Patent Publication Number: US-2015059179-A1

Title: Structure fixing diaphragm to drive shaft and method for fixing diaphragm to drive shaft

Description:
TECHNICAL FIELD 
     The present invention relates to a structure for fixing and a method for fixing diaphragm to drive shaft for fixing a flexible diaphragm with a base fabric embedded therein to an end of a drive shaft. 
     BACKGROUND ART 
     Conventionally, as an electromagnetic control valve, there exists the one configured to cancel out forces that a differential pressure between a primary chamber and a secondary chamber acts on a valve body of a valve rod by making a differential pressure between a mean pressure chamber communicated with a high-pressure side primary chamber and a low pressure chamber communicated with a low-pressure secondary chamber act on the valve rod via a diaphragm. It is disclosed, for example, in Japanese Patent Laid-Open No. 2011-169415 (Patent Document 1). This electromagnetic control valve is of the type that the valve rod having the valve body is disposed in a valve housing and the valve rod is axially displaced by an electromagnetic force generated by electric conduction to an electromagnetic coil, thereby controlling the opening of a valve port by the above-mentioned valve body. 
     In addition, in this electromagnetic control valve, the primary chamber that communicates with an inlet port and accommodates the valve body is provided on one side of the valve port and the secondary chamber that communicates with an outlet port is provided on the other side of the valve port. Further, the mean pressure chamber that communicates with the primary chamber via a mean pressure passage is provided on the secondary, chamber side to configure so as to act the pressure of the mean pressure chamber on the valve rod via the diaphragm, thereby cancelling the forces acting on the valve body due to the differential pressure between the primary chamber side pressure and the secondary chamber side pressure. 
     Thereby, in this electromagnetic control valve of the pressure balance system, it becomes possible to perform stable flow rate control that a fixed valve opening is maintained at constant current without being affected by the differential pressure between the primary chamber side pressure and the secondary chamber side pressure. 
     CONVENTIONAL DOCUMENT 
     Patent Document 
     
         
         Patent Document 1: Japanese Patent Laid-Open No. 2011-169415 A 
       
    
     DISCLOSURE OF THE INVENTION 
     Problems to be Solved by the Invention 
     However, in the above-mentioned electromagnetic control valve, a through-hole is formed in the center of the diaphragm in order to fix the diaphragm to the end of the valve rod (the drive shaft).  FIG. 10  is a central part schematic enlarged diagram of an essential part of the above-mentioned conventional electromagnetic control valve, an assembling process thereof and the diaphragm. As shown in  FIG. 10(A) , a coupling rod c whose leading end is made tubular is formed on an end of a piston section b in a valve housing a. A diaphragm d is of the type that a base fabric d 1  has been embedded in a rubber layer d 2  and a through hole d 3  is formed in the center. Conventionally, the through hole d 3  in the center of the diaphragm d is made to pass through the coupling rod c of the piston section b, a diaphragm guide e is inserted into the coupling rod c and a lower end of the coupling rod c is swaged to fix the diaphragm d to the piston section b as shown in  FIG. 10(B) . Then, a diaphragm presser f is fitted into a lower end part of the valve housing a and a lower end of the valve housing a is swaged as shown in  FIG. 10(C) . 
     In such a conventional assembling method, there existed such problems as follows. Since the through hole d 3  is made in the center of the diaphragm d in order to fix it to the piston section b, as a result, a through hole d 3 ′ is also made in the base fabric d 1  in the diaphragm d and the base fabric d 1  (fibers thereof) falls into a cut state. In general, in a rubber diaphragm or the like, air-tightness is afforded by the rubber layer d 2  and pressure tightness is afforded by the base fabric d 1 . That is, since the compressive strength of the diaphragm d depends on the strength of the base fabric d 1 , when it is used under a high pressure in a state that the base fabric d 1  is left in the cut state, the rubber layer d 2  stretches by being pressurized and also the base fabric d 1  is pulled, when the base fabric d 1  slips out of the rubber layer d 2  on a part that has been cut with the through hole d 3 , the pressure tightness of the diaphragm d is remarkably reduced, and when the diaphragm d is damaged, it becomes impossible to cancel out the forces acting on the valve body due to the differential pressure between the primary chamber side pressure and the secondary chamber side pressure. 
