JP6950022B2 - Injection molding mold - Google Patents

Description

The present invention relates to an injection molding method for a resin product and an injection molding die.

When forming a resin gear having a through hole at the center of rotation by injection molding, various measures are taken in order to suppress a decrease in the strength of the gear due to a weld line or a decrease in the shape accuracy of the gear. For example, Patent Document 1 discloses an invention in which a nest facing a cavity is rotated by a predetermined angle before the molten resin solidifies to form a weld line along the circumferential direction around the through hole.

Japanese Unexamined Patent Publication No. 7-290512

In the injection molding die described in Patent Document 1, the molten resin immediately after being injected into the cavity is rotated by the rotation of a nest in contact with the resin surface, and a weld line is formed orthogonal to the outer periphery of the gear. Instead, it is formed along the circumferential direction around the through hole. However, depending on the degree of solidification of the molten resin during nesting rotation, it may not be possible to form the weld line as intended. In other words, there is a problem that it is difficult to control the rotation timing of nesting in order to form a weld line as intended.

An object of the present invention is a portion of an injection molding method for forming a resin product having a through hole in the center by injection molding and a portion of the molten resin filled in the cavity corresponding to the through hole of the resin product. By injecting while rotating around the resin product, the weld line is not formed perpendicular to the outer periphery of the resin product, but is formed along the circumferential direction around the through hole.

In the first invention of the present invention, molten resin is injected from a fixed mold into a cavity formed between a movable mold and a fixed mold, and a resin product having a through hole in the center is formed by injection molding. In an injection molding method, a first step of rotating the gate for injecting the molten resin into a cavity, a second step of closing the movable mold with a first pressure with respect to the fixed mold, and the first step. In a state where the gate is rotated and the movable mold is closed by the first pressure with respect to the fixed mold in the second step, around the portion corresponding to the through hole of the resin product. The third step of injecting the molten resin from the gate, and the molten resin injected in a rotating state with respect to the molten resin first injected after the molten resin is first injected into the cavity are said. A fourth step of stopping the rotation of the gate, at least until contact is made around the portion corresponding to the through hole, and the fixed mold in a state where the rotation of the gate is stopped in the fourth step. The fifth step of increasing the mold clamping force of the movable mold to a second pressure higher than the first pressure, and the pressure of the molten resin into the cavity with the mold clamping force increased in the fifth step. Is provided with a sixth step of increasing the pressure to a pressure required for molding the resin product and then maintaining the pressure of the molten resin at a holding pressure until the molten resin hardens in the cavity.

In the first invention, the rotation of the gate can be started after the mold clamping force is set to the first pressure or before the mold clamping force is set to the first pressure. Further, it is desirable that the rotation stop of the gate is performed before or at the same time when the mold clamping force is increased from the first pressure to the second pressure, but the rotation stop of the gate is after the time when the mold clamping force is increased. Even so, there is no problem as long as the time from when the mold clamping force is increased until the gate rotation is stopped is short.

According to the first invention, the molten resin injected into the cavity is injected while rotating around the portion corresponding to the through hole of the resin product. At this time, in order to enable the rotation of the gate that injects the molten resin into the cavity and the molding of the resin product, the mold clamping force that closes the movable mold with respect to the fixed mold is relatively applied when the gate is rotated. The first pressure is a low pressure, and the second pressure is higher than the first pressure after the gate rotation is stopped. Therefore, the weld line is not formed orthogonal to the outer periphery of the resin product, but can be formed along the circumferential direction around the through hole.

In the second invention of the present invention, in the first invention, the first pressure is such that the molten resin injected into the cavity from the gate in the third step does not leak out of the cavity, and the second invention. The gate can be rotated in the step, and the second pressure can suppress burrs of the resin product formed in the cavity while the pressure of the molten resin is increased in the sixth step. It is said to be a degree.

According to the second invention, in order to enable the rotation of the gate for injecting the molten resin into the cavity and to suppress the generation of burrs on the resin product, a mold clamping force for closing the movable mold is applied to the fixed mold. When the gate is rotating, the first pressure is relatively low, and after the gate is stopped rotating, the second pressure is higher than the first pressure. Therefore, the weld line is not formed orthogonal to the outer periphery of the resin product, but can be formed along the circumferential direction around the through hole. Therefore, it is possible to effectively suppress a decrease in the strength of the resin product or a decrease in shape accuracy due to the weld line.

