JPH02149B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention mainly relates to a control method for controlling the pressurization speed in a pot in a low-pressure casting method. As shown in FIG. 1, a casting apparatus applying the low pressure casting method has a casting cavity 2a on a die plate 1.
A holding furnace 3 is installed below the die plate 1, a molten metal 5 is contained in the holding furnace 3, and a pot 4 is provided with a stalk 10.
A pressure air pipe 6 having a valve 7 and an exhaust pipe 8 having a valve 9 are connected to the pot 4. Open the valve 7 of the pressure air pipe 6 to release pressure air into the pot 4.
Since the surface of the molten metal 5 is pressurized, the molten metal 5 is injected into the casting cavity 2a through the stalk 10 and sprue 11 and cast. Then, after the sprue 11 has completed the hardening process, the valve 9 is opened to discharge the exhaust gas from the pot 4, thereby completing the casting. A pressurizing system for pressurizing the molten metal in the ladle 4 is shown in FIGS. 2A and 2B. That is, in the same figure A, the pressure air filtered by the filter 20 is transferred to the pressure reducing valve 23.
a, a primary pressure circuit 21 having a pressure gauge 24a, a needle valve 25, a check valve 26, and a solenoid valve 27a, or a secondary pressure circuit 22A having a pressure reducing valve 23b, a pressure gauge 24b, and a solenoid valve 27b;
It is supplied into the pot 4 through the. In FIG. 2B, the primary pressure circuit 21 is the same as in FIG. 2A, but the secondary pressure circuit 22B has circuits 22Ba to 22Bn having a pressure reducing valve 23b, a pressure gauge 24b, and a solenoid valve 27b installed in parallel. Each circuit 22Ba to 22Bn
The pressure reducing valves 23b having different performances are sequentially switched by a timer to make the secondary pressures different. In the pressurization system shown in FIG. 2A described above, the intermediate pressurization speed cannot be changed from the start of supply of pressurized air until the predetermined final pressure is reached. Further, as the final pressure reaches a predetermined final pressure, it is impossible to prevent the amount of pressurized air supplied from decreasing due to an increase in the pressure inside the pot. According to the pressurization system shown in Figure 2B, the above-mentioned drawbacks can be improved, but in reality, the response time of the valve is long and a large impact is generated during the pressurization increase, so smooth application is not possible. It is not possible to obtain a pressure curve. Therefore, in actual continuous low-pressure casting operations, it is impossible to always maintain the set pressurization speed due to changes in the molten metal level in the pot and leakage at each packing part. The purpose of the present invention is to eliminate the above-mentioned drawbacks by arbitrarily setting the casting speed when the molten metal fills the stalk and casting cavity, and modifying this set speed while observing the pressure inside the pot. It was designed to be cast. An embodiment of the present invention will be described below with reference to the drawings. FIG. 3 shows a pressurization control device to which the control method of the present invention is applied. 1 is a die plate, and 3 is a holding furnace installed below the die plate 1 and containing a pot 4 for storing molten metal 5. , the pot 4 has valve 7
A pneumatic air pipe 6 with a valve 9 and an exhaust pipe 8 with a valve 9 are connected. 10 is a stalk that supplies molten metal 5 to a casting cavity (not shown). Reference numeral 12 denotes a cylinder connected to the air pressure pipe 6, and a piston 12a housed within the cylinder 12 is moved by a servo motor 17 via a reduction gear 16. 13 is supplied to cylinder 12 and valve 1
4 and an intake pipe having a filter 15; 18, a drive circuit for the servo motor 17; 19, an interface incorporating a function generator 19a connected to a microcomputer 20; 21, between the interface 19 and the motor drive circuit 18; An amplifier 22 provided in the pan 4 is a pressure sensor connected to the pot 4 and to the interface 19 via an amplifier 23. Next, the operation of the pressurization control device configured as described above will be explained. First, before the start of pressurization, the piston 12a is returned to its normal position in the following manner. When the final pressure is reached (the state where the molten metal level reaches the bottom and it is necessary to supply the molten metal into the pan), the piston 12a is located at the leftmost position of the cylinder 12 in the figure, so the valve 7 is closed. , valve 1
4 is opened and the piston 12a is moved back to the right (at this time, the valve on the right side of the piston 12a is also opened). When the piston 12a retreats, the cylinder 12 (left side) becomes negative pressure, and the atmosphere flows into the filter 1.
5. Inhaled through the intake pipe 13 (inert gas in case of active metal). When the piston 12a reaches the rightmost position (on the left side of the right intake/exhaust pipe), the valves 14 and 9 are closed, and the valve 7 is opened. The above operation completes the operation of the piston 12a before the start of pressurization, but in parallel with this operation (or may be performed after the operation is completed), the pot 4 is moved and the inside thereof is filled with molten metal. The pressurization conditions in the pot 4 stored in the microcomputer 20, that is, the pressurization rate in the pot (pressure gradient), the final pressure (upper limit of pressure), and the holding time until the final pressure value are input to the interface 19, Based on instructions from 19, the servo motor 17 is
is driven. The servo motor 17 is driven to operate the piston 12a of the cylinder 12 via the reducer 16, supply pressurized air into the pot 4, and inject the molten metal into the casting cavity via the stalk 10. The following table shows an example of the relationship between the input pressure inside the pan and the pressurization rate (pressure gradient) inside the pan.

