JPH01301221A - Strong mold clamping method for injection molding machine of electric power type - Google Patents

Abstract

PURPOSE:To cause mold clamping to be carried out without using of other means such as oil pressure by achieving the control of strong mold clamping in mold clamping process by controlling the outputted torque of a servomotor. CONSTITUTION:Molds 14, 14 are almost closed, and then a movable platen 13 reaches the position of a position-detecting means 47 and is switched to a speed setting means V3 and a torque setting means F3. The speed-set value in this position is set in higher value than the set value of slow down speed. This is the operation for carrying out the start-up of strong mold clamping in short time. When the molds are perfectly in contact with each other and the advance of the movable platen 13 is prevented, the output of a servomotor 40 is increased since the actual value A1 of speed becomes zero, but heavy load acts there and the movable platen 13 does not advance, and then the actual value B1 of torque rises to torque-set value F3 between (g) and (h), whereby the molds 14, 14 are clamped strongly with the force of torque F3. The finish of this strong mold clamping is detected by the operation that the detected value of the current detecting means 60 of the servo motor 40 has reached the set value of a current setting means 61 by a comparator 59.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a strong mold clamping method during electric injection molding using a motor as a drive source.

[Traditional extraction technique]

Injection molding machines of the type that use an electric motor as a drive source and convert the rotational force into thrust force using mechanical means such as a screw shaft or a link mechanism to perform mold clamping are already known. These injection molding machines use an electric motor with a constant rotational speed as a drive source, and use a mechanical variable speed gear mechanism or the like to control speed and force.

[Problem to be solved by the invention J] By the way, when injection molding of synthetic MA resin is carried out using a molding machine whose drive source is an electric motor, force control is also required in addition to speed control, and speed and force control are required. Control of both is essential. For example, regarding the operation of the mold clamping device,
The movable plate moves forward at high speed to close the mold, then is controlled to move forward at low speed and enters low-pressure mold clamping to protect the mold. After checking for foreign objects between the molds, it is further controlled to strong mold clamping. .

Therefore, there is a speed control region and a force control region in the molding cycle, and unless some means are taken to control the force, which has not been done in the past, electric machines cannot be used as the drive source for the molding machine. could not be used.

For this reason, even though it is called an electric injection molding machine, it uses hydraulic pressure as an auxiliary force to control the force, and strictly speaking, it uses both electric power and hydraulic pressure. there were.

The present invention was developed based on the above-mentioned circumstances, and although the present invention uses an electric motor as a drive source, its purpose is to use other means such as hydraulic pressure to control the mold clamping force during strong mold clamping. It is an object of the present invention to provide a new mold clamping method for an electric injection molding machine that can be performed without using an electric injection molding machine.

[Means to solve the problem]

The feature of the present invention according to the above object is that a servomotor is used as the drive source of the mold clamping mechanism, and the rotational force of the servomotor is converted into the thrust of the movable platen through the transmission mechanism, and the opening of the mold and the mold clamping are performed. In doing so, the strong clamping force jJl in the strong mold clamping step is controlled by controlling the output torque of the servo motor (117).

[Example] The present invention will be explained in detail below using the illustrated injection molding machine as an example.

FIG. 1 shows the main structure of an injection molding machine in which a servo motor is used as a common driving source for a mold IS structure 1 and an injection mechanism 2.

The mold clamping mechanism 1 includes a pair of fixed plates 10.11 installed facing each other on the machine base 3, a required number of tie bars 12.12 and quivers 12.12 installed across the fixed plates io and it. 12 and a movable plate 13 which can be freely moved.

Molds 14 and 14 are provided on the facing surfaces of the fixed plate 11 and the movable plate 13, respectively.
A large-diameter plunger t15 with a ball-shaped U-groove formed on the outer circumferential surface is connected to the opposite surface. This plunger 15 is screwed into a screw receiver of a rotating shaft S16 which is rotatably mounted on a fixed platen 10, which is a fixed member, using a ball bearing or the like.
It moves in the axial direction by the rotation of G.

