JPWO2009011300A1 - Molding device for injection molding machine - Google Patents

Abstract

In the mold clamping device of the present invention, a ball screw (60) movably attached to a back platen (20) is rotated by a servo motor (40) to open and close the mold, and a mold clamping ram (50) is attached to the ball screw. This is a device for clamping a die by applying a clamping force to the integrated bowl-shaped member (62). Therefore, the movable platen (30) includes an operating shaft (31) and includes a ball nut (61) and a slide bearing (32) at the tip thereof. Further, the bowl-shaped member is disposed at a position where the mold clamping ram abuts only when the mold clamping ram advances during mold clamping. The mold clamping ram is pressed in the mold opening direction by the pushing means (53). Thus, the mold clamping device, while opening and closing the mold, slides the tip of the operating shaft of the movable platen within the back platen in a state where the mold clamping ram is separated from the bowl-shaped member by a predetermined gap L, At the time of mold clamping, the bowl-shaped member is pressed with the mold clamping ram.

Description

  The present invention relates to a mold clamping apparatus for an injection molding machine, which performs mold opening and closing electrically by a servo motor and performs mold clamping hydraulically by a mold clamping ram.

  A hybrid mold clamping apparatus that electrically opens and closes a mold and clamps the mold with hydraulic pressure precisely controls the mold opening and closing operation and performs the mold clamping operation with a strong mold clamping force. Such hybrid mold clamping devices include those that directly apply the mold clamping force to the ball screw and those that do not.

  The present invention relates to a mold clamping device that directly applies the former mold clamping force to a ball screw. Such a mold clamping device is, for example, proposed by Japanese Patent Publication No. 7-71807 (referred to as Patent Document 1). In the mold clamping device, a ball screw (corresponding to a ball screw) is fixed to the movable platen side, and a ball nut screwed into the end plate (corresponding to a back platen) is pivotally supported.

  More specifically, the mold clamping device includes a bearing retainer that fixes the ball nut and rotates so as to be movable with respect to the end plate, a mold clamping ram that generates hydraulic clamping force during mold clamping, and the mold And a friction clutch portion formed on the clamping ram, which separates the mold clamping ram from the bearing retainer when the mold is opened and closed, and abuts them when the mold is clamped. Therefore, the mold clamping device applies mold clamping force from the friction clutch to the ball screw through the bearing retainer at the time of mold clamping, and clamps the mold while preventing rotation occurring between the ball screw and the ball nut. On the other hand, when the mold is opened, the pressure oil is appropriately applied to the two oil chambers of the pressure oil chamber A and the pressure oil chamber C, and the mold is opened and closed while the mold clamping ram and the bearing retainer are separated from each other.

According to such a mold clamping device, the rotational torque generated between the ball screw and the ball nut at the time of mold clamping is blocked by the brake torque generated by the friction clutch, so that a load is applied between the ball screw and the ball nut. The clamping force that is applied is limited to static loads. Therefore, the ball screw and the ball nut can be reduced in size and diameter as compared with the case where a dynamic load is applied, and the life thereof is also extended.
Japanese Examined Patent Publication No. 7-71807

  By the way, recently, as the mold becomes more accurate, the fitting between the mold core and the cavity, or the fitting between the guide pin or the angular pin and the guide hole thereof is becoming more accurate. Also, the transfer surface of the molded product is miniaturized. Accordingly, there is an increasing demand for higher straightness of the mold opening / closing operation of the mold clamping device.

  However, the above mold clamping device is not intended to particularly improve the straightness of the mold opening / closing operation. This is because, firstly, the elongated ball screw is rotationally driven via a timing belt between the support points, although it is supported at both ends, and receives a force orthogonal to the axial direction. Secondly, the ball nut is supported by the bearing retainer and is coupled to the pulley via a connecting member. Thirdly, the ball nut is rotated.

  In the first configuration, since a ball screw that does not have sufficient rigidity in the bending direction is applied with the orthogonal force (vertical load) at an intermediate position between the sections supported at both ends, the ball screw is likely to be bent. As a result, the ball screw undergoes deflection due to the vertical load, that is, rotational runout, which directly affects the movable platen and tends to impair the straightness of the mold opening / closing operation. Of course, the configuration itself in which the vertical load is applied to the ball screw in a compressed state is a configuration that should be avoided as much as possible.

  In the second configuration, the rotational force driven by the timing belt is transmitted via a pulley, a connecting member, a ball nut, and a bearing retainer and a plurality of members. For example, concentricity) accumulates, and as a result, it is likely to cause unexpected rotational shake.

  Further, in the third configuration, there is a high possibility that the lubrication on the ball nut side will be insufficient. In general, rotating the ball nut side itself is not preferable because it causes leakage of lubricating oil.

  Accordingly, an object of the present invention is to propose a mold clamping device that solves the above-described problems even in a hybrid mold clamping device that applies a mold clamping force to a ball screw.

  The mold clamping device of the injection molding machine of the present invention is configured as follows in order to solve the above problems.

A mold clamping device of an injection molding machine according to a first aspect of the present invention includes a fixed platen, a back platen, and a movable platen that moves between them, and performs mold opening and closing by a feed screw mechanism that is rotationally driven by a servo motor. In a mold clamping device of an injection molding machine that performs mold clamping with a hydraulic device including a clamping ram;
The servo motor and the mold clamping ram are provided on the back platen side, and the feed screw mechanism comprises a ball screw pivotally supported on the back platen side and a ball nut fixed on the movable platen side. The ball screw is coupled to the servo motor via the rotation transmitting means at a position closer to the mold opening direction than the pivotally supported position, and the movable platen has an operating shaft protruding toward the back platen side. The ball nut and the slide bearing are mounted at the tip of the operating shaft, and a hollow hole is provided at the center to allow the ball screw to enter, and the back platen slideably supports the slide bearing. A perforated portion having a hole formed therein and a cylinder main body forming a mold clamping cylinder for advancing and retracting the mold clamping ram. While the material stops rotation of the mold clamping ram, the pushing means pushes the mold clamping ram backward with a pushing force greater than the mold opening / closing force. A bearing holding member that includes a flange-shaped member at a position that contacts the advanced clamping ram and that incorporates a support bearing that pivotally supports the ball screw is provided in a restricting member that is fixed to the rear end of the cylinder body. Movably accommodated in;
At the time of mold opening / closing, the bearing holding member is pushed by the mold clamping ram by the pushing force of the pushing means against the mold clamping ram, and retreats to the movement limit position, so that the bowl-shaped member is removed from the mold clamping ram. While the mold is clamped, the mold clamping ram moves forward against the pushing force to press the hook-shaped member and separate from the bearing holding member. The holding member is configured to release the load in the restricting member and allow the back platen to move back by the mold clamping allowance.

  A mold clamping device of an injection molding machine according to a second aspect of the present invention is the above-described first mold clamping device, wherein the friction coefficient of the contact surface between the flange-shaped member and the contact surface of the mold clamping ram is μ, and the ball screw The effective diameter D of the contact surface between the bowl-shaped member and the mold clamping ram is set to an outer diameter that is substantially (η / μπ) times larger than the lead P of the ball screw. It may be formed.

  According to a third aspect of the present invention, there is provided a mold clamping device according to the second mold clamping device, wherein the mold clamping cylinder is a single-acting cylinder having only a mold clamping side oil chamber, and the pushing means is the mold. It may be configured by a compression spring that pushes the clamping ram in the mold opening direction with the pushing force and moves backward.

  A mold clamping device for an injection molding machine according to a fourth aspect of the present invention is the double-acting cylinder according to the second mold clamping device, wherein the mold clamping cylinder has two oil chambers, a mold clamping side oil chamber and an anti-clamping side oil chamber. The pushing means is constituted by a hydraulic device that presses the mold clamping ram in the mold opening direction with the pushing force to move backward by supplying pressure oil to the anti-clamping side oil chamber. May be.

A mold clamping device for an injection molding machine according to a fifth aspect of the present invention further includes a safety device that allows the ball screw to retract when an abnormality occurs in the third or fourth mold clamping device, wherein the safety device includes the bearing. Including a buffer piston between the holding member and the restricting member that slides relative to any of the members;
Extruded oil in which a stepped portion is formed on the outer periphery of the buffer piston and the inner periphery of the regulating member so that a gap is generated when they are combined with each other, and the hydraulic fluid is supplied to the gap between the stepped portions A chamber is formed, and hydraulic oil is supplied to the oil chamber, so that the buffer piston is normally pushed forward and allowed to retreat in an abnormal state;
A stepped contact portion may be formed on the inner periphery of the buffer piston and the outer periphery of the bearing holding member to restrict the retreat limit position of the bearing holding member when they are combined with each other.

  The mold clamping device for an injection molding machine according to a sixth aspect of the present invention may be configured such that, in the third or fourth mold clamping device, the feed screw mechanism is a screw mechanism including a trapezoidal screw or a square screw.

  According to the first mold clamping device of the present invention, since the operating shaft of the movable platen is always supported and guided by the slide bearing in the guide hole of the back platen, the straightness of the mold opening / closing operation becomes high accuracy. Since the movable platen is supported at two positions apart from the tie bar and the sliding bearing, the straightness does not change in either the mold closing position or the mold opening position. In addition, since both the perforated bulged portion having the guide hole and the operating shaft are highly rigid members, straightness with high rigidity is ensured. Further, since the rotation transmitting means is located at a position deviating from the shaft support portion toward the mold opening direction, a force orthogonal to the ball screw portion receiving the compressive load does not act at all. Further, since the rotation transmitting means has a simple configuration only via the pulley, there is no possibility that the lack of rigidity of the member, the concentricity defect, or the like will give the ball screw unexpectedly large rotational vibration. In addition, since the ball nut is fixed to the non-rotating operating shaft, lubrication is not hindered. Further, when the mold is opened and closed, the mold clamping ram and the bowl-shaped member are separated from each other by a predetermined gap, so that the configuration and control for the separation operation are simplified. Increase reliability. Further, when the mold is clamped, the bearing holding member is separated from the mold clamping ram and the load is released, so that no mold clamping force is applied to the ball screw support bearing. Further, since only the mold opening / closing force is borne by the bearing holding member when the mold is opened / closed, the support bearing 55 only needs to be able to withstand a much smaller mold opening / closing force than the mold clamping force.

  According to the second mold clamping device of the present invention, the effective diameter D of the bowl-shaped member is configured to be larger than a predetermined ratio with respect to the lead P of the ball screw. The brake torque generated between the two is surely greater than the rotational torque generated by the ball screw. Therefore, the load applied between the ball screw and the ball nut is a stable static load.

  According to the third mold clamping device of the present invention, since the mold clamping device is configured as a single-acting cylinder and the pushing means is configured as a compression spring, the structure of the pushing means is simplified and the hydraulic control is simplified. .

  According to the fourth mold clamping device of the present invention, since the mold clamping device is configured as a double-acting cylinder and the pushing means is configured as an anti-clamping side oil chamber, the separation between the mold clamping ram and the bowl-shaped member is achieved. The operation is not a passive operation by a spring force but an active operation by a hydraulic pressure, and control is ensured. Further, a constant pushing force can be obtained regardless of the stroke.

  According to the fifth mold clamping device of the present invention, during normal mold opening / closing, the bearing holding member is positioned at the retreat limit position with respect to the buffer piston positioned at the advance limit position, and the support bearing is positioned relative to the restriction member. On the other hand, in the event of an abnormality, the bearing holding member is allowed to move backward with respect to the restriction member together with the buffer piston, and the support bearing is allowed to move backward with respect to the restriction member. Therefore, it is possible to add a function of allowing the entire screw to retreat at the moment when an impact occurs at the threaded portion of the ball screw in an abnormal state and buffering the impact.

  According to the sixth mold clamping device of the present invention, since the thread surface of the feed screw mechanism is a trapezoidal plane, the area subjected to a load is increased and the load resistance is improved. In addition, the lubrication effect between the screw and the nut is maintained during dynamic mold opening / closing, while the effect of increasing the friction between them is achieved during static mold clamping. Accordingly, since the rotational torque is hardly generated in the feed screw mechanism, the effective diameter of the bowl-shaped member can be reduced.

FIG. 1 is a sectional view showing the entire mold clamping apparatus of the present invention. FIG. 2 is a cross-sectional view showing the main part of the mold clamping apparatus of the present invention. FIG. 3 is a cross-sectional view showing a mold opening / closing state and a mold clamping state of the mold clamping device of the present invention. A sectional view above the center line shows a mold opening / closing state, and a lower sectional view shows a mold clamping state. FIG. 4 is a cross-sectional view showing a main part of a mold clamping device according to another embodiment of the present invention. FIG. 5 is a cross-sectional view showing a main part of a mold clamping device according to still another embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Mold clamping device 10 Fixed platen 20 Back platen 20a Guide hole 20b Perforated bulging part 30 Movable platen 31 Actuation shaft 31a Hollow hole 32 Sliding bearing 40 Servo motor 50 Mold clamping ram 51 Mold clamping cylinder (cylinder main part)
51a Mold clamping side oil chamber 51b Anti mold clamping side oil chamber 52 Anti-rotation member 53 Pushing means (compression spring)
54 restriction member 55 bearing for support 58 bearing holding member 59 buffer piston 59a oil chamber 59b stepped contact portion 60 ball screw 61 ball nut 62 hook-shaped member 70 rotation transmission means

  First, an outline of the mold clamping device will be described. As shown in FIG. 1, the mold clamping device 1 includes a fixed platen 10 on which a fixed mold 2 a is mounted, a back platen 20, and a movable platen 30 that moves with the movable mold 2 b mounted between them. The fixed platen and the back platen are fastened by a tie bar 3. The movable platen is opened and closed by an electric device such as a servo motor 40 and clamped by a hydraulic device including a mold clamping ram 50. The elongation of the tie bar 3 due to the mold clamping force appears as a moving distance of the back platen 20 in the mold opening direction (hereinafter referred to as the rear), as will be described later as a mold clamping allowance.

