JP4809500B1 - Control method of injection molding machine - Google Patents

Abstract

An injection molding machine control method capable of optimizing falling pressure response and rising pressure response characteristics in a pressure holding process, and in particular, pressure falling response characteristics immediately after the pressure holding process can be optimized. Provided is a method for controlling an injection molding machine.
A high response interval and a low response interval are divided in time series from the time when the pressure holding process starts or the time when the holding pressure is switched to the time when the holding pressure is changed to the next holding pressure. At least in some sections, for response characteristics set by the operator, the response time is set to zero, the response time is set to zero, the response time is decreased to a value other than zero, and the servo mechanism spool opening At least one of the three kinds of opening restriction command value expansion settings for expanding the opening restriction is set.

[Selection] Figure 5

Description

  The present invention relates to a control method for an injection molding machine, and relates to a control method capable of optimizing response characteristics of falling and rising of a holding pressure in a pressure holding process. In particular, the present invention relates to a control method capable of optimizing the response characteristic of the pressure fall immediately after the start of the pressure holding process.

Generally, an injection molding machine has at least a mold clamping device and an injection device, and the mold clamping device opens and closes and clamps the resin material plasticized and measured by the injection device. Filled by injecting.
Among them, the injection device is greatly divided into an in-line screw type injection device that performs both plasticization and injection filling with a single in-line screw, and a screw pre-plastic type injection device that performs plasticization with a plasticizing screw and injection filling with an injection plunger. Separated.
In the present specification, the in-line screw and the injection plunger are collectively referred to as “injection shaft”.
In recent years, it is desired to perform injection filling with high speed and high response in thin wall molding or precision molding. For this reason, for example, in an injection device that drives an injection shaft with a hydraulic piston / cylinder unit, an accumulator is provided in addition to a hydraulic pump as a hydraulic source, and the hydraulic oil accumulated in the accumulator at a high pressure and in a large amount is moved all at once. In addition to driving the injection shaft at high speed, a servo valve is arranged between the accumulator and the piston / cylinder unit, and the hydraulic oil to the piston / cylinder unit is controlled by controlling the drive of the servo valve. The injection axis is driven with high response and high precision by adjusting the supply amount and the supply direction.

In a general injection device, an injection process for injecting and filling a resin material into a cavity of a mold apparatus includes a filling process and a pressure-holding process. Usually, in a filling process in which the filling speed is controlled with priority. After filling molten resin material (molten resin) into the mold cavity, the heat shrinkage accompanying cooling of the molten resin filled in the cavity is compensated for in the pressure holding process where pressure is controlled with priority. Therefore, it is controlled to further fill the molten resin as much as necessary. Further, in the pressure holding step, pressure is applied to the molten resin in the cavity until the molten resin in the gate portion of the cavity is solidified. In addition, the pressure holding step also has an effect of degassing when bubbles enter the filled molten resin.
The switching between the filling process and the pressure holding process is called “VP switching”.
After completion of the injection process, the molten resin is solidified in the cooling process, and then the mold apparatus is opened to take out the solidified molded product.

In the filling process, feedback control is performed so that the injection speed matches the set value, and in the pressure holding process, feedback control is performed so that the pressure matches the set value. Prevents mold release defects and sink marks.
Also, the actual pressure value (detected pressure value) in the cavity detected at the time of VP switching is often considerably higher than the set value (set pressure value) at the start of the pressure holding process. If there is a large deviation from the set pressure value, there will be a time difference (time lag) from the start of the pressure holding process to the time when both coincide due to the characteristics of feedback control or the performance of the drive unit and control unit of the injection device. Occurs, which has a problem of adversely affecting the quality of the molded product.
In other words, in order to ensure the quality of the molded product, it is known that the so-called falling response characteristic until the detected pressure value is reduced to the set pressure value immediately after the start of the pressure holding process is important. .

