Abstract:
A flow control valve coupling structure that does not require complicated machining and facilitates the installation of a flow control valve. The coupling structure includes a fitting portion having a male thread that is formed on a peripheral surface of the flow control valve. A coupled member has a coupling hole to receive the flow control valve. A cylindrical elastic sealing member is engaged with the coupling hole to seal the space between the flow control valve and the coupling hole. The elastic sealing member has an inner surface defining a mounting hole in which the fitting portion is fitted. A female thread is formed on the inner surface and is mated with the male thread of the fitting portion.

Description:
BACKGROUND OF THE INVENTION 
   The present invention is related to a coupling structure of a flow control valve, and more particularly, to a coupling structure of a flow control valve for a blowby gas returning apparatus that is provided in an internal combustion engine. 
     FIG. 1  is a cross-sectional view showing a first example of a conventional flow control valve coupling structure  50  for a blowby gas returning apparatus (hereinafter a PCV valve). In the coupling structure  50 , a fitting portion  62  of the PCV valve  61  is fitted axially to a coupling hole  60  that is provided in a cylinder head cover H. The PCV valve  61  is detachably coupled to the cylinder head cover H. 
   In the coupling structure  50 , a cylindrical grommet  63  is first fitted to the coupling hole  60 . Next, the fitting portion  62  of the PCV valve  61  is fitted to a mounting hole  63   a  of the grommet  63  thereby coupling the PCV valve  61  to the cylinder head cover H. The cylinder head cover H is required to undergo only machining to form the round coupling hole  60 . 
   However, the fitting allowance of the fitting portion  62  requires high accuracy so that the fitting portion  62  of the PCV valve  61  does not fall out of the grommet  63 . This increases the number of steps necessary for fitting the PCV valve  61  in the grommet  63 . 
     FIG. 2  is a cross-sectional view showing a second example of a conventional PCV valve coupling structure  50 A. The coupling structure  50 A is disclosed in Japanese Unexamined Patent Publication No. 2000-161040. In the coupling structure  50 A, a female thread is formed in a coupling hole  70  of the cylinder head cover H and a male thread is formed on a fitting portion  71  of the PCV valve  72 . The PCV valve  72  is coupled to the cylinder head cover H by screwing the fitting portion  71  into the coupling hole  70 . In the coupling structure  50 A, it is not necessary to fit a grommet to the coupling hole  70 . However, since the coupling structure  50 A does not use a grommet, vibration of the internal combustion engine is transmitted directly to the PCV valve  72 . Further, the machining of the female thread in the coupling hole  70  increases the number of steps required to couple the PCV valve  72  to the cylinder head cover H. 
   BRIEF SUMMARY OF THE INVENTION 
   It is an object of the present invention to provide a flow control valve coupling structure that does not require complicated machining and simplifies coupling to a cylinder head cover. 
   To achieve the above object, the present invention provides a coupling structure for a flow control valve. The coupling structure includes a fitting portion having a male thread that is formed on a peripheral surface of the flow control valve. A coupled member has a coupling hole to receive the flow control valve. A cylindrical elastic sealing member is engaged with the coupling hole to seal the space between the flow control valve and the coupling hole. The elastic sealing member has an inner surface defining a mounting hole in which the fitting portion is fitted. A female thread is formed on the inner surface. The female thread is mated with the male thread of the fitting portion. 
   A further aspect of the present invention is a flow control valve received in a predetermined coupling hole. The valve includes a fitting portion engaged with the coupling hole and having a peripheral surface. A male thread is formed on the peripheral surface. A main body is connected to the fitting portion and formed from synthetic resin. 
   A further aspect of the present invention is a cylindrical elastic sealing member formed from a rubber material. The elastic sealing member receives a fitting body. The elastic sealing member includes a mounting hole for receiving the fitting body. A pressed portion is formed on a inner surface defining the mounting hole and pressed by the fitting body. The pressed portion radially expands the elastic sealing member when pressed by the fitting body. 
   Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention. 

   
     BREIF DESCRIPTION OF THE DRAWINGS 
     The invention, together with objects and advantages thereof, may best be understood by reference to the following description of the presently preferred embodiments together with the accompanying drawings in which: 
       FIG. 1  is a schematic cross-sectional view showing a first example of a prior art PCV valve coupling structure; 
       FIG. 2  is a schematic cross-sectional view showing a second example of a prior art coupling structure of a PCV valve; 
       FIG. 3  is a schematic cross-sectional view of a PCV valve coupling structure according to a first embodiment of the present invention; 
       FIG. 4  is a schematic perspective view showing the PCV valve coupling structure of  FIG. 3  in which a grommet is engaged with a coupling hole; 
       FIG. 5  is a cross-sectional view showing the PCV valve coupling structure of  FIG. 3 ; 
       FIG. 6A  is a cross-sectional view showing the grommet of employed in the coupling structure of  FIG. 3 ; 
       FIG. 6B  is a top view showing the grommet of  FIG. 3 ; 
       FIG. 7A  is a front view showing the grommet attached to the PCV valve; 
       FIG. 7B  is a front view showing the PCV valve fitted in the coupling hole; 
       FIG. 8  is a cross-sectional view showing the grommet engaged with the coupling hole; 
       FIG. 9  is a schematic cross-sectional view showing a PCV valve coupling structure according to a second embodiment of the present invention; 
       FIG. 10A  is a cross-sectional view showing a grommet that is employed in the coupling structure of  FIG. 9 ; 
       FIG. 10B  is a top view showing the grommet of  FIG. 9 ; and 
       FIG. 11  is a front view showing the PCV valve fitted in the coupling hole. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   In the drawings, like numerals are used for like elements throughout. 
     FIG. 3  is a schematic cross-sectional view showing a PCV valve coupling structure  100  according to a first embodiment of the present invention. The PCV valve coupling structure  100  includes a PCV valve  10  and a grommet (an elastic sealing member)  12 . 
   As shown in  FIG. 4 , the PCV valve  10  is detachably engaged with a coupling hole  11  (shown in FIG.  3 ), which is formed in an engine cylinder head cover H, by means of the grommet  12 . The head cover H serves as a coupled member to which the PCV valve  10  is coupled. A tubing hose T, which is connected to an intake system of an intake manifold (not shown), is connected to the PCV valve  10 . As shown in  FIG. 5 , the PCV valve  10  includes a main body  13 , a valve body  14 , and a coil spring  15 . 
   The main body  13  includes a lower piece  16  and an upper piece  17 , each of which is formed integrally from synthetic resin. The lower piece  16  includes a generally cylindrical fitting portion  18 . A generally cylindrical valve chamber  22  is formed in the fitting portion  18 . The valve chamber  22  is communicated with the atmosphere via a valve hole  22   a , which extends through the bottom of the fitting portion  18 . A male thread  23  is formed on the peripheral surface of the fitting portion  18 . 
   The upper piece  17  includes a generally cylindrical base  19 , a hose connector  20 , and tabs  21 . The base  19  has a diameter larger than that of the fitting portion  18 . The hose connector  20  is generally cylindrical and extends upward from the base  19 . 
   The tabs  21 , which define a rotating portion, are thin plates extending from opposite sides of the hose connector  20 . When the PCV valve  10  is attached to or detached from the head cover, the tabs  21  are used to rotate the PCV valve  10 . When the tubing hose T is connected to the hose connector  20 , the tabs  21  are used to position the tubing hose T. 
   A lower communication hole  24  that communicates with the upper portion of the valve chamber  22  extends through the base  19 . A step  25  facing the valve chamber  22  is formed in the lower communication hole  24 . 
   An upper communication hole  26 , which is communicated with the lower communication hole  24 , extends through the hose connector  20 . The tubing hose T is connected to the hose connector  20 . The upper communication hole  26  is communicated with the intake system of the engine by the tubing hose T. 
