JPH07227886A - Injection mold equipped with inner slide core - Google Patents

Abstract

PURPOSE:To provide a mold for an injection molding machine capable of molding a molded piece having an undercut such as an inner gear by injection molding without using any specific control means. CONSTITUTION:This injection molding machine has an inner mold for forming an inner gear 13 of a cam ring 11. An angle thetaB to be formed by parting faces 31c and 41c of first and second inner slide cores 31 and 41 which come into contact with each other at a closed position where the inner mold is closed and the moving direction of the first inner slide core 31 is set within a range which satisfies a relationship thetaF<=thetaB<=thetaA when a minimum angle where the parting faces 31c and 41c of the first and second inner slide cores 31 and 41 do not interfere each other at the closing position or other position than its vicinity is thetaF and a maximum angle relating to the moving direction of the first inner slide core 31 where the inner mold of the second inner slide core 41 does not interfere the first inner slide core 31 at opening/closing movement is thetaA.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection molding die having an inner slide core for injection molding a molded product having an undercut, for example, a tubular member having an internal gear.

[0002]

2. Description of the Related Art Generally, a mold of an injection molding machine for injection-molding a cylindrical article having an undercut on its inner circumference has an inner slide core divided into four, six or more parts. is doing.

However, when the undercut is an internal gear, the tooth tips of the internal slide core easily interfere with the molded internal gear and other divided internal slide cores, so that the adjacent internal slides are opened when the mold is opened. It was necessary to shift the timing of driving the core or change the driving speed of each core. For that purpose, a plurality of drive mechanisms and means for controlling each of them at a predetermined timing or at different predetermined speeds are required, and there is a problem that the configuration of the entire injection molding machine becomes complicated.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an injection molding machine capable of injection molding a molded product having an undercut such as an internal gear without using a special control means.

[0005]

SUMMARY OF THE INVENTION The present invention, which achieves this object, comprises a plurality of sets of first and second inner slides, each of which is a set of first and second inner slide cores in which inner molds having undercut forming portions are adjacent to each other. An injection molding machine having a core, wherein the first and second inner slide cores move at different speeds in a direction orthogonal to a central axis of the inner mold to open and close the inner mold, the first and second inner At the position where the slide cores close the inner mold, the angle θ _B formed by the parting surfaces contacting each other and the moving direction of the first inner slide core is defined by the parting surfaces of the first and second inner slide cores. Or a direction of movement of the first inner slide core in which the undercut molding portion of the second inner slide core does not interfere with the first inner slide core during the opening / closing movement at a minimum angle θ _F or more that does not interfere with each other except in the vicinity thereof. set to be equal to or smaller than the maximum angle θ _A for Things, to have a feature.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to illustrated embodiments. 3 and 4 are perspective views showing a main part of an inner slide core, which is an inner mold of an injection molding die to which the present invention is applied, in a closed state and an open state, and FIGS. It is the front view. The injection molding die of the present embodiment is a cylindrical molded product having an internal gear on its inner circumference, and forms the cam ring 11 of the photographing lens having the internal gear 13 on its inner circumference.

The mold 20 has a first inner slide core 31 as an inner slide core for molding the inner peripheral surface of the cam ring 11.
And a plurality of sets (six sets in this embodiment) of inner slide cores 31, 41, each including the second inner slide core 41, and these inner slide cores 31, 41 are aligned with the central axis of the cam ring 11. Positioned in the axial center space formed by the fixed plate 21 movably supported in the radial direction orthogonal to the central axis O of the mold and the inner peripheral surfaces 31a, 41a of the first and second inner slide cores 31, 41. A lock core 23 that advances and retreats in parallel with the central axis O about the central axis O and presses and holds the first and second inner slide cores 31 and 41 in the closed position at the forward position;
The movable plate 25 for moving the lock core 23 forward and backward and the movable plate 25 are fixed to the movable plate 25. When the movable plate 25 moves backward and forward, the first and second inner slide cores 31, 41 are opened and closed at different speeds. It is equipped with angular pins 27, 28 for driving. Although not shown in detail, the fixed plate 21 is fixed to a fixed block or the like of the injection molding machine, and the moving plate 25 is driven by a hydraulic cylinder, a press shaft or the like mounted on the fixed block or the like.

