Patent Description:
Conventionally, a fuel cell stack is made by stacking a plurality of fuel cell units, each having a power generation cell that is formed by sandwiching an electrolyte from both sides with a pair of electrodes and that generates power using supplied gas, and a separator that defines a flow path portion, i.e., a flow passage for the gas between the separator and the power generation cell (for example, refer to Patent Document <NUM>).

The fuel cell stack has a spring member that generates elastic force that presses the separator toward the power generation cell.

<CIT> describes a solid oxide fuel cell system (<NUM>) comprising a plurality of electrochemically active fuel cell cassettes (<NUM>) connected in electrical series and bonded together by a plurality of glass seals to form a fuel cell stack (<NUM>). A dummy cassette (<NUM>) containing a thermocouple is disposed within the fuel cell stack (<NUM>). Each cassette (<NUM>) may have at least one alignment tab for receiving a rod (<NUM>) to maintain stack alignment during sintering, and each fuel cell cassette (<NUM>) has electrical terminals extending from a side of the stack for performance testing. The distribution manifold (<NUM>) is attached to stack (<NUM>), and a spring subassembly (<NUM>) is disposed against the stack (<NUM>) and is attached to the manifold (<NUM>) by tie rods (<NUM>) to maintain a compressive load on the stack (<NUM>) through sintering and subsequent use to prevent unloading and rupture of the glass seals.

<CIT> describes a stack (<NUM>) interposed between upper and lower holders (<NUM>, <NUM>), and placed on a lower bolster (<NUM>). A spring (<NUM>), an inside bolster (4a), bellows (<NUM>), and an outside bolster (4b) are arranged in order on the upper holder (<NUM>). When preliminary treatment is performed, the stack (<NUM>) is fastened with the bellows (<NUM>) and the spring (<NUM>). At high temperature after preliminary treatment, the inner pressure of the bellows (<NUM>) is increased. After returning to the normal temperature, fastening with the bellows (<NUM>) is switched to that with the spring (<NUM>), and the bellows (<NUM>) are removed.

When the fuel cell units are stacked, it is necessary to support the components to be assembled with a spring member and to assembly the components in close contact with each other; thus, the spring member is required to have a high spring constant.

However, during operation of the fuel cell stack, the temperature of the spring member becomes high due to the heat that is generated from the power generation cell, etc. The higher the spring constant, the more readily the spring member undergoes creep deformation when the temperature of the spring member becomes high. Therefore, if a spring member with a high spring constant is used when the cell units are stacked, the spring member could undergo creep deformation and it may become impossible to ensure sufficient surface pressure between the power generation cell and the separator during operation of the fuel cell stack. As a result, there is the problem of reduced collector resistance between the power generation cell and the separator, and thus decreased power generation performance of the fuel cell.

An object of the present invention is to provide a spring member, a fuel cell unit, a fuel cell stack, and a method for manufacturing a fuel cell stack that can prevent the decrease in the power generation performance caused by the creep deformation of the spring member.

In order to achieve the object described above, the spring member according to the present invention is used in a fuel cell stack, comprising a first spring member that generates elastic force for pressing a separator toward a power generation cell, and a second spring member that generates elastic force independently of the first spring member. The spring constant of the first spring member decreases with applied heat. Since the spring constant of the first spring member is larger than the spring constant of the second spring member before the first spring member is heated, the spring member functions as a high reaction force spring, and, once heated, the spring member functions as a low reaction force spring as a result of the smaller spring constant of first spring member as compared prior to being heated.

In order to achieve the object described above, in the method for manufacturing the fuel cell stack, when the fuel cell units are stacked, a spring member including a first spring member that generates elastic force for pressing the separator toward the power generation cell, and a second spring member that generates the elastic force independently of the first spring member, is disposed. When the spring member described above is disposed, the spring member that functions as a high reaction force spring as a result of the larger spring constant of the first spring member relative to the spring constant of the second spring member. In said manufacturing method, the fuel cell units are stacked after which the spring member is heated, to thereby decrease the spring constant of the first spring member and cause the spring member to function as a low reaction force spring.

Embodiments of the present invention will be explained below, with reference to the appended drawings. In the drawings, the same members have been assigned the same reference symbols and redundant explanations have been omitted. In the drawings, the sizes and proportions of the members have been exaggerated for ease of understanding the embodiment, and may differ from the actual sizes and proportions.

The orientations of members constituting a fuel cell stack are shown using arrows indicated by X, Y, and Z in each of the drawings. The direction of the arrow indicated by X is the transverse direction X of the fuel cell stack. The direction of the arrow indicated by Y is the longitudinal direction Y of the fuel cell stack. The direction of the arrow indicated by Z is the stacking (height) direction Z of the fuel cell stack.

As shown in <FIG> and <FIG>, the fuel cell <NUM> is formed by sandwiching a cell stack assembly <NUM> from above and below with a cover <NUM> that protects the cell stack assembly <NUM> and an external manifold <NUM> that supplies gas from the outside.

As shown in <FIG> and <FIG>, the cell stack assembly <NUM> is formed by sandwiching a fuel cell stack <NUM> from above and below with an upper end plate <NUM> and a lower end plate <NUM>, which are then covered with an air shelter <NUM> that seals cathode gas CG.

As shown in <FIG> and <FIG>, the fuel cell stack <NUM> is formed by stacking an upper module unit 100P, a plurality of middle module units 100Q, and a lower module unit 100R.

As shown in <FIG>, the upper module unit 100P is formed by sandwiching a plurality of stacked cell units 100T (corresponding to a fuel cell unit) from above and below with an upper collector plate <NUM> that outputs electric power generated by the cell units 100T to the outside, and a module end <NUM>, which corresponds to an end plate.

As shown in <FIG>, the middle module unit 100Q is formed by sandwiching a plurality of stacked cell units 100T from above and below with a pair of module ends <NUM>.

As shown in <FIG>, the lower module unit 100R is formed by sandwiching a plurality of stacked cell units 100T from above and below with the module end <NUM> and a lower collector plate <NUM>.

As shown in <FIG>, the cell unit 100T includes a metal support cell assembly <NUM> provided with power generation cells <NUM> that generate power using supplied gas, a separator <NUM> that separates adjacent power generation cells <NUM>, sealing members <NUM> that partially seal the gap between the metal support cell assembly <NUM> and the separator <NUM> and restricts the flow of the gas, and grid springs <NUM> that are in conductive contact with one of the power generation cells <NUM> and that generates an elastic force that presses the separator <NUM> toward another of the power generation cells <NUM> that is adjacent to the one power generation cell <NUM>.

As shown in <FIG>, a joined body 100U includes the metal support cell assembly <NUM> and the separator <NUM>. In the joined body 100U, the metal support cell assembly <NUM> and the separator <NUM> are configured such that the outer edges thereof are annularly joined along a joining line V, as shown in <FIG>. The cell unit 100T is formed by disposing the sealing members <NUM> between the joined body 100U and the joined body 100U that are vertically adjacent to each other.

The fuel cell stack <NUM> will be described below for each configuration.

As shown in <FIG>, the metal support cell assembly <NUM> is provided with power generation cells <NUM> that generate power using supplied gas.

In the metal support cell assembly <NUM>, the power generation cell <NUM> is formed by sandwiching an electrolyte <NUM> between a fuel electrode-side electrode (anode 101T) and an oxidant electrode-side electrode (cathode 101U) as shown in <FIG> and <FIG>. A metal support cell 101N is configured from the power generation cell <NUM> and a support metal 101V that supports the power generation cell <NUM> from one side. The metal support cell assembly <NUM> is configured from a pair of metal support cells 101N and a cell frame 101W that holds the pair of metal support cells 101N from the periphery.

