JP7304331B2 - FUEL TANK AND FUEL TANK MANUFACTURING METHOD - Google Patents

Description

The present invention relates to a fuel tank and a method of manufacturing a fuel tank.

A fuel tank made of resin is known in which a tank lower and a tank upper are integrally formed by joining together in the circumferential direction (Patent Document 1). A flange portion and a recessed portion are provided on the outside of the tank lower and the tank upper over the circumferential direction.

When manufacturing the fuel tank, first, a tank lower and a tank upper are formed by, for example, injection molding. Then, the ends of the side walls of the tank lower and the tank upper are butted against each other, and a jig is inserted into the recess to apply vibration to the tank lower and the tank upper and press them vertically (vibration welding) to join them together. be able to.

JP 2006-182093 A

As described above, when joining, the ends of the side walls of the tank lower and the tank upper serve as welded portions (joint surfaces). When the tank lower and tank upper are injection-molded, there is a risk that voids and sink marks will occur in the vicinity of the end portions of the side walls of both of them, since the flow end portion of the both becomes the flow end portion of the resin. If voids or sink marks occur near the end portions of the side walls of the tank lower and tank upper, there is a high risk of joint failure during jointing, resulting in problems such as permeation of fuel and reduced joint strength.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a fuel tank and a method for manufacturing a fuel tank that can prevent voids from occurring in joints and increase joint strength.

In order to solve the above-mentioned problems, the present invention provides a resin-made fuel tank in which a tank lower and a tank upper formed by injection molding are welded together along the entire circumferential direction at their peripheral end portions , and the tank lower is and a joint portion formed wider than the side wall in the plate thickness direction and projecting outward from the end portions of the side wall of the tank upper, and further projecting outward from the joint portion through a constricted portion. Each has a flange portion and a concave portion formed between the outer surface of the side wall and the flange portion and into which a jig used for welding is inserted , and the opposing joint portions are welded together. , the cross-sectional area of a portion of the joint portion corresponding to the recess is smaller than the cross-sectional area of the flange portion, and the constricted portion is thicker than the joint portion between the joint portion and the flange portion. It is characterized by having a smaller width .

Further, the present invention provides a molding process for molding a resin tank lower and a tank upper by injection molding, a joint provided at an end of a side wall of the tank lower, and a joint provided at an end of the side wall of the tank upper. and a joining step of joining the joints by welding . A joint portion that is formed wide in the thickness direction and protrudes outward, a flange portion that protrudes further outward from the joint portion through a constricted portion, and is formed between the outer surface of the side wall and the flange portion. and a concave portion into which a jig used for welding is inserted , and in the forming step, the cross-sectional area of a portion of the joint portion corresponding to the concave portion is made larger than the cross-sectional area of the flange portion. It is characterized in that the constricted portion is formed between the joint portion and the flange portion and has a thickness smaller than that of the joint portion .

According to the present invention, since the cross-sectional area of the portion of the joint corresponding to the recess is smaller than the cross-sectional area of the flange, the fluidity of the resin near the joint is improved during molding. As a result, it is possible to prevent voids and sink marks from occurring in the joints during molding of the tank lower and tank upper. Therefore, when joining the tank lower and the tank upper, it is possible to prevent the occurrence of voids at or in the vicinity of the welded portion, and the joining can be performed favorably. In addition, since the joint portion is formed wider than the side wall, the welding area can be increased and the joint strength can be increased.

Moreover, it is preferable that the joint portion is perpendicular to the side wall.

According to the present invention, it is possible to increase the fluidity of the resin at the joints during molding of the tank lower and the tank upper, thereby further suppressing the occurrence of voids and sink marks.

According to the fuel tank and the fuel tank manufacturing method of the present invention, it is possible to prevent the occurrence of voids in the joint and increase the joint strength.

1 is a perspective view of a fuel tank according to an embodiment of the invention; FIG. FIG. 3 is a cross-sectional view around a joint portion of the fuel tank according to the present embodiment; FIG. 4 is a cross-sectional view of the tank upper according to the present embodiment before joining; 4 is a cross-sectional view of the tank upper according to Comparative Example 1 before joining; FIG. FIG. 11 is a cross-sectional view of a tank lower and a tank upper according to Comparative Example 2 before they are joined; FIG. 11 is a cross-sectional view of a fuel tank after joining according to Comparative Example 2;

Embodiments of the present invention will be described with reference to the drawings as appropriate. As shown in FIG. 1, a fuel tank 1 according to the present embodiment is a hollow container made of resin for storing fuel therein. The fuel tank 1 is formed by joining a tank lower 2 and a tank upper 3 together in the circumferential direction.

