JP3507250B2 - Injection unit of injection molding machine - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD 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 is already known in which a ball screw and a servomotor are used to perform an injection operation and a metering operation. FIG. 7 shows a schematic configuration of an injection unit of this type of electric injection molding machine.

The injection unit 100 shown in FIG. 7 is roughly slidable on a front plate 101 for attaching an injection cylinder, a rear plate 103 fastened to the front plate 101 via a guide rod 102, and a guide rod 102. The attached pusher plate 104, a ball screw nut 106 for feeding the pusher plate 104 to cause the screw 105 to perform an injection operation, a ball screw 107, and a screw sleeve 10 for rotationally driving the screw 105.
8 and.

The ball screw 107 is a rear plate 103.
Mounted on the rear plate 1 via an angular bearing 109 so as to be rotatable and axially immovable.
An injection servomotor (not shown) fixedly mounted on one side of 03 makes the rotation drive via a timing belt and an injection pulley 110. Further, a ball screw nut 106 screwed with the ball screw 107 is fixed to the back surface of the pusher plate 104 via a load cell 111 so as not to rotate and move axially.

Further, the screw 105 is a coupler 112.
The screw sleeve 108 is fixed on the pusher plate 104 via an angular bearing 113 so as to be rotatable and immovable in the axial direction.

Further, a screw rotating pulley 114 is integrally fixed to the outer peripheral portion of the screw sleeve 108, and a screw rotating servo motor (not shown) fixedly provided on one side of the pusher plate 104 interposes a timing belt. The screw 105 is rotated by driving the pulley 114 to perform the measurement and kneading work.

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

According to the above structure, the ball screw nut 106 for converting the rotational movement of the ball screw 107 into the linear movement.
Guide rod 102 as a means for preventing rotation of the
The provision of the pusher plate 104 and the pusher plate 104 is an indispensable requirement, and there is a problem in terms of the large number of parts and the size and weight of the injection unit.

In particular, since the screw rotation servomotor for rotating the screw 105 drives the screw rotation pulley 114 via the timing belt, it is necessary to prevent the timing belt from twisting or coming off. It is desirable to move integrally with the rotating pulley 114 in the injection axis direction, and as a result, it is necessary to fix the pusher plate 104 to one side. There is a problem that the weight is significantly increased, the acceleration / deceleration characteristic of the screw 105 in the injection operation is limited, or the output of the injection servo motor must be increased.

When replacing the screw 105, the coupler 112 is removed to separate the screw 105 from the screw sleeve 108, and then the nozzle unit at the tip of the injection cylinder is removed to pull out the screw 105 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 placed to allow the tip of the cylinder to escape from the stationary platen of the mold clamping part, and to perform the removal work. It will be necessary to secure a considerable working space. 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 out laterally around the swivel axis, so that the lateral work area is expanded.

Further, in order to perform this work, a structure for turning the injection unit base is required, and the mechanical strength is impaired due to the complicated structure, and the cylinder tip after the replacement work is completed. There is also a risk that the positioning accuracy will be hindered.

[0012]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned drawbacks of the prior art, reduce the number of parts of the injection unit, simplify and downsize the entire structure, and move integrally with the screw. It is an object of the present invention to provide an injection unit of an injection molding machine that can reduce the total weight of the members to perform a smooth injection operation.

[0013]

According to the present invention, there is provided a support bearing for rotatably and axially immovably supporting a ball screw nut screwed to a shaft provided with a ball screw groove and a ball spline groove, and a ball of the shaft. A support bearing that rotatably and axially immovably supports the spline outer sleeve slidably fitted in the spline groove is fixedly mounted on the injection unit base along the injection shaft, and the servo motor and the spline that rotationally drive the ball screw nut. A servo motor for rotating and driving an outer cylinder is provided on the injection unit base, a screw for injection and metering and kneading is integrally attached to the shaft, and a resin counter acting on the screw is installed.
The above-mentioned object was achieved by a configuration characterized in that a load cell for detecting a force was provided .

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

Since only the ball screw nut is rotationally driven while the rotation of the spline outer cylinder is stopped to directly feed the shaft linearly to move the screw, it is possible to prevent rotation and screw pressing means. This eliminates the need for a pusher plate and a guide rod, which reduces the number of parts and simplifies and downsizes the structure.

