JPH01210161A - Method for controlling temperature of die for casting - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method for controlling the temperature of a casting mold, and more specifically, a method for controlling the temperature of a casting mold by supplying cooling water to the casting mold to provide a primary cooling effect. A casting metal that stabilizes the quality of cast products and improves casting efficiency by applying a secondary cooling effect to deal with fluctuations in mold temperature based on a reference temperature after casting. This invention relates to a mold temperature control method.

[Background of the invention] In the casting process, after filling a cavity in a mold with molten metal, cooling water is passed through the mold to indirectly cool the molten metal and promote solidification of the molten metal. At the same time, the mold temperature is controlled within a predetermined range.

Conventionally, in this type of temperature control method, after filling a cavity with molten metal under pressure, the temperature of the mold is measured via a temperature sensor installed in the mold, and when the mold temperature reaches a predetermined temperature,
Open the on-off valve provided in the cooling water flow path to supply cooling water to the cooling part of the mold, and then, when the mold temperature drops to a predetermined temperature, close the on-off valve to prevent the mold from overheating. Prevents it from cooling down.

Generally, the casting process consists of a series of consecutive casting cycles. Furthermore, each casting cycle involves associated work such as removing the cast product, cleaning the mold, and setting the core, as well as troubles caused by malfunctions of the casting equipment.
Each casting cycle often varies due to various factors. Therefore, at the start of each casting cycle,
It is necessary to control the mold temperature so that it is within the required range.

Therefore, FIG. 1 shows a time chart related to the above-mentioned mold temperature control method. That is, in FIG. 1a, when the cavity in the mold is filled with molten metal, the mold temperature of the mold starts to rise, and reaches a predetermined lower limit temperature T based on the casting conditions.
, to exceed. At this time, cooling water is passed through the mold to start cooling the mold. Then, the mold temperature further increases,
Similar to the lower limit temperature T+, after the temperature reaches a peak exceeding the preset upper limit temperature T2, the mold temperature begins to drop due to the cooling effect of the cooling water, and when it reaches the upper limit temperature T2 or below, cooling is completed. Stop water flow. Here, the mold temperature gradually decreases, completing one step of the casting cycle.

By the way, due to fluctuations in the casting cycle, for example, the first
As shown in the figure, when a casting cycle is started with a low mold temperature, cooling water is passed through the mold when the lower limit temperature T is exceeded, but since the initial mold temperature is too low,
The mold is cooled by filtering rather than normal cooling, and the upper limit temperature T,
This led to a situation where the cooling water did not reach the maximum level, and the flow of cooling water continued from then on. In this way, mold temperature cannot be uniformly controlled due to the influence of fluctuations in the casting cycle.
There are disadvantages in that the solidification process of the molten metal is not constant, resulting in variations in the quality of the cast products and an increased incidence of defective products.

[Object of the Invention] The present invention has been made to overcome the above-mentioned disadvantages, and the upper temperature limit and lower limit temperature for passing cooling water are set in advance, and the temperature is set in advance to flow into the casting mold based on these. After primary cooling is performed by supplying cooling water, secondary cooling is performed to deal with fluctuations in mold temperature near each of the reference temperatures, thereby reducing the effects of fluctuations in the casting cycle.
In particular, it is an object of the present invention to provide a method for controlling the temperature of a casting mold, which suppresses overcooling of the mold and thereby stabilizes the quality of a cast product.

[Means for Achieving the Object] In order to achieve the above object, the present invention provides a method for manufacturing a casting mold by supplying a cooling medium into the mold after filling a cavity in the mold with molten metal. In this temperature control method, a reference lower limit temperature and an upper limit temperature are set in advance based on casting conditions, and when the mold temperature exceeds the lower limit temperature, the supply of cooling medium is started, and the mold temperature reaches the upper limit temperature. After the temperature exceeds the upper limit temperature, primary cooling is performed in which the supply of cooling medium is stopped when the temperature falls below the upper limit temperature.After that, when the mold temperature fluctuates near the upper limit temperature or lower limit temperature, the upper limit temperature and lower limit temperature are respectively referenced. It is characterized by performing secondary cooling by controlling the supply and disconnection of the cooling medium.

[Embodiments] Next, preferred embodiments of the method for controlling the temperature of a casting mold according to the present invention in relation to an apparatus for carrying out the method will be listed and explained in detail below with reference to the accompanying drawings. .

First, in FIG. 2, reference numeral 10 indicates a die casting mold to which the temperature control method according to the present invention is applied.

