JP2015003499A - Injection molding die and method for manufacturing resin molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an injection molding die capable of advantageously manufacturing a resin molding which is advantageously prevented from generation of a weld line and whose gate mark is made into a small size not requiring finishing processing.SOLUTION: A plurality of pores 76 communicating one end in an axial direction of a ring runner 58, formed of a cylindrical space into which a molten resin injected from an injection device is introduced, with a cavity 42 for molding a resin molding are provided between the cavity 42 and the ring runner 58 so as to be located with a distance from each other in a circumferential direction of the ring runner 58. A plurality of gates 74 are formed by the plurality of pores 76.

Description

  The present invention relates to an injection mold and a method for producing a resin molded product, and in particular, an improvement of an injection mold suitably used for injection molding a resin molded product having a cylindrical portion or a deep hole, The present invention relates to a method of advantageously producing such a resin molded product by injection molding.

  Conventionally, an injection molding technique is known as a kind of manufacturing method of resin molded products, and is used for manufacturing many types of resin molded products. When manufacturing a resin molded product using this injection molding technique, a cavity (molding cavity) for molding the resin molded product, a runner for guiding the molten resin injected from the injection device, and the runner into the cavity A so-called injection mold having a gate that communicates with the injection mold is used, but the quality of the finally obtained resin molded product greatly depends on how the gate is set for the injection mold.

  That is, for example, in the production of a resin molded product having a cylindrical portion, a deep hole, etc., among the cavities formed in the injection mold, a cavity portion comprising a cylindrical space that provides the cylindrical portion and the side wall portion of the hole portion When a porous gate is set only at one location on the circumference of the resin, the molten resin that has flowed into the cavity through such a gate passes through the cavity portion formed by the cylindrical space in both circumferential directions. It flows and joins in such a cavity part. For this reason, in the tube part of the resin molded product finally obtained and the side wall part of the hole part, a weld line is generated in a part where the flow of the molten resin is merged, resulting in a poor appearance.

  Under such circumstances, for example, Japanese Patent Application Laid-Open No. 59-143622 (Patent Document 1) discloses a cylindrical resin molding manufactured as a kind of injection mold used for manufacturing a cylindrical resin molded product. An injection mold that has been devised to prevent generation of weld lines in the product has been clarified. This injection mold has a ring runner composed of a cylindrical space for guiding a molten resin, and one end in the axial direction of the ring runner is communicated with a cavity composed of a cylindrical space through an annular ring gate. ing. In such an injection mold, the molten resin flows in the axial direction in the ring runner and is introduced into the cylindrical cavity through the ring gate so that the entire inside of the cavity flows in the axial direction. become. As a result, it is advantageously prevented that the molten resin flows in the circumferential direction in the cylindrical cavity and merges in the cavity. As a result, the weld in the resin molded product finally obtained is prevented. The generation of lines is effectively prevented.

  However, the conventional injection mold having such a ring gate has the following problems due to its structure.

  That is, in such a conventional injection mold, the solidified product obtained by solidifying the molten resin remaining in the ring gate is formed into a ring shape or a cylindrical shape corresponding to the ring gate when the target resin molded product is molded. On the other hand, in an injection mold having only one pore-shaped gate, the solidified material in the gate has a pin shape. For this reason, when a resin molded product is obtained using a conventional injection mold having a ring gate, the solidified material in the ring gate is cut by mold opening after the molding of the resin molded product, and the product is put into the ring runner. Compared to the case of using an injection mold having a pore-shaped gate, the cut marks remaining on the resin molded product when the remaining solidified solidified resin is separated from the resin molded product. It could be large and unsightly. Therefore, when a conventional injection mold having a ring gate is used, it is necessary to finish the resin molded product to remove the gate mark or make it beautiful after the resin molded product is molded. In such a case, an extra labor burden or an economic burden is imposed on the production of the resin molded product.

JP 59-143622 A

  Here, the present invention has been made in the background of the above-described circumstances, and the problem to be solved is to effectively prevent the occurrence of weld lines in the molded resin molded product. Another object of the present invention is to provide an injection mold in which the gate mark can be made small and beautiful to the extent that finishing processing is not necessary. In addition, the present invention provides a method capable of advantageously producing a resin molded product in which generation of a weld line is effectively prevented, and the gate mark is small and beautiful enough not to require finishing. Doing it is also a problem to be solved.

  And in order to solve this problem, the present invention provides (a) a cavity for molding a resin molded product, and (b) a ring runner comprising a cylindrical space for guiding the molten resin injected from the injection device, (C) a plurality of gates which are configured by a plurality of pores communicating with one end in the axial direction of the ring runner and the cavity, and are spaced apart from each other in the circumferential direction of the ring runner; An injection mold characterized in that the molten resin guided by the ring runner is introduced into the cavity from the ring runner through the plurality of gates. Is.

  According to one of the preferred embodiments of the present invention, an annular or cylindrical communication hole that connects the one end in the axial direction of the ring runner and the cavity to each other is provided with the ring runner. The inner surface is provided so as to be positioned coaxially and protrudes from one inner surface portion of the two inner surface portions facing each other in the direction perpendicular to the axis of the communication hole toward the other inner surface portion. The plurality of protrusions that contact the part are disposed in the communication hole so as to be spaced apart from each other in the circumferential direction of the communication hole, thereby adjacent to the circumferential direction of the plurality of protrusions. The pores are respectively provided between the plurality of pores, and the plurality of pores constitute the plurality of gates.

  According to one of the desirable aspects of the present invention, the opening area of the opening on the cavity side in the gate is made smaller than the opening area of the opening on the ring runner side.

  Then, the present invention uses the injection mold having the above-described features to inject molten resin from an injection apparatus and fill the cavity with the molten resin through the ring runner and the plurality of gates. A gist of a method for producing a resin molded product characterized by performing a molding operation is also provided.

  That is, according to the injection mold according to the present invention, the molten resin that has flowed in the axial direction in the ring runner formed of the cylindrical space is introduced into the cavity all at once through the plurality of gates arranged in the circumferential direction of the ring runner. Will come to be. Therefore, even if such a cavity has a cylindrical shape, for example, unlike the case where the molten resin is introduced from one place on the circumference of such a cylindrical cavity, the molten resin is contained in the cavity. Joining is prevented as much as possible, and as a result, generation of weld lines in the finally obtained resin molded product can be effectively prevented.

