JP2799454B2 - Pressure control method and pressure control device for low pressure casting machine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method and a device for pressurizing molten metal in a low-pressure caster used for molding a casting such as an automobile part.

(Prior art and its problems) Conventionally, in a low-pressure casting machine, when casting a molten metal in a mold by applying pressure to the molten metal in a holding furnace, the mold may be cold in an early stage of the casting. In addition, since the temperature of the molten metal in the holding furnace gradually decreases with the passage of time, for example, when the temperature of the mold and the temperature of the molten metal are lower than the control temperature range, when the molten metal is poured into the mold, The solidification time becomes shorter than the set value, and the molten metal at the lower part of the sprue solidifies while holding the riser pressure applied to the molten metal surface after filling the mold, making it difficult to take out the product. there were. On the other hand, when the mold temperature and the molten metal temperature are higher than the control temperature range, when the pressure applied to the molten metal surface is removed, the solidification of the gate is not completed, and when the product is taken out in this state, the cast product becomes defective. There was a problem. In actual operation, mold temperature control and hot water temperature control are used to maintain the mold temperature and the molten metal temperature within the control temperature range.
For example, it is extremely difficult to manually change the feeder pressure holding time or the exhaust time for each shot, and this has caused various casting defects.

(Means for Solving the Problems) The present invention has been devised in view of the above-mentioned conventional problems, and when the casting of the molten metal into the mold is repeatedly performed, the mold temperature and the molten metal temperature fluctuate. It is another object of the present invention to provide a pressurizing control method and a pressurizing control device for a low-pressure casting machine capable of selecting an optimum feeder pressure holding time and an exhausting time for each casting and repeatedly producing a cast product of the same quality. The first gist of the control method is to pressurize the molten metal and fill it into the mold, and then pressurize the metal for a certain period of time, and gradually reduce the pressure after the elapse of the time. In the pressurization control method of the low-pressure casting machine having an exhaust time, each temperature of the molten metal and the mold is detected, and based on the detected temperature value, the feeder pressure holding time and the exhaust time are detected. Is automatically selected to an appropriate value and pressurization is controlled. And

A second aspect of the present invention is to provide a pressurizing control device that pressurizes a molten metal in a holding furnace and fills the mold with a pressurizing means. In a pressurizing control device for a low-pressure casting machine, comprising: a control means for controlling each of the pressure means according to a control pattern having an evacuation time for reducing pressure later, a molten metal temperature sensor capable of detecting a temperature of the molten metal; A mold temperature sensor capable of detecting the temperature of the mold is provided, and each of the sensors is connected to the control means. In the control means, the riser pressure holding time and the exhaust time are based on the detected temperature values from the sensors. Is automatically selected to an appropriate value to control the pressurizing means.

(Action) The pressurizing control method for a low-pressure casting machine according to the first aspect detects the temperature of the molten metal and the temperature of the mold, respectively, and sets the riser pressure holding time and the evacuation time to appropriate values based on the detected values. Automatic control and pressurization control are performed, so that even when the temperature of the molten metal and the temperature of the mold fluctuate, the appropriate hot water pressure holding time and evacuation time can be obtained for each shot and cast into the mold. The solidification time of the molten metal becomes appropriate, the occurrence of defective products is prevented, the products can be taken out well, and castings of the same quality can be repeatedly produced.

Further, in the pressurizing control device according to the second aspect, a molten metal temperature sensor capable of detecting the temperature of the molten metal and a mold temperature sensor capable of detecting the mold temperature are provided, and a detection value from each sensor is controlled. To control the pressurizing means by calculating and selecting the appropriate riser pressure holding time and exhaust time based on the detected temperature value from each temperature sensor in the control means. The control is performed, and the continuous production of good products can be achieved without the occurrence of defective products.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic configuration diagram of a low-pressure casting machine, in which a molten metal holding furnace 1 is disposed below a lower die base 5 of the low-pressure casting machine, and a crucible 2 is provided in the molten metal holding furnace 1. The crucible 2 is disposed so that a molten metal 3 such as aluminum can be sealed in the crucible 2.

In the center of the crucible 2, a stalk 4 immersed in the molten metal 3 and suspended from the lower die base 5 is disposed, and the upper end of the stalk 4 is placed inside the upper die and the lower die. It is connected to the mold 6 in which the cavity space K is formed, and the molten metal 3 can be introduced into the cavity space K of the mold 6 via the stalk 4. The entrance of the cavity space K is a gate Ka.

A hot water supply port 13 is provided in the upper left portion of the crucible 2 in a communicating manner, and an air supply port 14 is connected to the hot water supply port 13. Further, the pressure sensor 9 is connected to the hot water supply port 13.

