JPH07119032B2 - Injection method of fluid in injection molding machine and method of measuring temperature and pressure used in this injection method - Google Patents

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 a synthetic resin in an injection molding machine or an extruder, and a method for measuring the temperature and pressure of the injection fluid useful in the injection method. is there.

[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 to form a molten fluid, and this fluid is pressurized from a nozzle into a mold. Are filled with and solidified in a mold to be molded into 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 supplied to the redi-filled mold should be heated and melted into a uniform molten state if the material is uniform. However, since the thermal conductivity and temperature conductivity (or thermal diffusivity) 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, If temperature unevenness occurs, there is a problem that the strength of the molded product is not uniform.

If the resin has a high viscosity due to insufficient melting, a pressure gradient occurs between the runner or gate and the end of the mold, which reduces the dimensional accuracy of the molded product and requires high pressure. Therefore, the dimensional accuracy of the molded product is particularly reduced in a large-shaped mold. These points are the same for extrusion molding performed by an extruder.

On the other hand, recently, it has been practiced to recover discarded synthetic resin moldings, prepare them as recycled raw materials, and use them by mixing them with the original raw material (virgin raw material). When mixed with virgin raw material, the melting temperature will be different due to the difference in molecular weight, etc., resulting in uneven temperature in the molten fluid injected from the molding machine, resulting in uneven strength of the molded product. There's a problem.

[0006]

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 unmelted raw pellets. When the presence or absence is checked and such temperature unevenness is detected, in order to eliminate the temperature unevenness, a method of injecting a fluid with an operation to complement the heating and melting, and irradiating with a strong ultrasonic wave An injection method that lowers the apparent viscosity to reduce 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 ever, and this The challenge is to develop a temperature and pressure measurement method useful for the method.

[0007]

The structure of the injection method of the present invention, which has been made for the purpose of solving the above-mentioned problems, is adopted 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 pressure of the fluid is measured by ultrasonic waves, and the sound velocity of the fluid is measured by irradiating the fluid with ultrasonic waves at one point or a plurality of points, and the measured sound velocity is a predetermined value under the pressure acting on the fluid. When it shows no melting temperature,
It is characterized in that an operation for complementing the melting and heating of the resin is added.

[0008]

EXAMPLES Next, an injection method of the present invention and an example of a method of measuring temperature and pressure used at that time will be described with reference to the pressure / sonic velocity-melting temperature diagram of FIG. 1 and FIGS. explain.

The inventor of the present invention has found that there is a relationship as shown in the diagram of FIG. 1 as a result of repeated experiments and research on the relationship between the melting temperature of the fluid being heated and melted and the sound velocity and pressure. I got it. 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 has been found that if the pressure and sonic velocity of the molten fluid can be detected, the temperature at the time of melting the fluid can be accurately detected in relation to the pressure.

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 speed of sound decreases as the temperature rises even in the molten state. Moreover, it was also found that the relationship between the sound speed and the melting temperature is established because the sound speed increases when the pressure acting on the resin is large and the sound speed is low when the pressure is small. It was also confirmed that such tendencies are almost the same even if the materials are different. By the way,
The fluid shown in FIG. 1 is a high density polyethylene melt fluid. The speed of sound of the fluid is the speed of sound propagating in the molten fluid.

In the above description, the reason why the pressure can be measured from the ultrasonic waves reflected at the boundary between the metal foil and the wall surface by adhering the metal foil to the wall surface of the passage through which the fluid flows is as follows. . For example, when the substance A and the substance B having different acoustic impedances are in complete contact with each other and ultrasonic waves are applied from one surface, the ultrasonic waves are partially reflected on the contact surface. The reflectance is determined by the value of the acoustic impedance of both substances. On the other hand, when the actual metal surfaces are in contact with each other, due to the surface roughness, there is a real contact portion where the metals directly contact with each other and a void portion caused by the surface roughness.
There is a fact that when such a contact surface is irradiated with ultrasonic waves, as a result, the amount of reflected ultrasonic waves is determined by the ratio of the true contact area of the ultrasonic waves to the projection surface. Therefore, applying this fact, when a metal foil is attached to a part of the metal wall that forms the flow path of the injection molding machine through which the molten resin flows, and ultrasonic waves are applied to that part, the pressure increases significantly due to the above principle. In that case, the actual contact area between the metal wall and the metal foil increases, so the amount of reflection of ultrasonic waves from that part decreases, and therefore,
By measuring the reflection amount of this ultrasonic wave, the pressure corresponding to the reflection amount can be measured.

