JP5189577B2 - Temperature control method for injection molding machine - Google Patents

Description

  The present invention relates to a temperature control method for an injection molding machine suitable for controlling the temperature of a heated part such as an injection nozzle heated by a heater.

  In general, the heating cylinder and the injection nozzle provided in the injection molding machine are heated by a heater provided corresponding to each heating zone, the temperature of each heating zone is detected by a sensor, and the detected temperature becomes a preset target temperature. As described above, temperature control is performed by a feedback control system including PID compensation. In this case, since the temperature of the heating cylinder and the injection nozzle directly affects the molten state of the resin, performing temperature control with high accuracy and avoiding unnecessary temperature fluctuations, etc., stably improves molding quality. But it is an important issue.

  Conventionally, a temperature control method that copes with such a problem is also known, and Patent Document 1 discloses an operation amount corresponding to a heat amount deficient due to continuous automatic molding of an injection molding machine as an operation amount simultaneously with the start of continuous automatic molding. When the rising of the signal during continuous automatic molding is detected, PID control is stopped only during the time set by the timer to prevent undershoot of the temperature of the injection heating cylinder at the start of continuous automatic molding as much as possible. A method for controlling the heater temperature of an injection molding machine is disclosed, and Patent Document 2 discloses that the object to be heated is heated and controlled by a heater driven by PID (proportional, integral, differential) control and molding. A plurality of temperature control periods according to the state of the machine are provided, and when performing temperature control according to each temperature control period, at least from a certain temperature control period to the next specific control period When the control period starts, the integral value and the offset value that have been set and held in advance for the next temperature control period are used for the calculation in the temperature control period for the arithmetic processing unit that performs temperature feedback control. The temperature at which stable temperature control can be performed with good transient response from the beginning of the transitioned temperature control period even when transitioning from one temperature control period to the next temperature control period. A molding machine using a control method is disclosed.

Japanese Patent Laid-Open No. 10-100188 JP 2003-25404 A

  However, the conventional temperature control method in the above-described injection molding machine has the following problems.

  First, Patent Document 1 aims to eliminate the undershoot associated with the start of plasticization and flow of the resin in the heating cylinder at the start of continuous automatic molding. Therefore, the effectiveness of the technology is limited to the same purpose, and cannot be applied to other operation processes that do not have the same purpose. In addition, since PID control is stopped for a certain time by the start of continuous automatic molding, the continuity with respect to temperature control is interrupted, and thereafter, when the stop is released and restarted, the control becomes unstable. Eventually, even if the undershoot can be reduced to some extent, it is insufficient from the viewpoint of ensuring high stability and control accuracy.

  On the other hand, Patent Document 2 gives an integration value and an offset value set and held in advance as initial values without stopping PID control, and aims to solve the problems of Patent Document 1. Yes. However, in this case, since the integral value and the offset value obtained by the case study are stored in advance and the integral value and the offset value that are fixed values are used at the time of control, it cannot be said that the same purpose can be sufficiently achieved. For example, when touching a nozzle, it is considered as the transition of a temperature control period in which the conduction rate to the heater is increased by heat conduction from the nozzle to the mold, but usually just before the room or mold temperature and nozzle touch The degree of temperature fluctuation varies greatly depending on the state (presence / absence of purge process and elapsed time). Eventually, optimization for temperature control is not performed, and as in Patent Document 1, even if overshoot and undershoot can be reduced to some extent, it is insufficient from the viewpoint of ensuring high stability and control accuracy.

  The object of the present invention is to provide a temperature control method for an injection molding machine that solves the problems existing in the background art.

The temperature control method of the injection molding machine M according to the present invention heats the heated portions 2a, 2b by the heaters 3a, 3b and also controls the temperature of the heated portions 2a ... When the temperature control is performed by the feedback control system Cf including the PID compensation system Cfs so that the detected temperature (PV _n ) becomes the preset target temperature (SP), the temperature variation in the heated parts 2a and 2b If it detects that a particular process adversely is performed, at least, calculated by arithmetically processing the integral term Σep in the PID compensation system Cfs to the heater 3a, the duty ratio O _n of 3b to a predetermined size, The obtained integral term Σep is immediately preset in the PID compensation system Cfs.