Further, during the injection operation, only the screw moves independently while leaving the spline outer cylinder and the servo motor, which is the drive source thereof, on the injection unit base, so that the total weight of the members that move integrally with the screw is increased. It is possible to significantly reduce the injection operation with excellent responsiveness.

Further, by forming a load cell by attaching a strain gauge to a tie rod for fastening the housing having the two support bearings 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 wall portion arranged in a circumferential groove is interposed between the tie rod for fastening the housing having the two support bearings fixedly attached thereto to the front plate of the injection unit base and the housing. However, a strain gauge may be attached to the thin portion to form the load cell.

Further, a support bearing for rotatably and axially immovably supporting the spline outer cylinder is fixedly provided at the tip of the cylindrical housing, while a ball screw nut is rotatably and axially provided at the rear end of the housing. A load cell is constructed by fixing a support bearing that supports immovably, and inserting an annular body in which a thin portion is 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 including such a load cell, the back pressure detected by the load cell is detected by the load cell while the ball screw nut and the spline outer cylinder are synchronously rotated to perform the weighing operation. When the pressure reaches the set value, the resin reaction force acting on the screw can be maintained at the set back pressure by differentially moving the ball screw nut or the spline outer cylinder in the direction in which the screw moves backward.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view showing the outline of the configuration of an injection unit 1 of an embodiment to which the present invention is applied.

As shown in FIG. 1, the injection unit 1 is roughly provided with 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. 1 set of ball screw and spline 5 attached
And a screw rotation servomotor 7 and an injection servomotor 6 fixed to the housing 4.

As shown in FIG. 3, the ball screw / spline 5 has one 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
1. A support bearing 12 that supports the shaft 1 rotatably and axially immovably, a spline outer cylinder 9 that slides into the ball spline groove 8b of the shaft 8, and a support bearing that supports the spline outer cylinder 9 rotatably and axially immovable. 1
It consists of 0 and.

A product in which the shaft 8, the ball screw nut 11, the spline outer cylinder 9, and the support bearings 10 and 12 are combined in a state as shown in FIG. 3 has already been commercially available under the names such as ball screw and spline. Since it is a well-known mechanical element used as a stroke / rotation unit, and the structure itself of the spline outer cylinder 9 is also known in Japanese Examined Patent Publication No. 59-28776, etc., detailed description of the structure of each part is omitted. To do.

In the present 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 tip portion (left end) of the cylindrical housing 4 with a bolt. Further, by fixing the flange portion 12a provided on the support bearing 12 of the ball screw nut 11 to the rear end portion (right end) of the cylindrical housing 4 with a bolt, the unit-structured support bearing 10 and support The bearing 12 is fitted in the housing 4 so that the spline outer cylinder 9 and the ball screw nut 11 are attached to both ends of the cylindrical housing 4 rotatably and immovably 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 interchanged on the left and right, there is no problem in one direction.

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

This injection unit base is for performing sprue break and nozzle touch operation by integrally moving the injection unit 1 as shown in FIG. 1 to and from the stationary platen of the mold clamping part. Therefore, it is an indispensable constituent element in a horizontal injection molding machine. Further, in the case of a vertical injection molding machine, since the front plate 2 also serves as the injection unit base, it is not necessary to separately provide the injection unit base, and the front plate 2 itself serves as 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 flexure element.

Further, as shown in FIG. 1, a screw rotation pulley 13 is integrally fixed to the end of the spline outer cylinder 9, and an injection pulley 14 is integrated to the end of the ball screw nut 11. And the screw rotation servomotor 7 and the injection servomotor 6 to which drive pulleys 15 and 16 for rotationally driving these pulleys 13 and 14 are fixedly mounted on both ends of the housing 4. , Timing belts 17, 18 for power transmission between the pulley 13 and the pulley 15 and between the pulley 14 and the pulley 16.
Is wound.

Of course, the screw 19 may be detachable from the shaft 8 as a separate structure, but in the case of this embodiment, it has a completely integrated structure as shown in FIG. Naturally, the axis of the screw 19 and the axis of the shaft 8 are completely aligned, and the axes of the support bearing 10 and the support bearing 12 are also completely aligned with the axis of the shaft 8. It can be said that the bearing 10 and the support bearing 12 are arranged along the injection axis.

Further, in this embodiment, the screw 19
In consideration of the case of removing, the diameter of the shaft 8 or, more strictly speaking, the inner diameter of the spline outer cylinder 9 is formed larger than the diameter of the screw 19, so that the support bearing 12 of the ball screw nut 11 is By removing the bolts 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.

