JP2009146853A - Laminate fastening structure and fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To check a change in a standard dimension caused by a drop in temperature when a laminate is fastened between end plates in the standard dimension by a shaft. <P>SOLUTION: A fastening shaft 100 includes: a first shaft 110 fixed to one end plate 10a; and a second shaft 130 fixed to the other end plate 10a, wherein a coupling shaft portion 134 is inserted into a closed end hole 116 for superimposing both shafts. A shaft fixing member 120 is disposed in an area where the shafts are superimposed to couple the first shaft 110 and the second shaft 130. The shaft fixing member 120 has a coefficient of thermal expansion β larger than that α of both shafts. As a result, the shaft fixing member 120 largely shrinks during the temperature drop, thereby: reducing the distance between an open-side end face of the first shaft 110 and an open-side end face of the second shaft 130; and extending the distance between an end face of the first shaft 110 on the end plate 10a side and an end face of the second shaft 130. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a laminated body fastening structure in which a laminated body is fastened between a pair of opposed end plates and a fuel cell in which a plurality of fuel cell units are laminated and fastened using the laminated body fastening structure.

  There are roughly two methods for fastening the laminated body between the end plates. One of them is a so-called constant load type fastening in which a load for pressing the laminated body in the laminating direction is a constant load, and the other is a so-called sizing type fastening that fastens the laminated body at a constant size. Both methods are common in that the laminate is fastened by a shaft disposed on the side of the laminate between the end plates.

  By the way, in a fuel cell in which a plurality of fuel cell units of power generation units are stacked, it is possible to maintain the power generation performance within a certain range of the load applied to each fuel cell unit in the stacking direction within the assumed operating environment temperature range. It is requested from the viewpoint of. To deal with these demands, it is easy to fasten the constant load method. For example, it is proposed to achieve constant load by expanding and contracting a part of the shaft (extension / contraction part) following the temperature change. (Patent Document 1).

JP 2007-115604 A

  In fixed-size fastening, the distance between the end plates (that is, the fixed dimension of fastening) is specified in consideration of the degree of expansion and contraction of the fuel cell unit in the assumed operating environment temperature range, and the width of this gap is suppressed. It has been done. Specifically, the width between the end plates is suppressed by forming the shaft disposed between the end plates from a material having a small linear expansion coefficient. In other words, in fixed-size fastening, if the distance between the end plates is within a certain range, even if the fuel cell unit expands or contracts due to a temperature change, a load change in the expandable range is allowed to maintain power generation performance. As a premise, the fixed size when the fuel cell unit is fastened is determined.

  In this case, the width of the gap between the end plates based on the expansion and contraction of the shaft causes a change in the load applied to the fuel cell unit although it is an allowable range, and the widening of the gap due to the extension of the shaft reduces the load. Excessive load reduction is a cause of inadvertent misalignment of the stacked fuel cell units. Therefore, it is desirable to avoid load reduction in order to prevent misalignment. Therefore, when fastening with the fixed size method, the interval between the end plates is determined assuming the upper limit of the operating environment temperature, and the shaft between the end plates is made of a material having a small linear expansion coefficient, so that the shaft shrinkage is reduced. It is supposed to be.

  In the fastening method of the constant load system proposed in Patent Document 1, not only the expansion / contraction part of the shaft but also the other part of the shaft (non-extension / contraction part) causes contraction when the temperature drops. Depending on the degree of contraction, the load change (load increase) due to the contraction may not be ignored. In addition, in the case of a fuel cell fastened by a constant load method, its outer dimensions, particularly the dimensions in the stacking direction, vary depending on the operating temperature. It must be taken into consideration and is limited by the degree of freedom of mounting.

  In the sizing method, since the size is fixed, the degree of freedom of mounting increases, and the smaller the contraction of the shaft between the end plates, the higher the mounting property. However, in order to reduce the shrinkage of the shaft between the end plates, the shaft has to be made of a material having a small linear expansion coefficient, and there is a limit in reducing the shrinkage of the shaft in terms of material selection.

  In view of the above-described problems, the present invention has an object to suppress a change in a sizing dimension due to a temperature drop when a laminate is fastened with a shaft between end plates.

  In order to achieve at least a part of the above object, the present invention adopts the following configuration.