In this case, according to a preferred aspect of the invention, an injection nozzle 13 that is provided at the tip of the heating cylinder 11 and fills the mold 12 with resin can be applied to the heated portion 2a. In addition, a nozzle touch process in which the injection nozzle 13 that contacts the mold 12 is performed at the start of molding can be applied to the specific process, and a nozzle back process in which the injection nozzle 13 that is performed at the end of molding is separated from the mold 12 can be applied. . In the nozzle back process, at least the target temperature for heating the injection nozzle 13 can be set higher than the target temperature for molding. On the other hand, the rear portion 15 of the heating cylinder 11 to which the hopper 14 for supplying the molding material is attached can be applied to the heated portion 2b. It should be noted that the predetermined magnitude with respect to the energization rate for obtaining the integral term by detecting that a specific process has been performed is preferably selected in the range of 80 to 150 [%] of the rated energization rate. Further, immediately before the integral term is preset, the integral gain in the PID compensation system Cfs is changed to a temporary set value that is larger than the integral gain when the specific process is detected, and the predetermined set time is changed. When the time has elapsed, the change of the temporary setting value can be cancelled. Note that the PID compensation system Cfs, it is possible to use a PID compensation system constructed in accordance with the derivative type, control based on the duty factor O _n can be performed by time proportional control or thyristor drive.

  According to the temperature control method of the injection molding machine M according to the present invention by such a method, the following remarkable effects are obtained.

(1) if the heated portion 2a, the specific process causing the temperature fluctuation 2b is detected that has been performed, at least, the heater 3a, PID compensation for the duty ratio O _n of 3b to a predetermined size Since the integral term Σep in the system Cfs is obtained by calculation processing, and the obtained integral term Σep is immediately preset in the PID compensation system Cfs, the temperature control is performed even when specific processing that causes temperature fluctuation is performed. While ensuring the continuity with respect to the temperature, the desired energization rate can be secured immediately, unnecessary temperature fluctuations such as undershoot can be reduced, high stability and accuracy for temperature control can be realized, and adverse effects on the resin temperature can be avoided. This can contribute to reduction of defective products and improvement of molding quality.

  (2) If the heated portion 2a is provided at the tip of the heating cylinder 11 and applied to the injection nozzle 13 that fills the mold 12 with resin, the temperature control related to the injection nozzle 13 can be optimized. The resin temperature in the injection nozzle 13 can be stabilized.

  (3) If a specific process is applied to a nozzle touch process in which the injection nozzle 13 performed at the start of molding abuts the mold 12 according to a preferred embodiment, useless temperature fluctuations that occur during the nozzle touch process, particularly the injection nozzle Therefore, it is possible to prevent troubles related to the early solidification or unfilling of the resin in the mold 12.

  (4) If a specific process is applied to the nozzle back process in which the injection nozzle 13 performed at the end of molding is separated from the mold 12 according to a preferred embodiment, unnecessary temperature fluctuations that occur during the nozzle back process can be prevented. It is possible to stabilize the resin temperature in the injection nozzle 13 during the nozzle back process.

  (5) If the target temperature for heating at least the injection nozzle 13 is set higher than the target temperature at the time of molding during the nozzle back process according to a preferred embodiment, the subsequent process (such as a second nozzle touch process) can be performed more smoothly. It can be carried out. In particular, in addition to this, if the target temperature for heating the rear portion 15 of the heating cylinder 11 is set to be lower than the target temperature at the time of molding, the plasticization associated with the retention of the molding material in the rear portion 15 of the heating cylinder 11 due to the material supply stop Since adverse effects can be avoided, it can contribute to reduction of defective products and improvement of molding quality.

  (6) According to a preferred embodiment, when the heated portion 2b is applied to the rear portion 15 of the heating cylinder 11 to which the hopper 14 for supplying the molding material is attached, it is generated when the molding material is supplied into the heating cylinder 11. Since unnecessary temperature fluctuations, in particular, heat shortage at the rear part of the heating cylinder 11 can be prevented, adverse effects on the plasticization of the solid material in the heating cylinder 11 can be avoided.

(7) According to a preferred embodiment, if a predetermined magnitude with respect to the energization rate for obtaining an integral term by detecting that a specific process has been performed is selected within the range of 80 to 150 [%] of the rated energization rate , even if the particular process causing the temperature variation is performed, since the duty ratio O _n at an early stage it can be secured to the 80 [%] to a maximum duty factor of the rated current ratio, high stability to temperature control In addition to ensuring the accuracy, the optimization can be achieved.

