Patent Publication Number: US-2023148383-A1

Title: Seal member

Description:
TECHNICAL FIELD 
     The present invention relates to a sealing member. 
     BACKGROUND ART 
     In manufacturing processes in various technical fields such as semiconductor manufacturing, medical/pharmaceutical manufacturing, and food processing/chemical industries, in a pipe path through which fluids such as chemical solutions, high-purity liquids, ultrapure water, or cleaning solutions flow, for example, a gasket for preventing fluid leakage is used as a connection structure that connects flow passage holes formed in two fluid devices (see, for example, PATENT LITERATURE 1). 
       FIG.  7    is an axial cross-sectional view of a conventional gasket. A conventional gasket  100  includes a cylindrical body portion  110 , an annular primary sealing portion  111  formed on the radially inner side of each axially outer end portion of the body portion  110  so as to project toward the axially outer side, and an annular secondary sealing portion  112  formed on the radially outer side of each axially outer end portion of the body portion  110  so as to project toward the axially outer side. 
       FIG.  8    is an axial cross-sectional view showing a state where flow passage holes  153 ,  153  formed in two fluid devices  150 ,  150  are connected by the conventional gasket  100 . The internal space of the body portion  110  is a communication hole  113  which provides communication between the flow passage holes  153 ,  153  of both fluid devices  150 ,  150 . The primary sealing portion  111  and the secondary sealing portion  112  are respectively press-fitted into an annular primary sealing groove  151  and an annular secondary sealing groove  152  formed on each fluid device  150 . Accordingly, sealing performance between each fluid device  150  and the gasket  100  is ensured to prevent a fluid from leaking to the outside. 
     CITATION LIST 
     Patent Literature 
     PATENT LITERATURE 1: Japanese Laid-Open Patent Publication No. 2019-173844 
     SUMMARY OF THE INVENTION 
     Technical Problem 
     As shown in  FIG.  8   , a cross-sectional shape of the primary sealing portion  111  is formed so as to be gradually tapered from the axially inner end thereof toward the axially outer end thereof. In addition, a cross-sectional shape of the primary sealing groove  151  is inclined along the tapered shape of the primary sealing portion  111 . Therefore, when the primary sealing portion  111  is press-fitted into the primary sealing groove  151 , the axially outer end of the primary sealing portion  111  may slip along the slope of the primary sealing groove  151  toward the axially outer side. When such a slip occurs, an inner circumferential surface 110a of the body portion  110  becomes bent and deformed so as to be recessed toward the radially outer side such that the inner circumferential side of the body portion  110  is bent. In this case, the contact surface pressure between the axially outer end of the primary sealing portion  111  and the primary sealing groove  151  may decrease, and the fluid may enter between the primary sealing portion  111  and the primary sealing groove  151  and stay therein or leak to the outside. 
     The present invention has been made in view of such circumstances, and an object of the present invention is to provide a sealing member that can suppress fluid leakage. 
     Solution to Problem 
     ( 1 ) A sealing member of the present invention is a sealing member for sealing and connecting flow passage holes formed in two fluid devices, respectively, the sealing member including: a cylindrical body portion having a communication hole for providing communication between the flow passage holes; and an annular sealing portion projecting from a radially inner side of an axially outer end portion of the body portion toward an axially outer side and to be press-fitted into an annular sealing groove formed at a connection end portion of the flow passage hole of one of the fluid devices, wherein, in a pre-press-fit state which is a state before the sealing portion is press-fitted into the sealing groove, at least a part of an inner circumferential surface of the body portion and/or a part of another portion, excluding an axially outer end portion, of an inner circumferential surface of the sealing portion is formed such that a diameter thereof gradually decreases from the axially outer side toward an axially inner side. 
     According to the present invention, in the pre-press-fit state, at least a part of the inner circumferential surface of the body portion and/or a part of the other portion of the inner circumferential surface of the sealing portion is formed so as to project toward the radially inner side. Accordingly, when the sealing portion is press-fitted into the sealing groove, even if the axially outer end of the sealing portion slips relative to the sealing groove, the inner circumferential surface of the body portion can be inhibited from becoming bent and deformed so as to be recessed toward the radially outer side. As a result, the contact surface pressure between the axially outer end of the sealing portion and the sealing groove can be inhibited from decreasing, so that a fluid can be inhibited from entering between the sealing portion and the sealing groove and leaking to the outside. 
     ( 2 ) In the pre-press-fit state, at least a part of the inner circumferential surface of the body portion is preferably formed such that the diameter thereof gradually decreases from the axially outer side toward the axially inner side. 
     In this case, in the pre-press-fit state, at least a part of the inner circumferential surface of the body portion is formed so as to project toward the radially inner side. Accordingly, when the sealing portion is press-fitted into the sealing groove, the inner circumferential surface of the body portion can be further inhibited from becoming bent and deformed so as to be recessed toward the radially outer side. 
     (3) In the pre-press-fit state, an entirety of the inner circumferential surface of the body portion is preferably formed such that the diameter thereof gradually decreases from both axially outer ends thereof toward the axially inner side. 
