JPH0550482A - Method and apparatus for controlling injection of injection molding machine - Google Patents

Abstract

PURPOSE:To make the filling state and filling amount of a resin to a mold constant. CONSTITUTION:The reference injection position of an injection cylinder 16 allowed to correspond to the elapsed time after the injection of a resin is started is stored in the reference injection position memory part 72 of an injection control unit 70. The actual injection position of the injection cylinder 16 is detected by a position detector 24 and a position deviation operating part 74 calculates the deviation between the detected injection position and the reference injection position and an injection speed correcting part 81 corrects the reference injection speed operated by a reference injection speed operation part 78 on the basis of said deviation. An injection speed adjusting part 86 compares the the actual injection speed obtained on the basis of the detection signal of the position detector 24 by an injection speed operation part 82 with the reference injection speed corrected by the injection speed correcting part 81 to calculate deviation to output the adjusting signal of the injection speed corresponding to the deviation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection molding machine for molding a molten resin into a predetermined shape, and more particularly to a method for controlling an injection process for filling a molten resin into a mold cavity and a control device therefor.

[0002]

2. Description of the Related Art Today, a wide variety of products are molded by synthetic resin, and an in-line screw type injection molding machine as shown in FIG. 2 is widely used for molding synthetic resin.
In this in-line screw type injection molding machine 10, a screw 14 having a spiral groove formed on its peripheral surface is housed in a heating cylinder 12 so as to be rotatable and axially reciprocable. The screw 14 has a heating cylinder 1 at the rear end.
It is supported by a piston rod 18 of an injection cylinder 16 formed integrally with the shaft 2 through a thrust bearing.
Further, the screw 14 is coaxially connected to a rotary shaft 22 of a hydraulic motor 20 that penetrates the piston rod 18 in the axial direction at the rear end thereof, and is rotated by the hydraulic motor 20 when measuring resin.

On the piston rod 18, the injection cylinder 1
A position detection device 24 including a magnetic scale and an encoder for detecting the injection position of 6 (the position of the screw 14) is provided, and the position detection device 24 detects the injection position of the injection cylinder 16 and outputs a detection signal. Is input to the injection speed calculation unit 52 of the cylinder control device 50.

A hopper 30 is attached to the heating cylinder 12, and a resin pellet 32 as a molding material is put into the hopper 30. Further, the heating cylinder 12 is provided with a heater (not shown) along the axial direction, and the hopper 3
Resin pellets 3 supplied from 0 to the heating cylinder 12
2 can be melted. The resin pellet 32 is melted and plasticized by the heat of the heater provided in the heating cylinder 12 and the shearing force generated by the rotation of the screw 10, and becomes the molten resin 36, which is the tip of the heating cylinder 12 to which the nozzle 34 is attached. Sent to. At this time, the screw 14 receives the reaction force of the molten resin 36 and retracts to the right in the figure.

On the other hand, the injection cylinder 16 is connected to a hydraulic pressure source 42 such as a pump via a hydraulic servo valve 40 by a pipe line 38, receives the hydraulic pressure from the hydraulic pressure source 42, and completes the measurement of the molten resin 36. The screw 14 is advanced to inject the molten resin 36 into the cavity of a mold (not shown).

The cylinder controller 50 compares the injection speed set in the injection speed program setting unit 56 by the speed deviation calculation unit 54 with the injection speed calculated by the injection speed calculation unit 52, and calculates the difference between them. It is sent to the injection speed signal generator 58. The injection speed signal generator 58 includes an injection speed deviation calculator 5
According to the magnitude of the deviation calculated by 2, the injection cylinder 16
A signal for adjusting the injection speed of is output to the servo amplifier 60. The servo amplifier 60 amplifies the output signal of the speed signal generator 58 and supplies the amplified signal to the hydraulic servo valve 42.
The injection speed of the injection cylinder 16 is controlled via 2.

