JP2002283422A - Injection molding method and molded product - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an injection molding method capable of reducing a molding sink generated in the appearance surface of a resin molded product having a region constituted of a plate part and a cylindrical rib part and capable of accurately molding the height of the cylindrical rib, and a molded product molded by the molding method. SOLUTION: At the time of injection-molding of the resin molded product, the recessed part of the cylindrical rib part formed to the back side of the resin molded product is partially compressed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to injection of a resin molded product which requires both sink reduction on the surface of a plate portion and height accuracy of a cylindrical rib in a portion constituted by a plate portion and a cylindrical rib portion. The present invention relates to a molding method, and more particularly to a resin toilet lid provided in a toilet seat unit of a toilet and a warm water flush toilet seat and a molding method thereof.

[0002]

2. Description of the Related Art In a resin molded product having a portion composed of a plate portion and a tubular rib portion, there are many cases where both sink reduction on the plate portion surface and accuracy of the height of the tubular rib are required. For example, a toilet seat unit provided in a toilet or a hot water flush toilet seat has a configuration in which a toilet lid cushion 12 is attached to a contact portion of the rear surface of a toilet lid 11 with the toilet seat, as shown in FIG. For this reason, the toilet lid 11 has a configuration in which a toilet lid cushion mounting portion 13 as shown in FIG. 4 is provided on the back surface of the toilet lid, and the toilet lid cushion 12 is inserted and fixed thereto. For this reason, when molded by normal injection molding, molding sink occurs due to the toilet lid cushion mounting portion 13 on the surface of the toilet lid 11,
There was a problem that appearance quality was unfavorable.

For example, as shown in FIG. 6, a coupling portion between a plate portion 4 serving as an outer surface of a toilet lid and a cylindrical rib portion 5 (or a cylindrical boss portion) serving as a toilet lid cushion mounting portion is provided. A thick portion is formed, and a sink 6 occurs due to shrinkage during solidification of the molten resin on the surface of the plate portion corresponding to the thick portion.

As an invention for solving such a problem, an injection compression molding die having an anti-sink structure as disclosed in, for example, JP-A-11-198198 is known. As shown in FIG. 7, this injection compression molding mold has a cavity mold 2 and a core mold 1, and the movable mold plate 14 is attached to the core mold 1 via a spacer block 19. An ejector plate 16 is provided in the space between the core die 1 and the movable-side mounting plate 14 formed by the spacer block 19 so as to be movable in the cavity direction. A center pin 29 penetrates through the ejector plate 16 and its tip reaches the inside of the cavity. On the outer peripheral surface of the center pin 29, a sleeve pin 30 connected to the hydraulic cylinder 24 via a connecting member 23 is provided.
Are slidably fitted in the axial direction. The hydraulic cylinder 24 is fixedly supported by the ejector plate 16.

[0005] In order to resin-mold the resin molded article 3 having the cylindrical rib portion 5 by using such a mold, molten resin is injected and filled into a cavity closed with the mold, and then the hydraulic cylinder 24 is operated. By driving the sleeve pin 30
Is moved toward the cavity 10 (to the right in FIG. 7), whereby the cylindrical rib portion 5 of the resin molded product before being cooled and solidified is pressed (compressed) toward the cavity mold 2 at the tip of the sleeve pin 30. . By this compressing action, a resin molded product that does not cause sink marks on the surface of the cylindrical rib portion 5 can be formed. Next, after the resin molded product is cooled and solidified, the ejector plate 16 is pushed rightward by an ejector cylinder (not shown) to
By pressing the ejector pin 17, the resin molded product is released from the mold and taken out.

[0006]

However, in these injection compression molding dies, the cylindrical rib portion 5 after being injected and filled in the mold is subjected to the compression action by the sleeve pin 30. In addition, it is possible to obtain a high quality resin molded product without sink marks in the thick part around the rib, but because the method of pressing the convex part of the cylindrical rib part is adopted, There was a problem.

