Abstract:
A magnetic switch includes: a housing; a cylinder coupled to an inner side of the housing; a stationary contact arm coupled to the housing; a movable contact arm positioned to be movable within the housing and brought into contact with the stationary contact arm or separated therefrom; a coil assembly installed within the housing and configured to form a magnetic field when a current is applied thereto; a movable shaft coupled to the movable contact arm in an upper portion thereof; a fixed core inserted into the cylinder and surrounding the movable shaft; and movable cores fixed to the movable shaft and configured to press the movable shaft by a magnetic field formed by the coil assembly to move the movable shaft.

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 Application No. 10-2014-0087645, filed on Jul. 11, 2014, the contents of which is incorporated by reference herein in its entirety. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present disclosure relates to a magnetic switch. 
     2. Background of the Invention 
     A magnet switch is a device used for switching (opening or closing) power of an electric line, and is extensively utilized for industrial, household, and vehicle purposes. In particular, a magnetic switch for a vehicle is used to supply and cut off DC power provided from a storage battery of a vehicle such as a hybrid vehicle, a fuel cell vehicle, or a golf cart. 
     Such a magnetic switch is closed and a current flows when a stationary contact arm and a movable contact arm are brought into contact with each other, and in particular, in order to control an arc generated when DC power having a high voltage is cut off, a permanent magnet is used. The magnetic switch employs a breaking mechanism in which a permanent magnet is appropriately disposed in the vicinity of a stationary contact arm and a movable contact arm where an arc is generated, and an arc is controlled and cooled to be extinguished using a force determined according to strength and a direction of magnetic flux generated in the permanent magnet, a current direction, and an elongated length of an arc. Here, an arc extinguishing unit and a motor magnet may be damaged by the generated arc, and thus, in order to enhance operational reliability of a magnetic switch, it is required to extinguish the arc and protect the magnetic switch against the arc. The present invention provides enhancement of operational reliability of a high voltage DC switch, and the foregoing requirements are satisfied by using a protecting device formed of a resin material. 
       FIG. 2  is a view illustrating a related art magnetic switch  100 . As illustrated in  FIG. 2 , the related art magnetic switch includes a moving unit  140  movable with a contact, a gas sealing unit for hermetically sealing an arc-extinguishing gas filling space for arc extinguishment, and a magnetic driving unit providing driving force to drive the moving unit  140 . Here, the moving unit includes a shaft  141 , a cylindrical movable core  145  connected to a lower portion of the shaft  141  such that the cylindrical movable core  145  can be linearly movable together with the shaft  141 , and disposed to be movable linearly by a magnetic pull from the magnetic driving unit, and a movable contact arm  150  connected to an upper end portion of the shaft  141  to form an electrical contact portion. A fixed core  143  is provided in a position facing the movable core  145  and surrounds the shaft  141 , and the fixed core  143 , the movable core  145 , the second barrier  118 , and the like, form a circuit providing a path along which magnetic flux moves. 
     The gas sealing unit is provided in the vicinity of an upper portion of the moving unit to form an arc extinguishing gas chamber in which an arc extinguishing gas of the magnetic switch is airtightly installed (or sealed), and includes a tubular insulating member, a pair of fixed electrodes  121  penetrating through the insulating member to connect the interior and exterior of the insulating member and airtightly coupled to the insulating member, a tubular airtight member provided between the insulating member and a second barrier  118  (to be described hereinafter) to airtightly seal the insulating member and the second barrier  18  and having a step, and a cylinder  160  formed of a non-magnetic material and installed to airtightly surround the movable core  145  and the fixed core  143 . Here, a DC power source side and a load side are connected to the pair of fixed electrodes  121  electrically, for example, through an electric line. 
     The magnetic driving unit for switching the magnetic switch by driving the movable core  145  and the movable contact arm  150  (to be described hereinafter) by generating a magnetic pull includes a magnetizing coil  131  and the second barrier  118 . Here, the magnetizing coil  131  is a driving coil provided in a lower portion of the magnetic switch. When a current is applied, the magnetizing coil  131  is magnetized, and when an application of a current is cut off, the magnetizing coil is demagnetized. The magnetizing coil  131  provides driving force to the moving unit for switching (or opening and closing) a contact by generating a magnetic pull in the magnetic switch. The second barrier  118  is installed above the magnetic coil  133 , and when the magnetic coil  133  is magnetized, the second barrier  118  forms part of a movement path of magnetic flux, together with the movable core  145  and the fixed core  143 . When the magnetic coil  133  is magnetized, a lower yoke forms a movement path of magnetic flux, together with the second barrier  118 , the movable core  145 , and the fixed core  143 . 
