Abstract:
A damper includes a housing having a substantially cylindrical shape and filled with viscous fluid; a rotor portion rotatably supported inside the housing; fin portions projecting from the rotor portion; and deformable portions provided in the fin portions for changing a clearance between an end of the fin portion and an inner peripheral surface of the housing in response to resistance received\ed from the viscous fluid. The deformable portion is provided in the fin portion to allow the fin portion to deform elastically in response to the resistance received from the viscous fluid, and to change the clearance between the end of the fin portion and the inner peripheral surface of the housing.

Description:
BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT  
         [0001]    The present invention relates to a rotary damper used for a glove box, ashtray, and the like in an automobile.  
           [0002]    As shown in FIG. 8, a conventional rotary damper used for a glove box, ashtray, and the likes in an automobile includes a cylindrical case  100  filled with viscous fluid such as silicone oil; a cover member (not shown in the figure) for closing the case  100 ; and a rotor  102  supported on an axis for rotating inside the case  100 .  
           [0003]    The rotor  102  is composed of a cylindrical shaft  104  and multiple fin portions  106  projecting from an outer peripheral face of the shaft  104 . One end side of the shaft  104  is exposed from the case  100 , and connected to a braking member (for example, a cover member of the glove box, etc.) requiring braking force.  
           [0004]    Since the viscous fluid is filled inside of the case  100 , when the shaft  104  is rotated, viscous torque by the viscous fluid is generated on the fin portions  106 . The braking force acts on the braking member through the fin portions  106  and the shaft  104 , and the braking member moves slowly.  
           [0005]    A certain type of rotary damper is designed to generate the braking force in only one direction so that when the braking member such as a cover member is opened, the cover member is slowly opened due to the braking force, and when the cover member is closed, the cover member is easily closed with little braking force.  
           [0006]    For example, Japanese Patent Publication (Tokkai) No. 06-2727 has disclosed a damper in which an axis of a rotor stored inside a case is shifted off an axis of the case. Further, fin portions are attached to the rotor in a state where the fin portions are inclined in one way and able to swing, so that the fin portions slide against an inner wall of the case. When the rotor rotates in a direction opposite to the inclined direction of the fin portions, the fin portions swing to open and rotate while sliding against the inner wall of the opening case. Accordingly, a space inside the case between the fin portions gradually increases, thereby increasing the viscous torque due to the viscous fluid and the braking force. When the rotor rotates in the same direction as the inclined direction of the fin portions, the fin portions swing to close. Thus, the viscous fluid does not generate a large amount of the viscous torque, thereby generating little the braking force on the rotor.  
           [0007]    However, in the rotary damper described above, the viscous fluid such as silicone oil is used to generate the braking force. Accordingly, there is a large difference in the viscous torque between summer and winter, that is, a viscosity becomes low in summer and the viscous torque on the fin portion decreases.  
           [0008]    The present invention has been made in view of the problem described above, and an object of the present invention is to provide a damper having a small temperature dependency.  
           [0009]    Further objects and advantages of the invention will be apparent from the following description of the invention.  
         SUMMARY OF THE INVENTION  
         [0010]    According to the present invention, a damper includes: a housing having a substantially cylindrical shape and filled with viscous fluid; a rotor portion supported on a shaft to be rotatable inside the housing; fin portions projecting from the rotor portion; and deformable portions provided in the fin portions for changing a clearance between an end of the fin portion and an inner peripheral surface of the housing in response to resistance received from the viscous fluid.  
           [0011]    In the present invention, the deformable portion is provided in the fin portion to allow the fin portion to deform elastically in response to the resistance received from the viscous fluid, and to change the clearance between the end of the fin portion and the inner peripheral surface of the housing.  
           [0012]    The viscous torque generated at the end of the fin portion depends on a flow volume of the viscous fluid passing through the clearance between the end of the fin portion and the inner peripheral surface of the housing. When the clearance becomes larger, the viscous torque due to the flow volume of the viscous fluid (hereinafter referred to as “first viscous torque”) at the end of the fin portion is decreased.  
