Abstract:
To avoid strict control of flatness of a pressing portion, while keeping stability, in a sealing device comprising a metal ring and a seal portion, a metal ring ( 2 ) has an annular pressing portion ( 5 ) provided with a predetermined width in a diametrical direction for pressing an opponent member ( 11 ) when the metal ring ( 2 ) shifts in the axial direction, pressing surface ( 7 ) of the pressing portion ( 5 ) is formed in a circular arc or wavy sectional shape protruding toward the opponent member ( 11 ), the pressing portion ( 5 ) is constituted by an outward flange portion ( 6 ) integrally formed at an end of a tubular portion ( 4 ) of the metal ring ( 2 ), and the flange portion ( 6 ) has a smaller thickness than the tubular portion ( 4 ) and is formed in a circular arc or wavy sectional shape so as to have a spring characteristic.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This is a national stage of the International Application No. PCT/JP2006/320697 filed on Oct. 18, 2006 and published in Japanese language. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a sealing device in accordance with a sealing technique, and more particularly to a sealing device which is suitably used as a bonded piston seal (BPS) in an automatic transmission (AT, CVT or the like) of a vehicle, for example, a motor vehicle. 
         [0004]    2. Description of the Conventional Art 
         [0005]    Conventionally, a bonded piston seal  51  shown in  FIG. 6  has been known as one kind of a sealing device. The bonded piston seal  51  has a metal ring  52 , and a seal portion  53  such as a packing or the like supported to the metal ring  52 , and is structured such as to engage a clutch by pressing a clutch plate  55  having a multilayer structure by the metal ring  52  of the bonded piston seal  51  displacing in an axial direction (a vertical direction in the drawing) on the basis of a pressure feed from a port  54  (refer to Japanese Unexamined Patent Publication No. 2001-132849). 
         [0006]    The metal ring  52  has an outward flange portion  52   b  integrally formed at an end of a tubular portion  52   a , and an annular pressing portion for pressing the annular clutch plate  55  is formed by the flange portion  52   b.    
         [0007]    However, since the flange portion  52   b  constructing the pressing portion has been conventionally formed in a flat plate shape which is perpendicular to a center axis O of the bonded piston seal  51 , the following disadvantage is generated. 
         [0008]    The flange portion  52   b  formed in an axially perpendicular flat plate shape is expected to be precisely worked so as to be widely in surface contact with the clutch plate  55  at a predetermined diametrical contact width w, as shown in  FIG. 7A , however, there is a case that it is actually formed with an angle θ as shown in  FIG. 7B  or  7 C due to a problem of work in a manufacturing process of the metal ring  52 . Therefore, there is a case that a contact position with respect to the clutch plate  55  is largely varied in a diametrical direction. If a downward taper is formed at the flange portion  52   b  such as in  FIG. 7B , the contact position with respect to the clutch plate  55  exists only at an outer peripheral edge portion of the expected contact width w, and if an upward taper is formed at the flange portion  52   b  such as in  FIG. 7C  on the contrary, the contact position with respect to the clutch plate  55  exists only at an inner peripheral edge portion of the expected contact width w. Accordingly, the contact position is extremely biased in any event. Therefore, a rattle due to an inclination or a biased abrasion is generated in the clutch plate  55  caused by the bias, so that a shift shock at a time of engaging the clutch becomes large, or a foreign sound is generated at a time of engaging the clutch. Since a countermeasure has been conventionally made by severely controlling a flatness of the flange portion  52   b  for preventing them, it has taken a lot of labor and time to manufacture the metal ring  52 , and a parts cost has become high. 
         [0009]    Further, there is a case that an undulation in a circumferential direction is formed in addition to the angle θ mentioned above, at the flange portion  52   b  formed in the axially perpendicular flat plate shape. In this case, since a pressure distribution in a circumferential direction becomes uneven with respect to the clutch plate  55 , there is also a risk that the rattle caused by the inclination or the biased abrasion is generated at the clutch plate  55 . 
         [0010]    Further, there has been developed a technique that a countermeasure is achieved by interposing a leaf spring member between the flange portion and the clutch plate. However, in this case, since a parts number and an assembling man hour are increased by interposing the leaf spring member, there is a disadvantage that a parts cost and a manufacturing cost are increased (refer to Japanese Patent No. 3515634). 
       SUMMARY OF THE INVENTION 
     Problem to be Solved by the Invention 
       [0011]    The present invention is made by taking the points mentioned above into consideration, and an object of the present invention is to provide a sealing device in which a contact position in a diametrical direction with respect to an opponent member can be stabilized and a pressure distribution in a circumferential direction with respect to the opponent member can be stabilized, without severely controlling a flatness of a pressing portion or a flange portion of a metal ring. 