     In  FIG. 2 , a bobbin  131  may allow the magnetizing coil  133  to be wound therearound, and supports the magnetizing coil  133 . A return spring  183  is installed above the shaft  141 , and when the magnetizing coil  133  is demagnetized, the return spring  183  provides elastic force to return the movable core  145  to the original position, that is, to a position spaced apart from the fixed core  143 . In  FIG. 2 , a contact spring is a spring for maintaining contact pressure between contacts when the movable contact arm  150  is in an ON position of the magnetic switch in which the movable contact arm  150  is in contact with the fixed electrode  121 . In  FIG. 1 , a housing  110  accommodates the magnetic switch according to the related art. 
     An operation of the magnetic switch according to the related art configured as described above will be described. When the magnetizing coil  133  is magnetized upon receiving a current, magnetic flux generated by the magnetic coil  133  may move along a movement path of the magnetic flux formed in the movable core  145 , the fixed core  143 , the second barrier  118 , and the lower yoke (not shown), forming a closed circuit of magnetic flux, and at this time, the movable core  145  linearly moves to be brought into contact with the fixed core  143 , and at the same time, the shaft  141  connected to be moved together with the movable core  145  moves upwardly. Then, the movable contact arm  150  installed in eh upper end portion of the shaft  141  is brought into contact with the fixed electrode  121  and the DC power source side and the load side are connected to enter an ON state in which DC power is supplied. 
     When a current supplied to the magnetizing coil  133  is cut off, the magnetizing coil  133  is demagnetized, and as the magnetizing coil  133  is demagnetized, the movable core  145  is returned to the original position spaced apart from the fixed core  143 , by the return spring  183 . Accordingly, the shaft  141  connected to be moved together with the movable core  145  moves downwardly. Then, the movable contact arm  150  installed in the upper end portion of the shaft  141  is separated from the fixed electrode  121 , entering an OFF state in which the DC power source side and the load side are separated and supply of the DC power is cut off. 
     When power is applied through a coil terminal, magnetic force is formed in a coil assembly and the movable core  145  moves to push up the shaft in a direction toward the fixed core. Here, short-circuit performance (operational performance) of the magnetic switch is determined by compressive force of the two types of springs when the magnetic switch is turned on, and, in general, since a load of the contact spring  181  is considerably large, compared with the return spring  183 , short-circuit performance of the magnetic switch relies on maximum compressive force of the contact spring. Compressive force of a spring is proportional to a maximum compression distance, and is determined by a distance between the fixed core and the movable core  145  and a distance between the fixed contact arm and the movable contact arm. 
     In general, short-circuit performance according to current capacity of a magnetic switch is determined according to maximum compressive force of the contact spring  181 . In the related art, maximum compressive force of a spring is proportional to a compression distance of the spring, it is not easy to enhance compressive force of the spring in a limited space such as in the related art. 
     SUMMARY OF THE INVENTION 
     Therefore, an aspect of the detailed description is to provide a magnetic switch having short-circuit performance enhanced by changing a shape of a movable core. 
     To achieve these and other advantages and in accordance with the purpose of this specification, as embodied and broadly described herein, a magnetic switch may include: a housing; a cylinder coupled to an inner side of the housing; a stationary contact arm coupled to the housing; a movable contact arm positioned to be movable within the housing and brought into contact with the stationary contact arm or separated therefrom; a coil assembly installed within the housing and configured to form a magnetic field when a current is applied thereto; a movable shaft coupled to the movable contact arm in an upper portion thereof; a fixed core inserted into the cylinder and surrounding the movable shaft; and movable cores fixed to the movable shaft and configured to press the movable shaft by a magnetic field formed by the coil assembly to move the movable shaft, wherein the movable cores include protrusion portions extending toward the movable shaft and fixed to the movable shaft and body portions configured to move in contact with an inner diameter of the cylinder, and the fixed core has an accommodation portion for accommodating the protrusion portions. 
     The protrusion portion and the body portion may be provided as separate members. 
     The magnetic switch may further include: a contact spring configured to provide elastic force to the movable shaft such that the movable contact arm moves in a direction in which the movable contact arm is brought into contact with the stationary contact arm; and a return spring configured to provide elastic force to the movable shaft such that movable contact arm moves in a direction in which the movable contact arm is separated from the stationary contact arm. 
     The protrusion portions may press a lower end of the movable shaft, and as the movable shaft is pressed by the protrusion portion, the movable shaft may be guided by the fixed core so as to be moved. 
     Outer surfaces of the protrusion portions may be in contact with an inner surface of the accommodation portion and guided to be moved. 
