JP2024002188A - Injection mold and resin molded product - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress burrs at gate traces on the molded product surface.

SOLUTION: The injection mold 10 has a core mold 14 and a cavity mold 12. The core mold 14 and the cavity mold 12 are superimposed on each other, and molten resin is injected into the cavity 13 formed between the core mold 14 and the cavity mold 12 to form a resin molded product. The mold 10 is provided with a pin gate 16 formed in the cavity mold 12 to inject molten resin into the cavity 13, and the opening diameter of the pin gate 16 is larger than the thickness of the cavity 13 at the position of the pin gate 16.

SELECTED DRAWING: Figure 1

COPYRIGHT: (C)2024,JPO&INPIT

Description

The present invention relates to an injection mold and a resin molded product.

Injection molding technology is conventionally known as a technology for molding resin molded products. Injection molding technology is a mold formed inside an injection mold (hereinafter also simply referred to as a "mold"), which is made by melting a resin material and processing a metal block to provide a flow path for the molten resin. The space (hereinafter also referred to as "cavity") is injected and filled with molten resin, cooled and solidified, and then the separable mold members that make up the mold are separated to open the molding space (hereinafter referred to as "cavity"). (also referred to as "mold opening") is a technique for molding a resin molded product by removing the molded product.

For example, Patent Document 1 discloses an injection mold in which a pin gate, which is an entrance for molten resin into a cavity, is formed.

Japanese Patent Application Publication No. 2010-208239

Generally, when molten resin is injected into a cavity through a pin gate, the molten resin is cooled and solidified by a core mold and a cavity mold. Then, when the cavity mold and the core mold are opened and a tensile force is applied between the solidified resin in the pin gate and the solidified resin in the cavity at the pin gate position, the pin gate opening (hereinafter also referred to as "gate opening") ) and the molded product, the resin is cut.

When the resin is cut in this way, as shown in the gate marks 16 in FIG. 1 of Patent Document 1, marks indicating the position of the gate on the molded product (hereinafter also referred to as "gate marks") .) may cause protruding burrs.

The present invention was made in view of the above-mentioned problem, and an object of the present invention is to suppress the occurrence of burrs in gate marks on a molded product.

The injection molding mold of the first aspect has a core mold and a cavity mold, the core mold and the cavity mold are overlapped, and the mold is melted into the cavity formed between the core mold and the cavity mold. An injection mold for molding a resin molded product by injecting resin, comprising a pin gate formed in the cavity mold and for injecting molten resin into the cavity,
The opening diameter of the pin gate is larger than the thickness of the cavity at the position of the pin gate.

In the injection mold of the first aspect, the opening diameter of the pin gate formed in the cavity mold is the thickness (hereinafter referred to as "thickness") at the position of the pin gate of the cavity formed between the core mold and the cavity mold. (Also called.) larger. Generally, when molten resin is injected into a cavity through a pin gate, the molten resin is cooled and solidified by the core mold and cavity mold, but there is a difference in heat capacity in the thin walled part compared to the thick walled part. The cooling speed of the molten resin is fast, and the solidification speed is also fast.

On the other hand, in this aspect, by making the opening diameter of the pin gate larger than the thickness of the cavity at the pin gate position, the amount of molten resin in the pin gate can be increased and the heat capacity can be increased. As a result, when the molten resin upstream of the gate opening is cooled and solidified by the surrounding cavity mold after the injection of molten resin is completed, the solidification speed is suppressed and relatively slow due to the closeness to the heat source. Become slow.

In this way, by controlling the difference in solidification speed between the molten resin in the pin gate and the molten resin in the cavity at the pin gate position and increasing the difference in heat shrinkage, the difference between the solidified resin at the gate opening and the molded product is controlled. Distortion occurs concentrated in layers at the boundary.

Generally, when the cavity mold and core mold are opened and a tensile force is applied between the solidified resin in the pin gate and the solidified resin in the cavity at the pin gate position, the boundary between the gate opening and the molded product is Since the solidified resin is constricted, stress is concentrated at this constricted part, and as the stress exceeds the breaking strength of the solidified resin, a crack, which is a partial break, occurs at the outer periphery of the constricted part, and then, The rupture progresses toward the center, eventually leading to separation.

