JP2005342935A - Injection foam molding machine and injection foam molding method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the occurrence of a swirl mark or silver by suppressing the entering of a foaming gas or air into the gap between a molded product and a mold. <P>SOLUTION: A first changeover means is connected so as to be changed over to a state that the connection of a first hydraulic chamber and a second hydraulic chamber is cut off, a state that hydraulic oil is supplied to the first hydraulic chamber of each of hydraulic mold clamping cylinders and the second hydraulic chamber is connected to a no-pressure oil discharge side and a state that hydraulic oil is supplied to the second hydraulic chamber of each of the hydraulic mold clamping cylinders and the first hydraulic chamber is connected to the no-pressure oil discharge side. A second changeover means is installed between the first hydraulic chambers of two sets of the diagonally arranged hydraulic mold clamping cylinders among four sets of the hydraulic mold clamping cylinders and the first changeover means to be connected so as to be capable of being changed over to the state that the first hydraulic chamber is connected to the no-pressure oil discharge state and a hydraulic oil supply state and two sets of mechanical means for synchronously moving the rams of two sets of the diagonally arranged hydraulic mold clamping cylinders in the direction of the first hydraulic chamber. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a mold clamping device of an injection foam molding machine provided with a mold clamping means using a hydraulic cylinder, by appropriately controlling the foam expansion speed of the foam molded product, and eliminating the problem that an irregular pattern is formed on the surface of the molded product. The present invention relates to an injection foam molding machine and an injection foam molding method in which molds are kept parallel.

As an injection foam molding method for injection foam molding products by an injection molding machine, after the surface is cured without foaming, a heat-plasticized foamable resin is injected into the mold and the injection is finished and the mold is in contact with the mold. 2. Description of the Related Art Conventionally, a technique is known in which after the surface of a molded product is cooled and hardened, the volume of the mold cavity is expanded to lower the internal pressure of the molded product and foam the inside of the molded product. According to this method, the inside can be highly foamed to improve the appearance of the appearance, and the molded product can be lightened.
However, in such an injection foam molding method, the foaming gas generated by the resin pressure of the foamable resin rapidly decreasing at the time of injection is confined in the mold cavity, or the mold cavity is filled up to the volume of the molded product. When expanding, the solidified layer on the resin surface cannot follow the movement of the inner surface of the mold, peels off from the inner surface of the mold, and a free-solidified surface of the resin that does not follow the inner surface of the mold is generated, so that the appearance of the injection foam molded product Swirl marks (foaming gas traces) and silver (silver stripes) are easily generated. As a method for preventing these problems and eliminating defects on the surface of the molded product, the following methods are known.
(A) An unsolidified molded product immediately after injection is once pressurized to be solidified in a state where surface foaming is suppressed, and then the volume is expanded.
(B) A material having a low thermal conductivity is used for the mold to delay the cooling, so that solidification and foaming are made uniform (for example, see Patent Document 1).

In addition, in the injection foam molding having a plurality of mold clamping cylinders, when the volume of the mold cavity is enlarged, the fixed side mold and the movable side mold are not clamped, so that the mold Depending on the position of the foam molded product with respect to the mold and the shape of the molded product, a relative inclination of the mold may occur, and the thickness of the foam molded product may be biased. A similar problem may also occur when the distribution of pressure in the mold during foam molding with respect to the mold is uneven.
The following is known as an injection molding machine having a mechanism that prevents the relative inclination of the mold and keeps the die plate attached with the mold parallel.
(C) Using an injection compression molding machine equipped with a mold opening / closing means using a servo motor and a ball screw device and a mold clamping means using a hydraulic cylinder, the fixed die plate and each tie bar The detection value of the relative position detection sensor is matched with the position of the movable die plate converted from the number of rotations of the ball screw of the movable die plate moving means. The movable die plate is kept parallel by operating the cylinder (see, for example, Patent Document 2).
JP 2000-71277 A JP 2003-181895 A

  However, in the techniques described in (A) and (B) above, when the mold for foaming is opened and closed using a hydraulic mechanism or a toggle mechanism, the mold is moved to a fixed position at a constant speed. It is difficult to cope with changes in temperature conditions of uncured resin. Furthermore, when the mold moving speed is too fast, the expansion due to foaming is not in time, and foaming gas or air enters between the molded product and the mold, and when the mold moving speed is slow, the resin hardens during the foam expansion. Again, foaming gas or air enters between the molded product and the mold, and in either case, swirl marks (foaming gas marks) and silver (silver stripes) are likely to be generated.

  The technology described in (C) above, which is used in an injection compression molding machine, prevents the relative inclination of the mold and keeps the die plate attached with the mold parallel. It can also be used for molding machines. However, in an injection foam molding machine equipped with a plurality of mold clamping cylinders, the operation of stopping the movable die plate at a predetermined position in accordance with the expansion of the foam using the plurality of mold clamping cylinders is referred to as the hydraulic cylinder operating pressure. When the back pressure is adjusted, the foaming pressure is significantly lower than the operating pressure of the hydraulic cylinder. Therefore, the larger the injection foam molding machine is, the more difficult it is to make fine adjustments. It is difficult to maintain parallelism. In addition, if there is a clearance in the opposite direction to the mold clamping between the groove provided on the tie bar and the concave groove of the nut attached to the movable mold that engages with this groove, only the clearance is provided by the mold opening operation. May cause a movement error. The groove is used as a means for fixing the tie bar and the movable mold.

  An object of the present invention is to move a mold using a mechanical moving means that allows easy speed control during foam molding by an injection foam molding machine, so that foaming gas or air enters between the molded product and the mold. An object is to provide an injection foam molding machine and an injection foam molding method capable of preventing the occurrence of swirl marks and silver by suppressing this. Another object of the present invention is to provide an injection foam molding machine and an injection foam molding method that can control the position of the movable die plate in parallel when foam molding is stopped, and make the thickness of the foam molded product uniform without error.

To solve the above problems, the present invention is characterized by the following configurations and methods.
(1) An injection foam molding machine according to the present invention uses a mold clamping device having four sets of hydraulic mold clamping cylinders, and after injection-filling a foamed resin melt-plasticized into the mold clamped, the mold In the injection foam molding machine that molds the foam cavity by increasing the mold cavity volume by opening a certain distance, the inside of the four hydraulic clamping cylinders is provided with a first hydraulic chamber provided on the tie bar side. A first switching means and a second switching means which are defined in a second hydraulic chamber provided on the opposite side of the tie bar and adjust the hydraulic pressure between the first hydraulic chamber and the second hydraulic chamber; A supply side of the first switching means is connected to a hydraulic pressure source and a drainage tank, and an output side of the first switching means is connected to the first hydraulic chamber and the second hydraulic chamber. A state of shutting off, supplying pressure oil to the first hydraulic chamber of each hydraulic clamping cylinder, 2 is connected to the non-pressure oil discharge side, pressure oil is supplied to the second oil pressure chamber of each hydraulic clamping cylinder, and the first oil pressure chamber is connected to the non-pressure oil discharge side. 2 sets of hydraulic mold clamping cylinders (molds) that are switchably connected to any one of the states connected to each other, and the second switching means is disposed at one diagonal of the four sets of hydraulic mold clamping cylinders. (Clamping cylinder A, mold clamping cylinder D) between the first hydraulic chamber and the first switching means, and connecting the first hydraulic chamber to the non-pressure oil discharge side; The hydraulic pressure source is connected so that it can be switched to either a state in which pressure oil is supplied, so that the high pressure oil can be supplied during the mold clamping process and the low pressure oil set during foam expansion of the molded product can be supplied. Two sets of hydraulic mold clamping cylinders, which are provided so as to be switchable and are arranged on one diagonal, are connected to the first hydraulic chamber. It has two sets of mechanical means for moving in synchronization with the direction.

