Fuel tank

Abstract

The present invention relates to a fuel tank (10), comprising: a steel lower plate (12) and a steel upper plate (11); and at least one steel support (100), which is arranged in an internal space (V) formed by the lower plate (12) and the upper plate (11) facing each other, and is fixed to the upper plate (11) in a state where a first end is fixed to the lower plate (12) and a second end is arranged in a hole formed in the upper plate (11).

Description

Technical Field

[0001] The present invention relates to a fuel tank, and more particularly to improving the pressure resistance and weight reduction of a steel fuel tank.

[0002] This application claims priority based on Japanese Patent Application No. 2019-109355 filed in Japan on June 12, 2019, the contents of which are incorporated herein by reference. Background Art

[0003] Automobile fuel tanks have long been made of steel, but in recent years, resin tanks have become more common. The reason is that multi-layered resin tanks have been developed as a measure to prevent fuel permeation, and resins are advantageous in terms of weight reduction due to the difference in specific gravity of the raw materials.

[0004] As one of the technologies that can reduce the weight of the resin box, for example, Patent Document 1 discloses a technology in which protrusions formed on the upper and lower surfaces of opposing resin boxes and protruding inward are welded to each other to serve as support columns.

[0005] The fuel tank is installed at the bottom of the vehicle body, close to the road surface. Therefore, especially in summer, the fuel tank and the fuel are heated due to the reflection from the road surface, and the fuel temperature sometimes rises to more than 50°C. It is conceivable that this softens the resin, and the resin bends due to the weight of the fuel. Furthermore, the deflection increases due to the increase in the pressure of the fuel vapor generated by the temperature increase. The deflection can be reduced by providing a support, and the deformation of the fuel tank can be suppressed.

[0006] In recent years, due to the popularity of HV (Hybrid Vehicle) and PHV (Plug-in Hybrid Vehicle), the engine operation time tends to be shorter, and the gasoline vapor generated inside the fuel tank is not cleared into the engine, causing the internal pressure to increase. Therefore, the fuel tank is made more pressure-resistant, and the rigidity of the resin tank is improved by adding more pillars inside than before. In steel tanks, this is dealt with by increasing the plate thickness, but increasing the plate thickness will increase the weight of the fuel tank and is also pointed out to affect the vehicle's fuel consumption. In HV and PHV, batteries and a housing to accommodate the batteries are required, and the overall weight of the vehicle increases. In view of the above situation, the call for pressure-resistant and lightweight fuel tanks is stronger than before.

[0007] Therefore, Patent Document 2 filed by the present applicant discloses a method of providing a resin support inside a steel tank to improve pressure resistance, thereby achieving a lighter fuel tank. This method is a method of threading a metal base and screwing the resin support, but it is necessary to provide a parallel surface of the base on at least the lower side of the fuel tank that is opposite to the upper side.

[0008] Prior art literature

[0009] Patent Literature

[0010] Patent Document 1: Japanese Patent Application Publication No. 2006-256462

[0011] Patent Document 2: Japanese Patent No. 6350781

[0012] Patent Document 3: Japanese Patent Application Publication No. 2012-245974 Summary of the invention

[0013] Problems to be solved by the invention

[0014] In recent years, there has been a trend towards larger capacity batteries for HVs and PHVs. As a result, a larger area under the vehicle floor has been gradually used to mount batteries. Attempts are being made to place the fuel tank around the battery mounting position and minimize the horizontal projection area. In other words, fuel tanks that are close to a cube or a rectangular parallelepiped are being used for HVs and PHVs. Furthermore, it is expected that the full tank capacity of the fuel tank will also be reduced due to improved fuel consumption.

[0015] The current fuel supply method for vehicles is dominated by the fuel injection system, and a fuel pump is provided inside the fuel tank. Therefore, an opening for installing the pump needs to be provided on the upper side plate. The diameter of the opening is usually 100 to 150 mm, but there is no place to provide a support around the opening, which is a part that is easily deformed due to pressure changes inside the fuel tank. Therefore, Patent Document 3 discloses the following method: In the case of a resin tank, the rigidity of the periphery of the opening is ensured by a resin support having a universal joint structure.

[0016] Even for a steel tank, it is important to prevent deformation of the pump mounting portion due to changes in internal pressure. However, since the horizontal projection area of ​​the fuel tank is small and an opening of about 100 to 150 mm in diameter is required at the pump mounting portion, it is difficult to secure a place for installing a metal base for mounting the support in the method of Patent Document 2. In order to prevent plate displacement due to pressure changes at the pump mounting portion, there is a limit to reducing the size of the steel fuel tank plate.

[0017] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to improve the pressure resistance of a fuel tank and to reduce the weight thereof.

[0018] Means for solving problems

[0019] The present invention proposes the following means.

[0020] (1) A fuel tank according to one embodiment of the present invention comprises: a steel lower plate and a steel upper plate; and at least one steel support column arranged in an internal space formed by opposing the lower plate and the upper plate, and fixed to the upper plate in a state where a first end portion is fixed to the lower plate and a second end portion is arranged in a hole formed in the upper plate.

[0021] (2) In the above (1), the fuel tank may include: a first nut made of steel, fixed to the inner surface of the lower plate, and engaged with the first end of the support; a flange, arranged on the inner surface of the upper plate and fixed to the support; and a second nut made of steel, arranged on the outer surface of the upper plate, and engaged with the second end of the support, so as to clamp the upper plate between the flange and the nut.

[0022] (3) In the above (2), the support column, the first nut, and the second nut may have a tin-plated layer or a tin-zinc-plated layer on their outer surfaces.

[0023] (4) In the above (2) or (3), the fuel tank may include a brazing material for sealing between the upper plate and the second nut.

[0024] (5) In any one of the above (1) to (4), a steel columnar beam may be mounted on a pair of opposing wall surfaces of at least one of the lower plate and the upper plate.

[0025] (6) In the above (5), a first baffle may be attached to the beam.

[0026] (7) In any one of the above (1) to (6), a second baffle may be attached to the support column.

