JP2010221747A - Fuel tank structure and fuel tank - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the stiffness fatigue characteristics of a fuel tank to inner pressure, and to materialize weight reduction. <P>SOLUTION: In a metallic fuel tank manufactured by press molding an upper shell 1 and a lower shell 2 and joining those each other, part wherein deformation amount under a positive pressure load is large, is wound and fastened with a fastening band 5. At part wherein deformation amount under a negative pressure load is large, recessed portions 6 are provided on the upper shell 1 and the lower shell 2 when press molding, and center axes of the recessed portions are made to be coincident with each other when joined. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a fuel tank structure and a fuel tank having the structure.

  The fuel tank attached to the automobile is subject to internal pressure fluctuations under the actual use environment, and the fuel tank is repeatedly expanded and contracted accordingly. Therefore, for example, if the thickness of the fuel tank body is reduced for the purpose of weight reduction, the rigidity of the fuel tank decreases, so the amount of deformation due to internal pressure fluctuation increases, and the peripheral parts and the fuel tank come into contact with each other. It is also conceivable that fatigue accumulates at a site that becomes the starting point of deformation, leading to fatigue failure.

  From the above, in order to realize weight reduction, it is necessary to increase the rigidity of the fuel tank accordingly. On the other hand, Patent Document 1 discloses a method in which the bottom surfaces of the upper shell and the lower shell are connected to each other by a stay to suppress deformation of the tank when subjected to internal pressure. Further, Patent Document 2 discloses a fuel tank whose pressure resistance is improved by making the fuel tank shape into a donut shape.

Japanese Patent Laid-Open No. 2005-162010 Japanese Patent Laid-Open No. 9-309347

  However, the prior art has the following problems. In the method disclosed in Patent Document 1, not only the component configuration becomes complicated and the productivity is remarkably lowered, but also the number of welding points that are likely to become the starting point of fatigue failure increases, so that the fatigue failure starting from the welded portion The possibility of is increased.

  Further, in the method disclosed in Patent Document 2, it is necessary to make the shape of the fuel tank into a donut shape, and the degree of freedom of the shape of the fuel tank is low and the center portion is hollow, so that the amount of the tank This means that the capacity is reduced, and is a disadvantageous shape in a fuel tank that is required to secure the maximum capacity in a limited space.

  The present invention has been made in view of the above-described problems, and realizes weight reduction of the fuel tank by suppressing the decrease in the degree of freedom of shape as much as possible and improving the rigidity of the fuel tank by a relatively simple method. The purpose is that.

  In order to solve the above problems, the fuel tank structure of the present invention includes (1) a fuel tank in which an upper shell and a lower shell formed by press molding are joined, and is disposed along the outer surface of the fuel tank. It is characterized by having a tightening band that presses the upper shell and the lower shell in a direction to approach each other.

  (2) In the configuration of (1), an upper-side recess that protrudes toward the lower shell is formed on the outer surface of the upper shell, and a lower-side recess that protrudes toward the upper shell is formed on the outer surface of the lower shell In addition, when viewed in the joining direction of the upper shell and the lower shell, the center axis of the upper side concave portion and the lower side concave portion can be configured to coincide with each other.

  (3) In the configuration of (2), a connection member that connects the bottom surface portion of the upper-side recess and the bottom surface portion of the lower-side recess can be provided.

  (4) In the configuration of (1), the fuel tank expands in accordance with a change in pressure inside the tank, and a tightening band can be disposed at a portion where the displacement amount becomes maximum during the expansion.

  (5) In the configuration of (4), the position where the fastening band is disposed can be determined based on the pressure analysis result by the finite element method.

  (6) In the configuration of (2) or (3), the band expands and contracts according to the pressure change inside the tank, and a tightening band is disposed at a portion where the displacement amount is maximum during expansion, and the displacement occurs during contraction. The upper side concave portion and the lower side concave portion can be formed in a portion where the amount is maximum.

  (7) In the configuration of (6), based on the pressure analysis result by the finite element method, the position where the fastening band is disposed, the position where the upper side concave portion and the lower side concave portion are formed can be determined.

  (8) A fuel tank provided with the fuel tank structure of (1) to (7).

  According to the present invention, deformation of the weakest portion of the fuel tank loaded with the internal pressure can be suppressed, the rigidity can be increased efficiently, and the fatigue characteristics can be improved. As a result, the thickness of the fuel tank body can be reduced, and a low-cost and lightweight fuel tank can be provided.

Perspective view of fuel tank It is a top view of a fuel tank. It is sectional drawing of a fuel tank It is sectional drawing of a recessed part. 10 is a cross-sectional view of a recess according to Modification 1. FIG. 10 is a cross-sectional view of a recess according to Modification 2. FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows an embodiment of a metal fuel tank according to claim 1 of the present invention, and this fuel tank has a high deformation suppressing effect especially for positive pressure. The X axis, the Y axis, and the Z axis indicate three different axes that are orthogonal to each other.

