JP2006088482A - Multi-point temperature control method in injection molding machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a multi-point temperature control method in an injection molding machine for suppressing the effect due to the difference of heat history on a control target by controlling the temperature rising speeds of the respective zones in the heating cylinder of the injection molding machine even if the target set temperatures of the respective zones are different to allow the temperature rising speeds to arrive at the target set temperatures at the same time. <P>SOLUTION: Sampling times of a plurality of times are provided with respect to the temperature rising speeds in the respective zones of the heating cylinder of the injection molding machine to measure the temperatures of the respective zones and the temperature rising speeds are respectively controlled by setting corrected target temperatures on the basis of the temperature results detected every time to allow the temperature rising speeds to arrive at the target temperatures arbitrarily set of the respective zones. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a temperature increase control method of a multi-point temperature control apparatus in an injection molding machine, and particularly relates to the synchronism of a set target temperature arrival time in each temperature adjustment region (zone).

In general, an injection molding machine is provided with a heating cylinder provided with an injection nozzle at the tip. In order to melt and inject the charged resin material, the heating cylinder is temperature-adjusted so as to have a temperature suitable for the injection nozzle. For example, the heating cylinder is divided into a plurality of temperature adjustment regions (zones), and a heating control unit including a heater and a temperature sensor is provided for each zone to perform multipoint temperature control. Examples of dividing these zones into three include a front portion corresponding to the metering zone, an intermediate portion corresponding to the compression zone, and a rear portion corresponding to the feed zone.
JP 2002-361705 A

  When the heating cylinder of the above-described injection molding machine starts temperature rising simultaneously by the respective heating control units in the above-described three divided zones, for example, arrival times ta and tb as shown in the temperature rising characteristics shown in FIG. , Tc. This difference in arrival time is because the temperature rate is different due to the difference in the heat capacity of the heated part. The problem due to the difference in arrival time is that if the heating cylinder is reheated when the operation is interrupted halfway and the operation is started again, the resin or the like that remains in the heating cylinder is exposed to a high temperature. Depending on the thermal characteristics of the resin, deterioration due to thermal decomposition is prevented and carbonization of the resin and toxic gas are generated.

In view of this, it has been considered to raise the temperature by shifting the temperature rise start timing in each zone so that the arrival time matches the arrival temperature in each zone.
On the other hand, in a multi-point temperature control apparatus for an injection molding machine, a control method for obtaining temporal synchronization with respect to the temperature rising time of each zone has been proposed. For example, Japanese Patent Application Laid-Open No. 2002-361705 discloses a technique in which the target temperature T1 of the heater whose temperature rises most slowly is first matched with another heater target temperature to reach T1, and then the temperature is switched appropriately. Yes.

  The method according to this publication is suitable when the set target values of the heaters are the same temperature, but when the set target temperatures of the respective zones are different, the final arrival times cannot be matched.

  Therefore, the present invention controls the heat history of the controlled object by reaching the same time by controlling the heating rate of the zones even when the target set temperatures of the zones in the heating cylinder of the injection molding machine are different. An object of the present invention is to provide a multi-point temperature control method in an injection molding machine that suppresses the influence due to the difference.

  In order to achieve the above object, the present invention provides a temperature controller for independently calculating and controlling energization rates to heaters respectively arranged at a plurality of heating parts of an injection molding machine, and each heating unit with respect to the temperature controller. Using a temperature control device comprising temperature detecting means for detecting the temperature of the part, a temperature controller for instructing the target temperature of each heating part, and a temperature setting means for setting the target temperature and giving it to the temperature controller And a method of controlling the temperature controller so that the heating times until the target temperatures of the plurality of heating parts are reached are the same, the targets of the heating parts at a predetermined time after the heating start by the heaters. A first step of calculating a deviation between the temperature and the detected temperature of each part and specifying a part corresponding to the maximum deviation among them; and detecting a target temperature at least in the specified heating part A second stage for calculating a deviation from the temperature at each predetermined time after the first stage, and a second stage from the target temperature for each of the other heating parts excluding the specified heating part. A temperature value obtained by subtracting the obtained deviation is calculated as a correction target value of each part at the time, and the correction target value is commanded to the temperature controller, and the deviation becomes zero. A multi-point temperature control method in an injection molding machine is provided, wherein the processes of the second and third stages are repeatedly performed at a sampling time arbitrarily determined as described above.

