JPH1034714A - Injection unit for injection molding machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the number of parts of an injection unit so as to simplify the whole structure of the unit and downsize it, and lighten a total weight of members which move integrally with a screw so as to carry out smooth injection operation. SOLUTION: A support bearing 12 which supports a ball thread nut 11 to be screwed into a ball groove 8a of a shaft 8 in a manner immovable in the direction of rotatable axial direction and a support bearing 10 which supports a spline outer cylinder 9 to be slidably fitted in a ball spline groove 8b of the shaft 8 in a manner immovable in the direction of rotatable axial direction are fixed to both ends of a housing 4 along an injection shaft. A servo motor 6 for rotating the ball thread nut 11 and a servo motor 7 for rotating the spline outer cylinder 9 are arranged on the housing 4 and a screw 19 is provided integrally with the shaft 8. As a pusher plate for pushing the screw 19 and a guide rod are not necessary, the number of parts of an injection unit 1 can be reduced, the unit can be downsized and lightened in weight. Also, as a mass which moves together with the screw 19 reduces, response property in injection operation is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an improvement of an injection unit of an injection molding machine.

[0002]

2. Description of the Related Art An electric injection molding machine which performs an injection operation or a metering operation by using a ball screw or a servomotor is already known. FIG. 7 schematically shows the configuration of an injection unit of this type of electric injection molding machine.

[0003] An injection unit 100 shown in FIG. 7 is generally slidable on a front plate 101 for mounting an injection cylinder, a rear plate 103 fastened to the front plate 101 via a guide rod 102, and a guide rod 102. A mounted pusher plate 104, a ball screw nut 106 for feeding the pusher plate 104 and causing the screw 105 to perform an injection operation, a ball screw 107, and a screw sleeve 10 for rotationally driving the screw 105.
And 8.

The ball screw 107 is connected to the rear plate 103
To the rear plate 1 via an angular bearing 109 so as to be rotatable and non-movable in the axial direction.
The motor is driven to rotate via a timing belt and an injection pulley 110 by an injection servomotor (not shown) fixed to one side of the injection motor 03. Further, a ball screw nut 106 screwed with the ball screw 107 is fixed to the back surface of the pusher plate 104 via the load cell 111 so as not to rotate and not move in the axial direction.

Further, the screw 105 is provided with a coupler 112.
The screw sleeve 108 is mounted on the pusher plate 104 via an angular bearing 113 so as to be rotatable and non-movable in the axial direction.

A screw rotation pulley 114 is integrally fixed to the outer periphery of the screw sleeve 108, and a screw rotation servomotor (not shown) fixed to one side of the pusher plate 104 via a timing belt. By driving the pulley 114, the screw 105 is rotated to perform the weighing and kneading operation.

The injection operation is performed by converting the rotational movement of the injection servomotor into a linear movement by a ball screw 107 and a ball screw nut 106, feeding the pusher plate 104 in the injection axis direction, and advancing the screw 105. .

[0008] According to the above configuration, the ball screw nut 106 for converting the rotational motion of the ball screw 107 into a linear motion.
Guide rod 102 as a means for preventing rotation of
And the provision of the pusher plate 104 are indispensable requirements, and there are problems in terms of the number of parts and the size and weight of the injection unit.

In particular, a screw rotation servomotor for rotating the screw 105 needs to prevent the timing belt from being twisted or disengaged because the screw rotation pulley 114 is driven via the timing belt. It is desirable to move integrally with the rotating pulley 114 in the direction of the injection axis, and as a result, it must be fixed to one side of the pusher plate 104. There is a problem that the weight is remarkably increased, the acceleration / deceleration characteristics of the screw 105 in the injection operation are restricted, or the output of the injection servomotor must be increased.

Further, when replacing the screw 105, the coupler 112 is detached to separate the screw 105 from the screw sleeve 108, and then the nozzle unit at the tip of the injection cylinder is removed and the screw 105 is pulled out from the tip of the injection cylinder. However, at this time, it is necessary to rotate the injection unit base on which the injection unit is mounted to release the tip of the cylinder from the stationary platen of the mold clamping part and perform the removal work.As a result, the side of the injection molding machine A considerable work space must be secured. This is because the screw 105, which is as long as or longer than the injection cylinder, protrudes from the tip of the injection cylinder that is swung laterally about the pivot axis, so that the working area on the side expands.

In order to perform this operation, a structure for turning the injection unit base is required. The mechanical strength is impaired due to the complicated structure, and the end of the cylinder after the completion of the replacement operation is required. There is also a risk that the positioning accuracy will be affected.

[0012]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned drawbacks of the prior art, to reduce the number of parts of the injection unit, to simplify the whole structure and to reduce the size, and to move integrally with the screw. It is an object of the present invention to provide an injection unit of an injection molding machine capable of performing a smooth injection operation by reducing the total weight of members to be formed.