     In this case, in the pre-press-fit state, the entirety of the inner circumferential surface of the body portion is formed so as to project toward the radially inner side. Accordingly, when the sealing portion is press-fitted into the sealing groove, the inner circumferential surface of the body portion can be further inhibited from becoming bent and deformed so as to be recessed toward the radially outer side. 
      ( 4 ) In the pre-press-fit state, the axially outer end portion of the inner circumferential surface of the sealing portion is preferably formed such that the diameter thereof gradually decreases from an axially outer end thereof toward an axially inner end thereof. 
     In this case, in the pre-press-fit state, the axially outer end portion of the inner circumferential surface of the sealing portion is located on the radially outer side with respect to the other portion of the inner circumferential surface. Accordingly, when the sealing portion is press-fitted into the sealing groove, even if the axially outer end of the sealing portion slips relative to the sealing groove, the axially outer end portion of the inner circumferential surface of the sealing portion can be inhibited from excessively projecting toward the radially inner side. Accordingly, the flow of the fluid in the communication hole of the body portion can be inhibited from being obstructed by the inner circumferential surface of the sealing portion. 
     ( 5 ) Preferably, in the pre-press-fit state, at least a part of the inner circumferential surface of the body portion is formed such that the diameter thereof gradually decreases from the axially outer side toward the axially inner side, and a degree of diameter decrease of the axially outer end portion of the inner circumferential surface of the sealing portion is larger than a degree of diameter decrease of the inner circumferential surface of the body portion. 
     In this case, since the degree of diameter decrease of the axially outer end portion of the inner circumferential surface of the sealing portion is larger than the degree of diameter decrease of the inner circumferential surface of the body portion, the radial thickness on the axially outer side of the sealing portion can be larger than in the case where the degree of diameter decrease of the sealing portion is the same as the degree of diameter decrease of the body portion. Accordingly, the contact surface pressure between the axially outer end of the sealing portion and the sealing groove can be further inhibited from decreasing. 
      (6) In the pre-press-fit state, an entirety of the inner circumferential surface of the sealing portion is preferably formed such that the diameter thereof gradually decreases from an axially outer end thereof toward an axially inner end thereof. 
     In this case, in the pre-press-fit state, the entirety of the inner circumferential surface of the sealing portion is formed so as to project toward the radially inner side. Accordingly, when the sealing portion is press-fitted into the sealing groove, the inner circumferential surface of the sealing portion can be further inhibited from becoming bent and deformed so as to be recessed toward the radially outer side together with the body portion, so that the contact surface pressure between the axially outer end of the sealing portion and the sealing groove can be further inhibited from decreasing. 
     (7) In the pre-press-fit state, the entirety of the inner circumferential surface of the body portion is preferably formed by a curved line projecting toward the radially inner side in an axial cross-sectional view. 
     In this case, in the pre-press-fit state, the entirety of the inner circumferential surface of the body portion is formed by the curved line projecting toward the radially inner side in an axial cross-sectional view. Accordingly, when the sealing portion is press-fitted into the sealing groove, the inner circumferential surface of the body portion can be further inhibited from becoming bent and deformed so as to be recessed toward the radially outer side. 
     (8) The entirety of the inner circumferential surface of the body portion is preferably formed so as not to become bent and deformed toward a radially outer side beyond a straight line extending in an axial direction in an axial cross-sectional view in a state where the sealing portion is press-fitted into the sealing groove. 
     In this case, in a state where the sealing portion is press-fitted into the sealing groove, the inner circumferential surface of the body portion can be inhibited from becoming bent and deformed toward the radially outer side beyond the straight line extending in the axial direction, so that the contact surface pressure between the axially outer end of the sealing portion and the sealing groove can be further inhibited from decreasing. 
     Advantageous Effects of the Invention 
     According to the present invention, it is possible to suppress fluid leakage. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1    is an axial cross-sectional view of a flow passage connection structure, in which a sealing member is used, according to a first embodiment of the present invention. 
         FIG.  2    is an axial cross-sectional view of a gasket. 
         FIG.  3    is an enlarged cross-sectional view of a main part of  FIG.  2   . 
         FIG.  4    is an axial cross-sectional view of a flow passage connection structure, in which a sealing member is used, according to a second embodiment of the present invention. 
         FIG.  5    is an axial cross-sectional view of an inner ring. 
         FIG.  6    is an enlarged cross-sectional view of a main part of  FIG.  5   . 
         FIG.  7    is an axial cross-sectional view of a conventional gasket. 
         FIG.  8    is an axial cross-sectional view showing a state where flow passage holes of two fluid devices are connected by the conventional gasket. 
     
    
    
     DETAILED DESCRIPTION 
      First Embodiment 
     Entire Configuration of Flow Passage Connection Structure 
       FIG.  1    is an axial cross-sectional view of a flow passage connection structure, in which a sealing member is used, according to a first embodiment of the present invention. A flow passage connection structure  1  shown in  FIG.  1    is used, for example, as a connection structure that connects flow passage holes  2   c ,  2   c  formed in two adjacent fluid devices  2 ,  2 , respectively, in a pipe path through which a chemical solution used in a semiconductor manufacturing apparatus flows. Examples of each fluid device  2  of the present embodiment include a pump, a valve, an accumulator, a filter, a flow meter, a pressure sensor, a pipe block, and an integrated module or integrated panel that unitizes these devices. 