In the third invention of the present invention, molten resin is injected from a fixed mold into a cavity formed between a movable mold and a fixed mold, and a resin product having a through hole in the center is formed by injection molding. A mold for injection molding, comprising a sprue bush having a primary sprue for receiving molten resin from a resin extruder, and a secondary sprue for injecting the molten resin received from the primary sprue into the cavity from the gate. A rotary core that is rotatably supported around a portion corresponding to the through hole in the fixed mold, a rotary drive mechanism that rotationally drives the rotary core, and the movable mold that is closed with respect to the fixed mold. A mold clamping mechanism for molding and molding, and a control device for controlling the operation of the mold clamping mechanism, the resin extrusion device, and the rotation drive mechanism are provided, and the control device operates the rotation drive mechanism to operate the rotation core. By the rotary core rotating means for rotationally driving the mold, the first mold clamping means for operating the mold clamping mechanism to mold the movable mold with the first pressure with respect to the fixed mold, and the first mold clamping means. The primary and secondary sprue from the resin extruder so as to start injection of the molten resin into the cavity in a molded state and during rotation of the rotating core by the rotating core rotating means. The molten resin supply means for supplying the molten resin and the molten resin injected in a rotating state with respect to the molten resin first injected into the cavity after the molten resin is first injected into the through hole. The rotation core stopping means for stopping the rotation of the rotating core and the fixing in a state where the rotation of the rotating core is stopped by the rotating core stopping means at least until contact is performed around the corresponding portion. A second mold clamping means in which the mold clamping force of the movable mold with respect to the mold is a second pressure higher than the first pressure, and the melting in the cavity with the mold clamping force increased by the second mold clamping means. The pressure of the resin is increased to the pressure required for molding the resin product, the pressure of the molten resin is maintained at a holding pressure until the molten resin hardens in the cavity, and the primary and secondary sprues are subjected to the resin extruder. The molten resin supply stopping means for stopping the supply of the molten resin is provided.

In the third invention, the rotation of the rotating core can be started after the mold clamping force is set to the first pressure or before the mold clamping force is set to the first pressure. Further, it is desirable that the rotation of the rotating core is stopped before or at the same time as the mold clamping force is increased from the first pressure to the second pressure, but the rotation of the rotating core is stopped from the time when the mold clamping force is increased. However, there is no problem as long as the time from when the mold clamping force is increased until the rotation of the rotating core is stopped is short.

According to the third invention, the molten resin is injected around the portion corresponding to the through hole of the resin product in the cavity in the state where the rotating core is rotated. At this time, in order to enable the rotation of the gate that injects the molten resin into the cavity and the molding of the resin product, the mold clamping force that closes the movable mold with respect to the fixed mold is relatively applied when the gate is rotated. The first pressure is a low pressure, and the second pressure is higher than the first pressure after the gate rotation is stopped. Therefore, the weld line is stably formed along the circumference of the through hole. Therefore, it is possible to suppress a decrease in the strength of the resin product or a decrease in shape accuracy due to the weld line.

In the fourth aspect of the present invention, in the third invention, the first pressure is such that the molten resin injected into the cavity from the gate in the third step does not leak out of the cavity, and the second invention is described. The gate is set to a degree that can be rotated in the process, and the second pressure is set to a degree that burrs of the resin product formed in the cavity can be suppressed.

According to the fourth invention, in order to enable the rotation of the gate for injecting the molten resin into the cavity and to suppress the generation of burrs on the resin product, a mold clamping force for closing the movable mold is applied to the fixed mold. When the gate is rotating, the first pressure is relatively low, and after the gate is stopped rotating, the second pressure is higher than the first pressure. Therefore, the weld line is not formed orthogonal to the outer periphery of the resin product, but can be formed along the circumferential direction around the through hole.