(2) The injection foam molding method of the present invention uses a mold clamping device having four sets of hydraulic mold clamping cylinders, and after injection-filling melt-plasticized foamable resin into the mold clamped mold, In the injection foam molding method in which the mold cavity volume is increased by opening a certain distance to form a foam molded article, the expansion of the mold cavity volume is increased using the injection foam molding machine described in (1) above. When performing, the step of connecting both the first hydraulic chamber and the second hydraulic chamber of the two diagonal hydraulic clamping cylinders to the non-pressure oil discharge side; The second hydraulic pressure is applied to the first hydraulic chamber of two sets of hydraulic mold clamping cylinders (the mold clamping cylinder B and the mold clamping cylinder C) on the other diagonal side of the hydraulic mold clamping cylinder. The step of connecting the chamber to the oil drain side and the two sets of oil pressure on the one diagonal The ram of the clamping cylinder is moved in the direction of the first hydraulic chamber synchronously by mechanical means, the tie bar coupled to the ram is pushed out, and the reaction force of the two other diagonal hydraulic clamping cylinders The step of moving the movable mold by mechanical mold opening means without the clearance between the tie bar and the detachable nut provided on the movable die plate engaged therewith, and the movable mold reaches the specified moving distance And stopping the ram and proceeding to the cooling process.

(3) The injection foam molding machine of the present invention uses a mold clamping device having four sets of hydraulic mold clamping cylinders, and after injection-filling a melt-plasticized foamable resin into the mold clamped mold, In the injection foam molding machine that molds the foam cavity by increasing the mold cavity volume by opening a certain distance, the inside of the four hydraulic clamping cylinders is provided with a first hydraulic chamber provided on the tie bar side. A second hydraulic chamber provided on the opposite side of the tie bar, and comprising a third switching means for adjusting a hydraulic pressure between the first hydraulic chamber and the second hydraulic chamber, The switching means shuts off all the first hydraulic chambers and the second hydraulic chambers, and supplies pressure oil to the first hydraulic chambers of each hydraulic clamping cylinder to The state connected to the non-pressure oil discharge side, the first hydraulic chamber and the second oil of each hydraulic clamping cylinder The chamber can be switched to either one connected to the non-pressure oil discharge side, and the rams of the two hydraulic clamping cylinders on one diagonal are synchronized with the direction of the first hydraulic chamber. And two sets of mechanical means for moving, and a flow rate and pressure adjusting means installed in the piping on the first hydraulic chamber side of the other two sets of hydraulic mold clamping cylinders on the other side.

(4) In the injection foam molding method of the present invention, a mold clamping device having four sets of hydraulic mold clamping cylinders is used to inject and fill the foamed resin melt-plasticized into the mold clamped mold, In the injection foam molding method in which the mold cavity volume is increased by opening the mold cavity volume to form a foam molded article, a foam expansion step for increasing the mold cavity volume using the injection foam molding machine described in (3) above is performed. When performing, the step of connecting all the first hydraulic chambers and the second hydraulic chambers of the four sets of hydraulic mold clamping cylinders to the non-pressure oil discharge side; A step of extruding tie bars belonging to the two diagonal hydraulic clamping cylinders by moving the ram of the hydraulic clamping cylinder synchronously by mechanical means in the direction of the first hydraulic chamber; A movable die play that engages the tie bar via a nut When the movable die is moved, the other diagonal of the other die is pulled by pulling a tie bar belonging to the two other hydraulic clamping cylinders engaged with each other via a detachable nut. The step of moving the rams of the two sets of hydraulic mold clamping cylinders and the first hydraulic chamber of the other two sets of hydraulic mold clamping cylinders are hydraulically controlled by a flow pressure adjusting means installed in the piping. And the oil pressure is balanced against the pushing force of the tie bar belonging to the two diagonal hydraulic clamping cylinders, and the detachable nut provided on the tie bar and the movable die plate engaged therewith The movable mold is moved in the mold opening direction via the movable die plate in a state where the clearance with the movable die plate is eliminated, and the ram is stopped when the movable mold reaches a predetermined movement distance, and the process proceeds to the cooling process. Including the.

(5) The mold clamping apparatus of the injection foam molding machine according to (1) and (3) above, wherein each of the two diagonal hydraulic mold clamping cylinders on the second hydraulic chamber side has the above-mentioned A through-hole extending along the sliding direction of the ram is provided in the wall facing the ram, the through-hole is hydraulically sealed, and the rams of the two diagonal hydraulic clamping cylinders are Two sets of mechanical means for moving in synchronism with the first hydraulic chamber side are provided so as to penetrate the through hole and project outside the cylinder, and a threaded portion is provided at the projecting portion, and the rotation direction A pair of ball screw shafts that are constrained and movable in the axial direction, a pair of ball screw nuts that are screwed into the ball screw shafts and that are constrained in the axial direction and are rotatable, and the ball screw nuts, respectively. It consists of a pair of servo motors that rotate, The ball screw nut is rotated synchronously by a servomotor, the moving speed of the movable mold is adapted to be controlled via the ram.

(6) The flow rate pressure adjusting means of the mold clamping device of (3) uses a flow rate adjusting throttle valve or a hydraulic pressure adjusting valve in which the throttle amount of the hydraulic oil passage is variable. (7) (1), (3) When using the mold clamping device of (5), (6) and performing foam molding by the foam molding method of (2) and (4) above, foaming in the mold is performed by a mold internal pressure sensor provided in the mold. The pressure is detected, the rotational speed of the servo motor is feedback-controlled so that the foaming pressure maintains the set pressure, the movable mold is moved backward, and this is stopped when the movable mold moves by a specified distance. The process is shifted to the cooling process.

(8) A mold clamping device for an injection foam molding machine according to the above (1), (3), (5), (6), which detects a relative position between a fixed die plate and a tie bar provided on each tie bar. A position detection sensor, and an opening / closing valve on the first hydraulic chamber side pipe of each hydraulic clamping cylinder.
(9) The injection foam molding method of (2), (4), (7) above, wherein the plurality of position detection sensors provided on the plurality of tie bars described in (8) When it is individually detected that the specified dimension has been reached, the drive servomotor of the ball screw shaft is controlled by a signal from a position detection sensor provided in one of the two hydraulic clamping cylinders on the one diagonal. At the same time as stopping, the hydraulic circuit of the hydraulic clamping cylinder belonging to each hydraulic cylinder is blocked by the on-off valve described in (8) above to individually stop the movement of the ram of the hydraulic clamping cylinder and proceed to the cooling process I am letting.

