JPH0520258B2 - - Google Patents

Description

Detailed Description of the Invention Field of Industrial Application The present invention relates to a pressure control device for controlling the mold closing (clamping) pressure in the mold closing process and the injection pressure and holding pressure in the injection process in an injection molding machine. .

<Prior Art> Conventionally, as this type of pressure control device, one that uses a hydraulic circuit for control is known. In other words, the mold closing (clamping) pressure in the mold closing process, the injection pressure in the injection process, the holding pressure, etc. are controlled using hydraulic pressure to prevent excessive force from being applied to the mold during mold closing, and At the same time, when injecting resin into the mold, maintain a specified mold clamping force, supply enough resin into the mold, and maintain the pressure applied to the resin within the mold to a specified value. The quality of the product molded inside the mold is maintained at a good level.

However, when pressure is controlled by hydraulic pressure as described above, the temperature of the hydraulic oil in the hydraulic circuit changes as injection molding is performed repeatedly, and the viscosity of the hydraulic oil changes accordingly. However, there is a problem in that the mold closing (clamping) pressure, injection pressure, holding pressure, etc. fluctuate, which causes a problem in that the quality of the molded product is adversely affected. In addition, it is affected by the sliding resistance of packing, etc., and the response is slow because it uses oil, and it is necessary to convert the detected oil pressure into resin pressure. There is also the problem that there is a large pressure loss when long piping or the like is involved.

Therefore, the present applicant proposed a new pressure control device for an injection molding machine using an electric motor (Japanese Patent Application No. 59-139575, Japanese Unexamined Patent Publication No. 61-19328). This pressure control device consists of a servo motor that opens and closes the mold and moves the injection screw, a mold position detector that detects the position of the mold, an injection position detector that detects the position of the screw, and a mold position detector that detects the position of the screw. A control mechanism that outputs a torque limiter command signal according to the outputs of the position detector and the injection position detector, and a servo motor drive mechanism that limits the current flowing to the servo motor based on the torque limiter command signal,
Each position detector detects the position of the mold or the screw, and the servo motor drive mechanism limits the servo motor current based on the torque limiter command signal output by the control mechanism according to these detected values. This suppresses the maximum torque generated by the servo motor, reducing mold closing (clamping) pressure during the mold closing process,
It is possible to easily and reliably control pressures such as injection pressure and holding pressure in the injection process, and back pressure in the plasticizing process, and it is possible to obtain a high-quality molded product.

〓Problems to be solved by the invention〓 By the way, as the demand for precision molded products increases, it has become necessary to perform even more precise pressure control during continuous and repeated molding.
The above-mentioned pressure control device may not be able to cope with the problem depending on the situation.

The present invention was made in view of the above circumstances, and
The purpose of this is a pressure control device for injection molding machines that can perform pressure control with high precision and good repeatability, and can prevent variations in the dimensions of molded products or damage to the mold due to fluctuations in mold clamping force and holding force. Our goal is to provide the following.

<Means for Solving the Problems> In order to achieve the above object, the present invention provides a first invention of the present application, which includes a servo motor that opens and closes a mold and moves an injection screw; It is equipped with a mold position detector that detects the position of the mold, and an injection position detector that detects the position of the screw, and according to the output of the mold position detector,
The pressure in the mold closing process is controlled by limiting the current flowing through the servo motor, and the current flowing through the servo motor is limited in accordance with the output of the injection position detector. In a pressure control device for an injection molding machine that controls pressure in the process, elastic deformation of a driving force transmission member interposed in a drive mechanism that moves the screw back and forth is measured at the base end of the screw to determine the driving side and driven side. A control mechanism is provided that includes a pressure detector that measures the pressure acting between the two sides, and compares the pressure detected by the pressure detector with a predetermined pressure setting value to control the torque generated by the servo motor. The configuration is as follows.

Further, a second invention of the present application includes a servo motor that opens and closes the mold and moves an injection screw, a mold position detector that detects the position of the mold, and a mold position detector that detects the position of the screw. and an injection position detector, and controls the pressure in the mold closing process by limiting the current flowing to the servo motor according to the output of the mold position detector, and
In a pressure control device for an injection molding machine that controls the pressure in the injection process by limiting the current flowing to the servo motor according to the output of the injection position detector, the drive mechanism that opens and closes the mold is controlled. A pressure detector is provided to measure the pressure acting between the driving side and the driven side by measuring the elastic deformation of the intervening driving force transmission member, and the pressure detected by the pressure detector and a predetermined pressure setting value are In comparison, the configuration includes a control mechanism that controls the torque generated by the servo motor.