In the fifth aspect of the present invention, in the third or fourth invention, the rotating core is provided at the end of the rotating core on the sprue bush side, and the molten resin from the primary sprue is used as the secondary sprue. The runner is provided with a runner to be supplied, and the runner has a disk shape so as to coincide with the center line of rotation of the rotating core, and receives the molten resin from the primary sprue at the center of the disk-shaped circle. , The secondary sprue is supplied from the outer peripheral portion of the disk shape.

According to the fifth invention, the disk-shaped runner is provided so that its center line coincides with the rotation center of the rotating core, receives the molten resin from the primary sprue at the position corresponding to the rotation center, and receives the molten resin from the primary sprue, and the outer peripheral portion of the disk shape. Supply the molten resin to the secondary sprue. Therefore, the runner can supply the resin from the primary sprue to the secondary sprue without being affected by the rotation of the rotating core. Then, the molten resin can be injected from the gate at the tip of the secondary sprue around the portion corresponding to the through hole of the resin product in the cavity.

A sixth aspect of the present invention is the third to fifth invention, wherein the through-nesting is provided at the center of the cavity and the rotating core is in contact with the through-nesting. The rotating core is nested on the fixed mold side that defines a part of the fixed mold side of the cavity, and the fixed mold on the outer peripheral side of the rotating core defines the rest of the fixed mold side of the cavity.

According to the sixth invention, the rotating core defines a part of the fixed mold side of the cavity in a state of being in contact with the through nest located at the center of the cavity, and the rest of the fixed mold side of the cavity is the rotating core. It is defined by a fixed mold on the outer peripheral side. Therefore, the cavity-side end of the rotating core is in contact with only the penetration nest and not with other members. Therefore, the frictional resistance during rotation of the rotating core can be suppressed.

It is sectional drawing of the mold for injection molding which is 1st Embodiment of this invention. It is a block diagram of the control device for the said mold for injection molding. It is a front view of the resin gear as a resin product formed by the said mold for injection molding. It is a flowchart which shows the control content of a control device. It is a time chart which shows the control content of a control device. It is explanatory drawing which shows the mode that the molten resin is injected into a cavity in 1st Embodiment. It is explanatory drawing which shows the appearance which the weld line formed in the resin gear as a resin product in 1st Embodiment is seen from above. It is explanatory drawing which shows the state which the same weld line as FIG. 7 was seen from the side (the direction of arrow VIII of FIG. 7). It is explanatory drawing which shows the state when the movable die and the fixed die of the injection molding die are opened. It is sectional drawing corresponding to FIG. 1 of the injection molding die which is 2nd Embodiment of this invention. It is explanatory drawing which shows the mode that the molten resin is injected into a cavity in 2nd Embodiment. It is explanatory drawing which shows the appearance which the weld line formed in the resin gear as a resin product in the 2nd Embodiment was seen from above. It is explanatory drawing which shows the appearance which the same weld line as FIG. 12 was seen from the side (the direction of arrow XIII of FIG. 12).

<Overall configuration of the first embodiment>
FIG. 1 shows an injection molding die according to the first embodiment of the present invention. The injection molding die of the first embodiment is for molding a resin gear P as a resin product by injection molding. The injection molding die includes a movable die 10 and a fixed die 20. Here, since the configurations of the mold drive mechanism and the like other than the movable mold 10 and the fixed mold 20 are the same as those in the prior art, illustration and detailed description thereof will be omitted. In FIG. 1, each direction is indicated by an arrow, and in the following description, the description regarding the direction shall be made with reference to this direction. Here, the injection molding mold is of a type in which the movable mold 10 and the fixed mold 20 are arranged in the vertical direction, but the movable mold 10 and the fixed mold 20 are arranged in the horizontal direction. May be.

<Structure of movable type 10>
The movable mold 10 is mainly composed of a movable side mold plate 11, a movable side receiving plate 12, a spacer block 13, and a movable mounting plate 14, as in the conventional case. The movable side template 11 has a cavity 17a in which the first and second nests 17 and 18 are held at the center in each of the left-right and front-rear directions and faces the parting line PL which is the boundary with the fixed mold 20. Is forming. Here, in order to mold the resin gear P, the outer shape of the resin gear P is formed by the first nest 17, and the second nest (corresponding to the penetration nest of the present invention) 18 penetrates the rotation center of the resin gear P. It forms a hole P1. FIG. 3 shows an enlarged example of the resin gear P formed by injection molding.

