JP2008110557A - Mold clamping device of injection molding machine and mold clamping control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mold clamping device of an injection molding machine capable of controlling mold clamping force without using a strain sensor while exerting direct mold clamping force on a mold from its back in the mold clamping device of the injection molding machine using a toggle mechanism and a mold clamping control method thereof. <P>SOLUTION: The mold clamping device 11 of the injection molding machine which performs mold clamping by the toggle mechanism 20 comprises arranging a first movable platen 28 on which the toggle mechanism 20 is mounted, a second movable platen 29 to which a movable mold 18 is attached, the hydraulic cylinder 30 arranged between the first and second movable platens 28 and 29, a hydraulic sensor 38 for detecting the pressure of the hydraulic cylinder 30 and, a control device 39 for detecting the pressure of the hydraulic sensor 38 to perform the feedback control of an actuator 21. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention relates to a mold clamping device and a mold clamping control method of an injection molding machine using a toggle mechanism, and more particularly to a mold clamping device and a mold clamping control method in which a hydraulic cylinder is disposed on a movable platen. .

As an injection molding machine using a general toggle mechanism, the one described in Patent Document 1 is known. However, in Patent Document 1, since the toggle mechanism is pivotally mounted in the vicinity of the upper and lower end portions of the movable platen, it is not possible to exert a clamping force directly from the back of the mold, and burrs are generated or melted. There was a problem that the resin could not be evenly pressurized.

In order to solve the above-described problem, a device described in Patent Document 2 is known in which a sealed hydraulic cylinder is disposed between a connecting plate and a moving plate separately from a toggle mechanism. And in patent document 2, the problem that the mold clamping force cannot be exerted directly from the back surface of the mold in patent document 1 can be solved, and the mold clamping force can be evenly transmitted to the mold. However, Patent Document 2 uses a hermetic hydraulic cylinder, but has a problem of oil leakage and cannot be used under the same conditions for a long time.

Patent Document 1 describes that a clamping sensor is attached to a tie bar to perform closed control of the mold clamping force. However, it is necessary to attach an expensive strain sensor, and the amount of extension of each tie bar varies depending on the design error and the temperature rise of the tie bar at the time of molding. Therefore, if a strain sensor is attached to only one tie bar, the exact clamping force Could not be detected.
JP-A-8-281747 (Claim 1, FIG. 1) Japanese Patent Laid-Open No. 10-258451 (claim 1, effect of the invention, FIG. 1)

Therefore, in the present invention, in view of the above problems, in the mold clamping device and the mold clamping control method of an injection molding machine using a toggle mechanism, the mold clamping force is applied directly from the back surface of the mold while the strain sensor is used. It is an object of the present invention to provide a mold clamping device and a mold clamping control method of an injection molding machine that can be controlled without being used.

According to a first aspect of the present invention, there is provided a mold clamping device for an injection molding machine, wherein a toggle mechanism disposed between a movable platen and a pressure receiving plate is used to move the movable plate relative to a fixed mold attached to the fixed platen. In a mold clamping device of an injection molding machine in which an attached movable mold is approached and separated, an actuator for driving a toggle mechanism, a first movable plate on which the toggle mechanism is pivotally mounted, and a second to which the movable mold is attached A movable platen, a hydraulic cylinder disposed between the first movable platen and the second movable platen, a hydraulic sensor for detecting the pressure of the hydraulic cylinder, and a control for feedback control of the actuator by detecting the pressure of the hydraulic sensor A device is provided.

According to a second aspect of the present invention, there is provided a mold clamping control method for an injection molding machine in which a movable plate is moved with respect to a fixed mold attached to the fixed platen by a toggle mechanism disposed between the movable platen and the pressure receiving platen. In a mold clamping control method of an injection molding machine in which a movable mold attached to and away from an actuator is mounted, an actuator for driving a toggle mechanism, a first movable plate on which the toggle mechanism is pivotally mounted, and a movable mold are attached A second movable platen, a hydraulic cylinder disposed between the first movable platen and the second movable platen, and a hydraulic sensor for detecting the pressure of the hydraulic cylinder are arranged to detect the pressure of the hydraulic sensor. The actuator is feedback-controlled.

The mold clamping control method for an injection molding machine according to claim 3 of the present invention is characterized in that, in claim 2, a pump is connected to the hydraulic cylinder, and oil is not fed from the pump to the hydraulic cylinder during mold clamping. .