(First Problem) In the cylindrical rib portion 5 as shown in FIG. 6, the rib height is important from the viewpoint of design. In the above-mentioned injection compression molding die, a target rib height is obtained. For this purpose, (1) the sleeve pin is pushed to the maximum movable stroke, and (2) the position of the ejector rod 20 receiving the reaction force of the pressing by the sleeve pin 30 can be controlled with high accuracy. Required. However, the stroke of the sleeve pin 30 changes depending on the solidified state of the cylindrical rib portion 5 (whether the sleeve pin is pushed to the specified position depends on the solidified state of the cylindrical rib portion).
It is difficult to find a molding condition for pushing the sleeve pin up to the maximum movable stroke while exerting the effect of preventing sink marks, and thus it is difficult to accurately mold the target rib height. Further, since a general injection molding machine cannot control the ejector rod 20 with high precision, even if the sleeve pin is pushed down to the maximum movable stroke, the rib height varies every molding. If the rib height of the cylindrical rib portion is not accurately formed for the above reason, the height of the contact position between the toilet lid cushion and the toilet seat will be different for each individual product when installed as a lid. As a result, the appearance silhouette as the toilet seat unit is different for each product, and even if the appearance of the toilet lid surface is improved, the intended appearance silhouette cannot be realized after all.

(Second Problem) In the above-mentioned molding by the injection compression molding die, it is necessary to select the optimal compression conditions, that is, the optimal compression stroke and the optimal compression timing that can provide the effect of preventing sink marks. In order to change the compression stroke in the injection compression molding die, it is necessary to change the position of the stroke setting block 31 and the position of the ejector rod 20, so that it is difficult to finely adjust the compression stroke. In addition, since the work of separating the mold is required each time the position of the stroke setting block is changed, the adjustment work becomes very complicated and the work load increases.

(Third problem) In the above-mentioned molding by the injection compression molding die, a method of pressing the convex portion of the cylindrical rib portion 5 is employed, but in this method, sink occurs once. Later, the ribs are pressed with an excessive pressure to forcibly smooth the surface, so that compression wrinkles remain on the surface of the molded product where there is sink.

The present invention has been made in view of these problems, and has been made to reduce sink marks on the surface of the plate portion and improve the accuracy of the height of the cylindrical rib in a portion constituted by the plate portion and the cylindrical rib portion. In the injection molding of a resin molded product that requires both, an injection molding method capable of reducing sink marks generated in the cylindrical rib portion and accurately molding the cylindrical rib height, and a molded product obtained by the molding method The purpose is to provide.

[0011]

According to a first aspect of the present invention, there is provided a method of injection molding a resin molded product having a portion formed by a plate portion and a cylindrical rib portion. An injection molding method of partially compressing the recess was adopted. This allows
By intentionally forming a thick portion in a portion where a sink occurs, it is possible to press without requiring excessive pressure, thereby reducing sink on the surface of the resin molded product without generating compression wrinkles. Things become possible. At the same time, the height of the cylindrical rib can be accurately formed.

In order to achieve the above object, a second aspect of the present invention is an injection molding method for a resin toilet lid according to the first aspect. This makes it possible to reduce sink marks on the toilet lid surface without generating compression wrinkles.

[0013] In order to achieve the above object, a third aspect is provided.
In the injection molding method according to claim 2, the cylindrical rib portion is a toilet lid cushion attachment portion. This allows
It is possible to reduce the occurrence of sink marks on the toilet lid cushion without generating compression wrinkles. Further, since the rib height of the cylindrical rib, that is, the height of the toilet seat cushion attaching portion can be accurately formed, a desired appearance silhouette can be achieved as a toilet seat unit when installed as a toilet lid.

[0014] In order to achieve the above object, the present invention is directed to claim 4.
Means that a resin molded product is molded by the injection molding method according to claim 1. This makes it possible to provide a molded article having good appearance quality. In particular, a better molded product can be obtained for a toilet lid or the like requiring appearance quality.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In order to further clarify the structure and operation of the present invention described above, preferred embodiments of the present invention will be described below.

[0016]

FIG. 2 shows an embodiment of an injection mold for carrying out the present invention. Reference numeral 2 denotes a cavity mold fixed to the fixed-side mounting plate 15, and 1 denotes a core mold corresponding to the cavity mold 2, and the core mold 1 is movable via a spacer block 19 and a cylinder mounting plate 22. Mounting plate 14
It is attached and held. Further, in the space 21 formed by the spacer block 19 between the core mold 1 and the cylinder mounting plate 22, the ejector rod 20 driven by an ejector cylinder (not shown) pushes the space 21 through the eject assist block 28. The ejector plate 16 is mounted so as to be movable in the cavity direction. Here, the eject assist block 28 is fixed to the ejector plate 16 and the ejector rod 20
The object of the present invention is to shorten the movable stroke of the motor and shorten the cycle time.

