JP2786957B2 - Forming method of parts with holes - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of forming a component having a large number of holes, such as a code plate provided in an optical encoder and a speaker grill covering an upper portion of a speaker.

[0002]

2. Description of the Related Art An optical encoder is generally composed of a code plate having a rotation axis, and a light emitting element and a light receiving element which are arranged to face each other via the code plate. ) Are arranged at a predetermined pitch in the circumferential direction. The above-mentioned code plate is usually formed by etching a metal plate. However, since the etching technique requires complicated steps such as a resist coating step and a masking step, there has been a problem in terms of cost. Therefore, recently, attempts have been made to mold the above-mentioned code plate by an inexpensive injection molding method.

FIGS. 11 and 12 are views for explaining a conventional example of such an injection molding method for a code plate. FIG. 11 is a sectional view of a mold apparatus when the mold is clamped, and FIG. It is sectional drawing of a type | mold apparatus. As shown in these figures, a plurality of projections 2 are provided on the cavity forming surface of the fixed mold (first mold) 20.
1 and a recess 22 are provided, while the cavity forming surface of the movable mold (second mold) 23 is formed flat. In the mold apparatus configured as described above, when the mold shown in FIG.
In this state, molten resin is injected into the cavity (that is, each concave portion 22) from a gate (not shown). This molten resin is cooled and cooled in the cavity.
When the mold is opened as shown in FIG. 12, it is taken out by an eject pin (not shown).
4 is obtained.

[0004]

In the above-mentioned conventional molding method, since the size of the hole 24 is determined by the size of the projection 21, the size of the code plate 25 is improved for the purpose of improving the resolution, for example. In order to reduce the size and the arrangement pitch of the holes 24, it is necessary to make the width of the projection 21 smaller than the height thereof, which necessitates an increase in the processing cost of the mold and a reduction in the life of the mold. I was In addition, such a problem is not limited to the above-mentioned code plate 25, and the same applies to a case where a hole is reduced in a molded part having a large number of holes.

[0005] The present invention has been made in view of such a situation of the prior art, and an object of the present invention is to provide a molded part having small holes at a low cost.

[0006]

In order to achieve the above object, the present invention provides a method for injecting a molten resin into a cavity defined between a first mold and a second mold, and dispensing the molten resin. In the method of forming a component having a large number of holes by cooling and solidifying in the cavity, a concave portion and a wider portion than the concave portion are formed on a cavity forming surface of each of the first mold and the second mold. The protrusions are provided continuously, and both ends of one protrusion on one side are brought into contact with two adjacent protrusions on the other side during mold clamping.

[0007]

According to the above means, the size of the hole formed in the molded part is the overlapping portion between the convex part of the first die and the convex part of the second die. The width of each projection can be set sufficiently larger than the width of the hole in the molded part. Further, since the depth of the hole is a size obtained by relaxing the height of each of the protrusions of the first mold and the second mold, the height of each protrusion is compared with the depth of the hole. Can be set small enough.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a front view of a code plate formed by a forming method according to a first embodiment of the present invention, FIG. 2 is a cross-sectional view taken along line AA of FIG. 1, and FIG. 3 forms the code plate of FIG. FIG. 4 is a cross-sectional view of a main part showing a mold clamping state of the mold apparatus, FIG. 4 is a cross-sectional view of a main part showing a mold opening state of the mold apparatus of FIG. 3, and FIG. FIG. 6 is a sectional view taken along line BB of FIG. 5, and FIG. 7 is a simplified view of a movable mold (second mold) provided in the mold apparatus of FIG. FIG. 8 is a cross-sectional view taken along line CC of FIG.