     The present invention has been made in order to solve the problems as mentioned above and sets it as a subject to improve the pressure tightness and the durability of the diaphragm in the electromagnetic control valve that the structure for fixing the diaphragm to the drive shaft is improved so as to cancel out the forces acting on the valve body due to the differential pressure, for example, by using the diaphragm. 
     Means for Solving the Problems 
     A structure for fixing diaphragm to drive shaft of an aspect is the structure for fixing diaphragm to drive shaft for fixing a flexible diaphragm with base fabric embedded therein to a drive shaft, including a diaphragm guide that nips and holds the aforementioned diaphragm together with the aforementioned drive shaft, wherein a needle-shaped projection is formed on one of the aforementioned drive shaft and the aforementioned diaphragm guide, an insertion hole into which the needle-shaped projection is to be inserted is formed in the other, the center of the aforementioned diaphragm is stuck on the aforementioned needle-shaped projection so as to make the needle-shaped projection pass through the diaphragm, and the needle-shaped projection and the aforementioned insertion hole are firmly fixed together to fix the aforementioned diaphragm to the aforementioned drive shaft. 
     Preferably, a structure for fixing diaphragm to drive shaft is the structure for fixing diaphragm to drive shaft, wherein the aforementioned needle-shaped projection is formed on the aforementioned drive shaft, the aforementioned insertion hole is formed in the aforementioned diaphragm, the aforementioned needle-shaped projection is inserted into the aforementioned insertion hole and a leading end of the aforementioned needle-shaped projection is welded so as to firmly fix together the aforementioned needle-shaped projection and the aforementioned insertion hole. 
     Preferably, a structure for fixing diaphragm to drive shaft is the structure for fixing diaphragm to drive shaft, wherein the aforementioned needle-shaped projection is formed on the aforementioned diaphragm guide, the aforementioned insertion hole is formed in the aforementioned drive shaft, and the aforementioned needle-shaped projection and the insertion hole are firmly fixed together by press-fitting the aforementioned needle-shaped projection into the aforementioned insertion hole. 
     A method for fixing diaphragm to drive shaft of another aspect is a method for fixing diaphragm to drive shaft for fixing a flexible diaphragm with base fabric embedded therein to a drive shaft, includes the steps of using a diaphragm guide that nips and holds the aforementioned diaphragm together with the aforementioned drive shaft, forming a needle-shaped projection on one of the aforementioned drive shaft and the aforementioned diaphragm guide and forming an insertion hole into which the needle-shaped projection is to be inserted in the other and sticking the center of the aforementioned diaphragm on the aforementioned needle-shaped projection to make the needle-shaped projection pass through the diaphragm, and firmly fixing together the needle-shaped projection and the aforementioned insertion hole so as to fix the aforementioned diaphragm to the aforementioned drive shaft. 
     Preferably, a method for fixing diaphragm to drive shaft is the method for fixing diaphragm to drive shaft, wherein the aforementioned needle-shaped projection is formed on the aforementioned drive shaft, a needle-shaped cap on a leading end part of the needle-shaped projection is made removable, the aforementioned insertion hole is formed in the aforementioned diaphragm guide, and the center of the diaphragm is stuck on the aforementioned needle-shaped cap of the aforementioned needle-shaped projection so as to make the needle-shaped projection pass through the diaphragm. 
     Preferably, a method for fixing diaphragm to drive shaft is the method for fixing diaphragm to drive shaft, wherein after the aforementioned needle-shaped projection has been made to path through the aforementioned diaphragm, the aforementioned needle-shaped cap of the aforementioned needle-shaped projection is inserted into the insertion hole in the aforementioned diaphragm guide, the needle-shaped cap is removed, and a leading end of the aforementioned needle-shaped projection from which the needle-shaped cap has been removed is swaged or welded so as to firmly fix together the needle-shaped projection and the aforementioned insertion hole. 
     Advantages of the Invention 
     According to the structure for fixing diaphragm to drive shaft, even when the diaphragm is stuck on the needle-shaped projection, the needle-shaped projection simply passes through a gap between fibers of the base fabric, a hole such as a through hole is not formed in the base fabric and the base fabric (the fibers thereof) is not cut. Accordingly, the pressure tightness and the durability of the diaphragm can be improved. 
     According to the structure for fixing diaphragm to drive shaft, the needle-shaped projection and the diaphragm guide can be firmly fixed, together strongly by welding in addition to the aforementioned effect. 
