JP2008183850A - Resin molded article and optical apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To assure the flatness of an end surface in a tube form resin molded article. <P>SOLUTION: An orifice 12 is formed in the inflow direction of a gate 2 in a side surface 11a which makes a tube form surface in a resin molded article 11 of a cylinder rod shape. The cooling efficiency of a resin molded article 11 of an M portion near a gate 2 improves by the existence of an orifice 12, and when a resin molded article 11 is taken out from mold nested pieces 13 and 14, the plastic temperature gradient of the N position distant from a gate 2 and the M position near the gate 2 becomes approximately the same as a mold temperature. By this, after the mold release of the resin molded article 11 is carried out, the time difference until the temperature of an end surface 3 of a cylinder rod shape falls into a normal temperature becomes fixed, the deformation by the contraction difference in this part is inhibited, thereby improving the flatness of an end surface 3. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a cylindrical resin molded product and an optical device including the resin molded product.

  When a resin molded product is molded by the pinpoint gate method, a simple mold structure can be formed if the mold release direction and the gate inflow direction of the molded product are constant. This is because the mold release direction of the runner part and the mold release direction of the molded product after cutting are constant, so that the mold product release and the runner part release can be performed by a one-way mold opening / closing operation. .

  The same applies when molding a cylindrical resin molded product, and a simple mold structure is formed in which the thrust direction inside the cylinder, which is the mold release direction of the molded product, and the gate inflow direction are constant. Therefore, a resin inlet is often installed on the end face of the cylinder.

In the cylindrical resin molded product in which the resin inlet is installed on the end face of the cylinder in this way, the cylindrical side surface is set to ensure accuracy such as roundness or cylindricity. The resin inflow port was installed in the center of the pillar part (for example, refer patent document 1).
JP 2002-5176 A

  A conventional cylindrical resin molded product will be described in detail with reference to an external perspective view of the cylindrical resin molded product shown in FIG.

  In FIG. 4, when molding the cylindrical resin molded product 1, the gate 2 into which the resin flows is installed on the end surface 3 of the resin molded product 1, and the resin molded product 1 is positioned away from the gate 2, for example, FIG. 4. Since the resin filled in the N portion is formed of the resin that has already passed through the gate 2, the time until the resin molded product 1 is removed from the mold is lowered by the mold surface. When the cooling time is generally adopted, the resin is cooled to the mold surface temperature and kept at the mold surface temperature.

  On the other hand, the resin filled in the M portion in the vicinity of the gate 2 has a high temperature due to the generation of shear heat because the resin flow path suddenly narrows at the gate 2 until the molded product is removed from the mold. The time is also short and the temperature is not sufficiently lowered to the mold temperature, and a temperature difference occurs between the N portion away from the gate 2 and the M portion near the gate 2.

  By the way, in recent years, as the demand for digital still cameras has increased, the molding cycle has been shortened to increase the amount of cylindrical resin molded products produced by a single molding machine per unit time. For this reason, it is essential to shorten the molding cycle, and in many cases, sufficient cooling time cannot be secured in the molding process.

  In FIG. 4, immediately after the resin molded product 1 is released from the mold, a temperature difference occurs between the N portion separated from the gate 2 and the M portion near the gate 2. There is a time difference until the resin reaches room temperature in the atmosphere. That is, a difference occurs in the shrinkage amount of the resin.

  FIGS. 5A to 5C are explanatory views of deformation due to shrinkage of the resin molded product, FIG. 5A is an overall perspective view, and FIG. 5B is a perspective view seen from the direction of arrow P in FIG. c) is a QQ partial cross-sectional view in (b), and as described above, a gate 2 is installed as a result of a time difference until the resin of the N portion and the M portion reaches room temperature in the atmosphere. The end surface 3 of the M portion contracts greatly, the circle tends to become smaller toward the center of the cylinder in the resin molded product 1, and tends to deform in the direction of arrow R toward the end surface 3 opposite to the gate 2.

  On the other hand, the end surface 3 near the N portion away from the gate 2 shrinks less than the M portion near the gate 2 and has a small temperature difference with the surrounding resin, so that it shrinks uniformly and maintains a circular shape. . Due to the above-described deformation, the flatness of the end face 3 is distorted.

  6 (a) to 6 (c) are views of a conventional cylindrical resin molded product viewed from the side centered on the gate, and a pinpoint gate type gold having the gate 2 as in this example. The process by which the gate 2 is cut in the mold is shown.

  In the state shown in FIG. 6 (a), the conventional cylindrical resin molded product 1 is pulled by the gate 2 in the direction of arrow S as shown in FIG. 6 (b) when the mold is opened. Receive. Then, as shown in FIG. 6C, since the force pulled in the S direction is applied to the cylindrical resin molded product 1 until the gate 2 is cut, the resin molded product 1 is deformed and resin molded. It was difficult to ensure flatness at the end surface 3 of the product 1.

  In the conventional cylindrical resin molded product 1 due to the two phenomena described with reference to FIGS. 5 and 6, the end surface 3 is deformed toward the surface opposite to the gate 2 due to the shrinkage difference due to the temperature difference of the resin. The gate 2 is deformed in the direction of the gate 2 by the tensile force generated in the cutting process. That is, the end surface 3 in the vicinity of the gate 2 is deformed in the opposite direction, and the end surface 3 is in a state of severe undulation.

  In a digital still camera in which this kind of cylindrical resin molded product is used as a constituent member, in recent years, higher magnification has been demanded, the number of constituent lenses has increased, and higher precision of each lens position has been demanded. . Along with this, higher accuracy of the position is also required in the lens barrel resin component that plays a role of driving each lens, and the accuracy defect of the lens barrel resin component greatly affects the optical characteristics, leading to a resolution failure.

  However, in the configuration of the conventional resin molded product, the flatness of the cylindrical end face cannot be secured extremely compared to the accuracy of the roundness or cylindricity of the cylindrical shape, and the lens fixed to the plane is inclined. There arises a problem that a cylindrical resin part positioned at the end face of the cylinder is inclined and the positional accuracy cannot be ensured. For this reason, after assembling as a product with a lens arranged inside the cylinder, the optical axis of the lens is significantly different from the designed value, often failing to satisfy the required optical characteristics and resulting in defective products.

  The present invention solves the above-described conventional problems, and an object of the present invention is to ensure the flatness of an end surface in a cylindrical resin molded product.

  In order to achieve the object, the invention according to claim 1 is a cylindrical resin molded product having a resin inflow gate on an end surface, and an opening is formed in the cylindrical surface of the resin molded product in the resin inflow direction of the gate. Is provided.

The invention according to claim 2 is the resin molded product according to claim 1, wherein the opening has a rectangular shape, and the gate side surface of the opening and the end surface of the resin molded product on which the gate is installed. When the distance is a and the width in the longitudinal direction of the gate side surface of the opening is b, the following expression (1) is satisfied.
(0.8 × E × t) / (A × A × B × Π) ≦ (a × a × a) / (b × b × b) (1)
However, E: Tensile elastic modulus of resin, A: Gate diameter, B: Fracture stress of resin, t: Thickness of resin molded product formed between gate surface and opening, Π: Circumferential ratio.

  According to a third aspect of the present invention, in the resin molded product according to the first or second aspect, the gate-side surface of the opening is a sloped surface whose opening area increases from the cylindrical inner diameter toward the outer diameter. It is characterized by.

  According to a fourth aspect of the present invention, in the resin molded product according to any one of the first to third aspects, the opening has a substantially rectangular shape, and the corner adjacent to the gate side surface of the opening is a curved surface. It is characterized by that.

  The invention according to claim 5 is the resin molded product according to any one of claims 1 to 4, wherein the cylindrical shape of the resin molded product is a cylindrical shape.

  According to a sixth aspect of the present invention, in the cylindrical resin molded product and an optical apparatus in which at least one lens is arranged inside the cylinder of the resin molded product, the resin molded product is any one of the first to fifth aspects. The resin molded product described in the item is used.

  With the above configuration, the resin in the vicinity of the gate can be efficiently cooled at the opening of the resin molded product, so that the temperature of the cylindrical end surface immediately after being released from the cylindrical resin molded product can be made uniform. In addition, it is possible to suppress deformation of the end face on which the gate is installed in a direction opposite to the gate in a direction opposite to that of the gate due to a contraction difference as in the related art.

  According to the resin molded product of the present invention, since the state of undulation of the end face in the cylindrical shape is improved, the flatness of the end face can be ensured.

