JP3607602B2 - Injection device and control method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an injection apparatus and a control method thereof.
[0002]
[Prior art]
Conventionally, in an injection molding machine, a screw is rotatably disposed in a heating cylinder of an injection device and can be moved forward and backward, and the screw can be rotated or moved forward and backward by driving a driving means. It can be done. In the metering step, when the screw is rotated, the resin supplied from the hopper into the heating cylinder is heated, melted, advanced in the heating cylinder, and stored in front of the screw head. Further, in the injection process, when the screw is advanced, the resin stored in front of the screw head is injected from the injection nozzle and filled into the cavity space of the mold apparatus.
[0003]
In this case, the position of the screw, that is, the screw position is detected, and the speed of the screw, that is, the screw speed is changed every time the screw reaches the preset speed switching position, and the speed control is performed. Subsequently, when the screw reaches the preset vP switching position, the injection process is completed, the speed control is switched to the pressure control, the pressure holding process is started, and the pressure holding process is set in advance. Until the holding time elapses, the screw is pressed with a predetermined pressing force to maintain the pressure of the resin in the cavity space. In the pressure holding step, the pressing force is a holding pressure.
[0004]
The pressure holding step is composed of a plurality of stages, and the pressure holding of each stage is lowered stepwise. During this time, the mold apparatus is cooled, and the resin filled in the cavity space is cooled and solidified to form a molded product.
[0005]
When the pressure holding process is completed, a predetermined amount of resin having a pressure corresponding to the pressure at the final stage of the pressure holding process remains in the space ahead of the screw head, that is, in the reservoir. In that case, if the weighing process is started with variations in the pressure of the resin, the resin cannot be stably stored in front of the screw head in the weighing process, and the quality of the molded product is deteriorated. . Therefore, when the pressure holding step is completed, the pressing force is set to zero (0), the pressure of the resin in the reservoir is lowered, and the metering step is started after a predetermined delay time has elapsed. .
[0006]
For this purpose, a control unit and a predetermined setting device are provided, and by operating the setting device, each speed switching position, screw speed, vP switching position, pressure holding time, pressure holding pressure, etc. can be set. It can be done. A load cell is provided for detecting the pressing force, and a screw position detector is provided for detecting the screw position.
[0007]
FIG. 2 is a time chart showing a change in the conventional pressing force.
[0008]
When the screw reaches the vP switching position SC at the timing t1, the injection process is completed, the pressure holding process is started, the screw is pushed with the holding pressure F1, and the pressure of the resin in the reservoir becomes Pa1. Subsequently, at timing t2, the screw is held at pressure F2.
F2 <F1
The pressure of the resin in the reservoir is Pa2
Pa2 <Pa1
become. Note that the pressure holding process is the final stage at the timing t2.
[0009]
When the pressure holding time τ1 elapses at timing t3, the pressure holding process is completed, the pressing force is reduced to zero, and the pressure of the resin in the reservoir is lowered. Subsequently, when a predetermined delay time τ2 elapses at timing t4, the weighing process is started.
[0010]
[Problems to be solved by the invention]
However, in the conventional injection device, when the pressure holding process is completed and the pressing force is reduced to zero, the pressure of the resin in the reservoir is affected by the variation in the pressure Pa2 in the final stage of the pressure holding process. Will remain. Therefore, the position of the screw when the metering process is started, that is, the measurement start position varies, and the density of the resin stored in front of the screw head when the metering process is completed also varies.
[0011]
As a result, the weighing cannot be performed stably, and the weight, size, and the like of the molded product vary between shots, and the quality of the molded product decreases.
[0012]
The present invention solves the problems of the conventional injection device, can prevent variations in the weight, dimensions, etc. of the molded product between shots, and can improve the quality of the molded product. It is an object of the present invention to provide an injection device that can be used and a control method thereof.
