JP2010018020A - Mold temperature controller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mold temperature controller which can more stabilize the pressure of a medium for controlling a mold temperature. <P>SOLUTION: The mold temperature controller 4 includes a circulation path 6 for circulating a medium for conducting the temperature regulation of the mold 2 in the mold 2, a heater 7 for heating the medium in the circulation path 6, a solenoid valve 10 which is connected to the circulation path 6 and can release pressure in the circulation path 6, and a control unit 12. The control unit 12 drives the solenoid valve 10 for an instant every time a waiting period TM<SB>2</SB>is elapsed. By this, the pressure P of the medium in the circulation path 6 is released. <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 Documents 1 and 2). In Patent Documents 1 and 2, the liquid for controlling the temperature of the mold is circulated in the liquid circulation path, and the temperature of the mold is increased by heating the liquid with a heater. It is supposed to be.
In Patent Documents 1 and 2, when the liquid in the liquid circulation path expands as the temperature rises, the expanded liquid passes through the relief valve and escapes outside the apparatus.

In Patent Document 2, an open / close valve connected to the circulation path is opened when the mold temperature is lowered at the end of the resin molding operation or when the mold is replaced. Thereby, a high temperature liquid is discharged | emitted to the outer side of a liquid circulation path, and the temperature of a metal mold | die is reduced. In Patent Document 2, when opening the on-off valve, the liquid is gradually discharged from the liquid circulation path by alternately repeating the open state and the closed state without leaving the on-off valve open. Prevents sudden drop in pressure. That is, the on-off valve is operated so that the pressure in the circulation path does not decrease as much as possible.
Japanese Patent No. 4047999 Japanese Patent No. 4048005

In Patent Documents 1 and 2, when the temperature of the mold is controlled, when the liquid reaches a certain pressure, the relief valve opens to discharge the liquid in the liquid circulation path. However, in the configuration using the relief valve, a pressure hunting phenomenon occurs, and it is difficult to stabilize the liquid pressure.
The present invention has been made in view of such circumstances, and an object of the present invention is to provide a mold temperature control device that can further stabilize the pressure of a medium for controlling the mold temperature. There is.

  In order to achieve the above object, the invention according to claim 1 is a mold temperature control device, wherein a supply path for supplying a medium for adjusting the temperature of the mold to the mold, and the mold is provided. A return path through which the medium is returned, connected to the circulation path, a circulation path for circulating the medium to the mold, a heater for heating the medium in the circulation path, and the circulation path A pressure relief valve capable of releasing the internal pressure, and a control means for releasing the pressure in the circulation path by driving the pressure relief valve every time a predetermined time elapses.

  According to such a configuration, the pressure relief valve can be intermittently driven, and thereby the pressure of the medium in the circulation path can be released. Thereby, the pressure of the medium which became high pressure in the circulation path by the heating of the heater can be reliably reduced. Further, the timing for driving the relief valve can be set without depending on the pressure of the medium in the circulation path. Unlike the case of using a relief valve that opens when the set pressure is exceeded, according to the configuration of the present invention, it is possible to reliably suppress the hunting phenomenon of the medium pressure in the circulation path by driving the relief valve. The pressure of the medium can be made more stable.

  According to a second aspect of the present invention, in the first aspect of the invention, the discharge path for discharging the medium in the circulation path, and the medium having a temperature equal to or lower than the temperature of the medium in the circulation path. And a switching valve for switching between a feeding path for sending to the circulation path, a first state in which movement of the medium to the discharge path is not allowed, and a second state in which movement of the medium to the discharge path is allowed. The pressure relief valve is constituted by the switching valve, and the control means drives the switching valve so as to switch from the first state to the second state, whereby the pressure in the circulation path is It is characterized by letting go.

According to such a configuration, the medium pressure in the circulation path can be lowered by allowing the medium in the circulation path to escape to the discharge path for discharging the medium. Since the switching valve can also be used as a pressure relief valve, the number of parts of the mold temperature control device can be reduced, and the manufacturing cost can be reduced.
According to a third aspect of the present invention, in the first or second aspect of the present invention, the control means is a pressure relief mode for releasing the pressure in the circulation path, and a temperature of the medium in the circulation path. The pressure relief mode is a mode for releasing the pressure in the circulation path by driving the pressure relief valve every time a predetermined time elapses, and the temperature relief mode. The control mode is a mode in which the heater is turned on when the temperature of the medium is lower than a predetermined target temperature, and the heater is turned off when the temperature of the medium exceeds a predetermined target temperature. And the control means is capable of simultaneously executing the pressure relief mode and the temperature control mode.

