JPH0446213B2 - - Google Patents

Description

Detailed Description of the Invention [Industrial Application Field] The present invention is directed to an electric injection molding machine in which the pressure (maintenance) applied to the resin in the mold via a screw during the process of supplying resin to the mold and solidifying it is The present invention relates to a pressure control device in an electric injection molding machine that controls the pressure (back pressure) applied to a rotating screw when supplying resin into an injection cylinder and plasticizing it.

[Prior Art] In recent years, injection molding machines equipped with electric drive devices have been used. This electric injection molding machine has advantages over the conventional hydraulically driven type in that it is easy to control, can be controlled precisely, and the device is simple and easy to handle. By the way, in such an injection molding machine, the mold closing pressure in the mold closing process, the injection pressure in the injection process, the mold clamping pressure, the holding pressure in the solidifying process, etc. are controlled to prevent excessive force from being applied to the mold during mold clamping. In addition to protecting the mold and maintaining a predetermined mold clamping force when injecting resin into the mold, it also supplies enough resin into the mold and protects the mold. The pressure applied to the mold is maintained at a predetermined value to maintain good quality of the product molded within the mold. As a control device for this purpose, one shown in FIG. 5 is used. This device uses an electric servo motor 82 that moves an injection screw 81.
and a motor 83 for screw rotation, and the rotational output of this electric servo motor 82 is transmitted to an injection ball screw 87 via a timing pulley 84, a timing belt 85, and a timing pulley 86.
The movable member 8 screwed into this ball screw
8, the screw 81 is moved back and forth. Then, the electric servo motor 82 is driven according to a preset program and the torque of the electric servo motor 82 is controlled to obtain a predetermined pressure inside the mold or injection cylinder.

[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 when continuously repeating molding with an injection molding machine. However, in the above-mentioned device, a ball screw is interposed between the electric servo motor and the screw, making it difficult to control with high precision. In addition, instead of this open control method, a method of interposing a load cell or the like between the screw and the movable member to detect the back pressure of the screw and then controlling the electric servo motor in a closed manner based on that value can be considered. There was a problem that the structure of the load cell mounting part became complicated and the cost increased.

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention converts the rotational output of an electric motor into linear motion via a moving mechanism, and In a pressure control device for an electric injection molding machine that moves the screw in the axial direction and injects the resin in the injection cylinder into the mold, there is a fluid pressure cylinder and this fluid between the moving mechanism and the screw. A pressure receiving mechanism consisting of a piston fitted into a pressure cylinder is provided, a fluid pressure detector is provided in this pressure receiving mechanism, and the detection value of this fluid pressure detector is compared with a preset pressure value to control the injection motor. It is equipped with a control device that controls the

[Function] In such a pressure control device, a pressure detector attached to a fluid pressure cylinder interposed between the screw and the moving mechanism detects the pressure applied to the resin in the mold, and controls the solidification process of the resin. The pressure inside the mold (holding pressure) during plasticization and the pressure inside the injection cylinder during plasticizing resin (back pressure) are detected accurately and without delay, and the injection motor is controlled according to the detected values, allowing the screw The required pressure is applied.

[Embodiment] An embodiment of the present invention will be described below with reference to FIGS. 1 to 4.

First, the structure of the present invention will be described with reference to the mechanism diagram in FIG. 1 and the actual diagram in FIG. 2.

