Piping structure in fuel cell systems

Abstract

The objective is to provide a piping structure for fuel cell systems that can achieve both reduced piping vibration and improved ease of assembly of piping groups. [Solution] In a piping structure for a fuel cell system comprising a fuel cell stack that generates electrical energy by reacting hydrogen gas and oxygen, an air supply unit that supplies air to the fuel cell stack, and a group of air piping connecting the air supply unit and the fuel cell stack, the group of air piping comprises an upstream pipe installed on the air supply unit side, a downstream pipe installed on the fuel cell stack side, and an intermediate pipe connected to the upstream and downstream pipes, wherein the upstream and downstream pipes are non-flexible pipes with greater rigidity than the intermediate pipe, and the intermediate pipe comprises a flexible first vibration damping hose connected to the upstream pipe, and the total length of the non-flexible pipes in the group of air piping is greater than the length of the first vibration damping hose.

Description

Technical Field

[0001] This invention relates to a piping structure in a fuel cell system.

Background Art

[0002] As a conventional technology of a piping structure in a fuel cell system, for example, a fuel cell-mounted device disclosed in Patent Document 1 is known. The fuel cell-mounted device disclosed in Patent Document 1 is a fuel cell-mounted device having a pumping device for pumping the gas inhaled and exhausted by the fuel cell. A vibration damping member for damping the vibration of the pipe is provided in the pipe through which the gas is delivered with pulsation by the pumping device. The vibration damping member suppresses the generation of noise caused by the vibration of the pipe.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the fuel cell-mounted device disclosed in Patent Document 1, although a vibration damping member for damping the vibration of the pipe is provided, the assemblability of the pipe group including the vibration damping member is not considered. Therefore, even though the vibration of the pipe can be reduced, there is a problem that the assemblability of the pipe group including the vibration damping member is poor.

[0005] This invention has been made in view of the above problems, and an object of this invention is to provide a piping structure in a fuel cell system that can achieve both reduction of pipe vibration and improvement of the assemblability of the pipe group.

Means for Solving the Problems

[0006] To solve the above problems, the present invention provides a piping structure for a fuel cell system comprising a fuel cell stack that generates electrical energy by reacting hydrogen gas and oxygen, an air supply unit that supplies air to the fuel cell stack, and a group of air piping units that connect the air supply unit and the fuel cell stack, wherein the group of air piping units comprises an upstream pipe installed on the air supply unit side, a downstream pipe installed on the fuel cell stack side, and an intermediate pipe connected to the upstream pipe and the downstream pipe, wherein the upstream pipe and the downstream pipe are non-flexible pipes having greater rigidity than the intermediate pipe, the intermediate pipe has a flexible first vibration damping hose connected to the upstream pipe, the first vibration damping hose is curved when connected to the upstream pipe, and the sum of the lengths of the non-flexible pipes in the group of air piping units is greater than the length of the first vibration damping hose.

[0007] In this invention, the first vibration damping hose is curved when connected to the upstream piping, and the total length of the non-flexible piping in the air piping group is greater than the length of the first vibration damping hose. Therefore, vibrations of the piping caused by the operation of the air compressor can be reduced. Furthermore, by using a flexible first vibration damping hose, the ease of assembly of the air piping group including the first vibration damping hose can be improved.

[0008] Furthermore, in the piping structure of the fuel cell system described above, the intermediate piping may have a joint piping connected to the first vibration damping hose, and a flexible second vibration damping hose connected to the joint piping and the downstream piping, wherein the joint piping is more rigid than the second vibration damping hose, and the total length of the non-flexible piping in the air piping group may be greater than the total length of the first vibration damping hose and the second vibration damping hose. In this case, the total length of the non-flexible pipes in the air piping group is greater than the total length of the first and second vibration-damping hoses. Since the joint piping, which is more rigid than the second vibration-damping hose, is connected to the first vibration-damping hose, and the flexible second vibration-damping hose is connected to the joint piping and the downstream piping, the second vibration-damping hose, in conjunction with the first vibration-damping hose, can reduce the vibration of the piping caused by the operation of the air compressor. Furthermore, by using the flexible second vibration-damping hose, the ease of assembly of the air piping group, including the first and second vibration-damping hoses, can be further improved.

[0009] Furthermore, in the piping structure of the fuel cell system described above, the joint piping may have an upstream pipe section connected to the first vibration damping hose, a downstream pipe section connected to the second vibration damping hose, and an intermediate pipe section between the upstream pipe section and the downstream pipe section, wherein the axial direction of at least one of the upstream pipe section and the downstream pipe section is not aligned with the axial direction of the intermediate pipe section. In this case, the axial direction of at least one of the upstream and downstream pipe sections does not coincide with the axial direction of the intermediate pipe section. Therefore, it becomes easier to connect the joint piping to one of the first and second vibration damping hoses first, and then to the other of the first and second vibration damping hoses.