Each of the first and second inner slide cores 31, 41
Includes inner mold parts 32, 42 integrally formed at the distal ends of the base parts 33, 43, and the inner mold parts 32, 42 are in close contact with other inner mold parts 32, 42 adjacent to each other in the closed state. The inner peripheral surface of the cam ring 11 is formed. Further, the base portions 33 and 43 include first and second inner slide cores 31 and 41 (inner die portion 3).
2, 42) are formed in the opening / closing direction (diameter direction). Hereinafter, the first and second inner slide cores 31 and 41 of each set have the basic structure and the structure and mechanism of parts related thereto except for the molds formed on the outer peripheral surfaces of the inner mold parts 32 and 42. Because they are the same, a set of first,
The second inner slide cores 31, 41 will be described.

The guide portions 34 and 44 are formed to have a cross section (details are not shown). On the other hand, the fixed plate 21 is formed with groove-shaped guide grooves 21b in a diametrical direction orthogonal to the central axis O (the central axis of the cam ring 11), and the guide portions 34 and 44 slide on these guide grooves 21b. It is movably fitted. In this fitted state, each inner mold part 32, 42 projects forward from the opening 21a formed in the fixed plate 21, and is constrained by the guide parts 34, 44 and the guide groove 21b to move in the radial direction.

When the inner mold parts 32 and 42 move toward the central axis O, they separate from each other to be in an open state in which the mold is opened. Further, when the inner mold parts 32, 42 move in the radial direction away from the central axis O and the outer peripheral surfaces contact the edge part 21c of the opening 21a, and further outward movement is blocked,
Close to each other and close the mold. This inner mold part 3
The positions and states of 2 and 42 are the closed position and the closed state.

External gear parts 35 and 45, which form the internal teeth 13 in the closed state, are formed on the outer peripheral surfaces of the inner mold parts 32 and 42. The cam ring 11 is not limited to the internal teeth 13,
There may be grooves, holes, ridges, protrusions, etc., and in such a case, the inner mold portions 32, 42 have ridges that form them,
Protrusions, grooves, holes, etc. are formed.

In order to form the end face of the cam ring 11 on the front surface of the fixed plate 21, the inner diameter of the opening 21a is formed to be substantially the same as the inner diameter of the cam ring 11, and the inner mold portions 32 and 42 protruding from the opening 21a are used. The inner peripheral surface of the cam ring 11 is formed.

The inner peripheral surfaces 31a and 41a of the first and second inner slide cores 31 and 41 are formed in a mortar shape that narrows toward the fixed mold 51 (front), and the lock core 23 is
The tapered portion 23a that contacts the inner peripheral surfaces 31a and 41a is formed in a truncated cone shape corresponding to the inner peripheral surfaces 31a and 41a. The central axis O is the taper portion 23a and the inner peripheral surfaces 31a and 41a.
Let θ _F be the angle formed with.

Further, angular pins 27 and 28 are fixed to the moving plate 25 for transmitting the linear movement in the front-rear direction parallel to the central axis O thereof to the first and second inner slide cores 31 and 41 as the movement in the opening / closing direction. Has been done. The tip end shaft portions 27a, 28a of the angular pins 27, 28 are formed in the guide holes 36, 4 formed in the first and second inner slide cores 31, 41, respectively.
6 are slidably fitted respectively.

The angular pins 27 and 28 are the first and second
In order to move the inner slide cores 31 and 41 at different speeds, they are fixed to the moving plate 25 at predetermined angles θ _D and θ _E with respect to the central axis O, respectively. The moving plate 25 has a screw hole 25 with a seat support whose axial center extension intersects with the central axis O and forms angles θ _D and θ _E with the central axis O, respectively.
a, 25b are formed, while angular pins 27, 2 are formed.
Male screw parts 27c, 28c near the heads 27b, 28b of No. 8
Are formed. And Angular Pins 27, 28
The front end shaft portions 27a, 28a are inserted into the screw holes 25a, 25b from the rear of the moving plate 25, and the male screw portions 27c, 28
c is screwed into the screw holes 25a and 25b. As a result, the angular pins 27 and 28 are fixed to the moving plate 25 at angles θ _D and θ _E with respect to the central axis O.

