Patent Publication Number: US-11035387-B2

Title: Fluid equipment

Description:
TECHNICAL FIELD 
     The present invention relates to fluid equipment, such as a hydraulic cylinder, applied to machines such as a vehicle, a construction machine, and an industrial machine and configured to transmit energy of operating fluid. 
     BACKGROUND ART 
     In machines such as a vehicle, a construction machine, and an industrial machine, a power transmission system is simplified using a fluid pressure circuit incorporating a hydraulic cylinder as fluid equipment configured to transmit energy or power by means of the pressure of operating fluid. The hydraulic cylinder moves a piston in the cylinder by first operating fluid, thereby causing the pressure to act on second operating fluid of a hydraulic chamber on the opposite side of the first operating fluid through the piston. In this manner, power is transmitted. 
     A fluid pressure cylinder disclosed in Patent Citation 1 mainly includes a cylindrical cylinder tube, a piston provided inside of the cylinder tube, a rod coupled to the piston, and a cylinder head slidably supporting the rod on the cylinder tube. A housing groove is formed at the outer periphery of the piston. A single seal ring slidably contacting the inner periphery of the cylinder tube and two backup wear rings sandwiching the seal ring are attached to the housing groove, and in this manner, the inside of the cylinder tube is substantially hermetically divided into a rod-side fluid pressure chamber and an end-side fluid pressure chamber. According to this configuration, the fluid pressure cylinder introduces, in the cylinder tube, operating fluid from a fluid pressure circuit into each fluid pressure chamber divided by the piston through a port, thereby reciprocating the piston. Accordingly, pressure acts on first operating fluid or second operating fluid through the piston to transmit power, and therefore, the rod can be operated to extend/contract relative to the cylinder tube. 
     CITATION LIST 
     Patent Literature 
     
         
         Patent Citation 1: JP 2012-197908 A (Page  4 ,  FIG. 2 ) 
       
    
     SUMMARY OF INVENTION 
     Technical Problem 
     However, in Patent Citation 1, when the operating fluid is introduced into each fluid pressure chamber from the fluid pressure circuit through the port to reciprocate the piston, friction due to sliding is caused between the inner periphery of the cylinder tube and each of the seal ring and the backup wear rings, and for this reason, there is room for improvement in operability of the piston. 
     The present invention has been made in view of the above-described problem, and is intended to provide fluid equipment capable of enhancing operability of a moving member in a container. 
     Solution to Problem 
     For solving the above-described problem, the fluid equipment according to a first aspect of the present invention is fluid equipment comprising a container capable of having a first fluid and a second fluid housed therein, a first fluid outlet/inlet path provided at the container for outflow and inflow of the first fluid, a second fluid outlet/inlet path provided at the container for outflow and inflow of the second fluid, and a moving member capable of moving in the container in response to the pressure of the first fluid, the fluid equipment transmitting energy from the first fluid to the second fluid. The fluid equipment further comprises a first bellows capable of expanding and contracting. The first bellows has a first end portion closed in a sealed state by the moving member and a second end portion fixed to a first inner surface part of the container in a sealed state. An inside of the first bellows is capable of communicating with the first fluid outlet/inlet path. 
     According to the first aspect, the first bellows whose the first end portion is closed by the moving member and the second end portion is fixed to the first axial end of the inner surface part of the container in the sealed state, and therefore, the first fluid flowing in or flowing out of the first fluid outlet/inlet path and the second fluid flowing in or flowing out of the second fluid outlet/inlet path in the container can be, in the sealed state, separated into the inside and outside of the first bellows. Thus, mixing of the first fluid and the second fluid in the container can be prevented. In addition, friction due to sliding between the container and the moving member is decreased so that operability of the moving member in the container can be enhanced. 
     In the fluid equipment according to a second aspect of the present invention, the first fluid and the second fluid are non-compressible fluid. 
     According to the second aspect, the non-compressible second fluid flows in or flows out of the outside of the first bellows in the container, and therefore, a damper effect utilizing fluid resistance of the non-compressible second fluid moving between the container and the moving member in association with movement of the moving member can be obtained. Thus, movement of the moving member in the container can be stabilized. 
     The fluid equipment according to a third aspect of the present invention includes a second bellows capable of expanding and contracting and having a smaller diameter than that of the first bellows and configured such that an first end portion of the second bellows is closed by the moving member, a second end portion of the second bellows is fixed to a second inner surface part of the container in a sealed state, and compressible fluid is sealed inside. 