Below the cavity 17a, an ejector pin 15 is provided so as to penetrate the first nest 17 and the movable side receiving plate 12 in the vertical direction. The upper end of the ejector pin 15 is positioned so as to face the cavity 17a, and the lower end is fixed to the upper ejector plate 16a and the lower ejector plate 16b. The upper and lower ejector plates 16a and 16b can be moved upward from the position shown in FIG. 1 by an ejector mechanism (not shown) provided below the ejector plates 16a and 16b. When the upper and lower ejector plates 16a and 16b are moved upward by the ejector mechanism, the ejector pin 15 is moved upward and the resin gear P formed in the cavity 17a can be pushed out from the cavity 17a.

<Structure of fixed type 20>
The fixed mold 20 is entirely composed of a fixed side mold plate 21, a fixed side receiving plate 22, a runner slipper plate 23, and a fixed mounting plate 24. A substantially cylindrical rotating core 26, which is a nest that defines a part of the upper surface of the cavity 17a, is rotatably supported on the fixed-side template 21 and the fixed-side receiving plate 22. The outer peripheral side region of the rotating core 26, which is the rest of the upper surface of the cavity 17a and protrudes from the rotating core 26, is defined by the lower surface of the fixed side template 21. The lower surface of the rotating core 26 has a cylindrical center portion, which is the center of rotation thereof, in contact with the second nest 18 so as to be relatively rotatable. Therefore, the lower surface of the rotating core 26 on the outer peripheral side does not come into contact with anything, and the lower surface of the rotating core 26 functions as a nest facing the cavity 17a. Further, bearings 28 are provided at the left, right, front and rear center portions of the fixed side receiving plate 22 on the upper portion of the rotating core 26, and a thrust bearing of the rotating core 26 is configured.

Sprue bushes 25 are provided at the left, right, front, and rear central portions of the upper portion of the rotating core 26 in a state of being in contact with the rotating core 26. In the sprue bush 25, a primary sprue 25a whose center line coincides with the second nest 18 is formed so as to penetrate in the vertical direction. At the upper end of the rotating core 26, a runner 26c, which is a disk-shaped cavity facing the primary sprue 25a, is formed. Further, a secondary sprue 26a is formed by penetrating the rotating core 26 in the vertical direction. In the disk-shaped runner 26c, the center of the disk circle is set to coincide with the center of the hole of the primary sprue 25a. On the other hand, the secondary sprue 26a is arranged so as to correspond to the outer peripheral portion of the runner 26c at the upper end thereof and to the outer peripheral side of the second nest 18 in the cavity 17a at the lower end portion.

When the sprue bush 25 receives the molten resin from the resin extruder 40 in the recess formed in the upper portion thereof, the sprue bush 25 supplies the resin from the primary sprue 25a to the cavity 17a via the runner 26c and the secondary sprue 26a. At the lower end of the secondary sprue 26a, a gate 26d is formed at the end where the molten resin is injected into the cavity 17a. FIG. 1 shows a state in which the resin is supplied to the primary sprue 25a, the runner 26c, and the secondary sprue 26a, and a state in which the resin serving as the resin gear P is injected into the cavity 17a.

<Structure of rotary drive mechanism 30>
A gear 35 is integrally provided on the outer peripheral side of the body of the rotating core 26, and the gear 35 is connected via the gears 34 and 33 so as to be rotationally driven by the output shaft 32 of the geared motor 31. .. The rotating shaft 27 of the gear 34 is rotatably coupled to the fixed-side template 21 and the fixed-side receiving plate 22. Further, the gear 33 is integrally coupled to the output shaft 32. In this way, the rotary core 26 is configured to be rotationally driven by the output shaft 32 of the geared motor 31, and the rotary drive mechanism 30 is configured. Here, the geared motor 31 is used as the power source of the rotary drive mechanism 30, but other drive sources may be used.

<Configuration of control device 60>
As shown in FIG. 2, the movable / fixed type operating device 50, the resin extrusion device 40, and the rotary drive mechanism 30 are configured to be operated and controlled by the control device 60. The control device 60 includes a digital computer. The movable / fixed type operating device 50 controls the mold closing and mold opening operations of the movable type 10 and the fixed type 20 based on the instruction of the control device 60. The movable / fixed type actuating device 50 includes a mold clamping mechanism for adjusting the mold clamping force of the movable mold 10 and the fixed mold 20.

