JP2002316337A - Method for molding resin pipe - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily mold a resin pipe excellent in surface properties and dimensional accuracy. SOLUTION: A plasticized resin composition is injected in the hollow part 11S of a monolithic mold main body 11 having the columnar hollow part 11S and inert gas such as nitrogen gas or the like is injected in the columnar hollow part 11S from the gas injection port 16S of a gas nozzle 16 at the time of injection of the resin composition and the injected resin composition is spread to mold the resin pipe 20 having a hollow part 21 formed therein.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for molding a resin pipe by a gas injection molding method.

[0002]

2. Description of the Related Art Conventionally, in a copying machine such as an electrophotographic copying machine or a laser printer, a columnar or cylindrical product such as a photosensitive drum base, a developing roller, a developing sleeve, or an intermediate transfer drum base. Are often adopted. Since these products require surface properties (surface roughness) and dimensional accuracy (runout, roundness, etc.), for example,
When manufacturing the photosensitive drum substrate, a metal material such as aluminum is used as a material, and the surface thereof is finished by cutting. Further, when a cylindrical molded product (solid product) is molded using a resin, voids, warpage, sink marks, and the like due to the thickness are easily generated, and the surface property and dimensional accuracy are poor. , After injection / extrusion molding, cutting /
It was necessary to perform secondary processing such as surface grinding. On the other hand, as a method of molding a hollow molded article such as a resin pipe, a gas injection injection molding method is often employed. FIG. 7 (a)
FIG. 1 is a schematic view showing a configuration of a resin pipe molding die 50 used in a gas injection injection molding method described in Japanese Patent Application Laid-Open No. Hei 5-258944, in which a fixed mold 51 and a movable mold 5 are provided.
And an injection molding machine 5 in a stepped columnar cavity 53 for molding a resin pipe with a shaft formed therebetween.
4, the plasticized resin composition is injected, and at the time of injection of the resin composition, an inert gas is injected into the cavity 53 from a gas nozzle 55 provided in the injection molding machine 54, and the injection is performed. Press the resin spread with gas pressure,
As shown in FIG. 7B, a shaft-mounted resin pipe 60 having a hollow portion 61 is formed. In addition, as the resin pipe, not only a pipe with a shaft, but also a pipe without a shaft, or a pipe provided with a concave portion for inserting a separately prepared shaft on one or both end sides is also manufactured. .

[0003]

According to the above-mentioned gas injection injection molding method, it is possible to obtain a molded product having extremely small occurrence of voids and sink marks and having better surface properties and dimensional accuracy than the above-mentioned cylindrical molded product. However, as shown in FIG. 8, a linear projection 62 called a parting line is formed on the side surface of the cylinder.
This is because the resin at the part corresponding to the boundary between the fixed mold 51 and the movable mold 52 was raised to form a mold parting surface.
When, for example, used as a substrate of the photosensitive drum,
Problems such as periodic lines entering the image occur. Therefore, also in this case, it was difficult to omit secondary processing such as cutting. As shown in FIG. 9, a method of forming a resin pipe 70 by inserting a core 71 therein is also performed. However, when the pipe diameter is small, a pipe for temperature adjustment is passed through the core 71. Not only was there a disadvantage that space could not be secured, but also the surface properties and dimensional accuracy were not sufficient.

[0004] The present invention has been made in view of the conventional problems, and has as its object to provide a method for easily molding a resin pipe having excellent surface properties and dimensional accuracy.

[0005]

According to a first aspect of the present invention, there is provided a method for molding a resin pipe, comprising the steps of: providing a molding die having a cylindrical main body having a cylindrical hollow portion in the cylindrical hollow portion; ,
The plasticized resin composition is fed under pressure, and an inert gas is injected into the cylindrical hollow portion, and the pressure of the injected gas forms a hollow portion in the resin composition. Thereby, it is possible to obtain a resin pipe having a uniform surface and excellent dimensional accuracy. In addition, the method for molding a resin pipe according to claim 2,
In order to produce a resin pipe with a shaft, the cylindrical hollow part is formed at one or both ends of a pipe molded part having an inner diameter substantially equal to the outer diameter of the resin pipe to be a product. And a stepped column formed by a shaft forming portion having a smaller diameter than the pipe forming portion. According to a third aspect of the present invention, there is provided a method for forming a resin pipe, wherein a recess for inserting a shaft is provided on one or both ends of the hollow portion. In the method for molding a resin pipe according to claim 4, the resin introduction side of the hollow portion includes:
A connecting part for connecting with the resin pipe such as a gear or a pulley is arranged, and the resin pipe and the connecting part are integrally formed. The resin pipe molding method according to claim 5, wherein the resin composition is a resin composition containing a conductive resin.
This makes it possible to obtain a photosensitive drum substrate having excellent surface properties and dimensional accuracy.

