JP4498803B2 - Ball screw nut structure and injection molding machine using the structure - Google Patents

Description

  The present invention relates to a ball screw nut portion structure capable of absorbing bending (twisting) applied to a ball screw nut with a simple structure and an injection molding machine using the structure.

For example, when molding a resin part, a resin material is melted in an injection molding machine, and the melted resin is injected into a molding cavity of a mold clamping device to mold a resin product.
In the past, hydraulic pressure was mainly used as a drive source for the linearly moving part of an injection molding machine. Recently, however, it has the advantage that it is easy to control the working environment, power energy efficiency, operating part speed, position, etc. As a result, electric driving is often used. Such an electric drive uses a ball screw for changing the rotation to a linear motion and a ball screw nut screwed into the ball screw.

FIG. 12 shows a mounting structure of a ball screw and a ball screw nut disclosed in JP-A-2002-317863. According to the technique of this publication, a ball screw 71 used in an injection molding machine is driven to rotate, whereby a ball screw nut 72 that is screwed into the ball screw 71 moves in the axial direction of the ball screw 71.
A flexible joint 73 is attached to the ball screw nut 72, and the flexible joint 73 is coupled using a moving frame 74, a support plate 75 fixed thereto, and a bolt 76. In the flexible joint 73, ring-shaped diaphragms 77a and 77b face each other to form ring-shaped liquid chambers 78a and 78b, and two sets of the ring-shaped hollow diaphragms 77a and 77b are connected to both sides of the ring-shaped mounting plate 79. Welded to. The liquid chambers 78a and 78b are filled with an incompressible liquid and sealed. The flexible joint 73 is attached by a moving frame 74 and a support plate 75 using bolts 76 provided on both sides thereof.

FIG. 13 shows a mounting structure of a ball screw and a ball screw nut for operating the movable plate of the mold clamping device disclosed in JP-A-2002-225101.
A connection bracket 86 is attached to the lower surface of the moving base 85 for moving a movable plate (not shown), and a ball screw 87 is inserted and disposed in a through hole formed in the lower portion thereof with a gap. Four disc springs 88 are installed on each side of the connection bracket 86, two back to back, and the disc springs 88 are housed in a spring chamber formed by a spring case 89 and a spring case lid 90. A ball screw nut 91 is fixed to the outer surface of the case lid 90. The disc spring 88 is compressed by the spring case 89 and the spring case lid 90 and is subjected to a strong preload. Further, the spring case 89 and the case lid 90 have a gap around the entire circumference with respect to the connection bracket 86.
JP 2002-317863 A JP 2002-225101A

When the ball screw nut 72 shown in FIG. 12 does not have the flexible joint 73, the mounting error or the moving frame 74 is deformed by a load. When the axis center line of the ball screw 71 is inclined with respect to the center line of the ball screw nut 72, a biased force is applied to the ball screw nut 72, and there is a risk of damage when the load is large.
On the other hand, in the structure having the flexible joint 73 as shown in FIG. 12, since the ball screw nut 72 is attached to the moving frame 74 via the flexible joint 73, the moving frame 74 (ball screw nut 72) and the ball screw 71 are arranged. When a relative angular displacement occurs between the two, the surfaces of the diaphragms 77a and 77b of the flexible joint 73 are elastically deformed to release the angular displacement of the ball screw nut 72, and the ball screw 71, the ball screw nut 72, and both An excessive load is not applied to the ball interposed in the screwing, and the rotational driving of the ball screw 71 can be converted into the driving in the linear direction safely and reliably.
In the mold clamping device shown in FIG. 13, when the ball screw nut 91 is slightly deformed and the ball screw 71 comes into contact with one piece in the mold clamping process, the disc spring 88 bends and relaxes the unbalanced load. Therefore, the action of bending force on the ball screw 87 can be avoided.

However, the structure shown in FIG. 12 is provided with a liquid chamber 78 and a diaphragm 77, and the structure shown in FIG. 13 requires a spring case 89 and a disc spring 88. Manufacturing time increases.
The present invention has been made in view of such circumstances, and an object of the present invention is to provide a ball screw nut portion structure having a simple structure so that the ball screw nut is flexible and an injection molding machine using the structure. To do.