In this embodiment, since the concentration of strain induces the progression of fracture along the weakened layer, the solidified resin can be easily and relatively smoothly cut. This suppresses the occurrence of burrs and the like in the gate marks on the molded product.

In the injection molding mold of the second aspect, in the injection molding mold of the first aspect, the core mold is formed at a position opposite to the pin gate, and when filling the cavity with molten resin, The injection mold includes a residual gas discharge section for discharging residual gas inside the injection mold to the outside of the injection mold.

When the thickness of the cavity is thin according to the shape specifications of the resin molded product, a higher injection pressure is required when injecting molten resin into the cavity than when the thickness of the cavity is thick. For this reason, an increase in the load on the molding machine, an increase in the flow rate of the molten resin, and accompanying distortion of the molded product are likely to occur.

Therefore, in this aspect, the core mold is provided with a residual gas exhaust part that discharges the residual gas in the cavity to the outside of the mold when filling the cavity with molten resin, at a position facing the pin gate provided in the cavity mold. is forming. As a result, a large amount of residual gas that is temporarily pushed out by the molten resin from within the sprue and the runner through the gate opening is discharged from the residual gas discharge section provided in the vicinity of the pin gate.

Therefore, compared to the case where there is no such residual gas discharge section, a large amount of residual gas that is temporarily pushed out from within the sprue and runner through the gate opening is added to the residual gas in the cavity, creating a high pressure. This reduces the degree to which the flow of the molten resin within the cavity is hindered. Furthermore, the molten resin can be quickly filled into the cavity even at a relatively low injection pressure, and the filling performance of thin-walled molding can be improved.

Furthermore, since the resin can be filled with a relatively low injection pressure, uneven distortion within the resin caused by high pressure is suppressed. Therefore, the solidified resin is easily and smoothly cut at the boundary between the gate opening and the molded product, and the occurrence of burrs and the like in the gate marks on the molded product is further suppressed.

In the injection molding mold of the third aspect, in the injection molding mold of the first aspect, in the core mold, a pool that is a depression along a spherical surface is formed in a portion facing the pin gate, and the pin gate The opening diameter of is larger than the maximum thickness of the cavity at the location of the pool.

In the injection mold of the third aspect, a molten metal pool, which is a concave depression along the spherical surface, is formed in the core mold portion facing the pin gate. For this reason, the wall thickness of the cavity directly below the pin gate becomes thicker by the depth of the molten water pool, and the flow path becomes wider. Further, since the molten resin injected at high speed from the pin gate hits the depressions along the spherical surface of the pool and rebounds in an oblique direction, the molten resin is deflected laterally along the depressions along the spherical surface. This allows the molten resin to flow more smoothly than when there is no pool. The homogeneity of the resin in this area is improved, and irregular irregularities on the fracture surface that occur when the solidified resin is cut at the gate opening position are suppressed, and furthermore, there are no dents in the gate marks on the molded product due to the fracture. Even if this occurs, the wall thickness of the gate mark portion can be ensured and the strength of the molded product can be maintained.

The resin molded product of the fourth aspect has a gate mark on one surface of the molded product, and the diameter of the gate mark is larger than the thickness of the resin at the position of the gate mark.

The resin molded product of the fourth aspect has gate marks. Generally, a resin molded article having gate marks is molded by injecting molten resin into a cavity formed between a core mold and a cavity mold through a gate.

Further, in the resin molded product of the fourth aspect, the diameter of the gate mark is larger than the thickness of the resin. That is, the opening diameter of the gate in the mold is larger than the thickness of the cavity. When molten resin is injected into the cavity through the gate, the molten resin is cooled and solidified by the core mold and the cavity mold. At this time, the gate portion having a large opening diameter is cooled at a slower rate than the cavity portion having a thinner thickness, and therefore the difference in solidification rate between the two portions becomes large.

Therefore, when the cavity mold and the core mold are opened, the resin is easily cut at the pin gate position, and the formation of protruding burrs at the gate marks on the molded product is suppressed. That is, since the diameter of the gate mark is larger than the thickness of the resin at the position of the gate mark, a relatively flat gate mark is formed, and the occurrence of burrs etc. that protrude at the gate position of the molded product is suppressed.

The resin molded product of the fifth aspect is the resin molded product of the fourth aspect, and has residual gas discharge portion marks on the other surface of the molded product facing the gate marks.