     According to the third aspect, the second bellows is configured to have a smaller diameter than that of the first bellows. In case that the outside of the first bellows and the outside of the second bellows are aligned in the axial direction thereof, a structure can be easily obtained, in which the second fluid in the outside of the second bellows moves to the outside of the first bellows. 
     In the fluid equipment according to a fourth aspect of the present invention, the second bellows is fixed to the moving member in a coaxial relationship with each other. 
     According to the fourth aspect, the second bellows is coaxial with the moving member. Accordingly, inclination of the moving member can be reduced, and the moving member can be more stably supported in the container. 
     In the fluid equipment according to a fifth aspect of the present invention, the moving member includes a guide portion contacting the inner periphery of the container. 
     According to the fifth aspect, inclination of the moving member can be prevented by the guide portion, and movement of the moving member can be guided along the inner periphery of the container. Thus, straightness upon movement of the moving member can be enhanced. 
     In the fluid equipment according to a sixth aspect of the present invention, a communication path penetrating the guide portion in a thickness direction and communicating with the outside of the first bellows is provided at the guide portion. 
     According to the sixth aspect, the second fluid is moved through the communication path penetrating the guide portion in the thickness direction in association with movement of the moving member. Accordingly, fluid resistance of the second fluid can be decreased, and the operability of the moving member can be enhanced. 
     In the fluid equipment according to a seventh aspect of the present invention, at least a part of the moving member is arranged inside the first bellows. 
     According to the seventh aspect, the moving member can be supported in a state in which the first bellows and the second bellows partially overlap with each other in the extension direction. Consequently, the container can be compactly configured without shortening expansion lengths of the first bellows and the second bellows. 
     In the fluid equipment according to an eighth aspect of the present invention, the first fluid and the second fluid are different types of fluid. 
     According to the eighth aspect, the first fluid and the second fluid as different types of fluid in the container can be prevented from mixing with each other. Thus, the fluid equipment can be applied between fluid pressure circuits using different types of fluid. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a schematic partial sectional view of a hydraulic cylinder constituting fluid equipment according to a first embodiment of the present invention. 
         FIG. 2  is a sectional view of the hydraulic cylinder according to the first embodiment in a non-drive state for not driving a load W. 
         FIG. 3  is a sectional view of the hydraulic cylinder according to the first embodiment in a drive state for driving the load W. 
         FIG. 4  is a sectional view of a hydraulic cylinder constituting fluid equipment according to a second embodiment of the present invention in a non-drive state for not driving a load W. 
         FIG. 5  is a sectional view of the hydraulic cylinder according to the second embodiment in a drive state for driving the load W. 
         FIG. 6  is a sectional view of a hydraulic cylinder constituting fluid equipment according to a third embodiment of the present invention in a non-drive state for not driving a load W. 
         FIG. 7  is a sectional view of a variation of the hydraulic cylinder constituting fluid equipment according to the present invention. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, modes for carrying out fluid equipment according to the present invention will be described based on embodiments. 
     First Embodiment 
     A hydraulic cylinder constituting fluid equipment according to a first embodiment of the present invention will be described with reference to  FIGS. 1 to 3 . 
     As illustrated in  FIG. 1 , a hydraulic cylinder  1 , for example, incorporated in a hydraulic device H of a construction machine, and through a first fluid outlet/inlet path  24  as a through-hole provided at a later-described oil port member  22 , is connected to a pressure pipe  11  forming a hydraulic circuit C 1 . In addition, the hydraulic cylinder  1  is, through a second fluid outlet/inlet path  26  as a through-hole provided at a later-described cover member  23 , connected to a pressure pipe  12  forming a hydraulic circuit C 2 . A hydraulic pump  14  is configured to increase the pressure of operating oil F 1  (shown as a first fluid and a non-compressible fluid) stored in a hydraulic reservoir  13  of the hydraulic circuit C 1 , thereby driving, e.g., a not-shown hydraulic motor for travelling. Moreover, the hydraulic cylinder  1  is operated by the operating oil F 1  for energy transmission between the operating oil F 1  and operating oil F 2  (shown as a second fluid and a non-compressible fluid) for driving a load W such as a rod in the hydraulic circuit C 2 . 
