JPH0459130B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention provides an injection filling operation of molding material into a cavity of a mold and its subsequent steps by moving an injection screw or an injection plastic gear forward based on the rotational power of an electric motor. The present invention relates to an electric injection device that performs a pressure holding operation, and particularly relates to an injection control method and an improvement of the injection control device.

(Prior Art) In this type of electric injection device, generally, during an injection filling operation in which molding material is filled into the cavity of a mold, the speed of the electric motor is controlled to advance the injection screw or injection plunger. The injection speed is controlled, and during the pressure holding operation after the injection filling operation, the electric motor is torque controlled to ensure the injection holding pressure. .

By the way, in order to stably mold a good molded product using such an electric injection device, the speed control of the electric motor during the injection filling operation and the torque control of the electric motor during the pressure holding operation must be adjusted to the molding conditions. Accordingly, it is necessary to perform the control accurately according to each predetermined control pattern. Therefore, in this type of conventional electric injection device, during the above-mentioned injection filling operation, the electric motor is generally controlled based on a rotational speed feedback control signal obtained by correcting the rotational speed signal of the electric motor with the rotational speed detection signal. During the above-mentioned pressure holding operation, the rotation of the electric motor is controlled based on a torque feedback control signal obtained by correcting the electric motor's torque command signal with the electric motor's torque detection signal. things are being done. In addition, during the above-mentioned injection filling operation, in order to prevent an increase in the output torque due to a decrease in the rotational speed of the electric motor, a torque limiter control is usually performed to suppress the output torque of the electric motor to a value smaller than a predetermined value. It is done in parallel.

In this way, during injection filling operation,
The rotational speed of the electric motor, and therefore the injection speed, as well as the output torque of the electric motor and the injection holding pressure during pressure holding operations, can be precisely controlled according to each control pattern depending on the molding conditions. Therefore, molded products of excellent quality can be stably molded.

(Problem) However, as described above, in such conventional injection control methods, the injection speed and injection holding pressure are controlled according to the molding conditions during the injection filling operation and the subsequent pressure holding operation. Although it is possible to control the electric motor accurately according to the pattern, it is difficult to say that the control stability is always good when switching the electric motor from speed control for injection filling operation to torque control for pressure holding operation, and If the load on the electric motor is small when control is switched to torque control,
There have been problems in which the electric motor momentarily rotates at high speed, leading to molding defects and, in extreme cases, damaging the mold.

The present invention has been made against this background, and its purpose is to provide an injection control method and an injection control device for an electric injection device that can eliminate the above-mentioned problems. It is in.

(Solution Means) In order to achieve the object, in the present invention, the injection screw or the injection plunger as described above is moved forward based on the rotational power of the electric motor, so that the inside of the mold cavity is In an electric injection device that performs an injection filling operation of molding material into a mold and a subsequent pressure holding operation,
During the injection filling operation, under torque limit control based on a predetermined torque upper limit command signal, the electric motor While controlling the rotation of the motor, during pressure holding operation,
Under torque limiter control based on a torque feedback control signal in which a predetermined torque upper limit command signal is corrected by the torque detection signal of the electric motor, the rotation speed command signal of the electric motor is corrected by the rotation speed detection signal. The rotation of the electric motor is controlled based on a speed feedback control signal.

Further, in the present invention, the injection screw or the injection plunger is moved forward based on the rotational power of the electric motor to perform the injection filling operation of the molding material into the cavity of the mold and the subsequent pressure holding operation. In the electric injection device, (a) a rotation speed detection means for detecting the rotation speed of the electric motor and outputting a rotation speed detection signal representing the rotation speed; and (b) rotation torque of the electric motor. (c) a torque detection means for detecting the rotational torque and outputting a torque detection signal representing the rotational torque; (d) rotational speed command signal correction means for correcting the rotational speed with the speed detection signal and outputting a rotational speed feedback control signal; and (d) a torque upper limit command signal outputted according to a preset torque control pattern from the torque detection means. (e) during the injection filling operation, outputs the torque upper limit command signal as it is as a torque upper limit signal; , during the pressure holding operation, torque upper limit signal switching means outputs the torque feedback control signal from the torque upper limit command signal correction means as a torque upper limit signal; and (f) the magnitude of the output current, the torque Torque limiter means for outputting a current drive signal having a magnitude corresponding to the rotational speed feedback control signal from the rotational speed command signal correction means while limiting the current to a magnitude smaller than the magnitude corresponding to the torque upper limit signal from the upper limit signal switching means; ,
(g) The injection control device is configured to include amplifying means for amplifying the drive signal output from the torque limiter means and supplying the amplified signal to the electric motor.

