KR19990013766A - Injection Mold - Google Patents

Abstract

According to the present invention, the number of molds driven by the slide mechanism is reduced, and an injection molding die is provided with improved precision of the positional relationship between the molds. The injection molding mold is to form a first mold having a first molding surface in contact with the injection molding resin and a first positioning surface continuous with the first molding surface to form a part of the molded article, and to form another part of the molded article. A second mold having a second molding surface and a second positioning surface for contacting the first molding surface of the first mold with the second molding surface at an acute angle, wherein the mold is divided in a plane including an axis of the molded article. The first shaping surface and the second shaping surface contact each other to form corner portions of a predetermined shape. The portion of the second mold having the second positioning surface is formed in the recess of the first mold having the first positioning surface such that the first and second positioning surfaces are held in contact with each other and the second mold is held in the first mold. Are accepted.

Description

Injection Mold

The present invention relates to an injection molding die, and more particularly to an injection molding die having an undercut portion and having a slide core for forming a molded article requiring high dimensional accuracy.

Until now, various types of injection molding dies have been used for injection molding rotary pulleys having a V-shaped groove for accommodating drive belts. 3A is a cross-sectional view of the central portion of such an injection molding die. Rotating pulleys as shaped articles are two-stage rotating pulleys having two V-shaped grooves of large and small diameters. The injection molding mold 50 cooperates with the third mold 3 serving as the movable mold (in the drawing) which is downwardly movable (in the drawing), the fourth mold 4 serving as the stationary mold, and the third mold 3 ( Consisting of a slide core 51 moving downwards, which slide core is moved in opposite directions by a slider 52 and a slide mechanism (not shown), and the slide core 51 also includes a plurality of slides ( 51a, 51b and 51c).

Resin is filled into the mold cavity formed when the injection molding die 50 is fastened or closed, and a molded article, that is, a rotary pulley 5 is molded. A large number of V-shaped grooves 5a are formed on the outer circumference of the molded product (rotary pulley) 5, and approximately triangular drive belts are accommodated in these V-shaped grooves 5a, respectively. These V-shaped grooves 5a have undercut portions, and therefore a mold structure having a slide core 51 including a plurality of slides for forming a molded article 5 of such a shape is generally used as an injection mold. .

The third mold 3 and the fourth mold 4 have a substantially cylindrical shape, have a common axis 50a coinciding with the rotation axis of the rotating pulley (molded product) 5, and forms a central portion of the molded product 5. Cores 56 and 55 are provided in the central portions of the third and fourth molds 3 and 4, respectively. A pin 57 for forming the rotary shaft mounting hole in the molded article 5 is formed vertically on the upper end of the core 56, and the core 55 has a hole 55a for accommodating the pin 57. Have A discharge pin 53 is provided on the third mold 3 to be used to remove the molded product 5 from the injection molding mold 50.

3B and 3C are enlarged views of the V-shaped grooves 5a ₁ , 5a ₂ in the outer circumference of the rotating pulley. The V-shaped grooves 5a ₁ , 5a ₂ comprise a pair of flanges 5b ₁ , 5b ₂ , 5b ₃ , 5b ₄ , such as a thin plate protruding from the upper and lower peripheral ends. These flanges 5b ₁ to 5b ₄ prevent the triangular belt from separating in the V-shaped grooves 5a ₁ , 5a ₂ and form important parts of this rotating pulley. Various other shapes may be used for the belt separator and the belt coupling. For example, instead of flanges, one may increase the depth of the V-shaped groove.

If a rectangular belt having a rectangular cross section is used in place of a triangular belt, it may be provided with flanges or formed with a convex arcuate cross section. In any case, however, the shape of this part becomes complicated.

As can be seen from FIG. 3B, when the V-shaped grooved convex portion 54 is formed on the slide core 51 to form the V-shaped groove 5a ₁ and the flanges 5b ₁ , the convex is convex. It is necessary to form a complex thin cavity or space that extends from the distal end of the portion 54 to the deep portion. In general, it is difficult to machine the slide core 51 in such a formation, and the slide core 51 thus includes an upper slide 51a, an intermediate slide 51b and a lower slide 51c. By this structure, for example, the intermediate slide 51b or the lower slide 51c can be easily machined into the desired shape, and the above-mentioned complicated thin cavity extending to the deep portion can be formed. As in this case, the flanges 5b ₃ can be formed in the complicated thin cavity provided by the upper slide 51a and the intermediate slide 51b as shown in FIG. 3C.

