Abstract:
A coupling structure for a piston used in a fluid-pressure cylinder. The piston in the fluid-pressure cylinder includes a piston hole that runs through a central part of the piston in an axial direction thereof. One end of a piston rod and a coupling body coupled to the one end are inserted into the piston hole. The coupling body includes: a main part that contacts the one end of the piston rod; and an angled part formed around the main part and inclined at a prescribed angle with respect thereto. When the coupling body is subjected to pressure inside the piston hole, the diameter of the coupling body increases and a pointed edge of the angled part engages with an inner surface of the piston hole such that the coupling body couples the piston and the piston rod.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a coupling structure and a coupling method for a piston, for connecting the piston and a piston rod, which are used in a fluid pressure cylinder that displaces the piston along the interior of a cylinder main body under the supply of a pressure fluid. 
       BACKGROUND ART 
       [0002]    Heretofore, as means for transporting workpieces, for example, a fluid pressure cylinder has been used having a piston displaced upon supply of a pressure fluid. With such a fluid pressure cylinder, for example, as disclosed in Japanese Patent No. 4067509, a piston is disposed displaceably in a cylinder chamber, which is defined in the interior of a cylindrically shaped cylinder main body. In addition, a piston rod is inserted into a hole of the piston, and paired engagement rings are plastically deformed between an annular groove formed on an outer circumferential surface of the piston rod and an annular groove formed on an inner circumferential surface of the piston hole, whereby the piston and the piston rod are connected together mutually. 
       SUMMARY OF THE INVENTION 
       [0003]    However, since coupling is performed through engagement of the engagement rings, it is necessary to machine an annular groove on the inner circumferential surface of the piston hole, and similarly, it is necessary to machine an annular groove on the outer circumferential surface of the piston rod, so that the number of manufacturing steps including machining of the grooves is increased, leading to a rise in manufacturing costs. 
         [0004]    Further, with the aforementioned fluid pressure cylinder, the piston abuts against a wall surface of the cylinder main body at an end position where the piston is displaced, whereupon shocks are applied with respect to the piston. For buffering such shocks, ordinarily, shock absorbing means such as dampers or the like, which are capable of absorbing shocks, are disposed on both ends of the piston. However, in this case, the number of parts is increased due to the provision of the shock absorbing means, together with increasing the number of assembly steps. 
         [0005]    On the other hand, a demand exists in the art to decrease material costs by reducing the weight of the piston, and to reduce the consumption amount of air that is supplied to the fluid pressure cylinder. 
         [0006]    A general object of the present invention is to provide a coupling structure and a coupling method for a piston, for coupling a piston that is used in a fluid pressure cylinder, which is capable of absorbing loads applied in an axial direction to the piston, together with reducing weight and manufacturing costs for the fluid pressure cylinder along with a simple structure. 
         [0007]    The present invention is characterized by a coupling structure for a piston used in a fluid pressure cylinder, the fluid pressure cylinder comprising a cylinder main body to which a pressure fluid is introduced to an interior thereof, a piston disposed displaceably in the interior of the cylinder main body, and a piston rod connected to the piston, the coupling structure being adapted to couple the piston with respect to the piston rod, 
         [0008]    wherein a hole is formed in a center portion of the piston, the hole extending in an axial direction with a diameter larger than an outside diameter of the piston rod, and between the piston and the piston rod, a coupling member, which is elastically deformable and is greater in diameter than the outside diameter of the piston rod, is provided for coupling the piston and the piston rod. 
         [0009]    According to the present invention, a coupling member, which is elastically deformable and is larger in diameter than the outside diameter of the piston rod, is disposed between the piston and the piston rod, whereby the piston and the piston rod are connected by the coupling member. Accordingly, in a fluid pressure cylinder including the piston, for example, when the piston is displaced and comes into abutment against the cylinder main body at the displacement end position, shocks (loads) applied to the piston are absorbed suitably by elastic deformation of the coupling member, and transmission of such shocks to the piston rod can reliably be prevented. 
         [0010]    As a result, for absorbing the aforementioned shocks, there is no need to provide a separate shock absorbing means for absorbing the shocks to the cylinder body or the piston, and with a simple structure including placement of the coupling member between the piston and the piston rod, the number of parts in the fluid pressure cylinder, manufacturing costs, and the number of assembly steps for manufacturing the fluid pressure cylinder can be reduced. 
         [0011]    Further, compared to the conventional fluid pressure cylinder in which the outside diameter of the piston rod is substantially equivalent with an inside diameter of the hole, since the hole of the piston is formed with a greater diameter than the outside diameter of the piston rod, the piston can be made lighter in weight, while simultaneously, material costs can be reduced and the load weight of workpieces transported via the piston rod can be increased. 
