JP2009196289A - Injection molding die and resin molded product - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an injection molding die that can mold a molded product effectively enhanced in rigidity and strength of a required part without causing airtightness during injection molding, at a low cost by incurring no increase of weight and a material cost. <P>SOLUTION: The injection molding die 1 composed of: a plurality of divided dies 2, 3 has a gate 6; a main cavity 11 that can mold a thin-walled molded product body part 24; and a rib molding cavity 12 provided recessed in a main cavity face 2a or 3a of at least one of the divided dies 2, 3 and communicating with the gate 6. The rib molding cavity 12 is disposed branching in branch shape downstream. The divided dies 2, 3 have projecting parts 7, 7a, 7b, 7c projected from the main cavity faces 2a, 3a in side positions on both sides of the downstream end 12b of the rib molding cavity 12. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention uses an injection mold used when injection molding a synthetic resin, in particular, an injection mold that can prevent molding defects such as air tight during injection molding, and the same mold. And injection molded resin products.

  In general automobiles, a fender protector made of synthetic resin is attached to the inside of the wheelhouse that covers the top of the tire, for example, for the purpose of protecting the car body and other components from splashes of muddy water and pebbles flying up during driving. A synthetic resin under cover is attached to the bottom of the engine room.

  Synthetic resin molded articles such as fender protectors and undercovers are usually produced in a desired shape by injection molding. For example, the fender protector is formed in an arch shape so as to cover a part of the tire from above, and is formed in a thin shape of about 0.8 to 1.3 mm for weight reduction and cost reduction. There are many cases.

  On the other hand, the fender protector protects other components such as a fender panel while maintaining a predetermined shape, and further, in order to stably maintain the mounting state of the fender protector even when the vehicle is running. There is a need to increase rigidity and strength. However, for example, in order to increase the rigidity and strength of the fender protector, it is conceivable to increase the thickness of the fender protector itself. When the thickness of the fender protector itself is increased in this way, the weight of the fender protector itself is increased. However, there is a problem that the weight becomes large and the weight cannot be reduced, and the manufacturing cost increases.

  On the other hand, when the fender protector is made as thin as possible in order to reduce the weight of the fender protector, there is a problem that the rigidity and strength of the fender protector are reduced. Further, when the thickness of the fender protector is reduced, the cross section of the resin flow path inevitably narrows in the mold cavity during injection molding, and the flow resistance of the synthetic resin increases. For this reason, the synthetic resin is not completely filled into the cavity and is easily cooled and solidified, and there is a problem that a molding defect called short shot (filling defect) is likely to occur.

  Therefore, in recent years, for example, a fender as shown in FIG. 7 is used in order to solve the above-described problems, to reduce the weight of the fender protector and to improve the rigidity and strength, and to ensure good mounting workability. The structure of the protector 41 has been proposed.

  The fender protector 41 shown in FIG. 7 includes an arch-shaped curved portion 42, a substantially fan-shaped extended portion 43, and a side wall portion disposed at a right angle to the extended portion 43 on the front inner side of the curved portion 42. 44. Further, a notch 53 into which a vehicle suspension (not shown) is inserted is formed in the top inner portion of the curved portion 42, and the rear end of the fender protector 41 is formed from the portion where the notch 53 is formed. A flange 47 is arranged across.

  In the fender protector 41, a step edge portion 46 having a step is provided on the outer edge of the curved portion 42 and the extending portion 43, and a part of the step edge portion 46 and the extending portion in the curved portion 42 are provided. 43 step edge portions 46 are formed as thick edge portions 45 that are thicker than the protector body. In this case, the thickness of the thin portion of the protector body is set to, for example, about 0.8 mm to 1.3 mm.

  Further, the fender protector 41 is formed with a gate portion 50 formed as a trace of a synthetic resin injection gate at the time of injection molding. Further, on one surface of the curved portion 42 and the extending portion 43 of the fender protector 41, a rib 48 is provided from the gate portion 50 in order to increase the rigidity of the fender protector 41 and to support the flow of the synthetic resin during injection molding. It is extended and formed. The rib 48 is branched and arranged from the gate portion 50 toward the downstream side so that the synthetic resin melted at the time of injection molding flows smoothly in the cavity.

