JP2009226878A - Method and apparatus for mold heating and cooling control - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and an apparatus for mold heating and cooling control, which allow inhibiting a fall in steam temperature accompanying a continuous fall of steam pressure in a boiler from the start of boiler steam delivery to the ignition of burner. <P>SOLUTION: Steam temperature control in a steam generating and supplying device is made in cooperation with a molding operation of an injection molding apparatus, when using steam as a mold heating medium in a molding process of the molding apparatus, in which temperature of a mold 11 is raised rapidly before injection molding a molten resin material into the mold 11, and cooled to at solidification temperature or below after injection. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to temperature control of a mold used in an injection molding machine or the like that uses steam generated by a boiler as a heating medium, and more particularly to a timing control method for ignition of a boiler corresponding to a mold heating and cooling process, and the control method. It is related with the temperature control apparatus which can be used.

  Conventionally, in a mold heating / cooling molding method, when a boiler is used for mold heating, when the steam pressure of the boiler reaches a predetermined pressure (temperature), the main burner is extinguished and heating is stopped. ing. After the die heating restart signal is output, the boiler is ignited after the pressure in the boiler has decreased, and heating is resumed. Thus, the fire extinguishing and ignition of the boiler burner are controlled by the steam pressure (temperature) of the boiler regardless of the molding process of the molding machine.

For example, a conventional mold heating / cooling molding machine system shown in Patent Document 1 is a mold for a molding machine including a heating medium supply unit and a cooling medium supply unit, and supplies the heating medium to the mold. The mold is heated to a set temperature, and the molten resin is filled into the mold cavity. The set temperature is maintained, and after a certain time, the heating medium in the mold is switched to the cooling medium and cooled below the solidification temperature of the resin material, and the temperature control cycle ends.
The heating medium supply unit supplies steam using a boiler, and the cooling medium supply unit supplies cold water using a chilling tower. The media of both units are temperature controlled independently of the molding process of the molding machine.
Japanese Patent Laying-Open No. 2007-83502 (FIG. 1)

  In the heating / cooling molding cycle, steam is intermittently supplied, so the boiler repeatedly stops supplying steam. For this reason, when a boiler starts steam discharge, the steam pressure in a boiler will fall. In a normal boiler, when the steam pressure in the boiler reaches a predetermined lower limit pressure value, the main burner ignition process starts.

  The steam pressure in the boiler continues to decrease during the period from when the boiler starts to discharge steam to ignite the main burner due to mold heating, but after the main burner ignites, the temperature in the boiler rises to a predetermined temperature. Return. However, in actual operation, the time required from the start of steam discharge to main burner ignition varies greatly depending on the steam pressure and discharge steam volume before steam discharge, and the degree of decrease in steam temperature in the boiler is not constant. . As a result, the time until the temperature in the boiler returns to a predetermined temperature is not constant, and the molding cycle time varies, causing molding defects.

  In the present invention, when the mold is heated using the steam generated by the boiler as a heating medium, the steam pressure in the boiler as described above continues to decrease during the period from the start of steam discharge to the burner ignition. It is an object of the present invention to provide a mold heating / cooling control method and apparatus relating to fuel ignition control capable of suppressing the accompanying decrease in steam temperature.

With respect to the above problems, the present invention aims to solve the problems by the following means.
(1) The mold heating / cooling control method of the first means is an injection molding machine that rapidly raises the temperature of the mold before injection molding the molten resin into the mold and cools it to the solidification temperature or less after injection. In this molding method, when steam is used as the mold heating medium, steam temperature control in the steam supply circuit is performed in cooperation with the molding process of the injection molding machine.

(2) The mold heating / cooling control method of the second means is characterized in that, in the mold heating / cooling control method of (1), the steam generation and supply device is a boiler.

(3) The mold heating / cooling control method of the third means is characterized in that the boiler ignition process of (2) is started by time-up of a mold heating start signal or a timer started by the heating signal. And
(4) The mold heating / cooling control method of the fourth means is characterized in that the boiler ignition process of (2) is started when the steam pressure of the boiler falls below a predetermined value.

