JPH05237901A - Injection control method for injection molding machine - Google Patents

Abstract

PURPOSE:To provide the injection control method for an injection molding machine of improving the quality of a molded product and achieve high energy- saving effect. CONSTITUTION:The reference injection pressure of an injection cylinder 10 for manufacturing a given molded product is measured preliminarily, and the injection pressure is set in a reference injection pressure setting section 54 of a control device 40. Also the discharge pressure of variable discharge amount found preliminarily corresponding to the reference injection pressure of a variable discharge amount pump 22 is set in a reference discharge pressure setting section 48. The injection pressure of the injection cylinder 10 at the time of injection is sensed by an injection pressure sensor 30, and the discharge pressure of the variable discharge amount pump 22 is controlled correspondingly to the difference between the sensed injection pressure and the reference injection pressure.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of controlling an injection process of filling a mold with a material to be molded in an injection molding machine.

[0002]

2. Description of the Related Art In an injection molding machine, when controlling the injection of a material to be molded by an injection cylinder, a hydraulic servo valve is provided in a pipeline for supplying hydraulic oil to the injection cylinder, and
It is widely used to perform feedback control for detecting an injection position (stroke amount) of an injection cylinder and controlling a hydraulic servo valve.

That is, the injection speed of the injection cylinder is generally set in multiple stages as indicated by VS in FIG. 6 (A). Further, the set discharge amount Q0 of the pump is the set injection speed V
The amount of oil supplied to the injection cylinder corresponding to the maximum value of S is set to a constant value with a margin of ΔQ, and the hydraulic servo valve is controlled to change the amount of oil supplied to the injection cylinder. The injection speed of the cylinder is controlled to reach the set value. At this time, the actual injection speed VV of the injection cylinder changes as shown in FIG.

The injection control using this hydraulic servo valve is
The throttle effect of the hydraulic servo valve is used to adjust the flow rate of the hydraulic oil supplied from the constant pressure supply source to the actuator (injection cylinder), and the response is fast and excellent control accuracy and operating characteristics can be obtained.

Further, in the injection molding machine, the energy saving effect is conventionally achieved by using a variable discharge amount pump capable of obtaining a discharge amount as required. The responsiveness of the variable discharge amount pump is improved to improve the pump performance. Feedback control has also been attempted in which the discharge amount is changed according to the position of the injection cylinder.

[0006]

However, while the hydraulic servo valve has excellent control characteristics, the flow rate is controlled by the throttling effect, so that the flow path resistance is large and power loss occurs. On the other hand, the variable discharge pump does not require useless pump energy in order to discharge the oil amount according to the hydraulic load, but on the other hand, the response time is 5 to 10 times as long as that of the hydraulic servo valve, resulting in high response and control accuracy. There is a problem in terms.

For this reason, in order to obtain an injection molding machine having excellent responsiveness and control accuracy and having a high energy saving effect, if a hydraulic servo valve and a variable discharge pump are simply combined, an injection molding machine The control performance is restricted by the response time of the variable discharge pump, the excellent high responsiveness of the hydraulic servo valve cannot be exhibited, and the intended injection molding machine cannot be obtained.

The present invention has been made to solve the above-mentioned drawbacks of the prior art, and it is an object of the present invention to provide an injection control method for an injection molding machine capable of improving the quality of a molded product and obtaining a high energy saving effect. Has a purpose.

[0009]

In order to achieve the above object, a first injection control method for an injection molding machine according to the present invention is provided.
Is an injection control method for an injection molding machine that supplies hydraulic oil discharged from a pump to an injection cylinder via a hydraulic servo valve and injects a material to be molded. The reference injection pressure is obtained in advance, the discharge pressure of the pump is set in the control device in accordance with the obtained reference injection pressure, and the injection of the injection cylinder at the time of injection of the molding material in the injection step of the injection molding machine is performed. The pressure is detected, the detected pressure is compared with the reference injection pressure, and the discharge pressure of the pump is controlled.