[Applicable: Laminated structure]
A laminated body fastening structure in which a laminated body is sandwiched between a pair of opposed end plates, and the laminated body is fastened to a fixed size by a shaft disposed on the lateral side of the laminated body between the end plates,
The shaft is
A first shaft fixed at one end plate to one end plate and shorter than the fixed dimension;
A second shaft fixed to the other end plate at an end face, extending toward the one end plate, overlapping the first shaft, and shorter than the fixed dimension;
The first shaft and the second shaft are arranged in a region where the first shaft and the second shaft overlap with each other, fixed to the first shaft on the open end side of the first shaft, and the second shaft on the open end side of the second shaft. And a fixed shaft fixing member,
The shaft fixing member is formed of a material having a larger linear expansion coefficient than both shafts and exhibits a larger shrinkage rate than both shafts. When the temperature drops, the shaft fixing member is fixed to both shafts by contraction of the shaft fixing members themselves. The gist is to narrow the gap between the points.

  In the laminate fastening structure having the above-described configuration, the first shaft extending from one end plate and the second shaft extending from the other end plate are arranged in a region where the shafts overlap with each other, and both shafts are opened. It connected with the shaft fixing member fixed by the end side. Therefore, in a state where they are connected by the shaft fixing member, the end surface (contact end surface) of the first shaft opposite to the above open end and the end surface (contact end surface) of the second shaft are fixed dimensions (fixed dimensions). Therefore, the first shaft is fixed to one end plate at its end face, and the second shaft is fixed to the other end plate at its end face, thereby fastening the laminate between the end plates at a fixed size. .

  Assuming that the shaft fixing member fixed to both the first shaft and the second shaft is made of the same material as that of the first shaft and the second shaft, the hypothetical shaft includes the first and second shafts. Although it is separated from the shaft fixing member, since the first and second shafts are fixed via the shaft fixing member, it is not different from a single shaft. Therefore, in this hypothetical shaft, when the temperature drops, the first and second shafts and the shaft fixing member cause contraction depending on the linear expansion coefficient of the common material, and the contact end surface of the first shaft and the first shaft The distance from the contact end surface of the two shafts is narrowed depending on the linear expansion coefficient of the common material, and this shrinkage is the same as the conventional fastening structure fastened by a single shaft.

  However, in the laminate fastening structure having the above-described configuration, the shaft fixing member fixed to both the first shaft and the second shaft is formed of a material having a larger linear expansion coefficient than both the first and second shafts. Since the shrinkage rate is larger than that of both shafts, it is as follows. Also in the laminated body fastening structure having the above-described configuration, both the first and second shafts and the shaft fixing member are contracted as the temperature drops. However, the shaft fixing member is The shrinkage is greater than when the first and second shafts are the same, and the distance between the fixed portions of both shafts by the shaft fixing member is narrowed. Since the distance between the fixed portions of the shaft fixing member before and after the temperature decrease is equivalent to the narrower overlapping range of the first and second shafts, this distance is reduced. Accordingly, the distance between the contact end surface of the first shaft and the contact end surface of the second shaft is increased. On the other hand, the first and second shafts are individually contracted separately from the contraction of the shaft fixing member. Therefore, the individual contraction of the first and second shafts is caused by the expansion of the distance between the contact end surface of the first shaft and the contact end surface of the second shaft due to contraction of the shaft fixing member. It will be offset by the minute. As a result, according to the laminated body fastening structure configured as described above, the change in the distance between the contact end surface of the first shaft and the contact end surface of the second shaft at the time of temperature drop can be suppressed. Even if it is in the fixed dimension of a laminated body, the change accompanying a temperature fall can be suppressed.

  The laminated body fastening structure described above can be configured as follows. For example, for the first shaft and the second shaft, both shafts can be formed from the same material. In this way, in forming the first and second shafts and the shaft fixing member, two types of materials, that is, the first and second shaft materials and the shaft fixing member material may be selected. Becomes easy. Further, when the first and second shafts are formed, machining of the same material may be performed, so that it is possible to share machining blades and simplify process management.

  In addition, the first shaft and the second shaft can be arranged coaxially between the pair of end plates. By so doing, the laminate sandwiched between both end plates can be fastened coaxially on the side thereof, so that inadvertent concentration of the tightening force (load) on the laminate can be avoided.

  In the present invention, the following configuration is adopted as the fuel cell in which the fuel cell unit is fastened by the above-described fixed-size fastening method of the laminate.

[Application: Fuel cell]
A fuel cell,
A plurality of fuel cell units that generate electricity by electrochemical reaction of hydrogen and oxygen are stacked and sandwiched between a pair of opposing end plates, and the stacked fuel cell units are defined between the end plates by the above-described stacked body fastening structure. The gist is to conclude with the dimensions.