     The flow passage connection structure  1  includes annular primary sealing grooves (sealing grooves)  2   d  and annular secondary sealing grooves  2   e  which are formed on end portions of the respective fluid devices  2 , a gasket  4 , and a clamp  5 . The gasket  4  is a sealing member that seals and connects the flow passage holes  2   c ,  2   c  of the two fluid devices  2 ,  2 . Hereinafter, in the present embodiment, the directions from the axial center toward both axial sides of the gasket  4  are referred to as an axially outer side, and the directions from both axial sides toward the axial center of the gasket  4  are referred to as an axially inner side. 
     The primary sealing groove  2   d  of each fluid device  2  is formed on the circumferential surface of a connection end portion of the flow passage hole  2   c  in a tapered shape that is cut such that the diameter thereof gradually increases from the axially outer end thereof toward the axially inner end thereof. The secondary sealing groove  2   e  of each fluid device  2  is located on the radially outer side with respect to the primary sealing groove  2   d  in each fluid device  2 , and is formed in a cylindrical annular shape. 
     The gasket  4  is formed from a synthetic resin material such as polyvinyl chloride (PVC), polypropylene (PP), polyethylene (PE), or a fluorine resin (perfluoroalkoxy alkane (PFA), polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), or the like). The gasket  4  includes a body portion  10  formed in a cylindrical shape, a pair of annular primary sealing portions (sealing portions)  11 , and a pair of annular secondary sealing portions  12 . A communication hole  10   a  which provides communication between the flow passage holes  2   c ,  2   c  of the two fluid devices  2 ,  2  is formed inside the body portion  10 . 
     The pair of primary sealing portions  11  are formed so as to project from the radially inner sides of outer end portions on both axial sides of the body portion  10 , respectively, toward the axially outer side. Each primary sealing portion  11  is formed so as to be tapered from the axially inner end thereof toward the axially outer end thereof in an axial cross-sectional view. An outer circumferential surface  11   a  of each primary sealing portion  11  is formed, so as to match the shape of the primary sealing groove  2   d , as a tapered surface formed such that the diameter thereof gradually increases from the axially outer end thereof toward the axially inner end thereof. Accordingly, each primary sealing portion  11  is press-fitted into the primary sealing groove  2   d  of the corresponding fluid device  2 . 
     The pair of secondary sealing portions  12  are formed so as to project from the radially outer sides of the outer end portions on both axial sides of the body portion  10 , respectively, toward the axially outer side. Each secondary sealing portion  12  is formed in a cylindrical annular shape and press-fitted into the secondary sealing groove  2   e  of the corresponding fluid device  2 . 
      With the above configuration, since the pair of primary sealing portions  11  and the pair of secondary sealing portions  12  of the gasket  4  are press-fitted into the primary sealing grooves  2   d  and the secondary sealing grooves  2   e  of the respective fluid devices  2 , sealing performance at a connection portion between the flow passage holes  2   c ,  2   c  in the two fluid devices  2 ,  2  can be ensured. 
     The clamp  5  is formed in a substantially C-shaped cross-sectional shape, for example, and connects both fluid devices  2 ,  2  in a state where the flow passage holes  2   c ,  2   c  of both fluid devices  2 ,  2  are connected by the gasket  4 . Specifically, the clamp  5  sandwiches and squeezes flange portions  2   f ,  2   f , which are formed at end portions of the respective fluid devices  2 ,  2 , in the axial direction. Accordingly, a sealed state where the gasket  4  is press-fitted into the primary sealing groove  2   d  and the secondary sealing groove  2   e  of each fluid device  2  can be maintained. The flow passage connection structure  1  may include other connection means such as a bolt and a nut, in addition to the clamp  5 . 
     Meanwhile, when each primary sealing portion  11  and each secondary sealing portion  12  of the gasket  4  are press-fitted into the primary sealing groove  2   d  and the secondary sealing groove  2   e  of each fluid device  2 , the axially outer end of the primary sealing portion  11  may slip along the slope of the primary sealing groove  2   d  toward the axially outer side. When such a slip occurs, an inner circumferential surface  10   b  of the body portion  10  becomes bent and deformed toward the radially outer side such that the inner circumferential side of the body portion  10  is bent. In the present embodiment, the inner circumferential surface  10   b  of the body portion  10  is formed in a shape that inhibits the inner circumferential surface  10   b  from becoming bent and deformed so as to be recessed toward the radially outer side in a press-fitted state which is a state where the primary sealing portions  11  and the secondary sealing portions  12  are press-fitted into the primary sealing grooves  2   d  and the secondary sealing grooves  2   e . Hereinafter, the detailed shape thereof will be described. 
     Shape of Inner Circumferential Side of Gasket 
       FIG.  2    is an axial cross-sectional view of the gasket  4  and shows a pre-press-fit state which is a state before the primary sealing portions  11  and the secondary sealing portions  12  are press-fitted into the primary sealing grooves  2   d  and the secondary sealing grooves  2   e  (see  FIG.  1   ). In  FIG.  2   , the entirety of the inner circumferential surface  10   b  of the body portion  10  of the gasket  4  is formed such that the diameter thereof gradually decreases from both axially outer ends thereof toward the axially inner side. 