According to such a configuration, since the pressure relief mode and the temperature control mode can be executed at the same time, an operation for releasing the pressure of the medium in the circulation path, and an operation for bringing the temperature of the medium in the circulation path close to the target temperature, Can be performed simultaneously. Therefore, the temperature of the medium in the circulation path can be quickly brought close to the target temperature.
The invention according to claim 4 is the invention according to any one of claims 1 to 3, further comprising a temperature sensor for detecting the temperature of the medium in the circulation path, wherein the control means is the temperature sensor. The pressure relief valve is driven each time the predetermined time elapses only when the detected temperature is equal to or lower than a predetermined reference temperature.

  According to such a configuration, since the temperature of the medium is equal to or lower than the predetermined reference temperature, the medium is circulated by the pressure relief valve when the increase in the temperature of the medium due to the heater is large, that is, when the increase in the pressure of the medium is large. Relieve the media pressure in the road. On the other hand, the pressure relief valve is not driven when the increase in the temperature of the medium due to the heater heating is small because the temperature of the medium is higher than the predetermined reference temperature, that is, when the increase in the pressure of the medium is small. Thus, since the pressure relief valve is driven only when it is necessary to relieve the pressure, the amount of energy released in the circulation path can be minimized, and the energy utilization efficiency can be increased.

The invention according to claim 5 is the invention according to claim 4, wherein the predetermined reference temperature is set lower than a target temperature of the medium in the circulation path.
According to such a configuration, when the temperature of the medium in the circulation path is the same as or close to the target temperature, the pressure relief valve does not release the pressure in the circulation path, so that the energy in the circulation path is reduced. It is possible to prevent a decrease in preparation, and it is easy to maintain the temperature of the medium in the circulation path at the target temperature.

As described above, according to the first aspect of the present invention, the hunting phenomenon of the pressure of the medium in the circulation path due to the driving of the relief valve can be reliably suppressed, and the pressure of the medium can be further stabilized.
According to the second aspect of the present invention, since the switching valve can also be used as a pressure relief valve, the number of parts of the mold temperature control device can be reduced, and the manufacturing cost can be reduced.

According to the third aspect of the present invention, the temperature of the medium in the circulation path can be quickly brought close to the target temperature.
According to the invention of claim 4, since the pressure relief valve is driven only when it is necessary to relieve the pressure, the amount of energy released in the circulation path can be minimized, and the energy utilization efficiency can be increased. .

  According to the invention described in claim 5, it is easy to maintain the temperature of the medium in the circulation path at the target temperature.

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 supply path 2c, and a 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.
An example of the resin material in this case is a thermoplastic resin such as polycarbonate. When molding a resin product using a polycarbonate resin, the male mold 2a and the female mold 2b are heated to, for example, about 100 ° C. to 180 ° C. by the mold temperature control device 4.

The supply path 2c of the mold 2 is for supplying a medium such as water to each of the male mold 2a and the female mold 2b. The medium is for adjusting the temperature of the mold 2. The supply path 2c of the mold 2 has an inlet 2f and an outlet 2g. The outlet 2g is connected to the male mold 2a and the female mold 2b, respectively.
The return path 2d of the mold 2 is a path through which the medium supplied to the male mold 2a and the female mold 2b is returned from the male mold 2a and the female mold 2b. The return path 2d has an inlet 2h and an outlet 2i. The inlet 2h is connected to the male mold 2a and the female mold 2b, respectively.

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, a feed path 11, and a control device 12 as a control means. Yes.
The circulation path 6 is for circulating the medium to the mold 2. The medium in the circulation path 6 flows in the circulation path 6 along the arrow A direction. 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.
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 circulation path 6. 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 adjusting 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 adjusting 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 i 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, and further, the supply path 2c of the mold 2, the male mold 2a, and It returns to the medium tank 13 through 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 66. The drain 66 is, for example, a drain outlet connected to a sewer.

  A solenoid valve 10 is provided in the discharge path 9. The electromagnetic valve 10 is a valve having both a function as a pressure relief valve capable of releasing the pressure in the circulation path 6 and a function as a switching valve for switching between a first state and a second state described later. 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.

When the electromagnetic valve 10 is closed, the movement of the fluid in the discharge path 9 is restricted, and the first state in which the movement of the medium from the medium tank 13 to the discharge path 9 is not allowed is realized. On the other hand, when the electromagnetic valve 10 is opened, the movement of the fluid in the discharge path 9 is allowed, and a second state in which the medium is allowed to move from the medium tank 13 to the discharge path 9 is realized.
The feed path 11 sends a medium having a temperature equal to or lower than the temperature of the medium in the circulation path 6 (or a medium having a temperature lower than that of the medium in the circulation path 6) to the circulation path 6, whereby the temperature in the circulation path 6. And has an inlet 11a and an outlet 11b. The inlet 11 a of the feed path 11 is connected to the medium supply source 67. The medium supply source 67 is a water supply that supplies pressurized water at room temperature, for example, and includes a medium supply valve 68 such as a faucet. An inlet 11 a of the feed path 11 is connected to the medium supply valve 68. An outlet 11 b of the feed path 11 is connected to the medium tank 13. The medium supply valve 68 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 66, and the low temperature from the medium supply path 67 is entered into the circulation path 6. Supply 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 66. At this time, a medium at the same temperature as the medium discharged from the medium tank 13 to the drain 66 flows from the medium supply valve 68 through the feed path 11 in the direction of the arrow B2 and is supplied to the medium tank 13. By supplying a medium temperature medium from the medium supply valve 68 to the medium tank 13, the temperature of the medium in the medium tank 13 is lowered.

  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 control waiting timer 26 and a pressure release timer 27. The temperature control waiting timer 26 and the pressure release timer 27 can measure time independently of each other.
The control device 12 further includes a cooling lamp 28 and a heating lamp 29. The cooling lamp 28 indicates that the medium is being cooled by the cooler 3. The heating lamp 29 indicates that the medium is being heated by the heater 7.

The control device 12 can execute a temperature control mode for controlling the temperature of the medium in the circulation path 6 and a pressure relief mode for releasing the pressure in the circulation path 6. These temperature control mode and pressure relief mode can be executed simultaneously.
FIG. 2 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.

In the temperature control mode, first, the pump 17 is turned on by the control device 12 (S1), and the medium in the medium tank 13 is sent to the lower supply path 142 of the circulation path 6. As a result, the medium moves along the arrow A direction in the lower supply path 142 and the mold 2.
After the pump 17 is turned on, the temperature control wait timer 26 is turned on (S2). After the temperature control waiting timer 26 is turned on, it waits until a predetermined waiting time TM ₁ (for example, 5 seconds) elapses (S3: NO), and after the waiting time TM ₁ has elapsed (S3: YES) The controller 12 determines the temperature of the medium in the circulation path 6 (S4).

Specifically, detected by the temperature sensor 18, the temperature TP of the medium circulation path 6 (hereinafter, simply referred to as medium temperature TP.) Or is higher as compared to the predetermined target temperature TP _0, or low, Or it is determined whether they are the same. The target temperature TP ₀ is set before the temperature control mode is executed, for example, by operating a control panel (not shown) of the control device 12.
When it is determined that the medium temperature TP is lower than the target temperature TP ₀ (S4: TP <TP ₀ ), the medium in the circulation path 6 is heated. Specifically, the electromagnetic valve 10 is closed by the control device 12 (S5). Thereby, the first state in which the movement of the medium in the discharge path 9 and the feed path 11 is not allowed is realized, and the medium in the medium tank 13 is not cooled by the medium supply medium 67 being supplied from the medium supply source 67. . Next, the cooling lamp 28 is turned off (S6), and the operator is notified that the medium in the medium tank 13 is not cooled.

