JPH0226722A - Injection apparatus of injection molding machine - Google Patents

Abstract

PURPOSE:To make it possible to plasticize with a high uniformity a relatively wide range of resin materials by means of one kind of a screw by vibrating relatively the screw and a heating cylinder in the axial direction and kneading and plasticizing a resin material during the screw in the heating cylinder is rotated. CONSTITUTION:A resin material fed from a hopper is transferred to an apex part of a screw while the resin material is kneaded and melted along the groove of the screw 6 and the screw 6 is started to retreat in accordance with the amt. of the molten resin which has been stored at its apex. When this initial micro-retreat is detected by means of a screw position detecting sensor 13, an operation controlling means 14 vibrates a piston rod 9 with a very small amt. and with a high speed. The screw 6 thereby begins to perform a vibrational movement e.g., with number of vibration of 100-200Hz and with a vibrational amplitude of 1-30% by peak to peak against the aimed back pressure. The resin material to which this vibrational energy is given receives a more complicated force from a number of directions and the molten resin is kneaded more effectively and with a high uniformity.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a screw-type injection device for an injection molding machine.

[Prior Art] In this type of screw-type injection device, as is well known, the resin material supplied from the hopper into the heating cylinder is kneaded by the unidirectional rotation of the screw inside the heating cylinder while being kneaded along the screw groove. and is sent to the tip of the heating cylinder.

Then, the temperature of the resin material increases due to the heat transferred from the heating cylinder heated by the band heater and the frictional heat generated between the resin materials and between the resin material and the metal surface due to the kneading action of the screw, and the resin material is plasticized and melted. It looks like this.

[Problems to be Solved by the Invention] By the way, in the plasticizing mechanism of the resin using external heating and simple unidirectional rotation of the screw as described above, it is necessary to change the plasticizing conditions (screw rotation speed, external heating temperature, back pressure). It has been difficult to uniformly plasticize the edges of various resin materials by using only plasticizing methods. Therefore, in order to respond to detailed requests, it is necessary to change the screw design, for example, L/D
(Screw effective length/screw diameter), P/D (screw thread groove pitch/screw diameter), distribution ratio of the supply section, compression section, and metering section of the screw, depth of the thread groove of each part of the screw, etc. However, there was no consideration given to going to the factory to achieve uniform plasticization.

[Problems to be Solved by the Invention] However, in the injection device of this type of injection molding machine, which is desired to be able to knead and plasticize a wide range of resin materials with the same screw, it is necessary to use a large number of screws with different screw designs as described above. Preparing them in advance poses problems in terms of economy and replacement workability, and there is a limit to achieving more uniform plasticization simply by changing the screw design.

Therefore, the technical problem to be solved by the present invention is to solve the above-mentioned problems of the prior art. An object of the present invention is to provide an injection device for an injection molding machine that can highly uniformly plasticize a wide range of resin materials.

[Means for Solving the Problems] The above-mentioned object of the present invention is to knead and plasticize a resin material by rotating a screw in a heating cylinder, and to rapidly advance the screw by an injection cylinder to inject the molten resin into a mold. In an injection device of an injection molding machine that injects inward, the screw and the heating cylinder are relatively vibrated in the axial direction while the screw is rotating to knead and plasticize (charge) the resin material. achieved by.

[Operation] As described above, the present invention vibrates the screw or the heating cylinder in the axial direction while the screw is rotating to knead and plasticize the resin material, so that the inner wall of the heating cylinder and the outer periphery of the screw are vibrated in the axial direction. The resin (molten resin and unmelted resin) in the melt pool zone (flow zone) between the two is effectively vibrated and plasticized and melted highly uniformly.

In other words, although detailed analysis of the behavior of the resin material in the flow region is difficult, the screw rotates in the direction of arrow X in Fig. 2 (
(forward rotation), a propelling flow Ql toward the nozzle direction Y based on the rotary transport action of the screw and a back pressure flow Q2 toward the nozzle direction based on the pressure difference between the front and rear of the screw are generated, and both Q1 and Q2 It is said that due to the combined effect of the above, a lateral flow Q3 is generated in a plane substantially perpendicular to the thread of the screw, and a leakage flow Q4 is also generated. In reality, these four types of flows do not occur separately, but are combined into a complex flow for kneading and plasticization.