[0006]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a view showing a configuration of a resin pipe molding die 10 according to the present embodiment. In FIG. 1, reference numeral 11 denotes a die body having a stepped cylindrical hollow portion 11S, and the hollow portion 11S is The cavity of the resin pipe molding die 10 is formed. The hollow portion 11S is
A pipe forming portion 11a having an inner diameter substantially equal to the outer diameter of a resin pipe to be a product;
And a shaft forming portion 11b having a smaller diameter than the pipe forming portion formed at the end opposite to the resin injection side. Reference numeral 12 denotes a resin introduction member having a sprue 13, a runner 14, and a gate 15. Reference numeral 16 denotes a gas nozzle which is connected to a pressure cylinder 17 via a pipe 18 and communicates with the gate 15. An injection nozzle of an injection molding machine (not shown) 19
The plasticized resin composition is injected into the cylindrical hollow portion 11S from the above, and at the time of injection of the resin composition, the gas is injected from the gas injection port 16S of the gas nozzle 16 into the cylindrical hollow portion 11S. An inert gas such as a nitrogen gas is injected into the resin pipe, and the injected resin composition is expanded by gas pressure to form a resin pipe 20 having a hollow portion 21 formed therein. In this example, a connecting part 30 such as a metal gear or a pulley is arranged on the gate 15 side of the cylindrical hollow portion 11S, and the resin pipe 20 and the connecting part 30 are integrally formed. I am trying to do it.

Next, a method of molding a resin pipe used for a photosensitive drum base using the resin pipe molding die (hereinafter, abbreviated as a mold) 10 having the above configuration will be described.
First, pellets of a resin composition mainly composed of a conductive resin obtained by blending a conductive substance with a thermoplastic resin such as nylon-66 as a raw material are prepared, and are put into an injection device (not shown). In the injection device, the resin composition is heated and plasticized, and is fed to the mold 10 at a predetermined pressure. The above materials are
After flowing through the sprue 13 and the runner 14 in the mold 10, it flows from the gate 15 into the cylindrical hollow portion 11 </ b> S of the mold body 11 which is a cavity. A predetermined time after the resin composition starts flowing into the cylindrical hollow portion 11S, the gas injection port 16S is opened and nitrogen gas is injected into the cylindrical hollow portion 11S.
S is injected into the S, and a hollow portion 21 is formed in the resin composition by the pressure of the injection gas. Thereafter, the resin composition is cooled and solidified while maintaining the gas pressure constant,
A resin pipe with a shaft 20 having the connecting part 30 integrated on one end side is obtained. The molded resin pipe 20 has a uniform surface since the cylindrical hollow portion 11S constituting the cavity does not have a joint portion, and is made of a metal such as that formed by a conventional mating die. Since the mold parting surface is not formed, a resin pipe 20 for a photosensitive drum substrate having excellent surface properties and dimensional accuracy can be obtained.

As described above, according to the present embodiment, the resin composition plasticized from the injection nozzle 19 into the hollow portion 11S of the integrated mold body 11 having the cylindrical hollow portion 11S. And at the time of injection of the resin composition, an inert gas such as nitrogen gas is injected into the hollow portion 11S from the gas injection port 16S of the gas nozzle 16, and the injected resin composition is gas-pressured. Since the resin pipe 20 in which the hollow portion 21 is formed is formed by being pushed and spread, a molded product having a uniform surface can be obtained. Therefore, for example, by using a resin composition containing a conductive resin as a main component as the above-mentioned resin composition, a photosensitive drum substrate excellent in surface properties and dimensional accuracy can be obtained. Further, the resin pipe 20 also has an advantage that the product can be reduced in weight as compared with a columnar product molded with solid.