(5) In the mold heating / cooling control method of the fifth means, the fire extinguishing of the boiler main burner of the above (2) to (4) is that the internal pressure or temperature of the boiler has reached a predetermined value, and Alternatively, the present invention is characterized in that the heating end timing of the mold is reached under the molding operation setting conditions.
(6) The mold heating / cooling control method of the sixth means is characterized in that the steam heating in (2) is performed only by turning on / off the fuel supply of the main burner without extinguishing the boiler fire. To do.

(7) A mold heating / cooling control device according to a seventh means includes a backflow prevention valve provided at an outlet portion of the boiler in a steam supply circuit used in the mold heating / cooling control method according to (2) to (6) above. And a pipe branching from the steam pipe from the backflow prevention valve to the mold, and steam is discharged from the boiler by the mold heating start signal, and the pressure or temperature in the boiler decreases. Then, the accumulator that can suppress the pressure in the pipe from being lowered by discharging the steam stored in advance into the pipe before the main burner ignites and the boiler internal pressure or temperature reaches a predetermined value. It is characterized by having.

(8) The mold heating / cooling control apparatus according to the eighth means is the mold heating / cooling control apparatus according to (7), wherein the accumulator installed in the steam piping of the steam supply circuit holds temperature or pressure. A heater and a temperature sensor or a pressure sensor are installed, and the temperature or pressure of the accumulator is controlled to be a set value.

(9) The mold heating / cooling control method of the ninth means uses the mold heating / cooling control apparatus provided with the accumulator according to the above (7) to (8), and the boiler ignition process according to the mold heating start signal. At the same time, the steam in the accumulator is discharged into the pipe to suppress the pressure drop in the pipe, and when the steam temperature in the boiler or the pressure exceeds the temperature in the accumulator or the pressure The steam is controlled so as to be discharged into the mold.

(10) A mold heating / cooling control device according to a tenth means includes a steam pipe that is directed to the mold from the boiler to the steam supply circuit used in the mold heating / cooling control method according to (2) to (6) above. A backflow prevention valve and an accumulator are installed in series.

(11) The mold heating / cooling control apparatus according to the eleventh means is the mold heating / cooling control apparatus according to (10), wherein the accumulator maintains the temperature of the steam discharged from the boiler at a predetermined temperature. And a pressure sensor or a temperature sensor, and the amount of heating is controlled so as to maintain the temperature of the steam at a predetermined temperature.

  The invention according to claims 1 to 5 is the mold heating / cooling control method of the first to fifth means, instructing the ignition of the boiler fire simultaneously with the mold heating start signal of the molding machine. As a result, the delay in the main burner ignition timing seen in the automatic temperature adjustment of the steam temperature generated by the boiler alone can be shortened, and the steam pressure rises faster, thus reducing the pressure (temperature) in the boiler due to steam discharge. Since it can be suppressed, the mold temperature raising time can be shortened and variation can be suppressed.

  The invention according to claim 6 is the mold heating / cooling control method of the sixth means described above, and it is carried out only by turning on / off the fuel supply of the main burner without extinguishing the boiler fire. The time required for ignition is unnecessary, and the main burner can be ignited in the shortest time. Accordingly, a decrease in boiler pressure (temperature) due to steam discharge can be minimized, so that the mold heating time can be shortened and variations can be suppressed.

  The invention according to claims 7 to 9 is a mold heating / cooling control device of the seventh to ninth means and a method using the mold heating / cooling control device, and from the boiler by a mold heating start signal. In response to the discharge of steam and the pressure or temperature in the boiler decreasing, the main burner ignites and the steam in the accumulator is passed through the pipe until the boiler internal pressure or temperature reaches a predetermined value. Therefore, the pressure and temperature drop of the steam supplied to the mold can be reduced, and the mold heating time can be shortened and the variation can be suppressed.

  The invention related to claims 10 to 11 is a mold heating / cooling control device of means 10 to 11, and the pressure drop of the boiler is caused by the steam discharged from the boiler and the pressure drop stored in the accumulator to the steam in the mold. Propagation can be suppressed, and the temperature drop of the steam in the mold can be minimized.

  In mold heating control using a boiler for heating molds such as injection molding machines, it is possible to minimize the amount and time of temporary steam pressure or temperature drop that occurs when heating is performed rapidly. Three embodiments of a mold heating / cooling control method relating to boiler ignition timing control and a mold heating / cooling control apparatus capable of using this control method will be described below. The molds illustrated in these embodiments are omitted from the drawings of the resin injection passage, the injection unit, and the like, and the control method related to the configuration of the boiler and the heating medium circuit and the heating process of the molding machine will be described.

(First embodiment)
A first embodiment will be described with reference to the drawings. FIG. 1 is a schematic diagram of a mold heating circuit capable of controlling the steam supply circuit according to the first embodiment, and FIG. 2 is a schematic diagram of the mold heating circuit of FIG. FIG. 3 is a diagram showing the steam temperature generated from the boiler with respect to time when heating, FIG. 3 is a boiler with respect to time when the mold is rapidly heated by the conventional boiler steam temperature control method in the mold heating circuit of FIG. It is a diagram which shows the vapor | steam temperature which generate | occur | produces more.

  In the steam supply circuit 20 of FIG. 1, the pair of molds 11 are in a clamped state, and a mold cavity 12 in which a molded product is molded is formed on the mating surface of the mold 11. The means for heating the mold 11 is a boiler 60 that generates water vapor, and the means for cooling the mold 11 is a cooling water supply circuit 26.

  When the open / close valve 69 is opened, the raw water subjected to the water pressure is softened by removing hard water components from the raw water through the water softener 62, and an anticorrosive agent or the like is injected from the medicine injector 61 through the pipe 64 in the middle of the pipe 71. To the boiler 60. In the boiler 60, soft water is heated to generate steam.

  The steam temperature T of the steam generated in the boiler 60 is detected by a temperature sensor T1 installed in the steam pipe (or the steam pressure P1 is detected by the pressure sensor 19), and the steam temperature T is a mold temperature control device. Compared with the set temperature upper limit TH of the water vapor stored in the boiler temperature (pressure) control circuit 81 of 30, the fuel supply valve 68 is turned on / off to send fuel to the main burner 65, and the switch for heating ignition (seeking ignition) Switch) 76 is turned on / off and main burner 65 is ignited or extinguished to control the steam temperature to the set temperature upper limit TH, but converted from steam pressure P1 detected by pressure sensor 19 The temperature may be the steam temperature T.

  A boiler steam temperature control method for reducing the drop in the steam temperature T when the mold is rapidly heated in the mold heating circuit of FIG. 1 will be described with reference to FIGS. FIG. 2 is a diagram showing the steam temperature T generated from the boiler with respect to time, controlled by the temperature control method according to the first to sixth aspects, and FIG. 3 shows a conventional boiler in the mold heating circuit of FIG. It is a diagram which shows the steam temperature T which generate | occur | produces from the boiler with respect to time when a metal mold | die is rapidly heated with the steam temperature control method.

  As shown in FIG. 3, conventionally, depending on the steam generation capability of the boiler 60, when the heating and cooling molding cycle is repeated, steam is intermittently supplied, so the boiler 60 repeatedly stops supplying steam. For this reason, when the boiler 60 starts discharging the steam, the steam pressure of the steam adjusted to the set temperature upper limit TH in the boiler 60 decreases. In normal boiler pressure (temperature) control, when the steam pressure (temperature) in the boiler reaches a predetermined lower limit pressure value (set temperature lower limit TL), boiler ignition processing (fuel supply start, seed ignition ignition processing) Starts, the main burner 65 is ignited, the steam temperature in the boiler 60 starts to rise, the set temperature upper limit TH is reached, and the main burner 65 is extinguished.

  In the present invention, in order to reduce the temperature drop of the steam when the boiler 60 starts the steam discharge, the timer 83 that is started by the mold heating start signal or the heating start signal emitted from the injection molding process circuit 80 is used. The ignition process of the boiler 60 is started when the time is up or when the steam pressure falls below a predetermined value.

  In the fire extinguishing of the main burner 65 of the boiler 60, the internal pressure of the boiler 60 or the steam temperature has reached the set temperature upper limit TH, which is a predetermined value, and / or the heating of the mold 11 is finished in the injection molding process circuit 80. This is performed on the condition that the time point (resin holding of resin has been completed) has been reached. The ignition of the main burner 65 may be performed only by turning on / off the fuel supply valve 68 for fuel supply without turning off the ignition plug 66 for ignition of the main burner, which is the seed of the boiler 60.