   The cylindrical valve body  14  is arranged in the valve chamber  22  and formed integrally from synthetic resin. The valve body  14  moves axially and has a predetermined stroke. The valve body  14  has a lower end, from which a valve flange  27  extends, and an upper end, on which a valve portion  28  is defined. 
   The valve flange  27  slidably contacts the wall surface of the valve chamber  22  at three points to radially support the lower portion of the valve body  14 . The valve flange  27  divides the valve chamber  22  into an upper portion and a lower portion, and the upper portion and the lower portion are communicated with each other through the valve flange  27 . When the valve body  14  is positioned at the lowest end of its stroke, the valve flange  27  closes the valve hole  22   a . In this state, the cross-sectional area of a flow passage defined between the step  25  and the valve portion  28  is maximum. The cross-sectional area of the flow passage becomes smaller as the valve body  14  moves upward. 
   The coil spring  15  is fitted on the valve body  14  and arranged between the step  25  and the valve flange  27 . The coil spring  15  urges the valve body  14  downward and causes the valve flange  27  to close the valve hole  22   a  when an upward force is not applied to the valve body  14 . 
   The negative pressure in the intake system of the engine is communicated to the valve chamber  22  via the lower and upper communication holes  24 ,  26  by the tubing hose T. The valve body  14  moves upward against the urging force of the coil spring  15  in accordance with the negative pressure and opens the valve hole  22   a . In the PCV valve  10 , as the negative pressure increases, the cross-sectional area of the flow passage decreases. This decreases the amount of blowby gas that flow through the valve hole  22   a  toward the intake system. 
   Referring to  FIGS. 6A and 6B , the grommet  12  is cylindrical and formed integrally from synthetic rubber. A grommet flange  29  extends from the basal end (the left end as viewed in  FIG. 6A ) of the grommet  12 . The outer diameter of the grommet  12  decreases from the basal end, in which the flange is formed, to the distal end. That is, a tapered surface  30  is defined on part of the peripheral surface of the grommet  12 . A groove  31  extends between the tapered surface  30  and the grommet flange  29 . The maximum outer diameter of the tapered surface  30  is slightly greater than the inner diameter of the coupling hole  11 . When the grommet  12  is fitted in the coupling hole  11 , it deforms slightly and the diameter of the tapered surface  30  is slightly decreased. The groove  31  has an outer diameter that does not change when the grommet  12  is fitted in the coupling hole  11 . 
   The grommet  12  has a fitting hole (a female screw hole)  32 , in which the fitting portion  18  of the PCV valve  10  is fitted. A female thread  32 A, which is meshed with a male thread  23  of the fitting portion  18 , is formed on the surface of the female screw hole  32 . A pressed portion  33  projects inward into an opening formed at the distal end of the grommet  12 . The inner diameter of the pressed portion  33  is smaller than the root diameter of the male thread  23 . 
   A stopper  34  is formed in the groove  31 . The stopper  34  prevents the grommet  12  from rotating in the coupling hole  11  when the male thread  23  is meshed with the female thread  32 A. 
   Referring to  FIG. 3 , the diameter of the coupling hole  11  is such that the groove  31  of the grommet  12  can be fitted in the coupling bole  11 . A stopper socket (rotation restricting structure)  11   a  is provided in the surface of the cylinder head H adjacent to the coupling hole  11 . The stopper (rotation restricting structure)  34  is received in the coupling hole  11  to restrict the rotation of the grommet  12  in the coupling hole  11 . 
   In the first embodiment, the PCV valve  10  is attached to the head cover H by fitting the grommet  12 , to which the fitting portion  18  is attached, into the coupling hole  11 . 
   Referring to  FIG. 8 , the distal end of the fitting portion  18  forces the pressed portion  33  outward (the direction indicated by arrow A). This radially expands the lower portion of the grommet  12 , When the male thread  23  is meshed with the female thread  32 A, the distal end of the fitting portion  18  presses the pressed portion  33  and expands the grommet  12 . 
