JP3367702B2 - Manufacturing method of resin fuel tank - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a resin fuel tank by blow molding. 2. Description of the Related Art Fuel tanks made of synthetic resin have various advantages such as weight reduction, rust prevention, and freedom of shape. Therefore, in recent years, fuel tanks formed by blow molding have been frequently used for automobiles. . However, in the case of a fuel tank for trucks, since the fuel tank is installed so as to be exposed to the outside of the vehicle, higher performance is required than that of a fuel tank of a passenger car, particularly, higher performance in flame resistance. At present, the spread is slow. [0003] For example, as shown in FIG. 4, a square resin fuel tank 1 similar to a conventional steel tank is used.
In the case of manufacturing by the conventional blow molding as shown in FIGS. 5 and 6, the extruder 2 extrudes a heat-softened thermoplastic plastic parison 3 into a tube shape.
A pair of left and right molds 4 and 4 where the mating surfaces are in close contact with the center
The compressed air is blown into the parison 3 from the pipe 5 at the same time as the compressed air is blown from the pipe 5 to expand the parison 3 in the cavity 6 formed by the two dies 4 and 4. However, when the resin fuel tank 1 is manufactured by the conventional blow molding as described above, the upper half 1A of the resin fuel tank 1 is divided by the parting line P. And the lower half 1B have the same thickness, and as shown in Tests # 1 and # 2 in Table 2, the thicknesses T1 to T4 of the corners A to D are also extremely thin. As a result, in the flame resistance test, fuel leaks and some holes in the upper half occurred, and the standards required by the Automobile Manufacturers Association, which are required by automakers to provide their own performance, were adopted. Could not be met. In order to solve the above-mentioned drawbacks, as shown in Test # 3 in Table 2 , the thickness of the upper half 1A and the lower half 1B and the thickness T1 of each of the corners A to D are set. ~ T
In order to increase each of the four and pass the flame resistance test, the product weight had to be increased to 11 kg, and as a result, the weight became incompatible with the steel tank, and the initial weight was reduced. There is a problem that the object cannot be achieved. [Table 2] [0007] Therefore, as a result of repeated experiments, the flame resistance test showed that the fuel tank 1 made of resin was used.
In the lower half 1B, a perforation phenomenon is unlikely to occur due to the cooling effect of the fuel in the tank 1, but in the upper half 1A, a hole or deformation is likely to occur due to the flame. For this reason, the pass / fail of the flame resistance test is based on the thickness of the upper half 1A, especially the corners A,
It depends on how to secure the thickness of B, and it has been found that this can be solved by the joining position of the pair of molds and the size of R at the corner. The present invention is based on the results obtained in this experiment, and by setting the joining position of a pair of molds to a position closer to the upper half forming side of a resin fuel tank, The thickness of the upper half can be increased while the thickness of the lower half can be smaller than this, and the R of the corner in the mold on the upper half side of the resin fuel tank can be increased. The object of the present invention is to provide a structure in which the thickness of the upper half corner portion can be increased by increasing the height of the corner portion R in the mold on the lower half portion forming side. The gist is that the fuel tank
A resin fuel tank whose upper half is thicker than the lower half
In this method, ink is manufactured using a blow molding die.
Te, 1 the blow molding mold in an area ratio within the cavity: 1 to 1: and half mold on joining with 1.5 a position when composed of a lower half mold In particular, a blow molding die formed by forming a radius of curvature of a corner in the cavity of the upper half molding die larger than a radius of curvature of a corner in the cavity of the lower half molding die. And a method for manufacturing a resin fuel tank characterized by performing blow molding. Hereinafter, the present invention will be described in detail with reference to FIGS. 1 is a perspective view of a resin fuel tank according to the present invention, FIG. 2 is a longitudinal sectional view of the fuel tank at the time of blow molding, and FIG. 3 is a sectional view taken along line II-II of FIG. In FIG. 1, reference numeral 10 denotes a resin fuel tank manufactured according to the present invention, and a parting line 11 thereof.
Is formed integrally with the upper half portion 12 and the lower half portion 13 with the boundary therebetween, and when this is blow-molded with a pair of molds M1 and M2, the position of the dividing line ab and the shape of the corner portion, etc. Are as follows. First, the thickness of the upper half portion 12 of the fuel tank 10, especially the thicknesses T1 and T2 of the corner portions A and B are 5
If it is less than mm, holes will be generated in the fire resistance test of the voluntary standard for trucks and buses. If the average thickness of the upper surface is 5 mm or less, the flame causes perforation or deformation, and the shape of the fuel tank 10 cannot be maintained. Therefore, the wall thickness required to pass the fire resistance test is at least 5 mm (actually, preferably 6 mm or more) in the upper half portion 12. On the other hand, the lower half 13 on the bottom side of the fuel tank 10 is less likely to be perforated or deformed by flame due to the cooling effect of the fuel contained in the fuel tank 10.
