JPH1110694A - Injection molding method and device for the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a product having excellent molding property by a method wherein correct control is effected so as to stop the execution of an injection molding process while predicting that the product will be defective or so as not to generate defective molding. SOLUTION: A device for injection molding is constituted so that a screw 13, provided in an injection cylinder 11, is rotated to send resin to the fore part of the injection cylinder 11 and weight the resin, then, the resin is injected into a mold 1 through a nozzle 12 at the tip end of the injection cylinder 11. In this case, the pressure of the resin in the nozzle 12 is measured at a measuring step to calculate a viscosity based on the measured pressure and a compare the calculated viscosity with a reference viscosity whereby the judging of good or bad of a molded form or the control of a molding condition is effected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection molding method and apparatus capable of calculating the viscosity of a resin in a measuring step and accurately determining a molded article defect or controlling molding conditions.

[0002]

2. Description of the Related Art As a conventional injection molding method, there is a method disclosed in Japanese Patent Application Laid-Open No. Hei 5-329864 as shown in FIG.

In this injection molding method, a pressure sensor 3 is provided at a nozzle 12 at a position just before entering a mold 1 of an injection molding machine, and the pressure of the resin is measured by the pressure sensor 3, and the viscosity is calculated from the pressure. Calculated based on theoretical formula. Then, based on the viscosity calculated in this way, the estimation determination of a molded article defect is performed.

[0004] In general, injection molding resins may cause molding defects due to the quality of the dried state and the variation in physical properties between production lots. However, since the viscosity of the molded product can be examined as described above, the occurrence of molding failure can be estimated and determined.

[0005]

However, in the above-mentioned conventional example, a pressure sensor is provided in the nozzle 12 to measure the pressure of the resin in the injection molding process. Therefore, a molded article defect is estimated and determined on the basis of the measured pressure. Therefore, in the case of molding this shot, there is a high possibility that a defective article is molded.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to stop the execution of the injection molding process by estimating a defect in advance and to prevent the defect from occurring. It is an object of the present invention to provide an injection molding method and apparatus capable of obtaining a product having good moldability by performing appropriate control as described above.

[0007]

According to the first aspect of the present invention, a screw 13 provided in an injection cylinder 11 is rotated to send a resin to a front portion of the injection cylinder 11 and measure the resin. In the injection molding method of injecting and filling a resin into the mold 1 from a nozzle 12 at the tip of the injection cylinder 11, the pressure of the resin melted in the injection cylinder 11 is measured in a measuring step, and the viscosity is determined based on the pressure. Is calculated, and the calculated viscosity is compared with the reference viscosity to determine the quality of the molded product or to control the molding conditions.

According to such an injection molding method, by examining the resin in the measuring step, judgment or control corresponding to the state of the resin is performed so that a non-defective product is accurately molded in the injection step. be able to.

According to a second aspect of the present invention, in the first aspect of the invention, a hydraulic cylinder for moving the screw 13 is provided.
The hydraulic pressure in the cylinder 10 is measured when the screw 13 moves, is measured, and the hydraulic pressure is used as the pressure of the resin melted in the injection cylinder 11.

According to such an injection molding method, the pressure of the resin is easily measured by measuring the oil pressure in the hydraulic cylinder 10. That is, the oil pressure measured here is the pressure generated when the injection cylinder 11 moves, and corresponds to the pressure difference between the resin before and after the check ring 2. In this case, since the pressure sensor 3 is provided at one position in the hydraulic cylinder 11, the pressure sensor 3 can be easily installed, and the pressure can be easily measured.

According to a third aspect of the present invention, in the first aspect, the resin is injected into the injection cylinder 11 in the measuring step.
Check ring 2 passing through the front part is screw 13
At the front end, two or more pressure sensors 3 are provided on the injection cylinder 11 at intervals in the screw movement direction, and the pressure of the resin before and after the check ring 2 is measured by these pressure sensors 3. doing.

According to such an injection molding method, the pressure before and after the check ring 2 is measured using at least two pressure sensors 3. Then, the viscosity of the resin can be calculated from the flow rate of the resin passing through the check ring 2 and the pressure difference before and after the check ring 2.

According to a fourth aspect of the present invention, in the first aspect, the resin is injected into the injection cylinder 11 in the measuring step.
Check ring 2 passing through the front part is screw 13
A pressure sensor 3 is provided on each of the screws 13 at positions at the front and rear of the check ring 2 before and after the check ring 2 to measure the pressure of the resin.

According to such an injection molding method, the viscosity of the resin can be calculated from the flow rate of the resin passing through the check ring 2 and the pressure difference before and after the check ring 2. In this case, the pressure before and after the check ring 2 is measured using the two pressure sensors 3 without selecting the position of the screw 13 in the injection cylinder 11.

[0015] The invention according to claim 5 is the invention according to claims 1 to 4.
In the invention according to any one of the above, the temperature of the resin is measured together with the pressure, and based on the viscosity calculated from the temperature and the pressure, the quality of the molded product is determined or the molding conditions are controlled. ing.