  According to the foam molding method using the injection foam molding machine of the present invention, in the foam molding process, the rams of one diagonal clamping cylinders A and D are extruded in a direction to open the mold by mechanical moving means, The other diagonal mold clamping cylinders B and C are movable by applying a hydraulic pressure to the first hydraulic chamber side so as to oppose the pushing force of the mechanical moving means of one diagonal mold clamping cylinders A and D. By eliminating the clearance at the joint between the die plate and tie bar, it is possible to suppress the floating of the movable die plate from the beginning to the end of the foam molding process, which has the effect of eliminating the dimensional error of the molded product. If the movement speed of the mold by a typical moving means is not exceeded the foam expansion speed of the molded product, the surface of the molded product during foam molding will always remain pressed against the mold with foaming pressure, Gas or air It is suppressed from entering, it is possible to prevent the occurrence of swirl marks or silver on the surface of the molded article. (Claims 1 and 2).

  In the foam molding process, the hydraulic pressures of all the clamping cylinders are set to zero, the rams of one diagonal clamping cylinders A and D are pushed out in the direction of opening the mold by mechanical moving means, and the other diagonal The flow rate adjusting valve (throttle valve with adjustable throttle) provided on the pipe connected to the first hydraulic chamber side of the mold clamping cylinders B and C, or the oil drain pipes of the mold clamping cylinders A and D by the hydraulic pressure adjusting valve At the same time that the flow resistance is applied to the mold, the moving speed of the mold can be adjusted so as not to exceed the foaming expansion speed of the molded product, so that the same effect as described above is obtained (claims 3, 4, 6).

Two sets of mechanical means for moving the rams of one diagonal mold clamping cylinder A and mold clamping cylinder D in synchronism with the mold opening direction penetrate the wall of the mold clamping cylinder from the outside and rotate in the rotational direction. And a pair of ball screw shafts for pushing the ram, a ball screw nut screwed to the ball screw shaft, and a servo motor for rotationally driving the ball screw nut so as to be rotated synchronously by the servo motor. In this case, the ram is pushed so that the moving speed of the movable mold can be controlled, so that the control is easy and the configuration of the hydraulic circuit is simplified (claim 5).
The same effect as described above can be obtained by controlling the movement speed of the mold by detecting the foaming pressure with an in-mold pressure sensor so that the foaming pressure is always positive (Claim 7). .

  In addition, when expanding the volume of the mold cavity during foam molding, the movable die plate and the mold are relatively inclined due to the frictional resistance of the hydraulic cylinder ram and the flow resistance within the piping, resulting in a foam molded product. However, as in the present invention, using a position sensor that can accurately detect the movement position of each tie bar, the ram of each clamping cylinder can be separately positioned at a predetermined position. If the stationary die plate and the movable die plate are kept parallel, the thickness of the foamed molded product can be prevented from being uneven (claims 8 and 9).

[First Embodiment]
The configuration of the injection foam molding machine according to the first embodiment of the present invention and the method of molding a foam molded product using this apparatus will be described with reference to FIGS. FIG. 1 is a side view showing a mold clamping device of an injection foam molding machine and a hydraulic system diagram of the mold clamping device, and FIG. 2 is a front view of a fixed die plate used in the mold clamping device shown in FIG. 3 is a schematic diagram showing a hydraulic cylinder and a hydraulic system, FIG. 3 is a block diagram showing a foam control procedure of the mold clamping device, FIG. 4 is a graph showing timing of a foam molding process of the mold clamping device, and FIG. 5 is a diagram of the mold clamping device. FIG. 6 is a perspective view showing the direction and strength of the force acting on the tie bar in the foam molding process. FIG. 6 is a diagram showing the force of the tie bar in the opposite direction in the foam molding process of the mold clamping device. It is a fragmentary sectional view showing the state where a clearance is pressed to one side.

The mold clamping device of the injection foam molding machine shown in FIG. 1 includes a base 1, and a fixed die plate 2 to which a fixed mold 4 is attached is fixed to one end of the base 1. A movable die plate 3 is movably mounted on the base 1 at a position facing the fixed die plate 2, and a movable mold 5 is attached to the movable die plate 3. This movable die plate 3 is supported by a base 26. On the other hand, a guide rail 22 is fixed on the base 1, and the base 26 can be moved on the guide rail 22 by a linear bearing 21.
The fixed die plate 2 is provided with four mold clamping cylinders 9A to 9D having a small stroke and a large cross-sectional area. The longitudinal sections of the clamping cylinders 9C and 9D and the clamping cylinders 9A and 9B are arranged symmetrically with respect to the longitudinal center plane of the fixed die plate 2 as shown in FIG. In the embodiment, each of the cylinders has a substantially rectangular shape having a vertex. The mold clamping cylinders 9A to 9D are provided with rams 6A to 6D that slide and reciprocate, respectively, and tie bars 7A to 7D are directly connected to one side of the rams 6A to 6D, respectively. Yes. The tie bars 7 </ b> A to 7 </ b> D pass through four insertion holes provided in the movable die plate 3 when the opposing movable die plate 3 approaches to close the mold.
The insides of the respective cylinders 9A to 9D are defined by a ram 6A to 6D into a first hydraulic chamber 101 on the movable die plate side and a second hydraulic chamber 102 on the opposite side. The first hydraulic chamber 101 is provided with an oil port 2a, and the second hydraulic chamber 102 is provided with an oil port 2b.

Mechanical means for moving the ram 6A in the mold clamping cylinder 9A and the ram 6D in the mold clamping cylinder 9D in synchronism with the mold opening direction on the second hydraulic chamber 102 side of the mold clamping cylinder 9A and the mold clamping cylinder 9D. Is provided. This mechanical means is configured as follows.
The mold clamping cylinders 9A and 9D incorporated in the fixed die plate 2 are respectively penetrated in the sliding direction of the rams 6A and 6D through the wall portions of the portions facing the rams 6A and 6D on the second hydraulic chamber 102 side. A through hole is provided. A ball screw shaft 61 is inserted into the through hole so as to be movable in the axial direction, and a fitting portion between the ball screw shaft 61 and the wall portion of the fixed die plate 2 is oil-tightly sealed. . A key 69 is embedded in the ball screw shaft 61 at a portion protruding outward from the fixed die plate 2, and a screw portion for a ball screw is provided at a portion further outside the key 69. . On the other hand, a support base 64 is attached to the fixed die plate 2, and a key groove that engages with the key 69 is provided inside the support base 64. This key groove constrains the rotation direction of the ball screw shaft 61. Further, a bearing cover 66 is attached to the support base 64, and this bearing cover 66 fixes the axial direction of the ball bearing 63. The ball bearing 63 rotatably supports the ball screw shaft 61. The ball screw nut 62 is screwed to the ball screw shaft 61, and a large gear 67 is fixed to the ball screw nut 62. Further, a pair of servo motors 65 are attached to the support base 64, and a small gear 68 is attached to the rotation shaft of the servo motor 65. A large gear 67 is engaged with the small gear 68.

  On the other hand, a plurality of ring groove portions having an equal pitch are formed at the tip portions of the tie bars 7A to 7D. Four pairs of split nuts 11 and a support base 15 are attached to the opposite side surface of the movable die plate 3 to which the movable mold 5 is attached. The split nut 11 meshes with the ring groove portions of the tie bars 7A to 7D, and moves in a direction perpendicular to the axis of the tie bars 7A to 7D to sandwich the tie bars 7A to 7D. The split nut 11 is operated by a hydraulic cylinder or the like (not shown). The support base 15 is provided with a hydraulic cylinder and a ram shaft 16. On the support base 15, a pressing plate 12 is provided on the side opposite to the movable die plate 3. The pressing plate 12 can reciprocate in the longitudinal direction of the tie bar by the ram shaft 16 of the support base 15. Each split nut 11 is sandwiched and fixed between the pressing plate 12 and the movable die plate 3 by the movement of the pressing plate 12. Reference numeral 8 denotes an injection cylinder.

  With these configurations, the rotational driving force of the servo motor 65 is transmitted to the ball screw shaft 61 via the small gear 68, the large gear 67, and the ball screw nut 62, and the ball screw shaft 61 rotates in the longitudinal direction. The surface of the ram 6A, 6D on the second hydraulic chamber 102 side is pressed. This pressing force moves the movable die plate 3 connected to the tie bars 7A and 7D. The servo motor 65 is driven synchronously, and the moving speed of the movable die plate 3 and the movable mold 5 fixed to the movable die plate 3 is controlled by the rotational speed control of the servo motor 65. .

  Position sensors 27A to 27D are attached to the tie bars 7A to 7D. The position sensors 27A to 27D are combined with a detection scale groove attached to the fixed die plate 2 or a scale having a detection scale magnet, and the relative positions of the fixed die plate 2 and the tie bars 7A to 7D (or In other words, the movement distances from the respective reference positions of the rams 6A to 6D) are detected.

Next, a configuration for opening the movable mold 5 at intervals at which the molded product can be taken out will be described.
Below the movable die plate 3, a bearing box 17 attached to the base 1, another bearing box (not shown), and a ball screw shaft 13 are provided. The ball screw shaft 13 is supported by a bearing housing 17 and another bearing housing so as to be axially restricted and rotatably supported. The ball screw shaft 13 is disposed in parallel with the moving direction of the movable die plate 3 and is driven by a servo motor (not shown). It is driven. On the other hand, a support base 25 is attached to the lower side of the movable die plate 3, and a ball screw nut 14 is attached to the support base 25. The ball screw nut 14 is screwed with the ball screw shaft 13. The ball screw shaft 13 rotates, and the ball screw nut 14 can move linearly in the axial direction of the ball screw shaft 13 by this rotation. If the operation opposite to the operation of opening the movable mold 5 is performed, the movable mold 5 can be closed for the next injection step, thereby enabling the mold opening and closing operation. The rotation speed and rotation speed of the ball screw shaft 13 are controlled by the control device 37 via a servo motor (not shown). The ball screw nut 14 can freely move during foam molding by torque control of a servo motor.

Next, the operation of the first exemplary embodiment of the present invention will be described.
In this mold clamping apparatus, the movable die plate 3 is moved by the rotation of the ball screw shaft 13 until the movable mold 4 and the fixed mold 5 are opened to the closed state. The platen moving speed control circuit built in the control device 37 accelerates the movable die plate 3 slowly, moves it at a constant speed, and then decelerates to stop just before the movable mold 5 contacts the fixed mold 4. I am doing so.

  The split nut 11 operates at the stop position of the movable die plate 3. The inner ring groove of the split nut 11 engages with the ring groove at the tip of the tie bars 7A to 7D to couple with the tie bars 7A to 7D. At the same time, hydraulic pressure is applied to a hydraulic cylinder provided in the support base 15 to pull the holding plate 12 and fix the split nut 11 to the movable die plate 3. Next, the control device 37 controls the drive torque of a servo motor (not shown) to zero so as to freely rotate the ball screw shaft 13 and release the restriction of the movement of the ball screw nut 14, and the first clamping cylinders 9 </ b> A to 9 </ b> D. The hydraulic chamber 101 is pressurized and clamped, and a certain amount of molten foamed resin is injected from the injection cylinder 8 into the mold cavity.

  After injection of the molten foamed resin, it is held for a fixed time. At the timing when the surface of the resin in the mold cavity starts to solidify, hydraulic oil is sent to the two pairs of mold clamping cylinders 9B and 9C of the mold clamping cylinder 9C on the opposite side of the fixed die plate 2. This hydraulic oil is sent until the set hydraulic pressure is reached. The three-way switching valve 43 is used to switch the hydraulic circuit to the oil port 2a of the first hydraulic chamber 101 of the mold clamping cylinder 9A and mold clamping cylinder 9D so as to be connected to the non-pressure oil discharge side. All of the diagonal two mold clamping cylinders 9B and 9C other than the first hydraulic chamber 101 side are connected to the oil discharge side, the servo motor 65 is driven in synchronization, and the ball screw nut 62 is rotated. The ball screw shaft 61 is moved in the axial direction, and the movable die plate 3 is moved via the tie bars 7A and 7D by pushing the back surfaces of the rams 6A and 6D. The pulling force of the rams 6B and 6C by the low pressure hydraulic oil on the first hydraulic chamber 101 side of the mold clamping cylinder 9B and the mold clamping cylinder 9C becomes a resistance force.

  In this manner, the axial pressing force of the mold clamping cylinder 9A and the mold clamping cylinder 9D by the ball screw shaft 61 and the pulling force in the axial direction of the tie bars 7B and 7C act in opposite directions, and the reaction force between them causes the tie bar. The movable mold 5 is moved in the direction of foaming expansion of the foamed resin through the movable die plate 3 with the clearance between the nut 7 and the split nut 11 provided on the movable die plate 3 engaged therewith eliminated. At this time, the linear speed of the ball screw shaft 61 due to the rotation of the servo motor 65 is controlled to a set speed, and when the movable mold 5 reaches the specified moving distance, the ram 6 is stopped and the process proceeds to the cooling process.

When the movable mold 5 is moved to the thickness dimension of the foam molded product, the hydraulic circuits of the respective clamping cylinders 9A to 9D are blocked by the detection signals of the position sensors 27A to 27D, and the rams 6A to 6D are fixed. The movement of the mold 5 is stopped.
While the foaming pressure is maintained, the molten foamed resin in the mold cavity is cooled and solidified to form a molded product having a foamed interior. After cooling and solidification, the hydraulic circuit blocks of the clamping cylinders 9A to 9D are unwound and the split nut 11 is removed. Loosen the pressing force of the holding plate 12 being pressed, reversely actuate the split nut 11 to remove the connection with the tie bars 7A to 7D, and rotate the ball screw shaft 13 reversely when the mold is closed to move the movable mold 5 The die plate 3 is moved to the open side and stopped at the original fully open position. After the molded product is taken out, the next mold closing process starts.