In FIG. 1, reference numeral 1 denotes a code plate made of a synthetic resin. A first hole group 2 having a small pitch interval and a small width is provided on the outer peripheral side of the code plate 1, and a first hole 2 is provided on the inner peripheral side. A second hole 3 having a larger pitch interval and a larger width dimension than the first hole 2 group
A group is provided for each. As is apparent from FIG. 2, the first group of holes 2 includes a front-side recess 4 continuously provided on the surface of the code plate 1 and a back-side recess continuously provided on the back surface of the code plate 1. 5 is formed by a portion that overlaps. That is, the front side recess 4 and the back side recess 5 are opposed to each other in a state of being displaced in the circumferential direction of the code plate 1. 6 is located, code plate 1
When viewed from the back surface, the resin portion 7 on the front surface is located at the center bottom of each back surface side concave portion 5. Therefore, two holes 2 are formed for one front side recess 4 or rear side recess 5. Although the detailed description is omitted, the second group of holes 3 is configured in exactly the same manner as the first group of two holes, though the size is different.

Next, a method of forming the above-configured code plate 1 will be described with reference to FIGS. 3 to 8 (only the first group of holes 2 will be described here for the sake of simplicity). The same applies to the second group of holes 3). As shown in FIGS. 3 and 4, the mold apparatus is composed of a first mold, a fixed mold 8 and a second mold.
The movable mold 9 is provided with a driving mechanism (not shown).
It can be moved back and forth between the mold opening state shown in FIG. As shown in FIGS. 5 and 6, a plurality of first protrusions 10 are provided on the cavity forming surface of the fixed die 8 via a first recess 11 in the circumferential direction, and a gate 12 is provided at the center. ing. The widths of the first protrusion 10 and the first recess 11 along the circumferential direction are set to a and b, respectively, and the height of the first protrusion (ie, the depth of the first recess 11). Is set to c. On the other hand, as shown in FIGS. 7 and 8, a plurality of second protrusions 13 are provided on the cavity forming surface of the movable mold 9 in the circumferential direction via the second recesses 14. Each dimension of the second concave portion 14 is the first
The protrusions 10 and the first recesses 11 are set in the same manner. However, the first protrusion 10 and the second protrusion 13 are displaced in the circumferential direction, and as is apparent from the mold clamping state shown in FIG.
The second concave portion 14 is provided so that one first convex portion 10 straddles two adjacent second convex portions 13, that is, in the center of the first convex portion 10.
Are displaced so as to face each other.

In the thus-configured mold apparatus, the cavity forming surfaces of the fixed mold 8 and the movable mold 9 are brought into abutment with each other to form a mold clamping state shown in FIG. 3, and in this state, the gate 12 melts into the cavity. Resin is injected. In this case, the first convex portion 10 abuts against two adjacent second convex portions 13 so as to cover the second concave portion 14, and the molten resin is injected into a cavity including the first concave portion 11 and the second concave portion 14. . This molten resin is cooled and solidified in the cavity. When the mold is opened as shown in FIG. 4, it is taken out by an eject pin (not shown) to obtain the code plate 1 shown in FIG.

According to the first embodiment, the width dimension (l dimension in FIG. 2) of the group of holes 2 of the formed code plate 1 is such that the overlapping portion between the first convex portion 10 and the second convex portion 13 is formed. That is,
Since l = (ab) ÷ 2, the width dimension a of the first and second protrusions 10 and 13 can be set sufficiently larger than the width dimension l of the hole 2. Further, the depth dimension of the hole 2 group (dimension d in FIG. 2) is obtained by relaxing the height dimension c of the first convex portion 10 and the second convex portion 13, that is, d = 2c. The height of the first and second projections 10 and 13 can be set to half of the depth dimension d of the first and second projections. Therefore, for example, assuming that holes 2 having a width of l = 1 mm are formed at a pitch of 3 mm in a code plate 1 having a thickness of 4 mm, the conventional method shown in FIGS. It is necessary to form a large number of convex portions 21 of 4 mm at intervals of 3 mm.
In the first embodiment, the first convex portion 10 and the second convex portion 13 having the width dimension a of 5 mm and the height dimension c of 2 mm are distributed to the fixed mold 8 and the movable mold 9 at a pitch of b = 3 mm. It should be good to form it. For this reason, when forming a code plate having the same shape as the conventional one, according to the first embodiment, the processing of the mold can be facilitated and the life of the mold can be prolonged. In the case of the same as the conventional case, the size of the hole of the code plate can be remarkably reduced in the first embodiment.