  Moreover, in the injection mold according to the present invention, the plurality of gates for introducing the molten resin from the ring runner into the cavity are constituted by a plurality of pores arranged at intervals in the circumferential direction of the ring runner. Has been. For this reason, the resin molded product molded using such an injection mold has a pin shape in which the molten resin remaining in each gate is solidified with respect to the solidified product of the molten resin remaining in the ring runner. It will be in the state connected via the some solidified thing to exhibit. Therefore, when the injection mold according to the present invention is used, for example, compared with the case of using an injection mold having a conventional ring gate in which a solidified product having a ring shape or a cylindrical shape is formed in the gate. The gate mark remaining on the resin molded product after cutting off the excess solidified material in the runner and the gate can be made sufficiently small and beautiful. Accordingly, it is possible to advantageously omit the finishing process for removing such a gate mark or making it beautiful from a series of manufacturing steps of the resin molded product.

  Therefore, in the injection mold according to the present invention as described above, it is possible not only to effectively prevent the occurrence of weld lines in the molded resin molded product, but also to make the gate mark small enough not to require finishing. And you can do it beautifully. As a result, it is possible to effectively improve the productivity of the target resin molded product and reduce the manufacturing cost.

  And, in the method for producing a resin molded product according to the present invention, the occurrence of a weld line is effectively prevented, and the resin molded product is small and beautiful so that the gate mark does not require finishing. Can be obtained very advantageously. As a result, it is possible to effectively improve the productivity of the target resin molded product and reduce the manufacturing cost.

It is sectional explanatory drawing which shows an example of the resin molded product manufactured using the injection mold which has a structure according to this invention. It is II arrow explanatory drawing in FIG. It is a section explanatory view showing one embodiment of an injection mold which has a structure according to the present invention in a mold opening state. FIG. 4 is a cross-sectional explanatory view showing the injection mold shown in FIG. 3 in a closed state. It is the elements on larger scale in the VV cross section of FIG. FIG. 5 is a partially enlarged explanatory view of FIG. 4. It is VII-VII cross-sectional explanatory drawing of FIG. It is explanatory drawing which shows one process example at the time of manufacturing the resin molded product shown by FIG. 1 using the injection mold shown by FIG.3 and FIG.4. It is explanatory drawing which shows the process example implemented following the process shown by FIG. It is a figure corresponding to FIG. 3 which shows the mold open state of another embodiment of the injection mold which has a structure according to this invention. FIG. 11 is a view corresponding to FIG. 4, illustrating a closed state of the injection mold illustrated in FIG. 10. It is the elements on larger scale in the XII-XII cross section of the injection mold shown by FIG. FIG. 12 is a partially enlarged explanatory view of FIG. 11. It is XIV-XIV sectional explanatory drawing of FIG. It is explanatory drawing which shows one process example at the time of manufacturing the resin molded product shown by FIG. 1 using the injection mold shown by FIG.10 and FIG.11. FIG. 16 is an explanatory diagram illustrating a process example performed subsequent to the process illustrated in FIG. 15.

  Hereinafter, in order to clarify the present invention more specifically, embodiments of the present invention will be described in detail with reference to the drawings.

  First, in FIG. 1 and FIG. 2, an example of a resin molded product injection-molded using an injection mold having a structure according to the present invention is shown in its cross-sectional form and top form. As is clear from FIGS. 1 and 2, the resin molded product 10 has an outer cylindrical portion 12. In addition, a disc-shaped partition wall 14 is integrally formed at the axially intermediate portion of the inner peripheral surface of the outer cylindrical portion 12 so as to partition the inner hole of the outer cylindrical portion 12 into two in the axial direction. ing. Furthermore, the inner cylindrical portion 16 is coaxially directed toward the opening on the one axial side of the outer cylindrical portion 12 at the center of one surface in the thickness direction of the disk-shaped partition wall portion 14. It is erected integrally so as to extend. The inner cylindrical portion 16 has an outer diameter smaller than the inner diameter of the outer cylindrical portion 12 and a height less than half the height of the outer cylindrical portion 12. In addition, a plurality of (here, 12) gate marks (gate marks) 17 are arranged on the front end surface of the inner cylindrical portion 16 at equal intervals in the circumferential direction on the inner peripheral portion thereof. It is formed with. In the following, for convenience, the side where the inner cylindrical portion 16 of the partition wall portion 14 in the resin molded product 10 is formed is referred to as the upper side, and the opposite side is referred to as the lower side.

  The resin molded product 10 having such a structure is advantageously manufactured by performing injection molding using an injection mold having a structure according to the present invention.

  3 and 4, an embodiment of an injection mold having a structure according to the present invention used for manufacturing a resin molded product 10 includes a longitudinal sectional form in a mold open state and a cross section in a mold closed state. The form is shown respectively. As is clear from FIGS. 3 and 4, the injection mold 18 of the present embodiment has a fixed mold 20 and a movable mold 22 disposed opposite to the fixed mold 20 below. Yes.

  More specifically, the fixed mold 20 has a rectangular block shape as a whole, and is fixed to the fixed platen via the fixed mold side mounting plate 24 on the upper surface opposite to the side facing the movable mold 22. 26 is attached. Thereby, the fixed mold 20 is fixedly arranged above the movable mold 22.

  A cavity forming recess 28 is provided at the center of the lower surface of the fixed mold 20 that faces the movable mold 22. At the center of the bottom surface of the cavity forming recess 28, a cylindrical protrusion 30 is integrally protruded having a height that is less than half the depth of the cavity forming recess 28. In addition, a cylindrical central protrusion 32 having a low height is integrally formed at the center of the cylindrical protrusion 30, and the tip surface of the cylindrical protrusion 30, that is, around the central protrusion 32, that is, An annular recess 34 that opens on the lower surface of the fixed mold 20 is provided.

