JP2007331160A - Control device of electromotive injection molding machine and pressure detection method of electromotive injection molding machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect the pressure of a resin by precisely removing the effect of inertial force from the detection value by a detection means for detecting the pressure of the resin and also removing high frequency noise. <P>SOLUTION: The transmission function of a transmission mechanism for transmitting the torque of a motor 3 for allowing a screw 1 to advance and retreat is specified on the basis of the transmission function of low order delay to be preset to a pressure correction part 21. The pressure correction part 21 calculates the acceleration of the screw from the angle-of-rotation acceleration of the motor calculated from the angle of rotation of the motor detected by an encoder 8 and the transmission function. The acceleration of the screw is multiplied by the whole mass from a member to which a load cell is attached to the screw to calculate inertial force. The detection force of the load cell is corrected by the inertial force to calculate the pressure estimate value of the resin. Since the detection force of the load cell is corrected by the inertial force based on the acceleration of the screw, the more accurate pressure estimate value of the resin is obtained. Further, since the transmission function of low order delay becomes a form of a low pass filter, high frequency noise is removed based on the pressure estimate value of the resin. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a control device for an electric injection molding machine that drives an injection mechanism with a motor and a pressure detection method for the electric injection molding machine.

  In an electric injection molding machine that drives an injection screw in the axial direction by a motor and moves the screw back and forth, the resin pressure is detected, and the motor is controlled based on the detected resin pressure. Controls such as back pressure during measurement. As a means for detecting the resin pressure, a pressure detecting means such as a load cell is provided in a transmission mechanism for transmitting the motor torque to the screw, and the injection pressure and pressure holding pressure are determined based on the detected value detected by the pressure detecting means. A method for controlling pressure, back pressure and the like is generally performed.

The detection force detected by this load cell is the sum of the resin pressure and the inertial force of the member in the transmission mechanism from the member to which the load cell is attached to the screw.
Load cell detection force = (resin pressure x screw cross-sectional area) + inertia force The force detected by the load cell in this way includes the inertia force of all members from the member to which the load cell is attached to the screw. Therefore, in order to detect the resin pressure, this inertial force must be removed from the load cell detecting force.

Therefore, the rotational speed of the injection motor that moves the screw back and forth is detected, the acceleration is differentiated by calculating the speed, and the acceleration is multiplied by the mass of the injection screw as shown in the following equation. Seeking power,
Inertia force = acceleration of injection motor × mass of injection screw There is known an invention in which this inertial force is corrected by adding it to the detected pressure with a load cell (see Patent Document 1).

  Further, the speed of the injection motor is detected, the detected speed is differentiated to obtain the acceleration of the injection motor, and the inertial force is obtained from the mass of the movable member interposed between the molten resin and the load cell. There is also known an invention that detects the resin pressure by correcting the detection force detected in (see Patent Document 2).

JP-A-4-29818 JP 2003-191285 A

  FIG. 1 is an explanatory view of a main part of an electric injection molding machine having a configuration in which a load cell as a detecting unit is arranged in the middle of a transmission mechanism for transmitting the torque of a motor to a screw to detect a resin pressure. The screw 1 is connected to the motor 3 via a transmission mechanism that transmits the torque of the motor 3, and a load cell 4 is attached to a member in the transmission mechanism, and the pressure from the resin 6 applied to the screw 1 (in the drawing, resin Is conceptually represented as a resistance element). In the example shown in FIG. 1, the rotational torque from the motor 3 is moved forward and backward by driving the screw 1 in the axial direction by linearly moving the pusher plate 2 via a torque transmission mechanism such as a timing belt mechanism or a ball screw / nut mechanism. The load cell 4 is attached as a pressure detection means to a member in the torque transmission mechanism to detect the resin pressure. In the figure, reference numeral 5 conceptually represents the transmission mechanism as a spring element. In particular, in the transmission mechanism, the screw 1 is attached to the pusher plate 2 and attached to the load cell and a member connected to the pusher plate. Therefore, the spring element 5 of the transmission mechanism is a member to which the load cell 4 is attached from the motor 3. The main causes are the transmission mechanism by the timing belt and the elasticity of the element by the ball screw / nut mechanism. Further, when the speed reducer is used without using the timing belt, the influence of the spring element of the speed reducer is large.

  Since the transmission mechanism includes the spring element 5 as described above, the rotational speed and acceleration of the motor 3 do not always coincide with the speed and acceleration of the screw 1. The speed and acceleration of the screw 1 are delayed from the speed and acceleration of the motor 3.

  Therefore, as in the prior art described in Patent Documents 1 and 2, the inertial force is estimated from the mass of the screw or the pusher plate integrated with the screw based on the acceleration of the motor, and the force detected by the load cell is calculated. Even if the correction is performed, the phase of the estimated inertial force does not match the phase of the true inertial force, and the inertial force estimation error increases. In particular, in the case where the pusher plate 2 is provided with a screw rotation motor for rotating the screw 1, a transmission mechanism, and the like, the mass of the member moving together with the pusher plate 2 increases, and the inertial force estimation error increases. There is also a problem that the load cell detection force corrected by this inertial force and the detected resin pressure obtained from the load cell detection force have a large error.

  The acceleration is obtained by time differentiation of the speed detection value detected by a speed detector such as an encoder attached to the motor. At this stage of time differentiation, the high frequency noise component included in the speed detection value is amplified. The calculated acceleration contains a lot of high frequency noise. Therefore, even if the inertial force is obtained by using the motor acceleration obtained by differentiating the detected speed of the motor with respect to time, and the detected resin pressure is obtained by correcting the load cell detecting force with this inertial force, the detected resin pressure Contains a lot of high-frequency noise. There is a problem that control is not stable even if pressure control such as injection pressure, holding pressure, and back pressure is performed using the detected resin pressure that contains a lot of high-frequency noise.

  Accordingly, the present invention is to provide a control device and a pressure detection method for an electric injection molding machine that improve the above-described problems of the prior art and can detect a resin pressure more accurately.

The invention according to claims 1 to 3 of the present application includes a motor for driving an injection screw in an axial direction, a transmission mechanism for transmitting motor torque to the screw, means for detecting motor rotation angular acceleration, and the transmission mechanism. A control device for an electric injection molding machine having pressure detecting means attached to a member for detecting a resin pressure, wherein the invention according to claim 1 is the motor rotational angular acceleration obtained by the means for detecting the motor rotational angular acceleration. Estimating means for estimating the screw acceleration based on the detected value and the set low-order lag transfer function of the transmission mechanism, and a movable member from the member to which the estimated value of the screw acceleration and the pressure detecting means are attached to the screw Correction means for obtaining a resin pressure by obtaining an inertial force from the total mass of the resin and correcting a detection value detected by the pressure detection means with the inertial force.
According to a second aspect of the present invention, the transmission mechanism is a transmission mechanism that uses a timing belt, and the screw acceleration is estimated using the transfer function of the transmission mechanism as a transfer function of a second-order lag. Further, in the invention according to claim 3, instead of the estimation means for estimating the screw acceleration, the gain of the transfer function of the transmission mechanism corresponds to the total mass of the movable member from the member to which the pressure detection means is attached to the screw. The estimating means for estimating the inertial force is used, and the correcting means corrects the detection value detected by the pressure detecting means with the inertial force estimated by the estimating means for estimating the inertial force to obtain the resin pressure. It was supposed to be.

The invention according to claims 4 to 8 includes a motor for driving an injection screw in the axial direction, a transmission mechanism for transmitting motor torque to the screw, means for detecting motor rotation angular acceleration, and a member in the transmission mechanism. A pressure detection method for an electric injection molding machine having pressure detection means for detecting a resin pressure attached to the motor, wherein the invention according to claim 4 is a transfer function of the transmission mechanism for converting a motor rotation angular velocity into a screw acceleration. Is determined as a low-order lag transfer function, the screw acceleration is estimated based on the motor rotation angular acceleration detected value by the motor rotation angular acceleration detection means and the transfer function, and the screw acceleration is estimated based on the estimated value of the screw acceleration. The detection value detected by the pressure detection means is corrected to obtain the resin pressure.
The invention according to claim 5 corrects the detected value detected by the pressure detecting means by calculating an inertial force from an estimated value of screw acceleration and the total mass of the movable member from the member to which the pressure detecting means is attached to the screw. Thus, the inertial force is corrected by subtracting it from the detected value detected by the pressure detecting means.

Furthermore, in the invention according to claim 6, as a method of determining the transfer function,
1. Without supplying resin material, only the screw is moved and the air shot is ejected.
2. Storing the pressure detection value and the motor rotation angular acceleration detection value during the injection operation;
3. The initial value is given to the coefficient of the transfer function, the motor rotation angular acceleration is input to the transfer function, the screw acceleration is obtained,
4). Identifying a coefficient of the transfer function from the pressure detection value and the obtained screw acceleration, and determining a transfer function;
It was supposed to be.

The invention according to claim 7 uses a transmission mechanism using a timing belt as the transmission mechanism, the transfer function is a second-order lag transfer function, and the second-order lag transfer function is defined as:
1. Determining the first coefficient of the transfer function so that the time of occurrence of the first peak of the pressure detection value is equal to the time of occurrence of the first peak of the obtained screw acceleration;
2. The ratio between the first peak value and the second peak value of the pressure detection value is equal to the ratio between the first peak value and the second peak value of the obtained screw acceleration. Determining a second coefficient of the transfer function;
The transfer function of the second-order lag is determined.
In the invention according to claim 8, as a method of obtaining the total mass of the movable member from the member to which the pressure detecting means is attached to the screw, a value obtained by multiplying the obtained first peak acceleration value by a gain is The gain of the transfer function was determined so as to coincide with the value of the first peak of the pressure detection value, and the gain was set as the mass.

  Since the estimated value of the screw acceleration is obtained and the detected value detected by the pressure detecting means is corrected based on the estimated value of the screw acceleration to detect the resin pressure, a more accurate resin pressure can be obtained. . Moreover, since the screw acceleration is obtained by inputting the detected value of the motor rotation angular acceleration into a low-order delay transfer function, the high-frequency noise is removed, and the resin pressure can be controlled stably without the high-frequency noise.

  As shown in FIG. 1, in the transmission mechanism from the motor 3 to the screw 1, a spring element exists between the motor 3 and the member to which the load cell 4 is attached. In particular, in the case of transmission means such as a transmission means using a timing belt mechanism or a speed reducer disposed between them, this spring element has a great influence, and problems such as the phase difference between the motor rotational acceleration and the screw acceleration occur. Due to the influence of the spring element, the rotational speed of the motor, the acceleration and the forward / backward speed and acceleration of the screw are different, so the member from the load cell 4 attached to the screw 1 is integrated (screw, pusher plate, load cell attached) Member 1), the mass is m, the acceleration of the screw is α, the resin pressure is Prgn, the cross-sectional area of the screw 1 is S, and the detection force (detection value) detected by the load cell is Fcell, the screw 1 and the pusher plate The equation of motion for 2 etc. is the following equation.

Fcell-Prgn × S = m × α (1)
Further, “m × α” on the right side of the above equation (1) is the inertial force of the transmission means from the member to which the load cell 4 is attached to the screw 1.

  From this equation (1), the resin pressure Prgn can be obtained by subtracting the inertial force from the load cell detection force (detection value) Fcell and dividing by the screw cross-sectional area S as shown in the following two equations. It will be sought.

Prgn = (Fcell−m × α) / S (2)
In the above formulas (1) and (2), the mass m and the screw cross-sectional area S of the movable member that moves together with the screw 1 from the member to which the load cell 4 is attached to the screw 1 can be obtained in advance and are known. Therefore, if the acceleration α of the screw 1 is known, the resin pressure Prgn corrected for the inertial force can be obtained.

  Therefore, the present invention estimates the inertial force by obtaining the acceleration of the screw 1 from the rotational angular acceleration of the motor, using the transfer function of the transmission mechanism that transmits the motor torque from the motor 3 to the screw 1 as a low-order delay transfer function. The inertial force is corrected for the detection value of the load cell, which is a pressure detector, to detect the resin pressure.

  FIG. 2 is a principal block diagram of an embodiment of the present invention. A load cell 4 as a detecting means is arranged in the middle of the transmission mechanism for transmitting the torque of the motor 3 shown in FIG. 1 to the screw 1 to detect the resin pressure and perform pressure control such as injection pressure, holding pressure, and back pressure. It is a principal part block diagram of the electric injection molding machine of a structure, and the structure of the mechanism part 10 is the same as the prior art example shown in FIG. However, as compared with FIG. 1, an encoder 8 as a position detector for detecting the rotation angle of the motor 3 and an amplifier 7 for driving the motor 3 are described.

  The motor 3 linearly moves the pusher plate 2 through a transmission mechanism that transmits a force such as a timing belt mechanism or a ball screw / nut mechanism, and moves the screw 1 attached to the pusher plate 2 back and forth. A load cell 4 is attached to a member in the transmission mechanism, and the pressure from the resin applied to the screw 1 is detected by the load cell 4. Reference numeral 5 in the drawing conceptually represents the transmission mechanism as a spring element.

  The detection force (detection value) of the load cell 4 is input to the pressure correction unit 21 of the control device 20 of the electric injection molding machine. Further, the motor rotation angle detected by the encoder 8 is also input to the pressure correction unit 21.

  The control unit 20 of the electric injection molding machine is a processor, a memory such as a ROM and a RAM, the position and speed of the motor that drives each movable part of the injection molding machine, and the axis control for force control, as in the conventional control unit. Department. This axis controller is also composed of a processor and a memory such as a ROM and a RAM, and is configured to digitally control the motor.

The pressure controller 21 and the pressure controller 22 for inputting the estimated resin pressure value obtained by the pressure corrector 21 are axes for servo-controlling the injection motor 3 for moving the screw 1 back and forth in the injection direction in the controller 20. It is provided in the control unit.
The present embodiment is characterized in that the pressure correction unit 21 is provided as compared with a conventional control device. Conventionally, the resin pressure is obtained from the detection value detected by the load cell 4 and passed to the pressure control unit 22, and the pressure control unit 22 performs pressure control such as feedback control so that the detected resin pressure matches the set resin pressure. The configuration of the pressure control unit 22 is the same as the conventional one, and the pressure correction unit 21 is different. Also in the inventions described in Patent Documents 1 and 2, an inertial force is obtained based on the rotational acceleration of the motor, and the detected force detected by the load cell 4 is corrected by the inertial force to obtain an estimated resin pressure value. In this embodiment, the inertial force is not obtained from the rotational acceleration of the motor, but the inertial force is obtained from the screw acceleration to correct the detection force at the load cell 4 in this embodiment. The configuration of the pressure correction unit 21 is different in that the estimated resin pressure value is obtained and output to the pressure control unit 22.

  That is, the pressure correction unit 21 of the present embodiment reads the detection force Fcell output from the load cell 4 and the rotation angle θ of the motor from the encoder 8 every predetermined cycle, and obtains the rotation angular velocity of the motor from the rotation angle θ of the motor. A movable member that moves together with the screw of the transmission means from the load cell 4 to the screw 1 by inputting the transfer function of the transmission mechanism from the motor 3 to the screw 1 set in advance to the rotational angular velocity of the motor to obtain the acceleration of the screw. The inertial force is obtained by multiplying the total mass of the screw by the acceleration of the obtained screw, and the value obtained by subtracting the inertial force from the detection force Fcell output from the load cell 4 by the cross-sectional area S of the screw is obtained. That is, the resin pressure Prgn is obtained by performing the calculation of the above-described equation (2) and output to the pressure control unit 22. The processing of the pressure control unit 22 is the same as that of the prior art.

  FIG. 3 illustrates a resin pressure estimation process performed by the processor of the shaft control unit that performs servo control of the injection motor 3 that moves the screw 1 of the control device 20 back and forth as the process of the pressure correction unit 21. It is a flowchart which shows an algorithm. When the resin pressure is detected at the time of injection / holding pressure, when controlling the resin pressure at the time of back pressure control at the time of metering, etc., the processor executes the process shown in FIG. 3 every predetermined period Δt.

The detection force Fcell of the output of the load cell 4 is read, and the motor rotation angle θ which is the output of the encoder 8 is read (steps 100 and 101).
The motor rotation angular velocity θ ′ is obtained by subtracting the motor rotation angle of the previous cycle stored in the reading register R (θ) in the previous cycle from the read motor rotation angle θ and dividing by the cycle Δt (step 102).
The motor rotation angle θ read in step 101 is stored in the register R (θ) (step 103).

  A motor rotation angular acceleration θ ″ is obtained by subtracting the motor rotation angular velocity θ ′ of the previous cycle obtained in the previous cycle from the motor rotation angular velocity θ ′ obtained in step 102 and stored in the register R (θ ′) and dividing it by the cycle Δt. (Step 104) The means for detecting the motor rotation angular acceleration of the present invention is constituted by the processing of this step 104 by the encoder 8 and the processor.

The motor rotational angular velocity θ ′ obtained in step 102 is stored in the register R (θ ′) (step 105).
The transfer function of the force of the transmission mechanism that transmits the output torque of the motor to the screw is set in advance, and the acceleration α of the screw 1 is obtained from this transfer function and the motor rotational angular velocity θ ″ obtained in step 104 (step 106).

  The obtained screw acceleration α is multiplied by the total mass m of the movable member that moves together with the screw 1 from the member provided with the preset load cell to the screw 1 together with the screw 1 after the member provided with the load cell. The inertial force (m × α) of the moving member is obtained (step 107).

The inertia force (m × α) is subtracted from the detection force Fcell at the load cell obtained in step 100, and divided by the period Δt to obtain an estimated value Prgn of the resin pressure (step 108).
The obtained estimated value Prgn of the resin pressure is output to the pressure control unit 22 (step 109), and the process of the cycle of the pressure correction unit 21 is ended.

  In the above-described embodiment, the motor acceleration θ ″ is obtained from the detected rotation angle θ of the motor. However, if a speed detector for detecting the rotation angular velocity of the motor is provided, it is detected by the speed detector. The rotational angular velocity of the motor may be obtained by differentiating the rotational angular velocity (dividing the difference between the detected rotational angular velocity and the detected rotational angular velocity in the previous period by the period Δt).

Next, a method for obtaining and setting the transfer function of the transfer mechanism set in the control device 20 of the electric injection molding machine will be described.
First, the type of transfer function is determined in accordance with the configuration of the force transmission mechanism from the motor 3 to the screw 1. This transfer function is a transfer function of a low-order delay element in the form of a low-pass filter. Then, the injection operation is performed by air shot in which only the screw 1 is moved and the injection operation is performed without supplying the resin material, the detection value of the load cell and the detection value of the motor rotation angle or the rotation angular velocity at this time are obtained and stored, and The motor rotation angular acceleration is obtained and stored from the stored motor rotation angle or rotation angular velocity. Determine the screw acceleration based on the motor rotation angular acceleration and the transfer function, determine the transfer function coefficient so that the screw acceleration pattern is almost similar to the detection force pattern detected by the load cell, and determine the transfer function. The transfer function is set in the control device.

  As an example, specification of a transfer function in the case of a transmission mechanism that transmits a motor torque to a screw using a timing belt mechanism will be described. In the case of a transmission mechanism using a timing belt mechanism, a second-order lag transfer function is suitable, and this transfer function is in the form of a low-pass filter. The second-order lag transfer function f (s) is expressed as follows.

f (s) = ω ² / (s ² + 2δωs + ω ² ) (3)
In the above equation (3), s is a complex variable of Laplace transform, ω is a natural angular frequency, and is a first coefficient necessary for specifying a transfer function. Further, δ is an attenuation coefficient and is a second coefficient necessary for specifying the transfer function. Once these two coefficients are determined, this transfer function is specified.

First, as described above, an injection operation is performed by air shot in which only the screw is moved and the injection operation is performed without supplying the resin material.
The detection value Fcell (t) detected by the load cell 4 at this time and the detected value of the motor rotation angular velocity θ ′ are obtained (the motor rotation angle is detected, the motor rotation angle is time-differentiated to obtain the motor rotation angular velocity) and stored. To do. Assume that the detection power detected by this load cell is as shown in FIG.
The motor rotation angular acceleration θ ″ is obtained and stored from the stored detected value of the motor rotation angular velocity.

  The screw acceleration α is obtained by inputting the motor rotational angular acceleration to the transfer function f (s) of the transfer mechanism in which the initial value is given to the coefficient of the predetermined transfer function. It is assumed that the screw acceleration α (t) is as shown in FIG.

In FIG.
t1: Time when the first peak value of the detection force Fcell (t) at the load cell 4 is obtained t′1: Time when the first peak value is obtained at the screw acceleration α (t) t2: The detection force Fcell (t) at the load cell 4 When the second peak value is obtained at t′2: When the second peak value is obtained at screw acceleration α (t),
The natural angular frequency ω, which is the first coefficient of the transfer function f (s), is adjusted and determined so that t1 = t′1.

  Next, the ratio between the first peak value Fcell (t1) of the load cell detection power and the second peak value Fcell (t2) is determined so that the first peak value α (t′1) of the screw acceleration and the second peak value α ( t′2) Attenuation which is the second coefficient of the transfer function f (s) so that the ratios coincide (Fcell (t1): Fcell (t2) = α (t′1): α (t′2)) The coefficient δ is adjusted and determined.

Thus, the transfer function f (s) of the transfer mechanism is specified and set in the control device.
As described above, since the transfer function f (s) of the transfer mechanism is a transfer function of a low-order lag element in accordance with the configuration of the transfer mechanism, a transfer function in the form of a low-pass filter is used. When the motor rotation acceleration is input to the low-pass filter of the transfer function f (s) in the unit 21 to obtain the estimated value of the screw acceleration α, the high-frequency noise included in the motor acceleration is removed, so that the estimated value of the screw acceleration α Does not contain high frequency noise. Therefore, the estimated resin pressure value corrected by the screw acceleration α does not include high-frequency noise, and pressure control such as injection pressure, holding pressure, and back pressure is performed based on the pressure that does not include high-frequency noise. Stable pressure control is possible.

  In addition, in the load cell detection force Fcell (t) and the screw acceleration α (t), the first peak value generation time is made the same, and the ratio of the first and second peak values is made the same so that the load cell detection force Fcell (t) Since the patterns of t) and screw acceleration α (t) are substantially similar, the estimated inertial force (m × α) is in phase with the true inertial force, and the inertial force is accurately determined. Since the load cell detection force Fcell (t) is corrected with this highly accurate inertial force to obtain an estimated value of the resin pressure, the resin pressure can be detected with high accuracy.

  Further, the mass m of the member from the member to which the load cell 4 is attached to the screw 1 may be determined by measuring and calculating the mass of the square member, but this transfer function f (s) The mass m may be obtained with this gain by adjusting the gain. In this case, the gain is adjusted so that a value obtained by multiplying the initial peak value α (t′1) of the screw acceleration by the gain K coincides with the initial peak value Fcell (t1) of the load cell detection force. That is, the gain K is determined so that Fcell (t1) = α (t′1) × K. After all, since the injection is performed by air shot, the gain K corresponds to the mass m of the member from the member to which the load cell 4 is attached to the screw 1, and therefore, the gain K may be set to the mass m. It is.

  Further, since the inertial force described above corrects the load cell detection value, if the gain of the transfer function is set to correspond to the mass m of the member from the member to which the load cell 4 is attached to the screw 1, If the motor acceleration is processed by this transfer function, an inertial force can be obtained instead of the screw acceleration, and the load cell detection value can be corrected by this inertial force.

  FIG. 5 shows waveforms of the load cell detection resin pressure Fcell (t) / S obtained by dividing the detection force Fcell detected by the load cell by the screw sectional area S, and the actual resin pressure Prgn and screw acceleration α (t). FIG. When the screw acceleration α (t) is increased in the positive direction, the inertial force (m × α (t)) increases. Therefore, the load cell detection resin pressure Fcell (t) / S is higher than the actual resin pressure Prgn. It is getting bigger. Further, when the screw acceleration α (t) is increased in the minus direction, the inertial force (m × α (t)) increases in the minus direction, so that the load cell detection resin pressure Fcell (t) / S is an actual value. It is smaller than the resin pressure Prgn. However, in the present invention, since the inertial force is corrected with respect to the load cell detection force to obtain the load cell detection resin pressure Fcell (t) / S, the influence of the inertia force is removed and the detection resin pressure is estimated. The value is close to the actual resin pressure Prgn.

It is principal part explanatory drawing of the electric injection molding machine of the structure which arrange | positions a load cell in the middle of the transmission mechanism which transmits the torque of a motor to a screw, and detects a resin pressure. It is a principal part block diagram of one Embodiment of this invention. It is a flowchart which shows the algorithm of the resin pressure estimation process in the pressure correction part in the embodiment. It is explanatory drawing of the relationship between the load cell detection force and screw acceleration in the procedure for determining the transfer function of a transmission means in the embodiment. It is a figure which shows the waveform of the resin pressure detected with a load cell, an actual resin pressure, and screw acceleration.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Screw 2 Pusher plate 3 Motor 4 Load cell 5 Spring element 6 Resin 7 Amplifier 8 Encoder 10 Mechanism part 20 Control apparatus 21 Pressure correction part 22 Pressure control part

Claims (8)

A motor for driving an injection screw in the axial direction, a transmission mechanism for transmitting motor torque to the screw, a means for detecting motor rotational angular acceleration, and a pressure detector for detecting resin pressure attached to a member in the transmission mechanism In a control device for an electric injection molding machine having means,
An estimation means for estimating a screw acceleration based on a detected value of the motor rotation angular acceleration obtained by the means for detecting the motor rotation angular acceleration and a low-order delay transfer function of the set transmission mechanism;
The inertial force is obtained from the estimated value of the screw acceleration and the total mass of the movable member from the member to which the pressure detecting means is attached to the screw, and the detected value detected by the pressure detecting means is corrected by the inertial force to obtain the resin pressure. A control device for an electric injection molding machine, comprising: a correcting means for obtaining   The control device for an electric injection molding machine according to claim 1, wherein the transmission mechanism is a transmission mechanism using a timing belt, and a transfer function of the transmission mechanism is a second-order lag transfer function.   Instead of estimating means for estimating the screw acceleration, the gain for the transfer function of the transmission mechanism is assumed to correspond to the total mass of the movable member from the member to which the pressure detecting means is attached to the screw, and the estimation for estimating the inertial force is performed. The correction means calculates the resin pressure by correcting the detection value detected by the pressure detection means with the inertia force estimated by the estimation means for estimating the inertia force. The control apparatus of the electric injection molding machine described in 1. A motor for driving an injection screw in the axial direction, a transmission mechanism for transmitting motor torque to the screw, a means for detecting motor rotation angular acceleration, and a pressure for detecting a resin pressure attached to a member in the transmission mechanism In the pressure detection method of the electric injection molding machine having the detection means,
The transfer function of the transfer mechanism that converts the motor rotation angular velocity to screw acceleration is defined as a low-order delay transfer function,
Based on the motor rotation angular acceleration detected value by the motor rotation angular acceleration detection means and the transfer function, the screw acceleration is estimated,
A pressure detection method for an electric injection molding machine, wherein a resin pressure is obtained by correcting a detection value detected by the pressure detection means on the basis of an estimated value of the screw acceleration.   The detection value detected by the pressure detection means is corrected by obtaining the inertial force from the estimated value of the screw acceleration and the total mass of the movable member from the member to which the pressure detection means is attached to the screw, and detecting the inertial force. The pressure detection method for an electric injection molding machine according to claim 4, wherein the correction is made by subtracting from the detected value detected by the means. The transfer function is defined as follows:
1. Without supplying resin material, only the screw is moved and the air shot is ejected.
2. Storing the pressure detection value and the motor rotation angular acceleration detection value during the injection operation;
3. The initial value is given to the coefficient of the transfer function, the motor rotation angular acceleration is input to the transfer function, the screw acceleration is obtained,
4). The coefficient of the transfer function is identified from the pressure detection value and the obtained screw acceleration,
Determine the transfer function,
The pressure detection method of the electric injection molding machine according to claim 4 or 5, wherein The transmission mechanism is a transmission mechanism that uses a timing belt, and the transfer function is a second-order lag transfer function.
1. Determining the first coefficient of the transfer function so that the time of occurrence of the first peak of the pressure detection value is equal to the time of occurrence of the first peak of the obtained screw acceleration;
2. The ratio between the first peak value and the second peak value of the pressure detection value is equal to the ratio between the first peak value and the second peak value of the obtained screw acceleration. Determining a second coefficient of the transfer function;
The pressure detection method of the electric injection molding machine according to claim 6, wherein the transfer function of the second-order lag is determined.   By determining the gain of the transfer function so that a value obtained by multiplying the value of the first peak of the obtained screw acceleration by a gain matches the value of the first peak of the pressure detection value, the gain is detected by the pressure detection. The pressure detection method for an electric injection molding machine according to claim 7, wherein the pressure is determined as the total mass of the movable member from the member to which the means is attached to the screw.

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