[0007]

By the way, conventionally, the injection cylinder 1 set in the injection speed program setting unit 56 is used.
The injection speed of No. 6 (screw 14) was as shown in FIG. That is, the injection speed V is equal to the injection cylinder 16
It is set to change stepwise with respect to the injection position x which is the stroke amount of the (screw 14). Therefore, the injection speed V of the injection cylinder 16 is equal to the hydraulic servo valve 4
By manipulating the 2, for example at a position x ₁ V ₁
Instantly switched to V ₂ from, V ₂ at position x ₂
To V ₃ instantaneously.

However, the response of the hydraulic servo valve 42 and the followability of the injection cylinder 16 are limited, and even if a speed switching signal is input to the hydraulic servo valve 42, the injection cylinder 1
The injection speed of 6 does not immediately reach the required injection speed,
A response delay occurs and the injection speed is not controlled, the resin filling state in the mold does not reach the target, and the surface quality of the molded product is adversely affected.

Further, it has been attempted to change the injection speed as smoothly as possible, but at the time of switching the injection speed, any overshoot or undershoot occurs, and the injection position with respect to the injection time (of the injection cylinder). Stroke) is deviated, and control is performed with this position deviated to cause variations in the filling amount of the molten resin.

Further, the load applied to the injection cylinder 16 varies depending on various conditions such as the shape of the mold cavity, the temperature of the mold and the heating cylinder 12, the physical properties of the resin to be injected, the sliding resistance of the machine, etc. If the injection speed of 16 cannot be maintained at a predetermined value, the filling state and filling amount of the resin in the mold will vary.

As described above, in the conventional injection molding machine 10, the injection speed is set corresponding to the injection position to perform the injection control. However, the resin which is continuously cooled is filled with the resin. Since the state varies from shot to shot, the flow of resin and the filling amount are not constant, which causes warpage and distortion in the molded product.In addition, the filling amount varies by several percent and the weight of the molded product varies. It was difficult to mass-produce high-precision products.

The present invention has been made in order to solve the above-mentioned drawbacks of the prior art, and the state of filling the mold with the molten resin,
An object of the present invention is to provide an injection control method and device for an injection molding machine, which can make the filling amount constant.

[0013]

In order to achieve the above object, an injection control method of an injection molding machine according to the present invention is an injection molding machine for driving an injection cylinder to fill a molten resin into a mold cavity. In the injection control method, the injection position detected in the injection step of the injection cylinder is compared with a reference injection position of the injection cylinder which is predetermined corresponding to the elapsed time from the start of the injection of the molten resin, It is characterized in that the injection speed of the injection cylinder is adjusted based on the deviation between the two.

Further, the injection control device of the injection molding machine according to the present invention controls the molten resin which is previously obtained in the injection control device of the injection molding machine which controls the injection cylinder for injecting and filling the molten resin into the mold cavity. A reference injection position storage unit that stores the data of the injection position of the injection cylinder corresponding to the elapsed time from the start of injection, and the position of the injection cylinder in the detected injection process and the reference position storage unit The reference injection speed of the injection cylinder is calculated based on the reference deviation position stored in the reference injection position storage unit and the position deviation calculation unit that obtains the deviation between the reference injection position and the reference injection position. A reference injection speed calculation unit; an injection speed correction unit that corrects the reference injection speed calculated by the reference injection speed calculation unit based on the position deviation calculated by the position deviation calculation unit; The injection speed adjusting unit outputs an injection speed adjusting signal according to the deviation between the injection position of the injection cylinder in the injection step and the corrected injection speed output by the injection speed correcting unit. There is.