  And while the inner peripheral surface shape of such cavity formation recess 28 is made into the cylindrical shape corresponding to the outer peripheral surface of the outer cylindrical part 12 in the resin molded product 10, the shape of the outer peripheral surface of the columnar protrusion 30 is The shape of the front end surface is a cylindrical shape corresponding to the inner peripheral surface portion located above the partition wall portion 14 of the outer cylindrical portion 12 and an annular surface shape corresponding to the upper surface of the partition wall portion 14. . Further, the shape of the annular recess 34 is a cylindrical shape corresponding to the inner cylindrical portion 16 of the resin molded product 10. Thus, the inner surface shape of the cavity forming recess 28 including the annular recess 34 is the outer peripheral surface shape of the entire resin molded product 10 and the inner shape of the resin molded product 10 above the partition wall portion 14. It is a shape corresponding to.

  On the other hand, the movable mold 22 as a whole has a rectangular block shape similar to that of the fixed mold 20, and is formed on the movable platen 38 via the movable mold-side mounting plate 36 on the lower surface opposite to the fixed mold 20. It is attached. The movable plate 38 is provided with a ram (not shown) of a hydraulic cylinder included in a mold clamping device (not shown) on the lower surface thereof, and is movable in the vertical direction by a projecting or retracting operation of the ram. . As the movable platen 38 moves up and down, the movable mold 22 moves toward or away from the fixed mold 20 fixedly disposed above, so that the movable mold 22 and the fixed mold 20 are moved. The mold is closed and opened. Further, when the movable mold 22 and the fixed mold 20 are opened, the fixed mold 20 and the fixed mold side mounting plate 24 are configured to be separated in the vertical direction by a known structure.

  A cavity forming protrusion 40 is integrally formed at the center of the upper surface of the movable die 22 which is the surface facing the fixed die 20. The cavity forming protrusion 40 has a circular tip surface corresponding to the lower surface of the partition wall portion 14 in the target resin molded product 10 and an inner peripheral surface located below the partition wall portion 14 of the outer cylindrical portion 12. A cylindrical outer peripheral surface corresponding to the portion. Thus, the outer surface shape of the cavity forming protrusion 40 is a shape corresponding to the inner shape below the partition wall portion 14 in the resin molded product 10 (outer cylindrical portion 12).

  As shown in FIG. 4, when the movable mold 22 and the fixed mold 20 are closed, the cavity forming protrusion 40 of the movable mold 22 is plunged into the cavity forming recess 28 of the fixed mold 20. It has become so. As a result, a molding cavity 42 having a shape corresponding to the target resin molded product 10 is formed between the movable mold 22 and the fixed mold 20 under the closed state of the movable mold 22 and the fixed mold 20. It is supposed to be done.

  In the injection mold 18, an insertion hole 44 is provided in one end side portion (left side portion in FIG. 4) in the length direction of the fixed plate 26 and the fixed die side mounting plate 24 in the thickness direction. It has been. A sprue bushing 46 is inserted into the insertion hole 44. One end surface of the sprue bushing 46 in the axial direction is a nozzle touch surface 50 which is a contact surface of the tip surface of the nozzle 48 of the injection device. Further, such a sprue bushing 46 is provided with a sprue 52 extending in the axial direction. The sprue 52 is open at the center of the nozzle touch surface 50 of the sprue bushing 46, and can thereby communicate with a nozzle hole (not shown) of the nozzle 48 disposed in contact with the nozzle touch surface 50. ing.

  On the other hand, the fixed mold 20 is provided with a runner 54 that guides molten resin injected from the nozzle 48 and flowing through the sprue 52 into the molding cavity 42. In this embodiment, the runner 54 communicates with the sprue 52 and extends straightly in the horizontal direction. The ring runner includes a cylindrical space that communicates with the straight runner portion 56 and extends in the vertical direction. Part 58.

  More specifically, in the injection mold 18 of the present embodiment, a central hole 60 that is open on the upper surface overlapping the fixed mold side mounting plate 24 is provided at the center of the fixed mold 20. The center hole 60 has an elongated cylindrical shape as a whole, and an inner peripheral surface on the center side of the annular recess 34 provided at the center of the lower surface of the fixed mold 20 (the center of the tip surface of the columnar protrusion 30). A diameter smaller than the diameter of the inner peripheral surface portion which is larger than the diameter of the portion and which is radially opposed to the inner peripheral surface portion on the center side of the annular recess 34, and a bottom surface near the bottom surface of the annular recess 34. Has a depth at which can be located.

  Further, as shown in FIG. 4, a through hole 62 is formed in the center portion of the fixed mold side mounting plate 24 and the center portion of the stationary platen 26 so as to penetrate them in the thickness direction. The through-hole 62 has a cylindrical inner peripheral surface having a diameter smaller than the inner diameter of the center hole 60 provided in the fixed mold 20, communicated with the center hole 60 and positioned coaxially. ing.

  A core pin 64 is inserted and disposed in the through hole 62 and the center hole 60 that are positioned coaxially so as to extend in the vertical direction. The core pin 64 is made of a metal rod having a length in the axial direction that is slightly shorter than the total extension length of the through hole 62 and the center hole 60.

  In the core pin 64, the outer diameter of the upper portion inserted and disposed in the through hole 62 is substantially the same as the inner diameter of the through hole 62, while the lower portion inserted and disposed in the center hole 60. The outer diameter of the side portion is set to be slightly smaller than the inner diameter of the center hole 60. Thereby, the outer peripheral surface of the upper part of the core pin 64 and the inner peripheral surface of the through hole 62 are in close contact with each other. A cylindrical space extending in the vertical direction is formed between the outer peripheral surface of the lower portion of the core pin 64 and the inner peripheral surface of the center hole 60.

  Thus, in the injection mold 18 of this embodiment, the ring runner portion 58 is provided in the center hole 60 between the outer peripheral surface of the lower portion of the core pin 64 and the inner peripheral surface of the center hole 60. It is formed by space. As described above, the ring runner portion 58 has the inside surface of the through hole 62 in close contact with the outer peripheral surface of the insertion portion of the core pin 64 into the through hole 62 and the inner peripheral surface of the through hole 62. Is not communicated.

