JP2001026040A - Injection mold - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately grasp a pressure of molten resin in a cavity by forming an evacuation part for increasing an evacuation transfer amount in the case where a first core part is transferred by evacuation on inner peripheral sides of a pair of peripheral side wall parts of the first core part to come into contact with the peripheral side wall part of a second core part. SOLUTION: In an internal slide core 14 wherein a molding face 24 is formed on the outer peripheral side, a plurality of sets of a first core part 25 of a short circumference length of the molding face 24 and a second core part 26 of a long circumference length of the molding face 24 are alternately arranged. Then, on inner peripheral sides of a pair of peripheral side wall parts of the first core part 25 to come into contact with the peripheral side wall part of the second core part 26, in the case the first core part 25 is transferred in evacuation radially inside to a mold releasing position of the first core part 25, an evacuation part 36 for increasing the evacuation transfer amount is formed. Thereby, an occurrence of trouble wherein the evacuation transfer amount of the second core part 26 is insufficient, and an injection molded product becomes hard to extract from the second core part 26 can be prevented, and the strength of the mold can be stably sured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection mold for manufacturing a cylindrical injection molded product, and more particularly to a mold suitable for application to a lens barrel part having an undercut portion on an inner peripheral surface. It is.

[0002]

2. Description of the Related Art An injection-molded article is taken out of the mold by removing the mold after injecting a molten resin at a high pressure into a cavity formed in the mold and holding and cooling the resin. Also, various types of molds are known according to the shape of the injection molded product, the gate method, and the like. When the injection molded product has an undercut portion, the mold structure is complicated accordingly. With a tendency to become. In particular, when there is an undercut portion on the inner peripheral side of a cylindrical injection molded product such as a lens barrel part shown in FIGS. 9 and 10, the mold becomes a very complicated structure. FIG. 9 shows the appearance of a lens barrel part, and FIG.
Represents its vertical cross-sectional structure. This lens barrel part 1 is
An annular concave / convex portion 2, for example, a multi-threaded female screw portion is formed as an undercut portion on the inner periphery. When such a concave / convex portion 2 is present on the inner peripheral side, the inner peripheral surface is formed. The amount of undercut S radially inward when removing the mold
It is necessary to retreat and move.

An angular pin is used as a mold structure for molding a cylindrical lens barrel component 1 having an uneven portion 2 as an undercut portion on the inner peripheral side as shown in FIGS. Japanese Patent Publication No. Hei 1-461296 and Japanese Patent Application Laid-Open No. 5-261776 using tapering are known. In each case, a cylindrical inner slide core provided with a molding surface on the outer peripheral side has an arc shape. Three first core portions having a short length and three second core portions having a long arc length are alternately arranged in an annular shape, and prior to the retreating movement of the second core portion inward in the radial direction, the first By moving the one core portion radially inward, interference between the undercut portion of the injection molded product and the inner slide core at the time of demolding is eliminated.

FIG. 11 shows a plan view of such an inner slide core at the time of molding, and FIG.
Shown in That is, the three first core portions 102 having a short arc length having the forming surface 101 formed on the outer peripheral side are displaced inward in the radial direction, and then the three first core portions 102 having the long forming arc surface 103 having the forming surface 103 formed on the outer peripheral side. When the two-core portion 104 is displaced inward in the radial direction, the outer diameter of the inner slide core 105 becomes smaller than the inner diameter of the injection molded product, and the inner slide core 10
5, it is possible to take out the injection molded product. S in the figure corresponds to the undercut amount described above.

FIG. 13 shows an exploded structure of a mold disclosed in Japanese Patent Application Laid-Open No. Hei 5-261776, in which the timing of retreating the first core portion 102 and the second core portion 104 in the radial direction is performed using tapering. Fig. 1
4 and FIG. 15 shows a cross-sectional structure taken along the line XV-XV, and FIG. 16 shows a cross-sectional structure when the mold is removed. That is, the tapered portions 106 and 107 are formed on the outer periphery of the lower portion of the inner slide core 105.
Are formed, and an annular core holder 109 having a tapered portion 108 surrounding the tapered portions 106 and 107 holds a lower portion of the inner slide core 105.
The tapered portion 106 of the first core portion 102 is
4 is longer (larger diameter) than the tapered portion 107 of the second core portion 104, and is always in contact with the tapered portion 108 of the core holder 109.
7 is a tapered portion 10 of the core holder 109 during molding.
8 is in a state of rising.