A second aspect of the present invention is to supply the hydraulic oil discharged by the pump to the injection cylinder via a hydraulic servo valve,
In an injection control method of an injection molding machine for injecting a material to be molded, a reference injection pressure and a reference injection speed of the injection cylinder required to obtain a predetermined molded product are obtained in advance, and the pump corresponding to the reference injection pressure is obtained. The discharge pressure of the pump and the discharge amount of the pump according to the reference injection speed are set in the control device, and the injection pressure and the injection speed of the injection cylinder at the time of injection of the material to be molded in the injection step of the injection molding machine. Is detected and the detected injection pressure and injection speed are compared with the reference injection pressure and the reference injection speed to control the discharge pressure and the discharge amount of the pump.

[0011]

According to the first aspect of the present invention configured as described above, the reference injection pressure of the injection cylinder necessary for obtaining a predetermined molded product is measured, and the discharge pressure of the pump is set according to the obtained injection pressure. Therefore, the response delay of the pump can be avoided. That is, by setting the discharge pressure in the control device in consideration of the response delay of the pump so that the reference injection pressure of the injection cylinder can be obtained, the discharge pressure of the pump is controlled prior to the change of the injection pressure of the injection cylinder. By changing the hydraulic servo valve, the high-speed response of the hydraulic servo valve is not restricted by the response of the pump, energy can be saved in the injection molding machine, control accuracy can be improved, and a high-quality molded product can be obtained.

When the injection speed of the injection cylinder is to be rapidly increased, it is desirable that the discharge pressure of the pump is made higher than usual so as to cover the servo characteristics.

Further, in the second aspect of the present invention, not only the discharge pressure of the pump is controlled, but also the reference injection speed of the injection cylinder is obtained in advance, and the discharge amount of the pump is also controlled according to the injection speed. Therefore, the control accuracy of the injection molding machine can be further improved.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of an injection control method for an injection molding machine according to the present invention will be described in detail with reference to the accompanying drawings. Figure 1
It is explanatory drawing of the injection molding machine to which the injection control method of the injection molding machine which concerns on 1st Example of this invention is applied.

In FIG. 1, an injection cylinder 10 is provided with an injection screw 12 for plasticizing and injecting a molten resin, which is a material to be molded (not shown). Further, the injection cylinder 10 is equipped with a position detection device 14 for detecting the injection position (the position of the injection cylinder 10 or the injection screw 12). The position detection device 14 is composed of a pinion rack mechanism 16 and a position detector 18, and a detection signal of the position detector 18 is input to a control device described later.

The injection cylinder 10 is connected to a variable discharge pump 22 via a pipe 20, and receives hydraulic oil from the pump 22 to drive the injection screw 12. The variable discharge rate pump 22 is driven by a motor 24, and the discharge rate can be changed by a discharge rate control mechanism 26. Further, a hydraulic servo valve 28 is provided in the pipe line 20 so that the flow rate of the hydraulic oil supplied to the injection cylinder 10 can be adjusted. Further, an injection pressure detector 30 is provided in the conduit 20 between the hydraulic servo valve 28 and the injection cylinder 10 so that the injection pressure of the injection cylinder 10 can be detected.

On the other hand, in the conduit 20 between the variable discharge pump 22 and the hydraulic servo valve 28, a relief valve 32 for adjusting the discharge pressure of the pump 22 is provided and the discharge pressure of the pump 22 is detected. A hydraulic pressure detector 34 is attached. The detection signal of the oil pressure detector 34 is used as the control device 40.
Entered in.

The control device 40 has a synchronization control unit 42 which receives an injection start command, takes in a clock signal output from a timer 44 as will be described later in detail, and sets a reference position setting unit 46 at a predetermined cycle. A data output command is given to the reference discharge pressure setting unit 48 and the reference discharge amount setting unit 50, and a calculation command is output to the injection pressure deviation calculation unit 52.

