JP2007130822A - Mold - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mold which can secure the supporting rigidity of a nesting member and a cavity insert by spherical bodies and mold durability. <P>SOLUTION: The mold 1 has the nesting 110 having a cavity surface Ca in the shape of a part of a molding and the body member 120 supporting the cavity insert 110 movably from the outside through a plurality of the spherical bodies 131. The spherical bodies 131, the nesting 110, and the body member 120 are formed, so that the value of pressurization generated by making the diameters of the spherical bodies 131 larger than the clearance between the nesting 110 and the body member 120 is 4 μm or below per spherical body, and the product of the pressurization and the total number of the spherical bodies is at least 30 μm. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a molding die that is movable with respect to a main body member when a nest having a cavity surface is supported by the main body member via a plurality of spherical bodies.

  In general, as a molding die for a plastic optical lens (hereinafter, also simply referred to as “optical lens”), a shape in which a cavity surface (molding surface) of a fixed-side mold corresponds to one optical surface of the optical lens, In addition, there is a type in which the cavity surface of the movable mold that can be separated from and attached to the fixed mold is made to correspond to the other optical surface of the optical lens. As such a mold, conventionally, a nest having a cavity surface formed at the tip thereof, a ball retainer that rotatably supports a plurality of spherical bodies at appropriate positions on a cylindrical peripheral wall, and via this ball retainer A main body member that supports the insert from the outside is known (see Patent Document 1). In such a mold, the molded article can be easily taken out by moving the insert relative to the main body member and projecting the cavity surface of the insert from the main body member.

JP 2003-231159 A

By the way, the bearings used in the mold (the ball retainer, the nest and the rolling part of the main body member that rolls on the ball retainer) are (1) the use temperature is high (approximately 80 ° C. to 150 ° C.), (2 ) Nesting and body member are deformed by pressure from resin and it is repeated hundreds of thousands of times. (3) Uneven load is repeated hundreds of thousands of times due to resin flow. The environment is special.
For the above reasons, there are problems of positional accuracy (including rigidity) and durability, and there is a problem that the bearing design guideline of the mold is not clear.

  Specifically, in the above-described mold, when the gap between the nest and the main body member is larger than the diameter of the spherical body, there arises a problem that the nest rattles against the main body member. If the diameter of the sphere is the same as or slightly smaller than the diameter of the sphere, the support rigidity of the nesting supported via a plurality of spheres is weak, so the problem arises that the nesting is tilted by the injection pressure of the molten resin. It was. In particular, when molding an optical component such as an optical lens or a lens frame, if the insert is tilted with respect to the main body member, the optical axis of the molded product is shifted, which may have a serious adverse effect on quality. Further, when the gap is considerably smaller than the diameter of the spherical body, there has been a problem that the durability of the mold (bearing) is lowered.

  Therefore, an object of the present invention is to provide a molding die that can ensure the supporting rigidity of the nest supported through a plurality of spherical bodies and also ensure the durability.

  The present invention that solves the above-described problems includes a nest having a cavity surface that represents a shape of a part of a molded product, and a main body member that supports the nest so as to be movable from the outside via a plurality of spherical bodies. In the molding die, the value of the pressure generated by making the diameter of the spherical body larger than the gap between the insert and the main body member is 4 μm or less per spherical body, and The spherical body, the insert and the main body member are formed so that the product of the total number of spherical bodies is 30 μm or more.

  Here, “pressurization” refers to applying pressure so that there is no gap between the spherical body and the inner wall (main body member) or outer wall (nesting), and the unit is the pressure unit (Pa). The difference between the gap between the inner wall and the outer wall and the spherical body diameter is “μm”.