[0013]

SUMMARY OF THE INVENTION The present invention relates to a support bearing for supporting a ball screw nut screwed to a shaft provided with a ball screw groove and a ball spline groove so as to be rotatable and immovable in the axial direction, and a ball of the shaft. A servo motor for rotatingly driving the ball screw nut, and a support bearing for fixing a support bearing for supporting a spline outer cylinder slidingly fitted in a spline groove so as to be rotatable and axially immovable on an injection unit base along an injection shaft. The above object is achieved by a configuration in which a servo motor for rotating and driving an outer cylinder is provided on the injection unit base, and a screw for injection and weighing and kneading is integrally attached to the shaft.

When the injection operation is performed, only the ball screw nut is rotated while the rotation of the spline outer cylinder is stopped to feed the shaft, and when the metering operation by the screw rotation is performed, the ball is rotated. Rotate the screw nut and spline outer cylinder synchronously.

By rotating only the ball screw nut while the rotation of the spline outer cylinder is stopped, the screw is moved by direct linear feed to the shaft. No pusher plate or guide rod is required, so that the number of parts can be reduced and the structure can be simplified and downsized.

In addition, during the injection operation, only the screw moves independently while the spline outer cylinder and the servo motor that drives the spline remain on the injection unit base, so that the total weight of the member that moves integrally with the screw is reduced. It is possible to perform an injection operation with greatly reduced response and excellent responsiveness.

Further, by forming a load cell by attaching a strain gauge to a tie rod for fastening the housing in which the two support bearings are fixed to the front plate of the injection unit base, a resin reaction force acting on the screw is formed. Can be detected.

Further, an annular body having a thin portion disposed in a circumferential groove shape is interposed between the tie rod for fastening the housing having the two support bearings fixed thereto to the front plate of the injection unit base and the housing. Alternatively, a load cell may be formed by attaching a strain gauge to the thin portion.

Further, a support bearing for supporting the spline outer cylinder so as to be rotatable and immovable in the axial direction is fixedly mounted on the distal end of the cylindrical housing, and a ball screw nut is rotatably and axially mounted at the rear end of the housing. A load bearing is formed by fixing a support bearing that is immovably supported, interposing an annular body having thin portions arranged in a circumferential groove shape in the center of the housing, and attaching a strain gauge to the thin portion. Is also possible.

In the configuration having such a load cell, the back pressure is detected by the load cell while performing the weighing operation by synchronously rotating the ball screw nut and the spline outer cylinder, and the back pressure detected by the load cell is detected. By making the ball screw nut or the spline outer cylinder differential in the direction in which the screw retreats when the pressure reaches the set value, the resin reaction force acting on the screw can be maintained at the set back pressure.

[0021]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view schematically showing a configuration of an injection unit 1 according to an embodiment to which the present invention is applied.

As shown in FIG. 1, the injection unit 1 generally includes a front plate 2 for mounting an injection cylinder, a cylindrical housing 4 fastened to the front plate 2 via a tie rod 3, and a housing 4. One set of mounted ball screw and spline 5
And an injection servomotor 6 and a screw rotation servomotor 7 fixed to the housing 4.

As shown in FIG. 3, the ball screw / spline 5 includes a single shaft 8 having a ball screw groove 8a and a ball spline groove 8b, and a ball screw nut screwed into the ball screw groove 8a of the shaft 8. 11 and ball screw nut 1
A support bearing 12 for supporting the shaft 1 in a freely rotatable and axially immovable manner, a spline outer cylinder 9 slidably fitted in a ball spline groove 8b of the shaft 8, and a support bearing for supporting the spline outer cylinder 9 in a freely rotatable and axially immovable manner. 1
0.

A product in which the shaft 8, the ball screw nut 11, the spline outer cylinder 9, and the support bearings 10, 12 are combined in a state as shown in FIG. 3 has already been generally marketed under the name of ball screw / spline. It is a well-known mechanical element used as a stroke / rotation unit, and the configuration itself of the spline outer cylinder 9 is also known in Japanese Patent Publication No. 59-28776. Therefore, detailed description of the configuration of each part is omitted. I do.

In this embodiment, the ball screw / spline 5 is used as it is, and the flange portion 10a provided on the support bearing 10 of the spline outer cylinder 9 is fixed to the distal end (left end) of the cylindrical housing 4 with bolts. Further, by fixing a flange portion 12a provided on the support bearing 12 of the ball screw nut 11 to a rear end (right end) of the cylindrical housing 4 with a bolt, the support bearing 10 and the support having a unit structure are formed. The spline outer cylinder 9 and the ball screw nut 11 are attached to both ends of the cylindrical housing 4 in such a manner that the bearing 12 is fitted inside the housing 4 so as to be rotatable and immovable in the axial direction. Of course, even if the mounting positions of the support bearing 10 of the spline outer cylinder 9 and the support bearing 12 of the ball screw nut 11 are switched on the left and right, there is no problem in any way.

Since the housing 4 is fixed on the injection unit base (not shown) via the tie rod 3 and the front plate 2, it can be said that the support bearings 10 and 12 are fixed on the injection unit base.