  An upper flange 3 </ b> A is formed at the lower end of the upper shell 1, and a lower flange 3 </ b> B is formed at the upper end of the lower shell 2. The upper side flange portion 3A and the lower side flange portion 3B are joined by seam welding. This joining method is not limited to seam welding, and other joining methods such as laser welding, brazing, adhesive, and caulking can also be used. The fuel tank is fixed by a fixed band 4 in a state of being suspended from the floor of the vehicle body. The method of fixing the fuel tank is not limited to this, and for example, a method of fixing the upper side flange portion 3A and the lower side flange portion 3B to the floor of the vehicle body with bolts may be used.

  Further, the fuel tank expands under the influence of a temperature change outside the fuel tank. In order to suppress deformation when the fuel tank expands, that is, when a positive pressure is applied, the fuel tank is wound with a tightening band 5. By placing and tightening the fastening band 5 along the outer surfaces of the upper shell 1 and the lower shell 2, the upper shell 1 and the lower shell 2 are made to approach each other against the expansion force of the fuel tank (one direction in the Z-axis direction). Can be pressed.

  The position and number of the tightening bands are not particularly defined, but a higher deformation suppressing effect can be obtained by disposing the tightening band in a portion where the deformation of the fuel tank is increased when a positive pressure is applied. Further, although the material, plate thickness, and width of the fastening band 5 are not particularly defined, the band strength can be increased by increasing the strength of the material or increasing the plate thickness or plate width. Thereby, a higher deformation suppressing effect can be obtained.

  FIG. 2 shows an embodiment of a metal fuel tank according to claim 2 of the present invention. 2A is a plan view of the fuel tank, and FIG. 2B is a cross-sectional view of the fuel tank taken along the plane AA ′. The fuel tank expands and contracts under the influence of a temperature change outside the tank. With reference to these drawings, the upper shell 1 is formed with an upper-side recess 6 </ b> A that protrudes toward the lower shell 2. The upper-side recess 6A is formed in a truncated cone shape whose inner diameter gradually decreases as it approaches the lower shell 2. The lower shell 2 is formed with a lower side recess 6 </ b> B that protrudes toward the upper shell 1. The lower side recess 6B is formed in a truncated cone shape in which the inner diameter dimension gradually decreases as the upper shell 1 is approached. These upper side recessed part 6A and lower side recessed part 6B are shape | molded by press work.

  The fuel tank contracts due to the negative pressure applied, but at this time, the upper side recess 6A and the lower side recess 6B abut each other in the Z-axis direction, and further deformation of the upper shell 1 and the lower shell 2 is suppressed. Therefore, a high deformation suppression effect can be obtained even for negative pressure.

  Further, when viewed in the Z-axis direction, the central axes of the upper-side concave portion 6A and the lower-side concave portion 6B coincide with each other. Thereby, when the fuel tank is contracted, the upper side concave portion 6A and the lower side concave portion 6B can be reliably brought into contact with each other, and deformation can be suppressed.

  2A and 2B show a case where the number of the upper-side recesses 6A and the lower-side recesses 6B is one, the number and positions of the recesses are not limited to this. By forming the upper side concave portion 6A and the lower side concave portion 6B in a portion where the deformation of the fuel tank is increased when a negative pressure is applied, a higher deformation suppressing effect can be obtained.

  FIG. 3 is a cross-sectional view of the upper-side recess 6A and the lower-side recess 6B. Since the upper-side recess 6A and the lower-side recess 6B are formed by pressing, in order to obtain a deeper recess (depth in the Z-axis direction), the hole diameter of the recess is increased and R flowing into the recess is used. Need to be bigger. However, since the internal volume of the fuel tank is reduced by the volume of the recess, it is not desirable to make the hole diameter or R of the recess too large. Therefore, the shape of the concave portion is determined by how much press formability and the decrease in the internal volume are allowed. As long as the center axes of the upper side concave portion 6A and the lower side concave portion 6B are coincident with each other. The shape is not particularly limited. Therefore, for example, the following modifications are also included in the present invention.

  FIG. 4 is a partial cross-sectional view of the fuel tank of the first modification, and corresponds to FIG. Except for the fact that the upper-side recess 6A and the lower-side recess 6B are not in contact with each other, the configuration is the same as that of the fuel tank shown in FIG. Referring to FIG. 4, the depths of upper side recess 6A and lower side recess 6B are smaller than those of the embodiment of FIG. 2A, and the bottom surfaces of upper side recess 6A and lower side recess 6B are mutually non-expanded and non-contracted. It is separated.