  The present invention is a configuration employed in such a hybrid mold clamping device, and the main part thereof will be described with reference to FIG.

  In the mold clamping apparatus 1 of the present invention, the servo motor 40 is fixed to the back platen 20. The mold clamping cylinder for moving the mold clamping ram 50 forward and backward constitutes an end portion on the rear side of the back platen 20 as the cylinder body 51. Then, the mold clamping ram 50 is rotationally stopped by the rotation preventing member 52 in the cylinder main body, and is pushed backward by the pushing means 53 with a pushing force greater than the mold opening / closing force.

  The feed screw mechanism includes a ball screw 60 pivotally supported on the back platen side and a ball nut 61 fixed to the movable platen side. The ball screw is coupled to the servo motor via a rotation transmission means 70, which will be described later, at a position behind the pivotally supported position, while the mold clamping ram 50 advanced during mold clamping comes into contact. A hook-shaped member 62 is provided at the position.

  The movable platen 30 includes an operation shaft 31 protruding toward the back platen side, and the operation shaft includes a ball nut 61 and an annular slide bearing 32 at the tip portion, and the ball screw enters the center thereof. It has a hollow hole 31a to be allowed. The sliding bearing is a known one called a so-called oil-free bush or oilless bearing.

  The back platen 20 includes a perforated bulged portion 20b on the rear side, and the perforated bulged portion 20b includes a guide hole 20a for slidingly supporting the sliding bearing 32 at the tip of the operating shaft 31. The back platen 20 includes a cylinder body 51 that forms the mold clamping cylinder at the rear end of the perforated bulged portion 20b, and the extended portion 60a of the ball screw 60 is moved to the rear end of the cylinder main body. A regulating member 54 is provided for pivotally supporting it.

  A more specific embodiment of the mold clamping device 1 of the present invention is configured as follows.

  The rotation transmission means 70 of the ball screw 60 is a conventionally known one comprising a pulley 71 on the servo motor side, a pulley 72 on the ball screw side, and a timing belt 73 stretched between them.

  The ball screw 60 includes an extended portion 60a that extends rearward from the screw portion and a step portion that is a boundary between the screw portion. Then, the hook-like member 62 is fixed to the threaded portion side of the extended portion 60a in a state where it is in contact with the stepped portion. Thus, the mold clamping force applied to the bowl-shaped member by the mold clamping ram 50 is transmitted from the stepped portion to the ball screw main body. On the other hand, the ball screw 60 is pivotally supported by a conventionally known support bearing 55 that is resistant to thrust load on the rear side of the extension portion 60a, and a pulley 72 is mounted further rearward than the pivot support position. The pulley 72, the support bearing 55, and the flange member 62 are fixed at their mounting positions by a spacer sleeve having an appropriate length. These pulleys and hook-like members are keyed and are prevented from rotating.

  In particular, the bowl-shaped member 62 is formed in a plane in which the end surface 62a on the mold clamping ram side is matched with the end surface of the mold clamping ram, and the back surface 62b is formed in a conical surface. It is configured. The mold clamping ram side end face 62a is formed in a perforated disk shape having a certain width in the radial direction. Further, the key groove formed in the inner hole that fits into the ball screw 60 of the bowl-shaped member 62 is disposed on the stepped portion side while avoiding the vicinity of the mold clamping ram side. This is because both can withstand a strong clamping force. Note that the mold clamping ram side end surface 62a that comes into contact with the mold clamping ram 50 may be formed into an uneven surface that is grooved at equal intervals instead of being formed into a flat surface, and may be formed into a more slippery surface.

  The mold clamping ram 50 includes a piston portion 50a that receives hydraulic pressure and a rod portion 50b that extends rearward. The mold clamping cylinder 51 is configured as a single acting cylinder having only a mold clamping side oil chamber 51a as shown in the figure, for example, and a hydraulic oil supply port (not shown) is communicated with the mold clamping side oil chamber. . More specifically, the rotation preventing member 52 for preventing the mold clamping ram 50 from rotating is a pin 52 implanted in the cylinder body 51 and slides with respect to the piston portion 50a.