       Means for Solving the Problem 
       [0012]    In order to achieve the object mentioned above, in accordance with a first aspect of the present invention, there is provided a sealing device comprising: 
         [0013]    a metal ring; and 
         [0014]    a seal portion such as a packing or the like supported to the metal ring; 
         [0015]    the metal ring having an annular pressing portion provided with a predetermined width in a diametrical direction for pressing an opponent member at a time when the metal ring is displaced in an axial direction, 
         [0016]    wherein a pressing surface of the pressing portion is formed in a circular arc cross sectional shape or a wave cross sectional shape protruding toward the opponent member. 
         [0017]    Further, in accordance with a second aspect of the present invention, there is provided a sealing device comprising: 
         [0018]    a metal ring; and 
         [0019]    a seal portion such as a packing or the like supported to the metal ring; 
         [0020]    the metal ring having an annular pressing portion provided with a predetermined width in a diametrical direction for pressing an opponent member at a time when the metal ring is displaced in an axial direction, 
         [0021]    wherein the pressing portion is constituted by an outward flange portion integrally formed at an end of a tubular portion of the metal ring, and the flange portion is formed in a circular arc cross sectional shape or a wave cross sectional shape as a whole. 
         [0022]    Further, in accordance with a third aspect of the present invention, there is provided a sealing device comprising: 
         [0023]    a metal ring; and 
         [0024]    a seal portion such as a packing or the like supported to the metal ring; 
         [0025]    the metal ring having an annular pressing portion provided with a predetermined width in a diametrical direction for pressing an opponent member at a time when the metal ring is displaced in an axial direction, 
         [0026]    wherein the pressing portion is constituted by an outward flange portion integrally formed at an end of a tubular portion of the metal ring, and the flange portion has a smaller thickness than the tubular portion and is formed in a circular arc cross sectional shape or a wave cross sectional shape so as to have a spring characteristic. 
         [0027]    Further, in accordance with a fourth aspect of the present invention, there is provided a sealing device as recited in any one of the first to third aspects, wherein the sealing device is constituted by a bonded piston seal used in an automatic transmission, and the opponent member is constituted by a clutch plate pressed by the metal ring of the bonded piston seal. 
         [0028]    In the sealing device in accordance with the first aspect of the present invention provided with the structure mentioned above, since the pressing surface of the pressing portion in the metal ring is not formed in the axially perpendicular flat surface shape, but is formed in the circular arc cross sectional shape or the wave (wavy line) cross sectional shape protruding toward the opponent member (the protruding shape toward the opponent member), there is no flat surface to be controlled in flatness. Accordingly, it is not necessary to control the flatness. The circular arc cross sectional shape corresponds to a shape having one circular arc cross section and being in line contact at one position in the diametrical direction, and the wave cross sectional shape corresponds to a shape having a plurality of circular arc cross sections and being in line contact at a plurality of positions in the diametrical direction. In any event, there is an advantage that the contact position with the opponent member is not changed so much in the diametrical direction, even if somewhat of shape error is generated in the circular arc cross section. Since the pressing portion is formed in the circular arc cross sectional shape or the wave cross sectional shape, an undulation in a circumferential direction is hardly generated. 
         [0029]    Further, in the sealing device in accordance with the second aspect of the present invention, since the flange portion of the metal ring serving as the pressing portion is not formed in the axially perpendicular flat surface shape, but is formed in the circular arc cross sectional shape or the wave cross sectional shape as a whole, it is unnecessary to control the flatness similarly to the invention in accordance with the first aspect. The circular arc cross sectional shape corresponds to a shape having one circular arc cross section and being in line contact at one position in the diametrical direction, and the wave cross sectional shape corresponds to a shape having a plurality of circular arc cross sections and being in line contact at a plurality of positions in the diametrical direction. In any event, there is an advantage that the contact position with the opponent member is not changed so much in the diametrical direction even if somewhat of shape error is generated in the circular arc cross section. Since the flange portion is formed in the circular arc cross sectional shape or the wave cross sectional shape so as to have a three-dimensional surface, an undulation in a circumferential direction is hardly generated. 
