JP2013136214A - Method of molding resin molded article, resin molded article, and mold for molding resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high-precision method of molding a resin molded article, the resin molded article, and a mold for molding resin, capable of preventing warp deformation in an axial direction.SOLUTION: A mold 20 for molding resin is prepared, which includes a cavity 21 for forming a resin molded article 1 and a plurality of gates 31 connected to one end surface 22a of a portion 22 corresponding to an axial body of the cavity 21. The portion 22 corresponding to the axial body has a size longer in the axial direction than in the radial direction. The resin molded article 1 is formed by injecting resin into the cavity 21 from each of the plurality of gates 31 of the mold 20 for molding resin.

Description

  The present invention relates to a method for molding a resin molded product, a resin molded product, and a mold for resin molding, and in particular, a method for molding a resin molded product including a shaft body having a dimension that is longer in the axial direction than in the radial direction. The present invention relates to a molded resin product and a resin molding die used in the molding method.

  A method for molding a resin molded product is disclosed in, for example, Japanese Patent Application Laid-Open No. 4-34260 (Patent Document 1) and Japanese Patent Application Laid-Open No. 8-118395 (Patent Document 2). These publications describe that the roundness is improved by increasing the number of gate points in the molding of the resin pulley so that the resin material can flow as uniformly as possible in the mold.

JP-A-4-34260 JP-A-8-118395

  However, the above two publications relate to molding of a resin pulley, and do not describe molding a resin molded product including a shaft body having a dimension longer in the axial direction than in the radial direction.

  When such a shaft body is resin-molded, conventionally, since the end face of the resin-molded product is limited, the type of the gate is a one-point gate of either a pin gate or a side gate, and is generally a pin gate. In this case, when the resin is filled in the mold, (1) the fountain flow is collapsed, and (2) the turbulent flow (irregular) is not laminar (regular). (3) Warp deformation occurs in the axial direction of the shaft body due to factors such as (3) the fact that glass is included in the material used, and the shrinkage due to fiber orientation is large when the resin shrinks. Due to this warpage deformation, it has been difficult to produce a resin molded product that can satisfy the coaxial tolerance of parts.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a highly accurate method for molding a resin molded product, a resin molded product, and a resin molding die that can suppress warping deformation in the axial direction. That is.

  The molding method of the resin molded product of the present invention is a molding method of a resin molded product including a shaft body having a dimension longer in the axial direction than in the radial direction, and includes the following steps.

  First, a mold having a cavity for forming a resin molded product and a plurality of gates connected to the tip of the portion corresponding to the shaft body of the cavity is prepared. Then, resin is injected into the cavity from each of the plurality of gates of the mold.

  According to the method for molding a resin molded product of the present invention, the resin is injected into the cavity from the tip of the portion corresponding to the shaft body through the plurality of gates. Thereby, the resin injected from each gate is filled in a regular rotation direction while being intertwined with each other in a spiral manner to form a resin molded product. For this reason, a highly accurate resin molded product in which warpage deformation in the axial direction is suppressed can be obtained.

  In the above method for molding a resin molded product, each of the plurality of gates is disposed at the distal end portion so as to be positioned on the inner peripheral side at least by the gate diameter from the outer diameter of the shaft body. Thereby, it becomes possible to arrange each of the plurality of gates close to each other, and it becomes easy to entangle the resin injected from each gate in a spiral.

  In the molding method of the resin molded product, in the step of injecting the resin into the cavity, the resin is spirally injected into the cavity from each of the plurality of gates. As a result, the resin injected from each gate is filled in a regular rotational direction, so that a resin molded product in which warpage deformation in the axial direction is suppressed can be obtained.

  In the method for molding a resin molded product, the cavity includes a portion corresponding to the shaft body and a portion corresponding to the flange portion extending on the outer peripheral side in the radial direction from the portion corresponding to the shaft body. In the step of injecting the resin into the cavity, the resin is injected into the portion corresponding to the shaft body to form the shaft body, and then the resin is injected into the portion corresponding to the flange portion to form the flange portion.

  The resin molded product of the present invention includes a shaft body that is manufactured by any of the above-described methods for molding a resin molded product and has a dimension that is longer in the axial direction than in the radial direction.

