JP2010131953A - Mold temperature controller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To allow a medium certainly prevented from boiling within an apparatus when discharging the medium to control mold temperature in a mold temperature controller. <P>SOLUTION: A mold temperature controller 4 is equipped with: a circulation path 6 for circulating the medium through a mold 2 to control temperature of the mold 2, a pump 17 to pressurize the medium in the circulation path 6, a heater 7 to heat the medium in the circulation path 6, a discharge path 9 connected with the circulation path 6 and discharges the medium from the circulation path 6 to lower temperature of the mold 2, a solenoid valve 10 prepared in the discharge path 9 and a controller 12 to control opening and closing of the solenoid valve 10. The controller 12 restricts a pressure drop in the circulation path 6 by closing the solenoid valve 10 while medium pressure P in the circulation path 6 remains higher than the saturated vapor pressure P1 after opening the solenoid valve 10. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a mold temperature control device.

The temperature of the mold used for injection molding or the like is controlled by a temperature control device (see, for example, Patent Document 1). In Patent Document 1, a liquid for controlling the temperature of a mold is circulated in a liquid circulation path, and the temperature of the mold is increased by heating the liquid with a heater. ing.
Also, at the end of the resin molding operation or when changing the mold, open the drain valve open / close valve connected to the circulation path to discharge the high-temperature liquid to the outside of the liquid circulation path. The temperature is lowered.

  By the way, the liquid in the liquid circulation path is heated by the heater and pressurized by the pump, and becomes a high temperature and a high pressure. When this liquid is released from the drainage pipe at once, the pressure in the circulation path is sharply lowered, the liquid boils and a vapor region is generated in the circulation path. When such a steam region is generated, the pump is in an operation state, and there is a possibility that seizure may occur in the pump bearing or the like.

Therefore, in the temperature control device of Patent Document 1, opening and closing of the on-off valve is alternately repeated by a timer provided in the control device, so that the hot circulating liquid in the liquid circulation path does not boil.
Japanese Patent No. 4048005

However, in a configuration in which the opening and closing of the on-off valve is simply repeated at regular intervals with a timer as in the temperature control device of Patent Document 1, the pressure in the circulation path is not sufficiently taken into account, and the boiling of the liquid in the circulation path Is not sufficient to reliably prevent this.
The present invention has been made in view of such circumstances, and an object of the present invention is to boil the medium in the mold temperature control device when the medium for adjusting the mold temperature is discharged. It is to ensure that it can be prevented.

  In order to achieve the above object, the invention according to claim 1 is a mold temperature control device, wherein a circulation path for circulating a medium for performing temperature adjustment of the mold to the mold, and the circulation path A pump for pressurizing the medium in the inside, a heater for heating the medium in the circulation path, a discharge valve connected to the circulation path and discharging the medium from the circulation path, and opening and closing of the discharge valve Control means for controlling the exhaust gas, and the control means closes the discharge valve after the discharge valve is opened while the pressure of the medium in the circulation path is higher than a saturated vapor pressure. .

  According to such a configuration, when discharging the medium from the discharge valve, the control means opens the discharge valve, and then closes the discharge valve while the pressure of the medium in the circulation path does not fall below the saturated vapor pressure. Thereby, when discharging a medium from the inside of a circulation path in order to reduce the temperature of a metal mold | die, it can prevent reliably that a medium boils in a circulation path. Therefore, it is possible to reliably prevent the pump operation (dry operation) in which the pump is operated in a steam atmosphere, and to prevent the pump bearings and seals from being scratched or seized due to poor lubrication. it can. In this way, it is possible to reliably prevent the occurrence of problems associated with boiling of the medium in the circulation path.

  The invention according to claim 2 is the invention according to claim 1, further comprising a temperature sensor for detecting the temperature of the medium in the circulation path, wherein the control means includes a first control mode and a second control mode. In the first control mode, when the detected deviation of the temperature of the medium with respect to a predetermined target temperature is less than a predetermined threshold, the discharge valve is controlled by an amount corresponding to the deviation. In the second control mode, when the detected deviation of the temperature of the medium with respect to the predetermined target temperature is equal to or greater than a predetermined threshold, the discharge is performed by a predetermined amount regardless of the deviation. It is a mode that opens the valve.

  According to such a configuration, the first control mode is executed when the medium temperature in the circulation path is close to the target temperature. In the first control mode, the amount by which the discharge valve is opened decreases as the medium temperature approaches the target temperature. Thereby, it is possible to prevent the medium temperature from being excessively lowered with respect to the target temperature, and it is possible to reliably bring the medium temperature close to the target temperature. In the first control mode, the amount of opening the discharge valve is small due to the small deviation of the medium temperature from the target temperature. Therefore, even if the discharge valve is opened by an amount corresponding to the deviation, the pressure in the circulation path can be prevented from dropping below the saturated vapor pressure, and the pressure in the circulation path can be reliably maintained at a value greater than the saturated vapor pressure.