           [0013]    The viscous fluid has a viscosity higher in winter than in summer. Thus, the viscous torque due to the viscosity of the viscous fluid (hereinafter referred to as “second viscous torque”) at the end of the fin portion is increased in winter. Accordingly, the fin portion elastically deforms in a larger extent.  
           [0014]    In other words, when the viscosity is increased, the second viscous torque is increased at the end of the fin portion. At this time, the fin portion elastically deforms in a larger extent, so that the clearance between the end of the fin portion and the inner peripheral surface of the housing is increased to decrease the first viscous torque at the end of the fin portion. As a result, both effects are offset each other, and total viscous torque is maintained almost constant.  
           [0015]    When the viscosity becomes low in a high temperature such as summer, the second viscous torque at the end of the fin portion becomes small as compared to a situation in a low temperature such as winter. As a result, the fin portion elastically deforms in a smaller extent, so that the clearance between the end of the fin portion and the inner peripheral surface of the housing is decreased to increase the first viscous torque.  
           [0016]    In other words, when the viscosity is low, the clearance between the end of the fin portion and the inner peripheral surface of the housing is decreased to increase the first viscous torque at the end of the fin portion. As a result, the decline in the viscous torque due to the decline of the viscosity is offset.  
           [0017]    With this configuration, the clearance between the end of the fin portion and the inner peripheral surface of the housing is adjustable according to the resistance received from the viscous fluid depending on the viscosity. Thus, the changes in the viscous torque are offset, so that the damper has a small temperature dependency.  
           [0018]    In the invention, the deformable portion may be formed in a narrow portion at a side of the rotor portion. With the narrowed portion, the fin portion elastically deforms easily.  
           [0019]    In the invention, the deformable portion may be formed in a leaf spring connecting the rotor portion and the fin portion. With the leaf spring, the fin portion elastically deforms easily. The leaf spring may be molded with insert molding. With the insert molding, it is not necessary to attach the leaf spring and the fin portion to the rotor portion, thereby reducing manpower for an operation and a cost.  
           [0020]    The end of the fin portion may be formed in an arc shape having a curvature radius smaller than an inside diameter of the inner peripheral surface of the housing. The curvature radius of the arc is gradually decreasing toward outside from the center of the end of the fin portion. With this configuration, when the fin portion elastically deforms, the end of the fin portion does not abut against the inner peripheral surface of the housing. Further, it is possible to increase the clearance between the end of the fin portion and the inner peripheral surface of the housing according to the elastic deformation of the fin portion.  
           [0021]    It is possible to provide projections projecting in the axial direction of the rotor portion on top and bottom faces at the end of the fin portion. With this configuration, the second viscous torque at the end of the fin portion can be increased, so that the fin portion elastically deforms easily.  
           [0022]    According to another aspect of the present invention, a damper includes a housing having a substantially cylindrical shape and filled with viscous fluid; a rotor portion supported on a shaft to be rotatable inside the housing; fin portions projecting from the rotor portion; and extension portions extending from one side from a centerline of the fin portion for changing a clearance between an end of the fin portion and the inner peripheral surface of the housing according to a rotational direction of the shaft.  
           [0023]    The extension portion extends to one side from the centerline of the fin portion, so that the clearance between the end of the extension portion and the inner peripheral surface of the housing is changed according to the rotational direction of the rotor portion. Thus, it is possible, for example, to decrease the clearance in one rotational direction to increase the braking force, and to increase the clearance in the other rotational direction to reduce the braking force (so-called one-way damper).  