The injection molding machine is composed of an injection device 1 and a mold clamping device 2, and the injection device 1 is connected to four tie bars 3 that connect a front fixed plate and a rear fixed plate (both not shown) that are erected facing each other. Supported. The front fixed plate is provided with a hopper 4 for supplying materials at the top,
An injection cylinder 5 is inserted and fixed in the center, and a material supply path 5a is formed between the two. A screw 6 is inserted into the injection cylinder 5 so as to be movable back and forth in the axial direction and rotatable around the axis.
A movable member 7 for rotating the screw 6 and moving it back and forth is slidably supported on the tie bar 3. This movable member 7
is a structure in which two plate-like members 7a and 7b are connected by a cylindrical member 8 that is externally mounted on the tie bar 3, and the base end of the screw shaft 6a provided on the rear end side of the screw 6 is located in the center of the cylindrical member 8. A cylindrical support member 9 containing the portion 6b is attached, and a ball screw mechanism 10 for moving the movable member 7 back and forth is provided between the movable member 7 and the rear fixed plate. This ball screw mechanism 10 includes the movable member 7
It consists of a cylindrical nut part 12 fixed to a mounting plate 11 fixed in parallel with the plate members 7a and 7b at the rear of the cylindrical nut part 12, and an injection ball screw 13 screwed into this cylindrical nut part 12. The rear end of the ball screw 13 is fixed to the injection output shaft 14. This output shaft 14 for injection is rotatably supported by the rear fixed plate, and an electromagnetic clutch 15 for injection is attached to the other end of the output shaft 14 for injection. An injection position detection encoder (injection position detector) 16 is installed to detect the axial position of the screw 6 by detecting the position. Further, a timing pulley 17 is rotatably attached to the injection output shaft 14 between the rear fixed plate and the injection electromagnetic clutch 15, and a timing pulley 17 is attracted to the injection electromagnetic clutch 15 side. The plates 17a are integrally connected, and when the injection electromagnetic clutch 15 is energized, the injection electromagnetic clutch 15 and the timing pulley 17 are connected. This timing pulley 17 is connected via a timing belt 18 to a timing pulley 20 attached to one end of a drive shaft 19, and the other end of the drive shaft 19 is connected via a joint 21 to a motor for injection/mold opening/closing. (AC electric servo motor) 22 is connected to one end of a rotating shaft 22a protruding from both ends thereof. A motor rotation detection encoder (rotation detector) 23 for detecting the rotation of the injection/mold opening/closing motor 22 is provided at the other end of the rotating shaft 22a. These, movable member 7, ball screw mechanism 10, injection output shaft 14, timing pulley 1
7, 20, the timing belt 18, the drive shaft 19, and the joint 21 constitute a moving mechanism A that moves the screw 6 back and forth.

Bushes 24a and 24b are fixed to the screw shaft base end 6b installed in the support member 9,
Around the bush 24b, a pair of thrust bearings 25a and 25b are arranged with the protrusion 24c of the bush 24b in between.
is fitted externally, and these thrust bearings 25a, 2
5b is installed inside the support member 9 so as to be freely movable in the axial direction. On the other hand, presser plates 26 and 27 are attached to both ends of the support member 9, respectively, and the presser plate 26 on the screw 6 side abuts the thrust bearing 25a, and the presser plate 27 on the opposite side is attached to the inner side of the support member 9. A protruding annular convex portion 27a is formed. A pressing member 28 is movably fitted in a space between the thrust bearing 25b in the support member 9 and the convex portion 27a. This pressing member 28 is formed with an annular groove 28a that fits into the convex portion 27a.
A gap S is formed between the groove 28a and the groove 28a, and the pressing member 28 can move freely in the axial direction within the support member 9 by the width of the gap S. A recess 28b is formed.

On the other hand, a cylinder 29 that opens toward the pressing member 28 is fixed to the surface of the mounting plate 11 facing the pressing member 28, and a piston 30 is slidably fitted into the cylinder 29. and the piston 30 constitute a pressure receiving mechanism B. A screw hole 30a is formed in this piston 30, into which a connecting bolt 31 is screwed, and the top portion 31a of this connecting bolt 31 is inserted into the recess 28 of the pressing member 28.
It has a curved surface shape corresponding to b and is in contact with the recess 28b, and by gripping and rotating the screw head 31b, the relative distance between the piston 30 and the cylinder 29 is changed, and the screw is applied from the cylinder 29 to the piston 30. The preload can be adjusted.
The inner chamber 29a of the cylinder 29 is sealed and filled with oil, and is provided with a pressure detector 32 for detecting the oil pressure in the inner chamber 29a. In addition, a screw rotation motor (DC motor) 3 is mounted on the upper part of the movable member 7.
3 is installed, and the timing pulleys 34, 35
The screw shaft 6a is rotated via a timing belt 36. This screw rotation motor 33 has a built-in brake device, and this brake device is energized to fix the rotating shaft 33a of the screw rotation motor 33.

