JP3505225B2 - Molding machine - Google Patents

Description

Detailed Description of the Invention

[0001]

The present invention relates, Ri engages into a molding machine such as an injection molding machine or a die casting machine, especially suitable feedback to control the speed and pressure of the hydraulic driving source such as an injection cylinder (hydraulic cylinder) Related to technology related to control.

[0002]

2. Description of the Related Art In an injection molding machine, a control condition of an injection speed corresponding to a forward speed of a piston rod of an injection cylinder and a control of an injection pressure corresponding to a pressure of hydraulic oil supplied to an oil chamber for advancing the injection cylinder. The condition is an important factor in molding a non-defective product, and various injection molding machines in which the injection speed and the injection pressure are feedback-controlled have been proposed.

In a conventional injection molding machine that performs feedback control, generally, in a primary injection process in which a molten resin is injected and filled in a cavity of a mold, a measured speed value approaches a speed setting value. The feedback control of the injection speed is performed, and the feedback control of the injection pressure is performed so that the measured pressure value approaches the pressure setting value in the pressure holding process of applying the holding pressure to the resin in the mold.

That is, the feedback control unit in the control system circuit of the injection molding machine uses a preset speed setting value Vo.
In addition, the measured pressure value Vm obtained by appropriately converting the pressure setting value Po and the measurement data of the sensor in the injection mechanism.
Also, the measured pressure value Pm is taken in, and the measured velocity value Vm is irrelevant during the primary injection stroke regardless of the measured pressure value Pm.
Is controlled so as to match the speed set value Vo, and during the pressure holding process, the feedback control is performed so that the measured pressure value Pm matches the pressure set value Po regardless of the measured speed value Vm. It was.

Further, in the case of the open control which does not have the feedback function, both the flow rate proportional solenoid valve and the pressure proportional solenoid valve are used for both the speed and pressure during both the primary injection stroke and the pressure holding stroke. Although the control is performed with priority given to either one, apparently both speed and pressure are controlled. That is, both the speed setting value and the pressure setting value are set over the entire injection control region, and one of the speed and pressure setting values serves as the upper limit value of the other actual output value.

[0006]

When the primary injection stroke is performed by the velocity feedback control as described above, the measured pressure value is neglected. During this time, the injection pressure is controlled substantially. In addition, when the pressure-holding process is performed by the pressure feedback control, the measured velocity value is ignored, so that the injection velocity cannot be controlled during this period. However, if such an injection process (primary injection process and pressure holding process) is controlled, for example,
At the end of the primary injection process, the resin in the mold approaches the completion of filling, and the reaction pressure from the resin in the mold increases the load pressure, causing the injection speed to drop, but the speed is always constant during the primary injection process. Since feedback control is performed, if the speed setting value at the end of the primary injection stroke is high, feedback control is performed so that the set speed is set to an unreasonable level, which causes an abnormal increase in load pressure and damages the mold. I was afraid. In addition, when the pressure-holding process for pressure feedback control is entered in a state where the resin is not completely filled in the mold (unfilled or insufficiently filled), the prescribed load pressure does not rise, so the pressure is too high. Feedback control is performed so as to generate pressure up to the set value, which causes an abnormal increase in speed, which may cause damage to the mold and the injection mechanism.

Further, in order to realize feedback control, it is impossible to use an inexpensive electromagnetic control valve used for open control but having a slow response.
The cost of the machine was increased because it was necessary to use an expensive servo electromagnetic control valve or high-speed proportional electromagnetic control valve with high-speed response.

Furthermore, in the initial stage of the feedback control, it is attempted to rise rapidly to the target set value.
Since hunting occurs and gradually converges, there is a problem that the hunting is unstable until the hunting stops.

Therefore, the technical problem to be solved by the present invention is to solve the above-mentioned problems of the prior art.
The purpose is to enable feedback control even with an inexpensive electromagnetic control valve having a slow response. It is another object of the present invention is to realize a feedback control with excellent possibility no safety breakage of the mold and injection mechanism portion. It is another object of the present invention is to realize the feedback control does not cause the hunting to start-up or the like of the feedback control.

[0010]

In order to achieve the above object, the present invention provides a speed (flow rate) control solenoid valve and a pressure control solenoid valve for driving and controlling a hydraulic drive source (for example, an injection cylinder). In a molding machine for feedback control of speed and pressure, a preset output value for open control and an output value for feedback control obtained by PID (proportional / integral / derivative) calculation are added, A means for driving and controlling the driver circuit of the speed control solenoid valve or the driver circuit of the pressure control solenoid valve according to the addition result is provided, and the speed feedback control period
In addition, if the measured pressure value exceeds the specified value, the speed control is opened.
Control to control only
If the measured speed value exceeds the specified value during the control period, the pressure will
The control is switched to open control only .

Further, when the speed or pressure is raised to the set value, the PID is set at the timing when the measured speed value or the measured pressure value reaches a predetermined area close to the set value.
The integrated value calculated is replaced with a proper value obtained by clearing or learning in advance.

Further, a predetermined limit width is provided for the output value for feedback control, and the maximum value of the feedback output value is regulated so that the feedback output value does not output indefinitely as in the conventional feedback control. To be done.

[0013]

[0014]

Since the output value for feedback control obtained by the PID calculation is added to the output value for open control, which gives a measured value (speed measured value or pressure measured value) close to the target set value, feedback is achieved. Since the control amount can be small and the feedback gain can be increased, it is possible to perform feedback control even with an electromagnetic control valve having a slow response. In other words, the main factor of the speed control or the pressure control is left to the open control output value, and the feedback control output value is compensated by an amount deviating from the target set value, so that the feedback gain can be increased. On the other hand, in the feedback control according to the conventional method in which the entire amount of control is carried by the feedback control output value, hunting occurs when the feedback gain is increased, and it becomes difficult to perform accurate feedback control.

Further, if feedback control by PID calculation is performed, in the initial state where the speed or pressure is raised to the set value, the influence of the integrated value ((1 / T _i ) ∫edt) which is abnormally accumulated when the speed or pressure is raised. Causes hunting. On the other hand, in the present invention, when the speed or pressure is raised to the set value, the integration by PID calculation is performed at the timing when the measured speed value or the measured pressure value reaches a predetermined region (steady state range) close to the set value. Since the value is replaced with an appropriate value obtained by clearing or learning in advance,
Hunting will no longer occur at startup,
It is possible to perform accurate feedback control from the time when it enters the steady state range.

Further, if the feedback gain is increased, the control width of the feedback is increased, and at this time, hunting may occur in the electromagnetic control valve having a slow response. Therefore, in the present invention, a predetermined limit width is provided for the output value for feedback control, and the maximum value of the feedback output value is restricted to prevent the occurrence of hunting when the feedback gain is increased.

Further, the speed feedback control is performed 1
At the end of the next injection stroke, when the resin in the mold approaches the completion of filling and the load pressure rises due to the reaction force from the resin in the mold, and this load pressure becomes higher than the pressure setting value of open control, The speed falls below the load pressure, and speed feedback control becomes impossible with the feedback control having a feedback control width. Alternatively, if the pressure-holding process for pressure feedback control is entered in a state where resin filling into the mold is not completely completed (unfilled or insufficiently filled), the predetermined load pressure does not rise, so feedback of With the feedback control having the control width, the pressure feedback control becomes impossible. Therefore, in the present invention, when the measured pressure value exceeds a predetermined value within the speed feedback control period, the speed control is switched to control of only open control, and the measured speed value exceeds the predetermined value within the pressure feedback control period. Then, the pressure control is switched to the control of only the open control. As a result, the pressure can be reduced and the speed feedback control can be performed again with the decrease in speed due to the open control, or the speed can be reduced with the decrease in pressure due to the open control. It is possible to reduce the pressure and perform pressure feedback control.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below with reference to one embodiment shown in FIGS. 1 to 6, which is applied to feedback control of an injection process (primary injection process and subsequent pressure-holding process) of an injection molding machine.

