JPH09207201A - Resin pipe and blow molding method thereof - Google Patents

Abstract

(57) Abstract: A fuel inlet pipe (10) has no notch on its inner wall (16a) along a parting line (PL) to increase its mechanical strength. A blow molding device (20) installs a parison (P) in a cavity (32) constituted by a first mold (40) and a second mold (50), and cuts a part of the parison (P) to cut it when the mold is clamped. The fuel inlet pipe 10 having a modified cross section is blow-molded by changing the diameter. The first to chop up
And the first and second mold holding portions 48, 5 of the second molds 40, 50.
8 is the longitudinal direction d of the first and second mold mating surfaces 46, 56.
2 along which the resin reservoir groove 48 formed to have substantially the same width.
a, 58a, and an inner cut portion 48b and an outer cut portion 48c, which are formed on the ridges along both sides of the resin reservoir grooves 48a, 58a, respectively, and which sandwich a part of the parison P during mold clamping. The inner wall 16a of the fuel inlet pipe 10 is made thick along the parting line PL.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin pipe such as a fuel inlet pipe and a hose, and a blow molding method therefor.

[0002]

2. Description of the Related Art Conventionally, as this type of resin pipe, a fuel inlet pipe used in a fuel tank of an automobile has been known. FIG. 9 is a perspective view showing a reduced diameter portion of the fuel inlet pipe 100. The fuel inlet pipe 100 includes a pipe main body 102 for supplying fuel to the tank main body through an opening from which the fuel cap is removed, and a return pipe connected to the pipe main body 102 for allowing fuel vapor in the tank main body to escape to the outside. 10
4 is provided. This fuel inlet pipe 1
00 has a part whose diameter is not constant over its entire length, and is formed in a three-dimensionally bent shape.

A blow molding method is one of the methods for molding the fuel inlet pipe 100 having a partially reduced diameter. 10 and 11 show a blow molding process in which a reduced diameter portion of the fuel inlet pipe 100 is manufactured, and FIG. 10 shows a state during mold clamping,
FIG. 11 is a diagram showing a state after mold clamping. The fuel inlet pipe 100 is molded by the following steps. That is, the parison P having the same cross section is set in the cavity 116 formed by the first die 112 and the second die 114, and then a part of the parison P is cut into the cut portions of the first die 112 and the second die 114. The bite portion Pa is sandwiched by 112a and 114a, and at substantially the same time, gas is pumped into the parison P, cooled and solidified, and then released, and the bite portion Pa is deburred. Thereby, the fuel inlet pipe 100 is molded.

[0004]

However, in the fuel inlet pipe 100 manufactured by the blow molding method described above, as shown in FIG. 9, it is the inner wall 100b of the cut-out portion along the parting line PL. Notches 100c may be formed. For this reason, when a large load is applied to the fuel inlet pipe 100 in the direction of the arrow d1, stress tends to concentrate on the notch 100c, and the strength may decrease.

The present invention solves the above-mentioned problems of the prior art, and an object of the present invention is to provide a fuel inlet pipe having high strength without forming a notch on its inner wall surface and a blow molding method thereof. To do.

[0006]

[Means for Solving the Problem and Its Action and Effect] A first invention made to solve the above problems is to provide a resin pipe having a modified cross section with a mold which is formed when the mold is clamped. Equipped with a tube body that has a reduced diameter portion that has a modified cross section by cutting off a part of the parison at the end, and is the inner wall of the reduced diameter portion and along the parting line, thicker than other inner walls It is characterized in that a thick portion is formed.

In the resin pipe according to the first aspect of the present invention, since the thick part is formed along the parting line on the inner wall of the reduced diameter part and the notch is not formed, stress concentration does not occur. It is possible to obtain strong strength.

A second invention is a blow molding method for producing the resin pipe according to the first invention. In the blow molding method, when the parison is set in the cavity formed by the first mold and the second mold of the molding die, when the mold is clamped, the cutting die portion of the molding die holds a part of the parison. As a result, the cut-out portion is formed and the parison itself is reduced in diameter. Here, the cutting die portion of the molding die is composed of a resin reservoir groove and inner and outer cut portions formed on the ridges on both sides of the resin reservoir groove,
When the mold is clamped, the resin part of the parison sandwiched between the cut-out mold parts secures a large amount and flows toward the center of the parison, and along the parting line along the inner wall of the resin pipe formed from the parison. And thicken. Therefore, since the notch is not formed along the parting line on the inner wall of the resin pipe, strong strength can be obtained without stress concentration.

In addition, since the inner and outer cut portions are formed on both sides of the resin reservoir groove in the bite-cut die portion and the area for holding the parison is small, the die clamping force does not increase.