[0027] Effects of the Invention

[0028] As described above, according to the present invention, it is possible to improve the pressure resistance of the fuel tank and reduce the weight. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a perspective view schematically showing a fuel tank according to one embodiment of the present invention.

[0030] Figure 2 It is a longitudinal sectional view showing an outline of the fuel tank according to this embodiment.

[0031] Figure 3 It is a cross-sectional view schematically showing a state in which the fuel tank of this embodiment is separated into an upper panel and a lower panel.

[0032] Figure 4 It is a cross-sectional view of the main part near the flange.

[0033] Figure 5 It is a top view of the inner surface side of the lower side plate.

[0034] Figure 6 It is a longitudinal sectional view showing the structure of a support column according to this embodiment.

[0035] Figure 7 It is a top view of the upper side panel.

[0036] Figure 8 This is a cross-sectional view of a fuel tank according to a modified example of one embodiment of the present invention.

[0037] Fig. 9 It is a three-dimensional diagram of the fixture.

[0038] Fig.10 This is a top view of the beam structure.

[0039] Fig.11 It is a top view of other beam structures.

[0040] Fig.12 It is a perspective view of the second baffle plate mounted on the support column.

[0041] Fig.13 It is a top view of the second baffle.

[0042] Fig.14 It is a top view of the first baffle installed on the beam.

[0043] Fig.15 It is a side view of the first baffle. DETAILED DESCRIPTION

[0044] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In addition, in this specification and the accompanying drawings, components having substantially the same functional configuration are denoted by the same reference numerals, and repeated descriptions are omitted.

[0045] <1. Structure of the fuel tank>

[0046] First, based on Figures 1 to 3 The general structure of a fuel tank according to one embodiment of the present invention will be described. Figure 3 This is a cross-sectional view schematically showing a state in which the fuel tank 10 according to the embodiment of the present invention is separated into an upper panel 11 and a lower panel 12 .

[0047] The fuel tank 10 of this embodiment is, for example, a fuel tank for an automobile, and is composed of a steel upper plate 11 and a steel lower plate 12. Compared with a resin fuel tank, the steel fuel tank 10 has a simple shape and is made of metal, so it has the advantage that gasoline vapor is unlikely to leak. Figure 2As shown, the upper plate 11 has a recessed portion 11a forming an internal space V for storing fuel, and a flange portion 11b formed at an edge of the recessed portion 11a for joining the upper plate 11 and the lower plate 12. Similarly, the lower plate 12 has a recessed portion 12a forming an internal space V for storing fuel, and a flange portion 12b formed at an edge of the recessed portion 12a for joining the upper plate 11 and the lower plate 12. The flange portion 11b of the upper plate 11 and the flange portion 12b of the lower plate 12 are joined, for example, by seam welding.

[0048] The internal space V is formed by the upper plate 11 and the lower plate 12 facing each other.

[0049] The fuel tank 10 is often installed in the vicinity of the battery mounting position in the vehicle. Therefore, it is preferably a rectangular parallelepiped shape that can minimize the horizontal projection area while maintaining the capacity of the fuel tank 10 as large as possible. In addition, the corners between adjacent faces of the six faces constituting the rectangular parallelepiped fuel tank 10 may also be rounded.

[0050] <2. Pillar>

[0051] [Pillar structure]

[0052] The fuel tank 10 of this embodiment is provided with a support 100 extending in the direction in which the upper plate 11 and the lower plate 12 are opposed to each other in the internal space V. The support 100 is a reinforcing member provided to improve the rigidity of the fuel tank 10. The support 100 is composed of a steel wire or bar (steel support). Here, the reason for selecting steel as the support 100 is that it is cheap and has high strength. In addition, the support 100 may be carbon steel or stainless steel, and may be appropriately coated with plating or the like. In addition, the number of the support 100 provided in the fuel tank 10 is not limited, and may be one or more than two. When there are three support 100, the volume occupied by the support in the internal space V can be minimized, and the deformation of the fuel tank 10 can be effectively suppressed. In particular, it is preferable to obtain the parts of the fuel tank 10 that are expected to deform relatively greatly by deformation analysis calculation, and to arrange three support 100 at these parts. By arranging the support in this way, the deformation of the upper plate 11 and the lower plate 12 can be effectively suppressed. In particular, by arranging the support column 100 so as to surround the first pump mounting hole 11 c , deformation of the fuel tank 10 including the upper plate 11 and the lower plate 12 can be effectively suppressed.

[0053] In the case of a high pressure tank, the internal pressure rises to, for example, about 40 kPa. Figure 1 The force applied by the inner surface of the upper plate 11 and the inner surface of the lower plate 12 of the fuel tank 10 is 40 kN / m 2Assuming that the inner surface area of ​​the fuel tank 10 is 1m 2 , a force of 40 kN (4.08 tons) is applied to the inner surface. Although not all of this force is applied to the support 100, it is necessary to design an appropriate plate thickness and design it to share the load applied to the wall surface of the fuel tank 10 and the load applied to the support 100.

[0054] A tensile force of several tens to several hundreds of kgf is applied to the support 100 when the pressure is positive, and a compressive force of the same magnitude is applied to the support 100 when the pressure is negative. For example, when a tensile force or a compressive force of 100 kgf (980 N) is applied and a support 100 having a diameter of 6 mm is used, the stress applied to the support 100 becomes 34.6 MPa according to the formula (100×9.8÷(3×3×3.14)). The tensile strength of S10C steel specified in JIS-G-4051:2016 is 310 MPa or more, so it can be seen that it has sufficient strength even with a diameter of 6 mm. The significance of providing the support 100 is to suppress the displacement of the plates 11 and 12 caused by pressure. Therefore, the length of the support 100 does not change significantly due to stress. The stress applied to the support 100 is below the elastic limit, preferably below half of the yield point. The yield point is generally defined as the 0.2% yield strength, that is, the load at which a permanent strain of 0.2% remains during a tensile test. However, since the stress-strain curve becomes slightly nonlinear near the yield point, the diameter of the support column 100 may be designed to a load at which the stress becomes less than half of the yield point in the sense of using the support column 100 in a completely elastic region.

