Abstract:
A rotary-type damper includes a housing filled with a working fluid, a shaft penetrating inside the housing and placed in a rotatable manner, a housing pin provided on the inner circumference of the housing to reach the side of the shaft used for limiting the movement of the working fluid, and an axis pin for coupling with the shaft to rotate with the shaft, and closely contacting the side of the shaft and the inner circumference of the housing as the position thereof varies according to the rotating direction of the shaft. The present invention increases the durability and the period of use, easily enables an accurate control of the working fluid, thereby eliminating the requirement for high precision in processing the component members, and enables the control of a unidirectional damping and the rotational speed of a rotary body which is the target of damping.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS AND CLAIM OF PRIORITY 
       [0001]    This patent application is a National Phase application under 35 U.S.C. §371 of International Application No. PCT/KR2012/003549, filed May 7, 2012, which claims priority to Korean Patent Application No. 10-2011-0042888 filed May 6, 2011, entire contents of which are incorporated herein by reference. 
     
    
     BACKGROUND 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a rotary-type damper, and more particularly, to a rotary-type damper wherein the durability and the period of use thereof is increased by minimizing the contact area between component members thereof, and reducing abrasions of the components during operation. Moreover, a rotary-type damper capable of controlling uni-directional dampening and rotational speed of a rotary body is described. 
         [0004]    2. Description of the Related Art 
         [0005]    In general, a damper is an apparatus configured to absorb vibration energy. A damper can also be referred to as a vibration controller or a vibration absorber. Among such dampers, a rotary damper is used to gently control the rotational speed of a rotary body by applying a predetermined braking force to the rotary body. 
         [0006]    In the rotary-type oil damper described herein, the dampening function is performed using oil and will be described with reference to the accompanying drawings below. 
         [0007]      FIG. 1  is a cross-sectional view of a conventional rotary-type oil damper disclosed in Korean registered patent No. 0205091 entitled, “Keyboard Lid Opening and Closing Device Using Oil Damper”. 
         [0008]    As illustrated in  FIG. 1 , the conventional oil damper  3  includes a casing  8 , including a hollow cylindrical chamber  6  with one end facing a shaft of which is closed and another end of which is open, and the inside of which is filled with a viscosity fluid  7 ; a pivoting member (not shown) assembled to be rotatable with respect to the casing  8  and includes a shaft unit  9  disposed in the chamber  6  to be rotated along a shaft line of the casing  8 ; a protrusion portion  10  extending in a shaft direction and along the peripheral surfaces of the shaft unit  9 ; a movable valve  11 , coupled to the protrusion portion  10 , having an opening in a rotational direction and having a side in contact with the protrusion portion  10  in the rotational direction of the casing  8 ; fluid passages  12 ,  13 , and  14  formed on the interface between the movable valve  11  and the protrusion portion  10  and one side and another side of the movable valve  11 , respectively, to cause the viscosity fluid  7 , having a resistance, to pass through the movable valve  11  as the casing  8  and the pivoting member (not shown) rotate relatively to one another; and a sealing member (not shown) including, for example, an O-shaped ring installed between the casing  8  and the pivoting member (not shown) to seal the viscosity fluid  7 . 
         [0009]    The casing  8  is installed on a place where the oil damper  3  is applied by tightening a screw. More specifically, the movable valve  11  is formed such that a cross section thereof comprises a channel shape. The distance between vertical walls  17  and  18 , both of which are the ends of the movable valve  11  in terms of the rotational direction of  11 , is actually greater than the width of the protrusion portion  10  in terms of the rotational direction of  10 . The movable valve  11  has an opening in the rotational direction of  11 , is placed on the protrusion portion  10 , and may be moved in a sliding manner to contact a surface of the inner wall  19  of casing  8 . The fluid passages  12  and  13  are actually formed on the vertical walls  17  and  18  of movable valve  11 , respectively, and the fluid passage  14  is formed by partially cutting the protrusion portion  10 . A stopper  23  extends in the shaft direction and is installed on the inner wall  19  of the chamber  6 . 
         [0010]    In the conventional rotary-type oil damper  3  described above, when the casing  8  starts to rotate in the direction indicated by the arrow (i.e., in a counterclockwise direction), the movable valve  11  is rotated by the viscosity fluid  7  as the stopper  23  rotates, thereby causing the vertical wall  18  to come into contact with the protrusion portion  10 . Consequently, the viscosity fluid  7  flows from fluid passage  13 , via fluid passage  14 , and then flows in the direction of the opening between vertical wall  17  and protrusion portion  10 , thereby decreasing the resistance of the viscosity fluid  7 . 