According to such an injection molding method, the flow rate of the resin can be accurately obtained from the relational expression between the temperature, the pressure and the flow rate, so that a highly accurate viscosity can be obtained. In other words, when calculating the viscosity from the pressure of the resin, the flow rate is necessary, but if this flow rate is obtained from the movement of the screw 13, the actual flow rate of the resin is obtained due to the effects of compression and stagnation of the resin. The fear of not being done is avoided.

The invention according to claim 6 is the invention according to claims 1 to 5
In the invention according to any one of the above, the pressure is measured at a predetermined time within one molding shot, and the viscosity is calculated from this pressure.

According to such an injection molding method, it is possible to easily determine the quality of a molded product or to control molding conditions based on the viscosity calculated at one point in one molding shot.

The invention according to claim 7 is the first to fifth aspects.
In the invention according to any one of the above, an average value of the viscosity within a predetermined time interval is obtained, and the average value is set as the calculated viscosity.

According to such an injection molding method, since it is based on the deviation between the average value of the viscosity within a predetermined time interval and the reference viscosity, erroneous determination or control can be performed according to the abnormal value at the temporary point. Sex is decreasing.

[0021] The invention according to claim 8 is the invention according to claims 1 to 7.
In the invention according to any one of the above, the deviation in each molding shot of the viscosity and the reference viscosity is obtained a ratio exceeding a certain range, characterized by automatically stopping injection molding when this ratio exceeds the reference excess rate Make up.

According to such an injection molding method, when a large number of defective products are produced beyond a certain range, the injection molding is automatically stopped.

The ninth aspect of the present invention provides the first to seventh aspects.
In the invention described in any one of the above, when the calculated viscosity is higher than the reference viscosity, the injection molding pressure is controlled to be increased.

According to such an injection molding method, the molding pressure is controlled so that a good product is molded according to the viscosity without greatly changing the injection molding speed.

The invention according to claim 10 is the invention according to claims 1 to 7
In the invention described in any one of the above, when the calculated viscosity is higher than the reference viscosity, the injection speed is controlled to be increased.

According to such an injection molding method, the injection speed is controlled so that a good product is molded in accordance with the viscosity.

The invention according to claim 11 is the invention according to claims 1 to 7
In the invention described in any one of the above, when the calculated viscosity deviates higher than the reference viscosity, control is performed so as to increase the holding pressure.

According to such an injection molding method, the holding pressure is controlled so that a good product is molded in accordance with the viscosity.

[0029] The invention described in claim 12 is the invention according to claims 1 to 7.
In the invention described in any one of the above, when the calculated viscosity is higher than the reference viscosity, the pressure is controlled so as to increase the dwell time.

According to such an injection molding method, the dwell time is controlled so that a good product is molded in accordance with the viscosity.

The invention described in claim 13 is the invention according to claims 1 to 7
In the invention described in any one of the above, when the calculated viscosity deviates higher than the reference viscosity, control is performed so as to increase the back pressure.

According to such an injection molding method, the back pressure is controlled so that a good product is molded according to the viscosity.

[0033] The invention according to claim 14 is the invention according to claims 1 to 7.
In the invention described in any one of the above, when the calculated viscosity is higher than the reference viscosity, the screw rotation speed is controlled to be increased.

According to such an injection molding method, the screw rotation speed is controlled so that a good product is molded in accordance with the viscosity.

The invention according to claim 15 is the invention according to claims 1 to 7
In the invention according to any one of the above, a moving average value of the viscosity in each molding shot of the determined viscosity is calculated, and the injection molding pressure, the injection speed, the holding pressure, or the holding pressure is calculated in consideration of the increase or decrease of the moving average value. It is characterized by controlling the pressure time.

According to such an injection molding method, since the control is performed based on the amount of increase or decrease of the moving average value, the tendency of the viscosity change is accurately predicted, and the control corresponding to the viscosity change due to long-term pulsation is performed. be able to.

The invention of claim 16 is characterized in that, in the invention of claim 15, control is performed such that the temperature of the injection cylinder 11 is increased when the moving average value increases.

According to such an injection molding method, injection molding is performed by controlling the temperature of the injection cylinder 11 so as to be suitable for the calculated viscosity and not to cause a defect. In this case, since the temperature of the injection cylinder 11 is controlled,
It can directly affect the viscosity of the resin, and can control with good response.

A seventeenth aspect of the present invention is characterized in that, in the invention of the fifteenth aspect, the mold temperature is controlled to increase when the moving average value increases.

According to such an injection molding method, injection molding is performed by controlling the mold temperature so as to be suitable for the calculated viscosity and not to cause a defect. In this case, the resin which is easily thermally degraded is not excessively heated in the injection cylinder 11.

The invention according to claim 18 is characterized in that the injection cylinder 11
A pressure sensor 3 for measuring the pressure of the resin melted in the measuring step, a calculation circuit 4 for calculating the viscosity from the pressure measured by the pressure sensor 3, and comparing the calculated viscosity with a reference viscosity, And a determination control circuit 5 for determining the quality of the molded product or controlling the molding conditions.