         [0012]    Next, with reference to the accompanying drawings, a preferred embodiment of the present invention will be described, and the aforementioned objects, along with other objects, characteristics and advantages of the present invention, will be made clear. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0013]      FIG. 1  is an overall cross sectional view of a fluid pressure cylinder to which a coupling structure and a coupling method for a piston according to an embodiment of the present invention are applied; 
           [0014]      FIG. 2  is an enlarged cross sectional view showing a vicinity of the piston shown in  FIG. 1 ; 
           [0015]      FIG. 3A  is a cross sectional view showing a condition prior to connecting a coupling body to a piston rod; 
           [0016]      FIG. 3B  is a cross sectional view showing a condition in which a coupling body is connected by welding to a piston rod; 
           [0017]      FIG. 3C  is a cross sectional view showing a condition in which the coupling body shown in  FIG. 3B  and a portion of the coupling body are inserted into a piston hole of the piston; 
           [0018]      FIG. 3D  is a cross sectional view showing a connected state of the piston and the piston rod, in which the coupling body is fastened by caulking with respect to the piston; 
           [0019]      FIG. 4A  is an enlarged cross sectional view showing a vicinity of the piston of a fluid pressure cylinder to which the coupling structure for a piston according to a first modified example is applied; 
           [0020]      FIG. 4B  is an enlarged cross sectional view showing a vicinity of the piston of a fluid pressure cylinder to which the coupling structure for a piston according to a second modified example is applied; 
           [0021]      FIG. 5A  is an enlarged cross sectional view showing a vicinity of the piston of a fluid pressure cylinder to which the coupling structure for a piston according to a third modified example is applied; 
           [0022]      FIG. 5B  is an enlarged cross sectional view showing a vicinity of the piston of a fluid pressure cylinder to which the coupling structure for a piston according to a fourth modified example is applied; 
           [0023]      FIG. 6A  is an enlarged cross sectional view showing a vicinity of the piston of a fluid pressure cylinder to which the coupling structure for a piston according to a fifth modified example is applied; 
           [0024]      FIG. 6B  is an enlarged cross sectional view showing a vicinity of the piston of a fluid pressure cylinder to which the coupling structure for a piston according to a sixth modified example is applied; 
           [0025]      FIG. 7A  is an enlarged cross sectional view showing a vicinity of the piston of a fluid pressure cylinder to which the coupling structure for a piston according to a seventh modified example is applied; 
           [0026]      FIG. 7B  is an exploded cross sectional view of the piston and the coupling body of  FIG. 7A ; 
           [0027]      FIG. 7C  is an enlarged cross sectional view showing a modification of the coupling structure of  FIG. 7A ; 
           [0028]      FIG. 8A  is an enlarged cross sectional view showing a vicinity of the piston of a fluid pressure cylinder to which the coupling structure for a piston according to an eighth modified example is applied; 
           [0029]      FIG. 8B  is an exploded cross sectional view of the piston and the coupling body of  FIG. 8A ; 
           [0030]      FIG. 8C  is an enlarged cross sectional view showing a modification of the coupling structure of  FIG. 8A ; 
           [0031]      FIG. 9A  is an enlarged cross sectional view showing a vicinity of the piston of a fluid pressure cylinder to which the coupling structure for a piston according to a ninth modified example is applied; 
           [0032]      FIG. 9B  is an exploded cross sectional view of the piston and the coupling body of  FIG. 9A ; 
           [0033]      FIG. 9C  is an enlarged cross sectional view showing a modification of the coupling structure of  FIG. 9A ; 
           [0034]      FIG. 10A  is an enlarged cross sectional view showing a vicinity of the piston of a fluid pressure cylinder to which the coupling structure for a piston according to a tenth modified example is applied; and 
           [0035]      FIG. 10B  is an exploded cross sectional view of the piston and the coupling body of  FIG. 10A . 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0036]    A preferred embodiment in relation to a coupling structure and a coupling method for a piston that is used in a fluid pressure cylinder according to the present invention will be described in detail below with reference to the accompanying drawings. In  FIG. 1 , reference numeral  10  indicates a fluid pressure cylinder to which the coupling structure for a piston according to the embodiment of the present invention is applied. 
         [0037]    As shown in  FIG. 1 , the fluid pressure cylinder  10  includes a bottomed cylindrically shaped cylinder tube (cylinder main body)  12 , a rod cover  14  installed on one end of the cylinder tube  12 , a piston  16  disposed displaceably in the interior of the cylinder tube  12 , a piston rod  18  connected to the piston  16  and which is supported displaceably in the rod cover  14 , and a coupling body (coupling member)  20  that connects the piston  16  and the piston rod  18 . 
         [0038]    The cylinder tube  12  includes a cylinder hole  22  that extends in the axial direction (the directions of arrows A and B) in a center portion thereof. The cylinder hole  22  opens toward one end side (in the direction of the arrow A) of the cylinder tube  12 . On the other hand, on the other end of the cylinder tube  12 , a wall portion  24  is formed, which closes the cylinder hole  22 . 
         [0039]    Further, on an outside surface of the cylinder tube  12 , a first port  26  and a second port  28  are formed through which a pressure fluid is supplied and discharged. The first port  26  is disposed in the vicinity of one end of the cylinder tube  12 , whereas the second port  28  is disposed in the vicinity of the other end of the cylinder tube  12 . Non-illustrated tubes are connected, respectively, through switching devices to the first port  26  and the second port  28 . In addition, the first and second ports  26 ,  28  communicate with the cylinder hole  22  through communication passages  30   a ,  30   b  that extend to the side of the cylinder hole  22 . 
         [0040]    The rod cover  14  includes a small diameter portion  32 , and a large diameter portion  34  disposed adjacent to the small diameter portion  32 . The small diameter portion  32  is arranged on the side of the wall portion  24  in the cylinder tube  12  (in the direction of the arrow B). In addition, a stepped portion, which is formed between the small diameter portion  32  and the large diameter portion  34 , is placed in engagement with a stepped portion formed on one end of the cylinder hole  22 , and by mounting of a retaining ring  36  in an annular groove formed on an inner circumferential surface of the cylinder hole  22 , the retaining ring  36  abuts against the end surface of the large diameter portion  34 , whereby the rod cover  14  is fixed and positioned in the cylinder hole  22 . 
         [0041]    Further, in a center portion of the rod cover  14 , a rod hole  38  is formed, which penetrates in the axial direction (the directions of arrows A and B), and the piston rod  18  is inserted through the rod hole  38 . A rod packing  40  is installed via an annular groove, which is formed at a position on the inner circumferential side of the small diameter portion  32 . The rod packing  40 , for example, is formed in an annular shape from a resilient material such as rubber or the like, and by sliding contact against the outer circumferential surface of the piston rod  18 , leakage of pressure fluid that passes to the exterior between the piston rod  18  and the rod cover  14  is prevented from occurring. 
         [0042]    As shown in  FIGS. 1 and 2 , the piston  16  is formed, for example, with a circular shape in cross section from a metal material such as aluminum or the like, and a piston packing  42  is installed through an annular groove on an outer circumferential surface thereof. In addition, by the piston packing  42  being in sliding contact with the inner circumferential surface of the cylinder hole  22 , leakage of pressure fluid that flows between the piston  16  and the cylinder hole  22  is prevented from occurring. 
         [0043]    Further, a piston hole (hole)  44  is formed that penetrates in the axial direction (the directions of arrows A and B) through the center of the piston  16 . The piston hole  44  is formed with a substantially constant diameter along the axial direction. In addition, the coupling body  20  and one end  18   a  of the piston rod  18  are inserted in the piston hole  44 . 
         [0044]    The piston rod  18  is formed, for example, from a metal material such as stainless steel or the like with a predetermined length in the axial direction, and is formed with a substantially constant diameter along the axial direction. In addition, one end  18   a  of the piston rod  18  is formed in a planar shape perpendicular to the axial direction, and a later-described coupling body  20  is connected thereto and is inserted in the piston hole  44  of the piston  16 . The other end of the piston rod  18  is inserted through the rod hole  38  of the rod cover  14 , and is supported for displacement in the axial direction (the directions of arrows A and B). 
