JPH0142813B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a mold clamping device for an injection molding machine that is capable of molding highly precise plastic products.

(b) Conventional technology As for the mold clamping device of conventional injection molding machines, for example, the Mechanical Engineering Handbook (revised 6th edition, published by the Japan Society of Mechanical Engineers)
There is a structure as shown in Figure 4, which is shown on page 33 of Vol. 18. The mold clamping device of this injection molding machine is
Mold clamping cylinder 80, flange 82 provided integrally with mold clamping cylinder 80, mold clamping cylinder 80
includes a mold clamping piston 84, a fixed plate 86, a tie rod 88 and a tightening nut 90 that connect the flange 82 and the fixed plate 86, and a mold clamping piston 8 guided by the tie rod 88.
4, a mold mounting plate 94 is attached to the fixed plate 86, and the fixed mold 96 is attached to the mold mounting plate 94.
A movable platen 98 is attached to. By controlling the supply of hydraulic pressure to the mold clamping cylinder 80, the movable platen 92 is moved back and forth to open and close the mold, and the mold clamping operation is performed by pressing the movable platen 98 against the fixed mold 96 with a large force. Can be done.

(c) Problems to be Solved by the Invention When the mold is clamped, the reaction force of the mold clamping force generated by the mold clamping cylinder 80 acts on the tie rod 88, and the tie rod 88 stretches in response to the mold clamping force. The force acting from tie rod 88 causes flange 82 and stationary platen 86 to deform as shown by the dashed lines in FIG. This deformation of the entire mold clamping device is a problem when molding products that require extremely high shape and surface accuracy, such as plastic lenses, hard disk substrates, optical disks, etc. Therefore, it was impossible to injection mold a product with a precision higher than a certain level. That is, since the rigidity of the fixed mold 96 and the movable mold 98 is relatively small, the fixed plate 86
When the movable platen 92 is deformed, the cavity 99 is also deformed and does not have a predetermined shape, making it impossible to obtain high shape accuracy. In addition, due to the deformation of the fixed mold 96 and the movable mold 98, the surface pressure on the mating surfaces of the outer periphery of the cavity 99 increases, and the air inside the cavity 99 cannot be discharged smoothly when filling with molten resin, so the filling speed should be increased. I couldn't do it. Therefore, during the filling process, the molten resin cooled and solidified on the surface of the cavity 99 without any pressure being applied, making it impossible to transfer the precision of the surface of the cavity 99 to the molded product. As a result, the surface precision of the molded product was also insufficient. In addition, due to deformation of the fixed mold 96 and movable mold 98 and a decrease in the positional accuracy of the movable platen 92 due to bending of the tie rod 88, excessive force is applied to the fitting parts such as guide pins, causing the mold to open. There is also the problem that galling occurs when the molded product is molded, and the resulting abrasion powder has an adverse effect on the molded product. Furthermore, the mold often needed to be repaired due to galling. The present invention aims to solve these problems.

In addition, in Japanese Patent Publication No. 46-7154 and pages 565 to 566 of "Hydraulic Technology Handbook" published by Nikkan Kogyo Shimbun Co., Ltd., uprights are used as reinforcing members to improve the rigidity of press equipment. What is installed is shown. The present invention aims to apply a reinforcing member to a mold clamping device of an injection molding machine, and to improve the positional accuracy of the movable platen by improving the supporting structure of the movable platen.

(d) Means for Solving the Problems The present invention solves the above problems by providing a reinforcing member with a preload and supporting the movable platen by the sliding surface of the reinforcing member. That is, the present invention provides a flange 12 that is provided integrally with the mold clamping cylinder 10, a fixed platen 14 that is arranged to face the flange, and a mold clamping cylinder that is arranged between the flange and the fixed platen. A movable platen 26 is connected to the piston 22 of the mold via a piston rod 24, and a mold mounting plate 32 is removably attached to a fixed plate. This device is intended for a mold clamping device of a molding machine, and includes a plurality of sets of tie rods 16 and tightening nuts 20 that can apply force to a flange and a fixed platen in a direction that brings them closer to each other, and a combination of the flange and fixed platen. The tightening nut is tightened so as to apply compressive force to the reinforcing member even when the mold clamping cylinder generates the maximum mold clamping force, and the tightening nut is movable. The board is movably guided in the axial direction of the reinforcing member by the sliding surface 18a of the reinforcing member, and the extension line of the sliding surface of each reinforcing member in the axial angular cross section of the reinforcing member passes through the center 26a of the movable board. It is characterized by being Note that the reference numerals in parentheses indicate corresponding members in the embodiments described later.

