mounted in a rear space of the magnetron, can not but increase the rear space of the microwave oven. Therefore, the inner case becomes smaller in comparison of a total size of the microwave oven. Moreover, the increase size of the microwave oven to require a more installation space can not but limit an installation space. 
     Second, the position of the fan mounted in a corner of one side of the outer case impedes the external air introduced through the base plate to cool the front transformer, smoothly. That is, since the front transformer is mounted in a blind area of air flow, cooling of the transformer has not been smooth. 
     Third, the fan motor in the related art microwave oven generates much heat when driven. However, since the related art microwave oven is not provided with a separate structure for cooling the fan motor, overheat of the fan motor causes a poor performance. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention is directed to a microwave oven that substantially obviates one or more of the problems due to limitations and disadvantages of the related art. 
     An object of the present invention is to provide a microwave oven in which cooling of various components are smooth. 
     Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings. 
     To achieve these objects and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described herein, the microwave oven includes an outer case forming a top and sides of a cabinet, a base plate forming a bottom of the cabinet, a front panel and a rear panel mounted in a front part and a rear part of the base plate for forming a front surface and a rear surface respectively, an inner case forming a cooking chamber on the base plate, first and second transformer mounted at corners of one side of the base plate, a fan above the second transformer for drawing external air, a fan motor connected to the fan for providing a driving power to the fan, a fan housing for protecting the fan, an air duct between the first and second transformers, having one end in communication with the fan housing and the other end branched to first and second branch ducts, and first and second magnetrons on an outside surface of the inner case, the first and second magnetrons connected to the first and second branch ducts, respectively. 
     The base plate includes a front part having a plurality of inflow holes, and the inner case includes a plurality of inlet holes for introduction of the air passed through the first and second branch ducts and the first and second magnetrons, and a plurality of outlet holes for discharging the air introduced into the inner case through the inlet holes. 
     The outlet holes are connected to a plurality of discharging ducts for guiding flow of air discharged from the inner case. The rear panel has a plurality of first outlet holes connected to the discharging ducts for discharging air to an outside of the cabinet. 
     The base plate is provided with a guide for uniform supply of external air introduced thereto through the inflow holes to the first and second transformers. The guide has a form of a square bar with one positioned between the inflow holes, and the other end positioned between the first and second transformers. 
     The rear panel has a third outflow holes for discharging the air passed through the second transformer, and the air duct is mounted spaced a distance apart from an inside wall of the outer case. The first and second branch ducts of the air duct include sloped duct walls respectively such that each of the ducts becomes the narrower as it goes closer to a part connected to the first or second magnetron. 
     The first branch duct is connected to a first duct for guiding air flow toward the fan motor, and the first magnetron is connected to the first duct. The rear panel has a second outflow hole for discharging the air cooled the fan motor through the first duct to an outside of the cabinet. 
     The air duct includes a split guide between the first and second branch ducts for guiding the air introduced thereto through the fan. The split guide is formed by bending an inside wall of the air duct. 
     In a second embodiment of the present invention, the first branch duct is connected to a second duct for guiding flow of air to the rear panel, and the first magnetron is mounted in the second duct. The rear panel includes a second outflow hole connected to the second duct for discharging the air introduced thereto to an outside of the cabinet. 
     The second duct includes a first communication hole formed therein for supplying air for cooling the fan motor. 
     In a third embodiment of the present invention, the second branch duct is connected to a third duct for guiding flow of air to the rear panel, and the second magnetron is in the third duct. 
     The rear panel includes a third outflow hole for discharging the air introduced thereto to an outside of the cabinet, and the third duct includes a second communication hole for guiding air flow to the fan motor. 