     After a current is applied to the coil assembly, the body portion and the protrusion portion may press the movable shaft together to move the movable shaft, and thereafter, the protrusion portion may be spaced apart from the body portion by a predetermined distance to further press the movable shaft and move within the accommodation portion. 
     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 perspective view of the related art magnetic switch. 
         FIG. 2  is a cross-sectional view of the related art magnetic switch. 
         FIG. 3  is a cross-sectional view of a magnetic switch according to an embodiment of the present disclosure. 
         FIG. 4  is a cross-sectional view of a moving unit according to an embodiment of the present disclosure. 
         FIG. 5  is a cross-sectional view of a moving unit according to another embodiment of the present disclosure. 
         FIGS. 6A and 6B  are cross-sectional views of the moving unit according to the embodiment of  FIG. 5 . 
         FIG. 7  is an exploded perspective view of the moving unit according to the embodiment of  FIG. 5 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Description will now be given in detail of the exemplary embodiments, with reference to the accompanying drawings. For the sake of brief description with reference to the drawings, the same or equivalent components will be provided with the same reference numbers, and description thereof will not be repeated. 
     Hereinafter, a magnetic switch according to an embodiment of the present disclosure will be described in detail with reference to the accompanying drawings. Parts of the magnetic switch similar to those of the related art will be briefly described within a range required for describing the characteristics of the present disclosure. 
       FIG. 3  is a cross-sectional view of a magnetic switch  200  according to an embodiment of the present disclosure. As illustrated in  FIG. 3 , a movable shaft  241  is positioned to be movable within a housing  210 , and a movable contact arm  250  is coupled to an upper portion of the movable shaft  241 . Accordingly, when movable cores  245 - 1  and  245 - 2  presses the movable shaft  241  and moves the movable shaft  241 , the movable shaft  241  and the movable contact arm  250  move together and the movable contact arm  250  is brought into contact with the stationary contact arm  220 . 
     The movable cores  245 - 1  and  245 - 2  are positioned within a cylinder  260 , and when a current is applied to a coil assembly, generated magnetic force is transferred to the movable cores  245 - 1  and  245 - 2 . Upon receiving the magnetic force, the movable cores  245 - 1  and  245 - 2  press the movable shaft  241  to move it. 
     The movable cores  245 - 1  and  245 - 2  include body portions  245   a  and  245   b  and protrusion portions  246   a  and  246   b , respectively. The protrusion portion  246   a  or  246   b  protrudes toward the fixed core  243 . The body portions  245   a  and  245   b  may be in contact with an inner side of the cylinder  260  and movable by a magnetic force. The protrusion portion  246   a  or  246   b  is fixed to a lower end of the movable shaft  241  by welding. The protrusion portions  246   a  and  246   b  of the movable cores  245 - 1  and  245 - 2  may be integrally manufactured with the movable cores  245 - 1  and  245 - 2 , or the protrusion portions  246   a  and  246   b  may be assembled, as separate components, to the body portions  245   a  and  245   b  of the movable cores  245 - 1  and  245 - 2 , respectively. As described hereinafter, the body portion  245   a  or  245   b  and the protrusion portion  246   a  or  246   b  may move together to press the movable shaft  241 , and thereafter, the protrusion portion  246   a  or  246   b  may be separated from the body portions  245   a  and  245   b  by a predetermined distance, respectively, to further press the movable shaft  241 . 
     The fixed core  243  is fixed to the cylinder  260  and has a hole formed in a length direction to guide and move the movable shaft  241  as described hereinafter. 
     The fixed core  243  may include an accommodation portion  244 . The accommodation portion  244 , a space for accommodating the protrusion portion  246   a  or  246   b , may be provided to be larger than the protrusion portion  246   a  or  246   b . An outer side of the protrusion portion  246   a  or  246   b  may be in contact with an inner side of the accommodation portion  244 . A depth of the accommodation portion  244  may be greater than or equal to a length of the protrusion portion  246   a  or  246   b  such that the protrusion portion  246   a  or  246   b  may sufficiently move to the inner side of the accommodation portion  244  so as to be accommodated therein. 
     Referring to  FIG. 3 , a contact spring  281  and a return spring  283  are positioned above the movable shaft  241 . The contact spring  281  applies elastic force to the movable shaft  241  such that the movable contact arm  250  is brought into contact with the stationary contact arm  220 , and maintains contact pressure between contacts when the movable contact arm  250  and the stationary contact arm  220  are in a position where they are in contact. The contact spring  281  is pressed between the movable contact arm  250  and a first rib of the movable shaft  241  so as to be elastically deformed. 
     The return spring  283  applies elastic force to the movable shaft  241  such that the movable contact arm  250  is separated from the stationary contact arm  220 . The return spring  283  is pressed between a second rib (not shown) of a first barrier  217  and a washer positioned in the movable shaft  241  so as to be elastically deformed. 
