JPH01237070A - Temperature control method for casting die - Google Patents

Abstract

PURPOSE:To uniformize the molten metal pouring start temp. of a die and the die opening temp. by arranging a heater, cooling water passage and temp. measuring element inside a die and correlatively controlling the heating state of the heater and the feeding state of the cooling water corresponding to the variation in the die temp. CONSTITUTION:A heater H, cooling water passage 60 and thermocouple 32 are provided inside a die 12. The output signal St1 corresponding to the die temp. Tx of the thermocouple 32 comes in a microcomputer 36. At the time when the temp. Tx is lower than the lower limit value of a pouring start/die opening optimum temp. TM the computor 36 subjects the heater H to PDI control, a current is fed to the heater H and the temp. Tx starts to rise rapidly. At this time the solenoid valve 56 for controlling turn-on/turn-off of a cooling water W2 is made in a turn-off state with the control signal SC3 interposing an interface circuit 46 by the output signal of the computor 36 being fed. At the time when the temp. Tx exceeds the upper limit of the TM the valve 56 is made in turn-on state.

Description

Detailed Description of the Invention [Industrial Application Field] 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. The casting process is performed by controlling the temperature of the mold by passing a cooling medium, preferably cooling water, through the cooling medium passage or heating a heater in response to temperature changes in the mold. The present invention relates to a method for controlling the temperature of a casting mold, which makes it possible to stabilize the quality of products and shorten the casting cycle.

[Background of the Invention] In a casting process using a mold, a cavity in the mold is filled with molten metal, and then cooling water is passed through the mold to cool the molten metal, thereby promoting solidification of the molten metal and The mold temperature is controlled within a predetermined range. In this case, care must be taken to remove the casting from the mold when the temperature of the casting in the mold has dropped to a certain temperature (hereinafter referred to as the optimum temperature) determined by the solidification characteristics of the molten metal used. Must be.

In other words, if the casting is taken out at a temperature higher than the optimum temperature, the casting will not separate from the mold and will damage the mold and shorten its life.At the same time, the distortion rate and shrinkage rate of the casting will increase after the casting is taken out, resulting in unstable dimensional accuracy. Otherwise, there is a risk that the defective rate and the width of quality variation will increase. On the other hand, keeping the casting in the mold for a longer time than necessary after the temperature of the casting in the mold has fallen to the above-mentioned optimum temperature will increase the casting cycle time, and the casting rate per unit time will increase. This results in a decrease in the number of pieces, that is, a decrease in production efficiency. Further, by overcooling the mold, casting defects such as cavities may occur, which directly leads to the generation of defective products.

Moreover, when performing continuous casting processes, the mold must be cooled in the previous casting process, the cast product must be taken out, and the mold must be raised to a predetermined temperature again to start the next casting process. However, the conventional technology has not yet reached the point where it is possible to accurately control the temperature of this type of mold in a short period of time.

By the way, the most reliable way to determine whether the temperature of the casting inside the mold has fallen to the optimum temperature is to directly measure the temperature of the casting inside the mold, but at present there are no methods suitable for direct measurement. There's nothing.

Therefore, in the past, a temperature measuring element was installed inside the mold, and the temperature change of the mold after the molten metal was injected was measured by the temperature measuring element, and the temperature change over 1 meter was recorded during the process. The cooling status of the casting temperature in the mold is indirectly estimated by monitoring the temperature of the casting in the mold.

However, this method of controlling the mold opening timing requires skill to perform the work, and also requires a certain degree of error in the mold opening temperature. The drawback is that it is difficult to increase efficiency.

[Object of the Invention] The present invention has been made in order to solve the above-mentioned technical problem, and includes providing a temperature detection element, a cooling medium passage, and a heater in a casting mold, and detecting temperature changes in the mold. By controlling the heating state of the heater and the supply state of cooling water in a corresponding manner, it is possible to always start molten metal at a constant mold temperature, and to open the mold at a predetermined mold temperature. The present invention relates to a method for controlling the temperature of a casting mold, which makes it possible to stabilize the manufacturing quality of cast products and improve production efficiency.