         [0030]    Further, in the sealing device in accordance with the third aspect of the present invention, since the flange portion of the metal ring serving as the pressing portion is not formed in the axially perpendicular flat surface shape, but is formed in the circular arc cross sectional shape or the wave cross sectional shape in addition to being thinned as a whole, it is unnecessary to control the flatness similarly to the invention in accordance with the first aspect. The circular arc cross sectional shape corresponds to a shape having one circular arc cross section and being in line contact at one position in the diametrical direction, and the wave cross sectional shape corresponds to a shape having a plurality of circular arc cross sections and being in line contact at a plurality of positions in the diametrical direction. In any event, there is an advantage that the contact position with the opponent member is not changed so much in the diametrical direction even if somewhat of shape error is generated in the circular arc cross section. Since the flange portion is formed in the circular arc cross sectional shape or the wave cross sectional shape so as to have a three-dimensional surface, an undulation in a circumferential direction is hardly generated. Further, since the flange portion is elastically deformed on the basis of the spring characteristic caused by the thinning, the flange portion can come into close contact with the opponent member over an entire periphery. 
       EFFECT OF THE INVENTION 
       [0031]    The present invention achieves the following effects. 
         [0032]    In the sealing device in accordance with the first aspect of the present invention, since the pressing surface of the pressing portion in the metal ring is formed in the circular arc cross sectional shape or the wave cross sectional shape protruding toward the opponent member, it is not necessary to control the flatness. Accordingly, it is possible to omit the work and the cost incurred for controlling the flat surface. Further, since the contact position with the opponent member is not changed so much in the diametrical direction on the basis of the cross sectional shape even if somewhat of shape error is generated, it is possible to stabilize the contact position in the diametrical direction with respect to the opponent member. Further, since the undulation in the circumferential direction is hardly generated on the basis of the cross sectional shape, it is possible to stabilize the pressure distribution in the circumferential direction with respect to the opponent member. 
         [0033]    Further, in the sealing device in accordance with the second aspect of the present invention, since the flange portion in the metal ring is formed in the circular arc cross sectional shape or the wave cross sectional shape as a whole, it is not necessary to control the flatness. Accordingly, it is possible to omit the work and the cost incurred for controlling the flat surface. Further, since the contact position with the opponent member is not changed so much in the diametrical direction on the basis of the cross sectional shape even if somewhat of shape error is generated, it is possible to stabilize the contact position in the diametrical direction with respect to the opponent member. Further, since the undulation in the circumferential direction is hardly generated on the basis of the cross sectional shape, it is possible to stabilize the pressure distribution in the circumferential direction with respect to the opponent member. 
         [0034]    Further, in the sealing device in accordance with the third aspect of the present invention, since the flange portion in the metal ring is formed in the circular arc cross sectional shape or the wave cross sectional shape in addition to being thinned as a whole, it is not necessary to control the flatness. Accordingly, it is possible to omit the work and the cost incurred for controlling the flat surface. Further, since the contact position with the opponent member is not changed so much in the diametrical direction on the basis of the cross sectional shape even if somewhat of shape error is generated, it is possible to stabilize the contact position in the diametrical direction with respect to the opponent member. Further, since the undulation in the circumferential direction is hardly generated on the basis of the cross sectional shape, it is possible to stabilize the pressure distribution in the circumferential direction with respect to the opponent member. Furthermore, since the flange portion is elastically deformed on the basis of the spring characteristic caused by the thinning at a time of being actuated, the flange portion can come into close contact with the opponent member over the entire periphery. Accordingly, it is possible to stabilize the pressure distribution in the circumferential direction also on the basis of this function. 
         [0035]    Further, in the sealing device in accordance with the fourth aspect of the present invention, the operations and effects obtained by the first to third aspects mentioned above can be applied to the bonded piston seal used in the automatic transmission. 
     
    
     
       BRIEF EXPLANATION OF DRAWINGS 
         [0036]      FIG. 1  is a cross sectional view of a bonded piston seal in accordance with a first embodiment of the present invention; 
           [0037]      FIG. 2A  is an enlarged view of a main portion in  FIG. 1 ; 
           [0038]      FIG. 2B  is an enlarged view of a portion B in  FIG. 2A ; 
           [0039]      FIG. 3  is a cross sectional view of a main portion of a bonded piston seal in accordance with a second embodiment of the present invention; 
           [0040]      FIG. 4  is a cross sectional view of a main portion of a bonded piston seal in accordance with a third embodiment of the present invention; 
           [0041]      FIG. 5  is a cross sectional view of a main portion of a bonded piston seal in accordance with a fourth embodiment of the present invention; 
           [0042]      FIG. 6  is a cross sectional view of a bonded piston seal in accordance with a prior art; 
           [0043]      FIG. 7A  is an enlarged cross sectional view of a main portion of the bonded piston seal; and 
           [0044]      FIGS. 7B and 7C  are cross sectional views showing problem generating states. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0045]    The following modes are included in the present invention. 
