Tank Retaining Structure

Abstract

To provide a tank holding structure which can prevent a cushioning material from getting out of an engagement hole in a frame member.SOLUTION: A tank holding structure 1 comprises: a frame member 10 which has a recess which supports a cylindrical tank 2 and of which side walls 12, 13 are provided with engagement holes 16, 17; a tank band 20 which is so located as to face the frame member 10, and is so formed as to be capable of pressing the tank 2 to the frame member 10 side; an energization member 30 which applies a pressing force to the tank 2 to the tank band 20; and a cushioning material 40 which is located between the tank 2 and the frame member 10, and are engaged with the engagement holes 16, 17.A lubricating member 50 is interposed between the tank 2 and the cushioning material 40.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a tank holding structure. [Background technology]

[0002] When mounting a gas tank on a vehicle, the tank is often held by using a holding member and a cushioning material from the viewpoints of robustness and quietness. For example, Patent Document 1 discloses a tank holding structure that includes a holding member made of two fixing plates that hold both ends of the tank and a connecting member that connects these fixing plates, and a cushioning material that is interposed between the holding member and the end of the tank. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2005-225477 A Summary of the Invention [Problem to be solved by the invention]

[0004] Recently, in response to the increase in the length of tanks due to the increase in the amount of stored gas, a structure has been adopted in which the end of the tank to which the main stop valve is attached is held by a neck mount system, while a frame member and a tank band are used to hold the tank. In order to prevent abnormal noise and vibrations that occur when the main stop valve is opened, a cushioning material is placed between the frame member and the tank. The cushioning material has an engagement claw that engages with an engagement hole provided in the frame member, and is fixed to the frame member by engaging the engagement claw with the engagement hole.

[0005] However, when the tank is filled with gas, it expands and stretches in its axial direction, causing the cushioning to shift in position relative to the frame member. If this positional deviation becomes too great, the cushioning may buckle and come out of the engagement hole in the frame member.

[0006] The present invention has been made to solve such technical problems, and has an object to provide a tank holding structure that can prevent the cushion material from slipping out of the engagement hole of the frame member. [Means for solving the problem]

[0007] The tank holding structure of the present invention is a tank holding structure for holding a cylindrical tank, comprising: a frame member having a recess for supporting the tank and an engagement hole provided in a side wall of the recess; a tank band arranged opposite the frame member and formed so as to be able to press the tank towards the frame member; a biasing member that imparts a pressing force against the tank to the tank band; and a cushioning material arranged between the tank and the frame member and engaged with the engagement hole, wherein a slippery member is interposed between the tank and the cushioning material.

[0008] In the tank holding structure according to the present invention, since a slippery member is interposed between the tank and the cushioning material, the slippery member can be used to reduce the frictional force generated between the tank and the cushioning material, thereby preventing the cushioning material from slipping out of the engagement hole of the frame member.

[0009] In the tank holding structure according to the present invention, the cushion material has a block-shaped cushion material main body and a pair of engaging claws that protrude from the cushion material main body and are engageable with the engaging holes, and when the direction along the axial direction of the tank is defined as the length direction of the cushion material, the direction along the circumferential direction of the tank is defined as the width direction of the cushion material, and the direction along the radial direction of the tank is defined as the thickness direction of the cushion material, the thickness of the cushion material main body between the engaging claws is h, the width of the cushion material main body between the engaging claws is b, the length of the cushion material between the engaging claws is l, the longitudinal elastic modulus of the cushion material is E, the coefficient of friction between the tank and the cushion material is μ, the constant of the circumference of the tank is π, and the maximum compressive force acting on the cushion material from the tank when the tank is full is N. maxThe maximum friction force F generated between the tank and the cushioning material is fmax F fmax = μN max When the sliding member is determined by the above formula, F fmax <(h 3 bEπ 2 / 6l 2 ) is preferably set so as to satisfy the relationship of . In this way, the frictional force generated between the tank and the cushioning material can be reduced, and therefore the cushioning material can be prevented from slipping out of the engagement hole of the frame member.