  Furthermore, a plurality of fixing portions 51 for fixing the fender protector 41 to a vehicle body side fender panel (not shown) are formed on a part of the outer edge portion of the fender protector 41 by a fastener such as a clip.

  In the conventional fender protector 41 having such a configuration, the rib 48 is formed on one surface thereof, whereby the fender protector 41 is reinforced to increase the rigidity and strength. At the same time, during the injection molding of the fender protector 41, the space for forming the rib 48 formed in the mold (rib molding cavity) serves as a flow path to assist the flow of the synthetic resin. For this reason, the synthetic resin is stably filled in the cavity, and the occurrence of short shots is effectively prevented.

  Further, the fender protector 41 is formed with the thick edge 45 on a part of the outer edge of the fender protector 41. As a result, rigidity and strength that sufficiently satisfy the required performance with the curved surfaces of the extended portion 43 and the curved portion 42 can be stably obtained, and the suitable flexibility of the fender protector 41 can be maintained, and good There is also an advantage that the mounting workability can be ensured.

However, the conventional fender protector 41 as shown in FIG. 7 has a problem that a molding defect called air tight occurs at the time of injection molding.
That is, when injection molding of the fender protector 41 is performed, the space (main cavity) for forming a thin portion serving as the protector main body is melted in the main cavity because the flow resistance of the synthetic resin increases. It becomes difficult for the synthetic resin to flow.

  For this reason, the molten resin 49 injected from the injection gate flows preferentially into the rib molding cavity having a larger flow path cross section in order to form the rib 48, as indicated by arrows in FIGS. (Note that in FIGS. 8 and 9, the flow of the molten resin is virtually shown in the fender protector 41, which is a molded product, in order to easily understand the flow of the molten resin.)

  Accordingly, the molten resin 49 injected into the mold through the gate is first filled into the rib molding cavity, and then flows from the rib molding cavity into the main cavity for molding the thin-walled body portion. become. At this time, at each downstream end branching on the downstream side of the rib forming cavity, the molten resin 49 that has flowed through the rib forming cavity collides with the end surface of the downstream end of the rib forming cavity and becomes thin. It gradually flows into the main cavity while spreading radially.

  Thereby, since the molten resin 49 is filled into the main cavity from the downstream end side of the rib forming cavity, a state occurs in which the filling of the molten resin is delayed in the main cavity near the rib branch portion ( (See FIG. 8).

  As a result, before the molten resin is filled into the main cavity near the rib branch portion, the molten resin merges between the downstream end portions of the adjacent rib forming cavities. In the main cavity, the air is surrounded by the molten resin, so that the gas cannot be vented. For this reason, air remains in the main cavity in the vicinity of the rib branching portion, resulting in a problem that a molding defect such as air tight 52 that impairs the appearance of the molded product occurs.

In view of this, for example, Japanese Patent Application Laid-Open No. 8-258100 (Patent Document 1) and Japanese Patent Application Laid-Open No. 2007-223397 (Patent Document 2) propose a technique for solving the above-described problem of air tightness during injection molding. Has been.
Specifically, in Patent Document 1, a plurality of control pins that can be put into and out of the mold cavity are arranged in the mold apparatus, and the tips of the plurality of control pins are placed at the mold during injection molding. An injection molding method is disclosed in which the flow direction, flow rate, and pressure distribution of the molten resin in the cavity are controlled by selectively withdrawing into and out of the cavity over time.

  According to such an injection molding method described in Patent Document 1, for example, when a molded product having ribs on a thin-walled main body portion is injection-molded as described above, air in the main cavity is appropriately discharged. As described above, since the flow direction, flow rate, and pressure distribution of the molten resin can be controlled by inserting and removing a plurality of control pins during injection molding, it is possible to prevent the occurrence of molding defects such as air tight. .

  On the other hand, the molded article described in Patent Document 2 is provided with ribs for reinforcing the thin-walled main body part and assisting the flow of molten resin (referred to as first and second ribs in Patent Document 2). And a rib having a short length for promoting the flow of the molten resin toward a region where air is easily surrounded by the molten resin when injection molding is performed (Patent Document) 2 is described as a third rib).

