JPH01249419A - Injection device of injection molder - Google Patents

Abstract

PURPOSE:To contrive to lighten the weight and to remarkably lower the inertial force and realize the improvement of the responsiveness, rapidity, stability, preciseness and reproducibility by a structure wherein a screw driving part is constituted by providing an outer tubular shaft, on the outer periphery of which a ball screw mechanism is provided, and an inner shaft, which pivotally inserted in the outer shaft. CONSTITUTION:Due to the normal rotation of a servo motor 27, the turning force of said motor 27 is transmitted through a course of a driving gear 28 a driven bear 25 a spline mechanism 24 an inner shaft 3 a coupling member 17 a screw 6. As a result, the screw rotates normally so as to be allowed to meter molten resin material. Further, by rotating the servo motor 27 in reverse direction, the screw 6 can be rotated reversely through the same course as described above. On the other hand, due to the normal rotation of a servo motor 22, the turning force of said motor 22 is transmitted through a course of a driving gear 23 a driven gear 20 an outer shaft 2 a ball screw mechanism 5 a sliding member 16 the coupling member 17. As a result, the screw 6 is advanced, resulting in allowing to inject the metered molten resin material in order to fill a mold. Furthermore, by rotating the servo motor 22 in reverse direction, the screw 6 can be retreated through the same course as described above.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an injection device for an injection molding machine equipped with an electric screw drive section.

[Prior art and its problems]

The injection device of the in-line screw type injection molding machine includes a screw that is inserted into the heating section, and a screw drive unit that controls the rotation and advance/retreat of the screw. In one step in total, the screw is rotated to accumulate molten resin material in front of the screw, and in the injection step, the screw is advanced to perform injection filling into the mold.

The screw drive unit built into a conventional injection device employs a configuration in which one of the rotation control system or advance/retraction control system includes the other system.For example, the rotation control system is directly connected to the screw to control the rotation of the screw. In addition, the screw can be controlled to move forward and backward by moving the rotation control system itself forward and backward using the forward and backward control system.

For this reason, when driving the screw, the inertial force in one control system (advance/retreat control system) becomes significantly large, making it difficult to control with high stability, responsiveness, promptness, accuracy, and reproducibility. There was a problem that the structure of the entire injection device became complicated and large.

[Means for solving problems]

The present invention aims to provide an injection device for an injection molding machine that solves the problems that exist in the prior art described above, and is achieved by an injection device 1 shown below.

That is, the injection device 1 of the injection molding machine according to the present invention includes, in its main part, a cylindrical outer shaft 2 disposed coaxially, and an inner shaft 3 rotatably inserted into the outer shaft 2. It becomes. The outer shaft 2 is rotated by a first motor 4, and a screw 6 is advanced and retreated via a ball screw mechanism 5 provided on the outer periphery. Further, the inner shaft 3 is rotated by the second motor 7, and the screw 6 is also rotated. Note that the first motor 4 and the second motor 7 are configured to be able to be independently controlled in forward and reverse rotation.

[For production]

Next, the operation of the injection device 1 according to the present invention will be explained.

In the injection device 1 according to the present invention, the screw advance/retreat control system and the rotation control system are independent. Therefore, the advance/retreat control system rotates the outer shaft 2 by the rotation of the first motor 4, and further converts the rotational motion into a linear motion via the ball screw mechanism 5 to advance or retreat the screw 6. That is, injection can be mainly performed. On the other hand, the inner shaft 3 is rotated by the rotation of the second motor 7, and the screw 6 is further rotated.

That is, it is possible to mainly perform weighing.

〔Example〕

Hereinafter, preferred embodiments of the present invention will be described in detail based on the drawings.

First, the overall basic configuration of the injection device 1 according to the present invention will be explained with reference to FIG.

Reference numeral 11 denotes a heating cylinder, equipped with an injection nozzle 12 at the front end, and a hopper 1 at the rear upper end for supplying molding material into the heating cylinder 11.
Equipped with 3. A screw 6 is inserted into the heating cylinder 11. Further, the rear end of the heating cylinder 11 is supported by a support plate 14, and the support plate 14 is further provided with a plurality of tie bars 15 extending horizontally toward the rear. Tie bar! 5... is provided with a sliding member 16 that is freely slidable in the front-rear direction, and a rotation regulating member 16a is inserted into the interior of this sliding member 16 to allow forward and backward directions and to restrict the rotating direction. Furthermore, a rotatable coupling member 17 is provided inside the member 16a. Coupling member 17
A ring-shaped load cell I is located between the rear end surface and the sliding member 16.
Interpose 8. On the other hand, the connecting member! The rear end of the screw 6 is connected to the front end of the screw 7. Further, the inner shaft 3 extending rearward is coupled to the rear end of the coupling member 17. The inner shaft 3 is inserted into a cylindrical outer shaft 2 which is rotatable coaxially, and a ball screw mechanism 5 for injection is disposed between the outer periphery of the outer shaft 2 and the sliding member 16.
to intervene. Note that this ball screw mechanism 5 has an outer shaft 2.
It consists of a ball screw shaft 5a utilizing the outer peripheral surface of the ball screw shaft 5a and a ball screw nut 5b coupled to the rear end of the sliding member 16. Also,
A driven gear 20 is attached to the rear end of the outer shaft 2, and this driven gear 20 is connected via a timing belt 21 to a drive gear 23 attached to an injection servo motor 22 (first motor 4).

On the other hand, a driven gear 25 is provided at the rear end of the inner shaft 3 via a spline mechanism 24, and this driven gear 25 is connected via a timing belt 26 to a servo motor 27 (second motor 7) for rotating the screw. Connect to gear 28.