     In the present embodiment, the entirety of the inner circumferential surface  10   b  of the body portion  10  is formed by a curved line  10   b   1  projecting most radially inward at a center in the axial direction thereof in an axial cross-sectional view. The curved line  10   b   1  of the inner circumferential surface  10   b  is formed such that, in the press-fitted state shown in  FIG.  1   , the curved line  10   b   1  becomes bent and deformed toward the radially outer side to be a straight line  10   b   2  extending in the axial direction. That is, a radius of curvature r1 of the curved line  10   b   1  is set such that the shape after the curved line  10   b   1  becomes bent and deformed toward the radially outer side becomes the straight line  10   b   2 . 
       FIG.  3    is an enlarged cross-sectional view of a main part of  FIG.  2   . In  FIG.  3   , the entirety of an inner circumferential surface  11   b  of the primary sealing portion  11  of the gasket  4  is formed such that the diameter thereof gradually decreases from the axially outer end thereof toward the axially inner end thereof. In the present embodiment, the entirety of the inner circumferential surface  11   b  of each primary sealing portion  11  is formed by a curved line projecting most radially inward at the axially inner end thereof in an axial cross-sectional view. 
     The degree of diameter decrease of an axially outer end portion  11   c  in the inner circumferential surface  11   b  of each primary sealing portion  11  is larger than the degree of diameter decrease of the inner circumferential surface  10   b  of the body portion  10 . That is, a radius of curvature r2 of the axially outer end portion  11   c  in the inner circumferential surface  11   b  of each primary sealing portion  11  is smaller than the radius of curvature r1 of the inner circumferential surface  10   b  of the body portion  10 . 
     The entirety of another portion  11   d , excluding the axially outer end portion  11   c , of the inner circumferential surface  11   b  of each primary sealing portion  11  is formed such that the diameter thereof gradually decreases from the axially outer end thereof toward the axially inner end thereof. In the present embodiment, the entirety of the other portion  11   d  is formed by a curved line  11   d   1  projecting most radially inward at the axially inner end thereof in an axial cross-sectional view. A radius of curvature r3 of the curved line  11   d   1  is equal to the radius of curvature r1 of the inner circumferential surface  10   b  of the body portion  10 . Therefore, the curved line  11   d   1  is formed such that, in the press-fitted state shown in  FIG.  1   , the curved line  11   d   1  becomes bent and deformed toward the radially outer side to be a straight line  11   d   2  extending in the axial direction. That is, the radius of curvature r3 of the curved line  11   d   1  is set such that the shape after the curved line  11   d   1  becomes bent and deformed toward the radially outer side becomes the straight line  11   d   2 . 
     Advantageous Effects of First Embodiment 
     In the gasket  4  of the present embodiment, in the pre-press-fit state, the entirety of the inner circumferential surface  10   b  of the body portion  10  is formed such that the diameter thereof gradually decreases from both axially outer ends thereof toward the axially inner side. That is, in the pre-press-fit state, the entirety of the inner circumferential surface  10   b  of the body portion  10  is formed so as to project toward the radially inner side. Accordingly, when each primary sealing portion  11  is press-fitted into the primary sealing groove  2   d , even if the axially outer end of the primary sealing portion  11  slips along the slope of the primary sealing groove  2   d  toward the axially outer side, the inner circumferential surface  10   b  of the body portion  10  can be inhibited from becoming bent and deformed so as to be recessed toward the radially outer side. As a result, the contact surface pressure between the axially outer end of the primary sealing portion  11  and the primary sealing groove  2   d  can be inhibited from decreasing, so that a fluid can be inhibited from entering between the primary sealing portion  11  and the primary sealing groove  2   d  and leaking to the outside. 
     Moreover, in the pre-press-fit state, the entirety of the inner circumferential surface  11   b  of each primary sealing portion  11  is formed such that the diameter thereof gradually decreases from the axially outer end thereof toward the axially inner end thereof. That is, in the pre-press-fit state, the entirety of the inner circumferential surface  11   b  of each primary sealing portion  11  is formed so as to project toward the radially inner side. Accordingly, when each primary sealing portion  11  is press-fitted into the primary sealing groove  2   d , the inner circumferential surface  11   b  of the primary sealing portion  11  can be further inhibited from becoming bent and deformed so as to be recessed toward the radially outer side together with the body portion  10 . As a result, the contact surface pressure between the axially outer end of the primary sealing portion  11  and the primary sealing groove  2   d  can be further inhibited from decreasing. 
     Moreover, in the pre-press-fit state, the axially outer end portion  11   c  of the inner circumferential surface  11   b  of each primary sealing portion  11  is formed such that the diameter thereof gradually decreases from the axially outer end thereof toward the axially inner end thereof. That is, in the pre-press-fit state, the axially outer end portion  11   c  of the inner circumferential surface  11   b  of each primary sealing portion  11  is located on the radially outer side with respect to the other portion  11   d  of the inner circumferential surface  11   b . Accordingly, when each primary sealing portion  11  is press-fitted into the primary sealing groove  2   d , even if the axially outer end of the primary sealing portion  11  slips relative to the primary sealing groove  2   d , the axially outer end portion  11   c  of the inner circumferential surface  11   b  of the primary sealing portion  11  can be inhibited from excessively projecting toward the radially inner side. Accordingly, the flow of the fluid in the communication hole  10   a  of the body portion  10  can be inhibited from being obstructed by the inner circumferential surface  11   b  of the primary sealing portion  11 . 