  In this fuel cell, after a plurality of fuel cell units are fastened to a fixed size, a change in the fixed size of the plurality of fuel cell units fastened between the end plates can be suppressed even if a temperature drop occurs. Therefore, since the load change in the fuel cell unit caused by the change in the fastening dimension can be suppressed, the power generation performance can be maintained and stabilized.

  Hereinafter, embodiments of the present invention will be described based on examples. FIG. 1 is an explanatory diagram showing a schematic configuration of a fuel cell 10 as an embodiment of the present invention, FIG. 2 is an explanatory diagram schematically showing the overall configuration of a fastening shaft 100 in perspective, and FIG. It is explanatory drawing explaining the mode.

  As shown in the drawing, the fuel cell 10 includes a fuel cell unit 40 that generates power by an electrochemical reaction between hydrogen and oxygen as a stack structure in which a plurality of layers are stacked between a pair of end plates 10a. Each fuel cell unit 40 is configured by sandwiching a membrane electrode assembly formed by joining an anode and a cathode on both surfaces of an electrolyte membrane having proton conductivity, with a separator. In the membrane / electrode assembly, each of the anode and the cathode includes a catalyst layer bonded to each surface of the electrolyte membrane and a gas diffusion layer bonded to the surface of the catalyst layer. In this example, a solid polymer membrane such as Nafion (registered trademark) is used as the electrolyte membrane. Other electrolyte membranes such as solid oxides may be used as the electrolyte membrane. Each separator is provided with a hydrogen flow path as a fuel gas to be supplied to the anode, an air flow path as an oxidant gas to be supplied to the cathode, and a cooling refrigerant flow path. The number of stacked fuel cell units 40 can be arbitrarily set according to the output required for the fuel cell 10.

  In the fuel cell 10, when the fuel cell unit 40 having the above-described stack structure is sandwiched between a pair of opposing end plates 10 a, an insulating plate 20 a and a current collecting plate 30 a are interposed on the end plate 10 a side. The end plate 10a, the insulating plate 20a, and the current collecting plate 30a are provided with supply ports / discharge ports for supplying / discharging hydrogen, supplying / discharging air, and supplying / discharging the refrigerant in each fuel cell unit 40. Each fuel cell unit 40 is discharged from a supply manifold (hydrogen supply manifold, air supply manifold, refrigerant supply manifold) for distributing and supplying hydrogen, air, and refrigerant, and a cathode and an anode of each fuel cell unit 40. And a discharge manifold (cathode offgas discharge manifold, anode discharge manifold, refrigerant discharge manifold) for collecting and discharging the off-gas and refrigerant outside the fuel cell 10 (not shown).

  The end plate 10a is formed of a metal such as steel in order to ensure rigidity. The insulating plate 20a is formed of an insulating member such as rubber or resin. The current collecting plate 30a is formed of dense carbon, a gas impermeable conductive member such as a copper plate. Each of the current collecting plates 30a is provided with an output terminal (not shown) so that the power generated by the fuel cell 10 can be output.

  The fuel cell 10 includes a fastening shaft 100 disposed on the side of the fuel cell unit 40 having a stack structure between a pair of opposed end plates 10a. The fastening shaft 100 fastens the fuel cell unit 40 having the above-described stack structure between a pair of end plates 10a facing each other. As shown in FIGS. 2 and 3, the fastening shaft 100 includes a first shaft 110 and a second shaft 130.

  The first shaft 110 has a dimension L1 shorter than a predetermined dimension (fixed dimension) L when the fuel cell unit 40 having a stack structure is fastened between a pair of opposed end plates 10a. One end side is a boss 112 inserted into the through hole 12 of the end plate 10a, and has a female screw 113. The first shaft 110 includes a bottomed hole 116 on the side opposite to the boss 112. The second shaft 130 is a shaft material made of the same material as that of the first shaft 110, and has a dimension L2 that is shorter than the above-described fixed dimension L. The boss 112 to be inserted into the boss 12 has a female screw 113. The second shaft 130 has a small-diameter connecting shaft portion 134 on the side opposite to the boss 112 and has a disk-shaped fixing piece 136 at the tip thereof.