The tank lower 2 and the tank upper 3 are formed of a substantially rectangular bottom portion 10 and four side walls 11 rising from the peripheral edge of the bottom portion 10 . Although the tank lower 2 and the tank upper 3 are made of a single-layer polyamide resin in this embodiment, they may be made of other resins or may have a multi-layer structure.

As shown in FIG. 2, the ends of the tank lower 2 and the tank upper 3 are welded together in the circumferential direction. Since the ends of the tank lower 2 and the tank upper 3 have substantially the same shape, the tank upper 3 will be described as an example. The tank upper 3 has a side wall 11 , a joint portion 12 , a flange portion 13 , a recessed portion 14 and a constricted portion 15 .

The side wall 11 is a wall of the fuel tank 1, and is formed with a generally uniform plate thickness. The joint portion 12 is formed at the end portion of the side wall 11 and is a portion that is welded to the joint portion 12 of the opposing tank lower 2 . The joint portion 12 is formed along the entire circumferential direction of the tank upper 3 . The width of the joint 12 is larger than the width (thickness) of the side wall 11 . That is, the joint portion 12 has a constant thickness and extends from the inner surface 11a of the side wall 11 to the side of the outer surface 11b. Also, the joint portion 12 protrudes only outward from the side wall 11 and does not protrude inward from the inner surface 11a. The width of the joint portion 12 may be appropriately set, but in this embodiment, it is about twice the width of the side wall 11 .

The flange portion 13 is a portion that protrudes further laterally (outward) from the joint portion 12 . Although the shape of the flange portion 13 is not particularly limited, it exhibits a substantially trapezoidal shape in this embodiment. The thickness of the flange portion 13 is greater than the thickness of the joint portion 12 . The flange portion 13 is formed along the entire circumferential direction of the tank upper 3 . A void V is formed inside the flange portion 13 .

The recess 14 is a groove formed between the outer surface 11 b of the side wall 11 and the flange portion 13 . The concave portion 14 is a portion into which a jig is inserted during vibration welding, which will be described later. Constricted portion 15 is formed between joint portion 12 and flange portion 13 .

As shown in FIG. 2, the tank lower 2 and the tank upper 3 are integrated by welding the ends of the side walls 11 to each other. That is, the joint surfaces of the opposing joint portions 12, 12 are welded and integrated over the entire width direction and the entire circumferential direction. The flange portions 13, 13 may be welded to each other, or may be spaced apart with a gap as in the present embodiment.

Of the joint portion 12 (the portion surrounded by the dotted line in FIG. 2), the cross-sectional area of the portion S (shaded portion) corresponding to the recess 14 is smaller than the cross-sectional area of the flange portion 13 . The cross-sectional area shown here is the cross-sectional area of each part with respect to the vertical direction.

Next, a method for manufacturing the fuel tank according to this embodiment will be described. In the fuel tank manufacturing method according to the present embodiment, a molding process, a butting process, and a joining process are performed. The molding process is a process of molding the tank lower 2 and the tank upper 3 . In the molding process, for example, the tank lower 2 and the tank upper 3 are molded by injection molding while applying a holding pressure with a predetermined pressure. Voids V are generated inside the flange portion 13 by the molding process. The state of occurrence of voids V will be described later.