         [0046]    (1) A contact position in a circumferential direction with a clutch plate is stabilized by forming an outer peripheral flange portion of the BPS in a circular arc shape curved with respect to the clutch plate. This structure can be applied to an aluminum piston which is processed by a cutting work. 
         [0047]    (2) Uniformization of a pressure distribution of the clutch plate is achieved by forming the outer peripheral flange portion of the BPS in a circular arc shape or a wave shape in addition to thinning so as to provide a spring characteristic. 
         [0048]    (3) In accordance with the mode (1) or (2) mentioned above, since the outer peripheral flange portion of the BPS is not formed in a straight shape, it is unnecessary to control flatness. Further, a cost can be reduced by reducing a parts number and improving an assembling workability, in comparison with a case that the leaf spring is independently interposed. 
       EMBODIMENT 
       [0049]    Next, a description will be given of embodiments in accordance with the present invention with reference to the accompanying drawings. 
       First Embodiment 
       [0050]      FIG. 1  shows a cross section of a bonded piston seal  1  serving as a sealing device in accordance with a first embodiment of the present invention.  FIG. 2  shows a main portion thereof in an enlarged manner. 
         [0051]    As shown in  FIG. 1 , the bonded piston seal  1  in accordance with the embodiment is embedded in an inner portion of a cylinder of an AT housing  14  together with a clutch plate  11 , a return spring  12 , a cancel seal  13  and the like. When a hydraulic pressure is introduced into a pressure chamber  15  from a pressure port (not shown), the bonded piston seal  1  is displaced downward against an elasticity of the return spring  12  so as to press an annular clutch plate  11  having a multi-disc (multilayer) clutch structure, and engages a clutch. Further, when the hydraulic pressure is drained, the bonded piston seal  1  is returned upward on the basis of an elasticity of the return spring  12 . Accordingly, on the basis of this reciprocating function, the bonded piston seal  1  may be called as a piston for an automatic transmission. 
         [0052]    The bonded piston seal  1  in accordance with the embodiment first has a metal ring  2  formed by press molding of a sheet metal (a steel plate), and a seal portion  3  constituted by a packing (a seal lip) made of a rubber-like elastic material is attached (baking bonded) to each of an outer peripheral portion and an inner peripheral portion of the metal ring  2 . The seal portion  3  slidably comes into close contact with an inner surface of the housing  14  so as to seal the hydraulic pressure mentioned above or the like. 
         [0053]    An outer periphery of the metal ring  2  is integrally provided with an outward flange portion  6  which is positioned at an end of a tubular portion  4  and serves as a pressing portion  5  with respect to the clutch plate  11 . If the pressing portion  5  or the flange portion  6  is formed in a flat plate shape which is perpendicular to a center axis O of the bonded piston seal  1 , a severe flatness control is necessary as mentioned above. 
         [0054]    Accordingly, in the embodiment, as shown in  FIG. 2  in an enlarged manner, the pressing portion  5  or the flange portion  6  is formed in a circular arc cross sectional shape having one circular arc cross section protruding toward the clutch plate  11  over a whole thickness, and a pressing surface  7  of the pressing portion  5  or the flange portion  6  is formed in a circular arc cross sectional shape having one circular arc cross section protruding toward the clutch plate  11  in the same manner. Therefore, the pressing surface  7  of the pressing portion  5  or the flange portion  6  having a curved surface corresponding to one circular arc cross section comes into contact with the clutch plate  11  in a line contact state at a contact point P which is one position at a middle portion of a width in a diametrical direction of the pressing portion  5  or the flange portion  6 , and presses the clutch plate  11 . 
         [0055]    Since the pressing portion  5  or the flange portion  6  formed in the circular arc cross sectional shape as mentioned above is not formed in a flat surface shape, it is not necessary to control the flatness. Accordingly, it is possible to omit the work and the cost incurred for controlling the flatness. 
         [0056]    Further, on the basis of the cross sectional shape of the pressing portion  5  or the flange portion  6 , the contact position thereof with respect to the clutch plate  11  is not changed so much in the diametrical direction, even if somewhat of shape error is generated. Accordingly, it is possible to stabilize the contact position in the diametrical direction with respect to the clutch plate  11 . 