According to such a technique described in Patent Document 2, the mold is provided with a third rib molding cavity for molding the third rib so that air in the main cavity is smoothly discharged during injection molding. It is done. By appropriately forming such a third rib molding cavity in the mold, the flow direction and flow rate of the molten resin flowing into the main cavity in the injection molding are controlled, and the molten resin is quickly put into the main cavity. Therefore, it is possible to prevent the occurrence of defective molding of air tight.
JP-A-8-258100 JP 2007-223397 A

  However, in the injection molding method in which a plurality of control pins are selectively taken in and out over time in a cavity at the time of injection molding as described in Patent Document 1, not only a plurality of control pins are included in a mold apparatus used for injection molding. In addition, it is necessary to install an air cylinder for taking in and out these control pins and a control device for controlling the taking in and out of the control pins. For this reason, there existed a problem that metal mold | die apparatus itself enlarged, an apparatus structure became complicated, and the manufacturing cost of the resin molded product increased significantly.

  On the other hand, when the third rib having a short length is formed in order to control the flow of the molten resin as in Patent Document 2, for example, a fender protector is affected by wind pressure when the vehicle travels such as a curved portion. It is effective to form the third rib at a portion where rigidity is required because air tightness can be prevented and the rigidity of the portion can be improved.

  However, in a fender protector, for example, in a portion such as a substantially fan-shaped extending portion that is parallel to the road surface when the vehicle is running and the influence of wind pressure can be ignored, the formation of the third rib prevents the occurrence of air tightness. Although it is possible, the rigidity and strength of the extending portion are sufficiently secured by the first and second ribs. For this reason, disposing the third rib in the extending portion only for the purpose of promoting the flow of the molten resin leads to an increase in the weight of the molded product and an increase in material cost, and therefore improvement is required. It was.

  Further, when the flow of the molten resin is controlled by forming the third rib as in Patent Document 2, for example, when the flow direction or flow rate of the molten resin is changed, a third rib is newly formed in the mold. For example, it is necessary to form a cavity for the third rib and to eliminate the already formed cavity for forming the third rib.

  The present invention has been made in view of the above-described conventional problems, and a specific object thereof is to provide a molded product in which rigidity and strength of a required portion are effectively increased without generating air tightness at the time of injection molding. To provide an injection mold that can be molded at a low cost without incurring an increase in weight or material cost, and a resin molded product that is injection-molded using the injection mold It is in.

  In order to achieve the above object, the injection mold provided by the present invention is constituted by a plurality of divided molds as a basic structure, and a main cavity capable of forming a gate and a thin molded product main body. And a rib forming cavity that is recessed in at least one main cavity surface of the split mold and communicates with the gate, and the rib forming cavity is branched and arranged on the downstream side thereof. The split mold has a protrusion protruding from the main cavity surface at at least one side position sandwiching at least one downstream end of the rib molding cavity. It has the most important feature.

  In the injection mold according to the present invention, it is preferable that the protrusions are arranged at both of the lateral positions of the downstream end portion.

  Moreover, it is preferable that the protrusion height of the protrusion is set to be 30% or more and 50% or less of the interval between the main cavities in which the protrusions are arranged. It is preferable that the distance from the downstream end to the protrusion is set to 0% to 300% of the width of the downstream end.

  In the injection mold according to the present invention, the protrusion is arranged in parallel to the downstream end of the rib molding cavity, and the downstream end of the rib molding cavity, It is arranged so as to be inclined so that the interval with the downstream end portion gradually widens or shrinks toward the downstream side, or bent toward the downstream end side of the rib forming cavity or the opposite side thereof. Alternatively, it is preferably arranged in a curved manner.

Furthermore, according to the present invention, there is provided a resin molded product that is injection-molded using the injection mold having the above-described configuration.
Moreover, it is preferable that the resin molded product which concerns on this invention is used for the fender protector or undercover for vehicles.

  An injection mold according to the present invention includes a plurality of divided molds, and includes a gate, a main cavity capable of forming a thin molded product main body, and at least one main cavity surface of the divided mold. And a rib forming cavity that communicates with the gate and branches downstream in a branch shape.

  Further, the at least one split mold in the mold has a ridge protruding from the main cavity surface at at least one side position of the downstream end sandwiching at least one downstream end of the rib forming cavity. have. In the present invention, the downstream side refers to the downstream direction when the molten resin is injected into the cavity from the gate and the molten resin flows through the cavity.