For example, Patent Document 1 discloses an initial period in which the injection pressure is controlled in an open loop until the injection speed reaches a predetermined target value after passing through the switching point from the filling process to the pressure holding process, and the injection speed reaches the target value. A pressure holding process control method is disclosed in which a target value of the injection pressure corresponding to is set, and an intermediate section in which the injection pressure is controlled in a closed loop and an end section in which the closed pressure is controlled so that the injection pressure becomes a set target value are disclosed. .
According to this method, in the initial section where a large deviation occurs between the detected pressure value and the set pressure value, open loop control is performed without performing closed loop control (feedback control) to suppress the occurrence of time lag, and the deviation is small. The detected pressure value can be quickly brought close to the set pressure value by returning to the closed loop control in the intermediate section.
Further, for example, in Patent Document 2, overshoot and undershoot immediately after the start of the pressure holding process are prevented, and the operation amount of the feedback control is set at the end of the filling process in order to quickly bring the detected pressure value close to the set pressure value. There is disclosed a control method for driving a servo valve with an operation amount obtained by adding a feedforward operation amount obtained by comparing and calculating a detected pressure value and a set pressure value.

Japanese Patent Laid-Open No. 9-277329 JP-A-11-77775

However, the above prior art has the following problems.
In other words, as the shape of molded parts has become more complex in recent years and the servo mechanism has become faster and more responsive, the response characteristics of the pressure drop immediately after the start of the pressure holding process as described above can be included as part of the molding conditions. There is a growing demand for optimization. The same can be said for the response characteristics of the rise and fall that occur each time the holding pressure is switched. In some cases, the same applies to the response characteristics of the pressure rise immediately after the start of the pressure holding process. I can say.
However, in the technique of Patent Document 1, open loop control is performed in the initial interval t1, and the control is returned to the closed loop control again in the next intermediate interval t2, and finally the detected pressure value coincides with the set pressure value PH1 in the final interval t3. That is, since it takes time t1 + t2 until the detected pressure value reaches the set pressure value PH1, there is a problem that the features of the servo mechanism with high speed and high response cannot be fully utilized.
Further, the technique of Patent Document 2 can only prevent overshoot and undershoot immediately after the start of the pressure holding process, and does not realize optimization of response characteristics of falling and rising.

  In view of such problems, the present invention provides a method for controlling an injection molding machine that can optimize the response characteristics of the holding pressure falling and rising in the pressure holding process, and in particular, the pressure falling immediately after the start of the pressure holding process. An object of the present invention is to provide an injection molding machine control method capable of optimizing the response characteristics of the injection molding machine.

  The present invention provides a pressure holding process for an injection molding machine in which a resin material is injected and filled into a cavity of a mold while controlling the drive of an injection shaft via a servo mechanism by feedback control. Specify at least the response time as a parameter of the response characteristic at the fall or rise that occurs each time the magnitude is switched, and from the time when the pressure holding process starts or when the magnitude of the holding pressure is changed to the next holding pressure. The time interval is divided into a high response interval and a low response interval, and in at least some of the high response intervals, the response time is set to zero for the response characteristics set by the operator, and the response Response time reduction setting to reduce the time to a value other than zero, and opening limit command value to increase the opening limit of the spool opening of the servo mechanism And performing three at least one of the settings of the large set.

In addition, the high response interval is divided into a first high response interval and a second high response interval in time series. In the first high response interval, the response time zero setting and the opening restriction command value expansion setting are performed, and the second high response interval is set. Then, the response time reduction setting is performed.
Further, the high response interval is divided into a first high response interval and a second high response interval in time series, and in the first high response interval, the response time zero setting and the opening restriction command value expansion setting are performed, and the second high response interval is set. The feature is that the opening limit command value is expanded.
Further, the high response interval is divided into a first high response interval and a second high response interval in time series, and in the first high response interval, the response time zero setting and the opening restriction command value expansion setting are performed, and the second high response interval is set. Then, the response time decrease setting and the opening limit command value expansion setting are performed.