This injection unit base is for performing a spre break and a nozzle touch operation by integrally moving the injection unit 1 as shown in FIG. 1 to and from a stationary platen of a mold clamping portion. Therefore, it is an essential component in a horizontal injection molding machine. In the case of a vertical injection molding machine, since the front plate 2 also serves as the injection unit base, there is no need to separately provide an injection unit base, and the front plate 2 itself becomes the injection unit base.

A strain gauge is attached to a part of the outer peripheral surface of the tie rod 3, and constitutes a load cell together with the tie rod 3 serving as a strain generating body.

Further, as shown in FIG. 1, a screw rotation pulley 13 is integrally fixed to an end of the spline outer cylinder 9, and an injection pulley 14 is integrally formed to an end of the ball screw nut 11. At the both ends of the housing 4, a screw rotation servomotor 7 and an injection servomotor 6 to which driving pulleys 15 and 16 for rotating these pulleys 13 and 14 are attached are fixedly mounted at both ends of the housing 4. Power transmission timing belts 17, 18 between the pulley 13 and the pulley 15 and between the pulley 14 and the pulley 16.
Has been wound.

Of course, the screw 19 can be configured to be detachable as a separate structure from the shaft 8, but in this embodiment, it is a completely integrated structure as shown in FIG. Naturally, the axis of the screw 19 and the axis of the shaft 8 completely coincide with each other, and the axes of the support bearings 10 and 12 also completely coincide with the axis of the shaft 8. It can be said that the bearing 10 and the support bearing 12 are provided along the injection axis.

Further, in this embodiment, the screw 19
Since the diameter of the shaft 8, more strictly speaking, the inner diameter of the spline outer cylinder 9 is formed larger than the diameter of the screw 19 in consideration of the case of removing the support bearing 12, the support bearing 12 of the ball screw nut 11 is formed. By removing the bolt fixed to the rear end (right end) of the housing 4, the shaft 8, the screw 19, the ball screw nut 11, and the support bearing 12 can be integrally pulled out to the rear of the housing 4.

The ball interposed between the ball spline groove 8b and the spline outer cylinder 9 is held by the retainer on the spline outer cylinder 9 side.
Although the ball does not fall off even if the shaft 8 is removed from the ball screw nut 11, the ball interposed between the ball screw groove 8 a and the ball screw nut 11 is completely independent of the ball screw nut 11. If the shaft 8 is pulled out from the shaft, the ball will roll out to the outside. Therefore, the ball screw nut 11 and the shaft 8 must be pulled out while being integrated.

Next, FIG. 4 shows a configuration example in which the screw 19 and the shaft 8 are separated from each other, and only the screw 19 is pulled backward through a through hole provided in the shaft 8. Needless to say, the shaft 8 in this case must be thicker than the maximum outer diameter portion of the screw 19, and the inner diameter of the through hole 22 provided in the shaft center must also be larger than the maximum outer diameter portion of the screw 19. . Obviously, the through hole 22 must be provided over the entire length of the shaft 8 when the screw 19 is pulled backward through the through hole 22.
Since the outer diameter of the screw 19 is smaller than the inner diameter of the screw 19, the screw 19 protrudes into the through-hole 22 even if the shaft 8 is advanced, so that the injection operation cannot be performed.

Therefore, in this embodiment, a supporter 23 as shown in FIG. 4A is interposed between the distal end surface of the shaft 8 and the base of the screw 19 to perform the injection operation. . FIG. 4 shows an example of the planar shape of the supporter 23.
Although shown in (b), the supporter 23 does not necessarily have to be a rectangular shape as shown in FIG. Since the supporter 23 is merely a means for supporting the screw 19 to the extent of getting tired, another means for fixing the screw 19 to the shaft 8, that is, a coupler member 25 as shown in FIG. is there.

An annular body having a through hole 24b slightly thicker than the screw 19 at the center thereof is integrally provided at the tip of the shaft 8, and a stepped through hole 25a is formed at the center of the tip. Member 2 consisting of a small-diameter toroid having
5 is formed with a fitting concave portion 24a.
In addition, a rectangular through-hole 24c as shown in FIG. 4C is formed in the annular body provided at the tip of the shaft 8 along the diametric direction, and the above-described through-hole 24c is formed in the through-hole 24c. Supporter 2
3 is to be inserted.

The base of the screw 19 has an outer peripheral groove 1.
9a is engraved over the entire circumference, and the outer circumferential groove 19a
When two arc-shaped cotters 26 and 27 are attached to
The outer peripheral portions and the end surfaces of the arc-shaped cotters 26 and 27 are supported by the large-diameter hole of the stepped through hole 25a of the coupler member 25 and the end surface of the step portion.

