JP2022059168A - Resin molded part and method for manufacturing the same - Google Patents

Abstract

To provide a resin molded part that hardly causes a crack from a weld line as a starting point when a pressure is applied.SOLUTION: There is provided a spacer 10 according to the embodiment comprising: a disk-shaped main body 11 having a through hole 12 in a center; and an opening 13 that is extended toward a peripheral portion of the main body 11, that is provided along a straight line connecting a center of the through hole 12 and a gate cut portion G, communicates with the through hole 12, and that is separated from the gate cut portion G when top-viewing the main body portion 11.SELECTED DRAWING: Figure 2

Description

The present invention relates to a resin molded part and a method for manufacturing the same.

When a resin part having a through hole in the center is manufactured by injection molding, the part is molded by filling the cavity of a molding die with a resin material melted from an injection port called a gate. In the center of the cavity, there is a core (pin) for forming a through hole. The resin material ejected from the gate is once divided into left and right by the core, wraps around the core, and then rejoins.

Weld lines with weak resin welding force are generated at these confluences. In an injection molded part with a through hole, the weld line appears on the downstream side of the through hole in a cross section along a straight line passing through the gate and the center of the through hole. The most serious point in this problem is that it becomes impossible to quantitatively grasp the amount of decrease in welding force at the location where the weld line occurs. Therefore, it becomes difficult to pre-verify the occurrence of cracks and breakage in parts where weld lines occur by structural analysis or the like, and unexpected defects may be detected in actual machine evaluation.

As a technique for controlling the generation of weld lines, for example, there are those disclosed in Patent Documents 1 to 3. Patent Document 1 discloses an injection-molded resin button having a through hole in the center. In Patent Document 1, the outer surface of the button body is divided into left and right by a virtual straight line connecting the gate position corresponding to the gate of the molding die of the button body and the center of the button. One or more recesses or protrusions are asymmetrically provided. As a result, a non-linear weld line is formed on the button body at least on the outer surface.

In Patent Document 2, in a resin injection-molded product in which a through hole is formed in a plate-shaped main body, a thick portion is provided around the through hole to prevent the occurrence of weld lines. Further, in Patent Document 3, in the molding die, a guide having a substantially triangular cross section is provided on the opposite side of the pin gate, that is, behind the pin. The flow of the resin material that circumvents the pin and wraps around behind is guided in the direction opposite to the gate based on the shape of the guide, and the formation of a weld line behind the pin is avoided.

Japanese Patent No. 6657483 Japanese Unexamined Patent Publication No. 11-291277 Japanese Unexamined Patent Publication No. 6-91708

As described above, when a weld line is generated in a resin molded part having a through hole, the strength of the portion is weakened. When a disk-shaped resin molded part having a through hole is used as a spacer to be inserted between the housing side boss and the base side boss when fixing the housing and the base of the device housing by screwing, screw tightening. When pressure is applied from above and below, the spacer cracks starting from the weld line and does not function as a spacer.

In view of the above-mentioned problems, an object of the present disclosure is to provide a resin molded part which is less likely to crack from a weld line as a starting point and a method for manufacturing the same when pressure is applied.

The resin molded component according to one aspect of the present invention has a disk-shaped main body portion having a through hole in the center and a straight line connecting the center of the through hole and the gate cut portion when the main body portion is viewed from above. It includes an opening that communicates with the through hole and extends toward the peripheral edge portion of the main body portion away from the gate cut portion.

In the method for manufacturing a resin molded part according to one aspect of the present invention, after supplying resin from the gate of a molding die to fill the inside of the cavity, the gate is cut to form a gate cut portion, and a through hole is formed in the center. Along a straight line connecting the center of the through hole and the gate cut portion when the main body portion is viewed from above, it communicates with the through hole and separates from the gate cut portion. It forms an opening extending toward the peripheral edge of the main body.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a resin molded part in which cracking starting from a weld line is unlikely to occur when pressure is applied, and a method for manufacturing the same.

It is a perspective view of the spacer which concerns on Embodiment 1. FIG. It is a top view of the spacer of FIG. It is a perspective view of the boss cap which concerns on Embodiment 2. FIG. It is a figure which shows the application example of the boss cap of FIG. It is a top view of the boss cap of FIG. It is a perspective view of the boss cap which concerns on Embodiment 3. FIG. FIG. 6 is a view of the left side portion of the boss cap of FIG. 6 cut by a alternate long and short dash line as seen from the arrow VIIA. It is the figure which looked at the right-hand part which cut the boss cap of FIG. 6 by the alternate long and short dash line from the arrow VIIB. It is a figure which shows the analysis result of how the resin is filled in the molding die of the boss cap of FIG. It is a figure which shows the analysis result of how the resin is filled in the molding die of the boss cap of FIG. It is a figure which shows the analysis result of how the resin is filled in the molding die of the boss cap of FIG. It is a figure which shows the analysis result of how the resin is filled in the molding die of the boss cap of FIG. It is a figure which reproduced the occurrence part of the weld line of the boss cap of FIG. 6 by the resin fluid analysis.

