Patent Publication Number: US-2021172526-A1

Title: Seal ring

Description:
TECHNICAL FIELD 
     The disclosure relates to a seal ring used in order to seal a fluid between an inner peripheral member and an outer peripheral member reciprocating relative to each other. 
     BACKGROUND ART 
     Seal rings, such as an O-ring and a D-ring, are used in clutches used in the AT (Automatic Transmission) and the CVT (Continuously Variable Transmission) of automobiles. The seal ring realizes the engagement of the clutch by holding a received pressure. 
       FIG. 5  illustrates an example of a seal ring described in Patent Document 1. A seal ring  100  contains a rubber-like elastic body and the shape of the cross section cut along a plane passing through an axial center O is formed into a flat D-shape (see the left half in  FIG. 5 ). The seal ring  100  is provided with a seal surface  101  forming a circular arc-shaped cross section bulged to the outer diameter side on the outer periphery and has side surfaces  102  on both sides located on the plane orthogonal to the axial center O and a seal inner peripheral surface  103  formed into a cylindrical shape. Such a seal ring  100  is generally referred to as a “D-ring”. 
     As illustrated in  FIG. 6 , the seal ring  100  is interposed between an outer peripheral member  200  and an inner peripheral member  300  of a clutch (the entire of which is not illustrated), for example, and seals a fluid flowing between the outer peripheral member  200  and the inner peripheral member  300 . As an example of the structure therefor, the seal ring  100  is mounted in a mounting groove  302  formed into an annular shape in an outer peripheral surface  301  of the inner peripheral member  300  with a gap and the seal surface  101  is projected to the outer diameter side from the mounting groove  302 . The seal surface  101  closely contacts an inner peripheral surface  201  of the outer peripheral member  200  in a slidable manner. 
     The seal ring  100  is fitted into the mounting groove  302  to seat a seal inner peripheral surface  103  on a groove bottom surface  302   a , and then receives the pressure of a hydraulic oil sealed to the side of a high-pressure space H to thereby bring one of the side surfaces  102  into close contact with an internal surface  302   b  of the mounting groove  302 . The seal surface  101  forms a circular arc-shaped cross section to thereby locally increase the seal surface pressure to the inner peripheral surface  201  of the outer peripheral member  200  to prevent the leakage of the hydraulic oil to a low-pressure space L from the high-pressure space H. 
     PRIOR ART DOCUMENT 
     Patent Documents 
     Patent Document 1: Japanese Unexamined Patent Application Publication No. 2011-163438 
     Patent Document 2: Japanese Unexamined Patent Application Publication No. 11-336908 
     SUMMARY 
     Problem to be Solved 
     In recent years, an improvement of fuel consumption and a reduction in energy loss have been demanded with the shift to a low carbon society as the background. Also in the fields of the AT and the CVT, a request for reducing the sliding resistance when the seal ring slides has increased. 
     As a technique of reducing the sliding resistance of the seal ring, measures of reducing a crushing margin or using a low-hardness rubber material have been taken. However, when a technique of reducing the crushing margin is adopted, the initial sealability has decreased or the seal performance has easily deteriorated by prolonged use. When a technique of using a low-hardness rubber material is adopted, the durability decreases. 
     In this point, Patent Document 2 discloses a seal ring  100  in which two kinds of members different in the hardness are combined (see FIG. 4 of Patent Document 2). The seal ring  100  is configured by an inner peripheral side ring  100   a  seated in a mounting groove  302  of an inner peripheral member  300  and an outer peripheral side ring  100   b  disposed on the outer peripheral surface of the inner peripheral side ring  100   a  to bring a seal surface  101  into contact with an inner peripheral surface  201  of an outer peripheral member  200  as illustrated in  FIG. 7 . The inner peripheral side ring  100   a  is a low hardness portion containing a low hardness rubber material. The outer peripheral side ring  100   b  is a high hardness portion containing a high hardness rubber material. 
     The seal ring  100  in which such two kinds of members different in the hardness are combined can reduce the sliding resistance when the seal ring  100  slides without reducing the crushing margin of the outer peripheral side ring  100   b  having the seal surface  101  and without using the low hardness rubber material for the outer peripheral side ring  100   b.    
