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, Patent Document <NUM> describes a fuel tank containing a built-in component with a head portion, a neck portion, and a shoulder portion. This fuel tank has the built-in component anchored thereto with air blown from outside during molding to shape a parison along the neck portion. In addition, Patent Document <NUM> discloses a fuel tank having a simple structure, and allowing for easily attaching and detaching a lid member to and from a protrusion part thereof. Patent Document <NUM> discloses an attachment structure for an insert member of a blow molding item which is used to attach the insert member by embedding the same in the outside wall of the blow molding item, eliminates the need of preliminary heating and causes less deformation of the insert member. Patent Document <NUM> discloses a mounting apparatus used for an internalized fuel system of a fuel tank, and including a support portion and a valve retainer arm attached about the support portion. Spaced legs are configured to disengage or detach from the support portion at a predetermined threshold pressure. Patent Document <NUM> discloses a fuel tank molding rigidity assembly in which two ends of the rigidity assembly are of up and down symmetrical structures, and a large disc and a small disc are arranged at each end. The large disc and small disc may be provided with holes. Patent Document <NUM> discloses a method of overmolding an insert of tubular shape in a parison. The edges of one of the ends of the insert are provided with annular projections constituting annular grooves. The parison is pressed so as to deform and fill the annular grooves.

It is desirable that the strength of anchorage between a tank body of the fuel tank and the built-in component is high, but the strength of anchorage is desired to be further improved because positive pressure and negative pressure act on the tank body due to external factors such as air temperature.

The present invention has been devised from such a viewpoint, and is intended to provide a fuel tank to increase the strength of anchorage between the tank body and the built-in component.

In order to solve the above problems, viewed from one aspect the present invention provides a fuel tank as defined by claim <NUM>.

According to the present invention, the deformation prevention structure prevents the wrapping parison portion wrapped around the neck portion of the built-in component from being deformed so that the strength of anchorage between the tank body and the built-in component is increased.

In addition, the neck portion preferably has a smaller diameter than the shoulder portion and the head portion, and erects from the surface of the shoulder portion to exhibit a columnar shape. Further, the deformation prevention structure may be preferably a rigid member integrally molded so as to cover, from outside, the head portion, the neck portion, and the wrapping parison portion wrapped around the neck portion. In this way, the deformation prevention structure can be easily formed.

Viewed from another aspect the present invention provides a fuel tank as defined by claim <NUM>.

According to the fuel tank of the present invention, the strength of anchorage between the tank body and the built-in component is increased.

A fuel tank T shown in <FIG> is a fuel tank to be mounted on a transportation means 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 the 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 the open/close direction of a pair of molding dies for manufacturing the fuel tank T.

The tank body Ta is a hollow container made of resin for storing fuel such as gasoline, and has a multi-layer structure including a barrier layer, for example. The tank body Ta is made of mainly a thermoplastic resin such as polyethylene and 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> is preferably made of a material that can be welded to a parison S (see <FIG>) as a precursor to the tank body Ta (i.e.; a thermoplastic resin such as PE (polyethylene)). The parison S 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.

As shown in <FIG>, the built-in component <NUM> includes a body portion 6a in a columnar shape, shoulder portions 6b formed at both ends of the body portion 6a, neck portions 6c formed on axially 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 paper). 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> is a portion as a main body of the built-in component <NUM>, and is symmetrical in mirror image with respect to an anteroposterior axis including an axis O as a central axis of the body portion 6a. A plurality of cutout holes 6e are formed in the body portion 6a. The cutout holes 6e are formed to reduce the weight and increase the capacity of the fuel tank T (see <FIG>).

The shoulder portion 6b in <FIG> is a portion 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 and size of the shoulder portion 6b are not particularly limited as long as the shoulder portions 6b can cover the recesses 3d and 4d. The shoulder portion 6b here has a disk shape, 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 in <FIG> is a portion connecting the shoulder portion 6b with the head portion 6d, and has a smaller diameter than the shoulder portion 6b and head portion 6d. The neck portion 6c here erects from a front surface 6f of the shoulder portion 6b to exhibit a columnar shape.