     According to the structure for fixing diaphragm to drive shaft, since the diaphragm guide needs only to be press-fitted to the drive Shaft side, assembling work is facilitated in addition to the aforementioned effect. In addition, the diaphragm fixing structure can be made strong by making the needle-shaped projection of the diaphragm guide thick. 
     According to the method for fixing diaphragm to drive shaft, the same effect as that aforementioned can be obtained. 
     According to the method for fixing diagram to drive shaft, the same effect as that aforementioned can be obtained and the diaphragm fixing structure can be made strong by making the needle-shaped projection thick. 
     According to the method for fixing diaphragm to drive shaft, since the needle-shaped cap is present when the diaphragm guide is to be inserted into the needle-shaped projection, an effect that the diaphragm guide is readily inserted can be obtained in addition to the aforementioned effect. In addition, since swaging or welding is performed by removing the needle-shaped cap, swaging and welding can be readily performed while making the diaphragm fixing structure strong by making the needle-shaped projection thick. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a longitudinal sectional diagram of a valve closed state of an electromagnetic control valve of a first embodiment to which the present invention has been applied; 
         FIG. 2A  is a sectional diagram and a schematic plan view before a diaphragm is fixed in an embodiment to which the present invention has been applied; 
         FIG. 2B  is a sectional diagram and a schematic plan view before a diaphragm is fixed in an embodiment to which the present invention has been applied; 
         FIG. 3A  is diagrams explaining a state of passing a needle-shaped projection through the diaphragm in the embodiment to which the present invention has been applied; 
         FIG. 3B  is diagrams explaining a state of passing a needle-shaped projection through the diaphragm in the embodiment to which the present invention has been applied; 
         FIG. 4A  is diagrams explaining an assembling process of an essential part of the electromagnetic control valve of the first embodiment to which the present invention has been applied; 
         FIG. 4B  is diagrams explaining an assembling process of an essential part of the electromagnetic control valve of the first embodiment to which the present invention has been applied; 
         FIG. 4C  is diagrams explaining an assembling process of an essential part of the electromagnetic control valve of the first embodiment to which the present invention has been applied; 
         FIG. 5  is a longitudinal sectional diagram of a valve closed state of an electromagnetic control valve of a second embodiment to which the present invention has been applied; 
         FIG. 6  is a longitudinal sectional diagram of a valve closed state of an electromagnetic control valve of a third embodiment to which the present invention has been applied; 
         FIG. 7A  is a sectional diagram and a schematic plan view before a diaphragm is fixed in the third embodiment to which the present invention has been applied; 
         FIG. 7B  is a sectional diagram and a schematic plan view before a diaphragm is fixed in the third embodiment to which the present invention has been applied; 
         FIG. 8A  is diagrams explaining an assembling process of an essential part of the electromagnetic control valve of the third embodiment to which the present invention has been applied; 
         FIG. 8B  is diagrams explaining an assembling process of an essential part of the electromagnetic control valve of the third embodiment to which the present invention has been applied; 
         FIG. 8C  is diagrams explaining an assembling process of an essential part of the electromagnetic control valve of the third embodiment to which the present invention has been applied; 
         FIG. 9  is a longitudinal sectional diagram of a valve closed state of an electromagnetic control valve of a fourth embodiment to which the present invention has been applied; 
         FIG. 10A  is a central part schematic enlarged diagram of an essential part of a conventional electromagnetic control valve, an assembling process thereof and a diaphragm thereof; 
         FIG. 10B  is a central part schematic enlarged diagram of an essential part of a conventional electromagnetic control valve, an assembling process thereof and a diaphragm thereof; and 
         FIG. 10C  is a central part schematic enlarged diagram of an essential part of a conventional electromagnetic control valve, an assembling process thereof and a diaphragm thereof. 