[0055] For example, assuming that a predetermined internal pressure is applied to the fuel tank 10, the diameter of the steel support 100 is 6 mm, and the portion located in the internal space V is determined by the height dimension of the fuel tank 10. Assume that the height of the fuel tank 10 (the length of the portion located in the internal space V of the support 100) is 200 mm. In this case, the portion of the steel support 100 located in the internal space V has a diameter of 5.65 cm. 3volume and a mass of 44.4g. Furthermore, in the case where the yield point strength of the steel support 100 is 300MPa, the allowable stress during use can be set to about 150MPa or less in the fully elastic region. In contrast, in the case where a resin support is applied to a fuel tank 10 that is subjected to the same internal pressure as the internal pressure specified above and has the same height dimensions, a general resin support (for example, polyoxymethylene, etc.) is designed to set the allowable stress during use to about 10MPa or less, taking into account the low strength such as tensile strength and yield strength, the melting point as low as about 160 degrees Celsius, and the low stability of mechanical properties such as Young's modulus, strength, and fully elastic region with respect to changes in ambient temperature. Therefore, when a resin support is used, its size is at least 24mm in diameter and 200mm in height (length). In this case, the portion of the resin support located in the internal space V has a width of 90cm. 3 The volume and mass of the support column 100 are both larger values ​​compared to the steel support column 100. In particular, the volume difference is very large. In this way, compared to the resin support column 100, the steel support column 100 can have a smaller volume and a smaller mass while maintaining the required strength. Therefore, the fuel tank 10 of the present embodiment can minimize the volume occupied by the support column 100 in the internal space V of the fuel tank 10. Therefore, the effective volume (capacity) for storing fuel in the internal space V of the fuel tank 10 can be ensured as much as possible. In addition, it is possible to achieve lightweighting while maintaining the strength of the support column 100, so that the fuel tank 10 including the support column 100 can be made lightweight and the yield strength against internal pressure can be improved.

[0056] In order to fix it with nuts, both ends of the support 100 are threaded. Figure 3 As shown, a first external thread 101 is formed at the lower end (first end) of the support 100, and a second external thread 102 is formed at the upper end (second end) of the support 100. In order to prevent the plates 11 and 12 from deforming when negative pressure is applied, as shown in FIG. Figure 2 as well as Figure 3As shown, an annular flange 105 is fixed at a position of the support 100 corresponding to the internal height of the fuel tank 10. The flange 105 is arranged so that the center axis of the annular flange 105 when viewed from above extends in a right-angled direction from the entire circumference of the outer periphery of the support 100 along the axis of the support 100. Thus, when the fuel tank 10 is under negative pressure, the support 100 can bear the load from the upper plate 11 with a larger area via the flange 105, thereby suppressing deformation near the second hole 11d including the inner edge of the second hole 11d formed in the upper plate 11. Therefore, the durability of the fuel tank 10 can be improved. Here, when under negative pressure, the upper plate 11 may be displaced and deformed with the outer peripheral edge of the flange 105 as a fulcrum and fatigued. Therefore, the outer diameter of the flange 105 is set in such a way that the target positive and negative pressure fatigue test passes. In addition, as Figure 4 As shown, the upper surface of the flange 105 is slightly tapered downward toward the radially outer side of the flange 105 , thereby reducing the amount of strain on the upper plate 11 side in contact with the outer peripheral edge of the flange 105 .

[0057] The fuel tank 10 must also consider collision safety. That is, in the event of a collision, the plates 11 and 12 on which the support 100 is mounted must be prevented from being damaged and leaking fuel. Therefore, the diameter, height and number of threads of the threads at the bottom of the support 100 can be adjusted to ensure that the fuel tank 10 is not damaged. Figure 2 as well as Figure 3 The threaded connection portion between the first nut 21 of the chamber support plate 20 attached to the lower plate 12 and the support column 100 is broken.

[0058] From the perspective of preventing corrosion, the support 100 may be subjected to surface treatment. Electroplating of zinc, electroplating of tin, electroplating of tin-zinc, and electroplating of nickel are recommended. That is, the outer surface of the support 100 may be provided with a zinc plating layer, a tin plating layer, a tin-zinc plating layer, or a nickel plating layer. When the plates 11, 12, and the baffle support plate are made of tin-zinc-plated steel sheets, electroplating of tin-zinc may be selected from the perspective of preventing electrical corrosion inside the fuel tank 10.

[0059] [Installation structure]

[0060] The support column 100 is mounted using a first nut 21 made of steel.

[0061] like Figure 5 As shown, a circular chamber support plate 20 is used to attach the first nut 21 on the lower plate 12 side. Figure 5The figure shows a state where the first nut 21 is installed at three locations of the chamber support plate 20. A hole having a diameter 1 mm larger than the hole diameter of the first nut 21 is opened at the installation portion of the first nut 21 on the chamber support plate 20. The first nut 21 is projection welded at this location. A projection may be provided on the first nut 21 side, or a projection (protrusion) may be provided on the chamber support plate 20 side.

[0062] The first nuts 21 are provided on the inner surface of the lower plate 12 corresponding to the support columns 100 .

[0063] The chamber support plate 20 with the first nut 21 installed is installed on the lower side plate 12 by spot welding. Figure 6 As shown in FIG. 1 , when a reinforcement member (reinforcement component) 22 is installed on the outer surface side of the lower plate 12, deformation of the lower plate 12 caused by pressure fluctuations can be suppressed. Figure 6 In the figure, reference numeral 23 denotes a welded portion formed by spot welding.

[0064] When the reinforcement 22 is installed, a gap may be generated between the lower plate 12 and the reinforcement 22 when the pressure changes. When dust enters the gap, the pressure fatigue strength of the fuel tank 10 may be reduced. Therefore, in order to prevent dust from entering the joint (gap), it is effective to apply an elastic coating to the peripheral portion of the reinforcement 22. Alternatively, the gap can be blocked by flowing tin-zinc solder into the gap. In particular, when solder is used, the strength is ensured in a surface manner, so the effect of the reinforcement 22 is improved.