[Means for achieving the object] In order to achieve the above-mentioned object, the present invention provides a casting mold with O.
A method for controlling the temperature of a casting mold, in which the temperature of the mold is controlled by flowing or stopping a cooling medium through an N/OFF type valve and providing a heater to supply or cut off current to the heater. When the mold temperature is lower than the lower limit of the optimum pouring start temperature, PDI control is performed by continuously supplying current to the heater, and the ON10 F type valve is turned OFF. It is characterized by controlling the mold temperature to increase.

Further, in the present invention, when the mold temperature rises and reaches the lower limit temperature of the pouring start temperature range, the current supplied to the heater is changed to ON10FF control to PI control to reach the optimum pouring start temperature. It is characterized by being controlled so that it is maintained.

Further, the present invention allows the temperature of the mold to be controlled by flowing or stopping a cooling medium through the casting mold via an ON/OFF type valve, and by arranging a heater and supplying or cutting off current to the heater. In this method of controlling the temperature of a casting mold, first, when the mold temperature is lower than the pouring start/mold opening temperature range, PDI control is performed by continuously supplying current to the heater. together with said ON/OFF
The mold valve is turned OFF to raise the mold temperature, and then, when the mold temperature reaches the lower limit temperature of the pouring start/mold opening temperature range, the current supplied to the heater is turned ON10.
FF control is changed to PI control, and the temperature is maintained at the optimum temperature for the start of pouring/start of pouring within the mold opening temperature range and the optimum temperature for opening the mold. When the upper limit temperature of the mold opening temperature range is exceeded, the current supply to the heater is stopped and the heater is turned off, and then when the mold temperature exceeds a preset first temperature higher than the upper limit temperature, the above-mentioned 0N10 F When the F-type valve is turned on and the flow starts, and after the mold temperature exceeds the preset second set temperature which is higher than the first set temperature, it decreases and crosses the second set temperature again. The ON/OFF type valve is turned OFF to stop the cooling medium, and then, when the mold temperature reaches the upper limit temperature of the pouring start/mold opening temperature range, the heater is turned ON/OFF by PI control. It is characterized by controlling to start the next pouring while keeping the temperature at the optimum temperature for starting the hot water/opening the mold.

Further, in the present invention, after starting pouring, if the mold temperature exceeds the first set temperature, then decreases without reaching the second set temperature and returns to the first set temperature again, the mold temperature The present invention is characterized in that the temperature gradient of the mold temperature is monitored, and when the temperature gradient of the mold temperature becomes zero, the 0N10 FF type valve is turned OFF and the cooling medium is stopped.

Furthermore, the present invention sets the OFF time of the ON/' OFF type valve when the mold temperature reaches the second set temperature after starting pouring, and after the OFF time has elapsed, the mold temperature reaches the first set temperature. ON only when the temperature is higher than the set temperature
The feature is that the /OFFH valve is turned ON and the cooling medium is controlled to flow through it.

[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. .

In FIG. 1, reference numeral 10 indicates a mold temperature control system according to this embodiment. The mold temperature control system 1
0 is composed of a cooling water control system 14 that controls the cooling water W flowing into the mold 12, a heater control system 16 that controls the heater H that heats the mold 12, and a control processing section 18.

The mold 12 basically consists of a movable mold 20 and a fixed mold 22, and a cavity 24 adapted to the shape of the product is defined on opposing surfaces of the movable mold 20 and the fixed mold 22. In this case, the fixed mold 22 is defined with a runner 26 and a sump 28 that communicate with the cavity 24 .

A molten metal injection mechanism 30 is disposed in the sump 28 and functions to push out the molten metal stored in the sump 28 into the cavity 24 via the runner 26.

A first thermocouple 32, which is a heat-sensitive element, is disposed on the side of the cavity 24, and the first thermocouple 32 corresponding to the mold temperature Tx is
The output signal St+ of the thermocouple 32 is introduced into a microcomputer 36 via an A/D converter 34. moreover,
A heater H is provided in the movable mold 20, and a current is supplied to the heater H from a power source 42 via a disconnection monitor 38 and a thyristor 40. In this case, the supply current from power supply 42 is controlled by control signal S C+. That is, the control signal SC+ is introduced from the microcomputer 36 to the thyristor 40 via the D/A converter 44. The output signal of the disconnection monitor 38 is introduced to the microcomputer 36 via an interface circuit 46, and is constantly monitored to see if a disconnection condition has occurred.