  By performing the injection molding of the synthetic resin using the injection mold of the present invention, the flow of the molten resin is supported by the rib molding cavity during the injection molding, and the molten resin has priority over the rib molding cavity. In addition, since it can flow smoothly from the rib forming cavity to the main cavity, the occurrence of short shots can be effectively prevented.

  At the same time, in the mold according to the present invention, when the split mold has the protruding portion, the molten resin flows into the main cavity from the downstream end of the rib forming cavity in the injection molding. Can be suppressed at the ridge. For this reason, molten resin is prevented from spreading radially from the downstream end of the rib forming cavity, and actively flows from the downstream end of the rib forming cavity toward the direction in which no protrusion is formed. Become.

  As a result, the timing at which the molten resin merges between the downstream end portions of the rib forming cavities adjacent to each other can be delayed, so that the air in the main cavity is surrounded by the molten resin as shown in FIG. It is possible to prevent the occurrence of air tight by preventing the removal of the air tight.

  In addition, the mold of the present invention can prevent the occurrence of short shots and air tights without taking in and out of the control pin during injection molding, for example, as described in Patent Document 1 above. Since the apparatus structure is not complicated, the cost increase of the resin molded product can be suppressed.

  Furthermore, the present invention can prevent the occurrence of air tight without specially forming the third rib as in Patent Document 2, for example, so that the weight of the molded product and the material cost are not increased. Injection molding can be performed at a low cost. In the present invention, for example, when changing the flow direction or flow speed of the molten resin, it is not necessary to greatly change the design of the mold, and the protrusions arranged on the main cavity surface can be formed or eliminated, or It is possible to easily cope with this by appropriately changing the shape, dimensions, and direction of the strip.

  In particular, in the injection mold according to the present invention, when the protrusions are arranged on both sides of the downstream end, the molten resin flows into the main cavity from the downstream end of the rib forming cavity. In addition, the flow of the molten resin can be suppressed at both side positions, and the flow of the molten resin can be promoted in the direction along the downstream end of the rib forming cavity. Thereby, it can prevent more reliably that the air in a main cavity is surrounded by molten resin, and can prevent generation | occurrence | production of air tighter more effectively.

  Moreover, in the metal mold | die of this invention, the protrusion height of a protrusion part is set to 30% or more and 50% or less of the space | interval of the main cavity in which the protrusion part is distribute | arranged. Thereby, the protrusion does not completely block the flow of the molten resin, and the flow of the molten resin can be appropriately suppressed so as to prevent the occurrence of air tightness. Furthermore, when injection molding is performed using such a mold of the present invention, the molded product obtained after molding is formed with a recess corresponding to the protruding portion at the lateral position of the rib tip, Since the protrusion formed on the mold has the above-described protrusion height, the strength of the molded product is not reduced by the recess.

  Furthermore, in this invention, the space | interval from the downstream edge part of a rib shaping | molding cavity to a protrusion part is set to 0% or more and 300% or less of the width dimension of the downstream edge part. Thereby, the flow of the molten resin flowing into the main cavity from the rib forming cavity can be appropriately suppressed by the protrusions, and the flow of the molten resin can be surely promoted in a predetermined direction.

  In the mold according to the present invention, the protrusion is arranged in parallel to the downstream end of the rib forming cavity. Thereby, the flow direction of the molten resin flowing from the downstream end portion of the rib forming cavity can be promoted in the direction along the downstream end portion of the rib forming cavity.

  Further, the protrusion may be inclined with respect to the downstream end of the rib forming cavity so that the distance from the downstream end gradually increases or decreases toward the downstream side. . Thereby, the flow range of the molten resin flowing from the downstream end of the rib forming cavity can be widened or narrowed, and the flow direction of the molten resin can be promoted in a predetermined direction.

  Furthermore, the protruding portion may be bent or curved on the downstream end side of the rib forming cavity or on the opposite side thereof. This also makes it possible to widen or narrow the flow range of the molten resin flowing from the downstream end portion of the rib forming cavity, and to control the flow rate.

  The resin molded product injection-molded using the injection mold of the present invention is a molded product in which short shots and air tightness are not generated, and the rigidity and strength of a required part are effectively enhanced by ribs. Become. Such a resin molded product according to the present invention can be particularly suitably used as a fender protector or undercover for a vehicle in which the main body portion is formed thin and high rigidity and strength are required at a required portion.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the accompanying drawings. It should be noted that the present invention is not limited to the following examples, and has a configuration substantially the same as the configuration described in the claims of the present invention and has the same operational effects. Various changes can be made.

