JPS6158714A - Metering and injecting device of thermoplastic resin - Google Patents

Abstract

PURPOSE:To obtain the titled device capable of accurate metering without undergoing any influence upon variation of density of resin by a method wherein a resin controlling valve is closed to give hydraulic pressure to the main cylinder by the timing based upon the detected output of a plunger position sensor and a resin temperature sensor. CONSTITUTION:The weight of resin supplied into an injection cylinder 2 is grasped by the output of a position sensor 11 and temperature sensor 15. A resin controlling valve 9 is closed to give a hydraulic pressure to a main cylinder 4 by the timing when the weight of resin arrives at the value determined correspondingly to the volume of a cavity 1e. This device is not influenced by variation of specific gravity of resin by change of pressure and temperature in the injection cylinder and resin does not flow back from the injection cylinder 2 into a plasticizing cylinder 5.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a metering injection device for thermoplastic resin, and more specifically, the present invention relates to a metering injection device for thermoplastic resin. This invention relates to a metering and injection device for thermoplastic resin that is capable of precise metering.

[Technical background of the invention]

When injecting plasticized resin into a mold from an injection device, it is ideal to accurately weigh and inject the resin to a predetermined weight. (2) It is required that the weighed resin be injected from the nozzle without backflow.

First, in order to accurately measure the plasticized resin (1) into the injection cylinder, the time for feeding the plasticized resin into the injection cylinder (or fb) is measured by a timer. The retraction of the screw or plunger caused by supplying resin into the injection cylinder is monitored using a limit switch or potentiometer, and the supply of resin into the injection cylinder is stopped when the screw or plunger retreats to a predetermined position. . Methods such as the following have been adopted in the past.

However, if the above method (al) is used, it is not possible to guarantee accurate wire if the amount of resin supplied per hour to the injection cylinder changes due to some factor, and also the above method (a) and ( Either method b) has the problem of not being able to deal with measurement errors due to fluctuations in the specific gravity of the resin caused by temperature fluctuations and pressure fluctuations within the injection cylinder.

In addition, in order to prevent backflow of the measured resin in (2),
Conventionally, a method has been widely adopted in which a buffet ring is provided at the tip of the screw, which moves toward the nozzle due to plasticizing pressure to form a flow path during plasticization, and during injection, the injection pressure causes the screw to retreat in one direction to close the flow path. has been done.

However, because the backflowing slides in the longitudinal direction of the screw along the recess formed around the entire circumference of the screw tip, the backflowing moves from the state where it moves toward the nozzle due to plasticizing pressure to the state where it retreats due to injection pressure. Since the flow path is not blocked until this time, there is a problem that backflow cannot be prevented during that time.

[Purpose of the invention]

The present invention has been made to solve such problems. That is, a first object of the present invention is to effectively deal with fluctuations in the specific gravity of plasticized resin caused by temperature fluctuations and pressure fluctuations within the injection cylinder, and to provide accurate measurement.
The purpose is to provide a metering and injection device for thermoplastic 444 fat that can effectively prevent backflow of the 43471 line supplied into the injection cylinder. An object of the present invention is to provide a metering injection device for thermoplastic resin.

(Means for Solving the Problems and Their Effects) In summary, the thermoplastic resin metering and injection device of the present invention independently comprises a plasticizing cylinder that houses a plasticizing screw and an injection cylinder that houses a plunger. In the injection device, the resin plasticized in the plasticizing cylinder and supplied to the injection cylinder is injected from a nozzle by applying pressure oil to a main cylinder arranged on the axis of the plunger. A resin control valve that opens and closes a flow path from the plasticizing cylinder to the injection cylinder, a position sensor that detects the amount of retraction of the plunger, and a temperature sensor that detects the temperature of the plasticized resin in the injection cylinder. The control valve is closed at the timing when the resin ff1l supplied into the injection cylinder reaches a value determined corresponding to the 8th station of the cavity, as determined by the outputs of the various sensors, and the control valve is closed. Pressure oil is added to the main cylinder, and by determining the timing in consideration of the output of the temperature sensor, it is possible to measure a constant weight of resin without being affected by changes in the specific gravity of the resin due to changes in pressure or temperature within the injection cylinder. By immediately closing the resin control valve when a predetermined amount of resin has been fed into the injection cylinder, the resin flow from the injection cylinder to the plasticizing cylinder caused by applying pressure oil to the main cylinder can be reduced. This prevents backflow of water.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings.

