Abstract:
A noise decreasing type electromagnetic switch includes a buffer disposed between a stationary core and a contact spring to electrically support a shaft and the stationary core. The buffer includes a buffering space therein. Accordingly, impact caused at the stationary core and the shaft can be effectively absorbed even by the buffering space as well as an elastic force of the buffer. The buffer is inserted in the stationary core for coupling so as to be prevented from being separated during operations, resulting in maintaining long-term durability. Also, the buffer may support the stationary core and a metal plate, whereby an assembly process can be simplified.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit of Korean Patent Application No. 10-2010-0100793, filed on Oct. 15, 2010, which is hereby incorporated by reference for all purposes as if fully set forth herein. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    This specification relates to a noise decreasing type electromagnetic switch capable of noise generated between a stationary core and a movable core. 
         [0004]    2. Background of the Invention 
         [0005]    In general, an electromagnetic switch is located between a battery and a direct current (DC) power converter of an electric vehicle, such as a hybrid car, a fuel cell car, an electric golf cart, an electric folklift truck and the like, and serves to supply power of the battery to the power converter, and supply power generated from a power generator to the battery. 
         [0006]    The electromagnetic switch includes a coil which is excited (magnetized) or demagnetized according to whether or not a control current flows, a yoke installed around the coil to define (form) a magnetic path in the vicinity of the coil, a metal plate installed to face the yoke and defining the magnetic path around the coil together with the yoke, a stationary core fixed to the metal plate, a movable core installed to face the stationary core, and movably installed to contact the stationary core when the coil is excited and to be separated from the stationary core when the coil is demagnetized, a shaft having one end portion coupled to the movable core and movable together with the movable core, and a return spring located between the stationary core and the movable core and having a larger elastic force than contact pressure of a contact spring such that the movable core is separated from the stationary core. 
         [0007]    In the structure of the related art electromagnetic switch, when a magnetic field is formed in response to power being applied to the coil, the movable core is attracted toward the stationary core, and an upper conductive portion is run by the shaft connected to the movable core. However, impact noise may be generated while the shaft movable in cooperation with the movable core contacts the stationary core, thereby causing degradation of a perceived quality of a product. 
       SUMMARY OF THE INVENTION 
       [0008]    Therefore, an aspect of the detailed description is to provide a noise decreasing type electromagnetic switch capable of simplifying a coupling process as well as maintaining long-term durability. 
         [0009]    To achieve these and other advantages and in accordance with the purpose of this specification, as embodied and broadly described herein, a noise decreasing type electromagnetic switch may include a coil, a yoke installed adjacent to the coil, a metal plate forming a magnetic path adjacent to the coil together with the yoke, a stationary core fixedly installed at the metal plate, a movable core contactable with the stationary core when the coil is excited, a return spring disposed between the movable core and the stationary core to apply an elastic force such that the movable core is separated from the stationary core, a shaft connected to the movable core to be movable together with the movable core, a movable contact point coupled to the shaft to be movable together with the shaft, a stationary contact point fixed to face the movable contact point and contactable with or separated from the movable contact point such that an electric circuit is closed or open, and a contact spring configured to elastically support the movable contact point to contact the stationary contact point, wherein a buffer is disposed between the stationary core and the contact spring to elastically support the shaft and the stationary core. 
         [0010]    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 
         [0011]    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. 
           [0012]    In the drawings: 
           [0013]      FIG. 1  is a sectional view showing an open state of a noise decreasing type electromagnetic switch in accordance with one exemplary embodiment; 
           [0014]      FIG. 2  is a sectional view showing a closed state of the noise decreasing type switch; 
           [0015]      FIG. 3  is a side view showing a stationary core in accordance with the one exemplary embodiment; 
           [0016]      FIG. 4  is a perspective view showing a buffer in accordance with the one exemplary embodiment; and 
           [0017]      FIG. 5  is a perspective view showing a buffer in accordance with another exemplary embodiment. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0018]    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. 
         [0019]      FIG. 1  is a sectional view showing an open state of a noise decreasing type electromagnetic switch in accordance with one exemplary embodiment,  FIG. 2  is a sectional view showing a closed state of the noise decreasing type switch,  FIG. 3  is a side view showing a stationary core in accordance with the one exemplary embodiment, and  FIG. 4  is a perspective view showing a buffer in accordance with the one exemplary embodiment. 
         [0020]    As shown in  FIGS. 1 and 2 , a noise decreasing type electromagnetic switch  10  may include a driving unit  100 , and a conducting unit  200  switched on or off with respect to the exterior with moving up and down by the driving unit  100 . The conducting unit  200  may have a contact-point switching structure, which includes a stationary contact point  220  and a movable contact point  210 , so as to allow switching with respect to an external device connected to the electromagnetic switch  10 . 
         [0021]    The driving unit  100  may control contact or non-contact between the contact points using an electric signal. The driving unit may include a coil  110  for generating driving forces of the contact points by a magnetic force generated by the electric signal, a yoke  120  installed adjacent to the coil  110  to form a magnetic path adjacent to the coil  110 , a metal plate  130  forming a magnetic path adjacent to the coil  110  together with the yoke  120 , a stationary core  140  fixed within the coil  110 , and a movable core  150  disposed to face the stationary core  140 . 
         [0022]    A coil bobbin  180 , on which the coil  110  is wound, may be located between the coil  110  and the stationary core  140  and the movable core  150 . The stationary core  140  and the movable core  150  may be disposed in a longitudinal direction based on an axial direction of the coil bobbin  180 . The stationary core  140  and the movable core  150  may form a magnetic path, through which magnetic flux generated by the coil  110  flows. The magnetic flux generated by the coil  110  may make the movable core  150  moved up and down. 
         [0023]    A core case  190  may be located between the coil bobbin  180  and the stationary and movable cores  140  and  150 . The core case  190  may be formed of a non-magnetic material and be in a cylindrical shape having an opening at a surface facing the conducting unit  200  and a bottom of an opposite surface blocked. That is, the core case  190  may have a shape like a case for accommodation of the stationary core  140  and the movable core  150  therein, and be formed in a cylindrical shape with an inner diameter, which is approximately the same as the outer diameter of each of the stationary core  140  and the movable core  150 . The movable core  150  may be movable in an axial direction of the core case  190 . 
         [0024]    The movable core  150  may be movable in the range between a position of being contactable with the stationary core  140  and an initial position where the movable core  150  is separated from the bottom of the opposite surface of the core case  190 . The movable core  150  may be contactable with the stationary core  140  by a contact spring  230  to be explained later and return to its original position by a return spring  160  to be explained later. 
         [0025]    A through hole may be formed through central portions of the stationary core  140  and the movable core  150  in an axial direction. A shaft  170  may be inserted through the through hole so as to connect the driving unit  100  and the conducting unit  200  to each other. The shaft  170  may be coupled with the movable contact point  210  at its upper end and the movable core  150  at its lower end so as to transfer a longitudinal motion of the movable core  150  to the movable contact point  210 . 
         [0026]    A cover  240  may be coupled to the driving unit  100  by being loaded on the driving unit  100 . The cover  240  may be box-shaped with an open lower side. Terminal holes (reference numeral not given) for insertion of the stationary contact point  220  and a fixing terminal therein may be formed at an upper portion of the cover  240 . 
         [0027]    The movable contact point  210  coupled to the shaft  170  below the stationary contact point  220  may be disposed within the cover  240 . A space for performing contact and separation between the stationary contact point  220  and the movable contact point  210  for a switching operation may be present between the stationary contact point  220  and the movable contact point  210  within the cover  240 . 
         [0028]    The contact spring  230  may be disposed at a lower side of the movable contact point  210 . The contact spring  230  may have an elastic force when the movable contact point  210  contacts the stationary contact point  220 . The contact spring  230  may allow the movable contact point  210  to remain in the contact state with the stationary contact point  220  by pressure more than a preset level. Also, when the movable contact point  210  is separated from the stationary contact point  220 , the contact spring  230  may reduce a movement speed of each movable core  150  and shaft  170 . Consequently, when the movable core  150  contacts the core case  190 , an impact may be relieved to minimize or prevent generation of noise and vibration. 
         [0029]    The movable contact point  210 , which is movable in response to movement of the shaft  170 , may be coupled to another end of the shaft  170 , and the stationary contact point  220  may be fixed above the movable contact point  210  to face the movable contact point  210 . As the stationary contact point  220  contacts or is separated from the movable contact point  210 , an electric circuit is closed or open. 
         [0030]    The contact spring  230  for providing an elastic force to the movable contact point  210  to contact the stationary contact point  220  may be installed at the lower side of the movable contact point  210  at the periphery of the shaft  170 . 
         [0031]    With the configuration of the electromagnetic switch  10 , when a magnetic field is formed in response to power being applied to the coil  110 , the movable core  150  is attracted toward the stationary core  140 , the upper conducting unit  200  is run by the shaft  170  connected to the movable core  150 . Here, the movable core  150  contacts the stationary core  140 , thereby generating impact noise, which may lower a perceived quality of a product. 
         [0032]    To address such problem, a buffer, which is in an annular shape having sawlike threads attached thereon, may be mounted between the stationary core and the shaft to decrease vibration and noise generated between the shaft and the stationary core. However, the sawlike buffer may probably experience an impact fatigue cumulative damage in view of its structural characteristic. Furthermore, as the buffer is simply mounted at the stationary core, upon repetitive operations, it may be separated from its initial position and sandwiched between other structures. 
         [0033]    Therefore, this exemplary embodiment aims to implementing a structure that a bowl-shaped buffer is coupled to a recess of the stationary core, has a buffering space therein, and supports the stationary core and the metal plate. 
         [0034]    To this end, a fixing recess  141 , which is recessed (concaved) inwardly, may be formed at an upper portion of the stationary core  140  along a periphery thereof. A fixing step  330  of a buffer  300  to be explained later may be inserted in the fixing recess  141 . 
         [0035]    The fixing recess  141  may preferably be formed such that the fixing step  330  to be explained later can be inserted therein so as to support the metal plate  130 . 
         [0036]    The buffer  300  may include a side wall portion portion  310  defining a cylindrical shape, an supporting portion  320  curved inwardly to support an upper end of the side wall portion portion  310 , namely, the contact spring  230 , and a fixing step  330  curved inwardly from a lower end of the side wall portion portion  310 . 
         [0037]    The side wall portion portion  310  may be formed in form of a smooth pipe. Alternatively, the side wall portion portion  310  may be formed in form of a bellows. 
         [0038]    The side wall portion portion  310  may be higher than a distance or gap between the fixing recess  141  and an upper surface of the stationary core  140  so as to define a specific buffering space  340  between an inner side surface of the side wall portion portion  310  and the stationary core  140 . 
         [0039]    When the inwardly recessed stationary recess  141  is formed at the upper side surface of the stationary core  140 , the fixing step  330  of the buffer  300  may be inserted in the fixing recess  141  of the stationary core  140  to prevent the separation of the buffer  300  upon driving the shaft  170 . 
         [0040]    In accordance with the noise decreasing type electromagnetic switch, the buffering space is formed within the buffer so as to absorb impact due to air staying in the buffering space, in addition to an elastic force of the buffer. Also, the buffer may be coupled to the recess of the stationary core to be prevented from being separated, thereby maintaining long-term durability. The buffer may support the stationary core and the metal plate, thereby simplifying an assembly process. 
         [0041]    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. 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. 
         [0042]    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 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.