  In the above-described configuration, when a negative pressure is applied to the fuel tank, the bottom surfaces of the upper-side recess 6A and the lower-side recess 6B come close to each other and come into contact with each other, so that further deformation can be suppressed. Therefore, in the initial state shown in FIG. 3, it is not always necessary that the bottom surfaces of the upper-side recess 6A and the lower-side recess 6B are in contact with each other, and there is no problem as long as the distance between them is within the contraction range of the fuel tank.

  With reference to FIG. 5, an embodiment of a metal fuel tank according to claim 3 of the present invention (hereinafter referred to as modified example 2) will be described. FIG. 5 is a partial cross-sectional view of the fuel tank of the second modification, and corresponds to FIGS. 3 and 4. The fuel tank shown in Modification 2 has the upper-side recess 6A and the lower-side recess 6B joined using joining means, and the other configuration is the same as that of the fuel tank of FIG. As the joining means, welding, brazing, an adhesive, or bolt joining can be used.

  According to the configuration of the modification example 2, when the fuel tank receives a positive pressure, the upper side concave portion 6A and the lower side concave portion 6B can be prevented from separating. Thereby, a deformation | transformation suppression effect can be heightened. In addition, the same effects as the configuration shown in FIG. 2 can be obtained.

  The fuel tank according to claim 4 is particularly effective for a fuel tank having a large deformation amount when a positive pressure is applied, and is fastened to a portion where the displacement amount becomes maximum when the fuel tank expands. A band 5 is arranged. The part where the displacement amount is maximum can be specified by performing pressure analysis in which a positive pressure is applied to the fuel tank using commercially available finite element method analysis software. Thereby, it is possible to effectively suppress the deformation of the weakest part with respect to the positive pressure of the fuel tank, and a higher deformation suppressing effect can be obtained. In the above-described configuration, the finite element method is used. However, the present invention is not limited to this, and pressure analysis can be performed using other methods such as a boundary element method and a finite difference method.

  The fuel tank according to claim 6 is effective for a fuel tank having a large deformation amount when a positive pressure and a negative pressure are applied, and the displacement amount becomes maximum when the fuel tank expands. The fastening band 5 is disposed at the site, and the upper side recess 6A and the lower side recess 6B are formed at the site where the displacement amount becomes maximum when the fuel tank contracts. The portion where the displacement amount is maximum can be specified by performing pressure analysis in which a positive pressure and a negative pressure are loaded into the fuel tank using commercially available finite element method analysis software. Thereby, it is possible to effectively suppress the deformation of the weakest part with respect to the positive pressure and the negative pressure of the fuel tank, and a higher deformation suppressing effect can be obtained. In the above-described configuration, the finite element method is used. However, the present invention is not limited to this, and analysis can also be performed using other methods such as a boundary element method and a finite difference method.

  The fuel tank of the present invention can accommodate various fuels necessary for driving the internal combustion engine of the vehicle, such as gasoline fuel, diesel fuel, and ethanol fuel. Further, the present invention can be applied not only to a vehicle that uses only the internal combustion engine as a power source, but also to a hybrid vehicle that uses both the internal combustion engine and a secondary battery or a fuel cell as power sources.

  Examples of the present invention will be described below. The fuel tank material used for the test has a plate thickness of 0.8 mm, and in mass%, C is 0.0015%, Si is 0.01%, Mn is 0.15%, P is 0.01%, S Is a steel plate in which Sn-8% Zn plating is applied to the surface of a mild steel plate having a tensile strength of 270 MPa, containing 0.01% of Ti, 0.06% of Ti and 0.0005% of B. The steel plate was press-formed to form an upper shell and a lower shell, and these flange portions were overlapped and joined by seam welding to form a fuel tank. The created fuel tank has an approximately rectangular parallelepiped shape, with a long side of 800 mm, a short side of 600 mm, and a height of 100 mm.

  This fuel tank was used as a comparative example and defined as tank A. Tank B is a fuel tank in which a winding band made of a mild steel plate having a plate thickness of 1.6 mm and a width of 30 mm is wound around tank A at a position one third of the length of the fuel tank. Tank C is formed by pressing a recess of 49.2mm in depth into the upper and lower positions of the fuel tank in the longitudinal direction and in the short side direction, so that the center axes of the recesses are aligned. Yes.

  Further, the same band as that used for the tank B is wound around a position of one third in the longitudinal direction. The tank D joins the concave bottoms of the tank C by spot welding. For the tank E, first, a pressure analysis for applying a positive pressure to the tank having the same shape as the tank A was performed using commercially available finite element method analysis software. As a result, since the amount of displacement becomes maximum at the center position of the fuel tank, the same band as that used for the tank B is wound around the portion.

  For the tank F, first, pressure analysis was performed by applying a positive pressure and a negative pressure in a tank having the same shape as the tank A, using commercially available finite element method analysis software. As a result, both the positive pressure and the negative pressure have the maximum displacement at the center position of the fuel tank. Therefore, the same band as that used for the tank B is tightened around the portion, and the same recess as the tank C is formed. Yes. For the tank G, first, pressure analysis was performed by applying a positive pressure and a negative pressure in a tank having the same shape as the tank A, using commercially available finite element method analysis software. As a result, both the positive pressure and the negative pressure have the maximum displacement at the center position of the fuel tank, so the same band as that used for the tank B is tightened around the portion, and the same recess as the tank C is formed. The bottom surfaces of the recesses are joined by spot welding.

  These fuel tanks are loaded with a positive pressure of 11 kPa and a negative pressure of 10 kPa, and the maximum displacement at that time is shown in Table 1. In order to avoid interference with peripheral parts, the maximum displacement is 10 mm or less, and if it is larger, it is rejected. The tank A is a comparative example, and it can be seen that the displacement amount is large and the standard is not satisfied because the tank has insufficient rigidity for both positive pressure and negative pressure.

  The tank B is an example of the present invention effective mainly for a tank to which a positive pressure is applied, and it can be seen that by tightening the band, the tank B has a high deformation suppressing effect against the positive pressure and satisfies the standard. The tank C is an example of the present invention that is effective for a tank to which positive pressure and negative pressure are applied, and is capable of suppressing deformation against positive pressure and negative pressure by winding a band and having a recess. It can be seen that each criterion is satisfied. The tank D is an example of the present invention effective for a tank to which a positive pressure and a negative pressure are loaded, and has a concave portion joined to the bottom surface by tightening the band, and thereby against the positive pressure and the negative pressure. It can be seen that it has a high deformation suppressing effect and satisfies each standard.

  The tank E is an example of the present invention which is effective mainly for a tank to which positive pressure is applied. A finite element method analysis software is used to identify a portion where deformation is maximized in advance, and an effective band is applied to the portion. It can be seen that by tightening, the deformation has a higher deformation suppressing effect than the tank B with respect to the positive pressure, and the standard is satisfied. The tank F is an example of the present invention that is effective for a tank to which positive pressure and negative pressure are applied. Using a finite element method analysis software, a portion where deformation is maximized is specified in advance, and deformation is maximized by positive pressure. By tightening the band around the part and having the recess in the part where deformation is maximized by negative pressure, it has a higher deformation suppressing effect than the tank C against positive pressure and negative pressure, It can be seen that the standard is satisfied.

  The tank G is an example of the present invention that is effective for a tank to which positive pressure and negative pressure are applied. A finite element method analysis software is used to identify a portion where deformation is maximized in advance, and the deformation is maximized by positive pressure. By tightening the band around the area where the pressure becomes, and having the recess where the bottom surface is joined at the area where deformation is maximized by negative pressure, the effect of suppressing deformation even higher than that of the tank D against positive pressure and negative pressure is achieved. It can be seen that each standard is satisfied.

○：有り ×：無し

○: Yes ×: No

Claims (8)

In the fuel tank structure in which the upper shell and the lower shell formed by press molding are joined,
A fuel tank structure comprising a fastening band that is arranged along an outer surface of the fuel tank to press the upper shell and the lower shell in a direction in which the upper shell and the lower shell are brought closer to each other. 2. The fuel tank structure according to claim 1, wherein an upper side concave portion projecting toward the lower shell is formed on an outer surface of the upper shell, and a lower side projecting toward the upper shell is formed on an outer surface of the lower shell. A fuel tank structure in which a recess is formed, and the central axes of the upper-side recess and the lower-side recess coincide with each other when viewed in the joining direction of the upper shell and the lower shell.   3. The fuel tank structure according to claim 2, further comprising a connection member that connects a bottom surface portion of the upper-side concave portion and a bottom surface portion of the lower-side concave portion. 4.   2. The fuel tank structure according to claim 1, wherein the fuel tank expands in response to a change in pressure inside the tank, and a tightening band is disposed at a portion where the displacement amount becomes maximum during the expansion.   The fuel tank structure according to claim 4, wherein a position where the fastening band is arranged is determined based on a pressure analysis result by a finite element method.   The fuel tank expands and contracts in response to a change in pressure inside the tank, and a fastening band is disposed at a portion where the displacement amount is maximized during expansion, and the upper portion is disposed at a portion where the displacement amount is maximized during contraction. 4. The fuel tank structure according to claim 2, wherein a side recess and the lower side recess are formed.   7. The fuel tank structure according to claim 6, wherein a position at which the fastening band is disposed, and a position at which the upper-side recess and the lower-side recess are formed are determined based on a pressure analysis result by a finite element method. .   A fuel tank comprising the fuel tank structure according to any one of claims 1 to 7.

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