[0010] Furthermore, in the piping structure of the fuel cell system described above, the upstream pipe section, the downstream pipe section, and the intermediate pipe section may each be formed by straight pipes. In this case, since the upstream, downstream, and intermediate pipe sections are formed from straight pipes, it becomes easier to manufacture the intermediate piping, and manufacturing costs can be reduced compared to when it is made from curved pipes.

[0011] Furthermore, in the piping structure of the fuel cell system described above, the first vibration-damping hose may be configured to be formed by a curved pipe. In this case, since the first vibration-damping hose is formed by a curved pipe, elastic deformation does not occur, and the cross-sectional area of ​​the flow path does not decrease, compared to the case where a straight pipe is bent to form a curved pipe. Therefore, pressure loss of the air passing through the first vibration-damping hose can be suppressed.

[0012] Furthermore, in the piping structure of the fuel cell system described above, the second vibration-damping hose may be configured to be formed by a curved pipe. In this case, since the second vibration damping hose is formed by a curved pipe, vibration reduction by the second vibration damping hose is possible in conjunction with the vibration reduction by the first vibration damping hose. [Effects of the Invention]

[0013] According to the present invention, it is possible to provide a piping structure for a fuel cell system that can achieve both reduced piping vibration and improved ease of assembly of piping groups. [Brief explanation of the drawing]

[0014] [Figure 1] This is a schematic diagram of a fuel cell system to which the piping structure according to the first embodiment is applied. [Figure 2] This is a side view of the piping structure in the fuel cell system according to the first embodiment. [Figure 3] This is a plan view of the piping structure in a fuel cell system according to the first embodiment. [Figure 4] (a) is a longitudinal cross-sectional view of the first flexible hose, and (b) is a longitudinal cross-sectional view of the second flexible hose. [Figure 5] (a) is a side view of the pipe fitting, and (b) is an exploded view of the pipe fitting. [Figure 6] (a) is a perspective view of the fitting piping just before it is connected to the second flexible hose, (b) is a perspective view of the fitting piping connected to the second flexible hose, and (c) is a perspective view of the fitting piping connected to the first flexible hose. [Figure 7] This is a side view of the piping structure in a fuel cell system according to the second embodiment. [Figure 8]It is a side view of a piping structure in a fuel cell system according to the third embodiment. [Figure 9] It is a side view of a piping structure in a fuel cell system according to the fourth embodiment.

Modes for Carrying Out the Invention

[0015] (First Embodiment) Hereinafter, the piping structure of the fuel cell system according to the first embodiment will be described with reference to the drawings. The fuel cell system of this embodiment is an in-vehicle fuel cell system, and the vehicle is a forklift as an industrial vehicle. First, a fuel cell system to which a piping structure (hereinafter simply referred to as "piping structure") in the fuel cell system is applied will be described.

[0016] As shown in FIG. 1, the fuel cell system 10 includes a fuel cell stack 11, a hydrogen gas tank 12 that stores hydrogen gas, and an air compressor 13 as an air supply unit that supplies air containing oxygen to the fuel cell stack 11. A hydrogen gas supply path 14 is connected between the hydrogen gas tank 12 and the fuel cell stack 11. The hydrogen gas in the hydrogen gas tank 12 is supplied to the fuel cell stack 11 through the hydrogen gas supply path 14.

[0017] An air supply path 15 that supplies air containing oxygen to the fuel cell stack 11 is connected to the fuel cell stack 11. The upstream end of the air supply path 15 is an air intake 16. The air compressor 13 as an air supply unit is installed so as to be located between the air intake 16 and the fuel cell stack 11 in the air supply path 15. Air is supplied to the fuel cell stack 11 by the air compressor 13. The air compressor 13 of this embodiment is a Roots-type compressor, but other types of air compressors may be used. An air strainer 17 that removes foreign substances in the air is provided on the upstream side of the air compressor 13 in the air supply path 15. An intercooler 18 that cools the air is installed on the downstream side of the air compressor 13 in the air supply path 15.

[0018] The fuel cell stack 11 has a stack structure in which numerous polymer-type single cells (not shown) are stacked, and generates high-output power (electrical energy) by electrochemically reacting the hydrogen and oxygen supplied in each cell. A fuel cell cell comprises an anode electrode to which hydrogen gas is supplied, a cathode electrode to which oxygen is supplied, and an electrolyte membrane placed between the anode electrode and the cathode electrode. The fuel cell cells are sandwiched by separators. The fuel cell stack 11 is, for example, a solid polymer fuel cell.