     
    
    
     MODE FOR CARRYING OUT THE INVENTION 
     Next, embodiments of the present invention will be described.  FIG. 1  is a longitudinal sectional diagram of a valve closed state of an electromagnetic control valve of a first embodiment to which the present invention has been applied. Although an electromagnetic control valve  10  of this embodiment is provided in pining of a fuel cell system, a fluid that flows through the piping of this fuel cell system is high in pressure and drastic in pressure fluctuation. The electromagnetic control valve  10  of this embodiment has a valve housing  1 . The valve housing  1  has a high-pressure side inlet port  1   a  through which the fluid flows in, a low-pressure side outlet port  1   b  through which the fluid flows out, a primary chamber  11  that communicates with the inlet port  1   a , a secondary chamber  12  that communicates with the outlet port  1   b  and a valve port  13  that communicates the primary chamber  11  with the secondary chamber  12 . The valve port  13  is circular in a horizontal sectional shape and a ring-shaped valve seat member  14  is disposed in its primary chamber  11  side opening. 
     A valve rod  2  as a “drive shaft” that is displaceable in a direction along an axial line L extends in the primary chamber  11 , the secondary chamber  12  and the valve port  13 . The valve rod  2  has a columnar valve body  21  that is located in the primary chamber  11  and is made touchable and releasable relative to the valve seat member  14 , a coupling rod  22  disposed to extend downward of the valve body  21 , a piston section  23  coupled to the valve body  21  by the coupling rod  22  and a coupling rod  24  disposed to extend upward of the valve body  21 . Incidentally, the valve seat member  14  may be eliminated so as to let only the primary chamber side opening in the valve port  13  remain as it is and a seal member that is equal to the valve seat member  14  may be provided around a lower end of the valve body  21 . 
     The valve body  21  sets the opening of the valve port  13  from a positional relationship with the valve seat member  14  determined by displacement in the direction along the axial line L of the valve rod  2 . The pressure of the primary chamber  11  is higher than the pressure of the secondary chamber  12 , the differential pressure between the pressure of this primary chamber  11  and the pressure of the secondary chamber  12  acts on the valve body  21  and the valve body  21  receives the force in a valve closing direction. The force that this differential pressure acts on the valve body  21  is determined by an inner diameter (an effective pressure receiving diameter of the valve body  21 ) of the valve port  13 . 
     A mean pressure chamber  15  is formed on a lower end of the valve housing  1  and this mean pressure chamber  15  is communicated with the primary chamber  11  through the inlet port  1   a  via a mean pressure guide path  16  formed in a not shown housing. A pressure balance part  17  is configured in the mean pressure chamber  15 . This pressure balance part  17  has a communication hole  17   a  formed in the valve housing  1 , a low pressure chamber  17   b  communicated with the secondary chamber  12  through the communication hole  17   a  and a rubber diaphragm  3  that is disposed by fitting into a space between the low pressure chamber  17   b  and the mean pressure chamber  15  side and a base fabric  3 A of which is embedded in a rubber layer  3 B. Incidentally, the diaphragm  3  has a convolution part  31  and this convolution part  31  is a rotor rotating around the axial line L and is swelled into the low pressure chamber  17   b  on the outer periphery of the piston section  23 . In addition, the diaphragm  3  has a columnar boss part  32  and a concave part  32   a  into which a later described needle-shaped projection  231  is to be buried is formed in the center of this boss part  32 . 
     The piston section  23  of the valve rod  2  is inserted into the communication hole  17   a  not in contact with the communication hole  17   a . The needle-shaped projection  231  is formed on a lower end of the piston section  23 . In addition, an insertion hole  17   c   1  into which the needle-shaped projection  231  is to be inserted is formed in a diaphragm guide  17   c  that nips and holds the diaphragm  3  together with the piston section  23 . Then, the needle-shaped projection  231  of the piston section  23  passes through the center of the concave part  32   a  in the diaphragm  3  and the diaphragm guide  17   c  is fitted on this needle-shaped projection  231  through the insertion hole  17   c   1 . Then, the boss part  32  of the diaphragm  3  is nipped by the diaphragm guide  17   c  and the piston section  23  and the diaphragm  3  is firmly fixed to the piston section  23  by spot-welding a leading end of the needle-shaped projection  231 . In addition, the diaphragm presser  17   d  is fitted into the lower end part of the valve housing  1  and the diaphragm presser  17   d  and the diaphragm  3  are fixed together by swaging the lower end of the valve housing  1 . The diaphragm  3  has flexibility and transmits the force that has been generated by the differential pressure between the primary chamber pressure and the secondary chamber pressure and acts on the mean pressure chamber  15  to the valve rod  2 . 
     An electromagnetic drive part  4  is provided on (the primary chamber  11  side) the valve housing  1 . The electromagnetic drive part  4  is provided with a cylindrical plunger tube  40 , an attracter  42  that is made of a magnetic material fixed to an upper end of the plunger tube  40  and an electromagnetic coil  43  that is arranged on the outer periphery of the plunger tube  40  and a winding of which is wound on a bobbin  43   a . Incidentally, the plunger tube  40  and the attracter  42  are fixed together by welding and so forth. The plunger  5  is disposed in the plunger tube  40  and a plunger spring  5   b  is disposed between the plunger  5  and the valve body  21 . Incidentally, the plunger  5  is made of a magnetic material and others of the plunger  5  except an air vent  53  are shaped to be rotationally symmetric respectively centering on the axial line L. Insertion holes  41 ,  51  that are coaxial with the axial line L are respectively formed in the attracter  42  and the plunger  5 . Then, the coupling rod  24  of the valve rod  2  is inserted into the insertion hole  51  in the plunger  5  and a tubular retaining member  7  that is made of a non-magnetic material is fitted on an end of the coupling rod  24  in the insertion hole  41  in the attracter  42 . This retaining member  7  and the end of the coupling rod  24  are firmly fixed together by welding. The retaining member  7  has a flange-like part  71  on an end on the plunger  5  side and this flange-like part  71  is located between this counter-face surface  5   a  and a counter-face surface  4   a  of the attractor  42  on the plunger  5  side in a state that it is in contact with the counter-face surface  5   a  of the plunger  5  on the attracter  42  side. 
     The plunger spring  5   b  is disposed in a compressed state that one end is brought into abutment on an inner-side bottom face  52  of the plunger  5  and the other end is brought into abutment on a spring bearing part  21   a  that is an end face of the valve body  21  on the plunger  5  side. Thereby, the plunger  5  is brought to a state that the counter-face surface  5   a  always abuts on the retaining member  7  (the flange-like part  71  thereof) and when this plunger  5  is attracted in a direction of the attracter  42 , the valve rod  2  displaces in a valve opening direction together with this plunger  5 . A clearance between the insertion hole  51  in the plunger  5  and the coupling rod  24  of the valve rod  2  is set larger than a clearance between the plunger  5  and the plunger tube  40 , and even when the plunger  5  displaces in a direction orthogonal to the axial line L, the valve rod  2  and the plunger  5  do not come into contact with each other. 
     A hole for adjustment part  42   a  that is larger in diameter than the insertion hole  41  is formed in the attracter  42  and a setting adjustment part  8  is disposed in this hole for adjustment part  42   a . This setting adjustment part  8  has an adjusting screw  81 , a spring bearing  82 , an adjusting spring  83  and a ball  84 . The adjusting spring  83  is disposed between the adjusting screw  81  and the spring bearing  82  in a compressed state and the ball  84  is disposed in the insertion hole  41  in the attracter  42  in a state that it abuts on the spring bearing  82 . Then, the adjusting spring  83  is actuating the ball  84  so as to come into abutment on an upper end of the retaining member  7  via the spring bearing  82 . In addition, the adjusting screw  81  is attached to the attracter  42  by screwing a male screw  811  on its outer periphery into a female screw  42   b  formed in an upper inner peripheral surface of the attracter  42 . 
     A slight clearance is provided between the ball  84  and the insertion hole  41  in the attracter  42  and thus the ball  84  can displace in the insertion hole  41  along the axial line L. In addition, a cylindrical part  72  that is in the form of a thin cylindrical shape is formed on the ball  84  side end of the retaining member  7  and this cylindrical part  72  is brought into spherical contact with the ball  84 . Thereby, an upper end of the retaining member  7  (and the valve rod  2 ) is always positioned on the axial line L. 
     A magnetic circuit is formed by electric conduction to the electromagnetic coil  43  of the electromagnetic drive part  4  and a magnetic attraction force is generated between the attractor  42  and the plunger  5 . This attraction force becomes the one corresponding to an electric current to be conducted to the electromagnetic coil  43 . 
     The electromagnetic control valve of the embodiment works as follows by the foregoing configuration. The setting adjustment part  8  actuates the valve rod  2  to the valve seat part  14  side by the adjusting spring  83  via the spring bearing  82 , the ball  84  and the retaining member  7 . The plunger  5  is attracted to the attractor  42  by exciting the electromagnetic coil  43 , the valve rod  2  displaces in a direction separated from the valve seat member  14  against an actuating force of the adjusting spring  83  to shift from valve closing to valve opening and the opening of the valve port  13  is controlled in accordance with a positional relationship between the valve body  21  and the valve seat member  14  in a direction along the axial line L. Incidentally, the one that the plunger  5  is at the uppermost end position and the valve opening turns to be fully open is the position that the flange-like part  71  of the retaining member  7  has abutted on the counter-face surface  4   a  of the attractor  42 . The flange-like part  71  plays the part of a stopper in this way and, thereby, prevents the plunger  5  from being sucked (tightly adhered) to the attractor  42 . 
     In addition, the valve body  21  sits on the valve seat member  14  and shifts to valve closing by eliminating excitation of the magnetic coil  43 . Incidentally, the actuating force that the adjusting spring  83  applies to the valve rod  2  is adjusted by a run-on amount of the adjusting screw  81  and an electromagnetic force (the attraction force) required for valve opening can be adjusted. The valve rod  2  displaces in the direction along the axial line L in accordance with an equilibrium relationship between the electromagnetic force that the electromagnetic coil  43  generates and the spring force of the adjusting spring  83  in this way and the opening of the valve port  13  is changed by the valve body  21 . 
     In addition, the differential pressure between the pressure of the primary chamber  11  and the pressure of the secondary chamber  12  acts on the valve body  21  as described above and the force is applied in a valve closing direction. On the other hand, since the mean pressure chamber  15  is communicated with the primary chamber  11  via the mean pressure guide path  16 , the differential pressure between the primary chamber side pressure that acts on the mean pressure chamber  15  and the secondary chamber side pressure that acts on the low pressure chamber  17   b  acts on the diaphragm  3  and the force in a valve opening direction is applied to the piston section  23  of the valve rod  2 . Then, since the inner diameter (the effective pressure receiving diameter of the valve body  21 ) of the valve port  13  and the effective pressure receiving diameter of the diaphragm  3  when valve closing that the valve body  21  has sat on the valve seat member  14  are equal to each other, the forces by the differential pressure mutually cancel out for the valve rod  2  and when the valve body  21  is separated from the valve seat member  14 , it is not affected by the differential pressure. 
       FIGS. 2A and 28  are each a sectional diagram and a schematic plan view before the diaphragm  3  is fixed to the valve rod  2 . This diaphragm  3  is of the type that the base fabric  3 A has been embedded in the rubber layer  3 B and a through hole as in the prior art is not formed in the center. Incidentally, although  FIG. 2B  schematically shows yarns of the base fabric  3  with lines, the base fabric  3  is flat-knitted as shown in  FIGS. 3A and 3B  and fibers (the yarns) are densely knitted. 
       FIGS. 4A to 4C  are diagrams explaining an assembling process of an essential part of the electromagnetic control valve of the first embodiment and fixing of the diaphragm  3  and the valve rod  2 , is performed as follows. As shown in  FIG. 4A , the center of the diaphragm  3  is stuck on the needle-shaped projection  231  formed on the lower end of the piston section  23  to make the needle-shaped projection  231  pass through the diaphragm  3 . In addition, the diaphragm guide  17   c  is inserted into the needle-shaped projection  231  through its insertion hole  17   c   1 . Then, the needle-shaped projection  231  and the diaphragm guide  17   c  are firmly fixed together by spot-welding the leading end of the needle-shaped projection  231  to nip and hold the diaphragm  3  together with the piston section  23  (the valve rod  2 ). In addition, the diaphragm presser  17   d  is fitted into the lower end part of the valve housing  1  and the diaphragm presser  17   d  and the diaphragm  3  are fixed together by swaging the lower end of the valve housing  1  as in  FIG. 4C . 
     Since the diaphragm  3  is held by sticking the diaphragm  3  on the needle-shaped projection  231  in this way, the base fabric  3 A of the diaphragm  3  is not cut. For example, even in a case where the needle-shaped projection  231  has stuck into between the yarns of the base fabric  3 A as shown in  FIG. 3A , and even in a case where the needle-shaped projection  231  has stuck to the yarn of the base fabric  3 A as shown in  FIG. 3B , the base fabric  3 A is not cut in either case. Therefore, the pressure tightness and the durability of the diaphragm  3  are improved. 