The average of the thicknesses T3, T4 and the bottom thickness of the corners C and D may be such that the shape can be maintained when the fuel is filled therein, and is set to about 3.5 mm. It is. The corners A, B of the upper half 12
The curvature radii R1 and R2 of the lower half 13 are
The curvature radii R3 and R4 of D are respectively set to be larger, so that the thicknesses T1 and T2 of the corners A and B in the upper half 12 formed by blow molding described below are reduced by the lower half 1
3 can be formed to be thicker than the thicknesses T3 and T4 of the corner portions C and D, respectively. [0014] The method of manufacturing is similar to the conventional blow molding shown in FIGS. 5 and 6, in which the extruder 2 extrudes a heat-softened thermoplastic plastic parison 3 into a tubular shape. Was sandwiched between a pair of left and right split molds M1 and M2 having close contact surfaces, and at the same time, compressed air was blown into the parison from a pipe 5 to expand in a cavity 6 formed by the pair of right and left molds M1 and M2. Thereafter, this is cooled and removed from the mold to obtain a resin fuel tank 10. Here, the pair of left and right dies M1 and M2 used for the blow molding are located at positions where the area ratio in the cavity is 1: 1 to 1: 1.5 as shown in FIG. Upper mold (upper half forming mold) M1 and lower mold (lower half forming mold) M2 set so as to join together
And the radii of curvature R1, R2 of the corners A, B in the cavity of the upper half forming mold M1.
Are set larger than the radii of curvature R3 and R4 of the corners C and D in the cavity of the lower half forming mold M2. In this case, the inside of the lower half-forming mold M2 having a large volume ratio in the cavity is more greatly extended by air pressure than the lower half-forming mold M1 having a smaller volume ratio. Therefore, the thickness in the upper half forming die M1 is larger than the thickness in the lower half forming die M2. Therefore, assuming that the length between the dividing lines a and b of the inner surface shape (engraving surface) of the pair of molds M1 and M2 is equal to the thickness of the parison, the length between the parting lines 11 of the upper half 12 (periphery) Length) L
Assuming that 1 is 1 and the thickness of the lower half is 3.5 mm, the upper half 12
In order to make the wall thickness 5 mm, the length (perimeter) L2 (x) between the parting lines 11 of the lower half 13 is 1 × 5 = 3.
5x, Δx = 1.43. That is, the circumference L2 of the lower half 13 is required to be about 1.43 times the circumference L1 of the upper half 12. That is, as x approaches 1, the thickness of the upper half 12 and the lower half 13 of the fuel tank 10 approximates, and as x approaches 1.5, the thickness of the upper half 12 becomes less elongated, Since the thickness can be secured, the position of the dividing line ab of the molds M1 and M2 is set to be within 1.0 ≦ x ≦ 1.5. Embodiment 1 The ratio of the peripheral lengths L1 and L2 of the upper half 12 and the lower half 13 with respect to the parting line 11 is 1.0:
The positions of the dividing lines ab of the molds M1 and M2 are set so as to be 1.0, and the curvature radii R of the corners A and B of the upper half 12 are set.
A resin fuel tank 10 for trucks having a capacity of 100 liters and a product weight of 8.8 kg was formed by setting R1, R2 to 150 mm, and radii of curvature R3, R4 of the corners C, D of the lower half 13 to 100 mm. The minimum thicknesses T1 and T2 of the corners A and B of the half portion 12 were 5.3 mm. This fuel tank 10 is referred to as "the voluntary standard for truck and bus fuel tanks".
(Hereinafter referred to as voluntary standards), they were subjected to a fire resistance test, which cleared the standards. [Embodiment 2] The ratio of the peripheral lengths L1 and L2 of the upper half portion 12 and the lower half portion 13 at the boundary of the parting line 11 is 1.0:
The positions of the dividing lines ab of the molds M1 and M2 are set so as to be 1.0, and the curvature radii R of the corners A and B of the upper half 12 are set.
The resin fuel tank 10 for trucks having a capacity of 100 liters and a product weight of 8.5 kg was formed by setting R1, R2 to 220 mm, and radii of curvature R3, R4 of the corners C, D of the lower half 13 to 100 mm. The minimum thicknesses T1 and T2 of the corners A and B of the half portion 12 were 5.5 mm. When this fuel tank 10 was subjected to a fire resistance test shown in “Independent Standard”, this standard was cleared. [Embodiment 3] The ratio of the perimeters L1 and L2 of the upper half 12 and the lower half 13 at the parting line 11 is 1.0:
The positions of the dividing lines ab of the molds M1 and M2 are set so as to be 1.0, and the curvature radii R of the corners A and B of the upper half 12 are set.
