JPH071457A - Mold - Google Patents

Abstract

PURPOSE:To keep the curing temp. distribution of the resin in a mold cavity constant by providing a cooling tank at the position of coming into contact with a mold and arranging a plurality of electronic coolers having self-controllability in the vicinity of the mold cavity and providing the radiation parts of the electronic coolers in the cooling tank. CONSTITUTION:A cooling tank 4 is arranged to the upper part of a mold 1 and the endothermic parts 8 of electronic coolers are provided in the vicinity of a cavity 2 at places requiring local cooling and the radiation parts 7 thereof are immersed in the cooling water received in the cooling tank 4. Each of the electronic coolers is formed as one unit by connecting several thermocouple elements 14 and these thermocouple elements 14 are connected to conductors and semiconductors of a different kind to constitute closed loop to perform radiation and heat absorption by Peltier effect. In order to provide self-controllability to each of the electronic coolers against temp., a part of each of the endothermic parts 8 is constituted of a temp.-sensitive part 13 suddenly increased in resistance at certain temp. by a closed circuit. Therefore, at the time of predetermined temp. or higher, cooling capacity is increased to hold constant temp. distribution. As a result, the curing temp. distribution of a resin can be kept constant.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molding die, and more particularly to a structure of a molding die for producing a large-sized molded product using a thermosetting resin.

[0002]

2. Description of the Related Art In molding, it is an important subject to prevent molding defects, especially warpage and deformation. Deformation due to thermal stress is considered to be the main cause of warpage / deformation, which is caused by the temperature distribution of the resin due to nonuniform cooling in general molding. Therefore, various methods for uniformly cooling the mold have been considered. One of them is a method of performing uniform cooling by controlling the flow rate of a coolant flowing through a plurality of cooling pipes installed in a mold. Further, as a method for increasing the cooling capacity, as shown in FIG.
There is a method described in Japanese Patent Publication. According to this method, the thermoelectric element 17 is arranged in the molds 1a and 1b near the surface of the molding die,
The heat absorbing surface of 7 is directed to the molding die surface side, and the heat radiating surface is cooled by the cooling water passing through the cooling holes 16, so that the cooling capacity of the mold device is enhanced.

[0003]

As described above, in the prior art relating to the temperature control of the molding die, the main object is to keep the temperature of the die as uniform as possible. When manufacturing a large-sized mold product using a thermosetting resin, the curing reaction is accelerated by heating from outside the mold, but the curing reaction rate varies depending on the temperature. In addition, because of its large size, curing shrinkage and flow of the melted portion due to gravity have a great influence on the formation of sink marks and cavities. Therefore, in order to prevent sink marks, it is necessary to control the curing in order from the bottom, and rather, a mold structure and temperature control that positively give a temperature distribution in the mold are required.

An object of the present invention is to provide a molding die capable of controlling local curing in a large-sized molded product.

[0005]

SUMMARY OF THE INVENTION The present invention provides an electronic cooler that uses a cooling tank outside the mold at a position in contact with the mold and thermoelectric elements at several locations near the cavity where local cooling is required. The electronic cooler is provided with self-controllability, and the heat dissipation surface of the thermoelectric element is installed in the cooling tank to achieve the above object.

[0006]

[Function] In addition to local cooling by a cooling tank installed in a part of the mold so as to be in contact with the mold, a self-controlling electronic cooler locally arranged near the cavity has a constant temperature distribution. The entire cavity is heated in the shape of a circle.
Further, by disposing the heat radiating surface of the electronic cooler in the cooling tank, it becomes possible to control the temperature so that the size of the mold remains the same as in the conventional case and the required hardening distribution is exhibited.