(Operation/Effect) In the method of the present invention, the rotation of the electric motor is controlled based on the rotational speed feedback control signal both during the injection filling operation and during the subsequent pressure holding operation. During a pressure holding operation in which the electric motor stops or is at an extremely low speed, the rotation of the electric motor is substantially controlled based on the torque feedback control signal as the torque upper limit signal.

In other words, during the injection filling operation, the electric motor is precisely controlled in speed according to the rotational speed command signal, and during the pressure holding operation, the electric motor is precisely controlled according to the torque upper limit command signal. This results in better torque control. Therefore, by setting the rotational speed command signal and the torque upper limit command signal according to the molding conditions, the rotational speed of the electric motor and, as a result, the injection speed can be controlled according to the molding conditions during the injection filling operation, similar to the conventional control method. It is possible to accurately control the torque of the electric motor and, by extension, the injection holding pressure during the pressure holding operation, according to the control pattern that corresponds to the molding conditions. , it is possible to stably mold molded products of excellent quality.

By the way, in the injection control method according to the present invention, as mentioned above, the electric motor is basically controlled in speed during the injection filling operation and the subsequent pressure holding operation, and under the speed control, the rotational speed of the electric motor is As the speed decreases, the control state is shifted from speed control to torque control, so the shock when switching from speed control to torque control is small and control stability is extremely excellent. Also, when switching from injection filling operation to pressure holding operation, if the load on the electric motor is small, the electric motor will continue to be controlled in speed, so the rotational speed of the electric motor will momentarily increase. This means that runaway of the electric motor can be effectively avoided, and therefore, problems caused by such runaway of the electric motor can also be avoided.

According to the apparatus of the present invention, such an injection control method can be advantageously implemented.

(Example) Hereinafter, in order to clarify the present invention more specifically, one example thereof will be described in detail based on the drawings.

First, FIG. 1 shows an example of an electric injection device according to the present invention. There, 10
is an injection screw, which is rotatably inserted into the heating cylinder 14 attached to the housing 12 so that it can move forward and backward, and has an injection screw at its base end.
Connected to the bearing box 16 is a rotatably held base block 18. A bearing box 16 that holds this base block 18
is a guide rod 22 disposed on the frame 20.
The injection screw 10 is supported by and can be moved in the axial direction of the injection screw 10, and a first electric servo motor 24 is disposed at its lower end. A pulley 26 is provided on the output shaft of the first electric servo motor 24 and a pulley 28 is provided on the base block 18 of the injection screw 10.
A belt 30 is wound between the injection screw 10 and the injection screw 10 so that the injection screw 10 is rotated by the first electric servo motor 24. As is clear from the above description, the bearing box 16 and the first electric servo motor 24 are adapted to be moved integrally with the injection screw 10.

A ball screw nut 32 is fixed to the bearing box 16, and a ball screw 34 is screwed into the ball screw nut 32 with a predetermined ball screw structure. Ball screw 34
is supported at its base end by the housing 12 so as to be rotatable and immovable in the axial direction,
A pulley 36 is provided in the intermediate portion.
A pulley 36 provided on this ball screw 34 and a pulley 4 provided on the output shaft of a second electric servo motor 38 provided in the housing 12.
A belt 42 is wound between the
As a result, the second electric servo motor 38
Based on the rotational power of the injection screw 10, the injection screw 10 is moved forward and backward in its axial direction.