         [0045]    The coupling body  20  is formed, for example, by press-molding a plate made from a metal material such as stainless steel or the like, and is constituted from a disk-shaped main body portion  46  and a bent portion (outer edge portion  48 ), which is inclined by bending an outer edge part of the main body portion  46  at a predetermined angle toward the axial direction (in the direction of the arrow A). The coupling body  20  is formed with a substantially constant width. 
         [0046]    Stated otherwise, the bent portion  48  of the coupling body  20  is arranged on the side of the rod cover  14  (in the direction of the arrow A) in the cylinder main body  12 . 
         [0047]    The main body portion  46  is formed in a planar shape, and one side surface thereof is connected coaxially by welding or the like in a state of surface contact with respect to the one end  18   a  of the piston rod  18 . In this case, the connection is made such that the bent portion  48  faces toward the side of the piston rod  18  (in the direction of the arrow A). 
         [0048]    Further, as shown in  FIG. 3C , on the coupling body  20 , the outside diameter D 1  of the bent portion  48  is set to be slightly smaller than the inside diameter D 2  of the piston hole  44  (D 1 &lt;D 2 ), and the hardness E 1  of the coupling body  20 , for example, is set to be greater than the hardness E 2  of the piston  16  (E 1 &gt;E 2 ). 
         [0049]    More specifically, when the coupling body  20  is installed in the piston hole  44  of the piston  16 , and after the coupling body  20  has been inserted in the piston hole  44 , the coupling body  20  is pressed in the axial direction (the direction of the arrow A) and the coupling body  20  is plastically deformed and expanded in diameter (refer to the outside diameter D 1 ′ in  FIG. 3D ), whereby an angled part  50  on an outer circumferential side that constitutes the bent portion  48  bites into and is fastened by caulking with respect to an inner circumferential surface  44   a  of the piston hole  44 . 
         [0050]    Furthermore, on the coupling body  20 , the outer circumferential side of the main body portion  46  that is connected to the piston rod  18  and the bent portion  48  are elastically deformable in the axial direction (the directions of arrows A and B) of the coupling body  20 . 
         [0051]    The fluid pressure cylinder  10  to which the coupling structure for the piston  16  according to the embodiment of the present invention is applied is constructed basically as described above. Next, a case of connecting the piston  16  and the piston rod  18  will be described with reference to  FIGS. 3A through 3D . 
         [0052]    At first, from the condition shown in  FIG. 3A , the main body portion  46  of the coupling body  20  is placed in abutment against the one end  18   a  of the piston rod  18 , such that the bent portion  48  is oriented toward the side of the piston rod  18  (in the direction of the arrow A), and is arranged coaxially with the piston rod  18 . In addition, heat is applied with respect to the main body portion  46  by a non-illustrated welding device, whereby a region in the vicinity of the abutment location between the main body portion  46  and the piston rod  18  is dissolved by high heat, and the main body portion  46  and the piston rod  18  are welded together mutually. Consequently, as shown in  FIG. 3B , the coupling body  20  is fixed firmly to one end  18   a  of the piston rod  18 . 
         [0053]    Next, as shown in  FIG. 3C , in a state in which the piston rod  18  is arranged coaxially with the piston hole  44  of the piston  16 , the coupling body  20  is inserted into the interior of the piston hole  44  together with the piston rod  18 , and the coupling body  20  is arranged substantially in the center along the axial direction of the piston hole  44 , for example. In this case, since the outside diameter D 1  of the coupling body  20  is formed to be slightly smaller than the inside diameter D 2  of the piston hole  44  (D 1 &lt;D 2 ), the coupling body  20  can be inserted easily into the piston hole  44 . 
         [0054]    In addition, after the piston  16  and the piston rod  18  have been fixed by a non-illustrated jig or the like, the coupling body  20  is pressed by a caulking apparatus in the axial direction toward the side of the piston rod  18  (in the direction of the arrow A), and as shown in  FIG. 3D , the coupling body  20  is plastically deformed so as to expand radially outward in diameter (refer to the outside diameter D 1 ′). As a result, the bent portion  48  expands in diameter toward the outer circumferential side, and since the hardness of the coupling body  20  is greater than that of the piston  16 , the angled part  50  on the outer circumferential side constituting the bent portion  48  bites into the inner circumferential surface  44   a  of the piston hole  44  (D 1 ′&gt;D 2 ). Consequently, the coupling body  20  is fastened by caulking in the piston hole  44  of the piston  16 . 
         [0055]    More specifically, by fixing the coupling body  20  to the piston hole  44  of the piston  16 , the piston  16  and the piston rod  18  connected to the coupling body  20  are connected reliably and firmly to each other. Further, since the bent portion  48  bites into the inner circumferential surface  44   a  of the piston hole  44 , flow of pressure fluid between the piston hole  44  and the coupling body  20  is blocked. 
         [0056]    Stated otherwise, the bent portion  48  of the coupling body  20  functions as a sealing means, which is capable of blocking flow of pressure fluid through the piston  16 . 
         [0057]    Moreover, the order in which the piston  16  and the piston rod  18  are connected is not limited to the above-described case. For example, the coupling body  20  may be caulked beforehand to the piston hole  44  of the piston  16 , and thereafter, the piston rod  18  may be connected by welding with respect to the coupling body  20 . 
         [0058]    Further, welding of the coupling body  20  with respect to the piston rod  18  and fitting of the piston rod  18  including the coupling body  20  onto the piston  16  may be carried out substantially simultaneously. In this case, since the coupling body  20  is in a heated condition as a result of being resistance welded to the piston rod  18 , when the coupling body  20  is caulked to the piston  16  by the non-illustrated caulking apparatus, such caulking can be carried out with a small pressing force, and thus the piston  16  and the piston rod  18  can be joined at a low cost using a small scale caulking apparatus. 
         [0059]    Furthermore, since the piston  16  is connected by way of the coupling body  20  that is welded to the piston rod  18 , even in the case that the piston  16  and the piston rod  18  are formed from different materials, the piston  16  and the piston rod  18  can be connected together reliably. 
         [0060]    Next, operations and advantageous effects of the fluid pressure cylinder  10  in which the aforementioned piston  16  and piston rod  18  are connected will be described. The condition shown in  FIG. 1 , in which the piston  16  is displaced (in the direction of the arrow B) toward the side of the wall portion  24  of the cylinder tube  12 , will be referred to as an initial position. 
