JPH058265A - Injection method of fluid in injection molding machine or the like - Google Patents

Abstract

PURPOSE:To improve the dimensional accuracy of a molding by applying an operation for correcting the injection pressure of fluid at the time of no measured pressure and pressure inclination indicating pressure and pressure inclination. CONSTITUTION:In a nozzle 2, a rectangularly sectional conduit 24 is formed at the part of a fluid conduit 21 and metallic foils 10, 11 are stuck on the conduit inner part and, on the exterior of the conduit 24, an ultrasonic oscillators as being pressure sensors 31, 32 are provided which irradiate liquid with ultrasonic waves when it passes through the conduit 24. The injection pressure or pressure inclination of fluid is observed in the conduit 24 and, when the pressure or pressure inclination proves not to be a predetermined one, e.g. the pressure is too high or pressure inclination is flat, the molten state of fluid is not a predetermined state, thus an operation is added to correct the injection pressure. As a pressure correcting operation, for example, the heating temperature of a heater 6 is controlled and, by driving a heater 61 separately provided on the inside of the conduit 21, or a heater 62 provided on the outside of the conduit 21, or an oscillator 9 for strong ultrasonic waves, the apparent viscosity of fluid is lowered so as to decrease the injection pressure.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for injecting a molten fluid such as synthetic resin in an injection molding machine or an extruder.

[0002]

2. Description of the Related Art In an injection molding machine or the like, a pellet-shaped fluid filled from a hopper is melted and kneaded in a heating cylinder portion by a screw and an electric heater, and this fluid is injected into a mold from a nozzle. It is filled with high pressure and solidified in a mold to form a molded product. Further, in an extruder, an extruded product is continuously molded by injecting and supplying a fluid from an injection nozzle to an extrusion die.

Theoretically, the molten fluid filled in the mold or supplied to the die should be heated and melted into a uniform molten state if the material is uniform. However, since the thermal conductivity and temperature propagation coefficient (or thermal expansion coefficient) of fluid are extremely smaller than that of metal, for example, in injection molding, temperature unevenness may occur during injection and filling from a nozzle into a mold. However, when this occurs, there is a problem that the strength of the molded product is not uniform. Also, if the viscosity is high, a pressure gradient will occur between the runner or gate and the end of the mold, and the dimensional accuracy of the molded product will decrease, and since high pressure is required, molding with a large mold The product dimensional accuracy is particularly reduced. These points are
The same applies to extrusion molding performed by an extruder.

On the other hand, recently, synthetic resin moldings that have been discarded are collected and prepared as recycled raw materials to produce the original raw material (bar).
However, if the recycled raw material is mixed with the virgin raw material, the melting temperature will be different due to the difference in molecular weight. There is a problem in that the temperature of the molten fluid is uneven, and as a result, the strength of the molded product is not uniform.

[0005]

SUMMARY OF THE INVENTION In view of the above problems, the present invention is directed to, for example, temperature unevenness of a molten fluid in injection molding or the like, specifically, temperature unevenness caused by the presence of raw pellets in an unmelted state. If the presence or absence of temperature unevenness is detected by checking the presence or absence, in order to eliminate the temperature unevenness, a method of injecting a fluid by adding an operation that complements heating and melting, and an apparent ultrasonic irradiation It is an object of the present invention to develop a method that lowers the viscosity of the product and the injection pressure, thereby improving the dimensional accuracy of the molded product and enabling molding using a mold or the like having a larger shape than the conventional one. To do.

[0006]

The structure of the method of the present invention made for the purpose of solving the above-mentioned problems is such that when molten resin is injected into a mold in an injection molding machine or an extruder,
The ultrasonic velocity is applied to the fluid to measure the sound velocity or pressure and pressure gradient of the fluid, or the sound velocity, pressure, and pressure gradient are measured in the same manner, and when the measured sound velocity does not indicate the predetermined melting temperature of the fluid, An operation of complementing the melting and heating of the fluid, or an operation of correcting the injection pressure of the fluid when the measured pressure or pressure gradient does not show the predetermined pressure or pressure gradient of the fluid, or It is characterized in that an operation for simultaneously complementing the melting and heating of the fluid and the injection pressure of the fluid is added.

[0007]

EXAMPLES Examples of the present invention will now be described with reference to the sonic velocity-melting temperature diagram and the drawings. The inventor of the present invention is
As a result of earnest experiments and studies on the relationship between the melting temperature of the fluid during heating and melting and the sound velocity, it was found that there is a relationship as shown in the diagram of FIG. We also found that the pressure can be measured by attaching a metal foil to the wall surface of the passage through which the fluid flows and measuring the ultrasonic wave reflected at the boundary surface between the metal foil and the wall surface. That is, it was learned that the temperature of the fluid can be detected if the pressure and the sound velocity of the molten fluid can be detected.

For example, as shown in FIG. 1, when a synthetic resin is melted into a fluid, this fluid is heated from room temperature and its temperature rises. Furthermore, it was found that the sound velocity decreases as the temperature rises even in the molten state. This trend is
It was also confirmed that the contents are almost the same even if the materials are different.
Incidentally, the fluid shown in FIG. 1 is a high density polyethylene melt fluid.

