JPH0745098B2 - Mold temperature control method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a temperature control method for a mold used for molding.

(Prior Art) In order to produce a molded product such as a die casting, a molding material such as aluminum is heated and melted and then filled in a mold, and then the molding material is cooled and solidified in the mold. In order to obtain a good molded product, it is necessary to set the mold temperature according to the shape of the molded product, and therefore the temperature control of the mold is an extremely important factor.

Conventionally, the temperature control of a mold has been performed by flowing a cooling liquid such as water through a large number of cooling holes formed in the mold and adjusting the flow rate of the cooling liquid. (JP-A-57-5026
(See JP-A No. 5 and JP-A-55-141370) (Problems to be solved by the invention) However, in the above control method, the cooling efficiency is poor, and in order to cool the mold efficiently, the cooling holes are formed in the mold. Since a large number of holes are drilled in the mold, cracks occur in the mold, causing cracks.

Further, even if the mold temperature is detected by a temperature sensor or the like and the flow rate of the cooling liquid is controlled, the cooling efficiency is poor, and the responsiveness is low and the mold temperature change cannot be followed. Therefore, it is difficult to maintain the mold temperature for obtaining an excellent molded product according to the shape of the molded product. Further, immediately after the start of molding, it is necessary to perform a large number of trial shots and discard shots in order to raise the temperature of the mold to a predetermined temperature, which causes a problem that work efficiency is deteriorated and productivity is lowered.

Accordingly, the present invention provides a mold temperature control method that quickly responds to mold temperature fluctuations.

(Means for Solving Problems) In order to solve the above problems, the present invention provides a cooling chamber provided in a part of a mold, in which a refrigerant is stored, and a cooling medium provided outside the mold. A closed circuit is formed with the device, and the temperature of the mold is detected as the molding process progresses, and according to the difference between the detected temperature and a predetermined set temperature, the amount of refrigerant in the closed circuit is increased or decreased to It is characterized in that the pressure in the cooling chamber is increased or decreased.

(Operation) Since the present invention is configured as described above, by controlling the increase / decrease of the amount of the refrigerant circulating in the closed circuit, the boiling point is increased to increase or the pressure is decreased to decrease the boiling point to obtain a good molded product. By matching the mold temperature according to the shape of the molded product for obtaining, and the boiling point of the refrigerant, with the temperature increase of the mold accompanying the molding process, when the temperature of the refrigerant rises above the set boiling point, Since the refrigerant boils and vaporizes, the heat of vaporization of the refrigerant immediately lowers the temperature of the mold to a temperature for obtaining a good molded product. Then, at the same time as the boiling of the refrigerant is stopped, the evaporation of the refrigerant is stopped.

In this way, if the temperature of the mold exceeds the boiling point of the refrigerant set in advance due to the molding process, the refrigerant vaporizes and immediately cools the mold, and the temperature of the mold exceeds the boiling point of the refrigerant. When not present, the refrigerant does not vaporize, so unnecessary cooling of the mold is performed, and the mold temperature does not become too low. Therefore, the temperature of the mold is quickly responded to, and the mold is controlled so as to be constantly maintained at the temperature for obtaining an excellent molded product.

(Example) Below, one Example of this invention is described in detail based on drawing.

First, the apparatus used to carry out the method of the present invention will be described.

In FIG. 1, reference numeral 1 denotes a mold temperature control device, and the mold temperature control device 1 mainly includes a cooling chamber 2, a refrigerant cooling device 3 and a reservoir tank 4.

The cooling chamber 2 is provided in the mold 5 and is filled with the coolant 6. The cooling chamber 2 and the refrigerant cooling device 3 are connected to the pipe 7,
14 are connected so as to form a closed circuit.

The coolant cooling device 3 is cooled by the cooling chamber 2 as the temperature of the mold 5 rises.
After taking in the vaporized refrigerant 6 through the pipe 7 with a cooling device (not shown), it is cooled to a temperature below the boiling point of the refrigerant 6 to be liquefied, and the liquefied refrigerant 6 is cooled in the cooling chamber 2 or the reservoir tank 4. It is to be carried in via a pipe.