Note that the residual gas discharge part trace refers to the trace of the residual gas discharge part provided in the core mold in the second embodiment that is seen on the surface of the resin molded product, that is, the boundary surface of the residual gas discharge part in the core mold. Refers to the part on a resin molded product where the boundary between the residual gas discharge part and other core mold parts can be identified due to slight burrs caused by molten resin seeping out along the boundary or color changes inside and outside the boundary.

In the resin molded product of the fifth aspect, the thickness of the resin is smaller than the diameter of the gate mark, similarly to the resin molded product of the fourth aspect. That is, the thickness of the cavity in the mold is smaller than the opening diameter of the gate. When the thickness of the cavity is thin as described above, injection pressure is required when injecting the molten resin into the cavity, compared to when the thickness of the cavity is thick.

Therefore, in the resin molded product of the fifth aspect, residual gas discharge portion marks are formed on the other surface facing the gate marks. In other words, a residual gas discharge section for discharging residual gas from the cavity is formed at a position facing the gate in the core mold. Therefore, a portion of the large amount of residual gas that is temporarily pushed out by the molten resin from within the sprue and the runner through the gate opening is discharged from this residual gas discharge section.

As a result, the degree to which the residual gas hinders the flow of the molten resin within the cavity is suppressed, and the molten resin can be quickly filled into the cavity. As a result, the filling properties of thin-walled molding can be improved. Furthermore, since the resin can be filled with a relatively low injection pressure, uneven distortion within the resin caused by high pressure is suppressed. As a result, the resin can be easily and smoothly cut at the boundary between the gate opening and the molded product, and the occurrence of burrs and the like in the gate marks on the molded product can be further suppressed.

According to the present invention, it is possible to suppress the occurrence of burrs exceeding the allowable range in gate marks on a molded product.

FIG. 1 is a cross-sectional view showing an injection mold according to the present embodiment. (A) is a sectional view showing an example of the injection molded product according to the present embodiment, (B) is a sectional view showing another example, and (C) is a sectional view showing still another example. FIG. 3 is a cross-sectional view showing an injection molded product according to a comparative example. FIG. 2 is a cross-sectional view showing a state in which resin is injected into the injection mold according to the present embodiment.

Embodiments of the present invention will be described below. In the description of the drawings below, the same or similar parts are denoted by the same or similar symbols. However, the drawings are schematic, and the relationship between thickness and planar dimensions, the ratio of the thickness of each device and each member, etc. differ from the reality. Therefore, specific thickness and planar dimensions should be determined with reference to the following explanation. Furthermore, the drawings include portions that differ in dimensional relationships and ratios.

<Injection mold>
As shown in FIG. 1, the injection molding die 10 according to this embodiment includes a cavity mold 12 and a core mold 14. In addition, only a part of the injection mold 10 is shown in FIG.

In the present invention, the injection mold is mainly divided into two parts so that the cavity, which is the molding space inside the mold, is filled with molten resin and the molded product can be taken out from the cavity after cooling and solidifying. has been done. Among these mold parts, the mold part that is connected to the molten resin injection nozzle of the injection molding machine and is provided with a gate that is an outlet for discharging the molten resin into the cavity is called a "cavity mold". On the other hand, of the two divided mold parts, the mold part that is placed opposite to the "cavity mold" is referred to as the "core mold".

In the injection mold 10 according to the present embodiment, a cavity mold 12 and a core mold 14 are overlapped, and a molten resin is poured into a cavity 13 (molding space) formed between the cavity mold 12 and the core mold 14. A resin molded product is formed by injection. The injection mold 10 also includes a pin gate 16 and a residual gas exhaust section 18.

In the present invention, "residual gas" refers to the gas that exists in the cavity during the process of filling the cavity with molten resin, and it is the gas that exists in the cavity during the process of filling the cavity with molten resin. It consists of air and volatile components of resin that are pushed out from the sprue and runners that are added.

(cavity)
The cavity 13 according to this embodiment includes a hot water pool 13A and a planar space 13B. The hot water reservoir 13A is a portion where the convex portion 30A of the resin molded product 30 is molded (see FIG. 2). Further, the hot water reservoir 13A is a concave depression (dimple) formed in a portion of the core mold 14 facing the pin gate 16 and along the spherical surface. In the present invention, the diameter of the spherical surface along which the molten water pool follows is not particularly limited, but in this embodiment, the diameter of the spherical surface along which the molten water pool 13A follows is approximately 5 mm in radius.