The dimensional accuracy of the molded article 5 is determined by various conditions such as the resin molding conditions during injection molding, the processing accuracy of the mold itself, and the properties of the resin. First of all, the position of the molds in the fastened state with respect to each other and the fixed strength of the molds in the fastened state with respect to each other are important factors for determining the dimensional accuracy of the molded article.

In the conventional injection mold 50, the positioning or fixing of the third mold 3, the fourth mold 4 and the slide core 51 with respect to each other at the fastening position is, for example, the slider 52. Is affected by the positioning mechanism (not shown) or the slide mechanism (not shown). Therefore, additional mechanisms for the slide mechanism or the positioning mechanism are needed. As the number of such mechanisms increases, various processing errors and assembly errors accumulate, resulting in a problem that the positional relationship between the molds is inaccurate and the fixed strength cannot be easily increased. In the case where the molded article 5 is a two-stage pulley, it is necessary in particular to form thin flanges 5b ₁ , 5b ₃ for forming two V-shaped grooves in the slide core 51. Moreover, since the slide core 51 is constituted by three molds, the positional relationship between the molds has been faced with a problem that is further affected by the accumulated error of these slide core molds.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to reduce the number of molds that are combined together when molding a molded article having a complex structure, and to reduce the number of fixed parts that are positioned relative to each other. Therefore, to provide an injection molding die that can improve the precision or fixed strength of the positional relationship between the molds.

1A is a cross-sectional view showing the entire structure of an injection molding die according to an embodiment of the present invention;

1B is a partially enlarged cross-sectional view of FIG. 1A;

2 is a perspective view showing a part of an injection molding mold according to an embodiment of the present invention;

Figure 3a is a cross-sectional view showing a conventional injection mold.

3B is an enlarged cross sectional view of a portion of a molded article; And

3C is an enlarged cross-sectional view of another portion of the molded article.

Explanation of symbols on the main parts of the drawings

1: first mold 2: second mold

3: third mold 4: fourth mold

10, 25: forming surface 11a, 11b: groove side

12: bottom of the groove 13: exhaust hole

21: first side portion 22: outer peripheral portion

26: second side part

The object is achieved by the injection molding mold of the present invention, the injection molding mold,

A first mold having a first forming surface for forming a portion of the molded article and a first positioning surface for mold positioning; A second mold having a second molding surface for forming another portion of the molded article, and a second positioning surface for contacting the first molding surface of the first mold with the second molding surface at an acute angle; The first and second molds are respectively divided into sections in a predetermined plane; When the first mold and the second mold are combined together, the first molding surface and the second molding surface contact each other to form a corner portion of the molded article; The portion of the second mold having the second positioning surface is fitted to and in contact with the portion of the first mold having the first positioning surface, thereby positioning and fixing the first and second molds with respect to each other.

In this injection molding mold, one or more divided sections of the second mold are held in the portion of the first mold having the first positioning surface to rotate about the axis of the molded product therein.

The forming surface and the second positioning surface of the second mold are arranged on the same plane to form a flat surface together.

Exhaust holes are opened toward the first and second positioning surfaces, respectively, to remove gas from the gaps between the first and second positioning surfaces.

The second mold has another second forming surface formed on the side facing away from the second forming surface, and the first mold has another first forming surface formed to be in acute angle contact with another second forming surface, The two forming surfaces and another first forming surface are in contact with each other to form corner portions of the molded article.

The portion of the first mold having the first positioning surface is formed as a recess, and the portion of the second mold having the second positioning surface is held in the recess so that the center of the forming portion is aligned.

In the injection molding die of the above-described configuration, when the first and second molds are combined together, the two molds are made to each other by contacting the first positioning surface of the first mold with the second positioning surface of the second mold. Positioning, and as a result, the first forming surface of the first mold and the second forming surface of the second mold are brought into contact with each other at an acute angle, whereby an acute portion constituting the corner portion of the molded article can be formed by the two molds, thus The number of these can be reduced compared to the conventional configuration. At this time, the portion of the second mold having the second positioning surface is inserted into and in contact with the portion of the first mold having the first positioning surface, thereby positioning and fixing the first and second molds with respect to each other, and thus The positional relationship between the molds is determined or set, the positional accuracy of the two molds with respect to each other is improved, and the strength in the fixed state is improved.

In this injection molding mold, each of the first mold and the second mold is divided into sections in a plane including an axis of the molded article, and at least one section of the second mold has a first positioning surface to rotate about an axis. It is held in part of the first mold. Thus, when the first and second molds are combined together, one section of the second mold can fit into one of the sections of the first mold having the first positioning surface and be positioned while rotating, thus the first mold Positioning of the second mold in the circumferential direction can be performed without having to accurately position the second mold with respect to the first mold in advance. Thereafter, another portion of the second mold may be positioned in the first mold and rotated in the first mold to be positioned or pressed against the first mold.

