JP2002225085A - Nozzle touch mechanism and its control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nozzle touch mechanism to impart a proper nozzle touch force to a die by utilizing hydraulic force, and to provide its control method. SOLUTION: An injection unit 4 is relatively displaced to a pedestal, and a nozzle 7 is made to nozzle-touch the die by this mechanism 10. Such a mechanism 10 is equipped with a cylinder 25, a piston 26 which seals a hydraulic oil in the cylinder 25, and driving devices 12, 20 and 22. Then, the injection unit 4 is advanced by applying the pressing force of a driving device to the hydraulic oil in the cylinder, and a nozzle touch force is generated by utilizing the hydraulic force. The cylinder 25 is equipped with a second piston 30, and has a pressurizing means which adjusts the hydraulic force in the cylinder by pressing the second piston 30. Also, the pressure of the hydraulic oil in the cylinder is increased by the first piston 26 accompanying the increase of the rotating force of the driving device, by following a clamping force signal from the control device of an injection-molding machine. Thus, a proper nozzle touch force is generated while interlocking with the clamping force.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an injection molding machine,
The present invention relates to a nozzle touch mechanism for bringing a nozzle of an injection unit into contact with a mold and a control method thereof.

[0002]

2. Description of the Related Art An injection molding machine is provided with an injection device for filling a molten resin heated in a heating cylinder at a high pressure into a cavity of a mold. This injection device has a nozzle disposed at the tip of a heating cylinder, and for moving the injection unit including the heating cylinder forward and backward to bring the nozzle into contact with the injection port of a mold attached to the injection molding machine. Nozzle touch mechanism is provided.

[0003] This nozzle touch mechanism is provided with, for example, a motor with a brake and a transmission mechanism for transmitting the rotational force of the motor with the brake to a nozzle via a spring, as shown in Japanese Patent Publication No. 6-17038. In a state in which the nozzle can expand and contract, the energy stored in the spring presses the nozzle against the mold with a predetermined pressure.

In this device, the nozzle is brought into contact with the mold and pressed by the rotating operation of the motor as a drive source, and when the pressing force reaches a predetermined value, the brake of the motor is actuated to the motor. Is stopped, and the nozzle touch is completed. At this stage, the energy stored by the compression of the spring is balanced with the pressing force acting between the nozzle and the mold.

Therefore, even if an excessive force generated by opening / closing of a mold or an impact of injection during a molding operation is applied, or slip occurs in a motor brake, the slip is absorbed according to the amount of expansion and contraction of a spring and a spring constant. Therefore, the pressing force acting on the nozzle is maintained substantially equal to the nozzle touch force at the time of completing the nozzle touch.

However, since the nozzle touch force based on the stored energy of the spring is changed by moving the set position of the limit switch corresponding to the position of the spring receiver for determining the compression amount of the spring, it is difficult to adjust the setting change. . Also, even if the amount of compression of the spring is accurately determined electrically using a potentiometer or encoder, the spring force changes over time due to the spring's change, so the nozzle touch force once set fluctuates, A constant pressing force cannot always be maintained. In addition, the elastic force of the spring has a small amount of strain with respect to the stress, and it is difficult to accurately control the force due to the influence of thermal expansion of each mechanism component.

In the nozzle touch mechanism using such a spring, for example, it is difficult to cope with the case where the accuracy of the parallelism of the mold is required for forming a light guide plate or the like, and the nozzle of the injection unit is pressed against the mold. Therefore, even if the base plate, that is, the fixed plate on which the mold is mounted falls down, the nozzle touch force cannot be easily reduced. Further, the fall of the base plate causes the core portion and the sliding pins to be entangled due to the structure of the mold.

Further, there is a method of pulling the injection device from the vicinity of the center of the base plate so that the base plate does not fall down by the nozzle touch force. However, there is a problem that the mechanism is complicated and the workability of operation is deteriorated. is there. The nozzle touch force basically opposes the injection pressure, and is desirably linked to the injection pressure. However, when this is performed, the generation of the nozzle touch force is delayed, and the resin may leak from the nozzle. .

