JP2000289053A - Method for molding roller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress generation of defects of appearance caused by generation of welds and flow marks and fluctuation of physical properties within a single roller in preparing a roller with high quality by using a mold with a cylindrical through-hole. SOLUTION: In molding a roller wherein an elastic material is formed cylindrically around a shaft-like core metal and integrally with a core metal member 4, a mold for molding the roller consists of a mold with a cylindrical through- hole and lid bodies fitted on opening parts of both ends each with a shape of a cylindrical hole for holding the shaft-like core metal member 4 concentrically to this cylindrical hole and at least a part of the lid bodies is a movable body provided with a feeding inlet 7 and a ring gate 5 for a molding material and by moving the movable lid body, a means for controlling the width of the gate and opening and closing is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of forming a roller formed integrally with a cored member by forming an elastic material into a cylindrical shape around a shaft-shaped cored bar. -Suitable for forming a high-performance roller used in an image forming apparatus such as an electrostatic recording apparatus.

[0002]

2. Description of the Related Art Conventionally, an extrusion method has been used for forming a cylindrical roller. However, in high-performance rollers used in image forming apparatuses such as electrophotographic apparatuses and electrostatic recording apparatuses, dimensional accuracy such as thickness and diameter is very important. A polishing step was required. Accordingly, an injection molding method having higher dimensional accuracy than the extrusion molding method has recently been used.

[0005] The failure phenomena occurring in the molded product by the injection molding method include a weld generated at a point where a material such as resin converges in the cavity, a flow mark generated by convection resistance with a mold wall surface, and the like. . Due to the occurrence of these defects, a low-strength portion is partially formed in the roller, which easily causes breakage and the like, and uneven distribution of a filler or the like present in the material due to flow resistance and disturbance of the orientation of the resin. As a result, the quality of the molded product is deteriorated, such as unevenness of the material characteristic value in the roller.

[0004] Therefore, attempts have been made to provide an air vent at the confluence of the resin material to quickly release air and volatile components in this portion, or to delete this portion after providing a material reservoir at a location where a defect occurs. However, there is a new problem that vent marks and material pool marks remain on the roller surface.
In particular, in the production of high-performance rollers used in image forming apparatuses such as electrophotographic apparatuses and electrostatic recording apparatuses, since the smoothness of the roller surface is important, a penetrating cylinder as shown in FIGS. In order to hold the shaft-shaped core member 4 concentrically with the cylindrical hole in the forming die 1 having a hole, a roller is formed by a metal mold using lids 21 and 22 at both openings of the cylindrical hole. It is common.

[0005] In this case, as a measure for preventing the occurrence of defects due to welds and flow marks generated in the molded body, the mold temperature is increased or the injection speed of the resin material is increased to reduce the shear rate applied to the resin material. It is conceivable that the viscosity of the material in the mold is reduced by a method of raising the material. However, when the mold temperature is increased, there is a problem that the productivity is reduced by extending the cooling time in the case of a material such as a thermoplastic resin. The material temperature becomes high and there is a problem of deterioration and deterioration of the material. Further, in the case of a thermoplastic resin or a thermo-crosslinking reaction elastomer, when the mold temperature is increased or the injection speed is increased, the curing reaction proceeds at the time of casting the material, which may result in molding failure.

Therefore, as a countermeasure on the mold surface, it has been considered to take a countermeasure by changing specifications such as the shape, size and number of gates through which the molding material passes toward the cavity.

For example, Japanese Patent Application Laid-Open No. Hei 7-290514 discloses a method in which a molding material is uniformly placed in a cavity by providing a ring gate in a runner or forming a width of a sub-gate so as to gradually increase toward the ring gate. Casting has been attempted.

However, the gate shape and gate width are
This is an important factor in molding that affects the flow of resin in the cavity, and its optimum value depends on the viscosity of the material to be molded and the casting speed and temperature. Therefore, it was necessary to redesign the mold every time the molding material or molding conditions were changed.

Further, when the molding material undergoes simultaneous curing and foaming reaction in a mold, such as a polyurethane foam, as shown in FIG. 3, the material in the runner expands due to volume expansion due to the foaming curing reaction. There is a problem in that the material enters the tee and the material characteristic values near the gate of the roller become non-uniform, and flow marks and welds are generated in this portion.

[0010]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and uses a molding die having a penetrating cylindrical hole to improve appearance and physical property variations due to occurrence of welds, flow marks, and the like. It is an object of the present invention to suppress the occurrence of defective phenomena, etc., and to stably provide a high-quality roller using the same mold even when using any material.

