JP2000313044A - Injection apparatus and controlling method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To lessen the frictional resistance exerted on resin in an injection process and also to improve the quality of a molded article by a constitution comprised of a means to advance a screw at a prescribed speed and a means to advance a flight at the speed lower apparently than that of the screw by driving a first drive means. SOLUTION: A screw being rotatable and movable forward and backward is provided in a heating cylinder. The screw is constituted of a flight part and a screw head provided in the front end thereof. A motor 41 for metering is provided as a first drive means and it rotates the screw in the normal or reverse direction. Moreover, a motor 53 for injection is provided as a second drive means and it moves the screw forward or backward. On the occasion when the screw is advanced by driving the motor 53 for injection in an injection process, the motor 41 for metering is driven to rotate the screw in the reverse direction and thereby a flight speed is made lower than a screw speed so that the flight may advance apparently in relation to the heating cylinder.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection device and a control method thereof.

[0002]

2. Description of the Related Art Conventionally, an injection molding machine has an injection device, and a screw is rotatable in a heating cylinder of the injection device.
In addition, the screw is provided so as to be able to move forward and backward so that the screw can be rotated and moved forward and backward by the driving means. Then, at the time of the measuring step, the resin dropped from the hopper is melted by moving backward while rotating the screw in the positive direction in the heating cylinder, the resin is advanced along the groove of the screw, and stored in front of the screw head, and the injection step is performed. At times, the resin stored in front of the screw head is injected from an injection nozzle by advancing the screw.

[0003] Therefore, in the screw,
In order from the rear to the front, a resin supply unit to which the resin dropped from the hopper is supplied, a compression unit to melt the supplied resin while compressing the resin, and a measuring unit to measure a fixed amount of the molten resin are formed. . The resin in the groove has a pellet-like shape in the resin supply unit,
It is placed in a semi-molten state in the compression section, and is completely melted and liquid in the metering section.

By the way, if the outer peripheral surface of the screw and the inner peripheral surface of the heating cylinder have the same roughness, even if the screw is rotated during the measuring step, the resin in the groove is rotated integrally with the screw. Do not move forward. Therefore, usually, the inner peripheral surface of the heating cylinder is made rougher than the outer peripheral surface of the screw.

[0005]

However, in the conventional injection device, since the inner peripheral surface of the heating cylinder is roughened, a large amount of resin near the inner peripheral surface of the heating cylinder is required when the screw is advanced. Friction resistance is added. In addition, the molten state of the resin in the groove of the screw changes while moving through the resin supply section, the compression section and the measuring section, so that the frictional resistance applied to the resin also changes.

Therefore, in the injection step, the injection power applied to the screw from the rear does not correspond to the injection pressure applied to the front end of the screw head, and not only can the resin not be injected with a sufficient injection pressure, but also The injection pressure varies with the change in frictional resistance.

As a result, the resin pressure in the mold, that is,
Variations also occur in the mold inner pressure, which degrades the quality of the molded product.

The present invention solves the problems of the conventional injection device, reduces the frictional resistance applied to the resin in the injection step, and improves the quality of the molded product. It is an object to provide a control method.

[0009]

For this purpose, in the injection apparatus of the present invention, a heating cylinder, a flight portion having a flight formed on the outer periphery of a screw body, and a screw head disposed at the front end of the flight portion are provided. A screw disposed rotatably and advancing and retracting in the heating cylinder, first driving means for rotating the screw, and second driving means for advancing and retracting the screw A screw advancing 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 make the flight apparent Flight speed control means for advancing at a flight speed lower than the screw speed.

In another injection apparatus of the present invention, a check ring is further provided around the screw head, and the check ring is rotated by a predetermined angle with respect to the screw head as the screw rotates. It is rotated to take a communication position for communicating between the front of the screw head and the flight section, and a blocking position for blocking between the front of the screw head and the flight section.

In still another injection device of the present invention, the speed ratio of the flight speed to the screw speed is set to be smaller than 1 and equal to or larger than the minimum value set in accordance with the type of resin.

In still another injection apparatus of the present invention, the screw speed is changed in multiple stages, and the flight speed is changed in multiple stages corresponding to the screw speed.