[0019] The fuel cell stack 11 is connected to a hydrogen gas circulation path 19 for circulating hydrogen off-gas, including unreacted hydrogen gas in the fuel cell stack 11, as well as an exhaust path 20 for releasing exhaust gas discharged from the fuel cell stack 11. The hydrogen gas circulation path 19 is connected to a hydrogen gas supply path 14. A gas-liquid separator 21 is installed in the hydrogen gas circulation path 19, which separates the generated water from the unreacted hydrogen gas. The unreacted hydrogen gas in the fuel cell stack 11 is mixed with the hydrogen gas. A diluent 22 is installed in the exhaust path 20, which is connected to the gas-liquid separator 21. The diluent 22 dilutes the hydrogen gas contained in the generated water with the exhaust gas from the exhaust path 20.

[0020] Next, the piping structure 24 of this embodiment will be described. The piping structure 24 includes an intercooler 18, an air compressor 13, and a plurality of air pipes (a group of air pipes) connecting the air compressor 13 and the intercooler 18. The group of air pipes constitutes part of the air supply passage 15 between the air compressor 13 and the intercooler 18. As shown in Figures 2 and 3, the group of air pipes includes a discharge pipe 25, an intercooler suction pipe 26, a first flexible hose 27, a second flexible hose 28, and a joint pipe 29. In this embodiment, the air compressor 13 and the intercooler 18 are spaced apart horizontally, and the air compressor 13 is installed at a higher position than the intercooler 18.

[0021] The discharge pipe 25 is a rigid, metal pipe connected to the discharge port 30 of the air compressor 13 and also to the first flexible hose 27. The discharge pipe 25 is installed furthest upstream in the air piping group and corresponds to the upstream piping installed on the air compressor 13 side. The discharge pipe 25 has a circular flow path cross-section and is a pipe composed of multiple curved pipe sections 31, 32 and straight pipe sections 33 connecting the curved pipe sections 31, 32, although it may also be a straight pipe. The shape of the discharge pipe 25 is formed considering the space constraints around the discharge pipe 25. The upstream end 34 of the discharge pipe 25 is fixed to the air compressor 13 by bolts or welding. The downstream end 35 of the discharge pipe 25 is inserted into the first flexible hose 27 and fixed by a hose clamp 36. The hose clamp 36 is made of metal. The position of the downstream end 35 is such that the first flexible hose 27 can be assembled by an operator.

[0022] The intercooler intake pipe 26 is a rigid metal pipe connected to the intake port 40 of the intercooler 18 and also to the second flexible hose 28. The intercooler intake pipe 26 is installed furthest downstream in the air piping group and corresponds to the downstream piping installed on the intercooler 18 side. The intercooler intake pipe 26 has a circular flow path cross-section and is an elbow-shaped bend at one point, but it may also be a straight pipe. The downstream end 41 of the intercooler intake pipe 26 is fixed to the intercooler 18 by bolts or welding. The upstream end 42 of the intercooler intake pipe 26 is inserted into the second flexible hose 28 and fixed by a hose clamp 36. The position of the upstream end 42 is such that the second flexible hose 28 can be assembled by an operator. Furthermore, the space between the downstream end 35 of the discharge pipe 25 and the upstream end 42 of the intercooler suction pipe 26 is a space in which an operator can assemble the first flexible hose 27, the second flexible hose 28, and the fitting pipe 29.

[0023] The first flexible hose 27 corresponds to the first vibration-damping hose for reducing vibration in the piping group. As shown in Figure 4(a), the first flexible hose 27 is formed by a curved pipe set with a specific radius of curvature R1. The effective length L1 at the axis P1 of the first flexible hose 27 is set, and the radius of curvature R1 corresponds to the distance between the arc at the axis P1 and the radius center O. The material of the first flexible hose 27 is, for example, a heat-resistant synthetic rubber such as silicone rubber or fluororubber, or it may be formed from an elastic material such as natural rubber or resin. In this embodiment, the first flexible hose 27, together with the fitting pipe 29 and the second flexible hose 28, constitutes an intermediate pipe connected to the upstream and downstream pipes. The upstream end 43 of the first flexible hose 27 is connected to the downstream end 35 of the discharge pipe 25. The downstream end 44 of the first flexible hose 27 is connected to the fitting pipe 29 and fixed by a hose band 36. By using the first flexible hose 27, which is elastically deformable, piping errors can be absorbed, and the ease of assembling the piping group is improved compared to when only metal piping is connected.