In the cooling water control system 14, first, the cooling water W1 is supplied from the cooling water supply system 48 via the 20th thermocouple 50 to the flow rate adjustment electromagnetic valve 52 that can adjust the flow rate of the cooling water W1. In this case, the output signal Stz of the second thermocouple 50
is connected to the microcomputer 36 via the A/D converter 34.
At the same time, a D/A converter 44 from the microcomputer 36 is connected to the control terminal of the flow rate regulating solenoid valve 52.
A flow regulation control signal SC2 is introduced via. Therefore, the cooling water W2 whose flow rate is adjusted according to the temperature of the supplied cooling water Wl flows through the electromagnetic flow 54 to O
N10FF is introduced into the electromagnetic valve 56 which is controlled. In this case, the output signal SF of the electromagnetic flowmeter 54 determines whether or not the flow rate adjusted by the flow control electromagnetic valve 52 is flowing.
, to the microcomputer 3 via the A/D converter 34
Confirmed by measuring at 6. The electromagnetic valve 56 is an ON/OFFN/type electromagnetic valve, and is turned on by introducing a control signal from the microcombinator 36 as a control signal SC3 to the control terminal of the electromagnetic valve 56 through the interface circuit V&46. /OFF control, that is, opening/closing control is performed.

The cooling water W3 whose opening/closing is controlled in this way is the cooling water W,
The passage 60 of the fixed mold 22 that constitutes the mold 12 is connected to the flow switch 58, which determines whether or not the flow is flowing.
will be introduced in In this case, an output signal SF indicating whether the flow switch 58 is opened or closed is introduced to the microcomputer 36 via the interface circuit 46.

The temperature of the cooling water W that has passed through the passage 60 defined in the fixed mold 22 is measured by the third thermocouple 62, and then is led out to the cooling water drainage system 64.

The output signal St3 of the third thermocouple 62 is sent to the A/D converter 3.
4 into the microcomputer 36. In this case, the microcomputer 36 operates under the control of the sequencer 66 based on a predetermined procedure.

The mold temperature control system implementing the method for controlling the temperature of a casting mold according to this embodiment is basically configured as described above, and its operation and effects will be explained next.

Here, the mold temperature control system according to this embodiment operates in three types of control modes: standard control mode, peak control mode, and timer control mode.

Therefore, first, let's talk about the standard control mode.
This will be explained using the operation explanatory diagrams shown in Figures a to C. In this case, FIG. 2a shows a characteristic curve of the mold temperature Tx derived by the first thermocouple 32. FIG. 2 shows a method of controlling the heater H (PDI (proportional + derivative-plus-integral) control or PI (proportionalist-integral) control) and the ON/OFF state of the heater H. FIG. 2C shows the target set temperature value (either the first set temperature T1 or the second set temperature T2) and the ON/OFF state of the electromagnetic valve 56. Note that in FIG. 2a, the horizontal axis represents time t, and the vertical axis represents temperature T. In this case, on the scale of temperature T, the optimum temperature T0 and the lower limit optimum temperature T0 are respectively shown.
. IN (hereinafter referred to as lower limit temperature), upper optimum temperature T.

AX (hereinafter referred to as upper limit temperature), first set temperature TI%
The reference numeral is attached to the position corresponding to the second set temperature T2.

First, at time t1, the output signal St of the first thermocouple 32
, is connected to the microcomputer 3 via the A/D converter 34
6, the temperature falls within the lower limit temperature T+ri++N in the optimum temperature range TX for starting pouring/opening the mold (hereinafter referred to as the optimum temperature range) indicated by the hatched part in the figure.
Since it is a small value compared to , the microcomputer 36
PDIs heater H based on a predetermined program.
control, that is, proportional-differential-integral control (times tl to t2). In this case, the output signal from the microcomputer 36 causes the thyristor 40 to close via the D/A converter 44. Therefore, current is supplied from the power source 42 to the heater H via the SIRISK 40 and the disconnection monitor 38, and the mold temperature Tx starts to rise rapidly. At this time, the disconnection monitor 38 always supplies information to the microcomputer 36 via the interface circuit 46 to monitor whether or not current is flowing.