An electromagnetic clutch 37 for opening and closing the mold is attached to the intermediate portion of the drive shaft 19. A timing pulley 38 is attached to the drive shaft 19 between the mold opening/closing electromagnetic clutch 37 and the timing pulley 20 so as to be relatively rotatable, and the mold opening/closing electromagnetic clutch 37 of the timing pulley 38
A suction plate 39 is integrally connected to the side,
When the mold opening/closing electromagnetic clutch 37 is energized, the mold opening/closing electromagnetic clutch 37 and the timing pulley 38 are connected. This timing pulley 38 is connected via a timing belt 40 to a timing pulley 42 attached to one end of a first transmission shaft 41, and a sliding joint 43 is connected to the other end of the first transmission shaft 41. via the second transmission shaft 44
are connected at one end. A timing pulley 45 attached to the other end of the second transmission shaft 44
However, the timing pulley 4 attached to one end of the mold opening/closing output shaft 47 via the timing belt 46
8, and the output shaft 4 for opening and closing the mold.
7 is rotatably supported by the end plate 50. Further, a base end portion of a ball screw 49 for mold opening/closing is integrally connected to the other end of the output shaft 47 for mold opening/closing.

The mold opening/closing ball screw 49 is attached to the mounting member 60
It is screwed into a nut portion 60a at the base end of. Further, a movable plate 61 is provided at the tip of the mounting member 60.
is attached, and this movable platen 61 is supported by a guide shaft 62 horizontally arranged between the fixed platen 51 and the end plate 50 of the mold clamping device 2, so that it can reciprocate in the horizontal direction. ing. A movable mold 61 attached to the movable plate 61
A and a fixed mold 51a attached to a fixed platen 51 are in close contact with each other, so that a cavity is formed inside by both molds 61a and 81a. Further, an electromagnetic brake 63 is attached to the timing pulley 48 side of the end plate 50, and a suction plate 64 is disposed on the timing pulley 48 to face the electromagnetic brake 63. When 63 is excited, the electromagnetic brake 63 and timing pulley 48 are connected, and the mold opening/closing output shaft 47 is fixed. Further, at one end of the mold opening/closing output shaft 47, there is a mold position detecting encoder (mold position detector) that detects the position of the movable mold 61a by detecting the rotation angle of the mold opening/closing output shaft 47.
65 is installed.

the injection position detector 16, the mold position detector 65,
and detection signals S ₁ , S ₂ , S ₃ from the pressure detector 32
is the speed of the screw 6 and the moving mold 61a,
By inputting the input to the state control mechanism 66 that performs position and pressure control, the state control mechanism 66 issues a rotation command signal S to the DC motor 33 based on various speed, position, and pressure setting values input in advance. ₅ , and outputs a speed command signal S ₆ and a torque limiter command signal S ₇ to the servo motor drive mechanism 67 that drives the AC servo motor 22, and also outputs the overall sequence (procedure) of the injection molding process. ) to the sequence control mechanism (sequence) 68 that controls the ejector retraction position signal,
It outputs a mold opening completion signal, a mold closing completion signal, a setting position signal, a mold protection position signal, a measurement completion signal, an internal pressure removal completion signal, etc. The sequence control mechanism 68 outputs excitation signals to the electromagnetic clutches 15 and 37, the electromagnetic brake 63, and the braking device of the DC motor 33 in accordance with the signals, and also outputs excitation signals to the state control mechanism 66. , mold closing command, mold opening command, injection command,
Screw non-rotating backward command, screw rotation command,
Outputs signals such as forward rotation pressure command, mold protection command, reverse rotation pressure command, etc., and also operates the servo motor drive mechanism 6.
7, signals such as rotatable, proportional control, forward rotation prohibited, reverse rotation prohibited, etc. are output.

