JP6930812B2 - Manufacturing method of workpieces with holes - Google Patents

Description

The present invention relates to a method for manufacturing a work having holes.

In recent years, in order to improve vehicle safety technology, the number of vehicles equipped with sensors, back sonar, etc. is increasing. Then, these sensors and back sonar are attached to the vehicle through the attachment holes provided in the bumper. Conventionally, this mounting hole has been formed by post-processing, for example, after the bumper is injection-molded, the bumper is drilled with a hydraulic drilling device.

However, if a separate drilling process is provided after injection molding in this way, it leads to an increase in cost during bumper manufacturing. For this reason, the number of vehicles equipped with sensors and back sonar is increasing, and it has been desired to form a hole shape together with a bumper shape portion by injection molding.

However, when the mounting hole is formed by injection molding, there is a problem that a weld line is formed around the mounting hole of the bumper. That is, as shown in FIG. 8, the resin material that has flowed from the injection gate to the mounting hole 101 during injection molding of the bumper 100 is placed on the bumper-shaped portions of one side 102 and the other side 103 across the mounting hole 101. The respective streams are separated (see the arrow in FIG. 8) and rejoined on the opposite side of the mounting hole 101. At this confluence position, there is a problem that the resin materials on the one side 102 and the resin material on the other side 103 come into surface contact with each other to form the weld line 104. Further, at the time of injection molding of the bumper 100, the internal weld 105 is formed separately from the weld line 104. In the case of a work such as the bumper 100 that constitutes the design surface of the vehicle, the formation of the internal weld 105 becomes a problem in terms of appearance quality.

In particular, in recent years, the wall thickness of bumpers has been decreasing due to demands for weight reduction and cost reduction of members. In this case, during injection molding, it becomes difficult for the injection material to flow in the cavity of the mold, so that weld lines and internal welds are likely to occur, and the above-mentioned problems become remarkable.

Therefore, for example, the invention of Patent Document 1 is disclosed as a countermeasure against welds formed around such a hole. In Patent Document 1, as shown in FIG. 9, the resin molded part is provided with an attachment portion 111 to another member. The mounting portion 111 is provided with a through hole 112 for mounting on another member. A thin-walled portion 115 is formed on one side 113 across the through hole 112 of the mounting portion 111. As a result, at the time of injection molding, the pressure on one side 113 provided with the thin-walled portion 115 becomes smaller than the pressure on the other side 114. As a result, when the resin material on one side 113 and the resin material on the other side 114 that are branched to the left and right are rejoined, the resin material on the other side 114 pushes in the resin material on one side 113, and the weld line 116 is formed in an oblique direction. Will be done. Therefore, as compared with the case where the weld line 116 is formed vertically (in the vertical direction in FIG. 9), cracking of the attachment portion 111 in the weld line 116 can be suppressed, and the strength of the attachment portion 111 can be improved.

Japanese Unexamined Patent Publication No. 2014-162097

As in Patent Document 1, the method of forming a partially thin portion on a work has a problem that it is difficult to apply the method to a work having rigidity depending on the thickness. Further, in the case of a configuration in which a through hole is provided at the tip of the mounting portion as in Patent Document 1, the above effect can be obtained only by thinning a part around the through hole, but the work is formed. Depending on the position of the formed hole, it is necessary to form a thin-walled portion over a wide area around the hole, and the influence on the characteristics such as the rigidity of the work cannot be ignored. As described above, the method of Patent Document 1 cannot always be adopted as a countermeasure against welds, and there are many cases where there is no choice but to form the work as it is. Therefore, the shape portion and the hole portion of the work are integrally molded by injection molding. Was in a difficult situation.

Under these circumstances, the present invention suppresses the formation of weld lines in a manufacturing method for molding a work having holes by injection molding without affecting characteristics such as rigidity required for the work. Is the subject.

