Fuel cell stack structure and fuel cell stack structure manufacturing method

Abstract

A fuel cell stack structure is basically provided with a stack entity and at least one tie rod. The stack entity includes a plurality of solid electrolyte fuel cell units stacked together in a stacking direction. The tie rod extends through the stack entity to fasten the solid electrolyte fuel cell units so that the solid electrolyte fuel cell units are pressed against each other in the stacking direction. The tie rod has an outer cylinder, an inner shaft fitting into the outer cylinder, and a fixing member that fastens the outer cylinder and the inner shaft together in an axial direction of the tie rod.

1 . A fuel cell stack structure comprising: 
 a stack entity including a plurality of solid electrolyte fuel cell units stacked together in a stacking direction; and    at least one tie rod extending through the stack entity to fasten the solid electrolyte fuel cell units so that the solid electrolyte fuel cell units are pressed against each other in the stacking direction, the tie rod having an outer cylinder, an inner shaft fitting into the outer cylinder, and a fixing member that fastens the outer cylinder and the inner shaft together in an axial direction of the tie rod.    
     
     
         2 . The fuel cell stack structure as recited in  claim 1 , wherein 
 the at least one tie rod includes a plurality of tie rods extending through the stack entity.    
     
     
         3 . The fuel cell stack structure as recited in  claim 1 , further comprising 
 a pair of end plates provided on both ends of the stack entity, the end plates having a larger mechanical strength than the solid electrolyte fuel cell units, and each of the end plates including a rod through hole with the tie rod passing therethrough, and    a gas sealing material arranged in an airtight manner between the tie rod and the rod through holes of the end plates.    
     
     
         4 . The fuel cell stack structure as recited in  claim 3 , wherein 
 the outer cylinder and the inner shaft include base end portions that are opposite from tip end portions where the outer cylinder and the inner shaft fit together, each of the base end portions of the outer cylinder and the inner shaft includes a head section that has a larger diameter than an opening diameter of the rod through hole of a corresponding one of the end plates.    
     
     
         5 . The fuel cell stack structure as recited in  claim 1 , wherein 
 one of the outer cylinder and the inner shaft of the tie rod includes at least one vent hole that communicates between a space formed inside the outer cylinder when the inner shaft is fitted therein and a space surrounding outside of the outer cylinder.    
     
     
         6 . The fuel cell stack structure as recited in  claim 1 , wherein 
 the outer cylinder of the tie rod includes a base end portion that is opposite from an end portion where the outer cylinder and the inner shaft fit together, the base end portion of the outer cylinder is open to a space surrounding outside of the outer cylinder.    
     
     
         7 . The fuel cell stack structure as recited in  claim 3 , wherein 
 a base end portion of one of the outer cylinder and the inner shaft of the tie rod includes an externally threaded section, and one of the end plates that is coupled to the base end portion of the one of the outer cylinder and the inner shaft of the tie rod includes an internally threaded section that engages with the externally threaded section.    
     
     
         8 . The fuel cell stack structure as recited in  claim 1 , wherein 
 the fixing member of the tie rod includes a joining material disposed between the outer cylinder and the inner shaft, the joining material is configured and arranged to maintain a cured state at an operating temperature.    
     
     
         9 . The fuel cell stack structure as recited in  claim 8 , wherein 
 at least one of an inner circumferential surface of the outer cylinder and an outer circumferential surface of the inner shaft that are opposing each other includes one of an intermittent groove and a continuous groove arranged around an center axis of the tie rod.    
     
     
         10 . The fuel cell stack structure as recited in  claim 8 , further comprising 
 a sealing material disposed between the solid electrolytic fuel cell units of the stack entity, the sealing material exhibiting a gas sealing characteristic at a temperature equal to or below a joining temperature of the joining material used as the fixing member.    
     
     
         11 . The fuel cell stack structure as recited in  claim 8 , wherein 
 the joining material is arranged on both of an inner circumferential surface of the outer cylinder and an outer circumferential surface of the inner shaft of the tie rod at least in a region where the inner circumferential surface of the outer cylinder and the outer circumferential surface of the inner shaft overlap, the joining material is configured and arranged to allow a sliding movement between the outer cylinder and the inner shaft at a temperature below a joining temperature of the joining material.    
     
     
         12 . The fuel cell stack structure as recited in  claim 8 , wherein 
 the joining material includes a metallic glass material so that the outer cylinder and the inner shaft of the tie rod are fixed together in the axial direction by crystallizing the metallic glass material.    
     
     
         13 . The fuel cell stack structure as recited in  claim 8 , wherein 
 the joining material includes a glass material having a melting point equal to or larger than the operating temperature after crystallization.    
     
     
         14 . The fuel cell stack structure as recited in  claim 8 , wherein 
 the joining material includes a ceramic glass material having a melting point equal to or larger than the operating temperature after crystallization.    
     
     
         15 . The fuel cell stack structure as recited in  claim 8 , wherein 
 the joining material includes a brazing filler material having a melting temperature sufficiently high with respect to the operating temperature.    
     
     
         16 . The fuel cell stack structure as recited in  claim 8 , wherein 
 the joining material includes a metallic compound.    
     
     
         17 . The fuel cell stack structure as recited in  claim 1 , wherein 
 the fixing member includes a plurality of claw-shaped parts provided on an inner circumferential surface of the outer cylinder and an outer circumferential surface of the inner shaft of the tie rod, the claw-shaped parts of the outer cylinder is configured and arranged to engage with the claw-shaped parts of the inner shaft such that a sliding movement of the inner shaft in a direction of entering into the outer cylinder is permitted and a sliding movement of the inner shaft in a direction of removal from the outer cylinder is restricted.    
     