In the above embodiment, the gas inlet 1
6S is provided so as to communicate with the gate 15, but FIG.
(A), (b), the cylindrical hollow portion 11
S forms shaft forming portions 11b and 11c at both end sides, and connects the gas injection port 16S to the resin forming side shaft forming portion 11c.
A structure may be provided on the side surface side or the runner 14 side. Alternatively, as shown in FIG. 4, the gas injection port 16S may be provided in the injection nozzle 19.
As shown in FIG. 5, on the end side of the hollow portion 11 </ b> S (here, the end side opposite to the connecting component 30),
Shaft insertion recess 11 for inserting a separately manufactured shaft
By providing R, a resin pipe 20A having a hole 23 for shaft insertion as shown in FIG. 6 can be formed. A hole for shaft insertion may be similarly provided on the other end of the resin pipe. Further, in the above-described example, the method of molding the resin pipe used for the photosensitive drum substrate has been described. However, the present invention is not limited to this, and a cylindrical product such as a developing roller and a developing sleeve of a copying machine, and a copying machine It is applicable to resin pipe products that are required for surface properties, dimensional accuracy, and weight reduction, which are used for general OA equipment other than the above.

[0010]

EXAMPLES Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to these examples. A resin pipe for a photosensitive drum substrate having an outer diameter of φ16 mm and a length of 240 mm is molded using the resin pipe molding die of the present invention, and its characteristics are solid.
The results of comparison with the products are shown in Table 1 below. As the resin, 66N-based conductive resin was used.

[Table 1] As is clear from Table 1, it was confirmed that the resin pipe of the present invention not only had a smaller surface roughness difference than the comparative example, but also had a smaller total runout value, and was excellent in surface properties and dimensional accuracy. Since the weight is also reduced by about 20% as compared with the comparative example, the weight can be reduced and the yield of the material can be improved.

[0011]

As described above, according to the present invention,
Into the hollow portion of the integral mold body having a cylindrical hollow portion, while pressure-feeding the plasticized resin composition, inject an inert gas into the hollow portion, by the pressure of the injected gas, Since the hollow portion is formed in the resin composition, a resin pipe having a uniform surface and excellent dimensional accuracy can be easily formed. Further, by using a resin composition containing a conductive resin as the resin composition, a photosensitive drum substrate excellent in surface properties and dimensional accuracy can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing a method for molding a resin pipe according to the present embodiment.

FIG. 2 is a cross-sectional view of the resin pipe according to the present embodiment.

FIG. 3 is a view showing a method for molding a resin pipe according to the present invention.

FIG. 4 is a view showing a method for molding a resin pipe according to the present invention.

FIG. 5 is a view showing another example of the mold body according to the present invention.

FIG. 6 is a sectional view showing an example of a resin pipe according to the present invention.

FIG. 7 is a view showing a conventional method for forming a resin pipe.

FIG. 8 is a view showing the appearance of a resin pipe formed by a conventional gas injection molding method.

FIG. 9 is a view showing another molding method of a conventional resin pipe.

[Explanation of symbols]

10 Mold for resin pipe, 11 Mold body, 11S
Cylindrical hollow part, 12 resin introduction member, 13 sprue, 14 runner, 15 gate, 16 gas nozzle, 16S gas injection port, 17 pressurized cylinder, 18 piping, 19 injection nozzle, 20 resin pipe, 21 resin pipe hollow section , 30 connecting parts.

Claims (5)

[Claims] 1. A plasticization-treated resin composition is pressure-fed into said cylindrical hollow portion of a molding die having a mold body having a cylindrical hollow portion, and an inert gas is discharged into said hollow portion. A method of molding a resin pipe, wherein a hollow portion is formed in the resin composition by injecting the resin composition into the resin composition with the pressure of the injected gas. 2. A pipe forming part having an inner diameter substantially equal to an outer diameter of a resin pipe to be a product, wherein said cylindrical hollow part is formed at one or both ends of said pipe forming part. The resin pipe molding method according to claim 1, wherein the resin pipe has a stepped cylindrical shape including a shaft molding portion having a smaller diameter than a portion. 3. A hollow portion for inserting a shaft is provided at one or both ends of the hollow portion.
Or the method of molding a resin pipe according to claim 2. 4. A part for coupling with a resin pipe such as a gear or a pulley is arranged on the resin introduction side of the hollow part,
The method for forming a resin pipe according to any one of claims 1 to 3, wherein the resin pipe and the connecting part are integrally formed. 5. The method for molding a resin pipe according to claim 1, wherein the resin composition is a resin composition containing a conductive resin.