According to such an injection molding apparatus, by examining the resin in the measuring step, judgment or control corresponding to the state of the resin is performed so that a non-defective product is accurately molded in the injection step. be able to.

According to a nineteenth aspect, in the eighteenth aspect, a temperature sensor 6 is provided in parallel with the pressure sensor 3, and the flow rate of the resin is calculated from the temperature measured by the temperature sensor 6. The arithmetic circuit 4 is configured to calculate the viscosity from the flow rate and the pressure measured by the pressure sensor 3.

According to such an injection molding apparatus, since the flow rate of the resin is accurately calculated from the relational expression between the temperature, the pressure and the flow rate, a highly accurate viscosity can be obtained.

[0045]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the accompanying drawings.

With reference to FIGS. 1 to 4, one injection molding method and one injection molding apparatus of this embodiment will be described below.

FIG. 1 is a cross-sectional view schematically showing the overall configuration of the injection molding apparatus according to this embodiment. FIG. 2 is an enlarged cross-sectional view showing the periphery of the check ring 2 of the injection molding apparatus. FIG. 2 is a partially broken front view showing a pressure sensor 3 provided on a hydraulic cylinder 10 of the injection molding apparatus. FIG. 4 is a block diagram showing a configuration of a circuit for processing the pressure detected by the pressure sensor 3 in the injection molding apparatus.

As shown in FIG. 1, this injection molding apparatus
The injection cylinder 11 has a screw 13 for filling a resin as a molding material into the mold 1 from a nozzle 12. The resin is supplied from the hopper 14 into the injection cylinder 11, and a heater is provided on the outer periphery of the injection cylinder 11.
By 15, it is configured to be melted by heating and filled in the mold 1.

The rear end of the screw 13 is provided with a piston 13e.
And housed in the hydraulic cylinder 10. That is, the screw 13 is formed to be movable in the front-rear direction (the left-right direction in the drawing) by hydraulic pressure. The screw 13 is configured to be driven to rotate by the motor 9.

In particular, in this injection molding apparatus, the hydraulic cylinder 10 is provided with a pressure sensor 3 for measuring the internal oil pressure.
Is provided.

As shown in FIG.
Is provided with a check ring 2 at its tip. That is, as shown in the figure, the tip of the screw 13 is formed as a cross section 13a, and a narrow section 13b is provided slightly behind the cross section 13a. A disc-shaped check ring 2 penetrating the center is slidably fitted in the constricted portion 13b in the front-rear direction. A plurality of through holes 2a through which the resin passes are formed as check ring slits at appropriate intervals in the outer peripheral portion of the check ring 2. A locking flange 13c is provided at the rear end of the constricted portion 13b so that the check ring 2 does not slide backward. The rear portion of the locking flange 13c has a helical screw. Screw body 13d.

That is, since the check ring 2 is configured as described above, in the measuring step, the resin passes through the passage hole 2a.
, And can be measured by passing through the front part of the injection cylinder 11. In the injection step, the check ring 2 comes into contact with the locking flange 13c and the passage hole 2a is closed, so that the measured resin is filled into the mold 1 by moving the screw 13. You can do it.

As shown in FIG. 3, the above-described pressure sensor 3
Is provided with a diaphragm 3a at the tip of the tubular body, and transmits the pressure received by the diaphragm 3a to the strain gauge by the liquid in the capillary 3b provided with the tip connected to the diaphragm 3a inside the body. It is configured to detect. Further, a metal push rod may be provided in place of such a capillary 3b, and the push rod may be formed so as to transmit pressure to the strain gauge.

According to the injection molding apparatus described above, in the measuring step, the screw 13 is rotated by the motor 9, and the molding material stored in the hopper 14 is rotated by the rotation of the screw 13 and the inner wall surface of the injection cylinder 11. And passes through the through hole 2a of the check ring 2 and is fed into the front of the injection cylinder 11 and the nozzle 12. The arrows in FIG. 2 indicate such a resin flow.

In such a measuring step, the pressure (oil pressure) in the hydraulic cylinder 10 is measured by the pressure sensor 3 provided in the hydraulic cylinder 10, and this pressure is taken into the arithmetic circuit 4 to perform the following processing. I'm trying to do it. The pressure P measured here is the pressure generated when the injection cylinder 11 moves, and corresponds to the pressure difference between the resin before and after the check ring 2.

That is, as shown in FIG. 4, the position signal of the screw 13 at this time as well as the pressure in the hydraulic cylinder 10 is taken into the arithmetic circuit 4 at the same time. The flow rate of the resin flowing through the passage hole 2a of the check ring 2 can be obtained from the position signal of the screw 13. Further, since the cross-sectional shape of the passage hole 2a is circular, the viscosity of the resin flowing through the runner 17 is calculated by an arithmetic circuit in the same manner as the viscosity measurement by the capillary rheometer, using the following well-known viscosity relational expression (1). 4 can be calculated.

