CN106393572B - Injection molding method and mold - Google Patents

Abstract

The invention provides an injection molding method. After a primary molded product (12) is molded in a cavity (C1) between a cavity side mold (58A) and a primary core side mold (52) after mold clamping, a second resin is injected into a cavity (C2) between the cavity side mold (58A) and a secondary core side mold (54) which hold the primary molded product (12), so that secondary molded products (14) of different colors are laminated and molded on the peripheral edge of the primary molded product (12). A plunger (72) of a telescopic mechanism (70) built in a cavity side die (58A) is once molded in a protruding form of a corresponding portion of a peripheral edge portion (12C) of a primary molded article crossing a cavity (C1), and then the plunger (72) is retracted when performing secondary molding. Until the second resin is injected, the peripheral edge portion (12c) is closely attached to the mold, and the resin does not enter between the peripheral edge portion (12c) and the mold.

Description

Injection molding method and mold

Cross Reference to Related Applications

This application claims priority to japanese patent application No. 2015-153249 entitled "injection molding method and mold" filed on 3/8/2015, the entire contents of which are incorporated herein by reference.

Technical Field

The present invention relates to a method and a mold for injection molding a two-color molded article formed by laminating a secondary molded article made of a second resin on a peripheral edge portion of a primary molded article made of a first resin.

Background

Conventionally, as one method of injection molding, there is known a method of injection molding a two-color molded article formed by providing a secondary molded article made of a second resin around a primary molded article made of a first resin.

As a mold for performing such injection molding, patent document 1 describes a mold having the following configuration: a primary core-side mold and a secondary core-side mold provided at positions separated from each other; a rotating member provided to be rotatable around an axis passing between the primary core-side mold and the secondary core-side mold; and a pair of cavity side dies which are fixed to the rotary member in a state in which the pair of cavity side dies can be closed and opened with respect to the primary core side die and the secondary core side die.

Injection molding of a two-color molded article was performed using the mold described in "patent document 1" in the following manner.

That is, as shown in fig. 9(a), a first resin material is injected into a first cavity s1 formed by clamping a first cavity side mold 5 and a primary core side mold 6 to form a primary molded article 1, then the molds 5, 6 are opened while the primary molded article 1 is held by the first cavity side mold 5, and a rotating member is rotated 180 degrees around an axis so that the first cavity side mold 5 holding the primary molded article 1 and the secondary core side mold 7 face each other, and as shown in fig. 9(b), a second resin material is injected into a second cavity s2 formed by clamping the two molds 5, 7 to form a secondary molded article in a peripheral portion of the primary molded article 1, thereby obtaining a two-color molded article.

Specifically, the following constitution is adopted: the first cavity-side die 5 is provided with a telescopic mechanism 3, and the telescopic mechanism 3 is configured to be able to project the plunger 3a into the first cavity s1 from a direction intersecting the mold closing and opening direction (the left-right direction in fig. 9), to form the primary molded article 1 in a state where the tip end portion of the plunger 3a projects into the first cavity s1, and thereafter to retract the plunger 3a during a period from the rotation of the rotating member to the taking out of the two-color molded article.

Therefore, the primary molded article 1 molded in the first cavity s1 is supported by the plunger 3a protruding from the molding surface 5a of the first cavity side mold 5, specifically, the tip end portion of the plunger 3a protruding in the direction orthogonal to the direction in which the primary molded article 1 tries to come off from the first cavity side mold 5 (the right direction in fig. 9 (a)), for example, at the time of mold opening, and therefore, the primary molded article 1 is less likely to come off from the first cavity side mold 5.

Further, for example, when the molds 5, 6 are opened after the primary molded article 1 is molded, the primary molded article 1 is reliably held by the first cavity-side mold 5 instead of the primary core-side mold 6. This makes the transition to the molding step of the secondary molded article smooth.

Documents of the prior art

Patent document

Patent document 1 Japanese patent laid-open No. 2014-168936

Disclosure of Invention

Problems to be solved by the invention

However, in the method according to patent document 1, the recessed portion 1b (see fig. 9(b)) formed when the plunger 3a is retracted remains as a mark in the peripheral edge portion of the two-color molded article, and the appearance is degraded. In particular, when a two-color molded article is used as a front cover of an automobile headlamp, a surface hard coating treatment having weather resistance, durability, and abrasion resistance is usually applied to the front cover, and the applied hard coating treatment liquid is accumulated in the concave portion 1b to look white, thereby further deteriorating the appearance.

Further, according to the method of patent document 1, when a two-color molded article formed by laminating a secondary molded article made of a second resin on the peripheral edge portion of a primary molded article 1 made of a first resin is injection molded, a part of the resin constituting the secondary molded article is rounded to the front surface side of the peripheral edge portion of the primary molded article 1, so-called "color coverage" occurs.

Then, the inventors have examined the cause of the occurrence of the "color overlay" and have found the following.

As shown in fig. 9(a), the primary molded article 1 is formed by injecting a first resin material into a first cavity s1 formed by closing the cavity-side die 5 and the primary core-side die 6, and then the die is opened, and as shown in fig. 9(b), the secondary molded article is laminated and formed at the peripheral portion of the primary molded article 1 by injecting a second resin material into a second cavity s2 formed by closing the cavity-side die 5 holding the primary molded article 1 and the secondary core-side die 7, but the primary molded article 1 shrinks during cooling due to contact with the atmosphere or the like due to opening of the die after being molded by the cavity-side die 5 and the primary core-side die 6. That is, the peripheral edge portion 1a shrinks in a direction of decreasing the surface area along the molding surface 5a of the mold 5 due to the heat shrinkage action of the resin material constituting the primary molded article 1, and is peeled from the molding surface 5 a. Then, when the second resin material is injected into the second cavity s2 with the gap s between the peripheral edge portion 1a and the molding surface 5a of the mold 5, secondary molding is performed in a state where a part of the second resin material enters the gap s between the flange-shaped peripheral edge portion 1a and the molding surface 5a of the mold 5. As a result, color coverage occurs in the peripheral edge portion of the molded two-color molded article.

The present invention has been made in view of the above circumstances, and an object thereof is to provide an injection molding method and a mold in which a retraction trace of a protrusion of a telescopic mechanism does not remain as a concave portion in a peripheral portion of a two-color molded article, and color coverage does not occur in the peripheral portion of the two-color molded article.

Means for solving the problems

The present application achieves the above objects by using a specific telescopic mechanism.

That is, the injection molding method according to the present invention is a method for injection molding a two-color molded article formed by laminating a secondary molded article on a peripheral edge portion of a primary molded article,

injecting a first resin material into a first cavity formed by clamping the cavity-side mold and the primary core-side mold to mold the primary molded article,

then, a second resin material is injected into a second cavity formed by closing the cavity-side mold and the secondary core-side mold holding the primary molded article to laminate and mold the secondary molded article at the peripheral edge portion of the primary molded article,

the cavity-side mold is provided with a retractable mechanism configured to be able to project at least one protrusion to a portion of the first cavity corresponding to a peripheral edge portion of the primary molded article,

molding the primary molded article in such a manner that the protrusion portion protrudes across a portion of the first cavity corresponding to a peripheral edge portion of the primary molded article,

thereafter, when the second resin material is injected into the second cavity to laminate and mold the secondary molded article, the protrusion is retracted to the molding surface of the cavity-side mold.

A mold according to the present invention is a mold for injection molding a two-color molded article formed by laminating a secondary molded article on a peripheral edge portion of a primary molded article, the mold comprising:

a primary molding die including a cavity-side die and a primary core-side die, the primary molding die being configured to mold the primary molded article by injecting a first resin material into a first cavity formed by mold clamping;

a secondary molding die including the cavity-side die and a secondary core-side die, the secondary molding die being configured to mold a secondary molded article in a stacked manner at a peripheral edge portion of the primary molded article by injecting a second resin material into a second cavity formed by clamping the cavity-side die and the secondary core-side die holding the primary molded article; and

a telescopic mechanism provided on the cavity side mold and configured to: the protrusion portion capable of advancing and retreating protrudes to and crosses a portion of the first cavity corresponding to the peripheral edge portion of the primary molded article.

The specific structure of the "telescopic mechanism" is not particularly limited, and for example, a hydraulic cylinder mechanism or a pneumatic cylinder mechanism that advances and retracts a plunger corresponding to the protrusion portion may be used.

Although the primary molded product molded in the first cavity tends to stick to the primary core-side mold due to thermal shrinkage at the time of mold opening, the force with which the resin constituting the peripheral portion of the primary molded product thermally shrinks to hold the protrusion of the expansion mechanism is greater than the force with which the primary molded product tends to stick to the primary core-side mold, and therefore the primary molded product is held by the cavity-side mold. Therefore, when the mold is opened after the primary molded product is molded, the primary molded product can be reliably held by the cavity-side mold, and therefore, the transition to the next step of closing the cavity-side mold holding the primary molded product and the secondary core-side mold becomes smooth.

Further, the primary molded article molded in the first cavity is brought into contact with the atmosphere by opening the mold, and the resin further thermally contracts and attempts to contract in a direction in which the surface area of the entire primary molded article is reduced. Therefore, during the period until the second resin material is injected into the second cavity formed by closing the cavity-side mold holding the primary molded article and the secondary core-side mold, the entire primary molded article in close contact with the molding surface of the cavity-side mold is shrunk and deformed in a direction to reduce the surface area thereof, and the peripheral edge portion of the primary molded article, which is displaced by thermal shrinkage to a large extent, is peeled off from the molding surface of the cavity-side mold, and a gap may be generated between the molding surface and the peripheral edge portion of the primary molded article, and this gap may be a factor causing "color-covering".

However, in the present invention, since the protrusion of the expanding and contracting mechanism protruding from the molding surface of the cavity-side mold crosses the peripheral edge of the primary molded article where a large displacement due to thermal contraction occurs, deformation due to thermal contraction in a direction in which the surface area of the entire primary molded article is reduced can be effectively suppressed. That is, the protrusion of the expanding and contracting mechanism which protrudes from the molding surface of the cavity-side mold and crosses the peripheral edge portion of the primary molded article suppresses deformation caused by thermal contraction in the direction in which the surface area of the entire primary molded article is reduced.

In particular, since displacement of the peripheral edge portion of the primary molded article, which exhibits large deformation due to thermal shrinkage, can be reliably suppressed, the primary molded article is held in a state in which the entire primary molded article including the peripheral edge portion thereof is in close contact with the molding surface of the cavity-side mold before the secondary molded article is laminated and molded by injecting the second resin material into the second cavity.

Therefore, so-called "color coverage" in which a part of the second resin material injected into the second cavity is wound between the peripheral edge portion of the primary molded article and the molding surface of the cavity-side mold does not occur.

When the secondary molded article is laminated and molded in a state in which the protrusion of the expanding and contracting mechanism is pulled out from the peripheral edge portion of the primary molded article and retracted to the molding surface of the cavity-side mold, although a through hole of a retraction trace of the protrusion of the expanding and contracting mechanism is formed in the peripheral edge portion of the primary molded article, a part of the second resin material injected into the second cavity is filled in the through hole and molded. That is, the convex portion on the secondary molded article side having the end face molded with the protrusion front end face of the telescopic mechanism as the molding face is engaged and integrated with the through hole formed in the peripheral edge portion of the primary molded article as the retraction trace of the protrusion.

In the injection molding method according to the present invention, it is preferable that the injection of the second resin material into the second cavity is performed after the retraction of the protrusion is confirmed by a sensor provided in the expansion/contraction mechanism. For example, in the case where a predetermined retraction amount of the protrusion is detected by a limit switch provided on the telescopic mechanism, it may be considered that a side valve gate communicating with the second cavity is opened for correlation.

When the projection of the expansion and contraction mechanism is retracted at a delayed timing when the mold is closed to laminate and mold the secondary molded article, the filling pressure of the second resin material filled in the second cavity changes (drops) in the middle, and stable injection molding cannot be performed. Further, since the molten resin adheres to the tip of the retracted protrusion, smooth driving of the telescopic mechanism (smooth telescopic operation of the protrusion) may be hindered.

However, in the present invention, since the second resin material is injected into the second cavity after the protrusion of the expanding and contracting mechanism is confirmed to be retracted to the molding surface of the cavity-side mold by the sensor provided in the expanding and contracting mechanism, the filling pressure of the second resin material does not change (drop) in the middle, and stable injection molding can be performed. Further, the molten resin does not adhere to the tip of the retracted protrusion, and the smooth driving of the telescopic mechanism (smooth telescopic operation of the protrusion) is not hindered.

In the mold according to the present invention, it is preferable that the tip of the protrusion of the expansion and contraction mechanism provided in the cavity-side mold is formed to follow the shape of the molding surface of the cavity-side mold in which the first cavity is formed.

Further, a two-color molded article according to the present invention is a two-color molded article formed by laminating a secondary molded article on a peripheral edge portion of a primary molded article, which is molded by the method according to the present invention, wherein at least one through hole formed when the protrusion of the expansion and contraction mechanism is retracted is provided in the peripheral edge portion of the primary molded article, and a convex portion of the secondary molded article laminated on the primary molded article is integrally engaged with the through hole.

Since the secondary molded article is laminated and molded in a state where the protrusion of the expanding and contracting mechanism is retracted to the molding surface of the cavity-side mold, when the protrusion of the expanding and contracting mechanism is retracted (pulled out from the peripheral edge of the primary molded article), a through hole as a retraction trace of the protrusion is formed in the peripheral edge of the primary molded article, but the through hole is integrally filled with the second resin material constituting the secondary molded article. That is, the convex portion on the secondary molded article side having the end face molded with the protrusion front end face of the telescopic mechanism as the molding face is engaged and integrated.

Further, since the front end face of the projecting portion of the telescopic mechanism is formed following the shape of the molding surface of the cavity-side mold forming the first cavity, the peripheral edge region of the through hole of the primary molded article formed by the molding surface of the cavity-side mold forming the first cavity and the end face of the projecting portion on the secondary molded article side formed by the front end face of the projecting portion of the telescopic mechanism and engaged with the through hole as a single body constitute a continuous surface of the peripheral edge portion of the two-color molded article.

Effects of the invention

As described above, according to the present invention, when a secondary molded article is laminated and molded on the peripheral edge portion of a primary molded article, although the protrusion of the expanding and contracting mechanism is retracted to the molding surface of the cavity-side mold, the retraction trace of the protrusion does not remain as a recess in the peripheral edge portion, and a two-color molded article in which color coverage does not occur in the peripheral edge portion can be provided.

Drawings

Fig. 1 is a side sectional view showing a mold used in an injection molding method according to an embodiment of the present invention.

FIG. 2 is a side sectional view showing a two-color molded article molded by the injection molding method.

Fig. 3(a) and 3(b) are (a) explanatory views of the injection molding method.

Fig. 4(c) and 4(d) are process explanatory views of the injection molding method (the second embodiment).

Fig. 5(e) and 5(f) are process explanatory views (third) of the injection molding method.

Fig. 6(g) and 6(h) are explanatory views (four) of the steps of the injection molding method.

Fig. 7(b), 7(e), and 7(f) are enlarged sectional views of main portions of fig. 3(b), 5(e), and 5 (f).

Fig. 8 is a view similar to fig. 6(g) showing a modification of the above embodiment.

Fig. 9 is a sectional view illustrating a problem in injection molding of a two-color molded article formed by laminating a secondary molded article on a peripheral edge portion of a primary molded article by the method according to the prior patent document, fig. 9(a) shows a step of molding the primary molded article, and fig. 9(b) shows a step of laminating the secondary molded article.

List of reference numerals:

10 two-color molded article

10A front surface part

10B peripheral surface part

10Ba flange part

10Bb annular projection

12 Primary molded article

12c flange part provided on the peripheral edge part of the primary molded article

12d through hole

14 Secondary molded article

14a protruding part of secondary formed article engaged with through hole

14b end face of the convex part

50. 150 mould

52. 152 primary core side mould

54. 154 secondary core side mould

56. 156 rotating part

58A, 58B, 158A, 158B cavity side mould

58A is provided on the molding surface of the cavity-side mold 58A

58B are provided on the molding surface of the cavity-side mold 58B

62 Movable disc

64 fixed disk

66. 68 heating cylinder

70. 170 hydraulic cylinder (Telescopic machanism)

72. 172 plunger (projection)

74 Limit switch as sensor arranged on the hydraulic cylinder

80 side valve gate

C1 first cavity

C2 second cavity

Detailed Description

Embodiments of the present invention will be described below with reference to the drawings.

Fig. 1 is a side sectional view showing a mold 50 used in an injection molding method according to an embodiment of the present invention. Fig. 2 is a side sectional view showing a two-color molded article 10 injection molded by the injection molding method according to the present embodiment.

First, the structure of the two-color molded article 10 will be described.

As shown in fig. 2, the two-color molded article 10 is a container-shaped light-transmitting cover to be assembled to a front surface opening of a lamp body of a vehicle lamp such as a headlamp, and includes: a front surface portion 10A; and a peripheral surface portion 10B extending rearward from the outer peripheral edge of the front surface portion 10A. The peripheral surface portion 10B is formed with a flange portion 10Ba of a predetermined width extending outward from the rear end position of the peripheral surface portion and an annular protrusion portion 10Bb as a seal leg protruding rearward from the rear surface of the peripheral surface portion.

The two-color molded article 10 adopts the structure: the primary molded article 12 and the secondary molded article 14 are stacked from the circumferential surface portion 10B to the back surface side of the flange portion 10 Ba. Namely, the structure is adopted: the secondary molded article 14 is superimposed from the middle of the circumferential surface portion 12b of the primary molded article 12 in the front-rear direction to the back surface side of the flange portion 12 c. In this case, the primary molded article 12 is made of a transparent first resin member, and the secondary molded article 14 is made of an opaque (specifically, black) second resin member.

Further, a plurality of through holes 12d are formed in the circumferential direction in the flange portion 12c formed in the peripheral edge portion of the primary molded article 12, and the convex portion 14a of the secondary molded article 14 provided on the back side is integrally engaged with each through hole 12 d.

Next, the structure of the mold 50 will be described. As shown in fig. 1, the mold 50 is a so-called opposed two-color molding mold.

That is, the mold 50 includes: a primary core-side die 52 and a secondary core-side die 54 provided in a state of facing each other on an X axis extending in a horizontal direction; a rotating member 56 provided between the primary core-side die 52 and the secondary core-side die 54 so as to be rotatable about a Y axis orthogonal to the X axis and extending in the vertical direction; a pair of cavity- side molds 58A, 58B of the same shape fixed to the rotating member 56 in a back-to-back state with respect to the Y axis; and a movable platen 62 that supports the primary core-side mold 52 and a fixed platen 64 that supports the secondary core-side mold 54.

At this time, the rotating member 56 is configured to be movable in the X-axis direction with respect to the fixed disk 64, and the movable disk 62 is configured to be movable in the X-axis direction with respect to the rotating member 56. In fig. 1, the direction of the relative movement is indicated by an arrow.

In this mold 50, a transparent first resin material supplied from a heating cylinder 66 supported by a movable platen 62 is injected into a first cavity C1 formed between a primary core side mold 52 and a first cavity side mold 58A brought into contact by clamping, and a black second resin material supplied from a heating cylinder 68 supported by a fixed platen 64 is injected into a second cavity C2 formed between a secondary core side mold 54 and a second cavity side mold 58B brought into contact by clamping with a primary molded article 12 interposed therebetween.

That is, the first cavity-side die 58A cooperates with the primary core-side die 52 to constitute a primary molding die for molding the primary molded article 12, and rotates 180 degrees integrally with the rotary member 56 to cooperate with the secondary core-side die 54 to constitute a secondary molding die for molding the secondary molded article 14. On the other hand, the second cavity-side die 58B, which is back-to-back with the first cavity-side die 58A via the rotating member 56, cooperates with the primary core-side die 52 to constitute a primary molding die for molding the primary molded article 12, and rotates 180 degrees integrally with the rotating member 56 to cooperate with the secondary core-side die 54 to constitute a secondary molding die for forming the secondary molded article 14.

In this way, the primary molded article 12 is molded by the primary molding die on the left side of fig. 1, and the secondary molded article 14 is laminated and molded (molded as the two-color molded article 10) by the secondary molding die on the right side of fig. 1.

