Fuel cell device

Abstract

Fuel cell device (10) comprising: a fuel cell body (110) with a plurality of stacked unit cells (102); a housing (500) in which the fuel cell body is arranged; and a bolt (600) which is in contact at one end with a part of the fuel cell body to fasten the fuel cell body, wherein a through-hole (510) is formed in the housing which penetrates the housing from the outside into the interior of the housing, the bolt is inserted into the through-hole and a sealing element (650) is provided on it which is formed at least on a part of an outer circumferential surface of the bolt, the through-hole has a constant inner diameter over a predetermined distance from a position in the housing to an outer boundary of the housing,In the case of a through-hole, the inner diameter between a section of the constant inner diameter and the outer boundary of the housing is larger than the constant inner diameter; in the case of a through-hole, at least part of the sealing element is placed on an edge of the section of the constant diameter in an outward direction of the housing; and the other end of the bolt is placed in the through-hole in a section between an end of the section of the constant inner diameter in the outward direction of the housing and the outer boundary of the housing.

Description

BACKGROUND OF THE INVENTIONField of InterestThis invention relates to a fuel cell device.Prior ArtIn a fuel cell including a cell stack made up of a plurality of stacked unit cells, the cell stack is fixed to a stack structure under a predetermined load to maintain the stack structure. For example, with respect to a fuel cell described in JP 2008-041 367 A, a spring member is disposed on an end surface side of a cell stack so as to be in contact with the cell stack. The spring member is loaded with a predetermined load in a direction toward the cell stack, thereby maintaining the stack structure of the cell stack. In this fuel cell, a nut is formed in an end plate disposed outside the spring module in a stacking direction. A screw is inserted into this nut from the outside so that the tip of the inserted screw is in contact with the spring element, whereby the spring element is continuously loaded with the predetermined load. Generally, the fuel cell is arranged in a housing. Therefore, by inserting a bolt into a nut formed in the housing, instead of the nut in the end plate, the load can be adjusted to the cell stack.JP 2014-183 015 A discloses a further fuel cell device which has a fuel cell body having a plurality of stacked unit cells and a housing in which the fuel cell body is arranged. A load adjusting screw is in contact at one end with a part of the fuel cell body to fix the fuel cell body, and a through hole is formed in the case, which penetrates the case from the outside into the inside of the case and has a constant diameter over the entire length. Regarding the prior art, reference is also made to U.S. Pat. No. 2015 / 0 162474 A1 and U.S. Pat. No. 2014 / 0 169 911 A1.When the fuel cell is used in a movable body such as a vehicle, it is not advantageous to engage the head of a bolt with the housing in an outwardly protruding position, because there is a risk of damage to a component located in the vicinity of the fuel cell in the event of a collision of the movable body. Therefore, it is preferable to use a set screw without a screw head and insert this screw in such a manner that the rear end of the screw in an insertion direction is located at a position on an inner side relative to a surface of the housing. The housing must be water resistant to prevent water from entering the fuel cell. Therefore, in a structure in which a nut is formed in the housing and a set screw is engaged with the nut, use of a set screw having an outer circumferential surface to which a sealing member is applied is an assumed method to ensure sealing performance between the housing and the set screw. However, according to this method, the sealing member with the screw thread of the nut near its insertion bore is removed while the set screw is inserted. In a state after completion of the insertion, the rear end of the adjustment screw is placed at a position lower than the insertion hole. As a result, it is not possible for the sealing member removed with the screw thread in the vicinity of the insertion bore to achieve sealing performance. This reduces the sealing performance between the housing and the screw, thereby creating a risk of lowering the water resistance of the housing. Therefore, a method for preventing the lowering of the water resistance of the housing by preventing the lowering of the sealing performance between the housing and the screw has been desired. These problems are not only applied to a bolt to be used for fastening a pressure plate, but are widely applied to various fuel cell devices including bolts to be inserted into housings for various purposes. These problems also exist in a bolt without a screw thread on its outer circumferential surface, which is to be inserted into a housing as an insertion element.SUMMARY OF THE INVENTIONThis invention has been made to solve at least a part of the above problems. This invention can be realized in accordance with the following aspects: (1) According to one aspect of the invention, there is provided a fuel cell apparatus. The fuel cell device may include a fuel cell body having a plurality of stacked unit cells, a case in which the fuel cell body is disposed in the case, and a bolt that is in contact at one end with a part of the fuel cell body to fix the fuel cell body. A through hole may be formed in the housing, which penetrates the housing from the outside into the interior of the housing. The bolt may be inserted into the through hole, and a sealing member formed on at least a part of an outer circumferential surface of the bolt may be provided thereon. The through bore may have a constant inner diameter over a predetermined distance from a position in the housing to a boundary of the housing outward. In the through hole, an inner diameter between a portion of the constant inner diameter and the boundary of the housing to the outside may be larger than the constant inner diameter. In the through hole, at least a part of the seal member may be placed at an edge of the constant diameter portion in an outward direction of the housing. The other end of the bolt in the through hole may be placed in a portion between an end of the constant inner diameter portion in the outward direction of the housing and the boundary of the housing outward. In the fuel cell device according to this aspect, the inner diameter between the constant inner diameter portion and the boundary of the case to the outside is larger than the constant inner diameter. The sealing member can be prevented from being removed at a position near an insertion hole of the through hole while the bolt is inserted into the through hole. Further, at least a part of the seal member is placed at the edge of the constant inner diameter portion in the outward direction of the housing. Thereby, a decrease in sealing performance between the housing and the bolt can be prevented, thereby preventing a decrease in water resistance of the housing. In addition, the other end of the bolt is placed in the through hole in the portion between the end of the constant diameter portion in the outward direction of the housing and the boundary of the housing outward. This prevents the bolt from protruding outward from the housing. It is possible to prevent a fuel cell device used in a movable body such as a vehicle from hitting a member located near the fuel cell device in a collision, and thereby to prevent damage to the member. (2) In the fuel cell device according to the above aspect, a screw thread may be formed on both the outer circumferential surface of the bolt and an inner circumferential surface of the constant diameter portion, and the bolt and the constant diameter portion may be threadedly engaged with each other. In the fuel cell device according to this aspect, the screw thread is formed on both the outer circumferential surfaces of the bolt and an inner circumferential surface of the constant diameter portion. This facilitates the insertion of the bolt into the through bore, while it also facilitates an adaptation of a screw connection degree of the bolt in an insertion direction. (3) In the fuel cell device according to the above aspect, the bolt may be configured as a set screw without a head. In the fuel cell device according to this aspect, by the absence of a bolt head, it is possible to locate the other end of the bolt in the through hole in the portion between the end of the constant diameter portion in the outward direction of the housing and the boundary of the housing outward without needing to increase the inner diameter between the constant inner diameter portion and the boundary of the housing outward. Therefore, as compared with a structure in which the inner diameter of the through hole between the constant inner diameter portion and the boundary of the housing to the outside is excessively large, water is prevented from entering the housing from the outside, whereby water is unlikely to collect in the through hole between the constant inner diameter portion and the boundary of the housing to the outside. (4) In the fuel cell device according to the above aspect, the through hole may be formed in a side surface portion of the case and may be opposed to a surface of the fuel cell body at one end in the stacking direction, and the one end of the bolt may be in contact with the surface of the fuel cell body at the one end. In the fuel cell device according to this aspect, the bolt inserted from the outside of the case is in contact with the surface of the fuel cell body at one end in the stacking direction, thereby maintaining a compressive load on a stack. Therefore, compared with a structure in which the bolt is inserted into the through hole formed in an end plate and the fuel cell body maintained under the compressive load is disposed in the housing, the end plate can be omitted to prevent an increase in size of the fuel cell device.This invention may be practiced in various aspects. This invention can be realized, for example, in aspects such as a fuel cell case, a fuel cell system including a fuel cell device, a vehicle to which a fuel cell vehicle is mounted, and a method of manufacturing the fuel cell case.BRIEF DESCRIPTION OF THE DRAWINGSFIG. 1 is a sectional view showing the outline of the structure of the fuel cell device as an embodiment of this invention; FIG. 2 is a plan view showing the external structure of a side surface portion; FIG. 3 is a sectional view explaining the structure of a through hole and that of a bolt in an enlarged form; FIG. 4A is an exemplary view showing the position of the bolt and that of the through hole relative to each other in a state before the bolt is inserted; FIG. 4B is an exemplary view showing the position of the bolt and that of the through hole with respect to each other in a state after completion of insertion of the bolt; FIG. 5A is an exemplary view schematically showing a through hole and a bolt in a fuel cell device of Comparative Example 1 in a state before insertion of the bolt; FIG. 5B is an exemplary view schematically showing a through hole and a bolt in a fuel cell device of Comparative Example 1 in a state after the end of insertion of the bolt; FIG. 6A is an exemplary view schematically showing a through hole and a bolt in a fuel cell device of Comparative Example 2 in a state before insertion of the bolt; and FIG. 6B is an exemplary view schematically showing a through hole and a bolt in a fuel cell device of Comparative Example 2 in a state after the end of insertion of the bolt.DESCRIPTION OF THE EMBODIMENTSA. EmbodimentA-1. Device StructureFIG. 