When the rotational power of the second electric servo motor 38 is transmitted to the ball screw 34 via the belt 42,
Based on the screw engagement with the ball screw 34, the ball screw nut 32 is moved in the axial direction of the injection screw 10, and as a result, the injection screw 10 is moved forward and backward in the axial direction.

Here, a thrust bearing 44 rotatably supports the base end of the ball screw 34.
and the pressure receiving member 46 of the housing 12 that receives the thrust load of the thrust bearing 44,
A load cell 48 is provided, and this load cell 48 controls the injection filling pressure or the injection holding pressure, which will be described later, and the second electric servo motor 38 during the injection filling operation and the subsequent pressure holding operation.
The output torque is detected. Further, the second electric servo motor 38 is provided with an encoder 50, and the actual rotational speed of the second electric servo motor 38 is detected by the encoder 50. Here, the load cell 48 constitutes a torque detection means, and the encoder 50 constitutes a rotational speed detection means.

The housing 12 is guided by a guide rod 22 and moved in the axial direction of the injection screw 10, thereby causing the heating cylinder 14 to move closer to the fixed platen 52 of the mold clamping device. The nozzle can then be touched to the mold. Although not shown, a material supply port for supplying molding material into the heating cylinder 14 is provided at the base end of the heating cylinder 14 .

By the way, in such an injection device, the plasticizing operation of the molding material is performed by the rotation of the injection screw 10 by the first electric servo motor 24, and after the plasticizing operation, the second electric servo motor 38 By moving the injection screw 10 forward toward the nozzle side of the heating cylinder 14, the injection filling operation of the molding material into the cavity of the mold and the subsequent pressure holding operation are performed. The second electric servo motor 38 is circuit-controlled by the control circuit shown in FIG. 2 to perform the injection filling operation and the pressure holding operation.

The method of this embodiment will be explained below while explaining the control circuit shown in FIG. That is, in FIG. 2, 54 is a controller that controls the rotation speed for commanding the rotation speed of the second electric servo motor 38 when the plasticizing operation of the molding material by the first electric servo motor 24 is completed. In addition to outputting a command signal, a torque upper limit command signal for specifying the maximum torque of the second electric servo motor 38 is output.

The rotational speed command signal is input to a subtracter 56, where it is subtracted and corrected using a rotational speed detection signal that is fed back from the encoder 50 and represents the actual rotational speed of the second electric servo motor 38. The rotational speed feedback control signal subtracted and corrected by the subtracter 56 is supplied to the speed control section 58 , where it is subjected to arithmetic processing and supplied to the torque limiter 60 .

As shown in FIG. 2, the rotational speed detection signal fed back from the encoder 50 is converted into a signal corresponding to the rotational speed command signal by the speed signal converter 62, and then supplied to the subtracter 56. be done.

On the other hand, the torque upper limit command signal is supplied to the torque limiter 60 as a torque upper limit signal through one of the open/close switches 64 and 66, which are selectively opened and closed in accordance with the open/close signal from the controller 54. Here, when the open/close switch 64 is closed, the torque upper limit command signal is supplied as is to the torque limiter 60, but when the open/close switch 66 is closed, the torque upper limit command signal is supplied to the subtracter 68 and the torque limiter 60. Control unit 70
The signal is converted into a torque feedback control signal and supplied to the torque limiter 60.

In other words, the subtracter 68 includes the load cell 4
A torque detection signal representing the actual output torque of the second electric servo motor 38 fed back from the second electric servo motor 38 is supplied, and a subtractor 68 to which the torque upper limit command signal is applied performs subtraction correction using the torque detection signal. It is becoming more and more common. Then, a torque feedback control signal obtained by subtracting and correcting this torque upper limit command signal by the torque detection signal is supplied to the torque control section 70, arithmetic processed by the torque control section 70, and sent to the torque limiter 60 as a torque upper limit signal. be made to supply.

Therefore, the rotation speed feedback control signal supplied to the torque limiter 60 is output from the torque limiter 60 as a signal whose maximum current is regulated by the torque upper limit command signal when the open/close switch 64 is closed. When the open/close switch 66 is closed, the torque limiter 60 outputs a signal whose maximum current is regulated by the torque feedback control signal. The output signal from the torque limiter 60 is then supplied to a subtracter 72, where the current detector 7
The current control section 76 is subjected to subtraction correction based on the current detection signal representing the actual drive current of the second electric servo motor 38 fed back from the current control section 76.
After being subjected to arithmetic processing in the current control section 76, the power is converted into power in the power conversion section 78 and then supplied to the second electric servo motor 38.

Here, during the injection filling operation after the plasticizing operation of the molding material, the opening/closing switch 64 is closed, and the torque limiter 6 is closed.
0, the torque upper limit command signal from the controller 54 is directly inputted as the torque upper limit signal. On the other hand, during the pressure holding operation after the injection filling operation, the open/close switch 66 is closed, and a torque feedback control signal is input from the torque control section 70 to the torque limiter 60. It is becoming more and more popular.

Therefore, during the injection filling operation, as described above, the rotational speed feedback control signal whose maximum current is limited by the torque upper limit command signal is output from the torque limiter 60, and as a result, the torque upper limit command signal With the maximum torque being limited, the second electric servo motor 38 is subjected to feedback control in accordance with the rotational speed command signal. Therefore, by setting the rotational speed command signal according to the molding conditions, the forward speed of the injection screw 10, that is, the injection speed, can be accurately controlled according to the control pattern according to the molding conditions, as in the conventional method. It can be controlled.

On the other hand, during the pressure holding operation after the injection filling operation, as described above, the torque limiter 60 outputs a rotational speed feedback control signal whose maximum current is limited by the torque feedback control signal output from the torque controller 70. However,
During such pressure holding operation, the injection screw 1
0, and as a result, the second electric servo motor 38 stops or becomes extremely slow, so the torque limiter 6
0, a current signal corresponding to the torque feedback control signal is outputted, and as a result, the second electric servo motor 38 substantially responds to the torque feedback control signal. Therefore, torque control is performed. Therefore, if the torque upper limit command signal during such pressure holding operation is set according to the molding conditions, the output torque of the second electric servo motor 38, and therefore the injection holding force, can be controlled to It is possible to perform accurate control according to a control pattern depending on the conditions.

As described above, according to this embodiment, during the injection filling operation and the subsequent pressure holding operation, the injection speed and the injection holding pressure are controlled at the same time as before and with precision according to the respective control patterns depending on the molding conditions. It can be well controlled, and molded products of excellent quality can be stably molded.

In this embodiment, as described above, the speed of the second electric servo motor 38 as an electric motor is basically controlled during both the injection filling operation and the subsequent pressure holding operation. Under the speed control, as the rotational speed of the second electric servo motor 38 becomes low, the control state is shifted from speed control to torque control.
The shock at the time of switching from speed control to torque control is small, and excellent control stability can be obtained at the time of the switch.

Furthermore, if the load is small when switching from injection filling operation to pressure holding operation, the speed of the second electric servo motor 38 is directly controlled, so that switching to pressure holding operation is not possible as in the conventional case. Runaway of the second electric servo motor 38, which is sometimes caused by a small load, can be effectively avoided. Any problems that may occur can be avoided.

Furthermore, in this embodiment, since the current supplied to the second electric servo motor 38 is effectively prevented from increasing beyond the level corresponding to the necessary injection holding pressure, the second electric servo motor 38 Another advantage is that the occurrence of hunting caused by excessive current flowing into the circuit can be well controlled.

Note that the switching from the injection filling operation to the pressure holding operation by switching the open/close switches 64 and 66 is performed based on, for example, detecting the forward position of the injection screw 10 with a limit switch or a timer, as in the past. Become. Further, as is clear from the above description, in this embodiment, the subtracters 56, 6
8 constitutes a rotational speed command signal correction means and a torque upper limit command signal correction means, respectively, open/close switches 64 and 66 constitute a torque upper limit signal switching means, and a power converter 78 constitutes an amplification means. are doing.