By the way, in the present invention, the screw and the heating cylinder are vibrated relative to each other in the axial direction while the screw is rotating, so the resin material that has been given this vibrational energy receives even more complex forces from multiple directions. It was confirmed that the molten resin can be kneaded more effectively and with high uniformity. Note that the arrows in the left region in FIG. 2 indicate resin materials A and B.

It shows very schematically that the vibration occurs in the 0 part (entire area), and in reality, it is a complex kneading process in which the flow shown in the right area of Figure 2 and the vibration shown in the left area are combined. - It should be understood that a flow/exothermic plasticization mechanism is generated.

[Example] Hereinafter, the present invention will be explained with reference to illustrated embodiments.

FIG. 1 is an explanatory diagram showing an injection device of an injection molding machine according to an embodiment of the present invention. In the figure, reference numeral 1 denotes a heating cylinder, and a band heater 2 is wrapped around the outer circumference of the cylinder, and a nozzle 4 is attached to a cylinder head 3 at the tip thereof. 5 is.

A headstock holding the end portion of the heating cylinder 1 is a member integrated with a base member of an injection device (not shown), and the resin material supplied from a hopper (not shown) is transferred into the heating cylinder 1. A hole is provided for guiding. Reference numeral 6 denotes a screw disposed within the heating cylinder 1 so as to be rotatable and movable in the axial direction, and a feed zone, a compression zone, and a metering zone are formed from the right side to the left side in the figure, as is known in the art. There is.

Reference numeral 7 denotes a hydraulic pressure monitor, the output shaft of which is connected to the rear end of the screw 6, and the rotation of the hydraulic motor 7 drives the screw 6 to rotate. 8 is the headstock 5
A support body 10 to which the hydraulic motor 7 is attached is connected to a piston rod 9 of a pair of hydraulic cylinders installed inside.

As the piston rod 9 moves back and forth in the left and right directions shown in the figure, the screw 6 is moved together with the hydraulic motor 7 between the forward position shown and the backward position not shown, and the high-speed axis of the piston rod 9 Due to directional vibration,
The screw 6 (and the hydraulic motor 7) is subjected to an axial vibratory motion. Note that 511 is a motor rotation detection sensor, 12 is a cylinder pressure detection sensor, and 13 is a screw position detection sensor.

14 is an arithmetic control means consisting of a microcomputer;
ROM that stores various I10 interfaces, main control programs and fixed data, etc. - RAM that reads and writes various flags and input data, etc., μC that manages overall control
It is equipped with a PU (micro central processor unit), etc., and drives and controls the hydraulic motor 7 and hydraulic cylinder 8 as described later. Although not shown, the arithmetic control means 14 exchanges data with an external recording means as necessary, and similarly displays arithmetic processing results on a display means such as a display as necessary. .

15 is an input means such as a keyboard switch, and the input means 15 allows the operator to input information such as resin material name, grade number, charge completion position, back pressure, type of screw used, etc. to the calculation control means 14 before operating the injection device. You are now required to enter configuration information. Arithmetic control means 14
calculates the number of revolutions of the screw 6, the frequency of vibration, the amplitude, etc. of the screw 6 using these setting information and a calculation table stored as a case study in advance in its own ROM or external storage means. Then, the calculation control means 14
is based on this calculation result and the sensor group of the injection device (for example, motor rotation detection sensor 11, cylinder pressure detection sensor 12,
Screw position detection sensor 13. Detection information Sl, S2 . ...... Servo amplifier 17 via D/A converter 16 based on SN.
．． 18, the servo amplifier 17 controls the hydraulic motor 7 via the servo valve 19, and the servo amplifier controls the hydraulic cylinder 8 via the servo valve 20.
are each driven as described below.

In the above configuration, at the start of one shot cycle during operation, the screw 6 is in the forward position shown in the first figure.