           [0024]    In the damper described above, it is possible to provide projections projecting in the axial direction of the rotor portion on top and bottom faces of the end of the extension portion. With this configuration, it is possible to increase the second viscous torque at the end of the extension portion, so that the fin portion elastically deforms easily. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0025]    [0025]FIG. 1 is an exploded perspective view showing a configuration of a damper according to the first embodiment of the present invention;  
         [0026]    [0026]FIG. 2 is a sectional view showing the damper according to the first embodiment of the present invention;  
         [0027]    [0027]FIG. 3 is a plan view showing the damper according to the first embodiment of the present invention;  
         [0028]    [0028]FIG. 4 is an operational view showing a state where fin portion in the damper of the first embodiment of the present invention deforms elastically;  
         [0029]    [0029]FIG. 5 is an operational view showing a state where fin portion in the damper of the second embodiment of the present invention deforms elastically;  
         [0030]    [0030]FIG. 6 is an operational view showing a state where the fin portion in the damper of the second embodiment of the present invention deforms elastically;  
         [0031]    [0031]FIG. 7 is an explanatory view of a modified example of a fin portion of the invention; and  
         [0032]    [0032]FIG. 8 is an exploded perspective view showing a configuration of a conventional damper. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0033]    Hereunder, embodiments of the present invention will be explained with reference to the accompanying drawings. As shown in FIGS. 1 and 2, a pair of fixed pieces  12  extends from an outer peripheral wall of a housing  10  having a substantially cylindrical shape with a bottom. The fixed pieces  12  have backsides flash with a backside of the housing  10 . A small diameter stage  14  and a large diameter stage  16  are coaxially formed at an axial part of the housing  10 , and the small diameter stage  14  is located on a top surface of the large diameter stage  16 .  
         [0034]    A fixed shaft  18  having a cylindrical shape projects at a central part of the small diameter stage  14 . The fixed shaft  18  is arranged to support a rotor portion  20  to be stored inside the housing  10 . The rotor portion  20  is formed of a shaft  22  and fin portions  24 . An engagement depression  22 A is formed at one end side of the shaft  22 , and the engagement depression  22 A has an inside diameter slightly larger than an outside diameter of the fixed shaft  18 . The engagement depression  22 A engages the fixed shaft  18 , so that the rotor portion  20  rotates relative to the housing  10 .  
         [0035]    A pedestal or base  26  having a ring shape is formed in the shaft  22 , and projects from an outer peripheral face at an end of the shaft  22 . A plurality of fin portions  24  projects radially from an outer peripheral face of the pedestal  26 . The fin portion  24  has a thickness thinner than that of the pedestal  26 , and has a backside flash with that of the pedestal  26 .  
         [0036]    The housing  10  is filled with viscous fluid, and a cover member  28  having a substantially cylindrical shape closes the housing  10 . The cover member  28  has an inside diameter of an inner peripheral surface same as an outside diameter of an outer peripheral surface of the housing  10 . The cover member  28  is welded and fixed to the housing  10  by ultrasonic welding.  
         [0037]    A through-hole  30  is formed at an axis part of the cover member  28  for receiving the other end side of the shaft  22 . A seal ring  32  is fitted in the outer peripheral face of the shaft  22  for sealing the housing  10  to prevent the viscous fluid inside the housing  10  from leaking.  
         [0038]    A large diameter stage  34  and a small diameter stage  36  having ring shapes project from the backside of the cover member  28 , and the small diameter stage  36  is located on the large diameter stage  34 . A space is provided between an outer peripheral surface of the large diameter stage  34  and an inner peripheral surface  10 A of the housing  10 . When the viscous fluid filled inside the housing  10  is expanded due to a temperature change, the space can absorb an excess volume.  
         [0039]    As shown in FIG. 3, the fin portion  24  is disposed horizontally parallel to a bottom face of the housing  10 . A narrowed portion  38  having a narrow width is formed at a base side of the fin portion  24 . As shown in FIGS. 2 and 3, a projection  40  is provided at an end of the fin portion  24 , and projects from top and bottom surfaces of the fin portion  24  in an axial direction of the shaft  22 . An arc face  24 A is formed at the end of the fin portion  24 , and faces an inner peripheral surface  10 A of the housing  10 .  