  (8) According to a preferred embodiment, immediately before the integral term is preset, the integral gain in the PID compensation system Cfs is changed to a temporary set value larger than the integral gain when it is detected that a specific process has been performed, If the specified set time has passed, the temporary set value change can be canceled, and the temperature control can be optimized when a specific process that causes temperature fluctuations is performed. Variations can be further reduced or avoided.

  (9) According to a preferred embodiment, if a PID compensation system configured by a differential preceding type is used for the PID compensation system Cfs, the calculation process of the feedback control system can be easily performed, and the cost can be reduced.

  (10) According to a preferred embodiment, if the control based on the current ratio is performed by time proportional control or thyristor phase control, the control can be facilitated and ensured, so that the control can be advantageously performed in terms of stabilization and cost. it can.

The flowchart which shows the operation | movement by the temperature control method of the injection molding machine which concerns on suitable embodiment of this invention, Partial cross-sectional configuration diagram including a temperature control system in the same injection molding machine, Block diagram of the temperature control system, Nozzle temperature characteristic diagram for shots when temperature is controlled by the same temperature control method, Current ratio characteristic diagram for shots when temperature is controlled by the same temperature control method, Heater energization waveform diagram with respect to time when temperature is controlled by the same temperature control method, The flowchart which extracts and shows a part of operation | movement by the temperature control method of the injection molding machine which concerns on the modified embodiment of this invention,

  Next, preferred embodiments according to the present invention will be given and described in detail with reference to the drawings.

  First, the configuration of an injection molding machine M that can implement the temperature control method according to the present embodiment will be described with reference to FIGS. 2 and 3.

  FIG. 2 shows the overall configuration of the injection molding machine M. The illustrated injection molding machine M is hydraulic, and includes an injection device Mi and a mold clamping device Mc on the upper surface of the machine base Mb. The injection device Mi is supported on the machine base Mb via an injection device advance / retreat mechanism 21 using a hydraulic cylinder, and is moved forward (nozzle touch processing) or moved backward (nozzle back processing) by the injection device advance / retreat movement mechanism 21. be able to.

  The injection device Mi includes a heating cylinder 11. The heating cylinder 11 has an injection nozzle 13 at the tip of the heating cylinder 11 and a hopper 14 attached to an attachment site 15 at the rear of the heating cylinder 11. A heater 3a such as an electrothermal band heater is attached to the outer peripheral portion of the injection nozzle 13, and a temperature sensor 4a such as a thermocouple is embedded in the meat portion of the injection nozzle 13. The heater 3a and the temperature sensor 4a are connected to the temperature control unit 31. On the other hand, a heater 3b such as a band heater is mounted on the outer peripheral portion of the heating cylinder 11, and a temperature sensor (not shown) such as a thermocouple similar to that on the injection nozzle 13 side is embedded in the meat portion of the heating cylinder 11. . These heater 3 b and temperature sensor are also connected to the temperature control unit 31. The heating cylinder 11 is divided into three zones, that is, a metering zone, a kneading zone, and a supply zone, from the front side to the rear side, and independent temperature control is performed. Thereby, while the injection nozzle 13 comprises the to-be-heated site | part 2a, the attachment site | part 15 (supply zone) comprises the to-be-heated site | part 2b. Furthermore, a screw 22 is loaded inside the heating cylinder 11, and a screw driving unit 23 that drives the screw 22 is provided at the rear end of the heating cylinder 11. The screw drive unit 23 includes an injection cylinder 23c that drives the screw 22 forward and backward, and a metering motor (oil motor) 23m that rotationally drives the screw 22.

  The mold clamping device Mc includes a fixed plate 24 and a movable plate 25 that support the mold 12, and includes a mold clamping cylinder 26 c that opens and closes the mold 12 and drives the mold 12 by moving the movable plate 25 forward and backward. A movable platen drive unit 26 is provided, and the fixed platen 24 and the movable platen drive unit 26 are fixedly installed on the upper surface of the machine base Mb. The stationary platen 24 includes a nozzle detection sensor 16 such as a proximity sensor that detects that the injection nozzle 13 has touched the nozzle. The nozzle detection sensor 16 is connected to the molding machine controller 51. As other actuators, although not shown in the figure, a protruding cylinder or the like for protruding a molded product (ejector) from the opened mold 12 is provided.

