JPH0664013A - Mold temperature controlling device and method - Google Patents

Abstract

PURPOSE:To provide a temperature controlling device and method for mold by a method wherein stable temperature controlling is made possible by utilizing a plurality of steams different in pressure from one another and molding with high transferability is made possible with extremely small scale and low cost facilities. CONSTITUTION:The numeral 1 representing a mold or the object of temperature controlling. The numeral 2 represents a steam generating device, which generates steam as heat medium. The steam generated at the device 2 is selectively changed over by control valves V1 and V2 to the pre-set pressure reducing valves in the circuit of medium passage. Thus, the pressure reducing valves B1, B2 and B3 control the steam to ones having pressures different from one another so as to introduce each of them in the mold 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a temperature control device and a temperature control method for a molding die, particularly a molding die used for a molded product such as a plastic lens which requires high precision.

[0002]

2. Description of the Related Art In recent years, as devices having optical systems such as projection television receivers, video cameras, and CD players have become widespread, mass productivity, cost merit, lightness, BACKGROUND ART Practical use and widespread use of plastic lenses having a high spherical aberration correction capability and the like are in progress.

In such a plastic lens, remarkably high shape accuracy is required as compared with a general resin molded product, and as one of means for realizing this, a resin surface layer portion after the resin has been cooled to some extent A method of raising the temperature again has been proposed (for example, Japanese Patent Publication No. Sho 61-19220 and Japanese Examined Patent Publication No. 1-34132). According to our study, in order to fully exert the effect of raising the temperature, the temperature raising temperature is considerably higher than the heat deformation temperature (125 ° C. in the case of PC) or the glass transition temperature (145 ° C.) of the resin. A high flow stop temperature (160 ° C) is required.

According to this method, it is expected that a high shape accuracy can be obtained by reducing non-uniform shrinkage, that is, so-called sink mark, which is caused by the fact that the rate of cooling and solidification of the resin greatly varies depending on the site.

As a concrete means for realizing the above-mentioned temperature control, conventionally, a relatively low temperature heating medium such as used for mold temperature control at the time of ordinary molding and resin for raising the temperature to near the flow stop temperature are used. Prepare two kinds of heat medium of relatively high temperature in the tank and introduce them into the mold alternately, or mix these to make medium temperature medium,
Methods such as realizing a ramp-shaped temperature control pattern have been implemented.

[0006]

However, in the above-mentioned structure, when two heating medium supply devices are used and the mixing means is used, the temperature of the returning medium can be multiplied by the temperature to be supplied, so that a stable temperature is supplied. In order to do so, an extremely large capacity and a heater are required, which causes a problem that the temperature control system becomes large in scale.

[0007]

In order to solve the above-mentioned problems, the temperature control device for a molding die of the present invention controls steam to different pressures using a steam generator and a plurality of pressure control valves. Is introduced into the mold by means of selectively switching.

Further, the method of controlling the temperature of the molding die of the present invention is such that, when a plurality of steams having different pressures are used to fill the resin, the saturation temperature is low such that the saturation temperature is about the glass transition temperature or lower, and then the saturation temperature. Is introduced into the mold at a high pressure such that it is near the flow stop temperature of the resin used, and at a low pressure such that it is below the glass transition temperature stepwise or immediately.

[0009]

According to the above-mentioned structure, a relatively simple equipment structure may be constituted by one steam generator, a plurality of pressure control valves and a pressure reducing valve, and a method of mixing different water or oil heat media. It can be carried out on an extremely small scale, and stable temperature control can be performed, and the sink marks generated during the cooling process can be eliminated by raising the temperature above the flow stop temperature to realize high transferability.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A temperature control device and a temperature control method according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of a temperature control device for a molding die of the present invention adapted for molding a polycarbonate resin.

In FIG. 1, 1 is a mold whose temperature is to be controlled, 2 is steam pressure 10 kg / cm ² (saturation temperature 180 ° C.)
A steam generator having the capacity of B1, B2, B3 is a pressure reducing valve, and the pressure from the steam generator 2 is 2 each.
kg / cm ² (saturation temperature 120 degrees), 7 kg / cm ² (same 164)
Is set to 4 kg / cm ² (143 degrees).
By controlling these with control valves V1 and V2, it becomes possible to selectively introduce steam of 120 °, 164 °, and 143 ° into the mold 1.