     First, a structure of the hydraulic cylinder  1  will be described in detail. As illustrated in  FIG. 2 , the hydraulic cylinder  1  mainly includes a metal cylinder container  2 , a moving member  3  movable in the cylinder container  2  in response to the pressures of the above-described operating oils F 1 , F 2 , and a first bellows  4  and a second bellows  5  capable of expanding and contracting, and supporting the moving member  3  in the cylinder container  2 . Note that the hydraulic cylinder  1  illustrated in  FIG. 2  is in a non-drive state in which the load W is not driven in the hydraulic circuit C 2 . Further, note that details of driving of the load W by means of energy transmission between the operating oils F 1 , F 2  in the hydraulic cylinder  1  will be described later. 
     The cylinder container  2  includes a cylindrical shell  21  having openings at both ends, the oil port member  22  welded and fixed to close one end (on a side of a hydraulic circuit C 1 , see  FIG. 1 ) of the shell  21 , and the cover member  23  welded and fixed to close the other end (on a side of a hydraulic circuit C 2 , see  FIG. 1 ) of the shell  21 . 
     The first fluid outlet/inlet path  24  as the through-hole for outflow and inflow of the operating oil F 1  from and to a first liquid chamber  40  set inside the first bellows  4  through the pressure pipe  11  (see  FIG. 1 ) forming the hydraulic circuit C 1  is provided at the substantially center of the oil port member  22  in a radial direction, and a metal stay  25  forming a substantially cup shape at the substantially half position in the radial direction is welded and fixed in a standing state. 
     Note that a communication hole  25   b  penetrating, in a thickness direction, the substantially center of a bottom plate  25   a  in the radial direction is formed at the stay  25 , and the first fluid outlet/inlet path  24  of the oil port member  22  and the first liquid chamber  40  set inside the first bellows  4  communicate with each other through the communication hole  25   b.    
     A gas sealing port  27  for injecting gas (compressible fluid) such as nitrogen gas into a gas chamber  60  set inside the later-described second bellows  5  is provided at the substantially center of the cover member  23  in the radial direction. The gas sealing port  27  is closed by a gas plug  28  after gas injection. 
     Moreover, the second fluid outlet/inlet path  26  as the through-hole for outflow and inflow of the operating oil F 2  from and to a second liquid chamber  50  set inside the second bellows  5  through the pressure pipe  12  forming the hydraulic circuit C 2  (see  FIG. 1 ) is provided on an outer diameter side of the cover member  23 . 
     The moving member  3  is configured such that an annular resin guide member  31  (a guide portion) is fitted onto a discoid metal outer peripheral portion. At the guide member  31 ,  12  communication paths  31   b  formed in a groove shape along the thickness direction on the outside of the first bellows  4  and arranged at equal intervals in a circumferential direction are provided. The operating oil F 2  flowing in or flowing out of the later-described second liquid chamber  50  is movable in the cylinder container  2  through the communication paths  31   b . Note that arrangement of the communication paths  31   b  and the number of communication paths  31   b  may be other arrangements and numbers than 12 paths at equal intervals. 
     Moreover, the moving member  3  is configured such that the diameter thereof is the substantially same dimension as the inner diameter of the shell  21  forming the cylinder container  2 . Thus, when the moving member  3  moves in the axial direction, an outer peripheral surface  31   a  of the guide member  31  slides on an inner wall surface  21   a  of the shell  21 , and as a result the inclination of the moving member  3  can be prevented. In addition, movement of the moving member  3  is smoothly guided along the inner wall surface  21   a  of the shell  21 . Note that a material of the guide member  31  may be metal having a low coefficient of friction and exhibiting abrasion resistance other than resin. Further, note that the guide member  31  may be configured such that only the outer peripheral surface  31   a  is made of a material having a low coefficient of friction. 
     An annular seal holder  32  obtained in such a manner that a metal circular disk is pressed into a crank shape as viewed in a section is welded and fixed to a first planar portion  3   a  of the moving member  3  on a side of an oil port member  22 , and a seal member  33  in a discoid shape is held between the first planar portion  3   a  of the moving member  3  and the seal holder  32 . Moreover, at a second planar portion  3   b  of the moving member  3  on a side of a cover member  23 , a protruding planar portion  3   c  is formed such that the substantially center of the second planar portion  3   b  in the radial direction protrudes in a circular shape toward the cover member  23 . 
     The first bellows  4  is a substantially-cylindrical expandable and contractible metal bellows opening at both ends. The first bellows  4  is welded and fixed to an inner surface (a first inner surface part) of the oil port member  22  to close a fixed end  4   a  (a second end portion) of the first bellows  4 , and is welded and fixed to an outer diameter side of the first planar portion  3   a  of the moving member  3  to close a floating end  4   b  (a first end portion) of the first bellows  4 . Note that the first bellows  4  is held by the guide member  31  forming the moving member  3  with the floating end  4   b  being pinched by the first planar portion  3   a  of the moving member  3 . 