   The grommet  12  is coupled to the coupling hole  11  in a state in which its lower portion is radially expanded. The grommet  12  is fixed at a proper position by fitting the groove  31  in the coupling hole  11 . When the grommet  12  is pulled together with the PCV valve  10  from the coupling hole  11 , the expanded lower portion of the grommet  12  prevents the grommet  12  from being removed from the coupling hole  11 . Therefore, the grommet  12  is not pulled out of the coupling hole  11  with the PCV valve  10 . 
   Next, the steps for coupling the PCV valve to the coupling hole  11  will be explained. 
   First, as shown in  FIG. 7A , the male thread  23  of the PCV valve  10  is halfway mated with the female thread  32 A of the grommet  12  to engage the grommet  12  with the fitting portion  18 . In this state, the fitting portion  18  is screwed into the female thread  32 A until the distal end of the fitting portion  18  reaches a position just before the distal end applies force to the pressed portion  33  of the grommet  12  so that the lower portion (the lower portion as viewed in  FIG. 7A ) of the grommet  12  is not radially expanded. 
   Next, referring to  FIG. 7B , the grommet  12 , which is engaged with the fitting portion  18 , is fitted in the coupling hole  11 . In this state, an end surface (the lower end surface in  FIG. 7A ) of the grommet flange  29  contacts the surface of the head cover H and the groove  31  is fitted in the coupling hole  11 . The stopper  34  is engaged with the stopper socket  11   a.    
   Finally, the tabs  21  are rotated to further screw the male thread  23  into the female thread  32 A, as shown in the state of FIG.  3 . In this state, the pressed portion  33  is forced outward by the distal end of the fitting portion  18 . This radially expands the lower portion of the grommet  12 . The expanded grommet  12  is fixed to the coupling hole  11 , and the PCV valve  10  is coupled in the coupling hole  11  by means of the grommet  12 . 
   Alternatively, when the PCV valve  10  is coupled to the grommet  12  after the grommet  12  is engaged with the coupling hole  11 , the male thread  23  of the fitting portion  18  is mated with the female thread  32 A of the grommet  12 . When the male thread  23  is fully mated with the female thread  32 A, the distal end of the fitting portion  18  applies force to the pressed portion  33  and expands the pressed portion  33  outward. 
   When removing the PCV valve  10  from the coupling hole  11 , the tabs  21  are rotated to disengage the male thread  23  from the female screw hole  32  so that the fitting portion  18  does not apply force to the pressed portion  33 . This returns the grommet  12  to the state shown in  FIG. 7B  in which the lower portion of the grommet  12  is not expanded. 
   Next, the PCV valve  10  is removed from the coupling hole  11  with the male thread  23  still halfway mated with the female thread  32 A. The PCV valve  10  is removed from the coupling hole  11  with the grommet  12 , as shown in the state of FIG.  7 A. Alternatively, the male thread  23  may be completely disengaged from the female screw hole  32 . In this state, the PCV valve  10  is removed from the coupling hole  11  with the grommet  12  engaged with the coupling hole  11 . 
   The following advantages are obtained in the PCV valve coupling structure  100  of the first embodiment. 
   (1) The male thread  23 , which is formed on the fitting portion  18  of the PCV valve  10 , is meshed with the female thread  32 A of the grommet  12 . Thus, the PCV valve  10  is engaged with the grommet  12  without requiring a highly accurate fitting allowance. The formation of the female screw hole  32  in the grommet  12  decreases the number of machining steps in comparison to when forming a female screw in the coupling hole  11 . Additionally, the vibration of the internal combustion engine is absorbed by the grommet  12  and the vibration is not transferred directly to the PCV valve  10 . Further, a step for engaging the PCV valve  10  to the grommet  12  is not necessary. 
   (2) The fitting portion  18  engaged with the female screw hole  32  expands the distal end of the grommet  12 . Therefore, the grommet  12  and the PCV valve  10  are securely engaged with the coupling hole  11 . 
