Fuel tank, and method for manufacturing the fuel tank

Abstract

To maintain outer appearance property of a fuel tank through pipes inside the tank even when being subject to restriction on manufacturing due to a material or size.SOLUTION: A fuel tank includes: an outer component (32) including an outer panel (41) forming a tank outer shell and an inlet plate (47) formed separately from the outer panel; an inner component (33) including an inner panel (61) forming a tank inner shell and an inner connection plate (71) formed separately from the inner panel; and pipes (81, 82) passing inside the outer panel and the inner panel and connecting the inlet plate to the inner connection plate, where the inlet plate is joined to the outer panel, the inner connection plate is joined to the inner panel and the inner panel is joined to the outer panel.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a fuel tank and a method for manufacturing a fuel tank. [Background technology]

[0002] Fuel tanks for saddle-ride vehicles are provided with piping such as a breather pipe and a drain pipe. One type of fuel tank of this kind has piping passing through the inside of the tank (see, for example, Patent Document 1). The fuel tank described in Patent Document 1 has a tank inlet provided in the outer panel, and piping extends from the tank inlet through the bottom wall of the inner panel to the outside of the tank. By hiding the piping inside the tank, unlike a structure in which piping passes through the outside of the tank, the appearance of the fuel tank is maintained without covering the outside of the fuel tank with a tank cover. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2005-008023 A Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, recent fuel tanks are manufactured using a variety of materials. When manufacturing the fuel tank described in Patent Document 1, brazing or the like is used to join the panels and pipes, but manufacturing constraints may arise depending on the material and size, making it difficult to manufacture the fuel tank.

[0005] The present invention has been made in consideration of the above points, and has an object to provide a fuel tank and a method for manufacturing a fuel tank that enable piping to be passed through the tank and maintain its appearance, even when manufacturing constraints are imposed by the material or size. [Means for solving the problem]

[0006] The fuel tank according to one embodiment of the present invention includes an outer panel that forms an outer shell of the tank. and, An inlet plate formed separately from the outer panel an outer pipe extending from the inlet plate into the tank; and an inner panel forming an inner shell of the tank. and, An inner connecting plate formed separately from the inner panel an inner pipe passing through the inner connection plate; and a pipe passing through the inside of the outer panel and the inner panel and connecting the inlet plate and the inner connection plate, wherein the inlet plate is joined to the outer panel, the inner connection plate is joined to the inner panel, and the inner panel is joined to the outer panel. The piping is connected to the outer pipe and the inner pipe, the outer pipe is joined to the inlet plate, and the inner pipe is joined to the inner connection plate, and the outer part and the inner part are made of titanium or a titanium alloy that require joining in an oxygen-free environment or a low-oxygen environment. This solves the above problem. Effect of the Invention

[0007] According to a fuel tank of one aspect of the present invention, the outer panel and the inlet plate are formed separately, and the inner panel and the inner connection plate are formed separately. Therefore, even if the work is suitable for the material of each component, but there is a size restriction on the work, the work can be performed on the inlet plate and the inner connection plate. In this way, the work that satisfies the manufacturing restrictions due to the material and size can be flexibly selected. Furthermore, by integrating the outer part and the inner part, a fuel tank with piping passing through the tank is manufactured. A large tank cover that covers the entire tank is not required to maintain the appearance, and the capacity of the fuel tank is not reduced without a double structure. [Brief description of the drawings]

[0008] [Figure 1] FIG. 2 is a left side view of the saddle-ride type vehicle of the present embodiment. [Diagram 2] FIG. 2 is a perspective view of the fuel tank of the present embodiment as viewed from above. [Diagram 3] FIG. 2 is a perspective view of the fuel tank of the present embodiment as viewed from below. [Figure 4] FIG. 4 is a cross-sectional view of the fuel tank taken along line AA in FIG. 3. [Diagram 5] FIG. 4 is a front view of the inner connection plate of the present embodiment. [Figure 6] 10A to 10C are diagrams showing a transition of a manufacturing method of a steel plate fuel tank according to a comparative example. [Figure 7] 10A to 10C are diagrams showing a transition of a manufacturing method of a steel plate fuel tank according to a comparative example. [Figure 8] 1 is a transition diagram showing a manufacturing method of a titanium fuel tank according to an embodiment of the present invention. [Figure 9] 1 is a transition diagram showing a manufacturing method of a titanium fuel tank according to an embodiment of the present invention. [Figure 10] 1 is a transition diagram showing a manufacturing method of a titanium fuel tank according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] A fuel tank according to one aspect of the present invention includes an outer part in which an inlet plate is joined to an outer panel forming an outer shell of the tank, and an inner part in which an inner connection plate is joined to an inner panel forming an inner shell of the tank. The outer panel and the inlet plate are formed separately, and the inner panel and the inner connection plate are formed separately. Therefore, even if the work is suitable for the material but has size restrictions, the work can be performed on the inlet plate and the inner connection plate. In this way, work that satisfies manufacturing restrictions due to the material and size can be flexibly selected. In addition, by integrating the outer part and the inner part, a fuel tank with piping passing through the tank is manufactured. A large tank cover that covers the entire tank is not required to maintain the appearance, and the capacity of the fuel tank is not reduced without a double structure. EXAMPLES