     The second bellows  5  is a substantially-cylindrical expandable and contractible metal bellows opening at both ends. The second bellows  5  is welded and fixed to an inner surface (a second inner surface part) of the cover member  23  opposed to the oil port member  22  to close a fixed end  5   a  (a second end portion) of the second bellows  5 , and is welded and fixed to the protruding planar portion  3   c  formed at the second planar portion  3   b  of the moving member  3  to close a floating end  5   b  (a first end portion) of the second bellows  5  forming an upper end. Moreover, the second bellows  5  is configured to have a smaller diameter than that of the first bellows  4 . Further, the first bellows  4  and the second bellows  5  are concentrically arranged in series in an expanding and contracting direction of the bellows on the center axis A (see  FIG. 2 ) of the cylinder container  2  with the moving member  3  being interposed between the first bellows  4  and the second bellows  5 . 
     An internal space of the cylinder container  2  has such a structure that the internal space is, in a sealed state, divided into the first liquid chamber  40  set inside the first bellows  4  and communicating with the first fluid outlet/inlet path  24  of the oil port member  22 , the second liquid chamber  50  set outside the first bellows  4  and the second bellows  5  and communicating with the second fluid outlet/inlet path  26  of the cover member  23 , and the gas chamber  60  set inside the second bellows  5 . 
     The first liquid chamber  40  is defined by an inner peripheral surface  4   c  of the first bellows  4 , the inner surface of the oil port member  22 , and the first planar portion  3   a  (the seal holder  32  and the seal member  33 ) of the moving member  3 , and the operating oil F 1  can flow in or flow out of the first liquid chamber  40  through the first fluid outlet/inlet path  24  by way of the pressure pipe  11  (see  FIG. 1 ) forming the hydraulic circuit C 1 . 
     The second liquid chamber  50  is defined by an outer peripheral surface  5   d  of the second bellows  5 , the inner wall surface  21   a  of the shell  21 , the inner surface of the cover member  23 , the second planar portion  3   b  of the moving member  3 , and the guide member  31 , and the operating oil F 2  can flow in or flow out of the second liquid chamber  50  through the second fluid outlet/inlet path  26  by way of the pressure pipe  12  forming the hydraulic circuit C 2 . Moreover, as described above, the communication paths  31   b  are provided on an outer diameter side of the guide member  31  forming the moving member  3 , and therefore, the operating oil F 2  flowing in or flowing out of the second liquid chamber  50  through the second fluid outlet/inlet path  26  can move, in the cylinder container  2 , on the outside (between an outer peripheral surface  4   d  of the first bellows  4  and the inner wall surface  21   a  of the shell  21 ) of the first bellows  4  through the communication paths  31   b.    
     The gas chamber  60  is defined by an inner peripheral surface  5   c  of the second bellows  5 , the inner surface of the cover member  23 , and the protruding planar portion  3   c  of the second planar portion  3   b  of the moving member  3 , and the gas is sealed in the gas chamber  60 . 
     Subsequently, energy transmission between the operating oils F 1 , F 2  in the hydraulic cylinder  1  will be described in detail. Note that an example where a not-shown load cylinder operable by the operating oil F 2  is, in the hydraulic circuit C 2 , connected to the load W and the load W is driven by the load cylinder will be described. 
     In the hydraulic cylinder  1 , the pressure of the operating oil F 1  of the hydraulic circuit C 1  is increased by the hydraulic pump  14 , and accordingly, the operating oil F 1  flows in the first liquid chamber  40  through the first fluid outlet/inlet path  24  of the oil port member  22  by way of the pressure pipe  11  forming the hydraulic circuit C 1  (see an arrow of  FIG. 3 ). Then, in response to the pressure of the operating oil F 1  having flowed in the first liquid chamber  40 , the moving member  3  moves toward the cover member  23 , and accordingly, extension of the first bellows  4  and contraction of the second bellows  5  occur. At this point, in association with movement of the moving member  3  toward the cover member  23 , the operating oil F 2  moves from the second liquid chamber  50  to the outside (between the outer peripheral surface  4   d  of the first bellows  4  and the inner wall surface  21   a  of the shell  21 ) of the first bellows  4  through the communication paths  31   b  of the guide member  31  (see an arrow of  FIG. 3 ). 
