Abstract:
A monostable permanent magnetic actuator using a laminated steel core, comprises: lamination cores formed as a plurality of metallic thin plates are laminated to each other; a coil disposed to be adjacent to the lamination cores, and configured to apply a magnetic force to the lamination cores by an external power; a mover mounted in the lamination cores so as to be movable in upper and lower directions; permanent magnets installed at the lamination cores, and configured to apply an upward and downward magnetic force to the mover; and an elastic means configured to apply an elastic force to the mover in an opposite direction to the permanent magnets.

Description:
RELATED APPLICATION 
       [0001]    The present disclosure relates to subject matter contained in priority Korean utility model Application No. 20-2008-0017509, filed on Dec. 31, 2009, which is herein expressly incorporated by reference in its entirety. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a monostable permanent magnetic actuator using a laminated steel core, and particularly, to an actuator to operate a circuit breaker, a switch, etc. of power equipment. 
         [0004]    2. Background of the Invention 
         [0005]    As an actuator for power equipment, a spring mechanism, and a hydraulic or pneumatic actuator are generally used. However, the actuator has a large number of components, and has to control mechanical energy so as to obtain an adjustment force. Accordingly, the actuator has a complicated structure, and requires to be repaired. 
         [0006]    In order to solve these problems, the conventional mechanism has been replaced by an actuator using permanent magnets and electric energy in the power equipment. The permanent magnetic actuator is configured such that a mover thereof is held at a stroke using magnetic energy of the permanent magnets, and electric energy is applied to a coil to move the mover to a stroke. 
         [0007]    The permanent magnetic actuator may be categorized into a bistable type and a monostable type depending on a mechanism that the mover is held at a preset position. The bistable type permanent magnetic actuator is configured such that a mover can be held at both ends of a stroke due to permanent magnets, whereas the monostable type permanent magnetic actuator is configured such that a mover is held at only one of both ends of a stroke. The mover of the bistable type permanent magnetic actuator is held at a preset position by magnetic energy of permanent magnets upon opening or closing power equipment. Accordingly, the bistable type permanent magnetic actuator is more advantageous than the monostable type requiring for a separate maintenance mechanism, in that it can perform the closing/opening operation without a mechanical component such as a spring. 
         [0008]    On the contrary, the monostable type actuator has the following advantages. Firstly, power equipment can be closed or opened by using one coil. 
         [0009]    Secondly, the monostable type actuator is mounted with an open spring, thereby opening power equipment without an additional energy storage device (e.g. spring) in an opening device for an emergent case. 
         [0010]    Thirdly, differently from the bistable type actuator, a closing or opening operation is implemented by one coil. This may allow a driving coil to have a large number of windings thereon. Since driving energy is proportional to a stroke, the mover of the monostable permanent magnetic actuator can be fabricated so as to have a long stroke. 
         [0011]      FIGS. 1 and 2  are sectional views of an actuator in accordance with the conventional art. The actuator  10  of  FIG. 1  comprises a middle cylinder  12  having a cavity, and a lower cylinder  14  coupled to a lower side of the middle cylinder  12 . A close coil  18  for applying a downward magnetic force to the mover  16  by receiving external power is installed below the middle cylinder  12 . An upper cylinder  20  is coupled to an upper side of the middle cylinder  12 . And, permanent magnets  22  for applying a downward magnetic force to the mover  16  are installed on an upper surface of the upper cylinder  20 . 
         [0012]    An open coil  24  for forming an attenuating magnetic force (i.e., a magnetic force opposite to a magnetic force from the permanent magnets  22 ) by external power is positioned on a bottom surface of the upper cylinder  20 . And, an open spring  26  for applying an upward elastic force to the mover  16  is installed on a bottom surface of the lower cylinder  14 . 
         [0013]    Referring to  FIG. 1 , the permanent magnets  22  are in a state to apply an attractive force to the mover  16 , and the open spring  26  is in a compressed state to apply an upward elastic force. However, the elastic force of the open spring  26  is less than the magnetic force of the permanent magnets  22 , the mover  16  maintains a downward moved state as shown in  FIG. 1 . Under this state, once power is supplied to the open coil  20 , a magnetic force is generated in an opposite direction to the magnetic force of the permanent magnets  22 . Accordingly, the magnetic force of the permanent magnets  22  is attenuated, and thereby the elastic force of the open coil  26  becomes relatively larger. As a result, the mover  16  is upwardly moved as shown in  FIG. 2 . 
