JP2002018883A - Injection molding machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent non-uniformity in molded components even when a flow rate in a runner and others of a mold is uneven, in the case when precision electronic components such as DVDs are to be molded by multi-cavity molding. SOLUTION: A molding material produced by a mechanism including a screw 23 is divided and sent to valves 37a and 37b and filled as molding materials 27a and 27b respectively in the space parts at the fore ends of injection plungers 28a and 28b. On the occasion, the amount of the molding material 27a filled at the injection plunger 28a through the valve 37a from the screw 23 is metered to be appropriate by controlling the moving-back position of the injection plunger 28a by a servomotor 30a. The amount of filling of the molding material 27b is also metered to be appropriate by a servomotor 30b and the two amounts are made the same. When the amounts become uneven, flow controls are made by the valves 37a and 37b so that they be the same. By injecting the molding materials 27a and 27b into molding tools 36a and 36b of the mold 35 by the injection plungers 28a and 28b respectively, the DVDs free of non-uniformity can be molded.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection molding machine for molding resin products, plastic products, and the like.
VD (Digital Video Disc, Digital Versatile Disc)
TECHNICAL FIELD The present invention relates to a low-pressure encapsulation-type precision injection molding machine for molding precision electronic components such as an optical disk as a recording medium represented by the above.

[0002]

2. Description of the Related Art Conventionally, electronic parts such as transistors, ICs, and optical disks are molded by injection molding a molding material such as plastic or resin into a multi-cavity mold to collectively mold a plurality of parts. Is produced. FIG.
1 is a schematic configuration diagram of a conventional injection molding machine. In FIG. 1, when a pellet 2 such as plastic is put into a hopper 1, a screw 3 is rotated by a motor 4, and the pellet 2 is conveyed forward (to the left in the figure). Then, the pellet 2 is melted by the heater 5, further uniformly stirred by the uniform plasticizing promoting section 6, becomes the molding material 7, and is injected into the empty space at the tip of the injection plunger 8.

[0003] When the injection plunger 8 is inserted forward (to the left in the figure) by pressing the hydraulic cylinder 9,
The molding material 7 is injected from the nozzle portion 10 into the mold 11. At this time, the amount of the molding material 7 injected into the empty space at the tip of the injection plunger 8 is measured by the position sensor 12 for detecting the retreat position of the injection plunger 8, so that a fixed amount of the molding material 7 is always supplied to the mold. 11. Further, although the details of the inside of the mold 11 are not shown in the drawing, in the case of multi-cavity molding, the molding material 7 injected into the mold 11 from the nozzle 10 uses a runner (not shown) for each molding part. It is branched and injected into the empty space. As a result, a plurality of parts are simultaneously molded at a time.

[0004]

By the way, in the simultaneous molding of a plurality of parts by the conventional injection molding machine as described above, the thickness of the molded parts depends on the variation of the flow rate of the molding material 7 flowing to each runner in the mold 11. Variations occur in the quality of the product. For example, since the thickness of the DVD is specified to be approximately 0.3 mm, when the DVD is molded with a two-piece mold, the position sensor 12 detects the retreat position of the injection plunger 8 and the two The amount of the molding material 7 for molding the DVD is measured, and the same amount is injected into each mold from each runner in the mold 11.
However, if dirt or the like adheres to the runners or other flow paths, the flow rate of the molding material 7 flowing through the two runners varies, and as a result, the two DVs formed are formed.
The thickness of D varies. In particular, since the thickness of a DVD is controlled with extremely high precision, even a slight variation in the molding material 7 flowing through each runner may cause a significant reduction in the product yield.

The present invention has been made in view of such circumstances, and has as its object to provide a mold runner or the like when a plurality of precision electronic components such as a DVD are to be obtained, particularly when two are to be obtained. An object of the present invention is to provide an injection molding machine in which the thickness of a molded part does not vary even if the flow rate varies.