[0013] In still another injection apparatus of the present invention, further, in a first stage before the injection step is started, the screw is rotated in the reverse direction, and the check ring is placed in the shut position. And a resin pressure lowering means for lowering the resin pressure of the flight section by rotating the screw in the reverse direction at a second stage before the injection step is started.

[0014] In still another injection apparatus of the present invention, the flight speed control means may advance the flight at a flight speed lower than the screw speed apparently until a predetermined time has elapsed since the start of the injection process. Let
After the time has elapsed, the flight is apparently advanced at a flight speed equal to the screw speed.

In the control method of the injection device of the present invention,
In the metering step, the first driving means is driven to rotate the screw in the forward direction, and in the injection step, the second driving means is driven to advance the screw at a predetermined screw speed, and By driving the driving means, the flight is apparently advanced at a flight speed lower than the screw speed.

[0016]

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

FIG. 1 is a control block diagram of an injection device according to a first embodiment of the present invention, FIG. 2 is an enlarged view of a main part of the injection device according to the first embodiment of the present invention, and FIG. FIG. 4 is a conceptual diagram of the injection device according to the first embodiment, and FIG. 4 is a time chart illustrating an operation of the injection device according to the first 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 rotatably and advancing and retracting inside 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 portion 21 includes a flight 23 formed in a spiral shape on the outer periphery of the screw body, and the flight 23 forms a spiral groove 24.
Is formed. In addition, the flight unit 21 has a rear portion (FIG. 2).
The resin supply unit P1 to which the resin dropped from the hopper 16 is supplied, the compression unit P2 which compresses and melts the supplied resin, and the molten resin are sequentially melted from the right side to the front side (left side in FIG. 2). A measuring section P3 for measuring a predetermined amount of the resin is formed. The bottom of the groove 24, that is, the outer diameter of the groove bottom is made relatively small in the resin supply part P1, gradually increased in the compression part P2, and made relatively large in the metering part P3. Therefore, a gap (gap) between the inner peripheral surface of the heating cylinder 11 and the outer peripheral surface of the screw 12 is made relatively large in the resin supply section P1, gradually reduced in the compression section P2, and compared in the measurement section P3. Target size.

When the screw 12 is retracted while rotating in the forward direction during the metering process, the resin dropped from the hopper 16 is supplied to the resin supply section P 1, is advanced in the groove 24, and is stored in front of the screw head 27. Can be The resin in the groove 24 has a pellet-like shape in the resin supply section P1 as shown in the figure, is placed in a semi-molten state in the compression section P2, and is completely melted in the measurement section P3. And become liquid.

When the screw 12 is advanced during 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 of a mold (not shown). At this time, a backflow prevention device is provided 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 on the outer periphery of the cylindrical portion 26, and a presser 29 is fixed to the front end of the flight portion 21.

In the check ring 28, holes 28a extending in the axial direction are formed at a plurality of positions in the circumferential direction, and a notch 28b is formed at a front end of the check ring 28 at a predetermined angle. 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 between the front of the screw head 27 and the flight section 21 and a blocking position for blocking between the front of the screw head 27 and the flight section 21.

The rear end 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 installed between the front injection support 31 and the rear injection support 32,
A pressure plate 34 is provided along the guide bar 33 so as to be able to move forward and backward. The front injection support 31
The rear injection support 32 is fixed to a slide base (not shown) by a bolt (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, a weighing motor 41 as a first driving means is provided. The weighing motor 41 includes pulleys 42 and 43 and a timing belt 44 between the weighing motor 41 and the drive shaft 35. First rotary transmission means is provided. Therefore, by driving the measuring motor 41, the screw 12 can be rotated in the forward or reverse direction. It should be noted that a hydraulic motor may be used in place of the measuring motor 41 as the first driving means. Further, a ball screw screwed together behind the pressure plate 34 (to the right in FIG. 3). Ball screw 4 including shaft 45 and ball nut 46
7 is provided, and the ball screw 47 constitutes a movement direction converting means for converting a rotational movement into a linear movement. The ball screw shaft 45 is rotatably supported by the rear injection support 32 by a bearing 48, and the ball nut 46 is fixed to the pressure plate 34 via the plate 51 and the load cell 52. further,
In order to move the screw 12 forward and backward, an injection motor 53 as a second driving means is provided.
A second rotation transmission means including pulleys 54 and 55 and a timing belt 56 is disposed between the ball screw shaft 3 and the ball screw shaft 45. Therefore, by driving the injection motor 53 and rotating the ball screw shaft 45, the ball nut 46 can be moved, and the screw 12 can be moved forward or backward. Note that an injection cylinder may be used instead of the injection motor 53 as the second drive unit.

