JPS61115108A - Temperature control method of hot runner multipoint gate - Google Patents

Abstract

PURPOSE:To suppress the fluctuation of an effluent rate of resin and to stabilize quality of a molded good by controlling the conductive current of a heating element in accordance with the gate temperature in a master nozzle chip side and controlling the conductive current of the heating element by holding the prescribed relation with the master nozzle chip in a slave nozzle chip side. CONSTITUTION:The master nozzle chip 14B detects the temperature of the gate 13B by a temperature sensor 19, and a comparator 23 compares the detected value with a set value, its difference being inputted to a phase control circuit 24. Corresponding to the difference, the phase control circuit 24 controls the ignition phase of a TRIAC21 and the conductive current, that is, the impression voltage of the heater 17B. In the slave nozzle chips 14A and 14C, a voltage controlled by the TRIAC21 is impressed to the heaters 17A and 17C, and moreover a current adjusted by variable resistances 22A and 22B flows. In a multipoint gate, if the temperature at each gate is controlled in such a way, a package control can be executed relation is held; therefore the quality by shot can be stabilized.

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to a temperature control method for an injection molding machine, and particularly to a temperature control method when a single cavity has multiple hot runner gates, so-called multi-point gates. This relates to a control method.

[Prior art and its problems]

In injection molding machines, a real runner is often used that heats the runner to keep the resin passing through it in a molten state, but when using this real runner method with multi-point gates, the temperature of each gate is Precise control is important to stabilize the quality of molded products. For this reason, conventionally,
The temperature of each gate was detected, and the current flowing through each heating element was individually controlled so that the temperature reached a predetermined temperature.

However, with this type of individual control method, the temperature of each gate is not necessarily maintained in a constant relationship due to control deviations, etc., so the amount of resin flowing out from each gate varies depending on the shot, and the position of the weld line changes, etc. It has been difficult to highly stabilize the quality of products.

[Means for solving problems and their effects]

The present invention has been made to solve the problems of the prior art as described above, and its control method is to divide a plurality of nozzle chips constituting a multi-point gate into a king nozzle chip and a slave nozzle chip, and to , a relationship setting means is provided to determine the relationship between the current flowing through the heating element of the main nozzle chip and the current flowing through the heating element of the slave nozzle chip, and the main nozzle chip detects the temperature of the gate and performs heating according to the temperature. The energizing current of the element is controlled, and the energizing current of the heating element of the secondary nozzle chip is controlled by maintaining a predetermined relationship with the energizing current of the heating element of the main nozzle chip by the above-mentioned relationship setting means. It is something.

In this way, the temperatures of each gate are collectively controlled while maintaining a predetermined relationship, so the relationship between each gate is always the same, and variations in quality from shot to shot can be extremely reduced.

〔Example〕

FIG. 1 shows an embodiment of the present invention, in which 11 is a mold of an injection molding machine, 12 is a cavity therein, and 13A is a mold of an injection molding machine;
-13C is a gate, and 14A-14c is a nozzle chip. In this example, 14B is the king nozzle tip, 14A.14
C is a slave nozzle tip. Each nozzle tip 14
A to 14C consist of a chip core 15 and a chip outer cylinder 16, and each chip core 15 has a resistance heater 1 inside.
7A-17C is built-in. That is, each of the nozzle chips 14A to 14C is of an internally heated type, and a real runner 18 is formed between the chip core 15 and the chip outer cylinder 16 to keep the resin in a molten state. Further, a temperature sensor (usually a thermocouple) 19 is built into the chip core 15 of the main nozzle chip 14B to detect the temperature at its tip (corresponding to the temperature of the gate). Each nozzle tip 14A-14c is connected to a manifold (not shown).

Further, 20 is an AC power source for the heaters 17A to 17C, and 21
2 is a tritic for controlling the applied voltage, 22A to 22C are variable resistors for setting the current ratio, 23 is a comparator for comparing the output of the temperature sensor 19 and a set value, and 24 is for controlling the firing phase of the trier 7 and 21. This is a phase control circuit.

Temperature control of each gate 13A to 13C is performed as follows. That is, in the king nozzle chip 14B, the temperature of the gate 13B is detected by the temperature sensor 19, the detected value and the set value are compared by the comparator 23, and the difference is input to the phase control circuit 24. controls the firing phase of the triac 21 according to the difference, and changes the applied voltage or current to the heater 17B to 111? I do. In other words, in the main nozzle chip 14B, feedback control is performed to reduce the current flowing through the heater 17B when the temperature of the gate 13B is higher than the set value, and to increase the current flowing through the heater 17B when the temperature is lower than the set value.