  According to the resin molded product of the present invention, since the resin molded product is manufactured by any one of the above-described methods for molding a resin molded product, warping deformation in the axial direction of the resin molded product is suppressed.

  The mold for resin molding of the present invention includes a cavity for forming a resin molded product including a shaft body having a dimension longer in the axial direction than the radial direction, and a tip portion of a portion corresponding to the shaft body of the cavity. And a plurality of connected gates.

  By performing resin molding using the resin molding die of the present invention, it is possible to obtain a resin molded product in which warpage deformation in the axial direction is suppressed.

  As described above, according to the present invention, the warpage deformation in the axial direction of the resin molded product can be suppressed.

It is a front view which shows roughly the structure of the resin molded product in one embodiment of this invention. FIG. 2 is a partially enlarged front view showing a portion corresponding to the gate of FIG. 1 in an enlarged manner. FIG. 2 is a partially enlarged perspective view showing a portion corresponding to the gate of FIG. 1 further enlarged. It is a top view which shows roughly the mode of arrangement | positioning of a some gate part in the resin molded product of FIG. It is a figure for demonstrating arrangement | positioning of several gates. It is sectional drawing which shows schematically the structure of the metal mold | die for resin molding in one embodiment of this invention. It is the elements on larger scale which expand and show the gate of FIG. FIG. 7 is a schematic diagram illustrating a state in which when a resin is injected from a plurality of gates into the cavity of the resin molding die in FIG. 6, each resin is filled in a regular rotation direction while being entangled with each other spirally. It is a front view which shows roughly the structure of the resin molded product in related technology in case the number of parts corresponding to a gate is one. FIG. 10 is a partially enlarged front view showing a portion corresponding to the gate of FIG. 9 in an enlarged manner. FIG. 10 is a partially enlarged perspective view showing a portion corresponding to the gate of FIG. 9 in a further enlarged manner. FIG. 10 is a plan view schematically showing an arrangement of one gate part in the resin molded product of FIG. 9. It is a figure for demonstrating the measurement location of the resin molded product for measuring a coaxial degree. It is a figure for demonstrating the calculation method of a coaxiality. It is figure (A)-(D) which shows the process of resin molding in order.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
First, the configuration of a resin molded product according to an embodiment of the present invention will be described with reference to FIGS.

  Referring mainly to FIG. 1, a resin molded product 1 of the present embodiment includes a shaft body 2, a plurality of flange portions 3 a and 3 b, and a gear portion 4. The shaft body 2 has, for example, a cylindrical shape, and has a configuration in which the axial dimension L (axial length) is longer than the radial dimension D (diameter). Each of the plurality of flange portions 3 a and 3 b has a shape that spreads more radially outward than the shaft body 2. The gear portion 4 is provided on the other end surface side opposite to the one end surface 2 a of the shaft body 2.

  One end surface 2a of the shaft body 2 of the resin molded product 1 is connected to one end side of a portion 12 corresponding to the secondary sprue with a portion 11 corresponding to the gate interposed therebetween. The other end side of the portion 12 corresponding to the secondary sprue is connected to one end side of the portion 14 corresponding to the primary sprue via the portion 13 corresponding to the runner.

  The resin molded product 1, the portion 11 corresponding to the gate, the portion 12 corresponding to the secondary sprue, the portion 13 corresponding to the runner, and the portion 14 corresponding to the primary sprue are made of the same resin material.

  This resin material is, for example, a material containing resin and fibers. As the resin used for the resin material, for example, a thermoplastic resin such as polyphenylene sulfide resin (PPS) is used, but polypropylene terephthalate resin (PPT) or polyacetal resin (POM) may be used. Moreover, glass fiber, carbon fiber, etc. are used for the fiber used for a resin material, for example.

  Referring mainly to FIGS. 2 and 3, a portion 11 corresponding to a plurality of gates is connected to one end surface (tip portion) 2 a of shaft body 2 of resin molded product 1 of the present embodiment. The portion 11 corresponding to a plurality of gates preferably has a portion 11 corresponding to three or more gates, for example, a portion 11 corresponding to four gates.