The head portion 6d in <FIG> has a disk shape made of a thin plate. 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 smaller than the outer diameter "rb" of the shoulder portion 6b. Due to such a shape, a 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 portion where the parison S enters during molding.

The shape and size of the head 6d are not particularly limited as long as the parison S can enter 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>). Note that a surface <NUM> of the head portion 6d may be formed with a plurality of ribs (not shown) erecting in a ring shape, for example. The ribs of the head portion 6d are formed along a circle about the axis O, for example.

The shoulder portion 6b is formed, at a portion thereof around the neck portion 6c, with two air vent holes 6i (see <FIG>). As shown in <FIG>, the air vent hole 6i communicates with the cutout holes 6e formed in the body portion 6a. As a result, the air in the gap 6j is dischargeable to a back surface <NUM> of the shoulder portion 6b through the air vent hole 6i (the air flow is indicated by a thick solid arrow in <FIG>), as shown in <FIG>.

The shoulder portion 6b is formed, on the front surface 6f thereof, with a stepped portion <NUM> in an annular shape about the axis O, as shown in <FIG>. The stepped portion <NUM> is a portion where the parison S enters, as well as the gap 6j, during molding. The shape, size, and the like of the stepped portion <NUM> are not particularly limited as long as the stepped portion <NUM> can prevent the wrapping parison portion, or the wrapping parison portion W, entered around the neck portion 6c from being deformed due to positive pressure and negative pressure acting on the tank body Ta.

The stepped portion <NUM> in the present embodiment mainly includes an upper step surface 6ha formed continuously from a peripheral edge of the shoulder portion 6b, a lower step surface 6hb formed lower than the upper step surface 6ha, and an inner wall 6hc formed to extend from the upper step surface 6ha to the lower step surface 6hb. Note that the stepped portion <NUM> is an example of a deformation prevention structure. The deformation prevention structure may be a structure other than the stepped portion <NUM> in <FIG> (e.g.; a convex portion or a concave portion formed on the front surface 6f of the shoulder portion 6b), as will be described below. The convex portion may be a vertical wall or a protrusion, for example, and the concave portion (not shown) may be a groove or a hole, for example. In addition, the deformation prevention structure may be configured to include at least one of the stepped portion <NUM>, the convex portion and the concave portion, or these shapes may be used in combination. Further, the stepped portion <NUM> may be formed to have a plurality of steps.

Two types of manufacturing methods are described in the present embodiment. A first one is a method to mold a parison SA in a cylindrical shape (see <FIG>) to manufacture the fuel tank T (see <FIG>). A second one is a method to mold parisons SB in a sheet shape (see <FIG>) to manufacture the fuel tank T.

A first fuel tank manufacturing device 1A shown in <FIG> is a device to blow-mold the parison SA in a cylindrical shape to manufacture the fuel tank T (see <FIG>) having a built-in component <NUM> therein. As shown in <FIG>, the first fuel tank manufacturing device 1A 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 is a supply means to supply the parison SA 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 precursor to the tank body Ta to constitute the fuel tank T (see <FIG>).

The first molding die <NUM> and second molding die <NUM> in <FIG> are molding means for clamp-molding 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 SA 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 the air pressure (blow pressure) in the first molding die <NUM> and second molding die <NUM> is suitably adjusted by a first positive pressure applying means (not shown). The parison SA is transferred to the molding portions 3a and 4a by the first positive pressure applying means.

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, and protrusions 3e and 4e are formed near the entrance. The outer corners of the protrusions 3e and 4e are chamfered. In addition, a plurality of air holes <NUM> and <NUM> are provided in bottoms 3f and 4f for the recesses 3d and 4d, respectively, for blowing air into the recesses 3d and 4d, so that the air pressure (blow pressure) in the recesses 3d and 4d is suitably adjusted by a second positive pressure applying means (not shown). Note that the protrusions 3e and 4e may be omitted.