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 load cell 52 is pressed through the pressure plate 34 and the drive shaft 35. Is done. 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.

For this purpose, the electric signal from the load cell 52 is sent to a control device 62, which controls the value set by the emission power setting device 63 and the load cell 52.
Calculates the firing power based on the electrical signal from the controller, generates current commands I _I and I _M , sends the current command I _I to the injection servo amplifier 64 to drive the injection motor 53, and outputs a rotation direction switching signal. the SG and the current command I _M send the metering servo-amplifier 65 drives the metering motor 41. The rotation direction switching signal SG takes positive and negative values as shown in FIG. 4. When the rotation direction switching signal SG takes a positive value, the metering motor 41 is driven in the positive direction. When the screw 12 is rotated in the forward direction and the rotation direction switching signal SG takes a negative value, the metering motor 41 is driven in the reverse direction to rotate the screw 12 in the reverse direction.

In the injection device having the above configuration, the control device 6
The communication means (not shown) in 2 drives the measuring motor 41 in the forward direction at the timing t1 to rotate the screw 12 in the forward direction at the screw rotation speed N1 for the time τ1. Therefore, the check ring 2 is
8 is rotated by the angle θ, the check ring 28 is placed at the communicating position, and the holes 28a, 29a are communicated. Subsequently, a weighing process is started at timing t2, and a weighing unit (not shown) in the control device 62 drives the weighing motor 41 in the forward direction to rotate the screw 12 in the forward direction at the screw rotation speed N2 for the time τ2. And the injection motor 53 is driven to
2 is retracted and weighed. During this time, the check ring 28
Is placed at the communication position, and the holes 28a and 29a are connected. As a result, the resin advances along the groove 24, during which it is heated and melted by the heating cylinder 11, then flows forward through the holes 28 a, 29 a and is stored in front of the screw head 27. .

When the weighing process is completed at the timing t3 in this manner, the interrupting means (not shown) in 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 12, and the check ring 28 is placed in the blocking position,
The holes 28a and 29a are blocked.

Subsequently, an injection step is started at a timing t5, and an injection means and a screw advance means (not shown) in the control device 62 drive the injection motor 53 to advance the screw 12 at a predetermined screw speed Vs. The resin stored in front of the screw head 27 is injected from the injection nozzle 13. At this time, screw head 2
A part of the resin stored in front of the nozzle 7 flows backward to move backward. However, since the holes 28a and 29a are closed, the resin in front of the screw head 27 flows back to the flight part 21. Can be prevented.

Therefore, the filling amount of the resin in the injection step can be stabilized, and the quality of the molded article 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 setter 66,
When the screw position detected by the position detector 71 reaches a predetermined position, the speed control is switched to the pressure control,
A pressure-holding control is performed based on the injection power, and a timing t6.
Completes the injection process.

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 forward rotation for the time τ1, the measuring process can be started immediately. Also,
Although a short period of time is allowed after the metering process is completed and before the injection process is started, the screw 12 can be rotated in the opposite direction immediately after the metering process is completed. Further, after the screw 12 is rotated in the reverse direction by the time τ3, a short time is allowed before the injection process is started.
After rotating 2 in the reverse direction by the time τ3, the injection process can be started immediately. In addition, suckback can be performed before starting the injection process.

By the way, if the outer peripheral surface of the screw 12 and the inner peripheral surface of the heating cylinder 11 have the same roughness,
Even if the screw 12 is rotated during the measuring process, the resin in the groove 24 is rotated integrally with the screw 12 and does not move forward. Therefore, the inner peripheral surface of the heating cylinder 11 is usually made rougher than the outer peripheral surface of the screw 12.

However, if the inner peripheral surface of the heating cylinder 11 is roughened, a large frictional resistance is applied to the resin near the inner peripheral surface of the heating cylinder 11 when the screw 12 is advanced. In addition, the molten state of the resin in the groove 24 changes while moving through the resin supply section P1, the compression section P2, and the measuring section P3, so that the frictional resistance applied to the resin also changes.

In the injection step, when the injection motor 53 is driven to advance the screw 12, the metering motor 41 is driven to rotate the screw 12 in the reverse direction. The speed at which the flight 23 apparently advances, that is, the flight speed Vf is set lower than the screw speed Vs.

That is, when the speed ratio of the flight speed Vf to the screw speed Vs is γγ = Vf / Vs, γ <1. In this case, the apparent flight speed Vf is reduced, so that the resin slides on the outer peripheral surface of the screw 12 and stagnates on the inner peripheral surface of the heating cylinder 11. Therefore, the frictional resistance applied to the resin near the inner peripheral surface of the heating cylinder 11 can be reduced.

However, when the flight speed Vf is reduced below a limit value determined by the type of the resin, the screw 12 moves forward while the resin is
Is almost stopped on the inner peripheral surface of the motor. In this case, as described above, during the injection process, the check ring 28 is placed in the blocking position, and the holes 28a and 29a are placed in the blocked state, so that the resin does not flow into the flight section 21 side. Therefore, from the resin supply section P1 to the measuring section P3
In particular, the resin pressure decreases particularly near the front end of the flight section 21. As a result, the measurement cannot be stably performed during the measurement process, and voids, silver streaks, and the like are generated in the molded product, and the quality of the molded product is deteriorated.

Therefore, assuming that the minimum value of the speed ratio γ set according to the type of resin is γ _MIN , γ _MIN ≦ γ. Therefore, the speed ratio γ is set to be smaller than 1 and equal to or larger than the minimum value γ _MIN , for example, in the range of 0.1 to 0.9.

Then, the flight speed setting device 68 sets a speed pattern of the flight speed Vf based on the speed ratio γ set in advance in this way, and sends the speed pattern to the control device 62 as a speed command value. The control device 62
The flight speed control means (not shown) controls the flight speed based on the speed command value sent from the flight speed setting device 68. For this purpose, the rotation speed calculation means in the flight speed control means is provided with the screw speed Vs
And the screw speed Nf based on the flight speed Vf
Is calculated, to generate a current command I _F on the basis of the screw rotation speed Nf, the electric current command I _F is sent to the metering servo-amplifier 65 drives the metering motor 41. as a result,
The screw 12 is rotated at a screw rotation speed Nf.

When the screw speed Vs is changed in multiple stages corresponding to the screw position, the screw speed set at each screw position S _i (i = 1, 2,...) Is set to Vs _i (i = 1, 2,...). , ...), the flight speed Vf _i (i = 1, i = 1, 2) corresponding to the screw speed Vs _i
2, ...) is also changed in the multi-stage, is set to Vf _i = γ · Vs _i. Similarly, or the screw speed Vs constant, ramp function, even if the or to change a function such as an exponential function, it is possible to change the flight speed Vf _i in correspondence to the screw speed Vs _i.

The speed pattern of the flight speed Vf can be stored in the memory 67 as storage means, and the speed pattern can be read to control the flight speed. Further, a screw rotation speed setting device may be provided instead of the flight speed setting device 68, and the screw rotation speed set by the screw rotation speed setting device may be sent to the control device 62.

Next, the minimum value γ _MIN will be described.

FIG. 5 is a diagram showing a first relationship between the speed ratio and the frictional resistance according to the first embodiment of the present invention, and FIG. 6 is a diagram showing a relationship between the speed ratio and the resin pressure according to the first embodiment of the present invention. 7, FIG. 7 is a second relationship diagram between the speed ratio and the frictional resistance in the first embodiment of the present invention, and FIG. 8 is a diagram showing the speed ratio, the resin pressure, and the pressure in the first embodiment of the present invention. 3 is a second relationship diagram of FIG. 5 and 7, the horizontal axis represents the speed ratio γ,
The ordinate represents the frictional resistance F applied to the resin near the inner peripheral surface of the heating cylinder 11 (FIG. 2). 6 and 8
In the graph, the horizontal axis represents the speed ratio γ, and the vertical axis represents the resin pressure Pf near the front end of the flight section 21.