  Referring mainly to FIG. 4, each of the portions 11 corresponding to the four gates is arranged on the one end face 2 a of the shaft body 2 at a position corresponding to, for example, a square corner. Even after the resin molded product 1 is removed from the portions 11 corresponding to the four gates, the resin molded product 1 is left with traces of the portions 11 corresponding to the four gates. For this reason, it is possible to identify whether or not the portions 11 corresponding to the plurality of gates are connected to the one end surface 2a of the shaft body 2 by the trace of the gate.

  Referring mainly to FIG. 5, the minimum value of the pitch Pa of the portion 11 corresponding to the gate is preferably twice the diameter d of the portion 11 corresponding to the gate (Pa = 2d). In addition, each of the portions 11 corresponding to the plurality of gates has one end surface (tip) so as to be located on the inner peripheral side at least by the diameter d of the portion 11 corresponding to the gate from the outer peripheral surface of the outer diameter (diameter D) of the shaft body 2. Part) 2a.

Further, when each of the portions 11 corresponding to the four gates is arranged at the corner of the square, the minimum value of the diagonal pitch Pb of the portion 11 corresponding to the gate is 2 ^1/2 × 2d. Is preferred. The maximum value of the diagonal pitch Pb of the portion 11 corresponding to the gate is preferably D (the outer diameter of the shaft body 2) -3d (the diameter of the portion 11 corresponding to the gate).

  Each of the pitches Pa and Pb is a distance between the centers of the portions 11 corresponding to the gates.

  Next, the structure of the resin molding die in this Embodiment for manufacturing the resin molded product 1 shown in FIGS. 1-5 is demonstrated using FIG. 6 and FIG.

  Referring mainly to FIG. 6, the mold 20 of the present embodiment includes a cavity 21 for molding the resin molded product 1 shown in FIG. 1, a gate 31, a secondary sprue 32, a runner 33, Primary sprue 34.

The cavity 21 has a portion 22 to be a shaft body, portions 23 a and 23 b to be flange portions, and a portion 24 to be a gear portion, corresponding to the shape of the resin molded product 1.
The portion 22 to be the shaft body has, for example, a cylindrical shape, and has a configuration in which the axial dimension (axial length) is longer than the radial dimension (diameter). Each of the portions 23a and 23b to be the plurality of flange portions has a shape that spreads more radially outward than the portion 22 to be the shaft body. The portion 24 to be the gear portion is provided on the other end surface side opposite to the one end surface 22a of the portion 22 to be the shaft body.

  One end surface of the secondary spru 32 is connected to one end face 22a of the cavity 21 with a gate 31 interposed therebetween. The other end side of the secondary sprue 32 is connected to one end side of the primary sprue 34 with a runner 33 interposed therebetween.

  A cylinder (not shown) is connected to the other end side of the primary sprue 34. A screw (not shown) is rotatably disposed in the cylinder.

  Referring mainly to FIG. 7, a plurality of gates 31 are connected to one end face 22 a of cavity 21. The plurality of gates 31 preferably include three or more gates 31, for example, four gates 31.

Each of the pitches and diagonal pitches of the gates 31 is the same as described in FIG.
Next, a method for molding a resin molded product according to the present embodiment will be described with reference to FIGS.

  First, a resin molding die 20 shown in FIG. 6 is prepared. As described above, a cylinder (not shown) in which a screw (not shown) is disposed is connected to the other end side of the primary sprue 34 in the mold 20.

  After the resin is melted in the cylinder, the melted resin is pushed out of the cylinder by the rotation of the screw. The resin extruded from the cylinder is injected into the cavity 21 through the primary sprue 34, the runner 33, the secondary sprue 32, and the plurality of gates 31.

  Referring to FIG. 8, each of the resins injected into the cavity 21 through the plurality of gates 31 is filled in the cavity 21 in a regular rotation direction while being entangled with each other spirally. Here, the reason why each of the resins injected into the cavity 21 through the plurality of gates 31 is spirally injected is that rotational force is applied to the resin by the rotation of the screw.

  In this way, after the portion 22 to be the shaft body of the cavity 21 is filled with the resin and the shaft body 2 is formed, the portions 23a and 23b to be the flange portions are filled with the resin, and the flange portions 3a and 3b are formed. It is formed. Thereafter, the resin molded product 1 of the present embodiment shown in FIGS. 1 to 5 is molded by removing the resin molded product from the mold 20.

