Abstract:
According to an aspect of the invention, a low profile can be achieved while the number of turns of the winding wire is secured. The magnetic element includes a rectangular-solid magnetic member and a conductor. A bellows-like metal flat plate snakes along a longitudinal direction in the conductor. In the bellows-like metal flat plate, snaking portions located in a direction perpendicular to the longitudinal direction are mutually projected toward opposite directions to form a space into which the magnetic member is inserted.

Description:
CLAIM OF PRIORITY 
       [0001]    This application claims the benefit of Japanese Patent Application No. 2006-111816 filed on Apr. 14, 2006, the entire contents of which are hereby incorporated by reference herein. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a magnetic element used in various electric instruments such as a portable telephone, a personal computer, and a television. 
         [0004]    2. Description of the Related Art 
         [0005]    Conventionally, there is known a magnetic element having a configuration in which a winding wire is wound about a drum-shape core. For example, Japanese Patent Laid-Open No. 2004-79917 discloses this kind of magnetic element. 
         [0006]    In the magnetic element disclosed in Japanese Patent Laid-Open No. 2004-79917, a magnet wire is wound about a circular cylindrical portion of the drum-shape core, and a sleeve core having a ring shape is arranged outside the drum-shape core so as to coaxially surround the drum-shape core. The drum-shape core has flanges at top and bottom ends of the circular cylindrical portion. 
         [0007]    However, the magnetic element disclosed in Japanese Patent Laid-Open No. 2004-79917 is one in which the drum-shape core is used. Generally, in the magnetic element in which the drum-shape core is used, for the view point of strength on a structure, it is necessary that a thickness of each flange be set to about 0.25 mm at the minimum. In consideration of cutting and the like in a production process, it is necessary that a height of the circular cylindrical portion be set to about 0.4 mm. Therefore, a dimension becomes 0.9 mm at the minimum in a height direction of the magnetic element in which the drum-shape core is used. Accordingly, there is a limitation to achievement of a low profile in the magnetic element in which the drum-shape core is used. 
         [0008]    In view of the foregoing, an object of the invention is to provide a magnetic element in which the low profile can be achieved while the number of turns of the winding wire is secured. 
       SUMMARY OF THE INVENTION 
       [0009]    A magnetic element according to a first aspect of the invention includes a rectangular-solid magnetic member; and a conductor in which, in a bellows-like metal flat plate snaking along a longitudinal direction, snaking portions located in a direction perpendicular to the longitudinal direction are mutually projected toward opposite directions to form a space into which the magnetic member is inserted. 
         [0010]    According to the magnetic element according to the first aspect of the invention, in the conductor, the snaking portions are arranged outside the magnetic member so as to face the magnetic member. Because the dimension in the height direction of the magnetic element becomes the sum of the thickness of the magnetic member and the thicknesses of the conductors located both sides of the magnetic member, the low profile is easily achieved in the magnetic element. Furthermore, because the magnetic member has the rectangular-solid shape, unlike the conventional drum-shape core, it is not necessary that the magnetic member be designed in consideration of securing of the winding frame and the strength of the flange. Accordingly, the dimension can easily be decreased in the height direction of the magnetic member, which allows the low profile to be achieved in the magnetic element. 
         [0011]    A magnetic element according to a second aspect of the invention includes a rectangular-solid magnetic member; and a conductor in which, in a bellows-like metal flat plate snaking along a longitudinal direction, snaking portions located in a direction perpendicular to the longitudinal direction are mutually projected toward only one direction to form a space into which the magnetic member is inserted. 
         [0012]    According to the magnetic element according to the second aspect of the invention, in the conductor, the snaking portions are arranged outside the magnetic member so as to face the magnetic member. Because the dimension in the height direction of the magnetic element becomes the sum of the thickness of the magnetic member and the thicknesses of the conductors located both sides of the magnetic member, the low profile is easily achieved in the magnetic element. Furthermore, because the magnetic member has the rectangular-solid shape, unlike the conventional drum-shape core, it is not necessary that the magnetic member be designed in consideration of securing of the winding frame and the strength of the flange. Accordingly, the dimension can easily be decreased in the height direction of the magnetic member, which allows the low profile to be achieved in the magnetic element. 