As shown in <FIG> and <FIG>, the electrolyte <NUM> allows oxide ions to pass from the cathode 101U to the anode 101T. The electrolyte <NUM> allows oxide ions to pass but does not allow gas and electrons to pass. The electrolyte <NUM> is formed into a rectangular parallelepiped shape. The electrolyte <NUM> is made of a solid oxide ceramic, such as stabilized zirconia in which yttria, neodymium oxide, samaria, gadria, scandia, and the like are dissolved.

As shown in <FIG> and <FIG>, the anode 101T is a fuel electrode, and reacts an anode gas AG (for example, hydrogen) with oxide ions to thereby generate an oxide of the anode gas AG and extract electrons. The anode 101T is resistant to a reducing atmosphere, allows the anode gas AG to pass therethrough, has high electrical conductivity, and has a catalytic action to react the anode gas AG with the oxide ions. The anode 101T is formed into a rectangular parallelepiped shape that is larger than the electrolyte <NUM>. The anode 101T is made of cemented carbide in which, for example, a metal such as nickel and an oxide ion conductor such as yttria-stabilized zirconia are mixed.

As shown in <FIG> and <FIG>, the cathode 101U is an oxidant electrode, and reacts a cathode gas CG (for example, oxygen contained in air) with electrons to convert oxygen molecules to oxide ions. The cathode 101U is resistant to oxidizing atmosphere, allows the cathode gas CG to pass therethrough, has high electric conductivity, and has a catalytic action to convert oxygen molecules into oxide ions. The cathode 101U is formed into a rectangular parallelepiped shape that is smaller than the electrolyte <NUM>. The cathode 101U is made of an oxide of, for example, lanthanum, strontium, manganese, or cobalt.

As shown in <FIG> and <FIG>, the support metal 101V supports the power generation cells <NUM> on the anode 101T side. The support metal 101V has gas permeability, high electric conductivity, and sufficient strength. The support metal 101V is formed into a rectangular parallelepiped shape that is sufficiently larger than the anode 101T. The support metal 101V is made of, for example, stainless steel, corrosion-resistant steel, or a corrosion-resistant alloy containing nickel and chromium.

As shown in <FIG>, the cell frame 101W holds the metal support cell 101N from the periphery. The cell frame 101W is formed into a thin rectangular shape. The cell frame 101W is provided with a pair of openings <NUM> along the longitudinal direction Y. Each of the pair of openings <NUM> of the cell frame 101W is formed of a rectangular through-hole, and is slightly smaller than the outer shape of the support metal 101V. The cell frame 101W is made of metal, and is insulated with an insulating material or a coating. The insulating material is formed, for example, by fixing aluminum oxide onto the cell frame 101W. The outer edge of the support metal 101V is joined to the inner edge of the opening <NUM> of the cell frame 101W to thereby join the metal support cell assembly <NUM> to the cell frame 101W.

As shown in <FIG> and <FIG>, the cell frame 101W is provided with circular extended portions (first extended portion 101p, second extended portion 101q, and third extended portion 101r) extending in the planar direction from the right end, the center, and the left end of one side along the longitudinal direction Y. The cell frame 101W is provided with circular extended portions (fourth extended portion <NUM> and fifth extended portion 101t) extending in the planar direction from two locations separated from the center of the other side along the longitudinal direction Y. In the cell frame 101W, the fourth extended portion <NUM> and the fifth extended portion 101t are located alternatingly with respect to the first extended portion 101p, the second extended portion 101q, and the third extended portion 101r, and are separated therefrom by the pair of openings <NUM> in the longitudinal direction Y.

As shown in <FIG> and <FIG>, in the cell frame 101W, an anode-side first inlet 101a, an anode-side second inlet 101b, and an anode-side third inlet 101c through which the anode gas AG passes (flows) are provided in the first extended portion 101p, the second extended portion 101q, and the third extended portion 101r, respectively. In the cell frame 101W, an anode-side first outlet 101d and an anode-side second outlet 101e through which the anode gas AG passes (flows) are provided in the fourth extended portion <NUM> and the fifth extended portion 101t, respectively. The inlets and the outlets are so-called manifolds.

As shown in <FIG>, in the cell frame 101W, a cathode-side first inlet 101f through which the cathode gas CG passes (flows) is provided in the space between the first extended portion 101p and the second extended portion 101q. In the cell frame 101W, a cathode-side second inlet <NUM> through which the cathode gas CG passes (flows) is provided in the space between the second extended portion 101q and the third extended portion 101r. In the cell frame 101W, a cathode-side first outlet <NUM> through which the cathode gas CG passes (flows) is provided on the right side of the fourth extended portion <NUM> in <FIG>. In the cell frame 101W, a cathode-side second outlet 101i through which the cathode gas CG passes (flows) is provided in the space between the fourth extended portion <NUM> and the fifth extended portion 101t. In the cell frame 101W, a cathode-side third outlet 101j through which the cathode gas CG passes (flows) is provided on the left side of the fifth extended portion 101t in <FIG>. In the cell frame 101W, the inlets and outlets of the cathode gas CG correspond to the space between the outer circumferential surface of the cell frame 101W and the inner-side surface of the air shelter <NUM>.

As shown in <FIG>, the separator <NUM> defines flow path portions <NUM>, which are flow passages for the anode gas AG and the cathode gas CG between the separator and the power generation cells <NUM>. The separator <NUM> is in conductive contact with the metal support cell 101N.

The separator <NUM> is disposed opposing the metal support cell assembly <NUM>. The separator <NUM> has the same outer shape as the metal support cell assembly <NUM>. The separator <NUM> is made of metal, and is insulated using an insulating material or a coating, excluding regions (flow path portions <NUM>) opposing the pair of power generation cells <NUM>. The insulating material is formed, for example, by fixing aluminum oxide onto the separator <NUM>. The separator <NUM> is provided with a pair of the flow path portions <NUM> arranged side by side in the longitudinal direction Y so as to oppose the pair of power generation cells <NUM>.

As shown in <FIG> as well as <FIG>, in the separator <NUM>, the flow path portions <NUM> are formed by arranging flow paths that extend along the direction of the flow of the gas (transverse direction X), in the direction (longitudinal direction Y) orthogonal to the direction of the flow of the gas (transverse direction X). As shown in <FIG>, <FIG>, and <FIG>, concave portions 102y are provided in the flow path portions <NUM> at regular intervals, so as to be recessed downward from flat portions 102x, in a plane defined by the longitudinal direction Y and the transverse direction X. The concave portions 102y extend along the direction of the flow of the gas (transverse direction X). The concave portions 102y are slightly recessed downward from the lower end of the separator <NUM>. As shown in <FIG>, <FIG>, and <FIG>, convex portions 102z are provided in the flow path portions <NUM> at regular intervals, so as to protrude upward from the flat portions 102x. The convex portions 102z extend along the direction of the flow of the gas (transverse direction X). The convex portions 102z slightly protrude upward from the upper end of the separator <NUM>. In the flow path portions <NUM>, the concave portions 102y and the convex portions 102z are alternatingly provided along the longitudinal direction Y, separated by the flat portions 102x.

As shown in <FIG>, in the separator <NUM>, the gap between the flow path portion <NUM> and the metal support cell assembly <NUM> located below (on the right in <FIG>) is configured to be the flow path of the anode gas AG. The anode gas AG flows from an anode-side second inlet 102b of the separator <NUM> shown in <FIG>, and the like, through a plurality of grooves 102q shown in <FIG> and <FIG>, into the flow path portion <NUM> on the anode side. As shown in <FIG> and <FIG>, in the separator <NUM>, the plurality of grooves 102q are formed from each of an anode-side first inlet 102a, the anode-side second inlet 102b, and an anode-side third inlet 102c, radially toward the flow path portion <NUM> on the anode side. As shown in <FIG> and <FIG>, in the separator <NUM>, the gap between the flow path portion <NUM> and the metal support cell assembly <NUM> located above (on the left in <FIG>) is configured to be the flow path of the cathode gas CG. The cathode gas CG flows from a cathode-side first inlet 102f and a cathode-side second inlet <NUM> of the separator <NUM> shown in <FIG>, over an outer edge 102p on the cathode side of the separator <NUM> shown in <FIG> and <FIG>, into the flow path portion <NUM> on the cathode side. As shown in <FIG>, in the separator <NUM>, the outer edge 102p on the cathode side is formed to be thinner than the other portions.