The present invention, in order to achieve the above object, the mounting of the ball screw nut to the support member, screwed to the ball screw nut to the ball screw, ball screw extending through the support member, the ball screw nut structure, the outer peripheral portion of the ball screw nut The cylindrical member surrounding the ball screw is provided between the flange provided on the support member and the support member, and both end portions of the hole in the axial direction of the cylindrical member are formed in an arc shape . (Claim 1)
In order the present invention to achieve the above objects, attach the ball screw nut to the support member, screwed ball screw to said ball screw nut, the ball screw penetrating the support member, the injection screw with a ball screw nut structure In the used injection molding machine , with respect to the ball screw nut portion structure, a plurality of circular rods connecting between a flange provided on one end side of the ball screw nut and the support member are arranged around the ball screw. A screw portion is formed at each of both ends in the longitudinal direction of the circular rod, one of the screw portions is attached to the support member, and the other screw portion is attached to the flange. So that the amount of deformation of the support member against the external force is absorbed between the flange and the support member. The Rukoto. (Claim 2)
Furthermore, in order to achieve the above object, the rod includes a shaft-shaped member disposed along a longitudinal direction of the ball screw, and a cylindrical portion into which the shaft-shaped member is inserted, and the circular rod Threaded portions are formed at both ends in the longitudinal direction of the shaft member, threaded portions are formed at both ends in the longitudinal direction of the shaft member, and the threaded portions protrude from both ends of the cylindrical portion in the longitudinal direction. ing. (Claim 3)
Furthermore, the present invention can be applied to an injection molding machine using the ball screw nut structure of claim 1 in order to achieve the above object . (Claim 4)

The present invention provides a ball screw nut attached to a support member, wherein the ball screw nut is screwed to the ball screw nut, and the ball screw penetrates the support member. A flange provided on the outer periphery of the ball screw nut and the support member Are provided in a cylindrical member that surrounds the periphery of the ball screw, and both end portions of the hole in the axial direction of the cylindrical member are formed in an arc shape . Mounting errors and bending deformations such as ball screws and moving frames can be absorbed, and durability and reliability can be improved.
The present invention is fitted with a ball screw nut to the support member, the screwed ball screw a ball screw nut in an injection molding machine using an injection screw having a ball screw nut structure in which the ball screw penetrates the support member, the ball screw nut Regarding the part structure, a plurality of circular rods connecting between the flange provided on one end side of the ball screw nut and the support member are disposed so as to surround the ball screw in a circumferential manner, Threaded portions are respectively formed at both ends in the longitudinal direction of the circular rod, and one of the threaded portions is attached to the support member, and the other of the threaded portions is attached to the flange. The deformation amount of the support member with respect to the external force is absorbed between the support member and the support member . The rod includes a shaft-like member disposed along a longitudinal direction of the ball screw, and a cylindrical portion into which the shaft-like member is inserted, and screw portions are provided at both ends in the longitudinal direction of the circular rod. The threaded portions are respectively formed at both ends in the longitudinal direction of the shaft member, and the threaded portions protrude from both ends in the longitudinal direction of the cylindrical portion. Therefore, in spite of reducing the cost, it is possible to absorb the mounting error of the device and the bending deformation of the ball screw, the moving frame, etc., and the durability and reliability can be improved. The amount of deflection can be easily adjusted simply by changing the thickness and number of rods .

The ball screw nut structure according to the first embodiment of the present invention will be described below with reference to the drawings.
FIG. 1 is a side view of an injection molding machine according to the present invention, and FIG. 2 is a plan view partially cut away. The injection molding machine 1 is provided with an injection cylinder 2 on a base 6, an injection screw 3 provided in the cylinder of the injection cylinder 2, and an electric motor 4 for rotationally driving the injection screw 3 at the rear part thereof. In the present specification, the front end side of the injection screw 3 will be described as the front. A pair of ball screw devices 5 are provided on both sides of the injection screw 3, and the ball screw device 5 is provided with a ball screw 7 oriented in the horizontal direction in the same manner as the axis of the injection screw 3.

