JPH02251355A - Low pressure casting apparatus - Google Patents

Abstract

PURPOSE:To prevent the development of defective product by outputting a signal after the lapse of the prescribed time from starting supplying of molten metal into cavity and providing control means for changing the pressurizing pattern to molten metal surface with this signal. CONSTITUTION:Pressurized air is supplied into a pressurizing chamber 20 through an air supply passage 42, and the molten metal in a crucible 12 is pushed up, supplied and packed into the cavity 32 in a mold 30 to produce the casting. When the filling-up of the molten metal completes, this is detected with a filling-up detecting sensor 58 fitted at the upper part of the mold 30, and CPU 62 outputs command for changing the pressurizing pattern. Even in the case the filling-up detecting sensor 58 is not normally worked, after the lapse of the prescribed time preset to a timer 60, the signal is transmitted to the CPU 62 and the CPU 62 outputs the command for changing the pressurizing pattern. Even if the filling-up detecting sensor becomes defective, the development of the defective product can be prevented.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to improvements in low pressure casting equipment.

(Prior art) Conventionally, when casting an aluminum cylinder head for an automobile engine, etc., a pressurizing means pressurizes the surface of the molten metal in a crucible to push up the molten metal, and the pushed up molten metal is used as a stalk. A low-pressure casting device is used that supplies the material into the cavity of the mold through the molten metal for casting.

In this case, it is desirable to pressurize the surface of the molten metal rapidly in order to prevent the temperature of the molten metal from dropping until the molten metal rises in the stoke and reaches the sprue of the mold. It is desirable to pressurize the molten metal surface at an appropriate pressure determined by the shape of the product, etc., until the molten metal is filled into the cavity.
In order to solidify the molten metal in a good condition, it is desirable to pressurize the surface of the molten metal at high pressure.

For this reason, as shown in Japanese Patent Publication No. 54-28373, a plurality of back pressure detection means for detecting the back pressure of the cavity have been provided in the mold, and based on the output signals of these back pressure detection means, the cavity is detected. A low-pressure casting apparatus is known in which the pressure pattern is changed depending on the level of molten metal within the casting machine. In addition, as shown in Japanese Patent Application Laid-Open No. 61-71166, an energized sensor is installed near the sprue of the stalk,
A low-pressure casting apparatus is known in which a pressurizing pattern is changed according to the rate at which molten metal is filled based on an output signal from this energized sensor. Furthermore, there is a filling detection sensor that detects that molten metal is filled into the cavity and outputs a charging signal, and a pressure that changes the pressurization pattern so that the pressure on the molten metal surface increases based on the filling signal from this filling detection sensor. Low-pressure casting apparatuses are also known which are equipped with variable control means.

(Problem to be Solved by the Invention) However, in a low-pressure casting apparatus that is equipped with a filling detection sensor that detects filling of molten metal and a pressure variable control means that changes the pressurization pattern based on a filling signal from the filling detection sensor, The filling detection sensor may be damaged due to the adhesion of mold coating to the filling detection sensor, air accumulation near the filling detection sensor during casting, disconnection or poor connection of the wiring system of the filling detection sensor during casting, etc. Detection failure may occur, and when the filling detection sensor is in a detection failure state, the pressure pattern of the pressure variable control means cannot be changed.

Therefore, in the conventional low-pressure casting apparatus, if the filling detection sensor has a detection failure, high pressure cannot be applied to the surface of the molten metal even after the molten metal is filled into the cavity. There is a problem in that the molten metal cannot be solidified in a good condition.

In particular, when placing a foundry sand core inside a mold, such as when casting aluminum cylinder heads for automobile engines, the heat of the molten metal may cause the inside of the foundry sand core to The mixed binder gasifies and ejects into the molten metal, and this gas reduces the bonding strength of the molten metal.
Cavities may form in the product, causing air leakage in the hollow portion, or product defects such as cracks may occur in the product.

In view of the above, the present invention maintains product quality at an acceptable level or higher even when the filling detection sensor is in a detection failure state,
The purpose of this is to prevent product defects from occurring.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides pressure variable control even if there is no filling signal from the filling detection sensor after a predetermined period of time has passed after the start of supply of molten metal to the cavity. The pressure pattern of the means is changed.