[0010] The present embodiment will be described in detail below with reference to the accompanying drawings. Fig. 1 is a left side view of a saddle riding type vehicle of the present embodiment. In the following drawings, the arrow FR indicates the front of the vehicle, the arrow RE indicates the rear of the vehicle, the arrow L indicates the left side of the vehicle, and the arrow R indicates the right side of the vehicle.

[0011] As shown in Fig. 1, the saddle-type vehicle 1 is configured by mounting various parts such as an engine 14 and an electrical system on a twin-spar body frame 10 formed by aluminum casting. The body frame 10 has a pair of main frames 11 that branch off to the left and right from a head pipe (not shown) and extend rearward, and a pair of down frames (not shown) that branch off to the left and right from the head pipe and extend downward. The pair of main frames 11 support a rear portion of the engine 14, and the pair of down frames support a front portion of the engine 14. Supporting the engine 14 on the body frame 10 ensures the rigidity of the entire vehicle.

[0012] The front portion of the main frame 11 forms a tank rail 12 located above the engine 14, and a fuel tank 30 is supported by the tank rail 12. The rear portion of the main frame 11 forms a body frame 13 located behind the engine 14, and a swing arm 15 is supported swingably at approximately the middle position in the up-down direction of the body frame 13. A seat rail (not shown) and a back stay (not shown) extend rearward from the upper portion of the body frame 13. A rider seat 21 and a pillion seat 22 are supported on the seat rail behind the fuel tank 30.

[0013] A pair of front forks 23 are steerably supported on the head pipe via a steering shaft (not shown). A front wheel 24 is rotatably supported on the lower part of the front forks 23, and an upper part of the front wheel 24 is covered by a front fender 25. The swing arm 15 extends rearward from the body frame 13. A rear wheel 26 is rotatably supported on the rear end of the swing arm 15, and an upper part of the rear wheel 26 is covered by a rear fender 27. The engine 14 is connected to the rear wheel 26 via a chain drive type transmission mechanism, and power from the engine 14 is transmitted to the rear wheel 26 via the transmission mechanism.

[0014] For reasons of productivity and cost, such straddle-type vehicles are often equipped with fuel tanks made of steel plate, but sometimes fuel tanks made of non-ferrous metals or resins, which have an advantage in terms of specific gravity, are also installed. Most non-ferrous metal fuel tanks use aluminum, while most resin fuel tanks use polyethylene (PE) or nylon (PA), both of which are manufactured using different methods than steel plate fuel tanks and require special manufacturing equipment and molds. Recently, the manufacture of titanium fuel tanks, a non-ferrous metal whose properties are closer to those of iron than aluminum, has been considered.

[0015] One of the properties of titanium is that it reacts with oxygen and easily deteriorates, which means that manual brazing (torch brazing) in air, which was previously done when manufacturing steel fuel tanks, cannot be done. Brazing fills the gaps between components by capillary action without melting the base material, so it is used as a welding method for parts with narrow working areas, such as pipe joints, in fuel tanks that require airtightness. Furnace brazing allows brazing in an oxygen-free environment, but large parts such as fuel tank panel parts cannot be placed in the furnace, and pipes cannot be directly welded to panel parts.

[0016] In the case of a steel fuel tank, brazing can be done in air, so pipes can be hand brazed to the tank inlet of the outer panel, and then passed through the tank and hand brazed directly to the inner panel. In the case of a titanium fuel tank, all welding must be done in an oxygen-free environment, but as mentioned above, it is difficult to pass pipes through the tank because pipes cannot be brazed in a furnace to the large inner panel. For this reason, a typical titanium fuel tank has a rubber hose extending from the tank inlet to the outside of the tank.

[0017] Furthermore, in order to maintain the appearance of the fuel tank, it is necessary to cover the fuel tank with a tank cover so as to hide the rubber hose outside the tank. When a tank cover is attached to the fuel tank, the weight reduction advantage of titanium is reduced, and the fuel tank has a double structure, reducing its capacity. Therefore, in the fuel tank 30 of this embodiment, the connection plate for the pipes is separated from the inner panel 61 in a size that allows for furnace brazing (see FIG. 4). This makes it possible to pass pipes through the inside of the tank and maintain the appearance, even in the case of a titanium fuel tank 30, which is subject to manufacturing restrictions due to the material and size.

[0018] The fuel tank will be described below with reference to Fig. 2 to Fig. 5. Fig. 2 is a perspective view of the fuel tank of this embodiment as seen from above. Fig. 3 is a perspective view of the fuel tank of this embodiment as seen from below. Fig. 4 is a cross-sectional view of the fuel tank taken along line AA in Fig. 3. Fig. 5 is a front view of the inner connection plate of this embodiment.

[0019] As shown in Fig. 2, the tank body 31 of the fuel tank 30 is formed by joining the outer edges of an outer panel 41 forming the outer shell of the tank and an inner panel 61 (see Fig. 3) forming the inner shell of the tank. The outer panel 41 and the inner panel 61 form a fuel storage space S (see Fig. 4). The outer panel 41 is formed by joining symmetrical panel members 42L, 42R along a center line in the front-rear direction, and is formed into a substantially dome shape that increases in height from the panel rear portion 43 toward the panel front portion 44. The surface of the panel front portion 44 of the outer panel 41 is generally one step lower, and is formed so that a tank cover 59 (see Fig. 10(C)) can be attached to the panel front portion 44.

[0020] A circular opening 45 is formed in the center of the panel front portion 44 of the outer panel 41, and a tank inlet 46 is joined to the circular opening 45. The tank inlet 46 has a cylindrical inlet plate 47 with a bottom, and an inlet pipe 49 attached to the bottom wall of the inlet plate 47. A tank cap (not shown) is attached to the inlet plate 47, and the fuel filler port of the inlet pipe 49 is opened and closed by the tank cap. With the tank cap open, a fuel filler nozzle (not shown) is inserted into the inlet pipe 49, and fuel is supplied from the fuel filler nozzle to the storage space S of the tank body 31.

[0021] An upper breather pipe 51 and an upper drain pipe 52 are joined as outer pipes to the bottom wall of the inlet plate 47. The upper breather pipe 51 and the upper drain pipe 52 extend from the bottom wall of the inlet plate 47 into the tank (see FIG. 4 in particular). The upper breather pipe 51 forms the upstream side of the breather pipe, and the upper drain pipe 52 forms the upstream side of the drain pipe. The inlet plate 47 is slightly recessed around the joint of the upper drain pipe 52, making it easier for liquid droplets on the inlet plate 47 to collect at the inlet of the upper drain pipe 52.

[0022] Furthermore, screw holes 54 for three nuts 53 (see FIG. 4) are exposed from the bottom wall of the inlet plate 47. The tank cap is attached to the tank inlet 46 by screwing it into these screw holes 54. Seat surfaces 55L, 55R of a cover bracket (not shown) are formed on both the left and right sides of the panel front portion 44 of the outer panel 41. A tank cover 59 (see FIG. 10(C)) is attached to the panel front portion 44 of the outer panel 41 via the cover bracket by joining the cover bracket to the seats 55L, 55R. The periphery of the tank cap is covered by the tank cover 59 to hide the tank inlet 46.

[0023] As shown in Fig. 3, the inner panel 61 has a panel rear portion 63 formed in a flat shape, and is formed in a substantially dome shape so as to rise from the front side of the panel rear portion 63 toward the panel front portion 64. A circular opening 65 is formed in the center of the bottom surface of the panel rear portion 63 of the inner panel 61, and the upper side of a fuel pump (not shown) is inserted into the tank through this circular opening 65. A plurality of screw holes 66 are formed around the circular opening 65, and a flange portion on the lower side of the fuel pump is screwed into these screw holes 66. The fuel pump pumps out fuel from within the tank and sends it to a fuel injector (not shown) of the engine 14 (see Fig. 1).

[0024] An oval opening 67 is formed next to the circular opening 65 (on the left side in this embodiment), and an inner connection plate 71 is joined to this opening 67. The inner connection plate 71 is formed in a dome shape that bulges into the tank, and a lower breather pipe 73 and a lower drain pipe 74 are joined to the upper bottom wall of the inner connection plate 71 as inner pipes. The lower breather pipe 73 and the lower drain pipe 74 penetrate the upper bottom wall of the inner connection plate 71 (see FIG. 4 in particular). The lower breather pipe 73 forms the downstream side of the breather pipe, and the lower drain pipe 74 forms the downstream side of the drain pipe.

[0025] 4, the upper breather pipe 51 and the upper drain pipe 52 are formed in a substantially L-shape, and the lower breather pipe 73 and the lower drain pipe 74 are formed straight. The downstream end of the upper breather pipe 51 and the upstream end of the lower breather pipe 73 are connected via a first breather hose (piping) 81, and the downstream end of the upper drain pipe 52 and the upstream end of the lower drain pipe 74 are connected via a first drain hose (piping) 82. The inlet plate 47 and the inner connection plate 71 are connected by the first breather hose 81 and the first drain hose 82 that pass inside the outer panel 41 and the inner panel 61.