Since the balls interposed between the ball spline groove 8b and the spline outer cylinder 9 are held on the side of the spline outer cylinder 9 by the retainer, the spline outer cylinder 9
Even if the shaft 8 is pulled out from the ball, the ball does not drop out, but the ball interposed between the ball screw groove 8a and the ball screw nut 11 is completely independent of the ball screw nut 11, and the ball screw nut 11 When the shaft 8 is pulled out from the ball, the ball will be rolled out, so the ball screw nut 11 and the shaft 8 must be pulled out while being integrated.

Next, FIG. 4 shows a structural example in which the screw 19 and the shaft 8 are formed as separate members, and only the screw 19 is pulled out rearward through a through hole provided in the shaft 8. Of course, in this case, the shaft 8 must be thicker than the maximum outer diameter portion of the screw 19, and the through hole 22 provided in the shaft center must also be thicker than the maximum outer diameter portion of the screw 19. . Of course, if the screw 19 is pulled out rearward through the through hole 22, the through hole 22 must be provided over the entire length of the shaft 8, but 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 will rush into the through hole 22 even if the shaft 8 is moved forward, and the injection operation cannot be performed.

Therefore, in this embodiment, a supporter 23 as shown in FIG. 4A is interposed between the tip surface of the shaft 8 and the base portion of the screw 19 to perform the injection operation. . An example of the planar shape of the supporter 23 is shown in FIG.
As shown in FIG. 4B, the supporter 23 does not necessarily have to have a rectangular shape as shown in FIG. This supporter 23 is merely a means for supporting the screw 19 until it gets tired, so that another means for fixing the screw 19 to the shaft 8, that is, a coupler member 25 as shown in FIG. is there.

A ring-shaped body having a through hole 24b slightly thicker than the screw 19 is integrally provided at the center of the tip of the shaft 8. The tip surface of the ring has a stepped through hole 25a in the center. Coupler member 2 consisting of a small-diameter torus having
A fitting recess 24a for fitting 5 is formed.
Further, the annular body provided at the tip of the shaft 8 is provided with a rectangular through hole 24c as shown in FIG. 4C along the diametrical direction. Supporter 2
3 is inserted.

The outer peripheral groove 1 is formed at the base of the screw 19.
9a is engraved over the entire circumference, and this outer peripheral groove 19a
Attaching the two arcuate cotters 26 and 27 to
The outer peripheral portions of the arcuate cotters 26 and 27 and their end faces are supported by the large diameter holes of the stepped through holes 25a of the coupler member 25 and the end faces of the step portions thereof.

Therefore, as a procedure of attaching the screw 19 to the shaft 8, first, the outer peripheral groove 1 of the screw 19 is attached.
After inserting the coupler member 25 into the tip side from 9a, the arc-shaped cotters 26 and 27 are attached to the outer peripheral groove 19a, and the large-diameter hole of the stepped through hole 25a of the coupler member 25 is attached to the arc-shaped cotters 26 and 27. Fitted with arc cotter 2
After pressing 6, 27, the through hole 22 is closed by passing the supporter 23 through the through hole 24c of the torus, the base of the screw 19 and the surface of the supporter 23, and the fitting recess 24a of the torus and the coupler member 25. The bottom surface is overlapped with each other, and the fastening bolts 3 are inserted into the plurality of bolt holes 28, 29, 30 formed at corresponding positions of the coupler member 25, the supporter 23, and the shaft 8.
1 is inserted and these members are fastened to the shaft 8 together with the bolt 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 to make the arc-shaped cotter 2
6 and 27 are removed from the screw 19 and the supporter 23 is extracted from the through hole 24c of the torus, the through hole 2 of the shaft 8
The screw 19 can be pulled out 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 screw 1
I am trying to pull out 9 backwards. It should be noted that the jig can be replaced with a bolt of 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 in the L-shaped form to form 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 out rearward through the through hole provided in the shaft 8. The difference from the embodiment of FIG. 4 is that a coupler member 33 is provided as a member corresponding to the annular body of the supporter 23 and the tip portion of the shaft 8 in FIG. 4, and this member is fitted in the tip portion of the shaft 8 internally. That is the point of attachment. The coupler member 33 is different from the toroidal body at the tip of the shaft 8 in FIG. 4, and is integrally provided with a bottom surface 33a for supporting the base of the screw 19, and the through hole 22 is provided with the shaft 8 of the shaft 8. A fitting portion 34 for supporting the coupler member 33 at the tip portion is provided so as to expand in the shape of a counterbore. The outer peripheral groove 19a of the screw 19 and the bolt hole 3
2 and the arcuate cotters 26 and 27 and the structure of the coupler member 25 are the same as those in FIG.