[0065] The diameter of the reinforcement member 22 is about 0 to 20 mm larger than the diameter of the chamber support plate 20. In the absence of the reinforcement member 22, stress concentration occurs at the welded portion 23 formed by spot welding the chamber support plate 20 and the lower plate 12, and the lower plate 12 is easily deformed. The position of the welded portion 23 by spot welding is not particularly specified, but it is preferably near the portion where the first nut 21 is projection welded, where stress is easily concentrated when the pressure changes. Figure 5 as well as Figure 6 An example of the welded portion 23 is shown. The first nut 21 is fixed to the inner surface of the lower plate 12 via the chamber support plate 20 .

[0066] The first external thread 101 formed at the lower end of the support 100 is fitted into the first nut 21, and the lower plate 12 and the support 100 are connected via the first nut 21 and the chamber support plate 20. Thus, the lower end of the support 100 is fixed to the lower plate 12.

[0067] In addition, the lower end of the support column 100 may be fixed to the lower plate 12 by welding or the like.

[0068] like Figure 6 as well as Figure 7As shown, the support column 100 on the upper plate 11 side is installed by the second nut 107. In addition, the upper plate 11 is provided with a first hole 11c for installing the pump. Here, the first hole 11c is formed in the center of the upper plate 11 when viewed from above. The upper plate 11 has an opening of a second hole (hole) 11d for installing the support column 100. The second hole 11d is opened at a position just above the installation position of the first nut 21 on the lower plate 12 side. The diameter of the second hole 11d is the same as the diameter of the support column 100. When the second hole 11d is expanded by about 0.5 mm larger than the diameter of the second hole 11d toward the outer surface side of the upper plate 11, a taper is added to the second hole 11d, making it easy to install the upper end of the support column 100. In addition, it is also possible to reach in from the first hole 11c, adjust the position of the support column 100, and put the upper end of the support column 100 into the second hole 11d.

[0069] Furthermore, stress concentration is likely to occur at the edge of the second hole 11d in the upper plate 11. Adding a taper to the second hole 11d by hole expansion is also effective in alleviating stress concentration associated with deformation of the plates 11 and 12 during pressure increase and decrease.

[0070] The lower portion of the upper end of the support 100 is disposed in the second hole 11 d , and the upper portion of the upper end of the support 100 protrudes upward from the second hole 11 d . That is, a portion of the support 100 is disposed in the internal space V. The flange 105 is disposed on the inner surface of the upper plate 11 .

[0071] The support column 100 is mounted by screwing the second nut 107 from the outside. The second nut 107 is arranged on the outer surface of the upper plate 11 and is engaged with the second external thread 102 formed on the upper end of the support column 100, thereby being fixed to the upper end of the support column 100. The second nut 107 and the flange 105 clamp the upper plate 11 in the vertical direction. In this way, the upper end of the support column 100 is fixed to the upper plate 11. In addition, the upper end of the support column 100 may also be fixed to the upper plate 11 by welding or the like.

[0072] In order to ensure the sealing performance, a packing (seal, gasket or sealing ring, not shown) is provided between the second nut 107 and the upper plate 11. The material of the packing is not particularly specified, but when considering the durability of the long-term specification, it can be an annular gasket 108A obtained by punching out a solder sheet (see Figure 4 ). After the washer 108A is screwed to the support 100 by the second nut 107, the washer 108A is heated to melt the washer 108A, and then the washer 108A is cooled and solidified to form the solder 108. Thus, the solder 108 seals (seals) between the upper plate 11 and the second nut 107, and the sealing performance of the fuel tank 10 can be ensured.

[0073] In addition, from the viewpoint of preventing the nut 21, 107 from corrosion, it is preferred to plate the nut 21, 107, and electroplating zinc, electroplating tin, electroplating tin zinc, and electroplating nickel are recommended. That is, it is preferred that the outer surface of the nut 21, 107 is provided with a zinc plating layer, a tin plating layer, a tin zinc plating layer, and a nickel plating layer.

[0074] In particular, when tin-zinc-plated steel sheets are used for the plates 11 and 12, electroplating tin-zinc is preferred from the perspective of reducing the possibility of electrical corrosion. In addition, when solder metal is used for sealing the fastening portion between the support 100 and the nuts 21 and 107, and the solder metal is melted by heating to ensure sealing, electroplating tin-zinc is preferred because electroplating tin-zinc has excellent solder wettability. Electroplating tin-zinc is also preferred from the perspective of ensuring sealing.

[0075] <3. Beam structure>

[0076] [Beam structure, mounting structure]

[0077] When the support 100 is provided at the edge of the pump, the displacement of the upper and lower surfaces of the plates 11 and 12 during positive and negative pressures can be suppressed, but wrinkles will appear near the seam-welded flanges 11b and 12b of the fuel tank 10. That is, the displacement of the wall surfaces of the plates 11 and 12 becomes larger. When the seam-welded flanges 11b and 12b of the fuel tank 10 are reinforced by reinforcement members and the fuel tank 10 is mounted to the vehicle frame via the reinforcement members and bolts, the rigidity of the vehicle frame is used to suppress the displacement in the lateral direction (the direction perpendicular to the direction in which the plates 11 and 12 are opposed), but when the fuel tank 10 is mounted to the vehicle frame using a belt, the lateral displacement of the fuel tank 10 cannot be suppressed.

[0078] In such a case, Figure 8 As shown, a steel cylindrical beam 30 can be provided inside the fuel tank 10. After the plates 11 and 12 are stamped, they are mounted on the wall surface by spot welding. Figure 8 as well as Fig. 9 The beam 30 shown is provided with a steel attachment tool 31 (attachment: accessory). Fig. 9 The beam 30 is indicated by a two-dot chain line.