  For example, in the following examples, a case where a fender protector is molded as a resin molded product according to the present invention is described. However, the present invention can be similarly applied to a case where a member such as an under cover, an instrument panel, a door trim or the like is formed. In addition, the shape and the like in the fender protectors of the following embodiments are merely examples, and can be appropriately changed according to the type of vehicle to be attached.

  FIG. 1 is a cross-sectional view showing a state where an injection mold according to Embodiment 1 of the present invention is clamped, and FIG. 2 is a cross-sectional view taken along the line II-II in FIG. FIG. 3 is an enlarged view of a main part schematically showing a main part of a fender protector injection-molded using the mold, and FIG. 4 is a downstream end part of a rib forming cavity formed in the mold. It is an enlarged view which expands and shows a protrusion part. In FIGS. 3 and 4, the state of the molten resin flowing into the main cavity from the rib forming cavity is indicated by a virtual line in order to easily understand the flow of the molten resin at the time of injection molding.

  The injection mold 1 according to the first embodiment is a mold that is attached to the inside of a wheel house of a fender panel of an automobile and can injection-mold a fender protector 21 that covers an upper portion of a tire. The fender protector 21 formed using the mold 1 of the first embodiment is arranged at right angles to the arch-shaped curved portion 22, the substantially fan-shaped extending portion 23, and the bay extending portion 23. It is comprised by the thin side wall part which is not shown in figure.

  Further, as shown in FIG. 3, the bending portion 22 and the extending portion 23 of the fender protector 21 are formed with a thin main body portion 24 and a rib formed by branching to one surface (upper surface) of the main body portion 24. 25, and a gate portion 26 is provided on the rib 25 as a trace of the metal gate 6 being disposed.

  The mold 1 capable of forming such a fender protector 21 includes a cavity plate 2 that is a fixed-side mold plate and a core plate 3 that is a movable-side mold plate, as shown in FIG. A fixed-side mounting plate 4 is disposed on the upper surface of the cavity plate 2. The injection mold 1 is connected to an injection molding machine (not shown) through a locating ring (not shown).

  Furthermore, the injection mold 1 was introduced into the mold through a cavity 10 formed between the plates 2 and 3 and a sprue (not shown) when the cavity plate 2 and the core plate 3 were clamped. A runner 5 for guiding the molten resin to the cavity 10 and a gate 6 for injecting the molten resin flowing through the runner 5 into the cavity 10 are provided. The molten resin injected from an injection device (not shown) is sprue, runner 5. , And the gate 10 to be supplied into the cavity 10.

  In the first embodiment, the position of the gate 6 is set at the extended portion 23 of the fender protector 21 obtained after injection molding and the curved portion 22 (not shown) as shown in FIG. The position of the gate 6 is not particularly limited, and can be arbitrarily set according to the shape of the molded product.

  As shown in FIG. 2, the cavity 10 formed in the injection mold 1 has a main cavity 11 capable of forming a thin main body 24 and a rib forming cavity 12 capable of forming a rib 25. is doing. The rib forming cavity 12 is recessed in the main cavity surface 2 a of the cavity plate 2, communicates with the gate 6, and is branched from the downstream side when viewed from the gate 6.

  In this case, the interval H between the main cavities 11 in which the main body 24 can be molded, that is, the interval H between the main cavity surface 2a of the cavity plate 2 and the main cavity surface 3a of the core plate 3 is 0.8 mm or more and 1.3 mm or less. , Preferably about 1.0 mm.

  The rib forming cavity 12 is formed in a substantially rectangular shape in cross section, or in a substantially mountain shape in which a base portion (base end portion) with the main cavity 11 is widened. The height h1 of the rib forming cavity 12, that is, the height h1 from the main cavity surface 2a of the cavity plate 2 to the top portion 12a of the rib forming cavity 12 is 3.0 mm to 4.5 mm, preferably about 3 mm. The width L at the base end portion of the rib forming cavity 12 is set to 2.5 mm to 4.5 mm, preferably about 2.5 mm.

  Furthermore, in the mold 1 of the first embodiment, the main cavity surface 2a of the cavity plate 2 is provided with a protrusion 7 protruding from the main cavity surface 2a with the downstream end 12b of the rib forming cavity 12 interposed therebetween. It is formed in parallel to the downstream end portion 12b at both sides of the sandwiched side (see FIGS. 2 and 4).

  In this case, the protrusion height h2 of the protrusion 7 is set to a dimension of 30% to 50%, preferably 35% to 45%, of the interval H (of the main cavity 11 in which the protrusion 7 is disposed. Thus, by setting the protrusion height h2 of the protrusion 7 to 30% or more of the interval H between the main cavities 11, the main cavity from the downstream end 12b of the rib forming cavity 12 at the time of injection molding. 11, the flow 20a of the molten resin 20 that has flowed into the inside can be effectively suppressed by the ridges 7, and the molten resin 20 can be prevented from spreading radially. 4 can be urged in a direction along the downstream end 12b of the rib forming cavity 12, as shown in FIG.

  On the other hand, by setting the protrusion height of the protrusion 7 to 50% or less of the interval between the main cavities 11, the flow 20 a of the molten resin 20 can be prevented from being completely blocked by the protrusion 7, and the molten resin 20 Can be filled into the main cavity 11 smoothly.

  In addition, the protrusion 7 is disposed away from the downstream end 12b of the rib forming cavity 12, and between the base end portion of the protrusion 7 and the base end portion of the downstream end 12b. Is provided with an interval D that is 0% or more and 300% or less, preferably 20% or more and 200% or less of the width of the downstream end 12b.

  Thus, by setting the distance D between the ridge 7 and the downstream end 12b to be 0% or more of the width dimension of the downstream end 12b, a sufficient space for the rib forming cavity 12 can be secured, and the rib The molten resin can be smoothly flowed into the molding cavity 12. On the other hand, by setting the distance D to 300% or less of the width dimension of the downstream end portion 12b, it is possible to stably suppress the molten resin 20 flowing into the main cavity 11 from spreading radially, and to change the flow direction of the molten resin. It can be easily urged in a desired direction.

  In the first embodiment, the ridges 7 are formed at both the left and right lateral positions of each downstream end 12b of the rib forming cavity 12, but depending on the shape of the molded product, the ridges are formed. 7 can be formed only at either the left or right side position in the downstream end portion 12b, and the formation of the ridge portion 7 may be omitted in some downstream end portions 12b of the rib forming cavity 12. Is possible.

  And when performing the injection molding of a synthetic resin using the injection mold 1 of the first embodiment as described above, the molten resin 20 injected from an injection device (not shown) is first passed through the sprue and the runner 5. Are introduced into the mold 1 and injected into the cavity 10 through the gate 6. In addition, as a synthetic resin used as the material of the fender protector 21, for example, an olefin-based thermoplastic resin such as polypropylene or polyethylene is used.

  Subsequently, the molten resin 20 injected into the cavity 10 is communicated with the gate 6 and is supported by the rib forming cavity 12 having a large flow path cross section, so that the rib forming cavity 12 and the rib forming It flows preferentially to a part of the main cavity 11 along the working cavity 12. As a result, the molten resin 20 flows toward the respective downstream end portions 12b of the rib forming cavities 12 and is filled in the rib forming cavities 12, and from the rib forming cavities 12 on the side close to the gate 6, It gradually flows into the cavity 11. For this reason, the molten resin 20 can be smoothly filled into the main cavity 11 and the rib forming cavity 12, and the occurrence of short shots can be prevented.

  Further, the molten resin 20 that has flowed to each downstream end 12 b of the rib forming cavity 12 flows into the main cavity 11 so as to collide with the downstream end surface 12 c of the rib forming cavity 12 and diffuse into the main cavity 11.

  At this time, since the protruding portion 7 is provided at a side position of the downstream end portion 12b of the rib forming cavity 12, the molten resin 20 that has flown so as to diffuse into the main cavity 11 from the downstream end portion 12b. As shown in FIG. 4, the flow 20a is suppressed in the direction from the downstream end portion 12b to the side by the ridge portion 7 and is urged in the direction in which the ridge portion 7 is not disposed. As a result, the molten resin 20 positively flows toward the front in the direction along the downstream end 12b of the rib forming cavity 12 (the extending direction of the rib forming cavity 12).

  Thereby, for example, between the downstream end portions 12b of the rib forming cavities 12 adjacent to each other, the protrusions 7 are formed at the timing when the molten resin 20 flowing into the main cavity 11 from each downstream end portion 12b joins. It becomes possible to delay compared with the case where there is no. As a result, it is possible to prevent the air in the main cavity 11 from being surrounded by the molten resin at the time of injection molding, so that it is not possible to outgas, thereby preventing the occurrence of air tightness.

  Then, by filling the cavity 10 of the mold 1 with a predetermined amount of the molten resin 20, and then cooling the molten resin 20, the fender protector 21 having the extending portion 23 shown in FIG. Can be manufactured. In addition, although the recessed part 27 which has a form corresponding to the said protrusion part 7 of the metal mold | die 1 is formed in the both-sides position of each front-end | tip part of the rib 25 in this fender protector 21, since this recessed part 27 is very small, it is. The appearance of the fender protector 21 is not impaired.

  Since the fender protector 21 obtained as described above has no short shot or air tightness, its appearance is very good, and the rigidity and strength of the extending portion 23 and the curved portion 22 are enhanced by the ribs 25. Is effectively enhanced.

  In addition, when the fender protector 21 is molded, for example, the protrusion 7 is provided in the main cavity 11 without using a control pin that can be inserted into and removed from the cavity of the mold at the time of injection molding. Since the molding is performed using the mold 1 having a simple structure as described above, the mold apparatus is not increased in size and the structure of the mold apparatus is not complicated.

  In addition, in a portion such as the extended portion 23 in which rigidity and strength are sufficiently secured, excessive ribs are not formed only to promote the flow of the molten resin as in Patent Document 2. Therefore, the fender protector 21 injection-molded using the injection-molding mold 1 of the first embodiment can be manufactured at a low cost by reducing the manufacturing cost.

  In the injection molding die 1 of the first embodiment, the ridge 7 protrudes from the main cavity surface 2a of the cavity plate 2, but the ridge 7 that suppresses the flow of the molten resin is For example, as shown in FIG. 5, it is also possible to project at a corresponding position on the main cavity surface 3 a side of the core plate 3. Further, the protruding portion 7 can be divided into, for example, a main cavity surface 2 a of the cavity plate 2 and a main cavity surface 3 a of the core plate 3, and can be provided to protrude from each.

  Thus, even when the protruding portion 7 is divided and provided on the main cavity surface 2a of the cavity plate 2 and the main cavity surface 3a of the core plate 3, the total protruding height of the divided protruding portions 7 is as follows. As in the first embodiment, it is preferably set to 30% or more and 50% or less of the interval H between the main cavities 11 where the ridges are arranged, and each ridge 7 and the rib forming cavity 12 are set. It is preferable that a gap D that is 0% or more and 300% or less of the width dimension of the downstream end portion 12a is provided between the downstream end portion 12a and the downstream end portion 12a.

  Further, in the first embodiment, the protrusion 7 protruding from the main cavity surface 2a of the cavity plate 2 is arranged in parallel with the downstream end 12a of the rib forming cavity 12 as described above. However, in the present invention, the shape and arrangement direction of the protrusions 7 protruding from the main cavity surfaces 2a and 3a of the cavity plate 2 and / or the core plate 3 are not particularly limited, and the size of the resin molded product is not limited. It can be appropriately changed according to the sheath shape.

  For example, as shown in FIG. 6A, the protrusion 7a projecting from the main cavity surface of the mold 1 is connected to the downstream end 12a of the rib forming cavity 12 with the downstream end 12b. The distance D can be inclined so as to gradually widen toward the downstream side. As a result, the flow of the molten resin that collides with the downstream end surface 12c of the rib forming cavity 12 and flows into the main cavity 11 is suppressed by the protrusion 7a in the direction from the downstream end 12b to the side. At the same time, it is urged to expand in the direction in which the protrusion 7a is not arranged. For this reason, it becomes possible to smoothly flow the molten resin toward a wide range in front of the rib forming cavity 12 in the extending direction.

  For example, as shown in FIG. 6B, the protrusion 7b protruding from the main cavity surface of the mold 1 is inclined with respect to the downstream end 12b of the rib forming cavity 12, and the both sides It can also arrange | position so that the protrusion part 7b of a position may become mutually parallel. Accordingly, it is possible to positively promote the flow direction of the molten resin that has flown so as to diffuse into the main cavity 11, not in the extending direction of the rib forming cavity 12, but in the direction in which the protrusions 7 b are inclined. It becomes.

