Patent Publication Number: US-7211724-B2

Title: Noise filter having case and core assembled therein

Description:
BACKGROUND OF THE INVENTION 
   The present invention relates to a noise filter including a case and a tubular core assembled therein. 
   Hitherto, in noise filters, a magnetic core is disposed over an outer circumferential surface of an electric cable, thus absorbing noise current flowing through the electric cable. The core is brittle because it was made by baking or sintering. A case composed of two complementary halves is used for protecting the core and for mounting the core at a desired position of the electric cable. 
   In a conventional noise filter, a cable retaining segment is provided in the case. The cable retaining segment nips the electric cable. In this case, however, the case is inevitably complicated in shape. Consequently, a metal mold for molding the case is complex in shape. This lowers the productivity of the noise filter. 
   Laid-open Japanese Patent Application Publication No. 2004-193316 discloses a noise filter, in which a cable retaining segment is provided for respective halves of the case. The cable retaining segments nip the electric cable in the direction that is substantially perpendicular to parting faces of the complementary halves. Then, the electric cable contacts the cable retaining segments only at two points. In this case, an excessive pressure will be applied to the cable at one point if nipping force is to be increased. This may degrade durability of the electric cable. 
   To hold the electric cable by solely cable retaining segments in the opposite directions, sufficient rigidity is required in the cable retaining segments. In the latter case, however, such cable retaining segments do not provide sufficient nipping for an electric cable having relatively large diameter. Hence, the case with the rigid cable retaining segments is not available for holding various kinds of electric cables having various outer diameters. 
   A noise filter may be attached to an electric cable that is would once or a few times in a loop fashion, forming a bundle. If two cable retaining segments are used to hold the bundle of electric cable from the opposite directions, the electric cable, thus bundled, can hardly be held appropriately in its entirety. 
   SUMMARY OF THE INVENTION 
   It is therefore, an object of the present invention to provide a noise filter provided with a case having a simplified construction and capable of holding the cable irrespective of cable diameter and number of cables of the bundle in case of looped setting. 
   This and other objects of the present invention will be attained by a noise filter including a case and a core. The case includes a tubular core holding section, a tubular coupling section, and a tubular cable guiding section. The core is accommodatable in the case and provides a hollow space through which the cable extends. The tubular coupling section is disposed at at least one end of the core holding section. The tubular cable guiding section is connected to the coupling section and provides an opening through which the cable extends. The cable guiding section is tetrameric by slits including a first slit part, a second slit part, a third slit part and a fourth slit part. At least the cable guide section is made from a resilient material. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawings: 
       FIG. 1  is a plan view of a noise filter according an embodiment of the present invention; 
       FIG. 2  is a side view of the noise filter according the embodiment of the invention; 
       FIG. 3  is a rear view of the noise filter according the embodiment of the invention; 
       FIG. 4  is a front view of the noise filter according the embodiment of the invention; 
       FIG. 5  is a plan view of the noise filter according the embodiment in which a casing is at its open state; 
       FIG. 6  is a cross-sectional view of the noise filter taken along the line VI—VI of  FIG. 1 ; 
       FIG. 7  is a schematic cross-sectional view of a clamp part of the noise filter according the embodiment of the invention; and 
       FIG. 8  is a cross-sectional view showing a cable-guiding section of a noise filter according to another embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   A noise filter according to an embodiment of the present invention will be described with reference to  FIGS. 1 through 7 .  FIG. 1  shows a noise filter  1  secured to a cable  100 . As shown in  FIG. 1 , the noise filter  1  includes a case  2  and a core  3 . The case  2  generally has a hollow cylindrical configuration and is made from resin provided with a resiliency. The core  3  is shaped like a hollow cylinder made from a magnetic substance and has a through hole allowing the cable  100  to pass therethrough. 
   As shown in  FIGS. 2 and 5 , the case  2  is composed of two complementary halves, i.e., a first case  21  and a second case  22 . Similarly, the core  3  is composed of two complementary halves, i.e., a first core  31  and a second core  32 . As shown in  FIG. 1 , the case  2  includes a hollow cylindrical core-holding section  4 , first and second cable-guiding sections  5  and  6 , and first and second coupling sections  7  and  8 . The first and second cable-guiding sections  5  and  6  are provided at the ends of the core-holding section  4 , respectively. The first coupling section  7  is arranged between the first cable-guiding section  5  and core-holding section  4  for coupling the core-holding section  4  to the first cable-guiding section  5 . The second coupling section  8  is arranged between the second cable-guiding section  6  and core-holding section  4  for coupling the core-holding section  4  to the second cable-guiding section  6 . In the description hereinafter, the direction from the first cable-guiding section  5  toward second cable-guiding section  6  (i.e., cable-guiding direction) in  FIG. 1  is defined as x-axis direction, and the direction from the first case  21  toward second case  22  and at right angles to the x-axis direction is defined as z-axis direction in  FIG. 2 . Further, the direction that is perpendicular to both the x-axis direction and the z-axis direction is defined as y-axis direction. 
