JPH0473689B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an injection molding machine for synthetic resin material having an injection mechanism driven by an electric motor, and particularly relates to an injection molding machine for synthetic resin material having a motor-driven injection mechanism.
[g] Injection molding machine with an injection volume of about 100 yen or more, in which the injection members such as the injection plunger and injection screw of a large injection molding machine are driven by a small output servo motor to improve the injection speed and pressure control performance. This relates to molding machines.

[Conventional technology]

In this type of injection molding machine, in order to inject molten resin into a mold cavity and obtain a high-quality molded product, the injection mechanism consists of a screw that heats, kneads, and plasticizes the resin raw material, and a plasticizing part. There is a pre-plasticization method that separates the resin raw material into a part that is injected by a plunger and achieves each function to the highest degree, or a method that uses a hydraulic cylinder to drive the injection plunger quickly and precisely. Drive systems using servo motors, ball screws, and thrust nuts are also being adopted.

However, in order to drive the injection plunger of an injection molding machine with a large injection volume, mechanisms such as servo motors, ball screws, and thrust nuts must also be large and have high output. Large items are currently difficult to secure,
Since the inertia of the rotating parts of the rotor and ball screw is large, the servo motor is not suitable for controlling the injection speed of an injection molding machine, where starting, stopping, and speed changes must be repeated frequently and quickly.

To improve this point, for example, JP-A-60
There is an injection molding machine described in No.-125618. In this injection molding machine, the driving forces of multiple motors, clutches, and gear mechanisms are combined to drive an injection screw/plunger via a pair of ball screws and thrust nuts. However, with this method, the inertia of the rotating part of the motor group can be reduced compared to when using a single high-output motor, but the ball screw and thrust nut for driving the screw are attached to the screw. 1
In addition to using a large set of large inertia,
Since it uses a so-called in-line system with a screw and plunger, the diameter of the screw must be increased to create a large-capacity machine.As a result, the overall inertia from the motor group to the screw is not very small, and the injection It is difficult to drive the plunger quickly and precisely.

[Problem that the invention seeks to solve]

The present invention has been made in view of the above points, and extends servo motor drive to injection control not only for small capacity machines but also for medium and larger injection molding machines, and provides a connection mechanism from the servo motor to injection members such as plungers. An object of the present invention is to provide an injection molding machine that can quickly repeat startup, stop, etc. by reducing the inertia of the machine, and can particularly improve the rise and fall characteristics of the injection speed to obtain high-quality precision molded products. The purpose is

[Means for solving problems]

In order to achieve the above object, the present invention includes a plasticizing cylinder, a screw rotatably housed in the plasticizing cylinder, an injection cylinder connected to the tip of the plasticizing cylinder, and an injection cylinder inside the injection cylinder. A single injection member housed in a movable unit so as to be movable back and forth, a plurality of servo motors, and a conversion means connected to the single injection member for converting rotational motion of each servo motor into linear motion. The synthetic resin molding material is kneaded, plasticized and supplied into the injection cylinder by the rotation of the screw, and the injection member is driven forward through the conversion means by cooperation of the plurality of servo motors to form the synthetic resin. This is characterized in that the molding material is supplied to a predetermined mold.

〔Example〕

FIG. 1 is a front view showing the injection molded part of the example;
FIG. 2 is a plan view of the same part, and FIG. 3 is a block diagram of the injection control stem.

The apparatus of the embodiment is an injection molding machine of a pre-plasticization type in which the molding material is heated, kneaded and plasticized by a screw, and the plasticized molding material is injected into the mold cavity by a plunger. be.

First, the structure of the injection device will be explained based on FIGS. 1 and 2.

The device includes an injection member 1 consisting of a plunger that injects plasticized synthetic resin molding material into a mold cavity (not shown), an injection cylinder 2 that movably accommodates the injection member 1, and an injection cylinder 2 in which the injection member 1 is movably housed. a screw 3 that supplies plasticized molding material;
Plasticizing cylinder 4 that movably accommodates the screw 3
, a plunger servo motor 5 for driving the injection member 1 , a hydraulic motor 6 for driving the screw 3 , and a hydraulic motor 6 interposed between the servo motor 5 and the injection member 1 to control the rotation of the servo motor 5 for the injection member. 1; a converting means 7 for converting into a linear motion; brackets 9, 10, 11, 12 for fixing the injection cylinder 2, plasticizing cylinder 4, servo motor 5, and hydraulic motor 6 to the pedestal 8, respectively; and the converting means 7. It is composed of a guide arm 13 that guides the linear movement of the robot.

The injection member 1 is equipped with a nozzle 2a for discharging molding material at its tip and can move straight forward and backward within the injection cylinder 2, and a connecting member 1a provided at its rear end connects a converting means 7, which will be described later, to a thrust nut 7a. It matches.

The screw 3 is rotatable within the plasticizing cylinder 4 and is connected to a hydraulic motor 6 via a drive shaft 3a. A connecting passage 4a is provided at the tip of the plasticizing cylinder 4, and this connecting passage 4a
is connected to the injection cylinder 2, and an intake hole 4b is formed at the rear end to take in molding material from a hopper (not shown).