  An auxiliary member 56 that enlarges the outer diameter of the movable platen as necessary is integrally attached to the outer periphery of the end surface on the movable platen side of the mold clamping ram 50 so as to be easily pressed by the pushing means 53. The pushing means 53 is incorporated as a compression spring 53 that pushes the auxiliary member 56. A plurality of compression springs 53 are embedded at equal intervals in the perforated bulging portion 20b, such that the total pushing force generated by the compression springs exceeds the mold opening force or mold closing force applied to the ball screw 60, and It is set to be lower than the clamping force.

  More specifically, the configuration for pivotally supporting the ball screw 60 is configured as follows. That is, a known support bearing 55 that supports the ball screw 60 is fixed in the bearing holding member 58, and the bearing holding member is movably accommodated in the regulating member 54. The bearing holding member 58 clamps and fixes the outer ring of the support bearing 55 by two members. The restricting member 54 is a cylindrical member in which a stepped hole is formed. When the restricting member 54 is fixed to the cylinder body 51, the hole forms a space in which the bearing holding member 58 can move between the hole and the cylinder body 51. Consists of. A plurality of shallow grooves are formed on the outer periphery of the bearing holding member 58 as oil grooves for lubrication, so that the sliding resistance of the bearing holding member 58 with respect to the cylinder body 51 is reduced.

The effective diameter D of the mold clamping ram side end face 62a of the bowl-shaped member 62 formed in the perforated disk can be roughly expressed as an arithmetic average of the outer diameter and the inner diameter of the perforated disk. Regarding the effective diameter D, it is desirable that the following relationship is satisfied. That is, the effective diameter D is preferably formed to have an outer diameter that is substantially (η / μπ) times larger than the lead (pitch) P of the ball screw.
That is,
D / P> η / μπ
It is.
Here, the friction coefficient μ is a friction coefficient at the contact surface between the flange-shaped member 62 and the mold clamping ram 50. The inverse efficiency η is an efficiency when converting linear motion into rotational motion, and is a coefficient determined by the lead angle of the ball screw.

The above magnification (ratio) is roughly derived as follows. First, the rotational torque T1 generated in the ball nut when the mold clamping force F is applied to the ball screw of the lead P,
T1 = ηFDP / 2πD = ηFP / 2π
It is.
On the other hand, the friction torque T2 (brake torque) generated on the contact surface between the flange-shaped member 62 and the mold clamping ram 50 by the mold clamping force F is assumed to be a friction coefficient μ and an effective diameter D.
T2 = μFD / 2
It is.
Therefore, when the friction torque and the rotational torque coincide with each other, T2 = T1.
ηFP / 2π = μFD / 2
After all,
D / P = η / μπ
Is guided.

More specific values are as follows, for example. Generally, the friction coefficient on the smooth surface between hardened steel materials does not become smaller than 0.05 even if an oil film adheres. The reverse efficiency at a lead angle of about 3 degrees is about 90%. Therefore,
D / P = 5.73
It becomes. If the screw outer diameter is 50 mm and the lead is 16 mm, the effective diameter D of the friction surface exceeds about 92 mm, which is a sufficiently realistic value.

  In the case of such a configuration, the brake torque (which is the above-mentioned friction torque) generated between the mold clamping ram 50 and the bowl-shaped member 62 during mold clamping is between the ball screw 60 and the ball nut 61. It surely exceeds the generated rotational torque. Therefore, the load applied between the ball screw 60 and the ball nut 61 is a stable static load that does not include a dynamic load, and the selection of the ball screw can be a small-diameter ball screw with a low rated load. The screw life is also improved.

  The mold clamping apparatus having the above configuration opens and closes the mold as shown in FIG. In addition, the drawing above the center line of FIG. 3 shows a state in which the mold is being opened and closed, and the lower drawing shows a state in which the mold is being clamped.

  A supplementary explanation will be given on the upper half of FIG. When the mold is opened and closed, the mold clamping ram 50 pressed by the push-in means 53 presses the bearing holding member 58 rearward in the regulating member 54 and holds it at the retreat limit position. Therefore, the clearance M between the bearing holding member 58 and the rear end wall of the mold clamping cylinder 51 at that time is a movement allowance of the bearing holding member 58, that is, the restriction member 54 can be retracted with respect to the bearing holding member 58. Indicates travel cost. In addition, the predetermined gap L between the mold clamping ram 50 and the bowl-shaped member 62 is a gap that appears when the mold clamping ram 50 moves backward together with the bearing holding member 58 to the retreat limit position of the bearing holding member 58. It is sufficient that the predetermined gap L is about 0.3 mm to 0.5 mm. In the present invention, since the predetermined gap L can be formed small, it is possible to shorten the time until the mold clamping ram 50 comes into contact with the bowl-shaped member 62 when switching to mold clamping. This contributes to speeding up the switching operation from mold closing to mold clamping. Of course, the basic configuration of the present invention, which eliminates the need for a pressure transmission device that switches between mechanical engagement and disengagement for transmission of mold clamping pressure, is most effective for speeding up the above, This is important in situations where recent molding cycles are being shortened to the limit.

  Next, a supplementary explanation will be given for the lower half of the figure. When the mold is clamped, the back platen 20 moves backward by a distance of the mold clamping allowance mainly due to the extension of the tie bar 3. The backward movement appears as a distance N, which is the backward movement of the regulating member 54 with respect to the bearing holding member 58. Here, since the distance M is greater than the distance N, the back platen 20 is allowed to move backward with respect to the bearing holding member 58 without difficulty. At this time, the ball screw 60 and the operating shaft 31 are of course slightly contracted, but the distance can be ignored. Therefore, this mold clamping allowance N is typically represented as an extension allowance of the tie bar.

  Thus, the mold opening / closing is performed by the servo motor 40 controlling the rotation of the ball screw 60, moving the ball nut 61 screwed to the ball screw 60, and moving the movable platen 30 together with the operating shaft 31. At this time, the pushing means 53 pushes the mold clamping ram 50 with a pushing force exceeding the mold opening / closing force, and the bearing holding member 58 pushed by the mold clamping ram is held in the retreat limit position in the regulating member 54. The As a result, the mold clamping ram 50 is maintained in a state of being separated from the flange-shaped member 62 by a predetermined gap L, so that the ball screw 60 is controlled to rotate without interfering with the flange-shaped member 62.

  On the other hand, in the mold clamping, the mold clamping ram 50 loaded with the mold clamping force moves forward against the pushing force of the pushing means 53 and presses the bowl-shaped member 62 to press the ball nut 61 and the operating shaft 31. Is done by. At this time, the braking force generated by the frictional force generated between the mold clamping ram 50 and the bowl-shaped member 62 prevents the ball screw 60 from rotating. Further, as the mold clamping ram 50 moves forward, the bearing holding member 58 is not separated from the mold clamping ram 50, so that a mold clamping load is not applied to the support bearing 55. Then, the back platen 20 moves backward by a distance approximately equal to the mold clamping allowance N with respect to the bearing holding member 58 as the tie bar 3 extends due to the mold clamping force.

  According to the mold clamping device of the present invention having the above configuration, the operating shaft 31 of the movable platen 30 is supported and guided by the slide bearing 32 in the guide hole 20a of the perforated bulged portion 20b of the back platen 20. The straightness of the opening / closing operation is highly accurate. Then, since the movable platen is supported by the sliding portions at two positions apart from the tie bar 3 and the slide bearing 32, the straightness of the mold opening / closing operation is changed regardless of the mold closing position or the mold opening position. Absent. Moreover, since both the perforated bulged portion 20b of the back platen 20 and the operating shaft 31 are highly rigid, high rigidity and straightness are guaranteed. Due to this highly rigid straightness, for example, even when a fitting failure with a guide pin or the like occurs asymmetrically with respect to the center of the mold, the mold does not twist and the straightness is not further deteriorated. Further, the vertical load by the rotation transmitting means 70 is not applied to the portion of the ball screw 60 that receives the compressive load on the flange-shaped member 62 or the ball nut 61 side. Further, since the rotation transmitting means 70 has a simple configuration only via the pulley 72, there is no possibility that a lack of rigidity of the member, a poor concentricity, or the like will give the ball screw 60 a cumulative runout. Further, since the ball nut 61 is fixed to the operation shaft 31 that does not rotate, it does not interfere with lubrication. Further, since the operation of separating the mold clamping ram 50 and the bowl-shaped member 62 from the predetermined gap L when the mold is opened and closed is performed only by the pressing by the pushing means 53 that is a spring, the configuration and control for these separating operations are performed. Becomes simple.

  Of course, the ball screw 60 may be a small-diameter ball screw having a low rated load with respect to a static load. This is because when the mold-clamping ram 50, which is rotationally stopped during mold clamping, presses the bowl-shaped member 62, the brake torque generated by the frictional force between them suppresses the rotational torque generated in the ball screw.

  Further, at the time of mold clamping, the bearing holding member 58 is released from contact with the mold clamping ram 50 and can move within the regulating member 54, so that the mold clamping force is borne on the support bearing 55. There is nothing. Further, since the mold clamping ram 50 and the bowl-shaped member 62 are separated when the mold is opened and closed, the force applied to the support bearing 55 is only the mold opening force or the mold closing force. Therefore, the support bearing 55 only needs to be able to withstand a mold opening / closing force that is much smaller than the mold clamping force.

  The mold clamping device of the present invention may be configured in an embodiment as shown in FIG. In this embodiment, the mold clamping cylinder 51 is configured as a double-acting cylinder having an anti-clamping side oil chamber 51b on the opposite side of the mold clamping side oil chamber 51a. In this case, the pushing means 53 is replaced with a hydraulic device that supplies the working oil to the anti-clamping side oil chamber 51b to generate a pushing force. Thus, when the pressure oil is supplied to the anti-clamping side oil chamber 51b when the mold is opened and closed, the mold clamping ram 50 is pressed backward by the pushing force described above. Therefore, the separating operation of the mold clamping ram 50 and the bowl-shaped member 62 is performed not by the passive force due to the spring force of the compression spring but by the active force due to the hydraulic pressure, and the control is ensured. Further, the pushing force becomes constant regardless of the stroke. In addition, it is possible to reduce the amount offset by the mold clamping force by applying the pushing force only when the mold is opened and closed.

  In another embodiment, a safety device may be added that allows the ball screw 60 to retract when an abnormality occurs. Here, the time of abnormality refers to a time when the mold closing operation is prevented due to an unexpected cause. This is a case where an impact force is generated. In preparation for such a case, the safety device is configured as shown in FIG. 5, for example. Here, the drawing above the center line in FIG. 5 shows a state in which the mold is being opened and closed, and the lower drawing shows a state in which the mold is being clamped.

  The safety device includes a bearing holding member 58 that fixes the support bearing 55 of the ball screw 60 and a restriction member 54 that restricts the movement of the bearing holding member 58 in the above configuration. Even in this case, the buffer piston 59 that slides is provided. In particular, a stepped portion is formed on the outer periphery of the buffer piston 59 and the inner periphery of the regulating member 54 so that a gap is formed when they are combined with each other, and hydraulic fluid is supplied to the gap between the stepped portions. An extrusion oil chamber 59a is defined. The projected area in the mold opening / closing direction of the oil chamber 59a is formed in advance as follows. That is, the projection area and the hydraulic pressure are set so that the buffer piston 59 is normally pushed forward under a predetermined hydraulic oil pressure, but is allowed to move backward in the event of an abnormality. In addition, a stepped contact portion 59b that restricts the retreat limit position of the bearing holding member 58 when they are combined with each other is formed on the inner circumference of the buffer piston 59 and the outer circumference of the bearing holding member 58.

  With such a configuration, when the mold is normally opened and closed, the bearing holding member 58 is positioned at the retreat limit position with respect to the buffer piston 59 positioned at the advance limit position. While being held at the retreat limit position, the bearing holding member 58 retreats with respect to the restricting member 54 together with the buffer piston 59 when abnormal, so that the support bearing 55 is allowed to retreat with respect to the restricting member 54 when abnormal. Is done. In addition, the backward movement of the regulating member 54 with respect to the bearing holding member 58 due to the clamping force generated at the time of the subsequent clamping is allowed in the same manner as the backward movement in the configuration not including the buffer piston 59. This is because only the retraction of the restricting member 54 occurs while the buffer piston 59 is stopped at the forward limit position and the bearing holding member 58 is stopped at the backward limit position. With such a configuration, it is possible to add a safety function that allows the entire screw to be retracted at the moment when an impact occurs at the threaded portion of the ball screw 60 in the event of an abnormality and cushions the impact.

  In still another embodiment, the feed screw mechanism may be a screw mechanism including a conventionally known trapezoidal screw or square screw. In this case, the ball screw is replaced with a trapezoidal screw (not shown), and the ball nut is replaced with a nut (not shown) screwed thereto. And naturally, a screw and a nut are comprised with a dissimilar material so that it may not bite, and lubricating oil is filled between them. By adopting such a screw mechanism, since the screw surface becomes a trapezoidal plane, the area subjected to a load is increased and the load resistance is improved. In addition, the lubrication effect between the screw and the nut is maintained during dynamic mold opening / closing, while the effect of increasing the friction between them is achieved during static mold clamping. Thus, the screw mechanism also makes it possible to reduce the effective diameter of the bowl-shaped member.

  The above-described configuration of the mold clamping device can also be employed in a precision press machine that requires high accuracy and high speed. This is because high-precision straightness of mold opening and closing and switching to a highly responsive mold clamping operation can be realized. The hydraulic device including the mold clamping ram is, for example, a driving device using electromagnetic force or a driving device using a piezoelectric element, and a device that switches to a more responsive mold clamping by reducing the predetermined gap L. You can also

Claims (6)

A fixed platen (10), a back platen (20), and a movable platen (30) that moves between them, are opened and closed by a feed screw mechanism that is rotationally driven by a servo motor (40), and a mold clamping ram ( 50) in a mold clamping device (1) of an injection molding machine that performs mold clamping with a hydraulic device including
The servo motor and the mold clamping ram are provided on the back platen side, and the feed screw mechanism includes a ball screw (60) pivotally supported on the back platen side and a ball nut (fixed on the movable platen side). 61), the ball screw is coupled to the servo motor via the rotation transmitting means (70) at a position closer to the mold opening direction than the pivotally supported position, and the movable platen is connected to the back platen. A hollow hole (31a) provided with a working shaft (31) projecting toward the side, the ball nut and the sliding bearing (32) being mounted at the tip of the working shaft and allowing the ball screw to enter the center thereof ), And the back platen has a perforated bulging portion (20b) in which a guide hole (20a) for slidingly supporting the sliding bearing is formed, and a mold clamping for moving the mold clamping ram forward and backward And a cylinder main body forming a Linda (51), in which the rotation-stopping member (52) prevents the mold-clamping ram from rotating while the pushing means (53) has a pushing force greater than the mold opening / closing force. The ball screw further includes a hook-like member (62) at a position where it comes into contact with the mold clamping ram that has been advanced during mold clamping, A bearing holding member (58) containing a support bearing (55) for supporting a screw is movably accommodated in a regulating member (54) fixed to the rear end of the cylinder body;
At the time of mold opening / closing, the bearing holding member is pushed by the mold clamping ram by the pushing force of the pushing means against the mold clamping ram, and retreats to the movement limit position, so that the bowl-shaped member is removed from the mold clamping ram. While the mold is clamped, the mold clamping ram moves forward against the pushing force to press the hook-shaped member and separate from the bearing holding member. A mold clamping device for an injection molding machine, wherein the holding member is released from the load in the regulating member and the back platen is retracted by a mold clamping allowance.   The effective diameter D of the contact surface between the bowl-shaped member and the mold clamping ram is when the friction coefficient of the contact surface with respect to the lead P of the ball screw is μ and the reverse efficiency of the ball screw is η. 2. The mold clamping device for an injection molding machine according to claim 1, wherein the outer diameter is substantially larger than (η / μπ) times.   A compression spring (53) in which the mold clamping cylinder is constituted by a single-acting cylinder having only a mold clamping side oil chamber (51a), and the pushing means pushes the mold clamping ram in the mold opening direction with the pushing force and moves backward. 3. The mold clamping apparatus for an injection molding machine according to claim 2, wherein   The mold clamping cylinder is constituted by a double-acting cylinder having two oil chambers of a mold clamping side oil chamber (51a) and a counter mold clamping side oil chamber (51b), and the pushing means pressurizes oil into the counter mold clamping side oil chamber. 3. The mold clamping apparatus for an injection molding machine according to claim 2, wherein the mold clamping ram is configured to be a hydraulic apparatus that presses the mold clamping ram in the mold opening direction with the pushing force and moves backward by supplying the. The mold clamping device further includes a safety device that allows the ball screw to retract when an abnormality occurs, and the safety device slides between the bearing holding member and the regulating member with respect to any of these members. Including a buffer piston (59);
Extruded oil in which a stepped portion is formed on the outer periphery of the buffer piston and the inner periphery of the regulating member so that a gap is generated when they are combined with each other, and the hydraulic fluid is supplied to the gap between the stepped portions One of the chambers (59a) is configured to supply hydraulic oil to the extrusion oil chamber, whereby the buffer piston is normally pushed forward and allowed to retreat in an abnormal state;
A stepped contact portion (59b) is formed on the inner periphery of the buffer piston and the outer periphery of the bearing holding member to restrict the retreat limit position of the bearing holding member when they are combined with each other. A mold clamping device for an injection molding machine according to claim 3 or 4.   5. The mold clamping apparatus for an injection molding machine according to claim 3, wherein the feed screw mechanism is constituted by a screw mechanism including a trapezoidal screw or a square screw.

Images