Η = (πR ⁴ · P) / (((3α + 1) / α) · Q · 2L) (1) In this equation, η is the viscosity, R is the radius of the passage hole 2a, and P is The pressure in the hydraulic cylinder 10, α is a constant determined by the resin, Q is the flow rate, and L is the length of the passage hole 2a. The relational expression (1) is shown in "Plastic molding" by Shosaburo Yamaguchi.

As described above, the viscosity calculated by the arithmetic circuit 4 is sent to the discrimination control circuit 5. On the other hand, the discriminator 5a in the discrimination control circuit 5 stores a reference viscosity previously obtained by an experiment or the like. The reference viscosity is determined based on manufacturing experimental data and the like, for example, as a viscosity range of a resin that does not produce molding defects. If the calculated viscosity is out of the reference viscosity, a failure signal is sent to a product take-out machine, and the take-out machine is controlled so as to take out the product determined to be defective as a non-defective product. . Alternatively, a deviation from the reference viscosity is sent to the control circuit 5b as a deviation signal, and the control circuit 5b sends a signal for controlling molding conditions to the control unit of the injection molding apparatus based on the deviation signal. That is, the control circuit 5b calculates a control gain corresponding to the deviation signal and controls the target molding condition parameter to an appropriate value.

From the measurement of the pressure to the calculation and comparison of the resin viscosity, the determination of defects or the control of the molding condition parameters,
It is performed before the injection process. Examples of the molding condition parameters include an injection molding pressure, an injection speed, a holding pressure, a holding time, a back pressure, and a screw rotation speed.

According to the injection molding apparatus or the injection molding method configured as described above, the resin in the measuring step can be checked, so that the determination or control corresponding to the state of the resin can be performed for the injection step. The molding can be performed accurately so that non-defective products are molded, and molding with a high non-defective product ratio can be performed. Alternatively, when it is determined that the resin becomes defective, it is possible to control so that the next injection step is not performed, and by such control, it is possible to prevent wasteful use of resin as a raw material.

Referring to FIG. 5, an injection molding apparatus and an injection molding method different from those described above will be described below. This figure is an enlarged sectional view showing the periphery of the check ring 2 of the injection molding apparatus.

As shown in FIG. 5, in this injection molding apparatus, two pressure sensors 3 are provided in the injection cylinder 11 in particular, and are provided at intervals slightly wider than the thickness of the check ring 2 in the screw moving direction. The pressure sensor 3 measures the pressure of the resin before and after the check ring 2.

That is, in the measuring step of the injection molding, the screw 13 retreats while rotating as the resin is charged into the front part of the injection cylinder 11 as shown by the arrow in the figure. At this time, the resin is filled into the front part of the injection cylinder 11 by passing the resin forward through the passage hole 2a of the check ring 2. Then, the check ring 2 measures the pressure at a certain timing between the two pressure sensors 3 as shown in FIG.

Checklin measured as described above
Pressure on the rear side (upstream side) of ₁And the front side (below
Pressure on the downstream side_TwoAnd P = P₁−P_TwoAs mentioned above
Calculate the resin viscosity using the equation (1)
Can be.

In this case, the viscosity of the resin can be calculated from the flow rate of the resin passing through the check ring 2 and the pressure difference before and after the check ring 2. That is, at least two pressure sensors 3 are required as compared with the case where the hydraulic pressure in the hydraulic cylinder 10 is measured. However, the pressure of the resin is directly measured to accurately calculate the viscosity of the resin.

In this case, it is necessary to measure the pressure at a timing when the check ring 2 is located between the two pressure sensors 3, and the timing is limited. The pressure can be measured at 13 positions. That is, the pressure sensor 3
Are provided at many intervals, and the pressure before and after the check ring 2 is measured by any two arbitrary pressure sensors 3.

Referring to FIG. 6, an injection molding apparatus and an injection molding method which are further different from those described above will be described below. This figure is an enlarged sectional view showing the periphery of the check ring 2 of the injection molding apparatus.

As shown in FIG. 6, in this injection molding apparatus, the pressure sensor 3 is provided on each of the screws 13 at positions before and after the check ring 2, that is, the constricted portion 13b. That is, in this injection molding apparatus,
The position of the pressure sensor 3 shown in FIG.
Changed to screw 13.

According to the injection molding method using such an apparatus, the pressure difference between before and after the check ring 2 can be similarly obtained by the pressure sensor 3 provided on the screw 13 and the viscosity of the resin can be calculated. . Moreover, in this case, only two pressure sensors 3 are used and the injection cylinder
The pressure before and after the check ring 2 can be measured at an arbitrary timing without selecting the position of the screw 13 in the inside 11.

Referring to FIG. 7, an injection molding apparatus and an injection molding method which are further different from those described above will be described below. This figure is an enlarged sectional view showing the periphery of the check ring 2 of the injection molding apparatus.

As shown in FIG. 7, in this injection molding apparatus, the temperature of the resin is measured together with the pressure, and based on the temperature and the viscosity calculated from the pressure of the resin, the quality of the molded product is determined or the molding conditions are determined. Is controlled.