[0024] Incidentally, the inventors have found through testing and other means that, in order to reduce vibration in the air piping group, it is preferable to make the flexible hose closest to the air compressor 13 a curved pipe. Furthermore, in order to improve vibration reduction, it is preferable to make the radius of curvature R1 of the first flexible hose 27 as small as possible, and also to shorten the effective length L1 of the first flexible hose 27 as short as possible. For this reason, in this embodiment, the radius of curvature R1 of the first flexible hose 27 is set to, for example, about twice the inner diameter φ1 of the first flexible hose 27, but it is acceptable to have a radius of about twice the inner diameter φ1, from 1.5 times the inner diameter φ1, to about twice the inner diameter φ1, which allows for the manufacture of the first flexible hose 27. The inner diameter φ1 of the first flexible hose 27 is approximately the same as the outer diameter of the discharge pipe 25. Also, the effective length L1 in this embodiment is approximately the same as the inner diameter φ1. The length N1 of the insertion allowance at the end, excluding the effective length L1, is greater than the effective length L1. Thus, in order to reduce vibration in the air piping group, the radius of curvature R1 of the first flexible hose 27 should be made as small as possible within the limits of what is feasible for manufacturing the first flexible hose 27, and the effective length L1 of the first flexible hose 27 should be shortened as much as possible. For this reason, the sum of the lengths of the non-flexible piping in the air piping group, i.e., the lengths of the discharge piping 25, the intercooler suction piping 26, and the fitting piping 29, is greater than the length of the first flexible hose 27.

[0025] The second flexible hose 28 is connected to the fitting pipe 29 and the intercooler suction pipe 26. The material of the second flexible hose 28 is, like the first flexible hose 27, synthetic rubber such as silicone rubber, or it may be formed from an elastic material such as natural rubber or resin. The second flexible hose 28 is formed from a straight pipe with an inner diameter φ2 and an effective length L2 at the axis P2. The inner diameter φ2 and the effective length L2 are approximately equal, and the length N2 of the insertion allowance at the end excluding the effective length L2 is approximately the same as the effective length L2. In this embodiment, the second flexible hose 28, together with the first flexible hose 27 and the fitting pipe 29, constitutes an intermediate pipe connected to the upstream and downstream pipes. The downstream end 45 of the second flexible hose 28 is connected to the upstream end 34 of the intercooler suction pipe 26. The upstream end 46 of the second flexible hose 28 is connected to the fitting pipe 29 and secured by a hose clamp 36. By using the elastically deformable second flexible hose 28, piping errors can be absorbed together with the first flexible hose 27, improving the ease of assembling the piping group compared to connecting only metal piping.

[0026] The joint piping 29 is a rigid metal pipe connected to the first flexible hose 27 and the second flexible hose 28. Because the joint piping 29 in this embodiment is lightweight, it is supported by the first flexible hose 27 and the second flexible hose 28. The joint piping 29 is a pipe composed of multiple straight sections. Specifically, as shown in Figure 5(a), the joint piping 29 comprises an upstream pipe section 51, an intermediate pipe section 52, and a downstream pipe section 53. The upstream pipe section 51 is connected to the downstream end 44 of the first flexible hose 27. The upstream end of the upstream pipe section 51 is the upstream end 54 of the joint piping 29. Most of the upstream pipe section 51 is inserted into 27. The downstream end of the upstream pipe section 51 is connected to the upstream end of the intermediate pipe section 52 by welding. The downstream end of the upstream pipe section 51 is connected to the upstream end of the intermediate pipe section 52 such that the axial direction of the upstream pipe section 51 and the axial direction of the intermediate pipe section 52 are different from each other. As shown in Figure 5(b), the flow path cross-section at the downstream end of the upstream pipe section 51 is inclined with respect to the axis Q1 of the upstream pipe section 51, and the flow path cross-sectional shape is elliptical.

[0027] The intermediate pipe section 52 is a pipe section interposed between the upstream pipe section 51 and the downstream pipe section 53 in the joint piping 29. The end face of the upstream end of the intermediate pipe section 52 is inclined with respect to the axis Q2 of the intermediate pipe section 52, and the flow path cross-sectional shape is elliptical, which substantially coincides with the flow path cross-sectional shape of the downstream end of the upstream pipe section 51. The end face of the downstream end of the intermediate pipe section 52 is inclined with respect to the axis Q2 of the intermediate pipe section 52, and the flow path cross-sectional shape is elliptical.

