JP3121032B2 - Injection control method for injection molding machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection control method for controlling an injection weight of a plasticized synthetic resin which is injected from a cylinder of an injection molding machine into a cavity of a molding die and filled.

[0002]

2. Description of the Related Art In injection molding of a plasticized synthetic resin using an injection molding machine, a molten resin pressure, a molten resin specific volume, or a molten resin temperature of a plastic synthetic resin at the time of molding (however, disturbance to a molding system). Changes), the injection weight of the plasticized synthetic resin injected and filled also changes, and there is a problem that it is difficult to keep the quality of the molded product constant. As a countermeasure, various types of adaptive control, also called adaptive control, have been proposed.
The technique described in Japanese Patent Publication No. 84493/1981 (1981) is an example thereof.

[0003] In general, adaptive control refers to the effect of disturbance on a molding system, or the detection of a change in molten resin pressure, molten resin temperature, mold temperature, or the like as a given condition. This method detects a change and changes controllable molding conditions (pressure, timer, etc.) other than the detection factor as a control factor to keep the quality of a molded product constant.

However, this method has the following problems. The correlation between the detection factor according to the mold and the quality of the molded product, and the correlation between the control factor and the quality of the molded product must be investigated and analyzed in advance. When the mold changes, the correlation between the detection factor and the quality of the molded product, and the correlation between the control factor and the quality of the molded product are completely different even if the plasticized synthetic resin used is the same. The difference is that you have to redo the survey analysis as described in.

SUMMARY OF THE INVENTION The present invention aims at solving the above-mentioned problems, and is intended to eliminate the influence of a disturbance on the molding system or the change of the molten resin pressure as a given condition. It is an object of the present invention to provide a versatile injection control method for an injection molding machine that maintains a constant quality and does not need to perform a survey and analysis from the beginning unlike adaptive control even when a mold is changed.

[0006]

SUMMARY OF THE INVENTION The injection control method for an injection molding machine according to the present invention basically achieves the above-mentioned object by basically setting a cavity of a molding die from inside a cylinder of the injection molding machine. In the injection control method of the injection molding machine for controlling the injection weight of the plasticized synthetic resin injected and filled in the injection molding machine, the moving distance S _D of the screw at the time of injection filling of the plasticized synthetic resin corresponding to the weight value G of the molded product. Is calculated by a predetermined calculation formula, and is set in advance. When the screw moves from the screw position immediately before injection to the predetermined screw moving distance _SD , the plasticity of the molding die to the cavity is adjusted. The injection filling of the synthetic resin is stopped.

Further, the calculation of the screw moving distance _SD at the time of injection filling of the plasticized synthetic resin corresponding to the weight value G of the molded product by a predetermined formula is performed by detecting or setting the plasticization immediately before injection. The molten resin pressure value P _I of the synthetic resin, the molten resin pressure value P _H of the plasticized synthetic resin at the time of holding pressure following injection, the detected screw position value S _I immediately before injection, and the plasticized synthetic resin. Based on the PV characteristic relational expression of the above, based on a constant molten resin temperature value T, the following equation

(Equation 4) S _H ; Screw position value during dwelling following injection A; Projected cross-sectional area of screw V (P _H ); Specific volume value of molten resin during dwelling following injection V (P _I ); Immediately before injection It is characterized in that it is carried out based on the specific volume value of the molten resin at the time.

Alternatively, the screw movement distance S at the time of injection filling of the plasticized synthetic resin corresponding to the weight value G of the molded product is represented by S
The calculation according to the predetermined formula of _D is the detected or set molten resin temperature value T of the plasticized synthetic resin to be injected, the molten resin pressure value P _I of the plasticized synthetic resin immediately before injection, and the holding pressure following injection. Resin pressure value P of plasticized synthetic resin at the time
_H and the detected screw position value S immediately before injection
_{Based on I} and the PVT characteristic relational expression of the plasticized synthetic resin,

(Equation 5) S _H ; Screw position value during dwelling following injection A: Projected cross-sectional area of screw V (P _H , T); Molten resin temperature T and dwelling pressure following injection at molten resin temperature T At the molten resin pressure value P _H and the molten resin specific volume value V (P _I , T); melting at the molten resin temperature value T and the molten resin pressure value P _I immediately before injection at the molten resin temperature value T It is characterized in that it is carried out from the specific resin volume value.

Note that the detected molten resin pressure value P _I of the plasticized synthetic resin immediately before injection and the molten resin pressure value P _H of the plasticized synthetic resin at the time of holding pressure following injection are further injected. The fluctuation range of the molten resin temperature value T of the plasticized synthetic resin during the short-term continuous molding is small, and in order to eliminate the instantaneous error and improve the detection accuracy, The average value of each of the molten resin pressure values P _I , P _H and the molten resin temperature value T detected based on a plurality of injection fillings may be used.

Further, when obtaining the specific volume value V of the molten resin from the molten resin pressure value P and the molten resin temperature value T based on the PVT characteristic relational expression, the molten resin pressure value P
Alternatively, the variation width of the molten resin temperature value T may be within a predetermined range and may be obtained by a plane approximation method.

[0011]

Next, a specific embodiment of the injection control method for an injection molding machine according to the present invention will be described with reference to the drawings.

First, in FIG. 1 (A), which shows an outline of the entire injection molding machine, a mold 10 for molding an injection molded product is shown.
At the time of injection molding, the injection molding machine 11 is joined at the nozzle 12. Inside the cylinder 13 of the injection molding machine 11, while melting and kneading resin pellets of the plasticized synthetic resin supplied from the material hopper 15 in the cylinder 13 heated by the heating device 14, the molten resin is measured. A screw 19 for injecting and filling a flow passage 16 formed in the nozzle portion 12 and a cavity portion 18 of the mold 10 via a gate 17 in the mold 10 is provided. The rotation of the screw 19 for melting and kneading the resin pellets is provided by a screw rotation motor 20, and the screw 19 and the screw rotation motor 20
Installed on 21. The base 21 is controlled by an electromagnetic flow valve 22 and an electromagnetic pressure valve 23 by a control device 24 to control a hydraulic piston device from a hydraulic source 25 through a pipe 26.
The pressure oil supplied to and discharged from 27 is driven in the left-right direction on the drawing. In other words, the molten resin to be injected is moved toward and away from the nozzle 12 of the screw 19 for the injection and filling of the measured molten resin into the cavity 18 of the mold 10 and the like. The application of a predetermined pressing force to the screw 19 for setting the molten resin to a predetermined molten resin pressure is performed via the base 21 by supplying and discharging pressurized oil to and from the hydraulic piston device 27. The base 21 includes a potentiometer, an encoder, and the like for detecting the position value of the screw 19 at the left end side of the cylinder 13 in FIG. The screw position detector 28 is engaged. The position value of the screw 19, which is detected every moment by the screw position detector 28, is obtained by calculating the PVT characteristic relational expression of the plasticized synthetic resin when the resin characteristic is detected by the controller 24, and the PVT characteristic relational expression during the injection control. The calculated value is supplied to a PVT calculation device 29 which supplies the movement distance of the screw 19 calculated to the control device 24 based on the formula. This PVT
The arithmetic unit 29 is also provided with a temperature value from a resin temperature detector 30 that detects the resin temperature of the molten resin in the cylinder 13. Further, a hydraulic pressure value is given from a hydraulic pressure detector 31 that detects the hydraulic pressure of the hydraulic piston device 27 as a pressing value of the pressing force applied to the screw 19, in other words, as a molten resin pressure value P of the molten resin in the cylinder 13. Reference numeral 32 denotes a measured value of the injected molten resin to the PVT arithmetic unit 29 when the resin characteristic is detected, and a molten resin pressure value P, a molten resin temperature value T and the like which are variously set at the time of detecting the resin characteristic. This is an external input device that is provided to the control device 24 via the computing device 29 and also provides the PVT computing device 29 with a target injection weight value of the molten resin to be injected and filled during injection molding.

On the other hand, the flow path 16 of the nozzle portion 12 is provided with a closing valve 33 which is a flow path opening / closing mechanism in the present invention for preventing the flow of the molten plasticized synthetic resin. This shut-off valve 33
Is opened and closed via an operation lever 35 by controlling the electromagnetic drive unit 34 by the control unit 24.

By the way, as shown in FIG. 1 (B), an axial direction is provided between the conical tip portion 36 of the screw 19 and the flange projection 38 provided at the end of the spiral strip 37. A ring-shaped sliding valve body 39 which can move forward and backward is fitted. The ring-shaped sliding valve body 39 comes into pressure contact with the flange projection 38 when the resin pressure of the molten resin on the left side of the screw 19 on the tip side of the screw 19 increases in the figure, so that the molten resin moves to the right side of the figure on the figure. Blocking backflow. These flange projections
The check valve 40 is constituted by the ring 38 and the ring-shaped sliding valve body 39. Even if the screw position detector 28 detects "0" as the position value of the screw 19, as shown in the drawing, the distance from the tip of the screw 19 to the closing valve 33 is
More specifically, the residual molten resin of the plasticized synthetic resin is interposed between the check valve 40 and the shut-off valve 33.

Next, each example of a method for detecting a resin characteristic when determining the PV (T) characteristic relation used in the injection control method of the injection molding machine according to the present invention will be described.

(Example 1) First, in the first stage, each molten resin temperature value T ₁ , at a fixed molten resin pressure value P ₀ ,
Each molten resin specific volume value V ₀₁ , V _{3 for} T ₂ , T ₃ ,.
_02, V _03, a., Melting the next three steps the resin temperature value T _1,
Are obtained by repeatedly performing T ₂ , T ₃ ,... Sequentially (see FIG. 2).

First Step The rotation of the screw 19 sends the melted plasticized synthetic resin to the front side of the screw 19, but in the first step, the screw is closed because the closing valve 33 is closed.
The screw 19 is retreated backward by the resin pressure of the molten resin at the distal end side of the screw 19, and moves to a preset initial position while measuring the amount of the injected molten resin to stop the rotation. The reaching of the initial position is detected by the control device 24 based on the position value of the screw 19 from the screw position detector 28. This initial based on the detection of the arrival of the position controller 24 performs oil pressure control, which is supplied to the hydraulic piston device 27 so as to impart a pressing force of a predetermined pressing pressure value p ₀ to the screw 19. By applying this pressing force to the screw 19, the screw 19 moves forward by the equilibrium movement and compresses the molten resin at the tip end side of the screw 19 together with the action of the check valve 40 to increase the resin pressure. The advance of the screw 19 stops at a position where the applied pressing force and the resin pressure of the compressed molten resin are balanced. The position value of the first stop position of the screw 19 stopped in this way is detected by the screw position detector 28 and given to the PVT arithmetic unit 29. The screw
The resin pressure value P ₀ of the molten resin on the tip side of 19 is
At the time of the stop of 19, it corresponds to the pressing value p _{0 of the} pressing force applied to the screw 19.