According to the present invention, by setting the product of the pressurization and the total number of spherical bodies to 30 μm or more, it is possible to ensure the supporting rigidity of the nesting by the main body member and the spherical body, and to make it 4 μm or less per spherical body, The durability of the mold (including all spherical bodies, inserts, and main body members) can be secured. In addition, the above-mentioned values of the pressurization and the number of spherical bodies are values obtained by inventor's earnest research. In other words, the inventor found that the controlling factor of durability is the pressurization. If the pressurization is too high, not only the spherical body but also the nesting and main body members are deteriorated, and the life of the mold is shortened (decrease in durability). In order to maintain 500,000 shots, which is a general life of an injection mold, it was found that the pressure is preferably 4 μm or less per spherical body. On the other hand, the inventor paid attention to the fact that the position accuracy (rigidity) is governed by the pressure and the number of balls, and that the position accuracy is improved by increasing the pressure and the number of balls. From the experiment, we found that the appropriate range of the number of balls should satisfy the following formula. (Pressure is per spherical body)
(Pressure [μm]) × (Total number of balls) ≧ 30 [μm]
By setting the pressurization and the number of spherical bodies in this way, it is possible to achieve two conflicting issues that could not be achieved in the past, such as securing the support rigidity of the insert and ensuring the durability of the mold. Yes.

  According to the present invention, the spherical body, the nest, and the main body member are formed so that the pressure is 4 mm or less per spherical body and the product of the pressure and the total number of spherical bodies is 30 μm or more. Therefore, the support rigidity of the insert can be ensured and the durability of the mold can be ensured.

  Next, embodiments of the present invention will be described in detail with reference to the drawings as appropriate. FIG. 1 is an overall cross-sectional view showing a molding die according to the present embodiment.

  As shown in FIG. 1, the molding die 1 is formed by forming a cavity C between the first die 100 and the second die 200 and supplying molten resin into the cavity C. The optical lens as a product is molded. The cavity C communicates with a spool or a gate (not shown) that serves as a passage for the molten resin. The first mold 100 and the second mold 200 are respectively attached to the movable side and the fixed side of an injection molding apparatus (not shown), and the first mold 100 is separated from the second mold 200. It is arranged so that it can be freely touched (movable in the axial direction).

  The first mold 100 includes a nest 110 having a cavity surface Ca formed at the tip thereof, which is shaped like one optical surface of the optical lens (a part of a molded product), and a body member into which the nest 110 is fitted. 120, and a ball retainer 130 is provided between the insert 110 and the main body member 120.

  The nesting 110 is a metal member configured as a separate part from the main body member 120, and the nesting main body 111 formed in a substantially columnar shape, and a central portion on one end side (right side in FIG. 1) of the nesting main body 111. And a columnar portion 112 extending from the column.

  The nesting body 111 is formed to have a larger diameter than the thick hole portion 122 of the body member 120 to be described later, so that the surface on one end side thereof is the surface on the other end side (left side in FIG. 1) of the body member 120. Contact is possible.

  The columnar portion 112 is a portion that fits with the main body member 120. In the present embodiment, the columnar portion 112 is continuous with the cylindrical small diameter portion 114 having the cavity surface Ca on one end side and the other end side of the small diameter portion 114. And a cylindrical-shaped large-diameter portion 115 formed with a larger diameter than the small-diameter portion 114.

  The main body member 120 is a metal member for holding the insert 110 from the outside, and has a cylindrical shape including a hollow portion at the center thereof. The hollow part of the main body member 120 includes a narrow hole part 121 into which the small diameter part 114 of the nest 110 is fitted, and a thick hole part 122 into which the large diameter part 115 of the nest 110 is loosely fitted. Further, a convex taper portion 123 having a truncated cone shape is provided on one end side of the main body member 120 so that the second member 200 can be centered.

  The narrow hole 121 is formed to be approximately the same as or slightly larger than the narrow diameter portion 114 of the insert 110. Specifically, the narrow hole portion 121 is preferably formed larger than the small diameter portion 114 by a diameter of about 10 to 30 μm (radius of about 5 to 15 μm), and a diameter of about 10 to 20 μm (radius of about 5 to 10 μm) is larger. More preferably, it is formed. Further, one end side of the narrow hole portion 121 is open to one end side of the main body member 120, and when the small diameter portion 114 of the nest 110 is fitted into the narrow hole portion 121, it is formed on one end side of the small diameter portion 114. The cavity surface Ca is exposed to one end surface of the main body member 120. In addition, in order to protrude the molded product from the cavity surface Ca, as shown in the drawing, between the surface on one end side of the large diameter portion 115 and the bottom surface of the thick hole portion 122, the surface on one end side of the nested body 111, and the body member The insert 110 and the main body member 120 are arranged so that a predetermined gap S is formed between the other end surface of 120. Thereby, after the 1st metal mold | die 100 leaves | separates from a 2nd metal mold | die, the cavity surface Ca protrudes and pushes out a molded article by pushing the nest | insert 110 with an ejector plate (not shown). .