The angles θ _D and θ _E are different so as to drive the first and second inner slide cores 31 and 41 at different speeds. In the present embodiment, the second inner slide core 41 is attached to the central axis O
Since it is configured to contact the first slide core 31 from the side,
When the fixed plate 25 moves back and forth, the second inner slide core 41
Is set to have a relationship of θ _D ≦ θ _E so that the moving body moves faster than the first inner slide core 31. The first and second inner slide cores 3 for advancing and retracting the lock core 23.
The moving speeds of the opening and closing directions (radial direction) of 1, 41 are
It becomes tan θ _D and tan θ _E.

The means for driving the first and second inner slide cores 31, 41 at different speeds is not limited to the angular pins 27, 28. For example, the inclined surface provided on the lock core 23 and the slide cores 31, 41 A structure in which the inclined surface provided on the peripheral surface is in sliding contact, or a structure in which a groove provided on one side and a ridge provided on the other side are slidably fitted may be used.

Further, in this embodiment, the taper portion 23a of the lock core 23 has the inner peripheral surface 3 at and near the closed position.
The inclination angle θ _G of the taper portion 23 a is set to θ _D ≦ θ so that the taper portion 23 a does not interfere with the 1 a and 41 a and interferes with other retracted positions.
The relationship is _E ≤ θ _G.

A more detailed structure of the first and second inner slide cores 31 and 41 will be described with reference to FIGS. 1 and 2. FIG. 1 is an enlarged front view showing the inner mold parts 32, 42 (first and second inner slide cores 31, 41), and FIG. 2 is a front view showing the inner mold parts 32, 42 further enlarged. .

As shown in FIG. 1, the adjacent first and second inner slide cores 31 and 41 move along the first and second slide direction lines O ₁ and O ₂ , respectively, and move along the central axis O. The basic shape is formed symmetrically with respect to the sliding direction lines O ₁ and O ₂ .

The contact and separation angle θ _C formed by the first and second sliding direction lines O ₁ and O ₂ with respect to the central axis O is set. This contact angle θ _C
Is determined by the total number of the first and second inner slide cores 31, 41, but in the present embodiment, the first and second inner slide cores 31, 4 are
Since there are 12 in total, θ _C = 360/12 = 30
(Degree).

Therefore, the first and second inner slide cores 3
When the 1, 41 are opened and closed, the parting surface 31c,
The moving speed ta of the first and second inner slide cores 31 and 41 is adjusted so that 41c does not interfere with each other except at or near the closed position.
n θ _D , tan θ _E and the contact angle θ _C satisfy the relationship of tan θ _D ≤ tan θ _E cos θ _C.

The first and second inner slide cores 31 and 41 are
Both sides in the circumferential direction (parting surfaces 31c, 41c)
Contact each other in the closed state to close the inner mold parts 32, 42. The parting surfaces 31c and 41c of the first and second inner slide cores 31 and 41 correspond to the first inner slide core 31.
The angle θ _B is measured counterclockwise with respect to the first sliding direction line O ₁ . This angle θ _B is formed so that the parting surface 41 c of the second inner slide core 41 contacts the parting surface 31 c of the first inner slide core 31 from the central axis O side. The parting surfaces 31c and 41c on both sides of the first and second inner slide cores 31 and 41 are formed symmetrically with respect to the surfaces extending the sliding direction lines O ₁ and O ₂ along the axis.