  When the medium temperature is high and far from the target temperature, the second control mode is executed. In the second control mode, the discharge valve is opened by a predetermined amount irrespective of the deviation of the medium temperature from the target temperature. Thereby, it is possible to prevent the amount of opening the discharge valve from becoming excessive. Therefore, the pressure drop in the circulation path due to the opening of the discharge valve can be prevented from becoming too large, and the pressure in the circulation path can be reliably maintained at a value larger than the saturated vapor pressure.

According to a third aspect of the present invention, in the first or second aspect of the invention, the control means opens and closes the discharge valve, and then the pressure of the medium in the circulation path is changed to the discharge valve. After the pressure before opening is recovered, the discharge valve is opened again.
According to such a configuration, the pressure of the medium in the circulation path after the discharge valve is closed is, for example, pressurization by a medium from a valve that supplies a medium having a lower temperature than the medium in the circulation path to the circulation path, It rises again due to the thermal expansion of the medium in the circulation path and the drive of the pump. Then, after the pressure of the medium in the circulation path returns to the value before opening the discharge valve, the discharge valve is opened again. As a result, when the discharge valve is opened again, the pressure of the medium in the circulation path is sufficiently high, and even when the discharge valve is opened again, the pressure in the circulation path decreases below the saturated vapor pressure. Can be prevented.

As described above, according to the first aspect of the present invention, when the medium is discharged from the circulation path in order to lower the mold temperature, it is possible to reliably prevent the medium from boiling in the circulation path.
According to the second aspect of the present invention, the pressure in the circulation path can be reliably maintained at a value larger than the saturated vapor pressure in both the first control mode and the second control mode.
According to the third aspect of the present invention, even when the discharge valve is opened again, the pressure in the circulation path can be prevented from decreasing below the saturated vapor pressure.

Preferred embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a schematic diagram showing a schematic configuration of an injection molding apparatus including a mold temperature control device according to an embodiment of the present invention.
In FIG. 1, an injection molding apparatus 1 is for forming a molten resin into a desired shape, and includes a mold 2 and a mold temperature control apparatus 4.

  The mold 2 includes a male mold 2a and a female mold 2b as a pair of left and right molds, a medium supply path 2c using a fluid such as water for temperature adjustment, and a medium return path 2d. . A cavity 2e is defined by the male mold 2a and the female mold 2b. By injecting molten resin into the cavity 2e from an injection device (not shown), a resin product having a desired shape can be formed.

The supply path 2c of the mold 2 is for supplying a medium to each of the male mold 2a and the female mold 2b. The supply path 2c of the mold 2 has one inlet 2f and two outlets 2g. The medium flowing in from the inlet 2f is branched and sent to the two outlets 2g. The outlet 2g is connected to each of the passages 2h and 2i formed in the male mold 2a and the female mold 2b.
The medium that has passed through the passages 2h and 2i of the male mold 2a and the female mold 2b is sent to the return path 2d of the mold 2. The return path 2d has two inlets 2j and one outlet 2k. The two inlets 2j are connected to the passages 2h and 2i of the male mold 2a and the female mold 2b, respectively. The media flowing in from the two inlets 2j merge and are sent to one outlet 2k.

The mold temperature control device 4 controls the temperature of the mold 2 using a medium. The mold temperature control device 4 includes a circulation path 6, a heater 7, a float switch tank 8, a discharge path 9, a solenoid valve 10 as a discharge valve, an injection path 11, and a control device 12 as a control means. Including.
The circulation path 6 is for circulating the medium through the mold 2. The medium in the circulation path 6 flows in the circulation path 6 along the direction of arrow A in FIG. The circulation path 6 includes a medium tank 13, a supply path 14, and a return path 15.

The medium tank 13 is for storing a medium. An overheat preventer 16 is attached to the medium tank 13 to prevent the medium in the medium tank 13 from being overheated by the heater 7.
The supply path 14 is for supplying the medium stored in the medium tank 13 to the mold 2. An inlet 14 a of the supply path 14 is connected to the medium tank 13. The supply path 14 is provided with a pump 17 such as an electric pump.