In this state, the arithmetic and control means 14 rotates the hydraulic motor 7 in one direction at a predetermined rotational speed to rotate the screw 6 in one direction.

As a result, the resin material supplied from a hopper (not shown) is kneaded and melted along the grooves of the screw 6 and sent to the tip of the screw 6. Start retreating accordingly. Then, at the time when the screw position detection sensor 13 (or cylinder pressure detection sensor 12) detects this initial slight retraction of the squirrel 6 (time T1 in FIG. 3), the arithmetic control means 14 moves the piston rod 9 a slight vibrate at high speed. As a result, the screw 6 has a vibration frequency of 10, for example.
0 to 200Hz, 1 peak to peak for target back pressure
Shake at ~30% amplitude! Start the lJ movement. (Incidentally, vibration may be applied to the screw 6 from the beginning of the rotation of the screw 6.) When the reaction force from the molten resin stored at the tip of the screw due to the rotation of the screw 6 reaches a predetermined pressure (see Fig. 3). 12), the arithmetic and control unit 14 causes the hydraulic cylinder 8 to control the backward speed of the screw 6 in order to keep the back pressure against the reaction force constant, and in combination with this, causes the screw 6 to vibrate. Make it last. and,
When the retracted position of the screw 6 reaches a predetermined position, in other words, when the amount of molten resin stored at the tip of the screw 6 reaches the amount equivalent to one shot (time T3 in FIG. 3), the arithmetic and control device 14 moves the screw 6 stop the rotation and vibration. The molten resin thus stored at the tip of the screw 6 is transferred to a metal (not shown) by rapidly advancing the screw 6 using the hydraulic cylinder 8 when the mold clamping of the next cycle is completed. It is designed to be injected into the mold device.

During the kneading and plasticizing process due to the rotation of the screw 6 described above, the screw 6 performs a compound movement in which vibration is added to the rotational movement. The material is kneaded to a high degree of uniformity by receiving complex forces from multiple directions, and also generates frictional self-heating effectively. Combined with the external heating from the heating cylinder 1, the material is melted evenly and with the desired high degree of uniformity. It was confirmed that a plasticized state could be obtained.

FIG. 4 shows another embodiment of the present invention. In this embodiment, the rotation of the screw is driven by an electric servo motor, and the screw is driven forward and backward as well as by vibration. ! Each of the 1IyjA movements is performed by an electric servo motor,
In this figure, members corresponding to those in the structure of FIG. 1 are designated by the same reference numerals, and their explanations will be omitted to avoid duplication.

In FIG. 4, 21 is a support body held on a base member of an injection device (not shown); 22 is a first electric servo motor for charging (hereinafter referred to as the first motor 22) attached to the support body 21; 23 is a second electric servo motor for injection (hereinafter referred to as the second motor 23) which is also attached to the support 21, and both motors 22 and 23 have built-in encoders for rotation detection, although not shown. There is.

The rotation of the first motor 22 is transmitted to a gear 25 fixed to the output shaft 24 of the first motor 22, a gear 26 that meshes with the gear 25, a ball spline body 27 that rotates integrally with the gear 26, and further , the ball spline body 27
It is transmitted to the screw 6 whose rear end is fixed to the charge drive shaft 28 via the charge drive shaft 28 which is spline-coupled with the charge drive shaft 28 . That is, the screw 6 is rotationally driven by the rotation of the first motor 22.

Further, the rotation of the second motor 23 is controlled by the rotation of the second motor 23.
The rotation of the nut body 32 is transmitted to the gear 30 fixed to the output shaft 29, the gear 31 meshing with the gear 30, and the collar 1 unit 32 that rotates integrally with the gear 31. This is converted into a linear motion of the injection drive shaft 33, and is transmitted as a linear motion to a coupling body 34 coupled to the injection drive shaft 33 and a drive body 35 coupled to the coupling body 34. Then, the driving body 35
, the charge drive shaft 28 is held so as to be rotatable only, and the charge drive shaft 28# and the screw 6 are linearly moved back and forth by the back and forth movement of the drive body 35 in the horizontal direction shown in the figure. It has become. That is, by the rotation of the second motor 23, the screw 6 is moved between the forward injection position shown in FIG. Axial vibration M! It is also now granted lJ. The second motor 23 also controls back pressure.