     Moreover, the hydraulic cylinder  1  decreases the volume of the second liquid chamber  50  set outside the second bellows  5  by movement of the moving member  3  toward the cover member  23  and contraction of the second bellows  5 , and accordingly, the operating oil F 2  in the second liquid chamber  50  is discharged to the pressure pipe  12  forming the hydraulic circuit C 2  through the second fluid outlet/inlet path  26  of the cover member  23  (an arrow of  FIG. 3 ). According to this configuration, a drive state for supplying the operating oil F 2  from the hydraulic cylinder  1  to the load cylinder to drive the load W is brought in the hydraulic circuit C 2 . 
     At this point, in the cylinder container  2 , the pressure of the operating oil F 2  in the second liquid chamber  50  and the gas pressure in the gas chamber  60  are balanced, and excessive stress is no longer applied to the contracted second bellows  5  in the radial direction. Thus, the shape of the second bellows  5  can be maintained, and damage can be reduced. 
     From the drive state illustrated in  FIG. 3 , the hydraulic cylinder  1  switches a not-shown valve provided on a downstream side of the hydraulic pump  14  in the hydraulic circuit C 1  to decrease the pressure of the operating oil F 1 . Accordingly, the operating oil F 2  flows in the second liquid chamber  50  from the load cylinder connected to the hydraulic circuit C 2  through the pressure pipe  12  and the second fluid outlet/inlet path  26  of the cover member  23  (see an arrow of  FIG. 2 ). A second planar portion  3   b  side of the moving member  3  receives the pressure of the operating oil F 2  having flowed in the second liquid chamber  50 , and accordingly, the moving member  3  moves toward the oil port member  22  to expand the second bellows  5  and contract the first bellows  4 . In this state, by the pressure of the gas compressed in the gas chamber  60  set inside the second bellows  5 , restoring force acts in the direction of expanding the second bellows  5 , and therefore, the moving member  3  easily moves toward the oil port member  22 . Moreover, in this state, the operating oil F 2  moves to the second liquid chamber  50  from between the outer peripheral surface  4   d  of the first bellows  4  and the inner wall surface  21   a  of the shell  21  through the communication paths  31   b  of the guide member  31  in association with movement of the moving member  3  toward the oil port member  22  (see an arrow of  FIG. 2 ). 
     Moreover, the hydraulic cylinder  1  decreases the volume of the first liquid chamber  40  set inside the first bellows  4  by movement of the moving member  3  toward the oil port member  22  and contraction of the first bellows  4 , and accordingly, the operating oil F 1  in the first liquid chamber  40  is discharged to the pressure pipe  11  forming the hydraulic circuit C 1  through the communication hole  25   b  of the stay  25  and the first fluid outlet/inlet path  24  of the oil port member  22  (an arrow of  FIG. 2 ). According to this configuration, the seal member  33  attached to the first planar portion  3   a  of the moving member  3  and the bottom plate  25   a  of the stay  25  provided at the oil port member  22  in the cylinder container  2  closely contact each other, and a non-drive state illustrated in  FIG. 2  is brought. 
     In this state, the seal member  33  and the bottom plate  25   a  of the stay  25  closely contact each other in the cylinder container  2  to form an annular seal portion S, and therefore, the communication hole  25   b  of the stay  25  is closed. According to this configuration, part of the operating oil F 1  is kept in the first liquid chamber  40 . The pressure of the kept operating oil F 1  and the pressure of the operating oil F 2  having flowed in the second liquid chamber  50  are balanced, and therefore, excessive stress is no longer-applied to the contracted first bellows  4 . Thus, the shape of the first bellows  4  can be maintained, and damage can be reduced. 
     As described above, the hydraulic cylinder  1  moves the moving member  3  in the cylinder container  2  in the axial direction by the pressure of the operating oil F 1 , and therefore, causes the pressure to act between the operating oils F 1 , F 2  through the moving member  3  to transmit the energy. 
     Moreover, in the cylinder container  2 , the operating oil F 1  flowing in/out through the first fluid outlet/inlet path  24  and the operating oil F 2  flowing in/out through the second fluid outlet/inlet path  26  can be, in the sealed state, divided to the inside and outside of the first bellows  4 . Thus, mixing of the operating oils F 1 , F 2  in the cylinder container  2  can be prevented. In addition, friction due to sliding between the cylinder container  2  and the moving member  3  is decreased, and operability of the moving member  3  in the cylinder container  2  can be enhanced. 
