JPH0462247B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a metering injection device for thermoplastic resin;
More specifically, the present invention relates to a thermoplastic resin metering and injection device that is capable of precise metering without being affected by backflow during injection, the temperature of the thermoplastic resin, or the pressure inside the cylinder.

[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 measured resin be injected from the nozzle without backflow.

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

However, when using method (a) above,
Accurate metering cannot be guaranteed if the amount of resin supplied per hour to the injection cylinder changes due to some factor, and injection There is a problem in that it cannot deal with measurement errors due to fluctuations in the specific gravity of the resin caused by temperature fluctuations and pressure fluctuations within the cylinder.

In addition, in order to prevent the measured resin from flowing backward in (2), during plasticization it moves toward the nozzle due to the plasticizing pressure to form a flow path, and during injection it moves back toward the screw due to the injection pressure. Conventionally, a method has been widely adopted in which a back flooring is provided at the tip of the screw to close the flow path.

However, since the back flooring slides in the longitudinal direction of the screw along the recess formed around the entire circumference of the screw tip, the injection pressure Since the flow path is not blocked during the time until it retreats, 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, the first object of the present invention is to effectively cope with fluctuations in the specific gravity of plasticized resin caused by temperature fluctuations and pressure fluctuations within the injection cylinder, and to perform accurate metering. The purpose is to provide a metering injection device for thermoplastic resin, and its second purpose is to provide a metering injection device for thermoplastic resin that can effectively prevent backflow of the resin supplied into the injection cylinder. The goal is to provide equipment.

[Means for solving problems and their effects]

In summary, the thermoplastic resin metering and injection device of the present invention independently includes a plasticizing cylinder containing a plasticizing screw and an injection cylinder containing a plunger, and the thermoplastic resin is plasticized in the plasticizing cylinder and then injected into the plasticizing cylinder. In an injection device that injects resin supplied to a cylinder from a nozzle by applying pressure oil to a main cylinder arranged on the axis of the plunger, opening and closing 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,
At the timing when the weight of the resin supplied into the injection cylinder, as determined by the outputs of the various sensors, reaches a value determined corresponding to the volume of the cavity, the resin control valve is closed and pressure oil is supplied to the main cylinder. 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, and By immediately closing the resin control valve when a predetermined weight of resin is supplied into the injection cylinder, it is possible to prevent the resin from flowing back from the injection cylinder to the plasticizing cylinder due to the application of pressure oil to the main cylinder. I have to.

[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, and the mold device 1 includes a fixed plate 1a fixed to the fuselage, and a fixed plate 1a fixed to the fuselage.
A fixed mold 1b is fixed to the movable mold 1b, a movable mold 1c is movable up and down by a cylinder mechanism (not shown), and a movable mold 1d is fixed to the movable plate 1c. A cavity 1e is formed by applying a clamping force toward the fixed mold 1b to the mold 1d, and
By separating the movable mold 1d from the fixed mold 1b using the cylinder mechanism, the cavity 1e is removed.
The product formed inside can be taken out.

Further, 2 in the figure indicates an injection cylinder, and the tip of the injection cylinder 2 is fitted with the fixed plate 1a,
A nozzle 2a protruding from the tip of the injection cylinder 2 is connected to a 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.

Further, the inner circumferential surface of the injection cylinder 2 has an inner diameter of the opening side inner circumferential surface 2b smaller than an inner diameter of the nozzle side inner circumferential surface 2c, and a gap between the opening side inner circumferential surface 2b and the nozzle side inner circumferential surface 2c. There is a step. The inner circumferential surface 2b on the opening side and the collection surface 3a of the plunger 3 are sealed, and a gap is created between the inner circumferential surface 2c on the nozzle side and the outer circumferential surface 3a of the plunger 3. Plasticized resin flows through the 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 shutoff 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 activated by the pressure difference between the injection pressure inside the injection cylinder 2 and the hydraulic pressure applied to the pressure chamber 4a of the main cylinder 4.
b.

Next, 5 indicates a plasticizing cylinder that plasticizes the thermoplastic resin introduced from the hopper 6.
The inner circumference of the plasticizing cylinder 5 is the same as that of the injection cylinder 2.
The side is formed into a concave conical shape, and the other end is opened, and the hydraulic motor 7 is connected from the opening.
A screw 8 driven by is inserted. 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, and a resin control valve for opening and closing the flow path 5a is disposed within this flow path 5a. There is.