  The other end side of the thick hole portion 122 opens to the end surface on the other end side of the main body member 120, and thus the columnar portion 112 of the insert 110 can be inserted. One end side of the thick hole portion 122 communicates with the other end side of the narrow hole portion 121. A predetermined gap S2 slightly smaller than the diameter of the spherical body 131 of the ball retainer 130 is formed between the thick hole portion 122 and the large diameter portion 115 of the insert 110 that is loosely fitted in the thick hole portion 122. Has been. The gap S2 will be described in detail later.

  The ball retainer 130 is a part that is interposed between the main body member 120 and the insert 110 to support and align the insert 110, and supports a plurality of spherical bodies 131 and these spherical bodies 131 to be rotatable. And a cylindrical support 132.

  The spherical body 131 is formed of a material harder than the material of the insert 110 or the main body member 120, such as bearing steel (hardness: HRC58) or stainless steel (SUS440, hardness: HRC56). Each spherical body 131 is formed in a uniform size with a very high accuracy of a diameter tolerance of 1 μm or less, and has a diameter slightly larger than the gap S2. Specifically, when the number of spherical bodies is 60, the pressurization pressure per spherical body is preferably 0.5 to 4 μm. Similarly, when the number of spherical bodies is 30, the pressure is preferably 1-4 μm, and when it is 100, the pressure is preferably 0.3-4 μm. In this way, the value of the preload applied to the insert 110, the main body member 120 or the spherical body 131 is 4 μm or less per spherical body, and the product of the pressurized pressure and the total number of spherical bodies is 30 μm. Therefore, the insert 110 is firmly supported and the durability of the mold can be ensured. The value (range) of the preload described above is a value obtained by earnest research by the inventors. By setting such a value, it is possible to ensure the support rigidity of the nesting and the durability of the mold. It has been confirmed by experiments and simulations that both conflicting issues such as securing can be realized.

  Here, the relationship between the above [durability of the mold] and [pressing pressure] and the relationship between [the support rigidity of the nesting] and [the product of the pressing force and the total number of spherical bodies] are shown in FIG. It looks like a graph. That is, as shown in FIG. 2A, the durability of the mold peaks at a predetermined small pressurization, and then gradually decreases as the pressurization increases. Therefore, it can be seen that the pressurization should be set to 4 μm or less in order to ensure sufficient durability. On the other hand, as shown in FIG. 2B, the rigidity increases substantially proportionally as the product of the pressurization and the total number of spherical bodies increases. Therefore, it can be seen that in order to ensure sufficient rigidity, the product of the pressurization and the total number of spherical bodies may be set to be 30 μm or more.

  The support body 132 has a plurality of support holes for rotatably supporting the spherical body 131, and each spherical body 131 supported by these support holes extends from the outer peripheral surface and the inner peripheral surface of the support body 132. By projecting and rolling to the nest 110 and the main body member 120, the nest 110 is movable with respect to the main body member 120.

  In the second mold 200, a concave taper portion 223 that fits with the convex taper portion 123 of the main body member 120 of the first mold 100 is formed on the other end side (left side in FIG. 1) of the main body member 220. Since it is formed and does not require a protruding mechanism, the first mold 100 is different from the first mold 100 in that it does not have a gap S1 as in the first mold 100, but the first mold 100 has the other structure. The structure is the same as that of the mold 100. In addition, the same code | symbol is attached | subjected to the component similar to the 1st metal mold | die 100 in the 2nd metal mold | die 200, and the description is abbreviate | omitted.

According to the above, the following effects can be obtained in the present embodiment.
Since the spherical body 131, the nest 110, and the main body member 120 are formed so that the value of the pressurization is 4 μm or less per spherical body and the product of the pressurization and the total number of spherical bodies is 30 μm or more. The support rigidity of 110 can be secured, and the durability of the mold can be secured.