On the other hand, between times tl and t2, since the mold 12 is in the middle of heating, the output signal of the microcomputer 36 is sent to the electromagnetic valve 56 for ON/OFF control of the cooling water W2 as a control signal SC3 via the interface circuit 46. The electromagnetic valve 56 is turned off by being supplied to its control terminal. Therefore, the cooling water passage 6
Cooling water W3 is not introduced into No.2. In this embodiment, it is assumed that the temperature of the cooling water W1 corresponding to the output signal St2 of the second thermocouple 50 is a constant temperature, and therefore the flow 1 regulating solenoid valve 52 is always adjusted to a certain constant value. It is assumed that the switch is in the ON state.

In this way, when time t2 is reached, the mold temperature Tx exceeds the lower limit temperature T)1)lIN, so the microcomputer 36 changes the control of the heater H from PDI control to PI control, that is, proportional-integral operation control. Mold temperature TX
is the optimum temperature T due to slow landing operation. control to reach. In this case, the mold temperature TX is
The mold temperature Tx is adjusted to the optimum temperature T by appropriately controlling the ON10 F F time of the heater H through feedback control using the output signal St of the thermocouple 32. It is possible to hold the

Therefore, pouring of molten metal is started at time t3. That is, the molten metal is supplied to the molten metal reservoir 2 of the lower mold 22 from the hot water supply port (not shown).
After pouring the molten metal into the cavity 24, the molten metal is filled into the cavity 24 under the control of the molten metal injection mechanism 30.

Therefore, the mold temperature Tx starts to rise rapidly as shown after time t3 in FIG. Therefore, when the mold temperature Tx exceeds the upper limit temperature TMMAX at time t4, the microcomputer 36 outputs the output signal St of the first thermocouple 32.
, the situation is determined and the heater H is turned off via the cyrisk 40.

On the other hand, at time t, the mold temperature TX changes to the target setting temperature (
When the first set temperature T1, which is (see Figure 2C) is reached,
The microcomputer 36 sets the electromagnetic valve 56 to N via the interface circuit 46. Therefore, the cooling water W
2 is connected to the passage 60 in the mold 12 via the flow switch 58.
The flow of electricity will begin. Cooling of the mold 12 is thereby started.

However, even in this state, the mold temperature TX rises, and after exceeding the peak value TPE□, it reaches the second temperature at time t6.
When the set temperature T2 is reached, the temperature corresponding to the second set temperature T2 is read by the microcomputer 36 through the output signal St+ of the first thermocouple 32, the electromagnetic valve 56 is turned off, and the cooling water W3 is removed from the mold 12. Flow to is stopped. Therefore, the mold 12 reaches a naturally cooled state.

Next, when the upper limit temperature T)IMAX is reached at time t7, the microcomputer 36 makes a buzzer (not shown) sound so that the operator knows when to open the mold 12, so that the operator opens the mold 12 and starts molding. Take out the casting as a product. In this case, the second
As shown in the figure, at time t7, the heater H
Since the mold temperature Tx is controlled to be 0N10FF, the mold temperature Tx is kept at a constant temperature, that is, the optimum temperature To for starting pouring/opening the mold. Normally, if pouring is started again after the casting is taken out after time t, the casting operation can be repeated stably. Note that the mold opening work can be automated by using a robot.

Next, for example, if we consider the case where the mold, etc. is replaced at time ts, in this case, the mold temperature Tx
is the lower limit temperature T. , N, the heater H is again turned ON under the control of the microcomputer 36, that is, the mold temperature Tx is rapidly raised again by PDI control. At this time, as shown in FIG. 2C, the electromagnetic valve 56 is in the OFF state after time t6, so the mold temperature Tx increases in an extremely short period of time without performing the cooling operation. It can be started. Therefore, when the lower limit temperature TI4MIN is reached again at time t,
Heater H is controlled by PI sub-control 0N10FF.

