JP2002166450A - Plasticizing device for injection molding machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To facilitate replacement of a load cell and to correctly detect a resin pressure. SOLUTION: A resin material is plasticized by rotating a screw 10 by a driving motor for rotation, the screw 10 is advanced with a pusher plate 8 by rotating a ball screw shaft 21 by a driving motor 25 for moving, and a molten resin is injected. The load in the axial direction of the screw 10 transmitted through a bearing 12, etc., is detected by the load cell 33 in an injection process. Since the rotational force and actuation heat of the screw 10 and the ball screw shaft 21 are not transmitted to the load cell 33 in the above actuation, the load in the axial direction can be detected precisely. The load cell can be replaced easily by removing a pressure receiving plate 36. Moreover, a seal member 41 prevents the adhesion of lubricating oil to the load cell 33. A fitting part 8b fits the step part 31a of a transmission member 31 to prevent the excessive advance of the transmission member 31.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a synthetic resin injection molding machine, and more particularly to a load cell mounting portion of a plasticizer for plasticizing a resin.

[0002]

2. Description of the Related Art As a plasticizing apparatus for an injection molding machine, the one shown in FIGS. 4, 5 and 6 is known. The plasticizing device 50 of the injection molding machine shown in FIG. 4 will be described. A rotating drive motor (not shown) is mounted on a heating cylinder 52 mounted on a front plate 51 with a radial bearing 54 and a thrust bearing 55 on a pusher plate 53. The screw 58 rotated by the transmission mechanism 57 through the transmission mechanism 57 is movably inserted in the axial direction, and is rotated by a moving drive motor (not shown) onto a ball nut 59 attached to the pressure receiving portion 53a of the pusher plate 53. A ball screw shaft 62 for moving the pusher plate 53 back and forth along the guide shaft 61 is screwed in so that its center axis coincides with the center line of the screw 58, and the thrust bearing 5.
5, a load cell 64 for detecting the axial load of the screw 58 transmitted through the thrust bearing 55 and the transmission ring 63 is provided between the transmission ring 63 and the pressure receiving portion 53a provided at the rear part. (Japanese Patent Laid-Open No. 4-77
226).

FIG. 5 shows a plasticizing device 50 of an injection molding machine.
A is a heating cylinder 5 attached to the front plate 51.
2, a screw 58 attached to the pusher plate 53 by bearings 54 and 55 and rotated by a rotation drive motor 56 via a transmission mechanism 57 is movably inserted in the axial direction, and is inserted into a rear plate 66 via a load cell 64. A ball screw shaft 62, which is rotated by a movement driving motor 60 to move the pusher plate 53 forward and backward along a guide shaft 61 between the front plate 51 and the rear plate 66, has its center axis lined to the attached ball nut 59. A screw 58 is screwed in such a manner as to coincide with the center axis of 58, and its front end is supported by a bearing 67 of a pusher plate 53 (Japanese Patent Laid-Open No. 8-19247).

FIG. 6 shows a plasticizer 50 of an injection molding machine.
B is a heating cylinder 5 attached to the front plate 51.
A screw 58 attached to the pusher plate 53 by a bearing and rotated by a rotation drive motor (not shown) is inserted into the pusher plate 53 movably in the axial direction, and is inserted along the guide shaft 61 between the front plate 51 and the rear plate 66. A load cell 64 is attached to a rear portion of the pusher plate 53 which can be moved back and forth, and a ball screw shaft 6 rotated by a movement drive motor 60 is provided between the pusher plate 53 and the rear plate 66.
Pressing plate 6 which is moved back and forth along guide shaft 61 by means of a ball nut 59 into which screw shaft 62 is screwed.
No. 9 has a structure in which a connecting bolt 70 fixed to the load cell 64 is movably inserted into the through hole 69a (Japanese Patent Laid-Open No. 10-217297).

In any of the above-described plasticizing devices 50, 50A and 50B of the injection molding machine, the screw 58 is rotated to plasticize and measure the resin material in the heating cylinder 52, and the molten resin is screwed by the pusher plate 53 into the screw 58. Is advanced from the nozzle of the heating cylinder 52 into the molding cavity of the mold, and the injection resin pressure at that time, that is, the axial load applied to the screw 58 is detected by the load cell 64.

[0006]

The plasticizers 50, 50A and 50B of the above injection molding machine have the following problems. (Plasticizer 50 of Injection Molding Machine of FIG. 4) Load Cell 64
Is provided between the bearings 55 and 71 and the ball nut 59, so that it is extremely difficult to replace it in case of breakage. In addition, heat is easily stored inside, and the load cell
A change in the precision of the molding has a negative effect on molding. Bearings 55 and 71
Lubricant may enter the load cell and cause electrical insulation failure.