  On the other hand, the temperature control unit 31 and the molding machine controller 51 constitute a temperature control unit CT, and the temperature control unit 31 and the molding machine controller 51 are connected to be able to communicate with each other. FIG. 3 shows a block system of the temperature control system, particularly the temperature control system for the injection nozzle 13. In this case, the molding machine controller 51 has a computer function for controlling the entire injection molding machine M. Accordingly, it includes hardware elements such as a CPU and a memory, and software elements such as a control program and a database.

  The temperature control unit 31 has a control function of performing substantial temperature control. Moreover, it has a computer function like the molding machine controller 51, and can perform various arithmetic processing and sequence control processing. Therefore, the temperature control unit 31 stores a sequence program for executing the temperature control method according to the present embodiment. In the temperature control unit 31, Cf is a feedback control system for the temperature of the injection nozzle 13, and includes a PID compensation system Cfs, in particular, a PID compensation system configured by a differential leading type. As a result, in the PID compensation system Cfs, the differential preceding PI-D compensation processing is performed. By using such a differential leading type PID compensation system Cfs, there is an advantage that the calculation process of the feedback control system Cf can be easily performed and the cost can be reduced.

  The PID compensation system Cfs includes a deviation calculator 33, a differential compensation calculator 34, an integral compensation calculator 35, a deviation calculator 36, and a proportional compensation calculator 37, and also includes a preset calculator 38. In this case, the temperature sensor 4 a is connected to the inverting input unit of the deviation calculating unit 33 and the input unit of the differential compensation calculating unit 34. An output port for outputting the target temperature (temperature target value SP) of the injection nozzle 13 in the molding machine controller 51 is connected to the non-inverting input unit of the deviation calculating unit 33. The output unit of the deviation calculation unit 33 is connected to the input unit of the integral compensation calculation unit 35, and the output unit of the integral compensation calculation unit 35 is connected to the non-inverting input unit of the deviation calculation unit 36. Furthermore, the output unit of the differential compensation calculation unit 34 is connected to the inverting input unit of the deviation calculation unit 36, and the output unit of the deviation calculation unit 36 is connected to the input unit of the proportional compensation calculation unit 37.

  On the other hand, the nozzle detection sensor 16 is connected to the input unit of the preset calculation unit 38 and the molding machine controller 51, and the output unit of the preset calculation unit 38 is connected to the integral compensation calculation unit 35. The output unit of the proportional compensation calculation unit 37 is connected to the input unit of the operation processing unit 41, and the output unit of the operation processing unit 41 is connected to the control input unit of the thyristor (SSR) 42. An AC power source, which is a supply source of AC power Pac, is connected to the input portion of the SSR 42, and an output portion of the SSR 42 is connected to the heater 3a.

  Next, a temperature control method according to the present embodiment using the injection molding machine M configured as described above will be described according to the flowchart shown in FIG. 1 with reference to FIGS.

  As shown in FIG. 2, the injection device Mi is moved backward by the injection device advance / retreat mechanism 21, and the tip of the injection nozzle 13 is at the nozzle back position Xr away from the mold 12. In this state, the purge process is performed. Assume that it is done. The temperature of the mold 12 is 30 [° C.], the temperature of the injection nozzle 13 is 310 [° C.], the resin temperature in the heating cylinder 11 is 350 [° C.], and the temperature control is normally performed. To do.

In the temperature control, the temperature of the injection nozzle 13 is detected by the temperature sensor 4a, and the detected temperature (temperature detection value PV _n [° C.]) is taken into the temperature adjustment unit 31 (step S1). Then, the temperature detection value PV _n of the captured is applied to the inverting input of the error calculator 33. On the other hand, since the target temperature (temperature target value SP [° C.]) for the injection nozzle 13 is given from the molding machine controller 51 to the non-inverting input unit of the deviation calculation unit 33, the deviation calculation unit 33 calculates [Equation 1]. Based on the calculation, a deviation e _n [° C.] between the temperature target value SP and the temperature detection value PV _n is obtained (step S2).