As shown in FIGS. 1 to 3A, the hydraulic control system for operating the mold clamping cylinders 9A to 9D of the control device 37 includes a mold clamping hydraulic pressure setter 53, a foaming movement hydraulic pressure setter 55, and a hydraulic pressure. Control circuit 54, tie bar position setting device 52 for determining the thickness of a foam molded product at the time of foam molding, a hydraulic pump drive motor 32, an inverter 38 for controlling the rotation of the motor 32, a hydraulic pump 31, and four-way switching A valve 33, a supply pipe 44 for supplying hydraulic oil fed from the hydraulic pump 31 to the hydraulic four-way switching valve 33, and a mold disposed from the hydraulic four-way switching valve 33 to the ports 2a of the clamping cylinders 9A to 9D. Clamping side pipes 45A to 45D, mold release side pipes 46A to 46D arranged from the four-way switching valve 33 to the port 2b of the mold clamping cylinders 9A to 9D, and opening / closing valves installed in the mold clamping side pipes 45A to 45D And 9A～49D, is constituted by a hydraulic sensor 39 installed in the mold clamping-side pipe 45.
In the mold clamping side pipes 45A to 45D and the mold release side pipes 46A to 46D, throttle valves 35A, 35B, 35C, and 35D that pass through on the supply side and generate a slight flow resistance on the discharge side are installed. Reference numeral 36 denotes a relief valve that serves as a safety valve, and reference numeral 40 denotes a hydraulic oil tank.

  A mechanical ball screw rotation control system for operating the mold clamping cylinders 9A and 9D is provided in the control device 37, and includes a foamed resin molding program 50, a ball screw rotation control circuit 58, and a ball screw rotation speed setting unit 59. It consists of and. The foamed resin molding program 50 includes mold clamping for a mold clamping device of a foam injection molding machine, injection of foamed resin, holding pressure, mold clamping pressure reduction, mold opening for foam expansion, holding cooling, mold for taking out a molded product. The opening process (shown in FIG. 4) is instructed to the ball screw rotation control circuit 58 and the hydraulic control circuit 54 at an appropriate timing. The ball screw rotation control circuit 58 controls the servo motor 65 in accordance with the instruction of the foamed resin molding program 50 to instruct the rotation direction of the ball screw shaft 61 and the start / stop timing to operate at an appropriate moving speed. .

Another method for controlling the moving speed of the movable die plate 3 and the movable mold 5 will be described with reference to FIG.
When the foam molding process starts, the hydraulic pressure to the mold clamping cylinders 9B and 9C is switched to the set value of the hydraulic pressure setting device 55 during foam movement, and the foam pressure of the molded product detected by the mold internal pressure sensor 28 always has a slight positive value. In order to keep it, the rotational speed of the servo motor 65 is feedback-controlled to suppress the moving speed of the mold 5 by the ball screw shaft 61.

  At the same time as the foam molding starts, the tie bar position sensors 27A to 27D start detecting the tie bar position, and the comparison circuits 51A to 51D individually compare the detected values of the tie bar position sensors 27 with the set values of the tie bar position setting device 52. When the detected value of the tie bar position sensor 27 becomes the same as the set value of the tie bar position setter 52, the on-off valves 49A to 49D of the hydraulic circuits of the corresponding clamping cylinders 9A to 9D are closed to block the circuit. Stop ram 6 (tie bar 7). In this way, the detected value of the tie bar position sensor 27 becomes the same as the set value of the tie bar position setter 52 one after another, the open / close valve 49 is closed, the circuit is blocked, and the four tie bars 7A to 7D are stopped. If the positions of the mold 4 and the mold 5 are kept parallel with the same set value, and the state is maintained, the foamed molded product can be shifted to solidification cooling with the thickness of the foam molded product being uniform.

The injection foam molding process will be described with reference to a graph showing the timing of the foam molding process of the mold clamping device of this embodiment shown in FIG.
(1) Mold closing: The ball screw shaft 13 is driven and rotated by a servo motor (not shown), and the movable die plate 3 is moved from the fully opened state to the closed side at high speed, and then the movable die plate 3 is used using the speed control function of the servo motor. The movable die plate 3 is stopped at a position where the movable mold 5 is close to the fixed mold 4.
(2) Coupling of tie bar and movable die plate: Four sets of split nuts 11 are operated to couple the movable die plate 3 and tie bars 7A to 7D, and hydraulic pressure is applied to the hydraulic cylinder of the support base 15 fixed to the movable die plate 3. , The holding plate 12 is pulled and the split nut 11 is fixed to the movable die plate 3.

(3) Clamping: The on-off valves 49A to 49D are passed, and the hydraulic pump 31 is driven at high speed to control the set pressure at the time of mold clamping. Then, the four-way switching valve 33 is switched from the fully closed state to the mold clamping side, the hydraulic oil is sent to the first hydraulic chamber 101 of the mold clamping cylinders 9A to 9D, and the fixed mold 4 and the movable mold 5 are closed.
(4) Injection: A predetermined amount of molten foam resin is injected into the mold cavity.
(5) Holding pressure: Hold for a specified time with the mold clamped until only the surface in contact with the mold of the molten foamed resin is solidified.

(6) Foam expansion- (I): The hydraulic pump 31 is held at a set pressure for foam molding, the three-way switching valve 43 is switched, and the hydraulic pressure on the first hydraulic chamber 101 side of the clamping cylinders 9A, 9D. If the oil is passed to the oil discharge side (zero pressure), the hydraulic pressure acts only on the first hydraulic chamber 101 of the mold clamping cylinders 9B and 9C. Here, the servo motor 65 is started, and the back surface of the rams 6A and 6D is pushed by the ball screw shaft 61 (the distance n as shown in FIG. 6 so that the ball screw shaft 61 contacts the back surface of the rams 6A and 6D during mold clamping). Just move it). The tie bars 7A and 7D pushed by the ball screw shaft 61 push the movable die plate 3 in the opening direction, and the hydraulic pressure on the first hydraulic chamber 101 side of the clamping cylinders 9B and 9C is the resistance in the direction to close the tie bars 7B and 7C. helpful. (See FIGS. 5 and 6. As shown by arrows, the acting force on the tie bars 7A and 7D is larger than the acting force F1 on the tie bars 7B and 7C, and the acting direction is the opposite direction. is there). Due to this conflicting force, the clearances C1 and C2 when the groove of the tie bar 7 and the inner groove of the split nut 11 are engaged are pressed against one opposite side as shown in FIG. Can keep. As described above, since the force on the mold clamping cylinders 9A and 9D side wins, the movable mold 5 moves in the opening direction.

(7) Foam expansion- (II): The unsolidified resin portion of the molded product starts to expand due to the foaming pressure. At this time, the moving speed of the ball screw shaft 61 (movable mold 5) becomes the foam expansion speed of the molded product. Make sure that the speed is appropriate. As a means for controlling the moving speed of the movable mold 5, a means for controlling the moving speed of the ball screw shaft 61 according to the foaming pressure of the molded product detected by the mold internal pressure sensor 28 can be used.
When the three-way selector valve 43 is switched, the tie bar position sensors 27A to 27D are instructed to detect the tie bar position.

(8) Movable die plate stop: The movable die plate 3 moves and the relative position between the tie bar 7 and the fixed die plate 2 reaches a set value (m1 for rams 6A and 6D, m2 for rams 6B and 6C, m1 = m2 + c1). In the order in which the tie bar position sensors 27A to 27D individually detect the positions of the tie bars, the on-off valves 49A to 49D are closed, the hydraulic circuits of the clamping cylinders 9A to 9D are blocked, and the movable die plate 3 is individually separated by the tie bar 7. When all the tie bars 7 are stopped, the fixed die plate 2 and the movable die plate 3, the fixed mold 4 and the movable mold 5 are kept parallel, and a foam molded product having a uniform thickness is obtained.
(9) Holding cooling: Holding cooling of the molded product is performed while the hydraulic circuits of all the clamping cylinders 9 are blocked.

(10) Fully open movable die plate: After holding and cooling the molded product, the control device 37 commands the stop detection of the positions of the tie bar position sensors 27A to 27D, and the hydraulic pressure of the hydraulic cylinder of the support base 15 is released to split the holding plate 12. Separated from the nut 11, the split nut 11 is reversely operated to disconnect from the tie bars 7 </ b> A to 7 </ b> D, and the ball screw shaft 13 is rotated in the reverse direction to that when the mold is closed to move the movable die plate 3 to the open side. Stop at. The molded product is taken out and one cycle of the injection foam molding process is completed.
The mold clamping speed can be controlled by the rotational speed of the hydraulic pump 31.
During the mold clamping process, injection of molten resin into the mold cavity and holding cooling are performed, and the hydraulic pump 31 is completely stopped while the molten resin is solidified.

As explained in the above step (7), the movable mold 5 can be adjusted to an appropriate speed according to the foam expansion speed of the molded product, so that the surface of the molded product during foam molding is always kept at the foam pressure. The foamed gas and air are prevented from entering between the molded product and the mold, and swirl marks and silver can be prevented from being generated on the surface of the molded product.
Since the detection of the individual tie bar positions by the tie bar position sensors 27A to 27D can be stopped during the foam molding movement, the fixed die plate 2 and the movable die plate 3 can be kept parallel, and the foam molded product can be maintained. It is possible to prevent the occurrence of uneven thickness.

[Second Embodiment]
A second embodiment of the present invention will be described with reference to the drawings.
In the injection foam molding method of the first embodiment, in the foam molding process, a pair of diagonal mold clamping cylinder A and mold clamping cylinder D rams are opened in a direction to open the mold using mechanical moving means. Extrusion, the other diagonal mold clamping cylinder B and mold clamping cylinder C are hydraulically applied to the first hydraulic chamber 101, eliminating the clearance of the joint between the movable die plate and the tie bar, and starting the foam molding process. It is possible to suppress the floating of the movable die plate from the end to the end, eliminate the dimensional error of the molded product, and set the moving speed of the mold according to the foam expansion rate of the molded product, This is a method of preventing defects on the surface of the molded product by preventing the foaming gas or air from entering between the molded product and the mold on the surface.
In the second embodiment, in the foam molding step after injection filling with the foamable resin, the dies of the pair of diagonal mold clamping cylinders A and D are opened by mechanical moving means. The mechanism and the method of pushing out the same are the same as those in the first embodiment, but without applying hydraulic pressure to the first hydraulic chamber 101 side of the other diagonal mold clamping cylinder B and mold clamping cylinder C, the mold clamping is performed. A flow pressure adjusting valve is provided in the pipe on the first hydraulic chamber 101 side of the ram (6B and 6C) of the cylinder 9B and the mold clamping cylinder 9C to push the mechanical moving means of the mold clamping cylinder A and the mold clamping cylinder D. This is a method that gives resistance to force. The movement speed of the mold is set to a speed corresponding to the foaming expansion speed of the molded product as in the first embodiment.

  The structure of the mold clamping device of the second embodiment is shown in FIGS. 7 and 8, and the control circuit is shown in FIG. 9. The difference from the first embodiment is that the first embodiment is different from the first embodiment in the hydraulic system. The three-way selector valve 43 provided in the above is omitted, and instead of the four-way selector valve 33, a four-way selector valve 41 is provided which can connect the pipes to all the mold clamping cylinders to the oil discharge side with zero hydraulic pressure. That is, throttle valves 75A and 75B (flow pressure adjusting valves) of variable throttles are installed in the pipes 45B and 45C on the cylinders 9B and 9C side. Other than this, there is no difference from the first embodiment, and therefore, most of the components constituting the mold clamping apparatus are assigned the same part numbers as those in the first embodiment, and description of the configuration is omitted.

The control of the moving speed of the movable mold by the mechanical movement mechanism and the flow resistance of the pipe during the foam molding of the mold clamping apparatus of the second embodiment will be described with reference to the graph showing the timing of the foam molding process in FIG. To do.
(1) Mold closing: The ball screw shaft 13 is driven and rotated by a servo motor (not shown), and the movable die plate 3 is moved from the fully opened state to the closed side at high speed, and then the movable die plate 3 is used using the speed control function of the servo motor. The movable die plate 3 is stopped at a position where the movable mold 5 is close to the fixed mold 4.
(2) Coupling of tie bar and movable die plate: Four sets of split nuts 11 are operated to couple the movable die plate 3 and tie bars 7A to 7D, and hydraulic pressure is applied to the hydraulic cylinder of the support base 15 fixed to the movable die plate 3. , The holding plate 12 is pulled and the split nut 11 is fixed to the movable die plate 3.

(3) Clamping: The on-off valves 49A to 49D are passed, and the hydraulic pump 31 is driven at high speed to control the set pressure at the time of mold clamping. Then, the four-way switching valve 41 is switched from the fully closed state to the mold clamping side, the working oil is sent to the first hydraulic chamber 101 of the mold clamping cylinders 9A to 9D, and the fixed mold 4 and the movable mold 5 are closed.
(4) Injection: A predetermined amount of molten foam resin is injected into the mold cavity.
(5) Holding pressure: Hold for a specified time with the mold clamped until only the surface in contact with the mold of the molten foamed resin is solidified.

(6) Foam expansion-(I): Stop hydraulic pump 31 and switch four-way switching valve 41 to drain hydraulic pressures of piping 45A to 45D of clamping cylinders 9A to 9D and pipings 46A to 46D. Through the side (zero pressure). Here, the servo motor 65 is started and the back surface of the rams 6A and 6D is pushed by the ball screw shaft 61 (the ball screw shaft 61 is moved by a distance n so as to contact the back surface of the rams 6A and 6D during mold clamping. deep). The tie bars 7A and 7D pushed by the ball screw shaft 61 push the movable die plate 3 in the opening direction, and the working oil flows into the pipes 45B and 45C connected to the first hydraulic chamber 101 side of the clamping cylinders 9B and 9C. A flow resistance is generated in the throttle valves 75A and 75B, and hydraulic pressure is generated in the pipes 45B and 45C, which becomes a reaction force of the pressing force of the ball screw shaft 61. As in the first embodiment, the acting force on the tie bars as shown in FIGS. 5 and 6 is indicated by the arrows, and the acting force F1 on the tie bars 7A and 7D is the acting force F2 on the tie bars 7B and 7C. It is larger and the direction of action is the opposite direction, and the force on the mold clamping cylinders 9A, 9D side wins, so the movable mold 5 moves in the opening direction. Due to this conflicting force, the clearances C1 and C2 when the groove of the tie bar 7 and the inner groove of the split nut 11 are engaged are pressed against one opposite side as shown in FIG. Can keep.