FIG. 9 is a cross-sectional view of a main part of a mold apparatus according to a second embodiment of the present invention, showing a mold-clamped state. FIG. 10 is a cross-sectional view of a main part of the mold apparatus of FIG. 3 and 4 are denoted by the same reference numerals. The second embodiment is different from the first embodiment in that the first projection 10 of the fixed mold 8 has a stepped shape of an upper projection 10a and a lower projection 10b, and the second projection of the movable mold 9 is formed. The other configuration is the same because 13 has a stepped shape of the upper convex portion 13a and the lower convex portion 13b. Here, assuming that the width of the first and second protrusions 10 and 13 is a, the width of the first and second recesses 11 and 14 is b, and the width of both upper protrusions 10a and 13a is m,
a, b, and m have a relationship of b <m <a / 2.

In the mold apparatus configured as described above,
At the time of the mold clamping shown in FIG. 9, the upper convex portion 10a of the first convex portion 10 is formed.
Are abutted against two lower convex portions 13b adjacent to the second concave portion 14 so as to cover the second concave portion 14, and the first concave portion 11 and the second concave portion 1
4 and a molten resin is injected into a space (cavity) defined between the upper protrusions 10a and 13a. When the mold is opened after cooling and solidifying the molten resin, as shown in FIG. 10, a code plate 1 having holes 2 between resin portions having a three-layer structure is formed. Therefore, in the case of the present embodiment, four holes 2 can be formed for each of the first protrusion 10 or the second protrusion 13.

In each of the above embodiments, a code plate used for an optical encoder is described as an example of a molded part. However, it goes without saying that the present invention can be applied to a molded part having other holes. .

[0016]

As described above, according to the present invention,
Since it is possible to mold a component having a hole smaller than the size of the convex portion provided in the first mold and the second mold, a reduction in processing cost and a long life of the mold can be achieved with respect to the mold apparatus. The size of the hole can be reduced in terms of parts,
Therefore, a molded part having small holes can be provided at low cost.

[Brief description of the drawings]

FIG. 1 is a front view of a code plate formed by a forming method according to a first embodiment of the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a sectional view of a main part showing a mold clamping state of a mold device for molding the code plate of FIG. 1;

FIG. 4 is a sectional view of a main part showing a mold opening state of the mold apparatus of FIG. 3;

FIG. 5 is a bottom view of a fixed mold provided in the mold apparatus of FIG. 3;

FIG. 6 is a sectional view taken along line BB of FIG. 5;

FIG. 7 is a plan view of a movable mold provided in the mold apparatus of FIG. 3;

FIG. 8 is a sectional view taken along line CC of FIG. 7;

FIG. 9 is a sectional view of a main part showing a mold clamping state of a mold apparatus used in a molding method according to a second embodiment of the present invention.

FIG. 10 is a sectional view of a main part showing a mold opening state of the mold apparatus of FIG. 9;

FIG. 11 is a cross-sectional view showing a mold clamping state of a mold apparatus according to a conventional example.

FIG. 12 is a sectional view showing a mold opening state of the mold apparatus of FIG. 11;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Code board (component) 2 1st hole (hole) 3 2nd hole (hole) 4 Front side recess 5 Back side recess 8 Fixed type 9 Movable type 10 1st convex part (convex part) 11 1st concave part Concave part) 13 Second convex part (convex part) 14 Second concave part (concave part) 10a, 13a Upper convex part 10b, 13b Lower convex part

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁶ , DB name) B29D 31/00 B29C 33/00-33/76 B29C 45/26-45/37 B29C 39/26-39 / 44

Claims (1)

(57) [Claims] 1. A molten resin is injected into a cavity defined between a first mold and a second mold, and the molten resin is cooled and solidified in the cavity to have a large number of holes. In the method of molding a part, a concave portion and a convex portion wider than the concave portion are continuously provided on each of the cavity forming surfaces of the first die and the second die. A method for forming a part with holes, characterized in that both ends of one projection are brought into contact with two adjacent projections on the other side.