The present invention has been made in view of the above points, and the molten state of a fluid that is melted and injected and injected into a mold or the like is determined by irradiating the fluid with ultrasonic waves immediately before the injection into the mold. By measuring the speed of sound and pressure, it is determined whether or not the temperature is in a predetermined uniform melting temperature state, and the content of the melting state, specifically, for insufficient melting or mixing of unmelted fluid pellets, It is designed to add an operation that complements heating. In the present invention, at the time of measuring the sound velocity, the pressure of the fluid is also measured by ultrasonic irradiation, or the pressure and the pressure gradient are also measured, and the operation of the heating supplement is performed based on the measured sound velocity and pressure, or the pressure. At the same time, the viscosity of the fluid is appropriately controlled to optimize the resin melting temperature and reduce the injection pressure. 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 sound velocity, and the fluid is measured. It is determined whether or not is in a uniform heating and melting state. When measuring the speed of sound, if the melting temperature of the fluid is predetermined under the pressure acting on the fluid, a constant speed of sound is detected, but pressure fluctuations due to fluctuations in the fluid temperature and passage of unmelted raw pellets, etc. If so, 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. However, in the present invention, a constant change appears for each injection cycle. In response to the change, the heating output of the heating device is controlled so as to be reinforced in synchronization with the change cycle.

On the other hand, sudden sound velocity change accompanied by pressure fluctuation,
That is, since the temperature change mainly occurs due to the mixing of the raw pellets, an operation for promoting the melting of the raw pellets is added in the present invention. For example, as shown in FIG. 2, a cock type valve 4 that can change the diameter of the fluid passage 21 by adjusting the opening / closing degree 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 the present invention, as shown in FIG. 2, an ultrasonic transducer for measuring the speed of sound is attached as a sound speed sensor 3 to the nozzle 2 of the heating cylinder 1 of an injection molding machine or the like, and at the vicinity of the nozzle 2 of the heating cylinder 1. The valve 4 was attached, the sound velocity was measured, and the mixed raw pellets were melted. In FIG. 2, 5 is a screw and 6 is a band heater.

Another example of the method for shearing the raw pellets is to control the operating speed (rotation speed or advancing / retreating speed) of the screw 5 or a plunger (not shown) so that the raw pellets are melted by shearing. May be. The adjustment control of the operating speed can also be performed as the adjustment of the injection pressure.

In the present invention, in addition to the above-mentioned operation of complementing the heating and melting, as shown in FIG. 3, a "puddle" 7 acting as a heat exchanger is provided before or after the nozzle 2 to melt the unmelted fluid. It may be promoted. In FIG.
Reference numeral 8 is a heater for the puddle 7, 41 and 42 are switching valves for guiding the fluid to the puddle 7, and 22 and 23 are passages for supplying and discharging the fluid to and from the puddle 7.

Furthermore, according to the present invention, a heating cylinder 1 having a nozzle 2 at its tip or a vibrator 9 for strong ultrasonic waves is attached to the nozzle 2, and ultrasonic power vibration is applied to the fluid to be melt-injected. The above operations can be complemented or enhanced. FIG. 2 shows an example in which a vibrator 9 for ultrasonic power vibration is attached to the nozzle 2.

Each replenishment operation for the above unmelted fluid is
These are performed individually or in combination, and whether the effect of this operation is effective or not is determined by the sonic velocity sensor 3 using the ultrasonic transducer as described above. If the sound velocity of is monitored at an appropriate sampling cycle, it can be easily determined.

Next, in the present invention, simultaneously with the measurement of the sound velocity, an operation of detecting the pressure of the fluid in the fluid passage 21 in the injection molding machine or the like and adjusting the injection pressure of the fluid to perform the 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, 11 are formed on the inner surface of the passage.
Is attached to the outside of the passage 24 and the pressure sensors 31, 32 are attached.
An ultrasonic transducer is provided to irradiate ultrasonic waves when the 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 differs 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 detected pressures of the sensors 31 and 32 indicates the pressure gradient.