         [0040]    When the arc face  24 A is located at a position closest to the inner peripheral surface  10 A of the housing  10 , there is an approximately 0.05 mm clearance between the arc face  24 A and the inner peripheral surface  10 A of the housing  10 .  
         [0041]    The arc face  24 A has a curvature radius smaller than an inside diameter of the inner peripheral surface  10 A of the housing  10 , and the curvature radius of the arc faces  24 A gradually decreases toward outside from the center of the fin portion  24 .  
         [0042]    The pedestal  26  is placed on the small diameter stage  14 . The pedestal  26  has an outside diameter roughly the same as that of the small diameter stage  14 . A space is provided between the large diameter stage  16  and the fin portion  24 . A projection  40 B of the fin portion  24  is placed in a groove portion  35  composed of an outer peripheral surface of the large diameter stage  16  and the inner peripheral surface of the housing  10 , and there is a space between the projection  40 B and the bottom face of the groove portion  35 .  
         [0043]    The small diameter stage  36  projecting from the backside of the cover member  28  is located at a position facing the large diameter stage  16  of the housing  10  in a state that the housing  10  is closed. Also, the large diameter stage  16  is located at a position facing the groove portion  35  of the housing  10 .  
         [0044]    A space is provided between a top surface of the fin portion  24  and the small diameter stage  36  of the cover member  28 . This space is roughly the same as a space between a back surface of the fin portion  24  and the large diameter stage  16  of the housing  10 . Also, a space is provided between the projection  40 A of the fin portion  24  and the large diameter stage  34  of the cover member  28 , and this space is roughly the same as the space between the projection  40 B of the fin portion  24  and the groove portion  35  of the housing  10 . With this configuration, the fin portions  24  receive the viscous torque balanced in the vertical direction, so that the fin portions  24  do not vibrate when moving in the viscous fluid.  
         [0045]    A distance between the small diameter stage  36  of the cover member  28  and the large diameter stage  16  of the housing  10  is smaller than a distance between the large diameter stage  34  of the cover member  28  and the groove portion  35  of the housing  10 . Thus, the viscous fluid flows easily at a side of the projections  40  of the fin portions  24 .  
         [0046]    In the damper  42  having the above configuration, the fixed pieces  12  are fixed to, for example, a main member of a glove box (not shown), to attach the damper  42  to the main member of the glove box. In this state, a pinion (not shown) is attached to the other end (a portion exposed from the cover member  28 ) of the shaft  22 , and a gear is attached to a cover portion of the glove box for engaging the pinion. When the cover portion is moved, the movement is transmitted to the pinion through the gear to rotate the shaft  22 . At this time, the fin portions  24  stir the viscous fluid, thereby generating the viscous torque at the projections  40  of the fin portions  24 , and applying the braking force on the shaft  22  through the fin portions  24 . Accordingly, the braking force is applied on the cover portion through the pinion and the gear, so that the cover portion opens slowly.  
         [0047]    Next, a damper effect of the present embodiment will be explained. As shown in FIGS. 3 and 4, the narrowed portion  38  with a narrow width is formed at the base side of fin portion  24 , so that the fin portion  24  elastically deforms easily according to resistance received from the viscous fluid. Also, it is possible to change the clearance between the arc face  24 A of the fin portion  24  and the inner peripheral surface  10 A of the housing  10  (hereinafter referred to as simply clearance) when the arc face  24 A of the fin portion  24  is located at a position closest to the inner peripheral surface  10 A of the housing  10 .  
         [0048]    The viscous fluid has a viscosity in winter higher than in summer, so that the viscous torque due to the viscosity of the viscous fluid (hereinafter referred to as “second viscous torque”) at the projections  40  of the fin portions  24  is increased in winter, and the fin portions  24  elastically deform in a larger extent.  