[0009]

SUMMARY OF THE INVENTION In view of such circumstances, the present invention provides a nozzle touch mechanism for applying an appropriate nozzle touch force to a mold using hydraulic pressure and a control method therefor. The purpose is. Another object of the present invention is to solve the problem of falling of the base plate in conjunction with the mold clamping force adjusted according to the injection pressure, and to perform the nozzle touch so as to obtain the nozzle touch force prior to the injection pressure. The purpose is to establish a way to control the mechanism.

[0010]

In order to achieve the above object, the present invention has the constitution described in each claim. More specifically, according to claim 1, a nozzle touch mechanism for relatively displacing an injection unit with respect to a mount of an injection molding machine and making a nozzle of the injection unit nozzle-touch a die, And a cylinder attached to one of the injection units, a piston for sealing the pressure oil to the cylinder, and a piston attached to the other of the gantry and the injection unit for reciprocating the piston while applying a load to the pressure oil. And a driving device for driving.

With this configuration, the nozzle touch mechanism of the present invention drives the piston to reciprocate while applying a load to the pressure oil in the cylinder by the driving device, and the injection unit uses the hydraulic pressure in the cylinder by the piston to move the injection unit to the mold. , And accurate pressure control can be performed using the elastic force of oil.

According to a preferred embodiment of the present invention, the cylinder has a second position slidably disposed with respect to the piston.
And a pressurizing means for adjusting the pressure of the pressurized oil in the cylinder by allowing the hydraulic piston to be pressed from the outside is incorporated in the cylinder. This pressurizing means has an adjusting bolt screwed to the cylinder, and adjusts the initial pressure of the pressure oil in the cylinder. This adjustment is performed by rotating the adjustment bolt (adjustment knob) while detecting the initial pressure with a pressure sensor. Therefore, fine resolution can be set since the resolution is high. The wobble due to the compression can be reliably eliminated.

According to another configuration of the present invention, air is mixed in the pressure oil sealed in the cylinder. Thereby, in the hydraulic mechanism of the nozzle touch mechanism, more stable cushioning performance can be added than the elastic force due to the spring operation.

Further, according to another configuration of the present invention, the piston has a small-diameter portion and a large-diameter portion, and is connected to a mechanism for converting the rotational force of the driving device into a linear motion and slides with respect to the cylinder. It further comprises a slidable second piston, comprising a possible first piston, disposed between an outer peripheral wall of the first piston and an inner peripheral wall of the cylinder. The first piston is a piston that generates a nozzle touch force by a hydraulic pressure generated by a pressure receiving area due to an area difference between the small-diameter portion and the large-diameter portion, while the second piston holds an initial hydraulic pressure by the adjusting bolt. It is characterized by having

With this arrangement, the injection unit moves forward through the linear movement mechanism of the driving device while the second piston applies a load to the hydraulic pressure in the cylinder, and after the nozzle of the injection unit touches the mold with the nozzle, the driving device With the increase of the rotational force, the pressure of the pressure oil in the cylinder is increased by the first piston to increase the nozzle touch force, so that control with extremely responsiveness can be realized.

According to another configuration of the present invention, the driving device comprises:
The motor includes a motor and a ball screw mechanism connected to the motor. A nut portion of the ball screw mechanism is connected to the first piston, and the motor is fixed to either the injection unit or the gantry.

Further, according to the control method of the nozzle touch mechanism of the present invention, the driving unit displaces the injection unit relative to the mount of the injection molding machine via the hydraulic mechanism, and moves the nozzle of the injection unit to the nozzle. In order to touch
By the piston connected to the linear moving means of the driving device, while applying the pressing force from the driving device to the pressure oil in the cylinder of the hydraulic mechanism, the injection unit is advanced with the displacement of the linear moving means, After the nozzle of the injection unit comes into contact with the mold, it detects that the pressure of the pressure oil in the sealed cylinder of the hydraulic mechanism has reached a predetermined value, and sets the operation of the driving device to a free state or stops. Then, the nozzle touching force to the mold is maintained by the hydraulic pressure in the cylinder.