For example, when molding is performed using a resin having a high viscosity such as a polymethyl methyl methacrylate resin (methacrylic resin), as shown in FIGS. In the range of γ <1, the lower the flight speed Vf, the lower the frictional resistance F and the lower the resin pressure Pf. When the speed ratio γ is in the range of 0 ≦ γ <0.2, the frictional resistance F
Does not substantially change, but the resin pressure Pf decreases and takes a negative value.

Further, for example, like a polyamide resin,
When molding is performed using a resin having a low viscosity, FIGS.
As shown in the above, when the speed ratio γ is in the range of 0.5 ≦ γ <1, as the flight speed Vf decreases, the frictional resistance F decreases and the resin pressure Pf decreases. When the speed ratio γ is in the range of 0 ≦ γ <0.5, the frictional resistance F
Does not substantially change, but the resin pressure Pf decreases and takes a negative value.

Therefore, when molding is performed using a resin having a high viscosity, such as the above-mentioned polymethyl methyl methacrylate resin, the speed ratio γ is set to 0.1 to 0.3, preferably about 0.2.
When molding is performed using a resin having a low viscosity, such as a polyamide resin, when the speed ratio γ is set to 0.4 to 0.6, preferably about 0.5, the resin pressure Pf of the flight section 21 is increased. , The frictional resistance F can be minimized without setting a negative pressure.

As described above, since the frictional resistance F applied to the resin near the inner peripheral surface of the heating cylinder 11 can be reduced, the injection force applied to the screw 12 from the rear and the screw head 27 The injection pressure applied to the front end can be made to correspond, and a sufficient injection pressure can be generated.

Further, even if the molten state of the resin in the groove 24 changes while moving through the resin supply section P1, the compression section P2 and the measuring section P3, the frictional resistance applied to the resin should be kept constant. Therefore, the injection pressure can be stabilized. And since the pressure in a mold can be stabilized, the quality of a molded article can be improved.

Since the screw 12 is always rotated in the reverse direction during the injection process, the check ring 28 is always placed in a state where a bias is applied to the blocking position. Therefore, the external force is not applied to the check ring 28 during the injection process, so that the check ring 28 is not placed at the communication position, so that the resin can be prevented from flowing backward. As a result, the measurement can be performed stably, and the quality of the molded article can be improved.

Since a sufficient injection pressure can be generated, the injection power can be reduced accordingly. Therefore, not only the size of the injection device can be reduced, but also the cost of the injection device can be reduced.
Further, since the frictional resistance is reduced, shear (heat) insulation received by the resin is reduced, and it is possible to prevent occurrence of resin burning.

Next, a second embodiment of the present invention will be described.

FIG. 9 is a time chart showing the operation of the injection device according to the second embodiment of the present invention.

In this case, as shown in the figure, at timing t11, the weighing motor 41 as the first driving means is used.
(FIG. 1) is driven in the forward direction to rotate the screw 12 (FIG. 2) in the forward direction at the screw rotation speed N1 for a time τ1. Subsequently, the measuring process is started at timing t12,
A weighing means (not shown) in the control device 62 drives the weighing motor 41 in the forward direction to rotate the screw 12 for a time τ.
While rotating the screw forward by 2 at the screw rotation speed N2,
The injection motor 53 as the second driving means is driven to retract the screw 12.

When the measuring step is completed at the timing t13, the cut-off means (not shown) in the control device 62
At timing t14, the measuring motor 41 is driven in the reverse direction to rotate the screw 12 in the reverse direction at the screw rotation speed N3 for the time τ4. Subsequently, at timing t15
The injection process is started, and the injection means and the screw advance means (not shown) in the control device 62 are driven by the injection motor 53.
Is driven to advance the screw 12, and the metering motor 41 is driven in the reverse direction to rotate the screw 12 in the reverse direction at the screw rotation speed Nf. Then, the injection step is completed at timing t16.

In this case, the time τ4 is set longer than the time τ3 (FIG. 4) in the first embodiment. Then, at the first stage of the time τ4, the shut-off unit places the check ring 28 in the shut-off position, and the unillustrated resin pressure lowering unit in the control device 62 operates at the second stage of the time τ4, The resin pressure Pf near the front end of the flight section 21 is reduced by a predetermined value. Therefore, the frictional resistance applied to the resin can be reduced before the injection step is started, so that the variation in the injection pressure during the injection step can be reduced.

Next, a third embodiment of the present invention will be described.