Note that 36 is a headstock integrated with a base member of an injection device (not shown), and has an opening 38 for guiding the resin material supplied from the hopper 37 into the heating cylinder 1.
is formed. Although it is simplified in the drawing, the coupling body 34 is provided with an injection pressure sensor.

As mentioned above, the arithmetic control means 14 is inputted with various setting information in advance and is supplied with various sensor information.
The first motor 22 is driven and controlled via the A converter 16 and the driver circuit 39, and the same <D/A converter 16
, drives and controls the second motor 23 via the driver circuit 40.

In the above configuration, at the start of one shot cycle during operation, the screw 6 is in the forward position shown in FIG.
In this state, the arithmetic and control means 14 rotates the first motor 22 in one direction at a predetermined rotation speed to rotate the screw 6 in one direction.

The second motor 23 is activated to vibrate the screw 6.

As a result, the resin material supplied from the hopper 37 is kneaded and melted along the grooves of the screw 6 and sent to the tip of the screw 6. At the same time, the arithmetic and control unit 1
4 drives the second motor 23 in the direction in which the screw 6 retreats, and thereby the screw 6 begins to retreat in accordance with the amount of molten PA tree i that has begun to be stored at its tip.

When the reaction force from the molten F71 resin stored at the tip of the screw reaches a predetermined pressure due to the rotation of the screw 6 accompanied by vibration, the arithmetic and control device 14 activates the second motor 23 to act as a backing force to resist this reaction force. Screw 6 to keep the pressure constant
While controlling the backward speed of the g! jJ! Continuing jJ's work. Then, when the retracted position of the screw 6 reaches a predetermined position, in other words, when the amount of molten resin stored at the tip of the screw 6 reaches the amount equivalent to one shot, the calculation control means 14 stops the rotation and vibration of the screw 6. let Then, when the mold clamping of the next cycle is completed, the second motor 23 is activated to rapidly move the screw 6 forward, and the molten resin stored at the tip of the screw 6 is injected into the mold device (not shown). It is supposed to be done.

Also in this example, during the kneading and plasticizing steps.

The screw 6 performs a compound motion in which a vibrational motion is added to a rotational motion, and the same effect as in the embodiment described above can be achieved.

In both of the embodiments described above, the screw 6 is vibrated, but the same effect can be expected even if the heating cylinder 1 is vibrated.

[Effects of the Invention] As described above, according to the present invention, it is possible to provide an injection device for an injection molding machine that can highly uniformly plasticize a relatively wide range of resin materials with one type of screw, and its industrial value is high. It's a huge amount.

[Brief explanation of the drawing]

1 to 3 relate to one embodiment of the present invention, and FIG. 1 shows the injection '! of an injection molding machine! Fig. 2 is an explanatory diagram schematically showing the behavior of the resin in the flow zone, Fig. 3 is an explanatory diagram showing the relationship between back pressure and screw position, and Fig. 4 is an explanatory diagram showing the relationship between back pressure and screw position. FIG. 2 is an explanatory diagram of an injection device of an injection molding machine according to an embodiment of the present invention. 1... Heating cylinder, 2... Band heater, 4... Nozzle, 5... Head stock, 6... Screw, 7... ...Hydraulic motor, 8...Hydraulic cylinder, 14...
Arithmetic control means, 17.18... Servo amplifier,
19.20... Servo valve, 22... First electric servo motor, 23... Second electric servo motor, 39.40... Driver circuit.

Claims (1)

[Claims] In an injection device of an injection molding machine, the resin material is kneaded and plasticized by rotation of a screw in a heating cylinder, and the screw is rapidly advanced by an injection cylinder to inject the molten resin into a mold. An injection device for an injection molding machine, wherein the screw and the heating cylinder are vibrated relative to each other in the axial direction while the screw is rotating to knead and plasticize (charge) a resin material.