Abstract:
The present invention relates to a magnetic switch, and more particularly, a magnetic switch capable of preventing degradation of breaking efficiency by utilizing magnetic force to the utmost, in a manner of matching contact centers of fixed and movable cores. A magnetic switch according to one embodiment includes a bobbin provided with a cylindrical body and a plurality of flanges and having a coil wound on an outer circumferential surface thereof, a fixed core fixed to an inside of the cylindrical body with a predetermined spaced interval from the cylindrical body, and a movable core slidably installed in the cylindrical body and contactable with or separated from the fixed core, wherein a guide portion protrudes from a lower portion of the cylindrical body along an inner circumferential surface of the cylindrical body, such that the movable core can linearly move along a central axis of the fixed core.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     Pursuant to 35 U.S.C. §119(a), this application claims the benefit of earlier filing date and right of priority to Korean Patent Application No. 10-2015-0057325, filed on Apr. 23, 2015, the contents of which are hereby incorporated by reference herein in its entirety. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This specification relates to a magnetic switch, and more particularly, a magnetic switch, capable of preventing degradation of breaking efficiency by utilizing magnetic force (magnetism) as much as possible, in a manner of matching contact centers of a fixed core and a movable core with each other. 
     2. Background of the Invention 
     In general, a magnetic switch or a direct current (DC) relay is a type of an electric circuit switch which transfers mechanical driving force and a current signal using a principle of an electromagnet, and installed in various industrial facilities, machines, vehicles and the like. 
     Specifically, a relay for an electric vehicle is disposed in a battery system of an electric vehicle, such as a hybrid vehicle, a fuel cell vehicle, a golf cart and an electric forklift truck, to serve to switch on or off a flow of a main current. 
       FIG. 1  is a longitudinal sectional view of a magnetic switch according to the related art, and  FIG. 2  is an exploded perspective view of  FIG. 1 . 
     A configuration and a fabricating process of the related art magnetic switch are described as follows. An arc chamber  2  with a fixed contact  1 , a movable shaft assembly  4  with a movable contact  3 , a plate  5 , a fixed core  6  and a movable core  7  are sequentially laminated in a downward direction. A lower end portion of the movable shaft  8  is completely fixed to the movable core  7  in a laser-welding manner. The upper arc chamber  2  is welded onto the plate  5  by laser beams so as to fully seal a space where the fixed contact  1  and the movable contact  3  operate. Also, the fixed core  6  and the movable core  7  are covered with a cylinder  9 . The cylinder  9  is then air-tightly welded onto a lower portion of the plate  5 . A coil assembly  5   a  wound with a coil  5   b  and a yoke  5   c  are coupled to the lower portion of the plate  5 . 
     In the magnetic switch, a magnetic path is formed along the plate  5 , the yoke  5   c , the movable core  7  and the fixed core  6 , by a magnetic field generated in the coil  5   b . In this instance, the movable core  7  is attracted to the fixed core  6  by a magnetic force generated in the fixed core  6 . Responsive to this, the movable shaft  8  fixed to the movable core  7  is moved to push up the movable contact  3  coupled to an upper portion of the movable shaft  8 . Accordingly, the movable contact  3  is brought into contact with the fixed contact  1  such that a current can flow therealong. 
     In the related art magnetic switch, the arc chamber  2  is filled therein with arc-extinguishing gas, and thus should have a sealed structure. Also, the fixed core  6  and the movable core  7  should have their centers accurately matching each other to prevent a loss of magnetic force. 
     Here, the cylinder  9  is fabricated by pressing, called deep drawing. However, in view of a characteristic of the pressing process, the structure of the cylinder  9  is made by pressing down a raw material. Accordingly, the material of the cylinder has a slightly inclined (tilt) angle, failing to be formed in an accurately straight form (form a right angle). This may be likely to cause interference between a lower portion of the cylinder  9  and the movable core  7 . Such interference has been avoided in a manner that an outer diameter of the movable core  7  is slightly smaller than an inner diameter of the cylinder  9 . 