[0079] The installation tool 31 is a hat-shaped structure, and the flanges 30a provided at both ends of the beam 30 are embedded in the installation tool 31. The fins 32 for preventing the installed beam 30 from falling off can also be installed in the opening 31a of the hat-shaped structure. When the flange 30a is embedded in the installation tool 31, the steel fins 32 are bent inward, and after the engagement, the flange 30a is prevented from falling off by the rebound of the fins 32. The size of the fins 32 is designed to have such strength that it can be engaged by manual operation. In addition, the flange shape of the beam 30 can be circular or rectangular. In the case of a quadrilateral, it becomes a trapezoid, and the upper base is shorter than the lower base. When inserted into the space of the steel installation tool 31 from the upper end side, the installation becomes easy.

[0080] The strength of the mounting tool 31 is controlled by the plate thickness and material of the mounting tool 31. However, the strength of the mounting tool 31 can be ensured in a planar manner by flowing solder metal into the gaps of the mounting tool 31.

[0081] like Fig.10 As shown in FIG. 1 , one end of the beam 30 has a flange structure having a flange 30a, and the other end has a threaded structure 34. A nut 34a is mounted on a quadrilateral steel plate by projection welding, and a threaded portion 34b of the beam 30 is screwed thereto to form the flange 30a on the other end side. When screwing, the length of the beam 30 can be adjusted by the number of rotations, so that the inner diameter deviation of the plates 11 and 12 caused by the stamping accuracy of the plates 11 and 12 can be absorbed.

[0082] If there is almost no deviation in the punching accuracy, the two ends of the beam 30 can be made into flange structures, or flange structures using threads and nuts. In the case of a flange structure using nuts and threads, it is necessary to increase the diameter of the U-shaped opening 31a of the installation tool 31 as a hat-shaped part.

[0083] In addition, if Fig.11 As shown, it is also possible to prepare two beams 30 with one end being a flange structure and the other end being a threaded structure, and to screw the extension nut 35 for bolt fastening with the threaded structure of the two beams 30. In this case, the thread processing of the two beams 30 needs to make one of them a right-hand thread and the other a left-hand thread. The purpose is to prevent the thread from rotating due to vibration and causing the fastening of the extension nut 35 to be disengaged. In this way, the following effects are achieved: when the two ends of the two beams 30 as a whole are made into a flange structure, the diameter of the U-shaped window of the steel installation tool 31 used for installation is reduced, and the rigidity of the installation tool 31 is improved.

[0084] Which type of beam 30 to use can be determined based on the shape accuracy of the plates 11 and 12, the cost of the mounting tool 31 for the beam structure, the complexity of the work during assembly, and the like.

[0085] The beam 30 is attached to a pair of opposing wall surfaces of at least one of the upper plate 11 and the lower plate 12 .

[0086] Due to pressure fluctuations, the wall surface of the fuel tank 10 tends to displace. The beam structure suppresses this displacement, but stress is concentrated on the spot weld of the mounting tool 31 for mounting the supporting beam 30. The places where stress is concentrated are the joint surface between the plates 11 and 12 of the fuel tank 10 and the steel mounting tool 31 for beam mounting, and the heat-affected part during spot welding. Due to pressure fluctuations, the plastic deformation of the plates 11 and 12 gradually develops, and finally the plates 11 and 12 of the fuel tank 10 are damaged. From the perspective of preventing this situation, a reinforcing plate for strengthening strength can be provided on the opposite side of the steel mounting tool 31 for beam mounting. In this way, the stress concentration in the heat-affected part can be dispersed. The reinforcing plate can be made of the same thickness as the plates 11 and 12, and its size can be the same as the size of the mounting tool 31 for beam mounting, or it can be larger by about 0 to 20 mm in both the vertical and horizontal directions.

[0087] However, as described above, when the pressure changes, a gap is generated between the lower plate 12 and the reinforcement 22, and dust enters the gap from the outside, which may reduce the fatigue strength. Therefore, in order to prevent dust from adhering, it is necessary to give the gap an elastic coating or block the gap portion with solder.

[0088] <4. Installation of baffle>

[0089] As mentioned above, the fuel tank of a hybrid vehicle (HV) or plug-in hybrid vehicle (PHV) requires a high-pressure tank. In such vehicles, the engine runs for a short time and the cabin is relatively quiet. Therefore, the sloshing sound of the fuel is easily heard during operation. In order to suppress the sloshing of the fuel, a support or a beam can be used.

[0090] like Fig.12 as well as Fig.13As shown in FIG. 1 , the fuel tank 10 may also include a sheet-like second baffle plate 40 (also referred to as a longitudinal plate). The second baffle plate 40 is arranged in the internal space V of the fuel tank 10 in such a manner that the thinnest plate thickness direction is along the horizontal direction, that is, in such a manner that the plate surface is along the vertical direction. The second baffle plate 40 may also be attached to the pillar 100. For example, a hole 41 is opened on the side surface of the second baffle plate 40 made of resin and processed into a cylindrical (hollow cylindrical) shape, and a fin 42 is further provided, thereby suppressing the flow of fuel. A small-diameter hollow cylindrical column structure 43 is installed on the side surface of the cylindrical (hollow cylindrical) second baffle plate 40 through which the pillar 100 passes. After the pillar 100 is attached to the lower side plate 12, such a second baffle plate 40 is passed from the upper part of the pillar 100, and the second baffle plate 40 can be attached in a state where the pillar 100 is embedded in the baffle plate 40. As a result, the sloshing of fuel generated during driving can be suppressed, and the generation of noise can be suppressed. When the second baffle plate 40 is made of resin, it is possible to reduce the weight per unit volume occupied in the internal space V. In addition, the second baffle plate 40 is not limited to being made of resin, and may be formed of other materials such as steel.

