JPH09239797A - Injection molding method and mold - Google Patents

Abstract

PROBLEM TO BE SOLVED: To hold the mirror surface of a molded product to high accuracy by eliminating the eccentricity between a pair of mutual mirror surface pieces at a time of injection molding. SOLUTION: Heating cartridge heaters 22, 23 are embedded only in the mirror surface pieces 15, 16 held to templates 3, 4 and the heating temp. thereof is detected by a thermocouple and the temp. thereof is also controlled by a controller 30 and the clearances 31, 32 between the templates 3, 4 and the mirror pieces 15, 16 are certainly brought to a close contact state to perform injection molding.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection molding method and an injection molding die for easily and highly accurately molding a component such as an optical lens which requires relatively high accuracy.

[0002]

2. Description of the Related Art As a conventional example of an optical lens molding die, as shown in FIG. 11, a part of a cavity C, for example, a mirror surface of a lens is provided in a mirror surface piece b held slidably with respect to a template a. The part f is formed, and the other part of the cavity C, for example, the part such as the lens outer peripheral part d is formed on the template a side, and the part that forms the optical surface is separated from the part that forms the other part. It is common to leave it.

However, in such a structure, since the clearance e of about 0.002 to 0.005 mm exists between the mirror surface piece b and the template a, the decentering accuracy of the lens itself after molding is improved. Not only cannot the clearance e be increased below the amount, but there is also the problem that burr, optical axis blurring, etc. occur. In order to solve such a problem, it is known that the invention disclosed in, for example, Japanese Patent Laid-Open No. 02-206523 is made.

The invention disclosed in the above publication has a clearance in the sliding portion between the inner piece and the outer piece before the injection step of the molten resin, but in the injection step, the molten resin injected into the mold is melted. When the mold is heated by the resin to a high temperature, the inner piece expands and the clearance in the sliding part between the inner piece and the outer piece is completely sealed before the first injection stroke. become. That is, the inner piece and the outer piece are in a completely fixed and fitted state. Thereby, even if the molten resin is poured into the mold, the resin does not flow out from the sliding portion. In this sealed state, a large clearance is generated between the inner piece and the outer piece when the temperature is lowered due to the cooling process for taking out the product, so that they can slide with each other. .

[0005]

However, in the conventional injection molding described above, the temperature stability is poor because no means for accurately controlling the temperature control is applied to the so-called inner piece such as a mirror piece. , It was not possible to maintain the upper limit of the temperature to close the clearance tightly. Therefore, when the clearance is large, the outer piece and the inner piece cannot be kept in a completely sealed state. Further, when the inner piece is a mirror surface piece, there is a problem that the surface accuracy of the mirror surface portion is deteriorated due to the compression action from the outer piece to the mirror surface piece when the inner piece is sealed.

Therefore, the present invention has been made in view of the above problems, and an injection molding die capable of forming a mold plate and a mirror surface piece in a state in which the clearance is surely brought into close contact with each other and eccentricity is extremely small. It is intended to provide an injection molding method.

[0007]

In order to achieve the above object, the present invention provides, as a means according to claim 1, a mirror plate portion of a cavity for a mold plate forming a part of the cavity. In the injection-molding die for molding the product, the clearance existing between both of the portions for holding the mirror surface piece having the obtained portion is sealed by thermal expansion by the heating means, and the heating means is provided only for the mirror surface piece. It is characterized by having. The means according to claim 2 is characterized in that a temperature control means for controlling the heating temperature is provided for the heating means provided only in the mirror surface piece. As a means according to claim 3, heating a clearance existing between a mold plate forming a part of a mold cavity and a part for holding a mirror surface piece having a part which can be a mirror surface part of the cavity. In an injection molding die for molding a product in a sealed state by thermal expansion by means, among the clearances existing between the mirror surface piece and the mold plate,
Only the clearance in the vicinity of the mirror surface portion of the mirror surface piece is formed larger than other portions. As a means according to claim 4, heating a clearance existing between a mold plate forming a part of a mold cavity and a part for holding a mirror surface piece having a part that can be a mirror surface part of the cavity. In the injection molding method of molding a product in a sealed state by thermal expansion by means, among the clearances present between the mirror surface piece and the template,
Only the clearance in the vicinity of the mirror surface portion of the mirror surface piece is formed to be larger than other portions, and heating means is embedded in the mirror surface piece, and the heating means controls only the temperature of the mirror surface piece by the temperature control means. After heating to a temperature range where the clearance is sealed, the molten resin is injected into the mold cavity.