         [0013]    A magnetic element according to a third aspect of the invention includes a conductor in which, in a bellows-like metal flat plate snaking along a longitudinal direction, snaking portions located in a direction perpendicular to the longitudinal direction are mutually projected toward opposite directions to form a space; and a compressed powder body which is arranged at least inside the conductor, the compressed powder body being made of magnetic powders. 
         [0014]    According to the magnetic element according to the third aspect of the invention, in the case where the compressed powder body is arranged inside the conductor, in the conductor, the snaking portions are arranged outside the magnetic member so as to face the compressed powder body. Because the dimension in the height direction of the magnetic element becomes the sum of the thickness of the magnetic member and the thicknesses of the conductors located both sides of the magnetic member, the low profile is easily achieved in the magnetic element. Furthermore, in the case where the compressed powder body is arranged not only inside the conductor but also outside the conductor, because the thickness of the compressed powder body arranged outside the conductor becomes the dimension in the height direction of the magnetic element, unlike the conventional magnetic element in which the drum-shape core is used, it is not necessary that the core be designed in consideration of securing of the winding frame and the strength of the flange. Accordingly, the low profile can be achieved in the magnetic element. 
         [0015]    In the magnetic element according to the first to third aspect of the invention, preferably a ring core having a frame shape is arranged to surround an outside of the magnetic element. Therefore, magnetic fluxes generated by the conductor enter the inside of the ring core after passing through the inside of the magnetic member. Then, the magnetic fluxes pass through the inside of the ring core to enter the inside of the magnetic member again. Accordingly, a closed magnetic path is formed between the magnetic member and the ring core, so that the magnetic flux can be prevented from leaking to the outside of the magnetic element. As a result, the generation of a noise or an eddy current can be prevented in various electric instruments equipped with the magnetic element. 
         [0016]    According to the invention, the low profile can be achieved while the number of turns of the winding wire is secured. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]      FIG. 1  is a perspective view showing a configuration of a magnetic element according to a first embodiment of the invention; 
           [0018]      FIG. 2  is a plan view showing the magnetic element according to a first embodiment of the invention; 
           [0019]      FIG. 3  is a front view showing the magnetic element according to a first embodiment of the invention; 
           [0020]      FIG. 4  is a perspective view showing a configuration of a conductor in  FIG. 1 ; 
           [0021]      FIG. 5  is a plan view showing the conductor in  FIG. 1 ; 
           [0022]      FIG. 6  is a front view showing a coil in  FIG. 1 ; 
           [0023]      FIG. 7  is a plan view showing a magnetic element according to a second embodiment of the invention; 
           [0024]      FIG. 8  is a front view showing the magnetic element according to a second embodiment of the invention; 
           [0025]      FIG. 9  is a plan view showing a magnetic element according to a third embodiment of the invention; and 
           [0026]      FIG. 10  is a view showing a modification of the invention. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     First Embodiment 
       [0027]    A magnetic element  10  according to a first embodiment of the invention will be described below with reference to the drawings. 
         [0028]      FIG. 1  is a perspective view showing a configuration of the magnetic element  10  of the first embodiment.  FIG. 2  is a plan view showing the magnetic element  10  of the first embodiment.  FIG. 3  is a front view showing the magnetic element  10  of the first embodiment. In the following description, it is assumed that a front side is indicated by a direction of an arrow X 1  shown in  FIGS. 1 to 9 , a rear side is indicated by a direction of an arrow X 2 , a left side is indicated by a direction of an arrow Y 1 , a right side is indicated by a direction of an arrow Y 2 , upper side is indicated by a direction of an arrow Z 1 , and lower side is indicated by a direction of an arrow Z 2 . 
         [0029]    As shown in  FIGS. 1 to 3 , the magnetic element  10  is a surface mounted type magnetic element, and the magnetic element  10  mainly includes a rectangular-solid magnetic member  12  and a spiral coil  14 . The magnetic member  12  is arranged inside the coil  14 . 
         [0030]    The magnetic member  12  is made of a magnetic material such as ferrite. However, other magnetic materials such as permalloy, sendust, iron, and carbonyl may be used as the material of the magnetic member  12 . 