Further, the mold clamping is carried out at a low speed after the parison starts to be clamped by the bite mold part, whereby fusion of the bite part of the parison is promoted to further prevent notches from being formed, and at the same time, the notch is formed in the parison. By performing the low pressure blow, it is possible to prevent the resin from dropping in the parison.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In order to further clarify the configuration and operation of the present invention described above, preferred embodiments of the present invention will be described below.

FIG. 1 is a perspective view showing a fuel tank FT equipped with a fuel inlet pipe 10 according to an embodiment of the present invention. The fuel inlet pipe 10 is connected to the pipe body 12 for supplying fuel to the tank body TB through an opening formed by removing a fuel cap (not shown), and is connected to the pipe body 12 so that the fuel vapor in the tank body TB is exposed to the outside. And a return line 14 for escaping. The fuel inlet pipe 10 is a pipe having an irregular cross section, and is formed in a three-dimensionally bent shape.

The fuel inlet pipe 10 is formed from a resin material (HDPE) by a blow molding method,
The parison having substantially the same cross-sectional shape is formed to have an irregular cross section and a three-dimensional shape. The fuel inlet pipe 10 has a reduced diameter portion 16 having a modified cross section by reducing the diameter by cutting off a part of the parison at the end of the forming die when the die is clamped in the blow molding process. FIG. 2 is an enlarged perspective view of the vicinity of the reduced diameter portion 16 taken along the line 2-2 of FIG. As shown in FIG. 2, a thick wall portion 16b which is the inner wall 16a of the reduced diameter portion 16 of the fuel inlet pipe 10 and is thicker than the other inner wall surface is formed along the parting line PL. There is. That is,
Inner wall 1 of reduced diameter portion 16 of fuel inlet pipe 10
The thick portion 16b is formed along the parting line PL in the portion 6a and is not in the notch shape. Therefore, even if a large load is applied to the pipe body 12 in the direction of the arrow d1, stress does not concentrate near the parting line PL.

Next, a blow molding method for molding the above-described fuel inlet pipe 10 will be described. This blow molding method is performed using the blow molding apparatus 20 shown in FIG. The blow molding device 20 includes a parison supply device 22, and a first mold 40 and a second mold 50 that form the molding die 30.

The parison supply device 22 has a nozzle 22a at its tip, and the parison P is pushed out and supplied from the nozzle 22a. A cavity 32 for forming the fuel inlet pipe 10 is formed in the first die 40 and the second die 50 of the forming die 30. That is, the cavity 32 is composed of a first die cavity portion 42 formed in the first die 40 and a second die cavity portion 52 formed in the second die 50, and the pipe body 12 and the return pipe having an irregular cross section. It is surrounded by molding surfaces 44, 54 that follow the contour of the passage 14.

The first die 40 and the second die 50 are respectively formed with a first die mating surface 46 and a second die mating surface 56 which are mated with each other by die clamping. FIG. 4 is an enlarged perspective view of the vicinity of the first die mating surface 46 and the second die mating surface 56. As shown in FIG. 4, the first mold-matching surface 46 and the second mold-matching surface 56 include the first mold clamping part 48 and the second mold clamping part 58 that clamp a part of the parison P, and the biting mold part 38. Is equipped with. The first die clamping portion 48 and the second die clamping portion 58 of the bite die portion 38 are made of resin having substantially the same width along the longitudinal direction d2 of the first die mating surface 46 and the second die mating surface 56. Inner cut portions 48b, 58b and outer cut portions 48c, which are formed on the protrusions along both sides of the reservoir grooves 48a, 58a and the resin reservoir grooves 48a, 58a, and which hold a part of the parison P during mold clamping,
58c. Inner cut parts 48b, 58b
The outer cut portions 48c and 58c are pulse-shaped so that the parison P can be cut and formed as described later, but the tops thereof are formed flat. Further, on the side of the biting die part 38, a relief recess 39 for letting the biting part Pa of the parison P escape is formed.

Next, the manufacturing process of the fuel inlet pipe 10 by the blow molding method will be described. FIG.
7 to 7 are sectional views showing the blow molding process in time sequence, and FIG. 8 is a timing chart showing the distance between the first die 40 and the second die 50 (die opening amount ST) and the blow air pressure Pr. is there. First, with the first mold 40 and the second mold 50 set with a predetermined gap, the parison supply device 22
The parison P is pushed out from the nozzle 22a of the first mold 40, and the parison P is moved to the first mold cavity portion 42 of the first mold 40 and the second mold 50
Between the second mold cavity 52 and the second mold cavity 52. Subsequently, the first die 40 and the second die 50 are rapidly moved at a predetermined distance (10
mm) to perform the high-speed mold clamping process of moving in the mold clamping direction (time t0 to t1 in FIG. 8, state in FIG. 5), and then
A low speed mold clamping process is performed in which the mold clamping speed is switched to a low speed (time points t1 to t2 in FIG. 8). In this low speed mold clamping process,
Part of the parison P is sandwiched by the first mold sandwiching portion 48 of the first mold 40 and the second mold sandwiching portion 58 of the second mold 50, and the bite-cut portion Pa in which a part of the parison P is reduced in diameter starts to be formed. .