     However, in this instance, abrasion due to friction between the movable core  7  and the cylinder  9  in case of a long-term use may be caused due to a gap present between the movable core  7  and the cylinder  9 . That is, a problem of residual iron powders which fell from components of the movable core  7  and the cylinder  9  is caused. In addition, a failure of a uniform linear motion of the movable core is caused, which results in non-use of magnetic force to the utmost, and degradation of breaking efficiency (performance), such as an increase in a breaking time or a generation of a voltage loss. 
     SUMMARY OF THE INVENTION 
     Therefore, to obviate the aforementioned drawbacks, an aspect of the detailed description is to provide a magnetic switch, capable of utilizing magnetic force as much as possible, by matching contact centers of a fixed core and a movable core with each other. 
     To achieve these and other advantages and in accordance with the purpose of this specification, as embodied and broadly described herein, there is provided a magnetic switch including a bobbin provided with a cylindrical body and a plurality of flanges, and having a coil wound on an outer circumferential surface of the cylindrical body, a fixed core fixed to an inner side of the cylindrical body with being spaced apart from the cylindrical body with a predetermined interval, and a movable core slidably installed in the cylindrical body and contactable with or separated from the fixed core, wherein a guide portion protrudes from a lower portion of the cylindrical body along an inner circumferential surface of the cylindrical body, such that the movable core is linearly moved along a central axis of the fixed core. 
     Here, an outer circumferential surface of the movable core may be uniformly maintained without a step or inclination along a lengthwise direction of the movable core. 
     An inner diameter of the guide portion may be the same as an outer diameter of the movable core. 
     An inner diameter of the guide portion may be smaller than an outer diameter of the fixed core. 
     A length of the guide portion may be shorter than a length of the movable core. 
     An upper end of the guide portion and an upper end of the movable core may be located at the same position in an open state. 
     The guide portion may be provided with a plurality of spline grooves formed along a lengthwise direction of the guide portion. 
     In a magnetic switch according to each exemplary embodiment disclosed herein, a guide portion for a movable core is formed on an inner circumferential surface of a bobbin so as to guide the movable core to linearly move along a central axis of a fixed core. This may allow for matching central axes of the movable core and the fixed core with each other, thereby exhibiting an optimized breaking performance without a loss of an operation time in a manner of utilizing magnetic force as much as possible without a voltage loss. 
     With a removal of a cylinder and a common use of the fixed core, a number of components required can be reduced, which may result in reducing fabricating costs and simplifying an assembling process. 
     Further scope of applicability of the present application will become more apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from the detailed description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate exemplary embodiments and together with the description serve to explain the principles of the invention. 
       In the drawings: 
         FIG. 1  is a longitudinal sectional view of a magnetic switch according to the related art; 
         FIG. 2  is an exploded perspective view of  FIG. 1 ; 
         FIG. 3  is a longitudinal sectional view of a magnetic switch in accordance with one exemplary embodiment of the present invention; 
         FIG. 4  is an exploded perspective view of  FIG. 3 ; 
         FIG. 5  is a sectional view of a part A-A of  FIG. 3 ; and 
         FIG. 6  is a sectional view of a part A-A in a magnetic switch in accordance with another exemplary embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Description will now be given of preferred configurations of the present invention, with reference to the accompanying drawings. However, those preferred embodiments of the present invention are merely illustrative to help those skilled in the art easily practice the invention, but should not be construed to limit the technical scope of the present invention. 
       FIG. 3  is a longitudinal sectional view of a magnetic switch in accordance with one exemplary embodiment of the present invention,  FIG. 4  is an exploded perspective view of  FIG. 3 , and  FIG. 5  is a sectional view of a part A-A of  FIG. 3 . Hereinafter, a magnetic switch according to one exemplary embodiment of the present invention will be described in detail with reference to the drawings. 
     A magnetic switch in accordance with one exemplary embodiment disclosed herein includes a bobbin  31  provided with a cylindrical body  32  and a plurality of flanges  33  and having a coil  35  wound on an outer circumferential surface of the cylindrical body  32 , a fixed core  20  fixed to an inner side of the cylindrical body  32 , and a movable core  25  slidably installed in the cylindrical body  32  of the bobbin  31  and contactable with or separated from the fixed core  20 . A guide portion  34  protrudes from a lower portion of the cylindrical body  32  along an inner circumferential surface of the cylindrical body  32 , such that the movable core  25  can linearly move along a central axis of the fixed core  20 . 