In order to solve the above problems, the present invention is a method for manufacturing a work in which a work having a hole is formed by injection molding, in which the shape portion and the hole of the work are molded and the hole is formed with the work. a step of forming an unnecessary portion which is continuous with the shape portion, said a step saw including removing unnecessary portion from the workpiece, in the step of forming the shaped portion and the hole portion of the workpiece, the injection material, forming said workpiece In the cavity of the molding die, the flow is divided from the upstream side of the hole portion in the flow direction of the injection material to one side and the other side opposite to each other across the hole portion, and the flow is divided with respect to the upstream side. The unnecessary portion flows to the downstream side which is the opposite side across the hole portion, and the unnecessary portion bridges the one side and the downstream side of the hole portion .

In such a method, an unnecessary portion continuous with the work is formed at a position corresponding to a hole of the work by injection molding. As a result, during injection molding, the path through which the injection material flows can be changed around the hole, and the flow path of the injection material and the inflow pressure can be adjusted without providing a thin portion in the work. Therefore, the formation of the weld line can be suppressed, and the direction in which the weld line is formed can be changed. It is also possible to suppress the formation of the internal weld and adjust the direction in which the internal weld is formed. Further, since unnecessary parts can be removed from the work in a subsequent process, the characteristics of the work as a product are not affected.

As described above, the unnecessary portion can be molded by the injection material flowing in from the side of the shape portion of the work at the time of injection molding of the work. As a result, at the time of injection molding, of the injection material that wraps around to one side of the hole and the injection material that wraps around to the other side, a part of the injection material moves to the side of the unnecessary part on the side where the unnecessary part is provided. The inflow reduces the pressure of the injection material compared to the other side. Therefore, when the separated injection materials are rejoined, the injection material on the side provided with the unnecessary portion is pushed into the injection material on the other side, and the formation of the weld line is suppressed or the formation direction thereof. Can be tilted to one side.

As the above method, an injection gate can be provided at a position of a cavity corresponding to an unnecessary portion of a mold for injection molding. As a result, the resin material can be poured from the side of the unnecessary portion to the side of the work during injection molding, and the resin material can be washed away at the position where the weld line is formed, and the formation of the weld line can be suppressed.

According to the present invention, the formation of weld lines can be suppressed or the formation direction thereof can be changed without affecting the characteristics of the work as a product.

It is a perspective view which shows the bumper. It is sectional drawing which shows the intermediate molded article which provided the unnecessary part. It is a figure which shows the state at the time of injection molding of a bumper. FIG. 3 is a cross-sectional view taken along the line AA of FIG. It is sectional drawing which shows the modification of the unnecessary part. It is sectional drawing which shows the modification of the unnecessary part. It is sectional drawing which shows the intermediate molded article in the bumper of a different embodiment. It is a figure which shows the weld line formed around the mounting hole. It is a perspective view which shows the conventional resin molded part.

As shown in FIG. 1, the bumper (work) 1 attached to the vehicle is provided with a plurality of attachment holes (holes) 2 for attaching a back sonar, a corner sensor, or the like. As an example, the mounting hole 2 is formed with a diameter of about 25 mm.

The bumper 1 is molded by injection molding. During injection molding, a fluid resin material (injection material) flows into the mold cavity from a plurality of gate positions, and the resin material filled in the cavity is cooled and solidified, so that the bumper including the mounting hole 2 is included. The shape of 1 is formed.

As shown in FIG. 2, the intermediate molded product 1a molded by injection molding is provided with an unnecessary portion 3 at the position of the mounting hole 2. The unnecessary portion 3 is a portion that does not form the final product shape of the work 1. The unnecessary portion 3 is a cut portion 3a, which is partially continuously provided on the main body portion of the bumper. In this embodiment, the case where the mounting hole 2 has a circular shape is illustrated, but the present invention is not limited to this, and the shape can be appropriately selected.