     However, as illustrated in  FIG. 8 , in the seal ring  100  described in Patent Document 2, a positional shift may occur between the inner peripheral side ring  100   a  and the outer peripheral side ring  100   b  due to the assembled state or the operation state of a device, the influence of the pressure, or the like. 
     When the inner peripheral side ring  100   a  shifts to the side of a low-pressure space L relative to the outer peripheral side ring  100   b  (see  FIG. 8 ), force in the floating direction (see white arrow) is applied to the outer peripheral side ring  100   b  by the action of the hydraulic pressure (arrows a, b). Then, both the reaction force and the friction of the seal surface  101  to an outer peripheral member  200  increase. 
     On the contrary, when the outer peripheral side ring  100   b  shifts to the side of a low-pressure space L relative to the inner peripheral side ring  100   a  (see  FIG. 9 ), force in the pressing direction (see white arrow) to a groove bottom surface  302   a  is applied to the inner peripheral side ring  100   a  by the action of the hydraulic pressure (arrows a, b). Then, both the reaction force and the friction of the seal surface  101  to the outer peripheral member  200  decrease, so that the seal performance deteriorates. 
     As described above, when the positional shift in the axial direction occurs between the inner peripheral side ring  100   a  and the outer peripheral side ring  100   b , a phenomenon in which the reaction force and the friction of the seal surface  101  to the outer peripheral member  200  are not stabilized occurs, and therefore an improvement has been demanded. 
     It is an object of the disclosure to prevent, in a seal ring in which two kinds of members different in the hardness are combined, a fluctuation in the reaction force and the friction of the seal surface to the mating surface accompanying the positional shift between the two kinds of members. 
     Means for Solving the Problem 
     One aspect of the disclosure is provided with a ring having two members of an inner peripheral side ring which is a rubber-like elastic body closely contacting an inner peripheral member reciprocating relative to an outer peripheral member and an outer peripheral side ring which is a rubber-like elastic body disposed on the outer peripheral surface of the inner peripheral side ring to closely contact the outer peripheral member, a seating surface provided in one of the two members and seated in a mounting groove provided in either one of the inner peripheral member and the outer peripheral member, a seal surface provided in the other one of the two members having hardness higher than that of the one of the two members and closely contacting the other one of the inner peripheral member and the outer peripheral member, and a recess-projection fitting portion provided along the annular direction on the contact surface between the inner peripheral side ring and the outer peripheral side ring to restrict a positional shift in the axial direction between the inner peripheral side ring and the outer peripheral side ring. 
     Another aspect of the disclosure is provided with an inner peripheral side ring which is a rubber-like elastic body closely contacting an inner peripheral member reciprocating relative to an outer peripheral member, an outer peripheral side ring which is a rubber-like elastic body disposed on the outer peripheral surface of the inner peripheral side ring to closely contact the outer peripheral member and having hardness higher than that of the inner peripheral side ring, a seating surface provided in the inner peripheral side ring and seated in a mounting groove provided in the inner peripheral member, a seal surface provided in the outer peripheral side ring and closely contacting the outer peripheral member, and a recess-projection fitting portion provided along the annular direction on the contact surface between the inner peripheral side ring and the outer peripheral side ring to restrict a positional shift in the axial direction between the inner peripheral side ring and the outer peripheral side ring. 
     Effect 
     The disclosure restricts the positional shift in the axial direction between the inner peripheral side ring and the outer peripheral side ring by the recess-projection fitting portion, and therefore can prevent a fluctuation in the reaction force and the friction of the seal surface to the mating surface accompanying the positional shift between the two kinds of members. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a figure illustrating an example of a seal ring of this embodiment, the left half of which is a cross-sectional view cut along the plane passing through an axial center O and the right half of which is a front view of the appearance. 
         FIG. 2  is a half cross-sectional view illustrating the mounting state of a reciprocating seal ring in the cross section cut along the plane passing through the axial center O. 
         FIG. 3  is a graph illustrating experimental results of the reaction force generated on the seal surface of various kinds of seal rings. 