Next, the control device 12 determines whether or not the medium temperature TP is lower than a predetermined protection temperature TP ₁ (S7). Protection temperature TP ₁ may, for example, the circulation path is a permissible temperature of the medium in the 6, is set higher than the target temperature _{TP 0 (TP 0 <TP 1} ).
When the medium temperature TP is protected temperature TP ₁ or more (S7: NO), it waits until the medium temperature TP is lower than the protection temperature TP _1. On the other hand, when the medium temperature TP is lower than the protection temperature TP ₁ (S7: YES), the controller 7 turns on the heater 7 (S8). Thereby, the medium in the circulation path 6 is heated and the medium temperature TP rises. After the heater 7 is turned on, the heating lamp 29 is turned on (S9). This notifies the operator that the medium is heated. After the heating lamp 29 is turned on, the process returns to S4, and the medium temperature TP is determined again.

In S4, when it is determined that the medium temperature TP exceeds the target temperature _{TP 0 (S4: TP> TP} 0), medium circulation path 6 is cooled. Specifically, the heater 7 is turned off by the control device 12 (S10). Thereby, the medium in the circulation path 6 is not heated by the heater 7. Next, the heating lamp 29 is turned off (S11), and the operator is notified that the medium is not heated by the heater 7.

  After the heating lamp 29 is turned off, the electromagnetic valve 10 is opened by the control device 12 (S12). As a result, a second state in which movement of the medium in the discharge path 9 and the feed path 11 is allowed is realized, and the medium is discharged from the medium tank 13 to the drain 66 through the discharge path 9 and from the medium supply valve 68. A medium temperature medium is supplied to the medium tank 13 through the feed path 11. As a result, the medium in the medium tank 13 is cooled. Next, the cooling lamp 28 is turned on (S13), and the operator is notified that the medium in the medium tank 13 is being cooled. After turning on the cooling lamp 28, the process returns to S4, and the medium temperature TP is determined again.

In S4, when it is determined that the medium temperature TP is equal to the target temperature _{TP 0 (S4: TP = TP} 0), the medium tank by medium from the heating medium in the medium tank 13 by the heater 7, and the medium supply source 67 Both cooling of the medium in 13 is stopped. Specifically, as described in S5, the electromagnetic valve 10 is closed by the control device 12 (S14), the first state is realized, and the medium in the medium tank 13 is not cooled. Become. Further, the cooling lamp 28 is turned off (S15), and the operator is notified that the medium in the medium tank 13 is not cooled.

  Next, as described in step S <b> 10, the heater 7 is turned off by the control device 12 (S <b> 16), so that the medium in the circulation path 6 is not heated by the heater 7. Next, the heating lamp 29 is turned off (S17), and the operator is notified that the medium is not being heated by the heater 7. After the heating lamp 29 is turned off, the process returns to S4, and the medium temperature TP is determined again.

FIG. 3 is a flowchart for explaining the flow of control in the pressure relief mode. With reference to FIGS. 1 and 3, the pressure relief mode will be described.
In the pressure relief mode, first, the pump 17 is turned on by the control device 12 (R1), and the medium in the medium tank 13 is sent to the lower supply path 142 of the circulation path 6. As a result, the medium moves in the circulation path 6 and the mold 2 along the arrow A direction.

After the pump 17 is turned on, the medium temperature TP is equal to or a predetermined reference temperature TP ₂ or less is determined (R2). Reference temperature TP ₂ is set to a value lower than the target temperature TP _0, for example, is set to 5 ° C. lower than the target temperature _{TP 0 (TP 2 = TP 0} -5).
When the medium temperature TP is higher than the reference temperature TP _2: to (R2 NO), it waits until the medium temperature TP is the reference temperature TP ₂ or less. On the other hand, when the medium temperature TP is equal to or lower than the reference temperature TP ₂ (R2: YES), the pressure release timer 27 is turned on (R3). Wait until the waiting time TM ₂ (for example, 30 seconds) as a predetermined time elapses after the pressure release timer 27 is turned on (R4: NO), and wait time after the pressure release timer 27 is turned on. after the TM ₂ has elapsed (R4: YES), the electromagnetic valve 10 is opened momentarily (R5), cooling the lamp 28 is turned on (R6). The moment at this time is, for example, the time for which the solenoid valve 10 is opened by giving a signal for opening the solenoid valve 10 to the solenoid valve 10 for one pulse, and is about several milliseconds.

