JPH0741653B2 - Injection molding machine - Google Patents

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, and more particularly to an injection molding machine configured to stably supply molten resin.

[0002]

2. Description of the Related Art Generally, when a resin molding material is melted to produce a molded product having a predetermined shape, an injection molding method is used in which a molten resin melted by an injection molding machine is filled in a resin molding die for molding. Used. In this type of injection molding method, a process of injecting a molten resin (polymer melt) into a resin molding die at a relatively high pressure and a high speed to obtain a predetermined molded article is important.

As an injection molding machine, for example, a machine in which a pellet-shaped or powder-shaped resin molding material supplied from a hopper is melted in a heating cylinder and filled in a resin molding die is often used. In this type of injection molding machine, a screw with a spiral groove formed on the outer periphery is inserted in the heating cylinder, and when the screw is driven to rotate in the heating cylinder, the resin molding material is kneaded in the spiral groove and sheared. It generates a molten resin which is fluidized by being subjected to a force and being heated.

The screw is divided into a supply portion to which the resin molding material is supplied, a compression portion for compressing the resin molding material to melt the resin molding material, and a measuring portion for extruding the molten resin at the tip of the screw. Since the screw softens and melts and extrudes the resin molding material, the depth of the spiral groove is deep at the supply portion and becomes shallower as it moves to the compression portion and the measurement portion.

[0005]

However, in the above injection molding machine, the heating cylinder is heated to a predetermined temperature by the heater provided on the outer periphery of the heating cylinder, and frictional heat is generated in the resin molding material by the rotating screw. Since the resin molding material is melted into a molten resin, the temperature of the resin molding material in the portion in contact with the heating cylinder becomes relatively high, and the temperature of the resin molding material in the portion in contact with the spiral groove of the screw becomes relatively low. Therefore, in the case of the conventional injection molding machine, there is a problem that the temperature distribution of the molten resin melted in the heating cylinder is not uniform and the viscosity of the molten resin is not uniform. In that case, when the molten resin injection pressure fluctuates when the molten resin is filled in the resin molding die, or the flow of the molten resin is not smooth,
Alternatively, the precision of the molded product molded in the cavity may decrease.

Therefore, an object of the present invention is to provide an injection molding machine that solves the above problems.

[0007]

According to the present invention, a resin molding material is supplied to a spiral groove of a screw rotating in a cylinder, and the resin molding material is melted as the screw rotates to fill a resin molding die. In the injection molding machine described above, the spiral groove of the screw is coated with a far-infrared radiator that emits far-infrared rays by absorbing heat generated by melting of the resin molding material.

[0008]

[Function] Since the spiral groove of the screw that produces the molten resin is coated with the far-infrared radiator that emits far infrared rays, the resin molding material that contacts the spiral groove of the screw during the process of producing the molten resin as the screw rotates It is possible to promote the melting by heat radiation of far infrared rays, improve the kneading effect by the screw, and make the melting temperature and viscosity of the molten resin uniform.

[0009]

1 to 3 show an embodiment of an injection molding machine according to the present invention.

In each of the drawings, an injection molding machine 1 is an in-line screw type molding machine, and generally comprises a resin melting unit 2 and
Screw drive unit 3 and base drive unit 4
And a mold opening / closing drive unit (not shown).

The resin melting unit 2 has a screw 6 inserted in a heating cylinder 5, and an injection nozzle 7 for injecting the molten resin into a resin molding die (not shown) is attached to the tip of the heating cylinder 5. Has been. A band heater 8 is wound around the heating cylinder 5 and is heated to a predetermined temperature from the outside when the molten resin is produced.

Further, the heating cylinder 5 is formed in a hollow shape in which a cylinder chamber 5a extending in the axial direction is bored. A screw 6 is inserted in the cylinder chamber 5a so as to be slidable and rotatable in the axial direction.