The operation of claim 1 is as follows. At normal molding temperature, the mirror surface piece and the mold plate have a clearance that allows them to slide relative to each other, but the heating element embedded in the mirror surface piece starts to be heated, and the heat is conducted to the mirror surface. When the temperature of the piece is increased, the mirror piece expands its outer diameter dimension due to its thermal expansion, so that the clearance between the mirror piece and the template is reduced. Furthermore, heating is continued to seal the space between the mirror surface piece and the mold plate, and when the two become incapable of sliding relative to each other, the molten resin is injected and filled into the cavity of the mold. When the shape of the molded product is adjusted, the heating element is not heated, the mirror surface piece is cooled to the original mold temperature, and the clearance enough to be slidable with the mold plate is restored. To take out the molded product, use that the template and mirror piece can slide,
The projection is performed by projecting the mirror-finished frame itself, but an ejector pin may be provided to project it. The operation of claim 2 is as follows. In addition to the function of claim 1, the heating element is heated to seal the space between the mirror surface piece and the mold plate, and when the two become incapable of sliding with each other, the heating element seals the mirror surface piece and the mold plate. The temperature control means regulates the temperature of the heating element so that the temperature becomes constant, and the compressive force acting from the template to the mirror surface piece is made constant. The operation of claim 3 is as follows. In addition to the effects of the first and second aspects, since the outer circumference of the mirror surface piece near the mirror surface portion is formed to be slightly smaller than the outer diameter of the surface fitted with the template, the template plate and the mirror surface piece are formed. The compressive force applied to the mirror-finished frame due to the gap being sealed does not directly act on the mirror-finished frame mirror-finished surface. The operation of claim 4 is as follows. The heating means provided on the mirror surface piece forcibly expands the mirror surface piece side to adjust the clearance between the template and the mirror surface piece. Also, so that the clearance between the mirror surface piece and the template due to thermal expansion of the mirror surface piece becomes appropriate,
The heating temperature of the heating means provided in the mirror surface piece, that is, the temperature of the mirror surface piece is controlled by the temperature control means. The operation of claim 5 is as follows. Even when the mirror surface piece and the template are hermetically sealed, that is, even when the clearance is hermetically sealed, since the clearance is always present near the mirror surface portion of the mirror surface piece, the compression portion does not act on the mirror surface portion of the mirror surface piece.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be specifically described below with reference to the drawings. In each of the embodiments, common points are assigned the same reference numerals and correspond to each other to omit redundant description.

[0010]

Embodiment 1 of the Invention FIG. 1 is a sectional view of an injection molding die showing Embodiment 1 of the present invention. The injection mold of the present invention is divided into a fixed mold 1 and a movable mold 2. The fixed mold 1 is mainly composed of a fixed mold plate 3 and a fixed mounting plate 4, and a movable mold 2.
Is composed of a movable side mold plate 5, a spacer 6, a movable side mounting plate 7 and a protruding plate 8. A cavity 14 is formed on the mating surface of the fixed die 1 and the movable die 2, and a spool 40 and a runner 41 are in communication with the cavity 14.

The fixed side mirror surface piece 15 is 0.002 to 0 in the cylindrical hole 17 of the fixed side mold plate 3, and the movable side mirror surface piece 16 is 0.002 to 0 in the cylindrical hole 18 of the movable side mold plate 5, respectively. .005
The movable rod-shaped mirror piece 16 is slidably retained with clearances 31 and 32 of about mm, and the extension rod 1 is disposed on the opposite side of the cavity 14.
It is fixed by a protruding plate 8 arranged between the movable side mold plate 5 and the movable side mounting plate 7 via 9. The mirror surface portions 14a and 14b forming the cavity 14 are formed in a concave shape, that is, the molded product is a biconvex surface.
The mirror surface portions 14a and 14b are surface-processed as optical mirror surfaces.