When the solenoid valve 10 is opened for a moment, a part of the medium in the medium tank 13 of the circulation path 6 moves to the discharge path 9 through the float switch tank 8 and the like, and is discharged to the drain 66. Thereby, the medium pressure P in the circulation path 6 falls. Further, when the medium is pushed out to the discharge path 9, a part of the medium in the feed path 11 moves from the feed path 11 to the medium tank 13, and mixes with the medium in the medium tank 13, so that the inside of the circulation path 6. The medium temperature TP decreases slightly. As the solenoid valve 10 is closed, the cooling lamp 28 is turned off (R7), and the pressure release timer 27 is reset (R8). After depressurizing timer 27 is reset, the process returns to R2, whether the medium temperature is the reference temperature TP ₂ or less is determined again.

With the above flow, when the medium temperature TP of the reference temperature TP ₂ below, each time the predetermined waiting time TM ₂ has elapsed, the electromagnetic valve 10 is opened momentarily. As a result, the first state is switched to the second state for a moment, and the medium pressure P in the circulation path 6 is released. Moreover, since the solenoid valve 10 is closed immediately after being opened and is switched from the second state to the first state, the amount of decrease in the medium temperature TP in the circulation path 6 is small.

FIG. 4 is a graph showing an example of the relationship between the elapsed time TM from the start of execution, the medium temperature TP, and the medium pressure P in the circulation path 6 when the temperature control mode and the pressure relief mode are executed simultaneously.
As shown in FIGS. 1 and 4, the elapsed time TM is until after the waiting time TM ₁ temperature control waiting timer 26, the medium temperature TP remains normal temperature TP _3. On the other hand, the pressure P of the medium in the circulation path 6 (hereinafter simply referred to as the medium pressure P) indicates the normal pressure P ₁ when the pump 17 is driven.

When the elapsed time TM is past the waiting time TM _1, the heating medium by the heater 7 is started, the medium temperature TP is gradually linearly increased. Thereby, the medium in the circulation path 6 expands thermally, and the medium pressure P increases linearly. Then, when the elapsed time TM = TM ₁ + TM ₂ , the solenoid valve 10 is opened for a moment. Thus, the medium pressure P drops steeply from _{P 2} to _{P 3.} Note that the medium pressure _{P 3} is greater than atmospheric pressure _{P 1 (P 3> P 1} ). Further, since a part of the normal temperature of the medium in the feed path 11 is pushed out in the medium tank 13, the medium temperature TP is lowered slightly from the predetermined temperature TP _4.

Thereafter, the medium temperature TP and the medium pressure P rise linearly by the heating of the heater 7 and the thermal expansion of the medium in the circulation path 6 accompanying the heating of the heater 7. When the elapsed time TM = TM ₁ + (2 × TM ₂ ), that is, when the waiting time TM ₂ has elapsed after the electromagnetic valve 10 has been opened for a moment, the electromagnetic valve 10 is again opened for a moment. Thus, the medium pressure P drops _{P 3} from _{P 2} again. Further, since a part of the medium in the feed path 11 is pushed out into the medium tank 13, the medium temperature TP slightly decreases from the predetermined temperature TP ₅ .

Thereafter, the medium temperature TP and the medium pressure P rise linearly by the heating of the heater 7 and the thermal expansion of the medium in the circulation path 6 accompanying the heating of the heater 7. When the elapsed time TM = TM ₁ + (3 × TM ₂ ), that is, when the waiting time TM ₂ has elapsed after the electromagnetic valve 10 has been opened for a moment, the electromagnetic valve 10 is again opened for a moment. Thus, the medium pressure P drops _{P 3} from _{P 2} again. Further, since a part of the medium in the feed path 11 is pushed out into the medium tank 13, the medium temperature TP slightly decreases from the predetermined temperature TP ₆ .