       FIG. 5  is a longitudinal sectional diagram of a valve closed state of an electromagnetic control valve of a second embodiment to which the present invention has been applied and in the following respective embodiments, the same numerals as those in  FIG. 1  are assigned to the same elements as those in the first embodiment and detailed description thereof is omitted. This second embodiment is of the type that a needle-shaped projection  17   c   2  has been formed on the diaphragm guide  17   c  and an insertion hole  232  into which the needle-shaped projection  17   c   2  is to be inserted has been formed in the piston section  23 . Also in this second embodiment, the needle-shaped projection  17   c   2  is stuck into the center of the diaphragm  3  to make the needle-shaped projection  17   c   2  pass through the diaphragm  3 . Then, the diaphragm  3  is nipped by press-fitting the diaphragm guide  17   c  (the needle-shaped projection  17   c   2 ) into the insertion hole  232  in the piston section  23  and thereby the diaphragm  3  is nipped and held by the diaphragm guide  17   c  together with the piston section  23  (the valve rod  2 ). The outer diameter of the needle-shaped projection  17   c   2  before assembled is made slightly larger than the inner diameter of the insertion hole  232  and the diaphragm guide  17   c  and the piston section  23  are firmly fixed together by press-fitting. Also in this second embodiment, that the pressure tightness and the durability of the diaphragm  3  are improved is the same as that in the first embodiment. 
       FIG. 6  is a longitudinal sectional diagram of a valve closed state of an electromagnetic control valve of a third embodiment to which the present invention has been applied.  FIGS. 7A and 7B  are each a sectional diagram and a schematic plan view before fixing the diaphragm in the third embodiment. In the diaphragm  3  of this third embodiment, a concave part  32   b  that is larger in diameter than the concave part  32   a  in the first embodiment is formed in the boss part  32 . In addition, a needle-shaped projection  233  that is larger in diameter (thicker) than the needle-shaped projection  231  in the first embodiment is formed on the lower end of the piston section  23 . Further, an insertion hole  17   c   3  that is larger in diameter than the insertion hole  17   c   1  in the first embodiment is formed in the diaphragm guide  17   c . Then, the needle-shaped projection (a part thereof)  233  passes through the center of the concave part  32   b  in the diaphragm  3  and the diaphragm guide  17   c  is fitted on this needle-shaped projection  233  through the insertion hole  17   c   3 . Then, the boss part  32  of the diaphragm  3  is nipped by the diaphragm guide  17   c  and the piston section  23  and the diaphragm  3  is firmly fixed to the piston section by swaging the leading end of the needle-shaped projection  233 . 
       FIGS. 8A to 8C  are diagrams explaining an assembling process of an essential part of the electromagnetic control valve of the third embodiment and fixing of the diaphragm.  3  and the valve rod  2  as the “drive shaft” is performed as follows. As shown in  FIG. 8A , a needle-shaped cap  233   b  is fitted into a swaging hole  233   a  in an end of the needle-shaped projection  233  of the piston section  23  as one part of the needle-shaped projection before assembled. The center of the diaphragm  3  is stuck on this needle-shaped cap  233   b  and the needle-shaped projection  233  to make the needle-shaped cap  233   b  and the needle-shaped projection  233  pass through the diaphragm  3 . As shown in  FIG. 83 , the diaphragm guide  17   c  is inserted into the needle-shaped cap  233   b  and the needle-shaped projection  233  through its insertion hole  17   c   3 . Then, as shown in  FIG. 8C , the needle-shaped cap  233   b  is removed and the needle-shaped projection  233  and the diaphragm guide  17   c  are firmly fixed together by swaging a part of the swaging hole  233   a  in the needle-shaped projection  233  outward to nip and hold the diaphragm  3  together with the piston section  23  (the valve rod  2 ). In addition, the diaphragm presser  17   d  is fitted into the lower end part of the valve housing  1  and the diaphragm presser  17   d  and the diaphragm  3  are fixed together by swaging the lower end of the valve housing  1 . Incidentally, they may be fixed together by welding the part of the swaging hole  233   a  in the needle-shaped projection  233 . 
     Since the diaphragm  3  is held by sticking the diaphragm  3  on the needle-shaped cap  233   b  and the needle-shaped projection  233  in this way, the base fabric  3 A of the diaphragm  3  is not cut even by the needle-shaped projection  233  that is thick in diameter. This is the same as that in the aforementioned embodiment described in  FIG. 3  and the pressure tightness and the durability of the diaphragm are improved. 