[0028] The upstream end of the downstream pipe section 53 is connected to the upstream end of the intermediate pipe section 52 by welding. The end face of the upstream end of the downstream pipe section 53 is inclined with respect to the axis Q3 of the downstream pipe section 53, and the flow path cross-sectional shape is elliptical, substantially coinciding with the end face of the downstream end of the intermediate pipe section 52. The axis Q3 of the downstream pipe section 53 is inclined with respect to the axis Q2 of the intermediate pipe section 52. The axis Q1 of the upstream pipe section 51 and the axis Q3 of the downstream pipe section 53 are in directions that do not intersect each other. By making the axis Q1 of the upstream pipe section 51 and the axis Q3 of the downstream pipe section 53 not intersect each other, the ease of assembly of the joint piping 29 is improved. The downstream pipe section 53 is connected to the downstream end 44 of the first flexible hose 27. The downstream end of the downstream pipe section 53 is the downstream end 55 of the joint piping 29.

[0029] In this embodiment, the joint piping 29 is relatively long because the first flexible hose 27 and the second flexible hose 28 connected to the joint piping 29 are shortened as much as possible. The sum of the lengths of the non-flexible piping in the air piping group, i.e., the lengths of the discharge piping 25, the intercooler suction piping 26, and the joint piping 29, is greater than the sum of the lengths of the first flexible hose 27 and the second flexible hose 28. Since the joint piping 29 has multiple straight pipe sections, namely the upstream pipe section 51, the intermediate pipe section 52, and the downstream pipe section 53, the flow path of the joint piping 29 is shortened. Because the axes Q1, Q2, and Q3 corresponding to the upstream pipe section 51, the intermediate pipe section 52, and the downstream pipe section 53 are different from each other, the joint piping 29 is easily assembled to the first flexible hose 27 connected to the discharge piping 25 and the second flexible hose 28 connected to the intercooler suction piping 26.

[0030] Next, the assembly procedure for the piping structure 24 according to this embodiment will be described. As shown in Figures 2 and 3, the positions of the air compressor 13 and the intercooler 18 in the fuel cell system 10 are fixed. Therefore, the positions of the discharge pipe 25 of the air compressor 13 and the intercooler intake pipe 26 of the intercooler 18 are also fixed. In the piping assembly work, the worker first connects the first flexible hose 27 to the discharge pipe 25 and the second flexible hose 28 to the intercooler intake pipe 26. At this time, the first flexible hose 27 and the second flexible hose 28 may be temporarily connected.

[0031] Next, the worker inserts the downstream end 55 of the fitting pipe 29 into the upstream end 47 of the second flexible hose 28. At this time, as shown in Figure 6(a), the worker rotates the fitting pipe 29 around the axis Q3 to check the position of the upstream end 54 so that the upstream end 54 of the fitting pipe 29 does not interfere with the first flexible hose 27, and inserts it into the second flexible hose 28. This prevents the upstream end 54 of the fitting pipe 29 from interfering with the first flexible hose 27, making it easier to assemble the fitting pipe 29 to the second flexible hose 28.

[0032] Next, as shown in Figure 6(b), with the fitting pipe 29 inserted into the second flexible hose 28, the worker rotates the fitting pipe 29 around the axis Q3 so that the upstream end 54 approaches the downstream end 44 of the first flexible hose 27. Then, the worker positions the upstream end 54 of the fitting pipe 29 below the downstream end 44 of the first flexible hose 27, and while elastically deforming the first flexible hose 27 and the second flexible hose 28, inserts the upstream end 54 into the downstream end 44 as shown in Figure 6(c). Since the fitting pipe 29 is connected to the first flexible hose 27 by utilizing the elastic deformation of the first flexible hose 27 and the second flexible hose 28 after bringing the upstream end 54 close to the downstream end 44, the assembly work of the fitting pipe 29 to the first flexible hose 27 becomes easier. Finally, the worker attaches and secures the hose clamps 36 to the first flexible hose 27 and the second flexible hose 28, respectively. This completes the piping assembly work. Note that the assembly procedure for the piping structure 24 is not limited to the procedure described above.

[0033] When the fuel cell system 10 is operated, the air compressor 13 is also operated. Vibrations occur in the piping on the discharge side of the air compressor 13 due to the operation of the air compressor 13. In addition to the pulsation caused by the air compressor 13, the pulsation is amplified in response to the increase in the internal pressure of the fuel cell stack 11. However, the vibrations in the piping due to pulsation are effectively reduced by the first flexible hose 27, whose effective length L1 is shortened as much as possible.

[0034] The piping structure 24 of this embodiment provides the following effects. (1) The first flexible hose 27, which is the first vibration damping hose, is curved when connected to the discharge pipe 25, which is the upstream piping, and the sum of the lengths of the non-flexible pipes in the air piping group is greater than the length of the first flexible hose 27. Therefore, vibration of the piping due to the operation of the air compressor 13 can be reduced. In addition, by using a first flexible hose 27 that is curved and has an effective length L1 that is as short as possible, the ease of assembly of the air piping group including the first flexible hose 27 can be improved.