The present invention focuses on this point, and measures the molten state of a fluid that is melted and injected and injected into a mold or the like by irradiating the fluid with ultrasonic waves immediately before the injection and measuring the speed of sound. It is determined whether or not it is in a uniform molten state by the operation, and the operation to supplement the heating for melting is added to the content of the molten state, specifically, insufficient melting or mixture of unmelted fluid pellets. Is. Further, the injection pressure is lowered by measuring the pressure and pressure gradient of the fluid by ultrasonic irradiation and appropriately controlling the viscosity of the fluid based on this. Hereinafter, an example in which the present invention is applied to injection molding will be described.

In the present invention, in order to perform the above-mentioned complementary operation, first, the temperature of the fluid filled in the mold as it passes through the nozzle is irradiated with the above-mentioned ultrasonic waves to measure the speed of sound, and the fluid is measured. It is determined whether or not is in a uniform heating and melting state. When measuring this speed of sound, a constant speed of sound is detected if the melting temperature of the fluid is predetermined, but if there is pressure fluctuation due to fluctuations in the fluid temperature or passing of unmelted raw pellets,
The sound velocity being measured changes.

Generally, in the injection molding, the temperature change of the fluid passing through the nozzle includes a constant change for each injection cycle and a sudden change. In the present invention, however, the constant change appears for each injection cycle. On the other hand, the heating output of the heating device is controlled so as to be reinforced in synchronization with the change cycle.

On the other hand, a sudden change in sound velocity, that is, a change in temperature is caused mainly by the mixture of raw pellets. Therefore, in the present invention, an operation for promoting the melting of the raw pellets is added. For example, as shown in FIG. 2, a cock type valve 4 which can change the diameter of the fluid passage 21 by adjusting the degree of opening and closing is provided in the middle of the passage 21 of the nozzle 2 and the opening degree of the valve 4 is reduced to The raw pellets are sheared, and the heat generated by the shearing causes the raw pellets to melt.

In FIG. 2, an example in which an ultrasonic transducer for measuring the sound velocity is attached as a sound velocity sensor 3 to the nozzle 2 of the heating cylinder 1 of an injection molding machine and the valve 4 is attached near the nozzle 2 of the heating cylinder 1. It is sectional drawing shown. In FIG. 2, 5 is a screw and 6 is a band heater.

Another example of the above-mentioned method of shearing the raw pellets is to change the injection speed.
The raw pellets may be sheared by controlling the operating speed (rotational speed or advancing / retreating speed) of 5 or a plunger (not shown). This operating speed adjustment control is
It can also be performed as an adjustment of the injection pressure.

In the present invention, in addition to the above-described complementary operation of heating and melting, as shown in FIG. 3, a "puddle" 7 acting as a heat exchanger is provided in front of or after the nozzle 2 to promote melting of the end-melting fluid. You may do it. In FIG. 3, 8
Is a heater for the basin 7, 41, 42 are switching valves for guiding the fluid to the basin 7, and 22, 23 are fluid supply / discharge passages for the basin 7.

Further, according to the present invention, a heating cylinder 1 having a nozzle 2 at the tip or a vibrator 9 for high-power ultrasonic waves is attached to the nozzle 2 to impart ultrasonic power vibration to the fluid to be melt-injected. It is also possible to complement or enhance each operation of. FIG. 2 shows an example in which the vibrator 9 is attached to the nozzle 2.

Each replenishing operation for the above unmelted fluid is
These are performed individually or in combination, but it is necessary to monitor the sound velocity of the fluid by the sound velocity sensor 3 using the ultrasonic transducer to determine whether the effect of this operation is effective. If so, it can be easily identified.

Next, in the present invention, an operation of detecting the pressure of the fluid in the fluid passage 21 of the injection molding machine or the like and adjusting the injection pressure of the fluid to perform correction control is added. The control operation for correcting the injection pressure is performed in combination with the above heating control supplement, or independently.

FIG. 4 shows an example of pressure correction control. In the nozzle 2, a passage 24 having a rectangular cross section is formed in a part of the fluid passage 21, and the metal foils 10 and 11 are attached to the inner surface of the passage. Ultrasonic transducers serving as pressure sensors 31 and 32 are provided outside the passage 24, and ultrasonic waves are emitted when a fluid passes through the passage 24.

Since the fluid passing through the passage 24 compresses the metal foil 10 by its injection pressure, the compression force also varies depending on the degree of the injection pressure, and this is detected by the pressure sensors 31, 32. The pressures at the respective points are detected by the pressure sensors 31 and 32, and the deviation between the pressures detected by the sensors 31 and 32 indicates the pressure gradient.

Therefore, when the injection pressure or the pressure gradient of the fluid in the passage 24 is known and the pressure or the pressure gradient is not predetermined, for example, when the pressure is too high or the pressure gradient is flat, the fluid Since the molten state is not the predetermined state, an operation for correcting the injection pressure is added.