As shown in <FIG>, <FIG>, and <FIG>, the separator <NUM> is provided with the anode-side first inlet 102a, the anode-side second inlet 102b, the anode-side third inlet 102c, an anode-side first outlet 102d, and an anode-side second outlet 102e through which the anode gas AG passes, such that the relative position with the metal support cell assembly <NUM> matches along the stacking direction Z. The separator <NUM> is provided with the cathode-side first inlet 102f, the cathode-side second inlet <NUM>, a cathode-side first outlet <NUM>, a cathode-side second outlet 102i, and a cathode-side third outlet 102j through which the cathode gas CG passes, such that the relative position with the metal support cell assembly <NUM> matches along the stacking direction Z. In the separator <NUM>, the inlets and outlets of the cathode gas CG correspond to the space between the outer circumferential surface of the separator <NUM> and the inner-side surface of the air shelter <NUM>.

As shown in <FIG>, the grid spring <NUM> is in conductive contact with the power generation cell <NUM> via an auxiliary collector layer <NUM>.

The auxiliary collector layer <NUM> forms a space through which the cathode gas CG passes between the power generation cell <NUM> and the grid spring <NUM>, equalizes the surface pressure, and assists the electrical contact between the power generation cell <NUM> and the grid spring <NUM>.

The auxiliary collector layer <NUM> is a so-called expanded metal. The auxiliary collector layer <NUM> is disposed between the power generation cell <NUM> and the flow path portions <NUM> of the separator <NUM>. The auxiliary collector layer <NUM> has the same outer shape as the power generation cell <NUM>. The auxiliary collector layer <NUM> has a wire mesh shape in which rhomboidal, etc., openings are provided in a lattice pattern.

The sealing members <NUM> are so-called gaskets, which function as a spacer and a seal.

As shown in <FIG> and <FIG>, the sealing members <NUM> are disposed between the cell frame 101W and the separator <NUM> and partially seal the gap between the cell frame 101W and the separator <NUM> to thereby restrict the flow of the gas.

The sealing members <NUM> prevent the anode gas AG from becoming mixed toward the cathode-side flow path of the separator <NUM> from an anode-side inlet (for example, the anode-side first inlet 102a) and an anode-side outlet (for example, anode-side first outlet 102d) of the separator <NUM>.

As shown in <FIG>, the module end <NUM> is a plate that holds the lower end or the upper end of the plurality of stacked cell units 100T.

The module end <NUM> is disposed at the lower end or the upper end of the plurality of stacked cell units 100T. The module end <NUM> has the same outer shape as the cell units 100T. The module end <NUM> is made of a conductive material that does not allow gas to permeate therethrough, and, except for partial regions that oppose the power generation cells <NUM> and the other module ends <NUM>, is insulated using an insulating material or a coating. The insulating material is formed, for example, by fixing aluminum oxide onto the module end <NUM>.

The module end <NUM> is provided with an anode-side first inlet 105a, an anode-side second inlet 105b, an anode-side third inlet 105c, an anode-side first outlet 105d, and an anode-side second outlet 105e through which the anode gas AG passes, such that the relative position with the cell units 100T matches along the stacking direction Z. The module end <NUM> is provided with a cathode-side first inlet 105f, a cathode-side second inlet <NUM>, a cathode-side first outlet <NUM>, a cathode-side second outlet 105i, and a cathode-side third outlet 105j through which the cathode gas CG passes, such that the relative position with the cell units 100T matches along the stacking direction Z. In the module end <NUM>, the inlets and outlets of the cathode gas CG correspond to the space between the outer circumferential surface of the module end <NUM> and the inner-side surface of the air shelter <NUM>.

The upper collector plate <NUM> is shown in <FIG>, and outputs electric power generated by the cell units 100T to the outside.

The upper collector plate <NUM> is positioned at the upper end of the upper module unit 100P. The upper collector plate <NUM> has the same outer shape as the cell units 100T. The upper collector plate <NUM> is provided with a terminal (not shown) that is connected to an external energizing member. The upper collector plate <NUM> is made of a conductive material that does not allow gas to permeate therethrough, and is insulated using an insulating material or a coating, excluding the terminal portion and regions that oppose the power generation cells <NUM> of the cell units 100T. The insulating material is formed, for example, by fixing aluminum oxide onto the upper collector plate <NUM>.

The lower collector plate <NUM> is shown in <FIG>, and outputs electric power generated by the cell units 100T to the outside.

The lower collector plate <NUM> is positioned at the lower end of the lower module unit 100R. The lower collector plate <NUM> has the same outer shape as the upper collector plate <NUM>. The lower collector plate <NUM> is provided with a terminal (not shown) that is connected to an external energizing member. The lower collector plate <NUM> is made of a conductive material that does not allow gas to permeate therethrough, and, except for the terminal portion and regions that oppose the power generation cells <NUM> of the cell units 100T, is insulated with an insulating material or a coating,. The insulating material is formed, for example, by fixing aluminum oxide onto the lower collector plate <NUM>.

The lower collector plate <NUM> is provided with an anode-side first inlet 107a, an anode-side second inlet 107b, an anode-side third inlet 107c, an anode-side first outlet 107d, and an anode-side second outlet 107e through which the anode gas AG passes, such that the relative position with the cell units 100T matches along the stacking direction Z. The lower collector plate <NUM> is provided with a cathode-side first inlet 107f, a cathode-side second inlet <NUM>, a cathode-side first outlet <NUM>, a cathode-side second outlet 107i, and a cathode-side third outlet 107j through which the cathode gas CG passes, such that the relative position with the cell units 100T matches along the stacking direction Z. In the lower collector plate <NUM>, the inlets and outlets of the cathode gas CG correspond to the space between the outer circumferential surface of the lower collector plate <NUM> and the inner-side surface of the air shelter <NUM>.

As shown in <FIG> and <FIG>, the lower end plate <NUM> holds the fuel cell stack <NUM> from below.

The lower end plate <NUM> is disposed at the lower end of the fuel cell stack <NUM>. Except for a portion, the lower end plate <NUM> has the same outer shape as the cell units 100T. Two ends of the lower end plate <NUM> are formed by linearly extending both ends along the longitudinal direction Y, in order to form an inlet and an outlet for the cathode gas CG. The lower end plate <NUM> is formed sufficiently thicker than the cell units 100T. The lower end plate <NUM> is made of metal, for example, and the upper surface thereof that contacts the lower collector plate <NUM> is insulated using an insulating material or a coating. The insulating material is formed, for example, by fixing aluminum oxide onto the lower end plate <NUM>.

The lower end plate <NUM> is provided with an anode-side first inlet 108a, an anode-side second inlet 108b, an anode-side third inlet 108c, an anode-side first outlet 108d, and an anode-side second outlet 108e through which the anode gas AG passes, such that the relative position with the cell units 100T matches along the stacking direction Z. The lower end plate <NUM> is provided with a cathode-side first inlet 108f, a cathode-side second inlet <NUM>, a cathode-side first outlet <NUM>, a cathode-side second outlet 108i, and a cathode-side third outlet 108j through which the cathode gas CG passes, such that the relative position with the cell units 100T matches along the stacking direction Z.

As shown in <FIG> and <FIG>, the upper end plate <NUM> holds the fuel cell stack <NUM> from above.