The second positioning surface and the second molding surface of the second mold are disposed on the same plane with each other to form a flat surface together, so that the first molding surface of the first mold and the second molding surface of the second mold are exactly lined with each other. Since it can be kept in contact and stable, the corner portion of the molded article can be formed precisely, and the flow of gas toward the second positioning surface can be kept to a minimum.

The exhaust holes are respectively opened toward the first positioning surface and the second positioning surface, through which the gas is removed from the gap between the first and second positioning surfaces. Thus, the gas inevitably generated from or pushed out of the resin during injection molding can be reliably removed from the gap between the first positioning surface and the second positioning surface, and thus the gas remaining in the gap, for example, on the molding surfaces. The flow of resin which flows by thermal expansion of is prevented, and the resin molding precision is prevented from falling by this.

The second mold has another forming surface formed on the side facing away from the second forming surface, and another positioning surface disposed in the same plane relationship with respect to this further forming surface. Therefore, when another forming surface of the second mold is held in contact with the forming surface of the first mold formed on the side facing away from the first positioning surface, the corner portion of the molded article can be precisely formed by the second forming surface. . For example, a coaxial rotating pulley, except for the pulley portion, formed by the second forming surface can be formed integrally therewith as in the double pulley structure.

The portion of the first mold having the first positioning surface is formed as a recess, and the portion of the second mold having the second positioning surface is held in the recess. Therefore, when the second mold is combined with the first mold, this operation is performed by sliding the two molds while joining the second mold to the first mold, so that each of the two molds can be surely centered with high precision. Can be.

The injection molding die of the present invention will be described below with reference to FIGS. 1A, 1B and 2. The injection molding die for molding the rotating pulley, which is a molded article in which two (large and small) V-shaped grooves 5a ₁ and 5a ₂ of different diameters are formed on the outer circumference thereof, includes a first mold 1 and a second mold 2 ), A third mold 3 acting as a movable mold, and a fourth mold 4 acting as a stationary mold. The first and second molds 1 and 2 are slidably combined together and divided into two sections in a predetermined plane through the axis thereof, and the third and fourth molds 3 and 4 are formed of the first and second molds. The two molds 1 and 2 are positioned so that they can be sandwiched between the third and fourth molds 3 and 4. The first mold 1 as shown in FIGS. 1A and 1B has two protruding inwards toward its central opening to form V-shaped grooves 5a ₁ , 5a ₂ and flanges 5b ₁ , 5b ₂ . Parallel convex portions 63 and 64, first forming surfaces 10 in contact with the injection molded resin (formed on the inner circumferential portions of the convex portions 63 and 64, respectively), and arranged so as not to contact the injection molded resin The first groove side 11a, the groove bottom face 12, and the second groove side face 11b which are arranged in a facing relationship with each other and which are not in contact with the injection molding resin, constitute the first positioning surface. An inner circumferential groove (for accommodating and positioning the second mold 2) and an opening toward the second groove side 11b to release the gas generated from the resin during injection molding and the gas generated in the mold to the outside of the mold. The exhaust hole 13, the truncated cone outer peripheral surface, and the truncated cone positioning contact surface. Is the axis of the truncated cone constituting a projection having a first flat end face 16 and a first conical face 17 disposed orthogonal to the axis of the truncated cone, the inner circumferential surface of the truncated cone, and another truncated cone positioning contact surface. A recess having a second flat end face 18 and a second conical face 19 disposed orthogonally to the circumferential groove 15 formed in the second groove side face 11b, and the second groove side face 11b. Screw holes 14 open to the side. The first mold 1 is divided into two sections (half) in a plane containing an axis of annular or truncated cone (as described below), the two sections being far away from each other (right and left) Each can be slid. The groove formed by the first groove side 11a, the second groove side 11b and the groove bottom 12 is annular and accommodates and positions the disc-shaped second mold 2.

The second mold 2 is used to form the inner walls of the rotating pulley interconnecting the hub and the grooves, which second mold 2 is in contact with the injection molding resin to form the inner walls 25, A second side portion 21 which faces the first side portion 21, the outer circumferential portion 22, and the first side portion 21 constituting the second positioning surface disposed so as not to be in contact with the injection-molded resin and is not in contact with the injection-molded resin 26, the second side portion 26 so as to fit into the exhaust groove 23 formed in the second side portion 26 and communicating with the exhaust hole 13, and the circumferential groove 15 formed in the first mold 1. And a projection 24 formed thereon and projecting therefrom. The second shaping surface 25 and the first side portion 21 are coplanar with each other and are interconnected. On the side of the second mold 2 facing away from the first side face 21, the second molding surface 25 and the second side face 26 are coplanar with each other. Like the first mold 1, the second mold 2 is divided into two sections (half) in the plane including its axis, which can each slide in the opposite direction away from each other.