Further, in this embodiment, when the screw 19 is removed, it is necessary to pull out the coupler member 33 buried in the fitting portion 34 of the shaft 8 to the front side, so that it becomes a handle for pulling out the coupler member 33. At least one tap hole 35 for screwing the bolt is provided on the coupler member 33. The arrangement of the bolt holes 28 and 36 for passing the fastening bolts 31 through the coupler members 25 and 33 is the same as that in FIG. 4C, but in this embodiment, as shown in FIG. One of the bolt holes 36 to be provided is configured as a blind hole-shaped female screw 36a, and one fastening bolt 31a shorter than the other is used.
The coupler member 25 and the coupler member 33 are directly fastened at 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 of FIG. 5). See the bolt holes).

Of course, after removing all the fastening bolts 31 and 31a and removing the coupler member 25, the fastening screw 31a is screwed into the female screw 36a again, and the coupler member 33 is pulled out by using this as a handle. It doesn't matter. Further, it is also possible to forcibly pull out the coupler member 33 fastened to the coupler member 25 by the bolt 31a by retracting the shaft 8 after removing all the fastening bolts 31. The last operation procedure is to remove the bolt 31a.

In the embodiment shown in FIG. 4 and FIG. 5, the shaft 8 is provided with a through hole 22 so that the screw 19 can be pulled out backward. Since the moment of inertia of the shaft 8 is also significantly 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 if it is not necessary to pull out 9 backward, the responsiveness can be improved by making the shaft 8 a hollow structure).

Further, since the screw 19 is pulled out rearward, it is not necessary to rotate 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 portion, and thus the injection unit base is eliminated. The turning mechanism itself is unnecessary, and the mechanical strength of the injection unit base is improved. Further, even if the screw 19 is replaced, the problem that the tip position of the injection cylinder is displaced does not occur. Therefore, there is also a problem that the mold sprue is damaged due to the contact of the nozzle at an inappropriate position and the resin leaks due to the damage. This eliminates the need to provide a working space for screw replacement at least on the side of the injection molding machine (a working space for screw replacement needs to be provided behind the injection molding machine).

Of course, a swivel mechanism similar to the conventional one may be adopted to remove the screw 19 from the tip of the injection cylinder, but in that case, the shaft 8 is made as thin as the screw 19, or The shaft 8 and the screw 19 must be separable from each other by using a coupler or the like similar to the conventional one.

Further, the spline outer cylinder 9 also serves as a rotation preventing means for the shaft 8 and the rotation of the ball screw nut 11 causes the shaft 8 to rotate.
Since the feed is directly applied to 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 together, except that the tie rod 3 receives the final resin reaction force acting on the screw. The use and the function are different from those of the rod 102.

When the injection operation is performed in such a structure, the screw rotating servomotor 7 is held in a stopped state, and the pulley 15, the timing belt 17, and the pulley 13 are held.
The servomotor 6 for injection is driven while suppressing the rotation of the spline outer cylinder 9, 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, the shaft 8 is fed in the injection axis direction, and the screw 19 fixed integrally with the shaft 8 is attached to the injection shaft. Will move in the direction.

Of course, at this time, only the screw 19 and the shaft 8 move in the injection axis direction, leaving 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 with the screw 19 is extremely small, and as shown in the conventional example of FIG. 4, the screw 105 is fed together 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 high response without increasing the output of the injection servomotor 6.

When performing a lightweight kneading operation, the ball screw nut 11 and the spline outer cylinder 9 are set to the set screw rotation speed while the injection servomotor 6 is subjected to a torque limit commensurate with 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 speed corresponding thereto.

Therefore, if the resin reaction force acting on the screw is less than or equal to the set back pressure, the ball screw nut 11 and the spline outer cylinder 9 will 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 spline outer cylinder 9, the shaft 8, that is, the screw 19 remains stopped in the axial direction.
Only the rotational movement of the set screw rotational speed is performed at the stop position.

