JP2014007283A - Housing and metal mold - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a housing using resin thin and light, while restraining deterioration of rigidity of the housing.SOLUTION: In a housing 3 having a thin plate section 4 formed of resin, honeycomb grooves 6 forming a honeycomb structure in which plural hexagonal cells 7 are aligned are formed on an inner surface 4a of the thin plate section 4. Plate thickness A of the thin plate section 4 is 1.5 mm or less, and a diameter B of an inscribed circle of the hexagonal cells 7 is 5000 μm or less. Also, it is preferable that the resin contains an inorganic filler. When a glass fiber is used as the inorganic filler, the diameter B of the inscribed circle of the hexagonal cells is 300 μm or more.

Description

  The present invention relates to a casing and a mold used for mobile devices such as a mobile phone, a smartphone, a personal computer, a tablet, a PDA, a game machine, GPS, navigation, a camera, a fish detector, a pedometer, a health meter, and a calculator. .

  In recent years, with the diversification of life, anyone can easily use mobile devices, and the need for weight reduction from handling and thinning from the design side has increased, and the flat rigidity as a housing has been improved more than ever. It has come to be required.

The planar rigidity of such a housing is simply defined as bending stiffness by material mechanics and is expressed by the following formula (1).
1 / (E × I) (1)
Here, E is the elastic modulus of the material, and I is the elastic second moment.

The elastic secondary moment I is expressed by the following equation (2).
I = (b × t ³ ) / 12 (2)
Here, b is the width of the plate, and t is the thickness of the plate.

  That is, the planar rigidity of the housing is proportional to the elastic modulus of the material and the cube of the thickness of the plate, and is inversely proportional to the thinning.

  However, since mobile devices are required to be thin and light in function, many cases using lightweight resin as a main material have been adopted, and Patent Document 1 is disclosed as a resin thinning technology. . In Patent Document 1, a plurality of convex portions protruding in a spherical shape are arranged on a plane portion by injection molding, and the diameter of the convex portions is set to 10 mm or more and 16 mm or less, so that sufficient rigidity can be obtained without increasing the plate thickness. It is described that can be secured.

JP 2010-023326 A

  However, since the technique described in Patent Document 1 has a large inscribed circle diameter of 10 mm or more and 16 mm or less, if the plate thickness is reduced, the shape of the protrusion becomes too large, and sufficient rigidity is obtained. It cannot be secured.

  Then, an object of this invention is to provide the housing | casing and metal mold | die which can achieve thickness reduction while suppressing the fall of rigidity in the housing | casing using resin.

  By the way, general resin molding is performed by injecting a molten resin into a mold, and the fine processing of the mold increases the manufacturing cost extremely. For this reason, in the field of resin molding that mass-produces resin molded products at low cost, it is uneconomical to form fine irregularities on the surface of resin molded products. Forming itself has never been thought of.

  However, as a result of earnest research beyond the common knowledge of those skilled in the art, the present inventors have performed micromachining of the mold by performing electrical discharge machining with carbon graphite, machining with laser, chemical treatment using an etching solution, etc. However, by forming a fine honeycomb structure on the surface of the resin casing, it is possible to obtain a casing that can be reduced in thickness and weight while suppressing a decrease in rigidity even in a casing using resin. And gained knowledge.

  That is, the casing according to the present invention is a casing having a thin plate portion formed of a resin, and a honeycomb groove that forms an outline of hexagonal cells arranged in a honeycomb structure is formed on the surface of the thin plate portion. The plate thickness of the thin plate portion is 1.5 mm or less, and the diameter of the inscribed circle of the hexagonal cell is 5000 μm or less.

  According to the housing according to the present invention, even if the plate thickness of the thin plate portion is reduced to 1.5 mm or less, the honeycomb groove is formed on the surface of the thin plate portion, and the hexagonal cell formed by the honeycomb groove is formed. By making the diameter of the contact circle as small as 5000 μm or less, it is possible to densely fill the honeycomb structure that exhibits high rigidity against loads from various directions. Weight reduction can be achieved.