1, a resin fuel tank 10 for trucks having a capacity of 100 liters and a product weight of 8.7 kg was formed by setting the radius R3 and R4 of the corners C and D of the lower half portion 13 to 330 mm and the lower half portion 13 to 100 mm. The minimum thicknesses T1 and T2 of the corners A and B of the half portion 12 were 5.7 mm. When this fuel tank 10 was subjected to a fire resistance test shown in “Independent Standard”, this standard was cleared. [Embodiment 4] The ratio of the peripheral lengths L1 and L2 of the upper half portion 12 and the lower half portion 13 at the boundary of the parting line 11 is 1.0:
The positions of the dividing lines ab of the molds M1 and M2 are set so as to be 1.2, and the curvature radii R of the corners A and B of the upper half 12 are set.
1, a resin fuel tank 10 for trucks having a capacity of 100 liters and a product weight of 8.5 kg was formed by setting the radius of curvature R3 and R4 of the corners C and D of the lower half 13 to 150 mm and the lower half 13 to 100 mm. The minimum thicknesses T1 and T2 of the corners A and B of the half portion 12 were 5.8 mm. When this fuel tank 10 was subjected to a fire resistance test shown in “Independent Standard”, this standard was cleared. Embodiment 5 The ratio of the circumferences L1 and L2 of the upper half 12 and the lower half 13 at the boundary of the parting line 11 is 1.0:
The positions of the dividing lines ab of the molds M1 and M2 are set so as to be 1.2, and the curvature radii R of the corners A and B of the upper half 12 are set.
A resin fuel tank 10 for trucks having a capacity of 100 liters and a product weight of 8.6 kg was formed by setting 1, R2 to 220 mm and the radius of curvature R3, R4 of the corners C, D of the lower half 13 to 100 mm. The minimum thicknesses T1 and T2 of the corners A and B of the half portion 12 were 6.2 mm. When this fuel tank 10 was subjected to a fire resistance test shown in “Independent Standard”, this standard was cleared. Embodiment 6 The ratio of the peripheral lengths L1 and L2 of the upper half 12 and the lower half 13 at the boundary of the parting line 11 is 1.0:
The positions of the dividing lines ab of the molds M1 and M2 are set so as to be 1.2, and the curvature radii R of the corners A and B of the upper half 12 are set.
1, a resin fuel tank 10 for trucks having a capacity of 100 liters and a product weight of 8.3 kg was formed by setting the radius R3 and R4 of the corners C and D of the lower half portion 13 to 330 mm and the lower half portion 13 to 100 mm. The minimum thicknesses T1 and T2 of the corners A and B of the half portion 12 were 6.5 mm. When this fuel tank 10 was subjected to a fire resistance test shown in “Independent Standard”, this standard was cleared. [Embodiment 7] The ratio of the peripheral lengths L1 and L2 of the upper half portion 12 and the lower half portion 13 at the boundary of the parting line 11 is 1.0:
The dividing line ab of the molds M1 and M2 is set to 1.45.
The position was set, and the radius of curvature R1, R2 of the corners A, B of the upper half 12 was 150 mm, and the radius of curvature R3, R4 of the corners C, D of the lower half 13 was 100 mm. When the resin fuel tank 10 for trucks of 0.4 kg was molded, the minimum thicknesses T1 and T2 of the corners A and B of the upper half portion 12 were 7.3 mm. When this fuel tank 10 was subjected to a fire resistance test shown in “Independent Standard”, this standard was cleared. Embodiment 8 The ratio of the peripheral lengths L1 and L2 of the upper half 12 and the lower half 13 at the parting line 11 is 1.0:
The dividing line ab of the molds M1 and M2 is set to 1.45.
The position is set, the radius of curvature R1 and R2 of the corners A and B of the upper half 12 are 220 mm, and the radius of curvature R3 and R4 of the corners C and D of the lower half 13 are 100 mm. When an 8.7 kg truck fuel tank 10 was molded, corners A and B of the upper half 12 were formed.
Had a minimum thickness T1 and T2 of 7.8 mm. When this fuel tank 10 was subjected to a fire resistance test shown in “Independent Standard”, this standard was cleared. Embodiment 9 The ratio of the circumferences L1 and L2 of the upper half 12 and the lower half 13 at the boundary of the parting line 11 is 1.0:
The dividing line ab of the molds M1 and M2 is set to 1.45.