As shown in FIG. 3, during injection molding, the resin material that has flowed from the gate position to the mounting hole 2 side is divided into one side 20 and the other side 30 across the mounting hole 2 (see the arrow in FIG. 3). ). Then, the resin material (hereinafter, also simply referred to as the resin material on the one side 20 and the resin material on the other side 30) that has flowed into the one side 20 and the other side 30 flows around the mounting hole 2 so as to wrap around. The bumper shape around the mounting hole 2 and the mounting hole 2 are formed.

At this time, in the present embodiment, a part of the resin material on one side 20 flows into the mold cavity corresponding to the unnecessary portion 3 to form the unnecessary portion 3. As a result, the pressure of the resin material flowing on one side 20 of the mounting hole 2 in the cavity of the mold becomes smaller than the pressure of the resin material on the other side 30. Therefore, when the resin material on the one side 20 and the resin material on the other side 30 merge again, the resin material on the other side 30 enters the one side 20 by pushing the resin material on the one side 20. Therefore, the formation of weld lines can be suppressed. Further, as shown by the dotted line L1 in FIG. 3, the weld line formation position can be formed so as to be inclined to one side 20.

As described above, by providing the unnecessary portion 3, the flow direction and the pressure of the resin material can be adjusted at the time of injection molding, the weld line can be suppressed, and the formation direction thereof can be adjusted. Therefore, the appearance of the bumper 1 can be improved and the quality thereof can be improved. Further, in the manufacturing method of the present embodiment, not only the weld line but also the internal weld (see FIG. 8) can be suppressed or the formation direction thereof can be changed.

After molding the intermediate molded product 1a by injection molding, the unnecessary portion 3 is removed from the bumper shape. Thereby, the bumper 1 having a desired shape can be obtained. The unnecessary portion 3 can be removed from the bumper body by manually cutting the unnecessary portion 3 at the portion of the cut portion 3a, for example. In this way, since the unnecessary portion 3 can be finally removed from the bumper 1, the mounting hole 2 can be formed by injection molding without affecting the final product shape, and the formation of the weld line can be suppressed. Can be done.

By the way, the unnecessary portion 3 aims to suppress the formation of a weld line by causing a pressure difference between the resin material on one side 20 and the resin material on the other side 30 when they merge (FIG. 6). 3). Therefore, it is preferable that the cutout portion 3a is provided on one side 20 in particular near the weld line forming position.

As shown in FIG. 4, the unnecessary portion 3 can be formed to have a thickness in the direction perpendicular to the bumper 1. As a result, the volume of the unnecessary portion 3 can be increased, and the time required for the resin material to be filled in the cavity corresponding to the unnecessary portion 3 and to be cooled and solidified at the time of injection molding can be lengthened.

By changing the volume of the unnecessary portion 3 as described above, the resin material can be flowed to the unnecessary portion 3 at a more preferable timing. That is, if the resin material on one side 20 and the resin material on the other side 30 wrap around the mounting hole 2 and merge with each other, the cavity corresponding to the unnecessary portion 3 is filled with the resin material. When the resin materials on the one side 20 and the resin material on the other side 30 merge, a sufficient pressure difference cannot be generated between the two, and the formation of the weld line cannot be sufficiently suppressed. Therefore, by increasing the volume of the unnecessary portion 3 as described above, the timing at which the filling of the resin material into the cavity of the mold corresponding to the unnecessary portion 3 is completed is delayed, and the resin material on one side 20 and the other side 30 is completed. At the time of merging, a pressure difference can be created between the two. In the present embodiment, the cross-sectional shape of the unnecessary portion 3 is circular, but the present invention is not limited to this, and the optimum shape can be selected in consideration of the volume of the unnecessary unnecessary portion 3 and the flow method of the resin material. ..