  Moreover, the housing | casing which concerns on this invention shall contain the inorganic filler in resin, and the diameter of the inscribed circle of a hexagonal cell shall be 300 micrometers or more. Thereby, a housing | casing can be reinforced with an inorganic filler and rigidity can be improved. Various inorganic fillers can be used for the resin, and glass fibers can be used from the viewpoint of cost. When the inorganic filler is contained in the resin, the inorganic filler is broken finely and shortened by molding the resin. Among inorganic fillers, inexpensive glass fibers have a number average glass fiber length after molding of 200 μm or more and less than 300 μm, which is longer than other inorganic fillers. However, since the diameter of the inscribed circle of the hexagonal cell is 300 μm or more, the inorganic filler can be filled into the hexagonal cell even if inexpensive glass fiber is adopted as the inorganic filler.

  The metal mold | die which concerns on this invention is a metal mold | die for shape | molding the housing | casing which has a thin plate part shape | molded by resin, Comprising: It has a thin plate part formation part which forms a thin plate part in the board thickness of 1.5 mm or less In the thin plate portion forming portion, honeycomb grooves that form the outline of hexagonal cells arranged in a honeycomb structure are formed, and the diameter of the inscribed circle of the hexagonal cells is 5000 μm or less.

  Moreover, the metal mold | die which concerns on this invention shall be a thing whose diameter of the inscribed circle of a hexagonal cell is 300 micrometers or more.

  By using such a mold, it is possible to easily form a casing that can obtain the above-described effects.

  ADVANTAGE OF THE INVENTION According to this invention, thickness reduction can be achieved, suppressing the fall of rigidity in the housing | casing using resin.

It is a schematic perspective view of the product which concerns on embodiment. It is a disassembled perspective view of the product shown in FIG. It is sectional drawing in the III-III line shown in FIG. It is an expansion perspective view of a thin plate part. It is sectional drawing in the VV line shown in FIG. It is a schematic sectional drawing of the metal mold | die which concerns on embodiment. It is the expansion perspective view which showed the inner surface of the inner side metal mold | die. It is sectional drawing in the VIII-VIII line shown in FIG.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, exemplary embodiments of a housing and a mold according to the invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals.

  The housing according to the present embodiment is a box that covers a device main body (not shown) including a substrate that allows a mobile device to function. This housing is formed by resin injection molding, and can be formed by resin injection molding containing an inorganic filler (inorganic filler) as appropriate.

  As the type of resin forming the housing, a thermoplastic resin used for extrusion, injection molding, hot pressing, and vacuum molding can be used in consideration of productivity. Among thermoplastic resins, polyamideimide, PPS resin, LCP resin, polycarbonate, polyacetal, polyamide, PBT resin, PET resin, modified PPO resin, modified PPE resin, AS resin, ABS resin, polystyrene, polypropylene, polyethylene, and these It is also possible to use alloy materials, copolymers, and the like that contain a component.

  In this case, since it is necessary to increase the rigidity even if the casing used for the mobile device is thin, it is preferable to add (contain) an inorganic filler to the resin forming the casing. In addition, it is preferable to add 20 to 70% wt of the inorganic filler with respect to the casing, and in this case, the resin to be used is preferably a crystalline resin in consideration of extrudability and thin wall fluidity.

  The types of inorganic fillers added to the resin include glass fibers, PAN and pitch carbon fibers, stainless fibers, metal fibers such as aluminum fibers and brass fibers, organic fibers such as aromatic polyamide fibers, gypsum fibers, and ceramics. Fiber, asbestos fiber, zirconia fiber, alumina fiber, silica fiber, participating titanium fiber, silicon carbide fiber, rock wool, potassium titanate whisker, silicon nitride whisker, wollastonite, etc., whisker-like filler, glass beads, glass Examples of the filler include balloons, talc, and barium sulfate. Among these, glass fiber is preferable in terms of rigidity, strength, and cost. The glass fiber becomes shorter than that at the time of addition in the extrusion process and the injection molding process at the time of pellet granulation, and the number average glass fiber length becomes about 200 μm or more and less than 300 μm. The glass fiber having an average diameter φ (diameter) of 3 μm or more and less than 50 μm can be used, and it is preferable to use a glass fiber having a diameter of 5 μm or more and less than 30 μm from the viewpoint of cost and strength.