     The magnetic switch includes the housing  210 , and the housing  210  may include a first housing  211  and a second housing  212 . 
     The first housing  211  is positioned in an upper portion of the magnetic switch, coupled to the first barrier  217 , and divide the upper portion of the magnetic switch into an arc extinguishing region in which the stationary contact arm  220  and the movable contact arm  250  come into contact and the other remaining region. The first housing  211  may be formed of a ceramic material for an insulation purpose. A pair of stationary contact arms  220  penetrate through an upper surface of the first housing  211  and airtightly coupled to the first housing  211 . 
     The second housing  212  is positioned in a lower portion of the magnetic switch and may be coupled to a second barrier  218 . The cylinder  260  is coupled to an actuator region formed by the second housing  212  and the second barrier  218 , and a coil assembly is installed around the cylinder  260 . 
     Hereinafter, an operation of an embodiment of the magnetic switch according to the present disclosure will be described in detail. 
     First, in a state in which a current is not applied to the coil assembly  230 , only elastic force of the return spring acts on the movable shaft  241 . Thus, the movable shaft  241  is maintained in a state of having moved downwardly, and accordingly, the movable contact arm  250  is separated from the stationary contact arm  220 . 
     Meanwhile, when a current is applied to the coil assembly  230  so the coil  233  is magnetized, magnetic flux is generated by the movable core  245 - 1  or  245 - 2 , the fixed core  243 , and the second barrier  218 , forming a closed circuit of magnetic flux, and accordingly, the movable core  245 - 1  or  245 - 2  moves. The movable core  245 - 1  or  245 - 2  presses the movable shaft  241 . The movable cores  245 - 1  and  245 - 2  include the body portions  245   a  and  245   b  and the protrusion portions  246   a  and  246   b , and as illustrated in  FIGS. 4 through 6 , the movable core  245 - 1  or  245 - 2  presses the movable shaft  241 . 
     In  FIG. 4 , the movable core  245 - 2  in which the protrusion  246   b  and the body portion  245   b  are integrated is illustrated, illustrating an embodiment in which the movable core  245 - 2  presses the movable shaft  241 . Here, pressing starts to compress the contact spring  281 . 
     In  FIG. 5 , the movable core  245 - 1  in which the protrusion portion  246   a  and the body portion  245   a  are separated is illustrated, illustrating another embodiment in which the movable core  245 - 1  presses the movable shaft  241 . Here, pressing starts to compress the contact spring  281 . 
     In  FIG. 6A , the protrusion portion  246   a  and the body portion  245   a  press the movable shaft  241  so the movable shaft  241  is moved upwardly. Here, the body portion  245   a  moves to a position as close as possible to the fixed core  243 , in a state of pressing the movable shaft  241 . The contact spring  281  is more compressed than that of  FIG. 5 . 
     In  FIG. 6B , the protrusion portion  246   a  may be separated from the body portion by a predetermined distance to further press the movable shaft  241 . The contact spring  281  is compressed as much as possible to enhance short-circuit performance of the fixed contact arm  220  and the movable contact arm  250 . The protrusion portion may be coupled to the body portion by a spring, and the protrusion portion may be separated from the body portion to further press the movable shaft, and here, a control unit for controlling this operation may be further provided. 
       FIG. 7  is an exploded perspective view illustrating the movable contact arm  250 , the first barrier  217 , the movable shaft  241 , and the movable core  245 - 1  or  245 - 2 . These components are assembled and exploded as illustrated. 
     When a current supplied to the magnetic coil  233  is cut off, the movable core  245 - 1  or  245 - 2  is returned to the original position spaced apart from the fixed core  243  by the return spring  283 . Then, an OFF state is entered in which the movable contact arm  250  installed in an upper end portion of the movable shaft is separated from the fixed contact arm  220 . 
     According to an embodiment of the present invention, the movable cores  245 - 1  and  245 - 2  include the protrusion portions  246   a  and  246   b , respectively, the fixed core  243  includes the accommodation portion, and the protrusion portions  246   a  and  246   b  of the movable cores  245 - 1  and  245 - 2  press the movable shaft within the accommodation portion and are moved, whereby a maximum compression distance of the contact spring  281  increases and short-circuit performance of the magnetic switch may be enhanced. 
     The foregoing embodiments and advantages are merely exemplary and are not to be considered 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. The features, structures, methods, and other characteristics of the exemplary embodiments described herein may be combined in various ways to obtain additional and/or alternative exemplary embodiments. 
     As the present features may be embodied in several forms without departing from the characteristics thereof, 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 considered 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.