<Action and effect of the first embodiment>
Hereinafter, the operation of the first embodiment based on the control of the control device 60 will be described with reference to the flowchart of FIG. 4 and the time chart of FIG. First, the molten resin is supplied from the resin extruder 40 to the sprue bush 25 in a state where the movable mold 10 and the fixed mold 20 are closed as shown in FIG. As a result, the molten resin is injected and filled into the cavity 17a from the gate 26d via the primary sprue 25a, the runner 26c, and the secondary sprue 26a. At this time, the rotary core 26 is rotationally driven by the geared motor 31 of the rotary drive mechanism 30 in advance, and the molten resin injected into the cavity 17a from the gate 26d at the tip of the secondary sprue 26a is as shown in FIG. The cavity 17a is filled so as to draw an arc centered on the second nest 18.

During this time, in step S1 of FIG. 4, the control device 60 closes the movable mold 10 with respect to the fixed mold 20. This situation is shown in FIG. 5 (A). At the time of T1 in FIG. 5, when the mold closing is completed and it is detected that the movable mold 10 is in contact with the fixed mold 20, step S2 in FIG. 4 is positively determined, and in step S3, the rotary drive is performed. The mechanism 30 is activated. Therefore, as shown in FIG. 5C, the rotating core 26 is rotated at a predetermined rotation speed. Further, in step S4 of FIG. 4, the mold clamping force of the movable mold 10 with respect to the fixed mold 20 is set as the first pressure as shown in FIG. 5 (B). By molding the movable mold 10 with the first pressure with respect to the fixed mold 20, the resin injected into the cavity 17a is prevented from leaking in the resin supply path from the sprue bush 25 to the cavity 17a. On the other hand, the rotating core 26 can be rotated. In this case, the mold clamping force is set to zero at the start of rotation of the rotating core 26. Therefore, the rotational friction at the start of rotation of the rotary core 26 is small, and the rotary core 26 is smoothly started.

After that, in step S5 of FIG. 4, it is determined whether or not the first time T10 has elapsed from the start of rotation of the rotating core 26. At the time of T2 in FIG. 5, when the first time T10 elapses and step S5 in FIG. 4 is positively determined, the resin extruder 40 is operated in step S6, and the cavity is as shown in FIG. 5 (D). The resin pressure in 17a is increased. In step S5, instead of determining whether or not the first time T10 has elapsed, it may be determined whether or not the rotating core 26 is rotating. In that case, if the rotating core 26 is rotating, step S5 is positively determined and the process proceeds to step S6.

FIG. 6 shows a state of the molten resin injected and filled into the cavity 17a from the gate 26d. In the rotation of the rotating core 26, at least the molten resin M injected during the rotation of the rotating core 26 is the first molten resin M injected into the cavity 17a from the gate 26d (shown by the solid line in FIG. 5). It continues until it makes one round around the nest 18 of 2 as shown by an arrow and makes contact (indicated by a virtual line in FIG. 5). Of course, the rotation of the rotating core 26 may be continued until the inside of the cavity 17a is completely filled with the molten resin injected from the gate 26d into the cavity 17a, and up to an appropriate time during this period.

In step S7 of FIG. 4, it is determined whether or not the rotation of the rotating core 26 has rotated by a predetermined amount based on whether or not the second time T11 has elapsed from the time point of T1 of FIG. At the time of T3 in FIG. 5, when the second time T11 elapses and step S7 in FIG. 4 is positively determined, the operation of the rotation drive mechanism 30 is stopped in step S8. In step S7, instead of determining whether or not the second time T11 has elapsed, it may be determined whether or not the rotating core 26 has completed one or more rotations.

In the next step S9, it is determined whether or not the resin pressure by the resin extruder 40 has reached the set pressure as shown in FIG. 5D. At the time of T3 in FIG. 5, when the resin pressure reaches the set pressure and step S9 is positively determined, in step S10, the mold clamping force of the movable mold 10 with respect to the fixed mold 20 is applied as shown in FIG. 5 (B). It is increased from the first pressure to the second pressure. By increasing the mold clamping force in this way, the resin gear P can be molded while suppressing the occurrence of burrs.