  Here, a gap formed by a disk-shaped space communicating with the ring runner portion 58 is formed between the tip surface of the core pin 64 and the bottom surface of the center hole 60. In addition, a step portion 66 is provided on the upper end side portion of the core pin 64 so that the upper end portion has a larger diameter than the other portions. The step portion 66 is an annular ring provided on the inner peripheral surface of the through hole 62. The planar engaging surface 68 is engaged in the vertical direction. Accordingly, the insertion positions of the core pin 64 into the through hole 62 and the center hole 60 are positioned.

  As shown in FIGS. 4 and 5, a groove 70 having a rectangular cross section is formed on the upper surface of the fixed mold 20 between the position corresponding to the sprue 52 of the sprue bushing 46 in the fixed mold 20 and the center hole 60. In addition, it is formed so as to extend straight in the horizontal direction. In the groove portion 70, an opening portion opened on the upper surface of the fixed mold 20 is covered with a fixed mold side mounting plate 24. Thereby, with respect to the fixed mold | type 20, the straight runner part 56 is formed of the inner space of the groove part 70 covered with the solid mold | type side attachment plate 24 and extended in a horizontal direction.

  Such a straight runner portion 56 communicates with the sprue 52 of the sprue bushing 46 at one end portion in the extending direction. Further, the other end is a connection port 72 that opens into the center hole 60, and the straight runner portion 56 is formed in the center hole 60 and further in the center hole 60 by the connection port 72. The ring runner 58 is connected so as to communicate with it.

  Thus, in the injection mold 18 of the present embodiment, the molten resin that is injected from the nozzle 48 of the injection device and circulates in the sprue 52 is introduced into the straight runner portion 56, and the inside of the straight runner portion 56 is also introduced. It circulates and is guided in the horizontal direction toward the center of the fixed mold 20. Further, the molten resin flowing in the straight runner portion 56 is introduced into the ring runner portion 58 through the connection port 72 and is allowed to flow downward in the ring runner portion 58.

  As shown in FIGS. 6 and 7, in the injection mold 18 of the present embodiment, the ring runner portion 58 and the gate 74 communicating with the molding cavity 42 at the lower end side portion are connected to the fixed mold 20. On the other hand, a plurality (here, 12) are provided.

  More specifically, a plurality of communication holes 76 (here, the communication holes 76 communicating with each other in the center hole 60 and the annular recess 34) extend in the vertical direction in the center of the fixed mold 20. 12). The communication hole 76 is a fine hole having a sufficiently smaller inner diameter than the center hole 60 and the through hole 62. In addition, the communication hole 76 has a tapered inner peripheral surface that gradually decreases in diameter toward the lower side, a large-diameter upper opening that opens at the bottom surface of the center hole 60, and the annular recess 34. It has a small-diameter lower opening that opens at the bottom.

  Here, the gate 74 is constituted by such a communication hole 76, and a plurality of the gates 74 are formed between the central hole 60 and the annular recess 34. It arrange | positions along with the predetermined interval in the circumferential direction of the annular recess 34, and is arrange | positioned. Further, among the openings on both sides in the axial direction of the plurality of gates 74, upper openings (openings on one end side in the axial direction) that open at the bottom of the center hole 60 are arranged on the outer periphery of the bottom of the center hole 60. On the other hand, lower openings (openings on the other end side in the axial direction) of the plurality of gates 74 that open on the bottom surface of the annular recess 34 are respectively disposed on the inner peripheral portion of the bottom surface of the annular recess 34. Yes.

  Thus, in the injection mold 18 of the present embodiment, the ring runner portion 58 provided on the outer peripheral side in the center hole 60 and the molding cavity 42 formed including the annular recess 34 include a plurality of gates 74. Communicate with each other. As a result, the molten resin that flows downward in the ring runner portion 58 is introduced into the molding cavity 42 through the plurality of gates 74. In addition, here, since each of the gates 74 has a tapered inner peripheral surface that gradually decreases in diameter downward, the opening area of the lower opening that opens into the molding cavity 42 of each gate 74 However, the opening area of the upper opening that opens into the ring runner 58 is made smaller.

  And when manufacturing the target resin molded product 10 using the injection mold 18 having such a structure, the operation is advanced according to the following procedure, for example.

  That is, first, as shown in FIG. 4, the movable mold 22 and the fixed mold 20 of the injection mold 18 are closed, and a molding cavity 42 is formed between the movable mold 22 and the fixed mold 20. .

  Next, as shown in FIG. 8, the molten resin 78 injected from the injection device (not shown) is caused to flow into the sprue 52 from the nozzle 48 and further into the straight runner portion 56. Then, after the molten resin 78 is circulated in the straight runner portion 56 and the ring runner portion 58, the molten resin 78 is caused to flow into the molding cavity 42 through the plurality of gates 74, and the inside of the molding cavity 42 is made into the molten resin 78. Fill.

  At this time, the molten resin 78 forms the inner cylindrical portion 16 from the entire circumference of the inner peripheral portion of the molding cavity 42 that forms the upper end surface of the inner cylindrical portion 16 of the target resin molded product 10. It flows into the molding cavity 42 portion. Then, after the inside of the molding cavity 42 flows in the axial direction of the inner cylindrical portion 16, the inside of the molding cavity 42 forming the annular plate-like partition wall portion 14 is changed from the center side to the outer peripheral side. It flows toward. Thereafter, the gas flows into the molding cavity 42 forming the outer cylindrical portion 12, and flows in the molding cavity 42 in the axial direction. Therefore, it can be advantageously avoided that a joining point of the molten resin 78 occurs in the molding cavity 42.

  Then, as shown in FIG. 9, after the molten resin 78 filled in the molding cavity 42 is cooled and solidified, the movable mold 22 and the fixed mold 20 are opened. At this time, the resin molded product 10 formed by solidifying the molten resin 78 in the molding cavity 42 is held by the cavity forming protrusion 40 of the movable mold 22. Thereby, the resin molded product 10 is released from the fixed mold 20.