[0035] (2) The intermediate piping includes a fitting pipe 29 connected to the first flexible hose 27, and a flexible second flexible hose 28 connected to the fitting pipe 29 and the intercooler intake pipe 26, wherein the fitting pipe 29 is more rigid than the second flexible hose 28. The total length of the non-flexible pipes in the air piping group is greater than the total length of the first flexible hose 27 and the second flexible hose 28. By using the flexible second flexible hose 28, piping errors can be absorbed more easily, and the assembly of the air piping group including the first flexible hose 27 and the second flexible hose 28 can be further improved.

[0036] (3) The joint piping 29 has an upstream pipe section 51 connected to the first flexible hose 27, a downstream pipe section 53 connected to the second flexible hose 28, and an intermediate pipe section 52 between the upstream pipe section 51 and the downstream pipe section 53. The axial directions of the upstream pipe section 51 and the downstream pipe section 53 do not coincide with the axial direction of the intermediate pipe section 52. Therefore, it is easier to connect the joint piping 29 to one of the first flexible hose 27 and the second flexible hose 28 first, and then to the other of the first flexible hose 27 and the second flexible hose 28.

[0037] (4) The upstream pipe section 51, the downstream pipe section 53, and the intermediate pipe section 52 of the joint piping 29 are formed from straight pipes. This makes it easier to manufacture the joint piping 29 and reduces manufacturing costs compared to when it is made from curved pipes.

[0038] (5) Since the first flexible hose 27 is formed by a curved pipe, the cross-sectional area of ​​the flow path of the first flexible hose 27 does not decrease compared to the case in which a straight pipe is bent to form a curved pipe, and air pressure loss can be suppressed.

[0039] (Second embodiment) Next, a piping structure according to the second embodiment will be described. The piping structure of this embodiment differs from the first embodiment in that both the first flexible hose and the second flexible hose are curved pipes. In this embodiment, for the same components as in the first embodiment, the description of the first embodiment will be used by reference, and the same reference numerals will be used.

[0040] As shown in Figure 7, the piping structure 60 includes a plurality of air pipes (a group of air pipes) connecting the air compressor 13 and the intercooler 18. The group of air pipes includes a discharge pipe 61 as an upstream pipe, an intercooler suction pipe 26 as a downstream pipe, a first flexible hose 27, a second flexible hose 62 as a first vibration damping hose, and a joint pipe 63.

[0041] The discharge pipe 61 is a rigid, metal pipe connected to the discharge port 30 of the air compressor 13 and also to the first flexible hose 27. The discharge pipe 61 is installed furthest upstream in the air piping group. The discharge pipe 61 has a circular cross-section and is a combination of curved and straight sections. The shape of the discharge pipe 61 was formed considering the space constraints around the discharge pipe 25. The upstream end 64 of the discharge pipe 61 is fixed to the air compressor 13. The downstream end 65 of the discharge pipe 61 is inserted into the first flexible hose 27 and secured by a hose clamp 36. The position of the downstream end 65 is such that the first flexible hose 27 can be assembled by an operator.

[0042] The upstream end 42 of the intercooler intake pipe 26 is inserted into the second flexible hose 62 and secured by a hose clamp 36. The space between the downstream end 65 of the discharge pipe 61 and the upstream end 42 of the intercooler intake pipe 26 is space that allows an operator to assemble the first flexible hose 27, the second flexible hose 62, and the fitting pipe 63.

[0043] The second flexible hose 62 corresponds to a second vibration-damping hose for reducing vibrations in the piping group. The shape and material of the second flexible hose 62 in this embodiment are the same as those of the first flexible hose 27. The second flexible hose 62 in this embodiment, together with the first flexible hose 27 and the fitting piping 63, constitutes an intermediate piping connected to the upstream and downstream piping. The downstream end 66 of the second flexible hose 62 is connected to the upstream end 42 of the intercooler intake piping 26. The upstream end 67 of the second flexible hose 62 is connected to the fitting piping 29 and secured by a hose clamp 36. The total length of the non-flexible piping in the air piping group, i.e., the sum of the discharge piping 61, the intercooler intake piping 26, and the fitting piping 63, is greater than the sum of the lengths of the first flexible hose 27 and the second flexible hose 62.

[0044] The fitting pipe 63 is a rigid, metal pipe connected to the first flexible hose 27 and the second flexible hose 62. The fitting pipe 63 is a straight pipe with a circular flow path cross-sectional shape and is more rigid than the second flexible hose 62. The fitting pipe 63 has an upstream end 68 connected to the downstream end 44 of the first flexible hose 27 and a downstream end 69 connected to the upstream end 67 of the second flexible hose 62.