         FIG. 4  is a graph illustrating experimental results of the friction generated on the seal surface of various kinds of seal rings. 
         FIG. 5  is a figure illustrating an example of a conventional seal ring, the left half of which is a cross-sectional view cut along the plane passing through an axial center O and the right half of which is a front view of the appearance. 
         FIG. 6  is a half cross-sectional view illustrating the mounting state of a reciprocating seal ring in the cross section cut along the plane passing through the axial center O. 
         FIG. 7  is a figure illustrating an example of a seal ring in which two kinds of members different in the hardness are combined as an example of the conventional seal ring, the left half of which is a cross-sectional view cut along the plane passing through an axial center O and the right half of which is a front view of the appearance. 
         FIG. 8  is a half cross-sectional view illustrating one aspect in which two kinds of members different in the hardness are shifted in the axial direction as the mounting state of the reciprocating seal ring illustrated in  FIG. 7  in the cross section cut along the plane passing through the axial center O. 
         FIG. 9  is a half cross-sectional view illustrating another aspect in which the two kinds of members different in the hardness are shifted in the axial direction as the mounting state of the reciprocating seal ring illustrated in  FIG. 7  in the cross section cut along the plane passing through the axial center O. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     One embodiment is described based on  FIG. 1  to  FIG. 4 . This embodiment is an example of a seal ring used in clutches used in the AT (Automatic Transmission) and the CVT (Continuously Variable Transmission) of automobiles. 
     As illustrated in  FIG. 1 , a seal ring  10  of this embodiment contains a rubber-like elastic material and the shape of the cross section cut along the plane passing through an axial center O has a flat D-shape (see the left half in  FIG. 1 ). In the seal ring  10 , two kinds of members different in the hardness are combined. One of the two members is an inner peripheral side ring  10   a  and the other one is an outer peripheral side ring  10   b.    
     The inner peripheral side ring  10   a  is an annular member occupying the inner peripheral side of the seal ring  10  and is seated in a mounting groove  32  (see  FIG. 2 ) of an inner peripheral member  30  described later. The outer peripheral side ring  10   b  is an annular member disposed on the outer peripheral surface of the inner peripheral side ring  10   a  and occupying the outer peripheral side of the seal ring  10  and brings a seal surface  11  into close contact with an inner peripheral surface  21  of an outer peripheral member  20  described later. 
     The inner peripheral side ring  10   a  of the two kinds of members is a low hardness portion containing a low hardness rubber material and the outer peripheral side ring  10   b  is a high hardness portion containing a high hardness rubber material. More specifically, the hardness of the side (outer peripheral side ring  10   b ) having the seal surface  11  of the inner peripheral side ring  10   a  and the outer peripheral side ring  10   b  is higher than the hardness of the side (inner peripheral side ring  10   a ) mounted and seated in the mounting groove  32 . 
     Between the inner peripheral side ring  10   a  and the outer peripheral side ring  10   b , a recess-projection fitting portion  12  is provided. The recess-projection fitting portion  12  is formed by a protrusion  12   a  provided along the annular direction in the outer peripheral surface of the inner peripheral side ring  10   a  and a recessed groove  12   b  provided along the annular direction in the inner peripheral surface of the outer peripheral side ring  10   b . Both the protrusion  12   a  and the recessed groove  12   b  are provided in the entire periphery in the circumferential direction of the inner peripheral side ring  10   a  and the outer peripheral side ring  10   b , respectively, and fitted to each other. Therefore, the recess-projection fitting portion  12  restricts a positional shift in the axial direction between the inner peripheral side ring  10   a  and the outer peripheral side ring  10   b.    
     The inner peripheral surface of the inner peripheral side ring  10   a  is a seal inner peripheral surface  13  as a seating surface formed into a cylindrical shape. The seal surface  11  provided in the outer peripheral side ring  10   b  is provided with a circular arc-shaped cross section bulged to the outer diameter side. The inner peripheral side ring  10   a  and the outer peripheral side ring  10   b  have side surfaces  14  on both sides located on the plane orthogonal to the axial center O. A portion formed by the inner peripheral side ring  10   a  of the side surfaces  14  is a side surface  14   a  and a portion formed by the outer peripheral side ring  10   b  thereof is a side surface  14   b.    