         [0011]    Furthermore, when casing  8  starts to rotate in the opposite direction (i.e., in a clockwise direction), stopper  23  is in a fully open state wherein stopper  23  is in contact with protrusion portion  10 , via movable valve  11 , and vertical wall  17  of movable valve  11  consequently comes in to contact with protrusion portion  10 . In this case, viscosity fluid  7  flows into fluid passage  12 , having a small cross section, and thus generates very high resistance. 
         [0012]    In conventional rotary-type oil dampers, the component members are likely to abrade during operation due to surface contact between the component members, thereby decreasing the durability and periods of use. 
         [0013]    Furthermore, in conventional rotary-type oil dampers, working fluids are difficult to control accurately, and the component members are thus required to be precisely processed, thereby increasing the efforts and costs to manufacture conventional rotary-type oil dampers like  3 . 
         [0014]    In conventional rotary-type oil dampers, mechanisms configured to generate resistance for working fluids are complicated, and accurately controlling the resistance of working fluids is equally limited during operations, thereby lowering the reliability of the dampening action. 
         [0015]    Lastly, conventional rotary-type oil dampers are not capable of controlling the unidirectional dampening and rotational speed of a rotary body, and are thus inapplicable to rotary bodies that require unidirectional dampening or variable rotational speeds. 
       SUMMARY 
       [0016]    The present invention provides a rotary-type damper wherein the durability and period of use are increased by minimizing the contact area between the component members thereof, thereby decreasing abrasions of the component members during operation. 
         [0017]    The present invention also provides a rotary-type damper which is capable of accurately controlling the working fluid and thereby does not require the precise processing of the component members thereof, thus reducing the effort and costs to manufacture the rotary-type damper. 
         [0018]    The present invention also provides a rotary-type damper capable of accurately controlling the resistance of the working fluid, thereby improving the reliability of the dampening action. 
         [0019]    The present invention also provides a rotary-type damper that is capable of controlling the unidirectional dampening and rotational speed of a rotary body, thus making it easily applicable to a rotary body that requires unidirectional dampening or variable rotational speeds. 
         [0020]    Additional aspects of the present invention will be set forth in part in the description which follows and, in part, will be apparent from the description, or may be learned by practice of the presented embodiments. 
         [0021]    According to an aspect of the present invention, there is provided a rotary type damper including a housing filled with a working fluid; a shaft installed to be rotatable while passing through the inside of the housing; a housing pin placed on an inner circumference of the housing to reach a side of the shaft, and configured to limit the movement of the working fluid; and an axis pin coupled to the shaft to rotate together with the shaft, and closely contacting the side of the shaft and the inner circumference of the housing as the position of the axis pin varies according to a rotation direction of the shaft. 
         [0022]    The axis pin may be coupled to the side of the shaft such that the axis pin rotates in opposite directions according to the rotation direction of the shaft and a resistance between the axis pin and the working fluid thereby. 
         [0023]    Both sides of the axis pin may closely contact the side of the shaft and the inner circumference of the housing, respectively, according to the resistance of the working fluid, with respect to the center of the axis pin. 
         [0024]    The axis pin may be meshed with the shaft in a circumferential direction of the shaft while having a clearance with the shaft. 
         [0025]    A first insertion groove having a curvature may be formed in one of a side of the axis pin and a side of the shaft, and a first insertion projection having a curvature may be formed on the other to be inserted into the first insertion groove. 
         [0026]    A pair of first insertion grooves and a pair of first insertion projections may be formed in parallel at a predetermined interval. 
         [0027]    Linear contact portions may be formed at both sides of the axis pin to cause the axis pin to linearly contact the inner circumference of the housing when the axis pin closely contacts the inner circumference of the housing. 
         [0028]    Both side surfaces of the axis pin may be formed to be inclined with respect to a radius of rotation of the shaft. 
         [0029]    A resistance decrease groove may be formed in the axis pin to allow the working fluid therethrough when the shaft rotates only in one direction. 
         [0030]    The resistance decrease groove may be formed in a side of a surface of the axis pin facing the inner circumference of the housing. 
         [0031]    A friction decrease groove may be formed in the surface of the axis pin facing the inner circumference of the housing in a lengthwise direction to be connected to the resistance decrease groove. 
