JPH1086177A - Manufacture of resin turntable and resin turntable obtained thereby - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a resin turntable in which warp is scarcely generated on the turntable after molding and provide a turntable obtained by the method. SOLUTION: The method for manufacturing the turntable comprises the steps of preparing a first mold 23 formed with a holding pin 21 and held with a center yoke 3 on the mold surface and a second mold 24 to be mated to the mold 23, mating the molds 23 and 24 after holding the yoke 3 at the pin 21, integrally molding the yoke 3 held by the pin 21 with resin by pouring the resin in a molding space 30 and solidifying the resin, and releasing a molding by releasing the molds 23 and 24. In this case, a relief space of a center part of the yoke 3 is formed between an upper surface center part of the yoke 3 and the surface of the mold 23 so that the center part of the yoke 3 is deflected above the upper surface by pouring pressure of the poured resin in the space 30 in the state that the yoke 3 is held at the pin 21.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a center yoke insert type resin turntable used for a spindle of a CD-ROM drive, a DVD drive or the like, and a resin turntable obtained by the method.

[0002]

2. Description of the Related Art In recent years, as a turntable used for a spindle of a CD-ROM drive, a DVD drive or the like, a resin turntable which is inexpensive and easy to mold as compared with a metal turntable has been increasingly required. Among such resin turntables, a center yoke insert type resin turntable in which a donut-shaped center metal fitting (hereinafter, referred to as a “center yoke”) is insert-molded at the center of the upper surface has been widely used. I have.

In the center yoke insert type resin turntable, as shown in FIG. 10, a turntable body 41 is formed in a disk shape, and a truncated cone-shaped disk centering portion for centering a compact disk or the like is provided in the center of the upper surface thereof. 40 are formed. A substantially cylindrical shaft insertion hole 43a in which a shaft insertion hole 43 penetrating vertically is formed at the center of the disc centering portion 40. Then, the slope portion 44 of the disk centering portion 40 and the shaft insertion hole portion 4
A doughnut-shaped center yoke 42 is insert-molded concentrically with the shaft insertion hole 43a between the center yoke 3a and the center yoke 42a. Is formed. A plurality of (in the figure, four) holes 47 are formed in the slope portion 44 of the disk centering portion 40. As shown in FIGS. 12 and 13, the center yoke 42 is formed in a donut shape, and the inner surface of the center hole 42a is chamfered to form an inclined surface 42b.

In the resin turntable (returned to FIG. 11), a shaft (not shown) of a motor or the like is press-fitted into a shaft insertion hole 43, and a compact disc 45 is mounted on an upper surface thereof.
Is mounted and rotates to rotate the compact disk 45. And compact disk 4
When mounting the compact disk 5 on a resin turntable, the compact disc 45 is mounted on the resin turntable such that the compact disk 45 is dropped from a slightly higher position. At this time, the inner diameter hole 46 of the compact disk 45 slides on the inclined surface 44 of the disk centering portion 40 having a truncated cone shape as a guide, and the inner diameter hole 46 is inserted into the disk centering portion 4.
0, and the compact disc 45 is positioned and mounted at the center of the resin turntable.

[0005] The resin turntable is manufactured as follows. That is, as shown in FIG. 14, a first mold 32 provided with a holding pin 31 for holding a center yoke 42 in a molding space 30 and a first mold 32
And a second mold 33 to be combined is prepared. The plurality of holding pins 31 are arranged at equal intervals at positions on the circumference surrounding the center yoke 42. And this holding pin 3
1 is a pin insertion hole 34 formed in the mold surface of the first mold 32.
And protrudes into the molding space 30. And
The side of the holding pin 31 contacts the outer peripheral wall of the center yoke 42 to hold the center yoke 42. In FIG. 14, reference numeral 48 denotes an ejector pin which protrudes into the molding space 30 so as to advance and retreat, and pushes out a molded product from the molding space 30. Next, after holding the center yoke 42 on the holding pin 31 of the first mold 32, the two dies 32 and 33 are combined, and a resin is injected into the molding space 30 to be solidified. The yoke 42 and the resin are integrally formed. After that, the first mold 32 and the second mold 3
3 and the ejector pin 48 is protruded to the left side in the figure, and the mold is removed. Thus, a molded product of the center yoke insert type resin turntable shown in FIGS. 10 and 11 is obtained. In the resin turntable thus formed, traces of the plurality of holding pins 31 holding the center yoke 42 are formed as a plurality of holes 47 in the slope portion 44 of the disk centering portion 40. In FIG. 14, reference numeral 35 denotes a gate for resin injection.