  In FIG. 8, the case where there are three gates 31 is described for convenience of explanation, but the number of gates 31 is not limited to this.

  Next, the examination regarding the warpage deformation in the axial direction performed by the present inventors will be described in comparison with the related art shown in FIGS.

  The present inventors examine the warpage deformation in the axial direction of both the resin molded product 1 of the present embodiment shown in FIGS. 1 to 5 and the resin molded product 1 of the related technology shown in FIGS. 9 to 12. Therefore, the coaxiality was examined.

  First, the resin molded product 1 of the present embodiment shown in FIGS. 1 to 5 was molded using a resin molding die 20 shown in FIGS. 6 and 7. The resin molded product 1 shown in FIGS. 1 to 5 is a four-point gate having four portions 11 corresponding to the gate. Moreover, the resin molded product 1 shown in FIGS. 9-12 was shape | molded using the metal mold | die which connected only one gate to the cavity. Therefore, the resin molded product 1 shown in FIGS. 9 to 12 is a one-point gate having one portion 11 corresponding to the gate.

  Thus, the configuration of the resin molded product 1 shown in FIGS. 9 to 12 is substantially the same as the configuration of the resin molded product 1 shown in FIGS. 1 to 5 except that the number of the portions 11 corresponding to the gate is one. It is. For this reason, the same code | symbol is attached | subjected about the element same as the resin molded product 1 shown in FIGS. 1-5 among the resin molded products 1 shown in FIGS. 9-12, and the description is not repeated.

  Moreover, the resin molded product 1 of this Embodiment shown in FIGS. 1-5 and the resin molded product 1 shown in FIGS. 9-12 were shape | molded so that it might become the mutually same dimension. Specifically, referring to FIG. 13, the distance La from the one end surface 2a of the shaft body 2 to the front of the gear portion 4 is 47.5 mm, and the diameter D of the shaft body 2 is 6 mm. Molded product was molded.

  And the coaxiality was measured about each of both the resin molded products 1. FIG. Regarding the measurement of the coaxiality, first, a circular shape is measured for each of the portions of the shaft body 2 indicated by reference numerals B1 and B2 in FIG. 13, and two circular shapes B1 and B2 are connected to form a cylindrical shape B0. did. Thereafter, the circular shape of each of the portions of the shaft body 2 indicated by reference signs A1 and A2 was measured in the same manner, and two circular shapes of A1 and A2 were connected to form a cylindrical shape A0.

  The two cylindrical shapes B0 and A0 obtained in this way were overlapped as shown in FIG. 14, and the deviation of the central axis of each cylindrical shape B0 and A0 was measured. Here, the deviation of the central axes of the respective cylindrical shapes B0 and A0 was defined as the concentricity C. The concentricity C was doubled to obtain the coaxiality E (that is, the coaxiality E = concentricity C × 2).

  In this way, the coaxiality E was measured for each of the three samples of the resin molded product 1 shown in FIGS. 1 to 5 and the three samples of the resin molded product 1 shown in FIGS. 9 to 12. The measurement results are described below.

  From the results of Table 1 above, the resin molded product 1 shown in FIGS. 1 to 5 which is a four-point gate has less coaxial variation than the resin molded product 1 shown in FIGS. 9 to 12 which is a one-point gate. It was also found that the average value of the coaxiality was small. Further, in the resin molded product 1 shown in FIGS. 9 to 12, the coaxiality exceeded 0.5 mm, but in the resin molded product 1 shown in FIGS. 1 to 5, no coaxiality exceeded 0.5 mm. It was.

  Similarly, in a multipoint gate of two or more points other than the four-point gate, the coaxiality variation is smaller than that of the resin molded product 1 shown in FIGS. It was also confirmed that it became smaller.

  In addition, the present inventors have examined the state of the resin in the cavity 21 when the resin molded product 1 shown in FIGS. The result is shown in FIG.