As a result, the present invention utilizes the elastic force of the oil and / or air in the cylinder via the hydraulic mechanism, so that the effect of the fall of the base plate is minimized, and the mechanical parts such as springs are not used. Since different oil pressures are used, there is no influence of aging or the like, control is easy and accurate, and resolution with respect to elastic force is good.

Further, this control method includes a step for increasing the nozzle touch force following the mold clamping force signal from the control device of the injection molding machine when the nozzle of the injection unit is in contact with the mold. Since the nozzle touch force can be controlled by detecting the pressure of the pressure oil in the cylinder, an appropriate nozzle touch force that follows the mold clamping force can be generated.

Further, when a peak value of the mold clamping force signal is detected, a brake attached to the driving device is operated by the signal, and the hydraulic pressure of the cylinder chamber is maintained so as to maintain the position of the piston at that time. Accordingly, control according to the mold clamping force can be performed with a minimum necessary force without excessively increasing the nozzle touch force.

[0021]

Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a partial cross-sectional front view showing a schematic configuration of an injection molding machine including a nozzle touch mechanism according to the present invention, and FIG. 2 is a plan view showing a partial configuration of the nozzle touch mechanism in detail. .

On the frame 2 of the injection molding machine 1 shown in FIG.
The fixed platen 3 on which the mold A (not shown) is mounted and the injection unit 4 are arranged to face each other. This injection unit 4
1 is guided by a guide member 13 (see FIG. 2) such as a linear guide provided on the slide base 5 of the frame 2 and FIG.
It slides back and forth in the middle and left and right directions (arrow B). Further, the slide base 5 is pivotally attached to the frame 2 so that the injection unit 4 can be pivoted forward. Note that the injection unit 4 may be a type that simply slides on a bed fixed to the frame 2. A frame base or a configuration including a frame and a slide base is herein defined as a gantry. 6 is a heating cylinder and 7 is a nozzle.

The nozzle touch mechanism 10 according to the present invention is attached to the slide base 5. The nozzle touch mechanism 10 is configured to apply the nozzle 7 to the sprue bush 8 of the mold A with a predetermined pressing force so that the molten resin injected from the injection unit 4 does not leak at the time of injection and the molded product does not become a short shot. This is a mechanism for contacting and pressing.

In the embodiment of the present invention, the nozzle touch mechanism 10 includes a drive motor 12 such as a servomotor, coupling means such as a gear and a coupling 14, and a ball screw 2.
0 and a nut portion 22, and a hydraulic mechanism 24 having oil preload means. The drive motor 12, the connecting means, and the ball screw mechanisms 20, 22 constitute a drive device for the nozzle touch mechanism.

The drive motor 12 of this drive device is preferably constituted by a combination of a geared motor with a speed reducer and an inverter or a servomotor, and is controlled via a control device 16 (see FIG. 3) of the injection molding machine. A brake-equipped one is desirable to reduce power consumption. As shown in FIGS. 1 and 2, the drive motor 12 is connected to a ball screw 20 via a power transmission coupling 14. Both ends of the ball screw 20 are bearing-supported and fixed with nuts 19 from the outside of the support portion 17a of the mounting housing 17, so that the ball screw 20 can rotate without moving in the front-rear direction. This ball screw 2
The nut portion 22 is screwed into 0. The nut part 22 is
A sleeve-shaped piston (hereinafter, referred to as a first piston) 26 used in a hydraulic mechanism 24 (see FIG. 2) described later.
The first piston 26 extends through a through hole of the first piston 26 so that the ball screw 20 can be inserted therein.

The hydraulic mechanism 24 includes a cylinder 25 as a housing body, a first piston 26, a flanged lid 28 for closing an opening of the cylinder 25, another hydraulic piston (second piston) 30, And the cylinder is filled with pressure oil P and sealed. The first piston 26 has a large-diameter portion 26a and a small-diameter portion 26b as shown in FIG. 2, and presses the sealed pressure oil in the cylinder to reduce the nozzle touch force by the pressure receiving area due to the difference between these areas. appear. The second piston 30 is provided with packings 31 on its outer peripheral surface and inner peripheral surface, and is slidable in contact with the inner wall surface of the cylinder and the large diameter portion 26a of the first piston.

On the other hand, the cylinder 25 has an opening at the top and a center hole 25b at the bottom, and houses the second piston 30 inside. The flanged lid 28 is attached to the opening at the top of the cylinder and fixed with bolts 35. The first piston 26 has a large diameter portion 26a fitted in the center hole of the second piston 30 and a small diameter portion 26b fitted in the center hole 25b of the cylinder. Therefore, the ball screw 20, the first
Piston 26, second piston 30, and cylinder 25
Are arranged coaxially. Center hole of cylinder 2
5b and the sliding surface between the small diameter portion 26b of the first piston, the inner circumferential surface of the second piston 30 and the sliding surface between the large diameter portion of the first piston 26, and the outer circumferential surface of the second piston 30 and the cylinder 25
Packing 31 is arranged on the sliding surface with the inner wall surface of the. The cylinder chamber is filled with pressure oil. The flanged lid 28 has a screw hole 37 at the center thereof, into which a male screw of a bush-shaped adjustment knob 38 is screwed. The adjusting knob 38 is connected to the large diameter portion 2 of the first piston.
6a, the bottom of which abuts on the upper surface of the second piston 30.

The injection unit 4 is connected to the outer surface 25 a of the cylinder 25 having the above-described structure via bolts 32 via a mounting plate 33. A stopper plate 34 fixed to the end of the first piston 26 is disposed outside the bottom of the cylinder 25. When the stopper plate comes into contact with the bottom of the cylinder 25, the nut portion 22 cannot move further backward. It has become.

The adjustment knob 38 can rotate the knob to press the second piston 30 and adjust the pressure while detecting the oil pressure in the cylinder chamber with the pressure sensor 40. Therefore, the adjusting knob 38 and the pressure sensor 40 constitute a pressurizing unit that eliminates wobble due to oil compression at the time of starting or the like. Also, by feeding back the value of the pressure sensor to the motor side, the pressing force of the nozzle can be controlled in multiple stages.

The configuration of the nozzle touch mechanism 10 has been described above. In this embodiment, the case where the cylinder 25 is fixed to the injection unit 4 and the motor 12 is mounted on the frame of the injection molding machine has been described. However, contrary to the above mounting method, it is of course possible to mount the cylinder 25 on the gantry side and the motor 12 on the injection unit side.

In the hydraulic mechanism according to the present invention, air is mixed into oil sealed in the cylinder in order to maintain the elastic force by the spring operation of the conventional nozzle touch mechanism, so that the hydraulic mechanism has a larger cushion. Performance can be added.

Next, the operation of the nozzle touch mechanism of the present invention having such a hydraulic mechanism will be described with reference to FIGS. In FIG. 1, when the motor 12 is rotated to rotate the ball screw 20 clockwise, the nut portion 22 retreats rightward in the figure. When the motor 12 is rotated in the reverse direction, the ball screw 20 rotates counterclockwise, so that the nut portion 22 advances leftward in the drawing.

Therefore, in order to bring the nozzle 7 into contact with the sprue bush 8 of the mold, first, the motor 12 is driven to transmit its rotational force to the linear moving means comprising the ball screw 20 and the nut portion 22. At the same time, the forward movement of the first piston 26 (step 50 in FIG. 5) starts. Therefore, the pressure oil in the cylinder of the hydraulic mechanism 24 is pressed based on the area difference between the small diameter portion and the large diameter portion of the first piston 26. However, the pressurized oil in the cylinder is sealed, and when the hydraulic pressure corresponding to the pressing force necessary to move the injection unit 4 is applied, that is, the pressurized oil in the cylinder reduces this pressing force (load force). In the received state, the cylinder 25 moves forward in FIG.

