Patent Publication Number: US-9424979-B2

Title: Magnetic element with multiple air gaps

Description:
TECHNICAL FIELD 
     The present disclosure relates to a magnetic element, and more particularly to a magnetic element with multiple air gaps. 
     BACKGROUND OF THE DISCLOSURE 
     Nowadays, magnetic elements such as inductors and transformers are widely used in power supply apparatuses or other electronic devices in order to generate induced magnetic fluxes. 
     Take an inductor as an example.  FIG. 1A  is a schematic exploded view illustrating an inductor with an air gap.  FIG. 1B  is a schematic assembled view illustrating a portion of the inductor of  FIG. 1A , in which the bobbin and the winding coil are not shown. The inductor  1  may be applied to a power factor correction circuit or a resonant circuit of a power supply apparatus. The conventional inductor  1  comprises a bobbin  10 , a first magnetic core  11 , a second magnetic core  12 , and a winding coil  13 . The bobbin  10  comprises a channel  101  and a winding section  102 . A middle post  111  of the first magnetic core  11  and a middle post  121  of the second magnetic core  12  are embedded within the channel  101 . The winding coil  13  is wound around the winding section  102 . The first magnetic core  11  and second magnetic core  12  are arranged on opposite sides of the bobbin  10 . Moreover, an air gap  14  is formed between a middle post  111  of the first magnetic core  11  and a middle post  121  of the second magnetic core  12 . After the bobbin  10 , the first magnetic core  11 , the second magnetic core  12  and the winding coil  13  are combined together, the inductor  1  with the air gap  14  is fabricated. 
     Recently, the magnetic element of the power supply apparatus is designed to have increased power (watt), reduced height and increased winding space. In the inductor  1 , the winding coil  13  is fixed on the bobbin  10  and arranged between the first magnetic core  11  and second magnetic core  12 , and the air gap  14  is covered by the winding coil  13 . Due to the volume of the bobbin  10 , the space between the first magnetic core  11  and second magnetic core  12  for accommodating the winding coil  13  is restricted and the coil utilization is reduced. Under this circumstance, since the diameter of the winding coil  13  is limited, the overall temperature of the inductor  1  is very high and the working efficiency of the inductor  1  is impaired. Moreover, the single air gap  14  between the middle post  111  of the first magnetic core  11  and the middle post  121  of the second magnetic core  12  may avoid the generation of magnetic saturation. However, the larger air gap may result in higher leakage flux. Under this circumstance, the eddy loss is increased, the overall temperature of the inductor  1  is increased, and the working efficiency of the inductor  1  is reduced. 
     Therefore, there is a need of providing a magnetic element with multiple air gaps in order to eliminate the above drawbacks. 
     SUMMARY OF THE DISCLOSURE 
     The present disclosure provides a magnetic element with multiple air gaps. The coils are directly wound around the magnetic cores without the need of using bobbin. Consequently, the fabricating cost is reduced, and the coil utilization is enhanced. Since the multiple air gaps of the magnetic element are dispersedly distributed, the eddy loss is reduced and the dispersing flux is decreased. Under this circumstance, the working temperature of the magnetic element is decreased, and the working efficiency of the magnetic element is enhanced. 
     The present disclosure provides a magnetic element with multiple air gaps. The magnetic cores are stacked in an asymmetric configuration and the winding coils are connected with each other in series, the magnetic force lines between the two winding coils are partially balanced. Under this circumstance, the thickness of the intermediate magnetic core is reduced, the overall volume is reduced, and the magnetic element is slim. 
     In accordance with an aspect of the present disclosure, there is provided a magnetic element with multiple air gaps. The magnetic element includes a first magnetic core, a second magnetic core, an intermediate magnetic core, a first winding coil, and a second winding coil. The intermediate magnetic core is arranged between the first magnetic core and the second magnetic core. After the first magnetic core and the intermediate magnetic core are coupled with each other, a first winding space and a first air gap are defined. After the second magnetic core and the intermediate magnetic core are coupled with each other, a second winding space and a second air gap are defined. The first winding coil is disposed within the first winding space and arranged around the first air gap. The second winding coil is disposed within the second winding space and arranged around the second air gap. The first winding coil and the second winding coil are connected with each other in series. 