         [0049]    In other words, when the viscosity is increased, the second viscous torque at the projections  40  of the fin portions  24  is increased. At the same time, the fin portions  24  elastically deform in a larger extent to increase the clearance between the arc face  24 A of the fin portion  24  and the inner peripheral surface  10 A of the housing, thereby decreasing the viscous torque due to viscous flow of the viscous fluid (hereinafter referred to as “first viscous torque”) at the projections  40  of the fin portions  24 . Therefore, the increment in the second viscous torque is offset by the decline in the first viscous torque.  
         [0050]    When the viscosity becomes lower in a high temperature such as in summer, the second viscous torque at the projections  40  of the fin portions  24  is decreased as compared to the condition in winter, so that the fin portions  24  elastically deform in a smaller extent. Therefore, the clearance between the arc face  24 A of the fin portion  24  and the inner peripheral surface  10 A of the housing  10  is decreased to increase the first viscous torque.  
         [0051]    In other words, when the viscosity becomes lower, the decline in the viscous torque part due to the decline in the viscosity is offset by the increment in the first viscous torque at the projections  40  of the fin portions  24  due to the increment in the clearance between the arc face  24 A of the fin portion  24  and the inner peripheral surface  10 A of the housing  10 .  
         [0052]    Accordingly, the clearance between the arc face  24 A of the fin portion  24  and the inner peripheral surface  10 A of the housing  10  is adjustable according to the resistance received from the viscous fluid depending on the viscosity. Therefore, the damper  42  has a low temperature dependency.  
         [0053]    The arc face  24 A of the fin portion  24  has the curvature radius smaller than the inside diameter of the inner peripheral surface  10 A of the housing  10 , and the curvature radius of the arc face  24 A is gradually decreased toward outside from the center of the projection  40  of the fin portion  24 . With this configuration, when the fin portion  24  elastically deforms, the arc face  24 A of the fin portion  24  does not abut against the inner peripheral surface  10 A of the housing  10 . Also, it is possible to increase the clearance between the arc face  24 A of the fin portion  24  and the inner peripheral surface  10 A of the housing  10  according to the elastic deformation of the fin portion  24 .  
         [0054]    Furthermore, the projection  40  projecting in the axial direction of the rotor portion  20  is formed on the top and bottom faces at the end of the fin portion  24 . Thus, the viscous torque at the end of the fin portion  24  is increased, and the fin portion  24  elastically deforms easily.  
         [0055]    Next, a damper according to the second embodiment of the present invention will be explained. The explanation regarding components same as those in the first embodiment is omitted.  
         [0056]    As shown in FIG. 5, a clearance between an end portion  45  of a plate-like fin portion  44  and an inner peripheral surface  10 A of the housing  10  is increased. Also, an extension portion  46  is formed at a left side of a centerline P of the fin portion  44  in the figure, and projects from the end portion  45  of the fin portion  44 .  
         [0057]    In the extension portion  46 , an arc face  44 A is formed to face the inner peripheral surface  10 A of the housing  10 . The arc face  44 A of the extension portion  46  is formed in an arc shape to have a center same as a rotational center when the fin portion  44  elastically deforms. There is an approximately 0.05 mm clearance between the arc face  44 A and the inner peripheral surface  10 A of the housing  10  when the arc face is located at a position closest to the inner peripheral surface (hereinafter referred to as “closest position”).  
         [0058]    The extension portion  46  has corners having a small curvature radius. One of the corners located at a side of the centerline P of the fin portion  44  has a curvature radius smaller than that of the other of the corners, thereby minimizing the effect of the viscous torque at the extension portion  46  when rotation begins.  
         [0059]    The closest position is located at a side of the centerline P of the fin portion  44 . Accordingly, when the shaft  22  rotates in the arrow A direction and the fin portion  44  deforms in the arrow B direction by the resistance of the viscous fluid, the closest position of the arc face  44 A moves in a direction away from the centerline P of the fin portion  44  before elastically deforms. Thus, the clearance between the arc face  44 A of the extension portion  46  and the inner peripheral surface  10 A of the housing  10  is gradually increased in proportion to the elastic deformation of the fin portion  44  to decrease the second viscous torque at the extension portion  46 .  
