JP2010131895A - Die protecting method for die clamping apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a die protecting method by which the abnormality detection for a die can accurately and instantly be performed. <P>SOLUTION: In a die clamping apparatus 1 includes a die closing means 3 which closes the die 6 through a hydraulic cylinder apparatus 2, a controlling apparatus 20 determines whether the pressure of the enclosed hydraulic cylinder apparatus 2 changes to a predetermined value or not during a period in which the die 6 moves from a predetermined position of the die closing stroke to a position slightly before the die closing completion position. When the pressure of the hydraulic cylinder apparatus 2 has changed to the predetermined value, it is determined that the die abnormality is present. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for preventing damage to a mold in a mold clamping device of a molding apparatus.

  Various methods for preventing damage to the mold in the mold clamping device of the molding apparatus have been proposed. Many of them reduce the driving force for closing the mold to such an extent that the mold is not damaged by the foreign matter sandwiched between the mold-matching surfaces of the mold, and when detecting that the mold-matching surface of the mold does not adhere The driving force is eliminated. However, in this mold protection system, there is a problem that the mold closing speed becomes unstable because it is necessary to reduce the driving force for mold closing in order to protect the mold. Further, since the metal mold keeps pressing the foreign material after the foreign material is sandwiched until the foreign material is detected, there is a possibility that the metal mold may be damaged even at a low pressure.

  As another example, as disclosed in Patent Document 1, for example, the driving force of the mold opening / closing / clamping driving device is continuously detected during the mold closing process, and the mold closing pressure reaches a set value. There is a mold protection method that issues an alarm when it does. According to this technique, the abnormality can be detected instantaneously, and the pressure applied to the mold can be kept small. However, since the driving force of the mold is detected by the pressure of the driving source itself, the extra driving force is detected due to the influence of the frictional force in the mechanism of the driving source, the minimum operating pressure, the surge pressure, or the like. Therefore, accurate abnormality detection cannot be performed. In addition, when the drive source is a toggle mechanism, the toggle at the time of detecting a foreign object or the like is about to extend. Therefore, when the pressing force of the foreign object is detected by the drive force of the toggle mechanism, the rate of change such as a torque increase of the drive source. Becomes extremely small, and the accuracy of foreign object detection decreases.

JP-A-1-113220

  The present invention has been made to solve the above-described problems, and an object thereof is to provide a mold protection method capable of accurately and instantaneously detecting a mold abnormality.

  In order to solve the above-mentioned problem, the invention described in claim 1 is a mold clamping device provided with a mold closing means for closing a mold via a hydraulic cylinder device, and is sealed while the mold is closed. The gist is to determine that the mold is abnormal based on the pressure of the hydraulic cylinder device being changed to a predetermined value.

  According to this, the abnormality detection of the mold can be accurately and instantaneously performed. In addition, since it is not necessary to reduce the driving force of the mold closing means, the mold closing operation can be controlled stably.

  According to a second aspect of the present invention, in the mold protection method for a mold clamping device according to the first aspect, the determination that the mold is abnormal is based on the fact that the pressure of the hydraulic cylinder device changes to a predetermined value. The gist of the present invention is that the mold is moved from a predetermined position of the mold closing stroke to a position slightly before the mold closing completion position.

  According to this, the pressure change in the hydraulic cylinder device can be detected stably.

  The gist of a third aspect of the present invention is that the mold closing means is a toggle mechanism in the mold protecting method of the mold clamping device according to the first or second aspect.

  According to this, the pressure change in the hydraulic cylinder device can be detected with high accuracy.

  The gist of a fourth aspect of the present invention is that the hydraulic cylinder device is driven and controlled by a servo valve in the mold protecting method for a mold clamping device according to the first to third aspects.

  According to this, the pressure change in the hydraulic cylinder device can be detected sensitively, and the mold can be protected in a short time.

  According to a fifth aspect of the present invention, in the mold protection method for a mold clamping device according to the fourth aspect, it is determined that the mold is abnormal based on the pressure of the hydraulic cylinder device changing to a predetermined value. The gist is to reduce the pressure of the hydraulic cylinder device.

  According to this, after it is determined that the mold is abnormal, the mold can be protected in a short time.

  The present invention provides a mold clamping device having a mold closing means for closing a mold through a hydraulic cylinder device, and the pressure of the enclosed hydraulic cylinder device reaches a predetermined value while the mold is closed. Since it is determined that the mold is abnormal based on the change, the abnormality of the mold can be detected accurately and instantaneously.

  Embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing an outline of a mold clamping apparatus for carrying out the present invention. FIG. 2 is a flowchart showing the mold protection method of the present invention.