The reference position setting section 46 stores the position of the injection screw 12 (injection cylinder 10) obtained by measurement in advance corresponding to the elapsed time of one cycle in the injection process. Further, the reference discharge pressure setting unit 48 stores the discharge pressure of the pump 22 obtained in advance corresponding to the elapsed time of one cycle in the injection process, and the reference discharge amount setting unit 50 stores the discharge pressure in the injection process. The discharge pressure of the pump 22 determined in advance corresponding to the elapsed time of one cycle is stored. Then, the injection pressure deviation calculation unit 52 is adapted to receive the detection signal of the injection pressure detector 30,
In response to a signal from the synchronization control unit 42, the injection pressure and the detection of the injection pressure detector 30 which are obtained by measuring in advance corresponding to the elapsed time of one cycle in the injection process set in the reference injection pressure setting unit 54. Find the deviation from the pressure.

The controller 40 further includes a position controller 5
6, a discharge pressure controller 58 and a pump controller 60 are provided. The position control unit 56 sends a flow rate control signal to the hydraulic servo valve 28 based on the detection signal of the position detector 18 and the output signal of the reference position setting unit 46. On the other hand, the discharge pressure control unit 58 receives the outputs of the injection pressure deviation calculation unit 52 and the reference discharge pressure setting unit 48, and sends a pressure setting signal to the relief valve 32. Further, a detection signal of a discharge amount detector 62 that detects the position of the discharge amount control mechanism 26 and detects the discharge amount of the variable discharge amount pump 22 is input to the pump control unit 60. A control signal is output to the ejection amount control mechanism 26 based on the signal and the reference ejection amount output by the reference ejection amount setting unit 50.

The injection control method by the injection molding machine configured as described above is performed as follows. First, the optimum injection conditions for obtaining a predetermined molded product are obtained in advance by experiments or the like. That is, the most suitable amount of resin for obtaining a predetermined molded product, the injection speed of the injection screw 12 corresponding to the passage of time of one cycle in the injection process, the injection screw 1
The position 2, the injection pressure of the injection cylinder 10, the discharge amount of the variable discharge pump 22, the discharge pressure, and the like are obtained. Then, the obtained position, injection pressure, discharge pressure, and discharge amount of the injection screw 12 are associated with the reference screw position (injection position), injection pressure, discharge pressure, and discharge amount in correspondence with the elapsed time of one cycle in the injection process. Corresponding to the setting units 46, 5
Set to 4, 48, 50.

That is, in the injection speed setting unit (not shown) of the control device 40, the set injection speed VS of the injection cylinder 10 (injection screw 12) in one cycle of the injection process is set.
Is set as shown by the broken line in FIG. Then, when the injection is performed according to the set injection speed VS, the actual injection pressure (load pressure) PV obtained by the measurement shown by the solid line in FIG.
Set to. Further, the reference discharge pressure setting unit 48 sets the discharge pressure PS of the variable discharge pump 22 as shown by the one-dot chain line in FIG.

The reference discharge pressure PS of the pump 22 is the reference injection pressure PV during the elapse of one cycle of the injection process.
On the other hand, it is set to be higher by at least 2 to 5 kg / cm 2. Also, the reference pump discharge pressure PS
Is set to be larger than the difference between the reference injection pressure PV and the normal reference injection pressure PV at the start of injection when the reference injection speed VS is suddenly increased, or at the portion indicated by the symbol a, as shown by the peaks m1 and m2. To cover. The peaks m1 and m2 are set to appropriate values by experiments or the like. For example, in the case of the peak m2, it is set to be higher than the reference injection pressure PV by about 15 kg / cm2.

In this way, the motor 24 is started by setting each reference value, and the discharge amount control mechanism 26 is adjusted so that the discharge amount of the variable discharge amount pump 22 becomes a predetermined value. When the variable discharge pump 22 is driven and the operator presses the injection start button of the injection molding machine, the controller 4
An injection start command is input to the synchronization control unit 42 of 0. When receiving the command to start the injection, the synchronization control unit 42 receives the timer 4
Based on the clock signal output from the No. 4, the measurement of the elapsed time of one cycle of the injection process is started, and the reference position setting unit 46, the reference discharge pressure setting unit 48, the reference discharge An instruction to output the reference value corresponding to the elapsed time of one cycle is given to the amount setting unit 50 and the reference injection speed setting unit (not shown).