[0013]
[Means for Solving the Problems]
Therefore, in the injection device of the present invention, a cylinder member, an injection member that is rotatably and reciprocally disposed within the cylinder member, a driving means for moving the injection member back and forth, and an injection Injection control means for performing injection by moving the injection member forward in the process; pressure holding control means for pressing the injection member at a predetermined holding pressure in the pressure holding process after the injection process is completed; and the pressure holding A decompression control means for forming a state in which the pressure of the molding material in the reservoir is not affected by the pressure in the pressure-holding step by setting a predetermined decompression force higher than 0 in the decompression step after the step is completed; After the pressure reducing step is completed, the metering step is started at a pressure higher than 0 of the molding material in the reservoir, and the metering control means performs measurement by rotating the injection member.
[0014]
And the said decompression force is made low with progress of time.
[0015]
The other injection device of the present invention further includes holding pressure control means for pressing the cylinder member at a predetermined holding pressure in the holding step after the pressure reducing step is completed and before the metering step is started.
[0016]
The holding pressure is set lower than the pressure reducing force.
[0017]
In the injection apparatus control method of the present invention, in the injection process, the injection member is advanced to perform injection, and in the pressure holding process after the injection process is completed, the injection member is pressed at a predetermined holding pressure, In the pressure reducing step after the pressure holding step is completed, by setting the pressure to a predetermined pressure higher than 0, the pressure of the molding material in the reservoir is not affected by the pressure in the pressure holding step, and the pressure reducing step Is completed, the metering process is started at a pressure higher than 0 of the molding material in the reservoir, and the injection member is rotated to perform metering.
[0018]
And the said decompression force is made low with progress of time.
[0019]
In another injection apparatus control method of the present invention, the cylinder member is pushed at a predetermined holding pressure in the holding step after the pressure reducing step is completed and before the metering step is started.
[0020]
The holding pressure is set lower than the pressure reducing force.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0022]
FIG. 3 is an enlarged view of a main part of the injection apparatus according to the embodiment of the present invention, and FIG. 4 is a conceptual diagram of the injection apparatus according to the embodiment of the present invention.
[0023]
In the figure, 11 is a heating cylinder as a cylinder member, 12 is a screw as an injection member that is rotatably disposed in the heating cylinder 11 and can be moved back and forth (moved in the left-right direction in FIG. 3). An injection nozzle formed at the front end (left end in FIG. 3) of the heating cylinder 11, 14 is a nozzle port formed in the injection nozzle 13, and 15 is near the rear end (right end in FIG. 3) of the heating cylinder 11. A resin supply port 16 formed at a predetermined position is a hopper which is attached to the resin supply port 15 and accommodates a resin as a molding material.
[0024]
The screw 12 includes a flight part 21 and a screw head 27 disposed at the front end of the flight part 21. In the flight part 21, the flight 23 is formed in a spiral shape on the main body of the screw 12, that is, the outer peripheral surface of the screw main body, and the spiral groove 24 is formed by the flight 23. Further, the flight part 21 is compressed in order from the rear (right side in FIG. 3) to the front (left side in FIG. 3), the resin supply part P1 to which the resin dropped from the hopper 16 is supplied, and the supplied resin is compressed. Thus, a compression part P2 for melting and a weighing part P3 for measuring the molten resin by a certain amount are formed. The bottom of the groove 24, that is, the outer diameter of the groove bottom is relatively small in the resin supply part P1, gradually increased from the rear to the front in the compression part P2, and relatively large in the measuring part P3. Therefore, the gap between the inner peripheral surface of the heating cylinder 11 and the outer peripheral surface of the screw main body is relatively large in the resin supply part P1, and is gradually reduced from the rear to the front in the compression part P2. The portion P3 is relatively small.
[0025]
In the measuring step, when the screw 12 is rotated in the forward direction, the resin dropped from the hopper 16 is supplied to the resin supply part P1 and moved forward (moved to the left in FIG. 3) in the groove 24. The screw 12 is moved backward (moved to the right in FIG. 3), and the resin is stored in front of the screw head 27. The resin in the groove 24 has a pellet shape in the resin supply part P1, is in a semi-molten state in the compression part P2, and is completely melted in the metering part P3 to become a liquid.
[0026]
In the injection process, when the screw 12 is advanced, the resin stored in front of the screw head 27 is injected from the injection nozzle 13 and filled in a cavity space of a mold apparatus (not shown). At this time, a backflow prevention device is disposed around the screw head 27 so that the resin stored in front of the screw head 27 does not flow back.
[0027]
For this purpose, the screw head 27 has a conical head body 25 in the front half (left half in FIG. 3) and a cylindrical part 26 in the rear half (right half in FIG. 3). 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. The check ring 28 and the presser 29 constitute a backflow prevention device.
[0028]
Further, the check ring 28 has holes 28a extending in the axial direction at a plurality of locations in the circumferential direction, and notches 28b are formed at the front end over a predetermined angle. Then, a locking projection 25a is formed on the head main body 25, and the locking projection 25a is placed in the notch 28b. In this case, the check ring 28 is rotated by a predetermined angle with respect to the screw head 27 as the screw 12 rotates, and further rotation is restricted.
[0029]
On the other hand, holes 29a extending in the axial direction corresponding to the holes 28a are formed in the presser 29 at a plurality of locations in the circumferential direction. Therefore, when 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 takes a communication position where the front of the screw head 27 communicates with the flight part 21 and a blocking position where the front of the screw head 27 and the flight part 21 are blocked.
[0030]
Incidentally, the rear end (the right end in FIG. 4) of the heating cylinder 11 is attached to the front injection support 31, and the 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, and a pressure plate 34 is disposed along the guide bar 33 so as to freely advance and retreat (move in the left-right direction in FIG. 4). . The front injection support 31 and the rear injection support 32 are fixed to a slide base (not shown) with bolts (not shown).
[0031]
Further, a drive shaft 35 is connected to the rear end of the screw 12, and the drive shaft 35 is rotatably supported by the pressure plate 34 by bearings 36 and 37. In order to rotate the screw 12, an electric measuring motor 41 is disposed as a first driving means, and between the measuring motor 41 and the drive shaft 35, the pulleys 42 and 43 and the timing belt 44 are used. The first rotation transmission means is provided. Therefore, by driving the metering motor 41, the screw 12 can be rotated in the forward direction or the reverse direction. In this embodiment, the screw 12 is rotated using the electric metering motor 41, but the screw 12 can also be rotated using a hydraulic motor.
[0032]
Further, a ball screw 47 including a ball screw shaft 45 and a ball nut 46 screwed to each other is disposed behind the pressure plate 34 (right side in FIG. 4), and the ball screw 47 linearly rotates the movement. Movement direction conversion means for converting into movement is configured. The ball screw shaft 45 is rotatably supported by a bearing 48 with respect to the rear injection support 32, and the ball nut 46 is fixed to the pressure plate 34 via a plate 51 and a load cell 52.
[0033]
The load cell 52 constitutes a pressing force detecting means for detecting a pressing force for pressing the screw 12. The pressing force is generated as a radiant output in the injection process, as a holding pressure in the pressure holding process, as a pressure reducing force in the pressure reducing process, and as a holding pressure in the holding process.
[0034]
Further, in order to move the screw 12 back and forth, an injection motor 53 as a second drive means is disposed. Between the injection motor 53 and the ball screw shaft 45, pulleys 54 and 55 and a timing belt 56 are used. The second rotational transmission means is provided. 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, and the screw 12 is moved forward (moved to the left in FIG. 4) or moved backward (in FIG. 4). To the right). In the present embodiment, the screw 12 is moved forward and backward using the injection motor 53 and the ball screw 47, but the plate 51 is moved using the injection cylinder to move the screw 12 forward and backward. It can also be made.
[0035]
Next, the control unit of the injection apparatus will be described.
[0036]
FIG. 1 is a time chart showing a change in pressing force in the embodiment of the present invention, and FIG. 5 is a block diagram for explaining a control unit of the injection apparatus in the embodiment of the present invention.