[0015]

According to the present invention constructed as described above, the reference injection position of the injection injection cylinder is set in advance in correspondence with the elapsed time from the start of the injection of the molten resin, and the detected injection cylinder is detected. Since the injection speed of the injection cylinder is adjusted every moment so that the injection position of the injection cylinder becomes the reference injection position, it is possible to quickly correct the displacement of the injection cylinder and to greatly reduce the fluctuation of the injection time, which was conventionally changing. The size can be reduced, and the resin filling state and filling amount in the mold can be made constant. Therefore, it is possible to eliminate warpage and distortion of the molded product, reduce variations in the weight of the product, and perform highly accurate molding. In addition, when the detection position coincides with the reference position, the injection speed of the injection cylinder 16 is adjusted according to the magnitude of the deviation between the detection position and the reference position, so that the deviation of the detection position from the reference position becomes large. Moreover, not only the deviation can be corrected early, but also excessive correction can be avoided.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of an injection control method and apparatus for an injection molding machine according to the present invention will be described in detail with reference to the accompanying drawings. The parts corresponding to the parts described in the above-mentioned prior art are designated by the same reference numerals, and the description thereof will be omitted.

FIG. 1 is an explanatory diagram of an injection control device of an injection molding machine according to an embodiment of the present invention. The injection control device 70
It has a reference injection position storage unit 72. The reference injection position storage unit 72 stores the moments of the injection cylinder 16 (screw 14) corresponding to the elapsed time from the start of the injection of the molten resin 36, which is obtained based on experiments or actual injection molding in advance. The position is stored as the reference injection position. This reference injection position is set so as to change, for example, with a curve as shown in the figure, and differs depending on the shape of the mold, the molded product, the resin used, and the like. It should be noted that the reference injection position shown in the figure has a positive stroke amount from the forward end position, which is the injection end point of the injection cylinder 16, to the molten resin measurement end position (reverse end), which is the injection start point. Becomes zero.

Further, the injection control device 70 is provided with a position deviation calculation part 74 to which a detection signal of the position detection device 24 including a magnetic scale and a reference injection position signal of the reference injection position storage part 72 are inputted, and a reference injection position. A reference injection speed stored in the storage unit 72 is read out, and a reference injection speed calculation unit 78 for calculating the reference injection speed is provided. Further, the output signal of the position deviation calculation unit 74 is received to correct the reference injection speed. A reference velocity correction unit 76 for obtaining a value, and this reference velocity correction unit 76
And an addition unit 80 that outputs a corrected reference injection speed by adding the calculation results of the reference shot speed calculation unit 78 and the injection speed correction unit 81.

Further, the injection control device 70 calculates the actual injection speed in the injection process of the injection cylinder 16 based on the detection signal of the position detection device 24.
2, an injection speed adjusting unit 86 to which the output signals of the injection speed calculating unit 82 and the adding unit 80 are input, the injection speed adjusting unit 8
A servo amplifier 90 that amplifies the output signal of No. 6 and outputs a control signal to a cylinder drive unit 92 composed of a switching valve, a hydraulic servo valve, and the like is provided.

The injection speed adjusting unit 86 includes an injection speed calculating unit 8
2 is calculated by the shot velocity deviation calculation unit 87 and the shot velocity deviation calculation unit 87, which obtain the deviation between the actual injection speed of the injection cylinder 16 obtained by 2 and the corrected reference injection speed output by the addition unit 80 of the injection speed correction unit 81. And an injection speed adjustment signal corresponding to the deviation is output to the servo amplifier 90.

The operation of the embodiment constructed as described above is as follows. When the screw 14 is rotated by the hydraulic motor 20 to reach the retreat limit while plasticizing the resin and the measurement of the resin is completed, the cylinder drive unit 92 is switched to the injection state, and the injection control device 70 receives a signal of an injection start command. Is input, the timer (not shown) is reset and the injection control program is started. Then, the reference injection position storage unit 72 of the injection control device 70 outputs the stored and set reference injection position signal in every predetermined cycle (for example, every 1 ms) in synchronization with the clock signal output from the timer.