Further, a hydraulic cylinder 70 as a telescopic mechanism is provided at a plurality of positions of each of the cavity- side molds 58A, 58B, and the hydraulic cylinder 70 is provided with a plunger 72 capable of advancing and retreating. At this time, as shown in fig. 7(b), the plurality of hydraulic cylinders 70 are arranged in the following manner: the plungers 72 thereof are caused to face the corresponding regions of the flange portions 12C of the primary molded article 12 on the respective molding surfaces 58A, 58B of the respective cavity- side molds 58A, 58B that form the first cavity C1, and the hydraulic cylinders 70 are spaced apart at predetermined intervals in the circumferential direction of the molding surfaces 58A, 58B. Each hydraulic cylinder 70 is configured as follows: the plunger 72 can be projected into the first cavity C1 from a direction parallel to the X axis (mold closing/opening direction).

Note that since the injection molding of the primary molded article 12 using the cavity-side mold 58A and the injection molding of the secondary molded article 14 (molding of the two-color molded article 10) and the injection molding of the primary molded article 12 using the cavity-side mold 58B and the injection molding of the secondary molded article 14 (molding of the two-color molded article 10) are the same, the injection molding of the primary molded article 12 using the cavity-side mold 58A and the injection molding of the secondary molded article 14 (molding of the two-color molded article 10) will be mainly described, and the description of the injection molding of the primary molded article 12 using the cavity-side mold 58B and the injection molding of the secondary molded article 14 (molding of the two-color molded article 10) will be omitted.

Next, an injection molding method according to the present embodiment will be described. FIGS. 3 to 6 are process diagrams showing the injection molding method.

First, as shown in fig. 3(a), the primary core-side mold 52 and the secondary core-side mold 54 are clamped to the pair of cavity- side molds 58A, 58B. At this time, the plunger 72 of each hydraulic cylinder 70 provided in the cavity-side die 58A constituting the primary molding die is caused to traverse the portion of the first cavity C1 corresponding to the flange portion 12C of the primary molded article 12 and to protrude into the first cavity C1. On the other hand, the plunger 72 of each hydraulic cylinder 70 provided on the cavity-side die 58B constituting the secondary molding die is set in a state retracted from the cavity between the die 58B and the die 54. Then, in this state, as shown in fig. 3(b), the transparent resin material supplied from the heating cylinder 66 is injected into the first cavity C1 to mold the primary molded article 12.

Next, as shown in fig. 4(c), the primary core-side mold 52 and the secondary core-side mold 54 are opened together with the pair of cavity- side molds 58A, 58B. At this time, although the primary molded product 12 tries to adhere to the primary core-side mold 52 due to the contraction action of the resin constituting the primary molded product 12, the plunger 72 of the hydraulic cylinder 70 penetrates and engages with the flange portion 12c of the primary molded product 12 from the direction parallel to the mold closing and opening direction, and therefore, when the molds 52 and 58A are opened, the primary molded product 12 is separated from the primary core-side mold 52 while being held on the cavity-side mold 58A. That is, the force with which the resin constituting the flange portion 12c of the primary molded article 12 thermally contracts to embrace the plunger 72 is greater than the force with which the resin constituting the primary molded article 12 thermally contracts to try to adhere to the primary core mold 52, and therefore, the primary molded article 12 is held on the cavity side mold 58A during mold opening.

Then, in this state, as shown in fig. 4(d), the rotating member 56 is rotated by 180 ° about the Y axis. At this time, although a centrifugal force acts on the primary molded article 12 held by the cavity side mold 58A, the plunger 72 is engaged with the flange portion 12c of the primary molded article 12, and thus the state of being held by the cavity side mold 58A is maintained. That is, since the force with which the resin constituting the flange portion 12c of the primary molded article 12 contracts thermally and grips the plunger 72 is larger than the centrifugal force acting on the primary molded article 12, the primary molded article 12 is held on the cavity-side die 58A without falling off when the rotating member 56 is rotated 180 ° about the Y axis.

Next, as shown in fig. 5(e), the primary core-side mold 52 and the secondary core-side mold 54 are clamped to the pair of cavity- side molds 58B and 58A. Then, in this state, the hydraulic cylinder 70 provided in the cavity-side die 58A is driven to retract the plunger 72 to the position of the molding surface 58A (see fig. 7(e)), and as shown in fig. 5(f), the black resin material supplied from the heating cylinder 68 is injected into the second cavity C2. Specifically, when the predetermined amount of retraction of the plunger 72 is detected by the limit switch 74 built in the hydraulic cylinder 70, the black resin material supplied from the heating cylinder 68 is injected into the second cavity C2 through the side valve gate 80 to mold the secondary molded article 14 (see fig. 7 (f)). This completes the secondary molded article 10 in which the primary molded article 12 and the secondary molded article 14 are integrally laminated.