[0011]

According to a first aspect of the present invention, there is provided a roller in which an elastic material is formed in a cylindrical shape around a shaft-shaped metal core and is integrally formed with the metal core member. In the molding of the roller molding die, a molding die having a cylindrical hole that penetrates, and a lid attached to both ends of the cylindrical hole to hold a shaft-shaped core metal member concentrically with the cylindrical hole. Consisting of
At least one of the lids is a movable lid provided with a molding material injection port and a ring gate, and gate width control means is provided by operating the movable lid with respect to a cylindrical mold. A method of forming a roller characterized by the following.

According to the present invention described above, the material injected from the material injection port is filled into the cavity through the runner, and at this time, the material is subjected to shearing force by a ring gate provided between the runner and the cavity. Since the material flows by this shearing force so as to spread in the circumferential direction of the cylindrical molded body perpendicular to the injection direction, the material injected from each injection port is stirred at the confluence point, and it is possible to prevent the occurrence of weld. I can do it.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As described above, the optimum value of the gate interval greatly changes depending on the characteristics of the molding material and molding conditions such as the injection temperature, material viscosity, and the amount of injection of the material. The movable lid makes it possible to arbitrarily change the gate interval, thereby controlling the shearing force applied to the injection material and using the same metal under any material and molding conditions. This makes it possible to produce a molded article free of flow marks or the like in a mold.

Further, in the present invention, the material injection path can be opened and closed by a movable lid in a more preferred embodiment in the above-described configuration. In this configuration, particularly when the molding material is cured and foamed simultaneously in the mold, such as a polyurethane foam, when the material is completely injected into the mold, the material injection path is set by the lid. By closing, the material in the runner can be prevented from entering the cavity due to volume expansion due to the foaming hardening reaction. As a result, it is possible to solve the problem that the material characteristic value near the gate of the molded body roller becomes non-uniform or that a flow mark or weld is generated in this portion.

As the material to be molded in the present invention, a thermoplastic elastomer, a thermosetting elastomer, an unvulcanized rubber containing a cross-linking agent, etc. can be cast into a mold, and is cured in the mold. The material is not particularly limited as long as it is a material for forming a compact.

[0016]

EXAMPLES The present invention will be described below in detail with reference to examples, but the present invention is not limited to these examples.

Comparative Example 1 FIG. 1 shows a half sectional view of a molding die using a conventional configuration. The molding die shown in FIG. 1 has a cylindrical mold 1 surrounding the core metal member 4 at a predetermined distance, for example, about 10 mm, from the outer peripheral surface of the core metal member 4, and the core metal member 4 is concentric with the mold 1. Are mounted. The lid 21 has an opening 8 for air release communicating with the outside. The lid 22 is provided with a ring gate 5 and a material injection port 7 communicating with the outside.
It has injection paths that open in four directions at an angle of 90 ° from the center of 2. FIG. 2 is a projection view of the lid 22. Lid 22
Is fixed to the cylindrical mold 1 by a fixed mold (not shown) unlike the molding mold of FIG. 4 of the embodiment.

Next, the procedure for forming an elastic roller using the above-described comparative device will be described. In this comparative example, the thickness is 10 mm.
Was molded.

First, the core metal member 4 to which an adhesive has been applied in advance
Is attached to the lid 21, and the lid 21 is fixed to the cylindrical mold 1 by a fixed mold (not shown). Next, the lid 22 provided with the material injection port is fixed to the metal core member 4 and the cylindrical mold 1. As a result, the gate interval of the ring gate 5 in the material injection path is fixed at a constant value. The gate interval here was 0.6 mm.

Thereafter, the mold was heated to 40 ° C., and carbon black and a vulcanizing agent were previously blended as conductive materials, and the viscosity was 50
00 cps silicone rubber was injected from the material injection port 7. Here, the molding material is filled into the cavity 3 through the ring gate 5 through the runner 6. After the casting, the mold was heated in an oven at 160 ° C. for 30 minutes to cure the molding material. After cooling, the lids 21 and 22 were removed from the cylindrical mold 1, and finally the rollers were extracted from the cylindrical mold 1 in the axial direction. Burrs at both ends of the obtained molded body were cut to obtain a roller molded body 101 as shown in FIG.

The flow mark and weld of the obtained roller molded body 101 were observed visually and by measuring the peripheral unevenness of the electric resistance of the roller molded body. As a result, the circumferential unevenness in the electric resistance is as shown in Table 1,
At 1.4 times, no flow mark weld was visually observed.

The electric resistance was measured by contacting the roller compact with a cylindrical metal drum, applying a voltage of 100 V DC between the roller core and the metal drum while rotating, and
The voltage applied to the resistor connected in series with the metal drum was measured, and the ratio between the maximum value and the minimum value was expressed as circumferential unevenness.