Thereafter, the medium temperature TP and the medium pressure P rise linearly by the heating of the heater 7 and the thermal expansion of the medium in the circulation path 6 accompanying the heating of the heater 7. When the elapsed time TM = TM ₁ + (4 × TM ₂ ), that is, when the waiting time TM ₂ has elapsed after the electromagnetic valve 10 has been opened for a moment, the electromagnetic valve 10 is again opened for a moment. Thus, the medium pressure P drops _{P 3} from _{P 2} again. Further, since the part of the medium in the feed path 11 is pushed out in the medium tank 13, the medium temperature TP is lowered slightly from the predetermined temperature TP _7, the reference temperature TP ₂ are exceeded.

As a result, when the elapsed time TM = TM ₁ + (4 × TM ₂ ), the medium temperature TP exceeds the reference temperature TP ₂ , so that the pressure release mode in the circulation path 6 by intermittent driving of the electromagnetic valve 10 is performed. Stopped. After that, heating of the heater 7 is continued, the medium temperature TP when the elapsed time TM = predetermined time TM ₃ reaches the target temperature TP _0, the heater 7 is turned off.
After that, since the medium temperature TP in such remaining heat of the heater 7 is increased, the medium temperature TP is greater than the target temperature TP _0. At this time, when the electromagnetic valve 10 is opened, the medium in the medium tank 13 is discharged to the discharge path 9 and the medium from the feed path 11 is supplied to the medium tank 13. Thereby, the medium temperature TP in the circulation path 6 falls.

Thus, when the medium temperature TP exceeds the target temperature TP ₀ , the medium temperature TP in the circulation path 6 is lowered by the medium from the feed path 11. On the other hand, when the medium temperature TP falls below the target temperature TP ₀ , by closing the solenoid valve 10, the medium flow in the discharge path 9 and the medium flow in the feed path 11 are stopped, and the medium from the feed path 11 is removed. The medium temperature TP in the circulation path 6 is raised by the heater 7 while preventing it from flowing into the medium tank 13. Such temperature increase and decrease are performed when the elapsed time TM is between TM ₃ and TM ₁ + (6 × TM ₂ ).

When the elapsed time TM = TM ₁ + (6 × TM ₂ ) elapses, the medium temperature TP converges to the target temperature TP ₀ , and both the heating and cooling of the medium in the circulation path 6 are stopped. At this time, the medium temperature P also converges to a predetermined pressure P _0.
As described above, according to the present embodiment, the solenoid valve 10 can be intermittently driven by executing the pressure relief mode, and thereby the medium pressure P in the circulation path 6 can be released. it can. Thereby, the medium pressure P of the medium which became high pressure in the circulation path 6 by the heating of the heater 7 can be reliably reduced.

Further, the timing for driving the electromagnetic valve 10 can be set without depending on the medium pressure P. Unlike the case where the pressure is released using a relief valve that opens when a predetermined set pressure is exceeded, according to the present embodiment, the hunting phenomenon of the medium pressure P in the circulation path 6 due to the drive of the electromagnetic valve 10 is reliably suppressed. The medium pressure P can be made more stable.
Furthermore, the medium pressure P can be lowered by letting the medium in the circulation path 6 escape to the discharge path 9. The solenoid valve 10 can be used as a switching valve for switching between the first and second states and can also be used as a pressure relief valve for releasing the medium pressure P. Therefore, the number of parts of the mold temperature control device 4 can be reduced, and manufacturing can be performed. Cost is low.

Further, since the temperature control mode and the pressure relief mode can be executed at the same time, an operation of bringing the medium temperature TP in the circulation path 6 close to the target temperature TP ₀ and an action of releasing the medium pressure P in the circulation path 6 are performed. Can be done simultaneously. Thus, the medium temperature TP of the circulation path 6 can be quickly brought close to the target temperature TP _0.
Further, in the pressure relief mode, the medium temperature TP is only when the reference temperature TP ₂ below, each time the elapsed waiting time TM ₂ in depressurization timer 27, thereby intermittently driving the solenoid valve 10.

When the large temperature rise of the medium by heating of the heater 7 since the medium temperature TP is the reference temperature TP ₂ or less, that is, when a large increase in the width of the medium pressure P, the medium pressure in the circulation path 6 by the solenoid valve 10 Let P escape.
On the other hand, when the rise of the medium temperature TP by heating of the heater 7 from the medium temperature TP is larger than the reference temperature TP ₂ is reduced, when that is rise of the medium pressure P becomes small, the solenoid valve 10 Is not driven. Thus, since the solenoid valve 10 is driven only when the medium pressure P needs to be released, the amount of energy released in the circulation path 6 can be minimized, and the energy utilization efficiency can be increased.