         [0014]    Then, power to the open coil  20  is cut off, and power is supplied to the close coil  18 . This allows the magnetic force of the permanent magnets  22  and the close coil  18  to become relatively larger than the elastic force of the open spring  26 . Accordingly, the mover  16  maintains the downward moved state as shown in FIG.  1 . 
         [0015]    However, the conventional monostable permanent magnetic actuator has the following problems. 
         [0016]    Firstly, when power is supplied to the close coil or the open coil so as to upwardly or downwardly move the mover  16 , an eddy current is generated by drastic change of a magnetic flux. This eddy current generates force in an opposite direction to the moving direction of the mover  16 , thereby lowering the operation of the mover  16 . Furthermore, this eddy current causes the actuator to have a long operation time and large operation energy, thereby badly influencing on the actuator. 
         [0017]    Secondly, the middle cylinder and the lower cylinder undergo mechanical processes to have cylindrical shapes. Here, the mechanical processes are performed with high costs. 
         [0018]    Thirdly, since a magnetic force to downwardly move the mover is applied only to an upper plate of the mover, it is difficult to obtain a sufficient attractive force. 
       SUMMARY OF THE INVENTION 
       [0019]    Therefore, an object of the present invention is to provide a monostable permanent magnetic actuator using a laminated steel core capable of reducing an eddy current that badly influences on an operation characteristic thereof. 
         [0020]    Another object of the present invention is to provide a monostable permanent magnetic actuator using a laminated steel core capable of facilitating mechanical processes, and reducing fabrication costs. 
         [0021]    To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described herein, there is provided a monostable permanent magnetic actuator using a laminated steel core, comprising: lamination cores formed as a plurality of metallic thin plates are laminated to each other; a coil disposed to be adjacent to the lamination cores, and configured to apply a magnetic force to the lamination cores by an external power; a mover mounted in the lamination cores so as to be movable in upper and lower directions; permanent magnets installed at the lamination cores, and configured to apply an upward and downward magnetic force to the mover; and an elastic means configured to apply an elastic force to the mover in an opposite direction to the permanent magnets 
         [0022]    A core of a magnetic circuit may be implemented as a plurality of thin plates are laminated to each other. This may prevent drastic change of a magnetic flux, and thus prevent the occurrence of an eddy current. 
         [0023]    The monostable permanent magnetic actuator may further comprise a movable core formed on an upper end of the mover by laminating a plurality of metallic thin plates. 
         [0024]    The monostable permanent magnetic actuator may further comprise a guide means disposed in the lamination cores so as to guide an upward and downward motion of the mover. 
         [0025]    According to another aspect of the present invention, there is provided a monostable permanent magnetic actuator using a laminated steel core, comprising: one pair of lamination cores formed as a plurality of metallic thin plates are laminated to each other, and disposed to face each other; one pair of fixed plates which form a space having a rectangular sectional surface by connecting ends of said one pair of lamination cores to each other; a coil disposed to be adjacent to the lamination cores in the space, and configured to generate a magnetic force to the lamination cores by external power; a mover mounted in the space so as to be moved in up and down directions; permanent magnets installed in the space, and configured to apply an upward and downward magnetic force to the mover; and an elastic means configured to apply an elastic force to the mover in an opposite direction to the permanent magnets. 
         [0026]    In the monostable permanent magnetic actuator, an eddy current may be prevented by using the lamination cores. And, the actuator may be formed to have a rectangular appearance, not a cylindrical shape requiring mechanical processes, the rectangular appearance implemented by assembling the lamination cores and the fixed plates with each other. Accordingly, the fabrication processes may be simplified. 
         [0027]    The mover may include a stem slidably inserted into a fixed core inside a bottom surface of the space; a head disposed above the stem; and a movable core disposed above the head, and formed as a plurality of thin plates are laminated to each other. 
         [0028]    The monostable permanent magnetic actuator may further comprise a guide means configured to guide an upward and downward motion of the mover. The guide means may include guide slots formed in the head in upper and lower directions, and guide bars supported by the fixed plates. Since the mover may move in a state that the guide bars have been inserted into the guide slots, the mover may stably move. 
         [0029]    A stopper contacting an inner surface of the fixed core may be additionally mounted to the end of the stem. And, in order to prevent noise and vibration that may occur when the stopper collides with the fixed core, a damping member for attenuating an impact due to contact between the stopper and the fixed core may be mounted to an inner surface of the fixed core. 
         [0030]    The monostable permanent magnetic actuator may have an enhanced operation characteristic by preventing the occurrence of an eddy current. And, the fabrication costs may be reduced by implementing the entire structure in a shape requiring minimized mechanical processes. 
