JPH0784019B2 - Manufacturing method of resin assembly parts - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention comprises a first member having a hole and a second member having a fitting portion for fitting with a clearance in the hole.
The present invention relates to a method for producing a resin-made assembly part including a member by injection molding.

[0002]

2. Description of the Related Art Conventionally, in order to manufacture an assembly part of this type,
A general method is to separately assemble the first member and the second member with a synthetic resin and then assemble them by fitting them. However, this method has a problem that productivity is low because an assembling step after molding is required and molding is performed separately.

As a solution to this, for example, Japanese Patent Laid-Open No. 51-151753 and Japanese Patent Publication No. 63-23.
The method described in Japanese Patent No. 894 has been proposed. The former is due to the difference in shrinkage between two types of synthetic resin materials, and the latter is due to the difference in shrinkage due to the difference in molding conditions between synthetic resins of the same material. Since a clearance is provided between both members, for example, in the case of a small engineering plastic assembly part having a thickness or shaft diameter of about 2 to 3 mm, the clearance between both members is at most 0.03 to 0.045.
It has a drawback that the sliding portion is liable to stick or stick to the sliding portion because it is only about mm (when the contraction rate of the second member is 1.5%).

[0004]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems of the prior art and is a method of manufacturing a resin-made assembly part for manufacturing a first member and a second member fitted thereto by an injection molding process. In, in the resin assembly, the clearance between the hole of the first member and the fitting portion of the second member can be enlarged, and the clearance required for smooth sliding (including rotation) can be secured even in a small resin assembly. It is intended to provide a method of manufacturing a component.

[0005]

According to the method of manufacturing a resin-made assembly of the present invention, a first member having a hole is primary molded with a synthetic resin, and the obtained first member is set in a mold, A second member having a fitting portion that fits into the hole is secondarily molded using a crystalline resin that has a lower melting temperature than the synthetic resin and does not fuse to the synthetic resin. Is annealed.

In the present invention, it is preferable to use an amorphous resin as the synthetic resin for the primary molding of the first member.

In the present invention, the secondary molding is 400
It is preferable to use a low injection pressure of ˜600 kg / cm ² .

[0008]

In the method of manufacturing a resin-made assembly according to the present invention, when the first member obtained by the primary molding is set in the mold and the secondary molding is performed, the resin temperature at the secondary molding is controlled. The melting temperature of the synthetic resin of the primary molding can be set below
Moreover, since both resins do not fuse, the assembled parts obtained by the secondary molding do not adhere to each other and have a gap between the hole and the shaft portion.

By further annealing this assembly, post-shrinkage occurs in the first member and the second member,
The clearance between both members expands. That is, since the crystalline resin undergoes a large amount of shrinkage due to the rearrangement of crystals due to the annealing treatment, especially when the first member is made of an amorphous resin in which post-shrinkage due to annealing hardly occurs, the clearance between both members is increased. Greatly expands. Even if both members are made of crystalline resin, the second
Since the crystalline resin forming the member has a higher molding shrinkage, the amount of post-shrinkage caused by the anneal treatment is also large, and the clearance between both members is enlarged.

The injection pressure at the time of secondary molding is 600 kg / cm
^If the pressure is lower than 2, the shrinkage rate of the second member will increase and the clearance between both members will further increase, but the injection pressure will be 400
If it is less than kg / cm ^2, the fluidity of the resin will deteriorate and molding defects will occur, so the injection pressure during secondary molding is 400-60.
It is recommended to set it to 0 kg / cm ² .

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. In FIG. 1, reference numeral 1 denotes a resin-made assembly manufactured by the method of the present invention, which is a first member 3 which is a roller having a hole 2 and a fitting portion which is fitted into the hole 2 with a clearance. It comprises a second member 6 having a collar 5 fixed to both ends of the shaft 4.