The present invention provides a high response to a section in which a follow-up delay with respect to a target value occurs under feedback control from the time when the pressure holding process starts or when the magnitude of the holding pressure is changed to the time when the holding pressure is changed to the next holding pressure. Sections and sections where no tracking delay occurs are divided into low response sections. And, by adopting a control method suitable for each section, it is possible to arbitrarily optimize the response characteristics immediately after the start of the pressure holding process and immediately after the holding pressure is switched regardless of the response time. Can be obtained.
In particular, by dividing the high response section into the first and second high response sections and adopting a control method suitable for each section, the response immediately after the start of the pressure holding process and immediately after the holding pressure is switched. The characteristics can be optimized more precisely.

The control method suitable for each section corresponds to zero response time setting and opening limit command value expansion setting for the first high response section. By changing the response time to zero seconds by setting the response time to zero, and performing feedback control, delays in response time due to the performance of the feedback control characteristics and the drive mechanism of the injection molding machine, etc. are minimized. Can do. In addition, the spool opening is made larger than the preset maximum value (opening restriction command value) by the opening restriction command value expansion setting, so that the pressure is lowered more rapidly than in normal control. Or it can be launched.
For the second high response interval, it is suitable to perform at least one of a response time decrease setting and an opening limit command value expansion setting. By slightly lowering the response time from the value set by the operator by the response time reduction setting, it is possible to eliminate the response time delay caused by the performance of the feedback control characteristics and the drive mechanism of the injection molding machine. In addition, by setting the opening limit command value expansion setting so that the spool opening is larger than the preset maximum value, the pressure can be lowered or raised more rapidly than in normal control. Thus, the response time delay described above can be eliminated.

It is the schematic which shows the apparatus structure of an injection molding machine. It is drawing for demonstrating the setting operation | work of the molding conditions of a pressure-holding process. It is drawing which shows the pattern of a response characteristic. It is drawing for demonstrating the setting operation | work of the molding conditions of a pressure-holding process. It is drawing for demonstrating a 1st high response area, a 2nd high response area, and a low response area. It is drawing which shows the spool opening degree in a high response area and a low response area. It is drawing for demonstrating the effect of an opening degree limit command value expansion setting. It is drawing which shows the other example of the spool opening degree in a 1st high response area. It is a figure for demonstrating a response time reduction setting. It is drawing which shows the example of the spool opening degree in a 2nd high response area. It is drawing which shows the other example of the spool opening degree in a 2nd high response area.

[First embodiment]
A first embodiment of a control method for an injection molding machine according to the present invention will be described.
First, the configuration of the injection molding machine will be described, but since the configuration is the same as that of a general injection molding machine including a servo mechanism, a detailed description is omitted.
As shown in FIG. 1, the injection molding machine 10 includes a piston / cylinder unit 20, a hydraulic drive mechanism 30, a controller 40, and the like.
The hydraulic drive mechanism 30 includes four ports A, B, P, and T, and includes a four-port servo valve 31, a hydraulic drive source 32, and an oil tank 33 that function as a part of the servo mechanism.
The hydraulic drive source 32 allows only the flow in the discharge direction connected to the discharge side of the hydraulic pump 34, the filter 36 connected to the suction side of the hydraulic pump 34, the pump motor 35 that drives the hydraulic pump 34, and the hydraulic pump 34. A stop valve 37 and an accumulator 38 connected to the discharge side of the check valve 37 are provided.