Since the purge process is performed before the nozzle touch process (operation) at the nozzle back position Xr, the step group Sx is not performed in FIG. 1, and the normal PI-D compensation process in the PID compensation system Cfs is performed from step S6. Is called. That is, the determined operation amount y _n by calculation based on the formula [2], the calculation based on the formula [3], the manipulated variable y _n are converted into duty factor O _n (step S6). The duty ratio O _n is obtained as the output of the proportional compensation calculation unit 37 in FIG. 3. In [Expression 2], Kp is a proportional band [° C.], Ti is an integration time [second], and Td is a differentiation time [° C.]. In [Equation 3], MR is a manual reset (PV = SP energization rate).

Thus, specifically, as shown in FIG. 3, with the deviation e _n described above is applied to the integral compensation computation section 35, further, the detected temperature PV _n is also applied to the differential compensation calculation unit 34. On the other hand, differential compensation calculation unit 34 is provided with a function for processing a differential term in Equation 2, the integral compensation operation unit 35, a function for processing the integral term including the deviation e _n in Equation 2 In addition, the proportional compensation calculation unit 37 has a function for calculating the proportional term (1 / Kp) in [Equation 2] and a function for calculating [Equation 3], and is proportionally compensated through the above PID processing system Cfs. duty ratio O _n is obtained at the output of the arithmetic unit 37.

In this case, when duty ratio O _n is less than zero duty ratio O _n is 0 (step S7, S8). On the other hand, the duty ratio O _n is 100 when duty ratio O _n is greater than 100 (step S9, S10). These limiter processes are performed by the operation processing unit 41. Further, the pulse width modulation based on the duty factor O _n the basic pulse the operation processing unit 41 (PWM) is performed, a pulse width modulated control pulse Dp is applied to the control input of SSR42. Thereby, time proportional control is performed and electric power proportional to the pulse width of the control pulse Dp is supplied to the heater 3a (steps S11 and S12). The period of the basic pulse is Δt (for example, 0.5 [second]). Thus, the control based on the duty factor O _n, be performed by time proportional control, for attained facilitation and reliably of control, there is an advantage that can be achieved an advantageous embodiment in the stabilization and cost control.

FIG. 6 shows an energization waveform of the heater 3a. Since the SSR42 AC power Pac is applied, in FIG. 6, for example, if the control pulse Dp is applied to duty factor O _n becomes 100 [%], (a), the AC power Pac Is output as it is, and the energization stop time (Δt−ts (ts is the energization time)) becomes zero. Further, if the control pulse Dp energization ratio O _n is 50 [%] is applied, (b), the first half of the half-wave of the AC power Pac (or late) the energization stop time (Delta] t-ts ) And only the second half (or first half) AC power Pac is output. Furthermore, if duty ratio O _n is 0% and comprising control pulse Dp is applied, as shown in (c), energization-stopping time period (Δt-ts) is 0, the AC power Pac is not supplied. Such time proportional control is continuously performed in the range of 0 to 100% corresponding to the control pulse Dp, and in the illustrated example, is repeated at intervals of Δt (about 0.5 seconds). Then, feedback control is performed so that the temperature detection value PV _n becomes the temperature target value SP (steps S13, S1,...).

  Next, a case where the purge process is completed will be described. Upon completion of the purge process, the process proceeds to the nozzle touch process (operation). In the nozzle touch process, the molding machine controller 51 controls the injection device advance / retreat mechanism 21 so that the injection device Mi moves forward. As shown in FIG. 3, when the tip of the injection nozzle 13 reaches the nozzle touch position Xt where it abuts on the mold 12, the nozzle detection sensor 16 detects the nozzle touch signal St, and the molding machine controller 51 and the preset calculation unit. 38. Nozzle touch is set as a specific process that causes temperature fluctuations in the injection nozzle 13 (the heated portion 2a), and therefore, the nozzle touch signal St is given to the molding machine controller 51 and the preset calculation unit 38, thereby causing a step. Processing of the group Sx (steps S3 to S5) is performed.

The reason for performing the step group Sx is as follows. In the purge process, the molten resin in the heating cylinder 11 is discharged from the injection nozzle 13 to the outside. At this time, since the resin temperature is 350 [° C.], the temperature of the injection nozzle 13 immediately after the purge process is It temporarily rises from the original 310 [° C.] to about 320 to 330 [° C.]. Further, when the purge process is completed, the process is normally promptly shifted to the nozzle touch process (operation) in order to avoid unnecessary interruption time. Therefore, when the nozzle touch is performed, the injection nozzle 13 is deprived of heat by the mold 12 having a low temperature (about 30 [° C.]), and the temperature of the injection nozzle 13 is lowered. Qr in FIG. 4 shows the temperature change at this time. On the other hand, since the target temperature (temperature target value SP) of the injection nozzle 13 is 310 [° C.], even if the temperature of the injection nozzle 13 is decreased, it is decreased from 320 to 330 [° C.] increased by the purge process. deviation e _n is not generated, the heating operation in the feedback control system Cf is not performed. That is, the duty ratio O _n to the heater 3a maintaining 0, so that the heating operation from the time when the temperature falls below 310 [℃] of the injection nozzle 13 is started. Wr in FIG. 5 shows this state.