As the driving force transmission member, a so-called strain gauge type load converter is usually employed.

<Operation> In the pressure control device of the present invention, when limiting the current flowing to the servo motor in the control mechanism according to the output of each position detector, the current limit value is adjusted to the output of the pressure detector and the pressure setting. The maximum torque generated by the servo motor is controlled by comparing the values and the mold is closed or the injection process is performed. In the first invention, a pressure detector is provided at the base end of the screw, and in the second invention, a pressure detector is provided in the drive mechanism for measuring the elastic deformation of the driving force transmission member, so that the screw or the mold is driven. The force acting on the drive mechanism is directly sensed. That is, since there is no play or backlash inherent in the drive mechanism that increases control errors, the control feedback loop is shortened and more accurate control is achieved.

Embodiment An embodiment of the present invention will be described below with reference to FIGS. 1 to 5.

In the figure, reference numeral 1 denotes an injection cylinder of an injection molding machine. A hopper 3 for supplying resin is provided. A screw 4 is inserted into the injection cylinder 1, and the base end of the screw 4 is attached to a spline shaft 5. This spline shaft 5 is fitted into a rotating member 5a whose outer peripheral portion is rotatably supported by one end of a support member 6, rotates together with the rotating member 5a, and is axially relative to the rotating member 5a. It is now possible to move. Also,
A timing pulley 7 attached to the tip of the rotating member 5a is connected via a timing belt 8 to a timing pulley 10 attached to a rotating shaft 9a of a screw rotation motor (DC motor) 9. By driving the motor 9, the screw 4 is rotated. Further, the screw rotation motor 9 has a built-in brake device, and the rotation shaft 9a of the screw rotation motor 9 is fixed by exciting this brake device.

Around the base end of the spline shaft 5, first and second bearing housing portions 11a and 1 are provided inside both ends, respectively.
A cylindrical member 11 having a shape 1b is loosely fitted,
One end side of the cylindrical member 11 (left end side in Fig. 2)
Between the first bearing accommodating part 11a and the base end of the spline shaft 5, a clamping member 12, a first pressure detector 13, and a thrust bearing 14 are arranged in order from the back side of the first bearing accommodating part 11a. 1 A presser member 15 fitted to the shoulder portion 11d of the bearing accommodating portion 11a and the spline shaft 5
It is attached while being held between the two. This first pressure detector 13 is a device in which a pressure detector such as a strain gauge is provided on a driving force transmission member that is interposed between the driving side and the driven side and transmits the driving force, and is applied to the screw 4. This is a strain gauge type load converter that converts pressure electrically. Further, between the second bearing accommodating portion 11b on the other end side of the cylindrical member 11 and the base end portion of the spline shaft 5, a radial bearing portion 16a is provided with one end attached to the central small diameter portion 11c inside the cylindrical member 11. A thrust bearing 16 into which the spline shaft 5 is inserted is fixedly attached by an intervening member 17 and a fixing member 18 screwed into the base end of the spline shaft 5. The proximal end portion of 5 is connected to the cylindrical member 11 so as to be rotatable in the circumferential direction. One end of a cylindrical movable member 19 is screwed into the outer periphery of the other end of the cylindrical member 11 .

An injection pole screw 20 is screwed into the nut portion 19a at the other end of the movable member 19, and a base end of the injection pole screw 20 is fixed to one end of an output shaft 21 for injection. The injection output shaft 21 is rotatably supported by the other end of the support member 6, and the injection output shaft 21 has a
An injection electromagnetic clutch 22 is attached, as well as an injection position detection encoder (injection position detector) 23 that detects the position of the screw 4 by detecting the rotational position of the injection output shaft 21. . Further, the injection output shaft 21 between the support member 6 and the injection electromagnetic clutch 22 has a
A timing pulley 24 is rotatably mounted, and a suction plate 25 is integrally connected to the injection electromagnetic clutch 22 side of the timing pulley 24. When the injection electromagnetic clutch 22 is excited, An injection electromagnetic clutch 22 and a timing pulley 24 are connected. This timing pulley 24 is connected via a timing belt 26 to a timing pulley 28 attached to one end of a drive shaft 27, and the other end of the drive shaft 27 is connected via a joint 29 to an injection molding It is connected to one end of a rotating shaft 30a that protrudes from both ends of the opening/closing motor (AC servo motor) 30. A motor rotation detection encoder (rotation detector) 31 for detecting rotation of the AC servo motor 30 is attached to the other end of the rotating shaft 30a.