As mentioned above, this invention is implemented in various forms, without being limited to the said embodiment.
In the above embodiment, the present invention is applied to a structure in which the ball retainer 130 constituted by the spherical body 131 and the support body 132 is provided between the insert 110 and the main body member 120. However, the present invention is not limited to this, for example, You may apply this invention to the structure which provides only a spherical body between the nest | insert 110 and the main-body member 120. FIG.
In the above embodiment, the present invention is applied to a mold for manufacturing an optical lens. However, the present invention is not limited to this, and a high-precision component that requires high concentricity, such as a lens frame that supports the optical lens. You may apply this invention to the metal mold | die for manufacturing.
In the above embodiment, the number of the spherical bodies 131 arranged in the axial direction (movement direction) of the nest 110 is four. However, the present invention is not limited to this. Good.

  In the above embodiment, the spherical bodies 131 are formed with substantially the same size, but the present invention is not limited to this. For example, in the case where three or more spherical bodies 131 are arranged in the moving direction of the nest 110 as in the above-described embodiment, a plurality of (four) spherical bodies 131 arranged in the moving direction of the nest 110 are arranged. Of these, the diameter of the inner part may be smaller than that of the inner part of the nest 110 in the moving direction (protruding direction or return direction). In addition, it is desirable that the spherical body diameter between the head and the tail (both ends) is 0.1 to 0.2% smaller than the spherical body diameter at both ends. Specifically, when the diameter of the spherical body 131 located at the head and tail (both ends of the ball retainer 130) in the moving direction of the nest 110 is 1000 μm, the diameter of the spherical body 131 between them is 998 μm to 999 μm. desirable. According to this, the support rigidity of the insert 110 is ensured by the large spherical body 131 at the head and the tail, and the durability of the mold is ensured by the other small spherical body 131. In this case, the preload values in the vicinity of the leading and trailing spheres 131 and the preload values in the vicinity of the other spheres 131 are different, but these preload values are the preload values described above. (4 μm or less per spherical body, and the product of the pressure and the total number of spherical bodies is 30 μm or more).

In the embodiment, the first mold 100 is attached to the movable side, and the second mold 200 is attached to the fixed side. However, the present invention is not limited to this, and the first mold 100 having a protruding mechanism is fixed. It may be attached to the side.
In the embodiment, the spherical body 131 is used for both the first mold 100 and the second mold 200, but only one side may be used.

In the above-described embodiment, the first mold 100 is the convex taper 123 portion, and the second mold is the concave taper portion 223, but the reverse is also possible.
In the above embodiment, the spherical body 131 is made of bearing steel or stainless steel. However, the spherical body 131 is not limited thereto, and is not limited as long as it is a commercially available bearing ball such as tool steel and ceramic balls.

  In the said embodiment, although the metal mold | die was metal, if it is a material generally used as a metal mold | die, such as aluminum, copper, brass, various steel materials, it will not limit. In addition, you may use the thing by which various coatings (plating for high precision processing, an antioxidant layer, etc.) were carried out to the members made from those materials as a metal mold | die.

It is a whole sectional view showing the metal mold for molding concerning this embodiment. It is the graph (a) which shows the relationship between durability of a metal mold | die, and pressurization, and the graph (b) which shows the relationship between the support rigidity of a nest | insert, and the product of pressurization and the total number of spherical bodies.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Molding die 100 1st metal mold | die 110 Nesting 111 Nesting main body 112 Columnar part 114 Thin diameter part 115 Large diameter part 120 Body member 121 Narrow hole part 122 Thick hole part 130 Ball retainer 131 Spherical body 132 Support body 200 2nd Mold 220 body member Ca cavity surface S2 gap

Claims (1)

A nesting having a cavity surface that represents the shape of a part of the molded product;
A body member that supports the nesting from outside through a plurality of spherical bodies, and a molding die,
The value of the pressurization generated by making the diameter of the spherical body larger than the gap between the insert and the main body member is 4 μm or less per spherical body, and the product of the pressurization and the total number of spherical bodies is The molding die, wherein the spherical body, the insert and the main body member are formed so as to be 30 μm or more.

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