JPH06122136A - Precise mold - Google Patents

Abstract

PURPOSE:To obtain a precisely molded form having a high accuracy by disposing an injection mold or a material, after the mold is mounted, which a strain level can be controlled by an electric or magnetic signal, expanding or contracting it, compensating a deformation due to concentration of a resin charging pressure at a center of the mold, and suppressing a decrease in parallelism of the cavity. CONSTITUTION:Resin injected in a mold is charged in a cavity through a sprue 1 and a rubber 2. In this case, particularly a center of a movable mold is pressure-received to be deformed toward an air gap 11 between a movable mold 8 and a mounting plate 10 by fluidized resin charging pressure, and a parallelism of surfaces (a) and (b) of a molded optical component 3', etc., is deteriorated. Then, a piezoelectric element 6 is, for example, disposed at a center of a heat insulation plate 5 at the side of the mold 8, and expanded in a thickness direction of the plate 5 by a voltage to be applied from a controller 12. As the element 6, piezoelectric ceramics are desirable. It is desirable that a plurality of the elements 6 are disposed and voltages to be applied to the individual elements 6 are controlled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plastic injection mold and, more particularly, to a parallelism reduction preventing structure for molding high precision precision molded products such as optical parts having excellent parallelism.

[0002]

2. Description of the Related Art Conventionally, in a high precision precision molding die for an optical component or the like, as described in Japanese Patent Publication No. 1-141010, heating is performed and a gate is cut off in order to improve precision.
Operations such as applying pressure were performed.

[0003]

In the above-mentioned prior art, although the mold and the resin in the cavity are heated and pressed, deformation of the mold due to these loads is not taken into consideration. In addition to these loads, deformation of the mold due to the resin filling pressure was unavoidable. Therefore, mold opening occurs, the cavity is deformed, the parallelism between the fixed mold and the movable mold is lowered, and there is a problem that the parallelism and dimensional accuracy of the molded product cannot be obtained.

An object of the present invention is to provide a mold structure for suppressing deterioration of parallelism of a mold for improving dimensional accuracy of parallelism of a molded product.

Another object of the present invention is to provide an injection molding die capable of obtaining a highly accurate and precise molded product in which the parallelism is suppressed.

[0006]

In order to achieve the above object, a part or a plurality of parts of a mold or a mold mounting plate can be applied with an arbitrary voltage or magnetic field by an external control device. A piezoelectric element, an electrostrictive element, or a magnetostrictive element.

[0007]

In the present invention, in order to compensate for the deformation at the center of the mold, which is caused by the filling pressure of the resin when the resin flows into the sprue and runner, which are the resin flow paths, and fills the cavity through the gate. , By applying a voltage or magnetic field to the piezoelectric element, electrostrictive element, or magnetostrictive element arranged on the mold or the mold mounting plate to expand or contract, so that the amount of deformation on the dividing surface of the mold becomes nearly uniform. , Suppress the decrease in parallelism. Thereby, a highly accurate molded product can be obtained.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention is shown in FIG. 1 and will be described in comparison with FIGS. 3 and 4 showing conventional examples.

FIG. 1 is a vertical sectional view of an injection molding die for forming an optical component and the like, and shows a cross section taken along the line AA 'in the front view of the heat insulating plate shown in FIG. In FIG. 1, reference numerals 1 and 2 respectively represent a sprue and a runner portion of a resin flow path through which resin from a molding machine (not shown) flows into the cavity. Numeral 3 is a cavity for forming a molded product, which is provided at four places in order to obtain four molded products. Reference numeral 7 is a fixed die that forms the fixed side of the cavity 3, 8 is a movable die that forms the movable side of the cavity 3, and 9 is a fixed mounting plate for fixing the fixed die 7 to a mold clamping unit (not shown) of the molding machine. Reference numeral 10 is a movable mounting plate for fixing the mold (movable side) to the mold clamping portion of the molding machine as in the case of 9. A heat insulating plate 4 and a heat insulating plate 5 are provided between the fixed die 7 and the fixed mounting plate 9 and between the movable die 8 and the movable mounting plate 10, respectively.

The resin (not shown) injected into the mold thus constructed passes through the sprue 1 and the runner 2 and is filled in the cavity 3. In the case of ordinary molding, the fluid filling pressure of the resin at this time is 1000 to 1500 kg / cm ² , and the sprue 1, runner 2, and cavity 3 receive pressure due to this fluid filling pressure, and as shown in FIG. The center part of the mold is deformed by pressure toward the gap 11 between the movable mold 8 and the mounting plate 10. As shown in FIG. 4, the optical component formed by this mold has poor parallelism between the a-face and the b-face. For example, when the flow filling pressure is 1500 kg / cm ² with respect to a φ80 molded product, an inclination of about 100 μm occurs. There is a limit to some extent by lowering the fluid filling pressure, but there is a limit. If the filling pressure is too low, short shots occur and molded articles cannot be formed.

Therefore, the piezoelectric element 6 is placed in the center of the heat insulating plate 5 on the side of the movable mold 8 so that the heat insulating plate 5 expands in the thickness direction of the heat insulating plate 5 by the voltage applied from the controller 12 connected by the conductor 13. I chose As the material of the piezoelectric element 6, piezoelectric ceramics having the same compressive strength and heat insulating property as the material of a commonly used heat insulating plate is used. Thereby, the parallelism can be improved by pressing the central portion of the movable mold 8 in the direction opposite to the resin filling pressure and reducing the deformation of the central portion of the movable mold 8.