As a result, the lightweight and kneaded molten resin gradually accumulates at the tip of the cylinder, and the back pressure, that is, 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 with the torque limit corresponding to the set back pressure, The spline outer cylinder 9 resists the rotational force generated by the circumferential force applied to the thread surface of the ball screw nut 11 by the resin reaction force acting along the shaft 8.
It becomes impossible to maintain the synchronous rotation with and, and the spline outer cylinder 9 is out of synchronization in the rotation direction corresponding to the direction in which the shaft 8 retracts.

That is, if the screw 1 in FIG.
If the metering operation is performed by clockwise rotation when viewed from the tip side of 9 (when the spiral of the screw 19 is a right-hand screw type), the rotation speed of the ball screw nut 11 is the set screw rotation speed. If it is slower than the rotating speed of the rotating spline outer cylinder 9, and if the metering operation is performed by the counterclockwise rotation when viewed from the tip end side of the screw 19 in FIG. In the case of the left screw type), the rotation speed of the ball screw nut 11 is faster than the rotation speed of the spline outer cylinder 9 that rotates at the set screw rotation speed. Of course, this is a phenomenon that occurs when the shaft 8 is of the right-handed screw type as shown in FIG. 1, and if the shaft 8 is of the left-handed screw type, there will be a synchronization deviation opposite to this. .

As a result, the shaft 8 is attached to the spline outer cylinder 9.
The resin reaction force acting on the screw 19 is always maintained at the set back pressure due to the synchronism shift of the ball screw nut 11 that occurs in the direction of retracting the.

Further, 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. It is also possible to maintain.

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

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. 1, the screw 19 is rotated clockwise when viewed from the tip side of the screw 19. If the metering operation is performed (when the spiral of the screw 19 is a right-hand screw type), the rotation speed of the ball screw nut 11 is slower than the rotation speed of the spline outer cylinder 9 rotating at the set screw rotation speed. 1 (in short, the correction value of the movement command is negative), and if the metering operation is performed by rotation in the counterclockwise direction as seen from the tip side of the screw 19 in FIG. 1 (the spiral of the screw 19 is In the case of the left-hand screw 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. 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-handed screw type as shown in FIG. 1, and if the shaft 8 is of the left-handed screw type, it is necessary to generate a synchronization shift which is completely opposite to this. 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 in which the shaft 8 is retracted, so that the resin reaction force acting on the screw 19 is It will always be maintained at the set back pressure.

Naturally, the screw rotational speed at the time of metering should be maintained at the set value, but within the range that does not affect the result of the metering and kneading of the resin, in response to the movement command to the injection servomotor 6, It is possible to achieve the same object by applying the correction in the opposite direction to the movement command to the screw rotation servomotor 7 instead of applying the correction. Next, FIG. 2 shows a configuration example in which a load cell for detecting an injection pressure or a back pressure acting on the screw 19 is incorporated in another position.

The main part of the structure of the injection unit 1'shown in FIG. 2 is exactly the same as that of the injection unit 1 in FIG.
It 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 a thin portion 21 is arranged in the shape of a circumferential groove, and the strain gauge attached to the thin portion 21 measures the deflection of the thin portion 21 to obtain a guide rod. 3, the resin reaction force such as injection pressure and back pressure is detected, and the resin reaction force detected by the load cell 111 is detected to perform feedback control of holding pressure and back pressure. It can be implemented in the same manner as.

In the conventional example shown in FIG. 7, the screw 105
Part of the resin reaction force that acts on the pusher plate 104
The friction of the sliding part between the guide rod 102 and the guide rod 102 disperses it to the side of the guide rod 102.
Although not all the resin reaction force acting on 05 is received by the load cell 111, in the embodiment shown in FIG. 2, all the tension acting on the tie rod 3, that is, the resin reaction force acting on the screw 19 in the axial direction. Since all of the above 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.
7 will be described. The biggest difference from each of the above-described embodiments is that the spline shaft 39 and the ball screw shaft 40 formed of individual members are replaced with bolts or the like instead of forming the shaft 41 provided with the ball screw groove and the ball spline groove from a single shaft. 1 and 2, a member corresponding to the support bearing 10 of the spline outer cylinder 9 in FIGS. 1 and 2 is omitted, and a function corresponding to the support bearing 10 is provided in a part of the housing 38. 1 and 2 in that the housing tip end constituent element 38a also serves as a constituent, and a spline outer cylinder 9'instead of the spline outer cylinder 9 in FIGS. 1 and 2 is directly attached to the housing tip end constituent element 38a. A member corresponding to the support bearing 12 of the ball screw nut 11 in FIG. The housing rear part component 38b forming a part of the housing 38 also has a function corresponding to 12, and the housing rear part component 38b has a ball screw nut 11 'instead of the ball screw nut 11 shown in FIGS. And a load cell 20 'having a structure similar to that of the load cell 20 in FIG. 2 is interposed between the housing front end component 38a and the housing rear part component 38b. This is also a part.