The ball screw 7 is rotatably engaged with the ball screw nut 8 at an intermediate position, and the tip side is attached via a large capacity angular contact bearing 10 so as to receive a load in a large thrust direction. The rotation of the ball screw 7 is transmitted to the ball screw 7 through the small pulley 12, the toothed belt 14, and the large pulley 13 using the injection drive motor 11 as a drive source, and the pair of ball screws 7 rotate synchronously.
The moving frame 9 can move horizontally on the rail 6a laid on the upper surface of the base 6, and when the pair of ball screws 7 rotate synchronously, the ball screw nuts 8 on both sides move simultaneously. The moving frame 9 is structured to advance and retract in the axial direction of the injection cylinder 2.

Hereinafter, details of the ball screw device 5 will be described.
The ball screw device 5 shown in FIG. 2 is provided with a pair on the left and right sides of the injection molding machine 1, and these structures are the same, so one side will be described. As shown in FIG. 2, the ball screw 7 passes through the support plates 17 a and 17 b on the front and rear sides of the moving frame 9 with this axial direction oriented horizontally. As shown in FIGS. 3 and 4, a cylindrical member 15 is provided on one front support plate 17 a. As shown in FIGS. 5A and 5B, the cylindrical member 15 is integrally formed with a casting, and is provided with a flange 18 at one end. A bolt hole 19 is formed in the flange 18, and is fixed to the support plate 17a by a bolt 20a. The A ball screw nut 8 is fixed to the bolt 20b at the other end of the cylindrical member 15.

  As shown to A of FIG. 5, the small diameter part 22 is provided in the intermediate position of the axial direction of the surrounding wall part 23 of the cylinder member 15, and it forms thinly. A plurality of long holes (or elliptical holes) 21 penetrating the peripheral wall portion 23 in the axial direction are formed in the peripheral wall portion 23 so as to be elongated in the axial direction. The shape of the long hole 21 may be a plurality of horizontally long diamond-shaped holes 24 as shown in FIG. As shown in FIGS. 7A and 7B, in addition to the long holes 21 and the rhombic holes 24 already described, circular holes 25a are formed at both ends as shown in FIG. 7C, and a slit-like hole is formed between them. You may communicate with 25b. Moreover, as shown to D of FIG. 7, the rectangular hole 26 may be sufficient, and as shown to E of FIG. 7, the long hole 27a may be formed and the wide part 27b may be formed in the middle.

  As shown in FIGS. 3 and 4, the ball screw nut 8 includes a cylindrical portion 28a and a flange portion 28b provided on the rear end side in the axial direction of the cylindrical portion 28a. A ball 29 is accommodated between the thread groove of the ball screw 7. A bolt hole 30 is formed in the flange portion 28b, and is fixed to the distal end portion of the cylindrical member 15 by the bolt 20b. Therefore, the cylindrical member 15 and the ball screw nut 8 are supported by the support plate 17a in a cantilever manner. The ball screw 7 passes through the support plate 17 a and the cylindrical member 15 and is screwed into the ball screw nut 8. The other ball screw device 5 has the same structure.

  With such a configuration, in the plasticizing process, the injection molding machine 1 rotates the electric motor 4 to rotate the injection screw 3, introduces resin pellets from the hopper 31, heats them while feeding them, and melts the resin. Plasticize. At the same time, the injection driving motor 11 is driven to move the moving frame 9 backward, the injection screw 3 is slowly retracted, and the molten resin is collected at the tip of the injection screw 3. When the resin for one shot has been accumulated in the mold clamping device (not shown), the moving frame 9 is in the retracted position, the injection drive motor 11 for the injection screw 3 is stopped, and the injection drive motor 11 is operated synchronously. Then, the injection screw 3 is advanced at a high speed, a nozzle (not shown) is brought into contact with the mold, and the resin is injected into the cavity of the mold. And it transfers to the process of resin feeding and plasticization for the next cycle, and repeats the same process.