[0006] From the state shown in FIG.
Rises and the center core 110 descends, the first core portion 1 that abuts on the tapered portion 108 of the core holder 109.
The first core portion 102 retreats inward in the radial direction via the 02 taper portion 106, and then the taper portion 107 of the second core portion 104 comes into contact with the taper portion 108 of the core holder 109, and with the rising operation of the core holder 109. The second core part 1
04 retreats inward in the radial direction.

When molding general resin materials, not limited to the injection molded products described above, one of the most important factors in the molding requirements is the pressure of the molten resin in the cavity during molding. It is. If this pressure is not transmitted evenly or varies from shot to shot, a molded product of stable quality cannot be obtained.

However, since the pressure of the molten resin cannot be directly detected in the cavity, the pressure in the cavity is conventionally transmitted to the outside of the mold, and the pressure is measured by a measuring instrument provided outside the mold. Has been implemented. Specifically, as disclosed in Japanese Patent Application Laid-Open No. Hei 7-290548, a nesting pin for transmitting pressure is provided in a mold portion forming a fixed side or movable side cavity as a means for transmitting pressure. A pressure sensor is connected to the base of the nesting pin to convert the detected pressure into an electrical signal, which is visualized by a recorder provided outside the mold, and the behavior of the molding pressure in the cavity is read.

Ideally, the graph by the recorder reproduces the pressure waveform for each shot exactly as it is.
Also, when the molding conditions are reproduced for each molding lot or when the initial molding conditions are determined by different molding machines, the waveform can be reproduced to make it extremely close to the basic molding conditions.

As a simpler method, a method of using an ejector pin on the movable core side is also known. A flange of the ejector pin is processed, a pressure sensor is assembled, and a lead wire of the ejector pin is connected to a metal via a guide member. They are drawn out of the mold.

In order to reduce the cost of lens barrel parts and to obtain complicated shapes which are difficult to machine with metal, FIGS.
When manufacturing a cylindrical lens barrel part 1 as shown in FIG. 0, it is necessary to suppress the dimensional error of the molded product to ± 0.015 mm or less in order to satisfy the optical accuracy. In order to achieve accuracy, it is necessary to maintain and control various molding conditions in addition to the pressure of the molten resin in the cavity in a stable state without variation.

[0012]

In the case of manufacturing a cylindrical injection molded product such as a lens barrel part 1 having an uneven portion 2 as an undercut portion on the inner peripheral portion as shown in FIGS. When the undercut amount S of the undercut portion is, for example, 1 mm or more, particularly 1.5 mm or more, or when the inner diameter of the injection molded product is less than 40 mm, the first core portion 102 of the inner slide core 105 is moved radially inward. In the case of retreating, as shown in FIG. 17 showing the state at that time, even if the inner peripheral surface is retracted until both ends in the circumferential direction collide, the second core portion 104 is undercut S
In some cases, it is difficult to evacuate.

In order to solve such a problem, the first
The arc length of the core portion 102 may be set shorter, the diameter of the center core 110 may be set larger to reduce the thickness of the first core portion 102, or the taper portions 106 to
It is conceivable that the taper angle of the inner slide core 105 is set to a large value.
The strength of the neck 111 of the core 102 tends to decrease, and the risk of breakage of the mold increases.

It is also conceivable to set the retraction stroke of the center core 110 large, but in this case, the mold opening stroke of the mold must be increased, which causes a problem that the entire injection molding equipment becomes large. .

When the pressure of the molten resin in the cavity is detected, it is desirable that the shape of the portion for detecting the pressure be as flat as possible with as little unevenness as possible, and that the diameter is about 2.0 to 2.5 mm. The pressure can be detected with the highest accuracy by using the pin. However, in the case of a cylindrical injection molded product having an undercut portion on the inner peripheral portion as shown in FIGS. 9 and 10, the thickness is 1.5 to 2.0 mm.
In some cases, it is difficult to secure a sufficient space for inserting the nesting pin on the end face side in the length direction of the molded product. It is also difficult to secure the area, and some ingenuity is required.