1 is a sectional view showing the outline of the structure of the fuel cell device as an embodiment of this invention. A fuel cell device 10 has a so-called polymer electrolyte fuel cell. The fuel cell device 10 constitutes a fuel cell system together with a supply portion for fuel gas and oxidizing gas as reaction gases, a supply portion for coolant, etc. This fuel cell system is mounted on a fuel cell vehicle and is used there as a system for driving.The fuel cell device 10 includes a fuel cell body 110, an end plate 190, a clamping shaft 300, a housing 500, and a cover 550. The fuel cell body 110 includes a cell stack 102S, a first current collector plate 160E, a second current collector plate 160F, a pressure plate 170, and a stack bus 180.The cell stack 102S has a structure in which a plurality of unit cells 102 are stacked in a stacking direction SD. The unit cells 102 each consist of a membrane electrode assembly, two gas diffusion layers between which the gas diffusion layers hold the membrane electrode assembly, two separators between which the separators hold a stack of the membrane electrode assembly, and the two gas diffusion layers. In this embodiment, an X-axis and a Y-axis are defined such that an X-Y plane extends parallel to a horizontal plane. The Y axis and the Z axis each run perpendicular to the X axis. A +Z direction corresponds to an upward vertical direction. A -Z direction corresponds to a downward vertical direction. As shown in FIG. 1, the fuel cell device 10 is arranged in a manner in which the stacking direction SD extends parallel to the X axis.The first current collector plate 160E is disposed so as to be in contact with an end surface of the cell stack 102S in a -X direction. In this embodiment, the first current collector plate 160E is made of aluminum. The second current collector plate 160F is disposed so as to be in contact with an end surface of the cell stack 102S in a +X direction. In this embodiment, the second current collector plate 160F has a three-layered structure including a titanium layer, an aluminum layer, and a titanium layer. The second current collector plate 160F has an outer periphery covered with rubber. The first and second current collector plates 160E and 160F decrease the current generated by each of the unit cells 102 and output the decreased current to the outside via a terminal not shown in the drawing. Like the second current collector plate 160F, the first current collector plate 160E may have a three-layered structure. The two current collector plates 160E and 160F may be made of any conductive material other than aluminum and titanium.The pressure plate 170 is disposed on an outer side in the stacking direction SD (-X direction) with respect to the first current collector plate 160E. An insulator not shown in the drawing is disposed between the pressure plate 170 and the first current collector plate 160E. The pressing plate 170 is fixed with bolts 600 and presses the cell stack 102S together.Each of the surfaces of each of the unit cells 102, the first and second current collector plates 160E and 160F, and the pressure plate 170 that are perpendicular to the stacking direction SD are formed substantially rectangular. Each unit cell 102, the first and second current collector plates 160E and 160F, and the pressing plate 170 are arranged such that their longitudinal direction extend parallel to the Y axis.The stack bus bar 180 is disposed so as to be in contact with a surface of the second current collector plate 160F in the +X direction. The stack manifold 180 includes a flow path for supplying the reaction gas and the coolant and a flow path for discharging the reaction gas and the coolant formed in the stack manifold 180. The stack bus line 180 connects the reaction gas supply portion and the coolant supply portion to the cell stack 102S, and supplies the reaction gas and the coolant to the cell stack 102S. A circulation line, a gas-liquid separator, etc. as constituent elements constituting a fuel gas supply system are attached to the stack manifold 180.The end plate 190 is disposed to be in contact with a surface of the stack manifold 180 in the +X direction. The end plate 190 is made of aluminum, and closes an opening formed in a side surface of the housing 500 in the +X direction. The end plate 190 is connected to the housing 500 through the clamp shaft 300.An edge of the clamp shaft 300 in the +X direction is connected to the end plate 190 by a nut not shown in the drawing. An edge of the chuck shaft 300 in the -X direction is connected to the housing 500. In this way, the clamping shaft 300 fixes the cell stack 102S, the end plate 190, and the housing 500, thereby maintaining the stack structure of the cell stack 102S. In this embodiment, three rod members constitute the tension shaft 300 whose longitudinal direction coincides with the stacking direction SD. The chuck shaft 300 is disposed vertically below the cell stack 102S and extends parallel to the stacking direction SD. The three rod members constituting the clamp shaft 300 are spaced apart from each other at predetermined intervals in a direction along the Y axis. The number of the rod members constituting the clamp shaft 300 is not limited to three, and may be another number. All three rod members constituting the chuck shaft 300 have circular cross-sectional shapes in a direction perpendicular to the stacking direction SD. These cross-sectional shapes of the elements may have any shapes other than a circular shape. All three rod members constituting the clamp shaft 300 are made of iron. These elements may be made of any metal other than iron, such as steel.The outer shape of the housing 500 is a substantially rectangular rectangular rectangular rectangular parallelepiped. In