[0007]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows an embodiment of a molding die for carrying out the present invention. In this embodiment, the cooling tank 4 is installed on the upper part of the mold 1, and the heat absorbing portion 8 of the electronic cooler is installed near the cavity at a place where local cooling is required. The heat absorbing portion 8 is connected to the terminal portion 9 outside the mold through the lead wire.
Connected with. The heat radiating portion 7 is installed at a position where the cooling water 5 in the cooling tank 4 is submerged from the terminal portion 9 through the power source 6 attached to the cooling tank 4. The water level of the cooling water 5 at which the cooling water is not depleted is set in consideration of the amount of evaporation of the cooling water 5 due to the heating for hardening. The electronic cooler comprises one unit by connecting a plurality of thermoelectric elements 14. The thermoelectric element uses a Peltier effect in which different types of conductors and semiconductors are connected to form a closed loop, and when a current is passed through the closed loop, heat is absorbed at one of the contacts at both ends and heat is released at the other. With this configuration, the lower part of the mold has a higher temperature, and an arbitrary temperature distribution that can meet local requirements such as a thick part can be set. Also, in the case of manufacturing a large mold product using a thermosetting resin, it is usually a three-step process of preheating, injection, and heating for curing, but it is necessary to control the temperature for each process separately. Since a furnace is used, when moving to the next step, the mold must be moved together.
According to this method, it suffices to fit the cooling tank in the upper part and connect the lead wire to the terminal portion before starting the heating step, and no extra equipment is required and the installation is easy. As a thermoelectric material, a material having a large Peltier effect, small generation of Joule heat, and small heat conduction from a high temperature portion to a low temperature portion is preferable.
Examples of such materials include Bi ₂ Tb ₃ · Sb ₂ Te ₃ and Bi ₂
There are Tb ₃ and Bi ₂ Se ₃ .

A temperature-sensitive relay using a bimetal or a shape memory alloy can be considered in order to give the electronic cooler self-controllability with respect to temperature. In this embodiment, however, the structure shown by the circle in FIG. 1 is adopted. In a closed circuit that constitutes an electronic cooler, a part of the heat absorption part 8 is made into a temperature sensing part 13 using a material (for example, barium titanate BaTiO ₂ ) whose resistance rapidly increases at a certain temperature, and is arranged in parallel with the contact 11. You can connect to. Ba
TiO ₂ shows the characteristics as shown in FIG. 3, and the set temperature T ₀ is lead P
It can be set arbitrarily by adding b. Therefore,
If the temperature sensing part 13 is installed near the heat absorbing part 8 and a constant current is made to flow, the resistance of the temperature sensing part 13 is large at a predetermined temperature or higher, and most of the current flows through the contact 11 side, and the temperature is a predetermined value. Below, the current flowing through the contact 11 side decreases relatively. Since the Peltier effect is proportional to the electric current, the cooling capacity increases at a predetermined temperature or higher, and a constant temperature distribution can be maintained.

[0010]

EFFECTS OF THE INVENTION According to the present invention, even a molded product having a complicated product shape can be maintained at a constant temperature distribution in order to control the curing of the resin in the cavity without external control, and the size of the product can be maintained as it is. A mold can be provided.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a first embodiment of the present invention.

FIG. 2 is a sectional view showing a conventional example.

FIG. 3 is a temperature-resistance characteristic diagram of a material forming the temperature sensing portion.

[Explanation of symbols]

1 ... Mold, 2 ... Cavity, 3 ... Injection port, 4 ... Cooling tank,
5 ... Cooling water, 6 ... Power supply, 7 ... Heat dissipation part, 8 ... Heat absorption part, 9 ...
Terminal portion, 10 ... Insulating material, 11 ... Contact, 12 ... Thermoelectric wire,
13 ... Temperature sensing part, 14 ... Compensation lead wire.

Claims (1)

[Claims] 1. A molding die, wherein a cooling tank is installed outside the molding die at a position in contact with the die, and a thermoelectric element having self-controllability with respect to temperature near the cavity of the molding die. One or a plurality of cooling means using a thermoelectric element are provided, and the heat radiation part of the cooling means using a thermoelectric element is installed in the cooling tank to control the temperature of the molding die. Mold for molding.