Embodiment 1 FIG. 4 is a half sectional view of a molding die using the structure of the first embodiment of the present invention. FIG. 6 shows lids 22A and 22A.
2B shows a projection view of FIG. In FIG. 4, the present apparatus comprises a cylindrical mold 1 surrounding the core metal member 4 at a predetermined interval, for example, about 10 mm, on the outer peripheral surface of the core metal member 4,
21 and 22 for holding concentrically with the cylindrical forming mold 1
A, 22B. The lid 21 has an air vent opening 8 communicating with the outside. Also, the lid 22B
Is provided with a ring gate 5 and a material injection port 7 communicating with the outside. The material injection port 7 has injection paths that open in four directions at an angle of 90 ° from the center of the lid 22B. Further, the lid 22B has a slide mechanism that operates in the longitudinal direction with respect to the lid 22A, and the gap between the ring gate 5 and the lid 22A is formed by the movement of the lid 22B (see FIG. 7). ) Is adjusted.

Next, the procedure for forming an elastic roller using the above-described apparatus of the present embodiment will be described. In this embodiment, an elastic roller having a core diameter of 6.0 mm, a rubber thickness of 10 mm (roller diameter 26 mm), and a rubber roller length of 240 mm was formed as in the comparative example.

First, the core metal member 4 to which an adhesive has been applied in advance
Is mounted on the lid 21, and the lid 21 is fixed to the cylindrical mold 1 by a fixed die (not shown).
Further, the lid 22A is fixed to the cylindrical forming die 1 by a fixing die (not shown). Next, the lid 22B provided with the material injection port is attached to the cored metal member 4 and the lid 22A. Here, the position of the lid 22B with respect to the lid 22A was adjusted such that the gate interval was 0.3 mm.

Thereafter, the mold was heated to 40 ° C., and silicone rubber having the same viscosity as that of Comparative Example 1 and having the same viscosity of 5000 cps and containing carbon black and a vulcanizing agent as conductive materials beforehand was injected through the material injection port 7. Here, the molding material is runner 6
Through the ring gate 5 and into the cavity 3. After the casting, the mold was heated in an oven at 160 ° C. for 30 minutes to cure the molding material. After cooling, lid 2
The rollers 1, 22A and 22B were removed from the cylindrical mold 1, and finally the rollers were extracted from the cylindrical mold 1 in the axial direction. Burrs at both ends of the obtained molded body were cut to obtain a roller molded body 102.

In the results of observing the flow mark and weld of the obtained roller molded body 102 (Table 1), the peripheral unevenness in electric resistance was 1.1 times, and flow mark weld was not visually observed.

Example 2 In the same manner as in Example 1, a roller molding 103 was obtained using a molding die shown in FIG. The used silicone rubber is 70
0 cps, and is the same as Example 1 except that the position of the lid 22B with respect to the lid 22A was adjusted so that the gate interval was 0.6 mm.

As a result of observing the flow mark and weld of the obtained roller molded body 103 (Table 1), the peripheral unevenness in electric resistance was 1.2 times, and the flow mark and weld were visually observed.
No weld was observed.

Comparative Example 2 In the same manner as in Comparative Example 1, a roller molded body 104 was obtained using the molding die shown in FIG. Here, a urethane material was used as a molding material.

First, the core metal member 4 to which an adhesive has been applied in advance
Is mounted on the lid 21, and the lid 21 is fixed to the cylindrical mold 1 by a fixed die (not shown).
Next, the lid 22 provided with the material injection port is fixed to the metal core member 4 and the cylindrical mold 1. As a result, the gate interval of the ring gate 5 in the material injection path is fixed at a constant value.
The gate interval here was 0.6 mm.

Thereafter, a soft urethane material having a viscosity of 700 cps, in which carbon black was previously blended as a conductive material, was injected through the material injection port 7. Here, the soft urethane rubber is sufficiently mixed before injection. The molding material passes through the runner 6, through the ring gate 5, and into the cavity 3
Filled into. After a predetermined amount of the material was injected, the mold was heated in an oven at 100 ° C. for 30 minutes to perform a foaming / curing reaction.

After the molding material was hardened, the lids 21 and 22 were removed from the cylindrical mold 1, and finally the rollers were extracted from the cylindrical mold 1 in the axial direction. Burrs at both ends of the obtained molded body were cut to obtain a roller molded body 104.

As a result of observing the flow mark and weld of the obtained roller molded body 104 (Table 1), the peripheral unevenness in electric resistance was 1.5 times, and weld was visually observed.