First, FIG. 1 is a sectional view of a thermoplastic resin metering injection device according to an embodiment of the present invention.

In the figure, 1 indicates a mold device, which includes a fixed mold 1a fixed to the machine body, a fixed mold 1b fixed to a fixed plate la, and a movable mold 1c that can be raised and lowered by a cylinder mechanism (not shown). (and mobile play) A movable mold 1d fixed to the IC is provided, and a cavity 1e is formed by applying a mold clamping force toward the fixed mold 1b to the movable mold 1d by a cylinder mechanism (not shown). And also,
The movable mold 1d is fixed to the mold 1b by the cylinder mechanism.
The product molded within the cavity 1e can be taken out by pulling it together.

Further, 2 in the figure indicates an injection cylinder, the tip of the injection cylinder 2 is fitted with the fixed plate 1a, and the injection cylinder 2 is fitted with the fixed plate 1a.
A nozzle 2a protruding from the tip is connected to the cavity 1e. The inner periphery of the injection cylinder 2 is formed into a concave conical shape on the nozzle 2a side, and is open at the other end, through which the plunger 3 is slidably inserted.

Furthermore, in the inner circumferential surface of the injection cylinder 2, the inner diameter of the opening side inner circumferential surface 2b is smaller than the inner diameter of the nozzle side inner circumferential surface 2C,
A step is formed between the opening side inner circumferential surface 2b and the nozzle side inner circumferential surface 2C. The inner circumferential surface 2b on the opening side and the outer circumferential surface 3a of the plunger 3 are sealed, and the inner circumferential surface 2b on the nozzle side
A gap is created between C and the outer peripheral surface 3a of the plunger 3,
Plasticized resin flows into the injection cylinder 2 through this gap.

The tip of the plunger 3 is formed into a convex conical shape that fits the concave conical part formed in the injection cylinder 2, and a shaft off valve is provided between the concave conical part of the injection cylinder 2 and the injection port of the nozzle 2a. 2d is arranged.

Further, the other end of the plunger 3 also serves as a piston rod of the main cylinder 4. Therefore, the plunger 3 is moved into the injection cylinder 2 by the differential pressure between the injection pressure in the injection cylinder 2 and the hydraulic pressure applied to the pressure chamber 4a of the main cylinder 4.
It slides along the inner circumferential surface 2b on the opening side.

Next, 5 indicates a plasticizing cylinder that plasticizes the thermoplastic resin charged from the hopper 6, and the inner periphery of the plasticizing cylinder 5 is formed into a concave conical shape on the injection cylinder 2 side, and on the other side. One end is open, and a screw 8 driven by a hydraulic motor 7 is inserted through the opening. Note that the contact surface between the open end surface of the plasticizing cylinder 5 and the hydraulic motor 7 is sealed. Further, the tip of the screw 8 is formed into a convex conical shape corresponding to the concave conical portion at the tip of the inner circumference of the plasticizing cylinder 5.

Further, the tip of the plasticizing cylinder 5 is connected to a stepped portion on the inner circumference of the injection cylinder 2 via a flow path 5a.
A resin control valve that opens and closes the flow path 5a is arranged inside the resin control valve a.

FIG. 2 shows an enlarged view of the inside of this flow path 5a.
The flow path 5a connects the stepped portion between the opening-side inner circumferential surface 2b and the nozzle-side inner circumferential surface 2C of the injection cylinder 2 and the concave conical portion 5b of the plasticizing cylinder 5 by bending at two places at right angles. A piston rod 10a of a hydraulic cylinder 10 is installed in a portion of the flow path 5b orthogonal to the plasticizing cylinder 5, penetrating through a hole 5C and slidable up and down, and the piston rod 10a and the hole 5C The contact surfaces are completely sealed. Further, a valve body 9 having a downward convex conical portion 9a is fixed to the upper end of the piston rod 10a.
Further, a concave conical valve seat 5d is formed at the upper end of a portion of the flow path 5a orthogonal to the plasticizing cylinder 5, which is in complete surface contact with the convex conical portion 9a.

Therefore, if pressure oil is added to the pressure chamber 10b of the pressure cylinder 10, the piston rod 10a will move down and the valve body 9
The convex conical portion 9a and the valve seat 5d are in close contact with each other to completely block the flow path 5a. If no pressure oil is applied to the pressure chamber 10b, the piston rod 10a will be pushed up by the spring 10c, and the valve body 9 will be released from the valve seat 5d and the flow path 5a will be pushed up.
to be opened.