As described above, in normal feedback control, there is a situation in which the heating operation is not performed in the initial stage. Therefore, as indicated by Qr in FIG. 4, the temperature of the injection nozzle 13 (temperature detection value PV _n ) is a normal temperature. The temperature lower than 310 [° C.] continues for a while. In the case of the example, the temperature of 306 [° C.] decreased by about 4 [° C.] from 310 [° C.] will continue for a while, and as a result, it directly affects the resin temperature as a factor, particularly complicated molding. In the case of a thin molded product such as a product or a media disk (CD or the like), molding defects such as premature solidification and insufficient filling and deterioration of molding quality are caused.

Therefore, in the temperature control method of this embodiment, obtains the integral term Σep in the PID compensation system Cfs to the duty ratio O _n of the heater 3a to a predetermined size by the arithmetic processor, the integral term Σep determined immediately PID Preset to compensation system Cfs. Preset timing, between steps S2 and S6, i.e., after a deviation e _n as described above is performed prior to calculating the duty ratio O _n.

Hereinafter, specific calculation processing will be described. Now, since the manipulated variable yp for obtaining the energization rate Op of the magnitude to be secured is obtained from [Equation 3] to [Equation 4] in an arbitrary control cycle n, [Equation 2] is calculated as an integral term. [Equation 5] can be obtained by applying the [Equation 4] by rearranging the mathematical expressions.

  Therefore, in the initial stage, for example, when it is desired to secure a current supply rate of 90 [%], 90 [%] may be selected as the current supply rate Op. In this case, it is desirable to set the magnitude of the electrification rate Op to be selected from the range of 80 to 150 [%] of the rated electrification rate. Although 150 [%] is a size that is impossible in reality, the use of 150 [%] has an advantage that the maximum energization rate can be reliably ensured. In this way, if the energization rate Op is selected in the range of 80 to 150 [%] of the rated energization rate, the rated energization is immediately performed even when specific processing that causes temperature fluctuations such as nozzle touch is performed. Since 80% of the rate to the maximum energization rate can be secured, high stability and accuracy with respect to temperature control can be secured, and optimization thereof can be achieved. In this case, the energization rate Op may be set at the time of factory shipment in advance, or when production is performed so that the user can set an arbitrary size in consideration of a temperature difference between the mold 12 and the injection nozzle 13 or the like. May be set.

On the other hand, actual calculation processing is performed as follows. First, if the nozzle touch described above is performed, the preset computing unit 38 computes an integral term Σep for immediate presetting based on [Equation 5] (steps S3 and S4). When the calculation process is completed, the integral compensation calculation unit 35 in the PID processing system Cfs is immediately preset by the obtained integral term Σep (step S5). Thus, if you choose the 90 [%] as the magnitude of the duty ratio Op, duty ratio O _n in the initial stage of the control cycle n-numbered, can be secured at 0 was selected without 90 [%]. Qi in Figure 4, along with showing the temperature change of the injection nozzle 13 in the case of performing such preset operation, Wi in FIG. 5 shows the change in the duty ratio O _n at that time.

By performing such preset operation, as is clear from Wi of FIG. 5, generation period duty ratio O _n is 0 in the initial stage it is avoided. Further, when the preset process is not performed, the temperature drop of the injection nozzle 13 is reduced by about 4 [° C.] from 310 [° C.] to 306 [° C.], which is a normal temperature, as indicated by Qr in FIG. However, by performing the preset process, it is possible to suppress a decrease of about 1-2 [° C.] from 308 to 309 [° C.] as indicated by Qi in FIG.