     Moreover, the operating oil F 2  as the non-compressible fluid flows in or flows out of the second liquid chamber  50  through the second fluid outlet/inlet path  26  in the cylinder container  2 , and therefore, a damper effect utilizing fluid resistance of the operating oil F 2  generated upon movement in the cylinder container  2  through the communication paths  31   b  of the guide member  31  provided outside the first bellows  4  in association with movement of the moving member  3  can be obtained. Thus, movement of the moving member  3  in the cylinder container  2  can be stabilized. 
     Further, the operating oil F 2  moves through the communication paths  31   b  provided at the guide member  31  in the cylinder container  2 . Accordingly, the fluid resistance of the operating oil F 2  can be decreased, and the pressures of the operating oils F 1 , F 2  necessary for movement of the moving member  3  can be decreased. Thus, the operability of the moving member can be enhanced. Note that the size of the communication path  31   b  provided at the guide member  31  is changed so that the fluid resistance of the operating oil F 2  moving through the communication paths  31   b  can be adjusted. Thus, the speed of movement of the moving member  3  in the cylinder container  2  can be controlled. 
     Moreover, the second bellows  5  is configured to have a smaller diameter than that of the first bellows  4 , and therefore, the outside of the first bellows  4  and the outside of the second bellows  5  are aligned in the expanding and contracting direction of the bellows. Thus, a structure can be easily obtained, in which the operating oil F 2  moves between the outside of the first bellows  4  and the outside of the second bellows  5  with respect to the moving member  3  and the guide member  31  in the second liquid chamber  50 . Further, the second bellows  5  is configured to have a smaller diameter than that of the first bellows  4 . Thus, it can be configured such that a pressure receiving area of the second planar portion  3   b  side of the moving member  3  for the operating oil F 2  flowing in or flowing out of the second liquid chamber  50  from the second fluid outlet/inlet path  26  is large, and it can be configured such that a pressure receiving area of the moving member  3  of a side of the first planar portion  3   a  for the operating oil F 1  flowing in or flowing out of the first liquid chamber  40  through the first fluid outlet/inlet path  24  is large. Consequently, responsiveness of the moving member  3  to the pressures of the operating oils F 1 , F 2  can be enhanced. 
     Moreover, the moving member  3  is, in the cylinder container  2 , supported by the first bellows  4  and the second bellows  5  concentrically arranged in series in the expanding and contracting direction, and therefore, the moving member  3  can be stably supported in the cylinder container  2 . Further, the shape of the second bellows  5  can be easily maintained by the pressure of the gas sealed in the gas chamber  60  set inside the second bellows  5 , and therefore, the moving member  3  can be more stably supported in the cylinder container  2 . 
     Moreover, the second bellows  5  is fixed to the substantially center of the moving member  3 . Accordingly, inclination of the moving member  3  can be reduced, and the moving member  3  can be more stably supported in the cylinder container  2 . As described above, the moving member  3  is stably supported by the first bellows  4  and the second bellows  5 , and therefore, straightness upon movement of the moving member  3  in the cylinder container  2  can be enhanced. 
     Moreover, as described above, the internal space of the cylinder container  2  can be, in the sealed state, divided into the inside and outside of the first bellows  4 , and therefore, mixing of the operating oils F 1 , F 2  between the first liquid chamber  40  and the second liquid chamber  50  can be prevented without enhancing sealability between the cylinder container  2  (the inner wall surface  21   a  of the shell  21 ) and the moving member  3  (the outer peripheral surface  31   a  of the guide member  31 ). 
     Specifically, as described above as the background art, in a case where a not-shown seal member slidably contacting the inner wall surface  21   a  of the shell  21  is, for example, provided at an outer peripheral portion of the moving member  3  to substantially hermetically divide the internal space of the cylinder container  2  into the first liquid chamber  40  and the second liquid chamber  50  by the moving member  3  to prevent mixing of the operating oils F 1 , F 2 , if an attempt is made to enhance sealability by the seal member to prevent mixing of the operating oils F 1 , F 2 , friction between the inner wall surface  21   a  of the shell  21  and the seal member of the moving member  3  is caused. In this case, the seal member is abraded due to repeated movement of the moving member  3  in the cylinder container  2 , and for this reason, there is a probability that the sealability by the seal member is lowered to cause mixing of the operating oils F 1 , F 2 . Moreover, in this case, sliding resistance of the moving member  3  against the inner wall surface  21   a  of the shell  21  is caused. For this reason, not only the pressures of the operating oils F 1 , F 2  necessary for moving the moving member  3  are increased, but also the hydraulic cylinder  1  needs to be regularly disassembled to replace the abraded seal member. This also lowers maintainability. 