As shown in fig. 3(a) and 3(b), the primary molded article 12 molded in the first cavity C1 is exposed to the atmosphere by opening the mold (see fig. 4(C)), and the resin is further thermally shrunk to shrink the entire surface area. Therefore, during the period until the second resin material is injected into the second cavity C2 formed by clamping the cavity side mold 58A holding the primary molded product 12 and the secondary core side mold 54 as shown in fig. 5(e) and 5(f), the entire primary molded product 12 in close contact with the molding surface 58A of the cavity side mold 58A is shrunk and deformed in a direction to reduce the surface area thereof, and the flange portion 12C of the primary molded product 12, which is displaced by the thermal shrinkage largely, is separated from the molding surface 58A of the cavity side mold 58A, and a gap may be generated between the molding surface 58A and the flange portion 12C, which causes the "color coverage".

However, in the present embodiment, as shown enlarged in fig. 7(e), the plunger 72 protruding from the molding surface 58A of the cavity-side die 58A crosses the flange portion 12c of the primary molded article 12 in which a large displacement due to thermal contraction occurs, and therefore deformation due to thermal contraction in a direction in which the area of the entire primary molded article 12 is reduced can be effectively suppressed. That is, the plunger 72 of the hydraulic cylinder 70 which projects from the molding surface 58A of the cavity-side mold 58A and crosses the flange portion 12c of the primary molded article 12 suppresses deformation caused by thermal contraction in a direction in which the area of the entire primary molded article 12 is reduced.

In particular, since the second resin material is injected into the second cavity C2 while the retraction of the plunger 72 of the hydraulic cylinder 70 is detected by the limit switch 74, the entire primary molded article 12 including the flange portion 12C is kept in a state in which it is in close contact with the molding surface 58A of the cavity side mold 58A until the second resin material is injected into the second cavity C2 to start the stack molding of the secondary molded article 14.

Therefore, so-called "color coverage" in which a part of the second resin material injected into the second cavity C2 is wound between the flange portion 12C of the primary molded article 12 and the molding surface 58A of the cavity-side mold 58A does not occur.

In the injection molding of the secondary molded article 14 in the state where the plunger 72 of the hydraulic cylinder 70 is retracted, although the through hole 12d, which is a mark when the plunger 72 is pulled out from the flange portion 12C, that is, a retraction mark of the plunger 72, is formed in the flange portion 12C of the primary molded article 12, as shown in fig. 7(f), a part of the second resin material injected into the second cavity C2 is filled in the through hole 12d to be molded and integrated. Therefore, the convex portion 14a on the secondary molded article 14 side is engaged with the through hole 12d, and the end face 14b of the convex portion 14a in black is exposed in the through hole 12 d.

As shown in fig. 7(e), the front end surface 72a of the plunger 72 of the hydraulic cylinder 70 is formed so as to follow the shape of the molding surface 58A of the cavity-side mold 58A for forming the first cavity C1, and as shown in fig. 7(f), the secondary molded article 14 is injection molded in a state in which the plunger 72 is retracted to a position where the front end surface 72a of the plunger 72 is aligned with the molding surface 58A of the mold 58A.

Therefore, as shown in fig. 2, the peripheral edge region 12d1 of the through hole 12d of the primary molded article 12 formed by the molding surface 58A of the cavity-side mold 58A forming the first cavity C1 and the end surface 14b of the convex portion 14a on the secondary molded article 14 side formed by the front end surface 72a of the plunger 72 and integrated with the through hole 12d constitute a continuous front surface of the flange portion 10Ba (the flange portion 12C of the primary molded article 12) of the two-color molded article 10.

Finally, as shown in fig. 6(g), the primary core-side mold 52 and the secondary core-side mold 54 are opened together with the pair of cavity- side molds 58B and 58A. At this time, since the plunger 72 is not engaged with the primary molded article 12, the two-color molded article 10 is in a state of being stuck to the secondary core side mold 54 at the time of mold opening. Then, in this state, as shown in fig. 6(h), the two-color molded article 10 is taken out. The two-color molded product 10 attached to the secondary core-side mold 54 is pushed out by a push-out pin, not shown, and is grasped by a take-out machine, not shown.

As shown in fig. 2, a through hole 12d as a retraction trace of the plunger 72 is formed in the front surface side of the flange portion 10Ba (flange portion 12c of the transparent primary molded article 12) of the two-color molded article 10 molded as described above, and the convex portion 14a of the black secondary molded article 14 stacked on the back surface side is engaged with the through hole 12d to be integrated, and the end surface 14b of the convex portion 14a is formed to be flush with the front surface of the flange portion 10Ba (flange portion 12 c).

Further, since the two-color molded region in which the primary molded article 12 and the secondary molded article 14 are laminated including the flange portion 10Ba is seen through the transparent primary molded article 12 on the front surface side to see the black color of the secondary molded article 14 on the back surface side, that is, the entire two-color molded region including the flange portion 10Ba appears black, the end face 14b of the black convex portion 14a exposed to the flange portion 10Ba (flange portion 12c) is completely invisible, and the appearance is excellent.

Even if the front cover 10 is subjected to a surface hard coating treatment having weather resistance, durability, and abrasion resistance in order to use the two-color molded article 10 as a front cover of an automobile headlamp, the end face 14b of the convex portion 14a of the secondary molded article 14 exposed on the front surface of the flange portion 10Ba and the front surface of the flange portion 10Ba are formed in one surface, and therefore, there is no problem that the hard coating treatment liquid applied is accumulated in the concave portion and appears whitish as in the conventional case.

Further, in the present embodiment, the two-color molded article 10 to be subjected to the injection molding is a translucent cover of a vehicle lamp, and the primary molded article 12 thereof is made of a transparent resin member and the secondary molded article 14 thereof is made of an opaque resin member, so that the primary molded article 12 is large and heavy. Therefore, the centrifugal force acting on the primary molded article 12 also increases when the rotating member 56 rotates, and the primary molded article 12 is easily detached from the cavity-side mold 58A. Therefore, the configuration according to the present embodiment is particularly effective.

In the above embodiment, the following configuration is adopted: when the limit switch 74 built in the hydraulic cylinder 70 detects the retraction of the plunger 72, the black resin material is injected into the second cavity C2 through the side valve gate 80. Therefore, before the molding of the secondary molded article 14 is started, the retracting plunger 72 can be reliably pulled out from the flange portion 12a of the primary molded article 12.

That is, when the mold is closed to laminate-mold the secondary molded article 14, if the retraction timing of the plunger 72 of the hydraulic cylinder 70 is delayed, the filling pressure of the second resin material changes (drops) in the middle, and stable injection molding cannot be performed, or molten resin adheres to the retracted plunger 72 at the tip thereof, and therefore smooth driving of the hydraulic cylinder 70 (smooth extending and contracting operation of the plunger 72) may be hindered.

However, in the present embodiment, since the second resin material is injected into the second cavity C2 after the plunger 72 is confirmed to be reliably retracted from the flange portion 12a of the primary molded article 12 by the limit switch 74, the filling pressure of the second resin material filled in the second cavity C2 does not change (drop) in the middle, and stable injection molding can be performed. Further, the molten resin does not adhere to the tip of the retracted plunger 72, and the smooth driving of the hydraulic cylinder 70 (smooth extending and retracting operation of the plunger 72) is not hindered.

In order to prevent the occurrence of "color coverage" in the peripheral edge portion of the two-color molded article, it is effective to set the timing at which the plunger 72 is retracted from the peripheral edge portion 12a of the primary molded article 12 as late as possible before the injected second resin material reaches the plunger 72. In addition, although it depends on the injection pressure and the flow rate of the second resin material, the arrival time from the side valve gate to the nearest plunger 72 is a predetermined time (for example, 0.5 second). Then, the opening action of the side valve gate 80 and the driving of the hydraulic cylinder 70 may be associated to retract the plunger 72 when a predetermined time (for example, 0.5 second) has elapsed after the opening of the side valve gate 80.

Although the example in which the hydraulic cylinders 70 are provided at a plurality of locations of the cavity- side molds 58A, 58B has been described in the above embodiment, in the case of a configuration in which the hydraulic cylinders 70 are provided at only one location, the prevention of the detachment from the cavity- side molds 58A, 58B can be realized by the shape of the primary molded article 12.

Although the above embodiment has been described with the plunger 72 of each hydraulic cylinder 70 projecting into the first cavity C1 from a direction parallel to the mold closing and opening direction, the plunger may project into the first cavity C1 from a direction oblique to the mold closing and opening direction as long as the primary molded article 12 is prevented from coming off the cavity-side mold 58A.

Although the two-color molded article 10 to be subjected to injection molding is described as an example of the light-transmitting cover of the vehicle lamp in the above embodiment, the same operational effects as those of the above embodiment can be obtained even when a resin molded article other than the two-color molded article is subjected to, for example, a sunroof, a rear window, or the like.

Next, a modified example of the above embodiment will be described. Fig. 8 is a view similar to fig. 6(g) showing the outline of the injection molding method according to the present modification.

As shown in this figure, in this modification, the configuration of the two-color molded article 10 to be injection molded is the same as that of the above-described embodiment, and the configuration of the mold 150 is the same as that of the above-described embodiment in terms of the configuration itself of the primary-core-side mold 152, the secondary-core-side mold 154, and the pair of cavity- side molds 158A and 158B, but the arrangement is different from that of the above-described embodiment.

That is, the mold 150 is a so-called rotary type two-color molding mold, and is configured as follows: the primary core-side die 152 and the secondary core-side die 154 are provided upward at positions spaced apart from each other, and a pair of cavity-side dies 158A and 158B having the same shape are provided downward on a rotating member 156 provided rotatably around a Y axis extending in the vertical direction between the primary core-side die 152 and the secondary core-side die 154. Then, the pair of cavity-side dies 158A and 158B are moved in the vertical direction together with the rotating member 156, whereby the primary-side die 152, the secondary-side die 154, and the pair of cavity-side dies 158A and 158B are clamped and opened.

Specifically, the first cavity-side mold 158A cooperates with the primary core-side mold 152 to form a primary molding mold for molding the primary molded article 12, and rotates 180 degrees integrally with the rotating member 156 to cooperate with the secondary core-side mold 154 to form a secondary molding mold for molding the secondary molded article 14. On the other hand, the second cavity-side mold 158B cooperates with the primary core-side mold 152 to form a primary molding mold for molding the primary molded article 12, and rotates 180 degrees integrally with the rotating member 156 to form a secondary molding mold for molding the secondary molded article 14 in cooperation with the secondary core-side mold 154.

When the cavity-side dies 158A and 158B are used as the primary molding dies, the primary molded article 12 is molded while the plungers 172 of the hydraulic cylinders 170 are protruded into the first cavities for molding the primary molded article 12, whereas when the cavity-side dies 158A and 158B are used as the secondary molding dies, the secondary molded article 14 is molded while the plungers 172 of the hydraulic cylinders 170 are retracted from the cavities between the dies.

In the case of the configuration of the present modification, for example, the plunger 172 of the hydraulic cylinder 170 is inserted into and engaged with the peripheral edge portion of the primary molded article 12 from the direction parallel to the mold closing and opening direction, and therefore, when the primary core-side mold 152 and the cavity-side mold 158B are opened, as shown in fig. 8, the primary molded article 12 is separated from the primary core-side mold 152 while being held on the cavity-side mold 158B, and the primary molded article 12 is held on the cavity-side mold 158B without being displaced by a centrifugal force and/or an impact force when the rotary member 156 rotates.

In the present modification, the plunger 172 of the hydraulic cylinder 170 which projects from the molding surface of the cavity-side mold 158B and crosses the flange portion 12a of the primary molded article 12 holds the primary molded article 12 in a state in which the entire periphery portion 12a thereof is in close contact with the molding surface of the cavity-side mold 158B before the secondary molded article is laminated and molded by injecting the second resin material into the second cavity. Therefore, so-called "color coverage" in which a part of the second resin material injected into the second cavity is wound between the peripheral edge portion of the primary molded article and the molding surface of the cavity-side mold does not occur.

In the injection molding of the secondary molded article 14 in the state where the plunger 172 of the hydraulic cylinder 170 is retracted, although the through hole 12d, which is a mark when the plunger 172 is pulled out from the flange portion 12c, is formed in the flange portion 12c of the primary molded article 12, a part of the second resin material constituting the secondary molded article 14 is filled in the through hole 12d and integrated.

Therefore, as shown in fig. 2, the convex portion 14a on the secondary molded article 14 side on the back side engages with the through hole 12d formed in the flange portion 10Ba of the two-color molded article 10 after molding (the flange portion 12c of the primary molded article 12), and the peripheral edge region 12d1 of the through hole 12d of the primary molded article 12 and the end face 14b of the convex portion 14a exposed to the through hole 12d constitute a continuous front surface of the flange portion 10Ba of the two-color molded article 10 (the flange portion 12c of the primary molded article 12).

As described above, the present modification also provides the same operational advantages as those of the above embodiment.

The present invention is not limited to the configurations described in the above embodiments and modifications thereof. For example, the specific configuration of the "telescopic mechanism" is not particularly limited, and a pneumatic cylinder or the like may be used in addition to the hydraulic cylinder, and various modifications may be made.

Claims (2)

1. An injection molding method for injection molding a two-color molded article formed by laminating a secondary molded article on a peripheral edge portion of a primary molded article,

injecting a first resin material into a first cavity formed by clamping the cavity-side mold and the primary core-side mold to mold the primary molded article,

then, a second resin material is injected into a second cavity formed by closing the cavity-side mold and the secondary core-side mold holding the primary molded article to laminate and mold the secondary molded article at a peripheral edge portion of the primary molded article,

the secondary molded article is formed so that the entire secondary molded article overlaps with the peripheral edge of the primary molded article,

the cavity-side mold is provided with a retractable mechanism configured to be able to cause at least one protrusion to protrude to a portion of the first cavity corresponding to a peripheral edge portion of the primary molded article,

forming the primary molded article in a form in which the protrusion portion protrudes across a portion of the first cavity corresponding to a peripheral edge portion of the primary molded article, a tip portion of the protrusion portion of the expansion mechanism being formed so as to follow a shape of a molding surface of a cavity-side mold forming the first cavity;

then, when the second resin material is injected into the second cavity to laminate and mold the secondary molded article, the tip end portion of the protrusion is retracted to be flush with the molding surface of the cavity-side mold, and after the retraction of the protrusion is confirmed by a sensor provided in the expansion and contraction mechanism, the second resin material is injected again.

2. A mold for injection molding of a two-color molded article formed by laminating a secondary molded article on a peripheral edge portion of a primary molded article, comprising:

a primary molding die including a cavity-side die and a primary core-side die, the primary molding die being configured to mold the primary molded article by injecting a first resin material into a first cavity formed by mold clamping;

a secondary molding die including the cavity-side die and a secondary core-side die, the secondary molding die being configured to mold a primary molded article in a stacked manner at a peripheral edge portion of the primary molded article by injecting a second resin material into a second cavity formed by clamping the cavity-side die and the secondary core-side die holding the primary molded article; and

a telescopic mechanism provided on the cavity side mold and configured to: a protrusion portion capable of advancing and retreating, protruding to a portion of the first cavity corresponding to a peripheral edge portion of the primary molded article and crossing the portion;

the telescopic mechanism further comprises a sensor capable of detecting the retraction of the protrusion,

the secondary molded article is formed so that the entire secondary molded article overlaps with the peripheral edge of the primary molded article,

the front end of the protrusion of the telescopic mechanism is formed to follow the shape of the molding surface of the cavity-side mold forming the first cavity.

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