The unnecessary portion 3 can be provided so that the cut portion 3a is partially thinned or the width of the cut portion 3a is reduced. This facilitates the work of cutting off the unnecessary portion 3 from the bumper 1. When the thickness and width of the cut portion 3a are reduced in this way, the area of the inlet portion when the resin material on one side 20 flows into the cavity corresponding to the unnecessary portion 3 becomes smaller, and the resin material is unnecessary. The speed at which the portion 3 is filled is slowed down. Therefore, the timing at which the resin material is filled in the cavity corresponding to the unnecessary portion 3 is delayed, and the pressure difference between the resin material on one side and the resin material on the other side is less likely to occur.

As described above, the thickness and width of the cutout portion 3a are the pressure difference of the required resin material, the timing of filling the cavity corresponding to the unnecessary portion 3, and the ease of cutting out the unnecessary portion 3. It is necessary to design with the optimum value in consideration of such factors. In other words, by adjusting the thickness and width of the cutout portion 3a, it is possible to adjust the timing at which the resin material flows into the cavity corresponding to the unnecessary portion 3. For example, by providing the cutout portion 3a with a small thickness and width, the timing at which the resin material flows into the cavity corresponding to the unnecessary portion 3 is delayed, and the timing at which the resin material on one side and the resin material on the other side merge. It is also possible to maximize the amount of the resin material flowing into the unnecessary portion 3 and more effectively suppress the formation of weld lines.

Further, in the present embodiment, the cutout portion 3a is provided at one place. That is, the resin material on one side 20 flows into the unnecessary portion 3 side at only one place. However, the present invention is not limited to this, and cutout portions 3a continuous with the unnecessary portion 3 may be provided at a plurality of locations on one side 20.

By the way, as described above, the cutting portion 3a is a portion that is manually cut in a subsequent process. Therefore, as shown in FIG. 4, the surface of the cut surface X1 of the bumper 1 becomes rough due to the cut of the unnecessary portion 3, so that the mounting surface of the sensor or back sonar (for example, the surface on which the claws or the like fit) is avoided. It is preferable to set. For example, the unnecessary portion 3 may be provided so as to be continuous with the lower surface X2 of the bumper 1, and the surface X1 may not be a cut surface of the unnecessary portion 3.

FIG. 5 shows a modified example of the configuration of the unnecessary portion.
As shown in FIG. 5, the unnecessary portion 3 of the present embodiment has two cutout portions 3a1 and 3a2. One of the cutout portions 3a1 is provided around a position where the resin material flows toward the mounting hole 2 during injection molding. Further, the other cutout portion 3a2 is provided at a position facing the cutout portion 3a1 with the center position of the mounting hole 2 interposed therebetween.

In the present embodiment, the resin material that has flowed into the mounting hole 2 during injection molding is placed on one side 20 and the other side 30 across the mounting hole 2 and on the side of the unnecessary portion 3 via the cutout portion 3a1. Divide into three directions. Then, the resin materials flowing to the one side 20 and the other side 30 merge at the merging position on the opposite side (hereinafter, also simply referred to as the merging position) with the mounting hole 2 in between. On the other hand, the resin material (hereinafter, also referred to as the third resin material) that has flowed to the side of the unnecessary portion 3 via the cut portion 3a1 flows into the side of the bumper-shaped portion again through the cut portion 3a2, and the above-mentioned merging position. Join in.

In the present embodiment, at the position where the resin materials on the one side 20 and the resin material on the other side 30 collide, the third resin material flows in from the direction intersecting the collision direction through the side of the unnecessary portion 3. As a result, the resin material is extruded in the direction in which the resin material on one side 20 and the resin material on the other side 30 intersect with each other, and the formation of the weld line can be suppressed or the formation direction can be changed at the confluence position. can. In the present embodiment, it is necessary that the third resin material merges at the timing when the resin material on one side 20 and the resin material on the other side 30 collide with each other. This timing can be adjusted by changing the thickness and width of the cutout portions 3a1 and 3a2 and the volume of the unnecessary portion 3 as in the above-described embodiment.