That is, all of these constituent elements are newly designed parts, and do not utilize the commercially available ball screw / spline 5 as in the examples of FIGS. 1 and 2.

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 with the bolt 42. A spline outer cylinder 9'supporting the spline shaft 39 so as to be non-rotatably and slidably mounted is provided around the outer peripheral part of the spline shaft 39, and a ball screw nut 11 screwed onto the outer peripheral part of the ball screw shaft 40. ′ Is attached. 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 ones.

Further, on the outer peripheral surface of the spline outer cylinder 9 ',
Inner rings of two angular bearings 43 having different directions are mounted at intervals, each of which is a C-ring-shaped retainer 44a mounted in the outer peripheral groove of the outer cylinder 9 ',
It is supported by 44b and 44c and the flange portion 45 of the outer cylinder 9'and is prohibited from moving in the axial direction. And 2
The outer ring of the two angular bearings 43 is attached to the inner peripheral surface of the cylindrical housing tip end component 38a,
The outer ring of the bearing 43 located on the right side in the drawing is supported by the step portion 48 on the inner peripheral surface of the housing tip end component 38a, while the outer ring of the other bearing 43 is supported on the left end face of the housing tip end component 38a. It is fixed by an annular retainer 47 that is bolted. Since the sleeve 46 is interposed between the outer rings of the two bearings 43, the retainer 44c will not be 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 end component 38a and is immovable in the axial direction.

Then, on the end surface of the spline outer cylinder 9 ',
As in the case of each of the embodiments shown in FIGS. 1 and 2, the screw rotating pulley 13 is fixed.

Screw 19 for spline shaft 39
5 is basically the same as that of the example of FIG. 5, but in the case of this embodiment, the screw 19 is not pulled backward, so that a component corresponding to the coupler member 33 of FIG. 5 is not necessary. The bottom of the blind hole 50 provided on the end surface of the spline shaft 39 directly supports the base of the screw 19.

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

Further, inner rings of two angular bearings 51 having different directions are attached to the outer peripheral surface of the ball screw nut 11 'screwed to the ball screw shaft 40 with a space therebetween, and located on the right side in the drawing. Angular bearing 5
One inner ring is supported by the collar portion 52 at the end of the ball screw nut 11 ', while the inner ring of the other angular bearing 51 is fixed by the double nut 53 screwed to the other end side of the ball screw nut 11'. The two angular bearings 51 are positioned by the sleeve 54 interposed between the inner rings of the two angular bearings 51.

Then, the two angular bearings 51
Is attached to the inner peripheral surface of the cylindrical housing rear part constituent element 38b, and the outer ring of the angular bearing 51 located on the right side in the drawing is the housing rear part constituent element 38b.
The outer ring of the other angular bearing 51 is supported by a step 55 at the end of the inner peripheral surface of b, while the outer ring of the other angular bearing 51 is an annular load cell 20 'whose outer periphery is bolted to the left end of the housing rear component 38b. It is fixed by the fitting protrusion 57 of. The load cell 20 'here
The distinction between the outer peripheral portion and the inner peripheral portion is based on the thin portion 56. As before, two angular bearings 51
Positioning is performed by interposing a sleeve 58 between the outer rings. Reference numeral 59 is an oil seal.

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

The end surface of the ball screw nut 11 'is shown in FIG.
The injection pulley 14 is fixed in the same manner as in the respective embodiments of FIG.

The operating principle of injection and metering is shown in FIG.
The embodiment is exactly the same as that shown in FIG.

Further, the load cell 20 'for detecting the resin pressure is provided in the central portion of the housing 38 with the housing front end component 38a and the housing rear component 38.
The servomotor for screw rotation is installed between
A housing 3 similar to the embodiment shown in FIGS. 1 and 2.
8 on the left end side, that is, the housing front end 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 servo motor and the screw rotation pulley 13.
No distortion occurs at 0 ', and the resin pressure can be detected more accurately.

