CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority benefit of Japan application serial no. 2020-099771, filed on Jun. 9, 2020. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of this specification.

BACKGROUND

Technical Field

The disclosure relates to a backflow prevention device of a light metal injection device and a backflow prevention method of a light metal injection device, which connect a melting unit that melts an unmelted light metal material into a molten metal and an injection unit that injects the molten metal into a mold by a communication path, open the communication path when the molten metal in the melting unit is supplied to the injection unit, and close the communication path when the molten metal in the injection unit is injected to the mold.

Related Art

A light metal injection molding machine injects a molten metal of a light metal material into a mold, and cools and solidifies the molten metal in the mold to manufacture a molded product. The light metal injection molding machine includes a light metal injection device and a mold clamping device. The light metal injection device melts an unmelted light metal material into a molten metal, and then injects the molten metal into the mold. The mold clamping device opens and closes the mounted mold and tightens the closed mold. The light metal material generally refers to a metal having a specific gravity of 4 or less. Practically, aluminum and magnesium are particularly effective as the light metal material.

The light metal injection device includes a melting unit, an injection unit, a communication path connecting the melting unit and the injection unit, and a backflow prevention device which opens and closes the communication path. The melting unit melts the unmelted light metal material into the molten metal. The injection unit injects the molten metal supplied from the melting unit through the communication path into the mold. The communication path is a flow path through which the molten metal passes. The backflow prevention device opens the communication path when the molten metal in the melting unit is supplied to the injection unit, and closes the communication path in order to prevent the molten metal from flowing back into the melting unit when the molten metal in the injection unit is injected to the mold.

The backflow prevention device includes, for example, a valve configured by a valve body and a valve seat. The valve closes the communication path by advancing the valve body to be seated on the valve seat on one hand, and opens the communication path by retracting the valve body to be separated from the valve seat on the other hand.

An injection device of a light metal injection molding machine in Patent literature 1 (United States Patent Laid-Open No. 2020/0108439) includes the backflow prevention device which opens and closes a communication path. The backflow prevention device includes the valve configured by a valve body and a valve seat. The valve seat is formed around an opening of a melting unit side end portion of the communication path. The valve body advances in a melting unit to be seated on the valve seat, and retracts in the melting unit to be separated from the valve seat.

A material supply device of a light metal injection molding machine in Patent literature 2 (U.S. Pat. No. 10,695,827) is included in an injection device of a light metal injection molding machine. The injection device of a light metal injection molding machine includes the backflow prevention device which opens and closes a communication path. The backflow prevention device includes the valve configured by a valve body and a valve seat. The valve seat is formed around an opening of an injection unit side end portion of the communication path. The valve body advances in an injection unit to be seated on the valve seat, and retracts in the injection unit to be separated from the valve seat.

Sealing performance when the valve body is seated on the valve seat is improved by bringing the valve body and the valve seat into surface-contact with each other. For example, regarding the valve body and the valve seat made of a corrosion-resistant and heat-resistant steel, by a predetermined pressure at which the valve body presses the valve seat, both the valve body and the valve seat are elastically deformed and come into surface-contact with each other.

However, for example, when the valve body and the valve seat made of a corrosion-resistant and heat-resistant steel are exposed to an aluminum molten metal, the surfaces of the valve body and the valve seat may be unevenly melting-damaged even for the corrosion-resistant and heat-resistant steel, and the valve body and the valve seat may be difficult to come into surface-contact with each other even if they are elastically deformed when the valve body is seated.

The surfaces of the valve body and the valve seat made of a ceramic are not melting-damaged even when the valve body and the valve seat are exposed to the aluminum molten metal, for example. However, generally, the ceramic is a material which has a higher hardness than that of the corrosion-resistant and heat-resistant steel, and the amount of elastic deformation under an external force is smaller than that of the corrosion-resistant and heat-resistant steel, resulting in brittle fracture without plastic deformation. The valve body and the valve seat made of a ceramic cannot be expected to come into surface-contact with each other by being elastically deformed, and thus high processing precision is required for the surface to be contacted. Furthermore, the valve body and the valve seat made of a ceramic may be chipped or cracked when the valve body is pressed against the valve seat at a large pressure in a state in which the valve body and the valve seat are in local contact with each other.

Therefore, the disclosure is to propose a backflow prevention device of a light metal injection device and a backflow prevention method of a light metal injection device, on one hand, which can seat the valve body made of a heat-resistant and corrosion-resistant steel on the valve seat made of a high-hardness ceramic and cause the valve body to deform elastically, and thereby bring the valve body and the valve seat into surface-contact with each other to easily obtain required sealing performance; on the other hand, which can easily detect the replacement time of the valve body that gradually wears out due to melting damage, plastic deformation or the like compared to the ceramic that has high-hardness and is not melting-damaged, and replace the valve body in a timely and easy manner to easily maintain and manage the required sealing performance. Additional features of the disclosure will be set forth in the description that follows.

SUMMARY

A backflow prevention device of a light metal injection device of the disclosure connects a melting unit which melts an unmelted light metal material into a molten metal and an injection unit which injects the metered molten metal into a mold by a communication path, opens the communication path when the molten metal in the melting unit is supplied to the injection unit, and closes the communication path when the molten metal in the injection unit is injected to the mold. The backflow prevention device of a light metal injection device includes: a valve which has a valve body made of a corrosion-resistant and heat-resistant steel and a valve seat made of a ceramic, and in which the valve body advances and is seated on the valve seat to close the communication path, and the valve body retracts and is separated from the valve seat to open the communication path; a valve body drive device which moves a drive body to which the valve body is connected in the front-rear direction together with the valve body; a position sensor which detects that the drive body has reached at least a predetermined advance limit position and outputs a signal indicating that the drive body has reached the predetermined position; and a valve body drive control device which connects the valve body drive device and the position sensor respectively, and controls the valve body drive device based on the signal of the position sensor.

A backflow prevention method of a light metal injection device of the disclosure connects a melting unit which melts an unmelted light metal material into a molten metal and an injection unit which injects the molten metal into a mold by a communication path, opens the communication path when the molten metal in the melting unit is supplied to the injection unit, and closes the communication path when the molten metal in the injection unit is injected to the mold. In the backflow prevention method of a light metal injection device, a valve body made of a corrosion-resistant and heat-resistant steel advances, and the valve body is seated on a valve seat made of a ceramic, thereby closing the communication path; the valve body retracts, and the valve body is separated from the valve seat, thereby opening the communication path; and a position sensor detects that a drive body which is connected to the valve body and is moved forward and backward by a valve body drive device has reached a predetermined advance limit position, and thereby it is detected that a wear-and-tear amount of the length of the valve body in the front-rear direction has reached an allowable maximum wear-and-tear amount.