The screw 6 includes a supply portion 6a to which a pellet-shaped or powder-shaped resin molding material (not shown) is supplied from the hopper 9, and a resin molding material obtained by compressing the resin molding material supplied from the supply portion 6a. melting and compression portions 6b, compression
The resin molding material supplied from the portion 6b is further melt-kneaded.
The molten resin that has reached a predetermined temperature by the tip of the cylinder chamber 5a.
Measuring part 6 that pushes out the injection amount required for molding a certain amount per minute
It is divided into c and. The screw 6 has a spiral groove 6d.
Since the resin molding material in the spiral groove 6d is compressed and kneaded while being rotationally driven to be softened and melted and the molten resin is pushed out into the heating cylinder 5, the depth of the spiral groove 6d is at the supply portion 6a. It is formed deeply and becomes shallower as it moves to the compression portion 6b and the weighing portion 6c. The hopper
The resin molding material supplied from 9 is the screw of the screw 6 mentioned above.
The above-mentioned supply by moving the spiral groove 6d of the screw 6 by rolling.
While passing through the portion 6a, the compression portion 6b, and the weighing portion 6c
After being melted and kneaded, the tip of the screw 6 and the cylinder chamber 5a
Filled between the tip. And weighing the screw 6
Molten tree discharged from the portion 6c to the tip of the cylinder chamber 5a
The screw 6 slides in the A direction as the oil filling amount increases.
Then, by moving the screw 6, the screw 6 is weighed.
Between the tip of the part 6c and the tip of the cylinder chamber 5a,
Molten resin filled in the created space volume is required for molding
It becomes a certain fixed amount (injection amount).

A backflow prevention valve 10 for preventing the molten resin extruded into the cylinder chamber 5a from flowing back is screwed into a screw hole 6e provided at the tip of the screw 6.
The check valve 10 is shaped like a pointed arrowhead, and has a ring-shaped seal member 11 at the constricted portion 10a.
Fit together. When the molten resin pushed out into the cylinder chamber 5a tries to flow backward, the seal member 11 pressed by the molten resin comes into contact with the tapered surface of the constricted portion 10a to prevent the backward flow. When the molten resin melted in the spiral groove 6d is pushed out into the cylinder chamber 5a, the sealing member 11
Is displaced toward the tip side, but is stopped at a substantially intermediate position of the constricted portion 10a, and extrusion of the molten resin is allowed.

The surface of the check valve 10 and the spiral groove 6d of the screw 6 is covered with a far-infrared radiator 12 which emits far-infrared rays by absorbing heat from the molten resin as the molten resin passes. It becomes.

The far-infrared radiator 12 is, for example, a plasma.
Far infrared ceramics by thermal spraying
Is a thin film coated on the outer periphery of
Between the screw 6 and the cylinder chamber 5a of the heating cylinder 5
The film thickness is formed within the allowable error range. In addition, far infrared
Examples of materials for wire ceramics include zirconia (Z
rO₂), Alumina (Al₂O₃), Silica (Si
O₂), Titania (TiO ₂) Etc. are used.

In the case of plasma spraying, the far-infrared ceramic particles that have been melted by spraying the above-mentioned far-infrared ceramic powder into the plasma jet are sprayed into the passage, so the far-infrared radiator 12 is adjusted by adjusting the spraying time. Can be formed to a desired film thickness, and the surface of the passage through which the molten resin flows can be coated with a uniform film thickness.

Further, by using far-infrared ceramics for the far-infrared radiator 12, it is possible to make the temperature distribution and viscosity of the molten resin uniform as will be described later, and at the same time, wear resistance of the screw 6 is improved. And the heat resistance are improved, and the life of the screw 6 can be extended.

The method of forming the far-infrared radiator 12 is not limited to plasma spraying, but may be, for example, a vapor deposition method, an ion plating method, a sputtering method, a CVD (Chemical Vapor) method.
A thin film forming technique such as Deposition) may be used.

In the process of producing the molten resin as described above, the far-infrared radiator 12 absorbs heat from the molten resin as the molten resin is produced and emits far-infrared rays. This far-infrared radiation is a phenomenon in which electromagnetic waves in a wavelength range having a large thermal effect propagate to space (in this embodiment, the cylinder chamber 5a), and far-infrared radiation is radiated to the molecular motion of the far-infrared ceramics. It is an oscillating wave of dependent electromagnetic force lines.

Infrared radiation is emitted from any material unless it is Kelvin zero (zero K in absolute temperature). If the temperature is low, long-wave infrared is weak, and if it is high, short-wave infrared is strongly emitted. In addition, it is known that each far-infrared ceramic has a unique infrared radiation profile, and the intensity distribution of electromagnetic waves of wavelengths associated with thermal radiation is closely related to temperature.

FIGS. 4A, 4B, and 4C show the spectral infrared emissivity at 200 ° C., 350 ° C., and 500 ° C. of far infrared ceramics made of aluminum titanate (TiO ₂ .Al ₂ O ₃ ). The relationship with wavelength is shown.

From the figure, at a relatively low temperature of 200 ° C.
Even if the temperature is as high as 500 ° C, there is almost no difference in each spectrum.
You can see that there is no. That is, aluminum titanate (T
iO ₂・ Al₂O₃) Of far infrared ceramics
Changes in phase and the size of structure / structure
When there is no significant change, the spectral infrared radiation curve shows
The curve will be almost the same no matter how many times.

As described above, the surface of the screw 6 is coated with the far-infrared radiator 12, so that the molten resin generated in the spiral groove 6d does not come into contact with the surface of the far-infrared radiator 12. Far infrared rays are radiated from the infrared radiator 12 and prevented from being cooled. Therefore,
The molten resin becomes a fluidized bed even at the portion in contact with the surface of the far infrared radiator 12, and is smoothly extruded into the cylinder chamber 5a.

Here, when the molten resin is filled in the resin molding die, the moving base 13 for supporting the resin melting unit 2 and the screw driving unit 3 by the base driving unit 4 moves on the fixed base 14 in the A direction. And the injection nozzle 7 is separated from the resin molding die (not shown). The screw 6 is rotationally driven at 100 to 150 rpm by the hydraulic motor 15 of the screw drive unit 3, and the heating cylinder 5 is heated by the band heater 8 to a temperature suitable for melting the resin molding material.

A pellet-shaped resin molding material is housed in the hopper 9, and the resin molding material is supplied into the spiral groove 6d as the screw 6 rotates. As described above, since the depth of the spiral groove 6d is deep at the supply portion 6a and becomes shallower as it moves to the compression portion 6b and the measuring portion 6c on the tip side, the resin molding material is supplied from the hopper 9 to the supply portion. 6
When supplied to a, it is kneaded between the spiral groove 6d and the inner wall of the cylinder chamber 5a of the heating cylinder 5 while moving along the spiral groove 6d. Further, since the heating cylinder 5 is heated by the band heater 8, the resin molding material supplied into the spiral groove 6d is easily heated and melted by heat conduction from the inner wall of the cylinder chamber 5a.

Therefore, the resin molding material becomes a fluid due to frictional heat in the process of moving from the supply portion 6a to the spiral groove 6d of the compression portion 6b, and further in the process of moving from the compression portion 6b to the spiral groove 6d of the measuring portion 6c. It is heated to a higher temperature and becomes molten resin. However, since the far-infrared radiator 12 is coated on the surface of the spiral groove 6d, the resin molding is heated to about 150 to 300 ° C in the process of moving from the compression portion 6b to the measurement portion 6c. Then, far infrared rays are radiated from the far infrared ray radiator 12 that has absorbed the heat. As a result, the resin molding material becomes a molten resin having a uniform temperature due to the heat conduction from the heating cylinder 5, the frictional heat due to the rotation of the screw 6, and the far infrared rays emitted from the far infrared ray radiator 12, and the viscosity is also uniform. And the kneading effect is improved.