     Therefore, the seal ring  10  forms a “D-ring” shape as a whole. 
     As illustrated in  FIG. 2 , the seal ring  10  is interposed between an outer peripheral member  20  and an inner peripheral member  30  of a clutch (the entire of which is not illustrated), for example, to seal a fluid flowing between the outer peripheral member  20  and the inner peripheral member  30 . As an example of the structure therefor, the seal ring  10  is mounted in the mounting groove  32  formed into an annular shape in an outer peripheral surface  31  of the inner peripheral member  30  with a gap and the seal surface  11  is projected to the outer diameter side from the mounting groove  32 . The seal surface  11  closely contacts the inner peripheral surface  21  of the outer peripheral member  20  in a slidable manner. 
     The seal ring  10  is fitted into the mounting groove  32  to seat the seal inner peripheral surface  13  as the seating surface on a groove bottom surface  32   a , and then receives the pressure of a hydraulic oil sealed to the side of a high-pressure space H to thereby bring the side surfaces  14  into close contact with an internal surface  32   b  of the mounting groove  32 . The seal surface  11  forms a circular arc-shaped cross section to thereby locally increase the seal surface pressure to the inner peripheral surface  21  of the outer peripheral member  20  to prevent the leakage of the hydraulic oil to a low-pressure space L from the high-pressure space H. 
     In the seal ring  10  of this embodiment, two kinds of members different in the hardness are combined and the inner peripheral side ring  10   a  on the inner peripheral side is set as the low hardness portion and the outer peripheral side ring  10   b  on the outer peripheral side is set as the high hardness portion. Therefore, the sliding resistance when the seal ring  10  slides can be reduced without reducing the crushing margin of the outer peripheral side ring  10   b  having the seal surface  11  and without using a low hardness rubber material for the outer peripheral side ring  10   b.    
     As described above based on  FIG. 8  and  FIG. 9 , in a seal ring in which two kinds of members different in the hardness are combined, e.g., the seal ring  100  illustrated in  FIG. 7 , a positional shift occurs between the inner peripheral side ring  100   a  and the outer peripheral side ring  100   b  in some cases. At this time, when the inner peripheral side ring  100   a  shifts to the low-pressure space L side relative to the outer peripheral side ring  100   b  (see  FIG. 8 ), the force in the floating direction is applied to the outer peripheral side ring  100   b . On the contrary, when the outer peripheral side ring  100   b  shifts to the low-pressure space L side relative to the inner peripheral side ring  100   a  (see  FIG. 9 ), the force in the pressing direction (see white arrow) to the groove bottom surface  302   a  is applied to the inner peripheral side ring  100   a . Therefore, the stability of the reaction force and the friction of the seal surface  101  to the outer peripheral member  200  is impaired. 
     In the seal ring  10  of this embodiment, the recess-projection fitting portion  12  restricts the positional shift between the inner peripheral side ring  10   a  and the outer peripheral side ring  10   b , and therefore the positional shift between the inner peripheral side ring  10   a  and the outer peripheral side ring  10   b  can be avoided. As a result, a fluctuation in the reaction force and the friction of the seal surface  11  to the outer peripheral member  20  occurring accompanying the floating of the outer peripheral side ring  10   b  which is illustrated in  FIG. 8  as an example or the pressing to the inner peripheral side ring  10   a  illustrated in  FIG. 9  as an example can be avoided and the stability of the sliding resistance when the seal ring  10  slides can be maintained. 