A mold clamping device and a mold clamping control method of an injection molding machine according to the present invention include an actuator for driving a toggle mechanism, a first movable plate on which the toggle mechanism is pivotally mounted, a second movable plate on which a movable mold is attached, A mold that includes a hydraulic cylinder disposed between the first movable platen and the second movable platen, a hydraulic sensor that detects the pressure of the hydraulic cylinder, and feedback control of the actuator by detecting the pressure of the hydraulic sensor. The mold clamping force can be controlled without using a strain sensor while exerting the mold clamping force directly from the back of the mold.

An embodiment of the present invention will be described with reference to FIG. FIG. 1 is a schematic view of a mold clamping device of an injection molding machine according to the present invention. FIG. 2 is a flowchart showing the mold clamping control method of the injection molding machine according to the present invention.

As shown in FIG. 1, a mold clamping device 11 of an injection molding machine is disposed on a bed 12 so as to face the injection device 13. The mold clamping device 11 includes a stationary platen 15 to which a stationary mold 14 is attached, a pressure receiving plate 16 disposed in parallel to the stationary platen 15, four tie bars 17 provided therebetween, and the tie bar A movable platen 19 and the like, which are movably disposed through 17 and to which a movable mold 18 is attached, are configured. A toggle mechanism 20 is disposed between the pressure receiving plate 16 and the movable platen 19. The toggle mechanism 20 is moved forward and backward by a ball screw mechanism 24 including a mold clamping servomotor 21 which is an actuator attached to the pressure receiving plate 16, a motor pulley, a belt, a ball screw pulley, a ball screw 22, a ball nut 23, and the like. A driving mechanism including a cross head 27 and the like is provided. In the present invention, the actuator that drives the toggle mechanism may be a hydraulic cylinder.

The toggle mechanism 20 includes a first link 25a having one end connected to the vicinity of both upper and lower ends of the back surface (on the side opposite to the fixed platen) of the movable platen 19 via a pin 26a and a bush, and the other end of the first link 25a. The second link 25b, one end of which is connected to the pressure receiving plate 16 via the pin 26b and the bush and the other end is connected to the pressure receiving plate 16 via the pin 26b and the bush, 26d and a third link 25c having one end connected via a bush, a cross head 27 to which the other end is connected to the third link 25c via a pin 26e and a bush and the ball nut 23 is fixed. A link mechanism is provided. Then, the forward / backward movement of the cross head 27 is converted into the mold opening / closing operation and the mold clamping operation of the movable plate 19 and the movable mold 18 via the link mechanism.

In this embodiment, the movable platen 19 includes a first movable platen 28 on which the toggle mechanism 20 is pivotally mounted on the back side and a second movable platen 29 on which the movable mold 18 is mounted on the mold mounting surface 29a. A cylinder of a hydraulic cylinder 30 is disposed inside the first movable platen 28. The hydraulic cylinder 30 is provided with an oil chamber 32 for sealed oil on the toggle mechanism 20 side with a piston 31 as a boundary, and a rod portion 33 and an oil chamber 34 for leaked oil on the fixed platen 15 side. A second movable plate 29 is connected to the end surface of the rod portion 33. In the present embodiment, the connection between the rod portion 33 and the second movable platen 29 is based on adhering, but it may be based on axial attachment or the like. The hydraulic cylinder may be provided between the first movable plate and the second movable plate. The hydraulic cylinder is provided on the second movable plate, and the rod portion is connected to the first movable plate. It may be.

Further, a conduit 36 is connected from the pump 35 (including a motor) to the oil chamber 32 for the sealed oil of the hydraulic cylinder 30. In this embodiment, the pump 35 may be a low-priced constant capacity type that has a small discharge amount. A check valve 37 that prevents backflow of oil to the pump 35 side is provided in the middle of the pipe line 36, and the hydraulic pressure of the oil chamber 32 for sealed oil is supplied to the hydraulic cylinder 30 side of the check valve 37. A hydraulic sensor 38 is provided that can be detected. The hydraulic sensor 38 is connected to the control device 39. The control device 39 is also connected to the motor of the pump 35, the mold clamping servomotor 21, and the rotary encoder 21 a of the mold clamping servomotor 21. A pipe 41 is also connected from the oil chamber 34 for leaking oil to the tank 40, and a pilot type check valve 42 is disposed in the pipe 41. A pilot pipe 43 is connected from the pipe 36 to the check valve 42. However, the pilot check valve 42 is not essential to the present invention.