In this case, in particular, two pressure sensors 3 are provided on the injection cylinder 11 at intervals slightly wider than the thickness of the check ring 2 in the moving direction of the screw 13. In addition, the temperature sensor 6 and the injection cylinder are arranged at substantially the same position with respect to the pressure sensor 3 and the screw 13 moving direction.
11 is provided two. The pressure sensor 3 or the temperature sensor 6 may be provided on the screw 13 side. That is, one or both of the pressure sensor 3 and the temperature sensor 6 are connected to the injection cylinder 11.
Alternatively, it is provided on the screw 13.

The arithmetic circuit 4 is configured to calculate the flow rate of the resin from the temperature measured by the temperature sensor 6 and calculate the viscosity from the calculated flow rate and the pressure measured by the pressure sensor 3. It is.

In this case, in order to obtain the flow rate from the measured resin temperature, the following well-known equation (2) for the resin flow rate can be used. Note that this relational expression (2)
Is shown in "Plastic Molding" by Shozaburo Yamaguchi in the same manner as in the above relational expression of viscosity (1).

Q = Q ₀ · em ^(t−t ₀ ⁾ · P ⁿ (2) In this equation, Q is a flow rate, Q ₀ is a flow rate at a temperature t ₀ , m and n are constants, and t is a resin. Temperature.

The above Q ₀ , m, and n are numerical values obtained in advance through experiments and the like. As described above,
Since the flow rate of the resin is accurately calculated from the relationship between the temperature, the pressure, and the flow rate, a highly accurate viscosity can be obtained. In other words, when the flow rate required for calculating the viscosity from the pressure of the resin is obtained from the movement of the screw 13, the error between the flow rate at the position where the actual pressure is measured and the flow rate at the position where the actual pressure is measured due to the effects of the compression and stagnation of the resin. Thus, it is possible to avoid the possibility that the accurate viscosity cannot be calculated.

With reference to FIG. 8 or FIG. 9, a specific example of judging the quality of a molded product or controlling molding conditions based on the calculated viscosity will be described below.

FIG. 8 is a graph showing an example of a change in the pressure measured by the pressure sensor 3 in one molding shot. FIG. 9 is a graph showing an example of a change between molding shots of the viscosity calculated based on the measured pressure.

As shown in FIG. 8, the change in pressure after receiving the signal of mold closing or injection start is as follows: during a period of about 25 seconds corresponding to the first injection step, a maximum of 120 kg / cm
A curve having ^two peaks is drawn, and a curve is maintained such that a pressure of about 50 kg / cm ² is maintained for about 10 seconds corresponding to the subsequent measuring step.

In the case of this molding, one example is to measure a pressure showing a substantially constant value at a predetermined time after a predetermined time of about 30 seconds has elapsed after receiving a signal of mold closing or injection start. The viscosity can be calculated, and the quality of the molded product can be determined or the molding conditions can be controlled based on the deviation between the viscosity and the reference viscosity.

According to such a method, determination or control is performed based on the calculated viscosity at a point in time, so that the number of pressure measurements and the number of times of calculation of the viscosity are reduced, and the quality of the molded product or the control of the molding conditions is simplified. Done in

As shown in FIG. 8, the average value of the viscosity within a predetermined time interval within one molding shot is obtained.
It is also one of the preferable methods to determine the quality of the molded product or control the molding conditions based on the deviation between the average value and the reference viscosity. In the example shown in this figure, the pressure is continuously measured at a predetermined time interval of about 8 seconds after 27 seconds from receiving the signal of mold closing or injection start, and the viscosity corresponding to the continuous pressure is measured. The average is calculated.

According to such a method, since it is based on the deviation between the average value of the viscosity within the predetermined time interval and the reference viscosity, there is a possibility that erroneous determination or control may be performed according to the abnormal value at the temporary point. is decreasing.

Further, the pressure is measured at each molding shot, and the injection molding is automatically stopped when the ratio of the deviation between the viscosity calculated from each pressure and the reference viscosity exceeds a certain range exceeds the reference excess ratio. This is one of the preferable control methods.

According to such a method, when the viscosity of the resin continuously deviates from a certain standard and a state where a large number of defective products are manufactured, the injection molding is automatically stopped. It is possible to prevent continuous production of many good products.

Hereinafter, the control of the molding parameters will be described more specifically. One of the controls is to increase the injection molding pressure when the calculated viscosity is higher than the reference viscosity, or to perform the injection molding when the calculated viscosity is lower than the reference viscosity. The idea is to reduce the pressure.

According to such control, the molding pressure is controlled so that a good product is molded in accordance with the viscosity without greatly changing the injection molding speed. For example, if burn defects are likely to occur when the injection speed is increased, the injection speed can be reduced to a low injection speed that does not cause burn defects, and the moldability can be improved by increasing the injection molding pressure.

As another example of control, when the calculated viscosity is higher than the reference viscosity, the injection speed is increased, or the calculated viscosity is lower than the reference viscosity. In such a case, control can be performed to reduce the injection speed.

According to such control, the injection speed is controlled so that a good product is molded in accordance with the viscosity.
That is, when the air trap or the weld line is easily conspicuous in the molded product, the injection speed can be increased at a low pressure, for example.