In this way, time t,. Thereafter, when molten metal is poured, time t. A series of casting cycles shown from t14 to t14 are performed. Note that this casting cycle is the same cycle as that from time t3 to T, so the explanation thereof will be omitted.

In this way, in the standard control mode, the optimum temperature T
It is possible to start pouring by o and open the mold at the optimum temperature T0, and when the mold temperature is low, the heater H is controlled by PDI control to bring the mold temperature to a state where the metal can be melted in an extremely short time. Tx can be increased. The above is an explanation of the standard control mode.

Next, the second peak control mode will be explained with reference to FIG. The arrangement of the characteristic diagrams in each of FIGS. 3a to 3C is the same as that of the characteristic diagrams shown in FIGS. 2a to 2C. This peak control mode is used for the case where the mold temperature Tx starts to decrease after passing through the peak temperature T without reaching the second set temperature T2, as shown in FIG. 3A. This is a mode for executing ON/OFF control of the In this case, the microcomputer 36 monitors the output signal St+ from the first thermocouple 32 and also monitors the temperature gradient, that is, the differential coefficient of temperature, and when the temperature differential coefficient reaches a value of zero, that is, , the electromagnetic valve 56 is turned off at time t23. Therefore, the heater H is controlled in the same manner as shown in FIG. Time t23 when it becomes zero
In this case, it is controlled to be OFF so that natural air cooling is performed.

Also in this case, the upper limit temperature T. Since the heater HltPI control, that is, ON/OFF control is performed when the temperature falls below AX, the mold temperature Tx can be maintained at a constant temperature. Therefore, even when the mold temperature Tx does not exceed the second set temperature T2 as described above, it is possible to accurately control the start of pouring into the mold 12 and the opening of the mold at the optimum temperature To.

The above explanation is about the peak control mode when the mold temperature T decreases without reaching the second set temperature.

Next, the timer control mode will be explained with reference to FIGS. 4a to 4c. In the timer control mode, as shown in FIGS. 4A to 4C, after the mold temperature Tx reaches the second set temperature T2, the solenoid valve 56 is turned on again after a predetermined set time tA, and the cold water W3 is passed through. It is in water mode. By using this mode when the mold temperature Tx has not reached the optimum temperature T0 even after a predetermined time tA has elapsed, the throughput of the casting cycle can be shortened. That is, by using this timer control mode, it is possible to shorten the casting cycle. Note that in this timer control mode, the heater H can be controlled in the same manner as in the peak control mode described above, so a description thereof will be omitted. As described above, the three operation control modes of the mold temperature control system according to the present embodiment, that is, the standard control mode, the peak control mode, and the timer control mode, have been explained.

In addition, in this embodiment, the mold temperature is controlled by one heater, one thermocouple, and one cooling water passage arranged in the mold, but the connection in this embodiment By combining methods in parallel, it is possible to configure a plurality of mold control systems, and it goes without saying that even more fine-grained temperature control can be achieved.

[Effects of the Invention] As described above, according to the present invention, a heater, a cooling water passage, and a temperature measuring element are arranged in a mold, and the current to be supplied to the heater is determined by the temperature signal of the temperature measuring element. It controls the energization time and the time for the cooling water to flow through the cooling water passage.

Therefore, the pouring start temperature and mold opening temperature of the mold can always be kept at the same temperature.

In addition, by using PDI control and PI control for the heater, if the mold temperature is significantly lower than the optimum temperature, PDI control can rapidly heat the mold and shorten the time until pouring starts. Immediately before the start of pouring, PI control is performed to stably maintain the pouring start temperature.

Furthermore, since the peak control mode and the timer control mode are introduced in addition to the standard control mode that uses the first set temperature and the second set temperature, it is possible to perform fine casting control. Furthermore, since the pouring start temperature and mold opening temperature are precisely controlled in this way, casting quality is extremely stable, and P.
Since the mold temperature is also controlled by DI control, for example, when the mold is replaced, the time until the next pouring can be made as short as possible. Therefore, it can be understood that the production efficiency of a casting system employing the present mold temperature control method is at an extremely high level.

