DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0078] Hereinafter, an embodiment of the present invention will be described in detail with reference to the attached drawings, wherein the like reference numerals refer to the like elements throughout. The present invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiment set forth herein. Rather, this embodiment is provided so that the present disclosure will be thorough and complete, and will fully convey the concept of the invention to those skilled in the art.

[0079] FIG. 1A shows a transformer assembly 10 according to an embodiment of the present invention. As shown in FIG. 1 A, the transformer assembly 10 includes a transformer 11 having a core 111 and coils 112 wound around the core 111 , and a container 12 receiving the transformer 11 therein. The coils 112 include a lower primary winding connected to an electric power source and an upper secondary winding for outputting current transformed by electromagnetic induction caused by the lower primary winding. The container 12 is hermetically sealed, and includes a base plate 123 on which the transformer 11 is fixedly mounted, and an enveloping part coupled to the base plate 123 to cover the transformer 12 . The enveloping part includes a wall body 121 defining side surfaces of the container 12 and a top plate 122 . The tubular wall body 121 is shaped as a cylinder or as a polygon, and has corrugated surface s to efficiently radiate heat and accommodate thermal expansion. The corrugated surface has at least two points having different distances from the center of the container 12 . That is, the wall body 121 efficiently radiates resistance heat generated from the coils 112 and resistance heat generated by eddy current on the core 111 during operation of the transformer 11 .

[0080] Although the container 12 may be made of copper or aluminum, which have excellent properties for efficiently radiating heat generated from the transformer 11 and for moldability, aluminum is lower in cost and weight.

[0081] The container 12 contains non-conductive oil 105 as a liquid for cooling the transformer 11 housed within the container 12 . Although any type of oil may be used as the non-conductive oil 105 serving as the cooling liquid, mineral oil minimizes environmental pollution and harmful effects on the human body. There is no requirement to use oil as the cooling liquid. Non-conductive liquid other than oil, and colloidal materials such as sols or gels, may be used as the cooling liquid. The cooling liquid, such as the non-conductive oil and the colloidal material, is considerably advantageous in that the cooling liquid absorbs vibration and noise generated from the transformer 11 , thereby reducing vibration and noise transmitted outside the transformer 11 during operation of the transformer 11 .

[0082] The non-conductive oil 105 is supplied to the container 12 such that a heating portion of the transformer 11 is submerged in the oil. Accordingly, the oil 105 must be supplied to the container 12 in an amount sufficient to submerge the coils 112 in the oil 105 , and both the coils 112 and the core 111 may be submerged in the oil. The amount of the oil 105 is reduced as much as possible while maintaining cooling efficiency for the transformer 11 by supplying the oil 105 to a level between, for example, the upper end of the core 111 and the upper end of the upper coil 112 . The space 17 above the oil 105 is maintained in a vacuum state.

[0083] The top plate 122 has an oil inlet 122 a to allow the oil 105 to be injected into the container 12 . The oil inlet 122 a is needed for injection of the oil 105 into the container 12 when both the base plate 123 and the top plate 122 are coupled to the wall body 121 before placing the oil 105 in the container 12 . However, when the oil 105 is injected into the container 12 before the top plate 122 is coupled to the wall body 121 and the base plate 123 is coupled to the wall body 121 , the oil inlet 122 a is dispensable.

[0084] The transformer 11 has input lines 14 for supplying external low-voltage electric power to the transformer 11 , and output lines 15 for outputting current transformed by electromagnetic induction. In the embodiment shown in FIG. 1 A, the input lines 14 and the output lines 15 are connected to the transformer 11 in the container 12 through the top plate 122 . More specifically, the input lines 14 are connected to the primary winding of the coils 112 , and the output line 15 are connected to the secondary winding of the coils 112 . Therefore, the container 12 has through holes 16 to allow the input lines 14 and the output lines 15 to enter the container 12 therethrough. The through holes 16 are formed at the top plate 122 of the container 12 , for example. Because the oil 105 contained in the container 12 must be prevented from leaking by maintaining an airtight condition within the container 12 , the through holes 16 , through which the input lines 14 and the output lines 15 respectively pass, are sealed with epoxy resin 18 to prevent the oil 105 from leaking from the container 12 and to make the container 12 airtight.

[0085] FIG. 1B shows the transformer assembly 10 according to an aspect of the present invention in which the top plate 122 of the container 12 has a terminal unit 19 to allow the input lines 14 and the output lines 15 to be connected to an external electric power source and to a magnetron (not shown), respectively. The terminal unit 19 allows the inside and the outside of the top plate 122 of the container 12 to be electrically connected to each other while maintaining the airtightness of the container 12 . Accordingly, the transformer assembly 10 according to the aspect of the invention shown in FIG. 1B is more advantageous than the transformer assembly 10 according to the aspect of the invention shown in FIG. 1A because there is no necessity to perform an additional epoxy sealing procedure.

[0086] The transformer assembly 10 according to an embodiment of the present invention, which is cooled by the cooling material 105 , has been described heretofore with reference to FIGS. 1A and 1B . A structure for mounting the transformer assembly 10 on a microwave oven is now described with reference to FIGS. 2A through 3C .

[0087] FIGS. 2A through 2D show structures for mounting the transformer assembly 10 , as shown in FIGS. 1A and 1B , on a bottom plate 118 via a bracket 20 - 23 .

[0088] FIG. 2A shows a bracket 20 for mounting the transformer assembly 10 on the bottom plate 118 . The bracket 20 includes a base part 201 closely attached to the base plate 123 of the container 12 , and mounting parts 202 outwardly extended from the ends of the base part 201 . The mounting parts 202 are mounted on the bottom plate 118 of an electrical components area (not shown) of the microwave oven by a fastening unit. More specifically, the mounting parts 202 of the bracket 20 and the bottom plate 118 of the electrical components area of the microwave oven respectively have screw holes 2 and 118 a and are fastened to each other using screws 119 .

[0089] Referring to FIGS. 2B and 2C , there are shown other brackets 21 and 22 for mounting the transformer assembly 10 on the bottom plate 118 of the electrical components area. The brackets 21 and 22 respectively include base parts 211 and 221 fixedly attached to the base plate 123 of the container 12 , and mounting parts 212 and 222 having extension portions 212 a and 222 a downwardly bent at the peripheral edges of the base parts 211 and 221 and extended downwardly, and fastening portions 212 b and 222 b outwardly bent at ends of the extension portions 212 a and 222 a with a spacing between the fastening portions 212 b and 222 b and the base parts 211 and 221 and fastened to the bottom plate 118 of the electrical components area. The fastening portions 212 b and 222 b are formed with screw holes 2 to allow the fastening portions 212 b and 222 b to be fastened to the bottom plate 118 using screws 119 . As shown in FIG. 2 C, the fastening portions 212 b and 222 b are positioned under the wall body 121 of the container 12 . That is, assuming that a distance between the center line “C” of the transformer 11 and a fastening point of the fastening portion 222 b is R 1 , and a distance between the center line “C” of the transformer 11 and the wall body 121 is R 2 , R 1 is less than R 2 . The mounting parts 202 and 212 FIGS. 2A and 2B occupy additional side space in addition to the space under the transformer assembly 10 . Thus, the bracket 22 of FIG. 2C is advantageous in that the space in the electrical components area can be efficiently used, and the size of the electrical components area can be reduced, thereby allowing miniaturization of the microwave oven.

[0090] FIG. 2D shows another bracket 23 . The bracket 23 includes a base part 231 fixedly attached to the base plate 123 of the container 12 , and mounting parts 232 having extension portions 232 a downwardly bent at the peripheral edges of the base part 231 and extended downwardly, and fastening portions 232 b inwardly bent at ends of the extension portions 232 a , with a spacing between the fastening portion 232 b and the base part 231 , and fastened to the bottom plate 118 of the electrical components area. Accordingly, the transformer assembly 10 of FIG. 2D has the same advantage as that of the transformer assembly 10 shown in FIG. 2C . That is, because a distance R1 between the center line “C” of the transformer 11 and a fastening point of the fastening portion 232 b is less than a distance R2 between the center line “C” of the transformer 11 and the wall body 121 , the fastening points at which the bracket 23 is fastened to the bottom plate 118 of the electrical components area using screws 119 are positioned under the wall body 121 of the transformer assembly 10 , thereby reducing the space required to install the transformer assembly 10 in the electrical components area.

[0091] Although joining of the fastening portions 212 b , 222 b , and 232 b of the transformer assemblies 10 and the bottom plate 118 of the electrical components area is easily achieved using the screw holes 2 and 118 a and screws 119 in the embodiments shown in FIGS. 2A through 2D , the joining may be achieved by other appropriate ways such as using bolts, rivets, and welding.

[0092] Referring to FIGS. 3A through 3C , there are shown transformer assemblies 10 according to other aspects of the present invention in which the base plate 123 of the container 12 serves as a bracket to mount the transformer assembly 10 on the bottom plate 118 of the microwave oven.

[0093] In the transformer assembly 10 shown in FIG. 3 A, the base plate 123 includes a base part 301 serving as a bottom of the container 12 , and mounting parts 302 outwardly extended from the base part 301 beyond the wall body 121 of the container 12 and having screw holes 2 to allow the mounting part 302 to be joined to the bottom plate 118 of the electrical components area using screws 119 .