FIG. 1 is a block diagram showing the configuration of an injection speed feedback control system of an injection molding machine according to one embodiment of the present invention, and FIG. 2 is an injection of the injection molding machine according to one embodiment of the present invention. It is a block diagram which shows the structure of a pressure feedback control system. In this embodiment, the primary injection stroke during the injection stroke is speed feedback controlled by the configuration of FIG. 1, and the pressure holding stroke during the injection stroke is pressure feedback controlled by the configuration of FIG. ing.

In FIG. 1, 1 is an input unit for a preset speed setting value, 2 is an open output value calculation unit, 3 is a comparator (subtractor), 4 is a PID calculation unit, and 5 is an addition output value calculation unit. , 6 is an adder, 7 is a D / A (digital / analog) converter, 8 is a driver amplifier, 9 is a solenoid valve for speed control, 1
Reference numeral 0 is an injection cylinder, 11 is a stroke sensor, and 12 is a speed calculation unit.

The speed setting value Vo preset according to the forward movement position (stroke) of the piston rod of the injection cylinder 10 is input to the input section 1, and the speed setting value Vo is inputted.
Is output to the open output value calculation unit 2 and the comparator 3. The open output value calculation unit 2 appropriately converts the speed set value Vo as in the case of the conventional open control, and outputs the open output value (output value for open control) corresponding to the speed set value to the adder 6. To do.

The stroke sensor 11 is the injection cylinder 1.
The forward stroke of the piston rod of 0 is detected and output to the speed calculation unit 12. The speed calculation unit 12 calculates the measured speed value Vm based on the input stroke information and the clock information, and outputs the calculated measured speed value Vm to the comparator 3. Further, the speed calculation unit 12 sets the PID at the timing at which the actual speed value Vm reaches the steady state range, which is a predetermined area close to the speed setting value Vo, at the time of starting the speed feedback control.
The clear signal CL is output to the arithmetic unit 4. The clear signal CL will be described later with reference to FIG.

The comparator 3 calculates the difference e between the speed setting value Vo and the actual speed value Vm and outputs it to the PID calculator 4. The PID calculation unit 4 performs a well-known PID (proportional / integral / derivative) calculation operation, and outputs an output of a size arbitrarily larger than the unit step input in the “P” calculation operation, and the unit step input in the “I” calculation operation. On the other hand, it is assumed that the output is linearly increased or decreased by the integral action, and the time advance is caused by the differential action by the "D" arithmetic operation, and these "P", "I",
The feedback operation amount u is calculated by simultaneously performing the “D” calculation operation, and is output to the addition output value calculation unit 5. For reference, the arithmetic expression executed by the PID arithmetic unit 4 is as follows. However, in the equation, P, T _i , and T _d are constants.

[0024]

[Equation 1]

The addition output value calculator 5 appropriately converts the feedback manipulated variable u as necessary and outputs it to the adder 6 as a feedback addition value. However, in the addition output value calculation unit 5, a predetermined limit width is provided for the feedback addition value, and the maximum value of the feedback addition value is regulated so that the feedback output value does not output infinitely like the conventional feedback control. It has become. The limit width will be described later with reference to FIG.

The adder 6 adds the feedback addition value to the open output value, and the addition result is D / A.
It is converted into an analog signal by the converter 7 and output to the driver amplifier 8. The driver amplifier 8 appropriately converts the input signal as necessary, and outputs a valve drive control signal to the speed control solenoid valve 9, whereby the speed control solenoid valve 9 controls the piston rod of the injection cylinder 10. Feedback control is performed so that the forward speed matches the speed set value Vo.

The injection pressure feedback control system shown in FIG.
It has substantially the same configuration as the injection speed feedback control system of FIG. 1 described above. In FIG. 2, reference numeral 21 is an input unit for a preset pressure set value, 22 is an open output value calculation unit, 23 is a comparator (subtractor), 24 is a PID calculation unit, 2
5 is an addition output value calculation unit, 26 is an adder, 27 is D / A
(Digital-analog) converter, 28 is a driver amplifier, 29 is a solenoid valve for pressure control, 10 is an injection cylinder same as in FIG. 1, 31 is a pressure sensor, and 32 is a pressure calculation unit.

A pressure setting value Po preset along the time axis in the pressure holding process is input to the input unit 21, and the pressure setting value Po is output to the open output value calculating unit 22 and the comparator 23. To be done. The open output value calculation unit 22
As in the case of the conventional open control, the pressure set value Po is appropriately converted and an open output value (output value for open control) corresponding to the pressure set value is output to the adder 6.

The pressure sensor 31 detects the oil pressure in the forward oil chamber of the injection cylinder 10 and outputs it to the pressure calculation unit 32. The pressure calculation unit 32 amplifies the input information and appropriately waveform-processes it, then converts it into a digital signal, and outputs this as a pressure actual measurement value Pm to the comparator 3. In addition, the pressure calculation unit 3
When the pressure feedback control is started, 2 outputs a clear signal CL to the PID calculator 24 at the timing when the measured pressure value Pm reaches a steady state range which is a predetermined region close to the pressure set value Po. The clear signal CL will be described later with reference to FIG.

The comparator 23 calculates the difference e between the pressure setting value Po and the actual pressure value Pm and outputs it to the PID calculator 24. The PID calculation unit 24 executes the “P”, “I”, and “D” calculation operations using the above equations to calculate the feedback manipulated variable u, which is then sent to the addition output value calculation unit 25. Output.

The addition output value calculation unit 25 appropriately converts the feedback manipulated variable u as necessary and outputs it to the adder 26 as a feedback addition value. However, in the addition output value calculation unit 25, a predetermined limit width is provided for the feedback addition value, and the maximum value of the feedback addition value is regulated so that the feedback output value does not output infinitely like the conventional feedback control. It has become. The limit width will be described later with reference to FIG.

The adder 26 adds the feedback addition value to the open output value, and the addition result is D /
It is converted into an analog signal by the A converter 27 and output to the driver amplifier 28. The driver amplifier 28 appropriately converts the input signal as necessary, and outputs the valve drive control signal to the pressure control solenoid valve 29.
Feedback control is performed by the pressure control solenoid valve 29 so that the forward hydraulic pressure of the injection cylinder 10, that is, the injection pressure, matches the pressure set value Po.

Here, in the present embodiment, the speed control solenoid valve 9 and the pressure control solenoid valve 29 are inexpensive and inexpensive solenoid control valves. But as mentioned above,
Target setting value (speed setting value Vo or pressure setting value P
o) actual measurement value (speed actual measurement value Vm or pressure actual measurement value P)
Since the operation amount for feedback control (feedback addition value) obtained by the PID calculation is added to the open output value from which m) is obtained, the feedback control amount can be small and the feedback gain can be increased. It is possible to perform feedback control even with a slow electromagnetic control valve. In other words, the main factor of the speed control or the pressure control is left to the open control output value, and the feedback control output value is compensated by an amount deviating from the target set value, so that the feedback gain can be increased.

Next, the operation at the time of starting the speed or pressure feedback control will be described. FIG. 3 is an explanatory diagram showing a state at the time of starting the speed or pressure feedback control according to the present embodiment, in which the horizontal axis represents time and the vertical axis represents speed or pressure.

For example, when the speed feedback control is started (when the speed feedback control is started in a form that mutually assists the speed open control), the measured speed value rapidly rises toward the set speed value. Since the PID calculation unit 4 is also performing the PID calculation operation at this startup,
The integral value ((1 / T _i ) ∫edt) becomes larger,
Hunting occurs as it is. Therefore, in this embodiment, the speed calculation unit 12 detects that the measured speed value has entered the steady state range Su shown in FIG. 3, and the PID calculation unit 4 outputs the clear signal CL for clearing the integrated value at this timing.
And the integrated value is cleared at time t1 in FIG. As a result, since the abnormally accumulated integral value disappears by the time t1, the speed actual measurement value immediately follows the speed setting value without causing hunting in the steady state range Su. On the other hand, if the integrated value is not cleared at time t1, hunting will occur as shown by the dotted line in FIG.

