JP4486512B2 - Injection molding machine - Google Patents

Description

  The present invention relates to an in-line screw type injection molding machine and a pre-plastic type injection molding machine, and more particularly to a technique related to nozzle temperature control in an injection molding machine.

  The temperature control of the nozzle of the injection molding machine is generally a temperature feedback control so that the measured temperature of the nozzle follows the set temperature by controlling the energization of the band heater (nozzle heater) wound around the nozzle by PID control. It is done in In the PID control of the band heater, the energization rate (on / off duty ratio) to the band heater is set so that the actually measured temperature of the nozzle coincides with the set temperature in the energization control period determined every certain period. This is done by adaptively performing variable control.

  However, since the energization control period for the band heater determined for each fixed period is set regardless of the period of the molding cycle of the injection molding machine, the energization control period for the band heater is one molding. For example, the band heater may or may not be energized during the mold closing (clamping) process. When the time of one molding cycle is long, since there are a plurality of energization control periods in one molding cycle, the amount of heat (heat energy) given from the band heater to the nozzle in each molding cycle is approximately equal when viewed on an average However, if one molding cycle is shortened, a molding cycle in which energization control is performed on the band heater and a molding cycle in which the band heater is not performed are generated.

FIG. 4 is a diagram showing a relationship between a conventional molding cycle and an energization control period for the band heater when the molding cycle is short (for example, when one molding cycle is about 2 seconds). As shown in FIG. 4, the energization control period to the band heater of the nozzle temperature control is because it is independently determined in a certain cycle and the molding cycle, there is the molding cycle C _n the current control period 51, the following In the molding cycle C _{n + 1} , the energization control period 51 does not exist, and in the next molding cycle C _{n + 2} , the energization control period 51 exists. A molding cycle that does not perform energization control is mixed. For this reason, in the molding cycle in which the energization control period 51 exists, heat is given from the band heater, but in the molding cycle in which the energization control period 51 does not exist, no heat is given from the band heater, and the energization control period 51 exists. The temperature of the nozzle in the molding cycle is higher than the temperature in the molding cycle in which the energization control period 51 does not exist. In the former molding cycle, the nozzle temperature is too high, and stringing is likely to occur. In the latter molding cycle, When the nozzle temperature is too low, silver is easily generated.

Therefore, the energization control period for the nozzle heater for adjusting the temperature of the nozzle is associated with the cycle of the molding cycle, that is, by the PID control for the band heater for adjusting the nozzle temperature only during the mold closing process period in one molding cycle. The applicant of the present application has previously proposed a technique that stabilizes the nozzle temperature immediately before injection in each molding cycle by providing an energization control period (see Patent Document 1).
Japanese Patent No. 3309345

  Although the technique disclosed in Patent Document 1 can substantially stabilize the nozzle temperature immediately before injection in each molding cycle, the band heater is used in the energization control period of the mold closing process in one molding cycle. Since the heating control is temperature feedback control based on PID (proportional / integral / derivative) operation, the energization rate (on / off duty ratio) to the band heater during the energization control period cannot be denied. . In other words, the amount of heat applied from the band heater to the nozzle in each molding cycle cannot be deviated slightly, and as a result, injection in a clean room where the temperature is constant as in the case of disk substrate molding performed recently. In molding, in order to obtain a higher quality molded product, it is not possible to satisfy the requirement that the amount of heat applied from the band heater to the nozzle in each molding cycle be completely constant. In addition, since temperature feedback control is based on PID operation, it is necessary to set each constant for PID calculation to an optimum value, and it is relatively easy for an engineer who is not familiar with software design for performing PID operation. Is a burdensome burden.

  The present invention has been made in view of the above points, and the object of the present invention is to obtain a higher quality molded product by making the amount of heat given from the heater to the nozzle completely uniform in each molding cycle. Is to make it. In addition, the temperature control of the heater for adjusting the nozzle temperature for that purpose is realized by a simple method.

In order to achieve the above-described object, the present invention advances the injection member in the heating cylinder while the nozzle attached to the tip of the heating cylinder is pressed near the resin inlet of the fixed mold, An injection molding machine that injects and fills molten resin into a mold includes a system controller that controls the entire injection molding machine, and the system controller is configured to control the nozzle based on a preset energization period and an energization current value. The heater wound around is heated at a predetermined energizing current value for a predetermined time during a predetermined process period in one molding cycle by open control, and the amount of heat applied from the heater to the nozzle is always constant for each molding cycle. It was set as the structure to do.

  According to the present invention, the heater wound around the nozzle (heater for adjusting the nozzle temperature) does not set a target set temperature for feedback control as in the prior art, and a predetermined process period in one molding cycle. (For example, during the mold closing process) Heating is performed for a predetermined time, and the amount of heat given from the heater to the nozzle is always controlled at every molding cycle. Therefore, the amount of heat applied from the heater to the nozzle in each molding cycle is always completely constant. Can be guaranteed. Therefore, for example, in the injection molding in a clean room where the temperature is constant, it becomes possible to obtain a molded product of higher quality. Further, since the operation control of the heater for adjusting the nozzle temperature can be performed by open control according to a predetermined condition, the software design can be made simple and easy.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. 1 to 3 relate to an injection molding machine according to an embodiment of the present invention (hereinafter referred to as the present embodiment), and FIG. 1 is a cross-sectional view of a main part showing a configuration in the vicinity of a nozzle of the injection molding machine of the present embodiment. FIG.

