JP2868139B2 - Injection control method and apparatus for injection molding machine - Google Patents

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 control method and a control apparatus for an injection step of filling a molten resin into a mold cavity.

[0002]

2. Description of the Related Art Today, a wide variety of products are molded with synthetic resins, and an in-line screw type injection molding machine as shown in FIG. 2 is widely used for molding synthetic resins.
In the in-line screw type injection molding machine 10, the screw 12 having a spiral groove formed on the peripheral surface is
4 and rotatably accommodated in the axial direction.
The screw 12 is connected to a piston rod 18 of an injection cylinder 16 having a rear end formed integrally with the heating cylinder 14.
Are supported via thrust bearings. The screw 12 is coaxially connected at the rear end thereof to a rotary shaft 22 of a hydraulic motor 20 having an axially penetrating piston rod 18, and is rotated by the hydraulic motor 20 at the time of resin measurement.

[0003] A piston rod 18 has an injection cylinder 1
6 is provided with a position detecting device 24 including a magnetic scale, an encoder, and the like for detecting the injection position (the position of the screw 12). The position detecting device 24 detects the injection position of the injection cylinder 16 and outputs a detection signal. It is input to the injection speed calculator 52 of the cylinder controller 50.

[0004] A hopper 30 is attached to the heating cylinder 14, and a resin pellet 32 as a molding material is put into the hopper 30. The heating cylinder 14 is provided with a heater (not shown) along the axial direction.
Resin pellets 3 supplied from 0 to the heating cylinder 14
2 can be melted. The resin pellets 32 are melted and plasticized by the heat of the heater provided in the heating cylinder 14 and the shearing force generated by the rotation of the screw 10 to form a molten resin 36, which is the tip of the heating cylinder 14 to which the nozzle 34 is attached. Sent to At this time, the screw 12 retreats to the right in the drawing due to the reaction force of the molten resin 36.

On the other hand, the injection cylinder 16 is connected to a hydraulic source 42 such as a pump via a hydraulic servo valve 40 via a pipeline 38, and receives the hydraulic pressure from the hydraulic source 42 to complete the measurement of the molten resin 36. The screw 12 is advanced, and the molten resin 36 is injected into a cavity of a mold (not shown).

The cylinder control unit 50 compares the injection speed set by the speed deviation calculation unit 54 in the injection speed program setting unit 56 with the injection speed obtained by the injection speed calculation unit 52, and obtains the difference between the two. It is sent to the injection speed signal generator 58. The injection speed signal generator 58 is configured to control the injection speed deviation calculator 5
2 according to the magnitude of the deviation calculated by the injection cylinder 16.
A signal for adjusting the injection speed 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.
2, the injection speed of the injection cylinder 16 is controlled.

[0007]

By the way, conventionally, the injection cylinder 1 set in the injection speed program setting section 56 has been known.
The injection speed of No. 6 (screw 12) was as shown in FIG. That is, the injection speed V
It is set so as to change stepwise with respect to the injection position x which is the stroke amount of the (screw 12). For this reason, the injection speed V of the injection cylinder 16 is
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
It is switched instantly to V ₃ from.

However, the responsiveness 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 is caused to cause a state in which the injection speed is not controlled, and the filling state of the resin in the mold is not as intended, which adversely affects the surface properties of the molded product.

Therefore, it has been attempted to change the injection speed as smoothly as possible when switching the injection speed. However, in the conventional injection control, the injection speed of the injection cylinder 16 is detected, and the detected injection speed is controlled so as to be equal to the reference injection speed. When the injection speed of the injection cylinder is low, such as at the end of injection or at the end of injection, the deviation between the detected speed and the set injection speed is extremely small, making it difficult to obtain a control gain substantially, and controlling the injection speed of the injection cylinder. Can not do.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned drawbacks of the prior art, and an injection molding machine capable of accurately controlling the stroke of an injection cylinder even when the injection speed of the injection cylinder is low. It is an object of the present invention to provide an injection control method and apparatus.

[0011]

To achieve the above object, an injection control method for an injection molding machine according to the present invention is directed to 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 speed of the injection cylinder in the injection step is detected and compared with a reference injection speed, and the injection speed of the injection cylinder is controlled so that the detected injection speed becomes the reference injection speed. In addition, when the detected injection speed or the reference injection output speed is smaller than a predetermined value, at least the injection position of the injection cylinder is detected and corresponds to the elapsed time from the start of injection of the molten resin. And comparing the detected injection position with the reference injection position.