The reference discharge amount setting unit 50 includes a synchronization control unit 42.
In accordance with the above command, the reference pump discharge pressure PS shown by the dashed line in FIG. 2 is output to the discharge pressure control unit 58. The discharge pressure control unit 58 takes in the detection signal of the oil pressure detector 34,
A control signal is sent to the relief valve 32 so that the discharge pressure of the variable discharge pump 22 becomes the reference pump discharge pressure PS.

On the other hand, when t1 has elapsed after receiving the injection start command, the synchronous control unit 42 receives the injection screw 12 (or the injection cylinder 1) stored in the reference position setting unit 46.
The position signal 0) is output to the position controller 56. And
The position control unit 56 outputs a control signal to the hydraulic servo valve 28 to start injection, reads the detection signal of the position detector 18, and determines the position of the injection screw 12 to be the reference position output by the reference position setting unit 46. So that the amount of hydraulic oil supplied to the injection cylinder 10 via the hydraulic servo valve 28 is adjusted.

Further, the synchronization control unit 42, when t1 time has elapsed after receiving the injection start command, the injection pressure deviation calculation unit 5
2 is given an operation instruction. The injection pressure deviation calculation unit 52 reads the reference injection pressure PV set in the reference injection pressure setting unit 54 in correspondence with the passage of time, fetches the detection signal of the injection pressure detector 30, and obtains the deviation between the two. And sends it to the discharge pressure controller 58. The discharge pressure control unit 58 controls the deviation ΔP between the current injection pressure P detected by the injection pressure detector 30 obtained by the injection pressure deviation calculator 52 and the reference injection pressure PV.
The reference pump discharge pressure PS output from the reference discharge pressure setting unit 48 is corrected using a correction formula or a correction table obtained in advance based on the above equation to obtain a predetermined reference pump discharge pressure PS.
The discharge pressure of the variable discharge pump 22 is controlled via the relief valve 32 so that

The pump control unit 60 compares the detection signal of the discharge amount detector 62 with the reference discharge amount output from the reference discharge amount setting unit 50 so that the discharge amount of the variable discharge amount pump 22 becomes the reference discharge amount. To the discharge amount control mechanism 26.

As described above, according to the injection control method of the embodiment, the reference pump discharge pressure PS of the variable discharge pump 22 is adjusted in accordance with the optimum injection pressure PV for obtaining a predetermined molded product.
Is set in the reference discharge pressure setting unit 48 and the relief valve 32 is controlled so that the set discharge pressure PS is obtained. Therefore, even if the variable discharge pump 22 and the hydraulic servo valve 28 are combined, the control performance is improved. The responsiveness of the variable discharge pump 22 is not restricted. For this reason, the injection molding machine to which the embodiment is applied can take advantage of the high-speed response of the hydraulic servo valve 28, is excellent in response, and can be controlled with high accuracy, and a high-quality molded product can be obtained. It is possible to perform control that can achieve a high energy saving effect of the variable discharge pump 22.

Further, the reference pump discharge pressure PS of the variable discharge pump 22 is a normal reference at the start of injection or at a position where the set injection speed VS is rapidly increased, as shown by the symbol a in FIG. Since it is sufficiently larger than the value added to the injection pressure PV, the servo characteristics can be covered and the delay with respect to the set injection speed VS of the injection cylinder 10 (injection screw 12) can be made extremely small, and the control performance can be improved. Can be planned.

FIG. 3 shows an example of the construction of an injection molding machine to which an injection control method according to another second embodiment is applied. The injection molding machine shown in FIG. 3 is different from the injection molding machine shown in FIG. 1 only in the control device 40, and a portion for controlling the discharge amount of the variable discharge pump 22 is added in consideration of the injection speed. ..