   The core-holding section  4  includes a first core-holding part  41  and a second core-holding part  42 , which are provided on the first case  21  and the second case  22 , respectively. The first core-holding part  41  and the second core-holding part  42  have a semicircular cross-section, in the plane defined by the y- and z-axes. As shown in  FIGS. 1 and 3 , a pair of hinge sections  10 ,  10  which connect the first core-holding part  41  and the second core-holding part  42  together are provided at one end of the first core-holding part  41  and the second core-holding part  42  with respect to the y-axis direction ( FIG. 1 ), and at two locations which trisect the first core-holding part  41  and the second core-holding part  42  in the x-axis direction ( FIG. 3 ). As shown in  FIG. 5 , the first core-holding part  41  and the second core-holding part  42  have parting faces  21 B and  22 B, respectively, at positions where the hinge sections  10 ,  10  are provided. The first and second cases  21  and  22  are in abutment with each other on the parting faces  21 B and  22 B, when the first and second cases  21  and  22  are closed together. 
   As shown in  FIG. 1 , a pair of engagement sections  9 ,  9  are provided at each free end of each of the first and second cases  21 ,  22  at a position opposite to the hinge sections  10 ,  10  in y-axis direction for maintaining the closed state of the first and second cases  21 ,  22 . The pair of engagement sections  9 ,  9  trisect the first core-holding part  41  and the second core-holding part  42  in the x-axis direction at positions corresponding to the pair of hinge sections  10 , 10 . As shown in  FIG. 5 , the first and second core-holding parts  41  and  42  have parting faces  21 A and  22 A, respectively, at the positions where the engagement sections  9  are provided. The first and second cases  21  and  22  are in abutment with each other on these parting faces  21 A and  22 A. 
   As shown in  FIG. 4 , each engagement section  9  is composed of an engagement-hole forming part  91 , an engagement-claw peripheral part  92 , and an engagement claw  92 A. The forming part  91  is provided on the first core-holding part  41  and has an engagement hole  91   a . The peripheral part  92  is provided on the second core-holding part  42 . The engagement claw  92 A is provided on the engagement-claw peripheral part  92 . As shown in  FIG. 1 , the first core-holding part  41  has a U-shaped elongated slot  41   a . The elongated slot  41   a  includes a first part extending in the x-axis direction and located close to the hinge sections  10  and second and third parts extending from the ends of the first part in the y-axis direction toward the engagement sections  9 . The elongated slot  41   a  defines a first core-pushing part  41 A that is continuous to the first core-holding part  41  at the side of the engagement sections  9 . The first core holding part  41  has an arcuate shape providing an imaginary center. The first core-pushing part  41 A has a free end near the hinge sections  10 . The free end is displaced toward the imaginary center from the arcuate contour of the first core-holding part  41  as viewed in the cross-section in a plane defined by the y- and z-axes. As shown in  FIGS. 3 and 4 , the second core-holding part  42  has an elongated slot  42   a  and a second core-pushing part  42 A, which are the same as those of the first core-holding part  41 . 
   Next, the first cable-guiding section  5 , second cable-guiding section  6 , first coupling section  7  and second coupling section  8  will be described. The first cable-guiding section  5  and first coupling section  7  are symmetrical to the second cable-guiding section  6  and second coupling section  8 , with respect to the core-holding section  4 . Therefore, only the first cable-guiding section  5  and first coupling section  7  will be described, though the sections  6  and  8  may be referred to in the following description. 
   As  FIG. 1  shows, the first cable-guiding section  5  is shaped like a truncated cone with its z-x cross-sectional area gradually decreasing in the x-axis direction, from the first core-holding part  41  toward its distal end. Since the first cable-guiding section  5  is shaped like such truncated cone, a smooth and continuous included peripheral surface can be spanned between the outer peripheral surface of the cable  100  and the core-holding section  4  that is the largest diameter region of the noise filter  1 . Hence, the truncated cone shape of the noise filter  1  can prevent other ambient cable or ambient stationary object from getting hung up on the noise filter  1  when the latter is disposed over the cable  100 . Thus, the noise filter  1  would not be an obstacle that may hinder a layout of the cable  100 . 