This ball screw has high transmission efficiency and starts F! ! There is little friction. Further, a gear 17 is attached to the rotary disk 16, and this gear 17 and a transmission gear to be described later mesh with each other.

The injection mechanism 2 includes an injection heating cylinder 21 containing an injection screw 20 therein, and a machine base 3 that also serves to hold the injection heating cylinder 21.
and an upper housing 22. Inside the housing 22, a rotary member 1124 equipped with a screw shaft 23 is horizontally mounted, and a movable member 25 is screwed onto the screw shaft 23. Further, at the rear end of the screw 20, an extension shaft 26 whose tip end is supported by the movable member 25 is integrally connected to the screw 20. Further, the rotating shaft 24 and the extension shaft 26 have a gear 27 for advancing the screw and a gear 28 for rotating the screw at positions that do not interfere with each other, and furthermore, at the end of the rotating shaft 24,
A back pressure control OII device 29 using a brake that includes a hysteresis brake fixed to the housing wall portion 22a is attached.

A transmission shaft 31 parallel to the rotation shaft 24 and the extension shaft 26 is provided in the lower part of the housing 22 and passes through the housing 22 . Further, a transmission shaft 30 parallel to the plunger 15 is installed below the mold clamping mechanism 1, passing through the pair of fixed plates 10 and 11. The two VJ shafts 30 and 31 are in contact with each other via a clutch mechanism 32 so as to be able to freely approach and separate.

The clutch 1 32 includes a clutch member 32a fixed to the shaft end of the transmission shaft 31, a clutch shaft 32b disposed on the extension axis of the transmission @ 31 and installed on the housing wall, and the clutch shaft 32b. Coupling 32 fixed to the inner end of
c, and the excitation part is fixed to the housing side. A transmission shaft 30 is attached to the outer end of the clutch shaft 32b.
The Iζth joint 33 that connects is the attachment. The joint 33 and the transmission shaft 30 are connected by a means 34 that allows movement in the axial direction, such as a spline or a key, so that when the injection mechanism 2 moves forward or backward relative to the mold clamping mechanism 1, they are mutually connected. This is to prevent the transmission shafts 30, 31 connected to the movement from being impaired.

A transmission gear 35 that meshes with the gear 17 of the rotary disc 16 is attached to the transmission shaft 30 in close proximity to the inside of the stationary plate 10, and the transmission gear 35 transmits the rotational force of e@30. The plunger 15, which is transmitted to the plate 16 and screwed into the rotating plate 16, is pushed out in the axial direction by the rotation of the rotating plate 16, and moves the movable plate 13 in the mold closing direction or in the mold opening direction, and moves the tie bars 12, 12 in the mold opening direction. Moves as a guide member.

Further, the transmission shaft 31 is provided with transmission gears 37.3 (+) via clutch members 38 and 39 which mesh with the gears 27 and 28, respectively.This clutch member 3.8.3
Reference numeral 9 includes a coupling connected to the transmission gear 36, 37, and an excitation part fixed to the housing side, and the movement of the clutch plate and the excitation part inside the coupling connects the transmission tooth width 36, 37 and the transmission shaft. 31 can be coupled or released.

Furthermore, the shaft portion of the transmission shaft 31 that protrudes outward from the housing wall portion 22a is connected to an electric servo motor 40 having a tachometer generator 41 fixed to the housing wall portion 22a.
It is connected with.

Further, the clutch mechanism 32 is provided with a device 42 for maintaining the mold clamping force. This force holding device 42 includes an electromagnetically actuated brake portion d fixed to the housing wall portion 22a.
42a and the coupling 42 attached to the clutch shaft side
It is composed of b.