     On the other hand, the hydraulic cylinder  1  of the present embodiment can divide, in the sealed state, the internal space of the cylinder container  2  into the inside and outside of the first bellows  4 , and therefore, mixing of the operating oils F 1 , F 2  between the first liquid chamber  40  and the second liquid chamber  50  can be prevented. Friction of the moving member  3  (the outer peripheral surface  31   a  of the guide member  31 ) against the inner wall surface  21   a  of the shell  21  is decreased. Thus, the hydraulic cylinder  1  can be provided, in which the operability of the moving member  3  in the cylinder container  2  can be enhanced and no abrasion of the moving member  3  is caused for a long period of time. In addition to mixing of the operating oils F 1 , F 2 , mixing of abrasion powder of the seal member can be also prevented. Thus, driving of the load W can be maintained with high accuracy. 
     Moreover, mixing of the operating oils F 1 , F 2  in the cylinder container  2  can be prevented. Thus, even in the case of different types of the operating oil F 1 , F 2 , the hydraulic cylinder  1  can be applied between the hydraulic circuits C 1 , C 2 . 
     Second Embodiment 
     Next, fluid equipment according to a second embodiment of the present invention will be described with reference to  FIGS. 4 and 5 . Note that the same reference numerals are used to represent the same components as those described in the above-described embodiment, and overlapping description will be omitted. 
     As illustrated in  FIGS. 4 and 5 , in a hydraulic cylinder  101  as the fluid equipment according to the second embodiment, a moving member  103  is arranged inside a first bellows  4 , and one end of a cylindrical coupling member  136  to be fitted in an inner peripheral portion of a guide member  131  is welded and fixed to an outer diameter side of a second planar portion  103   b  of the moving member  103 . 
     Moreover, a floating end  4   b  of the first bellows  4  is welded and fixed with the floating end  4   b  being sandwiched between the guide member  131  and the other end of the coupling member  136 . 
     According to this configuration, a floating end  5   b  of a second bellows  5  is closed by a protruding planar portion  103   c  of the moving member  103  arranged inside the first bellows  4 , and therefore, the moving member  103  can be supported in a state in which the first bellows  4  and the second bellows  5  partially overlap with each other in an extension direction. Consequently, a cylinder container  102  can be compactly configured without shortening expansion lengths of the first bellows  4  and the second bellows  5  upon movement of the moving member  103  in an axial direction. 
     Moreover, as illustrated in  FIG. 4 , in a non-drive state of the hydraulic cylinder  101 , a seal member  33  attached to a first planar portion  103   a  of the moving member  103  and an inner surface of a first fluid outlet/inlet path  124  of an oil port member  122  closely contact each other to form an annular seal portion S in the cylinder container  102 , and therefore, the first fluid outlet/inlet path  124  is closed. According to this configuration, part of operating oil F 1  is kept in a first liquid chamber  40 , and the pressure of the kept operating oil F 1  and the pressure of operating oil F 2  having flowed in a second liquid chamber  50  are balanced. Thus, excessive stress is no longer applied to the contracted first bellows  4 . Consequently, the shape of the first bellows  4  can be maintained, and damage can be reduced. 
     Third Embodiment 
     Next, fluid equipment according to a third embodiment of the present invention will be described with reference to  FIG. 6 . Note that the same reference numerals are used to represent the same components as those described in the above-described embodiments, and overlapping description will be omitted. Further, note that for the fluid equipment according to the third embodiment, only a non-drive state is illustrated in the figure, and a drive state is not shown in the figure. 
     As illustrated in  FIG. 6 , in a hydraulic cylinder  201  shown as the fluid equipment of the third embodiment, a second fluid outlet/inlet path  226  for outflow/inflow of operating oil F 2  as non-compressible fluid from/to a second liquid chamber  250  set inside a second bellows  5  through a pressure pipe  12  forming a hydraulic circuit C 2  (see  FIG. 1 ) is provided at the substantially center of a cover member  223  in a radial direction. 
     Moreover, a gas sealing port  227  for injecting gas such as nitrogen gas into a gas chamber  260  set outside the second bellows  5  is provided on an outer diameter side of the cover member  223 , and is closed by a gas plug  228  after gas injection. 