Next, the functions of the injection device 1 will be explained.

First, by forward rotation of the servo motor 27, the motor 2
The rotational force of 7 is transmitted along the path of drive gear 28 -> driven gear 25 -> spline mechanism 24 - inner shaft 3 - coupling member 17 -> screw 6. Therefore, the screw 6 rotates forward and the molten resin material can be measured. In addition, servo motor 2
By rotating the screw 7 in the opposite direction, the screw 6 can be rotated in the opposite direction along the same path.

On the other hand, due to the forward rotation of the servo motor 22, the motor 2
The rotational force of No. 2 is transmitted along the path of driving gear 23 -> driven gear 20 - outer shaft 2 -> ball screw mechanism 5 -> sliding member 16 - coupling member I7. Therefore, the screw 6 moves forward, and the measured amount of molten resin material can be injected and filled into the mold. Note that by rotating the servo motor 22 in the reverse direction, the screw 6 can be moved backward along the same path.

FIGS. 2 to 4 clearly show the structure of the main parts of the injection device 1 (FIG. 1). Note that Fig. 2 is a longitudinal side view showing the screw rotation control system in the injection device, and Fig.
The figure is a vertical side view clearly showing the vicinity of the motor of the screw advancement/retraction control system in the same device, and Figure 4 is a partially cutaway view taken along arrow A-A in Figure 3, and shows the same parts as Figure 1. have been given the same reference numerals to clarify their structure.

Next, an example of the operation of the injection device 1 will be explained with reference to FIG. 5.

First, in the weighing process, the central control unit 32 applies a weighing command signal and a weighing value signal based on a set value set by a weighing value setter (not shown) to the control circuit 33 that controls the servo motor 27 . As a result, the servo motor 27
rotates forward and performs weighing.

On the other hand, when a total of one process is completed, the process moves to the injection process. In the injection process, an injection command signal and an injection speed setting device 34 are sent from the central control unit 32 based on the completion of closing the mold (not shown).
An injection speed command signal based on the set value set by is given to the control circuit 36 that controls the servo motor 22. As a result, the servo motor 22 rotates and the screw 6
At the same time, a detection signal from a tachometer generator 38 that detects the speed of the motor coupled to the motor 22 is applied to the control circuit 36, and closed-loop control is performed so as to match the injection speed command signal.

By the way, at this time, the setting signal set by the screw reverse rotation speed setting device 39 is applied to the control circuit 33, and the servo motor 27 starts rotating in reverse. At the same time, a detection signal from the tachometer generator 40 coupled to the motor 27 is applied to the control circuit 33 to perform closed loop control so as to match the reverse rotation speed setting value. That is, the screw 6 rotates in a direction opposite to the rotation direction during measurement in the measurement step. In this way, the screw 6 in the injection process moves forward at a set speed and rotates in the opposite direction at a set predetermined speed, stopping the apparent movement of the crest of the screw 6 in the axial direction with respect to the forward movement of the screw 6. Or it can be made significantly smaller.

On the other hand, when the screw 6 moves to the pressure holding switching position, pressure holding control is performed, and after a predetermined period of time, each servo motor 2
2. Each control signal in 27 is turned OFF and the injection process is completely completed. In FIG. 5, 41 is a holding pressure switching position setter, 18 is a load cell for detecting resin pressure during holding pressure control, 44 is an amplifier, and 43 is a holding pressure setting device.

Although the embodiments have been described in detail above, the present invention is not limited to these embodiments, and the structure, shape, etc. can be modified as desired without departing from the gist of the present invention.

〔Effect of the invention〕

As described above, the injection device of the injection molding machine according to the present invention has a cylindrical outer shaft provided with a ball screw mechanism on the outer periphery and an inner shaft rotatably inserted into the outer shaft when configuring the screw drive section. Since it is equipped with a shaft, the following effects are obtained.

■ The screw rotation control system and advance/retreat control system can be configured as independent systems, and one system does not include the motor of the other system, unlike conventional motor systems. As a result, each prefecture is able to reduce weight, significantly reduce inertia, and improve responsiveness, speed, stability, and
Improved accuracy and reproducibility can be achieved.

■ The driving part can be simplified, and the entire injection device can be made smaller and lower in cost.

[Brief explanation of the drawing]

Fig. 1.2 A longitudinal side view showing the basic configuration of the injection device according to the present invention. Fig. 2: A longitudinal side view showing the screw rotation control system embodying the injection device according to the present invention. Fig. 3: The same A longitudinal side view clearly showing the vicinity of the motor of the screw advancement/retraction control system in the device, Figure 4: A partially cutaway view taken along the arrow A-A in Figure 3, Figure 5: Overall control system in the device FIG. 2 is a block circuit diagram showing only the main parts. In the drawing, 1: Injection device 2: Outer shaft 3: Inner shaft 4: First motor 5: Ball screw mechanism 6: Screw 7: Second motor Patent applicant Nissei Jushi Kogyo Co., Ltd. Representative Patent Attorney 1) Shigeru Figure 3 Figure 4 (,,' Go to Figure 5 4 (J 2/2 and 5b

Claims (1)

[Scope of Claims] [1] A cylindrical outer shaft that is rotated by a first motor and moves the screw forward and backward through a ball screw mechanism provided on the outer periphery; An injection device for an injection molding machine, comprising an inner shaft that is rotatably inserted into the interior of the machine to rotate a screw. [2] The injection device for an injection molding machine according to claim 1, wherein the first motor and the second motor are configured to be individually controllable in forward and reverse rotation.