The injection control device for an injection molding machine according to the present invention is an injection control device for an injection molding machine for controlling an injection cylinder for injecting and filling a molten resin into a mold cavity. A reference injection position storage unit for storing data of the reference injection position of the injection cylinder obtained in advance corresponding to the elapsed time from the start; storage of the detected injection position of the injection cylinder and the reference position in the injection process Compare with the reference injection position stored in the section,
An injection speed correction unit that calculates a correction value of the injection speed of the injection cylinder according to the difference between the two, and a reference injection speed of the injection cylinder based on a reference injection position stored in the reference injection position storage unit. A reference injection speed calculation unit to be calculated, an injection speed detected by the injection cylinder in the injection process, and a reference injection speed calculated by the reference injection speed calculation unit are compared, and an injection speed adjustment signal corresponding to a deviation between the two is calculated. The output signal of the injection speed adjusting unit to be output, and the output signals of the injection speed adjusting unit and the injection speed correcting unit are input, and the detected injection speed or the reference injection speed obtained by the reference injection speed calculating unit is a predetermined value. An injection speed judging unit that outputs a control signal of the injection cylinder based on at least an output signal of the injection speed correcting unit when the injection molding machine is smaller than the injection speed correcting unit. Injection control device.

[0013]

According to the present invention constructed as described above, the control based on the injection position of the injection cylinder is performed when the injection speed of the injection cylinder is lower than a predetermined value. , The stroke of the injection cylinder can be controlled accurately. In addition, the control of the injection position in the state where the injection speed is low is such that the reference injection position is determined according to the elapsed time from the start of the injection of the molten resin, so that the state of filling the resin into the mold is constant. It is possible to perform molding with high precision by preventing the occurrence of variations in the filling amount of the resin and the like.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the 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. Note that the same reference numerals are given to portions corresponding to the portions described in the above-described conventional technology, and description thereof is 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
A reference injection position storage unit 72 is provided. The reference injection position storage unit 72 stores the position of the injection cylinder 16 (screw 12) corresponding to the elapsed time from the start of the injection of the molten resin 36, which is obtained in advance based on experiments or actual injection molding. It is stored as the injection position. The reference injection position is set so as to change, for example, with a curve as shown in the figure with respect to the elapsed time from the start of injection, and varies depending on the shape of the mold, the molded product, the resin used, and the like. The reference injection position shown in the drawing has a positive stroke amount from the forward end position of the injection cylinder 16 as the injection end point to the molten resin measurement end position (retreat end) as the injection start point. Becomes zero.

Further, the injection control device 70 is provided with an injection speed correcting section 74. The injection speed correction unit 74 stores the actual injection position of the injection cylinder 16 detected by the position detection device 24 composed of a magnetic scale or the like and the reference injection position storage unit 7.
A position deviation calculator 76 for calculating a deviation from the reference injection position outputted by the second position calculation unit 2 calculates a correction value of the injection speed of the injection cylinder 16 based on an output signal of the position deviation calculator 76, and determines an injection speed described later in detail. The correction value calculator 78 outputs a calculation result to the section 80.

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. The reference injection speed calculator 84 reads out the position data stored in the reference injection position memory 72 and calculates the reference injection speed. The output signals of the reference injection speed calculator 84 and the injection speed calculator 82 are The output signals of the injection speed adjusting unit 86 and the injection speed judging unit 80 are amplified and the injection cylinder 1 is amplified.
6 is provided with a servo amplifier 90 that is provided to a cylinder driving unit 92 that drives the motor 6.

The injection speed adjusting unit 86 includes an injection speed calculating unit 8
2, a shot speed deviation calculator 87 for calculating a difference between the actual injection speed calculated by the reference injection speed calculator 84 and the reference injection speed output by the reference injection speed calculator 84, and adjustment of the injection speed according to the difference calculated by the shot speed deviation calculator 87. An adjustment value calculator 88 for outputting a signal to the injection speed judging section 80 is provided. Note that the injection speed determination unit 8
To 0, the reference injection speed obtained by the reference firing speed calculation unit 84 is input together with the output signal of the correction value calculator 78.

The operation of the embodiment constructed as described above is as follows. When the screw 12 is rotated by the hydraulic motor 20 and the retraction limit is reached while plasticizing the resin, and the measurement of the resin is completed, the cylinder driving unit 92 is switched to the injection state, and the injection of the resin by the injection cylinder 16 is started. . Further, a signal of an injection control start command is input to the injection control device 70, a timer (not shown) is reset, and an injection control program is started. And
The reference injection position storage unit 72 of the injection control device 70 stores and sets the injection cylinder 16 which is stored and set at a predetermined cycle (for example, every 1 ms) in synchronization with the clock signal output by the timer.
Is output.