     An upper frame  10  may be formed approximately in a shape of a box with a lower surface open. The upper frame  10  may be formed of a synthetic resin material, such as plastic and the like. The upper frame  10  may be made in an injection-molding manner. 
     A pair of contact holes  13  in which fixed contacts  11  are disposed is formed at an upper surface of the upper frame  10 . 
     Terminals  15  or bus bars which are connected to the fixed contacts  11 , respectively, may be inserted into a front surface of the upper frame  10 . Each terminal  15  may be formed of a material with high conductivity, such as silver (Ag) and the like. Also, a through hole  15   a  through which the fixed contact  11  is insertable may be formed through a part of each terminal  15 . 
     Permanent magnets  16  may be disposed at front and rear surfaces of the upper frame  10 . Permanent magnet holders  17  for fixing the permanent magnets  16 , respectively, may be provided at an upper portion of the upper frame  10 . 
     The pair of fixed contacts  11  are terminals which are inserted through the through holes  15   a  of the terminals  15  and contact holes  13  of the upper frame  10  so as to be exposed to an outside of the upper frame  10 , and connectable to a power source or a load. The pair of fixed contacts  11  may be made of a material with high conductivity, such as copper (Cu) and the like. Upper end portions of the pair of fixed contacts  11  may be connected to the power source or the load and lower end portions thereof may come in contact with a movable contact  12 . 
     The movable contact  12  is a terminal which is inserted into the upper frame  10  and is brought into contact with or separated from the pair of fixed contacts  11 . The movable contact  12  is brought into contact with the lower end portions of the pair of fixed contacts  11 , as aforementioned. The movable contact  12  includes a plate body formed in a flat shape and having a predetermined thickness, and a pair of contact portions contactable with the pair of fixed contacts  11 . The movable contact  12  is fixed to a shaft  23  installed in a coil assembly  30 . Accordingly, as the shaft  23  is linearly moved in an axial direction, the movable contact  12  may be brought into contact with or separated from the pair of fixed contacts  11 . When the movable contact  12  comes in contact with the pair of fixed contacts  11 , a circuit may be closed such that a current can flow. When the movable contact  12  is separated from the pair of fixed contacts  11 , the circuit may be open such that a current flow can be blocked. 
     The coil assembly  30  is configured to generate a magnetic field by control power. The coil assembly  30  supplies magnetic force using a principle of an electromagnet. The coil assembly  30  may include a bobbin  31 , a coil  35 , a coil terminal  36 , and the like. 
     The bobbin  31  is a structure of supporting and configuring the coil assembly  30 . The bobbin  31  may be provided with a cylindrical body  32 , and a plurality of flanges  33  formed at a periphery of the cylindrical body  32 . The bobbin  31  may be formed of a synthetic resin material, such as plastic and the like. Accordingly, it may generate less friction even though contacting the fixed core  20  and the movable core  25 , resulting in reduced abrasion. The fixed core  20  and the movable core  25  are inserted into the cylindrical body  32 , and the coil  35  is wound on an outer circumferential surface of the cylindrical body  32 . 
     The coil  35  receives external control power supplied through the coil terminal  36 . When the power is supplied to the coil  35 , a magnetic field is generated around the coil  35 . 
     The fixed core  20  is fixedly inserted into the cylindrical body  32 . The fixed core  20  is provided to increase magnetic flux density in a manner of being magnetized within the magnetic field generated around the coil  35 . The fixed core  20  may be integrally formed with a plate located between the upper frame  10  and a yoke  37 . That is, an upper surface of the fixed core  20  may be configured as a flange. The fixed core  20  may be formed of an iron material. Here, the fixed core  20  is spaced apart from the cylindrical body  32  by a predetermined distance, so as to be free from friction against the cylindrical body  32 . Accordingly, abrasion and the like due to opening/closing impact are not caused. Also, a cylinder component of the related art can be removed, and the fixed core  20  with the same size as that of the related art can be used without being adjusted to correspond to the cylindrical body  32 , resulting in a reduction of design and fabrication costs. 