An exhaust valve 15 is connected to the air supply port 14, a flow control valve 10 is provided upstream of the exhaust valve 15, and a pressure reducing valve 11 is further provided upstream of the exhaust valve 15. It is connected to a compressor and the like. Therefore, this air inlet 14
Air flows into the crucible 2 in a state where the flow rate is adjusted by the flow rate control valve 10 through the pressure reducing valve 11, and the inflow air applies pressure to the upper surface of the metal melt 3 in the crucible 2 to move the metal melt 3 downward. The metal metal 3 is pushed through the stalk 4 and injected into the cavity space K by the pressing force. The pressure sensor 9 can detect the pressure applied to the molten metal 3 at this time. Also, the pressure detection sensor 9
The flow control valve 10 is connected to control means 12 constituted by a microcomputer.

Further, in this example, the molten metal 3 in the crucible 2
A molten metal temperature sensor 7 is provided in a state of being immersed in the mold. Further, a mold temperature sensor 8 capable of detecting a mold temperature is provided on the mold 6, and these temperature sensors 7 and 8 are connected to the control means 12. It is connected to the.

In such an apparatus, the control means 12 has a second
A pressure-time pattern diagram as shown in the figure is stored, and pressurization control is performed according to the pressure-time pattern. That is, in FIG. 2, when the casting start button is pressed (S), the inlet 13 is connected to the hot water supply port 13 as described above.
Air pressure is applied from 14 to press the molten metal 3, and the molten metal 3 is injected into the cavity K via the stalk 4. Its injection start point is a point indicated by reference numeral P _1, filling of the cavity space K is finished at the time shown in the figure P _2, further air pressure for ₃ point P from the P ₂ points are added As a result, pressure is applied to the molten metal 3 in the cavity space K to perform a feeder process. Then between P ₃ of P ₄ is the time the feeder pressure was maintained, the time is in the feeder pressure holding time shown by A. After a lapse of the feeder dwell time A is in the exhaust valve 15 gradually opens the P ₅ from P ₄ is exhaust air, it is naturally cooled during the time of the evacuation time B, then into a cavity K More product is taken out and one shot is completed.

When the control means 12 performs control in accordance with the pressure-time pattern shown in FIG.
Is input to the control means 12, and a comparison operation is performed in the control means 12 based on this signal, and the result is sent to the flow control valve 10 as an electric signal, and the valve opening of the flow control valve 10 Is adjusted to perform control.

However, the pressure-time pattern shown in FIG. 2 is a standard pattern to the last, and the mold 6 may be cold in the initial stage of the casting operation, and the temperature of the molten metal 3 decreases with time. If the control is performed according to the pressure-time pattern of FIG. 2 in a state where the temperatures of the mold 6 and the molten metal 3 are low, the solidification time of the molten metal 3 in the cavity space K is shortened, and the feeder in FIG. During the pressure holding time A, the stalk 4 below the gate section Ka
When the temperature of the mold 6 and the molten metal 3 is high, after the evacuation time B is over, the molten metal in the inside of the gate Ka is still solidified, and it becomes difficult to take out the product from the mold 6. Solidification of the molten metal has not been completed, and if a product is taken out of the cavity space K in this state, a defective product will be generated.

Therefore, in this example, the temperature detection values from the molten metal temperature sensor 7 and the mold temperature sensor 8 are input to the control means 12,
Based on the data table shown in FIG. 3, the hot water pressure holding time A and the exhaust time B in FIG. 2 are corrected to appropriate values. That is, the data table shown in FIG. 3 arranges the molten metal temperature detected by the molten metal temperature sensor 7 and the mold temperature detected by the mold temperature sensor 8 in a stepwise manner on the vertical axis and the horizontal axis. The appropriate hot water pressure holding time A and the evacuation time B corresponding to the temperature value are respectively displayed in a matrix, and these data are prepared in advance based on past execution data and stored in the control means 12. It is.