[0094] In the transformer assembly 10 shown in FIG. 3 B, the base plate 123 includes a base part 311 serving as a bottom of the container 12 , and mounting parts 312 having extension portions 312 a downwardly bent at the peripheral edges of the base part 311 and extended downwardly, and fastening portions 312 b outwardly bent at ends of the extension portions 312 a , with a spacing between the fastening portions 312 b and the base part 311 , and fastened to the bottom plate 118 of the electrical components area.

[0095] In the transformer assembly 10 shown in FIG. 3 C, the base plate 123 includes a base part 321 serving as a bottom of the container 12 , and mounting parts 322 having extension portions 322 a downwardly bent at the peripheral edges of the base part 321 and extended downwardly, and fastening portions 322 b inwardly bent at ends of the extension portions 322 a , with a spacing between the fastening portions 322 b and the base part 321 , and fastened to the bottom plate 118 of the electrical components area. Like the brackets 22 and 23 shown in FIGS. 2C and 2D , because a distance R1 between the center line “C” of the transformer 11 and a fastening point of the fastening portion 322 b is less than a distance R2 between the center line “C” of the transformer 11 and the wall body 121 , the fastening points at which the base plate 123 is fastened to the bottom plate 118 of the electrical components area are positioned inwardly from the wall body 121 of the transformer assembly 10 , thereby reducing the space required to install the transformer assembly 10 in the electrical components area and, thus, allowing miniaturization of the microwave oven.

[0096] In the transformer assembly 10 in which the base plate 123 of the container 12 serves as a bracket, as shown in FIGS. 3A through 3C , the base plate 123 coupled to the wall body 121 of the container 12 is directly joined to the bottom plate 118 of the electrical components area, unlike the transformer assembly 10 shown in FIGS. 2A through 2D , in which the bracket 20 , 21 , 22 , and 23 is attached to the base plate 123 of the container 12 and then joined to the bottom plate 118 of the electrical components area. Accordingly, because the base plate 123 of the container 12 is directly joined to the bottom plate 118 by a single procedure, reduction of cost of material and simplification of the production process are achieved, thereby improving productivity.

[0097] FIGS. 4A and 4B are flowcharts showing processes of manufacturing the transformer assembly 10 according to the present invention.

[0098] In a process of manufacturing the transformer assembly as shown in FIG. 4 A, the wall body 121 is first coupled to the base plate 123 of the container 12 at operation 401 . The transformer 11 is mounted on the base plate 123 at operation 402 . Thereafter, input lines 14 for supplying external electric power to the transformer 11 , and output lines 15 for outputting current transformed by the transformer 11 , are installed on the top plate 122 at operation 403 . The top plate 122 is coupled to the wall body 121 at operation 404 to define the container 12 , and oil 105 is injected into the container 12 at operation 405 .

[0099] In particular, operation 401 , in which the wall body 121 is coupled to the base plate 123 is performed by a brazing process to assure the prevention of leakage of the oil 105 and the sealing ability of the container 12 . The wall body 121 has a corrugated surface to increase the radiating surface thereof. More specifically, the tubular wall body 121 , which includes a corrugated surface with at least two points having different distances from the center of the container 12 , is prepared, and one end of the wall body 121 is coupled to the base plate 123 .

[0100] The mounting of the transformer 11 on the base plate 123 is carried out by spot welding to assure secure fixation. Where the additional bracket 20 , 21 , 22 , or 23 is required to join the transformer assembly 10 to the base plate 123 , as shown in FIGS. 2A through 2D , the transformer 11 , the base plate 123 , and the bracket 20 , 21 , 22 , or 23 may all be combined together by spot welding. The bracket 20 , 21 , 22 , or 23 is first attached to the base plate 123 , and the transformer 11 and the integrated base plate 123 and bracket 20 , 21 , 22 , or 23 are combined together at one time.

[0101] At operation 403 , when the top plate 122 is formed with through holes 16 , installation of the input lines 14 and the output lines 15 on the top plate 122 is performed by introducing the input lines 14 and the output lines 15 into the container 12 through the through holes 16 and sealing the through holes 16 with epoxy resin 18 . On the other hand, when the top plate 122 is provided, at an outer surface thereof, with a terminal unit 19 , as shown in FIG. 1 B, the installation of the input lines 14 and the output lines 15 on the top plate 122 may be performed by connecting the input lines 14 and the output lines 15 to the terminal unit 19 .