the housing 500, the fuel cell body 110 having the cell stack 102S is disposed in the housing 500. An opening is formed in both the side surface of the housing 500 in the +X direction and the side surface of the housing 500 in the -Z direction. The opening in the side surface in the +X direction is closed by the end plate 190. The opening in the side surface in the -Z direction is closed by the cover 550. A side surface of the housing 500 in the -X direction (hereinafter also referred to as side surface portion 505) is opposed to a surface of the pressing plate 170 in the -X direction.FIG. 2 is a plan view showing the external structure of a side surface portion 505. In FIG. 2, the cover 550 is illustrated by broken lines. In the side surface portion 505, eight through holes 510 for passing the bolts 600, three pressing member inlets 520, and three clamping shaft inlets 530 are disposed. Further, a plurality of ribs protruding in the -X direction are formed on the side surface portion 505, with the intention of reducing the weight and maintaining the strength of the housing 500.The eight through holes 510 are formed in the vicinity of an edge of the side surface portion 505 in the +Z direction or an edge of the side surface portion 505 in the -Z direction. Four of the eight through holes 510 are disposed near the edge of the side surface portion 505 in the +Z direction and spaced apart from each other at predetermined intervals in the direction along the Y axis. The other four of the eight through holes 510 are disposed near the edge of the side surface portion 505 in the -Z direction, and are spaced apart from each other at predetermined intervals in the direction along the Y axis. Each of the through-holes 510 may be formed in various ways. As shown in FIG. 1, the screws 600 are inserted into each through hole 510, thereby fastening the pressing plate 170. In this embodiment, all the through holes 510 have the same internal structure. The structure of the through holes 510 will be described in detail below.The three pressing member inlets 520 are formed in the substantially central portion of the side surface portion 505. During assembly of the fuel cell device 10, the pressing members are inserted from the outside of the housing 500 into the pressing member inlets 520. The pressing members press the pressing plate 170 in the +X direction, thereby compressing the cell stack 102S in the stacking direction SD. Subsequently, the pressing plate 170 is fastened with the screws 600. Subsequently, the pressing members are pulled out, and each of the pressing member inlets 520 is closed with a pressing member cover not shown in the drawing.The three clamp shaft inlets 530 are disposed near the edge of the side surface portion 505 in the -Z direction and spaced apart from each other by a predetermined distance in the direction along the Y axis. The three rod members constituting the clamp shaft 300 are inserted into the respective clamp shaft inlets 530.The other side surfaces of the housing 500 (including a side surface in the +Y direction, a side surface in the -Y direction, and a side surface in the +Z direction) all have plate-like outer shapes. In this embodiment, the housing 500 is formed by aluminum die casting. The housing 500 may be formed of any metal other than aluminum, such as steel.As shown in FIG. 1, the cover 550 is disposed vertically below the cell stack 102S and closes an opening in the bottom surface of the housing 500. The cover 550 is a plate-like member having a substantially rectangular shape in plan view. The cover 550 has a size substantially corresponding to that of the bottom surface of the housing 500. The cover 550 is fixed to the housing 500 by a bolt not shown in the drawing. In this embodiment, the cover 550 is made of iron. However, the cover 550 may be made of any metal other than iron, such as steel.A-2. Detailed Structure of Through Hole and ScrewFIG. 3 is a sectional view explaining the structure of the through hole 510 and the bolt 600 in an enlarged form. FIG. 3 shows an enlarged portion Ar 1 represented by an alternate long and short dash line in FIG. 1. The sectional view in FIG. 3 corresponds to a cross section through A-A in FIG. 2, and in FIG. 3, an axis OL of the bolt 600 is indicated by an alternate long and two short dash line. Further, an insertion direction ID for the screw 600 and an outward direction OD of the housing 500 are represented by hollow arrows. In this embodiment, the insertion direction ID is parallel to the +X direction (the thickness direction of the side surface portion 505), and the outward direction OD is parallel to the -X direction. A surface of the side surface portion 505 in the +X direction faces the inside of the housing 500. A surface of the side surface portion 505 in the -X direction faces the outside of the housing 500. In this embodiment, the side surface portion 505 is thick in a region around the through hole 510. Alternatively, however, the thickness of the side surface portion 505 may be substantially equal to that of this surrounding area.The through hole 510 is formed to extend in the thickness direction of the side surface portion 505 to penetrate the housing 500 from the outside into the inside of the housing 500. The through hole 510 has a small diameter portion 511 and a large diameter portion 512 which are aligned in the thickness direction of the side surface portion 505 (X-axis direction). The small diameter portion 511 communicates with the inside of the housing 500 and the large diameter portion 512. The large diameter portion 512 communicates with the small diameter portion 511 and the outside of the housing 500. The small diameter portion 511 has a slightly smaller inner diameter than the large diameter portion 512. At the small diameter portion 511, a screw thread not shown in the drawing formed on the inner circumferential