[0037]
In the figure, 10 is a control unit for controlling the injection device, 61 is a speed control system for performing speed control, and 62 is a pressure control system for performing pressure control. The switch SW1 is turned on and the switch SW2 is turned off. By setting the speed control system 61, the speed control is performed and the switch SW1 is turned off and the switch SW2 is turned on to set the pressure control system 62 to switch from the speed control to the pressure control. it can. 63 is a setter for setting each speed switching position, screw speed, vP switching position, holding pressure time τ11, holding pressure F2, reducing pressure time τ12, reducing pressure, holding time τ13, holding pressure, and the like. The setting device 63 includes a position setting unit 64 and a pressure setting unit 65. The position setting unit 64 generates a predetermined screw speed pattern based on each speed switching position, screw speed, vP switching position, and the like, and generates a screw position command S _rf corresponding to the time, The screw position command S _rf is output to the subtractor 66. As shown in FIG. 1, the pressure setting unit 65 is configured to maintain the holding pressure in the pressure holding process based on the pressure holding time τ11, the holding pressure F2, the pressure reducing time τ12, the pressure reducing force, the holding time τ13, the holding pressure, and the like. the pattern L1, sends the pattern L2 of the reduced pressure in the vacuum process, to generate a pattern L3 of the holding pressure in the holding step, in correspondence with the time to generate a pressure command P _rf, the pressure command P _rf to the subtracter 74 .
[0038]
52 is a load cell, 53 is an injection motor (M), 67, 72 and 75 are compensators (K), 68 is a subtractor, 69 is an integrator (1 / S), and 71 is a speed limiting screw speed. The limiter 73 is a motor driver, and 81 is a screw speed sensor as a screw speed detector that detects the screw speed based on the rotational speed of the injection motor 53.
[0039]
In the speed control system 61, the screw speed detected by the screw speed sensor 81 is sent to the subtracter 68 and the integrator 69 as a speed detection value V _fb . The integrator 69 calculates a screw position based on the speed detection value V _fb , and sends the calculated screw position to the subtractor 66 as a position detection value S _fb . The subtractor 66 calculates a deviation ΔS between the screw position command S _rf and the position detection value S _fb and sends the deviation ΔS to the compensator 67. The compensator 67, on the basis of the deviation ΔS and calculating a first speed command value _{V rf1,} sends the first velocity command value _{V rf1} to the subtracter 68 through the switch SW1.
[0040]
While the speed control is being performed, the subtractor 68 calculates a deviation ΔVS1 between the first speed command value V _rf1 and the speed detection value V _fb and sends the deviation ΔVS1 to the speed limiter 71. Then, in the speed limiter 71, the screw speed is limited so that the deviation ΔVS1 does not exceed the upper limit value, and the deviation ΔVS1 after the screw speed is limited is sent to the compensator 72, and the deviation 72 ΔVS1 to correspond to the current command value _{I rf1} allowed to occur, it said current command value _{I rf1} is sent to the motor driver 73. The motor driver 73 supplies a current to the injection motor 53 in correspondence with the current command value I _rf1 and drives the injection motor 53.
[0041]
In this case, the screw speed sensor 81 and the integrator 69 constitute position detection means for detecting the screw position. In the present embodiment, the screw speed sensor 81 and the integrator 69 are used as position detecting means. However, a position for directly detecting the screw position instead of the screw speed sensor 81 and the integrator 69 is used. A detector can also be used.
[0042]
In the pressure control system 62, the pressing force detected by the load cell 52 is sent to the subtracter 74 as the pressure detection value P _fb . The subtractor 74 calculates a deviation ΔP between the pressure command P _rf and the pressure detection value P _fb and sends the deviation ΔP to the compensator 75. Then, the compensator 75, on the basis of the deviation ΔP calculates a second velocity command value _{V rf2,} and sends the second velocity command value _{V rf2} to the subtracter 68 via the switch SW2.
[0043]
While the pressure control is performed, the subtractor 68 calculates a deviation ΔVS2 between the speed detection value V _fb and the second speed command value V _rf2, and sends the deviation ΔVS2 to the speed limiter 71. In the speed limiter 71, the screw speed is limited so that the deviation ΔVS2 does not exceed the upper limit value, and the deviation ΔVS2 after the screw speed is limited is sent to the compensator 72, and the deviation 72 ΔVS2 to correspond to the current command value _{I rf2} allowed to occur, it said current command value _{I rf2} is sent to the motor driver 73. The motor driver 73 supplies a current to the injection motor 53 in correspondence with the current command value I _rf2 to drive the injection motor 53.
[0044]
Next, the operation of the control unit 10 will be described.
[0045]
The injection control means (not shown) of the control unit 10 turns on the switch SW1, turns off the switch SW2, starts the injection process, performs speed control, advances the screw 12 (FIG. 3), and performs injection.
[0046]
When the screw 12 reaches the vP switching position, the pressure holding control means (not shown) of the control unit 10 turns off the switch SW1 and turns on the switch SW2 to switch from speed control to pressure control. Start and push the screw 12 with a predetermined holding pressure to hold the pressure of the resin in the cavity space. The pressure holding step includes a plurality of stages, and the pressure holding of each stage is lowered stepwise. During this time, the mold apparatus is cooled, and the resin filled in the cavity space is cooled and solidified to form a molded product.
[0047]
By the way, when the pressure holding step is completed, a predetermined amount of resin having a pressure corresponding to the pressure at the final stage of the pressure holding step remains in the reservoir. For example, when the pressure holding process is composed of two stages, first, the screw 12 is pushed with the holding pressure F1, and the pressure of the resin in the reservoir becomes the pressure Pa1 corresponding to the holding pressure F1. Subsequently, in the final stage, the screw 12 is held at the holding pressure F2.
F2 <F1
Pressure Pa2 at which the pressure of the resin in the reservoir corresponds to the holding pressure F2.
Pa2 <Pa1
become.
[0048]
And if a measurement process is started with the variation in the pressure Pa2, the density of the resin stored in front of the screw head 13 will vary in the measurement process. As a result, the weighing cannot be performed stably, and the weight, size, and the like of the molded product vary between shots, and the quality of the molded product decreases.
[0049]
Therefore, when the pressure holding time τ11 elapses, the decompression control means (not shown) of the control unit 10 starts the decompression process at timing t11. In the depressurization step, the depressurization control means sets the depressurization force to a value G1 equal to the holding pressure F2 in the final stage of the pressure holding step.
G1 = F2
To value G2
G2 <G1
Gradually lower until In the present embodiment, the decompression force can be changed by a predetermined function, for example, a linear function, but the decompression force can also be changed by another function.
[0050]
Further, when the depressurization time τ12 elapses, the holding pressure control means (not shown) of the control unit 10 starts the holding process at timing t12, and the holding pressure is set to a value H lower than the value G2 in the holding process.
0 <H <G2
To.
[0051]
And when holding time (tau) 13 passes, the measurement control means (not shown) of the said control part 10 will start a measurement process at the timing t13. In the present embodiment, the holding step is started when the decompression step is completed. However, the measuring step can be started without starting the holding step.
[0052]
In this way, the decompression force is gradually lowered from the value G1 to the value G2 in the decompression step, and the retention pressure is set to a value H lower than the value G2 in the retention step, so that the pressure of the resin in the reservoir is The influence of the variation in the pressure Pa2 in the final stage does not remain. Therefore, it is possible to prevent variation in the measurement start position, so that there is no variation in the density of the resin stored in front of the screw head 13 when the measurement process is completed.
[0053]
As a result, the weighing can be performed stably, and variations in the weight, dimensions, etc. of the molded product between shots can be prevented, so that the quality of the molded product can be improved.
