JP6034741B2 - Injection molding machine that can detect a decrease in clamping force - Google Patents

Description

  The present invention relates to an injection molding machine including a device that detects rotation in a direction in which a mold clamping force is reduced when a mold clamping force is generated by a mold thickness adjusting motor of the injection molding machine.

  In order to obtain a good product with an injection molding machine, it is important to keep the clamping force at a predetermined value. In the injection molding machine, as the mold opening / closing motor generates a mold clamping force when the mold is tightened, a force is generated to rotate the tie bar nut in the direction of decreasing the mold clamping force. At this time, normally, the driving torque for maintaining the rotational position of the mold thickness adjusting motor and the friction force between the tie bar nut and the rear platen contact surface rotate the tie bar nut in the direction of decreasing the clamping force. Since the force is larger than the force, the driven gear coupled to the tie bar nut, the large gear coupled to the driven gear, and the mold thickness adjusting motor are not rotated.

  However, when the frictional force on the contact surface between the tie bar nut and the rear platen decreases due to the operation of the machine for a long time, the tie bar nut tries to rotate in a direction to decrease the mold clamping force when the mold clamping force is generated. As means for preventing the rotation in the opposite direction, there are techniques disclosed in the following patent documents.

In Patent Document 1, a lock is applied by a lock nut of a cylinder mechanism attached to a driven gear in order to prevent the tie bar nut from rotating in a direction that reduces the mold clamping force due to the twist angle of the tie bar when a mold clamping force is applied. A technique for preventing the tie bar nut from rotating is disclosed.
Further, in Patent Document 2, circumferential grooves and radial grooves are formed on the contact surface of the tie bar nut with the housing, and excess grease that exists between the contact surface and the housing when a clamping force is applied. Has been disclosed in which the tie bar nut is prevented from rotating by the local stress generated at the edge of the radial groove when a mold clamping force is applied.

JP 2002-361698 A JP 2007-112003 A

  Neither Patent Document 1 nor Patent Document 2 can detect the rotation of the tie bar nut when it occurs for some reason. When the mold clamping force is generated, the friction force between the tie bar nut and the rear platen contact surface causes the tie bar nut to rotate, and the mold thickness adjusting motor connected to the tie bar nut rotates in the direction of decreasing the mold clamping force. Sometimes. When the mold thickness adjusting motor rotates in the direction of decreasing the mold clamping force, the mold clamping force during mold clamping decreases, but the die height mechanism including the tie bar nut is generally covered with a cover for safety. Therefore, it is difficult to visually detect the rotation of the mold thickness adjusting motor.If molding is continued without noticing the rotation of the mold thickness adjusting motor, the injection pressure will eventually increase the actual clamping force. There is also a risk that burrs may occur in the molded product.

  Therefore, an object of the present invention is to provide an injection molding machine that can prevent molding defects such as burrs of molded products due to a decrease in clamping force.

The invention according to claim 1 of the present application includes a rear platen, a mold thickness adjusting motor, a tie bar nut in contact with the rear platen, and a transmission means for transmitting the rotation of the mold thickness adjusting motor to the tie bar nut. Rotation that directly or indirectly detects the rotational state of the tie bar nut in an injection molding machine that performs mold thickness adjustment by moving the rear platen by rotation of the tie bar nut by rotation of the mold thickness adjusting motor. a state detecting means comprises a clamping force drop judging means, and the mold clamping force low warning means, wherein the clamping force drop judging means, said rotational state detecting means the tie bar nut during generation of the mold clamping force It determines that the clamping force upon detection of a rotation exceeding the backlash of drops, the mold clamping force low warning means, the clamping force drop judging means, the clamping force is reduced Injection molding machine is provided which is characterized in that a warning when it is determined that.

That is, in the invention according to claim 1, when the mold clamping force is generated, it is determined that the mold clamping force has decreased when the rotation of the tie bar nut is detected, and the mold clamping force decrease warning means issues a warning. Therefore, it is possible to prevent molding defects such as generation of burrs in the molded product due to a decrease in mold clamping force.
Further, in consideration of the backlash portion of the tie bar nut, when the rotation state detecting means detects a rotation exceeding the backlash portion, the mold clamping force decrease determining means determines that the mold clamping force has decreased, thereby Since the movement of the backlash provided in the movement direction for smooth rotation of the mold can be ignored and the determination of the decrease in the mold clamping force can be performed, it is possible to prevent the malfunction of the determination of the decrease in the mold clamping force. .

The invention according to claim 2 of the present application provides the injection molding machine according to claim 1, wherein the rotation state detecting means is a rotation detector for detecting rotation of the mold thickness adjusting motor.
According to a third aspect of the present invention, there is provided the injection molding machine according to the first aspect, wherein the rotation state detecting means is a rotation detector that detects the rotation of the tie bar nut.
Furthermore, in the invention according to claim 4 of the present application, the injection molding machine according to claim 1, wherein the rotation state detection means is a rotation detector that detects rotation of a driven gear that rotates together with the tie bar nut. Provided.
That is, in the inventions according to claims 2 to 4 , the rotation detector detects the rotation of the mold thickness adjusting motor, the tie bar nut, and the driven gear that are connected to each other directly or indirectly. The rotation of the tie bar nut can be detected, and the decrease in the clamping force can be detected by detecting the rotation of the tie bar nut.

In the invention according to claim 5 of the present application, a rear platen, a mold thickness adjusting motor, a tie bar nut in contact with the rear platen, a transmission means for transmitting rotation of the mold thickness adjusting motor to the tie bar nut, and the mold An encoder that is provided in the thickness adjusting motor and detects the rotational position or rotational speed of the mold thickness adjusting motor, and the driving torque of the mold thickness adjusting motor so as to hold the rotational position of the mold thickness adjusting motor. Rotation position holding control means for controlling the mold thickness adjustment motor, and by adjusting the mold thickness adjustment motor, the rear platen is moved to adjust the mold thickness. In the injection molding machine, the drive torque of the mold thickness adjustment motor is detected. Drive torque detecting means and mold clamping force decrease warning means, wherein the drive torque detecting means detects a drive torque that is greater than a reference value when the mold clamping force is generated. When the injection molding machine is provided that the clamping force decreases warning means, characterized in that a warning.

That is, in the invention according to claim 5 , when the mold clamping force is generated, it is determined that the mold clamping force has decreased when a driving torque equal to or greater than the reference value is detected, and the mold clamping force reduction warning means issues a warning. As a result, it is possible to prevent molding defects such as the occurrence of burrs in the molded product due to a decrease in the clamping force.

  According to the present invention, it is possible to provide an injection molding machine that can prevent molding defects such as generation of burrs in a molded product due to a decrease in clamping force.

It is explanatory drawing of one Embodiment of this invention. It is the figure which showed the structure of the die height mechanism in 1st Embodiment. It is sectional drawing of the tie bar nut and driven gear vicinity in FIG. It is a figure explaining the rotation detection method in the modification of 1st Embodiment. FIG. 5 is an enlarged view of the vicinity of a driven gear in FIG. 4. It is the figure which showed the structure of the die height mechanism in 2nd Embodiment. It is a flowchart which shows the method of the rotation detection in 1st Embodiment. It is a flowchart which shows the method of the rotation detection in 3rd Embodiment (the 1). It is a flowchart which shows the method of the rotation detection in 3rd Embodiment (the 2).

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is an explanatory diagram of an embodiment of the present invention. In FIG. 1, 1 is a toggle type mold clamping device. The stationary platen 10 and the rear platen 11 are connected by a plurality of tie bars 15. The movable platen 12 is arranged so as to be guided by the tie bar 15 between the fixed platen 10 and the rear platen 11.
A fixed mold 13 a is attached to the fixed platen 10, and a movable mold 13 b is attached to the movable platen 12. A toggle mechanism 14 is disposed between the rear platen 11 and the movable platen 12.

  A movable platen forward / reverse motor 18 and a ball screw 19 for driving the toggle mechanism 14 are attached to the rear platen 11. The movable platen forward / reverse motor 18 is a servo motor for mold clamping. The ball screw 19 is attached to the rear platen 11 so as to be rotatable and immovable in the axial direction, and includes a driven pulley 21 at a rear end thereof (on the side opposite to the movable platen 12 with respect to the rear platen 11). A drive pulley 22 is attached to the output shaft of the movable platen forward / reverse motor 18. A timing belt 23 is hung between the drive pulley 22 and the driven pulley 21, and the ball screw 19 is driven to rotate by a movable platen forward / reverse motor 18.

  A nut fixed to the cross head 20 of the toggle mechanism 14 is screwed onto the tip of the ball screw 19. As the ball screw 19 rotates, the nut and crosshead 20 move left and right in the figure to expand and contract the toggle mechanism 14, and the movable platen 12 moves forward and backward (left and right in the figure) along the tie bar 15 to close the mold and clamp the mold. The mold is opened. Reference numeral 24 denotes a position detector for detecting the position of the movable platen forward / reverse motor.

  On the rear end face side of the rear platen 11 (on the side opposite to the movable platen 12 of the rear platen 11), a tie bar nut 16a that is screwed with a screw provided on the tie bar 15 is provided. A fixing member 16 is attached to the rear platen 11 so that the tie bar nut 16a cannot move in the axial direction. Further, a rear platen forward / reverse motor 17 is attached to the rear platen 11. A gear provided on the output shaft of the rear platen forward / reverse motor 17 and a driven gear 32 attached to a tie bar nut 16 a provided on each tie bar 15 are connected via a large gear 31.

  The rear platen forward / reverse motor 17 is a mold thickness adjusting motor. By driving the rear platen forward / reverse motor 17 to rotate the driven gear 32 connected to the large gear 31, the tie bar nut 16 a to which the driven gear 32 is attached moves the rear platen 11 forward or backward along the tie bar 15. Adjust the mold clamping force according to the mold thickness.

  In the toggle type mold clamping apparatus 1, the mold clamping force is generated by the reaction force of the tie bar 15 that is extended, and the elongation of the tie bar 15 and the generated mold clamping force are in a proportional relationship. Further, the tie bar 15 is stretched so that the movable platen forward / reverse motor 18 moves to the most advanced position after the movable side mold 13b comes into contact with the fixed side mold 13a and closes, and the toggle mechanism 14 is fully extended. It is equal to the moving amount of the movable platen to the position (moving amount of the movable mold). Therefore, the set clamping force can be obtained by moving the movable platen 12 forward (moving toward the fixed platen 10) by the amount of extension of the tie bar 15 corresponding to the clamping force set from the mold touch position.

(First embodiment)
FIG. 2 is a view showing a configuration of a die height mechanism for driving the rear platen 11, and the same members as those in FIG. 1 are denoted by the same reference numerals. 3 is a cross-sectional view of the vicinity of the tie bar nut 16a and the driven gear 32 in FIG. A driven gear 32 is provided around the tie bar 15 and is configured to rotate by rotation of the large gear 31. In the present embodiment, the rotation of the tie bar nut 16a is detected by an encoder provided in a rear platen forward / reverse motor 17 which is a drive source for driving the tie bar nut 16a. Here, when detecting, considering the backlash portion of the tie bar nut, when the rotation state detecting means detects a rotation exceeding the backlash portion, the mold clamping force reduction determining means is said to have reduced the mold clamping force. It is preferable to determine. As a result, even if the backlash provided in the direction of motion for smooth rotation of the machine element can be moved, it can be ignored and the decrease in the clamping force can be determined. Can be prevented.

Next, a method for detecting the rotation of the tie bar nut in the present embodiment will be described step by step based on FIG.
(Step SA1) Touch the mold.
(Step SA2) A mold clamping force is generated.
(Step SA3) In order to detect the rotation of the tie bar nut, it is determined whether or not the reverse rotation of the mold thickness adjusting motor is detected by using an encoder provided in the rear platen forward / reverse motor. When it is detected (YES), the process proceeds to Step SA10, and when it is not detected (NO), the process proceeds to Step SA4.
(Step SA4) An injection operation is performed.
(Step SA5) A pressure holding operation is performed.

(Step SA6) Perform the weighing / cooling operation.
(Step SA7) Perform mold opening and projecting operation.
(Step SA8) Whether to continue molding is determined. When the molding is continued (YES), the process proceeds to step SA9, and when the molding is not continued (NO), the process ends.
(Step SA9) The mold closing operation is performed.
(Step SA10) An alarm is notified that rotation of the tie bar nut has been detected, and the molding operation is terminated.

In the first embodiment, the rotation of the tie bar nut 16a is detected by the encoder provided in the rear platen forward / reverse motor 17. However, when the encoder is not provided, other methods are used. The rotation can be detected by.
FIG. 4 is a diagram for explaining a tie bar nut rotation detection method in a modification of the first embodiment, and FIG. 5 is an enlarged view of one driven gear 32 in FIG. The driven gear 32 is provided with a rotation detector 41 for detecting rotation. When the movement of the tooth of the driven gear 32 is detected, the rotation is detected by the encoder provided in the rear platen forward / reverse motor 17. Similarly, an alarm can be notified.

Further, as shown as the rotation detector 42 in FIG. 4, a rotation detector 42 is provided in the vicinity of the rear platen forward / reverse motor 17 instead of the rotation detector 41 to detect that the rear platen forward / backward motor 17 has rotated. It is also possible.
Further, as shown as the rotation detector 44 in FIG. 3, it is possible to detect that the tie bar nut 16a has been rotated by providing the rotation detector 44 in the vicinity of the tie bar nut 16a instead of the rotation detector 41. is there.
When detecting the rotation state of the tie bar nut 16a by the encoder or the rotation detector, the rotation position is detected by the encoder or the rotation detector, the change of the rotation position is detected, and the tie bar nut 16a is rotated. Alternatively, the rotation speed may be detected by an encoder or a rotation detector, and the rotation of the tie bar nut 16a may be detected by detecting the occurrence of the rotation speed.

(Second Embodiment)
FIG. 6 shows an example in which a chain is used as a mechanism for driving the rear platen in the die height mechanism. In the present embodiment, instead of the large gear 31 in the first embodiment, a chain 35 is provided that spans the four driven gears 32, and the rotational force from the rear platen forward / reverse motor 17 is transmitted through the chain 35. It is transmitted to the driven gear 32 and the tie bar nut 16a. In the present embodiment, the rotation of the tie bar nut 16a is detected by providing a rotation detector 43 for detecting the rotation of the chain in the vicinity of the chain 35, and detecting the reverse rotation of the chain by the rotation detector 43. Is detected as rotating.
Also in the second embodiment, an encoder may be provided in the rear platen forward / reverse motor 17, a rotation detector 42 is provided in the vicinity of the rear platen forward / backward motor 17, or a rotation detector 41 in the vicinity of the driven gear 32. Or a rotation detector 44 near the tie bar nut 16a.

(Third embodiment)
In the first embodiment and the second embodiment, the rotation of the tie bar nut 16a is detected directly or indirectly by the encoder or the rotation detector. However, in this embodiment, instead of detecting the rotation. Thus, the rotational state of the tie bar nut 16a is detected by detecting the value of the rotational torque.
In the case of an electric motor, when an external force that can be rotated in a direction in which the mold clamping force decreases is applied, the torque is increased to prevent the rotation. Normally, the frictional force between the contact surface between the tie bar nut 16a and the rear platen 11 is larger than the rotational force that causes the holding torque of the electric motor to rotate the tie bar nut 16a. It does not rotate in the direction of decreasing force.

  However, when the machine is operated and the frictional force gradually decreases, a rotational force for rotating the tie bar nut 16a is applied to the electric motor as an external force. Then, the electric motor increases the holding torque of the electric motor in order to prevent rotation due to external force. The value of the holding torque can be detected by detecting the amount of current flowing through the electric motor. When the value of the holding torque exceeds the maximum torque of the electric motor, an alarm notification is performed to finish the molding operation. In addition, although the maximum torque of the electric motor is not exceeded, when the value exceeds a predetermined torque value, the molding operation can be continued while notifying that effect. The rotational position holding control means controls the driving torque of the mold thickness adjusting motor by controlling the position loop, speed loop, and current loop so as to eliminate the deviation between the target rotational position and the detected rotational position. The driving torque of the mold thickness adjusting motor may be controlled by controlling the speed loop and the current loop so as to eliminate the deviation between the target rotational speed and the detected rotational speed.

Next, the rotation detection method of the rear platen forward / backward motor in the present embodiment will be described step by step based on FIGS.
(Step SB1) A mold touch is performed.
(Step SB2) A mold clamping force is generated.
(Step SB3) The value of the holding torque of the rear platen forward / reverse motor when the mold clamping force is generated is detected.
(Step SB4) It is determined whether or not the mold is clamped for the first time after replacing the mold. If it is the first mold clamping (YES), the process proceeds to step SB5. If it is not the first mold clamping (NO), the process proceeds to step SB6.
(Step SB5) The holding torque value detected in Step SB3 is stored in the memory, and the stored holding torque value is called as the holding torque stored in the memory.

(Step SB6) Recall the holding torque value stored in the memory.
(Step SB7) It is determined whether the holding torque value detected in step SB3 is larger than the holding torque value called from the memory. If larger (YES), the process proceeds to step SB8, and if not larger (NO), the process proceeds to step SB10.
(Step SB8) It is determined whether or not the holding torque value detected in step SB3 is within the threshold value of the torque of the rear platen forward / reverse motor. If it is within the threshold (NO), the process proceeds to step SB9, and if it exceeds the threshold (YES), the process proceeds to step SB16.
(Step SB9) Notification that the holding torque is increasing is performed.
(Step SB10) An injection operation is performed.
(Step SB11) The pressure holding operation is performed.

(Step SB12) The measurement / cooling operation is performed.
(Step SB13) The mold is opened and protruded.
(Step SB14) Whether to continue molding is determined. When the molding is continued (YES), the process proceeds to step SB15, and when the molding is not continued (NO), the process is terminated.
(Step SB15) The mold closing operation is performed.
(Step SB16) A warning is given that the value of the holding torque of the rear platen forward / reverse motor exceeds the torque threshold value, and the molding operation is terminated.

  In these embodiments, the rotation of the driven gear that rotates together with the tie bar nut, the rear platen forward / backward motor, and the tie bar nut is detected by the encoder or the rotation detector to detect a change in position or a change in speed. However, the detection target is not limited to these, and if the member rotates with the rotation of the tie bar nut, the rotation of the tie bar nut may be detected by detecting the position and speed of the other member. it can.

DESCRIPTION OF SYMBOLS 1 Toggle type mold clamping apparatus 10 Fixed platen 11 Rear platen 12 Movable platen 13a Fixed side mold 13b Movable side mold 14 Toggle mechanism 15 Tie bar 16 Fixed member 16a Tie bar nut 17 Rear platen back and forth motor 18 Movable platen back and forth motor 19 Ball screw 20 Crosshead 21 Driven pulley 22 Drive pulley 23 Timing belt 24 Position detector 31 Large gear 32 Driven gear 35 Chain 41, 42, 43, 44 Rotation detector

Claims (5)

The rear platen,
A mold thickness adjusting motor;
A tie bar nut that contacts the rear platen;
Transmission means for transmitting the rotation of the mold thickness adjusting motor to the tie bar nut;
In an injection molding machine that performs mold thickness adjustment by moving the rear platen by rotation of the tie bar nut by rotation of the mold thickness adjusting motor,
Rotation state detection means for directly or indirectly detecting the rotation state of the tie bar nut;
Mold clamping force decrease judging means;
A mold clamping force reduction warning means,
The mold clamping force decrease determining means determines that the mold clamping force has decreased when the rotation state detecting means detects rotation exceeding the backlash of the tie bar nut when the mold clamping force is generated,
The mold-clamping force decrease warning means issues a warning when the mold-clamping force decrease determination means determines that the mold-clamping force has decreased. 2. The injection molding machine according to claim 1, wherein the rotation state detection means is a rotation detector that detects rotation of the mold thickness adjusting motor . 2. The injection molding machine according to claim 1, wherein the rotation state detecting means is a rotation detector that detects the rotation of the tie bar nut . 2. The injection molding machine according to claim 1, wherein the rotation state detecting means is a rotation detector that detects rotation of a driven gear that rotates together with the tie bar nut. The rear platen,
A mold thickness adjusting motor;
A tie bar nut that contacts the rear platen;
A transmission means for transmitting rotation of the mold thickness adjusting motor to the tie bar nut;
An encoder that is provided in the mold thickness adjusting motor and detects the rotational position or rotational speed of the mold thickness adjusting motor, and the mold thickness adjusting motor is configured to hold the rotational position of the mold thickness adjusting motor. Rotational position holding control means for controlling the drive torque,
In an injection molding machine that performs mold thickness adjustment by moving the rear platen by rotation of the mold thickness adjusting motor,
Drive torque detecting means for detecting the drive torque of the mold thickness adjusting motor;
A mold clamping force reduction warning means,
When the driving torque detection means detects a driving torque that is equal to or higher than a reference value when the mold clamping force is generated, the mold clamping force reduction warning means issues a warning.
An injection molding machine characterized by that .

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