     The above contents of the present disclosure will become more readily apparent to those ordinarily skilled in the art after reviewing the following detailed description and accompanying drawings, in which: 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a schematic exploded view illustrating an inductor with an air gap; 
         FIG. 1B  is a schematic assembled view illustrating a portion of the inductor of  FIG. 1A , in which the bobbin and the winding coil are not shown; 
         FIG. 2  is a schematic perspective view illustrating a magnetic element according to a first embodiment of the present disclosure; 
         FIG. 3  is a schematic cross-sectional view illustrating the magnet cores of the magnetic element of  FIG. 2 ; and 
         FIG. 4  is a schematic cross-sectional view illustrating the magnet cores of a magnetic element according to a second embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The present disclosure will now be described more specifically with reference to the following embodiments. It is to be noted that the following descriptions of preferred embodiments of this disclosure are presented herein for purpose of illustration and description only. It is not intended to be exhaustive or to be limited to the precise form disclosed. 
       FIG. 2  is a schematic perspective view illustrating a magnetic element according to a first embodiment of the present disclosure.  FIG. 3  is a schematic cross-sectional view illustrating the magnet cores of the magnetic element of  FIG. 2 . The magnetic element  2  of this embodiment may be applied to a power factor correction circuit or a resonant circuit of a power supply apparatus. Moreover, the magnetic element  2  is bobbinless. An example of the magnetic element  2  includes but is not limited to an inductor or a transformer. As shown in  FIGS. 2 and 3 , the magnetic element  2  comprises an intermediate magnetic core  20 , a first magnetic core  21 , a second magnetic core  22 , a first winding coil  23 , and a second winding coil  24 . The first magnetic core  21 , the intermediate magnetic core  20  and the second magnetic core  22  are sequentially stacked on each other along a first direction d 1  so as to be defined as a stacked magnetic core assembly. The intermediate magnetic core  20  is arranged between the first magnetic core  21  and the second magnetic core  22  and coupled with the first magnetic core  21  and the second magnetic core  22 . The first magnetic core  21  and the second magnetic core  22  are located at opposite sides of the intermediate magnetic core  20 . After the first magnetic core  21  and the intermediate magnetic core  20  are coupled with each other, a first winding space  26  and a first air gap  27  are defined. The first air gap  27  is arranged between the first magnetic core  21  and the intermediate magnetic core  20 . After the second magnetic core  22  and the intermediate magnetic core  20  are coupled with each other, a second winding space  28  and a second air gap  29  are defined. The second air gap  29  is arranged between the second magnetic core  22  and the intermediate magnetic core  20 . The first winding coil  23  is disposed within the first winding space  26  and arranged around the first air gap  27 . The second winding coil  24  is disposed within the second winding space  28  and arranged around the second air gap  29 . The first winding coil  23  and the second winding coil  24  are connected with each other in series. Consequently, the magnetic cores of the magnetic element  2  are stacked in an asymmetric configuration. 
     In this embodiment, the magnetic element  2  further comprises a base plate  25 . For example, the base plate  25  is an insulation plate. Moreover, the second magnetic core  22  has a bottom surface (not shown), which is opposed to the intermediate magnetic core  20 . The base plate  25  is attached on the bottom surface of the second magnetic core  22 . Moreover, the base plate  25  has plural perforations  250 . The outlet terminals of the first winding coil  23  and the second winding coil  24  may be penetrated through the perforations  250  so as to be fixed by the base plate  25 . In this embodiment, the base plate  25  is attached on the bottom surface of the second magnetic core  22  via an adhesive (not shown). 