The upper end plate <NUM> is disposed at the upper end of the fuel cell stack <NUM>. The upper end plate <NUM> has the same outer shape as the lower end plate <NUM>. Unlike the lower end plate <NUM>, the upper end plate <NUM> is not provided with an inlet and an outlet for the gas. The upper end plate <NUM> is made of metal, for example, and the lower surface thereof that contacts the upper collector plate <NUM> is insulated using an insulating material or a coating. The insulating material is formed, for example, by fixing aluminum oxide onto the upper end plate <NUM>.

As shown in <FIG> and <FIG>, the air shelter <NUM> forms a flow path for the cathode gas CG between the air shelter and the fuel cell stack <NUM>.

The air shelter <NUM> covers the fuel cell stack <NUM>, which is sandwiched between the lower end plate <NUM> and the upper end plate <NUM>, from the top. The air shelter <NUM> forms the inlet and the outlet for the cathode gas CG, which is a constituent element of the fuel cell stack <NUM>, with a gap between the inner-side surface of the air shelter <NUM> and the side surface of the fuel cell stack <NUM>. The air shelter <NUM> has a box-like shape, with the entire lower portion and part of the side portion open. The air shelter <NUM> is made of metal, for example, and the inner-side surface thereof is insulated using an insulating material or a coating. The insulating material is formed, for example, by fixing aluminum oxide onto the air shelter <NUM>.

As shown in <FIG> and <FIG>, the external manifold <NUM> supplies gas from the outside to the plurality of cell units 100T.

The external manifold <NUM> is disposed below the cell stack assembly <NUM>. The external manifold <NUM> has an outer shape obtained by simplifying the shape of the lower end plate <NUM>. The external manifold <NUM> is formed sufficiently thicker than the lower end plate <NUM>. The external manifold <NUM> is made of metal, for example.

The external manifold <NUM> is provided with an anode-side first inlet 111a, an anode-side second inlet 111b, an anode-side third inlet 111c, an anode-side first outlet 111d, and an anode-side second outlet 111e through which the anode gas AG passes, such that the relative position with the cell units 100T matches along the stacking direction Z. The external manifold <NUM> is provided with a cathode-side first inlet 111f, a cathode-side second inlet <NUM>, a cathode-side first outlet <NUM>, a cathode-side second outlet 111i, and a cathode-side third outlet 111j through which the cathode gas CG passes, such that the relative position with the cell units 100T matches along the stacking direction Z.

As shown in <FIG> and <FIG>, the cover <NUM> covers and protects the cell stack assembly <NUM>.

The cover <NUM> sandwiches the cell stack assembly <NUM> from above and below, together with the external manifold <NUM>. The cover <NUM> has a box-like shape, with an open lower portion. The cover <NUM> is made of metal, for example, the inner surface of which is insulated with an insulating material.

<FIG> is a perspective view schematically illustrating the flow of the anode gas AG in the fuel cell stack <NUM>. <FIG> is a perspective view schematically illustrating the flow of the cathode gas CG in the fuel cell stack <NUM>.

The anode gas AG passes through the respective inlets of the external manifold <NUM>, the lower end plate <NUM>, the module end <NUM>, the separator <NUM>, and the metal support cell assembly <NUM>, and is supplied to the anode 101T of each of the power generation cells <NUM>. That is, the anode gas AG is distributed and supplied to the flow path on the anode side provided in the gap between the separator <NUM> and the metal support cell assembly <NUM>, which are stacked in alternating fashion from the external manifold <NUM> to the terminal upper collector plate <NUM>. Thereafter, the anode gas AG reacts in the power generation cells <NUM>, passes through the respective outlets of each of the constituent elements described above, and is discharged in the form of exhaust gas.

In <FIG>, the anode gas AG passes through the anode-side first inlet 102a, the anode-side second inlet 102b, and the anode-side third inlet 102c of the separator <NUM> positioned below in <FIG>, passes through the anode-side first inlet 101a, the anode-side second inlet 101b, and the anode-side third inlet 101c of the metal support cell assembly <NUM>, then flows into the flow path portions <NUM> of the separator <NUM> positioned above in <FIG>, and is supplied to the anodes 101T of the power generation cells <NUM> of the metal support cell assembly <NUM>. The anode gas AG that has reacted in the anode 101T flows out of the flow path portions <NUM> of the separator <NUM> positioned above in <FIG> in the form of exhaust gas, passes through the anode-side first outlet 101d and the anode-side second outlet 101e of the metal support cell assembly <NUM>, passes through the anode-side first outlet 102d and the anode-side second outlet 102e of the separator <NUM> positioned below in <FIG>, and is discharged to the outside.

The cathode gas CG passes through the respective inlets of the external manifold <NUM>, the lower end plate <NUM>, the module end <NUM>, the separator <NUM>, and the metal support cell assembly <NUM>, and is supplied to the cathodes 101U of the power generation cells <NUM>. That is, the cathode gas CG is distributed and supplied to the flow path on the cathode side provided in the gap between the metal support cell assembly <NUM> and the separator <NUM>, which are stacked in alternating fashion from the external manifold <NUM> to the terminal upper collector plate <NUM>. The cathode gas CG then reacts in the power generation cells <NUM>, passes through the respective outlets of each of the constituent elements described above, and is discharged in the form of exhaust gas. The inlet and the outlet of the cathode gas CG in each of the constituent elements described above are configured by the gaps between the outer circumferential surface of each constituent element and the inner-side surface of the air shelter <NUM>.

In <FIG>, the cathode gas CG passes through the cathode-side first inlet 102f and the cathode-side second inlet <NUM> of the separator <NUM> positioned below in <FIG>, flows into the flow path portions <NUM> of the separator <NUM>, and is supplied to the cathodes 101U of the power generation cells <NUM> of the metal support cell assembly <NUM>. The cathode gas CG that has reacted in the cathode 101U flows out of the flow path portions <NUM> of the separator <NUM> positioned below in <FIG> in the form of exhaust gas, passes through the cathode-side first outlet <NUM>, the cathode-side second outlet 102i, and the cathode-side third outlet 102j of the separator <NUM>, and is discharged to the outside.

As shown in <FIG>, <FIG>, <FIG>, and <FIG>, the grid spring <NUM> (corresponding to the spring member) includes a first spring member <NUM> that generates elastic force for pressing the separator <NUM> toward the power generation cell <NUM>, and a second spring member <NUM> that generates elastic force independently of the first spring member <NUM>.

The grid spring <NUM> has a flat substrate <NUM> (corresponding to a first base portion and a second base portion).

The first spring member <NUM> has a plurality of elastically deformable first raised pieces 130A (corresponding to spring portions) that are raised so as to be cantilevered from the substrate <NUM>. The second spring member <NUM> has a plurality of elastically deformable second raised pieces 130B (corresponding to spring portions) that are raised so as to be cantilevered from the substrate <NUM>.

The raised pieces 130A, 130B function as a spring that generates surface pressure between the substrate <NUM> and the cathode 101U as well as between the separator <NUM> and the anode 101T, by generating elastic force in the stacking direction Z.

The raised pieces 130A, 130B are arranged in the planar direction of the substrate <NUM>. The first raised pieces 130A are arranged at the corners and the center of the substrate <NUM>. The first raised pieces 130A and the second raised pieces 130B are arranged in alternating fashion such that the raised directions thereof are opposite each other in the longitudinal direction Y. The installation area occupied by the first raised pieces 130A on the substrate <NUM> is between <NUM>% and <NUM>%, preferably between <NUM>% and <NUM>%.

The spring constant k1 of the first raised pieces 130A decreases when the grid spring <NUM> is heated. The heating temperature and the heating time of the grid spring <NUM> will be described further below in the method for manufacturing the fuel cell stack <NUM>.