         [0057]    Further, on the basis of the cross sectional shape of the pressing portion  5  or the flange portion  6 , an undulation thereof in a circumferential direction is hardly generated. Accordingly, it is possible to stabilize a pressure distribution in the circumferential direction with respect to the clutch plate  11 . 
       Second Embodiment 
       [0058]    In a bonded piston seal in accordance with a second embodiment shown in  FIG. 3 , the pressing portion  5  or the flange portion  6  is formed in a wavy cross sectional shape having two circular arc cross sections protruding toward the clutch plate  11  over an entire thickness, and the pressing surface  7  of the pressing portion  5  or the flange portion  6  is formed in a wavy cross sectional shape having two circular arc cross sections protruding toward the clutch plate  11  in the same manner. Accordingly, the pressing surface  7  of the pressing portion  5  or the flange portion  6  having the curved surface corresponding to two circular arc cross sections comes into contact with the clutch plate  11  in the line contact state, at each of two contact points P 1  and P 2  close to an inner periphery and an outer periphery of the width in the diametrical direction of the pressing portion  5  or the flange portion  6 , and presses the clutch plate  11 . 
         [0059]    In accordance with this embodiment, there is obtained an advantage that a clutch surface pressure can be optimally controlled by changing a share ratio of two contact points P 1  and P 2 , in addition to the operations and effects described in the first embodiment mentioned above. 
       Third Embodiment 
       [0060]    In a bonded piston seal in accordance with a third embodiment shown in  FIG. 4 , the pressing portion  5  or the flange portion  6  is structured such that a thickness t 1  thereof is thinner than a thickness t 2  of the tubular portion  4 , and is formed in a circular arc cross sectional shape having one circular arc cross section protruding toward the clutch plate  11  over an entire thickness so as to have a spring characteristic in an axial direction, and the pressing surface  7  of the pressing portion  5  or the flange portion  6  is formed in the circular arc cross sectional shape having one circular arc cross section protruding toward the clutch plate  11  in the same manner. Accordingly, the pressing surface  7  of the pressing portion  5  or the flange portion  6  having the curved surface corresponding to one circular arc cross section comes into contact with the clutch plate  11  in a line contact state at one contact point P which is one position at a middle portion of the width in the diametrical direction of the pressing portion  5  or the flange portion  6 , and presses the clutch plate  11 . 
         [0061]    In accordance with the third embodiment, in addition to the operations and the effects described in the first embodiment mentioned above, since the pressing portion  5  or the flange portion  6  is elastically deformed at a time of being actuated on the basis of the spring characteristic in the axial direction, the pressing portion  5  or the flange portion  6  comes into close contact with the clutch plate  11  over an entire periphery. Accordingly, there is obtained an advantage that it is possible to stabilize the pressure distribution in the circumferential direction also by this function. Further, it is possible to expect a buffering effect and a rattle preventing effect by the spring characteristic. 
       Fourth Embodiment 
       [0062]    In a bonded piston seal in accordance with a fourth embodiment shown in  FIG. 5 , the pressing portion  5  or the flange portion  6  is structured such that the thickness t 1  thereof is thinner than the thickness t 2  of the tubular portion  4 , and is formed in a wavy cross sectional shape having two circular arc cross sections protruding toward the clutch plate  11  over an entire thickness so as to have a spring characteristic in an axial direction, and the pressing surface  7  of the pressing portion  5  or the flange portion  6  is formed in the wavy cross sectional shape having two circular arc cross sections protruding toward the clutch plate  11  in the same manner. Accordingly, the pressing surface  7  of the pressing portion  5  or the flange portion  6  having the curved surface corresponding to two circular arc cross sections comes into contact with the clutch plate  11  in a line contact state at each of contact points P 1  and P 2  which are two positions close to an inner periphery and an outer periphery of the width in the diametrical direction of the pressing portion  5  or the flange portion  6 , and presses the clutch plate  11 . 
         [0063]    In accordance with the fourth embodiment, in addition to the operations and the effects described in the first embodiment mentioned above, since there is an advantage that the clutch surface pressure can be optimally controlled by changing a share ratio of the contact points P 1  and P 2  at two positions. Further, since the pressing portion  5  or the flange portion  6  is elastically deformed at a time of being actuated on the basis of the spring characteristic in the axial direction, the pressing portion  5  or the flange portion  6  comes into close contact with the clutch plate  11  over an entire periphery. Accordingly, there is obtained an advantage that it is possible to stabilize the pressure distribution in the circumferential direction also by this function. Further, it is possible to expect a buffering effect and a rattle preventing effect by the spring characteristic.