Second step: The closing valve 33 is opened, and an appropriate amount of molten resin for a predetermined distance of the screw 19 is injected by the screw 19 moving the distance by the pressing force applied to the screw 19. An appropriate amount of the injected molten resin is weighed by an external measuring device, and the weight value G is input to the external input device 32 and given to the PVT calculating device 29.

Third step: The closing valve 33 is closed again, and in a state where the closing valve 33 is closed, a pressing force of a predetermined pressing value p ₀ is applied to the screw 19 by the controller 24 in the same manner as in the first step. Controls hydraulic pressure. By this pressing force, the screw 19 moves forward or backward by the equilibrium movement, compresses the molten resin on the tip side of the screw 19 based on the pressing force, and the pressing force applied similarly and the resin pressure of the molten resin are balanced. Stop in position. The position value of the second stop position of the screw 19 stopped in this way is also detected by the screw position detector 28 and given to the PVT arithmetic unit 29.

Next, the PVT computing device 29, the molten corresponding to the difference between S _T, the injected molten resin other words the weight value G between the position value and the position value of the second stop position of the first stop position A resin volume value is calculated, and the molten resin volume value is divided by the above-mentioned weight value G to obtain a molten resin specific volume value V
₀ is calculated.

In this manner, a series of steps are performed while maintaining the predetermined pressing value p ₀ (the molten resin pressure value P ₀ ) of the pressing force applied to the screw 19 to the molten resin temperature values T ₁ , T ₂ ,
By repeating T ₃ ,..., The respective molten resin specific volume values V ₀₁ , V ₀₂ , V ₀₃ are obtained.

Next, in the second stage, the molten resin temperature values T ₁ , T ₂ , T ₃ ,... Are variously changed to molten resin pressure values P ₁ , P ₂ , P ₃ ,. Corresponding molten resin volume values V ₁₁ , V ₂₁ , V ₃₁ ,...; V ₁₂ , V ₂₂ , V ₃₂ ,.
_13, V _23, V _33, a., Melting the following two steps the resin temperature value T _1, T _2, T _3, obtained by carrying out repeatedly while sequentially changing the ... (Figure 3 reference).

First Step As in the first step in the first step, the screw 19 is rotated backward while the shut-off valve 33 is closed and the screw 19 is retracted backward to a preset initial position while measuring the molten resin. And stop the rotation. Next, the molten resin is compressed by advancing by applying a pressing force of a predetermined pressing pressure value p ₀ to the screw 19. The position value of the first stop position of the screw 19 at which the molten resin pressure of the compressed molten resin and the pressing force applied to the screw 19 are balanced and the screw 19 stops is detected by the screw position detector 28. It is provided to the PVT arithmetic unit 29. Others are the same as the first step of the first stage.

Second Step While maintaining the closing valve 33 in the closed state, the pressing value p of the pressing force applied to the screw 19 is gradually increased with reference to the pressing value p ₀ in the first step, p ₁ , p ₂ , p ₃ , ...
Is selected to compress the molten resin. Screws to which these pressing values p ₁ , p ₂ , p ₃ ,.
The position values of the second, third, fourth, etc. stop positions of the screw 19 in which the 19 has stopped due to equilibrium are likewise determined by a screw position
It is detected by 28 and given to the PVT arithmetic unit 29.

Next, in the PVT arithmetic unit 29, the first
Each second relative position value of the stop position of the third, the molten resin volume value by the difference S _T and the stop position of the fourth or the like is calculated. Next, the first molten resin volume value is calculated from the calculated values.
Specific volume value of molten resin V ₀₁ (V ₀₂ , V
₀₃ ,...) And the specific volume value of the molten resin V ₁₁ , V
_{21, V 31, ··· (V} 12, V 22, V 32, ···; V 13, V 23,
V ₃₃ , ...). This ratio calculation shows that, under the same molten resin temperature value T and the same weight value G, the molten resin pressure value P ₀ (pressing value p ₀ ) is the molten resin pressure value P ₁ , P ₂ , P ₃ ,... (Press values p ₁ , p ₂ , p ₃ ,
..) Is based on the fact that the molten resin specific volume value V is obtained by the ratio of the molten resin volume values.

In this way, each molten resin temperature value T ₁ ,
A series of steps are repeatedly performed on T ₂ , T ₃ ,..., And the pressing values p ₁ , p ₂ , p ₃ ,. Resin pressure value P ₁ ,
, P ₂ , P ₃ ,...), The respective molten resin specific volume values V ₁₁ , V ₂₁ , V ₃₁ ,...; V ₁₂ , V ₂₂ , V ₃₂ ,.
_{·; V 13, V 23,} V 33, get a .... The change of the molten resin temperature value T is performed by the control device 24 controlling the heating device 14.