[0045] The piping structure 24 according to this embodiment provides effects equivalent to those of the first embodiment (1), (2), and (5). Furthermore, in this embodiment, the total length of the non-flexible pipes in the air piping group is greater than the total length of the first flexible hose 27 and the second flexible hose 62. Since the second flexible hose 62 is formed from the same curved pipe as the first flexible hose 27, vibration reduction by the second flexible hose 62 is possible in conjunction with vibration reduction by the first flexible hose 27.

[0046] (Third embodiment) Next, a piping structure according to the third embodiment will be described. In this embodiment, the first flexible hose is a curved pipe and the second flexible hose is a straight pipe, but the discharge piping is longer and the joint piping is shortened, which is different from the first embodiment. In this embodiment, for the same configuration as in the first embodiment, the description of the first embodiment will be used by reference and the same reference numerals will be used.

[0047] As shown in Figure 8, the piping structure 70 includes a plurality of air pipes (a group of air pipes) connecting the air compressor 13 and the intercooler 18. The group of air pipes includes a discharge pipe 71 as an upstream pipe, an intercooler suction pipe 26 as a downstream pipe, a first flexible hose 72, a second flexible hose 28, and a joint pipe 73.

[0048] The discharge pipe 71 is a rigid, metal pipe connected to the discharge port 30 of the air compressor 13 and also to the first flexible hose 27. The discharge pipe 71 is installed furthest upstream in the air piping group and corresponds to the upstream piping installed on the air compressor 13 side. The discharge pipe 71 has a circular flow path cross-section and is a pipe that combines multiple curved pipe sections 74, 75 and straight pipe sections 76, 77 connecting the curved pipe sections 31, 32. In other words, the discharge pipe 71 is made as long as possible. The shape of the discharge pipe 71 is formed considering the space constraints around the discharge pipe 71. The upstream end 78 of the discharge pipe 71 is fixed to the air compressor 13. The downstream end 79 of the discharge pipe 71 is inserted into the first flexible hose 72 and fixed by a hose clamp 36. The position of the downstream end 35 is such that the first flexible hose 72 can be assembled by an operator.

[0049] The first flexible hose 72 corresponds to the first vibration-damping hose for reducing vibration in the piping group. The first flexible hose 72 is a curved pipe that has been shortened as much as possible and is basically the same as the first flexible hose 27, but the radius of curvature and effective length are slightly different. The material of the first flexible hose 72 is the same as that of the first flexible hose 27. In this embodiment, the first flexible hose 72, together with the fitting pipe 73 and the second flexible hose 28, constitutes an intermediate pipe connected to the upstream and downstream pipes. The upstream end 81 of the first flexible hose 72 is connected to the downstream end 79 of the discharge pipe 71. The downstream end 82 of the first flexible hose 27 is connected to the fitting pipe 73 and secured by a hose clamp 36.

[0050] The fitting pipe 73 is a rigid, metal pipe connected to the first flexible hose 72 and the second flexible hose 28. The fitting pipe 73 is a straight pipe with a circular flow path cross-section. The fitting pipe 73 has an upstream end 83 connected to the downstream end 82 of the first flexible hose 72, and a downstream end 84 connected to the upstream end 46 of the second flexible hose 28. The fitting pipe 73 is shortened as much as possible by making the discharge pipe 71 as long as possible. The total length of the non-flexible pipes in the air piping group, i.e., the sum of the discharge pipe 71, the intercooler suction pipe 26, and the fitting pipe 73, is greater than the sum of the lengths of the first flexible hose 72 and the second flexible hose 28.

[0051] The piping structure 70 according to this embodiment provides the same effects as those of the first embodiment (1), (2), and (5). Furthermore, in this embodiment, the discharge piping 71 is made as long as possible, thereby shortening the joint piping 73. As a result, the first flexible hose 72 and the second flexible hose 28 are located closer together, further improving the ease of assembly of the air piping group including the first flexible hose 72.

[0052] (Fourth embodiment) Next, a piping structure according to the fourth embodiment will be described. The piping structure of this embodiment differs from the first embodiment in that only the first flexible hose is used, and fittings and the second flexible hose are not used. In this embodiment, for the same configuration as in the first embodiment, the description of the first embodiment will be used by reference, and the same reference numerals will be used.