Further, the servo motor drive mechanism 67 drives the AC servo motor 22 in accordance with the rotation detection signal S ₈ from the rotation detector 23 and each signal from the state control mechanism 66 and the sequence control mechanism 68. The signal _S9 is output, and its outline will be explained based on FIG. 3.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 22 detected by the rotation direction detection circuit 72 based on the rotation detection signal _S8 , and the current limiting 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 this current comparison circuit 74 and the current value calculated by the current detection circuit 76 according to the output of two detectors 75, 75 that detect the current of the injection/mold opening/closing motor 22 are connected to the current control circuit. 77
The PWM control circuit 78 inputs a pulse width modulated pulse signal to the power transistor circuit 79 based on the output value of the current control circuit 77 which is input to the current control circuit 77 and output according to the difference between the two. There is. This power transistor circuit 79 is configured to limit the conduction timing of the transistor based on the pulse signal, and the direct current exchanged from the commercial frequency alternating current in the rectifier circuit 80 is controlled by the power transistor circuit 79 to control the PWM control. According to the pulse signal of the circuit 78, the alternating current of a predetermined frequency is exchanged and supplied to the alternating current servo motor 22.

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

First, prior to operation of the injection molding machine, various speed, position, and pressure setting values are input in advance to the state control mechanism 66. 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, which was energized at the end of one injection molding process, and energizes the mold opening/closing electromagnetic clutch 37 to connect the AC servo motor 22 and the movable mold 61a. At this time, the servo motor drive mechanism 67
The AC servo motor 22 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 33 is excited by the sequence control mechanism 68. The screw rotation motor 33 does not rotate. In this state, when the mold closing start time t ₀ comes, the state control mechanism 66 starts the first
A speed command signal (voltage) _S6 that commands the mold closing speed is output to the servo motor drive mechanism 67, and a torque limiter command signal (negative Voltage) Outputs _S7 . This results in
Servo motor drive mechanism 67 is AC servo motor 2
2, the AC servo motor ₂₂ is feedback-controlled in the reverse direction and rotates at a rotational speed based on the first mold closing speed. At this time, the current of the AC servo motor 22 is not limited to 300% of the rated current. The rotation of the AC servo motor 22 is caused by the joint 21,
Drive shaft 19, mold opening/closing electromagnetic clutch 37, suction plate 39, timing pulley 38, timing belt 40, timing pulley 42, first transmission shaft 41,
The mold opening/closing ball screw 49 connected to the mold opening/closing output shaft 47 is transmitted through the sliding joint 43, second transmission shaft 44, timing pulley 45, timing belt 46, and timing pulley 48 to the mold opening/closing output shaft 47. rotates, and the mounting member 60 into which the mold opening/closing ball screw 49 is screwed approaches the fixed platen 51 side. Therefore, the movable platen 61 attached to the mounting member 60 slides while being supported by the guide shaft 62, and the movable die 61a attached to the movable platen 61 approaches the fixed die 51a at the first mold closing speed. Note that when the AC servo motor 22 starts rotating, the injection electromagnetic clutch 15 is not excited, so the injection output shaft 14 does not rotate. Then, as the mold opening/closing output shaft 47 rotates,
The mold position detector 65 attached to the mold opening/closing output shaft 47 outputs the detection signal S ₂ to the state control mechanism 66, and the state control mechanism 66 receives the detection signal S ₂
and a first position setting value that has been input in advance. As a result of this comparison, if the two match (time
t ₁ ), a speed command signal (voltage) S ₆ that commands the second mold closing speed replaces the speed command signal (voltage) S ₆ that commands the first mold closing speed that has been output until now.
is output to the servo motor drive mechanism 67, so the servo motor drive mechanism 67 performs feedback control on the AC servo motor 22 to rotate it at a rotational speed based on the second mold closing speed. As a result,
The movable mold 61a approaches the fixed mold 51a at the second mold closing speed instead of the first mold closing speed. Similarly, in the state control mechanism 66, the detection signal
As a result of comparing S ₂ with the second position setting value that has been input in advance, if the two match (at time t ₂ ), the third mold closing speed is changed to the second mold closing speed that has been output until now. It approaches the fixed mold 51a at high 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 sends a limited torque limiter command signal (voltage) S ₇ to the servo motor drive mechanism 67 based on a first pressure setting value inputted in advance.
Output for. As a result, the current of the AC servo motor 22 is limited, and the current of the AC servo motor 22 is limited.
Since the torque generated in step 2 is suppressed, even if a molded product or the like is caught between the movable mold 61a and the fixed mold 51a, the mold will not be damaged because the mold closing force is kept low. do not have.