[0016]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an injection mold capable of stably forming a cylindrical injection molded article having a relatively large undercut or a relatively small inside diameter.

Another object of the present invention is to provide an injection molding die capable of accurately grasping the pressure of a molten resin injected into a cavity in such an injection molding die.

[0018]

According to the present invention, there is provided an injection molding die comprising: a cylindrical inner slide core having a molding surface on an outer peripheral side; and an inner peripheral side opposed to the molding surface of the inner slide core. An injection molding die for injecting a molten resin into a cylindrical cavity formed between an annular outer slide core provided with a forming surface to form a cylindrical injection molded product, The inner slide core has at least two first core portions having a short arc length and at least two second core portions having a long arc length, and the first core portions and the second core portions are alternately annular. And a core driving means for moving the first core portion and the second core portion in the radial direction at different timings between the molding position and the die-cutting position, the core driving portion being arranged in a circumferential direction of the second core portion. Of the first core portion which can contact the side wall portion At least the inner circumferential side of the circumferential side wall portion of the pair, is characterized in that the relief portion for increasing the retraction movement amount when retracting movement of the first core portion is formed.

According to the present invention, when taking out an injection-molded article injected into the cavity, the first core-driving means is used for the first molded article.
The core is retracted radially inward, and then the second core is retracted radially inward. In this case, a relief portion is formed on the inner peripheral side of the pair of circumferential side wall portions of the first core portion, whereby the amount of retreat movement is greater than when there is no relief portion, and the retraction of the second core portion is performed. The movement amount also relatively increases.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION In the injection molding die of the present invention, the core driving means moves the second core after the first core moves from the molding position to the die removing position, and the second core moves. The first core portion may be moved after moving from the die removing position to the molding position.

Further, the apparatus further includes a rod-shaped center core which is in contact with the inner peripheral surface of the inner slide core and holds the inner slide core at the time of molding, and the core driving means moves the center core along a longitudinal direction thereof to a molding position. It may be one that moves between the die-cutting position.

The inner peripheral surface of the inner slide core and the outer peripheral surface of the center core may have a tapered surface whose diameter becomes smaller toward the molding position with respect to the retracted position of the center core.

The cylindrical injection-molded article may have an undercut at least on its inner peripheral surface.

The outer slide core comprises a plurality of arc-shaped core pieces, is embedded in at least one core piece,
A pressure sensor for detecting the pressure of the molten resin filled in the cavity at the time of molding by facing the molding surface of the core piece may be further provided. In this case, the core piece in which the pressure sensor is embedded preferably has a groove for accommodating a lead wire connected to the pressure sensor, and the core piece in which the pressure sensor is embedded has an opening in the groove. It is effective that a cover plate covering at least a part of the portion and preventing the lead wire from falling out of the groove is attached.

[0025]

9 and 10 show an injection mold according to the present invention.
An embodiment applied to an angular pin type of injection-molding an injection-molded product as shown in Fig. 1 will be described in detail with reference to Figs. 1 to 7; however, the present invention is not limited to such an embodiment. The present invention can be applied to other technologies to be included in the concept of the present invention described in the claims of this specification.

FIG. 1 shows the cross-sectional structure of the injection mold according to the present embodiment, FIG. 2 shows the appearance of the inner slide core, and FIG. 3 shows the appearance of the first core. That is,
As shown in FIGS. 9 and 10, the injection-molded product in this embodiment has a small diameter and a thin wall and has an undercut portion on both the inner peripheral side and the outer peripheral side. And there is no space in which an ejector pin and the like can be arranged.

Center core 1 implanted in movable mold 11
2 has a tapered surface 13 which is tapered at the distal end. A tapered surface 13 corresponding to the tapered surface 13 of the center core 12 is formed on the inner peripheral side of the cylindrical inner slide core 14 surrounding the center core 12. Surface 15 is formed.
An annular positioning core 17 surrounding the neck portion 16 of the inner slide core 14 is surrounded by an annular outer slide core 19 that forms a cavity 18 into which the molten resin is injected together with the inner slide core 14. A tapered surface 20 is formed on the outer peripheral side of the outer slide core 19,
A locking ring 22 having a tapered surface 21 corresponding to the tapered surface 20 is provided on a fixed mold 23.