On the other hand, when the injection cylinder 16 is operated to start the injection of the molten resin by the screw 14, the position (injection position) of the injection cylinder 16 (the screw 14) is read by the position detecting device 24, and the injection control device is controlled. 70
Are given to the injection speed correction unit 74 and the injection speed calculation unit 82.

The position deviation calculator 76 of the injection speed corrector 74
Is the injection cylinder 1 output from the reference injection position storage unit 72.
6, the reference position corresponding to the elapsed time from the start of injection is compared with the actual injection position of the injection cylinder 16 detected by the position detection device 24, and the deviation between them is calculated and input to the correction value calculator 78. . The correction value calculator 78 calculates the injection speed of the injection cylinder 16 necessary for eliminating the deviation obtained by the position deviation calculator 76 within a predetermined time (for example, within 50 ms) and sends it to the injection speed determination unit 80. .

The injection speed calculating section 82 takes in the detection signal of the position detecting device 24 at predetermined time intervals, calculates the actual injection speed of the injection cylinder 16 and calculates the injection speed adjusting section 8.
6 is output to the shooting speed deviation calculator 87. Then, the reference firing speed calculation unit 84 fetches the position signal output from the reference injection position storage unit 72 every 10 ms, for example, and
Calculates the instantaneous reference injection speed corresponding to the elapsed time from the start of injection, and sends it to the shot speed deviation calculator 87 and the injection speed determination unit 80.

The injection speed adjusting unit 86 is provided with the firing speed deviation calculator 8
7 calculates the deviation between the reference injection speed output from the reference firing speed calculator 84 and the actual injection speed output from the injection speed calculator 82, and the adjustment value calculator 88 calculates the deviation output from the shooting speed deviation calculator 87. , An adjustment value of the reference injection speed such that the actual injection speed becomes the reference injection speed is calculated and input to the injection speed determination unit 80.

The injection speed judging section 80 includes a reference firing speed calculating section 8
4 receives the determined reference injection speed, the reference injection speed is compared with a preset value. When the injection speed is low, such as at the start of injection or immediately before the end of injection, and the reference injection speed obtained by the reference injection speed calculation unit 84 is smaller than a set value (for example, 10 mm / s),
The output signal of the injection speed adjustment unit 86 is cut, and the injection speed correction signal sent from the injection speed correction unit 74 is sent to the servo amplifier 90. In addition, the injection speed determination unit 80 determines that the reference injection speed obtained by the reference injection speed calculation unit 84 is equal to or higher than a set value.
The signal output by the injection speed correction unit 74 is cut, and the output signal of the injection speed adjustment unit 86 is sent to the servo amplifier 90. The servo amplifier 90 amplifies the signal from the injection speed judging section 80 and supplies the amplified signal to the cylinder driving section 92. That is, when the reference injection speed obtained by the reference injection speed calculation unit 84 is smaller than the predetermined set value, the injection speed determination unit 80
A control signal is output based on the injection position of No. 6 and, if the reference injection speed is equal to or higher than the set value, a control signal based on the injection speed of the injection cylinder 16 is output.

The cylinder driving section 92 adjusts the amount of oil supplied to the injection cylinder 16 and the oil pressure based on the output signal of the servo amplifier 90 and drives the injection cylinder 16. That is, the cylinder drive unit 92 is
If the control signal received via the control signal 0 is output from the injection speed correction unit 74, the injection position of the injection cylinder 16 corresponding to the elapsed time from the start of injection is stored in the reference injection position storage unit 72. The injection speed of the injection cylinder 16 is adjusted so as to be at a certain reference injection position. When the control signal received via the servo amplifier 90 is output from the injection speed adjusting unit 86, the cylinder driving unit 92 outputs the injection speed obtained by the injection speed calculating unit 82 to the reference firing speed calculating unit 84.
Injection cylinder 16 so that the reference injection speed outputted by
Adjust the injection speed of.

As described above, in the embodiment, when the injection speed of the injection cylinder 16 is low, such as at the start of injection or at the end of injection, the injection speed of the injection cylinder 16 is determined based on the injection position of the injection cylinder 16. Therefore, the stroke of the injection cylinder 16 can be accurately controlled even when the injection speed is low. For this reason, the filling state of the resin in the mold does not differ for each shot, the variation in the filling amount of the resin and the like are reduced, and molding with high precision is possible.

In the above embodiment, the injection speed judging unit 80 controls the output from the injection speed correcting unit 74 based on the reference injection speed obtained by the reference firing speed calculating unit 84, or adjusts the injection speed. Although the case where it is determined whether to perform the control based on the output of the unit 86 has been described, the determination may be made based on the actual injection speed obtained by the injection speed calculation unit 82.

In the above embodiment, when the reference injection speed is equal to or higher than a predetermined set value, control is performed based on the detected injection speed (output signal of the injection speed adjusting unit 86), and the reference injection speed is set to a value smaller than the set value. The case where the control is performed based on the detected injection position (the output signal of the injection speed correction unit 74) when the injection speed is small is described. However, when the reference injection speed is smaller than the set value, the injection speed correction unit 74 and the injection speed adjustment unit 86 are used. The injection speed of the injection cylinder 16 may be controlled using both output signals of the injection speed correction unit 74 and the injection speed adjustment unit 86 at all times. Good. Further, in the above embodiment, the reference injection position stored and set in the reference injection position storage unit 72 is
The case where the curve changes with the elapsed time from the start of injection has been described, but the reference injection position changes linearly with the elapsed time, a combination of a plurality of straight lines having different inclination angles, or a straight line and a curve. May be combined.

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 with elapsed time, or may be changed by combining a straight line and a curve. And in the said Example, although the in-line screw type injection molding machine was demonstrated,
The present invention can be applied to other injection molding machines such as a plunger type injection molding machine and a prepra type injection molding machine.

[0030]

As described above, according to the present invention, when the injection speed of the injection cylinder is lower than a predetermined value, control based on the injection position of the injection cylinder is performed. Even when the control gain cannot be obtained, accurate stroke control of the injection cylinder can be performed.

[Brief description of the drawings]

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

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

FIG. 3 is an explanatory diagram of a setting example of an injection speed in a conventional injection molding machine.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Injection molding machine 12 Screw 16 Injection cylinder 24 Position detecting device 70 Injection control device 72 Reference injection position storage unit 74 Injection speed correction unit 80 Injection speed judgment unit 82 Injection speed calculation unit 86 Injection speed adjustment unit

──────────────────────────────────────────────────の Continued on the front page (58) Field surveyed (Int. Cl. ⁶ , DB name) B29C 45/46-45/50 B29C 45/76-45/77 B29C 45/82 B22D 17/32

Claims (2)

(57) [Claims] 1. An injection control method for an injection molding machine for filling an injection molding machine with a molten resin by driving an injection cylinder, the method comprising controlling an elapsed time from the start of injection of the molten resin.
The injection position of the injection cylinder as a reference injection position.
Predetermined and corresponds to the injection position of the injection cylinder in the injection process.
To determine the actual injection speed,
The injection speed of the injection cylinder is controlled such that the actual injection speed becomes the reference injection speed, compared with a reference injection speed obtained based on a change with respect to time , and the actual injection speed or the reference If the injection speed is smaller than a predetermined value, at least the injection position of the injection cylinder is detected and compared with the reference injection position.
The injection speed at which the deviation of the operator becomes zero within a predetermined time
An injection control method for an injection molding machine , comprising controlling an injection speed of an injection cylinder . 2. An injection control device of an injection molding machine for controlling an injection cylinder for injecting and filling a molten resin into a mold cavity, wherein the injection control device obtains a value in advance corresponding to an elapsed time from the start of the injection of the molten resin. A reference injection position storage unit storing the data of the reference injection position of the injection cylinder, and comparing the detected injection position of the injection cylinder in the injection step with the reference injection position stored in the reference injection position storage unit. An injection speed correction unit that calculates a correction value of the injection speed of the injection cylinder to make the difference between the two zero within a predetermined time; and a reference injection position stored in the reference injection position storage unit .
A reference injection speed calculation unit that calculates a reference injection speed of the injection cylinder based on a change with respect to the elapsed time, and a reference injection speed calculation unit that corresponds to an injection position of the injection cylinder in an injection process.
The actual injection speed obtained by the above is compared with the reference injection speed obtained by the reference injection speed calculating section, and the injection is performed in accordance with the deviation between the two.
An injection speed adjusting unit for outputting a signal for adjusting a speed; an output signal of the injection speed adjusting unit and the output signal of the injection speed correcting unit being input; and an actual injection speed or a reference injection determined by the reference injection speed calculating unit. An injection speed determination unit that outputs an injection speed control signal of the injection cylinder based on at least an output signal of the injection speed correction unit when the speed is lower than a predetermined value. Injection control device.