[0091] The possibility of increasing the use of a rectangular parallelepiped PHV fuel tank is mentioned. In the case of this shape, when the vehicle is running, the fuel moves laterally due to centrifugal force when turning, and when it collides with the side of the fuel tank, its wave rebounds and the fuel falls along the upper surface of the fuel tank. At this time, a sound is generated due to the collision of liquids. This sound is called splashing sound. Fig.14 as well as Fig.15 As shown, the fuel tank 10 may also include a sheet-like first baffle 50 (also referred to as a transverse plate). The first baffle 50 is arranged in the internal space V of the fuel tank 10 in such a manner that the thinnest plate thickness direction is along the vertical direction, that is, in such a manner that the plate surface is along the horizontal direction. The first baffle 50 may also be attached to the support 100. If two or more beams 30 are provided, when the sheet-like first baffle 50 is provided in such a manner that the thickness direction of the sheet is along the up-down direction (vertical direction) by utilizing these beams 30 to be erected in the transverse direction (horizontal direction) across the plurality of beams 30, it is possible to receive the falling fuel and reduce the splashing sound. That is, the first baffle 50 is supported in a state of being erected across the plurality of beams 30, so that it can withstand the impact of the falling fuel, and can shield the collision of the liquids, and can effectively reduce the splashing sound. In this way, since the first baffle plate 50 is mounted on the beam 30, the beam 30 can be used to suppress deformation of the plates 11 and 12 and to support the first baffle plate 50, so that the durability of the fuel tank 10 can be improved, and the fuel swing generated during driving can be suppressed, thereby suppressing the generation of noise. In addition, it is also possible to form a plate-like body extending in the vertical direction from one end or both ends of the resin first baffle plate 50, and to make the cross-sectional shape of one end or both ends of the first baffle plate 50 into an L shape, so that it has the function of a longitudinal plate.

[0092] The type of resin forming the second baffle plate 40 and the first baffle plate 50 is not particularly limited, and high-density polyethylene, polyoxymethylene, nylon, etc. can be considered. After being assembled into the fuel tank 10, when the baffle plates 40 and 50 are painted and sintered, it is necessary to select a resin corresponding to the sintering temperature. The melting point of the resin must be above the sintering temperature.

[0093] The resin baffles 40 and 50 do not need to be obtained by integral molding, but may be molded by dividing a sheet-like plate into several parts and combining them with a snap-fit ​​structure.

[0094] <5. Functions of pillars and beams>

[0095] [pillar]

[0096] When the upper plate 11 and the lower plate 12 are placed opposite to each other and the flanges 11b and 12b are overlapped, the upper end of the support 100 mounted on the lower plate 12 passes through the second hole 11d opened on the upper surface of the upper plate 11. The second hole 11d is provided around the first hole 11c for pump installation. Therefore, even if the arrangement accuracy of the support 100 is poor and the support 100 cannot pass through the second hole 11d of the upper plate 11, the position of the support 100 can be adjusted by inserting a hand into the first hole 11c for pump installation, thereby making it easy to make the upper end of the support 100 enter the second hole 11d. After the upper end of the support 100 passes through the second hole 11d, the support 100 is fixed from the outside of the upper plate 11 through the sealing packing by the second nut 107. In this way, the support 100 can be easily constructed in the internal space V of the fuel tank 10.

[0097] At least one, preferably three or more, support columns 100 are provided in the fuel tank 10. In the case of one support column 100, displacement of the plates 11 and 12 due to pressure cannot be sufficiently suppressed, and the plates 11 and 12 may be deformed with the portion where the support column 100 is provided as a fulcrum, causing strain to be concentrated around the support column 100. In the case of two support columns 100, there is a concern that the plates 11 and 12 may be displaced so that they rotate with the line connecting the ends of the two support columns 100 as an axis. If three support columns 100 are provided, the surface connecting the ends of the three support columns 100 is completely fixed, and the rigidity of the fuel tank 10 can be ensured. If four or more support columns 100 are provided, although the load on each support column 100 can be reduced, the load on the installation work of the support column 100 increases.

[0098] Here, the fuel tank is provided in the vehicle and is used as a component for storing fuel such as gasoline, but the gasoline stored in the fuel tank is heated by the external gas and the exhaust pipe near the fuel tank due to the structure. Therefore, the vapor pressure of the gasoline rises and the inside of the fuel tank becomes positive pressure. For example, when the vehicle is parked at night, the vapor pressure of the fuel decreases due to the decrease in temperature, and sometimes the inside of the fuel tank becomes negative pressure. In addition, as the fuel is consumed during driving, the liquid volume decreases and the pressure inside the fuel tank sometimes decreases. Furthermore, it can also be considered that the gasoline vapor is purged to the engine side through the filter canister during driving, and the pressure inside the fuel tank decreases. In this way, the inside of the fuel tank repeatedly becomes positive pressure and negative pressure. When the shape of the fuel tank changes due to this pressure change, there is a concern that the strain generated in a part of the plate will exceed the yield point of the steel and enter the plastic region, causing low-cycle fatigue. The deformation of the fuel tank can be suppressed by increasing the plate thickness, so the plate thickness is usually designed in a way that does not cause low-cycle fatigue.

[0099] In addition, in the design of plate thickness, vibration fatigue, i.e. high cycle fatigue, is also taken into consideration. The fuel tank is mounted on the lower part of the vehicle by bolts or belts. When the vehicle is running, the vibration from the road is transmitted to the fuel tank. The fuel tank has a predetermined vibration characteristic value. When the plate thickness is reduced, the characteristic value decreases and approaches the input frequency from the road, which is easy to cause resonance. Therefore, the plate thickness is sometimes determined to avoid vibration fatigue.

[0100] As described above, conventionally, it has been difficult to reduce the thickness of a steel fuel tank in order to avoid pressure fatigue and vibration fatigue.

[0101] Furthermore, in recent years, there has been a growing demand for fuel tanks with higher pressure resistance. In order to cope with the trend of strengthening evaporation emission regulations, an activated carbon canister is used to prevent gasoline vapor from escaping from the fuel system into the atmosphere. The gasoline vapor adsorbed on the canister is removed during engine operation and is not released into the atmosphere. At this time, the canister is dried. However, in electric vehicles and plug-in hybrid vehicles with generators, the engine runs for a short time, and the gasoline adsorbed on the canister is difficult to dry. In order to reduce the load on the canister, the opening pressure of the isolation valve between the canister and the fuel tank needs to be increased, and the pressurization amount is 30 to 40 kPa. Usually, in order to build a steel fuel tank that can withstand this pressure, a plate with a thickness of about twice the normal plate must be used, which increases the weight of the fuel tank.