The inner slide core 14 having the molding surface 24 formed on the outer peripheral side includes a first core portion 25 having a short circumference of the molding surface 24 and a second core portion 26 having a long circumference of the molding surface 24. And a plurality of sets are alternately arranged. The intermediate mold 27 movable along the longitudinal direction of the center core 12 with respect to the fixed mold 23 is moved from the molding position shown in FIG. As the center core 12 retreats to the extraction position, FIG.
Are held so as to be able to retreat from the molding position shown in FIG. In the present embodiment, three sets of the first core portion 25 and the second core portion 26 are alternately provided in the intermediate mold 27, but two or four or more sets are provided depending on the dimensions of the cavity 18 and the like. It is also possible.

The molding surface 24 of the inner slide core 14
The outer slide core 19 having a molding surface 28 facing the inner side formed on the inner peripheral side includes a plurality of core pieces 29 (see FIG. 4).
With respect to the core holder 30 on which the positioning core 17 is fitted,
The core holder 30 holds the center core 12 separately from the intermediate die 27 with respect to the fixed die 23 from the molding position shown in FIG. 1 to the die release position shown in FIG. Can be moved along the longitudinal direction of.

The positioning core 17 is not formed in a divided form like the slide cores 14 and 19 described above, but is fitted into the core holder 30 in a completely integrated annular shape. And the outer slide core 19 is positioned between the inner slide core 14 and the locking ring 22 to maintain a constant thickness of the cavity 18 formed between the inner slide core 14 and the inner slide core 14. .

Pin engagement holes 31 and 32 are formed at the base end of the inner slide core 14.
The distal ends of the angular pins 33 implanted in the movable mold 11 are slidably inserted into 1 and 32. In the fitting state of the distal end portion of the angular pin 33 with the pin fitting hole 32 of the second core portion 26 at the molding position, the gap on the radially inner side is set larger than the pin fitting hole 31 of the first core portion 25. When the injection molded product W is removed from the mold, the movable mold 1
1, the first core portion 25 starts retreating inward in the radial direction, and then moves to the second position.
The core section 26 is retracted and moved inward in the radial direction.

Similarly, pin engagement holes 34 are formed in each core piece 29 of the outer slide core 19, and the pin engagement holes 34 are provided with the angular pins 35 implanted in the fixed mold 23. The leading end is slidably inserted, and the core piece 30 of the outer slide core 19 held by the core holder 30 moves along with the core holder 30 retreating from the fixed mold 23 when the injection molded product W is released. It retreats outward in the radial direction.

On the inner peripheral side of the pair of circumferential side wall portions of the first core portion 25 which can contact the circumferential side wall portion of the second core portion 26,
When the first core portion 25 is retracted radially inward to the die-cutting position shown in FIG. 7, an escape portion 36 is formed to increase the amount of the retracted movement. Due to the formation of the escape portion 36, the first portion is formed more easily than when the escape portion 36 is not formed.
The core portion 25 can be further retracted inward in the radial direction, and when the undercut amount S (see FIG. 7) of the undercut portion formed on the inner periphery of the injection molded product W is large, or when the injection diameter is small. Even in the case of the molded product W, the inner slide core 14 can be retreated more inward in the radial direction, so that the injection molded product W can be reliably removed from the inner slide core 14.

The relief 36 does not need to be specially designed, a chamfer having a width of, for example, about 0.3 mm is sufficient, and simple equipment such as a surface grinder can be used. Depending on the case, it is also possible to machine by hand work such as a hand grinder or a diamond tool.

As described above, the tapered surface 1 of the first core portion 25
By forming the relief portions 36 at both ends in the circumferential direction of No. 5, the first core portion 25 and the second core portion 25 can be formed without lowering the strength of the first core portion 25 or adversely affecting other mold components. It is possible to increase the retreat movement amount of the core part 26. For this reason, as shown in FIG. 17, both ends in the circumferential direction of the first core portion 25 at the die release position interfere with each other, and the amount of retreat movement of the second core portion 26 is insufficient, so that the second core portion 26 does not move. It is possible to prevent such a trouble that the injection molded product W cannot be removed.