   (3) When the grommet  12  is fitted to the coupling hole  11 , the stopper  34  is received in the stopper socket  11   a . Therefore, when the male thread  23  is mated with the female thread  32 A, the grommet  12  does not rotate in the coupling hole  11 . As a result, the PCV valve  10  is easily attached to and detached from the coupling hole  11 . 
   (4) The stopper socket  11   a  is formed adjacent to the coupling hole  11  without extending through the cylinder head H. Thus, the stopper socket  11   a  does not affect the seal of the coupling hole  11 . 
   (5) When the PCV valve  10  is attached to or detached from the coupling hole  11 , the tabs  21  are manually rotated to mate the male thread  23  of the PCV valve  10  and the female thread  32 A of the grommet  12  with an appropriate fastening torque. Therefore, the PCV valve  10  is easily attached to or detached from the coupling hole  11  without using any tools such as a spanner. Further, the fastening torque is easily controlled. 
   (6) The tabs  21  increase the rigidity of the hose connector  20 . Thus, the tabs  21  increase the durability and reliability of the hose connector  20 , which may repeatedly be connected with a hose. 
   (7) The PCV valve  10  must be rotated about its axis when the PCV valve  10  is coupled to and removed from the coupling hole  11 . Thus, the tubing hose T must be removed from the PCV valve  10 . When the PCV valve  10  is removed from the coupling hole  11 , the tubing hose T is also removed from the PCV valve. Therefore, if the engine is operated in such state, the engine speed would abnormally increase such that one would recognize that the PCV valve  10  is not in place. 
     FIG. 9  is a schematic cross-sectional view showing a PCV coupling structure  200  according to a second embodiment of the present invention. The PCV valve coupling structure  200  includes a PCV valve  10  and a grommet  40 . The PCV coupling structure  200  of the second embodiment differs from the coupling structure  100  of the first embodiment only in the grommet. 
   Referring to  FIGS. 10A and 10B , the grommet  40  of the second embodiment is cylindrical and formed integrally from synthetic rubber or synthetic resin. A grommet flange  41  extends from the basal end (the left end in  FIG. 10A ) of the grommet  40 . The diameter of the peripheral surface  40   a  of the grommet  40  is substantially equal to the diameter of the coupling hole  11 . Therefore, when the grommet  40  is fitted in the coupling hole  11 , the diameter of the peripheral surface  40   a  remains substantially the same. 
   The grommet  40  has a mounting hole (a female screw hole)  42  in which the fitting portion  18  of the PCV valve  10  is received. A female thread  42 A, which is meshed with the male thread  23  of the fitting portion  18 , is formed on the inner surface of the female screw hole (mounting hole)  42 . 
   Four equally spaced pressed portions  43  project radially from the inner surface at the distal end of the grommet  40 . The diameter of a circle tangential to the distal ends of the four pressed portions  43  is smaller than the root diameter of the male thread  23 . 
   Further, a stopper  44  is arranged on the peripheral surface  40   a  of the grommet  40  adjacent the grommet flange  41 . When the male thread  23  is mated with the female thread  32 A, the stopper  44  prevents the grommet  40  from rotating in the coupling hole  11 . 
   As shown in  FIG. 11 , the PCV valve  10  is coupled to the head cover H by fitting the grommet  40 , which is attached with the fitting portion  18 , into the coupling hole  11 . 
   Referring to  FIG. 9 , the distal end of the fitting portion  18  forces each of the pressed portions  43  outward (the direction indicated by arrow B) and expands the lower portion of the grommet  40  in the radial direction of the coupling hole  11 . The enlarged grommet  40  is held in the coupling hole  11 . The mating of the male thread  23  with the female thread  32 A enlarges the distal end of the grommet  40  and fixes the PCV valve  10  in the axial direction. 
   Next, the procedure for coupling the PCV valve  10  to the coupling hole  11  will be explained. 