     The seal ring  10  of this embodiment is provided with the inner peripheral side ring  10   a  which is a rubber-like elastic body closely contacting the inner peripheral member  30  reciprocating relative to the outer peripheral member  20  and the outer peripheral side ring  10   b  which is a rubber-like elastic body disposed on the outer peripheral surface  31  of the inner peripheral side ring  10   a  to closely contact the outer peripheral member  20  and having hardness higher than that of the inner peripheral side ring  10   a . The inner peripheral side ring  10   a  is provided with the seal inner peripheral surface  13  as the seating surface seated in the mounting groove  32  provided in the inner peripheral member  30 . The outer peripheral side ring  10   b  is provided with the seal surface  11  closely contacting the outer peripheral member  20 . The seal ring  10  is provided with the recess-projection fitting portion  12  provided along the annular direction on the contact surface between the inner peripheral side ring  10   a  and the outer peripheral side ring  10   b  and restricting the positional shift in the axial direction between the inner peripheral side ring  10   a  and the outer peripheral side ring  10   b.    
     As another embodiment, the mounting groove  32  may be provided in the outer peripheral member  20 . In this case, the seating surface seated in the mounting groove  32  is provided in the outer peripheral surface of the outer peripheral side ring  10   b  and the seal surface  11  is provided on the inner peripheral surface of the inner peripheral side ring  10   a.    
     As still another embodiment, the recessed groove  12   b  of the recess-projection fitting portion  12  is provided in the inner peripheral side ring  10   a  and the protrusion  12   a  may be provided in the outer peripheral side ring  10   b.    
     In the implementation of the disclosure, various kinds of modifications and alternations are permitted. 
     EXAMPLES 
     In order to compare the reaction forces to the seal surface  11 , the analysis by the finite element method (FEM) was conducted supposing models of six kinds of seal rings  10 . All the models contain an acrylic rubber having a product inner diameter ϕ of 50.5 and a crushing margin of 0.2 mm. Each specification is as follows. 
     (Model 1) 
     A single raw material in which the size of a part of the cross-sectional shape is 1.7×3.4 (mm) and the hardness is 60. 
     (Model 2) 
     A single raw material in which the size of a part of the cross-sectional shape is 1.7×3.4 (mm) and the hardness is 70. 
     (Model 3) 
     A single raw material in which the size of a part of the cross-sectional shape is 1.7×3.4 (mm) and the hardness is 90. 
     (Model 4) 
     An inner peripheral side ring has a size of a part of the cross-sectional shape of 1.7×1.7 (mm) and a hardness of 60. 
     An outer peripheral side ring has a size of a part of the cross-sectional shape of 1.7×1.7 (mm) and a hardness of 90. 
     (Model 5) 
     An inner peripheral side ring has a size of a part of the cross-sectional shape of 1.7×1.1 (mm) and a hardness of 60. 
     An outer peripheral side ring has a size of a part of the cross-sectional shape of 1.7×2.3 (mm) and a hardness of 90. 
     (Model 6) 
     An inner peripheral side ring has a size of a part of the cross-sectional shape of 1.7×2.3 (mm) and a hardness of 60. 
     An outer peripheral side ring has a size of a part of the cross-sectional shape of 1.7×1.1 (mm) and a hardness of 90. 
       FIG. 3  illustrates the analysis results of the reaction forces generated on the seal surface  11  when the pressure applied by a fluid sealed between the outer peripheral member  20  and the inner peripheral member  30  is 0 MPa and when the pressure by the fluid is 2 MPa. 
     With respect to the single raw material models (Models 1 to 3), it was found that, while there are no great differences in the reaction force between the model 1 having a hardness of 60 and the model 2 having a hardness of 70 also when the pressure by the fluid is 0 MPa and also when the pressure by the fluid is 2 MPa, the reaction force greatly increases in the model 3 having a hardness of 90. 
     With respect to the models (Models 4 to 6) in which two kinds of members different in the hardness are combined, although the hardness of the outer peripheral side ring  10   b  is set to 90, the reaction force drastically decreases in all the models 4 to 6 as compared with that of the model 3 containing the single raw material having a hardness of 90. The reduction rate of the reaction force becomes larger in the order of the models 5, 4, and 6 also when the pressure by the fluid is 2 MPa and also when the pressure by the fluid is 0 MPa. More specifically, the reaction force decreases as the dimension ratio of the inner peripheral side ring  10   a  using a low hardness rubber material is larger. 