[0010] In the tank holding device according to the present invention, the slipping member is preferably a sheet made of polytetrafluoroethylene or polyethylene terephthalate. Polytetrafluoroethylene or polyethylene terephthalate is a material having a relatively low coefficient of friction, and therefore can reduce the frictional force generated between the tank and the cushioning material. This makes it possible to prevent the cushioning material from slipping out of the engagement hole of the frame member.

[0011] In the tank holding structure according to the present invention, the slipping member is preferably a rubber layer formed on the surface of the cushioning material and containing resin particles or fibers with a low friction coefficient, which can reduce the frictional force generated between the tank and the cushioning material, thereby preventing the cushioning material from slipping out of the engagement hole of the frame member.

[0012] In the tank holding structure according to the present invention, the slipping member is preferably a layer formed by applying a densification treatment or a high hardness treatment to the surface of the cushioning material. In this way, the frictional force generated between the tank and the cushioning material can be reduced, and the cushioning material can be prevented from slipping out of the engagement hole of the frame member.

[0013] In the tank holding structure according to the present invention, the slipping member is preferably a fiber-reinforced resin layer formed by winding resin fibers with a low friction coefficient impregnated with a matrix resin around the outer circumferential surface of the tank, thereby reducing the frictional force generated between the tank and the cushioning material, and preventing the cushioning material from slipping out of the engagement hole of the frame member.

[0014] Furthermore, in the tank holding structure according to the present invention, it is preferable that the slipping member is a roller disposed between the tank and the cushion material and rotatable along the axial direction of the tank. In this way, the slipping member rotates following the expansion of the tank, thereby reducing the frictional force between the tank and the cushion material, and preventing the cushion material from slipping out of the engagement hole of the frame member. Effect of the Invention

[0015] According to the present invention, the cushion material can be prevented from slipping out of the engagement hole of the frame member. [Brief description of the drawings]

[0016] [Figure 1] 1 is a front view showing a tank holding structure according to a first embodiment. [Diagram 2] FIG. 2 is a cross-sectional view taken along line AA in FIG. [Diagram 3] FIG. 3 is a cross-sectional view taken along line BB in FIG. [Figure 4] 1 is a cross-sectional view for explaining a problem with a conventional tank holding structure. [Diagram 5] FIG. 4 is a cross-sectional view showing a cushioning material. [Figure 6] FIG. 4 is a cross-sectional view showing a cushioning material. [Figure 7] FIG. 6 is a partial cross-sectional view showing a tank holding structure according to a second embodiment. [Figure 8] FIG. 11 is a partial cross-sectional view showing a tank holding structure according to a third embodiment. [Figure 9]FIG. 11 is a partial cross-sectional view showing a tank holding structure according to a fourth embodiment. [Figure 10] FIG. 13 is a front view showing a tank holding structure according to a fifth embodiment. [Figure 11] FIG. 11 is a cross-sectional view taken along line DD in FIG. [Figure 12] FIG. 13 is a partial cross-sectional view showing a tank holding structure according to a sixth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Hereinafter, an embodiment of a tank holding structure according to the present invention will be described with reference to the drawings. In the description of the drawings, the same elements are given the same reference numerals, and duplicated description will be omitted. In the following description, the up, down, left, and right directions are expedient directions corresponding to the state shown in the drawings, and do not limit the posture or arrangement of the tank holding structure.

[0018] [First embodiment] Fig. 1 is a front view showing a tank holding structure according to a first embodiment, Fig. 2 is a cross-sectional view taken along line AA in Fig. 1, and Fig. 3 is a cross-sectional view taken along line BB in Fig. 2. The tank holding structure 1 of this embodiment is for holding a tank 2 mounted on, for example, a fuel cell vehicle (not shown), and for fixing the tank 2 to the body of the fuel cell vehicle.