         [0061]    First, in the initial position, pressure fluid from a pressure fluid supply source (not shown) is introduced to the second port  28 , and the pressure fluid is supplied through the communication passage  30   b  to the cylinder hole  22 , whereupon the piston  16  is pressed and displaced toward the side of the rod cover  14  (in the direction of the arrow A) by the pressure fluid, which is supplied between the piston  16  and the wall portion  24 . In this case, the first port  26  is in a state of being open to atmosphere. 
         [0062]    Accordingly, the piston rod  18  is displaced together with the piston  16  in a direction (the direction of the arrow A) away from the wall portion  24 , and gradually projects outwardly with respect to the rod cover  14  until the displacement end position is reached, at which the end surface of the piston  16  comes into abutment against the end surface of the rod cover  14 . 
         [0063]    At this time, shocks (loads) are applied to the piston  16  when the piston  16  abuts against the rod cover  14 . The shocks applied to the piston  16  are absorbed by elastic deformation of parts of the main body portion  46  and the bent portion  48  of the coupling body  20  in a direction (the direction of the arrow B) away from the rod cover  14 , about a joined location as a fulcrum point where the coupling body  20  joins with the piston rod  18 . Owing thereto, shocks are prevented from being applied to the piston rod  18  from the piston  16 . More specifically, simultaneously with serving to connect the piston  16  and the piston rod  18 , the coupling body  20  functions as a damper, which is capable of preventing loads (shocks) applied to the piston  16  from being transmitted to the piston rod  18 . 
         [0064]    Next, in the case that the piston  16  is to be restored again to the initial position from the aforementioned displacement end position, the pressure fluid that had been supplied to the second port  28  is supplied instead to the first port  26  through operation of a non-illustrated switching device, and the pressure fluid is supplied through the communication passage  30   a  to the cylinder hole  22 , whereupon the piston  16  is pressed gradually away from the rod cover  14  (in the direction of the arrow B) by the pressure fluid. In this case, the second port  28  is in a state of being open to atmosphere. 
         [0065]    In addition, together with displacement of the piston  16 , the piston rod  18  is displaced so as to become accommodated gradually in the interior of the rod cover  14 , and the piston  16  abuts against the wall portion  24  in the cylinder tube  12 , whereupon the initial position is restored upon stopping supply of the pressure fluid. 
         [0066]    In this case as well, although shocks (loads) are applied to the piston  16  when the piston  16  abuts against the wall portion  24 , since the shocks applied to the piston  16  are absorbed by elastic deformation of the bent portion  48  of the coupling body  20  toward the side of the rod cover  14  (in the direction of the arrow A), the shocks are prevented from being applied to the piston rod  18  from the piston  16 . 
         [0067]    In the foregoing manner, with the present embodiment, the bent portion  48  and the part of the main body portion  46  of the coupling body  20  that connect the piston  16  and the piston rod  18  are deformable elastically in the axial direction (the directions of arrows A and B). Therefore, when the piston  16  is displaced and comes into abutment against the rod cover  14  or the wall portion  24  of the cylinder main body  12 , shocks (loads) applied to the piston  16  are absorbed suitably by elastic deformation of the bent portion  48  of the coupling body  20 , and such shocks are prevented reliably from being transmitted to the piston rod  18 . 
         [0068]    More specifically, shocks applied to the piston  16  are prevented from being transmitted to another apparatus connected to the piston rod  18 , or to a workpiece that is transported by the piston rod  18 . As a result, the aforementioned shocks are absorbed, and it is unnecessary to provide a dedicated structure such as an air cushion or a damper on the cylinder main body  12 , the piston  16 , or the rod cover  14 . Therefore, by means of a simple structure of disposing the coupling body  20  on the end of the piston rod  18 , the number of parts, manufacturing costs, and the number of assembly steps for producing the fluid pressure cylinder in the fluid pressure cylinder  10  can be reduced. 
         [0069]    Further, compared to a conventional fluid pressure cylinder, since the piston hole  44  formed in the center of the piston  16  can be formed with a greater diameter than the outside diameter of the piston rod  18 , the piston  16  can be made lighter in weight, while at the same time, material costs can be reduced. As a result, accompanying the reduction in weight of the piston  16 , the load weight of workpieces or the like transported by the piston rod  18  can be increased, together with enabling the piston  16  to be operated with less pressure fluid, and energy savings can be realized. 
         [0070]    Furthermore, at the same time that the piston  16  and the piston rod  18  are connected by fitting the coupling body  20  in the piston hole  44  of the piston  16 , sealing is carried out between the piston hole  44  and the coupling body  20 , and thus an airtight condition can be maintained in the interior of the cylinder hole  22  without any need to provide a separate sealing member on the coupling body  20 . 
         [0071]    Still further, by carrying out welding of the coupling body  20  with respect to the piston rod  18  substantially simultaneously with connection of the piston rod  18  including the coupling body  20  to the piston  16 , the coupling body  20 , which has been heated for example by resistance welding, can be caulked with respect to the piston  16  with a small pressing force, and the piston  16  can be connected to the piston rod  18  at a low cost using a small scale caulking apparatus (not shown). 
         [0072]    Still further, since connection of the coupling body  20  and the piston rod  18  is carried out by welding in a state of surface contact therebetween, and without providing mutual holes or the like in the coupling body  20  and the piston rod  18 , there is no need to provide a sealing member between the coupling body  20  and the piston rod  18 , and compared with the fluid pressure cylinder according to the conventional technique, in which a sealing member is provided, the number of parts and the number of assembly steps can be reduced. Furthermore, since it is unnecessary to provide an annular groove on the piston rod  18  for installation of a sealing member, the number of process steps can be reduced. 
         [0073]    Further, since the piston  16  is connected via the coupling body  20 , which is welded to the piston rod  18 , and the piston  16  and the piston rod  18  are not welded directly to each other, it is possible for the piston  16  and the piston rod  18  to be formed from different materials. 
         [0074]    In the above-described embodiment, a case has been described in which the bent portion  48  of the coupling body  20  is inclined with respect to the main body portion  46  (in the direction of the arrow B) toward the side of the piston rod  18 . However, the present invention is not limited to this feature, and for example, in a condition of being connected to the piston rod  18 , a coupling body  20  may be used in which the bent portion  48  thereof is inclined in a direction (the direction of the arrow B) away from the piston rod  18 . 