Hereinafter, specific embodiments to which the present invention is applied will be described in detail with reference to the drawings. However, the present invention is not limited to the following embodiments. Further, in order to clarify the explanation, the following description and drawings have been simplified as appropriate. In each drawing, the same components are designated by the same reference numerals, and the description thereof will be omitted as appropriate.

Embodiment 1.
FIG. 1 is a perspective view of a spacer 10 which is an example of a resin molded part according to the first embodiment. As shown in FIG. 1, the spacer 10 includes a main body portion 11 provided with a through hole 12 and an opening portion 13. The main body 11 is a disk-shaped resin molded part. A round hole-shaped through hole 12 is provided in the center of the main body 11.

The spacer 10 is arranged between the base-side boss and the housing-side boss into which the screw is screwed, for example, when the base of the device housing and the housing are screwed and fixed. Screw holes are formed in the base side boss and the housing side boss, respectively. The screw is inserted from the screw hole of the base side boss into the through hole 12 of the spacer 10 and screwed into the screw hole of the housing side boss to fasten the base and the housing. When the screw is a self-tapping screw, the boss may have a mere hole instead of a screw hole.

FIG. 2 is a top view of the spacer 10 of FIG. The spacer 10 is formed by supplying resin from a gate, which is a resin material injection port, into the cavity of the molding die, filling the cavity, and then cutting the gate. The resin flows in the direction of the arrow shown in FIG. A gate cut portion G is formed at a portion where the gate is cut. In the example shown in FIG. 2, the gate cut portion G is located on the peripheral edge portion of the main body portion.

When the main body portion 11 is viewed from above, the opening portion 13 is provided along a straight line connecting the center of the through hole 12 and the gate cut portion G. The opening 13 communicates with the through hole 12 and extends toward the peripheral edge portion on the side away from the gate cut portion G. That is, the opening 13 is provided on the downstream side of the through hole 12. The opening 13 penetrates the main body 11 and has an elongated hole shape smaller than the diameter of the through hole. Therefore, a keyhole-shaped hole is formed in the main body portion 11 in which one end of the elongated hole-shaped opening 13 is connected to the round hole-shaped through hole 12. Further, the tip portion E of the opening portion 13 has an R shape.

The molding die for forming the spacer 10 is formed with a first core for forming the through hole 12 and a second core for forming the opening 13. In the resin filled from the gate cut portion G, the flow of the material is once divided into left and right by the first core, and the resin wraps around the first core. In the present embodiment, the opening 13 exists on the downstream side of the through hole 12. Therefore, the resin that wraps around the first core flows along the second core, wraps around the tip portion thereof, and rejoins. A weld line is generated at this confluence.

Since the tip E of the opening 13 has an R shape, the tip of the second core has an R shape. This makes it possible to fill the molding die with the resin without obstructing the flow of the resin around the tip of the second core.

When only the through hole is provided in the main body, a weld line is generated immediately after the downstream side of the through hole. In such a spacer, when a screw is inserted through a through hole and fastened, the axial force of the screw may cause an unexpected crack or breakage starting from the weld line. The cause of this problem is that when the spacer is injection-molded, the resin merges in the vicinity of the through hole through which the screw is inserted.

On the other hand, in the embodiment, the weld line appears not immediately after the through hole 12 of the main body portion 11, but at the tip of the tip end portion E of the opening portion 13, that is, on the side surface of the main body portion 11. That is, according to this spacer 10, the location where the weld line is generated can be moved to a location away from the through hole 12 through which the screw is inserted. With such a spacer 10, it is possible to suppress the occurrence of cracks starting from the weld line when pressure is applied in the vertical direction.

Embodiment 2.
FIG. 3 is a perspective view of the boss cap 1 which is an example of the resin molded part according to the second embodiment. This component is a spacer component mounted to fill the gap created between the housing and the base when assembling the PHS base station terminal. The boss cap 1 further includes a side surface portion 14 erected from the peripheral edge portion of the main body portion 11 of the spacer 10 of FIG. The side surface portion 14 is a tubular member that extends downward and is provided so that the operator can easily pick up the boss cap 1 with his / her fingers when fixing the housing and the base of the apparatus housing with screws. be. That is, the boss cap 1 has a truncated cone shape with the main body 11 as a top surface and is opened downward so as to have a space inside.