Specifically, the solution taken by the present invention includes a mold having a cavity into which molten metal is supplied that is pushed up by pressure applied to the molten metal surface, and a mold that outputs a filling signal when it detects that the molten metal is filled into the cavity. Assuming a low-pressure casting apparatus equipped with a filling detection sensor and a pressure variable control means that changes the pressurization pattern of the pressure based on a filling signal from the filling detection sensor, after starting to supply the molten metal into the cavity, The apparatus is configured to include a timer that outputs a elapsed signal when a predetermined time has elapsed, and a pressurization pattern control means that operates the pressure variable control means to change the pressurization pattern based on the elapsed signal from the timer. .

(Function) With the above configuration, when the detection state of the filling detection sensor is normal, the filling detection sensor outputs a filling signal when the cavity is filled with molten metal, and this causes the pressure adjustment pattern of the pressure variable control means to be adjusted. is changed and the detection state of the filling detection sensor is poor, the timer outputs a elapsed signal after a predetermined time has elapsed since the supply of molten metal into the cavity was started, and this elapsed signal causes the pressure variable control means to The pressure pattern can be changed.

(Example) Hereinafter, one embodiment of the present invention will be described based on the drawings.

FIG. 1 shows the overall configuration of a low-pressure casting apparatus A according to an embodiment of the present invention, and 10 is a heat-retaining furnace of the low-pressure casting apparatus A, and this heat-retaining furnace 10 is formed in a box shape with an open top. has been done. A crucible 12 for storing molten metal (molten metal) is placed on a metal 14 and housed inside the heat retention furnace 10 , and a heater 16 for heating the molten metal in the crucible 12 is arranged on the inner wall surface of the heat retention furnace 10 . It is set up. Further, the upper opening of the heat retention furnace 10 is hermetically closed by a removable furnace lid 18, so that a crucible 12 is placed inside the heat retention furnace 10.
An airtight pressurized chamber 20 is formed to cover the.

A through hole 18a is formed in the center of the furnace lid 18, and a stalk 22 is inserted into the through hole 18a at its upper end flange 22a.
is brought into contact with the upper surface of the furnace lid 18, and the lower part is brought into contact with the crucible 12.
It is fitted by being immersed in the molten metal inside.

? N! ! A mold 30 consisting of an upper mold 24 , a lower mold 26 and a side mold 28 is mounted on the upper surface of the lid 18 and the stalk 22 is attached to the lid 18 .
It is fixed so as to pinch the upper end flange 22a of. Inside the cavity 32 formed by the inner surfaces of the upper mold 24, lower mold 26, and side mold 28, an oil jacket core 34, a water jacket core 36, and a boat core 38 are arranged in order from the top. Furthermore, this cavity 32 is communicated with the upper end opening of the stalk 22 via a sprue 40 formed in the lower mold 26.

The pressurizing chamber 20 is connected to an air supply path 42 that supplies pressurized air to the pressurizing chamber 20.
The pressure of the pressurized air supplied through the crucible 12
The molten metal inside is pushed up, and the pushed up molten metal is supplied and filled into the cavity 32 of the mold 30 through the stalk 22, thereby producing a casting.

The air supply path 42 is provided with an open/close type air supply valve 44 that switches between supplying and stopping pressurized air, and the air supply path 42 on the upstream side of the open/close type air supply valve 44 includes: A pressure control valve 46 is provided to adjust the pressure of the pressurized air. Further, this pressure control valve 46 is attached with a servo mechanism 48 that controls its opening degree, and these pressure control valves 46 and servo mechanisms 48 perform pressure variable control that changes the pressurization pattern of the pressure applied to the molten metal. Means 50 is configured.

A ring-shaped insulator 52 is inserted into the upper mold 24 of the mold 30, and two wires are connected to each other at the top of the upper mold 24 on both sides of the insulator 52, which are electrically connected when the cavity 32 is filled with molten metal. Further, both wirings 54 are connected to a molten metal filling detection circuit 56 that sends out a filling signal when these two wirings 54 are electrically connected to each other, and both wirings 54 are connected to a molten metal filling detection circuit 56 that sends a filling signal when the wirings 54 are electrically connected to each other. The detection circuit 56 constitutes a filling detection sensor 58 that detects filling of the cavity 32 with molten metal.