By the way, even when the position value of the screw 19 is "0", the residual molten resin is interposed between the tip of the screw 19 and the closing valve 33, so that the position value of each stop position of the screw 19 also becomes This is a result of compressing the residual molten resin by the screw 19 to which the pressing force is applied. Therefore, PV
If an attempt is made to apply the PVT characteristic relational expression to an injection molding machine of another model that has a difference in the residual molten resin volume value other than the injection molding machine that obtained the T characteristic relational expression, an error of a size that cannot be ignored is accompanied. Also.

Next, a method for obtaining a molten resin specific volume value V corrected by the remaining molten resin volume will be described. i) First, the residual molten resin volume value is known as a design value of the machine, if the remaining molten resin volume value is given by the moving distance S ₀ in terms of the movement distance of the screw 19.

After pressing the molten resin having the same molten resin temperature value T and the same weight value G, each of the pressing values p _X and p _{Y is} measured.
Each correction position by adding the movement distance S ₀ position value S _x, in S _y of the stop position of the pressing each molten resin pressure value power screw 19 is imparted stops P _X, screw 19 when P _Y of Assuming the values S _X (= S _x + S ₀ ) and S _Y (= S _y + S ₀ ), the molten resin specific volume values V _X and V _Y are represented by the following equations.

(Equation 6)

(Equation 7) D; diameter of screw 19 Next, if the ratio of these equations (1) and (2) is taken, the following equation is obtained.

(Equation 8)

From this equation (3), the molten resin specific volume value V _X is
The molten resin specific volume value V _Y can be easily obtained by setting the molten resin specific volume values V ₀₁ , V ₀₂ , V ₀₃ ,... Obtained in the first stage. Therefore, in the case of this example in which the molten resin specific volume value V is obtained by the same ratio calculation, this method can be directly applied as it is.

Ii) Next, the case where the residual molten resin volume value is unknown. As shown in FIG. 4, the amount by which the molten resin is compressed, that is, the moving distance ΔS of the screw 19 required for compression is the volume before compression, that is, the screw before compression.
Proportional to the position value S _m of 19. Therefore, while maintaining the molten resin pressure value P and the molten resin temperature value T a constant draw a linear function graph by changing the position value several stages S _m of the screw 19, lever movement distance S ₀ to extrapolate on the graph Easy to get. Others are the same as the above-mentioned case.

Subsequently, in the third stage, each molten resin pressure value P ₀ , obtained in the first stage and the second stage,
P ₁ , P ₂ ,..., Each molten resin specific volume value V ₀₁ , V ₀₂ ,
_{V 03, ···; V 11,} V 12, V 13, ···; V 21, V 22, V 23, ·
.. And substituting into general formulas of PVT characteristics based on the respective molten resin temperature values T ₁ , T ₂ , T ₃ ,.

By the way, from the equation (3), it is possible to obtain a generalized function as shown in the following equation.

(Equation 9) P, V; arbitrary molten resin pressure value and molten resin specific volume value at the molten resin pressure value P ₀ , V ₀ ; reference molten resin pressure value and molten resin specific volume value at the molten resin pressure value The molten resin pressure values P and P ₀ and the molten resin specific volume values V and V ₀ are values at the same molten resin temperature value T.

From the equation (4), the inventor has found that the PV characteristic can be approximated by the following equation.

(Equation 10) a; constant

Therefore, if the value of the constant a is obtained by changing an arbitrary molten resin pressure value P to various values, a PV (T = constant) characteristic relational expression can be grasped.

Further, the present inventor has found that the value of the constant a is a function of the molten resin temperature value T, and can be approximated by the following equation.

[Equation 11] b, c; constant

Therefore, the following general formula is obtained from the formulas (4), (5) and (6).

(Equation 12)

In the equation (7), the molten resin pressure values P ₀ , P ₁ , P ₂ ,... Obtained in the first and second stages are shown.
, Each molten resin specific volume value V ₀₁ , V ₀₂ , V ₀₃ ,.
By substituting V ₁₁ , V ₁₂ , V ₁₃ ..., V ₂₁ , V ₂₂ , V ₂₃ ... And each molten resin temperature value T ₁ , T ₂ , T _3. Thus, the PVT characteristic relational expression is determined.

The molten resin temperature value T is changed at the reference molten resin pressure value P ₀ to obtain a molten resin specific volume value V.
_{When 0} is obtained, the molten resin temperature value T and the molten resin specific volume value V are approximated as linear equations as in the following equation.

(Equation 13) α, β; constant

Therefore, by substituting equation (8) for equation (7), the following equation can be obtained.

[Equation 14]

In the above case, the constant a is approximated by a linear expression. However, the constant a changes as a variable when the molten resin temperature value T changes. By using a polynomial approximation of the molten resin temperature value T, it is possible to make a correction suitable for an actual machine.

(Equation 15) b ', b "・ ・ ・ b ^m , C; constant

Similarly, when the molten resin temperature value T changes even when the molten resin specific volume value V ₀ and the fixed molten resin pressure value P change, the molten resin temperature value T changes as a variable. It is preferable to employ a polynomial approximation of the resin temperature value T.

(Equation 16) α ', α ", ... α ^n' , β '; constant

(Example 2) Next, Example 2 will be described.
In particular, only portions different from Example 1 will be described, and description of overlapping portions will be omitted.