[0026] A second breather hose 83 is connected to the downstream end of the lower breather pipe 73 outside the tank, and a second drain hose 84 is connected to the downstream end of the lower drain pipe 74 outside the tank. In this manner, the upper breather pipe 51, the first breather hose 81, the lower breather pipe 73, and the second breather hose 83 form a breather pipe that guides gas components in the tank inlet 46 to the outside of the fuel tank 30. The upper drain pipe 52, the first drain hose 82, the lower drain pipe 74, and the second drain hose 84 form a drain pipe that discharges liquid droplets in the tank inlet 46.

[0027] The oval opening 67 of the inner panel 61 is formed along an outer peripheral edge 75 of the inner connecting plate 71, and the opening edge 68 of the inner panel 61 protrudes outside the tank around the entire circumference. The outer peripheral edge 75 of the inner connecting plate 71 protrudes outside the tank from the opening 67, and the lower end face of the outer peripheral edge 75 of the inner connecting plate 71 is aligned with the lower end face of the opening edge 68 of the inner panel 61. Since the opening edge 68 of the inner panel 61 and the outer peripheral edge 75 of the inner connecting plate 71 protrude outside the tank, the outer peripheral edge 75 of the inner connecting plate 71 is easily and reliably joined to the opening edge 68 of the inner panel 61 from outside the tank.

[0028] At this time, the lower breather pipe 73 and the lower drain pipe 74 penetrate approximately vertically through the upper bottom wall of the inner connection plate 71. When the inner connection plate 71 is viewed from the front, i.e., when facing the inner connection plate 71, the downstream end of the lower breather pipe 73 and the downstream end of the lower drain pipe 74 are located inside the outer circumferential edge 75 of the inner connection plate 71 (see FIG. 5). Therefore, when the inner connection plate 71 and the inner panel 61 are joined by welding, the lower breather pipe 73 and the lower drain pipe 74 protruding outside the tank do not get in the way of the welding torch.

[0029] When manufacturing this fuel tank 30, an outer part 32 consisting of the outer panel 41 and outer-related parts, and an inner part 33 consisting of the inner panel 61 and inner-related parts are manufactured separately. Then, after connecting a first breather hose 81 and a first drain hose 82, the outer part 32 and the inner part 33 are integrated to manufacture the fuel tank 30. The outer part 32 and the inner part 33 are each made of titanium or a titanium alloy, and the members are welded together in an oxygen-free environment to reduce the weight of the fuel tank 30 and improve weather resistance and rust resistance.

[0030] As described above, the pipes and the plates need to be joined by furnace brazing in an oxygen-free environment, so the inlet plate 47 and the inner connection plate 71 are formed to a size that can be accommodated in the furnace. In this way, the outer panel 41 and the inlet plate 47 are formed separately, so that the inlet plate 47, the upper breather pipe 51, and the upper drain pipe 52 can be brazed in the furnace. Similarly, the inner panel 61 and the inner connection plate 71 are formed separately, so that the inner connection plate 71, the lower breather pipe 73, and the lower drain pipe 74 can be brazed in the furnace.

[0031] A method for manufacturing a fuel tank will be described with reference to Fig. 6 to Fig. 10. Fig. 6 and Fig. 7 are transition diagrams showing a method for manufacturing a fuel tank made of steel plate as a comparative example. Fig. 8 to Fig. 10 are transition diagrams showing a method for manufacturing a titanium fuel tank of this embodiment. The steel fuel tank of the comparative example differs from the fuel tank of this embodiment in that the breather pipe and the drain pipe are each formed of a single pipe, and in that no inner connection plate is formed.

[0032] In the manufacturing method of a fuel tank made of steel plate shown in the comparative example, individual components of the fuel tank are manufactured. For example, various panels are press-formed by manufacturing equipment such as a press. Next, as shown in Figs. 6(A)-(C), a manufacturing operation of an outer part 91 is carried out. First, a forming operation of an outer panel 92 shown in Fig. 6(A) is carried out. In this case, a shielding gas is sprayed onto the mating surfaces of the panel members 93L and 93R, and the mating surfaces of the panel members 93L and 93R are plasma-welded in an oxygen-free environment. Also, inlet-related parts such as a cover bracket are spot-welded to the outer panel 92.

[0033] Next, a joining operation of a breather pipe 95 and a drain pipe 96 to the inlet plate 94 shown in Fig. 6(B) is performed. In this case, with the breather pipe 95 and the drain pipe 96 inserted into the inlet plate 94, the breather pipe 95 and the drain pipe 96 are hand brazed to the inlet plate 94 in the atmosphere. Next, a joining operation of the inlet plate 94 to the outer panel 92 shown in Fig. 6(C) is performed. In this case, the outer peripheral edge of the inlet plate 94 is MAG (Metal Active Gas) welded to the opening edge of the outer panel 92 while spraying a shielding gas.

