JPS5857930A - Temperature controlling unit of injection molding machine - Google Patents

Abstract

PURPOSE:To keep the temperature of resin at the time of injection precisely at a desired value in the titled temperature controlling device for controlling a heater by a detected resin temperature by controlling temperature change factors too due to the performance of a movable part. CONSTITUTION:Resin 14 taken from a hopper 11 into a cylinder 12 is heated and melted in a heater and a screw 16 is moved by a driving source 18 toward the left to inject resin 14 into a mold 17. In above-mensioned unit, resin temperature T detected by a temperature detector 15 and the pressure P detected by a pressure detector 20 when the resin is injected are transmitted to an arithmetic unit 30 (marks 27, 28 show amplifiers) to obtain a correction quantity epsilon indicated by the formula (x is a set temperature; K1, K2 are constants; DELTAT indicates the increment part of resin temperature parallel to pressure P). Then, this epsilon is transmitted to a heater driving circuit 31 to correct the operational quanity to the heater 13. Using injection speed V, injection quantity D, number N of revolution of the screw, etc. along with the pressure P injected as mentioned above, the precision of temperature control can be lifted.

Description

[Detailed description of the invention] In general, an injection molding machine heats and melts resin filled in a cylinder using a heater, and extrudes the molten resin into a mold using a screw to form a predetermined shape. Molding the product. In order to manufacture products of constant quality with good reproducibility using such injection molding machines, it is necessary to maintain the temperature of the molten resin at a constant level. For this purpose.

Conventionally, a temperature control device detects the temperature of the cylinder or resin heated by a heater with a temperature sensor, compares the detected temperature with a set temperature, and controls the temperature so that the deviation between the two is reduced. It is attached to the molding machine.

According to the observations of the present inventor, the temperature of the cylinder or resin changes slightly depending on dynamic factors during injection, such as the pressure during injection, injection speed, injection amount, or rotational speed of the screen. It was confirmed that during repeated injections, temperature changes due to these dynamic factors became so large that they could no longer be ignored.

The conventional temperature control device described above does not reflect temperature changes due to dynamic factors during injection into temperature control. Therefore, injection molding machines equipped with conventional temperature control devices cannot avoid product variations, and therefore cannot meet more stringent requirements for product quality. Furthermore, conventional temperature control devices also have the disadvantage that it takes time to stabilize the temperature when the molding conditions are changed.

SUMMARY OF THE INVENTION An object of the present invention is to provide a temperature control device for an injection molding machine that can control temperature with high precision, taking into account temperature changes during injection, and can therefore reduce product variations.

Another object of the present invention is to provide a temperature control device for an injection molding machine that can quickly stabilize the temperature even when molding conditions are changed.

According to the present invention, in a temperature control device for an injection molding machine that detects temperature with a temperature detector and controls a heater section based on the detected temperature, the temperature changes dynamically when a movable section of the injection molding machine operates. Factor 1: For example, from a detection element that detects pressure, injection speed, position of the movable part, rotation speed of the movable part, etc., and the relationship between the factors detected by the detection element and the temperature from the temperature detector.

A temperature control device for an injection molding machine is obtained, which includes a real-time calculation device that calculates and corrects the operation amount of the heater portion in real time during the operation of the movable portion.

This will be explained below with reference to one drawing.

Referring to FIG. 1, an injection molding machine to which the present invention can be applied has a hole A for storing resin. -11 and the hora/”-
The cylinder 12 is filled with resin from 11. A heater 13 is attached to this cylinder 12, and the heater 13 is heated according to the amount of operation from a heater drive circuit, which will be described later. The resin 14 filled in the cylinder 12 is heated by the heater 13 and melted.

The temperature of the cylinder 12 or the temperature T of the tree 11 or 14 inside the cylinder 12 is detected by a temperature sensor 15 and sent to a temperature control device which will be explained with reference to FIG.

During injection, the resin 14 in the cylinder is extruded into a mold 17 by a screw 16 constituting a movable part, and is molded within the mold 17. The screw 16 is driven by a screw drive source 18 during injection.

It is driven to the left in the figure. Further, as the screen 16 rotates, the resin 14 is measured, and a certain amount of the resin is injected into the mold.

In this embodiment, not only the temperature sensor 15.

A pressure detector 20 for detecting the pressure P during injection is provided in the screw driving cylinder 21. The pressure P detected by the pressure detector 20 is sent to the temperature control device as a dynamic factor during the injection operation. Furthermore, a screw position detector 24. An injection speed detector 25, a screw rotation speed detector 26, etc. may be provided. Incidentally, it is also possible to detect the injection site from the position of the screw position detector 24.

Referring to FIG. 2, a temperature control device according to an embodiment of the present invention includes a temperature control panel f27. Pressure amplifier 28 that receives pressure P from pressure detector 20. A computing device 30 such as a microprocessor that processes the temperature T and pressure P given from these amplifiers in real time, and a heater drive circuit 31 that sends the processing results of this computing device to the heater 13 in the form of manipulated variables. have.

The heater 13 is controlled by the output of the heater drive circuit 31, taking into consideration dynamically changing pressure during injection.

Referring to FIG. 3, the relationship between pressure P and temperature (especially resin temperature) T during the injection IB process is shown. As is clear from the figure, when the pressure reaches Po due to the advance of the scree 16, the temperature T increases by ΔTo from the set temperature.

In other words, the resin temperature increases in proportion to the pressure during the injection process, and therefore.

It can be seen that the set temperature cannot be maintained during the injection process.

The calculation device shown in Fig. 2 changes the pressure P and resin temperature T (
A pressure detector 20 detects the pressure P by considering ΔT).
The temperature change (ΔT) is calculated in accordance with the signal from the heater 13, and the operation amount to the heater 13 is corrected. For example, 1 is required for this correction.
The following correction formula can be used.

ε= x −KIT K2ΔT (1) (where ε is the deviation, or set temperature + Kl + K2 is a constant) Refer to FIG. is a multiplier (K1) that multiplies the temperature T from the temperature sensor 15 by a constant Kl f, and the pressure P from the pressure sensor 20.
It has a multiplier (K2) that multiplies the temperature change (ΔT) obtained from the constant by 2. The set temperature X is given to a subtracter, and the subtracter subtracts the output value KI T h K2ΔT from each multiplier from the set temperature X to obtain the deviation ε. The calculated deviation ε is supplied to the heater 13 as a manipulated variable via the heater drive circuit 31.

In addition, 1. using the pressure Po set before injection. Predict the temperature change ΔTo,' according to the relationship shown in FIG.

It is also possible to determine the amount of operation to the heater 13 without delaying the injection operation. in this case.

For example, a linear expression can be used.

ε=z−KITK2(ΔT−Δ′rO) (2)(
In equation 2), the term (ΔT−ΔTo) is a correction term for correcting the deviation between the set value and the detected value.

In the embodiments shown in FIGS. 2 to 4, only the relationship between pressure and temperature change was explained, but according to the experiments of the inventor, the injection speed V and the change ΔT in resin temperature are also as shown in FIG. A proportional relationship was observed. Therefore, by using the relationship between the injection speed V and the change in resin temperature ΔT,
The operation amount of the heater 13 can be corrected.

Referring to FIG. 5, the temperature control device according to another embodiment of the present invention controls, in addition to temperature T and pressure P, injection speed V, injection amount (screw IJ, -position) D,' and screw rotation speed N.
are also considered as dynamic factors during injection, and the temperature change ΔT is calculated from the relationship between these factors. This embodiment includes an A/b converter 33 that converts each factor supplied in the form of an analog signal from each detector into a digital signal, and each digital signal is generated by a digital arbitrary function generator 34 configured with a microprocessor. given to. By the way.

The function generated by this generator can be determined experimentally from the relationship between each factor. This digital arbitrary function generator 34 sends the temperature change ΔT calculated based on the above-mentioned function together with the detected temperature value T to the D/A converter 35 in the form of a digital signal. The temperature detection value T and temperature change ΔT converted into analog signals by the D/A converter 35 are provided to an adder 38 via amplification circuits 36 and 37, respectively.

The adder 38 calculates the set temperature
Supply to 1. The heater drive port ji31 sends the deviation ε to the heater 13 as a heater operation amount.

Although the above-mentioned embodiment described only the temperature control in the injection process, the present invention can be similarly applied to the temperature side (goods) in the metering process. Here, the measuring process is performed while rotating the screen 16 prior to the injection process in order to maintain a constant amount of resin to be injected into the mold.

This is a step of measuring at the tip of the cylinder 12.

During this weighing process, the number of rotations of the screen, pressure,
and 9. The heat of fusion and shear calorific value of the resin vary depending on the value of the resin amount. These appear as fluctuations in resin temperature. Temperature fluctuations during this metering process also affect the injection process,
Affects the quality of the final product. Therefore, with reference to the detected values of rotation speed, pressure, and quantity during this measuring process.

Temperature control is extremely effective. Needless to say, the number of rotations and the like in this case are factors that change as the screw moves.

As described above, according to the present invention, it is possible to obtain a temperature control device that performs temperature control in real time by referring not only to temperature but also to factors other than temperature when controlling the temperature of an injection molding machine. . Therefore, according to the present invention, the temperature can be controlled not only when the movable part is stopped, but also while the movable part is performing some operation, and it is possible to mold plastic products of high quality and precision without dust.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an injection molding machine used in the present invention,
FIG. 2 is a block diagram showing a temperature control device according to an embodiment of the present invention, FIG. 3 is a diagram showing the pressure dependence of resin temperature, and FIG. 4 shows a concrete example of the calculation device shown in FIG. and FIG. 5 are block diagrams showing a temperature control device according to another embodiment of the present invention. Explanation of symbols 11: Hopper, 12 Niji cylinder - 113: Heater, 1
4: Resin, 15: Temperature detector, 16: Screw, 17
: Mold, 18 Niscrew drive source 20: Pressure detector, 2
1: Drive cylinder. 24: Screw IJ, -position detector, 25: Injection speed detector, 26: Screw rotation speed detector, 27, 28: Anzo, 30: Arithmetic device, 31: Heater drive circuit +' 3
3: A/ll converter, 34: Dinotal arbitrary function generator, 35: D/A converter, 36.37: Amplifier, 38: Adder.

Claims (1)

[Claims] (1) Used in an injection molding machine equipped with a heater section that heats resin and a movable section that operates to extrude the resin heated by the heater section, the temperature caused by the heating of the heater section The temperature control device detects the temperature using a temperature detector and controls the heater section according to the detected temperature, and the temperature control device detects a factor other than the temperature that changes during operation of the movable section. , further comprising a real-time calculation device that corrects the temperature of the heater section in real time while the movable section is operating, based on the relationship between the factor detected by the element and the detected temperature. Temperature control device for injection molding machines.