         [0032]    The housing pin may be installed on the housing such that the position of the housing pin varies according to the rotation direction of the shaft and a resistance of the working fluid thereby, and to cause the housing pin to closely contact the side of the shaft and the inner circumference of the housing. 
         [0033]    The housing pin may be meshed with the inner circumference of the housing in a circumferential direction of the housing while having a clearance with the housing. 
         [0034]    A second insertion groove having a curvature may be formed in one of the housing pin and the inner circumference of the housing, and a second insertion projection having a curvature may be formed on the other to be inserted into the second insertion groove. 
         [0035]    The housing pin may be shaft-coupled to a bottom surface of the housing to be rotatable with respect to the bottom surface of the housing. 
         [0036]    Linear contact portions may be formed at both sides of a portion of the housing pin facing the shaft to cause the housing pin to linearly contact the shaft when the housing pin closely contacts the shaft. 
         [0037]    Both side surfaces of the housing pin may be formed to be inclined with respect to the radius of rotation of the shaft. 
         [0038]    The durability and period of use of a rotary type damper according to the present invention may be increased by minimizing a contact area between component members thereof to decrease abrasion of the component members during an operation. Also, the rotary type damper is capable of accurately controlling a working fluid and thus does not require a high precision and accuracy to process the component members, thereby reducing the efforts and costs to manufacture the rotary type damper. Also, the rotary type damper is capable of accurately controlling a resistance of the working fluid to improve the reliability of a damping action and controlling a unidirectional damping and a rotational speed of a rotary body which is a target of damping, and is thus easily applicable to a rotary body that requires a unidirectional damping or a variable rotational speed. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0039]      FIG. 1  is a cross-sectional view of a conventional rotary type oil damper, 
           [0040]      FIG. 2  is an exploded perspective view of a rotary type damper according to a first embodiment of the present invention, 
           [0041]      FIG. 3  is a side cross-sectional view of the rotary type damper according to the first embodiment of the present invention, 
           [0042]      FIG. 4  is an enlarged view of main parts of the rotary type damper of  FIG. 3 , 
           [0043]      FIG. 5  is a perspective view of the rotary type damper according to the first embodiment of the present invention, 
           [0044]      FIG. 6  is a plan view of a state in which an axis pin is closed in the rotary type damper according to the first embodiment of the present invention, 
           [0045]      FIG. 7  is an enlarged plan view of main parts of the rotary type damper of  FIG. 6 , 
           [0046]      FIG. 8  is a plan view of another state in which the axis pin is closed in the rotary type damper according to the first embodiment of the present invention, 
           [0047]      FIG. 9  is an enlarged plan view of main parts of the rotary type damper of  FIG. 8 , 
           [0048]      FIGS. 10 and 11  are plan views illustrating an operation of a housing pin of the rotary type damper according to the first embodiment of the present invention, 
           [0049]      FIG. 12  is a plan view of various examples of the housing pin of the rotary type damper according to the first embodiment of the present invention, 
           [0050]      FIG. 13  is an exploded perspective view of a rotary type damper according to a second embodiment of the present invention, 
           [0051]      FIGS. 14 to 16  are plan views of states in which an axis pin is closed in the rotary type damper according to the second embodiment of the present invention, 
           [0052]      FIG. 17  is an enlarged plan view of main parts of the rotary type damper in which the axis pin is closed in the rotary type damper according to the second embodiment of the present invention, 
           [0053]      FIGS. 18 to 20  are plan views of states in which the axis pin is open in the rotary type damper according to the second embodiment of the present invention, and 
           [0054]      FIG. 21  is an enlarged plan view of main parts of the rotary type damper in which the axis pin is open according to the second embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0055]    The present invention may be embodied in different forms and in various embodiments. Thus, exemplary embodiments of the present invention will be illustrated in the drawings and described in detail below. However, the present invention is not limited to the embodiments set forth herein. Exemplary embodiments are described so as to cover all modifications, equivalents, and alternatives falling within the scope of the present invention. Accordingly, it will be understood that various changes in form and detail may be made therein without departing from the spirit and scope of the following claims. 
         [0056]    Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. The same or corresponding component members are assigned the same reference numerals and are not redundantly described herein. 
         [0057]      FIG. 2  is an expanded perspective view of a rotary type damper  100  according to a first embodiment of the present invention.  FIG. 3  is a side cross-sectional view of the rotary type damper  100  according to the first embodiment of the present invention. 