The 4-port servo valve 31 has an A port connected to the rear oil chamber 22 (piston head side oil chamber) of the injection hydraulic cylinder 21, a B port connected to the front oil chamber 23 (piston rod side oil chamber), and the P port It is connected to the accumulator 38 and the T port is connected to the oil tank 33.
Although not shown, the 4-port servo valve 31 is formed with A, B, P, and T ports in a cylindrical sleeve, and accommodates a spool that is displaced in the axial direction therein.
The controller 40 controls various controls of the injection molding machine 10, and the output side is connected to the command signal input unit 39 of the 4-port servo valve 31. Further, a pressure sensor 50 for detecting the pressure in the rear oil chamber 22 is connected to the rear oil chamber 22 of the cylinder, and this pressure sensor 50 is connected to the input side of the controller 40. Further, a position sensor 60 for detecting the position of the injection shaft 24 is connected to the input side of the controller 40.
Then, based on the molding conditions set by the operator, a command signal (control signal) is output from the controller 40 to the command signal input unit 39, and the injection shaft 24 is driven via the 4-port servo valve 31, that is, in the spool sleeve. Is adjusted by feedback control, and the molten resin 70 is injected and filled into the cavity 81 of the mold 80.

Next, a control method of the injection molding machine 10 will be described.
In the present embodiment, the injection process of the injection molding machine 10 includes a filling process and a pressure holding process, and the driving of the injection shaft 24 is controlled via the servo mechanism by the feedback control described above in each process.
In the filling process, the position of the injection shaft 24 and the filling speed are controlled, and in the pressure holding process that continues across the VP switching position (hereinafter also referred to as “VP switching”), the pressure holding time and the holding pressure are controlled. The VP switching can also be switched by various methods such as a method of switching when the time from the start of filling reaches a set time, and a method of switching when the injection pressure during filling reaches a predetermined pressure.

Referring to FIG. 2, the setting operation of the molding conditions of the pressure holding process by the operator will be described with reference to FIG. 2. The worker has one or more sections from the time of VP switching to the end of pressure holding (in this embodiment, three sections A to A). C).
In the sections A to C, the holding pressure times are set to T1 to T3, respectively, and by setting the holding pressure values P1 to P3 for each section, the molding conditions are set in a three-step shape.
Next, the operator sets response characteristics at the time when the holding pressure changes, that is, the time Y0 when the holding pressure changes from P0 to P1, the time Y1 when the holding pressure changes from P1 to P2, and the time Y2 when the holding pressure changes from P2 to P3.

As a response characteristic parameter, at least the response time is defined in the pressure holding process.
Here, in many cases, since the detected pressure value P0 in the injection hydraulic cylinder 21 at the VP switching position is higher than the set pressure value at the start of the pressure holding process, that is, the holding pressure value P1 in the section A, the pressure holding process starts. The response characteristic immediately after the detection pressure value is decreased to the holding pressure value P1 has a falling shape.
As the response characteristics of the fall immediately after the start of the pressure holding process, various patterns are assumed from those that suddenly fall immediately after the start to those that fall gently as shown in FIG.
The operator sets not only the section A but also the sections A to C in consideration of the shape of the molded product and the like, and sets at least a response time as a parameter to obtain optimum response characteristics. The setting operation of molding conditions as shown is completed. Note that it is not always necessary to set response characteristics for all sections. The response characteristics may be controlled according to a waveform pattern set by a function or the like.

FIG. 5 is an enlarged view of only the section A starting immediately after the start of the pressure-holding process. In this embodiment, the first section A of the pressure-holding process is time-series from the pressure-holding process start time (VP switching time). Are divided into a high response section and a low response section, and the high response section is further divided into a first high response section and a second high response section in time series from the start of the pressure holding process.
The low response section is a section in which when the feedback control is performed with the molding conditions set by the operator, the actual response time matches the response time set and no response time delay (follow-up delay) occurs.