surface thereof is disposed. Therefore, the small diameter portion 511 serves as a nut. The screw thread of the small diameter portion 511 (hereinafter also referred to as a "nut") is threadedly engaged with a screw thread, not shown in the drawing, formed on the outer circumferential surface of the screw 600 while the screw 600 is inserted into the through hole 510. No screw thread is formed on the inner circumferential surface of the large diameter portion 512.In this embodiment, the inner diameter of the small diameter portion 511 is constant. In this embodiment, the length of the small diameter portion 511 in the X-axis direction is 20 mm, and that of the large diameter portion 512 in the X-axis direction is 15 mm. The respective lengths of the small diameter portion 511 and the large diameter portion 512 in the X-axis direction are not limited to 20 mm and 15 mm, but may be set to arbitrary lengths. The respective lengths of the small diameter portion 511 and the large diameter portion 512 may correspond to each other. Alternatively, the small diameter portion 511 may be shorter than the large diameter portion 512. Here, it is preferable that the small diameter portion 511 has a sufficient length with which the sealing performance described below can be ensured. Further, it is preferable that the large diameter portion 512 has a sufficient length with which dimensional imprecision of the cell stack 102S in the stacking direction SD described below can be controlled.Each screw 600 is inserted from the outside of the housing 500 into a corresponding through hole 510, and is screwed in the insertion direction ID with a predetermined tool to be in contact with the pressing plate 170, thereby fastening the pressing plate 170. In this way, the fuel cell body 110 is fastened with each of the bolts 600. By adjusting a screw degree of each of the screws 600 in the insertion direction ID, dimensional imprecision of the cell stack 102S that occurs when the cell stack 102S is fixed with a predetermined load is controlled in the stacking direction SD.In this embodiment, the screw 600 is a set screw having a substantially circular outer shape without a head. The set screw is generally referred to as a hollow set screw. In this embodiment, the screw 600 has a nominal diameter of M12. The screw 600 may have any nominal diameter other than M12. In this embodiment, the length of the bolt 600 in a direction along the axis OL is set to a length that allows control of dimensional imprecision of the cell stack 102S in the stacking direction SD, while also preventing protrusion of the bolt 600 to the outside of the housing 500. In this embodiment, each of the screws 600 is made of iron. Each of the bolts 600 may be made of any metal other than iron, such as steel.The screw 600 has a threadably engaged portion 620 and a tip portion 630. The screw-engaged portion 620 constitutes most of the screw 600 and is placed on the -X direction side along the axis OL. In this embodiment, the outer diameter of the threadedly engaged portion 620 is constant. The screw-engaged portion 620 has a screw thread not shown in the drawing formed on its outer circumferential surface. The screw-engaged portion 620 serves as an externally threaded screw.A sealing member 650 is mounted on the outer circumferential surface of the screw-engaged portion 620. In particular, the sealing element 650 is applied to the screw thread of the screw 600. In this embodiment, the sealing member 650 is comprised of a pre-coat type reactive sealant. The precoating type reactive sealant contains materials for an adhesive enclosed in a microcapsule. These materials are blended and cured under pressure generated by the threaded engagement. Therefore, the pre-coat type reactive sealant is suitably used as the sealing member 650. The sealing member 650 may be made of any other kind of sealant than the pre-coat type reactive sealant, such as a pre-coat type non-reactive sealant. The sealing member 650 may be applied to a part of the screw-engaged portion 620 extending in the direction along the axis OL. Here, in order to ensure sealing performance, it is preferable that the sealing member 650 is applied to at least a part of the screw-engaged portion 620 that is to make threaded engagement with the nut in a state after the end of the insertion of the screw 600.A tool-mounted portion 625 is formed on an edge of the screw-engaged portion 620 in the -X direction. The tool-mounted portion 625 is a hexagonal recess having a hexagonal cross-sectional shape with respect to the axis OL as a center. The tool-mounted portion 625 is to be engaged with a hex wrench. The tool-mounted portion 625 may have any other structures that can be engaged with a tool, rather than a hexagonal recess, such as a rectangular recess, a cruciform recess, or a slot.The tip portion 630 is placed at an end of the bolt 600 in the direction along the axis OL. In the state after the end of the insertion of the screw 600, an end surface of the tip portion 630 in the +X direction (hereinafter referred to as "tip surface S 1") is in contact with the pressing plate 170. The tip portion 630 has a smaller outer diameter than the threadedly engaged portion 620. On the outer circumferential surface of the tip portion 630, no screw thread is formed. This makes it possible to reduce the number of times the bolt 600 needs to be tightened during the insertion of the bolt 600. The tip portion 630 may have the same outer diameter as the threadedly engaged portion 620. A screw thread may be formed on the outer circumferential surface of the tip portion 630.In the state after the end of the insertion of the bolt 600, an end surface of the bolt 600 in the -X direction (hereinafter referred to as "rear end surface S 2") is placed on an inner side (on the +X direction side) with respect to a part of an outer surface (in the -X