Before the grid spring <NUM> is heated, the spring constant k1 of the first raised pieces 130A is larger than the spring constant k2 of the second raised pieces 130B, so that the grid spring <NUM> functions as a high reaction force spring. In the present Specification, "high reaction force spring" means a spring that generates a reaction force necessary for supporting components to be assembled when the cell units 100T are stacked. The reaction force necessary for supporting the components to be assembled is about 100N, for example. The ratio between the spring constant k1 of the first raised pieces 130A and the spring constant k2 of the second raised pieces 130B before the grid spring <NUM> is heated is about k1:k2 = <NUM> to <NUM>:<NUM>.

After the grid spring <NUM> is heated, the grid spring <NUM> functions as a low reaction force spring, since the spring constant k1 of the first raised pieces 130A decreases with applied heat. In the present Specification, "low reaction force spring" means a spring that generates a reaction force necessary for absorbing displacement and deformation of members (the separator <NUM> and the power generation cells <NUM>) in the stacking direction Z. The reaction force necessary for absorbing displacement and deformation of members in the stacking direction Z is, for example, about <NUM>% to <NUM>% of the reaction force necessary for supporting the components to be assembled described above. The ratio between the spring constant k11 of the first raised pieces 130A before heating and the spring constant k12 of the first raised pieces 130A after heating is about k11:k12 = <NUM>:<NUM> to <NUM>.

Before the grid spring <NUM> is heated, the reaction force generated by the first raised pieces 130A is greater than the reaction force generated by the second raised pieces 130B, since the spring constant k1 of the first raised pieces 130A is larger than the spring constant k2 of the second raised pieces 130B. Thus, the stress that acts on the first raised pieces 130A is greater than the stress that acts on the second raised pieces 130B. Therefore, when the grid spring <NUM> is heated, the first raised pieces 130A undergo creep deformation preferentially over the second raised pieces 130B, and the spring constant k1 of the first raised pieces 130A decreases.

After the grid spring <NUM> is heated, the spring constant k1 of the first raised pieces 130A is less than or equal to the spring constant k2 of the second raised pieces 130B.

The first raised pieces 130A curve and extend from the substrate <NUM> toward the separator <NUM>, and the distal end portions thereof contact the separator <NUM>. The second raised pieces 130B curve and extend from the substrate <NUM> toward the separator <NUM>, and the distal end portions thereof contact the separator <NUM>. The raised pieces <NUM> undergo bending deformation, thereby generating the elastic force in the stacking direction Z of the cell units 100T.

The bending angle θ1 of the first raised pieces 130A with respect to the substrate <NUM> is larger than the bending angle θ2 of the second raised pieces 130B with respect to the substrate <NUM>.

The plate thickness H1 of the first raised pieces 130A is essentially constant from the substrate <NUM> to the separator <NUM>. The plate thickness H2 of the second raised pieces 130B decreases from the substrate <NUM> to the separator <NUM>.

The section modulus of the first raised pieces 130A is larger than the section modulus of the second raised pieces 130B.

As shown in Figure 17B, the width B1 of the first raised pieces 130A is larger than the width B2 of the second raised pieces 130B. The width B2 of the second raised pieces 130B decreases from the substrate <NUM> to the separator <NUM>.

The width B1 and the plate thickness H1 of the first raised pieces 130A and the width B2 and the plate thickness H2 of the second raised pieces 130B are not particularly limited as long as the section modulus of the first raised pieces 130A is larger than the section modulus of the second raised pieces 130B.

The method for manufacturing the fuel cell stack <NUM> comprises a Step S1 for stacking the cell units 100T and a Step S2 for reducing the spring constant K of the grid spring <NUM>.

In the Step S1 for stacking the cell units 100T, a grid spring <NUM> provided with the first raised pieces 130A that generate elastic force for pressing the separator <NUM> toward the power generation cell <NUM> and the second raised pieces 130B that generate elastic force independently of the first raised pieces 130A is disposed.

When the grid spring <NUM> is disposed, the grid spring <NUM> that functions as a high reaction force spring as a result of the spring constant k1 of the first raised pieces 130A being larger than the spring constant k2 of the second raised pieces 130B is disposed.

As shown in <FIG>, in the Step S2 for reducing the spring constant K of the grid spring <NUM>, for a period of time Δt, the grid spring <NUM> is heated from a first temperature T1 to a second temperature T2, thereby subjecting the first raised pieces 130A to creep deformation. The spring constant k1 of the first raised pieces 130A thus decreases. As the spring constant k1 of the first raised pieces 130A decreases, the spring constant K of the grid spring <NUM> decreases, and the grid spring <NUM> starts to function as a low reaction force spring.

When the fuel cell stack <NUM> is used, the second temperature T2 is higher than the temperature T3. The first temperature T1 is normal temperature, the second temperature T2 is about <NUM>, and the temperature T3 is about <NUM>. The heating time Δt is about one hour.

The heating of the grid spring <NUM> is carried out during a trial operation of the fuel cell stack <NUM> before shipment of the fuel cell stack <NUM>. The heating of the grid spring <NUM> is carried out using thermal energy generated from the power generation cells <NUM> during the trial operation of the fuel cell stack <NUM> and thermal energy of the high-temperature cathode 101U gas that is supplied to the power generation cells <NUM>.

As shown in <FIG>, in the Step S1 for stacking the cell units 100T, one of the power generation cells <NUM> and the separator <NUM> are brought relatively closer to each other by distance Δd, to thereby apply stress to the first spring member <NUM> that is greater than the yield point, and cause the first spring member <NUM> to yield.

As described above, the grid spring <NUM> includes the first raised pieces 130A that generate elastic force for pressing the separator <NUM> toward the power generation cell <NUM> and the second raised pieces 130B that generate elastic force for pressing the separator <NUM> toward the power generation cell <NUM> independently of the first raised pieces 130A.

As shown in <FIG>, the grid spring <NUM> can be understood as a spring in which first raised pieces 130A and second raised pieces 130B, each of which functions as an independent spring, are connected in parallel. As shown by the following equation, the spring constant K of the grid spring <NUM> is equal to the sum of the spring constant k1 of the first raised pieces 130A and the spring constant k2 of the second raised pieces 130B.

Before the grid spring <NUM> is heated, the spring constant k1 of the first raised pieces 130A is larger than the spring constant k2 of the second raised pieces 130B. As a result, before the grid spring <NUM> is heated, the spring constant k1 of the first raised pieces 130A is predominant, as shown by the following equation.

As shown in <FIG>, before the grid spring <NUM> is heated, when a pressing force F0 is applied to the fuel cell stack <NUM> in the stacking direction Z, the components to be assembled (the power generation cells <NUM>, the separator <NUM>, and the like) are supported by a high reaction force F1 generated by the first raised pieces 130A. Thus, it is possible to assemble the components in a state of close mutual contact.

When the grid spring <NUM> is heated, the first raised pieces 130A undergo creep deformation preferentially over the second raised pieces 130B. As a result, the spring constant k1 of the first raised pieces 130A decreases, as shown in <FIG>.

In <FIG>, the spring constant of the first raised pieces 130A and the spring constant of the second raised pieces 130B before creep deformation are respectively indicated by k11 and k21, and the spring constant of the first raised pieces 130A and the spring constant of the second raised pieces 130B after creep deformation are respectively indicated by k12 and k22.

When the heating temperature exceeds a first threshold Tc1, the first raised pieces 130A undergo creep deformation and the spring constant k1 decreases. When the heating temperature exceeds a second threshold Tc2, the second raised pieces 130B also undergo creep deformation and both the spring constant k1 of the first raised pieces 130A and the spring constant k2 of the second raised pieces 130B decrease. When the heating temperature exceeds the third threshold Tc3, the spring constant k12 of the first raised pieces 130A after creep deformation becomes less than or equal to the spring constant k22 of the second raised pieces 130B. The third threshold Tc3 is about <NUM>.