Further, in the present invention, the depth of the hot water pool is not particularly limited, but in this embodiment, the depth H1 of the hot water pool 13A is about 0.7 mm. Further, the depth H1 is the depth in the vertical direction from the surface forming the planar space 13B in the core mold 14, and is the depth of the center (bottom) of the pool 13A and the deepest depth. .

The planar space portion 13B according to the present embodiment is a portion where a planar portion 30B is molded around the convex portion 30A of the resin molded product 30 (see FIG. 2). In the present invention, the thickness of the planar space is not particularly limited, but in this embodiment, the thickness H2 of the planar space 13B is approximately 0.2 mm. The thickness H2 is the thickness in the direction perpendicular to the plane forming the planar space 13B, and is the distance between the surface of the cavity mold 12 and the surface of the core mold 14.

The maximum thickness of the cavity 13 in the portion where the molten metal pool 13A is formed is the thickness H3. Thickness H3 is the thickness of cavity 13 at the position of pin gate 16, and is the sum of depth H1 and depth H2 (H3=H1+H2).

(Gate)
In this embodiment, the pin gate 16 injects molten resin toward the hot water pool 13A of the cavity 13. The pin gate 16 includes a sprue 16A through which the molten resin injected into the cavity 13 flows, and a gate land 16B. The gate land 16B is provided at the tip of the pin gate 16, that is, at the end on the cavity 13 side, and is a tapered portion whose diameter decreases toward the cavity 13 side. The tip of the gate land 16B, that is, the end on the cavity 13 side, is called a gate opening 16C, and the opening diameter φ1 of the gate opening 16C is larger than the maximum thickness H3 of the cavity 13 at the position of the pool 13A (φ1> H3).

(Residual gas discharge part)
In this embodiment, the residual gas exhaust section 18 includes a gas vent hole 18A and a plug member 18B. The residual gas discharge part 18 is formed in the core mold 14 at a position facing the pin gate 16 of the cavity mold 12, and discharges the residual gas in the cavity 13.

Note that, in the present invention, the location where the residual gas discharge section is formed is not limited to this. For example, the residual gas discharge part can be provided at a separate location in the core mold or in the cavity mold. Further, the residual gas exhaust portion may be formed on the parting surface. Furthermore, in the present invention, the installation of a residual gas discharge section is one of the options and is not essential.

(Gas vent hole)
The gas vent hole 18A according to this embodiment reaches the center (deepest part) of the hot water pool 13A from the outside of the mold. In other words, the gas vent hole 18A opens at the center of the hot water pool 13A.

However, in the present invention, the opening position of the gas vent hole is not limited to the center of the pool, but may be placed at any position between the center and the outer edge (boundary with the planar space) of the pool, for example. Can be placed. The gas vent hole 18A according to this embodiment is provided so as to discharge residual gas remaining from the center of the hot water pool 13A to the vicinity of the center. Specifically, the residual gas is air remaining in the vicinity of the center of the hot water pool 13A, a gas such as a resin volatile component, or a mixed gas thereof.

In this embodiment, the opening of the gas vent hole 18A facing the resin molded product 30 (see FIG. 2) has a circular shape with a diameter of about 2.0 mm. Note that in the present invention, the dimensions and shape of the opening can be changed as appropriate. The shape of the gas vent hole according to the present invention can be set to any geometric shape, such as a polygonal shape or an elliptical shape. Therefore, the shape of the residual gas exhaust part mark formed on the resin molded product also changes depending on the shape of the gas vent hole.

(Plug member)
The plug member 18B according to this embodiment is provided in a state in which it is detachably inserted into the gas vent hole 18A. The plug member 18B is a cylindrical member that is in close contact with the inner periphery of the gas vent hole 18A. The plug member 18B has a shaft and a head (flange) whose diameter is larger than the shaft. Although not shown, the head can be detachably fixed to the core mold 14 with screws or the like. The outer diameter of the cylindrical shaft of the plug member 18B is approximately equal to the inner diameter of the gas vent hole 18A. In the present invention, the shape of the plug member is not limited to a cylindrical shape, but may be other shapes such as a prismatic shape depending on the shape of the gas vent hole.