Therefore, the procedure for attaching the screw 19 to the shaft 8 is as follows.
After inserting the coupler member 25 on the distal end side from 9a, the arc-shaped cotters 26 and 27 are attached to the outer peripheral groove 19a, and the large-diameter holes of the stepped through holes 25a of the coupler member 25 are inserted into the arc-shaped cotters 26 and 27. Fitted and arc-shaped cotter 2
6, 27, the through-hole 22 is closed through the supporter 23 in the through-hole 24c of the annular body, and the base of the screw 19 and the surface of the supporter 23, and the fitting recess 24a of the annular body and the coupler member 25 The bottom surface is overlapped, and a plurality of bolt holes 28, 29, and 30 formed at corresponding positions of the coupler member 25, the supporter 23, and the shaft 8 are fastened to the fastening bolts 3.
1 are inserted, and these members are jointly fastened to the shaft 8 with the bolts 31.

When the screw 19 is to be removed from the shaft 8, all the fastening bolts 31 are removed, and the coupler member 25 is moved to the screw tip side so that the arc-shaped cotter 2 is removed.
By removing the supporters 23 from the through-hole 24c of the annular body by removing the screws 6 and 27 from the screw 19, the through-hole 2 of the shaft 8 can be obtained.
The screw 19 can be pulled backward from 2.

In this embodiment, a bolt hole 32 for removal is screwed into the base of the screw 19, and a jig inserted from the rear end of the shaft 8 is screwed into the bolt hole 32 to remove the screw 1.
9 is pulled backward. The jig can be replaced with a bolt of an appropriate length, but if there is no bolt of sufficient length, this jig can be easily created by engraving a male screw with a die at the tip of the rod material. can do. If the base of the rod material is bent into an L-shape and used as a handle, it is easy to apply force.

FIG. 5 is a view showing another example of the structure in which only the screw 19 is pulled backward through the through hole provided in the shaft 8. As shown in FIG. 4 is different from the embodiment of FIG. 4 in that a coupler member 33 is provided as a member corresponding to the supporter 23 and the annular body at the distal end of the shaft 8 in FIG. It is a point that is attached. The coupler member 33 is different from the annular body at the distal end of the shaft 8 in FIG. 4, and is integrally provided with a bottom surface 33 a for supporting the base of the screw 19. A fitting portion 34 for supporting the coupler member 33 at the distal end portion is provided so as to have a counterbore hole-like diameter. The outer circumferential groove 19a of the screw 19 and the bolt hole 3
The structures of the second and arc-shaped cotters 26 and 27 and the coupler member 25 are the same as those in FIG.

In this embodiment, when removing the screw 19, it is necessary to pull out the coupler member 33 buried in the fitting portion 34 of the shaft 8, so that it becomes a handle for pulling out the coupler member 33. At least one tap hole 35 for screwing a bolt is provided on the coupler member 33. The arrangement of the bolt holes 28, 36 for passing the fastening bolts 31 through the coupler members 25, 33 is the same as in FIG. 4C, but in this embodiment, as shown in FIG. One of the bolt holes 36 to be provided is formed as a blind-hole-shaped internal thread 36a, and one fastening bolt 31a shorter than the other is used.
The coupler member 25 and the coupler member 33 are directly fastened in only one place, and the above-mentioned tap hole 35 is provided coaxially with the blind hole-shaped female screw 36a (the lower side shown in the cross section in FIG. 5). Bolt holes).

Of course, after removing all the fastening bolts 31 and 31a and removing the coupler member 25, the fastening bolt 31a is screwed into the female screw 36a again, and the coupler member 33 is pulled out by using this as a handle. It does not matter. Also, after removing all the fastening bolts 31, it is possible to forcibly pull out the coupler member 33 fastened to the coupler member 25 with the bolt 31 a by retreating the shaft 8. The last work procedure is to remove the bolt 31a.

In the embodiment shown in FIGS. 4 and 5, the through hole 22 is formed in the shaft 8 so that the screw 19 can be pulled out rearward. In addition, since the moment of inertia of the shaft 8 is greatly reduced, there is a merit that the responsiveness of the motion related to the rotation and the linear motion of the shaft is improved (of course, the screw 1)
Even when it is not necessary to pull out the rear part 9, the response can be improved by making the shaft 8 hollow.)

Further, since the screw 19 is pulled backward, it is not necessary to turn the injection unit base to remove the screw 19 to offset the tip of the injection cylinder from the stationary platen of the mold clamping unit. The turning mechanism itself becomes unnecessary, and the mechanical strength of the injection unit base is improved. In addition, even if the screw 19 is replaced, the problem that the tip position of the injection cylinder is shifted does not occur, so that the problem of damage to the mold sprue due to contact of the nozzle with an inappropriate position and leakage of resin due to the problem. It is no longer necessary to provide a work space for screw replacement at least on the side of the injection molding machine (the work space for screw replacement needs to be provided behind the injection molding machine).

Of course, the screw 19 may be removed from the tip of the injection cylinder by adopting the same turning mechanism as in the prior art. In this case, the shaft 8 may be made as thin as the screw 19, or The shaft 8 and the screw 19 need to be configured to be separable by using a coupler or the like as in the related art.