Therefore, the injection pressure of the fluid in the passage 24 or the pressure gradient is measured to detect that the pressure or the pressure gradient is not predetermined, for example, the pressure is too high or the pressure gradient is flat. If so, the melted state of the fluid is not in a predetermined state, so an operation for correcting the injection pressure is added.

As the pressure correction operation, for example, the heater 6
By controlling the heating temperature of the heater, driving the heater 61 separately provided in the passage 21 as shown in FIG. 4, or the heater 62 provided outside the passage 21, or the transducer 9 for strong ultrasonic waves. , The apparent viscosity of the fluid is lowered 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 inside the passage 21 and the fluid to be ejected may collide with this. In this sense, the heater 61 is the passage 2
It is desirable to have a configuration in which it can freely appear and disappear in 1. 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.

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

[0028]

The present invention is as described above, and the sound velocity and pressure data obtained by the ultrasonic sensor are constantly or
If it is taken out at an appropriate sampling cycle, and based on these data, a control signal such as start and stop for each of the above temperature complementing operations is formed, and by driving and controlling each of the above temperature complementing operations, the molten state is always kept constant. It is possible to realize injection molding and extrusion molding using the fluid.

Further, if a pressure correction operation is performed based on both the pressure and sonic velocity data from the ultrasonic sensor, injection molding and extrusion molding can be realized with a fluid in which the molten state is kept constant.

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

[Brief description of drawings]

FIG. 1 is a diagram showing a relationship between a melting temperature of a fluid, a pressure, and a sound velocity.

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 Nozzle 3 Sound Velocity Sensor 4 Valve 7 Hot Water Pool 9 Ultrasonic Transducer

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location B29C 45/78 7365-4F 47/36 9349-4F G01L 7/00 L 11/04

Claims (12)

[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 pressure of the fluid is measured by ultrasonic waves, and the fluid is superposed at one or more points. The sound velocity of the fluid is measured by irradiating a sound wave, and when the measured sound velocity does not show a predetermined melting temperature under the pressure acting on the fluid, an operation for complementing the melting and heating of the resin is added. Fluid ejection method. 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 fluid according to claim 1, wherein the operation for complementing the melting and heating of the fluid is to control the moving speed or the rotating speed or the moving speed and the rotating speed of an injection member such as a screw in an injection molding machine or the like. Injection 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 method of injecting a fluid according to claim 1, wherein the operation of complementing the melting and heating of the fluid is controlled by reheating the fluid by a heater provided in a passage of an injection nozzle in an injection molding machine or the like. 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 the strong ultrasonic wave causes the wall surface of the fluid passage to vibrate with the strong ultrasonic wave, or a cock type valve for varying the cross-sectional area of the fluid passage to vibrate with the strong ultrasonic wave. Injection method. 8. 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 pressure of the fluid is ultrasonically measured at one point or a plurality of points and ultrasonic waves are applied to the fluid. A method for measuring the temperature of an ejected fluid, characterized in that the fluid melting temperature is measured by measuring the sound velocity of the fluid. 9. 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 this metal foil portion, and the pressure of the fluid is measured by the ultrasonic waves reflected at the boundary surface between the metal foil and the wall surface, and the measured pressure or pressure and pressure gradient. Is not showing a predetermined pressure or pressure and pressure gradient of the fluid, an operation of correcting the injection pressure of the fluid is added. 10. The method of injecting a fluid according to claim 9, 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. 11. The operation for correcting the injection pressure is performed according to claim 1.
The fluid ejection method according to claim 9 or 10, which is performed in combination with any one of the operations for complementing the melting and heating of the fluid used in the fluid ejection method according to any one of claims 1 to 7. 12. 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, and ultrasonic waves are applied at one or more points of the fluid flowing through the metal foil portion. A method for measuring pressure, which comprises irradiating and measuring the pressure of a fluid from ultrasonic waves reflected at a boundary surface between the metal foil and a wall surface.