FIG. 10 is a time chart showing the operation of the injection device according to the third embodiment of the present invention.

In this case, as shown in the figure, at timing t21, the weighing motor 41 as the first driving means is used.
(FIG. 1) is driven in the forward direction to rotate the screw 12 (FIG. 2) in the forward direction at the screw rotation speed N1 for a time τ1. Subsequently, the measuring process is started at timing t22,
A weighing means (not shown) in the control device 62 drives the weighing motor 41 in the forward direction to rotate the screw 12 for a time τ.
While rotating the screw forward by 2 at the screw rotation speed N2,
The injection motor 53 as the second driving means is driven to retract the screw 12.

When the weighing process is completed at the timing t23, the cut-off means (not shown) in the control device 62
At timing t24, the metering motor 41 is driven in the reverse direction to rotate the screw 12 in the reverse direction at the screw rotation speed N3 for the time τ3. Subsequently, at timing t25
Injection means and screw advancing means (not shown) in the control device 62 drive the injection motor 53 to advance the screw 12 and drive the metering motor 41 in the reverse direction to drive the screw 12 The time τ
The screw is rotated in the reverse direction by 5 at the screw rotation speed Nf. Next, the measuring motor 41 is stopped at a timing t26,
The flight 23 is advanced at a flight speed Vf equal to the screw speed Vs. Then, the injection step is completed at timing t27.

In this case, while the frictional resistance due to the static friction at the start of the forward movement of the screw 12 and the kinetic friction immediately after the start is large, the friction due to the kinetic friction after a predetermined time has elapsed since the start of the forward movement. Since the resistance is small, if the frictional resistance in the initial stage of the advancement of the screw 12 can be reduced, the variation in the injection pressure can be reduced without rotating the screw 12 in the reverse direction thereafter. Therefore, the time for driving the weighing motor 41 is shortened, so that the cost for operating the injection device can be reduced.

It should be noted that the present invention is not limited to the above-described 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.

[0064]

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 periphery of the screw body, and the front end of the flight portion are provided. A screw provided rotatably in the heating cylinder, and a screw disposed movably forward and backward, first driving means for rotating the screw, and a second screw for moving the screw forward and backward. 2 driving means, a screw advancing means for driving the second driving means in the injection step to advance the screw at a predetermined screw speed, and a driving means for the first driving means in the injection step, Flight speed control means for apparently advancing the flight at a flight speed lower than the screw speed.

In this case, the frictional resistance applied to the resin near the inner peripheral surface of the heating cylinder can be reduced.
In the injection step, the injection power applied to the screw from the rear can correspond to the injection pressure applied to the front end of the screw head, and a sufficient injection pressure can be generated.

Further, even if the molten state of the resin in the groove formed by the flight changes while moving in the flight section, the frictional resistance applied to the resin can be kept constant, so that the injection pressure can be stabilized. Can be done. And
Since the pressure in the mold can be stabilized, the quality of the molded product can be improved.

Further, since a sufficient injection pressure can be generated, the injection power can be reduced accordingly. Therefore, not only the size of the injection device can be reduced, but also the cost of the injection device can be reduced.
Further, since the frictional resistance is reduced, the shearing heat received by the resin is reduced, and the occurrence of resin burning can be prevented.

In another injection device of the present invention, a check ring is further provided around the screw head, and the check ring is rotated by a predetermined angle with respect to the screw head as the screw rotates. It is rotated to take a communication position for communicating between the front of the screw head and the flight section, and a blocking position for blocking between the front of the screw head and 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, so that the filling amount of the resin in the injection step can be stabilized, and the quality of the molded product can be improved. Can be improved. In addition, since the resin in the flight section during the injection step can be stabilized, the measurement can be performed stably during the measurement step, the heat history of the resin can be stabilized, and further, the temperature of the resin can be stabilized. be able to.

Further, since the screw is always rotated in the reverse direction during the injection process, the check ring is always placed in a state where a bias is applied to the blocking position. Accordingly, the external force is not applied to the check ring during the injection step, so that the check ring is not placed at the communication position, so that the resin can be prevented from flowing backward. As a result, the measurement can be performed stably, and the quality of the molded article can be improved.

In still another injection apparatus of the present invention, the speed ratio of the flight speed to the screw speed is set to be smaller than 1 and equal to or larger than the minimum value set in accordance with the type of the resin.