Further, the spline outer cylinder 9 also serves as a rotation stopping means for the shaft 8, and the rotation of the ball screw nut 11 causes the shaft 8 to rotate.
The guide rod 102 and the pusher plate 104 as shown in the conventional example of FIG.
Is unnecessary, the injection unit 1 is reduced in size and weight as a whole, and the number of parts is reduced. The tie rod 3 is merely a means for fastening the front plate 2 and the housing 4 and receives a final resin reaction force acting on the screw, except for a guide as shown in the conventional example of FIG. The rod 102 has different uses and functions.

When performing the injection operation in such a structure, the stopped state of the screw rotation servomotor 7 is maintained, and the pulley 15, the timing belt 17, the pulley 13
Then, the injection servomotor 6 is driven while the rotation of the spline outer cylinder 9 is suppressed, and the pulley 16, the timing belt 18,
Only the ball screw nut 11 is rotated via the pulley 14. Since only the ball screw nut 11 rotates while the rotation of the shaft 8 is suppressed by the spline outer cylinder 9, feed in the injection axis direction is applied to the shaft 8, and the screw 19 fixed integrally with the shaft 8 becomes the injection shaft. Will move in that direction.

Naturally, in this case, only the screw 19 and the shaft 8 move in the injection axis direction except for the spline outer cylinder 9, the pulley 13, the timing belt 17, the pulley 15, and the screw rotation servomotor 7. That is,
The inertial mass that moves together with the screw 19 is extremely small, and as shown in the conventional example of FIG. 4, the inertia mass is fed to the screw 105 integrally with the pusher plate 104, the pulley 114, and the screw rotation servomotor. However, the moving speed of the screw 19 can be controlled with a high response without increasing the output of the injection servomotor 6.

When the light kneading operation is performed, the ball screw nut 11 and the spline outer cylinder 9 are adjusted to the set screw speed while the injection servomotor 6 is subjected to a torque limit corresponding to the set back pressure. The rotation speeds of the injection servomotor 6 and the screw rotation servomotor 7 are controlled so that they rotate synchronously at a corresponding speed.

Therefore, if the resin reaction force acting on the screw is equal to or less than the set back pressure, the ball screw nut 11 and the spline outer cylinder 9 rotate completely synchronously at the set screw rotation speed. Since there is no phase difference in rotational position between the spline outer cylinder 9 and the shaft 8, that is, the screw 19 is stopped in the axial direction,
At the stop position, only the rotational motion of the set screw rotational speed is performed.

As a result, the lightly kneaded molten resin gradually accumulates at the tip of the cylinder, and the back pressure, ie, the resin reaction force acting on the tip of the screw 19, gradually increases.

When the resin reaction force acting on the tip of the screw 19 reaches the set back pressure, the ball screw nut 11 driven by the injection servomotor 6 having a torque limit corresponding to the set back pressure is The spline outer cylinder 9 resists the rotational force generated by the circumferential reaction force exerted on the screw surface of the ball screw nut 11 by the resin reaction force acting along the shaft 8.
Cannot be maintained in synchronization with the spline outer cylinder 9, and a synchronization shift occurs in the rotation direction corresponding to the direction in which the shaft 8 moves backward with respect to the spline outer cylinder 9.

That is, if the screw 1 in FIG.
Assuming that the weighing operation is performed by clockwise rotation when viewed from the tip side of the screw 9 (when the spiral of the screw 19 is a right-handed screw type), the rotation speed of the ball screw nut 11 is the set screw rotation speed. Assuming that the rotation speed is lower than the rotation speed of the rotating spline outer cylinder 9 and that the weighing operation is performed by the counterclockwise rotation when viewed from the tip side of the screw 19 in FIG. In the case of the left-hand thread type, the rotation speed of the ball screw nut 11 is faster than the rotation speed of the spline outer cylinder 9 rotating at the set screw rotation speed. Of course, this is a phenomenon that occurs when the shaft 8 is a right-handed screw type as shown in FIG. 1, and if the shaft 8 is a left-handed screw type, a completely opposite synchronization shift will occur. .

As a result, the shaft 8 is
As a result, the resin reaction force acting on the screw 19 is always maintained at the set back pressure.

Instead of setting the torque limit on the injection servomotor 6 and maintaining the set back pressure, the set back pressure is set based on the current value of the detected pressure from the load cell composed of the tie rod 3 and the strain gauge. Can be maintained.

In this case, the reference rotation speed of the injection servomotor 6 and the screw rotation servomotor 7 is set so that the ball screw nut 11 and the spline outer cylinder 9 rotate synchronously at a speed corresponding to the set screw rotation speed. Strictly speaking, a movement command per unit time is determined, and each time the current value of the detected pressure exceeds the set back pressure, the shaft 8 is moved backward relative to the spline cylinder 9 only in the distribution cycle. Then, a predetermined correction amount is added to or subtracted from the position command to the injection servomotor 6 and output, and the screw 19 is slightly retracted to increase the cylinder capacity to maintain the internal pressure of the molten resin at the set back pressure. To do.