[0034] As shown in Fig. 7(A), a manufacturing operation for the inner part 99 is carried out. In this case, inner-related parts such as a mounting part for a fuel pump and a bracket for a vehicle frame are spot-welded to an inner panel 97. As shown in Fig. 7(B), an integration operation for the outer part 91 and the inner part 99 is carried out. In this case, the outer peripheral edge of the outer panel 92 and the outer peripheral edge of the inner panel 97 are mated, and the breather pipe 95 and the drain pipe 96 are inserted into the through holes of the inner panel 97. Then, the outer peripheral edge of the outer panel 92 and the outer peripheral edge of the inner panel 97 are seam-welded to integrate the outer part 91 and the inner part 99.

[0035] As shown in Fig. 7(C), a joining operation of a breather pipe 95 and a drain pipe 96 to an inner panel 97 is performed. In this case, the breather pipe 95 and the drain pipe 96 are hand-brazed to the inner panel 97 in the atmosphere. As shown in Fig. 7(D), a surface treatment operation is performed on the outer panel 92. In the case of a fuel tank 90 made of a steel plate, a painting process is selected as the surface treatment of the outer panel 92. By painting the surface of the outer panel 92, the appearance, weather resistance, and rust resistance of the outer panel 92 are improved. Then, a tank cover 98 is attached to the outer panel 92, and the fuel tank 90 is manufactured.

[0036] The titanium fuel tank shown in this embodiment shares some of the manufacturing equipment with the steel fuel tank because the properties of titanium are closer to iron than to aluminum. First, the individual components of the fuel tank are manufactured. For example, the outer panel 41 and the inner panel 61 are press-formed. At this time, the manufacturing equipment such as the molds and presses for the steel fuel tank 90 can be used for press-forming the outer panel 41 and the inner panel 61, which are the most expensive. Also, the manufacturing equipment for the steel fuel tank 90 can be used for manufacturing some of the peripheral parts of the outer panel 41 and the inner panel 61.

[0037] As shown in Fig. 8(A)-(C), a manufacturing operation of the outer part 32 (a step of manufacturing the outer part) is performed. First, a forming operation of the outer panel 41 shown in Fig. 8(A) is performed. In this case, a shielding gas is sprayed onto the mating surfaces of the panel members 42L, 42R, and the mating surfaces of the panel members 42L, 42R are plasma welded in an oxygen-free environment. In addition, inlet-related parts such as a cover bracket are spot welded to the outer panel 41. For these welding operations, manufacturing equipment for the fuel tank 90 made of steel plate can be used. Note that, in spot welding, the joint surfaces of the members are isolated from the atmosphere, so the effect of oxygen on the titanium outer panel 41 is minimized.

[0038] Next, the joining operation (sub-step of furnace brazing) of the upper breather pipe 51 and the upper drain pipe 52 to the inlet plate 47 shown in Fig. 8(B) is performed. In this case, the inlet plate 47 is housed in a furnace with the upper breather pipe 51 and the upper drain pipe 52 inserted therein, and the upper breather pipe 51 and the upper drain pipe 52 are furnace brazed to the inlet plate 47 in an oxygen-free environment. Since the inlet plate 47 is formed to a size that can be accommodated in the furnace, furnace brazing that is subject to size restrictions can be performed.

[0039] Next, the joining operation (TIG welding sub-step) of the inlet plate 47 to the outer panel 41 shown in Fig. 8(C) is performed. In this case, the outer peripheral edge of the inlet plate 47 is TIG (Tungsten Inert Gas) welded to the opening edge of the outer panel 41 while spraying shielding gas. By partially modifying the welding equipment for the steel plate fuel tank 90, it is possible to perform not only MAG welding but also TIG welding. Therefore, the manufacturing equipment for the steel plate fuel tank 90 can be used for welding the outer panel 41 and the inlet plate 47.

[0040] 9(A)-(C), a manufacturing operation of the inner part 33 (a step of manufacturing the inner part 33) is carried out. First, a forming operation of the inner panel 61 shown in Fig. 9(A) is carried out. In this case, inner-related parts such as mounting parts for a fuel pump and a bracket for a body frame are spot welded to the inner panel 61. For these welding operations, manufacturing equipment for a fuel tank 90 made of steel plate can be used.

[0041] Next, the joining operation (sub-step of furnace brazing) of the lower breather pipe 73 and the lower drain pipe 74 to the inner connection plate 71 shown in Fig. 9(B) is performed. In this case, the inner connection plate 71 is housed in a furnace with the lower breather pipe 73 and the lower drain pipe 74 inserted therein, and the lower breather pipe 73 and the lower drain pipe 74 are furnace brazed to the inner connection plate 71 in an oxygen-free environment. Since the inner connection plate 71 is formed to a size that can be accommodated in the furnace, furnace brazing that is subject to size restrictions can be performed.