         [0075]    Next, fluid pressure cylinders  100 ,  106 ,  110 ,  130 ,  150 ,  170 , to which coupling structures for pistons according to first through sixth modified examples are applied, will be described with reference to  FIGS. 4 through 6 . Constituent elements thereof, which are the same as those of the fluid pressure cylinder  10  to which the coupling structure for a piston  16  according to the aforementioned embodiment are applied, are denoted using the same reference numerals, and detailed description of such features is omitted. 
         [0076]    First, the coupling structure for a piston  16  according to the first modified example differs from the coupling structure for the piston  16  according to the aforementioned embodiment, in that, as in the fluid pressure cylinder  100  shown in  FIG. 4A , instead of connecting the coupling body  20  to one end  18   a  of the piston rod  18 , a flange (coupling member)  102 , which is formed substantially in the same shape as the coupling body  20 , is formed integrally on one end of the piston rod  104 . The piston rod  104  having the flange  102  thereon is formed, for example, by a machining process such as cutting or the like. 
         [0077]    In the foregoing manner, by providing the piston rod  104  having the flange  102 , the process steps for welding the coupling body  20  and the piston rod  18  can be dispensed with, and since a welding apparatus also is unnecessary, manufacturing costs can be reduced. Stated otherwise, by applying the aforementioned coupling structure to the fluid pressure cylinder  100  having a small diameter piston  16 , for example, in cases where the welding strength with respect to the coupling body is made smaller commensurate with reducing the diameter of the piston rod  104 , by providing the flange  102 , which corresponds to the coupling body, integrally with the piston rod  104 , it is possible to reliably connect the piston  16  and the piston rod  104 . 
         [0078]    Further, with a coupling structure for a piston  16  according to a second modified example, as in the case of the fluid pressure cylinder  106  shown in  FIG. 4B , a displaceable body  108  may be provided in which the piston  16 , the piston rod  18 , and the coupling body  20  are formed integrally. 
         [0079]    The displaceable body  108  is made up from a piston section  108   a  having the piston hole  44  in the interior thereof, a coupling section  108   b  disposed on an end surface of the piston section  108   a , and a piston rod section  108   c  connected to the center of the coupling section  108   b . The piston rod section  108   c  extends in a direction (the direction of the arrow A) away from the piston section  108   a.    
         [0080]    In the foregoing manner, by providing the displaceable body  108 , in which the piston section  108   a  having the piston hole  44 , the coupling section  108   b  disposed on the end surface of the piston section  108   a , and the piston rod section  108   c  connected to the center of the coupling section  108   b  are formed together integrally, and by disposing the displaceable body  108  displaceably in the interior of the cylinder tube  12 , it is unnecessary for the piston and a flange portion of the piston rod to be connected by caulking or the like, as in the case of the fluid pressure cylinder  100  shown in  FIG. 4A . 
         [0081]    In this manner, for example, in the case that the outside diameter of the piston section  108   a , which functions as a piston, is of a small diameter, together with making the displaceable body  108  lightweight, shocks that occur when the piston section  108   a  abuts against the cylinder tube  12  or the rod cover  14  can suitably be absorbed by the coupling section  108   b.    
         [0082]    Next, a coupling structure for a piston  16  according to a third modified example differs from the coupling structure for a piston  16  according to the aforementioned embodiment, in that, as in the fluid pressure cylinder  110  shown in  FIG. 5A , a coupling body  112  is connected by a bolt  116  with respect to one end  18   a  of a piston rod  114 . 
         [0083]    The bolt  116  is inserted through a hole  118  penetratingly provided substantially in the center of the coupling body  112 . On the other hand, a bolt hole  120  with screw threads engraved on the inner circumferential surface thereof is formed in one end  18   a  of the piston rod  114 , and the bolt  116 , which is inserted through the hole of the coupling body  112 , is screw-engaged with the bolt hole  120 . Consequently, the main body portion  46  of the coupling body  112  abuts against the one end  18   a  of the piston rod  114 , and is connected by the bolt  116  in a state of surface contact therewith. 
         [0084]    In addition, after the coupling body  112  has been inserted in the piston hole  44  of the piston  16 , the coupling body  112  is pressed by a non-illustrating caulking apparatus, and the coupling body  112  is plastically deformed and expanded in diameter in a radial outward direction, whereby the bent portion  48  of the coupling body  112  bites into the inner circumferential surface  44   a  of the piston hole  44 . The coupling body  112  is now fastened by caulking to the piston hole  44  of the piston  16 . Accordingly, without the piston  16  and the piston rod  18  being displaced relatively in the axial direction, the piston  16  and the piston rod  18  are connected together mutually through the coupling body  112 . 
         [0085]    Next, a coupling structure for a piston  16  according to a fourth modified example differs from the coupling structure for a piston  16  according to the aforementioned embodiment, in that, as in the fluid pressure cylinder  130  shown in  FIG. 5B , a coupling body  132  is connected by caulking with respect to one end  18   a  of a piston rod  134 . 
         [0086]    A projection  138  formed on one end  18   a  of the piston rod  134  is inserted through a hole  136  penetratingly provided substantially in the center of the coupling body  132 . The projection  138  projects a predetermined height in the axial direction (the direction of the arrow B) with respect to one end  18   a  of the piston rod  134 , and is formed with a slightly smaller diameter than the inside diameter of the hole  136 . 
         [0087]    In addition, the projection  138  is inserted through the hole  136  of the main body portion  46 , and the main body portion  46  is placed in abutment against the one end  18   a , such that the bent portion  48  of the coupling body  132  is oriented toward the side of the piston rod  134  (in the direction of the arrow A). 
         [0088]    Next, the distal end of the projection  138  that projects with respect to the main body portion  46  is pressed and is deformed plastically by a non-illustrated caulking apparatus, so that the projection  138  is expanded in diameter in a radial outward direction, thereby forming a caulked portion  140 . Consequently, the main body portion  46  of the coupling body  132  is sandwiched and fixed between one end  18   a  of the piston rod  134  and the diametrically expanded caulked portion  140 . 
         [0089]    Lastly, after the coupling body  132  has been inserted in the piston hole  44  of the piston  16 , the coupling body  132  is pressed by a non-illustrated caulking apparatus, and the coupling body  132  is plastically deformed and expanded in diameter in a radial outward direction, whereby the bent portion  48  of the coupling body  132  bites into the inner circumferential surface  44   a  of the piston hole  44 , and the coupling body  132  is fastened by caulking to the piston hole  44  of the piston  16 . Accordingly, without the piston  16  and the piston rod  18  being displaced relatively in the axial direction, the piston  16  and the piston rod  18  are connected together mutually through the coupling body  132 . 
