JPH0476286B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for easily manufacturing a mold for casting a roll having a convex shape (crown shape) or a concave shape (inverted crown shape).

(Background of the Invention) In order to maintain good straightness or conveyance of conveyed paper in electrophotographic devices and other office equipment, it is required to form the roll surface into a convex or concave shape.

When manufacturing this type of roll, if the roll has a structure that allows grinding and shaping, such as a simple rubber roll, it is sufficient to grind a straight cylinder roll into a predetermined shape, but for example, a roll with a thin layer of PFA resin on the surface, etc. cannot be ground, so it must be formed into a predetermined shape by roll forming.

It is extremely difficult to economically manufacture a mold that can mold such rolls all at once.

That is, it is practically impossible to grind the inner surface of a mold and finish it with high surface accuracy, and no convex or concave rolls have been manufactured by cast molding yet.

(Objective) The present invention provides a method for manufacturing a mold for casting a medium-convex or medium-concave roll at low cost, easily, and with high precision.

(Structure) The present invention obtains a matrix by mirror-finishing the inner surface of a metal straight cylindrical body with a relatively large coefficient of linear expansion, and cutting the outer circumferential surface into a shape symmetrical to the desired outer circumferential surface shape of the roll. , the mother mold is inserted into a holding mold made of a material with a relatively small coefficient of linear expansion, the whole is heated to expand the mother mold, and the outer peripheral surface of the mother mold is brought into close contact with the inner surface of the holding mold. After cooling, the inverted mother mold is extracted or used as it is as a roll mold for cast molding.

In the present invention, a suitable material for the matrix is, for example, aluminum (linear expansion coefficient: 0.00231/100°C).

The material of the holding type is iron (linear expansion coefficient 0.00132/
100℃) or ceramics.

After the inner and outer surfaces of the mother die are machined to a uniform diameter, the inner surface is precisely polished to a mirror finish (inner diameter d ₁ ), and the outer surface is cut into a shape opposite to the desired roll shape (maximum diameter D ₁ ). .

The inner surface of the holding mold is machined to have a uniform diameter (D ₂ ) in consideration of the outer diameter of the mother mold.

The above-mentioned required dimensions can be determined by calculation, but they can also be determined based on numerical values from simple preliminary experiments.

The present invention makes it easy to create molds with a large crown amount or reverse crown amount by cutting the outer surface of the mother mold, inserting it into a holding mold, heating and cooling it, and pulling it out, and repeating this series of steps. Obtainable.

(Example 1) An example of manufacturing a mold for a roll having an inverted crown shape (center concave) with an inner diameter of 40.2 mm at the center and an inner diameter of 40.3 mm at both ends.

Prepare an aluminum straight cylinder 1 with an outer diameter of 50.1 mm, an inner diameter of 40.36 mm, and a length of 350 mm.

The inner surface 2 of the straight cylinder is given a mirror finish.

The outer diameter of the outer surface 3 of the straight cylinder is 49.919 at the center.
A mother mold 4 was obtained by cutting to have a crown shape of 49.838 mm at both ends. (Fig. 1) This matrix has an outer diameter of 60 mm, an inner diameter of 50.04 mm, and a length of 350 mm.
After inserting it into the inside of the straight cylindrical iron holding mold 5 (Fig. 2), it was heated to 400°C (Fig. 3).
The outer surface 3 of the mother mold is brought into close contact with the inner surface 6 of the holding mold, and the mother mold is inverted and deformed.

The mold was left to cool at room temperature (FIG. 4) to obtain an inverted casting mold 7.

When we measured the internal shape of the mold, we found that the center part was
40.2mm, both ends were finished in an inverted crown shape of 40.3mm.

The obtained casting mold 7 is installed as shown in Fig. 5,
Inside is an iron core bar 8 with a diameter of 30 mm and a length of 350 mm.
Insert a 38 mm, 50 μm thick PFA resin tube (manufactured by Gunze) and fix the flange 9 at both ends, then apply silicone rubber liquid (X34-
061), vulcanize at 150℃ for 30 minutes, remove the roll from the mold, and then
Secondary vulcanization was performed at 200°C for 4 hours to obtain a PFA resin coated silicone rubber roll.