[0042] Next, the joining operation (sub-step of TIG welding) of the inner connection plate 71 to the inner panel 61 shown in Fig. 9(C) is performed. In this case, the outer peripheral edge of the inner connection plate 71 is TIG (Tungsten Inert Gas) welded to the opening edge of the inner panel 61 while spraying shielding gas. As described above, by partially modifying the welding equipment for the steel plate fuel tank 90, it is possible to perform not only MAG welding but also TIG welding. Therefore, the manufacturing equipment for the steel plate fuel tank 90 can be used for welding the inner panel 61 and the inner connection plate 71.

[0043] As shown in Fig. 10(A) and (B), an operation of integrating the outer part 32 and the inner part 33 (an integration step) is performed. First, an operation of connecting the first breather hose 81 and the first drain hose 82 to the pipes shown in Fig. 10(A) (a sub-step of connecting) is performed. In this case, the upper breather pipe 51 of the outer part 32 and the lower breather pipe 73 of the inner part 33 are connected via the first breather hose 81. Also, the upper drain pipe 52 of the outer part 32 and the lower drain pipe 74 of the inner part 33 are connected via the first drain hose 82. For the first breather hose 81 and the first drain hose 82, a rubber hose or a resin hose having flexibility and oil resistance is used.

[0044] Next, the joining operation (seam welding sub-step) of the outer panel 41 and the inner panel 61 shown in Fig. 10(B) is performed. In this case, the outer peripheral edge of the outer panel 41 and the inner panel 61 are joined together, and the outer peripheral edge of the outer panel 41 and the inner panel 61 are seam welded together. For the seam welding, the manufacturing equipment for the steel plate fuel tank 90 can also be used. Note that, in seam welding, the joining surfaces of the outer panel 41 and the inner panel 61 are isolated from the atmosphere, so the effect of oxygen on the titanium outer panel 41 and the inner panel 61 is minimized.

[0045] As shown in FIG. 10(C), a surface treatment operation (roughening step) is performed on the outer panel 41. For the titanium fuel tank 30, shot blasting is selected as the surface treatment for the outer panel 41. Titanium has excellent weather resistance and rust resistance, so there is no deterioration in physical properties even without painting, but the surface of the outer panel 41 has processing marks such as press scratches and beads. The processing marks are removed by the shot blasting, and the appearance is improved by the metal surface exposed to the outside. Then, a tank cover 59 is attached to the outer panel 41 to manufacture the fuel tank 30. The tank cover 59 can be the same cover as that of the steel fuel tank 90.

[0046] As described above, according to this embodiment, the outer panel 41 and the inlet plate 47 are formed separately, and the inner panel 61 and the inner connection plate 71 are formed separately. Therefore, even if furnace brazing is suitable for titanium but has size restrictions, furnace brazing can be used to join pipes to the inlet plate 47 and the inner connection plate 71. In this way, it is possible to flexibly select an operation that satisfies manufacturing restrictions due to materials and sizes. In addition, by integrating the outer part 32 and the inner part 33, the fuel tank 30 with piping passing through the tank is manufactured. A large tank cover that covers the entire tank is not required to maintain the appearance, and the capacity of the fuel tank 30 is not reduced without a double structure.

[0047] The fuel tank of this embodiment can also be applied as appropriate to other straddle-type vehicles such as buggy-type three-wheeled motor vehicles. Here, the term "saddle-type vehicle" is not limited to vehicles in general on which a rider sits astride a seat, but also includes scooter-type vehicles on which a rider does not sit astride a seat.

[0048] In addition, although the present embodiment describes a method for manufacturing a titanium fuel tank, this manufacturing method can also be applied to the manufacture of fuel tanks made of other materials, and is particularly effective for the manufacture of fuel tanks made of materials that require joining in an oxygen-free or low-oxygen environment.

[0049] In this embodiment, the breather pipe is formed from four parts, the upper breather pipe, the first breather hose, the lower breather pipe, and the second breather hose, but the breather pipe may be formed from one part. Similarly, in this embodiment, the drain pipe is formed from four parts, the upper drain pipe, the first drain hose, the lower drain pipe, and the second drain hose, but the drain pipe may be formed from one part.

[0050] In addition, in this embodiment, the outer part and the inner part are made of titanium, but some of the outer part and the inner part may be made of other materials. For example, the upper breather pipe, the lower breather pipe, the upper drain pipe, and the lower drain pipe may be made of iron.

[0051] In addition, in this embodiment, joining methods such as plasma welding, spot welding, furnace brazing, TIG welding, and seam welding are used, but other joining methods in which the effect of oxygen on the objects to be joined is less can be used.