[0006]

However, in the above conventional example, the center yoke 42 made of metal is insert-molded on the upper surface side of the turntable body 41, and the lower portion of the center yoke 42 is made of a resin material. I have. In such a center yoke insert type resin turntable, there is a problem that the resin turntable itself after molding is warped as shown by a chain line in FIG. 11 due to a difference in shrinkage between the metal center yoke 42 and the resin. There is. That is, when the resin turntable is molded, the center yoke 42 inserted on the upper surface side has almost no dimensional change, and the resin existing below the center yoke 42 shrinks. As a result, a contraction force as shown by an arrow E in FIG. 11 acts on the resin portion of the resin turntable after molding, and the center yoke 42 inserted on the upper surface side does not contract, so that the bimetal just bends. , Contraction side (lower side, arrow G
). For this reason, when a mold is designed with a shrinkage ratio when only a resin is molded, there is a problem in that the obtained resin turntable is warped, and the warped portion deviates from a target dimensional tolerance.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a method of manufacturing a resin turntable in which a molded resin turntable is unlikely to be warped, and to provide a resin turntable obtained by the method. .

[0008]

In order to achieve the above object, a method of manufacturing a resin turntable according to the present invention comprises forming a disc centering portion having a truncated cone shape at the center of the upper surface of a turntable body. A method for manufacturing a resin turntable in which a donut-shaped center metal is insert-molded between an outer diameter portion of a shaft insertion hole and a center metal holding portion is formed and the center metal is held on a mold surface. A step of preparing a first mold and a second mold to be fitted with the first mold; and a step of holding the center fitting in the center fitting holding portion and then combining the first mold and the second mold. A step of injecting and solidifying the resin in the molding space, and integrally molding the resin with the center metal held in the center metal holder, and dividing the first mold and the second mold with each other. And releasing the molded product from the mold. In a state where the center fitting is held by the center fitting holding portion, the center portion of the center fitting is positioned above the upper surface by the injection pressure of the resin injected into the molding space. The gist is that an escape space of the center portion of the center fitting is formed between the center portion of the upper surface of the center fitting and the mold surface of the first die so as to bend.

The resin turntable according to the present invention has a resin-made turntable body having a truncated cone-shaped disk centering portion projecting at the center of the upper surface and a shaft insertion hole formed in the center of the disk centering portion in the axial direction. A donut-shaped center metal fitting buried in the disk centering portion in a state of being arranged concentrically with the shaft insertion hole, and a concave portion is formed in a center portion of the upper surface of the center metal fitting. And

That is, according to the method of manufacturing a resin turntable of the present invention, the center portion of the center fitting is formed by the injection pressure of the resin injected into the molding space while the center fitting is held by the center fitting holding portion. An escape space at the center portion of the center fitting is formed between the center portion of the upper surface of the center fitting and the mold surface of the first mold so as to bend upward.
For this reason, when the first mold and the second mold are combined and the resin is injected into the molding space, the center metal held by the center metal holder is pressed by the injection pressure of the resin injected into the molding space. , Flexing in the direction of its upper surface. Then, in this state, the center fitting and the resin are integrated, and when the first and second molds are divided and the molded product is released, the central portion is bent to the upper surface side by the injection pressure of the resin. The center metal fittings restored to their original shape. Due to the restoring force of the center fitting, a portion around the resin turntable tends to warp to the upper surface side. On the other hand, since the resin portion present below the center fitting shrinks, the shrinking force tends to cause the peripheral portion of the resin turntable to warp to the lower surface side, contrary to the above. As described above, the warpage caused by the restoring force of the center fitting and the warpage caused by the contraction force of the resin portion are balanced, and as a result, a resin turntable having almost no warpage can be obtained.

In the method of manufacturing a resin turntable according to the present invention, a recess is formed in the center of the upper surface of the center metal, and the center metal is held by the center metal holder with the upper surface in contact with the mold surface. By doing so, when the recess is formed in the escape space,
In particular, an escape space can be formed without processing the mold. In addition, there is an advantage that the thickness of the center fitting is reduced by the amount corresponding to the concave portion formed in the center fitting, and the center fitting is easily bent.

In the method of manufacturing a resin turntable according to the present invention, a concave portion is formed in a portion of the mold surface facing the center of the upper surface of the center metal held by the center metal holding portion, and the inside of the concave is formed as a clearance space. In this case, the escape space can be formed without changing the design of the center fitting itself or the like.

[0013]

Next, embodiments of the present invention will be described in detail.