Further, as another example of control, when the calculated viscosity deviates higher than the reference viscosity, the holding pressure is increased, or the calculated viscosity deviates lower than the reference viscosity. If so, control can be performed to reduce the holding pressure.

According to such control, the holding pressure is controlled so that a good product is molded in accordance with the viscosity. In other words, when the viscosity is high and the sink failure is likely to occur, the holding pressure is increased to prevent the sink failure.
Such control of the holding pressure is particularly effectively performed when molding a resin having a relatively short cooling time.

Further, as another control, when the calculated viscosity is higher than the reference viscosity, the dwell time is increased or the calculated viscosity is lower than the reference viscosity. In such a case, control can be performed to reduce the dwell time.

According to such control, the dwell time is controlled so that a good product is formed in accordance with the viscosity.
In other words, when the viscosity is high and sink marks are likely to occur, the dwell time is increased to prevent sink marks from occurring.

Further, as another control, when the calculated viscosity is higher than the reference viscosity, the back pressure or the screw rotation speed is increased, or the calculated viscosity is lower than the reference viscosity. In the case where it is broken, it can be controlled to reduce the back pressure or the screw rotation speed.

According to such an injection molding method, the back pressure or the number of rotations of the screw is controlled and the kneading state of the resin is appropriately adjusted so that a good product is molded in accordance with the viscosity.

Further, as shown in FIG. 9, the viscosity of the resin usually varies between molding shots and changes so as to pulsate for a long time. In this figure, a line graph indicated by a solid line plots the viscosity at each molding shot.
The broken line shows a curve that smoothly connects the moving average values of the viscosity.

Since such a moving average value shows the tendency of the increase and decrease of the viscosity, the injection molding pressure, the injection speed, the holding pressure, the holding time, the back pressure or the back pressure are based on the increasing and decreasing amounts of the moving average value. By controlling a molding parameter such as a screw rotation speed, it is intended to realize a control corresponding to a change in viscosity of a resin due to a long-term pulsation.

For example, taking the example in FIG. 9 as an example, when the moving average value exceeds 68 Pa · S and the increase exceeds 0.5 Pa · S, control is performed when the resin viscosity is too high. To On the contrary, 67 Pa · S
When the weight loss exceeds 0.5 Pa · S,
The control is performed when the resin viscosity is too low. By performing such control, the arrow A in FIG.
Alternatively, as shown by B, molding can be performed without departing from the non-defective range.

According to such a method, since the control is performed based on the amount of increase or decrease of the moving average value, the tendency of the change in viscosity can be accurately predicted, and control corresponding to the change in viscosity due to long-term pulsation can be performed. There is an advantage that molding defects caused by the pulsation can be reduced.

In this case, control is performed so as to increase the temperature of the injection cylinder 11 when the moving average value increases, or to decrease the temperature of the injection cylinder 11 when the moving average value decreases. Injection molding can be performed so as to be suitable for the calculated viscosity and not cause a defect. In this case, since the temperature of the injection cylinder 11 is controlled, it is possible to directly influence the viscosity of the resin, and control with good response can be performed.

Also, instead of the temperature of the injection cylinder 11, the mold temperature is controlled to increase when the moving average value increases, or to decrease the mold temperature when the moving average value decreases. You may. In this case, the resin which is susceptible to thermal degradation is not excessively heated in the cylinder 11,
It is particularly suitable for molding a resin which is easily deteriorated by heat.

[0102]

According to the first aspect of the invention, it is possible to check the resin in the measuring step, so that the discrimination or control corresponding to the state of the resin is performed so that a good product is formed in the injection step. The molding can be performed accurately and the molding with a high yield can be performed. Alternatively, when it is determined that a failure occurs, control can be performed so that the next injection step is not performed, and such control can prevent wasteful use of resin.

According to the second aspect of the present invention, since the pressure sensor is provided at one position in the hydraulic cylinder, the pressure sensor can be easily installed and the pressure can be easily measured.

According to the third aspect of the invention, the viscosity of the resin can be calculated from the flow rate of the resin passing through the check ring and the pressure difference before and after the check ring. In this case, in order to determine the pressure difference before and after the check ring at different screw positions, a large number of pressure sensors are provided at intervals and the pressure before and after the check ring is measured by any two pressure sensors. Can be.

According to the fourth aspect of the present invention, since the pressure sensor is provided on the screw, the pressure before and after the check ring can be obtained using only two pressure sensors regardless of the position of the screw in the injection cylinder. Can be measured. Since only two pressure sensors are used,
With a simple configuration, the pressure difference before and after the check ring can be measured with the screw position as an arbitrary position.

According to the fifth aspect of the present invention, an accurate flow rate can be obtained from the relational expression between temperature, pressure and flow rate, and a highly accurate viscosity can be obtained based on the accurate flow rate value. Therefore, the quality of the molded product can be determined without fail, and the molding conditions can be controlled appropriately so that molding defects do not occur.