In FIGS. 2 and 3, reference numeral 10 denotes a slide type mold similar to the slide type used in the two-color molding method.
An injection molding machine, which is not shown in its entirety, includes a fixed mold 12 mounted on a fixed plate 11 and a movable mold 14 mounted on a movable plate 13.

The movable die 14 is formed by attaching a movable side die plate 17 to a movable side attachment plate 15 via a spacer lock 16.
At the primary molding position shown in FIG. 2, after the primary molding is performed by being pressed against the fixed-side mold plate 21 for the primary molding, the obtained first member 3 is held and slid in the mold open state. At the secondary molding position shown in (1), the second member 6 is injection-molded by being press-contacted to the stationary-side mold plate 22 for secondary molding. 18 is a movable side template 17
The forming member for forming the first member 3 and the forming member 19 for forming the shaft 4 part each have a semi-cylindrical surface.

Reference numeral 23 is a runner plate for holding the fixed side mold plates 21 and 22, 24 is a runner stripper plate, 25 is a fixed side mounting plate, 26 is a primary side nozzle, and 27 is a secondary nozzle. This is the secondary nozzle. 28 is the fixed-side template 2
1 is a cavity for molding the first member 3 and 29 is a cavity for molding the shaft 4 part provided on the stationary mold plate 22 and each has a semi-cylindrical surface.

Reference numeral 31 is a primary side slide core which is slidably supported in the axial direction on a fixed side template 21 for primary molding.
A pin portion 32 for forming the hole 2 of the member 3 is provided at the tip, and the pin portion 32 is fitted into the cavity 19 of the movable side mold plate 17 and the groove 33 having a semicircular cross section cut in the fixed side mold plate 21. Then
In the advanced state of the pin portion shown in FIG. 2, the resin is prevented from flowing out from the cavities 18 and 28 for primary molding. The primary slide core 31 is driven backward and forward in conjunction with the opening and closing of the mold by an unillustrated pin whose base is fixed to the fixed mounting plate 25. 34
Is the primary runner leading to cavities 28 and 18.

Reference numerals 41 and 41 designate secondary side slide cores which are slidably supported in the axial direction by a fixed side template 22 for secondary molding, and a cavity 42 for molding the collar portion 5 of the second member 6 is provided at the front end. It has a face. This secondary slide core 41
Is driven backward and forward by the same drive mechanism as the primary slide core 31. Reference numeral 43 denotes a concave portion provided on the fixed-side template 22 into which the lower half portion of the first member 3 after the primary molding is fitted and removed. A secondary runner 44 extends to the cavities 29 and 19.

In an injection molding machine equipped with the mold 10 having the above construction, as shown in FIG. 2, a molten resin 51 for primary molding is used.
Is injected from the primary side nozzle 26, and the first member 3 is primarily molded in the cavities 18 and 28. Next, the primary-side slide core 31 is retracted to open the mold, and the movable-side mold plate 17 holding the first member 3 is moved to the secondary-side position shown in FIG. The molten resin 52 made of resin is injected from the secondary side nozzle 27 to secondarily mold the cavities 19, 29, 42 and the second member 6 having the shaft 4 in the hole 2 of the first member 3. Then, the secondary side slide core 41 is retracted and the mold is opened to obtain the assembled parts of the first member 3 and the second member 6 thus obtained.
Annealing is performed in an annealing furnace (not shown) to obtain a finished resin assembly 1.

Next, the above resin assembly 1 is manufactured by the above method.
(However, the outer diameter of the first member 3 is 8 mm, the width is 9 mm, the inner diameter of the hole 2 is 2.5 mm, the diameter of the shaft 4 of the second member 6 is 2.5 mm,
A specific example in which the length: 23.5 mm) is molded will be described.