(e) Action When hydraulic pressure is applied to the mold clamping cylinder to generate mold clamping force, a tensile force is applied to the tie rod, and the tie rod tends to deform the joint between the flange and fixed plate in the direction of moving them closer to each other. shall be. However, since the tightening nut is tightened so that a compressive force acts on the reinforcing member even when the mold clamping force reaches its maximum state, the reinforcing member must be compressed in order for the flange and stationary plate to deform. Therefore, the flange and stationary platen cannot be easily deformed, and have increased rigidity. That is, the reinforcing member functions to prevent deformation of the flange and fixed platen. If the deformation of the flange and fixed plate is reduced in this way, the bending of the tie rod will also be reduced.
The conventional problems as mentioned above are solved. In other words, the deformation of the mold that follows the deformation of the mold clamping device is reduced, and the cavity is maintained in the predetermined shape.
Improves the shape accuracy of molded products. In addition, since the air in the cavity is discharged in a predetermined manner when filling with molten material, filling can be performed rapidly and the surface precision of the molded product can be improved. Furthermore, galling of the guide pins is also prevented. Furthermore, since the movable platen is supported by the sliding surface of the reinforcing member as described above, the positional accuracy of the movable platen is ensured regardless of changes in the movable platen due to temperature changes.

(F) Embodiment FIGS. 1 and 2 show an embodiment of the present invention. A flange 12 integrated with the mold clamping cylinder 10 and a fixed platen 14 are arranged so as to face each other, and both
They are connected by a book tie rod 16 and a reinforcing member 18 provided around its outer periphery. That is, one end of the tie rod 16 that passes through the hole 12a of the flange 12, the hole 18a of the reinforcing member 18, and the hole 14a of the fixed platen 14 is provided with a head 16a, and the other end is provided with a male threaded portion 16b. Ori,
A tightening nut 20 is tightened into this male threaded portion 16b, thereby applying a compressive force to the reinforcing member 18. The tightening force of the tightening nut 20 is set to a value that applies a compressive force to the reinforcing member 18 under all conditions of use of the mold clamping device (that is, even when the maximum mold clamping force is generated). A mold clamping piston 22 is fitted into the inner diameter of the mold clamping cylinder 10, and the mold clamping cylinder 10 has oil holes 10a and 10b communicating with both sides of the mold clamping piston 22, respectively. The mold clamping piston 22 is connected to a movable platen 26 by a piston rod 24. The movable platen 26 is supported so as to be movable in the axial direction with respect to the reinforcing member 18 via four movable plate guide members 28 integrally attached thereto. As shown in FIG. 2, each reinforcing member 18 and movable plate guide member 28
8a and sliding surface 28a. The extension lines of each slide surface 18a and slide surface 28a in the axis-perpendicular cross section (FIG. 2) are all arranged to pass through the center 26a of the movable platen 26. A movable platen 30 is attached to the movable platen 26. Further, a fixed mold 34 is attached to a mold mounting plate 32 that is connected to the fixed plate 14 by fitting. The movable mold 30 and the fixed mold 34 constitute a mold, and a cavity 36 and a sprue 38 are formed in the mold. Molten resin can be injected onto the sprue 38 from an injection nozzle 40.