A compression pin 9 attached to the connecting member 23 penetrates through the ejector plate 16, and a tip of the compression pin 9 penetrates a cylindrical rib forming hole provided in the core mold 1. It has reached the inside of the cavity 10. An ejector sleeve 7 is provided on the outer peripheral surface of the compression pin 9.
Are slidably fitted in the axial direction, and the ejector sleeve 7 is fixed to the ejector plate 16. The compression pin 9 is connected to the operating shaft of a hydraulic cylinder 24 via a connecting member 23. Here, since a plurality of compression pins 9 can be attached to one connecting member 23, there is no limitation due to the attachment position and the attachment space of the hydraulic cylinder 24. Therefore, the present embodiment can be applied to a plurality of adjacent cylindrical rib portions without any problem.

The hydraulic cylinder 24 is fixedly held on a cylinder mounting plate 22. 25 is a spacer,
The spacer 25 is attached to the cylinder mounting plate 2 as shown in FIG.
The movable stroke d (see FIG. 1) of the compression pin 9 is restricted by being inserted in the space between the second member 2 and the connecting member 23. By replacing the spacer 25 with another spacer having a different thickness, the movable stroke d of the compression pin 9 can be easily changed.
Further, by adopting a mold structure that can be inserted from the side of the mold, the spacer 25 can be easily replaced.
Reference numeral 17 denotes an ejector pin fixed to the ejector plate 16, and reference numeral 18 denotes an injection nozzle for molten resin.

Next, the operation of the embodiment constructed as described above will be described with reference to FIGS. 1 and 2. First, the cavity mold 2 and the core mold 1 are closed and then injected into the cavity 10. The molten resin is injected and filled from the nozzle 18. Next, the hydraulic cylinder 24 is driven, and its operating shaft is directed toward the cavity 10 (rightward in FIGS. 1 and 2).
When the compression shaft 9 is moved forward, the operation of the operating shaft is transmitted to the compression pin 9 via the connecting member 23, and the operation of the compression pin 9 in the direction of the cavity 10 (stroke d) causes the cavity 10 to move.
The concave portion of the cylindrical rib portion 5 to be formed in the cavity is pressed (compressed) in the direction of the cavity mold 2 at the tip of the compression pin 9, so that the resin in the cavity 10 is likely to sink. On the resin molded product surface corresponding to 5,
Sink is reduced. However, as a matter of course, the compression timing, the compression time, and the compression stroke d need to be appropriately set to a condition under which the sink reducing effect is sufficiently exhibited.

Here, in the present invention, the rib height of the cylindrical rib portion is determined by the ejector sleeve 7 and the cavity mold 2 and is not affected by the partial compression step, so that the rib height dimension can be accurately formed. It is possible. In addition,
Even if the compression pin 9 cannot be pushed down to the set maximum movable stroke d, there is no inconvenience because the thickness of the cylindrical rib at the concave portion does not affect the height of the cylindrical rib. Further, in the present invention, by adopting a method of pressing the concave portion of the cylindrical rib, a thick portion is intentionally formed, and the curing of the resin in the thick portion is delayed. Accordingly, since the pressing can be performed in a state where the molten resin remains in the thick portion, excessive pressure is not required unlike the case where the convex portion of the cylindrical rib portion is pressed. Therefore, it is possible to reduce sink marks without generating compression wrinkles, which is a problem in pressing the convex portion.

After the resin is formed in the cavity 10 as described above, the resin is cooled and the mold is opened. Immediately after the mold is opened, the ejector rod 20 is advanced toward the ejector plate 16 by an extruder (not shown). Then, the ejector plate 16 is pushed rightward in FIG. 2 via the eject assist block 28. With the operation of the ejector plate 16, the ejector plate 16
The ejector pin 17 and the ejector sleeve 7 which are supported by the protrusion protrude toward the cavity 10, whereby the resin molded product 3 in the cavity 10 is released. In addition,
The above molding method is not limited to the toilet lid, and requires both sink reduction on the surface of the plate portion and accuracy of the height of the cylindrical rib in a portion composed of the plate portion and the cylindrical rib portion as in the present embodiment. The present invention is applicable to a resin molded product and is not limited by the type of the resin molded product. For example, in a resin toilet seat formed by integrally molding a toilet seat cushion portion that is a contact portion between the toilet seat and the toilet, it is necessary to level the toilet seat horizontally without deteriorating the appearance quality of the toilet seat. . For this purpose, it is necessary to reduce both sink marks on the surface of the toilet seat and the height dimensional accuracy of the seat cushion mounting portion, so that the application of the present invention is effective.