By removing the plug member 18B according to this embodiment from the gas vent hole 18A, the plug member 18B and the gas vent hole 18A can be easily cleaned when not being molded.

(Gas flow path)
A gas flow path 20 having an opening diameter through which the molten resin cannot pass and which allows the residual gas to pass is formed on the outer circumferential surface of the cylindrical material of the plug member 18B according to this embodiment. The gas passage 20 is a narrow gas passage leading from the inside of the cavity 13 to the outside of the mold, through which residual gas can pass, but through which the molten resin cannot pass.

The opening diameter of the gas flow path 20 according to this embodiment is approximately 2/100 mm. Note that in the present invention, the opening diameter of the gas flow path is not limited to this. For example, when designing a mold, consider factors such as the type of resin material used for molding, the temperature of the molten resin, molding conditions such as injection pressure, and the length and flexibility of the gas flow path, and The opening diameter can be determined arbitrarily.

The gas flow path 20 illustrated in FIG. 1 is configured such that the outer surface of the plug member 18B and the inner surface of the gas vent hole 18A are in close contact with each other, and the inner surface of the gas vent hole 18A and the outer surface of the shaft portion of the plug member 18B are in close contact with each other. formed between. The gas flow path 20 is formed by a gap 18B1 formed on the outer peripheral surface of the plug member 18B along the axial direction of the plug member 18B.

The gap 18B1 according to this embodiment is formed by cutting out the outer peripheral surface of the plug member 18B in a plane parallel to the axial direction of the plug member 18B. In the present invention, the gap serving as the gas flow path may be formed by forming a groove on the outer peripheral surface of the plug member along the axial direction of the plug member. In addition, the number of gaps that serve as gas flow paths is arbitrary, and it is also possible to merge or branch in the middle, and the cross-sectional dimensions of the gaps are also determined so that the molten resin cannot pass through in the part that contacts the cavity and the residual gas does not pass through. The other downstream portions may be arbitrarily large as long as they have an opening diameter that allows them to pass through.

<Resin molded products>
By using the injection mold 10 according to this embodiment, a resin molded product 30 (hereinafter also simply referred to as molded product 30) shown in FIG. 2(A) can be molded. The molded product 30 includes a convex portion 30A and a flat portion 30B formed around the convex portion 30A.

The convex portion 30A is a thick portion formed of resin filled in the pool 13A of the injection mold 10. Moreover, the plane part 30B is a thin part formed of the resin filled in the plane space part 13B in the injection mold 10.

In addition, in the present invention, "thin wall" means that the flow resistance of the molten resin is high due to the thin thickness of the cavity, and accordingly, a high injection pressure of the molten resin is required, which increases the load on the molding machine. This refers to a wall thickness that is likely to cause an increase in the flow rate of the molten resin, distortion of the molded product, etc. due to this, and does not mean that the wall thickness is less than a specific thickness.

A gate mark 32 and a residual gas discharge part mark 34 are formed at the position of the convex portion 30A in the molded product 30 according to this embodiment. The gate mark 32 is formed on the surface of the molded product 30 that comes into contact with the cavity die 12 during molding, and has a shape corresponding to the opening shape of the pin gate 16 (gate land 16B). On the other hand, the residual gas discharge part trace 34 is formed on the surface of the molded product 30 that comes into contact with the core mold 14 during molding, and has a shape corresponding to the cavity side end shape of the residual gas discharge part 18 .

The diameter φ1A of the gate mark 32 is approximately equal to the opening diameter φ1 of the gate land 16B (see FIG. 1), and is larger than the thickness (thickness) H3A of the resin at the position where the gate mark 32 is formed. Moreover, this thickness H3A is approximately equal to the maximum thickness H3 (see FIG. 1) of the cavity 13 at the position of the molten metal pool 13A.

In the example shown in FIG. 2A, the gate mark 32 is formed substantially flush with the surrounding area of the gate mark 32. In the example shown in FIG. On the other hand, in the example shown in FIG. 2(B), the gate mark 32 is formed so as to be recessed from a portion around the gate mark 32. Furthermore, in the example shown in FIG. 2C, the gate mark 32 is formed to swell from the area around the gate mark 32.