  Furthermore, the inorganic filler has its surface pretreated with an organic onium ion in the case of coupling agents such as silane coupling agents and titanate coupling agents, other surface treatment agents and swellable layered silicates. It is preferable because more excellent mechanical strength can be obtained.

  Next, the shape of the housing according to the embodiment will be described with reference to FIGS.

  FIG. 1 is a schematic perspective view of a product according to the embodiment. FIG. 2 is an exploded perspective view of the product shown in FIG. 3 is a cross-sectional view taken along the line III-III shown in FIG. As shown in FIG. 1 to FIG. 3, the product 1 according to the present embodiment is formed in a thin rectangular parallelepiped, and is disposed on the front side of the mobile device so that the display / operation panel P of the mobile device is disposed. 2 and a housing 3 arranged on the back side of the mobile device or the like. Although not shown in the drawing, a resin battery lid may be attached to the housing 2 so that the secondary battery can be easily replaced.

  The housing 3 includes a rectangular flat plate-shaped thin plate portion 4 and a peripheral edge portion 5 that is erected from the peripheral edge of the thin plate portion 4 and connected to the housing 2.

  FIG. 4 is an enlarged perspective view of the thin plate portion 4. 5 is a cross-sectional view taken along line VV shown in FIG. As shown in FIGS. 4 and 5, the thin plate portion 4 has an inner surface 4 a and an outer surface 4 b formed in a substantially planar shape. On the inner surface 4a, a plurality of hexagonal cells 7 arranged in a honeycomb structure, that is, the outline of the hexagonal cells 7 are formed by a honeycomb groove 6 in which the inner surface 4a is recessed toward the outer surface 4b.

  The hexagonal cell 7 is a regular hexagonal cell constituting a honeycomb structure, and is formed in a flat surface flush with the inner surface 4a. The honeycomb groove 6 extends in a net shape so as to surround the hexagonal cell 7, and is recessed in a V shape (triangular valley shape) from the periphery of the hexagonal cell 7 toward the outer surface 4 b side. Note that the convex and concave corners (corners) formed by the honeycomb grooves 6 are rounded so as to have a curved surface (R is attached) in order to suppress concentration of stress acting on the housing 3. Is).

  The plate thickness A of the thin plate portion 4 is 1.5 mm or less, and preferably 0.50 mm or more from the viewpoint of manufacturability. By setting the plate thickness A to 1.5 mm or less, it is possible to reduce the thickness and weight of the mobile device. On the other hand, by setting the plate thickness A to 0.50 mm or more, even when the housing 3 is produced by an inexpensive method by injection molding, the molten resin can be easily spread over the entire mold. Yield can be improved.

  The diameter B of the inscribed circle of the hexagonal cells 7 constituting the honeycomb structure is 5000 μm or less, and is preferably 300 μm or more from the viewpoint of the orientation of the inorganic filler 8 added to the resin. By setting the diameter B to 5000 μm or less, a honeycomb structure that exhibits high rigidity with respect to loads from various directions can be densely packed. Thin and light weight can be achieved. In addition, as described above, when glass fiber is added to the resin as the inorganic filler 8, it is shorter than the addition in the extrusion process and the injection molding process during pellet granulation, and the number average glass fiber length is about 200 μm or more. It becomes less than 300 μm. Therefore, by setting the diameter B to 300 μm or more, the hexagonal cell 7 can be filled with the glass fiber inorganic filler 8, so that the casing 3 is reinforced with the glass fiber inorganic filler 8 to increase the rigidity. Can be increased.