Although one embodiment of the present invention has been described in detail above,
This is a literal illustration, and the present invention should not be interpreted as being limited to such specific example.
It goes without saying that various changes, modifications, improvements, etc. can be made without departing from the spirit of the invention.

For example, a part of the control circuit can be configured by a computer, and the rotational speed and output torque of the second electric servo motor 38 as an electric motor can be determined by sensors other than the encoder 50 and the load cell 48, respectively. It is also possible to detect it by other means.

Further, in the above embodiment, an example was described in which the present invention is applied to an in-line screw type injection device in which the injection filling operation and the subsequent pressure holding operation are performed based on the forward movement of the injection screw 10. The present invention can also be applied to an injection device in which the injection filling operation and the holding operation are performed based on the forward motion of the injection plunger.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an example of an injection device according to the present invention, and FIG. 2 is a circuit diagram showing an example of a control circuit for rotationally controlling the second electric servo motor in FIG. . 10: injection screw, 38: second electric servo motor (electric motor), 48: load cell (torque detection means), 50: encoder (rotational speed detection means), 56: subtractor (rotational speed command signal correction means), 58: Speed control section, 60: Torque limiter,
64, 66: Open/close switch (torque upper limit signal switching means), 68: Subtractor (torque upper limit command signal correction means), 70: Torque control section, 78: Power conversion section (amplification means).

Claims (1)

[Claims] 1. By moving the injection screw or the injection plunger forward based on the rotational power of an electric motor, the injection filling operation of the molding material into the cavity of the mold and the subsequent pressure holding operation are performed. An injection control method for an electric injection device, wherein during the injection filling operation, the rotational speed command signal of the electric motor is converted into a rotational speed detection signal under torque limiter control based on a predetermined torque upper limit command signal. The electric motor is controlled to rotate on the basis of the rotational speed feedback control signal corrected by the rotational speed feedback control signal, while during the pressure holding operation, the predetermined torque upper limit command signal is used to detect the torque of the electric motor. Under the torque limiter control based on the torque feedback control signal corrected by the signal, the electric motor is rotated based on the rotation speed feedback control signal obtained by correcting the rotation speed command signal of the electric motor using the rotation speed detection signal. An injection control method in an electric injection device, characterized in that the injection control method is performed in an electric injection device. 2. In an electric injection device that performs injection filling operation of molding material into the cavity of a mold and subsequent pressure holding operation by moving the injection screw or injection plunger forward based on the rotational power of an electric motor. An injection control device, comprising: a rotational speed detection means for detecting the rotational speed of the electric motor and outputting a rotational speed detection signal representing the rotational speed; and detecting the rotational torque of the electric motor and detecting the rotational torque. a torque detection means for outputting a torque detection signal representing the rotation speed; and a rotation speed command signal outputted according to a preset speed control pattern, corrected by the rotation speed detection signal from the rotation speed detection means to provide rotation speed feedback. Rotational speed command signal correction means for outputting a control signal; and torque feedback control by correcting a torque upper limit command signal outputted according to a preset torque control pattern with a torque detection signal from the torque detection means. Torque upper limit command signal correction means for outputting a signal; during the injection filling operation, the torque upper limit command signal is output as is as a torque upper limit signal, and during the pressure holding operation, the torque upper limit command signal correction means outputs the torque upper limit command signal as it is; a torque upper limit signal switching means for outputting a torque feedback control signal of the torque upper limit signal as a torque upper limit signal; Torque limiter means for outputting a drive signal of a current having a magnitude corresponding to the rotation speed feedback control signal from the rotation speed command signal correction means; and amplifying the drive signal output from the torque limiter means and supplying the amplified drive signal to the electric motor. An injection control device for an electric injection device, comprising: an amplifying means.