43 is a mold stop position detector, 44 is a mold opening deceleration position detector, 45 is a mold opening deceleration position detector, 46 is a low pressure mold clamping position detector, 47 is a strong mold clamping position detector, 48 is a metering stop position The detectors include a secondary pressure switching position detector 49 and a retraction position detector 50, which are comprised of a proximity switch, a limit switch, a phototube, and the like.

FIG. 2 shows an example of a control device, in which a central control device 51
, servo motor 40 and tachometer generator 41
Between the servo motor control amplifier 52 connected to It is provided for.

The servo motor control amplifier 52 has the function of controlling forward/reverse rotation of the servo motor 40, as well as the number of rotations (speed), maximum torque (current), etc., according to commands from the central control device 51, and controls the signal of the tachometer generator 41. This provides feedback to perform closed-loop control of the rotational speed (speed).

In addition, the central control device @51 includes the position detectors 43 to 50.
and the time setting device 0 to T7, the force holding device 42, the clutch mechanism 32, 38, 39, and the control amplifier 51 of the screw back pressure control device 29 that operates according to commands from the setting device 56.
, an operation switch 58, and a comparator 59 connected to the central control device 51, a current detector 60 of the servo motor 40, a current setting device 61 for detecting strong mold clamping, and a current for detecting injection filling. The setting device 62 is connected via a signal switch 63 that is activated by a command from the central control device 51.

Next, control of the mold clamping mechanism 1 will be explained.

FIG. 3 is a diagram showing the control relationship between rotational speed and torque in the servo motor 40, and set values A and B indicate the main operating side of forward and reverse rotation. Further, the speed setting value and the torque setting value are indicated by setting the maximum speed and maximum torque of the nervo motor 40 as 100, respectively, and the setting device V described above.

~V and F-F7 operating ranges are designated by the same reference numerals.

Note that current and torque are in a proportional relationship.

Furthermore, although the execution values A and B1 are shown in a simplified manner, the state of increase or decrease changes depending on the characteristics of the servo motor 40 and the servo motor control amplifier 52, and the state of the mechanism and load.

In the above control device, a common setting device V is used. , Fo set the maximum speed and maximum torque, and the time setting device T. Within the range of one molding cycle time set by The torque setting in B is set as the output 1 to torque upper limit value of the servo motor 40.

1. Due to the high-speed mold closing input, the servo motor 40 is accelerated between a and b and rotates at high speed to the set value of Vl, as shown by the execution value A1. At this time, a large starting current is generated in the servo motor 40 for acceleration, but a large load other than during starting is
l) Since the torque setting device F1 is not activated, the torque will rise and fall as shown in the actual value B1, and b-c
During this time, the movable platen 13 moves forward at high speed in the mold clamping direction.

2. Mold closing slowdown When the movable platen 13 reaches the operating position of the position detector 45, the signal is turned off! The A device 53 is activated and the speed is switched to the setting speed of the speed setting device 2. As a result, the area between c and d becomes a deceleration region, where regenerative braking occurs in the motor, resulting in slowdown, and the area between d and e becomes a low speed. In other words, when decelerating, a torque of 1-lux is applied in reverse rotation.

3. Low-pressure mold clamping When the movable platen 13 reaches the operating position of the position detector 46, the signal switch 54 is actuated by a signal and switched to the torque setting device F2. This torque setting value is set lower than the torque required for the speed setting value, so v
The rotational speed necessary to maintain the speed of F2 cannot be obtained, and the tachometer generator 41 applies feedback to reach the set speed, and attempts to increase the output of the servo motor 40, but the output torque exceeds the torque setting of F2. Since the upper limit is regulated by the value, a torque higher than F2 is not generated, and the lI plate 13 moves with a low force of 1.rook F2, and low-pressure mold clamping is performed there.