The inner teeth 13 of the cam ring 11 are internal gears whose tooth lines extend parallel to the central axis O and whose end faces are continuous in the spiral direction. It forms a flat surface from which 42 can be pulled out. In this embodiment, the inner mold part 3
Parting lines 2, 42 are formed so as to be located at the bottoms of the outer teeth 35, 45. Here, if the number of teeth per revolution of the inner teeth 13 is Z and the number of divisions of the inner mold parts 32 and 42 is S, Z = (n / 2) S (where n is a positive integer)
Have a relationship. In this embodiment, S = 12 as described above.

The maximum angle θ _A is such that the outer teeth 35 interfere with the mold part 42 or the outer teeth 45 when the first and second inner slide cores 31, 41 are opened and closed. As for the maximum angle θ _A , as in the illustrated embodiment, a straight line connecting the corner portion 35 a of the outer tooth 35 and the outermost vertex (corner portion) 45 a of the outer tooth 45 is the first slide direction line O ₁ . It is an angle. This maximum angle θ
_A changes depending on the position of the parting line (the position where the external teeth 35 and 45 are divided), but it is desirable that the divided position be located at the valley bottom by avoiding the tooth surface in terms of strength.

Further, the minimum angle θ _F which the parting surfaces 31c and 41c can move to the open / close position without interfering with each other and the first sliding direction line O ₁ is defined by the following equation. It θ _F = tan ^-1 {sin θ _C tan θ _E / (tan θ _E cos θ _C
-Tan θ _D )} However, as described above, θ _C is the angle formed by the sliding direction lines O ₁ and O ₂ of the first and second inner slide cores 31 and 41, and θ _D is the angular axis O of the angular pin 27. Angle to make,
θ _E is the angle that the angular pin 28 makes with the central axis O.

The angle θ _B formed by the parting surfaces 31c and 41c with respect to the sliding direction line O ₁ of the first inner slide core 31 is larger than the minimum angle θ _F and smaller than the maximum angle θ _A. That is, by setting so as to satisfy θ _F ≦ θ _B ≦ θ _A , the first and second inner slide cores 31, 41, that is, the inner mold parts 32, 42 move without interfering with each other. It is opened and closed in conjunction with the movement of the plate 25.

The opening / closing operation of the first and second inner slide cores 31, 41 will be described with reference to FIGS. 8, 10 and 12 show the first and second inner slide cores 31 and 41.
Front view for explaining the relationship, FIG. 7, 9, 11 sliding direction sliding direction lines O _1, respectively, in FIG 8, 10, 12,
FIG. 6 is a cross-sectional view showing a first inner slide core 31 on the lower side and a second inner slide core 41 on the upper side, cut along a plane passing through O ₂ .

In the closed state where the inner mold parts 32 and 42 are in close contact with each other, the lock core 23 advances, and the taper part 23a of the lock core 23 causes the inner peripheral surfaces 31a and 41a of the first and second inner slide cores 31 and 41 to move. And presses in the closing direction (outward direction). The first and second inner slide cores 31 and 41 that have received this pressing force are urged in the closing direction (outward direction) along the guide groove 21b, and the parting surfaces 31c and 41c are in close contact with each other and the inner mold The parts 32 and 42 are closed (see FIGS. 3, 5, 7, and 8).

In this closed state, the outer mold 51 is fitted to the inner mold parts 32 and 42, and between the outer peripheral surfaces of the inner mold parts 32 and 42 and the inner peripheral surface of the outer mold 51, and the fixing plate 21. A cavity for molding the cam ring 11 is formed between the cavity and the front surface of the. Although not shown in the drawing, a synthetic resin is injected by an injection plunger or the like and solidified or cured to mold the cam ring 11.

In order to take out the molded cam ring 11,
When the moving plate 25 is retracted from this closed state, the lock core 23 and the angular pins 27 and 28 are integrally retracted. By these retreats, the first and second inner slide cores 3
1, 41, that is, the inner mold parts 32, 42 are tapered parts 23a.
The constraint due to is released and it becomes possible to move in the opening direction (direction toward the central axis O). In addition, Angular Pin 27,
Since 28 is retracted at the same time, the inner mold parts 32, 42 are constrained by the angular pins 27, 28 to move in the opening direction,
The inner mold parts 32 and 42 separate from the inner teeth 13 and separate from each other (see FIGS. 9 and 10).