[0102] As such, it is difficult to reduce the thickness of the plate of a conventional steel fuel tank in order to ensure rigidity. Therefore, the following method is disclosed in Patent Document 2 filed by the present applicant: a resin support is provided inside a steel tank to improve pressure resistance, thereby achieving a lightweight fuel tank. This method is a method of threading a metal base and screwing the resin support, but it is necessary to provide at least a parallel surface of the base on the lower side of the fuel tank that is opposite to the upper side. Therefore, in order to prevent the peripheral edge of the pump opening of the fuel tank from being deformed due to pressure, the present invention can replace the base with a support provided in a very small area such as a nut.

[0103] [Liang]

[0104] In the process of studying the support structure connecting the upper and lower surfaces, the lateral expansion near the flange part of the fuel tank where the seam welding is performed has become a problem. In the case of a flat fuel tank, the expansion in the vertical direction is large, and the lateral expansion is not so much of a problem, but in the case of a fuel tank with a large gap between the upper and lower surfaces, that is, a high fuel tank, the phenomenon of lateral expansion can be observed when the vertical expansion is suppressed. As a method of suppressing this expansion, a belt that mounts the fuel tank to the floor is generally used, but since this belt is also a structure in which the upper side contacts the floor and is supported from the bottom by the belt, it has almost no effect on the lateral expansion.

[0105] In the case of a steel box, the upper and lower side plates are manufactured by stamping, and baffles, piping, ducts, and valves are installed inside them. Therefore, a beam structure can also be installed. So far, there have been cases where baffles are used as beam structures. For example, in tank-type oil tanks for commercial vehicles, sometimes after the main body is wound and longitudinal seam welding is performed, a quadrilateral baffle is pressed into the inside of the main body that becomes a square tube, and the flanges at the four corners of the baffle are fixed by spot welding. This can be done when there are fewer components installed inside, but in the high-pressure box for PHV, various components for pressure adjustment are expected to be installed, which can be considered to interfere with the baffle. In this case, if it is a columnar beam structure, there will be less interference with the components.

[0106] <6. A design example>

[0107] The fuel tank 10 of the present embodiment described above can be designed, for example, using a computer simulation using the finite element method. Specifically, first, in a state where the support 100 is not provided, when the internal pressure of the fuel tank 10 is made positive pressure or negative pressure, the position where the strain range generated by the fuel tank is high is determined. The support 100 is installed at a location close to the maximum strain range position and where a hand can be inserted from the first hole 11c for the fuel tank 10. Since it is unstable with only one support 100, two support pillars 100 are provided as much as possible. Next, a third support pillar 100 is provided at the vertex of an isosceles triangle having the point at which the two support pillars 100 are provided as the base. A second hole 11d is opened near the first hole 11c for pump installation of the upper plate 11, and the support 100 is passed through the second hole 11d and is threadedly fixed by a second nut 107. In order to install the pump, Figure 1 The metal base with a thickness of 2 to 4 mm, called the retainer 15, is attached to the opening periphery of the first hole 11c in the upper plate 11, but the support 100 is preferably provided near it. The reason is that when assembling the fuel tank 10, the user can reach in through the retainer 15 to perform the work, and the rigidity of the retainer 15 can be used to prevent fatigue of the mounting portion of the support 100 on the upper plate 11 side.

[0108] Next, the force applied to the support 100 is calculated by computer simulation, and the diameter of the support 100 that can ensure sufficient tensile force and compressive buckling force is determined. The strength of the support 100 is preferably at least twice the force applied to the support 100. This is to use the support 100 in the complete elastic region to prevent fatigue failure of the support 100.

[0109] Proper support 100 is installed around the retainer 15, and pressure calculation is further performed. If the expansion in the lateral direction increases, and an increase in strain is observed near the seam-welded flanges 11b and 12b, and fatigue failure is concerned, the beam 30 is installed. The beam 30 is installed near the part with large strain.

[0110] As a specific example, the plate thickness of a general steel high-pressure tank is assumed to be 1.6 mm. In addition, the sum of the weights of the upper plate 11 and the lower plate 12 is set to 16 kg. When three pillars 100 are set in the fuel tank 10, it is found that the plate thickness can be reduced to 1.2 mm while ensuring the same pressure resistance as when the plate thickness is 1.6 mm. The weight of the plate at this time is 12 kg. Furthermore, when the plate thickness is set to 1.0 mm, the possibility of fatigue cracks appears near the seam weld bead. Therefore, it is found that by adding a beam 30, pressure resistance can be ensured even with a plate thickness of 1.0 mm. The weight of the plate at this time is 10 kg. When a steel pillar 100 with a diameter of 6 mm is used, the weight of each pillar 100 and beam 30, including the weight of the nut, is less than 100 g. Even with this weight, it can be greatly reduced compared to the original weight.

[0111] Next, the relationship between the shape of the fuel tank, the pillar 100, and the beam 30 will be described.

[0112] In the steel fuel tank 10, the upper plate 11 and the lower plate 12 with flanges are stamped, and after the internal components are installed, the flanges 11b and 12b are overlapped and seam-welded to form an integral component. The side of the fuel tank 10 has increased rigidity due to its seam-welded portion, so the rigidity of the upper and lower surfaces is relatively low. Therefore, the upper and lower surfaces of the fuel tank 10 are connected by the support 100, thereby improving the rigidity of the entire fuel tank 10, that is, the pressure resistance.

[0113] The internal pressure of the fuel tank 10 is uniformly applied to the inner surface of the fuel tank 10. Therefore, the deformation of the surface with lower rigidity becomes larger, thereby causing pressure fatigue failure. When the rigidity of the upper and lower surfaces is increased by providing the support 100 on the upper and lower surfaces and the amount of change is reduced, fatigue failure can be observed in the seam weld bead portion of the side surface. That is, when the upper and lower surfaces are not supported by the support 100, the rigidity of the upper and lower surfaces is lower than that of the side surfaces, but when the upper and lower surfaces are supported by the support 100, the high-low relationship of the rigidity is reversed, and the rigidity of the side surfaces becomes lower than that of the upper and lower surfaces.

