JPH0345327A - Dwell controlling device of injection molder - Google Patents

Abstract

PURPOSE:To uniformize the quality of molded item by making smooth the changing-over of the hydraulic pressure controlling means of an injection cylinder by a structure wherein a resin pressure closed loop controlling means, the hydraulic pressure closed loop controlling means and a changing-over zone controlling means are equipped in a control device. CONSTITUTION:During an A zone, which ranges from the starting time point t1 of dwell process to a time point t2, a manipulated variable u1 is controlled so as to be run along a curve a' by means of a resin pressure closed loop controlling means, in which the output of a comparator 9 comparing the resin pressure set point set by a setter 8 with the value measured by a detector 5 is given through a resin pressure compensator 10 to a servo motor 4. Next, during a B zone, which ranges from the time point t2 to a time point t3, a manipulated variable u(k+1) is controlled so as to be run along a curve (c) by means of a changing-over zone controlling means, in which the outputs of compensators 10 and 12 are given to a changing-over zone controlling manipulated variable calculating calculating means 13 so as to be processed through the predetermined operation in order to give the processed output to the servo valve 4. Next, during a C zone, which follows the time point t3, a manipulated variable u2 is controlled so as to be run along a curve b' by means of a hydraulic pressure closed loop controlling means, in which the output of a comparator 11 comparing the hydraulic pressure set point set by the setter 8 with the value measured by a detector 6 is given through a hydraulic pressure compensator 12 to the servo valve 4. The time points t2 and t3 are set in advance by a control device 7 and measured with a timer.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is an injection molding machine that controls the holding pressure applied to the resin when changing the resin from a molten state to a solidified state after filling a mold with the resin. This relates to a device for

[Prior Art] In an injection molding machine, there is a device that detects the resin pressure in the mold with a pressure detector during the pressure holding process and controls the resin pressure in the mold based only on the detected resin pressure value. It is being In this device, the pressure detected by the pressure detector is that on the surface of the molded product molded in the mold, and the pressure distribution of the resin in the mold is uneven over time and position. In the latter stage of the pressure holding process after the resin at the gate part has solidified, the pressure difference between the pressure application part and the pressure detection part becomes large, resulting in excessive pressure being applied to local parts of the molded product, resulting in a molded product with uneven density. will be created.

Therefore, conventionally, as a holding pressure control device for injection molding machines,
It has been proposed to switch the control amount from the resin pressure in the mold to the oil pressure in the injection cylinder in the pressure holding process (for example, see Japanese Patent Laid-Open No. 62-261.419).

[Issue 8 to be solved by the invention] In conventional devices, when switching the control amount, the hydraulic pressure of the injection cylinder at the end of controlling the resin pressure in the mold is set to Although we use arithmetic control means that can replace the process pressure command value, the compensator for the resin pressure in the mold is different from the compensator for the oil pressure in the injection cylinder.
At the time of switching the controlled variable, the controlled variable (
This method has the disadvantage that an inflection point occurs in the input terminal value), and as a result, an inflection point occurs in the resin pressure in the mold or the oil pressure of the injection cylinder.

An object of the present invention is to enable smooth switching from a resin pressure control means for controlling resin pressure in a mold to a hydraulic pressure control means for controlling oil pressure in an injection cylinder in an injection molding machine, and for this purpose. An object of the present invention is to provide a holding pressure control device that can make the quality of molded products uniform.

[Means for Solving the Problems] The present invention provides a resin pressure closed loop control means that controls resin pressure based on the measured value of a resin pressure detector that detects resin pressure in a mold, and a resin pressure closed loop control means that detects the oil pressure of an injection cylinder. A total of 1 oil pressure detector
1111 value, and a switching section control means for switching these, the switching section control means controls the operating position and the hydraulic closed loop control by the resin pressure closed loop control means. It is characterized in that control is performed to switch the manipulated variable so as not to cause an inflection point in the manipulated variable by the means.

[Function] The present invention controls the manipulated variable by the resin pressure closed loop control means during the time from the start time t of the pressure holding process to the time t2, and then controls the manipulated variable by the switching interval control means during the time from time t2 to time t3. The operation amount is controlled and the second time point t2
The operation amount is controlled by the switching section control means during the time from t to the time t, and the operation amount is first controlled by the pressure closed loop control means after the time t3, and the resin pressure at one time t2 is controlled by the pressure closed loop control means. The operation amount in the switching section indicated by the curve connecting the point on the control operation amount curve and the point on the hydraulic control operation amount curve at time t is calculated by the switching section control operation Q calculation means (2, based on this calculation value, switching is performed) The section control means or the manipulated variable is controlled.

[Embodiments] Next, the embodiments of the present invention are shown in Figure +'f+i.
+YIII will explain.

In FIG. 1, number n] indicates an injection molding machine. The injection molding section 1 consists of a mold 2 and an injection section 3 that injects resin into the mold. Oil 3b is stored in the rear part of the injection cylinder 3a of the injection section 3, and a servo valve 4 is provided to control the oil pressure of the oil 3b by injecting and discharging this well 3b into and out of the cutting cylinder 3a. It is located.

When the oil pressure is changed by this servo valve 4, the position of the screw 3c is changed, and the pressure of the resin in the mold 2 is changed. The hydraulic pressure may be controlled by a ratio valve instead of the servo valve 4.

A resin pressure detector 5 is arranged in the mold 2 to detect the resin pressure in the cavity. A hydraulic pressure detector 6 for detecting hydraulic pressure is arranged at the rear of the injection cylinder 3a.

These resin pressure detector 5 and oil pressure detector 6 are installed in the control device 7.

A 1/-1 target value setter 8 for manually inputting information such as a resin pressure target value and an oil pressure target value is connected to the control device 7. A sub-valve is connected to the output terminal of the control device 6.

The control device 7 is equipped with a resin pressure closed loop control means, a ura pressure closed loop control means, and a switching section control means.

The resin pressure closed loop control means, as shown in FIG.
The resin pressure target value set in the II target value setter 8 and the measured value from the resin pressure detector 5 are transferred to the comparator 9, and the output of this comparator 9 is passed through the resin pressure compensator 10. and is applied to the servo valve 4.

The pressure closed loop control means compares the surface pressure target value set in the target value setter 8 and the measured value from the oil pressure detector 6 with the comparator 1! Moreover, the output of this comparator 11 is given to the servo valve 4 via the hydraulic compensator 12.

The switching section control means inputs the outputs of the resin pressure compensator 10 and the hydraulic compensator 2 to the switching section control operation amount calculation means 13, and the switching section control operation amount calculation means 13 performs a predetermined calculation. The output is then sent to the servo valve 4.

The resin pressure compensator 10. Ura E [The output terminals of the compensator 12 and the switching section control manipulated variable calculation means 13 are:

It is connected to the servo valve 4 via the control switching means 14. The control switching means 14 applies the respective outputs of the resin pressure compensator 10, the hydraulic compensator 12, and the switching section control operation amount calculating means]3 to the servo valve 4 only for a predetermined time.

Next, the operation of the holding pressure control device for an injection molding machine of the present invention will be explained based on FIG.

In FIG. 3(a), reference numeral a is a curve showing a change in resin pressure over time, and reference numeral s is a curve showing a change in surface pressure over time.

In FIG. 3(b), the symbol a' is a resin pressure control operation amount curve showing the change over time of the operation ffi u + to the servo valve 4 by the resin pressure closed loop control means, and the symbol b' is a resin pressure control operation amount curve showing the change over time of the operation ffi u + to the servo valve 4 by the resin pressure closed loop control means. Operation ffi to servo valve 4 by means
It is a hydraulic control operation amount curve showing the change over time of u2,
Further, the symbol C is a switching section control operation amount curve showing a change over time in the operation fitu(k+1) on the servo valve 4 by the switching section control means. This switching section control operation amount curve C includes points c1 and 1 of the resin pressure control operation amount curve a' at time t2, which is a predetermined time elapsed from the start time t of the pressure holding process.
This is a curve that connects point c2 of hydraulic control operation amount curve b' at time t3, which is a predetermined time elapsed from time tl.

Operation amount u (k+1) of the switching section control operation amount curve C
is calculated by one sampling, one time point t2
When is set to -0, T=t2-tl, and τ is the sampling time, it is expressed by the following equation.

u (0) ” u 1 (0)
...(],)u(k+I) =u(k) +[1
, 12(k)-1JI (k)] r/(τ in T-)
・−・・・(2) These <1),
Based on equation (2), the switching section control manipulated variable calculating means]3 calculates the manipulated variable U(k + i).

In section A from the start time t1 to time t2 of the pressure holding process, the resin pressure control operation amount curve a is controlled by the resin pressure closed loop control means.
121 Then, in the section B from time t2 to time t3, the operation f1m is controlled so as to follow the switching section control operation amount curve C by the switching section control means.
u(k+1), and firstly, in section C after time t3, the operation ffi u 2 is controlled by the hydraulic closed loop control means so as to follow the hydraulic control operation amount curve b'.

The time point t2 + t3 is set in advance in the control device 7 as the point in time when the switching starts and the special product switching is completed.
Those 11 and 7 points will be measured by a timer installed at the time.

[Effects of the Invention] The present invention enables smooth switching from the resin pressure control means that controls the resin pressure in the mold to the oil pressure control means that controls the oil pressure of the injection cylinder in an injection molding machine.
Moreover, for this reason, the quality of the molded product can be made uniform.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing the configuration of the present invention, FIG. 2 is a block diagram showing the configuration of the present invention, and FIG. 3 is a diagram for explaining the operation of the present invention. 0 2... Mold, 3... Injection part, 5... Resin pressure detector, 6... Oil pressure detector, 7... Control device, ]0...
Resin pressure compensator, 12... Hydraulic compensator, 13... Switching section control operation amount calculation means, 14... Control switching means.田E $elX ())

Claims (1)

[Claims] (1) A resin pressure detector detects the resin pressure in the mold, an oil pressure detector detects the oil pressure of the injection cylinder, and the resin pressure is controlled by comparing the measured value by the resin pressure detector with the target value. a resin pressure closed loop control means for controlling the hydraulic pressure by comparing a measured value by the oil pressure detector with a target value, and a temporal change in a manipulated variable for control in the resin pressure closed loop control means. A predetermined period of time has elapsed from the start time t_1 of the pressure holding process based on a resin pressure control operation amount curve showing a change in the operation amount for control in the hydraulic closed loop control means and a hydraulic pressure control operation amount curve showing a change over time in the operation amount for control in the hydraulic closed loop control means. The point on the resin pressure control operation amount curve at time t_2,
A switching section control operation amount calculation means for calculating an operation amount in a switching section indicated by a curve connecting a point on a hydraulic control operation amount curve at time t_3 when a predetermined time has elapsed from time t_2, and switching section control obtained thereby. As shown in the manipulated variable curve, the manipulated variable is controlled by the switching interval control means that controls the manipulated variable and the resin pressure closed loop control means from the start time t_1 of the pressure holding process to the time t_2, and then from the time t_2 to the time t_2. The operation amount is controlled by the switching section control means in the time up to t_3, and then at time t_3
1. A pressure holding control device for an injection molding machine, comprising a control switching means for controlling an operation amount by a hydraulic closed loop control means at a subsequent time.