         [0031]      FIG. 4  is a perspective view showing a configuration of the coil  14 .  FIG. 5  is a plan view of the coil  14 .  FIG. 6  is a front view of the coil  14 . 
         [0032]    As shown in  FIG. 5 , when the coil  14  is viewed from above, the coil  14  is wound in a longitudinal direction while snaking along the longitudinal direction. Preferably the coil  14  is made of a metal such as copper having excellent conductivity, although the coil  14  may be made of a metal such as stainless steel, iron, and aluminum. 
         [0033]    As shown in  FIGS. 4 and 5 , the coil  14  has an upper extended portion  16 , a right side portion  18 , a lower extended portion  20 , and a left side portion  22 . The upper extended portion  16  is extended in a crosswise direction perpendicular to the longitudinal direction of the coil  14 . The right side portion  18  located on the right side is extended in the longitudinal direction of the coil  14 . The lower extended portion  20  is extended in the crosswise direction. The left side portion  22  located on the left side is extended in the longitudinal direction. The upper extended portion  16  is extended from a rear end portion  22   a  of the left side portion  22  toward the substantially crosswise direction. The right side portion  18  is extended from a front end of the upper extended portion  16  toward the substantially longitudinal direction. The lower extended portion  20  is extended from a rear end portion  18   a  of the right side portion  18  toward the substantially crosswise direction. The left side portion  22  is extended from a front end of the lower extended portion  20  toward the substantially longitudinal direction. Thus, the coil  14  is wound such that the upper extended portion  16 , the right side portion  18 , the lower extended portion  20 , and the left side portion  22  are continuously connected. 
         [0034]    Both the right side portion  18  and the left side portion  22  are formed in a flat shape along the longitudinal direction of the coil  14 . The right side portion  18  and the left side portion  22  are located on the right side and left side of the coil  14  respectively. As shown in  FIG. 6 , the right side portion  18  and the left side portion.  22  are located on the same plane. The right side portion  18  is horizontally projected toward the right side of the coil  14 . The left side portion  22  is horizontally projected toward the left side of the coil  14 . 
         [0035]    As shown in  FIGS. 4 and 6 , the upper extended portion  16  includes an upper flat plate portion  16   a , a lower right curved portion  16   b , and a lower left curved portion  16   c . The upper flat plate portion  16   a  formed in flat shape is extended in the crosswise direction of the coil  14 . The lower right curved portion  16   b  is extended while curved downward from a right end of the upper flat plate portion  16   a . The lower left curved portion  16   c  is extended while curved downward from a left end of the upper flat plate portion  16   a . The front end of the lower right curved portion  16   b  is connected to a front end portion  18   b  of the right side portion  18 , and the front end of the lower left curved portion  16   c  is connected to the rear end portion  22   a  of the left side portion  22 . 
         [0036]    The lower extended portion  20  includes a lower flat plate portion  20   a , an upper right curved portion  20   b , and an upper left curved portion  20   c . The lower flat plate portion  20   a  formed in flat shape is extended in the crosswise direction of the coil  14 . The upper right curved portion  20   b  is extended while curved upward from the right end of the lower flat plate portion  20   a . The upper left curved portion  20   c  is extended while curved upward from the left end of the lower flat plate portion  20   a . The front end of the upper right curved portion  20   b  is connected to the rear end portion  18   a  of the right side portion  18 , and the front end of the upper left curved portion  20   c  is connected to a front end portion  22   b  of the left side portion  22 . 