The control device 70 shown in FIG. 3 is the same as the control device 40 shown in FIG.
4. The configuration is such that an injection speed deviation calculation unit 76 is added. The reference injection speed setting unit 72 displays the injection speed as shown in FIG.
When the injection speed of the injection cylinder 10 (injection screw 12) is controlled so as to reach the set injection speed VS shown in (A), the actual injection speed VV obtained by measurement is used as the reference injection speed, and the injection process is performed. It is set corresponding to the passage of time of one cycle in.

In the reference discharge amount setting section 50, the reference discharge amount QS of the variable discharge amount pump 22 corresponding to the actually measured reference injection speed VV is set. That is, when the injection cylinder 10 injects the resin at the reference injection speed VV, the discharge amount QS of the pump 22 which is slightly larger than the supply amount of the hydraulic oil to the injection cylinder 10 necessary to obtain the injection speed VV.
Is calculated and calculated, and is set and stored in the reference discharge amount setting unit 50 as the reference discharge amount QS.

For example, when the set injection speed VS increases stepwise as described in the prior art (see FIG. 6), the reference discharge amount Q set in the reference discharge amount setting section 50 is set.
S becomes like FIG. 4 (B). That is, the reference discharge amount Q
S is the injection cylinder 10 at the reference injection speed VV
The discharge amount of the pump 22 is set to be larger than the inflow amount of the hydraulic oil by ΔQ.

On the other hand, the injection speed calculator 74 receives the detection signal from the position detector 18 of the position detection device 14, calculates the injection speed V of the injection cylinder 10, and calculates the calculated injection speed V.
Is input to the injection speed deviation calculation unit 76. Then, the injection speed deviation calculation unit 76 receives a calculation command from the synchronization control unit 42, compares the detected injection speed V with the reference injection speed VV read from the reference injection speed setting unit 72, obtains the difference between the two, and calculates the pump difference. It is designed to be sent to the control unit 60.

In the injection molding machine configured as described above, the position control unit 56 and the discharge pressure control unit 58 perform the same control as in the above embodiment. On the other hand, the injection speed calculation unit 74 takes in the output signal of the position detector 18 at every predetermined time and changes the injection screw 1 detected by the position detector 18 from moment to moment.
The injection speed V is calculated from the injection position of 2 (the injection cylinder 10), and is input to the injection speed deviation calculation unit 76.

The injection speed deviation calculation unit 76 includes a synchronization control unit 4
2, the reference injection speed VV corresponding to the time elapsed after receiving the injection start command is read from the reference injection speed setting unit 72, and compared with the injection speed V obtained by the injection speed calculation unit 74.
The difference between the two is calculated and sent to the pump control unit 60. The pump control unit 60, which has received the deviation of the injection speed from the injection speed deviation calculation unit 76, corrects the reference discharge amount input from the reference discharge amount setting unit 50 based on a predetermined formula or table, and discharges it. A control signal is output to the quantity control mechanism 26 so that the injection speed of the injection screw 12 is the reference injection speed VV.
The discharge amount of the variable discharge pump 22 is controlled so that

In the present embodiment, not only the discharge pressure of the pump 22 but also the reference injection speed is measured in advance and the reference discharge amount QS is set correspondingly, and the pump 22 is adjusted according to the detected injection speed. Since the discharge amount is controlled so as to become the reference discharge amount QS, it is possible to perform control with higher accuracy.

FIG. 5 shows an injection control device 80 to which the third embodiment is applied. A part for detecting the injection pressure and controlling the discharge pressure is omitted, and the injection speed is detected to perform the variable discharge. An example of a control device 80 in the case of performing injection control by a portion that controls the discharge amount of the metering pump 22 and a position control portion that controls the hydraulic servo valve 28 by the detection signal of the position detector 18 is shown. .. Also in this embodiment,
High-speed response is possible without being restricted by the response of the pump 22 having a slow response speed, a high-quality molded product can be obtained, and energy saving of the injection molding machine can be achieved.