direction) of the side surface portion 505 around the through hole 510. Further, the rear end surface S 2 is placed at a position that extends further in the outward direction OD (-X direction) than an end of the small diameter portion 511 in the outward direction OD. Specifically, the rear end surface S 2 is placed in the large diameter portion 512. That is, the rear end surface S 2 of the bolt 600 is placed in the through hole 510, in a portion between the end of the small diameter portion 511 in the outward direction OD and a boundary of the housing 500 outward.In this embodiment, the bolt 600 corresponds to a bolt in the claims, the tip surface S1 corresponds to the one end in the claims, and the rear end surface S2 corresponds to the other end in the claims. The small diameter portion 511 corresponds to a constant inner diameter portion in the claims. The large diameter portion 512 corresponds to a portion from an end of the constant inner diameter portion in the outward direction of the housing to a boundary of the housing outward in the claims. The side surface portion 505 corresponds to a side surface portion in the claims, and the surface of the pressing plate 170 in the -X direction corresponds to a surface of the fuel cell body in a stacking direction in the claims.A-3. Shape of Through Hole and Sealing PerformanceFIG. 4A is an exemplary view showing the position of the screw 600 and that of the through hole 510 relative to each other in a state before the screw 600 is inserted. FIG. 4B is an exemplary view showing the position of the bolt 600 and that of the through hole 510 relative to each other in a state after completion of insertion of the bolt 600. FIGS. 4A and 4B schematically show the shape of the through hole 510 and that of the bolt 600. In FIGS. 4A and 4B, a portion of the bolt 600 to which the sealing member 650 is applied, specifically, a portion corresponding to the threadedly engaged portion 620, is shaded.The screw 600 is inserted into the through hole 510 in the insertion direction ID indicated by a hollow arrow in FIG. 4A. A tip of the screw-engaged portion 620 in the insertion direction ID (tip surface S 1) reaches to the small diameter portion 511 without coming into contact with the large diameter portion 512. The screw thread formed on the outer circumferential surface of the screw-engaged portion 620 is screw-engaged with the screw thread formed on the inner circumferential surface of the small diameter portion 511. Then, the screw 600 is screwed until the tip surface S 1 is in contact with the pressing plate 170 not shown in FIGS. 4A and 4B. As shown in FIG. 4B, in the state after the end of the insertion of the screw 600, the rear end surface S 2 corresponding to the rear end of the screw 600 in the insertion direction ID is placed in the large diameter portion 512. In this way, while the screw 600 is inserted, contact of the outer circumferential surface of the screw 600 with the inner circumferential surface of the large diameter portion 512 is prevented. Thereby, the sealing member 650 can be prevented from being removed from the outer circumferential surface of the screw 600 by the large diameter portion 512 during the insertion of the screw 600. In addition, the rear end surface S 2 does not reach the inside of the small diameter portion 511. Therefore, even when the sealing member 650 is removed by the screw thread disposed on the small diameter portion 511, the sealing member 650 remains between the small diameter portion 511 and the outer circumferential surface of the screw 600. This allows the remote seal member 650 to achieve sealing performance between the housing 500 and the bolt 600. Therefore, a decrease in sealing performance between the small diameter portion 511 and the bolt 600 is prevented, thereby preventing a decrease in water resistance of the housing 500. For example, entry of water from the outside of the housing 500 into the housing 500 is prevented in rainy weather.The screw 600 of this embodiment has the screw thread. This facilitates insertion of the screw 600 into the through hole 510, while also facilitating adjustment of a screw degree of the screw 600 in the insertion direction ID. Further, the screw 600 of this embodiment is a set screw without a screw head. This makes it possible to place the rear end surface S 2 of the bolt 600 in the large diameter portion 512 without requiring the inner diameter of the large diameter portion 512 to be excessively increased. Therefore, as compared with a structure in which the large diameter portion 512 is excessively large, entry of water from the outside of the housing 500 into the large diameter portion 512 can be prevented, thereby making it unlikely that water will collect in the large diameter portion 512. The absence of a bolt head contributes to weight reduction and size reduction of the fuel cell device 10.In this embodiment, the through hole 510 is formed in the side surface portion 505 of the housing 500. This enables the pressing plate 170 to be fastened to the bolt 600 inserted from the outside of the housing 500, thereby maintaining a pressing load on the cell stack 102S. Therefore, compared to a structure in which the bolt 600 is inserted into the through hole 510 formed in an end plate and the cell stack 102S maintained under the compressive load is disposed in the housing 500, the end plate can be omitted to prevent an increase in size of the fuel cell device 10.B. Comparative ExamplesB-1. Comparative Example 1FIG. 5A is an exemplary view schematically showing a through hole 810 and a bolt 820 in a fuel cell device of Comparative Example 1 in a state before insertion of the bolt 820. FIG. 5B is an exemplary view schematically showing a through hole 810 and a bolt 820 in a fuel cell device of Comparative Example 1 in a state after the end of insertion of the bolt 820. The through hole 810 of