(Plasticizer 50A of the injection molding machine in FIG. 5)
Since the load cell 64 exists outside independently of the bearing portion, there is no problem as in the plasticizing device 50 of the injection molding machine in FIG. However, there is only one ball screw shaft 62 on the screw 58 shaft, and the load cell 64 is a ball nut 59
Since the structure is directly connected to the ball screw shaft 62, it receives all the torque acting on the ball screw shaft 62, and it is difficult to accurately detect only the axial load.

(Plasticizer 50B of the injection molding machine in FIG. 6)
Although the torque is not applied to the load cell 64, the connecting bolt 70 connecting the load cell 64 and the pressurizing plate 69 is free to move. A gap is formed between the load cell 64 and the pressure plate 69 during the operation of removing the internal pressure, that is, so-called internal pressure removal. If the injection is performed in this state, an impact load is applied and the life of the load cell 64 may be shortened. In addition, the contact surface of the pressure plate 69 is deformed (dents are formed) due to the impact, and as a result, the position of the screw 58 is shifted.

In many cases, the load cell 64 used in a molding machine is manufactured so as to apply only compression, and may be damaged if an excessive tensile load is applied. In the plasticizing devices 50A and 50B of FIGS. 5 and 6, when a tensile load acts on the screw 58 for some reason (runaway of the moving drive motor or the like), the load acts directly on the load cell 64.

[0010] In view of the above situation, the present invention can easily replace the load cell without storing the load cell inside the bearing, can perform accurate measurement without applying a torque at the time of injection, and can provide an axial clearance. It is an object of the present invention to provide a plasticizing device that does not generate an impact load due to the above.

[0011]

In order to achieve at least one of the above-mentioned objects, the invention according to claim 1 is characterized in that a heating cylinder attached to a front plate is attached to a pusher plate by a thrust bearing. In a plasticizing device of an injection molding machine in which a screw rotated in a circumferential direction by a rotation drive motor is inserted movably in an axial direction,
A plurality of driving means such as a screw mechanism for moving the pusher plate forward and backward in the axial direction of the screw along the guide member is provided on the pusher plate symmetrically with respect to the screw, and a transmission member is provided at a rear portion of the thrust bearing. And a load cell for detecting the axial load of the screw transmitted through the thrust bearing and the transmission member is provided between the transmission member and the pressure receiving portion of the pusher plate behind the transmission member.

With this means, the torque of the screw mechanism does not act on the load cell. In addition, since a plurality of driving means are provided symmetrically with respect to the screw and are laterally separated from the load cell disposed behind the screw, replacement of the load cell becomes easy, and the load cell reduces the operating heat of the driving means. I do not receive it. The guide member may be a linear guide laid on the base plate, a guide shaft (rod) laid between the front plate and the rear plate, or the like.

As the driving means, a hydraulic cylinder can be used in addition to the screw mechanism operated by the driving motor for movement. When the driving means is a screw mechanism including a ball screw shaft and a ball nut, this can be provided between the front plate and the pusher plate or between the pusher plate and the rear plate. Further, the screw mechanism, a method of moving the pusher plate back and forth together with the ball nut or the ball screw shaft by rotation of the ball nut,
There is a method in which the pusher plate is moved forward and backward together with the ball screw shaft or the ball nut by rotation of the ball screw shaft, but any method may be used. In the above method, both the ball nut and the ball screw shaft may be simultaneously rotated in different directions or in the same direction.

[0014] In the plasticizing apparatus for an injection molding machine according to the first aspect, the thrust bearing and the transmission member can be provided in a storage hole formed in the pusher plate. With this configuration, the thrust bearing and the transmission member do not protrude from the outer surface of the pusher plate, and thus the size can be reduced.

In the plasticizing apparatus for an injection molding machine according to a second aspect of the present invention, a seal member such as an oil seal for making the thrust bearing side and the load cell side of the transmission member liquid-tight is provided between the transmission member and the storage hole. Preferred (claim 3). In this configuration, since the thrust bearing and the load cell are separated by the seal member, lubricating oil of the thrust bearing does not adhere to the load cell.

In the plasticizing apparatus for an injection molding machine according to any one of the first to third aspects, it is preferable that the forward movement of the transmission member is restricted by a locking portion (claim 4). In this configuration, the locking portion prevents the transmission member from excessively moving forward. For this reason, an excessive tensile load does not act on the load cell. The locking portion is usually formed in the storage hole, but may be provided in another portion.