[0102] At operation 405 , which injects oil 105 into the container 12 , the top plate 122 with the oil inlet 122 a is prepared, and the oil 105 is injected into the container 12 through the oil inlet 122 a . After the injection of the oil 105 , the oil inlet 122 a is sealed with epoxy resin 18 to maintain the container 12 in a hermetically sealed condition at operation 405 a . At this point, the oil 105 is injected into the container 12 such that a level of the injected oil 105 is maintained between the top plate 122 of the container 12 and the upper end of the coils 112 of the transformer 11 . That is, because the coils 112 are dominant heating elements among the elements of the transformer 11 , the oil 105 is injected such that the coils 112 are completely submerged in the oil 105 . Because the core 111 is also a heating element, the oil 105 may be supplied by an amount sufficient to submerge the core 111 in the oil 105 . However, the oil 105 is supplied to a certain level between the upper end of the core 111 and the upper end of the coils 112 to reduce the amount of oil 105 as much as possible without deteriorating its cooling efficiency.

[0103] In another process of manufacturing the transformer assembly 10 as shown in FIG. 4 B, operations 406 , 407 , and 408 are similar to operations 401 , 402 , and 403 of FIG. 4A . As shown in FIG. 4 B, the wall body 121 is first coupled to the base plate 123 at operation 406 , and the transformer 11 is mounted on the base plate 123 at operation 407 . The input lines 14 for supplying external power to the transformer 11 , and the output lines 15 for outputting the current transformed by the transformer 11 to the magnetron, are installed through the top plate 122 at operation 408 . The oil 105 is injected into the container 12 at operation 409 , and the top plate 122 is coupled to the wall body 121 at operation 410 . According to the manufacturing process shown in FIG. 4 B, because the oil 105 is injected into the container 12 before the top plate 122 is coupled to the wall body 121 , unlike the process shown in FIG. 4 A, it is possible to omit the operation of sealing the oil inlet 122 a , as well as the operation of forming the oil inlet 122 a on the top plate 122 .

[0104] FIG. 5 shows a microwave oven 30 with the transformer assembly 10 as described above. More specifically, FIG. 5 shows a microwave oven 30 , in which the transformer assembly 10 shown in FIG. 3C is mounted on a bottom plate 118 of an electrical components area 501 of the microwave oven 30 . Operation of the microwave oven 30 according to the present invention is described below with reference to FIG. 5 . When external commercial power is applied to the transformer 11 to operate the microwave oven 30 , electric current, which has been boosted in its voltage by electromagnetic induction, is supplied to a magnetron 503 , and the magnetron 503 generates microwaves into a cooking chamber 502 . When the microwave oven 30 is operated for an extended period of time, the transformer 11 radiates high-temperature resistance heat generated from the coils 112 and the core 111 . The heat radiated from the transformer 11 is immediately absorbed into mineral oil 105 contained in the container 12 of the transformer assembly 10 and then convected to the container 12 , thereby causing the heat to be transmitted to the container 12 . Because the wall body 121 of the container 12 has a large radiating area due to its corrugated surface, the container 12 of the transformer assembly 10 is efficiently cooled by external cool air introduced into the machine room 501 by a cooling fan 504 . The cooling action for the transformer 11 is quickly and efficiently performed because the transformer 11 is surrounded by mineral oil 105 , which serves as an efficient cooling medium. Furthermore, because the heat absorbed by the mineral oil 105 is dispersed throughout the mineral oil 105 by convection of the oil 105 and transmitted to the container 12 having a relatively large radiating area, the heat transmitted to the container 12 can be efficiently and quickly removed by external air blown by the cooling fan 504 . Accordingly, even though the transformer 11 may operate for a long period of time due to continuous operation of the microwave oven 30 , the transformer 11 maintains a stable and constant output without loss of efficiency.

[0105] As is apparent from the above description, the present invention provides a transformer assembly for a microwave oven, which has an improved operational efficiency due to its excellent cooling ability. Consequently, because the sizes of some of the components, such as the core and the coils, can be reduced by the improvement of the operational efficiency, production cost for the transformer assembly can be reduced. In addition, because high-density metal components are omitted and a low-density cooling material and container are used, it is possible to achieve miniaturization and weight reduction of the transformer assembly.

[0106] Furthermore, the present invention provides a transformer assembly for a microwave oven, in which a transformer is securely installed in a container and the container is hermetically sealable by an improved assembly structure.

[0107] Where non-conductive liquid is used as the cooling material, because the present invention provides an improved structure for efficiently installing a transformer assembly to a microwave oven, an improvement in productivity due to simplification of the assembly operation can be achieved. In addition, because the space required to install the transformer assembly in an electrical components area of a microwave oven is significantly reduced, the remaining space in the machine room can be used for other applications, or the microwave oven can be miniaturized due to a reduction in size of the electrical components area.

[0108] According to the present invention, because oily or colloidal material is used as the cooling material, vibration and noise of the transformer can be reduced, thereby improving reliability of products using the transformer assembly.

[0109] Although a few aspects of the present invention have been shown and described, it would be appreciated by those skilled in the art that changes may be made in these aspects without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents.