JPH0639891A - Apparatus for controlling injection process in motor-driven injection molding machine - Google Patents

Abstract

PURPOSE:To make repeating characteristic good and to make setting and switching of injection speed and driving force easy. CONSTITUTION:A control part 21 receives detecting signals of a driving force sensor 14 and a position sensor 18 and when the actual driving force o a screw becomes larger than the driving force set in a setting part 26, it outputs a signal controlling rotational speed of a motor 6 so as to be the actual driving force equal to a set driving force and when the actual driving force >the set driving force, it outputs a signal controlling the rotational speed of the motor 6 in such a way that the screw 17 is forwarded by the speed set in a setting part 24. A driver part 22 controls the rotational speed of the motor 6 in accordance with a position feedback signal and a speed feedback signal of the position sensor 18 and a control signal of the control part 21.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a filling process control device in an electric injection molding machine, which enables a high-speed low-pressure molding method for filling a resin into a mold at high speed and low pressure.

[0002]

2. Description of the Related Art Thrust (injection pressure) of an injection screw during an injection process in order to improve warpage and twist of a plastic molded product, improve transfer of grain, prevent damage to pins such as connectors, and prolong life. The high-speed low-pressure molding method in which the injection screw is advanced to fill the resin into the mold at high speed and low pressure is widely adopted.

In order to realize this high-speed low-pressure molding method, an injection molding machine has been developed in which a multistage hydraulic cylinder advances an injection screw (Japanese Patent Publication No. 59-1529).
No. 5).

[0004]

However, since the conventional injection molding machine is hydraulically driven, it has the following problems. (A) Repetitive characteristics are problematic because they are easily affected by disturbances such as power supply fluctuations, hydraulic oil temperature and room temperature. (B) During the injection process, since the multistage hydraulic cylinder for injection is switched by the electromagnetic switching valve to change the maximum value of the thrust of the injection screw, it is difficult to set the injection speed and the thrust. Moreover, a shock noise is generated at the time of switching, and smooth switching of speed and thrust cannot be performed. (C) Since there is no feedback of the screw thrust, the fluctuation of the supply pressure directly causes the fluctuation of the screw thrust, and the repeatability is also inferior in this respect as well. (D) Energy efficiency is low due to the hydraulic drive system.

The present invention has good repeating characteristics, and it is easy to set and switch the injection speed and thrust of the injection screw.
An object of the present invention is to provide an injection process control device for an electric injection molding machine, which can control the injection process with high accuracy and energy saving.

[0006]

In order to achieve the above object, the present invention provides an injection screw inserted in a heating cylinder,
In an electric injection molding machine that is moved axially by a motor through a screw mechanism, a thrust sensor that detects the thrust of the injection screw when filling the resin in the mold, and a position that detects the position and injection speed of the injection screw. When the actual thrust of the injection screw exceeds the set thrust set in the thrust setting section corresponding to the position of the injection screw detected by the position sensor, by receiving the detection signals of the sensor, the thrust sensor and the position sensor. In addition, a control signal for controlling the rotation speed of the electric motor is output so that the actual thrust of the injection screw becomes equal to the set thrust set in the thrust setting section, and the actual thrust of the injection screw is set in the thrust setting section. When the thrust becomes smaller than the set thrust, the set speed of the injection screw set in the speed setting section corresponding to the position of the injection screw detected by the above position sensor. Screw forward control unit that outputs a control signal for controlling the rotation speed of the electric motor so as to advance the injection screw, a speed feedback signal and a position feedback signal of the position sensor, and the control output from the screw forward control unit. And a servo motor driver unit for controlling the rotation speed of the electric motor according to the signal.

[0007]

The screw forward control unit receives the detection signals of the thrust sensor and the position sensor, and the actual thrust of the injection screw is equal to or more than the set thrust set in the thrust setting unit in correspondence with the position of the injection screw detected by the position sensor. If the actual thrust of the injection screw becomes equal to the set thrust set in the thrust setting section, a control signal is output to control the rotation speed of the electric motor, and the actual thrust of the injection screw is output to the thrust setting section. When the thrust becomes smaller than the set thrust, the rotation of the electric motor moves the injection screw forward at the set speed of the injection screw set in the speed setting section corresponding to the position of the injection screw detected by the position sensor. Output a control signal to control the speed. Further, the servo motor driver unit controls the rotation speed of the electric motor according to the velocity feedback signal and the position feedback signal of the position sensor and the control signal output from the screw forward movement control unit.

Since it is of the electric type, it is less susceptible to the effects of disturbance, has good repeatability, and can save energy. Further, the speed and thrust of the injection screw can be easily set in the speed setting unit and the thrust setting unit, and the already set value can be easily switched to another set value. Furthermore, the injection process can be accurately feedback-controlled without generating an operating noise unlike the electromagnetic switching valve.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment of an injection process control device for an electric injection molding machine according to the present invention. Reference numeral 1 in this figure
Is the front plate. A heating cylinder 2 is fixed to the front plate 1. A rear plate 3 is provided behind the front plate 1 (on the right side in FIG. 1) in parallel with the front plate 1, and a pair of identical ball screw shafts 4 and 4 are mounted between the plates 1 and 3. It is rotatably supported by 1a and 3a. Each ball screw shaft 4
Pulleys 5 having the same diameter are attached to the end portions of the.

An electric motor (servo motor) 6 is fixed to the rear plate 3, and an endless timing belt 9 is wound between a drive pulley 8 and a pulley 5, 5 provided on an output shaft 7 of the electric motor 6. It is hung. Electric motor 6
Rotates the ball screw shafts 4, 4 in the circumferential direction in synchronization with each other via the drive pulley 8, the timing belt 9, and the pulleys 5, 5.

A ball nut 1 is attached to each of the ball screw shafts 4 and 4.
1 are screwed together, and the pair of ball nuts 1
A pressure plate 12 is installed between 1 and 11. The pressure plate 12 has each ball screw shaft 4, 4
When is rotated, it moves in the front-back direction (left-right direction in FIG. 1) together with the ball nuts 11, 11. A bearing housing 13 is attached to the front surface of the pressure plate 12 on the heating cylinder 2 side via a pressure sensor 14 such as a load cell.

A bearing 15 is provided in the bearing housing 13, and a rotary shaft 16 is rotatably supported by the bearing 15. An injection screw 17 is attached to the rotating shaft 16. The injection screw 17 is inserted in the heating cylinder 2 and moves in the axial direction together with the pressure plate 12. The electric motor 6 includes a position sensor 18 such as a pulse encoder.
Is provided.

Reference numeral 21 is a screw forward control unit, 2
2 is a servo motor driver unit. The screw forward control unit 21 includes a sequence man-machine servo program control unit (hereinafter, program control unit) 23 and a speed setting unit 2.
4, the speed switching control unit 25, the thrust setting unit 26, the thrust switching control unit 27, the comparing units 28, 29 and 30, the switching unit 31, the AND circuit 32, and the like are mainly included. The servo motor driver unit 22 includes a deviation counter circuit 34, a switch 35, and an addition circuit 36.

The detection signal of the pressure sensor 14 is input to the program control unit 23 and the comparison units 28 and 30 via the interface 38. In addition, the position sensor 18 is connected to the program control unit 23, the speed switching unit 25, the thrust switching control unit 27, the comparison unit 29, the deviation counter circuit 34, and the addition circuit 36 via the interface 39, and a position feedback signal. Is input to the program control unit 23, both switching control units 25 and 27, and the deviation counter circuit 34, and the speed feedback signal is input to the comparison unit 29 and the addition circuit 36.

The speed setting unit 24 sets the injection speed corresponding to the injection forward position of the injection screw 17 in multiple stages, and the thrust setting unit 26 sets the injection position of the injection screw 17 in the filling process and the elapsed time in the pressure holding process. The injection thrust corresponding to is set in multiple stages. Speed switching control unit 25
Receives the position signal from the position sensor 18 and the injection screw 1
A speed setting value corresponding to the forward movement position of No. 7 is selected from the speed setting unit 24. The thrust force switching control unit 27 has a timer function, receives a position signal from the position sensor 18, and selects from the thrust force setting unit 26 a thrust force setting value that matches the forward position of the cru 17 in the filling process. Select the thrust setting value that corresponds to the elapsed time at.

The speed setting value selected by the speed switching control section 25 becomes a speed control command from the speed setting section 24 and is output to the deviation counter circuit 34 as a pulse train via the switch 31. The servo motor driver unit 22 detects the difference between the speed control command given to the deviation counter circuit 34 and the speed feedback signal output from the interface 39 with the adder circuit 36, and via the servo amplifier 40 so as to obtain the set speed. Control the rotation speed of the electric motor 6. This control is continued until the position feedback signal output from the interface 39 to the deviation counter circuit 34 reaches the number of pulses output from the speed setter 24 to the deviation counter circuit 34. From the speed setting unit 24 to the comparison unit 29
The speed setting value is output as a digital value.

The set thrust force (value) selected by the thrust force switching control unit 27 is from the thrust force setting unit 26 to the comparing units 28 and 30.
Is output to. During the injection process, the comparison unit 30
The set thrust and the actual thrust (value) are compared, and when the set thrust ≦ actual thrust, the contact point (1) of the switching devices 31, 35 is switched to the contact point (2) to stop the speed command pulse train. .

When set thrust> actual thrust, the comparison unit 30
From the AND circuit 32. The comparison unit 29 outputs to the AND circuit 32 when set speed ≦ actual speed. When the above two conditions (set thrust> actual thrust, set speed ≦ actual speed) are satisfied, the AND circuit 32 switches the contact (2) of the switching devices 31, 35 to the contact (1), and again sets the speed command pulse train. It is configured to output.

The comparison unit 28 compares the set thrust force with the actual thrust force and outputs the output signal from the amplifier 4 so that the set thrust force = actual thrust force.
It outputs to the contact (2) of the switching device 35 via 1. For this reason, when the contact (1) of the switching devices 31, 35 is switched to the contact (2), the servo motor driver unit 22 controls the rotation speed of the electric motor 6 so that the actual thrust becomes equal to the set thrust.

When the set thrust is less than the actual thrust, the electric motor 6
Control is performed so that the current rotation speed is maintained when the set thrust = actual thrust, and when the set thrust> actual thrust, the rotation speed is increased and the set thrust = actual thrust. To do.
In the above, when the actual thrust does not reach the set thrust even if the rotation speed of the electric motor 6 is increased and the injection speed of the injection screw 17 reaches the set speed, the above-mentioned two conditions are satisfied in the AND circuit 32. The contact (2) of the switching devices 31 and 35 is switched to the contact (1) to enter the speed control mode, and the speed command pulse train is output.

Injection screw 17 for speed setting unit 24
2 shows an example of setting the injection speed of the injection screw and an example of setting the thrust of the injection screw 17 with respect to the thrust setting unit 26. In this example,
The injection speed of the injection screw 17 in the injection process is set in the speed setting unit 24 in 6 stages of V _{1 to} V ₆ , and the thrust is set in the thrust setting unit 26 in 5 stages of P _{1 to} P _5. ing. In this figure, symbols S _{1 to} S ₆ indicate the forward positions of the injection screw 17 in the filling process, T is the time of the injection process,
T ₁ and T ₂ indicate the elapsed time in the pressure holding process. The time T is measured by a timer incorporated in the program control unit 23, and the times T ₁ and T ₂ are measured by a timer incorporated in the thrust force switching control unit 27.

Next, the operation of the injection process control device of the electric injection molding machine according to the present invention constructed as described above will be described with reference to FIG.
Through the flow chart of FIG. When the measurement of the resin is completed, an injection command is output from the program control unit 23 (step S1), and a timer built in the control unit 23 starts counting (step S2). Next step S3
Then, it is determined whether or not the built-in timer is counting up. If Y (YES), the latch relay inside the control unit 23 is reset (step S4), and the process ends.
If N (NO), it is determined whether or not the internal latch relay is turned on (step S5), and if Y, the process proceeds to step S33. If N in step S5,
It is determined whether the injection screw 17 is located between the positions S _{1 and} S ₂ (step S6).

If the determination in step S6 is N, the process proceeds to step S11. If Y is determined, the speed setting unit 24 outputs the set speed V ₁ and the thrust setting unit 26 outputs the set thrust P ₁ (step S7). ). Next, set thrust P ₁ >
It is judged whether or not it is the actual thrust (step S8), and Y
In the case of, the rotation speed of the electric motor 6 is controlled so that the injection screw 17 moves forward at the set speed V ₁ (step S9).
When N, that is, when the set thrust P ₁ ≦ actual thrust, the rotational speed of the electric motor 6 is controlled so that the thrust of the injection screw 17 becomes the set thrust P ₁ (step S10). The above control is continued until (Step S6) becomes N.

[0024] In the case of N at step S6, whether the injection screw 17 is between the positions S ₂ to S ₃ is determined (step S11) is a step between the position S ₂ ~S ₃ S6~S15 control, control of steps S16~S20 between position S ₃ to S _4, the control of steps S21~S25 between position S ₄ to S _5, the control of steps S26~S30 between position S ₅ to S _6, the Step S6 ~
The contents are the same except for the control of S10 and the output values of the set speed and the set thrust.

If N in step S26, step S3
Moving to 1, it is determined whether the injection screw 17 has reached position S ₆ . In the case of Y, the internal latch relay is set (step S32), and the timer of the thrust force switching control unit 27 starts counting (step S33). The filling step until the injection screw 17 reaches the position S _6, a pressure holding process after reaching.

In the next step S34, it is determined whether or not the timer has counted up after the time T1 has elapsed. If Y, the process proceeds to a determination step S39, and if N, the set speed V ₆ is set by the speed setting unit 24. Then, the thrust setting unit 24 outputs the set thrust P ₃ (step S35). When the set values V ₆ and P ₃ are output from both the setting units 24 and 26, it is determined in step S36 whether or not the set thrust P ₃ > actual thrust. As a result, in the case of Y, the rotation speed of the electric motor 6 is controlled so that the injection screw 17 moves forward at the set speed V ₆ (step S37), and in the case of N, that is, the set thrust P.
_{When 3} ≦ actual thrust, the rotation speed of the electric motor 6 is controlled so that the thrust of the injection screw 17 becomes the set thrust P ₃ (step S38).

If Y in step S34, the timer counts (step S39), and in the next step S40, it is determined whether or not the time T ₂ has elapsed and the timer has counted up. As a result, if Y, the process proceeds to step S45. If N, the speed setting unit 24 continuously outputs the set speed V ₆ , and the thrust setting unit 26 outputs the set thrust P ₄ (step S41). When the set values V ₆ and P ₄ are output from both the setting units 24 and 26, it is determined whether or not the set thrust> actual thrust (step S42). As a result, Y
In the case of, the rotation speed of the electric motor 6 is controlled so that the injection screw 17 moves forward at the set speed V ₆ (step S43),
In the case of N, the rotation speed of the electric motor 6 is controlled so that the thrust of the injection screw 17 becomes the set thrust P ₄ (step S4).
4).

If Y in step S40, the speed setting unit 2
The set speed V ₆ is continuously output from 4 and the thrust setting unit 2
The set thrust P ₅ is output from 6 (step S4).
5). When the set values V ₆ and P ₅ are output from both the setting units 24 and 26, it is determined whether or not the set thrust> actual thrust (step S46). As a result, in the case of Y, the rotation speed of the electric motor 6 is controlled so that the injection screw 17 moves forward at the set speed V ₆ (step S47), and in the case of N, the thrust of the injection screw 17 becomes the set thrust P _5. The rotation speed of the electric motor 6 is controlled (step S48). The control of steps S2, S3, S5 to S48 is performed by the program control unit 2
It continues until the timer built in 3 counts up, and when it finishes counting up (Y in step S3),
The internal latch relay is reset (step S4) and the process ends.

[0029]

As described above, the injection process control device for an electric injection molding machine according to the present invention is an electric injection machine in which an injection screw inserted in a heating cylinder is axially moved by a motor through a screw mechanism. In a molding machine, a thrust sensor that detects the thrust of the injection screw when filling the mold with resin, a position sensor that detects the position and injection speed of the injection screw, and a detection signal from the thrust sensor and the position sensor. ,
When the actual thrust of the injection screw exceeds the set thrust set in the thrust setting section corresponding to the position of the injection screw detected by the position sensor, the actual thrust of the injection screw is set in the thrust setting section. It outputs a control signal to control the rotation speed of the electric motor so that it becomes equal to the set thrust, and when the actual thrust of the injection screw becomes smaller than the set thrust set in the thrust setting section, it is detected by the above position sensor. The screw advancing control unit that outputs a control signal for controlling the rotation speed of the electric motor so as to advance the injection screw at the set speed of the injection screw set in the speed setting unit corresponding to the position of the injection screw, According to the speed feedback signal and the position feedback signal of the sensor and the control signal output from the screw forward control unit, It has the following advantages because it is a structure in which and a servo motor driver unit for controlling the rotation speed.

(B) Since it is an electric type, it is not easily affected by fluctuations in the power source and disturbances such as room temperature, stable molding is possible, and energy saving and noise reduction can be achieved. (B) Since the thrust and speed of the injection screw are controlled by the feedback method, the repeatability can be improved. (C) Since the thrust and speed of the injection screw are changed by controlling the rotation speed of the electric motor, smooth gear shifting and voltage change can be performed. (D) Since the thrust and speed of the injection screw can be set in industrial units, setting and switching are easy.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of an injection process control device of an electric injection molding machine according to the present invention.

FIG. 2 is a diagram showing an example of setting a speed and a thrust of an injection screw in an injection process.

FIG. 3 is a flowchart showing a part of control by the injection process control device of the present invention.

FIG. 4 is a flowchart showing another part of the control by the injection process control device of the present invention.

FIG. 5 is a flowchart showing yet another part of control by the injection process control device of the present invention.

FIG. 6 is a flowchart showing another part of control by the injection process control device of the present invention.

FIG. 7 is a flowchart showing yet another part of control by the injection process control device of the present invention.

[Explanation of symbols]

 2 heating cylinder 4 screw shaft 6 electric motor 11 ball nut 14 pressure sensor 17 injection screw 18 position sensor 21 screw forward control unit 22 servo motor driver unit 24 speed setting unit 26 thrust setting unit

Claims (1)

[Claims] 1. An electric injection molding machine in which an injection screw inserted into a heating cylinder is axially moved by a motor through a screw mechanism to detect a thrust force of the injection screw when filling a mold with resin. The thrust sensor, the position sensor that detects the position and the injection speed of the injection screw, and the detection signals of the thrust sensor and the position sensor, the actual thrust of the injection screw corresponds to the position of the injection screw detected by the position sensor. When the thrust exceeds the set thrust set in the thrust setting section, the control signal for controlling the rotation speed of the electric motor is output so that the actual thrust of the injection screw becomes equal to the set thrust set in the thrust setting section. It also corresponds to the position of the injection screw detected by the above position sensor when the actual thrust of the injection screw becomes smaller than the set thrust set in the thrust setting section. And a screw forward control unit that outputs a control signal that controls the rotation speed of the electric motor so as to advance the injection screw at the set speed of the injection screw set in the speed setting unit, and the speed feedback signal and position feedback of the position sensor. An injection process control device for an electric injection molding machine, comprising: a signal and a servo motor driver section for controlling the rotation speed of the electric motor according to the control signal output from the screw forward control section.