Therefore, according to such a temperature control method according to the present embodiment, by detecting that a specific process that causes a temperature fluctuation in the injection nozzle 13 (the heated portion 2a), that is, that a nozzle touch has been performed. , because of the so determined integral term Σep in the PID compensation system Cfs to the duty ratio O _n of the heater 3a to a predetermined size by the arithmetic processor, preset immediately PID compensation system Cfs an integral term Σep determined, temperature Even when specific processing that causes fluctuations (nozzle touch processing) is performed, the desired energization rate can be secured immediately while ensuring continuity with respect to temperature control, and unnecessary temperature fluctuations such as undershoot can be avoided. As a result, high stability and accuracy with respect to temperature control can be realized, and adverse effects on the resin temperature can be avoided to contribute to reduction of defective products and improvement of molding quality.

  In particular, in the case of the example, since the heated portion 2a is applied to the injection nozzle 13 provided at the tip of the heating cylinder 11 and filling the mold 12 with the resin, the temperature control related to the injection nozzle 13 can be optimized, The resin temperature in the injection nozzle 13 can be stabilized. Further, since the specific process is applied to the nozzle touch process in which the injection nozzle 13 performed at the start of molding comes into contact with the mold 12, it is possible to prevent unnecessary temperature fluctuations that occur during the nozzle touch process, in particular, the temperature drop of the injection nozzle 13. As a result, it is possible to avoid troubles related to early solidification and unfilling of the resin in the mold 12.

  Next, a temperature control method according to a modified embodiment of the present invention will be described with reference to FIGS.

  FIG. 7 shows a flowchart in which a part of the operation by the temperature control method according to the modified embodiment is extracted. That is, steps corresponding to steps S3 to S5 in FIG. 1 are extracted and shown. In the temperature control method according to the modified embodiment, if the nozzle touch of the injection nozzle 13 (the heated portion 2a) is detected, the integral gain in the PID compensation system Cfs is set to the nozzle touch immediately before performing the integral term preset process described above. Is changed to a temporary set value larger than the integral gain at the time of detection (normal time), and time measurement is started simultaneously with the change to the temporary set value (step S14). Then, when a predetermined set time has elapsed, the change of the temporary set value is canceled (steps S15 and S16).

  In this case, the step group Sy (steps S14 to S16) in FIG. 7 is performed simultaneously with the step group Sx in FIG. 1, but the timing for changing the integral gain to the temporarily set value is immediately before performing the integral term preset processing. Set as follows. Note that the processing of the step group Sx (steps S3 to S5) is not changed. The temporary set value is set to be larger than the integral gain at the time of nozzle touch detection (normal time), but it is desirable to select the maximum integral gain that can be set. Furthermore, the setting time for setting and using the temporary setting value is preferably about 30 [seconds].

  Therefore, by performing the process related to the step group Sy at the same time as the preset process of the integral term Σep, the temperature control is optimized when the nozzle touch is performed, thereby reducing unnecessary temperature fluctuations such as undershoot. Or it can be avoided. FIG. 4 shows the temperature change of the injection nozzle 13 when Qe in FIG. 4 uses the integral gain temporary setting value. As is clear from Qe in FIG. 4, the temperature drop can be further suppressed as compared with the above-described Qi, and it does not fall below 310 [° C.] which is the normal temperature even in the initial stage. In addition, a change in the energization rate when We in FIG. 5 uses a temporarily set value of the integral gain is shown. As is clear from We in FIG. 5, in addition to avoiding the occurrence of a period in which the energization rate becomes 0 in the initial stage, unnecessary fluctuations are further suppressed as compared to Wi described above.

  On the other hand, as another modified embodiment, as shown in FIG. 2, the heated portion 2b may be applied to the rear portion 15 of the heating cylinder 11 to which the hopper 14 for supplying the molding material is attached. In this case, basic processing (operation) can be performed in accordance with the processing (operation) for the injection nozzle 13 described above. Thus, if the rear part 15 of the heating cylinder 11 is applied as the heated portion 2b, useless temperature fluctuations that occur when the molding material is supplied into the heating cylinder 11, particularly the heat at the rear part of the heating cylinder 11 are obtained. Since shortage can be prevented, there is an advantage that an adverse effect on the plasticization of the solid material in the heating cylinder 11 can be avoided.