Similarly, when the pressure / velocity feedback control is started, the pressure calculating unit 32 detects that the measured pressure value has entered the steady state range Su shown in FIG. 3, and the integral value is cleared at this timing. The clear signal CL is output to the PID calculator 24 so that the integrated value is cleared at time t1 in FIG.

The steady-state range Su may be of any size, but is preferably within ± several% to ± 10% of the set value. Also, instead of clearing the integrated value at time t1,
When the proper integrated value at one time point is known in advance by a case study, it may be replaced with this proper integrated value.

Next, the limit width of the above-mentioned feedback addition value in this embodiment will be described with reference to FIG. FIG. 4 is an explanatory diagram showing the limit width of the feedback addition value. In FIG. 4, the horizontal axis represents time and the vertical axis represents the control output value for the driver amplifier.

As described above, when the feedback gain is increased, the feedback control width (amplitude width of the control output value) increases, and at this time, hunting may occur in the electromagnetic control valve having a slow response. Therefore, in the present embodiment, a predetermined addition value limit width Sr is provided for the output value for feedback control (feedback addition value), and the maximum value of the feedback addition value is regulated to prevent hunting when the feedback gain is increased. I try to prevent it from happening.

In FIG. 4, hatching indicates that
The feedback addition value limited by the present embodiment, and the dotted line shows the feedback output value that would cause hunting, which is assumed when the addition value limit width Sr is not provided. Although the size of the additional value limit width Sr is arbitrary, it is preferably about ± several% to ± 10% of the open output value (setting value).

By the way, at the end of the primary injection stroke in which the velocity feedback control is performed, the resin in the mold approaches the completion of filling, and the reaction pressure from the resin in the mold increases the load pressure. When approaching the pressure setting value of the open control, the speed loses the load pressure, and the speed feedback control becomes impossible. Alternatively, if the pressure-holding process for pressure feedback control is entered in a state where resin filling into the mold is not completely completed (unfilled or insufficiently filled), the predetermined load pressure does not rise, so pressure feedback It becomes impossible to control.

Therefore, in this embodiment, when the actual pressure value Pm exceeds a predetermined value within the speed feedback control period,
The speed control is switched to the control for only the open control, and when the measured speed value Vm exceeds the predetermined value within the pressure feedback control period, the pressure control is switched to the control for only the open control.

FIG. 5 is a state transition diagram showing the above switching operation. In FIG. 5, (a) shows the speed feedback control period (primary injection region), and (b) shows the pressure feedback control period. (Holding area) is shown.

During the feedback control operation of the speed, during the feedback control operation, the monitoring control unit (not shown) monitors the actual pressure measurement value Pm.
If the “+ allowable pressure value Pc” exceeds the pressure setting value Po, it is determined that the feedback control is not possible, and a calculation control command is output to the PID calculation unit 4 to stop the PID calculation, and the PID calculation is stopped. , Switch to speed open control based on only the above-mentioned open output value. As a result, the pressure measurement value Pm is reduced as the speed is reduced by the open control and the speed is lost. Then, when the “actual speed measurement value Vm + allowable speed value Vc” exceeds the speed setting value Vo, the monitoring control unit determines that it is within the feedback controllable range, and issues a calculation control command to restart the PID calculation. To start the PID calculation,
The speed feedback control is restarted.

On the other hand, during the feedback control period of the pressure, during the feedback control operation, the monitoring control unit (not shown) monitors the measured speed value Vm, and the measured speed value Vm + the allowable speed value Vc is the speed setting. If the value Vo is exceeded,
It is determined that the feedback control is out of range, and the PID
A PID calculation unit 24 sends a calculation control command to stop the calculation.
To stop the PID calculation and switch to the pressure open control based on only the above-mentioned open output value. As a result, the speed is reduced in accordance with the decrease in pressure due to the open control. Then, "the measured pressure value Pm
If the “+ allowable pressure value Pc” exceeds the pressure setting value Po, the monitoring control unit determines that the feedback control is possible and enters the calculation control command to start the PID calculation.
It outputs to the calculating part 24, starts PID calculation, and starts pressure feedback control.