FIG. 4 shows an appearance of one core piece 29 constituting the outer slide core 19 in this embodiment, and FIG. 5 shows a sectional structure thereof. That is, the pressure sensor 37 is used to detect the pressure of the molten resin injected into the cavity 18.
Is incorporated in a core piece 29, a molten resin is injected from an injection nozzle of a molding machine (not shown) to fill the cavity 18, and a pressure change in a series of steps leading to cooling is detected. The signal is converted to a target signal, transmitted to a recorder 39 via a lead wire 38, and the pressure waveform can be recorded and stored on a recording sheet 40 attached to the recorder 39.

Core piece 29 in which pressure sensor 37 is incorporated
Is mainly composed of a base 41 and a holder 43 integrally fixed to the base 41 via fixing bolts 42. The pressure sensor 37 is connected to the molding surface 2 of the holder 43.
The base 41 is formed with a groove 44 for accommodating the lead wire 38 connected to the pressure sensor 37. The pressure sensor 37 and the holder 43 are provided with a fitting gap of about 0.01 mm. If the fitting gap is too large, the molten resin enters the fitting gap and burrs the injection molded product W. When the fitting gap is too small, a preload is always applied to the pressure sensor 37, and it is difficult to accurately detect the pressure.

The pressure of the molten resin measured by the pressure sensor 37 is approximately 500 kg / cm ^{2 to} 1500 kg /
cm ² , and the tip surface of the pressure sensor 37 is formed on the molding surface 28
Cylindrical bush 45 receiving back pressure so as to be flush with
Is incorporated in the holder 43 and is located between the base 41 and the pressure sensor 37.

The lead wire 38 drawn from the rear end of the pressure sensor 37 passes through the bush 45, is housed in a groove 44 formed in the base 41, and is drawn out of the mold from the rear end of the base 41. Connected to recorder 39. In order to prevent the lead wires 38 accommodated in the grooves 44 from protruding out of the grooves 44, a plurality of holding plates 46 covering the open ends of the grooves 44 are respectively provided on the base 41 via fixing bolts 47. 41. It is preferable to use a polyfluorinated ethylene resin (Teflon manufactured by DuPont) or the like that can withstand a mold temperature of about 100 ° C. as these holding plates 46.

The lead wire 38 is obtained by protecting an extremely thin conductive wire with a resin coating, and has extremely low mechanical strength. However, the injection molding die to which the present invention is applied repeats the closing and opening of the mold for each shot of the molten resin.
It is necessary to repeat forward and backward movement in the radial direction, and to complete the respective operations of closing and opening the mold within 3 to 5 seconds. In such a severe situation, the above-mentioned groove 44 for accommodating the lead wire 38 functions extremely effectively in order to draw the lead wire 38 out of the mold without being damaged.

Lead wire 38 pulled out from base 41
In this embodiment, it is necessary to secure a sufficient bending so as to be able to follow the movement of the core piece 29. In this embodiment, when the core piece 29 retreats to the die release position, the lead wire 38 can be bent. Then, the lead wire holder 48 is placed on the core holder 30.
The lead wire 38 is held via the.

The pressure sensor 37 thus protected
The lead wire 38 can completely follow the opening and closing of the mold and the operation of the outer slide core 19, accurately detect the pressure of the molten resin injected into the cavity 18, and strictly monitor the molding conditions. Thereby, the quality of the injection molded product W can be stabilized.

The order in which the parting surfaces of the mold are opened has a very important meaning for the injection molded product W. Unless the mold is opened in the order intended by the mold designer, not only the mold release failure of the injection molded product W, but also In extreme cases, it can even cause mold destruction. The opening order of the molds is regulated by a mechanism (not shown), and is performed in the following order.

