Patent Description:
A method has been known for attaching a component, such as a valve, to a blow-molded product, such as a fuel tank of an automobile, as a built-in component. For example, <CIT>, corresponding to the preamble of claim <NUM>, describes a manufacturing method for a fuel tank containing a built-in component with a head portion, a neck portion, and a shoulder portion. In the manufacturing method for the fuel tank, this fuel tank has the built-in component anchored to a tank body, with air blown from outside a parison during molding a tank body to shape the parison along the neck portion. At that time, the air around the neck portion is discharged toward the tank body through holes communicating the neck portion with the tank body.

<CIT> discloses a mounting apparatus for an internalized fuel system of a fuel tank. A support portion of the mounting apparatus has a body with a flange at a first end and a reduced cross sectional portion at the other end. <CIT> discloses a molded reservoir support structure that is rotated into position relative to an anchor.

To increase strength of anchorage of the built-in component, it is effective to increase a diameter of the head portion or neck portion. The built-in component with a larger diameter of the head portion or neck portion needs to have a hollowed head portion or neck portion, instead of a solid one, so as to prevent voids during molding. However, in a case where hollowed portions are open to an end surface of the head portion, when the built-in component is anchored to the tank body, the parison enters the hollowed portions. If the parison enters the hollowed portions, a thickness of the parison may vary, and a barrier layer may break.

The present invention is devised from the viewpoint described above, and is intended to prevent a parison from entering hollowed portions formed in a head portion and neck portion of a built-in component.

To solve the problems above, a fuel tank includes a tank body and a built-in component, which has a head portion, a neck portion, and a shoulder portion, the built-in component being anchored to the tank body with a parison wrapped around the neck portion during molding of the tank body. The head portion and the neck portion are formed with at least one hollowed portion, which is open to an end surface of the head portion, and a cap member is provided to seal an opening of the at least one hollowed portion.

According to the present invention, a cap member is provided on an opening of hollowed portion, to prevent a parison from entering the hollowed portions formed in the head portion and neck portion during molding, so that variation in thickness of the parison is reduced and a barrier layer is prevented from being ruptured.

In addition, it is preferable that the neck portion is formed with a first communicating portion which communicates an outside thereof with the hollowed portion, the shoulder portion is formed with a second communicating portion which communicates the hollowed portion with an interior of the tank body, and air outside the neck portion flows into the interior of the tank body through the first communicating portion and the second communicating portion. With the structure above, air around the neck portion is discharged into the tank body, to securely allow the parison to be shaped around the neck portion.

Further, it is preferable that a plurality of the hollowed portions are formed, and a third communicating portion is formed to communicate adjacent hollowed portions with each other. With the structure above, air around the neck portion is efficiently discharged into the interior of the tank body through the first communicating portion, the second communicating portion, and the third communicating portion.

A fuel tank of the present invention prevents a parison from entering hollowed portions formed in the head portion and neck portion.

A fuel tank T shown in <FIG> is configured to be mounted on a transportation such as an automobile, a motorcycle, and a ship, and mainly includes a tank body Ta and a built-in component <NUM>. As shown in <FIG>, the present embodiment exemplarily provides a columnar reinforcing member for maintaining strength of the fuel tank T, as the built-in component <NUM>, but the built-in component <NUM> may be a valve, a wave-eliminating plate, or the like. In the following description, "up-down" and "right-left" follow arrows in <FIG>. These directions are defined for the purpose of illustration and do not limit the present invention. Note that the right-left direction in <FIG> corresponds to an open-close direction of a pair of molding dies used for manufacturing the fuel tank T.

The tank body Ta is a hollow container made of a resin for storing fuel such as gasoline, and has a multi-layered structure including a barrier layer, for example. The tank body Ta is made of mainly a thermoplastic resin such as polyethylene or high-density polyethylene. The tank body Ta is formed by blow molding, for example.

A configuration of the built-in component <NUM> is described below, with reference to <FIG>. The built-in component <NUM> may be made of a material (thermoplastic resin such as PE (polyethylene) that can be welded to a parison S (see <FIG>) as a pre-shaped body of the tank body Ta or a material (such as POM) that cannot be welded to the parison S. The parison S is formed to have a multi-layered structure in cross section made of HDPE (high-density polyethylene), EVOH (ethylene-vinyl alcohol copolymer), an adhesive layer, and the like.

As shown in <FIG>, the built-in component <NUM> includes a body portion 6a, shoulder portions 6b formed at both ends of the body portion 6a, neck portions 6c formed on outer sides of the shoulder portions 6b, and head portions 6d. The structure of the built-in component <NUM> is bilaterally symmetrical in mirror image (vertically on the plane of a drawing sheet). Thus, only one side is described here, unless otherwise specified. In addition, in the description of the built-in component <NUM>, a surface facing the body portion 6a is referred to as a "back surface" and a surface opposite to the "back surface" is referred to as a "front surface".

The body portion 6a in <FIG> serves as a main body of the built-in component <NUM>. The body portion 6a has a cylindrical shape, with a tip thereof expanding toward the shoulder portion 6b. An end of the body portion 6a is formed with a plurality of columnar hollow holes <NUM>. The columnar hollow holes <NUM> serve to communicate communicating portions <NUM> (<FIG>) with the tank body Ta. The columnar hollow holes <NUM> serve to circulate air when the parison S to be described below is welded to the built-in component <NUM>.

The shoulder portion 6b in <FIG> serves to cover a recess 3d of a first molding die <NUM> or a recess 4d of a second molding die <NUM> shown in <FIG>. The shape or size of the shoulder portion 6b is not particularly limited as long as the recess 3d or 4d can be covered therewith. The shoulder portion 6b here has a disk shape made of a thin plate, and an outer diameter rb of the shoulder portion 6b is larger than an outer diameter ra of the body portion 6a, as shown in <FIG>.

The neck portion 6c shown in <FIG> serves to couple the shoulder portion 6b with the head portion 6d and has a smaller diameter than the shoulder portion 6b and the head portion 6d, as shown in <FIG>. The neck portion 6c here erects from a front surface 6f of the shoulder portion 6b to exhibit a columnar shape. A corner between the shoulder portion 6b and the neck portion 6c and a corner between the head portion 6d and the neck portion 6c are rounded (R-surface).

As shown in <FIG>, the neck portion 6c is formed with six communicating portions (first communicating portions) <NUM> along a circumferential direction thereof. The communicating portions <NUM> are holes to communicate an outside of the neck portion 6c with hollowed portions <NUM> (see <FIG>). The communicating portions <NUM> serve as air discharge paths to discharge air in a gap 6j (described below) when the parison S enters the gap 6j during molding. The shape, the number, and the like of the communicating portions <NUM> are not particularly limited as long as the air can be discharged therethrough.

The head portion 6d in <FIG> has a thicker disk shape than the shoulder portion 6b. Note that a thickness relationship between the shoulder portion 6b and the head portion 6d here is merely an example, and the shoulder portion 6b may be formed thicker than the head portion 6d. As shown in <FIG>, an outer diameter rd of the head portion 6d is larger than an outer diameter rc of the neck portion 6c and is smaller than the outer diameter rb of the shoulder portion 6b. Due to the shapes described above, the gap 6j with the neck portion 6c as a bottom is defined between the shoulder portion 6b and the head portion 6d. The gap 6j is a space into which the parison S enters during molding.

The shape or size of the head portion 6d is not particularly limited as long as the parison S enters around the head portion 6d and neck portion 6c to anchor the built-in component <NUM> to the tank body Ta (see <FIG>). A portion of the parison S wrapping around the neck portion 6c is referred to as a "wrapping parison portion W" (see <FIG>).

A cap member 6e in <FIG> is configured to be placed on an end surface of the head portion 6d to seal openings (see <FIG>) of the hollowed portions <NUM>. The cap member 6e seals the openings of the hollowed portions <NUM> to prevent the parison S from entering the hollowed portions <NUM> during molding. A material of the cap member 6e is not particularly limited, but in the present embodiment, the cap member 6e is formed of the same material as the built-in component <NUM>, for example.

As shown in <FIG>, the head portion 6d and neck portion 6c are formed with a plurality of the hollowed portions <NUM>. The hollowed portions <NUM> are open to the end surface of the head portion 6d and are hollow from the head portion 6d to the neck portion 6c. In the present embodiment, the openings of the hollowed portions <NUM> are sealed by the cap member 6e.

As shown in <FIG>, the cap member 6e is formed with a lid 6e1 and a leg 6e2. When the lid 6e1 is placed so as to seal the openings of the hollowed portions <NUM>, the leg 6e2 is inserted into and engages with the hollowed portion <NUM>. The leg 6e2 is engaged in the hollowed portion <NUM> so that the lid 6e1 is prevented from rotating and can be fixed in place.

The lid 6e1 is formed to have a flat surface and serves to close the openings of all the hollowed portions <NUM> so as to prevent the parison S or the like from entering the hollowed portions <NUM>. The lid 6e1 has any shape to seal the openings of the hollowed portions <NUM> and may be formed appropriately according to the shape of the head portion 6d.

The leg 6e2 is formed in two halves, and is inserted into the hollowed portion <NUM> to be fixed therein. The shape of leg 6e2 is not limited as long as the lid 6e1 can be prevented from coming off or rotating. Note that the leg 6e2 may be omitted if other mechanisms are provided to fix the lid 6e1.

As shown in <FIG>, the head portion 6d is formed with six grooved communicating portions (third communicating portions) 6i in a circumferential direction thereof. The communicating portions 6i are formed in the end surface of the head portion 6d to serve as air discharge holes when the cap member 6e is placed on the head portion 6d. For example, a communicating portion 6ia communicates a hollowed portion 6kc, which is formed in the center, with a hollowed portion 6ka, which is formed on an outer side in the radial direction thereof. In addition, for example, a communicating portion 6ib communicates the hollowed portion 6kc, which is formed in the center, with a hollowed portion 6kb, which is formed on an outer side in the radial direction thereof.

In addition, the shoulder portion 6b is formed with four communicating portions (second communicating portions) <NUM>. As shown in <FIG>, the communicating portions <NUM> are formed to communicate the hollowed portions <NUM> with the body portion 6a (inside the tank body Ta) as shown in <FIG>. Note that the shapes, the number, and the like of the communicating portions 6i and communicating portions <NUM> are not particularly limited as long as air can be discharged.

Next, a description is given of an air flow during molding, with reference to <FIG> (see also <FIG>, as appropriate). For example, air entering from an outside of the neck portion 6c into a communicating portion 6ma is discharged into the tank body Ta through the hollowed portion 6ka, a communicating portion 6ha, and the columnar hollow hole <NUM>. Similarly, for example, air entering through a communicating portion 6mb of the neck portion 6c is discharged into the tank body Ta through the hollowed portion 6kb, the communicating portion 6ib, the hollowed portion 6kc, the communicating portion 6ia, the hollowed portion 6ka, the communicating portion 6ha, and the columnar hollow hole <NUM>. The air flow described above is an example, and the hollowed portion 6kc, which is formed in the center, communicates with a plurality of the communicating portions 6i, respectively, in the present embodiment so that the air entering through the communicating portion 6ma can flow through either any one of or all of the communicating portions 6ha, 6hb, 6hc, and 6hd.

A fuel tank manufacturing device <NUM> shown in <FIG> is configured to blow-mold the parison S in a cylindrical shape to manufacture the fuel tank T (see <FIG>) having the built-in component <NUM> inside. Note that the fuel tank T may be manufactured with a parison in a sheet shape (not shown).

As shown in <FIG>, the fuel tank manufacturing device <NUM> mainly includes a die <NUM>, a first molding die <NUM> and a second molding die <NUM> in a pair, and an elevator <NUM> to be moved up and down between the first molding die <NUM> and second molding die <NUM>.

The die <NUM> is arranged above the first molding die <NUM> and second molding die <NUM>, and serves to supply the parison S to the first molding die <NUM> and second molding die <NUM>. The parison SA has a multi-layered structure in cross section made of HDPE (high-density polyethylene), EVOH (ethylene-vinyl alcohol copolymer), an adhesive layer, and the like, and is a pre-shaped body of the tank body Ta to constitute the fuel tank T (see <FIG>).

The first molding die <NUM> and second molding die <NUM> in <FIG> serve to clamp-mold the fuel tank T (see <FIG>). The first molding die <NUM> and second molding die <NUM> are arranged to face each other, and are formed, in the facing surfaces thereof, with molding portions 3a and 4a in a concave shape. The first molding die <NUM> and second molding die <NUM> can be moved in the right-left direction so as to be opened and closed, and the parison S is supplied in a state that the first molding die <NUM> and second molding die <NUM> are opened (the state shown in <FIG>). In addition, the first molding die <NUM> and second molding die <NUM> are provided with blow pins (not shown) for blowing air into the first molding die <NUM> and second molding die <NUM>, so that air pressure (blow pressure) in the first molding die <NUM> and second molding die <NUM> is suitably adjusted by a first positive pressure applying device (not shown). The parison S is transferred to the molding portions 3a and 4a by the first positive pressure applying device.

The first molding die <NUM> is configured to be separable, and includes a main body portion 3b and a separating portion 3c that can be separated from the main body portion 3b. Similarly, the second molding die <NUM> is configured to be separable, and includes a main body portion 4b and a separating portion 4c that can be separated from the main body portion 4b. The separating portions 3c and 4c are respectively formed with the recesses 3d and 4d corresponding to the shapes of both ends of the built-in component <NUM>, and the recesses 3d and 4d partly accommodate the built-in component <NUM>. The recesses 3d and 4d here are formed into a columnar shape. In addition, the recesses 3d and 4d are provided, in bottoms 3f and 4f therefor, with a plurality of air holes <NUM> and <NUM>, respectively, for blowing air into the recesses 3d and 4d, so that air pressure (blow pressure) in the recesses 3d and 4d is suitably adjusted by a second positive pressure applying device (not shown).

The elevator <NUM> serves to move the built-in component <NUM> to a mounting position. The mounting position here is inside the parison S in a cylindrical shape and between the separating portions 3c and 4c.

Next, a description is given of operation of the fuel tank manufacturing device <NUM>. Before describing the whole process of the method of manufacturing the fuel tank T (see <FIG>) with the fuel tank manufacturing device <NUM>, a description is given of transferring the parison around ends of the built-in component <NUM>.

A description is given of transferring the parison S around the ends of the built-in component <NUM> during molding, with reference to <FIG> and <FIG> (see <FIG> as appropriate). Note that a description is given here of the first molding die <NUM>, but the same applies to the second molding die <NUM>. <FIG> and <FIG> show the built-in component <NUM> in cross section taken along a line B-B in <FIG>. In the fuel tank manufacturing process, the first molding die <NUM> is moved in the arrow direction, as shown in <FIG> for clamping so that the neck portion 6c and head portion 6d of the built-in component <NUM> are pushed into the recess 3d along with the parison S.

As shown in <FIG>, when the shoulder portion 6b contacts the parison S and covers an opening of the recess 3d, and the neck portion 6c and head portion 6d are completely pushed (accommodated) into the recess 3d, air is blown into the first molding die <NUM> to generate a positive pressure P1 (first positive pressure) in the parison S so that the parison S is transferred to the first molding die <NUM>. In addition, air is blown into the recess 3d through the air hole <NUM> formed in the recess 3d to generate a positive pressure P2 (second positive pressure) in the recess 3d, so that the parison S is made to enter the gap 6j between the shoulder portion 6b and head portion 6d for the transferring. The air in the gap 6j is discharged into the tank body Ta through the communicating portions (first communicating portions) <NUM>, the communicating portions (second communicating portions) <NUM>, the communicating portions (third communicating portions) 6i, the hollowed portions <NUM>, and the columnar hollow holes <NUM>, as appropriate.

Further, at this time, the parison S is pressed between the shoulder portion 6b and the first molding die <NUM> so that the parison S and the shoulder portion 6b are welded to each other. In addition, the parison S is pressed to the head portion 6d by the positive pressure P2 so that the parison S and the head portion 6d are welded to each other. Note that the built-in component <NUM> may be pushed toward the recess 3d to hold the parison S between the head portion 6d and the bottom portion 3f, to weld the parison S and the head portion 6d to each other.

Next, a description is given of the whole process of the first fuel tank manufacturing device <NUM>.

The die <NUM> injects the parison S in a cylindrical shape into a space between the first molding die <NUM> and second molding die <NUM> which are both opened, as shown in <FIG>.

Next, the elevator <NUM> is moved up, with the built-in component <NUM> held, to move the built-in component <NUM> to the mounting position, as shown in <FIG>. Here, the mounting position is located inside the parison S and between the separating portions 3c and 4c.

Next, the separating portions 3c and 4c of the first molding die <NUM> and second molding die <NUM> are moved closer in a direction of facing each other, to hold the built-in component <NUM> from both ends, as shown in <FIG>. Then, the elevator <NUM> is moved down, with the built-in component <NUM> released, and retracts to an initial position. The initial position of the elevator <NUM> can be any position as long as it does not interfere with the main bodies 3b and 4b of the first molding die <NUM> and second molding die <NUM> when they are closed.

Next, the main bodies 3b and 4b of the first molding die <NUM> and second molding die <NUM> are moved closer in the direction of facing each other, and the first molding die <NUM> and second molding die <NUM> are clamped, as shown in <FIG>.

Next, the first positive pressure applying device (not shown) applies the positive pressure P1 (first positive pressure) from inside the parison S in the first molding die <NUM> and second molding die <NUM>, as shown in <FIG>. This causes the parison S to be pressed to the molding portions 3a and 4a of the first molding die <NUM> and second molding die <NUM> and transferred. In addition, the second positive pressure applying device (not shown) applies the positive pressure P2 (second positive pressure) from outside the parison S in the recesses 3d and 4d (see <FIG>) of the first molding die <NUM> and second molding die <NUM>. This causes the parison S to be shaped along the neck portion 6c of the built-in component <NUM> (see <FIG>). Note that the methods and order of applying the positive pressure P1 and positive pressure P2 are not particularly limited. The positive pressure P2 is preferably set higher than the positive pressure P1.

Next, a cooling device (not shown) is used to circulate cooling air C in the first molding die <NUM> and second molding die <NUM>, as shown in <FIG>. This causes the parison S to be cooled and cured.

Next, the first molding die <NUM> and second molding die <NUM> are opened and a molded product U is taken out, as shown in <FIG>. Then, unnecessary burrs formed at both ends are cut to finish the fuel tank T (see <FIG>).

According to the embodiment described above, the cap member 6e is placed on the head portion 6d of the built-in component <NUM>, to prevent the parison S from entering the hollowed portions <NUM> during molding. Therefore, variations in thickness of the parison S can be suppressed and a barrier layer can be prevented from being ruptured or damaged.

In addition, the shoulder portion 6b is formed with the communicating portions <NUM>, to allow the air in the hollowed portions <NUM> to be discharged to the body portion 6a. That is, the air in the gap 6j flows through the communicating portions <NUM> to the hollowed portions <NUM>, and the air in the hollowed portions <NUM> is discharged through the communicating portions <NUM> into the tank body Ta. Thus, the air can be securely discharged, and the parison can be securely shaped around the neck portion 6c.

In addition, a plurality of the hollowed portions <NUM> are formed, and the communicating portions (third communicating portions) 6i are formed to communicate the adjacent hollowed portions <NUM> with each other. Therefore, the air around the neck portion 6c is more efficiently discharged into the tank body Ta through the communicating portions (first communicating portions) <NUM>, the communicating portions (second communicating portions) <NUM>, and the communicating portions 6i. Especially, in the present embodiment, the hollowed portion 6kc, which is formed in the center, communicates with a plurality of the communicating portions 6i, respectively. Therefore, for example, the air entering through the communicating portion 6ma is discharged through any one of or all of the communicating portions 6ha, 6hb, 6hc, and 6hd, to increase air discharge efficiency.

The embodiment of the invention have been described above, but can be appropriately modified within the scope of the present invention. For example, in the present embodiment, the columnar hollow holes <NUM> are formed to have a mesh-pattern in cross section, but any shape may be taken as long as the air in the hollowed portions <NUM> can flow into the tank body Ta. Further, in the present embodiment, the communicating portions 6i are formed to have a groove shape at the opening ends of the hollowed portions <NUM>, but may be formed as holes as with the communicating portions <NUM> or the communicating portions <NUM>. When the communicating portions 6i are formed to have a hole shape, they may be formed at any position as long as the adjacent hollowed portions <NUM> can be communicated with each other.

In addition, in the present embodiment, the parison is wrapped around the neck portion by the positive pressure (blow molding) from the outside of the parison to anchor the built-in component, but other molding methods may be used.

Claim 1:
A fuel tank (T) comprising a tank body (Ta) and a built-in component (<NUM>), which includes a head portion (6d), a neck portion (6c), and a shoulder portion (6b), the built-in component being anchored to the tank body with a parison (S) wrapped around the neck portion during molding of the tank body, wherein
the head portion (6d) and the neck portion (6c) are formed with at least one hollowed portion (<NUM>), which is open to an end surface of the head portion,
characterized in that
a cap member (6e) is provided to seal an opening of the at least one hollowed portion.