(A) First Example A PBT resin which is a crystalline resin (molding shrinkage rate 1.8%, melting temperature 228 ° C.) was used as a synthetic resin for primary molding.
Polyacetal resin (molding shrinkage 2.0%, melting temperature 165 ° C.) was used as a crystalline resin for secondary molding, primary molding was performed at an injection pressure of 1200 kg / cm ² , a nozzle temperature of 250 ° C., and an injection pressure of 600 kg / Secondary molding was performed at cm ² and a nozzle temperature of 190 ° C. Then, the obtained assembly parts were annealed at 150 ° C. for 20 hours, and the clearance (total for both sides) between the shaft 4 and the hole 2 of the resin assembly part 1 was 0.08 mm. It was

(B) Second Example As a synthetic resin for primary molding, ABS which is an amorphous resin is used.
Resin (molding shrinkage 0.5%, melting temperature 190 ° C) is used, and polyacetal resin (molding shrinkage 2.0%, melting temperature 165 ° C) is used as a crystalline resin for secondary molding, and injection pressure is used. Primary molding was performed at 1200 kg / cm ² and a nozzle temperature of 250 ° C., and secondary molding was performed at an injection pressure of 600 kg / cm ² and a nozzle temperature of 185 ° C. Then, the obtained assembly part was annealed at 110 ° C. for 20 hours. As a result, the clearance (total on both sides) between the shaft 4 and the hole 2 of the resin assembly part 1 was 0.06 mm. It was

As a comparative example, when the anneal treatment was omitted in the first embodiment, the clearance (total value on both sides) between the shaft 4 and the hole 2 was 0.05 mm. When the treatment was omitted, the above clearance (total value on both sides) was 0.05 mm.

The present invention is not limited to the above embodiments, and various combinations other than the above can be used as the combination of the synthetic resin for primary molding and the crystalline resin for secondary molding.
The mold used for molding may be of other type such as a rotary type. In addition, the present invention includes various types such as a first member having a square hole and a hole such as a C-shape that partially opens laterally, and a second member having a fitting portion that fits into these holes. It can be widely applied to the production of shaped resin-made components.

[0023]

As described above, according to the present invention,
Since the assembly obtained by the primary molding and the secondary molding is annealed, the clearance between the hole of the first member and the fitting portion of the second member can be increased, and even in a small resin assembly part. The clearance required for smooth sliding can be secured.

[Brief description of drawings]

FIG. 1 is a perspective view showing an example of a resin assembly part manufactured by the method of the present invention.

FIG. 2 is a vertical cross-sectional view of a mold at the time of primary molding showing a method for manufacturing the assembly part of FIG.

FIG. 3 is a vertical cross-sectional view of a mold at the time of secondary molding showing a method of manufacturing the assembly part of FIG.

[Explanation of symbols]

1 ... Resin assembly part, 2 ... Hole, 3 ... 1st member, 4 ... Shaft,
6 ... 2nd member, 10 ... Mold, 12 ... Fixed type, 14 ... Movable type, 17 ... Movable side template, 18 ... Cavity, 19 ... Cavity, 21 ... Fixed side template, 22 ... Fixed side template, 26 ...
Primary-side nozzle, 27 ... Secondary-side nozzle, 28 ... Cavity, 29 ... Cavity, 31 ... Primary-side slide core, 3
2 ... Pin portion, 33 ... Groove, 41 ... Secondary side slide core, 4
2 ... Cavity, 43 ... Recess, 51 ... Molten resin, 52 ...
Molten resin.

Claims (3)

[Claims] 1. A first member having a hole is primary molded with a synthetic resin, and the obtained first member is set in a mold to have a lower melting temperature than that of the synthetic resin and to be melted in the synthetic resin. A second member having a fitting portion that fits into the hole is secondarily molded using a non-stick crystalline resin, and the obtained assembly part is annealed.
A method for manufacturing a resin-made assembly, comprising: 2. The method for manufacturing a resin-made assembly according to claim 1, wherein an amorphous resin is used as the synthetic resin for primary molding the first member. 3. The method for manufacturing a resin-made assembly according to claim 1, wherein the secondary molding is performed at an injection pressure of 400 to 600 kg / cm ² .