     
         18 . The fuel cell stack structure as recited in  claim 1 , wherein 
 the outer cylinder of the tie rod includes at least one lengthwise slit extending in a region where the outer cylinder and the inner shaft fit together.    
     
     
         19 . The fuel cell stack structure as recited in  claim 1 , wherein 
 a portion of the inner shaft of the tie rod that fits into the outer cylinder has a tapered shape.    
     
     
         20 . The fuel cell stack structure as recited in  claim 1 , wherein 
 the inner shaft of the tie rod includes a plurality of tapered annular protruding parts on a portion of the inner shaft that fits into the outer cylinder.    
     
     
         21 . The fuel cell stack structure as recited in  claim 1 , wherein 
 a tip end portion of the inner shaft of the tie rod inserted into the outer cylinder is exposed at a base end portion of the outer cylinder that is opposite from a tip end portion of the outer cylinder where the inner shaft is inserted into the outer cylinder, and    the fixing member includes a metallic glass material disposed between the tip end portion of the inner shaft and the base end portion of the outer cylinder, the metallic glass material is configured and arranged to fasten the outer cylinder and the inner shaft of the tie rod together in the axial direction by undergoing plastic deformation.    
     
     
         22 . The fuel cell stack structure as recited in  claim 12 , wherein 
 the joining material is configured and arranged to be raised to a glass transition temperature and then to be crystallized to fasten the outer cylinder and the inner shaft of the tie rod together in the axial direction.    
     
     
         23 . The fuel cell stack structure as recited in  claim 22 , wherein 
 the joining material is raised to the glass transition temperature and then held in a temperature region in which a glass transition state is exhibited until the joining material is crystallized to fasten the outer cylinder and the inner shaft of the tie rod together in the axial direction.    
     
     
         24 . The fuel cell stack structure as recited in  claim 22 , wherein 
 the joining material is raised to the glass transition temperature and then raised further to a crystallization temperature to crystallize the joining material to fasten the outer cylinder and the inner shaft of the tie rod together in the axial direction.    
     
     
         25 . A fuel cell stack structure comprising: 
 electricity generating means for generating electricity;    first fastening means for pressing a first end of the electricity generating means in a first direction;    second fastening means for pressing a second end of the electricity generating means in a second direction that is opposite from the first direction; and    fixing means for fastening the first and second fastening means together in an axial direction of the first and second fastening means.    
     
     
         26 . A fuel cell stack structure manufacturing method comprising: 
 forming a stack entity by stacking a plurality of solid electrolyte fuel cell units in a stacking direction;    inserting a tip end portion of an outer cylinder of a tie rod into the stack entity from a first end of the stack entity, and inserting a tip end of an inner shaft of the tie rod into the stack entity from a second end of the stack entity;    fitting the outer cylinder and the inner shaft of the tie rod together such that a joining material is disposed between an inner circumferential surface of the outer cylinder and an outer circumferential surface of the inner shaft; and    heating the joining material disposed between the outer cylinder and the inner shaft of the tie rod while applying an axial compressive pressure to the tie rod.    
     
     
         27 . The fuel cell stack structure manufacturing method as recited in  claim 26 , wherein 
 the fitting of the outer cylinder and the inner shaft of the tie rod together includes fitting the outer cylinder and the inner shaft of the tie rod together such that a metallic glass material used as the joining material is disposed between the inner circumferential surface of the outer cylinder and the outer circumferential surface of the inner shaft, and    the heating of the joining material includes heating and crystallizing the metallic glass material disposed between the outer cylinder and the inner shaft of the tie rod while applying the axial compressive pressure to the tie rod.    
     
     
         28 . The fuel cell stack structure manufacturing method as recited in  claim 26 , wherein 
 the heating of the joining material includes electrifying the tie rod such that the tie rod emits heat.    
     
     
         29 . A fuel cell stack structure manufacturing method comprising: 
 forming a stack entity by stacking a plurality of solid electrolyte fuel cell units in a stacking direction;    inserting a tip end portion of an outer cylinder of a tie rod into the stack entity from a first end of the stack entity, and inserting a tip end of an inner shaft of the tie rod into the stack entity from a second end of the stack entity;    fitting the outer cylinder and the inner shaft of the tie rod together; and    fastening the outer cylinder and the inner shaft of the tie rod together in an axial direction of the tie rod by engaging a claw-shaped part of the outer cylinder and a claw-shaped part of the inner shaft while applying an axial compressive pressure to the tie rod.    
     
     
         30 . A fuel cell stack structure manufacturing method comprising: 
 forming a stack entity by stacking a plurality of solid electrolyte fuel cell units in a stacking direction;    inserting a tip end portion of an outer cylinder of a tie rod into the stack entity from a first end of the stack entity, and inserting a tip end of an inner shaft of the tie rod into the stack entity from a second end of the stack entity;    fitting the outer cylinder and the inner shaft of the tie rod together while exposing the tip end portion of the inner shaft at a base end portion of the outer cylinder with a metallic glass material being disposed between the tip end portion of the inner shaft and the base end portion of the outer cylinder; and    causing the metallic glass material to undergo plastic deformation while applying an axial compressive pressure to the tie rod to fasten the outer cylinder and the inner shaft of the tie rod together in an axial direction of the tie rod.