In FIG. 3, the smooth forward movement of the injection unit 4 is based on the fact that the motor 12 is driven at a torque higher than the starting torque and the maximum rotational speed until the nozzle 7 reaches the deceleration limit switch (LS-NSD). Being a rapid move. And limit switch (LS-NSD)
Is turned on (step 52), the injection unit 4 is decelerated, the motor torque is reduced to a semi-fixed value because the starting torque is not applied, and the injection unit 4 moves in a decelerated state to a position where the nozzle 7 contacts the mold. Then, when the nozzle touch limit switch (LS-NF) is turned on at the mold contact position of the nozzle 7 (step 54), the pressure oil in the cylinder increases, and a nozzle touch force is generated. This pressure increase in the cylinder chamber occurs instantaneously, and the pressure of the pressure oil in the cylinder chamber is detected by the pressure sensor 40, whereby the nozzle touch force at that time can be controlled.

The retracting operation of the injection unit 4 is performed by reversing the motor 12 in response to a signal from the control device 16 of the injection molding machine, rotating the ball screw 20 clockwise, and moving the nut portion 22 rightward in FIG. This is done by retreating.

The present invention is characterized in that the nozzle touch force is controlled in conjunction with the mold clamping force. Therefore, when the nozzle 7 comes into contact with the mold A and the nozzle touch force is generated by the nozzle touch mechanism 10, the mold switch control of the mold is started in conjunction with the operation of the limit switch (LS-NF). Is done.

Therefore, as shown in FIG.
Is input to the control device 16 of the injection molding machine, the control device 1
6 instructs the motor 12 to perform the rotational drive based on the torque limit value A (step 56). As a result, following the rise of the mold clamping force based on the mold clamping signal S from the control device 16 (step 58), the nozzle touch force increases along the characteristic curve shown in FIG.

When the peak of the mold clamping force is detected (step 60), the brake of the motor 12 is turned on by a command from the control device 16 (step 62).
The power consumption is reduced and the motor is prevented from being burned by stopping or stopping the motor (step 64) so as not to transmit the torque of Step 2. Also, the first piston 26
, The appropriate nozzle touch force is maintained. The motor 12 can be rotated and stopped by an operator using a selector switch or the like for the nozzle touch operation.

When an appropriate mold clamping force and nozzle touching force are applied, or after a short time lag, injection control is started by a command from the control device 16 and the injection cylinder in the injection unit 4 is operated. Thus, injection and filling of the measured molten resin into the mold A is started (step 66). After the end of the injection operation, the control device 16
The motor torque is set to a torque limit value B smaller than the torque limit value A (step 68).

Subsequently, the brake of the motor 12 is released (step 70), and at the same time as the opening operation of the mold A, the motor 12 is reversed to return the nozzle touch force to the initial value, or the nozzle is retracted (step 70). 72). FIG. 5 is a flowchart showing the flow of such control. In addition,
When the molding operation is repeated continuously in a state where the nozzle is in contact with the mold, the motor 12 is rotated again to set the torque limit value A (step 56), and the mold opening operation is performed again.
A series of operations up to (Step 72) is repeated.

【The invention's effect】

As is clear from the above description,
According to the nozzle touch mechanism of the present invention, since the hydraulic mechanism is connected between the injection unit and the driving device, and the pressing force from the driving device is applied through the pressure oil sealed in the cylinder of the hydraulic mechanism, The proper nozzle touch force to the mold can be maintained, and as a result, the base plate does not fall due to the excessive force caused by the conventional inappropriate nozzle touch force, and the galling occurring in the mold can be prevented, and the molding can be performed. Work can be performed smoothly and efficiently.

According to the present invention, since the oil pressure is used to generate the nozzle touch force, it is easy to detect the pressure of the pressure oil in the cylinder chamber, and the control can be performed accurately. . Furthermore, since the hydraulic mechanism is provided with the pressurizing means and the initial setting is performed, the responsiveness and resolution of the nozzle movement are good, and the adjustment can be performed easily and accurately.

Further, according to the control method of the present invention, since the pressing force from the driving device is applied to the nozzle of the injection unit via the hydraulic pressure of the hydraulic mechanism to press the mold, the oil sealed in the cylinder is provided. And / or the air acts as a buffer, and furthermore, the operation of the driving device is released by detecting a predetermined pressure value of the pressure oil, so that an excessive nozzle touch force can be prevented from being generated. Further, since the nozzle touch force is increased in accordance with the mold clamping force signal from the control device of the injection molding machine, it is possible to control an appropriate nozzle touch force interlocked with the mold clamping force with extremely high responsiveness.