  According to the present invention, even when the target set temperatures of the zones in the heating cylinder of the injection molding machine are different, the heat history to the controlled body is reached by reaching the same time by controlling the temperature increase rate of the zones. It is possible to provide a multi-point temperature control method in an injection molding machine that suppresses the influence due to the difference between the two.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a diagram showing a schematic configuration of a multipoint temperature control system for an injection molding machine (heating cylinder) for explaining a multipoint temperature control method in an injection molding machine of the present invention.

  In this injection molding machine 1, a temperature adjustment region obtained by dividing the mold 2 and the heating cylinder 3 into a plurality of zones is defined as zones 13 (13a, 13b, 13c, 13d, 13e), and a heater 4 (4a) is provided in each of these zones 13. , 4b, 4c, 4d, 4e) and the temperature sensor 5 (5a, 5b, 5c, 5d, 5e). Further, the injection molding machine 1 includes a temperature controller 6 that adjusts the temperature of the individual heaters 4 by energization rate control, a temperature controller 7 that controls the temperature controller 6 to control the overall temperature, and a temperature controller 7. And a temperature setting unit 8 for setting the target temperature or the corrected target temperature of the heater 4.

  Here, as the heater 4, a heater member with good thermal efficiency such as a ceramic heater is used. If the temperature sensor 5 is a contact type sensor, for example, a thermocouple temperature sensor or the like, or if it is a non-contact type temperature sensor, for example, an infrared temperature sensor or the like can be used. The temperature controller 6 has a known configuration, and is not limited to one that performs PID (proportional, integral, derivative) control. Moreover, the combination of only P, only PI, or only PD may be sufficient.

  The mold 2 is used after being exchanged according to the article to be manufactured. Therefore, unlike the heater 4 in each zone of the heating cylinder 3, the heater 4e attached to the mold 2 may be attached with a heater that generates an optimal amount of heat according to the size of the mold and heat transfer characteristics. If possible, one heater having a large heat generation amount may be used and the heat generation level may be appropriately changed. These heaters are appropriately controlled by previously registering various characteristics such as heating characteristics in the temperature controller 7 so as to follow the control described later.

Next, FIG. 2 shows a functional control block of the temperature controller 7 in the present embodiment and will be described in detail.
The temperature controller 7 includes a data memory 9, a program memory 10, a central processing unit (CPU) 11, a temperature controller 6 and a temperature setting unit 8, and an interface unit (iF) 12 for exchanging control signals and data. It consists of. These parts are connected by a bus line 14, and signal and data are propagated.

  Among these, the program memory 9 stores a processing program (multi-point simultaneous arrival control program) for performing a multi-point temperature control method to be described later. A setting table corresponding to each heater 4 is provided in the data memory 9. This setting table includes, for example, the type of heater, the set target temperatures TG1, TG2, TG3, TG4, TG5 for the heating of the heater, the current detected temperatures DT1, DT2, DT3 of each zone 3 detected by the temperature sensor 5. DT4, DT5, mid-calculation data (deviation value) in which sequential computation is performed on the temperature increase rate (temperature change) until reaching the ultimate temperature, and the corrected target temperature TG1 ′ set each time according to the computation data , TG2 ′, TG3 ′, TG4 ′, and TG5 ′ are provided.

  Next, a multipoint temperature control method in the multipoint temperature control system configured as described above will be described. Here, FIG. 3 is a flowchart showing a sequence in the multipoint simultaneous arrival control program stored in the program memory 9, and FIG. 4 is a setting table exemplifying the temperature rise of the three heaters 4a, 4b, 4c. An example is shown, and FIG. 5 is a diagram showing an example of a temperature change in the zone 13 detected by the temperature sensor 5. Here, in order to make the explanation easy to understand, an example in which the three zones 13a, 13b, and 13c are set to three set target temperatures TG1 = 230 ° C., TG2 = 200 ° C., and TG3 = 180 ° C. will be described.