Furthermore, at time t ₄ , the sequence control mechanism 6
According to the command signal from 8, the state control mechanism 66
Instead of the torque limiter command signal (voltage) _S7 that has been limited up to now, a torque limiter command signal (voltage) _S7 that allows the current of the AC servo motor 22 up to 300% is output to the servo motor drive mechanism 67. As a result, the AC servo motor 22
The generated torque returns to its original state again, and the predetermined mold clamping force is ensured. In this state, at time t ₅ ,
Since the sequence control mechanism 68 excites the electromagnetic brake 63, the mold opening/closing output shaft 47 is fixed.
As a result, the movable mold 61a is firmly fixed to the fixed mold 51a in close contact with the fixed mold 51a by the predetermined mold clamping force. After that, at time t ₆ , the state control mechanism 66 stops outputting the speed command signal (voltage) S ₆ that commands the third mold closing speed according to the command signal from the sequence control mechanism 68 . , the injection electromagnetic clutch 15 is energized, and the AC servo motor 22 and the screw 6 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 22) S ₇
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 22, so that the AC servo motor 22 is feedback-controlled and rotates at a rotational speed based on the first injection speed. The rotation of the AC servo motor 22 is
Joint 21, drive shaft 19, timing pulley 20,
timing belt 18, timing pulley 17,
It is transmitted to the injection output shaft 14 via the suction plate 17a and the injection electromagnetic clutch 15, so that the injection output shaft 1
The injection ball screw 13 connected to 4 rotates,
The movable member 11 into which the injection ball screw 13 is screwed is advanced toward the mold clamping device 2 side. Therefore, the cylinder 29 fixed to the movable member 11 moves forward,
The oil in the inner chamber 29a presses the piston 30, the screw 6 moves forward at the first injection speed, and the resin that has been plasticized in the injection cylinder 5 in advance begins to be injected into the mold. Then, the injection position detector 16 attached to the injection output shaft 14 outputs the detection signal S ₁ to the state control mechanism 66, and the state control mechanism 66 receives the detection signal S ₁ and the state control mechanism 66 that has been inputted in advance. Compare with the injection position setting value of No.1. 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 is set in place of the second injection speed, and the detection signal
When S ₁ and the third injection position setting value match (time
t ₁₀ ), a speed command signal (voltage) that commands the fourth injection speed instead of the third injection speed.
_S6 is output from the state control mechanism 66 to the servo motor drive mechanism 67, so the servo motor drive mechanism 67 performs feedback control on the AC servo motor 22 to achieve the second, third, and fourth injection speeds, respectively. Rotate at a rotation speed based on . Therefore,
The screw 6 moves forward based on each speed and continues to supply the plasticized resin into the injection cylinder 5 into the mold. At time _t11 , when the detection signal _S1 and the fourth injection position set value match, injection speed control is switched to injection pressure control, and then to holding pressure control. During the pressure holding process, the state control mechanism 66 is activated by a command signal from the sequence control mechanism 68.
outputs a predetermined torque limiter command signal (voltage) _S7 that improves responsiveness when pressure holding is performed in accordance with the sequence. And the state control mechanism 6
6 compares the first holding pressure setting value input in advance with the pressure detection value S ₃ of the pressure detector 32 and outputs a speed command signal (voltage) S ₆ , thereby controlling the servo motor drive mechanism 67 is AC servo motor 22
is rotated until the pressure detection value _S3 of the pressure detector 32 matches the first holding pressure setting value.

Further, at time _S12 , the state control mechanism 66 replaces the first holding force setting value with a second holding force setting value, and at time _t13 , changes the holding force setting value to the second holding force setting value. Instead, the third holding pressure setting value is
A speed command signal (voltage) _S6 is output by comparing the pressure detection value _S3 of the pressure detector 32, and the AC servo motor 22 is rotated until each setting value matches the pressure detection value _S3 . 6. Performs pressure (holding pressure) control. As a result, the holding forces are maintained at respective predetermined values and reliably suppressed, and a high-quality molded product is molded.

Next, when the injection process is completed (at time _t14 ), the state control mechanism 66 controls the pressure detector 3 according to a command signal from the sequence control mechanism 68.
The detected pressure value S ₃ of Step 2 is compared with a back pressure set value input in advance to control the speed command signal S 6 and also to control the speed command signal S ₆ to a predetermined torque limiter command signal (voltage) S ₇
Output. Therefore, the servo motor drive mechanism 67
The AC servo motor 22 is controlled and rotated based on the respective signals S ₆ and S ₇ to adjust the back pressure applied to the screw 6 in accordance with the set back pressure value. Further, the sequence control mechanism 68 demagnetizes the brake device of the screw rotation motor 33 that has been energized up to now, and demagnetizes the screw rotation motor 33.
After making the rotatable state possible, at time _t15 , the screw rotation motor 33 is rotated by a rotation command signal _S5 from the state control mechanism 66. As a result, the timing pulley 34 and the timing belt 3
6. The screw shaft 6a rotates via the timing pulley 35, and the supply of resin from the hopper 4 into the injection cylinder 5 and plasticization are started, and the resin is supplied into the injection cylinder 5 until time _t16 . While being plasticized, the resin molded product filled in the mold is cooled. As a result, the screw 6 retreats as the resin is supplied into the injection cylinder 5 and plasticized, but at this time, the screw 6 is controlled to have a back pressure so that a back pressure based on the above-mentioned back pressure setting value is applied. Since this is controlled, the resin in the injection tube 5 is maintained in a predetermined kneaded state. Then, at time _t16 , the state control mechanism 6 is activated by a command signal from the sequence control mechanism 68.
6 outputs a speed command signal (voltage) S ₆ based on a pre-input setting value and a torque limiter command signal (voltage) S ₇ to the servo motor drive mechanism 67. controls the AC servo motor 22 in a feedback manner,
Rotate in the reverse direction at a rotation speed based on the set value. Therefore, the screw 6 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 33, and the sequence control mechanism 68
Since the brake device of the screw rotation motor 33 is excited, the screw rotation motor 33 fixes its rotating shaft 33a, and thereby the screw rotation motor 33 fixes its rotating shaft 33a.
moves backwards without rotating. When the internal pressure of the injection cylinder 5 is completely removed (at time _t17 ), the injection electromagnetic clutch 15 is demagnetized by a command signal from the sequence control mechanism 68, and the AC servo motor 22 stops rotating. Screw 6 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 37 is energized, the AC servo motor 2
2 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, the state control mechanism 66 outputs a speed command signal (voltage) _S8 that commands the first mold opening speed to the servo motor drive mechanism 67. As a result, the AC servo motor 22 rotates in the forward direction.
Since the movable mold 61a rotates at a rotational speed based on the first mold opening speed, the fixed mold 51a rotates at the first mold opening speed.
Starts to move away from a. Next, when the first mold opening setting position is reached (at time _t20 ), the state control mechanism 66
is a speed command signal (voltage) _S6 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 _t21 ), 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 22 rotates at a rotation speed based on the first, second, and third mold opening speeds, so that the movable mold 61a can
It leaves the fixed mold 51a at the second mold opening speed (between time _t20 and _t21 ) or at the third mold opening speed (between time _t21 and _t22 ). Then, at time _t22 , a command signal from the sequence control mechanism 68 causes
The electromagnetic brake 63 for opening and closing the mold is energized and the speed command signal _S6 is invalidated, so the movable mold 61a stops. Next, the electromagnetic clutch 37 for opening and closing the mold is demagnetized, and one cycle of the injection molding process is completed.