Next, the mold clamping control method of the injection molding machine of the present invention will be described with reference to FIG. First, the movable mold 18 is opened with respect to the fixed mold 14, and the description starts from the state in which the previous molded product is taken out. First, when the mold is opened, the pump 35 is operated, oil is supplied to the oil chamber 32 for the sealed oil of the hydraulic cylinder 30, and the piston 31 is moved to the forward limit (S1). At this time, the pilot type check valve 42 is opened when the pressure in the pipe line 36 and the pilot pipe 43 becomes equal to or higher than a predetermined value, and the oil in the oil chamber 34 for leaking oil is collected in the tank 40. This operation is performed in order to replenish the amount of oil leaked from the oil chamber 32 for the enclosed oil to the oil chamber 34 for the leaked oil by the time of the previous molding. It may be performed every number of times. When the set pressure is reached when the mold is opened (S2), the pump 35 is immediately stopped (S3). At this time, the pump 35 may be stopped by the time elapsed by the timer or the current value sent to the motor of the pump 35.

Next, the mold clamping servomotor 21 is driven (S4), and the movable platen 19 is moved forward with respect to the fixed platen 15. When the mold clamping servomotor 21 is driven, the cross head 27 is advanced through the ball screw 22 and the ball nut 23 as is well known. Then, as the cross head 27 advances, the first link 25a and the second link 25b extend to move the movable plate 19, and eventually the movable mold 18 comes into contact with the fixed mold 14 and is illustrated between the two molds. A cavity that is not formed is formed, and the mold closing is completed. After that, the mold clamping servomotor 21 is driven, and the movable mold 18 is clamped toward the fixed mold 14 through the oil in the oil chamber 32 for the sealed oil of the hydraulic cylinder 30. At the same time, as the first link 25a and the second link 25b are further extended, the tie bar 17 is extended, the pressure receiving plate 16 is slightly retracted, and a mold clamping force is generated. In this embodiment, since the mold clamping force of the toggle mechanism 20 is directly transmitted to the back surface of the movable mold 18 via the rod portion 33 of the hydraulic cylinder 30 at this time, the problem that the movable plate 19 is curved hardly occurs. .

At this time, the pump 35 is stopped as described above, and the oil feeding is stopped. The check valve 37 also prevents backflow of oil in the oil chamber 32 for sealed oil in the hydraulic cylinder 30. The hydraulic pressure in the oil chamber 32 of the hydraulic cylinder 30 is detected by a hydraulic pressure sensor 38, and the value is sent to the control device 39. Then, a signal is sent from the control device 39 to the mold clamping servomotor 21, and the closed loop control by the pressure is performed so that the pressure of the hydraulic sensor 38 becomes the set pressure at the time of mold clamping (S5). With the conventional toggle type mold clamping device, the mold clamping force cannot be easily detected, and it is necessary to apply an excessive mold clamping force to the mold. In the present invention, the mold can be clamped with the optimum mold clamping force. It became. In addition, a strain sensor attached to a tie bar or a link mechanism has a problem that distortion does not occur in all tie bars or link mechanisms at all due to a temperature rise of the tie bar or the like, but the present invention has an advantage that such a problem does not occur. is there. However, when the mold is clamped, a mold clamping force is exerted on the oil chamber 32 for the enclosed oil, so that a very small amount of hydraulic oil leaks through the packing of the piston 31 to the oil chamber 34 side for the leaked oil.

Next, when it is detected by the timer that a predetermined delay time has elapsed (S6), the injection motor is driven by a signal from the control device, the screw (not shown) is advanced, and molten resin is injected and filled into the cavity. (S7). At this time, the pressure of the oil chamber 32 for the oil sealed in the hydraulic cylinder 30 also reaches a peak due to the injection pressure of the injection device, but the movable platen 19 is controlled by controlling the servomotor 21 for clamping against an excessive pressure increase. It is also possible to reverse the position. It is also possible to perform control to increase or decrease the mold clamping force with a slope according to the time constant. The mold clamping servomotor 21 is controlled so that the hydraulic cylinder 30 remains at the set pressure even after injection filling (S8, S9). When a predetermined cooling time elapses by the timer (S10), the mold opening / closing servo motor is driven again (S11), the toggle mechanism is bent, and the mold is opened. At this time, the pilot type check valve 42 communicating with the oil chamber 34 for leaking oil is closed, and the hydraulic oil in the oil chamber 34 is rapidly discharged toward the tank so that no impact is applied to the mold opening operation. . When the cross head 27 is retracted to a predetermined position, it is determined that the mold opening completion position is reached (S12), and the driving of the mold clamping servo motor is stopped (S13). Then, the molded product is taken out. If the molding operation is not terminated, the process proceeds to the next cycle (S14).

