Method for producing resin molded article by injection molding, and injection molding device

Provided is a technology with which, when producing a resin molded article, the inside of which is provided with an insert component such as a terminal fitting, it is possible to prevent the insert component from being exposed at an inappropriate position, and to ensure the desired positional accuracy. In an injection molding device, the accuracy of the position of a terminal is improved by allowing a core-back mold to move after a terminal, which is an insert component, has been inserted in a terminal tip holding section of a slide mold. By allowing the core-back mold to move by only a prescribed amount prior to injection molding, a resin wall is formed between the core-back mold and the terminal. The inappropriate exposure and shorting of and the adhesion of foreign substances to, and the like, the terminal can thus be prevented.

TECHNICAL FIELD

The present invention relates to a method for producing a resin molded article by injection molding, and an injection molding device.

BACKGROUND ART

There are known injection molding techniques using a mold as techniques for producing a resin molded article. As one of such injection molding techniques, a core-back injection molding is known and universally used. In the core-back injection molding, a resin containing a foaming agent (e.g., a gas or chemical foaming agent) is injected/filled in a mold and then the mold is opened by a prescribed degree, so that the resin is foamed. Specifically, according to the core-back injection molding, a core of the mold is moved such that a cavity in the mold can be expanded. Types of the core-back injection molding include: a core-back injection molding employing an operation of a platen, a core-back injection molding employing a movement of a taper-shaped pressure receiving block, a core-back injection molding employing a movement of a movable core-back plate capable of receiving a mold clamping pressure; injection pressure, and the like.

InFIG. 9, a device (i.e., a molding machine1) intended to enhance accuracies of velocity control or stop position control in a core-back injection molding is shown. In the molding machine1, one or two more fixed molds4and movable molds3, which are of the same number as that of the fixed molds4, are arranged to face each other, and each set of the fixed molds4and the movable molds3is clamped. Then, all of the movable molds3are opened from the opposing fixed molds4by moving them by a prescribed amount, and a pressure receiving block8removably mounted on each of the fixed molds4is removed from the respective fixed molds4. Next, the fixed molds4are moved by a prescribed amount in the mold-opening direction by servomotor control or hydraulic pressure control.

PRIOR ART DOCUMENT

Patent Documents

SUMMARY OF INVENTION

Problems to be Solved by Invention

However, for a resin molded article having therein an insert component, such as a terminal fitting, there are problems in that an inappropriate exposure, a poor positional accuracy and a deformation of the terminal fitting and the like can be caused. Specifically, when the terminal fitting and the like are exposed, the shorting and the adhesion of foreign substances are likely to occur. Also, if the positional accuracy of the terminal fitting is poor upon molding, the deformation thereof can occur and cause a product defect. The technology described in Patent document 1 doesn't consider such an insert component at all and thus is not applied as it is. Accordingly, another technology is required.

Accordingly, the present invention has been made keeping in mind the above problems, and an object of the present invention is to provide a technique capable of solving the problems.

Means for Solving Problems

According to one aspect of the present invention, there is provided a method for producing a resin molded article, using an injection molding device including a fixed mold, a movable mold and a slide mold, and adapted to inject a resin material into a space defined by the molds, wherein the resin molded article includes a terminal fitting as an insert component. The method for producing the resin molded article includes: a terminal fitting positioning step of positioning the terminal fitting into a first terminal inserting means and into a terminal disposing groove, wherein the first terminal inserting means is provided in the fixed mold to allow a first end of the terminal fitting to be inserted therein, and the terminal disposing groove is formed on an outer surface of a core-back mold, which is provided in the fixed mold disposed so as to enable a core-back operation; a movable mold positioning step of moving the movable mold to a prescribed location after the terminal fitting has been positioned; a slide mold positioning step of moving the slide mold to a prescribed location in a space defined by the fixed mold and the movable mold, such that a second end of the terminal fitting, which is opposite to the first end can be inserted into a second terminal inserting means provided on the slide mold; a core-backing step of moving the core-back mold by a prescribed amount in a direction away from the terminal fitting; and a resin material injecting step of injecting and filling with the resin material in the space defined by the fixed mold, the movable mold and the slide mold.

Also, the terminal fitting may have a shape bent at approximately right angle and the bent portion thereof is inserted into the first terminal inserting means, and an opening portion of the first terminal inserting means, in which the first end is inserted may not be covered with the moveable mold when the movable mold is positioned in the movable mold positioning step, and the terminal fitting may be covered with the resin material in the resin material injecting step.

According to another aspect of the present invention, there is provided an injection molding device including a fixed mold, a movable mold and a slide mold, wherein a resin material is injected and filled in a space defined by the fixed mold, the movable mold, and the slide mold. In the injection molding device, the fixed mold is provided with a first terminal inserting means adapted to allow a first end of a terminal fitting to be inserted therein, and a core-back mold which is disposed so as to enable a core-back operation, wherein the terminal fitting can be disposed in the first terminal inserting means and a terminal disposing grooves formed on an outer surface of the core-back mold. The core-back mold is movable by a prescribed amount in a direction away from the terminal fitting, and the slide mold is provided with a second terminal inserting means adapted to allow a second end of the terminal fitting, which is opposite to the first end to be inserted therein, when the slide mold is moved to a prescribed location in a space defined by the fixed mold and the movable mold.

In addition, the terminal fitting may have a shape bent at approximately right angle and the bent portion thereof is inserted into the first terminal inserting means, and wherein an opening portion of the first terminal inserting means, in which the first end is inserted, may not be covered with the moveable mold when the movable mold is moved to a prescribed location, and the terminal fitting may covered with the resin material injected.

Advantageous Effects of Invention

According to the present invention, there is provided a technology in which, when producing a resin molded article having therein an insert component such as a terminal fitting, it is possible to prevent the insert component from being exposed at an inappropriate position, and to ensure the positional accuracy thereof as desired.

EMBODIMENTS OF INVENTION

A mode for implementing the present invention (hereinafter, referred to “embodiment”) will be now described in detail with reference to the accompanying drawings. The embedment relates to a core-back injection molding, in which molding is performed while moving a prescribed mold in injection molding of a resin molded article. Accordingly, the following description will be focused on a movement of the mold for a core-back operation in injection molding.

FIGS. 1A and 1Bare views schematically showing a configuration of a connecting terminal device60according to the embodiment of the present invention, whereinFIG. 1Ais a perspective view thereof andFIG. 1Bis a sectional view thereof. The connecting terminal device60is used, for example, in an ECU case of a motor vehicle and the like, and is fitted in and connected to other corresponding connecting device. As shown, the connecting terminal device60includes a resin-made terminal case70having a case cavity71formed therein, and terminals90as an insert component. Herein, there is illustrated a structure in which the number of the terminals90is nine. Each of the terminals90has a shape in which a rod-shaped conductive metal is bent at the right angle along its way. The terminals90are embedded together in the terminal case70when the terminal case70is molded, and are disposed at prescribed locations. In the terminals90, a terminal outside connecting section91, which corresponds to a portion extending in a vertical direction, is exposed and extended from a back side rib-shaped section77formed on a back side of the terminal case70and connected to an exterior circuit board and the like. In addition, a terminal inside connecting section92, which corresponds to a portion extending in a horizontal direction, has a terminal tip93exposed into the case cavity71by a prescribed length. Hereinafter, a technique for producing the connecting terminal device60will be described.

FIG. 2is a view schematically showing a sectional structure of an injection molding device100. Herein, there is shown a sectional structure focused on a mold, and therefore a resin injection device (such as a hot runner) or moving means for the mold (such as a hydraulic cylinder) is omitted. In addition, reference numerals in the following drawings will be designated only to representatives of each component, and thus will be properly omitted.

As shown, the injection molding device100includes a fixed mold20, a movable mold30, a slide mold40, and a core-back mold50. In this case, the fixed mold20is disposed at a lower position, and the movable mold30is disposed at an upper position to face the fixed mold20. In addition, the slide mold40is inserted from the left into a space defined by the fixed mold20and the movable mold30. Also, the core-back mold50is movably disposed in a core-back mounting section21of the fixed mold20. Also, terminals90, which are insert components, are disposed at prescribed locations. Then, a resin is injected into a mold cavity80and the core-back mold50is core-backed, thereby forming the terminal case70which is a resin molded article having a desired shape as shown inFIGS. 1A and 1B.