The supply path 14 includes an upper supply path 141 disposed upstream of the pump 17 in the direction of arrow A, and a lower supply path 142 disposed downstream of the pump 17 in the direction of arrow A. .
One end of the upper supply path 141 is an inlet 14 a of the supply path 14. The other end of the upper supply path 141 is connected to the suction port 17 a of the pump 17. One end of the lower supply path 142 is connected to the discharge port 17 b of the pump 17. The other end of the lower supply path 142 is an outlet 14 b of the supply path 14.

By driving the pump 17, the medium in the medium tank 13 is sucked into the suction port 17 a of the pump 17 through the upper supply path 141 and pressurized by the pump 17. The medium pressurized by the pump 17 is discharged to the lower supply path 142 from the discharge port 17b.
The pressurized medium is sent toward the mold 2 through the lower supply path 142. On the downstream side of the pump 17 in the direction of arrow A, a temperature sensor 18 is provided as temperature detection means. The temperature sensor 18 detects the temperature of the medium in the lower supply path 142 as the temperature of the medium in the circulation path 6.

  A relief valve 19 is provided on the downstream side of the temperature sensor 18 in the arrow A direction. The relief valve 19 releases the pressure in the lower supply path 142 when the pressure in the lower supply path 142 of the circulation path 6 exceeds a predetermined fail pressure, and uses the pressure in the lower supply path 142 as a power source. It is a valve that opens. Normally, the pressure relief in the circulation path 6 by the relief valve 19 is not performed, and the relief valve 19 is opened and the pressure relief is performed only when some abnormality occurs.

  A pressure gauge 20 is provided on the downstream side of the relief valve 19 in the arrow A direction. The pressure gauge 20 is connected to the lower supply path 142 so that the operator can check the pressure in the lower supply path 142. A bypass path 21 is provided on the downstream side of the pressure gauge 20 in the arrow A direction. The bypass path 21 connects the lower supply path 142 and the medium tank 13. The bypass passage 21 is provided with a pressure adjustment valve 22 such as a gate valve, and the pressure in the lower supply passage 142 is adjusted by, for example, manually adjusting the opening degree of the pressure adjustment valve 22. Can do. The outlet 14 b of the supply path 14 is connected to the inlet 2 f of the supply path 2 c of the mold 2.

The return path 15 is configured to return the medium from the mold 2. The inlet 15 a of the return path 15 is connected to the outlet 2 k of the return path 2 d of the mold 2. An outlet 15 b of the return path 15 is connected to the medium tank 13.
With the above configuration, the medium in the medium tank 13 is sent to the lower supply path 142 of the circulation path 6 by the pump 17 and moves along the direction of the arrow A. Further, the supply path 2c of the mold 2 and the male mold 2a It is returned to the medium tank 13 through the passage 2h, the passage 2i of the female mold 2b, the return path 2d of the mold 2, and the return path 15 of the circulation path 6.

The heater 7 is an electric heater, for example, and heats the medium in the medium tank 13.
The float switch tank 8 is a tank including the float switch 23, and is connected to the medium tank 13 through the first communication path 24 and is connected to the medium tank 13 through the second communication path 25.

  The discharge path 9 is for discharging the medium in the circulation path 6 to the outside of the circulation path 6, and has an inlet 9a and an outlet 9b. An inlet 9 a of the discharge path 9 is connected to the float switch tank 8. Thus, the discharge path 9 is connected to the medium tank 13 of the circulation path 6 via the float switch tank 8 and the first and second communication paths 24 and 25. The outlet 9 b of the discharge path 9 is connected to the drain 26. The drain 26 is a drain outlet connected to the sewer, for example.

A solenoid valve 10 is provided in the discharge path 9. The solenoid valve 10 includes a solenoid (not shown), for example, and controls the opening and closing of the solenoid valve 10 by turning on / off the power to the solenoid.
By opening the solenoid valve 10, the fluid in the medium tank 13 flows to the discharge path 9 through the first communication path 24 and the float switch tank 8, and is further discharged to the drain 26 from the outlet 9 b of the discharge path 9. The The medium is discharged from the solenoid valve 10 when, for example, the medium in the circulation path 6 is discharged to the drain 26 in order to lower the temperature of the mold 2.

On the other hand, when the electromagnetic valve 10 is closed, the movement of the medium in the discharge path 9 is restricted, and the medium does not move from the medium tank 13 to the discharge path 9.
The injection path 11 is for lowering the temperature in the circulation path 6 by sending a medium having a temperature lower than that of the medium in the circulation path 6 to the circulation path 6, and has an inlet 11a and an outlet 11b. is doing. The inlet 11 a of the injection path 11 is connected to the medium supply source 27. The medium supply source 27 is, for example, a water supply that supplies pressurized water at room temperature, and includes a medium supply valve 28 such as a faucet. An inlet 11 a of the injection path 11 is connected to the medium supply valve 28. The outlet 11 b of the injection path 11 is connected to the medium tank 13. The medium supply valve 28 remains open while the mold temperature control device 4 controls the temperature of the medium in the circulation path 6.

  When the temperature of the medium in the circulation path 6 is decreased in order to decrease the temperature of the mold 2, the medium in the circulation path 6 is discharged to the drain 26, while the medium in the circulation path 6 is more than the medium in the circulation path 6. Even supply low temperature media. Specifically, the electromagnetic valve 10 is opened. As a result, the medium in the circulation path 6 moves from the medium tank 13 to the float switch tank 8, passes through the discharge path 9 along the direction of the arrow B <b> 1, and is discharged to the drain 26. At this time, the medium at the same temperature as the medium discharged from the medium tank 13 to the drain 26 flows from the medium supply valve 28 through the injection path 11 in the direction of arrow B2 and is supplied to the medium tank 13. By supplying the pressurized medium at normal temperature from the medium supply valve 28 to the medium tank 13, the temperature of the medium in the medium tank 13 is lowered and the medium pressure P is increased.

  The control device 12 controls the heater 7, the pump 17, and the electromagnetic valve 10, and includes a CPU, a ROM, and a RAM. A heater 7, a pump 17, and a solenoid valve 10 are connected to the control device 12. The control device 12 controls on / off of the heater 7, on / off of the pump 17, and opening / closing of the electromagnetic valve 10. Further, a temperature sensor 18 is connected to the control device 12.

  The control device 12 includes a temperature setting unit 29 and a counter 30 as a counter. The temperature setting unit 29 is for setting the target temperature T1 of the medium in the circulation path 6, and is operated by an operator, for example. The control device 12 employs a PID control method, and can execute a temperature control mode in which the temperature T of the medium in the circulation path 6 (hereinafter simply referred to as the medium temperature T) is set to the target temperature T1.

By executing the temperature control mode, the medium temperature T can be set to the target temperature T1 while preventing the medium in the circulation path 6 from boiling. The start of execution of the temperature control mode may be automatically determined by a control program stored in the ROM, or may be determined by an operator operating an operation panel (not shown) of the control device 12.
FIG. 2 is a graph for explaining the amount by which the electromagnetic valve 10 is opened in the temperature control mode. The deviation ΔT on the horizontal axis in the graph of FIG. 2 is the deviation of the medium temperature T in the circulation path 6 detected by the temperature sensor 18 with respect to the target temperature T1 (ΔT = T−T1). The value of C corresponds to the amount by which the solenoid valve 10 is opened. Note that the amount of opening the electromagnetic valve 10 refers to, for example, the time during which the electromagnetic valve 10 is open within a certain period of time.

As can be seen from the graph of FIG. 2, while the deviation ΔT is up to a predetermined threshold value ΔT1 (for example, 2 ° C.), the amount by which the solenoid valve 10 is opened increases in proportion to the value of the deviation ΔT. . On the other hand, when the deviation ΔT is equal to or greater than the threshold value ΔT1, the amount by which the electromagnetic valve 10 is opened is constant regardless of the value of the deviation ΔT.
FIG. 3 is a flowchart for explaining a control flow in the temperature control mode. The temperature control mode will be described with reference to FIG. 1 and FIG.

When the temperature control mode is executed, the control device 12 determines the deviation ΔT (S1). If the medium temperature T is higher than the target temperature T1, and the deviation ΔT is positive (S1: YES), the medium temperature T is lowered. Specifically, the heater 7 is turned off (S2). Next, the value C of the counter 30 of the control device 12 is reset to zero (S3).
Thereafter, it is determined whether or not the deviation ΔT is greater than or equal to a threshold value ΔT1 (S4). For example, when the medium temperature T is high and the deviation ΔT is greater than or equal to the threshold value ΔT1 (S4: YES), the second control mode is executed in which the solenoid valve 10 is opened by a predetermined amount regardless of the value of the deviation ΔT. The

Specifically, the electromagnetic valve 10 is opened (S5), and thereafter, incrementing the value C of the counter 30 by one over a predetermined time is performed (S6). This increment is repeated while the value C of the counter 30 is less than the predetermined value α × ΔT1 (S7: NO). Α is a predetermined constant and is set as appropriate.
When the value C of the counter 30 reaches the predetermined value α × ΔT1 (S7: YES), the solenoid valve 10 is closed (S8). That is, regardless of the deviation ΔT, when the value C of the counter 30 reaches the predetermined value α × ΔT1, the electromagnetic valve 10 is closed. The predetermined value α × ΔT1 is such that the pressure P of the medium in the circulation path 6 (hereinafter simply referred to as medium pressure P) can be maintained higher than the saturated vapor pressure P1 until the electromagnetic valve 10 is opened and closed. Set to

  In other words, the time for opening the solenoid valve 10 is set so that the medium in the circulation path 6 does not boil due to the pressure drop between the opening and closing of the solenoid valve 10. In the second control mode, the time from when the solenoid valve 10 is opened to when it is closed is constant regardless of the medium temperature T. Further, the medium pressure P immediately before opening the electromagnetic valve 10 is set to a constant value P2. For this reason, regardless of the medium temperature T, the amount of decrease in the medium pressure P caused by opening the electromagnetic valve 10 is substantially constant.

  Further, (ii) if the medium pressure P is always higher than the saturation vapor pressure P1 of the medium at the allowable temperature of the medium in the mold temperature control device 4, the medium will not boil in the circulation path 6. In the second control mode, based on the above (i) and (ii), even when the solenoid valve 10 is opened, the medium pressure P is always greater than the saturation vapor pressure P1 of the medium at the allowable temperature. The predetermined value α × ΔT1 is set so that In this way, the decrease in the medium pressure P is regulated.

  When the solenoid valve 10 is closed, the increment of incrementing the value C of the counter 30 by one over a predetermined time is performed again (S9). This increment is repeated while the value C of the counter 30 is less than the predetermined value C2 (S10: NO). During this time, the pressure of the medium going to the medium tank 13 through the medium supply valve 28 and the injection path 11 acts on the medium in the medium tank 13. As a result, the pressure of the medium such as in the medium tank 13 increases, and the medium pressure P recovers to the pressure before opening the electromagnetic valve 10 (P = P2).

The increase in the medium pressure P when the electromagnetic valve 10 is closed is not limited to the increase caused by the medium supplied from the medium supply valve 28 pressurizing the medium in the circulation path 6. The rise may be due to other pressure sources, such as a rise due to thermal expansion of the medium inside, or a rise due to pressurization of the medium from the medium tank 13 by the pump 17.
When one cycle of the temperature control mode is completed by setting the value C of the counter 30 to the predetermined value C2 (S10: YES), the process returns to S1 again.

On the other hand, in S4, when the medium temperature T is close to the target temperature T1, and the deviation ΔT is less than the threshold value ΔT1 (S4: NO), the solenoid valve 10 is opened by an amount corresponding to the value of the deviation ΔT. One control mode is executed.
Specifically, the solenoid valve 10 is opened (S11), and then incremented by one to increase the value C of the counter 30 by one over a predetermined time (S12). This increment is repeated while the value C of the counter 30 is less than the value α × ΔT proportional to the deviation ΔT (S13: NO). The value α × ΔT proportional to the deviation ΔT is smaller than the predetermined value α × ΔT1 (α × ΔT <α × ΔT1). When the value C of the counter 30 becomes a value α × ΔT proportional to the deviation ΔT (S13: YES), the solenoid valve 10 is closed (S14).

  In the first control mode, since the deviation ΔT is small, the time until the value C of the counter 30 becomes a value α × ΔT proportional to the deviation ΔT is short. Therefore, the time during which the solenoid valve 10 is opened is short, and the amount of decrease in the medium pressure P is small. For this reason, in the first control mode, as in the second control mode, the medium pressure P is larger than the saturated vapor pressure P1, and the medium in the circulation path 6 does not boil due to the pressure drop.

  When the solenoid valve 10 is closed, the increment of incrementing the value C of the counter 30 by one over a predetermined time is performed again (S9). This increment is repeated while the value C of the counter 30 is less than the predetermined value C2 (S10: NO). When the value C of the counter 30 becomes the predetermined value C2 (S10: YES), when one cycle of the temperature control mode is completed, the process returns to S1.

The above is the control when the medium temperature T is higher than the target temperature T1. On the other hand, when the medium temperature T is equal to or lower than the target temperature T1 (S1: NO), it is determined whether or not the deviation ΔT is zero (S15). When the deviation ΔT is zero, that is, when the medium temperature T is equal to the target temperature T1 (S15: YES), the heater 7 is turned off (S16), and the process proceeds to S1.
On the other hand, when the deviation ΔT is a negative value (S15: NO), since the medium temperature T is lower than the target temperature T1, the heater 7 is turned on (S17) and the medium in the circulation path 6 is heated. Then, it progresses to S1.

FIG. 4 is a graph showing an example of the relationship between the open / close state of the solenoid valve 10 and the medium pressure P when the temperature control mode is executed.
Referring to FIG. 4, for example, when the temperature control mode is executed in a state where deviation ΔT is equal to or greater than threshold value ΔT1 because medium temperature T is sufficiently higher than target temperature T1, in the first cycle, Two control modes are executed. At this time, the solenoid valve 10 is opened until the value C of the counter 30 reaches a predetermined value α × ΔT1 from zero. During this time, the medium pressure P continues to decrease, but the medium pressure P3 immediately before closing the solenoid valve 10 remains higher than the saturation vapor pressure P1 of the medium at the allowable temperature of the mold temperature control device 4.

When the value C of the counter 30 reaches a predetermined value α × ΔT1, the electromagnetic valve 10 is closed. As a result, the circulation path 6 is closed, and the medium pressure P is restored to P2 by the medium supplied from the medium supply valve 28 pressurizing the inside of the circulation path 6.
When the value C of the counter 30 reaches the predetermined value C2, the first cycle ends and the temperature control mode is executed again.

  Even if the first cycle is completed, if the deviation ΔT is equal to or greater than the threshold value ΔT1, the second control mode is executed again in the second cycle. The solenoid valve 10 is opened until the value C of the counter 30 becomes zero to a predetermined value α × ΔT1. During this time, the medium pressure P continues to decrease, but the medium pressure P3 immediately before closing the solenoid valve 10 remains higher than the saturation vapor pressure P1 of the medium at the allowable temperature of the mold temperature control device 4.

When the value C of the counter 30 reaches a predetermined value α × ΔT1, the electromagnetic valve 10 is closed. As a result, the circulation path 6 is closed, and the medium pressure P is restored to P2 by the medium supplied from the medium supply valve 28 pressurizing the inside of the circulation path 6.
When the value C of the counter 30 reaches the predetermined value C2, the second cycle ends and the temperature control mode is executed again.

  Even if the second cycle is completed, if the deviation ΔT is equal to or greater than the threshold value ΔT1 due to the high medium temperature T, the second control mode is executed again in the third cycle. The solenoid valve 10 is opened until the value C of the counter 30 becomes zero to a predetermined value α × ΔT1. During this time, the medium pressure P continues to decrease, but the medium pressure P3 immediately before closing the solenoid valve 10 remains higher than the saturation vapor pressure P1 of the medium at the allowable temperature of the mold temperature control device 4.

When the value C of the counter 30 reaches a predetermined value α × ΔT1, the electromagnetic valve 10 is closed. As a result, the circulation path 6 is closed again, and the medium pressure P is restored to P2 due to the medium supplied from the medium supply valve 28 pressurizing the inside of the circulation path 6.
When the value C of the counter 30 reaches the predetermined value C2, the third cycle ends and the temperature control mode is executed again.

  When the medium temperature T approaches the target temperature T1 due to the completion of the third cycle and the deviation ΔT becomes less than the threshold value ΔT1, the first control mode is executed in the fourth cycle. The solenoid valve 10 is opened until the value C of the counter 30 reaches a value α × ΔT proportional to the deviation ΔT from zero. During this time, the medium pressure P continues to decrease, but the medium pressure P4 immediately before closing the solenoid valve 10 remains larger than the saturation vapor pressure P1 of the medium at the allowable temperature of the mold temperature control device 4.

When the value C of the counter 30 becomes a value α × ΔT proportional to the deviation ΔT, the electromagnetic valve 10 is closed. As a result, the circulation path 6 is closed, and the medium pressure P is restored to P2 by the medium supplied from the medium supply valve 28 pressurizing the inside of the circulation path 6.
When the value C of the counter 30 reaches the predetermined value C2, the fourth cycle ends and the temperature control mode is executed again.

If the medium temperature T coincides with the target temperature T1 due to the completion of the fourth cycle, the electromagnetic valve 10 remains closed.
As described above, after the medium temperature T coincides with the target temperature T1, as shown in FIG. 5, the target temperature T1 is, for example, 150 ° C. (saturated vapor pressure is about 0.38 MPa) to 140 ° C. (saturated vapor pressure is The case where it is changed to about 0.27 MPa) will be described. In this case, when the temperature control mode is executed, in the first cycle, the deviation ΔT is 10 ° C., which is equal to or greater than the threshold value ΔT1, and the second control mode is executed. As a result, the solenoid valve 10 is opened until the value C of the counter 30 becomes zero to the predetermined value α × ΔT1. During this time, the medium pressure P continues to decrease, but the medium pressure P3 immediately before closing the solenoid valve 10 remains higher than the medium saturated vapor pressure P1 at the allowable temperature.

When the value C of the counter 30 reaches a predetermined value α × ΔT1, the electromagnetic valve 10 is closed. As a result, the circulation path 6 is closed, and the medium pressure P is restored to P2 by the medium supplied from the medium supply valve 28 pressurizing the inside of the circulation path 6.
When the value C of the counter 30 reaches the predetermined value C2, the first cycle ends and the temperature control mode is executed again.

For example, the second temperature and the third cycle similar to the first cycle are executed, so that the medium temperature T substantially matches the target temperature T1. After the end of the third cycle, the medium temperature T is slightly lower than the target temperature T1, but the medium temperature T is quickly returned to the target temperature T1 by the heating by the heater 7.
On the other hand, referring to FIG. 2, as indicated by a dotted line in FIG. 2, even when the deviation ΔT is equal to or greater than the threshold value ΔT1, control is performed to open the solenoid valve 10 by an amount corresponding to the deviation ΔT (first control mode). 6), as shown in FIG. 6, the amount by which the solenoid valve 10 is opened becomes too large, and the medium pressure P is greatly reduced. As a result, the medium pressure P decreases to P4 that is equal to or lower than the saturated vapor pressure P1, and the medium boils in the circulation path 6.

  In such control, a case will be described in which the target temperature T1 is changed from 150 ° C. to 140 ° C., for example, as shown in FIG. 7 after the medium temperature T coincides with the target temperature T1. In this case, the deviation ΔT becomes as large as 10 ° C. at the start of execution of the temperature control mode (first cycle). For this reason, the time for opening the solenoid valve 10 is from the time when the counter C becomes zero to a value α × ΔT proportional to the deviation ΔT, and becomes longer according to the deviation ΔT. During this time, the medium pressure P continues to decrease and decreases to P4 that is equal to or lower than the saturation vapor pressure P1 of the medium. As a result, the medium boils in the circulation path 6, and a pumping operation state occurs in the pump 17.

Also in the second cycle, since the time during which the solenoid valve 10 is opened and the medium-temperature medium is supplied from the medium supply valve 28 becomes longer, the rate of decrease in the medium temperature T becomes faster, and the medium temperature T becomes the target. The temperature T1 is greatly reduced once. For this reason, it takes time to reheat the medium in the circulation path 6 with the heater 7 and set the medium temperature T to the target temperature T1.
As described above, according to the present embodiment, the controller 12 opens the electromagnetic valve 10 and then opens the electromagnetic valve 10 while the medium pressure P in the circulation path 6 is greater than the saturated vapor pressure P1. close. Therefore, when the medium in the circulation path 6 is discharged from the electromagnetic valve 10 of the discharge path 9, after the control device 12 opens the electromagnetic valve 10, the electromagnetic valve 10 is set while the medium pressure P does not fall below the saturated vapor pressure P 1. Close. Thereby, when the medium is discharged from the circulation path 6 in order to lower the temperature of the mold 2, it is possible to reliably prevent the medium from boiling in the circulation path 6.

Therefore, it is possible to reliably prevent the pump operation (dry operation) in which the pump 17 is operated in a steam atmosphere, and to ensure that the bearings and seals of the pump 17 are scratched or seized due to poor lubrication. Can be prevented. In this way, it is possible to reliably prevent the occurrence of problems associated with the boiling of the medium in the circulation path 6.
Further, when the medium temperature T is close to the target temperature T1, the first control mode is executed. In the first control mode, the amount by which the solenoid valve 10 is opened decreases as the medium temperature T approaches the target temperature T1. As a result, the medium temperature T can be prevented from dropping too much with respect to the target temperature T1, and the medium temperature T can be reliably brought close to the target temperature T1.

  In the first control mode, the amount of opening of the solenoid valve 10 is small because the deviation ΔT of the medium temperature T with respect to the target temperature T1 is small. Therefore, even if the solenoid valve 10 is opened by an amount corresponding to the deviation ΔT of the medium temperature T with respect to the target temperature T1, the medium pressure P can be prevented from dropping below the saturated vapor pressure P1, and the pressure in the circulation path 6 can be reduced to saturated steam. It can be reliably maintained at a value larger than the pressure P1.

  When the medium temperature T is high and far from the target temperature T1, the second control mode is executed. In the second control mode, the solenoid valve 10 is opened by a predetermined amount regardless of the deviation ΔT of the medium temperature T with respect to the target temperature T1. As a result, even when the deviation ΔT is large, the amount by which the solenoid valve 10 is opened can be prevented from becoming excessive. Therefore, the pressure drop in the circulation path 6 due to the opening of the electromagnetic valve 10 can be prevented from becoming too large, and the medium pressure P can be reliably maintained at a value larger than the saturated vapor pressure P1.

  Further, the control device 12 opens and closes the electromagnetic valve 10 and then opens the electromagnetic valve 10 again after the medium pressure P in the circulation path 6 recovers to the pressure P2 before the electromagnetic valve 10 is opened. With such a configuration, the medium pressure P after the electromagnetic valve 10 is closed rises again because the medium supplied from the medium supply valve 28 pressurizes the inside of the circulation path 6. And after the medium pressure P returns to the value P2 before opening the solenoid valve 10, the solenoid valve 10 is opened again. Thus, when the electromagnetic valve 10 is opened again, the medium pressure P in the circulation path 6 is sufficiently high, and even when the electromagnetic valve 10 is opened again, the medium pressure P in the circulation path 6 is equal to the saturated vapor pressure. It can prevent falling below P1.

The present invention is not limited to the contents of the above embodiments, and various modifications can be made within the scope of the claims. For example, when the mold 2 is cooled, each part of the mold 2 may be soaked by once fixing the medium temperature T over a plurality of times. Thereby, the dispersion | variation in the temperature of each part of the metal mold | die 2 can be eliminated, and the thermal distortion of the metal mold | die 2 can be prevented.
Specifically, after a predetermined time has elapsed after the medium temperature T reaches the target temperature T1, and the entire mold 2 reaches the same temperature as the target temperature T1, the target temperature T1 is lowered. As described above, after a predetermined time has elapsed after the medium temperature T reaches the target temperature T1, and the entire mold 2 reaches the same temperature as the target temperature T1, the operation of decreasing the target temperature T1 is repeated.

  Further, a map may be stored in the ROM of the control device 12, and an amount for opening the electromagnetic valve 10 may be set based on this map. In this case, the amount by which the solenoid valve 10 is opened can be set according to the target temperature T1, and fine pressure control can be performed.

It is a schematic diagram which shows schematic structure of an injection molding apparatus provided with the metal mold | die temperature control apparatus concerning one Embodiment of this invention. It is a graph for demonstrating the part which opens the solenoid valve 10 in temperature control mode. It is a flowchart for demonstrating the flow of control in temperature control mode. It is a graph which shows an example of the relationship between the opening-and-closing state of a solenoid valve, and a medium pressure at the time of performing temperature control mode. It is a graph which shows the relationship between medium temperature, the opening-and-closing state of a solenoid valve, and medium pressure at the time of changing target temperature. In a comparative example, it is a graph which shows an example of the relationship between the opening-and-closing state of a solenoid valve, and a medium pressure at the time of performing temperature control mode. In a comparative example, it is a graph which shows the relationship between medium temperature, the opening-and-closing state of a solenoid valve, and medium pressure at the time of changing target temperature.

Explanation of symbols

2 Mold 4 Mold temperature control device 6 Circulation path 7 Heater 10 Solenoid valve (discharge valve)
12 Control device (control means)
17 Pump 18 Temperature sensor T Medium temperature T1 Target temperature ΔT Deviation ΔT1 Threshold value P Medium pressure P1 Saturated vapor pressure P2 pressure (pressure before the discharge valve is opened)

Claims (3)

A circulation path for circulating a medium for performing temperature adjustment of the mold to the mold;
A pump for pressurizing the medium in the circulation path;
A heater for heating the medium in the circulation path;
A discharge valve connected to the circulation path for discharging the medium from the circulation path;
Control means for controlling the opening and closing of the discharge valve,
The mold temperature control device according to claim 1, wherein the control means closes the discharge valve after opening the discharge valve while the pressure of the medium in the circulation path is higher than a saturated vapor pressure. A temperature sensor for detecting the temperature of the medium in the circulation path;
The control means is capable of executing a first control mode and a second control mode;
The first control mode is a mode in which when the detected temperature deviation of the medium with respect to a predetermined target temperature is less than a predetermined threshold, the discharge valve is opened by an amount corresponding to the deviation,
The second control mode is a mode in which when the detected deviation of the temperature of the medium with respect to the predetermined target temperature is equal to or greater than a predetermined threshold, the discharge valve is opened by a predetermined amount regardless of the deviation. The mold temperature control apparatus according to claim 1, wherein the mold temperature control apparatus is provided.   The control means opens and closes the discharge valve, and then opens the discharge valve again after the pressure of the medium in the circulation path is restored to the pressure before the discharge valve is opened. The mold temperature control device according to claim 1 or 2.

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