  The mold clamping device 1 connects the four corners of the fixed platen 5 and the pressure receiving plate 14 with tie bars 4, and slides the first movable platen 7 and the second movable platen 10 onto the tie bar 4 between the fixed platen 5 and the pressure receiving plate 14. In addition to being a part of an injection molding machine equipped with an injection device, it can be used alone as a compression molding machine or the like. On the opposing surfaces of the fixed platen 5 and the first movable platen 7, a mold 6 composed of a fixed die and a movable die is attached to each plate so that they can be matched. The first movable platen 7 and the second movable platen 10 are connected by a piston 8 of the hydraulic cylinder device 2 built in the second movable platen 10. A toggle mechanism 11 as the mold closing means 3 is provided between the second movable platen 10 and the pressure receiving plate 14. The toggle mechanism 11 is expanded and contracted by a ball screw 12 rotatably provided at the center of the pressure receiving plate 14 and a ball nut 13 screwed to the ball screw 12 so that the second movable plate 10 is brought close to the fixed plate 5. Retract and open and close the mold. The ball screw 12 is rotationally driven by a servo motor 18 and a belt 19. The hydraulic cylinder device 2 serving as mold clamping means includes a cylinder 9 provided by drilling in a second movable plate 10 and a piston 8 fitted into the cylinder 9 so as to be reciprocally movable. A decompression chamber 21 on the first movable platen 7 side that is provided by a piston 8 in the cylinder 9 and connected to a hydraulic pressure source when the mold clamping pressure is reduced, and a hydraulic pressure source that is provided by the piston 8 in the cylinder 9 and that is provided with a mold clamping pressure. A servo valve 15 provided in the vicinity of the hydraulic cylinder device 2 is connected to the pressurizing chamber 22 on the second movable platen 10 side to be connected. The servo valve 15 is connected to a hydraulic pressure source including a pump 16 and the like. A pressure sensor 17 is attached to a conduit communicating with the pressurizing chamber 22. A signal from the pressure sensor 17 is input to the control device 20, and a control signal is output from the control device 20 to the servo valve 15 and the servo motor 18.

  The operation of the mold clamping device 1 when closing the mold will be described in detail with reference to FIG.

  The control device 20 outputs a mold closing command according to a control sequence program stored / stored therein. The servo valve 15 is controlled by a control signal based on a mold closing command so that both ports are disconnected or in a servo lock state as shown in the figure, and hydraulic oil is supplied to the decompression chamber 21 and the pressurization chamber 22 of the hydraulic cylinder device 2. The piston 8 operates so as to become a rigid body by being contained. Therefore, the state in which the hydraulic oil is contained in the hydraulic cylinder device 2 includes a servo lock state in which the sprue of the servo valve moves in a fine range in order to perform positioning control at the stop position. Then, the control device 20 drives the servo motor 18 to extend the toggle mechanism 11 and starts mold closing (S1).

  The control device 20 is set in the vicinity of the mold closing completion position where the half piece of the mold 6 attached to the first movable platen 7 is the farthest end of the mold closing stroke and the mold mating surface of the mold 6 is in close contact. It is then determined whether or not a predetermined position as a mold protection start position has been reached (S2). The mold closing completion position and the predetermined position can be set in the control device 20 as a mold closing completion position value and a mold protection start position value, respectively, and this setting operation can be performed even during the mold closing operation.

  When the mold 6 reaches a predetermined position, a calculation process for determining whether or not the pressure of the hydraulic cylinder device 2 has changed to a predetermined value is started in the control device 20 (S3). This process will be described in detail. When a foreign matter such as a burr of a molded product is present on the mold mating surface or the fitting portion of the mold 6 or when the insertion resistance at the fitting portion of the mold 6 is increased due to thermal expansion or the like, the hydraulic cylinder device Since the hydraulic oil in the second pressurizing chamber 22 is sealed, the pressure rises. The pressure in the pressurizing chamber 22 is detected by the pressure sensor 17 and input to the control device 20. The control device 20 calculates the pressure in the pressurizing chamber 22 and obtains the rate of change and / or the amount of change. That is, when the half of the mold 6 of the first movable platen 7 is stopped or decelerated by a foreign substance or the like during the mold closing movement, the pressure in the pressurizing chamber 22 is changed at a rate of change according to the mold closing speed. It changes with the amount of change according to the driving force. The control device 20 has a set value that can be set to an arbitrary value as a predetermined value for each of the change rate and the change amount. This predetermined value can be arbitrarily set even during the mold closing operation. The control device 20 determines whether or not the positive change rate and / or positive change amount in the pressure of the pressurizing chamber 22 has reached a predetermined value. The rate of change is determined by the pressure value that changes every unit time. The amount of change is preferably obtained from the absolute value of the pressure, but may be an amount changed from the stored pressure in the normal case where the mold is not protected. Although the pressure sensor 17 has been described as detecting the pressure in the pressurizing chamber 22, the pressure sensor may be provided in a pipe line communicating with the decompression chamber 21 to detect the pressure in the decompression chamber 21. In that case, when the mold 6 is stopped or decelerated due to foreign matter or the like, the hydraulic oil in the decompression chamber 21 of the hydraulic cylinder device 2 is sealed, so the pressure drops. And although the control apparatus 20 calculates the pressure of the pressure reduction chamber 21, the change rate and / or change amount become a negative thing. Therefore, the predetermined value for it is also a negative value.

  When the pressure in the hydraulic cylinder device 2 changes to a predetermined value, the control device 20 causes the servo motor 18 to stop suddenly and then servo-locks (S4). At the same time, the control device 20 controls the servo valve 15 to pressurize the decompression chamber 21 and decompress the pressurization chamber 22. Thereby, the rigidity of the piston 8 is released and the piston 8 can be freely moved, and can be forcibly driven in the mold opening direction when the pressure in the decompression chamber 21 is large (S5). In this way, the pressing force of foreign matter or the like in the mold 6 is released in a short time, so that the mold can be effectively prevented from being damaged. Here, the control for reducing the pressure of the hydraulic cylinder device 2 and releasing the pressing force of the foreign material or the like of the mold 6 is extremely small because the volume of the hydraulic cylinder device 2 is small and the servo valve 15 is used. Since it is performed rapidly and is often faster than the stop control of the second movable plate 10 and the mold closing means 3 having a large inertial force, the pressing time of the foreign matter in the mold 6 is shortened to prevent the mold 6 from being damaged. Effective in terms.

  Simultaneously with the steps S4 and S5, the control device 20 issues a mold protection abnormality alarm to inform the operator of the abnormality and cope with it (S6).

  On the other hand, when it is determined that the pressure of the hydraulic cylinder device 2 does not change to the predetermined value in the stroke S3, the control device 20 adds the half value of the mold 6 to the added value of the mold closing completion position value and the α value stored and stored in advance. It is determined whether or not the detected position value has reached (S7). The α value is a fixed value (0.1 mm in the embodiment) set according to the size and state of the mold clamping device 1 and has the purpose of preventing malfunction. The position of the added value is between a predetermined position as a mold protection start position and a mold closing completion position, and is a position in front of the mold closing completion position at a slight distance.

  When the detected position value of the half of the mold 6 reaches the added value, the pressure monitoring of the hydraulic cylinder device 2 in the step S3 is stopped (S8). Thereafter, the mold 6 closes the distance corresponding to the α value and reaches the mold closing completion position. Then, the control device 20 controls the servo valve 15 to supply the pressure oil of the pump 16 to the pressurizing chamber 22 and clamp the mold 6 (S9).

  Since the mold clamping device 1 is configured as described above, the hydraulic cylinder device 2 has only a minimum stroke required for mold clamping of the mold 6. A servo valve 15 that contains the decompression chamber 21 and the pressurization chamber 22 is disposed in the vicinity of the hydraulic cylinder device 2. For this reason, the volume of the decompression chamber 21 and the pressurization chamber 22 contained is extremely small. This is even more remarkable when compared with a normal direct pressure type clamping cylinder. As described above, the volume of the hydraulic cylinder device 2 is small and the servo valve is further provided, so that the pressure change in the hydraulic cylinder device 2 can appear sensitively.

  In addition, this invention includes what can be implemented in the aspect which added various change, correction, improvement, etc. based on the knowledge of those skilled in the art. Further, it goes without saying that any of the embodiments to which the above-mentioned changes are added is included in the scope of the present invention without departing from the gist of the present invention. For example, the mold clamping device may be a vertical type or a horizontal type. The mold closing means may have a mold clamping function as well as mold closing and mold opening / closing, and is not limited to a toggle mechanism, but only a cylinder, crank, linear motor, electromagnet, or ball screw and ball nut. It may be configured. Moreover, although the hydraulic cylinder apparatus showed the aspect provided in a 2nd movable board, you may provide in a 1st movable board or a metal mold | die. The hydraulic cylinder device has been described as a double-acting type provided with a piston, but may be a single-acting type or a sealed flexible container.

It is a block block diagram which shows the outline | summary of the mold clamping apparatus which implements this invention. It is a flowchart which shows the metal mold | die protection method of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Mold clamping apparatus 2 Hydraulic cylinder apparatus 3 Mold closing means 4 Tie bar 5 Fixed board 6 Mold 7 1st movable board 8 Piston 9 Cylinder 10 2nd movable board 11 Toggle mechanism 12 Ball screw 13 Ball nut 14 Pressure receiving board 15 Servo valve 16 Pump 17 Pressure sensor 18 Servo motor 19 Belt 20 Control device 21 Decompression chamber 22 Pressurization chamber

Claims (5)

In a mold clamping device provided with a mold closing means for closing a mold through a hydraulic cylinder device,
A mold protecting method for a mold clamping device, wherein a mold abnormality is determined based on a change in pressure of the enclosed hydraulic cylinder device to a predetermined value while the mold is closed.   The determination that the mold is abnormal based on the pressure of the hydraulic cylinder device changing to a predetermined value is performed while the mold moves from a predetermined position of the mold closing stroke to a position slightly before the position of completing the mold closing. 2. A mold protecting method for a mold clamping apparatus according to 1.   The mold protecting method for a mold clamping apparatus according to claim 1, wherein the mold closing means is a toggle mechanism.   4. The mold protecting method for a mold clamping device according to claim 1, wherein the hydraulic cylinder device is driven and controlled by a servo valve.   5. The mold protecting method for a mold clamping device according to claim 4, wherein when it is determined that the mold is abnormal based on a change in pressure of the hydraulic cylinder device to a predetermined value, the pressure of the hydraulic cylinder device is reduced. .

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