In the above description, it has been described that the second time T11 elapses at the time of T3 in FIG. 5, and the resin pressure reaches the set pressure at the same time. However, the time point at which the second time T11 elapses and the time point at which the resin pressure reaches the set pressure may be different. However, as described above, it is desirable that both time points are the same or close to each other, and the process of step S9 can be eliminated. Further, step S7 may be replaced by step S9. The reason why it is desirable that both time points are the same or close to each other is that when the mold clamping force is increased from the first pressure to the second pressure, it becomes difficult to rotate the rotating core 26, so that the mold clamping force increases. At times, it is desirable that the rotation of the rotating core 26 is stopped, or stopped at the same time. Even if the rotation of the rotating core 26 is not stopped when the mold clamping force is increased, it is desirable that the rotation of the rotating core 26 is stopped within a short time after the mold clamping force is increased. This is because the rotating core 26 cannot physically rotate due to the increased mold clamping force, and an overload current flows through the geared motor 31, but this does not pose a big problem for a short time.

In step S11 of FIG. 4, it is determined whether or not the third time T12 has elapsed since the resin pressure by the resin extruder 40 reached the set pressure as shown in FIG. 5 (D) at the time of T3 of FIG. Will be done. When the third time T12 elapses at the time of T4 in FIG. 5 and step S11 is positively determined, in step S12, the resin extrusion operation of the resin extrusion device 40 is stopped, and the resin pressure is maintained at a predetermined holding pressure. Is retained. Therefore, as shown in FIG. 5D, the resin pressure peaks at the time of T4, and is subsequently maintained so as not to fall below the holding pressure. Therefore, the holding pressure is maintained in the resin in the cavity 17a so that voids are not generated in the resin gear P as the resin is cooled. In step S11, instead of determining whether or not the third time T12 has elapsed, it may be determined whether or not the filling of the resin into the cavity 17a is completed.

When the molten resin filled in the cavity 17a solidifies, step S13 in FIG. 4 is positively determined, and in step S14, the movable mold 10 is opened with respect to the fixed mold 20. That is, as shown in FIG. 9, the movable mold 10 and the fixed mold 20 are opened. Then, the ejector pin 15 pushes out the resin gear P as shown by the virtual line, and the resin gear P is taken out as a product. When the fixed mounting plate 24 and the runner slipper plate 23 are separated from the fixed side receiving plate 22 and the runner slipper plate 23 is further separated from the fixed mounting plate 24, the runner resin L solidified in the primary sprue 25a, the runner 26c and the secondary sprue 26a. Is removed from the primary sprue 25a, runner 26c and secondary sprue 26a.

In the flowchart of FIG. 4, step S3 corresponds to the first step of the present invention, steps S1 and S4 correspond to the second step of the present invention, and steps S5 and S6 correspond to the third step of the present invention. However, steps S7 and S8 correspond to the fourth step of the present invention, steps S9 and S10 correspond to the fifth step of the present invention, and steps S11 and S12 correspond to the sixth step of the present invention.

Further, in the flowchart of FIG. 4, step S3 corresponds to the rotating core rotating means of the present invention, steps S1 and S4 correspond to the first mold clamping means of the present invention, and steps S5 and S6 correspond to the first mold clamping means of the present invention. Corresponding to the molten resin supply means, steps S7 and S8 correspond to the rotating core stopping means of the present invention, steps S9 and S10 correspond to the second mold clamping means of the present invention, and steps S11 and S12 correspond to the present invention. Corresponds to the molten resin supply stopping means of the present invention.

The resin gear P thus formed is formed so that the weld line W draws an arc around the through hole P1 formed by the second nest 18, as shown in FIGS. 7 and 8. On the other hand, the weld line W of the prior art in which the molten resin is not injected while rotating in the cavity and is injected while being fixed is orthogonal to the outer circumference of the resin gear P as shown by virtual lines in FIGS. Is formed in. Therefore, according to the above embodiment, the strength of the resin gear P can be increased. Further, according to the embodiment, since the weld line is formed along the outside of the outer shape of the resin gear P, the dimensional accuracy of the shape of the resin gear P can be improved. When a fiber such as carbon fiber is blended with the resin as an additive in order to increase the strength of the resin gear P, the fiber is formed along the weld line, and the above effect becomes more remarkable.