[0052] As described above, the fuel tank (30) of the present embodiment includes the outer part (32) having the outer panel (41) forming the outer shell of the tank and the inlet plate (47) formed separately from the outer panel, the inner part (33) having the inner panel (61) forming the inner shell of the tank and the inner connection plate (71) formed separately from the inner panel, and the piping (first breather hose 81, first drain hose 82) passing through the inside of the outer panel and the inner panel and connecting the inlet plate and the inner connection plate, and the inlet plate is joined to the outer panel, the inner connection plate is joined to the inner panel, and the inner panel is joined to the outer panel. According to this configuration, the outer panel and the inlet plate are formed separately, and the inner panel and the inner connection plate are formed separately. Therefore, even if the work is suitable for the material of each member, but there is a size restriction on the work, the work can be performed on the inlet plate and the inner connection plate. In this way, it is possible to flexibly select a work that satisfies manufacturing restrictions due to the material and size. In addition, by integrating the outer and inner parts, a fuel tank can be manufactured with piping running through it. A large tank cover that covers the entire tank is no longer necessary to maintain the appearance, and the fuel tank capacity is not reduced because it does not have a double structure.

[0053] In the fuel tank of this embodiment, the outer part and the inner part are made of titanium or a titanium alloy. With this configuration, the members can be joined together in an environment suitable for titanium or a titanium alloy, making it possible to reduce the weight of the fuel tank and improve weather resistance and rust resistance.

[0054] In the fuel tank of this embodiment, an opening (67) is formed in the inner panel along the outer circumferential edge (75) of the inner connection plate, the outer circumferential edge of the inner connection plate protrudes from the opening to the outside of the tank, the opening edge (68) of the inner panel protrudes to the outside of the tank, and the outer circumferential edge of the inner connection plate is joined to the opening edge of the inner panel. With this configuration, the outer circumferential edge of the inner connection plate can be easily and reliably welded to the opening edge of the inner panel from outside the tank.

[0055] In the fuel tank of this embodiment, the outer part has outer pipes (upper breather pipe 51, upper drain pipe 52) extending from the inlet plate into the tank, and the inner part has inner pipes (lower breather pipe 73, lower drain pipe 74) penetrating the inner connection plate, with piping connected to the outer pipes and inner pipes, the outer pipe joined to the inlet plate, and the inner pipe joined to the inner connection plate. According to this configuration, the inlet plate and the outer pipe are formed separately, and the inner connection plate and the inner pipe are formed separately. For this reason, it is possible to use a joining method suitable for the material and size of the inlet plate and the outer pipe, and a joining method suitable for the material and size of the inner connection plate and the inner pipe.

[0056] In the fuel tank of this embodiment, when facing the inner connection plate, the end of the inner pipe protruding outside the tank is located inside the outer periphery of the inner connection plate. With this configuration, the end of the inner pipe protruding outside the tank does not get in the way when joining the inner connection plate to the inner panel.

[0057] The manufacturing method of the fuel tank of this embodiment includes the steps of manufacturing an outer part by joining an inlet plate formed separately from the outer panel to an outer panel forming the outer shell of the tank, manufacturing an inner part by joining an inner connection plate formed separately from the inner panel to an inner panel forming the inner shell of the tank, and connecting the inlet plate and the inner connection plate with a pipe passing through the inside of the tank, and joining the outer panel and the inner panel to integrate them. According to this configuration, the outer panel and the inlet plate are formed separately, and the inner panel and the inner connection plate are formed separately. Therefore, even if the work is suitable for the material of each member, but there is a size restriction on the work, the work can be performed on the inlet plate and the inner connection plate. In this way, it is possible to flexibly select a work that satisfies the manufacturing restrictions due to the material and size. Furthermore, by integrating the outer part and the inner part, a fuel tank with a pipe passing through the tank is manufactured. A tank cover that covers the entire tank is not required to maintain the appearance, and the capacity of the fuel tank is not reduced without a double structure.

[0058] In the method for manufacturing a fuel tank according to the present embodiment, the step of manufacturing an outer part includes a sub-step of furnace brazing an outer pipe to an inlet plate and a sub-step of TIG welding the inlet plate to an outer panel, the step of manufacturing an inner part includes a sub-step of furnace brazing an inner pipe to an inner connection plate and a sub-step of TIG welding the inner connection plate to the inner panel, and the step of integrating includes a sub-step of connecting the outer pipe and the inner pipe with piping and a sub-step of seam welding the outer panel and the inner panel. With this configuration, the fuel tank can be manufactured satisfactorily even if each part is made of a material that is difficult to weld in the atmosphere.