     Moreover, since the degree of diameter decrease of the axially outer end portion  11   c  of the inner circumferential surface  11   b  of each primary sealing portion  11  is larger than the degree of diameter decrease of the inner circumferential surface  10   b  of the body portion  10 , the radial thickness on the axially outer side of the primary sealing portion  11  can be larger than in the case where the degree of diameter decrease of the primary sealing portion  11  is the same as the degree of diameter decrease of the body portion  10 . Accordingly, the contact surface pressure between the axially outer end of the primary sealing portion  11  and the primary sealing groove  2   d  can be further inhibited from decreasing. 
      Moreover, in the pre-press-fit state, the entirety of the inner circumferential surface  10   b  of the body portion  10  is formed by the curved line  10   b   1  projecting toward the radially inner side. Accordingly, when each primary sealing portion  11  is press-fitted into the primary sealing groove  2   d , the inner circumferential surface  10   b  of the body portion  10  can be further inhibited from becoming bent and deformed so as to be recessed toward the radially outer side. 
     Moreover, the curved line  10   b   1  of the inner circumferential surface  10   b  of the body portion  10  and the curved line  11   d   1  of the other portion  11   d  of the inner circumferential surface  11   b  of each primary sealing portion  11  are formed such that, in the press-fitted state, the curved line  10   b   1  and the curved line  11   d   1  become bent and deformed toward the radially outer side to be the straight lines  10   b   2  and  11   d   2 . Accordingly, the inner circumferential surface  10   b  of the body portion  10  can be further inhibited from becoming bent and deformed so as to be recessed toward the radially outer side in the press-fitted state. As a result, the contact surface pressure between the axially outer end of the primary sealing portion  11  and the primary sealing groove  2   d  can be further inhibited from decreasing. 
     Second Embodiment 
     Entire Configuration of Flow Passage Connection Structure 
       FIG.  4    is an axial cross-sectional view of a flow passage connection structure, in which a sealing member is used, according to a second embodiment of the present invention. In  FIG.  4   , similar to the first embodiment, a flow passage connection structure  20  of the present embodiment is used, for example, in a pipe path through which a chemical solution (fluid) used in a semiconductor manufacturing apparatus flows. The flow passage connection structure  20  includes a joint body  22 , a union nut  23 , and an inner ring  24 . Hereinafter, in the present embodiment, for convenience, the right side of  FIG.  4    is referred to as an axially outer side, and the left side of  FIG.  4    is referred to as an axially inner side (the same applies to  FIG.  5    and  FIG.  6   ). 
     The inner ring  24  is formed in a cylindrical shape, for example, from a synthetic resin material such as polyvinyl chloride (PVC), polypropylene (PP), polyethylene (PE), or a fluorine resin (perfluoroalkoxy alkane (PFA), polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), or the like). The inner ring  24  includes a body portion  25  formed in a cylindrical shape, a bulge portion  26  formed at an axial inner end portion of the body portion  25 , and a connection portion  27  formed at an axially outer end portion of the body portion  25 . 
     The bulge portion  26  is formed at the axial inner end portion of the body portion  25  so as to project toward the radially outer side. The bulge portion  26  is press-fitted into an end portion of a tube  28 , which is made of a synthetic resin material (PFA or the like), to increase the diameter of the end portion. The connection portion  27  is connected to an end portion of the joint body  22  and seals a connection portion therebetween. The configuration of the connection portion  27  will be described later. A communication hole  25   a  which provides communication between a flow passage hole  22   c  formed inside the joint body  22  and a flow passage hole  28   a  formed inside the tube  28  is formed inside the body portion  25 . 
     The joint body  22  is formed in a cylindrical shape, for example, from a synthetic resin material such as PVC, PP, PE, or a fluorine resin (PFA, PTFE, or the like). The inner diameter of the joint body  22  is set to substantially the same dimension as the inner diameter of the body portion  25  of the inner ring  24  such that the movement of the chemical solution is not hindered. A receiving portion  22   a  is formed at an end portion of the joint body  22 . The inner ring  24  press-fitted into the end portion of the tube  28  is fitted to the inner circumference of the receiving portion  22   a . Accordingly, the end portion of the joint body  22  is mounted on the outer circumference of the end portion of the tube  28 . An external thread portion  22   b  is formed on the outer circumference of the receiving portion  22   a . 
     The joint body  22  has an annular primary sealing groove (sealing groove)  22   d  and an annular secondary sealing groove  22   e  which are formed on the radially inner side with respect to the receiving portion  22   a . The primary sealing groove  22   d  is formed on the circumferential surface of a connection end portion of the flow passage hole  22   c  in a tapered shape that is cut such that the diameter thereof gradually increases from the axially outer end thereof toward the axially inner end thereof. The secondary sealing groove  22   e  is formed in a cylindrical annular shape on the radially outer side with respect to the primary sealing groove  22   d  in the joint body  22 . 