  Particularly in the parts of optical equipment, since the flatness of the end face on which the gate is installed can be ensured, positioning on the end face can be performed without using any special means and configuration, which is effective in miniaturization and the like.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is an external perspective view of a cylindrical resin molded product according to an embodiment of the present invention, and FIGS. 2A and 2B are a cylindrical resin molded product and a molded product according to the present embodiment. It is explanatory drawing with the metal mold | die for doing, Comprising: (a) is sectional drawing centering on the gate position, (b) is an expanded sectional view of the principal part (X part), FIG.3 (a)-(c) These are explanatory drawing of the gate cutting process of the resin molded product in this Embodiment centering on a gate. 1 to 3, members corresponding to those described in FIGS. 4 to 6 are denoted by the same reference numerals, and detailed description thereof is omitted.

  The cylindrical resin molded product 11 in the present embodiment has a rectangular opening 12 in the inflow direction of the gate 2 on the side surface 11a forming the cylindrical surface. The opening 12 is formed by a mold insert piece 13 provided with a convex portion 13a shown in FIG. 2 and a pair of mold insert pieces 14.

  According to the configuration of the present embodiment, at the time of molding, the molten resin that has passed through the gate 2 and reached the N portion away from the gate 2 and the resin that is finally filled in this N portion are the surface of the mold 13. Cooled while in contact with. On the other hand, the resin finally filled in the M portion in the vicinity of the gate 2 has a short time of contact with the surface of the mold 13, but the heat of the M portion is the contact surface 12 a with the resin on the inner peripheral wall of the opening 12. Is conducted to the mold insert pieces 13 and 14 via.

  For this reason, compared with the shape of the conventional resin molded product, the cooling efficiency of the M-shaped resin molded product 11 is improved, and when the resin molded product 11 is taken out from the mold insert pieces 13 and 14, it is separated from the gate 2. The resin temperature difference between the N position and the M position near the gate 2 becomes substantially constant with the mold temperature. Thereby, after the resin molded product 11 is released, the time difference until the temperature of the cylindrical end surface 3 is lowered to room temperature becomes constant, and deformation due to the shrinkage difference at this portion is suppressed, and the flatness of the end surface 3 is improved. The

  Further, in the present embodiment, the contact area 12a which is the surface on the gate 2 side in the opening 12 has an opening area from the inner surface of the side surface of the resin molded product 11 toward the outer surface as shown in FIG. The slope is widened.

  For this reason, the resin that has passed through the gate 2 reaches the upper surface of the opening 12, that is, the contact surface 12a, and then fills in the circumferential direction in the cylindrical shape of the resin molded product 11 along the contact surface 12a. The resin filled in the inner surface of the cylinder is pushed toward the outer periphery of the cylinder by centrifugal force, but the contact surface 12a has the above-mentioned gradient surface, so that the resin and the contact surface pushed away from the circumference by centrifugal force. 12a comes into contact at an angle closer to the vertical, thereby reducing the disturbance of the fiber gradient of the resin and reducing the entrainment of gas due to the disturbance of the flow of the resin. And the gate 2 can be satisfactorily filled with resin, and the strength at this portion can be improved.

  With reference to FIGS. 3A to 3C, the gate cutting process of the present embodiment in a pinpoint gate type mold such as the gate 2 will be described.

  When the gate 2 is cut when the mold is opened and closed, the gate 2 is cut by receiving a force pulled in the direction of arrow F as shown in FIG. Until the gate 2 shown in FIG. 3 (c) is completely cut, the mold insert piece 13 exists in the opening 12 of the molded product and holds the resin molded product 11, and the gate removal direction (F direction). ) Is also applied to the resin molded product 11, but the vicinity of the gate 2 is bent in the gate pulling direction with the corner 12 b of the opening 12 as a fulcrum, and the angle formed by the gate 2 and the end surface 3 of the resin molded product 11 is molded. It becomes larger than the time, and cracks are likely to occur at the contact portion between the gate 2 and the end face 3 of the resin molded product 11.

  Thereby, in this Embodiment, compared with the past, the cutting force when the gate 2 is cut | disconnected from the resin molded product 11 becomes significantly small, and the tensile force until it cut | disconnects is absorbed. For this reason, the elongation by the tension | pulling of the resin molded product 11 is reduced significantly, and the flatness of the end surface 3 is ensured. Further, the force applied to the gate 2 side by the opening 12 is also alleviated by the bending with the corner 12b of the opening 12 as a fulcrum, so that the distortion is less than in the conventional case.