  From this result, as shown in FIG. 15 (A), in the initial stage of resin molding, it is confirmed that each of the resins injected from a plurality of gates is filled in a regular rotational direction while being intertwined in a spiral shape. I understood. After this, it was found that the resin was filled in the portion corresponding to the shaft in the cavity as shown in FIG. After the filling of the portion corresponding to the shaft body is completed and the shaft body is formed, the portion corresponding to the flange portion in the cavity is filled with resin as shown in FIGS. 15 (C) and 15 (D). It was found that a flange portion was formed.

Next, the effect of this Embodiment is demonstrated.
According to the molding method of the resin molded product of the present embodiment, as shown in FIG. 6 and FIG. Is injected into the cavity 21. As a result, the resin injected from each gate 31 is filled in a regular rotational direction while being entangled with each other spirally as shown in FIG. For this reason, it becomes possible to obtain the highly accurate resin molded product 1 in which warpage deformation in the axial direction is suppressed.

  The reason why the axial deformation of the resin molded product 1 can be suppressed in the present embodiment is that the resin is filled in a regular rotational direction while being intertwined in a spiral manner as shown in FIG. This is considered to be because the fibers (glass fiber, carbon fiber, etc.) contained in the cavity 21 were regularly oriented in a spiral manner, so that it was difficult to deform in the axial direction when the resin contracted.

  In the present embodiment shown in FIGS. 6 and 7, the configuration in which a plurality of gates 31 are connected to one secondary sprue 32 has been described. However, one gate 31 is connected to one secondary sprue 32. A plurality of objects may be connected to the cavity 21 at one end face 22a.

  Further, in the present embodiment shown in FIGS. 6 and 7, the configuration in which the plurality of gates 31 are connected to the runner 33 through the secondary sprue 32 has been described. The gate 31 may be directly connected to the runner 33.

  Further, in the present embodiment shown in FIGS. 6 and 7, the configuration in which the plurality of gates 31 are connected to the one end surface 22 a of the cavity 21 has been described, but the plurality of gates 31 is the other side opposite to the one end surface 22 a. It may be connected to the end face.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  INDUSTRIAL APPLICABILITY The present invention is advantageous for a method for molding a resin molded product having a shaft body having a dimension longer in the axial direction than in the radial direction, a resin molded product manufactured thereby, and a resin molding die used for the molding method. Can be applied.

  DESCRIPTION OF SYMBOLS 1 Resin molded product, 2 shaft body, 2a one end surface, 3a, 3b flange part, 4 gear part, 11 part corresponding to gate, 12 part corresponding to secondary sprue, 13 part corresponding to runner, 14 primary sprue , 20 resin molding die, 21 cavity, 22 part corresponding to shaft body, 22a one end face, 23a, 23b part corresponding to flange part, 24 part corresponding to gear part, 31 gate, 32 2 Next sprue, 33 runners, 34 primary sprue.

Claims (6)

A method for molding a resin molded product comprising a shaft having a dimension longer in the axial direction than in the radial direction,
Preparing a mold having a cavity for forming the resin molded product and a plurality of gates connected to the tip of a portion corresponding to the shaft body of the cavity;
And a step of injecting a resin into each of the cavities from each of the plurality of gates of the mold.   2. The method for molding a resin molded product according to claim 1, wherein each of the plurality of gates is disposed at the tip portion so as to be positioned on the inner peripheral side at least by the diameter of the gate from the outer diameter of the shaft body. .   The method for molding a resin molded product according to claim 1 or 2, wherein, in the step of injecting the resin into the cavity, the resin is spirally injected into the cavity from each of the plurality of gates. The cavity includes a portion corresponding to the shaft body, and a portion corresponding to a flange portion extending on the outer peripheral side in the radial direction from the portion corresponding to the shaft body,
In the step of injecting the resin into the cavity, the resin is injected into a portion corresponding to the shaft body to form a shaft body, and then the resin is injected into a portion corresponding to the flange portion. The method for molding a resin molded product according to any one of claims 1 to 3, wherein a flange portion is formed.   A resin molded article comprising a shaft body manufactured by the method for molding a resin molded article according to any one of claims 1 to 4 and having a dimension that is longer in the axial direction than in the radial direction. A cavity for forming a resin molded product having a shaft body having a dimension longer in the axial direction than in the radial direction;
A mold for resin molding, comprising: a plurality of gates connected to tip portions of portions of the cavity corresponding to the shaft body.