[0019] The tank 2 is, for example, a hydrogen tank for storing high-pressure hydrogen, and is a cylindrical container with rounded left and right ends in a dome shape. The tank 2 includes a liner 3 having a storage space for storing hydrogen gas, a reinforcing layer 4 provided in close contact with the outer circumferential surface of the liner 3, and a nozzle 5 attached to both left and right ends of the liner 3.

[0020] The liner 3 is formed of a resin material having gas barrier properties against, for example, hydrogen gas. Examples of the resin material include thermoplastic resins such as polyamide, polyethylene, ethylene-vinyl alcohol copolymer resin (EVOH), and polyester, and thermosetting resins such as epoxy. The reinforcing layer 4 is formed by winding fibers impregnated with a thermosetting resin multiple times around the outer circumferential surface of the liner 3. The fibers are formed of a composite material in which, for example, carbon fibers, glass fibers, or aramid fibers are inserted into plastic to improve strength.

[0021] The nozzle 5 is made of a metal material such as aluminum. As shown in Fig. 1, the nozzles 5 are attached to both the left and right ends of the liner 3, and a main stop valve 6 is attached to one of them. When the main stop valve 6 opens, the high-pressure hydrogen stored in the tank 2 is reduced in pressure by a pressure reducing valve (not shown) and supplied to a fuel cell stack (not shown).

[0022] A tank 2 having such a structure is held by a neck-mounted type holding structure 7 at a nozzle 5 to which a main stop valve 6 is attached, and is held by a tank holding structure 1 in the vicinity of the nozzle 5 to which the main stop valve 6 is not attached.

[0023] The tank holding structure 1 comprises a frame member 10 that supports the tank 2, a tank band 20 that is arranged opposite the frame member 10 and presses the tank 2 toward the frame member 10, a biasing member 30 that applies a pressing force to the tank band 20 against the tank 2, and a cushioning material 40 that is arranged between the tank 2 and the frame member 10.

[0024] The frame member 10 is a member that constitutes, for example, a part of the body of a fuel cell vehicle, and is made of a metal material. As shown in Fig. 2, the frame member 10 is disposed, for example, below the tank 2 so as to support the tank 2 from below, and has a hat-shaped cross section that opens upward.

[0025] Specifically, the frame member 10 has a bottom plate portion 11, a pair of side walls 12, 13 extending obliquely upward from both ends of the bottom plate portion 11, and a pair of flange portions 14, 15 bent from the upper ends of the side walls 12, 13 to be parallel to the bottom plate portion 11. An engagement hole 16 is provided in the side wall 12, and an engagement hole 17 is provided in the side wall 13. The side wall 12, the bottom plate portion 11 and the side wall 13 form a recess for supporting the tank 2. The frame member 10 having such a structure is formed, for example, by drilling holes at predetermined positions in a metal plate and then pressing it into a hat-shaped cross section.

[0026] The tank band 20 is formed in a band shape from, for example, stainless steel, which has excellent strength and elastic deformation, and is disposed on the opposite side of the frame member 10 so as to press the upper side of the tank 2. The tank band 20 has a base end 21 fixed to the flange portion 14 of the frame member 10, a curved portion 22 extending from the base end 21 and curved to follow the outer peripheral shape of the tank 2, and a biasing member connecting portion 23 having one end fixed to the curved portion 22 and the other end connected to the biasing member 30 and having an L-shaped cross section. The base end 21 of the tank band 20 is fixed to the flange portion 14 of the frame member 10 by a bolt 8. The biasing member connecting portion 23 has a through hole 24 formed therein. The material used for the tank band 20 may be other metal materials having excellent strength and elastic deformation, in addition to stainless steel.

[0027] The urging member 30 includes a bolt 31, a receiving member 32, a coil spring 33, and a nut 34. The bolt 31 is inserted through a through hole 24 formed in the urging member connecting portion 23 of the tank band 20, screwed into a screw hole formed in the flange portion 15 of the frame member 10, and further screwed into the nut 34. The receiving member 32 is disposed between the head 35 of the bolt 31 and the urging member connecting portion 23. The inner diameter of the receiving member 32 is smaller than the outer diameter of the head 35 of the bolt 31. In this way, the receiving member 32 can be prevented from slipping out of the bolt 31. The diameter of the through hole 24 formed in the urging member connecting portion 23 of the tank band 20 is set to a degree that allows the urging member connecting portion 23 to slide in the axial direction of the bolt 31.

[0028] The coil spring 33, with the bolt 31 inserted therein, is disposed between the receiving member 32 and the biasing member connecting portion 23 of the tank band 20. The coil spring 33 biases the biasing member connecting portion 23 toward the frame member 10. This generates a pressing force in the tank band 20 that presses the tank 2 toward the frame member 10.

[0029] The cushioning material 40 is a member for preventing abnormal noise, suppressing vibration, and absorbing shock. More specifically, when the main stop valve 6 is opened, the high-pressure hydrogen in the tank 2 flows through the flow path in the main stop valve 6 all at once, generating abnormal noise and vibration accompanied by shock waves. If the abnormal noise and vibration are transmitted to the vehicle body via the tank 2 and the frame member 10, a loud noise may be generated. In order to prevent abnormal noise and suppress vibration, it is necessary to place the cushioning material 40 between the tank 2 and the frame member 10. In addition, when a fuel cell vehicle travels on a rough road, the tank 2 may be subjected to a large impact. In order to protect the tank 2 from such impact, it is also required to place the cushioning material 40 between the tank 2 and the frame member 10.

[0030] The cushion material 40 has a block-shaped cushion material main body 41 and a pair of engagement claws 42 that protrude from the cushion material main body 41 and are engageable with the engagement holes 16, 17 of the frame member 10. The cushion material 40 is fixed to the frame member 10 by the engagement of the engagement claws 42 with the engagement holes 16, 17. The cushion material 40 is preferably made of a vibration-resistant material such as rubber or elastomer. In this embodiment, the cushion material 40 is made of rubber.

[0031] Here, the circumstances that led to the present invention will be described.

[0032] When hydrogen gas is filled into the tank, the tank expands in both the axial and radial directions. Of the axial and radial directions, the amount of expansion in the axial direction is the largest. Due to this axial expansion, the tank 2 extends along the axial direction as shown in FIG. 4 (in FIG. 4, it extends to the left). Furthermore, in the case of fuel cell vehicles, it is required to ensure a cruising range of 800 km or more, which is the same as that of internal combustion engine vehicles. In order to increase the amount of hydrogen gas stored, for example, there is a method of lengthening the tank 2, so to speak, making it longer. However, as the length of the tank 2 increases, the amount of expansion of the tank 2 due to gas filling also increases, and the tank 2 also extends more. For example, when a 1.5 m long tank 2 is filled to the brim with hydrogen gas, the tank 2 extends approximately 5 mm.

[0033] In addition, as the tank 2 expands, a positional shift occurs between the tank 2 and the cushion material 40, so that a frictional force F f The friction force F f is calculated by the following formula (1).

[0034] F f =μN (1) In formula (1), μ is the coefficient of friction between the tank 2 and the cushioning material 40, and N is the compressive force that the tank 2 exerts on the cushioning material 40. The compressive force N that the tank 2 exerts on the cushioning material 40 depends mainly on the pressing force from the tank band 20 to the tank 2, the weight of the tank 2, the weight of the hydrogen gas filled in, and the amount of radial expansion of the tank 2. The compressive force N that the tank exerts on the cushioning material is largest (maximum compressive force N) when the tank 2 is full (i.e., when the tank 2 is most expanded). max At that time, the friction force F between the tank 2 and the cushion material 40 is f also becomes maximum (maximum friction force F fmax becomes).

[0035] In addition, as the positional deviation occurs between the tank 2 and the cushion material 40, a positional deviation also occurs between the frame member 10 and the cushion material 40. Then, the friction force F fIf this becomes large, there is a possibility that the cushion material body 41 will buckle and the engaging claws 42 will come out of the engaging holes 16, 17 provided in the frame member 10, as shown in FIG.

[0036] Therefore, as a result of intensive research, the inventors of the present application have found that by interposing a slippery member 50 between the tank 2 and the cushioning material 40, the slipperiness between the tank 2 and the cushioning material 40 is improved, and the frictional force F generated between the tank 2 and the cushioning material 40 is reduced. f It has been found that this reduces the amount of pressure applied to the cushion material 40, thereby preventing the cushion material 40 from slipping out of the engagement holes 16, 17 of the frame member 10, and has led to the completion of the present invention.

[0037] Therefore, in this embodiment, the slippery member 50 is interposed between the tank 2 and the cushion material 40. The slippery member 50 is set so as to satisfy the following relational expression.

[0038] That is, assuming that the direction along the axial direction of the tank 2 is the length direction of the cushion material 40, the direction along the circumferential direction of the tank 2 is the width direction of the cushion material 40, and the direction along the radial direction of the tank 2 is the thickness direction of the cushion material 40, as shown in FIG. 5, the thickness of a central portion 43 between the engaging claws 42, 42 of the cushion material main body 41 is h, the width of the central portion 43 is b, the length of the central portion 43 is l, the modulus of longitudinal elasticity of the cushion material 40 is E, the coefficient of friction between the tank 2 and the cushion material 40 is μ, the value of pi is π, and the maximum compressive force acting on the cushion material 40 from the tank 2 when the tank 2 is full is N max The maximum friction force F generated between the tank 2 and the cushion material 40 is fmax F fmax = μN max When the relationship between the sliding member 50 and the sliding surface is determined by the above formula, the sliding member 50 is set to satisfy the relationship of the following formula (2). In Fig. 5, the cross-sectional view on the left side is a cross-sectional view taken along the line BB in Fig. 2, and the cross-sectional view on the right side is a cross-sectional view taken along the line CC in the cross-sectional view on the left side.

[0039] F fmax <(h 3 bEπ 2 / 6l 2) (2)

[0040] Therefore, in order to satisfy the relationship of formula (2), for example, the friction force F generated between the tank 2 and the cushioning material 40 is adjusted by selecting the material or adjusting the configuration of the slippery member 50 interposed between the tank 2 and the cushioning material 40. f By reducing the amount of the cushion material 40, it is possible to prevent the cushion material 40 from slipping out of the engagement holes 16, 17 of the frame member 10.

[0041] For this reason, the sliding member 50 of the present embodiment has a friction force F f The slippery member 50 is made of a material having a low coefficient of friction to reduce the friction. More specifically, the slippery member 50 is made of polytetrafluoroethylene (PTFE) or polyethylene terephthalate (PET) having a relatively low coefficient of friction, and is formed in a sheet shape having the same size as the area of ​​the cushion material 40 that comes into contact with the tank 2, for example.

[0042] In the tank holding structure 1 configured in this manner, the slippery member 50 is interposed between the tank 2 and the cushioning material 40, so that the frictional force F generated between the tank 2 and the cushioning material 40 when the tank 2 is extended is reduced by using the slippery member 50. f As a result, buckling of the cushion material main body 41 can be suppressed, and the cushion material 40 can be prevented from slipping out of the engagement holes 16, 17 of the frame member 10.

[0043] The slipping member 50 of the present embodiment is not limited to being made of the above-mentioned polytetrafluoroethylene (PTFE) or polyethylene terephthalate (PET), and may be made of other materials having a low coefficient of friction.

[0044] Based on the above formula (2), the friction force F between the tank 2 and the cushion material 40 is fBy selecting a material with a low friction coefficient that can reduce this, and by increasing the thickness h of the central portion 43 (see Figure 6), or by increasing the width b of the central portion 43, or by decreasing the length l of the central portion 43, the cushioning material 40 can be prevented from slipping out of the engagement holes 16, 17 of the frame member 10.