  Next, detailed dimensions in the present embodiment will be described with reference to FIG.

  As the cylindrical diameter D of the resin molded product 11 increases during the shrinkage at the time of cooling, the temperature at which the resin molded product 11 is released becomes the same as the N portion away from the gate 2. As a result, the ratio of the deformation range in the M portion near the gate 2 to the diameter of the cylindrical shape is reduced, and the deformation amount of the M portion is reduced.

  When the cylindrical diameter D and the total length L are larger than the tensile force E at the time of gate cutting, the rigidity of the resin is increased, so that the amount of strain due to the tensile force is reduced. In addition, when the diameter D of the cylindrical shape is small, the time and area in contact with the mold in the flow resin at the N position away from the gate 2 are small, so that the M position near the gate 2 and the gate 2 are separated. The temperature difference between the resin and the N position is reduced, and the shrinkage difference is less likely to occur.

  Therefore, the opening 12 is provided when the cylindrical diameter D of the resin molded product 11 is about 30 to 50 mm and the total length L of the cylindrical shape is a resin molded product equal to or less than one time the cylindrical diameter D. As a result, the effect of ensuring the flatness of the cylindrical end face 3 appears more remarkably.

  Here, A is the diameter of the gate 2, B is the fracture stress of the resin, E is the tensile modulus of the resin, t is the thickness of the resin molded product that forms between the gate surface and the opening 12, and the wrinkle is the circumference ratio Then, the cross-sectional area of the gate 2 is expressed as (A × A × Π / 4), and the force required to cut the gate 2 is (gate cross-sectional area × resin breaking stress), that is, (A × A XΠ / 4) xB.

  When the gate 2 is cut, the resin between the opening 12 and the installation surface of the gate 2 is pulled, and if the distance pulled in the gate pulling direction is large, the corner 12b of the opening 12 may crack. The amount of deflection in the gate removal direction is desirably 0.05 mm or less.

  As described above, when the distance from the gate 2 side surface of the opening 12 to the gate 2 is a and the width of the opening 12 is b, as shown in FIG. From the calculation formula of the beam supported at both ends with the opening 12 fixed, the following formula is obtained.

Deflection amount to 0.05 ≧ gate drawing direction = (force × ^b 3 applied to the gate cut) / (48 × E × I ), I ( second moment) = t × ^a 3/12
Thus, 0.05 ≧ ((A × A × Π / 4) × B × b 3) / (48 × E × t × a 3/12) , and the
(0.8 × E × t) / (A × A × B × Π) ≦ (a × a × a) / (b × b × b) (1)
It is expressed.

  An example of the detailed dimensions of each part in the present embodiment will be described.

The diameter A of the gate 2 is 0.8 to 1.2 mm, but is 0.8 mm in this example. The wall thickness t of the resin molded product 11 is 0.8 to 1.5 mm, but is 0.8 mm in this example. Further, a polycarbonate glass filler attached material is used as the resin molded article 11 for the lens barrel, and this resin characteristic generally has a fracture stress of 100 to 130 Mpa (10.2 to 13.3 Kgf / mm ² ). Considering the strength of the mold insert pieces 13 and 14, the width b of the opening 12 is set to 5 mm, and the height c of the opening 12 is set to 3 mm. The tensile modulus E is 448 kg / mm ² when the glass filler attached to a polycarbonate of a commonly used resin material is 10%.

  From the above, when using the equation (1), it is calculated that the distance a between the gate 2 and the opening 12 needs to be 2.8 mm or more.

  As the distance a between the gate 2 and the opening 7 decreases, the amount of resin in the vicinity of the gate 2 decreases, so that the cooling efficiency by the opening 12 is improved. However, if the distance is too close, the resin flow path becomes narrower. Therefore, the filling property is deteriorated, and a problem that a short occurs at the flow end of the resin molded product 11 occurs. The cross-sectional area perpendicular to the resin flow direction of the gate 2 and the area of the cross-sectional portion 11a of the resin molded product 11 close to the gate 2 in FIG. 2B are expressed as follows: (the cross-sectional area of the gate 2 <the area of the cross-section 11a) It is necessary to satisfy.