As shown in these examples, in the present invention, the gate mark may be substantially flush with the surrounding portion, may be recessed, or may be raised. In each of these cases, the gate marks do not necessarily need to be visible or palpable to the naked eye. The gate mark 32 may be formed by concavities and convexities that can be seen under magnification of about 100 times or more or about 1000 times or more with an optical microscope, for example. The same applies to the traces of the residual gas discharge portion. Note that, as described above, the residual gas exhaust part is not essential to the injection mold of the present invention, and the residual gas exhaust part mark is not essential to the molded product.

<Action and effect>
According to the injection mold 10 according to this embodiment, as shown in FIG. 1, the opening diameter φ1 of the pin gate 16 formed in the cavity mold 12, that is, the opening diameter φ1 of the gate opening 16C, The thickness H3 of the cavity 13 formed between the pin gate 16 and the cavity mold 12 is greater than the thickness H3 at the pin gate 16 position.

Generally, as shown in FIG. 4, for example, when molten resin is injected into a cavity through a pin gate, the molten resin is cooled and solidified by a core mold and a cavity mold. In the thinner part, the molten resin is cooled faster and solidified faster than in the thicker part due to the difference in heat capacity.

In this embodiment, the opening diameter φ1 of the pin gate 16 is made larger than the thickness H3 of the cavity 13 at the position of the pin gate 16. This increases the amount of molten resin within the pin gate 16, increasing the heat capacity. For this reason, when the molten resin upstream of the gate opening 16C is cooled and solidified by the surrounding cavity mold 12 after the injection of the molten resin is finished, the solidification speed is suppressed due to the closeness to the heat source. relatively late.

In this way, by controlling the difference in solidification speed between the molten resin in the pin gate 16 and the molten resin in the cavity 13 at the position of the pin gate 16, and increasing the difference in thermal contraction, the solidified resin can form the gate opening 16C. Strain is concentrated in a layered manner at the boundary between the molded product and the molded product.

Therefore, in this embodiment, when the cavity mold 12 and the core mold 14 are opened and a tensile force is applied between the solidified resin in the pin gate 16 and the solidified resin in the cavity 13 at the position of the pin gate 16, the gate Stress is concentrated at the constricted portion at the boundary between the opening 16C and the molded product, and first a crack, which is a partial break, occurs at the outer periphery of the constricted portion. Then, the fracture progresses toward the center and is finally separated at this portion. The progression of this fracture is guided along the boundary between the gate opening 16C and the molded product, where strain is concentrated and a weakened layer is formed, so that the solidified resin is easily and relatively smoothly cut. It becomes easier. As a result, as shown in FIGS. 2(A) to 2(C), the occurrence of burrs and the like in the gate marks 32 on the molded product 30 is suppressed.

Further, in general, when the thickness of the cavity is thin according to the shape specifications of the resin molded product, a higher injection pressure is required when injecting molten resin into the cavity than when the thickness of the cavity is thick. For this reason, an increase in the load on the molding machine, an increase in the flow rate of the molten resin, and accompanying distortion of the molded product are likely to occur.

Therefore, the injection mold 10 according to the present embodiment has a residual gas discharge part 18 for discharging the residual gas in the cavity 13 in the core mold 14 at a position facing the pin gate 16 provided in the cavity mold 12. It is set up. This residual gas discharge part 18 has a gas passage 20 as a narrow gas passage leading from the inside of the cavity 13 to the outside of the mold, through which the residual gas can pass but the molten resin cannot pass through. As a result, a large amount of residual gas that is temporarily pushed out by the molten resin from inside the sprue 16A (and inside the runner if there is a runner) through the gate opening 16C is transferred to the residual gas discharge section 18 in the vicinity of the pin gate 16. The gas is discharged from a gas flow path 20 provided therein.

With the configuration of this embodiment, a large amount of residual gas that is temporarily pushed out from within the sprue 16A through the gate opening 16C is removed from the residual gas remaining in the cavity 13, compared to the case where such residual gas discharge section 18 is not provided. By adding to the gas and creating a high pressure, the degree to which the flow of the molten resin within the cavity 13 is obstructed is alleviated. Therefore, it is possible to quickly fill the cavity 13 with the molten resin even at a relatively low injection pressure, that is, it is possible to improve the filling performance in thin-walled molding.

Further, by providing the residual gas discharge section 18, filling can be performed at a relatively low injection pressure, thereby suppressing uneven distortion inside the resin caused by high pressure. Therefore, the resin can be easily and smoothly cut at the boundary between the gate opening 16C and the molded product 30 (see FIG. 2), and the occurrence of burrs, etc. in the gate marks 32 of the molded product 30 is further suppressed. .

Furthermore, in the injection mold 10 according to the present embodiment, a pool 13A, which is a concave depression along the spherical surface, is formed in a portion of the core mold 14 facing the pin gate 16. Therefore, the wall thickness of the cavity 13 directly below the pin gate 16 becomes thicker by the depth H1 of the pool 13A, and the flow path becomes wider.

In addition, the molten resin injected at high speed from the pin gate 16 does not bounce vertically off the wall of the core mold 14, but the reflection is deflected laterally by the slope of the depression along the spherical surface, so compared to the case where there is no pool 13A, The flow of molten resin becomes smooth.

This also improves the homogeneity of the solidified resin in the portion of the pool 13A, and suppresses the occurrence of irregularities exceeding the allowable range in the gate marks 32 when the solidified resin is cut at the gate opening 16C. Further, as shown in FIG. 2(B), even if a dent occurs in the gate mark 32 of the molded product 30 due to breakage, the thickness of the gate mark 32 portion is ensured, and the strength of the molded product 30 can be maintained.

Furthermore, the resin molded product 30 according to this embodiment has gate marks 32, as shown in FIG. As shown in FIG. 1, the resin molded product 30 having the gate marks 32 is molded by injecting molten resin into the cavity 13 formed between the core mold 14 and the cavity mold 12 through the pin gate 16. .

In this resin molded product 30, the diameter φ1A of the gate mark 32 is larger than the thickness H3A of the resin at the position where the gate mark 32 is formed. That is, the opening diameter φ1 of the gate opening 16C in the mold 10 shown in FIG. 1 is larger than the thickness H3 of the cavity 13.

Generally, as shown in FIG. 4, for example, when molten resin is injected into a cavity through a pin gate, the molten resin is cooled and hardened by the core mold and the cavity mold. In the molding of the resin molded product 30 according to the present embodiment, the molten resin in the gate opening 16C portion having a large opening diameter is cooled at a slower rate than the molten resin in the cavity 13 portion having a thinner thickness. The difference in curing speed becomes large.

Therefore, when the cavity mold 12 and the core mold 14 are released, the resin is easily cut at the gate opening 16C of the pin gate 16, and as shown in FIG. The protruding burrs that occur are suppressed. That is, since the diameter φ1A of the gate mark 32 is larger than the thickness H3A of the resin at the position of the gate mark 32, the gate mark 320A according to the comparative example shown by the two-dot chain line in FIG. 2(C) or the comparative example shown in FIG. Compared to the above, a relatively flat gate mark 32 as shown in FIG. .

Although the height of the protruding burr in the gate mark 320A shown in FIG. 2(C) is approximately equal to the diameter φ1A of the gate mark 320A, the height of the burr is generally irregular and It may be larger or smaller than the diameter of the scar, making it difficult to control. On the other hand, in the resin molded product of the present invention, even if the gate mark is formed to be higher than the surrounding area, the height of the burr is small, as in the gate mark 32 shown in FIG. 2(C), for example. It is suppressed to be lower than the diameter of the gate scar.

FIG. 3 shows a molded product 300 according to a comparative example. The molded product 300 is an injection molded product in which the thickness of the solidified resin (approximately the thickness of the cavity) H100 is relatively thick. A gate mark 320 is formed in the molded product 300. The gate marks 320 are formed on the surface of the molded product 300 that comes into contact with the cavity mold (not shown) during molding, and are shaped to correspond to the opening shape of a pin gate (not shown) provided in the cavity mold. This is a trace with a diameter of φ100.

Unlike the present invention, the diameter φ100 of the gate mark 320 according to this comparative example is smaller than the thickness H100 of the molded product 300 (φ100<H100). That is, the opening diameter of a gate opening (not shown) in a mold (not shown) for molding this molded product 300 is smaller than the thickness of the cavity.