(7) Foam expansion- (II): The unsolidified resin portion of the molded product in the mold cavity begins to expand due to the foaming pressure. At this time, the moving speed of the ball screw shaft 61 (movable mold 5) is the molded product. An appropriate speed is set according to the foam expansion rate.
When the four-way switching valve 41 is switched, the tie bar position sensors 27A to 27D are instructed to detect the tie bar position.

(8) Movable die plate stop: The movable die plate 3 moves, the relative position between the tie bar 7 and the fixed die plate 2 reaches the set value, and the tie bar position sensors 27A to 27D individually open and close the positions of the tie bars. When the valves 49A to 49D are closed, the hydraulic circuits of the clamping cylinders 9A to 9D are blocked, the movable die plate 3 is individually stopped by the tie bar 7, and when all the tie bars 7 are stopped, the fixed die plate 2 and the movable die The plate 3, the fixed mold 4 and the movable mold 5 are kept parallel, resulting in a foam molded product having a uniform thickness.
(9) Holding cooling: Holding cooling of the molded product is performed while the hydraulic circuits of all the clamping cylinders 9 are blocked.

(10) Fully open movable die plate: After holding and cooling the molded product, the controller 57 commands the detection stop of the positions of the tie bar position sensors 27A to 27D, and the hydraulic pressure of the hydraulic cylinder of the support base 15 is released to split the holding plate 12. Separated from the nut 11, the split nut 11 is reversely operated to disconnect from the tie bars 7 </ b> A to 7 </ b> D, and the ball screw shaft 13 is rotated in the reverse direction to that when the mold is closed to move the movable die plate 3 to the open side. Stop at. The molded product is taken out and one cycle of the injection foam molding process is completed.
The mold clamping speed can be controlled by the rotational speed of the hydraulic pump 31.
During the mold clamping process, injection of molten resin into the mold cavity and holding cooling are performed, and the hydraulic pump 31 is completely stopped while the molten resin is solidified.

The surface of the molded product during foam molding is always kept pressed against the mold by the force of one part of the foaming pressure, and foaming gas and air can enter between the molded product and the mold. It is possible to suppress the occurrence of swirl marks and silver on the surface of the molded product.
When the volume of the mold cavity is expanded during foam molding, the fixed mold 4 and the movable mold 5 are in a free state where they are not tightened, but, as in the first embodiment, the fixed die plate 2 and Since the parallelism when the movable die plate 3 is stopped can be maintained, the occurrence of uneven thickness of the foam molded product can be suppressed.
Although the flow rate pressure adjusting valve has been described as a variable throttle valve, there is an advantage that remote setting is facilitated by using a proportional valve or a hydraulic servo valve. Further, when the flow resistance is used, the pressure can be adjusted similarly by a pressure means such as a counter balance valve.

1 is a side view showing a mold clamping device of an injection foam molding machine according to a first embodiment of the present invention and a hydraulic system diagram of the mold clamping device. It is a schematic diagram which shows the front of the fixed die plate of the mold clamping apparatus of FIG. 1, a hydraulic cylinder, and a hydraulic system. It is a block diagram which shows the foaming control procedure of the mold clamping apparatus of FIG. It is a graph which shows the timing of the foam molding process of the mold clamping apparatus of FIG. It is a perspective view which shows the direction and strength of the force which acts on a tie bar in the foam molding process of the mold clamping apparatus of FIG.1 and FIG.7. FIG. 8 is a partial cross-sectional view showing a state in which the engagement groove of the tie bar and the clearance of the split nut are pressed to one side by the acting force in the opposite direction of the tie bar in the foam molding process of the mold clamping device of FIGS. 1 and 7. It is the side view which shows the mold clamping apparatus of the injection foam molding machine which concerns on the 2nd Embodiment of this invention, and the hydraulic system figure of a mold clamping apparatus. It is a schematic diagram which shows the front of the fixed die plate of the mold clamping apparatus of FIG. 7, a hydraulic cylinder, and a hydraulic system. It is a block diagram which shows the foaming control procedure of the mold clamping apparatus of FIG. It is a graph which shows the timing of the foam molding process of the mold clamping apparatus of FIG.

Explanation of symbols

2 fixed die plate 3 movable die plate 4 fixed mold 5 movable mold 6A, 6B, 6C, 6D ram 7A, 7B, 7C, 7D tie bar 8 injection unit 9A, 9B, 9C, 9D mold clamping cylinder 11 split nut 13 ball Screw shaft 14 Ball screw nut 27A, 27B, 27C, 27D Tie bar position sensor 28 Type internal pressure sensor 31 Hydraulic pump 33 Four-way switching valve 37, 57 Control device 39 Hydraulic sensor 41 Four-way switching valve 43 Three-way switching valve 49A, 49B, 49C, 49D On-off valve 61 Ball screw shaft 62 Ball screw nut 64 Support base 65 Servo motor 69 Key 75A, 75B Throttle valve (flow pressure adjustment valve)
101 1st hydraulic chamber 102 2nd hydraulic chamber

Claims (9)