First, 1 is set to the number of samplings i (step S1). Next, the sampling start time t is set [t ← ti] (step S2).
After the setting, it is determined whether or not the number of times of sampling i = 1 (step S3). In this determination, “1”, that is, in the case of the first sampling (YES), each deviation value between the set target values TG1 to TG5 of each heater 4 and each detected temperature DT1 to DT5 is calculated (step S4). ). Of the obtained deviation values, the heater corresponding to the maximum deviation value (here, assumed to be HT1) is specified (step S5). On the other hand, in the determination in step S3, a deviation value (TG1-DT1) with respect to HT1 specified in step S5 in the previous sequence is calculated (step S6).
In steps S5 and S6, after the heater 4 is specified or the deviation value is calculated, the corrected target temperature TGi ′ of each heater 4 is calculated based on the formula (1) using the latest deviation value (TG1-DT1). (Step S7). Based on this calculation result, temperature control (temperature increase or temperature decrease) of each heater 4 is performed (step S8). However, TG1 ′ remains as TG1.
HT1 → TG1 ′ = TG1
HT2 → TG2 ′ = TG2- (TG1-DT1)
HT3 → TG3 ′ = TG3- (TG1-DT1)
Next, it is determined whether or not the deviation value is 0, that is, TG1 = DT1 (step S9). When this determination is made, it is assumed that the temperature of each heater 4 has reached a set target temperature (in FIG. 5, TG1 = 230 ° C., TG2 = 200 ° C., TG3 = 180 ° C. at the time of arrival). . If TG1 = DT1 (YES), the corrected target temperatures TG1 ′, TG2 ′, TG3 ′ of the heaters are reset to the set target temperatures TG1, TG2, TG3 (step S10), and this sequence is performed. finish.

On the other hand, if it is determined in step S9 that TG1 = DT1 is not satisfied (NO), each temperature sensor 5 detects the temperature of each zone 13 and waits for the next sampling time (step S12). While waiting, the number of samplings is incremented (i = i + 1), the process returns to step 2 and the sampling time t is set again. Note that the number of samplings and the sampling time can be set by setting the number of samplings and the time interval in advance if the temperature rise characteristics of the heater used as a calculation reference, for example, HT1, are known, or the rate at which the temperature of HT1 is raised. Accordingly, the arrival time to the intermediate temperature may be predicted at any time, and the number of times and arrival of time intervals may be sequentially set while controlling the temperature.

Next, with reference to FIG. 4 and FIG. 5, the multipoint temperature control for the heating cylinder of the injection molding machine according to the sequence as described above will be described.
First, as shown in FIGS. 4 and 5, sampling times t1, t2, t3, and t4 are determined in advance based on either the measurement temperature or the predetermined measurement time interval in the zone 13a (HT1) serving as a measurement reference. The sampling time is not limited and can be changed as appropriate. However, it does not make sense to set the time to be shorter than the response of the heater 4. There is no restriction on which time the first sampling time t1 after the start of temperature increase is set, that is, the start timing of the multipoint temperature control. At this time, the set target temperatures of the zones 13a, 13b, and 13c are set as TG1 = 230 ° C., TG2 = 200 ° C., and TG3 = 180 ° C., respectively.

  After starting to heat up the heater 4 at room temperature, when it reaches an arbitrarily determined sampling time t1 (in this example, the time when the temperature of the temperature sensor 4a of the zone 13a reaches 100 ° C.), the zone 13b (HT2) , 13c (HT3) detected by the temperature sensors 4b and 4c were 105 ° C. and 80 ° C., respectively. If such a temperature rising rate is maintained, the zone 13b and the zone 13c will reach the set target temperature before the predicted arrival time for reaching 230 ° C. in the zone 13a. For this reason, the temperature increase rate of each zone 13b and zone 13c is reduced. In this example, the corrected target temperature is set to zone 13b = 70 ° C. and zone 13c = 80 ° C. so that the temperature is once lowered.

  The temperature setting is maintained, and the temperature of the zone 13b and the zone 13c is measured when the next sampling time t2 (in this example, the time when the temperature sensor 4a of the zone 13a reaches the detection temperature 150 ° C.) is reached. To do. Here, the temperatures detected in the zones 13b and 13c are lowered to 70 ° C. and 80 ° C., respectively, so as to aim at the corrected target temperature set to be lowered in the previous stage. At the sampling time t2, the next corrected target temperatures are set as TG2 = 120 ° C. and TG3 = 100 ° C. In this way, by providing the corrected target temperatures so that the temperature increase rates of the zones 13b and 13c reach the set target temperatures TG2 and TG3 at the same time as the set target temperature TG1 of the zone 13a as a reference, the temperature increase rate is reduced. Control.