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 schematic configuration diagram of a mold temperature control system that implements the temperature control method for casting molds according to the present invention, and Fig. 2 is an explanatory diagram of the operation of the standard control mode in the temperature control method according to the present invention. , FIG. 3 and FIG. 4 show the temperature control method according to the present invention,
FIG. 3 is an explanatory diagram of the operation of peak control mode and timer control mode, respectively. 10... Mold temperature control system 12... Mold 14
... Cooling water control system 16 ... Heater control system 18 ... Control processing section 20 ... Movable type 2
2... Fixed type 24... Cavity 26... Runner 28... Water reservoir 30... Molten metal injection mechanism 32... First thermocouple 34... A/D converter 36...・Microcomputer 44...D/A converter 46...Interface circuit 50...Second
Thermocouple 52... Flow rate adjustment solenoid valve 54... Electromagnetic flow meter 56... Solenoid valve 62...
3rd thermocouple W...Cooling water H...Heater TX...Mold temperature Patent applicant Honda Motor Co., Ltd. FIG, 4 START STOP

Claims (5)

[Claims] (1) The temperature of the mold is controlled by flowing or stopping a cooling medium through the casting mold via an ON/OFF type valve, and by providing a heater and supplying or cutting off current to the heater. The method for controlling the temperature of a casting mold includes continuously supplying current to the heater when the mold temperature is lower than the lower limit of the optimal pouring start temperature.
Perform DI control and turn off the ON/OFF type valve.
A method for controlling the temperature of a casting mold, characterized by controlling the temperature of the mold to be in the F state and increasing the mold temperature. (2) In the method according to claim 1, when the mold temperature rises and reaches the lower limit temperature of the pouring start temperature range, the current supplied to the heater is changed to ON/OFF control. A method for controlling the temperature of a casting mold, characterized in that the temperature is controlled to be maintained at an optimum temperature for starting pouring. (3) Controlling the temperature of the mold by flowing or stopping a cooling medium through the casting mold via an ON/OFF type valve and arranging a heater to supply or cut off current to the heater. A method for controlling the temperature of a casting mold, in which first, when the mold temperature is lower than the pouring start/mold opening temperature range, current is continuously supplied to the heater to perform PDI control, and the The ON/OFF type valve is turned OFF to raise the mold temperature, and then, when the mold temperature reaches the lower limit temperature of the pouring start/mold opening temperature range, the current supplied to the heater is turned ON/OFF. The control is changed to PI control to maintain the temperature at the optimum pouring start/mold opening temperature within the pouring start/mold opening temperature range, and then pour the molten metal until the mold temperature reaches the pouring start/mold opening temperature range. When the upper limit temperature of the temperature range is exceeded, the current supply to the heater is stopped and the heater is turned off, and then when the mold temperature exceeds a preset first temperature higher than the upper limit temperature, the heater is turned on/off. When the OFF type valve is turned on and the flow starts, and after the mold temperature exceeds a preset second set temperature which is higher than the first set temperature, it decreases and crosses the second set temperature again. The OFF type valve is turned OFF to stop the cooling medium, and then, when the mold temperature reaches the upper limit temperature of the pouring start/mold opening temperature range, the heater is turned ON/
A method for controlling the temperature of a casting mold, characterized in that the temperature is controlled to be maintained at the optimum pouring start/mold opening temperature by PI control, which is an OFF control, and then the next pouring is started. (4) In the method according to claim 3, when the mold temperature exceeds the first set temperature after starting pouring, it decreases and returns to the first set temperature again without reaching the second set temperature. In this method, the temperature gradient of the mold temperature is monitored, and when the temperature gradient of the mold temperature becomes zero, the ON/OFF type valve is turned on.
A method for controlling the temperature of a casting mold, characterized by controlling the temperature so that the cooling medium is stopped in an FF state. (5) In the method according to claim 3, when the mold temperature reaches the second set temperature after starting pouring, the ON/O
The OFF time of the FF type valve is set, and after the OFF time has elapsed, the ON/OFF type valve is turned on only when the mold temperature is in a temperature range higher than the first set temperature, and the cooling medium is controlled to flow through. A method for controlling the temperature of a casting mold, characterized in that: