JP4199585B2 - Mold clamping device and core back method for injection molding machine, etc. - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a mold clamping apparatus such as an injection molding machine and a core back method for injecting a molten resin into an injection mold and molding a molded product.
[0002]
[Prior art]
A mold clamping device such as an injection molding machine that molds a molded product by injecting molten resin into an injection mold, and a fixed mold with a fixed mold attached, and a movable mold attached to the fixed plate via a tie bar And a movable board that is movable forward and backward with respect to the fixed mold.
[0003]
The stationary platen is provided with a hydraulic clamping cylinder for moving the tie bar back and forth and a tie bar sliding servo motor for moving the tie bar back and forth in the axial direction. The movable board is advanced and retracted on the tie bar by a mold opening / closing servo motor, and the movable board is locked to the tie bar by a mold clamping half nut at a predetermined position. In the injection press step, the hydraulic mold clamping cylinder is driven to press the fixed mold and the movable mold (see, for example, Patent Document 1).
[0004]
Further, a fixed plate with a fixed mold attached thereto, a movable mold attached to the fixed plate via a tie bar, a movable plate movable forward and backward with respect to the fixed die, and a fitting provided protruding from the movable plate. A mold clamping ram having an insertion part and a hydraulic mold clamping cylinder for inserting and retracting the fitting insertion part of the mold clamping ram so that the mold clamping ram can be freely moved back and forth. The fixed mold and the movable mold are pressed by moving the movable board via the movable board (for example, see Patent Document 2).
[0005]
[Patent Document 1]
Japanese Patent Laid-Open No. 10-296739
[Patent Document 2]
Japanese Patent Laid-Open No. 6-182838
[Problems to be solved by the invention]
By the way, in Patent Documents 1 and 2, the tie bar is moved forward and backward by a tie bar slide servo motor, the phase of the mold clamping half nut and the thread portion of the tie bar is adjusted, and the mold clamping half nut and the thread portion of the tie bar are engaged with each other. After that, the hydraulic mold clamping cylinder is driven to press the fixed mold and the movable mold.
[0008]
Also, after filling the cavity formed by the fixed mold and the moving mold by injecting the molten resin containing the foam material from the injection molding machine, the moving mold is fixed as the foam material progresses. Retreat from the core and perform the core back operation to expand the cavity.
[0009]
Conventionally, since this core back operation is performed by hydraulic control of the hydraulic clamping cylinder, there is a problem that the positional accuracy can vary and the dimensional accuracy of the molded product can vary.
[0010]
In view of this, there is also an apparatus in which a moving screw is additionally equipped with a ball screw and a servo motor for driving the ball screw, thereby performing a core back operation. However, in this case, each time the mold is replaced, the apparatus is replaced, or a ball screw and a servo motor for driving the ball screw are provided for each mold, which causes an increase in cost.
[0011]
The present invention has been made paying attention to the above circumstances, and its object is to perform a core back operation without additionally providing a ball screw and a servo motor for driving the ball screw, thereby reducing the cost and An object of the present invention is to provide a mold clamping device such as an injection molding machine and a core back method that can improve the positional accuracy.
[0012]
[Means for Solving the Problems]
In order to achieve the above-mentioned object, according to the present invention, a fixed plate having a fixed mold attached thereto, and a movable mold attached to the fixed plate via a tie bar, the advancing and retreating relative to the fixed mold are provided. A movable moving plate, a mold opening / closing servo motor for moving the moving plate back and forth on the tie bar, a mold clamping half nut for locking the movement of the moving plate at a predetermined position, and a piston provided on the tie bar In a mold clamping device such as an injection molding machine comprising a hydraulic clamping cylinder that inserts and moves a tie bar forward and backward, a feed screw that moves the moving plate to the fixed plate via the tie bar and drives the feed screw A servo motor for half nut positioning and core back is provided, and the half nut positioning and core back servo motor is driven during the core back in the injection molding process. Characterized by core back moving mold through the movable platen by.
[0013]
According to a second aspect of the present invention, there is provided a fixed plate with a fixed mold attached thereto, a movable mold attached to the fixed plate via a tie bar, and a movable plate movable forward and backward with respect to the fixed mold, and the movable plate on the tie bar. A mold opening / closing servo motor to be moved forward and backward, a mold clamping half nut for locking the movement of the movable platen at a predetermined position, and a mold clamping ram having a fitting insertion portion provided protruding from the movable platen, In a mold clamping apparatus, such as an injection molding machine, which includes a hydraulic mold clamping cylinder for inserting and retracting the fitting insertion portion of the mold clamping ram so as to move forward and backward, the movable disc is moved to the hydraulic mold clamping cylinder via the mold clamping ram. And a half nut positioning / core back servo motor for driving the feed screw, and driving the half nut positioning / core back servo motor during core back in the injection molding process. Characterized by core back moving mold through the movable platen by means of screws.
[0014]
According to a third aspect of the present invention, in the method of core-backing the movable mold using a mold clamping device such as the injection molding machine according to the first or second aspect, a molten resin containing a foam material is injected from an injection nozzle of the injection molding machine. After filling the cavity formed by the fixed mold and the moving mold, the servo motor for half nut positioning and core back is driven and the moving mold is core-backed by the feed screw through the moving plate. It is characterized by doing.
[0015]
According to the above configuration, when the molten resin containing the foam material is injected from the injection nozzle of the injection molding machine and filled into the cavity formed by the fixed mold and the movable mold, the molten resin foams in the cavity. . As the molten resin foams, the servomotor for half-nut positioning and core-back is driven and the moving mold is core-backed by the feed screw through the moving plate. The cavity thus filled is filled with molten resin.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0017]
FIG. 1 shows a first embodiment, and FIG. 1 is a vertical side view of a mold clamping device of an injection molding machine. In the figure, 1 is a fixed platen and 2 is a moving platen. A fixed mold 3 is attached to the fixed platen 1, and a movable mold 4 facing the fixed mold 3 is attached to the movable platen 2. The fixed platen 1 is provided with a plurality of tie bars 5 protruding so that the movable platen 2 can move forward and backward on these tie bars 5.
[0018]
The fixed mold 3 is provided with a nozzle touch surface 7 for joining with an injection nozzle 6 of an injection molding machine (not shown). The nozzle touch surface 7 is connected to the fixed mold 3 and the movable mold 4 via a resin passage 8. Are communicated with a cavity 9 provided between the two. The fixed platen 1 is provided with an opening 10 through which the injection nozzle 6 opens so as to be able to advance and retract.
[0019]
A hydraulic clamping cylinder 11 is provided at a portion where the fixed platen 1 is connected to the tie bar 5. The hydraulic mold clamping cylinder 11 is fitted with a piston portion 12 provided integrally with the base end portion of the tie bar 5, and the interior of the hydraulic mold clamping cylinder 11 is sandwiched between the mold clamping side chamber 13 a and the mold opening side chamber. 13b.
[0020]
Further, the base end portion of the piston portion 12 penetrates the partition wall 14 of the hydraulic mold clamping cylinder 11 and projects into the positioning box 15. A half-nut positioning / core-back servomotor (hereinafter referred to as a first servomotor) 17 is attached to the positioning box 15. A bearing 18 is provided coaxially with the piston portion 12 on the rear surface of the positioning box 15, and a screw shaft 20 of a ball screw 19 as a feed screw is rotatably supported on the bearing 18. A base end portion of the screw shaft 20 protrudes from the back surface of the positioning box 15, and a driven pulley 21 is fitted to the protruding portion.
[0021]
The servomotor 17 is provided with a driving pulley 22, and a timing belt 23 is stretched between the driving pulley 22 and the driven pulley 21 so that the screw shaft 20 of the ball screw 19 rotates. A screw portion 24 is provided at the tip of the screw shaft 20, and the screw portion 24 is screwed with a nut portion 25 fitted to the shaft center portion of the piston portion 12. Accordingly, the rotational motion of the screw shaft 20 is converted into a linear motion via the nut portion 25 by the ball screw 19.
[0022]
The fixed platen 1 is provided with a plurality of mold opening / closing servomotors (hereinafter referred to as second servomotors) 27 via brackets 26. A screw portion 29 is provided on the rotating shaft 28 of the servo motor 27. A nut portion 30 is screwed to the screw portion 29, and the nut portion 30 is fixed to the moving plate 2 to constitute a feed screw 31 as a ball screw. Accordingly, when the second servo motor 27 is driven to rotate the screw portion 29, the movable platen 2 advances and retreats with respect to the fixed platen 1 via the nut portion 30, and the movable die 4 moves relative to the fixed die 3. Is designed to open and close.
[0023]
The tie bar 5 protrudes through the movable board 2, and an engagement groove 5a made of a screw thread or an annular groove is provided on the outer peripheral surface of the tie bar 5. Further, a mold clamping half nut 33 that is opened and closed by an open / close cylinder 32 and engages / disengages with the engagement groove 5a of the tie bar 5 is provided on the back side of the movable board 2.
[0024]
Next, the operation of the mold clamping device of the injection molding machine configured as described above will be described. When the fixed mold 3 and the movable mold 4 are attached and the mold thickness is adjusted, the opening / closing cylinder 32 releases the meshing relationship between the mold clamping half nut 33 and the engagement groove 5 a of the tie bar 5.
[0025]
Next, the mold closing operation is performed by driving the second servomotor 27. In this case, at the mold closing limit, the mold clamping half nut 33 is closed by the open / close cylinder 32 and meshes with the engagement groove 5 a of the tie bar 5 so that the movable platen 2 is engaged with the tie bar 5.
[0026]
At this time, the mold clamping half nut 33 and the engagement groove 5a of the tie bar 5 may be properly meshed with each other. However, if the meshing is not performed due to a difference in pitch between the two, the first servo motor 17 is driven. That is, when the first servo motor 17 is driven, the ball screw 19 slightly moves the tie bar 5 forward through the piston portion 12, and the mold clamping half nut 33 and the engagement groove 5a of the tie bar 5 are properly engaged with each other. Then, the first servo motor 17 is stopped.
[0027]
At this time, the position of the tie bar 5 is read and stored by position detecting means (not shown). In the subsequent molding operation, the first servo motor 17 is controlled so that the tie bar 5 is always in this position at the limit of the forward movement of the mold by the movable platen 2. In this way, the mold thickness adjustment operation is completed.
[0028]
As described above, after the meshing position adjustment of the mold clamping half nut 33 is performed, the second servo motor 27 is driven to advance the movable board 2 and after reaching an arbitrary position near the forward limit. The first servo motor 17 is driven, and the tie bar 5 is moved backward (rightward in the figure) by the ball screw 19 to control the speeds of the second servo motor 27 and the first servo motor 17 and the relative speeds thereof. Are synchronized (that is, the relative speed is set to 0). Then, when the forward speeds of the movable platen 2 and the tie bar 5 are synchronized and the relative speed at the specific position is 0, the mold clamping half nut 33 is closed and meshed with the engagement groove 5 a of the tie bar 5.
[0029]
After adjusting the meshing position of the mold clamping half nut 33 in this manner, an injection molding process including a mold clamping operation is started. First, when the second servo motor 27 is driven to move the moving board 2 forward and the moving board 2 reaches an arbitrary position near the mold closing limit, the second servo motor 27 is located leftward from the previously stored position. The tie bar 5 starts to move backward (rightward in the figure) by driving the first servo motor 17, and controls the speed of each servo motor 17 and 27 to calculate the relative speed between the moving board 2 and the tie bar 5. (Ie, the relative speed is set to 0).
[0030]
Then, when the moving speed of the moving plate 2 and the tie bar 5 in the right direction is synchronized at a predetermined position, the engagement between the mold clamping half nut 33 and the engagement groove 5a of the tie bar 5 is detected. If the meshing is in an appropriate position, the mold clamping half nut 33 is closed and meshed with the engagement groove 5a of the tie bar 5 while maintaining the speed control so that the relative speed becomes zero. When the meshing is completed and the movable board 2 reaches the mold closing limit, the position of the tie bar 5 is read by a position detector (not shown) and compared with the position of the tie bar 5 stored at the time of the above-described mold thickness adjustment. If the comparison results match, the mold clamping / injection press operation is started.
[0031]
After the fixed mold 3 and the movable mold 4 are clamped, when a molten resin containing a foam material is injected from the injection nozzle 6 of the injection molding machine, the molten resin is filled into the cavity 9 through the resin passage 8. . Since the molten resin containing the foam material filled in the cavity 9 is foamed in the cavity 9, the first servo motor 17 is driven as the foaming progresses, and the tie bar 5 is advanced by the ball screw 19 (left direction in the figure). ), And the movable mold 4 performs the core back operation with respect to the fixed mold 3 through the movable board 2.
[0032]
Accordingly, the cavity 9 is expanded, and the molten resin containing the foaming material is foamed in the expanded cavity 9, and the first servo motor 17 stops after the movable mold 4 cores back by a predetermined amount. And a molded article is shape | molded through a holding pressure and a cooling process.
[0033]
After molding the molded product, the mold opening process is started, and the pressure oil in the mold opening side chamber 13b of the hydraulic mold clamping cylinder 11 is introduced, while the second servo motor 27 is driven and the ball screw 31 advances the moving plate 2 ( When leftward in the figure), the fixed mold 3 and the movable mold 4 are opened, and the molded product can be taken out. Further, during the mold opening, the engagement between the mold clamping half nut 33 and the engagement groove 5a of the tie bar 5 is released. At the same time, the first servomotor 17 is driven in reverse to move the tie bar 5 in the left direction, completing the one-cycle operation of injection molding.
[0034]
According to the first embodiment, the position accuracy at the time of molding is improved by driving with the first servo motor and the ball screw during the core back operation in the injection molding process. Further, by using the servo motor for positioning the half nut for the core back operation, it is not necessary to add a servo motor to the moving mold or the moving board, and the cost can be reduced.
[0035]
FIG. 2 shows a second embodiment, and the same components as those of the first embodiment are denoted by the same reference numerals and description thereof is omitted. A hydraulic clamping cylinder 40 is provided on the back side of the moving board 2 supported by a plurality of tie bars 5. The hydraulic mold clamping cylinder 40 is provided with a hydraulic chamber 41 that opens on the back side of the movable platen 2, and a mold clamping ram 42 is fitted into the hydraulic chamber 41 so as to freely advance and retract. The tip end of the mold clamping ram 42 is connected to the moving board 2.
[0036]
The hydraulic clamping cylinder 40 is provided with a stepped through hole 43 in series with the hydraulic chamber 41, and a screw shaft 45 constituting a feed screw 44 as a ball screw is inserted into the through hole 43 so as to freely advance and retract. . A flange 45 a is provided at one end of the screw shaft 45, and the flange 45 a is connected to the mold clamping ram 42. The other end portion of the screw shaft 45 protrudes rearward of the hydraulic clamping cylinder 40, and a screw portion 46 is formed on the protruding portion. A nut portion 47 constituting a ball screw 44 is screwed to the screw portion 46, and a driven pulley 48 is integrally fitted to the nut portion 47.
[0037]
The hydraulic mold clamping cylinder 40 is provided with a half-nut positioning / core-back servomotor (hereinafter referred to as a first servomotor) 50 by a bracket 49. The first servo motor 50 is provided with a driving pulley 51, and a timing belt 52 is stretched between the driving pulley 51 and the driven pulley 48. Accordingly, the nut portion 47 of the feed screw 44 is rotated by driving the first servomotor 50, and the rotation of the nut portion 47 is converted into a linear motion, so that the screw shaft 45 moves forward and backward in the axial direction. .
[0038]
Next, the operation of the mold clamping device of the injection molding machine configured as described above will be described. When the fixed mold 3 and the movable mold 4 are clamped as shown in FIG. 2 by the same action as in the first embodiment, and then a molten resin containing a foam material is injected from the injection nozzle 6 of the injection molding machine. The molten resin is filled into the cavity 9 through the resin passage 8. Since the molten resin containing the foaming material filled in the cavity 9 foams in the cavity 9, the first servo motor 50 is driven as the foaming proceeds, and the mold clamping ram 42 is moved in the left direction in the figure by the ball screw 44. The movable mold 4 performs a core back operation with respect to the fixed mold 3 through the movable board 2.
[0039]
Therefore, the cavity 9 is expanded, and after the molten resin containing the foaming material is foamed in the expanded cavity 9 and the movable mold 4 cores back by a predetermined amount, the first servo motor 50 stops. And a molded article is shape | molded through a holding pressure and a cooling process.
[0040]
After the molded product is molded, when the second servomotor 27 is driven and the moving plate 2 is moved leftward in the figure by the ball screw 31, the fixed mold 3 and the movable mold 4 are opened, and the molded product is opened. Can be taken out. Further, during the mold opening, the engagement between the mold clamping half nut 33 and the engagement groove 5a of the tie bar 5 is released. At the same time, the first servo motor 50 is driven in the reverse direction to move the mold clamping ram 42 in the left direction to complete one cycle operation of injection molding.
[0041]
According to the second embodiment, the position accuracy at the time of molding is improved by driving with the first servo motor and the ball screw during the core back operation in the injection molding process. Further, by using the servo motor for positioning the half nut for the core back operation, it is not necessary to add a servo motor to the moving mold or the moving board, and the cost can be reduced.
[0042]
In the first and second embodiments, a pulley and a belt are used for power transmission between the first servo motor and the ball screw. However, power transmission may be performed by a gear, and the invention is not limited to the ball screw. A feed screw mechanism such as a screw or a planetary roller screw may be used as long as the rotary motion is converted into a linear motion.
[0043]
In addition, although the mold clamping apparatus of the injection molding machine has been described, it can be similarly applied to, for example, a die casting machine, a press machine, and the like.
[0044]
Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. Moreover, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, you may combine suitably the component covering different embodiment.
[0045]
【The invention's effect】
As described above, according to the present invention, the core back operation can be performed without additionally providing a ball screw and a servo motor for driving the ball screw, and there is an effect that cost reduction and position accuracy can be improved.
[Brief description of the drawings]
FIG. 1 is a longitudinal side view of a mold clamping device of an injection molding machine showing a first embodiment of the present invention.
FIG. 2 is a longitudinal side view of a mold clamping device of an injection molding machine showing a second embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Fixed board, 2 ... Moving board, 3 ... Fixed metal mold, 4 ... Moving metal mold, 5 ... Tie bar, 11 ... Hydraulic clamping cylinder, 17 ... 1st servo motor (half nut positioning and core back servo motor , 19 ... Ball screw (feed screw), 27 ... Second servo motor (servo motor for mold opening / closing), 33 ... Half nut for clamping, 40 ... Cylinder for hydraulic mold clamping, 44 ... Ball screw (feed screw) 50 ... 1st servo motor (servo motor for half nut positioning and core back)

Claims (3)

A fixed plate with a fixed mold, a movable plate attached to the fixed plate via a tie bar, a movable plate that can move forward and backward with respect to the fixed die, and a mold opening and closing that moves the movable plate forward and backward on the tie bar Injection molding comprising: a servo motor for use, a mold clamping half nut for locking the movement of the moving plate at a predetermined position, and a hydraulic mold clamping cylinder for inserting and inserting a piston portion provided on the tie bar to advance and retract the tie bar In mold clamping devices such as machines,
The fixed plate is provided with a feed screw for moving the moving plate via the tie bar and a servo motor for half-nut positioning / core back for driving the feed screw, and the half-nut positioning / core at the time of core back in the injection molding process. A mold clamping apparatus for an injection molding machine or the like, wherein a back servomotor is driven to core-back a movable mold through the movable plate by the feed screw. A fixed plate with a fixed mold, a movable plate attached to the fixed plate via a tie bar, a movable plate that can move forward and backward with respect to the fixed die, and a mold opening and closing that moves the movable plate forward and backward on the tie bar Servo motor, mold clamping half nut for locking the movement of the moving plate at a predetermined position, mold clamping ram having a fitting insertion portion provided protruding from the moving plate, and the mold clamping ram In a mold clamping device such as an injection molding machine composed of a hydraulic mold clamping cylinder for inserting and retracting a fitting insertion part,
The hydraulic mold clamping cylinder is provided with a feed screw for moving the moving plate via the mold clamping ram and a half-nut positioning / core-back servomotor for driving the feed screw, and the half-positioning and core-back servo motor is driven during the core back in the injection molding process A mold clamping apparatus for an injection molding machine or the like, wherein a servomotor for nut positioning and core back is driven to core a movable mold through the movable plate by the feed screw. In the method of core-backing the movable mold using a mold clamping device such as an injection molding machine according to claim 1 or 2,
After injecting a molten resin containing a foam material from an injection nozzle of an injection molding machine and filling the cavity formed by the stationary mold and the moving mold,
A core back method for a mold clamping device of an injection molding machine or the like, wherein the half nut positioning / core back servo motor is driven to core the movable mold through the movable plate by the feed screw.

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