That is, this die casting mold 10 basically consists of an upper mold 12 and a lower mold 14, and the opposed surfaces of the upper mold 12 and the lower mold 14 form a cavity 1 corresponding to the shape of the product.
6 is defined.

In this case, the lower mold 14 is defined with a runner 18 communicating with the cavity 16 and a pool 20.

Next, a cylinder portion 22 is disposed on the lower mold 14 so as to correspond to the position of the hot water reservoir portion 20, and a plunger 2 is slidably attached to the cylinder portion 22 via a sleeve 24.
6 is fitted. The plunger 26 slides within the sleeve 24 under the driving action of an actuator (not shown) and functions to push out the molten metal stored in the molten metal reservoir 20 into the cavity 16.

Further, a cooling block 28 is disposed below the lower mold 14, and passages 30a to 30c defined in the cooling block 28 correspond to passages 32a to 32C formed in the lower mold 14.
communicate with each other. Pipes 34a to 34C for introducing cooling water into the passages 32a to 32c are inserted from outside the cooling block 28, and the pipes 34a to 34C are inserted into the passages 32a to 32c.
A to 34c are connected to a cooling water control means 40, which will be described later. In this case, the cooling water introduced into the passages 32a to 32c via the pipes 34a to 34C is transferred to the pipe 3.
The inside of the lower mold 14 is circulated by flowing along the outer periphery of the cooling water 4a to 34C and further leading to a cooling water discharge system (not shown) via the passages 30a to 30c.

On the other hand, the upper mold 12 is formed with passages 36a to 36C similarly to the lower mold 14, and is configured to be able to circulate cooling water via a cooling block (not shown); It is exactly the same as the case of 14. Therefore, the cooling water control means 4 disposed for the lower die 14 will be described below.
0 will be explained.

That is, the cooling water control means 40 includes electromagnetic valves 42a to 42C, a controller 44 that executes opening/closing operations of the electromagnetic valves 42a to 42c, and a mold temperature sensor 46 embedded in a predetermined portion of the lower mold 14. It is comprised of a microcomputer 48 that processes temperature data and controls the controller 44. In this case, the pipe extending from the cooling water supply system (not shown) is branched to pipe 5.
0a to 50c are the electromagnetic valves 42a to 42C, respectively.
The outlet side is connected to the population side of the pipes 52a to 52.
It is connected to the pipes 34a to 34c via c.

The mold temperature data detected by the temperature sensor 46 is processed in a predetermined manner by the microcomputer 48, and based on this, the microcomputer 48 controls the controller 4.
The opening/closing signals for the electromagnetic valves 42a to 42c are sent to the electromagnetic valves 42a to 42c.

The die-casting mold 10 is basically constructed as described above.Next, a method for controlling the temperature of the casting mold according to this embodiment will be explained below by exemplifying the lower mold 14. .

In the die casting mold 10, after pouring molten metal into the molten pool 20 of the lower die 14 from the molten metal feed port (not shown), the plunger 26 is driven by the actuator (not shown).
is displaced upward, and the molten metal in the molten metal pool 20 is pushed out into the cavity 16 via the runner 18, thereby filling the cavity 16 with the molten metal. Meanwhile, in parallel with this, the cooling water control means 40 causes the microcomputer 48 to execute temperature control on the lower mold 14 under an initial state in which the solenoid valves 42a to 42C are respectively closed. In this case, the microcomputer 48 operates based on a program written based on the flowchart shown in FIG. Note that FIG. 3 is a time chart related to the temperature control corresponding to FIG. 4. Hereinafter, reference will be made to FIGS. 2, 3, and 4 as appropriate.

When the cavity 16 begins to be filled with molten metal at the start of the casting cycle, the temperature of the lower mold 14 gradually increases as it receives heat from the molten metal. That is, as an example, a mold temperature curve 60 in FIG. 3a is shown. In the figure, the lower limit temperature T Low and the upper limit temperature T'htgh are set after the optimum values are obtained experimentally when performing temperature control on the lower mold 14 and are also set in the microcomputer 48. This is a constant that is stored in advance.

Therefore, in step 1 shown in the flowchart of FIG. 4, measurement of the mold temperature Td of the lower mold 14 is started via the temperature sensor 46. Thereafter, the mold temperature T is stored as data in the data area in the memory of the microcomputer 48. In the subsequent step 2, the microcomputer 48 calculates the mold temperature Td and the lower limit temperature T Lo
The mold temperature Td is the lower limit temperature T, by performing a temporal comparison process with the mold temperature Td. Have them judge when the number exceeds 8.