  FIG. 1 shows a clamping state. In FIG. 1, 1 is a heating cylinder, 2 is a nozzle attached to the tip of the heating cylinder 1, and 3 is a band heater wound around the nozzle 2 (for nozzle temperature adjustment). (Band heater) 4 is a nozzle temperature sensor for detecting the temperature of the nozzle 2, 5 is a fixed die plate, 6 is a fixed die mounted on the fixed die plate 5, and 7 is a movable die plate (not shown). The mounted movable side mold 8 is a cavity which is a molding space formed by the fixed side mold 6 and the movable side mold 7, 9 is a sprue part connected to the cavity 8, and 10 is connected to the spur part 9. The resin inlet 11 is a resin.

  In the configuration shown in FIG. 1, a movable die plate (not shown) on which a movable mold 7 is mounted is driven back and forth in FIG. 1 by the force of a mold clamping drive source (not shown), and is movable in the mold closing process. The die plate is driven forward from the mold opening completion position, and in a state where the movable mold 7 is pressed against the fixed mold 6 with a predetermined mold clamping force, the mold closing (mold clamping) is completed, and in the mold opening process The movable die plate is driven backward from the mold clamping completion position, and when the mold opening completion position is reached, the mold opening operation ends. Further, during the continuous molding operation, the tip of the nozzle 2 is located in the vicinity of the resin inlet 10 of the fixed mold 6 by a known nozzle touch / nozzle back mechanism (not shown) and a servo motor for nozzle touch which is a driving source thereof. In the injection process, an injection member (not shown) in the heating cylinder 1 (screw or pre-plastic injection in an inline screw type injection molding machine) is placed in the mold cavity 10 in the mold clamping state. With the rapid advance of the injection plunger in the molding machine, the molten resin is injected and filled via the nozzle 2, the resin injection port 10, and the sprue portion 9. In the present embodiment, the pressing force that presses the nozzle 2 against the stationary mold 6 can be adjusted by an operator's operation.

  FIG. 2 is a block diagram showing a configuration relating to nozzle temperature control in the injection molding machine of the present embodiment. In FIG. 2, reference numeral 21 denotes a system controller that controls the entire injection molding machine. Here, only the configuration related to nozzle temperature control is depicted in the system controller 21. In this system controller 21, 22 has an energization period setting unit 22 a and an energization current value setting unit 22 b, a nozzle temperature control unit that performs temperature control of the nozzle 2 by open control, and 23 is a servo motor for nozzle touch Nozzle 27 performs drive control to drive a nozzle touch / nozzle back mechanism (not shown) to control nozzle touch operation and nozzle back operation, or control to vary the pressing force for pressing the nozzle 2 against the fixed mold 6. The touch / nozzle back control unit 24 is a nozzle temperature monitoring unit that receives a temperature detection signal from the nozzle temperature sensor 4 and monitors the temperature of the nozzle 2. Reference numeral 25 denotes a heater driver for energizing and driving the band heater 3 for adjusting the nozzle temperature based on a command output from the nozzle temperature control unit 22. Reference numeral 26 denotes a nozzle driver based on the command output from the nozzle touch / nozzle back control unit 23. The motor driver drives the servo motor 27 for touch.

  In the configuration shown in FIG. 2, the energization period setting unit 22a of the nozzle temperature control unit 22 can be rewritten with data indicating how long the band heater 3 is heated during which process period in one molding cycle. Stored in The setting data for the energization period setting unit 22a is written in advance at the time of shipment of the machine, but can be rewritten by an operator of the machine at the work site. Here, in the energization period setting unit 22a, data indicating that energization control is performed on the band heater 3 in the entire period of the mold closing process period in one molding cycle (the entire period of the mold closing process period of each molding cycle is indicated). It is assumed that data defined as the energization period is written in advance. In addition, in the energization current value setting unit 22b of the nozzle temperature control unit 22, data of a current value for energizing the band heater 3 is stored in a rewritable manner during the energization period. The setting of data in the energization current value setting unit 22b is performed by the operator of the machine at the work site, and the current value to be energized to the band heater 3 is set as appropriate, so that the nozzles from the band heater 3 to the nozzle are set for each molding cycle. 2 is determined.