     It is to be understood that both the foregoing description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention claimed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principle of the invention. In the drawings; 
         FIG. 1  illustrates a disassembled perspective view of a related art microwave oven, schematically; 
         FIG. 2  illustrates an inner case of a related art microwave oven; 
         FIG. 3  illustrates a rear panel of a related art microwave oven; 
         FIG. 4  illustrates a side view of an inside structure of a related art microwave oven; 
         FIG. 5  illustrates a back view of an inside structure of a related art microwave oven; 
         FIG. 6  illustrates a disassembled perspective view of a microwave oven in accordance with a first preferred embodiment of the present invention, schematically; 
         FIG. 7  illustrates front view of an inner case of a microwave oven of the present invention; 
         FIG. 8  illustrates a rear panel of a microwave oven of the present invention; 
         FIG. 9  illustrates a side view of an inside structure of a microwave oven of the present invention; 
         FIG. 10  illustrates a fitted state of a first duct of an air duct in the microwave oven of the present invention, schematically; 
         FIG. 11  illustrates an inside structure of an air duct in the microwave oven of the present invention in accordance with a preferred embodiment of the present invention; 
         FIG. 12  illustrates an inside structure of an air duct in the microwave oven of the present invention in accordance with another preferred embodiment of the present invention; 
         FIG. 13  illustrates a disassembled perspective view showing an inside structure of a microwave oven in accordance with a second preferred embodiment of the present invention, schematically; 
         FIG. 14  illustrates a fitted state of a second duct of an air duct in the microwave oven of the present invention, schematically; and 
         FIG. 15  illustrates a disassembled perspective view showing an inside structure of a microwave oven in accordance with a third preferred embodiment of the present invention, schematically. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. In describing the embodiments, same parts will be given the same names and reference symbols, and repetitive description of which will be omitted. 
     Referring to  FIG. 6 , the first embodiment microwave oven of the present invention includes an outer case  110 , a base plate  120 , a front panel  140 , and a rear panel  150  to form a cabinet of the microwave oven. 
     The outer case  110  forms side surfaces and a top surface, and the base plate  120  forms a bottom of the cabinet. The front panel  140 , and the rear panel  150  are mounted in a front part and the rear part of the base plate  120 , to form a front face and a rear face of the cabinet. 
     There is an inner case  130  formed above the base plate  120 . The inner case  130  is used as a cooking chamber, and has transformers, an air duct  190 , and various electronic components, such as magnetrons, fitted at sides thereof. 
     The transformer includes first and second transformers  161  and  162  mounted at corners of one side of the base plate  120 . As shown in  FIG. 9 , there is a fan  181  above the second transformer  162  for drawing external air. The fan  181  is protected by the fan housing  183 , and coupled with the fan motor  182 . 
     The air duct  190  is fitted between the first and second transformers  161  and  162 , and has one end in communication with the fan housing  183 , and the other end branched into first and second branch ducts  190   a , and  190   b.    
     The magnetron is mounted on an outside surface of the inner case  130 , and includes first and second magnetrons  171  and  172  connected to the branch ducts  190   a  and  190   b . The first and second magnetrons  171  and  172  are cooled by the air introduced into the first and second branch ducts  190   a  and  190   b.    
     The base plate  120  has a plurality of inflow holes  121  in a front surface thereof. The inflow holes  121  serves as ducts of external air introduced into the cabinet by the fan  181 . 
     Referring to  FIG. 7 , the inner case  130  has a plurality of inlet holes  131   a  and  131   b  for introduction of the air having cooled the magnetrons  171  and  172 . There are a plurality of outlet holes  132   a  and  132   b  in an upper surface or lower surface of an opposite side of the inlet holes  131   a  and  131   b . The outlet holes  132   a  and  132   b  discharge the air introduced into the inner case  130  through the inlet holes  131   a  and  131   b.    
     There are discharge air ducts  134  and  135  fitted to an outside surface of the inner case  130  having the outlet holes  132   a  and  132   b  formed therein. The discharge air ducts  134  and  135  guide air discharged through the outlet holes  132   a  and  132   b , respectively. 
     There may be one or more than one discharge ducts  134  and  135 , and the first embodiment of the present invention suggests the first and second discharge air ducts  134  and  135 . The first discharge air duct  134  is connected to the outlet holes  132   a  on the top surface of the inner case  130 , and the second discharge air duct  135  is connected to the outlet holes  132   a  in a bottom thereof. 
     Referring to  FIG. 8 , the rear panel  150  has a plurality of first outflow holes  51   a  and  151   b . The first outflow holes  151   a  and  151   b  are connected to the discharge air ducts  134  and  135  for discharging air to an outside of the cabinet, respectively. Therefore, positions of the first outflow holes  151   a  and  151   b  are dependent on end positions of the discharge air ducts, respectively. In the first embodiment of the present invention, the first outflow holes  151   a  and  151   b  are in an upper part and a lower part of one side part of he rear panel  150 . 
     The rear panel  150  also has a third outflow hole  153  for discharging the air passed through the second transformer  162 . The third outflow hole  153  discharges the portion of air that is not introduced into the air duct  190  of the air introduced through the inflow holes  121  and cooled the second transformer  162 . According to this, air flow in the microwave oven becomes smooth, to increase a flow rate of inflow/outflow air, to improve a cooling efficiency of the transformers  161  and  162 . 