The conversion means 7 includes two ball screws 7b connected to two servo motors 5 via a gear coupling 15 in a bearing case 14, and two thrust nuts screwed onto the outer circumferences of the ball screws 7b, respectively. 7a, and one thrust combining member 7c fixed to two thrust nuts 7a and guided in linear movement by the guide arm 13, and one thrust combining member 7c is connected to the one injection member 7a. The first connecting member 1a is engaged with the first connecting member 1a.

In addition, 16 is a load cell (thrust sensor) arranged between the injection member 1 and the connecting member 1a,
Although not shown, a backflow prevention mechanism is naturally provided in the injection cylinder 2, and a heater and the like are provided on the outer periphery of the plasticizing cylinder 4.

Next, the operation of the above embodiment will be explained.

The thermoplastic synthetic resin molding material taken into the plasticizing cylinder 4 from a hopper (not shown) through the intake hole 4b is heated in the plasticizing cylinder 4 and kneaded by the screw 3, and in a molten state is passed through the connecting passage. It is supplied into the injection cylinder 2 via 4a. The resin pressure inside the injection cylinder 2 is detected by the load cell 16, and the two servo motors 5 are reversely rotated based on this signal to retract the injection member 1 so that the resin pressure is uniform. The amount of resin at that time is controlled to a predetermined value by the rotational speed of the absolute encoder PG.

When the amount of resin in the injection cylinder 2 reaches a predetermined value, the two servo motors 5 start to rotate forward in response to the injection start signal, and the two ball screws 7b rotate through the gear coupling 15 at each point. As a result, the two thrust nuts 7a are connected to the ball screw 7b.
Go straight ahead on top. Therefore, one thrust combining member 7 is connected to both of the two thrust nuts 7a.
c moves straight while being guided by two guide arms 13, and the injection member 1 injects the resin molding material in the injection cylinder 2 into the mold from the nozzle 2a via the connecting member 1a that engages with the thrust member 7c. .

The injected resin molding material is put into a pressure holding process in the mold as is well known in the art. At this time, the reaction force exerted on the injection member 2 by the resin pressure in the mold is detected by the load cell 16, and the servo motor 5 By programmatically controlling the torque of

FIG. 3 is a control block diagram of the control device for the injection member 2. As shown in FIG.

The control system includes a control unit body 20 consisting of a digital controller 21 and a motor interface 22.
, a pressure control printed board (IF) 23 connected to the digital controller 21, a master amplifier 24 that drives one servo motor 5, a slave amplifier 26 that drives the other servo motor 5, and a rear end of the injection member 1. attached load cell 16,
It consists of a speed detector for the servo motors 5 (TG in Fig. 3), etc., and the set pressure is determined by command data inputted in advance to the digital controller 21, and the master amplifier 24 drives the two servo motors 5 together. The injection member 1 is moved back and forth. On the other hand, thrust force data applied to the injection member 1 from the load cell 16, servo motor speed data from the servo motor speed detector, etc. are always input to the digital controller 21, master amplifier 24, and slave amplifier 26, and these actual measurement value data and the set value, and the rotation of the servo motor 5 is controlled based on the deviation data.

In such an embodiment, the thrust combining member 7c is made of a highly rigid and lightweight material, and the screw 3 and the injection member (plunger) are provided separately to make the diameter of the injection member smaller and the stroke longer. Therefore, the inertia of the entire drive device is extremely small.

Furthermore, since speed control is performed by electrically equalizing the rotational speeds of the plurality of servo motors 5, the load applied to the plurality of servo motors 5 is equalized.

〔Effect of the invention〕

The present invention is as described above, and a single injection member is driven by a rotation-to-linear conversion mechanism connected to each of a plurality of servo motors, and a screw for kneading and plasticizing the injection member is used. Because they are separated, the inertia of the drive system is small, and frequent and rapid control of the injection member, such as starting, stopping, and shifting, is possible.

[Brief explanation of the drawing]

FIG. 1 is a front view of an injection mechanism in an injection molding machine according to an embodiment of the present invention, FIG. 2 is a plan view of the injection mechanism, and FIG. 3 is a block diagram of an injection control system. DESCRIPTION OF SYMBOLS 1... Injection member, 3... Screw, 5... Servo motor, 7... Conversion means, 7a... Thrust nut, 7b... Ball screw.

Claims (1)

[Scope of Claims] 1. A plasticizing cylinder, a screw rotatably housed within the plasticizing cylinder, and an injection cylinder connected to the tip of the plasticizing cylinder,
A single injection member housed in the injection cylinder so as to be movable back and forth, a plurality of servo motors, and a converter that converts the rotational motion of each servo motor into linear motion and is connected to the single injection member. means for kneading and plasticizing the synthetic resin molding material and supplying it into the injection cylinder by the rotation of the screw, and driving the injection member forward via the conversion means by cooperation of the plurality of servo motors. 1. An injection molding machine characterized in that a synthetic resin molding material is supplied to a predetermined mold.