JPH07214622A - Resin temperature measuring device in injection molding machine - Google Patents

Abstract

PURPOSE:To control a resin temperature at a high accuracy, reduce a variation in temperature and stably obtain a molded article of a high dimensional accuracy by a method wherein a temperature sensor capable of directly measuring a temperature of a molten resin passing through the side of a screw head during a weighing stage is provided in the screw head part. CONSTITUTION:A screw 6 is inserted into a heating cylinder 2 so as to rotate and move forward and backward. A nozzle 1 is mounted on the top of the heating cylinder 2. A hydraulic chamber 9 of an injection cylinder 19 consists of a rod-side hydraulic chamber 9a and a head-side hydraulic chamber 9b. An operating oil is supplied from a hydraulic pump to the hydraulic chamber 9 and controlled by a hydraulic-operated valve 15. A temperature sensor 16 is provided for directly detecting a temperature of a molten resin passing through between a screw head 3 and the heating cylinder 2. As the sensor 16, a thermocouple using a thermoelectromotive force or IR rays temperature sensor detecting an emission amount of IR rays is used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for measuring resin temperature in an injection molding machine, which is designed to directly measure the temperature of resin melted in a measuring step of the injection molding machine.

[0002]

9 to 12 are drawings for explaining the prior art, FIG. 9 is an explanatory view showing a screw position at the start of the measuring process, and FIG. 10 is an explanatory view showing a screw position after the completion of the measuring process. FIG. 11 is a cross-sectional view showing a temperature control state of the heating cylinder, and FIG. 12 is an explanatory view showing a change in resin temperature measured by a thermometer arranged in the nozzle portion.

In FIG. 9, 1 is a nozzle, 2 is a heating cylinder, 3 is a screw head, 4 is a check ring, 5 is a check sheet, 6 is a screw, 7 is a heater, 8 is a molten resin, and 10 is a mold. 10a is a fixed mold, 10b
Is a movable mold, 13 is a mold cavity, 12 is a thermocouple, 2
0 indicates the front part of the screw head.

That is, the plastic resin material fed from the hopper (not shown) from the forward limit position of the screw 6 shown in FIG. 9 is rotated by a driving device such as a motor, and the screw 6 itself acts on an injection cylinder (not shown). From the forward limit position of the screw 6 shown in FIG. 9 against the hydraulic pressure, FIG.
The screw 6 moves backward (to the right in the figure) to the backward limit position of the screw 6.

The plastic resin material is transferred in the heating cylinder 2 forward and melted by being heated by the heater 7 and sheared by the rotation of the screw 6, and is stored in front of the screw 6, that is, a predetermined amount. It is weighed in an amount determined by the retracted distance of the screw 6.

When this measurement is completed, hydraulic oil is pressed into the injection cylinder and the screw 6 starts to move forward from the backward limit, and the molten resin 8 accumulated in front of the screw 6 is passed through the nozzle 1 to the mold cavity. 13 is injection filled.

When the molten resin 8 is injected and filled into the mold cavity 13, the temperature distribution of the molten resin stored in the screw head front portion 20 has a great influence on the quality of the product after molding. Whether the temperature distribution of the molten resin 8 is stored slowly or uniformly is an important item for obtaining a good product with high dimensional accuracy.

In general, the temperature of the molten resin stored in the front portion 20 of the screw head is higher at the temperature at the start of injection than at the temperature at the end of injection. This is because although the screw 6 is at the forward limit position shown in FIG. 9 at the start of weighing, the resin pellets fed from the hopper (not shown) are sufficiently preheated in the long feeding zone, but when the weighing is near the end, the screw 6 It is considered that this occurs because the length of the resin pellet supply zone becomes shorter with the backward movement and preheating is not performed.

Further, when a temperature distribution of the molten resin temperature stored in the screw head front portion 20 occurs, the molten resin temperature and the resin density have a relationship as shown in FIG. The weight of the molded product 11 injection-filled into the mold cavity 13 also varies greatly.

Conventionally, such a screw head front portion 20 is used.
1 so that the temperature of the molten resin 8 stored in the
The control was performed while measuring the temperature of the heating cylinder 2 as shown in 1 with the thermocouple 12.

[0011]

However, the thermocouple 12
The temperature measured in 1 is not the direct resin temperature, but the temperature of the heating cylinder 2 is directly measured. In order to solve this, the temperature detection part of the temperature sensor 16 is exposed on the inner wall surface of the heating cylinder 2. At the same time, when trying to measure the resin temperature stored in the screw head front portion 20 with the lapse of time in the weighing process, a large number of temperature sensors 16 must be arranged on the heating cylinder 2 side with a predetermined length. In addition to being complicated, there is a problem that the molten resin easily leaks because the pressure inside the heating cylinder 2 becomes high during the injection process.

The object of the present invention has been made in view of the above problems, and the measurement of the resin temperature in an injection molding machine, which directly measures the temperature of the molten resin passing through the side of the screw head during the measuring process. A device is provided.

[0013]

In order to achieve the above object, according to the present invention, a temperature sensor capable of directly measuring the temperature of the molten resin passing through the side of the screw head during the measuring process is arranged in the screw head portion. I set it up.