FIG. 4 is a diagram showing an application example of the boss cap 1 of FIG. The boss cap 1 is arranged between the base-side boss of the base 2 (not shown) and the housing-side boss of the housing 3 (not shown). In FIG. 4, as shown by the white arrow, the screw is inserted into the through hole 12 of the spacer 10 from the screw hole of the base side boss and screwed into the screw hole of the housing side boss to fasten the base and the housing. Is done.

FIG. 5 is a top view of the boss cap of FIG. As described with reference to FIG. 1, the main body 11 is provided with a through hole 12 at the center thereof. In the second embodiment, the gate cut portion G is located substantially at the center of the side surface portion in the height direction. When the main body portion 11 is viewed from above, the opening portion 13 is provided along a straight line connecting the center of the through hole 12 and the gate cut portion G. The opening 13 communicates with the through hole 12 and extends toward the peripheral edge portion on the side away from the gate cut portion G.

In the second embodiment, the resin filled from the gate cut portion G spreads to the side surface portion 14 and then reaches the main body portion 11. In the main body 11, the flow of the material is once divided into left and right by the first core, and wraps around the first core, as in the first embodiment. Further, the resin that wraps around the first core flows along the second core, wraps around the tip E of the opening 13, and rejoins. Then, the resin spread to the left and right from the gate cut portion G joins at a position located at the tip of the tip portion E of the side surface portion 14. In the second embodiment, the weld line is generated from the side surface of the main body 11 to the side surface 14 at the tip of the tip E of the opening 13.

In this way, since the location where the weld line is generated can be moved to a location away from the through hole 12 through which the screw is inserted, the occurrence of cracks starting from the weld line is suppressed when pressure is applied in the vertical direction. It becomes possible to do.

Embodiment 3.
FIG. 6 is a perspective view of the boss cap 1A, which is an example of the resin molded part according to the third embodiment. Even if the opening 13 is provided in the main body 11 as in the second embodiment, the effect of repelling the weld line immediately after the downstream side of the through hole 12 can be expected. However, if you want to take a weld line workaround more reliably, you can control the position of the weld line with the following configuration.

The difference between the third embodiment and the second embodiment is that the columnar portion 15 projecting inward from the side surface portion 14 is further provided, and the joint portion between the columnar portion 15 and the side surface portion 14 is provided on the side away from the main body portion 11. Is the point where the resin pool 16 is formed. Hereinafter, the columnar portion 15 and the resin pool 16 will be described in detail with reference to FIGS. 7A and 7B.

FIG. 7A is a view of the left side portion of the boss cap of FIG. 6 cut along the alternate long and short dash line as viewed from the arrow VIIA. FIG. 7B is a view of the right side portion of the boss cap of FIG. 6 cut along the alternate long and short dash line as viewed from the arrow VIIB. In FIGS. 7A and 7B, for the sake of explanation, the inner structure that cannot be seen by the outer surface of the boss cap 1A is shown by a dotted line.

The weld line has the property that it tends to occur at the final confluence of the resin in the molding die. Therefore, it is desirable to make the order in which the resin is filled in the molding die as early as possible at the place where it is desired to avoid the occurrence of the weld line, and to avoid that the place becomes the final confluence point of the resin. For this reason, many resin molded parts are provided with a resin injection portion (gate) in the vicinity of a portion where the occurrence of weld lines is desired to be avoided.

Even in the boss cap, it is ideal that the main body portion 11 which is the top surface portion is avoided as the final confluence point, and the side surface portion 14 where there is no problem even if a weld line is generated is the final confluence point. However, in the boss cap, it is difficult to provide a gate near the top surface due to the shape and use of the parts.

Therefore, in the third embodiment, the columnar portion 15 and the resin pool 16 are provided in order to control the final confluence point of the resin. In the example shown in FIGS. 7A and 7B, the boss cap 1A is provided with three columnar portions 15. The three columnar portions 15 are arranged on the side surface portions 14 at equal intervals. As shown in FIG. 7A, two columnar portions 15 are provided so as to be symmetrical with the opening 13 interposed therebetween. Further, as shown in FIG. 7B, one columnar portion 15 is provided at a position opposite to the opening 13 and the through hole 12.