[0017]

Embodiments of the present invention will be described with reference to the accompanying drawings. 1 to 3 show an embodiment of a plasticizing device 1 for an injection molding machine according to the present invention. In these figures, reference numeral 2 denotes a machine body.

A base plate 3 is provided on the machine body 2.
The base plate 3 is provided with a front plate 5 and a linear guide (guide member) 6. The front plate 5 is provided vertically, and the linear guide 6 is laid horizontally in the front-rear direction (left and right in FIGS. 1 and 3). A heating cylinder 7 is mounted horizontally on the front plate 5, and a pusher plate 8 is supported on the linear guide 6 so as to be movable back and forth.

Reference numeral 10 denotes a screw, which is rotatably mounted on the pusher plate 8 by a radial bearing 11 and a thrust bearing 12 in a circumferential direction, and is inserted into the heating cylinder 7 so as to be movable in the axial direction. The screw 10 is provided with a drive motor 14 for rotation such as a servomotor, and pulleys 15 and 1.
6 and a timing belt 17 wound therearound. The resin material supplied to the heating cylinder 7 from the hopper 19 is
Can be rotated to be plasticized in the heating cylinder 7. The rotation drive motor 14 is attached to the pusher plate 8.

Two ball screw shafts 21 are supported on the pusher plate 8 by bearings 23 by screwing their tip ends into ball nuts 22 fixed to the front plate 5.
A drive motor 25 for movement such as a servomotor is connected to the ball screw shaft 21 via pulleys 26 and 27 and a timing belt 28 wound around the pulleys 26 and 27. , 21 by rotating the pusher plate 8 together with the ball screw shafts 21, 21.
, The plasticized resin in the heating cylinder 7 can be injected from the nozzle 29 into the molding cavity of the mold. The movement drive motor 25 is also attached to the pusher plate 8.

The ball screw shafts 21 and 21 are arranged symmetrically with respect to the screw 10 and constitute a screw mechanism together with the ball nut 22.

The radial bearing 11 and the thrust bearing 12
The transmission members 31 and 32 and the load cell 33 are stored in a circular storage hole 8 a formed in the pusher plate 8. The cylindrical transmission member 31 is disposed behind the thrust bearing 12, and the disk-shaped transmission member 32 is attached to the rear end of the transmission member 31 in a gas-tight (liquid-tight) manner with bolts 35. The load cell 33 includes a transmission member 32 and a pressure receiving plate 36.
And attached to the transmission member 32 and the pressure receiving plate 36 with mounting bolts 37 and 38. Pressure plate 36
Are fixed to the pusher plate 8 with fixing bolts 40 while closing the storage holes 8a, and constitute a pressure receiving portion of the pusher plate 8.

The storage hole 8a is provided with a step 31 of the transmission member 31.
a to prevent the transmission member 31 from moving excessively forward,
An engaging portion 8b for preventing an excessive tensile force from being applied to the load cell 33 is formed. Note that the maximum movement amount of the transmission member 31 is normally set to a fraction of a millimeter to a few tenths of a millimeter. A seal member 41 such as an oil seal is fitted around the outer periphery of the transmission member 31 to close a gap between the outer peripheral surface of the transmission member 31 and the inner peripheral surface of the storage hole 8a. The communication on the load cell 33 side is cut off.

The transmission members 31 and 32 transmit the axial load applied to the screw 10 when the screw 10 moves forward and injects the molten resin to the load cell 33 through the thrust bearing 12. This is to detect the axial load. Reference numeral 43 denotes the transmission member 31
The bearing is provided between the screw and the screw 10.

As described above, the plasticizing apparatus 1 of the injection molding machine having the above-described structure rotates the screw 10 by the rotation drive motor 14 to plasticize the resin material, and the movement drive motor 25 The screw 10 is advanced by rotating the ball screw shafts 21 and 21 together with the pusher plate 8 to inject the molten resin.

In the above injection process, the axial load applied to the screw 10 is controlled by the thrust bearing 12 and the transmission member 3.
The load cell 33 is transmitted to the load cell 33 via the first and the second 32, and detects the load in the axial direction and outputs the detected load as a control signal.

In this case, since the ball screw shafts 21 and 21 for advancing the pusher plate 8 are arranged beside the screw 10 and the rotational force thereof is not transmitted to the load cell 33 at all, the shafts can be precisely formed. A directional load is detected. In addition, since the rotational force of the screw 10 in the plasticizing step is cut off by the thrust bearing 12 and is not transmitted to the load cell 33, the detection performance of the load cell 33 is not impaired. Furthermore, since the lubricating oil of the bearings 11, 12, 43 is stopped by the seal member 41 to prevent the lubricating oil from adhering to the load cell 33, troubles such as insulation failure due to the lubricating oil are avoided.