When the spring constant k1 of the first raised pieces 130A decreases, the spring constant K of the entire grid spring <NUM> decreases. As a result, the force that acts on the grid spring <NUM> becomes the low reaction force spring F2, and the creep resistance of the grid spring <NUM> is improved. Therefore, when the fuel cell stack <NUM> is used, it is possible to stably secure sufficient surface pressure between the anode 101T and the separator <NUM> as well as between the cathode 101U and the grid spring <NUM> using the elastic force generated by the grid spring <NUM>.

The action and effects of the above-described embodiment will be described below.

The fuel cell stack <NUM> is the fuel cell stack <NUM> made by stacking the plurality of cell units 100T, each having the power generation cell <NUM> that is formed by sandwiching the electrolyte <NUM> from both sides with the anode 101T and the cathode 101U and that generates power using supplied gas, and the separator <NUM> that defines the flow path portions <NUM>, which are flow passages for the gas between the separator and the power generation cell <NUM>, and that is in conductive contact with the anode 101T. The fuel cell stack <NUM> comprises the grid spring <NUM> provided with the first raised pieces 130A that generate elastic force for pressing the separator <NUM> toward the power generation cell <NUM> and the second raised pieces 130B that generate elastic force independently of the first raised pieces 130A. The spring constant k1 of the first raised pieces 130A decreases when the grid spring <NUM> is heated. Before heating, the spring constant k1 of the first raised pieces 130A is larger than the spring constant k2 of the second raised pieces 130B, so that the grid spring <NUM> functions as a high reaction force spring. After heating, the grid spring <NUM> functions as a low reaction force spring since the spring constant k1 of the first raised pieces 130A decreases with applied heat.

According to the fuel cell stack <NUM>, the cell unit 100T, the grid spring <NUM>, and the method for manufacturing the fuel cell stack <NUM>, before the grid spring <NUM> is heated, the spring constant k1 of the first raised pieces 130A is larger than the spring constant k2 of the second raised pieces 130B. As a result, when the cell units 100T is stacked, the components to be assembled (the power generation cells <NUM>, the separator <NUM>, and the like) can be supported by a high reaction force generated by the first raised pieces 130A, and the components can be assembled in a state of close mutual contact. On the other hand, after the grid spring <NUM> is heated, the grid spring <NUM> functions as a low reaction force spring since the spring constant k1 of the first raised pieces 130A decreases with applied heat. Therefore, the creep resistance of the grid spring <NUM> is improved, and even if the temperature of the grid spring <NUM> becomes high when the fuel cell stack <NUM> is used, it is possible to stably secure sufficient surface pressure between the anode 101T and the separator <NUM> as well as between the cathode 101U and the grid spring <NUM> using the second raised pieces 130B. Thus, using the fuel cell stack <NUM>, the cell unit 100T, the grid spring <NUM>, and the method for manufacturing the fuel cell stack <NUM>, it is possible to prevent a decrease in the power generation performance caused by creep deformation of the grid spring <NUM>.

In particular, since the fuel cell stack <NUM> according to the present embodiment is a solid oxide fuel cell (SOFC), which uses a solid oxide ceramic as the electrolyte <NUM>, the operating temperature is extremely high, at approximately <NUM> to <NUM>. Therefore, compared to a solid polymer membrane fuel cell, the grid spring <NUM> is relatively easily subjected to creep deformation at the time of operation. With the configuration described above, the fuel cell stack <NUM> can maintain power generation performance, even for long periods of operation in a high-temperature state.

In addition, using the fuel cell stack <NUM>, the cell unit 100T, the grid spring <NUM>, and the method for manufacturing the fuel cell stack <NUM>, the spring constant k1 of the first spring member <NUM> is less than or equal to the spring constant k2 of the second spring member <NUM> before the grid spring <NUM> is heated.

In addition, using the fuel cell stack <NUM>, the cell unit 100T, the grid spring <NUM>, and the method for manufacturing the fuel cell stack <NUM>, the spring constant K of the grid spring <NUM> can be more reliably reduced following heating. Therefore, it is possible to more reliably improve the creep resistance of the grid spring <NUM>.

In addition, using the fuel cell stack <NUM>, the cell unit 100T, the grid spring <NUM>, and the method for manufacturing the fuel cell stack <NUM>, the first raised pieces 130A curve and extend from the substrate <NUM>, and the distal end portions thereof contact the separator <NUM>. Moreover, the second raised pieces 130B curve and extend from the substrate <NUM>, and the distal end portions thereof contact the separator <NUM>. Then, the grid spring <NUM> generates elastic force as a result of the bending deformation of the first raised pieces 130A and the second raised pieces 130B.

In addition, using the fuel cell stack <NUM>, the cell unit 100T, the grid spring <NUM>, and the method for manufacturing the fuel cell stack <NUM>, it is possible to generate elastic force using a simple configuration involving bending deformation. Therefore, according to the fuel cell stack <NUM> and the method for manufacturing the fuel cell stack <NUM>, manufacture of the fuel cell stack <NUM> can be facilitated.

In addition, using the fuel cell stack <NUM>, the cell unit 100T, the grid spring <NUM>, and the method for manufacturing the fuel cell stack <NUM>, the bending angle θ1 of the first raised pieces 130A with respect to the substrate <NUM> is larger than the bending angle θ2 of the second raised pieces 130B with respect to the substrate <NUM>.

In addition, using the fuel cell stack <NUM>, the cell unit 100T, the grid spring <NUM>, and the method for manufacturing the fuel cell stack <NUM>, it is possible to adjust the spring constant of the first raised pieces 130A and the spring constant of the second raised pieces 130B using a simple method of varying the bending angle θ1 of the first raised pieces 130A and the bending angle θ2 of the second raised pieces 130B.

In addition, using the fuel cell stack <NUM>, the cell unit 100T, the grid spring <NUM>, and the method for manufacturing the fuel cell stack <NUM>, the section modulus of the first raised pieces 130A is larger than the section modulus of the second raised pieces 130B.

In addition, using the fuel cell stack <NUM>, the cell unit 100T, the grid spring <NUM>, and the method for manufacturing the fuel cell stack <NUM>, it is possible to adjust the spring constant of the first raised pieces 130A and the spring constant of the second raised pieces 130B using a simple method of varying the section modulus of the first raised pieces 130A and the section modulus of the second raised pieces 130B.

In addition, using the fuel cell stack <NUM>, the cell unit 100T, the grid spring <NUM>, and the method for manufacturing the fuel cell stack <NUM>, the width B2 of the second raised pieces 130B decreases from the substrate <NUM> to the separator <NUM>.

Using the fuel cell stack <NUM>, the cell unit 100T, the grid spring <NUM>, and the method for manufacturing the fuel cell stack <NUM>, the bending rigidity of the second raised pieces 130B increases with increasing distance from the side that contacts the separator <NUM>. As a result, the bending stress acts more uniformly on the second raised pieces 130B. Therefore, since the stress that acts on the second raised pieces 130B can be dispersed, creep deformation of the second raised pieces 130B can be more reliably suppressed.

In addition, using the fuel cell stack <NUM>, the cell unit 100T, the grid spring <NUM>, and the method for manufacturing the fuel cell stack <NUM>, the plate thickness H2 of the second raised pieces 130B decreases from the substrate <NUM> to the separator <NUM>.

In addition, using the fuel cell stack <NUM>, the cell unit 100T, the grid spring <NUM>, and the method for manufacturing the fuel cell stack <NUM>, the bending rigidity of the second raised pieces 130B increases with increasing distance from the side that contacts the separator <NUM>. As a result, the bending stress acts more uniformly on the second raised pieces 130B. Therefore, since the stress that acts on the second raised pieces 130B can be dispersed, the creep deformation of the second raised pieces 130B can be more reliably suppressed.