By the time the moving plate 27 further retracts and reaches the open position, the outer gear parts 35, 45 of the inner mold parts 32, 42 are completely removed from the inner teeth 13 of the cam ring 11, and the cam ring 11 is pulled out. Is possible (see FIGS. 4, 6, 11, and 12). In this open position, the outer mold 51 separates and the cam ring 1
1 is pulled out, and further, the cam ring 11 is pulled out from the outer die 51. In this open state, the first and second inner slide cores 31 and 41 connect the inclined surfaces 31a and 41a and the parting surfaces 31c and 41c to the connecting surfaces 31b and 41b.
Is in the closest state. These contact surfaces 31b, 4
It goes without saying that 1b is formed in a shape that does not interfere with each other when the first and second inner slide cores 31 and 41 move between the closed position and the open position. The cam ring 1
If the outer circumference of 1 also has an undercut, the outer mold 5
1 is also a split mold.

As described above, according to the injection molding die of this embodiment, the first and second inner slide cores 31 and 41 move at different speeds in the opening / closing direction only by moving the moving plate 25 forward and backward without interfering with each other. Therefore, a cylindrical molded product having an undercut on the inner circumference, for example, the cam ring 11 can be easily injection-molded by a simple configuration and control.

Although the case where the cam ring 11 is molded as an injection-molded product having an undercut has been described in the present embodiment, it goes without saying that the present invention can be applied to a molded product other than the cam ring 11.

[0035]

As is apparent from the above description, the present invention is
The parting surfaces of the first and second inner slide cores close to each other at an angle θ _B formed by the parting surfaces of the first and second inner slide cores that open and close at different speeds and the moving direction of the first inner slide core. It is larger than the minimum angle θ _F that does not interfere with each other except at the position or in the vicinity thereof, and the undercut forming portion of the second inner slide core does not interfere with the first inner slide core during opening / closing movement. Since the maximum angle with respect to the moving direction is set to a range smaller than θ _A, it is possible to open and close the inner slide core without providing special control means, and the configuration of the control means and drive means of the injection molding machine Became easier.

[Brief description of drawings]

FIG. 1 is a front view showing a structure of an embodiment of an injection molding die having a plurality of sets of first and second inner slide cores to which the present invention is applied.

FIG. 2 is an enlarged front view for explaining the configuration of the first and second inner slide cores in more detail.

FIG. 3 is a perspective view showing the first and second inner slide cores of the same embodiment in a closed state.

FIG. 4 is a perspective view showing the first and second inner slide cores of the same embodiment in an open state.

FIG. 5 is a front view showing the first and second inner slide cores of the same embodiment in a closed state.

FIG. 6 is a front view showing the first and second inner slide cores of the same embodiment in an open state.

FIG. 7 is a cross-sectional view of the first and second inner slide cores cut along a plane passing through a sliding direction of the first and second inner slide cores in a state where the first and second inner slide cores are closed so that the first inner slide core portion is located on the lower side. FIG. 7 is a sectional view showing the second inner slide core portion on the upper side.

8 is a front view for explaining the positional relationship between the first and second inner slide cores in the closed state of FIG.

FIG. 9 is a view showing a state where the first and second inner slide cores of the same embodiment are in the middle of opening and closing, cut along a plane passing through a sliding direction of the first and second inner slide cores to lower the first inner slide core portion. It is a sectional view which shows the 2nd inner slide core part on the side and the upper side.

FIG. 10 is a front view for explaining the positional relationship between the first and second inner slide cores in the state of being opened and closed in FIG.

FIG. 11 is a sectional view of the first and second inner slide cores in the opened state of the embodiment taken along a plane passing through a sliding direction of the first and second inner slide cores, so that the first inner slide core portion is located downward. ,
It is sectional drawing which shows the 2nd inner slide core part on the upper side.

FIG. 12 is a front view illustrating the positional relationship between the first and second inner slide cores in the open state of FIG.

[Explanation of Codes] 11 Cam Ring 13 Internal Teeth 21 Fixed Plate 23 Lock Core 23a Tapered Part 25 Moving Plate 27 First Angular Pin 28 Second Angular Pin 31 First Inner Slide Core 31a Tapered Inner Surface 31c Parting Surface 32 Type Part 35 Outer tooth part 41 Second inner slide core 41a Tapered inner peripheral surface 41c Parting surface 42 Mold part 45 Outer tooth part O Center axis θ _A The minimum angle θ _B where the first and second slide cores do not interfere Angle with the moving direction of the first slide core θ _C Angle between the first and second inner slide cores θ _D Angular pin of the first inner slide core is the central axis O
Angle θ _E The angular pin of the second inner slide core is the central axis O
Angle θ _F maximum angle θ _G angle formed by the tapered part of the lock core with the central axis O

Claims (6)

[Claims] 1. An inner mold having an undercut forming portion has a plurality of sets of first and second inner slide cores, each of which is a set of first and second inner slide cores adjacent to each other. Two
An injection molding die in which an inner slide core moves at different speeds in a direction orthogonal to a central axis of the inner die to open and close the inner die, wherein the first and second inner slide cores are mutually positioned at a position where the inner die is closed. The angle θ _B between the contacting parting surface and the moving direction of the first inner slide core is defined as a minimum angle at which the parting surfaces of the first and second inner slide cores do not interfere with each other except at the closed position or in the vicinity thereof. θ _F , when the maximum angle with respect to the moving direction of the first inner slide core is θ _A , at which the undercut molding portion of the second inner slide core does not interfere with the first inner slide core during the opening and closing movement, An injection molding die having an inner slide core, characterized in that the range is set to satisfy θ _F ≤ θ _B ≤ θ _A. 2. The molded product formed by the inner mold according to claim 1, wherein the molded product is a cam ring having an internal gear as an undercut, and the parting lines of the first and second internal slide cores are the internal teeth. It is formed on the bottom of the tooth mold of the forming part,
The maximum angle θ _A is the second angle when the parting line of the first and second inner slide cores is formed on the tooth bottom of the tooth mold.
An injection mold provided with an inner slide core, wherein the tooth tips of the inner slide core have a maximum angle that does not interfere with the first inner slide core. 3. The first and second inner slide cores according to claim 1 or 2, wherein each of the first and second inner slide cores moves toward and away from a fixed plate at a predetermined angle θ _C in a radial direction orthogonal to the central axis. An injection molding die having an inner slide core, which is slidably supported, and closes the inner die when the first and second inner slide cores are most outwardly moved. 4. The guide according to any one of claims 1 to 3, wherein the guide is movably parallel to the central axis in an inner peripheral space formed by inner peripheral surfaces of the first and second inner slide cores. A lock core that presses and holds each of the first and second inner slide cores in a closed position where the contact surfaces contact each other when moving forward, and allows the opening of the first and second inner slide cores when moving backward. An injection molding die having an inner slide core, which is characterized in that: 5. The lock core according to claim 4, wherein the lock core is fixed to a moving plate, and the moving plate is further slidably inserted into a guide hole formed in each of the first and second inner slide cores. Each of the angular pins is fixed to the central axis so as to drive the first and second inner slide cores at different speeds in the opening / closing direction when the moving plate moves. Predetermined angle θ
Injection molding die with an inner slide core characterized in that it is fixed at _D and θ _E , but satisfies θ _D ≤ θ _E and tan θ _D ≤ tan θ _E cos θ _C. 6. The minimum angle θ _{F according to} claim 5, wherein θ _F = tan ⁻¹ {sin θ _C tan θ _E / (tan θ _E cos θ _C
−tan θ _D )} where θ _C : angle formed by the sliding directions of the first and second inner slide cores θ _D : angle formed by the angular pin of the first inner slide core with the central axis θ _E : second inner slide core An injection mold with an inner slide core characterized in that the angular pin of is given at an angle with the central axis.