   As shown in  FIG. 2 , the first cable-guiding section  5  shaped like a truncated cone is divided into four parts  51 ,  52 ,  53  and  54 , which are sectioned by four slits  51   a ,  52   a ,  53   a  and  54   a  and sequentially arranged in the circumferential direction of the first cable-guiding section  5 . In the y-z cross-section, the first cable-guiding section  5  is divided into the four parts,  51 ,  52 ,  53 ,  54  by the slits  51   a ,  52   a ,  53   a  and  54   a  those arranged in a cruciform fashion whose crossing center is coincident with an imaginary apex of the truncated cone. The first cable-guiding section  5  has an opening  5   a  in its distal end. The opening  5   a  has an inner diameter smaller than the outer diameter of the cable  100  prior to setting the noise filter  1  over the cable  100 . Further, parting faces of the first case  21  and the second case  22  are in alignment with and within width of the first slit  51   a  and the third slit  53   a . Thus, the first and second parts  51  and  52  belong to the first case  21 , and the third and fourth parts  53  and  54  belong to the second case  22 . In other words, it is unnecessary to positively form a slit between first part  51  and the fourth part  54 , and between the second part  52  and the third part  53 , since the parting faces of the firs and second cases  21  and  22  can function as slits. Further, the cruciform arrangement of the slits can provide substantially equal shape among these parts  51  through  54 . Therefore, these parts  51 – 54  can provide uniform and symmetrical pressure to the cable  100 . 
   As shown in  FIG. 2 and 5 , the first to fourth parts  51  to  54  have distal ends provided with first to fourth claws  51 A to  54 A, respectively. The first to fourth claws  51 A to  54 A protrude radially inwardly in hook like fashion in the y-z plane. These claws  51 A to  54 A project toward a center of the opening  5   a , and each being gradually thinning toward its radially innermost end. With this arrangement, the claws  51 A to  54 A can provide a stronger clamping force when a force for moving the cable  100  in its axial direction is applied relative to the case  2 . The first to fourth claws  51 A to  54 A constitute a chuck part  5 A and define the opening  5   a.    
   The first coupling section  7  ( FIG. 1 ) that couples the first cable-guiding section  5  to the core-holding section  4  has a first elongated slot  71   a  ( FIG. 4 ), a second elongated slot  72   a  ( FIG. 1 ), a third elongated slot  73   a  ( FIG. 3 ) and a fourth elongated slot  74   a  ( FIGS. 3 and 4 ). These elongated slots  71   a  to  74   a  extend in the circumferential direction of the case  2  and are located at the proximal ends of the first to fourth slits  51   a  to  54   a , respectively. The elongated slots  71   a  to  74   a  have substantially the same shape. These elongated slots  71   a  to  74   a  are in communication, at each intermediate portion in the circumferential direction, with the first to fourth slits  51   a  to  54   a , respectively. A first connecting part  71  ( FIG. 1 ) lies between the first elongated slot  71   a  and the second elongated slot  72   a . Further, a second connecting part  72  ( FIG. 1 ), a third connecting part  73  ( FIG. 3 ), and a fourth connecting part  74  ( FIG. 4 ) are similarly defined. The first to fourth connecting parts  71  to  74  connect the first to fourth parts  51  through  54 , respectively, to the core-holding section  4 . Each of the first through fourth connecting parts  71  through  74  is positioned, respectively, at each of the intermediate positions of the first to fourth parts  51  to  54  in the circumferential direction. Hence, the first to fourth parts  51  to  54  are pivotally movable in the y-z plane so as to increase or decrease the diameter of the opening  5   a  with the first through fourth connecting parts  71  through  74  functioning as fulcrums. Further, these elongated slots  71   a  through  74   a  can increase flexibility of the cable guide section  5 , which is particularly available for a cable having a relatively large diameter or a looped cable providing a cable bundled part. 
   As shown in  FIG. 6 , core retaining segments  41 B and  41 C are provided. These core retaining segments  41 B,  41 C are in the form of L-shape, and each having a radial part extending toward the center of the opening  5   a  (z-axis direction) and defining one side wall of the second elongated slot  72   a  and an axial part extending from a radially innermost end of the radial part toward a longitudinal center of the first core  31  (x-axis direction). Similarly, core retaining segments  42 B and  42 C are in the form of L-shape, and each has a radial part extending toward the center of the opening  5   a  (z-axis direction) and defining one side wall of the fourth elongated slot  74   a  and an axial part extending from a radially innermost end of the radial part toward a longitudinal center of the second core  32  (x-axis direction). Since the radial part of each of the core retaining segments serves as a wall of each of the elongated slots, a space-saving structure can be provided in the case  2 . 
