JPS62207622A - Injection controlling of motor-driven injection machine - Google Patents

Abstract

PURPOSE:To make it possible to perform a stable molding operation by a method wherein injection speed is gradually lowered by the filling resistance of molten resin during the period ranging from the finish of a filling process to the start of a dwell process. CONSTITUTION:The forward speed of a screw 10 is controlled by speed changeover positions and speeds which are set on the speed changeover position setters 30a, 30b and 30c and the speed setters 32a, 32b and 32c of a setting device 28. Thus, when the screw 10 advances and reaches a starting position of free reduction of speed set by a starting position setter 34 of reduction of speed a signal which corresponds to a value set at a limiting torque setter 38 is sent from a torque limiter 26 to a controlling device 24 so as to limit a current fed to an injection motor 18. As a result, the speed of a screw 10 is lowered gradually, because the screw 10 undergoes the filling resistance of molten resin. Accordingly, the shifting of the screw 10 due to its large inertial energy and the fluctuation of its shifting time is dissolved and a stable molding operation can be performed.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to an injection control method for an electric injection machine.

(b) Conventional technology When a dynamic injection machine is used, conventionally, the filling process is generally switched to the holding pressure process as shown in Figure 3.In other words, in the filling process, the setting As the screw moves forward at speeds V, V2 and v3, the mold is filled with molten resin, and when the screw reaches the holding pressure switching position (point P), the rotational speed control of the motor is changed to Switch to torque control and enter pressure holding process.

As a result, the holding force is applied at the set torques T, □, and TH2 for predetermined times t1 and t2, respectively. However, in the case of an electric injection machine, the rotation of the electric motor is converted into forward motion of the screw by a ball screw mechanism, gear mechanism, etc., so the inertia of the power transmission member is large, and the inertia of the power transmission member is large. Even if a command signal is output to the electric motor to switch from rotational speed control to torque control, it will not be decelerated to the low speed (V□) corresponding to the set torque (T u + ), and the screw will move to point Q due to inertia. This will result in Therefore, the pressure holding time for the set torque T, 11 is 1. Even if the time is set, the actual pressure holding time is only 71', and if the molten state of the resin changes, the position of the Q point also changes, so there is a problem that stable molding work cannot be performed.

In order to solve such problems, Japanese Patent Application Laid-Open No. 59-224324 discloses a pressure-holding switching position (two points).
A method is shown to rapidly decelerate the motor just before the

(c) Problems to be solved by the invention However, in the case of this method, it is necessary to brake the electric motor to rapidly decelerate it, so in addition to requiring braking energy for deceleration, A large resistor is required because it is necessary to absorb the inertial energy of the moving electric motor, power transmission member, screw, etc. and release it as heat. Therefore, there are problems in that the power loss is large, the cost of the device is high, and the sudden braking causes severe wear and tear on the power transmission members.

(d) Means for solving the problems The present invention solves the above problems by gradually reducing the injection speed due to the filling resistance of the molten resin between the end of the filling process and the start of the pressure holding process. solve. That is, in the injection control method for an electric injection machine according to the present invention, when filling with molten resin, the rotational speed of the electric motor is controlled by +l+(J) so that the injection speed is set in advance, and the screw reaches the first position. When the screw moves forward, the torque of the injection motor is limited to a preset value, and in this state, the screw moves forward while decreasing the injection speed, and after reaching the second position, the injection motor is set so that the holding force is as set. The gist is to control the torque of the electric motor.

(e) Operation In the filling process, the injection speed is controlled by controlling the rotational speed of the injection motor as in the conventional case. When the screw reaches the first position (free deceleration start position), the current value input to the injection motor is limited, and the torque of the motor is controlled so that it reaches a predetermined limit torque value. Gradually reduce the injection speed. When the screw reaches the second position (pressure holding switching position) while gradually decreasing the injection speed due to the filling resistance of the molten resin, a pressure holding process for controlling the torque of the injection motor is started. At this point, the injection speed has sufficiently decreased, so the inertial energy is small, and torque control as set can be started immediately.

(F) Embodiments Hereinafter, embodiments of the present invention will be described based on 1st and 2(2) of the accompanying drawings.