The high response interval is an interval in which a delay in response time occurs when feedback control is performed with the molding conditions set by the operator.
Such a delay in response time may be caused by a characteristic of feedback control itself in which a control operation and a target value are compared and a correction operation is performed so as to match them, or a drive mechanism (hydraulic drive mechanism) constituting the injection molding machine 10. 30), a drive circuit, various sensors (pressure sensor 50, position sensor 60, etc.), controller 40, and the like.
That is, for example, when the pressure in the injection hydraulic cylinder 21 is gradually lowered immediately after the pressure holding process is started (corresponding to the response characteristic L1 in FIG. 5 in the case of low response), the feedback control functions perfectly, so that Although there is no delay in the response time, the response time is delayed due to the above reason when it suddenly falls (corresponding to response characteristics L2 and L3 in the case of high response).
These sections are set in advance according to the performance of the drive mechanism, drive circuit, various sensors (pressure sensor 50, position sensor 60, etc.), controller 40, etc. that constitute the injection molding machine 10, and the molding conditions are determined. There is no need to set it every time. Of course, the first high response is determined based on the presence or absence of the response time delay, the degree of delay, etc. by determining whether the response time is delayed or not while actually performing the injection filling operation under the molding conditions set by the operator. A section, a second high response section, and a low response section may be set.

Next, the first high response interval will be described.
For example, the first high response section is a section corresponding to a case where the pressure value in the injection hydraulic cylinder 21 is suddenly lowered in a short time immediately after the start of the pressure holding process.
In this first high response section, after the operator sets the response characteristics (at least response time), the controller 40 determines that the response time is set to zero, and the servo mechanism spool opening degree is opened by the controller 40. The opening limit command value expansion setting for increasing the degree limit is performed.
The zero response time setting is performed when the operator sets the response characteristics and the controller 40 recognizes that the response time is within the first high response interval. This means that the set response time (for example, 0.08 seconds) is changed to zero seconds, and this is output as a command signal.

In this way, when feedback control is performed with the response time changed to zero seconds, the response time delay due to the characteristics of the feedback control and the performance of the drive mechanism as described above is minimized. However, there is still a slight response time delay.
However, this slight delay in response time is caused by feedback control, so the reproducibility is high and becomes a substantially constant value every time.

Therefore, the opening limit command value expansion setting is performed together with the response time zero setting. Hereinafter, the opening limit command value expansion setting will be described.
As described above, the pressure in the injection hydraulic cylinder 21 is controlled by adjusting the position of the spool with respect to each port of the 4-port servo valve 31 and adjusting the supply amount and supply direction of the hydraulic oil to the injection hydraulic cylinder 21. Is called.
That is, for example, when the pressure is lowered immediately after the pressure holding process is started, the A port connected to the rear oil chamber 22 and the T port connected to the oil tank 33 are connected to each other in the rear oil chamber 22. It is necessary to return the hydraulic oil to the oil tank 33.

In a normal injection molding machine, the maximum value of the spool opening, that is, the maximum flow rate per unit time of hydraulic oil is set as a constant value throughout the injection process, and the spool position is within a range not exceeding this maximum value. Is adjusted appropriately to control the pressure in the injection hydraulic cylinder 21. Also in the present embodiment, the pressure control is performed within the preset maximum range of the spool opening in the low response section.
However, the opening limit command value expansion setting is characterized in that the spool opening is set larger than a preset maximum value. The maximum value also has an absolute limit value due to the mechanical specifications of the 4-port servo valve 31, and is set within a range of values that do not exceed the absolute limit value. That is, if the vicinity of the absolute limit value is set to the maximum value of the spool opening, the response time delay is further eliminated.