         [0058]    As illustrated in  FIGS. 2 and 3 , the rotary type damper  100 , according to the first embodiment of the present invention, may include a housing  110  filled with a working fluid  1 , a shaft  120  installed within the housing  110 , a housing pin  130  placed on an inner circumference of the housing  110 , and an axis pin  140  placed on the shaft  120  such that the position thereof is variable. Examples of a rotary body include various doors, robot arms, wheels, rotary mechanisms, rotation members, rotation devices, and the like. Here, working fluid  1  may be one of various viscous fluids such as oils and the like. 
         [0059]    The inside of the housing  110  is filled with the working fluid  1  such that the working fluid  1  does not leak. A cap  111  is coupled to a side of the housing  110  and detachable so that the inside of the housing  110  may be opened. A sealing member may be interposed between a portion of housing  110  and a portion of cap  111 , which are coupled to each other, so as to make an air-tight seal with the housing  110 , and may be fixed on, for example, a supporting structure for supporting the rotary body directly or via a bracket or additional member. 
         [0060]    As illustrated in  FIG. 4 , the housing  110  may have a gap G 1  allowing flow of the working fluid  1 , via tolerance between an inner side of the housing  110  and the housing pin  130  illustrated in  FIG. 3 , or between the inner side of the housing  110  and the axis pin  140 ; or processing a portion between the inner side of housing  110  and the housing pin  130  illustrated in  FIG. 3 , or between the inner side of the housing  110  and the axis pin  140 . Thus, the working fluid  1  may pass through the housing  130  and the axis pin  140  via the gap G 1 . The size of the gap G 1  may vary according to dampening characteristics. 
         [0061]    In the housing  110 , the working fluid  1  may travel between both spaces defined by the housing pin  130  and the axis pin  140  by forming a groove on a surface of the inner side of the housing  110 , or forming a groove on an outer circumference of the shaft  120 , or forming a hole to pass through the shaft  120 , or using a tolerance between the component members (e.g., an assembling tolerance of the housing  110 , shaft  120 , housing pin  130 , and axis pin  140 . Such a flow of the working fluid  1  may also be applied to all other embodiments wherein one or a plurality of methods above may be used. When the movement of the working fluid  1  is allowed to bypass the housing pin  130  via a fluid path groove  122  on the outer circumference of the shaft  120 , the rotational speed of the shaft  120  may be easily controlled using changes in the cross-sectional area or specifications of the fluid path groove  122 . 
         [0062]    The shaft  120  is installed to be rotatable within the inside of the housing  110 , and one or both ends of the shaft  120  may be exposed to or protrude from the housing  110 , thereby fixing the rotary body. Thus, the rotary-type damper  100  is configured to absorb the rotational energy generated by the rotational movement of the rotary body. The rotary body may be returned to its original position via a restoring member, such as a spring, and the rotary-type damper  100  may absorb rotational energy when the rotary body is returned to its original position. 
         [0063]    The shaft  120  may be installed in the housing  110  to be rotatable via a bearing, and a sealing member may be installed in a contact area between the shaft  120  and the housing  110 . 
         [0064]    Rotation of the shaft  120  means rotation of the shaft  120  relative to the housing  110 , and may be applied throughout the present disclosure. Thus, the shaft  120  may function as a fixed shaft to fix the rotary body into the housing  110 . 
         [0065]    The housing pin  130  is placed on the inner circumference of the housing  110  so that the housing pin  130  may reach a side of the shaft  120  to limit the movement of the working fluid  1 . Here, the limiting of the movement of the working fluid  1  includes not only completely blocking the movement of the working fluid  1  via the housing pin  130 , but also allows minute movement of the working fluid  1  through a clearance between the housing pin  130  and the shaft  120 . Thus, in rotary-type dampers according to the present embodiment and subsequent embodiments, the housing pin  130  and the axis pin  140  are configured to completely block the movement of the working fluid  1 , but still allow the minute movement of the working fluid  1 , as described above with respect to the limiting of the movement of the working fluid  1 , thereby allowing the rotation of the shaft  120 . 
         [0066]    As illustrated in  FIGS. 5 to 9 , the axis pin  140  is coupled to the shaft  120  so that the axis pin  140  may be rotated together with the shaft  120 , and the position of the axis pin  140  may vary according to a rotational direction of the shaft  120 . Thus, the axis pin  140  may closely contact a side of the shaft  120  and the inner circumference of the housing  110 . 