         [0090]    More specifically, by the coupling body  112 ,  132  being inserted and fastened by caulking with respect to the piston hole  44  of the piston  16 , for example, even in the case that a space cannot be assured for fixing the coupling body  112 ,  132  with respect to the piston rod  18  by a screw connection or a retaining ring or the like, the above-described coupling structure for the piston  16  is capable of reliably connecting the piston  16  and the piston rod  18 . 
         [0091]    Next, a coupling structure for a piston  16  according to a fifth modified example differs from the coupling structure for a piston  16  according to the aforementioned embodiment, in that, as in the fluid pressure cylinder  150  shown in  FIG. 6A , a coupling body  152  does not have a bent portion, but is formed only from a planar shaped main body portion  154 , and the coupling body  152  is connected by a plurality of bolts  156  with respect to an end surface of the piston  16 . 
         [0092]    A center portion of the coupling body  152  is connected by welding or the like with respect to the one end  18   a  of the piston rod  18 , and on an outer circumferential side thereof, the coupling body  152  includes a plurality of holes  158  that penetrate therethrough in the axial direction (the directions of arrows A and B). Bolts  156  are inserted through the holes  158  and are screw-engaged, respectively, in bolt holes  160  that are formed on an end surface of the piston  16 . Accordingly, the coupling body  152  abuts with respect to the end surface of the piston  16 , and is fixed by the plural bolts  156  in a state of surface contact therewith. As a result, the piston  16  and the piston rod  18  are joined to one another without relative displacement thereof in the axial direction (the directions of arrows A and B). 
         [0093]    The holes  158  and the bolt holes  160  are provided at substantially equal intervals mutually in the circumferential direction of the coupling body  152  and the piston  16 . 
         [0094]    Further, in the case that shocks (loads) are applied in the axial direction with respect to the piston  16 , after such loads have been transmitted to the coupling body  152  from the piston  16 , the outer circumferential region thereof is flexed, so as to become deformed elastically with respect to the center portion connected to the piston rod  18 . Consequently, since shocks applied to the piston  16  are absorbed suitably by the coupling body  152 , the shocks are prevented from being transmitted to the piston rod  18 . 
         [0095]    Next, a coupling structure for a piston  16  according to a sixth modified example differs from the coupling structure for the piston  16  according to the aforementioned embodiment, in that, as in the fluid pressure cylinder  170  shown in  FIG. 6B , a coupling body  172  does not have a bent portion, but is formed only from a planar shaped main body portion  174 , and the coupling body  172  is inserted in the piston hole  44  of the piston  16  and fixed by a pair of retaining rings  176   a ,  176   b.    
         [0096]    The outside diameter of the coupling body  172  is substantially the same or slightly smaller than the inside diameter of the piston hole  44  of the piston  16 , and the center of the coupling body  172  is connected by welding with respect to one end  18   a  of the piston rod  18 . Further, an O-ring  178  is installed via an annular groove on the outer circumferential surface of the coupling body  172 , such that when the coupling body  172  is inserted in the piston hole  44 , the O-ring  178  abuts against the inner circumferential surface  44   a  of the piston hole  44 . 
         [0097]    A pair of ring grooves  180   a ,  180   b  is formed in the piston hole  44 , the ring grooves  180   a ,  180   b  being separated mutually in the axial direction (the directions of arrows A and B) from a substantially central portion where the coupling body  172  is inserted. Additionally, in a state in which the coupling body  172  is inserted in the piston hole  44  and is disposed between one of the ring grooves  180   a  and the other of the ring grooves  180   b , C-shaped retaining rings  176   a ,  176   b  are inserted respectively from the one opening and the other opening in the piston hole  44 , and are positioned respectively in engagement with the ring grooves  180   a ,  180   b.    
         [0098]    When placed in engagement with the ring grooves  180   a ,  180   b , since the retaining rings  176   a ,  176   b  are installed so as to project circumferentially inward with respect to the inner circumferential surface  44   a  of the piston hole  44 , the coupling body  172  is retained between the retaining rings  176   a ,  176   b . As a result, along with the coupling body  172  being held in the piston hole  44  of the piston  16 , the piston  16  and the piston rod  18  are connected together mutually without relative displacement thereof in the axial direction. 
         [0099]    Further, in the case that shocks (loads) are applied in the axial direction with respect to the piston  16 , after such loads have been transmitted to the retaining rings  176   a  ( 176   b ) from the piston  16 , the coupling body  172  is pressed by the retaining rings  176   a  ( 176   b ) and the outer circumferential region of the coupling body  172  is flexed, so as to become deformed elastically with respect to the center portion connected to the piston rod  18 . Consequently, since shocks applied to the piston  16  are absorbed suitably by the coupling body  172 , the shocks are prevented from being transmitted to the piston rod  18 . 
         [0100]    In the fluid pressure cylinders  150 ,  170 , for example, in the event that a large diameter piston  16  is used, since the coupling bodies  152 ,  172  are not fastened by caulking with respect to the piston  16 , but instead can be connected reliably using the bolts  156  or the retaining rings  176   a ,  176   b , it is unnecessary to carry out caulking of the coupling bodies  152 ,  172  at an excessive load with respect to the large diameter piston  16 , it further is unnecessary to prepare a large scale caulking apparatus to perform such caulking, and manufacturing costs including investment in equipment can be suppressed. 
         [0101]    Next, a coupling structure for a piston  192  according to a seventh modified example differs from the coupling structure for a piston  16  according to the aforementioned embodiment, in that, as in a fluid pressure cylinder  190  shown in  FIGS. 7A and 7B , an annular groove  194  is formed on the inner circumferential surface of the piston hole  44  in the piston  192 , and the coupling body  20  connected to the piston rod  18  is engaged with respect to the annular groove  194 . 
         [0102]    The annular groove  194 , for example, is formed substantially centrally along the axial direction (the directions of arrows A and B) of the piston  192 , and is formed at a constant depth along the inner circumferential surface of the piston hole  44 . 
         [0103]    In addition, as shown in  FIG. 7B , when the coupling body  20 , which is mounted on the end of the piston rod  18 , is installed in the piston hole  44  of the piston  192 , after the coupling body  20  has been inserted in the piston hole  44 , the coupling body  20  is pressed in the axial direction (in the direction of the arrow A) and is plastically deformed in a radial outward direction and expanded in diameter, whereby the angled part  50  on the outer circumferential side constituting the bent portion  48  is inserted into the annular groove  194  of the piston hole  44  in engagement therewith. 