Here, FIG. 6 shows the spool opening in the high response interval and the low response interval.
The spool opening degree is controlled so as to be directly proportional to the voltage value output as a command signal from the controller 40 to the 4-port servo valve 31. Depending on the configuration of the injection molding machine 10, the spool opening may be controlled to be directly proportional to the current value, not the voltage value.
Here, when the spool is in the neutral position with the voltage value of zero, that is, when all the ports are shut off, the A port and the T port are connected to lower the pressure in the injection hydraulic cylinder 21 immediately after the pressure holding process starts. When the hydraulic oil in the rear oil chamber 22 is returned to the oil tank 33, for example, the voltage value becomes a negative value, and the larger the difference from the voltage value at the neutral position, the larger the spool opening degree. Will grow.
Therefore, in this case, as the voltage value is increased in the negative direction, the spool opening degree is increased, and the hydraulic oil can be discharged from the injection hydraulic cylinder 21 at a high speed.
Incidentally, in the present embodiment, when the A port and the P port are connected to raise the pressure in the injection hydraulic cylinder 21 by the above-described 4-port servo valve 31, the hydraulic oil is supplied from the accumulator 38 to the rear oil chamber 22. In this case, the voltage value is a positive value, and if the difference from the voltage value at the neutral position is increased, the spool opening is increased, and the supply can be performed at a higher speed. The neutral position of the spool is not necessarily the voltage value zero as in the present embodiment, and may be on either the positive or negative side of the voltage value. Further, the moving direction of the spool with respect to the positive or negative voltage value may be opposite to that of the present embodiment.

Here, in the present specification, the voltage value is referred to as a “command value”. Therefore, the “opening restriction command value” is a voltage value (−1.5V in FIG. 6) corresponding to the maximum value of each spool opening when the preset A port is connected to the P port and the T port, respectively. ). Then, by “decreasing the opening limit command value”, the voltage value increases in the negative direction (−3.0 V in FIG. 6). Therefore, the discharge speed of the hydraulic oil from the injection hydraulic cylinder 21 is increased, It becomes possible to rapidly reduce the pressure in the injection hydraulic cylinder 21.
In other words, by setting the opening limit command value expansion setting, the pressure is lowered (or raised) more rapidly than in normal control by making the spool opening larger than the preset maximum value. Is possible.

Next, the effect of the opening limit command value expansion setting will be described using a graph.
FIG. 7 shows an example of falling, where the vertical axis is the command value and the horizontal axis is time.
FIG. 7A shows a case where the spool is controlled within a range not exceeding a preset maximum value of the spool opening as in the prior art. A symbol M indicates an opening restriction command value (voltage value) corresponding to a preset maximum value of the spool opening.
For example, in the first high response section, it is necessary to rapidly lower the pressure, but in the conventional control method, the horizontal portion H of the graph is not used to prevent the spool opening from becoming larger than the maximum value (opening restriction command value M). In this state, the pressure drop speed is limited. Then, as the actual pressure value in the injection hydraulic cylinder 21 approaches the holding pressure value set in the section after a predetermined time has elapsed, the command value is gradually increased to reduce the flow rate so as to avoid overshoot. In this manner, the spool drive is stopped when it finally matches the holding pressure value.
On the other hand, in FIG. 7B, the spool is opened beyond the preset maximum value of the spool opening (opening restriction command value M), that is, in the case of the present embodiment, the opening restriction command value is encoded. By further reducing the value from M, the pressure can be rapidly lowered, and the time until the pressure in the injection hydraulic cylinder 21 matches the holding pressure value can be shortened.
Note that, as in the embodiment of FIG. 6, the response characteristic (at least the response time) set by the operator corresponds to the first high response interval, and is constant regardless of the set response characteristic, as determined by the controller 40. When the opening degree limit command value is changed together with the response time zero setting described above, even if the operator changes the response characteristic setting in the first high response interval, The actual response characteristic is constant. Therefore, as shown in FIG. 8, in the first high response section, the opening degree restriction command value is set and changed in the direction of increasing the spool opening degree as the response time is set in the shorter direction. Also good. Then, it is possible to change the actual response characteristic according to the operator changing the response characteristic setting even with the opening limit command value expansion setting. In addition, although not shown in the drawing, it is changed according to the opening restriction command value that is a constant value regardless of the response time set by the worker and the response time set by the worker in the first high response section. The opening limit command value may be combined.