[0006]

To achieve the above object, an injection molding machine according to the present invention is an injection molding machine for injecting a molding material into a mold for taking a plurality of precision electronic components.
A screw mechanism that supplies and transports raw materials for precision electronic components and generates a molding material by heating and melting, and filling the molding material individually distributed from the screw mechanism, and filling the molding material in a mold. A plurality of injection plunger mechanisms for individually injecting into a corresponding mold, and a plurality of injection plunger mechanisms, each of which controls a retreat position, and is filled in a void formed in a front part of the injection plunger moved to the retreat position. A servomotor for advancing an injection plunger to inject the molding material into a corresponding mold in a mold.

[0007] That is, with such a configuration, the same amount of the molding material is measured in advance and charged into each injection plunger mechanism. Then, each injection plunger mechanism individually injects a molding material into a corresponding mold in the mold. As a result, even if the flow rate of the runner of each mold varies,
The same amount of molding material is injected into each mold. Therefore, there is no variation in the thickness and the like of the formed precision electronic component, and it is possible to produce a formed component having a high yield. The amount of molding material charged into each injection plunger mechanism is accurately controlled by the servomotor that drives each injection plunger, so that the retracted position of the injection plunger is filled at the tip of each injection plunger. The molding materials to be used are weighed so as to have the same amount.

Further, the injection molding machine of the present invention, in the above invention, further comprises a molding device for injecting a molding material from a screw mechanism to each of the injection plunger mechanisms into each of the cavities of the injection plunger mechanism. A valve for adjusting the flow rate of the material is provided. That is,
Since each servomotor controls the retreat position of each injection plunger, the molding material is weighed by the same amount.However, if there is variation in the servomotor or the feed mechanism of the injection plunger, each injection plunger will be weighed. A slight variation may occur in the amount of molding material charged into the mechanism. In such a case, a valve is provided in each flow path flowing into each injection plunger, and the flow rate of the molding material filled in each injection plunger mechanism is finely adjusted. This ensures that the same amount of molding material is injected into each injection plunger mechanism regardless of the variation in the servomotor mechanism, and as a result, a molded part without variation can be produced.

In a specific embodiment of the injection molding machine according to the present invention, the number of the dies is two, and the injection plunger mechanism is provided for each of the two dies in the dies. And a servo motor provided in each of the two injection plungers to control a retreat position of each of the two injection plungers. It is an injection molding machine. As a result, the same amount of molding material is injected into the two molds, so that there is no variation in the two molded parts. Also, 2
Even in the case of individual picking, when the filling amount of the molding material to be filled in the two injection plunger mechanisms is not the same, a valve for adjusting the flow rate of the molding material is provided so that the filling amount is the same. . Note that a three-way valve may be used as the valve. Further, as a specific application of the injection molding machine of the present invention, 2
If the present invention is applied to an injection molding machine for molding individual optical disks, for example, a DVD having a thickness of 0.3 mm can be produced at an extremely high yield.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the injection molding machine of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a configuration diagram of the injection molding machine of the present invention viewed from the side, and FIG. 2 is a configuration diagram of the injection molding machine of FIG. 1 viewed from above. This embodiment shows a case where two DVDs are taken. In FIG. 1, when a pellet 22 such as plastic is put into a hopper 21, a screw 23 is driven by a motor 24.
And the pellet 22 is transported forward (to the left in the figure). Then, the pellets 22 are melted by the heater 25, further uniformly stirred by the uniform plasticizing promoting section 26, become the molding material 27, and injected into the empty space at the tip of the injection plunger 28.

On the other hand, a drive mechanism for moving the injection plunger 28 forward and backward has a servomotor 30 capable of detecting a position and performing position control, and one end rotatably supported by a fixed member 29 and rotated by the servomotor 30. Ball screw 31, a moving nut 32 that is moved by the rotation of the ball screw 31, and the moving nut 32 and the injection plunger 28 are connected so as to move the injection plunger 28 in parallel with the moving nut 32. Connecting rod 3
3. Therefore, when the injection plunger 28 that moves in parallel with the moving screw 32 that moves linearly with the rotation of the servomotor 30 moves rearward (to the right in the drawing), the molding material 27 fills the empty space at the tip of the injection plunger 28. You. At this time, the retracted position of the moving nut 32, that is, the retracted position of the injection plunger 28 is detected so that the amount of the molding material 27 filled in the empty space at the tip of the injection plunger 8 is equal to the amount of one molded product. The servo motor 30 is configured to control the rotation while rotating.

The molding material 27 filled in the tip of the injection plunger 28 is moved from the nozzle portion 34 to the left by advancing the injection plunger 28 together with the moving nut 32 to the left in FIG. Type 35
It is injected into. Although the inside of the mold 35 is not shown in the drawing, the molding material 27 injected into the mold 35 from the nozzle portion 34 is injected into one molding die even in the case of two pieces. It has become.

A more detailed description will be given with reference to the top view of the injection molding machine shown in FIG. That is, as shown in FIG. 2, the injection molding machine of this embodiment has two systems of branch flow paths including a valve for branching the molding material with respect to one set of screw mechanisms for supplying the molding material, 2 in the mold
It is characterized in that it comprises two sets of injection plunger mechanisms for individually injecting a molding material into each of the molding dies. Therefore, when pellets 22 such as plastic are put into the hopper 21, the screw 23 is rotated by the motor 24, and the pellets 22 are transported forward (to the left in the figure). Then, the pellet 22 is heated by the heater 25.
, And further uniformly stirred by the uniform plasticization promoting section 26 to form a molding material. Further, the molding material is branched into a valve 37a and a valve 37b, and the injection plunger 2
8a and the space at the tip of the injection plunger 28b are filled as a molding material 27a and a molding material 27b, respectively. The valves 37a and 37b may be three-way valves instead of separate valves.

At this time, the valve 3 is
The filling amount of the molding material 27a to be filled into the empty portion of the injection plunger 28a through 7a is measured to an appropriate amount by controlling the retreat position of the injection plunger 28a by the servomotor 30a. Similarly, the filling amount of the molding material 27b to be filled into the space of the injection plunger 28b through the valve 37b is measured to an appropriate amount by controlling the retreat position of the injection plunger 28a by the servomotor 30b. In this way, the molding material 27a on the side of the injection plunger 28a and the molding material 27b on the side of the injection plunger 28b are weighed to the same amount with extremely high precision, and are respectively filled.

However, variations in the position detection accuracy of the servomotors 30a and 30b and the ball screw 31
Injection plungers 28a and 28b may have variations in positional accuracy due to variations in the pitch mechanisms a and 31b. In such a case, the valves 37a, 37
The flow rate can be finely adjusted by adjusting the opening degree of b so that the molding material 27a and the molding material 27b have the same amount.

Thus, the molding materials 27a, 27b
And the injection plunger 28a is advanced leftward in the figure by the servo motor 30a, the nozzle portion 34a
Molding material 27 injected into the mold 36a of the mold 35 from the mold
One DVD is formed by a. Similarly, when the injection plunger 28b is advanced leftward in the figure by the servo motor 30b, another DVD is molded by the molding material 27b injected from the nozzle portion 34b into the molding die 36b of the mold 35. You. At this time, since the molding material 27a and the molding material 27b to be injected have the same amount, the two molded DVDs have the same thickness. The two injection plunger mechanisms are simultaneously filled with the molding material, and the two molding dies are simultaneously injected with the molding material.

That is, the conventional injection molding machine is a DVD2
The injection plunger was filled with the molding material for the sheet, and the injection plunger was injected into a mold. Then, the mold was branched into two molds by a runner. Therefore, if there is a variation in the flow rate in a flow path such as a runner, the thickness of the two DVDs is not uniform. However, according to the injection molding machine of the present invention, in the injection molding machine, the molding material to be injected into the two molding dies is divided into equal amounts before being injected into each of the molding dies. Even if there is a variation in the flow rate, the same amount of molding material is always injected into all the molds.
VD can be molded to the same thickness.