As the pressure correction operation, for example, the heater 6
Control the heating temperature of the heater, a heater 61 separately provided in the passage 21 as shown in FIG. 4, or a heater provided outside the passage 21.
62, or the oscillator 9 for high-intensity ultrasonic waves is driven to lower the apparent viscosity of the fluid to lower the injection pressure, or the diameter of the passage cross section is changed so that the fluid receives a shearing action. Further, the operating speed of the screw 5 and the plunger may be changed and operated, or the heater 61 may be provided so as to project into the passage 21 and the fluid to be ejected may collide with this. In this sense, it is desirable that the heater 61 be configured so that it can be retracted into the passage 21. The vibrators provided as the pressure sensors 31 and 32 can also be used as a temperature sensor. Further, it goes without saying that the arrangement order of the respective members in FIG. 4 is not limited to the illustrated example.

Although the case where the method of the present invention is applied to injection molding has been described above, the heating temperature complementing operation or the injection pressure correcting operation of the above embodiment can be applied to extrusion molding as it is. It is a thing.

[0024]

Therefore, the sound velocity data or the pressure data by the ultrasonic sensor, or both the sound velocity and the pressure data are taken out constantly or at an appropriate sampling cycle, and the data are used to obtain the above-mentioned data. By forming a control signal such as start and stop for each temperature complementing operation and driving control of each temperature complementing operation, it is possible to realize injection molding and extrusion molding with a fluid whose melted state is always kept constant. .

Further, pressure data or sonic velocity data obtained by the ultrasonic sensor, or both pressure and sonic velocity data are taken out constantly or at an appropriate sampling cycle, and the pressure is measured based on this data. If the correction operation is performed, injection molding or extrusion molding can be realized by the fluid which maintains the molten state constant.

Therefore, by performing the temperature supplementing operation and the pressure correcting operation individually or in combination as appropriate, it is possible to mold a considerably large molded product in a homogeneous state, which was impossible in the prior art. It will be possible.

[Brief description of drawings]

FIG. 1 is a diagram showing the relationship between the melting temperature of a fluid and the speed of sound.

FIG. 2 is a sectional view showing a main part of a heating cylinder of an injection molding machine or the like to which the method of the present invention is applied.

FIG. 3 is a sectional view of a nozzle portion of another example.

FIG. 4 is a sectional view of a nozzle portion of another example.

[Explanation of symbols]

1 heating cylinder 2 nozzles 3 sound velocity sensor 4 valves 7 hot water pool 9 Ultrasonic transducer

Claims (10)

[Claims] 1. When a molten fluid such as a synthetic resin is injected into a mold or the like in an injection molding machine or an extruder, the fluid is irradiated with ultrasonic waves at one or more points to measure the speed of sound of the fluid. ,
A method for injecting a fluid, wherein when the measured sound velocity does not indicate a predetermined melting temperature of the fluid, an operation of complementing the melting and heating of the resin is added. 2. The method of injecting a fluid according to claim 1, wherein the operation of complementing the melting and heating of the fluid is to control a heat generation state of a heating cylinder portion of an injection molding machine or the like. 3. The operation of complementing the melting and heating of a fluid is to control a moving speed or a rotating speed or a moving speed and a rotating speed of an injection member such as a screw in an injection molding machine or the like. Fluid ejection method. 4. The method of injecting a fluid according to claim 1, wherein the operation of complementing the melting and heating of the fluid is to variably control the passage diameter of an injection nozzle in an injection molding machine or the like. 5. The operation of complementing the melting and heating of the fluid is a heater provided in the passage of an injection nozzle in an injection molding machine or the like.
The method for injecting a fluid according to any one of claims 1 to 4, wherein the fluid is reheat-controlled by means of. 6. The injection of the fluid according to claim 1, wherein the operation for complementing the melting and heating of the fluid is to control reheating by irradiating the fluid with strong ultrasonic waves in a passage portion of an injection nozzle of an injection molding machine or the like. Method. 7. The irradiation of strong ultrasonic waves vibrates the wall surface of the fluid passage with power ultrasonic waves, or vibrates the Kot valve for varying the cross-sectional area of the fluid passage with power ultrasonic waves. Fluid ejection method. 8. When a molten fluid is injected into a mold in an injection molding machine or the like, a metal foil is attached to a wall surface through which the fluid flows,
Ultrasonic waves are radiated at one or more points of the fluid flowing through the metal foil portion, and the pressure of the fluid is measured from the ultrasonic waves reflected at the boundary surface between the metal foil and the wall surface. A method for ejecting a fluid, wherein an operation for correcting the ejection pressure of the fluid is added when the fluid does not exhibit a predetermined pressure and pressure gradient. 9. The method of injecting a fluid according to claim 8, wherein the operation of correcting the injection pressure is performed by irradiating the fluid with intense ultrasonic waves to increase the amount of heat generated by the fluid and reduce the apparent viscosity. 10. The operation for correcting the injection pressure is performed according to any one of claims 1 to 1.
9. The melting heating of No. 7 is performed in combination with the operation of complementing the heating.
Or the fluid injection method of 9.