[Table] Meanwhile, while the servo motor 17 is driving, the pressure inside the pot 4 is detected by the pressure sensor 22 and fed back to the interface 19. This fed back pressure inside the pot is interface 19.
As shown in the flowchart of FIG. 4, the pressure is compared with the pressure indicated by the microcomputer 20. When the pressure inside the pot is lower than the commanded pressure, the servo motor 17 is driven to move the piston 12a of the cylinder 12 forward, and pressurized air is supplied into the pan 4 to increase the pressure and make it equal to the commanded pressure. Conversely, when the pressure inside the pot is higher than the commanded pressure, the piston 12a of the cylinder 12 is moved back, thereby reducing the pressure inside the pan 4 and making it equal to the commanded pressure. Then, the final pressure is reached while the piston 12a moves forward and backward repeatedly. The comparison operation is 0.1sec
Do it at intervals. Figure 5 shows a comparison between the input data and the actual measured values. As is clear from the figure, the pressure inside the pot 4 follows the input data. After the pot making is completed (after holding the final pressure for a certain period of time), as shown in Fig. 3, when the valve 7 is closed, the valves 9 and 14 are opened, and the cylinder 12a is retracted, the atmosphere is sucked into the cylinder 12 again. , the next casting state occurs. As explained above, according to the present invention, even if there is a change in the molten metal level or a leak in the packing part, the pressurization speed can be controlled to the specified one, so reliability for continuous operation can be improved. can. Further, it is possible to infinitely change the pressurization speed during the period from zero pressure in the pot to a predetermined final pressure. Furthermore, since a valve with poor response is not used, a smooth pressurization curve can be obtained.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view of a low-pressure casting apparatus, FIG. 2 is a configuration diagram of a conventional pressurizing system, and FIGS. 3 and 4 are configuration diagrams and action explanatory diagrams showing one embodiment of the control method of the present invention. , FIG. 5 is an explanatory diagram of the characteristics of the present invention and the conventional one. 4... Pot, 12... Cylinder, 17... Servo motor, 19... Interface, 20... Microcomputer, 22... Pressure sensor.

Claims (1)

[Claims] 1. A method for controlling the pressurization speed in a pot, in which a gas is supplied onto the surface of the molten metal in the pot, and the molten metal is injected into the mold cavity through a conduit, in which the pressure in the atmosphere in the pot is detected by a pressure sensor. This detected value is compared with a set pressure value stored in advance in a computer, and a servo motor is driven so that the detected value becomes the set pressure, and this servo motor operates a cylinder that is linked to this, and this cylinder A method for controlling the pressurization speed in a pot, comprising supplying pressure generated by the operation of the pot to the atmosphere in the pot, and adjusting the pressure in the pot to a set pressure.