In this case, the frictional resistance applied to the resin near the inner peripheral surface of the heating cylinder can be reduced without reducing the resin pressure in the flight section to a negative pressure.

According to still another injection apparatus of the present invention, in a first stage before the injection step is started, the screw is rotated in the reverse direction, and the check ring is placed at the shut position. And a resin pressure lowering means for lowering the resin pressure of the flight section by rotating the screw in the reverse direction at a second stage before the injection step is started.

In this case, since the frictional resistance applied to the resin can be reduced before the injection step is started, the variation in the injection pressure during the injection step can be reduced.

In still another injection device of the present invention, the flight speed control means may advance the flight at a flight speed lower than the screw speed apparently until a predetermined time has elapsed since the start of the injection process. Let
After the time has elapsed, the flight is apparently advanced at a flight speed equal to the screw speed.

In this case, the frictional resistance due to the static friction at the start of the forward movement of the screw and the kinetic friction immediately after the start is large, while the frictional resistance due to the kinetic friction after a predetermined time has elapsed since the start of the forward movement. Since the frictional resistance in the initial stage of the advance of the screw can be reduced, the variation in the injection pressure can be reduced thereafter without rotating the screw in the reverse direction. Therefore, the time for driving the first driving unit is shortened, so that the cost for operating the injection device can be reduced.

[Brief description of the drawings]

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

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

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

FIG. 4 is a time chart illustrating an operation of the injection device according to the first embodiment of the present invention.

FIG. 5 is a first relationship diagram between a speed ratio and a frictional resistance according to the first embodiment of the present invention.

FIG. 6 is a first relationship diagram between a speed ratio and a resin pressure according to the first embodiment of the present invention.

FIG. 7 is a second relationship diagram between the speed ratio and the frictional resistance according to the first embodiment of the present invention.

FIG. 8 is a second relationship diagram between the speed ratio and the resin pressure in the first embodiment of the present invention.

FIG. 9 is a time chart illustrating an operation of the injection device according to the second embodiment of the present invention.

FIG. 10 is a time chart illustrating an operation of the injection device according to the third 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 Pf Resin pressure γ Speed ratio

Claims (7)

[Claims] 1. A heating cylinder comprising: (a) a heating cylinder; (b) a flight section having a flight formed on an outer periphery of a screw body; and a screw head disposed at a front end of the flight section. (C) first driving means for rotating the screw, (d) second driving means for moving the screw forward and backward, and (c) first driving means for rotating the screw. e) a screw advancing means for driving the second driving means in the injection step to advance the screw at a predetermined screw speed; and (f) driving the first driving means in the injection step to perform the flight. And a flight speed control means for apparently advancing at a flight speed lower than the screw speed. 2. A check ring is provided around the screw head, and the check ring is rotated by a predetermined angle with respect to the screw head with rotation of the screw. 2. A communication position that communicates between the screw head and the flight unit, and a blocking position that blocks between the front of the screw head and the flight unit.
3. The injection device according to claim 1. 3. The injection device according to claim 1, wherein the speed ratio of the flight speed to the screw speed is smaller than 1 and is equal to or greater than a minimum value set in accordance with the type of resin. 4. The injection apparatus according to claim 1, wherein (a) the screw speed is changed in multiple stages, and (b) the flight speed is changed in multiple stages corresponding to the screw speed. 5. In a first stage before the injection step is started, the screw is rotated in a reverse direction to place the check ring in a blocking position, and (b) the injection step includes: The injection apparatus according to claim 1, further comprising: a resin pressure lowering unit configured to rotate the screw in a reverse direction to reduce a resin pressure of the flight unit in a second stage before the start. 6. The flight speed control means apparently advances the flight at a flight speed lower than the screw speed until a predetermined time elapses from the start of the injection step, and when the time elapses, the flight apparently 2. The injection device according to claim 1, wherein the injection device is advanced at a flight speed equal to the screw speed. 7. In the (a) measuring step, the first driving means is driven to rotate the screw in the forward direction. (B) In the injection step, the second driving means is driven to turn the screw into a predetermined screw. A method of controlling an injection device, wherein the injection device is advanced at a speed, and the first driving means is driven to apparently advance at a flight speed lower than the screw speed.