[0014]

[Function] The temperature of the molten resin passing through the side of the screw head during the measuring process is directly measured by the temperature sensor attached to the screw head, which facilitates highly accurate feedback control in real time. Stable molding of high quality products.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A concrete embodiment of a method for controlling a resin temperature in an injection molding machine according to the present invention will be described in detail below with reference to the drawings. FIG. 1 is a schematic view showing a simplified configuration of a main part of an injection molding machine according to one embodiment of the present invention, FIG. 2 is an enlarged view of a main part when a temperature sensor is attached to a screw head, and FIG. 3 is a rear part of an injection cylinder. FIG. 4 is a detailed sectional view, FIG. 4 is a detailed sectional view of a contact terminal portion that enables detection by a resin temperature sensor, FIG. 5 is a sectional view showing positions of screw heads at the start and end of injection, and FIG. 6 is screw head positions. FIG. 7 is a diagram for correcting a heating cylinder temperature in FIG. 7, FIG. 7 is a relationship diagram of temperature-density-pressure of molten resin, and FIG. 8 is an explanatory view showing a deformed state of a molded product due to nonuniform resin temperature.

In FIG. 1, a screw 6 is inserted into the heating cylinder 2 so as to be able to move forward and backward from rotation, a nozzle 1 is attached to the tip of the heating cylinder 2, and the screw 6 is attached to the rear end of the screw 6. An injection cylinder 19 in which a piston 17 which is movable in a direction and is rotatably attached is inserted is attached.

The hydraulic chamber 9 of the injection cylinder 19 is composed of a rod-side hydraulic chamber 9a and a head-side hydraulic chamber 9b. The hydraulic chamber 9 is supplied with hydraulic oil from a hydraulic pump (not shown), and the hydraulic valve 15 is operated. Controlled by.

A resin temperature sensor 16 for directly detecting the resin temperature when the molten resin passes between the screw head 3 and the heating cylinder 2 is provided. Here, as the resin temperature sensor 16, a thermocouple using thermoelectromotive force or an infrared temperature sensor for detecting the amount of infrared radiation can be used. The resin temperature sensor 16 may be attached to the front inclined portion of the screw head 3.

A hydraulic actuating valve 15 is provided in the hydraulic chamber 9 of the injection cylinder 19, and the rod side hydraulic chamber 9a is provided.
Is provided with a rod-side hydraulic operation valve 15a, and the head-side hydraulic chamber 9b is provided with a head-side hydraulic operation valve 15b.

This injection device 30 includes a screw head 3
A control device 22 of the molding machine is provided which feeds back the measured value of the resin temperature from the temperature sensor 16 arranged in the above to control the resin temperature so as to reach the target resin temperature.

The screw head 3 is screwed to the tip of the screw 6 with the check sheet 5 placed thereon. The screw head 3 has a substantially conical shape toward the tip and is located behind the conical shape (right side in the figure). Has a stepped shape and has a small diameter, and a check ring 4 which is slidable in the axial direction is inserted in the small diameter portion 3a.

The temperature sensor 16 is used as a molding machine control device 2
In order to connect to the screw 2, a through hole 26 is bored along the axis of rotation of the screw head 3, the screw 6, the piston 17 and the rear of the injection cylinder 19 while rotating.

As shown in FIG. 3, the through hole 26 is L at the rear.
It is bent in a letter shape and annularly behind the injection cylinder 19 so that the temperature can always be measured by the resin temperature sensor 16 even when the screw 6 is rotated through the conducting wire 27 connected to the control device 22 of the molding machine. A road 21 is provided, and this ring road 21
A contact terminal 28 is arranged along the line. On the other hand, the lead wire 27
A brush 29 is provided at the end of the screw 6, and when the screw 6 rotates, the brush 29 also simultaneously rotates while rubbing against the contact terminal 28, and signal transmission is possible even while the screw 6 is rotating.

Reference numeral 24 indicates a hopper, 24a indicates a resin pellet, and screw head front portions 20 and 22 indicate a control device of the molding machine, respectively.

Next, a method for controlling the resin temperature in the injection molding machine of the present invention will be described.

At the start of the measuring process, the screw 6 is located at the point a shown by the dotted line in FIG. 5, and the screw 6 is rotated with a slight back pressure being applied to the head side hydraulic chamber 9b by the head side hydraulic operating valve 15b. Then, the pellets 24a are supplied from the hopper 24 to the right end side of the screw 6, and the pellets 24a are stored in the screw head front portion 20 as a molten resin while being sent leftward by the screw 6.

When the temperature measured by the resin temperature sensor 16 is lower than the target resin temperature during the storage process, the pressure in the head-side hydraulic chamber 9b is increased to increase the backward reaction force of the screw 6 to increase the backward speed. Lower, heating cylinder 2
The heating time and the shearing heat generation by the heater 7 on the outer periphery of the resin are extended, the amount of heat necessary for melting the resin pellets 24a is appropriately supplied, and the target resin temperature is controlled in real time. Further, when it is desired to rapidly bring the molten resin temperature to the target temperature, the shearing heat generation amount may be increased by increasing the rotation speed of the screw 6 with the backward reaction force of the screw 6 being increased.