The screw 10 of the injection machine is held by a member 14 that is integral with a ball nut 12. A ball screw 16, which constitutes a ball screw mechanism in combination with the pole nut 12, can be rotated by an injection motor 18. The rotational position and rotational speed of the injection motor 18 are determined by the position/speed detector 2.
detected by o. rotational speed of the injection motor 18;
The torque, rotation 1, etc. are controlled by a control device 24 via a drive amplifier 22. Signals are manually input to the control device 24 from the aforementioned position/speed detector 20, torque limiter 26, and setting device 28.

The signal from the setting device 28 is also input manually to the torque limiter 26 . The setting device 28 includes a speed switching position setting device 30a for setting in advance the position at which the screw speed is changed;
30b and 30c, speed setters 32a, 32b and 32c for setting the screw speed in advance, deceleration start position setter 34 for setting the free deceleration start position (first position), and holding pressure switching position (second position). ) for setting the holding pressure switching position setting device 36, and the limit torque setting device 3 for setting the limit value of the output torque of the injection motor 18.
It has 8.

Next, the operation of this embodiment will be explained. The screw 10 is rotationally driven by a plasticizing electric motor (not shown), the resin material is plasticized, and the screw 10 is retracted until a predetermined amount of molten resin has accumulated. Next, the operation of the injection motor 18 is controlled by the control device 24, and the rotation of the injection motor 18 is converted into a linear motion of the screw 10 by the ball screw 16 and the pole nut 12, so that the screw 10 is advanced in plane. Screws 10 and 11 at that time
The linear speed is determined by the speed switching position setter 30a of the setting device 28.
, 30b and 30c, and the speed switching position and speed set in advance in the speed setters 32a, 32b and 32c, for example, as shown in FIG. 2, the speed V,
, V2 and V3. When the screw 10 advances in this way and reaches the free deceleration start position set by the deceleration start position setting device 34 (point R in FIG. 2)
, a signal is sent from the torque limiter 26 to the control device 24 according to the set value of the limit torque setter 38, and the injection motor 1
8 is limited, and as a result, the generated torque is
It is limited to Tc shown in the figure. For this reason, screw 10
is subject to the filling resistance of the molten resin, and its speed gradually decreases. The screw 10 moves forward while decreasing its speed, and reaches the holding pressure switching position S point set in the holding pressure switching position setting device 36. When the 8th point is reached, the pressure holding process is started and the torque of the injection motor 18 is controlled. That is, the torque THI is applied for a time t3, and then the torque Tl42 is applied.
is applied for a time t2. The injection speed Vs of the screw 10 when the screw 10 reaches the 8th point is the generated speed M when the set torque TH1 is applied in the next pressure holding process
If the limit torque Tc is set close to HI, the injection speed of the screw 10 can be extremely smoothly adjusted to the holding pressure speed v.
It is possible to move to H.

Therefore, the movement of the screw 10 due to large inertial energy and the variation in the movement time are eliminated, stable molding can be performed, and the variation in quality of the molded product is significantly reduced. In addition, since there is no need to suddenly decelerate the screw 10 immediately before the pressure holding process, there is no need for large resistors, reducing the cost of the device, and since no impact is applied to power transmission members, the lifespan of these members can be extended. Can be extended.

(g) As described in detail, according to the present invention, the injection speed is reduced by the filling resistance of the molten resin when switching from the filling process to the pressure holding process, thereby stabilizing the molding conditions. This makes it possible to obtain high-quality molded products, eliminates the need for equipment costs for rapid deceleration, and reduces impact, thereby extending the life of the power transmission member.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention, FIG. 2 is a diagram showing changes in injection speed and torque according to the present invention, and FIG. 3 is a diagram showing changes in injection speed and torque according to the conventional method. 10...Screw, 12...Pole nut, 16
...Ball screw, 18...Injection electric motor, 20...
・Position/speed detector, 24...control device, 26...
Torque limiter, 28...setting device. Patent applicant Nikki Steel Co., Ltd. Agent Patent attorney Toshiyuki Miyauchi Figure 2

Claims (1)

[Claims] In an injection control method for an electric injection machine using an electric motor as a drive source, the rotational speed of the electric motor is controlled to a preset injection speed when filling with molten resin, and the screw is rotated. When the screw advances to the first position, the torque of the injection motor is limited to a preset value, and in this state, the screw advances while decreasing the injection speed, and after reaching the second position, the holding force becomes as set. An injection control method for an electric injection machine, characterized in that the torque of an injection motor is controlled as follows.