Further, 110 is a heater for melting the thermoplastic resin charged into the plasticizing cylinder 5 from the hopper 6, and the heater 110 is provided on the outer periphery of the plasticizing cylinder 5.

Next, reference numeral 11 in the figure indicates a position sensor that detects the amount of retraction of the plunger 3 (in other words, the volume of resin supplied into the injection cylinder 2). Specifically, the position sensor 11 is fixed to the Mu body, for example. The stator 11a is made of a resistor, and the slider 11b is fixed to the plunger 3 and comes into contact with the stator 11a. Since the slider 11b slides on the stator 11a as the plunger 3 moves, if a constant voltage is applied across the stator 11a, a level corresponding to the amount of retraction of the plunger 3 will be applied. It is led out to the slider 11b. The output of this position sensor 11 is input/output interface 12.
It is added to the CPU 13 via.

Further, in the figure, 14 indicates a pressure sensor for measuring the pressure of the resin supplied into the injection cylinder 2, and 15 indicates a temperature sensor for measuring the temperature of the resin supplied into the injection cylinder 2. The detection output of the temperature sensor 15 is also input.
It is applied to the CPUI 3 via an output interface 12.

Further, 16 indicates a memory, which has an area for storing general control programs and intermediate data.

The characteristic point of this embodiment is that the memory 16 contains data (such as a correction table and a correction calculation expressions, etc.) are used.

That is, in order to obtain a product with stable quality, it is required to inject a constant weight of resin into the cavity 1e, and in this embodiment, the injection cylinder measured as the output of the position sensor 11 is primarily used. When the volume of the cavity 1e reaches a set value determined corresponding to the volume of the cavity 1e, the plasticizing operation is stopped and the injection operation is performed. However, the specific gravity of the resin supplied from the plasticizing cylinder 5 to the injection cylinder 2 varies depending on the pressure and temperature inside the injection cylinder 2, so if the pressure fluctuations and temperature fluctuations inside the injection cylinder 2 are large, the resin will not be injected into the cavity 1e. A large error occurs in the resin weight.

Therefore, in this embodiment, the pressure sensor 14 and the temperature sensor 1
5 and the data prepared in the memory 16, a correction coefficient is determined based on the output of the cavity 1.
The set value determined in accordance with the volume of e is corrected so that a constant weight of resin is injected into the cavity 1e.

The specific method for determining the correction coefficient is (it varies depending on the properties of the LJ resin, but in terms of −j, if the pressure inside the injection cylinder 2 increases, the specific gravity of the resin also increases, and the temperature inside the injection cylinder 2 increases. As the temperature increases, the specific gravity of the resin decreases.

Therefore, in this embodiment, an arithmetic expression for calculating a correction coefficient, or a pressure and A table of correction coefficients specified by temperature as an address is prepared in the memory 16, and the CPU 13
is a correction coefficient determined based on the outputs of the pressure sensor 14 and the temperature sensor 15 to the set value determined corresponding to the volume of the cavity 1e, and when the output of the position sensor 11 reaches the corrected set value Known digital bells 17 and 18 are turned on to stop the injection of plasticized resin into the injection cylinder 2, and the cavity 1 is turned on.
Injection into e'f I am trying to start making JJ.

Although the digital valves 17 and 18 are known in terms of their construction, in this embodiment, it is assumed that the digital valves 17 and 18 have a response of several milliseconds, and the digital valve 17 is in the on state. Accordingly, the pressure oil supplied from the pump 19 via a known flow control valve 20 is added to the pressure chamber 4a of the main cylinder 4, and the digital valve 1
Reference numeral 8 is a mallet that applies pressure oil supplied from the pump 19 via the flow rate control valve 20 to the pressure chamber 10b of the hydraulic cylinder 10 when turned on.

Next, one embodiment of the present invention will be explained in detail with reference to the above matters. First, prior to the plasticizing operation of the raw resin, the hydraulic motor 7
At the same time, the heater 110 is energized to raise its temperature sufficiently.

Further, when the raw resin is plasticized, the shaft off valve 2d is closed by the action of a spring (not shown), so that the resin in the injection cylinder 2 does not flow into the cavity le. Further, the digital valves 17 and 18 are placed in an OFF state.

First, when the digital valve 17 is turned off, the pressure chamber 4a of the main valve 4 is brought into a low pressure state, and when the digital valve 18 is turned off, the hydraulic cylinder 10 is closed due to the biasing force of the spring 10c. Push up the main body 9 to open the flow path 5a.

In this state, when raw resin is introduced into the plasticizing cylinder 5 from the hopper 6, the raw resin is plasticized due to the rotation of the screw 8 and heating by the heater 110, and passes through the flow path 5a to the injection cylinder 2. It is supplied into the injection cylinder 2 through the gap between the nozzle-side inner peripheral surface 2c and the outer peripheral surface 3a of the plunger 3.

On the other hand, on the injection cylinder 2 side, the shaft off valve 2d is closed and the pressure chamber 4 of the main cylinder 4 is closed.
Since the pressure at a is lowered, the plunger 3 is moved backward by the resin pressure injected into the injection cylinder 2, and accordingly, the slider 11b connected to the plunger 3 also moves toward the stator 11.
Retreat along a.

Then, the level corresponding to the amount of retreat of the slider 11b is
It is applied to the CPU 13 via the output interface I2, and the CPU 13 grasps the amount of retraction of the plunger 3 (in other words, the volume of the injection cylinder 2) based on the level of the slider 11b, and when this reaches the set value, the plasticization is started. After completing the operation, perform the injection operation.

By the way, in this embodiment, the CPU 13 corrects the set value based on the outputs of the pressure sensor 14 and the temperature sensor 15, and ends the plasticizing operation when the output level of the slider 11b reaches the corrected set value. However, the characteristic point of this embodiment is that the positions P1, P2, and P3 of the stator 11a are determined in advance as measurement points, and the CPU The set value is corrected each time it passes.

Specifically, when the output level of the slider 11b indicates the measurement point P1, the CPU 13 receives the outputs of the pressure sensor 14 and the temperature sensor 15 at that time, and uses the values in the calculation for determining the correction coefficient in the memory 16. Substitute it into the equation or use the value from the correction coefficient table in the memory 16? Read out the ili positive coefficient and set it to the predetermined setting value corresponding to the volume of cavity 2 above. The corrected setting value is calculated by multiplying by the ili positive coefficient.

When the output level of the slider 11b indicates the corrected set value, the CPU 13 terminates the plasticizing operation and executes the injection operation as described later.

In addition, in this embodiment, the CPU 3 executes setting value correction operations at measurement points P2 and P3 in addition to measurement point P1 in the same manner as described above, and finalizes the setting value calculated at measurement point P3. The timing of the end of the plasticizing operation is determined as a set value, but this is to deal with temperature fluctuations and pressure fluctuations within the injection cylinder 2 that may occur while the plunger 3 is retreating. The greater the number of measurement points, the better the measurement accuracy.

Then, the CPU 13 simultaneously turns on the digital valves 17 and 18 at the timing when the output level of the slider 11b reaches the final corrected setting value at the measurement point P3.

First, when the digital valve 18 is turned off, the pressure oil supplied from the pump 19 via the flow rate control valve 20 is supplied to the pressure chamber 10b of the hydraulic cylinder 10, so that the piston rod 1a is turned off by the spring 10c. The valve body 9 is pulled down against the pressure, and the convex conical portion 9a of the valve body 9 reliably closes the valve seat 5d in the flow path 5a.

Furthermore, when the digital valve 17 is turned on, the pressure oil supplied from the pump 19 via the flow rate control valve 2o is supplied to the pressure chamber 4a of the main cylinder 4, so that the pressure in the pressure chamber 4a increases. , the pressure in the pressure chamber 4a pushes the plunger 3 into the injection cylinder 2 against the pressure in the injection cylinder 2, and the resin stored in the injection cylinder 2 passes through the nozzle 2a and is injected into the cavity le. .

At this time, as the plunger 3 is pushed into the injection cylinder 2, the pressure inside the injection cylinder 2 increases, but due to the shape of the valve body 9 and the valve seat 5d,
As the internal pressure increases, the tightening force between the valve body 9 and the valve seat 5d increases, and backflow of resin through the flow path 5a is reliably prevented.

Therefore, a constant amount of resin Iα supplied into the injection cylinder 2 is always stably supplied into the cavity 1e and molded there.