[0059] In the manufacturing method of the fuel tank of this embodiment, the outer part and the inner part are made of titanium or titanium alloy, and the method includes a step of roughening the surface of the outer panel joined to the inner panel by performing a shot blasting process. This configuration makes it possible to eliminate processing marks such as scratches and welding marks on the surface of the outer panel. In addition, there is no need to cover the surface of the outer panel with a coating or the like, and the metal surface made of titanium or titanium alloy can be exposed to the outside to improve the appearance. In addition, the weight of the fuel tank can be reduced and the weather resistance and rust resistance can be improved.

[0060] Although the present embodiment has been described, other embodiments may be made by combining the above-described embodiments and modifications in whole or in part.

[0061] In addition, the technology of the present invention is not limited to the above examples, and may be modified, substituted, or altered in various ways without departing from the spirit of the technical idea. Furthermore, if the technical idea can be realized in a different way due to the progress of technology or a different technology derived therefrom, the invention may be implemented using that method. Therefore, the claims cover all embodiments that may be included within the scope of the technical idea. [Explanation of symbols]

[0062] 30: Fuel tank 32: Outer parts 33: Inner parts 41: Outer panel 47: Inlet plate 51: Upper breather pipe (outer pipe) 52: Upper drain pipe (outer pipe) 61: Inner panel 67 :Aperture 68: Opening edge 71: Inner connection plate 73: Lower breather pipe (inner pipe) 74: Lower drain pipe (inner pipe) 75: Outer edge 81: First breather hose (piping) 82: First drain hose (piping)

Claims

1. an outer part including an outer panel forming an outer shell of a tank, an inlet plate formed separately from the outer panel, and an outer pipe extending from the inlet plate into the tank; an inner part including an inner panel forming an inner shell of a tank, an inner connection plate formed separately from the inner panel, and an inner pipe penetrating the inner connection plate; a pipe passing through the inside of the outer panel and the inner panel and connecting the inlet plate and the inner connection plate, the inlet plate is joined to the outer panel, the inner connection plate is joined to the inner panel, and the inner panel is joined to the outer panel, the piping is connected to the outer pipe and the inner pipe, the outer pipe is joined to the inlet plate, and the inner pipe is joined to the inner connection plate; 1. A fuel tank, wherein the outer part and the inner part are made of titanium or a titanium alloy which require joining in an oxygen-free or low-oxygen environment.

2. An opening is formed in the inner panel along an outer circumferential edge of the inner connection plate, and the outer circumferential edge of the inner connection plate protrudes from the opening to the outside of the tank, 2. The fuel tank according to claim 1, wherein an opening edge of the inner panel projects outside the tank, and an outer periphery of the inner connecting plate is joined to the opening edge of the inner panel.

3. 2. The fuel tank according to claim 1, wherein, when facing the inner connection plate, an end portion of the inner pipe protruding outside the tank is positioned inside an outer circumferential edge of the inner connection plate.

4. manufacturing an outer part by joining an inlet plate formed separately from an outer panel to an outer panel that forms an outer shell of a tank; manufacturing an inner part by joining an inner connection plate formed separately from an inner panel to an inner panel that forms an inner shell of the tank; connecting the inlet plate and the inner connection plate with a pipe passing through a tank, and joining the outer panel and the inner panel together; and performing a shot blasting process on the surface of the outer panel joined to the inner panel to roughen the surface of the outer panel. the step of manufacturing the outer part includes a sub-step of furnace brazing an outer pipe to the inlet plate, and a sub-step of TIG welding the inlet plate to the outer panel, The step of manufacturing the inner part includes the sub-steps of furnace brazing an inner pipe to the inner connection plate and TIG welding the inner connection plate to the inner panel, the integrating step includes a sub-step of connecting the outer pipe and the inner pipe with the piping, and a sub-step of seam-welding the outer panel and the inner panel, The method for manufacturing a fuel tank, wherein the outer part and the inner part are made of titanium or a titanium alloy which require joining in an oxygen-free or low-oxygen environment.

5. an outer part including an outer panel forming an outer shell of a tank and an inlet plate formed separately from the outer panel; an inner part including an inner panel forming an inner shell of a tank and an inner connection plate formed separately from the inner panel; a pipe passing inside the outer panel and the inner panel and connecting the inlet plate and the inner connection plate, the inlet plate is joined to the outer panel, the inner connection plate is joined to the inner panel, and the inner panel is joined to the outer panel, A fuel tank characterized in that an opening is formed in the inner panel along the outer peripheral edge of the inner connection plate, the outer peripheral edge of the inner connection plate is joined to the edge of the opening of the inner panel, and the inner connection plate is exposed to the outside of the tank and forms part of the inner shell of the tank.

6. A fuel tank as described in claim 5, characterized in that the outer peripheral edge of the inner connecting plate protrudes outside the tank from the opening, and the opening edge of the inner panel protrudes outside the tank.

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