The reference temperature TP ₂ is set lower than the target temperature TP _0. According to such a configuration, the medium temperature TP of the circulation path 6 is the same as or target temperature TP _0, when in the vicinity of the target temperature TP _0, since not the depressurization Kiga circulation passage 6 by the solenoid valve 10, energy circulation passage 6 can be prevented from being reduced inadvertently, easy to maintain the medium temperature TP of the circulation path 6 to the target temperature TP _0.

Further, when the reference temperature TP ₂ is lowered by about 5 ° C. with respect to the target temperature TP ₀ , the medium temperature TP has only a narrow fluctuation range of about 5 ° C. before reaching the target temperature TP ₀ from the reference temperature TP _2. Does not fluctuate. That is, until the medium temperature TP reaches the reference temperature TP ₂ to the target temperature TP _0, the medium pressure P does not vary much. Therefore, since the medium pressure P hardly fluctuates until the medium temperature TP reaches the target temperature TP ₀ after the pressure relief mode is not executed, the medium pressure P does not become too high.

  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, the medium supply valve 68 may be opened / closed in accordance with the on / off of the medium supply from the feed path 11 to the medium tank 13.

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 flowchart for demonstrating the flow of control in temperature control mode. It is a flowchart for demonstrating the flow of control in a pressure relief mode. It is a graph which shows an example of the relationship between the elapsed time from the start of execution, the medium temperature, and the medium pressure in the circulation path when the temperature control mode and the pressure relief mode are executed simultaneously.

Explanation of symbols

2 Mold 4 Mold temperature control device 6 Circulation path 7 Heater 9 Discharge path 10 Solenoid valve (pressure relief valve, switching valve)
11 Feeding path 12 Control device (control means)
14 Supply path 15 Return path 18 Temperature sensor P Medium pressure (pressure in the circulation path)
TM ₂ waiting time (predetermined time)
TP medium temperature TP ₁ target temperature TP ₂ reference temperature

Claims (5)

A supply path for supplying a medium for adjusting the temperature of the mold to the mold, and a return path for returning the medium from the mold, and a circulation path for circulating the medium to the mold;
A heater for heating the medium in the circulation path;
A pressure relief valve connected to the circuit and capable of relieving pressure in the circuit;
A mold temperature control device comprising: a control means for releasing the pressure in the circulation path by driving the pressure relief valve every time a predetermined time elapses. A discharge path for discharging the medium in the circulation path, and a feed path for sending the medium having a temperature equal to or lower than the temperature of the medium in the circulation path to the circulation path;
A switching valve that switches between a first state that does not allow movement of the medium to the discharge path and a second state that allows movement of the medium to the discharge path;
The pressure relief valve is constituted by the switching valve,
2. The mold temperature control according to claim 1, wherein the control means releases the pressure in the circulation path by driving the switching valve so as to switch from the first state to the second state. apparatus. The control means can execute a pressure relief mode for releasing the pressure in the circulation path and a temperature control mode for controlling the temperature of the medium in the circulation path,
The pressure relief mode is a mode in which the pressure in the circulation path is released by driving the pressure relief valve every time a predetermined time elapses.
In the temperature control mode, the heater is turned on when the temperature of the medium is lower than a predetermined target temperature, and the heater is turned off when the temperature of the medium exceeds a predetermined target temperature. Mode
The mold temperature control apparatus according to claim 1, wherein the control unit can simultaneously execute the pressure relief mode and the temperature control mode. A temperature sensor for detecting the temperature of the medium in the circulation path;
4. The control device according to claim 1, wherein the control unit drives the pressure relief valve every time the predetermined time elapses only when the temperature detected by the temperature sensor is equal to or lower than a predetermined reference temperature. The mold temperature control apparatus in any one.   The mold temperature control apparatus according to claim 4, wherein the predetermined reference temperature is set lower than a target temperature of the medium in the circulation path.

Images