Further, the fixed and movable mirror surface pieces 15,
16 are provided with drill holes 20 and 21 in the axial direction from the opposite sides of the respective mirror surface portions 14a and 14b, and the depth thereof is such that when the mirror surface portions 14a and 14b receive resin pressure. , 14b are set so as not to deteriorate the mirror surface precision. The distances from the mirror surface portions 14a and 14b at this time are substantially the same on both the fixed side and the movable side. Cartridge heaters 22 and 23, to which lead wires 24 and 25 are electrically connected, are embedded as heating means in the drill holes 20 and 21, respectively. The lead wires 24 and 25 have a clearance hole 28 provided on the fixed side mounting plate 4 on the fixed side and an extension rod 19 on the movable side.
And an escape hole 29 provided in the protruding plate 8 for connection.

As an operation effect of the injection molding die having this structure, only the mirror surface pieces 15, 16 can be forcibly thermally expanded, so that the clearance between the template and the mirror surface piece can be easily adjusted.

[0014]

Embodiment 2 of the Invention FIG. 2 is a sectional view of an essential part of an injection molding die showing Embodiment 2 of the present invention. In the present embodiment, a thermocouple (not shown) is provided as a temperature control means for the cartridge heaters 22 and 23 in the cartridge heaters 22 and 23 embedded in the mirror surface pieces 15 and 16 in the first embodiment, and a thermocouple is provided. The difference is that the controller 30 is electrically connected via the lead wire 26, and the other configurations are the same as those in the first embodiment. The thermocouple lead wires 26, 27
Are wired in parallel with the lead wires 24 and 25, and
It is connected to the thermocouple provided in each of 5 and 16.

The operation and effect of this embodiment are as follows.
In the first embodiment, the cartridge heater 22,
By detecting the temperature to be heated by 23 with a thermocouple and adjusting it to an appropriate temperature with the controller 30, it becomes possible to adjust the temperature easily and accurately.

[0016]

Embodiment 3 of the Invention FIG. 3 is a cross-sectional view showing a mirror surface piece of an injection molding die and its vicinity according to Embodiment 3 of the present invention. In the present embodiment, the outer diameters of the fixed-side or movable-side mirror surface pieces 15 and 16 in the vicinity of the mirror surface portions 14a and 14b of the second embodiment are 0.005 to 0 as compared with the diameters of other portions. Relief part 1 reduced by about 0.010 mm
5a and 16a are provided, and the width thereof is formed to be slightly larger than the depth of the mirror surface concave portion.

The operation and effect of this embodiment are as follows.
Since the outer diameters of the mirror surface pieces 15 and 16 in the vicinity of the mirror surface portions 14a and 14b are made smaller than the other portions, a clearance is always provided at that portion.
Even if a compressive force due to thermal expansion acts on 5 and 16, the compressive force does not affect the vicinity of the mirror surface portion. Therefore, the mirror surface portion 14
The surface accuracy of a and 14b does not decrease due to the compression force. Further, since the escape portions 15a and 16a are formed on the mirror surface pieces 15 and 16 side, it is easy to form the escape portions.

[0018]

[Fourth Embodiment of the Invention] FIG. 4 is a sectional view of an essential part of an injection molding die showing a third embodiment of the present invention. In the present embodiment, in the third embodiment, each mirror surface piece 15,
Instead of providing escape portions 15a and 16a in which the diameters of the mirror surfaces 16 near the mirror surface portions 14a and 14b are smaller than the diameters of the other portions, holes 17 and 18 formed on the template plates 3 and 5 are provided. A portion corresponding to the position of the mirror surface portions 14a and 14b of each mirror surface piece 15 and 16 is 0.005 to 0.01 with respect to the inner diameter.
With a depth of about 0 mm, the width of the mirror surface portions 14a, 14b
The difference is that relief portions 15b and 16b are provided which are slightly deeper than the depth of the concave portion formed by the spherical surface, and other configurations are the same as those in the third embodiment.

The effect of this embodiment is that the clearance is always present on the inner diameter side of the holes 17 and 18 corresponding to the vicinity of the mirror surface portions 14a and 14b of the mirror surface pieces 15 and 16, respectively. Even if a compressive force due to thermal expansion acts on Nos. 16 and 16, the compressive force does not affect the vicinity of the mirror surface. Therefore, the surface accuracy of the mirror surface portions 14a and 14b does not decrease.

[0020]

Fifth Embodiment of the Invention FIGS. 5 to 10 show a third embodiment of the present invention, FIG. 5 is a diagram showing a flow of injection molding of the present invention, and FIGS. 6 to 10 explain a process of injection molding. FIG.

This embodiment will be described with reference to FIGS. 6 to 10 in accordance with the injection molding flow of FIG. First, at the start stage, the injection molding die, as shown in FIG. 6, has the fixed and movable mirror surface pieces 15 and 16 and the holes 17 and 18 of the respective mold plates 3 and 5 at a normal molding temperature. The clearances 31 and 32 provided between the clearances are kept large enough to slide with each other. When the controller 30 starts heating the cartridge heaters 22 and 23 embedded in the mirror surface pieces 15 and 16, the temperature of the mirror surface pieces 15 and 16 is also increased by heat transfer. This time,
Due to the thermal expansion of the respective mirror surface pieces 15, 16, the outer diameter dimension is increased, and the clearances 31, 32 provided between the mirror surface pieces 15, 16 and the holes 17, 18 begin to shrink. If this operation is continued, the mirror surfaces 15 and 16 and the holes 17 and 18 will be hermetically sealed, and they will not be slidable with respect to each other, as shown in FIG.

The mirror surface portions 14a of the mirror surface pieces 15 and 16 are
Since the outer peripheral portions near 14b are provided with relief portions 15a and 16a each having a slightly reduced outer diameter, the mirror surface portion 14 can be formed even if the clearances 31 and 32 are completely sealed.
Since only the portions a and 14b are not hermetically sealed, no compressive force acts on the mirror surface portions 14a and 14b of the mirror surface pieces 15 and 16, respectively. Thereby, the mirror surface portions 14a and 14b can always maintain the initial surface accuracy.

When the clearances 31 and 32 are thus sealed, the temperatures of the cartridge heaters 22 and 23 are detected by the thermocouples (not shown) having the lead wires 26 and 27, respectively, and the controller 30 detects the temperature of the cartridge heaters. The temperature of the heaters 22 and 23 is set as the temperature when the clearances 31 and 32 are sealed, and the compressive force acting from the template plates 3 and 5 to the mirror surface pieces 15 and 16 is kept constant.

As shown in FIG. 8, a spool 40 and a runner 41
The molten resin 42 is injected and filled into the cavity 14 through the through hole and the pressure is maintained. When the shape of the molded product is adjusted, the heating of the cartridge heaters 22 and 23 is finished and the cartridge heaters 22 and 23 are not heated. In this state, as shown in FIG. 9, each mirror surface piece 15, 16 is cooled to the original mold temperature, and each mold plate 3, 5 and each mirror surface piece 1 are cooled.
The slidable clearances 31 and 32 are restored between the clearances 5 and 16. After that, each template 3, 5 and mirror surface piece 15, 1
Utilizing the fact that 6 is slidable, as shown in FIG. 10, the molded product 50 is taken out by projecting the mirror surface piece 16 in conjunction with the operation of the projecting plate 8 in the mold opening / closing direction.

According to the present embodiment, the clearances 31 and 32 between the template 3 and 5 (or the sleeve fitted thereto) and the mirror surface pieces 15 and 16 are set to the forced temperature of the mirror surface pieces 15 and 16. Since the molding is performed after completely sealing under control, the eccentricity between the mirror surface pieces 15, 16 is almost eliminated, and even when heated, the vicinity of the mirror surface portions 14a, 14b is always in a non-compressed state, so that a high surface is obtained. It is possible to obtain a molded product with high accuracy.