         [0037]    Dimensions in height directions of the lower right curved portion  16   b  and lower left curved portion  16   c  are equal to dimensions in height directions of the upper right curved portion  20   b  and upper left curved portion  20   c  respectively. That is, as shown in  FIG. 6 , a height H from the right side portion  18  is equal to a height H from the left side portion  22  of the upper flat plate portion  16   a . Similarly, a height I from the right side portion  18  is equal to a height I from the left side portion  22  of the lower flat plate portion  20   a . Therefore, the coil  14  is formed in the spiral shape by the upper extended portions  16  and the lower extended portions  20  through the right side portions  18  and the left side portions  22 , which allows an air-core portion  24  to be formed inside the coil  14 . The air-core portion  24  is inserted into the coil  14  in the longitudinal direction. In the first embodiment, the lower extended portion  20  located at the front end in the coil  14  and the lower extended portion  20  located at the rear end in the coil  14  become terminal ends  26  of the coil  14 . The coil  14  is formed by vertically pressing and/or forming a bellows-like metal plate which is extended in the longitudinal direction while snaking along the longitudinal direction in the same plane. For example, terminal portions of the coil  14  can be formed by the pressing and/or forming. In the first embodiment, the terminal ends  26  and  26  correspond to the terminal portions. In the case where the magnetic element  10  is mounted on a circuit board, because the lower side of the magnetic element  10  is bonded on the circuit board, the terminal ends  26  and  26  are electrically connected to the circuit board. 
         [0038]    As shown in  FIGS. 1 and 3 , the magnetic member  12  is arranged in the substantial center of the air-core portion  24  in the coil  14 . In this state of things, as shown in  FIGS. 1 and 2 , the conductor constituting the coil  14  is wound in the substantially spiral shape about the magnetic member  12 . As shown in  FIG. 3 , an upper surface  12   a  of the magnetic member  12  faces an inside surface  16   d  of the upper flat plate portion  16   a . A space J is formed between the upper surface  12   a  and the inside surface  16   d . A lower surface  12   b  of the magnetic member  12  faces an inside surface  20   d  of the lower flat plate portion  20   a . A space K is formed between the lower surface  12   b  and the inside surface  20   d . A space L is formed between the right side portion  18  and the right side face  12   c  of the magnetic member  12 , and a space M is formed between the left side face  12   d  and the left side portion  22 . However, preferably the spaces J, K, L, and M are provided as narrow as possible between the magnetic member  12  and the coil  14 . Only a part of the spaces J, K, L, and M may be provided while remaining spaces are not provided. The magnetic element  10  is mounted on the circuit board with the side of the lower extended portion  20  down. 
         [0039]    In the magnetic element  10  having the above configuration, the magnetic member  12  is arranged in the air-core portion  24  of the coil  14  having the spiral shape. Therefore, the upper extended portion  16  and the lower extended portion  20  are arranged in the vertical outside of the magnetic member  12  such that wide surfaces of the upper extended portion  16  and lower extended portion  20  face the magnetic member  12 . Accordingly, the dimension in the height direction of the magnetic element  10  becomes a distance from the upper flat plate portion  16   a  to the lower flat plate portion  20   a , so that the low profile can be achieved in the magnetic element  10 . Furthermore, because the magnetic member  12  has the rectangular-solid shape, unlike the conventional drum-shape core, it is not necessary that the magnetic member  12  be designed in consideration of securing of the winding frame and the strength of the flange. Accordingly, the dimension can easily be decreased in the height direction of the magnetic member  12 , which allows the low profile to be achieved in the magnetic element  10 . 
       Second Embodiment 
       [0040]    A magnetic element  30  according to a second embodiment of the invention will be described below with reference to the drawings. In the magnetic element  30  of the second embodiment, the same component as that of the first embodiment is designated by the same numeral, and the description is neglected or simplified. 
         [0041]      FIG. 7  is a plan view showing the magnetic element  30  of the second embodiment.  FIG. 8  is a front view showing the magnetic element  30  of the second embodiment. 
         [0042]    As shown in  FIGS. 7 and 8 , the magnetic element  30  mainly includes a compressed powder body  32  and a coil  34 . The compressed powder body  32  is formed by compressing magnetic powders. 