Therefore, although the range between e and g is within the operating range of the speed setter ■2, it automatically switches to force control in relation to the torque setting value, and speed control (from the II area to the force control area ■
Changes to. Then, there was a foreign object between the molds, and the movable platen 1
When the forward movement of the mold 3 is restricted, an abnormal signal is generated due to the time-up of the time setting device T7, and the input to the servo motor 40 is interrupted, thereby preventing damage to the mold.

4 The strong clamping die 14.14 is almost closed, the movable platen 13 reaches the position of the position detector 47, and the speed setting device V is activated by the signal.
The speed setting value at this position is set higher than the slowdown speed setting value. At this point, the molds 14° 14 are already in contact or are just about to contact. , It seems unnecessary to set a high speed as in V3, but this is because the start-up of strong mold clamping is performed in a short time.

When the molds are completely in contact with each other and the movable platen 13 is prevented from moving forward, the speed execution value A1 becomes the O value, so the Reebo motor 40 increases its output, but a large load is applied to the movable platen, causing the movable platen to move forward. 13 does not move forward, the torque execution value B1 exceeds the torque setting value F3 between g and h, and the mold 1 is moved by the force of torque F3.
4.14 Strongly clamp the mold 3゜Completion of this strong mold clamping is as follows.
The comparator 59 detects that the detected value of the current detector 60 of the servo motor 40 has reached the set value of the current setter 61. In addition, instead of the comparator, the time setting 5T
You can also check it using 2.

When the completion of strong mold clamping is detected, the force holding device 42 operates to maintain the force holding state (later, the clutch mechanism 32 is opened and the servo motor 40 is released from the mold clamping mechanism 1 side). Therefore, the torque execution value B1 of the servo motor at the end of the mold clamping stroke becomes the O value as shown in the figure.Therefore, e-h
The area between them is l of force, IJ l area ■.

5. After the high-speed mold opening stroke is completed, the clutch mm32 is opened and the force holding device 742 is released, and then the speed setting device 4 and the torque setting device F4 are activated by the inter-mold signal.

In this case, the rotation direction of the 1-nervo motor 40 is opposite to the rotation direction during the mold clamping stroke, and the rotation speed is increased to the set value A.
-J accelerates and rises. Moreover, the torque only increases due to the starting load and then decreases. As a result, the a-type plate 13 moves backward at high speed between j- and opens the mold.

6. Low-speed mold opening When the A-type board 13 reaches the position of the above-mentioned position detector 44, the speed setter V5 is activated by a signal, the speed is decelerated between ki+, and the speed is moved backward between I and m at low speed. This low-speed die interval is performed to prevent the molded product from ejecting or from shock when stopped.If you want to limit the ejection force by mechanical knocking, switch to a low 1~lux setting to control the force. You can also do that. Above is possible a! 13 low speed mold opening is performed until the position of the position detector 43 is reached.

Next, control of the injection device 2 will be explained.

FIG. 4 is a diagram showing the control 611ryA of the rotational speed and torque of the servo motor 40 in the injection device 2, and shows set values and the like as in the case of FIG. 3. Also, the rotation is reversed.

1. The servo motor 40 is set to the actual value △1 by the injection stroke speed setting device v6.
As shown in the figure, the motor is accelerated to the set value A and becomes a high-speed rotation.

Normally, even if the torque setting device F5 operates, the effective value B1 will be as shown in the figure unless a large load is applied to the injection screw 20 after the motor is started. Then, when the resin filling is completed at point r, the i-luke suddenly increases upwards.When the torque reaches the setting value α of the current setting device 62 for detecting the injection/filling, the time setting is completed. Then, at three points, due to an increase in the load, the torque execution value B1 reaches the set value B, and then the speed decreases as shown in the execution value A1, and the injection screw 20 Fill with resin.

When the torque reaches the current set value α, the control starts at the speed IIm.
From area 1, enter force control 2D area ■. This switching is automatically performed by the correlation between the speed setting value and the torque setting value, and filling and backing is completed under the control of the torque of F5. At point t, when the time setting device T3 times out, the time setting device T4 is driven, and the torque setting device “6” is activated.
Switch to Since the output torque of the ribo-seventer 40 is limited, the torque setting value of F6 increases, and the advancement of the injection screw 20 to that torque setting value causes the secondary pressure (
Holding pressure) is applied, and the injection stroke ends when the timer [4, which is controlled to hold pressure, times up. This compensates for the shortage caused by cooling shrinkage of the resin.

Note that the injection time may be controlled by setting a timer that is activated at the start of injection.

Further, the switching to the secondary pressure may be performed by detecting the position of the injection screw 20 using the detector 49. Further, although the time setting device T3 switches to the secondary pressure after a certain period of time, this time is extremely short, so the switching may be performed immediately at the α point. Furthermore, if an excessive starting torque is required at the start of injection, such as a mold for a bin point [・gate], during that time,
The setting value of a setting device other than the injection filling torque may be used.

2. Charging process Due to the time-up of the above time setting device T4, the time setting device T
5 is activated to cool the mold. Then, the time setting BT6 is activated due to time-up, and after that, the speed setting device 7 and the torque setting device 7 are switched, and the servo motor 40 rotates forward and starts charging.At this time, the back pressure control brake 29 to apply back pressure to the injection screw 120.The injection screw 20 is pressed by the resin pressure and moves backward, and metering is completed by the action of the metering stop position detector 48.Furthermore, drooling is prevented. Therefore, when the screw is retreated in the axial direction, it stops at the operating position of the retreat position detector 50.

In the above embodiments, the servo motor is used for driving all of the mold clamping, injection, and weighing functions, but it may be provided independently for each driving section.

[Advantageous Effects of the Invention 1] As mentioned above, in the present invention, by controlling the output 1 to torque of the servo motor, strong mold clamping force can be controlled (torque control), and the speed and force can be controlled. Switching of the control area is done electrically based on the set value, so
Centralized control is easy and operation is easy, and since the 4-no-vota controller directly controls the driving ILJ source, even when controlling multiple movable parts, there is no pressure control valve or flow control valve for each acticoator, unlike conventional hydraulic systems. There is no need to provide a product control valve or the like to control it, and the following effects are also achieved.

(1) Since the speed is open-loop controlled, it has excellent reproducibility and stability, allowing precise and stable molding.

(2) Movement of movable members such as a movable plate is performed by a rotating means and a screw shaft, and slips due to axial inertia do not occur, and the Hi11 drive source provides smooth operation and accurate position control.

■ Accurate molding conditions can be obtained because it is not affected by oil temperature or regulating valve characteristics in a fluid-driven type, and the actual values for speed and force almost match the set values.

(4) By attaching the speed detector to the drive source, it can be handled easily and inexpensively. Also, by attaching the encoder to the drive source, it is simpler without installing a position detector on the movable part. It is possible to have a similar structure.

[Brief explanation of the drawing]

The drawings illustrate the control method of an electric injection molding machine according to the present invention, and FIG. 1 is a vertical sectional view of the electric injection molding machine, FIG. 2 is a block diagram of the control device, and FIG. 3 is a mold diagram. FIG. 4 is a diagram showing the control relationship between the speed and torque of the drive source in the tightening device. FIG. 4 is a diagram showing the control relationship between the speed and torque of the drive source in the injection device. 1...Drawing of mold clamping machine, 2...Injection mechanism 15...
・Plunger, 20...Screw, 40...
Servomotor. Patent applicant: Nissei Jushi Kogyo Co., Ltd., 1st generation Teruo Akimoto...1.・・1 other person Figure 3

Claims (1)

[Claims] A servo motor is used as the drive source of the mold clamping mechanism, and the rotational force of the servo motor is converted into the thrust of the movable platen through a transmission mechanism to open and close the mold and clamp the mold. A strong mold clamping method for an electric injection molding machine, characterized in that force is controlled by controlling the output torque of a servo motor.