     With respect to the models (Models 4 to 6) in which two kinds of members different in the hardness are combined, the reaction force decreases when the pressure by the fluid is 2 MPa even when compared with that of the model 1 containing the single raw material having a hardness of 60 and the model 2 containing the single raw material having a hardness of 70. More specifically, it is found in the models 4 to 6 that a difference in the reaction force to a fluctuation in the pressure of the fluid becomes small. 
     The analysis results above clarify that the models (Models 4 to 6) in which two kinds of members different in the hardness are combined can reduce the reaction force to the seal surface  11  as compared with that of the single raw material models (Models 1 to 3), although the crushing margins are the same and 0.2 mm. 
     Next, in order to compare the friction generated in the seal surface  11 , the analysis by the finite element method (FEM) was conducted supposing models of three kinds of seal rings  10 . All the models contain an acrylic rubber having a product inner diameter ϕ of 50.5 and a crushing margin of 0.2 mm. 
     Each specification is as follows. 
     (Model 7) 
     A single raw material in which the size of a part of the cross-sectional shape is 1.7×3.4 (mm) and the hardness is 70. 
     (Model 8) 
     An inner peripheral side ring has a size of a part of the cross-sectional shape of 1.7×2.3 (mm) and a hardness of 60. 
     An outer peripheral side ring has a size of a part of the cross-sectional shape of 1.7×1.1 (mm) and a hardness of 90. 
     (Model 9) 
     An inner peripheral side ring has a size of a part of the cross-sectional shape of 1.7×2.3 (mm) and a hardness of 60. 
     An outer peripheral side ring has a size of a part of the cross-sectional shape of 1.7×1.1 (mm) and a hardness of 90. 
     A recess-projection fitting portion is provided between the inner peripheral side ring and the outer peripheral side ring. 
       FIG. 4  illustrates the analysis results of the friction generated in the seal surface  11  when the pressure applied by a fluid sealed between the outer peripheral member  20  and the inner peripheral member  30  is 0 MPa and when the pressure is 2 MPa. 
     When the pressure applied by the fluid is 0 MPa, a difference is hard to arise in values of the friction generated in the seal surface  11  in all the models 7 to 9. 
     When the pressure applied by the fluid is 2 MPa, the friction sharply increases in the model 8. This is because the phenomenon illustrated in  FIG. 8  as an example occurs, i.e., a phenomenon in which, when the positional shift occurs between the inner peripheral side ring and the outer peripheral side ring due to the operation state of a device in which the seal ring is used or the influence of pressure, so that the inner peripheral side ring shifts to the low-pressure space side relative to the outer peripheral side ring, force is applied to the outer peripheral side ring in a direction of floating from the inner peripheral side ring due to the action of the hydraulic pressure occurs. Thus, the friction of the seal surface to the outer peripheral member increases. 
     In this point, when focusing on the model 9, the friction generated in the seal surface  11  is markedly low as compared with that of the model 8 although the model 9 is a seal ring in which two kinds of members different in the hardness are combined as with the model 8. This is considered to be because the recess-projection fitting portion is interposed between the inner peripheral side ring and the outer peripheral side ring, and therefore the inner peripheral side ring and the outer peripheral side ring do not cause the positional shift in the axial direction. More specifically, the phenomenon illustrated in  FIG. 8  does not occur in the first place, and therefore the outer peripheral side ring does not float. 
     With respect to the model 9, the friction generated in the seal surface  11  is low even when compared with that of the model 7 containing the single raw material. This is considered to be because the hardness (=60) of the inner peripheral side ring is lower than the hardness (=70) of the model 7. 
     The analysis results above verify the superiority of the model 9 with respect to the friction generated in the seal surface  11 . 
     DESCRIPTION OF REFERENCE NUMERALS 
     
         
         
           
               10  seal ring 
               10   a  inner peripheral side ring 
               10   b  outer peripheral side ring 
               11  sealing surface 
               12  recess-projection fitting portion 
               12   a  protrusion 
               12   b  recessed groove 
               13  seal inner peripheral surface (seating surface) 
               14  side surface 
               14   a  side surface 
               14   b  side surface 
               20  outer peripheral member 
               21  inner peripheral surface 
               30  inner peripheral member 
               31  outer peripheral surface 
               32  mounting groove