According to the sixth aspect of the present invention, the quality of the molded product is determined or the molding conditions are controlled based on the viscosity calculated at the temporary point. Therefore, it is not necessary to calculate and use a large number of viscosities frequently. , Simple determination or control can be performed.

According to the seventh aspect of the present invention, since it is based on the deviation between the average value of the viscosity within a predetermined time and the reference viscosity, there is a possibility that erroneous determination or control may be performed according to an abnormal value at a temporary point. Is reduced, and highly accurate determination or control can be performed.

According to the eighth aspect of the invention, it is possible to prevent a large number of defective products from being manufactured continuously. According to the ninth aspect of the present invention, the injection conditions can be controlled so that a good product is molded in accordance with the viscosity without greatly changing the injection molding speed. For example, if burn defects are likely to occur when the injection speed is increased, the injection speed can be reduced to a low injection speed that does not cause burn defects, and the moldability can be improved by increasing the injection molding pressure.

According to the tenth aspect of the present invention, the injection conditions can be controlled so that a good product is molded in accordance with the viscosity without greatly changing the molding pressure. For example,
When an air trap or a weld line or the like is conspicuous in a molded product, it is possible to cope with the condition of low pressure in which a defect of the air trap or the weld line is unlikely to occur and increase the injection speed.

According to the eleventh aspect of the present invention, since the holding pressure is controlled in accordance with the viscosity, sink marks are less likely to occur. In the case of molding a resin having a relatively short cooling time, such holding pressure control is effectively performed.

According to the twelfth aspect of the present invention, since the dwell time is controlled in accordance with the viscosity, sink marks are less likely to occur.

According to the thirteenth aspect, by controlling the back pressure in accordance with the viscosity, the kneading state can be set to a state suitable for molding a good product.

According to the fourteenth aspect of the present invention, the kneading state can be changed to a state suitable for molding a good product by controlling the screw rotation speed in accordance with the viscosity.

According to the fifteenth aspect of the present invention, the tendency of the change in the viscosity is accurately predicted, and the molding conditions are controlled in accordance with the tendency of the change. This is prevented from occurring.

According to the sixteenth aspect of the present invention, the injection molding is performed by controlling the temperature of the injection cylinder so as to be suitable for the calculated viscosity and to prevent occurrence of defects. In this case, in particular, since the temperature of the injection cylinder is controlled, the viscosity of the resin can be directly affected, and control with good response can be performed.

According to the seventeenth aspect of the present invention, injection molding is performed by controlling the temperature of the mold so as to conform to the calculated viscosity and to prevent occurrence of defects. In this case, since the resin is not heated excessively in the injection cylinder, it is particularly suitable for molding a resin which is easily deteriorated by heat.

According to the eighteenth aspect of the present invention, it is possible to check the resin in the measuring step, so that the discrimination or control corresponding to the state of the resin is properly performed so that a good product is formed in the injection step. The molding can be performed with a high yield rate. Alternatively, when it is determined that a failure occurs, control can be performed so that the next injection step is not performed, and such control can prevent wasteful use of resin.

According to the nineteenth aspect, the flow rate is calculated from the relational expression between the temperature, the pressure and the flow rate of the resin, and the viscosity is calculated based on the accurate flow rate. And the accuracy of discrimination or control is improved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically showing an overall configuration of one injection molding apparatus according to an embodiment of the present invention.

FIG. 2 is an enlarged cross-sectional view showing a periphery of a check ring in the above injection molding apparatus.

FIG. 3 is a partially broken front view showing a pressure sensor provided in the mold of the above.

FIG. 4 is a block diagram showing a configuration of a circuit for processing a detected pressure in the above injection molding apparatus.

FIG. 5 is an enlarged cross-sectional view showing a periphery of a check ring of one injection molding apparatus according to the embodiment of the present invention.

FIG. 6 is an enlarged cross-sectional view showing a periphery of a check ring of one injection molding apparatus according to the embodiment of the present invention.

FIG. 7 is an enlarged cross-sectional view showing a periphery of a check ring of one injection molding apparatus according to the embodiment of the present invention.

FIG. 8 is a graph illustrating an example of a change in a pressure measured by a pressure sensor in one injection molding apparatus according to an embodiment of the present invention in one molding shot.

FIG. 9 is a graph showing an example of a change between molding shots of a viscosity calculated based on a pressure measured by a pressure sensor in one injection molding apparatus according to an embodiment of the present invention.

FIG. 10 is a cross-sectional view illustrating a main part of a conventional injection molding apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Mold 2 Check ring 2a Passing hole 3 Pressure sensor 3a Diaphragm 3b Capillary 4 Arithmetic circuit 5 Discrimination control circuit 5a Discriminator 5b Control circuit 6 Temperature sensor 9 Motor 10 Hydraulic cylinder 11 Injection cylinder 12 Nozzle 13 Screw 13a Cross section 13b Constriction Part 13c locking flange 13d screw body 13e piston 14 hopper 15 heater

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[Procedure amendment]

[Submission date] July 25, 1997

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0010

[Correction method] Change

[Correction contents]

According to such an injection molding method, the pressure of the resin is easily measured by measuring the oil pressure in the hydraulic cylinder 10. That is, the oil pressure measured here is the pressure generated when the injection cylinder 11 moves, and corresponds to the pressure difference between the resin before and after the check ring 2. In this case, since the pressure sensor 3 is provided at one position in the hydraulic cylinder 10 , the pressure sensor 3 can be easily installed, and the pressure can be easily measured.