     The union nut  23  is formed in a cylindrical shape, for example, from a synthetic resin material such as PVC, PP, PE, or a fluorine resin (PFA, PTFE, or the like). The union nut  23  has an internal thread portion  23   a  formed on the inner circumference of an axially outer end portion thereof, and a pressing portion  23   b  formed at an axial inner end portion thereof so as to project toward the radially inner side. The internal thread portion  23   a  is tightened to the external thread portion  22   b  of the joint body  22 . By the tightening, the union nut  23  is attached to the joint body  22 , and an axial inner end portion of the pressing portion  23   b  also presses the outer circumferential surface of the tube  28  by the bulge portion  26  of the inner ring  24 . 
     With the above configuration, by tightening the internal thread portion  23   a  of the union nut  23  to the external thread portion  22   b  of the joint body  22 , sealing performance at the attachment point between the receiving portion  22   a  of the joint body  22  and the end portion of the tube  28  can be ensured, and the tube  28  can be prevented from being removed. 
     The connection portion  27  of the inner ring  24  includes an annular primary sealing portion (sealing portion)  31  and an annular secondary sealing portion  32 . 
     The primary sealing portion  31  is formed so as to project from the radially inner side of the axially outer end portion of the body portion  25  toward the axially outer side. In addition, the primary sealing portion  31  is formed so as to be tapered from the axially inner end thereof toward the axially outer end thereof in an axial cross-sectional view. An outer circumferential surface 31a of the primary sealing portion  31  is formed, so as to match the shape of the primary sealing groove  22   d , as a tapered surface formed such that the diameter thereof gradually increases from the axially outer end thereof toward the axially inner end thereof. Accordingly, the primary sealing portion  31  is press-fitted into the primary sealing groove  22   d  of the joint body  22 . 
     The secondary sealing portion  32  is formed so as to project from the radially outer side of the axially outer end portion of the body portion  25  toward the axially outer side. The secondary sealing portion  32  is formed in a cylindrical annular shape and press-fitted into the secondary sealing groove  22   e  of the joint body  22 . 
     With the above configuration, when the union nut  23  is tightened, the primary sealing portion  31  and the secondary sealing portion  32  of the inner ring  24  are press-fitted into the primary sealing groove  22   d  and the secondary sealing groove  22   e  of the joint body  22 , respectively. Accordingly, sealing performance at the connection portion between the inner ring  24  and the joint body  22  can be ensured. Therefore, the inner ring  24  functions as a sealing member that seals and connects the flow passage hole  28   a  of the tube (fluid device)  28  and the flow passage hole  22   c  of the joint body (fluid device)  22 . 
     Meanwhile, when the primary sealing portion  31  and the secondary sealing portion  32  of the inner ring  24  are press-fitted into the primary sealing groove  22   d  and the secondary sealing groove  22   e  of the joint body  22  by tightening the union nut  23 , the axially outer end of the primary sealing portion  31  may slip along the slope of the primary sealing groove  22   d  toward the axially outer side. When such a slip occurs, an inner circumferential surface  25   b  of the body portion  25  becomes bent and deformed toward the radially outer side such that the inner circumferential side of the body portion  25  is bent. In the present embodiment, the inner circumferential surface  25   b  of the body portion  25  is formed in a shape that inhibits the inner circumferential surface  25   b  from becoming bent and deformed so as to be recessed toward the radially outer side in a press-fitted state which is a state where the primary sealing portion  31  and the secondary sealing portion  32  are press-fitted into the primary sealing groove  22   d  and the secondary sealing groove  22   e . Hereinafter, the detailed shape thereof will be described. 
     Configuration of Inner Circumferential Side of Inner Ring 
       FIG.  5    is an axial cross-sectional view of the inner ring  24  and shows a pre-press-fit state which is a state before the primary sealing portion  31  and the secondary sealing portion  32  are press-fitted into the primary sealing groove  22   d  and the secondary sealing groove  22   e  (see  FIG.  4   ). In  FIG.  5   , the entirety of the inner circumferential surface  25   b  of the body portion  25  in the inner ring  24  is formed such that the diameter thereof gradually decreases from both axially outer ends thereof toward the axially inner side. 
      In the present embodiment, the entirety of the inner circumferential surface  25   b  of the body portion  25  is formed by a curved line  25   b   1  projecting most radially inward at a center in the axial direction thereof in an axial cross-sectional view. The curved line  25   b   1  of the inner circumferential surface  25   b  is formed such that, in the press-fitted state shown in  FIG.  4   , the curved line  25   b   1  becomes bent and deformed toward the radially outer side to be a straight line  25   b   2  extending in the axial direction. That is, a radius of curvature r11 of the curved line  25   b   1  is set such that the shape after the curved line  25   b   1  becomes bent and deformed toward the radially outer side becomes the straight line  25   b   2 . 
       FIG.  6    is an enlarged cross-sectional view of a main part of  FIG.  5   . In  FIG.  6   , the entirety of an inner circumferential surface  31   b  of the primary sealing portion  31  of the inner ring  24  is formed such that the diameter thereof gradually decreases from the axially outer end thereof toward the axially inner end thereof. In the present embodiment, the entirety of the inner circumferential surface  31   b  of the primary sealing portion  31  is formed by a curved line projecting most radially inward at the axially outer end thereof in an axial cross-sectional view. 