         [0067]    Alternatively, the axis pin  140  may be coupled to a side of the shaft  120  so that the axis pin  140  may rotate in a direction opposite the rotational direction of the shaft  120  due to resistance between the axis pin  140  and the working fluid  1 . For example, when the shaft  120  rotates in a counterclockwise direction as illustrated in  FIG. 6 , the axis pin  140  is moved in a direction while rotating due to a resistance of the working fluid  1  to cause contact portions  141 ,  142 , and  143  to closely contact the inner circumference of the housing  110  and the side of the shaft  120 , thereby suppressing the movement of the working fluid  1 , as illustrated in  FIG. 7 . When the shaft  120  rotates in a clockwise direction, as illustrated in  FIG. 8 , the axis pin  140  is moved in a counterclockwise direction while rotating due to the resistance of the working fluid  1  thereby causing other contact portions  144 ,  145 , and  146  to closely contact the inner circumference of the housing  110  and the side of the shaft  120 , thereby suppressing the movement of the working fluid, as illustrated in  FIG. 9 . 
         [0068]    As in the present embodiment, the linear contact portions  141  and  144  among the contact portions  141  to  146  may be formed at both ends of the axis pin  140  to cause the axis pin  140  to linearly contact the inner circumference of the housing  110  when the axis pin  140  closely contacts the inner circumference of the housing  110 . The linear contact portions  141  and  144  may have any shape necessary to linearly contact the inner circumference of the housing  110  and reduce abrasion of the axis pin  140  when the axis pin  140  comes into contact with the inner circumference of the housing  110 , thereby making it easier to manufacture the axis pin  140 . The axis pin  140  may be shaped such that the contact portions  142 ,  143 ,  145 , and  146 , and not linear contact portions  141  and  144 , linearly contact the side of the shaft  120 . 
         [0069]    A side of the axis pin  140  facing the inner circumference of the housing  110  may be formed to have a curvature that is same as or similar to that of the housing  110  without limitation, and may have any of other various shapes. 
         [0070]    As in the present embodiment, both sides of the axis pin  140  may closely contact the side of the shaft  120  and the inner circumference of the housing  110 , respectively, with respect to the center of the axis pin  140  (e.g., a radius of rotation passing through the center of the axis pin  140 ) according to the resistance of the working fluid  1 . In this case, the both sides of the axis pin  140  may be symmetric to each other with respect to the center of the axis pin  140 . Otherwise, both sides of the axis pin  140  may be formed asymmetric to one another. 
         [0071]    As illustrated in  FIGS. 7 and 9 , the axis pin  140  may be meshed with the shaft  120  along a circumferential direction of the shaft  120  while still having clearance with the shaft  120 . To this end, for example, a first insertion groove  121  having a curvature may be formed on one side of the axis pin  140  and on a side of the shaft  120 , and a first insertion projection  147  having a curvature may be formed on the other side to be inserted into the first insertion groove  121 . In the present embodiment, the first insertion groove  121  is formed into the shaft  120  and the first insertion projection  147  is formed on the axis pin  140 , without limitation wherein the locations of the first insertion groove  121  and the first insertion projection  147  may be switched relative to one another. 
         [0072]    The number of each of the first insertion grooves  121  and the first insertion projections  147  may be one or greater than one. Alternatively, as in the present embodiment, a pair of insertion grooves  121  and a pair of insertion projections  147  may be formed in parallel at predetermined intervals so that the axis pin  140  may stably rotate with respect to the shaft  120  to change the position thereof. 
         [0073]    As illustrated in  FIG. 6 , both side surfaces  148   a  and  148   b  of the axis pin  140  may be formed to be inclined with respect to the radius of rotation of the shaft  120  so that the axis pin  140  may be easily moved while rotating by the pressure of working fluid  1 . 
         [0074]    The housing pin  130  may protrude from the inner circumference of the housing  110  to be integrally formed with the housing  110 . Alternatively, as in the present embodiment, the housing pin  130  may be formed separately from the housing  110  and installed on the housing  110 . For example, the housing pin  130  may be installed on the housing  110  (e.g., the inner circumference of the housing  110 ) to closely contact a side of the shaft  120  and the inner circumference of the housing  110  as the position of the housing pin  130  may vary according to the rotational direction of the shaft  120  and the resistance of the working fluid  1 . 