[0054]
In addition, this invention is not limited to the said embodiment, It can change variously based on the meaning of this invention, and does not exclude them from the scope of the present invention.
[0055]
【The invention's effect】
As described above in detail, according to the present invention, in the injection device, the cylinder member, the injection member disposed in the cylinder member so as to be rotatable and movable back and forth, and the injection member are advanced and retracted. Driving means for causing the injection member to move in the injection process, injection control means for performing injection by moving the injection member forward, and holding pressure for pressing the injection member at a predetermined holding pressure in the pressure holding process after the injection process is completed. The pressure control means and the pressure reducing step after the pressure holding step is completed, a state in which the pressure of the molding material in the reservoir is not affected by the pressure in the pressure holding step by setting a predetermined pressure reducing force higher than 0. Decompression control means to be formed and measurement control means for starting measurement after the pressure reduction process is completed at a pressure higher than 0 of the molding material in the reservoir and rotating the injection member to measure Having.
[0056]
And the said decompression force is made low with progress of time.
[0057]
In this case, when the pressure-holding step is completed, the pressure-reducing step is started, and the pressure-reducing force is gradually lowered in the pressure-reducing step, and the pressure of the molding material in the reservoir is affected by the pressure variation in the final stage of the pressure-holding step. A state that does not remain is formed. Therefore, it is possible to prevent variation in the measurement start position.
[0058]
As a result, the weighing can be performed stably, and variations in the weight, dimensions, etc. of the molded product between shots can be prevented, so that the quality of the molded product can be improved.
[Brief description of the drawings]
FIG. 1 is a time chart showing changes in pressing force according to an embodiment of the present invention.
FIG. 2 is a time chart showing a change in conventional pressing force.
FIG. 3 is an enlarged view of a main part of the injection device according to the embodiment of the present invention.
FIG. 4 is a conceptual diagram of an injection apparatus according to an embodiment of the present invention.
FIG. 5 is a block diagram illustrating a control unit of the injection apparatus according to the embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Control part 11 Heating cylinder 12 Screw 53 Injection motor

Claims (4)

(A) a cylinder member;
(B) an injection member which is rotatably and reciprocally disposed within the cylinder member;
(C) driving means for advancing and retracting the injection member;
(D) injection control means for performing injection by moving the injection member forward in the injection step;
(E) a pressure holding control means for pressing the injection member at a predetermined pressure in the pressure holding process after the injection process is completed;
(F) In the pressure reducing step after the pressure holding step is completed, a state where the pressure of the molding material in the reservoir is not affected by the pressure in the pressure holding step is formed by setting the pressure to a predetermined pressure higher than 0. Decompression control means;
(G) after the decompression process is completed, which has a metering control means starts metering process at a pressure higher than 0 of the molding material in the reservoir, perform metering by rotating the injection member,
(H) The injection device characterized in that the decompression force is lowered with time. (A) In the holding step after the pressure reducing step is completed and before the metering step is started, the holding member has a holding pressure control means for pressing the cylinder member with a predetermined holding pressure;
(B) The injection device according to claim 1, wherein the holding pressure is lower than the pressure reducing force. (A) In the injection process, the injection member is advanced to perform injection,
(B) In the pressure holding step after the injection step is completed, the injection member is pressed at a predetermined pressure,
(C) In the pressure reducing step after the pressure holding step is completed, by setting a predetermined pressure reducing force higher than 0 , a state in which the pressure in the pressure holding step does not remain in the pressure of the molding material in the reservoir is formed. ,
After; (d) reduced pressure process is completed, start the metering process at a pressure higher than 0 of the molding material in the reservoir, performs metering by rotating the injection member,
(E) The method for controlling an injection apparatus, wherein the pressure reducing force is lowered with time. (A) In the holding step after the pressure reducing step is completed and before the weighing step is started, the cylinder member is pushed at a predetermined holding pressure;
(B) The injection apparatus control method according to claim 3, wherein the holding pressure is lower than the decompression force.

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