  The first shaft 110 is fixed to the end plate 10a with the bolt 102 in a state where the boss 112 is inserted into the through hole 12 of one end plate 10a and is in contact with the end plate end surface. In the second shaft 130, the boss 112 is inserted into the through hole 12 of the other end plate 10a and is in contact with the end plate end surface, and is fixed to the end plate 10a by the bolt 102, and the connecting shaft portion 134 is inserted into the fixed piece 136 and the bottomed hole 116 of the first shaft 110 and overlaps the first shaft 110 over the insertion range. In this case, the first shaft 110 and the second shaft 130 are coaxial between the end plates 10a, and even if they are in the through holes 12 into which the bosses 112 of both shafts are inserted, they are coaxial on the opposing end plates 10a. Yes. The fastening shaft 100 includes a shaft fixing member 120 in a region where both the first shaft 110 and the second shaft 130 overlap. This shaft fixing member 120 is a cylindrical body having a length L3 of the overlapping region of both shafts, and is fixed to a fixing piece 114 fixed to the open end surface of the first shaft 110 on one end side. On the end side, the second shaft 130 is fixed to a fixing piece 136 at the tip (open end side end surface) of the connecting shaft portion 134 of the second shaft 130. That is, the shaft fixing member 120 is fixed to the first shaft 110 at the open end surface of the first shaft 110 via the fixing piece 114 and the fixing piece 136, and the second shaft 130, specifically, the connecting shaft portion 134. The opening side end surface is fixed to the second shaft 130, and the distance between the opening side end surface of the first shaft 110 and the opening side end surface of the second shaft 130 is defined. FIG. 4 is an explanatory view showing a manufacturing process of the fastening shaft 100.

  As shown in FIG. 4, first, the shaft fixing member 120 is brought into contact with the fixing piece 114 and welded, and the welded product is attached to the connecting shaft portion 134 so that the fixing piece 114 is on the second shaft 130 side. set. Thereafter, the fixing piece 136 is welded to the open end (tip) of the connecting shaft portion 134, the shaft fixing member 120 is brought into contact with the fixing piece 136, and the shaft fixing member 120 is welded to the fixing piece 136. Next, the connecting shaft portion 134 of the second shaft 130 is inserted into the bottomed hole 116 of the first shaft 110, the fixed piece 114 is brought into contact with the open end of the first shaft 110, and the fixed piece is fixed to the first shaft 110. 114 is welded. By doing so, the fastening shaft 100 having the first shaft 110 and the second shaft 130 coaxially and having the shaft fixing member 120 in the overlapping range of both shafts is obtained. As shown in FIG. 3, the fuel cell unit 40 having a stack structure is fastened with a fixed dimension L between the opposed end plates 10 a. The fixed dimension L of the fastening is determined at the upper limit temperature of the assumed temperature range of use of the fuel cell 10 as described above from the viewpoint of preventing inadvertent misalignment of the fuel cell unit 40 due to the widening of the fastening dimension. ing.

  The transition of the fixed dimension when the fuel cell unit 40 is fastened by the fastening shaft 100 will be described. FIG. 5 is an explanatory view showing a state in which a fuel cell unit 40 having a stack structure is fastened with a fixed dimension L using a single shaft S and a state where the fuel cell unit 40 is fastened with a fixed dimension L using a fastening shaft 100. It is. The upper part of the figure shows a single shaft S corresponding to an assumed shaft when it is assumed that the fastening shafts 100 of the form shown in FIG. 3 are all made of the same material (linear expansion coefficient α). The shrinkage allowance ΔLS of the shaft S when the temperature drops by ΔT ° C. is expressed by the following equation. In this case, since the contraction rate of the shaft S is proportional to the linear expansion coefficient α, α can also be used as the contraction rate.

ΔLS = L x α x ΔT
= (L1 + L2-L3) · α · ΔT
= (L1 + L2) · α · ΔT-L3 · α · ΔT

  On the other hand, as shown in the lower part of the figure, both the first shaft 110 and the second shaft 130 in the fastening shaft 100 of the present embodiment are formed of the same material having a linear expansion coefficient α, and the shaft fixing member 120 It is made of a material having a linear expansion coefficient β larger than the linear expansion coefficient α of the shaft. The shrinkage allowance ΔL100 of the fastening shaft 100 is expressed by the following equation. In this case, since the contraction rate of the shaft fixing member 120 is proportional to the linear expansion coefficient β, β can also be set as the contraction rate, and β> α.

  ΔL100 = (L1 + L2) · α · ΔT−L3 · β · ΔT

  The difference (ΔLS−ΔL100) between the two shrinkage allowances ΔLS and ΔL100 is as follows.