Next, the operation of this embodiment will be explained. When oil pressure is supplied to the oil hole 10a with the oil hole 10b open, the mold clamping piston 22 moves to the right in FIG. 1, and the movable platen 26 moves toward the fixed platen 14. As a result, the movable mold 30 and the fixed mold 34 come into contact to close the mold, and then by further increasing the hydraulic pressure, a predetermined mold clamping force can be applied to the movable mold 30 and the fixed mold 34. can. In this state, the molten resin is injected from the injection nozzle 40 through the sprue 38 into the cavity 36, and is cooled and solidified to obtain a molded product. When the mold clamping force is acting, a larger force acts on the tie rod 16 than when no mold clamping force is acting, and the tie rod 16 will expand. Therefore, a force is applied from the tie rod 16 to the flange 12 and the fixed platen 14 to deform them, but the deformation of the flange 12 and the fixed platen 14 is reduced by the reinforcing member 18. That is, the reinforcing member 18
A compressive force is applied to the flange 12 and the fixed platen 14 even during the mold clamping force (that is, the reinforcing member 18 is in contact with the flange 12 and the fixed platen 14 at both ends thereof under pressure), and the flange 12 and the fixed platen 14 are The flange 12 and fixed platen 14 cannot be easily deformed because the reinforcing member 18 needs to be further compressed in order to deform. The increase in rigidity due to the reinforcing member 18 will be explained based on the diagram shown in FIG. 3. In Figure 3, line segment OC is tie rod 16
The relationship between the amount of elongation (horizontal axis) and the acting force (vertical axis) is shown. Point A on the line segment OC is the point before the mold clamping force is applied, and the tensile force f ₁ (line segment GA) is applied to the tie rod 16, while the reinforcing member 18 is receiving the compressive force f ₁ . It is. In this condition, tie rod 16
extends by l ₁ (line segment OG), and the reinforcing member 18 extends by l ₂ (line segment
GI), and the line segment IA represents the relationship between the acting force and the shrinkage weight of the reinforcing member 18. When a mold clamping force is generated in this state and the force acting on the tie rod 16 is increased, the balance position shifts from point A to point B, for example. That is, the elongation of the tie rod 16 increases by l ₃ (line segment GH), and the amount of contraction of the reinforcing member 18 decreases by l ₃ . In other words, the line segment OH indicates the amount of elongation (l ₁ + l ₃ ) of the tie rod 16, and the line segment
HI indicates the amount of shrinkage (l ₂ −l ₃ ) of the reinforcing member 18. The tensile force of the tie rod 16 at this balance point B
f ₂ is indicated by line segment BH, while compressive force f ₃ of reinforcing member 18 is indicated by line segment JH, and line segment BJ, which is the difference between the two, indicates mold clamping force f ₄ . Note that when point B is further moved to point C, the amount of contraction of the reinforcing member 18 becomes 0, and no compressive force is applied, but as mentioned above, tighten the tightening nut 20 in advance so as not to exceed point C. It is assembled with. In this way, the tie rod 16 and the reinforcing member 18
By stretching and contracting by l ₃ (line segment GH), f ₄
A mold clamping force of (line segment BJ) can be obtained. On the other hand, if the reinforcing member 18 is not provided, even if the tie rod 16 is extended by l ₃ (line segment GH), the mold clamping force that increases accordingly will be f ₅
(line segment BK). From this, in the case of the mold clamping device of the injection molding machine according to the present invention, the mold clamping force generated for the same amount of elongation of the tie rod 16 is increased compared to the conventional one (f ₄ > f ₅ ), that is, the rigidity increases and it is not easily deformed. Therefore, the flange 12 and the fixed platen 1
4 is less deformed, the tie rod 16 and reinforcing member 18 are less bent, and the movable platen 26 is hardly deformed. Therefore, the movable mold 30 attached to the fixed platen 14 and the movable platen 26 with small deformation
The deformation of the fixed mold 34 is also very small, and the cavity 36 formed by both has a predetermined shape, and the movable mold 30 and the fixed mold 3
4 and the mating surfaces are in even contact with each other,
When the injection nozzle 40 is filled with molten resin, the air in the cavity 36 is quickly discharged, increasing the filling speed of the molten resin. Therefore, the molten resin is pressed against the surface of the cavity 36 under pressure and is cooled and solidified, so that the surface precision of the molded product is improved in accordance with the surface precision of the cavity 36. Further, since the deformation of the movable mold 30 and the fixed mold 34 is reduced, galling of the guide pin fitting portion is prevented, and molding defects due to worn metal powder are prevented from occurring. Furthermore, the frequency of mold repair is also reduced.

In addition, since the movable platen 26 has a support structure that is not affected by heat, the movable platen 26 can be accurately aligned with the mold mounting plate 32, and the movable mold 30 and the fixed mold 34 can be connected with high precision. The mold can be opened and closed. That is, the movable mold 30 and the fixed mold 3
4 is controlled to a predetermined relatively high temperature by a heating device such as a heater during the molding operation, and the heat of the movable mold 30 and the fixed mold 34 acts on the movable platen 26 by thermal conduction, and the movable platen 26 also rises in temperature. As a result, the movable platen 26 expands in the vertical and horizontal directions, but as shown in FIG. Moreover, the extension line of the slide surface 18a and the slide surface 28a is the center 26a of the movable platen 26.
Therefore, even if the movable platen 26 expands, the slide surface 28a only moves on the slide surface 18a, and the position of the movable platen 26 itself does not change. Therefore, even if the temperature rises, the movable platen 26 maintains the same accuracy as when it was assembled and adjusted before the start of operation. In this manner, in addition to the increased rigidity of the mold clamping device described above, the positional accuracy of the movable platen 26 is high, making it even more difficult for galling to occur at the fitting portion of the guide pin. Furthermore, the mold mounting plate 32 is detachably attached to the fixed platen 14, so that the movable platen 2
When making final assembly adjustments such as parallelism and straightness between the mold mounting plate 32 and the mold mounting plate 32, the mold mounting plate 32 can be easily adjusted.

Molding was actually carried out using the injection molding machine as described above, and it was confirmed that the following good results could be obtained.

Molded product...Plastic substrate material for hard disks...Polyetherimide Outer diameter...130±0.13mm Wall thickness...1.905±0.025mm Surface roughness...Ra=0.008 microns Mold life...twice that of conventional products The accuracy of such molded products is This is something that cannot be achieved with conventional equipment, and in particular the surface roughness of the molded product has an accuracy that almost corresponds to the surface roughness of the cavity surface of the mold.

In addition, although the above embodiment is an application of the present invention to a horizontal type direct pressure type mold clamping device, the present invention can also be applied to a vertical type mold clamping device, and can also be applied to a toggle type or other type of mold clamping device. It can also be applied to The number of tie rods 16 and reinforcing members 18 can be selected arbitrarily. Further, this mold clamping device can also be used for compression molding, transfer molding, insert molding, etc. In addition, reinforcing member 1
8 can also be constructed integrally with the flange 12 or the fixed platen 14. The flange 12 can also have a structure in which a plurality of plate materials are stacked one on top of the other. Further, the arrangement of the injection nozzle 40 with respect to the mold clamping device may also be other than the embodiment described. Reinforcement member 1
The sliding surface 18a of No. 8 and the sliding surface 18a of the movable platen guide member 28 may have a structure in which surface pressure can be adjusted.

(g) Effects of the invention As explained below, according to the present invention, the rigidity of the mold clamping device is increased by providing a reinforcing member, so that
This prevents deformation of the mold, aligns the movable mold and fixed mold with high precision, and makes it possible to easily mold highly precise plastic products.It also prevents the generation of mold abrasion powder. This can significantly extend the life of the mold.

Furthermore, the movable platen is guided by the sliding surface of the reinforcing member, and the extension line of this sliding surface passes through the center of the movable platen, so even if the temperature of the movable platen changes, the center position of the movable platen will not change. It is possible to obtain the effect that the positional accuracy of the movable platen is maintained at the same level as the accuracy at the time of assembly and adjustment.

[Brief explanation of drawings]

Fig. 1 is a diagram showing a mold clamping device of an injection molding machine according to the present invention, Fig. 2 is a sectional view taken along the - line in Fig. 1, and Fig. 3 is a diagram showing the acting force and expansion/contraction of the mold clamping device shown in Fig. 1. A diagram showing the relationship with quantity, FIG. 4 is a diagram showing a mold clamping device of a conventional injection molding machine. 10... Mold clamping cylinder, 12... Flange,
14... fixed plate, 16... tie rod, 18...
Reinforcement member, 18a...Sliding surface, 20...Tightening nut, 22...Mold clamping piston, 24...Piston rod, 26...Movable platen, 28...Movable platen guide member, 28a...Sliding surface, 30 ...Movable type, 32...Model mounting plate, 34...Fixed type, 36...
... Cavity.

Claims (1)

[Claims] 1. A flange 12 provided integrally with the mold clamping cylinder 10, a fixed platen 14 arranged to face the flange, and a mold clamping plate arranged between the flange and the fixed platen. A movable platen 26 connected to the piston 22 of the cylinder via a piston rod 24
and a mold mounting board 3 that can be detachably attached to the fixed board.
2, in a mold clamping device for an injection molding machine in which a fixed mold is attached to a mold mounting plate and a movable mold is attached to a movable plate, a force is applied to the flange and the fixed plate in a direction that brings them closer together. It has a possible plurality of sets of tie rods 16 and tightening nuts 20, and a reinforcing member 18 provided on the outer periphery of each tie rod between the flange and the fixed plate, and the tightening nuts are arranged so that the mold clamping cylinder generates the maximum mold clamping force. Even in the state, the movable platen is tightened so as to apply a compressive force to the reinforcing member, and the movable platen is movably guided in the axial direction of the reinforcing member by the sliding surface 18a of the reinforcing member. A mold clamping device for an injection molding machine, wherein an extension line of the sliding surface of each reinforcing member is configured to pass through the center of the movable platen 26a.