That is, in the molding state shown in FIG.
When the cavity 18 is filled with the molten resin and the cooling is completed, first, as shown in FIG. 6 showing the die-cutting state and FIG. 7 showing the state where the inner slide core 14 is held at the die-cutting position, first, the movable side A gap is formed between the mold 11 and the intermediate mold 27 when the mold 11 starts retreating, and at the same time, the tapered surface 15 of the inner slide core 14 separates from the tapered surface 13 of the center core 12 as the center core 12 retreats.

When the retreat amount of the movable mold 11 reaches a certain level, the angular pin 33 pushes into the pin engaging hole 31 of the first core part 25, and the first core part 25 retreats inward in the radial direction. start. Further, as the retreating movement of the movable mold 11 proceeds, the angular pin 33 is pressed against the pin engaging hole 32 of the second core part 26, and the retreating movement of the second core part 26 inward in the radial direction is started. When the retreat movement amount of the movable mold 11 advances to some extent, the first core portion 25 and the second core portion 26 reach the die-cutting position, and the stopper mechanism (not shown) radially moves the first and second core portions 25 and 26. Further movement inward is constrained. In this way, the die-cutting of the injection-molded product W from the molding surface 24 of the inner slide core 14 is completed.

Thereafter, the core holder 3 is removed from the fixed mold 23.
0, the core piece 29 of the outer slide core 19 starts retreating radially outward through the angular pin 35 attached to the fixed mold 23, and reaches the die-cutting position. Then, the die removal of the injection molded product W from the molding surface 28 of the outer slide core 19 is completed.

Further, from the core holder 30 to the intermediate mold 27
Is retracted, so that the injection-molded product W moves to the positioning core 1.
While being held at 7, the inner slide core 14 is pushed upward, and the injection molded product W is taken out of the mold using an unillustrated auto hand or the like.

When the mold is returned to the molding position shown in FIG. 1 and the molten resin is injected into the cavity again, the procedure is reversed.

In the above-described embodiment, the angular pin type mold has been described. However, the present invention can be applied to a tapering type mold as shown in FIGS. The appearance of the first core portion is shown in FIG. 8, and portions having the same functions as those in the previous embodiment will be denoted by the same reference numerals, and duplicate description will be omitted. That is, a tapered surface 49 corresponding to the tapered surface 108 of the tapered ring 109 shown in FIG. 13 is formed at the lower end of the inner slide core 14, and the movement of the tapered ring 109 along the axis is performed. The clearance is converted into the movement of the inner slide core 14 in the radial direction through the inner surface of the first core portion 25. At the both ends in the circumferential direction of the molding surface 24 of the first core portion 25, relief portions 36 are formed. The amount of evacuation movement to is earned.

[0050]

According to the injection molding die of the present invention, the pair of circumferential side wall portions of the first core portion which can contact the circumferential side wall portion of the second core portion having a large circumferential length of the inner slide core. Since at least the inner peripheral side is provided with a relief portion for increasing the amount of retreat movement when the first core portion is retracted, it is possible to increase the amount of retreat movement of the first core portion compared to the case where there is no relief portion. It is also possible to relatively increase the amount of retreat of the second core portion in accordance with this, and it is a cylindrical injection molded article having a relatively large amount of undercut or a relatively small inner diameter. Also, this can be formed stably without causing a decrease in the strength of the mold.

Further, since the pressure sensor is incorporated in the core piece constituting the outer slide core, the pressure of the molten resin injected into the cavity is constantly monitored even for an injection molded product having a small diameter and a thin cylindrical shape. As a result, the supply state can be accurately grasped, and the molding conditions can be kept constant. Moreover, when a groove for accommodating a lead wire connected to the pressure sensor is provided in the core piece in which the pressure sensor is embedded, the lead wire can be protected without impairing the original function of the mold.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a schematic structure of an embodiment of an injection molding die according to the present invention, showing a state during molding.

FIG. 2 is a perspective view schematically showing an appearance of an inner slide core in the embodiment shown in FIG.

FIG. 3 is a perspective view illustrating an appearance of a first core portion forming a part of the inner slide core illustrated in FIG.

FIG. 4 is a perspective view showing a schematic structure of one core piece of the outer slide core in the embodiment shown in FIG.

FIG. 5 is a sectional view of the core piece shown in FIG. 4;

FIG. 6 is a cross-sectional view showing a schematic structure of an embodiment of an injection mold according to the present invention, and shows a state during die cutting.