On the contrary, when the measured temperature obtained by the resin temperature sensor 16 during the storage process is higher than the target resin temperature,
The backward reaction force of the screw 6 is reduced to increase the backward speed, and the screw 6 is moved at a low speed from the forward limit position (point a) of the screw head 3 shown in FIG. 5 to the backward limit position (point b) in a short time. Control is performed so that the metering process is completed sooner by reversing while rotating.

In this way, the molten resin temperature measured by the resin temperature sensor 16 is controlled to reach the target resin temperature.
The screw 6 retracts as it is stored in the screw head front portion 20, and, for example, when a limit switch (not shown) detects this, the rotation of the screw 6 is stopped and the measurement of the molten resin is completed (FIG. 5).

When the measuring process is completed, the screw 6 is moved forward while the rotation is stopped, that is, when a so-called injection process is started, the molten resin 8 stored in the screw head front part 20 by the measuring process is transferred to the metal through the nozzle 1. Mold cavity 1
3 is injection-filled.

At this time, if the molten resin temperature varies from shot to shot and is injected and filled in the mold cavity 13, the resin density changes greatly as shown in FIG. Therefore, the weight of the obtained molded product 11 is not constant and varies.

Further, the variation in the temperature of the molten resin injected and filled within one shot appears as a deformation of the molded product 11 as shown by the solid line in FIG. For example, FIG. 8 shows a state in which a thin rectangular product is deformed by shrinkage when it is molded. The shrinkage deformation shown in FIG. 8 has a problem that the molten resin 8 stored in the front portion 20 of the screw head during the measuring process has a temperature distribution (the temperature of the resin filled at the start of the injection process is As a result, the temperature of the resin filled at the time of completion of the process becomes higher than the temperature of the resin filled at the time of completion of the process.

Further, the resin (B part) having a low temperature filled later has a smaller cooling temperature drop than that of the A part, and as a result, the shrinkage becomes smaller. The shape is distorted as shown by the solid line in Fig. 8.

In the present invention, the reason why the resin temperature control is focused is that the magnitude of the resin viscosity also has a correlation with the resin temperature change, which in turn affects the fluidity of the resin in the injection process.

In particular, when the molten resin is injected and filled by real-time pressure control, the difference in viscosity causes the amount of the molten resin 8 to be filled in the mold cavity 13 to vary, and a good product having high dimensional accuracy is stabilized. It becomes difficult to mold.

[0036]

As is apparent from the above description, in the present invention, the temperature sensor capable of directly measuring the temperature of the molten resin passing through the side of the screw head during the measuring step is provided in the screw head portion. As a result, the temperature of the molten resin sent from the screw side to the front of the screw head can be directly measured as the screw retreats during the metering process, enabling highly accurate control of the resin temperature in real time.
It is possible to stably produce good products with high dimensional accuracy by reducing temperature variations.

[Brief description of drawings]

FIG. 1 is a schematic view showing a simplified configuration of a main part of an injection molding machine according to an embodiment of the present invention.

FIG. 2 is an enlarged view of a main part when a temperature sensor is attached to the screw head.

FIG. 3 is a detailed sectional view of the rear portion of the injection cylinder.

FIG. 4 is a detailed cross-sectional view of a contact terminal portion that enables detection by a resin temperature sensor.

FIG. 5 is a cross-sectional view showing the position of the screw head at the start of injection and at the end of injection.

FIG. 6 is a diagram for correcting a heating cylinder temperature at a screw head position.

FIG. 7 is a relationship diagram of temperature-density-pressure of molten resin.

FIG. 8 is an explanatory diagram showing a deformed state of a molded product due to uneven resin temperature.

FIG. 9 is an explanatory diagram showing screw positions at the start of a measuring process.

FIG. 10 is an explanatory diagram showing a screw position after the completion of the measuring process.

FIG. 11 is a cross-sectional view showing a temperature control state of the heating cylinder.

FIG. 12 is an explanatory diagram showing a change in resin temperature measured by a thermometer provided in a nozzle portion.

[Explanation of symbols]

 1 Nozzle 2 Heating Cylinder 3 Screw Head 3a Small Diameter Section 4 Check Ring 5 Check Sheet 6 Screw 7 Heater 8 Molten Resin 9 Hydraulic Chamber 9a Rod Side Hydraulic Chamber 9b Head Side Hydraulic Chamber 10 Mold 10a Fixed Mold 10b Movable Mold 11 Molding Item 12 Thermocouple 13 Mold cavity 15 Hydraulically actuated valve 15a Rod side hydraulically actuated valve 15b Head side hydraulically actuated valve 16 Resin temperature sensor 17 Piston 19 Injection cylinder 20 Screw head front part 21 Annular path 22 Molding machine control device 26 Through hole 27 Conductive wire 28 Contact terminal 29 Brush 30 Injection device

Claims (1)

[Claims] 1. A resin temperature measuring device in an injection molding machine, wherein a temperature sensor capable of directly measuring the temperature of a molten resin passing laterally of a screw head during a measuring step is provided in a screw head portion. .