[0114] Then, the following knowledge was obtained: when the rigidity of the upper and lower surfaces exceeds the rigidity of the side surfaces by providing the support pillars 100, fatigue cracks can be observed on the side surfaces. In this case, it is known that further improvement in pressure resistance can be obtained by adopting a beam structure (a structure in which a steel cylindrical beam 30 is attached to at least one of the lower plate 12 and the upper plate 11). The shape of the fuel tank 10 that should use the beam structure is supplemented.

[0115] Hereinafter, the dimensions of the rectangular parallelepiped fuel tank 10 are defined as width W, length L, and height H, the surface (upper and lower surfaces) surrounded by the width W and the length L are defined as the WL surface, and the pressure applied to the WL surface is defined as PWL. Similarly, the surface (side surface) surrounded by the width W and the height H are defined as the WH surface, and the pressure applied to the WH surface is defined as PWH, the surface (side surface) surrounded by the length L and the height H are defined as the LH surface, and the pressure applied to the LH surface is defined as PLH. On the WH surface and the LH surface, which are the side surfaces of the fuel tank 10, a seam weld line (weld bead) is continuously provided so as to surround the fuel tank 10.

[0116] The shape of the fuel tank 10 can be roughly divided into three types: a cubic box, a flat box, and a rectangular parallelepiped box. A cubic box is a shape in which the width W, length L, and height H are substantially equal. A flat box is a shape in which the width W and length L are substantially equal, and the height H is smaller than the width W and length L. A rectangular parallelepiped box is a shape in which the width W or the height H is larger, and the length L is smaller.

[0117] Hereinafter, the considerations of the support column 100 and the beam 30 in the case where the shape of the fuel tank 10 is a cubic box, a flat box, and a rectangular parallelepiped box will be described.

[0118] (1) Cube box

[0119] In PHVs, a battery or a device for controlling the battery is sometimes installed under the rear seat, and a fuel tank is installed next to it. Its shape is close to a cube. When the capacity of the fuel tank is Vo and the surface area is S, the hexahedron that maximizes the volumetric efficiency Vo / S is a cube, which can also be said to be a reasonable shape.

[0120] Since it is a cube, PWL = PWH = PLH. Here, the pressure applied to the opposite faces is the same. Since the side faces are more rigid than the upper and lower faces due to the seam welded flange structure, the rigidity of the entire fuel tank 10 can be equalized by providing the support 100 on the upper and lower faces with relatively low rigidity, and the beam 30 does not need to be provided.

[0121] (2) Flat box

[0122] In order to obtain a larger space inside the vehicle, the height H of the fuel tank 10 is sometimes set to about 100 to 200 mm. In such a fuel tank 10, the area of ​​the upper and lower surfaces is enlarged, so the pressure load becomes relatively large compared to the load applied to the side. That is, since PWL>PWH(PLH), even if the rigidity of the upper and lower surfaces is increased by providing the support 100, it will not exceed the rigidity of the side. Therefore, it is not necessary to provide the beam 30.

[0123] (3) Rectangular box

[0124] Sometimes, a fuel tank 10 is provided behind the storage battery. In this case, a rectangular parallelepiped tank is adopted in which the width W or height H of the fuel tank 10 in the left-right direction of the vehicle is larger and the length L in the front-rear direction of the vehicle is smaller. The internal pressure applied to this fuel tank 10 is as described below.

[0125] (When the length L = height H) PWL = PWH or

[0126] (When the length L < height H) PWL < PWH

[0127] When struts 100 are provided on the upper and lower surfaces, the rigidity of the upper and lower surfaces is increased, so the rigidity of the WH surface becomes the lowest. In order to make up for this, a beam 30 is required.

[0128] When studying the setting of the beam 30 in the case of L < H, when the ratio of the width W to the height H exceeds 1.5, it is preferable to provide the beam 30. The LH surfaces on both sides thereof suppress (support) the deformation of the WH surface due to pressure. Therefore, when the width W becomes larger, the deflection of the WH surface also becomes larger, and the deformation of the central portion of the WH surface becomes larger. Therefore, there is a concern about fatigue failure of the WH surface due to pressure fluctuations. Therefore, it is preferable that when W / H > 1.5, one or more beams 30 are provided, whereby deformation can be suppressed and pressure rigidity and fatigue resistance can be improved. Since a pump for sucking fuel is provided in the fuel tank 10, it can be provided at a position avoiding the pump. The position and number of the beams 30 are determined by computer simulation.

[0129] Industrial applicability

[0130] It is possible to improve the pressure resistance of the fuel tank and achieve weight reduction.

[0131] Explanation of symbols

[0132] 10: Fuel tank; 11: Upper side plate; 12: Lower side plate; 30: Beam; 40: Second baffle; 50: First baffle; 100: Strut; 108: Solder; V: Internal space.

Claims

1. A fuel tank comprising: steel lower side panels and steel upper side panels; At least one steel support column is disposed in an internal space formed by opposing the lower plate and the upper plate, and is fixed to the upper plate in a state where a first end portion is fixed to the lower plate and a second end portion is disposed in a hole formed in the upper plate; A first nut made of steel, fixed to the inner surface of the lower plate, for the first end of the support column to be engaged; A flange having a conical shape, disposed on the inner surface of the upper plate and fixed to the support column; and A second nut made of steel is disposed on the outer surface of the upper plate, is engaged with the second end of the support column, and clamps the upper plate between the second nut and the flange.

2. The fuel tank according to claim 1, wherein: The support column, the first nut, and the second nut have tin-plated layers or tin-zinc-plated layers on their outer surfaces.

3. The fuel tank according to claim 1, wherein: A solder for sealing between the upper plate and the second nut is provided.

4. The fuel tank according to any one of claims 1 to 3, wherein: A steel columnar beam is attached to a pair of opposing wall surfaces of at least one of the lower plate and the upper plate.

5. The fuel tank according to claim 4, wherein: A first baffle is mounted on the beam.

6. The fuel tank according to any one of claims 1 to 3, wherein: A second baffle is mounted on the support column.

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