After that, move the movable mold 1d to form the cavity l.
Take out the product in e.

In the above example, three /1111 fixed points were used, but it goes without saying that the measurement accuracy improves as the number of measurement points increases.

In addition, in the above, the volume of the injection cylinder is determined as a set value, and a correction coefficient is calculated by applying the outputs of the pressure sensor 14 and temperature sensor 15 to the calculation formula and correction coefficient table prepared in the memory 16. Although we have shown an example in which the corrected setting value is calculated by multiplying the setting value by for example,
In addition to preparing the resin ml to be injected into the cavity le as a set value, an arithmetic formula for calculating weight based on temperature, pressure, and volume and a weight table that is addressed based on temperature, pressure, and volume are prepared in the memory 16. Then, the weight of the resin supplied into the injection cylinder Z is calculated by applying the outputs of the position sensor 11, pressure sensor 14, and temperature sensor 15 to the calculation formula and weight table prepared in the memory 16, and the calculated value is The plasticizing operation may be terminated when a set value is reached.

Furthermore, although the above example shows an example in which the spring IOC is arranged inside the hydraulic cylinder 10 in order to improve the responsiveness of the valve 9, since the valve 9 is also opened by the plasticizing pressure inside the plasticizing cylinder 5, the spring 10c is It's not necessarily necessary.

Further, although the above example has shown an example in which the pressure sensor 14 is disposed inside the injection cylinder 2 in addition to the temperature sensor 15, the pressure inside the injection cylinder 2 can also be predicted based on the low pressure in the pressure chamber 4a. The pressure sensor 14 is not necessarily arranged inside the injection cylinder 2.

Further, in the above, the plunger 3 is located at 4' in the injection cylinder 2,
Although an example has been shown in which the plunger only functions to push in the oil, the plunger may also be configured with a screw to also function as a plasticizer.

〔Effect of the invention〕

As explained above, according to the present invention, the final setting value is determined by taking into account the fluctuation in the specific gravity of the resin caused by temperature fluctuations and pressure fluctuations, so the influence of temperature fluctuations and pressure fluctuations inside the injection cylinder This makes it possible to always measure the exact weight of resin without being affected.

In addition, in the case of the present invention, instead of preventing resin backflow by a backflow ring that is passively activated by applying injection pressure, the flow path is ensured by a resin control valve that is actively activated when the final metering is completed. Since injection pressure is applied after the cavity is closed, it is possible to reliably prevent resin from flowing backwards due to injection pressure, and it is possible to precisely inject accurately measured resin into the cavity. Become.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of one embodiment of the present invention, and FIG. 2 is an enlarged sectional view of a flow path 5a in the first embodiment.

Claims (4)

[Claims] (1) A plasticizing cylinder containing a plasticizing screw and an injection cylinder containing a plunger are independently provided, and the resin plasticized in the plasticizing cylinder and supplied to the injection cylinder is placed on the axis of the plunger. In an injection device that injects pressure oil from a nozzle by applying pressure oil to a main cylinder disposed in the main cylinder, the resin control valve opens and closes a flow path from the plasticizing cylinder to the injection cylinder, and a resin control valve that controls the amount of retraction of the plunger. a position sensor for detecting the temperature of the plasticized resin in the injection cylinder, and a timing determined based on the detection output of the position sensor and the detection output of the temperature sensor; A metering injection device for thermoplastic resin, characterized in that when the resin control valve is closed, pressure oil is applied to the main cylinder. (2) In the thermoplastic resin metering injection device according to claim 1, the resin control valve is closed at the timing when the detection output of the position sensor reaches a predetermined set value, and the main A metering injection device for thermoplastic resin, characterized in that pressure oil is applied to the cylinder and the set value is corrected based on the detection output of the temperature sensor. (3) In the thermoplastic resin metering and injection device according to claim 1, the weight of the resin supplied into the injection cylinder is calculated based on the detection output of the position sensor and the detection output of the temperature sensor. , the thermoplastic resin is characterized in that the resin control valve is closed and pressure oil is applied to the main cylinder at the timing when the calculated value reaches a predetermined set value corresponding to the volume inside the mold. metering injection device. (4) In the thermoplastic resin plasticizing apparatus according to claim 2 or 3, the temperature sensor detects each time the detection output of the position sensor indicates a value at a predetermined measurement point. A thermoplastic resin metering injection device characterized by receiving output.