That is, as a result of filling the cavity 16 with the molten metal, the mold temperature Td of the lower mold 14 reaches the lower limit temperature T. When the value exceeds 0 (time 1+ in FIG. 3), the microcomputer 4
8 outputs a signal to the controller 44, thereby opening the solenoid valves 42a to 42c (SrF2). Cooling water supplied from a cooling water supply system (not shown) passes through the solenoid valves 42a to 42C, and further to the pipes 34a to 34.
c into the passages 32a to 32c, thus
The lower mold 14 is cooled by removing heat from the cooling water. At this time, the cooling water flows along the outer periphery of the pipes 34a to 34c, and the cooling water flows along the outer periphery of the pipes 34a to 34c, and
The water is led out from 0C to a cooling water drainage system (not shown). This cooling water flow situation is shown by the shaded area in Figure 3.

After time t1, the mold temperature T continues to rise further and reaches a maximum peak exceeding the upper limit temperature Th19h. The microcomputer 48 confirms that the peak value at this time is within the appropriate range, that is, higher than the upper limit temperature T h 1q h (SrF4).

That is, it is possible that the peak value is reached before the upper limit temperature Tht9h is exceeded, and in such a case, if the supply of cooling water is continued, the lower mold 14 will be supercooled. If the mold temperature T reaches the peak value before the upper limit temperature Th1qh as described above, it is considered that some kind of trouble has occurred, so the casting cycle is stopped.

Subsequently, the mold temperature Td starts to decrease due to the cooling effect and becomes lower than the upper limit temperature T h i q h (at time t
2). The microcomputer 48 detects this and outputs a closing signal to the electromagnetic valves 42a to 42C. These electromagnetic valves 42a to 42c are closed and the supply of cooling water is stopped (SrF5.6).

After time t2, the mold temperature T further decreases, but even though the cooling water has a cooling effect and the temperature of the lower mold 14 decreases, the molten metal in the cavity 16 is indirectly cooled, so the water supply is stopped. After that, the mold temperature Td may rise again due to the heat of the molten metal in the cavity 16. Therefore, in step 7, the microcomputer 48 detects whether the mold temperature T rises again.

If the mold temperature T, is steadily decreasing without rising, in step 8, the mold temperature T, and the lower limit temperature T L
Comparison processing with ow is performed. On the other hand, the mold temperature T
, will be explained in the course of the next casting cycle.

Subsequently, in step 8, the mold temperature T is lowered.

becomes below the lower limit temperature T Low (time t3)
Thereafter, the microcomputer 48 checks whether or not the mold temperature T increases (SrF2), and stops temperature control of the lower mold 14 when the mold temperature T drops to a predetermined temperature.

On the other hand, as shown in FIG. 3a, when the mold temperature Td increases, the mold temperature Td and the lower limit temperature T. While comparing 1 (STPIO), the mold temperature T is the lower limit temperature T. When the value exceeds 0 (time ti), the microcomputer 48 opens the solenoid valves 42a to 42c via the controller 44 (STPII), thereby supplying cooling water to the lower mold 14. Then, the mold temperature Td is the lower limit temperature T. When the value falls below 1 (time t5), microcomputer 4
8 is a control roller 44 that connects solenoid valves 42a to 42c.
(STPI, 2), and the supply of cooling water is stopped. Thereafter, the process returns to step 9 and the above procedure is repeated until the mold temperature Td falls to a predetermined temperature.

In this casting cycle, the lower limit temperature T,. Temperature control is being carried out to deal with fluctuations in the mold temperature Td, which once fell below 8. That is, based on factors such as the heat transfer efficiency when the heat of the molten metal in the cavity 16 is transferred to the lower mold 14, there is actually a difference between the mold temperature Td detected by the temperature sensor 46 and the molten metal temperature. Therefore, even if the lower mold 14 is cooled with cooling water, the cooling effect on the molten metal remains indirect, so after the supply of cooling water is stopped, the mold temperature T rises again due to the heat of the molten metal. Cases happen. Conventionally, the lower set temperature is the standard that starts the supply of cooling water when the mold temperature exceeds it, and the upper set temperature is the standard that stops the supply of cooling water when the mold temperature falls below that level. The standard was to turn the cooling water ON and OFF.

However, in the casting cycle, - degrees, upper limit temperature T
After stopping the supply of cooling water based on hl, h, the lower limit temperature T, with respect to the variation of the mold temperature T, which occurs near the lower limit temperature T low. The control of supplying and stopping the cooling water based on Step 8 is substantially performed as secondary cooling in steps 9 to 13 described above.

Finally, the mold is opened after the mold temperature Td reaches a specified mold opening temperature, and the cast product is taken out to complete the casting cycle.

Then, following the above casting cycle, the next casting cycle is carried out in the same manner. The transition of the mold temperature T in this case is shown by a mold temperature curve 62.

Temperature control for the lower mold 14 is performed in the same manner, and when the mold temperature T exceeds the lower limit temperature TLow (time t6), the microcomputer 48 opens the solenoid valves 42a to 42c and turns off the cooling water. is introduced into the passages 32a to 32c of the lower die 14 via pipes 34a to 34C. After this, the lower mold 1 is cooled by the cooling water circulating inside the lower mold 14.
4 is cooled. Mold temperature T.

After passing through the peak value at which T
When the temperature drops below hi, h (time 11), the microcomputer 48 detects this and activates the corresponding solenoid valves 42a to 4.
2C is closed to stop the supply of cooling water. The temperature control up to this point is similar to the previous casting cycle shown in steps 1 to 7.

Therefore, in this casting cycle, the mold temperature T at the start of the casting cycle was relatively high. occurs quickly, and as a result, the cooling time from time t6 to t7 becomes relatively short. Therefore, after time t7 when the cooling water is stopped, the mold temperature T rises again due to the heat of the molten metal. At this time, in step 7, the microcomputer 48 detects the rise in the mold temperature T, and the mold temperature T is the upper limit temperature T h Iq
The solenoid valves 42a to 4 wait until the time exceeds h (time to).
Open 2C (STP14.15). As a result, the lower mold 14 is cooled again by the cooling water. Thereafter, the process returns to step 5, and when the mold temperature T falls below the upper limit temperature Thigh (time ts), the solenoid valves 42a to 42C are closed to stop the supply of cooling water. As described above, secondary cooling is performed by controlling the supply and stop of cooling water in response to variations in the mold temperature T with the upper limit temperature T h i q h as a reference.

In this way, after the temperature control for the lower mold 14 works properly and the mold temperature T falls smoothly, the mold is opened and the cast product is taken out, and the casting cycle is completed. Needless to say, in that case, the procedures of steps 7 to 9 described in the previous casting cycle are executed.

The temperature control for the lower mold 14 described above is carried out for the upper mold 12 in exactly the same manner.

[Effects of the Invention] As described above, according to the present invention, the preset upper limit source 1
and the lower limit temperature, start supplying cooling water to the mold when the mold temperature exceeds the lower limit temperature, and then,
In addition to the basic temperature control that stops the supply of cooling water when the temperature drops below the upper limit control temperature, if the mold temperature rises again after falling from the upper limit temperature, secondary control is performed based on the upper limit temperature. The cooling water is supplied and stopped, and even if the mold temperature drops near the lower limit temperature, the cooling water is supplied and stopped to perform secondary cooling based on the lower limit temperature in order to cope with mold temperature fluctuations. Supply and suspension are in progress. For this reason, fine temperature control according to fluctuations in mold temperature is possible.

Therefore, the effects of fluctuations in the casting cycle can be suppressed as much as possible, the quality of cast products can be kept constant, the incidence of defective products can be reduced, and production efficiency can be improved.

Although the present invention has been described above with reference to preferred embodiments, the present invention is not limited to these embodiments.
Of course, various improvements and changes in design are possible without departing from the gist of the present invention.

[Brief explanation of the drawing]

FIG. 1 is a graph explaining the temperature control method for a mold according to the prior art; FIG. 2 is an explanatory diagram showing the configuration of a casting mold used in the method for controlling the temperature of a casting mold according to the present invention; FIG. 3 is a time chart showing changes in mold temperature in the temperature control method, and FIG. 4 is a flowchart showing the steps related to the temperature control method. 10...Die-casting mold 12...Upper die 14...Lower die 16...
・Cavity 18... Runner 20... Hot water pool 26... Plunger 28... Cooling block 40... Cooling water control means 42a to 42C
... Solenoid valve 44 ... Controller 46 ... Temperature sensor 48 ... Microcomputer time

Claims (1)

[Claims] (1) A method of controlling the temperature of a casting mold by supplying a cooling medium into the mold after filling a cavity in the mold with molten metal, in which the lower limit temperature and upper limit temperature that serve as standards are set in advance for casting. Set based on the conditions, start supplying the cooling medium when the mold temperature exceeds the lower limit temperature, and supply the cooling medium when the mold temperature exceeds the upper limit temperature and becomes below the upper limit temperature. After that, when the mold temperature fluctuates near the upper limit temperature or lower limit temperature, the cooling medium is controlled to be supplied and cut off based on the upper limit temperature and lower limit temperature, respectively, and secondary cooling is performed. Characteristic temperature control method for casting molds.