  The cooling water supply circuit 26 sucks up the cooling water stored in the cooling water tank 25 by the pump 27 and supplies it to the mold 11. The high-temperature cooling water discharged from the mold 11 is cooled by the cooling tower 48 and returned to the cooling water tank 25. The cooling water tank 25 is provided with a water level gauge, and when it is detected by the water level gauge that the water level has fallen by a certain value or more, water is supplied from the on-off valve 56.

  The mold temperature control device 30 includes a mold heating circuit 82 that controls the steam 11 to be rapidly heated by switching steam, a mold cooling circuit 84 that switches to cooling water to cool the mold 11, A heating / cooling transition circuit 85, a steam boiler temperature (pressure) circuit 81 generated by the boiler 60, and a timer 83 for adjusting the ignition timing of the main burner 65 are provided.

  The mold heating control action will be described. At the start of heating, the mold heating circuit valve 45, the on-off valve 55, and the on-off valve 72 are opened, and water vapor as a heat medium is supplied to the in-mold heat medium flow path 11a of the mold 11 through the steam pipe 35. Is heated and the molten resin is injected. At this time, the steam discharged from the mold 11 is mixed with the cooling water supplied through the on-off valve 72 in the mixer 90 to lower the temperature, and then flows into the cooling tower 48. When the resin temperature in the mold cavity 12 (the temperature of the surface of the mold cavity 12 detected by the temperature sensor TM) has passed a predetermined temperature or the time determined from the actual measurement, the mold heating circuit valve 45 and the on-off valve 55 is closed and the supply of steam is stopped, and after holding for an appropriate time, the on-off valve 49 and the on-off valve 55 are opened and switched to cooling water to cool to below the solidification temperature of the resin.

  After confirming that the temperature sensor TM on the surface of the mold cavity 12 has fallen below the resin solidification temperature, the open / close valve 49 of the cooling water supply pipe 39 is closed and the open / close valve 55 is open, and the air supply is opened / closed. Opening the valve 51 to expel the cooling water in the heat medium passage 11a in the mold and emptying it means that the amount of heat of the steam supplied to the heat medium passage 11a in the mold in the next step is taken by the cooling water. It is effective for preventing and saving energy.

Using a test mold, the mold was rapidly heated using a boiler, and the temperature drop state of the steam generated in the boiler and the ignition delay time were measured. The injection molding machine used was an injection molding machine with a clamping force of 450 tons, the mold used was a car center panel mold, and the boiler used was a boiler with a steam generation amount of 500 kg / h. The test results are shown in Table 1. As can be seen from Table 1, the ignition delay time t1 of the main burner and the temperature return time t2 until the steam temperature in the boiler returns to the set value are clearly shortened, and the temperature drop ΔT in the boiler is suppressed. It can be seen that the present invention is effective.

(Second Embodiment)
A second embodiment will be described with reference to a schematic diagram of a mold heating circuit capable of controlling the steam supply circuit of FIG. The control method of the steam supply circuit 70 of the second embodiment is different from the control method of the steam supply circuit 20 of the first embodiment described above in that the accumulator 50 is arranged in parallel with the steam generation supply device (boiler 60). Since the cooling device and the like other than the accumulator 50 are the same as those in the first embodiment and the mold heating / cooling control method is the same, the common parts are numbered using the same numbers. Descriptions other than those related to 60 and the accumulator 50 are omitted.

  A backflow prevention valve 17 is provided at the outlet of the same boiler 60 as in the first embodiment, and an accumulator 50 is installed in parallel at a pipe branch that branches from the steam pipe 35 directed from the backflow prevention valve 17 to the mold 11. In this accumulator 50, the steam in the boiler 60 is discharged in response to the mold heating start signal, the steam temperature and pressure in the boiler 60 are once lowered, the main burner 65 is ignited, and the internal pressure or temperature of the boiler 60 is changed to the accumulator. The accumulator has a capacity capable of supplying steam only until the internal pressure of 50 or the temperature is exceeded.

  The accumulator 50 is provided with a heat retaining heater 50a and a temperature sensor T1 for holding temperature or pressure, or a pressure sensor (not shown), and the temperature of steam in the accumulator 50 (measured value of the temperature sensor T1). Is compared with the set temperature of the steam in the boiler 60 (measured by the temperature sensor T0), and both measured values are controlled to be the same. Further, the heat loss may be suppressed by surrounding the outer periphery of the accumulator 50 with a heat insulating material 50b.

  FIG. 4 illustrates a heat retaining heater 50a such as an electric heater for maintaining the steam temperature in the accumulator 50. The temperature detected by the temperature sensor T1 is compared with the set temperature, and the current sent from the power source 44 is supplied by the heat retaining heater switch 75. Although the temperature of the temperature sensor T1 is controlled to be turned ON / OFF, other heating methods such as current induction heating, heat pump heating, and microwave heating may be used without being limited to the electric heater.

  In the mold heating control method using the steam supply circuit 70 provided with the accumulator 50 and the mold temperature control device 40, when the steam pressure in the boiler 60 decreases, the steam in the accumulator 50 is discharged into the mold 11. Heating of the mold 11 is started. Thereafter, when the temperature or pressure of the steam in the boiler 60 exceeds the pressure of the steam in the accumulator 50, the heating steam of the boiler 60 is supplied to the mold 11.

(Third embodiment)
A third embodiment will be described with reference to a schematic diagram of a mold heating circuit capable of controlling the steam supply circuit of FIG. The steam supply circuit 79 of the third embodiment is different from the steam supply circuit 70 of the second embodiment described above in that the backflow prevention valve 17 is connected in series to the steam pipe 35 from the boiler 60 to the mold 11. It is that the accumulator 50 is installed, and other than this is the same as the second embodiment, and the mold heating / cooling control method is also the same. Descriptions other than those related to the accumulator 50 are omitted.

  In FIG. 5, a pressure reducing valve 16, a backflow prevention valve 17, and an accumulator 50 are installed in series with a steam pipe 35 from the boiler 60 toward the mold 11. The mold heating circuit valve 45 is opened by the mold heating start signal, and the steam in the boiler 60 is discharged toward the mold 11 while being stored in the accumulator 50. Even if the steam temperature and pressure in the boiler 60 are once reduced due to the discharge of steam, the steam does not flow back from the accumulator 50 side by the backflow prevention valve 17 and the steam stored in the accumulator 50 causes the boiler to flow. Since the pressure drop of 60 can be prevented from propagating to the steam in the mold 11, the temperature drop of the steam in the mold 11 can be minimized.

  If the pressure reducing valve 16 is provided between the boiler 60 and the accumulator 50 as shown in FIG. 5, the steam pressure in the boiler 60 can be set higher than the predetermined pressure supplied to the mold 11 by the pressure reducing valve 16. Due to the pressure difference between the upstream side and the downstream side of the pressure reducing valve 16, the amount of decrease in the steam pressure of the boiler 60 can be absorbed, and the amount by which the steam pressure supplied to the mold 11 decreases below a predetermined pressure can be reduced. Therefore, even better.

  The accumulator 50 is provided with a heat retaining heater 50a and a temperature sensor T1 or a pressure sensor for maintaining temperature or pressure, and both measurements are made in comparison with the set temperature of steam in the boiler 60 (measured by the temperature sensor T0). The values are controlled to be the same. The outer periphery of the accumulator 50 may be surrounded by a heat insulating material 50b to suppress heat loss. The heater of the accumulator 50 is not limited to the electric heater, and other heating methods such as current induction heating, heat pump heating, and microwave heating may be used.

  Since the present invention mainly focuses on temperature control during the injection molding cycle, the configuration of each part of the steam supply circuits 20, 70, 79 is not intended to be limited to the above, and can be changed as appropriate. Is allowed. In addition to this, as long as it does not deviate from the intention of the present invention, the configuration described in the above embodiment can be selected or changed to another configuration as appropriate.

It is a schematic diagram of the metal mold | die heating circuit in which the control method of the steam supply circuit concerning the 1st Embodiment of this invention is possible. FIG. 2 is a diagram showing the steam temperature generated by the boiler with respect to time when the mold is rapidly heated by the boiler steam temperature control method of the present invention in the mold heating circuit of FIG. 1. FIG. 2 is a diagram showing steam temperature generated from a boiler with respect to time when the mold is rapidly heated by the conventional boiler steam temperature control method in the mold heating circuit of FIG. 1. It is a schematic diagram of the metal mold | die heating circuit in which the control method of the steam supply circuit concerning the 2nd Embodiment of this invention is possible. It is a schematic diagram of the metal mold | die heating circuit in which the control method of the steam supply circuit concerning the 3rd Embodiment of this invention is possible.