When the first mold 1 and the second mold 2 are combined together, each of the two molds is divided in a plane including the axis of the cone, which will be described later, and at least one section of the second mold 2 The first mold 1 is rotatably received, and when the two molds 1 and 2 are shifted from the divided state to the combined state, the position of one section of the second mold 2 with respect to the first mold 1 Although not predetermined, it is determined automatically through the rotation of one section of the second mold 2, which is desirable. According to this structure, one section of the second mold 2 does not have to be accurately set in advance at a predetermined position in the circumferential direction with respect to the first mold 1. The 1st side part 21 of the 2nd metal mold | die 2 is pressed against the 1st groove side surface 11a of the inner peripheral groove in the 1st metal mold | die 1 by the screw 6 in the screw hole 14, and a 2nd The mold 2 is fixed in the first mold 1 in the axial direction. The outer peripheral part of the 2nd metal mold | die 2 fixes the 2nd metal mold | die 2 radially in the 1st metal mold | die 1 by contacting with the groove bottom face 12 of the inner peripheral groove in the 1st metal mold | die 1. As shown in Fig. 2, each of the first mold 1 and the second mold 2 can be divided in a plane including its axis so that the injection molded article 5 can be removed from the injection molding mold. After the second die 2 is rotated and inserted into the inner circumferential groove of the first die 1 formed by the first groove side 11a, the second groove side 11b and the groove bottom face 12, the second The protrusion 24 of the mold 2 is coupled to the circumferential groove 15 of the first mold 1 so that the second mold 2 is prevented from being separated from the first mold 1. Each of the first forming surfaces 10 of the first mold 1 is in contact with the corresponding second forming surfaces 25 of the second mold 2 (preferably at an angle of 90 degrees or less) (linear contact) Thus, a corner portion of a predetermined shape corresponding to the shape of the flange of the rotating pulley or the V-shaped groove is formed. As shown, the second forming surfaces 25 are formed on both sides of the second mold 2, and each second forming surface 25 is the first forming surface 10 of the first mold 1. ) In contact with This allows the second mold 2 to act as a slide core to form corner portions at its two positions. A very small gap is formed between the second groove side 11b of the inner circumferential groove of the first mold 1 and the second side portion 26 of the second mold 2, which gap is formed into the first mold 1. This allows for the smooth insertion of the second mold 2 of, and also with this very small gap the gas can be effectively released from the mold.

The 3rd metal mold | die 3 is connected to the 1st metal mold 1 side which has a truncated cone-shaped inner peripheral surface. The third mold 3 has a first exhaust hole opened toward the flat end face 35, the conical face 36, and the end face 35 which are arranged orthogonal to the axis of the frustoconical constituting the frustoconical positioning contact surface. 34), the second exhaust hole 33 in communication with the exhaust hole 13 in the first mold 1, and the hub and the V-shaped groove 5a of the rotary pulley and the rotation interconnecting the hub and the V-shaped groove. And a molding surface 31 in contact with the injection molded resin to form part of the pulley. The forming surface 31 and the end surface 35 are connected together to shape the relevant parts of the rotary pulley. The conical surface (outer circumferential surface) 36 of the third mold 3 is in contact with the conical surface (inner circumferential surface) 19 of the first mold 1, and is also an end face 35 of the truncated cone portion of the third mold 3. By contacting the end face 18 of the truncated cone-shaped recess of the first mold 1, the first and third molds 1 and 3 are fixed radially and axially with respect to each other. The shaping surface 31 of the third mold 3 is in linear contact with the shaping surface 10 of the first mold 1 so as to form a shape corresponding to the shape of the flange or the V-shaped groove of the rotatable pulley.