Next, the second high response interval will be described.
As shown in FIG. 5, the second high response section is a section sandwiched between the first high response section and the low response section, and it is not necessary to decrease the pressure as rapidly as the first high response section. If this is done, the response time is delayed.
In the second high response section, after the operator sets the response characteristics (at least response time), the response time is set to decrease to a value other than zero according to the determination of the controller 40.
The response time decrease setting is performed when the controller 40 recognizes that the response time is within the second high response interval when the operator sets the response characteristics. As shown, it means that the response time (for example, 0.15 seconds) set by the operator is lowered to a value other than zero (for example, 0.10 seconds) and output as a command signal.
Note that the response time after the response time decrease setting may exceed the time range initially set for the section in which the response time decrease setting is performed. For example, as shown in FIG. 9, the operator sets the first high response interval from 0.10 seconds to 0.10 seconds from the start of the pressure holding process, and the second high response interval from 0.10 seconds to 0.20 seconds. However, when the response time of the fall immediately after the start of the pressure-holding process is set to 0.12 seconds, the response time after the response time reduction setting by the controller 40 is 0.04 seconds, the range initially set in the second high response interval ( The value may be less than 0.10 to 0.20 seconds.

  When feedback control is performed in the second high response section, the response time is delayed due to the characteristics of the feedback control and the performance of the drive mechanism, etc., as described above. By slightly lowering the value, the response time delay can be eliminated, and the actual response characteristic can be brought closer to the ideal response characteristic set by the operator.

[Second Embodiment]
A second embodiment of the control method of the injection molding machine of the present invention will be described.
In addition, the description is abbreviate | omitted about the location which becomes the same structure as the said 1st Embodiment, and it demonstrates below centering on the characteristic part of this Embodiment.
The present embodiment is characterized in that in the second high response section, the opening restriction command value expansion setting similar to that shown in the first high response section in the first embodiment is performed.
That is, after the operator sets the response characteristics (at least response time), the controller 40 determines that the opening limit command value for the spool opening of the servo mechanism is lowered, thereby setting the maximum spool opening that is set in advance. Control is performed to open the spool beyond the value.

As shown in FIG. 10, in the second high response section, the opening restriction command value gradually increases continuously from the end time of the first high response section, and at the end time of the second high response section, the low response section. Is set so as to coincide with the opening limit command value (-1.5 V) corresponding to the preset maximum value of the spool opening.
As shown in FIG. 11, the second high response interval is larger than the opening limit command value (−3.0 V) in the first high response interval and corresponds to a preset maximum value of the spool opening. It is good also as a fixed value (for example, -2.5V) in the range smaller than the opening degree restriction | limiting command value (-1.5V) to perform. Further, the present invention is not limited to FIGS. 10 and 11, and the opening degree limit command values of the first high response section and the second high response section are set so that one gradually increases continuously in the section, and the other. May be set to a constant value throughout the section. Further, in the same section, the opening degree limit command value may be combined with a setting that gradually increases gradually and a setting that is a constant value.
According to the invention shown in the present embodiment, the pressure can be rapidly lowered in the second high response section, and the above-described delay in response time can be eliminated.

[Third Embodiment]
A third embodiment of the control method of the injection molding machine of the present invention will be described.
In addition, the description is abbreviate | omitted about the location which becomes the same structure as the said 1st and 2nd embodiment, and it demonstrates below centering on the characteristic part of this Embodiment.
In this second embodiment, in the second high response section, the response time reduction setting similar to that shown in the first embodiment and the opening restriction similar to that shown in the second embodiment are used. The command value enlargement setting is performed.