In addition, in FIG. 1, 60 is the cavity 32 of the molten metal.
A timer 62 that sends out a elapsed signal when a preset predetermined period of time has elapsed after the start of supply into the interior of the tank; 62 has a built-in CPU;
This is a pressurization pattern control means that changes the pressurization pattern of the pressure variable control means 50 based on the progress signal from the pressure variable control means 50.

Hereinafter, a pressurization control method of the low pressure casting apparatus 1\A will be explained based on the flowchart of FIG. 2 and the pressurization pattern diagram of FIG. 3.

First, in step STI, from the air supply path 42 to the pressurizing chamber 2
Pressurized air is supplied to the crucible 12 to push up the molten metal in the crucible 12, and this molten metal is supplied to the cavity 32 of the mold 30 through the stalk 22 to start casting.
2, the timer 60 starts. In this case, as shown in the pressurizing pattern (a) in FIG.
Until the time t1 has elapsed, the pressure is rapidly increased to push the molten metal up quickly to prevent the temperature of the molten metal from decreasing, and after the scheduled time t1 for the molten metal to reach the sprue 40, the molten metal is between the sand cores. Reduce the rate of pressure rise to ensure smooth filling.

Next, in step ST3, it is determined whether or not the filling detection sensor 58 has detected the filling of molten metal based on the presence or absence of the filling signal. If the filling detection sensor 58 has detected the filling, the gas is discharged from the sand core. In order to prevent spouting into the molten metal, in step ST4, the pressure inside the pressurizing chamber 20 is increased as shown in the pressurizing pattern (b) in FIG. 3, and the filling detection sensor 58 is functioning normally. Therefore, the timer 60 is stopped in step ST5.

If the filling detection sensor 58 does not detect the filling of molten metal in step ST3, then in step ST6, after receiving the elapsed signal outputted from the timer 60 after a predetermined time t2 has elapsed after the start of pressurized air supply, the flowchart shown in FIG. The pressure inside the pressurizing chamber 20 is increased as shown in the pressurizing pattern (C). In this way, even when the filling detection sensor 58 has a detection failure, the pressure chamber 20
Since the internal pressure can be increased, product defects can be prevented.

Next, in step ST7, the timer 30 is reset to prepare for the next casting process, and in step ST8, the casting is completed.

FIG. 4 shows a pressurization control system diagram of the low-pressure casting apparatus A according to the embodiment, in which the open/close type air supply valve 44 is turned on and the pressurized air is supplied to the pressurization chamber 20. pressurization start signal switch that outputs an on signal when the pressurization is started;
66 is a filling signal switch that outputs an on signal in response to a filling signal sent from the filling detection sensor 58 when the cavity 32 is filled with molten metal, and 68 is a casting completion switch that outputs an on signal when casting is completed. Further, the timer 60 starts when it receives an on signal from the pressurization start signal switch 64, outputs an on signal when a predetermined time t2 has elapsed after starting, and resets when it receives an on signal from the casting completion switch 68. It is set.

In addition, in FIG. 4, when 70 receives an ON signal from the pressurization start signal switch 64, it controls the pressure variable control means 50 to rapidly increase the pressure in the pressurization chamber 20, and after the pressurization starts, After the predetermined time t1 has elapsed, the pressure increase rate is slowed down, and when an ON signal is received from either the filling signal switch 66 or the timer 60, the current pressure is maintained, and when an ON signal is received from the casting completion switch 68, the pressure is increased. This is a first CPU that outputs a ml pressurization signal of a pressurization pattern that returns the pressure inside the chamber 20 to normal pressure. Further, in the same figure, 72 increases the pressure in the pressurizing chamber 20 when it receives an ON signal from either the pressurization start signal switch 64 or the timer 60, and when this pressure reaches a predetermined value, the current pressure is increased. The second CPU outputs a second pressurization signal of a pressurization pattern that returns the pressure in the pressurization chamber 20 to normal pressure upon receiving an ON signal from the casting completion switch 68. Furthermore, 74 is an addition circuit that adds the first pressure signal and the second pressure signal, and the first CPU 70, second CPU 72, and addition circuit 74 constitute the pressure pattern control means 62.