  When the nozzle temperature control unit 22 receives the signal S1 indicating the start of mold closing, the nozzle temperature control unit 22 instructs the heater driver 25 to heat the band heater 3 with the current value according to the data set in the energization current value setting unit 22b. Thus, the heater driver 25 starts energizing the band heater 3 with a drive current having a predetermined current value. Thereafter, the nozzle temperature control unit 22 monitors whether or not the signal S2 indicating completion of mold closing has arrived, and upon receiving the signal S2 indicating completion of mold closing, instructs the heater driver 25 to stop energization, thereby The energization to the band heater 3 is stopped. As described above, the nozzle temperature control unit 22 heats the band heater 3 only during the mold closing step during one molding cycle by the open control. The nozzle temperature control unit 22 controls the nozzle temperature monitoring unit 24 that the band heater 3 is continuously energized for a predetermined time before the start of the continuous molding operation and the temperature of the nozzle 3 reaches the allowable temperature range. Needless to say, it will be done after confirmation.

  In the present embodiment, the pressing force for pressing the nozzle 2 against the fixed mold 6 can be varied to adjust the amount of heat transferred from the nozzle 2 to the fixed mold 6 every molding cycle. . That is, when the nozzle touch / nozzle back control unit 23 receives the pressing force adjustment instruction signal S3 based on the operator's input instruction, the nozzle touch / nozzle back control unit 23 drives and controls the nozzle touch servomotor 27 via the motor driver 26. The pressing force for pressing the nozzle 2 against the fixed mold 6 is adjusted.

FIG. 3 is a diagram showing the relationship between the molding cycle and the energization period to the band heater in the injection molding machine of the present embodiment. As shown in FIG. 3, in this embodiment, the energization period 31 to band heater 3 is a mold closing process period of one molding cycle, and, since power control is an open control, the molding cycle C _n , C _{n + 1} , C _{n + 2, etc.} , the energization to the band heater 3 is performed under the same conditions during the mold closing process, and is given from the band heater 3 to the nozzle 2 in each molding cycle C _n , C _{n + 1} , C _{n + 2.} The amount of heat generated is always completely constant. The energization to the band heater 3 may be continuous energization or energization with an on / off duty ratio.

  As described above, in the present embodiment, the band heater 3 is heated only during the mold closing process period in one molding cycle by open control without defining a target set temperature for feedback control as in the prior art, and each molding is performed. Since the amount of heat given from the band heater 3 to the nozzle 2 is controlled to be always constant every cycle, it can be guaranteed that the amount of heat given from the band heater 3 to the nozzle 2 in each molding cycle is always completely constant. Therefore, for example, in the injection molding in a clean room where the temperature is constant, it becomes possible to obtain a molded product of higher quality. In addition, since the operation control of the band heater 3 is based on open control according to a predetermined condition, software design can be simplified and easy.

  In the above-described embodiment, the band heater 3 for energizing the nozzle temperature is energized in the entire period of the mold closing process. However, the band heater 3 is energized for a predetermined time in a part of the mold closing process. You may make it do. Further, the energization period to the band heater 3 may extend over a plurality of processes in one molding cycle, that is, for example, extend over the mold closing process period and the first half period of the injection process.

It is principal part sectional drawing which shows the structure of the nozzle vicinity of the injection molding machine which concerns on one Embodiment of this invention. It is a block diagram which shows the structure in connection with nozzle temperature control in the injection molding machine which concerns on one Embodiment of this invention. It is explanatory drawing which shows the relationship between the molding cycle and the energization period to a band heater in the injection molding machine which concerns on one Embodiment of this invention. It is explanatory drawing which shows the relationship between the molding cycle and the energization period to a band heater in the conventional injection molding machine.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Heating cylinder 2 Nozzle 3 Band heater 4 Nozzle temperature sensor 5 Fixed die plate 6 Fixed side metal mold 7 Movable side metal mold 8 Cavity 9 Sprue part 10 Resin inlet 11 Resin 21 System controller 22 Nozzle temperature control part 22a Energization period setting part 22b Energizing current value setting unit 23 Nozzle touch / nozzle back control unit 24 Nozzle temperature monitoring unit 25 Heater driver 26 Motor driver 27 Servo motor for nozzle touch 31 Energization period

Claims (4)

Injection that injects and fills molten resin into the mold by advancing the injection member in the heating cylinder with the nozzle attached to the tip of the heating cylinder pressed near the resin injection port of the fixed mold In the molding machine,
System controller that controls the whole injection molding machine
The system controller applies a predetermined energization current for a predetermined time during a predetermined process period in one molding cycle by opening the heater wound around the nozzle based on a predetermined energization period and an energization current value. injection molding machine and heated at a value, which always features that you constant the amount of heat supplied from the heater at every molding cycle the nozzle. The injection molding machine according to claim 1,
An injection molding machine characterized in that the amount of heat applied from the heater to the nozzle is adjusted for each molding cycle by changing a current value to be supplied to the heater. The injection molding machine according to claim 1,
An injection molding machine characterized in that the amount of heat transferred from the nozzle to the fixed side mold is adjusted for each molding cycle by varying a pressing force for pressing the nozzle against the fixed side mold. The injection molding machine according to claim 1,
An injection molding machine, wherein a servo motor is used as a drive source of a nozzle touch mechanism that presses the nozzle against the fixed mold.

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