     In the meantime, the base plate  120  has a guide  122  for supplying the external air introduced through the inflow holes  121  both to the first and second transformers  161  and  162  at the same time. The guide  122 , in a form of a bar, is provided between the first and second transformers  161  and  162 . 
     In more detail, the guide  122  has one end positioned between the inflow holes  121 , and the other end positioned between the first, and second transformers  161  and  162 . Accordingly, the external air is provided to the first and second transformers  161  and  162  at the same time by the guide  122 , and cools the first and second transformers  161 , and  162 , uniformly. 
     Of course, there can be a variety of forms and fitting positions of the guide  122 . For an example, the guide  122  may be formed such that the external air passes through the first and second transformers  161  and  162  in succession. However, uniform cooling of the transformers  161  and  162  is more favorable for improving performance of the transformers  161  and  162 . Therefore, in the embodiments of the present invention, the guide  122  is formed such that an end of the guide  122  is directed a point substantially in the middle of the transformers  161  and  162 . 
     In the meantime, the air duct  190  is spaced a distance from an inside wall of the outside case  110 . Therefore, as there is a gap between the air duct  190  and the outside case  110 , flow of an inside air becomes smooth. 
     The first and second branch ducts  190   a  and  190   b  of the air ducts  190  has a sloped duct walls such that the duct becomes the narrower as it goes closer to a part connected to the first and second magnetrons  161  and  162 . This structure increases a flow speed of the air passing through the first and second branch ducts  190   a  and  190   b , to enable smooth outflow and inflow of the air. 
     Referring to  FIG. 11 , the air duct  190  has a split guide  190   c  formed between the first and second branch ducts  190   a  and  190   b . The split guide  190   c  guides the air introduced thereto through the fan  181  to the first and second branch ducts  190   a  and  190   b . The split guide  190   c  may be formed by bending an inside wall of the air duct  190 , or as a separate unit projected from the inside wall of the air duct  190  as shown in FIG.  12 . 
     The first branch duct  190   a  is connected to a first duct  191  for guiding air to the fan motor  182 . The first magnetron  171  is connected to the first duct  191 . Therefore, the air introduced into the first branch duct  190   a  cools the fan motor  182  and the first magnetron  171  following the first duct  191 . It is preferable that the first duct  191  is formed as a unit with the air duct  190 . 
     In the meantime, there can be a variety of variations of the first duct  191 . That is, a part of the air duct  190  at a position of the fan motor  182  may be opened, for guiding a portion of the air from the air duct  190  to the fan motor  182 , for cooling the fan motor  182 . 
     Moreover, for discharging the air that cooled the fan motor  182  through the first duct  191 , a second outflow hole  152  is formed in the rear panel  150 , additionally. 
     A process of air flow in the microwave oven will be described with reference to  FIGS. 9 and 10 . 
     Upon putting the microwave oven into operation, the fan  181  is driven by the fan motor  182  to draw external air. In the instance, the external air is introduced into the cabinet through the inflow holes  121  in the base plate  120 . 
     Then, the external air is guided to the first transformer  161  and the second transformer  162  at the same time by the guide  122  on the base plate  120 , to cool the transformers  161  and  162 , respectively. 
     Most of the air that cooled the second transformer  162  is introduced into the air duct  190  through the fan  182 , rest of the air is discharged to rear of the microwave oven through the third outflow hole  153  in the rear panel  150 . 
     Most of the air that cooled the first transformer  161  flows identical to the air that cooled the second transformer  162 . However, a portion of the air is introduced into spaces of the second outflow hole  152  and the third outflow hole  153  through a gap between the air duct  190  and the outside case  110  respectively, and discharged to an outside of the cabinet through the outflow holes  152  and  153 . 
     The air flowing through the air duct  190  is split into the first and second branch ducts  190   a  and  190   b  by the split guide  190   c . The air introduced into the first branch duct  190   a  moves along the first duct  191  and passes through the first magnetron  171 . A portion of the air passed through the first magnetron  171  is introduced into the cooking chamber in the inner case  130  through the inlet holes  131   a . Rest of the air moves along the first duct  191  to a space the fan motor  182  is positioned therein, and cools the fan motor  182 . Then, the air that cooled the fan motor  182  is discharged to rear of the microwave oven through the second outflow holes  152  in the rear panel  150 . 