  Further, when the resin molded product 10 is released from the fixed mold 20 by opening the movable mold 22 and the fixed mold 20, a plurality of gates 74, runners 54 (straight runner portion 56 and ring runner portion 58), and sprue. The solidified material 79 in which the molten resin 78 remaining in each of the solidified materials 52 is solidified is cut at the portion of the solidified material 79 located in the lower opening of each gate 74 formed of pores, and is separated from the resin molded product 10.

  As described above, the lower opening of each gate 74 has a smaller opening area than the upper opening. Therefore, the portion of the solidified material 79 positioned in the lower opening of each gate 74 is the smallest in cross-sectional area of the entire solidified material 79, and thereby, of the entire solidified material 79. The most fragile part (the part with the lowest tensile strength). In addition, the solidified material 79 portion is equally arranged on the inner peripheral portion of the upper surface of the inner cylindrical portion 16 in the resin molded product 10 at equal intervals in the circumferential direction corresponding to the arrangement positions of the plurality of gates 74. Has been.

  For this reason, when the movable pair 22 and the fixed mold 20 are opened, the solidified product 79 is more easily cut from the resin molded product 10. In addition, a plurality (here, a plurality of traces of solidified material 82 inevitably formed on the inner peripheral portion of the upper end surface of the inner cylindrical portion 16 in the resin molded product 10 from which the solidified material 79 is separated. 12) gate marks 17 (see FIG. 2) are sufficiently smaller than, for example, a gate mark generated when an injection mold having a conventional ring gate is used, and are less noticeable and more beautiful. .

  When the movable mold 22 and the fixed mold 20 are opened, the resin molded product 10 is ejected from the movable mold 22 by an ejector mechanism (not shown) having an ejector pin provided on the movable mold 22 and separated. Mold. Thus, the intended resin molded product 10 having the structure shown in FIGS. 1 and 2 is obtained. Although not shown, when the movable mold 22 and the fixed mold 20 are opened, the fixed mold 20 is separated from the fixed mold side mounting plate 24 by a known structure, and a plurality of gates 74 are provided under this state. The excess solidified material 79 solidified in the runner 54 and the sprue 52 is detached from the fixed mold 20 and the sprue bushing 46 by an ejector mechanism or the like (not shown).

  As is apparent from the above description, the use of the injection mold 18 of the present embodiment advantageously eliminates the occurrence of a joining point of the molten resin 78 in the molding cavity 42 into which the molten resin 78 flows and flows. The As a result, the resin molded product 10 having a good appearance and no weld line can be more reliably manufactured.

  Moreover, if the injection mold 18 of the present embodiment is used, the gate mark 17 inevitably remaining in the molded resin molded product 10 can be made sufficiently small to make it inconspicuous and beautiful. As a result, the finishing process for removing the traces of the gate mark 17 from the resin molded product can be advantageously omitted from a series of manufacturing steps of the resin molded product 10, and as a result, the production of the resin molded product 10 can be performed. The improvement of the property and the reduction of the manufacturing cost can be effectively realized.

  Further, in the injection mold 18 of the present embodiment, the ring runner portion 58 is configured in a cylindrical space and is connected to the straight runner portion 56 at the upper end portion opposite to the lower end portions communicating with the plurality of gates 74. Connected through the mouth 72. Therefore, for example, unlike the case where the ring runner portion 58 has an annular shape, the molten resin 78 flowing in from the connection port 72 has sufficiently spread over the entire ring runner portion 58 before the ring runner portion 58. The molten resin 78 therein is introduced into the molding cavity 42 through a plurality of gates 74. As a result, the amount of molten resin 78 introduced from the ring runner portion 58 into the molding cavity 42 through the plurality of gates 74 is made to be a substantially uniform amount for each gate 74. Generation of a weld line in the case can be effectively prevented. In addition, since the ring runner portion 58 is configured in a cylindrical space, the structural strength of the ring runner portion 58 is increased as compared with a case where the ring runner portion 58 is formed in an annular shape. Further, since the volume of the solidified product 79 portion located in the ring runner portion 58 is larger than the case where the ring runner portion 58 has an annular shape, the volume shrinkage of the solidified product 79 portion also increases. Thus, such a solidified part 79 is surely peeled off from the inner peripheral surface of the center hole 60. Thereby, when the solidified product 79 is separated from the fixed mold 20, it is advantageously prevented that a part of the solidified product 79 remains in the ring runner portion 58. As a result, the remaining part of the solidified material 79 in the ring runner portion 58 prevents the smooth flow of the molten resin 78 in the ring runner portion 58 at the next injection molding, resulting in molding defects. Such a thing can be prevented very effectively.

  Furthermore, the resin molded product 10 molded using the injection mold 18 of the present embodiment is, for example, as a piston head in a pressure regulating reservoir used in a vehicle brake device that performs ABS control (anti-skid control). It is advantageously used. As described above, by using the resin molded product 10 molded using the injection mold 18 of the present embodiment, the pressure regulating reservoir, and hence the brake device can be reduced in weight and cost. This can be achieved very effectively compared to the one using a metal piston head.

  Next, FIG. 10 and FIG. 11 show another embodiment of an injection mold having a structure according to the present invention, which is used for manufacturing a resin molded article 10, and shows a longitudinal sectional form in a mold open state and a mold closed state. It is shown in the sectional form in the state. As is apparent from FIGS. 10 and 11, the injection mold 80 of the present embodiment includes the fixed mold 20 and the movable mold 22, and has the same basic features as the injection mold 18 according to the first embodiment. It has a structure. In the injection mold 80, the ring runner portion 58 and the plurality of gates 74 are provided with a structure different from that of the injection mold 18 according to the first embodiment. In addition, regarding the injection mold 80 of the present embodiment, members and parts having the same structure as the injection mold 18 according to the first embodiment are denoted by the same reference numerals as in FIGS. Detailed description thereof will be omitted.