  On the other hand, as another modified embodiment, a specific process may be applied to a nozzle back process in which the injection nozzle 13 performed at the end of molding is separated from the mold 12. As described above, when applied to the nozzle back processing, useless temperature fluctuations that occur during the nozzle back processing can be prevented, so that the resin temperature in the injection nozzle 13 during the nozzle back processing can be stabilized. In the nozzle back process, the target temperature for heating the injection nozzle 13 is set higher than the target temperature for molding, and the target temperature for heating the rear portion 15 of the heating cylinder 11 is set lower than the target temperature for molding. It is desirable. In this way, if the target temperature is changed and set, subsequent processing (second nozzle touch processing or the like) can be performed more smoothly, and accompanying the retention of the molding material in the rear portion 15 of the heating cylinder 11 due to the material supply stoppage. There is an advantage that it can contribute to the reduction of defective products and the improvement of molding quality by avoiding adverse effects on plasticization.

  As described above, the preferred embodiment (modified embodiment) has been described in detail. However, the present invention is not limited to such an embodiment, and the detailed configuration, shape, material, quantity, numerical value, technique, etc. Changes, additions, and deletions can be arbitrarily made without departing from the scope of the present invention. For example, although the hydraulic injection molding machine is illustrated as the injection molding machine M, an electric injection molding machine may be used. Moreover, although it is desirable to select the predetermined magnitude | size with respect to the electricity supply rate for calculating | requiring an integral term in the range of 80-150 [%] of a rated electricity supply rate, it is not limited to this range. Furthermore, although the case where the PID compensation system comprised by the differential precedence type was used for the PID compensation system Cfs was shown, other types of PID compensation systems may be used if necessary. On the other hand, the case where time proportional control is performed as the control based on the energization rate has been shown, but thyristor phase control can be similarly implemented. It should be noted that detecting that a specific process has been performed is not only directly detected by a sensor as illustrated, but also by using other signals generated by performing a specific process. Various methods for knowing that processing has been performed are included.

  The temperature control method according to the present invention can be used for various injection molding machines having a heated portion heated by a heater.

  2a: heated part, 2b: heated part, 3a: heater, 3b: heater, 4a ...: temperature sensor, 11: heating cylinder, 12: mold, 13: injection nozzle, 14: hopper, 15: heating cylinder Rear, M: injection molding machine, Cf: feedback control system, Cfs: PID compensation system

Claims (10)

  Injection that heats the heated part with a heater, detects the temperature of the heated part with a temperature sensor, and performs temperature control by a feedback control system including a PID compensation system so that the detected temperature becomes a preset target temperature In the temperature control method of the molding machine, if it is detected that a specific process causing temperature fluctuation is performed on the heated part, at least the PID compensation for making the energization rate of the heater a predetermined magnitude An injection molding machine temperature control method characterized in that an integral term in the system is obtained by arithmetic processing, and the obtained integral term is immediately preset in the PID compensation system.   2. The temperature control method for an injection molding machine according to claim 1, wherein the heated portion is an injection nozzle that is provided at a tip of a heating cylinder and fills a mold with resin.   The temperature control method for an injection molding machine according to claim 2, wherein the specific process is a nozzle touch process in which the injection nozzle is brought into contact with the mold at the start of molding.   3. The temperature control method for an injection molding machine according to claim 2, wherein the specific process is a nozzle back process for separating the injection nozzle from the mold performed at the end of molding.   5. The temperature control method for an injection molding machine according to claim 4, wherein at the time of the nozzle back processing, at least a target temperature for heating the injection nozzle is set higher than a target temperature for molding.   2. The temperature control method for an injection molding machine according to claim 1, wherein the heated portion is a rear portion of a heating cylinder attached with a hopper for supplying a molding material.   2. The predetermined magnitude with respect to the energization rate for obtaining an integral term by detecting that the specific processing has been performed is selected in a range of 80 to 150 [%] of the rated energization rate. The temperature control method of the injection molding machine in any one of -6.   Immediately before presetting the integral term, the integral gain in the PID compensation system is changed to a temporary set value that is larger than the integral gain when the specific processing is detected, and a predetermined set time has elapsed. If it does, the change of the said temporary setting value will be cancelled | released, The temperature control method of the injection molding machine in any one of Claims 1-7 characterized by the above-mentioned.   9. The temperature control method for an injection molding machine according to claim 1, wherein the PID compensation system uses a PID compensation system constituted by a differential preceding type.   The temperature control method for an injection molding machine according to any one of claims 1 to 9, wherein the control based on the energization rate is performed by time proportional control or thyristor phase control.

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