As a particularly preferred embodiment, when the cylindrical rib portion 5 is a cylindrical rib having a recess area 27 sufficiently larger than the rib area 26 of the cylindrical rib, for example, as shown in FIG. In the case of a shape like a toilet lid cushion attachment portion, the pressing area (= recess area) is relatively larger than the rib area 5, so that the amount of compressible molten resin relative to the volume of the thick part of the rib base is relatively large. , Whereby the effect of reducing sink marks works more effectively.

[0023]

As described above, according to the molding method of the present invention, the concave portion of the cylindrical rib portion is partially compressed during the injection molding of a resin molded product having a portion composed of a plate portion and a cylindrical rib portion. By doing so, sink marks generated in the cylindrical rib portion can be reduced, so that the appearance quality of the resin molded product surface, which has conventionally been a problem, can be improved, and a high quality resin molded product can be provided. Become. Further, since the height of the cylindrical rib can be accurately formed, the function of the cylindrical rib can be sufficiently achieved. For example, in a toilet lid, it is possible to control the height of the contact position between the toilet lid cushion and the toilet seat, and as a result, it is possible to achieve a desired external silhouette.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a main part illustrating a partial compression of a cylindrical rib portion during injection molding of a resin molded product of the present invention.

FIG. 2 is a cross-sectional view of a main part showing one embodiment of an injection mold for carrying out the present invention.

FIG. 3 is a perspective view showing a toilet lid back surface and a toilet lid cushion attached state.

FIG. 4 is an essential part perspective view showing a toilet lid cushion mounting portion with the toilet lid cushion removed.

FIG. 5 is a perspective view illustrating a rib area and a concave area of a cylindrical rib portion.

FIG. 6 is a sectional view of an essential part for explaining sink marks of a cylindrical rib portion in a conventional resin molded product.

FIG. 7 is a cross-sectional view of a main part of a conventional injection compression molding die.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Core type, 2 ... Cavity type, 3 ... Resin molding, 4 ...
Plate part, 5 ... tubular rib part, 6 ... sink mark, 7 ... ejector sleeve, 8 ... center pin, 9 ... compression pin, 10 ... cavity, 11 ... toilet lid, 12 ... toilet cushion, 13 ... toilet cushion mounting Reference numeral 14: movable mounting plate, 15: fixed mounting plate, 16: ejector plate, 17: ejector pin, 18: injection nozzle, 19: spacer block, 2
0: ejector rod, 21: space, 22: cylinder mounting plate, 23: connecting member, 24: hydraulic cylinder, 25: spacer, 26: rib area, 27: concave area, 28: eject assist block, 29: center pin, 30 ... Sleeve pin, 31 ... Stroke setting block

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hironobu Morita 2-1-1 Nakajima, Kokurakita-ku, Kitakyushu-shi, Fukuoka Tochiki Kiki Co., Ltd. (72) Inventor Jun Hatakeyama 2 Nakajima, Kokurakita-ku, Kitakyushu-shi, Fukuoka No. 1-1, Totoki Kiki Co., Ltd. (72) Inventor Seiichiro Inoue 2-1-1, Nakajima, Kokurakita-ku, Kitakyushu-shi, Fukuoka F-term in Totoki Kiki Co., Ltd. 2D037 AA12 AA13 4F202 AG28 AH49 AH81 AM34 CA11 CB01 CK52 CM02 4F206 AG28 AH81 AM34 JA07 JQ81

Claims (4)

[Claims] In an injection molding method for a resin molded product having a portion composed of a plate portion and a cylindrical rib portion, a concave portion of a cylindrical rib portion formed on the back side of the plate portion of the resin molded product is partially compressed. Injection molding method. 2. The injection molding method according to claim 1, wherein the resin molded product is a toilet lid. 3. The injection molding method according to claim 2, wherein the cylindrical rib portion is a toilet lid cushion mounting portion. 4. A molded article formed by the injection molding method according to claim 1.