FIG. 7 is a plan view of the inner slide core corresponding to FIG. 6;

FIG. 8 is a perspective view illustrating an appearance of another embodiment of the first core portion.

FIG. 9 is a perspective view showing the appearance of a cylindrical injection molded product to which the present invention is applied.

FIG. 10 is a longitudinal sectional view of the injection molded product shown in FIG.

FIG. 11 is a plan view of an inner slide core of a conventional injection mold, showing a state during molding.

FIG. 12 is a plan view of an inner slide core of a conventional injection molding die, showing a state during die cutting.

FIG. 13 is an exploded perspective view of a main part of a conventional injection mold using a taper ring.

FIG. 14 is a plan view corresponding to FIG.

FIG. 15 is a sectional view taken along the line XV-XV in FIG. 14, showing a state during molding.

FIG. 16 is a cross-sectional view corresponding to FIG. 15, showing a state during die cutting.

FIG. 17 is a plan view of an inner slide core of a conventional injection molding die, and shows a state during die cutting.

[Explanation of symbols]

 Reference Signs List 11 movable side mold 12 center core 13 taper surface 14 inner slide core 15 taper surface 16 neck portion 17 positioning core 18 cavity 19 outer slide core 20, 21 taper surface 22 locking ring 23 fixed mold 24 molding surface 25 first core portion 26 second core part 27 intermediate mold 28 molding surface 29 core piece 30 core holder 31, 32 pin engagement hole 33 angular pin 34 pin engagement hole 35 angular pin 36 relief part 37 pressure sensor 38 lead wire 39 recorder 40 recording sheet 41 Base 42 Fixing bolt 43 Holder 44 Groove 45 Bush 46 Pressing plate 47 Fixing bolt 48 Lead wire press 49 Tapered surface W Injection molded product S Undercut amount

Claims (8)

[Claims] 1. A cylindrical inner slide core having a forming surface on an outer peripheral side, and an annular outer slide core having a forming surface on an inner peripheral side of the inner slide core facing the forming surface. An injection molding die for forming a cylindrical injection molded product by injecting a molten resin into a cylindrical cavity formed therebetween, wherein the inner slide core has at least two short arc lengths. A first core portion and at least two second core portions having a long arc length, and the first core portion and the second core portion are alternately arranged in a ring shape; Core driving means for moving the two cores in the radial direction at different timings between the molding position and the die removing position; and a pair of the first cores capable of contacting the circumferential side wall of the second core. At least on the inner peripheral side of the circumferential side wall portion, A mold for injection molding, wherein a relief portion is formed to increase a retreat amount when the first core portion is retreated. 2. The core driving means moves the second core after the first core moves from the molding position to the molding position, and moves the second core from the molding position to the molding position. The injection mold according to claim 1, wherein the first core portion is moved after the operation. 3. A core drive unit further comprising a rod-shaped center core that is in contact with an inner peripheral surface of the inner slide core and holds the inner slide core during molding.
The injection mold according to claim 1 or 2, wherein the center core is moved between a molding position and a die cutting position along a longitudinal direction thereof. 4. An inner peripheral surface of the inner slide core and an outer peripheral surface of the center core have a tapered surface that becomes smaller in diameter toward the molding position with respect to the retracted position of the center core. The injection mold according to any one of claims 1 to 3. 5. The injection mold according to claim 1, wherein the cylindrical injection-molded article has an undercut at least on an inner peripheral surface thereof. 6. The outer slide core includes a plurality of arc-shaped core pieces, is embedded in at least one of the core pieces, and faces the molding surface of the core pieces and is filled in the cavity during molding. 6. The injection mold according to claim 1, further comprising a pressure sensor for detecting a pressure of the molten resin. 7. The injection molding according to claim 6, wherein the core piece in which the pressure sensor is embedded has a groove for accommodating a lead wire connected to the pressure sensor. Mold. 8. A cover plate for covering at least a part of the opening of the groove and preventing the lead wire from coming off from the groove is attached to the core piece in which the pressure sensor is embedded. The injection mold according to claim 7, characterized in that: