JP2001030316A - Injection apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten a molding cycle and to prevent molding inferiority and the seizing of a resin by providing a non-return ring to the periphery of a screw head, and allowing a screw to advance while allowing flights to retreat apparently in an injection process. SOLUTION: A non-return ring 28 is provided to the periphery of the columnar part 26 of a screw head 27. When a screw 12 is allowed to advance by driving an injection motor in an injection process, a weighing motor is driven to rotate the screw 12 in a reverse direction to allow flights 23 to retreat apparently. Therefore, the screw 12 advances but the resin in grooves 24 retreats. In this case, since the non-return ring 28 is set to a cutting-off position and the holes 28a, 29a thereof are cut off, the resin in front of the screw head 27 does not flow back toward a flight part 21. By this constitution, suck-back is dispensed with by a simple process and, in the succeeding weighing process, no irregulality is generated in the amt. of the resin in front of the screw head 27.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection device.

[0002]

2. Description of the Related Art Conventionally, in an injection molding machine, an injection device is disposed, and a screw is disposed in a heating cylinder of the injection device so as to be rotatable and advanceable and retractable. The second drive means can rotate and move forward and backward. A spiral flight is formed on the body of the screw, that is, the outer peripheral surface of the screw body, and a groove is formed by the flight.

When the screw is rotated in the forward direction during the measuring step, the resin dropped from the hopper attached to the heating cylinder is melted in the heating cylinder, and is advanced along the groove. Along with that,
The screw is retracted and the resin is stored in front of the screw head. When the screw is advanced during the injection step, the resin stored in front of the screw head is injected from the injection nozzle, and is filled in the cavity space in the mold apparatus. After that, the resin in the cavity space is cooled to form a molded product. At this time, the resin shrinks with the cooling. Therefore, pressure is maintained to replenish the contracted resin into the cavity space, and the pressure of the resin in the heating cylinder is maintained.

[0004] When a hot runner type mold device is used, the resin injected from the injection nozzle during the injection step passes through a sprue in the mold device, passes through the hot runner, and fills the cavity space. It is supposed to be. In this case, the resin in the hot runner is heated by the heater for heating even after the injection step is completed and the measuring step is started, and is placed in a molten state. , The pressure is maintained.

[0005] Therefore, if the mold is opened during the weighing process, the resin drips into the cavity space.

Therefore, by performing suckback at a timing before the start of the measuring step, the pressure of the resin in the hot runner is reduced.

[0007]

However, in the above-described conventional injection apparatus, the number of steps for molding is increased by the amount of suckback, so that the molding cycle is lengthened. As a result, molding defects such as silver streaks and resin burning occur in the molded product.

In addition, since the screw is retracted with the suckback, the amount of resin accumulated in front of the screw head varies in the subsequent measuring step, and molding can be performed stably. Will be gone.

The present invention solves the above-mentioned problems of the conventional injection device, shortens the molding cycle, and prevents molding defects and resin burning from occurring.
An object of the present invention is to provide an injection device capable of performing molding in a stable manner.

[0010]

For this purpose, in the injection apparatus of the present invention, a heating cylinder, a flight portion having a flight formed on an outer peripheral surface of a screw body, and a screw disposed at a front end of the flight portion are provided. A screw provided rotatably and advancing and retreating in the heating cylinder, a check ring disposed around the screw head, and a first ring for rotating the screw. Drive means, second drive means for moving the screw forward and backward, screw advance control means for driving the second drive means in the injection step to advance the screw at a predetermined screw speed, and the injection step And flight control means for driving the first drive means to apparently retreat the flight.

[0011] In another injection device of the present invention, the check ring is further rotated by a predetermined angle with respect to the screw head with the rotation of the screw, so that the front of the screw head and the flight portion are connected to each other. And a blocking position for blocking the front of the screw head from the flight section.

[0012]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 2 is an enlarged view of a main part of the injection device according to the embodiment of the present invention, and FIG. 3 is a conceptual diagram of the injection device according to the embodiment of the present invention.

In the drawing, 11 is a heating cylinder as a cylinder member, 12 is a screw as an injection member disposed rotatably and advancing and retracting in the heating cylinder 11, and 13 is a front end of the heating cylinder 11. An injection nozzle formed at the left end (in FIG. 2), 14 is a nozzle port formed in the injection nozzle 13, and 15 is formed at a predetermined position near the rear end (the right end in FIG. 2) of the heating cylinder 11. The resin supply port 16 is a hopper attached to the resin supply port 15 and containing the resin.

The screw 12 has a flight section 21,
And a screw head 27 disposed at the front end of the flight section 21. The flight part 21 is a flight 2 formed in a spiral shape on the outer peripheral surface of the screw body.
The flight 23 forms a spiral groove 24. In the flight section 21, a resin supply section P1 to which the resin dropped from the hopper 16 is supplied in order from a rear side (right side in FIG. 2) to a front side (left side in FIG. 2), compresses the supplied resin. A compression section P2 for melting while melting and a measuring section P3 for measuring a fixed amount of the melted resin are formed. The bottom of the groove 24,
The outer diameter of the groove bottom is made relatively small in the resin supply part P1, gradually increased from the rear to the front in the compression part P2, and made relatively large in the measurement part P3. Therefore, the inner peripheral surface of the heating cylinder 11 and the screw 12
The gap (gap) between the shaft portion and the outer peripheral surface is relatively large in the resin supply section P1, gradually reduced from the rear to the front in the compression section P2, and relatively reduced in the measurement section P3.

When the screw 12 is rotated in the forward direction during the weighing step, the resin dropped from the hopper 16 is supplied to the resin supply section P1, and is advanced in the groove 24 (moved to the left in FIG. 2). Accordingly, the screw 12
Is retracted (moved to the right in FIG. 2), and the resin is stored in front of the screw head 27. The resin in the groove 24 has a pellet-like shape in the resin supply section P1 as shown in the figure, becomes a semi-molten state in the compression section P2, and is completely melted in the measurement section P3. Become liquid.

When the screw 12 is advanced in the injection step, the resin stored in front of the screw head 27 is injected from the injection nozzle 13 and is filled in a cavity space in a mold device (not shown). At this time, a backflow prevention device is provided around the screw head 27 so that the resin stored in front of the screw head 27 does not flow backward.

For this purpose, the screw head 27
Has a conical (conical) head body 25 in the front half and a column 26 in the rear half. An annular check ring 28 is rotatably disposed around the cylindrical portion 26, and a presser 29 is fixed to the front end of the flight portion 21. In addition,
The check ring 28 and the presser 29 constitute a backflow prevention device.

In the check ring 28, holes 28a extending in the axial direction are formed at a plurality of positions in the circumferential direction, and cutouts 28b are formed in the front end at predetermined angles. Then, a locking projection 25a is formed on the head body 25, and the locking projection 25a is placed in the notch 28b. In this case, the check ring 28 is
With the rotation of the screw head 27, the screw head 27 is rotated by a predetermined angle θ, and further rotation is restricted.

On the other hand, holes 29a extending in the axial direction corresponding to the holes 28a are formed at a plurality of positions in the circumferential direction of the presser 29. Therefore, the check ring 28
Is rotated with respect to the screw head 27, the holes 28a and 29a are selectively communicated. The check ring 28 has a communication position for communicating the front of the screw head 27 with the flight portion 21 and a blocking position for blocking the front of the screw head 27 and the flight portion 21.

The rear end (right end in FIG. 3) of the heating cylinder 11 is attached to a front injection support 31, and a rear injection support 32 is disposed at a predetermined distance from the front injection support 31. A guide bar 33 is provided between the front injection support 31 and the rear injection support 32, and a pressure plate 34 is disposed along the guide bar 33 so as to be able to advance and retreat. The front injection support 31 and the rear injection support 32 are
It is fixed to a slide base (not shown) by bolts (not shown).

A drive shaft 35 is connected to the rear end of the screw 12, and the drive shaft 35
Is rotatably supported on the pressure plate 34 by bearings 36 and 37. In order to rotate the screw 12, an electric weighing motor 41 as a first driving means is provided.
A first rotation transmission means including pulleys 42 and 43 and a timing belt 44 is disposed between the first rotation transmission means and the drive shaft 35. Therefore, by driving the measuring motor 41, the screw 12 can be rotated in the forward or reverse direction. In the present embodiment, an electric weighing motor 4 is used as the first driving means.
Although 1 is used, a hydraulic motor may be used instead of the electric weighing motor 41.

A ball screw 47 composed of a ball screw shaft 45 and a ball nut 46 screwed to each other is provided behind the pressure plate 34 (to the right in FIG. 3). Motion direction conversion means for converting the motion into a linear motion is configured. The ball screw shaft 45 is rotatably supported by the rear injection support 32 by a bearing 48, and the ball nut 46 is formed by a plate 51 and a load cell 52.
And is fixed to the pressure plate 34 via. Further, in order to move the screw 12 forward and backward, an injection motor 53 as a second driving means is provided, and pulleys 54 and 55 are provided between the injection motor 53 and the ball screw shaft 45.
And a second rotation transmission means including a timing belt 56. Therefore, by driving the injection motor 53 and rotating the ball screw shaft 45, the ball nut 46 and the pressure plate 34 are moved,
The screw 12 can be advanced (moved to the left in FIG. 3) or retracted (moved to the right in FIG. 3).
In this embodiment, the injection motor 53 is used as a means for moving the pressure plate 34, but an injection cylinder may be used instead of the injection motor 53.

Next, a control circuit of the injection device having the above configuration will be described.

FIG. 1 is a block diagram of a main part of a control circuit of an injection apparatus according to an embodiment of the present invention, FIG. 4 is a schematic diagram of a control circuit of the injection apparatus according to an embodiment of the present invention, and FIG. FIG. 6 is a first time chart showing the operation of the injection device in the embodiment, and FIG. 6 is a second time chart showing the operation of the injection device in the embodiment of the present invention.

In the figure, 41 is a measuring motor, 53 is an injection motor, 62 is a control device, 64 is an injection servo amplifier, 65 is a measuring servo amplifier, 66 is a screw speed setting device as screw speed setting means, 67 is a memory as storage means, 68 is a flight speed setting device, 71
Is an injection motor speed detector for detecting the injection motor speed n _I , 72 is a metering motor speed detector for detecting the metering motor speed n _M , 81 is the position of the screw 12 (FIG. 3). It is a screw position detector to detect.

The control device 62 includes an injection motor rotation speed setting device 73, subtracters 74 and 78, a gain setting device (-K) 75 as a measurement motor rotation speed calculation means, and a measurement motor rotation speed setting device. Consisting of a vessel 77. The flight speed setting unit 68 and the gain setting unit 75 constitute a flight speed setting unit.

[0028] In the control circuit of the arrangement, during the metering step, the metering motor rotational speed setting device 77 sends a preset metering-motor-rotational-speed command N _M to the subtracter 78.
Subtracter 78, the receiving the metering-motor-rotational-speed command N _M and the metering-motor-rotational-speed n _M, calculates the deviation [Delta] n _M of the metering motor rotational speed command N _M and the metering-motor-rotational-speed n _M and it sends it to the metering servo-amplifier 65 the deviation [Delta] n _M as a current command I _M. Thus, the control device 62 drives the weighing motor 41.

At the time of the injection step, the screw speed Vs
Are changed in multiple stages corresponding to the screw positions S _i (i = 1, 2,...). For this purpose, the screw speed setting device 66 sets the screw speed command Vs _oi (i = 1, 2,...) In correspondence with each screw position S _i .
And sends the screw speed command _Vsoi to the motor rotation speed setting device 73 for injection. Injection-motor rotational speed setting unit 73 receives the screw speed command Vs _oi, the screw speed command Vs _oi to in correspondence the injection-motor-rotational-speed as shown in FIG. 6 command N _Ii (i = 1, 2,...), And subtracts the _injection motor rotational speed command _NIi
And to the gain setting device 75. The subtracter 74 receives the injection-motor-rotational-speed command N _Ii and the injection-motor-rotational-speed n _I, and calculates a deviation [Delta] n _I of the injection-motor-rotational-speed command N _Ii and the injection-motor-rotational-speed n _I And the deviation Δn _I as a current command I _I ,
Send to In this way, the control device 62 drives the injection motor 53 to move the screw 12 forward.

In this case, as the screw 12 is advanced, a reaction force is generated by the resin stored in front of the screw head 27, and the pressure plate 34
Then, the load cell 52 is pressed via the drive shaft 35. At this time, the distortion of the load cell 52 is converted into an electric signal, and based on the electric signal, an ejection force for pushing the screw 12 from behind at a predetermined pressure is calculated.

The flight speed setting device 68 sends a preset speed ratio γ to the gain setting device 75. The gain setting unit 75 sets the speed ratio γ and the injection motor rotation speed command N _Ii sent from the injection motor rotation speed setting unit 73.
Upon receiving the, as a gain of the speed ratio gamma, FIG as flight speed command corresponding to each screw position S _i 6
The measurement motor rotation speed command N _Fi (i =
1, 2,...), And sends a metering motor rotation speed command N _Fi to the subtractor 78. When the subtractor 78 receives the metering motor speed command N _Fi and the metering motor speed n _M , the subtractor 78 calculates a deviation Δn _F between the metering motor speed command N _Fi and the metering motor speed n _M. and sends to the metering servo-amplifier 65 the deviation [Delta] n _F as the current command I _F. Thus, the control device 62 drives the measuring motor 41 to rotate the screw 12 at the screw rotation speed Nf.
The gain setting unit 75 and the subtractor 78 constitute a flight control unit, and the flight control unit controls the flight speed Vf.

[0032] Incidentally, in the memory 67, and stores the rotational speed pattern of the metering-motor-rotational-speed command N _Fi, it is also possible to control the flight speed Vf reads the rotational speed pattern.

Next, the operation of the injection device will be described.

In the injection device having the above configuration, the control device 6
The communication control means (not shown) drives the measuring motor 41 in the forward direction at the timing t1 to
Is rotated in the forward direction at a screw rotation speed N1 for a time τ1. Therefore, the check ring 28 is
With the rotation of the screw head 27, the screw head 27 is rotated by the angle θ and placed at the communication position, and the holes 28a (FIG. 2) and 29a are communicated. Subsequently, at timing t
2, the weighing control means (not shown) of the control device 62 drives the weighing motor 41 in the forward direction to rotate the screw 12 for the time τ2 by the screw rotation speed N.
Weigh by rotating in positive direction at 2. During this time, the check ring 28 is placed in the communicating position and the hole 28
a and 29a are communicated. As a result, while the resin in the heating cylinder 11 advances along the groove 24, and is heated and melted by the heating cylinder 11,
It flows forward through the holes 28a, 29a and is stored in front of the screw head 27. Accordingly, the injection motor 53 is driven, and the screw 12 is retracted.

When the weighing process is completed at the timing t3 in this way, the cut-off control means (not shown) of the control device 62 drives the weighing motor 41 in the reverse direction at the timing t4 to rotate the screw 12 by the time τ3. It is rotated in the reverse direction at a rotation speed N3. Therefore, the check ring 28 is rotated by the angle θ with respect to the screw head 27 with the rotation of the screw 12 and is placed in the blocking position, and the holes 28a and 29a are blocked.

Subsequently, the injection process is started at timing t5, and the injection control means and the screw advance control means (not shown) of the control device 62 drive the injection motor 53 to advance the screw 12 at the screw speed Vs. The resin stored in front of the screw head 27 is injected from the injection nozzle 13. During this time, the gain setting device 75
And the subtractor 78 is driven in the reverse direction to retract the apparent flight 23 in accordance metering-motor-rotational-speed command N _Fi the metering motor 41.

At this time, a part of the resin stored in front of the screw head 27 tends to move backward by flowing backward. However, since the holes 28a and 29a are blocked,
The resin is prevented from flowing back to the flight section 21.
Therefore, the filling amount of the resin during the injection step can be stabilized, and the quality of the molded product can be improved. In addition, since the resin in the flight section 21 during the injection step can be stabilized, the measurement can be stably performed during the measurement step, the heat history of the resin can be stabilized, and the temperature of the resin can be stabilized. Can be done.

The controller 62 performs speed control based on the speed pattern of the screw speed Vs preset by the screw speed setting device 66,
When the screw position S _i detected by the screw position detector 81 reaches a predetermined position, switching from speed control to pressure control is performed, and pressure holding control is performed based on the injection power,
The injection step is completed at timing t6.

In the present embodiment, after the screw 12 is rotated in the positive direction by the time τ1, a short time is allowed before the measuring step is started. After the rotation in the positive direction by the time τ1, the weighing process can be started immediately.
After the completion of the weighing step, the screw 12 is set for a time τ.
Although a short time is required until the screw 12 is rotated in the reverse direction, the screw 12 may be rotated in the reverse direction by the time τ3 immediately after the weighing process is completed. Further, after the screw 12 is rotated in the reverse direction by the time τ3, a short time is allowed until the injection step is started. However, after the screw 12 is rotated in the reverse direction by the time τ3, Alternatively, the injection process can be started immediately.

When a hot runner type mold device (not shown) is used, the injection nozzle 1
The resin injected from 3 passes through a sprue in a mold device (not shown), passes through a hot runner, and fills a cavity space. In this case, the resin in the hot runner is heated by the heater for heating even after the injection step is completed and the measuring step is started, and is placed in a molten state. , The pressure is maintained.

Therefore, if the mold is opened during the measuring process thereafter, the resin drips into the cavity space.

Therefore, in the injection step, when the screw 12 is moved forward by driving the injection motor 53, the metering motor 41 is driven by the gain setter 75 and the subtractor 78 to move the screw 12 in the reverse direction. Rotate
The flight 23 is apparently retracted.

Therefore, while the screw 12 advances, the resin in the groove 24 is retracted. in this case,
The check ring 28 is placed in the shut-off position and the holes 28a,
Since 9a is shut off, the resin stored in front of the screw head 27 does not flow back to the flight section 21 side. Therefore, from the resin supply part P1 behind the check ring 28 and the presser 29 to the measuring part P3,
In the vicinity of the front end of the measuring section P3, the pressure of the resin is reduced, and a negative pressure region is formed.

Then, before the weighing process to be started subsequently, the screw 12 is rotated in the forward direction and the check ring 2 is rotated.
When the seal 8 of the backflow prevention device is released by placing the position 8 in the communication position, the negative pressure in the negative pressure region reaches the hot runner, so that the hot runner can be depressurized.

Therefore, when the mold is opened thereafter and the pressure in the cavity space becomes low, the resin drops in the cavity space because the pressure of the resin in the hot runner is low at that time. Can be prevented.

Further, since the pressure of the resin in the hot runner can be reduced only by rotating the screw 12 in the forward direction and placing the check ring 28 at the communicating position, there is no need to perform suckback. Therefore, the number of steps for molding can be reduced, and the molding cycle can be shortened. As a result, molding defects such as silver streaks and resin burning do not occur in the molded product.

Further, since it is not necessary to perform suck-back in order to lower the pressure of the resin in the hot runner, the amount of the resin stored in front of the screw head 27 varies in the subsequent measuring step. Nothing. Therefore, molding can be performed stably.

The present invention is not limited to the above embodiment, but can be variously modified based on the gist of the present invention, and they are not excluded from the scope of the present invention.

[0049]

As described above in detail, according to the present invention, in the injection device, the heating cylinder, the flight portion having the flight formed on the outer peripheral surface of the screw body, and the front end of the flight portion are arranged. Equipped with a screw head, rotatably in the heating cylinder, and
A screw disposed to be able to move forward and backward, a check ring disposed around the screw head, first driving means for rotating the screw, and a second drive for moving the screw forward and backward Means, screw driving control means for driving the second driving means in the injection step to advance the screw at a predetermined screw speed, and driving the first driving means in the injection step to change the flight. Flight control means for apparently retreating.

In this case, in the injection step, the flight control means apparently retreats the flight, so that the screw advances, while the resin in the groove between the flights is retracted. Then, since the check ring is located at the blocking position, the pressure of the resin behind the backflow prevention device is reduced, and a negative pressure region is formed.

When the check ring is placed at the communicating position before the weighing process to be subsequently started, the negative pressure in the negative pressure area reaches the hot runner, so that the hot runner can be depressurized. .

Therefore, when the mold is opened and the pressure in the cavity decreases, the pressure of the resin in the hot runner decreases at that point. Can be prevented from dripping.

In another injection device of the present invention, the check ring is further rotated by a predetermined angle with respect to the screw head with the rotation of the screw, so that the front of the screw head and the flight section are connected to each other. And a blocking position for blocking the front of the screw head from the flight section.

In this case, the resin can be prevented from flowing backward to the flight section only by rotating the screw in the reverse direction, and the front of the screw head and the flight section can be prevented only by rotating the screw in the forward direction. Can be communicated.

Further, since the pressure of the resin in the hot runner can be reduced only by placing the check ring at the communicating position, suckback is not required. Therefore, the number of steps for molding can be reduced, and the molding cycle can be shortened. As a result, molding defects such as silver streaks and resin burning do not occur in the molded product.

Further, since it is not necessary to perform suck-back in order to lower the pressure of the resin in the hot runner, the amount of the resin stored in front of the screw head varies in the subsequent measuring step. There is no.
Therefore, molding can be performed stably.

[Brief description of the drawings]

FIG. 1 is a main block diagram of a control circuit of an injection device according to an embodiment of the present invention.

FIG. 2 is an enlarged view of a main part of the injection device according to the embodiment of the present invention.

FIG. 3 is a conceptual diagram of an injection device according to an embodiment of the present invention.

FIG. 4 is a schematic diagram of a control circuit of the injection device according to the embodiment of the present invention.

FIG. 5 is a first time chart illustrating an operation of the injection device according to the embodiment of the present invention.

FIG. 6 is a second time chart illustrating an operation of the injection device according to the embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Heating cylinder 12 Screw 21 Flight part 23 Flight 27 Screw head 28 Check ring 41 Metering motor 53 Injection motor 62 Control device 75 Gain setting device 78 Subtractor

Claims (2)

[Claims] 1. A heating cylinder comprising: (a) a heating cylinder; (b) a flight section having a flight formed on an outer peripheral surface of a screw body; and a screw head disposed at a front end of the flight section. Rotatable and
(C) a check ring disposed around the screw head, and (d) first driving means for rotating the screw.
(E) second drive means for moving the screw forward and backward, (f) screw advance control means for driving the second drive means in the injection step to advance the screw at a predetermined screw speed, g) flight control means for driving the first drive means in the injection step to apparently retreat the flight. 2. The communication device according to claim 2, wherein the check ring is rotated by a predetermined angle with respect to the screw head with rotation of the screw, and a communication position for communicating a front portion of the screw head with a flight portion; The injection device according to claim 1, wherein the injection device adopts a blocking position for blocking a front portion of the vehicle and the flight portion.