The 4th metal mold | die 4 is connected to the 1st metal mold | die 1 side which has a truncated cone-shaped recessed part. The fourth mold 4 has a flat end face 46, a conical face 47 and a hub and a V-shaped groove 5a which are arranged orthogonal to the axis of the truncated cone constituting the truncated cone-shaped positioning contact surface. A forming surface 41 in contact with the injection molded resin to form a portion of the rotating pulley interconnecting the hub and the V-shaped groove, and an exhaust hole 43 open toward the end surface 46. The forming surface 41 and the end surface 46 are connected together to form the relevant portions of the rotary pulley. The conical surface 47 of the truncated cone-shaped recess of the fourth mold 4 is in contact with the conical surface 17 of the truncated cone-shaped projection of the first mold 1, and also the end face of the truncated cone-shaped recess of the fourth mold 4 ( 46 contacts the end faces 16 of the truncated conical recesses of the first mold 1, thereby fixing the first and fourth molds 1 and 4 radially and axially with respect to each other. The shaping surface 41 of the fourth mold 4 is in linear contact with the shaping surface 10 of the first mold 1 so as to form a corner portion at a substantially right angle. The forming surfaces 10, 25, 31 and 41 of the first, second, third and fourth molds 1, 2, 3 and 4 are combined or connected together as described above to form a forming cavity Resin is injected into this molding cavity, and a molded article (rotary pulley) is injection molded.

When resin is injected into the molding cavity to perform the injection molding operation, the first mold 1 is subjected to a force to move the first mold 1 in the mold opening direction, but by the above structure, the axis of the first mold Directional and radial positional relationships are determined by the third and fourth molds, so that the positional relationship between the molds can be firmly fixed. In addition, this structure can make two sections, and the slide core is typically divided into three sections.

Although the shapes formed by the plurality of first forming surfaces 10 in contact with the plurality of second forming surfaces 25 are all in the shape of V-shaped grooves and flanges as shown in FIGS. 1A, 1B and 2 However, the present invention is not limited thereto, and other shapes such as grooves and flanges for flat belts or timing belts may be adopted. The number of grooves is not limited to that of the embodiment. That is, when the plurality of first forming surfaces 10 and the second forming surfaces 25 are in contact with each other with a narrow space, this case corresponds to the contact made at an acute angle. In addition, these numbers are not limited to the thing of an Example. In the structure of this embodiment, an injection molding die comprising a first molding surface 10, a first positioning surface, a frustoconical positioning contact surface, and a disk-shaped second mold 2 for forming the molded article 5. All major parts of are circular or annular with their centers arranged on a common axis (the axis of rotation of the molded part 5). Therefore, when the mold is formed by, for example, a lathe or a turning machine, the accuracy of the positional relationship between the molds can be easily improved to a high degree. In the present embodiment, although the structure of the second mold 2 that is rotated and inserted into the first mold 1 is adopted, the structure is not limited to this structure, and the second mold 2 is the second mold 2. May be inserted into the first mold 1 so as to move directly orthogonally to the divided surfaces of the first mold 1 and the second mold 2.

As described above, in the present invention, a molded article formed by using a slide core and having parts of complicated shape, that is, a rotary pulley can be formed with high dimensional precision by a mold for injection molding having a simple structure. In addition, the molds can be easily formed by machining into such a shape.

Claims (6)

In the injection molding mold, A first mold having a first molding surface forming a part of the molded article and a first positioning surface for mold positioning; And A second mold having a second molding surface for forming another part of the molded article, and a second positioning surface for contacting the first molding surface of the first mold with the second molding surface at an acute angle; The first mold and the second mold are each divided into sections in a predetermined plane thereof; When the first mold and the second mold are combined together, the first molding surface and the second molding surface contact each other to form a corner portion of the molded article; And The portion of the second mold having the second positioning surface is fitted to and in contact with the portion of the first mold having the first positioning surface, thereby positioning and fixing the first and second molds with respect to each other. Injection molding mold, characterized in that. The injection mold as claimed in claim 1, wherein one or more divided sections of the second mold are held in a portion of the first mold having the first positioning surface to rotate about an axis of the molded article therein. Mold for molding. The injection molding mold according to claim 1, wherein the molding surface and the second positioning surface of the second mold are disposed on the same plane to form a flat surface together. 2. The exhaust gas of claim 1, wherein exhaust holes are opened toward the first and second positioning surfaces, respectively, so that gas is removed from the gap between the first and second positioning surfaces through the exhaust holes. Injection molding mold. The method of claim 1, wherein the second mold has another second forming surface formed on the side facing away from the second forming surface, and the first mold is further formed to be in acute contact with the another second forming surface. An injection molding mold having a first molding surface, wherein the second molding surface and the second molding surface are in contact with each other to form a corner portion of the molded article. The method of claim 1, wherein the portion of the first mold having the first positioning surface is formed as a recess, and the portion of the second mold having the second positioning surface is recessed so that the center of the molded article can be centered. Injection molding mold, characterized in that the insert is held.