     In addition, in this third embodiment, since the needle-shaped projection  233  is made thicker than the needle-shaped projection  231  of the first embodiment, the fixing structure for the diaphragm  3  becomes strong and high durability is obtained, for example, even in a case where it is used under a high pressure. Incidentally, since in a case where the needle-shaped cap  233   a  and a thick needle-shaped projection such as the needle-shaped projection  233  are to be applied, the amount that it protrudes from the insertion hole  17   c   3  in the diaphragm guide  17   c  is increased accordingly, as it stands, swaging and welding will be difficult, however, since the needle-shaped cap  233   b  is configured to be removable in this third embodiment, swaging and welding can be readily performed. Further, since in the third embodiment, the swaging hole  233   a  in the needle-shaped projection  233  is utilized for attachment of the needle-shaped cap  233   b , attaching and detaching of the needle-shaped cap  233   b  are facilitated. 
       FIG. 9  is a longitudinal sectional diagram of a valve closed state of an electromagnetic control valve in a fourth embodiment to which the present invention has been applied and this fourth embodiment is of the type that a needle-shaped projection  17   c   4  that is larger (thicker) in diameter than the needle-shaped projection  17   c   2  in the second embodiment has been formed on the diaphragm guide  17   c  and an insertion hole  234  into which the needle-shaped projection  17   c   4  is to be inserted and that is larger in diameter than the insertion hole  232  in the second embodiment has been formed in the piston section  23 . Also in this fourth embodiment, the needle-shaped projection  17   c   4  is stuck into the center of the diaphragm  3  to make the needle-shaped projection  17   c   4  pass through the diaphragm  3 . Then, the diaphragm  3  is nipped by press-fitting the diaphragm guide  17   c  (the needle-shaped projection  17   c   4 ) into the insertion hole  234  in the piston section  23 , thereby nipping and holding the diaphragm  3  by the diaphragm guide  17   c  together with the piston section  23  (the valve rod  2 ). The outer diameter of the needle-shaped projection  17   c   4  before assembled is made slightly larger than the inner diameter of the insertion hole  234  and the diaphragm guide  17   c  and the piston section  23  are firmly fixed together by press fitting. Also in the fourth embodiment, that the pressure tightness and the durability of the diaphragm  3  are improved is the same as that in the aforementioned embodiments. 
     Further, in the fourth embodiment, since the needle-shaped projection  17   c   4  is made thicker than the needle-shaped projection  17   c   2  of the second embodiment, the fixing structure for the diaphragm  3  becomes strong and the high durability is obtained, for example, even in a case where it is used under the high pressure. 
     Although, in the foregoing, detailed description has been made on the embodiments of the present invention with reference to the drawings, the concrete configuration is not limited to these embodiments and even when there exist design changes and so forth in a range not deviating from the gist of the present invention, they are included in the present invention. The drive shaft is not limited to the valve rod and it can be also applied to other devices and other structures as long as it is of the type of fixing the diaphragm to the drive shaft that is moved in the axial direction and the high pressure tightness and durability of the diaphragm can be obtained. 
     DESCRIPTION OF REFERENCE NUMERALS 
     
         
         
           
               1 : Valve housing 
               11 : Primary chamber 
               12 : Secondary chamber 
               13 : Valve port 
               15 : Mean pressure chamber 
               16 : Mean pressure guide path 
               17 : Pressure balance part 
               17   a : Communication hole 
               17   b : Low pressure chamber 
               17   c : Diaphragm guide 
               17   c   1 : Insertion hole 
               17   d : Diaphragm presser 
               2 : Valve rod (Drive shaft) 
               21 : Valve body 
               22 : Coupling rod 
               23 : Piston section 
               231 : Needle-shaped projection 
               3 : Diaphragm 
               3 A: Base fabric 
               3 B: Rubber layer 
               17   c   2 : Needle-shaped projection 
               232 : Insertion hole 
               17   c   3 : Insertion hole 
               233 : Needle-shaped projection 
               233   b : Needle-shaped cap 
               17   c   4 : Needle-shaped projection 
               234 : Insertion hole 
               4 : Electromagnetic drive part