[0078]

According to the present invention, it is not necessary to provide a pusher plate for pressing a screw or a guide rod for preventing rotation of the pusher plate.
The number of parts of the injection unit can be reduced, and the structure can be simplified and downsized.

Further, since there is no pusher plate that moves integrally with the screw, it is not necessary to move the screw rotation servomotor for driving the screw to rotate integrally with the screw. The weight is significantly reduced, and it is possible to perform an injection operation with excellent responsiveness even when using a low-output injection servomotor.

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

As a result, it is not necessary to rotate 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 working space for screw replacement on the side of the injection molding machine.
Since the turning mechanism itself of the injection unit is also unnecessary, it is possible to improve the mechanical strength by eliminating unnecessary moving parts from the injection unit.

Furthermore, according to the construction in which the spline outer cylinder is attached to the tip of the cylindrical housing, 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 rotation pulley of the spline outer cylinder, and the resin pressure can be detected more accurately.

[Brief description of drawings]

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

FIG. 2 is a cross-sectional view showing the outline of the configuration of an injection unit of 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 have separate structures, and only the screw is pulled out rearward through a through hole provided in the shaft.

FIG. 5 is a diagram showing a main part of a configuration example in which a screw and a shaft are separate structures, and only the screw is pulled out rearward through a through hole provided in the shaft.

FIG. 6 is a sectional view showing the outline of the configuration of an injection unit of still another embodiment.

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

[Explanation of symbols]

1 injection unit 1'injection unit 2 Front plate 3 tie rods 4 housing 4a Flange part 4'housing 5 Ball screws and splines 6 Injection servo motor 7 Screw rotation servo motor 8 axes 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 Drive pulley 17,18 Timing belt 19 screw 19a peripheral groove 20 load cell 20 'load cell 21 Thin part 22 Through hole 23 Supporters 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 holes 29 bolt holes 30 bolt holes 31 Fastening bolt 31a Fastening bolts shorter than others 32 bolt holes 33 Coupler member 33a bottom 34 Fitting part 35 tap holes 36 bolt holes 36a Blind hole 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 axis 42 volt 43 Angular Bearing 44a retainer 44b retainer 44c retainer 45 Flange 46 Sleeve 47 retainer 48 step 49 oil seal 50 blind hole 51 Angular Bearing 52 Collar 53 double nut 54 sleeve 55 Step 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 Screw rotation pulley

Continuation of front page (56) Reference JP-A-5-345337 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) B29C 45/00-45/84

Claims (7)

(57) [Claims] 1. A support bearing for supporting a ball screw nut screwed on 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 spline outer member slidably fitted in the ball spline groove of the shaft. A support bearing that supports the cylinder rotatably and immovably in the axial direction 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. Is disposed on the injection unit base, and a screw for injection and weighing and kneading is integrally attached to the shaft ,
Load cell for detecting resin reaction force acting on the screw
An injection unit of an injection molding machine, which is provided with . 2. The injection unit of the injection molding machine according to claim 1, wherein only the ball screw nut is rotated to perform an injection operation 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 synchronously rotated to perform a measuring operation. 4. The method of claim 1, characterized in that to constitute a load cell by attaching a strain gauge tie rod for fastening the housing fixedly provided the two support bearings injection unit base of the front plate, wherein Term
The injection unit of the injection molding machine according to claim 2 or claim 3 . 5. An annular body, in which a thin portion is arranged in a circumferential groove shape, is interposed between a tie rod for fastening a housing having the two support bearings fixedly attached thereto to a front plate of an injection unit base and the housing. The injection unit of the injection molding machine according to claim 1, 2 or 3 , wherein a strain gauge is attached to the thin portion of the load cell. 6. A support bearing for supporting a spline outer cylinder rotatably and axially immovably at the tip of a cylindrical housing, while a ball screw nut is rotatably and axially provided at the rear end of the housing. A load bearing is constructed by fixing a support bearing that immovably supports, and inserting an annular body in which a thin portion is 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 the injection molding machine according to claim 1, claim 2, or claim 3 . 7. The method according to any one of claims 1 to 6.
In the injection unit of the injection molding machine, the back pressure detected by the load cell is detected while the ball screw nut and the spline outer cylinder are synchronously rotated to perform a weighing operation, and the back pressure detected by the load cell reaches a set value. When it reaches, the ball screw nut or the spline outer cylinder is differentially moved in the direction in which the screw moves backward to maintain the resin reaction force acting on the screw at a set back pressure, the injection unit of the injection molding machine. .