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

Next, a description is given of operation of the first fuel tank manufacturing device 1A. Before describing the whole process of the method of manufacturing the fuel tank T (see <FIG>) with the first fuel tank manufacturing device 1A, a description is given of transferring the parison around ends of the built-in component <NUM>.

A description is given of transferring the parison SA around the ends of the built-in component <NUM> during molding, with reference to <FIG> and <FIG> (see <FIG> as required). Note that a description is given here of the first molding die <NUM>, but the same applies to the second molding die <NUM>. In the fuel tank manufacturing process, the first molding die <NUM> is moved in the arrow direction, as shown in <FIG>, and then clamed 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 SA.

As shown in <FIG>, when the shoulder portion 6b contacts the parison SA and covers the 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 SA so that the parison SA is transferred to the first molding die <NUM>. In addition, air is blown into the recess 3d from 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 SA is made to enter into the gap 6j between the shoulder portion 6b and head portion 6d as well as the stepped portion <NUM> and is then transferred. The air in the gap 6j is discharged through the air vent holes 6i formed in the shoulder portion 6b.

At this time, the parison SA is pressed between the shoulder portion 6b and the protrusion 3e, so that the parison SA and the shoulder portion 6b are welded to each other. In addition, the parison SA is pressed to the head portion 6d by the positive pressure P2, so that the parison SA 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 SA between the head portion 6d and the bottom portion 3f, so that the parison SA and the head portion 6d are welded to each other.

Next, a description is given of the whole process of the method of manufacturing the fuel tank T with the first fuel tank manufacturing device 1A. The die <NUM> injects the parison SA 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 a mounting position, as shown in <FIG>. Here, the mounting position is located inside the parison SA 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 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 the 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 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 means (not shown) applies the positive pressure P1 (first positive pressure) from inside the parison SA in the first molding die <NUM> and second molding die <NUM>, as shown in <FIG>. This causes the parison SA 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 means (not shown) applies the positive pressure P2 (second positive pressure) from outside the parison SA in the recesses 3d and 4d (see <FIG>) of the first molding die <NUM> and second molding die <NUM>. This causes the parison SA to be shaped along the neck portion 6c of the built-in component <NUM> (see <FIG>). Note that the means 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 means (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 SA 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>).

A second fuel tank manufacturing device 1B shown in <FIG> is a device to blow-mold the parisons SB in a sheet shape to manufacture the fuel tank T (see <FIG>) having the built-in component <NUM> (see <FIG>). The second fuel tank manufacturing device 1B blow-molds the parisons SB in two steps such that the tank body Ta (see <FIG>) is molded in a first blow-molding, and the parisons SB are shaped onto the built-in component <NUM> in a second blow-molding.

The second fuel tank manufacturing device 1B mainly includes, as shown in <FIG>, chucks <NUM>, a pair of first molding die <NUM> and second molding die <NUM>, an intermediate die <NUM>, and a robot arm <NUM> (see <FIG>).

The chucks <NUM> are devices to push portions, closer to upper ends, of the parisons SB from outside to move the parisons SB toward the intermediate die <NUM>. The parison SB 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 precursor to the tank body Ta constituting the fuel tank T (see <FIG>).

The first molding die <NUM>, second molding die <NUM>, and intermediate die <NUM> in <FIG> are molding means for clamp-molding the fuel tank T (see <FIG>). The first molding die <NUM> and second molding die <NUM> are arranged to face each other, and molding portions 13a and 14a in a concave shape are formed in the facing surfaces. The intermediate die <NUM> is movable in the vertical direction or the front-rear direction (front-back direction of the plane of paper in <FIG>). The intermediate die <NUM> is located between the first molding die <NUM> and second molding die <NUM> in <FIG> during the primary molding, and the intermediate mold <NUM> is removed during the secondary molding.

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 parisons SB are supplied with the first molding die <NUM> and second molding die <NUM> opened (as shown in <FIG>). In addition, the first molding die <NUM> and second molding die <NUM> include blow pins (not shown) for blowing air into the first molding die <NUM> and second molding die <NUM> and for removing the air, so that the air pressure (blow pressure) in the first molding die <NUM> and second molding die <NUM> is suitably adjusted by the first positive pressure applying means and a first negative pressure applying means, which are not shown. The parisons SB are pressed to the molding portions 13a and 14a by the first positive pressure applying means and first negative pressure applying means.

The first molding die <NUM> is configured to be separable, and includes a main body portion 13b and a separating portion 13c that can be separated from the main body portion 13b. Likewise, the second molding die <NUM> is configured to be separable, and includes a main body portion 14b and a separating portion 14c that can be separated from the main body portion 14b. The separating portions 13c, 14c can be moved back with respect to the main body portions 13b, 14b, and recesses 13d, 14d are defined with the separating portions 13c, 14c moved back. The recesses 13d, 14d correspond to the shapes of both ends of the built-in component <NUM>, and partly accommodate the built-in component <NUM>. The recesses 13d, 14d are here defined in a columnar shape, and the main body portions 13b, 14b are formed with protrusions 13e, 14e near the entrances to the recesses 13d, 14d. The outer corners of the protrusions 13e, 14e are chamfered. In addition, a plurality of air holes <NUM>, <NUM> for blowing air into the recesses 13d, 14d are respectively formed between the main body portions 13b, 14b and the separating portions 13c, 14c, and air pressure (blow pressure) in the recesses 13d, 14d is suitably adjusted by the second positive pressure applying means (not shown).

The robot arm <NUM> (see <FIG>) is a moving means for moving the built-in component <NUM> to the mounting position. The mounting position here is inside the parisons SB in a sheet shape and between the separating portions 13c, 14c.

Next, a description is given of operation of the second fuel tank manufacturing device 1B. Before describing the whole process of the method of manufacturing the fuel tank T (see <FIG>) with the second fuel tank manufacturing device 1B, a description is given of transferring the parisons around the ends of the built-in component <NUM>.

A way of transferring the parisons around the ends of the built-in component <NUM> with the second fuel tank manufacturing device 1B is the same as the way of transferring the parison with the first fuel tank manufacturing device 1A. That is, the second fuel tank manufacturing device 1B has the positive pressure P2 (second positive pressure) generated in the recesses 13d and 14d formed in the first molding die <NUM> and second molding die <NUM>, so that the parisons SB are made to enter into the gap 6j between the shoulder portion 6b and head portion 6d as well as the stepped portion <NUM> and are then transferred (see <FIG> and <FIG>).

Next, a description is given of the whole process of the method of manufacturing the fuel tank T with the second fuel tank manufacturing device 1B. A feeding means <NUM> feeds the parisons SB in a sheet shape to both sides of the intermediate die <NUM>, as shown in <FIG>. Next, the chucks <NUM> hold the portions, closer to the upper ends, of the parisons SB and guide the parisons SB toward the intermediate die <NUM>, as shown in <FIG>.

Next, the first molding die <NUM> and second molding die <NUM> are moved in a direction of facing each other so as to be combined on both sides of the intermediate die <NUM>, and the first molding die <NUM> and second molding die <NUM> are clamped, as shown in <FIG>. Then, the first negative pressure applying means (not shown) generates a negative pressure N1 in the first molding die <NUM> and second molding die <NUM>. In addition, a third positive pressure applying means (not shown) applies a positive pressure P3 from inside the parisons SB in the first molding die <NUM> and second molding die <NUM>. This causes the parisons SB to be pressed to the molding portions 13a and 14a of the first molding die <NUM> and second molding die <NUM> and transferred. Here, there is no gap between the main body portion 13b and separating portion 13c of the first molding die <NUM>, so that the parison SB does not leak from between the main body portion 13b and separating portion 13c. Likewise, there is no gap between the main body portion 14b and separating portion 14c of the second molding die <NUM>, so that the parison SB does not leak from between the main body portion 14b and separating portion 14c.

Next, the first molding die <NUM> and second molding die <NUM> are opened and the intermediate mold <NUM> is removed, as shown in <FIG>. This causes a space to be defined between the first molding die <NUM> and second molding die <NUM>. Note that the parisons SB remain transferred to the first molding die <NUM> and second molding die <NUM>, which are opened.

Next, the separating portions 13c and 14c of the first molding die <NUM> and second molding die <NUM> are moved back with respect to the main body portions 13b and 14b, and recesses 13d and 14d are defined in the first molding die <NUM> and second molding die <NUM>, as shown in <FIG>. In addition, the robot arm <NUM> is moved up, with the built-in component <NUM> held, to move the built-in component <NUM> toward the first molding die <NUM> and arrange the built-in component <NUM> in the recess 13d, as shown in <FIG>. Then, the robot arm <NUM> is moved down, with the built-in component <NUM> released, and retracts to the initial position. The initial position of the robot arm <NUM> can be any position as long as it does not interfere with the first molding die <NUM> and second molding die <NUM> when they are closed.

Next, the first molding die <NUM> and second molding die <NUM> are moved 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 means (not shown) applies the positive pressure P1 (first positive pressure) from inside the parisons SB in the first molding die <NUM> and second molding die <NUM>, as shown in <FIG>. This causes the parisons SB to be pressed to the molding portions 13a and 14a of the first molding die <NUM> and second molding die <NUM> and transferred. In addition, the second positive pressure applying means (not shown) applies the positive pressure P2 (second positive pressure) from outside the parisons SB in the recesses 13d and 14d (see <FIG>) of the first molding die <NUM> and second molding die <NUM>. This causes the parisons SB to be shaped along the neck portion 6c of the built-in component <NUM>. Note that the means 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 means (not shown) is used to circulate the cooling air C in the first molding die <NUM> and second molding die <NUM>, as shown in <FIG>. This causes the parisons SB to be cooled and cured.

Next, the first molding die <NUM> and second molding die <NUM> are opened and the 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>).

Here, in a case of a conventional fuel tank, the resin around the neck portion may be deformed (displaced) so as to be separated outward in the radial direction from the neck portion, when positive pressure and negative pressure act on the tank body, to have a risk of the strength of anchorage between the built-in component and the tank body being reduced. However, according to the first embodiment described above, the parison S enters the gap 6j and the stepped portion <NUM> to prevent the resin around the neck portion 6c of the built-in component <NUM> (wrapping parison portion W) from being deformed. More specifically, the present embodiment has the resin around the neck portion 6c (wrapping parison portion W) received by the inner wall 6hc (see <FIG>) of the stepped portion <NUM>, to prevent the resin around the neck portion 6c from being deformed (displaced) outward in the radial direction from the neck portion 6c. This increases the strength of anchorage between the built-in component <NUM> and the tank body Ta. In addition, the deformation prevention structure can be easily formed because the only thing to do is to provide the stepped portion <NUM>.

A second embodiment has a first convex portion <NUM> formed on the front surface 6f of the shoulder portion 6b, as a deformation prevention structure, as shown in <FIG>. The first convex portion <NUM> has an annular shape about the axis O, and is formed to surround the whole circumference of the neck portion 6c. The first convex portion <NUM> has a rectangular shape in cross section.

The second embodiment described above gives advantageous effects substantially equivalent to those of the first embodiment. That is, the parison S enters the space defined by the gap 6j and the first convex portion <NUM>, to prevent the resin around the neck portion 6c of a built-in component <NUM> (wrapping parison portion W) from being deformed. More specifically, the present embodiment has the resin around the neck portion 6c (wrapping parison portion W) received by the first convex portion <NUM>, to prevent the resin around the neck portion 6c from being deformed (displaced) outward in the radial direction from the neck portion 6c. This increases the strength of anchorage between the built-in component <NUM> and the tank body Ta. In addition, the deformation prevention structure can be easily formed because the only thing to do is to provide the first convex portion <NUM>.

A third embodiment has a plurality of (here, four) second convex portions <NUM> formed on the front surface 6f of the shoulder portion 6b, as a deformation prevention structure, as shown in <FIG>. The second convex portions <NUM> are arranged about the axis O circumferentially at equal intervals. The second convex portions <NUM> are each curved and each have a rectangular shape in cross section.

The third embodiment described above gives advantageous effects substantially equivalent to those of the first embodiment. That is, the parison S enters the space defined by the gap 6j and the second convex portions <NUM>, to prevent the resin around the neck portion 6c of a built-in component <NUM> (wrapping parison portion W) from being deformed. More specifically, the present embodiment has the resin around the neck portion 6c (wrapping parison portion W) received by the second convex portions <NUM>, to prevent the resin around the neck portion 6c from being deformed (displaced) outward in the radial direction from the neck portion 6c. This increases the strength of anchorage between the built-in component <NUM> and the tank body Ta. In addition, the deformation prevention structure can be easily formed because the only thing to do is to provide the second convex portion <NUM>.

A fourth embodiment has a third convex portion <NUM> formed on the front surface 6f of the shoulder portion 6b as a deformation prevention structure, as shown in <FIG>. The third convex portion <NUM> has an annular shape about the axis O, and is formed to surround the whole circumference of the neck portion 6c. The third convex portion <NUM> has a rectangular shape in cross section. The third convex portion <NUM> has four through holes 46he formed in a circumferential direction thereof at equal intervals. The through holes 46he are portions where the parison S enters during molding. The through holes 46he are formed in the radial direction of a built-in component <NUM> so as to communicate an inner side of the third convex portion <NUM> with an outer side of the third convex portion <NUM>.

The fourth embodiment described above gives advantageous effects substantially equivalent to those of the second embodiment. In addition, in the fourth embodiment, the parison S also enters the through holes 46he during molding, to further increase the strength of anchorage.

A fifth embodiment has a plurality of (here, four) fourth convex portions <NUM> formed on the front surface 6f of the shoulder portion 6b, as a deformation prevention structure, as shown in <FIG>. The fourth convex portions <NUM> are arranged about the axis O circumferentially at equal intervals. The fourth convex portion <NUM> are each curved, and each have a rectangular shape in cross section. The fourth convex portions <NUM> each have a through hole 56he formed therein. The through holes 56he are portions where the parison S enters during molding. The through hole 56he is formed in the radial direction of a built-in component <NUM> so as to communicate an inner side of the fourth convex portion <NUM> with an outer side of the fourth convex portion <NUM>.

The fifth embodiment described above gives advantageous effects substantially equivalent to those of the third embodiment. In addition, in the fifth embodiment, the parison S also enters the through holes 56he during molding, to further increase the strength of anchorage.

A sixth embodiment has a rigid member <NUM> integrally molded on the front surface 6f of the shoulder portion 6b, as a deformation prevention structure, as shown in <FIG>. The rigid member <NUM> is inserted from outside the parison S shaped to a built-in component <NUM> and attached to the built-in component <NUM>, during molding. The rigid member <NUM> is made of resin or metal.

The inside of the rigid member <NUM> has a shape corresponding to the head portion 6d and neck portion 6c, so that the rigid member <NUM> accommodates the head portion 6d and neck portion 6c. The rigid member <NUM> here has a bottomed cylindrical shape in which one end of the cylinder is closed, and mainly includes a peripheral wall portion 67a in a cylindrical shape and a bottom portion 67b in a disk shape. The front surface 6f of the shoulder portion 6b is formed therein with a groove <NUM> in an annular shape corresponding to the end of the peripheral wall portion 67a.

The peripheral wall portion 67a is formed therein with four through holes 67c circumferentially at equal intervals. The through hole 67c is a portion where the parison S enters during molding. The shapes, positions, number, and the like of the through holes 67c are not particularly limited as long as the parison S can enter the through holes 67c to fix the rigid member <NUM> to the tank body Ta.

The bottom portion 67b is formed therein with a plurality of (here, two) air holes 67d for blowing air into the rigid member <NUM>. This allows, for example, for blowing air through the air holes <NUM> formed in the recess 3d (see <FIG>) to generate the positive pressure P2 (second positive pressure) in the rigid member <NUM>, so that the parison S is fed into the gap 6j between the shoulder portion 6b and head portion 6d and transferred. A gap may be defined between the rigid member <NUM> and the tank body Ta. Such a gap Is preferably defined between the through holes 67c and the tank body Ta so that water or the like entered into the rigid member <NUM> through the air holes 67d can be drained through the gap after the fuel tank T6 has been mounted on a means of transportation such as an automobile, a motorcycle, and a ship.

The sixth embodiment described above gives advantageous effects substantially equivalent to those of the first embodiment. That is, the parison S enters the gap 6j and the rigid member <NUM>, to prevent the resin around the neck portion 6c of the built-in component <NUM> (wrapping parison portion W) from being deformed. More specifically, the present embodiment has the resin around the neck portion 6c (wrapping parison portion W) received by the rigid member <NUM>, to prevent the resin around the neck portion 6c from being deformed (displaced) outward in the radial direction from the neck portion 6c. This increases the strength of anchorage between the built-in component <NUM> and the tank body Ta. In addition, the deformation prevention structure can be easily formed because only thing to do is to attach the rigid member <NUM>.

As shown in <FIG>, a seventh embodiment has the stepped portion <NUM> as a deformation prevention structure, as with the first embodiment, but a head portion 76d and a neck portion 76c are configured differently from those of the first embodiment. A built-in component <NUM> includes the body portion 6a in a columnar shape, the shoulder portions 6b formed at both ends of the body portion 6a, the neck portions 76c formed on axially outer sides of the shoulder portions 6b, and the head portions 76d, as shown in <FIG>.

The neck portion 76c here has a cylindrical shape erecting from the front surface 6f of the shoulder portion 6b, and is formed with four through holes <NUM> circumferentially at equal intervals. The through holes <NUM> are portions where the parison S enters during molding. In addition, four air vent holes 76i are formed in the shoulder portion 6b surrounded by the neck portion 76c. The air vent holes 76i each communicate, at one end thereof, with the cutout holes 6e formed in the body portion 6a. This allows the air in the recesses 3d and 4d to be discharged outside the recesses 3d and 4d through the air vent holes 76i.

The head portion 76d has a ring shape made of a thin plate. A plurality of ribs <NUM> erecting in a ring shape are formed on a surface <NUM> of the head portion 76d. The ribs <NUM> are formed along circles about the axis O. Note that the ribs <NUM> may be omitted.

The seventh embodiment described above gives advantageous effects substantially equivalent to those of the first embodiment. That is, the parison S enters the gap 6j and the stepped portion <NUM>, to prevent the resin around the neck portion 76c of the built-in component <NUM> (wrapping parison portion W) from being deformed. More specifically, the present embodiment has the resin around the neck portion 76c (wrapping parison portion W) received by the stepped portion <NUM>, to prevent the resin around the neck 76c from being deformed (displaced) outward in the radial direction from the neck portion 76c. This increases the strength of anchorage between the built-in component <NUM> and the tank body Ta. In addition, the present embodiment further increases the strength of anchorage because the parison S also enters the through holes <NUM> during molding. Further, the deformation prevention structure can be easily formed because the only thing to do is to provide the stepped portion <NUM>.

Claim 1:
A fuel tank (T) having a built-in component (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>) with a head portion (6d), a neck portion (6c), and a shoulder portion (6b), and having the built-in component (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>) anchored to a tank body (Ta) with a parison (S, SA) wrapped around the neck portion (6c) during molding, wherein
the fuel tank (T) comprises:
a deformation prevention structure (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>) configured to prevent a wrapping parison portion wrapped around the neck portion (6c) from being deformed due to pressure acting on the tank body, and configured to include at least one convex stepped portion provided on the shoulder portion (6b),
characterized in that
the shoulder portion (6b) is formed, at a position thereof around the neck portion (6c), with two air vent holes (6i) such that air in a gap (6j) defined between the shoulder portion (6b) and the head portion (6d) is dischargeable to a back surface (<NUM>) of the shoulder portion through the air vent holes (6i).