     The degree of diameter decrease of an axially outer end portion  31   c  of the inner circumferential surface  31   b  of the primary sealing portion  31  is larger than the degree of diameter decrease of the inner circumferential surface  25   b  of the body portion  25 . That is, a radius of curvature r12 of the axially outer end portion  31   c  of the inner circumferential surface  31   b  of the primary sealing portion  31  is smaller than the radius of curvature r11 of the inner circumferential surface  25   b  of the body portion  25 . 
     The entirety of another portion  31   d , excluding the axially outer end portion  31   c , of the inner circumferential surface  31   b  of the primary sealing portion  31  is formed such that the diameter thereof gradually decreases from the axially outer end thereof toward the axially inner end thereof. In the present embodiment, the entirety of the other portion  31   d  is formed by a curved line  31   d   1  projecting most radially inward at the axially inner end thereof in an axial cross-sectional view. A radius of curvature r13 of the curved line  31   d   1  is equal to the radius of curvature r11 of the inner circumferential surface  25   b  of the body portion  25 . Therefore, the curved line  31   d   1  is formed such that, in the press-fitted state shown in  FIG.  4   , the curved line  31   d   1  becomes bent and deformed toward the radially outer side to be a straight line  31   d   2  extending in the axial direction. That is, the radius of curvature r13 of the curved line  31   d   1  is set such that the shape after the curved line  31   d   1  becomes bent and deformed toward the radially outer side becomes the straight line  31   d   2 . 
     Advantageous Effects of Second Embodiment 
     In the inner ring  24  of the present embodiment, in the pre-press-fit state, the entirety of the inner circumferential surface  25   b  of the body portion  25  is formed such that the diameter thereof gradually decreases from both axially outer ends thereof toward the axially inner side. That is, in the pre-press-fit state, the entirety of the inner circumferential surface  25   b  of the body portion  25  is formed so as to project toward the radially inner side. Accordingly, when the primary sealing portion  31  is press-fitted into the primary sealing groove  22   d , even if the axially outer end of the primary sealing portion  31  slips along the slope of the primary sealing groove  22   d  toward the axially outer side, the inner circumferential surface  25   b  of the body portion  25  can be inhibited from becoming bent and deformed so as to be recessed toward the radially outer side. As a result, the contact surface pressure between the axially outer end of the primary sealing portion  31  and the primary sealing groove  22   d  can be inhibited from decreasing, so that a fluid can be inhibited from entering between the primary sealing portion  31  and the primary sealing groove  22   d  and leaking to the outside. 
     Moreover, in the pre-press-fit state, the entirety of the inner circumferential surface  31   b  of the primary sealing portion  31  is formed such that the diameter thereof gradually decreases from the axially outer end thereof toward the axially inner end thereof. That is, in the pre-press-fit state, the entirety of the inner circumferential surface  31   b  of the primary sealing portion  31  is formed so as to project toward the radially inner side. Accordingly, when the primary sealing portion  31  is press-fitted into the primary sealing groove  22   d , the inner circumferential surface  31   b  of the primary sealing portion  31  can be further inhibited from becoming bent and deformed so as to be recessed toward the radially outer side together with the body portion  25 . As a result, the contact surface pressure between the axially outer end of the primary sealing portion  31  and the primary sealing groove  22   d  can be further inhibited from decreasing. 
     Moreover, in the pre-press-fit state, the axially outer end portion  31   c  of the inner circumferential surface  31   b  of the primary sealing portion  31  is formed such that the diameter thereof gradually decreases from the axially outer end thereof toward the axially inner end thereof. That is, in the pre-press-fit state, the axially outer end portion  31   c  of the inner circumferential surface  31   b  of the primary sealing portion  31  is located on the radially outer side with respect to the other portion  31   d  of the inner circumferential surface  31   b . Accordingly, when the primary sealing portion  31  is press-fitted into the primary sealing groove  22   d , even if the axially outer end of the primary sealing portion  31  slips relative to the primary sealing groove  22   d , the axially outer end portion  31   c  of the inner circumferential surface  31   b  of the primary sealing portion  31  can be inhibited from excessively projecting toward the radially inner side. Accordingly, the flow of the fluid in the communication hole  25   a  of the body portion  25   can be inhibited from being obstructed by the inner circumferential surface  31   b  of the primary sealing portion  31 . 
     Moreover, since the degree of diameter decrease of the axially outer end portion  31   c  of the inner circumferential surface  31   b  of the primary sealing portion  31  is larger than the degree of diameter decrease of the inner circumferential surface  25   b  of the body portion  25 , the radial thickness on the axially outer side of the primary sealing portion  31  can be larger than in the case where the degree of diameter decrease of the primary sealing portion  31  is the same as the degree of diameter decrease of the body portion  25 . Accordingly, the contact surface pressure between the axially outer end of the primary sealing portion  31  and the primary sealing groove  22   d  can be further inhibited from decreasing. 
     Moreover, in the pre-press-fit state, the entirety of the inner circumferential surface  25   b  of the body portion  25  is formed by the curved line  25   b   1  projecting toward the radially inner side. Accordingly, when the primary sealing portion  31  is press-fitted into the primary sealing groove  22   d , the inner circumferential surface  25   b  of the body portion  25  can be further inhibited from becoming bent and deformed so as to be recessed toward the radially outer side. 