The reservoir tank 4 contains the refrigerant 6, and the reservoir tank 4, the cooling chamber 2 and the refrigerant cooling device 3 are connected to the pipe 14
Is connected via the electromagnetic valve 13. This allows
The reservoir tank 4 and the cooling chamber 2 are separated from each other, and the reservoir tank 4 and the refrigerant cooling device 3 are separated from each other by closing the electromagnetic valve 13, and are opened by opening the electromagnetic valve 13. As a result, the total amount of the refrigerant 6 circulating in the closed circuit including the cooling chamber 2 and the refrigerant cooling device 3 increases as the refrigerant 6 in the reservoir tank 4 flows into the closed circuit, while the refrigerant 6 is closed circuit. It is reduced by flowing from the inside into the reservoir tank 4. The electromagnetic valve 13 is a mold temperature control circuit.
Controlled to 11.

A mold temperature control circuit 11 presets the boiling point of the refrigerant 2 in the cooling chamber 2 and closes the electromagnetic valve 13 based on the set temperature (boiling point of the refrigerant 6) data. The boiling point of the coolant 6 is determined by increasing or decreasing the total amount of the coolant 6 in the circuit and increasing or decreasing the amount of the coolant 6 in the cooling chamber 2 while increasing or decreasing the pressure in the cooling chamber 2.

Reference numeral 9 is a temperature sensor for transmitting the temperature data of the mold 5 to the mold temperature control circuit 11 via the transmission line 12, and 10 is transmission of the pressure data in the cooling chamber 2 to the mold temperature control circuit 11 via the transmission line. It is a pressure sensor for

As a result, the mold temperature control circuit 11 causes the preset refrigerant 6
Based on the boiling point data of, and the pressure data of the pressure sensor 10, while controlling the electromagnetic valve 13 via the transmission line 12,
The refrigerant 6 in the cooling chamber 2 is controlled by controlling a pump (not shown).
Increase or decrease the amount of. Therefore, the boiling point of the refrigerant 6 in the cooling chamber 2 is arbitrarily set by the mold temperature control circuit 11.

Here, when the amount of the refrigerant 6 in the cooling chamber 2 is increased, since the refrigerant 6 is pressurized, the boiling point of the refrigerant 6 rises,
Similarly, since the pressure is reduced when the amount of the refrigerant 6 is decreased, the boiling point of the refrigerant 6 is lowered.

Further, when the temperature of the mold 6 is rapidly changed due to an accident or the like, the mold temperature control circuit 11 adjusts the boiling point of the refrigerant 6 by the electromagnetic valve 13, the pressure sensor 10 and the pump based on the temperature data of the temperature sensor 9. . The mold temperature control circuit 11 is provided with data on the relationship between the boiling point of the refrigerant 6 and the pressure.

8 is a cavity (molded product).

Next, the method of the present invention using the apparatus having the above structure will be described with reference to FIG.

First, the temperature of the mold 5 for obtaining a good molded product is set in the mold temperature control circuit 11 according to the shape of the molded product. As a result, the mold temperature control circuit 11 increases / decreases the amount of the refrigerant 6 in the cooling chamber 2 by the pressure sensor 10, the electromagnetic valve 13 and the pump to increase the boiling point of the refrigerant 6 and the mold 5 for obtaining an excellent molded product. Match the temperature of. At the same time, the mold 5 is heated by the start of the molding process.

Next, when the temperature of the inner wall of the cooling chamber 2 rises as the temperature of the mold 5 rises and becomes equal to or higher than the boiling point (preset temperature) of the refrigerant 6, as shown by A in the figure, The coolant 6 boils at a portion of the inner wall of the cooling chamber 2 having a temperature equal to or higher than the boiling point of the coolant 6. As a result, the refrigerant 6 starts to vaporize, and the heat of vaporization of the refrigerant 6 rapidly cools the mold 5 from the inner wall of the cooling chamber 2.

At this time, when the refrigerant 6 undergoes a phase transition from the liquid phase to the gas phase, its latent heat specific heat is 540 cal / g in the case of water, which is about 500 times or more when compared with the sensible heat specific heat of 1 cal / g.dcg. Has cooling efficiency. As a result, when the coolant 6 starts to boil as the temperature of the mold 5 rises, the mold 5 is immediately deprived of a large amount of heat by the heat of vaporization of the coolant 6.

Then, when the temperature of the mold 5 falls below the boiling point of the refrigerant 6 in the cooling chamber 2, the cooling of the mold 5 is stopped because the boiling of the refrigerant 6 in the cooling chamber 2 is stopped. When the temperature of the mold 5 does not reach the boiling point of the coolant 6 in the cooling chamber 2, the coolant 6 does not boil and thus does not vaporize. Therefore, the mold 5 is not cooled more than necessary. On the other hand, when the temperature of the mold 5 becomes equal to or higher than the boiling point of the refrigerant 6, the refrigerant 6 immediately starts boiling. As a result, the mold 5 is immediately cooled by the heat of vaporization of the refrigerant 6. The cooling of the mold 5 by the heat of vaporization of the refrigerant 6 is started immediately when the boiling point of the refrigerant 6 is reached even in a small part of the mold 5.

Further, when the temperature of the mold 5 largely deviates from the set temperature due to an accident or the like, as described above, the temperature of the mold 5 is detected by the temperature sensor 9 and the pressure in the cooling chamber 2 is circulated in the closed circuit. Reset by increasing / decreasing control of the amount of the refrigerant 6 to be performed. As a result, the temperature of the mold 5 is immediately responded to, and the mold 5 is quickly restored to the temperature for obtaining an excellent molded product.

That is, when the pressure in the cooling chamber 2 increases due to the increase in the amount of the refrigerant 6, the boiling point temperature of the refrigerant 6 rises, while when the pressure inside the cooling chamber 2 decreases due to the decrease in the amount of the refrigerant 6, the refrigerant 6
The boiling temperature of is lowered. Therefore, when the temperature of the mold 5 is lower than the set temperature, the amount of the refrigerant is increased, and when the temperature of the mold 5 is higher than the set temperature, the amount of the refrigerant is decreased, so that the metal is cooled during the molding process. The temperature of the mold 5 can be brought close to the set temperature easily and quickly depending on the molded product and the molding material.

Further, the vaporized refrigerant 6 is carried into the refrigerant cooling device 3 via the pipe 7 and then cooled and liquefied, and the liquefied refrigerant 6 is passed from the refrigerant cooling device 3 to the reservoir tank 4 or the cooling via the pipe 14. It is carried into the chamber 2.

(Effect of the invention) Since the present invention is configured as described above, by utilizing the heat of vaporization of the refrigerant, the temperature control that quickly responds to the temperature change of the mold can be performed only by the increase / decrease control of the refrigerant amount. It can be done easily, quickly, and carefully in whole or part of the mold, and when the temperature of the mold rises locally and exceeds the boiling point of the refrigerant, the refrigerant is immediately As it boils, the refrigerant vaporizes and maintains the temperature of the entire mold evenly, so the quality of the molded product can be kept constant,
Product reliability can be improved and defects in molded products can be reduced, thus improving productivity.

Also, until the mold temperature reaches the temperature set to obtain a good molded product, the mold is not unnecessarily cooled, so useless trial striking to raise the temperature of the mold, Since we have reached the minimum of discarding, we improve productivity.

Further, since the cooling efficiency is extremely better than that of the cooling water, it is not necessary to form a large number of cooling holes in the mold, which has an economical effect that the life of the mold is extended. It is excellent in that it does not require any special equipment to control the temperature of the mold, such as eliminating the space for installing equipment for cooling the mold from the outside, and preventing complicated equipment configurations. Has an effect.

[Brief description of drawings]

FIG. 1 is a partial sectional view showing an example of an apparatus used for carrying out the method of the present invention. 2 ... Cooling chamber, 3 ... Refrigerant cooling device 5 ... Mold, 6 ... Refrigerant 7 ... Pipe, 14 ... Pipe

Claims (1)

[Claims] 1. A mold which forms a closed circuit with a cooling chamber provided in a part of a mold and containing a refrigerant, and a cooling device provided outside the mold, and the mold accompanying the progress of molding process. And a pressure in the cooling chamber is increased / decreased by increasing / decreasing the amount of refrigerant in the closed circuit in accordance with a difference between the detected temperature and a predetermined set temperature.