The position was set, and the radius of curvature R1, R2 of the corners A, B of the upper half 12 was 330 mm, and the radius of curvature R3, R4 of the corners C, D of the lower half 13 was 100 mm. When a resin fuel tank 10 for trucks of 0.6 kg was molded, the minimum thicknesses T1 and T2 of the corners A and B of the upper half 12 were 8.0 mm. When this fuel tank 10 was subjected to a fire resistance test shown in “Independent Standard”, this standard was cleared. COMPARATIVE EXAMPLE Upper half 1 at parting line 11
2 and the lower half 13 have a ratio of 1.0: 1.
The positions of the dividing lines ab of the dies M1 and M2 are set so as to be 0, and the radii of curvature R1 and R2 of the corners A and B of the upper half 12 are set.
A resin fuel tank 1 for trucks having a capacity of 100 liters and a product weight of 8.5 kg, wherein R2 is 100 mm, and radii of curvature R3 and R4 of the corners C and D of the lower half 13 are 100 mm.
As a result, the minimum thicknesses T1 and T2 of the corners A and B of the upper half portion 12 were 4.0 mm. When this fuel tank 10 was subjected to a fire resistance test shown in the “voluntary standard”, the fuel tank 10 could not meet the standard and a hole and a fuel leak occurred. Table 1 summarizes Examples 1 to 9 and Comparative Examples. [Table 1] According to the method of manufacturing a resin fuel tank according to the present invention, as described above, the thickness of the upper half of the fuel tank is reduced to the lower half.
For blow molding resin fuel tanks larger than the wall thickness
A method of manufacturing with a mold, wherein the blow molding mold is formed in an area ratio in a cavity of 1: 1 to 1: 1.5.
The upper half molding die and the lower half molding die are joined at a position where the upper half molding die is formed, and the radius of curvature of the corner portion in the cavity of the upper half molding die is set to the lower half. The thickness of the upper half of the resin fuel tank is characterized by being blow-molded with a blow-molding mold formed so as to be larger than the radius of curvature of the corner in the cavity of the part-forming mold. The thickness of the lower half can be made smaller than this, while the thickness of the upper half corner can be made large, and the weight of the light and fire resistance test can be reduced. A resin fuel tank that meets the standard can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a resin fuel tank according to the present invention. FIG. 2 is a longitudinal sectional view of the fuel tank at the time of blow molding. FIG. 3 is a sectional view taken along line II-II of FIG. FIG. 4 is a perspective view in which a part of a conventional resin fuel tank is cut away. FIG. 5 is an explanatory view of a first step of the blow molding method. FIG. 6 is an explanatory view of a second step of the blow molding method. [Description of Signs] 10 Resin fuel tank 11 Parting line 12 Upper half 13 Lower half M1 Mold M2 Mold ab Dividing line A Corner B Corner C Corner D Corner R1 Curvature radius R2 Curvature Radius R3 radius of curvature R4 radius of curvature T1 thickness T2 thickness T3 thickness T4 thickness

Continuing from the front page (72) Inventor Junichi Kasai Isuzu Motors Co., Ltd. Fujisawa Plant, No. 8 Fujisawa City, Kanagawa Prefecture (72) Inventor Masakatsu Kuramoto 3- 25-1, Tonomachi, Kawasaki-ku, Kawasaki-shi, Kanagawa Isuzu Motors Limited (72) Inventor Mikio Nemoto 3 Chigusa Coast, Ichihara-shi, Chiba Mitsui Oil Chemical Industry Co., Ltd. (72) Inventor Osamu Nakato 3-5-1 Fujisaki, Kawasaki-ku, Kawasaki-ku, Kanagawa Prefecture Tokyo Radiator Manufacturing (72) Inventor Hideki Yamaji 3-5-1 Fujisaki, Kawasaki-ku, Kawasaki-shi, Kanagawa Prefecture Tokyo Radiator Manufacturing Co., Ltd. (72) Inventor Akihiro Takahara 3-5-1 Fujisaki, Kawasaki-ku, Kawasaki-shi, Kawasaki Tokyo (56) References JP-A-63-183815 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B60K 15/00-15/077

Claims (1)

(57) [Claims] (1) The thickness of the upper half of the fuel tank is the thickness of the lower half.
A resin fuel tank larger than the thickness is used as a blow mold
Therefore a method of producing the 1 blow molding mold in an area ratio within the cavity: 1 to 1: the top half of joining with 1.5 a position mold and for the lower half mold When configured with a mold, the radius of curvature of the corner in the cavity of the upper half molding die is formed larger than the radius of curvature of the corner in the cavity of the lower half molding die. A method for manufacturing a resin fuel tank, comprising blow molding with a blow mold.