[0045] [Second embodiment] The tank holding structure 1 of the second embodiment differs from that of the first embodiment in the configuration of the sliding member, and only this difference will be described below.

[0046] 7, the slipping member 51 is a part of the cushioning material 40, and is a rubber layer formed on the surface of the cushioning material 40 and containing resin particles or fibers with a low friction coefficient. Examples of resin particles with a low friction coefficient include high density polyethylene (HDPE) resin particles. On the other hand, examples of fibers with a low friction coefficient include polyester, polyamide, and polyolefin fibers.

[0047] According to the tank holding structure 1 including such a slipping member 51, similarly to the above-described first embodiment, it is possible to reduce the frictional force generated between the tank 2 and the cushion material 40, and to prevent the cushion material 40 from slipping out of the engagement holes 16, 17 of the frame member 10. Note that in this embodiment, the entire cushion material 40 may be formed of high density polyethylene (HDPE) resin or the like.

[0048] [Third embodiment] The tank holding structure 1 of the third embodiment differs from that of the first embodiment in the configuration of the sliding member, and only this difference will be described below.

[0049] Specifically, as shown in Fig. 8, the slipping member 52 is a part of the cushion material 40, and is a layer formed by performing a densification treatment on the surface of the cushion material 40. In other words, the slipping member 52 is the surface of the cushion material 40 that comes into contact with the tank 2, and is a high-density layer. The densification treatment increases the density of the surface of the cushion material 40, for example, by increasing the carbon ratio and the ratio of an inorganic filler such as silica.

[0050] According to the tank holding structure 1 equipped with such a sliding member 52, as in the first embodiment described above, the frictional force generated between the tank 2 and the cushion material 40 can be reduced, and the cushion material 40 can be prevented from slipping out of the engagement holes 16, 17 of the frame member 10.

[0051] [Fourth embodiment] The tank holding structure 1 of the fourth embodiment differs from that of the first embodiment in the configuration of the sliding member, and only this difference will be described below.

[0052] 9, the slipping member 53 is a part of the cushion material 40, and is a layer formed by performing a high-hardness treatment on the surface of the cushion material 40. That is, the slipping member 53 is the surface of the cushion material 40 that comes into contact with the tank 2, and is a high-hardness layer. The high-hardness treatment increases the hardness of the surface of the cushion material 40, for example, by increasing the crosslink density or adding a polyolefin resin or a phenol resin.

[0053] According to the tank holding structure 1 equipped with such a sliding member 53, as in the first embodiment described above, the frictional force generated between the tank 2 and the cushion material 40 can be reduced, and the cushion material 40 can be prevented from slipping out of the engagement holes 16, 17 of the frame member 10.

[0054] [Fifth embodiment] The tank holding structure 1 of the fifth embodiment differs from that of the first embodiment in the configuration of the sliding member, and only this difference will be described below.

[0055] 10 and 11, the slipping member 54 is a fiber-reinforced resin layer formed by winding resin fibers with a low friction coefficient impregnated with a matrix resin around the outer circumferential surface of the tank 2. Specifically, the slipping member 54 is formed by winding resin fibers with a low friction coefficient, such as high-strength polyethylene impregnated with a matrix resin, such as epoxy, only around the outer circumferential surface of the tank 2 corresponding to the portion that comes into contact with the cushioning material 40 of the tank 2.

[0056] According to the tank holding structure 1 equipped with such a sliding member 54, as in the first embodiment described above, the frictional force generated between the tank 2 and the cushion material 40 can be reduced, and the cushion material 40 can be prevented from slipping out of the engagement holes 16, 17 of the frame member 10.

[0057] [Sixth embodiment] The tank holding structure 1 of the sixth embodiment differs from that of the first embodiment in the configuration of the sliding member, and only this difference will be described below.