The detailed producing processes and the features of each component will be now described.

FIGS. 3A to 3Cand4A to4C are views respectively showing steps for producing the connecting terminal device60. As shown inFIG. 3A, the terminals90which are insert components are firstly mounted in the fixed mold20. Specifically, a space of a prescribed shape vertically extending from a cavity surface25which is an upper surface of the fixed mold20is formed to communicate with the outside, thereby serving as the core-back mounting section21. The shape of the space is approximately a rectangular parallelepiped shape, and is adapted to allow the core-back mold50to be movably disposed.

Now, the core-back mold50will be described. InFIGS. 5A to 5C, there is shown an exterior shape of the core-back mold50.FIG. 5Ashows only the core-back mold50,FIG. 5Bshows a state that the terminals90is disposed, andFIG. 5Cshows a state that, after disposing the terminals90, the core-back mold90is downwardly moved by a prescribed amount D as a core-back operation.

As shown, the core-back mold50has terminal holding grooves51formed in a shape to allow the terminal inside connecting sections92of the terminals90to be disposed therein. More particularly, the terminal holding grooves51are formed at a prescribed depth in a front-and-back direction on an upper surface of the core-back mold50. As shown inFIG. 5B, a width d1of the terminal holding grooves51is approximately equal to a width d2of the terminals90(i.e. the terminal outside connecting sections91), and is adapted to allow the terminal inside connecting sections92to be smoothly disposed. In addition, an upper opening portion of the terminal holding grooves is provided with a taper-shaped inclined surface52formed to be widened outward. Also, the depth of the terminal holding grooves51or the shape (such as a size or an opening angle) of the inclined surface52needs to be designed in consideration of the flowability of resin and the like, when the core-back mold50is moved and the resin is molded as described below.

The description with reference toFIGS. 3A to 3Cwill be returned. When the terminals90are disposed in the fixed mold20, the terminal outside connecting sections91are inserted into insert grooves22formed on the right side of the fixed mold20. The insert grooves22are formed in a shape corresponding to a shape of the terminal outside connecting sections91.

Also, the core-back mold50is disposed at a prescribed position in the core-back mounting section21of the fixed mold20. In addition, since the insert grooves22are formed in the mold cavity20, upper sides of the insert grooves22, i.e., bended portions of the terminals90, are covered with resin, upon resin molding, and thus the back side rib-shaped section77is formed by such resin molding.

Also, after the entire quantity (in case of the present embodiment, nine) of the terminals90are appropriately disposed at prescribed locations as shown inFIGS. 3B and 5B, the movable mold30is moved to face the upper surface of the fixed mold20and thus is disposed at a prescribed location as shown inFIG. 3C.

Next, as shown inFIG. 4A, the slide mold40, which is a mold portion defining a shape of the case cavity71of the terminal case70, is inserted at a prescribed location in a space defined between the fixed mold20and the movable mold30from left to right in the drawings. The slide mold40is provided with terminal tip holding sections41which provide a space allowing the terminal tips93to be inserted therein, such that the terminal tips93can be appropriately exposed by a prescribed length after resin molding.FIG. 4Bshows a state that the slide mold40is inserted. In this time, since the terminal inside connecting sections92of the terminals90are disposed in the terminal holding grooves51of the core-back mold50such that the positional accuracy of the terminal tips93can be ensured, the terminal tips93can be inserted in the terminal tip holding sections41. For a configuration in which the core-back mold50was not used, if the direction of the terminals90was misaligned, the slide mold40would bend or break the terminals90as the slide mold40was inserted, and accordingly defects were caused in the connecting terminal device60as a finished product. However, since the terminal holding grooves51of the core-back mold50can serve as a kind of guide as in the embodiment, the terminals90can be appropriately positioned, thereby preventing misalignment of the direction thereof.

Subsequently, when the slide mold40is inserted and appropriately disposed in a state shown inFIG. 4B, the core-back mold50is then downwardly moved by the prescribed amount D.FIG. 5Cshows a relation between the core-back mold50and the terminals90when the core-back mold50is core-backed. In this time, since the terminal tips93are inserted and held in the slide mold40and also the terminal outside connection sections91are inserted and held in the inert grooves22, the terminals90are held in a position-fixed state. Then, in a state ofFIG. 4C, a molten resin material is injected into the mold cavity80which is a space defined by the fixed mold20, the movable mold30and the slide mold40.

InFIGS. 6A and 6B, after the connecting terminal device60(i.e., the terminal case70) has been formed, the connecting terminal device60together with the core-back mold40is shown.FIG. 6Ais a perspective view, andFIG. 6Bis a cross-sectional view of a region where the core-back mold50is disposed. Also,FIG. 7is a sectional view showing the connecting terminal device60with the core-back mold50removed from the state shown inFIG. 6B.

As shown inFIG. 6Bor7, a resin wall75is formed in a portion provided as the core-back mold50is moved by the prescribed amount, i.e., between lower surfaces of the terminal inside connecting sections92of the terminals90and the terminal holding grooves51. As a result of such a structure, the terminal inside connecting sections92are not inappropriately exposed, and also the function of protecting the terminal tips93is provided, thereby improving strength.

As set forth above, the producing processes of the present embodiment can be briefly summarized as the following. Namely, the associated producing method includes the steps of: positioning a terminal fitting, positioning a movable mold, positioning a slide mold, core-backing, and injecting a resin material. In the step of disposing the terminal fitting, the terminal90is disposed in the terminal holding groove51of the core-back mold50and in the insert groove22of the fixed mold20. Then, the movable mold30is moved at a prescribed location as the step of disposing the movable mold, and also the slide mold40is inserted into a space defined between the fixed mold20and the movable mold30as the step of disposing the slide mold. In this time, the terminal tip93of the terminal90is inserted into the terminal tip holding section41. Subsequently, the core-back mold50is downwardly moved by the prescribed amount D as the step of core-backing, and a resin is injected into the mold cavity80as the step of injecting the resin material, thereby completing the connecting terminal device60as shown inFIGS. 1A and 1B.

According to the injection molding device100and the producing method as described above, timing for moving the core-back mold50is after the terminal90(i.e., the terminal tip93), which is the insert component, is inserted into the terminal tip holding section41of the slide mold40, thereby improving the positional accuracy of the terminal90. Also, by moving the core-back mold50by the prescribed amount D before injection molding, the resin wall is formed between the core-back mold50and the terminal90, thereby preventing the inappropriate exposure and shorting of the terminal90and the adhesion of foreign substances to the terminal90, and the like. In addition, as shown inFIG. 8, the back side rib-shaped section77(seeFIGS. 1A and 1B) is formed near to the bent portion of the terminal90on the back side of the terminal case70(i.e., an upper portion of the terminal90), such that the terminal90can be pressed by the resin pressure upon injection molding (arrows A and B shown). As a result, the improved positional accuracy and deforming prevention of the terminal90can be achieved.

The present invention has been described hereinabove with reference to the embodiment. It should be apparent to those skilled in the art that the embodiment is illustrative and that various alternatives can be made to the components and the combination thereof described in the embodiment and still fall within the scope of the present invention.

Although the present invention has been described with referenced to the detailed and specific embodiment, it should be apparent to those skilled in the art that numerous changes and modifications can be made without departing the scope and spirit of the present invention.

This application claims the benefit of Japanese Patent Application Serial No. 2010-130001 filed Jun. 7, 2010, the entire contents of which are incorporated herein by reference.

INDUSTRIAL APPLICABILITY

According to the method for producing the resin molded article by injection molding and the injection molding device of the present invention, there is provided a technology in which, when producing a resin molded article having therein an insert component such as a terminal fitting, it is possible to prevent the insert component from being exposed at an inappropriate position, and to ensure the positional accuracy thereof as desired.

DESCRIPTION OF REFERENCE NUMERALS

21Core Mounting Section

41Terminal Tip Holding Section

60Connecting Terminal Device

91Terminal Outside Connecting Section

92Terminal Inside Connecting Section