[0026]

According to the invention of claim 1, the clearance between the template and the mirror surface piece can be easily adjusted. According to the invention of claim 2, by heating only the mirror surface piece side and controlling the heating temperature by the temperature control means, the clearance can be easily and surely brought into close contact with the mirror surface piece, It can be managed so that unnecessary compression force is not applied. According to the third aspect of the present invention, since the clearance is always maintained in the vicinity of the mirror surface portion of the mirror surface piece, even if a compressive force due to thermal expansion acts on the mirror surface piece, it does not act on the mirror surface portion. This makes it possible to maintain the mirror surface portion with high surface accuracy. According to the invention of claim 4,
It is possible to provide the heating means only on the mirror surface piece side and control the heating means to a predetermined temperature by the temperature control means, so that the clearance existing between the template and the mirror surface piece can be surely adjusted to a sealed state. Therefore, a product with extremely small eccentricity can be obtained. According to the invention of claim 5, since there is always a clearance in the vicinity of the mirror surface portion, the mirror surface portion of the mirror surface piece can be maintained with high accuracy even when the clearance is sealed, so that a product with high surface accuracy can be obtained.

[Brief description of drawings]

FIG. 1 is a sectional view of a main part of an injection molding die showing a first embodiment of the present invention.

FIG. 2 is a sectional view of a main part of an injection molding die showing a second embodiment of the present invention.

FIG. 3 is a sectional view of an essential part of an injection molding die showing a third embodiment of the present invention.

FIG. 4 is a sectional view of a main part of an injection molding die showing a fourth embodiment of the present invention.

FIG. 5 is a diagram showing a flow of injection molding showing a fifth embodiment of the present invention.

FIG. 6 is an explanatory view of an injection molding process.

FIG. 7 is an explanatory diagram of an injection molding process.

FIG. 8 is an explanatory diagram of an injection molding process.

FIG. 9 is an explanatory diagram of an injection molding process.

FIG. 10 is an explanatory diagram of an injection molding process.

FIG. 11 is an explanatory view of a conventional injection molding die.

[Explanation of symbols]

 1 Fixed type 2 Movable type 3 Fixed side type plate 4 Fixed side mounting plate 5 Movable side type plate 6 Spacer 7 Movable side mounting plate 8 Ejection plate 14 Cavity 15 Fixed side mirror surface piece 16 Movable side mirror surface piece 17, 18 Cylindrical hole 19 Extension rod 20,21 Drill hole 22,23 Cartridge heater 24,25 Lead wire 26,27 Thermocouple lead wire 28,29 Clearance hole 30 Controller 31,32 Clearance 40 Spool 41 Runner 42 Molten resin 50 Molded product

Continuation of front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical display area B29C 45/78 B29C 45/78 // B29L 11:00

Claims (5)

[Claims] 1. A clearance existing between a mold plate forming a part of a mold cavity and a part for holding a mirror-finishing piece having a part that can be a mirror-finishing part of the cavity is controlled by a heating means. An injection molding mold for molding a product in a closed state by expansion, wherein the mirror surface piece is provided with a heating means. 2. The heating means provided on the mirror surface piece,
The injection molding die according to claim 1, further comprising temperature control means for controlling a heating temperature. 3. A mold plate forming a part of a mold cavity is provided with a clearance between a part for holding a mirror surface piece having a part which can be a mirror surface part of the cavity and a clearance provided by a heating means. In an injection mold for molding a product in a closed state by expansion, among the clearances existing between the mirror surface piece and the mold plate, only the clearance in the vicinity of the mirror surface portion of the mirror surface piece is set to another portion. An injection molding die characterized by being formed larger than that. 4. A mold plate forming a part of a mold cavity is provided with a clearance between a part for holding a mirror surface piece having a part which can be a mirror surface part of the cavity and a clearance provided by a heating means. In an injection molding method for molding a product in a state of being sealed by expansion, a heating means is embedded in the mirror surface piece, and the clearance is sealed while the temperature control means controls the temperature of only the mirror surface piece by the heating means. The molten resin is injected into the mold cavity after being heated up to the temperature range described above. 5. The clearance according to claim 4, wherein among the clearances existing between the mirror surface piece and the template, only the clearance in the vicinity of the mirror surface portion of the mirror surface piece is larger than the other portions. Injection molding method.