The outer diameter of the obtained roll was shrunk by secondary vulcanization, resulting in the result shown in FIG.

(Example 2) Inner diameter of center part 40.420mm, inner diameter of both ends 40.280mm
An example of manufacturing a mold for a crown-shaped roll.

Prepare a straight aluminum cylinder with an outer diameter of 50.1 mm, an inner diameter of 40.50 mm, and a length of 350 mm, and finish the inner surface with a mirror finish.

A mother mold was obtained by cutting the straight cylinder so that its outer diameter was opposite to that of Example 1 and having an inverted crown shape.

This matrix has an outer diameter of 60 mm, an inner diameter of 50.04 mm, and a length of 350 mm.
After inserting it inside the straight cylindrical iron holding mold of
It was heated to 400°C and left to cool at room temperature to obtain an inverted mold for casting.

When we measured the internal shape of the mold, we found that the center part was
40.42mm, with both ends finished in a 40.28mm crown shape.

Inside the resulting casting mold is a diameter of 30 mm and a length of 350 mm.
After inserting a steel core bar and a PFA resin tube (manufactured by Gunze) with a diameter of 38 mm and a thickness of 50 μm, fixing both ends with flanges, and filling the tube with silicone rubber liquid (X34-061, manufactured by Shin-Etsu Chemical) from the end. 30 at 150℃
After vulcanization for a minute, the roll was removed from the mold, and the roll was further subjected to secondary vulcanization at 200° C. for 4 hours to obtain an OFA resin-coated silicone rubber roll.

The outer diameter shape of the obtained roll shrank due to secondary vulcanization, resulting in a result as shown in FIG.

From Examples 1 and 2, it was possible to easily obtain a mold having the desired inner surface shape.

However, the outer diameter of the rubber filled in the mold shrinks due to secondary vulcanization, and in the case of an inverted crown shape as in Example 1, the amount of inverted crown tended to be larger than the amount set in the mold. .

However, since this tendency is reproducible, it is possible to calculate the inner surface shape of the mold by calculating backward from the shape and dimensions of the roll, and easily obtain the required roll.

(Effects of the present invention) According to the present invention, it has become possible to easily manufacture a mold having a crown or an inverted crown shape.

Since the inner surface of the mold can be given a mirror finish by straight honing, etc., the inner surface of the finished inverted mold maintains very good surface precision.

Further, in the present invention, since the outer circumferential surface of the mother die is processed by cutting, it is easy to process and can be manufactured at low cost.

Therefore, rolls having the desired crown shape or inverted crown shape can be manufactured with high precision and at low cost, and can be effectively used in manufacturing fixing rolls for electrophotographic devices and the like.

[Brief explanation of the drawing]

Figure 1 is a longitudinal sectional view of the mother mold, Figure 2 is a sectional view of the mother mold inserted into the holding mold, Figure 3 is a sectional view of the mother mold after heat treatment, Figure 4 is a sectional view of the mother mold in a cooled state, and 5
The figure is a cross-sectional view of the casting mold in use, and Figure 6 is a dimensional drawing showing the outer shape of the inverted crown roll and the mold.
FIG. 7 is a dimensional drawing showing the outer surface shapes of the crown roll and the mold. 1...Material mold, 5...Holding mold, 7...Reverse casting mold.

Claims (1)

[Claims] 1. The inner surface of a metal straight cylindrical body with a relatively large coefficient of linear expansion is polished to a mirror finish, and the outer peripheral surface is cut into a shape symmetrical to the desired shape of the outer peripheral surface of the roll to obtain a mother mold, and the mother molds are compared. The mold is inserted into a holding mold made of a material with a small coefficient of linear expansion, and the whole is heated to expand the mother mold, and the outer circumferential surface of the mother mold is brought into close contact with the inner surface of the holding mold, and the mold is reversely deformed. A method for producing a roll mold characterized by obtaining a mold.