ΔLS−ΔL100 = ((L1 + L2) · α · ΔT−L3 · α · ΔT) − ((L1 + L2) · α · ΔT−L3 · β · ΔT)
= -L3 · α · ΔT + L3 · β · ΔT
= L3 · ΔT (β-α)

  Since the relationship between the linear expansion rate (shrinkage rate) α and β is β> α as described above, the difference between the shrinkage allowances of the shaft S and the fastening shaft 100 (ΔLS−ΔL100) is a positive value. It becomes. For this reason, the shrinkage allowance at the time of temperature drop when the fuel cell unit 40 having the stack structure is fastened by the single shaft S with the fixed dimension L is the same as the fastening shaft of the present embodiment. It becomes larger than the case where it is fastened with a fixed dimension L at 100. Therefore, according to the fastening shaft 100 of the present embodiment, the shrinkage (shortening) of the shaft at the time of temperature drop can be suppressed, so that the fixed size of the fuel cell unit 40 of the stack structure fastened between the end plates 10a is maintained. it can.

  Such a phenomenon can be explained as follows. In the fastening shaft 100, the shaft fixing member 120 fixed to both the first shaft 110 and the second shaft 130 is formed of a material having a larger linear expansion coefficient β (> α) than both the first and second shafts. As a result, the shrinkage rate is larger than both shafts. Therefore, the shrinkage of the shaft fixing member 120 accompanying the temperature drop of ΔT ° C. is larger than when the overlapping range of the first shaft 110 and the second shaft 130 is the same material (linear expansion coefficient α <β). Thus, the distance between the open end surface of the first shaft 110 to which the shaft fixing member 120 is fixed and the open end surface of the second shaft 130 becomes narrow. The narrowing of the gap between the open end faces of both shafts due to the temperature drop of ΔT ° C. corresponds to the narrowing of the overlapping range of the first and second shafts. As a result, the distance between the end surfaces of the first shaft 110 and the second shaft 130 on the end plate 10a side is widened.

  On the other hand, both the first shaft 110 and the second shaft 130 are individually contracted separately from the contraction of the shaft fixing member 120. For this reason, the individual contraction of both shafts is offset by the expansion of the gap between the end surfaces of the first shaft 110 and the second shaft 130 on the end plate 10a side due to the contraction of the shaft fixing member 120. Will be. As a result, when the fuel cell unit 40 having the stack structure is fastened with the fixed dimension L by the fastening shaft 100 of the present embodiment, the distance between the both end faces of the first shaft 110 and the second shaft 130 on the end plate 10a side is separated. Can be maintained even when a temperature drop occurs, so that the fixed dimension L of the fuel cell unit 40 having a stack structure fastened between the end plates can be maintained.

  In the present embodiment, the following was performed. As described above, the expansion of the gap between the both end surfaces of the first shaft 110 and the second shaft 130 on the end plate 10 a side due to the contraction of the shaft fixing member 120 is caused by both the first shaft 110 and the second shaft 130. Although the individual contraction of the shaft is offset, if the contraction of the shaft fixing member 120 is excessive, the separation between the both end surfaces becomes large, which may be undesirable for maintaining the fixed dimension L.

  Now, it is assumed that there is no shaft fixing member 120 in the fastening shaft 100. Then, the first shaft 110 and the second shaft 130 having a linear expansion coefficient α are individually contracted with a temperature drop of ΔT ° C., and L1 · (1−α · ΔT) and L2 · (1−α · ΔT), respectively. When the length of the overlapping range of both shafts is LW, this LW is expressed by the following equation.

  LW = (L1 · (1−α · ΔT) + L2 · (1−α · ΔT)) − L

  Here, when the first shaft 110 and the second shaft 130 are connected by the shaft fixing member 120 as described above, the shaft fixing member 120 having a coefficient of thermal expansion β contracts with a temperature drop of ΔT ° C. and becomes L3. The length is (1−β · ΔT). If the length after this contraction becomes smaller than the above-described shaft overlap range LW, the distance between both end surfaces of the first shaft 110 and the second shaft 130 on the end plate 10a side becomes too wide. did. As shown in FIG. 3, L3 = L1 + L2-L.

LW ≦ L3 · (1-β · ΔT)
(L1 · (1−α · ΔT) + L2 · (1−α · ΔT)) − L ≦ L3 · (1−β · ΔT)
(L1 + L2-L)-(L1 + L2) · α · ΔT ≦ L3-L3 · β · ΔT
(L1 + L2-L)-(L1 + L2) .alpha..DELTA.T.ltoreq. (L1 + L2-L) -L3.beta..DELTA.T
L3 · β · ΔT ≦ (L1 + L2) · α · ΔT
β ≦ ((L1 + L2) / L3) · α

  Then, from the above-described relationship of β> α, in the present embodiment, the first shaft 110 and the second shaft 130 are selected in selecting the material for forming the shaft fixing member 120, the first shaft 110, and the second shaft 130. Is used as a material satisfying the following linear expansion coefficient β.