FIG. 3 is a cross-sectional view of the tank upper according to the present embodiment before joining. A step formed between the joint surface 12a of the joint portion 12 and the bottom surface 13a of the flange portion 13 before the joining step is a portion that serves as a welding margin during welding. The joint portion 12 is a portion surrounded by a joint surface 12a, an inner surface 12b, an imaginary outer surface 12c, and an imaginary upper surface 12d. The joint surface 12a is a portion that becomes an end surface (lower surface) of the joint portion 12 and is flat across the width direction. The inner surface 12b is a portion that extends flush with the inner surface 11a of the side wall 11 . The imaginary outer surface 12c is a portion that rises perpendicularly to the joint surface 12a from the outer edge of the joint surface 12a. 12 d of imaginary upper surfaces are parts which contact the bottom part 14a of the recessed part 14, and become parallel to the joint surface 12a. Even before the joining step, the cross-sectional area of the portion S (shaded portion) corresponding to the concave portion 14 in the joint portion 12 (the portion surrounded by the dotted line in FIG. 3) is smaller than the cross-sectional area of the flange portion 13. It's becoming A portion S of the joint portion 12 corresponding to the concave portion 14 is a portion surrounded by the joint surface 12a, the virtual outer surface 12c, the virtual upper surface 12d, and the virtual inner surface 12e. The imaginary inner surface 12 e is a portion that is flush with the outer surface 11 b of the side wall 11 . Also, the thickness of the constricted portion 15 is smaller than the thickness of the joint portion 12 . Moreover, the thickness of the flange portion 13 is larger than the thickness of the joint portion 12 .

The abutting step is a step of abutting the joint portion 12 provided at the end portion of the side wall 11 of the tank lower 2 and the joint portion 12 provided at the end portion of the side wall 11 of the tank upper 3 in the circumferential direction.

The joining step is a step of joining the tank lower 2 and the tank upper 3 together. Although the method of joining the tank lower 2 and the tank upper 3 is not particularly limited, they are welded by vibration welding in this embodiment. By inserting jigs into the recessed portion 14 of the tank lower 2 and the recessed portion 14 of the tank upper 3 and vibrating them, they can be welded together by pressing them toward each other. As described above, the fuel tank 1 is formed.

Here, the effects of this embodiment will be described in comparison with a comparative example. FIG. 4 is a cross-sectional view of the tank upper before joining according to Comparative Example 1. FIG. The tank upper 100 according to Comparative Example 1 includes a side wall 111, a joint portion 112 provided at an end portion of the side wall 111, an intermediate portion 115 formed on the outer surface 111a of the side wall 111, and a portion formed outside the intermediate portion 115. and a concave portion 114 formed between the outer surface 111 a of the side wall 111 and the flange portion 113 . The intermediate portion 115 is set back upward from the joint surface 112a of the joint portion 112 in order to secure a welding margin.

When injection-molding the tank upper 100 of Comparative Example 1, the joint portion 112 becomes the end portion of the mold cavity. In other words, the portion where the joint portion 112 is formed becomes the flow end portion of the resin during injection molding, so the flow of the resin becomes poor. Also, the joint portion 112 (dotted line portion in FIG. 4) has a larger cross-sectional area (volume) than the intermediate portion 115 and the flange portion 113 . As described above, the fluidity of the resin is poor at the end of the cavity, which has a relatively large volume, and the temperature difference between the part near the molding die and the inside of the resin is large. Sink marks (not shown) are likely to occur.

If the joining process is performed with voids V or sink marks occurring in the joint 112, the void V may remain in the welded portion between the joints 112 or in the vicinity of the welded portion, resulting in poor joint. In addition, the presence of the voids V may reduce the bonding strength and permeate the fuel.

On the other hand, according to the present embodiment, as shown in FIG. ing. Since the joint portion 12, particularly the portion S, has a smaller cross-sectional area (volume) than other portions, the joint portion 12 is cooled relatively quickly and the resin hardens. Therefore, it is possible to suppress the occurrence of voids V and sink marks in the joint portion 12 .

In other words, in this embodiment, the portion of the flange portion 13 is the end portion of the cavity and has a relatively large cross-sectional area (volume). In other words, it is possible to use the flange portion 13 instead of the joint portion 12 as a portion where voids V and sink marks are likely to occur. Even if a void V or a sink mark occurs in the flange portion 13, the flange portion 13 does not contribute to the bonding (welding) strength, so it does not cause poor bonding. As described above, according to the present embodiment, it is possible to prevent defective bonding by controlling the locations where voids V and sink marks are generated. In addition, since voids V and sink marks are intentionally generated in the flange portion 13 , it is difficult to generate sink marks in the joint portion 12 , so generation of voids V and sink marks in the joint portion 12 can be prevented.

In addition, in the present embodiment, since the joint portion 12 is formed wider than the side wall 11, a large welding area can be secured and the joint strength can be increased.

Also, the joint portion 12 according to the present embodiment is perpendicular to the side wall 11 . In other words, the joint surface 12a of the joint portion 12 is flat across the width direction, and the inner surface 11a of the side wall 11 and the joint surface 12a of the joint portion 12 are perpendicular to each other (the inner surface 11a of the side wall 11 and the joint portion 12 are perpendicular to each other). 12 and the joint surface 12a of the joint portion 12 are perpendicular). This makes it easier for the resin to flow from the side wall 11 to the flange portion 13 , and can prevent the flow of the resin from being lowered at the joint portion 12 .

A constricted portion 15 is preferably formed between the joint portion 12 and the flange portion 13 . This makes it easier for the resin to flow toward the flange portion 13 during molding.

FIG. 5 is a cross-sectional view of a tank lower and a tank upper according to Comparative Example 2 before they are joined. FIG. 6 is a cross-sectional view of the fuel tank according to Comparative Example 2 after joining. Here, the occurrence of voids V in the injection molding of the tank lower 20 and the tank upper 30 of Comparative Example 2 and the state after joining will be described.

As shown in FIG. 5 , the tank lower 20 includes side walls 31 , joints 32 , flanges 33 and recesses 34 . The tank upper 30 has the same structure as the tank lower 20. - 特許庁The cross-sectional area of the joint portion 32 (dotted line portion in FIG. 5) is larger than the cross-sectional area of the flange portion 33 . When injection molding is performed for each of them, voids V are generated in a portion near the joint surface in the joint portion 32 of the tank upper 30 . Since the cross-sectional area of the joint portion 32 is larger than the cross-sectional area of the flange portion 33 as in Comparative Example 2, voids V are formed in the joint portion 32 .

As shown in FIG. 6, when the tank lower 20 and the tank upper 30 are joined, the void V formed in the tank upper 30 remains in the vicinity of the welded portion even after joining. New voids Va, Va are also formed.

As in Comparative Example 2 described above, if voids V or sink marks are formed in the joint 32 after injection molding, when the joints 32 and 32 are welded together, the voids V are formed at or near the welded portion. is more likely to remain. If the void V remains in or near the welded portion, the joint strength will decrease, and the risk of fuel permeation will also increase.

In contrast, according to the present embodiment described above, the generation of voids V and sink marks in the joint portion 12 during injection molding is prevented. , and can be suitably bonded.

REFERENCE SIGNS LIST 1 fuel tank 2 tank lower 3 tank upper 11 side wall 12 junction 13 flange 14 recess 15 neck

Claims (3)

A resin fuel tank in which a tank lower and a tank upper formed by injection molding are welded together along the entire circumferential direction at their peripheral ends ,
Between the ends of the sidewalls of the tank lower and the tank upper,
a joint formed wider than the side wall in the plate thickness direction and projecting outward;
a flange portion projecting further outward from the joint portion via a constricted portion ;
a concave portion formed between the outer surface of the side wall and the flange portion and into which a jig used for welding is inserted ,
The joint portions facing each other are welded together, and the cross-sectional area of a portion of the joint portion corresponding to the recess is smaller than the cross-sectional area of the flange portion,
The fuel tank, wherein the constricted portion has a thickness smaller than that of the joint portion between the joint portion and the flange portion. 2. The fuel tank of claim 1, wherein said joint is perpendicular to said side wall. A molding process for molding resin tank lower and tank upper by injection molding,
a butting step of circumferentially abutting the joint provided at the end of the side wall of the tank lower and the joint provided at the end of the side wall of the tank upper;
a joining step of joining the joints by welding ,
The end portions of the side walls of the tank lower and the tank upper are formed to be wider than the side walls in the plate thickness direction and protrude outward, and further extend outward from the joint portion via a constricted portion. and a concave portion formed between the outer surface of the side wall and the flange portion and into which a jig used for welding is inserted ,
In the forming step, the cross-sectional area of a portion of the joint corresponding to the recess is formed to be smaller than the cross-sectional area of the flange, and the joint is formed between the joint and the flange. A method of manufacturing a fuel tank , wherein the constricted portion is formed to have a thickness smaller than that of the fuel tank.

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