It is effective to dispose a plurality of piezoelectric elements 6 in order to obtain an action force corresponding to the pressure distribution on the mold dividing surface. In this case, the amount of deformation of the divided surface can be reduced by controlling the voltage applied to each piezoelectric element according to the pressure distribution on the divided surface of the mold. As an example of the arrangement of the piezoelectric elements 6 when arranging a plurality of them, as shown in FIG. 5, a method of arranging them corresponding to the places where the resin filling pressure acts, such as the runner 2 and the cavity 3, is arranged in a matrix as shown in FIG. There is a way to place it. Since the applied voltage Ei to each piezoelectric element 6i is changed to E1 to En according to the distribution of the resin filling pressure as shown in FIG. 7, the deformation amount of the mold dividing surface can be compensated with high accuracy. High precision molding is possible.

Further, as shown in FIG. 8, the piezoelectric element 6 is also arranged on the outer peripheral portion of the heat insulating plate 5 so as to be contracted at the time of molding and the deformation amount of the outer peripheral portion is increased, so that the difference in the deformation amount from the central portion is reduced. There are ways to reduce and improve parallelism. At this time, as shown in FIG. 9, the entire heat insulating plate 5 may be composed of only a large number of piezoelectric elements.

The above-mentioned piezoelectric element 6 may be arranged not only by replacing it with a heat insulating plate but also by providing it on the outside separately from the heat insulating plate as shown in FIG. In that case, the heat insulating effect of the heat insulating plate is not deteriorated, and therefore the arrangement shown in FIG. 10 is effective. The element generating the strain may be arranged at any position effective for compensating for the deformation of the mold dividing surface. As shown in FIGS. 11 and 12, a part of the movable mold 8 or the fixed side may be arranged. You may arrange.

Another embodiment of the present invention is shown in FIG. FIG. 13 is a vertical cross-sectional view of a mold provided with a piezoelectric element strain sensor 14 for generating an electric signal by the stress acting on the mold. In the mold having this structure, as shown in FIG.
As shown in FIG. 14 (b), the electric signal generated in the piezoelectric element strain sensor 14 by the resin filling pressure is directly supplied to the controller 1 or
By feeding back to the piezoelectric element 6 via 2, the deformation of the mold can be efficiently compensated.

In the above examples, the piezoelectric material is used as the element for generating the pressing force for compensating the deformation at the center of the mold, but the same effect is obtained when the electrostrictive material and the magnetostrictive material are used. is there.

[0017]

According to the present invention, a part of the heat insulating plate on the movable side is used as a piezoelectric element, an electrostrictive element or a magnetostrictive element, and a voltage or a magnetic field is applied to thereby reverse the resin filling pressure to the central portion of the movable die. A directional pressing force is generated, and the difference between the deformation amount at the outer peripheral portion of the die and the central portion of the die is reduced. This has the effect of obtaining an optical component with improved parallelism.

[Brief description of drawings]

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

FIG. 2 is a front view of an injection molding die showing an embodiment of the present invention.

FIG. 3 is a vertical cross-sectional view showing a deformation of a conventional mold due to a resin filling pressure in the vicinity of a cavity.

FIG. 4 is a vertical cross-sectional view showing a decrease in parallelism of a molded product.

FIG. 5 is a front view of an injection molding die showing another embodiment of the present invention.

FIG. 6 is a front view of an injection molding die showing another embodiment of the present invention.

FIG. 7 is a connection diagram of a piezoelectric element according to another embodiment of the present invention.

FIG. 8 is a front view of an injection molding die showing another embodiment of the present invention.

FIG. 9 is a front view of an injection molding die showing another embodiment of the present invention.

FIG. 10 is a vertical sectional view of an injection molding die showing another embodiment of the present invention.

FIG. 11 is a vertical sectional view of an injection molding die showing another embodiment of the present invention.

FIG. 12 is a vertical cross-sectional view of an injection molding die showing another embodiment of the present invention.

FIG. 13 is a vertical sectional view of an injection molding die showing another embodiment of the present invention.

FIG. 14 is a connection diagram of a piezoelectric element according to another embodiment of the present invention.

[Explanation of symbols]

 1 ... Sprue, 2 ... Runner, 3 ... Cavity, 6 ... Piezoelectric element, 8 ... Movable type.

Front page continuation (72) Inventor Masahiko Ozawa 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Stock Video Media Research Laboratory, Hitachi, Ltd. (72) Inventor Masumi Kutomi 292 Yoshida-cho, Totsuka-ku, Yokohama, Kanagawa Hitachi, Ltd Video Media Laboratory (72) Inventor Masayuki Muranaka 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Hitachi Ltd. Video Media Laboratory

Claims (4)

[Claims] 1. An injection molding die in which a cavity for molding a molded product is formed on a split surface of a fixed mold and a movable mold,
A material whose strain amount can be controlled by an electrical or magnetic signal from the outside is placed on a part of the mold or the mold mounting plate, and by expanding or contracting this material, the central part of the mold dividing surface A precision molding die characterized by compensating for deformation due to the concentration of resin filling pressure and preventing the parallelism of the cavity from decreasing. 2. The precision molding die according to claim 1, wherein a piezoelectric ceramic is used for a part of the heat insulating plate as an element for generating strain. 3. A mold can be highly accurately deformed by arranging a plurality of materials whose strain amount can be controlled by an external signal on a mold or a mold mounting plate, and by inputting different control signals to each. Claim 1 or 2 which can be compensated
Precision molding mold as described. 4. A strain sensor such as a piezoelectric element is provided to generate an electric signal by the stress acting on the mold, and the generated electric signal is fed back to compensate the deformation of the mold. The precision molding die according to Item 1, 2 or 3.