On the other hand, in the slave nozzle chips 14A-14c, the heater 17
A voltage controlled by a trier 721 is applied to A-17C, and tfL adjusted by variable resistors 22A and 22B flows. In other words, heater 17A
- Through variable resistors 22A to 22C, a current that is kept at a predetermined ratio to the current of the heater 17B flows through the gates 13A and 17C.
The temperature of the gate 3c is controlled by IS while maintaining a predetermined relationship with the temperature of the gate 13B.

In multi-point gates, it is necessary to set the temperature of each gate according to the cavity shape, gate position, gate characteristics, etc., but if the above control is performed, the temperature of each gate can be set in advance. Since batch control can be performed while maintaining a predetermined relationship, the quality of each shot can be stabilized.

2 and 3 each show another embodiment of the present invention. In these figures, parts corresponding to those in FIG. 1 are given the same reference numerals. Although the mold, cavity, gate, nozzle chip, etc. are not shown and only the electrical system is shown, it is important to note that the heaters 17A to 17C correspond to the respective nozzle chips and gates.
It is similar to the figure.

In the embodiment of FIG. 2, the voltage applied to each heater 17A-17c is controlled by tri-hooks 21A-21C, and the firing phase of triacs 21A-21C is individually controlled by phase control circuits 24A-24C, respectively. It has become. The current flowing through the heater 17B of the main nozzle chip is determined by the comparator 23,
The point that feedback control is performed by the phase control circuit 24B and the triac 21B is the same as in the case of FIG. 1, but
The current flowing through the heaters 17A to 17C of the slave nozzle chips is controlled by phase fi control circuits 24A and 24, respectively, which generate output phases having a predetermined relationship with the output phase of the phase control circuit 24B.
It is controlled by C. The relationship between the output phase of the phase control circuit 24A and the output phase of the phase control circuit 24B and the relationship between the output phase of the phase control circuit 24C and the output phase of the phase control circuit 24B are set in advance in consideration of the shape of the cavity, the position of the gate, and the like.

Compared to the control method shown in FIG. 1, this control method does not use a variable resistor, so power loss is small.

In the embodiment shown in FIG. 3, a temperature sensor 19 is also provided on the slave nozzle chip.
A-19C and comparators 23A and 23C are provided, and the output phases of the phase control circuits 24A and 24C are corrected depending on the temperature. The rest of the configuration is the same as that in FIG. 2. This control method is based on the heater 17B of the king nozzle chip and the heaters 17A and 17c of the slave nozzle chips.
This is effective when it is necessary to change the relationship between the applied current and the current depending on the temperature.

In the above embodiment, the case where the number of gates, that is, the number of nozzle chips is three, has been described, but the present invention is not limited to this, and can be applied to all cases where one cavity has two or more gates. be.

Further, in the above embodiments, the case where an internally heated nozzle tip is provided is described, but the present invention is equally applicable to an externally heated nozzle tip.

Further, in the above embodiments, a case has been described in which a resistance heater is used as the heating element of the nozzle tip, but the present invention can be similarly applied to a case where an induction tracking coil is used as the heating element.

〔Effect of the invention〕

As explained above, according to the present invention, a plurality of nozzle chips constituting a multi-point gate are divided into a main nozzle chip and a sub-nozzle chip, and the main nozzle chip detects the temperature of the gate and controls the temperature according to the temperature. Controls the current flowing through the heating element,
In the secondary nozzle 1000 knobs, the energization of the heating element is controlled according to the energization current of the heating element of the main nozzle tip so as to maintain a predetermined relationship with it, so that the temperature of each gate maintains the predetermined relationship. Therefore, the relationship between each gate is always maintained in almost the same state, which has the advantage of highly stabilizing the quality of each molded product.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1 to 3 are control system diagrams showing embodiments of the control method of the present invention. 11 ~ Mold, 12 ~ Cavity, 13A -13B -
13c ~ Gate, 14B ~ Ball nozzle tip, 14A -
149 ~ slave nozzle chip, 17B ~ ball nozzle chip heater, +7A/17B ~ slave nozzle chip heater, 19
~Temperature sensor, 20~AC power supply, 21/21A/21B
・21C~triack, 22A/22B/22C~variable resistor (relationship setting means), 24/24B~phase control circuit, 24A24C~phase control circuit (relationship setting means). Figure 1 Figure 2

Claims (1)

[Claims] A relationship setting method that divides a plurality of nozzle chips constituting a multi-point gate into a main nozzle chip and a sub-nozzle chip, and determines the relationship between the current flowing through the heating element of the main nozzle chip and the current flowing through the heating element of the sub-nozzle chip. In the main nozzle chip, the temperature of the gate is detected and the current flowing through the heating element is controlled according to the detected temperature, and in the secondary nozzle chip, the current flowing through the heating element of the main nozzle chip and the current flowing through the heating element are controlled by the above-mentioned relationship setting means. A temperature control method for a hot runner multi-point gate, characterized in that the current flowing through a heating element is controlled while maintaining a predetermined relationship.