On the side of each columnar portion 15 away from the main body portion 11, a resin pool 16 is formed at the joint portion between the columnar portion 15 and the side surface portion 14. The resin pool 16 has, for example, a cylindrical shape. 8A to 8D are reproductions of the state in which the resin is filled in the molding die of the boss cap 1A of FIG. 6 by resin fluid analysis.

In FIG. 8A, the resin is supplied from the gate located substantially in the center of the side surface portion 14 in the height direction. As shown in FIG. 8B, since the resin pool 16 is provided on the side surface portion 14, the resin is preferentially filled in the main body portion 11 which is the top surface portion. Then, as shown in FIG. 8C, the resin joins at the tip portion E of the opening portion 13 before the side surface portion 14. By providing the resin pool 16 in this way, it is possible to prevent the resin from spreading to the main body 11 earlier than the side surface 14 and the main body 11 becoming the final confluence point of the resin.

FIG. 9 is a diagram in which the location where the weld line WL of the boss cap 1A of FIG. 6 is generated is reproduced by resin fluid analysis. As shown in FIG. 9, the weld line WL is generated in a range extending from the tip portion E of the opening portion 13 to the side surface portion 14. Further, in the third embodiment, the resin pool 16 allows the main body portion 11 to be filled with the resin earlier than the side surface portion 14. With these two measures, it is possible to eliminate the concern that a weld line will occur at the load location due to the axial force of the screw.

As described above, according to the embodiment, it is possible to control the weld line generation location in the injection molded part. The present invention is not limited to the above embodiment, and can be appropriately modified without departing from the spirit. For example, regarding the truncated cone-shaped boss cap 1, only the opening 13 was formed in the second embodiment, and both the opening 13 and the columnar portion 15 and the resin pool 16 were formed in the third embodiment. If the opening 13 cannot be provided in communication with the through hole 12 due to some restriction, the opening 13 may not be formed and only the columnar portion 15 and the resin pool 16 may be formed.

Further, the present invention can be applied to all resin molded parts having an opening and having no aesthetic restrictions on the appearance. Therefore, the present invention is applicable to a component having a screw fastening structure to a wall or a ceiling, such as a wall-mounted option of a telephone, in addition to the spacer described above.

Some or all of the above embodiments may also be described, but not limited to:

(Appendix 1)
A disk-shaped main body with a through hole in the center,
The side surface portion erected from the peripheral portion of the main body portion and
On the side away from the main body portion, a resin pool provided at a joint portion between the columnar portion protruding inward from the side surface portion and the side surface portion,
including,
Resin molded parts.
(Appendix 2)
A disk-shaped main body with a through hole in the center,
The side surface portion erected from the peripheral portion of the main body portion and
When the main body is viewed from above, along a straight line connecting the center of the through hole and the gate cut portion, on the downstream side of the through hole, the through hole is communicated with the peripheral portion of the main body. An extending opening and / or a resin pool provided at a joint between a columnar portion protruding inward from the side surface portion and the side surface portion on a side away from the main body portion.
including,
Resin molded parts.

1 Boss cap 2 Base 3 Housing 10 Spacer 11 Main body 12 Through hole 13 Opening 14 Side 15 Columnar 16 Resin pool G Gate cut E Tip WL Weld line

Claims (8)

A disk-shaped main body with a through hole in the center,
When the main body is viewed from above, it communicates with the through hole along a straight line connecting the center of the through hole and the gate cut portion, and toward the peripheral edge portion of the main body away from the gate cut portion. With an extending opening,
including,
Resin molded parts. Further provided with a side surface portion erected from the peripheral portion of the main body portion.
The resin molded part according to claim 1. Further provided with a columnar portion protruding inward from the side surface portion.
The resin molded part according to claim 2. On the side away from the main body portion, a resin pool is formed at the joint portion between the columnar portion and the side surface portion.
The resin molded part according to claim 3. The gate cut portion is located on the peripheral edge portion of the main body portion.
The resin molded part according to any one of claims 1 to 4. The gate cut portion is located substantially in the center of the side surface portion in the height direction.
The resin molded part according to any one of claims 2 to 4. The opening is elongated and its tip is R-shaped.
The resin molded part according to any one of claims 1 to 6. After supplying resin from the gate of the molding die to fill the inside of the cavity, the gate is cut to form a gate cut portion.
The gate communicates with the through hole along a straight line connecting the disc-shaped main body portion having a through hole in the center and the center of the through hole and the gate cut portion when the main body portion is viewed from above. It forms an opening extending toward the peripheral edge of the main body away from the cut portion.
Manufacturing method for resin molded parts.

Images