The reference shot speed calculator 78 takes in the position signal output from the reference injection position storage 72, for example, every 10 ms, and calculates and outputs the reference injection speed corresponding to the elapsed time from the start of injection of the injection cylinder 16. To do. The injection speed calculated by the reference shot speed calculator 78 is given to the servo amplifier 90 via the adder 80 and the injection speed adjuster 86, amplified by the servo amplifier 90 and given to the cylinder driver 92 as a drive signal.

The injection cylinder 16 operates to operate the screw 1
When the injection of the molten resin by No. 4 is started, the injection position of the injection cylinder 16 (screw 14) is changed to the position detection device 24.
And is sent to the position deviation calculator 74 and the injection speed calculator 82 of the injection control device 70.

The injection speed calculation unit 82 fetches the detection signal of the position detection device 24 at every predetermined time, and the injection cylinder 1
The actual injection speed of No. 6 is calculated and output to the shot speed deviation calculation unit 87 of the injection speed adjustment unit 86. On the other hand, the position deviation calculator 7
Reference numeral 4 compares the reference injection position, which the reference injection position storage unit 72 outputs every moment corresponding to the elapsed time from the start of injection, with the actual injection position detected by the position detection device 24, and obtains the deviation between them. And sends it to the reference shot speed correction unit 76 of the injection speed correction unit 81.

Upon receipt of the position deviation from the position deviation calculation unit 74, the reference injection speed correction unit 76 calculates a correction value of the injection speed necessary for eliminating this deviation within a predetermined time, for example within 100 ms. And outputs it to the adder 80. The addition unit 80 adds the correction value calculated by the reference injection speed correction unit 76 to the reference injection speed calculated by the reference injection speed calculation unit 78, and inputs the result to the injection speed deviation calculation unit 87 of the injection speed adjustment unit 86. ..

The rate-of-shoot deviation calculating section 87 is provided in the injection-speed calculating section 8
2 and the actual speed of the injection cylinder 16 determined by the addition unit 8
0 is compared with the corrected reference injection speed, and the deviation between the two is calculated and sent to the speed signal generator 88. The velocity signal generator 88 outputs an injection velocity adjustment signal according to the deviation of the injection velocity obtained by the shot velocity deviation calculator 87. The speed adjustment signal is input to the servo amplifier 90, amplified, and given to the cylinder drive unit 92. Then, the cylinder drive unit 92
Adjusts the amount of oil supplied to the injection cylinder 16 and the hydraulic pressure based on the output signal of the servo amplifier 90, and the injection position corresponding to the elapsed time from the start of injection of the injection cylinder 16 is
The injection speed of the injection cylinder 16 is adjusted so that the reference injection position stored in the reference injection position storage unit 72 is reached.

As described above, in the embodiment, the actual injection position of the injection cylinder 16 is controlled to be the reference position corresponding to the elapsed time from the start of the injection of the predetermined molten resin. Therefore, it is possible to avoid that the filling state of the molten resin in the mold with the passage of time in the injection process is different from shot to shot, and it is possible not only to improve the surface quality of the molded product, but also to It is possible to prevent the occurrence of warpage and distortion. Also, the injection molding machine 1
Since the resin can be stably filled through each shot of 0, the variation in the filling amount in the mold can be made extremely small, the variation in the weight of the molded product can be eliminated, and highly accurate molding can be performed. And so-called precision molding is possible.

Moreover, when the detection position is made to coincide with the reference position, the injection speed of the injection cylinder 16 is adjusted according to the magnitude of the deviation between the detection position and the reference position, so the deviation of the detection position from the reference position is large. In the case where the deviation occurs, not only can the deviation be corrected early, but also excessive correction can be avoided especially when a minute deviation occurs.

Although the in-line screw type injection molding machine has been described in the above embodiment, the invention can be applied to other injection molding machines such as a plunger type injection molding machine and a preplas type injection molding machine. Further, in the above embodiment, the case where the reference injection position stored and set in the reference injection position storage unit 72 changes in a curve with respect to the elapsed time from the start of injection has been described. May be changed linearly, or a combination of a straight line and a curved line may be changed.

[0030]

As described above, according to the present invention, the reference injection position of the injection injection cylinder is predetermined in correspondence with the elapsed time from the start of injection of the molten resin,
Since the injection speed of the injection cylinder is adjusted so that the detected injection position of the injection cylinder becomes the reference injection position, it is possible to quickly correct the displacement of the injection cylinder and perform molding with a constant injection time. Therefore, it is possible to make the resin filling state and the filling amount into the mold constant.

Moreover, when the detection position is made to coincide with the reference position, the injection speed of the injection cylinder is adjusted according to the magnitude of the deviation between the detection position and the reference position, so the deviation of the detection position from the reference position becomes large. In this case, not only can the deviation be corrected early, but also excessive correction can be avoided.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an injection control device of an injection molding machine according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of an injection control device of a conventional injection molding machine.

FIG. 3 is an explanatory diagram of a conventional method of setting an injection speed of an injection cylinder.

[Explanation of symbols]

 10 injection molding machine 14 screw 16 injection cylinder 24 position detection device 70 injection control device 72 reference injection position storage unit 76 reference injection speed correction unit 78 reference injection speed calculation unit 81 injection speed correction unit 82 injection speed calculation unit 86 injection speed adjustment unit 88 Speed signal generator 92 Cylinder driver

─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] September 26, 1991

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Claim 2

[Correction method] Change

[Correction content]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0014

[Correction method] Change

[Correction content]

Further, the injection control device of the injection molding machine according to the present invention controls the molten resin which is previously obtained in the injection control device of the injection molding machine which controls the injection cylinder for injecting and filling the molten resin into the mold cavity. A reference injection position storage unit that stores the data of the injection position of the injection cylinder corresponding to the elapsed time from the start of injection, and the position of the injection cylinder in the detected injection process and the reference position storage unit The reference injection speed of the injection cylinder is calculated based on the reference deviation position stored in the reference injection position storage unit and the position deviation calculation unit that obtains the deviation between the reference injection position and the reference injection position. A reference injection speed calculation unit; an injection speed correction unit that corrects the reference injection speed calculated by the reference injection speed calculation unit based on the position deviation calculated by the position deviation calculation unit; Was deviation between the injection speed and the corrected injection speed of the injection rate correction unit has output of said injection cylinder in the injection process was determined, as characterized by having an exit speed adjusting unit for outputting an injection speed adjustment signal corresponding to the difference There is.

Claims (2)

[Claims] 1. In an injection control method of an injection molding machine for driving an injection cylinder to fill a mold cavity with a molten resin, an injection position detected in an injection step of the injection cylinder is started to inject the molten resin. The injection control of the injection molding machine is characterized in that the injection speed of the injection cylinder is adjusted on the basis of the deviation between the reference injection position of the injection cylinder and a predetermined reference injection position corresponding to the elapsed time. Method. 2. An injection control device of an injection molding machine for controlling an injection cylinder for injecting and filling molten resin into a mold cavity, which corresponds to a predetermined elapsed time from the start of injection of molten resin. The reference injection position storage unit that stores the data of the injection position of the injection cylinder and the detected position of the injection cylinder in the injection process and the reference injection position stored in the reference position storage unit are compared, and both of them are compared. A position deviation calculation unit for obtaining a deviation, a reference injection speed calculation unit for calculating a reference injection speed of the injection cylinder based on the reference injection position stored in the reference injection position storage unit, and the position deviation calculation unit. Based on the calculated position deviation,
An injection speed correction unit that corrects the reference injection speed calculated by the reference injection speed calculation unit, and a deviation between the detected injection position of the injection cylinder in the injection process and the corrected injection speed output by the injection speed correction unit are obtained. An injection control device for an injection molding machine, comprising: an injection speed adjusting unit that outputs an injection speed adjusting signal according to a deviation.