A mold closing electromagnetic clutch 32 is attached to the intermediate portion of the drive shaft 27. A timing pulley 33 is rotatably attached to the drive shaft 27 between the mold closing electromagnetic clutch 32 and the timing pulley 28, and a timing pulley 33 is attached to the mold opening/closing electromagnetic clutch 32 side by suction. The plates 34 are integrally connected, and when the mold opening/closing electromagnetic clutch 32 is energized, the mold opening/closing electromagnetic clutch 32 and the timing pulley 33 are connected. This timing pulley 33 is connected via a timing belt 35 to a timing pulley 37 attached to one end of the first transmission shaft 36, and a sliding joint 38 is connected to the other end of the first transmission shaft 36. One end of the second power transmission shaft 39 is connected to the second power transmission shaft 39 . A timing pulley 40 attached to the other end of the second transmission shaft 39 is connected via a timing belt 41 to a timing pulley 43 attached to one end of the mold opening/closing output shaft 42. A base end of a mold opening/closing pole screw 44 is integrally connected to the other end of the opening/closing output shaft 42 .

Around the connecting part between the mold opening/closing output shaft 42 and the mold opening/closing pole screw 44, there is a cylinder body 46a and a collar part 46 formed on one end side of the cylinder body 46a.
b, and has an insertion hole 46c and the cylinder body 46a.
A bottomed cylindrical body 46 is loosely fitted into the through hole 45a of the end plate 45. Further, as shown in FIG. 3, between the inside of the cylindrical body 46 and the connecting part of the mold opening/closing output shaft 42, a thrust bearing 47 and a second pressure detector 48 are arranged in order from the bottom 46d side.
and the thrust bearing 49 is inside (output shaft 4 for mold opening/closing)
2 side), and two intervening members 50 and 51 are respectively arranged on the outside (cylindrical body 46 side),
A holding member 56 to which four radial bearings 52, 53, 54, and 55 are respectively mounted and screwed into the inside of the flange 46b of the cylindrical body 46, and an output shaft 42 for mold opening/closing located opposite to this holding member 56. It is fixed by a presser member 57 screwed into.
And each of the above bearings 47, 49, 52, 53, 5
4 and 55, a mold opening/closing output shaft 42 is rotatably supported by the end plate 45. Note that the second pressure detector 48 is a pressure sensor such as a strain gauge provided in a driving force transmission member that is interposed between the driving side and the driven side and transmits the driving force, and is a pressure sensor such as a strain gauge. (Tightening) It is a strain gauge type load converter that electrically converts pressure, and the cylindrical body 46
A fixing member 58 is inserted into the insertion hole 46c of the bottom 46d.
A seal member 59 is attached by.

The mold opening/closing pole screw 44 is attached to the mounting member 60.
It is screwed into a nut portion 60a at the base end of. Further, a moving plate 61 is provided at the tip of the mounting member 60.
The movable plate 61 is supported by a guide shaft 62 horizontally disposed between the fixed plate 2 and the end plate 45, and is configured to reciprocate in the horizontal direction. When the movable plate 61 is located closest to the fixed plate 2 side, the movable die 61a attached to the movable plate 61 and the fixed die 2b attached to the fixed plate 2 come into close contact with each other.
A cavity is formed inside from a and 2b. Further, an electromagnetic brake 63 is attached to the timing pulley 43 side of the end plate 45, and a suction plate 64 is disposed on the timing pulley 43 to face the electromagnetic brake 63. 63 is excited, the electromagnetic brake 63 and timing pulley 43 are connected, and the mold opening/closing output shaft 42
is becoming fixed. Also, at one end of this mold opening/closing output shaft 42, a mold opening/closing output shaft 4 is provided.
A mold position detection encoder (mold position detector) 65 is installed to detect the position of the movable mold 61a by detecting the rotation angle of the mold 61a.

The detection signals S ₁ , S ₂ , S ₃ , S ₄ from the injection position detector 23, the mold position detector 65, and the first and second pressure detectors 13, 48 are the speeds of the screw 4 and the movable mold 61a. , position, and pressure control, the state control mechanism 66 controls the DC motor 9 based on various speed, position, and pressure setting values input in advance.
A rotation command signal _S5 is output to the servo motor drive mechanism 67 that drives the AC servo motor 30, and a speed command signal _S6 and a torque limiter command signal _S7 are output to the servo motor drive mechanism 67 that drives the AC servo motor 30. For the sequence control mechanism (sequencer) 68 that controls the sequence (procedure), ejector retreat position signal, mold opening completion signal, mold closing completion signal, setting position signal, mold protection position signal, metering completion signal,
It is designed to output an internal pressure removal completion signal, etc. The sequence control mechanism 68 outputs excitation signals to the electromagnetic clutches 22 and 32, the electromagnetic brake 63, and the braking device of the DC motor 9 according to the signals, and also outputs excitation signals to the state control mechanism 66. The servo motor drive mechanism 67 outputs signals such as a mold closing command, a mold opening command, an injection command, a screw non-rotation backward command, a screw rotation command, a forward rotation pressure command, a mold protection command, and a reverse pressure command. Rotatable against, proportional control,
It is designed to output signals such as forward rotation prohibition and reverse rotation prohibition.

Further, the servo motor drive mechanism 67 drives the AC servo motor 30 in response to a rotation detection signal S ₈ from the rotation detector 31 and signals from the state control mechanism 66 and sequence control mechanism 67. The signal _S9 is output, and its outline will be explained based on FIG. 4.The speed command signal _S6 from the state control mechanism 66 is input to the speed control circuit 70 of the servo motor drive mechanism 67. This speed control circuit 70 receives the speed command signal.
_S6 is compared with the speed detection value (speed feedback value) calculated by the speed detection circuit 71 based on the rotation detection signal _S8 . The output signal of this speed control circuit 70, the rotation direction signal of the injection/mold opening/closing motor 30 detected by the rotation direction detection circuit 72 based on the rotation detection signal _S8 , and the current limit control circuit (amplifier) 73 are input. The current comparator circuit 74 to which the torque limiter command signal _S7 is inputted is configured to prevent the output value of the speed control circuit 70 from exceeding the output value of the current limit control circuit 73. The output value of the current comparison circuit 74 and the current value calculated by the current detection circuit 76 according to the output of the two detectors 75, 75 that detect the current of the injection/mold opening/closing motor 30 are connected to the current control circuit. 7
7, and based on the output value of the current control circuit 77, which is output according to the difference between the two, PWM
The control circuit 78 is configured to input a pulse width modulated pulse signal to the power transistor circuit 79. This power transistor circuit 79 is
The conduction timing of the transistor is controlled based on the pulse signal, and the direct current converted from the commercial frequency alternating current by the rectifier circuit 80 is passed through the power transistor circuit 79 to the PWM control circuit 7.
The AC servo motor 30 is supplied with alternating current of a predetermined frequency according to the pulse signal No.8.

Next, the operation of the pressure control device in the injection molding machine configured as described above will be explained.

First, prior to operation of the injection molding machine, various speeds, positions, and
Enter the pressure setting value. Next, the injection molding process is performed continuously, and one cycle of the process will be described in detail based on the operation chart shown in FIG.

The sequence control mechanism 68 demagnetizes the electromagnetic brake 63 that was energized at the end of one injection molding process, and also energizes the mold opening/closing electromagnetic clutch 32 to connect the AC servo motor 30 and the movable mold 61a side. At this time, the servo motor drive mechanism 67
The AC servo motor 30 is in a state where it can be rotated by the rotatable signal from the sequence control mechanism 68, and the brake device of the screw rotation motor 9 is excited by the sequence control mechanism 68. The screw rotation motor 9 does not rotate. In this state, when the mold closing start time t ₀ comes, the state control mechanism 66 transmits a speed command signal (voltage) S ₆ instructing the first mold closing speed to the servo motor drive mechanism in response to a command signal from the sequence control mechanism 68. 67, and also outputs a torque limiter command signal (negative voltage) _S7 that can output up to the maximum generated torque (300% value of the rated current of the AC servo motor 30). As a result, the servo motor drive mechanism 67 outputs the drive signal _S9 to the AC servo motor 30, so the AC servo motor 30 is feedback-controlled and
It rotates at a rotation speed based on the mold closing speed. At this time,
The current of AC servo motor 30 is 300% of the rated current
There are no restrictions until then. The rotation of the AC servo motor 30 is controlled by the joint 29, the drive shaft 27,
Mold opening/closing electromagnetic clutch 32, suction plate 34, timing pulley 33, timing belt 35, timing pulley 37, first transmission shaft 36, sliding joint 3
8. The mold opening/closing pole screw 44 is connected to the mold opening/closing output shaft 42 because it is transmitted to the mold opening/closing output shaft 42 via the second transmission shaft 39, timing pulley 40, timing belt 41, and timing pulley 43.
rotates, and the mounting member 60 into which the mold opening/closing pole screw 44 is screwed approaches the fixed plate 2 side. Therefore, the movable plate 61 attached to the mounting member 60 slides while being supported by the guide shaft 62, and the movable mold 61a attached to this movable plate 61 approaches the fixed mold 2b at the first mold closing speed. Note that when the AC servo motor 30 starts rotating, the injection electromagnetic clutch 22 is not excited, so the injection output shaft 21 does not rotate. As the mold opening/closing output shaft 42 rotates, this mold opening/closing output shaft 4
The mold position detector 65 attached to S 2 outputs a detection signal S ₂
is output to the state control mechanism 66, and the state control mechanism 66 compares the detection signal _S2 with a first position setting value that has been input in advance. As a result of this comparison, if the two match (at time t ₁ ),
Since the speed command signal (voltage) S ₆ that commands the second mold closing speed is output to the servo motor drive mechanism 67 instead of the first mold closing speed that has been output until now, the servo motor drive mechanism 67 is The servo motor 30 is subjected to feedback control and rotated at a rotation speed based on the second mold closing speed. As a result,
The movable mold 61a approaches the fixed mold 2b at the second closing speed instead of the first mold closing speed. Similarly, in the state control mechanism 66, the detection signal S ₂
As a result of comparing the second position setting value that has been input in advance, if the two match (at time t ₂ ), the third type closing speed command voltage is replaced with the second type closing speed command voltage that has been output until now. Since the state control mechanism 66 outputs the speed command signal (voltage) S ₆ that commands the closing speed to the servo motor drive mechanism 67, the servo motor drive mechanism 67 controls the AC servo motor 30.
is rotated at a rotational speed based on the third mold closing speed. Therefore, the movable mold 61a approaches the fixed mold 2b at the third mold closing speed instead of the conventional second mold closing speed.

Next, when the movable mold 61a reaches the mold protection position (at time _t3 ), the sequence control mechanism 68
outputs command signals to the state control mechanism 66 and servo motor drive mechanism 67, respectively.
The state control mechanism 66 outputs a limited torque limiter command signal (voltage) _S7 to the servo motor drive mechanism 67 based on the first pressure setting value input in advance. Then, the state control mechanism 66 compares the pressure detection value _S4 of the second pressure detector 48 for detecting the mold closing pressure with the first pressure set value, and based on the result, the state control mechanism 66
Since 6 controls the torque limiter command signal (voltage) _S7 , the current of the AC servo motor 30 is adjusted, and the mold closing force is controlled to a predetermined value by the torque generated in the AC servo motor 30. be done. Therefore, in the unlikely event that the movable mold 61a and the fixed mold 2b
Even if a molded product or the like is caught between the two, the mold will not be damaged because the mold closing force is suppressed to a predetermined value.

Furthermore, at time _t4 , the state control mechanism 66 receives a command signal from the sequence control mechanism 68.
Instead of the torque limiter command signal (voltage) _S7 which was limited based on the first pressure setting value, it was limited based on the second pressure setting value to ensure a predetermined mold clamping force. A torque limiter command signal (voltage) _S7 is output to the servo motor drive mechanism 67. And the second part detects the mold clamping pressure.
The state control mechanism 66 compares the pressure detection value of the pressure detector 48 and the second pressure set value, and based on the result, the state control mechanism 66 controls the torque limiter command signal (voltage) _S7. Therefore, by adjusting the current of the AC servo motor 30, the mold clamping force is maintained at a predetermined value by the torque generated in the AC servo motor 30. In this state, at time _t5 , the sequence control mechanism 68 excites the electromagnetic brake 63, so the mold opening/closing output shaft 42 is fixed, and the movable mold 61a is thereby moved to the fixed mold 2b for the predetermined mold clamping. It is firmly fixed in a close contact state by force. After this, at time t ₆ , the sequence control mechanism 68
According to the command signal from the state control mechanism 66,
The output of the speed command signal (voltage) S ₆ that commands the third mold closing speed is stopped, the mold opening/closing electromagnetic clutch 32 is demagnetized, and the AC servo motor 30 is demagnetized.
The connection between the servo motor 30 and the movable mold 61a side is cut off, and the injection electromagnetic clutch 22 is energized, so that the AC servo motor 30 and the screw 4 side are connected.

Subsequently, in this state, at injection start time t ₇ , the state control mechanism 66 receives a command signal from the sequence control mechanism 68 to control the speed command signal (voltage) S ₆ that commands the first injection speed and the maximum generated torque. Torque limiter command signal (positive voltage) that can output up to (300% value of rated current of AC servo motor 30)
_S7 is output to the servo motor drive mechanism 67. As a result, the servo motor drive mechanism 67 outputs the drive signal _S9 to the AC servo motor 30, so that the AC servo motor 30 is feedback-controlled and rotates at a rotational speed based on the first injection speed. The rotation of the AC servo motor 30 is controlled by the joint 29, the drive shaft 27, and the timing pulley 2.
8, timing belt 26, timing pulley 2
4. Since it is transmitted to the injection output shaft 21 via the adsorption plate 25 and the injection electromagnetic clutch 22, the injection pole screw 20 connected to the injection output shaft 21 rotates, and the injection pole screw 20 is screwed into the injection pole screw 20. The movable member 19 is moved forward toward the fixed plate 2. Therefore,
The spline shaft 5 connected to the movable member 19 and the screw 4 connected to the spline shaft 5 move forward at the first injection speed, and the resin that has been plasticized in the injection cylinder 1 in advance is injected into the mold. start.
As the injection output shaft 21 rotates, the injection position detector 23 attached to the injection output shaft 21
outputs the detection signal S ₁ to the state control mechanism 66, and the state control mechanism 66 compares the detection signal S ₁ with a first injection position setting value inputted in advance. As a result of this comparison, if the two match (at time t ₈ ), the second injection speed will be set instead of the first injection speed that has been output until now, and the detection signal S ₁ and the second injection position will be set. When the values match (at time t ₉ ), the third injection speed replaces the second injection speed.
Furthermore, when the detection signal _S1 and the third injection position set value match (at time _t10 ), the fourth injection speed is changed in place of the third injection speed.
Since the speed command signal (voltage) S ₆ for each command is output from the state control mechanism 66 to the servo motor drive mechanism 67, the servo motor drive mechanism 6
7 performs feedback control on the AC servo motor 30 to rotate it at a rotational speed based on the second, third, and fourth injection speeds, respectively. Therefore, the screw 4 moves forward based on each speed and continues to supply the resin that has been plasticized into the injection tube 1 into the mold. Further, when the detection signal S ₁ and the fourth injection position set value match (at time t ₁₁ when the injection speed is switched to the injection pressure reference), the state control mechanism 6
6 is a fourth
Outputs a speed command signal (voltage) S ₆ that commands the speed at holding pressure instead of the injection speed, and also outputs a torque limiter command signal (voltage) S that is limited based on the first holding pressure setting value input in advance. Outputs ₇ . Then, the state control mechanism 66 compares the pressure detection value _S3 of the first pressure detector 13 that detects the holding force with the first holding force setting value, and based on the result, the state control mechanism 66 Since the torque limiter command signal (voltage) _S7 is controlled, the holding force is maintained at the first holding force setting value by the torque generated in the AC servo motor 30 by adjusting the current of the AC servo motor 30. be done.

Further, the state control mechanism 66 operates based on the second holding force set value instead of the first holding force set value at time _t12 , and based on the second holding force set value at time _t13 . Instead, the torque limiter command signal (voltage) _S7 is controlled based on the third holding force setting value so that the detected pressure value _S3 matches each holding force setting value. As a result, due to the torque generated in the AC servo motor 30 by adjusting the current of the AC servo motor 30,
Since the holding pressure is maintained at a predetermined value, reliable and stable holding pressure control is performed, and a high-quality molded product is molded.