  That is, in the injection mold 80 of the present embodiment, the first through hole 82 is provided in the center of the fixed mold 20. The first through hole 82 has a stepped cylindrical inner peripheral surface whose upper side is larger in diameter than the lower side. As a result, the upper portion of the first through hole 82 is a large-diameter hole portion 84 that opens on the upper surface of the fixed mold 20, while the lower portion thereof has a small diameter that opens into the cavity forming recess 28. It is a hole 86. The small-diameter hole portion 86 constitutes a part of the molding cavity 42, specifically, a molding cavity 42 portion that gives the inner cylindrical portion 16 of the resin molded product 10. Thus, the opening on the lower side (small diameter hole 86 side) of the large diameter hole portion 84 communicates with the molding cavity 42.

  Further, the ring runner portion forming bush 88 extends in the up-down direction in the large-diameter hole portion 84 of the first through-hole 82 with its outer peripheral surface being in close contact with the inner peripheral surface of the large-diameter hole portion 84. Is placed in the insert. This ring runner portion forming bush 88 has substantially the same height as the extended length of the large-diameter hole portion 84. Further, in the ring runner portion forming bush 88, the inner peripheral surface 91 of the inner hole 90 is formed into a tapered surface shape that gradually becomes smaller in diameter toward the lower side, and the diameter of the lower opening portion of the smaller diameter is increased. The first through-hole 82 is made smaller than the diameter of the small-diameter hole portion 86 by a predetermined dimension. Further, the upper end surface of the ring runner portion forming bush 88 is provided with a cutout portion 92 that opens the inner hole 90 toward the side at one place on the circumference thereof.

  On the other hand, a groove 70 is provided on the upper surface of the fixed mold 20 (the overlapping surface with the fixed mold-side mounting plate 24) so as to extend in the horizontal direction. Further, the groove portion 70 communicates with the sprue 52 of the sprue bushing 46 at one end portion in the extending direction, and communicates with the first through hole 82 through the connection port 72 at the other end portion in the extending direction. . Then, by arranging the fixed mold 20 and the fixed mold side mounting plate 24 so as to overlap each other, the groove part 70 is covered with the fixed mold side mounting plate 24, and therefore, in such a groove part 70, A straight runner portion 56 is configured.

  Further, the ring runner portion forming bush 88 inserted into the large diameter hole portion 84 of the first through hole 82 is in a state where the notch portion 92 is communicated with the connection port 72 of the straight runner portion 56 (groove portion 70). Has been placed. Further, the ring runner portion forming bush 88 has a lower end surface thereof stepped with a large diameter hole portion 84 and a small diameter hole portion 86 arranged at an intermediate portion in the axial direction of the inner peripheral surface of the first through hole 82. While being brought into contact with the stepped surface, the upper end surface is arranged in contact with the fixed mold side mounting plate 24. Thereby, the inner hole 90 of the ring runner portion forming bush 88 communicates with the straight runner portion 56 through the notch portion 92 and the connection port 72 under the closed state of the upper opening portion by the fixed mold side mounting plate 24. At the same time, it communicates with the molding cavity 42 through the lower opening.

  Further, a second through hole 94 is formed in the center portion of the fixed mold side mounting plate 24 and the center portion of the fixed platen 26 so as to penetrate them in the thickness direction. The second through hole 94 has a cylindrical shape having a diameter smaller than the diameter of the large upper opening of the ring runner portion forming bush 88 inserted into the large diameter hole portion 84 of the first through hole 82. The inner circumferential surface of the ring runner portion forming bush 88 communicates with the inner hole 90 and is coaxially positioned. Thus, the second through hole 94 and the inner hole 90 of the ring runner portion forming bush 88 pass through the center of the fixed plate 26, the fixed mold side mounting plate 24, and the fixed mold 20 so as to extend in the vertical direction. Has been placed. As a result, the center hole 96 extending across the center part of the fixed plate 26, the fixed mold side mounting plate 24, and the fixed mold 20 is formed into the second through hole 94 and the ring runner part forming bush. 88 inner holes 90.

  In the center hole 96, the core pin 98 is inserted and arranged so as to extend in the vertical direction. The core pin 98 is made of a metal round bar having a length slightly longer than the extension length of the center hole 96. In addition, the core pin 98 has a base end large-diameter portion 100 having a large-diameter columnar shape at the upper portion thereof, and a lower portion having a sufficiently smaller diameter than the base end large-diameter portion 100. An intermediate taper having a small diameter cylindrical portion 102 having a small diameter, and an intermediate portion located between the small diameter portion 102 and the large large diameter portion 100 gradually having a taper shape with a gradually decreasing diameter downward. Part 104 is designated. Further, the intermediate taper portion 104 has a taper angle substantially the same as the taper angle of the tapered cylindrical inner peripheral surface 91 in the inner hole 90 of the ring runner portion forming bush 88, while the smaller diameter side. And the outer diameter on the larger diameter side are the inner diameter of the lower opening of the tapered cylindrical inner peripheral surface 91 in the inner hole 90 of the ring runner portion forming bush 88 and the upper opening of the larger diameter. Each of these is made smaller than the inner diameter by a predetermined dimension.

  Then, under such a state that the core pin 98 is inserted into the center hole 96, the base end large diameter portion 100 of the core pin 98 is in the second through hole 94, and the outer peripheral surface is the inner peripheral surface of the second through hole 94. It is placed in close contact with. Further, the intermediate taper portion 104 of the core pin 98 has a predetermined distance from the inner peripheral surface 91 of the ring runner portion forming bush 88 in the inner hole 90 of the ring runner portion forming bush 88. In a separated state, they are arranged coaxially. Furthermore, the tip small diameter portion 102 of the core pin 98 is in a state where the outer peripheral surface is separated from the inner peripheral surface of the small diameter hole portion 86 by a predetermined distance in the small diameter hole portion 86 of the first through hole 82. It is arranged coaxially.

  Here, the lower end of the small-diameter portion 102 of the tip end of the core pin 98 projects into the small-diameter hole portion 86 of the first through hole 82, so that the core pin 98 is disposed in the molding cavity 42. Further, a step portion 66 is provided on the outer peripheral surface of the axially intermediate portion of the base end large diameter portion 100 in the core pin 98 to make the upper end side portion of the base end large diameter portion 100 larger in diameter than the lower end side portion. The portion 66 is engaged in the up-down direction with a ring-shaped engagement surface 68 provided on the inner peripheral surface of the second through hole 94. As a result, the insertion position of the core pin 98 into the center hole 96 is positioned.