         [0075]    As illustrated in  FIGS. 10 and 11 , the housing pin  130  may be meshed with the inner circumference of the housing  110  in the circumferential direction of the housing  110  while still having clearance with the housing  110 . For example, a second insertion groove  112  having a curvature may be formed on one of the housing pins  130  and the inner circumference of the housing  110 , and a second insertion projection  131  having a curvature may be formed on the other to be inserted into the second insertion groove  112 . Here, as in the present embodiment, the second insertion projection  131  may be formed on the housing pin  130 , and the second insertion groove  112  may be formed on the inner circumference of the housing  110 , without limitation wherein the locations of the second insertion projection  131  and the second insertion groove  112  may be switched to relative to one another. 
         [0076]    Both sides of the housing pin  130  may be formed to be symmetric to each other as in the present invention or may be formed to be asymmetric to each other. As illustrated in  FIGS. 12(   a ) and ( b ), the housing pin  130  may have various shapes. Referring to  FIG. 12(   b ), the housing pin  130  may be shaft-coupled to a bottom surface of the housing  110  by forming a shaft hole, a shaft groove, or a shaft thereon so that the housing pin  130  may rotate with respect to the bottom surface of the housing  110 . 
         [0077]    Linear contact portions  132  and  133  may be formed on both sides of a portion of the housing pin  130  facing the shaft  120  so that the housing pin  130  may linearly contact the shaft  120 . Here, each of the linear contact portions  132  and  133  may be in a linear shape as in the present embodiment, but may also be in a curved shape or a combination of linear and curved shapes. Thus, when the shaft  120  rotates in a counterclockwise direction as illustrated in  FIG. 6 , the housing pin  130  is rotated, or is moved while rotating, in one direction by the pressure of the working fluid  1  compressed by the axis pin  140  as illustrated in  FIG. 10 . Thus, the linear contact portion  132  on one side of the housing pin  130  comes in close contact with the inner circumference of the shaft  120 , and the second insertion projection  131  comes in close contact with the inside of the second insertion groove  112 , thereby preventing the working fluid  1  from being moved by the housing pin  130 . Also, when the shaft  120  rotates in the clockwise direction as illustrated in  FIG. 8 , the housing pin  130  is rotated, or is moved while rotating, in another direction by the pressure of the working fluid  1  compressed by the axis pin  140  as illustrated in  FIG. 11 . Thus, the linear contact portion  133  on another side of the housing pin  130  comes in close contact with the inner circumference of the shaft  120  and the second insertion projection  131  comes in close contact with the inside of the second insertion groove  112 , thereby preventing the working fluid  1  from being moved by the housing pin  130 . 
         [0078]    Both side surfaces  134  and  135  of the housing pin  130  may be formed to be inclined with respect to the radius of rotation of the shaft  120  as illustrated in  FIG. 6 . Thus, a moment may be easily applied onto the housing pin  130  to rotate or to make a rotational motion by the pressure of the working fluid  1 . 
         [0079]      FIG. 13  is an expanded perspective view of a rotary-type damper  200  according to a second embodiment of the present invention.  FIG. 14  is a plan view of the rotary type damper  200  according to the second embodiment of the present invention. 
         [0080]    As illustrated in  FIGS. 13 and 14 , the rotary type damper  200  according to the second embodiment of the present invention may include a housing  210 , a shaft  220 , a housing pin  230 , and an axis pin  240 , akin to the rotary-type damper  100  according to the first embodiment of the present invention. The rotary-type damper  200  differs from the rotary-type damper  100  in that a resistance decrease groove  241  is formed in the axis pin  240  so that working fluid is allowed to pass through the axis pin  240 , when the shaft  220  only rotates in one direction. Thus, in the rotary-type damper  200 , the working fluid is prevented from moving in one direction by the axis pin  240  thereby allowing movement in only the other direction, thus enabling unidirectional dampening. 
         [0081]    The resistance decrease groove  241  may be formed in various locations on the axis pin  240  and in various shapes to allow the working fluid to only move in one direction. For example, the resistance decrease groove  241  may be formed on a side of the surface of the axis pin  240  facing the inner circumference of the housing  210 . 
         [0082]    A friction decrease groove  242  may be formed on the surface of the axis pin  240  facing the inner circumference of the housing  210  in a lengthwise direction to be connected to the resistance decrease groove  241 . Thus, a contact area between the axis pin  240  and the inner circumference of the housing  210  may be minimized to reduce friction between the axis pin  240  and the housing  210 . 