The embodiment described above is an example for describing the present invention, and the present invention is not limited to the above-described embodiment, and various modifications are possible within the scope of the invention. is there. For example, in the above embodiment, the case where the molding materials of the two sets of injection plunger mechanisms are simultaneously filled and measured is described. However, the molding materials to be filled in the respective injection plunger mechanisms are filled at different timings. May be weighed. Furthermore, in the above-mentioned embodiment, the case where the molding material is simultaneously injected into the two molding dies with the two-cavity mold is described. However, the molding is performed by alternately injecting the molding material for each molding die. You may. Regardless of the molding method, if the position control of the injection plunger by each servomotor is adjusted in the same way, and it is configured so that fine adjustment of each flow rate can be performed by a valve,
A DVD of the same thickness can be generated.

[0019]

As described above, according to the injection molding machine of the present invention, instead of injecting the molding material into the mold and then branching to each mold, the injection material is previously injected into each mold. Since the molding material to be measured is measured and then injected into each mold in the mold, it is possible to mold the thickness of molded parts such as DVDs with extremely high precision even if there is a variation in the flow rate of the runner etc. I can do it. Therefore, it is possible to provide an injection molding machine that can mold a precision electronic component having a very high yield.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an injection molding machine of the present invention as viewed from a side.

FIG. 2 is a configuration diagram of the injection molding machine of FIG. 1 as viewed from above.

FIG. 3 is a schematic configuration diagram of a conventional injection molding machine.

[Explanation of symbols]

 1,21 Hopper 2,22 Pellet 3,23 Screw 4,24 Motor 5,25 Heater 6,26 Uniform plasticization promoting part 7,27,27a, 27b Molding material 8,28,28a, 28b Injection plunger 9 Hydraulic cylinder 10 , 34, 34a, 34b Nozzle portion 11, 35 Mold 29, 29a, 29b Fixing member 30, 30a, 30b Servo motor 31, 31a, 31b Ball screw 32, 32a, 32b Moving nut 33, 33a, 33b Connecting rod 36a, 36b Mold 37a, 37b Valve

Claims (6)

[Claims] 1. An injection molding machine for injecting a molding material into a mold for taking a plurality of precision electronic components, wherein the raw materials for the precision electronic components are charged and conveyed, and heated and melted to generate the molding material. Screw mechanism, filling the molding material individually distributed from the screw mechanism, the molding material, in a corresponding mold in the mold,
A plurality of injection plunger mechanisms for individually injecting, and controlling the retreat position of each of the plurality of injection plunger mechanisms, and filling the molding material filled in a void formed in a front part of the injection plunger moved to the retreat position. And a servomotor for advancing the injection plunger to inject into a corresponding mold in the mold. 2. A valve for adjusting a flow rate of the molding material to be injected into each space of the injection plunger mechanism is provided in a flow path through which molding material is distributed from the screw mechanism to the plurality of injection plunger mechanisms. The injection molding machine according to claim 1, wherein the injection molding machine is used. 3. The injection plunger mechanism comprises two sets of injection plunger mechanisms for injecting the same amount of molding material into two molding dies in the mold. 3. The injection according to claim 1, wherein the servo motor is provided in each of the two sets of injection plungers, and controls a retreat position of each of the two sets of injection plungers. 4. Molding machine. 4. The valve according to claim 1, wherein when the filling amounts of the molding materials into the two molds are different, the valve adjusts the flow rate of the molding material so that the filling amounts are the same. The injection molding machine according to claim 3, characterized in that: 5. The injection molding machine according to claim 4, wherein the valve is a three-way valve. 6. The injection molding machine according to claim 3, wherein the precision electronic component is an optical disk as a recording medium.