     The air introduced into the second branch duct  190   b  is introduced into the inner case  130  through the inlet holes  131   b  via the second magnetron  172 . 
     In the meantime, the air introduced into the cooking chamber circulates inside of the cooking chamber, and introduced into the first and second discharge ducts  134  and  135  through the outlet holes  132   a  and  132   b , respectively. Then, the air moves along the discharge ducts  134  and  135 , and discharged to rear of the microwave oven through the first outflow holes  151   a  and  151   b.    
     In the meantime, as shown in  FIGS. 13 and 14 , the second embodiment of the present invention suggests a second duct  193  connected to the first branch duct  190   a  for guiding air flow to the rear panel  150 . The second duct  193  is connected to the second outflow hole  152  in the rear panel  150  directly, and the first magnetron  171  is installed in the second duct  193 . 
     A fact, that a flow rate of the air introduced into the inner case  130  through the first magnetron  171  is very small in comparison to a flow rate introduced through the air duct  190 , is taken into account in a structure of the second duct  193 . Therefore, a portion of the air introduced into the second duct  193  is introduced into the inner case  130  through the first magnetron  171 , and rest of the air is discharged to outside of the cabinet. In conclusion, the second duct  193  reduces an air flow resistance which may be caused by the air that fails to pass through the first magnetron  171  smoothly to the maximum. 
     In the meantime, the second duct  193  has a first communication hole  193   a  for cooling the fan motor  182 . The first communication hole  193   a  guides a portion of the air flowing through the second duct  193  to the fan motor  182  to cool the fan motor  182 . 
     Accordingly, a portion of the air introduced into the second duct  193  is introduced into the inner case  130  through the inlet holes  131   a , and rest of the air is discharged to an outside of the cabinet through the second outflow hole  152  via the second duct  193 . In this instance, a portion of the air flowing toward the second outflow hole  152  along the second duct  193  is introduced into a space of the fan motor  182  through the first communication hole  193   a , and cools the fan motor  182 . 
     Description of the air flow introduced into the second branch duct  190   b , given in detail in the first embodiment, will be omitted. 
     At the end, the second duct  193  discharges the air introduced into the cabinet by the fan  181  as quick as possible to an outside of the cabinet. Therefore, by increasing a flow rate of the air introduced into the second duct  193 , an overall cooling efficiency of the microwave oven can be improved. 
     In the meantime, as shown in  FIG. 15 , the third embodiment of the present invention suggests a third duct  194  connected to the second branch duct  190   b  for guiding air flow toward the rear panel  150 . The third duct  194  is connected to the third outflow hole  153  in the rear panel  150 , and the second magnetron  172  is mounted inside of the third duct  194 . 
     The third duct  194  also has a second communication hole  194   a  for cooling the fan motor  182 , too. Therefore, if the third duct  194  and the second duct  193  are fitted together, not only the cooling efficiency of the fan motor  182  can be improved, but also an internal air flow can be made smoother. In this instance, the third duct  194  may, or may not be formed as a unit with the second duct  193 . 
     In the meantime, the structures of the foregoing embodiments may be applied to microwave ovens for stores which have two transformers and two magnetrons, or even to microwave ovens for domestic use having one of the magnetrons and the transformers removed therefrom. 
     The microwave oven having one of the magnetrons and the transformers removed therefrom can be a domestic microwave oven. Therefore, by adjusting numbers of the magnetrons and the transformers mounted thereon, the microwave ovens of the present invention can be used as microwave ovens for stores or for homes. 
     As has been described, the microwave oven of the present invention has the following advantages. 
     First, by adjusting arrangements of the magnetrons and the transformers appropriately, a front to rear length of the microwave oven can be reduced. According to this, a size of the cooking chamber can be enlarged, to provide a more useful structure. 
     Second, by cooling the transformers uniformly, performances of the transformers can be improved. That is, the structure of the present invention permits smooth cooling of the transformer in a part air flow thereto is poor in the related art by guiding air thereto. 
     Third, the smooth cooling of the fan motor can minimizes damage to the fan motor caused by overheating of the fan motor. 
     Fourth, the microwave oven of the present invention permits manufacturing of microwave ovens of different purposes of use with one production line. 
     That is, because structures of microwave oven for home and microwave oven for stores are different in the related art, different production lines are required for each of purposes of use of the microwave ovens. However, what is required for the microwave oven of the present invention is change of the numbers of magnetron and transformers, manufacturing of the microwave oven with only one production line is possible. 
     It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.