         [0104]    Consequently, the piston rod  18  is connected coaxially with the piston  192  through the coupling body  20 . Further, as noted above, the invention is not limited to a case in which the coupling body  20  and the piston  192  are connected to each other beforehand, but for example, after the coupling body  20  has been installed with respect to the piston  192 , the end of the piston rod  18  may be connected by welding or the like with respect to the main body portion  46  of the coupling body  20 . 
         [0105]    In the foregoing manner, by providing the annular groove  194  on the inner circumferential surface of the piston hole  44 , and causing the coupling body  20  to expand in diameter with respect to the annular groove  194  and be placed in engagement therewith, the coupling body  20  can easily and reliably be installed with respect to the piston  192 , along with enabling connection of the piston  192  and the piston rod  18 , which is connected to the coupling body  20 . 
         [0106]    Further, for example, when the piston  192  abuts against the rod cover  14 , although shocks (loads) are applied to the piston  192  in a direction (the direction of the arrow B) away from the rod cover  14 , the shocks applied to the piston  192  are absorbed by elastic deformation of parts of the main body portion  46  and the bent portion  48  of the coupling body  20  in a direction (the direction of the arrow B) away from the rod cover  14  about a joined location as a fulcrum point where the coupling body  20  joins with the piston rod  18 . 
         [0107]    On the other hand, although shocks (loads) also are applied when the piston  192  abuts against the wall portion  24  of the cylinder tube  12 , the shocks applied to the piston  192  are absorbed by elastic deformation of parts of the main body portion  46  and the bent portion  48  of the coupling body  20  in a direction (the direction of the arrow A) away from the wall portion  24  about the joined location as a fulcrum point where the coupling body  20  joins with the piston rod  18 . Together therewith, by the bent portion  48  being secured in engagement with the annular groove  194 , the coupling body  20  is reliably prevented from being pulled out with respect to the piston  192 . 
         [0108]    Owing thereto, shocks that are applied in the axial direction (the directions of arrows A and B) with respect to the piston  192  are suitably absorbed by the coupling body  20  and are prevented from being applied to the piston rod  18  from the piston  192 . Additionally, by engagement of the coupling body  20  with respect to the annular groove  194 , the coupling body  20  and the piston rod  18  can be connected more securely with respect to the piston  192 . 
         [0109]    Further, as in the coupling structure shown in  FIG. 7C , the piston  192  and the piston rod  18  may be connected using a coupling body  196 , in which a bent portion  198  is formed substantially in parallel with the main body portion  46  and is offset therefrom in the axial direction (the direction of the arrow A). In the coupling body  196 , the bent portion  198  is offset with respect to the main body portion  46  by a predetermined distance substantially in parallel toward the side of the piston rod  18  (in the direction of the arrow A), and extends in a radial outward direction perpendicularly to the axis of the piston rod  18 . 
         [0110]    In addition, after the coupling body  196  has been inserted in the piston hole  44  of the piston  192 , by pressing the coupling body  196  in the axial direction (the direction of the arrow A) to cause plastic deformation and diametric expansion thereof in a radial outward direction, the distal end of the bent portion  198  is brought into engagement with respect to the annular groove  194 . Consequently, compared to the coupling structure for the piston  192  according to the seventh modification, since the bent portion  198  can be inserted on a straight line with respect to the annular groove  194 , a large region of contact between the bent portion  198  and the annular groove  194  can be assured. As a result, leakage of pressure fluid between the piston  192  and the coupling body  196  can be prevented more reliably, and sealability can be improved. 
         [0111]    Next, a coupling structure according to an eighth modified example differs from the coupling structure for a piston  16  according to the aforementioned embodiment, in that, as in a fluid pressure cylinder  200  shown in  FIGS. 8A and 8B , a piston hole  204  for a piston  202  is constituted from first and second hole sections  206 ,  208  having different inside diameters, and the coupling body  20  is installed with respect to the second hole section  208 , which is formed with a larger diameter. 
         [0112]    In the piston hole  204 , the small diameter first hole section  206  is formed on one end side (in the direction of the arrow A) of the piston  202  in which the piston rod  18  is inserted, and the second hole section  208 , which is larger in diameter than the first hole section  206 , is formed on the other end side (in the direction of the arrow B) of the piston  202 . 
         [0113]    In addition, in a state in which the coupling body  20  is inserted in the second hole section  208  and abuts against a boundary region  210  between the first hole section  206  and the second hole section  208 , the coupling body  20  is pressed in the axial direction (the direction of the arrow A) and is plastically deformed in a radial outward direction so as to expand in diameter, whereby the distal end of the bent portion  48  is brought into engagement with respect to the inner circumferential surface of the second hole section  208 . 
         [0114]    Further, as shown in  FIG. 8C , a disk shaped plate body  212  may be inserted together with the coupling body  20  with respect to the second hole section  208  of the piston, such that the plate body  212  is arranged on the side of the first hole section  206  (in the direction of the arrow A). In addition, in a state in which the plate body  212  is placed in abutment against the boundary region  210  between the first hole section  206  and the second hole section  208 , the coupling body  20  is pressed (in the direction of the arrow A) and is plastically deformed in a radial outward direction so as to expand in diameter, whereby the distal end of the bent portion  48  is brought into engagement with respect to the inner circumferential surface of the second hole section  208 , and hence, the coupling body  20  is connected with respect to the second hole section  208 , together with the plate body  212  being gripped between the coupling body  20  and the boundary region  210 . 
         [0115]    Consequently, when the piston  202  abuts against the rod cover  14 , although shocks (loads) are applied to the piston  202  in a direction (the direction of the arrow B) away from the rod cover  14 , the shocks applied to the piston  202  are absorbed by elastic deformation of parts of the main body portion  46  and the bent portion  48  of the coupling body  20  in the direction (the direction of the arrow B) away from the rod cover  14  about the joined region as a fulcrum point where the coupling body  20  joins with the piston rod  18 . 