[0053] As shown in Figure 9, the piping structure 90 has an intercooler suction pipe 91. The intercooler suction pipe 91 is a pipe that integrates the joint pipe 29 and the intercooler suction pipe 26 of the first embodiment. The downstream end 92 of the intercooler suction pipe 91 is fixed to the intercooler 18 by bolts or welding. The upstream end 93 of the intercooler suction pipe 91 is inserted into the downstream end 44 of the first flexible hose 27 and fixed by a hose clamp 36. The length of the non-flexible pipes in the air piping group, i.e., the sum of the discharge pipe 25 and the intercooler suction pipe 91, is greater than the length of the first flexible hose 27.

[0054] The piping structure 90 according to this embodiment provides the same effects as the effects (1) and (5) of the first embodiment. Furthermore, according to this embodiment, since the intercooler intake piping 91 is a pipe that integrates the joint piping 29 and the intercooler intake piping 26 of the first embodiment, the number of parts can be reduced, and the manufacturing cost of the piping structure 90 can be suppressed.

[0055] The present invention is not limited to the embodiments described above, and various modifications are possible within the scope of the invention. For example, the following modifications may be made.

[0056] ○ In the first embodiment described above, the joint piping is composed of a combination of multiple straight pipes, but this is not limited to this. The joint piping may be composed of, for example, a combination of multiple curved pipes and straight pipes. ○ In the embodiments described above, the joint piping having an intermediate pipe is lightweight and therefore supported by the first vibration-damping hose and the second vibration-damping hose, but this is not limited to this. For example, if the joint piping is heavy, the joint members may be supported by members surrounding the joint piping. ○ In the embodiments described above, an air compressor was used as an example of an air supply device, but the invention is not limited to this. The air supply device may be, for example, an air pump, and the type and model of the pump are not limited. ○ In the embodiments described above, the piping structure of a fuel cell system mounted on a forklift as an industrial vehicle has been explained, but the system is not limited thereto. The fuel cell system may also be a stationary fuel cell system installed on the ground or on a structure. [Explanation of Symbols]

[0057] 10 Fuel cell systems 13. Air compressor (air supply machine) 15 Air supply path 16 Air intake 18 Intercooler 19. Hydrogen gas circulation path 20 Exhaust passage 21 Gas-liquid separator 22 Diluter 24, 60, 70, 90 piping structure 25, 61, 71 Discharge piping 26, 91 Intercooler intake piping 27, 72 First flexible hose (first vibration damping hose) 28, 62 Second Flexible Hose 29, 63, 73 Piping Fittings 51 Upstream pipe section 52 Intermediate pipe section 53 Downstream pipe section L1, L2 Effective length P1, P2 axis center Q1, Q2, Q3 axis center R1 radius of curvature φ1, φ2 Pipe inner diameter

Claims

1. A fuel cell stack that generates electrical energy by reacting hydrogen gas and oxygen, An air supply unit that supplies air to the fuel cell stack, In a fuel cell system comprising the air supply unit and a group of air pipes connecting the fuel cell stack, The aforementioned group of air piping is The upstream piping installed on the air supply unit side, The downstream piping installed on the fuel cell stack side, It has intermediate piping connected to the upstream piping and the downstream piping, The upstream and downstream piping are non-flexible pipes that have greater rigidity than the intermediate piping. The intermediate piping has a flexible first vibration-damping hose connected to the upstream piping. The first vibration damping hose is curved when connected to the upstream piping. A piping structure in a fuel cell system characterized in that the total length of the non-flexible pipes in the group of air pipes is greater than the length of the first vibration-damping hose.

2. The aforementioned intermediate piping is The joint piping connected to the first vibration damping hose, It comprises a flexible second vibration-damping hose connected to the aforementioned joint piping and the aforementioned downstream piping, The aforementioned joint piping has greater rigidity than the second vibration-damping hose. The piping structure in the fuel cell system according to claim 1, characterized in that the sum of the lengths of the non-flexible pipes in the group of air pipes is greater than the sum of the lengths of the first vibration-damping hose and the second vibration-damping hose.

3. The aforementioned joint piping is, The upstream pipe section connected to the first vibration damping hose, The downstream pipe section connected to the second vibration damping hose, It has an intermediate pipe section between the upstream pipe section and the downstream pipe section, The piping structure in a fuel cell system according to claim 2, characterized in that the axial direction of at least one of the upstream pipe section and the downstream pipe section is inconsistent with the axial direction of the intermediate pipe section.

4. The piping structure in a fuel cell system according to claim 3, characterized in that the upstream pipe section, the downstream pipe section, and the intermediate pipe section are each formed by straight pipes.

5. The piping structure in a fuel cell system according to claim 1 or 2, characterized in that the first vibration-damping hose is formed by a curved pipe.

6. The piping structure in a fuel cell system according to claim 2 or 3, characterized in that the second vibration-damping hose is formed by a curved pipe.

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