Whether the movement command to the injection servomotor 6 is increased or decreased from the reference value is as described above. For example, in FIG. If the metering operation is performed (when the spiral of the screw 19 is a right-handed screw type), the rotation speed of the ball screw nut 11 is lower than the rotation speed of the spline outer cylinder 9 rotating at the set screw rotation speed. If the weighing operation is performed in a certain direction (that is, the correction value of the movement command is negative) and in FIG. In the case of a left-hand screw type), the rotation speed of the ball screw nut 11 is higher than the rotation speed of the spline outer cylinder 9 rotating at the set screw rotation speed. Consisting direction (short, the correction value of the movement command is positive) is that.

Of course, this is the case where the shaft 8 is of the right-hand thread type as shown in FIG. 1, and if the shaft 8 is of the left-hand thread type, it is necessary to cause a completely opposite synchronization deviation. is there.

As a result, every time the internal pressure of the molten resin increases, a minute feed is applied to the spline outer cylinder 9 in the direction of retreating the shaft 8, so that the resin reaction force acting on the screw 19 becomes smaller. It will always be kept at the set back pressure.

Naturally, the screw rotation speed at the time of metering should be kept at the set value, but if it does not affect the result of the metering and kneading of the resin, a movement command to the injection servomotor 6 is given. The same purpose can be achieved by performing the correction in the opposite direction to the movement command to the screw rotation servomotor 7 instead of performing the correction. Next, FIG. 2 shows a configuration example in which a load cell for detecting an injection pressure and a back pressure acting on the screw 19 is incorporated at another position.

The main part of the construction of the injection unit 1 'shown in FIG. 2 is exactly the same as that of the injection unit 1 in FIG.
1 differs from the embodiment of FIG. 1 in that a portion corresponding to the flange portion 4a (see FIG. 1) is removed from the housing 4 'and a load cell 20 is interposed between the tie rod 3 and the housing 4'.

The load cell 20 is formed by an annular body in which the thin portions 21 are arranged in a circumferential groove shape, and the bending of the thin portions 21 is measured by a strain gauge attached to the thin portions 21 so that the guide rod is formed. 3, the resin reaction force such as injection pressure and back pressure is detected. The resin reaction force detected by the load cell 111 is detected, and the feedback control of the holding pressure and the back pressure is performed. Can be carried out in the same manner as described above.

In the conventional example shown in FIG.
Of the resin reaction force acting on the pusher plate 104
Is dispersed on the guide rod 102 side by friction of a sliding portion between the guide rod 102 and the
All of the resin reaction force acting on the tie rod 3 cannot be received by the load cell 111, but in the embodiment shown in FIG. 2, all of the tension acting on the tie rod 3, that is, the resin reaction force acting in the axial direction of the screw 19. Are received by the load cell 20, it is possible to expect higher detection accuracy than the conventional example shown in FIG.

Next, the injection unit 3 of still another embodiment will be described.
7 will be described. The most significant difference from the above-described embodiments is that instead of forming the shaft 41 provided with the ball screw groove and the ball spline groove from a single shaft, the spline shaft 39 and the ball screw shaft 40 made of individual members are bolted. 1 and 2, the member corresponding to the support bearing 10 of the spline outer cylinder 9 in FIGS. 1 and 2 is omitted, and the function corresponding to the support bearing 10 is partially provided by the housing 38. The spline outer cylinder 9 'instead of the spline outer cylinder 9 shown in FIGS. 1 and 2 is directly attached to the housing front end component 38a, as shown in FIGS. A member corresponding to the support bearing 12 of the ball screw nut 11 in FIG. The function corresponding to 12 is shared by a housing rear part component 38b constituting a part of the housing 38, and the housing rear part component 38b is provided with a ball screw nut 11 'instead of the ball screw nut 11 of FIGS. 2 and a load cell 20 ′ having the same structure as the load cell 20 in FIG. 2 is interposed between the housing front end component 38 a and the housing rear component 38 b, and The point is that they also serve as a part.

That is, these components are all newly designed parts, and do not use a commercially available ball screw / spline 5 as in the examples of FIGS.

First, as described above, the shaft 41 has a structure in which the spline shaft 39 having only the ball spline groove 39b and the ball screw shaft 40 having only the ball screw groove 40a are integrally joined by the bolt 42. A spline outer cylinder 9 'for supporting the spline shaft 39 in a non-rotatable and slidable manner is mounted around the outer peripheral portion of the spline shaft 39, and the ball screw nut 11 screwed to the outer peripheral portion of the ball screw shaft 40 is provided on the outer peripheral portion. 'Is mounted. The structure of the fitting surface between the ball spline groove 39b and the spline outer cylinder 9 'and the structure of the screwing surface between the ball screw groove 40a and the ball screw nut 11' are the same as the conventional one.

Further, on the outer peripheral surface of the spline outer cylinder 9 ',
Inner rings of two angular bearings 43 having different directions are attached at intervals, and each of them is a C-ring shaped retainer 44a, which is attached to the outer circumferential groove of the outer cylinder 9 '.
Supported by the flanges 45b and 44c and the flange 45 of the outer cylinder 9 ', the movement in the axial direction is prohibited. And 2
The outer rings of the two angular bearings 43 are attached to the inner peripheral surface of the cylindrical housing tip component 38a,
The outer ring of the bearing 43 located on the right side in the drawing is supported by a step portion 48 on the inner peripheral surface of the housing tip component 38a, while the outer ring of the other bearing 43 is attached to the left end face of the housing tip component 38a. It is fixed by an annular retainer 47 which is bolted. Since the sleeve 46 is interposed between the outer rings of the two bearings 43, the retainer 44c is not deformed even if the retainer 47 is strongly tightened. Incidentally, 49 is an oil seal.

As a result, the spline outer cylinder 9 'is rotatable with respect to the housing tip component 38a and is not movable in the axial direction.

Then, on the end face of the spline outer cylinder 9 ',
A screw rotation pulley 13 is fixedly provided in the same manner as in the embodiments of FIGS. 1 and 2.

The screw 19 for the spline shaft 39
5 is basically the same as the example of FIG. 5, but in this embodiment, since the screw 19 is not pulled out backward, a component corresponding to the coupler member 33 of FIG. 5 is not necessary. The base of the screw 19 is directly supported at the bottom of the blind hole 50 provided in the end face of the spline shaft 39.

Further, an inner peripheral portion of a load cell 20 'formed of an annular body having a thin portion 56 arranged in a circumferential groove shape is fixed to the right end surface of the housing distal end component 38a by bolts.

Further, on the outer peripheral surface of the ball screw nut 11 'screwed to the ball screw shaft 40, inner rings of two angular bearings 51 having different directions are attached at an interval, and are located on the right side in the figure. Angular bearing 5
While one inner ring is supported by the flange 52 at the end of the ball screw nut 11 ', the inner ring of the other angular bearing 51 is fixed by a double nut 53 screwed to the other end of the ball screw nut 11'. The two angular bearings 51 are positioned by a sleeve 54 interposed between the inner rings of the two angular bearings 51.

The two angular bearings 51
Is mounted on the inner peripheral surface of the cylindrical housing rear component 38b, and the outer ring of the angular bearing 51 located on the right side in the drawing is the housing rear component 38.
b, while the outer ring of the other angular bearing 51 is supported by a stepped portion 55 at the end of the inner peripheral surface of the annular load cell 20 'whose outer peripheral portion is bolted to the left end surface of the housing rear component 38b. Are fixed by fitting projections 57. The load cell 20 'referred to here
Is distinguished by the thin portion 56 as a boundary. As before, two angular bearings 51
Positioning is performed by interposing a sleeve 58 between the outer races. Reference numeral 59 denotes an oil seal.

As a result, the ball screw nut 11 'is rotatable with respect to the housing rear component 38b,
And it cannot move in the axial direction.

The end face of the ball screw nut 11 'is
An injection pulley 14 is fixedly provided in the same manner as in the respective embodiments of FIG.

FIG. 1 shows the principle of operation of injection and metering.
And is completely the same as the embodiment shown in FIG.

A load cell 20 ′ for detecting resin pressure is provided at the center of the housing 38 with a housing tip component 38 a and a housing rear component 38.
b, the servo motor for screw rotation is
As in the embodiment shown in FIGS.
8, the housing tip component 38a
The load cell 2 is fixed on the load cell 2 by the tension of the timing belt wound between the screw rotation servomotor and the screw rotation pulley 13.
No distortion occurs at 0 ', and the resin pressure can be detected more precisely.

[0078]

According to the present invention, there is no need to provide a pusher plate for pressing the screw or a guide rod for preventing the pusher plate from rotating.
The number of parts of the injection unit can be reduced, and the structure can be simplified and downsized.

Further, there is no pusher plate that moves integrally with the screw, and there is no need to move the screw rotation servomotor for rotating the screw integrally with the screw. The weight is greatly reduced, and an injection operation with excellent responsiveness can be performed even when a low-output injection servomotor is used.

If the diameter of the shaft provided with the ball screw groove and the ball spline groove is formed larger than the diameter of the screw, the screw can be detached from the rear of the injection unit when replacing the screw.

As a result, there is no need to pivot the injection unit to pull out the screw from the tip of the injection cylinder, and at least it is not necessary to provide a work space for screw replacement at the side of the injection molding machine.
Since the turning mechanism itself of the injection unit becomes unnecessary, it is possible to eliminate unnecessary movable parts from the injection unit and to improve mechanical strength.

Further, according to the configuration in which the spline outer cylinder is attached to the tip of the cylindrical housing and the ball screw nut is attached to the rear end of the housing, and the load cell is interposed in the center of the housing, The load cell is not distorted by the tension of the timing belt wound between the servo motor and the screw pulley of the spline outer cylinder, and the resin pressure can be detected more precisely.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically illustrating a configuration of an injection unit according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view schematically illustrating a configuration of an injection unit according to another embodiment.

FIG. 3 is a perspective view showing an assembled state of a shaft, a spline outer cylinder, a ball screw nut, and a support bearing of the injection unit of each embodiment.