When the cylindrical member 15 shown in FIG. 4 is not arranged, the moving frame (support plate 17) 9 is deformed by a load during operation of the injection molding machine 1, so that the axis of the ball screw nut 8 with respect to the center line a of the ball screw 7 Assume that the center line b is inclined by an angle α. In such a case, the ball screw 7 is biased against the ball screw nut 8 and causes the ball screw device 5 to be damaged.
However, in the present embodiment, since the long hole 21 is formed in the cylindrical member 15, the cylindrical member 15 absorbs the deformation amount of the support plate 17a, eliminates the displacement of the ball screw nut 8, and prevents the ball screw 7 from hitting one piece. . Since the cylindrical member 15 forms the thin small diameter part 22 and forms the multiple long holes 21, it becomes easy to bend, and when load deformation becomes small, it will return to the original state again.
Note that the long hole 21 having both ends of the circular arc has an advantage that stress concentration does not occur even when a load is applied to the cylindrical member 15. Therefore, as shown in FIG. 7B, it is desirable to form both end corners of the diamond-shaped hole 24 in an arc shape as shown in FIG.
As described above, since the cylindrical member 15 is flexible, the ball screw 7 is not damaged and can have a long life. Since the cylindrical member 15 is cast, the small-diameter portion 22 is formed and the thickness of the peripheral wall portion is reduced. Therefore, there is an effect of saving material.

Next, a second embodiment of the ball screw nut part structure of the present invention will be described. The ball screw device 5 shown in FIG. 8 of the present embodiment differs from the first embodiment only in the structure of the cylindrical member 15 and uses the same member for the other parts, so that description thereof will be given. Is omitted.
As shown in FIG. 8, the ball screw nut 8 is coupled to the support plate 17 provided on the moving frame 9 via a plurality of rods 32. Each rod 32 is arranged in the shape of a birdcage so that the shaft center is arranged in parallel with the ball screw 7 and surrounds the ball screw 7 at an equal distance from the shaft center of the ball screw 7 in the radial direction.

As shown in FIG. 9, each rod 32 includes a shaft-shaped member 33 and a cylindrical portion 34, and the shaft-shaped member 33 is inserted into the cylindrical portion 34. Screws 35 a and 35 b are formed at both ends of the shaft-shaped member 33, and the portions of the screws 35 a and 35 b protrude from the cylindrical portion 34. One screw 35a is screwed to the support plate 17a so that the rod 32 can be erected from the support plate 17a, and the other screw 35b is inserted into the bolt hole 30 (see FIG. 4) of the ball screw nut 8 and the nut 36 Thus, the flange portion 28 is fixed.
In addition, although the rod-shaped member 33 and the cylindrical part 34 were made into a different body, the rod 32 may be integrally formed, and the sectional shape of the shaft-shaped member 33 may be a shape other than a circle.
In such a ball screw device 5, during the operation of the injection molding machine 1, the moving frame (support plate 17a) 9 is deformed by a load, so that the axis center line of the ball screw nut 8 is inclined with respect to the center line of the ball screw 7. When doing so, the rod 32 as a whole absorbs the deflection of the support plate 17a between the flange portion 28 and the support plate 17a, thereby eliminating the displacement of the ball screw nut 8 and preventing the ball screw 7 from hitting one piece. Furthermore, the present ball screw device 5 can easily adjust the amount of deflection by simply changing the thickness and number of rods.

Next, the ball screw nut part structure of the 3rd Embodiment of this invention is demonstrated.
In the present embodiment, the cylindrical member 15 of the first embodiment is omitted, and a ball screw nut 37 shown in FIGS. 10A and 10B is directly fixed to the support plate 17.
As shown in FIGS. 10A and 10B, the ball screw nut 37 formed of a casting is composed of a cylindrical portion 38 and a flange portion 39, and bolts are inserted into a large number of through holes 40 formed in the flange portion 39 to support them. It is directly fixed to the plate 17a. The ball screw 7 is screwed into the inner hole 42 of the cylindrical portion 38 through the ball 29 (see FIG. 4). An annular groove 41 is formed in the flange portion 39 around the base end side of the cylindrical portion 38. The number of the grooves 41 (three in this embodiment) is determined as appropriate, and the width and depth of the grooves 41 may be the same, different, or may be spiral. However, the cylindrical portion 44 is formed to have flexibility in consideration of the magnitude of the load applied to the moving frame 9 and the like. Other configurations are the same as those in the first embodiment.
Since such a ball screw nut 37 is formed with the groove 41, the cylindrical portion 38 has flexibility. Therefore, during the operation of the injection molding machine 1, when the moving frame (support plate 17) 9 is deformed by a load, when the axial center line of the ball screw nut 37 is inclined with respect to the central line of the ball screw 7, the groove 41 is formed. The bending of the support plate 17a is absorbed, the displacement of the ball screw nut 37 is absorbed, and the ball screw 7 is prevented from coming into contact with one piece. The ball screw device 5 can be implemented at a lower cost than the first and second embodiments.

Next, a ball screw nut structure according to a fourth embodiment of the present invention will be described.
In the present embodiment, the cylindrical member 15 of the first embodiment is omitted, and the ball screw nut 43 shown in FIGS. 11A and 11B is directly fixed to the support plate 17.
As shown in FIGS. 11A and 11B, the ball screw nut 43 formed of a casting is composed of a cylindrical portion 44 and a flange portion 45, and bolts are inserted into a large number of bolt holes 46 formed in the flange portion 45. And fixed directly to the support plate 17a. A thread groove is formed in the inner hole 48 of the cylindrical portion 44, and a ball 29 is attached to the inner hole 48 and screwed into the ball screw 7 (see FIG. 4). A spiral groove 47 is formed on the outer peripheral surface of the cylindrical portion 44 and on the proximal end side. The groove 47 may be a plurality of annular grooves. The width and depth of the groove 47 are flexible on the proximal end side of the cylindrical portion 44 in consideration of deformation and the like applied to the moving frame 9.
Since such a ball screw nut 43 is formed with the groove 47, the proximal end side of the cylindrical portion 38 of the ball screw nut 43 is bent with respect to the external force. Therefore, during the operation of the injection molding machine 1, when the moving frame (support plate 17 a) 9 is deformed by a load, when the axial center line of the ball screw nut 43 is inclined with respect to the central line of the ball screw 7, the ball screw nut 43. The portion with the groove 41 absorbs the deflection of the support plate 17a, thereby absorbing the displacement on the tip side of the ball screw nut 37 and preventing the ball screw 7 from coming into contact with one piece. The ball screw device 5 can be implemented at a lower cost than the first and second embodiments.

Although the embodiments of the present invention have been described above, the present invention is of course not limited thereto, and various modifications and changes can be made based on the technical idea of the present invention.
The ball screw nuts 8 of the first embodiment and the second embodiment are changed to the ball screw nuts 37 and 43 of the third embodiment and the fourth embodiment, and the ball screw nuts 37 and 43 are replaced with cylinders. You may make it fix to the member 15 via the some rod 32. FIG. In the ball screw nut 43 of the fourth embodiment, the groove 41 described in the third embodiment may be formed together as shown by the phantom line in FIG.
Moreover, in the said expansion example, although it was set as the ball screw nut part structure of the injection molding machine 1, it can be used also as a ball screw nut part structure of the mold clamping apparatus of the prior art example demonstrated in FIG.
Moreover, although the cylindrical member 15 and the ball screw nuts 8, 37, 43 are formed by casting, the material may be made of other metals.

It is a schematic side view of the injection molding machine which has adopted the ball screw nut part structure by each embodiment of the present invention (note that an injection screw exists in a retreat position). FIG. 2 is a schematic plan view in which a part of the injection molding machine of FIG. 1 is partially broken (note that the injection screw is in the forward position). 1 is a perspective view of a ball screw device according to a first embodiment of the present invention. It is sectional drawing of the VV line direction in FIG. FIG. 5A is a side view of the cylindrical member of the ball screw device of FIG. 3, with the lower part broken away from the axis of the cylindrical member, and FIG. FIG. It is a perspective view by the modification of the cylinder member of the 1st Embodiment of this invention. 7A is a view of the hole in the state where the outer peripheral hole of the cylindrical member is formed as a long hole, and FIG. 7B is a view of the hole in the state where the hole is formed in a diamond shape from above. 7C is a view of a hole in a state where circular holes are formed at both ends of a slit-like hole as viewed from above, and FIG. 7D is a hole with a hole formed in a rectangular shape. FIG. 7E is a view of the hole in a state where the central portion of the long hole is formed widened, as viewed from above. It is a perspective view of the ball screw apparatus of the 2nd Embodiment of this invention. It is a perspective view which shows the structure of the rod of FIG. FIG. 10A is a perspective view of a ball screw nut of a ball screw device according to a third embodiment of the present invention, and FIG. 10B is a cross-sectional view in the XX line direction of A of FIG. 11A is a perspective view of a ball screw nut of a ball screw device according to a fourth embodiment of the present invention, and FIG. 11B is a cross-sectional view in the YY line direction of FIG. 11A. It is sectional drawing of the ball screw apparatus of the conventional injection molding machine. It is sectional drawing of the ball screw apparatus of the conventional mold clamping apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Injection molding machine 2 Cylinder 3 Injection screw 4 Electric motor 5 Ball screw apparatus 6 Base 6a Rail 7 Ball screw 8 Ball screw nut 9 Moving frame 10 Bearing 11 Injection drive motor 12 Small pulley 13 Large pulley 14 Toothed belt 15 Cylindrical member 16 Plate Surface 17a, 17b Support plate 18 Flange 19 Screw through hole 20 Bolt 21 Long hole 22 Small diameter part 23 Peripheral wall part 24 Diamond hole 25a Circular hole 25b Slit hole 26 Rectangular hole 27a Long hole 27b Slit-like hole 28a Tube part 28b Flange part 29 Ball 30 Screw through hole 31 Hopper 32 Rod 33 Shaft-shaped member 34 Cylindrical portion 35a, 35b Screw 36 Nut 37 Ball screw nut 38 Tube portion 39 Flange portion 40 Through hole 41 Groove 42 Inner hole 43 Ball screw nut 44 Tube portion 4 Flange portion 46 through hole 47 groove 48 holes

Claims (4)

In the ball screw nut part structure , the ball screw nut is attached to the support member, the ball screw is screwed to the ball screw nut, and the ball screw penetrates the support member.
A cylindrical member surrounding the ball screw is provided between a flange provided on the outer periphery of the ball screw nut and the support member, and the cylindrical member absorbs the deformation amount of the support member with respect to external force. A ball screw nut structure , wherein both ends of the hole in the axial direction of the cylindrical member are formed in an arc shape . In an injection molding machine using an injection screw having a ball screw nut portion structure, wherein a ball screw nut is attached to a support member, a ball screw is screwed into the ball screw nut, and the ball screw penetrates the support member.
Regarding the ball screw nut structure, a plurality of circular rods that connect between the flange provided on one end of the ball screw nut and the support member are arranged so as to surround the ball screw in a circumferential manner. A screw portion is formed at each of both ends of the circular rod in the longitudinal direction, one of the screw portions is attached to the support member, and the other of the screw portions is attached to the flange. An injection molding machine characterized in that a deformation amount of the support member with respect to an external force is absorbed between the flange and the support member . The rod includes a shaft-like member disposed along the longitudinal direction of the ball screw, and a cylindrical portion into which the shaft-like member is inserted, and screw portions are respectively provided at both ends in the longitudinal direction of the circular rod. 3. The injection molding machine according to claim 2, wherein the injection molding machine is formed, and screw portions are respectively formed at both longitudinal ends of the shaft member, and the screw portions protrude from both longitudinal ends of the cylindrical portion. An injection molding machine using the ball screw nut structure according to claim 1.

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