[0058] 12, the slippery member 55 is disposed between the tank 2 and the cushion material 40, and is a roller that is rotatable along the axial direction of the tank 2. The material of the slippery member 55 is, for example, rubber or resin. In this case, protrusions 44 are formed on both ends of the upper surface of the cushion material main body 41 to prevent the slippery member 55 from coming off.

[0059] According to the tank holding structure 1 equipped with such a sliding member 55, the sliding member 55 rotates in response to the expansion of the tank 2, thereby reducing the frictional force between the tank 2 and the cushion material 40, thereby preventing the cushion material 40 from slipping out of the engagement holes 16, 17 of the frame member 10.

[0060] Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments, and various design modifications can be made without departing from the spirit of the present invention as described in the claims. [Explanation of symbols]

[0061] 1: tank holding structure, 2: tank, 3: liner, 4: reinforcing layer, 5: nozzle, 6: main stop valve, 7: neck-mounted holding structure, 8: bolt, 10: frame member, 11: bottom plate portion, 12, 13: side wall, 14, 15: flange portion, 16, 17: engagement hole, 20: tank band, 21: base end portion, 22: curved portion, 23: biasing member connecting portion, 24: through hole, 30: biasing member, 31: bolt, 32: receiving member, 33: coil spring, 34: nut, 35: head portion, 40: cushioning material, 41: cushioning material main body, 42: engagement claw, 43: center portion, 44: protrusion portion, 50 to 55: slippery member

Claims

1. A tank holding structure for holding a cylindrical tank, comprising: a frame member having a recess for supporting the tank, the frame member having an engagement hole in a side wall of the recess; a tank band disposed opposite the frame member and configured to be able to press the tank toward the frame member; a biasing member that applies a pressing force against the tank to the tank band; a cushioning material disposed between the tank and the frame member and engaged with the engagement hole; Equipped with A tank holding structure, characterized in that a slippery member is interposed between the tank and the cushion material.

2. The cushion material has a block-shaped cushion material body and a pair of engagement claws protruding from the cushion material body and capable of engaging with the engagement holes, When the direction along the axial direction of the tank is defined as the length direction of the cushion material, the direction along the circumferential direction of the tank is defined as the width direction of the cushion material, and the direction along the radial direction of the tank is defined as the thickness direction of the cushion material, The thickness of the portion of the cushion material body between the engaging claws is h, the width of the portion of the cushion material body between the engaging claws is b, the length of the portion of the cushion material between the engaging claws is l, the longitudinal elastic modulus of the cushion material is E, the coefficient of friction between the tank and the slipping member is μ, the constant of the circumference of the tank is π, and the maximum compressive force acting on the cushion material from the tank via the slipping member when the tank is full is N ｍａｘ The maximum friction force F generated between the tank and the cushion material with the sliding member interposed therebetween is ｆｍａｘ F ｆｍａｘ = μ N ｍａｘ When requested by The slippery member is F ｆｍａｘ <(h ３ bEπ ２ / 6l ２ 2. The tank holding structure according to claim 1, wherein the relationship is set to satisfy:

3. 3. The tank holding structure according to claim 1, wherein the slipping member is a sheet made of polytetrafluoroethylene or polyethylene terephthalate.

4. 3. The tank holding structure according to claim 1, wherein the slipping member is a rubber layer formed on a surface of the cushioning material and containing resin particles having a low friction coefficient or fibers having a low friction coefficient.

5. 3. The tank holding structure according to claim 1, wherein the slipping member is a layer formed by subjecting a surface of the cushioning material to a densification treatment or a hardness treatment.

6. 3. The tank holding structure according to claim 1, wherein the slipping member is a fiber-reinforced resin layer formed by winding resin fibers having a low friction coefficient and impregnated with a matrix resin around the outer circumferential surface of the tank.

7. 3. The tank holding structure according to claim 1, wherein the slipping member is a roller disposed between the tank and the cushion material and rotatable along the axial direction of the tank.

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