   The second cable-guiding section  6  is similar in configuration to the first cable-guiding section  5 . The section  6  is divided into first to fourth parts  61 ,  62 ,  63  and  64  by a cruciform slit (when the case  2  is closed). The cruciform slit includes first slit  61   a  to fourth slit (not shown). The first to fourth parts  61 ,  62 ,  63  and  64  are connected to the core-holding section  4  by first to fourth connecting parts  81  to  84  that are defined by first to fourth elongated slots  81   a  to  84   a . An L-shaped core retaining segment  41 D extends from the first part  61 , and an L-shaped core retaining segment  41 E extends from the second part  62 . These segments  41 D and  41 E define one side wall of the second elongated slot  82   a . Similarly, an L-shaped core retaining segment  42 D extends from the fourth part  64 , and an L-shaped core retaining segment  42 E extends from the third part  63 . These segments  42 D and  42 E define one side wall of the fourth elongated slot  84   a.    
   The first core  31  has a semicircular and arcuate cross-section in a plane perpendicular to its axis. As shown in  FIG. 5 , the first core  31  has a pair of first core-abutment surfaces  31 A and  31 B at the ends of the arc. The core-abutment surfaces  31 A,  31 B provide smooth planes and at a diametrical position of the resultant core  3 . Similar to the first core  31 , the second core  32  has a semicircular and arcuate cross-section and has a pair of second core-abutment surfaces  32 A and  32 B at the ends of the arc. The second core-abutment surface  32 A is in contact with the first core-abutment surface  31 A, and the second core-abutment surface  32 B is in contact with the first core-abutment surface  31 B as a result of assembly of the core  3 . The core-abutment surfaces  32 A,  32 B provide smooth planes at a diametrical position of the resultant core  3 . 
   The first core  31  is positioned in the semi-circular space of the first core holding part  41  as shown in  FIG. 5 . The core retaining segments  41 B to  41 E hold the inner circumferential surface of the first core  31 . In this state, the first core-pushing part  41 A pushes the first core  31  radially inwardly of the first core holding part  41 , so that the pair of first core-abutment surfaces  31 A and  31 B of the first core  31  projects from an imaginary plane connecting the parting faces  21 A and  21 B of the first case  21 . Similarly, the second core  32  is positioned in the semi-circular space of the second core holding part  42 , and the core retaining segments  42 B to  42 E hold the inner circumferential surface of the second core  32 . In this state, the second core-pushing part  42 A urges the second core  32  radially inwardly of the second core holding part  42 , so that the pair of second core-abutment surfaces  32 A and  32 B of the second core  32  projects from an imaginary plane connecting the parting faces  22 A and  22 B of the second case  22 . 
   In this state, the cable  100  is held between the third claw  53 A and the fourth claw  54 A and between the third claw  63 A and the fourth claw  64 A. Thereafter, the first case  21  is pivotally moved about the hinge sections  10 ,  10  toward the second case  22 . The first core  31  and the second core  32  are thereby closed, superposing the first core-abutment surface  31 A,  31 B with the second core-abutment surface  32 A,  32 B, respectively, as is illustrated in  FIG. 1 . In this case, the engagement-claw  92 A of each engagement section  9  is inserted into the engagement hole  91   a  and is brought into engagement with the engagement-hole forming part  91 . Further, the engagement-hole forming part  91  is in intimate contact with the engagement-claw peripheral part  92 . At this time, the first core  31  and the second core  32  are urged radially inwardly by the first core-pushing part  41 A and the second core-pushing part  42 A, respectively, so that the resultant core  3  can provide a sealed hollow construction. Moreover, the urging force acts between the engagement claw  92 A and the engagement-hole forming part  91  to move them away from each other. Therefore, the locking engagement at the engagement section  9  can be ensured. Since the core  3  can be held with the urging force, inadvertent movement of the first core  31  and second core  23  within the case  2  can be prevented. 
   The chuck part  5 A clamps the cable  100 . In this state, the first to fourth parts  51  to  54  are resiliently pivotally moved about the first to fourth connecting parts  71  to  74  functioning as fulcrums. Since the case  2  is made from a soft resin material, pivoting mobility of the first to fourth parts  51  to  54  is sufficient to easily broaden the cross-sectional area of the opening  5   a , as long as the cable  100  is insertable into the core  3  or as long as the number of cables is small enough that all cables can be inserted into the core  3 . The cable  100  can therefore be held from four directions in a desirable fashion. 
