JP2000263608A - Screw for injection molding machine and method for positioning it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a screw of an injection molding machine capable of dwelling at a set dwelling pressure. SOLUTION: During a dwelling step, a flight 11 of a screw 10 disposed near forward opening edge 8 of an injection material supply hole 4 of an injection cylinder 1 is lowered in its height from another part, and deformed at 12 by cutting out or the like to release an injecting material bitten during the dwelling step.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection cylinder having an injection material supply hole formed rearward, and a screw provided in the cylinder hole of the injection cylinder so as to be drivable in a rotational direction and an axial direction. When the screw is driven to rotate, the injection material supplied from the injection material supply hole is weighed and stored in front of the injection cylinder, and when the screw is driven in the axial direction, the weighed injection material is injected into the mold, The present invention relates to a screw of an injection molding machine adapted to apply a pressure in an axial direction to a screw when a predetermined amount is injected and reaches a pressure holding position, thereby holding the screw.

[0002]

2. Description of the Related Art Injection molding machines are well known without mentioning a document name. As shown in FIG. 4A, an injection cylinder 50 and a cylinder hole 5 of the injection cylinder 50 are provided.
1 includes a screw 60 and the like provided so as to be drivable in the rotation direction and the axial direction. Injection cylinder 50
A material supply hole 52 is opened near the rear of the device, and a hopper (not shown) is provided in the material supply hole 52. A flight 61 having a predetermined height is formed on the outer peripheral portion of the screw 60, and the screw 60 is driven in the rotational direction and the axial direction at the rear end of the screw 60, also not shown in the drawing. Drive device is provided.

Accordingly, a molded article can be obtained as follows. That is, when the pellet-shaped injection material is put into the hopper and the screw 60 is driven to rotate, the injection material is supplied from the supply hole 52 to the cylinder hole 51 and is sent to the front of the injection cylinder 50 by the flight 61 of the screw 60. In the process of being fed, the injection material is melted by heat applied from the outside of the injection cylinder 50 and heat generated by a shearing action, a friction action, and the like when the screw 60 is rotationally driven, and is accumulated in front of the injection cylinder 50. You.
The screw 60 is retracted with the aid of accumulated injection material pressure or suckback. After melting a predetermined amount,
That is, after the measurement, the screw 60 is driven in the axial direction, and the screw 60 is injected into a mold cavity (not shown). The molded product can be obtained by holding the pressure at a predetermined pressure for a predetermined time and then waiting for cooling and solidification to open the movable mold.

[0004]

As described above, a molded product can be obtained by a conventional injection molding machine, but the holding pressure is not constant and the weight and quality of the molded product may vary. . The reason will be described with reference to FIG.
FIG. 4 (b) is a plan view as viewed from the direction of arrow in FIG. 4 (a). As shown in FIG. Although it is pushed in the direction of the arrow by a set pressure with a hydraulic cylinder or the like, the height of the flight 61 of the screw 60 is selected to be close to the cylinder hole 51 of the injection cylinder 50, and when the screw 60 moves forward in the pressure holding direction. The opening edge 53 in front of the material supply hole 52
There is a possibility that the injection material P in the form of a pellet may be caught between the air and the flight 61. If bitten, the injection material P cannot escape and becomes resistance in the holding pressure direction. As a result, the set holding pressure cannot be obtained, and the actual holding pressure decreases.
Since the amount of biting of the injection material P is not constant, or the substantial holding pressure fluctuates depending on the presence or absence of biting, the holding pressure is set to be constant. Nevertheless, the weight and quality of the molded product will vary.

The present invention aims to provide an injection molding machine which solves the above-mentioned drawbacks of the conventional injection molding machine, and more specifically, a screw of the injection molding machine which can accurately hold the pressure at a set holding pressure. Another object of the present invention is to provide a screw of an injection molding machine capable of obtaining a molded product having a constant weight and quality, and a method of positioning such a screw.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a shape of a flight so that an injection material trapped between a front opening edge of an injection material supply hole formed in an injection cylinder and a flight is released. Is achieved by deforming That is, in order to achieve the above object, according to the first aspect of the present invention, an injection cylinder having an injection material supply hole formed at a rearward position, and a driving direction and an axial direction driving in the cylinder hole of the injection cylinder. When the screw is driven to rotate, the injection material supplied from the injection material supply hole is metered and accumulated in front of the injection cylinder, and when the screw is driven in the axial direction, the metering is performed. The accumulated injection material is injected into the mold,
A screw in an injection molding machine adapted to apply a pressure in the axial direction to the screw when it is injected at a predetermined pressure and reaches a pressure-holding position, and the pressure is maintained in the injection cylinder during the pressure-holding step of the screw. The flight located in the vicinity of the opening edge in front of the injection material supply hole is deformed so that the height of the flight is made lower than other parts, cutout, etc., so as to escape the injection material that bites during the pressure holding process. I have. Claim 2
The present invention provides a method for positioning a screw of an injection molding machine, wherein a deformed portion of the screw according to claim 1 is positioned near an opening edge in front of an injection material supply hole during a pressure holding step. A position where the deformed portion is located near the opening edge in front of the injection material supply hole of the injection cylinder at the time of the most forward movement of the screw during the pressure holding step is set as a screw most forward movement reference position, The screw most advanced position is compared with the screw most advanced position when the molding condition is determined, and the screw most advanced position is corrected by the difference. When correcting the screw most advanced position described in 2, the screw position, such as the pressure-holding start position, the plasticization completion position, the rotation and back pressure switching position, the injection speed and the pressure switching position, is also simultaneously corrected by the same amount. Configured so that.

[0007]

Embodiments of the present invention will be described below. FIG. 1 is a view showing an injection molding machine according to the present embodiment, in which (a) is a substantially entire side view and (b) is a plan view near an injection material supply hole. As shown in the figure, the injection molding machine according to the present embodiment also includes an injection cylinder 1. A screw 10 is provided in the cylinder hole 2 of the injection cylinder 1 so as to be drivable in the axial direction and the rotational direction. In FIG. 1A, an injection nozzle 3 is integrally provided at the left side, that is, at the front of the injection cylinder 1, and a substantially square injection material supply hole 4 is opened toward the rear. Then, the cylindrical supply portion of the hopper 5 is inserted into the injection material supply hole 4,
Alternatively, as shown in FIG. 1A, the hopper 5 is attached so that the lower end of the supply unit rides on the outer peripheral portion of the injection material supply hole 4. A drive device 6 composed of a hydraulic or electric motor is provided behind the injection cylinder 1, and the screw 10 is driven in the rotational direction and the axial direction by the drive device 6. The heater 7 is provided on the outer periphery of the injection cylinder 1 as conventionally known.
7,... Are provided.

[0008] On the outer periphery of the screw shaft of the screw 10,
As is well known in the art, flights 11 having a predetermined pitch and a predetermined height are provided integrally over substantially the entire length thereof. In the embodiment shown in FIG. The flight 11 located in the vicinity of the opening edge 8 in front of 4 has a cutout portion 12 cut off from the top by a certain depth. To elaborate further,
FIG. 1A also shows the position of the screw 10 in which the distance between the tip of the injection nozzle 3 and the tip of the screw 10 becomes (X) when the screw 10 advances most during the pressure holding process. However, at this time, the tip of the screw 10 and the injection material supply hole 4
The distance between the opening 11 and the front opening edge 8 is A, and the notch 12 is formed in the flight 11 at this position in such a manner that the flight 11 is cut off forward and backward from the opening edge 8 by a predetermined distance from the top to a certain depth. . Thereby, the screw 10 during the pressure holding process is
Even if the most advanced position is slightly shifted, the injection material is prevented from being caught during the pressure holding process.

As is well known in the art, the mold clamping device includes a fixed platen 4.
1, a movable plate 42 paired with the fixed plate 41, four tie bars 43, 43,..., Etc. The fixed plate 41 has a fixed mold 44, and the movable plate 42 has a movable mold 45. The cavities 46, 46 are formed in these molds 44, 45 as is well known in the art.

Next, the operation will be described. The injection material in the form of pellets or chips is put into the hopper 5, and the screw 10 is driven to rotate by, for example, a hydraulic motor of the driving device 6. Then, the injection material is supplied from the supply hole 4 to the cylinder hole 2 and sent to the front of the injection cylinder 1 by the flight 11 of the screw 10. In the process of being sent,
The injection material is melted by heat applied from heaters 7, 7,... Provided on an outer peripheral portion of the injection cylinder 1 and heat generated by a shearing action, a friction action, and the like when the screw 10 is driven to rotate. It is stored in front of one. The screw 10 is retracted with the aid of accumulated injection material pressure or suckback. When a predetermined amount is measured, the screw 10 is driven in the axial direction by, for example, a piston cylinder unit, and is injected into the cavities 46, 46 of the clamped dies 44, 45. The pressure is maintained at a predetermined pressure for a predetermined time, and after cooling and solidification, the movable mold 45 is opened to take out the molded product. Hereinafter, molding is performed in the same manner.

According to the present embodiment, the notch 12 is formed in the flight 11 located in the vicinity of the opening edge 8 in front of the injection material supply hole 4 at the time of the pressure holding step, by cutting off a certain depth from the top. The screw 10
The injection material to be caught between the flight 11 and the opening edge 8 in front of the injection material supply hole 4 escapes rearward through the notch 12. Therefore, the resistance due to the biting is eliminated, that is, the influence of the presence or absence of the biting is eliminated, and the holding pressure as set from the driving device 6 is reduced to the screw 10.
Is transferred to the injection material in the molten state at the tip end, so that a molded article having a constant weight and quality can be obtained.

In the above embodiment, the notch 12 is formed in the flight 11 of the screw 10.
Obviously, the same operation can be performed by reducing the height of the flight 11 instead of the flight 2. The symbol α in (b) of FIG. 1 represents the pitch angle of the flight 11,
It is also possible to increase the angle α so that the injected material is easily released and the biting resistance is reduced. It is also apparent that a low melting point metal material can be used as the injection material as in the case of the synthetic resin.

As described above, according to the present embodiment, the notch 12 is formed in the flight 11 of the screw 10 over a predetermined length. When the screw 10 is located near the opening edge 8 in front of the hole 4, the resistance due to the bite disappears and the pressure is maintained at the set holding pressure. However, the position of the screw 10 at the start of the holding pressure is the same as other molding conditions. The notch 12 may be displaced from the vicinity of the opening edge 8 because the operator makes the setting. FIG. 2A is a cross-sectional view showing a main part of the embodiment shown in FIG. 1A, in which the notch 12 is located near the opening edge 8 in front of the injection material supply hole 4. In other words, although the tip of the screw 10 is located at the screw most forward reference position (X), in the embodiment shown in FIG. It is shifted by e (e = XY) from the most advanced reference position (X). Therefore, an embodiment for automatically correcting the "displaced position" is shown in FIG.

In FIG. 3, the same or similar components as those in the embodiment shown in FIG. 1 are denoted by the same reference numerals and will not be described repeatedly. Is composed of a hydraulic motor 6a and a hydraulic piston cylinder 6b. A relief valve 22, a check valve 23 for passing pressure oil toward an accumulator 24, an accumulator 24 for discharging hydraulic oil at the time of injection, an electromagnetic opening / closing valve, and a pipe 20 connecting the cylinder chamber 6 c of the hydraulic piston cylinder 6 b and the hydraulic pump 21. Valve 25, servo valve 2 for controlling the flow rate of hydraulic oil supplied to cylinder chamber 6c, etc.
6 etc. are interposed. The servo valve 26 includes a servo valve main body 27 including a throttle section and the like, and a servo amplifier 28. Therefore, when a signal controlled by the control device 30 described later is applied to the servo amplifier 28, the screw 1
0 is driven in the injection direction at the set speed, pressure, etc., and is maintained at the set pressure. The hydraulic motor 6a
FIG. 3 does not show a hydraulic circuit for supplying and discharging hydraulic oil to and from the hydraulic circuit.

In the present embodiment, the control device 30 includes a screw position comparator 31, a screw most advanced position comparator 32,
It comprises a screw position set value corrector 33 and the like.
One input terminal of the screw position comparator 31 has a screw position detector 3 provided in association with the screw 10.
A signal relating to the position of the screw 10 detected at 5 is input through a signal line a, and a signal relating to the screw position set or corrected from the changeover switch 36 is input to the other input terminal via a signal line b. ing. The screw position comparator 31 compares these signals, and detects a screw 1 detected by the screw position detector 35.
A control signal is output to the servo amplifier 28 of the servo valve 26 via the signal line c so that the position of 0 becomes the set or corrected screw position.

The screw position setting unit 38 is used by an operator to set values relating to the position of the screw 10, such as a plasticization completion position, a rotation and back pressure switching position, an injection speed and a pressure switching position, and a holding pressure switching position. The set value set by the screw position setter 38 is input to the screw position set value corrector 33 via a signal line d, and is input to the changeover switch 36 via a signal line f. The screw most forward reference position setting device 39 is a screw 1
A value in which the notch 12 of the flight 11 is located in the vicinity of the opening edge 8, in other words, a value (X) specific to the screw 10 shown in FIG. Although the control device 30 has a constant value except when the control device 30 is applied to another injection molding machine, the screw most advanced reference position set by the screw most advanced reference position setting device 39 is controlled by the signal line g. The signal is input to one input terminal of the forward position comparator 32. The other input terminal of the screw most advanced position comparator 32 has a signal line a
The screw 1 detected by the screw position detector 35
A signal relating to the position 0 is input, and the screw most advanced position comparator 32 and the screw position set value corrector 33 are connected by the signal line h, and the screw position set value corrector 3
3 and the changeover switch 36 are connected by a signal line i, respectively. The deviation signal calculated and compared by the screw most advanced position comparator 32 is input to the screw position set value corrector 33 and corrected by the screw position set value corrector 33. The input signal is input to one input terminal of the changeover switch 36.

Next, the operation will be described. In the screw position setting device 38, molding conditions relating to the position of the screw 10, such as a plasticization completion position, a rotation and back pressure switching position, an injection speed and a pressure switching position, and a holding pressure switching position, are set. In addition,
The screw most forward position at this time differs depending on the operator, and the screw most forward reference position (X) where the notch 12 of the flight 11 of the screw 10 is located near the opening edge 8.
This is generally different from (Y) as shown in (B) of FIG. 2, for example. The changeover switch 36
Is a screw position setting device 3 as shown in FIG.
The molding condition set to 8 is switched to the S contact input to the screw position comparator 31 in advance. Then, a signal related to the position of the screw 10 set by the screw position setting device 38 and a signal detected by the screw position detector 35 are input to the screw position comparator 31, and the screw position detected by the screw position detector 35 A signal is output to the servo amplifier 28 such that the signal related to the position 10 coincides with the set value. As described with reference to FIG. 1, the screw 10 is weighed by the hydraulic motor 6a until the screw 10 reaches the plasticizing completion position. When a predetermined amount is measured, injection is performed. At this time, the injection speed, the pressure holding start position, and the like are controlled as set by the screw position setting device 38. After holding the pressure, the movable mold 45 is opened after cooling and solidification, and the molded product is taken out.

While the molding is being performed in the same manner, the setting values set by the screw position setting device 38 are appropriately changed to determine satisfactory molding conditions. Then, the changeover switch 36
To the contact T manually or automatically. The screw most advanced reference position (X) set in the screw most advanced reference position setting unit 39 is input to the screw most advanced position comparator 32, and the screw position detector 3
5, the screw forward position (Y) is also input, and the difference (X−Y) is output to the screw position set value corrector 33.
In, the set value set by the screw position setter 38 is corrected by (X−Y) and output to the screw position comparator 31. Therefore, thereafter, the position of the screw 10 is controlled by the corrected set value. As a result, the notch 12 is positioned near the opening edge 8 in front of the injection material supply hole 4, that is, the tip of the screw 10 is positioned at the screw most forward reference position (X), and the injection is performed. The resistance due to the biting of the material is eliminated. It is clear that the same can be implemented even if the driving device 6 is constituted by an electric motor.

[0019]

As described above, according to the present invention, the flight of the screw located in the vicinity of the opening edge in front of the injection material supply hole of the injection cylinder during the pressure-holding step has the height of another portion. Since the injection material is deformed so as to escape the injection material that bites during the pressure holding process by lowering, notching, etc., the injection material is in contact with the opening edge in front of the injection material supply hole of the injection cylinder during the pressure holding process. Biting during screw flight is prevented. Therefore, the present invention has the advantage that the resistance due to biting is eliminated, and the holding pressure acting from the rear of the screw is accurately transmitted to the molten injection material at the tip of the screw, and a molded product with a constant weight and quality can be obtained. Specific effects can be obtained. According to another aspect of the present invention, a position where a portion deformed at the time of the most forward movement of the screw during the pressure holding step is located near the opening edge in front of the injection material supply hole of the injection cylinder is set as the most forward movement reference position of the screw. In advance, the screw most advanced reference position is compared with the screw most advanced position at the time when the molding conditions are determined, and the screw holding pressure start position, plasticization completion position, rotation and back pressure switching position, injection speed and Since all screw positions, such as the pressure switching position, are configured to be simultaneously corrected by the same amount, the deformed portion is located near the opening edge in front of the injection material supply hole of the injection cylinder during the pressure holding process. Will be accurately located. Therefore, it is possible to obtain a molded article having a constant holding pressure and a constant weight and quality. However, since the deformed portion is precisely located near the opening edge in front of the injection material supply hole of the injection cylinder, it is possible to obtain a molded product. ,
The same effect can be obtained even if the deformed portion is made smaller, and the provision of the deformed portion can minimize the reduction in plasticizing ability.

[Brief description of the drawings]

FIG. 1 is a view showing an embodiment of the present invention, in which (a) is a schematic side sectional view showing substantially the entirety of an injection molding machine according to the embodiment, and (b) is the vicinity of an injection material supply hole. FIG.

FIG. 2 is a side sectional view showing a most advanced position of the screw according to the embodiment of the present invention, wherein (a) is a reference position and (b) is a deviated position.

FIG. 3 is a schematic diagram showing a substantially entire injection molding machine and a control device used for executing a screw positioning method according to an embodiment of the present invention.

FIG. 4 is a view showing a main part of a conventional injection molding machine, in which (A) is a side sectional view showing the vicinity of an injection material supply hole, and (B9) is a plan view taken along the arrow in FIG. FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Injection cylinder 4 Injection material supply hole 5 Hopper 8 Front opening edge 10 Screw 11 Flight 12 Notch 27 Servo valve body 30 Control device 31 Screw position comparator 32 Screw most advanced position comparator 33 Screw position set value corrector 38 Screw Position setting device 39 Screw forward most reference position setting device

Claims (3)

[Claims] 1. An injection cylinder (1) having an injection material supply hole (4) drilled toward the rear and a cylinder hole (2) of the injection cylinder (1) that can be driven in a rotational direction and an axial direction. Consisting of the screw (10) provided in the
When the screw (10) is rotationally driven, the injection material supplied from the injection material supply hole (4) is metered and accumulated in front of the injection cylinder (1), and the screw (10) is rotated.
Is driven in the axial direction, the injection material that has been weighed and accumulated is injected into the mold (40), and when a predetermined amount is injected and reaches the pressure-holding position, axial pressure is applied to the screw (10) to hold the screw. Screw (1)
0), wherein the screw (10) has an opening edge (8) in front of the injection material supply hole (4) of the injection cylinder (1) during the pressure holding step.
The flight (11) located in the vicinity of is deformed (12) so that the height of the flight (11) is made lower than that of the other parts, and cutouts or the like are performed so as to escape the injection material caught during the pressure holding process. Characteristic screw of injection molding machine. 2. The deformed part (12) of the screw (10) according to claim 1 being located in the vicinity of the opening edge (8) in front of the injection material supply hole (4) during the pressure-holding step. A method for positioning a screw (10) of an injection molding machine to be aligned, wherein the deformed portion (12) is formed in an injection material supply hole (4) of an injection cylinder (1) when the screw is advanced most during a pressure holding process. A position located near the front opening edge (8) is set as the screw most advanced reference position (X), and the screw most advanced reference position (X) and the screw most advanced position when the molding conditions are determined. (Y), and correcting the screw most advanced position by the difference (X−Y). 3. A screw position such as a pressure-holding start position, a plasticizing completion position, a rotation and back pressure switching position, an injection speed and a pressure switching position, etc., when correcting the screw most advanced position (Y) according to claim 2. A method of positioning a screw of an injection molding machine, which simultaneously corrects the same amount (X-Y).