The allowable speed value Vc and the allowable pressure value Pc can be set to arbitrary constant values. However, in the present embodiment, for example, they are set to about 1/2 of the steady state range Su. There is.

FIG. 6 is a diagram showing an example of speed set values, speed measured values, pressure set values, and pressure measured values in the primary injection area and the pressure holding area when the above feedback control and open control are switched. Is. In the example shown in the figure, 1
There is a speed feedback uncontrollable period before the end of the next injection, and there is a pressure feedback uncontrollable period at the beginning of the holding pressure.

[0048]

As described above, according to the present invention, it is possible to perform feedback control even when an inexpensive electromagnetic control valve having a slow response is used, and it is possible to reduce the machine cost. In addition, the electromagnetic control valve of the conventional machine with only open control,
The machine can be modified into a machine that can perform feedback control without replacing with an expensive servo electromagnetic control valve or a high-speed proportional electromagnetic control valve with good response. Further, it is possible to realize feedback control excellent in safety without fear of damage to the mechanism, and further to realize feedback control which does not cause hunting at the time of starting the feedback control.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an injection speed feedback control system of an injection molding machine according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of an injection pressure feedback control system of an injection molding machine according to an embodiment of the present invention.

FIG. 3 is an explanatory diagram showing a state at the time of start-up of speed or pressure feedback control according to an embodiment of the present invention.

FIG. 4 is an explanatory diagram showing a limit width of a feedback addition value according to an embodiment of the present invention.

FIG. 5 is a state transition diagram showing switching between feedback control and open control according to one embodiment of the present invention.

FIG. 6 shows a speed setting value, a speed actual measurement value, a pressure setting value in a primary injection area and a pressure holding area according to an embodiment of the present invention.
It is explanatory drawing which shows an example of a pressure measurement value.

[Explanation of symbols]

1,21 Input section 2,22 Open output value calculator 3,23 Comparator 4,24 PID calculator 5,25 Addition output value calculator 6,26 adder 7,27 D / A converter 8,28 driver amplifier 9 Speed control solenoid valve 10 injection cylinder 11 Stroke sensor 12 Speed calculator 29 Solenoid valve for pressure control 31 Pressure sensor 32 Pressure calculator

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-63-34302 (JP, A) JP-A-59-9704 (JP, A) JP-A-6-168004 (JP, A) JP-A-1- 238919 (JP, A) JP-A 2-102902 (JP, A) JP-A 58-602 (JP, A) JP-A 4-141408 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B29C 45/76-45/82 B22D 17/32 G05B 11 / 32,11 / 42

Claims (3)

(57) [Claims] 1. A molding machine comprising a speed (flow rate) controlling solenoid valve for driving and controlling a hydraulic drive source and a pressure controlling solenoid valve, wherein the speed and the pressure are feedback-controlled, and for a preset open control. And an output value for feedback control obtained by PID calculation, and means for driving and controlling the driver circuit of the speed control solenoid valve or the driver circuit of the pressure control solenoid valve according to the addition result. Is provided , and the measured pressure value is
If the specified value is exceeded, speed control will be open control only
To the pressure feedback control period,
When the measured speed value exceeds the specified value, pressure control is opened.
A molding machine characterized by switching to control of control only . 2. The PID calculation according to claim 1, wherein when the speed or the pressure is raised to a set value, the speed measured value or the pressure measured value reaches a predetermined region close to the set value. A molding machine characterized by replacing the integral value obtained by (5) with an appropriate value obtained by clearing or learning in advance. 3. The molding machine according to claim 1, wherein the output value for the feedback control is provided with a predetermined limit width.