Note that when pressure is applied to the cylinder 29, the positions of the timing pulleys 34 and 35 shift by the amount of compression in the inner chamber 29a of the cylinder 29, but this shift is absorbed by the timing belt 36, and the rotation is transmitted. will not be hindered. In this process, the reaction force that the screw 6 receives from inside the molds 51a, 61a or from inside the injection tube 5 (the pressure that the screw applies to the resin inside them) is directly detected by the pressure detector 32 attached to the cylinder 29. Since the detection value S 3 is measured accurately, an accurate detection value S ₃ with no delay can be obtained. Therefore, if the above-mentioned closed control is performed based on this value, holding pressure and back pressure control can be performed reliably according to the predetermined setting conditions, and conditions such as the type of resin, shape and size of the molded product, etc. The detailed and stable control required by

[Effects of the Invention] As detailed above, the present invention converts the rotational output of the electric motor into linear motion via the moving mechanism, moves the screw inserted into the injection cylinder in the axial direction, and moves the screw inserted into the injection cylinder. In a pressure control device for an electric injection molding machine that injects resin in a cylinder into a mold, a pressure receiving mechanism consisting of a fluid pressure cylinder and a piston fitted into the fluid pressure cylinder is provided between the moving mechanism and the screw. This pressure receiving mechanism is provided with a fluid pressure detector and a control device that controls the injection motor based on the detected value of this fluid pressure detector and a preset pressure value, so that the screw The reaction force received from within the mold or the injection tube (equal to the pressure exerted by the screw on the resin within them) is directly measured by a pressure detector attached to the cylinder, providing accurate and timely detection values. In addition, the structure of this part does not become complicated and manufacturing costs are reduced. By comparing this detected value with a preset pressure value and controlling the injection motor, pressure control (holding pressure control) during the resin solidification process in the mold and rotation motor control are performed. Controls that affect the quality of molded products, such as pressure control (back pressure control) when rotating the screw to supply resin into the injection cylinder for plasticization, can be performed accurately.
This provides an excellent effect in that high-quality molded products can be continuously and stably manufactured.

[Brief explanation of the drawing]

Figures 1 to 4 show an embodiment of the present invention. Figure 1 is a mechanical diagram showing the outline of the entire device, Figure 2 is a partial sectional view of the main parts, and Figure 3 is a servo motor drive. Block diagram showing the main parts of the mechanism, No. 4
The figure is an operation chart, and FIG. 5 is a schematic diagram of a conventional device. 5... Injection tube, 6... Screw, 22... Injection/mold opening/closing motor (servo motor), 29...
Cylinder, 30...Piston, 32...Pressure detector, 66...State control mechanism, 68...Sequence control mechanism, A...Movement mechanism, B...Pressure receiving mechanism.

Claims (1)

[Claims] 1 An electric type that converts the rotational output of an electric motor into linear motion via a moving mechanism, moves the screw inserted into the injection cylinder in the axial direction, and injects the resin in the injection cylinder into the mold. In a pressure control device for an injection molding machine, a pressure receiving mechanism consisting of a fluid pressure cylinder and a piston fitted into the fluid pressure cylinder is provided between the moving mechanism and the screw, and this pressure receiving mechanism is equipped with a fluid pressure detector. and a control device for controlling the injection motor by comparing the detected pressure value of the fluid pressure detector with a preset pressure value. Pressure control device in molding machine.