FIG. 2 shows an enlarged view of the inside of the flow path 5a, which is formed by the step between the opening-side inner circumferential surface 2b of the injection cylinder 2 and the nozzle-side inner circumferential surface 2c and the plasticizing cylinder 5. The concave conical portion 5b is bent at two places at right angles and connected. A piston rod 10a of the hydraulic cylinder 10 is inserted through a hole 5c in a portion of the flow path 5b orthogonal to the plasticizing cylinder 5.
is installed inside the piston so as to be able to freely slide up and down, and the contact surface between the piston rod 10a and the hole 5c is completely sealed. Further, the valve body 9 has a downward convex conical portion 9a at the upper end of the piston rod 10a.
Further, a concave conical valve seat 5d is formed at the upper end of the 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, when pressure oil is applied to the pressure chamber 10b of the hydraulic cylinder 10, the piston rod 10a descends and
The convex conical portion 9a of the valve body 9 and the valve seat 5d are in close contact with each other to completely block the flow path 5a. Moreover, the pressure chamber 10b
If no pressure oil is applied to the piston rod 10a, 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, opening the flow path 5a.

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). A stator 11a formed of a resistor, and a slider 11 fixed to the plunger 3 and in contact with the stator 11a.
It is composed of b. And the slider 11
b indicates the stator 1 as the plunger 3 moves.
Since it slides on the stator 1a, if a constant voltage is applied to both ends of the stator 11a, a level corresponding to the amount of retreat of the plunger 3 is derived to the slider 11b. The output of this position sensor 11 is then applied to the CPU 13 via the input/output interface 12.

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 applied to the CPU 13 via the input/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 formulas, etc.) are available.

That is, in order to obtain a product with stable quality, it is required to inject a certain weight of resin into the cavity 1e, and in this embodiment, the injection cylinder that is primarily measured as the output of the position sensor 11 is required. 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, since 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, if the pressure fluctuations and temperature fluctuations inside the injection cylinder 2 are large, the A large error occurs in the weight of the resin injected.

Therefore, in this embodiment, a correction coefficient is obtained from the outputs of the pressure sensor 14 and the temperature sensor 15 and data prepared in the memory 16, and the setting is determined based on the correction coefficient in accordance with the volume of the cavity 1e. A correction is made to the value so that a constant weight of resin is injected into the cavity 1e.

The specific method for determining the correction coefficient differs depending on the properties of the resin, but in general, as the pressure inside the injection cylinder 2 increases, the specific gravity of the resin also increases, and as the temperature inside the injection cylinder 2 increases. In this case, the specific gravity of the resin decreases.

Therefore, in this embodiment, the pressure and A table of correction coefficients specified with temperature as an address is prepared in the memory 16, and the CPU 13 determines the correction coefficients corresponding to the volume of the cavity 1e based on the outputs of the pressure sensor 14 and the temperature sensor 15. Add correction to the set value and position sensor 1
When the output of No. 1 reaches the corrected set value, known digital valves 17 and 18 are turned on to stop the injection of plasticized resin into the injection cylinder 2, and at the same time, start the injection operation into the cavity 1e. I try to do that.

Although the digital valves 17 and 18 are structurally known, in this embodiment, it is assumed that the digital valves 17 and 18 have a response in the order of several milliseconds, and of these, the digital valve 17 is in an on state. The digital valve 18 is configured to apply pressure oil supplied from the pump 19 via a known flow rate control valve 20 to the pressure chamber 4a of the main cylinder 4, and when the digital valve 18 is turned on, the flow rate is also controlled from the pump 19. It is configured to apply pressure oil supplied via the control valve 20 to the pressure chamber 10b of the hydraulic cylinder 10.

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 is rotated and the heater 110 is energized to raise the temperature. be sufficiently raised.

Further, when the raw resin is plasticized, the shutoff 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 1e. Also, digital valve 1
7 and 18 are placed in the 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 moved to the spring 10c.
The urging force pushes up the valve body 9 and opens the flow path 5a.

When raw resin is introduced into the plasticizing cylinder 5 from the hopper 6 in this state, 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. Nozzle side inner peripheral surface 2c and outer peripheral surface 3a of plunger 3
It is supplied into the injection cylinder 2 from the gap between the two.

On the other hand, on the injection cylinder 2 side, the shutter-off valve 2d is closed and the pressure chamber 4a of the main cylinder 4 is reduced in pressure, so the plunger 3 is moved back by the resin pressure injected into the injection cylinder 2. Accordingly, the slider 11b connected to the plunger 3 also retreats along the stator 11a.

Then, a level corresponding to the amount of retraction of the slider 11b is transmitted via the input/output interface 12.
It is added to CPU13, and CPU13 is this slider 1.
The amount of retraction of the plunger 3 (in other words, the volume of the injection cylinder 2) is determined by the level of 1b, and when this reaches the set value, the plasticizing operation is terminated.
Perform the injection operation.

By the way, in this embodiment, the CPU 13 corrects the above 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 stator 11
Positions P ₁ , P ₂ , and P ₃ of a are predetermined as measurement points, and the CPU 13 performs a correction operation for the set value every time the slider 11b passes the measurement points P ₁ , P ₂ , and P ₃ . Execute.