Comparative Example 1 has the same inner diameter in an arbitrary portion in an insertion direction, and has a screw thread not shown in the drawing formed on its inner circumferential surface. The screw 820 of Comparative Example 1 is a set screw to which a sealing member 830 is applied in a region represented by diagonal lines in a state before the screw 820 is inserted. The screw 820 is inserted into the through hole 810 in the insertion direction shown by the hollow arrow. In the state after the completion of the insertion, the rear end of the screw 820 in the insertion direction is placed in the through hole 810. During insertion, the seal member 830 mounted on the screw 820 is removed in an area Ar 2 indicated by an alternate long and short dash line in FIG. 5B with the thread located near an insertion hole of the through hole 810. In the state after the completion of the insertion, the rear end of the screw 820 is at a lower position than the insertion hole. As a result, it is not possible for the sealing member 830 removed with the screw thread in the vicinity of the insertion bore of the through bore 810 to achieve sealing performance. This reduces the sealing performance between a housing and the screw 820, thereby reducing the water resistance of the housing.In contrast, in the fuel cell device 10 of the above-described embodiment, the large diameter portion 512 of the through hole 510 communicates with the outside of the housing 500. This can prevent the seal member 650 having the screw thread located near an insertion hole of the through hole 510 from being removed.In addition, the rear end surface S 2 does not extend to the inside of the small diameter portion 511. Accordingly, the seal member 650 is located in a range in which the small diameter portion 511 and the bolt 600 are threadedly engaged with each other. Thereby, a decrease in sealing performance between the small diameter portion 511 and the bolt 600 can be prevented, thereby preventing a decrease in water resistance of the housing 500.B-2. Comparative Example 2FIG. 6A is an exemplary view schematically showing a through hole 910 and a bolt 920 in a fuel cell device of Comparative Example 2 in a state before insertion of the bolt 920. FIG. 6B is an exemplary view schematically showing a through hole 910 and a bolt 920 in a fuel cell device of Comparative Example 2 in a state after the end of insertion of the bolt 920. Like the through hole 810 of Comparative Example 1, the through hole 910 of Comparative Example 2 has the same inner diameter in an arbitrary portion in an insertion direction, and has a screw thread not shown in the drawing formed on its inner circumferential surface. The screw 920 of Comparative Example 2 has a screw head and has a seal member 930 applied in a region indicated by diagonal lines. The screw 920 is inserted into the through hole 910 in the insertion direction shown by a hollow arrow. However, due to the presence of the screw head of the screw 920, the rear end of the screw 920 in the insertion direction may not be disposed in the through hole 910, whereby the screw head protrudes to the outside of a housing as shown in FIG. 6B. As a result, the bolt 920 hits a member located near the fuel cell device in a collision, thereby damaging this member.In contrast, in the fuel cell device 10 of the above embodiment, the bolt 600 does not have a bolt head, whereby the rear end of the bolt 600 in the insertion direction (rear end surface S 2) is placed in the large diameter portion 512. This makes it possible to prevent the bolt 600 from hitting a component located in the vicinity of the fuel cell device 10 in the event of a collision, whereby damage to this component can be prevented.C. ModificationsC-1. First ModificationIn the above embodiment, a member to be inserted into the through hole 510 is a screw 600 having a screw thread. However, the invention is not intended to be limited thereby. Instead of the screw 600, a bolt without a screw thread may also be inserted into the through hole 510. Even with this structure, the pressing plate 170 can be fixed similarly by a frictional force acting between the outer circumferential surface of the bolt and the inner circumferential surface of the through hole 510 (small diameter portion 511). Further, by forming the sealing member 650 on the outer circumferential surface of the bolt, the sealing performance between the bolt and the housing 500 can be secured. In addition, placing the rear end of the bolt in the insertion direction in the large diameter portion 512 can prevent the bolt from hitting a member located near the fuel cell device 10 in a collision, whereby damage to this member can be prevented.C-2. Second ModificationIn the above embodiment, the screw 600 is a set screw without a screw head. However, the invention is not intended to be limited thereby. The presence of a screw head on the screw 600 is possible in a structure in which the inner diameter of the large diameter portion 512 is larger than the outer diameter of the screw head. Even with this structure, it is also possible that the rear end of the screw 600 in the insertion direction is placed in the large diameter portion 512 in the state after the end of the insertion of the screw 600.C-3. Third ModificationIn the above embodiment, the rear end surface S 2 of the bolt 600 is placed in the large diameter portion 512. However, the invention is not intended to be limited thereby. The rear end surface S 2 of the bolt 600 may alternatively be placed at a boundary between the exterior of the housing 500 and the large diameter portion 512. As another alternative, the rear end surface S 2 of the bolt 600 may be placed at a boundary between the small diameter portion 511 and the large diameter portion 512. Even in these structures, a similar effect to that of the embodiment can be obtained. Specifically, the rear end