  Thus, as shown in FIGS. 10 to 12, in the injection mold 80 of the present embodiment, the outer peripheral surface 106 of the intermediate taper portion 104 of the core pin 98 and the inner peripheral surface 91 of the ring runner portion forming bush 88. A tapered cylindrical space that extends in the vertical direction and gradually decreases in diameter as it goes downward is formed therebetween. In addition, the tapered cylindrical space communicates with the straight runner portion 56 through the cutout portion 92 and the connection port 72 at the upper portion thereof, and communicates with the molding cavity 42 at the lower opening portion having a small diameter. ing. Thereby, a portion excluding the lower end portion of the tapered cylindrical space extending in the vertical direction communicates with the straight runner portion 56 and the molding cavity 42 and receives the molten resin flowing through the straight runner portion 56. The ring runner portion 58 is guided to the molding cavity 42 located below.

  13 and 14, in the injection mold 80 of the present embodiment, the outer peripheral surface 106 of the intermediate taper portion 104 of the core pin 98, and the inner peripheral surface 91 of the ring runner portion forming bush 88, Of the tapered cylindrical space formed between the lower end side portion excluding the portion constituting the ring runner portion 58, a cylindrical communication hole for allowing the ring runner portion 58 and the molding cavity 42 to communicate with each other is formed. Yes. Further, of the lower end portion of the outer peripheral surface 106 of the intermediate taper portion 104 and the lower end portion of the inner peripheral surface 91 of the ring runner portion forming bush 88 forming the lower end portion of such a tapered cylindrical space, the ring runner portion is formed. A plurality (16 in this case) of protrusions 108 are integrally formed at the lower end of the inner peripheral surface 91 of the bush 88.

  Each of the plurality of projecting portions 108 has a relatively thin flat plate shape, and is arranged at equal intervals in the circumferential direction of the inner peripheral surface 91 of the ring runner portion forming bush 88. That is, the plurality of protrusions 108 are ring runners in the tapered cylindrical space formed between the outer peripheral surface 106 of the intermediate taper portion 104 of the core pin 98 and the inner peripheral surface 91 of the ring runner portion forming bush 88. It arrange | positions so that it may extend radially in the lower end side part except the part which comprises the part 58. FIG. Further, each of the protrusions 108 has a protrusion height from the inner peripheral surface 91 of the ring runner portion forming bush 88 such that the lower end portion of the inner peripheral surface 91 of the ring runner portion forming bush 88 and the outer periphery of the intermediate taper portion 104. The distance is the same as the distance from the lower end of the surface 106. As a result, all of the plurality of protruding portions 108 are in contact with the lower end portion of the outer peripheral surface 106 of the intermediate tapered portion 104 at the front end surface. Thus, one gate 74 for connecting the ring runner portion 58 and the molding cavity 42 is formed between the projecting portions 108 and 108 adjacent to each other in the circumferential direction of the inner peripheral surface 91 of the ring runner portion forming bush 88. Has been. Each of the plurality (16 in this case) of the gates 74 is configured by a pore having a sufficiently smaller inner diameter than the inner hole 90 of the ring runner portion forming bush 88.

  And when manufacturing the target resin molded product 10 using the injection mold 80 having such a structure, the operation is performed according to the following procedure, for example.

  That is, first, as shown in FIG. 11, the movable mold 22 and the fixed mold 20 of the injection mold 80 are closed, and a molding cavity 42 is formed between the movable mold 22 and the fixed mold 20. .

  Next, as shown in FIG. 15, the molten resin 78 injected from the injection device (not shown) is caused to flow into the sprue 52 from the nozzle 48 and further into the straight runner portion 56. Then, after the molten resin 78 is circulated in the straight runner portion 56 and the ring runner portion 58, the molten resin 78 is caused to flow into the molding cavity 42 through the plurality of gates 74, and the inside of the molding cavity 42 is made into the molten resin 78. Fill.

  At this time, as in the case of performing the injection molding operation using the injection mold 18 according to the first embodiment, the molten resin 78 is a part of the molding cavity 42 that provides the inner cylindrical portion 16 in the molding cavity 42. After flowing in the axial direction, the inside of the molding cavity 42 that gives the annular plate-shaped partition wall portion 14 flows from the center side toward the outer peripheral side, and then the outer cylindrical portion 12 is formed. It flows in the molding cavity 42 part in the axial direction. This advantageously avoids the occurrence of a joining point of the molten resin 78 in the molding cavity 42.

  Then, as shown in FIG. 16, after the molten resin 78 filled in the molding cavity 42 is cooled and solidified, the movable mold 22 and the fixed mold 20 are opened. Thus, the resin molded product 10 in which the molten resin 78 is solidified in the molding cavity 42 is released from the fixed mold 20 while being held by the cavity forming protrusions 40 of the movable mold 22.

  At this time, the plurality of gates 74, runners 54 (straight runner portion 56 and ring runner portion 58), and sprue 52, as in the case of performing the injection molding operation using the injection mold 18 according to the first embodiment. The solidified product 79 in which the molten resin 78 remaining therein is solidified is a solidified product located in the lower opening of each gate 74 which is the most fragile portion (lowest tensile strength portion) of the solidified product 79. 79 parts are cut from the resin molded product 10. For this reason, the excess solidified material 79 is easily separated from the resin molded product 10, and the plurality of gate marks 17 of the solidified material 79 remaining on the inner peripheral portion of the upper end surface of the inner cylindrical portion 16 in the resin molded product are sufficient. It is made small, inconspicuous, and beautiful.

  When the movable mold 22 and the fixed mold 20 are opened, the resin molded product 10 is moved to the movable mold 22 in the same manner as when the injection molding operation is performed using the injection mold 18 according to the first embodiment. The excess solidified material 79 located in the plurality of gates 74, the runners 54, and the sprue 52 is also released from the fixed die 20 and the sprue bushing 46. Thus, the intended resin molded product 10 having the structure shown in FIGS. 1 and 2 is obtained.

  As is clear from the above description, even when the injection mold 80 of the present embodiment is used, the joining location of the molten resin 78 is the same as when the injection mold 18 according to the first embodiment is used. Is advantageously eliminated in the molding cavity 42, and the gate mark 17 remaining in the resin molded product 10 can be made sufficiently small and beautiful. As a result, it is possible to manufacture the resin molded article 10 having a good appearance and no weld line with higher productivity and at the lowest possible cost without performing finishing.

  Further, in the injection mold 80 of the present embodiment, a plurality of abutting lower end portions of the outer peripheral surface 106 of the core pin 98 are in contact with the lower end portion of the inner peripheral surface 91 of the ring runner portion forming bush 88 fitted into the fixed die 20. A plurality of gates 74 made of pores are formed by providing the protruding portions with a gap in the circumferential direction. Therefore, in the injection mold 80, the strength of the fixed mold 20 and the movable mold 22 is sufficiently higher than that of the injection mold having the gates 74 formed in the fixed mold 20. In addition, the maintenance performance can be advantageously improved. As a result, further improvement in the operability of the injection mold 80 and, in turn, the productivity of the intended resin molded product 10 can be effectively realized.

  The specific configuration of the present invention has been described in detail above. However, this is merely an example, and the present invention is not limited by the above description.

  For example, in the injection mold 18 according to the first embodiment, the number, the shape, and the size of the communication holes 76 constituting the plurality of gates 74, or the injection mold 18 according to the first embodiment Needless to say, the number, shape, size, and the like of the protruding portions 108 provided for forming the gate 74 can be changed as appropriate.

  Further, in the injection mold 18 according to the first embodiment, the ring runner portion 58 is formed of a cylindrical space, while in the injection mold 88 according to the second embodiment, the ring runner portion 58 is a tapered cylindrical shape. It consisted of space. However, the ring runner portion 58 only needs to be configured in a cylindrical space. Therefore, the shape of the ring runner portion 58 is appropriately set regardless of the formation structure of the plurality of gates 74.

  Furthermore, in the second embodiment, the plurality of projecting portions 108 are integrally formed on the lower end portion of the inner peripheral surface 91 of the ring runner portion forming bush 88, whereby the plurality of gates 74 made of pores are formed. The ring runner portion 58 and the molding cavity 42 are provided so as to communicate with each other. However, the plurality of projecting portions 108 for forming the plurality of gates 74 are provided in place of or in addition to the lower end portion of the inner peripheral surface 91 of the ring runner portion forming bush 88, and the lower end of the outer peripheral surface 106 of the core pin 98. You may integrally form in a part. Further, the plurality of projecting portions 108 can be configured by members separate from the ring runner portion forming bush 88 and the core pin 98. In this case, for example, the protruding portion 108 is provided on the outer peripheral surface or inner peripheral surface of the ring portion separate from the ring runner portion forming bush 88 and the core pin 98, and the ring portion is used for forming the ring runner portion. The protrusion 108 is disposed between the ring runner 58 and the molding cavity 42 by being inserted into the lower end of the bush 88 or extrapolated into the lower end of the core pin 98, and a plurality of them are interposed between them. The gate 74 is formed. In this case, between the lower end portion of the inner peripheral surface 91 of the ring runner portion forming bush 88 and the lower end portion of the outer peripheral surface 106 of the core pin 98, that is, in the annular or cylindrical space in which the ring portion is to be disposed. Thus, a communication hole for communicating the ring runner portion 58 and the molding cavity 42 with each other is formed.

  The ring runner portion forming bush 88 can be omitted. Therefore, when the ring runner portion forming bush 88 is omitted, for example, a plurality of protrusions 108 are provided on the inner peripheral surface of the through-hole through which the core pin 98 is inserted, so that a plurality of gates are provided. 74 will be formed.

  In addition, in the said embodiment, although the specific example of what applied this invention to the injection mold used for manufacture of the resin molded product which has a cylindrical part, and the manufacturing method of this resin molded product was shown, this invention For example, it can be advantageously applied to an injection mold used for manufacturing a resin molded product having various shapes including a shape having a deep hole, and a method for manufacturing such a resin molded product. Of course.

  In addition, although not enumerated one by one, the present invention can be carried out in a mode to which various changes, modifications, improvements, etc. are added based on the knowledge of those skilled in the art. It goes without saying that all are included in the scope of the present invention without departing from the spirit of the present invention.

DESCRIPTION OF SYMBOLS 10 Resin molded product 17 Gate mark 18,88 Injection mold 20 Fixed mold 22 Movable mold 42 Molding cavity 54 Runner 56 Straight runner part 58 Ring runner part 64, 98 Core pin 74 Gate 76 Communication hole 91 Inner peripheral surface 106 Outer peripheral surface 108 Projection Part

Claims (4)

A cavity for molding a resin molded product,
A ring runner comprising a cylindrical space for guiding the molten resin injected from the injection device;
A plurality of gates configured by a plurality of pores communicating with one end in the axial direction of the ring runner and the cavity, and spaced apart from each other in the circumferential direction of the ring runner;
An injection mold characterized in that the molten resin introduced by the ring runner is introduced into the cavity from the ring runner through the plurality of gates.   Between the one end of the ring runner in the axial direction and the cavity, an annular or cylindrical communication hole is provided so as to communicate with each other so as to be coaxial with the ring runner. A plurality of projecting portions projecting from one inner surface portion of the two inner surface portions facing each other in the direction perpendicular to the axis of the communication hole toward the other inner surface portion and contacting the other inner surface portion, The pores are provided between the adjacent ones in the circumferential direction of the plurality of protrusions by being arranged in the hole so as to be spaced apart from each other in the circumferential direction of the communication hole. The injection mold according to claim 1, wherein the plurality of gates are constituted by the plurality of pores.   The injection mold according to claim 1 or 2, wherein an opening area of the opening on the cavity side of the gate is smaller than an opening area of the opening on the ring runner side. Using the injection mold according to any one of claims 1 to 3, the molten resin is injected from an injection device, and the molten resin is passed through the ring runner and the plurality of gates. A method for producing a resin molded product, comprising performing an injection molding operation for filling a cavity.

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