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0072

[Correction method] Change

[Correction contents]

In this case, in particular, two pressure sensors 3 are provided on the injection cylinder 11 at intervals slightly wider than the thickness of the check ring 2 in the moving direction of the screw 13. Further, these pressure sensors 3, substantially the same position relative to the screw 13 moving direction, the injection temperature sensor 6 cylinder 11
Are provided in two. The pressure sensor 3 or the temperature sensor 6 may be provided on the screw 13 side. That is, one or both of the pressure sensor 3 and the temperature sensor 6 are provided on the injection cylinder 11 or the screw 13.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI B29C 45/84 B29C 45/84

Claims (19)

[Claims] An injection molding method in which a screw provided in an injection cylinder is rotated to send a resin to a front portion of the injection cylinder, weigh the resin, and then inject the resin into a mold from a nozzle at the tip of the injection cylinder. In the measuring step, the pressure of the resin melted in the injection cylinder is measured, the viscosity is calculated based on this pressure, and the calculated viscosity is compared with the reference viscosity to determine whether the molded product is good or bad. An injection molding method comprising controlling conditions. 2. The method according to claim 1, wherein the oil pressure in the hydraulic cylinder for moving the screw is measured when the screw moves, and the oil pressure is used as the pressure of the resin melted in the injection cylinder. 2. The injection molding method according to 1. 3. A check ring for allowing the resin to pass to the front of the injection cylinder in the metering step is provided at the front end of the screw, and two or more pressure sensors are provided on the injection cylinder at intervals in the screw moving direction. 2. The injection molding method according to claim 1, wherein the pressure of the resin before and after the check ring is measured. 4. A check ring for allowing the resin to pass through the front portion of the injection cylinder in the measuring step is provided at the front end of the screw, and pressure sensors are provided on the screws at positions before and after the check ring to measure the pressure of the resin. 2. The injection molding method according to claim 1, wherein: 5. The method according to claim 1, wherein the temperature of the resin is measured together with the pressure, and the quality of the molded product is determined or the molding conditions are controlled based on the viscosity of the resin calculated from the temperature and the pressure. 5. The injection molding method according to any one of claims 1 to 4. 6. The injection molding method according to claim 1, wherein a pressure is measured at a predetermined time within one molding shot, and a viscosity is calculated from the pressure. 7. An average value of viscosities within a predetermined time interval is obtained,
The injection molding method according to any one of claims 1 to 5, wherein the average value is used as the calculated viscosity. 8. The method according to claim 1, wherein a ratio in which a deviation between the viscosity and the reference viscosity in each molding shot exceeds a predetermined range is determined, and the injection molding is automatically stopped when the ratio exceeds the reference excess ratio. 8. The injection molding method according to any one of items 1 to 7. 9. The injection molding method according to claim 1, wherein when the calculated viscosity is higher than the reference viscosity, the injection molding pressure is controlled to increase. 10. The injection molding method according to claim 1, wherein when the calculated viscosity is higher than the reference viscosity, the injection speed is controlled to be increased. 11. The injection molding method according to claim 1, wherein when the calculated viscosity deviates higher than the reference viscosity, control is performed to increase the holding pressure. 12. The injection molding method according to claim 1, wherein when the calculated viscosity deviates higher than the reference viscosity, control is performed to increase the dwell time. 13. The injection molding method according to claim 1, wherein when the calculated viscosity is higher than the reference viscosity, control is performed so as to increase the back pressure. 14. The injection molding method according to claim 1, wherein when the calculated viscosity deviates higher than the reference viscosity, control is performed to increase the screw rotation speed. A moving average value of each of the determined viscosities in each molding shot is calculated, and an injection molding pressure, an injection speed, a holding pressure, a holding pressure time, a back pressure, The injection molding method according to any one of claims 1 to 7, wherein a screw rotation speed is controlled. 16. The injection molding method according to claim 15, wherein the temperature of the injection cylinder is controlled to increase when the moving average value increases. 17. The injection molding method according to claim 15, wherein the temperature of the mold is controlled so as to increase when the moving average value increases. 18. A pressure sensor for measuring a pressure of a resin melted in an injection cylinder in a measuring step, an arithmetic circuit for calculating a viscosity from a pressure measured by the pressure sensor, and a calculated viscosity as a reference viscosity. An injection molding apparatus, comprising: a determination control circuit for determining the quality of a molded product or controlling molding conditions. 19. A method comprising: providing a temperature sensor juxtaposed with a pressure sensor; calculating a flow rate of the resin from a temperature measured by the temperature sensor; and calculating a viscosity from the flow rate and the pressure measured by the pressure sensor. 19. The injection molding apparatus according to claim 18, further comprising an arithmetic circuit.