  Further, for example, as shown in FIG. 6C, the protrusion 7 c protruding from the main cavity surface of the mold 1 may be curved and arranged on the downstream end 12 b side of the rib forming cavity 12. it can. As a result, the flow direction of the molten resin flowing so as to diffuse into the main cavity 11 is directed forward in the extending direction of the rib forming cavity 12, and the flow speed of the molten resin is reduced by narrowing the flow range of the molten resin. It becomes possible.

  For example, as shown in FIGS. 6 (a) to 6 (c), changing the arrangement direction and shape of the ridges is, for example, a mold apparatus or a metal mold in Patent Document 1 or Patent Document 2. Compared with the case where the mold itself is changed, it is possible to cope with it easily, and the burden on the manufacturing cost can be reduced.

It is sectional drawing which shows the state by which the metal mold | die for injection molding which concerns on Example 1 of this invention is clamped. It is the II-II sectional view taken on the line in FIG. It is a principal part enlarged view which shows typically the principal part of the fender protector injection-molded using the metal mold | die. It is a principal part enlarged view which expands and shows the downstream end part and protrusion part of the rib shaping | molding cavity formed in the metal mold | die. It is sectional drawing which shows the modification of the metal mold | die. It is a principal part enlarged view which shows another modification of the metal mold | die. It is a perspective view which shows the conventional fender protector for vehicles. It is a principal part enlarged view which shows the extension part of the same fender protector. It is a principal part enlarged view which expands and shows the downstream end part of the rib shaping | molding cavity in the metal mold | die used when injection-molding the same fender protector.

Explanation of symbols

1 Mold 2 Cavity Plate 2a Main Cavity Surface 3 Core Plate 3a Main Cavity Surface 4 Fixed Side Mounting Plate 5 Runner 6 Gate 7 Projection 7a, 7b, 7c Projection 10 Cavity 11 Main Cavity 12a Top 12b Downstream End 12c Downstream end face 12 Rib forming cavity 20 Molten resin 20a Flow 21 Fender protector 22 Bending part 23 Extension part 24 Body part 25 Rib 26 Gate part 27 Concave part

Claims (9)

A plurality of split molds (2, 3), a gate (6), a main cavity (11) capable of molding a thin molded body (24), and at least one of the split molds (2, 3) A rib forming cavity (12) recessed in the main cavity surface (2a, 3a) and communicating with the gate (6), and the rib forming cavity (12) has a branch shape downstream thereof. An injection mold (1) formed by branching,
The split mold (2, 3) is formed from at least one side position sandwiching at least one downstream end (12b) of the rib forming cavity (12) from the main cavity surface (2a, 3a). An injection mold characterized by having protruding ridges (7, 7a, 7b, 7c).   The injection mold according to claim 1, wherein the protrusions (7, 7a, 7b, 7c) are arranged at both of the lateral positions of the downstream end (12b).   The protrusion height (h2) of the protrusions (7, 7a, 7b, 7c) is not less than 30% of the interval (H) of the main cavity (11) in which the protrusions (7) are arranged. The injection mold according to claim 1 or 2, wherein the mold is set to not more than%.   The distance (D) from the downstream end (12b) of the rib forming cavity (12) to the ridge (7, 7a, 7b, 7c) is the width dimension (L) of the downstream end (12b). The injection mold according to any one of claims 1 to 3, wherein the mold is set to 0% or more and 300% or less.   The injection molding die according to any one of claims 1 to 4, wherein the protrusion (7) is arranged in parallel to the downstream end (12b) of the rib molding cavity (12).   The protrusions (7a, 7b) are gradually widened or contracted toward the downstream side with respect to the downstream end (12b) of the rib forming cavity (12) with respect to the downstream end (12b). The injection mold according to any one of claims 1 to 4, wherein the injection mold is arranged so as to be inclined.   The said protrusion part (7c) is bent or curvedly arranged by the downstream end part (12b) side of the said rib shaping | molding cavity (12), or the other side, In any one of Claims 1-4 The mold for injection molding as described.   A resin molded product, which is injection molded using the injection mold (1) according to any one of claims 1 to 7.   The resin molded product according to claim 8, which is used for a fender protector (21) or an under cover for a vehicle.

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