     According to this configuration, in the non-drive state of the hydraulic cylinder  201 , the pressure of the operating oil F 2  for moving a moving member  3  toward an oil port member  22  can be received by a protruding planar portion  3   c  formed at a substantially center portion of the moving member  3  in the radial direction in the second liquid chamber  250  hermetically set inside the second bellows  5 . Thus, the pressure of the operating oil F 2  can be efficiently utilized to enhance operability of the moving member  3  in a cylinder container  202 . 
     Moreover, the gas chamber  260  is interposed between a first liquid chamber  40  and a second liquid chamber  50 , and therefore, operating oil F 1  and the operating oil F 2  are less mixed. That is, even when sealing of a first bellows  4  or the second bellows  5  becomes insufficient, the operating oil F 1  and the operating oil F 2  are less mixed. 
     The embodiments of the present invention have been described above with reference to the drawings, but specific configurations are not limited to these embodiments. Changes and additions made without departing from the gist of the present invention are also included in the present invention. 
     In the above-described embodiments, the operating oils F 11 , F 2  have been described as an example of operating fluid used for the hydraulic cylinder  1 , but at least one of the operating fluids may be compressible fluid. 
     Moreover, in the above-described embodiments, it has been described that the first bellows  4  and the second bellows  5  are provided in the cylinder container  2 ,  102 ,  202 . However, at least one bellows may be provided in the cylinder container, and the operating fluids flowing in or flowing out of the first fluid outlet/inlet path and the second fluid outlet/inlet path may be, in the sealed state, separated by the bellows. 
     Further, in the above-described embodiments, the aspect has been described, in which the gas is sealed in the second bellows  5 . However, a restoring unit configured to provide the restoring force to the contracted second bellows may be provided inside the second bellows. For example, a spring etc. may be provided inside the second bellows to provide the restoring force in the direction of expanding the second bellows. 
     In addition, in the above-described embodiments, the aspect has been described, in which the separate guide member  31  is fitted onto the metal discoid outer peripheral portion forming the moving member  3 . However, the guide portion may be integrally configured with the metal discoid outer peripheral portion forming the moving member. 
     Moreover, in the above-described embodiments, the aspect has been described, in which the outer peripheral surface of the guide member  31 ,  131  slides on the inner wall surface  21   a  of the shell  21  in association with movement of the moving member  3 ,  103 . However, the outer peripheral surface of the guide member may be separated from the inner wall surface of the shell to reduce sliding between the inner wall surface of the shell and the outer peripheral surface of the guide member. 
     Further, in the above-described embodiments, it has been described that the communication paths  31   b  are provided at the guide member  31 . However, as long as the communication paths are on the outside of the first bellows  4 , the communication paths may be provided at the metal disk forming the moving member  3 . 
     In addition, the communication path  31   b  is not limited to the groove shape, but may be in a through-hole shape or a slit shape. 
     Moreover, the example has been described, in which the cylinder container  2  is configured such that the shell  21 , the oil port member  22 , and the cover member  23  are formed from separate members. However, the shell  21  and the oil port member  22  or the cover member  23  may be formed as a single member. 
     Further, instead of the stay  25 , a seal member  133  (see  FIG. 7 ) having a lip seal  135  may be provided integrally with the oil port member  22 , and the first planar portion  3   a  of the moving member  3  may be directly closely contact the lip seal  135 . 
     In addition, the first bellows  4  and the second bellows  5  are not limited to the metal bellows, and may be made of resin etc. 
     REFERENCE SIGNS LIST 
     
         
         
           
               1  hydraulic cylinder 
               2  cylinder container 
               3  moving member 
               4  first bellows 
               4   a  fixed end (second end portion) 
               4   b  floating end (first end portion) 
               5  second bellows 
               5   a  fixed end (second end portion) 
               5   b  floating end (first end portion) 
               11 ,  12  pressure pipe 
               21  shell 
               22  oil port member 
               23  cover member 
               24  first fluid outlet/inlet path 
               26  second fluid outlet/inlet path 
               27  gas sealing port 
               31  guide member (guide portion) 
               31   b  communication path 
               40  first liquid chamber 
               50  second liquid chamber 
               60  gas chamber 
               101  hydraulic cylinder (fluid equipment) 
               201  hydraulic cylinder (fluid equipment) 
             C 1 , C 2  hydraulic circuit 
             F 1 , F 2  operating oil (first fluid, second fluid) 
             H hydraulic device 
             S seal portion 
             W load