  The distance a between the gate 2 and the opening 12 is preferably 5 mm or less. This is because the cooling efficiency of the resin molded product 11 near the gate 2 decreases as the distance increases. Further, when the vicinity of the gate 2 is pulled in the gate drawing direction F, it is preferable to provide a curved fillet with a radius of 0.5 mm or more at the corner 12b so that the corner 12b of the opening 12 does not crack.

  In this embodiment, an example in which one opening 12 is provided has been described. However, when there are a plurality of gates, a plurality of openings may be provided corresponding to the plurality of gates.

  In the present embodiment, a cylindrical resin molded product has been described. However, the present invention can also be applied to a polygonal cylindrical shape such as a triangle or a square.

  In particular, it is effective in parts that require high precision and downsizing of the unit, such as an optical part having a lens. If the flatness of the end face 3 in the cylindrical shape in which the gate 2 is installed can be secured, the end face 3 The lens can be positioned, and it is not necessary to separate the surface on which the gate is installed from the position where the lens is fixed as in the prior art, and the optical component unit can be miniaturized. Further, since the end face on which the gate is installed can also be used for positioning, it is not necessary to set the positioning shape separately from the end face on which the gate is installed, which is also effective for downsizing the unit.

  INDUSTRIAL APPLICABILITY The present invention has an effect of ensuring flatness at a cylindrical end face in a resin molded product, and can be applied to a resin molded product such as a lens barrel component for a camera that requires accuracy. In particular, it is suitable for use in a lens barrel on which an optical lens is mounted. More specifically, it is particularly effective for portable optical devices such as film cameras and digital still cameras.

External perspective view of cylindrical resin molded product according to an embodiment of the present invention (A), (b) is explanatory drawing of the cylindrical resin molded product in this Embodiment, and the metal mold | die for shape | molding this molded product, (a) is sectional drawing centering on a gate position, (b) ) Is an enlarged cross-sectional view of the main part (X part) (A)-(c) is explanatory drawing of the gate cutting process of the resin molded product in this Embodiment centering on a gate. External perspective view of conventional cylindrical resin molded product (A)-(c) is explanatory drawing of the deformation | transformation by the shrinkage | contraction of the conventional resin molded product, (a) is a whole perspective view, (b) is the perspective view seen from the arrow P direction in (a), (c) ) Is a QQ partial cross-sectional view in (b) (A)-(c) is the figure which looked at the side from the position centering on the gate of the conventional cylindrical resin molded product

Explanation of symbols

2 Gate 3 End Surface 11 of Resin Molded Product Resin Molded Product 12 Opening 12a Contact Surface (Gradient Surface) of Opening
12b Corners 13 and 14 of the opening 13 Die insert piece 13a Protrusion a Distance between the gate and the opening b Width of the opening c Height of the opening D Diameter of the cylindrical portion of the resin molded product N From the gate in the resin molded product Distant part M Resin molded part near gate L Total length of resin molded part

Claims (6)

  A cylindrical resin molded product having a resin inflow gate on an end surface, wherein an opening is provided in the cylindrical surface of the resin molded product in the resin inflow direction of the gate. The opening has a rectangular shape, the distance between the gate side surface of the opening and the end surface of the resin molded product on which the gate is installed is a, and the longitudinal direction of the gate side surface of the opening The resin molded product according to claim 1, wherein when the width is b, the following formula (1) is satisfied.
(0.8 × E × t) / (A × A × B × Π) ≦ (a × a × a) / (b × b × b) (1)
However, E: Tensile elastic modulus of resin, A: Gate diameter, B: Fracture stress of resin, t: Thickness of resin molded product formed between gate surface and opening, Π: Circumferential ratio.   3. The resin molded product according to claim 1, wherein the gate-side surface of the opening is a sloped surface having an opening area that increases from a cylindrical inner diameter toward an outer diameter.   4. The resin molded product according to claim 1, wherein the opening has a substantially rectangular shape, and a corner adjacent to the gate-side surface of the opening is a curved surface.   The resin molded product according to any one of claims 1 to 4, wherein the cylindrical shape of the resin molded product is a cylindrical shape.   In a cylindrical resin molded product and an optical device in which at least one lens is arranged inside a cylinder of the resin molded product, the resin molded product according to any one of claims 1 to 5 is used as the resin molded product. Optical equipment characterized by that.

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