surface S 2 of the bolt 600 may be generally placed in the through hole 510 in the portion from the end of the constant inner diameter portion in the outward direction OD of the housing 500 to the boundary of the housing 500 outward.C-4. Fourth ModificationIn the above embodiment, the inner diameter of the small diameter portion 511 is constant. However, the invention is not intended to be limited thereby. The inner diameter of the small diameter portion 511 may be at least partially constant. For example, the inner diameter of the small diameter portion 511 in some portions may be larger than that of the small diameter portion 511 in other portions. For example, the inner diameter of the small diameter portion 511 at an edge thereof in the +X direction may be larger than that of the small diameter portion 511 in the other portion. Even in these structures, a similar effect to that of the embodiment can be obtained. Here, assuming that the small diameter portion 511 has a sufficient length in the insertion direction to ensure sealing performance, it is preferable that the small diameter portion 511 has a constant inner diameter. Specifically, the small diameter portion 511 may generally have an inner diameter constant for a predetermined distance from a position in the housing 500 to the boundary of the housing 500 outward.C-5. Fifth ModificationIn the above embodiment, all the through holes 510 have the same internal structure. Alternatively, all the through holes 510 may have different internal structures from each other. For example, the length of the small diameter portion 511 or that of the large diameter portion 512 may be different from each other at the through holes 510. Alternatively, the inner diameter of the small diameter portion 511 and that of the large diameter portion 512 may be different from each other at the through holes 510.In the above embodiment, all the screws 600 have the same shape. Alternatively, all of the screws 600 may have different shapes from each other. For example, a length in the direction of the axis OL may deviate from each other at the bolts 600. As another example, a region where the sealing member 650 is applied may be different from each other at the bolts 600. In particular, the screw 600 used may generally have any shape with a sealing member 650 formed on at least a part of the outer circumferential surface of the screw 600. In the above embodiment, the eight through holes 510 are formed in the side surface portion 505 of the housing 500, and the housing 500 has the eight screws 600. Alternatively, the number of through holes 510 and that of bolts 600 may be any other number, which is not limited to eight.C-6. Sixth ModificationIn the above embodiment, the tip surface S 1 of the bolt 600 is in contact with the pressing plate 170. The tip surface S 1 may be in contact with any member as the pressure plate 170, such as an end plate. In the above embodiment, the through hole 510 is formed in the side surface portion 505 of the housing 500. The through hole 510 may be formed at different positions of the housing 500. In this structure, the screw 600 can be used to fix another component in the housing 500. Specifically, the bolt 600 to be disposed may generally contact a part of the fuel cell body 110 at one end thereof to fix the fuel cell body 110.C-7. Seventh ModificationIn the above embodiment, the fuel cell device 10 is used as built-in to a fuel cell vehicle. The fuel cell device 10 may be installed in any movable body other than a fuel cell vehicle. Alternatively, the fuel cell device 10 may be used as a stationary fuel cell. Even with this structure, a similar effect to that of the embodiment is obtained, and an impact of the bolt 600 with a member located near the fuel cell device 10 can be prevented, for example, when the fuel cell falls, thereby preventing damage to this member.

Claims

A fuel cell device (10) comprising: a fuel cell body (110) including a plurality of stacked unit cells (102); a case (500) in which the fuel cell body is disposed; and a bolt (600) that is in contact at one end with a part of the fuel cell body to fix the fuel cell body, wherein a through hole (510) is formed in the case, penetrating the case from the outside into the inside of the case, the bolt is inserted into the through hole, and a sealing member (650) is provided thereon, which is formed on at least a part of an outer circumferential surface of the bolt, the through hole having a constant inner diameter over a predetermined distance from a position in the case to a boundary of the case from the outside, wherein, an inner diameter between a constant inner diameter portion and the boundary of the housing toward the outside is larger than the constant inner diameter, wherein, at the through hole, at least a part of the sealing member is placed at an edge of the constant diameter portion in an outward direction of the housing, and the other end of the bolt is placed in the through hole in a portion between an end of the constant inner diameter portion in the outward direction of the housing and the boundary of the housing toward the outside.The fuel cell device according to claim 1, wherein a screw thread is formed on both outer circumferential surfaces of the bolt and an inner circumferential surface of the constant diameter portion, and the bolt and the constant diameter portion are threadedly engaged with each other.The fuel cell device of claim 2, wherein the bolt is configured as a set screw without a head.The fuel cell device according to any one of claims 1 to 3, wherein the through hole is formed in a side surface portion of the case and is opposed to a surface of the fuel cell body at one end in the stacking direction, and the one end of the bolt is in contact with the surface of the fuel cell body at the one end.

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