FIG. 5 shows a specific pressurization pattern of the pressurization control method in the embodiment, in which one
The lcPU 70 and the timer 60 are activated, and 8 seconds after the start of pressurization, the first CPU 70 slows down the pressure increase speed, and when the filling detection sensor 58 outputs a filling signal (usually at 13 seconds after the start of pressurization).
seconds later), while the first CPU 70 maintains the pressure at that time, the second CPU 72 increases the pressure in the pressurizing chamber 20,
When the pressure within the pressurizing chamber 20 reaches a predetermined value (usually 20 seconds after pressurizing starts), the second CPU 72 also maintains the pressure at that time. In this case, the timer 60 is set to output an on signal and start the second CPU 72 18 seconds after the start of pressurization, and even if the filling detection sensor 58 has a detection failure, the second CPU 72 starts up 18 seconds after the start of pressurization. do.

FIG. 6 shows a pressurization pattern of a modification of the pressurization control method, and in this modification, a sprue passage sensor is installed in the lower die 26 of the mold 30 to output a passage signal when the molten metal passes through the sprue 40. , the first CPU 70 and the second CPU 70 are arranged.
In addition to the CPU 72, a third CPU is installed. and,
When the sprue passage sensor outputs a passage signal (usually 9 seconds after the start of pressurization), the first CPU 70 maintains the pressure at that time, while the second CPU 72 increases the pressure in the pressurization chamber 20, and the filling detection sensor 58 Based on the filling signal from (usually 13 seconds after the start of pressurization), the second CPU 72 maintains the current pressure, while the 30th PU sets a pressurization pattern that increases the pressure inside the pressurization chamber 20. I'll keep it. In this case, the timer 60 is set to output an on signal and start the third CPU 15 seconds after the start of pressurization or 5 seconds after receiving the passage signal from the gate passage sensor, whichever is earlier. I'll keep it.

By setting the pressurization pattern as in this modification, it is possible to reduce the error that occurs between the elapse of time and the degree of rise of the molten metal, so the third CPU can be started 15 seconds after the start of pressurization, and the In the case of a specific example (18 seconds after the start of pressurization)
Since the product can be started up earlier than the above, even if the filling detection sensor 58 has a detection failure, the quality of the product can be maintained at a high level. Furthermore, since the sprue passage sensor is provided, the rate of increase in pressure until the molten metal passes through the sprue 40 can be made faster than in the specific example, so that a drop in the temperature of the molten metal can be prevented.

Furthermore, while a sprue passage sensor is required, the first CPU
Since a CPU with a simple function can be used as the CPU 70, it is also advantageous in terms of cost.

(Effects of the Invention) As explained above, according to the low-pressure casting apparatus according to the present invention, when the filling detection sensor is normal, the filling signal causes
If the filling detection sensor has a detection failure, a progress signal will indicate
Since the pressure variable control means operates to change the pressurization pattern, the pressurization pattern can be changed regardless of whether the detection state of the filling detection sensor is normal or defective. Therefore, according to the low-pressure casting apparatus of the present invention, even if a detection failure occurs in the filling detection sensor, the quality of the product can be maintained at a permissible level or higher, thereby preventing the occurrence of product defects.

[Brief explanation of drawings]

FIG. 1 is an overall configuration diagram of a low-pressure casting device according to an embodiment of the present invention, FIGS. 2 and 3 show a pressurization control method for the low-pressure casting device, FIG. 2 is a flowchart, and FIG. is a pressure pattern diagram, FIG. 4 is a pressure control system diagram of the low pressure casting device, FIG. 5 is a pressure pattern diagram showing a specific pressure control method of the low pressure casting device, and FIG. 6 is a pressure control system diagram of the low pressure casting device. It is a pressurization pattern diagram which shows the modification of the pressurization control method of a casting apparatus. A... Low pressure casting device 30... Mold 2... Cavity 0... Pressure variable control means 8... Filling detection sensor 0... ...Timer 2...Pressure pattern control means

Claims (1)

[Claims] (1) A mold having a cavity into which molten metal is supplied that is pushed up by pressure applied to the molten metal surface, a filling detection sensor that detects that the molten metal is filled into the cavity and outputs a filling signal, and a filling detection sensor that outputs a filling signal when the molten metal is filled into the cavity. In a low-pressure casting apparatus equipped with a pressure variable control means that changes the pressurization pattern according to a filling signal from a sensor, a progress signal is output when a predetermined time has elapsed after the start of supply of molten metal into the cavity. 1. A low-pressure casting apparatus comprising: a timer for controlling the pressure; and a pressure pattern control means for operating the variable pressure control means to change the pressure pattern in response to a elapsed signal from the timer.