In addition, the following examples are also assumed for the present invention. In the first embodiment, closed loop control is performed by detecting the hydraulic pressure of a hydraulic cylinder disposed on the stationary platen side with two fixed platens.
In particular, a fixed platen is provided in the middle stage, a movable platen is provided in the upper stage with respect to the fixed platen, and a pressure receiving plate is provided in the lower stage, and a toggle mechanism is provided between the fixed platen and the pressure receiving plate. In a vertical injection molding machine provided with an injection device on the side, it is effective to dispose a hydraulic cylinder on the stationary platen.

As Example 2, as a hydraulic cylinder disposed between the first movable platen and the second movable platen, a rod portion is provided at the center of the first movable platen itself, This is a type in which the rod part is inserted. An oil chamber is formed in the recess of the second movable platen. Alternatively, the first movable platen is provided with a recess, and the rod portion of the second movable plate is inserted into the recess. In the case of such a structure, it is natural that a stopper is required to prevent the first movable plate and the second movable plate from opening more than a predetermined amount when the mold is opened. In the structure of the second embodiment, the leaked oil may be recovered by dropping onto the bed from the periphery of the rod portion.

In the third embodiment, a bladder (rubber bag) is placed in an oil chamber for oil contained in a hydraulic cylinder disposed between the first movable platen and the second movable platen, and oil is enclosed in the bladder. When oil is completely enclosed in the bladder, the pressure is close to normal pressure when the mold is opened, and the pressure is increased by clamping. Then, the hydraulic pressure in the bladder or the pressure on the bladder surface is detected. By adopting such a configuration, the amount of oil leakage can be eliminated or reduced slightly. Further, hydraulic oil may be supplied from the pump to the prada.

Further, in the embodiment shown in FIG. 1 and Examples 1 to 3, the pressure detection value of the hydraulic sensor 38 can be used in the mold protection process for detecting foreign object pinching. That is, in the mold protection control, whether the movable platen 19 or the like has advanced is detected by the position of the cross head 27, and an increase in the mold clamping force is detected by an increase in the pressure of the hydraulic sensor 38 to detect an abnormality. As an application thereof, it is possible to detect abnormalities of the sliding part of the mold, the spring, etc. by detecting the pressure from the hydraulic sensor 38.

Needless to say, the present invention can be implemented with various modifications without departing from the spirit of the invention.

It is the schematic of the mold clamping apparatus of the injection molding machine of this invention. It is a flowchart figure which shows the mold-clamping control method of the injection molding machine of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Clamping apparatus 14 Fixed mold 15 Fixed board 18 Movable mold 19 Movable board 20 Toggle mechanism 21 Servo motor for mold clamping 28 First movable board 29 Second movable board 30 Hydraulic cylinder 31 Piston 35 Pump 38 Hydraulic sensor 39 Controller

Claims (3)

Clamping of an injection molding machine in which the movable mold attached to the movable plate is moved closer to or away from the fixed mold attached to the fixed platen by a toggle mechanism disposed between the movable platen and the pressure receiving plate. In the device
An actuator for driving a toggle mechanism, a first movable plate on which the toggle mechanism is pivotally mounted, a second movable plate to which a movable mold is attached, and disposed between the first movable plate and the second movable plate An injection molding machine comprising: a hydraulic cylinder that is operated; a hydraulic sensor that detects a pressure of the hydraulic cylinder; and a control device that detects the pressure of the hydraulic sensor and feedback-controls the actuator. Clamping device. Clamping of an injection molding machine in which the movable mold attached to the movable plate approaches and is separated from the fixed mold attached to the fixed platen by a toggle mechanism disposed between the movable platen and the pressure receiving plate. In the control method,
An actuator for driving a toggle mechanism, a first movable plate on which the toggle mechanism is pivotally mounted, a second movable plate to which a movable mold is attached, and disposed between the first movable plate and the second movable plate A mold clamping control method for an injection molding machine, comprising: a hydraulic cylinder to be detected; and a hydraulic sensor for detecting a pressure of the hydraulic cylinder, wherein the actuator is feedback-controlled by detecting the pressure of the hydraulic sensor . 3. The mold clamping control method for an injection molding machine according to claim 2, wherein a pump is connected to the hydraulic cylinder, and oil is not fed from the pump to the hydraulic cylinder during mold clamping.

Images