Next, when the injection process is completed (at time _t14 ), the state control mechanism 66 receives a command signal from the sequence control mechanism 68, which has been previously input with the pressure detection value _S3 of the first pressure detector 13. It compares the back pressure setting value and controls the speed command signal (voltage) _S6 based on the result, and outputs a predetermined torque limiter command signal (voltage) _S7 . Therefore, the servo motor drive mechanism 67 controls and rotates the AC servo motor 30 based on the signals S ₆ and S ₇ so that a back pressure corresponding to the set back pressure value is applied to the screw 4. It will be adjusted. Further, the sequence control mechanism 68 demagnetizes the brake device of the screw rotation motor 9 that has been energized until now, and makes the screw rotation motor 9 rotatable, and then at time _t15 , the state control mechanism 66 The screw rotation motor 9 is rotated by a rotation command signal S from the screw rotation motor 9. As a result, the rotating member 5a rotates via the timing pulley 10, timing belt 8, and timing pulley 7, and the screw 4 further rotates via the spline shaft 5, so that the resin is discharged from the hopper 3 into the injection tube 1. supply,
Injection tube 1 until plasticization starts and reaches time t ₁₆ .
While resin is supplied into the mold and plasticized, the resin molded product filled in the mold is cooled. As a result, as the resin is supplied into the injection cylinder 1 and plasticized,
The screw 4 retreats, but at this time, the moving speed is controlled so that back pressure is applied to the screw 4 based on the above-mentioned back pressure setting value, so that the resin in the injection tube 1 is kneaded to a predetermined level. kept in condition. Then, at time t ₁₆ , the sequence control mechanism 6
According to the command signal from 8, the state control mechanism 66
Since the speed command signal (voltage) S ₆ and the torque limiter command signal (voltage) S ₇ based on the pre-input setting values are output to the servo motor drive mechanism 67, the servo motor drive mechanism 67 operates as an AC servo. The motor 30 is subjected to feedback control and rotated in the reverse direction at a rotation speed based on a set value.
Therefore, the screw 4 starts moving backward at a moving speed based on the set value, the state control mechanism 66 stops the rotation of the screw rotation motor 9, and the sequence control mechanism 68 causes the screw rotation motor 9 to stop rotating. Since the brake device 9 is energized, the screw rotation motor 9 has its rotating shaft 9a.
is fixed, so that the screw 4 moves backward without rotating. When the internal pressure of the injection cylinder 1 is completely removed (at time _t17 ), the injection electromagnetic clutch 22 is demagnetized by a command signal from the sequence control mechanism 68, and the AC servo motor 30 stops rotating. Screw 4 stops retreating.

Next, when the supply (cooling) process is completed and the mold opening (pause) process begins (at time _t18 ), the sequence control mechanism 68 first demagnetizes the electromagnetic brake 63 that has been energized until now, and Since the mold opening/closing electromagnetic clutch 32 is energized, the AC servo motor 3
0 and the movable mold 61a side are connected. In this state, at time _t19 , the sequence control mechanism 68
In response to the command signal from , the state control mechanism 66 outputs a speed command signal (voltage) S ₆ that commands the first mold opening speed to the servo motor drive mechanism 67 . As a result, the AC servo motor 30 rotates in the normal rotation direction at a rotation speed based on the first mold opening speed, so that the movable mold 61a rotates at the fixed mold 2b at the first mold opening speed.
start to move away from Next, when the first mold opening setting position is reached (at time _t20 ), the state control mechanism 66
is a speed command signal (voltage) S ₆ that commands the second mold opening speed instead of the first mold opening speed, and when the second mold opening setting position is reached (at time t ₂₁ ), the second mold opening speed is A speed command signal (voltage) _S6 that commands the third mold opening speed instead of the speed is output to the servo motor drive mechanism 67, respectively. As a result, the AC servo motor 30 rotates at the number of revolutions based on the second and third mold opening speeds, so the movable mold 61a rotates at the second mold opening speed (from time t ₂₀ to t ₂₁ ) or Fixed mold 2b at the third mold opening speed (between time t ₂₁ and t ₂₂ )
move away from Then, at time _t22 , the mold opening/closing electromagnetic brake 63 is excited by the command signal from the sequence control mechanism 68, and the speed command signal _S6 is invalidated, so that the movable mold 61a stops. Next, the mold opening/closing electromagnetic clutch 32 is demagnetized to complete one cycle of the injection molding process.