That is, when the operator sets the response characteristics and the controller 40 recognizes that the response time is within the second high response interval, the response time set by the operator (for example, 0.15 seconds). Is reduced to a value other than zero (for example, 0.10 seconds) and output as a command signal, and control is performed to lower the opening degree limit command value of the spool opening of the servo mechanism.
According to the invention shown in the present embodiment, it is possible to rapidly decrease the pressure by performing the opening restriction command value expansion setting in the second high response section, and the response time can be reduced by the response time decrease setting. Since the delay can be eliminated, the actual response characteristic can be brought close to the ideal response characteristic set by the operator.
In response time reduction setting and opening limit command value expansion setting, response time change and opening limit command value change considering response time delay with respect to the response time set by the operator in advance It is also possible to use what has been previously stored in the controller 40 or the like in the form of a function or a data table in the form of a function or a data table, etc. after the change obtained by experiment for each response time. Further, as described above, the controller 40 may automatically change the response characteristic set by the operator to the response time and the opening limit command value considering the delay of the response time. The user himself / herself may directly set the response time and the opening limit command value changed so as to obtain an ideal response characteristic in consideration of the delay of the response time.
In each of the above embodiments, the high response interval is divided into a first high response interval and a second high response interval. In the first high response interval, response time zero setting and opening limit command value expansion setting are performed. 2 At least one of the response time decrease setting and the opening limit command value expansion setting is performed in the high response interval, but not limited to this, the response time zero setting and response time decrease in at least a part of the high response interval The effect of the present invention can be achieved by performing at least one of the setting and the opening limit command value expansion setting.
Further, in each of the above embodiments, the present invention is applied to the response characteristic at the fall immediately after the start of the pressure holding process. However, the present invention is not limited to this, and at the fall immediately after the holding pressure is switched. The present invention can be applied. Similarly, in the rising response characteristics, the spool moving direction of the 4-port servo valve 31 is only opposite, and the present invention can be applied.
As the servo valve drive system, a linear servo system capable of high-speed response is most suitable. However, a hydraulic system or a pneumatic system may be used, and the servo valve 4 described in the above embodiment may be used. In addition to the port type servo valve, a known servo valve such as a 2-port, 3-port or 5-port type can be used.

  The present invention relates to a method for controlling an injection molding machine that can optimize the response characteristics of the falling and rising of the holding pressure in the pressure holding process, and has industrial applicability.

DESCRIPTION OF SYMBOLS 10 Injection molding machine 20 Piston / cylinder unit 21 Injection hydraulic cylinder 22 Rear oil chamber 23 Front oil chamber 24 Injection shaft 30 Hydraulic drive mechanism 31 4-port servo valve 32 Hydraulic drive source 33 Oil tank 34 Hydraulic pump 35 Pump motor 36 Filter 37 Reverse Stop valve 38 Accumulator 39 Command signal input unit 40 Controller 50 Pressure sensor 60 Position sensor 70 Molten resin 80 Mold 81 Cavity

Claims (4)

In the pressure-holding process of the injection molding machine that injects and fills the resin material into the mold cavity while controlling the drive of the injection shaft via the servo mechanism by feedback control,
Specify at least the response time as a parameter of the response characteristic at the fall or rise immediately after the start of the pressure holding process or whenever the holding pressure is switched,
The time from the start of the pressure holding step or the time when the magnitude of the holding pressure is switched to the time when the holding pressure is switched to the next holding pressure is divided into a high response interval and a low response interval in time series,
In at least a part of the high response interval, for the response characteristic set by an operator, a response time zero setting for setting the response time to zero and a response time decrease setting for reducing the response time to a value other than zero are set. And at least one of three types of opening limit command value expansion settings for increasing the opening limit of the spool opening of the servo mechanism. The high response interval is divided into a first high response interval and a second high response interval in time series,
In the first high response section, the response time zero setting and the opening restriction command value expansion setting,
The method for controlling an injection molding machine according to claim 1, wherein the response time reduction setting is performed in the second high response interval. Dividing the high response interval into a first high response interval and a second high response interval in time series;
In the first high response section, the response time zero setting and the opening restriction command value expansion setting,
The method of controlling an injection molding machine according to claim 1, wherein the opening restriction command value expansion setting is performed in the second high response interval. Dividing the high response interval into a first high response interval and a second high response interval in time series;
In the first high response section, the response time zero setting and the opening restriction command value expansion setting,
2. The method of controlling an injection molding machine according to claim 1, wherein the response time decrease setting and the opening restriction command value expansion setting are performed in the second high response interval.

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