When molding the molded article 300 according to this comparative example, the molten resin injected into the cavity is cooled and hardened by the core mold (not shown) and the cavity mold, as in the case of the present invention. However, unlike the case of the present invention, the difference in the cooling rate of the molten resin in the gate opening portion where the opening diameter is relatively small is relatively small compared to the molten resin in the cavity portion where the thickness is relatively thick. For this reason, a weak layer with concentrated strain is not sufficiently formed at the gate opening position, and therefore, when the cavity mold and core mold are separated, the solidified resin cannot be cut smoothly at the gate opening position. As shown in FIG. 3, relatively large protruding burrs are likely to occur in the gate marks 320 of the molded product 300. Generally, when fracture is forcibly caused by tensile force, the shape of the unevenness that occurs on the fracture surface is controlled by chance and cannot be predicted. It is possible that it will become. (H100≠φ100)

Further, in the resin molded product 30 according to the present embodiment, the thickness H3A of the solidified resin is smaller than the diameter φ1A of the gate mark 32. That is, the thickness H3 of the cavity 13 in the mold 10 shown in FIG. 1 is smaller than the opening diameter φ1 of the gate opening 16C. Generally, when injecting resin into a cavity, if the cavity is thin, more injection pressure is required than if the cavity is thick.

In the resin molded product 30 according to the present embodiment, a residual gas discharge part mark 34 is formed on the other surface facing the gate mark 32. That is, in the core mold 14 shown in FIG. 1, a residual gas discharge part 18 for discharging gas from the cavity 13 is formed at a position facing the pin gate 16 of the cavity mold 12. Therefore, a portion of the large amount of residual gas that is temporarily pushed out from inside the sprue 16A through the gate opening 16C by the molten resin is transferred to the gas flow path 20 provided in the residual gas discharge section 18 immediately adjacent to the sprue 16A. is discharged from.

As a result, the degree to which residual gas obstructs the flow of the molten resin within the cavity 13 is suppressed, the molten resin can be quickly filled into the cavity 13, and the filling properties of thin-walled molding can be improved. Furthermore, since filling can be performed at a relatively low injection pressure, uneven distortion within the solidified resin caused by high pressure is suppressed. As a result, the resin can be easily and smoothly cut at the boundary between the gate opening 16C and the molded product 30, and the occurrence of burrs and the like in the gate marks 32 of the molded product 30 is further suppressed.

<Other embodiments>
In the above embodiment, as shown in FIG. 1, the cavity 13 includes the hot water pool 13A and the planar space 13B, but the embodiment of the present invention is not limited to this. For example, the cavity does not have to include a hot water reservoir. In this case, it is sufficient that the opening diameter of the pin gate formed in the cavity type, that is, the opening diameter of the gate opening, is larger than the thickness of the planar space.

Note that even in an embodiment that does not include a hot water pool, a residual gas discharge part for discharging residual gas in the cavity can be formed at a position facing the pin gate provided in the cavity type.

Although the present invention has been described by the embodiments disclosed above, the statements and drawings that form part of this disclosure should not be understood as limiting the present invention. The present invention includes embodiments in which each of the embodiments described above is appropriately combined, and various embodiments not described above, and the technical scope of the present invention can be understood from the above description. It is determined only by matters specifying the invention in the claims.

10 Injection mold 12 Cavity mold 13 Cavity 13A Hot water pool 14 Core mold 16 Pin gate 18 Residual hot gas discharge part 30 Molded product 32 Gate trace 34 Residual gas discharge part trace

Claims (5)

A resin molded product is formed by having a core mold and a cavity mold, overlapping the core mold and the cavity mold, and injecting molten resin into the cavity formed between the core mold and the cavity mold. An injection mold,
A pin gate formed in the cavity type and for injecting molten resin into the cavity,
The opening diameter of the pin gate is larger than the thickness of the cavity at the position of the pin gate.
Mold for injection molding. In the injection molding mold of the first aspect, the core mold is formed at a position facing the pin gate, and when filling the cavity with molten resin, residual gas in the cavity is transferred to the injection molding mold. equipped with a residual gas exhaust section to discharge the residual gas to the outside,
The injection mold according to claim 1. In the core mold, a hot water pool, which is a depression along a spherical surface, is formed in a portion facing the pin gate,
The injection mold according to claim 1, wherein the opening diameter of the pin gate is larger than the maximum thickness of the cavity at the position of the molten metal pool. There are gate marks on one surface of the molded product,
The diameter of the gate mark is larger than the thickness of the resin at the position of the gate mark.
Resin molded product. having a residual gas discharge part mark on the other surface of the molded product facing the gate mark;
The resin molded article according to claim 4.