Further, the third resin material may be configured to flow in from one side and merge at the merging position. That is, as shown in FIG. 6, the unnecessary portion 3 has a cut portion 3a1 on one side 20 and a cut portion 3a2 near the confluence position of the one side 20 and the other side 30. In the present embodiment, a part of the resin material on one side 20 is divided into the cutout portion 3a1 side and flows into the unnecessary portion 3 side. Then, the separated resin material flows again to the side of the shape portion of the bumper through the cutout portion 3a2, and merges at the merging position.

In the present embodiment, as in the embodiment shown in FIG. 3, the pressure of the resin material on one side 20 is smaller than the pressure of the resin material on the other side 30 because the resin material on one side 20 is split in the middle. Become. Therefore, at the merging position, the resin material on the other side 30 pushes the resin material on the one side 20. Further, the resin material that has been split on one side 20 and has flowed to the side of the unnecessary portion 3 is rejoined at the merging position, so that the resin on one side 20 and the other side 30 is formed as in the embodiment shown in FIG. It is also possible to obtain the effect of pushing out the resin material in the direction in which the materials collide with each other.

In the configuration of the embodiment shown in FIG. 7, the resin material injection gate 4 is provided at a position corresponding to the unnecessary portion 3. The unnecessary portion 3 is provided with a cut portion 3a at one position, and the cut portion 3a is located at a position facing the confluence position of the resin materials flowing from the one side 20 and the other side 30 across the mounting hole 2. , Or in the vicinity of it.

In the present embodiment, the third resin material flows in from the side of the unnecessary portion 3 at the confluence position of the resin materials on one side 20 and the other side 30. Therefore, at the merging position, the resin material can be swept away in the direction intersecting the direction in which the resin materials on the one side 20 and the other side 30 collide, and the formation of the weld line can be suppressed or the formation direction thereof can be changed. can. In particular, in the present embodiment, by providing the injection gate 4 at a position corresponding to the unnecessary portion 3, the resin material can be positively flowed to the side of the merging position. Further, the resin material poured from the vicinity of the injection gate 4 has a higher pressure than the resin materials on the one side 20 and the other side 30 which are injected from the injection gate farther away and wrap around the mounting hole 2. Therefore, at the merging position, the resin materials on one side 20 and the other side 30 can be pushed away more strongly, and the formation of weld lines can be suppressed more effectively. Further, since the timing of injection of the resin material from the injection gate 4 can be arbitrarily adjusted, it is easy to pour the third resin material at the timing when the resin materials on the one side 20 and the resin material on the other side 30 merge. be.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and it goes without saying that various modifications can be made without departing from the gist of the present invention.

In the above description, a bumper having a mounting hole is shown as an example of a work having a hole, but the present invention is not limited to this, and the manufacturing method of the present invention can be applied when injection molding a work having a hole. Is.

1 Bumper (work)
1a Intermediate molded product 2 Mounting hole (hole)
3 Unnecessary part 3a1, 3a2 Cut part 4 Injection gate

Claims (2)

In a method for manufacturing a work in which a work having holes is formed by injection molding,
A step of forming a shape portion and a hole portion of the work and forming an unnecessary portion continuous with the shape portion of the work in the hole portion.
Look including a step of removing the unnecessary portion from the workpiece,
In the step of molding the shape portion and the hole portion of the work, the injection material sandwiches the hole portion from the upstream side of the hole portion in the flow direction of the injection material in the cavity of the molding mold for molding the work. The flow is divided into one side and the other side, which are opposite to each other, and flows to the downstream side, which is the opposite side with the hole portion in between, with respect to the upstream side.
The unnecessary portion is a method for manufacturing a work, characterized in that one side of the hole portion and the downstream side thereof are bridged. The work manufacturing method according to claim 1, wherein the unnecessary portion is formed by an injection material that has flowed in from the side of the shape portion of the work at the time of injection molding of the work.

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