In addition, using the fuel cell stack <NUM>, the cell unit 100T, the grid spring <NUM>, and the method for manufacturing the fuel cell stack <NUM>, the grid spring <NUM> is configured by arranging the first raised pieces 130A and the second raised pieces 130B along the planar direction of the separator <NUM>. The first raised pieces 130A are arranged at the corners and the center of the grid spring <NUM>.

Using the fuel cell stack <NUM>, the cell unit 100T, the grid spring <NUM>, and the method for manufacturing the fuel cell stack <NUM>, the separator <NUM> can be uniformly pressed in the planar direction toward the anode 101T using the larger spring constant of the first raised pieces 130A relative to the second raised pieces 130B at the first temperature T1. Therefore, the accuracy of assembly of the components during stacking of the cell units 100T is improved.

In addition, using the method for manufacturing the fuel cell stack <NUM>, when the power generation cells <NUM> are stacked, one of the power generation cells <NUM> and the separator <NUM> are brought relatively close to each other, to thereby apply a force to the first raised pieces 130A in the stacking direction Z and cause the first raised pieces 130A to yield.

Using the method for manufacturing the fuel cell stack <NUM>, the first raised pieces 130A are subjected to plastic deformation by causing the first raised pieces 130A to yield. It is thereby possible to promote creep deformation of the first raised pieces 130A when the grid spring <NUM> is heated. Therefore, it is possible to more reliably decrease the spring constant K of the entire grid spring <NUM> as the spring constant k1 of the first raised pieces 130A decreases. As a result, it is possible to more reliably improve the creep resistance of the grid spring <NUM>.

In the embodiment described above, both the first raised pieces 130A and the second raised pieces 130B are configured in the form of cantilever beams in order to generate bending deformation. However, the form of the raised pieces <NUM> is not particularly limited so long as bending deformation can occur.

As shown in <FIG> and <FIG>, the first raised pieces 130A may be in the form of a hoop spring.

Using the fuel cell stack <NUM>, the cell unit 100T, and the grid spring <NUM> of the present modified example, the first spring constant k1 of the first raised pieces 130A can easily be made larger than the spring constant of the second raised pieces 130B using a simple configuration in which the first raised pieces 130A are hoop springs.

In addition, the second raised pieces 130B may be equal moment beams, as shown in <FIG> and <FIG>. An equal moment beam means that the sectional secondary moment is constant in the direction in which the second raised pieces 130B extend.

The second raised pieces 130B have openings <NUM> for adjusting the moment. The width of the opening <NUM> increases from the substrate <NUM> to the distal end of the second raised pieces 130B. The opening <NUM> has a triangular shape.

The second spring member <NUM> may also include a restricting portion <NUM> that restricts the displacement of the second raised piece 130B in the stacking direction Z.

The restricting portion <NUM> extends from the second raised piece 130B toward the substrate <NUM> side. The restricting portion <NUM> has a form in which part of the second raised piece 130B is notched and raised. The opening <NUM> for adjusting the moment can be formed together with the restricting portion <NUM>.

According to the fuel cell stack <NUM>, the cell unit 100T, and the grid spring <NUM> of the present modified example, the second raised pieces 130B are equal moment beams. As a result, the bending stress acts more uniformly on the second raised pieces 130B. Therefore, since the stress that acts on the second raised pieces 130B can be dispersed, the creep deformation of the second raised pieces 130B can be more reliably suppressed.

In addition, using the fuel cell stack <NUM>, the cell unit 100T, and the grid spring <NUM> of the present modified example, the second raised pieces 130B have restricting portions <NUM> that restrict the displacement of the second raised pieces 130B in the stacking direction Z. As a result, the fuel cell stack <NUM> can prevent excessive bending deformation of the second raised pieces 130B. Therefore, it is possible to apply surface pressure more reliably between the cathode 101U and the substrate <NUM> as well as between the anode 101T and the separator <NUM>.

In the embodiment described above, the grid spring <NUM> is configured by arranging the first raised pieces 130A and the second raised pieces 130B on one substrate <NUM>. However, as shown in <FIG>, <FIG>, <FIG>, and <FIG>, the grid spring <NUM> may be configured by arranging the first raised pieces 130A and the second raised pieces 130B on different substrates <NUM>.

The grid spring <NUM> includes the first grid spring 120A (refer to <FIG>) and the second grid spring 120B that generates elastic force independently of the first grid spring 120A (refer to <FIG>). The grid spring <NUM> is configured by stacking the second grid spring 120B on the first grid spring 120A (refer to <FIG>).

The first grid spring 120A includes a flat first substrate 125A (corresponding to the first base portion) and a plurality of elastically deformable first raised pieces 130A (corresponding to the first spring portion) raised so as to be cantilevered from the first substrate 125A.

The second grid spring 120B includes a flat second substrate 125B (corresponding to the second base portion) and a plurality of elastically deformable second raised pieces 130B (corresponding to the second spring portion) raised so as to be cantilevered from the second grid spring 125B.

The plate thickness H2 of the second raised pieces 130B is thinner than the plate thickness H1 of the first raised pieces 130A.

The plate thickness H1 of the first raised pieces 130A and the plate thickness of the first substrate 125A are the same. The plate thickness H2 of the second raised pieces 125B and the plate thickness of the second raised pieces 130B are the same.

The second substrate 125B has an opening <NUM> for housing the first raised pieces 130A. The opening <NUM> houses the first raised pieces 130A in a state in which the second grid spring 120B is stacked on the first grid spring 120A (refer to <FIG>).

Using the fuel cell stack <NUM>, the cell unit 100T, and the grid spring <NUM> of the present modified example, the grid spring <NUM> is formed by stacking the second grid spring 120B on the first grid spring 120A. Thus, since the first grid spring 120A and the second grid spring 120B can be formed in independent steps, the manufacture of the first grid spring 120A and the second grid spring 120B, which have different spring constants, can be facilitated.

Using the fuel cell stack <NUM>, the cell unit 100T, and the grid spring <NUM> of the present modified example, the plate thickness H2 of the second raised pieces 130B is thinner than the plate thickness H1 of the first raised pieces 130A. Thus, when the cell units 100T are stacked, the anode 101T and the separator <NUM> can be pressed since the first raised pieces 130A have a larger plate thickness than the second raised pieces 130B. At this time, since the stress acting on the first raised pieces 130A is greater than that acting on the second raised pieces 130B, it is possible to preferentially cause the first raised pieces 130A to undergo creep deformation when the grid spring <NUM> is heated. As a result, the overall spring constant K of the grid spring <NUM> can be more reliably reduced as the spring constant k1 of the first raised pieces 130A decreases. Therefore, the creep resistance of the grid spring <NUM> can be more reliably improved.

In the embodiment described above in the Third Modified Example, the grid spring <NUM> may further include a positioning mechanism <NUM> for carrying out positioning between the first raised pieces 130A and the second raised pieces 130B, and a circulation portion <NUM> for circulating gas from one side to the other side of the first grid spring 120A and the second grid spring 120B in the stacking direction Z, as shown in <FIG>, <FIG>.

The second grid spring 120B has an opening <NUM> for housing the first raised pieces 130A. The positioning mechanism <NUM> has a concave portion <NUM> at the edges that configure the opening <NUM> and a convex portion <NUM> that fits the concave portion <NUM> on the first substrate 125A.

The circulation portion <NUM> has a first opening <NUM> opened in the plate thickness direction of the first substrate 125A, and a second opening <NUM> opened in the plate thickness direction of the second substrate 125B. The first opening <NUM> and the second opening <NUM> communicate with each other in a state in which the first grid spring 120A and the second grid spring 120B are stacked. The first opening <NUM> and the second opening <NUM> are offset in the transverse direction X (refer to <FIG>), when the grid spring <NUM> is seen in a plan view in a state in which the first grid spring 120A and the second grid spring 120B are stacked.