According to the first embodiment, since the molten resin injected into the cavity 17a is supplied so as to draw an arc around the through hole P1, the molten resin after being injected into the cavity 17a is rotated by an external force. Compared with the conventional technique, the weld line can be stably formed so as to draw an arc around the through hole P1. Moreover, in the case of the prior art, since the molten resin that is solidifying is rotated, the rotational load may become unstable and large depending on the progress of solidification of the resin, whereas in the present embodiment, the molten resin is used. Since it is supplied so as to draw an arc around the through hole P1 in the process of injecting into the cavity 17a, it is possible to prevent the rotational load of the rotating core 26 from becoming unstable and large.

According to the first embodiment, the disk-shaped runner 26c is provided corresponding to the rotation center of the rotating core 26, receives the molten resin from the primary sprue 25a at the position corresponding to the rotation center, and receives the molten resin from the primary sprue 25a, and the outer peripheral portion of the disk shape. The molten resin is supplied to the secondary sprue 26a. Therefore, the runner 26c can supply the resin from the primary sprue 25a to the secondary sprue 26a without being affected by the rotation of the rotating core 26. Then, the molten resin can be injected from the gate 26d at the tip of the secondary sprue 26a around the portion corresponding to the through hole P1 of the resin gear P of the cavity 17a.

According to the first embodiment, at the upper end of the rotary core 26, the outer peripheral portion of the rotary core 26 is in contact with the runner slipper plate 23, but at the lower end of the rotary core 26, only the rotation center portion of the rotary core 26 is the first. It is in contact with the nest 18 of 2. Therefore, the contact area with other members at the lower end of the rotating core 26 is suppressed, and the frictional resistance of the rotating core 26 during rotation can be suppressed.

<Second embodiment>
FIG. 10 shows a second embodiment of the present invention. The feature of the second embodiment with respect to the first embodiment is that the number of secondary sprues (26a, 26b) in the rotating core 26 is increased from one to two. The other configurations are the same for both, and the same parts are designated by the same reference numerals, and the description thereof will be omitted again.

In FIG. 10, the secondary sprue 26a has the same configuration as the secondary sprue 26a of FIG. 1 (first embodiment). On the other hand, the secondary sprue 26b is provided at a position symmetrical with the secondary sprue 26a with the rotation center of the rotating core 26 interposed therebetween.

Therefore, the molten resin from the primary sprue 25a is branched into the secondary sprue 26a and 26b by the runner 26c, and is injected into the cavity 17a from the gates 26d and 26e at the lower ends of the secondary sprue 26a and 26b. FIG. 11 shows a state of the molten resin injected from the gates 26d and 26e into the cavity 17a and filled. The rotating core 26 is first injected into the cavity 17a from at least the gates 26d and 26e, and the molten resins M1 and M2 injected during the rotation of the rotating core 26 are second with respect to the filled molten resins M1 and M2. It is rotated about half a circle around the nest 18 until it comes into contact with it. Of course, the rotating core 26 is ejected from the gates 26d and 26e into the cavity 17a, and the cavity 17a is completely filled with the molten resins M1 and M2 to be filled, and the rotating core 26 continues until an appropriate time during this period. It may rotate.

In the second embodiment, the molten resin is injected into the cavity 17a from the two secondary sprues 26a and 26b, but the weld line in the resin gear P is formed so as to draw an arc around the through hole P1. In that respect, it is basically the same as the first embodiment. Therefore, the same actions and effects as those of the first embodiment can be achieved in the second embodiment. 12 and 13 show weld lines W formed on the resin gear P in the second embodiment.