         [0031]    The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0032]    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 embodiments of the invention and together with the description serve to explain the principles of the invention. 
           [0033]    In the drawings: 
           [0034]      FIGS. 1 and 2  are sectional views of an actuator in accordance with the conventional art; 
           [0035]      FIG. 3  is a perspective view of an actuator according to one embodiment of the present invention; 
           [0036]      FIG. 4  is an exploded perspective view of the actuator of  FIG. 3 ; 
           [0037]      FIG. 5  is a sectional view of the actuator of  FIG. 3 ; 
           [0038]      FIG. 6  is a sectional view of the actuator of  FIG. 3 , which shows that a mover has been downwardly moved; and 
           [0039]      FIGS. 7 and 8  are views showing magnetic flux distribution while the actuator of  FIG. 3  is operated. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0040]    Description will now be given in detail of the present invention, with reference to the accompanying drawings. 
         [0041]    Hereinafter, an actuator according to the present invention will be explained in more detail with reference to the attached drawings. 
         [0042]    Referring to  FIG. 3 , an actuator  100  according to one embodiment of the present invention comprises one pair of fixed plates  102  disposed to face each other. The fixed plates  102  are configured to provide coupling surfaces with external devices as lower ends  102  thereof are bent. An opening  106  through which a bobbin and a coil that will be later explained are partially exposed out is formed at an upper side of the fixed plates  102 . And, a cut-out portion  108  is formed at a central portion of an upper end of the fixed plates  102 , through which a head of a mover  120  can be moved in upper and lower directions. Lamination cores  110  are fixed between said one pair of fixed plates  102 . As the fixed plates  102  and the lamination cores  110  are coupled to each another, an assembly having a rectangular sectional surface is implemented. The assembly serves as an outer body of the actuator. In the assembly, the mover  120  is mounted so as to be movable in up and down directions. The mover  120  includes a movable core  122  formed as thin plates are laminated to each other, and a head  124  fixed to a lower side of the movable core  122 . The mover  120  further includes a stem, which will be later explained. 
         [0043]    The head  124  is inserted into a bobbin  130 , and a coil  132  is wound on an outer surface of the bobbin  130 . Referring to  FIG. 4 , an insertion opening  134  is formed at a central portion of the bobbin  130 , and the head  124  is inserted into the insertion opening  134 . A shaft type of stem  126  extending to one direction is fixed to a bottom surface of the head  124 . And, the stem  126  is inserted into a stem fixing hole  142  formed at a fixed core  140  positioned between the lamination cores  110 . 
         [0044]    One pair of permanent magnets  150  are fixed between the fixed core  140  and the lamination cores  110 . The permanent magnets  150  transmit a magnetic force to the fixed core  140  and the lamination cores  110  by contacting thereto. 
         [0045]    A spring guide  160  is positioned below the fixed core  140 , and an open spring  164  is inserted into a guide hole  162  formed at a central portion of the spring guide  160 . A stopper  128  having a hook shape contacts an upper end of the open spring  164 , and is fixed to the end of the stem  126 . Accordingly, an elastic force of the open spring  164  is transmitted to the stem  126  through the stopper  128 . 
         [0046]    A spring guide hole  144  (refer to  FIG. 5 ) is formed on a bottom surface of the fixed core  140 , and an upper end of the open spring  164  is inserted into the spring guide hole  144 . A damping member  146  is interposed between the stopper  128  and the fixed core  140 , thereby preventing noise and vibration that may occur when the stopper  128  collides with an inner surface of the spring guide hole  144 . 
         [0047]    One pair of guide slots  125  are extendingly formed at the head  124  in parallel to the up and down direction of the head  124 . One guide bar  170  is inserted into each of the guide slots  125 . Here, the guide bar  170  has an outer diameter equal to or a little smaller than a width of the guide slot  125 . Fixed blocks  172  are coupled to both ends of the guide bar  170 . The fixed blocks  172  are fixed between said one pair of fixed plates  102 . Accordingly, the guide bars  170  are fixed by the fixed plates  102 , thereby guiding motion of the head  124  in upper and lower directions. 
         [0048]    Hereinafter, the operation of the monostable permanent magnetic actuator according to the present invention will be explained. 
         [0049]      FIG. 5  is a sectional view of the actuator of  FIG. 3 , which shows that the mover  120  is located at an upper position. And,  FIG. 6  is a sectional view of the actuator of  FIG. 3 , which shows that the mover  120  is located at a lower position. 
         [0050]    Referring to  FIG. 6 , a magnetic flux of the permanent magnets  150  is implemented by a magnetic circuit composed of the movable core  122 , the head  124 , and the fixed core  140 . Accordingly, the mover  120  is located at a lower position by a magnetic force from the permanent magnets  150 . Under this state, once a current (close current) is applied to the coil  132  in an opposite direction to the direction of the magnetic flux of the permanent magnets  150 , an attractive force toward the head  124  and the movable core  122  is decreased. Accordingly, the magnetic force of the permanent magnets  150  becomes less than the elastic force of the open spring  164 . As a result, the mover  120  is moved to an upper position as shown in  FIG. 5 . 
         [0051]    Under this state, even if a current applied to the coil is cut-off, the elastic force of the open spring  164  is larger than the magnetic force of the permanent magnets  150 . Accordingly, the mover  120  can be still disposed at the upper position. 
         [0052]    Then, once a current (open current) is applied to the coil  132  in the same direction as the direction of the magnetic flux of the permanent magnets  150 , a magnetic force between the movable core  122  and the lamination cores  110  is small due to a large air gap therebetween, whereas a magnetic force between the head  124  and the fixed core  140  is relatively large at first. Accordingly, a main magnetic path is formed between the head  124  and the fixed core  140 . Then, if the air gap is decreased as the mover  120  gradually moves in a downward direction, a main magnetic path is formed between the movable core  122  and the lamination cores  110 , whereas a supplementary magnetic path is formed between the head  124  and the fixed core  140 . As the magnetic force is continuously applied to the moved  120 , the mover  120  is moved to be in the state of  FIG. 6 . And, the mover  120  can maintain its state shown in  FIG. 6  by the magnetic force of the permanent magnets  150  even if current supply is cut off. 
         [0053]      FIGS. 7 and 8  are views showing magnetic flux distribution while the actuator of  FIG. 3  is operated. 
         [0054]    The left drawing of  FIG. 7  shows magnetic flux distribution when a close current has been applied to a coil so as to move the mover  120  to a lower position from an upper position. On the contrary, the right drawing of  FIG. 7  shows magnetic flux distribution when the close current has been cut-off under a state that the mover  120  has been moved to the lower position. 
         [0055]    Referring to the left drawing of  FIG. 7 , the mover is disposed at the upper position when a close current is applied. Before the mover moves by a current applied to a coil, a magnetic resistance on the supplementary magnetic path (red loop) is smaller than that on the main magnetic path (blue loop). Accordingly, the supplementary magnetic path has larger magnetic flux than the main magnetic path. This is implemented so as to enhance the efficiency by flowing a small current to the coil by decreasing a magnetic resistance at the first time. Once the mover moves to the lower position by the magnetic flux distributed on the main magnetic flux and the supplementary magnetic flux, the magnetic flux on the main magnetic flux is continuously increased. However, once the mover reaches the lower position, the current applied to the coil is not applied to the mover by a controller. Here, the mover is held only by magnetic energy from the permanent magnets. In this case, the magnetic flux is distributed only on the main magnetic path, not on the supplementary magnetic path, thereby holding the mover  120 . The holding force occurs at three parts, i.e., at contact portions near both ends of the movable core of the mover (pink colors of right and left sides of an upper end), and a contact portion of a middle part of a lower end. Accordingly, the holding force can be increased. 
         [0056]    The right drawing of  FIG. 8  shows magnetic flux distribution under a state that an open current has been applied to the mover being disposed at the lower position. On the contrary, the left drawing of  FIG. 8  shows magnetic flux distribution under a state that the open current applied to the mover has been cut-off after the mover moved to the upper position. 
         [0057]    Referring to the right drawing of  FIG. 8 , the mover is disposed at the lower position before applying an open current. Once the open current is applied to the coil, a magnetic flux occurs in an opposite direction to the direction of the magnetic flux of the permanent magnets. Accordingly, the magnetic flux of the permanent magnets for holding the mover at both ends and central contact portion of the movable core is decreased, thereby decreasing the holding force of the mover. As the holding force is continuously decreased to be less than force applied to the mover from the open spring and the outside (contact pressure spring of a circuit breaker), the mover is moved to the upper position by the force transmitted from the open spring and the outside. Once the mover reaches the upper position, the current applied to the coil is not applied to the mover by the controller, but only the magnetic flux of the permanent magnets remains. The magnetic flux of the permanent magnet is more distributed on the supplementary magnetic path (blue loop) than on the main magnetic path (brown loop). Accordingly, the holding force of the mover becomes far less, and the mover is held at the upper position by the elastic force of the open spring. 
         [0058]    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. 
         [0059]    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.