     Moreover, the curved line  25   b   1  of the inner circumferential surface  25   b  of the body portion  25  and the curved line  31   d   1  of the other portion  31   d  of the inner circumferential surface  31   b  of the primary sealing portion  31  are formed such that, in the press-fitted state, the curved line  25   b   1  and the curved line  31   d   1  become bent and deformed toward the radially outer side to be the straight lines  25   b   2  and  31   d   2 . Accordingly, the inner circumferential surface  25   b  of the body portion  25  can be further inhibited from becoming bent and deformed so as to be recessed toward the radially outer side in the press-fitted state. As a result, the contact surface pressure between the axially outer end of the primary sealing portion  31  and the primary sealing groove  22   d  can be further inhibited from decreasing. 
     Others 
     The sealing member (the gasket  4 , the inner ring  24 ) of the present invention can be applied to the liquid crystal/organic EL field, the medical/pharmaceutical field, automotive-related fields, etc., in addition to a semiconductor manufacturing apparatus. In addition, the present invention can also be applied to a sealing member merely having a primary sealing portion. 
     It is sufficient that the curved line  10   b   1  or  25   b   1  of the inner circumferential surface  10   b  or  25   b  of the body portion  10  or  25  of the sealing member is formed so as not to become bent and deformed toward the radially outer side beyond the straight line  10   b   2  or  25   b   2  in the press-fitted state. For example, the curved line  10   b   1  or  25   b   1  of the inner circumferential surface  10   b  or  25   b  may be formed so as to be a curved line projecting toward the radially inner side in the press-fitted state. 
     In the pre-press-fit state, the curved line  10   b   1  or  25   b   1  of the inner circumferential surface  10   b  or  25   b  of the body portion  10  or  25  is formed so as to project most radially inward at the center in the axial direction thereof, but may be formed so as to project most radially inward at an arbitrary position other than both axially outer ends thereof. 
     It is sufficient that in the pre-press-fit state, at least a part of the inner circumferential surface  10   b  or  25   b  of the body portion  10  or  25  and/or a part of the other portion  11   d  or  31   d  of the inner circumferential surface  11   b  or  31   b  of the primary sealing portion  11  or  31  is formed such that the diameter thereof gradually decreases from the axially outer side toward the axially inner side. For example, only a part of the inner circumferential surface  10   b  or  25   b  of the body portion  10  or  25  may be formed such that the diameter thereof gradually decreases from the axially outer side toward the axially inner side. In addition, only a part or the entirety of the other portion  11   d  or  31   d  of the inner circumferential surface  11   b  or  31   b  of the primary sealing portion  11  or  31  may be formed such that the diameter thereof gradually decreases from the axially outer side toward the axially inner side. 
     In the pre-press-fit state, the entirety of the axially outer end portion  11   c  or  31   c  of the inner circumferential surface  11   b  or  31   b  of the primary sealing portion  11  or  31  may be formed by a straight line extending in the axial direction in an axial cross-sectional view. 
     In addition, in the pre-press-fit state, the inner circumferential surface  11   b  or  31   b  of the primary sealing portion  11  or  31  may be formed by a straight line extending in the axial direction over the entirety in the axial direction in an axial cross-sectional view. 
     In the pre-press-fit state, as long as the inner circumferential surface  10   b  or  25   b  of the body portion  10  or  25  is formed such that the diameter thereof gradually decreases from the axially outer side toward the axially inner side, the inner circumferential surface  10   b  or  25   b  may be formed in a shape (for example, by a tapered line) other than a curved line. Similarly, as long as the inner circumferential surface  11   b  or  31   b  of the primary sealing portion  11  or  31  is formed such that the diameter thereof gradually decreases from the axially outer side toward the axially inner side, the inner circumferential surface  11   b  or  31   b  may be formed in a shape (for example, by a tapered line) other than a curved line. 
      The embodiments disclosed herein are merely illustrative in all aspects and should not be recognized as being restrictive. The scope of the present invention is defined by the scope of the claims rather than the meaning described above, and is intended to include meaning equivalent to the scope of the claims and all modifications within the scope. 
     REFERENCE SIGNS LIST 
     
         
           2  fluid device 
           2   c  flow passage hole 
           2   d  primary sealing groove (sealing groove) 
           4  gasket (sealing member) 
           10  body portion 
           10   a  communication hole 
           10   b  inner circumferential surface 
           10   b   1  curved line 
           10   b   2  straight line 
           11  primary sealing portion (sealing portion) 
           11   b  inner circumferential surface 
           11   c  axially outer end portion 
           11   d  other portion 
           22  joint body (fluid device) 
           22   c  flow passage hole 
           22   d  primary sealing groove (sealing groove) 
           24  inner ring (sealing member) 
           25  body portion 
           25   a  communication hole 
           25   b  inner circumferential surface 
           25   b   1  curved line 
           25   b   2  straight line 
           28  tube (fluid device) 
           28   a  flow passage hole 
           31  primary sealing portion (sealing portion) 
           31   b  inner circumferential surface 
           31   c  axially outer end portion 
           31   d  other portion