[Brief description of the drawings]

FIG. 1 is a partial sectional configuration diagram of an injection molding machine showing a nozzle touch mechanism according to the present invention in a sectional shape, and showing an arrangement relationship between an injection unit and a fixed platen.

FIG. 2 is a plan view showing in detail a partial configuration of a nozzle touch mechanism according to the present invention.

FIG. 3 is a schematic configuration diagram showing an operation of the injection unit according to the present invention.

FIG. 4 is a graph showing a relationship between a nozzle touch force and a mold clamping force in the nozzle touch mechanism of the present invention.

FIG. 5 is a flowchart illustrating a procedure of a control method according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Injection molding machine 2 Frame 4 Injection unit 5 Slide base 7 Nozzle 12 Motor 16 Control device 20 Ball screw 22 Nut part 24 Hydraulic mechanism 25 Cylinder 26 First piston 30 Second piston 38 Adjustment knob 40 Pressure sensor

Claims (8)

[Claims] 1. A nozzle touch mechanism for relatively displacing an injection unit with respect to a mount of an injection molding machine and making a nozzle of the injection unit nozzle-touch a mold, wherein one of the mount and the injection unit is provided. A cylinder mounted on the cylinder, a piston sealing the pressurized oil in the cylinder, and a drive unit mounted on one of the gantry and the injection unit and reciprocating the piston while applying a load force to the pressurized oil. A nozzle touch mechanism characterized in that: 2. The cylinder has a hydraulic piston separate from the piston, and pressurizing means for adjusting the pressure of hydraulic oil in the cylinder by allowing the hydraulic piston to be pressed from the outside is assembled to the cylinder. The nozzle touch mechanism according to claim 1, wherein: 3. The nozzle touch mechanism according to claim 1, wherein air is mixed in the pressure oil sealed in the cylinder. 4. The piston has a small diameter portion and a large diameter portion,
A first piston is connected to a mechanism for converting the rotational force of the driving device into a linear motion and is slidable with respect to the cylinder. The first piston is disposed between an outer peripheral wall of the first piston and an inner peripheral wall of the cylinder. And a second piston slidable, wherein the first piston is a piston that generates a nozzle touch force by a hydraulic pressure generated by a pressure receiving area due to an area difference between the small diameter portion and the large diameter portion. The nozzle touch mechanism according to claim 1. 5. The driving device includes a motor and a ball screw mechanism connected to the motor. A nut portion of the ball screw mechanism is connected to the piston, and the motor is fixed to one of the injection unit and the gantry. The nozzle touch mechanism according to claim 1, wherein: 6. A method of controlling a nozzle touch mechanism for causing a driving device to relatively displace an injection unit via an oil pressure mechanism with respect to a frame of an injection molding machine and to cause a nozzle of the injection unit to nozzle-touch a mold. With the piston connected to the linear movement means of the drive device, while applying a pressing force from the drive device to the pressure oil in the cylinder of the hydraulic mechanism, the injection unit is moved together with the displacement of the linear movement means. After the nozzle of the injection unit comes into contact with the mold, it is detected that the pressure of the pressure oil in the sealed cylinder of the hydraulic mechanism has reached a predetermined value, and the operation of the driving device is set to the free state. Alternatively, the control method is characterized in that the nozzle is stopped and the nozzle touch force to the mold is held by the hydraulic pressure in the cylinder. 7. The method according to claim 1, further comprising a step of increasing a nozzle touch force following a mold clamping force signal from a control device of the injection molding machine when the nozzle of the injection unit is in contact with the mold. The control method according to claim 6. 8. When a peak value of the mold clamping force signal is detected, a brake attached to the driving device is actuated by the signal, and the hydraulic pressure of the cylinder chamber is maintained so as to maintain the position of the piston at that time. The control method according to claim 7, wherein the control is maintained.