In the above-mentioned embodiment, the case where the invention is applied to the in-line screw type injection molding machine is explained, but the invention can also be applied to other injection machines such as the plunger type. Further, although the case where the material to be molded is a resin has been described in the above embodiments, it can be applied to injection molding of new ceramics or the like.

[0041]

As described above, according to the injection control method for the injection molding machine of the present invention, the discharge pressure of the pump is set according to the injection pressure of the injection cylinder required to obtain a predetermined molded product. Therefore, the response delay of the pump can be avoided. That is, by setting the discharge pressure in the control device in consideration of the response delay of the pump so that the reference injection pressure of the injection cylinder can be obtained, the discharge pressure of the pump is controlled prior to the change of the injection pressure of the injection cylinder. By changing it, it is possible to eliminate the adverse effects caused by the delay in the response of the pump, and take advantage of the high-speed response of the hydraulic servo valve.
Energy saving of the injection molding machine can be achieved, control accuracy can be improved, and high quality molded products can be obtained.

Further, in the second aspect of the present invention, not only the discharge pressure of the pump is controlled, but also the reference injection speed is previously obtained by actual measurement, and the reference discharge amount of the pump is set according to the actually measured reference injection speed. Since the discharge amount of the pump is also controlled based on the injection speed measured in the injection process, the control accuracy of the injection molding machine can be further improved.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an injection molding machine to which a first embodiment of the present invention is applied.

2 is a diagram showing an example of a reference injection pressure and a reference pump discharge pressure set in a reference injection pressure setting unit and a reference discharge pressure setting unit of the control device shown in FIG.

FIG. 3 is an explanatory diagram of an injection molding machine to which a second embodiment of the present invention is applied.

FIG. 4 is a reference injection pressure setting unit of the control device shown in FIG.
It is a figure which shows an example of the reference injection pressure set to the reference discharge pressure setting part, the reference injection speed setting part, and the reference discharge amount setting part, the reference pump discharge pressure, the reference injection speed, and the reference discharge amount.

FIG. 5 is an explanatory diagram of an injection molding machine to which a third embodiment of the present invention is applied.

FIG. 6 is an explanatory diagram of an injection control method of a conventional injection molding machine.

[Explanation of symbols]

 10 injection cylinder 12 injection screw 18 position detector 22 variable discharge amount pump 26 discharge amount control mechanism 28 hydraulic servo valve 30 injection pressure detector 32 relief valve 34 hydraulic pressure detector 40, 70, 80 control device 62 discharge amount detector

Claims (2)

[Claims] 1. An injection control method for an injection molding machine, wherein a hydraulic fluid discharged from a pump is supplied to an injection cylinder via a hydraulic servo valve to inject a material to be molded, the method being required to obtain a predetermined molded product. The reference injection pressure of the injection cylinder is obtained in advance, the discharge pressure of the pump is set in the control device in accordance with the obtained reference injection pressure, and the injection at the time of injection of the molded material in the injection step of the injection molding machine is performed. An injection control method for an injection molding machine, comprising: detecting an injection pressure of a cylinder, comparing the detected pressure with the reference injection pressure, and controlling a discharge pressure of the pump. 2. An injection control method for an injection molding machine, wherein the hydraulic fluid discharged from a pump is supplied to an injection cylinder via a hydraulic servo valve to inject a material to be molded, the method being required to obtain a predetermined molded product. The reference injection pressure and the reference injection speed of the injection cylinder are obtained in advance, and the discharge pressure of the pump corresponding to the reference injection pressure and the discharge amount of the pump according to the reference injection speed are set in the control device, and The injection pressure and injection speed of the injection cylinder at the time of injection of the material to be molded in the injection step of the injection molding machine are detected, and the detected injection pressure and injection speed are compared with the reference injection pressure and the reference injection speed. An injection control method for an injection molding machine, comprising controlling a discharge pressure and a discharge amount of the pump.