Under such conditions, control is performed in the control means 12 according to the flowchart shown in FIG.
That is, when the start button for each shot is pressed, a pressurization program according to the above-described pressure-time pattern in FIG. 2 is started in step 1 (S1). At the same time, the timer starts counting in step 2 (S2). After the timer counts up (after a certain time), the temperature detection values from the molten metal temperature sensor 7 and the mold temperature sensor 8 are compared. If so, the timer is reset in S8 because there is no need to change the pattern, and the pressurization program according to the standard pattern in S1 is continued. When it is determined in S3 that the mold temperature and the metal melting temperature have changed and it is necessary to change the pattern, the data table shown in FIG. 3 is viewed in S4. Next, in S5, a combination of the hot water pressure holding time A and the evacuation time B under optimum conditions is selected from the data table based on the temperature detection values from the molten metal temperature sensor 7 and the mold temperature sensor 8 (S6). In accordance with this selection, the feeder pressure holding time A and the evacuation time B are exchanged in S7, and in S9, the feeder pressure holding time A and the evacuation time B in the pressure-time pattern in FIG. 2 are newly selected. Replaced each time. Therefore, the program proceeds along the replaced hot water pressure holding time A and the evacuation time B, and the pressurization control is performed. As described above, within a certain period of time after the start of pressurization, the control means 12 is controlled based on the temperature of the molten metal 3 detected by the molten metal temperature sensor 7 and the temperature of the mold 6 detected by the mold temperature sensor 8. Thus, the program is automatically changed, and the pressurization control is performed along the best hot water pressure holding time A and the evacuation time B. Therefore, even when the temperature of the mold and the temperature of the molten metal fluctuate, it is possible to obtain the optimum riser pressure holding time A and the evacuation time B for each shot, and to repeatedly produce cast products of uniform quality in good condition. Can be.

(Effect of the Invention) In the pressurization control method of the low-pressure casting machine of the present invention, the temperatures of the molten metal and the mold are detected, and based on the detected temperature values, the riser pressure holding time and the evacuation time are set to appropriate values. Since automatic selection and pressurization control are performed, even if the mold temperature and molten metal temperature fluctuate for each shot during repeated casting, the optimum pressurizing pressure holding time and evacuation time are selected to optimize the pressurization. Control can be performed, and it is possible to repeatedly produce a cast product of uniform quality.

Further, the pressurizing control device according to the second invention comprises a pressurizing means capable of pressurizing the molten metal in the holding furnace and filling the mold with the pressurized metal; A pressure control device for a low-pressure casting machine, comprising: a control unit that controls the pressurizing unit by a control pattern having a depressurizing exhaust time, and a molten metal temperature sensor capable of detecting a temperature of the molten metal; A mold temperature sensor capable of detecting the temperature of the mold is provided, the sensors are connected to the control means, and the feeder pressure holding time and the exhaust pressure are controlled in the control means based on the detected temperature values from the sensors. By automatically selecting the appropriate time and controlling the pressurizing means, the optimum pressurizing condition is automatically set for each shot based on the temperature detection values from the molten metal temperature sensor and the mold temperature sensor. Select hand and pressurize hand Controls have the advantage of being able to obtain a good product in the best conditions.

[Brief description of the drawings]

FIG. 1 shows an embodiment of the present invention, FIG. 1 is a schematic configuration system diagram of a low-pressure casting machine, FIG. 2 is a pressure-time pattern diagram stored in a control means, and FIG. FIG. 4 is a flowchart showing a control program of the control means. DESCRIPTION OF SYMBOLS 1 ... Molten holding furnace, 2 ... Crucible 3 ... Metal melt, 4 ... Stoke 6 ... Mold, 7 ... Melt temperature sensor 8 ... Mold temperature sensor, 9 ... Pressure sensor 10 ... Flow control valve , 11... Pressure reducing valve 15... Exhaust valve A... Riser pressure holding time, B... Exhaust time K... Cavity space, Ka..

Claims (2)

(57) [Claims] 1. A low-pressure system having a feeder pressure holding time in which a molten metal is pressurized and filled in a mold, and then is heated for a certain time, and an exhaust time in which the pressure is gradually reduced after the elapse of the feeder pressure holding time. In the pressurization control method for a casting machine, the temperatures of the molten metal and the mold are detected, and based on the detected temperature values, the riser pressure holding time and the evacuation time are automatically selected and added to appropriate values. A pressure control method for a low-pressure casting machine, comprising controlling pressure. 2. A control having a pressurizing means capable of pressurizing a molten metal in a holding furnace and filling the mold with the molten metal, a feeder pressure holding time for feeding the molten metal for a certain time after filling, and an evacuation time for reducing the pressure after the filling. A pressure control device for a low-pressure casting machine, comprising: a control unit for controlling the pressing unit by a pattern; a molten metal temperature sensor capable of detecting a temperature of the molten metal; and a mold temperature sensor capable of detecting a temperature of the mold. And connecting the sensors to the control means, and automatically selecting the riser pressure holding time and the exhaust time to appropriate values based on the detected temperature values from the sensors in the control means, A pressure control device for a low-pressure casting machine, characterized in that the pressure control means can be controlled.