For each molten resin temperature value T ₁ , T ₂ , T ₃ ,.
The PVT characteristic relational expression is determined by repeatedly performing the following three steps. First Step Similar to the first step of the first stage in the first embodiment, the screw 19 is rotated backward while rotating the screw 19 while the closing valve 33 is closed, and the rotation is stopped. Next, the pressing values p _S0, p _S1, p
A pressing force of _S2 ,..., P _Sn is applied to compress the molten resin. Each pressing pressure value _{p S0, p S1, p S2} , ···, each position value of the first stop position of the screw 19 the screw 19 stops moving at the time of pressing force _{p Sn S S0, S S1,} S S2 ,..., S _Sn are sequentially detected by the screw position detecting device 28 and PV
It is given to the T arithmetic unit 29. Others are the same as the first step in the first stage of Example 1.

The second step is to return to the pressure value p just before injection during regular production, apply a pressing force to the screw 19, open the shut-off valve 33, and dispense one injection weight of the molten resin into the cavity of the mold 10. The part 18 is injected and filled to perform actual molding, and then the pressure value is applied to the screw 19 at the pressure value p at the time of holding pressure following the injection during the regular production, and the pressing force is applied to the screw 19 to close the closing valve 33. The weight value G of the injection-filled molten resin is measured by an external measuring device.
Is supplied to the PVT arithmetic unit 29 via the external input device 32.

Third Step The same pressing values p _S0, p _S1, p _S2 ,..., P _Sn as in the first step are sequentially applied to the screw 19, and the pressing values p _S0, p
_S1, p _{S2, ···,} each position value of the second stop position of the screw 19 the screw 19 is stopped at the time of pressing force _{p Sn S F0, S F1,} S F2, ···, the S _Fn successively Is detected by a screw position detector 28 and given to a PVT arithmetic unit 29.

In these series of steps, it is assumed that the molten resin having the weight value G is injected and filled n times. Therefore, at a constant molten resin temperature value T, the following equation is established.

[Equation 17] A: Projected cross-sectional area of screw 19 S ₀ : Moving distance obtained by converting residual molten resin volume value to moving distance of screw 19

On the other hand, by substituting equation (5) into equation (4), the following equation is obtained.

(Equation 18)

By calculating this equation (10), the injection weight of the molten resin to be injected at the molten resin pressure (P) during one injection filling without fear of adversely affecting the actual molded product The relational expression affecting G can be obtained.

By substituting equation (10) into equation (9), the following equation is obtained.

[Equation 19]

The equation (11) is an equation relating to the PV characteristic at a constant molten resin temperature value T. The PVT arithmetic unit 29 calculates the PV characteristic at a constant molten resin temperature value T by calculating based on the equation (11). The relational expression is determined. Similarly, the PVT characteristic relational expression is determined by performing the process for each of the molten resin temperature values T ₁ , T ₂ , T ₃ ,.

In Examples 1 and 2, the following equation found by the inventor was used to determine the PVT characteristic relational equation.

(Equation 20)

However, instead of this equation, Spencer &
Gilmore's equation may be used.

(Equation 21) T: molten resin temperature value π _i , ω, R '; constant determined according to the type of plasticized synthetic resin

The values of the constants π _i , ω, R ′ may be obtained as follows. First, a specific molten resin volume value V _{0 at} a fixed molten resin pressure value P ₀ and a molten resin temperature value T ₀ .
In the same manner as in the first stage in Example 1. Next, the value of the constant ω is obtained by changing the molten resin temperature value T at the same molten resin pressure value P ₀ . Subsequently, at a fixed molten resin temperature value T ₀ , a molten resin volume value when the molten resin pressure value P is set to the molten resin pressure value P ₁ is obtained in the same manner as in the second stage in Example 1, and the above-mentioned molten resin ratio is obtained. obtaining a molten resin specific volume value V ₁ in the molten resin pressure value P ₁ by proportional calculation from the volume value V _0. From the molten resin pressure values P ₀ , P ₁ , the molten resin specific volume values V ₀ , V ₁ and the constant ω, the value of the constant π _i is obtained by the following equation.

(Equation 22)

If the values of these constants ω and π _i are obtained, (1
From equation (2), a constant R 'is also obtained. For other plasticized synthetic resins, the constants ω, π _i ,
What is necessary is just to obtain the value of R '.

The case where the PVT characteristic relational expression is determined based on Spencer &Gilmore's equation has been described above. For example, the PVT characteristic relational expression based on experimental analysis means (multivariable successive approximation method) in an experiment design method has been described. Formulas can also be fixed.

Next, the PV determined and obtained as described above
Prior to describing each embodiment of the injection control method for an injection molding machine according to the present invention based on the T characteristic relational expression, a calculation formula for obtaining a moving distance of the screw 19 for keeping an injection weight value used for injection control constant. This will be described with reference to FIG.

First, at a constant molten resin temperature value T ₁ , each molten tree pressure value P, the position value S of the screw 19, and the molten resin specific volume value V immediately before injection and at the time of holding pressure following injection are calculated as follows. As expected. Injection immediately preceding value: the molten resin pressure value; P _I1 position value of the screw 19; S _I1 molten resin specific volume _{value; V (P I1, T 1} ) subsequent to the injection rather holding time: molten resin pressure value; P _H1 screw 19 S _H1 molten resin specific volume value; V (P _H1 , T ₁ )

Note that the position values S _I1 , S
_H1 is based on the distance of the screw 19 from the “0” position value. The position values S _I1 and S _H1 of the screw 19 are corrected position values corrected when the above-described correction of the remaining molten resin volume is required.

Next, the injection weight value G of the molten resin filled in the cavity portion 18 of the mold 10 by one injection filling is as follows. Here, A is the projected sectional area of the screw 19.

(Equation 23)

This equation (13) can be transformed into the following equation.

(Equation 24)

The moving distance _SD of the screw 19 during injection filling is as follows.

(Equation 25)

If the equation (15) is substituted into the equation (14) and rearranged, the following equation is obtained.

(Equation 26)

In equation (16), the projected sectional area A of the screw 19 is known, the position value S _I1 of the screw 19 immediately before injection is detected by the screw position detector 28, and the molten resin specific volume value V (P _I1 , T ₁ ), V (P _H1 , T ₁ ) are obtained from the molten resin temperature value T ₁ and the molten resin pressure values P _I1 , P _H1 detected by the resin temperature detector 30 and the hydraulic pressure detector 31, or The PV obtained as described above from the set molten resin temperature value T ₁ and the molten resin pressure values P _I1 and P _H1.
It is obtained from the T characteristic relational expression. Therefore, by using the expression (16), the moving distance _SD of the screw 19 for keeping the injection weight value G constant can be obtained.

(First Embodiment) First, in this embodiment, as shown in FIG. 6, a screw position detector 28 detects a position value S _I1 of the screw 19 immediately before injection, a resin temperature detector From 30 the melting state value T ₁ and the oil pressure detector 31
The following describes a case where the molten resin pressure values P _I1 and P _H1 are detected immediately before injection and at the time of holding pressure subsequent to injection and are supplied to the PVT arithmetic unit 29.

First, an injection weight value G, which is a target weight value of a molded product, is given to the PVT arithmetic unit 29 via the external input device 32. Next, after stopping the measurement and rotation of the molten resin by retreating while measuring the amount of the molten resin injected by the screw 19, a pressing force is applied to the screw 19, and the closing valve 33 immediately before the injection is still closed, The position value S _I1 of the screw 19 and the molten resin pressure value P _I1 (pressing value p _I1 ) of the screw 19 in the state where the
31 and the molten resin temperature value T ₁
And is supplied to the PVT arithmetic unit 29.

Next, the shut-off valve 33 is opened to start injection, and as the screw 19 advances, the cavity 18 of the mold 10 is opened.
Is filled with a molten resin, and the pressure is maintained when the filling is substantially completed. The molten resin pressure value P _H1 (pressing value p _H1 ) at the time of holding pressure subsequent to this injection is also detected by the hydraulic pressure detector 31 as PV.
It is provided to the T arithmetic unit 29. In the PVT calculating device 29, the moving distance _SD is calculated from the position value S _I1 , the molten resin pressure values P _I1 , P _H1 and the molten resin temperature value T ₁ , and the equation (16) based on the PVT characteristic relational equation. You. The moving distance S _D is given to the control device 24, and the control device 24 compares the moving distance S _D with the position value detected from the screw position detector 28, and closes the closing valve 33 when the position value matches. . Thereby, the cavity 18 of the mold 10 is
The injection filling of the molten resin for one time is completed. Therefore, according to the present embodiment, even if the molten resin pressure values P _I1 and P _H1 and the molten resin temperature value T ₁ change, the moving distance _SD for obtaining a constant injection weight value G can be obtained.

(Second Embodiment) In this embodiment, the seventh embodiment
As shown in the figure, the position value S _I1 of the screw 19 immediately before injection is detected and given to the PVT arithmetic unit 29,
Other molten resin pressure values P _I1 , P _H1 and molten resin temperature value T
₁ is set in the control device 24 in advance, and a case where these set values P _I1 , P _H1 , and T ₁ are given from the control device 24 to the PVT calculation device 29 will be described. It should be noted that only the portions different from the first embodiment will be described, and the description of the overlapping portions will be omitted.

The control device 24 controls the electromagnetic flow valve 22 and the electromagnetic pressure valve 23 so that the set molten resin pressure values P _I1 and P _H1 are obtained, and sets the heating device 14 to the set molten resin temperature T T. Control so that ₁ is obtained. Also, PV
In the T calculating device 29, the position value S _I1 of the screw 19 immediately before the injection from the screw position detector 28 is
Molten resin pressure value P _I1, P _H1 and molten resin temperature value T ₁ that is set in, and further calculates the travel distance S _D based on the PVT characteristics relationship, the control device the movement distance S _D to the calculated 24 Give to. Others are the same as the first embodiment.

In the first embodiment, the moving distance _SD of the screw 19 is calculated based on the molten resin pressure values P _I1 and P _H1 and the molten resin temperature value T ₁ which are detected this time. The fluctuation range of P _I1 , P _H1 , and T ₁ during injection molding during short-term continuous molding is very small. In other words, even if these values P _I1 , P _H1 , and T ₁ are detected for each injection and filling, these values P _I1 , P _H1 , and T ₁ are often within the detection error, and each value P having an error is detected. _I1, be computed with at P _H1, T _1, variation in the actual molding increases conversely. In addition, the change in the molten resin pressure and the molten resin temperature is a gradual change due to the change in the outside air temperature, the water temperature, and the like over a long-term continuous molding. , Changes over time after several thousand injections. Therefore, in order to improve the detection accuracy on the premise of the detection error of the molten resin pressure and the molten resin temperature, the average value of the detection values P _I1 , P _H1 , and T ₁ for a short period of 2 to 10 times may be used. In addition, P _I1 detected this time,
P _H1, the value detected last time without a T ₁ P _I1, P _H1,
T ₁ may be used, or an average value of each of the values P _I1 , P _H1 , and T _{1 from} the previous 2 to 10 times may be used.