Embodiment 3 Next, the procedure for forming an elastic roller using another configuration of the present invention will be described. In the present embodiment, the molding die of FIG. 4 is used as in the first embodiment, and the same urethane material as that of the comparative example 2 is used as the molding material.
I got

First, the core metal member 4 to which an adhesive has been applied in advance
Is mounted on the lid 21, and the lid 21 is fixed to the cylindrical mold 1 by a fixed die (not shown).
Further, the lid 22A is fixed to the cylindrical forming die 1 by a fixing die (not shown). Next, the lid 22B provided with the material injection port is attached to the cored metal member 4 and the lid 22A. Here, the position of the lid 22B with respect to the lid 22A was adjusted so that the gate interval was 0.5 mm.

After that, the same as Comparative Example 2, carbon black was previously blended as a conductive material, and the viscosity was 700 cps.
Was injected through the material injection port 7. Here, the soft urethane rubber is sufficiently mixed before injection. The molding material is filled into the cavity 3 through the runner 6 and the ring gate 5. After a predetermined amount of the material was injected, the lid 22B was moved to shut off the material injection path as shown in FIG. Thereafter, the mold was heated in an oven at 100 ° C. for 30 minutes to perform a foaming / curing reaction.

After the injection molding material is cured, the lids 21 and 22
A and 22B were removed from the cylindrical mold 1, and finally the rollers were extracted from the cylindrical mold 1 in the axial direction. The burrs at both ends of the obtained molded body were cut to form a roller molded body 1
05 was obtained.

As a result of observing the flow mark and weld of the obtained roller molded body 105 (Table 1), the peripheral unevenness in electric resistance was 1.2 times, and the flow mark and weld were visually observed.
No weld was observed.

[0040]

[Table 1]

[0041]

As summarized in Table 1, in the molding method using the conventional mold of Comparative Example 1, the resistance unevenness was as high as 1.4.
It cannot be used as a conductive roller for electrophotography.

On the other hand, in the first and second embodiments, the gate interval is adjusted with respect to the material. Even if materials having greatly different viscosities are used, the gate interval can be changed so that the same mold is used. A roller having no flow mark and having small resistance unevenness is obtained.

In Comparative Example 2, a soft urethane foam material was molded using a conventional mold. Since the material in the runner enters the cavity during the foaming and curing reaction, a flow mark is generated. Also, resistance unevenness is large. On the other hand, in the third embodiment, the mold of the patent is used and the material injection path is closed after the material injection, so that the material in the runner does not enter the cavity during the foaming and curing reaction, and the flow is reduced. A roller having no mark and small resistance unevenness is obtained.

As described above, according to the present invention, when a roller is formed using a forming die having a cylindrical hole penetrating,
It is possible to stably provide a high-quality roller that suppresses the appearance due to the occurrence of welds, flow marks, and the like, and the occurrence of defects such as variations in physical properties, using the same mold, regardless of the material used.

[Brief description of the drawings]

FIG. 1 is a half sectional view of roller production in Comparative Examples 1 and 2.

FIG. 2 is a projection drawing of a lid for manufacturing a roller in FIG. 1;

FIG. 3 is a schematic diagram of a foamed and hardened material entering a cavity in Comparative Example 2.

FIG. 4 is a half sectional view of roller production in Examples 1 to 3.

FIG. 5 is another half cross-sectional view of the roller manufacturing in Examples 1 to 3 (when the material injection path is closed).

FIG. 6 is a projection view of a lid for roller production in Examples 1 to 3.

FIG. 7 is an enlarged view of a gate portion in roller production in Examples 1 to 3.

FIG. 8 is a sectional view of a forming roller.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cylindrical forming die 21, 22 Lid 22A, 22B Movable lid 3 Cavity 4 Core metal member 5 Ring gate 6 Runner 7 Material injection port 8 Air vent opening 9 Coating layer

Claims (3)

[Claims] In forming a roller in which an elastic material is formed in a cylindrical shape around a shaft-shaped core metal and is integrally formed with the core metal member, a roller forming die has a cylindrical hole penetrating therethrough. A mold and a lid attached to both ends of the cylindrical hole to hold a shaft-shaped core metal member concentrically with the cylindrical hole,
At least one of the lids is a movable lid provided with a molding material injection port and a ring gate, and the gate width is controlled by operating the movable lid with respect to the cylindrical mold. Roller molding method. 2. A lid having an air vent opening channel, another lid comprising a fixed lid A and a lid B having a material injection port and having a slide mechanism, and a cylindrical mold. The method according to claim 1, wherein a molding material is injected into a cavity formed by the core metal member. 3. The method of forming a roller according to claim 1, wherein the material injection port can be opened and closed by the movable lid.