   The cable  100  may be pulled from the chuck part  5 A by a short distance Δt, toward the core-holding section  4  in the direction (x-axis direction) as shown in  FIG. 7 , with respect to the noise filter  1 . In this case, the first cable-guiding section  5  including the chuck part  5 A moves in the x-axis direction by the distance Δt, together with the cable  100 . The first cable-guiding section  5  only is pivotally moved about the first coupling section  7  acting as a fulcrum, since the core-holding section  4  provides rigidity higher than that of the first cable-guide section  5  because of the hollow cylindrical shape. Hence, when the first cable-guiding section  5  moves in the x-axis direction by the distance Δt, the first cable-guiding section  5  is pivotally moved toward inside of the core-holding section  4  as shown by a broken line  5 ′. As a result, the chuck part  5 A further bites into the cable  100 , preventing the cable  100  from displacing a distance longer than the distance Δt. Similar to the first cable-guiding section  5 , the second cable-guiding section  6  can prevent the cable  100  from moving even if the cable  100  is pulled from the chuck part  6 A ( FIG. 1 ) toward the core-holding section  4  with respect to the noise filter  1 . 
   The positions of the core retaining segments  41 B to  41 E and the core retaining segments  42 B to  42 E are coincident with the position of the elongated slots  72   a ,  82   a  of the first and second coupling sections  7  and  8 . Therefore, complicated metal molds for molding the first case  21  and second case  22  are not required. Rather, the core retaining segments can be shaped after molding the semi-cylindrical parts of the first case  21  and second case  22 . Further, since the chuck parts  5 A and  6 A are provided at axially both ends of the noise filter, the chuck parts  5 A and  6 A can prevent the cable  100  from moving in both rightward and leftward in  FIG. 1  in its axial direction relative to the case  2 . 
     FIG. 8  shows a modification to first and second cable-guiding sections. In the foregoing embodiment, the first and second able guiding sections  5  and  6  have conical shape. In contrast, in the embodiment shown in  FIG. 8  first cable-guiding section  151 ,  154  provide substantially the same outer diameter as the core-holding section  4 . In this case, the first cable-guiding sections  151 ,  154  are resiliently pivotally movable at the coupling section  7 , and the chuck part  105 A moves with reducing the diameter of the opening  105   a  when the cable  100  is pulled rightward in  FIG. 8  relative to the noise filter. As a result, the chuck part  105 A tightens the cable  100 , preventing the cable  100  from being displaced. 
   Thus, according to the above-described embodiments, the cable  100  can be held only by the case  2  of the noise filter  1 . Therefore, the noise filter can provide a simplified structure, and a configuration of a metal mold for molding the case  2  can also be simplified. Further, since the cable  100  can be held at four sides by the resilient cable guide sections  5 ,  6  each divided into four parts for example, the parts  51  through  54 . Accordingly, the cable  100  can be stably held by the cable guide sections even if a force applied to the cable  100  by each part  51  through  54  is small. Consequently, inadvertent crush of the cable  100  at the pressed part can be avoided to provide a prolonged service life of the cable  100 . In other words, since the cable  100  can be held under a small pressure from the four parts, the cable guide section needs not be formed from a material having relatively high rigidity but can be formed from a resilient material providing sufficient flexibility. Accordingly, a cable having a relatively large outer diameter is available for the noise filter. Furthermore, since the cable is pressed at four sides, the noise filter can be disposed over a cable bundled part of a looped cable, in such a manner that four parts can desirably press the bundled part. 
   While the invention has been described with reference to the specific embodiment thereof, it would be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the spirit and scope of the invention. For example, the inner peripheral surface of the chuck part  5 A, which abuts on the cable  100 , may have a zigzag form in a cross-section as viewed in the x-axis direction. In this case, the chuck part  5 A assumes a plane-contact with the cable  100 . This not only suppresses the deterioration of the cable surface, but also prevents the cable  100  from slipping out of the chuck part because of increase in frictional resistance by the zigzag arrangement. 
   Further, the first to fourth slits  51   a  to  54   a  can be shaped, such that a width of each slit is gradually decreased toward the opening  5   a . With this arrangement, all slits will have the same width when the width of the slit at a free end expands as a result of insertion of the cable through the opening  5   a . This sufficiently increases the contacting area of the claws  51 A,  52 A,  61 A,  62 A with the cable  100 .