         [0043]    The coil  34  has the substantially same configuration as the coil  14  of the first embodiment. The coil  34  differs from the coil  14  in that an outside electrode  36   a  and an outside electrode  38   a  are formed at terminal ends  36  and  38  corresponding to the terminal ends  26  and  26  of the first embodiment respectively. As shown in  FIG. 8 , the outside electrode  36   a  has a side electrode portion  36   b  and a bottom electrode portion  36   c . The side electrode portion  36   b  is extended downward from the front end of the terminal end  36 , and the bottom electrode portion  36   c  is extended toward the leftward direction from the front end of the side electrode portion  36   b . The outside electrode  38   a  has a side electrode portion  38   b  and a bottom electrode portion  38   c . The side electrode portion  38   b  is extended downward from the front end of the terminal end  38 , and the bottom electrode portion  38   c  is extended toward the rightward direction from the front end of the side electrode portion  38   b . Preferably the coil  34  is made of a metal such as copper having excellent conductivity, although the coil  34  may be made of a metal such as stainless steel, iron, and aluminum. 
         [0044]    As shown in  FIGS. 7 and 8 , except the outside electrodes  36   a  and  38   a , the outside of the coil  34  is covered with the compressed powder body  32 . That is, the outside electrodes  36   a  and  38   a  are exposed to the outside of the compressed powder body  32 . As shown in  FIG. 8 , the side electrode portion  36   b  is formed on the right side of the right side face  32   a  so as to be brought into contact with the right side face  32   a  of the compressed powder body  32 . The side electrode portion  38   b  is formed on the left side of the left side face  32   b  so as to be brought into contact with the left side face  32   b  of the compressed powder body  32 . The bottom electrode portions  36   c  and  38   c  are formed beneath the bottom surface  32   c  so as to be brought into contact with the bottom surface  32   c  of the compressed powder body  32 . Therefore, when the magnetic element  30  is mounted on the circuit board, each of the bottom electrode portions  36   c  and  38   c  is electrically connected to the circuit board. 
         [0045]    The coil  34  is embedded in the magnetic powder constituting the compressed powder body  32 , and heat and pressure applied from the outside, which forms the magnetic element  30 . Pressure forming can be cited as an example of the method of applying the heat and pressure, although the method is not limited to the pressure forming. Metal magnetic powders mainly containing soft-magnetic ferrite or iron powder can be cited as an example of the magnetic powder, although the magnetic powder is not limited to the soft-magnetic ferrite or iron powder. 
         [0046]    In the magnetic element  30  having the above configuration, the coil  34  is wound such that the wide surface of the coil  34  faces the inside. Therefore, the dimension can be decreased in the height direction of the coil  34 . Furthermore, because the compressed powder body  32  is arranged such that the outside of the coil  34  is covered with the compressed powder body  32 , unlike the conventional drum-shape core, it is not necessary that the design be performed in consideration of securing of the winding frame and the strength of the flange. Accordingly, the dimension can easily be decreased in the height direction of the compressed powder body  32 , which allows the low profile to be achieved in the magnetic element  30 . 
       Third Embodiment 
       [0047]    A magnetic element  40  according to a third embodiment of the invention will be described below with reference to the drawing. In the magnetic element  40  of the third embodiment, the same component as that of the first embodiment is designated by the same numeral, and the description is neglected or simplified. 
         [0048]      FIG. 9  is a plan view showing the magnetic element  40  of the third embodiment. 
         [0049]    In the magnetic element  40 , a ring core  42  having a substantially square frame shape is arranged outside the magnetic element  10  of the first embodiment. A rear end face  44  of the magnetic member  12  abuts on an inside rear surface  42   a  of the ring core  42 . The inside rear surface  42   a  is located inside the ring core  42  and on the rear side of the ring core  42 . The rear end face  44  and the inside rear surface  42   a  are fixed to each other with a bonding agent. A gap  48  is formed between a front end face  46  of the magnetic member  12  and an inside front surface  42   b  of the ring core  42 . The inside front surface  42   b  is located inside the ring core  42  and on the front side of the ring core  42 . Preferably, as with the magnetic member  12 , the ring core  42  is made of a magnetic material such as ferrite. However, other magnetic materials such as permalloy, sendust, iron, and carbonyl may be used as the ring core  42 . 
         [0050]    In the magnetic element  40  having the above configuration, the ring core  42  is arranged so as to surround the outside of the magnetic element  40 . Therefore, magnetic fluxes generated by the coil  14  enter the inside of the ring core  42  after passing through the inside of the magnetic member  12 . Then, the magnetic fluxes pass through the inside of the ring core  42  to enter the inside of the magnetic member  12  again. Because the closed magnetic path is formed between the magnetic member  12  and the ring core  42 , the magnetic flux can be prevented from leaking to the outside of the magnetic element  40 . As a result, the generation of the noise or the eddy current can be prevented in various electric instruments equipped with the magnetic element  40 . 