  α <β ≦ ((L1 + L2) / L3) · α

  As described above, in this embodiment, since the stack structure fuel cell unit 40 is fastened to the end plate 10a with the fixed dimension L using the fastening shaft 100 having the above-described configuration, even if a temperature drop occurs. This fixed dimension L can be maintained. In this embodiment, since the fastening object is the fuel cell unit 40 constituting the fuel cell 10, the fastening dimension (fixed dimension) is determined after the plurality of fuel cell units 40 are fastened with the fixed dimension L. Since the load change in the fuel cell unit 40 caused by the change in the dimension) can be suppressed, the power generation performance can be maintained and stabilized.

Moreover, in the present Example, when the laminated body fastening structure described above formed the first shaft 110, the second shaft 130, and the shaft fixing member 120, the first and second shafts were formed from the same material. Therefore, when forming both shafts and the shaft fixing member 120, it is only necessary to select two kinds of materials, that is, the materials of both the first and second shafts and the material of the shaft fixing member 120. Become. In forming both the first and second shafts, machining of the same material may be performed, so that the machining tools can be shared and process management can be simplified. For example, a first shaft 110 a second shaft 130 formed of titanium (linear expansion coefficient 8x10 ^-6 K) and cast iron (linear expansion coefficient 10x10 ^-6 K), the shaft fixing member 120 aluminum (coefficient of linear expansion 23X10 ^-6 K) and stainless steel (linear expansion coefficient 17 × 10 ⁻⁶ K). The dimensions L1 and L2 of the shafts and the dimension L3 of the shaft fixing member 120 may be selected so as to satisfy the above relational expressions for the linear expansion coefficients α and β.

  In the present embodiment, both shafts are coaxially disposed between the pair of end plates 10a so that the connecting shaft portion 134 of the second shaft 130 is inserted into the bottomed hole 116 of the first shaft 110. Therefore, since the fuel cell unit 40 having the stack structure sandwiched between the end plates 10a can be coaxially fastened on the side thereof, inadvertent concentration of the tightening force (load) on the fuel cell unit 40 can be avoided.

  Next, another form of the fastening shaft 100 will be described. FIG. 6 is an explanatory view showing a schematic configuration of a modified fastening shaft 100A, and FIG. 7 is a view corresponding to FIG. 5, and a fuel cell unit 40 having a stack structure is fastened with a fixed dimension L using the modified fastening shaft 100A. It is explanatory drawing which shows a mode made.

  As shown in the drawing, the fastening shaft 100A of this modification has a configuration in which its constituent members are formed from a prismatic shaft material. That is, the fastening shaft 100A fixes the first shaft 110A and the second shaft 130A formed from a material having a linear expansion coefficient α in contact with the end plate 10a, and a material having a linear expansion coefficient β in the overlapping range of both shafts. 120A of shaft fixing members formed from the above. Even in this shaft fixing member 120A, like the shaft fixing member 120 in the fastening shaft 100, it is fixed at one end side to the fixing piece 114A fixed to the open end surface of the first shaft 110A, and at the other end side, The two shafts 130A are fixed to a fixed piece 136A on the open end side end face. Even in the fastening shaft 100A, the same effects as those of the fastening shaft 100 can be achieved by satisfying the relationship between the linear expansion coefficients α and β described above.

  FIG. 8 is an explanatory view schematically showing a configuration of a main part of a fastening shaft 100B of another modified example in perspective, FIG. 9 is a sectional view taken along line 9-9 in FIG. 8, and FIG. 10 is a production of the fastening shaft 100B. It is explanatory drawing which shows a process. The fastening shaft 100B of this modification is characterized in that the first shaft 110B and the second shaft 130B are overlapped so that a shaft having a two-sided width is inserted into the slit portion.