<Other embodiments>
Although the specific embodiments have been described above, the present invention is not limited to their appearance and configuration, and various changes, additions, and deletions can be made. For example, in the above embodiment, the resin gear P is shown as an injection-molded resin product, but various products other than the resin gear P can be manufactured as long as the resin product has a through hole in the center. Further, in the above embodiment, an example in which the number of secondary sprues is one and an example in which the number of secondary sprues is two are shown, but the number may be three or more. Further, in the above embodiment, although the example in which the cavity 17a is formed in the movable side mold plate 11 is shown, the cavity may be formed in the fixed mold side.

10 Movable type 11 Movable side template 12 Movable side receiving plate 13 Spacer block 14 Movable mounting plate 15 Ejector pin 16a Upper ejector plate 16b Lower ejector plate 17 First nest 17a Cavity 18 Second nest (through nest)
20 Fixed type 21 Fixed side template 22 Fixed side receiving plate 23 Lannas slipper plate 24 Fixed mounting plate 25 Sprue bush 25a Primary sprue 26 Rotating core 26a, 26b Secondary sprue 26c Runner 26d, 26e Gate 27 Rotating shaft 28 Bearing 30 Rotating drive Mechanism 31 Geared motor 32 Output shafts 33, 34, 35 Gear 40 Resin extrusion device 50 Movable / fixed type actuator 60 Control device P Resin gear (resin product)
P1 through hole L runner resin M, M1, M2 molten resin W weld line

Claims (3)

An injection molding die that injects molten resin from a fixed mold gate into a cavity formed between a movable mold and a fixed mold to form a resin product with a through hole in the center by injection molding. ,
A sprue bush with a primary sprue that accepts molten resin from a resin extruder,
A rotating core provided with a secondary sprue that ejects the molten resin received from the primary sprue into a cavity from the gate, and is rotatably supported with a portion corresponding to the through hole in the fixed mold as a rotation center. ,
A rotary drive mechanism that rotationally drives the rotary core,
A mold clamping mechanism that closes and clamps the movable mold to the fixed mold,
The mold clamping mechanism, the resin extrusion device, and a control device for controlling the operation of the rotation drive mechanism are provided.
The control device
A rotary core rotating means that operates the rotary drive mechanism to rotationally drive the rotary core,
A first mold clamping means that operates the mold clamping mechanism to mold the movable mold with a first pressure with respect to the fixed mold.
The primary from the resin extruder so as to start injection of the molten resin into the cavity while the rotating core is being molded by the first mold clamping means and during the rotation of the rotating core by the rotating core rotating means. And the molten resin supply means for supplying the molten resin to the secondary sprue,
At least the line from the first injection of the molten resin into the cavity until the molten resin injected in a rotational state with respect to the first injected molten resin comes into contact around the portion corresponding to the through hole. A rotating core stopping means for stopping the rotation of the rotating core in a broken state,
A second mold clamping means that sets the mold clamping force of the movable mold with respect to the fixed mold to a second pressure higher than the first pressure while the rotation of the rotating core is stopped by the rotary core stopping means.
With the mold clamping force increased by the second mold clamping means, the pressure of the molten resin into the cavity is increased to the pressure required for molding the resin product, and the molten resin is further solidified in the cavity. A molten resin supply stopping means for maintaining the pressure of the molten resin at a holding pressure and stopping the supply of the molten resin to the primary and secondary sprues by the resin extruder is provided.
At the center of the cavity, a through nested to form the through hole,
In a state where the rotating core is in contact with the penetrating nest, the rotating core is a nest on the fixed mold side that defines a part of the fixed mold side of the cavity, and the fixed mold on the outer peripheral side of the rotating core is formed. An injection mold that defines the rest of the cavity on the fixed mold side. In claim 1 ,
The first pressure is such that the molten resin ejected from the gate into the cavity by the molten resin supply means does not leak out of the cavity, and the gate can be rotated by the rotating core rotating means. ,
The second pressure is an injection molding die whose degree is such that burrs of the resin product molded in the cavity can be suppressed. In claim 1 or 2 ,
The rotating core is provided at the end of the rotating core on the sprue bush side, and includes a runner that supplies the molten resin from the primary sprue to the secondary sprue.
The runner has a disk shape so that the center line of rotation of the rotating core coincides with the center line. The molten resin from the primary sprue is received at the center of the disk-shaped circle, and the outer circumference of the disk shape is received. A mold for injection molding that is supplied from the part to the secondary sprue.

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