Explanation of symbols

11 ... Mold,
12 ... mold cavity,
16 ... pressure reducing valve,
17 ... backflow prevention valve,
19 ... Pressure sensor,
20, 70, 79 ... steam supply circuit,
26: Cooling water supply circuit,
30, 40 ... Mold temperature control device,
35 ... Steam piping,
39 ... Cooling water supply piping,
44 ... Power supply,
45 ... Mold heating circuit valve,
50 ... Accumulator,
60 ... boiler,
65 ... Main burner,
66 ... ignition plug for main burner ignition,
76 ... Switch for heating and ignition,
80 ... injection molding process circuit,
81 ... Boiler temperature (pressure) control circuit,
82 ... Mold heating circuit,
T1 ... temperature sensor (steam),
TM ... Temperature sensor (resin)

Claims (11)

  In the molding method of an injection molding machine that rapidly raises the temperature of the mold before injection molding the molten resin material into the mold and cools to the solidification temperature or less after injection, when using steam as the mold heating medium, A mold heating / cooling control method, wherein steam temperature control in a steam generation and supply device is performed in cooperation with a molding process of an injection molding machine.   The mold heating / cooling control method according to claim 1, wherein the steam generation and supply device is a boiler.   3. The mold heating / cooling control method according to claim 2, wherein the ignition process of the boiler is started by a mold heating start signal or a timer that is started by a heating signal.   3. The mold heating / cooling control method according to claim 2, wherein the ignition processing of the boiler is started when the steam pressure of the boiler falls below a predetermined value.   Fire extinguishing of the main burner of the boiler is characterized in that the boiler internal pressure or temperature has reached a predetermined value and / or that the timing of the end of heating of the mold has been reached in the molding operation setting conditions. The mold heating and cooling control method according to any one of claims 2 to 4.   3. The mold heating / cooling control method according to claim 2, wherein the heating of the steam is performed only by ON / OFF of fuel supply to the main burner without extinguishing the boiler seed.   A steam supply circuit used in the mold heating and cooling control method according to any one of claims 2 to 6, comprising a backflow prevention valve provided at an outlet of the boiler, and a steam from the backflow prevention valve toward the mold It is installed at the end of the pipe branched from the pipe, steam is discharged from the boiler by the mold heating start signal, the main burner is ignited in response to the pressure or temperature in the boiler falling, the boiler internal pressure, or The mold is provided with an accumulator capable of suppressing the pressure in the pipe from being lowered by discharging steam stored in advance into the pipe until the temperature reaches a predetermined value. Heating and cooling control device.   8. The mold heating / cooling control device according to claim 7, wherein a heater and a temperature sensor or a pressure sensor for maintaining the temperature or pressure of the steam are included in the accumulator installed in the steam pipe of the steam supply circuit. A mold heating / cooling control device that is installed and controlled so that the temperature or pressure of the accumulator becomes a set value.   A mold heating / cooling control device including the accumulator according to any one of claims 7 to 8 is used, and a boiler ignition process is started by a mold heating start signal, and steam in the accumulator is simultaneously supplied to the piping. The pressure in the piping is suppressed by discharging into the boiler so that the steam in the boiler is discharged to the mold when the temperature of the steam in the boiler or the pressure exceeds the temperature or pressure in the accumulator A mold heating / cooling control method, characterized by:   In the steam supply circuit used in the mold heating and cooling control method according to any one of claims 2 to 6, a backflow prevention valve and an accumulator are installed in series with a steam pipe from the boiler to the mold. A mold heating / cooling control device characterized by comprising:   11. The mold heating / cooling control device according to claim 10, wherein the accumulator is provided with a heater and a pressure sensor or a temperature sensor for maintaining the temperature of the steam discharged from the boiler at a predetermined temperature. A mold heating / cooling control apparatus, wherein the heating amount is controlled so as to maintain the temperature at a predetermined temperature.

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