<Effects of the Invention> As explained above, the first invention of the present application includes a servo motor that opens and closes a mold and moves an injection screw, and a mold position detector that detects the position of the mold. , an injection position detector for detecting the position of the screw, and according to the output of the mold position detector,
The pressure in the mold closing process is controlled by limiting the current flowing through the servo motor, and the current flowing through the servo motor is limited in accordance with the output of the injection position detector. In a pressure control device for an injection molding machine that controls pressure in the process, elastic deformation of a driving force transmission member interposed in a drive mechanism that moves the screw back and forth is measured at the base end of the screw to determine the driving side and driven side. A control mechanism is provided that includes a pressure detector that measures the pressure acting between the two sides, and compares the pressure detected by the pressure detector with a predetermined pressure setting value to control the torque generated by the servo motor. With this configuration, the force acting on the screw can be directly detected, greatly reducing control errors such as play and bumps inherent in the screw drive mechanism from the screw to the servo motor, and distortion and deflection of the connecting members that transmit the driving force. Since there are no factors causing this, the control feedback loop becomes shorter and more accurate control is achieved. Therefore, the holding force can be suitably and finely controlled in the injection process, and the resin can be smoothly and sufficiently supplied to the cavity in the mold. Therefore, the quality of the products formed in the mold can be easily maintained, and even when precision molded products are continuously injection molded, the quality of the molded products is stable and there is no possibility of defective products. can reduce the occurrence of

In addition, the second invention of the present application opens and closes the mold,
and a servo motor for moving an injection screw, a mold position detector for detecting the position of the mold, and an injection position detector for detecting the position of the screw, and according to the output of the mold position detector. By limiting the current flowing to the servo motor, the pressure in the mold closing process is controlled.
In a pressure control device for an injection molding machine that controls the pressure in the injection process by limiting the current flowing to the servo motor according to the output of the injection position detector, the drive mechanism that opens and closes the mold is controlled. A pressure detector is provided to measure the pressure acting between the driving side and the driven side by measuring the elastic deformation of the intervening driving force transmission member, and the pressure detected by the pressure detector and a predetermined pressure setting value are In comparison, since the structure includes a control mechanism for controlling the torque generated by the servo motor, the pressure applied to the mold when the mold is opened and closed can be directly detected. As a result, control can be performed without factors that increase control errors such as play and backlash inherent in the drive mechanism that opens and closes the mold, and deflection of the drive force transmission member, so the control feedback loop is shortened. More precise control is achieved. Therefore, in each process of injection molding,
It is possible to check not only the position but also the pressure force data on the mold, and based on this data, it is possible to accurately adjust the mold closing force when closing the mold, and it is also possible to apply a predetermined mold clamping force. This prevents accidents such as mold damage and contributes to the molding of high-quality products.

[Brief explanation of the drawing]

1 to 5 show an embodiment of the present invention, in which FIG. 1 is a schematic diagram of the entire device, FIG. 2 is a sectional view of the mounting part of the first pressure detector, and FIG. FIG. 4 is a block diagram illustrating the main parts of the servo motor drive mechanism, and FIG. 5 is an operation chart. 2b... Fixed type, 4... Screw, 13...
First pressure detector, 23... Injection position detection encoder (injection position detector), 30... Injection/mold opening/closing motor (AC servo motor), 48... Second pressure detector, 61a... Mobile type , 65...Mold position detection encoder (mold position detector), 66...State control mechanism, _S3 , _S4 ...Detection signal (pressure detection value).

Claims (1)

[Scope of Claims] 1. A servo motor that opens and closes the mold and moves an injection screw, a mold position detector that detects the position of the mold, and an injection position detector that detects the position of the screw. Controls the pressure in the mold closing process by limiting the current flowing to the servo motor according to the output of the mold position detector, and according to the output of the injection position detector, In a pressure control device for an injection molding machine that controls the pressure in the injection process by limiting the current flowing through the servo motor, a drive mechanism is provided at the base end of the screw that moves the screw back and forth. A pressure detector is provided to measure the pressure acting between the driving side and the driven side by measuring the elastic deformation of the force transmitting member, and the pressure detected by the pressure detector and a predetermined pressure setting value are set. In comparison, a pressure control device for an injection molding machine is provided with a control mechanism for controlling the torque generated by the servo motor. 2. A servo motor that opens and closes the mold and moves an injection screw, a mold position detector that detects the position of the mold, and an injection position detector that detects the position of the screw, The pressure in the mold closing process is controlled by limiting the current flowing through the servo motor according to the output of the position detector, and the current flowing through the servo motor according to the output of the injection position detector is controlled. In a pressure control device for an injection molding machine that controls the pressure in the injection process by limiting the A pressure detector is provided to measure the pressure acting between the driven sides, and the pressure detected by the pressure detector is compared with a predetermined pressure setting value to control the torque generated by the servo motor. A pressure control device for an injection molding machine, characterized by being provided with a control mechanism.