The molten resin thus generated is filled between the tip of the screw 6 and the cylinder chamber 5a,
The screw 6 slides in the A direction as the filling amount increases. That is, the amount of molten resin in the cylinder chamber 5a can be known based on the amount of movement of the screw 6 and the screw drive unit 3.

When the amount of molten resin required for one molding is generated, the base driving unit 4 causes the resin melting unit 2 to
And a moving base 1 for supporting the screw drive unit 3
3 slides in the B direction, and the injection nozzle 7 is inserted into the sprue bush (not shown) of the resin molding die. Then, only the screw 6 is pressed in the B direction by the hydraulic cylinder (not shown) of the screw drive unit 3, and the molten resin filled in the tip of the cylinder chamber 5a is screwed in the screw 6 (not shown).
The resin is extruded by the check valve 10 provided at the tip of and is injected into the resin molding die.

The molten resin filled in the tip of the cylinder chamber 5a is heated by the band heater 8 and is emitted by far infrared rays emitted from the far infrared ray radiator 12 coated on the surface of the check valve 10. It is kept warm and remains molten. Therefore, at the time of injection into the mold, the molten resin is smoothly filled in a laminar flow state, and the molten resin can be injected up to the cavity end in the mold.

Further, since the molten resin is smoothly filled, molding is possible even at a low injection pressure, the variation in temperature distribution is eliminated, the residual internal stress after filling is reduced, and the molding precision of the molded product is improved. At the same time, burr can be prevented,
Stable and highly accurate molding is possible.

When the mold is completely filled with the molten resin and the mold is cooled, the moving base 13 slides in the direction A and the injection nozzle 7 is separated from the mold for resin molding. Then, the resin molding die is opened by the mold opening operation, and the molded product is taken out.

The far-infrared radiator 12 is, of course, not limited to the far-infrared ceramics described in the above embodiment, and the point is that the far-infrared ray is absorbed by absorbing heat from the molten resin when the molten resin is generated. It is sufficient that the radiating far-infrared radiator covers the spiral groove of the screw.

In the above embodiment, the in-line screw type is given as an example, but the present invention is not limited to this, and the present invention is applied to, for example, a screw pre-plastic type having an injection plunger for injecting a molten resin in addition to the screw. Of course, it is also good.

[0035]

As described above, in the injection molding machine according to the present invention, the spiral groove of the screw for producing the molten resin is coated with the far-infrared radiator that radiates far-infrared rays. In the process of generating, the resin molding material in contact with the spiral groove of the screw can be melted by heat radiation of far-infrared rays, and the kneading effect of the screw can be improved to make the melting temperature and viscosity of the molten resin uniform. In addition, it is possible to mold even with low injection pressure, the residual internal stress after filling is reduced, the molding accuracy of the molded product is improved, burr can be prevented, and stable and highly accurate molding is possible. Have.

[Brief description of drawings]

FIG. 1 is a front view of an embodiment of an injection molding machine according to the present invention.

FIG. 2 is an enlarged vertical sectional view showing a heating cylinder and a screw.

FIG. 3 is a vertical cross-sectional view showing an enlarged tip portion of a screw.

FIG. 4 is a diagram showing the relationship between spectral infrared emissivity and wavelength of ceramics at various temperatures.

[Explanation of symbols]

 1 Injection Molding Machine 2 Resin Melting Unit 3 Screw Drive Unit 4 Base Drive Unit 5 Heating Cylinder 6 Screw 6d Spiral Groove 7 Injection Nozzle 8 Band Heater 9 Hopper 10 Backflow Prevention Valve 12 Far Infrared Radiator

Claims (1)

[Claims] 1. An injection molding machine for supplying a resin molding material to a spiral groove of a screw rotating in a cylinder, melting the resin molding material as the screw rotates, and filling the resin molding die with the screw. An injection molding machine, characterized in that the spiral groove is covered with a far-infrared radiator that emits far-infrared rays by absorbing heat generated by melting of the resin molding material.