That is, during the low-speed mold clamping process, the parison P between the bite mold parts 38 is covered with the resin reservoir groove 48.
Since the first and second die clamping portions 48 and 58 including a and 58a are clamped in a state where a large amount of resin is secured, the amount flowing out to both sides of the parison P (arrow direction d3) is reduced. Will increase. At this time, the mold clamping is slow,
The fusion of the fusion-bonded portion Pb of the cut-out portion Pa of the parison P is promoted, and the thick-walled portion Pc, which is the inner wall of the parison P and is thickened along the parting line PL, is formed (FIG. State 6). The parison P is partly separated by the cutting action of the inner and outer cut portions 48c and 58c of the biting die portion 38 to become the biting portion Pa and is released to the escape recess 39.

Then, a gas having a low pressure Pr1 is blown into the parison P (time points t3 to t4 in FIG. 8)). This low-pressure blowing step promotes the fusion of the bite portion Pa of the parison P at the fusion portion Pb following the above-described step, and the parison P sags, that is, when no pressure is applied to the parison P. This prevents the resin from sagging as shown by the chain double-dashed line in FIG. The start time and pressure of the air blow in the low-pressure blow process are determined in consideration of the promotion of the fusion of the fusion bonding portion Pb in the cut-out portion Pa and the sagging of the resin.

Further, a high pressure blow process is performed to increase the blow air pressure Pr to the normal pressure Pr2 (time points t4 to t5 in FIG. 8). In this high-pressure blowing process, it is possible to prevent the resin of the parison P from dripping and
The molding surfaces 44 and 54 of the mold 40 and the second mold 50 are imitated (state of FIG. 7). Then, after the high-pressure blowing step is completed, the parison P is cooled in the cavity 32 of the molding die 30, and the first die 40 and the second die 50 are opened to remove the die, and the bite cut portion is further removed. By removing Pa, the fuel inlet pipe 10 of FIG. 1 is completed.

In the blow molding method according to the above embodiment, during the low speed mold clamping step, the part of the parison P between the cutting die parts 38 is filled with the resin reservoir grooves 48a, 58a.
Since the first and second mold clamping portions 48 and 58 including the resin are clamped in a state where a large amount of resin is secured, the amount of flow toward the inner wall of the parison P increases,
Moreover, since the mold clamping is performed at a low speed, fusion of the parison P at the cut-out portion Pa is promoted. As a result, the thick wall portion 16 that is the inner wall 16a of the fuel inlet pipe 10 and has a thick wall thickness along the parting line PL.
b is reliably fused and formed. Moreover, since the resin of the parison P is prevented from dripping even when the mold is clamped at a low speed, the gas of low pressure Pr1 is blown into the parison P, so that the fuel inlet pipe 10 having a desired shape is manufactured. It

Therefore, in the fuel inlet pipe 10 manufactured by the blow molding method, the thick portion 16b is formed along the parting line PL of the inner wall 16a.
Therefore, the occurrence of notches can be eliminated, the mechanical strength is high, and the shape defect due to the sagging of the parison P does not occur.

Further, the inner cut portion 4 of the biting die portion 38
8b, 58b and the outer cut portions 48c, 58c have flat tops to promote the flow of the resin of the parison P, but their widths are also narrow, so the mold clamping force does not increase. The shape of the bite mold part 38 is determined in consideration of the mold clamping force and the amount of resin flow.

Furthermore, the molds are clamped at a high speed and then at a low speed, and the molds are clamped at a low speed of only about 10 mm, so the mold clamping time is not so long and the productivity is improved. It does not decrease.

The present invention is not limited to the above embodiments, but can be carried out in various modes without departing from the scope of the invention, and the following modifications can be made.

(1) Biting die portion 38 of the molding die 30
May be formed on the first mold matching surface 46 and the second mold matching surface 56, respectively, or may be formed on one of the first mold matching surface 46 and the second mold matching surface 56, that is, the resin amount of the parison P. It suffices if it can be cut while securing a large number of holes.

(2) The first and second mold holding portions 48, 58 for cutting the parison P are provided with resin reservoir grooves 48a, 58a.
The inner cut portions 48b and 58b and the outer cut portions 48c and 58c are provided on both sides of the groove. However, the width and number of the grooves and the number of the cut portions are not particularly limited. Can be determined as appropriate.

(3) In the above embodiment, low-pressure air blowing is performed after completion of mold clamping, but it may be performed simultaneously with low-speed mold clamping or before low-speed mold clamping.
In particular, when the resin of the parison P is likely to sag, it is effective to apply the blow pressure from the initial stage.

[Brief description of drawings]

FIG. 1 is a perspective view showing a fuel tank FT including a fuel inlet pipe 10 according to an embodiment of the present invention.

2 is a perspective view showing a reduced diameter portion 16 of the fuel inlet pipe 10 taken along the line 2-2 in FIG.

FIG. 3 is a perspective view showing a blow molding device 20.

4 is a perspective view showing the vicinity of a first die mating surface 46 and a second die mating surface 56 of the molding die 30. FIG.

FIG. 5 is an explanatory diagram illustrating a blow molding method.

FIG. 6 is an explanatory diagram showing a step that follows FIG.

FIG. 7 is an explanatory diagram showing a step that follows the step of FIG.

FIG. 8 is a timing chart illustrating a blow molding process.

FIG. 9 is a perspective view showing a conventional fuel inlet pipe 100.

FIG. 10 is an explanatory diagram illustrating a blow molding method for manufacturing a conventional fuel inlet pipe 100.

11 is an explanatory diagram showing a step that follows the step of FIG.

[Explanation of symbols]

 FT ... Fuel tank TB ... Tank body P ... Parison Pa ... Eating part Pb ... Fusion part Pc ... Thick part PL ... Parting line 10 ... Fuel inlet pipe 12 ... Pipe body 14 ... Return pipe 16 ... Reducing part 16a ... Inner wall 16b ... Thick part 20 ... Blow molding device 22 ... Parison supply device 22a ... Nozzle 30 ... Molding die 32 ... Cavity 38 ... Eating part 39 ... Concave 40 ... First mold 42 ... First mold cavity 44, 54 ... Molding surface 46 ... First mold mating surface 48 ... First mold sandwiching portion 48a, 58a ... Resin reservoir groove 48b, 58b ... Inner cut portion 48c, 58c ... Outer cut portion 50 ... Second die 52 ... Second Mold cavity portion 56 ... Second mold mating surface 58 ... Second mold holding portion

Claims (3)

[Claims] 1. A resin pipe having a modified cross section, wherein a pipe body having a reduced diameter portion having a modified cross section by cutting off a part of the parison at the end of the mold when the mold is clamped is formed. A resin pipe, characterized in that the resin pipe has an inner wall of the reduced diameter portion and a thick wall portion formed to be thicker than the other inner wall along the parting line. 2. A blow molding method for manufacturing a resin pipe having an irregular cross section, wherein a parison supply means for supplying a parison, a molding die having a first mold and a second mold, and a first mold and a second mold are formed. And a cavity surrounded by a molding surface that follows the outer shape of the resin pipe having an irregular cross section and provided in the first mold and the second mold, respectively, and are aligned with each other when the first mold and the second mold are clamped. Provided on the first and second die mating surfaces, and on the first and second die mating surfaces of the first die and the second die,
A biting die part for sandwiching a part of the parison; and the biting die part, which has substantially the same width along the longitudinal direction of the upper die and the second die mating surface;
Formed on the ridges along both sides of the resin reservoir groove,
Using a blow molding device having an inner cut portion and an outer cut portion for holding a part of the parison when the mold is clamped, the parison supply means is provided with the first mold and the second mold separated from each other by a predetermined distance. From the parison setting step of setting the parison between the cavities of the first and second molds, and by clamping the first mold and the second mold, and clamping at least a part of the parison by the bite mold part, A mold clamping step of forming a reduced diameter part of the parison with a reduced diameter, and clamping the resin while directing the resin of the parison located in the upper cutting die part including the resin reservoir groove toward the center side of the parison. And a blow step of blowing gas into the parison during or after the mold clamping step, and a blow molding method. 3. The mold clamping step according to claim 2,
A step of performing low-speed mold clamping after high-speed mold clamping is provided.
A low-pressure blow process that blows a low-pressure gas into the parison to promote fusion of the reduced diameter part of the parison, and prevents the resin from dripping in the parison, and a gas that raises the blow air pressure to the normal blow pressure. A blow molding method comprising: a step of feeding the parison into the parison so that the parison follows the molding surfaces of the first mold and the second mold.