After the injection is completed, in order to release the resin pressure at the tip of the screw 10 (removing the internal pressure), the driving motor 25 for rotation is rotated in the reverse direction to push the pusher plate 8 and the screw 10.
At this time, the locking portion 8b locks the step portion 31a of the transmission member 31 to prevent the transmission member 31 from moving forward relative to the pusher plate 8. For this reason, no excessive tensile force is applied to the load cell 33, and the detection performance is not impaired in this respect as well.

Unlike a conventional plasticizing device in which a screw mechanism is provided in the back of the load cell in a straight line with the load cell,
Since the driving means such as a screw mechanism is provided apart from the load cell 33, the pressure receiving plate 36 is removed and the load cell 33 is removed.
Can be easily maintained and inspected, and is less susceptible to the heat generated by the operation of the driving means. In addition, since the radial bearing 11, the thrust bearing 12, the load cell 33, and the like are housed in the housing hole 8a of the pusher plate 8, they can be made compact and compact.

[0030]

As described above, according to the first aspect of the present invention, the load cell can be easily replaced, and the axial load of the screw, that is, the resin, is not affected by the torque and operating heat of the driving means. It is possible to provide a plasticizing device of an injection molding machine capable of accurately detecting a pressure.

In the plasticizing apparatus for an injection molding machine according to the first aspect, in the configuration in which the thrust bearing and the transmission member are provided in the storage hole formed in the pusher plate, the thrust bearing and the transmission member project from the outer surface of the pusher plate. Therefore, miniaturization becomes possible.

In the plasticizing apparatus for an injection molding machine according to the present invention, a seal member such as an oil seal for making the thrust bearing side and the load cell side of the transmission member liquid-tight is provided between the transmission member and the storage hole. In the configuration, the lubricating oil of the thrust bearing is prevented from flowing to the load cell side and adhering to the load cell, so that adverse effects such as poor insulation due to the lubricating oil do not occur.

[0033] In the plasticizing apparatus for an injection molding machine according to any one of claims 1 to 3, in a configuration in which the forward movement of the transmission member is restricted by the locking portion, an excessive tensile load is applied to the load cell. Thus, the load cell is prevented from being damaged by the tensile load.

[Brief description of the drawings]

FIG. 1 is a sectional view seen from above showing an embodiment of a plasticizing device of an injection molding machine according to the present invention.

FIG. 2 is a view of the plasticizing device of the injection molding machine of FIG. 1 as viewed from right to left.

FIG. 3 is also a side view.

FIG. 4 is a cross-sectional view of a plasticizing device of a conventional injection molding machine.

FIG. 5 is a sectional view of a plasticizing device of another conventional injection molding machine.

FIG. 6 is a sectional view of a plasticizing device of another conventional injection molding machine.

[Explanation of symbols]

Reference Signs List 5 front plate 6 linear guide (guide member) 7 heating cylinder 8 pusher plate 8a storage hole 8b locking portion 10 screw 11 radial bearing 12 thrust bearing 14 rotation driving motor 21 ball screw shaft 22 ball nut 25 moving driving motor 31, Reference Signs List 32 transmission member 31a step 33 load cell 36 pressure receiving plate (pressure receiving portion) 41 seal member

Claims (4)

[Claims] 1. A plastic injection molding machine in which a screw mounted on a pusher plate by a thrust bearing and rotated in a circumferential direction by a rotation drive motor is inserted in a heating cylinder mounted on a front plate so as to be movable in an axial direction. A plurality of drive means such as a screw mechanism for moving the pusher plate back and forth in the axial direction of the screw along a guide member along the guide member, while the thrust bearing is provided on the pusher plate. A transmission cell is provided at a rear portion, and a load cell for detecting an axial load of the screw transmitted through the thrust bearing and the transmission member is provided between the transmission member and a pressure receiving portion of a pusher plate behind the transmission member. A plasticizing device for an injection molding machine, which is provided. 2. The plasticizing device for an injection molding machine according to claim 1, wherein the thrust bearing and the transmission member are provided in a storage hole formed in the pusher plate. 3. The injection according to claim 2, wherein a seal member such as an oil seal that makes the thrust bearing side and the load cell side of the transmission member liquid-tight is provided between the transmission member and the storage hole. Plasticizer for molding machines. 4. The plasticizing device for an injection molding machine according to claim 1, wherein the forward movement of the transmission member is restricted by the locking portion.