  As illustrated, the fastening shaft 100B includes a first shaft 110B and a second shaft 130B. The first shaft 110B includes a flange portion 114B on the open end side, and a shaft portion having a small diameter within a predetermined range from the flange portion. The slit 152 is slit into the shaft portion 150 from the flange portion 114B. In the second shaft 130B, a flange 136B is provided on the open end side, a predetermined range from the flange is a small-diameter connecting shaft part 134B, and a region extending from the flange 136B to the connecting shaft part 134B is divided into two surfaces. The width portion 138 is used. Since the width of the two-surface width portion 138 is smaller than that of the slit 152, the second shaft 130B is inserted into the slit 152 of the first shaft 110B so that the two-surface width portion 138 is inserted. It overlaps with the first shaft 110B over the insertion range. In this case, the first shaft 110B and the second shaft 130B are fixed by the shaft fixing member 120B so as to be coaxial. The shaft fixing member 120B has a curved plate shape in which the cylindrical body is divided in half, and is arranged vertically in a region where both the first shaft 110B and the second shaft 130B overlap, and the flange portion 114B of the first shaft 110B. The end surface 114S of the second shaft 130B and the end surface of the flange 136B of the second shaft 130B are fixed by welding. In FIG. 8, the welding region of the shaft fixing member 120B is indicated by a zigzag line. Even in the fastening shaft 100B, the same effect as that of the fastening shaft 100 can be obtained by satisfying the relationship between the linear expansion coefficients α and β described above.

  FIG. 11 is an explanatory diagram showing a state of fastening by the fastening shaft 100 in which the first shaft 110, the second shaft 130, and the shaft fixing member 120 are formed from materials having different linear expansion coefficients. In the fastening shaft 100, the first shaft 110 is formed from a material having a linear expansion coefficient α1, the second shaft 130 is formed from a material having a linear expansion coefficient α2, and the shaft fixing member 120 is formed from a material having a linear expansion coefficient β. . The shrinkage allowance ΔL100 in this case is expressed by the following equation. In this case, β is larger than α1 and α2, and α1 and α2 do not matter, but for convenience of explanation, α1> α2.

  ΔL100 = (L1 · α1 + L2 · α2) · ΔT−L3 · β · ΔT

  Therefore, the difference (ΔLS−ΔL100) between the shrinkage allowance ΔLS of the single shaft S (thermal expansion coefficient α1) shown in FIG. 5 and the above-described shrinkage allowance ΔL100 is as follows.

ΔLS−ΔL100 = ((L1 + L2) · α1 · ΔT-L3 · α1 · ΔT) − ((L1 · α1 + L2 · α2) · ΔT−L3 · β · ΔT)
= L2 ・ (α1−α2) ・ ΔT−L3 ・ α1 ・ ΔT + L3 ・ β ・ ΔT
= L2 · (α1−α2) · ΔT + L3 · ΔT (β−α)

  Since the relationship between the linear expansion rate (shrinkage rate) α and β is β> α and α1> α2 as described above, the difference between the shrinkage allowances of both the shaft S and the fastening shaft 100 (ΔLS−ΔL100). ) Is a positive value. For this reason, as shown in FIG. 11, even if the first shaft 110, the second shaft 130, and the shaft fixing member 120 are formed of materials having different linear expansion coefficients, the shrinkage allowance at the time of temperature drop can be reduced. As described above, the fixed size of the fuel cell unit 40 having a stack structure fastened between the end plates 10a can be maintained.

  Further, regarding the linear expansion coefficient β of the shaft fixing member 120, the relationship between the spread of the gap between both end surfaces of the first shaft 110 and the second shaft 130 on the end plate 10a side described above can be similarly considered. That is, it is assumed that there is no shaft fixing member 120 in the fastening shaft 100 shown in FIG. Then, the first shaft 110 having the linear expansion coefficient α1 and the second shaft 130 having the linear expansion coefficient α2 are individually contracted with a temperature drop of ΔT ° C., and L1 · (1−α1 · ΔT) and L2 · (1 −α2 · ΔT), where the length of the overlapping range of both shafts is LW, this LW is expressed by the following equation.

  LW = (L1 · (1−α1 · ΔT) + L2 · (1−α2 · ΔT)) − L

  Then, the length L3 · (1−β · ΔT) after the shrinkage accompanying the temperature drop of ΔT ° C. with respect to the shaft fixing member 120 having the coefficient of thermal expansion β is set to be equal to or greater than the above-described shaft overlapping range LW.

LW ≦ L3 · (1-β · ΔT)
(L1 · (1−α1 · ΔT) + L2 · (1−α2 · ΔT)) − L ≦ L3 · (1−β · ΔT)
(L1 + L2-L)-(L1 · α1 + L2 · α2) · ΔT ≦ L3-L3 · β · ΔT
(L1 + L2-L)-(L1 · α1 + L2 · α2) · ΔT ≦ (L1 + L2-L) −L3 · β · ΔT
L3 · β · ΔT ≦ (L1 · α1 + L2 · α2) · ΔT
β ≦ (L1 · α1 + L2 · α2) / L3

  Then, in order to form the first shaft 110, the second shaft 130, and the second shaft 130 from materials having different linear expansion coefficients from the above-described relationship of β> α, the respective linear expansion coefficients are as follows. What is necessary is just to make it the material to fill.