         [0116]    Further, although shocks (loads) also are applied when the piston  202  abuts against the wall portion  24  of the cylinder tube  12 , the shocks applied to the piston  202  are absorbed by elastic deformation of parts of the main body portion  46  and the bent portion  48  of the coupling body  20  in a direction (the direction of the arrow A) away from the wall portion  24  about the joined location as a fulcrum point where the coupling body  20  joins with the piston rod  18 . Together therewith, by abutment of the coupling body  20  against the boundary region  210  between the first hole section  206  and the second hole section  208 , the coupling body  20  is reliably prevented from being pulled out from the piston hole  204 . 
         [0117]    Further, as shown in  FIG. 8C , by providing the plate body  212  on a side opposite from the direction in which the piston rod  18  connected to the coupling body  20  extends, even in the event that loads are applied with respect to the piston  202  toward the side of the piston rod  18 , the coupling body can be prevented assuredly from falling out from the piston hole  204  by the plate body  212 . Stated otherwise, the plate body  212  includes the function of a pull out preventative means, which is capable of preventing falling out of the coupling body  20  in the piston hole  204 . 
         [0118]    Next, a coupling structure according to a ninth modified example differs from the coupling structure for a piston  16  according to the aforementioned embodiment, in that, as in a fluid pressure cylinder  220  shown in  FIGS. 9A and 9B , a pair of first and second coupling bodies  222   a ,  222   b  is connected to the end of the piston rod  18 , where the first and second coupling bodies  222   a ,  222   b  are engaged with respect to the piston hole  44 . 
         [0119]    In the case of the first coupling body  222   a , the bent portion  48  thereof is arranged in the piston hole  44  so as to be oriented toward one end side of the piston  16  (in the direction of the arrow A), whereas in the case of the second coupling body  222   b , the bent portion  48  thereof is arranged in the piston hole  44  so as to be oriented toward the other end side of the piston  16  (in the direction of the arrow B). Further, the main body portions  46  of the first and second coupling bodies  222   a ,  222   b  are disposed in mutually abutting relation to each other, with the end of the piston rod  18  being connected to the main body portion  46  of the first coupling body  222   a.    
         [0120]    Furthermore, in a state in which the first and second coupling bodies  222   a ,  222   b  are arranged in the piston hole  44 , the first and second coupling bodies  222   a ,  222   b  are pressed in the axial direction (the direction of the arrow A) and are plastically deformed and expanded radially outward in diameter, whereby the distal ends of the bent portions  48  are brought into engagement, respectively, with respect to the inner circumferential surface of the piston hole  44 , and the first and second coupling bodies  222   a ,  222   b  are connected with respect to the piston  16 . 
         [0121]    At this time, concerning the first coupling body  222   a , since the bent portion  48  thereof is engaged while being bent toward the side of one end of the piston  16  (in the direction of the arrow A), for example, when loads are applied to the piston  16  that are directed toward the side of the piston rod  18  (in the direction of the arrow A), a firm connection is established by the bent portion  48 , which bites in deeply with respect to the inner circumferential surface of the piston hole  44 , and together therewith, the loads are absorbed and are prevented from being transmitted to the piston rod  18 . 
         [0122]    Further, concerning the second coupling body  222   b , since the bent portion  48  thereof is engaged while being bent toward the opposite end side of the piston  16  (in the direction of the arrow B), for example, when loads are applied to the piston  16  that are directed away from the piston rod  18 , a firm connection is established by the bent portion  48 , which bites in deeply with respect to the inner circumferential surface of the piston hole  44 , and together therewith, the loads are absorbed and are prevented from being transmitted to the piston rod  18 . 
         [0123]    More specifically, the coupling structure for the piston  16  according to the above ninth embodiment includes the first and second coupling bodies  222   a ,  222   b , which are arranged symmetrically with respect to the mutually abutting main body portions  46 , and by connecting the first and second coupling bodies  222   a ,  222   b  in the piston hole  44  of the piston  16 , even in the case that loads are applied respectively to the piston  16  at the side of the rod cover  14  and at the side of the wall portion  24  of the cylinder tube  12 , such loads can be suitably absorbed, respectively, by the first and second coupling bodies  222   a ,  222   b  and can be prevented from being transmitted to the piston rod  18 . 
         [0124]    Further, as shown in  FIG. 9C , a gap  224  may be disposed between the first coupling body  222   a  and the second coupling body  222   b . The gap  224  is disposed between the main body portion  46  of the first coupling body  222   a  and the main body portion  46  of the second coupling body  222   b , and is constructed such that mutually confronting end surfaces of the main body portions  46  are recessed at predetermined depths. By means of such a structure, when loads are applied in the axial direction with respect to the piston  16  and the first and second coupling bodies  222   a ,  222   b  are deformed, since the deformation can be made greater by using the gap  224 , such loads can be prevented from being transmitted from the piston  16  to the piston rod  18 , and shocks can be mitigated more suitably, compared with the structure of the piston  16  according to the ninth embodiment. 
         [0125]    Next, a coupling structure according to a tenth modified example differs from the coupling structure for a piston  16  according to the aforementioned embodiment, in that, as in a fluid pressure cylinder  230  shown in  FIGS. 10A and 10B , the piston  16  and the piston rod  18  are connected by using a coupling body  234  having a curved portion  232 , which is curved between the bent portion  48  and the main body portion  46 . 
         [0126]    The coupling body  234  includes the curved portion  232  on the outer edge part of the main body portion  46 , which is formed in a planar shape, and the curved portion  232  is formed with an arcuate shape in cross section bulging in an opposite direction to the direction in which the bent portion  48  is bent. Stated otherwise, the coupling body  234  is formed with a wavy or undulating shape in cross section from the main body portion  46 , the curved portion  232 , and the bent portion  48 . 
         [0127]    In accordance with such a structure, when loads are applied in the axial direction with respect to the piston  16  and the coupling body  234  is deformed, by means of the curved portion  232 , such loads can be suitably absorbed, and therefore, transmission of the loads from the piston  16  to the piston rod  18  can be prevented, and shocks can be absorbed more effectively. 
         [0128]    More specifically, connection of the pistons  16 ,  192 ,  202  and the piston rods  18 ,  104 ,  114 ,  134  may be accomplished by selecting and adopting an optimum structure from among the coupling structure for a piston according to the aforementioned present embodiment, and the coupling structures for pistons according to the first through eleventh modified examples. 
         [0129]    While the coupling structure and the coupling method for a piston used in a fluid pressure cylinder according to the present invention have been described above, the present invention is not limited to the above-described embodiments. It is a matter of course that various additional or alternative features could be adopted therein without departing from the scope and gist of the present invention.