     The movable core  25  is slidably installed below the fixed core  20 . The movable core  25  is coupled to a lower end portion  23   a  of the shaft  23  so as to be movable along with the shaft  23 . The movable core  25  may also be formed of an iron material, similar to the fixed core  20 . 
     The shaft  23  is inserted through centers of the fixed core  20  and the movable core  25 . The movable core  25  is fixedly coupled to the lower end portion  23   a  of the shaft  23 , and the shaft  23  is slidably installed in the fixed core  20 . 
     A guide portion  34  may protrude from an inner circumferential surface of the cylindrical body  32 . The guide portion  34  is provided to support the movable core  25  and guide a movement of the movable core  25 , which will be explained later. An outer circumferential surface of the movable core  25  is uniformly maintained along a lengthwise direction of the movable core  25  without a step or inclined angle. 
     An inner diameter of the cylindrical body  32  may be the same as an outer diameter of the movable core  25 . Accordingly, when the movable core  25  is moved, the movable core  25  can perform a uniform linear motion according to the guide of the guide portion  34 . 
     An inner diameter of the guide portion  34  may be smaller than an outer diameter of the fixed core  20 . This may allow the guide portion  34  to have a sufficient thickness so as to provide a stable supporting force. 
     The guide portion  34  may be formed of a synthetic resin material and the like. Thus, when the guide portion  34  comes in contact with the movable core  25 , less friction and less abrasion of components may be enabled. 
     The movable core  25  can be linearly moved along a central axis by the guide portion  34 . Accordingly, when the movable core  25  is attracted to the fixed core  20 , a loss of magnetic force can be minimized, thereby maintaining a stable breaking performance. 
     The guide portion  34  may be formed smaller than the movable core  25  in length. This may result in a reduction of a contact area between the guide portion  34  and the movable core  25 , minimizing friction therebetween. Of course, the length of the guide portion  34  may be decided within a range without losing the supporting force by the guide portion  34 . 
     In an open state, an upper end of the guide portion  34  and an upper end of the movable core  25  may be located at the same position (same height). Accordingly, a contact area between the guide portion  34  and the movable core  25  may be reduced during a breaking operation, resulting in a reduced friction. Also, the upper end portion of the guide portion  34  may be formed to be inclined. This may allow for increasing the supporting force of the guide portion  34  and reducing contact resistance at the upper end portion. 
       FIG. 6  illustrates a magnetic switch in accordance with another exemplary embodiment of the present invention. A guide portion  44  is provided with a plurality of spline grooves  45  formed along a lengthwise direction thereof. This may reduce a contact surface of the guide portion  44  with the movable core  25  with increasing rigidity of the guide portion  44 , which can arouse a reduction of friction. 
     In a magnetic switch according to each exemplary embodiment disclosed herein, a guide portion for a movable core is formed on an inner circumferential surface of a bobbin so as to guide the movable core to linearly move along a central axis of a fixed core. This may allow for matching central axes of the movable core and the fixed core with each other, thereby exhibiting an optimized breaking performance without a loss of an operation time in a manner of utilizing magnetic force as much as possible without a voltage loss. 
     With a removal of a cylinder and a common use of the fixed core, a number of components required can be reduced, which may result in reducing fabricating costs and simplifying an assembling process. 
     Iron powders which are generated between the movable core and the cylinder or misaligned (non-matched) coupling which takes place in the related art can be avoided. 
     The foregoing embodiments and advantages are merely exemplary and are not to be construed as limiting the present disclosure. The present teachings can be readily applied to other types of apparatuses. This description is intended to be illustrative, and not to limit the scope of the claims. Many alternatives, modifications, and variations will be apparent to those skilled in the art. Therefore, it should also be understood that the above-described embodiments are not limited by any of the details of the foregoing description, unless otherwise specified, but rather should be construed broadly within its scope as defined in the appended claims, and therefore all changes and modifications that fall within the metes and bounds of the claims, or equivalents of such metes and bounds are therefore intended to be embraced by the appended claims.