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
The value is substituted into the calculation formula for determining the correction coefficient in the memory 16, or the correction coefficient is read out from the correction coefficient table in the memory 16 using the value, and the correction coefficient is determined in advance according to the volume of the cavity 2. A corrected setting value is calculated by multiplying the setting value by the correction coefficient.

Then, 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 this embodiment, in addition to the measurement point _P1 , the CPU 13
At measurement points P ₂ and P ₃ , the setting value correction operation is performed in the same manner as above, and the timing for ending the plasticizing operation is determined by using the setting value calculated at measurement point P ₃ as the final setting value. However, this is to deal with temperature fluctuations and pressure fluctuations within the injection cylinder 2 that may occur while the plunger 3 is retracting, and the greater the number of measurement points, the better the measurement accuracy will be.

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 set value at the measurement point _P3 .

First, when the digital valve 18 is turned on, pressure oil supplied from the pump 19 via the flow control valve 20 is transferred to the pressure chamber 1 of the hydraulic cylinder 10.
Since it is supplied to 0b, the piston rod 10
a pulls down the valve body 9 against the spring 10c, and the convex conical portion 9a of the valve body 9 is connected to the flow path 5.
Securely close the valve seat 5d inside a.

Further, when the digital valve 17 is turned on, the pressure oil supplied from the pump 19 via the flow rate control valve 20 is transferred to the pressure chamber 4 of the main cylinder 4.
a, 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 inside the injection cylinder 2,
The resin stored in the injection cylinder 2 is transferred to the nozzle 2a.
and is injected into the cavity 1e.

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 configuration of the valve body 9 and the valve seat 5d, the pressure inside the injection cylinder 2 does not increase as much. The fastening force between the valve body 9 and the valve seat 5d increases, and the flow path 5
Backflow of resin through a is reliably prevented.

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

Then, the movable mold 1d is moved to take out the product in the cavity 1e.

In addition, although the example in which three measurement points were prepared was shown above, 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 set value is calculated by multiplying the set value by for example,
The weight of the resin to be injected into the cavity 1e is prepared as a set value, and the temperature and temperature are stored in the memory 16.
An arithmetic formula for calculating weight based on pressure and volume and a weight table that is addressed based on temperature, pressure, and volume are prepared, and the position sensor 11 The weight of the resin supplied into the injection cylinder 2 may be calculated by applying the outputs of the pressure sensor 14 and the temperature sensor 15, and the plasticizing operation may be terminated when the calculated value reaches a set value.

Furthermore, although the above example shows an example in which the spring 10c is disposed within 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 in the plasticizing cylinder 5, the spring 10c is 10c is not necessarily necessary.

Further, although the above example shows that 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 is controlled by the pressure chamber 4a.
The pressure sensor 14 is not necessarily located within the injection cylinder 2, since it is also predictable with a low pressure of .

Furthermore, in the above example, the plunger 3 only functions to push the resin inside the injection cylinder 2, but if the plunger is configured with a screw,
It may also have a plasticizing effect.

〔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.

Also, in the case of the present invention, instead of preventing resin backflow by a backflowing ring which is activated passively by applying injection pressure, a resin control valve which is activated actively upon completion of final metering is used. Since the injection pressure is applied after the flow path is securely closed, it is possible to reliably prevent the resin from flowing back due to the injection pressure, and accurately inject the accurately measured amount of resin into the cavity. becomes possible.

[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. 1... Mold device, 2... Injection cylinder, 3...
Plunger, 4... Main cylinder, 5... Plasticizing cylinder, 5a... Channel, 5d... Valve seat, 9...
... Valve body, 10 ... Hydraulic cylinder, 11 ...
Position sensor, 13...CPU, 14...Pressure sensor, 15...Temperature sensor, 16...Memory, 1
7, 18...Digital valve, _P1 , _P2 , _P3 ...
measurement point.

Claims (1)

[Scope of Claims] 1. A plasticizing cylinder having a plasticizing screw inside and an injection cylinder having a plunger inside are independently provided, and the resin plasticized in the plasticizing cylinder and supplied to the injection cylinder is transferred to the plunger. In an injection device that injects pressure oil from a nozzle by applying pressure oil to a main cylinder arranged on the axis of a main cylinder, the resin control valve opens and closes a flow path from the plasticizing cylinder to the injection cylinder; a position sensor that detects the amount of retraction; and a temperature sensor that detects the temperature of the plasticized resin in the injection cylinder, and is determined based on the detection output of the position sensor and the detection output of the temperature sensor. At the right time,
A metering injection device for thermoplastic resin, characterized in that when the resin control valve is closed, hydraulic pressure is applied to the main cylinder. 2. 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. 3. The metering and injection device for thermoplastic resin according to claim 2, characterized in that the detection output of the temperature sensor is received every time the detection output of the position sensor indicates a value at a predetermined measurement point. A measuring injection device for thermoplastic resin.