JPH04368832A - Mold protecting method in electrically-driven injection molder - Google Patents

Abstract

PURPOSE:To prevent molds or the like from being broken by a method wherein the movement of the molds under the condition that foreign matter is left in the molds is immediately detected when the magnitude of disturbance estimated by a disturbance estimation observer, which is assembled in the speed loop of servo circuit relating to mold clamping mechanism, exceeds the set point. CONSTITUTION:Disturbance estimation abserver 50 is assembled in the speed loop of servo circuit relating to mold clamping mechanism. The magnitude y=TL of the disturbance estimated by the disturbance estimation observer 50 is detected. When the detected value (y) exceeds the set point TS, molds are judged so as to be putting into motion under the condition that foreign matter is left in the molds. As a result, alarm is issued from a comparator 62 and the motion of the molds is stopped.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mold protection method for an electric injection molding machine in which the mold clamping mechanism of the injection molding machine is driven by a servo motor.

0002

[Prior Art] In the mold clamping process of an injection molding machine, if the mold is clamped with foreign matter such as a molded product remaining between the molds, there is a risk of damaging the mold. A so-called mold protection zone is established at a slightly earlier position, and in this mold protection zone, a torque limit is applied to the servo motor that moves the mold, limiting its output torque, and the mold is moved with low torque. It was designed to touch the mold (see JP-A-61-114834 and JP-A-63-286315). By doing this, even if the mold is moved with foreign matter such as a molded product remaining between the molds due to a defective drop of the molded product, a large impact force will be applied to the mold, etc., and the mold and molded product will be damaged. This was done to prevent damage to the product.

0003

[Problem to be Solved by the Invention] In mold protection using a servo motor as described above, a timer is normally started when the mold protection start position is reached, and the control is performed from the NC side until the time is up. It is determined whether positioning to the mold touch position has been completed. However, with this method, even after a mold with residual foreign matter is clamped, a weak but additional mold clamping force is applied until the timer times out, and it takes time to make a decision after the occurrence of an event, making it difficult to respond quickly. It lacks. Furthermore, even if you try to increase work efficiency by moving the mold at high speed up to the mold protection zone and then slowing it down from the mold protection start position, the servo motor will not brake in the mold protection zone where the torque limit is applied. Due to the inertia of the mold and the movable platen that fixes the mold, this inertia exceeds the torque of the motor, and there is a risk that the mold will collide without being sufficiently slowed down at the starting point of mold protection. there were.

[0004] Therefore, the present invention provides a mold protection method that can promptly detect that a mold in which foreign matter such as a molded product remains is caught in the mold clamping process, and immediately stop the movement of the mold. The purpose is to provide

[0005]

[Means for Solving the Problems] The present invention includes a disturbance estimation observer for the speed loop of a servo circuit related to a mold clamping mechanism, and when the magnitude of the disturbance estimated by the disturbance estimation observer exceeds a set value. The above-mentioned problem is solved by immediately detecting when the mold is being driven with foreign matter remaining in the mold.

[0006]

[Operation] If a disturbance estimation observer is set up, the disturbance torque can be estimated. Therefore, the torque fluctuation that occurs when a mold with residual foreign matter is sandwiched in the mold closing process is regarded as disturbance torque, and when the disturbance torque estimated by the above observer reaches a set value or more, it is considered that the molded product is not falling properly. If a mold with residual foreign matter is caught in the mold closing process, the movement of the mold is immediately stopped. If the above setting value is set according to the strength of the mechanical part, the mold with residual foreign matter can be removed during the mold closing process before torque that would damage the mold or molded product is generated. It is possible to detect that the object is caught between the two.

[0007]

[Example] Figure 2 shows proportional (P) control for position.
This is a block diagram of a servo motor control system for a mold clamping servo motor of an injection molding machine that performs proportional and integral (PI) control on speed, where KP of transfer function 10 is the position gain in the position loop, and transfer function 12 is In the transfer function in the velocity loop, K1 is an integral constant and K2 is a proportional constant. Further, transfer functions 14 and 16 are motor transfer functions, Kt is a torque constant, J is inertia, and transfer function 18 is a transfer function that calculates position θ by integrating speed θ'. Further, TL is the disturbance torque.

The feedback value of the current position θ is subtracted from the position command value θr, and the difference in position deviation ε (=θr−θ)
is multiplied by the position gain KP to obtain the speed command value Vc, perform PI control using the difference (speed deviation) between the speed command value Vc and the actual speed θ', and obtain the current command value I as the torque command value. The motor is driven by the current command value I. Then, the motor rotates at a speed θ′, and this speed θ′
The current position θ can be found by integrating.

A disturbance estimation observer is assembled for the servo system shown in FIG. FIG. 3 is a block diagram of a model for an observer in a servo motor, and reference numeral 14 denotes a transfer function of the torque constant Kt of the servo motor shown in FIG. 2, and 16a
The transfer function 16 in FIG. 2 is divided into a transfer function 16a of inertia J and an integral term 16b. In this FIG. 3, I is a torque command as an input, θ',
TL means speed and disturbance torque as state variables.

In the model of FIG. 3, the state variable θ'
, TL is as follows.

θ″=(1/J)・TL+(K
t/J)・I・・・・・・(1)
TL'=0...(2)

Note that in equation (1) above, θ'' means acceleration, and in equation (2), TL' means the degree of change in disturbance torque over time.However, in equation (2) above, assuming that there is no change in disturbance torque TL in a short time, It is assumed that TL'=0 as shown below.

From the equations shown in equations (1) and (2) above, if the same-dimensional observers for estimating the velocity θ' and the disturbance TL are assembled using the general method of assembling observers, the observer indicated by reference numeral 50 in FIG. Become. K3 and K4 of terms 52 and 53 of this disturbance estimation observer 50 are parameters of the disturbance estimation observer, and term 51 is the value of a parameter multiplied by the current command value I as a torque command actually output to the servo motor. It is the value obtained by dividing the torque constant Kt by the inertia J. 54 is an integral term.

The term 53 of the observer 50 in FIG.
The output x becomes TL/J. This will be explained below. First, [I・Kt +TL]・[1/(J・S)
]=θ′・・・・・・(3) [I・
(Kt/J)+(θ'-v)K3

+(θ'-v)K4/S)]
(1/S)=v...(4)
(Note that v is the output of the integral term 54 and is the estimated speed.) From the above equation (3),

I=(θ′・J・S−T
L)/Kt...(5)
So, by substituting equation (5) into equation (4) and rearranging, we get
(θ'・J・S-TL)/J
+(θ'-v)K3

+(θ'-v)(K4/S)=v・S...
(6) Also, S(θ′-v)+(θ′-v)・
K3
+(θ
'-v)(K4/S)=TL/J...
(7) From this equation (7), (θ'-v)=(TL/J)・[1/(S+K3
+(K4/S)]


(8) From the above equation (8), the output x of term 53 is expressed by the following equation (9).

[0014] x=(θ'-v)・(K4/S)
=(TL /J)・[K4 (S2 +K3 ・S+
K4 )] ... (9) Therefore, in the above equation (9), if the parameters K3 and K4 are selected so that the control system is stable, x = TL /J ...
...(10), and the value obtained by dividing the disturbance torque TL by the inertia J is estimated.

In this way, the value x (=TL /J) proportional to the disturbance TL obtained by the disturbance estimation observer 50
By multiplying by the parameter J・A of term 60 (J is inertia, A is a constant for matching the unit system), the disturbance torque y=
TL is estimated. The comparator 62 compares this estimated disturbance torque y=TL with the set value Ts set to detect the pinching of a mold with residual foreign matter, and if the estimated disturbance torque y is large, an alarm is activated. The value of the integrator of the speed loop is set to "0", and the subsequent speed command Vc is set to "0" to stop the mold clamping servo motor.

[0016] The above-mentioned setting value Ts, which is set to detect the pinching of a mold with residual foreign matter, is a value that is larger than the static friction of the mold clamping mechanism and smaller than the breaking limit of the mold or molded product. Set to . Thereby, in the mold closing process, it is possible to reliably detect that a mold in which foreign matter remains is caught, and to stop the motor, before the mold or the molded product is destroyed.

FIG. 4 shows a digital servo control system in which the servo control for controlling the output torque, speed, and position of the servo motor used in the present invention is controlled by software using a microprocessor and a control program.

FIG. 4 is a block diagram of essential parts of an embodiment of the present invention, in which reference numeral 1 is a screw, 2 is a fixed platen, and 3 is a movable platen. Types m1 and m2 are attached. The movable platen 3 is adapted to be moved left and right in FIG. 4 by a servo motor M. 4 is a pulse coder attached to the motor shaft of the servo motor M as a position/speed detector. 5 is a cylinder.

Further, 20 is an NC device for controlling the injection molding machine, and the NC device 20 is connected to an NC CPU 31, P
CPU3 for MC (programmable machine controller)
2, the NC CPU 31 is connected to a ROM 37 storing a control program and a RAM 38 used for temporary storage of data, etc., and is connected to the PMC CPU 31 by a bus 45.
U32 is a ROM39 that stores the sequence program.
, RAM 40 used for temporary storage of data, etc. is connected to bus 4.
They are joined by 5. 34 is BAC, which stores NC programs and various setting values, and is used by CPU 31 for NC and C for PMC.
A shared RAM 35 that can be accessed by both the PUs 32, and
The above NC CPU 31 and PMC CPU 32 are connected to the bus 45.
The BAC 34 controls the bus used by the BAC 34. Further, a CRT/MDI 42 is connected to the BAC 34 via an operator panel controller 41.

Reference numeral 33 denotes a CPU for controlling the output torque, speed, and position of the servo motor for each axis of the injection molding machine, that is, for servo control. Servo shared RAM 3 that stores the output circuit 44 and control programs for servo control, etc.
6 is connected, and the servo shared RAM 36 has an NC CP
U31 is connected to the bus.

The input/output circuit 44 includes a driver (D/A
A power amplifier 6 is connected via a converter (including a converter) 7, and the output of the power amplifier 6 drives a mold clamping servo motor M. Further, the input/output circuit 44 receives the output of the power amplifier 6, that is, the drive current value data obtained by converting the drive current of the mold clamping servo motor M by the A/D converter 9, and the output of the pulse coder 4. It looks like this.

In the above configuration, when the injection molding machine is operated, the PMC CPU 32 performs sequence control based on the sequence program stored in the ROM 39, and the NC CPU 31 performs sequence control based on the sequence program stored in the ROM 39.
Each operation of the injection molding machine is controlled by the NC program stored in 5, and movement commands are output to the servo shared RAM 36 for the servo motors of each axis and stored. The servo CPU 33 performs position control, speed control, and torque control of the servo motor for each axis in response to the movement command for each axis. For example, the mold closing command is sent to the servo shared RAM.
36, the servo CPU 33 subtracts the feedback pulse from the pulse coder 4 from this movement command value to obtain the position deviation amount ε, and multiplies this position deviation amount by the position gain KP to obtain the speed command. Based on the speed command, the servo motor M detected by the pulse coder
The current speed of is subtracted to find the speed deviation, speed loop processing is performed to find the current command value to the servo motor M, and this current command value is input via the A/D converter 9 and the input/output circuit 44. Current loop processing is performed based on the difference between the current drive current value of the servo motor M and the current is output to the power amplifier 6 via the input/output circuit 44 and the driver 7, thereby driving the mold clamping servo motor M. .

FIG. 5 shows the servo CP of the NC device 20.
It is a flowchart of the process which U33 performs every position and velocity loop process cycle in response to the command from NC CPU31.

Based on the position command output from the NC device 20 and the current position (position feedback value) detected by the pulse coder 4 attached to the servo motor M, position loop processing is performed in the same manner as in the past to obtain the speed command value Vc. is calculated (step S101). Next, it is determined whether the current position of the movable platen 3 detected by the pulse coder 4 is within the mold protection zone (step S102).
. That is, it is determined whether the current position has exceeded the mold protection start position or reached the mold touch position. If the mold protection zone has not been reached or the mold protection zone has been exceeded, the process moves to step S109, and step S10
Based on the speed command value Vc obtained in step 1 and the actual speed of the servo motor M obtained from the pulse coder 4, speed loop processing is performed in the same manner as before to calculate the current command value I as the torque command value, and this calculated current The command value I is stored in the register together with the actual speed θ' (step S109), the current command value I is delivered as the torque command value to the current loop (step S110), and the processing for the cycle is ended.

On the other hand, if the current position is within the mold protection zone, then it is determined whether or not flag F regarding alarm occurrence is set ("1") (step 103). Note that this flag F is set to "0" by default,
The state of "0" is maintained as long as it is not detected that a mold with residual foreign matter is caught in the mold clamping process. Here, if the flag F is not "1", the processing of the disturbance estimation observer 50 and block 61 shown in FIG. 1 is executed to obtain the estimated disturbance torque y (step S104). To obtain this estimated disturbance torque y, the period before the relevant period (flag F=
This is done by calling up the current command value I and the actual speed θ', which were obtained in the state of zero (0 state) and temporarily stored in a register or the like, and inputting them to the disturbance estimation observer 50 shown in FIG. Note that the subroutine of this step will be described later. Then, it is determined whether the estimated disturbance torque y obtained in this way is larger than a threshold value Ts set to detect that a mold in which a foreign object remains is pinched (step S10).
4) If it is smaller than the threshold Ts, the process moves to step S109, and from the actual speed of the servo motor M obtained by processing the speed command value Vc obtained in step S101 and the position data from the pulse coder 4, The current command value I (torque command value) is calculated by performing speed loop processing in the same manner as before, and after storing this calculated current command value I in a register together with the actual speed θ', the current command value is input to the current loop. I is delivered (steps S109, S110), and the processing of the cycle is ended.