FIGS. 1 and 2 show a center yoke insert type resin turntable formed by the method of manufacturing a resin turntable of the present invention. This is basically the same as that shown in FIGS. 10 and 11, and the same parts are denoted by the same reference numerals. In this method of manufacturing a resin turntable, a center yoke 3 as shown in FIGS. 3 and 4 is used. The center yoke 3 is formed in a donut disk shape with a chamfered inner peripheral upper surface side of a central hole 3a to form an inclined surface 3b, and a ridge 1 is formed all around the upper surface peripheral portion. A central portion of the upper surface surrounded by is formed in the concave portion 2. Then, the center yoke 3 is inserted into the resin turntable with the surface on which the concave portion 2 is formed facing upward (see FIGS. 1 and 2).

In the present invention, the above resin turntable is manufactured as follows.

That is, as shown in FIG.
Mold 23 and a second mold 24 that fits the first mold 23
And prepare. The first die 23 is provided with four holding pins 21 which are inserted into pin insertion holes 22 formed in the die surface, protrude into the molding space 30 and hold the outer periphery of the center yoke 3. I have. The holding pins 21 are provided at four positions (only two upper and lower positions are visible in the figure) at equal intervals so as to surround the center yoke 3.
Is held in the radial direction. on the other hand,
A gate 35 for injecting resin into the molding space 30 is formed in the second mold 24. The gate 35 is provided at a position that opens toward the lower surface of the center yoke 3 held by the holding pins 21. In FIG. 5, 48
Reference numeral denotes an ejector pin which protrudes into the molding space 30 so as to advance and retreat, and pushes out a molded product from the molding space 30.

Next, the center yoke 3 is held by four holding pins 21 projecting from the mold surface of the first mold 23. The center yoke 3 holds the ridge 1 formed on the upper surface so as to abut the mold surface of the first mold. At this time, a minute gap is formed between the concave portion 2 at the center of the upper surface of the center yoke 3 and the mold surface, and this minute gap is an escape space 4 at the center of the center yoke 3.

Next, the first die 23 and the second die 24
And the resin is injected into the molding space 30 from the gate 35. At this time, as shown in FIGS. 6 and 7, the center yoke 3 held by the holding pins 21 is pressed toward the upper surface by the injection pressure of the resin injected into the molding space 30. Thereby, the center yoke 3
Is bent toward the upper surface as shown by arrow B in FIG. 6, and the central portion of the center yoke 3 escapes into the escape space 4 (see FIG. 7). At this time, the gate 35
Is provided at a position that opens toward the lower surface of the held center yoke 3, so that the pressure of the injected resin directly acts on the lower surface of the center yoke 3, so that the force that causes the center yoke 3 to bend. Becomes stronger. When the center yoke 3 is bent, the central portion of the center yoke 3 escapes into the escape space 4, and the distance between the upper edge of the center hole 3a of the center yoke 3 and the mold surface is reduced. The resin hardly flows into the upper surface side of 3.

Then, after the center yoke 3 and the resin are integrated in this state, the first mold 23 and the second mold 24 are integrated.
Then, the ejector pin 48 is protruded leftward as shown in FIG. 7 to release the molded product of the resin turntable. When the resin turntable is removed from the mold, the center yoke 3 which has been bent in the direction of the upper surface due to the injection pressure of the resin is restored to the original shape as shown by an arrow C in FIGS. Due to the restoring force of the center yoke 3, the peripheral portion of the resin turntable tends to warp to the upper surface side (arrow D shown in FIG. 2). On the other hand, as described above, since the resin portion contracts, the contraction force (arrow E shown in FIG. 2) causes the peripheral portion of the resin turntable to be warped to the lower surface side (arrow G shown in FIG. 2). ). As described above, the warp of the center yoke 3 toward the upper surface due to the restoring force (arrow D) and the warp toward the lower surface due to the contraction force of the resin portion (arrow G) are balanced. It is possible to obtain a turntable without any resin (Fig. 2
reference).

The depth of the recess 2 formed on the upper surface of the center yoke 3 is such that the resin does not flow into the upper surface of the center yoke 3 when the resin is injected into the molding space 30, and It is set appropriately depending on the amount of deformation required when the resin is injected.

FIG. 8 shows a second embodiment of the present invention.

In this embodiment, a center yoke 42 (see FIGS. 12 and 13) similar to the conventional example is used instead of the center yoke 3 having the ridge 1 formed on the upper surface. The concave portion 5 having a predetermined depth is formed in a portion of the mold surface of the first mold 23 facing the center of the upper surface of the center yoke 42 held by the holding pin 21. The peripheral portion of the concave portion 5 is formed in a contact portion 6 that contacts the upper surface of the center yoke 42.

In the case of manufacturing a resin turntable with the above configuration, the center yoke 42 is held by the holding pins 21 as in the case of the first embodiment. At this time, the peripheral edge of the upper surface of the center yoke 42 comes into contact with the contact portion 6 of the mold surface, and the clearance space 4 is formed between the center portion of the upper surface of the center yoke 42 and the recess 5.