The first raised pieces 130A and the second raised pieces 130B are arranged along the transverse direction X. The concave portion <NUM> is formed near the center of the edge portion along the transverse direction X configuring the opening <NUM>. The convex portion <NUM> is arranged between one first raised piece 130A and another first raised piece 130A. The convex portion <NUM> has a form in which a portion of the first substrate 125A sandwiched between the one first raised piece 130A and the other first raised piece 130A is curved toward the side in which the second grid spring 120B is disposed when the second grid spring 120B is stacked on the first grid spring 120A.

The first opening <NUM> is disposed on the first substrate 125A at a position different from that of the first raised piece 130A.

The second raised piece 130B has a form in which a part of the second substrate 125B is notched and raised. The second opening <NUM> is formed together with the formation of the second raised piece 130B.

Using the fuel cell stack <NUM>, the cell unit 100T, and the grid spring <NUM> of the present modified example, the grid spring <NUM> has the positioning mechanism <NUM> for carrying out positioning between the first raised pieces 130A and the second raised pieces 130B. It is thereby possible to easily carry out positioning between the first raised pieces 130A and the second raised pieces 130B when the first grid spring 120A and the second grid spring 120B are stacked. Therefore, using the fuel cell stack <NUM>, the manufacture of the grid spring <NUM> can be facilitated.

In addition, the fuel cell stack <NUM>, the cell unit 100T, and the grid spring <NUM> of the present modified example are provided with the circulation portion <NUM> for circulating gas from one side to the other side of the first grid spring 120A and the second grid spring 120B in the stacking direction Z. As a result, it is possible to circulate gas from one side to the other side of the first grid spring 120A and the second grid spring 120B in the stacking direction. Therefore, since the amount of gas that is supplied to the power generation cells <NUM> is increased, the electrical power generated by the power generation cells <NUM> can also be increased.

In the Third and Fourth Modified Examples described above, the first raised pieces 130A and the second raised pieces 130B are arranged at different positions of the grid spring <NUM> in plan view, in a state in which the second grid spring 120B is stacked on the first grid spring 120A.

However, as shown in <FIG>, <FIG>, the first raised pieces 130A and the second raised pieces 130B may be arranged in superimposed fashion in the stacking direction Z.

As shown in <FIG>, the first raised pieces 130A press against the separator <NUM> at the first temperature T1. As shown in <FIG>, the first raised pieces 130A restrict the deformation of the second raised pieces 130B in the stacking direction Z at the second temperature T2.

Using the fuel cell stack <NUM>, the cell unit 100T, and the grid spring <NUM> of the present modified example, the first raised pieces 130A can prevent the excessive deformation of the second raised pieces 130B in the stacking direction Z at the second temperature T2. As a result, it is possible to more reliably apply surface pressure between the cathode 101U and the substrate <NUM> as well as between the anode 101T and the separator <NUM>.

As shown in <FIG>, the raised pieces <NUM> can have a positioning mechanism <NUM> for positioning the raised pieces <NUM>.

The positioning mechanism <NUM> includes a joint positioning portion <NUM> for joining the raised piece <NUM> to the separator <NUM>, a planar direction positioning portion <NUM> for carrying out positioning of the separator <NUM> in the planar direction, and a stacking direction positioning portion <NUM> for carrying out positioning in the stacking direction Z.

The joint positioning portion <NUM> has a planar portion <NUM> that comes into surface contact with the separator <NUM>. In the planar portion <NUM>, the raised piece <NUM> is welded and joined to the separator <NUM>.

The planar direction positioning portion <NUM> abuts a concave portion 102y of the separator <NUM> to thereby position the raised piece <NUM> in the planar direction of the separator <NUM>. The planar direction positioning portion <NUM> extends from the planar portion <NUM> toward the concave portion 102y of the separator <NUM>. The distal end of the planar direction positioning portion <NUM> is bent toward the recessed side of the concave portion 102y.

The stacking direction positioning portion <NUM> extends from the raised piece <NUM> toward the separator <NUM> in the stacking direction Z. When the raised piece <NUM> is displaced, the stacking direction positioning portion <NUM> abuts the separator <NUM> to thereby restrict the displacement of the raised piece <NUM> in the stacking direction Z. It is thus possible to prevent the excessive deformation of the raised pieces <NUM> in the stacking direction Z.

By means of the fuel cell stack <NUM>, the cell unit 100T, and the grid spring <NUM> of the modified example, the grid spring <NUM> has the positioning mechanism <NUM> for carrying out positioning of the raised pieces <NUM>. As a result, when the grid spring <NUM> is disposed between the power generation cell <NUM> and the separator <NUM>, the grid spring <NUM> can be easily positioned. Therefore, by means of the fuel cell stack <NUM>, the manufacture of the fuel cell stack <NUM> can be facilitated.

As shown in <FIG> and <FIG>, the grid spring <NUM> may include the first grid spring 120A that disappears when the grid spring <NUM> is heated, and the second grid spring 120B that generates elastic force independently of the first grid spring 120A.

The first grid spring 120A is made of a material that disappears when the grid spring <NUM> is heated from the first temperature T1 to the second temperature T2. The first grid spring 120A can be made of carbon paper, for example.

The second grid spring 120B has the second raised pieces 130B. The configuration of the second raised pieces 130B is the same as that of the embodiments described above.

As shown in <FIG>, the first grid spring 120A has a frame body <NUM> (corresponding to the first spring portion) and an opening <NUM> that houses the second raised pieces 130B of the second grid spring 120B when the second raised pieces are stacked on the second grid spring 120B.

As shown in <FIG>, the first grid spring 120A presses against the separator <NUM> with the frame body <NUM> before the grid spring <NUM> is heated.

By means of the present modified example, it is possible to prevent a decrease in the power generation performance of the fuel cell stack <NUM> caused by creep deformation of the grid spring <NUM>, in the same manner as in the embodiments described above.

In addition, by means of the cell unit 100T, the grid spring <NUM>, and the method for manufacturing the fuel cell stack <NUM> of the present modified example, since the first grid spring 120A disappears when the grid spring <NUM> is heated, the spring constant K of the entire grid spring <NUM> can be more reliably reduced. Therefore, it is possible to more reliably improve the creep resistance of the grid spring <NUM>.

Other than the foregoing, various modifications to the present invention based on the configurations described in the Claims are possible, which also belong to the scope of the present invention.

For example, the first temperature, the second temperature, the third temperature, and the heating time are not limited to the values described above in the description of the embodiments.

In addition, the heating of the grid spring is not limited to heating by means of trial operation before shipment as described above; the grid spring may be heated together with the firing of a sealing material used for the fuel cell stack, or the like.

Claim 1:
A spring member used for a fuel cell stack (<NUM>) in which are stacked a plurality of fuel cell units (100T), each of the fuel cell units having a power generation cell (<NUM>) that is formed by sandwiching an electrolyte (<NUM>) from both sides with a pair of electrodes (101T, 101U) and that generates power by means of supplied gas, and a separator (<NUM>) that defines a flow path portion (<NUM>), which is a flow passage for the gas between the separator and the power generation cell, and that is in conductive contact with the power generation cell, comprising:
a first spring member (<NUM>) that generates elastic force for pressing the separator toward the power generation cell; and
a second spring member (<NUM>) that generates the elastic force independently of the first spring member,
the first spring member having a spring constant that decreases upon the spring member being heated,
characterized in that
the spring constant of the first spring member is larger than a spring constant of the second spring member before being heated such that the spring member functions as a high reaction force spring, the high reaction force spring being a spring that generates a reaction force necessary for supporting components to be assembled when the fuel cell units are stacked, and
the spring constant of the first spring member being smaller after being heated as compared to before being heated such that the spring member functions as a low reaction force spring, the low reaction force spring being a spring that generates a reaction force necessary for absorbing displacement and deformation of the separator and the power generation cell in a stacking direction (Z).