Using a mold clamping device equipped with 4 sets of hydraulic mold clamping cylinders, the mold mold is injected and filled with melt-plasticized foamable resin, and then the mold is opened by a certain distance to increase the mold cavity volume. In an injection foam molding machine that molds foam molded products,
The interiors of the four hydraulic clamping cylinders are defined as a first hydraulic chamber provided on the tie bar side and a second hydraulic chamber provided on the opposite side of the tie bar, and the first hydraulic chamber and A first switching means and a second switching means for adjusting the hydraulic pressure with the second hydraulic chamber;
The supply side of the first switching means is connected to a hydraulic pressure source and an oil discharge tank, and the output side of the first switching means is disconnected from the first hydraulic chamber and the second hydraulic chamber. A state in which pressure oil is supplied to the first hydraulic chamber of each hydraulic mold clamping cylinder and the second hydraulic chamber is connected to a non-pressure oil discharge side; A pressure oil is supplied to the second hydraulic chamber, and the first hydraulic chamber is switchably connected to a state where the first hydraulic chamber is connected to the non-pressure oil discharge side;
The second switching means is arranged between the first hydraulic chamber and the first switching means of two sets of hydraulic mold clamping cylinders arranged at one diagonal of the four sets of hydraulic mold clamping cylinders. The first hydraulic chamber is connected to be switched to either a state in which the first hydraulic chamber is connected to a non-pressure oil discharge side or a state in which pressure oil is supplied,
The hydraulic pressure source is provided so as to be switchable so that high pressure oil can be supplied during the mold clamping process and low pressure oil set during foam expansion of the molded product can be supplied.
Injection comprising two sets of mechanical means for moving the rams of two sets of hydraulic clamping cylinders arranged at one diagonal in synchronization with the direction of the first hydraulic chamber Foam molding machine. Using a mold clamping device equipped with 4 sets of hydraulic mold clamping cylinders, the mold mold is injected and filled with melt-plasticized foamable resin, and then the mold is opened by a certain distance to increase the mold cavity volume. In an injection foam molding method for molding a foam molded product,
When performing the foam expansion that increases the mold cavity volume using the injection foam molding machine according to claim 1,
Connecting both the first hydraulic chamber and the second hydraulic chamber of the two diagonal hydraulic clamping cylinders to the non-pressure oil discharge side;
A step of connecting the second hydraulic chamber to the oil discharge side by applying hydraulic pressure to the first hydraulic chamber of the other two pairs of hydraulic mold clamping cylinders among the four sets of hydraulic mold clamping cylinders; When,
The two rams of the two hydraulic clamping cylinders on one diagonal are moved synchronously by mechanical means in the direction of the first hydraulic chamber, the tie bars coupled to the ram are pushed out, and the other diagonal A step of moving the movable mold by mechanical mold opening means in a state in which the clearance between the tie bar and the detachable nut provided on the movable die plate engaged with the tie bar is eliminated by the reaction force of the two sets of hydraulic mold clamping cylinders When,
And a step of stopping the ram when the movable mold reaches a specified moving distance and shifting to a cooling process. Using a mold clamping device equipped with 4 sets of hydraulic mold clamping cylinders, the mold mold is injected and filled with melt-plasticized foamable resin, and then the mold is opened by a certain distance to increase the mold cavity volume. In an injection foam molding machine that molds foam molded products,
The interiors of the four hydraulic clamping cylinders are defined as a first hydraulic chamber provided on the tie bar side and a second hydraulic chamber provided on the opposite side of the tie bar, and the first hydraulic chamber and Comprising a third switching means for adjusting the hydraulic pressure with the second hydraulic chamber;
The third switching means supplies the pressure oil to the first hydraulic chamber of each hydraulic clamping cylinder by shutting off all the first hydraulic chambers and the second hydraulic chambers, and supplying the second hydraulic chambers to the first hydraulic chambers. Either the state where the hydraulic chamber is connected to the no-pressure drain side or the state where the first hydraulic chamber and the second hydraulic chamber of each hydraulic clamping cylinder are connected to the no-pressure drain side It can be switched,
Two sets of mechanical means for moving the rams of two diagonal hydraulic clamping cylinders in one diagonal direction in synchronization with the direction of the first hydraulic chamber;
An injection foam molding machine comprising flow rate pressure adjusting means installed in piping on the first hydraulic chamber side of the other two pairs of hydraulic mold clamping cylinders on the other diagonal. Using a mold clamping device equipped with 4 sets of hydraulic mold clamping cylinders, after injecting and filling melt-plasticized foamable resin into the mold clamped, the mold is opened for a certain distance and the mold cavity volume is increased. In an injection foam molding method for molding a foam molded article,
When performing the step of foam expansion that increases the mold cavity volume using the injection foam molding machine according to claim 3,
Connecting all the first hydraulic chambers and the second hydraulic chambers of the four sets of hydraulic clamping cylinders to a non-pressure oil discharge side;
The two diagonal hydraulic clamping cylinders of the one diagonal are moved synchronously by mechanical means in the direction of the first hydraulic chamber into the two diagonal hydraulic clamping cylinders. Extruding the tie bar to which it belongs;
When the movable die plate and the movable mold engaged with the tie bar are moved via the detachable nut, the two other hydraulic mold clamping cylinders of the other diagonal are engaged with the movable die plate via the detachable nut. Moving the rams of the other two diagonal hydraulic clamping cylinders by pulling a tie bar belonging to
In the first hydraulic chambers of the other two pairs of hydraulic mold clamping cylinders, hydraulic pressure is generated by flow rate pressure adjusting means installed in the piping, and the hydraulic pressures are divided into the two pairs of one diagonal. Balancing against the pushing force of tie bars belonging to the hydraulic clamping cylinder of
With the clearance between the tie bar and the detachable nut provided on the movable die plate engaged with the tie bar removed, the movable die is moved in the mold opening direction via the movable die plate, and the movable die reaches a predetermined moving distance. And a step of stopping the ram and moving to a cooling process when the injection foam molding method is performed. A through hole extending along a sliding direction of the ram is provided in a wall portion facing the ram on each second hydraulic chamber side of the two diagonal hydraulic clamping cylinders, The through hole is hydraulically sealed,
Two sets of mechanical means for moving the rams of the two diagonal hydraulic clamping cylinders on the one diagonal side in synchronism with the first hydraulic chamber side,
A pair of ball screw shafts, which are provided so as to protrude through the through-holes and protrude outside the cylinder, are provided with screw portions, are restricted in the rotation direction, and are movable in the axial direction;
A pair of ball screw nuts that are respectively screwed into the ball screw shafts, the axial direction of which is restricted and rotatable;
Each of the ball screw nuts is composed of a pair of servo motors for rotationally driving the pair of ball screw nuts, and the pair of ball screw nuts are synchronously rotated by the servo motor so that the moving speed of the movable mold can be controlled via the ram. The injection foam molding machine according to claim 1 or 3, wherein the injection foam molding machine is provided.   The injection foam molding machine according to claim 3, wherein the flow rate pressure adjusting means is a flow rate adjusting throttle valve or a hydraulic pressure adjusting valve in which a throttle amount of the hydraulic oil passage is variable.   When foam molding is performed using the mold clamping device according to any one of claims 1, 3, 5, and 6, a foam pressure in the mold is detected by a mold internal pressure sensor provided in the mold, and the foam pressure is set to a set pressure. The rotational speed of the servo motor is feedback-controlled so as to hold, the movable mold is retracted, and when the movable mold moves by a specified distance, this is stopped, and the process proceeds to the cooling step. The injection foam molding method according to claim 2 or 4.   A plurality of position detection sensors provided on each tie bar for detecting a relative position between the fixed die plate and the tie bar, and an opening / closing valve in the pipe on the first hydraulic chamber side of each hydraulic clamping cylinder The injection foam molding machine according to any one of claims 1, 3, 5, and 6.   9. When the plurality of position detection sensors provided on the plurality of tie bars according to claim 8 individually detect that the movement distance of the tie bars has reached a specified dimension, the two diagonal hydraulic types of the one diagonal 9. The hydraulic circuit of the hydraulic mold clamping cylinder belonging to each hydraulic cylinder is described at the same time that the drive servo motor of the ball screw shaft is stopped by a signal of a position detection sensor provided in one set of the clamping cylinders. The injection foam according to any one of claims 2, 4 and 7, wherein the ram of the hydraulic clamping cylinder is individually blocked by an on-off valve to stop the movement of the ram, and the process proceeds to a cooling process. Molding method.

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