In the first and second embodiments,
The three-dimensional PVT characteristic relational expressions obtained in Examples 1 and 2 described above, in other words, the molten resin pressure axis P, the molten resin specific volume axis V, and the molten resin temperature axis T as shown in FIG. PVT forming a PVT surface in coordinates
The characteristic relational expression is directly used to calculate the moving distance _SD of the screw 19. However, during the actual continuous injection molding, the range in which the molten resin pressure value P and the molten resin temperature value T change is very small, so that the fluctuation range of the molten resin pressure value P and the molten resin temperature value T is sufficiently flat. It can be treated as a value of a region that can be approximated. Therefore,
Even if the PVT characteristic relational expression obtained as described above is not used as it is, the molten resin specific volume value V (P, T) is approximated to the plane as the molten resin specific volume value V (P ± ΔP, T ± ΔT). It is possible to calculate using an expression. Note that ΔP and ΔT are expected fluctuation ranges within an allowable range. As a method for obtaining the molten resin specific volume value V (P _I , T) and the molten resin specific volume value V (P _H , T), P _I → P _I
The result of forcibly changing ± ΔP _I, P _H → P _H ± ΔP _H, T → T ± ΔT and the weight value of the molded product obtained from these changed results are directly approximated by a plane approximation. May be obtained by substituting into

In the first and second embodiments,
The moving distance S _{D of the} screw 19 using the PVT characteristic relational expression
Is calculated assuming that the variation width of the molten resin temperature value T is small and constant, and based on the equations (5) and (11), P
The moving distance _SD of the screw 19 may be calculated using the V characteristic relational expression. When using the PV characteristic relational expression, during stable molding, the position values S _IO and S _H0 of the screw 19 at the time immediately before injection and at the time of holding pressure subsequent to injection so that the injection weight value G is constant during stable molding are taken as a reference. If it is known that the molten resin pressure values P _IO and P _H0 just before the injection and at the time of holding the pressure after the injection, the moving distance _SD of the screw 19 can be obtained by the following equation.

[Equation 27]

In other words, the values other than the position values S _IO , S _H0 , and S _{I1 of} the screw 19 are expressed as a ratio of the molten resin specific volume value V, and the ratio of the molten resin specific volume value V is a constant molten resin temperature value T Can be obtained as a ratio of the volume value of the molten resin. Therefore, when the variation of the molten resin temperature value T is almost negligible and only the molten resin pressure values P _I and P _H fluctuate, the closing valve 33 is closed and the measurement is performed by the screw 19. It is possible to keep the weight value G of the molded product constant only by obtaining the compression characteristics of the injected molten resin.

As another embodiment, when the shut-off valve 33 is not provided in the flow path 16 of the nozzle portion 12, the gate of the mold 10 is
A shut-off valve provided at 17 may be used like the shut-off valve 33.

[0075]

As described above, according to the injection control method for an injection molding machine according to the present invention, even if there is an influence due to disturbance to the molding system, or if the molten resin pressure or the like as a given condition changes. Also, the quality of the molded product can be kept constant by automatically controlling the moving distance of the screw that keeps the weight value G of the molded product constant. Further, even if the mold is changed, it is not necessary to perform the investigation and analysis from the beginning unlike the adaptive control. Further, the molten resin pressure value and the like are often changed at the stage of setting the conditions for determining the molding conditions. In such a case, the moving distance of the screw is automatically controlled to a predetermined weight value G. It is easy to obtain molding conditions.

According to the present invention, an appropriate screw moving distance can be calculated on the basis of the resin characteristics and furthermore, the calculation formula. Therefore, the injection control method of the injection molding machine according to the present invention is particularly suitable when the mold is changed.

[Brief description of the drawings]

FIG. 1 is a half-illustrated longitudinal sectional view and a partially enlarged longitudinal sectional view of an entire injection molding machine of a preferred embodiment of an injection control method for the injection molding machine according to the present invention.

FIG. 2 is a longitudinal sectional view schematically showing an operating state of a screw in a first example of a method of detecting a resin characteristic when a PV (T) characteristic relational expression used in an injection control method of an injection molding machine according to the present invention is determined. It is.

FIG. 3 is a longitudinal sectional view schematically showing an operation state of a screw in a second example of a method of detecting a resin characteristic when determining a PV (T) characteristic relation used in an injection control method of an injection molding machine according to the present invention. It is.

FIG. 4 is a graph showing that a residual molten resin volume value on the tip side of the screw described in Example 1 is obtained by an extrapolation method.

FIG. 5 is a longitudinal sectional view schematically showing an operation state of a screw when obtaining a calculation formula relating to a movement distance of a screw for making an injection weight value used for injection control constant in an injection control method for an injection molding machine according to the present invention. It is.

FIG. 6 is a first diagram illustrating an injection control method for an injection molding machine according to the present invention.
It is a half-illustrated longitudinal cross-sectional view of a specific example apparatus of the injection control method of the example.

FIG. 7 shows a second embodiment of the injection control method for the injection molding machine according to the present invention.
It is a half-illustrated longitudinal cross-sectional view of a specific example apparatus of the injection control method of the example.

FIG. 8 is a graph for explaining a plane approximation method of PVT characteristics according to another embodiment of the injection control method of the injection molding machine according to the present invention.

[Explanation of symbols]

 10 Mold 11 Injection molding machine 12 Nozzle part 13 Cylinder 14 Heating device 15 Material hopper 16 Flow path 17 Gate 18 Cavity part 19 Screw 20 Cavity rotating motor 21 Base 22 Electromagnetic flow valve 23 Electromagnetic pressure valve 24 Control device 25 Hydraulic source 26 pipe Path 27 Hydraulic piston device 28 Screw position detector 29 PVT calculator 30 Resin temperature detector 31 Oil pressure detector 32 External input device 33 Shutoff valve 34 Electromagnetic drive 35 Operation lever 36 Conical tip 37 Helical part 38 Flange protrusion 39 Ring-shaped sliding valve body 40 Check valve

Claims (7)

(57) [Claims] 1. An injection control method for an injection molding machine for controlling an injection weight of a plasticized synthetic resin to be injected and filled into a cavity of a molding die from the inside of a cylinder of the injection molding machine. The moving distance S _D of the screw at the time of injection filling of the plasticized synthetic resin corresponding to G is calculated and set in advance by a predetermined formula, and the predetermined moving distance S _D of the screw is set to the value immediately before the screw is injected. An injection control method for an injection molding machine, wherein the injection filling of the plasticized synthetic resin into the cavity of the molding die is stopped at a time point when the screw is moved from the position of the screw. 2. The calculation according to a predetermined formula of the screw moving distance _SD at the time of injection filling of the plasticized synthetic resin corresponding to the weight value G of the molded product is performed by detecting or setting the plasticized synthetic resin immediately before injection. The molten resin pressure value P _{I of the} resin and the molten resin pressure value P of the plasticized synthetic resin at the time of holding pressure following injection.
_H and the detected screw position value S immediately before injection
_{Based on I} and the PV characteristic relational expression of the plasticized synthetic resin, based on a constant molten resin temperature value T, the following equation: S _H; projected cross-sectional area V (P _H) of the _screw; position value A of the screw subsequent to the injection rather pressure holding the molten resin specific volume value V (P _I) of the subsequent the injection rather holding time; injection immediately before time The injection control method for an injection molding machine according to claim 1, wherein the method is performed by using a specific volume value of a molten resin. 3. The detected molten resin pressure value P _I of the plasticized synthetic resin immediately before injection and the molten resin pressure value P _H of the plasticized synthetic resin at the time of holding pressure subsequent to injection are determined during continuous molding. 3. The injection control method for an injection molding machine according to claim 2, wherein each of the molten resin pressure values P _I and P _{H is} an average value detected based on a plurality of short-time injection fillings. 4. The molten resin pressure value P _I of the plasticized synthetic resin immediately before the injection and the molten resin pressure value P of the plasticized synthetic resin at the time of holding pressure subsequent to the injection as the weight value G of the molded article.
_{If H} is equal, A: Projected sectional area of screw ΔS ₀ ; Molten resin pressure value P just before screw injection
Claim 2 or characterized by using the difference [Delta] S ₀ using the relational expression of the difference between the position values in the melt of the subsequent dwell time on the position value and the injection of _I resin pressure value P _H (= P _I) 3. The injection control method for an injection molding machine according to any one of 3. 5. The calculation according to a predetermined formula of the screw moving distance _SD at the time of injection filling of the plasticized synthetic resin corresponding to the weight value G of the molded article is performed by detecting or setting the injected plasticized synthetic resin. The molten resin temperature value T, the molten resin pressure value P _I of the plasticized synthetic resin immediately before injection, the molten resin pressure value P _H of the plasticized synthetic resin during holding pressure following injection, and the detected immediately before injection. Based on the screw position value S _I and the PVT characteristic relational expression of the plasticized synthetic resin, the following equation is obtained. S _H ; Screw position value during dwelling following injection A: Projected cross-sectional area of screw V (P _H , T); Molten resin temperature T and dwelling pressure following injection at molten resin temperature T Resin specific volume value V (P _I , T) at the time of molten resin pressure value P _H at the time of molten resin temperature value T and molten resin pressure value P _I immediately before injection at molten resin temperature value T The injection control method for an injection molding machine according to claim 1, wherein the method is performed based on a specific volume value of a molten resin. 6. The detected molten resin temperature value T of the injected plasticized synthetic resin, the molten resin pressure value P _I of the plasticized synthetic resin immediately before the injection, and the plasticization synthesis at the time of the pressure holding following the injection. The molten resin pressure value P _H of the resin is an average value of each molten resin temperature value T and the molten resin pressure values P _I and P _H detected based on a plurality of short-time injection fillings during continuous molding. The injection control method for an injection molding machine according to claim 5, wherein: 7. A variation range of the molten resin pressure value P and the molten resin temperature value T when obtaining the molten resin pressure ratio value V from the molten resin pressure value P and the molten resin temperature value T based on the PVT characteristic relational expression. 7. The injection control method for an injection molding machine according to claim 5, wherein the distance is within a predetermined range and is obtained by a plane approximation method.