On the other hand, when the estimated disturbance torque y calculated in step S105 is equal to or greater than the threshold value Ts, an alarm is output because it is detected that a mold with residual foreign matter has been pinched (step S106), and the flag F is set to " 1” (step S107), and set the speed command value Vc to “0”.
, after setting the velocity loop integrator to "0" (step S108), perform velocity loop processing (step S109)
. In this speed loop process, a current command value I is determined and passed to the current loop. Also, in this step, the current command value I obtained above is stored in the register together with the actual speed θ'. In this way, the speed command value Vc is "0" and the integrator of the speed loop is "0", so the current command value output by the speed loop processing is the current command value (torque command) in the direction opposite to the mold closing direction by speed feedback. value), so
The servo motor M will stop rapidly. or
It is also possible to bring it into an emergency stop state and end the mold closing operation. In other words, the power amplifier 6 and the mold clamping servo motor U
, V, and W phase winding terminals, and connect the U-phase terminal to the V-phase terminal, the V-phase terminal to the W-phase terminal, and the W-phase terminal to the V-phase terminal through resistors. The mold closing operation is ended by bringing it to a stopped state.

Since the flag F is set to "1" from the next cycle, steps S103 to S
The process moves to step S108, where speed loop processing is performed with the speed command set to "0" and the speed loop integrator set to "0", and the current command value I (torque command value) is determined (step S10
9), it is handed over to the current loop (step S110), and the processing of the cycle is ended.

The subroutine of step S104 (observer processing) in the flowchart of FIG. 5 is shown in the flowchart of FIG. This explains the operation of the disturbance estimation observer 50 shown in FIG. When the process reaches step S104 in the flowchart of FIG. 5, first, the value obtained by multiplying the input current command value I of the previous cycle by the parameter Kt/J is stored in the register R1 (step S201). Next, the actual speed θ′ of the previous cycle
and the estimated speed stored in the accumulator A(v) (which is the estimated speed v of the previous cycle) {θ'-A(v)
} multiplied by the parameter K3 is stored in the register R2 (step S202). Then, the difference {θ'-A(v)} between the actual speed θ' of the previous cycle and the estimated speed stored in the accumulator A(v) is stored in the accumulator A.
Integration is performed by accumulating 1 (step S203).
. Then, the value obtained by multiplying the value accumulated in the accumulator A1 by the parameter K4 is stored in the register R(x) (step S204). Next, steps S201, S202, S20 are applied to accumulator A(v).
Values R1 and R2 respectively calculated in step 3 and stored in the registers
, R(x). After performing the above processing, multiply the R(x) obtained in step S204 by the inertia J and the constant A to obtain the estimated disturbance torque y, and set it in the register R(y).
Store in. Then, the process returns to step S105 in the flowchart of FIG.

[0029]

As described above, according to the present invention, a disturbance estimation observer is installed for the speed loop of a servo circuit related to a mold clamping mechanism, and the magnitude of the disturbance estimated by the disturbance estimation observer is greater than or equal to a set value. By immediately detecting that the mold is being driven with foreign matter remaining in the mold, damage to the mold or molded product can be completely avoided.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a disturbance estimation observer according to an embodiment of the present invention.

FIG. 2 is a block diagram of a servo motor control system.

FIG. 3 is a block diagram of a model that includes a disturbance estimation observer.

FIG. 4 is a block diagram of essential parts showing a digital servo used to control a mold clamping servo motor in the present invention.

FIG. 5 is a flowchart of position and velocity loop processing and disturbance estimation observer processing of this embodiment performed by the digital servo processor.

FIG. 6 is a flowchart of disturbance estimation observer processing.

[Explanation of symbols]

2 Fixed mold 3 Movable mold 4 Pulse coder 20 NC device 50 Disturbance estimation observer M Mold clamping servo motor I Current command value TL as torque command value Disturbance torque θ' Actual speed y of servo motor Estimated disturbance torque

Claims (1)

[Claims] 1. A mold protection method for an electric injection molding machine in which a servo motor is drive-controlled to drive a mold clamping mechanism, the method comprising: configuring a disturbance estimation observer for the speed loop of the servo circuit; Find the value of
A mold protection method for an electric injection molding machine that outputs a mold closing abnormal signal indicating that a foreign object is present in the mold when the detected value exceeds a set value.