  Next, when the sampling time t3 (in this example, the time when the temperature of the temperature sensor 4a of the zone 13a reaches the detected temperature 180 ° C.) is reached, the temperatures of the zones 13b and 13c are measured. Here, when the detected temperatures of the zone 13b and the zone 13c are 110 ° C. and 100 ° C., the next corrected target temperatures are set as TG2 = 150 ° C. and TG3 = 130 ° C. Similarly, when the sampling time t4 (in this example, the time when the temperature of the temperature sensor 4a of the zone 13a reaches the detected temperature 210 ° C.) is reached, the zone 13b and the zone 13c set the correction target temperature to TG2 = 180 ° C., TG3 = 160 ° C. is set, and this rate of temperature rise is maintained to reach the set target temperatures TG1 = 230 ° C., TG2 = 200 ° C., and TG3 = 180 ° C., which are the final reached temperatures during the arrival time “tarrive”.

  As described above, according to the present embodiment, in the multi-point temperature control for the heating cylinder of the injection molding machine, by controlling the temperature rising rate in each zone of the heating cylinder, The set target temperature can be reached at the same time. As a result, the molded member made of resin or the like remaining inside the heating cylinder continues to be exposed to high temperature, and depending on the thermal characteristics of the resin, deterioration due to thermal decomposition is prevented, and carbonization of the resin and generation of toxic gas are prevented. Can do.

  Further, for example, after t4 shown in FIG. 5, the sampling time (temperature control timing) is set at a corrected target temperature at a sampling time in finer increments according to the temperature change (temperature increase rate) state. In addition, the sampling period may be changed as appropriate during one heating process.

It is a figure which shows the schematic structure of a multipoint temperature control system in order to demonstrate the multipoint temperature control method in the injection molding machine of this invention. It is a figure which shows the function control block of the temperature controller in this embodiment. It is a flowchart for demonstrating the multipoint simultaneous arrival control program stored in the program memory of the multipoint temperature control system in this embodiment. It is an example of a setting table which illustrates progress of the temperature rising of the heater of the multipoint temperature control system in this embodiment. It is a figure which shows an example of the temperature change of the zone detected by the temperature sensor of the multipoint temperature control system in this embodiment. It is an example of a setting table which illustrates progress of the temperature rising of the heater of the conventional multipoint temperature control system.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Injection molding machine, 2 ... Mold, 3 ... Heating cylinder, 4, 4a, 4b, 4c, 4d, 4e ... Heater, 5, 5a, 5b, 5c, 5d, 5e ... Temperature sensor, 6 ... Temperature controller , 7 ... Temperature controller, 8 ... Temperature setting unit, 9 ... Data memory, 10 ... Program memory, 11 ... Central processing unit (CPU), 12 ... Interface unit (iF), 13 ... Zone, 14 ... Bus line, TG1, TG2, TG3, TG4, TG5 ... set target temperature, DT1, DT2, DT3, DT4, DT5 ... detected temperature, TG1 ', TG2', TG3 ', TG4', TG5 '... corrected target temperature.

Claims (5)

A temperature controller for independently calculating and controlling the energization rates to the heaters respectively disposed in the plurality of heating parts of the injection molding machine, and a temperature detecting means for detecting the temperature of each heating part with respect to the temperature controller; By using a temperature control device that includes a temperature controller that commands a target temperature of each heating part and a temperature setting unit that sets the target temperature and applies the target temperature to the target temperature of the plurality of heating parts. A method of controlling the temperature controller so that the heating time of
A first stage of calculating a deviation between a target temperature of each heating part and a detected temperature of each part at a predetermined time after the start of temperature increase by each heater, and specifying a part corresponding to the maximum deviation among them;
A second stage for calculating a deviation between the target temperature and the detected temperature at least in the identified heating portion at each predetermined time after the first stage;
A temperature value obtained by subtracting the deviation obtained in the second stage from the target temperature for each of the other heating parts excluding the specified heating part is calculated as a correction target value for each part at the time, and the correction target A third step of commanding a value to the temperature controller;
The multi-point temperature control method in an injection molding machine is characterized in that the processes of the second and third stages are repeatedly performed at arbitrarily set sampling times until the deviation becomes zero. In the multipoint temperature control method,
2. The multi-point temperature control method for an injection molding machine according to claim 1, wherein the temperature raising start is started at an arbitrary timing of the temperature raising process. In the multipoint temperature control method,
The multipoint temperature control method for an injection molding machine according to claim 2, wherein the calculation of the deviation in the second stage is performed in real time. In the multipoint temperature control method,
The multi-point temperature control method for an injection molding machine according to claim 1, wherein a plurality of sampling times are set based on a temperature rise time required to reach a target temperature of the identified heating part. In the multipoint temperature control method,
The multipoint temperature control method for an injection molding machine according to claim 1, wherein the sampling time is set to the next sampling time based on the measured temperature result of the identified heating part.

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