         [0051]    In the magnetic element  40 , the gap  48  is provided between the front end face  46  of the magnetic member  12  and the inside front surface  42   b  of the ring core  42 , which allows permeability to be decreased between the magnetic member  12  and the ring core  42 . Accordingly, saturation of magnetization can be prevented in the magnetic element  40 . 
         [0052]    Although the embodiments of the invention are described above, the invention is not limited to the above embodiments, and various modifications can be made. 
         [0053]    In the above embodiments, the upper extended portion  16  and the lower extended portion  20  are extended toward the substantially crosswise directions of the coils  14  and  34  respectively. Alternatively, both or one of the upper extended portion  16  and the lower extended portion  20  may be obliquely extended with respect to the crosswise directions of the coils  14  and  34 . In the above embodiments, the right side portion  18  and the left side portion  22  are extended toward the substantially longitudinal directions of the coils  14  and  34  respectively. Alternatively, both or one of the right side portion  18  and the left side portion  22  may be obliquely extended with respect to the longitudinal directions of the coils  14  and  34 . 
         [0054]    In the above embodiments, the upper extended portion  16  is formed above the right side portion  18  and the left side portion  22 , and the lower extended portion  20  is formed below the right side portion  18  and the left side portion  22 . Alternatively, as shown in  FIG. 10 , a magnetic element  50  may be formed such that the lower extended portion  20  constitutes the same plane along with the right side portion  18  and the left side portion  22 . 
         [0055]    In the above embodiments, in the coils  14  and  34 , the heights H from the right side portion  18  and the left side portion  22  to the upper flat plate portion  16   a  are equal to each other, and the heights I from the right side portion  18  and the left side portion  22  to the lower flat plate portion  20   a  are equal to each other. However, the invention is not limited to the embodiment. The height H from the right side portion  18  to the upper flat plate portion  16   a  may differ from the height H from the left side portion  22  to the upper flat plate portion  16   a , and the height I from the right side portion  18  to the lower flat plate portion  20 . a  may differ from the heights I from the left side portion  22  to the lower flat plate portion  20   a.    
         [0056]    In the second embodiment, the compressed powder body  32  is arranged such that the outside of the coil  34  is covered with the compressed powder body  32 . However, the invention is not limited to the second embodiment, but the compressed powder body  32  may be arranged only inside the coil  34 . 
         [0057]    In the second embodiment, the outside electrodes  36   a  and  38   a  are formed while being integral with the terminal ends  36  and  38  respectively. However, the invention is not limited to the second embodiment, but the outside electrodes  36   a  and  38   a  may be formed independently of the terminal ends  36  and  38  respectively. 
         [0058]    In the first or third embodiment, the magnetic member  12  is arranged in the substantial center of the air-core portion  24  of the coil  14 . However, it is not necessary to particularly specify the position where the magnetic member  12  is arranged in the air-core portion  24 . For example, the magnetic member  12  may be arranged in the air-core portion  24  such that the lower surface  12   b  of the magnetic member  12  is brought into contact with the inside surface  20   d  of the coil  14 . 
         [0059]    In the third embodiment, the rear end face  44  of the magnetic member  12  abuts on the inside rear surface  42   a  of the ring core  42 . For example, the rear end face  44  may be configured so as not to abut on the inside rear surface  42   a , and a gap is provided between the rear end face  44  and the inside rear surface  42   a . The front end face  46  may also be configured so as to abut on the inside front surface  42   b  while the rear end face  44  abuts on the inside rear surface  42   a.    
         [0060]    In the third embodiment, the ring core  42  has the substantially square frame shape. However, the invention is not limited to the square frame shape, but the ring core  42  may have other frame shapes such as an elliptical frame shape and a circular frame shape. 
         [0061]    The magnetic element of the invention can be applied to electric instruments such as a portable telephone, a personal computer, and a television.