  The depth C of the honeycomb groove 6 is 5 μm or more and 500 μm or less, and preferably 50 μm or more and 300 μm from the viewpoint of resin orientation. By setting the depth C to 5 μm or more, the amount of meat stealing can be increased, and thus the weight of the housing 3 can be reduced. On the other hand, by setting the depth C to 500 μm or less, the rigidity of the housing 3 can be maintained.

  The width D of the honeycomb groove 6 is 5 μm or more and 500 μm or less, and preferably 5 μm or more and 200 μm or less. Since the amount of meat theft can be increased by setting the width D to 5 μm or more, the weight of the housing 3 can be reduced. On the other hand, the rigidity of the housing | casing 3 can be hold | maintained because the width D shall be 500 micrometers or less.

  Next, with reference to FIGS. 6-8, the metal mold | die which concerns on this embodiment is demonstrated.

  FIG. 6 is a schematic cross-sectional view of a mold according to the embodiment. As shown in FIG. 6, a mold 11 according to this embodiment is a mold for injection-molding the casing 3, and an outer mold 12 that forms the outer surface of the casing 3, and the casing 3 and an inner mold 13 that forms the inner surface of 3.

  A thin plate portion forming portion 14 for forming the outer surface 4 b of the thin plate portion 4 of the housing 3 is formed on the inner surface into which the molten resin of the outer mold 12 is poured. Further, a thin plate portion forming portion 15 for forming the inner surface 4 a of the thin plate portion 4 of the housing 3 is formed on the inner surface into which the molten resin of the inner mold 13 is poured.

  The mold 11 is formed by injecting molten resin into the interior with the outer mold 12 and the inner mold 13 being overlapped, and then cooling to separate the outer mold 12 and the inner mold 13. The resin molded product of the housing 3 can be formed. Then, in order to set the plate thickness A of the thin plate portion 4 to 1.5 mm or less, the separation distance between the thin plate portion forming portion 14 and the thin plate portion forming portion 15 when the outer mold 12 and the inner mold 13 are overlapped with each other. Is 1.5 mm or less.

  FIG. 7 is an enlarged perspective view showing the inner surface of the inner mold. 8 is a cross-sectional view taken along line VIII-VIII shown in FIG. As shown in FIGS. 7 and 8, the thin plate portion forming portion 15 is formed with unevenness opposite to the unevenness of the inner surface 4a corresponding to the inner surface 4a. That is, the thin plate portion forming portion 15 is formed with a honeycomb groove forming convex portion 16 for forming the honeycomb groove 6 and a hexagonal cell forming flat portion 17 for forming the hexagonal cell 7.

  The hexagonal cell formation plane portion 17 is formed in a planar regular hexagon, and the honeycomb groove formation convex portion 16 is raised in an inverted V shape (triangular mountain shape) from the periphery of the hexagonal cell formation plane portion 17. It has a shape. Note that the convex and concave corners (corners) formed by the honeycomb groove forming convex portions 16 are rounded (R is attached) in the same manner as the housing 3.

  The diameter b of the inscribed circle of the hexagonal cell forming plane portion 17 is 5000 μm or less, and preferably 300 μm or more, like the diameter B of the inscribed circle of the hexagonal cell 7.

  The raised height c of the honeycomb groove forming convex portion 16 with respect to the hexagonal cell forming flat portion 17 is not less than 5 μm and not more than 500 μm, and preferably not less than 50 μm and not more than 300 μm, similarly to the depth C of the honeycomb groove 6.

  The width d of the honeycomb groove forming convex portion 16 is 5 μm or more and 500 μm or less, and preferably 5 μm or more and 200 μm or less, like the width D of the honeycomb groove 6.

  For example, the honeycomb groove forming convex portion 16 and the hexagonal cell forming flat portion 17 are formed on the flat thin plate portion forming portion 15 by electrical discharge machining using carbon graphite, laser machining, or chemical treatment using an etching solution. The hexagonal cell formation plane part 17 can be depressed by performing the above. Further, by forming the honeycomb groove forming convex portion 16 and the hexagonal cell forming flat portion 17 and then performing sandblasting or the like, the convex shape formed by the honeycomb groove forming convex portion 16 and the hexagonal cell forming flat portion 17 and The concave corners can be rounded.

  As described above, according to the present embodiment, the honeycomb groove 6 is formed on the surface of the thin plate portion 4 even if the plate thickness A of the thin plate portion 4 is reduced to 1.5 mm or less. By reducing the diameter B of the contact circle to 5000 μm or less, it is possible to densely fill the honeycomb structure that exhibits high rigidity against loads from various directions. Thin and light weight can be achieved.

  Further, by including the inorganic filler 8 in the resin, the casing 3 can be reinforced with the inorganic filler 8 to increase the rigidity, and even if glass fiber is used as the inorganic filler 8, the diameter B By setting the thickness to 300 μm or more, the hexagonal cell 7 can be filled with the inorganic filler 8 of glass fiber, so that the casing 3 can be reinforced with the inorganic filler 8 of glass fiber to increase the rigidity. .

  The preferred embodiment of the present invention has been described above, but the present invention is not limited to the above embodiment.

  For example, in the embodiment described above, the honeycomb groove 6 is formed in the thin plate portion 4 of the housing 3 disposed on the back side of the mobile device. However, the honeycomb groove may be formed in any portion of the thin plate portion of the housing. You may form, for example, you may form in the outer surface 4b, the peripheral part 5, the housing | casing 2 arrange | positioned at the front side of a mobile apparatus, etc. Moreover, although the said embodiment demonstrated as what was formed in a thin rectangular parallelepiped, the shape of a housing | casing is not specifically limited, A various deformation | transformation is possible by a design etc.

  DESCRIPTION OF SYMBOLS 1 ... Product, 2 ... Housing, 3 ... Housing, 4 ... Thin plate part, 4a ... Inner surface, 4b ... Outer surface, 5 ... Peripheral part, 6 ... Honeycomb groove, 7 ... Hexagonal cell, 8 ... Inorganic filler , 11 ... mold, 12 ... outer mold, 13 ... inner mold, 14 ... thin plate portion forming portion, 15 ... thin plate portion forming portion, 16 ... honeycomb groove forming convex portion, 17 ... hexagonal cell forming flat portion, A Plate thickness of thin plate portion, B ... Diameter of inscribed circle of hexagonal cell, C ... Depth of honeycomb groove, D ... Width of honeycomb groove, a ... Thickness of space corresponding to thin plate portion, b ... Six The diameter of the inscribed circle of the square cell forming flat part, c: the height of the protrusion of the honeycomb groove forming convex part, d: the width of the honeycomb groove forming convex part, P: the display / operation panel.

Claims (4)

A housing having a thin plate portion formed of resin,
On the surface of the thin plate portion, honeycomb grooves that form the outlines of hexagonal cells arranged in a honeycomb structure are formed,
The thickness of the thin plate portion is 1.5 mm or less,
A diameter of an inscribed circle of the hexagonal cell is 5000 μm or less,
Enclosure. The resin contains an inorganic filler,
A diameter of an inscribed circle of the hexagonal cell is 300 μm or more,
The housing according to claim 1. A mold for molding a housing having a thin plate portion formed of resin,
A thin plate portion forming portion for forming the thin plate portion to a thickness of 1.5 mm or less,
The thin plate portion forming portion is formed with a honeycomb groove forming convex portion for forming a honeycomb groove forming the outline of the hexagonal cells arranged in the honeycomb structure, and the diameter of the inscribed circle of the hexagonal cells is 5000 μm. Is
Mold. A diameter of an inscribed circle of the hexagonal cell is 300 μm or more,
The mold according to claim 3.

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