FIG. 4 is a diagram showing a main part of a configuration example in which a screw and a shaft are separated from each other, and only the screw is pulled rearward through a through hole provided in the shaft.

FIG. 5 is a diagram showing a main part of a configuration example in which the screw and the shaft are separated from each other, and only the screw is pulled backward through a through hole provided in the shaft.

FIG. 6 is a cross-sectional view schematically illustrating the configuration of an injection unit according to yet another embodiment.

FIG. 7 is a cross-sectional view schematically showing a configuration of an injection unit of a conventional electric injection molding machine.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Injection unit 1 'Injection unit 2 Front plate 3 Tie rod 4 Housing 4a Flange part 4' Housing 5 Ball screw / spline 6 Injection servomotor 7 Screw rotation servomotor 8 Shaft 8a Ball screw groove 8b Ball spline groove 9 Spline outer cylinder 9 'Spline outer cylinder 10 Support bearing 10a Flange part 11 Ball screw nut 11' Ball screw nut 12 Support bearing 12a Flange part 13 Screw rotation pulley 14 Injection pulley 15, 16 Driving pulley 17, 18 Timing belt 19 Screw 19a Outer periphery Groove 20 Load cell 20 'Load cell 21 Thin part 22 Through hole 23 Supporter 24a Fitting recess 24b Through hole 24c Through hole 25 Coupler member 25a Stepped through Hole 26 arc-shaped cotter 27 arc-shaped cotter 28 bolt hole 29 bolt hole 30 bolt hole 31 fastening bolt 31a fastening bolt shorter than others 32 bolt hole 33 coupler member 33a bottom surface 34 fitting portion 35 tap hole 36 bolt hole 36a blind Hole-shaped female screw 37 Injection unit 38 Housing 38a Housing tip component 38b Housing rear component 39 Spline shaft 39b Ball spline groove 40 Ball screw shaft 40a Ball screw groove 41 Shaft 42 Bolt 43 Angular bearing 44A Retainer 44B Retainer 44C Retainer 45 Flange part 46 Sleeve 47 Retainer 48 Step part 49 Oil seal 50 Blind hole 51 Angular bearing 52 Flange part 53 Double nut 54 Sleeve 55 Step part 56 Thin part 57 Fitting protrusion 58 Sleeve 59 Oil seal 100 Injection unit 101 Front plate 102 Guide rod 103 Rear plate 104 Pusher plate 105 Screw 106 Ball screw nut 107 Ball screw 108 Screw sleeve 109 Angular bearing 110 Injection pulley 111 Load cell 112 Coupler 113 Angular bearing 114 Pulley for screw rotation

Claims (8)

[Claims] 1. A support bearing for supporting a ball screw nut screwed to a shaft provided with a ball screw groove and a ball spline groove so as to be rotatable and immovable in an axial direction, and a spline outside which is slidably fitted in the ball spline groove of the shaft. A support motor that supports the cylinder rotatably and axially immovable is fixedly mounted on the injection unit base along the injection axis, and a servo motor that rotationally drives the ball screw nut and a servo motor that rotationally drives the spline outer cylinder. The injection unit of an injection molding machine, wherein is disposed on the injection unit base, and a screw for injection and metering and kneading is integrally attached to the shaft. 2. The injection unit of an injection molding machine according to claim 1, wherein the injection operation is performed by rotating only the ball screw nut while the rotation of the spline outer cylinder is stopped. . 3. The injection unit of an injection molding machine according to claim 1, wherein the ball screw nut and the spline outer cylinder are rotated synchronously to perform a weighing operation. 4. An injection unit for an injection molding machine according to claim 1, further comprising a load cell for detecting a resin reaction force acting on the screw. 5. The load cell according to claim 4, wherein a strain gauge is attached to a tie rod for fastening the housing, on which the two support bearings are fixed, to a front plate of the injection unit base. Injection unit of injection molding machine. 6. An annular body in which a thin portion is provided in a circumferential groove shape between a tie rod for fastening a housing on which the two support bearings are fixed to a front plate of an injection unit base and the housing. The injection unit of an injection molding machine according to claim 4, wherein a load cell is formed by attaching a strain gauge to the thin portion. 7. A support bearing for supporting the spline outer cylinder so as to be rotatable and immovable in the axial direction is fixedly mounted on the distal end of the cylindrical housing, while a ball screw nut is rotatably and axially mounted on the rear end of the housing. A load bearing is provided by fixing a support bearing that is immovably supported, interposing an annular body having a thin portion arranged in a circumferential groove shape in the center of the housing, and attaching a strain gauge to the thin portion. The injection unit of an injection molding machine according to claim 4, wherein: 8. The injection unit of an injection molding machine according to claim 4, wherein the ball screw nut and the spline outer cylinder are rotated synchronously to perform a weighing operation. The back pressure is detected by the load cell, and when the back pressure detected by the load cell reaches a set value, a resin reaction force acting on the screw by causing the ball screw nut or the spline outer cylinder to differentially move in a direction in which the screw retreats. An injection unit of an injection molding machine, wherein the pressure is maintained at a set back pressure.