         [0083]    When the shaft  220  rotates in a counterclockwise direction as illustrated in  FIGS. 14 to 16 , contact portions  243 ,  244 , and  245  of the axis pin  240  closely contact the inner circumference of the housing  210  and an outer circumference of the shaft  220 , thereby preventing the working fluid from being moved due to the axis pin  240 , as illustrated in  FIG. 17 . 
         [0084]    In contrast, when the shaft  220  rotates in a clockwise direction as illustrated in  FIGS. 18 to 20 , the other contact portions  246 ,  247 , and  248  of the axis pin  240  closely contact the inner circumference of the housing  210  and the outer circumference of the shaft  220 , akin to the rotary-type damper  100  according to the first embodiment, but the working fluid may pass through a gap G 2  formed between the axis pin  240  and the inner circumference of the housing  210  via the resistance decrease groove  241 , as in  FIG. 21 , since the resistance decrease groove  241  is formed near the contact portion  246  contacting the inner circumference of the housing  210 , thereby reducing or suppressing the dampening action. 
         [0085]    Although some embodiments of the present invention have been shown and described with reference to the accompanying drawings, it will be appreciated by those of ordinary skill in the art that changes can be made to these exemplary embodiments without departing from the principle and spirit of the invention along with the scope of which is defined in the appended claims and their equivalents. 
         [0086]    According to one aspect of the present invention, there is provided a rotary type damper including a housing filled with a working fluid; a shaft installed to be rotatable while passing through the inside of the housing; a housing pin placed on an inner circumference of the housing to reach a side of the shaft, and configured to limit the movement of the working fluid; and an axis pin coupled to the shaft to rotate together with the shaft, and closely contacting the side of the shaft and the inner circumference of the housing as the position of the axis pin varies according to a rotation direction of the shaft. 
         [0087]    The axis pin may be coupled to the side of the shaft such that the axis pin rotates in opposite directions according to the rotation direction of the shaft and a resistance between the axis pin and the working fluid. 
         [0088]    Both sides of the axis pin may closely contact the side of the shaft and the inner circumference of the housing, respectively, according to the resistance of the working fluid, with respect to the center of the axis pin. 
         [0089]    The axis pin may be meshed with the shaft in a circumferential direction of the shaft while having a clearance with the shaft. 
         [0090]    A first insertion groove having a curvature may be formed in one of a side of the axis pin and a side of the shaft, and a first insertion projection having a curvature may be formed on the other to be inserted into the first insertion groove. 
         [0091]    A pair of first insertion grooves and a pair of first insertion projections may be formed in parallel at a predetermined interval. 
         [0092]    Linear contact portions may be formed at both sides of the axis pin to cause the axis pin to linearly contact the inner circumference of the housing when the axis pin closely contacts the inner circumference of the housing. 
         [0093]    Both side surfaces of the axis pin may be formed to be inclined with respect to a radius of rotation of the shaft. 
         [0094]    A resistance decrease groove may be formed in the axis pin to allow the working fluid therethrough when the shaft rotates only in one direction. 
         [0095]    The resistance decrease groove may be formed in a side of a surface of the axis pin facing the inner circumference of the housing. 
         [0096]    A friction decrease groove may be formed in the surface of the axis pin facing the inner circumference of the housing in a lengthwise direction to be connected to the resistance decrease groove. 
         [0097]    The housing pin may be installed on the housing such that the position of the housing pin varies according to the rotation direction of the shaft and the resistance of the working fluid to cause the housing pin to closely contact the side of the shaft and the inner circumference of the housing. 
         [0098]    The housing pin may be meshed with the inner circumference of the housing in a circumferential direction of the housing while having a clearance with the housing. 
         [0099]    A second insertion groove having a curvature may be formed in one of the housing pin and the inner circumference of the housing, and a second insertion projection having a curvature may be formed on the other to be inserted into the second insertion groove. 
         [0100]    The housing pin may be shaft-coupled to a bottom surface of the housing to be rotatable with respect to the bottom surface of the housing. 
         [0101]    Linear contact portions may be formed at both sides of a portion of the housing pin facing the shaft to cause the housing pin to linearly contact the shaft when the housing pin closely contacts the shaft. 
         [0102]    Both side surfaces of the housing pin may be formed to be inclined with respect to the radius of rotation of the shaft.