     Please refer to  FIG. 3  again. In this embodiment, the intermediate magnetic core  20 , the first magnetic core  21  and the second magnetic core  22  are all E-shaped cores. It is noted that the shapes of these magnetic cores  20 ,  21  and  22  are not restricted. Moreover, the intermediate magnetic core  20  comprises a connection part  200 , a middle post  201 , and two lateral legs  202 . The first magnetic core  21  comprises a connection part  210 , a middle post  211 , and two lateral legs  212 . The second magnetic core  22  comprises a connection part  220 , a middle post  221 , and two lateral legs  222 . In this embodiment, the connection part  200  of the intermediate magnetic core  20 , the connection part  210  of the first magnetic core  21  and the connection part  220  of the second magnetic core  22  have the same shape and the same cross-section area. Moreover, the middle post  201  of the intermediate magnetic core  20 , the middle post  211  of the first magnetic core  21  and the middle post  221  of the second magnetic core  22  are cylindrical structures and have identical diameter. The centers of the middle posts  201 ,  211  and  221  are arranged along the same axial line A-A′. Moreover, the lateral legs  202  of the intermediate magnetic core  20 , the lateral legs  212  of the first magnetic core  21  and the lateral legs  222  of the second magnetic core  22  have the same cross-section shape and the same cross-section area. When the first magnetic core  21 , the intermediate magnetic core  20  and the second magnetic core  22  are coupled with each other, the first air gap  27  is formed between the middle post  211  of the first magnetic core  21  and a top surface  200   a  of the connection part  200  of the intermediate magnetic core  20 , and the second air gap  29  is formed between the middle post  201  of the intermediate magnetic core  20  and the middle post  221  of the second magnetic core  22 . A first magnetic path is defined by the intermediate magnetic core  20 , the first magnetic core  21  and the first air gap  27  collaboratively. A second magnetic path is defined by the intermediate magnetic core  20 , the second magnetic core  22  and the second air gap  29  collaboratively. After the stacked magnetic core assembly with the three magnetic cores, the first winding coil  23  and the second winding coil  24  are combined together, the magnetic element  2  is fabricated. The magnetic element  2  has two magnetic paths with leakage flux. 
     Please refer to  FIG. 2  again. In this embodiment, the first winding coil  23  is a coil pancake that wound around the middle post  211  of the first magnetic core  21  and arranged around the first air gap  27 . The first winding coil  23  has a first outlet terminal  231  and a second outlet terminal  232 . The first outlet terminal  231  and the second outlet terminal  232  are outputted from two opposite sides of the middle post  211  of the first magnetic core  21 . Similarly, the second winding coil  24  is a coil pancake that wound around the middle post  201  of the intermediate magnetic core  20  and the middle post  221  of the second magnetic core  22  and arranged around the second air gap  29 . The second winding coil  24  has a first outlet terminal  241  and a second outlet terminal  242 . The first outlet terminal  241  and the second outlet terminal  242  are outputted from two opposite sides of the middle post  201  (or the middle post  221 ). The second outlet terminal  232  of the first winding coil  23  and the second outlet terminal  242  of the second winding coil  24  are connected with each other by a welding means for example. The first outlet terminal  231  of the first winding coil  23  and the first outlet terminal  241  of the second winding coil  24  are outputted downwardly from the first winding space  26  and the second winding space  28  and penetrated through the corresponding perforations  250 , respectively. Consequently, the first outlet terminal  231  of the first winding coil  23  and the first outlet terminal  241  of the second winding coil  24  are fixed by the base plate  25 . The first outlet terminal  231  of the first winding coil  23  and the first outlet terminal  241  of the second winding coil  24  may be further electrically connected with an external circuit (not shown). In this embodiment, the first winding coil  23  and the second winding coil  24  are wound in the same winding direction. For example, the first winding coil  23  and the second winding coil  24  are wound in the clockwise winding direction. 
     In this embodiment, the connection part  200  of the intermediate magnetic core  20 , the connection part  210  of the first magnetic core  21  and the connection part  220  of the second magnetic core  22  have the identical thickness. The lateral leg  202  of the intermediate magnetic core  20  has a first length H 1 , the lateral leg  212  of the first magnetic core  21  has a second length H 2 , and the lateral leg  222  of the second magnetic core  22  has a third length H 3 . In this embodiment, the second length H 2  is larger than the first length H 1  and the third length H 3 , and the first length H 1  is equal to the third length H 3 . It is noted that the relationship between the first length H 1 , the second length H 2  and the third length H 3  is not restricted. For example, the relationship between the first length H 1 , the second length H 2  and the third length H 3  may be adjusted according to the turn numbers of the first winding coil  23  and the second winding coil  24  and the practical requirements. In this embodiment, the air-gap length of the first air gap  27  is equal to the air-gap length of the second air gap  29 . It is noted that the air-gap length of the first air gap  27  and the air-gap length of the second air gap  29  may be adjusted according to the first length H 1 , the second length H 2  and the third length H 3  and the practical requirements. In case that the first length H 1  is equal to the third length H 3 , the length of the middle post  201  of the intermediate magnetic core  20  is equal to the length of the middle post  221  of the second magnetic core  22 . Consequently, the second air gap  29  is uniformly distributed between the intermediate magnetic core  20  and the second magnetic core  22 . 
     In this embodiment, the intermediate magnetic core  20  and the first magnetic core  21  are coupled with each other through adhesive and/or tape (not shown), and the intermediate magnetic core  20  and the second magnetic core  22  are coupled with each other through adhesive and/or tape (not shown). 
     As shown in  FIG. 1B , the conventional inductor  1  only has a single air gap and the air-gap length is larger than the present disclosure. In the magnetic element  2  of the present disclosure, the first winding coil  23  and the second winding coil  24  are connected with each other in series, and the magnetic element  2  has multiple air gaps. Under this circumstance, the air gaps are dispersed and the portions of the middle posts of the magnetic cores to be scraped off are reduced. That is, the overall air-gap length is reduced. For example, the air-gap length of the air gap  14  of the conventional inductor  1  is 6.10 mm and uniformly distributed among the first magnetic core  11  and the second magnetic core  12 . That is, the air-gap length of the first magnetic core  11  and the air-gap length of the second magnetic core  12  are both 3.05 mm. That is, the portion of the middle post of the first magnetic core  11  to be scrapped off is 3.05 mm, and the portion of the second magnetic core  12  to be scrapped off is 3.05 mm. For achieving the same inductance value, the overall air-gap length of the magnetic element  2  of this embodiment is only 4 mm. For example, the air-gap length of the first air gap  27  and the air-gap length of the second air gap  29  are both 2 mm. The second air gap  29  is uniformly distributed among the intermediate magnetic core  20  and the second magnetic core  22 . That is, the air-gap length of the intermediate magnetic core  20  is 1 mm, and the air-gap length of the second magnetic core  22  is also 1 mm. That is, when compared with the conventional inductor  1 , the portions of the middle post  201  of the intermediate magnetic core  20 , the middle post  211  of the first magnetic core  21  and the middle post  221  of the second magnetic core  22  to be scraped off are reduced. Since the overall air-gap length is reduced, the eddy loss is decreased, and the overall temperature of the magnetic element  2  is reduced. In other words, the magnetic cores stacked in the asymmetric configuration can reduce the overall air-gap length and enhance the working efficiency. 
       FIG. 4  is a schematic cross-sectional view illustrating the magnet cores of a magnetic element according to a second embodiment of the present disclosure. As shown in  FIG. 4 , the magnetic element  3  comprises an intermediate magnetic core  30 , a first magnetic core  31 , a second magnetic core  32 , a first winding coil (not shown), a second winding coil (not shown), a first winding space  33 , a first air gap  34 , a second winding space  35 , and a second air gap  36 . Except for the following items, the configurations of the magnetic element  3  are substantially identical to those of the magnetic element  2  of the first embodiment. In comparison with the magnetic element  2  of the first embodiment, the types of the magnetic cores of the magnetic element  3  of this embodiment are distinguished. The intermediate magnetic core  30  is a Y-shaped core or a combination of a U-shaped core and a T-shaped core. The first magnetic core  31  is a T-shaped core, and the second magnetic core  32  is a U-shaped core. A first magnetic path is defined by the intermediate magnetic core  30 , the first magnetic core  31  and the first air gap  34  collaboratively. A second magnetic path is defined by the intermediate magnetic core  30 , the second magnetic core  32  and the second air gap  36  collaboratively. After the stacked magnetic core assembly with the three magnetic cores, the first winding coil and the second winding coil are combined together, the magnetic element  3  is fabricated. The magnetic element  3  has at least two magnetic paths with leakage flux. In this embodiment, the U-shaped core and the T-shaped core of the intermediate magnetic core  30  are connected with each other via an adhesive. In this embodiment, the intermediate magnetic core  30  and the first magnetic core  31  are coupled with each other through adhesive and/or tape (not shown). The intermediate magnetic core  30  and the second magnetic core  32  are coupled with each other through adhesive and/or tape (not shown). 
     Please refer to  FIG. 4  again. The intermediate magnetic core  30  comprises a connection part  300 , a middle post  301 , and two lateral legs  302 . The first magnetic core  31  comprises a connection part  310 , and a middle post  311 . The second magnetic core  32  comprises a connection part  320 , and two lateral legs  321 . The connection part  300  of the intermediate magnetic core  30  comprises an upper connection section  3001  and a lower connection section  3002 . The bottom surface of the upper connection section  3001  is coupled with the top surface of the lower connection section  3002 . The two lateral legs  302  of the intermediate magnetic core  30  are protruded from two edges of the upper connection section  3001 . The middle post  301  of the intermediate magnetic core  30  is protruded from the lower connection section  3002 . In this embodiment, the upper connection section  3001  and the lower connection section  3002  of the intermediate magnetic core  30 , the connection part  310  of the first magnetic core  31  and the connection part  320  of the second magnetic core  32  have the same thickness. 
     In this embodiment, both of the intermediate magnetic core  30  and the first magnetic core  31  comprise a T-shaped core. Consequently, the first winding coil and the second winding coil may be wound around the middle post  311  of the first magnetic core  31  and the middle post  301  of the intermediate magnetic core  30  by an automatic winding machine. Since the first winding coil and the second winding coil can be automatically wound, the cost of winding the coils will be reduced. 
     From the above descriptions, the present disclosure provides a magnetic element with multiple air gaps. The coils are directly wound around the magnetic cores without the need of using bobbin. Consequently, the fabricating cost is reduced, and the coil utilization is enhanced. Since the multiple air gaps of the magnetic element are dispersedly distributed, the eddy loss is reduced and the dispersing flux is decreased. Under this circumstance, the working temperature of the magnetic element is decreased, and the working efficiency of the magnetic element is enhanced. Moreover, since the magnetic cores are stacked in an asymmetric configuration and the winding coils are connected with each other in series, the magnetic force lines between the two winding coils are partially balanced. Under this circumstance, the thickness of the intermediate magnetic core is reduced, the overall volume is reduced, and the magnetic element is slim. 
     While the disclosure has been described in terms of what is presently considered to be the most practical and preferred embodiments, it is to be understood that the disclosure needs not be limited to the disclosed embodiment. On the contrary, it is intended to cover various modifications and similar arrangements included within the spirit and scope of the appended claims which are to be accorded with the broadest interpretation so as to encompass all such modifications and similar structures.