   First, the female thread  42 A is halfway mated with the male thread  23  of the PCV valve  10 . The fitting portion  18  is screwed into the female screw hole  32  until the distal end of the fitting portion  18  reaches a position just before the distal end applies force to the pressed portions  43  of the grommet  40  so that the grommet  12  is not radially expanded. 
   Next, as shown in  FIG. 11 , the grommet  40 , which is attached with the fitting portion  18 , is fitted in the coupling hole  11  so that an end surface of the grommet flange  41  contacts the surface of the head cover H. In this state, the stopper  44  is received in to the stopper socket  11   a.    
   Finally, the PCV valve  10  is rotated to fully mate the male thread  23  and the female thread  42 A, as shown in the state of FIG.  9 . Thus, the distal end of the fitting portion  18  applies outward force to each pressed portion  43  and radially expands the lower portion of the grommet  40 . The expanded grommet  40  is fixed in the coupling hole  11 . This, in turn, fixes the PCV valve  10 , which is attached to the grommet  40 , to the coupling hole  11 . Alternatively, the grommet  40  may first be engaged with the coupling hole  11 , and the male thread  23  of the fitting portion  18  may be mated with the female thread  42 A afterward. 
   To remove the PCV valve  10  from the coupling hole  11 , the operator rotates the PCV valve  10  until the fitting portion  18  does not apply force to the pressed portions  43 . This returns the grommet  40  returns to the state shown in  FIG. 2  in which the lower portion is not expanded, Next, the PCV valve  10 , the male thread  23  of which is halfway mated with the female thread  42 A, is pulled out of the coupling hole  11  together with the grommet  40 . Alternatively, the male thread  23  may be fully disengaged from the female screw hole  42 . In this state, the PCV valve  10  is removed from the coupling hole  11  with the grommet  40  remaining in the coupling hole  11 . 
   The following advantage is obtained in the coupling structure  200  of the PCV valve of the second embodiment in addition to the advantages of the first embodiment. 
   The four pressed portions  43  are equally spaced in the opening of the grommet  40 , and the distal end of the fitting portion  18  applies force to the pressed portion  43  to expand the grommet  40 . Accordingly, the entire circumference in the opening of the grommet  40  does not have to be enlarged. This enables the grommet  40  to be made of synthetic rubber or synthetic resin that is harder and has a longer durability. 
   It should be apparent to those skilled in the art that the present invention may be embodied in many other specific forms without departing from the spirit or scope of the invention. Particularly, it should be understood that the present invention may be embodied in the following forms. 
   The male thread  23  may be formed only on the basal end of the fitting portion  18  and the female threads  32 A,  42 A may be formed only in part of the grommet flanges  29 ,  41 . This facilitates the attachment of the grommet  12  to the PCV valve  10 . Further, this results in forcible removal of the tubing hose T when the PCV valve  10  is coupled and removed. 
   The male thread  23  of the fitting portion  18  and the female thread  32 A of the grommet  12  do not have to be formed. In this case, the fitting portion  18  is fitted halfway in the grommet  12 , to engage the grommet  12  with the fitting portion  18 . Then, the grommet  12  is fully fitted in the coupling hole  11  to expand the grommet  12 . The coupling hole  11  does not necessarily have to be circular and may be, for example, elliptic or square. If the coupling hole  11  is square, the four corners may be curved. 
   The pressed portions  33 ,  43  need not be formed in the female screw holes  32 ,  42  of the grommets  12 ,  40  so that the fitting portion  18  does not expand the grommets  12 ,  40 . 
   The tabs  21  may be replaced by, for example, a hexagonal nut. 
   The main body  13  and the valve body  14  of the PCV valve  10  may be formed from metal or ceramic. 
   The PCV valve may be coupled with to a coupling hole formed in a crank case. 
   Therefore, the present examples and embodiments are to be considered as illustrative and not restrictive, and the invention is not to be limited to the details given herein, but may be modified within the scope and equivalence of the appended claims.