Then, when the resin is injected into the molding space 30, the injection pressure causes the center yoke 42 to bend toward the upper surface thereof as shown in FIG. after that,
The first mold 23 and the second mold 24 are divided, and the molded product is released. Also in this embodiment, a molded product having almost no warpage can be obtained by the same operation as that of the first embodiment.

In this embodiment, the first mold 23
The depth of the concave portion 5 formed on the mold surface is required to be such a depth that the resin does not flow into the upper surface side of the center yoke 42 when the resin is injected into the molding space 30 and is necessary when the resin is injected. It is set appropriately according to the amount of deformation to be performed.

[0026]

As described above, according to the present invention, when the resin is injected into the molding space by combining the first mold and the second mold,
The center fitting held by the center fitting holding portion bends toward the upper surface thereof by the injection pressure of the resin injected into the molding space. Then, in this state, the center fitting and the resin are integrated, and when the first and second molds are divided and the molded product is released, the central portion is bent to the upper surface side by the injection pressure of the resin. The center metal fittings restored to their original shape. Due to the restoring force of the center fitting, a portion around the resin turntable tends to warp to the upper surface side. On the other hand, since the resin portion present below the center fitting shrinks, the shrinking force tends to cause the peripheral portion of the resin turntable to warp to the lower surface side, contrary to the above. Thus, the warping due to the restoring force of the center fitting
The warpage due to the contraction force of the resin portion is balanced, and as a result, a resin turntable with almost no warpage can be obtained.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a resin turntable manufactured by a manufacturing method according to an embodiment of the present invention.

FIG. 2 is an HH sectional view showing the resin turntable.

FIG. 3 is a plan view showing a center yoke used in the above manufacturing method.

FIG. 4 is a sectional view showing the center yoke.

FIG. 5 is a cross-sectional view showing a step of the manufacturing method.

FIG. 6 is a cross-sectional view showing a state in which a center yoke is bent in the above manufacturing method.

FIG. 7 is a cross-sectional view showing a step of the manufacturing method.

FIG. 8 is a cross-sectional view showing steps of a manufacturing method according to the second embodiment of the present invention.

FIG. 9 is a cross-sectional view showing a step of the manufacturing method.

FIG. 10 is a perspective view showing a conventional resin turntable.

FIG. 11 is an FF sectional view showing the resin turntable.

FIG. 12 is a plan view showing a center yoke used for the resin turntable.

FIG. 13 is a sectional view showing the center yoke.

FIG. 14 is an explanatory view showing a manufacturing process of a conventional resin turntable.

[Explanation of symbols]

 REFERENCE SIGNS LIST 3 center yoke 4 relief space 21 holding pin 23 first mold 24 second mold 30 molding space

Claims (4)

[Claims] 1. A frustum-shaped disk centering portion is formed at the center of the upper surface of a turntable body, and a donut-shaped center metal fitting is insert-molded between the disk centering portion and an outer diameter portion of a shaft insertion hole. A method for manufacturing a resin turntable, comprising: preparing a first mold in which a center fitting holding portion is formed and a center fitting is held on a mold surface; and a second mold matching the first mold. A step of holding the center metal fitting in the center metal holding part and then combining the first mold and the second mold, and injecting a resin into a molding space to solidify the resin and holding the resin in the center metal holding part. A step of integrally molding the center metal and the resin, and a step of splitting the first mold and the second mold to release the molded product. The center metal is held in the center metal holder. In the held state, the center portion of the center fitting is bent above the upper surface by the injection pressure of the resin injected into the molding space. A method of manufacturing a resin turntable, wherein an escape space in the center of the center fitting is formed. 2. A recess is formed in the center of the upper surface of the center fitting, and the center fitting is held by the center fitting holding portion in a state where the upper face is in contact with the mold surface, so that the recess becomes an escape space. The method for producing a resin turntable according to claim 1, wherein the resin turntable is formed. 3. A concave portion is formed in a portion of the mold surface facing the center of the upper surface of the center metal held by the center metal holding portion, and the inside of the concave portion is formed as an escape space. The method for manufacturing the resin turntable described. 4. A resin turntable body having a truncated conical disk centering portion projecting from the center of the upper surface and a shaft insertion hole formed in the center of the disk centering portion in the axial direction, and concentric with the shaft insertion hole. A resin turntable, comprising: a donut-shaped center metal fitting embedded in the disk centering portion in a state of being arranged in a shape, and a concave portion being formed in a center portion of an upper surface of the center metal fitting.