         [0060]    As shown in FIG. 6, when the shaft  22  is rotated in the arrow C direction (opposite to the arrow A direction), and the fin portion  44  deforms in the arrow D direction, the closest position of the arc face  44 A passes the centerline P of the fin portion  44  before elastically deforms.  
         [0061]    The fin portion  44  elastically deforms around the centerline P of the fin portion  44 . Therefore, as long as the fin portion  44  elastically deforms (the fin portion  44  deforms by approximately 15 degrees in the drawing) within a range of an arc L of the arc face  44 A of the extension portion  46  (a distance between the corners of the arc face  44 A), the clearance between the inner peripheral surface  10 A of the housing  10  is maintained at approximately 0.05 mm.  
         [0062]    With the above-mentioned configuration, when the shaft  22  is rotated in the arrow C direction, the clearance between the arc face  44 A of the extension portion  46  and the inner peripheral surface  10 A of the housing  10  is maintained even if the fin portion  44  elastically deforms, thereby obtaining a predetermined braking force. When the shaft  22  is rotated in the direction opposite to the arrow C direction, the clearance between the arc face  44 A of the extension portion  46  and the inner peripheral surface  10 A of the housing  10  is increased due to the elastic deformation of the fin portion  44 , thereby minimizing the braking force. Thus, the damper performs as a so-called one-way damper.  
         [0063]    The damper of the present invention is not limited to the glove box, and can be used for a covering member of an AV instrument, or for a braking member moving horizontally such as an ashtray or cup holder placed inside a vehicle. At this time, a rack engaging a pinion is disposed in the ashtray or cup holder. The damper can be attached to the braking member as well.  
         [0064]    In the embodiments, the fin portions are disposed in a horizontal position relative to the bottom face of the housing. Alternatively, the fin portions can be disposed in a vertical position relative to the bottom face of the housing, or in a declined position relative to the bottom face of the housing. The projection is provided at the end of the fin portion, but it is not necessary to provide the projection.  
         [0065]    It is possible to form the shaft and fin portions as a unit, thereby reducing the steps for attaching the fin portions to the shaft and a cost. Alternatively, the narrowed portion is formed of a leaf spring  38 ′ as shown in FIG. 7, and the fin portion  24 ′ is connected to the shaft through the leaf spring  38 ′. In this case, the leaf spring can be formed as a unit with the shaft and fin portions by insert molding. With the insert molding, it is not necessary to attach the leaf spring and fin portions to the shaft, thereby reducing the manufacturing steps and the cost.  
         [0066]    The clearance between the arc face of the fin portion and the inner peripheral surface of the housing is arranged to be 0.05 mm in the state where the fin portion does not elastically deform. The clearance can be modified according to the viscosity of the viscous fluid, or the shape of the fin portions.  
         [0067]    In the present invention having the configuration mentioned above, the changes in the viscous torque are offset as the clearance between the end of the fin portion and the inner peripheral surface of the housing is adjusted according to the resistance received from the viscous fluid depending on the viscosity, so that the damper has a low temperature dependency.  
         [0068]    In the present invention, the fin portion elastically deforms easily. It is not necessary to attach the leaf spring and fin portions to the rotor portion, thereby reducing the manpower and the cost.  
         [0069]    When the fin portion elastically deforms, it is arranged that the end of the fin portion does not abut against the inner peripheral surface of the housing. Further, it is possible to increase the clearance between the end of the fin portion and the inner peripheral surface of the housing according to the elastic deformation of the fin portion. Also, it is possible to increase the viscous torque at the end of the fin portion.  
         [0070]    In the damper of the invention, it is possible to generate the braking force in one direction by decreasing the clearance, and to minimize the braking force in the other direction by increasing the clearance.  
         [0071]    While the invention has been explained with reference to the specific embodiments of the invention, the explanation is illustrative and the invention is limited only by the appended claims.