  α1, α2 <β ≦ (L1, α1 + L2, α2) / L3

  As mentioned above, although the embodiment of the present invention has been described in the embodiments, the present invention is not limited to the above-described embodiments and modifications, and can be implemented in various modes without departing from the gist thereof. Is possible. For example, in the above-described embodiment, the case where the fuel cell unit 40 having a stack structure is fastened with a fixed size has been described. You can also

It is explanatory drawing which shows schematic structure of the fuel cell 10 as an Example of this invention. It is explanatory drawing which shows schematically the whole structure of the fastening shaft 100 by a perspective view. It is explanatory drawing explaining the mode of the fastening by this fastening shaft. FIG. 5 is an explanatory view showing a manufacturing process of the fastening shaft 100. FIG. 4 is an explanatory view showing a comparison between a state in which a fuel cell unit 40 having a stack structure is fastened with a fixed dimension L by a single shaft S and a state in which the fuel cell unit 40 is fastened with a fixed dimension L by a fastening shaft 100. It is explanatory drawing which shows schematic structure of the fastening shaft 100A of a modification. FIG. 6 is an explanatory view showing a state in which a fuel cell unit 40 having a stack structure is fastened with a fixed dimension L using a fastening shaft 100A of a modified example, corresponding to FIG. It is explanatory drawing which shows roughly the structure of the principal part of the fastening shaft 100B of another modification in a perspective view. It is sectional drawing of the 9-9 line in FIG. It is explanatory drawing which shows the manufacture process of the fastening shaft 100B. It is explanatory drawing which shows the mode of the fastening by the fastening shaft 100 which formed the 1st shaft 110, the 2nd shaft 130, and the shaft fixing member 120 from the material of a respectively different linear expansion coefficient.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Fuel cell 10a ... End plate 12 ... Through-hole 20a ... Insulating plate 30a ... Current collecting plate 40 ... Fuel cell unit 100 ... Fastening shaft 100A ... Fastening shaft 100B ... Fastening shaft 102 ... Bolt 110 ... First shaft 110A ... First Shaft 110B ... first shaft 112 ... boss 113 ... female screw 114 ... fixing piece 114A ... fixing piece 114B ... collar 114S ... end face 116 ... bottomed hole 120 ... shaft fixing member 120A ... shaft fixing member 120B ... shaft fixing member 130 ... 2nd shaft 130A ... 2nd shaft 130B ... 2nd shaft 134 ... connection shaft part 134B ... connection shaft part 136 ... fixed piece 136A ... fixed piece 136B ... collar part 138 ... two-sided width part 150 ... shaft part 152 ... slit

Claims (4)

A laminated body fastening structure in which a laminated body is sandwiched between a pair of opposed end plates, and the laminated body is fastened to a fixed size by a shaft disposed on the lateral side of the laminated body between the end plates,
The shaft is
A first shaft fixed at one end plate to one end plate and shorter than the fixed dimension;
A second shaft fixed to the other end plate at an end face, extending toward the one end plate, overlapping the first shaft, and shorter than the fixed dimension;
The first shaft and the second shaft are arranged in a region where the first shaft and the second shaft overlap with each other, fixed to the first shaft on the open end side of the first shaft, and the second shaft on the open end side of the second shaft. And a fixed shaft fixing member,
The shaft fixing member is formed of a material having a larger linear expansion coefficient than both shafts and exhibits a larger shrinkage rate than both shafts. When the temperature drops, the shaft fixing member is fixed to both shafts by contraction of the shaft fixing members themselves. Laminated body fastening structure that narrows the gap between points.   The laminated body fastening structure according to claim 1, wherein the first shaft and the second shaft are formed of the same material.   The laminated body fastening structure according to claim 1 or 2, wherein the first shaft and the second shaft are disposed coaxially between the pair of end plates. A fuel cell,
4. The fuel cell unit according to claim 1, wherein a plurality of fuel cell units that generate electricity by an electrochemical reaction between hydrogen and oxygen are sandwiched and sandwiched between a pair of opposing end plates, and the fuel cell units are stacked. A fuel cell that is fastened to a fixed size between the end plates by a laminate fastening structure.

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