FIG. 2 is a graph showing a temperature control pattern when molding the polycarbonate resin using the apparatus of the embodiment shown in FIG.

In FIG. 2, the horizontal axis is the time showing the molding process and the injection completion time is t0. The vertical axis is the temperature, the solid line graph is the set temperature of water vapor, and the wavy line is the mold temperature of the portion in contact with the resin.

First, at the injection completion time t0, the control valve V1 is used for the mold 1 from the previous stage and the pressure reducing valve B1 is selected, and then the pressure: P1 = 2 kg / cm ² (saturation temperature: T1 = 120
Steam) is introduced and the temperature is maintained at T1. This is realized by selecting the 1-2 circuit of the control valve V1 and forming it by the steam generator 2 in the block diagram of the temperature controller shown in FIG. In this state, the resin has a glass transition temperature over the entire area: Tg = 140 to 145.
It is held until time t1 when the temperature reaches about 0 degrees. Next, time t1
At that time, the control valve V1 is switched to the 1-3 circuit,
Further, steam is supplied to the pressure reducing valve 2 by using the 1-2 circuit of the control valve V2, and the pressure to the mold 1 is P2 = 7 kg / cm ² (saturation temperature: T
(3 = 164 degrees) steam is introduced. By the introduction of the temperature T3, the flow stop temperature: Tnf =
When the temperature approaches 160 degrees, the resin is rearranged so that the pressure distribution becomes uniform, and the sink factor caused by the difference in the cooling rate of each part of the resin in the process before time t1 is canceled.

At this time point t2, only the control valve V2 is switched to the 1-3 circuit to supply steam to the pressure reducing valve 3 and the pressure to the mold 1 is P3 = 4 kg / cm ² (saturation temperature: T2 = 143).
Steam) is introduced. After maintaining this state until time t3 when the entire resin region becomes almost glass transition temperature: Tg, the control valve V1 is switched to the 1-2 circuit and the control valve V2 is switched to the 1-2 circuit, and the pressure reducing valve 1 is again heated to the temperature T1. Steam is introduced into the mold 1. And this state is maintained until the mold is opened.

By using such a temperature control device and temperature control method, it is possible to cancel the sink mark due to non-uniform cooling by softening the resin surface layer again, and furthermore, after re-softening, the temperature distribution is uniform around the glass transition temperature. As a result, the sink marks generated after re-softening can be reduced and high transferability can be realized.

Moreover, according to such a method, ideal temperature control can be realized with a simple structure without requiring a large-scale facility which is required in the method of mixing the heat medium.

The times t1, t2, and t3 can be determined by conducting an unsteady heat transfer analysis or a preliminary experiment in advance.

[0020]

As described above, according to the temperature control device and the temperature control method for a molding die of the present invention, it is possible to realize a highly accurate molding with a minimum scale of equipment and a facility cost. In particular, it is effective when high shape accuracy is required such as a plastic lens, and is most suitable for a material having a heat distortion temperature of 100 degrees or more.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of a temperature control device for a molding die of the present invention.

FIG. 2 is a temperature control pattern diagram showing a mold temperature control method in the apparatus of the embodiment.

[Explanation of symbols]

 1 mold 2 steam generator V1-V2 control valve B1-B3 pressure reducing valve

Claims (2)

[Claims] 1. A steam generator, a means for generating steam at a plurality of different pressures from the steam generator using a pressure control valve, and a plurality of steams at different pressures are selectively introduced into a mold, A temperature control device for a molding die, comprising steam switching means that operates according to a preset pattern. 2. A plurality of steams having different pressures are used, and when the resin is filled, a steam having a low pressure whose saturation temperature is equal to or lower than the glass transition temperature of the resin used is introduced into a mold, and then the saturation temperature is used. Introducing steam with a low pressure such that its saturation temperature is below the glass transition temperature into the mold either stepwise or immediately after introducing steam with a high pressure that is near the flow stop temperature of the resin into the mold. A method for controlling the temperature of a molding die, the method comprising: